Abstract:
The invention relates to a high-pressure cleaning appliance with a high-pressure pump, comprising at least one pump chamber which is connected to a suction line and a pressure line. The pressure line is in flow connection with the suction line via a return flow line, and a relief valve with a through-channel extending from a valve inlet to a first valve outlet is arranged in the return flow line. A valve element which in a closed position bears against a valve seat is held for movement in the through-channel. At least one outlet channel, which opens into a second valve outlet, branches off from the through-channel. To design the high-pressure cleaning appliance so that it is less susceptible to failure, it is proposed that in the direction away from the valve seat, at a spacing from the at least one outlet channel, the valve element be surrounded by a sealing ring which seals off an inlet area of the through-channel adjacent to the valve inlet from an outlet area of the through-channel adjacent to the first valve outlet.

Description:
[0001]    This application is a continuation of international application number PCT/EP2008/002818 filed on Apr. 10, 2008. 
         [0002]    The present disclosure relates to the subject matter disclosed in international application number PCT/EP2008/002818 of Apr. 10, 2008 and German application number 10 2007 017 970.9 of Apr. 11, 2007, which are incorporated herein by reference in their entirety and for all purposes. 
     
    
     BACKGROUND OF THE INVENTION 
       [0003]    The invention relates to a high-pressure cleaning appliance with a high-pressure pump, comprising at least one pump chamber which is connected to a suction line and a pressure line, the pressure line being in flow connection with the suction line via a return flow line, and a relief valve being arranged in the return flow line, the relief valve having a through-channel, which extends from a valve inlet to a first valve outlet, and which forms a valve seat, at least one outlet channel, which opens into a second valve outlet, branching off from the through-channel downstream of the valve seat, and a valve element adapted to be positioned by a return spring in a sealing manner against the valve seat being held for movement in the through-channel. 
         [0004]    Such high-pressure cleaning appliances are known from DE 297 12 659 U1. A surface to be cleaned can be acted upon with a pressurized cleaning liquid, for example, with water, by means of these. For this purpose, a high-pressure hose carrying at its free end, for example, a spray lance for spraying the surface to be cleaned can be connected to the pressure line. 
         [0005]    During normal operation, cleaning liquid can be supplied to the pump chamber via the suction line. The cleaning liquid is pressurized inside the pump chamber, for example, by means of a piston which is reciprocatingly displaceable and enters the pump chamber. The pressurized cleaning liquid can then be fed to a consumer via the pressure line. In this operating state, the relief valve is in its closed position, so that the direct connection between the pressure line and the suction line via the return flow line is interrupted. When a certain pressure value inside the pressure line is exceeded, as occurs, for example, upon closing a spray lance connected to the free end of the high-pressure hose, the relief valve transfers to its open position by the valve element, in opposition to the returning force exerted by the return spring, lifting off of the valve seat, so that cleaning liquid can flow back directly from the pressure line via the return flow line through the relief valve to the suction line and the pressure in the pressure line thereby dropping. The pressure drop may have the consequence that shortly after lifting off of the valve seat, the valve element is pressed back onto the valve seat again by the return spring, to then lift off of the valve seat again. The transition of the relief valve from the closed position to the open position of the relief valve may therefore be accompanied by an oscillating movement of the valve element and the return spring. This oscillating movement constitutes a considerable mechanical load. This may lead to failure of the high-pressure cleaning appliance. 
       SUMMARY OF THE INVENTION 
       [0006]    The object of the present invention is to so develop a high-pressure cleaning appliance of the kind mentioned at the outset that it is less susceptible to failure. 
         [0007]    This object is accomplished, in accordance with the invention, in a high-pressure cleaning appliance of the generic kind in that in the direction away from the valve seat, at a spacing from the at least one outlet channel, the valve element is surrounded by a sealing ring which seals off an inlet area of the through-channel adjacent to the valve inlet from an outlet area of the through-channel adjacent to the first valve outlet. 
