EP0916492A1

EP0916492A1 - Device for supplying liquid cleaner

Info

Publication number: EP0916492A1
Application number: EP97119983A
Authority: EP
Inventors: Marco Corti; Riccardo Fumagalli
Original assignee: Elettra Srl
Current assignee: FINELETTRA INTERNATIONAL S.A.
Priority date: 1997-11-14
Filing date: 1997-11-14
Publication date: 1999-05-19
Anticipated expiration: 2017-11-14
Also published as: ATE205783T1; ES2161407T3; DE69706868T2; EP0916492B1; DE69706868D1; DK0916492T3

Abstract

The branches of the channels for feeding the cleaning fluids, formed in the dispensing bar (1), continue to fork (B1, B2, B3, B4, B5, B6, B7, B8, B9, B10, B11, B12, B13, B14, B15), optionally finally splitting into three-way branches (T1, T2, T3, T4, T5, T6, T7, T8), until each dispensing hole (10) is fed by its own channel, so that the flow of fluids is distributed essentially in equal amounts and at the same pressure between the various dispensing holes (10) in the bar. The cleaning liquids are fed by respective reciprocating positive displacement pumps (63, 163) which are activated by pneumatic actuators (65, 165) having a piston which is suitably larger than the piston (64, 164) of the said pumps and being activated by the stream of air produced by the same source and at the same pressure as that conveyed to the dispensing bar, mixed together with the liquids dispensed by the pumps, in order to convey and atomize the said liquids. This ensures that the delivery pressure of the cleaning liquids is always correlated to and greater than the pressure of the stream of air, even when the latter is subject to variations in pressure.

Description

In the course of producing and using apparatuses for automatically cleaning the inking rollers and the natural-rubber covered cylinders of printing machines, hereinafter referred to as "rubber-covered cylinders", as described in Italian patents Nos. 1 257 766 and 1 257 769 and application No. BO95A000432 in the name of the same applicant and to which the broadest reference is made, it became apparent that certain modifications would be useful in order to improve the performance of the means for dispensing fluids for cleaning the said rollers and cylinders, and in particular to ensure that the said fluids are distributed uniformly to the various dispensing holes so as to avoid a situation in which the liquid is concentrated in different areas of the sprayed surface and consequently forms drips.
In order to overcome these drawbacks, further improvements have been made to the structure of the channels that distribute the cleaning fluids from a single pipe to the various dispensing holes and a specific system has been designed for feeding these fluids to this pipe. There is also the option of connecting porous inserts to the dispensing holes instead of the usual nozzles, these inserts coming into direct contact with the cloth for cleaning the rubber-covered cylinders. The features of the invention, together with the advantages that derive therefrom, will be apparent from the following description of preferred embodiments of the invention, illustrated by way of non-limiting example in the figures of accompanying in which:

Fig. 1 is a cross-section on I-I in Figure 2 showing the improved bar according to the invention, in the version equipped with nozzles for dispensing the cleaning fluids and designed to clean the rubber-covered rollers in printing machines;
Figs 2 and 2a are a plan view from above, split into two portions with the cutting line running along the midpoint, of the bar in Figure 1 showing the channels which ensure that the cleaning fluids are distributed uniformly to the various nozzles;
Figs 3 and 3a are a plan view from above, split into two portions at the midpoint, of a variant embodiment of the bar showing the channels which ensure that the cleaning fluids are distributed uniformly to the various nozzles;
Fig. 4 illustrates an enlargement of the final branch of the channels that feed the nozzles in the bar shown in Figures 3 and 3a;
Fig. 5 illustrates additional details of the bar of Figure 3, in cross-section on V-V;
Fig. 6 illustrates a diagram showing how the circuit for feeding the cleaning fluid to the dispensing bar operates;
Figs 7 and 8 illustrate, in cross-section and in two different stages of operation, a cleaning fluid dispensing bar which incorporates porous inserts instead of the usual nozzles;
Fig. 9 is a view of the front of the bar shown in Figs 7 and 8.

