GB2224334A

GB2224334A - Improvements in fluid valves

Info

Publication number: GB2224334A
Application number: GB8921883A
Authority: GB
Inventors: Richard Voss
Original assignee: Voss Richard Grubenausbau GmbH
Current assignee: Voss Richard Grubenausbau GmbH
Priority date: 1988-10-03
Filing date: 1989-09-28
Publication date: 1990-05-02
Anticipated expiration: 2009-09-28
Also published as: GB2224334B; DE8812456U1; GB8921883D0

Abstract

A self-sealing valve (1) constructed, in particular, as a non-return valve has a sealing piston (10) which is displaceable in a bore (3) of a housing (2). A spring (17) urges a sealing face (11) of an end portion (12) of the piston (10) against a sealing face (9) of a seating (6) in the housing (2). To render the valve reliable and self sealing the piston is flexible to a limited extent in the region of the sealing face corresponding to the valve seating. To achieve this the end portion (12) of the piston is provided with a plastics coating or consists entirely of plastics material. When this flexible material is pressed onto the valve seating by the compression spring it is deformed and ensures a perfect seal. <IMAGE>

Description

IMPROVEMENTS IN FLUID VALVES The present invention relates to valves, for use with HFA, HFC or HFD pressure fluids.

Fluid valves usually employ spring-loaded sealing elements or closing components, such as balls, plates or pistons, which are moved predominantly in the direction of flow during actuation, within a bore of a housing.

Sealing or checking between sealing faces of the sealing element and an associated seating should be absolutely free from leakage. The valve sealing element is usually composed of hard material which strikes roughness in the associated seating so that leakages frequently occur after only a short operating period. In cases where mineral oil cannot be used for safety reasons and/or where HFA, HFC or HFD pressure fluids are used instead, leakages which occur either from the beginning or after a few stress cycles and then lead to associated problems can easily occur in the known valves.

An object of the invention is to provide an improved valve, in particular a non-return valve, which seals completely and reliably even with an hydraulic fluid which is not mineral oil.

According to the invention, there is provided a valve for use with HFA, HFC or HFD pressure fluids; said valve comprising a sealing piston or the like which seals in one direction displaceably mounted in a bore in a housing, and a compression spring biasing the piston against the desired direction of flow and onto a valve seating, the valve piston and the valve seating having inter-engaging sealing faces, wherein the sealing piston is constructed so as to be flexible to a limited extent in the region of its sealing face. This tenders the valve self-sealing. The flexibility can be achieved by coating the piston or by forming the piston at least in part, from an appropriate material, typically plastics as described in more detail hereinafter.

Owing to the particular design of the sealing element or piston, a complete seal is achieved permanently with such a valve even with the pressure fluids which gave rise to problems of sealing as it rests with its sealing faces quite tightly on the faces of the valve seating and is deformed owing to the influence of the loading compression spring. Therefore, it is surprisingly possible to construct valves, in particular non-return valves, completely tightly, the seal always being guaranteed even after a plurality of stress cycles.

Furthermore, the sealing seating can no longer be dam aged. A further advantage is that optimum guidance of the pressure fluid through the interior of the valve is achieved owing to the construction of the sealing faces.

The shifting forces now remain permanently the same as the same sealing face is invariably predetermined and obtained.

The piston can have an end portion which is conical or frusto-conical and defines the sealing face thereof.

The sealing faces can be planar or curvilinear.

According to an embodiment of the invention it is proposed that the end portion of the sealing piston be constructed so as to be flexible to a limited extent and to be detachably connected to the remainder of the sealing piston. The region of the sealing piston which is important for the effect of the sealing faces can therefore have the optimum construction for the respective application. The entire sealing piston does not have to be specially designed but merely a part which can be connected to the actual sealing piston, for example by screwing or the like.

In another embodiment, it is proposed that the sealing piston be provided with a coating, for example of plastics material, which is flexible to a limited extent.

With this arrangement, it is sufficient to provide a relatively thin coating as the deformation mentioned above can be achieved in the region of the sealing faces.

The thickness of the coating can be adjusted according to the strength of the compression spring in order to achieve the desired sealing effect in the region of the sealing faces.

The sealing piston can also be constructed so as to be flexible overall to a limited extent, and this has the advantage that further preparatory work due to the assembly of individual parts of the sealing piston is avoided. Instead, the entire sealing piston is injection moulded, for example from a plastics material, and it has surprisingly been found that special machining of the sealing faces is not necessary but that bodies produced by conventional machining processes are most suitable as sealing pistons. Complicated preparatory work is thus avoided and the production costs are considerably reduced.

Optimum guidance of the flow of pressure fluid can be achieved and pressure loss inside the valve can be reduced to a minimum by using a sealing piston which has a conical end portion with a corresponding obliquely extending sealing face. The shape of the valve cone ensures a rapid return of the sealing piston under a corresponding pressure load but at the same time a flow which is as uniform as possible through the system as such and therefore uniformly reliable operation of the valve.

