EP2483561B1 - Pump for a high-pressure cleaning device - Google Patents

Description

The invention relates to a pump for a high-pressure cleaning device for conveying a cleaning liquid with at least one pumping chamber into which at least one reciprocating piston is immersed and which is connected via at least one inlet valve to a suction line and at least one outlet valve to a pressure line, and with a bypass line leading from the pressure line to the suction line, in which an overflow valve is arranged, whose valve body is connected via a piston rod to an actuator which moves the valve body into a closed position or an open position and a position depending on the flow rate of the cleaning liquid in the pressure line Valve body coupled switching plunger for actuating a switching element in a first or a second switching position shifts.

Such pumps are from the DE 196 07 881 A1 known. With their help, a cleaning liquid, such as water, can be pressurized and then directed, for example, via an attachable to the pressure line pressure hose and arranged at the free end of the pressure hose nozzle head to an object. Thus, the mechanical load on the pump and heat losses can be reduced, the pumped from the pump cleaning fluid is performed with closed nozzle head with the lowest possible flow resistance in the circuit, ie it is returned from the pressure line back to the suction line, so that the pressure in the pressure line can be reduced can. For this purpose, the pressure line is connected via a bypass line to the suction line and in the bypass line is arranged an overflow valve. During operation of the pump, ie when the nozzle head is open, the overflow valve closes the flow connection between the pressure line and the suction line. If the nozzle head is closed, the overflow valve releases the flow connection between the pressure line and the suction line, so that the pressure prevailing in the pressure line is reduced. The valve body of the overflow valve is connected for this purpose via a piston rod with an actuator which moves the valve body in response to the flow rate of the cleaning liquid in the pressure line in a closed position or an open position. The flow rate of the cleaning liquid in the pressure line depends on whether the nozzle head is open or closed. If the nozzle head is closed, the flow rate drops, and this causes the actuator to move the valve body of the spill valve in its open position, so that the pressurized cleaning fluid can flow to the suction line with the lowest possible flow resistance. If the nozzle head is opened, the flow rate in the pressure line increases and this causes the actuator to move the valve body of the spill valve to the closed position, so that the pump goes into normal operation.

In addition to its function of controlling the spill valve, the actuator has the function of displacing a switch plunger coupled to the valve body. By means of the switching plunger, a switching element can be actuated. The switching element, for example, a drive device of the pump, preferably an electric motor, on and off. By actuating the switch plunger thus the pump can be activated and deactivated. If the liquid flow in the pressure line is prevented, then there is the one

Overflow valve, the flow connection between the pressure line and the suction line freely, so that the pressure prevailing in the pressure line pressure can be reduced, and on the other hand, the switching plunger is moved to a first switching position, so that the switching element shuts off the pump. To achieve this switching position, however, the switch plunger has to overcome a certain distance. For this purpose, the valve body should, if possible, be subjected to the greatest possible differential pressure in order to assist the movement of the switching tappet coupled to it. However, such a differential pressure has the consequence that the cleaning fluid in the bypass line suffers considerable flow losses. This leads to heat losses of the pump and to a considerable mechanical load of the same. If, after releasing the flow connection between the pressure line and the suction line, it is ensured that the pump is switched off reliably, short-term loading of the pump during cycle operation is tolerable. However, should the pump not be shut down, for example, due to damage to the switching element, continued pump operation may result in damage if the high differential pressure on the valve body of the spill valve persists.

Object of the present invention is therefore to develop a pump of the type mentioned in such a way that the switching plunger reliably overcomes a certain distance to actuate the switching element at the transition of the pump in the circulation operation, the cleaning liquid undergoes the least possible flow losses during longer cycle operation.

This object is achieved in a pump of the generic type according to the invention that the valve body in the transition from its closed position in its open position upstream of the valve seat releases a permeable by cleaning fluid passage whose flow cross-section widens when the valve body occupies a predetermined distance to the valve seat.

If the liquid flow in the pressure line is prevented in the pump according to the invention, the valve body of the overflow valve moves from its closed position to its open position, lifting it from the valve seat and releasing a passage through which the cleaning fluid can flow. The flow cross-section of the passage widens when the valve body occupies a predetermined distance from the valve seat. The flow cross-section of the passage can therefore initially be kept very low when lifting the valve body from the valve seat, so that sets a considerable pressure drop on the valve body and the cleaning fluid from the pressure line can flow only very gradually to the suction line. This has the consequence that the switch plunger is first moved over a certain distance until the valve body occupies a predetermined distance from the valve seat. Then, the flow cross-section of the released from the valve body passage widens, so that the cleaning liquid then suffers in the region of the overflow only relatively small pressure losses. The switching plunger can therefore be reliably moved to its first switching position, in which he can actuate the switching element for switching off the pump, and only then the cleaning liquid is performed with the lowest possible flow resistance of the pressure line via the bypass line to the suction line. If the switching element is damaged or incorrectly mounted on the pump, so that it does not switch off the pump despite the operation of the switch plunger, so the cleaning fluid is recycled in the then continued circulation operation of the pump with relatively low flow losses. The heat load and the mechanical stress of the pump in the permanent cycle operation can therefore be kept low. On the other hand, it is ensured that the switching plunger in each case first overcomes a predetermined distance when lifting the valve body from the valve seat. This distance corresponds to the predetermined distance of the valve body to the valve seat, in which increases the flow cross-section of the flow-through of the cleaning liquid passage in the overflow valve.

