Patent Publication Number: US-RE38355-E

Title: Electrohydraulic control device for double-acting consumer

Description:
This is a reissue of application Ser. No.  08 / 796 , 921 , filed Feb.  6 ,  1997 , now U.S. Pat. No.  5 , 799 , 485  which is a continuation of PCT/DE 96 / 00314 , filed Feb.  24 ,  1996 . 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to electrohydraulic control devices for double-acting consumers. 
     The invention is based on an electrohydraulic control device for a double-acting consumer. One such electrohydraulic control device is already known from European Patent Disclosure EP 0 110 126 A1, in which to control a double-acting consumer a longitudinally movable control slide can be actuated for a 4/3-way function of two magnets disposed oppositely on the housing. To keep the leakage slight, each consumer connection is secured in the manner of a seat valve by a hydraulically controlled blocking valve. The pilot control of these blocking valves is performed by those tappets that transmit the switching motion of the magnets to the control slide. Along with the functions of raising, holding and lowering, a fourth, free-float position can additionally be attained by briefly exciting both magnets at the same time. Moreover, the control device can also be used to control a single-acting consumer. A disadvantage of this control device, however, is that it works with magnets that merely switch, so that sensitive, proportional volumetric flow control is not possible. Moreover, the embodiment of the tappet as pilot control member makes for a relatively complicated structural design. The disposition of the switching magnets on opposite sides of the housing, in combination with the 4/3-way longitudinal slide and the tappets used for pilot control makes for a very long structure in the slide axis, which makes the control device unfavorable for mobile use. 
     An electrohydraulic control device is also known from German Patent Disclosure DE 41 40 604 A1; it works with a proportional magnet and is suitable for fine control of volumetric flows. The pilot control valve member disposed in a main valve member is actuated by the proportional magnet and cooperates like a followup controller with the main valve member, so that short response times and hence good regulating behavior are attained. The valve members for the main and pilot control stages are embodied as seat valves, which keeps the leakage slight. The control device is also embodied such that there is no need for a separate control oil supply. An unfavorable aspect of this control device is that it can execute only a 2/2-way function and is therefore unsuitable in this form for controlling a double-acting consumer. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide an electrohydraulic control device for a double-acting consumer of the above-described type which avoids the above-described disadvantages. 
     According to the invention the electrohydraulic control device for a double-acting consumer includes 
     a first and second consumer connection, a first and second work conduit communicating with the first and second consumer connection respectively and including first and second blocking valves for blocking the consumer connections, a first lowering conduit communicating with the second consumer connection and a second lowering conduit communicating with the first consumer connection, each lowering conduit by-passing the blocking valves; and 
     electromagnetically actuable control means for blocking or connecting at least one consumer connection, which comprises a first four-way, two-position proportional magnet valve and a second four-way, two-position proportional magnet valve identical to the first four-way, two position proportional magnet valve. Each magnet valve includes a slidable valve member provided with control edges and having an initial position in which the connected work conduit is relieved, an inlet connection, a return connection, a first motor connection alternatively connected to the inlet connection or the return connection by operation of the slidable valve member with the control edges, a second motor connection and valve seat means for controlling, e.g. closing, the second motor connection. The first motor connection of the first magnet valve communicates with the first work conduit and the first motor connection of the second magnet valve communicates with the second work conduit. The second motor connection of the first magnet valve is connected with the first lowering conduit and thus the second consumer connection and the second motor connection of the second magnet valve is connected with the second lowering conduit and thus the first consumer connection. 
     The electrohydraulic control device according to the invention has the advantage over the prior art that while having a proportional mode of operation, it can control a double-acting consumer with little leakage. The magnet valves, because of the slide drives chosen, enable short response times, which leads to good regulating performance of the control device. The control device can attain a total of four work positions with only two magnets, so that in additional to the usual functions of raising, holding and lowering, a fourth, free-float position is possible by exciting both magnets; the switching sequence is arbitrary. The control device functions without a separate control oil supply and can moreover be used for a single-acting consumer. The control device is also compact in structure and is therefore suitable for mobile applications. 
     In preferred embodiments of the control device according to the invention used for regulating volumetric flow in each magnet valve the second motor connection is blocked by the seat valve means and the inlet connection is blocked by the slidable valve control member in its initial position and the slidable valve control member has a work position in which the inlet connection communicates with the first motor connection and the second motor connection communicates with the return connection. 
     Advantageously each slidable valve control member comprises a longitudinally movable main control member and each magnet valve comprises a pilot-controlled valve including the main control member, a proportional magnet and a pilot control member actuable by the proportional magnet to cooperate with the main control member so as to act as a followup controller. The seat valve means includes a main valve cone disposed on the main control member for blocking the second motor connection and is connected in series with a fine-control edge provided on the main control member for communication with the return connection and the control edges are disposed on the main control member spatially separated from each other. 
     In a particularly preferred embodiment the main control member has a thickened end portion having an end face defining an end-face pressure chamber adjoining the main control member so that a pressure in this pressure chamber urges the main control member in a closing direction. The pilot-controlled valve includes means for relieving the end-face pressure chamber including a slide edge, a pilot control cone connected in series with the slide edge, the slide edge and pilot control cone begin provided on the pilot control member, and a spring arranged to urge the pilot control member in a direction toward the initial position and opposite to another direction of motion of the pilot control member caused by operation of the proportional magnet. The main control member advantageously has at least one differential face and the main control member is urged in an opening direction by a pressure at the second motor connection acting on the at least one differential face. The main control member has a second differential face and is positionable so that a pressure at the inlet connection acts on the second differential face urging the main control member in an opening direction and the pilot-controlled valve includes means for connecting the end-face pressure chamber with the second motor connection or the inlet connection so that the end-face pressure chamber is selectively acted on by a higher pressure at the second motor connection or the inlet connection, and the means for connecting includes check valves and inlet throttles. 
