US20170225296A1

US20170225296A1 - Device And Method For Blasting A Suspension Onto Workpieces

Info

Publication number: US20170225296A1
Application number: US15/502,139
Authority: US
Inventors: Werner Hunziker; Jurg Scholz; Remo Giger
Original assignee: Individual
Current assignee: Individual
Priority date: 2014-08-04
Filing date: 2015-07-31
Publication date: 2017-08-10
Also published as: EP3177432A1; WO2016020275A1; DE102014111043A1

Abstract

A device for irradiating a suspension on workpieces, the device including at least one pressure vessel for the suspension; at least one feed line for the suspension connected to the pressure vessel, the feed line is connected or can be connected to a radiation device; at least one valveswitched between the pressure vessel and the radiation device; at least one prechamber connected to the pressure vessel by a valve; at least one return line for the suspension, connected to the prechamber; and a line and a valve, by which the prechamber can be connected to a compressed air source or by which the prechamber is connected to a compressed air source. The valve between the prechamber and the pressure vessel is a check valve connected at its one upper, connection at a pressure vessel connection, which discharges into the pressure vessel through the bottom of the pressure vessel at the lowest point thereof, and which is connected at its other connection to the prechamber, wherein the flow direction of the check valve is directed toward the pressure vessel.

Description

FIELD OF THE INVENTION

The present invention relates to a device, in particular for blasting a suspension onto one or more workpieces, wherein the device encompasses: At least one pressure vessel for the suspension, at least one feed line for the suspension connected to the pressure vessel at its one end, the other end of which is or can be connected to a blasting device, which can preferably be a blasting gun, at least one valve that is switched between the pressure vessel and blasting device, at least one prechamber for the suspension, which is connected to the pressure vessel with at least one valve interposed, at least one return line for the suspension, which is connected to the prechamber, preferably with a valve interposed, and a line and a valve, with which the prechamber is or can be connected to a compressed air source separate from the device, or with which the prechamber is connected to a compressed air source belonging to the device.

BACKGROUND OF THE INVENTION

Generic devices are conventionally used for the surface treatment of workpieces by having the pressure from a blasting gun apply (i.e., “blast”) a suspension containing water and preferably fine-grained blasting agents onto the workpiece surface. Such a wet blasting treatment can have a grinding effect on the workpiece surface, for example, due to the abrasively acting blasting agent. Also known is a dry blasting treatment, in which a blasting agent is blasted onto the surface of workpieces without a liquid phase.
Very fine-grained, as a rule mineral, blasting agents, such as corundum, silicon carbide, glass powder, glass pearls, ceramic pearls, etc., can be used dry in blasting systems only to a very limited extent, because in addition to undesirably forming dust, they have virtually no effect on the surface of a workpiece to be machined. For this reason, they are reacted with a liquid, as a rule water, for purposes of wet blasting. This flowable mixture, consequently referred to as a suspension, can be handled similarly to a liquid, e.g., conveyed by a pump in pipes or tubes. One major challenge in systems or blasting devices that work with such suspensions involves the extremely specific differences in weight between the liquid phase and solid blasting agents in the suspension. For example, the ratio for the specific weight between water and corundum measures 1:4. An attempt is often made to keep the blasting agent suspended by means of agitating mechanisms. However, since such devices operate with rotating elements, there is a tendency for the blasting agent therein to nonetheless be deposited in the outer regions. This is more or less of a problem, depending on the blasting agent concentration in the suspension. For this reason, low concentrations have as a rule been used previously, at which the weight ratio between the solid blasting agent and liquid phase in the suspension lies within a value range of only 1:10-1:20. One requirement and concurrent difficulty has to do with the uniform distribution of the blasting agent in the liquid. The blasting result on a workpiece will to a great extent be advantageously influenced by a uniform distribution, and disadvantageously influenced by a non-uniform distribution. In order to be able to pump a suspension for a blasting process, there is also the difficulty that a centrifugal pump also acts as a centrifuge, for example, i.e., that it causes the heavier blasting agent to separate from the water, which is lighter by comparison. The higher the blasting agent concentration, the more serious the separation effect as well. This can also result in two streams forming next to each other in a pipe system, one rapidly flowing liquid stream and one slowly blasting agent stream.
In conventional blasting systems, the suspension is as a rule conveyed into an injector blasting gun by a centrifugal pump. Also known is to blow compressed air into the suspension stream. However, a large portion of the water is atomized or evaporated as a result, and the blasting agent grains impacting the workpiece thus have more or less the same “hacking” effect as when dry blasting without liquid. The difference then practically lies only in the absence of a dust problem. A generic device of the kind mentioned at the outset is known in prior art from WO 2013/079490 A2.

