Patent GB-904718-A (GB)
Title: Elevating means for loading skips
Inventor: SMITH ARTHUR HENRY
IPC: B28C7/08
Filed: 1957-12-03
Abstract: 904,718. Weighing-skips. BENFORD Ltd. Dec. 3, 1958 [Dec. 3, 1957], No. 37565/57. Class 143. [Also in Group XXX] In apparatus, such as a concrete mixer, comprising a skip movable by means of an hydraulic ram between a lowered weighing and loading position and a raised discharging position, shock on the weighing mechanism (hydraulic capsule) during loading and lowering of the skip is damped or avoided by means of a restrictor device 26 connected in the fluid duct 22 of the ram so that it operates to damp or retard the movement of the skip when near the weighing position and is automatically inoperative when the ram piston-rod 23 raises the skip a predetermined distance from the loading position. As shown in Fig. 2, the hydraulic fluid enters the ram cylinder through a duct 22 provided by a tube 33 fixed within the outer end of the hollow piston-rod 23 and continued by a separate tube 28 extending through the piston 24. The tube 28 is slidable axially within a bore in the piston 24 and is spaced from the tube 33 by a compression spring 30. The tube 28 carries the restrictor device 26 spigoted in its end and housed, in the lowered position of the ram, within an enlargement 25 of the piston bore, the restrictor device having an axial bore controlled by a non-return ball valve 36, and intersecting bores 37. In operation, with the skip in its loading position, fluid is supplied through the tube 33, piston-rod 23 and tube 28, past the ball valve 36 into the cylinder chamber 39, thereby raising the piston 24 which initially slides over the tube 28 so that a slot 40 in the wall thereof eventually emerges clear of the piston bore and provides for increased flow of the fluid. Thereafter, with the compression of spring 30 relieved, the tube 28 and its restrictor device 26 move with the piston-rod. On descent of the skip, the hydraulic fluid is initially evacuated through the slot 40 into duct 22, the ball valve 36 now being in its closed position. When the restrictor device 26 is stopped by the end wall 41 of the cylinder, the piston 24 telescopes over the now stationary tube 28 and encloses the slot 40 so that the passage of the escaping fluid is restricted to the narrow clearance between the tube 28 and the piston bore for the latter portion of the skip's descent. Fig. 4 shows an alternative arrangement wherein the restrictor device comprises a cylindrical plug 44 pinned at one end to the cylinder end wall and tapering at its other end 48 to a spigot 49 carrying a guide tube 50 extending within the hollow piston-rod 23. In the lowered position of the ram the cylindrical plug 44 is received within the central bore of a bush 58 in the piston 24. The bush 58 has two axial, bores 51, 54 radially outwardly of the plug receiving central bore and communicating therewith adjacent the tapered portion 48 of the plug, the bore 54 having a non-return ball valve 56 and the bore 51 having a restricting member 52. For raising the skip the hydraulic fluid passes into the cylinder chamber 39 initially via bore 54 until the piston clears the plug 44. During descent of the skip, when the piston telescopes over the plug 44, the fluid escape is restricted to the orifice 53 in the member 52 of bore 51. Specification 837,043 is referred to.