Patent GB-190719244-A (GB)
Title: Power Storage and Safety Device for Elevators or Lifts.
Inventor: GROOM WALLACE PRATT
Filed: 1907-08-27
Granted: 1908-03-19
Abstract: 19,244. Groom, W. P. Aug. 31, 1906, [date applied for under Patents Act, 1901]. Lifts.-In an arrangement for balancing and regulating the speed of descent of a lift; the cage is connected by a cable other than the hoisting- cable to a piston 27 moving in a hollow cylinder 22. The cylinder may be caused to act as an aircompressor to store air under various pressures which may be employed to assist the ascent of the cage. A sheave 35 is preferably mounted at the head of the piston-rod 33, round which the secondary cable 36 passes, this cable being anchored at one end to a fixed point 39 and at the other end passing round sheaves 38, 37 to the lift cage. In the simplest form, restricted outlets are provided at each end of the cylinder. In the arrangement shown in Fig. 1, the cylinder has an opening 23 at the lower.end and an inlet valve 24 at the upper end. High, intermediate, and low-pressure reservoirs 40, 41, 42 are provided for storing the air under pressure, these reservoirs being connected by pipes 49, 50 having safety-valves 51, 52. The lowpressure reservoir is provided with a safety-valve 53. The upper end of the cylinder 22 is connected to the reservoir 40 by a pipe 43, in which is interposed a coil 46 or a length of pipe doubled on itself so as to retard the passage of air from the cylinder. The reservoirs 41, 42 may be connected to a pipe 47 leading to the upper end of the cylinder 22 by a three-way valve 55, the spindle of which is provided with sheaves 65, 66, round one of which is passed a cord connected to a weight 68 for restoring the valve to its normal position ; round the other sheave passes an operating-cord 69 extending the length of the well. The cord 69 is either operated directly from the cage or by a second cord, shown in dotted lines in Fig. 7, passing round a sheave 80 and serving to swing aside an arm 76 carrying sheaves 77, 78 for deflecting the cord 69. The valve 55 is employed for admitting air under pressure from either of the reservoirs 41, 42 to the upper end of the cylinder 22 so as to serve as a check to the cage when descending and to impart extra power thereto when ascending. A self-closing valve 83 in a pipe 82 may also be automatically operated when desired by the cage on reaching the upper limit of its travel in order to admit air from the reservoir 41 above the piston. This valve is connected by a cord 84 to a bell-crank 86 linked to a swinging bar 89 which may be engaged by an adjustable tappet 90 on the cage. The main hoisting-cable 21 is fastened to a plunger 95, Fig. 9, moving in a box 97, between which and the top of the cage a spring 96 is interposed. The plunger 95 is connected by a rod 98 to one arm of a lever 99, the other arm of which is linked to an indicator 100, having a projection 102 adapted to ring a bell 104 when the tension in the cable 21 diminishes below a certain amount. Should the hoisting-cable 21 break, the fall of the cage is arrested by the air in the cylinder, and the descent can be controlled by operating the valve 55 by band. The Specification in the original form as published under the Act of 1901 comprises also,the use of diaphragm regulators or ball and socket valves to control the cylinder outlets when no reservoirs are employed. A modification of the main apparatus is also described in which the cylinder is closed at both ends so as to utilize also the tendency to vacuum and the inlet and outlet exchange offices on reversal of the piston. The spring 96 is of leaf form and the plunger 95 is connected by suitable means to the cord passing round the pulley 80 so that the operation of the valve 55 may take place automatically as the tension in the hoisting-cable 21 diminishes. The piston is cushioned at the lower end by a downward extension below the valve, and at the upper end by a short supplemental cylinder containing a piston fitting closely and loosely on the rod 33 and having check valves so that, should the car run over slightly in its descent, the piston is cushioned by catching up the supplementary piston which compresses the air in the extension of the cylinder. If this air be released by a cock, the run of the cage may be extended lower, for example into a basement. This subject-matter does not appear in the Complete Specification as accepted.