GB326556A - Improvements in or relating to ratchet mechanism - Google Patents

Abstract

326,556. Beeston, J. P., and Pawsey, G. Jan. 30, 1929. Jacks.-Ratchet-and-pawl mechanism for lifting and lowering loads, applicable to lifting-jacks and winches &c., comprises a ratchet wheel 13, or an arcuate or straight rack, a holding pawl or detent 14 on a fixed pivot 15, and an operating pawl 18 carried by a lever 17 fulcrummed at 16 eccentrically to the ratchet wheel, both the detent and the operating pawl being connected by rods 20, 23 to spring controlling means located at the outer or free end of the lever and adjustable to two positions, (1) for lifting, in which both pawls are resiliently pressed into engagement, and (2) for lowering, in which the pawls tend to disengage, but, as the lever is rocked, are brought alternately into engagement at opposite ends of the stroke, being retained in engagement by the pressure of the teeth. In the form shown in Fig. 1, the connecting rods 20, 23, supported intermediately by pins 26, 26<a>, are coupled at their outer ends, through pivoted links 28, 31, to springs, such as 30, carried by a stay 34 pivoted on the lever 17. In the postion shown, the springs tend to retain the pawls in engagement for lifting. When, for lowering, the stay is rocked to the postion 37 indicated in broken lines, the springs tend to draw the pawls out of engagement, but the action thereof is limited by engagement of notches 32, 33 in the links 28, 31 with a stop 38 on the lever. Thus, when the lever is rocked, the pawl 18 engages the ratchet wheel at the lower end of the stroke, the detent 14 being held out of action, whilst at the upper end of the stroke the detent is brought into engagement, and as soon as it takes the load the pawl 18 is drawn out of action, descent of the load being thereby controlled. If the stroke is continued after the pawl or detent engages, the parts yield thereto without damage. The parts may be so proportioned that, when descent of a load has been started, the pressure on the pawls may cause the lever to rock and at the same time control the rate of descent in the manner of an escapement. In the form shown in Fig. 2, the outer attachments 39 of the springs 30 are fixed whilst the stop 38 is replaced by a lever 40 adjustable in a slot 42 by means of a link 41 and lever 43, the setting for lifting being shown in full lines. Specification 313,660 is referred to.