Self-powered switch initiation system

#1. Field of the Invention

#The present invention relates generally to switching devices for energizing lights, appliances and the like. More particularly, the present invention relates to a self-powered switch initiator device to generate an activation signal for a latching relay. The power is generated through a piezoelectric element and is sent through signal generation circuitry coupled to a transmitter for sending RF signal (which may be unique and/or coded) to one or more receivers that actuate the latching relay. The receivers are also trainable to respond to multiple transmitters.

#2. Description of the Prior Art

#FIG. 1 is an elevation view showing the details of construction of a flextensional piezoelectric actuator used in the present invention;

#FIG. 1a is an elevation view showing the details of construction of the flextensional piezoelectric actuator of FIG. 1 having an additional prestress layer;

#FIG. 2 is an elevation view showing the details of construction of an alternate multi-layer flextensional piezoelectric actuator used in a modification the present invention;

#Electroactive Actuator

#Piezoelectric and electrostrictive materials (generally called “electroactive” devices herein) develop a polarized electric field when placed under stress or strain. The electric field developed by a piezoelectric or electrostrictive material is a function of the applied force causing the mechanical stress or strain. Conversely, electroactive devices undergo dimensional changes in an applied electric field. The dimensional change (i.e., expansion or contraction) of an electroactive device is a function of the applied electric field. Electroactive devices are commonly used as drivers, or “actuators” due to their propensity to deform under such electric fields. These electroactive devices or actuators also have varying capacities to generate an electric field in response to a deformation caused by an applied force.

#Electroactive devices include direct and indirect mode actuators, which typically make use of a change in the dimensions of the material to achieve a displacement, but in the present invention are preferably used as electromechanical generators. Direct mode actuators typically include a piezoelectric or electrostrictive ceramic plate (or stack of plates) sandwiched between a pair of electrodes formed on its major surfaces. The devices generally have a sufficiently large piezoelectric and/or electrostrictive coefficient to produce the desired strain in the ceramic plate. However, direct mode actuators suffer from the disadvantage of only being able to achieve a very small displacement (strain), which is, at best, only a few tenths of a percent. Conversely, direct mode generator actuators require application of a high amount of force to piezoelectrically generate a pulsed momentary electrical signal of sufficient magnitude to activate a latching relay.