Variable resistance device for thick film circuitry

Claim 1

A variable resistance device for use in miniaturized thick film circuitry located on a continuous insulating substrate, comprising thick film circuit means (16, 20) on a first side of said substrate (10) connected in circuit with said miniaturized thick film circuitry and including first and second spaced conductive films (14, 18) having different electrical impedances located adjacent an opening (12) within said continuous insulating substrate (10), and impedance control means including a carrier having an opening removably connected to said substrate and including impedance varying means (32, 38) located adjacent said first side and providing circuit means (38) engaging said first and second films and movable with respect to at least one of said first and second film to vary the impedance in said thick film circuit, and a control member (22) journalled for movement within said opening and including a first portion (30, 36) formed to engage said impedance varying means and including a flexible projection extending through and beyond said carrier opening to present a part thereof that is exposed when said variable resistance device is assembled to permit removal of said impedance varying means and disassembly of said variable resistance device by manipulation, said part being selectively manipulatable between an expanded first position in which said first control member portion engages said carrier to maintain the engagement of said circuit means with said first and second films and a contracted second position in which said first control member portion disengages said carrier to remove said impedance varying means from said substrate, said control member including a second portion (24, 26) located adjacent a second side of said substrate to move said removably connected impedance varying means to vary the impedance in said thick film circuit in response to movement of said second portion.