GB2043210A - Controlled pressure-release valve - Google Patents

Abstract

The valve has a housing (1) with high-pressure and low-pressure spaces (2, 3) which are put into communication upon leftward displacement of a valve member (9) having axial passages (10) and throttling passages (16). A spring- biassed actuating piston (18) is movable under the action of fluid pressure supplied through 22 to move the valve member (9) and thereby initiate restricted release of the high-pressure in space (2) via throttling passages (16). An auxiliary piston (24) accommodated in an axial bore (23) of the piston (18) cooperates with the valve member (9) for further displacing the latter to allow more rapid release via the axial passages (10) when the effort applied by the auxiliary piston (24) to the valve member (9) overcomes the effort applied thereto from the partially-relieved high-pressure space (2). <IMAGE>

Description

SPECIFICATION Pressure valve The present invention relates to pressure valves.

The invention provides a pressure valve comprising a housing having a high-pressure space and a low-pressure space, communicable via openings in the housing with a fluid source and separated from each other by a partition having an axial throughbore therein, a cylindrical valve member reciprocatably mounted in the bore of the partition having in the body thereof axial passages for establishing communication between the two spaces upon the displacement of a valve member; a pressure-relief piston accommodated in the low-pressure space, the pressure relief piston being resiliently biassed away from the partition and being movable under the action of fluid pressure, supplied, to effect the relieving of the pressure in the high-pressure space, upon the end face of said pressure-relief piston remote from the valve member, the pressure relief piston having therein an axial through-bore, accommodating an auxiliary piston adapted to cooperate with the valve member to transmit thereto the displacement of the pressure-relief piston under the action thereupon of the fluid pressure supplied to effect the relieving of the high-pressure space, the body of the valve member having therein, adjacent to the low-pressure space, throttling passages communicating with the axial passages of the valve member, the throttling passages offering a flow passage area which is substantially smaller than that offered by the axial passages of the valve member, so that, in use, during the operation of relieving the pressure in the high-pressure space, the highpressure space and the low-pressure space communicate via the throttling passages until the effort applied to the valve member by the auxiliary piston overcomes the effort applied to the valve member by the pressure acting thereupon from the highpressure space.

Such a pressure valve can be used to utmost effectiveness in the hydraulic circuitry of powered mine roof supports, e.g. as the hydraulic lock of a hydro-operated mine roof support prop. Also it can be utilized in various other industries and technologies, wherever a pressurized fluid is to be reliably sealed in a space or spaces of a mechanism, with subsequent gradual relieving of this pressure.

The valve is incorporable both in hydraulic systems and in pressurized-gas systems, e.g. pneumatic systems.

This structure of the pressure valve provides in the course of the relieving action, e.g. pressure-relieving of a hydraulic prop, gradual two-stage reduction of the pressure down to a zero value, preventing the occurrence of a hydraulic shock and oscillation of the valve member. The herein disclosed structure of the pressure valve combines simplicity of the design with a high reliability of performance, as compared with the hitherto known structures, owing to the throttling passages being recurrently flushed with the very working fluid, which precludes their clogging.

The incorporation of the disclosed pressure valve, e.g. in the hydraulic props of powered mine roof supports, enables to prolong the service life of the powered roof support and of its hydraulic circuitry.

Preferably, the dimensions of said low-pressure space, of said pressure-relief and auxiliary valves, and of said valve member are so selected that with said pressure-relief valve displaced into its extreme position abutting against said partition under the action of the fluid pressure supplied to effect the relieving of said high-pressure space, said highpressure space and said low-pressure space communicate via said throttling passages, whereby gradual reduction of the pressure in said highpressure space is effected.

This selection of the relative dimensions of the components of the pressure valve makes it possible to positively define the moment at which pressure reduction commences and to provide for the stability of the performance of the components of the valve at gradual reduction of the pressure in the highpressure space. This further enhances the reliability of the performance of the valve.

Advantageously, the throttling passages are defined by flats provided on the cylindrical surface of the end portion of said valve member, adjacent to said low-pressure space, the surface of these flats defining the throttling passages jointly with the internal surface of said bore in said partition, these flats being arranged so as to balance the efforts exerted upon the valve member by the pressure of the fluid flowing through said throttling passages.

The arrangement of the throttling passages in the described manner enhances still further the reliability of the performance of the valve member, prevents the latter jamming and simplifies the manufacture of the valve member.

