CN110832200B

CN110832200B - High pressure cleaning device

Info

Publication number: CN110832200B
Application number: CN201780092707.1A
Authority: CN
Inventors: 安德烈亚斯·黑格勒; 约翰纳斯·格茨; 维尔纳·施瓦布
Original assignee: Alfred Kaercher SE and Co KG
Current assignee: Alfred Kaercher SE and Co KG
Priority date: 2017-06-29
Filing date: 2017-06-29
Publication date: 2021-08-10
Anticipated expiration: 2037-06-29
Also published as: WO2019001719A1; EP3645885B1; CN110832200A; EP3645885A1

Abstract

The invention relates to a high-pressure cleaning appliance (10) having a pump (14) which has a suction line (24) and a pressure line (30), wherein a check valve (34) is arranged in the pressure line (30), and the pump has a relief valve (84) which releases a flow path through a relief line (74) as a function of pressure in order to let cleaning liquid flow out of the pressure line (30). The overflow valve (84) has a closing body (86) which rests in a liquid-tight manner against a valve seat (82) in a closed position, can be moved against a closing force of a closing spring (92) into an open position spaced apart from the valve seat (82), and is connected to a control piston (58) which is held in a movable manner in a control chamber (56) and can be charged with cleaning liquid under pressure. In order to reduce the size of the relief valve (84) without using an injector, the control piston (58) divides the control chamber (56) into a discharge pressure chamber (64) and a relief chamber (66). The outlet pressure chamber (64) is connected to a region of the pressure line (30) which is arranged downstream of the check valve (34) and has a first through-opening (96) which is penetrated by a piston rod (94) which is fastened to the control piston (58). The overflow chamber (66) is connected to a region of the pressure line (30) which is arranged upstream of the check valve (34) and has a second through-opening (80) which forms a valve seat (82). The through-openings (96, 80) are not equally large, and the control piston (58) can be loaded on its side facing the larger through-opening to close the closing force of the spring (92).

Description

High pressure cleaning device

Technical Field

The invention relates to a high-pressure cleaning device having a pump for delivering a cleaning liquid, wherein the pump has a suction line and a pressure line, and a check valve is arranged in the pressure line, and wherein the pump has an overflow valve which, depending on the pressure of the cleaning liquid present in the pressure line, releases a flow path through the overflow line for the cleaning liquid to flow out of the pressure line, wherein the overflow valve has a closing body which rests in a liquid-tight manner on a valve seat in a closed position, can be moved into an open position spaced apart from the valve seat against the closing force of a closing spring, and is connected by a valve rod to a control piston which is held in a movable manner in a control chamber and can be charged with the cleaning liquid under pressure.

Background

With such a high-pressure cleaning device, a cleaning liquid, preferably water, can be placed under pressure and directed towards the surface to be cleaned. The high-pressure cleaning appliance has a pump which can be driven by a motor, preferably an electric motor, and which has at least one piston which can be moved back and forth and which is immersed in a pump chamber. Preferably, the pump comprises three reciprocable pistons, each of which is immersed in a pump chamber. The cleaning liquid under pressure can be conveyed by a liquid conveying line, for example by a suction hose, to a pump, and the cleaning liquid under pressure can be conveyed by the pump by a liquid outlet line, for example by a high-pressure hose, to a liquid outlet device, for example a spray gun or a spray bar. The liquid outlet means has a valve which can be opened and closed by a user. The cleaning liquid can be output under pressure when the valve is open, and the liquid output can be ended by closing the valve.

The high-pressure cleaning appliance has a relief valve which opens in dependence on the pressure prevailing in the pressure line and releases the flow path so that cleaning liquid can flow out of the pressure line through the relief line in order to reduce the pressure in the pressure line. If the valve of the liquid outlet means is closed, the pressure of the cleaning liquid in the pressure line is increased on the basis of the continued activation of the pump. When a preset maximum value of the pressure is exceeded, the overflow valve releases the flow path so that cleaning liquid can flow out of the pressure line through the overflow line.

For example, it can be provided that the flow path extends from the pressure line to the suction line through the overflow line, so that the overflow valve opens when a preset maximum value of the pressure prevailing in the pressure line is exceeded, and that cleaning liquid can flow from the pressure line to the suction line through the overflow line. The pump can thus be operated cyclically.

It can also be provided that the flow path extends from the pressure line through the overflow line to the outlet, through which the cleaning liquid can be discharged when a preset maximum value of the pressure prevailing in the pressure line is exceeded.

