PISTON PUMP FOR A HIGH-PRESSURE CLEANING DEVICE

Description

[0001] The invention relates to a piston pump for a high-pressure cleaning device for conveying a cleaning fluid with the features of the preamble of claim 1.

[0002] Piston pumps for a high-pressure cleaning device for pumping a cleaning fluid are known from DE 10 2009 049 095 A1. The piston pumps have a pump housing comprising a first housing part and a second housing part, each made of metal, wherein the first housing part forms a suction line and a pressure line, and wherein the second housing part forms several pump chambers into which a reciprocating piston is immersed and which are in flow communication with the suction line via an inlet channel and with the pressure line via an outlet channel, wherein the inlet channel can be closed by an inlet valve and the outlet channel by an outlet valve, wherein the inlet valve has a first insert part inserted into the inlet channel and an inlet closing element that is movable back and forth relative to the first insert part.wherein the first insert has an inlet valve seat and a guide member arranged offset from the inlet valve seat, and wherein the inlet closing element has an inlet valve disc that can be sealed against the inlet valve seat and an inlet valve stem adjoining the inlet valve disc, which is slidably mounted on the guide member. Using the piston pumps, a cleaning fluid, for example water, supplied via the suction line can be pressurized and discharged via the pressure line. A pressure hose, for example, can be connected to the pressure line, which has a nozzle head at its free end through which the pressurized cleaning fluid can be directed onto an object. The piston pump is driven by a drive motor.which, for example, is coupled to the pistons of the piston pump via a swashplate drive, driving them into a reciprocating stroke. The reciprocating motion of the pistons, each immersed in a pump chamber, results in a periodic increase and decrease in the volume of the pump chambers, so that cleaning fluid is drawn into the pump chambers through the inlet channels and discharged under pressure through the outlet channels. The pressure can be, for example, at least 80 bar. To withstand the pressure load, the pump housing has a first and a second housing section, each made of metal. The first housing section forms the suction line and the discharge line, and the second housing section forms the pump chambers as well as the inlet and outlet channels through which the pump chambers are connected to the suction line and the discharge line, respectively.

[0003] The inlet ports are each closable by an inlet valve, and the outlet ports are each closable by an outlet valve. DE 10 2009 049 095 A1 proposes inlet valves, each comprising an insert and an inlet closing element that is slidable relative to it. The insert forms an inlet valve seat and a guide element offset from the inlet valve seat in the direction of the associated pump chamber. The inlet closing element has an inlet valve disc that seals against the inlet valve seat and an inlet valve stem extending from this disc in the direction of the associated pump chamber, which is slidably mounted on the guide element. The insert is typically made of stainless steel and pressed into the inlet port or held in it by flanging to prevent rotation and axial displacement. This involves considerable manufacturing costs.

[0004] In the piston pump known from DE 10 2009 049 095 A1, the guide element and the inlet valve stem, which is slidably mounted on it, are arranged downstream of the inlet valve seat with respect to the flow direction of the cleaning fluid. This increases the volume of the pump chamber that cannot be displaced by the piston when moving towards the inlet valve seat, i.e., the so-called dead space. This, in turn, impairs the suction performance of the piston pump.

[0005] Piston pumps for high-pressure cleaning equipment are known from WO 2008 / 086950 A1 and EP 2 805 050 B1, in which the two housing parts of the pump housing are made of a plastic material. This allows the inlet valve seat to be molded directly into a housing part that also forms a guide element for the inlet closing element, with the guide element being arranged upstream of the inlet valve seat. However, pump housings made of a plastic material have a lower pressure resistance than pump housings formed from metal parts.

[0006] A piston pump with the features of the preamble of claim 1 is known from DE 198 01 146 C1.

[0007] The object of the present invention is to further develop a piston pump of the type mentioned at the outset in such a way that it can be manufactured more cost-effectively and has improved suction behavior.

[0008] This problem is solved by a piston pump with the features of claim 1.

[0009] The pump housing of the piston pump according to the invention comprises two housing parts, each made of metal and therefore exhibiting very high pressure resistance. The second housing part forms inlet channels into which a first insert made of a plastic material is inserted. The first insert has an annular inlet valve seat body, which faces the associated pump chamber and forms the inlet valve seat. With respect to the flow direction of the cleaning fluid upstream of the inlet valve seat body, i.e., offset towards the suction line from the inlet valve seat body, the first insert forms a guide element on which the inlet closing element is slidably mounted.The first insert, made of plastic, allows for the cost-effective provision of an inlet valve seat without requiring extensive post-processing of the second housing part, which is made of metal. Since the first insert is made of plastic, its manufacturing costs are relatively low. The first insert can be inserted into the inlet channel from the side of the inlet channel facing the associated pump chamber, so that the guide element formed by the first insert occupies a position upstream of the inlet valve seat. This makes it possible to keep the volume not displaced by the piston, i.e., the so-called dead space, very small. The piston pump according to the invention is therefore characterized by relatively low manufacturing costs and improved suction performance.