The present invention will be further described in connection with embodiments thereof, with reference being made to the accompanying drawings, wherein: Figure 1 is a longitudinally sectional view of a pressure valve embodying the invention, wherein the valve member and auxiliary piston are separate components, the drawing schematically illustrating the connection of the pressure valve to a powered mine roof support as the latter is hydraulically compressed; Figure 2 is a sectional viewtaken on line Il-Il of Figure 1; Figure 3 is a perspective view of the valve member of the pressure valve embodying the invention; Figure 4 is a longitudinally sectional view of the pressure valve embodying the invention, showing the relative positions of the components of the valve at the initial moment of the relieving action;; Figure 5 is a longutidnally sectional view of the pressure valve embodying the invention, showing the relative positions of the components of the valve at the final moment of the relieving action.

Figure 6 is a longitudinally sectional view of the pressure valve embodying the invention, wherein the valve member is made integral with the auxiliary piston.

Following hereinbelow is a description of a prac tical embodiment of the pressure valve, also called a hydraulic lock, constructed in accordance with the invention and illustrated in a longitudinally sectional view in Figure 1.

The description refers to the pressure valve used for controlling the pressure in the hydraulically operated prop of a powered mine roof support, which, however, is not intended to narrow the essence and scope of the present invention.

The pressure valve has a metal housing 1, having therein a high-pressure space 2 and a low-pressure space 3. The high-pressure space 2 communicates with the lower chamber 4 of a hydraulic prop 5, e.g.

via a line 6. The low-pressure space 3 communicates with a pressurized-fluid source (not shown).

The high- and low-pressure spaces and 3, respectively, are separated from each other by a partition 7 having a cylindrical through bore 8 therein..

The bore 8 accommodates a reciprocable cylindrical valve member 9. The valve member 9 has longitudinal axial passages 10 (Figures 1 and 2) therein. As shown in Figure 3, the axial passages 10 comprise diametrally opposing recesses in the body of the valve member 9, which is cross-shaped (see Figure 2) in the zone of the passages 10. However, the number and the shape of the axial passages 10 can be selected at random.

The diameter of the valve member 9 (Figure 1) equals the diameter of the bore 8 in the partiton 7. To provide fluid-tight separation between the high- and low-pressure spaces 2 and 3 respectively, the end portion of the valve member 9, adjacent to the high-pressure space 2, has an annular groove therein, accommodating a seal 11. To protect the seal 11 from damage, the valve member 9 receives thereon a spring-biassed cap 12. The valve member 9 is spring-biassed relative to the cap 12 by a compression spring 13, while another compression spring 14 biasses the cap 12 relative to the housing 1, one end ofthe spring 14 abutting against the housing 1, and the opposite end thereof abutting against a shoulder of the cap 12.The spring 14 is intended to retain the cap 12on the valve member 9, as the latter reciprocates, and also to return the valve member 9 into its initial position. The spring 13 is intended to retract the valve member 9 and its seal 11 from the cap 12 at the return stroke of the valve member 9.

To facilitate assembly of the components of the pressure valve, the housing is provided with a threaded lip 15 at the high-pressure space 2 side thereof.

The flow passage area of the axial passages 10 is selected to provide for rapid and reliable relieving of the chamber 4 below the piston of the hydraulic prop 5 from the pressureized liquid.

The length of the axial passages 10 is such that in the extreme position of the valve member 9, where it abuts jointly with the cup 12 against the lid 15, the high- and low-pressure spaces 2 and 3, respectively, communicate via the axial passages 10, which provides for rapid relieving of the pressure in the high-pressure space 2.

Adjacent to the low-pressure space 3, the body of the valve member 9 has throttling passages 16 (Figure 2). In the herein described embodiment of the invention, these throttling passages 16 are formed externally of the body of the valve member 9 and comprises flats 17 (Figures 2 and 3). The throttling passages 16 per se are defined by the surface oftheflats 17 and the internal surface or wall of the bore 8 (Figure 1) of the partition 7, while the valve member 9 is within this bore 8. The flats 17 are so arranged on the body of the valve member 9, that the balance the efforts exerted upon the valve member 9 by the pressure of the liquid flowing through these throttling passages 16 (Figure 2).As shown in Figure 2, the flats are arranged in diametral opposition to each other, to mutually counterbalance the unwanted biassing effort created by the pressure of the liquid flowing throughthethrottling passages 16. This feature precludes jamming of the valve member 9 in the bore 8 of the partition 7 and prolongs the service life of the valve member 9 and of the pressure valve unit, as a whole.

in the embodiment illustrated in Figure 2, two flats 17 are formed in the body of the valve member 17; however, other number of the flats 17 may be selected. The actual number of these flats depends on the total value of the low passage area required of the throttling passages 16; however, the arrangement of the flats 17 is preferably such that the abovementioned condition of balancing the efforts exerted by the pressure of the liquid is satisfied.

