Patent GB-190411916-A (GB)
Title: Improvements in Elevator Valve Mechanism.
Inventor: ADAM MATTHEW ATKINSON
Filed: 1904-05-25
Granted: 1905-01-19
Abstract: 11,916. Adam, M. A., [Stokes, W. E. D.]. May 25. Lifts. - Relates to valve gear for hydraulic elevators or lifts, and comprises a pilot valve fitted with means for preventing sudden movement or reversal of the main valve, and a valve and gearing adapted to stop the cage gradually at the limits of its travel or in the event of accident. Fig. 1 shows the valve gearing and the cage, and Fig. 2 a section of the valves. The main valve comprises the pistons 24, 26 controlling the communication between the pressure and exhaust pipes 18, 19 and the pipes 20, 21 connected through the automatic stop valve S to the pipe 22 leading to the ram cylinder. The main valve is moved by means of pressure or exhaust admitted to the outer side of the piston 23 by means of the pilot valve P. This valve comprises the valves proper 31, 35 working in perforated bushes so as to give a graduated opening, and hence a slow movement of the main valve, and the valves 32, 34, which, when the valve is central, are closed to prevent leakage. The lever 16, operated in a usual way from the cage, i; connected to the valve P through a screw-and-nut connection 37, 36. The screwed spindle 37 carries a broad pinion gearing with a rack on the main valve spindle, the arrangement being such that the movement of the main valve always returns the pilot valve to central position. Upon the sp'ndle 37 are fixed helical cams 44, 45, of the same pitch as the screw 37, and so placed that, when the valve is central, they are at a distance equal to the pitch of the screw from similar fixed cams 42, 43 respectively. It results from this construction, that, when the lever 16 is out of its central position, the distance between the respective helical cams is correspondingly reduced, and to such an extent that the lever cannot be returned past its central position until the main valve is also central. Further, in the event of the screw connection 37, 36 becoming deranged, the cams themselves return the pilot valve to central position. The stop valve S comprises two similar valves 63, the right-hand one for stopping the cage at the bottom of its travel and the left-hand one at the top. Each valve is connected to a weighted arm 48, which is normally in its lowest position, the valve then allowing free communication between the pipe 20 or 21 and the pipe 22. A sheave 49 on the arm 48 lies in the bight of a rope 50 having one end secured to the top of the cage and the other to the bottom. The points of attachment are, however, unsymmetrically placed, as shown, the effect of which is that, on the cage nearing the limit of its travel, one end of the rope makes an increasing angle with the vertical, and is therefore paid out less rapidly than the other end is pulled up, so that the arm 48 is raised and the valve 63 gradually closed. Should the rope break, the arm 48 drops, and communication with the pipe 22 is closed by a ring valve 64 on the same spindle as the valve 63. The movement is in this case retarded by the passage of water through small throttling-holes in the lift valve 66.