In order to gain a better understanding of the objects that the invention intends to achieve, it would be helpful briefly to recall that some of the apparatuses to which reference is made - i.e. those designed to clean the rubber-covered rollers of printing machines - comprise a fixed bar 1 made of a lightweight alloy, which is positioned parallel to and a short distance from each rubber-covered cylinder 2 and which, on its side facing the said cylinder, carries a longitudinal straight recess 3 in which a presser element 4 with a yielding elastic membrane 5 is guided. The same bar 1 also houses the pneumatic actuators 6 which, on command, push the presser element 4, 5 against the cylinder 2 so as to bring the latter into contact with the intermediate cloth 7 onto which cleaning fluids are sprayed by nozzles 9 mounted in one or more seats 8 formed in that side of the bar that faces the cloth. These nozzles connect up, via holes 10, with channels 1000 milled along a flat face of the said bar on which a gasket 12 is then placed and a covering means 13 fixed by means of screws 14, thereby turning the said channels into proper pipes. These channels are symmetrically connected to other feed conduits which are arranged in circuits flowing parallel to each other, come together at forks and gradually decrease in number until they join up with a single fluid feed pipe 15 located at one end of the bar 1. In the last patent application mentioned in the introduction to the present description, the fact was claimed that each fork in the said channels is essentially "Y"-shaped and occurs in a straight section of pipe, and that the channels produced by the fork are structured such that they offer essentially the same degree of resistance to the passage of the fluids, so that the latter split into flows of essentially equal volume at each fork in the pipe. The number of forks is such that each terminal channel is of limited length and feeds a limited number of nozzles 9. In the embodiment illustrated in the application cited above, the terminal channels fed three nozzles in series. In the variant embodiment proposed in the present patent application, and which will now be described with reference to Figures 1, 2 and 2a, the channels continue to fork until each terminal channel produced by a fork feeds a single nozzle, in order to ensure an even more uniform distribution of the cleaning fluids to the various nozzles of the apparatus.
In Figures 2 and 2a, the reference numeral 15 denotes the pipe located at one end of the bar and connected to the cleaning fluid delivery system mentioned earlier. The pipe 15 communicates, via the perpendicular hole 16, with a first channel 100 formed longitudinally in the bar 1 and which, before it reaches the middle 18 of the bar, forks at B1 into two opposite straight pipes 101, 201 which, before they reach the middle of each respective half-bar, fork at B2 and B3 respectively, forming corresponding pairs of identical, mutually aligned pipes 102, 202 and 103, 203 which in turn fork at B4, B5 and B6, B7 respectively forming pairs of pipes 104, 204, 105, 205 and 106, 206, 107, 207 which then fork again, for the last time, at B8, B9, B10, B11 and B12, B13, B14, B15 respectively, which, via their respective conduits 108, 208, 109, 209, 110, 210, 111, 211, 112, 212, 113, 213, 114, 214 and 115, 215, feed the holes 10 of associated nozzles 9. Following each main channel are two initially straight channels located a short distance from each other and parallel to and equidistant from the channel upstream. The common wall via which the channels formed by each fork join up with the channel upstream has a "V" shape when viewed from above and has a sharp point. Of the two arms that follow each fork, one has a "Z" or "S" shape, and the other a "U" or "C" shape.
The reference numeral 26 denotes straight milled portions formed in the base of the conduit 11 which carries the channels for conveying the cleaning liquids. These milled portions contain the threaded blind holes 114 in which the screws 14 engage in order to screw down the components 12, 13 which define the said channels according to the known art (Fig. 1).
In order to spread losses in pressure equally, the channels formed by each fork are of appropriate depth and width, as may be seen in Figure 1. For example, in the bar produced by the applicant and illustrated in Figures 2 and 2a, and which has fifteen forks and sixteen dispensing nozzles, the initial conduit 100 is approximately 10 mm deep and approximately 5 mm wide, while the arms of the final forks are approximately 3 mm wide and approximately 2.5 mm deep.
The bar illustrated in Figures 3 and 3a actually has twenty-four nozzles supplied by channels containing fifteen forks, essentially as in the previous bar except that the final forks subsequently split into three-way branches T1, T2, T3, T4, T5, T6, T7, T8, immediately after their straight sections, as illustrated in the detail shown in Figure 4. These branches are symmetrically and centrally positioned relative to the fork, with one arm having an "S" or "Z" shape, one having a "U" or "C" shape and the intermediate arm having a rounded "L" shape, each of the three arms feeding the hole 10 of one nozzle 9.
