WO2010125500A2

WO2010125500A2 - Pressure relief valve

Info

Publication number: WO2010125500A2
Application number: PCT/IB2010/051753
Authority: WO
Inventors: Franz-Heinrich Suilmann; Oliver Dwornik
Original assignee: Bucyrus Europe Gmbh
Priority date: 2009-04-29
Filing date: 2010-04-21
Publication date: 2010-11-04
Also published as: CN102428253B; RU2011148438A; EP2425097A2; WO2010125500A3; ZA201108679B; CN102428253A; AU2010243223A1; DE202009004753U1

Abstract

The invention relates to a pressure relief valves, especially a rock-burst safety valve for the hydraulic face support, having a consumer connection (3) with a bore (2) a fluid outlet (4), and a valve piston which is arranged in the valve and pressed against a valve seat (7) by means of a valve spring system (6) for separating consumer connection and fluid outlet. In order to improve the valve with regard to construction and functioning such that a rapid and reliable response behaviour for the opening and closing movements can be achieved, the valve seat (7), the bore (2) of the consumer connection (3) and the fluid outlet (4) are formed on a head piece (1) having a guide bore (24) for the valve piston (5). Furthermore, the valve spring system (6) has at least one disc spring stack (12) having disc springs (11) which are arranged in the valve housing (13), wherein the actuating force of the spring stacks is applied against an end of the valve piston (5) that is remote from the sealing seat (7).

Description

Description Title of Invention: PRESSURE RELIEF VALVE

[1] The invention relates to a pressure relief valve for hydraulic units, in particular a pressure relief valve for mining, such as in particular a rock-burst safety valve for the hydraulic face support, having a valve housing, having a consumer connection comprising a bore for connecting a hydraulic unit to be protected against hydraulic overload, having a fluid outlet, and having a valve piston which is arranged in the valve, bears with a sealing cone against a valve seat in the closed state by means of the actuating force of a valve spring system for separating consumer connection and fluid outlet and, during hydraulic overload, can be lifted off the valve seat against the restoring force of the valve spring system for opening a connection between consumer connection and fluid outlet.

[2] Pressure relief valves are used in many different configurations in the most diverse areas of hydraulic supply for hydraulic units. In mining, in particular in hydraulic face support, corresponding pressure relief valves must be able to cope with relative large nominal connection diameters, since flow rates of more than 2000 1/min can occur, and the valve must also withstand extremely high loads, since the hydraulic fluid can have a pressure of more than 100 bar and up to 800 bar and above. In a rock-burst safety valve, in the event of an overload, which can occur almost abruptly on account of a sudden rock movement (rock burst) or another, unforeseeable situation, enormous flow rates through the pressure relief valve have to take place. Pressure relief valves designed as rock-burst safety valves for face hydraulics are therefore subject to special requirements which do not exist for valves for small flow rates or hydraulic pressures that are used in other sectors of technology.

[3] For the main field of application of the pressure relief valve according to the invention - hydraulic face support - there are already numerous solution proposals in the prior art in order to achieve a rapid response behaviour of the pressure relief valve and also ensure large flow rates in the event of an overload. The pressure relief valves used on the market either have, virtually universally, a gas compression spring as valve spring system or they are provided with a coil spring as disclosed by way of example in DE 199 46 848 Al or DE 10 2005 046 541 Al. In both pressure relief valves of the type in question for face support, the coil spring interacts with a hat-shaped spring plate which interacts in turn with a valve spool, such that hydraulic fluid can flow over from the consumer connection to the fluid outlet only when an annular seal on the valve spool has passed a feed bore for a pressure compensation space.

[4] A rock-burst safety valve in which both a non-return valve having a sealing cone and conical sealing seat and a pressure relief valve are integrated into one valve is known from DE 39 09 461 Al.

[5] The object of the invention is to improve a pressure relief valve with regard to construction and functioning, such that a rapid and reliable response behaviour for the opening and closing movements can be achieved, in particular under the requirements in face hydraulics, namely high flow rates with at the same time high hydraulic fluid pressures.