[0010] The first insert has at least one retaining arm that connects to the intake valve seat body in the direction of the suction line and is held rotationally fixed relative to the intake port. In the embodiment according to the invention, the first insert has at least one retaining arm upstream of the intake valve seat body. The retaining arm allows the first insert to be easily fixed to the intake port. The at least one retaining arm extends into the intake port.

[0011] Preferably, at least one retaining arm extends through the inlet channel.

[0012] The first insert part forms a single-piece molded plastic part.

[0013] The first housing part and / or the second housing part is preferably designed as a die-cast part or as a formed part.

[0014] Preferably, the first housing part and / or the second housing part is made of an aluminum or brass material.

[0015] It is advantageous if the intake valve seat body protrudes from the intake channel in the direction of the pump chamber.

[0016] It is advantageous if the second housing part forms an annular first support surface extending towards the pump chamber and adjoining the inlet port, which is oriented perpendicular to the longitudinal axis of the inlet port and against which the inlet valve seat body rests with a contact surface. With such a design, the inlet valve seat body is supported by the first support surface of the second housing part.

[0017] Preferably, the inlet valve seat body has a sealing ring receptacle adjoining the contact surface, in which a sealing ring is arranged that seals the inlet valve seat body axially against the first support surface. With respect to the longitudinal axis of the inlet port, the sealing ring arranged between the inlet valve seat body and the first support surface of the second housing part forms a seal acting in the axial direction. This has the advantage that any grooves oriented parallel to the longitudinal axis of the inlet port, which may occur during the manufacture of the second housing part, do not impair the sealing effect of the sealing ring. Such grooves can occur particularly when the second housing part is designed as a die-cast part, during whose manufacture demolding is carried out.Any grooves that occur during demolding extend in the demolding direction, meaning they extend parallel to the longitudinal axis of the inlet channel, but not parallel to the first support surface, as this is oriented perpendicular to the longitudinal axis of the inlet channel. Therefore, grooves that occur during demolding of the second housing part cannot impair the axially acting seal.

[0018] In an advantageous embodiment of the piston pump according to the invention, the sealing ring receptacle forms an annular groove circumferentially surrounding the inlet valve seat body, with a first groove wall adjoining the contact surface, to which a second groove wall adjoins. The outer diameter of the inlet valve seat body increases from the second groove wall as it approaches the contact surface. This increasing outer diameter towards the contact surface reduces the risk of the sealing ring inserted into the receptacle unintentionally becoming dislodged during the assembly of the first insert. Furthermore, this design allows the contact surface to be relatively large.

[0019] The first groove wall can, for example, be designed in the form of a cone, wherein the cone angle is preferably about 10° to about 30°, preferably about 15° to about 25°, and in particular about 20°.

[0020] It is advantageous if the outer diameter of the inlet valve seat body increases continuously across the second groove wall with increasing distance from the contact surface. With such a design, the sealing ring receptacle is shaped like a circumferential groove into which a sealing ring can be inserted without the risk of the sealing ring detaching from the receptacle when the first insert is placed into the inlet port.

[0021] Advantageously, the first insert is held rotationally fixed and axially immovable relative to the inlet channel.

[0022] For example, it may be provided that the first insert part can be locked into the second housing part.

[0023] It is particularly advantageous if at least one retaining arm engages behind the inlet channel on its side facing the suction line. This ensures that the first insert, after being inserted into the inlet channel from the side facing the associated pump chamber to such an extent that at least one retaining arm engages behind the inlet channel on the side facing away from the pump chamber, cannot subsequently be easily removed from the inlet channel.

[0024] In a preferred embodiment of the invention, the at least one retaining arm is materially bonded to the inlet valve seat body. In such an embodiment, the at least one first retaining arm, together with the inlet valve seat body, forms a one-piece molded plastic part.

[0025] Preferably, the first insert has two retaining arms that are diametrically opposed to each other with respect to the longitudinal axis of the inlet channel. The two retaining arms allow for a mirror-symmetrical and therefore highly load-bearing design of the first insert.

[0026] As already mentioned, the inlet closing element has an inlet valve stem that is slidably mounted on a guide member of the first insert part. It is advantageous if the guide member is fixed to at least one retaining arm.

[0027] Preferably, the guide element is materially bonded to the at least one retaining arm. In such a design, the guide element, together with the at least one retaining arm and preferably together with the inlet valve seat body, forms a one-piece molded plastic part.

[0028] It is advantageous if at least one retaining arm has an end section facing away from the inlet valve seat body, which dips into a recess in the second housing part.

[0029] In particular, it can be provided that the end section of the at least one retaining arm forms a positive fit with the recess of the second housing part. This makes it easy to fix the first insert part to the second housing part in a rotationally fixed manner.

[0030] It is particularly advantageous if the end section of the at least one retaining arm is thermoformable. This allows the at least one retaining arm to be easily reshaped by thermal treatment after it has been inserted into the inlet channel from the side of the inlet channel facing the associated pump chamber. For this purpose, the at least one retaining arm can be made of a thermoformable plastic material.

[0031] The at least one retaining arm can, for example, be designed in a straight line before being inserted into the inlet channel and can be thermally reshaped into a curved or angled shape after being inserted into the inlet channel.

