Patent GB-364536-A (GB)
Title: Improvements in or relating to friction devices such as brakes and clutches
IPC: F16D65/14
Filed: 1930-08-26
Abstract: 364,536. Band brakes. PUGH, J. V., Meriden House, Meriden, Warwickshire. Aug. 26, 1930, No. 25472. [Class 103 (i).] A flexible brake band formed of one or more parts is supported on friction links which permit movement of the band through a predetermined clearance plus any further movement necessitated by wear of the friction surfaces and means compensating for variations in the position of the brake band to maintain a constant release position of the brake-operating lever. The two halves of the band 3 are connected by a plurality of links 9 to a central disc 13. The connection 10 between the links 9 and the brake band is provided with a small clearance to allow of brake application any further movement necessitated by wear is allowed by the slotted connections 16 between the links 9 and the disc 13, a spring on a rivet 15 frictionally preventing return movement. The band, at one pair of adjacent ends, is cut away as shown in Fig. 3 and each end is engaged by a pin 33 on an actuating member 19 pivoted centrally of the band and about an axis at right-angles to it and actuated by a lever 26. The band 3 is accommodated in a triangle 5 supported on a disc 6 positioned within the brake drum. A spring 28 returns the actuating means and the parts of the band 3 through the clearance at the points 10 and presses these parts against the links 9. If these have been moved out on brake application the ends of the parts of the band opposite the applying means separate and this movement is taken up by wedge-like anchoring means. These means may comprise a plate 39, 65 having a slot 41 guided on a fixed pin 42 and engaging pins 46, 47 on the ends of the parts of the bands by means of inclined slots 44, 45. A spring 43 tends to draw the plate 39 across the band tending to separate the ends of the parts' of the band. In an alternative arrangement a spring-drawn wedge arranged between the two ends tends to force them apart and the ends are connected by links to a lever pivoted on a pin passing through the trough 5. In a further arrangement pins 44, Fig. 7,.on the ends of'the band are engaged by opposed helical slots 46 in a barrel-shaped member 48 rotatably mounted on and projecting through the trough 5. A coiled spring 53 tends to rotate the member 48. In a modification of the invention the band is provided with pairs of lugs 61, Fig. 8, each pair supporting between them three parallel, circumferentially arranged links 62 by rivets 63 having a clearance to permit of application of the band to the brake drum. The lugs are bifurcated to separate the links. Between the members of each set of three parallel links 62 are arranged friction members 68 on a fixed pin 66, held in engagement with the links by a spring on the pin. On wear occurring the links 62 will also be moved on brake application and maintained in the new position by the friction members. The links 62 vary in size to allow of unequal movement of the band.. The band may be anchored at one end. A spring 601 attached to the ends of the band maintains it contracted. The band may be operated by a pair of levers giving unequal movement of the ends of the band. One-way clutch or ratchet mechanism is associated with the levers to maintain a constant release position of the brake lever. In an arrangement in which two halves of a band are mounted on radial links 77, Fig. 11, having a predetermined clearance at the rivets 74 and friction abutment means at the spring bolt connections 80 to a plate 76, the anchorage means which take up slack comprise cams 94 engaging the flat sides 93 of apertures in lever arms 89 fitted to the adjacent ends of the brake band and pivoted by means of slots on pins 90. Spiral springs on the shafts of the cams tend to turn the cams to move the lever's 89, owing to the shape of the cams, through equal angles and move the ends of the band away from one another. The slope.of the cams is such that the pressure of the levers will not produce reverse movement. The band is operated by a cam 84 between the opposite adjacent ends which are turned over at 85, and are drawn together by a spring 83 between the adjacent links of opposite halves of the band. The band is also released by radially arranged springs 81 connected to the bolts 75 supporting the plate 76. The cam 84 may mount between two lever arms 97, Fig. 14, attached to the ends of the band and engaging pivots 98 by means of slats 99. An alternative anchorage means which compensates for wear to maintain a constant release position of the operating- lever comprises two levers 103, .Fig. 15, attached to adjacent ends of the bands and pivoted at 102 and having a spring-drawn distance-piece 104 drawn by a spring between curved surfaces on the levers. The invention may also be applied to clutches. The Provisional Specification describes an external band and also a band made in four pieces having two adjustment stops and two operating levers articulated together, also cone and disc brakes are referred to. Eccentrics and wedges in duplicate for taking up movement at the anchorage-are referred to.