Abstract:
A valve, in particular a valve for use in fire-fighting, includes a valve housing and components being in frictional engagement with each other or with the housing during use of the valve. At least one of the frictional engaging components is mounted in the housing so as to be removable for maintenance or replacement.

Description:
TECHNICAL FIELD  
       [0001]     The invention relates to a valve, in particular to a valve for use in fire-fighting.  
       BACKGROUND OF THE INVENTION  
       [0002]     Fire-fighting valves mainly having two connecting ports so that flow through the valve can be affected in either of two opposite directions are known, for example, as oblique-seat valves. Such valves are used as they facilitate an approximately straight flow therethrough in order to obtain the least possible pressure loss in the valve, especially if the media flowing through the valve are more flow-sensitive than water without additives. One of the connecting ports, fitted in most cases with a cap nut, is connected either to a hydrant, so that the water drawn from that source will flow through a hose that is connected to the other port and forms the supply line between the hydrant and the fire-fighting pump, or it is connected to the fire-fighting pump with the water reaching the valve coming from the hose that forms the supply line. In the first situation, water flows from the screw port to the hose port and, in the second situation, water passes from the hose port to the screw port. At the hose port, the hose may be kinked or cracked. Sometimes this can be avoided by using special elbow bends. If such valves were designed for wide diameter coupling and hoses, the forces acting on the large cross section become so strong in the case of high pressures, that the valve-closing handwheels must have a diameter sufficient to obtain the necessary torque. Little can be done about this problem even by using special spindle threads, for instance expensive multi-thread types. Therefore, it is necessary in valves designed for large flow diameters, such as 100 mm or more, to provide pressure relief to reduce the forces required for closing the valve. Since the valves are used for flow in either of two directions, pressure relief must be available in either flow direction. Where connecting channels from chambers situated ahead or behind the closing devices are used for pressure relief, however, such connecting channels are likely to become soiled or frozen in the winter, because of their small internal diameter.  
         [0003]     Therefore, the primary demands on a valve of the type described above, are a large flow cross section and pressure relief in both flow directions without the use of narrow channels which might become soiled or frozen. The valve should enable easy opening and closing operation using a handwheel with a diameter that is as small as possible. Furthermore, the valve should be constructed so that the risk of kinking hoses connected in both flow directions is avoided.  
         [0004]     A valve meeting the above demands is known from German Utility Model No. 81 23 268.3, which is incorporated herein by reference. The valve body of this known valve is a circular (annular) piston that is axially displaceable by rotating an actuating spindle. The annular piston is formed as a hollow cylinder with radially inwardly directed ribs supporting a hub containing a female thread in engagement with the thread on the spindle. On its outer circumferential surface, the annular piston has different diameter end sections separated by a circular groove extending in the axial direction of the annular piston. The valve housing forms a guide cylinder for the annular piston and the surface of the guide cylinder forms a groove defining a space encircling the annular piston. The actual dimensions of the circular groove in the annular piston and of the encircling space in the guide cylinder surface are such that in the closed and opened positions of the annular piston, the circular groove is in communication with the encircling space formed in the guide cylinder. One of the two connecting ports formed in or supported on the valve housing extends obliquely downward relative to the other connecting port which is disposed for operation in a substantially horizontal axial position. The pressure compensation for operation in either flow direction is achieved without narrow connecting spaces. Due to the angular disposition of the connecting ports relative to one another, provided for in the construction of the valve housing, it is unnecessary to use special bends for hose connections.  
         [0005]     In fire-fighting situations not only clean water but mainly water from public waters is used that is more or less soiled. The soiling supports chemical reactions in the valves that are usually made of aluminum alloys, resulting in corrosion of some materials. Since corrosion is a time dependent process it may be slowed down by consistent rinsing and draining of the valves after use, but normally it cannot be completely avoided. A possible solution to solve this problem is the use of high-grade materials having better chemical resistance characteristics, like brass or stainless steel. However, valve components made of high-grade materials are not only more expensive but also render the handling of the valve more intricate. Moreover, because of the significantly higher weight of valves with components made of such materials, the load capacity of a fire-fighting truck may be impaired.  
