Patent GB-254791-A (GB)
Title: Improvements in and relating to the production from photographs of models, images, busts or the like
IPC: G03F7/00
Filed: 1925-04-07
Abstract: 254,791. Jeffreys, S. T., and Petty, H. J. April 7, 1925. Statuary, reproducing.-A method of producing models of a solid object from a series of photographs each bearing a profile view of the object taken from a different circumferential position relative thereto, consists in marking or projecting the profiles in turn on a screen and following them by a pointer the longitudinal movements of which down the profile cause exact or proportional relative longitudinal movements between a tool and a block of plastic or other material, while the lateral movements of the pointer are obtained by manual operation and control the feeding and withdrawing movements of the tool relative to the block, the block being partially rotated after each longitudinal movement to expose a fresh part to the action of the tool moving in accordance with the next profile placed on the screen. In the apparatus shown in Figs. 1 and 2, a rod 27 bearing a pointer 28 and a tool 30 at its ends is slidably mounted in a carriage 24 which is driven along slides 22, 23 by means of a screw 40 and a half-nut 47. A handle 36 enables the pointer 28 to follow a profile 69 marked or projected on a screen 38 as the carriage is driven longitudinally of the screen, and the tool thus makes a corresponding cut in a block 37 of plastic material mounted for rotation about an axis 68. At the end of the stroke of the carriage 24, the half-nut 47 is put out of engagement with the screw 40 by projections 59 pressing down the nut, the handle 36 is moved over to the left and keeps the nut disengaged by a projection 56 riding over a cam 48, and the carriage is then returned to its starting position. A ratchet-wheel 63 is moved and rotates the block 37 through gearing 60, 61 to bring the block into a position corresponding to the next profile to be marked or projected on the screen 38. A centre-line 67 enables the profile to 'be set correctly with reference to the axis 68 of the block 37. In a modification, the block 37 is moved longitudinally as the pointer moves. both being actuated by an electric motor, the tool being rotated b a motor and advanced into the block in accordance with the movements of the pointer across the profile. Figs. 10 and 11 show an apparatus which may be operated similarly to that shown in Figs. 1 and 2. a tool 30 driven by a motor 110 moving longitudinally of the block 37, or for working hard materials, the tool may be moved intermittently, alternate feeding and withdrawing motions radially of the block being imparted through a gear-box 141. In the first method, the pointer 28 is carried in a slide 93 which is driven in a vertical direction by screws 90, 91 geared to a shaft 71A, and a carriage 149 bearing the motor 110 is mounted on screws 153 also geared to the shaft, so that the pointer and tool move simultaneously. The motor 72 is connected to the shaft 71A through gears 160, 165 and 167, 173, the gears 165, 167 being slid into position by a handle 164. A handle 36 drives a shaft 92 by which a transverse movement is given to the pointer 28, a rack 134 being provided on the pointer, and the handle also drives a shaft 140 through gears 190, 191. The shaft, 140 being connected to a screw 109 which gives the motor 110 its feeding and withdrawing movements across the carriage 149, the motor moves in accordance with the path traced out by the pointer 28. The block 37 is rotated after each longitudinal cut by a handle 80<a>. In the second method, the motor 72 is disconnected from the shaft 71<A> and drives the reversing gear box 141. The gears 191, 190 are also disconnected. Electromagnets 175, 176 control the direction of drive of the shaft 140 from the gear-box, and each of the magnets is adapted to be cut out by the contact-breakers 186, 188 opening the contacts 185. 187 respectively. The handle 36 drives a rack bar 136 through a gear 135, and so moves a block 137 carrying the contact-breaker 186 into a position corresponding to the position of the pointer 28. The shaft 140 is rotated from the gear-box 141 to feed the tool 30 until a block 192 carried on a screwed part 174 of the shaft causes the contacts 185 to be opened by the member 186. The gear-box is then reversed and the tool withdrawn until the contacts 187 are opened, again feeding the tool. At or about this reversal. a projection 192 on the block 184 strikes a push-rod 193 which moves a ratchetwheel 196, so driving the shaft 71A through gears 166, 173 and moving the pointer and tool into position for the next cut. This proceeds until the whole profile has been copied, when the block 37 is rotated and a new profile placed on the screen 38. A ratchet gear may be employed to turn the handle 80<a> automatically after each profile has been completed. The photographs employed are obtained by intercepting a beam of light projected on to the object in such a manner that a shadow falls across the object, and a camera situated at an angle of 90‹ C. or less to the direction of illumination takes a series of photographs as the object is rotated. These photographs represent true or foreshortened profiles, and by suitable projection, the true profiles can be shown on the screen 38, the outline being marked on the screen or used directly for the reproduction of the model.