Electrical switch assembly encapsulated against moisture intrusion

An electrical switch assembly that is especially useful in a damp or moisture laden atmosphere. It can be used to operate remotely located electrical equipment, including household garbage disposers, hot tubs, spas and swimming pools. The assembly includes a receptacle and a piezoelectric element that is carried by an insert slidably fitted within the receptacle. Conductive wires in engagement with the element extend into a recess in the insert for engagement with a plug in the recess. Resiliently deformable potting material is poured through passageways in the insert to fill the insert and the receptacle, and to surround the element and the plug to prevent moisture entry. An end wall of the receptacle can be depressed to deform the element to generate electrical signals which are picked up by the plug and transmitted to an exterior control to operate the electrical equipment.

FIELD OF THE INVENTION 
The present invention relates to an electrical switch assembly encapsulated 
against moisture intrusion, and more particularly to such an assembly 
having a piezoelectric element deformable within a resiliently flowable 
encapsulating material for generating an electrical signal to operate 
remotely located electrical equipment. 
DESCRIPTION OF THE PRIOR ART 
Electronic components are susceptible to corrosion damage by moisture, and 
it is common to encapsulate components such as transistors and even entire 
circuit boards to seal them off from corrosive environments. Encapsulating 
or potting materials for this purpose are well known in the art. 
However, most electrical switches include a component which is movable to 
make or break mechanical contacts. Most forms of encapsulation interfere 
with such movement. Consequently, resort has been had to totally enclosing 
the electrical switch in a waterproof housing, but this has proved to be 
an expensive expedient, and one which is prone to failure because of the 
need to use sealing members such as rubber boots, O-rings, gaskets and the 
like which deteriorate over a period of time. 
The systems disclosed in U.S. Pat. Nos. 4,618,797 and 5,332,944, issued to 
co-inventor Dave J. Cline, are effective to overcome the foregoing 
deficiencies of the prior art by employing a piezoelectric element that 
can be flexed or deformed in a resiliently flowable encapsulating material 
to generate an electrical signal for operating remotely located equipment. 
However, the manufacture, location and placement of certain system 
components involves procedures that can be time consuming. 
More particularly, the system of the later patent U.S. Pat. No. 5,332,944 
includes an enclosure which is filled with encapsulating material. A 
circuit board is held within the enclosure in relatively deeply recessed 
position by screw attachment to posts or standoffs that are integral with 
the enclosure. The circuit board supports a piezoelectric element that is 
deformable by pressing a touch panel on the outside of the enclosure. This 
moves an actuator whose shank engages the element. The presence of the 
touch panel is also effective to prevent extrusion of encapsulating 
material past the actuator to the exterior of the enclosure. 
Conductive wires are soldered to the piezoelectric element and extend to 
the circuit board where they are soldered in place. Further wires attached 
to the circuit board extend to remotely located controls for operating 
electrical equipment such as swimming pool or spa pumps, blowers and 
heater controls, and the like. 
The arrangement sometimes results in entrapment of air bubbles during 
filling of the enclosure with encapsulating material. The enclosure is 
purged of bubbles by maintaining it below atmospheric pressure until the 
bubbles migrate and escape to the environment. 
SUMMARY OF THE INVENTION 
According to the present invention, an electrical switch assembly is 
provided which includes piezoelectric means located within a hollow 
receptacle, and adapted to generate an electrical signal upon being flexed 
or deformed. One extremity or end wall of the receptacle can be pressed 
inwardly to engage and deform the piezoelectric element. 
An insert is fitted within the receptacle and includes a recess which is 
adapted to receive a telephone-type plug. 
A pair of conductors in the form of resilient wires are arranged to engage 
the opposite sides of the piezoelectric element. One of the extremities of 
each of the wires is arranged to extend from the element, through troughs 
or grooves in the side of the insert, at which point such extremities are 
reversely formed to extend into the insert recess where they can be 
engaged in a wiping contact action by the complemental conductors of a 
telephone-type plug. The arrangement eliminates any need for a circuit 
board within the receptacle. 
The recess is provided with specially configured and located filling 
openings so that encapsulating material is enabled to flow and fill the 
spaces within the insert and receptacle, particularly surrounding the 
piezoelectric element and the associated electrical conductors. The 
filling arrangement permits air bubbles to freely migrate at atmospheric 
pressure and escape to the outside. 
The switch assembly is easy to assemble by simply placing the piezoelectric 
element upon the insert, with the pair of contact wires resting against 
opposite sides of the element, inserting the element within the 
receptacle, where it is releasably locked in position with the wires held 
against the element, reversely forming the wires so they extend into the 
insert recess, pouring encapsulating material such as a potting gel into 
the assembly through the filling ports of the insert, and finally pushing 
the telephone-type plug into the insert recess to displace some of the 
potting gel and establish contact with the wires extending from the 
piezoelectric element. The gel selected is well known in the art for its 
resilient flowability so that it does not prevent the flexure of the 
piezoelectric element necessary to generate an electric signal.