         [0006]     It is therefore an object of the invention to provide a valve that can be adapted to the regional water quality in an optimum manner.  
       SUMMARY OF THE INVENTION  
       [0007]     The valve according to the invention comprises a valve housing and components being in frictional engagement with each other or with the housing during use of the valve. At least one of the frictionally engaging components is mounted in the housing so as to be removable for maintenance or replacement. The invention is based on the finding that, among the valve components getting in contact with the media flowing through the valve, those components that are in frictional engagement suffer from deterioration most. The invention provides the possibility of removing critical valve components and thus allows for a flexible adaptation of the valve to different water qualities. For example, a basic version of the valve can be equipped with components made of a standard material like an aluminum alloy or even a synthetic material. When it turns out that in the local region in which the valve is normally used, some components fail due to corrosion within a short period of time, these components may be easily maintained, or replaced by components made of the same or of a high-grade material. Accordingly, the durability and the economic efficiency of the valve (under particular consideration of the maintenance costs) can be improved as required.  
         [0008]     Maintenance or replacement of the valve according to the invention can be particularly facilitated by a housing that has an opening through which the frictional engaging component can be removed. The opening is closed by a separate lid during use of the valve.  
         [0009]     In a preferred embodiment of the invention the housing defines a hollow cylinder in which a guide bush is held. The valve comprises an annular piston that is slidably held in the guide bush. A so-formed annular piston valve is especially suitable for use in fire-fighting equipment. The guide bush, which is in frictional engagement with the annular piston due to the sliding fit, can be made of a high-grade material while the housing can still be formed of an aluminum alloy, for example.  
         [0010]     According to one aspect of the invention, the frictional engaging component is part of a valve member and separable from the valve member. Thus, it is not necessary that the whole valve member is made of a high-grade material, or that the whole member is maintained or replaced in case of failure.  
         [0011]     Another critical valve member is the valve body. Preferably a valve according to the invention comprises an annular piston that includes an inner bearing sleeve and an outer sleeve slid onto the inner bearing sleeve, the outer sleeve being in a sliding fit with a guiding portion in the housing. The sleeves may be made of different materials.  
         [0012]     According to an advantageous valve body construction, the annular piston further includes a gasket ring held in a press fit between a flange of the inner bearing sleeve and the outer sleeve. The press fit can be secured by bolts connecting the inner bearing sleeve to the outer sleeve.  
         [0013]     These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]      FIG. 1  shows an exploded view of the housing components and the handwheel of a valve according to the invention;  
         [0015]      FIG. 2  shows a sectional view of the valve; and  
         [0016]      FIG. 3  shows an exploded view of the piston parts and the spindle of the valve.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0017]     The valve illustrated in  FIGS. 1 and 2  includes a die-cast housing  10  made of an aluminum alloy. The housing  10  forms a hollow cylinder  14  in which a guide bush  16  is held. The inner surface of the guide bush  16  provides a sliding fit for an annular piston  18  that serves as the closing member (valve body) of the valve.  
         [0018]     A connecting port  20 , extending in the axial direction of the cylinder  14 , is formed in one piece with the housing  10 . A bushing  21  made of stainless steel is inserted into the port  20  and forms a valve seat for the annular piston  18 . Another port  22 , also formed as an integral part of the housing  10 , has substantially the same inside diameter as the port  20  and is inclined obliquely downward with respect to the port  20 . For operation of the valve, the axis A of port  20  is horizontal. A hose-coupling device (not illustrated) such as a “Storz” quick-coupling device, can be screwed onto port  22 .  
         [0019]     As can be seen in  FIGS. 2 and 3 , the annular piston  18  is a hollow cylindrical member that is mainly composed of an inner bearing sleeve  24 , an outer sleeve  26  and a gasket ring  46 . On its inside surface, the inner bearing sleeve  24  of the annular piston  18  has radially inwardly extending ribs  36 , spaced angularly apart, and supporting a hub  38  with a female thread  40  in the inside surface of the hub  38 . The thread  40  of the hub  38  is in engagement with a matching male thread  42  of an actuating spindle  44 . On its outside surface, the inner bearing sleeve  24  has a cranked flange  25  formed at one axial end. The inner bearing sleeve  24  is integrally formed with an axial front end cover  32  of the annular piston  18  having several bores  34 . The outer bearing sleeve  26  has an encircling groove  27  into which an O-ring  50  is inserted. The gasket ring  46 , which is made of an elastomeric material, has an encircling collar  48 . An axial groove is formed on the collar  48  between two projections  49 .  