It can also be provided that the flow path extends from the pressure line to a collecting space which, when the pressure prevailing in the pressure line is exceeded, receives cleaning liquid from the pressure line.

It may be provided that the pump is shut off after the overflow valve has been opened.

The overflow valve has a closing body which in a closed position rests in a liquid-tight manner against a valve seat and can be moved against a closing force of a closing spring into an open position in which the closing body is at a distance from the valve seat and thereby releases a flow path from the pressure line through the overflow line. The control of the closing body is effected by means of a control piston which is rigidly connected to the closing body via a valve rod and can be acted upon by a pressurized cleaning liquid.

High-pressure cleaning devices of the aforementioned type are known from WO 2016/015763 a 1. In this high-pressure cleaning appliance, the pressure prevailing in the pressure line acts on one side of the control piston during the discharge of the cleaning liquid, and on the opposite side the control piston is loaded with a closing force of the closing spring. The closing force of the closing spring therefore acts against the pressing force which is composed of the pressure loading the control piston with the cleaning liquid present in the pressure line. During the discharge of the cleaning liquid, the pressure of the cleaning liquid can be greater than 100bar, in particular at least 150 bar. It is therefore necessary to use very strong closing springs whose closing force acting on the control piston must be carefully adjusted during assembly in order to ensure that the closing body connected to the control piston is reliably held in its closed position by the closing spring when the liquid outlet means is open, i.e. during the delivery of cleaning liquid, and is moved into its open position against the closing force of the closing spring when the liquid outlet means is closed, i.e. when a preset maximum value of pressure is exceeded. The strong closing spring required for this makes the relief valve of considerable overall size and the adjustment of the closing body required makes the assembly of the high-pressure cleaning appliance difficult.

From DE 102009049096 a1 a high-pressure cleaning appliance is known, in which the overflow valve can be actuated depending on the flow rate of the cleaning liquid present in the pressure line. For this purpose, a throttle element (in the form of an injector) is arranged in the region of the pressure line downstream of the non-return valve, said throttle element having a through-opening which is first narrowed and then widened again in the flow direction, and a transverse bore branching off from the narrowest point of the through-opening. The pressure of the cleaning liquid present in the transverse bore is related to its flow rate and is taken into account for controlling the overflow valve. In this embodiment, the closing spring of the overflow valve can be constructed more weakly and with a smaller overall size, but the use of an injector leads to considerable flow losses, since the injector exhibits a non-negligible flow resistance. This in turn leads to a higher energy consumption of the high-pressure cleaning appliance.

Disclosure of Invention

The object of the present invention is therefore to improve a high-pressure cleaning device of the type mentioned at the outset in such a way that the overall size of the relief valve is reduced without the use of an injector and the assembly of the high-pressure cleaning device can be simplified.

This object is achieved according to the invention in a high-pressure cleaning appliance of the generic type in that the control piston divides the control chamber into a discharge pressure chamber and an overflow chamber, wherein the discharge pressure chamber is connected via a pressure channel to a region of the pressure line which is arranged downstream of the check valve and has a first through-opening which is penetrated by a piston rod which is fastened to the control piston in a liquid-tight manner, and wherein the overflow chamber is connected via a line section of the overflow line to a region of the pressure line which is arranged upstream of the check valve and has a second through-opening which forms a valve seat, wherein the two through-openings are not equally large and the control piston can be loaded on its side facing the larger through-opening with a closing force of the closing spring.

In the high-pressure cleaning appliance according to the invention, the control chamber is divided by the control piston into a discharge pressure chamber and a spill chamber. Preferably, the control piston is surrounded in the circumferential direction by a sealing element, for example a sealing ring, which seals the discharge pressure chamber against the overflow chamber.

The discharge pressure chamber can be charged with the pressure prevailing in the pressure line downstream of the non-return valve. The outlet pressure space is connected to this end via a pressure channel to a region of the pressure line which is arranged downstream of the non-return valve. The overflow chamber constitutes an area of the overflow line. The overflow chamber is connected via a line section of the overflow line to a region of the pressure line which is arranged upstream of the non-return valve. The overflow chamber can thus be charged with the pressure prevailing upstream of the non-return valve in the pressure line.

