GB2278663A

GB2278663A - Non-return valve with flow limiter

Info

Publication number: GB2278663A
Application number: GB9409849A
Authority: GB
Inventors: Maurice Tardy
Original assignee: SOC D FABRICATION ET D ETUDES
Current assignee: SOC D FABRICATION ET D ETUDES
Priority date: 1993-05-19
Filing date: 1994-05-17
Publication date: 1994-12-07
Anticipated expiration: 2014-05-17
Also published as: GB2278663B; GB9409849D0; ITMI940362U1; ITMI940362V0; FR2705424B1; IT233432Y1; FR2705424A1

Abstract

This non-return valve consists of: - a body (2) having an inner chamber (5), - a valve (3), with spring-operated return 23 and differential hydraulic control, and - a slide valve (4), with spring-operated return (24) and differential hydraulic control. According to the invention, the valve (3) has, on the one hand, at least one axial bore (15), one end of which is sealed by a plug (10) and, on the other hand, several radial bores (22) causing its axial bore 15 to communicate with the chamber (5) of the body 2. - while the regulating slide valve (4), mounted in the axial bore (15) of the valve (3), has, on the one hand, a nozzle (32) and, on the other hand, the outlet of at least one channel (35) for pressurising a chamber (12) which, produced in the valve (3), between the plug (10) of this valve and the slide valve (4), controls this slide valve. <IMAGE>

Description

NON-RETURN VALVE WITH FLOW LIMITER In certain hydraulic circuits, for example in circuits supplying hydraulic jacks, used in civil-engineering or handling machinery for raising, lowering or moving loads with weights which vary from one application to another, or offering variable resistances, it is known that a flow limiter can be interposed between the hydraulic unit and at least one of the chambers of the jack or jacks.

The invention concerns flow limiters consisting of: - a body having an inner chamber communicating through at least one radial channel with part of the hydraulic circuit, and through an axial channel with the other part of the same circuit, - a valve, with spring-operated return and differential hydraulic control, able to occupy a closed position bearing on a seat in the body when the fluid is circulating in the direction benefitting from the regulation of its flow, and an open position when the fluid is circulating in the other direction, and - a slide valve, with spring-operated return and differential hydraulic control, regulating the flow by the longitudinal movement of a regulating edge, with respect to bores communicating with the upstream part of the hydraulic circuit, this regulating edge being juxtaposed with an external throat which, provided between two guiding surfaces of the slide valve, communicates, by means of radial bores and an axial bore of the slide valve, with the downstream part of the same hydraulic circuit.

In the flow limiters mounted in a capsule, of the same type as those described in FR-A-2 657 140, the non-return valve is disposed inside the slide valve, which is itself mounted so as to slide in the body of the capsule. This arrangement provides the fluid with complex passage circuits which, under high flow rates above 80 1/mien, cause considerable head losses, even when the limiter is in the free-passage position, that is with its non-return valve raised.

As a result of this, the application of flow limiters contained in capsules is limited and they cannot be used in installations requiring heavy flows in free passage.

Through FR-A-2 236 131, a stabilised-flow, regulating non-return valve is known, having, in a body through which coaxial inlet channels pass, a non-return valve in which a slide valve with spring-operated return stabilises, during the regulation phase, the flow of fluid using oblique channels of the valve emerging outside its seat, through the dynamic effect of the fluid passing through an upstream axial bore of the slide valve.

In free passage, such a device causes heavy head losses and, in the non-return phase, does not provide rigorous regulation but only stabilisation of the flow.

The aim of the present invention is to remedy these drawbacks by providing a non-return valve with a flow limiter providing, in free passage, reduced head losses and using, apart from the body, only cylindrical parts which have simple shapes and are easy to produce and robust.

To this effect, the non-return valve with a built-in flow limiter, according to the invention, is of the type described above but differs from it in the following ways: - the valve has, on the one hand, an axial bore, one end of which communicates with the part of the hydraulic circuit which is downstream in the regulation direction and the other end of which is sealed by a plug, and on the other hand several radial bores causing its axial bore to communicate with the chamber of the body, - while the regulating slide valve, mounted with its return means in the axial bore of the valve, has, in its axial bore communicating with the axial channel of the body, on the one hand, a nozzle and, on the other hand, the outlet of at least one channel for pressurising a chamber which, provided in the valve between the plug of this valve and the slide valve, controls this slide valve.