SUMMARY OF THE INVENTION

The object of the invention is to advantageously further develop such a generic device. In particular, the aim is to be able to thereby entirely or at least partially eliminate individual or several of the described previously existing limitations and disadvantages. The aim in particular is to advantageously further develop a generic device for blasting suspensions, thereby making a suspension suitable for the blasting process that has a higher percentage of blasting agent by comparison to the weight ratios indicated above possible in prior art. In particular, the aim is further to not have to blow compressed air into the suspension before the blasting nozzle, and spread or atomize the suspension jet.
In a first aspect of the invention, the object is initially and essentially achieved in conjunction with the features in which the valve between the prechamber and pressure vessel is a check valve, which at its one, preferably upper, terminal is connected directly or indirectly to a pressure vessel terminal that discharges into the pressure vessel through the floor of the pressure vessel, preferably at its lowest point, and its other, preferably lower, terminal is directly or indirectly connected to the prechamber, wherein the passage direction of the check valve is directed toward the pressure vessel, and the blocking direction of the check valve is directed toward the prechamber. The pressure vessel is preferably located above, either directly above or laterally above, the prechamber. In light of the described components, reference could also be made to a blasting installation or a blasting system instead of a blasting device. Within the framework of the invention, the term connected or terminal includes a direct or alternatively an indirect (e.g., interposing additional components, such as lines, valves or the like) terminal. A terminal permits a fluidic connection, which either exists permanently or, given an interposed valve, with the valve open.
The features proposed by the invention make it possible to supply a suspension into the pressure vessel from below through the floor from the prechamber. This advantageously agitates the suspension in the pressure vessel. The suspension directed upwardly from below, i.e., against gravity, enables a uniform distribution of the blasting agent in the liquid phase of the suspension without any additional measures.
In a preferred further development, the device can encompass a vacuum generating device, for example a vacuum injector or a vacuum pump, to which the prechamber is connected by means of at least one line and one valve. Alternatively or additionally, for example, a pump can be switched between the prechamber and return line, or a pump can be connected to the end of the return line facing away from the prechamber, wherein the conveying direction of the pump during operation is directed toward the prechamber. In a second aspect of the invention, these features can also be important independently of the features of the first aspect of the invention, i.e., also be independent of the characterizing features in claim 1, optionally independent of or in combination with the features indicated in the first section of the text. Here as well, the device encompasses at least one pressure vessel for a suspension and at least one prechamber for a suspension. If the return line is connected to a collection receptacle of a blasting cabinet for flowable media, e.g., for a suspension, these variants each enable a transport of the suspension from the preferably collection receptacle of a blasting cabin, which is preferably ventilated, and thus at ambient temperature or at the pressure prevailing inside the blasting cabin. In particular during the blasting operation, the suspension that downwardly deposits, downwardly flows, drips or the like in the interior of the blasting cabin accumulates in such a collection receptacle of a blasting cabin. Instead of a collection receptacle, reference could also be made to a collection terminal. The collection terminal can preferably be formed on the lower side, for example on the floor, of the blasting cabin. It is possible for the collection receptacle to encompass a receiving vessel that is at least partially open toward the top or toward the interior of the blasting cabin (“blasting chamber”). For example, this can be a cup-shaped vessel. For example, the vessel can be situated underneath an opening in the floor of the blasting cabin, which is preferably located at the lowest point of the floor, in particular underneath a grate. Reference could also be made to a collection vessel for a suspension or to an outflow vessel. The receiving vessel could also be tubular in design. Depending on the capacity of the receiving vessel, the collection receptacle can, alternatively or additionally to a receiving vessel, encompass the in particular funnel-shaped floor of the blasting cabin or a region thereof. If a vacuum generating device is used to return a suspension, the suspension can be conveyed from a collection receptacle for flowable media (e.g., a suspension) of a blasting cabin back into the pressure vessel, partially exposed to a negative pressure or partially exposed to an overpressure, and the device according to the invention requires neither pumps nor agitators given a suitable configuration. Since the suspension flows into the pressure vessel through a terminal in the floor, undesirable deposits of blasting agent can be avoided.
In a conventional blasting process, even during conventional wet blasting, blasting agent grains fly through the air from the blasting nozzle up to the workpiece surface, and their effect is based on their impact on the workpiece. Reference could thus be made to a hacking effect. By way of derogation from the above, the device according to the invention allows the solid particles added to the liquid in the suspension to be always or at least predominantly embedded in the liquid phase, so that their effect is not one of hacking, but rather of grinding. Therefore, reference could also be made to a device or method for liquid jet grinding. As relates to the mentioned aspects of the invention, there are numerous other options for preferred further development.
For example, it is possible for the device to encompass a compressed air source. However, this is not necessary. In one expedient embodiment, the device can be or is connected to a compressed air source that is separate from it, e.g., in a manner yet to be described.
In order to return a suspension from a blasting cabin, the return line can be or is connected to the latter, specifically preferably to a collection receptacle for flowable media, e.g., for a suspension, of the blasting cabin.
The valve that can be used to connect the vacuum generating device to the prechamber can preferably be a pneumatically or electrically actuated valve, for example a so-called pinch valve, which can be optionally opened or closed by means of a control valve to be electrically switched.
It is possible for the device to encompass a valve switched between the return line and prechamber, which consists of a check valve whose passage direction is directed toward the prechamber, and whose blocking direction is directed toward the return line. It is preferred that this check valve be connected preferably at its one, preferably upper, terminal directly or indirectly to a prechamber terminal, which discharges into the prechamber through the floor of the prechamber, preferably at its lowest point, and at its other, preferably lower, terminal directly or indirectly to the return line. It is possible for this check valve to be structurally identical to the check valve switched between the prechamber and pressure vessel. If this additional valve is connected to a floor terminal of the prechamber, suspension is conveyed out of the return line from the bottom up, i.e., against the sinking direction of blasting agent in the suspension, and into the prechamber, which then leads to a uniform mixing of the suspension even there.
For example, it is possible that the floor of the pressure vessel have a conical or curved shape, so that the cross section of the pressure vessel perpendicular to a vertical direction tapers downwardly, and/or that the floor of the prechamber have a conical or curved shape, so that the cross section of the prechamber perpendicular to a vertical direction tapers downwardly.
It is possible that the device encompass at least one line and one valve, with which the pressure vessel can be or is connected to a compressed air source separate from the device, or with which the pressure vessel is connected to a compressed air source belonging to the device.
In order to be able to connect the prechamber in a preferred embodiment to a compressed air source that does not comprise part of the device, i.e., is external in relation to the device, it can preferably be connected by means of a line and a valve to a compressed air terminal of the device. In order to be able to connect the pressure vessel in a preferred embodiment to a compressed air source that does not comprise part of the device, i.e., is external in relation to the device, it can preferably be connected by means of a line and a valve to a compressed air terminal of the device. Such a compressed air terminal of the device is intended for compressed air supply in the device or from an external compressed air supply line or, for example, directly from an external compressed air source (e.g., a compressor). Reference could therefore also be made to a compressed air receiving terminal of the device. For example, the compressed air terminal can encompass a pneumatic terminal element, e.g., a pneumatic plug terminal or a pneumatic threaded terminal or the like.
A vent valve is preferably connected to the pressure vessel. A throttle valve or pressure relief valve can here preferably be involved.
It is possible that the check valve switched between the prechamber and pressure vessel and/or the check valve switched between the return line and prechamber encompass at least the following components: A sealing element comprised of an elastically deformable material and a valve sleeve, which forms a seal seat that expands in the passage direction of the check valve, in particular conically, wherein the sealing element forms a sealing edge extending along its periphery, which when the sealing element moves out of an open position in a direction toward the seal seat along the sealing edge, in particular initially only along a circle, comes into contact with the seal seat.
Both check valves can preferably have an identical structural design. Viewed as expedient is an installation position for the check valves, in which the sealing element is located at the top end of the valve, and the passage direction points from the bottom up. If the sealing element is pressed toward the top from the suspension flow, this opens an annular gap through which the suspension can flow, and the check valve is in the open position. If the flow moving toward the top comes to a standstill or an unpressurized state arises, the sealing element that can move relative to the valve sleeve (i.e., the valve body) sinks toward the bottom under its own weight. The sealing element can preferably be fabricated out of an elastic material, such as rubber or polyurethane. To increase the weight, a plate, e.g., made of metal, of a desired thickness can be secured thereto. The lower edge of the sealing element can be sharp-edged at the sealing edge. As the sealing element sinks down, the first contact with the inclined valve seat thus takes place only in the form of a line. As a result, the probability that blasting agent grains will get jammed in the process is minimal. As soon as contact in the unpressurized state has occurred, the suspension located above the sealing element, which can be designed as a valve cone, bears down on the latter from above, which leads to a certain pressure being exerted on the valve seat. A certain additional pressure on the valve seat can arise if a negative pressure exists in the prechamber. The valve element is preferably constituted so as not to be deformed by this yet. The sealing element is preferably designed in such a way that it deforms at its outer edge that contacts the valve seat as the pressure in the suspension located above the valve increases, thereby resulting in a sealing surface, and the sealing element further approaches the seal seat to some extent. The deformation preferably does not take place suddenly; rather, a wedge-shaped gap preferably arises first, which successively closes from the top down, thereby downwardly forcing out liquid and solids. If no pressure gradient from the top down is present any longer, or if a pressure gradient from the bottom up prevails, the valve body once again assumes its original shape. The movability of the sealing element toward the valve seat is preferably limited, e.g., by means of a positive stop, so as to limit the deformation of the sealing element.
It is viewed as expedient that the sealing edge be bordered by two surfaces of the sealing element, which in a cross section oriented transverse to its circumferential direction run inclined to each other, in particular at a right angle to each other, wherein both surfaces of the sealing element each include an acute angle with the surface of the seal seat in a cross section perpendicular to the circumferential direction of the sealing edge. Alternatively or additionally, it is possible that the sealing element be accommodated in a longitudinally displaceable manner in the valve sleeve parallel to its longitudinal central axis, to which end the sealing element is connected in particular with guiding means that leave one or several flow-through openings in the valve cross section, and on their radially outer edge form a longitudinal guide with an inwardly pointing cylindrical surface of the valve sleeve. For example, the longitudinal guide can have a slight radial clearance of approx. 0.5 mm, which ensures an exact guidance. For example, the guiding means can be plate-like guiding lamellae, e.g., which have a thickness of only about 2 mm. The guiding lamellae thereby offer virtually no resistance to the flow, and given the only narrow radial outer edge that interacts with the valve sleeve as a guide, blockage by jammed blasting agents can be precluded. The components of the check valves preferred by the invention can also be removed and replaced in the event of wear.
It is viewed as expedient that the feed line extends through the wall of the pressure vessel and into the latter, wherein the distance between the mouth of the feed line and lowest point of the pressure vessel measures less than half, in particular less than one fourth, in particular less than one eighth, of the height of the interior of the pressure vessel. Alternatively or additionally, it is possible for the check valve switched between the prechamber and pressure vessel to be connected to a riser, in particular a riser pipe, at its lower terminal in the installation position, which extends through the upper side wall of the prechamber into its interior, wherein the distance between the lower opening of the riser and the lowest point of the prechamber measures less than half, in particular less than one fourth, in particular less than one eighth, of the height of the interior of the prechamber.
It is possible for the device to encompass a bypass line and a valve accommodated therein, wherein the one end of the bypass line discharges into the interior of the pressure vessel, in particular at more than half or three fourths of its height, in particular inside of an ascending sifter placed in the pressure vessel, and wherein the other end of the bypass line discharges into the interior of the prechamber, in particular at less than half or one fourth of its height.
In a further development viewed as expedient, the device encompasses two prechambers for a suspension, two return lines and four, preferably structurally identical, check valves, the prechambers are connected in parallel with each other and, interposing a respective check valve between each prechamber and the pressure vessel for the suspension, with the pressure vessel, and a respective return line is connected to a respective prechamber, interposing a respective check valve between the return line and prechamber.
Viewed as an expedient embodiment is that at least the pressure vessel, the prechamber or the prechambers, the check valve(s), the bypass line or bypass lines, the vacuum generating device and/or the pump as a combined assembly be situated in particular in a shared or cubic housing, out of which the feed line and return line extend, the assembly encompasses a compressed air terminal that is or can be connected to a compressed air source that belongs to the assembly or is separate from the assembly, the prechamber is connected to the compressed air terminal by at least one valve, the pressure vessel is connected to the compressed air terminal by at least one valve, and the vacuum generating device and/or pump is connected to the compressed air terminal. This enables an autonomous configuration of the device according to the invention. The blasting chamber need not be integrated into the device according to the invention; rather, the device can also be connected to a separate blasting chamber. The blasting chamber serves to blast treat the workpiece and collect the suspension used in the process in a collection receptacle, so as to return it to the circulation. A separate controller can be used to provide the device according to the invention even when blasting cabins are present, and is thus also suitable for subsequently equipping or converting blasting cabins. If the blasting cabin is not integrated into the device according to the invention, it is also possible, for example, to arrange all components of the device according to the invention (possibly with the exception of certain longitudinal sections of the feed and return lines) in a shared housing, for example in a switch cabinet, which can also contain a controller.
Depending on the different tasks at hand, nozzles with varying size and varying shape (e.g., round, square or flat shapes) can be used on the blasting device in the device according to the invention. As evident from the preceding description, the device according to the invention can be operated continuously. The suspension flows from the pressure vessel to the blasting devices, is collected in the blasting chamber once again, and conveyed back into the pressure vessel again from the bottom up. This continuous flow from the bottom up, i.e., opposite the blasting agent deposition process in the liquid phase, produces a constant and uniform mixing. An especially advantageous mixing of the suspension is achieved by introducing the latter into the pressure vessel through a terminal on the bottom side. Mixing can be improved even further by also returning the suspension into the prechamber from below through its floor. Even after prolonged downtimes, the device according to the invention enables a restarting of a plant, even after standing idle for several weeks. The described bypass line is suitable for this purpose. After a prolonged operational interruption or prolonged service life, the means described in relation thereto can be used to extract clean liquid from the pressure vessel via deposited blasting agent, and press it into the prechamber from below. From there, the liquid or suspension can again be pressed into the pressure vessel from below. Even a compact mass in the pressure vessel can be broken up and again mixed by taking this measure. Emulsion is preferably not stocked in the prechamber for a prolonged period. Instead, it is preferred that, once operation has been interrupted, e.g., with the prechamber only partially filled, a transport process be automatically initiated after a prescribed period of time, e.g., after approx. 2 minutes, in which suspension is pressed into the pressure vessel from the prechamber. Even when turning off a plant, the controller can first effect the evacuation of the prechamber.
By comparison to the check valves preferred by the invention, conventional, commercially available check valves with a flap or ball would also be suitable as a sealing element for the intended purpose, but less suitable for a variety of reasons. Solids could also become deposited on the sealing element and impede its function. Solids between the movable sealing element and valve seat could hamper or prevent the seal. The check valves preferred according to the invention are especially well suited for the circumstances that exist during suspension blasting, especially at a high blasting agent concentration. Apart from the tendency for blasting agent to sink into the liquid phase, turbulences in the mixture flow can also exert uncontrollable forces onto the movable valve part in the case of such suspensions. Therefore, it is preferred that the sealing element be precisely and robustly guided and centered.
The invention also relates to a method for wet blasting one or several workpieces, comprising at least the following procedural steps: Providing a device that exhibits individual or several of the preceding features; providing a blasting cabin if the provided device encompasses no blasting cabin; introducing the blasting device for the suspension, and in particular at least one longitudinal section of the supply line for the suspension into the interior of the blasting cabin; connecting one end of the return line for the suspension to a collection receptacle for flowable media (e.g., flowable suspension) of the blasting cabin, and introducing flowable suspension into the collection receptacle of the blasting cabin, e.g., for startup or, e.g., during operation of the device. Against the backdrop of the prior art described at the outset, the object of the invention is to advantageously further develop a generic method, so that in particular individual or several of the described limitations or disadvantages that previously existed can be diminished or avoided. As a solution, the invention proposes that the invention encompass the following as an additional procedural step:Aspirating suspension through the end of the return line connected to the collection receptacle of the blasting cabin, preferably by generating a vacuum in the prechamber and/or by turning on a pump arranged between the collection receptacle and prechamber, and opening a vent valve connected to the prechamber.
There are various options for preferred further development. It is preferred that the method encompass at least the following procedural step: Ending the aspiration of suspension through the end of the return line connected to the collection receptacle of the blasting cabin; supplying compressed air into the prechamber at least partially filled with suspension, and opening a vent valve connected to the pressure vessel, for example which is a throttle valve or a pressure relief valve. It is preferred that the method encompass at least the following procedural step: Aspirating suspension through the end of the return line connected to the collection receptacle of the blasting cabin, in particular by generating a vacuum in the prechamber and/or turning on a pump arranged between the collection receptacle and prechamber, and opening a vent valve connected to the prechamber; as this takes place, supplying compressed air to generate overpressure in the pressure vessel at least partially filled with suspension; and, given an overpressure in the pressure vessel, at least intermittently opening the valve allocated to the feed line so as to blast suspension onto one or several workpieces.
It is preferred that the method encompass at least the following: Turning off the compressed air supply in the pressure vessel; generating overpressure in the prechamber by supplying compressed air into the prechamber; given an overpressure in the prechamber, at least intermittently opening the valve allocated to the feed line, and blasting suspension onto one or several workpieces, and in particular at least intermittently opening a vent valve connected to the pressure vessel. In a preferred further development, the method encompasses at least the following procedural steps: Generating overpressure in the pressure vessel by supplying compressed air into the pressure vessel and opening the valve allocated to the bypass line, so that at least the liquid phase of the suspension or the suspension is transported from the pressure vessel into the prechamber; once a specific level has been reached in the prechamber, ending, in particular automatically ending, the supply of compressed air into the pressure vessel and generating overpressure in the prechamber by supplying compressed air, and in the process at least intermittently opening a vent valve connected to the pressure vessel and/or opening the valve allocated to the feed line for blasting suspension out of the blasting device. Alternatively or additionally, it is preferred that the suspension be blasted onto one or several workpieces, wherein the weight ratio between the overall solid phase contained in the suspension and the overall liquid phase contained in the suspension is greater than 0.5, in particular greater than 0.9, and in particular has the value 1.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in more detail below with reference to the attached drawings, which show preferred exemplary embodiments. Shown therein on:

FIG. 1 is a schematically simplified view of a device according to the invention in a first preferred exemplary embodiment;

FIG. 2 is a schematically simplified view of a device according to the invention in a second preferred exemplary embodiment, in a preferred procedural step;

FIG. 3 is the device according to FIG. 2, in another preferred procedural step;

FIG. 4 is the device according to FIG. 2, in another preferred procedural step;

FIG. 5 is the device according to FIG. 2, in another preferred procedural step;

FIG. 6 is the device according to FIG. 2, in another preferred procedural step;

FIGS. 7-7 a are sectional views through a check valve, which corresponds to the check valves depicted on FIG. 1-6;

FIG. 8 is a sectional view along sectional plane VIII-VIII on FIG. 7;

FIG. 9 in an exploded view are components of the check valve depicted on FIG. 7;

FIG. 10 is a perspective magnified cutout of cutout X on FIG. 7;

FIG. 10a is a perspective magnified cutout according to FIG. 10, but after the guiding lamellae have been fastened;

FIG. 11 is a sectional view of the check valve comparable to FIG. 7 in an open position;

FIG. 12 is a sectional view comparable to FIG. 11, while transitioning from the open to the closed position;

FIG. 12a is a magnified cutout of detail XII on FIG. 12;

FIG. 13 is a sectional view similar to FIG. 11, 12, but with the check valve in the closed position;

FIG. 14 is a cutout of a device according to the invention in another preferred exemplary embodiment, magnified in comparison to FIGS. 1 to 6, and

FIG. 15 is another preferred exemplary embodiment of a device according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

