| 摘要 |
527,144. Loft ladders. LOFT LADDERS, Ltd., BERNER, C. A. O., and GORHAM, P. H. March 31, 1939, No. 10172. [Class 20 (ii)] A loft ladder is formed as an extension ladder in two sliding sections, one section being secured to the loft door or floor, while the other section is moved on it by means of a cable, and counterbalancing means is provided between the sections. Each ladder section comprises a main part and an offset part with a clamp 5 between the parts to prevent rattling, as described in Specification 364,186. The lower section 2 is retained in its two extreme positions on the upper section 1 by a spring catch 6 which can be released to allow relative movement between the sections by a handle 8 from below or by a cord 9 from above. The upper section is provided with a spring shaft 13 and side drums 14 on which the cords 17 attached to the lower ladder section at each side are wound as the lower ladder section is raised, the spring being tautened as the lower ladder section is pulled downwardly, so that this section is counterbalanced. The shaft is provided with a handle 15 whereby it may rotate to raise the lower ladder section. The operating cords 17 are interconnected by a tension compensating gear comprising pivoted blocks 18 and a pivoted cross-bar 20. The ladder and trap door may also be provided with counterbalancing means as described in Specifications 453,968 and 453,969. |
