GB1045917A - Hydraulic lift truck - Google Patents

Abstract

1,045,917. Masted lift trucks. EATON YALE & TOWNE Inc. Sept. 18, 1963 [Oct. 2, 1962], No. 36704/63. Heading B8H. A lift truck T comprises primary uprights 11 secured to the truck, secondary uprights 12 sliding on the primary uprights 11 and tertiary uprights 13 sliding on the secondary uprights 12 with a load carriage 14 sliding on the tertiary uprights 13. A lift ram 10 has an outer cylinder 15 mounted on the secondary uprights 12 at 18 with an outer telescoping tubular piston 16 slidably mounted in the cylinder 15 and an inner telescoping tubular piston 17 slidably mounted in the piston 16, a pair of sheaves 19 being mounted on the outer end of the piston 17. A pair of lift chains 20 is secured at one end to the carriage 14, extend over the sheaves 19 and over a pair of sheaves 21 secured to the secondary uprights 12 adjacent the lower ends and are secured at the opposite ends to the top of the primary uprights 11. When the ram 10 is actuated, pistons 16, 17 extend together relative to the cylinder 15 and the carriage 14 moves to the top of the upright 13, the uprights 12, 13 remaining collapsed. Continued actuation of the ram 10 then fully extends the uprights (Fig. 2). In order to reduce the difference in lifting speeds provided by the piston 16 and the piston 17 the outer diameter d of the piston 17 is made substantially equal to the outer diameter D of the first piston 16 so that the difference in effective areas of the two pistons 16, 17 (represented by the diameters d, D) is made very small. The piston 16 has a guide member 31 with a stop surface 31a cooperating with a stop surface 24a. The piston 17 has a guide member 40 with a stop surface 51 internal to the piston 17 which co-operates with a stop surface 50 attached to a tubular member 46 carrying an annular member 48 providing a stop surface 52 engaging a shoulder 53 on the guide member 31. Thus, when the piston 17 is extended relatively to the piston 16, stop surfaces 50, 51 engage and stop surfaces 52, 53 engage to limit extension of the second piston 17 relatively to the first piston 16. Fluid seals 27 and 36 are provided, unsealed surfaces being sufficiently rough to allow passage of pressure fluid.