During the discharge of the cleaning liquid, the pressure prevailing downstream of the non-return valve in the pressure line and upstream of the non-return valve in the pressure line is equally large, apart from the small pressure loss which the cleaning liquid undergoes when flowing through the non-return valve. During the discharge of the cleaning liquid, therefore, virtually the same pressure prevails in the discharge pressure chamber and the overflow chamber, wherein a first piston side of the control piston is acted upon by the pressure prevailing in the discharge pressure chamber, and wherein a second piston side of the control piston facing away from the first piston side is acted upon by the pressure prevailing in the overflow chamber.

According to the invention, the discharge pressure chamber has a first through opening which is penetrated in a liquid-tight manner by a piston rod which is fastened to the control piston. A piston rod extends from the control piston through the discharge pressure chamber to the first through opening. In this way, the area of the control piston that can be pressurized in the direction of the overflow chamber is reduced in the discharge pressure chamber. The larger the first through opening, the smaller the area that can be loaded with pressure, since this area is reduced due to the piston rod passing through the first through opening. This in turn results in a reduction of the pressure force acting on the control piston in the outlet pressure chamber, which pressure force is directed in the direction of the overflow chamber.

The overflow chamber likewise has a through opening, which is currently referred to as second through opening. The second through opening constitutes a valve seat of the overflow valve. During the delivery of the cleaning liquid, the closing body of the overflow valve rests against the valve seat. The closing body is connected to the control piston via a valve rod. The valve rod extends from the control piston through the overpressure chamber to the closing body which rests against the valve seat of the second through-opening. In this way, the area of the control piston that can be acted upon with pressure in the direction of the discharge pressure chamber is reduced in the overflow chamber, and therefore the pressing force acting on the control piston in the overflow chamber, which is directed in the direction of the discharge pressure chamber, is also reduced.

One of the two through openings is larger than the other through opening, for example the second through opening is larger than the first through opening according to the invention. The control piston is subjected to a smaller pressure load on the side facing the larger through opening than on the side facing the smaller through opening.

The resulting pressure load, which acts on the control piston and causes it to move, results from the difference in pressure loads, which act on the control piston in the discharge pressure chamber and the overflow chamber. The different sizes of the two through openings result in a resulting pressure load which urges the control piston in the direction of the larger through opening. This resultant pressure load acts against the closing force of a closing spring which loads the control piston on the side facing the larger through-opening.

The closing force required for reliably retaining the closing body in its closed position during the delivery of cleaning liquid can therefore be kept small. The only decisive factor for the required strength of the closing force is the difference between the pressing forces acting on the control piston in the outlet pressure chamber and the overflow chamber. What is important for this difference is again the difference in size between the two through openings. The smaller the difference in size, the smaller the closing force required.

The pressing force is related to the pressure of the cleaning liquid present in the pressure line. The greater the pressure, the greater the pressing force acting on the control piston. The closing force exerted by the closing spring on the control piston, unlike the pressing force, is independent of the pressure of the cleaning liquid. If the pressure in the pressure line exceeds a preset maximum value, the closing force exerted by the closing spring on the control piston is not sufficient to hold the control piston firmly, but instead the control piston moves under the effect of the pressure load and the closing body connected to the control piston via the valve stem lifts off the valve seat and releases the flow path from the pressure line through the overflow line, so that cleaning liquid flows out of the pressure line and the pressure in the pressure line can thereby be reduced.

In order to hold the closing body in its closed position, the closing spring merely has to apply a closing force to the control piston, which is rigidly connected to the closing body via the valve rod, which corresponds to the difference in the pressing forces acting on the control piston. This allows the use of a closing spring with a comparatively small overall size without the injector having to be arranged in the pressure line for this purpose. Due to the absence of an ejector, the flow losses of the cleaning liquid under pressure can be kept small in the high-pressure cleaning device according to the invention.

The closing spring is preferably arranged in the overflow chamber.

In an advantageous embodiment of the invention, the closing spring is clamped between the control piston and the valve seat element, wherein the valve seat element forms the second through-opening and the valve seat.

In a preferred embodiment of the invention, the control piston carries a valve rod on its side facing the second through-opening, wherein the valve rod passes through the overflow chamber and the second through-opening and carries the closing body on its region projecting from the overflow chamber, and wherein the valve seat is arranged on the side of the valve seat element facing away from the overflow chamber, and the closing body can be loaded against the closing force of the closing spring to the pressure of the cleaning liquid present in the overflow chamber. In this embodiment of the invention, the closing body is arranged on the side of the valve seat element facing away from the overflow chamber and is acted upon in the closed position by the second through-opening for the pressure prevailing in the overflow chamber. The pressure loading acts against the closing force of the closing spring. The pressure acting on the closing body acts on the control piston via the valve rod, so that the control piston receives both the pressing force acting directly on the control piston and the pressing force acting on the closing body.

