Patent GB-645939-A (GB)
Title: Improvements in or relating to machines embodying one-revolution clutches
Inventor: NASMITH JOHN IRVING
IPC: G05G15/04
Filed: 1946-10-07
Abstract: 645,939. Gearing for starting and stopping machinery. VICKERS - ARMSTRONGS, Ltd. Oct. 7, 1946, No. 29895. [Class 80(ii)] In a wire-stitching or other machine performing a complete cycle under control, e.g. of a one-revolution clutch 7, 8, automatic mechanism for predetermining the number of complete cycles of operation to be made sequentially comprises stepwise mechanism making one complete step per cycle and arrested at the end of a pre-set linear travel in each direction in such a manner that the mechanism is left at each end of the travel in a condition functionally equivalent to that which obtained at starting. Thus, when the clutch-bolt 8, Fig. 3, of the one-revolution clutch is drawn downwardly by an operator-controlled treadle or by entry of the blank to be processed, the machine starts, and a cam-drum 2 on the clutch-shaft 1 oscillates, through a crank 4, a plate 6, Fig. 4, carrying two pairs of oppositely-acting pawls 13a, 13b, 14a, 14b, one or other' pair, e.g. 13b, 14b of which is raised to an idle position by a pawl-selector plate 17, whilst the other pair, e.g. 13a, 14a is free to engage teeth of a pair of parallel sliding racks 9, 10, which are thereby advanced alternately in steps in the same direction during any one series of operations by the backward and forward oscillations of the pawl-plate 6, each step of each rack corresponding to a half revolution of the clutch-shaft 1 and so a half-cycle. The number of steps thus predetermines the number of cycles, on completion of which the clutch-bolt 8 is automatically raised to stop the machine and the pawls 13, 14 are reversed ready for the next identical series of cycles during which the racks 9, 10 are stepped in the opposite direction, the stop and reverse being as follows. The racks 9. 10 are secured respectively to forward parallel extensions 11, 12 and carry pawlreversing stops 24, 25, an appropriate one of which, during the last step of a series in either direction, contacts with and moves the pawl selector plate 17, Fig. 4, to the left or right depending on the direction of movement of the racks, thus raising the operative pawls, e.g. 13a, 14a and freeing the previously idle pawls 13b, 14b for engagement with the racks in preparation for the next series of operations, during which the racks will step together in the opposite direction. At the same time one or other of two clutch-control stops 34, 35, adjustably or non-adjustably fixed to the front slides 11, 12 of the respective racks, strikes a horizontal lever 37 or 38, Fig. 2, which pushes inwardly on and releases the hooked end 46 of a latch-lever 44, Fig. 3, loaded outwardly by a spring-plunger 48 and previously hooked over a fixed catchplate 47 on which the levers 37, 38 are pivoted, so as to act through a lever 39 to hold the clutch-bolt 8 out of the path of the disengaging cam 7, thus maintaining the clutch continuously engaged. The release of the latch-lever 44 permits a spring 49 to raise the clutch-bolt 8 into the path of the release cam 7 which latter then disengages the clutch at the end of the last revolution. The number of rack-steps and so the number of machine-cycles before automatic stopping is determined by the distance between the pawl-reverse stops 24, 25 which can be pre-set after first operating a hand-lever 26, Fig. 1, to open up a pair of levers 28 simultaneously lifting all the pawls 13, 14 to free the racks 9, 10, which can then be slidden relatively to one another to vary the spacing of the pawl-reverse stops which is indicated by a scale 32 on the front extension 11 of one rack 9 tracked by an arrow 33 on the other. The machine may be stopped and reset at any point during a series of operations by the pawl-release lever 26, the lower end 53 of which strikes the lever 38 to unhook and release the clutch-rod 44 and allow the clutch-bolt 8 to rise into the stopposition. In addition to controlling sequentral operation of the one-revolution clutch the mechanism may also be provided with a slidable cam-plate 50, Fig. 2, operated by the pawl-reverse stops 24, 25 during the last three steps in either direction, this cam-plate 50 operating a follower 51 controlling, e.g. means for placing double stitches at the beginning and end of each series of operations in the wire-stitching machine.