FR2483099A1 - HYDRAULIC DEVICE FOR CONTROLLING PRESSURIZED FLUID FLOW - Google Patents

Abstract

DEVICE DELIVERING A CONSTANT FLOW TO A CLOSED CIRCUIT, PRIORITY FOR A BRAKING FUNCTION, AND THE RESIDUAL FLOW OR A TOTAL FLOW TO AN OPEN CIRCUIT INTENDED FOR A SECOND USE. A CONTROL DRAWER 21, BEFORE THE FLOW OF PUMP 12, IS CONNECTED TO A STAGE PISTON 47 AND ACTS ON A FLOW OF CONTROL OIL, DERIVED FROM THE PUMP FLOW AND CAN BE DIRECTED TO TANK 69 BY A CHANGE 32 AND A PRESSURE CONTROLLED VALVE 23 IN THE ACCUMULATOR 14, THE PRESSURE DROP PRODUCED BY THE THROTTLE 32 CAN ACT ON THE PISTON STAGE 47. THE CONTROL DRAWER 21 PILOT SWITCHES WITH PRECISION AND ALWAYS TILTS IN STABLE LIMIT POSITIONS, ON WHICH IT ALSO WORKS AS A FLOW REGULATOR.

Description

The present invention relates to a hydraulic control device of the

  flow of pressurized fluid supplied from a source in a closed circuit comprising an accumulator and a use, and / or in an open circuit comprising a second use, with a control spool influencing these connections, loaded by at least one spring, controlled by function of the pressure and to which is

  affected a valve influenced by the pressure in the accumula-

  and delivering a control oil flow derived from the source at at least one throttle, and with a non-return valve connected downstream of the control spool and protecting the accumulator. U.S. Patent No. 3,142,962 discloses such a device which includes a hydraulic brake valve inserted in the closed circuit and a steering valve inserted into the open circuit. A pump

  can supply both circuits with fluid under pressure; a regular

  flow transmitter delivers first, via a relay

  pressure, a constant flow rate to the closed circuit including accumula-

  and the residual flow to the steering circuit. When the

  emulator is loaded, the pressure relay reverses, the drawer

  flow regulator operating as an inversion valve and

  showing the total flow from the pump to the steering circuit. This solution has the disadvantage that the function of the charge valve of the accumulator is ensured in this case by a direct control valve, because the pressure relay spool, actuated by the pressure in the accumulator, directly controls the flow rate. constant delivered to the accumulator. The spool of the pressure relay consequently has a relatively high outside diameter, which causes a large friction and consequently imprecise switching of the device. The

  pressure relay drawer also functions with an

  mechanical ball bearing, the construction of which is relatively

  which does not allow precise switching pressures for the charging function of the battery. In this device, the drawer

  The pressure relay may also become immobile in a posi-

  the flow regulator slide, which produces a phenomenon called "fixed throttling", in which the pump is forced against a pressure

  relatively high and thus risk rapid destruction. The provision

  In addition, the known safety device has the following risk: in the case of a charged accumulator and a pressure in the open circuit greater than the pressure in the accumulator, leakage oil is transmitted by the pressure relay spool. to the accumulator and continues to

load it.

  According to an essential characteristic of the invention, the control spool is coupled by a spring to a stepped piston, a second spring maintains in a first limit position; and one

  second throttle, inserted into the oil flow circuit

  mande, displaces by its differential pressure the stepped piston in a

  second limit position, against the force exerted by the second spring.

  The hydraulic device according to the invention has the advantage of

  enable precise switching for the load function of the

  accumulator, through the use of a piloted dispenser, and also prohibit the risk of a fixed throttle when switching

  both directions. The valve charged by the pressure in the accumulator

  now only a pilot valve, which has a simple influence

  a flow of control oil. The valve can thus be small, resulting in reduced friction and consequently precise switching. it is also possible to reduce control oil losses, despite

the use of a pilot.