DESCRIPTION OF A PREFERRED EMBODIMENT 
Referring now to the drawings, the present electrical switch assembly 
comprises, generally, a cylindrical enclosure or receptacle 10 which is 
molded of electrically non-conductive material such as a rigid or 
inelastic plastic material. The receptacle 10 includes a hollow 
cylindrical space or interior 12 closed at the top by an end wall 14, and 
open at its opposite or lower extremity 16. 
The upper periphery of the receptacle 18 includes external threads 21 
extending down to a peripheral flange 20. An internally threaded top or 
cap 18 is threaded onto the threads 21 until the cap engages the 
peripheral flange 20. In this position a flexible touch panel or disk 22 
secured within a shallow upper recess of the cap 18 overlies the end wall 
14. 
The disk 22 preferably carries indicia (not shown) which identifies the 
function of the associated switch assembly. For example, "PUMP" would 
indicate that pressing upon the disk 22 will initiate operation of a 
remotely located component such as a spa pump (not shown). As will be 
apparent, similar indicia could be used to designate a blower, heater or 
the like. 
A number of such switch assemblies can be located in a single control panel 
(not shown) for placement next to the spa, where it is readily accessible 
to a user. The user can then operate any one or more components by merely 
pressing the disk 22 associated with the particular spa component that is 
to be operated. The switch assembly or assemblies are electrically 
isolated from the power circuits that actually operate the spa components 
so that there is no exposure of the user to shock hazards. 
Although spa and swimming pool components such as pumps, blowers, heaters 
and the like have been mentioned by way of example, the present switch 
assemblies are equally adapted for the operation of all manner of remotely 
located components, particularly including household items such as 
dishwashers, garbage disposers and the like. These are typically operated 
by on-off switches that directly interrupt the power circuit to the item. 
A short circuit in the on-off switch can thus be a shock hazard to the 
user. The system of the present switch assembly eliminates any such 
hazard. 
Many other applications for the present switch assemblies will immediately 
suggest themselves to those skilled in the art, and all such applications 
are intended to be within the scope of the present invention. 
In the switch assembly illustrated; the end wall 14 is sufficiently thin 
that it can be resiliently deflected downwardly by applying slight 
pressure to the disk 22. Preferably the end wall 14 includes a centrally 
located, downwardly directed actuator or projection 24 which concentrates 
any pressing force to a confined area. As will be seen, the pressing force 
acts upon a resilient electrical conductor or wire 25 which overlies and 
engages a sensor, transducer or piezoelectric assembly 26. The wire 
transmits the force to the assembly 26, deflecting or deforming it to 
generate an electrical signal. 
Generation of such a signal by even slight bending or deforming of a 
piezoelectric means is well known. The amount of deflection necessary can 
be as little 0.02 millimeters. This makes the present switch assembly 
quite sensitive to slight pressures exerted by a user upon the disk 22. 
The piezoelectric assembly 26 is preferably circularly configured and 
comprises upper and lower disks of electrically conductive material whose 
opposite faces are electrically coupled by a thin layer of a suitable 
adhesive material such as epoxy that has very low electrical resistance. 
The specific construction, thickness and configuration of the assembly 26 
is not critical to the proper operation of the present electrical assembly 
as long as the assembly is effective to generate the desired electrical 
output pulse or signal upon undergoing slight bending or deformation. 
The switch assembly is normally vertically oriented, and such terms as 
"lower", "upper", "downwardly"and "upwardly" are used in this disclosure 
merely for convenience. Such terms are intended to comprehend equivalent 
directions in the event the switch is oriented horizontally or otherwise. 
As best seen in FIG. 2, the lower disk of the piezoelectric assembly 26 
rests upon a resilient lower electrical conductor or wire 36 similar to 
the wire 25 which engages the upper disk of the assembly. However, the 
wire 36 is supported upon a circumferential shelf or seat 33 provided in a 
cylindrical insert 32. The wires 25 and 36 are the conductors which pick 
up the characteristic electrical signal that is generated when the 
assembly 26 is deflected or deformed. 
The insert 32 is slidably fitted within the hollow interior 12 of the 
receptacle through its open lower end 16. It includes a central plug 
recess 34 that is downwardly open and thereby accessible through the open 
lower end 16 of the receptacle 10. This permits receipt of a telephone 
style plug 44, as will be seen. 
The insert 32 also includes a generally vertically oriented filling passage 
38 which, as best seen in FIGS. 6 and 7, can be filled in an inverted 
position of the insert 32 with a resiliently deformable potting means or 
gel 40 from a suitable filling device 42. The gel 40 is able to flow 
downwardly through the passage 38 into spaces 46 which are located 
adjacent the upper disk of the piezoelectric assembly 26. From there the 
gel can flow laterally through the spaces 46, then down and laterally 
across the lower disk of the assembly 26. The flow can then continue 
upwardly through vertically oriented filling passages 48, and through the 
plug recess 34. 
