Abstract:
The aim of the invention is to protect hydraulic assemblies, in particular those used for hydraulic longwall working in coal mining. To achieve this, pressure regulating valves ( 1 ) are used, the damping chambers of which ( 20 ) are located, configured and connected to the inlet side ( 5 ) in such a way that a system pressure constantly prevails in said chamber ( 20 ) and only drains in a restricted manner when the pressure in the regulating valve ( 1 ) is released, thus preventing the occurrence of detrimental vibrations.

Description:
This application claims the benefit of PCT/DE2007/000581 filed Mar. 30, 2007 and German Application No. 10 2006 018 542.0 filed Apr. 21, 2006, which are hereby incorporated by reference in their entirety. 
     The present invention relates to a pressure regulating valve for the protection of hydraulic assemblies, in particular of hydraulic longwall working, against rock burst and other sudden overload, comprising a valve housing with a connection, the inlet side and outlet side of the valve housing being separated from one another by a closure device which is movable against the force of a valve spring and features a sealing ring, with a fixed piston and a hat-shaped valve spring plate that is movable thereon, whereby during an overload said sides are connected to one another via an inner bore in the connection and piston and via radial bores for discharging the pressure medium, a damping chamber being configured between the upper side of the piston and the lower side of the valve spring plate and connected to the inlet side via the inner bore. 
     A pressure regulating valve of this type is apparent from DE 10 2004 005 745 A1. Pressure regulating valves of this type are especially used in subsurface coal mining for protecting longwall cavities, but also for preserving the shield framework used in the gallery against rock bursts and other sudden overload situations. These pressure regulating valves are designed and configured such that a valve piston, which is movable along a bore, is pressed against the spring plate (DE 199 46 848 A1) during a corresponding overload, moving the spring plate against the force of the valve spring with a correspondingly high overload and overruns a sealing ring until the radial bores configured in it create a connection between the blind hole in the valve piston and the outlet bores. The pressure medium may then rapidly flow off so that the corresponding hydraulic assembly is discharged and the pressure regulating valve closes again. Since with these simpler pressure regulating valves vibrations cannot always be avoided in the system due to upstream devices, in accordance with DE 10 2004 005 745 A1, a fixed piston, i.e. a piston coupled to the connection, is provided, on which the actual valve spring plate is arranged in a movable manner, overrunning and/or releasing the radial bores configured in the piston such that the pressure medium may then flow out through outlet bores configured on the bottom of the valve housing. A long throttle bore is configured in the piston, and directly exposes and/or connects the damping chamber configured between the piston and the valve spring plate to the system pressure. This means that when there is an overload, the pressure medium acted on by the system pressure not only provides that the spring plate is lifted and the radial bores exposed, but also that the damping chamber is simultaneously filled via the throttle bore, so that the retraction of the spring plate during discharge is only possible in a restricted manner, i.e. by simultaneously pressing out the pressure medium from the damping chamber via the throttle bore. In this way the vibrations in the system are impeded. But it has been found that a reaction, especially during faster vibrations, is practically impossible due to the special configuration of the throttle bore, in particular its length. In addition, the discharge of the pressure medium through the outlet bores configured on the bottom and/or through the connecting washer of the valve housing is unsatisfactory. Hence, the pressure regulating valves configured in this way do not meet all safety requirements and do not always produce the desired direct damping. 
     It is therefore the object of the present invention to prevent as completely as possible detrimental vibrations from the opening or closing of pressure regulating valves used in subsurface mining and similar industrial areas. 
     This object is attained according to the invention in that the damping chamber is connected to the inlet side via an inner three-step bore, only the uppermost partial bore being configured as a throttle bore, while the partial bore serving as a large-volume discharge bore extends marginally over the radial bores, and the central partial bore to the throttle bore has a reduced diameter relative to the discharge bore, and a significantly larger diameter relative to the throttle bore. 
