GB685757A - Extensible ladders - Google Patents

Abstract

685,757. Ladders. AKTIEBOLAGET WIKSTRAND & BERG WIBE. March 3, 1949 [Dec. 13, 1948], No. 5869/49. [A Specification was laid open to inspection under Sect. 91 of the Acts, Sept. 5, 1949.] Class 20(ii) A latch for an extensible ladder comprises a hooking arm 2 mounted on one ladder unit and held by a spring 15 in the operative position as shown in the Figure so as to be engageable with the rungs of the next lower ladder unit and a stronger spring 11 adapted when tensioned to hold the arm 2 inoperative by overpowering the spring 15. When the upper ladder unit is raised the arm 2 and a feeler 3 having a return spring 12 are pressed in against their return springs by each rung of the lower unit and the upper unit is held in the required position by engaging the arm 2 with a lower unit rung, whereupon the feeler 3 is turned anti-clockwise and carries with it by means of catches 8, 9 a member 4 pivoted on the same axle 6, and which tensions the spring 11 and also moves the lower end of the spring past the dead centre position of the spring and the member 4 so that when the arm 2 is disengaged from the rung it will be moved to inoperative position by the spring 11 and allow the extension ladder to be lowered, the feeler 3 returning to initial position and clicking over the rungs. If now the upper unit is raised the feeler 3 will be turned clockwise by a rung and return, by means of a pin 10, the member 4 past the dead centre position and release the spring 11.