[6] This object is achieved according to the invention in that the conical valve seat for the sealing cone on the valve piston, the bore of the consumer connection and the bore(s) for the fluid outlet are formed on a head piece having a guide bore for the valve piston and connected to the valve housing, and in that the valve spring system has at least one disc spring stack which is arranged in the valve housing and the actuating force of which can be applied against an end of the valve piston that is remote from the sealing seat. In the pressure relief valve according to the invention, the conical seat between valve piston and valve seat surface is used, with which conical seat the fluid outlet and the consumer connection are separated from one another, wherein, by the integration of the valve seat, of the bore of the consumer connection and of the fluid outlet in the head piece, there are extremely short flow paths and at the same time relatively short cross sections of flow which make possible a favourable and rapid response behaviour of the pressure relief valve. A pressure relief valve of this design can be built in a large size and also permits the use of disc spring stacks as a valve spring system, as a result of which even extremely high pressures of the hydraulic fluid can be permitted and reliably coped with.

[7] According to an especially preferred configuration, the fluid outlet consists of at least one radial bore, preferably of a plurality of radial bores, wherein it is in particular preferred if the orifice opening(s) of the radial bore(s) is (are) arranged in an extension section of the guide bore for the valve piston at or close to the transition between the guide bore and the valve seat. With a plurality of radial bores, substantially the same cross section of flow downstream of the sealing cone of the valve piston as is also available in the bore at the consumer connection, therefore upstream of the valve piston, can be achieved, and, in the event of an overload, the hydraulic fluid flows off immediately after the sealing cone on the valve piston has lifted off the associated conical valve sealing seat surface. Since the hydraulic fluid discharges from the radial bores at relatively high pressure and high flow velocity in the event of an overload, it is especially advantageous if a splash ring is fastened to the outer circumference of the valve housing, said splash ring projecting with a funnel-shaped annular casing axially beyond the end openings of the radial bore(s). A collecting tank or a collecting line can adjoin the annular casing, or else the annular casing can allow the hydraulic fluid to flow out into the environment in the event of an overload, wherein specific run-off of the hydraulic fluid, which as a rule consists of special oils or water/oil emulsions, can be achieved via the splash ring.

[8] In an advantageous configuration according to the invention, a pressure disc can be arranged between the disc spring stack and the valve piston end, said pressure disc having a bearing surface on the spring side for a disc spring of the disc spring stack(s) and a pressure surface on the valve-piston side for the valve piston end. In this configuration, the force of the disc spring stacks can be introduced relatively uniformly into the valve piston. It is especially advantageous when the pressure surface consists of a recess and when the valve piston end is designed as a ball head which is arranged with its spherical surface inside the recess, as a result of which the actuating force or restoring force of the disc spring stacks is introduced into the valve piston substantially parallel to the guide axis of the guide bore. In order to ensure a reliable sealing seat of the sealing cone on the conical valve seat for a long operating period even in the case of corrosive hydraulic fluids and/or high pressures, the valve piston has, in an especially advantageous configuration, a multi-piece sealing cone which can preferably be at least partly disassembled and exchanged, wherein part of the sealing cone preferably consists of a plastic bush having a conical slope, which bush can be fitted into a blind hole in the sealing cone. This configuration firstly enables metal/metal contact at the valve seat to be prevented by a suitable material being selected for the plastic bush and secondly enables the pressure relief valve to be renewed and its full functionality restored by only the plastic bush being exchanged if wear is caused in the event of a plurality of overloads.

[9] The valve spring system preferably has a plurality of disc spring stacks, wherein each disc spring stack preferably consists of two disc springs which in each case bear against one another with their narrower annular surfaces. The next disc spring stack then correspondingly adjoins the outer, larger annular surfaces of the individual disc springs.