Figure 5 illustrates how, in the variant embodiment of Figures 3 and 3a, the channels for conveying the cleaning fluids also have differing widths and depths in order to compensate for losses in pressure. In the bar produced by the applicant, the initial pipes are, for example, 4 mm wide and 8 mm deep. After the first fork their width goes down to 3 mm and their depth to 6 mm. After the next fork their width remains the same but their depth is reduced to 3 mm. At the next fork their depth remains the same but their width is reduced to 2 mm. The arms of the final fork are 2.5 mm deep and this depth, and the width of 2 mm, remain unchanged to the end. The detail in Figure 4 shows that the outer arms of each final three-way branch are oriented tangentially to the holes 10 feeding the associated nozzles, while the inner arm is centred with respect to its hole 10 which, like all the other holes, has a diameter of 3 mm.
With reference to Figures 7, 8 and 9, it may be seen that, according to a variant embodiment of the invention, the nozzles 9 can be replaced by a rectinlinear pad 70, made of any suitable porous material which will not oxidize or be broken down by the liquids to be dispensed but is nevertheless permeable to them, housed in a straight recess 71 formed in the active face of the bar 1, parallel to the recess 3. At the base of the recess 71 there is a small continuous chamber 72 which acts as a reservoir and into which the holes 10 for dispensing the cleaning fluid open. The pad 70 may advantageously be formed by a plurality of inserts 70' which have the same dimensions and are identical to each other, except for the end inserts 70'' which have one rounded end so that they can fit in a leaktight manner into the corresponding ends of the recess 71 (Fig. 9). The inserts 70', 70'' are held in the recess 71 by suitable means so that, if need be, they can be easily removed, for example so that they can be cleaned or replaced periodically. To this end the inserts 70', 70'' are dimensioned such that they can be inserted very accurately into the recess 71 and may also have a longitudinal hole 73 through which a support rod 74 passes which also passes through holes formed in the ends of the bar 1, the threaded ends of the said rod being fixed to the ends of the bar by means of nuts 75.
Figure 7 shows that the pad 70 is preferably positioned so that its face is in view and lies in the same plane as the wall of the bar 1 which comes into contact with the cloth 7 when the presser element 4, 5 is in the retracted rest position. At this point, the liquid to be sprayed is fed via the holes 10 into the small manifold 72 from which it is uniformly fed to the pad 70 which uniformly wets the cloth 7. During this stage the cloth 7 is preferably stationary. Once the liquid has been dispensed, the cloth 7 is moved until its wetted part is in front of the presser element 4, 5 which is then activated, as shown in Figure 8, so as to clean the rubber-covered roller 2.
The circuit that feeds the cleaning fluids to the dispensing bar will now be described with reference to Figure 6. The circuits employed in the previous patents differed from known solutions in that, while appropriate amounts of detergent liquid were being injected into the system as and when needed, a continuous stream of air was simultaneously being injected, via a circuit parallel to the circuit for feeding the liquid to the dispensing bar. This air acted as a conveying medium and was necessary for the atomization and the uniform dispersion of the liquid by the said dispensing bar and was, for this purpose, kept at a suitable pressure below that of which the liquid was injected. The circuit embodiment adopted involved using pressure regulators on the pneumatic circuit and the hydraulic circuit and using hydropneumatic compensators on the latter circuit, all of which made the system complex in terms of construction and unreliable whenever there were pressure variations in the pneumatic circuit. The invention provides a simple and reliable solution to this problem, ensuring that the liquid injection pressure is always correlated to the air injection pressure and is always greater than the latter by an exact amount, even if the air injection pressure is subject to sudden and substantial variations. This technical problem has been solved by using reciprocating positive displacement pumps activated by pneumatic actuators which are fed by the same source and at the same pressure as the air which is conveyed towards the dispensing bar, the pistons of these actuators having a diameter suitably greater than that of the pump. In Figure 6, the reference numerals 43 and 44 denote the water and solvent tanks respectively which, by means of immersed elements 60, 160, filters 61, 161 and one- way valves 62, 162, are connected to the chambers C1, C1', which have identical sections, of respective positive displacement pumps 63, 163, the pistons are 64, 164 of which is activated by respective cylinder and piston units 65, 165 having identical characteristics. The diameter of the pistons in these units is suitably greater than that of their associated pumps. As is known, the pressure produced is inversely proportional to the section of the piston of the unit generating it, so that the pumps will deliver a pressure which is always greater than that of the pneumatic actuating circuit, which is the pressure conveyed to the dispensing bar. In this particular example, the chambers C2, C2' communicate freely with the atmosphere, also acting as indicators to warn of any failure in the sealing efficiency of the pump pistons. It should be understood, however, that the scope of the invention also encompasses a variant embodiment in which the pumps 63, 163 are used as double-acting machines. It should also be understood that the units consisting of the pumps and their actuators need not necessarily be made according to the integrated embodiment illustrated in Figure 6 in which the bodies of the pumps are coaxially integral with the bodies of the actuators and the piston of each pump/actuator unit is integral with a common rod.
