GB2172964A

GB2172964A - Distributor slide with a built-in balancing valve for hydraulic circuits

Info

Publication number: GB2172964A
Application number: GB08602864A
Authority: GB
Inventors: Maurice Tardy; Andre Rousset
Original assignee: Bennes Marrel SA
Current assignee: Bennes Marrel SA
Priority date: 1985-02-05
Filing date: 1986-02-05
Publication date: 1986-10-01
Also published as: FR2577002B1; IT8619304A1; FR2577002A1; IT1188330B; DK55986D0; GB8602864D0; DE3603425A1; IT8619304A0; DK55986A; GB2172964B

Abstract

A hydraulic distributor comprises two half-slides (121) and (122) slidable on a tie rod (113) within a stator (101). In the embodiment shown the balance between the supply pressure at (103) acting on a gap (125) and the opposing thrust of springs (135) and (139) defines the balance position of each of the half- slides (121) and (122), on the tie rod (113). Means may be provided to compensate the drive force to ensure operation at a constant flow rate. <IMAGE>

Description

SPECIFICATION Slide valve distributor for use in a hydraulic circuit The present invention relates to a distributor slide of a new type, equipped with a built-in balancing valve, especially for providing control or switching on hydraulic circuits.

In general, these balancing valves are separate from the actual distributor, to which they have to be connected by means of ducts, the length of which affects the operating characteristics of the circuit. This results in various disadvantages in terms of operation, assembly and maintenance.

The object of the present invention is to avoid these disadvantages by providing a hydraulic distributor slide, in which a balancing valve is directly incorporated. More particularly, although not exclusively, the present invention aims to equip a proportional hydraulic distributor of the type described in French Patent 2,562,632.

A distributor device according to the invention comprises a grooved distributor slide which slides in a stator bore, along which are arranged distribution, supply and return ports, and it is characterized in that the slide is constructed by assembling at least three parts movable relative to one another, namely: a longitudinal connecting tie rod, the central body of which is cylindrical; -two half-slides, each provided with an inner longitudinal bore and with outer grooves, these two half-slides being mounted slidably, one in the extension of the other, on the cylindrical body of the tie rod which passes through their longitudinal bores.

According to another characteristic of the invention, the opposite ends of the two halfslides each have a widened bearing flange for receiving the thrust of a helical compression spring which otherwise bears on the stator.

According to another characteristic of the invention, the connecting tie rod has, at each of the two ends of its cylindrical body, a shoulder which is capable of receiving, up against it, the widened end of the corresponding half-slide, and then, beyond this shoulder, a cylindrical portion, the end of which is widened to define a second shoulder of larger diameter, the outside diameter of which is substantially equal to that of the corresponding widened end of the half-slide, a second helical compression spring being arranged between the two widened flanges, that of the tie rod and that of the end of the half-slide.

According to another characteristic of the invention, the end diameters of each half-slide and the calibration of the first and second springs which correspond to it, are defined so that this half-slide detaches itself from its stop shoulder on the corresponding end of the tie rod only when the pressure in the stator port corresponding to the supply of a receiver device falls below a predetermined threshold.

This corresponds particularly to the case where the receiver device performs a drive function (the case, for example, of a retainer jack driven by the weight of the load which it handles), in which case the relative movements of the half-slide or half-slides ensure an operation in the manner of a balancing or braking value incorporated in the slide.

The attached drawing given by way of nonlimiting example will make it possible to understand the characteristics of the invention more clearly.

Figure 1 is a view in longitudinal section of the device according to the invention in the position of rest.

Figure 2 shows the same device in operation, when the load to be moved is receptive, that is to say when it opposes a resistance to the hydraulic receiver device.

Figure 3 shows the device in operation, when the load to be moved is a driving load, that is to say when it tends, for example as a result of its own weight, to drive the hydraulic receiver device.

Figure 4 is a partial longitudinal section through a distributor with a sliding slide according to the invention, intended more particularly to compensate the drive force so as to ensure operation at a constant flow rate.

Figure 5 is a similar section relating to an alternative form which ensures compensation during variable-flow operation.

