EP0942103B1 - Valve device for an hydraulic motor driving a large inertial mass - Google Patents

Description

The present invention relates to a valve device for less a hydraulic motor capable of driving a mass of inertia important, the engine having two main lines, respectively fluid supply and exhaust, which are likely to be closed for stopping the engine. In the following, the mass that the motor serves to train will be called "driven mass".

The motor to which this valve device applies is used for example to ensure the rotation of a turret of a machine such as a hydraulic shovel, or to ensure the translation of tracked or tire-bearing vehicles having a mass important.

It can be a hydraulic motor of the so-called "fast motor" type. (1000 to 2000 rpm) driving a reducer or a motor called "motor slow "(whose speed of rotation is for example of the order of 100 rpm, for example of the radial piston type.

In operation, a circulation of fluid is maintained in the engine and one of the main lines is pressurized to play the role of supply line, while the other of these lines is in relative vacuum and is connected to a fluid outlet for play the role of exhaust pipe.

From an operating situation at a speed given drive, the engine is stopped by performing a deceleration phase, then closing the supply lines and exhaust. During the deceleration phase, the pressure in the supply line becomes low pressure while pressure in the exhaust pipe becomes high pressure. Finally, when closing the main lines of the engine, i.e. when from the isolation of this motor, the fluid located in the pipe exhaust is at a higher pressure than the fluid located in the supply line. This phenomenon is further reinforced by the fact that, due to its high inertia, the driven mass has tendency to continue its initial movement.

On flat ground, the system is only balanced when pressures in the supply and exhaust lines are substantially equal. On sloping ground or when the mass driven is arranged on a slope, the balance of the system is reached when the difference between the pressures in the supply line and in the exhaust pipe reaches a given value (positive or negative) which compensates for the slope to maintain the mass motionless.

In any event, so that the engine and the driven mass are effectively stopped in a stable position, the pressure difference between exhaust supply lines reaches a given value, zero, positive or negative.

It was previously indicated that when closing the pipes supply and exhaust, the exhaust pipe is in overpressure, overpressure which is further increased by the inertia of the mass driven. This overpressure tends to push back the entrained mass in a reverse movement in the opposite direction, which amounts to rocking towards the supply line which is blocked, the overpressure of the exhaust pipe which is also closed.

In addition, the hydraulic fluid is slightly compressible. Of this fact, after the engine is isolated, the mass of inertia continues its movement until the pressure in the exhaust pipe reaches a maximum value corresponding to the compression of the fluid present in this conduct. The mass return movement will have increases the pressure in the supply line to bring the fluid present in this line to a pressure of compression substantially equal to the maximum pressure prevailing in the exhaust pipe just before this phase of return.

Of course, this return phase is followed by another phase of displacement in the initial direction, during which it produces expansion in the supply line and compression in the exhaust pipe.

So after shutting off the supply lines and exhaust, the driven mass is driven by an oscillating movement whose frequency, for turrets of machines such as shovels hydraulic, is of the order of 1 Hz. Although this oscillating movement has a small relative amplitude and that it is finally naturally braked from the makes friction phenomena, it is obviously extremely annoying, especially when it comes to placing the mass driven by the engine in a very precise position by stopping the engine without braking mechanical.

Paradoxically, this phenomenon of oscillating movement was less annoying when the training was carried out using poorly performing engines in which relatively leaks limits the compression in the supply lines and exhaust. The engines were gradually improved, in to improve the yield, to decrease the duration of acceleration phases and to facilitate handling in difficult conditions, for example on slopes.

To limit the oscillations, i.e. to reduce the amplitude and finally stop them, it is known, see for example US-A-4 520 625 gold EP-A-0 793 022 to use a device amortization consisting in creating, between the supply lines and exhaust, leaks that feed a transfer volume. Following engine isolation, the pressure difference between the supply and exhaust lines can be at least partially compensated by the fluid available in this volume of transfer.

Another system is to allow permanent leaks between the engine supply and exhaust lines.

These systems are not entirely satisfactory to the extent where, on the one hand, they amount to reducing the efficiency of the engine which has also sought to increase by perfecting this engine and where they make precise positioning of the mass practically impossible driven to stop the engine. Indeed, for example when the engine is used to drive the turret of a hydraulic excavator, the effective stop of the turret will be done with an angular difference corresponding to the circulation of the fluid available in the transfer volume, relative to the position target angular in which the engine isolation was controlled.

The invention aims to remedy the aforementioned drawbacks by proposing a simple and reliable device, which makes it possible to brake and cancel very system oscillations quickly after the engine has been isolated, whatever the mass training conditions, in particular that they are driven on a slope or slope, or on level ground.

This object is achieved thanks to the fact that the device comprises two main conduits respectively intended to be connected to the two main lines of the engine, which it includes means for said main conduits in communication situation when the fluid pressures in these conduits are substantially equal and for put said main conduits in a situation of isolation in which these conduits are isolated from each other when the pressures of fluid in these conduits are different and that it further comprises delay means capable of limiting the speed of passage between the communication situation and isolation situation.