  A particularly simple construction of the device is pos-

  when, according to another characteristic of the invention, the control spool is in the form of a hollow drawer containing

  the first strangulation. According to another particular characteristic-

  In an advantageous embodiment of the invention, the control spool comprises a first sector which, at a first limit position, connects a supply chamber to an accumulation chamber, isolates them on a

  second limit position and strangles them on the intermediate positions.

  as well as a second sector which, in the first position

  limit, blocks the connection with the open-center circuit chamber.

  An additional charge of the accumulator with leakage oil is thus avoided in the case of a pressure in the open circuit greater than the pressure of the charged accumulator. According to another characteristic of the invention, the hollow drawer closes the connection between the pump and the accumulator when the connection between the pump and the open circuit is open; and a section of the closed circuit, located between the nonreturn valve and the hollow spool, discharges into the reservoir, in particular by the stepped piston located on

its second limit position.

  Other features and advantages of the invention will be

  better understood using the detailed description below of

  two exemplary embodiments and the appended drawings in which FIG. 1 represents the simplified diagram of a first device; and FIG. 2 partially shows a second device, in which the function of the control spool of FIG. 1 is assumed by a

hollow drawer.

  FIG. 1 represents a device 10, in which a distribution

  scorer He accumulator charge distributes fluid under pressure

  delivered by a pump 12 in a closed circuit 13 comprising an accumulator

  emulator 14 and a brake valve 15, and / or in an open circuit 16 comprising a distributor 17 and a second use 18. The

  charge distributor 11 of the accumulator is essentially

  arranged by a flow regulator 19 comprising a control spool 21., a non-return valve 22 protecting the accumulator 14, and a valve 23 charged by the pressure of the accumulator 14 and

  controlling the control spool 21. The latter is housed in a

  which comprises, in the form of annular enlargements, a feed chamber 25, an accumulation chamber 26 and an open-center circuit chamber 27. While the feed chamber is connected directly to the pump 12, the accumulation chamber 26

  is connected to the accumulator 14 by a channel 28, a first choke

  29 and the non-return valve 22. The open circuit 16 is connected to the open-center circuit chamber 27. An annular control groove 31 is machined in the bore 24 of the slide, away from the open center circuit chamber 27, and connected by a second

  32 to a control bore.

  Mande 34 is derived on the channel 28, downstream of the first throat 29 in the closed circuit 13, and opens into the bore 24 of the drawer, in the vicinity of the control groove 31. The control line 34 is divided, in the vicinity its mouth in the bore 24 of the drawer, in a first branch 35, which contains a third constriction 36, and a second branch line 37. While the latter opens into the bore 24 of the drawer, between the control groove 31 and the open center circuit chamber 27, the first branch pipe 35 opens into the bore 24, on the other side of the control groove 31. The end of the bore 24 opposite the accumulation chamber 26 carries a shoulder constituting a stop 38, and an annular groove 39 located in a housing

  41 piston and connected by a bore 42 to the control bore 33.

  The drawer 21 controls by its first sector 43 in the form of piston

  the connection between the feed chamber 25 and the storage chamber

  26. By a second sector 44 in the form of a piston, it controls the connection between the feed chamber 25 and the open-center circuit chamber 27. The first sector 43 comprises control grooves 45 which, in the first limit position represented by the control spool 21, open the connection between the pump 12 and the circuit

  13. The first sector 43 also has a port of

  This connection permanently connects the feed chamber 25 to the accumulation chamber 26. In the left limit position shown in the control spool 21 and the link being open between the pump 12 and the accumulator circuit 13, the second sector 44 closes the connection between the pump 12 and the open circuit 16. An axis 48 is fixed

  on the second sector 44, in the direction of a piston 47. A floor

  52 fate bandaged bears on this axis 48 by a bowl 49 and a ring 51? A first inner sector 53 of the piston floor 47, with a smaller diameter, is applied to the bowl 49 of the spring. A second sector 54 of the piston piston stage 47, at higher diameter, bears on the stop 38, under the action of the force exerted by a second spring and the pressure in the housing 41 of the piston. The sectors opposite the stepped piston 47 and the control spool 21 have the same external diameter and delimit between them a first pressure chamber 56, into which the control pipe 34 opens and which contains the control groove 31. The first spring 52, housed in the pressure chamber 56, couples the control spool 44 to the stepped piston 47 by force action. The length of the axis 48 is in