Besides, in the presently described embodiment the flats 17 are arranged on the body of the valve member 9 so that the throttling passages 16 defined thereby present a continuation of the respective axial passages 10 (Figures 1 and 3).

The total flow passage area of the throttling passages 16 is substantially smaller than the total flow passage area of the axial passages 10, and is selected so that at the initial stage of the relieving of the high-pressure space 2 from pressure, gradual and smooth reduction of the pressure in the highpressure space 2 should be provided for by the pressurized liquid flowing via the throttling passages 16, and unwanted oscillation of the valve member 9 should be thus precluded.

Mounted in the low-pressure space 3 is a pressurerelief piston 18 (Figure 1) biassed by a compression spring 19 away from the partiton 7. The spring 19 serves to return the pressure-relief piston 18 into its initial position.

To prevent escape of the pressure-relief piston 18 from the housing 1, the former is provided with stroke-limiting means in the form of a lock ring 20.

The end face 21 of the pressure-relief piston 18, remote from the valve member 9, is open or exposed to be acted upon by the pressure relief-initiating pressure of the liquid fed via the line 22 connected to a pressurized-liquid source (not shown).

The pressure-relief piston 18 has an axial bore 23 therein. This axial bore 23 accommodates an auxiliary piston 24. The bore 23 is of stepped-diameter, the larger diameter end facing the interior of the low-pressure space 3, while the smaller diameter end thereof faces outwardly of the low-pressure space 3 and is intended for the feed of the reliefinitiating pressure from the line 22 to the auxiliary piston 24. However, this structure of the bore 23 is not mandatory, and the bore may be of a uniform diameter, in which case it is preferably provided with a lock ring to prevent the escape of the auxiliary piston 24 from this bore 23 of the pressure-relief valve 18.

The auxiliary piston 24 is arranged concentrically with the pressure-relief piston 18 and coaxially with the valve member 9 the adjacent end face of which it permanently engages. Both the pressure-relief piston 18 and the auxiliary piston 24 are provided with corresponding appropriate ring seals.

It should be pointed out that the axial length of the flats 17 is selected so that upon the relief-initiating pressure being fed via the line 22 to the end face 21 of the pressure-relief piston 18, the throttling passages 16 (Figure 2) should establish communication between the high- and low-pressure spaces 2 and 3, respectively, until the effort applied to the valve member 9 (Figure 1) by the auxiliary piston 24 under the action of the relief-initiating pressure thereupon overcomes the effort exerted by the pressure in the high-pressure space 2 upon the valve member 9.

Furthermore, the dimensions of the low-pressure space 3, of the pressure-relief piston 18 of the auxiliary piston 24, and of the valve member 9 are so selected that with the pressure-relief piston 18 occupying its extreme position where it abuts against the partition 7 under the action of the relief-initiating pressure supplied via the line 22 to its end face 21, the high- and low-pressure spaces 2 and 3, respectively, communicate via the throttling passages 16 (Figure 2), to provide for smooth reduction of the pressure in the high-pressure space 2 (Figure 1). The combination of the above features precludes the occurrence of a hydraulic shock and of oscillation of the valve memberS, which enhances the reliability of the performance of the pressure valve unit and prolongs its service life.

When the herein disclosed pressure valve is installed for controlling the pressure in the hydraulic prop of a powered mine roof support, the pressure valve unit is accommodated in a structure (not shown) incorporating a safety valve 25 limiting the buildup of the pressure in the chamber 4 below the piston of the hydraulic prop 5.

The high-pressure space 2 (Figure 1) communicates via openings 26 in the housing 1 and via a line 27 with the safety valve 25, while via the line 6 it communicates with the chamber 4 of the hydraulic prop 5.

The low-pressure space 3 communicates via open ings 28 in the housing 1 and a line 29 with a pressurized working liquid source (not shown).

In the embodiment described, four such openings 26 are provided in the housing 1 of the pressure valve unit to communicate the high-pressure space 2 with the safety valve 25 and with the hydraulic prop 5, and four such openings 28 are provided in the housing 1 to communicate the low-pressure space with the pressurized liquid source (not shown).

However, this number of the openings in the hous ing 1 of the pressure valve is not mandatory, and may be either greater or smaller.