Figure 6 is a section along the line VI-VI (Fig. 5).

Figure 7 is a graph illustrating the variation in the drive force as a function of the stroke of the slide, relating to a device according to the main patent.

Figure 8 is a similar graph relating to the embodiment for a constant rate of Figs. 5 and 6.

Figure 9 is a similar graph for the embodiment of Fig. 7, corresponding to a compensation for variable-flow.

In the drawings, the same reference numerals as in the main patent have been retained for the component elements to which they correspond.

The device illustrated in the drawings is intended, for example, to replace the slide 3 shown in the stator 1, in French Patent 2,562,632. As in this case, the stator 101 according to the invention has a bore 102, along which several distribution ports are distributed, namely; -a central port 103 connected by a duct 104 to a hydraulic power source suppiying the pressurized fluid; -two distribution grooves or ports 105 and 106 connected by ducts 107 and 108 to a hydraulic receiver device (for example, to each of the two chambers of a double-acting jack); return ports 109 and 110 connected to a return circuit; -ports 111 and 112 provided at the two ends and both connected in the known way to a common duct for detecting the operating pressure (in English: "load sensing").

Inside the bore 102 slides a slide which, according to the invention, is formed by assembling the three following elements: -a connecting tie rod 113 provided with a central part or cylindrical body 114, the ends of which are connected by two shoulders 115 and 116 to cylindrical end portions 117 and 118 which each terminate in a widened bearing flange 119, 120; -two half-slides, 121 and 122, each having a tubular form the central cylindrical bore of which 123, 124 slides along the cylindrical body 114.

When the two half-slides 121 and 122 are each up against their respective shoulders 115, 116 (Fig. 1) in the position of rest, their ends facing one another define between them a gap 125, in which the supply pressure of the channel 104 can be exerted on each of the two opposite ends 126, 127.

Machined in the known way on the outer cylindrical wall of the half-slide 121 are distribution notches 128, 129 which move opposite the various stator ports 105, 109, 111.

Likewise, distribution notches 130, 131 are machined on the periphery of the cylindrical half-slide 122.

A first helical return spring 134 is arranged round the half-slide 121 and is compressed between its widened rear flange 132 and the corresponding stator wall 133. Behind the flange 132 bears a second helical return spring 135 which is otherwise compressed against the rear flange 119 of the tie rod 113.

This spring 135 is arranged around the cylindrical portion 117.

At the other end of the distributor there is a similar arrangement, in which a first spring 136 is compressed between a widened rear flange 137 of the half-slide 122 and the corresponding transverse face of the stator 138. A second helical spring 139 arranged around the cylindrical portion 118 is compressed against the rear face of the flange 137.

Each of the two ends of the movable assembly 113, 121, 122 is covered by a leakproof cap 140, 141, provided with an orifice 132, 143 which receives the control pressure of the device.

The mode of operation is as follows: When the assembly as a whole is at rest, it occupies the dead-centre position illustrated in Fig. 1, as defined by the balance of the opposing springs 134 and 136.

When the user conveys the pilot pressure into the orifice 143 in order to move a receptive load (that is to say, one in which the movement opposes a resistance), the hydraulic power source (port 103) is under pressure.

When the control pressure has pushed back the movable assembly 113, 121, 122 to the left, the pressure from the port 103 is conveyed via the notches 130 to the distribution channel 108. Moreover, the pressure in the orifice 103 is exerted between the two halfslides 121 and 122, in the region of the gap 125 separating their opposing ends. Because of the thrust resulting from this, each of the two half-slides 121 and 122 remains up against its rear shoulder 115, 116, of the tie rod 113. In this configuration, the springs 135 and 139 are pre-stressed. The supply and return functions are synchronized in the known way.

If, on the other hand, the load to be moved is a driving load (for example, if it tends to accelerate its displacement movement as a result of its own weight), when the user conveys the control pressure into the orifice 143, the device occupies the position illustrated in Fig. 3. In this case, the half-slide 122 and the tie rod 113 move to the left as before, but this time, because of the drive of the load, the pressure in the port 103 can be low and even zero. Under these conditions, when this pressure drops it crosses the prestress threshold, beyond which the effect of the spring 135 becomes predominant in relation to the opposing thrust which the pressure in the port 103 exerts (from right to left in Fig.

