GB399347A - Improvements in or relating to shutters, doors and the like - Google Patents

Abstract

399,347. Brakes. MILNERS' SAFE CO., Ltd., 12, Newgate Street, London, and JACKSON, J. F., Phoenix Safe Works, Liverpool. Dec. 16, 1932, No. 35675. [Class 103 (i).] In hand-operating gear for doors or shutters which tend to close under their own weight, a brake is arranged to oppose downward movement of the door under normal conditions, but means are also provided whereby the brake may be released, for example in case of fire, to allow the door to close by its own weight, the brake being reapplied, to restore normal operating conditions, after an interval of time sufficient for the closing of the door. The door is operated by gearing from a vertical shaft 18 which is connected by bevel gears to a handoperated horizontal shaft 21 ; the shaft 18 carries a governor 30 which restrains the speed of motion by friction means. A brake drum 32, freely mounted on the shaft 21 and connected thereto by pawls and ratchet gear 35 to rotate when the door is descending, is normally engaged by a brake shoe 40 carried on a pivoted lever 37, which is connected at one end to a sliding bar 36. The operation of the release means, which may be a fusible link or equivalent device, allows the bar 36 to fall under its own weight, and thus release the brake 40. The initial movement of the bar 36 also carries a lug 53 on it clear of an arm 63 on a governor 57, which is thus released to rotate under the action of a torsion spring 56, kept normally wound up. The consequent movement of the governor arms forces down a sleeve 61 into contact with a plate on the end of a lever 50 connected to the bar 36; the downward movement of the bar 36 is thus arrested until the spring 56 is unwound and the governor ceases to rotate, the period of motion of the governor being sufficient to allow the door to close. The bar 36 can then complete its downward movement, bringing a second brake shoe 39, on another pivoted lever connected to the bar 36, into contact with the brake drum 32 to resist the falling tendency of the door when it is subsequently opened. The governor gear for obtaining the requisite time interval between the release of brake shoe 40 and the application of shoe 39 may be replaced by a dashpot connected to lever 37, an additional weight being provided to overcome the resistance of the dashpot.