Introduced with regard to FIG. 1 is a first preferred exemplary embodiment of a device 1 according to the invention. The device serves to blast suspension onto one or several workpieces, wherein the flowable suspension used for workpiece blast treatment is not also shown on FIG. 1. A workpiece 19 and its workpiece receptacle 18 are denoted by dashed lines, since they are not part of the device. The device 1 encompasses a pressure vessel 2 for holding suspension, and a feed line 3 connected to the pressure vessel 2, whose end remote from the pressure vessel 2 is connected to a blasting device 4, for example a blasting gun. Reference number 4′ denotes a nozzle holder, which on its part can be immovably fixed to a preferably adjustable bracket (not also shown). The feed line 3 encompasses a riser pipe 5 and a flexible tube 6, between which a valve 7 is switched (i.e., interposed). The housing of the pressure vessel 2 has a pressure-tight design. The riser pipe 5 extends from the top through a pressure-tight terminal in the cover 8 vertically downward, wherein the distance between the mouth 9 of the feed line 3 and the lowest point of the pressure vessel measures less than one fourth of the height of the interior of the pressure vessel 2. The device 1 encompasses a prechamber 10 for the suspension. The latter has a pressure-tight housing, and is situated underneath the pressure vessel 2. The prechamber 10 is connected to the pressure vessel 2 by a check valve 11 situated between the respective terminals of the pressure vessel 2 and the prechamber 10. The device 1 further encompasses a return line 12, which is connected by means of another check valve 13 to a terminal of the prechamber 10 on the bottom side, interposing the check valve 13. A blasting cabin is marked 14. Just as the pressure vessel 2, prechamber 10 (and other components yet to be mentioned), the blasting cabin is shown in a simplified, cut view, thereby making the interior visible. For example, the interior 15 of the blasting cabin 14 can incorporate an adjustable, e.g., tripod-like fixation means (not also shown on the figures) for the blasting device, along with one or several workpiece receptacles 18 for one or several workpieces 19, which are to be blasted with a suspension. The interior 15 of the blasting cabin 14, which is also referred to as blasting chamber, is enveloped by the blasting cabin 14 on all sides. It is bordered from below by a funnel floor 16, which downwardly tapers. In the example, the bottom side of the funnel floor 16 is connected to a cup-shaped receiving vessel 17′, which together with the funnel floor 16 yields a collection receptacle 17 for the suspension. The suspension hitting the funnel floor 16 can be accommodated by the funnel floor 16 even above the receiving vessel 17′, depending on quantity. The receiving vessel 17′ is connected with the interior 15 so as to be upwardly open at all times. The end 20 of the return line 12 remote from the prechamber 10 is connected to the collection receptacle 17. In the operating state, the suspension circulates through the described components. It is possible for the blasting cabin 14 to be integrated into the device 1 according to the invention, and for it to be fixedly joined with the device 1, for example. Alternatively, it is possible that the blasting cabin 14 not be integrated into the device 1, but rather that the device 1 can optionally be connected as an in particular modular, autonomous unit to one or various blasting cabins 14 as required, or detached therefrom.
During operation of the arrangement shown on FIG. 1, suspension gets out of the pressure vessel 2 through the feed line 3 and blasting device 4 into the interior 15 of the blasting cabin 14, and can there be blasted onto a workpiece 19 accommodated by the workpiece receptacle 18 for grinding the workpiece surface. The suspension is composed of solid, finely dispersed blasting agent and, for example, water, and is here preferably blasted onto the workpiece surface as a liquid jet for grinding the latter. In this regard, the device 1 according to the invention could also be referred to as a liquid jet grinding system, i.e., as a system for grinding by means of a liquid jet. The suspension then accumulates in the collection receptacle 17, and can from there be transported through a valve 13 into the prechamber 10, from where the suspension can again be transported back into the pressure vessel 2 through the valve 11.
The device 1 encompasses a compressed air terminal 22, which is centralized in the example, and serves to supply the device 1 according to the invention with compressed air. To this end, for example, the compressed air terminal can be connected to an external compressed air supply line or, for example, directly to a compressed air source (e.g., to a compressor), which either belongs to the device 1 according to the invention or is not integrated into the latter. The device 1 encompasses a pneumatic line 21, in which a valve 23 is placed, and which is connected to the compressed air terminal 22 by means of a regulator unit 24. The pneumatic line 21 is connected to the pressure vessel 2 on its upper side. The pressure vessel 2 is pressure-tight in design, so that it can be exposed to a pressure freely selectable with the regulator unit 24 with the valve 23 open. For example, the valve 23 can be a two-way valve, which can optionally be opened or closed. During operation, the suspension as a rule does not fully take up the interior of the pressure vessel 2, so that an air cushion forms above the suspension, and dynamically adjusts to a varying level of suspension in the pressure vessel 2, so that the same pressure set with the regulator unit 24 always acts on the suspension during pressurization. The device 1 also encompasses a pneumatic line 25 and a valve 26 placed therein, by means of which the prechamber 10 is connected to the compressed air terminal 22. In the example, the upper side of the prechamber 10 has connected to it a line 27, whose other end is connected to a crossing 28. In the example (i.e., not necessarily), the crossing 28 has four line terminals, which are connected with each other, permanently open. The mutually open connection is symbolically denoted by a point. One end of the line 25 is connected to the crossing 28, and the other end to a line junction 29, from which the line 21 also branches, and which is connected with the compressed air terminal 22 with the regulator unit 24 interposed. The line 21 has placed into it a line junction 30 from which a throttle valve 31 branches. A vent valve 32 is connected to the prechamber 10. The vent valve 32 can be optionally opened or closed by means of a valve 33 connected thereto, which in this regard can also be referred to as a control valve. In the example, the vent valve involves a known, so-called pinch valve. The valve 33 used to control the latter is located in a line 34 that is connected to the vent valve 32, and branches away from a line 35 that is connected to the compressed air terminal 22 with an additional regulator unit 36 interposed. If the valve 33 is opened, compressed air flows into the vent valve 32, thereby closing the latter. By contrast, if the valve 33 is moved into a switch position that allows air to flow out of the pinch valve through a vent terminal of the valve 33, the vent valve 32 is opened. The valve 33 is preferably a three-way valve.
The device 1 encompasses a vacuum generating device 37, which is connected to the prechamber 10 by means of a line 38 and by means of a valve 39. In the example, the vacuum generating device 37 involves a vacuum injector. In the example, the line 38 is connected to a terminal of the crossing 28, and thereby connected to the prechamber. The vacuum generating device 37 functions based on the Venturi principle in the example. The vacuum generating device 37 is connected by means of a line 40 that incorporates a valve 41 and by means of an additional regulator unit 42 with a pressure supply line 43, which extends from the compressed air terminal 22, and from which the regulator units 24 and 36 also branch in the example (also not necessarily). For example, the valve 41 can be a two-way valve, which can optionally be opened or closed. If the valve 41 is opened, compressed air flows through the vacuum generating device 37 into the environment, which creates negative pressure in the line 38. The valve 39 also involves a pinch valve in the example. Connected to the latter for control purposes is a line 44, which in the example branches away from the line 35, and in which is placed a valve 45, a three-way valve in the example. If the valve 45 is opened, compressed air flows into the valve 39 (i.e., into the pinch valve), which is thereby closed. On the other hand, if the valve 45 is moved to a valve position in which air can escape from the valve 39 into the environment through the line 44 and through a vent terminal of the valve 45, the valve 39 is opened, thereby resulting in an open connection between the prechamber 10 and vacuum generating device 37.
The valve 7 also involves a pinch valve in the example. Connected thereto for control purposes is a line 46 with valve 47 placed therein for control purposes. The line 46 is connected with the compressed air terminal 22, with the regulator unit 36 interposed. The valve 47 involves a three-way valve in the example. If the latter is opened, compressed air flows into the valve 7, which is thereby closed. On the other hand, if the valve 47 is moved into a valve position in which air can escape from the valve 7 into the environment through the line 46 and through a terminal of the valve 47 serving as a vent, the valve 7 is opened.
The device 1 encompasses a bypass line 48 for a suspension and a valve 49 situated therein. The one end 50 of the bypass line 58 discharges into the interior of the pressure vessel 2. In the example, the pressure vessel 2 has an ascending sifter 51 placed into it from above, into which the bypass line 48 enters from above. The bypass line 48 leads pressure-tight through the wall of the prechamber, and its corresponding end 52 discharges into the interior of the prechamber 10. In the example, the valve 49 also involves a pinch valve. For control purposes, the latter is also connected to a line 53, into which is placed a valve 54, a three-way valve in the example, and which in the example is connected with the compressed air terminal 22, with the regulator unit 36 interposed. If the valve 54 is opened, compressed air flows into the valve 49, so that the latter is closed. On the other hand, if the valve 54 is switched to a valve position in which air can flow out of the valve 49 and into the environment through the line 53 and through a terminal of the valve 54 serving as a vent, the valve 49 is opened.
In the example, the regulator units 24, 36 and 42 each involve a pressure regulating valve. For example, a proportional valve can be involved. An air pressure can be set on the regulator unit 24 and used to pressurize the interior of the pressure vessel 2 and/or the interior of the prechamber 10, depending on the position of the valves 23 and 26. As will be explained below, the regulator unit 24 can be used to set or regulate the jet pressure with which the suspension is pressed out of the blasting device as a jet, i.e., blasted. For example, the valves 23, 26 involve two-way valves. As described, the valves 33, 45, 47 and 54 serve to pre-control the valves 32, 39, 7 and 49, which each involve a pinch valve. The pressure of the compressed air with which the pinch valves are actuated can be set or regulated by means of the regulator unit 36. The valve 41 can once again involve a two-way valve, for example. The regulator unit 42 can be used to set or regulate the pressure of the compressed air flowing through the vacuum generating device 37 with the valve 41 open.
It goes without saying that the described terminals of the pressure vessel 2 and prechamber 10 are outwardly pressure-tight in design on their respective housing. Secured to the pressure vessel 2 is a level sensor 55, so as to detect when the fill level of liquid or suspension has dropped below a specific level. Secured to the prechamber 10 in its lower half is a level sensor 56, so as to detect when the suspension or liquid has dropped below a specific, minimal level. In addition, the prechamber 10 has secured to it an upper level sensor 57, so as to detect when the suspension or liquid has exceeded a specific upper level. In order to automate the device 1, the valves 23, 26, 31, 33, 41, 45, 47 and 54 in the example involve electric valves, i.e., valves that can be electrically switched between the different valve positions. These valves and the level sensors 55-57 are connected with a controller of the device 1 (in a manner not shown on the figures). Marked 58 is a sensor connected to the receptacle 17, which detects the presence of the suspension, and can also be connected to the controller.
The valve 11′ between the pressure vessel 2 and prechamber 10 involves a check valve 11, which is only schematically depicted on FIG. 1, and will be described in greater detail with reference to FIG. 7-13, which have been magnified by comparison. As illustrated by the cutouts in the sectional view on FIG. 7, the check valve 11 in the installation position shown is connected at its upper terminal 59 to a pressure vessel terminal 60, which discharges into the pressure vessel 2 through the floor 61 of the pressure vessel 2 at the lowest point of the floor 61. At its other lower terminal 62 in the depicted installation position, the check valve 11 is connected to the prechamber 10 by means of a riser pipe 63, only the upper section of which is shown on FIG. 7. The riser pipe 63 is guided pressure-tight through the closed upper side of the prechamber 10 into its interior, wherein the lower, open end 64 of the riser pipe 63 is located only a slight distance over the lowest point of the prechamber 10. The passage direction 65 of the check valve 11 is denoted with an arrow on FIG. 7. The latter is directed from the prechamber 10 to the pressure vessel 2, and the locking direction of the check valve 11 is directed oppositely thereto from the pressure vessel 2 to the prechamber 10. As shown in further detail on FIG. 7-13, the check valve 11 encompasses a sealing element 66, which is conical in the example, and a valve sleeve 67, which preferably consists of a material that is less easily deformable by comparison to the sealing element 66. The valve sleeve 67 is placed in a valve housing 68. The valve sleeve 67 envelops a passage opening for a suspension to flow through. Its inwardly facing surface runs cylindrically in a longitudinal section 69. In a longitudinal section that adjoins the latter in the passage direction 65 and is situated at the top in the installation position, the valve sleeve 67 forms a seal seat 70 that conically expands in the passage direction 65. The sealing element 66 forms a sealing edge 71 that extends along its circumference.
FIG. 11 shows the check valve 11 in an open position, in which the sealing element 71 is spaced apart from the seal seat 70, so that the suspension 72 denoted by arrows can flow through the check valve 11 in the passage direction 65. If the sealing element 66 is moved in the direction toward the seal seat 70 proceeding from this open position, initially only the sealing edge 71 of the sealing element 66 comes into contact with the seal seat 70 along a circle 73, as illustrated on FIG. 12. The sealing edge 71 is bordered by two surfaces 74, 75 of the sealing element 66, which in a cross section oriented transversely to its circumferential direction (see FIG. 12a ) run at a right angle to each other, and which each include a respectively acute angle α or β with the surface of the seal seat 70 in this cross section. As also depicted on FIG. 12, when moved from the open position toward the seal seat 70, the sealing edge 71 of the sealing element 66 hits an annular zone spaced apart from the tapered end of the seal seat 70. Proceeding from the state shown on FIG. 12, if the sealing element 66 is exposed to a pressure P opposite the passage direction 65, the latter triggers an elastic deformation of the sealing element 66 in the area of its sealing edge 71, as a result of which the sealing element 66 then abuts flat against the seal seat 70 along its circumference, as illustrated on FIG. 13. The check valve 11 is closed in this position. If the sealing element 66 is subsequently removed from the valve sleeve again in the passage direction 65, its outer circumference resiliently deforms back into the shape depicted on FIG. 11.
As relates to the selected exemplary embodiment of the check valve, for example, FIGS. 7 and 9 show in further detail that the sealing element 66 exhibits a passage opening 76, into which a sleeve 7 is adhesively bonded or pressed, for example. The surface 78 of the sealing element pointing opposite the passage direction 65 runs flatly and transversely to a geometric longitudinal central axis 79 of the check valve 11. A fastening plate 80 abuts against the lower surface 78, and has a nut 82 aligned flush with its central borehole 81, which is secured to the fastening plate 80, for example. Four passage openings 83 each spaced apart by 90° relative to each other in the circumferential direction extend through the fastening plate 80 near the edge. The latter are used for fastening two respective plate-shaped guiding lamellae 84, 85. The guiding lamellae 84, 85 have edge contours that are essentially identical to each other. Proceeding from two lateral projections 86, the radially outer edges 87 diminished a bit in their lateral spacing extend parallel to each other, and transition into a respective upper side 88, proceeding from which two respective tongues 89 extend. The one guiding lamella 84 has a central slot proceeding from the side with the projections 86, and the other guiding lamella 85 is slotted proceeding from the opposing side, so that the two guiding lamellae 84, 85 can be plugged together in the mutually orthogonal position depicted on FIG. 9, so that their edges align flush with each other during a rotation around the longitudinal central axis 79 as viewed in projection. In order to secure the assembled guiding lamellae 84, 85 to the fastening plate, a respective pair of the tongues 89 can be inserted through a respective passage opening 83 (see FIG. 10), and therein be outwardly bent to achieve a positive fit (see FIG. 10a ). The fastening plate 80 can then be secured to the sealing element 66 by means of a screw 90, which is inserted through the sleeve 77 and screwed by the nut 82. The guiding lamellae 84 comprise guiding means, which, e.g., as illustrated on FIG. 8, are left in the valve cross section of several flow-through openings 91, and whose radially outer edge 87 forms a longitudinal guide with the inwardly pointing cylindrical surface of the valve sleeve 67 in its longitudinal section 69. The latter allows the sealing element 66 and guiding lamellae 84 to move relative to the valve sleeve 67, concentrically and parallel to the longitudinal axis 79. The relative movement is limited in the passage direction 65 if the radial projections 86 run against an annular surface of the valve sleeve 67.
