GB1424730A - Overrun brake - Google Patents

Abstract

1424730 Winch brakes C H ARNOLD 30 May 1973 25811/73 Heading B8B [Also in Division F2] A power-driven hoist shaft 2 rotatable against a load is braked to hold the load if the power is removed; the braking is accomplished by a disc brake assembly which is energized by the action of interengaging cam members 10, 15 adapted for relative axial and circumferential movement one of which members, 15, is formed with camming surfaces which act to give relative axial movement increasing as a function of the relative circumferential movement as such circumferential movement increases to thereby give braking adjusted to the value of the load. As shown in Fig. 1 the cam member 15 is secured to and moves with the shaft 2 and the cam member 10 is secured to a brake disc 8 adapted to engage a brake plate 7. A brake disc 4 secured to shaft 2 is adapted to engage a brake plate 6 and the brake plates 6, 7 are urged apart by springs 12. Rotation of the plates 6, 7 is prevented by studs 13 which also permit movement of the plates 6, 7 toward and away from each other. The shaft 2 is driven by a driving member 18 secured to a driven pulley 16; the driving member 18 drives the cam member 15 counterclockwise (as seen in Fig. 6) to hoist the load via lugs 26 on the cam member 15 whilst radially aligned lugs 25 on cam member 10 act to prevent any axial force being exerted by the cam members 10, 15. In clockwise rotation to lower the load the driving member 18 drives the lugs 25. The cam member 15 has three camming surfaces 30, 31, 32 co-operable with complementary surfaces 33, 34, 35 on cam member 10, and radially outwardly of surfaces 30, 31, 32 the cam member 15 has camming surfaces 38, 39, 40 co-operable with complementary camming surfaces 41, 42, 43 on cam member 10, and at a greater angle to a plane perpendicular to the shaft axis than surfaces 30, 31, 32. Should power to the shaft 2 be removed, lugs 26 rotate with cam member 15 in a clockwise direction (Fig. 6) so that the inner camming surfaces first engage and subsequently the outer camming surfaces engage to thereby give a braking force dependent on the load, disc 8 engaging plate 7 and plate 6 engaging disc 4. In the embodiment of Fig. 4 a cam member 50 attached to brake disc 8 has three rollers 56, 57, 58 co-operable with camming surfaces 53, 54, 55 on cam member 51 secured to shaft 2. Camming surfaces 53, 54, 55 increase in slope as relative rotation between the members 50, 51 increases. Fig. 4 also incorporates wear adjusting means to adjust the positions of brake plates 6, 7 to compensate for wear of elements 5, 9 of discs 4, 8. Fig. 15 illustrates a multiple disc brake with brake plates 6, 7 and interposed friction discs 93. Cam members 91, 92 are provided which allow the load to be driven in either direction. The arrangement of lugs on the cam members 91, 92 in such a bidirectional hoist is illustrated in Figs. 17-19 (not shown). (For Figure see next page.)