  Furthermore, after crossing a limited race, the

  The axis of said axis abuts on the small sector 53 of the stepped piston 47. The piloting valve 23 comprises an inlet chamber 57, connected to the control bore 33. The inlet chamber 57 is connected to a chamber of FIG. return 58 by a seat 59, on which a spring 61 applies a spherical shutter 62. An opening piston 63, provided with a pin 64, is assigned to the shutter 62; its end face bearing the pin 64 can be loaded by the pressure of the inlet chamber 57 and its opposite end face, of the same surface, by the pressure in the accumulator 14, transmitted by a channel 65. The effective surface of the piston opening 63 is approximately 20% greater than the effective surface of the seat 59, so as to obtain a determined switching range. A channel 66 further connects the annular groove

  39 to the outlet chamber 58 of the valve 23.

  The fre-n valve 13, controlled by the braking equipment 67 of a towing vehicle, makes it possible to control the pressure in the brake

68 of the trailer.

  The operation of the device 10 according to Figure 1 is as follows.

  The trailer brake 68, actuated by an external force, must always be ready for operation; it is consequently inserted in a closed circuit 13 comprising an accumulator 14 and the pump 12

  feeds primarily with the pressurized fluid, via

  11 of the battery charge distributor 11. A substantially constant oil flow is sufficient for the second use 18, which is any hydraulic working system, when the engine of the vehicle equipped with the device 10 is running. The total volume delivered by the constant flow pump 12 flows accordingly, when

  the accumulator 14 is charged, by the distributor 11 of charge of ac-

  accumulator in the open circuit 16, then the tank 69. When the accumulator 14 is not loaded, the distributor 11 derives against a constant volume of the pressurized fluid delivered by the pump 12 in the closed circuit 13, while the fluid volume in

  excess reaches the open circuit 16.

  Some operating states are described below with the

  following designations of the various pressures in the device 10.

  p is the instantaneous pressure in the accumulator 14; pl is the branch pressure at which charging of the accumulator starts; p2 is the cut-off pressure at which the charge of the accumulator ceases; p3 is the brake pressure, acting in the brake cylinder 68 of the trailer; p4 is the control pressure prevailing in the braking equipment 67 of the motor vehicle; p5 is the pressure

  instant in the additional use 18.

  The charge of the accumulator 14 is the first state of function

  described in which the pressure p is lower than the pressure p2. The position represented by the control elements in the charge distributor 11 of the accumulator corresponds to this state of

  operation. The control spool 21 then occupies the first posi-

  limiting pressure shown, so that the pressurized fluid delivered by the pump 12 in the supply chamber 25 flows through the channel 28, including the first throat 29, and the check valve 22 to the accumulator 14 and load this last. The pressure in the channel 28, downstream of the first throat 29, is also established in the first pressure chamber 56 by the control line 34. The pressure drop produced by the first throat 29 therefore acts against the force exerted by the first spring 52, on the

  control spool 21 which thus limits upwards and maintains

  both the flow of fluid under pressure flowing to the accumulator 14. When the flow rate of the pump 12 exceeds the constant flow to the accumulator 14, the second sector 44 of the control spool 21 opens the connection between the chamber of supply 25 and the open center circuit chamber 27, so that a residual flow reaches the open circuit 16. This residual flow flows without constriction in the reservoir 69 when the distributor 17 is at rest. During this flow control, the first spring 52 is supported on the first sector 53 of the stepped piston 47. The effective pressure in the first pressure chamber 56 can also be established in the housing 41 of the piston, by the second constriction 32, the control bore 33 and the bore 42. In the housing 41, said pressure is exerted on the larger effective surface of the second sector 54 of the piston stage 47, thus applying the latter to the stop 38. The pressure prevailing in the first pressure chamber 56 also reaches the inlet chamber 57 of the valve 23, in which it acts on the effective bearing surface of the shutter 62 and simultaneously on the front face of the opening piston 63, the face opposite frontal of the piston

  63 is charged directly by the pressure in the accumula-

  14, through the channel 65, so that the opening piston 63 is subjected to a substantially total hydraulic pressure compensation. The operating state described below is the one in which

  the pressure p of the accumulator 14 reaches the cut-off pressure p2.