As previously indicated during deceleration and stopping the engine (blocking the main lines of this engine), the fluid pressure in the exhaust pipe is higher than the fluid pressure in the supply line. Therefore, during the deceleration phase and until the engine stops, the ducts of the valve device according to the invention remain in the situation isolation. Due to its high inertia, the driven mass continues its initial movement until the pressure in the line of delivery reaches a maximum value (compression). From this situation, the entrained mass initiates a movement back during from which the difference between the pressures in the pipes exhaust and supply decreases until it becomes appreciably nothing. At this time, the two main conduits of the device are put in communication situation, situation in which the volume of fluid in excess in the engine exhaust line may spill into the supply line.

If the delay means were not present, this communication situation would be too brief to dump, in the supply line, all excess fluid in the line exhaust. So the mass linked to the engine having naturally tendency to continue its return movement, the pressure in the supply line would become greater than the pressure in the exhaust pipe, so the device would come again put the main conduits in isolation. So, it would be simply during the very short transit time of the oscillating mass by the neutral point of the oscillations (which occurs every half oscillation periods) that the main conduits would be placed in communication situation. Braking would be relatively slow since the excess fluid volume in the engine exhaust line does not would finally come back completely into the supply line that after a given number of passes through the situation of communication.

Thanks to the presence of the timing means, we make sure that as soon as the mass has described about half of the return movement oscillations it has just started, that is to say as soon as the pressures in the supply line in the exhaust line become substantially equal, the main conduits of the device according to the invention are placed in a communication situation and tend to stay in this communication situation long enough to allow at least a large part of the volume of fluid in excess in the exhaust pipe to spill into the pipe Power. Thus, the mass linked to the engine is braked as soon as it has describes half of a return movement and hardly moves not beyond.

The timing means of the invention limit the speed of passage between the situation of communication and the situation of isolation, that is, they make sure that once the situation of communication is obtained, this situation persists for at least one some time (on the order of a few tenths of a second to a second), necessary for the transfer of excess fluid in the pipe exhaust to the supply line. We can also consider that the means of delay serve to hinder the passage from the situation of communication to the situation of isolation.

According to a particularly advantageous embodiment, the means to put the main conduits in a situation of communication include means forming a calibrated restriction, the cross section of the fluid likely to flow through this restriction when the main conduits are in a situation of communication being much lower than the current section of the conduits main (1% to 5% of this current section).

This calibrated restriction is particularly useful when starting the engine from a situation where the pressures in the supply and exhaust lines are equal. Indeed, to start the engine, feed the supply line in fluid and, for the engine to work, this fluid must pass through the pistons cylinders before being evacuated by the pipe exhaust. In other words, you have to make sure that a loss of load is quickly installed between the supply lines and exhaust. Thanks to the presence of the calibrated restriction, the fluid supplying the first main conduit of the device will preferably go in the main engine supply line, only a small amount of fluid which can then "short-circuit" the engine and be evacuated by the second main conduit of the device via the restriction calibrated. Thus, a significant pressure difference will settle quickly between the supply and exhaust lines, this pressure difference obviously having the effect of putting the conduits of the device in isolation, so that the engine works normally.

We understand that the means of delay mentioned previously and the calibrated restriction referred to above must be chosen so as to be able to effectively ensure a time delay that is to say to hinder the passage of communication to the situation isolation when the lines are no longer positively supplied in fluid, while allowing a quick start of the engine, i.e. transition as quickly as possible from the communication situation to the isolation situation when the pipes are supplied with fluid.

Advantageously, the device comprises a movable member likely to be requested between three positions under the effect of the difference between the fluid pressures prevailing in the two main conduits, these three positions comprising a first and a second position extremes in which the two main conduits are in situation isolation from each other and an intermediate position in which said main conduits are in communication situation with each other, the movable member being placed in its first position extreme when the pressure in the first main duct is higher than the pressure in the second main duct while it is placed in its second extreme position when the pressure in the second main duct is higher than the pressure in the first main duct and placed in its intermediate position when the pressures in the two main conduits are substantially equal.

This movable member is preferably formed by a mounted drawer sliding in a bore, a portion of which extends between the two main ducts, this drawer being equipped with means forming a duct of communication which connects the main conduits in the position drawer and which is closed by the bore wall in the two extreme drawer positions.

Advantageously, the device comprises means for provide a first and a second control chamber, respectively located at a first and a second end of the drawer, the first chamber communicating with the first duct main through a first communication pass, while the second bedroom communicates with the second main duct by a second communication passage, the first control being capable of being supplied with fluid to repel the drawer to its first extreme position when the fluid pressure in the first main conduit becomes greater than the fluid pressure in the second main duct and empty to allow the moving the drawer to its second extreme position when the fluid pressure in the second main conduit becomes greater than the fluid pressure in the first main conduit, and the second control chamber being capable of being supplied with fluid for push the drawer back to its second extreme position when the pressure of fluid in the second main duct becomes greater than the fluid pressure in the first main duct and to empty for allow the drawer to move to its first extreme position when the fluid pressure in the first main duct becomes higher than the fluid pressure in the second main conduit.

These provisions are a simple way to order hydraulically the device according to the invention to obtain the two extreme isolation positions and the intermediate position of communication.

According to a first advantageous embodiment of the means of delay, we can predict that at least one of the first and second communication passages is equipped with a calibrated restriction for obstruct the flow of fluid through these passages.

As will be seen below, it is also possible to provide, alternative or complementary way, that the bottom of the control constitutes a movable stop for the ends corresponding to the drawer, this movable stop being recalled in permanence by return means in the direction of a reduction in the volume of control chambers.