     First of all, a pressure regulating valve configured this way ensures that the pressure medium entering the pressure regulating valve at high pressure when the pressure regulating valve is activated may safely flow out via the large-volume discharge bore and radial bores in order to achieve an early as possible relief of the downstream hydraulic assembly. At the same time, however, the damping area has the necessary amount of pressure medium available because the central partial bore leading in that direction has an accordingly augmented volume and/or an enlarged diameter. The actual throttle bore itself forms only the uppermost partial area of the entire inner bore, so that although there is always system pressure in the damping chamber, but due to the shortness of the throttle bore, a fast reaction to vibrations is possible. Thus, vibrations that arise are immediately and completely prevented, so that the actual pressure regulating valve remains unaffected. Since in most cases the vibrations are produced by up-stream hydraulic assemblies, they are in fact transferred to the pressure regulating valve itself, but rendered “harmless” in it. As already mentioned, however, the amount of pressure medium that is required for the relief can rapidly flow out, first reaching, as will be explained below, the interior of the valve housing, in order to be subsequently discharged via the shortest and fastest path. 
     According to an advantageous embodiment of the invention, it is provided that the central partial bore at the upper border of the radial bores is configured with a funnel-shaped lug connecting to the outflow bore. By means of this embodiment, the central partial bore important for the transfer of the system pressure to the damping chamber is always supplied with sufficient pressure medium, which may then flow into the damping chamber via the partial bore and the short throttle bore. Potentially detrimental turbulence is also avoided in this area. 
     The detrimental vibrations of the valve, or rather in the valve, are prevented according to the invention in that the throttle bore features an at least considerably reduced length, preferably ⅙ of the length of the central partial bore, and an accordingly reduced diameter, in order to prevent the vibrations of the valve and/or valve spring plate. This means that on the one hand, enough pressure medium under high pressure will enter the damping chamber in a short time, and on the other hand, a corresponding amount will also flow out again via the throttle bore when the valve is closed, but accordingly throttled, so that the desired damping takes place rapidly and safely for the necessary time. Thus the vibrations may be systematically and safely prevented. 
     Fast and safe dispersion of the pressure medium flowing over the inner bore and radial bores is achieved in that the connection is coupled to the valve housing via a connecting washer and that the spring adjustment screw is fitted with a through hole acting as an outlet bore for the dispersing pressure medium. Hence in contrast to the prior art, the pressure medium is guided simply into the valve housing, so that first of all there is a pressure release in this area, without the risk of high-pressure pressure medium getting into the longwall. The pressure medium, already somewhat depressurized in the valve housing, in fact is discharged to the atmosphere after flowing through the entire valve housing via the through hole in the spring adjustment screw. In this way, a fast and even discharge is ensured. 
     In order to prevent dirt from entering the valve housing via the through hole, it is provided that the through hole in the spring adjustment screw is covered by a protective cap attached to the upper border of the valve housing. The pressure medium, which has already been depressurized at this point, may thus largely flow off evenly from the valve housing, namely below the protective cap, which at the same time can fully function as an through hole cover. 
     As a result of the through hole provided in the spring adjustment screw, the actual spring adjustment screw cannot be used for guiding the valve spring. Rather, according to the invention, it is provided that the spring adjustment screw has a spring bore receiving and guiding the valve spring, which merges into the reduced through hole. Accordingly, it is at the same time possible for the pressure medium to flow through the spring, but also past it into the through hole. The upper part of the valve spring is thus guided safely, being additionally guided at the lower part by the accordingly bulging spring plate. 
     Placement of the hat-shaped valve spring plate on the fixed piston is facilitated during assembly in that the valve spring plate features a chamfered section on the inner surface of its flat part. Thus, a sort of guide is provided when the valve spring plate is mounted on the fixed piston. 
     For better assembly and simpler production, the invention likewise provides that the piston has a relief at the transition to the connection. This simultaneously ensures that the hat-shaped spring valve plate may be adequately pressed into the rest position by the valve spring and held in that position. The base of the flat part thus tightly abuts the surface of the connection, and an effective seal of the radial bores in the fixed piston is ensured. This is particularly the case when the relief is configured to reach the lower border of the radial bores, in order to achieve a secure seat of the hat-shaped valve spring plate. 
     In order to facilitate assembly, it is provided that the connection as well as the connecting washer and/or the valve housing have corresponding holding lugs and retaining collars. In this way, it is possible to slide the connecting washer as well as the connection into the valve housing from above, and accordingly fix them in the housing by means of the valve spring plate and the actual valve spring without the need for bolting, pinning, or similar procedures. 
