PNEUMATIC CONTROL SYSTEM AND CONDITION RESPONSIVE VALVE CONSTRUCTION THEREFOR OR THE LIKE

1299652 Valves ROBERTSHAW CONTROLS CO 13 April 1970 [14 April 1969] 17519/70 Heading F2V A thermally actuated valve has a surface 15 provided with inlet and outlet parts (18), 19, a slide 31 provided with a channel 35, and a bimetal strip 39 arranged to move the slide to open or close a flow path between the parts through channel 35. The slide is of laminated construction with a porous compressible layer 34 which forces the outer layers 32, 33 into sealing contact with the walls of slot 15, and which forms a filter adjacent a hole 38 which is aligned with and vents output port 19 when the valve is closed. The bi-metal strip is of U-shape with its end 44 attached to slide 31, and its other end 40 secured to casing 11 which has opaque portions surrounding the anchored striplimb and a transparent window 53 over the free limb so that this limb can be heated by a heater 29 when it is actuated by a control 27 fed through the valve with fluid from a source 25. The subsequent movement of slide 31 cuts off the fluid supply to control 27 which cuts off the heater so that the bi-metal strip returns the parts to their starting positions. Limb 39 compensates the valve for changes in ambient temperature.