         [0020]     The annular piston  18  is assembled in the following manner: The gasket ring  46  and the outer sleeve  26  are slid onto the inner bearing sleeve  24 . The gasket ring  46  is held in an axial press fit (biased) between the outer sleeve  26  and the cranked flange  25  of the inner bearing sleeve  24 . The axial press fit is secured by bolts  28  radially extending through corresponding openings formed in the inner and outer sleeves  24 ,  26 . As can be seen in  FIG. 2 , the gasket ring  46  enters a form-fit between the cranked flange  25  and the axial end of the outer sleeve  26 . Thus, under no circumstances can the gasket ring  46  slip down from the annular piston  18 .  
         [0021]     The annular piston  18  is slidably held in the guide bush  16  with the O-ring  50  sealing the annular piston  18  relative to the guide bush  16 . The annular piston  18  is axially movable in a manner described further below. In the closed position of the valve shown in  FIG. 2 , the gasket ring  46  of the annular piston  18  rests on the valve seat formed by the bush  21 . In this position the port  22  is closed. In particular, the O-ring  50  and the gasket ring  46  of the annular piston  18  seal an opening  30  of the port  22 . In the open position of the annular piston  18 , only the front end cover  32  of the annular piston  18  extends into the direct flow through opening  30 . Because of the bores  34  formed in the front end cover  32 , the annular piston  18  is always pressure relieved, except for the closed position shown in  FIG. 2 .  
         [0022]     At its rear side (the right side in  FIG. 2 ) the housing  10  has an opening  52  that corresponds to the rear axial end of the cylinder  14 . The opening  52  is closed by a separate lid  54  that is connected to the housing  10  by several screws, for example. The lid  54  is also used to axially secure the guide bush  16  in the housing  10 . To this end, the guide bush  16  has an annular collar  56  that is clamped between the housing  10  and the lid  54 . The collar  56  only slightly exceeds the outer diameter of the guide bush  16  and is surrounded by an adjoining O-ring. The O-ring seals the housing  10  and the lid  54  relative to the outside on the one hand, and also seals the guide bush  16  relative to the cylinder  14  of the housing  10  on the other hand.  
         [0023]     The actuating spindle  44  is supported in the lid  54  by a bearing ring  58 . The lid  54 , the bearing ring  58  and the spindle  44  are detachable from each other. The end of the spindle  44  projecting outwardly from the lid  54  is fixed to a handwheel  60 . Rotation of the handwheel  60  is transformed by the spindle thread  42  cooperating with the thread  40  of the hub  38  into an axial movement of the annular piston  18 . Unwanted rotation of the annular piston  18  is prevented in that the groove formed between the projections  49  on the gasket ring  46  is engaged by an axially extending rib  62  integrally formed with the housing  10 . Due to the pressure relieving bores  34  in the front end cover  32  of the annular piston  18 , the actuating force required to rotate the handwheel  60  is minimized.  
         [0024]     After use of the valve, the lid  54  can be removed to check the condition of the valve components in the housing  10 . The opening  52  allows for an easy deinstallation of the guide bush  16  and the annular piston  18 , if required. The outer sleeve  26  of the annular piston  18  can be separated from the bearing sleeve  24  and be attended to separately. Further, the spindle  44  and the bearing ring  58  are also easy to be maintained or replaced because they are separable from the lid  54  as mentioned before.  
         [0025]     Depending on the quality of the water used for fire-fighting, one or more of the before-recited valve components may be made of an aluminum alloy, a synthetic material like POM (polyoxymethylene), an alloy having a high share of copper like brass or red brass (red bronze), or stainless steel.  
         [0026]     Although a preferred embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.