[10] In the especially preferred configuration, the preloading, and in this respect also the actuating force, of the disc spring stack or stacks can be adjusted by means of an adjusting screw which is supported on the inner circumference of the valve housing via a thread in such a way that it can be screwed and in this respect axially adjusted. By the adjusting screw being turned, the disc spring stacks can be either loaded or relieved in order to thereby also set the limit pressure at which the valve piston is to lift off the valve seat. It is especially advantageous in this case if the valve housing consists of a housing cylinder having an internal thread, into the front end of which the head piece is screwed and into the rear end of which the adjusting screw is screwed. In this configuration, the individual parts of the pressure relief valve according to the invention can be produced separately and if need be from different materials and are only fitted together during the final assembly. In order to enable the preloading to be set, it is also advantageous if an end disc is arranged in an axially displaceable manner between the adjusting screw and disc spring stack and/or if the adjusting screw has a preferably central through-hole for an assembly mandrel, with which the disc springs can be pushed together by axial pressure on the end disc. In this configuration, the assembly mandrel can therefore exert a force on all the disc springs of the spring stacks through the through-hole from the rear side, as a result of which the adjusting screw can be turned without being loaded by the pressure forces of the spring stack. In order to reliably fix the loading force of the disc spring stack even during pronounced vibrations, in particular also in the case of a variable adjustment of the preloading force of the disc spring stack, after a setting operation, it is furthermore advantageous if the adjusting screw is provided on the thread-turn side with a transverse slot, the slot width of which can be varied by means of a screw, such as, for example, a grub screw, for wedging the adjusting screw on the thread turn of the valve housing.

[11] Further advantages and configurations of a pressure relief value according to the invention in an embodiment as a rock-burst safety valve for the face hydraulics in mining follow from the description below of a preferred exemplary embodiment shown schematically in the drawing, in which:

[12] Fig. 1 shows a pressure relief valve according to the invention in section through the valve longitudinal axis;

[13] Fig. 2 shows, in section, a detailed view of the head piece of the pressure relief valve according to the invention, with a valve piston in the closed position;

[14] Fig. 3 shows the valve piston in the open position in the same sectional view as in

Fig. 2; and

[15] Fig. 4 shows, in a sectional view through the rear end of the pressure relief valve, the setting tool and the adjusting operation for hanging the preloading of the disc spring stacks.

[16] A pressure relief valve according to the invention is shown overall in Fig. 1 by reference numeral 10. The pressure relief valve of multi-piece construction is preferably dimensioned as a roof collapse safety valve and comprises, as essential components, a head piece 1, having a bore 2 which is arranged on the central axis Z of the pressure relief valve 10 and which forms a part of a consumer connection designated symbolically by reference numeral 3, a fluid outlet designated symbolically by reference numeral 4, and a valve piston 5 which, in the closed position shown in Fig. 1, is pressed against a conical valve seat 7 by means of a valve spring system 6, as a result of which a fluid connection between the bore 2 and the radial bores 8 in the head piece 1 that lead to the fluid outlet 4 is shut off. In the pressure relief valve 10 according to the invention, the valve spring system 6 consists of disc springs 11, thirty- six in this case, wherein each two disc springs are arranged in opposite orientation to one another and form a disc spring stack 12. All the disc spring stacks 12 bear directly against one another and are arranged in the interior space 39 of a valve housing 13, which is formed here by a tubular housing cylinder and which is closed at the bottom end by means of the screwed-in head piece 1 and at the rear end by means of an adjusting screw 20 screwed onto an internal thread 14 in the housing cylinder. The entire valve spring system 6 consisting of the disc spring stacks 12 presses on the valve piston 5 with preloading, which in this case is preset in an adaptable manner, as a result of which said valve piston 5, with a sealing cone 9, is pressed at its bottom end against the valve seat 7 in the head piece 1 by a preset closing force. The conical valve seat 7, the bore 2 leading to the hydraulic unit to be protected, the radial bores leading to or forming the fluid outlet 4 and a guide bore 24 for the valve piston 5 are integrally formed in the head piece 1.