[0032] For example, it may be provided that the end section of the at least one retaining arm facing away from the inlet valve seat body is thermally deformed radially outwards after the retaining arm is inserted into the inlet channel, so that the end section is directed outwards after the thermal deformation with respect to the longitudinal axis of the inlet channel and engages behind the inlet channel on the side facing away from the pump chamber.

[0033] Preferably, the first insert part consists of a POM material (polyoxymethylene material).

[0034] The inlet valve assembly comprises the inlet valve disc and the inlet valve stem, which adjoins the inlet valve disc on its side facing away from the pump chamber. The inlet valve disc can be sealed against the inlet valve seat of the first insert, and the inlet valve stem is slidably mounted on the guide element of the first insert. Preferably, the inlet valve disc is metallurgically bonded to the inlet valve stem.

[0035] The guide element is preferably designed in a ring shape.

[0036] It is advantageous if the inlet valve stem extends through the guide member and protrudes from the guide member in the direction of the suction line.

[0037] The valve stem section has a spring retainer attached to it, with an inlet valve spring clamped between the spring retainer and the guide member. The inlet valve spring, supported on one side by the spring retainer and on the other by the guide member, exerts a spring force on the inlet valve stem and, consequently, on the inlet valve head. This force presses the inlet valve head against the inlet valve seat. During a suction movement of the piston as it enters the pump chamber, the inlet valve head can lift off the inlet valve seat against the force of the inlet valve spring, allowing cleaning fluid to flow from the suction line through the inlet valve into the pump chamber.If the piston performs an opposing pressure movement, the inlet valve disc is pressed against the inlet valve seat by the inlet valve spring, so that the cleaning fluid cannot flow back into the suction line via the inlet valve.

[0038] In an advantageous embodiment of the invention, the guide member forms a stop that limits the movement of the intake valve stem towards the pump chamber and thus also the movement of the intake valve head towards the pump chamber. As the intake valve stem moves towards the pump chamber, the spring retainer fixed to the intake valve stem increasingly approaches the guide member and finally comes into contact with its stop, thus preventing further movement of the intake valve stem towards the pump chamber and consequently also preventing further lifting of the intake valve head from the intake valve seat.

[0039] A further reduction in the manufacturing costs of the piston pump according to the invention is achieved in an advantageous embodiment by having the second housing part have a valve receptacle into which the outlet channels open, and by having the piston pump have an outlet valve assembly that forms all the outlet valves. The outlet valve assembly has a second insert, made of a plastic material, which is inserted into the valve receptacle and has several annular outlet valve seat bodies, each forming an outlet valve seat. In such an embodiment, the second housing part, which is designed as a metal part, has a valve receptacle. A second insert of an outlet valve assembly is inserted into the valve receptacle.The second insert consists of a plastic material and has several annular exhaust valve seat bodies, each forming an exhaust valve seat aligned with an exhaust port. The exhaust valve seats are thus provided by the second insert, eliminating the need for complex post-processing of the second housing part, which is made of metal. A single second insert is used, which incorporates all the exhaust valve seats of the piston pump according to the invention. This simplifies the assembly of the piston pump.

[0040] Preferably, the valve receptacle is arranged on the side of the second housing part facing the first housing part.

[0041] The exhaust valve assembly is advantageously designed as a pre-assemblable unit. This allows the exhaust valve assembly, which comprises all the exhaust valves, to be assembled as a self-contained, manageable unit before the assembly of the complete piston pump. The exhaust valve assembly can be assembled at a first assembly location and then transported to a second assembly location where the complete piston pump is assembled.

[0042] In a preferred embodiment of the invention, the second housing part forms several annular secondary support surfaces in the area of ​​the valve receptacle. These surfaces are oriented perpendicular to a longitudinal axis of the valve receptacle and, in the direction of flow of the cleaning fluid, each connect to an outlet channel. An outlet valve seat body rests against each of these secondary support surfaces with a sealing ring interposed between them. The perpendicular orientation of the secondary support surfaces allows the sealing rings resting against them to be designed as axial seals. This ensures that any grooves that may occur during the manufacture of the second housing part in the area of ​​the valve receptacle and are oriented parallel to the longitudinal axis of the valve receptacle do not impair the sealing effect of the sealing rings. Such grooves can occur particularly when the second housing part is designed as a die-cast part, during which demolding is performed.Any grooves that occur during demolding in the area of ​​the valve receptacle extend in the demolding direction, meaning they extend parallel to the longitudinal axis of the valve receptacle, but not parallel to the second support surfaces, as these are oriented perpendicular to the longitudinal axis of the valve receptacle. Therefore, any grooves that occur during demolding of the second housing part in the area of ​​the valve receptacle cannot impair the axially acting seal.

[0043] Preferably, the second support surfaces are connected to an outlet channel in the direction of flow of the cleaning fluid.

[0044] It is advantageous if each exhaust valve has an exhaust closing element that is movable back and forth relative to the second insert. This element comprises an exhaust valve disc that seals against an exhaust valve seat and an exhaust valve stem that extends away from the exhaust port. With respect to the flow direction of the cleaning fluid, the exhaust valve stem is positioned downstream of the exhaust valve seat. This further reduces the dead space in the associated pump chamber and thus improves the suction performance of the piston pump.