     Assured lifting of the valve spring plate and thus the necessary lifting effect is ensured if the upper part of the connection is configured to be slightly protruding over the upper part of the connecting washer in the direction of the base of the flat part of the valve spring plate. The bottom, or rather the base of the flat part, then only abuts on the connection and/or upper side of the connection and secure lifting of the valve and elevation of the valve spring plate without the risk of a spring plate adhesion is possible when the valve is activated. 
     The invention is especially characterized by the fact that a pressure regulating valve has especially been created for use in hydraulic longwall working in coal mining, which reacts quickly and safely during a sudden overload and also during vibrations, mostly caused by other hydraulic assemblies, and rapidly reduces and/or renders the vibrations entirely harmless, so that they have no detrimental effect on the interior of the pressure regulating valve. The relatively short throttle bore at the upper part of the fixed piston, and thus at the upper end of the inner bore ensures that the pressure medium adequately and rapidly passes through the throttle bore into the damping chamber, but ensuring an even retraction of the valve spring plate on the fixed piston when the valve is again closed and/or during vibrations, so that said vibrations are not noticeably detrimental. The relatively short throttle makes a rapid reaction to the occurring vibrations possible. Thus the valve immediately reacts and can fulfill its function, allowing the pressure medium released via the inner bores and radial bores to be safely discharged through the valve housing and then proceed to the atmosphere via the through hole in the spring adjustment screw. 
     Further details and advantages of the subject matter of the present invention will be apparent from the following description of the corresponding drawing, which illustrates a preferred exemplary embodiment including the necessary details and individual parts. In the drawing: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a cross-section of a pressure regulating valve in the rest position (right side) and in the active position (left side) and 
         FIG. 2  shows an enlarged reproduction of the connection with the piston. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  shows a cross-section of the pressure regulating valve  1 , where it becomes apparent that a valve spring  3  is arranged in the valve housing  2  such that it holds the valve spring plate  8 , configured in a hat shape, on the piston  9 , which is part of the connection  4  is firmly secured to the connection  4 . The connection  4  forms the inlet side  5  of the pressure regulating valve  1 , which is connected to a hydraulic assembly that is not shown. During an overload, the pressure medium is pressed upward from the inlet side  5  through the inner bore  14  up to the radial bores  15 ,  16 , said pressure medium at the same time connecting the damping chamber  20  to the system pressure and/or filling said pressure chamber  20  through the inner bore  14 . As soon as the valve spring plate  8  is raised against the pressure of the valve spring  3  to the extent that the radial bores  15 ,  16  are free, the hydraulic fluid and/or pressure medium sprays into the interior of the valve housing  6  and is guided through it and through the interior of the valve spring  7  in the direction of the outlet side  11  and thus in the direction of the spring adjustment screw  38  and discharged into the atmosphere via the outlet  13  and or outlet  40 . This outlet  40  and/or through hole  41  is covered by a protective cap  42 , so that dirt is prevented from entering the interior of the valve housing  6 . 
     Leakage of the pressure regulating valve  1  is prevented in that the inner bore  14  is sealed against the radial bores  15 ,  16  via a sealing ring  10 , so that the pressure medium may flow out via the radial bore  15 ,  16  only when the hat-shaped valve spring plate  8  is raised high enough against the force of the valve spring  3 . 
     The damping chamber  20  addressed above is configured between the upper side  17  of the piston  9  and the lower side  18  of the valve spring plate  8 , namely at the upper hat-shaped part of the valve spring plate  8 . This damping chamber  20  is connected to the uppermost partial bore  21  in the form of a throttle bore  22  to the central partial bore  25  and then again to the partial bore  23 , acting as an outflow bore  24 , so that the system pressure is connected to the damping chamber  20  via this three-step inner bore  14 . Thus the damping chamber  20  is always under the system pressure. This assures the corresponding damping automatically even when the valve is activated and the valve spring  3  is again retracted. The upper part of the damping chamber  20  is labeled  26 , but this tapering chamber attachment  26  may also be dispensed with if necessary. This is a production measure. 