The pump according to the invention is thus characterized on the one hand by the fact that the switching plunger reliably overcomes a predetermined distance when the liquid flow in the pressure line is prevented, so that the switching element can be operated properly. On the other hand, the pump according to the invention is characterized in that in a continuous cycle operation, which may occur, for example, in a damage of the switching element, the cleaning liquid can flow with low flow losses from the pressure line to the suction line and therefore the pump in the continued cycle operation of a low heat and pressure load is subject.

When the valve body of the overflow valve is lifted off the valve seat, the passage through which the cleaning liquid can flow preferably has a first flow cross section on a first part of the stroke movement of the valve body. The valve body completes a stroke during the transition from its closed position to its open position. During a first portion of the lifting movement of the flow cross-section remains the passage, which releases the valve body, preferably unchanged. This ensures that despite the gradual transition of the valve body from the closed position to the open position initially only a constant amount of cleaning fluid per unit time can flow through the spill valve, so that after the blocking of the liquid flow in the pressure line, the pressure in the pressure line only completely can gradually degrade, although the valve body of the spill valve occupies an increasing distance to the valve seat. The initially only slowly occurring pressure drop ensures that the valve body is moved by the actuator in the direction of the open position and thus also the coupled to the valve body switching plunger is moved further in the direction of its first switching position. Only when this switching position is reached, ie when the valve body has taken a predetermined distance to the valve seat, the flow cross-section of the released from the valve body passage, so that now a larger amount of cleaning liquid per unit time can flow through the passage and therefore the pressure in the Accelerated pressure line can accelerate.

In an advantageous embodiment, the passage on a second section of the stroke movement of the valve body which follows the first partial section has a constant second flow cross-section which is greater than the first flow cross-section. After overcoming the first part of the lifting movement, the valve body releases a larger flow cross-section for the passage through which cleaning fluid can flow. The enlarged flow cross-section is then maintained unchanged during the overcoming of the second part of the stroke movement of the valve body. Thus, although the flow cross-section of the passage widens, After the valve body has reached a predetermined distance from the valve seat, but the enlarged flow cross-section then undergoes no further change during the second part of the stroke movement of the valve body.

It is advantageous if the valve body is designed as a radial extension of the piston rod, wherein the piston rod engages through a valve housing of the overflow valve and the valve housing forms a valve seat, wherein the diameter of the piston rod narrows upstream of the valve body at a predetermined distance. The design of the valve body as a radial extension of the piston rod enables a particularly cost-effective production. The change in the flow cross-section of the passage, which can be traversed by the cleaning of the valve body from the valve seat of cleaning liquid can be advantageously achieved by a variation of the diameter of the piston rod. The piston rod may have a constriction at a predetermined distance from the valve body upstream thereof. The constriction ensures that the flow cross-section of the passage released from the valve body increases by the predetermined distance.

It can be provided, for example, that the piston rod has a first cylindrical portion of constant diameter, which connects upstream of the valve body. At the transition of the valve body from its closed position in which it rests against the valve seat of the valve housing, in its open position in which it occupies a distance from the valve seat, first defined by the upstream of the valve body first cylindrical portion of the piston rod in combination with that of the Piston rod passed valve housing the flow cross-section of the passage, which can be traversed by cleaning fluid. This flow cross section can be kept relatively low by the diameter of the first cylindrical portion is only slightly smaller than the diameter of the penetrated by the piston rod opening of the valve housing. Between the opening of the valve housing and the first cylindrical portion then forms an annular gap whose width is determined by the diameter of the opening and the diameter of the cylindrical portion.

The diameter of the first cylindrical section is preferably at least 90%, in particular approximately 95%, of the diameter of the valve opening.

Conveniently, the piston rod upstream of the first cylindrical portion has a second cylindrical portion of constant diameter, wherein the diameter of the second cylindrical portion is smaller than the diameter of the first cylindrical portion. When the valve body is lifted off the valve seat, first the first cylindrical section of the piston rod assumes a position within the opening of the valve housing which is penetrated by the piston rod and therefore defines a first annular gap, which can be very narrow. Upon further movement of the valve body in the direction of its open position then reaches the second cylindrical portion of the piston rod a position within the opening of the valve housing. Since the second cylindrical section has a smaller diameter than the first cylindrical section, it defines a larger annular gap, ie the passage in the valve housing released by the valve body has a larger flow cross section, so that the cleaning fluid With lower flow losses, the overflow valve can flow through.

