A device for preventing an object from moving in one direction when such object is in at least one predetermined position

摘要

921,722. Pawl and rack fastenings. HUNTER DOUGLAS INTERNATIONAL CORPORATION. Sept. 5, 1960 [Sept. 4, 1959], No. 30597/60. Class 44. A device for preventing an object from moving in one direction comprises a spring-biased pawl co-operating with a stop member provided with a setting surface for setting the spring in one of two directions to bring the pawl into an operative or an inoperative position. As shown a combined guide and stop member 1 comprises a channel of U-section having in one flange 3 a longitudinal slot 5 in which slides the pin 6 of a pawl 2, the nose 20 of which co-operates with a rack formed by slots 12 in the bottom web 4 of the member 1. A spring 7 has two legs 8, 9 which are at right angles to each other when unloaded. The slot 5 has at top and bottom curved slots 11 which receive the tail 13 of the pawl spring leg 9. As the pawl passes down the slot 5 from the top position shown in Fig. 1a the spring is brought to the loaded position shown in Fig. 1b so that the pawl engages with the rack, preventing the pawl from being moved upward. On reaching the bottom of the slot 5, the tail 13 of the spring leg 9 enters the lower curved slot 11, whereupon the spring is unstressed and the pawl can be moved upward in the inoperative position shown in Fig. 2. As applied to a sun-blind 16, Fig. 4, the guide 1 is attached to the face of a building and a strut 18 is hinged to the pawl pin 6, the pawl being urged upward by a spring 19 which tends to roll up the blind. In a modification (Figs. 3a, 3b, 3c, not shown) the slots 11 are replaced by semi-circular recesses and the rack slot 12 by projecting teeth. In another embodiment (Figs. 6 to 8, not shown) the guide and stop member 1 is formed as a hollow box-shaped member having a longitudinal slot 23 (corresponding to the slot 5) in its outer face, the pawl pin 6 being guided within it on rollers and the slots 11 being replaced by recesses at the sides of the longitudinal slot. In a further embodiment, Fig. 10, the pawl is formed as a hook 28 and its pin 27 is fixed; it co-operates with a stop member 31 forming an extension of a vertically sliding guide member 34 to which is hinged at 37 an arm 38 carrying a sun blind (see Fig. 9, not shown). As shown in Fig. 10, the guide and stop member 31, 34 is prevented from moving downwards but can be moved upwards; if this is done and the member then moved down again, the projection 30 strikes the spring leg 9 and moves the pawl hook 28 clear of the stop member 31 so that the member 31, 34 can continue to move downward (see Figs. 11 to 14, not shown).