By virtue of this design, and notably by virtue of the inclusion of the slide valve within the valve, the channels ending in the chamber of the body may have large cross sections and the chamber of this body may be sufficiently sized so as to produce the minimum amount of head losses when the valve is away from its seat and the fluid is passing through the body in the direction which does not require the flow to be regulated. This structure does not in any way disrupt the functioning of the regulation because the slide valve and its hydraulic control means have adequate dimensions to react to upstream and downstream pressure variations.

Other characteristics and advantages will emerge from the following description, with reference to the accompanying diagrammatic drawing, showing, by way of non-limiting examples, several embodiments of the valve according to the invention.

Figures 1, 2 and 3 are views in longitudinal section of a first embodiment of the valve when it is, respectively, in its idle position, in its regulating position with maximum travel of the slide valve, and in free-passage position with maximum opening travel, Figures 4, 5, 6, 7 and 8 are views in longitudinal section showing other embodiments of the valve according to the invention, Figure 9 is a partial view in cross section showing, to an enlarged scale, a variant embodiment of the means of pressurising the control chamber applied in valves of Figures 6 to 8.

In general, the valve according to the invention consists of a body 2, a valve 3 and a slide valve 4 disposed inside the valve. The body 2 has an inner chamber 5 into which a radial channel 6 emerges. This chamber is interposed between an axial channel 7 and an axial bore 8 with a larger diameter than the former, sealed by a threaded plug 9. This plug delimits, with the plug 10 of the valve 3, a control chamber 12 for the valve 3. The outlet of the channel 7 in the chamber 5 forms a circular edge 13, visible in detail in Figure 3, which forms a seat for the tapered nose 14 of the valve 3.

The channels 6 and 7 of the body 2 are, in a known manner, connected to the two parts of a single hydraulic circuit, joined to one of the chambers of a hydraulic receiver, for example a jack.

When the hydraulic fluid passes through the body on its way from the channel 6 to the channel 7, it benefits from the regulation provided by the slide valve 4, whereas, when it is flowing in the opposite direction, it causes the valve 3 to be raised in order to obtain the free passage shown in Figure 3.

The valve 3 has an axial bore 15 which, emerging in the axial channel 7 of the body, is closed at its other end by the plug 10.

In the embodiment shown in Figures 1 to 3 and 8, the bore 15 is extended, in the direction of the plug 10, by a bore 16 with a larger diameter, to which it is connected by a shoulder 17.

In the other embodiments, the bore 15 extends over the greater part of the length of the valve but communicates with the axial channel 7 of the body by means of a bore 18 produced in the diametral wall 19 of the nose of this valve.

The valve is guided in translation by its rear part mounted so as to slide in the axial bore 8 of the body 2. The front part of the valve, comprising the nose 14, has an external diameter smaller than that of its rear part in order to facilitate the circulation of the fluid about it in the chamber 5 of the body.

According to one characteristic of the invention, the rear part of the valve 3 or bore 8 has machined areas, such as grooves or longitudinal flats, making it possible to form, between this valve and the wall of the bore 8, channels causing the control chamber 12 to communicate with the inner chamber 5 and, in consequence, with the radial channel 6 connected to the hydraulic circuit. Such a machined area is shown at 20 in Figure 9.

The front part of the valve has several radial bores 22 which, being regularly distributed angularly in the same diametral plane, cause its axial bore 15 to communicate with the chamber 5 and consequently with one of the parts of the hydraulic circuit.

Finally, the valve 3 is associated with a return spring 23 which is interposed between its plug 10 and that of the body 2.

The slide valve 4, which is mounted with its return means 24 inside the valve 3, consists, in the embodiment shown in Figures 1 to 3, of a body 25 with a cylindrical stem 26.

The body 25 has two cylindrical surfaces 27, mounted so as to slide fluid-tight in the bore 15. They are separated from each other by a throat 28, one of the sides of which forms the regulation edge 28a. Radial bores 29 pass through the end of the throat, communicating with a central chamber 30. This chamber itself communicates, on the channel 7 side of the body, with a threaded bore designed to receive a nozzle 32 and, on the other side, with an axial bore 33 receiving a calibrated nozzle 34. The axial channel 35 of the nozzle 34 has a smaller diameter than that of the nozzle 32.

The return means of the slide valve consist of a spring 24 which is interposed between a flange 36, integral with the stem 26 of the slide valve, and a collar 37, mounted so as to slide on this stem. It will be noted that the collar 37 may come to bear against the rear diametral face of the body 25 of the slide valve, and also against the shoulder 17, provided between the bores 15 and 16 of the valve.

In the embodiment shown in Figures 1 to 3, the return means of the slide valve are disposed in the control chamber 40 which is formed, in the bore 16 of the valve, between the plug 10 of this valve and the body 25 of the slide valve.

