INTERMITTENT DRIVE MECHANISM HAVING SELF-COMPENSATING MEANS FOR OFFSETTING THE EFFECTS OF DEVELOPED COUNTERTORQUE

摘要

In a variable ratchet drive, particularly for an unloading conveyer of a motor truck or trailer, wherein a driven member is periodically moved stepwise by way of a one-way clutch and prevented from back-running by a one-way brake, and wherein the non-driving return stroke of the driving member of the clutch is limited by a manually adjustable abutment to vary the driven member stroke, load-variable driven member stroke loss, due to transmission resilience particularly in the clutch and brake parts, is compensated for, and hence driven member stroke (e.g. conveyer feed) for a particular manual setting thereof is rendered substantially uniform irrespective of load, by mounting the reaction member of the one-way brake so as to react against spring means and using the load-variable periodic reaction movement of said reaction member to effect a periodic overriding movement of the adjustable abutment to render the non-driving return stroke of the driving member proportional to the driven member load. The one-way clutch and brake may be linear or, as shown, rotary. As shown, a cam 11 keyed on an input shaft 4 acts on a follower roller 13 rotatably mounted on a spring-returned bell-crank lever 14. The latter, in turn, is connected by parallel links 18 to the driving outer race 22 of a one-way clutch the driven inner race of which is keyed on an output shaft 26. The inner race 24 also forms the rotatable member of a one-way brake having a reaction outer race 27. The one-way clutch and brake have tilting or rolling gripping means 23, 28. The reaction outer race 27 is pivotally connected at 30, 31 to one arm of a three-armed lever 32 having a second arm 34 engaging a stack of Belleville spring washers 36 via a guide pin 35, and a third arm 37 pivoted to a plate 39 guided by a screw-pin and slot 40, 41. The manually adjustable abutment limiting the non-driving return stroke of the follower roller 13 and the driving outer race 22 is provided by an abutment cam 42 adjustably rotatable, via a tube 5 welded thereto, between limits defined by cam edges 43, 44 and the screw-pin 40. The plate 39 surrounds the tube 5 such that on load-variable periodic reaction movement of the reaction outer race 27, the lever 32 and the plate 39, the Belleville washers permitting greater movement with greater reaction load, the tube 5 and hence the abutment cam 42 are moved leftwardly back to increase the non-driving return stroke. The tube 5 may be rotated by a pulling means engaging a wheel of the tube, by a pair of such pulling means oppositely directed for operation from more than one station, or, shown, by a hand wheel (9) adjacent the driver's seat and acting through worm gearing 7, 6.