  When this is so, the spherical shutter 62 opens into the valve 23. A flow of control oil is then derived from the channel 28 to the reservoir 69, through the control line 34, the first (35). ) and the second branch pipe 37, the first pressure chamber 56, the control bore 33, the inlet chamber 57 and, with passage over the shutter 62, the outlet chamber 58. The second constriction 32 traversed by the control oil flow produces a

  pressure drop, which is sensitive in the housing 41 of the piston.

  When the effective surface area of the second sector 54 of the stepped piston 47 is, for example, 30% greater than the effective area of the first sector 53, the stepped piston 47 is detached from the stop 38 only for

  a pressure drop of about 30%, compared to the opening pressure

  shutter 62, then moved by its first sector 53

  to the right, against the force exerted by the second spring 55.-

  The decreasing pressure produced by the second constriction 32 in the control bore 33 is also exerted in the inlet chamber

  57 of the pressure relay 23, while the pressure p of the accumula-

  14 is exerted on the opposite end face of the opening piston 63.

  The effective front surface of the opening piston 63 is also approximately 20% greater than the effective surface of the seat 59, the fall

  pressure on the second constriction 32 produces an additional force

  the force exerted by the spring 61 and promoting the opening of the shutter 62. This force, self-amplified when the friction is overcome, leads to the total opening of the shutter 62 by canceling the pressure in the inlet chamber 57. A fixed restriction of the charge distributor 11 of the accumulator is

  thus prohibited because the switching of the control spool 21 does not

  after a fall of about 30% of the pressure on the second constriction 32 and the force, self-amplifying at this moment, has already

  sufficiently increased to exclude the establishment of a state of equi-

free.

  As a result of the pressure drop described in the chamber of

  57 and the resulting pressure drop in the housing 41 of the piston, the stepped piston 47 passes into its second right limit position, the end end of its second sector 54 abuts on the

  housing 41. The stepped piston 47 is maintained in this position.

  by its first sector 53, whose front face facing the first pressure chamber 56 is subjected to the pressure in the control oil circuit, upstream of the second constriction 32. An expansion of the second spring 52, serving regulation spring,

  is prohibited during this movement of the stepped piston 47, since said resistor

  The fate is supported on the axis 48 of the control spool 21 via

  of a bowl 49 and a stop ring 51.

  Mande 21 is consequently moved the same distance as the stepped piston 47 to the right, towards its second limit position. The

  second sector 44 of the control spool 21 then closes the second channel

  derivative 37, so that the control oil can only flow through the first branch pipe 35 having the

  third throttle 36. During this movement of the

  21 to the right, a control bevel 50 of its second

  The driver 44 further enters the control groove 31 forming a fourth adjustable constriction 71. The control spool 21 thus forms with the second spring 52 a pressure balance assigned to the third throttle 36, so that the control oil flow flowing in the valve 23 is kept constant at a low value,

  even in the case of high pressure in the open circuit 16.

  The following operation case described is that o the charge of the accumulator 14 is complete, the pressure p being greater than the connection pressure pl, but otherwise equal to or less than the cutoff pressure p2. The adjustment piston 47 is then in its second right limit position. The pressurized fluid discharged by the pump 12 flows essentially into the open circuit 16, by the distributor Il of charging the accumulator. The control grooves 45 of the control spool 21 are closed. Control oil flows from the feed chamber 25 to the reservoir 69 through the throttling orifice 46 of the first sector 43,

  the channel 28, the control line 34, the first channel

  derivative 35 having the third throttle 36, the fourth throttle 71, the second throttle 32, the control bore 33 and the shutter 62 open. The pressure drop in the fourth (71) and the second throttle 32 maintains the stage piston 47 in its second right limit position. The pressure drop produced by the third restriction 36 likewise holds the control spool 21 in its second limit position, said spool adjusting according to

  pressure in the open circuit 16, so as to maintain

  both the control oil flow. The fluid flow under pressure

  delivered by the pump 12, and decreased by the flow rate of the control oil

  forming in the valve 23 to the reservoir 69, flows thus in

  the open circuit 16, where the distributor 17 makes it possible to control the use