• les figures 1 à 3 montrent, en coupe axiale, un dispositif conforme à l'invention selon un premier mode de réalisation, dans trois situations différentes,
• la figure 4 illustre un circuit hydraulique d'alimentation d'un moteur hydraulique, incluant un dispositif conforme aux figures 1 à 3,
• les figures 5 à 7 montrent un dispositif conforme à l'invention, selon un deuxième mode de réalisation, dans trois situations différentes,
• les figures 8 à 10 montrent un dispositif conforme à l'invention selon un troisième mode de réalisation, dans trois situations différentes, et
• la figure 11 illustre une variante du troisième mode de réalisation.

The invention will be well understood and its advantages will appear better on reading the detailed description which follows, of embodiments shown by way of nonlimiting examples. The description refers to the accompanying drawings in which:

• FIGS. 1 to 3 show, in axial section, a device according to the invention according to a first embodiment, in three different situations,
• FIG. 4 illustrates a hydraulic circuit supplying a hydraulic motor, including a device in accordance with FIGS. 1 to 3,
• FIGS. 5 to 7 show a device according to the invention, according to a second embodiment, in three different situations,
• FIGS. 8 to 10 show a device according to the invention according to a third embodiment, in three different situations, and
• FIG. 11 illustrates a variant of the third embodiment.

The device shown in Figures 1 to 3 comprises a body 10 in which two main conduits 12 and 14 are drilled, respectively intended to be connected to the supply lines and hydraulic motor exhaust. A bore 16 is made in the body 10, this bore having a middle portion which extends between the two main conduits 12 and 14, on either side of which extend two extreme portions located beyond the conduits 12 and 14. A drawer 18 is slidably mounted in this bore, in which it can occupy three particular positions. The first, visible in Figure 1, is a first extreme position in which the fluid pressure in the first main duct 12 is greater than the pressure in the second main duct 14 and in which the drawer isolates these two main conduits. The drawer 18 can also occupy a second extreme position, shown in Figure 3, which corresponds to the situation reverse in which the fluid pressure in the second conduit main is greater than the pressure in the first main duct and in which the drawer isolates these two conduits. The drawer can still occupy a third position which is an intermediate position illustrated by FIG. 2, in which the pressures in the conduits 12 and 14 are substantially equal and in which these conduits are placed communication.

To this end, the drawer 18 includes a communication conduit which, in the example shown, has a central bore 20, which opens on the wall of the drawer by first holes 22 and second holes 24 which are spaced from each other in the sliding direction of the drawer, so that, in the first extreme position, the orifices 22 are closed by the cylindrical wall of the bore 16, while in the intermediate position, the orifices 22 and 24 open respectively in the first and second main conduits 12 and 14 and that in the second extreme position shown in FIG. 3, the orifices 24 are closed by the wall of the bore 16.

We see that the orifices 22 and 24 are located in grooves, 23 and 25 respectively, made on the outer periphery of the drawer, this which allows the main conduits 12 and 14 to remain in communication via conduit 20 even when the drawer 18 is slightly shifted to one of its extreme positions from the intermediate position.

The conduit 20 comprises a section with a small passage section forming a calibrated restriction 21. As indicated previously, this restriction is used to generate a pressure drop when starting the motor, that is to say when one of the conduits 12 and 14 is supplied with fluid with the engine supply line to which it is connected.

Of course, Figures 1 to 3 show an exemplary embodiment of the communication conduit which comprises the conduit 20, the orifices 22 and 24 as well as restriction 21. One can imagine making the conduit for communication in another way, especially by providing grooves, possibly stepped to form restriction 21, on the outer periphery of the drawer.

To control the drawer 18 between its three positions, the device includes means for providing a first and a second control chambers 28 and 30, respectively located at a first and at a second end, 18A and 18B, of the drawer. The first bedroom 28 is supplied with fluid via the first main duct 12, with which it communicates by a first pass communication 32. Likewise, the second control chamber 30 communicates with the second main conduit 14 via a second communication passage 34. When the fluid pressure in the first conduit 12 becomes greater than the pressure in the second line 14, the first control chamber is supplied with fluid to push the drawer back into its first position shown in the figure 1. On the other hand, when the fluid pressure in the second conduit main 14 is greater than the pressure in the first main duct 12, it is the second control chamber 30 which is supplied with fluid, as seen in Figure 3.

We see in the figures that the control chambers 28 and 30 have first and second bottom walls respectively mobile, respectively designated by the references 38 and 40. These bottom walls constitute stops with which the first and second ends of the drawer to limit movement of this last. The bottom walls 38 and 40 are movable in the direction of translation of the drawer and the device comprises a first return means, comprising for example a first mechanical spring 39, capable of permanently recall the bottom wall 38 towards the end 18A of the drawer, that is to say towards a position in which it tends to decrease the volume of the first control chamber 28. Likewise, the device comprises a second reminder means, comprising for example a mechanical spring 41, capable of permanently recalling the second wall bottom 40 in the direction going closer to the second end 18B of the drawer. In fact, the bottom walls 38 and 40 constitute the faces active pistons in bores 42 and 44, respectively practiced in parts 10A and 10B which are attached to the body 10 so that the bores 42 and 44 are in the extension of the bore 16 in which the slide 18 slides. Of course, the fixing parts 10A and 10B on the body 10 is sealed using seals.

