Patent Publication Number: US-7213501-B2

Title: Hydraulic control arrangement

Description:
The invention relates to a hydraulic control arrangement for the load-independent control of a consumer in accordance with the preamble of claim  1 . 
   The basic structure of such a control arrangement is known, for instance, from WO 95/32364 A1. In this load pressure-independent flow distribution (LUDV) 1  system each consumer is provided with an adjustable metering orifice including a pressure compensator down the line, the latter keeping the pressure drop above the metering orifice constant so that the amount of pressure medium flowing to the respective hydraulic consumer is solely dependent on the opening cross-section of the metering orifice and not on the load pressure of the consumer or on the pump pressure. Since, for instance, in mobile working implements a plurality of such valve arrangements are connected in parallel, it is achieved by the pressure compensators of the system that, in the case that a hydro pump of the system has been adjusted up to the maximum stroke volume and the pressure medium flow is not sufficient to maintain the predetermined pressure drop above the metering orifices of the respective valve arrangements allocated to a consumer, the pressure compensators of all operated hydraulic consumers are adjusted in the closing direction so that all pressure medium flows are reduced by the same percentage. Due to this load-pressure independent flow distribution (LUDV) then all operated consumers move at a velocity reduced by the same percentage value. In the known solution it may occur when a consumer is supported for a quite long time that it drops due to a leakage flow via the distribution valve.  1 German abbreviation (lastdruckunabhängige Durchflussverteilung) 
   This drawback is eliminated in a solution according to the data sheet RD 64 284/06.00 (hydro valves for mobile applications) by a releasable check valve which is inserted in the pressure medium flow path between the distribution valve and a consumer connection and which ensures the oil-leakage free shut-off thereof. In this known solution moreover a pressure/feed valve by which the consumer is protected against overload and against cavitation phenomena in the case of a lacking supply of the corresponding consumer connection with pressure medium. 
   In the solution known from FR 2,756 349 to each consumer connection a suction valve is allocated which extends perpendicularly to the plane of a valve disk accommodating the valve arrangement. This known solution lacks a stop valve for oil-leakage free shut-off of the consumer, however. 
   Compared to this, the object underlying the invention is to provide a hydraulic control arrangement in which all components required for controlling the consumer are combined in a compact manner in a valve housing portion, preferably a valve disk. 
   This object is achieved by a hydraulic control arrangement comprising the features of claim  1 . 
   In accordance with the invention, the control arrangement is preferably integrated in a valve disk, wherein a distribution valve forming a LUDV metering orifice as well as two stop valves allocated to a consumer connection are located in the valve disk plane and two pilot valves allocated to the two stop valves are incorporated such that the axes thereof are oriented perpendicularly to the two axes of the distribution valve and of the stop valves. The pressure/anti-cavitation valve allocated to a consumer connection is arranged perpendicularly to the axes of the afore-described valve elements, i.e. perpendicularly to the disk plane. Moreover it is a particular feature of the invention that the pilot valves arranged perpendicularly to the axis of the distribution valve are actuated mechanically via a tappet which is axially movable by a slide valve of the distribution valve so as to release the stop valves and to permit discharge of pressure medium from the consumer. 
   The solution according to the invention excels by a special compactness, wherein all substantial components required in a LUDV system are accommodated in a minimum construction space. 
   Solutions in which the pilot valve is actuated mechanically via the slide valve of the distribution valve are known as such for instance from DE 196 27 306 A1 or U.S. Pat. No. 3,595,271 or U.S. Pat. No. 3,125,120. But these documents include no information about the compact structure according to the invention of a valve disk for a LUDV system. 
   In a preferred embodiment of the invention the distribution valve, the stop valves and the pilot valves are arranged in parallel to the disk plane ( FIG. 1 ) and the anti-cavitation valve is arranged perpendicularly to the disk plane so that the valve disk can be manufactured with a minimum effort due to the simple passage guiding. 
   In this variant it is preferred when also the axis of the LUDV pressure compensator downstream of the metering orifice of the distribution valve extends in the disk plane. 