The diameter of the second cylindrical section is preferably at most 80%, in particular approximately 75%, of the diameter of the valve opening.

The coupled to the valve body switching plunger is designed in a preferred embodiment of the invention as an axial extension of the piston rod, via which the valve body is connected to the actuator. In such an embodiment of the invention, the piston rod protrudes beyond the valve body on the side of the valve body facing away from the actuator and forms the switching tappet in this projecting region.

The switching plunger can dive with its free end into a receptacle of the pump, in which the switching element is arranged.

The piston rod is preferably aligned parallel to the pressure line.

In a preferred embodiment of the invention, the pump has a rear housing part and a front housing part, which are joined together tightly in a joining region, and a suction line section extends in the joining region between the two housing parts and the bypass line opens into the Saugleitungsabschnitt. The rear housing part faces a drive device of the pump, for example an electric motor, wherein a transmission and / or a swash plate and a piston guide can be arranged between the electric motor and the rear housing part. The front housing part sits on the rear housing part and is the drive device facing away from the pump. In the joining region between the two housing parts, ie in the region in which the two housing parts lie close to each other, a Saugleitungsabschnitt is arranged according to this advantageous embodiment of the invention, in which opens the bypass line. The Saugleitungsabschnitt can be made inexpensively before joining the two housing parts in a simple manner. Thereby, the manufacturing cost of the pump can be reduced. In addition, the bypass line can be selected very short by the arrangement of the Saugleitungsabschnitts in the joining region between the two housing parts. This has the advantage that the flow losses of the cleaning liquid in the bypass line can be kept low. The arranged between the two housing parts suction line section may have a relatively large flow cross-section. As a result, the flow losses of the cleaning liquid in the circulation operation of the pump can be additionally reduced.

The arrangement of the Saugleitungsabschnitts in the joining region between the front and the rear housing part has the additional advantage that the geometric shape of the Saugleitungsabschnitts subject to lower boundary conditions, because before the joining of the two housing parts of the joining area for machining and shaping is directly accessible. For the arranged between the two housing parts Saugleitungsabschnitt therefore a curvy course can be chosen if necessary, without thereby increasing the production costs are significantly increased. This in turn gives the designer the opportunity to optimize the arrangement of the remaining lines and receiving spaces of the pump in terms of the smallest possible size and the lowest possible use of materials. Especially the course of the bypass line can be optimized so that the bypass line has the lowest possible flow resistance.

The sealing of the running between the two housing parts Saugleitungsabschnittes can be done in a cost effective manner by means of sealing rings, which are arranged between the two housing parts.

In particular, it may be provided that the suction line section arranged between the two housing parts extends between a first sealing ring and a second sealing ring, which are positioned between the two housing parts. The two sealing rings can not only have the function of sealing the arranged between the two housing parts Saugleitungsabschnitt tight, but they can also take over the function to seal the joint area between the two housing parts.

It is advantageous if the suction line section extending between the two housing parts forms an outlet section of the suction line. At least one input line may connect to the output section, which receives an input valve and leads to a pumping chamber. The bypass line is thus connected to at least one input line via the suction line section arranged in the joining region between the two housing parts, which leads to a pumping chamber. Thus, the flow losses of the cleaning liquid in the circulation operation of the pump can be additionally reduced.

Conveniently, the suction line comprises an input section arranged in the front housing part and that in the joining region between the two housing parts extending suction line section forms an output section of the suction line. The inlet section can start from a suction connection of the pump and be aligned, for example, transversely to the pressure line. At the input portion of the arranged between the two housing parts output section can connect directly.

The suction line section running in the joining region is preferably arcuately curved, at least in one section. The arcuate curvature is particularly advantageous in view of the limited space of the pump, because thereby the suction line section receiving spaces for the inlet and outlet valves and for the actuator and, if necessary, the pressure line surrounded. Above all, a circular arc-shaped course of the suction line section arranged in the joining region has proved favorable.

In a particularly preferred embodiment of the pump according to the invention, the suction line section extending in the joining region is designed as a self-contained ring. In such an embodiment, an annular space may extend in the joining region between the rear housing part and the front housing part, which forms the said suction line section. The annular space can have a relatively large flow cross section, so that the at least one pumping chamber can be supplied with the cleaning fluid to be pumped with low flow resistance. In particular, in the circulation operation of the pump, the cleaning liquid can be returned with low flow losses, starting from the pumping chamber via the pressure line, the bypass line and the suction line to the pumping chamber.