The chambers C1, C1' of the pumps are connected by means of one-way valves 66, 166 - which are inverse to the previous one-way valves 62, 162 - to solenoid valves 34, 35, the outlets of which are connected in parallel to each other and to the pipe 32 that feeds the abovementioned pipe 15 of the dispensing bar. This pipe 32 is also connected, via a parallel circuit which includes a one-way valve 67, to the outlet of any suitable solenoid valve 31 which is connected upstream to the compressed air source 27 via a pressure regulator 30 of any suitable type together with corresponding manometers 53. This same compressed air feed circuit is connected to any suitable solenoid valve 68 which is capable of switching the feed to and discharge from the cylinder and piston units 65, 165 that activate the positive displacement pumps 63, 163, this solenoid valve 68 also having an intermediate state in which it shuts off the pneumatic feed to the said units.
The following complete the system as regards its main components: an optional manostat 69 on the compressed air feed circuit and optional manostats 70, 170 on the liquid feed circuits, together with corresponding manometers 153. The manostats interface with a processor 51 which controls the various solenoid valves and which can be suitably programmed by means of the keyboard/ display unit 52. The operation of the system thus designed as regards its main components is simple and self-evident. On command the solenoid valve 68 switches into the state 168 in which the actuators 65, 165 generate an increase in the volume of the chambers C1, C1' of the pumps, thereby sucking the liquids up from the tanks 43, 44 via the valves 62, 162 which open. The valves 66, 166, on the other hand, remain closed and isolate the pumps from the delivery circuit. The end of the suction stroke of the pumps can be detected by the manostat 69 or can be controlled by a timer circuit (not illustrated) which is also connected to the processor 51 which, at the appropriate stage, switches the solenoid valve 68 into the intermediate state thereby shutting off the pneumatic feed to the units 65, 165. This stage in which the positive displacement pumps are filled is carried out at any time prior to each washing cycle, in other words before the apparatus in question is to feed the dispensing bar. When the dispensing bar needs to be fed, the processor 51 switches the solenoid valve 68 into the state 268 which causes the actuators 65, 165 to reduce the volume of the chambers C1, C1'. The solenoid valves 34, 35 and 31 are also switched in phase. The liquids discharged from the pumps flow through the valves 66, 166, through the solenoid valves 34, 35 and arrive at the pipe 32 that feeds the dispensing bar, mixed with air arriving via the solenoid valve 31. The two liquid flows are at the same pressure - which is suitably greater than the pressure of the compressed air arriving via the valves 31, 67, so that the entire mixture tends to flow uniformly towards the pipe 32 which is at atmospheric pressure. Good results have, for example, been achieved in cases where the diameters of the pistons of the actuators and of the pumps differ by between 5 and 10 mm, for example by approximately 7 mm. Operating at an air pressure of approximately 7 bar, the pump piston has been given a diameter of approximately 63 mm, while the piston of the corresponding pneumatic actuator has, for example, been given a diameter of approximately 70 mm. A pneumatic circuit pressure of 7 bar corresponds to a liquid overpressure of 1.64 bar. A pneumatic pressure of 6 bar corresponds to a liquid overpressure of 1.4 bar, that is 0.24 bar less than the initial overpressure - an amount virtually undetectable by the conveying and dispensing system. In terms of volume, a reduction of 0.24 bar corresponds to a decrease of approximately 15% in the flow of liquid and air to the bar with the nozzles and onto the cloth which nevertheless is still sprayed and lubricated within values that can be tolerated by the physical characteristics of the rubber-covered cylinder to be cleaned. It should be borne in mind, however, that a pressure drop of 1 bar is quite large and unlikely to occur in a pneumatic system which is always equipped with a suitable accumulation reservoir and possibly even with a suitable hydropneumatic accumulator.
The volumetric capacity of the pumps 63, 163 is preferably greater than the maximum amount of liquid that needs to be sprayed onto the cleaning cloth during each cycle. At the end of each cycle, the pumps are switched to suction mode, they return to their maximum filled state and then stand by to carry out the next cycle.
By varying the length of time that the solenoid valves 34, 35 remain open and closed, it is possible suitably to choke the liquids conveyed to the dispensing bar so that, if need be, only water or only solvent or only air could be conveyed to the bar.

