GB697569A - Lifting jack - Google Patents

Abstract

697,569. Load-handling appliances; winding and paying-out apparatus. LUNDSTROM, C. M. Sept. 28, 1951. No. 22661/51. Classes 78 (iii) and 78 (v). In a ratchet and pawl operated hoist the operating lever is moved through one arc for raising the load and through a larger arc for lowering the load during which latter movement the driving and holding pawls are each disengaged from one tooth of the ratchet and re-engaged with the succeeding tooth. As shown in Fig. 1, a ratchet wheel 6 is secured to a shaft having a sprocket for a chain 4 and an operating lever 8. To raise the load, the lever is depressed through an arc limited by a pin 18 engaging a slot on the lever. A pawl 13, connected by a toggle link and spring pressed plunger 14 to the lever engages the ratchet and drives it through the distance of one tooth, the load then being held by a pawl 9 secured to the housing by a toggle link and spring pressed plunger 12. To lower the load the movement of the lever is increased by removing the pin 18. The lever is then raised so that the pawl 13 is disengaged from the ratchet by the pin 15 to allow the lever to be depressed without driving, the pawl rides over one tooth then re-engages with the next tooth of the ratchet when the pawl strikes the stop 16. Further depressing of the lever causes a slight raising of the load, the pin 10 on the lever disengages the pawl 9 from the ratchet and holds it out of engagement against the stop 11 to allow lowering of the load under gravity as the lever is raised. The pawl 9 re-engages the succeeding tooth of the ratchet by the action of the pin 10 on the cam of the pawl. The operation is repeated obtaining step-by-step lowering. To free the ratchet from the pawls, the pin 18 is removed and a spring pressed pin 17 is released to hold the pawl 13 disengaged from the ratchet, the lever is then depressed to withdraw the pawl 9.