The front housing part of the pump has a rear parting surface, which is placed with the interposition of at least one sealing element on a front-side parting surface of the rear housing part. Preferably, a channel is formed in at least one of the parting surfaces, which forms at least a part of the arranged in the joining region between the two housing parts Saugleitungsabschnittes. The channel is arranged on an outer side of at least one of the housing parts and can thereby be produced very inexpensively.

It is advantageous if in the rear parting surface of the front housing part, a channel is formed, which is covered by the front-side parting surface of the rear housing part and which forms the arranged in the joining region between the two housing parts Saugleitungsabschnitt.

Alternatively, for example, be provided that in the front-side parting surface of the rear housing part, a channel is formed, which is covered by the rear parting surface of the front housing part and forms the Saugleitungsabschnitt.

The running in the joining region between the two housing parts suction line section engages in an advantageous embodiment of the invention, the pressure line at a distance. In particular, it may be provided that the suction line section extending in the joining region surrounds the pressure line in an annular manner.

The actuator is configured in an advantageous embodiment of the invention as a control piston, which divides a control chamber of the front housing into a low pressure chamber and a high pressure chamber, is displaceable in the control chamber and is connected via the piston rod to the valve body of the overflow valve, wherein the low pressure chamber via a control line is connected downstream of a throttle point with the pressure line and the high-pressure chamber is connected via an upstream of the spill valve arranged portion of the bypass line to the pressure line. In such an embodiment, a throttle point is arranged in the pressure line of the pump, for example an injector, with the aid of which a cleaning chemical can be sucked in and mixed with the cleaning fluid under pressure. In the presence of a liquid flow in the pressure line, the throttle point has the consequence that the pressure downstream of the throttle point differs from the pressure upstream of the throttle point. Since the low-pressure chamber via the control line downstream of the throttle point is in communication with the pressure line, whereas the high-pressure chamber is connected upstream of the throttle point via a first portion of the bypass line to the pressure line, the control piston is subjected to a liquid pressure in the presence of a liquid flow through the pressure line with a differential pressure. Due to the differential pressure acting on it, the control piston via the piston rod displaces the valve body of the overflow valve against the direction of flow prevailing in the bypass line into a closed position in which the valve body bears against the valve seat of the overflow valve. If the liquid flow is interrupted, the throttle point causes no pressure drop and the pressure in the low pressure chamber corresponds to the pressure in the high pressure chamber. In the absence of a differential pressure between the two chambers, the control piston with one of the

Pressure applied to the two chambers dependent resulting force, by which it is displaced in the control chamber so that the connected via the piston rod with him valve body goes into an open position, d. H. occupies a distance from the valve seat, and thereby releases the flow connection between the pressure line and the suction line for a circulation operation of the pump.

The movement of the control piston is transmitted via the piston rod to the valve body. Preferably, the control piston is displaceable parallel to the pressure line and the piston rod is aligned parallel to the pressure line.

The switching plunger immersed in a preferred embodiment of the invention in a molded-in in the rear housing part recording in which the switching element is arranged. The switching plunger thus passes through the joining region between the two housing parts.

It is particularly advantageous if the bypass line has a section which receives the overflow valve and which opens into the suction line section running in the joining region between the two housing parts and is aligned with the control chamber. Said portion of the bypass line can connect directly to the control chamber, and due to the positioning of the Saugleitungsabschnittes in the joining region between the two housing parts, the overflow valve receiving portion can be selected very short.

Conveniently, the control chamber and the overflow valve receiving portion of the bypass line are aligned parallel to the pressure line.

In an advantageous embodiment of the pump according to the invention, the control chamber and the overflow valve receiving portion of the bypass line are arranged in a passageway which passes through the front housing part from an end face to a rear parting surface. This simplifies the manufacture of the pump and thereby reduces the manufacturing costs. In addition, the provision of the passage channel simplifies the assembly of the pump, since both the overflow valve and the control piston can be inserted in the axial direction in the through-channel.

Figur 1:

einen Längsschnitt einer erfindungsgemäßen Pumpe;

Figur 2:

eine perspektivische, in einem vorderen Gehäuseteil teilweise geschnittene Darstellung der Pumpe aus Figur 1 schräg von vorne;

Figur 3:

eine perspektivische, in einem hinteren Gehäuseteil teilweise geschnittene Darstellung der Pumpe aus Figur 1 schräg von hinten;

Figur 4:

eine Teilschnittdarstellung der Pumpe aus Figur 1 im Bereich eines Überströmventils, dessen Ventilkörper eine Schließstellung einnimmt;

Figur 5:

eine vergrößerte Teilschnittdarstellung der Pumpe aus Figur 1 im Bereich des Überströmventils, wobei der Ventilkörper seine Schließstellung einnimmt;

Figur 6:

eine vergrößerte Teilschnittdarstellung der Pumpe entsprechend Figur 5, wobei der Ventilkörper eine erste Teilstrecke seiner Hubbewegung von seiner Schließstellung zu seiner Offenstellung zurückgelegt hat, und

Figur 7:

eine vergrößerte Teilschnittdarstellung der Pumpe entsprechend Figur 5, wobei der Ventilkörper seine Offenstellung einnimmt.