  18. This is so as long as the pressure is

  in the open circuit 16 is less than the pressure p in the ac-

  When the pressure p5 in the open circuit 16 is greater than the pressure p in the accumulator 14, an additional partial flow circulates in the throttling orifice 46 and the non-return valve 22 accumulator 14 and the charge until its pressure p is equal to or greater than the pressure p5. The following operating state is described when the pressure p in the accumulator 14 has fallen to a value lower than the connection pressure pl, so that the distributor 11 switches to the function "charge of the accumulator". At the end of the charge of the accumulator, the pressure fell in the inlet chamber 57 of the valve 23 and the spherical shutter 62 is still fully open. The position of the shutter 62 open results from the instantaneous pressure p in the accumulator 14, which loads through the channel 65 the surface of the opening piston 63, greater than 20%. The shutter 62 then begins to close when the pressure in the accumulator 14 decreases by about 20%. The pressure then increases in the inlet chamber 57 and acts through the bore 42 in the housing 41 of the piston. The stepped piston 47 is thus moved from its second right limit position to the left towards its first limit position, on which it straps the first spring 52 more strongly. An upper tire of the spring, however, simultaneously produces an increase in the volume of the spring. control oil and so

  a further increase in the pressure in the inlet chamber 57.

  As a result of the difference of the surfaces of the opening piston 63 and the shutter 62 loaded by a pressure, the pressure rise

  growing in the entrance chamber 57 produces a self-sustaining force

  amplifier, which promotes closure of the shutter 62. The valve 23 thus switches and the shutter 62 locks the discharge to the tank 69. During the leftward movement of the stepped piston 47, its right limit position to its first position left limit, the first sector 53, after increasing the tire of the first spring 52, finally applies to the axis 48, then drives the control spool 21 to the left, towards its first limit position. The control groove 31 is thus completely open, so that the fourth constriction 71 no longer acts. During further leftward movement, the second branch line 37 is opened and produces a sharp increase in the volume of control oil, and consequently a corresponding increase in pressure in the inlet chamber 57 of the valve 23. increasing the volume of control oil during the movement of the control spool 21 and the stepped piston 47 to the left promotes the switching of the valve 23. This point is particularly advantageous because the force of

  closing, resulting from the difference in the piston opening surfaces

  seat 63 and seat 59 loaded by pressure, is relatively low. When the spherical shutter 62 finally completely closes the discharge to the reservoir 69, so that no control oil flow is no longer possible, the stepped piston 47 and the spool

  control 21 can reach their first left limit position.

  A charge of the accumulator 14 can then begin, as previously

  described above. The next operating state described is the braking operation. When the braking equipment 67 of the towing vehicle is actuated, the braking pressure that is established is applied to the control connection of the brake valve 15. The latter regulates

  the pressure in the cylinders of the proportional trailer brake 68

  this control pressure. As long as the control pressure p4 and the brake pressure p3 are in equilibrium, the valve of

  brake 15 closes the connections between the trailer brake 68 and the

  The equilibrium 14 and the reservoir 69. When the equilibrium is disturbed by an increase in the brake pressure, the brake valve opens the connection between the accumulator 14 and the trailer brake 68, the discharge to the reservoir 69 being blocked. A decrease in the braking pressure produces conversely a blockage of the connection between the trailer brake 68 and the accumulator 14, and the discharge of the

  trailer brake 68 in the tank 69.