The mobility of the bottom walls 38 and 40 and the presence of the means recall 39 and 41 allows, as seen in Figure 2, to make more stable the intermediate position of the drawer 18 in which it is communicate conduits 12 and 14. Indeed, the system is dimensioned so that the minimum spacing between the bottom walls 38 and 40 when they are pushed back to the maximum by the return means 39 and 41, corresponds substantially to the length L of the drawer 18.

In addition, the return means 39 and 41 can in themselves contribute to the delay since, in order to be able to move towards one from its extreme positions from its intermediate position, the drawer 18 must first push one of the bottom walls 38 and 40 against the stress exerted on this wall by the return means 39 or 41. However, it may be desirable not to provide the springs 39 and 41 too great a stiffness, in order to avoid that, when starting the motor, the drawer 18 does not have to overcome an excessive resistance force for come and place oneself in one of its extreme positions which corresponds to normal engine operation.

In fact, in the example of FIGS. 1 to 3, the springs 39 and 41 rather constitute simple means of recall tending to replace the bottom walls 38 and 40 in their "advanced" positions once they have been pushed back by the drawer, and the delay means in themselves are made hydraulically.

Thus, the device shown in Figures 1 to 3 includes a first and second damping chambers respectively designated by the references 46 and 48. The first bedroom damping communicates with the first main conduit 12 by a first communication and amortization pass which, for reasons which will be detailed below, advantageously includes two branches 50 and 52. Similarly, the second bedroom damping communicates with the second main conduit 14 by a second communication and damping pass which comprises two branches 54 and 56.

In a balanced situation, insofar as the first bedroom damping 46 and the first control chamber 28 both communicate with the first main conduit 12, the pressures are equal on both sides of the piston forming the bottom wall 38. The spring 39 therefore makes it possible, despite this equal pressure, to place this piston in its advanced position in Figures 1 and 2. In the same situation, the spring 41 makes it possible to place the piston carrying the bottom wall 40 in its advanced position shown in FIGS. 2 and 3.

We see that branch 52 of the first communication pass and depreciation includes a calibrated restriction 53 which limits the passage of the fluid in this region. Similarly, branch 56 of the second communication and depreciation pass includes a calibrated restriction 57. In the intermediate position shown in the Figure 2, the two damping chambers 46 and 48 are filled with fluid. From this situation, to allow passage of the drawer in its first extreme position shown in Figure 1, it will not only that the fluid supplying the first conduit 12 and entering the first control chamber 28 tends to move the drawer towards the right, but also that this movement is allowed by emptying at less partial damping chamber 48. Restriction 57 allows to impede the flow of fluid through passage 56 when the room 48 is emptied. In other words, restriction 57 allows "slow down" the emptying of chamber 48, which prevents the drawer from passing too quickly from its intermediate position to its first position extreme. Similarly, the restriction 53 "slows down" the emptying of the chamber 46 when, the pressure in the main duct 14 becomes greater than the pressure in the conduit 12, the drawer tends to move from its position intermediate towards its second extreme position shown in the figure 3.

As previously indicated, it is desirable to hinder the moving the drawer to one of its extreme positions from its intermediate position when the engine is stopped, while avoiding oppose restarting the engine. The different elements of device according to the invention are dimensioned accordingly. Through example, for hydraulic motors operating up to pressures of 300 bars, we will choose for main conduits 12 and 14 a diameter of approximately 9 mm, for restriction 21 a diameter of approximately 1mm and, for restrictions 53 and 57, a diameter of approximately 0.3mm, while the stiffness of the springs 39 and 40 will be of the order of 1 N / mm.

Despite the presence of restrictions 53 and 57, it may be desirable that damping chambers 46 and 48 are able to fill with fluid as quickly as possible so that the pistons carrying the bottom walls 38 and 40 can resume very quickly their advanced positions after being pushed back by the drawer. It's here reason for the existence of branches 50 and 54 of the passages of communication and depreciation, these branches actually constituting respectively a first and a second feeding passage equipped each of a non-return valve 51, 55, so as to allow circulation fluid from a main conduit 12 or 14 considered, that in the direction of filling of the corresponding chamber 46 or 48.

The different conduits machined in the body 10, in the parts 10A and 10B and in the drawer 18 are closed by tight plugs. Furthermore, the advanced position of the bottom walls 38 and 40 is defined by their abutment against wall elements, respectively 38A and 40A, made at the interface between the body 10 and the parts 10A and 10B. Communication and amortization lines for damping chambers 46 and 48 form extensions of the communication passages for control chambers 28 and 30.

It will also be noted that the orifices 22 and 24 of the conduit of communication in drawer 18 are arranged so that the orifices 22 communicate with the main conduit 12 when the drawer occupies its second extreme position shown in Figure 3, while that the orifices 24 communicate with the second main conduit 14 when the drawer occupies its first extreme position shown on the figure 1.

Restrictions 53 and 57 can be directly practiced in the pistons which carry the bottom walls 38 and 40 if the passage between the damping chambers and main ducts is done at this place.

In addition, it is possible, in addition, to provide restrictions on the communication passages 32, 34 of the control chambers.