3) on the end of the corresponding half-slide 121 at the gap 125 which is therefore reduced and possibly eliminated, as in the case of Fig. 3. The half-slide 121 therefore approaches the half-slide 122 to a greater or lesser extent, and the effect of this relative movement is to reduce the passage crosssection between the distribution port 105 and the return channel 109. This results in a selfadjusting throttling effect by means of the notches 129, which brakes the return to the tank of the receiver and which generates in the receiver device a pressure which produces the braking force or torque on the load. When the braking force is sufficient, the port 103, which still receives the receiver supply flow, stabilizes at the pressure value which defines the precise opening of the return notches 129, that is to say the value desired for the size of the gap 125.

Of course, the scope of the invention would not be exceeded if the practical embodiment of the positioning or restoring means for the longitudinal movements of the movable assembly 113, 121, 122 was modified. In particular, the two springs 135 and 139 could be replaced by a single spring at one end.

In the case of Fig. 4, the shoulder 115 is equipped with a sliding sealing gasket 201 which defines a compensating chamber 202 inside the fixed cap 140. The volume of this compensating chamber 202 varies according to the movements of the half-slide 121. The chamber 202 has a calibrated leakage nozzle 203 which connects it to the rear chamber, in which the spring 135 is located.

Furthermore, another calibrated nozzle 205 is pierced transversely in the half-slide 121 to connect the chamber 202 to the hydraulic braking pressure. For this purpose, the nozzle 205 opens onto the axial inner space of the half-slide 121 around the groove 206 provided on the tie rod 114. Moreover, a perforation 208 made in the half-slide 121 near the stator groove 111 and a perforation 214 located near the stator groove 105 open into this groove 206.

Finally, a fixed stator bush 207 serves, by means of its inner bore, as a shut-off guide for the leak-proof sliding of the half-slide 121 which, in this zone, carries the supply nozzle 205. The latter can therefore be exposed, or shut off, by the bush 207 according to the position of the slide.

The mode of operation is as follows: For reference, a graph illustrating the variation in the longitudinal force F tending to act on the half-slide 121 as a function of its stroke C has been plotted in Fig. 7. It will be seen that the ideal force is illustrated by the straight line 208. On the other hand, it is found, in practice, that, where the distributor of Figs. 1 to 3 is concerned, an interfering drive force also arises on the half-slide 121.

This distorts the curve which from then on assumes the profile designated by reference numeral 209.

On the other hand, in the case of the device according to Fig. 4, it is the curve 210 which is observed. It will be seen that it returns to the ideal straight line 208 at a point 211 corresponding to a given fixed flowrate, for which the compensation of the hydrodynamic drive force is ensured.

Fig. 9 illustrates the curve 212 obtained with the structure illustrated in Figs. 5 and 6.

It will be seen that this curve 212 remains very close to the ideal straight line 208 over its entire length, with the result that compensation is practicaliy ensured, whatever the position of the half-slide 121. Compensation with variable flow rate is thus obtained.

For this purpose (Figs. 5 and 6), the supply perforation 208 opens into a longitudinal slot 212 provided in the outer bearing surface of the half-slide 121 in the vicinity of the stator groove 111. Moreover, this slot 212 stops at a distance 213 from the end 133 of the bore of the stator. This produces a supply nozzle of variable cross-section, which consists of the slot 212, where the length 213 is equal to the stroke executed by the slide as a whole, so as to obtain the start of the opening of the notch when it ensures the return.

Of course, the same device is provided on the two half-slides 121 and 122 at each of the ends of the distributor.

Claims

1. Distributor device comprising a grooved distributor slide which slides in a stator bore (102), along which are arranged distribution (107, 108), supply (103) and return (109), (110) ports, characterized in that the slide is constructed by assembling at least three parts movable relative to one another, namely: -a longitudinal connecting tie rod (113), the central body (114) of which is cylindrical; -two half-slides (121), (122), each provided with an inner longitudinal bore (123), (124) and with outer notches (128), (129), (130), (131), these two half-slides (121), (122) being mounted slidably, one in the extension of the other, on the cylindrical body (114) of the tie rod (113) which passes through their longitudinal bores (123), (124).

