Abstract:
A solenoid operated valve of the type intended to be operated with a constant frequency variable duty cycle electrical pulse signal. The valving member/armature has an elastomeric cap provided on one end which functions to close one face on a valve seat when the solenoid is de-energized and the opposite face functions to act as a limit stop for valving member movement in the opposite direction when the solenoid is energized.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Not Applicable 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable 
     MICROFICHE APPENDIX 
     Not Applicable 
     BACKGROUND OF THE INVENTION 
     This invention concerns a solenoid valve for regulating the flow of fluids in a circuit, with special application to gas circuits, more specifically a pulsed solenoid valve piloted by a square electrical signal with a variable cyclic ratio and a fixed or variable frequency, the output rate of the valve being proportional to the cyclic ratio. This flow-regulating solenoid valve has special application to gas-powered home appliances, such as cooking or heating appliances, where it controls the flow of gas to the burners. 
     Such flow-regulating solenoid valves in gas burner control applications must work at relatively high temperatures; furthermore, in the type of application mentioned above, they must be able to go through a large number of cycles, on the order of several hundred million. Silent operation is also desirable. 
     The foregoing objectives are not fully satisfied by known flow-regulating solenoid valves. Specifically, it should be noted that in known solenoid valves, the magnet-actuated moving assembly, which includes the cylindrical moving core, as well as an obturator which cooperates with a fixed seat, is in most cases relatively massive. This assembly moves back and forth at the frequency of the electrical pulses which pilot the solenoid valve; and, it produces noise-generating internal shocks in the course of operation. Specifically, a shock can occur each time the oscillating assembly reaches the end-position furthest from the fixed seat, when the moving core comes into direct, unabsorbed contact with its guide. In addition to unwanted noise, such shocks produce wear and tear of the solenoid valve, which shortens its useful life. 
     BRIEF SUMMARY OF THE INVENTION 
     The aim of this invention is to provide a flow-regulating solenoid valve for fluid circuits, with special application to gas circuits, which, despite its very simple structure, eliminates internal shocks and most of the operating noise, and thus offers increased reliability and useful life in addition to practically silent operation. 
     The object of the invention is a solenoid valve for regulating the flow of fluids in circuits, with special application to gas circuits. More specifically, it is a pulsed solenoid valve with a variable cyclic ratio, featuring a body with a fluid inlet port, a fluid exit port, and an internal chamber. One of the ports is connected to said chamber via a short channel, the exit end of which forms an annular seat. The valve also features an electromagnet with a coil and a fixed magnetic circuit mounted around a central guide with a cylindrically shaped recess which opens into the internal chamber. The recess houses a moving magnetic core, retracted by a return spring. One end of the moving magnetic core features a flap designed to cooperate with the annular seat. The solenoid valve is defined by the fact that one end-face of the flap, which is made of an elastic material, is more or less circular or annular in shape, and cooperates with the annular seat when the solenoid valve is closed; while the other annular end-face of the flap, facing in the opposite direction, abuts the wall of the internal chamber opposite the annular seat when the solenoid valve is in the open position. 
     Thus, a defining characteristic of the invention is that the end position of the moving core, which corresponds to the open position of the solenoid valve, is achieved by the stop of a part made of elastic material, i.e. the flap on the moving core, and not by the stop of rigid parts or by the return spring, as is usually the case. This eliminates shocks and noise, as well as excessive wear of the spring. 
     In a preferred embodiment of the invention, the central guide, in the recess of which the moving core glides, features an end flange attached to the body of the solenoid valve. This flange constitutes the boundary of the internal chamber mentioned above. The assembly is designed so that when the solenoid valve is closed, the annular end face of the flap stops against one of the faces of the central guide&#39;s end flange. 
     Further, it is advantageous to give the moving core of the flow-regulating solenoid valve according to the invention an elongated, roughly cylindrical shape, with one of its ends profiled as a head on which the flap is mounted and retained. Thus, the moving assembly is of limited mass. 
    
    
     The invention will be further clarified by the following description, which refers to the appended schematic drawing of an example of an embodiment of the flow-regulating solenoid valve for fluid circuits, with special application to gas circuits, where: 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a general view, in longitudinal cross section, of a solenoid valve according to the invention; 
     FIG. 2 is a skeleton diagram showing the mechanical operation of the solenoid valve of FIG. 1, in the open position; 
     FIG. 3 is a skeleton diagram similar to FIG. 2, but shows the solenoid valve in the closed position. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 shows a flow-regulating solenoid valve for a gas circuit, with most of its components arranged along a central axis 1. The solenoid valve features a body 2, with a lateral gas inlet port 3, opening into internal chamber 4 of body 2, and an axial gas exit port 5. Exit port 5 is connected, via a short axial channel 6, to the center of internal chamber 4, and an annular seat 7 is formed at the point where channel 6 enters said internal chamber 4. 
