Patent GB-782554-A (GB)
Title: Improvements in or relating to a timing mechanism for the operation of an electric circuit or circuits
IPC: H01H43/10
Filed: 1955-11-01
Abstract: 782,554. Time switches. KODAK, Ltd. Nov. 1, 1955 [Nov. 3, 1954], No. 31186/55. Class 38 (5). A timer adapted for timing a succession of photographic printing operations or alternatively a printing operation followed by a developing operation, comprises a motor adapted to drive a shaft 31 carrying cams 36, 37, the broad portions of which can respectively block the operating members 69 of two switches. The arrangement is such that only one switch can be operated at a time, the particular switch depending on the position of the shaft 31 and cams. One switch is adapted to connect in circuit the motor and the lamps for the printing. The other switch energizes the motor by itself. In operation, a knob 34, Fig. 5, is first rotated to a set position corresponding to the time desired for the printing operation, say 15 seconds. The shaft 31, which is spring- biased, follows this movement, an arm 43 on the shaft remaining in contact with a stud 441 on the knob. A hand lever 60 is then depressed causing the rotation of a member 62, Fig. 2, about an axis 61 and the upward movement of two blade springs 64, arranged one behind the other and which bear on the operating members 69 tending to close the two switches. Movement of one member 69 is prevented by a pin 71 engaging the broad portion of a cam 37, but a similar pin on the other member 69 is opposite the narrow portion of the cam 36 and this member 69 therefore moves to the dotted position and through a snap-action mechanism closes contacts 53 and 55 to the lamps and motor. The motor starts, clutches itself to the shaft 31 and rotates it till after 15 seconds, the broad portion of the cam 36 pushes the member 69 back to its original position, reopening the contacts 53, 55. The motor stops, is automatically declutched from the shaft 31, and then, if a knob 104, Fig. 5, is in position A, the spring biasing the shaft 31 returns it to its original " set " position, after which a further interval of 15 seconds for printing can be obtained by again pressing lever 60. If, however, it is wished to follow the printing operation by a developing operation, knob 104 is moved to position B causing rotation of a shaft 103, Fig. 2, and the positioning of a stop 111 in the path of an arm 98 projecting through a hole in a gear-wheel carried on the shaft 31. This stop 111, at the end of the printing operation, holds the shaft 31 in its zero position, and prevents it returning to its set position. If the lever 60 is now depressed, the cams 36, 37 are in such a position that the other member 69 and the other switch are operated. This other switch closes the circuit to the motor but not to the lamps and the motor now rotates the cams counter-clockwise, Fig. 2, till after another time interval suitable for development, the cam 37 by means of its broad portion pushes back the member 69 and reopens the switch. The motor stops, is declutched, and the biasing spring rotates the shaft 31 right back to its original set position, the arm 98 being automatically moved out of the way of the stop 111 during this movement by engaging a fixed washer in the wall of the housing, Figs. 7 and 8 (not shown). The snap-action switches operated by the members 69 each comprise blade contact springs operated by the centre portion of a U-shaped blade spring 79, the legs of which pivot on the member 69. A coiled tension spring connects the centre of the U spring to a pin 72 on the member 69 and is adapted to move over a dead-centre position.