  The device described thus makes it possible to supply pressurized fluid, using the distributor 11 for charging the accumulator, a closed circuit 13, preferably with a constant flow rate, and an open circuit 16, practically continuously, the open circuit that can be charged. As a result of its coupling with the stepped piston 47, the control spool 21 can particularly advantageously occupy two limit positions, since mechanical stops secure the stage piston 47 in two positions. The control spool 21 can,

  in a limit position, operate using the first throttle-

  29 in the regulator of the flow of pressurized fluid charging the accumulator 14. The control spool 21 can also, in its other limit position and in connection with the third restriction 36, operate as a regulator of the control oil flow, because the free section of the third throttle 36 is significantly lower than that of the first throttle 29. The coupling of the control spool 21 to the stepped piston 47 and the guiding and throttling mode of the control oil flow furthermore ensure switching

  distributor 11 for charging the accumulator on one of the two posi-

  stable limit This is the case when the distributor 11 is switched both at the beginning and at the end of a charge operation of the accumulator 14. The safe switching of the charging distributor 11 of the accumulator is reached, although operates in a controlled drawer and allows precise switching pressures to be achieved. It is also possible to maintain relatively low control oil losses, despite the piloting. This action is

  moreover obtained with relatively simple constructive elements.

  It is convenient to realize the stepped piston in two separate sectors, but it can also if necessary be in one piece. Another advantage lies in the possibility of also connecting, if necessary, a second closed circuit to the distributor 11, instead of the circuit

open 16 shown.

  Figure 2 is the partial longitudinal section of a distribution

  battery charger 81 forming part of a second device

  80. The elements assuming the same functions as in Figure 1

  are designated by the same references, provided, however, with the sign prime. A key difference is that the Compartment Drawer

  coaxial with the stepped piston is produced in this case in the form of a

  hollow drawer 21 '. As a result of this realization, the body of the

  scorer 81 first contains the supply chamber 25 ', then the open center circuit chamber 27', the accumulation chamber 26 ', a first intermediate chamber 82, the first control groove 31', and finally a second intermediate chamber 83 and the second annular groove 39 '. The first sector 43 'of the hollow titrator 21' contains the first constriction 29 'and externally carries the grooves of

  30 .: control 45 ', next to a ring of circulation bores 84.

  These are in the vicinity of a first annular groove, which separates a second sector 86 of the first sector 45 '. A

  second annular groove 87 and a third sector 88 come next.

  In the vicinity of the second sector 86 is a third annular groove 89, which radial bores 91 connect to the interior of the hollow drawer 21 '. The latter contains, in the zone between

  the circulation bores 84 and the radial bores 91, a plug -

  92 containing the third constriction 36 '. The control bevel 50 'is on the outside of the second sector 86, facing the annular groove 87. The second constriction 32' is formed in this case in the form of a radial bore in the vicinity of the second annular groove 87 The hollow drawer 21 contains, in the zone comprised

  between the second constriction 32 'and the radial bores 91, a collar

  let 93 on which the head of a screw 94 constituting a coupling member. The screw 94 is locked in the first sector 53 'of the stepped piston 471. The first biased spring 52' bears on the first sector 53 'of the piston stage 47' and on the collar 93 in the hollow spool 21 '. Bores 95 in the screw 94 allow the control oil freely to reach the first pressure chamber 56 '. The first sector 53 'of the stepped piston 47' has a fourth annular groove 96 which, in the first left limit position represented by the stepped piston, is connected to the second chamber

  83. The latter is connected by a transverse bore

  at channel 28 ', in the area between the storage chamber

  26 'and the non-return valve 22'. The charge distributor 81 of the accumulator also differs essentially from that of FIG. 1 in that the valve 23 'and the non-return valve 22' are arranged along the same axis 97, parallel to that of the hollow spool 21 . The fre in valve 15 is further housed in the body

  distributor 81, on a third axis 98.