     The pilot-controlled valve is provided with a slide bore for the main control member. This slid bore includes an inlet chamber, a first motor chamber, a return chamber, an intermediate chamber and a second motor chamber arranged in a preferred embodiment in succession spaced from each other in the slide bore with the inlet chamber being closest to the proportional magnet and the second motor chamber being furthest from the proportional magnet. The connections of the magnet valve are assigned to respective chambers of the slide bore. 
     In another embodiment of the control device the pilot-controlled valve advantageously includes a housing provided with slide bore through which the main control member is moved. This slide bore includes a return chamber, a second motor chamber, a first motor chamber, an inlet chamber and a magnetic-end pressure chamber arranged in succession with the magnet-end pressure chamber closest to the proportional magnet and the return chamber furthest from the proportional magnet. In this embodiment the main valve cone controls communication with the return chamber, a spring is provided in the return chamber and is arranged to urge the main control member towards the initial position and to press the main valve cone against a valve seat fixed in the housing of the pilot-controlled valve. The magnet-end pressure chamber is bounded by an end of the main control member closest to the proportional magnet so that pressure in the magnet-end pressure chamber urges the main control member in a direction toward a work position against action of the spring. The magnet-end pressure chamber is connected to the return connection via a throttle bore and is connected with the return connection by means of the pilot control member and the proportional magnet is provided with an armature and another spring braced against the housing and holding the pilot control member against the armature of the proportional magnet. Advantageously the main control member is provided with a throttle bore and a damping piston guided slidably in the throttle bore, protruding into the return chamber and provided with a return throttle. The first motor chamber is arranged side-by-side of the second motor chamber, the inlet chamber is located between the first motor chamber and the proportional magnet and an intermediate chamber is located between the second motor chamber and the return chamber. 
     According to a preferred embodiment the blocking valves each have an inlet-side inlet, a spring-loaded back end, a control connection communicating with the spring-loaded back end and means for transmitting a pressure prevailing at the inlet-side inlet of one blocking valve to the control connection of the other blocking valve and thus to the spring-loaded back end thereof so as to block the other blocking valve. Advantageously each blocking valve is provided with a throttle check valve and the control connections of both blocking valves communicate with each other for transmission of the pressure prevailing at the inlet-side inlet of one blocking valve to the spring-loaded back end of the other. This provides a reliable mode of operation and permits a space-saving, inexpensive structural design. 
     In one embodiment of the control device that can be used for an LS system the electromagnetically actuable control means includes an alternating valve which has a spring-centered middle position, is connected between the two first motor connections of both magnet valves and has two opposite end connections connected to the respective first motor connections and a middle connection connected to a load pressure line so that, when one end connection of the alternating valve is pressurized, a maximum pressure is transmitted into the load pressure line. 
     If the proportional magnets are arranged on one side of the housing of the control device, mechanical actuation is possible without major effort. This also results in a compact, space-saving design. 
     Valve seats are advantageously provided in the housing for the main valve members so that the control device can be manufactured economically. 
     The two blocking valves and the alternating valve are advantageously arranged in the housing in a region between the two magnet valves in various preferred embodiments. Particularly the magnet valves are arranged with their longitudinal axes in two planes parallel to each other and spaced from each other. The blocking valves are arranged axially parallel in the housing in different transverse planes spaced apart from each other and parallel to each other. The transverse planes are advantageously spaced apart a distance greater than a distance between the longitudinal planes in which the magnet valves are located. The location of the blocking valves in this embodiment leads to a space-saving structure and the resulting shortened conduits are also favorable for regulating performance. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     The objects, features and advantages of the invention will now be illustrated in more detail with the aid of the following description of the preferred embodiments, with reference to the accompanying figures in which: 
     FIG. 1 is a simplified hydraulic circuit diagram of an electrohydraulic control device for a double-acting consumer; 
     FIG. 2 is a longitudinal cross-sectional view through a proportional magnet valve having a simplified structural design in accordance with the circuit diagram for it in the lower part of FIG. 1; 
     FIG. 3 is simplified control circuit of a portion of the control device of FIG. 1 including the blocking valves; 
     FIG. 4 is a detailed longitudinal cross-sectional view through a single blocking valve of a simple structural design; 
     FIG. 5 is a detailed cross-sectional view through the device shown in FIG. 4 taken along the section line V—V in FIG. 4; 
     FIG. 6 is a longitudinal cross-sectional view through the control device of FIG. 1 taken along the sectional line VI—VI in FIG. 7; 
     FIG. 7 is a cross-sectional view of the control device of FIG. 1 taken along the section line VII—VII of FIG. 6; 
     FIG. 8 is a cross-sectional view through the control device of FIG. 1 taken along the sectional line VIII—VIII of FIG. 6; 
     FIG. 9 is a cross-sectional view taken along the section line IX—IX of FIG. 7; and 
     FIG. 10 is a cross-sectional view through another embodiment of a proportional magnet valve for use in the control device of FIG.  1 . 