The following description of a preferred embodiment of the invention serves in conjunction with the drawings for further explanation. Show it:

FIG. 1:

a longitudinal section of a pump according to the invention;

FIG. 2:

a perspective, partially cut in a front housing part representation of the pump FIG. 1 diagonally from the front;

FIG. 3:

a perspective, partially cut in a rear housing part representation of the pump FIG. 1 diagonally from behind;

FIG. 4:

a partial sectional view of the pump FIG. 1 in the region of an overflow valve whose valve body assumes a closed position;

FIG. 5:

an enlarged partial sectional view of the pump FIG. 1 in the region of the overflow valve, wherein the valve body assumes its closed position;

FIG. 6:

an enlarged partial sectional view of the pump accordingly FIG. 5 , wherein the valve body has traveled a first portion of its stroke from its closed position to its open position, and

FIG. 7:

an enlarged partial sectional view of the pump accordingly FIG. 5 , wherein the valve body assumes its open position.

In the drawing, a pump 10 is shown schematically for a high-pressure cleaner. The pump 10 comprises a pump housing 12 with a rear housing part 14 and a front housing part 16. The two housing parts are preferably designed in the form of aluminum die-cast parts. The front housing part 16 is provided with a rear parting surface 20 which is placed on a front side parting surface 22 of the rear housing part 14 with the interposition of an outer sealing ring 24 and an inner sealing ring 26. The two sealing rings 24 and 26 are concentric with each other at the outer or inner edge of a molded into the rear parting surface 20 of the front housing part 16 annular channel 28 is arranged. The annular channel 28 is made in particular FIG. 3 clear. It forms an output section 30 of a suction line, whose input section 32 is formed in the form of a blind hole in the front housing part 16.

The rear housing part 14 accommodates pumping chambers 34, in each of which a cylindrical piston 36a or 36b is inserted. The pistons 36a, 36b are sealed off from the respective pumping chamber 34 by a lip-shaped annular seal 38a or 38b. Overall, the rear housing part 14 has three pumping chambers, in each of which a piston is immersed. To achieve a better overview, only one pumping chamber 34 and two pistons 36a and 36b are shown in the drawing. All pistons are inserted by a not shown in the drawing, known per se swash plate oscillating in the respective pumping chamber 34 and pulled out by a surrounding the respective piston coil spring 40 back out of the pumping chamber, so that the volume of the pumping chambers 34 changes periodically.

Each pumping chamber 34 is in fluid communication with the annular outlet section 30 of the suction line via an input line 42 formed in the rear housing part 14 into which an inlet valve 44 is inserted. For this purpose, the input line 42 opens into the front-side parting surface 22 of the rear housing part 14. This is for example FIG. 2 clear.

Via an outlet line 46 molded into the rear housing part 14 into which an outlet valve 48 is inserted, each pumping chamber 34 is in fluid communication with a pressure line 50 extending in the longitudinal direction of the pump 10 and molded into the front housing part 16. For this purpose, the output line 46 opens into the front-side parting surface 22 of the rear housing part and the pressure line 50 extends from the rear parting surface 20 of the front housing part 16 and extends to a front side 52 of the front housing part 16 facing away from the rear housing part 14. The end face 52 forms the front end of the pump 10. The area between the output lines 46 of the pumping chambers 34 and the pressure line 50 is sealed radially outwardly from the inner sealing ring 26.

In the pressure line 50, a central pressure valve 54 is arranged and downstream of the pressure valve 54, the pressure line 50 receives a throttle element in the form of an injector 56. This includes in a conventional manner a first in the flow direction narrowing and then again expanding through-hole 58, from the narrowest point of a transverse bore 60 branches off.

Parallel to the pressure line 50 extends from the end face 52 to the rear parting surface 20 a staged Enriched passage 62 through the front housing part 16 therethrough. The end-side end region of the through-channel 62 accommodates a sealing plug 64, which closes off the through-channel 62 on the face side. In the region adjoining the sealing plug 64, the through-channel 62 defines a control chamber 66, to which a lower section 70 of a bypass line explained in more detail below connects via a step 68. The lower section 70 receives an overflow valve 72 and opens into the annular channel 28 and thus into the arranged in the joining region between the two housing parts 14, 16 output section 30 of the suction line.