  The operating principle of the device 80, comprising the charge distributor 81 of the accumulator, is substantially identical to that of the device 10 according to FIG. 1. Only the differences are hereby underlined below. As a result of the embodiment in the form of hollow spool 21 ', the sampling of the control oil flow is no longer done downstream of the control grooves', but upstream of the latter, in the feed chamber'. When the first sector 43 'completely closes the link with the check valve 22', the accumulator 14 being charged, the first sector 53 'of the stepped piston 47' is therefore also in a second limit position not shown. In this second limit position, the fourth annular groove 96 connects the second intermediate chamber 83 to the annular groove 39 ', which discharges to the outlet chamber 58' of the valve 23 'and consequently to the reservoir 69. pressure p5 in the open circuit 16 exceeds the pressure p in the accumulator 14, the leakage of fluid under pressure

  in the channel 28 ', by the first sector 43', can only be

  to the reservoir, through the transverse bore 99, the second intermediate chamber 83, the fourth annular groove 96, the annular groove 39 ', the channel 66' and the outlet chamber 58, but not continue to charge the accumulator 14 through the flapper

  of no return 22 '. The accumulator circuit 14 is thus better

  overloaded. Another advantage lies in the fact that the control oil flow, derived from the flow of the pump and directed by the valve 23 'towards the reservoir, circulates only in the cavities of the hollow spool 21' or in annular grooves 85, 89, in the area between the feed chamber 'and the second constriction 32'. Complex and expensive channel assemblies are thus removed in the pipeline system from the body of the charge distributor 81 of the accumulator. It is thus easy to arrange the second (32 ') as well as the third throat 36' in the hollow drawer 21 '. The second branch pipe 37 'is also simply achievable by the radial bores 91 and the annular groove 89 in the hollow spool 21'. Function

  the fourth throttle 71 can be assumed by the bevel of com-

  50 'which, in the case of a throttling, operates in liaison

  with the right edge of the control groove 31 'of the body. Contrary

  In the case of FIG. 1, the fourth throttle 71 'is then downstream of the second throttle 32' with respect to the control oil flow, in the charge distributor 81 of the accumulator. The

  particular coupling mode using screw 94 ensures

  coupling by force action of the hollow spool 21 'to the stepped piston 47 when switching the two elements from a first left limit position to a second right limit position, while in the reverse switching direction, the hollow spool 21' is mated by

  safety in the first sector 53 '. In addition to its advanced construction

  the dispenser 81 thus also has the advantages

of the distributor 11 according to FIG.

  Of course, various modifications may be made by those skilled in the art to the principle and to the devices which have just been described solely by way of nonlimiting examples, without

depart from the scope of the invention.

Claims (22)