The desirable flow behaviour of the pressure fluid inside the valve can also be achieved with a similar design in which the end portion of the sealing piston directed against the direction of flow has a sealing face which extends in the form of a curve and in that the valve seating has a sealing face curved in the opposite direction. The direction in which the sealing face of the valve seating and, conversely, the sealing face of the sealing piston are curved is irrelevant.

It is also conceivable to use a sealing piston having a frusto-conical end portion with a sealing face extending obliquely and parallel to the sealing face of the valve seating. In this embodiment, a larger through flow area is available in the region of the bore supplying the pressure fluid. This larger area ensures rapid opening of the valve and at the sae time provides a large sealing face in the region of the valve seating.

If the edges between the sealing faces are suitably rounded on the valve piston, good and uniform guidance of the pressure fluid results.

When the valve opens and the fluid flows between the sealing faces, the fluid preferably enters a duct in the housing or in the piston. One or more radial bores can lead from the duct into a fluid passage or bore in the piston which opens away from the valve sealing faces to permit the fluid to escape.

A self-sealing valve constructed in accordance with the invention can be used as a non-return valve and as a pressure-relief valve designed to operate reliably with a long service life. Few changes are necessary to enable the valve to perform as a pressure-limiting valve.

Essentially the spring force is crucial and preferably the pre-stressing of the spring is controlled with an adjusting screw fitted in the housing. The opening pressure at which the valve opens and discharges can then be established via the compression spring. The discharged pressure medium can be collected.

The invention is particularly advantageous when used in underground mining and tunnelling, on the one hand because a valve which is self-sealing and operates accurately, with a long service life, is advantageous and, on the other hand, because great versatility is achieved, allowing use as a non-return or pressure-limiting valve.

This versatility is such that the valve can be adopted as a setting valve. This can be achieved by using the selfsealing piston to replace the conventional ball in the setting valve. Preferably the sealing face of the piston is composed of plastics material and the sealing seating in the setting valve is composed of metal. The invention acts particularly advantageously in the application to the setting valve or a setting gun owing to the complete tightness of the system and the good service lives which can be achieved, inter alia owing to the uniform shift forces.

The invention is distinguished, in particular, by the creation of a valve design which is invariably tight, even to HFA, HFC or HFD pressure fluids. Even after long service lives, it is not possible for pressure fluid to seep through as the sealing faces prevent this owing to their construction. Even the relatively slight force of the compression spring is sufficient to press the sealing face of the sealing piston sufficiently far onto the valve seating to achieve the permanent seal by appropriate deformation. It is also advantageous that desirable flow control is guaranteed in the region of the sealing piston owing to the particular shape and design of the sealing piston, so that the opening as well as the subsequent closure of the valve but, in particular, the uniform guidance of the fluid is invariably permitted.

The sealing face on the valve seating is not affected by the shifting cycles so that the shifting forces are invariably equal independently of the frequency of the shifting cycles. The versatility of the proposal according to the invention should also be emphasised since the design of the sealing piston, if suitably adapted, can be used in non-return valves and pressurelimiting valves as well as in setting valves and similar valves.

Further details and advantages of the invention may appear from the following description.

Embodiments of the invention will now be described, by way of examples only, with reference to the accompanying drawings, wherein: Figure 1 is a sectional view of a non-return valve constructed in accordance with the invention and employing a sealing piston composed overall of flexible material; Figure 2 depicts a valve in which the sealing piston is coated in the region of its sealing face; Figure 3 depicts a valve in which the sealing piston is rounded in the region of its sealing faces; Figure 4 depicts part of a valve in which the sealing piston is curved inwardly in the region of its sealing face; Figure 5 depicts a valve in which the sealing piston is of frusto-conical form; Figure 6 depicts part of a valve in which the sealing piston is provided overall with a coating;; Figure 7 depicts part of a valve in which the sealing piston has a ring-shaped duct and a coating in the region of its sealing face; and Figure 8 is a sectional view of a pressure limiting valve constructed in accordance with the invention.

Figure 1 shows a valve 1 designed as a non-return valve. The valve 1 has a sealing piston 10 displaceable in an internal bore 3 of a housing 2. Plug-in connectors 4,5 at the ends of the housing 2 enable simple connections to be established with pressure tubes.

The valve 1 opens in the flow direction 6 and a tight sealing is achieved in that the sealing piston 10 has a sealing face 11 which is pressed against a sealing face 9 of a valve seating 8 by a compression spring 17.

The piston 10 has a conical end portion 12 defining the face 11 which is particularly advantageous to the flow.

In accordance with the invention, the piston 10 is produced at least partly from or is coated with an appropriate flexible material such that the pressure of the compression spring 17 is sufficient to achieve a certain amount of deformation in the region of the sealing face 11. For continuous operation, it is important that the sealing face 11 or part or all of the entire sealing piston 10 is composed of material which is flexible to a limited extent to ensure an invariably equal throughput and equal shifting forces. This would not be unequivocally guaranteed with the conventional construction as the rigid sealing piston would impair the sealing face 9 of the valve seating 8.

