Patent GB-762822-A (GB)
Title: Photocomposing mechanism
Inventor: KLYCE BATTLE HARGROVE
IPC: B41B27/36
Filed: 1954-10-08
Abstract: 762,822. Photo-electric control of photocomposing machines. TIME, Inc. Oct. 8, 1954, No. 29093/54. Class 40 (3). [Also in Group XX] In a photo-composing device the platen or equivalent carrying the photo-sensitive material is moved continuously and each exposure, other than the first in each line, takes place when the platen &c. has travelled a prescribed distance having regard to the previously printed character or at an instant determined by a received " word space " signal. General operation. A disc 26, Fig. 1, carries a number of font grids, each of which carries 225 characters. The grid 27 selected for operation is brought by means not described to a position in which the characters thereon can, with the aid of a projection discharge tube 20, condenser lenses 21, 22 and lenses 36, be focused in a plane 23 and thence projected on to the sensitive surface. The particulat letter for projection is selected by the operation of a shutter slide 46, 51 in each of two sets of 15. Each representation of a character in the font grid is accompanied by the representation in the form of an 8-digit binary code of the width of that character and this representation is reflected by a prism 25 via condenser lenses 144a on to a group of photo-cells 145 ... 152. The frame carrying the platen has a transparent window ruled with lines 131 (say 500 to the inch) which interrupt the light from a lamp 132 and so produce impulses in the circuit of a cell 134. These impulses build up a binary counter from a point determined by the width value registered by the tubes 145 ... 152 and when the counter is full, the next exposure takes place, the counter is re-set and is then re-primed in accordance with the new width. The control of the shutters for the selection of the letters for printing is effected by an 8-digit binary code signal from a tape record. The record may also contain signals for determining word spacing, starting a new line, changing the scale of reproduction, selecting a particular font grid, &c. Circuit arrangements; decoding. The control tape 54, Fig. 2, which may be magnetic but, as shown, is optical, carries the information in the form of rows of marks in nine positions, one position discriminating between characterselecting signals and signals concerned with format and word-spacing and the others selecting the particular character or format control or word space. Photo-cell 72 which responds to light passing through the sprocket holes controls a pulse-generator 82 (wave C, Fig. 10) and the generated pulses trigger a mono-stable circuit 92 to produce wave D which temporarily closes gates 83 ... 91 in the paths of the code signals until the code marks are in the optimum position in relation to the optical system. The pulse from 82 also triggers a mono-stable circuit 102 (wave F) which closes further gates 93 ... 96 and 98 ... 101 to impose a slight additional delay on the numerical signals but not on the discriminating signal, if any, from photo-cell 67. Four digits of the numerical part of the code go to a conventional matrix 105 and the other four to a similar matrix 110. Each of these has fifteen output leads energized singly in response to the respective binary numbers other than four zeros and these leads are effective on tubes or tube sections 107 or 108 and 112 or 113 according as the discriminating signal on photocell 67 is absent or present. The tubes 107, 112 control the horizontal and vertical shutters by means of electromagnetically controlled fluidpressure valves. Codes in which a signal does appear in the circuit of photo-cell 67 are divided into two groups. The thirty codes in which one of the matrices receives four zeros are used for format operations. The signal produced by 67 (wave K) is differentiated to produce wave L which switches over bi-stable trigger circuits 115, 116 to make the groups of tubes or sections 108, 113 effective instead of the groups 107, 112. A selection of the required format operation is then made in accordance with the particular output lead of the groups 106, 111 energized. If, however, the numerical part of the code involves the application of a signal to both matrices, a triplecoincidence circuit 120, actuated by one or more signals corresponding to each matrix together with a signal from the discriminating photocell, applies wave 0 to trigger a bi-stable circuit 121 (wave P) which actuates circuits 122, 123 to prevent the reversing action of 115, 116 and disable the normally connected groups 107, 112. The numerical part of the code is registered in bi-stable circuits 181 ... 188. Circuit arrangements; control of exposure (spacing). The pulses from 134, as the platen travels horizontally, normally pass through a gate 136, which is closed during the return movement, and a switching pair 137, 138 to a counter 124. When the latter is full, it clears and resets itself and produces a pulse (wave S) which passes by a delay line 139 to trigger a mono-stable flip-flop 141 which'lights the exposure lamp 20 for the duration of the pulse (wave U). The pulse from 141 also controls a differentiating circuit 143 to produce short pulses (wave V) which are passed to circuit 144 which suppresses the negative-going pulse and passes on a pulse (wave W) to circuit 103 to cause the code carrying tape to be stepped on. The distance travelled between printing impulses is made to depend on the character printed by the initial registration on the counter of the number set up on the photo-cells 145 ... 152 by the code signal accompanying the printed character. The counter builds up from this number instead of from zero. In the case of spaces between words, the control comes from the tape 54 and the associated photo-cell signals registered on bi-stable circuits 181 ... 188, the outputs of which are normally blocked by circuits 191 ... 198 to make their response to character and format signals ineffective. Word space signals as described above (decoding) cause a circuit 21 to produce an output (wave P) which is applied to a double coincidence circuit 199 and when the latter receives a further signal from the exposure controlling circuit 141, it opens the gates 191 ... 198 (wave Z) and the registered number is transferred to the counter 124 to determine the number of impulses required before the counter resets and controls the printing of the next character. Circuit arrangements; control of exposure (new line). When the code signal received indicates a shift to a new line, the first character is printed at the extreme left-hand position instead of waiting for a signal from the counter which, having received no priming signal, would have to build up from zero. A new line is indicated by a signal on line 206 which (see Fig. 9) charges over circuit 520. The positivegoing output pulse is differentiated at 524 and the resultant positive pulse is passed on to charge over a bi-stable circuit 203 and so reverse the condition of switching device 138 so that the first pulse from 134 goes direct to the exposurecontrolling flip-flop 141 instead of to the counter. This impulse also, via a delay line 205, restores the circuit 203 to its normal state. Circuit arrangements; platen feed control. A continuously driven motor 500 is normally clutched to a pinion engaging a horizontal rack on the platen frame and drives it against a fly-back spring. The reception of a " new line " code puts a signal, as previously described, on line 206. This reverses 520 to release the clutch and allow the frame to be restored by its spring. It also changes over a mono-stable circuit 530, Fig. 9, which transiently reverses the conductivity of a gas-tube circuit 533 to give an impulse to motors 515, 516 and so raise the platen by a distance of one line. In the normal horizontal position, springs 506 restore 520 to normal and clutch 501 is re-energized. Resetting operated circuits; control of tape feed. Circuit 144 on receiving a signal when a printing operation, a word space, a change of line or a format change have been completed provides an output pulse (wave W) which is applied to various bi-stable circuits to restore them, if necessary to normal and to a circuit 103 which changes over, removes a brake from the tape feed shaft and engages the clutch. When a new step has been completed, the pulse due to the sprocket hole photo-cell 72 restores 103 to reverse these actions. Circuit details. Details of known coupling and gating circuits used in the above arrangements are given in Figs. 4 to 8 (not shown). Modifications. It is stated without detailed description that the platen carrying the photosensitive material can be replaced by a drum arranged for axial and rotational movement and that exposure can be effected by the control of a Kerr cell or the like. The code dots 35a can surround the representation of the character instead of being in a line, as shown. Reference has been directed by the Comptroller to Specification 735,863.