GB506792A - Improvements in and relating to extending and raising gear for ladders, telescopic masts, extensible platforms and the like - Google Patents

Abstract

506,792. Winding and paying - out apparatus. HUMBOLDT - DEUTZMOTOREN AKT.-GES. Nov. 29, 1937, No. 32967. Convention date, Nov. 28, 1936. [Class 78 (v)] [Also in Groups XXI and XXIV] The. winding-drum of a ladder, telescopic mast, or the like is driven through epicyclic gearing controlled by a fluid pump, the speed of rotation of the drum being determined by the setting of a throttling device which controls the resistance of the pump circuit. Overload on the drum is effective to open a fluid actuated clutch, between the epicyclic gear and the prime mover. A motor 1 is connected by a clutch 2, 3, controlled by a pressure cylinder 21 to a worm gear 4, 5 which drives the sun wheel 7 of the epicyclic gear, the second sun wheel 10 of which is connected by a shaft 11 to a gear pump 13. The planet wheels 8, 9 are mounted in the rope drum 12. The pump 13, Fig. 3, includes pressure and suction valves 15, 16 connected by links 14, 34, 35 and adapted to be operated in unison by a rod 36. Pressure fluid for actuating the clutch 2, 3 can be supplied to the cylinder 21 by a pump 20 by way of a pipe 37, valve 17, passage 40 in the valve 15, and pipe 31. The valve 17 has a lever 18 stressed by a spring 19 but held in the position shown by the rod 42 of a piston 45. The latter is exposed to the pressure side of the pump 13 and is biassed to the position shown by a spring 44, the tension of which is controlled by a cam 23 carried by the valve 16. The cam is such that movement of the valve in a direction corresponding to the driving of the drum 12 is effective to increase the tension of the spring 44. To start the apparatus, the link 35 is moved to the position a, Fig. 3. This connects the passage 40 to the pipe 31, so that the clutch 2, 3 is closed and the wheel 7 is driven. The circuit resistance of the pump 13 is low, so that the wheels 8, 9 drive the wheel 10 without rotating the drum 12. As the link 35 is moved progressively towards position d, the valve 15 is progressively closed, the circuit resistance of pump 13 rises, and the drum 12 is driven up to a maximum speed at the position d. If the drum is overloaded, as by the ladder striking an obstruction, the drum is locked, the wheel 10 and pump 13 are then driven at a higher speed, and the pump pressure acts on piston 45 to release lever 18. The valve 17 then connects the pipe 31 to the pump casing, so that the clutch 2, 3 opens. Simultaneously, the valves 15, 16 are returned to starting position through rods 48, 36, so that the ladder can descend under the braking action of the reverselydriven pump 13 and the worm gearing. For lowering the ladder, the link 35 is moved to the positions a<1>-d<1>. In a modification, the clutch 2, 3 and worm gearing 4, 5 are replaced by a combined clutch and brake mechanism controlled by the cylinder 21.