The line 22 through which the working liquid is supplied from the source to act upon the end face 21 of the pressure-relief piston 18 also communicates with the chamber 30 above the piston of the hydraulic prop 5.

In the initial state of the operation, the components of the above described pressure valve occupy the following positions.

The pressure-relief piston 18 is maintained by the action of the spring 19 in its position most remote from the partition 7. The valve member 9 acted upon by the springs 13 and 14maintainsthe auxiliary piston 24 likewise in the latter's position which is the most remote from the partition 7. The valve member 9 occupies a position whereat its axial and throttling passages 10 and 16, respectively, open into the low-pressure space 3, while the seal 11 provides a fluid-tight seal between the light-pressure space 2 and the low-pressure space 3.

With the pressure valve in the above specified state, the associated hydraulic prop 5 can be either in a loaded or in a relieved state.

Let us assume that in Figure 1 the hydraulic prop 5 is in a relieved state.

When the hydraulic prop 5 is to be extended or loaded, the pressure valve aperates, as follows. The working liquid is supplied from the source (not shown) via the line 29 and the openings 28 into the low-pressure space 3, the safety valve 25 preventing the access of the working liquid via the line 27 into the high-pressure space 2. The action of the pressure of the liquid, exerted upon the valve member 9, displaces the latter so that it compresses the springs 13 and 14, and moves in the direction of the high-pressure space 2. Upon the axial passages 10 opening into the high-pressure space 2, the intense filling up of the high-pressure space 2 with the working liquid commences, and the working liquid flows via the openings 26 and the line 6 into the chamber 4 of the hydraulic prop 5. The seal 11 of the valve member 9 is now located within the cap 12, which prevents wear of the seal 11.The piston rod of the hydraulic prop is raised, and the working liquid is supplied to the chamber 4 until the required pressure is built up therein.

When the required pressure has built up in the hydraulic prop 5, the supply of the pressurized working liquid into the low-pressure space 3 is terminated, whereby the valve member is returned by the combined action of the pressure of the liquid in the high-pressure space 2 and of the springs 13, 14 to its initial position where it seals the high-pressure space 2 from the low-pressure space 3.

Thus, the seal 11 reliably maintains pressurized working liquid in the high-pressure space 2 and in the chamber 4 of the hydraulic prop 5.

To relieve the hydraulic prop 5 from the pressure, the following is done.

The working liquid is fed from the source via the line 22 under a pressure called the pressure reliefinitiating pressure simultaneously to the chamber 30 of the hydraulic prop 5 and to the end face 21 of the pressure-relief piston 18. The relief-initiating pressure value should be sufficient to develop an effort capable of overcoming the effort exerted upon the pressure-relief piston 18 by the combined action of the springs 13, 14, 19 and of the pressure of the liquid in the high-pressure space 2. Under the action of the relief-initiating pressure of the thus selected value, the pressure-relief piston 18 is displaced toward the partition 7, moving therealong the auxiliary piston 24 and the valve member 9. This displacement of the pressure-relief piston 18 continues until it abuts against the partition 7.At this position of the pressure-relief piston 18, the throttling passages 16 open into the high-pressure space 2, so that smooth outflow of the working liquid commences from the high-pressure space 2 into the low-pressure space 3 via the throttling passages 16, and therefrom via the openings 28 into the line 29 leading to drain. Owing to the throttling passages 16 having a relatively small total flow passage area, the reduction of the pressure in the high-pressure space 2 and in the chamber 4 of the hydraulic prop 5 takes place smoothly and gradually. Meanwhile, the valve member 9 is stationary, occupying the position shown in Figure 4, while the auxiliary piston 24 is retained by the pressure thereupon of the valve member 9 within the bore 23 of the pressure-relief piston 18.

The piston rod of the hydraulic prop 5 (Figure 1) is in the meantime practically stationary. In this way the first stage of the relieving of the hydraulic prop 5 is effected.

This smooth reduction of the pressure in the high-pressure space 2 and the communication between the two spaces 2 and 3 via the throttling passages 16 continue until the pressure applied to the valve member 9 by the auxiliary piston 24 acted upon by the relief-initiating pressure overcomes the effort of the pressure acting upon the valve member 9 from the high-pressure space 2, in combination with the effort of the springs 13 and 14 also acting upon the valve member 9.

