FIELD OF THE INVENTION 
     The present invention relates to toilet room flush valves and more particularly to such flush valves in which a flexible diaphragm functions to separate the flush valve inlet and outlet. Conventionally, such diaphragm type flush valves have a pressure chamber located above the diaphragm to maintain the diaphragm on its seat to provide valve closure. There is a bypass orifice in the diaphragm which connects the flush valve inlet to the pressure chamber to provide the water necessary to move the diaphragm to the valve closing position. Frequently, the water system supplying flush valves for use in toilet rooms may contain particles which will clog the bypass orifice with the result that the valve becomes non-functional. The present invention provides a peripheral screen located at the upstream side of the valve orifice to filter particles from passing to the orifice and thereby preventing the valve from malfunctioning. Preferably the mesh size of the screen is such that no particle can pass through the screen unless it is smaller in diameter than the diameter of the bypass orifice. 
     SUMMARY OF THE INVENTION 
     The present invention relates to diaphragm type toilet room flush valves and more particularly to an improved filter for protecting the bypass orifice in such a valve. 
     A primary purpose of the invention is to provide a simply constructed, reliable, filter located at the upstream side of the bypass orifice for a diaphragm type flush valve. 
     Another purpose is to provide a filter of the type described which includes a peripherally extending screen, mounted in a screen carrier with the carrier being captured at its inner peripheral edge to the diaphragm assembly and at its outer peripheral edge to the flush valve body. 
     Another purpose is a flush valve with diaphragm assembly including a filter screen as described in which the size of the screen openings is smaller than the opening in the bypass orifice. 
     Other purposes will appear in the ensuing specification, drawings and claims. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     The invention is illustrated diagrammatically in the following drawings wherein: 
     FIG. 1 is an axial section thru a flush valve of the present invention; 
     FIG.  2 . is an axial section of the diaphragm assembly; 
     FIG. 3 is a top view of the filter assembly: and 
     FIG. 4 is a section along plane  4 — 4  of FIG.  3 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A flush valve of the type used in toilet rooms for both water closets and urinals is shown in the drawings, and more specifically the flush valve shown is of the type sold by the assignee of the present application, Sloan Valve Company of Franklin Park, Ill., under the trademark Regal. The filter which will be described in detail herein also has application in other types of flush valves, for example, a diaphragm type flush valve sold by Sloan Valve Company under the trademark Royal, as well as in other diaphragm type flush valves. 
     By the nature of their design, diaphragm type flush valves have not lent themselves well for the inclusion of a filtering element prior to the metering bypass hole. A good filter design in a diaphragm valve should provide a large filtering area that only filters the water that goes through the bypass. Previous inline filters in diaphragm valves filtered all the water going through the valve. As these filters trapped debris in the water, they would begin to restrict the flow through the valve, which would degrade the flushing performance. Filter designs that were only centered around the bypass orifice were small. The small filtering area in these designs meant that these filters could clog within a short period of time. 
     The large peripheral screen that is described herein extends 360° around the diaphragm. This provides a very large filtering area. As very little water actually flows through the metering bypass during the flush, this large filter area means that the valve will function for a very long time without the possibility of completely fouling the filter. 
     The peripheral design of the filter also allows it be captured by the diaphragm and valve cover. When the cover is put on the valve, it not only holds the diaphragm in place, but it also holds the filter in place. The peripheral design of the filter allows it to seal both at the outer and inner edges, preventing any unfiltered water from getting to the bypass or leaking out of the valve. The filtering surface itself extends 360° around the diaphragm, so water can get from the internal valve chamber to the bypass from any position from within the valve. The peripheral surface of the filter ensures that there will always be a portion of the filter in the direct flow stream of the valve. The turbulence of this flow stream during the flush will help keep the screen surface free of particles and debris. 
     The flush valve includes a body  10  having an outlet  12  and an inlet  14 . A conduit  16  is attached at the inlet  14  and may be coupled to a control valve, as is conventional in flush valve installations. At the upper end of the body  10  is a valve cover  18  which overlies an inner cover  20 , with the cover  18  and the inner cover being attached to the body  10  at a threaded connection  22 . The inner cover  20  defines the upper side of a pressure chamber  24  which is directly above a diaphragm assembly indicated generally at  26 . Water will flow from the inlet  14  through a bypass orifice to be described into the pressure chamber which will maintain the diaphragm assembly  26  in a closed position on a valve seat  28  which is at the upper end of a barrel  30  formed as a part of the casting which forms the body  10 . 
     The body  10  may have a boss  32  shown mounting a nut  34  and there may be either a manual handle attached at this point to operate the flush valve or there may be a sensor operated solenoid attached to cause operation of the flush valve. 