     The solenoid valve electromagnet indicated generally at 8 is placed above the body 2 of the valve. This electromagnet features an excitation coil 9, wound around an insulating carcass or bobbin 10, which itself surrounds a fixed magnetic circuit constituted by two opposite tubular components, 11 and 12. Electrical terminals 13, which power excitation coil 9, are mounted on carcass or bobbin 10. 
     The assembly constituted by coil 9, 10 and magnetic circuit 11, 12 is arranged around a central guide 14, one end of which is enlarged into an end flange 15 which rests against body 2 and is attached to it by screws 16. An annular gasket or seal ring 17 is inserted between the flange and the body. The other end of guide 14 features an elastic retaining ring 18, which rests against component 12 of the fixed magnetic circuit. 
     Guide 14 features, on part of its length, a cylindrical recess or bore 19 which opens into internal chamber 4, opposite annular seat 7. The moving magnetic core 20, which is of an elongated, roughly cylindrical shape, is mounted inside recess 19 of guide 14. A return spring 21, housed and compressed at the &#34;bottom&#34; or upper end of recess 19, pushes one end of moving core 20 toward body 2. 
     The other end of moving core 20 is located inside internal chamber 4, and is profiled in the shape of a head 22. Elastic flap 23 is mounted and retained on head 22 of moving core 20. The outside of flap 23 is of roughly cylindrical shape; thus, it has a circular end face 24 (facing toward annular seat 7), and, on the opposite side, an annular end face indicated generally at 25, turned toward one face 26 of end flange 15 of guide 14, with face 26 marking the boundary of internal chamber 4. 
     When the solenoid valve is in the closed position (which is also its rest position), moving core 20 is pushed &#34;back&#34; or downward by return spring 21; and, the circular end face 24 of flap 23 forms a seal against annular seat 7. In this position, gas inlet port 3 and gas exit port 5 are completely isolated from each other (see FIGS. 1 and 3). 
     When the solenoid valve is in the open position (FIG. 2), moving core 20, attracted by electromagnet 8, is more deeply drawn into recess 19, which further compresses return spring 21 and lifts flap 23 away from annular seat 7. In this position, gas inlet port 3 and gas exit port 5 communicate with each other via internal chamber 4. 
     An important characteristic of the solenoid valve according to the invention is the fact that, in the open position, end face 25 of flap 23 rests against face 26 of end flange 15 of guide 14, and there is no contact whatsoever between moving core 20 and the wall of recess 19 of guide 14. 
     When the flow-regulating solenoid valve is in operation, moving core 20 moves back and forth between the closed and open positions, cyclically and at a given frequency which depends on the electrical pulses sent to excitation coil 9. Specifically, such pulses can be of variable cyclical ratio or duty cycle (duration of each pulse/cycle period), while the frequency itself is fixed and of a value in the 20 to 25 Hz range, for instance. The cyclical ratio or duty cycle can also vary in a range of 0 to 100%; and, the rate of gas flow at the exit port of the solenoid valve is proportional to the value of the duty cycle or cyclical ratio, since said ratio is also that of the time during which the solenoid valve is opened over the period of the cycle. 
     As the moving core 20 moves back and forth between the closed and open positions, flap 23 alternates between stops against annular seat 7 (via its circular end face 24) and end flange 15 of guide 14 (via its annular end face 25). Since flap 23 is made of synthetic rubber, it absorbs to a considerable extent the shocks produced by the moving assembly (moving core 20+flap 23) against both annular seat 7 and guide 14, thus eliminating noise. The severity of the impacts in this case are further weakened by the low mass of the mobile assembly actuated by electromagnet 8. 
     The scope of the invention is not limited to the single example of an embodiment of the flow-regulating solenoid valve which has been described above, but that it encompasses all possible variants embodiments and applications which use the same principle. Specifically, changes might be made to the construction details of the valve, or to the materials used, or the same flow-regulating solenoid valve may be used in a liquid circuit, without leaving the scope of the invention.