Advantageously, the closing spring is configured as a helical spring surrounding the valve rod.

In an advantageous embodiment of the invention, the piston rod and the valve rod are of cylindrical design and have different diameters. In particular, it can be provided that the diameter of the piston rod is greater than the diameter of the valve rod.

It is particularly advantageous if a sliding sleeve is arranged in the control chamber, in which sliding sleeve the control piston is mounted in a displaceable manner. Preferably, the control piston has a sealing ring which bears in a fluid-tight manner against the sliding sleeve. The sealing ring which surrounds the control piston in the circumferential direction slides on the sliding sleeve along the latter during the movement of the control piston, and the friction between the sealing ring and the sliding sleeve can be kept small by suitable material selection. In the event of wear, the sliding sleeve can be replaced in a simple manner.

The sliding sleeve is preferably at least partially, in particular completely, made of a plastic material or of metal.

In a preferred embodiment of the invention, the control piston has a first piston part and a second piston part rigidly connected to the first piston part.

The two piston parts can advantageously be connected to each other in a releasable manner. In particular, it can be provided that the two piston parts can be screwed together.

The piston rod is advantageously arranged on the first piston part.

Preferably, the first piston part is integrally connected with the piston rod.

The first piston part and the piston rod are preferably constructed as a one-piece component from a metal or plastic material.

The valve stem is advantageously arranged on the second piston part.

It may be provided that the second piston part is integrally connected with the valve rod.

Alternatively, it may be provided that the second piston part is connected to the valve rod in a detachable or non-detachable manner. In particular, it can be provided that the second piston part can be screwed to the valve rod.

It is particularly advantageous to integrate a pressure relief valve in the control piston, which releases the flow path between the discharge pressure chamber and the overflow chamber as a function of the pressure difference between the pressure of the cleaning liquid present in the discharge pressure chamber and the pressure of the cleaning liquid present in the overflow chamber. If the pressure difference reaches a preset limit value, the pressure compensation can be performed by means of a pressure relief valve, which is opened. If the pressure difference is less than a preset limit value, the pressure relief valve is closed.

The outlet pressure chamber is connected via a pressure channel to a region of the pressure line which is arranged downstream of the non-return valve. The overflow chamber is connected via a first line section of the overflow line to a region of the pressure line which is arranged upstream of the non-return valve. Preferably, a second line section of the overflow line is connected to a valve seat of the overflow valve, and the flow connection between the overflow chamber and the second line section of the overflow line can be released and interrupted by the overflow valve as a function of the pressure of the cleaning liquid. The cleaning liquid placed under pressure can be conveyed to a liquid output device, such as a spray gun or spray bar, through a pressure line and a liquid output line coupled to a pressure connection of the high pressure cleaning apparatus. If the liquid outlet means is open, the cleaning liquid placed under pressure flows through the pressure line, wherein the non-return valve opens and the overflow valve closes. If the liquid outlet means is closed, the pressure of the cleaning liquid rises on account of the pump acting in the pressure line. If the pressure of the cleaning liquid exceeds a preset maximum value, the overflow valve opens and cleaning liquid can flow from the pressure line through the overflow line, for example to the suction line. The check valve is thereby moved into its closed position and thus interrupts the flow connection between the region of the pressure line arranged upstream of the check valve and the region of the pressure line arranged downstream of the check valve. In order to ensure that the region of the pressure line which is arranged downstream of the non-return valve also experiences a pressure drop, a pressure relief valve is preferably integrated into the control piston, which pressure relief valve is transferred into its open position on the basis of the high pressure prevailing in the pressure line downstream of the non-return valve and thus releases the flow connection between the discharge pressure chamber and the overflow chamber. The pressure of the cleaning liquid present downstream of the non-return valve can thereby be reduced by the cleaning liquid being able to flow from the region of the pressure line downstream of the non-return valve via the pressure channel, the discharge pressure chamber and the open pressure relief valve to the overflow chamber and from the overflow chamber via a second line section of the overflow line, for example to the suction line. Thus, when closing the liquid outlet means, the pressure in the liquid outlet line, e.g. a high-pressure hose, is reduced. This makes it easy for the user to subsequently open the liquid outlet means again.