Referring to Figure 4, we now describe a circuit hydraulics incorporating the device of FIGS. 1 to 3 shown so schematic. This circuit is of the so-called "open circuit" type insofar as the hydraulic pump 100 which is used to supply the motor M is a single direction pump, the fluid exhaust being connected to a tank R at atmospheric pressure. The engine M includes main lines 112 and 114 which, depending on the direction of operation conditioned by one or other of the extreme positions a distribution valve 120, used for feeding or engine exhaust. In a manner known per se, the circuit comprises also a booster pump 110 and pressure limiters 102 and 103. Figure 4 illustrates the engine isolation situation, in which the valve 120 occupies an intermediate position which closes the pipes 112 and 114, the fluid delivered by the pump 100 going directly to the reservoir A. The booster pump 110 is used to ensure a given minimum pressure in lines 112 and 114. In a manner known per se, it is connected to these pipes by non-return valves 104 and 105, associated with pressure relief valves 106 and 107.

The device of the invention is located in block B1 in FIG. 4. We recognize the standardized representation of the drawer 18 mobile between three positions. In Figure 4, it is shown in its position intermediate in which the lines 12 and 14 of the device respectively connected to the main pipes 112 and 114 of the motor M, are put in communication via the passage of communication including the calibrated restriction 21. Displacement of the drawer is controlled by the connected control chambers respectively to conduits 12 and 14 by the communication passages 32 and 34. The passage of the drawer 18 from its intermediate position to one of its extreme positions is hampered by the damping chambers respectively connected to conduits 12 and 14 by the passages of communication and depreciation each comprising their two branches 50, 52 and, respectively, 54, 56. The entire block B1 can be part of a hydraulic block intended to be fixed on the motor housing hydraulic M. This block B1 can, with the block B2 which includes the valves check valves 104 and 105, as well as pressure limiters 106 and 107 constitute the same fixed hydraulic block ("flanged") on the casing of the engine. The engine can be a single displacement engine or multiple operating displacements, in which case the hydraulic block comprising block B1 can also include the means for selecting the engine displacement. Furthermore, the device according to the invention associated with a single engine M. In particular for training in translation of an extremely heavy mass, one can plan to use a group of several motors arranged in series or in parallel. In this case, this device can be associated with all of the motors of this group, its first and second main conduits 12 and 14 being respectively connected to the supply and exhaust lines of the engines of the group.

We now refer to Figures 5 to 7 which show another embodiment of the device according to the invention. The elements common to the two embodiments are assigned in FIGS. 5 to 7 with the same references as in FIGS. 1 to 3 increased by 200. The main conduits 212 and 214 are formed in the body 210 of the device, the slide 218 being axially movable in a bore 216 formed in the body 210 and extending partly between the conduits 212 and 214.

As in the embodiment of Figures 1 to 3, the drawer is capable of occupying two extreme positions (Figures 5 and 7) and one position intermediate (Figure 6). In its intermediate position, the drawer 218 sets communication conduits 212 and 214 by a communication conduit which includes a first section of blind bore 220A which opens onto the external axial periphery of the drawer by orifices 222, a first 221A calibrated restriction which communicates the blind bore portion 220A with a communication chamber 219 and a second 221B calibrated restriction similar to the first, which communicates the communication chamber 219 with a second section of bore blind 220B, which opens on the periphery of the drawer by holes 224. Restrictions 221A and 221B play a role similar to that of restriction 21 of Figures 1 to 3.

The communication conduit is closed by the wall of the bore 216 in the two extreme positions of the drawer 218.

However, it can be seen that the first main conduit 212 can continue to stay in communication with room 219 in the first extreme position (figure 5) of the drawer, while the second conduit 214 can continue to stay in communication with this room in the second extreme position of the drawer (Figure 7).

The sections of conduits 220A and 220B are blind, that is to say that they do not meet inside the drawer. However, they open respectively on the ends 218A and 218B of the drawer 218.

As a result, sections 220A and 220B also play the role of first and second communication passages, allowing respectively to communicate the first and second conduits main 212 and 214 with, respectively, a first chamber of control 228 and a second control chamber 230. When the pressure in conduit 212 is greater than pressure in conduit 214, the first control chamber 228 is filled with fluid for push the drawer back into its first extreme position, while in the reverse situation, it is the second control chamber 230 which is filled with fluid. In the intermediate position of the drawer shown in the Figure 6, the volume of the chambers 228 and 230 is substantially equal to the half the maximum volume of each of these chambers. Indeed, in the balanced situation in which pressures in conduits 212 and 214 are equal, pressures are equal in chambers 228, 219 and 230 which communicate with each other via the conduits 220A and 220B with restrictions 221A and 221B.

In the second embodiment, at least one of the first and second communication passages (formed in the example shown, by sections 220A and 220B respectively) is equipped of a calibrated restriction to impede the flow of fluid through these passages. In fact, in the example shown, the open end of the blind section 220A is fitted with a first restriction calibrated 253, while the open end of the blind pipe section 220B is fitted with a second 257 calibrated restriction. that, from the position shown in Figure 6, the passage of the drawer in either of its two intermediate positions is not possible only if one of the chambers 228 and 230 is emptied while, concomitantly, the other of these chambers is filled with fluid. So the restriction 253 is used to limit the cross-section of the fluid, which amounts to to hinder the filling of the chamber 228 for the passage from the position intermediate to the first extreme position of the drawer, or to hinder emptying of this chamber 228 for the passage from the intermediate position to the second extreme position of this drawer. Restriction 257 has the same effect with regard to room 230. Insofar as the emptying of a room is always concomitant with the filling of the other room, only one of the two restrictions 253 and 257 could be provided.