     The pressure medium entering the inner bore  14  and/or partial bore  23  is guided into the interior of the valve housing  6  via the radial bores  15 ,  16  when the pressure regulating valve is open. In order to ensure that the pressure medium is also present in the central partial bore  25 , and therefore in the throttle bore  22 , a funnel-shaped attachment  30  is formed in the area of the upper border  28  of the radial bores  15 ,  16  with which the actual central partial bore  25  then merges. In  FIG. 1  and  FIG. 2  it is further apparent that the sealing ring  10  is arranged and attached such that the lower border  29  of the radial bores  15 ,  16  are also covered in the closed state of the pressure regulating valve  1 . The pressure medium then cannot flow past the sealing ring  10  in this state, but at the most through the groove between the piston  9  and the hat-shaped valve spring plate  8 , whereby these small amounts of pressure medium are then guided into the area of the damping chamber  20 . 
     During assembly of a pressure regulating valve  1  of this type, the connecting washer  32  and the connection  4  are pushed into the empty valve housing  2  from above. They are connected to one another and to the inner wall  37  of the valve housing  2  via the holding lugs  33 ,  34  and/or retaining collars  35 ,  36  and connected and/or nested in one another such that they are finally secured after placement of the hat-shaped valve spring plate  8 , fitting of the valve spring  3 , and tensioning of the valve spring  3  by means of the spring adjustment screw  38 . In particular in  FIG. 2 , it is apparent that the upper side  51  of the connection  4  slightly protrudes over the upper side  50  of the connecting washer  32 , so that the base  52  of the flat part  45  only abuts on the upper side  51 , which is illustrated very well in  FIG. 2 . 
     A protective cap  42  is provided at the upper border  39  of the valve housing  2 , and indeed is arranged and configured such that the pressure medium may flow past this protective cap  42  after leaving the through hole  41  without the risk of dirt particles entering the interior of the valve housing  6  by that route. The spring adjustment screw  38  features the already mentioned through hole  41 , so that the pressure medium may reach the atmosphere past the protective cap  42  via that outlet. The spring adjustment screw  38  itself is configured such that a spring bore  43  is present at the lower side, and is used for guiding the valve spring  3 . 
     On the inner surface of the hat-shaped valve spring plate  8 , a chamfered section  46  is provided, which facilitates placement the valve spring plate  8  on the piston  9 . This is likewise promoted by the fact that the piston  9  likewise features a chamfer at its free end, which promotes this placement. 
     An exact seat of the hat-shaped valve spring plate  8  on the piston  9 , according to  FIG. 1  and  FIG. 2  is promoted by the fact that a relief  49  is provided at the transition  48  from the piston  9  to the connection  4 , which may especially be discerned from  FIG. 2 . 
     During an overload, the pressure on the valve spring plate  8  increases as pressure medium reaches the damping chamber  20  via the three-step inner bore  14 . The valve spring plate  8  is lifted against the pressure of the valve spring  3  in the direction of the spring adjustment screw  38 , so that it assumes the position shown on the left side of  FIG. 1 , in which the radial bores  15 ,  16  are now free. Thus, it is possible for the pressure medium to flow out into the interior of the valve housing  6  via the partial bore  23  and radial bores  15 ,  16  and from there out of the pressure regulating valve  1 , doing so via the outlet  40  and/or through hole  41 . The damping chamber  20  is still connected to the system pressure, i.e. the incoming pressurized fluid, and accordingly also filled with pressure medium. If there is now pressure release because enough pressure medium has dispersed, or a vibration has arisen, provoked by a third hydraulic assembly, the valve spring  3  will attempt to push the valve spring plate  8  back to the initial position, as illustrated on the right side of  FIGS. 1 and 2 . Since the damping chamber  20  is filled, this is not easily possible, but rather only by displacement of the pressure medium in the damping chamber  20 . Direct discharge is not possible in this case because the upper end, i.e. the uppermost partial bore is configured as a throttle bore and acts as a throttle bore  22 . This means that the pressurized medium in the damping chamber  20  can only flow off slowly and within limits, so that the valve spring plate  8  accordingly also only sinks slowly, and is can release the valve spring  30  gradually and evenly. Consequently the valve spring plate and/or valve spring  3  cannot vibrate. This applies to the entire distribution path of the pressure medium, which has to be discharged from the damping chamber  20  via the throttle bore  22  in order to permit the return of the valve spring plate  8  to the position shown on the right side of  FIGS. 1 and 2 . 
     All mentioned features, including those solely disclosed in the drawings, are considered to be essential to the invention both alone and in combination.