Thus, with the pressure within the high-pressure space 2 reduced to a predetermined sufficiently low value, the auxiliary piston 24 starts moving under the action thereupon of the pressure of the working liquid supplied via the line 22. This outward motion and this action of the pressure of the working liquid upon the auxiliary piston 24 have, been made possible exclusively by the provision of the through bore 23 in the pressure-relief piston 18.

The outward displacement of the auxiliary piston 24 results in the simultaneous displacement of the valve member 9 toward the high-pressure space 2.

This displacement of the valve member 9 results in that at a certain moment the axial passages 10 open into the high-pressure space 2, whereby there commences intensive outflow of the liquid via the axial passages and the line 29 to drain. The pressure in the space 2 and in the chamber 4 rapidly drops, and the piston rod of the hydraulic prop 5 is retracted. In this manner the second stage of the relieving of the hydraulic prop 5 is effected. At this stage the valve member 9 is in its extreme projected position illustrated in Figure 5.

When the piston rod of the hydraulic prop 5 has been retracted into a desired position, the supply of the pressurized liquid to the line 22 (Figure 1) is discontinued, whereby the auxiliary and pressurerelief pistons 24 and 18, respectively, are relieved from the action of this pressure thereupon. The action of the springs 13, 14 and 19 now returns the valve member 9, the auxiliary piston 24 and the pressure-relief piston 18 to their respective initial positions shown in Figure 1.

The above described structure of the pressure valve, enabling the relieving operation to be conducted in two stages, with the smooth reduction of the high pressure during the first stage, significantly reduces the dynamic loads acting upon all the major components of the pressure valve, which enhances its reliability and prolongs its service life.

In a modification of the pressure valve illustrated in Figure 6, the auxiliary piston 31 is made integral with the valve member 32. In this embodiment the diameter of the auxiliary piston 31 has to be smaller than that of the valve member 32 proper. The rest of the components of the pressure valve unit are identical to those described hereinabove, and the operation of the pressure valve of this modification is similar to that described in connection with the embodiment illustrated in Figures 1 to 5.

The above described pressure valves can be used profitably in association with various designs of hydraulic props of various mine roof support systems, which, however, in no way precludes its efficient utilization in fluid-pressure systems of various other industries.

Claims (5)

1. A pressure valve comprising a housing having a high-pressure space and a low-pressure space, communicable via openings in the housing with a fluid source and separated from each other by a partition having an axial through bore therein, a cylindrical valve member reciprocatably mounted in the bore of the partition and having in the body thereof axial passages for establishing communication between the two spaces upon the displacement of the valve member; a pressure-relief piston accommodated in the low-pressure space, the pressure relief piston being resiliently biassed away from the partition and being movable under the action of fluid pressure, supplied, to effect the relieving of the pressure in the high-pressure space, upon the end face of said pressure-relief piston remote from the valve member, the pressure relief piston having therein an axial through-bore accommodating an auxiliary piston adapted to cooperate with the valve member to transmit thereto the displacement of the pressure-relief piston under the action thereupon of the fluid pressure supplied to effect the relieving of the high-pressure space, the body of the valve member having therein, adjacent to the lowpressure space, throttling passages communicating with the axial passages of the valve member, the throttling passages offering a flow passage area which is substantially smallerthan that offered by the axial passages of the valve member, so that, in use, during the operation of relieving the pressure in the high-pressure space, the high-pressure space and the low-pressure space communicate via the throttling passages until the effort applied to the valve member by the auxiliary piston overcomes the effort applied to the valve member by the pressure acting thereupon from the high-pressure space.

2. A pressure valve as claimed in Claim 1, wherein the dimensions of said low-pressure space, of said pressure-relief and auxiliary valves, and of said valve member are so selected that with said pressure-relief valve disposed into its extreme position abutting against said partition under the action of the fluid pressure supplied to effect the relieving of said high-pressure space, said high-pressure space and said low-pressure space communicate via said throttling passages, whereby gradual reduction of the pressure in said high-pressure space is effected.

3. A pressure valve as claimed in Claim 1 or 2, wherein said throttling passages are defined by flats provided on the cylindrical surface of the end portion of said valve member, adjacent to said low-pressure space, the surface of these flats defining the throttling passages jointly with the internal surface of said bore in said partition, these flats being arranged so as to balance the efforts exerted upon the valve member by the pressure of the fluid flowing through said throttling passages.

4. A pressure valve as claimed in cny one of Claims 1 to 3, wherein said valve member is formed integrally with said auxiliary piston.

5. A pressure valve substantially as hereinbefore described with reference to and as shown in Figures 1 to 5 or as modified by Figure 6 of the accompanying drawings.