         [0008]    As mentioned above, when a pressure peak occurs in the pressure line, the relief valve transfers to its open position in which the valve element lifts off of the valve seat. The flow connection between the valve inlet and the second valve outlet is thereby opened, so that cleaning liquid can flow through the inlet area of the through-channel via the at least one outlet channel to the second valve outlet. In the inlet area of the through-channel, i.e., in the area of the through-channel between the valve inlet and the sealing ring, the valve element is, therefore, under a considerable pressure load. On the side of the sealing ring facing away from this area, namely within the outlet area of the through-channel, the valve element is, in contrast, subjected to a considerably lower pressure load. The pressure difference acting as a result on the valve element has the consequence that the tendency of the valve element to oscillate is strongly reduced. Use of the sealing ring, which seals off the inlet area of the through-channel from its outlet area, therefore, has the consequence that the mechanical load on the valve element and the return spring can be reduced. The risk of spring breakage, caused by unintentional oscillatory movement of the valve element, can thereby be significantly reduced. The high-pressure cleaning appliance according to the invention, is therefore, characterized by a low susceptibility to failure. 
         [0009]    The opening force acting on the valve element in the open position of the relief valve, which results from the above-explained pressure difference, is dependent upon the size of the sealed-off surface defined by the sealing ring. Therefore, the opening force can be influenced by the choice of the size of the surface. 
         [0010]    Upon occurrence of a pressure peak, the liquid flowing into the relief valve can flow back from the pressure line of the high-pressure cleaning appliance into the suction line via the at least one outlet channel and the second valve outlet. Cleaning liquid, which in the case of leakage, can flow past the sealing ring surrounding the valve element, can flow out of the relief valve via the first valve outlet. The first valve outlet therefore forms a leakage opening. It also enables pressure compensation between the pressure prevailing in the suction line and the pressure in the outlet area of the through-channel. After reduction of the pressure peak in the pressure line, the relief valve automatically returns to its closed position again on account of the returning force of the return spring acting on the valve element. 
         [0011]    The sealing ring may, for example, be arranged in a groove machined in the wall of the through-channel, and the valve element may be movable back and forth relative to the sealing ring, with the sealing ring bearing in a sealing manner on the circumference of the valve element. 
         [0012]    Alternatively, it may be provided that the sealing ring is arranged in a circumferential groove of the valve element. In such a configuration, it is of advantage for the inner diameter of the sealing ring to be greater than the diameter of the bottom of the circumferential groove of the valve element. For, this has the consequence that the sealing ring is accommodated by the circumferential groove, but does not bear with its inner rim on the bottom of the circumferential groove. There is, however, a sealing contact between the outer rim of the sealing ring and the wall of the through-channel. It has been found that the valve element can thereby be held with greater ease of movement in the through-channel. 
         [0013]    It is of advantage for the valve element to comprise a closure member which is adapted to be positioned in a sealing manner against the valve seat, and a pressure member which is surrounded by the sealing ring at a spacing from the closure member. The closure member may, for example, be of spherical or conical configuration. Closure member and pressure member may be connected to each other with a substance-to-substance bond, more particularly, it may be provided that closure member and pressure member form a valve element of integral configuration. 
         [0014]    In a preferred embodiment of the invention, the through-channel comprises a guide section, on the inner wall of which the pressure member is mounted for displacement, with the sealing ring disposed between these. The guide section forms a sliding guide for the valve element and provides on its inner wall the sealing surface associated with the sealing ring. 
         [0015]    To ensure that upon occurrence of a pressure peak in the pressure line, the desired pressure drop will require a certain time, i.e., the relief valve, starting from its open position, will only gradually adopt its closed position in which the valve element again bears in a sealing manner on the valve seat, it is of advantage for the flow cross section of the through-channel in the area upstream of the at least one outlet channel to be greater than the flow cross section of the outlet channel. The outlet channel therefore forms a throttle element, so that a considerable pressure arises upstream of the outlet channel when the relief valve adopts its open position. The flow of cleaning liquid entering the relief valve encounters a resistance in the area of the decreasing flow cross section, so that the pressure prevailing in the inlet area of the through-channel is gradually reduced. 