In the selected example, an installation position is selected for the check valve 11 in which the longitudinal central axis 79 runs vertically, and the sealing element 66 points upwardly. During operation of the device 1, the sealing element 66 shifts automatically relative to the immovably mounted valve sleeve 67 as a function of the pressures and forces acting on the sealing element 66. Therefore, the valve need not be separately actuated. If the pressure in the prechamber 10 is greater than the pressure in the pressure vessel 2, the pressure difference produces a resultant compressive force that acts on the sealing element 66 in the passage direction 65. If the latter is greater than the opposing weight of the movable valve parts, the sealing element 66 with the valve components fastened thereto is upwardly displaced relative to the valve sleeve 67 into the open position shown on FIG. 11, in which further movement is prevented by the projections 86. As a result of the pressure difference, the suspension denoted with arrows on FIG. 11 then flows through an annular passage that envelops the sealing element 66. If the pressure in the prechamber 10 corresponds to the pressure in the pressure vessel 2, the sealing element 66 with the components connected thereto sinks downwardly owing to gravitational force, wherein it only linearly abuts against the seal seat 70 in the manner shown on FIG. 12 given a deformability of the sealing element 66 that has been suitably adjusted to the weight of the movable valve parts. Any blasting agent that has been deposited onto the seal seat 70 is expelled from the continuous sealing edge 71 of the sealing element 66 as the latter sinks downward, and the blasting agent located underneath the sealing element 66 sinks downward along the seal seat 70. If the pressure in the pressure vessel 2 is greater than the pressure in the prechamber 10, the pressure and weight together act downward. Depending on the level of the pressure difference, the sealing element 66 can deform at its radially outer edge in the manner shown on FIG. 13, so that a tight abutment of the sealing element 66 comes about along the circumference, with the latter extending over a certain width in a cross section lying transverse to the circumferential direction. In the example on FIG. 13, a planar, conical contact zone or sealing zone results, wherein the check valve 11 is in the closed position.
In the exemplary embodiment shown on FIG. 1 (and also in the examples according to FIGS. 2, 14 and 15), the check valves 11 and 13 are structurally identical. The check valve 13 (see FIG. 7a ) is also situated in such a way that its longitudinal central axis 96 runs vertically. The upper terminal 93 of the check valve 13 is connected to a prechamber terminal 94, which discharges into the prechamber 10 through the floor 95 of the prechamber 10 at its lowest point. At its lower terminal 97, the check valve 13 is connected to the return line 12. A comparison of FIGS. 7 and 7 a reveals that the two check valves 11, 13 are structurally identical. For simplification purposes, the displaceable valve components are labeled with the same reference numbers for both check valves 11, 13. The installation position is also selected in such a way for the check valve 13 that the sealing element 66 is at the upper valve end, i.e., that it abuts downwardly against the seal seat 70 in the closed position. As a consequence, the passage direction 98 (as with the check valve 11) is upwardly directed for the check valve 13 as well.
In the example on FIG. 1, the floor 61 of the pressure vessel 2 and the floor 95 of the prechamber 10 are made out of sheet metal and conically shaped, so that the cross section of the pressure vessel 2 or prechamber 10 tapers downwardly. The check valve 11 is outwardly sealed pressure-tight from below at the lowest and narrowest cross section of the floor 61, as is the check valve 13 from below at the lowest and narrowest cross section of the floor 95. As shown on FIGS. 7 and 7 a, the outer diameter of the annular flow cross section formed in the check valve corresponds to the outer diameter of the respective funnel-shaped floor present at the terminal in the example with the valve in the open position.
In the example on FIG. 1, the device encompasses a cyclone separator 99. The latter is used to separate out of the suspension fines that can be separated out by means of the ascending sifter. Such fines can arise during operation over time due to a certain wear of the blasting agent, and potentially also as erosion from machined workpieces, and become concentrated in the suspension over time. Such fines can be separated out in the ascending sifter 51 in that they rise higher than the blasting agent during a very slow upward flow. A smaller partial flow of liquid can be diverted at the top of the ascending sifter 51, and fed to the cyclone separator 99 through a line 100. Purified liquid can be passed through another line 101 into the blasting cabin 14, and thus fed back to the circulation. The ascending sifter 51 is a pipe that is open. The overpressure prevailing in the pressure vessel 2 during operation causes the liquid in the ascending sifter 51 to rise according to the quantity flowing off above, on the one hand through the terminal 102 for rinsing the workpieces, and on the other hand diverted into the cyclone separator 99 through the terminal 103. If necessary, liquid can be tapped at the terminal 102 for rinsing already blasted workpieces. The liquid tapped there has risen through the entire height of the ascending sifter 51, and thus contains practically no blasting agent or suspended particles. The liquid diverted to the cyclone separator 99 is removed through the riser pipe 104, which is also integrated into the bypass line 48, at roughly half the height of the ascending water column, i.e., in a region where hardly any blasting agent is present, but suspended particles still are. The quantity of liquid diverted to the cyclone separator 99 is preferably slight, but can measure approx. 0.5 to 3 liters per minute, depending on the type of plant. The diverted quantity of liquid determines the rate of ascension in the ascending sifter 51; therefore, it should preferably be possible to exactly determine it. A throttle plate is built into the screw connection at the upper outlet of the cyclone separator 99, i.e., in its pure water area. Throttle plates with varying boreholes enable an exact and permanent determination of flow rate. The cyclone separator 99 is exposed to the same pressure as the pressure vessel 2. This also facilitates the draining of sludge with a hand valve 106 provided for this purpose. An exchangeable nozzle 107 is provided at the inlet of the liquid into the cyclone separator 99. The liquid flowing into the cyclone separator 99 must have a certain speed so as to impart rotation to the water column. The hand valve 108 can be used to operatively detach the cyclone separator 99 from the remaining device 1.
FIGS. 2 to 6 show a device 1 according to the invention in a second preferred exemplary embodiment, and illustrate a preferred exemplary embodiment of the method according to the invention. The device depicted on FIG. 2-6 corresponds with the exemplary embodiment shown on FIG. 1, except for the cyclone separator 99, which is not present in the example on FIGS. 2 to 6. A feed line 3 with a valve 7 leads from the pressure vessel 2 to a nozzle holder 4′ and a blasting device 4 (e.g., a blasting gun). As in the other exemplary embodiments, several feed lines 3, e.g., each with one valve and each with one blasting device, could branch from the pressure vessel 2.
Suspension 72 present in the pressure vessel 2 is pressed out of the blasting device 4 with the pressure prevailing in the pressure vessel 2. The feed line 3 encompasses the hose 6 and riser pipe 5 connected thereto. The riser pipe 5 passes from above through a wall of the pressure vessel 2, and extends vertically downward therein. Its downwardly open mouth 9 is located in a lower region of the interior of the pressure vessel 2, in the area of the funnel-shaped floor 61 in the example. During operation, the level probe 55 can be used to ensure that the downwardly open mouth 9 of the feed line is always immersed in the suspension 72, specifically in a container region in which a through mixing of the suspension is always ensured during operation. As illustrated by the following description, the structural design of the device 1 allows the operating process in which suspension is blasted onto one or more workpieces 19 to run independently of the processes in the pressure vessel 2, e.g., independently of the respective level of the suspension in the pressure vessel 2. The blasting process can thus run permanently, i.e., if needed over a prolonged period without interruption, or also in intervals. In order to ensure a continuous operation, the suspension in the blasting cabin 14 that exits the blasting device 4 (e.g., a blasting gun) must be returned to the pressure vessel 2 again. To this end, the prechamber 10 is provided underneath the pressure vessel 2, and connected to the return line 12 hooked up to the collection receptacle. A respective one of the check valves 11 or 13 already described with reference to FIG. 7, 7 a with a passage direction pointing from the bottom up is arranged or interposed between the pressure vessel 2 and prechamber 10 (on the one hand) and between the prechamber 10 and return line 12 (on the other). The check valves 11, 13 selected in the exemplary embodiment are specially constructed to prevent a liquid that exhibits a large percentage of abrasive solids (in particular blasting agent) from flowing back. In a very cost-effective manner and without requiring special control measures, these check valves ensure that a flowing direction can only be from the bottom up. The suspension diverted by the feed line 3 from the pressure vessel 2 can be replaced in batches from below out of the prechamber 10. This influx from below, i.e., opposite the sinking direction of heavy particles in the suspension, enables the achievement of a very uniform and constant mixing of liquid and the solids therein. This can eliminate the need for additional measures, such as agitators.
Alternatively, it would be possible to install (e.g., pneumatically or electrically) controllable valves, e.g., pinch valves, instead of the check valves 11, 13. Since activation is required for opening and closing such valves as needed, this would necessitate a greater outlay. In addition, pneumatic pinch valves would open given a compressed air supply failure, and allow the suspension located above to drain uncontrollably.
FIG. 2 shows a preferred first procedural step of a method according to the invention. This step serves to fill the device 1 with suspension 72, and is thus potentially no longer necessary after a preceding operation of the device 1. The suspension 72 was poured onto the funnel floor 16 of the blasting cabin, and accumulates in the collection receptacle 17 for the suspension, which in the example is comprised of a cup-shaped receiving vessel 17′ and a funnel floor 16 that discharges therein from above.
FIGS. 2 to 6 indicate symbolically different switching and operating states for the valves 23, 26, 31, 33, 41, 45, 47 and 54. If one of the valves 23, 26, 31, 41 is marked “X”, it means that the valve is closed at this point in time, i.e., if not marked “X”, the valve is open. For the valves 33, 45, 47 and 54, an “X” means that the valve in this state does not allow through any compressed air supplied by the compressed air terminal 22 via the regulator unit 36, but air that serves to control the respectively connected pinch valve can flow back from the pinch valve and escape into the environment through the respective valve 33, 45, 46 or 54. If a valve 33, 45, 47 or 54 is not marked “X”, the respective valve is open at this point in time, so that inflowing compressed air from the compressed air terminal 22 is allowed through to the connected pinch valve. No such designation is made for the pinch valves 7, 32, 39 and 49, which can be pneumatically closed or opened, since they are always closed when the pneumatic line controlling them is exposed to compressed air, and on the other hand opened when the pneumatic line controlling them is vented. Therefore, the valve position results from the designated position of their control valve. During the procedural step 2 shown on FIG. 2, the vacuum generating device 37 is activated by means of the open valve 41. The valve 39 is opened, and the valves 26 and 32 are closed, so that the vacuum generating device 37 inside of the prechamber 10 generates a vacuum, i.e., a pressure lying under the ambient pressure. As a result, the pressure in the prechamber 10 is lower than in the pressure vessel 2, so that the check valve 11 is automatically closed. The pressure inside of the prechamber 10 is also lower than the pressure in the collection receptacle 17, so that the check valve 13 automatically opens. The vacuum causes suspension 72 to be siphoned upwardly into the prechamber 10 from the collection receptacle 17 through the return line 12 and through the check valve 13. Because the suspension enters into the prechamber 10 from below, i.e., against the force of gravity, the suspension 72 is continuously mixed in the prechamber 10. A negative pressure of approx. 100 to 200 cm water column may be sufficient to aspirate the suspension through the return line 12. The latter can be generated in various ways. In the vacuum generating device 37 schematically depicted on FIG. 3, the example involves a pneumatic injector. However, this task can instead also be handled by a vacuum pump or, for example, a blower. Since a pulsed application is involved, and the negative pressure is slight, a pneumatically, hydraulically or mechanically activated bellows would also be possible, for example, as would a pneumatically, hydraulically or mechanically activated piston pump. If the level in the prechamber 10 reaches the level probe 57, the described aspiration process is ended, and the negative pressure in the prechamber 10 can be automatically switched over to overpressure.
FIG. 3 shows a preferred procedural step with which the suspension can be upwardly pumped out of the prechamber 10 into the pressure vessel 2. To this end, the aspiration of suspension from the collection receptacle 17 into the prechamber 10 was first ended. While the valves 32 and 39 are closed, compressed air is guided through the open valve 26 into the prechamber 10 partially filled with suspension 72, so as to generate overpressure inside of the prechamber 10, i.e., pressure lying over the ambient pressure, which bears down on the suspension 72. The vent valve 31 (a throttle valve in the example) connected to the pressure vessel 2 is here open. Since the pressure in the prechamber 10 thus exceeds the pressure in the pressure vessel, the check valve 11 opens automatically. As a result, suspension 72 is upwardly pumped out of the prechamber 10 into the pressure vessel 2 from below through the riser pipe 63 and through the check valve 11. Since the suspension 72 enters the pressure vessel 2 from the bottom up, this causes the suspension to be continuously mixed in the pressure vessel 2. While upwardly pumping the suspension into the pressure vessel 2, its vent valve 31 is open, so that air can escape from the latter. If the level of the suspension 72 in the prechamber 10 has reached the level probe 56 as the result of this “pumping process”, the valve 26 and vent valve 31 close, and the valve 23 simultaneously opens. In a preferred embodiment, the vent valve 32 also opens simultaneously for one to two seconds. The extremely fast pressure drop in the prechamber 10 prompts the check valve 11 to close automatically. Cooling gives rise to condensate. Air diverted out of the prechamber 10 can be diverted into the blasting chamber, i.e., into the interior of the blasting cabin 14. After a prescribed period of time, the vent valve 32 can again close, and a switch can again be made to the suction operation depicted on FIG. 2, for example, provided the sensor 58 relays a message that suspension 72 is present in the collection receptacle 17. The direction of the arrows situated over the surface of the suspension 72 schematically denotes whether the level is rising or falling (as also the case for the remaining figures).
FIG. 4 shows another preferred step during the implementation of a method according to the invention. During this procedural step, suspension 72 is blasted onto a workpiece 19 from the blasting device 4 (e.g., blasting nozzle), so that the fill level of the pressure vessel 2 drops, while suspension 72 is simultaneously upwardly aspirated out of the collection receptacle 17 into the prechamber 10. In the example, upward aspiration takes place as in the procedural step described for FIG. 2. In order to press suspension 72 out of the pressure vessel 2 through the blasting device 4 during this time, an overpressure is generated in the pressure vessel 2 by introducing compressed air through the open valve 23. As a consequence, the pressure in the pressure vessel 2 is greater than in the prechamber 10, so that the check valve 11 is automatically closed. On the other hand, the pressure in the prechamber 10 is also less than the pressure in the collection receptacle 17, so that the check valve 13 automatically opens. The valve 7 is opened for the desired duration so as to press suspension 72 out of the blasting device 4, i.e., for the blasting process.