claims   1. Hydraulic device for controlling the fluid flow under pres-   provided by a source in a closed circuit including   accumulator and use, and / or in an additional circuit   comprising a second use, with a control spool influencing these links, loaded by at least one spring, controlled according to the pressure and to which a valve is assigned   influenced by the pressure in the accumulator and   puts a control oil flow derived from the source to a choke   at least, and with a non-return valve connected downstream of the control spool and protecting the accumulator, said device being characterized in that the control spool (21) is coupled by the spring (52) to a piston step (47), that a second spring (55)   maintains in a first limit position; and a second strangling   (32), inserted into the control oil flow circuit, displaces the stepped piston (47) in a second limit position by its differential pressure against the force exerted by the second spring (55). 2. Device according to claim 1, characterized in that the   stepped piston (47) has a first sector (53) of smaller diameter   and a second sector (54) of greater diameter; and the first sector (53) delimits with the coupled control spool (21) a first pressure chamber (56) which guides the control oil flow in the area between the first (29) and the second (29). throttling (32).   Device according to claim 2, characterized in that the first pressure chamber (56) discharges into the reservoir (69).   by the second constriction (32) and the valve (23).   4. Device according to one of claims 1 and 2, characterized in   the effective surfaces of the control spool (21) and the first   first sector (53) of the piston, delimiting the first chamber of pressure (56) are equal.   5. Device according to any one of claims 1 to 4,   characterized in that the valve (23) comprises a shutter (62) and an opening piston (63), assigned to said shutter and whose effective surface, determining the switching range, differs from that of the seat (59).   6. Device according to claim 5, characterized in that the   effective area of the opening piston (63), loaded by the pressure   the accumulator, is greater than the seat surface (59) assigned to the shutter (62).   7. Device according to any one of claims 2 to 6,   characterized in that the pipe (34) traversed by the control flow is divided, in the zone between the first constriction (29) and the first pressure chamber (56), into a first branch pipe (35), in which is inserted a third constriction (36), and a second branch (37).   8. Device according to claim 7, characterized in that the sec-   free of the third throttle (36) is significantly lower   to that of the first throttling (29). -   9. Device according to one of claims 7 and 8, characterized in that   the second branch pipe (37) is open when the control spool (21) is in the first limit position and closed when the stepped piston (47) is in the second limit position; and the first branch pipe (35) is open independently   the position of the control spool (21).   10. Device according to any one of claims 1 to 9, characterized   controlled by the coaxial arrangement of the control spool (21) and the stepped piston (47).   11. Device according to any one of claims 1 to 10, characterized   characterized in that the spring (52) inserted between the control spool   (21) and the stepped piston (47) is bandaged with the aid of the feed organism.   coupling (48); and the control spool (21) constitutes an abutment   mechanical for the stepped piston (47).   12. Device according to any one of claims 1 to 11, characterized   characterized in that the first throttle (29) constitutes with the control spool (21) a flow regulator, which limits to a   constant value the flow in the closed circuit (13).   13. Apparatus according to any one of claims 2 to 12, characterized   trimmed by a stop (38) integral with the body and assigned to the second sector (54) of the piston, and by a discharge channel (39, 66), located   in the vicinity of said stop (38) and deriving the leakage oil from the stepped piston (47).   14. Device according to any one of claims 2 to 13, characterized   characterized in that a fourth throttle (71), formed by a bevel (50) or notch of the control spool (21), is inserted into the control oil circuit, in series with the third (36) and the second constriction (32).   15. Device according to any one of claims 1 to 14, characterized   characterized in that the control spool (21) has a first sector (43) which, at a first limit position, connects a supply chamber (25) to an accumulation chamber (26), isolates them on   a second limit position and strangles them on the international positions   and a second sector (44) which, on the first posi-   limit the connection with the circuit chamber (27) at open center.   Device according to claim 15, characterized in that a throttling orifice (46) connecting the feed chamber (25) to the   accumulation register (26) is arranged in particular in the first first sector (43).   17. Device according to any one of claims 1 to 4 and 7 to   14, characterized in that the control spool is in the form of   a hollow spool (21 ') containing the first throttle (29').   Device according to claim 17, characterized in that the   hollow drawer (21 ') closes the connection between the pump (12) and the accumulator   lateur (14 ') when the connection between the pump (12) and the open circuit (16') is open; and a section (28 ') of the closed circuit, located between the non-return valve (22') and the hollow spool (21 '), discharges into the reservoir (69), in particular by the stepped piston   (47 ') being in its second limit position.   19. Device according to one of claims 17 and 18, characterized in   what the second (32 ') and the third throttling (36') are housed in the hollow drawer (21 ').   Device according to any one of claims 17 to 19,   characterized in that the coupling between the hollow spool (21 ') and the stepped spool (47') is formed so that the spool (21 ') drives the first sector (53') by means of a connection ( 52 ') by force action, upon closing of.'la connection between the pump (12) and the closed circuit (13), and in the opposite direction when   opening, by means of a connection (94) for safety.   21. Device according to claim 20, characterized in that the or-   coupling shaft is a screw (94) fixed in the stepped piston (47 '), whose head is supported on a collar (93) in the hollow spool (21'), and on which the spring loaded also applies (52 '), arranged   between the hollow spool (21 ') and the stepped piston (47').   22. Device according to claim 19, characterized in that the third constriction (36) is arranged in the hollow drawer (21 '), in the zone between circulation bores (84) and radial bores (91).