Intermittent motion device

摘要

1,130,408. Friction clutches and brakes; clutch-brake combinations; control. P. G. FORET, Inc. 11 Oct., 1966 [20 Oct., 1965], No. 45423/66. Headings F2C, F2E, F2F and F2L. A clutch, brake, or clutch-brake, for recording tape winders, tape transports, textile machinery, copying machines, machine tool positioning, and indexing, comprises a thin, flexible, flat, metal (e.g. aluminium) disc 19 fixed on a rotatable but axially immovable shaft, and having a peripheral marginal edge normally spaced from and engageable with a hard silicon rubber friction ring 28 on an adjacent wall, the disc and the wall defining a chamber 27 from which, under the control of a valve 14, air may be evacuated at a faster rate than air can enter between the disc and friction ring, for resilient flexing of the disc into clutching or braking engagement with the friction ring. In the clutch-brake shown, a rotatable shaft 11 is mounted within a stationary housing (12) and a driving flywheel 13 belt-driven from a motor. Brake and clutch discs 19, 19a are engageable with friction rings 28, 28a respectively provided on the housing and the flywheel. Chambers 27, 27a bounded by the discs 19, 19a and the housing and the flywheel, respectively, form brake and clutch vacuum-energized servomotors. The gaps between the discs 19, 19a and the friction rings 28, 28a provide for cooling air flow. The servomotors 27, 27a are in communication respectively directly, and through a bore 30 in the flywheel, with ports 29 opening, via notches 46 in rings 44, into brake and clutch valves 14, 14a mounted in the housing. Each valve comprises a valve chamber 41 provided with the servomotor-connected port 29, a vacuum source-connected port 43, and a vent port 37; a coil and core 35, 36 forming an electromagnet surrounding said vent port 37; and an iron or steel freely-floating armature disc 42 which is movable by energization of said electromagnet from a venting position in which it closes, and is held by vacuum at, the port 43 and establishes communication between the ports 29, 37, to a servo-energizing position in which closes the vent port and establishes communication between the ports 29, 43. The vacuum force acting on the disc 42 may be preselected by determining the effective opening area of the port 43 by means of the ring 44. The disc 42 may be frusto-conical to maximize magnetic flux. A passageway 16 in the housing permits lubrication of the shaft bearings and aids heat dissipation. A hard rubber lipped ring seal 25 is provided between the housing and the flywheel. Shaft bearings 24, 26 of porous bronze provide additional air sealing. Separate manually actuated switches may be used for the valves, but preferably a conventional switch simultaneously energizes the brake valve 14 and de-energizes the clutch valve 14a and vice versa. In Fig. 4 (not shown), a single valve and disc arrangement is provided for braking a loaded freely rotatable shaft.