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1, in a simplified circuit diagram, shows an electrohydraulic control device  10  for controlling a double-acting consumer  11 , of the kind that can be used for LS systems. The control device  10  has a first magnet valve  12  and a structurally identical second magnet valve  13 . Both magnet valves  12 ,  13  are embodied as proportional valves with a four-way, two-position function, which are each actuatable by a respective proportional magnet  14  and  15 . Each magnet valve  12 ,  13  is adjustable by its magnet  14  and  15 , respectively, counter to the force of a spring  16 , out of its initial position  17  into a work position  18 . The volumetric flow is controllable continuously via the magnet valve  12  or  13  in proportion to the electrical input variable. 
     The magnet valves  12 ,  13 , which are identical to one another, each have an inlet connection  19 , designated P. Both inlet connections connected to an adjusting pump  21  that supplies them with pressure fluid. In addition, each magnet valve  12 ,  13  has a return connection  22 , designated R, and the return connections are relived to a tank  23 . Moreover, each magnet valve  12 ,  13  has a first motor connection  24 , designated A, and a second motor connection  25 , designated B. In the initial position shown, the inlet connection  19  is hydraulically blocked. The first motor connection  24  communicates with the return connection  22 , and the second motor connection  25  is closed by seat valve means  26  of the magnet valve  12 ,  13 . Upon deflection into the work position  18 , the inlet connection  19  communicates with the first motor connection  24 , while the second motor connection  25  is relieved to the return connection  22 , and these communications are continuously controllable. 
     In the control device  10 , a first work conduit  27  leads from the first motor connection  24  at the first magnet valve  12  to a first consumer connection  28 . The hydraulically controllable first blocking valve  29  is connected into this work conduit  27 . The blocking valve  29  is embodied as a controlled check valve. Its inlet  31  communicates with the first motor connection  24 , while its outlet  32  communicates with the first consumer connection  28 , while a control connection  33  can be acted upon by pressure via a first control line  34 . From the first motor connection  25  of the first magnet valve  12 , a first lowering conduit  35  leads to a second consumer connection  36 , bypassing the blocking valves. 
     Similarly to the case of the first magnet valve  12 , in the second magnet valve  13  a second work conduit  37  leads from the first motor connection  24  to the second consumer connection  36 , and a second blocking valve  38  is connected into this work conduit  37  and is structurally identical to the first blocking valve  29 . From the second motor connection  25  of the second magnet valve  13 , a second lowering conduit  41  leads to the first consumer connection  28 , bypassing the blocking valves  29 ,  38 . 
     The control device  10  also has an alternating valve  42 , whose slide  43  has a spring-centered middle position. The alternating valve  42  is connected by its face-end pressure connections  44 ,  45  to the first and second work conduits  27  and  37 , respectively, in each case upstream of the respective blocking valves  29 ,  38 , while its middle connection  46  reports the maximum load pressure at the time to the adjusting pump  21 . If pressure is absent or the pressures are the same relieves this middle connection  46  to a tank connection  47 . 
     FIG. 2 shows a longitudinal section through a first magnet valve  12 , embodied in simplified structural form, and as shown merely schematically in FIG.  1 . The structural design of the control device of DE 41 40 604 A1 is expressly assumed to be known; the essential components and mode of operation can be learned from this reference. In the magnet valve  12  of FIG. 2, elements identical to those of FIG. 1 are provided with the same reference numerals. 
     In FIG. 2, the magnet valve  12 , in a housing  50 , has a continuous, repeatedly stepped slide bore  51 , in which an inlet chamber  52 , a first motor chamber  53 , a return chamber  54 , an intermediate chamber  55 , and a second motor chamber  56  are embodied. These chambers communicate correspondingly with the associated inlet connection  19  (P), the first motor connection  24  (A), the return connection  22  (R), and the second motor connection  25  (B). A main control member  57  is guided in this slide bore  51  and in its interior receives a pilot control member  58 , which is actuatable by the armature  70  of the proportional magnet  14  counter to the force of the spring  16 . The main control member  57  and pilot control member  58  cooperate in the manner of a followup controller; both control members  57 ,  58  have a seat valve means for the sake of secure closing of the second motor chamber  56 . The main control member  57  to that end has a main valve cone  59 , on its end remote from the magnet  14 . This cone cooperates with a seat  60  solidly joined to the housing between the second motor chamber  56  and the intermediate chamber  55 . With its main valve cone  59 , the main control member  57 , defines a pressure chamber  61  on its face end, thereby forming a first circular pressure face  62 , which urges the main control member  57  in the direction of its initial position  17 . In addition, the main valve cone  59  is embodied such that it forms a first differential face  63 , which is acted upon by the pressure in the second motor chamber  56  and acts upon the main control member  57  in the opening direction. The communication of the second motor chamber  56  with the return chamber  54  via the intermediate chamber  55  is controlled downstream of the main valve cone  59  by a first piston portion  64  with fine-control chambers  65 . On the main control member  57 , spaced apart from this first piston portion  64  in the region of the first motor chamber  53 , there is a second piston portion  66 , which with a second control edge  67  and an associated fine-control groove  68  controls the communication from the inlet chamber  52  to the first motor chamber  53 . The end of the main control member  57  is embodied such that it forms a second differential face  69 , acted upon by the pressure in the inlet connection  19 ; on pressurization, together with the first pressure face  63 , it urges the main control member  57  in the opening direction. On the main control member  57 , the second piston portion  56  has a third control edge  71 , which in the initial position  17  shown connects the first motor chamber  53  with the return chamber  54 . 
