Patent GB-671330-A (GB)
Title: Improvements in or relating to devices for the control of electrical circuits according to a predetermined program
IPC: G04C23/34
Filed: 1948-07-13
Abstract: 671,330. Time switches. INTERNATIONAL BUSINESS MACHINES CORPORATION. July 13, 1948. [Aug. 12, 1947] No. 18792/48. Class 38 (v). [Also in Group XXXVIII] A device for performing desired electrical operations at predetermined times comprises a rotatable drum having two sets of teeth thereon, a set of stop fingers which co-operate with one set of teeth to prevent movement of the drum except at predetermined times, and a set of normally open contacts which are closed by teeth of the other set by the motion of the drum at the said predetermined times. In the embodiment described, Fig. 3, four sleeves 106, 108, 110, 112 are mounted on a shaft 104 which is stepped rotationally once per minute to perform a complete rotation in ten minutes. The sleeve 112 is coupled directly to the shaft 104 and thus rotates once every ten minutes. Sleeve 110 is coupled to the sleeve 112 by Geneva gearing whereby it makes a complete rotation once every two hours. Sleeves 108 and 106 are similarly caused to rotate completely twice every day and once every week respectively. A spiral series of teeth 146 is arranged around each of the sleeves and an additional series of teeth spaced alternately as shown is arranged upon the sleeve 106. As the sleeve 112 rotates the teeth 146 thereon come into successive operative contact with stop fingers 80, successive fingers being raised for a period of one minute and the cycle of operations repeating itself once every ten minutes. At the end of each ten minute period the sleeve 110 steps forward one twelfth of a rotation, whereby successive teeth thereon lift successive fingers 80. The sleeve 110 comprises a double spiral of teeth so that the cycle of operations upon the fingers is repeated once every hour. The sleeve 108 steps forward one twelfth of a rotation once per hour to cause successive fingers 80 to be raised for hourly periods with the cycle repeating itself once every twelve hours. The sleeve 106 is stepped forward one-fourteenth of a rotation once every twelve hours to cause the two fingers 80 at the right-hand end of the sleeve to be operated for alternate twelve-hour periods. The teeth at the left-hand end of sleeve 106 co-operate with contact-operating fingers 82 causing successive contacts to be closed each for a period of one day once per week. (In a modification of the system stop fingers as used with the remainder of the system are used in place of the contactmaking fingers 82 for co-operation with the sleeve 106.) The fingers 80, 82 co-operate with teeth 78 on a "programme-bar" 50 (see also Fig. 3a). The programme-bars are mounted in radial slots in a drum 30 which is coupled by a ratchet-and-pawl mechanism to the shaft 104 which steps the drum round one-sixtieth of a rotation once per minute so long as the drum is free to move. The drum comprises sixty radial slots so that each step round of the drum brings a fresh bar, or a space therefor, into the operative position with respect to the fingers 80, 82. A bar is used for each time of day at which the desired electrical operation, e.g. the ringing of a bell, is to occur, and teeth 78 are broken therefrom in accordance with the chosen time ; thus the bar indicated on Fig. 3a is for causing the desired operation at 3.12 p.m. Teeth are broken off for the days of the week on which this operation is to occur ; thus in the example shown, the operation is to occur on Mondays only. The bar also comprises teeth 48 which are used to determine which of a plurality of circuits is required to function. Thus as shown circuit 3 is operated on Mondays at 3.12 p.m. The stop fingers 80 engage with the teeth 78 when lifted by the teeth 146 and prevent the drum 30 from rotating. Thus the stop fingers hold the bar 50 with which they are co-operating until the time of day for which the bar is set when the drum 30 turns through one-sixtieth of a rotation. Simultaneouslv contacts controlling the circuits determined by the teeth 48 are closed. These contacts are in series with that controlled by the fingers 82 so that if the bar is also set for the appropriate day of the week the desired electrical operation occurs. The drum 30 is then stepped forward at minute intervals until a further bar 50 comes into the operative position when the drum is again held stationary until the time determined by the teeth broken off the bar. In this arrangement comprising separate bars for each time of day the drum 30 makes one complete revolution each day. In the modification previously referred to, wherein the fingers 82 are replaced by stop fingers a separate bar is required for every time in the week that the operation is to occur and the drum 30 makes a complete revolution once per week. Electrical circuits, Fig. 15. The system comprises six contacts a, b, c, d, e, f which are the contacts controlled by the teeth 48 of the programme bars, and contacts a<SP>1</SP>, b<SP>1</SP>, c<SP>1</SP>, d<SP>1</SP>, e<SP>1</SP>, f<SP>1</SP> which are adapted to be closed manually by levers 181, as shown in greater detail in Fig. 4 (not shown). Each of these contacts controls a corresponding relay and bell circuit, which are energized from a source of power SC through a transformer T. The contacts a, b, c, d, e, f are arranged in series with contacts D, H and K. The contact D is controlled by the fingers 82 which are actuated by teeth 146 on the sleeve 106, and is shown also in Fig. 5 (not shown.). The contact H is controlled by the ratchet-and-pawl mechanism coupling the shaft 104 and the drum 30 and is so arranged that it closes only when the drum is free to move, thus preventing continued actuation of the initially actuated circuits when the drum is held in one position for any length of time. The contact K is momentarily closed once per minute by the action of the rotating cam 250 to provide a uniform duration of the closure of all the circuits involved. Ratchet-and-pawl mechanism controlling drum 30, Fig. 2. A ratchet wheel mounted upon shaft 104 is stepped through 36 degrees once per minute, thus raising pawl 116 and causing pawl 118 to engage with ratchet wheel 122 in a manner tending to make it rotate. Ratchet wheel 122 is coupled to the drum 30 through gear wheels 128 and 130 so that when the drum is not free to move the pawl 116 is held in an elevated position with respect to the ratchet wheel 114. An arm 174 attached to pawl 116 closes the normally open contacts H when the pawl engages the ratchet wheel 114 fully. Since this happens only when the drum 30 is stepped round, the contacts H prevent the circuits comprising the contacts a ... f from being closed for an extended period when the drum is held in one position. Means for driving shaft 104 at controlled rate, Fig. 15. Pulses are applied from points A and B via the contacts j, j<SP>1</SP> to the electromagnet 208 at normally one-minute intervals. When a pulse is applied thereto the arm 212 is lowered so that the shoulder 214 no longer engages the cam-follower 218 and the tip of the arm 212 underlies the contacts 206. Upon the deenergization of the magnet 208, the arm 212 rises to close the contacts 206, thereby completing the circuit of the motor M which commences to operate, rotating the shaft 136 carrying the cam 224. The shaft 136 makes one complete rotation when the cam-follower 218 restores the arm 212 to its normal position out of engagement with the contacts 206. The shaft 136 is geared to the shaft 104 which is therefore stepped round by an accurately controlled amount at minute intervals. The pulses applied to the magnet 208 are derived from a master-clock system such as described in Specification 236,199, [Class 139]. The contacts j, j<SP>1</SP> the closing of which is controlled by slots cut in the sleeves 110 and 112 are used for maintaining synchronism between the master-clock and the shaft 104 in the manner described in the abovementioned specification.