Pressure switch with linearly movable can-actuating means and overstress-responsive safety valves

Claim 1

A fluid pressure operated switch device comprising: a. a movable abutment subject in opposing relation to a first pressure in one chamber at one side thereof and to a second pressure in a second chamber at the opposite side, said abutment being shifted in opposite directions respectively from a neutral position accordingly as the pressure in one of said chambers exceeds the pressure in the other of said chambers; b. an operating rod secured at one end to said abutment for movement therewith and having formed thereon adjacent its opposite end two spaced-apart inclined cam surfaces; c. one switch means having an operating member disposed in contacting relation to one of said inclined cam surfaces so that said switch means is operated from an open position to a closed position upon shifting of said abutment out of its neutral position in one direction a distance less than that required to cause said operating member to travel the length of said one inclined cam surface; d. another switch means having an operating member disposed in contacting relation to the other of said inclined cam surfaces so that said another switch means is operated from an open position to a closed position upon shifting of said abutment out of its neutral position in an opposite direction a distance less than that required to cause said operating member to travel the length of said other of said inclined cam surfaces; wherein the improvement comprises; and e. a first valve means operated, upon shifting of said abutment in said one direction out of the neutral position thereof a distance greater than that required to effect closing of said one switch means, to establish a communication via which to introduce into said one chamber fluid under pressure for restoring a balance of fluid pressure forces on said abutment to effect restoration thereof to neutral position.