[0045] Preferably, the exhaust valve assembly comprises a guide body made of a plastic material and featuring several guide elements, each of which holds an exhaust valve stem slidably mounted. In this design, all exhaust valve stems are guided by the guide body. This further simplifies the assembly of the piston pump.

[0046] The guide body has several guide elements, each of which guides an exhaust valve stem of an exhaust closing element. In a preferred embodiment of the invention, the guide elements each form a guide recess into which an exhaust valve stem dips.

[0047] It is advantageous if the guide mounts each have at least one internal groove extending longitudinally along the guide mount. Cleaning fluid can escape from the respective guide mount via this internal groove.

[0048] An exhaust valve spring is advantageously clamped between each of the guide elements and the exhaust valve head. The exhaust valve spring allows the exhaust valve head to be pre-tensioned towards the corresponding exhaust valve seat.

[0049] In an advantageous embodiment of the invention, the guide body can be detachably and fluid-tightly connected to the second insert. This allows the exhaust valve assembly to be designed as a pre-assembled unit in a particularly simple manner. In a first assembly step, the exhaust valve stems can each be inserted into a guide recess of the guide body, wherein the exhaust valve stems, in their area protruding from the guide recesses, are surrounded by an exhaust valve spring, which is supported on one side by a guide recess and on the other side by an exhaust valve head. The guide body can then be fluid-tightly connected to the second insert, preferably with an interposed sealing ring. In a subsequent assembly step, the second insert, connected to the guide body, can be inserted into the valve recess of the second housing part.The two housing parts of the pump housing can then be joined together.

[0050] Preferably, the guide body is connectable to the second insert part in a pluggable manner. For example, it can be provided that the guide body can be plugged into the second insert part with at least one sealing ring in between.

[0051] It is particularly advantageous if the guide body forms a check valve seat for a central check valve located downstream of the exhaust valves. In such a design, the second insert forms the valve seats of the exhaust valves, and the guide body forms the valve seat of the central check valve. This further simplifies the assembly of the piston pump. A check valve closing element can be positioned directly downstream of the check valve seat formed by the guide body and can be biased towards the check valve seat by a check valve spring.

[0052] The central check valve is preferably located in the pressure line.

[0053] It can be provided that the first housing part has a housing recess aligned with the valve receptacle of the second housing part, into which the guide body immerses with at least one sealing ring interposed. In such a design, the exhaust valve assembly occupies a position between the first housing part and the second housing part, wherein the first housing part has a housing recess on its side facing the second housing part, into which the guide body immerses, and wherein the second housing part has a valve receptacle on its side facing the first housing part, aligned with the housing recess, into which the second insert is inserted.The guide body is connected to the first housing part in a liquid-tight manner, and the second insert part is connected to the second housing part in a liquid-tight manner, and furthermore, the guide body and the second insert part are connected to each other in a liquid-tight manner.

[0054] The pressure line is advantageously connected to the outlet valve assembly in the direction of flow of the cleaning fluid.

[0055] It is advantageous if the at least one sealing ring, which is arranged between the guide body and the housing recess of the first housing part, surrounds the guide body in the circumferential direction.

[0056] It is particularly advantageous if the guide body has an outwardly projecting annular projection to which a step in the housing recess, directed radially inward relative to the longitudinal axis of the housing recess, is associated, with a sealing ring arranged between the annular projection and the step. The sealing ring can form an axial seal, so that grooves which may occur during the manufacture of the first housing part in the area of ​​the housing recess and which are aligned parallel to the longitudinal axis of the housing recess, do not impair the sealing effect of the sealing ring. Such grooves can occur particularly if the first housing part is designed as a die-cast part, during whose manufacture demolding is carried out.Any grooves that form during demolding in the area of ​​the housing recess extend in the demolding direction, meaning they extend parallel to the longitudinal axis of the housing recess, but not parallel to the radially inward-facing step. Therefore, any grooves that form during demolding of the first housing part in the area of ​​the housing recess cannot impair the axially acting seal.

[0057] The following description of a preferred embodiment of the invention, in conjunction with the drawing, serves for further explanation. The drawing shows: Figure 1: a sectional view of a piston pump; Figure 2: an enlarged partial view of the piston pump made of Figure 1 Figure 3: an enlarged sectional view of detail X from Figure 2, which shows an exhaust valve assembly of the piston pump; Figure 4: a perspective view of a second housing part of the piston pump; Figure 5: an enlarged sectional view of detail Y from Figure 2 , which shows an inlet valve of the piston pump; Figure 6: a sectional view of the inlet valve made of Figure 5 along line 6-6; Figure 7: a perspective view of a first insert part of the inlet valve made of Figure 5 before its assembly; Figure 8: a sectional view of the first insert made of Figure 7 Figure 9: a perspective view of the first insert of the inlet valve after its installation; Figure 10: a sectional view of the first insert made of Figure 9 Figure 11: a sectional view of the exhaust valve assembly made of Figure 3 .