         [0016]    It is particularly advantageous for the relief valve to comprise a single outlet channel, as the costs for manufacturing the relief valve can thereby be kept low, and a considerable throttle effect can be produced by the single outlet channel. 
         [0017]    It is expedient for the valve element to at least partially open the at least one outlet channel in both the open position and the closed position of the relief valve. Such a configuration has the effect that once the valve element lifts off of the valve seat, a continuous flow connection from the valve inlet via the inlet area of the through-channel and the outlet channel to the second valve outlet is immediately ensured, i.e., incoming liquid can already flow through the relief valve upon a slight lifting movement of the valve element off of the valve seat, it not being necessary for the valve element to adopt a minimum spacing from the valve seat in order to open the flow connection between valve inlet and second valve outlet. 
         [0018]    In a preferred embodiment, there is associated with the valve element a stop on which the valve element bears when the relief valve is in the open position. The stop forms a defined delimitation for the stroke of the valve element, so that the desired stroke of the valve element may be structurally predefined by the position of the stop. 
         [0019]    It may be provided that the stop is formed by a narrowing of the through-channel. For example, the through-channel may form a step on which the valve element can bear when the relief valve is in the open position. 
         [0020]    Alternatively, it may be provided that the stop is formed by a supporting element arranged in the through-channel. Such a configuration has the advantage that the position of the stop delimiting the stroke of the valve element can be predefined by choice of the supporting element. In a preferred configuration, the supporting element projects radially inwardly from an inner wall of the through-channel. 
         [0021]    In a preferred configuration, the relief valve comprises a first housing part and a second housing part, which are connectable to each other with a sealing ring disposed between these. A releasable or also an unreleasable connection, for example, a locking or screw connection, may be used to connect the two housing parts. 
         [0022]    The first housing part preferably comprises the valve inlet, the valve seat and the at least one outlet channel and the second valve outlet, and the second housing part preferably comprises the first valve outlet. 
         [0023]    It is expedient for the second housing part to comprise an insert which is insertable into the first housing part with a sealing ring disposed between these. It is of advantage for the insert to carry on the outside an annular groove in which the sealing ring is arranged. The insert may be of, for example, cup-shaped configuration and accommodate the end area of the valve element that faces away from the valve seat. In this end area, the valve element may comprise an annular groove in which there is arranged the sealing ring surrounding the valve element. 
         [0024]    The return spring is preferably clamped between a collar of the valve element and an end face of the second housing part. 
         [0025]    The following description of two preferred embodiments of the invention serves for a more detailed explanation in conjunction with the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]      FIG. 1  shows a schematic side view of a high-pressure cleaning appliance according to the invention; 
           [0027]      FIG. 2  shows an enlarged longitudinal sectional view of the pump head of the high-pressure cleaning appliance from  FIG. 1 ; 
           [0028]      FIG. 3  shows a longitudinal sectional view of a first embodiment of a relief valve of the high-pressure cleaning appliance from  FIG. 1 ; and 
           [0029]      FIG. 4  shows a longitudinal sectional view of a second embodiment of a relief valve of the high-pressure cleaning appliance from  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0030]    A high-pressure cleaning appliance  10  having an appliance housing  12  which accommodates a motor pump unit  14  is shown diagrammatically in  FIGS. 1 and 2 . The motor pump unit  14  comprises an electric motor  15  followed by a gearing  16  and a piston pump  18  driven via a swash plate  17  and having a number of pistons  19  reciprocatingly displaceable in the axial direction of the high-pressure cleaning appliance  10 . These respectively enter a pump chamber  21  of a pump head  22  of the high-pressure cleaning appliance  10 . The pump chambers  21  are respectively connected via a suction valve  24  to a suction line  25  and via a pressure valve  27  to a pressure line  28 . Here the suction line  25  and the pressure line  28  are common to all pump chambers  21  of the pump head  22 . 
