Patent GB-702428-A (GB)
Title: Improvements in process timers
IPC: G04C23/16
Filed: 1952-01-16
Abstract: 702,428. Time switches. VEEDER-ROOT, Inc. Jan. 16, 1952 [Jan. 25, 1951], No. 1239/52. Class 38(5) [Also in Groups VI and XXIX] A process timer controlling a switch of e.g. a kitchen range, comprises a clock mechanism having a driving element, a driven element adapted to be driven by the driving element, and separate setting means selectively operable for moving the driven element relatively to the driving element. A motor M drives normal minute and hour spindles 43, 48 over gearing 41, and, over a pinion 46, a gear 49 carrying a bevel gear 50 meshing with a gear 51 on a sleeve 52. The latter is free on a spindle 56 freely carrying a gear 54 which has a pin 55 cooperatimg with a projection 53 on sleeve 52 which rotates once in twelve hours, the sleeve 52 and gear 54 constituting the driving and driven elements, respectively. Gear 54 is urged axially towards the sleeve 52 by a spring 134 and meshes permanently with a wide gear 60 forming part of a differential 61 and rotatable on a shaft 62. The differential also has a disc 64 rotatable on a shaft 65, the shafts 62, 65 being connected by pinions 66 meshing with pinions 67, 68 on the ends of the respective shafts which at their outer ends carry gears 69, 70. Thus by rotating gears 69, 70, the position of gear 54 may be varied over the differential so as to vary the angular distance between pin 55 and projection 53. Gear 69 is rotated by a knob 20 connected thereto over gears 78, 77, 75 and spindle 76, which also carries minute and hour number wheels 24, 25 so that the desired switching-off time may be selected by the knob 20. Similarly, a knob 21 is connected to gear 70 over gears 93, 92, 90 and a spindle carrying number wheels 28, 29 by which the cooking period may be set. The order of the numbers on wheels 28, 29 is opposite to that on wheels 24, 25 so that whilst clockwise rotation of the latter causes movement of pin 55 away from projection 53 by a distance corresponding to the interval between the actual setting time and the desired switching-off time, setting of wheels 28, 29 returns the pin 55 by a distance corresponding to the desired cooking period. The setting operations may be carried out in any order, or simultaneously. The spindle 76 is locked, after setting, by a spring 84 engaging in one of a number of holes 85 in wheel 24, so that gear 69 is stationary whilst the differential is driven by gear 54 and 70. After setting, the projection 53 advances freely until it reaches the pin 55 which is then moved round also to rotate gears 54, 60, 69 and 70 to return wheels 28, 29 to zero. A shaft 31, having a knob 22, is biased counter-clockwise. Fig. 8, so that a lug 107 bent over from a spring arm 108 attached to the shaft is pressed against the side of a wheel 105 mounted on shaft 65 and having one long radial notch 106<SP>1</SP> and a lot of short notches 106. In this position of shaft 31, a mark " SET " on a sector plate 32 is visible through a hole 33 in the front of the timer casing 19. The lug 107 is short enough to pass through the first notch 106 to come opposite it as soon as wheel 105 is rotated by gears 54, 60. Shaft 31 thus turns counter-clockwise until a longer lug 111 on a spring arm 109 engages the side of wheel 105, a mark " ON " on plate 32 thereby being made visible. When the notch 106<SP>1</SP> coincides, with lug 111, shaft 31 is turned further counter-clockwise, an " OFF mark appearing in hole 33. The shaft 31 also carries a cam 125 cooperating with a bell-crank lever 122, Fig. 7, which normally holds a switch lever 127 open against the tion of a spring 126. The switch is thus closed when the shaft moves to the " ON " position and is opened upon the later movement to the " OFF " position. A second bell-crank lever 130 operable by cam 125 has a bifurcated arm embracing a hub portion 133 of gear 54 which is thereby moved axially away from sleeve 52 when the switch opens, so as to disengage pin 55 from the projection 53 to stop the drive. A cam 144 on shaft 31 engages a lever 141 which moves the gear 90 axially to disengage gears 92, 93 when the shaft 31 moves to the " ON " position. The shaft is axially movable to disengage a finger from a fixed stop so that the shaft may be rotated to a fourth, manual, position, thereby closing the switch for so long as the shaft remains in this position.