GB814553A - Improvements in or relating to timing devices - Google Patents

Abstract

814,553. Toasters. KENWOOD MANUFACTURING CO. Ltd. July 25, 1957 [July 28, 1956; Oct. 12, 1956], Nos. 23387/56 and 31177/56. Class 28 (1). [Also in Group XXXVII] A timing device for an electric toaster comprises a rack bar 49 actuated by a bi-metallic strip 68, the movement of the rack bar being slowed down or allowed to accelerate by its rotating through reduction gearing 53, Fig. 4, an aluminium disc 46 rotating in a slot in the field of a permanent magnet 55, the speed of the disc and magnet being affected by the ambient temperature in the toaster. Bread placed on cross-bars 21 of parallel links 13, 14 is lowered by hand depressing a knob on an arm 69 so that a nose 31 engages a ledge 32 to press and hold the bread down whereby a ledge 32 of transverse plate engages under a nose 31 on a latch arm 29. The remote ends of links 13 pivot up to tension springs 18 and moves switch arm 24 to close the switch to energize the heating element 12. The downward movement of 17 also tensions springs 61, thus pulling down the cross-bar 57 and the rack bar 49. The rack 49 is pulled down to rotate disc 54 through gears 53 and roller 59, Fig. 3, moves down to engage cam edge 42 on 41 which pivots out, taking with it the nose 31 clear of ledge 32 so that the bread plate 17 jumps up. Toasting time depends on the distance which roller 59 has to travel before displacing latch arm 29, Fig. 1, sufficiently to release 31 from 32, and also depends on the rate at which pinion 51 revolves. The distance which 59 has to travel is set manually by rotating spindle 35, Fig. 2, thus moving cross-bar 37 and bar 41 up or down. The pinion is braked by magnet 55 on disc 54 and since this braking effect decreases as temperature rises the toasting time for a given setting of bar 41 decreases as the ambient temperature rises. A further control of the braking effect is made by moving magnet 55 relative to 54, i.e. towards 54 with increase of ambient temperature by the bending of the bi-metal 68 while this link 65 rocks the magnet carrying lever 63 about its pivot. Compensation for excessive reduction of toasting time may also be done by a shunt mounted against one of the faces of the magnet parallel to 54 to reduce the field strength of the magnet so that the field acting on 54 increases with ambient temperature.