[0058] The drawing schematically illustrates an advantageous embodiment of a piston pump according to the invention for a high-pressure cleaning device, and is designated by reference numeral 10. A cleaning fluid, preferably water, can be pumped by means of the piston pump 10. The piston pump 10 comprises a pump housing 12 with a first housing part 14 and a second housing part 16. Both housing parts 14 and 16 are made of metal. In the illustrated embodiment, they are each made of die-cast aluminum.

[0059] The first housing part 14 defines the front 18 of the piston pump 10 and forms a suction line 20 and a pressure line 22. The second housing part 16 forms three pump chambers, each containing a piston. For clarity, only one pump chamber 24 and two pistons 26, 28 are shown in the drawing. All pistons are oscillatingly inserted into their respective pump chambers 24 by a swashplate (not shown in the drawing) and pushed back out of the pump chambers by a helical spring 30 surrounding each piston, causing the volume of the pump chambers 24 to change periodically.

[0060] Each pump chamber 24 is connected to the suction line 20 via an inlet channel 32 of the second housing part 16. Each pump chamber 24 is connected to the pressure line 22 via an outlet channel 34 of the second housing part 16. The inlet channels 32 are aligned parallel to each other and each has a longitudinal axis 33.

[0061] Adjoining the inlet channels 32 on the side facing the suction line 20 are two diametrically opposed recesses 36, 38 of the second housing part 16. This is particularly evident from Figure 4 clearly. In the direction of the pump chambers 24, an annular first support surface 40 adjoins each of the inlet channels 34. This support surface is formed by the second housing part 16 and faces the respective pump chamber 24. This is particularly evident from Figure 2 and 5 clearly. The first support surfaces are aligned perpendicular to the longitudinal axes 33.

[0062] Cleaning fluid to be pressurized can be drawn into the respective pump chamber 24 via the inlet channels 32, and the cleaning fluid can be discharged from the pump chambers 24 via the outlet channels 34. The outlet channels 34 open into a central valve receptacle 42 of the second housing part 16, which is circumferentially bounded by a cylinder wall 44. The valve receptacle 42 is located on the side of the second housing part 16 facing the first housing part 14 and has a longitudinal axis 43 that is aligned parallel to the longitudinal axes 33 of the inlet channels 32.

[0063] The first housing part 14 has a housing recess 46 on its side facing the second housing part 16, which is aligned with the valve receptacle 42 of the second housing part 16 and to which the pressure line 22 connects in the direction of the front side 18 of the first housing part 14.

[0064] A bypass line 48 branches off from the housing recess 46. This bypass line is formed by the first housing part 14 and contains a bypass valve 50, which is known per se and therefore only shown schematically in the drawing. The bypass line 48 establishes a flow connection between the housing recess 46 and the suction line 20 and can be closed by means of the bypass valve 50.

[0065] The inlet ports 32 can each be closed by an inlet valve 52. The inlet valves 52 are identical in design and each has a first insert 54 made of a plastic material, preferably a POM material, which is inserted into an inlet port 32. Furthermore, the inlet valves 52 each have an inlet closing element 56 which is axially movable back and forth relative to the first insert 54.

[0066] The first insert part 54 has an inlet valve seat body 60, which forms an inlet valve seat 62 of the respective inlet valve 52. The inlet valve seat body 60 projects into the respective pump chamber 24 and is supported with a contact surface 64 facing away from the respective pump chamber 24 on the first support surface 40 adjoining the respective inlet channel 32 in the direction of the pump chamber 24.

[0067] Adjoining the contact surface 64 is a sealing ring receptacle 66 in the form of an annular groove 68, which extends over the circumference of the inlet valve seat body 60 and has a first groove wall 70 directly adjacent to the contact surface 64 and a second groove wall 72 adjoining the first groove wall 70. The outer diameter of the inlet valve seat body 60 decreases continuously with increasing distance from the contact surface 64 via the first groove wall 70, and the outer diameter of the inlet valve seat body 60 increases continuously with increasing distance from the contact surface 64 via the second groove wall 72. This is particularly evident from the Figure 7 and 9 clearly.

[0068] The sealing ring receptacle 66 accommodates a first sealing ring 74, which seals the inlet valve seat body 60 against the first support surface 40 in the axial direction.

[0069] Adjoining the inlet valve seat body 60 of the first insert part 54 in the direction of the suction line 20 are two retaining arms 76, 78, diametrically opposed to each other with respect to the longitudinal axis 33 of the inlet channel 32. These arms extend through the inlet channel 34 and each has an end section 80, 82 facing away from the inlet valve seat body 60. This end section projects out of the inlet channel 32 on the side facing away from the pump chamber 24 and, when the inlet valve 52 is installed, engages behind the respective inlet channel 32 by immersing itself in a recess 36, 38 of the second housing part 16 and forming a positive connection with it. This will be explained in more detail below.

[0070] The retaining arms 76, 78 accommodate an annular guide element 84 between them in the area of ​​the inlet channel 32. The outer diameter of the guide element 84 is smaller than the diameter of the inlet channel 32. This allows the cleaning fluid to flow around the guide element 84 within the inlet channel 32.

[0071] The guide member 84 is materially bonded to the retaining arms 76, 78, and the retaining arms 76, 78 are materially bonded to the inlet valve seat body 60.