FIG. 5 shows another preferred step during implementation of the method according to the invention. It is here possible to simultaneously press the suspension out of the blasting device 4 and transport the suspension 72 from the prechamber 10 into the pressure vessel 2. To this end, the compressed air supply into the pressure vessel 2 was ended by closing the valve 23, while instead opening the valve 26, so that compressed air is now pressed into the prechamber at the same pressure, and an overpressure is generated therein. This causes the check valve 13 to close automatically. Since the vent valve 31 of the pressure vessel 2 is opened, the pressure in the prechamber 10 rises in excess of the pressure in the pressure vessel 2, so that the check valve 11 automatically opens. As a consequence, the overpressure generated in the prechamber 10 upwardly presses suspension 72 out of the prechamber 10 into the pressure vessel 2. The vent valve 31, which in the example is a throttle valve, is selected in such a way that a pressure higher by comparison to the ambient pressure is also retained in the pressure vessel 2. This pressure can be somewhat lower than or equal to the pressure in the prechamber 10. The vent valve 31 could also involve a pressure relief valve, for example. The latter could limit the pressure in the pressure vessel 2 to 3 bar, for example. The pressure generated by supplying compressed air into the prechamber 10 could measure 3 bar or somewhat more than 3 bar, for example, wherein it is understood that pressures deviating from this numerical example would also be possible. Depending on how large the pressure drop from the prechamber 10 to the pressure vessel, suspension is upwardly pumped from the prechamber 10 into the pressure vessel 2. In order to allow this suspension volume flow to exceed the suspension volume flow dispensed by the blasting device 4, in particular averaged over time, the vent valve 31 of the pressure vessel can be opened. During the procedural step depicted on FIG. 5, the compressed air routed into the prechamber 10 thus carries out a dual function. On the one hand, it causes suspension 72 to be upwardly pumped into the pressure chamber 2, and also causes suspension to be pressed out of the blasting gun.
FIG. 6 shows another preferred step in implementing the method according to the invention. This procedural step can be used in particular after the operation of the device 1 was interrupted for a certain period of time (e.g., for several minutes). Given such an interruption, the heavy, solid particles in the suspension 72 begin to sink, thereby initiating a segregation. In order to sustain the operating mixture, the device 1 can be switched to the circulation mode shown on FIG. 6, in particular automatically, given an operational interruption of a prescribed duration. Also possible is to activate the circulation mode in adjustable intervals, e.g., lasting 2 minutes or longer, depending on the used blasting agent. Opening the valve 49 diverts liquid with only a few solids out of the upper region of the pressure vessel 2 or out of the ascending sifter 51 into the prechamber 10 through the bypass line 48. If the liquid level in the prechamber 10 reaches its level probe 57, a switch can again be made to another operating state, e.g., to the operating state described for FIG. 3. Even after a prolonged downtime of the device 1, e.g., for several weeks, thorough mixing in the suspension 72 can again be smoothly achieved by repeatedly, e.g., manually, switching the described circulation process.
The blasting process results in a certain atomization of the liquid. In order to keep the mixing ratio in a tolerable range and not disrupt the operation of the device 1, liquid can periodically be replenished. The level probe 55 of the pressure vessel 2 monitors a minimum level. Depending on the type of plant, a warning is issued at too low a level, or a valve can be directly switched to automatically compensate for the lost liquid until at least the minimum level has again been reached.
Needless to say, several feed lines 3 can be connected to the pressure vessel 2 as needed, to which one or several respective blasting devices 4 can be connected.
In the example, the device encompasses a controller that is connected with the described valves used for controlling the pinch valves and with the level probes, which is adapted to set the operating states described for FIG. 2-6 (or only selected operating states from among the latter, as needed) in an automatic sequence on the device.
FIG. 14 shows a cutout from a device 1 according to the invention in another preferred exemplary embodiment. This device 1 once again also encompasses a pressure vessel 2, but, as opposed to the examples on FIGS. 1 to 7, two prechambers 10, two return lines 12 and thus a total of four check valves 11, 13, which in the example are all structurally identical in design, and correspond to the valves depicted on FIG. 7, 7 a. The two prechambers 10 are connected to the pressure vessel 22 in parallel with each other, each with a respective check valve 11 interposed. The floor 61 of the pressure vessel 2 is conical in shape, and forms a downwardly tapering funnel. Provided in the lower portion of the inclined funnel wall are two passage openings, to which one of the check valves 11 is connected on its upper side by means of a curved pipe segment 109, wherein the passage direction 65 points up. The respective floor 95 of the prechambers 10 is also conical in shape, and forms a downwardly tapering funnel. A check valve 13 is connected to the lowermost, and hence narrowest, cross section of the floor 95 on its upper side, so that its passage direction 98 points up. The lower side of each check valve 13 is connected to a respective return line 12, which at its respective other end can be connected to a collection receptacle of a blasting cabin. The fact that two prechambers 10 are present makes the plant a better performing one by comparison to the above exemplary embodiments. The advantage to the embodiment is that larger quantities of suspension can be passed through the system, so that several or larger blasting nozzles can thus be used. The prechambers 10 alternatingly enhance each other in their function. For example, during operation, this makes it possible, while aspirating suspension from the interior 15 of the blasting cabin 14 in the one prechamber 10, to convey suspension into the pressure vessel 2 from the other prechamber 10. The two prechambers 10 can alternate their function with each other in specific time intervals. For example, the switch can take place with only brief interruptions (e.g., of about 2 seconds). A permanent flow of suspension 72 can be achieved, both from the blasting cabin 14 into the prechambers 10, and from the prechambers 10 into the pressure vessel 2. The fact that there is a practically continuous influx of suspension from below into the pressure vessel 2, which corresponds to the quantity flowing away through the blasting device 4 or blasting nozzles, ensures a lasting, optimal mixing of the liquid and blasting agent in the suspension. In the example, a hand valve 110 is provided to remove samples of the liquid-blasting agent mixture. When opening the hand valve 110, the overpressure in the pressure vessel 2 presses suspension up through a riser pipe 111. The riser pipe 111 reaches down into the region of the pressure vessel 2, where the suspension is drained through the mouth 9 of the riser pipe 5 from the feed line 3 to the blasting device 4. This ensures that the samples taken correspond to the mixture exiting the blasting device 4. It is preferred that all lines through which suspension flows be open toward the bottom. As a consequence, given a prolonged shutdown of the plant (e.g., for weeks), solids can downwardly sink out of the lines, and no blockages can arise.
FIG. 15 shows a device 1 according to the invention in yet another preferred exemplary embodiment. The device is designed independently of a blasting cabin, but can be connected to a blasting cabin for operation (e.g., to a blasting cabin of the type depicted on FIGS. 1 to 7). The device 1 encompasses a housing 112, which in the example can (i.e., does not have to) travel on wheels 113. Outwardly exiting the housing are a pneumatic line 114 for connecting the compressed air terminal 22 with a compressed air source (not also shown on FIG. 15), a portion of the feed line 3 with a blasting device 4 (e.g., blasting nozzle) potentially connected thereto, and a longitudinal section of the return line 12. The feed line 3 and return line 12 are used for connection to a blasting cabin. All remaining components of the device 1 are located inside of the housing 112. In this regard, reference can be made to an autonomous or modular construction of the device 1.
It goes without saying that a wide range of variations from the described exemplary embodiments is possible for implementing the invention. For example, individual or several of the described components can be omitted (for example, the cyclone separator), or replaced by other, in particular identically or similarly acting components.
The above statements serve to explain the inventions encompassed by the application as a whole, which further develop the prior art least by way of the following feature combinations, each taken separately, specifically:
A device 1, characterized in that a valve 11′ between the prechamber 10 and pressure vessel 2 is a check valve 11, that its one, in particular upper, terminal 59 is connected to a pressure vessel terminal 60 that discharges into the pressure vessel 2 through the floor 61 of the pressure vessel 2, in particular at its lowest point, and that its other, in particular lower, terminal 62 is connected to the prechamber 10, wherein the passage direction 65 of the check valve 11 is directed toward the pressure vessel 2.
A device 1, characterized in that the device 1 encompasses a vacuum generating device 37, in particular a vacuum injector or a vacuum pump, to which the prechamber 10 is connected by means of at least one line 38 and one valve 39, and/or that a pump is switched between the prechamber 10 and return line 12, or a pump is connected to the end of the return line 12 facing away from the prechamber 10, wherein the conveying direction of the pump during operation is directed toward the prechamber 10.
A device 1, characterized in that the device 1 encompasses a valve 13′ switched between the return line 12 and prechamber 10, which involves a check valve 13, wherein this check valve 13 is connected at its one, especially upper, terminal 93 to a prechamber terminal 94, which discharges into the prechamber 10 through the floor 95 of the prechamber 10, in particular at its lowest point, and at its other, preferably lower, terminal 97 to the return line 12, and wherein the passage direction (98) of this check valve 13 is directed toward the prechamber 10, and wherein it is provided in particular that this check valve 13 be structurally identical to the check valve (11) switched between the prechamber 10 and pressure vessel 2.
A device 1, characterized in that the floor 61 of the pressure vessel 2 has a conical or curved shape, so that the cross section of the pressure vessel 2 perpendicular to a vertical direction tapers downwardly, and/or that the floor 95 of the prechamber 10 has a conical or curved shape, so that the cross section of the prechamber 10 perpendicular to a vertical direction tapers downwardly.
A device 1, characterized in that the device 1 encompasses at least one line 21 and one valve 23, with which the pressure vessel 2 can be connected to a compressed air source separate from the device 1, or with which the pressure vessel (2) is connected to a compressed air source belonging to the device 1.
A device 1, characterized in that the check valve 11 switched between the prechamber 10 and pressure vessel 2 and/or the check valve 13 switched between the return line 12 and prechamber 10 encompasses at least the following: A sealing element 66 comprised of an elastically deformable material and a valve sleeve 67, which forms a seal seat 70 that expands in the passage direction 65 of the check valve 11, in particular conically, wherein the sealing element 66 forms a sealing edge 71 extending along its periphery, which when the sealing element 66 moves out of an open position in a direction toward the seal seat 70 along the sealing edge 71, in particular initially only along a circle 73, comes into contact with the seal seat 70.
A device 1, characterized in that the sealing edge 71 is bordered by two surfaces 74, 75 of the sealing element 66, which in a cross section oriented transverse to its circumferential direction run inclined to each other, in particular at a right angle to each other, wherein both surfaces of the sealing element 66 each include an acute angle α, β with the surface of the seal seat 70 in a cross section perpendicular to the circumferential direction of the sealing edge 71.
A device 1, characterized in that the sealing element 66 is accommodated in a longitudinally displaceable manner in the valve sleeve 67 parallel to its longitudinal central axis 79, to which end the sealing element 66 is connected in particular with guiding means that leave one or several flow-through openings 91, and on their radially outer edge 87 form a longitudinal guide with an inwardly pointing cylindrical surface of the valve sleeve 67.
A device 1, characterized in that, when moved from an open position toward the seal seat 70, the sealing edge 71 of the sealing element 66 hits an annular zone of the seal seat 70 spaced apart from the tapered end of the seal seat 70, and that pressurizing the sealing element 66 against the seat seal 70 triggers an elastic deformation of the sealing element 66, as a result of which the sealing element 66 abuts flat against the seal seat 70 along its circumference.
A device 1, characterized in that the feed line 3 extends through the wall of the pressure vessel 2 into its interior, wherein the distance between the mouth 9 of the feed line 3 and lowest point of the pressure vessel 2 measures less than half, in particular less than one fourth, in particular less than one eighth, of the height of the interior of the pressure vessel 2.
A device 1, characterized in that the check valve 11 switched between the prechamber 10 and pressure vessel 2 is connected to a riser, in particular a riser pipe 63, at its lower terminal in the installation position, which extends through the upper side wall of the prechamber 10 into its interior, wherein the distance between the lower opening 64 of the riser and the lowest point of the prechamber 10 measures less than half, in particular less than one fourth, in particular less than one eighth, of the height of the interior of the prechamber 10.
A device 1, characterized in that the device 1 encompasses a bypass line 48 and a valve 49 accommodated therein, wherein the one end 50 of the bypass line 48 discharges into the interior of the pressure vessel 2, in particular at more than half or three fourths of its height, in particular inside of an ascending sifter 51 placed in the pressure vessel 2, and wherein the other end 52 of the bypass line 48 discharges into the interior of the prechamber 10, in particular at less than half or one fourth of its height.
A device 1, characterized in that the device 1 encompasses two prechambers 10, two return lines 12 and four, in particular structurally identical, check valves 11, 13, that the prechambers 10 are connected in parallel with each other and, interposing a respective check valve 11, with the pressure vessel 2, and that a respective return line 12 is connected to a respective prechamber 10, interposing a respective check valve 13.
A device 1, characterized in that at least the pressure vessel 2, the prechamber 10 or the prechambers 10, the check valve(s) 11, 13, the bypass line 48 or bypass lines 48, the vacuum generating device 37 and/or the pump as a combined assembly are situated in particular in a shared or cubic housing 112, out of which the feed line 3 and return line 12 extend, that the assembly encompasses a compressed air terminal 22 that is or can be connected to a compressed air source that belongs to the assembly or is separate from the assembly, that the prechamber 10 is connected to the compressed air terminal 22 by at least one valve 26, that the pressure vessel 2 is connected to the compressed air terminal 22 by at least one valve 23, and that the vacuum generating device 37 and/or pump is connected to the compressed air terminal 22.
A device 1, characterized in that the device 1 is connected to a blasting cabin 14 or encompasses a blasting cabin 14, wherein the respective blasting cabin 14 exhibits an interior 15 into which the feed line 3 extends, and wherein the return line 12 is connected to a collection receptacle 17 of the blasting cabin 14 for flowable media, e.g., for a flowable suspension, wherein it is provided in particular that the drain 17 always be in a state of pressure equalization with the environment.
A method characterized by the following procedural step:— Aspirating suspension 72 through the end 20 of the return line 12 connected to the collection receptacle 17 of the blasting cabin 14 for the suspension, in particular by generating a vacuum in the prechamber 10 and/or by turning on a pump arranged between the collection receptacle 17 and prechamber 10, and opening a vent valve 32 connected to the prechamber 10.
A method, characterized in that the method, in particular subsequently, encompasses at least the following:

- Ending the aspiration of suspension 72 through the end 20 of the return line 12 connected to the collection receptacle 17 of the blasting cabin 14,
- Supplying compressed air into the prechamber 10 at least partially filled with suspension 72, and opening a vent valve connected to the pressure vessel 2, for example which is a throttle valve 31 or a pressure relief valve.

A method, characterized in that the method, in particular subsequently, encompasses at least the following:

- Aspirating suspension 72 through the end 20 of the return line 12 connected to the collection receptacle 17 of the blasting cabin 14, in particular by generating a vacuum in the prechamber 10 and/or turning on a pump arranged between the collection receptacle 17 and prechamber 10, and opening a vent valve 32 connected to the prechamber 10,
- As this takes place, supplying compressed air to generate overpressure in the pressure vessel 10 at least partially filled with suspension, and
- Given an overpressure in the pressure vessel 2, at least intermittently opening the valve 7 allocated to the feed line 3 so as to blast suspension 72 onto one or several workpieces 19.

- Turning off the compressed air supply in the pressure vessel 2,
- Generating overpressure in the prechamber 10 by supplying compressed air into the prechamber 10,
- Given an overpressure in the prechamber 10, at least intermittently opening the valve 7 allocated to the feed line 3, and blasting suspension 72 onto one or several workpieces 19, and in particular at least intermittently opening a vent valve connected to the pressure vessel 2.

- Generating overpressure in the pressure vessel 2 by supplying compressed air into the pressure vessel 2 and opening the valve 49 allocated to the feed line 48, so that at least the liquid phase of the suspension 72 or the suspension 72 is transported from the pressure vessel 2 into the prechamber 10,
- Once a specific level has been reached in the prechamber 10, ending, in particular automatically ending, the supply of compressed air into the pressure vessel 2 and generating overpressure in the prechamber 10 by supplying compressed air,
- And in the process at least intermittently opening a vent valve connected to the pressure vessel 2 and/or opening the valve 7 allocated to the feed line 3 for blasting suspension 72 out of the blasting device 4.

A method, characterized in that suspension 72 is blasted onto one or several workpieces 19, wherein the weight ratio between the overall solid phase contained in the suspension 72 and the overall liquid phase contained therein is greater than 0.5, in particular greater than 0.9, and in particular has the value 1.
All disclosed features are essential to the invention (whether taken separately or in combination with each other). The disclosure content of the accompanying/attached priority documents (copy of prior application) is hereby included in the disclosure of the application in its entirety, to include for the purpose of also incorporating features in these documents into the claims of the present application. The features in the subclaims characterize independent inventive further developments of prior art, in particular so as to generate partial applications based upon these claims.


Reference List:

	1	Device
	2	Pressure vessel
	3	Feed line
	4	Blasting device
	4’	Nozzle holder
	5	Riser pipe
	6	Hose
	7	Valve
	8	Cover
	9	Mouth
	10	Prechamber
	11	Check valve
	11’	Valve
	12	Return line
	13	Check valve
	13’	Valve
	14	Blasting cabin
	15	Interior
	16	Funnel floor
	17	Collection receptacle
	18	Workpiece receptacle
	19	Workpieces
	20	End
	21	Line
	22	Compressed air terminal
	23	Valve
	24	Regulator unit
	25	Line
	26	Valve
	27	Line
	28	Crossing
	29	Line junction
	30	Line junction
	31	Throttle valve
	32	Vent valve
	33	Valve
	34	Line
	35	Line
	36	Regulator unit
	37	Vacuum generating device
	38	Line
	39	Valve
	40	Line
	41	Valve
	42	Regulator unit
	43	Pressure supply line
	44	Line
	45	Valve
	46	Line
	47	Valve
	48	Bypass line
	49	Valve
	50	End
	51	Ascending sifter
	52	End
	53	Line
	54	Valve
	55	Level probe
	56	Level probe
	57	Level probe
	58	Sensor
	59	Terminal
	60	Pressure vessel terminal
	61	Floor
	62	Terminal
	63	Riser pipe
	64	End
	65	Passage direction
	66	Sealing element
	67	Valve sleeve
	68	Valve housing
	69	Longitudinal section
	70	Seal seat
	71	Sealing edge
	72	Suspension
	73	Circle
	74	Surface
	75	Surface
	76	Through opening
	77	Sleeve
	78	Surface
	79	Longitudinal central axis
	80	Fastening plate
	81	Borehole
	82	Nut
	83	Passage opening
	84	Guiding lamella
	85	Guiding lamella
	86	Projection
	87	Edge
	88	Upper side
	89	Tongue
	90	Screw
	91	Flow-through opening
	92	Annular surface
	93	Terminal
	94	Prechamber terminal
	95	Floor
	96	Longitudinal central axis
	97	Terminal
	98	Passage direction
	99	Cyclone separator
	100	Line
	101	Line
	102	Terminal
	103	Terminal
	104	Riser pipe
	105	Screwed connection
	106	Hand valve
	107	Nozzle
	108	Hand valve
	109	Pipe segment
	110	Hand valve
	111	Riser pipe
	112	Housing
	113	Wheel
	114	Line
	α	Angle
	β	Angle