     For controlling the control oil flow from the pressure chamber  61  to the return chamber  54 , the pilot control member  58  has a slide edge  72  that takes on the task of fine control and a pilot control code  73  that takes on the task of secure sealing; this edge and cone are connected in succession in the control oil flow. The pilot control member  58  is guided with pressures balanced and is urged, by the spring  16  braced solidly against the housing, in the direction of the initial position  17 , in which it is braced by its pilot control cone  73  on the associated valve seat in the main control member  57 . The pressure chamber  61  can be acted upon in alternation with pressure fluid; the pressure in the inlet chamber  52  can reach the pressure chamber  61  via a longitudinal bore  74  and a check valve  75 , fixed to the housing, with an inlet throttle  79 . If the load pressure in the second motor chamber  56  is higher, then pressure fluid flows into the pressure chamber  61  via a second check valve  76 , disposed in the main valve cone  59  and having the inlet throttle  79 . For the outflow of control pressure fluid from the pressure chamber  61  via the pilot control member  58 , transverse bores  77  are disposed in the main control member  57  and are located in the region between the two piston portions  64  and  66 . 
     The mode of operation of the electrohydraulic control device  10  will be explained as follows, referring to FIGS. 1 and 2. 
     In a first, neutral position, the two proportional magnets  14 ,  15  are without current, and the magnet valves  12  and  13  each assume their respective initial positions  17 . Thus their inlet connection  19  is blocked, as illustrated in FIG. 2 by the second control edge  67  on the second piston portion  66 . Also in the initial position  17  of each magnet valve  12 ,  13 , the first motor connection  24  is relieved to the return connection  22 . In FIG. 2, the third control edge  71  on the second piston portion  66  opens up the communication from the first motor chamber  53  to the return chamber  54 . In this initial position  17 , the second motor connection  25  is also sealed off by the seat valve function  26  of the magnet valves  12  and  13 , in order to keep any leaking oil flow slight. The main valve cone  59  is pressed against the associated valve seat  60  by the pressure prevailing in the pressure chamber  61 , since the higher of the pressures prevailing in the second motor chamber  56  or in the inlet chamber  52  can reach the pressure chamber  61  via the check valve  76  and  75 , respectively, and there act upon the large pressure face  62 . The closing force on the main control member  57  is greater in any case than the opening forces that can be exerted by the pressure in the second motor connection  25  on the first differential face  63  and/or by the pressure in the inlet chamber  55  on the second differential face  69 . The pressure chamber  61  is also securely sealed off by the pilot control cone  73  of the pilot control member  58 . The pilot control member  58  itself is pressed by the spring  16 , against an associated valve seat in the main control member  57 . 
     In this neutral position, the magnet valves  12 ,  13  relieve their adjacent portions of the work conduits  27  and  37 , respectively, so that the inlet  31  at the each blocking valve  29  and  38  is pressureless. Via the control lines  34 ,  39 , whose paths cross one another, the control connections  33  of the two blocking valves  29 ,  38 , are also pressure relieved. The closing members of the blocking valves  29 ,  38  are each urged by their spring into their blocking position, so that the outlet  32  is hydraulically blocked. Thus the first consumer connection is also hydraulically blocked by the first blocking valve  29  and the seat valve means  26  in the second magnet valve  13 , while the second consumer connection  36  is blocked by the second blocking valve  38  and by the seat valve means  26  in the first magnet valve  12 . The piston rod  78  in the double-acting consumer  11  is thus hydraulically blocked. 
     In the second, raising work position, which here corresponds to a an extension of the piston rod  78  from the consumer  11 , the proportional magnet  14  of the first magnet valve  12  is supplied with current, and as a result a proportional regulation of volumetric flow to the consumer  11  is possible. The magnet  15  at the second magnet valve  13  remains currentless in the process. If the first magnet valve  12  is shifted into its work position  18 , then it connects the inlet connection  19  with the first motor connection  24 , so that pressure fluid can flow from the adjusting pump  21  via the magnet valve  12  into the first work conduit  27  and via the opening blocking valve  29  to the first consumer connection  28  and thus into the cylinder chamber of the consumer  11 . The first blocking valve  29  here acts purely as a check valve, since its control connection  33  is relieved to the tank via the first control line  34 , a portion of the second work conduit  37 , and the second magnet valve  13 . At the same time, the second magnet valve  13  blocks off the second lowering conduit  41 , with its seat valve means  26 . Pressure fluid from the annular chamber of the consumer  11  flows via the second consumer connection  36  and the first lowering conduit  35  to the second motor connection  25  on the first magnet valve  12 , from which it is removed to the tank  23 . The pressure prevailing between the first magnet valve  12  and the first blocking valve  29  in the first work conduit  27  also builds up via the second control line  39  in the control connection  33  of the second blocking valve  38 , and as a result this valve acts as a blocked check valve and blocks off its outlet  32  from the inlet  31 . The pressure prevailing in the first work conduit  27  passes via the pressure connection  44  into the alternating valve  42 , whose other pressure connection  45  is relieve to the tank. The slide  43  of the alternating valve  42  migrates to its right-hand terminal position, and the pressure from the first pressure connection  44  is carried via the middle connection  46  to the load pressure line to the adjusting pump  21 , while the tank connection  47  is blocked. The control device  10  can thus function as an LS system in a known manner. 