[0072] In the illustrated embodiment, the first insert part 54 forms a one-piece plastic molded part that defines the inlet valve seat body 60, the retaining arms 76, 78 and the guide member 84.

[0073] The inlet valve body 56 has an inlet valve disc 88 and an inlet valve stem 90, which is integrally connected to the inlet valve disc 88 on the side facing away from the pump chamber 24. The inlet valve disc 88 can be sealed against the inlet valve seat 62 of the inlet valve seat body 60, and the inlet valve stem 90 extends through the guide element 84 towards the suction line 20.

[0074] A spring retainer 94 is fixed to a stem section 92 of the intake valve stem 90, which projects from the guide member 84 towards the suction line 20. An intake valve spring 96 is clamped between the spring retainer 94 and the guide member 84. The intake valve spring 96 is designed as a coil spring, which is supported on one side by the spring retainer 94 and on the other side by the guide member 84, and surrounds the intake valve stem 90 circumferentially in the area between the guide member 84 and the spring retainer 94. Under the action of the intake valve spring 96, the intake valve head 88, which is integrally connected to the intake valve stem 90, is pressed against the intake valve seat 62 of the intake valve seat body 60, so that the intake valve 52 assumes its closed position.

[0075] When the piston 26, 28, immersed in the respective pump chamber 24, moves in the direction away from the inlet channel 32, the inlet valve 52 opens. This occurs when the inlet valve head 88 lifts off the inlet valve seat 62 against the spring force of the inlet valve spring 96, thereby creating a flow connection from the suction line 20 to the pump chamber 24. This allows cleaning fluid to flow from the suction line 20 into the pump chamber 24 via the inlet channel 32. The cleaning fluid can flow around the spring retainer 94, the inlet valve spring 96, and the guide element 84 on the outside, thus minimizing flow losses.

[0076] The intake valve head 88 can lift off the intake valve seat 62 until the spring retainer 94 comes to rest against a stop 98 of the guide member 84, which is designed as a projection or sleeve. The stop 98 thus limits the stroke of the intake valve head 96.

[0077] When the piston 26, 28 moves towards the intake port 32, the intake valve plate 88 takes its position on the intake valve seat, so that the cleaning fluid cannot flow back into the suction line 20.

[0078] To mount the inlet valve 52, in a first assembly step the first insert part 54 with initially straight-aligned retaining arms 76, 78, as shown in the Figures 7 and 8The first insertion part 54 is inserted into the inlet channel 32 from the side facing the pump chamber 24, so that the contact surface 64 comes into contact with the first support surface 40 and the end sections 80, 82 of the retaining arms 76, 78 protrude from the inlet channel 32 on the side of the inlet channel 32 facing away from the pump chamber 24. The end sections 80, 82 can then be thermoformed, whereby the end sections 80, 82 are pressed radially outwards and immerse themselves in the recesses 36, 38, forming a positive fit with them. This results in the first insertion part 54 being held axially immovable and rotationally fixed to the inlet channel 32. In a further assembly step, the inlet closing element 56 can then be mounted on the first insert part 54 by inserting the inlet valve stem 90 into the first insert part 54 from the side facing the pump chamber 24, whereby the inlet valve stem 90 passes through the guide member 84.The inlet valve spring 96 can then be placed on the side facing away from the pump chamber 24 onto the shaft section 92 projecting from the guide member 84, and subsequently the spring retainer 94 can be fixed to the shaft section 92. The fixing of the spring retainer 94 to the shaft section 92 can be done, for example, by ultrasonic welding.

[0079] The exhaust ports 34 opening into the valve receptacle can each be closed by an exhaust valve 99. The exhaust valves 99 are identical in design and are formed by a pre-assembled exhaust valve assembly 100, which is received by the valve receptacle 42 of the second housing part 16 and the housing recess 46 of the first housing part 14.

[0080] The exhaust valve assembly 100 is in the Figures 3 and 11Shown enlarged. It comprises a second insert 102, which is made of a plastic material, for example, a POM material. The second insert 102 is inserted into the valve receptacle 52 and has several annular exhaust valve seat bodies 104, each forming an exhaust valve seat 106 of an exhaust valve 99.

[0081] In addition to the second insert part 102, the exhaust valve assembly 100 has a guide body 108, which is also made of a plastic material, for example, a fiber-reinforced plastic material, and which can be detachably and fluid-tightly connected to the second insert part 102. The guide body 108 forms guide elements 110 in the form of guide receptacles 112, each of which is aligned with an exhaust valve seat 106.

[0082] The second insert 102 and the guide body 108 accommodate several exhaust valve closing elements 114 between them, which are slidable back and forth relative to the second insert 102 and the guide body 108 and each have an exhaust valve head 116 and an exhaust valve stem 118 of an exhaust valve 99 integrally connected to it. The exhaust valve head 116 can be sealed against an exhaust valve seat 106, and the exhaust valve stem 118, which connects to the exhaust valve head 116 on the side facing away from the exhaust valve seat 106, engages in a guide receptacle 112 in which it is slidably mounted.