The pressure relief valve integrated into the control piston preferably has a valve body which can be acted upon by a valve spring with a closing force, under the action of which the valve body bears against a valve seat. If the pressure of the cleaning liquid present downstream of the non-return valve in the pressure line exceeds a preset value, the valve body of the pressure relief valve is displaced against the action of the valve spring into an open position in which it releases the flow path between the discharge pressure chamber and the overflow chamber.

It is particularly advantageous if the pump has a valve chamber into which the overflow device with the overflow valve can be inserted in the form of a preassembled structural assembly. This makes the assembly of the high-pressure cleaning appliance easy. The pre-assembled assembly preferably has the valve seat element and the closing body of the overflow valve, the control piston and the piston rod, the valve rod and the closing spring, which is supported on the control piston on the one hand and on the valve seat element on the other hand. As already mentioned, the pressure relief valve can be integrated into the control piston.

Drawings

The following description of advantageous embodiments is provided to illustrate the invention in detail with reference to the accompanying drawings. Wherein:

figure 1 shows a schematic side view of a high pressure cleaning apparatus;

FIG. 2 shows a partial cross-sectional view of the pump of the high pressure cleaning apparatus of FIG. 1;

fig. 3 shows an enlarged view of the overflow of the pump from fig. 2, wherein the overflow is designed with a pre-assembled structural assembly and has an overflow valve.

Detailed Description

In the figures, an advantageous embodiment of a high-pressure cleaning appliance according to the invention is schematically shown and generally designated by reference numeral 10. The high-pressure cleaning appliance 10 has a motor 12 which drives a pump 14 and is designed in the embodiment shown as an electric motor. The pump 14 has a cylinder head 16, which forms a plurality of pump chambers, wherein, for a better overview, only one of the total three pump chambers is schematically illustrated in the drawing and is designated by reference numeral 18. A piston 20 is sunk into the pump chamber 18 and is driven by the motor 12 to reciprocate. The pump chamber 18 is connected to a suction connection 26 via an inlet valve 22 and a suction line 24, and the pump chamber 18 is connected to a pressure connection 32 via an outlet valve 28 and a pressure line 30.

In a conventional manner, a liquid carrying line, which is known per se and is therefore not shown for a better overview, for example a suction hose, can be coupled to the suction connection 26, via which the pump 12 can be carried cleaning liquid, preferably water, which is placed under pressure. In a conventional manner, a liquid outlet line, for example a high-pressure hose, which is known per se and is therefore not shown in the figures for a better overview, can be coupled to the pressure connection 32, which liquid outlet line has a closable liquid outlet means, for example a spray gun or a spray bar, at its free end. The liquid outlet means can be supplied with cleaning liquid via a liquid outlet line, which is put under pressure by means of a pump 14.

A check valve 34, which is preferably of springless design and has a check valve body 36, is arranged in the pressure line 30. The check valve body 36 can be placed in a liquid-tight manner with the sealing ring 38 in the middle on a check valve seat 40, and for the discharge of pressurized cleaning liquid, it can assume an open position, not shown in the drawings, in which it is arranged at a distance from the check valve seat 40.

The cylinder head 16 has a valve chamber 42 of stepped design, which can be closed in a fluid-tight manner by means of a closure plug 44, and into which an overflow 46 is inserted in the form of a preassembled structural unit.

The valve chamber 42 has an inwardly directed first step 48 at a distance from the closure plug 44, and the valve chamber 42 has an inwardly directed second step 50 at a distance from the first step 48.

The valve chamber 42 is of cylindrical design and accommodates a sliding sleeve 52 in the region between the closure plug 44 and the first step 48, which sliding sleeve rests against the wall of the valve chamber 42 with the interposition of a sealing ring 54. In the illustrated embodiment, the sliding sleeve 52 is made of a plastic material. The sliding sleeve may also be made of metal.

The sliding sleeve 52 encloses a control chamber 56 in the region between the closure plug 44 and the first step 48, which control chamber extends to the second step 50 and in which a control piston 58 is held so as to be movable parallel to a longitudinal axis 60 of the valve chamber 42. The control piston 58 has an annular groove extending upward on the outer circumference of the control piston 58, in which a second sealing ring 62 is arranged, which bears in a fluid-tight manner against the sliding sleeve 52.