Restrictions 221A and 221B allow loss of load between conduits 212 and 214 when, when restarting the engine, the pressure in the supply line increases rapidly. The diameter of these restrictions could for example be of the order of 1mm at 1.5mm, while that of restrictions 253 and 257 will be more or less 0.1 to 0.3 mm for motors operating up to pressures of 300 bars.

In fact, in the variant of FIGS. 5 to 7, the chambers 228 and 230 act both as control chambers and as chambers depreciation, due to 253 and / or 257 restriction (s).

The device which has just been described in relation to FIGS. 5 to 7 can be placed, in place of that of FIGS. 1 to 3, in block B1 of the circuit of Figure 4, to operate in the same manner. Of course, in either case, the circuit can be opened as shown in the Figure 4 or of the "closed" type in which the pump used is a two operating directions to which the lines are connected supply and exhaust.

In the stabilized situation at the stop of the mass driven by the motor, the drawer 18 or 218 normally occupies its intermediate position (the pressures are the same in the two main conduits 12, 14 or 112, 114). This is in fact generally the case on flat ground in which, at the stop, no particular constraint that must be exerted on the mass driven to keep it in position.

On the other hand, on sloping or sloping ground, this mass is naturally subject to a constraint (gravity) which must be compensated by the engine stopped to maintain this mass in position. Thereby, one of the main lines of the engine (so one of the lines of the device of the invention) is slightly overpressure and the drawer 18 or 218 occupies its corresponding extreme position.

We will now describe Figures 8 to 10, in which the elements similar to those of FIGS. 1 to 3 are given the same references, increased by 300.

Main conduits 312 and 314 are connected to bore 316 formed in the body 310. The drawer 318 is movable in this bore between a first extreme position (Figure 8) in which the pressure in the conduit 312 is greater than the pressure in conduit 314 and a second extreme position (figure 10) corresponding to the situation reverse. FIG. 9 shows the intermediate position of the drawer 318, in which allows the communication of conduits 312 and 314. The bore is closed at both ends by plugs, respectively 319A and 319B.

In the first and second extreme positions, the conduits 312 and 314 are isolated by the cooperation of the wall of the middle portion bore 316 which extends between conduits 312 and 314 with, respectively, zone 318A and zone 318B of the cylindrical face drawer exterior.

In the intermediate position of the drawer, the communication of main ducts 312 and 314 goes through a calibrated restriction 321 constituted, in the example shown in Figures 8 to 10, by a calibrated flat formed on an area 318C of the drawer which is between the zones 318A and 318B. In the intermediate position, only this area 318C is located in the middle portion of the bore, so that the 321 calibrated flat determines the pressure drop between the conduits key. The communication conduit is therefore defined between this flat and the wall of the middle portion of the bore 316.

Figure 11 shows, also in the intermediate position of the drawer, a variant of the third embodiment of the invention, which distinguishes from that presented in FIGS. 8 to 10 only by the conformation of the calibrated restriction. In Figure 11, this restriction is produced by a calibrated bore 421 which constitutes a nozzle. In that case, zone 318C of the drawer is dimensioned so as to establish contact with the wall of bore 316 by its external surface. Jet 421 is drilled obliquely in this area, so as to put in communication the two spaces delimited on either side of zone 318C of the drawer. The communication conduit is then defined by the calibrated hole 421 in the middle portion of bore 316.

Of course, the skilled person could slightly modify the embodiment of FIGS. 1 to 3 to replace restriction 21 by a conformation similar to that of calibrated restrictions 321 and 421.

The embodiment of Figures 8 to 11 differs from the previous ones by the configuration of the means for controlling the movement of the drawer and that of the timing means.

Thus, the control means comprise a first and a second control chamber 328 and 330 which are both formed in the drawer 318. The first chamber 328 is connected in permanence at the first main duct 312 while it is isolated from the second main duct 314. The situation is the opposite for the second room 330, which is permanently connected to conduit 314 while being isolated of conduit 312. For example, chambers 328 and 330 are made in blind holes 327 and 329 which open respectively on the first and second axial ends 318D and 318E of the drawer. As will be seen below, these rooms are however closed from side of these axial ends.

Radial holes 332 and 334 extend respectively between the bores 327 and 329 and the axial periphery of the drawer and establish the permanent communication between, respectively, room 328 and the main duct 312, and chamber 330 and duct 314. These holes are possibly provided in gorges.

Pressure differences between lines 312 and 314 conditions the pressure differences between the chambers of command 328 and 330, which causes the drawer to move between its extreme positions, passing through its intermediate position.

In the example shown, the walls of the chambers 328 and 330 which are on the side of the ends 318D and 318E of the drawer are fixed, so that the increase in pressure in one of these chambers, which causes a displacement of the drawer, also results in an increase in volume of the chamber considered.

The delay means which serve to limit the speed of passage of the drawer between one and the other of its extreme positions include a first damping chamber 346, located between the first end 318D of the drawer and the first end of bore 316 closed by plug 319A, as well as a second chamber damping 348, located between the second end 318E of the drawer and the second end of the bore 316 closed by the plug 319B.

Rooms 346 and 348 are in permanent communication with a "buffer" fluid enclosure via at least one restriction. In the example shown, this enclosure is constituted by an axial bore 360 communicating with the chambers 346 and 348 by transverse holes, respectively 366 and 368. For the rest, the buffer enclosure is closed by plugs 361. The volume of the enclosure is constant and therefore contains a volume of buffer fluid predetermined and is permanently isolated from the main conduits, under reserve for possible leaks due to functional play.