         [0031]    Inserted in the pressure line  28  is a spring-loaded non-return valve  30 , which is followed in the direction of flow by an injector  31  which reduces the flow cross section of the pressure line  28 . At its narrowest point, the injector  31  is connected via a suction channel  32  to a chemical intake line  33 , which is closed by a non-return valve  34 . 
         [0032]    In the area between the non-return valve  30  arranged in the pressure line  28  and the injector  31 , a return flow line  36 , which widens in stepped configuration in the direction of flow, leads directly from the pressure line  28  to the suction line  25 . Inserted in the return flow line  36  is a relief valve  38 , which is configured as a cartridge that can be handled independently. The relief valve  38  is surrounded in the circumferential direction by a sealing ring  39  which bears in a sealing manner against the wall of the return flow line  36 . 
         [0033]    The relief valve  38  is shown on an enlarged scale in  FIG. 3 . It comprises a two-part housing with a first housing part  41 , which carries the sealing ring  39  in a circumferential groove  42  and is insertable in a sealed manner into the return flow line  36 . The relief valve  38  also comprises a second, cup-shaped housing part  44  with a cylindrical casing  45  and a bottom wall  46 . The second housing part  44  is locked to the first housing part  41 . For this purpose, the first housing part  41  has at its end directed away from the circumferential groove  42  an annular groove  48  in which an inwardly projecting annular shoulder  49  of the second housing part  44  may engage elastically when the second housing part  44  is pushed in the axial direction onto the first housing part  41 . 
         [0034]    The two housing parts  41  and  44  define a through-channel  50  which, starting from a valve inlet  52  at an end face, forms a first channel section  53 , which passes via a spherical widening  54  into a second channel section  56 . The widening  54  forms a valve seat  58  for the closure member  60  of a valve element  61  held in the through-channel  50  for movement in the longitudinal direction of the through-channel  50 . The closure member  60  is in the form of a spherical cap and bears in a sealing manner against the valve seat  58  in the closed position of the relief valve  38  shown in  FIG. 3 . The closure member  60  is followed in the axial direction by a pressure member  63  of the valve element  61 . The pressure member  63  is in the form of a piston and carries on its outer side a circumferential groove  64  in which a sealing ring  66  surrounding the valve element  61  in the circumferential direction is arranged. The sealing ring  66  bears against the wall of the through-channel  50  in the area of its second channel section  56 . 
         [0035]    The second channel section  56  is followed in the axial direction via a conical widening  68  by a third channel section  69 , which passes via a stepped widening  71  into a fourth channel section  72 . The fourth channel section  72  is defined by the casing  45  of the second housing part  44 . It comprises axially extending longitudinal ribs  74 , which project radially inwardly from the casing  45  and extend as far as first valve outlets  75  which penetrate the bottom wall  46 . 
         [0036]    The fourth channel section  72  accommodates a return spring  77  configured as a helical spring, which is supported, on the one hand, on the bottom wall  46  of the second housing part  44  and, on the other hand, on the underside  78  of the pressure member  63 , which faces the bottom wall  46 . The pressure member  63  and the closure member  60  are acted upon by a spring force in the direction of the valve seat  58  by means of the return spring  77 , so that in the closed position of the relief valve  38 , the closure member  60  bears tight against the valve seat  58 , as shown in  FIG. 3 . 
         [0037]    The upper end face  80  of the longitudinal ribs  74 , which faces the pressure member  63 , forms a stop for the pressure member  63  of the valve element  61 , when, in the open position of the relief valve  38 , the pressure member  63  lifts off the valve seat  58 . This will be explained in further detail hereinbelow. 
         [0038]    The first housing part  41  has at a spacing from the valve seat  58  in the second channel section  56  of the through-channel  50  a radially extending outlet channel  88 , whose radially outwardly lying end area forms a second valve outlet  89  of the relief valve  38 . 
         [0039]    The sealing ring  66  surrounding the valve element  61  in the circumferential direction divides the through-channel  50  into an inlet area  91  and an outlet area  92 . The inlet area  91  is formed by the first channel section  53 , the spherical widening  54  and the area of the second channel section  56  that surrounds the closure member  60 . The outlet area  92  is formed by the area of the second channel section  56  that follows the closure member  60 , by the conical widening  68 , by the third channel section  69  and by the stepped widening  71  and the fourth channel section  72 . 