   In an embodiment having a particularly compact design the axis of the individual pressure compensator is arranged centrally between the axes of the two pilot valves so that the valve disk has an almost axially symmetrical structure. 
   In this variant it is preferred when the axis of the two anti-cavitation valves is arranged in the area which is encompassed by the axis of the two stop valves, the two axes of the pilot valves and the axis of the distribution valve. 
   For actuating the pilot valve the slide valve of the distribution valve has an operating portion by which a tappet guided perpendicularly to the distribution valve axis is axially movable for controlling the pilot valve to be opened. In a preferred embodiment of the invention this tappet is guided in a portion of the valve disk or the valve housing. 
   In a particularly compact embodiment the axis of the pilot valve intersects the axis of the respective allocated stop valve. 
   The mounting of the anti-cavitation valves is especially simple when in the area of these anti-cavitation valves working passages leading to the consumer connections are located in a plane which is arranged offset with respect to a plane of the valve disk including a reservoir passage. 
   Other advantageous further developments of the invention constitute the subject matter of further subclaims. 

   
     Hereinafter a preferred embodiment of the invention will be illustrated in detail by way of schematic drawings in which: 
       FIG. 1  shows a schematic sectional view of a valve disk comprising the control arrangement according to the invention; 
       FIG. 2  shows a detailed representation of a distribution valve of the valve disk from  FIG. 1 ; 
       FIG. 3  is a detailed representation of a stop valve, a pilot valve and a pressure compensator of the distribution valve from  FIG. 1  and 
       FIG. 4  is a cut side view of the valve disk from  FIG. 1  including a pressure/anti-cavitation valve. 
   

     FIG. 1  shows a section across a valve disk  1  of a control block of a mobile working implement, for instance a dipper dredger, wherein the valve elements for each function (for example traveling drive, lifting/lowering, operating the shovel etc.) are each combined in a valve disk. The valve disk  1  shown in  FIG. 1  has two consumer connections A, B and a pressure connection P (not shown), a reservoir connection T (not shown) as well as plural control connections (inter alia an LS connection). In the valve disk  1  a continuously variable distribution valve  2  is provided including a slide valve  4  which is guided to be axially movable in an axial bore  6  passing through the valve disk  1  in the transverse direction. As explained in more detail hereinafter, the slide valve  4  together with the axial bore  6  forms a velocity member, which is also referred to as metering orifice  8 , and two directional members  10 ,  12  via which the direction of the pressure medium flow from and to the consumer connections A, B is defined. 
   Downstream of the metering orifice an individual pressure compensator  14  (LUDV pressure compensator) is provided to which in the opening direction the pressure downstream of the metering orifice  8  is applied and in the closing direction the force of a not shown control spring and the maximum load pressure of the consumers is applied. This load pressure is tapped off via a load pressure detecting line  16  and is signaled to the spring chamber of the pressure compensator. Under certain circumstances the control spring can also be dispensed with. 
   In the valve disk  1  moreover two stop valves  18 ,  20  each allocated to a consumer connection A, B are arranged via which the consumer connections A, B can be shut off in an oil-leakage free manner. In order to permit a reflux each stop valve  18 ,  20  can be released by means of a pilot valve  22 ,  24 . In the embodiment represented in  FIG. 1  the axes of these pilot valves  22 ,  24  extend perpendicularly to the axis of the distribution valve  2  and the common axis of the two stop valves  18 ,  20 , the axes of the pilot valves  22 ,  24  intersecting the axis of the allocated distribution valve  18  and  20 , respectively. Each of the pilot valves  22 ,  24  is actuated via a tappet  30 ,  32  which is axially movable by the slide valve  4 . 
   Perpendicularly to the plane of projection in  FIG. 1 , in the valve disk  1  two further pressure/anti-cavitation valves  26 ,  28  are inserted which control a connection to the reservoir connection T to be opened when a predetermined pressure at the consumer connection A, B is exceeded and which permit feeding of pressure medium from the reservoir in the case of a lacking supply of pressure medium. According to  FIG. 1 , the two axes of the pressure/anti-cavitation valves  26 ,  28  are located inside the area formed by the common axis of the two stop valves  18 ,  20 , the axis of the distribution valve  2  as well as the two axes of the pilot valves  22 ,  24 . 