Claims

1. A device, for blasting a suspension onto one or more workpieces, wherein the device encompasses:

at least one pressure vessel,

at least one feed line for suspension that is connected to the pressure vessel, and is or can be connected to a blasting device,

at least one valve, which is switched between the pressure vessel and blasting device,

at least one prechamber, which is connected to the pressure vessel by a valve,

at least one return line for suspension, which is connected to the prechamber by a valve,

a line and valve, with which the prechamber can be connected to a compressed air source separate from the device, or with which the prechamber is connected to a compressed air source belonging to the device, characterized in that the valve between the prechamber and pressure vessel is a check valve, which at its one, upper, terminal is connected to a pressure vessel terminal that discharges into the pressure vessel through the floor of the pressure vessel, and that its other, lower, terminal is connected to the prechamber, wherein the passage direction of the check valve is directed toward the pressure vessel.

2. A device, for blasting a suspension onto one or more workpieces, wherein the device encompasses:

at least one pressure vessel,

at least one prechamber, which is connected to the pressure vessel by a valve,

at least one return line for suspension, which is connected to the prechamber, by a valve,

a line and valve, with which the prechamber can be connected to a compressed air source separate from the device, or with which the prechamber is connected to a compressed air source belonging to the device, characterized in that the device encompasses a vacuum generating device, a vacuum injector or a vacuum pump, to which the prechamber is connected by means of at least one line and one valve, and/or that a pump is switched between the prechamber and return line, or a pump is connected to the end of the return line facing away from the prechamber, wherein the conveying direction of the pump during operation is directed toward the prechamber.

3. The device according to claim 2, characterized in that the valve between the prechamber and pressure vessel is a check valve, which at its one, upper, terminal is connected to a pressure vessel terminal that discharges into the pressure vessel through the floor of the pressure vessel, at its lowest point, and that its other, lower, terminal is connected to the prechamber, wherein the passage direction of the check valve is directed toward the pressure vessel.

4. The device according to claim 1, characterized in that the device encompasses a valve switched between the return line and prechamber, which involves a check valve, wherein this check valve at its one, upper, terminal is connected to a prechamber terminal that discharges into the prechamber through the floor of the prechamber, at its lowest point, and at its other, lower, terminal is connected to the return line, and wherein the passage direction of this check valve is directed toward the prechamber, and wherein it is provided that this check valve is structurally identical to the check valve switched between the prechamber and pressure vessel.

5. The device according to claim 1, characterized in that the floor of the pressure vessel has a conical or curved shape, so that the cross section of the pressure vessel perpendicular to a vertical direction tapers downwardly, and/or that the floor of the prechamber has a conical or curved shape, so that the cross section of the prechamber perpendicular to a vertical direction tapers downwardly.

6. The device according to claim 1, characterized in that the device encompasses at least one line and one valve, with which the pressure vessel can be connected to a compressed air source separate from the device, or with which the pressure vessel is connected to a compressed air source belonging to the device.

7. The device according to claim 1, characterized in that the check valve switched between the prechamber and pressure vessel and/or the check valve switched between the return line and prechamber encompasses the following: A sealing element comprised of an elastically deformable material and a valve sleeve, which forms a seal seat that expands in the passage direction of the check valve, conically, wherein the sealing element forms a sealing edge extending along its periphery, which when the sealing element moves out of an open position in a direction toward the seal seat along the sealing edge, initially only along a circle, comes into contact with the seal seat.

8. The device according to claim 1, characterized in that the sealing edge is bordered by two surfaces of the sealing element, which in a cross section oriented transverse to its circumferential direction run inclined to each other, at a right angle to each other, wherein both surfaces of the sealing element each include an acute angle with the surface of the seal seat in a cross section perpendicular to the circumferential direction of the sealing edge.

9. The device according to claim 1, characterized in that the sealing element is accommodated in a longitudinally displaceable manner in the valve sleeve parallel to its longitudinal central axis, to which end the sealing element is connected with a guide that leaves one or several flow-through openings, and on their radially outer edge form a longitudinal guide with an inwardly pointing cylindrical surface of the valve sleeve.

10. The device according to claim 1, characterized in that, when moved from an open position toward the seal seat, the sealing edge of the sealing element hits an annular zone of the seal seat spaced apart from the tapered end of the seal seat, and that pressurizing the sealing element against the seat seal triggers an elastic deformation of the sealing element, as a result of which the sealing element (66) abuts flat against the seal seat along its circumference.

11. The device according to claim 1, characterized in that the feed line extends through the wall of the pressure vessel into its interior, wherein the distance between the mouth of the feed line and lowest point of the pressure vessel measures less than one eighth of the height of the interior of the pressure vessel.

12. The device according to claim 1, characterized in that the check valve switched between the prechamber and pressure vessel is connected to a riser pipe, at its lower terminal in the installation position, which extends through the upper side wall of the prechamber into its interior, wherein the distance between the lower opening of the riser and the lowest point of the prechamber measures less than one eighth, of the height of the interior of the prechamber.

13. The device according to claim 1, characterized in that the device encompasses a bypass line and a valve accommodated therein, wherein the one end of the bypass line discharges into the interior of the pressure vessel, at more than half of its height, inside of an ascending sifter placed in the pressure vessel, and wherein the other end of the bypass line discharges into the interior of the prechamber, at less than half of its height.

14. The device according to claim 1, characterized in that the device encompasses two prechambers, two return lines and four, structurally identical, check valves, that the prechambers are connected in parallel with each other and, interposing a respective check valve, with the pressure vessel, and that a respective return line is connected to a respective prechamber, interposing a respective check valve.

15. The device according to claim 1, characterized in that at least the pressure vessel, the prechamber or the prechambers, the check valve(s), the bypass line or bypass lines, the vacuum generating device and/or the pump as a combined assembly are situated in a shared or cubic housing, out of which the feed line and return line extend, that the assembly encompasses a compressed air terminal that is or can be connected to a compressed air source that belongs to the assembly or is separate from the assembly, that the prechamber is connected to the compressed air terminal by at least one valve, that the pressure vessel is connected to the compressed air terminal by at least one valve, and that the vacuum generating device and/or pump is connected to the compressed air terminal.

16. The device according to claim 1, characterized in that the device is connected to a blasting cabin or encompasses a blasting cabin, wherein the respective blasting cabin exhibits an interior into which the feed line extends, and wherein the return line is connected to a collection receptacle of the blasting cabin for flowable media, wherein it is provided that the collection receptacle always be in a state of pressure equalization with the environment.

17. A method for wet blasting one or several workpieces, comprising at least the following procedural steps:

providing a device according to claim 1,

providing a blasting cabin if the provided device encompasses no blasting cabin,

introducing the blasting device for the suspension and at least one longitudinal section of the supply line for the suspension into the interior of the blasting cabin,

connecting one end of the return line for the suspension to a collection receptacle of the blasting cabin for flowable media,

introducing suspension into the collection receptacle of the blasting cabin, characterized by the following procedural step:

aspirating suspension through the end of the return line connected to the collection receptacle of the blasting cabin, by generating a vacuum in the prechamber and/or by turning on a pump arranged between the collection receptacle and prechamber, and opening a vent valve connected to the prechamber.

18. The method according to claim 17, characterized in that the method, subsequently, encompass at least:

ending the aspiration of suspension through the end of the return line connected to the collection receptacle of the blasting cabin,

supplying compressed air into the prechamber at least partially filled with suspension, and opening a vent valve connected to the pressure vessel, for example which is a throttle valve or a pressure relief valve.

19. The method according to claim 17, characterized in that the method, subsequently, encompass at least:

aspirating suspension through the end of the return line connected to the collection receptacle of the blasting cabin, by generating a vacuum in the prechamber and/or turning on a pump arranged between the collection receptacle and prechamber, and opening a vent valve connected to the prechamber,

as this takes place, supplying compressed air to generate overpressure in the pressure vessel at least partially filled with suspension,

and, given an overpressure in the pressure vessel, at least intermittently opening the valve allocated to the feed line so as to blast suspension onto one or several workpieces.

20. The method according to claim 17, characterized in that the method, subsequently, encompass at least:

turning off the compressed air supply in the pressure vessel,

generating overpressure in the prechamber by supplying compressed air into the prechamber,

given an overpressure in the prechamber, at least intermittently opening the valve allocated to the feed line, and blasting suspension onto one or several workpieces, and at least intermittently opening a vent valve connected to the pressure vessel.

21. The method according to claim 20, characterized in that the steps of:

turning off the compressed air supply in the pressure vessel,

given an overpressure in the prechamber, at least intermittently opening the valve allocated to the feed line, and blasting suspension onto one or several workpieces, and at least intermittently opening a vent valve connected to the pressure vessel are repeatedly executed alternately in time relative to the steps of:

22. The method according to claim 17, characterized in that the method, subsequently, encompass at least:

generating overpressure in the pressure vessel by supplying compressed air into the pressure vessel and opening the valve allocated to the bypass line, so that at least the liquid phase of the suspension or the suspension is transported from the pressure vessel into the prechamber,

once a specific level has been reached in the prechamber, ending the supply of compressed air into the pressure vessel and generating overpressure in the prechamber by supplying compressed air, and

in the process at least intermittently opening a vent valve connected to the pressure vessel and/or opening the valve allocated to the feed line for blasting suspension out of the blasting device.

23. The method according to claim 17, characterized in that suspension is blasted onto one or several workpieces, wherein the weight ratio between the overall solid phase contained in the suspension and the overall liquid phase contained in the suspension has the value 1.

24. A method according to claim 1, characterized in that suspension is blasted onto one or several workpieces, wherein the weight ratio between the overall solid phase contained in the suspension and the overall liquid phase contained in the suspension is greater than 0.5.