Claims

Apparatus for dispensing fluids for cleaning the rubber-covered cylinders (2) and inking rollers of printing machines, of the type that comprises at least one row of means (9) for dispensing the said fluids, which means are parallel to the surface to be cleaned and are located on a dispensing bar (1) having transverse dispensing holes (10) which convey the fluid to the said dispensing means and are in turn connected to channels obtained along one face of the said bar and closed by proper sealing means (12, 13) so as to form proper pipes proper pipes, these channels being connected to other feed channels which are arranged in parallel to each other, come together at forks and gradually decrease in number until they join up with a single fluid feed pipe (15),
characterized by the fact that
each fork in the said channels is essentially "Y"-shaped and occurs at least as regards its initial part in a straight section of pipe.
Apparatus according to Claim 1), in which the total number of forks is at least equal to the number of dispensing holes (10).
Apparatus according to Claim 1), characterized in that, according to a variant embodiment, the final forks (B8, B9, B10, B11, B12, B13, B14, B15) subsequently split into centrally positioned three-way branches (T1, T2, T3, T4, T5, T6, T7, T8) so that it is possible to feed half as many dispensing holes (10) again as the number that can be fed by the forks alone.
Apparatus according to Claim 3), in which the wall dividing the final forks is in alignment with the midpoint of the central arm of the final three-way branch and these three arms are of the same width as the arms of the said forks.
Apparatus according to Claim 3), in which the arms of the final three-way branches connect up with corresponding perpendicular terminal holes (10) designed to feed corresponding nozzles (9) or other suitable dispensing means, the said holes having a diameter which is suitably greater than the width of each of the arms.
Apparatus according to Claim 5), in which the dispensing holes (10) fed by each final three-way branch are positioned so that their circumference lies tangentially relative to the outer arms, whereas they are positioned centrally relative to the inner arm of the said branches.
Apparatus according to the preceding claims, characterized in that, in order to compensate for losses in pressure resulting from the various branches and from the increased overall width of the channels for conveying the cleaning fluids, the depth of these channels decreases progressively in the direction of the terminal dispensing holes (10).
Apparatus according to Claim 1), in which the depth of the final forks is, for example, approximately 2.5 mm and their width is approximately 3 mm, the same as that of the holes (10) for feeding the nozzles.
Apparatus according to Claim 3), in which the depth of the final three-way branches is approximately 2.5 mm and their width is approximately 2 mm, while the dispensing holes (10) which connect up with these branches are approximately 3 mm wide.
Apparatus according to the preceding claims, in which, rather than feeding a corresponding dispensing nozzle (9), the holes (10) which finally dispense the cleaning fluids connect up with a small rectilinear chamber (72) which acts as a reservoir and opens at the base of a straight recess (71) in the dispensing bar, formed parallel to the recess (3) housing the presser element (4, 5) and engaging with a pad (70) made of any suitable porous material which is permeable to the said cleaning fluids, one face of which is in transverse contact with the cloth (7) when the said presser element is in the retracted rest position, so that the fluid dispensed by the said holes (10) passes through the said pad and wets the cloth uniformly, without dripping.
Apparatus according to Claim 10), in which the face of the porous pad is in view and lies essentially in the same plane as that surface of the dispensing bar (1) with which the cloth (7) comes into contact and over which it slides when the presser element (4, 5) is in the retracted rest position.
Apparatus according to Claim 10), in which the porous pad is formed by a plurality of inserts (70') placed next to each other and having the same dimensions, except for the end inserts (70'') if these are to engage in corresponding rounded ends of the housing recess (71).
Apparatus according to Claim 12), in which the inserts that form the porous pad (70) are inserted accurately into the housing recess (71) and means are provided for holding the said inserts and enabling them to be easily removed if need be.