The control piston 58 divides the control chamber 56 into a discharge pressure chamber 64 and a spill chamber 66. The outlet pressure chamber 64 is arranged between the control piston 58 and the closing plug 44 and is connected via a pressure channel 68 to a region of the pressure line 30 arranged downstream of the check valve 34.

The overflow chamber 66 is arranged between the control piston 58 and a valve seat element 70 arranged on the second step 50 and is connected via a first line section 72 of an overflow line 74 to a region of the pressure line 30 arranged upstream of the check valve 34. The second line section 76 of the overflow line 74 is coupled to the second step 50 of the valve chamber 42 and opens into the suction line 24.

The valve seat element 70 is surrounded by a third sealing ring 78 which bears in a liquid-tight manner against the wall of the valve chamber 42.

On its side facing the discharge pressure chamber 64, the control piston 58 has a piston rod 94, which is oriented coaxially with the longitudinal axis 60 of the valve chamber 42. The closure plug 44 has a first through opening 96 oriented coaxially with the longitudinal axis 60. The piston rod 94 passes through the discharge pressure chamber 64 and the first through opening 96, wherein the piston rod is surrounded by a fourth sealing ring 98. The piston rod 94 projects from the outlet pressure chamber 64 with a free end 100 facing away from the control piston 58.

The valve seat element 70 has a second through-opening 80, which is oriented coaxially to the longitudinal axis 60 of the valve chamber 42 and which forms a valve seat 82 of a relief valve 84 at its end facing the second line section 76 of the relief line 74. The closing body 86 of the overflow valve 84, which widens conically in the direction of the second line section 76, rests in the closed position shown in fig. 2 and 3 in a liquid-tight manner against the valve seat 82. The closing body 86 is rigidly connected to the control piston 58 via a valve rod 88. The valve rod 88 is oriented coaxially with the longitudinal axis 60, passes through the overflow chamber 66 and the second through-opening 80, and projects with its free end 90 facing away from the control piston 58 into the second line section 76 of the overflow line 74.

The valve rod 88 is surrounded by a closing spring 92, which is embodied as a helical spring, is clamped between the control piston 58 and the valve seat element 70 and loads the control piston 58 with a closing force.

The piston rod 94 is of cylindrical design like the valve rod 88, wherein the diameter of the piston rod 94 is greater than the diameter of the valve rod 88. The first through-opening 96 is of cylindrical design like the second through-opening 80. The diameter of the first through opening 96 is only slightly larger than the diameter of the piston rod, whereas the diameter of the second through opening 80 is significantly larger than the diameter of the valve rod 88. In the region of the second through-opening 80, the valve rod 88 is surrounded by an annular space 89, through which the annular surface 91 of the closing body 86 can be acted upon by the pressure of the cleaning liquid present in the overflow chamber 66. The diameter of the first through opening 96 is smaller than the diameter of the second through opening 80 and therefore also smaller than the diameter of the valve seat 82. The diameter of the first through opening 96 may be, for example, 4.0mm, and the diameter of the second through opening 80 and the valve seat 82 may be, for example, 4.3 mm.

The control piston 58 has a first piston portion 102 and a second piston portion 104. The first piston part 102 is connected integrally to the piston rod 94 and, together with the piston rod 94, forms a one-piece component made of metal or of a plastic material. The second piston part 104 forms an annular piston section 106 which has the second sealing ring 62 on its outer side and to which a piston skirt 108 is integrally coupled. The piston skirt 108 is rigidly connected to the valve stem 88 by a screw connection 110.

The first piston part 102 has a piston sleeve 112 which is inserted into the annular piston section 106 of the second piston part 104 and is detachably connected to the second piston part 104 by means of a screw connection with the interposition of a fifth sealing ring 114.

A pressure relief valve 116 is integrated into the control piston 58, which has a spherical valve body 118, which is pressed against a valve seat 122 by a valve spring 120.

The first piston part 102 has a first radial bore 124, to which a stepped axial bore 126 is coupled, which axially passes through the piston sleeve 112, the axial bore forming the valve seat 122. The discharge pressure chamber 64 is in flow connection with the overflow chamber 66 via a first radial bore 124, an axial bore 126 and a second radial bore 128 of the second piston part 104, wherein the flow connection can be released and interrupted by means of the spring-loaded valve body 118 depending on the pressure difference between the pressure of the cleaning liquid present in the discharge pressure chamber 64 and the pressure of the cleaning liquid present in the overflow chamber 66.