         [0040]    During normal operation of the high-pressure cleaning appliance  10 , i.e., when pressurized cleaning liquid is issued through the pressure line  28  to a high-pressure hose (not shown in the drawings) connectable to the pressure line  28 , the valve element  61  is pressed by the return spring  77  against the valve seat  58 , so that the relief valve  38  adopts its closed position in which the flow connection from the valve inlet  52  via the inlet area  91  of the through-channel  50  and the outlet channel  88  to the second valve outlet  89  is interrupted. 
         [0041]    When a certain pressure value of the cleaning liquid is exceeded, as may occur, for example, when switching off the high-pressure cleaning appliance  10 , the valve element  61  is lifted off the valve seat  58  against the spring force of the return spring  77  and displaced downwards in the direction away from the valve seat  58  until the pressure member  63  bears with its underside  78  against the free end face  80  of the longitudinal ribs  74 . The longitudinal ribs  74  therefore delimit the stroke of the valve element  61 . The flow connection between the valve inlet  52  and the second valve outlet  89  is opened by the lifting of the valve element  61  off of the valve seat  58 , and a considerable pressure arises within the inlet area  91  of the through-channel  50 , whereas a considerably lower pressure, namely the pressure prevailing in the suction line  25 , is present in the outlet area  92  of the through-channel  50 , which is separated from the inlet area  91  by the sealing ring  66 . Therefore, in the open position of the relief valve  38 , a pressure difference acts on the valve element  61 , as a result of which a force acting axially in opposition to the action of the return spring  77  is applied to the valve element  61 , which reliably holds the valve element  61  at a spacing from the valve seat  58  until the pressure of the cleaning liquid in the inlet area  91  has dropped so far that the force of the return spring  77  is adequate to return the valve element to the valve seat  58 . The pressure difference acting on the valve element  61  when the relief valve  38  is in the open position reduces the occurrence of oscillatory movements of the valve element  61 . 
         [0042]    A second embodiment of a relief valve, which may be used alternatively to the relief valve  38  in the high-pressure cleaning appliance  10 , is shown in  FIG. 4 . It is generally denoted by reference numeral  98 . The relief valve  98  has a first housing part  101  and a second housing part  102 . On the outside, the first housing part  101  carries a circumferential groove  104 , which accommodates a sealing ring  105 , which bears in a sealing manner against the wall of the return flow line  36  upon insertion of the relief valve  98 , configured as a cartridge that can be handled independently, into the return flow line  36 . 
         [0043]    The housing parts  101  and  102  are locked to each other. Alternatively, a screw connection could, for example, also be used to releasably connect the two housing parts  101 ,  102 . 
         [0044]    The two housing parts  101  and  102  define a through-channel  107 . This starts from a valve inlet  109  at the end face of the first housing part  101  and extends with a first cylindrical channel section  111  to a first conical widening  112 , which is followed by a second cylindrical channel section  113 , which passes via a second conical widening  114  into a third cylindrical channel section  115 . The third cylindrical channel section  115  is surrounded by a casing  117  of the first housing part  101 . With a cup-shaped insert  119 , which defines a fourth cylindrical channel section  120  of the through-channel  107 , the second housing part  102  enters the casing  117 . 
         [0045]    The insert  119  is integrally connected to a bottom wall  122  of the second housing part  102 , which closes off the free end of the casing  117  of the first housing part  101 . At the side facing away from the insert  119 , the bottom wall  122  is followed by a cylindrical extension  123 , which like the bottom wall  122  has an axially extending through-bore  124  passing through it. The through-bore  124  forms a fifth cylindrical channel section  125  of the through-channel  107 , with a stepped narrowing  126  arranged in the area of transition between the fourth channel section  120  and the fifth channel section  125 . 