     Upon deflection of the magnet valve  12  to the raising position or work position  18 , the force of the proportional magnet  14  would not suffice for the direct control of the hydraulic power in question here. For this reason, the main control member  57  requires an additional drive, which is embodied here in the manner of a followup controller. The pilot control member  58  disposed in the main control member  57  is embodied in pressure equilibrium for this purpose, and in FIG. 2 it is deflected into its work position  18 , or in other words to the left in FIG. 2, by the armature  59  of the proportional magnet  14  solely counter to the force of the spring  16 . 
     In the process, its pilot control cone  73  opens the communication from the pressure chamber  61  to the return chamber  54  via the pilot control member  58  and the transverse bores  77 . While the pilot control cone  73  takes on the task of tight blocking, the slide edge  72  on the pilot control member  58  assures fine control of this control oil flow, so as to control the pressure in the pressure chamber  61  continuously. If this control oil connection is opened via the slide edge  72  and the pilot control cone  73 , then the pressure in the pressure chamber  61  drops, and hence the closing force on the main control member  57  drops as well. The load pressure in the second motor chamber  56 , acting upon the first differential face  63 , and the inlet pressure in the inlet chamber  52  acting upon the second differential face  69  move the main control member  57  to the left in terms of FIG.  2 . In a manner known per se, the main control member  57  follows the pilot control member  58  in the manner of a followup controller. In this opening motion, the main valve cone  59  lifts up from the valve seat  60  fixed to the housing, and it connects the second motor chamber  56  to the intermediate  55 , which in turn is relieved to the return chamber  54  via the fine-control chambers  65 . The magnitude of the volumetric flow from the second motor connection  25  to the return connection  22  is regulated continuously and hence proportionally to the current value at the magnet  14 . In this opening motion of the main control member  57 , its third control edge  71  on the second piston portion  66  blocks off the communication from the first motor chamber  53  to the return chamber  54 , while at the same time the second control edge  67  opens up the communication from the inlet chamber  52  to the first motor chamber  53 . The magnitude of the volumetric flow is controlled by the fine-control grooves  68 . During this control operation, the higher pressure is selected for operation of the main control member  57 , by means of the two small check valves  75  and  76 , which are each in series with two associated inlet throttles  79 . This higher pressure is either the pump pressure in the inlet chamber  52  or the load pressure in the second motor chamber  56 , above all if a pulling load predominates. This higher pressure always acts upon the large pressure face  62  and produces the closing force there. In the “raising” position, the volumetric flow to and from the double-acting consumer  11  is thus controlled with the first magnet valve  12 . The work position  18  extends over a portion of the stroke of the main control member  57 , so that the volumetric flow is controllable in proportion to the current value at the magnet  14 . 
     In the third, lowering, position, which corresponds to a retraction of the piston rod  78  of the consumer  11 , only the second magnet valve  13  is actuated, while the first magnet valve  12  is not excited. The volumetric flow is then in the correspondingly opposite direction to or from the double-acting consumer  11 . Pressure fluid is directed by the adjusting pump  21  to the second consumer connection  36  and on into the annular chamber of the consumer  11  via the second magnet valve  13 , which is in its work position  18 , the second work conduit  37 , and the second blocking valve  38  acting as a check valve. At the same time, pressure fluid flows away to the tank  23  from the cylinder chamber of the consumer  11 , via the first consumer connection  28  and the second lowering conduit  41  as well as the second magnet valve  13 . The first blocking valve  29  then functions as a blocked check valve, while the alternating valve  42  assumes its other terminal position and connects the pressure connection  45  with the middle connection  46  and hence with the adjusting pump  21 . The second magnet valve  13  functions in the same way as the structurally identical first magnet valve  12 , in the manner of the followup controller described. 
     For the fourth position of the control device  10 , namely the free-float position, the magnets  14 ,  15  of the two magnet valves  12 ,  13  are simultaneously supplied with maximum current and thus deflected to their work positions  18 . The same pressure then prevails in the two work conduits  27  and  37  in their portions upstream of the respective blocking valves  29  and  38 . This pressure, via the crossing control lines  34  and  39 , is present at the control connections  33  of the two blocking valves  29  and  38 , causing them to act as blocked check valves. Because of the pressure equality, the slide  43  of the alternating valve  42  also remains in the middle position shown, so that the middle connection  46  is relieved to the tank connection  47 , while the pressure connections  44 ,  45  are blocked. This means there is no LS signal to the pressure supply of the adjusting pump  21  and hence no increase in the pressure. The two lowering conduits  35  and  41  are relieved to the tank by the associated magnet valves  12  and  13 , respectively, so that free-float conditions exist for the double-acting consumer  11 . 
     With the control device  10 , a single-acting function can be realized as well, for instance if instead of the double-acting consumer  11  a single-acting consumer is connected only to the first consumer connection  28 , while the second consumer connection  36  is unused. The neutral position can then be attained as before, if both magnets  14 ,  15  are not excited. A raising position can be attained by supplying current to the first magnet valve  12  only. The lowering position can be attained by supplying current to both magnet valves  12 ,  13 , with the valve  13  being deflected only in accordance with the desired lowering current. 
     With the present control device  10 , along with a double-acting function, a single-acting function can accordingly be realized; if two magnets are used, a total of four work positions are possible. The control device  10  then functions without a separate control pressure supply and, because of its seat valve means, it operates with the little leakage. On free-float or lowering in a single-acting function, no unblocking pressure and hence no raising of pump pressure is necessary. Because of the slide drives chosen, the magnet valves  12 ,  13  can attain short response times, so that the control device  10  has good regulating performance. 