When idle, the mechanism as a whole is in the position shown in Figure 1, with the valve bearing on the seat 13, under the thrust of its spring 23, and with the slide valve in the position shown in Figure 1, that is with its regulating edge 28a in the immediate proximity of the radial bores 22 in the body of the valve.

When the fluid circulates in the direction of the arrow 41, ie enters the body through the channel 6, it passes through the radial bores 22 of the valve and those 29 of the slide valve, enters the chamber 30 and, from there, rejoins the channel 7 of the body, passing through the nozzle 32.

The original pressure Po prevailing in the channel 6 is transmitted to the control chamber 12 of the valve through the longitudinal channels 20. Under these conditions, the valve is maintained on its seat, since the pressure Po being exerted on the cross section T, delimited by the seat 13, receives a force which is greater than that exerted on the front part of this valve corresponding to the product of the same cross section T of the seat 13 and the useful pressure Pu prevailing in the bore 7, and the smaller Pu is, in comparison with Po, the greater this effect, taking into account the head losses caused by passing through the device.

The passing of the fluid through the nozzle 32 generates, upstream of this injector and in the chamber 30 of the slide valve, a pressure Pg which, via the bore 33 and the channel 35 of the injector 34, becomes established in the control chamber 40 of the slide valve. This pressure Pg, which is applied to the whole of the cross section S of the body 25 of the slide valve, results in a longitudinal force tending to cause this slide valve to move in the direction of the arrow 42 in Figure 2 against the action of its return spring 24. During this movement, the edge 28a of this slide valve progressively blanks off the bores 22 of the valve 3 until a position of equilibrium is reached, providing regulation, with the possibility of closing them off completely, as shown in Figure 2.

Under flow-regulation conditions, the forces exerted on the slide valve 4 comprise opening forces consisting of: - the return force Fr of the spring 24, - the force resulting from the pressure Pu being applied to the cross section S of the slide valve 3, having the value Pu x S, and - a closing force corresponding to the product of the pressure Pg being exerted from the other side on the cross section S of this same slide valve, ie Pg x S.

At equilibrium, Pg x S = Pu x S + Fr which gives Pg - Pus = Fr/S At equilibrium, Fr/S being constant, it is clear that Pg - Pu is constant.

This exposition demonstrates that the device, thus designed, maintains a constant pressure drop on each side of the injector 32 and that the flow in the injector 32, and therefore in the device, is constant.

When the fluid is circulating in the direction of the arrow 43 in Figure 3, ie is passing through the body 2 when moving from the channel 7 to the channel 6, and when the valve 3 is on its seat, the pressure Pu exerted in the channel 7 is greater than the pressure Po exerted in the bore 6.

The entire valve 3 is therefore subjected, on the channel 7 side, to the pressure Pu which is applied to the cross section T of the seat 13 and, in the inner chamber 5 of the body 2, to the pressure Po which produces effects on the same cross section T. As a result, the valve 3 opens, ie moves away from its seat 13 when Pu - Po > Fo/T, in which expression Fo corresponds to the force of the return spring 23 which by nature is very weak.

Figure 3 shows that, because of the large size which may be given to the channels 6 and 7, and to the chamber 5, the opening of the valve 3 immediately provides a passage with a large cross section resulting in low head losses, when the fluid circulates in free passage in the direction of the arrow 43.

It is therefore clear from the above that the regulation device according to the invention does indeed make it possible to obtain, in controlled passage, a satisfactory flow regulation and, in free passage, low head losses which, for example, if the diameter of channels 6 and 7 is 20 mm, are around 3 bars with a flow of 200 1/mien.

The embodiments shown with reference to Figures 4 to 8 are variant designs of the apparatus which may be chosen according to the fitting conditions encountered in the different uses of the device.

In the embodiment shown in Figures 4 to 6, the return spring 44 of the slide valve 4 is interposed between the diametral wall 19 of the nose of the valve 3 and a shoulder 45 produced at the end of a bore 46 formed in the slide valve 4.

In practice, this bore 46 has a diameter sufficient to serve as a housing for the spring 44 and to guide it. It will be noted that the spring does not bear directly on the shoulder 45, but that it pushes a perforated washer 32a against this shoulder, performing the same function as the injector 32 in the embodiment shown in Figures 1 to 3. Apart from other differences in shape, the device functions in the same way as the one described previously.

In the embodiment shown in Figures 5 and 7, the return spring 48 is interposed between the wall 19 of the valve and a shoulder 49 connecting the body of the slide valve 4 to a cylindrical nose 51. The nozzle 32b is disposed in an axial bore 50 of the slide valve 4.