The first piston side 132 of the discharge pressure chamber 64 and thus also of the control piston 58 facing the discharge pressure chamber 64 can be acted upon by the pressure channel 68 for the pressure of the cleaning liquid present in the pressure line 30 downstream of the check valve 34. The overflow chamber 66 and thus also the second piston side 134 of the control piston 58 facing the overflow chamber 66 can be acted upon by the pressure of the cleaning liquid present upstream of the check valve 34 via the first line section 72 of the overflow line 74. The pressure of the cleaning fluid acting on the first piston side 132 exerts a first pressing force on the control piston 58, which is oriented parallel to the longitudinal axis 60 and is directed opposite the closing force of the closing spring 92, and the pressure of the cleaning fluid acting on the second piston side 134 exerts a second pressing force on the control piston 58, which is oriented parallel to the longitudinal axis 60 and is directed opposite the first pressing force. In addition, the control piston 58 is acted upon in the closed position of the closing body 86 with a pressing force resulting from the action of the pressure which acts on the annular surface 91 in the closed position of the closing body 86 and is transmitted to the control piston 58 via the valve rod 88.

If cleaning liquid under pressure is output by the high-pressure cleaning appliance 10, the check valve 34 opens and the pressure of the cleaning liquid present upstream of the check valve 34 in the pressure line 30 and downstream of the check valve 34 in the pressure line 30 is as great, except for the small pressure loss which the cleaning liquid suffers in the pressure flow of the springless check valve 34. Thus, in the discharge pressure chamber 64, in fact, the same pressure is present as in the overflow chamber 66, and the pressing force acting on the control piston 58 is determined by the size of the first piston side 132 and the second piston side 134 and the size of the annular surface 91 of the closing body 86, which is acted on by the pressure present in the overflow chamber 66. The valve seat 82 of the overflow valve 84 has a larger diameter than the first through opening 96, whereas the two

piston sides

132, 134 are equally large. This results in the control piston 58 being loaded with a resulting differential pressure which is directed counter to the closing force of the closing spring 92. The closing spring 92 acts counter to the direction of the differential pressure acting, so that the closing body 86 reliably assumes its closed position during the discharge of the pressurized cleaning liquid and thus interrupts the flow connection from the pressure line 30 to the suction line 24 via the overflow line 74. The closing force of the closing spring 92 required for this purpose is comparatively small, so that the closing spring 92 can have a small overall size.

If the output of cleaning liquid put under pressure is interrupted, increased pressure builds up in the pressure lines upstream and downstream of the check valve 34 as long as the pump 14 is not switched off. The increased pressure of the cleaning liquid acts via the pressure channel 68 and the discharge pressure chamber 64 on the first piston side 132 and via the first line section 72 of the overflow line 74 and the overflow chamber 66 on the second piston side 134, and the annular surface 91 of the closing body 86 which can be acted on by the pressure of the cleaning liquid present in the overflow chamber 66. The increased pressure of the cleaning liquid results in an increased differential pressure which acts counter to the closing force of the closing spring 92. If the pressure in the pressure line 30 exceeds a predetermined maximum value, the control piston 58 is moved in the direction of the valve seat element 70 against the closing force of the closing spring 92, so that the closing body 86 is lifted from the valve seat 82 and assumes the open position. Starting from the region of the pressure line 30 which is arranged upstream of the check valve 34, the flow connection to the suction line 24 is thus released via the overflow line 74 and the open overflow valve 84. The pressure of the cleaning liquid present in the pressure line upstream of the check valve 34 is significantly reduced. Due to the pressure drop in the region upstream of the check valve 34, the check valve 34 closes, so that a higher pressure prevails in the discharge pressure chamber 64 than in the overflow chamber 66. This results in the pressure relief valve 116 being opened by: the valve body 118 lifts off the valve seat 122 against the force of the valve spring 120 and thereby releases the flow path from the discharge pressure chamber 64 to the spill chamber 66 through the first radial bore 124, the axial bore 126 and the second radial bore 128. Thus, in the region of the pressure line 30 arranged downstream of the check valve 34, the pressure can also be reduced. This allows, in particular, a reduction in the pressure in the liquid outlet line coupled to the pressure connection 32.

Since only the springless check valve 34 is arranged in the pressure line 30, but no additional throttle point in the form of an injector is arranged, the cleaning liquid is subjected to only a small pressure loss when flowing through the pressure line 30. This reduces the energy consumption of the high-pressure cleaning appliance 10 when delivering cleaning liquid.