The flow of pressure fluid is guided inside the valve 1 such that the pressure fluid passing between the faces 9,11 subsequently passes into an annular duct 16 and thence through one or more radial bores in the piston 10,15 into a central blind passage 14 in the piston 10,14 from whence it can issue from the housing 2. The annular duct 16 is constructed such that the necessary quantity of pressure medium can enter and can simultaneously continue via the radial bores 15.

The compression spring 17 abuts a ring 18 held by a groove in the bore 3 via a supporting ring 19. This ensures that the sealing piston 10 is pressed onto the valve seating 8 with the necessary force. In the embodiment shown in Figure 1, the entire sealing piston 10 consists of a material which is flexible to a limited extent so that the reliable seal in the region of the sealing faces 9,11 is achieved and permanently guaranteed.

In the embodiment shown in Figure 1, the tip 20 of the sealing piston 10 or the end portion 12 is a genuine tip. The pressure fluid is therefore intentionally guided into the gap between the faces 9,11 produced during the opening and shifting of the sealing piston 10.

According to Figure 2, the tip 20 of the piston 10 is provided with a coating 22, preferably consisting of plastics material, while the remainder of the sealing piston 10 is composed of normal metal, e.g. steel.

Complex machining of the sealing face 11 is also dispensed with in this embodiment as the coating 22 guarantees a complete and reliable seal.

The design according to Figure 3 and according to Figure 4 differs from the design according to Figure 1 in that the end portion 12 on the tip 20 of the piston 10 is constructed as a rounded head. According to Figure 3, the end portion 12 is convex and the valve seating 8 or the face 9 thereof is correspondingly concave. In the design according to Figure 4 these curvatures are reversed. In both cases, however, uniform guidance of the pressure medium is intentionally achieved in this region.

In the valve shown in Figure 5, the valve piston 10 and its sealing face 11 are dimensioned the same as in the other constructions except the end portion 12 is cut away at 21 to form a frusto-conical shape instead of the conical shape.

Figures 6 and 7 depict embodiments in which a complete coating 23 or a partial coating 23' is provided on the sealing piston 10. The essential difference in these embodiments is that the annular duct 16 is provided in the housing 2 according to Figure 6 while a ringshaped duct 25 is provided in the sealing piston 10 according to Figure 7. The coating 23 of the piston 10 is interrupted in Figure 7, but it is also conceivable for the internal faces of the duct 25 also to be coated if the coating is applied accordingly after production of the ring-shaped duct 25.

Figure 8 shows a pressure-limiting valve 1, in which the pressure arises from an hydraulic unit to be protected at the plug-in connection 4. If the pressure on this side of the valve exceeds the pressure produced by the compression spring 17 then the sealing piston 10 is lifted from the valve seating 8 and the pressure medium can enter the annular duct 16, and flow through the radial bores 15 into the passage 14 into a spring chamber 26. The compression spring 17 can be prestressed via an adjusting screw 28 which can be adjusted via the impulse screw 27, so that the opening pressure can also be predetermined accurately. The adjusting screw 28 is provided with an outlet passage 29 so that the pressure medium can leave the housing 2. The compression spring 17 is simultaneously guided in the upper part by the particular design of the adjusting screw 28 so that tilting cannot occur. The sealing face 11 of the piston 10 is constructed in accordance with the principles discussed above.

Claims

1. A valve for use with HFA, HFC or HFD pressure fluids; said valve comprising a sealing piston which seals in one direction displaceably mounted in a bore in a housing, and a compression spring biasing the piston against the desired direction of flow and onto a valve seating, the valve piston and the valve seating having inter-engaging sealing faces, wherein the sealing piston is constructed so as to be flexible to a limited extent in the region of its sealing face.

2. A valve according to claim 1, wherein the piston has a conical or frusto-conical end portion defining the sealing face thereof and this end portion is constructed so as to be flexible to a limited extent.

3. A valve according to claim 1, wherein the sealing piston is provided with a coating, preferably of plastics material, which is flexible to a limited extent.

4. A valve according to claim 1, wherein the sealing piston is constructed so as to be flexible overall to a limited extent.

5. A valve according to claim 4, wherein the sealing piston is made from plastics material.

6. A valve according to any one of claims 1 to 5, wherein the sealing faces are planar.

7. A valve according to any one of claims 1 to 5, wherein the sealing faces are curvilinear.

8. A valve according to any one of claims 1 to 7, wherein an annular duct is provided in the housing to receive pressure fluid flowing between the sealing faces.

9. A valve according to any one of claims 1 to 7 wherein a ring-shaped duct is provided in the piston to receive fluid flowing between the sealing faces.

10. A valve according to claim 8 or 9, wherein the duct communicates with one or more radial bores in the piston leading to a blind passage in the piston from whence the fluid can escape from the housing.

11. A valve according to claim 1 adapted as a setting valve , wherein the sealing piston replaces a ball of a conventional setting valve, the sealing face of the piston is composed of plastics material and the sealing face of the seating of the setting valve is comprised of metal.

12. A valve substantially as described with reference to, and as illustrated in any one or more of the Figures of the accompanying drawings.