Electricity: circuit makers and breakers – Fluid pressure – Diaphragm
Reexamination Certificate
2000-07-18
2001-11-06
Scott, J. R. (Department: 2832)
Electricity: circuit makers and breakers
Fluid pressure
Diaphragm
C200S0830SA, C200S302100, C200S405000
Reexamination Certificate
active
06313419
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to fluid pressure responsive electrical switches and more particularly to such switches used to control on/off cycles of automatic air conditioning compressors.
BACKGROUND OF THE INVENTION
Switches presently used for this purpose typically comprise a pressure responsive snap acting disc member mounted in a housing with one face of the disc in fluid receiving communication with the fluid being monitored. The disc, upon snapping from one dished configuration to an opposite dished configuration, is adapted to transfer motion to a pin slidably disposed on the opposite face side of the disc. The pin extends between the disc and an elongated movable contact arm cantilever mounted in a switch chamber within the housing. A movable electrical contact is mounted on the movable contact arm at the distal free end thereof and is adapted to move into and out of engagement with a stationary contact mounted in the housing. The movable contact arm and the stationary contact arm are attached to respective terminals mounted in spaced apart relation on the housing as by riveting or welding.
Designs of the type described have inherent quality concerns due to the relatively large number of operations involved in manufacturing the switches such as pin gauging, pin length sizing, riveting and so on. Another limitation of the prior art switches relates to the type of switching mechanism employed. Once the disc has snapped causing the motion transfer pin to force the movable contact arm toward the stationary contact and into engagement with the stationary contact, the movable contact arm becomes, in effect, a simply supported beam and concomitantly the stresses in the movable contact arm become very high, relatively to the yield strength of the material used for the movable contact arm, generally beryllium copper (yield strength of approximately 140,000 psi).
SUMMARY OF THE INVENTION
An object of the present invention is the provision of a pressure responsive electrical switch particularly useful for use with automatic air conditioning units for cycling, the AC compressors on and off which is free of the prior limitations noted above. Another object of the invention is to provide a pressure responsive electrical switch which is less expensive to manufacture than prior art switches while at the same time providing such a switch which has fewer quality concerns. Yet another object of the invention is the provision of a pressure responsive switch which has improved reliability and improved longevity.
Briefly stated, a pressure responsive electrical switch made in accordance with the invention comprises a base member formed of electrically insulative material having a bottom wall with opposite first and second face surfaces formed with a generally circular disc seat lying in a plane on the first face surface. A recess is formed in the first face surface within the area defined by the disc seat with first and second bores extending through the bottom wall aligned with the recess. First and second combination terminals and movable contact arms, each formed from a single piece of suitable material, such as beryllium copper or stainless steel, has a terminal section with a selected terminal thickness frictionally received in a respective bore. An attenuated, movable arm section extends from the terminal section and has a generally L-shaped configuration with a portion extending transversely over and spaced from the bottom surface of the recess with a free distal end portion disposed above the plane in which the disc seat lies. The transversely extending portions of the movable contact arms extend in directions generally parallel and opposite to one another. An electrically conductive snap acting, dish shaped disc is disposed on the disc seat with the distal end portions of the movable contact arms out of engagement with the disc when the disc is in a downwardly concave configuration and in engagement with the disc when the disc is in a downwardly convex configuration to close a circuit path between the first and second terminal sections. A flexible sheet is placed over the disc to maintain the disc at the disc seat and form a fluid seat between a port fitting receiving fluid whose pressure is to be monitored and the disc and disc seat.
In an alternate embodiment, a calibration beam is provided for one or both combination terminal, movable contact arm members to permit adjustment of the release pressure of the snap acting disc, i.e., the pressure at which the disc snaps back to its normal downwardly concave configuration.
Additional objects and features of the invention will be set forth in part in the description which follows and in part will be obvious from the description. The objects and advantages of the invention may be realized and attained by means of the structures particularly pointed out in the appended claims.
REFERENCES:
patent: 3268683 (1966-08-01), Palmer
patent: 3573410 (1971-04-01), Budzich et al.
patent: 4121073 (1978-10-01), Bileski et al.
patent: 4243888 (1981-01-01), Place
patent: 4616114 (1986-10-01), Strasser
patent: 5004876 (1991-04-01), Sogge et al.
patent: 5822173 (1998-10-01), Dague et al.
patent: 6049047 (2000-04-01), Miyashima et al.
Baumann Russell E.
Scott J. R.
Telecky , Jr. Frederick J.
Texas Instruments Incorporated
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