FILTERING OF FLOW IN A VALVE
BACKGROUND OF THE INVENTION The present invention relates to filtering or trapping particles in the flow through a valve, particularly particles found in water flowing through an electrically operated valve of the type used in household appliances connected to a municipal water supply. or domestic. Such valves are commonly used to control the flow of water in household appliances such as dishwashers, laundry washing machines and ice-forming appliances in refrigerators. Such household appliance water valves are typically operated by a low current solenoid operator with only a few ounces or grams of force available to open and close the valve member. Such valves in this manner are susceptible to the effects of small foreign particles in the water supply that are trapped between the valve seat or between moving parts, which results in failure of the valve to close and leakage. Up to now, filter meshes having small openings or a fine mesh in them for trapping minute particles at the inlet of the valve have been employed to prevent such particles from being lodged between the movable valve member and the valve seat. However, the fine mesh of such wire filter meshes has shown a propensity during service to be clogged with an accumulation of particles trapped from the water supply, resulting in a reduced or blocked flow to the valve. In order to remedy this situation, users have disconnected the valve from the water supply and forcefully removed the filter mesh to allow flow to the valve. Once the filter screen has been removed from the valve, the valve is left without protection against foreign particles; and experience has shown that the valve is soon caused to leak from the particles housed between the valve member of the valve seat. Thus, for a long time it has been desired to provide an effective cost way to provide residual filtering or blockage of particles to a supply valve after the user's deliberate removal of the primary filter mesh. SUMMARY OF THE INVENTION It is an object of the present invention to provide an auxiliary or backup filtering grid to protect a valve in service after the removal of the primary mesh by the user. It is a further object of the invention to provide an auxiliary or backup filter grid for a water flow valve having the grid formed in a cup shape and elastically closed at the valve inlet with the filter mesh closed elastically in the cup-shaped grid member. The auxiliary or backup filter grid of the present invention comprises an integrally formed, cup-shaped grid member having a plurality of spaced filter openings provided in the closed end of the cup shape. The grid member is snapped tightly or elastically closed at the valve inlet. In preferred practice, the cup-shaped member has a conically tapered side wall with an internal groove therein formed to receive the flange of a cup-shaped primary wire mesh filter in snap-fit connection or elastic closure. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 has an axonometric view of an electrically operated valve assembly employing the present invention; Figure 2 is a portion of a sectional view taken along section lines 2-2 of Figure 1; Figure 3 is a portion of an isometric view of the unit filter grid of the present invention; and Figure 4 is a sectional view taken along section lines 4-4 of Figure 1. Detailed Description Referring to Figures 1 and 4, an electrically operated valve assembly generally indicated at 10 includes a valve body 12 having an input fitting 14, an output fitting 16 and a solenoid operator 18 having a magnetic pole frame 20 with electrical terminals 22, 24 for connection of the solenoid to a power source. The solenoid 18 includes an electrically conductive wire coil 26 encapsulated in insulating material such as plastic, denoted by reference numeral 28 and having tubular well pieces 30, 32 disposed within the coil and axially spaced to define an air-free space. between them. The tubular pole pieces 30, 32 extend towards each other between the opposite ends of the generally C-shaped pole frame 20. An armature guide tube 34 having a closed end extending outward towards the pole pieces. pivoted 30, 32 is provided and has therein, slidably received, a frame member 38 polarized in a downward direction by means of a spring 40. The spring 40 has its upper end recorded against the lower surface of the closed end of the frame. guide 34 and its lower end piloted on the upper end of the frame. The pole frame 20 is secured to the body 12 by any suitable fastening means, such as screws 36. The lower end of the armature guide 34, opposite the closed upper end, has an enlarged diameter portion 42 which is received in a cavity formed in body 12 and sealed therein. The brow flange 44 of a flexible diaphragm 46 comprises an elastic seal ring that seals the diaphragm in the body and forms a pilot cavity 48 on the diaphragm. The central portion of the diaphragm is somewhat thickened and its lower surface forms a valve member for seating against a valve seat 50 formed in the body. The thickened portion