Piston positioning indicator

Claim 1

A piston slidably received in a cylinder, and fluid pressure means to move said piston longitudinally in said cylinder; the improvement in means to indicate externally of said cylinder the position of said piston in said cylinder, comprising: (a) at least a first insulated contact device inserted through a wall of said cylinder, and positioned so as to be pressed against by said piston as it moves to its first extreme position; (b) said contact device comprising; (1) tubular housing means inserted, locked, and sealed through said wall of said cylinder, said housing means comprising a cavity; (2) elastomeric insulating means inserted into said cavity in said housing means; (3) a substantially rigid rod-like probe means inserted through an axial opening in said insulating means into said cylinder; and (4) means to compress said insulating means and cause it to clamp and hold said probe means while permitting lateral deflection of the probe means at the point of clamping of said probe means due to deformation of said elastomeric insulating means so that said probe means including the portion externally of said cylinder is laterally deflected through a selected angle; whereby when said piston presses against said probe means said probe means will be deflected from its normal position; and (d) means attached to said probe means externally of said cylinder to provide a signal in response to the deflection thereof.