[17] Reference will now made first of all to Figs 2 and 3, which show the head piece 1 together with valve piston 5 in the closed position (Fig. 2) and in the open position (Fig. 3) of the valve piston 5. At its section projecting from the valve housing 13, the head piece 1 has a valve connection thread 14 for a valve nominal diameter of preferably at least DN 25, and the head piece 1 is provided at the bottom end with a sealing collar 15, on the circumference of which an annular groove is formed for accommodating a sealing ring 16. The sealing ring 16 seals the valve connection or consumer connection 3 when, for example, the pressure relief valve 10 is fastened via the head piece 1 in a valve connection bore of a prop and the hydraulic fluid of the consumer (not shown) to be protected is present in the bore 2. The fluid present in the bore 2 with the pressure of the hydraulic consumer presses against the bottom end of the valve piston 5, as a result of which a force is exerted on the valve piston and attempts to displace the valve piston 5 upwards against the restoring force and preloading of the disc springs 11. In the exemplary embodiment shown, the valve piston 5 is provided with a multi-piece sealing cone 9, wherein only a rear and outer base region, integrally formed on the valve piston, is provided at the end face with a conical slope 5' in order to form the rear part of the sealing cone 9. The base region is defined towards the tip of the cone by a blind hole 16, into which a stepped plastic bush 18, provided in turn with a conical slope 17, is inserted as a further and, if need be, interchangeable part of the sealing cone 9. The plastic bush 18 is fastened to the base region by means of a fastening screw 19 and a multi-stepped clamping bush 60. The conical slope 17 on the plastic bush 18 preferably projects slightly beyond the conical slope 5' on the valve piston 5, for which reason, in the closed state, substantially only the conical slope 17 of the plastic bush 18 bears against the conical valve seat 7. In order to transmit the actuating force for the closed position shown in Fig. 2 uniformly to the valve piston 5, said actuating force being produced by means of the preloading of the disc springs 11, the rear end, or the top end in the figures, of the valve piston 5 is provided with a hemispherical ball head 21 which plunges into a recess 22, in the shape of a pointed cone, on the underside of a hat-shaped pressure disc 23. The disc springs 11 bear against the rear side of the pressure disc 23, and the ball head 21 has approximately only half the thickness as the valve piston 5 in the region of the guide bore 24. By this measure, the guide bore 24, which is integrally formed on the rear end of the head piece 1 and accommodates the valve piston 5 in an axially movable manner, is kept free of transverse forces to the greatest possible extent. The preloading force of the disc springs 11 and the force exerted via the hydraulic fluid in the bore 2 in opposition to the spring force of the disc springs 11 act substantially only parallel to the guide bore 24. The valve piston 5 remains in the closed position shown in Fig. 2 as long as the pressure of the hydraulic fluid in the hydraulic unit to be protected does not exceed a limit pressure level which is preset with the closing force, exerted by the preloading of the disc springs 11, on the valve piston 5. [18] If, for example as a result of a rock burst, the pressure at the hydraulic unit or consumer now assumes a pressure level which exceeds the normal load and reaches an overload pressure level, valve piston 5, as shown in Fig. 3, is displaced into the open position by this excess pressure that occurs and the sealing cone 9, in particular the conical slopes 17 on the plastic bush 18, lift off the conical sealing seat 7 in the head piece 1. Only in this open position can hydraulic fluid now flow over, as indicated in Fig. 3 by the arrows, from the bore 2 to the fluid outlet 4 via the radial bores 8 oriented transversely to the axis Z and preferably arranged in a circumferentially distributed manner. Since the hydraulic pressure of the hydraulic fluid in the hydraulic unit is applied directly at the end face of the valve piston 5, the latter, when excess pressure occurs, is immediately displaced into the open position and hydraulic fluid can flow off until the hydraulic pressure in the hydraulic unit again drops below that pressure level at which an overload is no longer present. The radial bores 8 open on the inside into an extension section of the guide bore 24, as can readily be seen in Fig. 3 with reference to the two inner orifice openings 25. Since, on account of the conical slopes 17 that project relative to the conical slopes 5' on the valve piston 5, a relative wide flow path is already cleared immediately the plastic bush 18 lifts off the sealing surface 7, the response behaviour of the pressure relief valve 10 according to the invention is exceptionally rapid. Since the hydraulic pressure of the hydraulic consumer is applied at the valve piston, the pressure relief valve 10 is a direct-acting valve. The orifice openings 25 lie directly adjacent to the transition between the guide bore 24 and the conical sealing seat 7, an extension section being formed there, preferably assisted by stepped narrowing at the valve piston 5, there being no contact between valve piston 5 and guide bore 24 within said extension section. In order to avoid leakages of the hydraulic fluid into the interior space of the valve housing 13 when valve piston 5 is open, at least one sealing ring 29 is arranged between the guide bore 24 and the outer circumference of the valve piston 5.

