Patent GB-939565-A (GB)
Title: A device for controlling intermittent movement of an element
IPC: G03B17/42
Filed: 1961-08-15
Abstract: 939,565. Kinematography. EASTMAN KODAK CO. Aug. 15, 1961 [Aug. 15, 1960], No. 29374/61. Class 97 (1). [Also in Group XXIV] A mechanism for advancing a film strip in a camera and giving either relatively small or large increments of movement to a driven member comprises a friction slip coupling connecting the driven member to a driving member, and a double pawl-and-ratchet stop arrangement selectively operated to prevent movement of the driven member, causing the coupling to slip. As shown, a continuously rotating electric motor 10, Fig. 1, is connected through belt gearing 12, 19, 21 and a friction slip coupling 24 Fig. 2, to a driven shaft 23 carrying ratchet wheels 30, 31 engaged as required by detent pawls 32; 33, 34, Fig. 3, according to the incremental movement required at the driven member. The preferred embodiment has a cam 26 on the shaft 23 engaging a roller 27 on a slide 28 reciprocated back-and-forth to step a film F along in a camera, but alternatively the final driven member may be a shaft or the like turned a step at a time. The ratchet wheel 30, Fig. 2, is provided with relatively coarse teeth engaged by the detent pawl 32, Fig. 3, pivoting at 35 on a casing 25 and withdrawn against the bias of a spring 41 to the disengaged position on energization, either momentarily or for a sustained period, of a solenoid 39. Thus the shaft 23 may be stepped round or may rotate. The ratchet wheel 31 has relatively fine teeth, engaged by the pair of pawls 33, 34 pivoting at 45, 49 on the casing 25 and actuated by cams 54, 55 engaging their tails and fast with a shaft 53. To obtain a small increment of movement of the driven member, a solenoid 92, Fig. 5, is energized to withdraw a detent pawl 86 pivoting at 88 on the casing from engagement with a ratchet wheel 83 on an auxiliary shaft 80, this serving also to permit springs 104, 105 to move a link 101 and engage a friction idler wheel 82 between discs 15,81 fast with a shaft 14 driven by the electric motor 10 and the shaft 80, respectively. The shaft 80 is geared to the shaft 53 carrying the two cams 54, 55, which accordingly 'rotate to withdraw one of the pawls 33, 34 from engagement with its ratchet wheel 31 and engage the other therewith, the arrangement being such that the ratchet wheel is allowed to rotate through an angle corresponding to half its tooth pitch. The pawl 86, Fig. 5, rides over the ratchet wheel 83 during a complete revolution of the shaft 80, maintaining the idler wheel 82 in engagement with its two friction discs 15, 81, until the pawl 86 slips back to engage the single tooth of its ratchet wheel. A detent 84 pivoting on the ratchet wheel 83 then engages a link 99 connected to the pawl 86, and a slot 100 therein engages a pin upon the link 101 carrying the friction idler 82 to eject the latter downwardly against the bias of the springs 104, 105 to a position free of the two friction discs. The process may be repeated by further momentarily energization of the solenoid 92. To withdraw the pawls 33, 34 from engagement with their ratchet wheel 31 during energization of the solenoid 39, for a relatively large increment of movement of the driven member, a solenoid 65, Fig. 3, is energized to pull a link 63 connected to a link 60 so that a pin 62 connecting the two links engages the pawl 34, and withdraws it from the ratchet teeth, while a roller 66 carried by the link 60 simultaneously engages the pawl 33 and likewise withdraws it from the ratchet teeth. Control is effected by a circuit including A.C. power lines 120, 121, Fig. 7, connected on closure of a switch 122 to the motor 10, a rectifier 123 supplying D.C. current to lines 124, 125 energizing the pawl control solenoids 39, 65, 92. Two interlocked switches 126, 127 as shown connects the solenoid 39 to the lines 124, 125. The switch 126, which is open, prevents energization of the solenoid 65 and withdrawal of the two pawls 33, 34. On closure of a switch 133, the solenoid 92 is momentarily energized to withdraw the pawl 89 from the ratchet wheel 83, and to engage the friction idler 82 between the discs 15, 81, so that the shaft 80 rotates, the cam 54, 55 turn the two pawls 33, 34 and the driven shaft 23 is stepped round through a small angle. By instead closing the switch 126 and opening the switch 127 the solenoid 39 is deenergized, and the solenoid 65 is energized to withdraw the two pawls 33, 34 to their disengaged positions. On closure of a switch 134, the solenoid 39 can be energized to withdraw the pawl 32 from its ratchet wheel 30, and the driven shaft 23 is turned through a relatively large angle. The switches in the control circuit may be actuated either manually, or by cams driven from the shaft 14 for automatic actuation of the mechanism.