Strain gauge pump control switch
A control switch incorporates a solid state transducer, a strain gauge. The transducer responds to a local environmental condition, such as fluid level, or pressure and exhibits a parameter change which can be detected as an electrical output. Control circuits coupled to the transducer can sense the parameter change and switch a source of electrical energy to a load in response thereto.
1. A switch comprising:
a housing having an open end which defines an interior region;
a ring having an annular shape and carried in the housing adjacent to the open end thereof, the ring including molded members which extend radially toward the center of the ring;
an elongated plate with first and second ends where one end of the plate is coupled to a radial member of the ring, and the other end of the plate has an opening, and is deflectable, a strain gauge is carried on the plate and extends radially toward the opening in the plate;
a cylindrical pressure plate with an axial connector prong which engages the opening of the deflectable end with a friction fit and, in response to one of applied fluid level, or fluid pressure, the plate moves axially in a first direction, relative to the ring, to generate a signal of a first polarity at a selected electrical circuit, wherein the circuit is carried in the housing with the strain gauge located between the pressure plate and the circuit;
an electrical port at a second end of the housing, displaced from the open end wherein a power cord with an end extends through the port and the end connects to the circuits, the power cord includes a vent tube which extends from the housing to a free end of the cord; and
a diaphragm carried by the housing adjacent to the pressure plate, the diaphragm closes the open end of the housing wherein the housing is water tight.
2. A switch as in claim 1 where the electrical circuit includes a solid state switching element connected in parallel with a relay to provide a motor starting current.
3. A switch as in claim 1 where the free end carries a power input plug.
4. A switch as in claim 3 where the plug has first and second spaced apart surfaces with electrical prongs extending from the first surface and with an electrical socket defined in the plug adjacent to the second surface.
5. A switch as in claim 4 where the prongs are adapted to receive electrical energy and the socket is adapted to be releasably connectable to an electrical load.
6. A switch as in claim 5 where the circuit has first and second states and switches therebetween in response to movement of the plate when in the first state an electrical circuit is completed between at least one of the prongs in the socket.