2. Distributor device according to Claim 1, characterized in that the opposite ends of the two half-slides (121), (122) each have a widened bearing flange (132), (137) for receiving the thrust of a first helical compression spring (134), (136) which otherwise bears on the stator (101).

3. Distributor device according to Claim 2, characterized in that the connecting tie rod (113) has, at each of the two ends of its cylindrical body (114), a transverse shoulder (115), (116) which is capable of receiving, up against it, the bearing flange (132), (137) of the corresponding half-slide (121), (122), and then, beyond this shoulder (115), (116), a cylindrical portion (117), (118), the end of which is widened to define a second flange (119), (120) of larger diameter, the outside diameter of which is substantially equal to that of the corresponding widened flange (132), (137) of the half-slide (121), (122), a second helical compression spring (135), 139) being arranged between the two widened flanges (132), (119) and (137), (120), that of the tie rod (113) and that of the end of the half-slide (121), (122).

4. Distributor device according to any one of the preceding claims, characterized in that the diameters of the opposite ends of each half-slide (121), (122) (gap ('25)) and the calibration of the first (134), (136) and second (135), (139) spring which correspond to it are defined so that this half-slide (121), (122) detaches itself from its stop shoulder (115), (116) on the corresponding end of the tie rod (113) only when the pressure in the stator port (103) corresponding to the supply of a receiver device falls below a predetermined threshold, this corresponding particularly to the case where the receivier device has a driving operation, with the result that the relative movements of the half-slide or half-slides (121), (122) ensure operation in the manner of a balancing or braking valve incorporated in the slide.

5. Hydraulic distributor slide according to any one of the preceding claims, comprising two half-slides (121) and (122) sliding along a cylindrical tie rod or spindle (114) connecting them, whilst at each end it possesses a shoulder (115), (116) movable inside a leak-proof stator cap (140), (141), characterized in that each shoulder (115), (116) has means ensuring a calibrated leakage cross-section and a calibrated supply cross-section to the variablevolume compensating chamber (202) defined by the leak-proof sliding of the half-slide (121), (122) in the stator cap (140), (141).

6. Distributor slide according to Claim 5, characterized in that each shoulder (115), (116) has a sealing gasket (201) sliding against the inner wall of the cap (140), (141).

7. Distributor slide according to either one of Claims 5 and 6, characterized in that the chamber (202) has a calibrated leakage nozzle (203) which connects it to the rear chamber (204), in which the return spring (135), (139) of the corresponding half-slide is located.

8. Distributor slide according to any one of Claims 5 to 7, characterized in that the compensating chamber has a calibrated nozzle (205) pierced transversely in the corresponding half-slide (121), (122) and which opens onto the axial inner space of the half-slide (121), (122) in question.

9. Distributor slide according to any one of Claims 5 to 8, characterized in that each calibrated nozzle (205) opens opposite a groove (206) provided in the tie rod (114), this groove (206) also being connected to a perforation (214) in the half-slide (121), (122) opening out in the vicinity of the stator groove (105), (106) in question.

10. Distributor slide according to any one of Claims 5 to 9, characterized in that fixed stator bush (207) serves as a guide for the leak-proof sliding of the half-slide (121), (122) which, in this zone, has a supply nozzle (205).

11. Distributor slide according to any one of Claims 5 to 10, characterized in that the perforation (208) opens into a longitudinal slot (212) provided in the outer bearing surface of the half-slide (121), (122) in the vicinity of the stator groove (111), (112) and stops at a distance (213) from the corresponding end (133), (138) of the bore of the stator.

12. Distributor device having a grooved distributor slide which slides in a stator bore, along which are arranged distribution, supply and return ports, the slide comprising, two sub-slides that are slidably mounted by bores therein, on a longitudinal connecting tie rod.

13. A Distributor device constructed and arranged substantially as herein before described with reference to and as illustrated in the accompanying drawings.