In general, the embodiments shown in Figures 6, 7 and 8 differ from those previously described in the means used to place the control chamber 40 of the slide valve in communication with the chamber 30 of the slide valve or with the bore 33 constituting it or extending it in this slide valve. Indeed, in these embodiments, and as is shown in greater detail in Figure 9, the bore 33 communicates by means of at least one and preferably two radial channels 52 with a peripheral throat 53 produced near its end which adjoins the chamber 40. In these circumstances, the pressurisation of the chamber 40 depends on the clearance J shown in Figure 9, provided between the slide valve 4 and the internal bore 15 of the valve in which the slide valve slides.

Control of this clearance, on the short surface produced between the channels 52 and the rear end face of the slide valve, makes it possible to control the transfer of pressure commands between the central chamber of the slide valve, located upstream of the injector 32-32a-32b-32c, and the control chamber 40, in which the pressure Pg is applied, controlling the movements of this slide valve.

The various figures show that the injector 32-32a32b-32c-32d may have different forms. The internal diameter of its axial channel is of course suited to the requirements of the installation on which the device is mounted and, to this end, the injector, as is also the case with the one 32 in the embodiment in Figures 1 to 3, is interchangeable.

Claims

1. Non-return valve with flow limiter, characterised in that it consists of: - a body (2) having an inner chamber (5), communicating through at least one radial channel (6) with part of the hydraulic circuit and through an axial channel (7) with the other part of the same hydraulic circuit, a seat (13) and an axial bore (8) sealed at the opposite end to the seat by a plug (9), - a valve (3), with spring-operated return and differential hydraulic control, able to occupy a closed position bearing on the seat (13) in the body when the fluid is circulating in the direction benefitting from the regulation of its flow, and an open position when the fluid is circulating in the other direction, this valve having, on the one hand, at least one axial bore (15), one end of which communicates with the part of the hydraulic circuit which is downstream in the regulation direction and the other end of which is sealed by a plug (10), and on the other hand several radial bores (22) causing its axial bore to communicate with the chamber (5) of the body, and - a regulating slide valve (4) mounted with its spring-operated return means (24, 44, 48) in the axial bore (15) of the valve, to regulate the flow by the movement of a regulating edge (28a) with respect to radial bores (22) in the valve communicating with the chamber (5), this regulating edge (28a) consisting of one of the two sides of an external throat (28) of the slide valve, itself communicating, by means of radial bores (29) and an axial bore (30, 33), with the axial channel (7), this slide valve having, in its axial bore (30, 33) communicating with the axial channel (7) of the body (2), on the one hand, a nozzle (32, 32a, 32b, 32c, 32d) and, on the other hand, the outlet of at least one channel (35, 52) for pressurising a chamber (40) which, provided in the valve (3), between the plug (10) of this valve and the slide valve (4), controls this slide valve.

2. Valve according to Claim 1, characterised in that the channel for pressurising the control chamber (40) of the slide valve (4) is formed by the axial bore (35) of a calibrated nozzle (34) fixed in an axial bore (33) of the slide valve (4) communicating with the radial bores (29) of this slide valve.

3. Valve according to Claim 1, characterised in that the channel for pressurising the control chamber (40) of the slide valve (4) is formed by at least one radial channel (52) which, emerging externally in a peripheral throat (53), produced in the slide valve (4) and near to its end on the control chamber (40) side, emerges internally into an axial bore (33) communicating with the radial bores (29) of this slide valve.

4. Valve according to any one of Claims 1 to 3, characterised in that the return spring (44) of the slide valve (4) is disposed between the diametral wall (19) forming the nose of the valve (3) and a shoulder (45) formed at the end of an axial bore (46) of the slide valve, this bore partly receiving this spring.

5. Valve according to any one of Claims 1 to 3, characterised in that the return spring (48) of the slide valve (4) is disposed between the diametral wall (19) of the nose of the valve (3) and an outer shoulder (49) of the slide valve (4) and is guided by a cylindrical and central nose (49), protruding axially from the corresponding end of this slide valve.

6. Valve according to any one of Claims 1 to 3, characterised in that the return spring (24) of the slide valve (4) is disposed in the control chamber (12) of this slide valve and around a cylindrical stem (26) fixed to the latter, between on the one hand a flange (36) integral with the end of the rod (26) and on the other hand a collar (37) mounted so as to slide on this stem and able to come to bear against a shoulder on the stem of the slide valve and against a connecting shoulder (17) between the axial bore (15) of the valve guiding the slide valve (4) and an internal bore (16) with a larger diameter defining the control chamber (12).