         [0046]    The cup-shaped insert  119  carries on its outer side an annular groove  129 , in which a sealing ring  130  is arranged, which ensures a fluid-tight connection between the first housing part  101  and the second housing part  102 . 
         [0047]    Mounted for movement inside the through-channel  107  is a valve element  132  with a closure member  133  in the form of a spherical cap and a pressure member  134  following the closure member  133  in the axial direction. In the closed position of the relief valve  98  shown in  FIG. 4 , the closure member  133  bears tight against a valve seat  136  formed by the first conical widening  112 . The pressure member  134  extends from the closure member  133  into the area of the fourth channel section  120  where it carries on the outside an annular groove  138  in which there is arranged a sealing ring  139 , which surrounds the valve element  132  in the circumferential direction. The inner diameter of the sealing ring is selected so as be larger than the diameter of the bottom of the annular groove  138 . This has the consequence that the sealing ring  139  is spaced from the bottom of the annular groove  138 , as shown in  FIG. 4 . At the outside, the sealing ring  139  bears tight against the wall of the fourth channel section  120 . 
         [0048]    At a spacing from the closure member  133 , the pressure member  134  has a collar  144  below the longitudinal axis  141  of a radially extending outlet channel  142 . A return spring  146  configured as a helical spring, which surrounds the pressure member  134  in the third channel section  115  in the circumferential direction, is supported, on the one hand, on the free end face  148  of the cup-shaped insert  119 , which faces the valve seat  136 , and, on the other hand, on the underside  149  of the collar  144 , which faces away from the valve seat  136 . The valve element  132  is acted upon with a spring force in the direction towards the valve seat  136  by the return spring  146 . 
         [0049]    The fifth channel section  125  passing through the bottom wall  122  and the axial extension  123  forms with its free end area a first valve outlet  151 , and the outlet channel  142  starting from the through-channel  107  forms with its radially outwardly lying end area a second valve outlet  152 . The through-channel  107  is divided by the sealing ring  139  surrounding the valve element  132  in the circumferential direction into an inlet area  154  and an outlet area  155 , which are separated from each other in a fluid-tight manner by the sealing ring  139 . The inlet area  154  is formed by the first channel section  111 , the first conical widening  112 , the second channel section  113 , the second conical widening  114 , the third channel section  115  and the part of the fourth channel section  120  that is adjacent to the free end face  148 . The outlet area  155  of the through-channel  107  is formed by the part of the fourth channel section  120  that is adjacent to the stepped narrowing  126  and by the fifth channel section  125 . 
         [0050]    During normal operation of the high-pressure cleaning appliance, the relief valve  98  adopts its closed position in which the valve element  132  bears with the closure member  133  tight against the valve seat  136 . When a certain pressure value of the cleaning liquid inside the pressure line  28  is exceeded, the valve element  132  is lifted off of the valve seat  136  in opposition to the force of the return spring  146  until the pressure member  134  bears with its end facing away from the closure member  133  against the stepped narrowing  126 . The stepped narrowing  126  therefore forms a stop for delimiting the stroke of the valve element  132 . A flow connection from the valve inlet  107  to the second valve outlet  152  is opened by the valve element  132  lifting off of the valve seat  136 , so that excess liquid can escape from the pressure line  28  through the return flow line  36  to the suction line  25 . A considerable pressure thereby arises in the inlet area  154  of the through-channel  107 , whereas a considerably lower pressure, namely the pressure prevailing in the suction line  25 , is present in the outlet area  155 . This causes a differential pressure to act on the valve element  132 , which results in a force being applied away from the valve seat  136 . Owing to the application of this force, the valve element  132  maintains its position at a spacing from the valve seat  136  until the excess pressure drops in the pressure line  28 . The pressure drop occurs gradually as the flow cross section of the outlet channel  142  is chosen so as to be smaller than the flow cross section of the through-channel upstream of the outlet channel  142 . The outlet channel  142  forms a throttle element for the cleaning liquid flowing through the relief valve  98 , which ensures that a considerable pressure builds up in the inlet area  154  of the through-channel  107  when the relief valve  98  adopts its open position.