Patent GB-987229-A (GB)
Title: Industrial brake
IPC: F16D49/16
Filed: 1961-05-21
Abstract: 987,229. External shoe drum brakes. P. TROMBETTA. May 12, 1961 [June 8, 1960], No. 17461/61. Heading F2E. A brake for winding apparatus comprises external shoes 12, 13 acting on a drum 11, the shoes being carried by respective levers 16, 17 pivoted at 19, 20 to a base 18, and applying and releasing mechanism including a floating linkage which consists of a bell crank 30, 30a pivoted at 22 on the lever 16 and a link 34 connecting the arm 30a of the bell crank to the lever 17, the arm 30 of the bell crank being acted on in opposite directions by spring means and by power means. The construction is such that the 'floating linkage can be assembled in two ways either a shown in Fig. 3 or with the bell crank inverted, Fig. 6, and with the link 34 connected lower down on the lever 17, so that the brake is convertible from a spring-applied, power-released brake to a power-applied, spring- released brake and vice-versa by changing the arrangement of the bell crank and link. A spring-applied, power-released brake is shown in Fig. 3, power-release being effected by a solenoid 60 having an armature 61 connected by a link to the arm 30 of the bell crank. Energization of the solenoid pulls down the arm 30 against the action of an applying spring 54, arranged in a cylinder 41 which is mounted by a recess 56 in its base co-operating with the head of a rivet 55 on the base 18. The upper end of the spring bears against a disc 48 which is provided with a threaded aperture to engage a screwthreaded rod 46 extending out from the cylinder to engage the arm 30. Pin 49 secured to the disc 48 extends into diametrically opposite vertical slots in the cylinder to prevent rotation of the disc, and the upper end of rod 46 is formed as a nut for engagement by a spanner to effect manual adjustment of spring compression. A rebound stop is provided which cushions return of the armature 61 when the solenoid is deenergized, the stop consisting of alternate layers of leather and metal plates 73 secured to a support 70 and engaging a bumper 75 on the link 64. Each of the levers 16, 17 is a hollow casting arranged to provide a bifurcated lower portion for pivotal attachment to the base 18 and provided with a part-spherical recess 26 in which a hemispherical projection on the respective brake shoe is received and is retained by a bolt 28 and locked nuts 29 so as to allow universal swivelling of the shoe to conform with the drum surface. The upper end of lever 16 is bifurcated to receive the bell crank 30, 30a which is of channel form. The link 34 includes a screw-threaded rod portion 34a received within an aperture 37 in the lever 17 and having locked nuts 38 adjustable to compensate for wear of the brake linings 14 on the shoes. Another aperture lower down the lever 17 allows of the alternative arrangement shown in Fig. 6 in which-the bell crank is inverted but the arrangement of the solenoid 60 and spring unit is as before, excepting that the rebound stop for the armature 61 is omitted. As shown in Fig. 4 two solenoids 81, 82 may be used in place of a single solenoid, each having a pair of brackets 94, 95, respectively, to which the armature 85 or 86 may be locked by a pin 98, so that a lever 89 pivotally connected at its ends to the respective armatures may be arranged to pivot about one or the other end whereby one solenoid may be used normally to act via the lever 89 and a link 88 on the arm 30 with the other solenoid merely acting as a spare, failure of the solenoid in use then merely necessitating a reposition of the pin 98 to lock the armature of the damaged solenoid and free the armature of the spare solenoid which is then wired into the circuit so that the brake can be put back into service quickly. In the embodiment of Fig. 8 fluid pressure power means is used, the brake being applied by a spring 120 arranged in a cylinder 107 to act downwardly on a piston 112 while either compressed air or hydraulic fluid is supplied to the cylinder below the piston for releasing the brake.' The piston 112 is connected to the arm 30 of the bell crank by a rod 113 including a bumper 129 for engagement with a rebound stop as in the first embodiment, and a threaded adjuster 114 is provided for varying the spring compression. U.S.A. Specification 2,693,886 is referred to.