   The individual pressure compensator  14  as well as the stop valves  18 ,  20 , the pilot valves  22 ,  24  and the pressure/anti-cavitation valves  26 ,  28  are inserted in valve bores of the valve disk  1  which are bored from outside, i.e. from the end faces (pressure compensator, pilot valves, stop valves) or from the large area of the valve disk  1  (pressure/anti-cavitation valves) and are shut off after inserting the respective valve bodies by screw plugs or the like. 
   Further details of the valve arrangement will be illustrated hereinafter by way of the detailed representations. 
     FIG. 2  shows the distribution valve  2  of the valve disk  1 . 
   The slide valve  4  includes a plurality of annular grooves by which it is subdivided into a central metering orifice collar  34 , two control collars  36 ,  38  arranged on both sides thereof and two reservoir collars  40 ,  42  arranged laterally thereof. The two end portions  44 ,  46  project from the valve disk  1 . In this area, housings which accommodate the centering springs for the slide valve  4  or control members are flanged to the valve disk. 
   The annular end faces of the two reservoir collars  40 ,  42  located externally in  FIG. 2  are in the form of inclined control faces  50 ,  52  against which the tappet  30  and/or  32  is not biased in the central position of the control slide. The two other annular end faces of the reservoir collar  40 ,  42  are provided with control notches  54 ,  56 . In a similar way fine control notches  58 ,  60  also end in the annular faces of the central metering orifice collar  34 . 
   The non-represented pressure connection P opens into a pressure chamber  62  which is formed by an annular groove of the axial bore  6 . In addition to this pressure chamber  62 , the axial bore is further extended to a connecting chamber  64 , two annular chambers  66 ,  68 , two outlet chambers  70 ,  72  as well as two external reservoir chambers  74 ,  76 . Between each of the aforementioned chambers there remain lands which cooperate with the control edges of the slide valve  4 . 
   According to  FIG. 1  and  FIG. 2  the connecting chamber  64  opens into a pressure compensator passage  78  leading to the inlet of the individual pressure compensator  14 . The outlet of the individual pressure compensator is connected to the annular chambers  66 ,  68  via two passages  80 ,  82 . Each of the two outlet chambers  70 ,  72  opens into a consumer passage  84 ,  86  extending toward the inlet of the stop valves  18  and  20 , respectively. 
   In each of the two reservoir chambers  74 ,  76  a reservoir chamber  88 ,  90  (cf.  FIG. 1 ) opens which leads to the corresponding pressure/anti-cavitation valve  26 ,  28 . 
   In  FIG. 3  that part of the valve disk  1  is represented in which the stop valve  20  and the pilot valve  24  as well as a part of the individual pressure compensator  14  are housed. The stop valve  20  has a stop piston  96  which is guided to be axially movable in a stop valve bore  94 . The latter is shut off by a screw plug  98  supporting a spring  100  via which the stop piston  96  is biased against a valve seat  102 . The stop piston  96  is designed to have a seat difference. In the shown locking position the connection between the consumer passage  86  and a working passage  104  connected to the consumer connection B is closed. 
   This working passage  104  extends from the consumer connection B to the pressure/anti-cavitation valve  28 . 
   In the shell of the stop piston  96  a nozzle  106  is provided by which a spring chamber  108  accommodating the spring  100  is connected to the operating passage  104 . This spring chamber  108  can be relieved via the pilot valve  24  toward the reservoir T. The pilot valve includes a seat lining  110  inserted in a bore  112 . In the valve lining  110  a pilot seat  114  is formed against which a valve body  116  is biased by means of a pilot spring  118 . The latter is supported on a circlip  120  inserted in the lining  110 . As one can take especially from  FIG. 3 , the bore  112  intersects the stop valve bore  64 , wherein in the representation according to  FIG. 3  the valve lining  110  is inserted with the valve body  116  and the pilot spring  118  in an area of the bore  112  which is arranged opposite to the stop valve bore  94 . The opening area of the bore  112  distant from the valve lining  110  is shut off by a screw plug  112 . The axis of the bore  112  extends coaxially with respect to the axis of the tappet  82  guided in a guide projection  124  of the valve disk  1 . The bore  112  ends in the reservoir chamber  76  so that the end portion of the tappet  32  located on the top in  FIG. 3  can dip into the opening encompassed by the pilot seat  114  and can be brought into contact with the valve body  116 . 