     FIG. 3 schematically shows a portion of the control device  10  having the blocking valves  29 ,  38 , which differ from one another by a simplified control line circuit  81 . To avoid the crossing of the control lines  34 ,  39  as shown in FIG. 1, because the development of such a course is undesirable in a valve housing, in FIG. 3 the control line circuit  81  has a main control line  82 , which connects the two control connections  33  of the two blocking valves  39 ,  38  with one another. The valve bodies  83  of both blocking valves  29 ,  38  also each contain a small check valve  84 , and a throttle  85  is provided parallel to the check valve. The small check valve  84  in the valve body  83  serves to allow the blocking valve  29  or  38  itself to function as a simple check valve on switching of a magnet valve  12  or  13 , and it must therefore open relatively fast. Via the parallel throttles  85 , the blocking pressures can now be passed through the valve cone  83  to its back side, thus averting a crossing of the lines. If only one magnet valve, such as  12 , is actuated, then the pressure p1 in the inlet  31  is greater than the pressure p3 in the control connection  33 , and the blocking valve  29  itself operates as a check valve, and the valve body  83  lifts from the seat. If both magnet valves  12  and  13  are actuated simultaneously, then the pressures p1 and p3 are of equal magnitude, so that an associated spring  86  keeps the valve body  83  closed. The control line circuit  81  is simplified substantially by making do with only a single main control line  82 . This function of the blocking valves  29  and  38  is still preserved if there is a throttle  85  disposed in only one of the two valve bodies  83 . 
     FIG. 4 shows a longitudinal section through a structurally embodied blocking valve  90 , with which the functions of the blocking valve  29  shown schematically in FIG. 3 can be executed. The valve bodies schematically shown in FIGS. 1 and 3 are embodied such that the ratio of their seat diameter to their shaft diameter is 1. A prerequisite of such an embodiment is hardened valve seats, which is unfavorable for a version of the control valve  10  in a cast metal housing. In order therefore to make it easier to attain the function of the blocking valve  29  of FIG. 3 in a cast metal housing, the structurally embodied blocking valve  90  of FIG. 4 is embodied as a differential face valve, which does not require an exact seat diameter but instead works with a relatively broad seat geometry and therefore makes do with a low pressure per unit of surface area in the cast metal housing. For the embodiment as a differential face valve, the blocking valve  90  has a tubular valve body  91 , which controls the communication from the inlet  31  to the outlet  32  and is guided tightly and slidingly on a boltlike extension  92  of a blocking piston  93 . The valve body  91  is braced via a spring  94  against the blocking piston  93 , on whose extension  92  a collar  95  is formed. The blocking piston  93  is tightly and slidingly guided in a housing bore  96  and defines a chamber  97  that receives the spring  94  and that communicates with the outlet  32  via a throttle groove  98 . A passage  99  leading from the inlet  31  to the control connection  33  is formed in the blocking piston  93 , and a throttle check valve known per se is also incorporated in this passage. The function of the check valve  84  of FIG. 3 is taken over by a triangular disk  101 , in which the throttle  85  is embodied centrally as a small bore. In the cross section of FIG. 5, the shape of this triangular disk  101  can clearly be seen. 
     With this blocking valve  90  of FIG. 4, the function of the blocking valve  29  of FIG. 3 can be attained structurally, with only a single main control line  82  leading away from the control connection  33 . In this blocking valve  90 , if the control connection  33  is relieved and if p3 is equal to 0, then upon a volumetric flow arriving at the inlet  31 , the valve body  91  will open and, if the pressure of p1 is larger, direct the volumetric flow into the outlet  32 , whose pressure p2 is lower than p1. Conversely, if the control connection  33  is acted upon, and if its pressure p3 is of equal magnitude to the pressure p1 in the inlet  31 , then the blocking valve  90  blocks the communication with the outlet  32 . The blocking piston  93  is displaced counter to the force of the spring  94  by the pressure in the control connection  33  and is braced by its collar  95  on the tubular valve body  91 , as a result of which this valve body is pressed against the associated valve seat solidly attached to the housing. 
     FIG. 6, in the form of a longitudinal section, now shows the structural design of the control device  10  of FIG. 1; identical components to those of FIGS. 1-5 are again provided with the same reference numerals. In the control device of FIG. 6, in addition to the control device shown schematically in FIG. 1, an individual pressure compensating valve  105  is provided in the housing  50 ; it is preceded by the two magnet valves  12  and  13 . For explanation of the control device of FIG. 6, reference is made to FIGS. 7-9, which show cross sections taken through the lines VII—VII, VIII—VIII of FIG. 6 and a section taken along the line IX—IX of FIG.  7 . Moreover, the precise course of the longitudinal section of FIG. 6 is represented by the line VI—VI of FIG.  7 . 
     In the control device  10  of FIG. 6, the housing  50  is essentially parallelepiped in shape, since the device is designed for a disk type of design in an LS system. In the housing, the two magnet valves  12  and  13  are disposed with their longitudinal axes parallel to one another, in such a way that both proportional magnets  14 ,  15  are mounted on one end face  106 . Because of the joint disposition of both magnets on one side, the control device  10  is also especially advantageous for a mechanical actuation. On the housing  50  opposite the end face  106 , a flat installation face  107  is formed, toward which the two continuous, repeatedly offset slide bores  51  of both magnet valves  12 ,  13  open. The installation face  107  is covered by a cap  108 , in which the first consumer connection  28  is formed, while the second consumer connection  36  is located in the housing  50  itself. Both consumer connections  28 ,  36  are open toward one surface  109 . In the slide bore  51  located closer to the surface  109  in the housing  50 , the first magnet valve is provided, while the second magnet valve  13  is located in the slide bore  51  below it. As can be seen in more detail in FIG. 6, the inlet chambers  52  of both magnet valves  12 ,  13  communicate with one another and also lead into the pressure compensating valve  105 , which can be supplied with pressure fluid by the adjusting pump  21  via the pump connection  111 . 
