Patent GB-794499-A (GB)
Title: Improvements in or relating to differential devices
IPC: B41B21/20
Filed: 1954-08-04
Abstract: 794,499. Photographic type composing. HIGONNET, R. A E., and MOYROUD, L.M. Aug. 4, 1954 [Aug. 21, 1953], No. 22655/54 Class 98(1). A differential device consists-of two input members and an output member, means for advancing the input members individually or in combination from initial positions to produce a movement in the output member, and resetting means, independent of the driving means, for returning the input members to their intial positions. A number of such devices may be connected together the output member of each device (except the last) being connected, to one input-member of the next stage, with means for advancing the remaining input members in selected combinations to produce a movement in the final output member, and means, independent of the driving means, for resetting the input members. The device may form part of the character-spacing means of a photographic type-composing machine. As shown in Fig. 1, the photographic type-composing machine is similar to that described in Specification 754,104. A line of text is typed on a keyboard 2 and recorded in code form in one of two registers 6, 8, as described in Specification 691,761. Information representing the width of each character in binary notation is set to a multiplier 12, where it is multiplied by a factor corresponding to the set width of the characters, the product being supplied to an accumulator 14. At the .end of the line, the total from the accumulator is sent to a justifier 16 which computes the spacing to be added to the interword spacing to bring the line to the standard length. The register with the line stored in coded form is used to control the projection of characters from a continuously rotating disc 26 by means of a flashing light 30 and a lens system 34 on to a film 44, as described in Specification 691,763. Character spacing is effected by means of a rack 46 and pinion 48, the pinion being driven by the output member of a multi-stage differential device which is controlled by selective energization of input leads E1 to E256 connected to justifier 16 and to a multiplier 50 which receives information as to character width from the register and' multiplies it by a factor corresponding to the set width of the characters. The differential device consists of eight stages, each comprising a differential supported in a frame 56. The first differential has two input shafts L1, L2. Each subsequent differential is connected to the previous stage and also has an input shaft L4, L8-L256. The gear ratios are 1':1 1 except for L1, which has a 2: 1 gear ratio, with the first differential. Thus the carry-over and direct input rotations are scaled down in the ration of 2:1 and a  binary series is produced. Clock springs 58 urge the shafts in the: direction of the arrows. Relays 62, when energized by electric impulses from justifier 16 or multiplier 50, actuate ratchet mechanisms 60 which allow rotation of the shafts through a given angle. As a result,.after the projection of each character the rack 46 is moved through the distance required to effect proper character spacing. For resetting the device'on completion of,a line, a lost-motion mechanism 122 is provided at the end of each input shaft, and a similar control mechanism 123 is provided on a shaft 133. A resetting shaft 124, driven through bevel gear from a shaft 128 connected to a reversible electric motor M, has alternate right-hand and left-hand threaded worms 130 engaging gears 132 forming part of the mechanisms 122, 123. As shown in Fig. 4, the control mechanism 123 consists of discs 150, 134 fixed to shaft 133, and a number of delay wheels 142, which, together with gear 132, are loosely mounted on shaft 133. The mechanisms 122 are similar to mechanism 123, except that disc 150 is omitted and there is one more delay wheel 142. Wheels 142 are separated by spacers 144 and are formed with lugs 146 as shown in Fig. 6. Before transcription of a line begins, a pin 138 on disc 134 bears against the uppermost lug 146 of the wheels 142, and the lowermost lug bears against a pin 140 on gear 132, with the intermediate lugs in engagement to prevent rotation of shaft 133 in the direction opposite to that indicated by the arrow. During transcription, each of the shafts L1, L2, &c. rotate so that pin 138 moves away from its lug until it engages it from the other side: Thereupon the uppermost wheel 142 is moved, and its downwardly extending lug moves away from the upwardly extending lug of the next wheel until it engages it from the other side, and so on. There are sufficient wheels to ensure that even in the transcription of the longest line the lowermost lug 146 will not engage pin 140 on gear 132. Mechanism 123, however, remains in the position shown in Fig. 4, so that a. pin 148 on disc 150 bears on a pin 152 on an arm 154. Arm 154 is carried by a shaft 156 jburnalled in the machine frame, and the shaft also carries an arm 158 with an insulated roller 160. As long as pin 152 bears on pin 148, roller 160 holds contacts B open against action of a spring 162, and a pair of stop arms 166, 168 fixed to shaft 156 are held in the position shown in Fig 8, with arm 166 engaging a cam 170 and arm 168 free of a cam 172. Both cams are mounted on shaft 128. At the end of transcription, a key K is closed which energizes a relay R1 which is held on by a circuit through its normally open contacts and through normally closed contacts of a relay R2. A second pair of contacts of relay R1 close a circuit through lead 174 to motor M causing it to drive shaft 128 in the direction of the arrow. In the first revolution, cam 170 acting through lever 166 rocks arm 158 to a central position and allows contacts B to close. Continued rotation causes engagement, one after the other, of the delay wheels 142 of mechanism 123 until disc 134 is engaged. Shaft 133 is then driven until pin 148 on disc 150 engages pin 152 to rock lever 154 and shaft 156. This rocks arm 158 to close contacts A, stopping the motor M, and moves arm 168 into position to engage cam 172 and stop shaft 128. At various times during the rotation of shaft 128, the mechanisms 122 become engaged and transmit motion from shaft 124 to the input shafts, which are thereby returned to their initial positions when shaft 128 stops. The closing of contacts A energizes relay R2 through contacts B (now closed), a pair of normally open contacts completing a holding-on circuit. At the same time the holding-on circuit of relay R1 is opened, and the circuit to motor M through lead 174 is broken. The motor is now energized by a circuit through lead 176 so that it drives shaft. 128 in the opposite direction. This resets all the mechanisms 122, 123 back to their original positions, without moving the input shafts. The movement is stopped when pin 148 of mechanism 148 engages pin 152 and rocks shaft 156 back to its initial position, in which contacts B are opened to release relay R2 and stop motor M, and arm 166 engages cam 170 to stop shaft 128. Specification 691,738 also is referred to.