of the diaphragm forming the valve member is denoted by the reference numeral 52 in Fig. 4. The valve member 52 has at least one and preferably a plurality of relatively small diameter bleeding holes 54 formed thereon. through to allow limited flow of the main valve chamber 56 formed on the underside of the diaphragm. It will be understood that the rigid insert 60 has a corresponding bleeding passage 61 arranged to communicate with the bleeding hole 54 formed in the valve member 52 to provide communication to the pilot valve chamber 48. The main valve chamber 56 communicates with the an inlet passage 58 formed in the valve body. The valve member portion of the diaphragm has a rigid insert 60 having therethrough formed a central pilot passage 62 which communicates with the outlet passage 64 of the valve body. The upper end of the pilot passage 62 in the insert 60 has a pilot valve seat 66 formed around it against which sits a pilot valve member 68 attached to the end of the armature 38. In operation, when the coil 26 is energized, the magnetic forces acting on the armature 38 overcome the polarization of the spring 40 and move the armature upwards, raising the pilot valve member 48 to flow out through the outlet 68. Loss of fluid pressure in the chamber of pilot 48 causes the fluid pressure in the main valve chamber 56 acting through the lower surface of the diaphragm 46 to move the valve member 52 upwards, thereby opening the flow through the main valve seat 50. When the coil 26 is de-energized, the pilot valve member 68 under the polarization of the spring 40 closes against the pilot seat 66 and the flow of bleeding through the diaphragm holes. agma 54 compensates for pressure across the diaphragm, allowing the spring 40 to urge the diaphragm and the valve member 52 against the main valve seat 50 to close the valve. Referring to figure 2, the inlet fitting 14 of the valve is shown having a slightly conically tapered bore 70 formed therein communicating with an inlet passage 58 to the valve chamber 56 (see Figure 1). The tapered perforation 70 has a cut-off annular portion 72 formed near its open end. The inner end of the perforation 70 has a shoulder or flat bottom 74 adapted for registration against it. Referring to FIGS. 2 and 3, a filter grid member generally indicated at 76 having a generally cup-shaped configuration has its outer cylindrical surface 78 tapered and dimensioned to closely match the tapered bore 70 in the valve body 12. The cup-shaped grid member 76 has its closed end formed in a generally planar surface configuration denoted by the reference number 80; and when the member 76 is inserted in the perforation 70, the annular periphery of the flat surface 80 is recorded in the shoulder 74 in the valve body 12. The rim of the cup-shaped member 76 adjacent to its open end has a shoulder or relieved portion 82 formed therein which is elastically closed in the lower cutout 72 formed in the perforation 70. The closed end 80 of the cup-shaped member 76 has a plurality of openings 84 there formed in a separate arrangement and sized to allow particles greater than a predetermined size are caught in the face of the closed end of the grid. In presently preferred practice, the apertures have a length to width ratio of at least 0.8; and, the grid apertures are preferably spaced from center to center at least 1.8 times their width or diameter. In presently preferred practice, the internal periphery of the filter grid cup has an axial length to transverse width ratio or diameter of at least 1.0; and the cup is preferably formed integrally of molded plastic material. The inner periphery of the cup-shaped member 76 adjacent its open end or flange has an annular spine 90 formed around it for registration of the flange 86 of a cup-shaped mesh member 88 therein. In presently preferred practice, the cup-shaped grid member 76 is first installed in the bore 70 in the valve block 12; and subsequently the filter mesh 88 is installed therein. However, it will be understood that if desired, the filter mesh can be first assembled in the cup-shaped member 76 with the shoulder of the mesh 86 registered against the shoulder 90 formed in the cup-shaped grid member, with this forming a sub-assembly of the mesh and the grid that can then be installed in the perforation 70 in the valve body. The present invention thus provides an auxiliary or backup filter screen for a filter screen used to filter foreign particles in the flow entering a valve. The grid is formed as a unitary member in the form of a cup insertable into the inlet with the primary filter mesh insertable therein. The arrangement of the filter screen of the present invention remains in the valve inlet in case the screen is jammed and removed. The grid then provides some measure, although rather thick, to filter in the absence of the mesh.
Although the invention has been described in the foregoing with respect to the illustrated embodiments, it will be understood that the invention is capable of modifications and variations and is limited only by the following claims.