   The pressure compensator piston  126  is biased with an axial projection  128  against a wall of the pressure compensator passage  78  and at the adjacent annular front includes control notches  130  constituting a control edge by which the connection between the pressure compensator passage  78  and the passages  80 ,  82  can be opened. 
   The pressure-limiting valve is a unit. The pressure spring presses on the seat element  138  and the disk  142  which is positively connected to  144  and  146 . 
   The elements  144  and  146  are one component. The tapered end of  146  is pulled by the pressure spring to the internal seat in  138 . The tapered spring  200  presses the entire unit  138  onto the seat in the housing. 
     FIG. 4  shows a cut side view in the area of the pressure/anti-cavitation valve  26 . The consumer connection A opens into a working passage  132 . The latter (corresponding to the working passage  104  of the working connection B) leads to a radial connection of the pressure/anti-cavitation valve  18 . This valve is inserted in an anti-cavitation bore  134  through which the working passage  132  can be connected to the reservoir passage  88 . By the anti-cavitation bore  134  an anti-cavitation valve seat  136  is formed against which an anti-cavitation cone  138  is biased via a pressure spring  140 . This spring is supported on a spring plate  142  which, in turn, is mounted on a piston rod  144  of a pressure-limiting piston  146  guided in the anti-cavitation cone  138 . The piston rod  144  including the spring plate  142  is supported on a supporting screw  148  which is screwed into the anti-cavitation bore  134  from a large area of the valve disk  1 . In the anti-cavitation cone  138  a seat for the pressure-limiting piston  146  is provided against which the latter is biased by the force of the pressure spring  140 . The pressure in the spring chamber of the pressure/anti-cavitation valve  26  is signaled to the seat for the pressure-limiting piston  146  via pressure bores  150  of the anti-cavitation cone  138 . When a predetermined maximum pressure is exceeded in the working passage  132 , the pressure-limiting piston  146  lifts off the seat against the force of the pressure spring  140  and against the pressure acting on the pressure-limiting piston  146  in the reservoir passage  88  to the left ( FIG. 4 ) so that pressure medium can flow from the working passage  132  into the reservoir passage  88 —the pressure in the working passage  132  thus being restricted to the maximum value. In the case of a lacking supply, in the reservoir passage  88  a higher pressure is prevailing than in the working passage  132  so that the anti-cavitation cone  138  can lift off its anti-cavitation valve seat  136  against the force of the pressure spring so that pressure medium can flow from the reservoir into the working passage  132 , sufficient supply with pressure medium is ensured and cavitation cannot occur. 
   The structure according to the invention having a design symmetrical in the representation according to  FIG. 1  with respect to the axis of the individual pressure compensator  14  and the intersecting axes of the stop valve  18 ,  20  and the allocated pilot valve  22 ,  24  and the pressure/anti-cavitation valves  26 ,  28  arranged perpendicularly thereto permits to combine all hydraulic components required for a LUDV control and a leakage-free support of a consumer in a minimum space. 
   For a better comprehension of the invention, hereinafter the function of the control arrangement  1  according to the invention will be briefly explained. It is assumed that the slide valve  4  of the distribution valve  2  is moved to the right in the representation according to  FIG. 1  so as to pass pressure medium via the consumer connection A to the consumer and from the latter via the consumer connection B back to the reservoir T. By the axial displacement of the slide valve  4  to the right a metering orifice cross-section is controlled to be opened via the control notches  58  of the metering orifice collar  34  so that pressure medium can flow from the pressure chamber  62  into the pressure compensator passage  78 . With a sufficient pump pressure the pressure compensator is moved to an opening position by the pressure effective in the opening direction so that the pressure medium can flow via the passage  80  and the annular chamber  66  into the opened outlet chamber  70 . From there the pressure medium passes via the consumer passage  84  to the inlet of the stop valve  18 . With a sufficient pressure in the consumer passage  84  the stop piston  96  of the stop valve  18  is lifted off its valve seat  102  against the force of the spring  100  so that the pressure medium is supplied toward the consumer A. The load pressure building up at the consumer is signaled via the LS passage  74  to the spring chamber of the individual pressure compensator  14 . This compensator adjusts a control position in which the pressure drop is kept constant above the inlet metering orifice. 