[0083] An exhaust valve spring 120 of an exhaust valve 99 is clamped between the guide receptacles 112 and the exhaust valve heads 116. The spring is supported on one side by a guide receptacle 112 and on the other side by an exhaust valve head 116, and surrounds an exhaust valve stem 118 in the circumferential direction in the area between the exhaust valve head 116 and the guide receptacle 112. This is particularly evident from Figure 11 clearly.

[0084] The guide receptacle 112 has an internal groove 122 extending in the longitudinal direction of the guide receptacle 112, through which cleaning fluid can escape from the guide receptacle 112.

[0085] In the area of ​​the valve receptacle 42, the second housing part 16 forms annular second support surfaces 124, which each connect to an exhaust port 34 in the direction of the valve receptacle 42 and are oriented perpendicular to the longitudinal axis 43 of the valve receptacle 42. The exhaust valve seat bodies 114 are supported with their end face 126 facing away from the respective exhaust valve seat 106 on a second support surface 124, wherein a second sealing ring 128 is arranged between the end faces 126 and the second support surfaces 124, which seals the respective exhaust valve seat body 104 against the second housing part 16 in the axial direction.

[0086] The guide body 108 is surrounded circumferentially by an annular groove 130 in which a third sealing ring 132 is arranged. The third sealing ring 132 ensures a liquid-tight connection between the second insert part 102 and the guide body 108.

[0087] Adjoining the annular groove 130 towards the housing recess 46 is an annular projection 134 extending over the outer circumference of the guide body 108. At a distance from the annular projection 134, the housing recess 46 forms a radially inwardly directed step 136. A fourth sealing ring 138 is positioned between the annular projection 134 and the step 136, sealing the guide body 108 axially against the first housing part 14.

[0088] In its area immersed in the housing recess 46, the guide body 108 forms a check valve seat 140 facing away from the second insert part 102, to which a check valve closing element 142 can be sealed. In combination with the check valve closing element 142, the check valve seat 140 forms a central check valve 144.

[0089] The exhaust valve assembly 100 is designed as a pre-assembled unit and can be inserted into the valve receptacle 42 and the housing recess 46 during the assembly of the piston pump 10. Since the exhaust valve assembly 100 forms all the exhaust valves 99, this simplifies the assembly of the piston pump 10.

[0090] As already mentioned, the two housing parts 14 and 16 are made of metal. These two housing parts can each be, for example, die-cast or formed. They can be made of aluminum or brass, for instance. Providing the inlet valves 52 and the outlet valves 99 does not require any subsequent machining of the metal parts, as the inlet and outlet valves 52 and 99 are plastic components inserted into the metal parts and have the corresponding valve seats. The piston pump 10 can therefore be manufactured cost-effectively.

[0091] Furthermore, the piston pump 10 is characterized by good suction behavior, since the volume of the pump chambers 24 that cannot be displaced by the pistons 26, 28 of the piston pump 10 can be kept very low.

Claims

1. Piston pump for a high pressure cleaning device for conveying a cleaning liquid, having a pump housing (12), which comprises a first housing part (14) and a second housing part (16), wherein the first housing part (14) forms a suction conduit (20) and a pressure conduit (22), and wherein the second housing part (16) forms a plurality of pump chambers (24) into each of which a reciprocally movable piston (26, 28) dips and which are each in flow connection with the suction conduit (20) by way of an inlet channel (32) and with the pressure conduit (22) by way of an outlet channel (34), wherein the inlet channel (32) is closable by an inlet valve (52) and the outlet channel (34) is closable by an outlet valve (99), wherein the inlet valve (52) comprises a first insert part (54) inserted into the inlet channel (32) and an inlet closing body (56) that is reciprocally displaceable relative to the first insert part (54), wherein the first insert part (54) comprises an inlet valve seat (62) and a guide member (84) arranged offset from the inlet valve seat (62), and wherein the inlet closing body (56) comprises an inlet valve plate (88) that is able to sealingly abut against the inlet valve seat (62) and an inlet valve stem (90) that adjoins the inlet valve plate (88) and is displaceably mounted on the guide member (84), wherein the first insert part (54) consists of a plastic material and comprises an annular inlet valve seat body (60), which points toward the pump chamber (24) and forms the inlet valve seat (62), wherein the guide member (84) is arranged upstream of the inlet valve seat (62) relative to the flow direction of the cleaning liquid, wherein the first insert part (54) forms a one-piece plastic molded part, characterized in that the first housing part (14) and the second housing part (16) are each configured as a metal part and in that the first insert part (54) comprises at least one holding arm (76, 78), which adjoins the inlet valve seat body (56) in the direction of the suction conduit (20) and is held in a rotationally-fixed manner relative to the inlet channel (32).

