Patent GB-1080034-A (GB)
Title: Braking mechanism
IPC: F16D63/00
Filed: 1966-04-15
Abstract: 1,080,034. Inertia brakes. INTERNATIONAL BUSINESS MACHINES CORPORATION. April 15, 1966 [April 19, 1965], No. 16551/66. Heading F2E. Braking mechanism for a rotating member, such as a drive shaft for a tape reel of a magnetic tape storage device of a computer, comprises a planetary gear system including a sun-wheel 40 the hub 30 of which is driven through a bidirectional overriding clutch from the drive shaft 8, planet wheels 42 journalled on pins 48 carried between plates 44, 46 which are freely rotatable on the hub 30 and possess substantial inertia, means for selectively locking the plates 44, 46 to the hub, and inertia arms 50 associated with the planet wheels, the arrangement being such that when the plates 44, 46 are unlocked from the hub the arms 50 act in opposition to the torque of the drive shaft to stop the shaft (the drive to the shaft being simultaneously discontinued, e.g. by switching off the driving motor). Owing to the overriding clutch, once the drive shaft has been stopped it is uncoupled from the brake mechanism, since the hub 30, together with the planetary gear system, continues to free-wheel until either it is stopped by other brake means (not shown) the drive to the drive shaft 8 is re-started in either direction. Each of the arms 50 is secured to one of the planet wheels for rotation with the latter between two different retracted positions (the one shown in Fig. 1 and a reverse-orientated position, Fig. 3, not shown), passing through an intermediate position (Fig. 2, not shown) in which the arms are extended radially. The arms are locked in each of the retracted positions by a latching arm 70 co-operating with a recess 72 in a ring 60 secured to the hub 30, the latching arm being integral with another arm 74 forming a lever which is pivoted between brackets carried by plate 46. Thus, when arm 74 is engaged and moved by a suitable trip, a roller carried by the arm 70 is lifted out of recess 72 against the action of a spring 61. allowing arms 50 to fly out by centrifugal force and, owing to the inertia of the plates 44, 46, exert an opposing torque on the shaft 8 to stop the latter. The over-riding clutch, which at this time automatically uncouples the shaft from the hub, comprises rollers 12 co-operating with the interior of hub 30 and with flats on a block 10 shrunk on the shaft 8, so that freewheeling of the planetary gear and hub takes place except when the shaft 8 is driven in either direction, whereupon the rollers wedge themselves between the flats on the block 10 and the interior surface of the hub 30. Ball-bearings 20, 22 rotatably support the hub 30 on a fixed support 16 to enable freewheeling of the planetary gear independently of the shaft 8. The hub is retained against axial movement by a set screw (not shown) engaging a spacer 28 held between the ball-bearings 20, 22. When the shaft commences to be driven in the desired direction the planet gears are rotated by the sun-wheel in the appropriate direction so as to automatically retract the arms 50 into the correct one of their two possible retracted positions to enable them to subsequently stop the shaft 8 when released, the roller on the arm 70 entering the recess 72 to lock the arms 50 as soon as they are retracted, and before centrifugal force can act to swing them out again.