The control chamber 66 is cylindrical and receives a sliding sleeve 74, which rests with the interposition of a sealing ring 76 on the wall of the control chamber 66. In the sliding sleeve 74, an actuator in the form of a control piston 78 is held displaceable parallel to the longitudinal axis of the pressure line 50. The control piston 78 divides the control chamber 66 into a sealing plug 64 facing low pressure chamber 80 and a closure plug 64 facing away from the high pressure chamber 82 to which the lower portion 70 of the bypass line connects.

In the lower portion 70 of the bypass line, a valve housing of the overflow valve 72 in the form of a valve sleeve 86 is inserted with the interposition of a sealing ring 84, which surrounds a cylindrical valve opening 87 and a valve seat 88 of the overflow valve 72 is formed. To the valve seat 88 is a valve body 90 of the spill valve 72 in a closed position, which in the FIGS. 4 and 5 is shown, sealing applied. The valve body 90 is formed by a radial extension of a piston rod 92, which extends parallel to the longitudinal axis of the pressure line 50 and is connected with its closure plug 64 facing the end with a molded onto the control piston 78 shaft 94. The piston rod passes through the valve opening 87.

On the side of the valve body 90 facing away from the shaft 94, the piston rod 92 forms a switch plunger 96, which is slidably guided in a guide sleeve 98 with the interposition of a sealing ring 100. The guide sleeve 98 is arranged in alignment with the valve housing 86 of the overflow valve 72 and at a distance therefrom in the annular channel 28 of the rear parting surface 20 of the front housing part 16.

The switch plunger 96 dips with its free end in a receptacle 102 which is laterally formed in the rear housing part 14 and a known per se and in FIG. 1 recorded dot-dash line switching element 104, which can be actuated by the switch plunger 96. The switch plunger passes through the joining region between the two housing parts 14 and 16.

The arranged in the pressure line 50 injector 56 has on its outer side an annular groove 106 into which the transverse bore 60 opens. At the annular groove 106, a control line 108 connects, via which the annular groove 106 is in fluid communication with the low pressure chamber 80.

Upstream of the injector 56 and the central pressure valve 54 extends from the pressure line 50 to the high-pressure chamber 82, an upper portion 110 of the bypass line. At the upper portion 110 joins in the passage 62, the already mentioned lower portion 70 of the bypass line. The bypass line formed by the two sections 70 and 110 defines a flow connection between the pressure line 50 and the outlet section 30 of the suction line. This flow connection can be released and prevented depending on the position of the valve body 90 of the overflow valve 72.

As in particular from FIG. 3 becomes clear, surrounds the annular channel 28 and thus the output section 30 of the suction line both the pressure line 50 and all output lines 46 of the individual pumping chambers 34 in the circumferential direction. A radially arranged high pressure section of the joining region between the two housing parts 14 and 16 is thus surrounded by the annular channel and is sealed relative to the annular channel by means of the inner sealing ring 26. The inner sealing ring 26 separates the radially centered high-pressure section of the joining region from an annular low-pressure section of the joining region. The low pressure section surrounds the High pressure section. It is designed in the form of the annular channel 28 and sealed radially on the outside by means of the outer sealing ring 24.

The pumping chambers 34 can be supplied with cleaning fluid to be delivered via the inlet section 32 and the outlet section 30 of the suction line and the inlet lines 42 adjoining the outlet section 30 in the joining area. In the pumping chambers 34, the cleaning liquid is pressurized due to the oscillating movement of the pistons, and via the output lines 46, the pressurized liquid is supplied to the pressure line 50.

In normal operation of the pump 10, the pressurized cleaning fluid flows through the injector 56. This forms in the pressure line 50, a throttle point at which the flowing cleaning fluid suffers a pressure drop, so that the upstream of the injector 56 arranged region of the pressure line 50 has a higher pressure As long as the pressure line 50 is flowed through with cleaning liquid, thus the lower pressure chamber 80 connected via the control line 108 with the transverse bore 60 is subjected to a lower pressure than that via the upper portion 110 of the As a result, the control piston 78 is displaced in the direction of the closure stopper 64, so that the valve body 90 of the overflow valve 72 on the valve seat 88 tightly rests and thereby the Strömungsve bond between the pressure line 50 and the output section 30 of the suction line is interrupted. The movement of the control piston 78 in the direction of the closure stopper 64 is controlled by a compression spring 116 supports, which surrounds the shaft 94 and rests on the one hand on the control piston 78 and on the other hand on the valve sleeve 86.