   At the same time, the tappet  32  is displaced upwards via the control surface  52  in the axial direction (view according to  FIG. 1 ) by the axial movement of the slide valve  4  to the right so that the valve body  116  is lifted off its pilot seat  114  and the spring chamber  108  of the stop valve is correspondingly relieved toward the reservoir chamber  76 . The pressure prevailing at the working connection B then suffices to lift the stop piston  96  off its valve seat  102  against the force of the spring  100  so that the pressure medium can flow from the working connection B via the consumer passage  86  and the discharge cross-section opened by the reservoir collar  42  including the control notches  56  into the reservoir chamber  76  and from there to the reservoir. 
   In the event in which a pulling load occurs (for instance when pouring out or lowering a load) it may happen that not sufficient pressure medium is fed to the working connection A so that the pressure at this connection falls below the pressure in the outlet. In other words, the inlet pressure falls below the reservoir pressure so that the pressure/anti-cavitation valve is opened in the above-described manner and pressure medium can continue to flow from the reservoir passage  88  into the working passage  132 . 
   A hydraulic control arrangement is disclosed for the load pressure independent control of a consumer, comprising a distribution valve forming an inlet metering orifice, a corresponding individual pressure compensator, a stop valve provided for each consumer connection which may be released by means of a pilot valve and an anti-cavitation valve by means of which pressure medium can be drawn from a reservoir to avoid cavitation. According to the invention, the distribution valve and the stop valves are arranged along two parallel axes, while the axes of the two pilot valves are arranged perpendicularly to these two axes. The anti-cavitation valves in turn extend perpendicularly to the axes of the distribution valves, the stop valves and the anti-cavitation valves. 
   LIST OF REFERENCE NUMERALS 
   
       
         1  Valve disk 
         2  distribution valve 
         4  slide valve 
         6  axial bore 
         8  metering orifice 
         10  directional member 
         12  directional member 
         14  individual pressure compensator 
         16  LS passage 
         18  stop valve 
         20  stop valve 
         22  pilot valve 
         24  pilot valve 
         26  pressure/anti-cavitation valve 
         28  pressure/anti-cavitation valve 
         30  tappet 
         32  tappet 
         34  metering orifice collar 
         36  control collar 
         38  control collar 
         40  reservoir collar 
         42  reservoir collar 
         44  end portion 
         46  end portion 
         50  control surface 
         52  control surface 
         54  control notch 
         56  control notch 
         58  fine control notch 
         60  fine control notch 
         62  pressure chamber 
         64  connecting chamber 
         66  annular chamber 
         68  annular chamber 
         70  outlet chamber 
         72  outlet chamber 
         74  reservoir chamber 
         76  reservoir chamber 
         78  pressure compensator passage 
         80  passage 
         82  passage 
         84  consumer passage 
         86  consumer passage 
         88  reservoir passage 
         90  reservoir passage 
         94  stop valve bore 
         96  stop piston 
         98  screw plug 
         100  spring 
         102  valve seat 
         104  working passage 
         106  nozzle 
         108  spring chamber 
         110  valve lining 
         112  bore 
         114  pilot seat 
         116  valve body 
         118  pilot spring 
         120  circlip 
         122  screw plug 
         124  guide projection 
         126  pressure compensator piston 
         128  axial projection 
         130  control notches 
         132  working passage 
         134  anti-cavitation bore 
         136  anti-cavitation valve seat 
         138  anti-cavitation cone 
         140  pressure spring 
         142  spring plate 
         144  piston rod 
         146  pressure limiting piston 
         148  supporting screw 
         150  pressure bores