     As FIGS. 7 and 8 show in more detail, the magnet valves  12  and  13  are located in different longitudinal planes, which extend parallel to the flange faces  112  of the housing  50 . Because of the spaced-apart longitudinal planes through the magnet valves  12 ,  13 , these valves can be disposed closer together in terms of height, which makes a compact design and short conduits possible. As FIG. 7 in combination with FIG. 9 shows in more detail, the two blocking valves  29 ,  38  and the alternating valve  42  are located in a region of the housing  50  that extends between the two magnet valves  12  and  13 . It can be seen from FIG. 7 that the distance between the longitudinal planes extending through the blocking valves  29  and  38  is still considerably greater than the distance between the longitudinal planes through the magnet valves  12 ,  13 . Moreover, the blocking valves  29  and  38  are offset in height relative to one another, to enable an especially compact design. It is clearly shown in FIG. 7 that the second consumer connection  36  communicates with the second motor chamber  56  of the first magnet valve  12  and also communicates with the outlet  32  of the second blocking valve  38 . In the same sectional plane, the second motor chamber  56  of the second multiposition valve  13  also communicates at the top with the outlet  32  of the first blocking valve  29 , and at the same time it communicates with the first consumer connection  28 , via a lower bay  113 , via a transverse conduit  114  and a vertically extending work conduit  115 . 
     As also seen from FIG. 8, the first motor chamber  53  of the first magnet valve  12  has a kidney-shaped bay protruding obliquely downward, so that it communicates with the inlet  13  of the first blocking valve  29 , as shown in further detail in FIG.  9 . Correspondingly, the first motor chamber  53  of the second magnet valve  13  has a kidney-shaped bay protruding obliquely upward, so that it communicates with the inlet  31  of the second blocking valve  38 , as shown in detail in FIG.  9 . The return chambers  54  of both magnet valves  12  and  13  communicate with one another via continuous return conduits  116  and a connection or end plate not shown in further detail. The pump conduit  111  penetrates the housing  50  in the same way as the return conduits  116 . 
     As seen from FIG. 6 in combination with FIG. 9, what this arrangement of the magnet valves  12  and  13  and the blocking valves  29  and  38  attains is that all the valve seats fixed in the housing, in the two slide bores  51  of the magnet valves  12  and  13  and in the housing bores  96  for the blocking valves  29  and  38 , are open toward the installation face  107  and can readily be machined from there. With the structural version of the control device  10  of FIG. 6, all the functions and advantages described in conjunction with the control device of FIG. 1 can be attained. Moreover, the spatial arrangement of the two magnet valves  12 ,  13 , the two blocking valves  29 ,  38  and the alternating valve  42  in the housing  50  results in an extremely space-saving, compact design that is especially suitable for mobile applications. As also seen from FIG. 9, in the case of the blocking valves  29  and  38  the function of the disklike check valve  101  can also be dispensed with entirely, so that only the throttle restriction  85  is provided. The blocking valves  29  and  38  can continue to perform their function then, but the pressure in the intervening main control line  82  in that case is only half as high as the load pressure. 
     The mode of operation of the control device  10  of FIG. 6 is fundamentally the same as that of FIG. 1, and the mode of operation of the magnet valve  12  of FIG.  2  and the blocking valve  90  of FIG. 4 are also referred to expressly here. Therefore the following description will merely briefly discuss the flow course in the housing  50  that arises in the raising and lowering positions. If in the raising position only the magnet valve  12  is actuated, then the volumetric flow flowing from the pump conduit  111  into the inlet chamber  52  via the pressure compensating valve  105  reaches the first motor chamber  53  via the second control edge  67 . As seen in FIG. 8, the volumetric flow there enters the lower kidney-shaped recess and from there can reach the inlet  31  of the second blocking valve  29 , as can be seen from FIG.  9 . This blocking valve  29  opens the communication with its outlet  32 , from whence the volumetric flow—as can be seen from FIG.  7 —flows via the second motor chamber  56  of the second magnet valve  13  farther downward into the pocket-like bay  113 , from whence it reaches the first consumer connection  28  via the transverse conduit  114  and the work conduit  115  in the cap  108 . At the same time, the volumetric flow returning from the consumer is deflected into the second consumer connection  36 , from whence it can reach the return chamber  54 , via the second motor chamber  56  of the first magnet valve  12  and its opened main valve cone  59 , via the intermediate chamber  55  and the fine-control chambers  65 . As also shown in more detail in FIG. 7, this returning volumetric flow also reaches the outlet  32  of the second blocking valve  38 , which however, because of the imposition of pressure via the main control line  82 , acts as a blocked check valve and blocks the communication with its inlet  31 . 