Apparatus according to Claim 13), in which the inserts that form the porous pad are provided with at least one corresponding hole (73) and have a small rod (74) passing through them which also passes through end holes formed in the dispensing bar (1), the threaded ends of the said rod being fixed to the bar with nuts (75) and/or other suitable means.
Apparatus for feeding fluids for cleaning the rubber-covered cylinders of printing machines, of the type that comprises a straight presser element with at least one yielding elastic wall that faces and lies parallel to the said cylinder and which is pushed, on command, against the said cylinder with the insertion of a cloth suitably sprayed with the cleaning fluids dispensed by a dispensing bar expediently associated with the said presser element, and in which the said fluids consist, for example, of precise amounts of water and/or solvent which are taken from respective tanks by pumping means and are fed on command to the nozzle bar, partly by means of a stream of air at a precise pressure which acts as a medium for conveying the said liquids and is used to atomize and uniformly distribute the said liquids onto the cleaning cloth, characterized in that it comprises means which ensure that the pressure of the cleaning liquids injected into the stream of air is always directly proportional to that of the stream of air and never falls below that of the latter, even when this stream is subject to variations in pressure.
Apparatus according to Claim 15), characterized in that the cleaning liquids are taken from their respective tanks (43, 44) by means of respective positive displacement pumps (63, 163) having non-return valves (62, 162) respectively, these pumps being activated by corresponding double-acting, fluid-pressure cylinder and piston units (65, 165), the pistons of which have a diameter which is in a suitable ratio to that (64, 164) of the said pumps and are fed by the same source and at the same pressure as the stream of air which, via a circuit consisting of a control solenoid valve (31) and a one-way valve (67), feeds the dispensing bar (1) on command, the apparatus as a whole being such that, when the pumps are switched to delivery mode and convey the liquid which has been sucked up beforehand to the dispensing bar via respective non-return valves (66, 166) and respective control solenoid valves (34, 35), the flow of liquids reaches the pipe (32) that feeds the bar at a pressure which is always directly proportional to that of the stream of air, even when pressure variations occur in the latter.
Apparatus according to Claim 16), in which the diameter of the pistons of the pneumatic actuators (65, 165) that activate the positive displacement pumps (63, 163) for sucking up and delivering the cleaning liquids is suitably greater than the diameter of the pistons of the said pumps, in order that the flow of liquids reaches the pipe (32) that feeds the dispensing bar at a pressure which is always suitably greater than that of the stream of air, even when pressure variations occur in the latter.
Apparatus according to Claim 16), in which the positive displacement pumps (63, 163) for sucking up and delivering the two cleaning liquids to the dispensing bar have the same dimensional characteristics.
Apparatus according to Claim 16), in which the capacity of the positive displacement pumps (63, 163) is expediently greater than the maximum amount of liquid that needs to be dispensed by the dispensing bar during each operating cycle.
Apparatus according to Claim 16), in which the pneumatic actuators (65, 165) of the two positive displacement pumps (63, 163) are fed, via a parallel circuit, by a common solenoid valve (68) connected to the compressed air circuit which is fitted with a pressure regulator (30) and an optional manostat (69) which detects any pressure peaks and signals them to the processor (51) which controls the various solenoid valves in the system, with other optional manostats (70, 170) being provided on the pump delivery circuit, these manostats also being connected to the said processor which controls the solenoid valve (31) that delivers the air to the dispensing bar and the solenoid valves (34, 35) that deliver the liquids coming from the pumps to this bar, in such a way, moreover, as to be able suitably to choke the feed of the liquids.
Apparatus according to Claim 20), in which the solenoid valve (68) that feeds the pneumatic actuators (65, 165) of the positive displacement pumps (63, 163) is of the type which is normally closed, having two switching states (168, 268) so as to retract and extend the rods of the said actuators, means being provided which bring about the suction and filling of the pumps before the cleaning fluids are needed, after which the said solenoid valve switches to its rest state and stands by until the pumps are switched to delivery mode.