As already mentioned, the closing spring 92 can have a small overall size. This allows the overall size of the overflow 46 to be kept small, wherein the overflow 46 can be inserted into the valve chamber 42 in the form of a preassembled structural unit. This also simplifies the assembly of the high-pressure cleaning appliance 10.

Claims

1. High-pressure cleaning device (10) having a pump (14) for delivering a cleaning liquid, wherein the pump (14) has a suction line (24) and a pressure line (30), and a check valve (34) is arranged in the pressure line (30), and wherein the pump (14) has a relief valve (84) which, as a function of the pressure of the cleaning liquid present in the pressure line (30), releases a flow path through a relief line (74) for the cleaning liquid to flow out of the pressure line (30), wherein the relief valve (84) has a closing body (86) which, in a closed position, rests liquid-tightly against a valve seat (82), which can be moved against the closing force of a closing spring (92) into an open position spaced apart from the valve seat (82), and which is held movably in a control chamber (56) and can be moved by a valve stem (88) A control piston (58) which is charged with cleaning liquid under pressure, characterized in that the control piston (58) divides the control chamber into a discharge pressure chamber (64) and an overflow chamber (66), wherein the discharge pressure chamber (64) is connected via a pressure channel (68) to a region of the pressure line (30) which is arranged downstream of the check valve (34) and has a first through opening (96) which is passed through by a piston rod (94) which is fastened in a liquid-tight manner on the control piston (58), and wherein the overflow chamber (66) is connected via a line section (72) of the overflow line (74) to a region of the pressure line (30) which is arranged upstream of the check valve (34) and has a second through opening (80) which forms the valve seat (82), wherein the two through-openings (96, 80) are not equally large and the control piston (58) can be loaded on its side facing the larger through-opening with the closing force of the closing spring (92).

2. A high-pressure cleaning appliance according to claim 1, characterized in that the closing spring (92) is arranged in the overflow chamber (66).

3. High pressure cleaning device according to claim 1, wherein the closing spring is clamped between the control piston (58) and a valve seat element (70) configuring the second through opening (80) and the valve seat (82).

4. High-pressure cleaning device according to claim 3, characterized in that the control piston (58) carries the valve rod (88) on its side (134) facing the second through-opening (80), wherein the valve rod (88) passes through the overflow chamber (66) and the second through-opening (80) and carries the closing body (86) on the region of the valve rod protruding from the overflow chamber (66), and wherein the valve seat (82) is arranged on the side of the valve seat element (70) facing away from the overflow chamber (66), and the closing body (86) is loadable against the closing force of the closing spring (92) to the pressure of the cleaning liquid present in the overflow chamber (66).

5. High-pressure cleaning device according to claim 1, 2, 3 or 4, characterized in that the piston rod (94) and the valve rod (88) are cylindrically designed and have different diameters.

6. High-pressure cleaning device according to claim 1, 2, 3 or 4, characterized in that a sliding sleeve (52) is arranged in the control chamber (56), in which sliding sleeve the control piston (58) is movably supported.

7. High pressure cleaning device according to claim 1, 2, 3 or 4, characterized in that the control piston (58) has a first piston part (102) and a second piston part (104) rigidly connected to the first piston part (102).

8. The high pressure cleaning apparatus according to claim 7, characterized in that the first piston portion (102) is integrally connected with the piston rod (94).

9. The high pressure cleaning apparatus according to claim 7, wherein the second piston portion (104) is detachably or non-detachably connected to the valve stem (88).

10. The high pressure cleaning apparatus according to claim 7, wherein the second piston portion (104) is screw-connected to the valve stem (88).

11. High-pressure cleaning device according to claim 1, 2, 3 or 4, characterized in that a pressure relief valve (116) is integrated in the control piston (58), which relief valve releases the flow path between the discharge pressure chamber (64) and the overflow chamber (66) in dependence on the pressure difference between the pressure prevailing in the discharge pressure chamber (64) and the pressure prevailing inside the overflow chamber (66).

12. A high-pressure cleaning appliance according to claim 11, characterized in that the pressure relief valve (116) has a valve body (118) which can be loaded by a valve spring (120) with a closing force under the effect of which the valve body (118) bears against a valve seat (122).

13. The high-pressure cleaning appliance according to claim 1, 2, 3 or 4, characterized in that the pump (14) has a valve chamber (42) into which an overflow device (46) with the overflow valve (84) can be inserted in the form of a preassembled structural assembly.