In the position of FIG. 8, the volume of the chamber 346 is maximum, while that of room 348 is zero or practically zero. The situation is opposite in the position of figure 10. However, in the intermediate position shown in FIGS. 9 and 11, of the two damping chambers have substantially the same volume.

We therefore understand that, for the drawer 318 to move from from its intermediate position to come and occupy one of its positions extremes, it is necessary that the fluid contained in the buffer enclosure moves to reduce the volume of a room damping to increase the volume of the other.

Restriction means, comprising at least one restriction calibrated, are arranged in the buffer enclosure to hinder this fluid displacement. In the example shown, two restrictions, respectively 367 and 369, respectively arranged in holes 366 and 368.

Therefore, when, from the intermediate position, the pressure in one of the main conduits 312 and 314 becomes greater than the pressure in the other main duct, these ducts continue temporarily to be in communication before the drawer moves enough towards either of its extreme positions for the area 318A or area 318B of the drawer prevents this communication by cooperating with the wall of the middle portion of the bore 316.

The first and second control chambers 328 and 330 each have a useful surface on which the fluid pressure acts to cause the drawer to move to its first, respectively towards its second position. Similarly, the damping chambers 346 and 348 each have a useful surface on which the pressure acts of fluid to hinder the decrease in the volume of this chamber.

For each set of a control chamber (for example room 328) and the damping room (for example the room 348) associated, whose emptying is necessary for movement of drawer 318 in the direction controlled by an increase in pressure in this control chamber, the ratio between the useful surface of the control chamber and the useful area of the damping chamber constitutes a parameter for controlling the speed of movement of the drawer in the direction of emptying the damping chamber in question.

The passage sections of the restriction means 367 and 369, as well as these relationships between the useful surfaces of the associated order and depreciation, may be determined at using simulations to get, in either direction of drawer movement, the desired delay time. Most of the time, we will choose equal time durations for both direction of movement.

It was previously indicated that rooms 328 and 330 were formed in blind bores, closed on the ends of the drawer. More specifically, the first control chamber 328 is separated from the first damping chamber 346 by a first cylindrical rod 376 of small cross section which is arranged in the bore blind 327, as well as the second control chamber 330 is separated from the second damping chamber 348 by a second cylindrical rod 378 of small section disposed in bore 329.

Rods 376 and 378 are arranged in shirts, respectively 377 and 379, in bores 327 and 329. A contact of slip (made substantially watertight by minimal functional play) is established between these rods and these shirts, so that the rods 376 and 378 remain generally fixed when the drawer is moved. The useful surface of the first control chamber 328 is determined by the area of the free end of the rod 376 which is in this chamber, likewise that the usable area of the second control chamber 330 is determined by the area of the free end of the rod 378 which is in this room.

On the other hand, the useful surface of the damping chamber 346 is a function of the section of the first end of the drawer 318D, possible deduction of the section of the rod 376, as well as the useful area of the second damping chamber 348 is a function of the section of the end 318E of the drawer, deduction possibly made of the section of the rod 378.

Another parameter influencing the amortization time is the volume moved in the buffer enclosure and, in particular, the volume "depreciation" for rooms 346 and 348. The depreciation volume of chamber 346 is the volume of fluid which, from the position intermediate of figure 9, must be evacuated from this room during the displacement of fluid in the buffer enclosure to allow movement of the drawer 318 over a stroke sufficient to close the communication between conduits 312 and 314. In general, we will choose the same depreciation volumes for rooms 346 and 348.

Advantageously, the cylindrical rods 376 and 378 are respectively mounted free in holes 327 and 329 (more specifically, in folders 377 and 379). This facilitates the mounting of these rods by avoiding the problems of concentricity between the rods and the bores.

Claims (15)

