Patent GB-594975-A (GB)
Title: Improvements in or relating to time switches
IPC: G04C23/34
Filed: 1945-01-09
Abstract: 594,975. Time switches. VENNER TIME SWITCHES, Ltd., and HORGAN, W. F. Jan. 9, 1945, No. 771. [Class 38(v)] [Also in Group XXIX] A time switch comprises a timing element having hands which at predetermined times impart impulses to a mechanism for actuating one or more electric switches or other control elements, means capable of being pre-set being provided to render the actuating mechanism effective and ineffective during certain intervals. Fig. 1 shows a time switch in which the timing element 22 is situated behind a plate 1 which carries the actuating mechanism for operating electric switch units 9 which may be of the kind described in Specification 594,973 and which are operated by a cam assembly as described in Specification 594,974. The plate 1 is attached to a support 13 which is shaped to provide sufficient space between the plate 1 and the back of the casing to accommodate timing elements of different sizes as described in Specification 594,972. Fig. 3 is a front view of the plate 1 with the actuating mechanism and support 8 for the switch units and Fig. 23 is an exploded view of the actuating mechanism, support 13 and cam assembly 10. Rocking levers 115, 116 adapted to be moved by the hands of the timing element or clock and a lever 117 for manual operation by a test-button 21, Fig. 3, are mounted on a common pivot pin 91a on the plate 1 and are connected by springs 119 to a post 118. The forward ends of the levers 115, 116 extend radially in front of an arcuate gap 6 in the plate 1, the lever 117 being cut off short of the gap. On the lower end of each lever 115, 116, 117 is pivoted a pawl 126 which engages a ratchet wheel on the cam assembly, the pawl on the manually operated lever 117 being held by a spring 127 in engagement with the wheel 92 and the pawls on the levers 115, 116 engaging the wheels 96, 97. Further pawls 130 are mounted on the lower ends of levers 115, 116 and are connected by springs 129 to the pawls 126. On the pivot pin 91a are also mounted two blocking levers 121 the ends 121a of which rest on projections 128 extending from the pawls 126. Springs 125 anchor the levers 121 to the post 118. Two selector discs 133, 134, Figs. 3 and 23, are provided which can be pre-set to vary the sequence of operations to be performed by the actuating mechanism. The discs are rotatably mounted on a pillar 131 on the plate 1 and are radially divided into seven equal sectors each of which is provided with three equally spaced screw-threaded apertures 135. Each disc has secured to its underside a ratchet wheel 136 having twenty-one teeth and which is engaged by one of the pawls 130. The discs are angularly movable relatively to one another and one may be advanced relatively to the other by one, two or three steps each step corresponding to one tooth space of the wheels 136. When one disc has been advanced three steps relatively to the other further movement of the disc results in both discs moving together. The pawls 130 are prevented from moving laterally out of engagement with their ratchet wheels by guard discs 141 and spring spiders 137 having pins 139 which engage apertures 140 in the guard discs. In the normal position of the mechanism the pawls 126 on the levers 115, 116 are kept disengaged from the ratchet wheels 96, 97 of the cam assembly by the engagement of the projections 128 and lever ends 121a. In this position the blocking levers 121 rest with their ends 123 over the edges of the selector discs 133, 134 and in the path of the apertures 135. The timing element rocks the levers 115, 116 at predetermined intervals but while the pawls 126 are kept out of engagement with the ratchet wheels 96, 97 by the ends 121a of the blocking levers 121 no movement is imparted to the cam assembly. A series of screw-threaded studs is provided any of which can be fitted into any of the apertures in the selector discs. When one of these studs reaches the corresponding blocking lever end 123 the lever is rotated on its pivot sufficiently to raise its other end 121a and allow the pawl 126 to rise into engagement with its ratchet wheel 96 or 97 on the cam assembly. A rocking movement imparted by the clock hands to the levers 115, 116 rotates the corresponding selector disc by the pawl 130 through an angle corresponding to one tooth of the wheel 136 which is the same as the spacing between adjacent apertures in the selector discs. In the example shown in Fig. 3 each sector of the disc 133 corresponds to a day of the week and each aperture in the sector bears an identification symbol. The discs are fixed rotatably on the'pillar 131, Fig. 23, by a screw and disc 143 carrying an index 145. The clock dial 45 carries six hands which can be secured in any position round the dial, three of the hands marked " ON " of which one is shown in Fig. 3, operating on the lever 116, and three " OFF " hands operating on the lever 115. The series of switching operations can be varied by altering the number of switch or control units 9 and varying their connections, by using different cams 102 arranged in various ways on the shaft 87 and varying the setting of the hands on the clock dial and the studs in the selector discs. The Specification describes the settings required for one particular sequence of operations.