Thermostatic valve with PTC resistors - has two annular resistors around piston unit with flexible element causing piston rod to move in response to temp. changes

摘要

The thermostatic valve incorporates a temp. sensor with a pair of annular positive temp. coefft. resistors (1, 2) covered by thermal insulators (7, 8) and surrounding a closed cylindrical working unit (3). The sensors on one side are connected together to the same positive voltage source (4, 5) and on the other side to a common earth. In the centre of the working unit is a rubber packing element (10), retaining the end of a piston rod (11) terminating in a spring-loaded plunger (16, 17). The action of the unit is determined by differential movement of the annuli which in conjunction with a conical insert causes the piston to move up and down and cause the spring-loaded plunger to open or close the flow aperture in the valve housing (15).