[19] In order for the hydraulic fluid that discharges radially via the radial bores 8 and thus perpendicularly to the central axis Z at high speed when valve piston 5 is open to be collected and if need be fed to a collecting tank, and at the same time in order to prevent the discharging hydraulic fluid from contaminating the hydraulic units, persons or other equipment in an uncontrolled manner, a splash ring 26 is slipped onto the outer circumference of the valve housing 13 and pushed against a stop on the valve housing. The splash ring 26 is provided with an annular casing 27 as funnel-shaped widening which extends axially downwards beyond the end openings 28 of the radial bores. The annular casing 27 is preferably at a distance from the head piece which is equal to or greater than the diameter of the end openings 28 so that the fluid can flow off in an unrestricted manner. The funnel slope 27A of the annular casing 27 can also extend up to at least the centre of the end openings 28 so that the fluid flowing out in the event of an overload is deflected downwards by the inclination of the funnel slope and can flow off in an optimum manner.

[20] The valve spring system 6 constructed from disc springs 11 or disc spring stacks 12 can cope with even extremely high hydraulic pressures of a face hydraulic system without any problems, even in the case of large-sized valves having nominal connections of considerably more than 25 mm, and the pressure relief valve 10 shown can also cope with flow rates of 5000 1/min and more. In order to be able to set the maximum pressure relatively accurately until the valve piston 5 opens, in particular with a multiplicity of disc spring stacks 12 used, the adjusting screw 20 can be moved axially upwards or downwards. The adjustment of the position of the adjusting screw 20 changes the preloading of the individual disc springs 11. The setting of the preloading and/or the change in the preloading is preferably effected by means of an adjusting tool which is depicted overall in Fig. 4 by the reference numeral 40 and which comprises, inter alia, an assembly mandrel 41 which can be placed against an end disc 32 through a through-hole 31 in the adjusting screw 20, said end disc 32 being arranged between the last disc spring 11 and the adjusting screw 20 and being freely axially movable inside the interior space 39 of the valve housing 13. Despite the relatively small through-hole 31, the entire stack of disc springs 11 can be pushed together by means of the assembly mandrel 41 on account of the end disc 32, as a result of which the adjusting screw 20 is released from the forces of the disc springs 11 and can be screwed inside the internal thread 33 on the inner circumference of the housing cylinder 13. The adjusting screw 20 is screwed in and out by means of an adjusting nut 45, having a nut head 46 to which a spanner can be applied, and by means of driving pins 47 on the underside of the adjusting nut 46 which can engage in associated driving holes 34 on the rear side of the adjusting screw 20 in order to direct into the adjusting screw 20 the torque transmitted to the adjusting nut 45 via the spanner. Since the disc springs 11 are preferably lifted off the adjusting screw 20 during the adjusting operation by a corresponding axial force being applied to the end disc 32 and the disc spring stack via the assembly mandrel 41, even relatively small forces are sufficient in order to move the adjusting screw 20 downwards or upwards by a certain angle or by several thread turns. If the preloading of the disc springs 11 that is desired for the limit pressure above which the pressure relief valve is to open is then set, e.g. on a test bench, this position of the adjusting screw 20 can be fixed by locking the adjusting screw 20 on the internal thread 33 or the inner side of the valve housing 13. For this purpose, in the exemplary embodiment shown, the adjusting screw 20 is provided with a transverse slot 35 which is open to the circumference of the adjusting screw 20 and the external thread 36 located there. By a grub screw 37, shown in Fig. 1, being screwed into the transverse slot 35, the slot width can be widened in such a way that the edge tab 38 located above the slot 35 is wedged with the thread turn thereof on the internal thread 33 of the valve housing 13. Such wedging prevents any possible movements of the adjusting screw 20 relative to the valve housing 13, even under extreme vibrations.

[21] For the person skilled in the art, numerous modifications which are to come within the scope of protection of the attached claims emerge from the above description. It is clear to the person skilled in the art that different nominal diameters of the disc springs or disc spring stacks and different numbers of disc springs or disc spring stacks can be selected depending on the pressure level that occurs during normal load and during overload. The larger the number of disc springs selected, or the higher the spring constant of the individual disc springs, the higher the force on the valve piston has to be in order to lift the sealing cone off the valve seat. The spring stack can also have an odd number of disc springs. The figures show a rock-burst safety valve which can be screwed into place with the head piece thereof directly in a bore in a prop or the like. The connection to the hydraulic unit could also be made via a hose connection, which is connected in a different way to the head piece or the valve housing. The means of assembly in which load-free displacement or adjustment of the adjusting screw is made possible represents only the preferred configuration. It goes without saying that, at lower actuating forces of the valve spring system, the adjusting movement could also be introduced directly into the adjusting screw with disc springs in contact.