     If in the lowering position only the second magnet valve  13  is actuated, then the volumetric flow arriving via the pressure compensating valve  105  flows from the common inlet chamber  52  into the first motor chamber  53  of the second multiposition valve  13 . As FIG. 8 shows in more detail, the volumetric flow from there passes via the obliquely upward-pointing bay in the first motor chamber  53  to reach the inlet  31  of the second blocking valve  38 . This valve functions as a check valve and opens the communication with its outlet  32 , from whence—as FIG. 7 shows in detail—the volumetric flow moves past the second motor chamber  56  of the first magnet valve  12  to the first consumer connection  36  and from there flows to the consumer  11 . The volumetric flow leaving the consumer  11  passes via the first consumer connection  28 , the work conduits  115  and  114 , to reach the pocketlike bay  113  and flows on into the second motor chamber  56  of the second magnet valve  13 , by way of whose opened main valve cone the flow of pressure fluid can likewise flow away to the return chamber  54  via the intermediate chamber  55 . The other functions of the alternating valve  42  and the volumetric flows in the free-float position can be seen from FIG.  1 . 
     FIG. 10 shows a longitudinal section through another structural embodiment of a magnet valve  120 , of the kind that can be used in the control device  10  for the schematically shown magnet valves  12  and  13 . In terms of its basic design, the magnet valve  120  is comparable to the magnet valve  12  of FIG. 2 in the sense that it has a main control member  121  and a pilot control member  122  disposed therein, which cooperate in the manner of a followup controller; the pilot control member  122  is actuated by the armature  59  of the proportional magnet  14 . The magnet valve  120  has a continuous, repeatedly offset slide bore  123  in the housing  50 , in which bore an inlet chamber  124 , a first motor chamber  125 , a second motor chamber  126 , and intermediate chamber  127 , and a return chamber  128  are formed by annular expansion. The inlet chamber  124  communicates with the inlet connection  19  (P), the first motor chamber  125  communicates with the first motor connection  24  (A), the second motor chamber  126  correspondingly communicates with the second motor connection  25  (B), and the return chamber  128  communicates with the return connection  22  (R). In the region between the intermediate chamber  127  and the return chamber  128 , a valve seat  129  fixed in the housing is formed, which cooperates with a main valve cone  131  that is disposed on the end of the main control member  121  remote from the magnet  14 . Spaced apart from that, the main control member  121  has a first piston portion  132  with fine-control notches  133 , which control the communication between the intermediate chamber  127  and the second motor chamber  126 . The second motor chamber  126  is also sealed off by a O-ring  134  in the main control member  121 . On a second piston portion  135  in the region of the first motor chamber  125 , a second control edge  136  is provided, with adjoining fine-control grooves  137  that control the communication from the inlet chamber  124  to the first motor chamber  125 . A third control edge  138  on the second piston portion  135  serves to relieve the first motor chamber  125 ; this relief is effected into the return chamber  128  via a recess  139 . With a slide edge  142 , the pilot control member  122 , protruding into a blind bore  141  of the main control member  121 , controls a communication from the inlet chamber  124  to a face-end pressure chamber  143 , into which the end of the main control member  121  toward the magnet  14  protrudes. Via a main throttle bore  144 , the bind bore  141  communicates with the recess  139 , into which a damping piston  145  is fitted. A main spring  146  disposed in the return chamber  128  presses the main control member  121  into its initial position  17 , in which its main valve cone  131  is braced against the valve seat  129  fixed in the housing. A ring insert  147  is also installed fixed in the housing on the side of the magnet  14  in a widened portion of the slide bore  123 . A spring  148  is braced against this insert and on its other end presses the pilot control member  122  against the armature  59  of the magnet  14 . 
     In principle, the mode of operation of the magnet valve  120  is similar to that of the magnet valve  12  of FIG.  2 . When the magnet  14  is not excited, the switching connections shown for the magnet valve  12  in FIG. 1 are attained, in which the second motor connection  25  is tightly blocked off by the main valve cone  131  and thereby attains the seat valve function  26 . The O-ring  134 , which may also be embodied as a slide ring or piston ring, serves to seal off the second motor connection  25  from the first motor chamber  125 . A longer narrow gap at this point would also be possible as a seal. Supplying current to the magnet  14  deflects the magnet valve  120  into a work position  18 , in which the pilot control member  122  and the main control member  121  cooperate in the manner of a followup controller. The pilot control member  122  is in pressure-equilibrium, so that the armature  59  needs to overcome only the force of the spring  147 . Via the slide edge  142 , the pilot control member  122  can raise the pressure in the pressure chamber  143 , so that the opening force on the main control member  121  predominates, and the main control member is pressed to the left into its work position counter to the force of the main spring  146 . In this process, the main valve cone  131  lifts away from its assigned seat  129 , and with the fine-control notches  133  that then open, the magnitude of the volumetric flow leaving the second motor chamber  126  for the return  22  via the intermediate chamber  127  is regulated. It is understood that this control of the volumetric flow is proportional to the magnitude of the current signal at the proportional magnet  14 . Simultaneously with this opening motion, the communication from the first motor chamber  125  to the return  22  via the recess  139  is closed by the third control edge  138 , while at the same time the second control edge  136  opens the communication to the inlet  19 . Via the fine-control grooves  137 , the volumetric flow from the inlet chamber  124  to the first motor chamber  125  can be regulated in its magnitude. The pressure in the pressure chamber  143 , whose magnitude effects the opening motion of the main control member  121 , is reduced by means of a control oil flow that flows away continuously to the return  22  via the throttle bore  144 . The damping piston  145  assures uniform, damped motions of the main control member  121 . 
     The magnet valve  120  of FIG. 10, in a similar way to the magnet valve  12  of FIG. 2, can be disposed in a housing  50  together with the other functional elements in such a way that the same actions and advantages as in the control device of FIG. 6 are attained. 
     It is understood that modifications of the embodiments shown may be made without departing from the concept of the invention.