2. Piston pump in accordance with Claim 1, characterized in that the inlet valve seat body (60) protrudes out of the inlet channel (32) in the direction of the pump chamber (24), preferably in that the second housing part (16) forms an annular first support surface (40) that adjoins the inlet channel (32) in the direction of the pump chamber (24) and is oriented perpendicularly to a longitudinal axis (33) of the inlet channel (32) and against which the inlet valve seat body (60) abuts with an abutment surface (64), in particular in that the inlet valve seat body (60) comprises a sealing ring receptacle (66), which adjoins the abutment surface (64) and in which a sealing ring (74) that seals off the inlet valve seat body (60) relative to the first support surface is arranged, and preferably in that the sealing ring receptacle (66) forms an annular groove (68) surrounding the inlet valve seat body (60) in the circumferential direction, with a first groove wall (70) that adjoins the abutment surface (64) and is adjoined by a second groove wall (72), wherein the outer diameter of the inlet valve seat body (60) increases commencing from the second groove wall with increasing proximity to the abutment surface (64), and preferably in that the outer diameter of the inlet valve seat body (60) increases over the second groove wall (72) with increasing distance from the abutment surface (64).

3. Piston pump in accordance with Claim 1 or 2, characterized in that at least one of the following applies: - the at least one holding arm (76, 78) engages behind the inlet channel (32) on its side pointing toward the suction conduit (20); - the at least one holding arm (76, 78) is materially bonded to the inlet valve seat body (60); - the first insert part (54) comprises two diametrically opposed holding arms (76, 78) with respect to a longitudinal axis (33) of the inlet channel (32); - the guide member (84) is fixed to the at least one holding arm (76, 78); - the guide member (84) is materially bonded to the at least one holding arm (76, 78).

4. Piston pump in accordance with Claim 1, 2, or 3, characterized in that the at least one holding arm (76, 78) comprises an end portion (80, 82), which points away from the inlet valve seat body (60) and dips into a recess (36, 38) of the second housing part (16).

5. Piston pump in accordance with Claim 4, characterized in that the end portion (80, 82) of the at least one holding arm (76, 78) forms a positive engagement with the recess (36, 38) and / or in that the end portion (80, 82) of the at least one holding arm (76, 78) is thermally deformable.

6. Piston pump in accordance with any one of the preceding Claims, characterized in that the inlet valve stem (90) passes through the guide member (84) and comprises a stem portion (92), which protrudes out of the guide member (84) in the direction of the suction conduit (20) and to which a spring holder (94) is fixed, wherein an inlet valve spring (96) is clamped between the spring holder (94) and the guide member (84), preferably in that the guide member (84) forms a stop, which delimits the movement of the inlet valve plate (96) in the direction of the pump chamber (24).

7. Piston pump in accordance with any one of the preceding Claims, characterized in that the second housing part (16) comprises a valve receptacle (42) into which the outlet channels (34) open, and in that the piston pump (10) comprises an outlet valve assembly (100) that forms all outlet valves (99), wherein the outlet valve assembly (100) comprises a second insert part (102), which consists of a plastic material and is inserted into the valve receptacle (42) and comprises a plurality of annular outlet valve seat bodies (104), which each form an outlet valve seat (106).

8. Piston pump in accordance with Claim 7, characterized in that at least one of the following applies: - the outlet valve assembly (100) is configured as a unit that is able to be preassembled; - the second housing part (16) in the region of the valve receptacle (42) forms a plurality of annular second support surfaces (124), which are oriented perpendicularly to a longitudinal axis (43) of the valve receptacle (42) and each adjoin an outlet channel (34) in the flow direction of the cleaning liquid and against each of which a respective outlet valve seat body (104) abuts with the interposition of a sealing ring (128).

9. Piston pump in accordance with Claim 7 or 8, characterized in that the outlet valves (99) each comprise an outlet closing body (114), which is reciprocally displaceable relative to the second insert part (102) and which comprises an outlet valve plate (116) that is able to sealingly abut against an outlet valve seat (106) and comprises an outlet valve stem (118) adjoining the outlet valve plate (116) in the direction pointing away from the outlet channel (34).

10. Piston pump in accordance with Claim 9, characterized in that the outlet valve assembly (100) comprises a guide body (108), which consists of a plastic material and comprises a plurality of guide elements (110) on each of which an outlet valve stem (118) is displaceably mounted, in particular in that the guide elements (110) each form a guide receptacle (112) into which an outlet valve stem (118) dips, preferably in that the guide receptacles (112) each comprise at least one inner groove (122) extending in the longitudinal direction of the guide receptacles (112).

11. Piston pump in accordance with Claim 10, characterized in that at least one of the following applies: - a respective outlet valve spring (120) is clamped between the guide elements (110) and the outlet valve plates (116); - the guide body (108) is connectable to the second insert part (102) in a releasable and liquid-tight manner; - the guide body (108) forms a check valve seat (140) for a central check valve (144) arranged downstream of the outlet valves (99) relative to the flow direction of the cleaning liquid.

12. Piston pump in accordance with Claim 10 or 11, characterized in that the first housing part (14) comprises a housing recess (46) oriented in alignment with the valve receptacle (42), into which the guide body (108) dips with the interposition of at least one sealing ring (132, 138).

13. Piston pump in accordance with Claim 12, characterized in that the at least one sealing ring (132, 138) surrounds the guide body (108) in the circumferential direction, and / or in that the guide body (108) comprises an outwardly protruding annular projection (134), with which a radially inwardly directed step (136) of the housing recess (46) of the first housing part (14) is associated, wherein a sealing ring (138) is arranged between the projection (134) and the step (136).