1. Valve device (10, 210, 310) for at least one hydraulic motor (M) adapted to drive a high inertia mass, the motor having two principal ducts (112, 114), respectively for supply and exhaust of fluid, which are capable of being obturated to stop the motor,
      characterised in that it comprises two principal conduits (12, 14; 212, 214; 312, 314), respectively intended to be connected to the two principal ducts of the motor; in that it comprises means (18, 20, 22, 24, 28, 30; 218, 220A, 220B, 228, 230; 318, 321; 318, 421) for placing said principal conduits in situation of communication when the fluid pressures in these conduits are substantially equal and for placing said principal conduits in a situation of isolation in which these conduits are isolated from one another when the fluid pressures in these conduits are different, and in that it further comprises delaying means (39, 41; 46, 53, 48, 57; 228, 253, 230, 257; 346, 348, 367, 369, 376, 378) adapted to limit the speed of passage between the situation of communication and the situation of isolation.
2. Device according to Claim 1, characterised in that the means for placing the principal conduits in situation of communication comprise means forming a calibrated restriction (21; 221A, 221B; 321, 421), the cross-section of passage of the fluid capable of flowing through this restriction when the principal conduits are in situation of communication being much smaller than the current cross-section of the principal conduits (12, 14; 212, 214; 312, 314).
3. Device according to Claim 1 or 2, characterised in that it comprises a mobile member (18, 218; 318) capable of being urged between three positions under the effect of the difference between the fluid pressures prevailing in the two principal conduits (12, 14; 212, 214; 312, 314), these three positions including a first and a second end position in which the two principal conduits are in situation of isolation with respect to each other and an intermediate position in which said principal conduits are in situation of communication with each other, the mobile member (18, 218; 318) being placed in its first end position when the pressure in the first principal conduit (12; 212, 312) is greater than the pressure in the second principal conduit (14; 214; 314), while it is placed in its second end position when the pressure in the second principal conduit is greater than the pressure in the first principal conduit and it is placed in its intermediate position when the pressures in the two principal conduits are substantially equal.
4. Device according to Claim 3, characterised in that the mobile member is formed by a slide element (18, 218; 318) mounted to slide in a bore (16; 216; 316) of which a portion extends between the two principal conduits (12, 14; 212, 214; 312, 314), this slide element being equipped with means forming a communication conduit (20, 22, 24; 220A, 221A, 221B, 220B, 222, 224; 321, 421) which connects the principal conduits (12, 14; 212, 214; 312, 314) in the intermediate position of the slide element (18; 218; 318) and which is obturated by the wall of the bore (16; 216; 316) in the two end positions of the slide element.
5. Device according to to Claim 4, characterised in that it comprises means for forming a first and a second control chamber (28, 30; 228, 230; 328, 330), respectively located at a first and a second end (18A, 18B; 218A, 218B; 318D, 318E) of the slide element, the first chamber (28; 228; 328) communicating with the first principal conduit (12, 212; 312) via a first communication passage (32; 220A; 332), while the second chamber (30; 230; 330) communicates with the second principal conduit (14; 214; 314) via a second communication passage (34; 220B; 334), the first control chamber (28; 228; 328) being capable of being supplied with fluid to push the slide element towards its first end position when the fluid pressure in the first principal conduit (12; 212; 312) becomes greater than the fluid pressure in the second principal conduit (14; 214; 314) and of emptying to allow the displacement of the slide element towards its second end position when the fluid pressure in the second principal conduit becomes greater than the fluid pressure in the first principal conduit, and the second control chamber (30; 230; 330) being capable of being supplied with fluid to push the slide element towards its second end position when the fluid pressure in the second principal conduit (14; 214; 314) becomes greater than the fluid pressure in the first principal conduit (12; 212; 312) and of emptying to allow displacement of the slide element towards its first end position when the fluid pressure in the first principal conduit becomes greater than the fluid pressure in the second principal conduit.
6. Device according to Claim 5, characterised in that at least one of the first and second communication passages (220A, 220B) is equipped with a calibrated restriction (253, 257) to hinder the flow of the fluid through said passages.
7. Device according to Claim 5 or 6, characterised in that the first and the second control chamber (28, 30) respectively comprise a first and a second bottom wall (38, 40) with which the first and the second end (18A, 18B) of the slide element (18) are respectively adapted to cooperate in abutment, in that said bottom walls are mobile in the direction of slide of the slide element, and in that the device comprises a first return means (39) or a second return means (41) respectively, adapted to permanently return the first bottom wall (38) or the second bottom wall (40) respectively in the sense of bringing it closer to the first end (18A) of the slide element (18), or the second end (18B) of the slide element, respectively.
8. Device according to Claim 7, characterised in that it comprises a first damping chamber (46) communicating with the first principal conduit (12) via a first communication and damping passage (50, 52), as well as a second damping chamber (48) communicating with the second principal conduit (14) via a second communication and damping passage (54, 56), and in that the first and second communication and damping passage each comprise a calibrated restriction (53, 57) to hinder the flow of the fluid through said passages at least in the sense of emptying the damping chambers (46, 48).
9. Device according to Claim 8, characterised in that the first and the second damping chamber (46, 48) communicate respectively with the first and second principal conduits (12, 14) via, respectively, a first and a second booster passage (50, 54) equipped with a non-return valve (51, 55).
10. Device according to Claim 5, characterised in that the first and the second control chamber (328, 330) are made in the slide element (318), respectively in the vicinity of each of the two ends (318D, 318E) of the latter.
11. Device according to Claim 10, characterised in that the damping chambers are located at the ends of the slide element.
12. Device according to Claim 11, characterised in that it comprises a first damping chamber (346) located between a first end (318D) of the slide element (318) and a first end (319A) of the bore (316) in which the slide element is mounted, as well as a second damping chamber (348) located between a second end (318E) of the slide element and the second end (319B) of said bore, these damping chambers being in permanent communication with a closed enclosure (360, 366, 368) containing a volume of buffer fluid having to be displaced between one and the other of these damping chambers (346, 348) in order to allow the displacement of the slide element (318) controlled with the aid of the control chambers (328, 330).
13. Device according to Claim 12, characterised in that calibrated restriction means (367, 369) are disposed in the closed enclosure (360, 366, 368).
14. Device according to either one of Claims 12 and 13, characterised in that the first control chamber (328) is made in a first blind bore (327) opening on the first end (318D) of the slide element (318) and is separated from the first damping chamber (346) by a first cylindrical rod (376) disposed in this bore (327), and in that the second control chamber (330) is made in a second blind bore (329) opening on the second end (318E) of the slide element (318) and is separated from the second damping chamber (348) by a second cylindrical rod (378) disposed in this second bore (329).
15. Device according to any one of Claims 1 to 14, characterised in that it forms part of a hydraulic unit intended to be fixed on the casing of a hydraulic motor.

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