If the flow of the cleaning liquid is interrupted by the pressure line 50, for example by a nozzle head, which is connected via a pressure hose to the pressure line 50 is closed, resulting in the narrowing of the injector 56 no dynamic pressure reduction, the pressure in this area Rather, the same as the upstream of the pressure valve 54 prevailing pressure. In this case, equal pressures result in the low-pressure chamber 80 and the high-pressure chamber 82, and according to a suitable dimension of the effective pressure surfaces of the control piston 78, this is thereby displaced against the action of the compression spring 116 in the direction away from the closure stopper 64. Consequently, the valve body 90 lifts from the valve seat 88, so that the spill valve 72 releases the flow connection from the pressure line 50 via the portions 70 and 110 of the bypass line to the output section 30 of the suction line. As a result, the pressure prevailing in the pressure line 50 pressure can be lowered.

The movement of the control piston 78 and connected to this piston rod 92 via the switching plunger 96 also leads to an actuation of the switching element 104. As a result, the drive of the pump 10 can be switched off. An unnecessary operation of the drive with a closed nozzle head is thereby avoided.

As already mentioned, the valve body 90 of the overflow valve 72 is designed in the form of a radial extension of the piston rod 92. The valve seat 88 facing the valve body 90 forms a frusto-conical inclined surface 118, with which it rests tightly in the closed position of the overflow valve 72 on the valve seat 88. This is especially true of the FIGS. 4 and 5 clear.

Upstream of the inclined surface 118, a first cylindrical portion 120 of the piston rod 92 connects to the valve body 90, which extends in the direction of the control piston 78 with a constant outer diameter D over an axial length L of the piston rod 92. A second cylindrical section 124 of the piston rod 92 adjoins the first cylindrical section 120 in the direction of the control piston 78 via a conical constriction 122. The second cylindrical portion 124 extends in the direction of the control piston 78 with a constant outer diameter d over an axial length l of the piston rod 92. This is in particular from the Figures 5 . 6 and 7 clear. The diameter D of the first cylindrical portion 120 is only slightly smaller than the diameter of the cylindrical valve opening 87 of the spill valve 72, whereas the diameter d of the second cylindrical portion 124 is chosen to be much lower. For example, the diameter d of the second cylindrical portion may be less than 80%, in particular about 75% of the diameter of the cylindrical valve opening 87, whereas the diameter D of the first cylindrical portion 120 more than 90%, in particular about 95% of the diameter of the cylindrical valve opening 87th is.

At the transition of the valve body 90 of the in the FIGS. 4 and 5 shown closed position in the in FIG. 7 shown open position, the valve body releases a passage, which can be traversed by cleaning fluid. The passage is through the annular gap between the cylindrical Valve opening 87 and the outer diameter of the piston rod 92 defined. When lifting the valve body 90 from the valve seat 88 initially takes the first cylindrical portion 120 a position within the valve opening 87, so that forms a very narrow annular gap between the first cylindrical portion 120 and the cylindrical valve opening 87, which serves as the passage for the cleaning liquid Available. Only when the valve body 90 takes a predetermined distance to the valve seat 88, which is determined by the length L of the first cylindrical portion 120, the passage of the cleaning liquid available increases, now the second cylindrical portion 124 a position in the cylindrical valve opening 87th occupies and thereby releases a considerably larger annular gap. The flow cross-section of the passage, which is released from the valve body 90 when lifted from the valve seat 88, thus expands after the valve body 90 has overcome a first section in the form of the axial length L of the first cylindrical section 120. During the further stroke movement of the valve body 90, no further enlargement of the flow cross-section takes place in the second cylindrical section 124.

When lifting the valve body 90 from the valve seat 88, initially only a relatively small amount of cleaning fluid per unit time can flow through the overflow valve 72. The cleaning fluid flowing through the overflow valve 72 thus initially experiences a constant high flow resistance when the valve body 90 is lifted off the valve seat 88, and a considerable pressure drop takes place on the piston rod 92 in the region of the overflow valve 72. This has the consequence that the control piston 78 and the piston rod 92 in the direction of the closure plug 64 opposite direction be shifted, so that the switch rod 96 formed by the free end portion of the piston rod 92 is reliably moved into the receptacle 102. This ensures that the switching element 104 arranged in the receptacle 102 can be actuated in order to switch off the pump 10.

Only after the valve body 90 has been moved so far into its open position that the second cylindrical portion 124 occupies a position within the valve opening 87, the flow resistance, the cleaning liquid and thus also the pressure drop across the piston rod 92. The return of cleaning fluid from the Pressure line 50 via the sections 70 and 110 of the bypass line to the output section 30 of the suction line can now be done with low flow losses. If due to incorrect positioning of the switching element 104 or due to damage of the switching element 104, the pump has not been switched off beforehand, the further circulation operation of the pump can now take place with very low pressure losses. This has the advantage that only a relatively low pressure is formed in the circulation operation within the pump 10, for example a pressure of at most 10 bar, so that only relatively small heat losses and a low mechanical load on the pump 10 occur in circulation operation.