It has been found that this arrangement of filling passages enables the 
potting gel 40 in its liquid state to easily flow into and occupy the 
spaces just mentioned without the entrapment of air bubbles. The presence 
of such bubbles is undesirable because of their potential adverse affect 
upon the integrity of the waterproof gel barrier. It has been found that 
such bubbles can be eliminated by using the described configuration and 
arrangement of filling passages. There is no need to place the switch 
assembly in a vacuum chamber to rid it of such unwanted air bubbles. 
The potting gel 40 is resiliently deformable, resistant to moisture, and 
should be selected for resistance to whatever harmful chemicals are 
anticipated in the operating environment. The degree of resilient 
deformability must be such that it will permit the desired deflection of 
the piezoelectric assembly 26, but also sufficient to aid in returning the 
assembly 26 to its undeflected state when the deflecting force is removed. 
A silicone dielectric gel, marketed by Dow Corning as Q3-6527 A and B, has 
been found to give good results. It is a high dielectric substance and 
totally hydrophobic or resistant to water penetration. 
After the gel 40 is poured into the open spaces in the switch assembly, the 
telephone style plug 44 is pushed into the recess 12. Partial insertion of 
the plug and displacement of the gel is seen in FIG. 6, whereas FIG. 1 
shows the plug fully inserted, and the disposition of the gel after it 
sets up or cures. In its cured state the gel is resiliently deformable but 
it is not liquid so that it cannot leak or flow out of the receptacle 10. 
The telephone style plug 44 is preferred because it not only operates 
satisfactorily, but it is readily available on the market. Such plugs are 
common for connecting telephone lines to a telephone base, for example, 
and for connecting the base to a handset. Of course, any male connector 
could be used if it has contacts adapted to be engaged by the wires 25 and 
36. 
The plug 44 is characterized by conductors or wires carried in recessed 
relation within seats or grooves that extend along one side of the plug. 
This location adapts the wires for wiping or slidable connection to the 
complemental wires 25 and 36 of the piezoelectric assembly 26. 
More particularly, as best seen in FIGS. 2, 3 and 4, the upper wire 25 
includes a generally Z-shaped midportion 50 which engages and overlies the 
upper face of the assembly 26. In similar fashion, the lower wire 36 
includes a generally Z-shaped midportion 51 which engages and underlies 
the lower face of the assembly 26. 
The outer or left end extremities 52 and 54 of the wires 25 and 36, 
respectively, extend to the left, as seen in FIGS. 2-4, then bend 
downwardly, extending about halfway down the insert 32 within suitable 
orienting grooves that are provided in the outer surface of the insert. 
The opposite outer or right end extremities 56 and 58 of the wires 25 and 
36, respectively, extend to the right, also bend downwardly, extending 
within suitable orienting grooves provided in the outer surface of the 
insert. However, these right end extremities 56 and 58 extend downwardly 
the full depth of the insert and, at the bottom of the insert, they are 
reversely formed to extend upwardly inside the plug recess 34. In this 
position they are adapted to engage the complemental conductors of the 
plug 44 when it is inserted into the recess 34. 
This engagement is adapted to carry any signals from the piezoelectric 
assembly 26 through a connecting cable 60 to a remotely located circuit 
board and system (not shown), where the signals are amplified sufficiently 
to operate the associated spa, swimming pool, household, etc. components. 
In operation, the present switch assembly is actuated by manually 
depressing the flexible disk 22. This moves the projection 24 of the 
receptacle end wall 14 downwardly to deflect the piezoelectric assembly 26 
and the associated supporting wires 25 and 36. The downward deflection of 
the assembly 26 displaces adjacent potting gel 40, which resiliently 
deforms or "flows" out from the flexure spaces 46 between the assembly 26 
and the overlying receptacle end wall 14 to other areas filled with the 
gel. The degree of deformation is relatively small, but it is sufficient 
to permit the desired mechanical flexure of the piezoelectric assembly 26 
for generating the desired electrical signal. 
Upon release of manual pressure, the disk 22, end wall 14 and assembly 26 
return to their undeflected or previous states by reason of the resilience 
of the assembly 26, the end wall 14 and the wires 25 and 36. This return 
is also aided by the resilience of the potting gel 40, which acts upon the 
gel to return it to its original disposition. 
With the foregoing arrangement, the switch assembly electrical contacts are 
located deep within the assembly, where they are electrically isolated 
from the exterior and protected from moisture and outside contaminants. 
Although a specific embodiment of the invention has been described and 
illustrated, it will be understood that the invention is not to be limited 
to the specific forms or arrangement of parts described and illustrated, 
and that various changes can be made without departing from the scope of 
the appended claims.