GB799828A - Control device - Google Patents

Abstract

799,828. Clockwork-actuated valves. ROBERTSHAW-FULTON CONTROLS CO., and WANTZ, C. July 15, 1955 [Aug. 9, 1954], No. 20593/65. Class 135. [Also in Group XXIV] In a time-controlled valve in which a knob 56, Fig. 1, is depressed to open the valve 32 and is then turned to the required time setting, thereby winding up beyond its initial stress the spiral spring of an escapement mechanism 86, the knob 56 is held depressed against the action of the valve spring 42 by a nearly-slipping helical cam assembly 64 which is disengaged as the escapement mechanism returns the knob 56 to its initial angular position. The poppet valve 32 is mounted in a plug valve 20 actuated by a knob forming a housing 50. The stem of valve 32 is received in the end of the shaft 54 of knob 56. The shaft 54 is connected for rotation with a coaxial-pinion 106 loose on the valve stem by a pair of leaf springs allowing axial movement therebetween. The escapement mechanism 86 is geared to a wheel 100 a flange on which frictionally grips a cup-shaped element on a gear 96 meshing with the pinion 106, and a prestressed spiral spring is housed in the cup-shaped element so that when the pinion 106 is rotated by the knob 56 the spring is wound up further, the frictional connection 100-96 slipping to avoid disturbance of the escapement mechanism. The cam assembly 64, Fig. 4, is fixed in the housing 50 and comprises a pair of coaxial helical cam surfaces 66, 68, one within the other, having an identical lead and extending through approximately 350 degree to provide a pair of diametrically opposite recesses 67. The shaft 54 carries a plate formed with a pair of axiallydirected projections constituting followers 58, 60 which seat in the recesses 67 when the valve 32 is closed. When the shaft 54 is depressed and turned to time-set the valve 32 the two followers 58, 60 are respectively placed on the two helical surfaces and hold the valve open. Since the two surfaces have the same lead but different radii they have different helix angles and these angles are so related to the coefficient of friction that the steeper surface 68 tends to permit slipping under the axial load of the valve spring 42 while the other surface tends to prevent slipping. It is arranged that the two tendencies are substantially balanced so that only a small torque need be applied to the shaft 54 by the escapement mechanism to slide the followers over the helical surfaces. At the end of the required time interval the followers reach the ends of their respective helical surfaces and are axially moved by the spring 42 into their respective recesses, this movement simultaneously closing the valve 32. The escapement mechanism 86 is thus stalled and further unwinding of its spiral spring is prevented. Preferably the helical surfaces 66, 68, Fig. 5, terminate in flat portions 70, 71 disposed normal to the axis and if it is desired to hold the valve 32 open independently of the timing mechanism the knob 56 is depressed and turned in a direction opposite to the time-setting direction to place the followers 58, 60 on the portions 70, 71. Any operation of the timing mechanism will then tend to force the follower 58 against a stop 72.