The cycle operation is terminated by the nozzle head is opened again, because it can be discharged through the nozzle head cleaning liquid, so that forms a liquid flow in the injector 56 and due to the throttling action of the injector 56 in the low pressure chamber 80, the pressure drops. Consequently, the control piston 78 under the effect of the pressure conditions and under the action of the compression spring 116 again so far in shifted the direction of the closure plug that the valve body 90 assumes its closed position in which it rests against the valve seat 88. In addition, by the displacement of the control piston 78 and the switching plunger 96 is moved in the direction of the closure plug 64 facing direction, so that by means of the switching element 104, the drive of the pump 10 can be turned on again.

Claims (13)

1. Pump for a high-pressure cleaning apparatus for delivering a cleaning liquid, said pump comprising at least one pump chamber (34) into which at least one reciprocally movable piston (36a, 36b) plunges and which is connected via at least one inlet valve (44) to a suction conduit (30, 32) and is connected via at least one outlet valve (48) to a pressure conduit (50), and a bypass conduit (70, 110) leading from the pressure conduit (50) to the suction conduit (30, 32) and having arranged therein a bypass valve (72), the valve body (90) of which is connected, via a piston rod (92), to a control member which displaces the valve body (90) as a function of the flow rate of the cleaning liquid in the pressure conduit (50) to a closed position or an open position and displaces a switch plunger (96) which is coupled to the valve body (90) to a first or a second switch position to actuate a switch element, characterized in that the valve body (90), as it transitions from its closed position to its open position, opens a passage upstream of the valve seat (88) permitting cleaning liquid to flow therethrough, the flow cross-section of said passage becoming wider when the valve body (90) is at a predetermined distance (L) from the valve seat (88).
2. Pump in accordance with claim 1, characterized in that the passage has a first constant flow cross-section along a first partial distance of the stroke movement of the valve body (90).
3. Pump in accordance with claim 2, characterized in that the passage has a second constant flow cross-section along a second partial distance of the stroke movement of the valve body (90) following the first partial distance, said second flow cross-section being larger than the first flow cross-section.
4. Pump in accordance with any one of the preceding claims, characterized in that the valve body (90) is configured as a radial extension of the piston rod (92), wherein the piston rod (92) extends through a valve housing (86) of the bypass valve (72), wherein the valve housing (86) forms a valve seat (88), and wherein the diameter of the piston rod (92) is constricted upstream of the valve body (90) at a predetermined distance (L) therefrom.
5. Pump in accordance with claim 4, characterized in that the piston rod (92) has a first cylindrical section (120) of constant diameter (D) following the valve body (90) in an upstream direction.
6. Pump in accordance with claim 5, characterized in that the piston rod (92) has a second cylindrical section (124) of constant diameter (d) in a direction upstream of the first cylindrical section (120), wherein the diameter (d) of the second cylindrical section (124) is smaller than the diameter (D) of the first cylindrical section (120).
7. Pump in accordance with any one of the preceding claims, characterized in that the switch plunger (96) is configured as an axial extension of the piston rod (92).
8. Pump in accordance with any one of the preceding claims, characterized in that the pump (10) has a rear housing part (14) and a front housing part (16), which are tightly joined together in a joining area, wherein a suction conduit section (30) extends in the joining area between the two housing parts (14, 16) and the bypass conduit (70, 110) opens out into the suction conduit section (30).
9. Pump in accordance with claim 8, characterized in that the suction conduit section (30) is configured as a self-contained ring.
10. Pump in accordance with claim 8 or 9, characterized in that the control member is configured as a control piston (78) which divides a control chamber (66) of the front housing part (16) into a low-pressure chamber (80) and a high-pressure chamber (82), is displaceable in the control chamber (66), and is connected to the valve body (90) of the bypass valve (72) via the piston rod (92), wherein the low-pressure chamber (80) is connected to the pressure conduit (50) via a control conduit (108) downstream of a restriction and the high-pressure chamber (82) is connected to the pressure conduit (50) via a section (110) of the bypass conduit arranged upstream of the bypass valve (72).
11. Pump in accordance with claim 10, characterized in that the bypass conduit includes a section (70) accommodating the bypass valve (72), said section (70) opening out into the suction conduit section (30) arranged in the joining area between the two housing parts (14, 16), and being aligned with the control chamber (66).
12. Pump in accordance with claim 11, characterized in that the control chamber (66) and the section (70) of the bypass conduit accommodating the bypass valve (72) are oriented parallel to the pressure conduit (50).
13. Pump in accordance with claim 11 or 12, characterized in that the control chamber (66) and the section (70) of the bypass conduit accommodating the bypass valve (72) are arranged in a through-channel (62) which extends through the front housing part (16) from an end face (52) to a rear-end parting surface (20).

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