GB802289A - Improvements in control devices - Google Patents

Abstract

802,289. Cam mechanism. WANTZ, C. April 13, 1956 [Aug. 1, 1955], No. 11345/56. Class 80 (3). [Also in Group XXXVII] A control device, e.g. a switch for sequentially switching off the heater and motor of an electric clothes dryer, comprises a stationary cam with a helical surface engageable by a follower mounted on a shaft, the follower being adapted to make these movements relative to the cam under the control of a timing device: (1) a rotatable sliding movement, (2) an axial non- rotatable movement, (3) a further rotatable movement, and (4) a further axial non-rotatable movement. As shown, a plate 32 carrying bridging contacts 34, 36 is secured to a flexible plate 40 having slots 44 engaging fixed pins 42, thus allowing pivotal movement of the plate about the axis x-x. A sleeve 50 is slidable in the plate and normally has a shoulder 54 thereon pressed against the plate by springs 56, 58, one of which is fixed to the sleeve and the other of which is fixed to the plate. A shaft 46, slidable and rotatable in the sleeve, bears on a screw 52 carried by the sleeve, and carries a plate 88 having cam followers 90, 92 co-operating respectively with helical faces 102, 104 and 106, 108 on a fixed cam 94. Initially, the followers 90, 92 are in depressions 114 in the cam faces and are disengaged therefrom by depression of the shaft 46 by a knob 86. This causes the lever 32 to be pressed down against the action of a further spring 72 to bridge contacts 16, 18 and 24, 26 in the heater and motor circuits respectively. The knob is then rotated to move the followers 90, 92 along the helical faces 102, 106 to a desired extent, thereby depressing the shaft 46 and sleeve 50 relatively to the plate 32. This rotation winds up a clockwork mechanism 120 over a gear 122 and a pinion 124 which is connected to a spring 126 in turn connected at 130 to a spring 128 fixed to the plate 88. The angles of the faces 102, 104, 106, 108 are such that the axial pressure on shaft 46 of springs 56, 58 and 72 is insufficient to cause a rotary sliding movement of the followers relative to the cam faces. However, when the knob 86 is released, the clockwork rotates the shaft 46 back again until, when the followers 90, 92 are aligned with steps 110, 112 on the cam, the shoulder 54 is again in contact with the plate 32, so that as the followers 90, 92 drop down the steps, the shoulder 54 causes the plate 32 to pivot about the lower end of shaft 46 to open contacts 16, 18, 34. After further rotation of the shaft, the followers 90, 92 drop into depressions 114 and the plate 32 moves upwards until its left-hand end hits a stop 74 about which the plate then pivots to separate contacts 24, 26, 36.