Claims

[Claim 1] 1. Pressure relief valve for hydraulic units, in particular a rock-burst safety valve for the hydraulic face support, witha valve housing, with a consumer connection (3) having a bore (2) for connecting a hydraulic unit to be protected against overload, with a fluid outlet (4), and with a valve piston being arranged in the valve, bearing with a sealing cone (9) against a valve seat (7) in the closed state by means of the actuating force of a valve spring system (6) for separating consumer connection and fluid outlet and being, during overload, liftable off the valve seat (7) against the restoring force of the valve spring system (6) for opening a connection between consumer connection (3) and fluid outlet (4), characterized in that the valve seat (7), the bore (2) of the consumer connection (3) and the fluid outlet (4) are formed on a head piece (1) comprising a guide bore (24) for the valve piston (5) and beeing connected to the valve housing (13), and in that the valve spring system (6) has at least one disc spring stack (12) having disc springs (11) which are arranged in the valve housing (13), wherein the actuating force of the disc springs (11) is applied against an end of the valve piston (5) that is remote from the sealing seat (7).

[Claim 2] 2. Pressure relief valve according to Claim 1, characterized in that the fluid outlet (4) consists of at least one radial bore (8), the orifice opening (25) of which is preferably arranged on an extension section of the guide bore (24) at or close to the transition to the valve seat (7).

[Claim 3] 3. Pressure relief valve according to Claim 2, characterized in that a plurality of radial bores (8) are provided in the head piece (1).

[Claim 4] 4. Pressure relief valve according to Claim 2 or 3, characterized in that a splash ring (26) is fastened to the outer circumference of the valve housing (13), said splash ring (26) projecting with a funnel- shaped annular casing (27) axially beyond end openings (28) of the radial bore(s) (8).

[Claim 5] 5. Pressure relief valve according to one of Claims 1 to 4, characterized in that a pressure disc (23) is arranged between the at least one disc spring stack (12) and the valve piston end, said pressure disc (23) having a bearing surface on the spring side for a disc spring (11) of the disc spring stack (12) and a pressure surface on the valve-piston side for the valve piston end.

[Claim 6] 6. Pressure relief valve according to Claim 5, characterized in that the pressure surface consists of a recess (22) and in that the valve piston end is designed as a ball head (21).

[Claim 7] 7. Pressure relief valve according to one of Claims 1 to 6, characterized in that the valve piston (5) has a multi-piece sealing cone, wherein part of the sealing cone is formed by a bush (18) preferably made of plastic and having a conical slope (17), which bush (18) can be fitted or is fitted into a blind hole (16) in the sealing cone, wherein preferably the conical slope (17) projects axially beyond a conical surface (5') on the valve piston (5).

[Claim 8] 8. Pressure relief valve according to one of Claims 1 to 7, characterized in that the valve spring system (6) has a plurality of disc spring stacks (12), wherein each disc spring stack (12) consists of two disc springs (11).

[Claim 9] 9. Pressure relief valve according to one of Claims 1 to 8, characterized in that the preloading of the disc spring stack or stacks (12) can be adjusted by means of an adjusting screw (20) which is supported via a thread (36) on the inner circumference of the valve housing (13) in such a way that it can be screwed in the axial direction.

[Claim 10] 10. Pressure relief valve according to Claim 9, characterized in that the valve housing (13) consists of a housing cylinder having an internal thread (33), into the front end of which the head piece (1) is screwed and into the rear end of which the adjusting screw (20) is screwed.

[Claim 11] 11. Pressure relief valve according to Claim 9 or 10, characterized in that an end disc (32) is arranged in an axially displaceable manner between adjusting screw (20) and disc spring stack (12) and/or in that the adjusting screw (20) has a through-hole (31) for an assembly mandrel (41) for displacing the disc spring stack (12) together with the end disc (32).

[Claim 12] 12. Pressure relief valve according to one of Claims 9 to 11, characterized in that the adjusting screw (20) is provided on the thread- turn side with a transverse slot (35), the slot width of which can be varied by a screw (37) for wedging the adjusting screw (20) on the valve housing (13).