     The diaphragm assembly  26  includes a diaphragm  36  which is flexible and formed of a suitable elastomeric material. The outer periphery  38  of the diaphragm  36  is held in position by the inner cover  20  when the diaphragm is mounted between the inner cover and filter assembly  42 . The diaphragm assembly further includes a refill head  40 , details of which may be found in U.S. Pat. No. 5,649,686, assigned to Sloan Valve Company and the disclosure of which is incorporated by reference. The refill head is positioned directly beneath the filter assembly  42  which will be described in detail herein after. A ring  44  attaches the filter assembly to the diaphragm assembly  26  by threading into guide  46  and compressing the diaphragm and filter assembly. The diaphragm assembly includes, in addition to the components described above, the tubular guide  46  which is threaded to the ring  44 , and a flow ring  48 , the details of which are shown in U.S. Pat. No. 5,295,655, also assigned to Sloan Valve Company and the disclosure of which is incorporated by reference. 
     Located within the guide  46  is an auxiliary valve assembly  50 , which includes a relief valve head  52  attached to a relief valve stem  54 . Slidably movable on the stem  54  is a sleeve  56  which will be contacted by a reciprocally movable piston attached to the valve operator mounted in the opening  32 . Details of the relief valve, the stem and the movable sleeve are shown in U.S. Pat. No. 5,755,253, also owned by Sloan Valve Company and the disclosure of which is incorporated by reference. 
     The diaphragm  36  includes a bypass orifice  58  which is in communication with the inlet  14  through the filter assembly  42 . This is required as water must flow through this pathway to reach the pressure chamber  24  in order to effect closure of the diaphragm upon the seat  28 . In normal valve operation, once the diaphragm is seated and the pressure chamber is filled with water to maintain the diaphragm in a closed position, the valve is operated by tipping of the auxiliary valve assembly, which moves the relief valve off of its seat within the ring  44  permitting water from within the chamber  24  to vent to the valve outlet  12 . Water from the inlet  14  will then cause the diaphragm to raise up from its seat causing water to flow directly from the inlet  14  to the outlet  12 . As soon as this action starts, the pressure chamber begins its refill cycle through the bypass orifice  58 . Thus, to maintain a properly functioning valve, the bypass orifice must always be clear and open. Typically a bypass orifice will have a diameter of from 0.010 to 0.025 inch. However, water normally flowing in a public water system will have sediment or particles which may be of a size/geometry to clog such a very small opening. The filter assembly  42  is to stop particles from reaching the bypass orifice which would prevent its normal function. 
     The filter assembly  42  includes a ringlike screen element  70  which is located within a screen carrier  62 . The screen mesh is of a size such that no particle can pass which is not smaller than the diameter of the bypass orifice. Thus, any particle which moves through the screen will also pass through the bypass orifice. 
     The screen carrier  62  is in two parts, an inner portion  64  and an outer portion  66 . The inner portion, ringlike in configuration, has a peripheral groove  68  to mount the inner edge of the screen  70 . The inner portion  64  also has an inner peripheral bead  72  which, when the screen is mounted in the diaphragm assembly, is clamped between the underside of the diaphragm and the top of the flow control ring  40 . This mounts the inner periphery of the filter assembly. 
     The outer filter carrier  66  has a recess  74  which mounts the outer edge of the screen  70  and it has an outer peripheral bead  76  which is clamped on top of the body  10  and beneath the outer edge of the diaphragm when the cover  18  and the inner cover  20  are mounted to the valve body  10 . Preferably the outer carrier  66  has a peripheral or circumferential raised area or bead  78  which strengthens the filter assembly and allows it to maintain its shape as water under substantial pressure flows in the area directly beneath the filter. Between the filter assembly and the underside of the diaphragm is a chamber  80  which receives water which is passed through the screen  70 , with the sediment removed, with the bypass orifice  58  being in communication with the chamber  80 . Thus, water flows from the inlet  14 , into the area beneath the filter assembly, through the filter screen  70 , into the chamber  80 , then through the bypass orifice  58  and finally into the pressure chamber  24  where it performs its normal function. 
     Of importance in the invention is the use of a large peripheral strengthened filter in a form of a peripheral screen which removes any sediment which might otherwise clog the bypass orifice. Most present day diaphragm type flush valves do not have a screen for preventing debris flow into the bypass. The present invention provides a simple, reliably operable device for performing this function. 
     Whereas the preferred form of the invention has been shown and described herein, it should be realized that there may be many modifications, substitutions and alterations thereto.
A diaphragm assembly for use in a diaphragm type toilet room flush valve includes a diaphragm formed of a flexible material and adapted to separate an inlet and outlet of the flush valve. There is a bypass orifice in the diaphragm. A filter assembly is positioned on the flush valve inlet side of the diaphragm and upstream from the bypass orifice. The filter assembly includes a peripherally extending screen spaced from the underside of the diaphragm with the screen being secured to the diaphragm assembly about an inner peripheral portion thereof.