Patent GB-495742-A (GB)
Title: Improvements in chairs
IPC: A61G15/02
Filed: 1938-01-15
Abstract: 495,742. Adjustable chairs etc.; hydraulic jacks. PIEPER, O. H., and PIEPER, A. F. Jan. 15, 1938, No. 1413. Convention date, Feb. 4, 1937. [Classes 52 (ii) and 52 (iii)] In an adjustable chair of the kind used by dentists, barbers, &c., or in an operating table, the seat or table is raised and lowered by means of fluid working in a cylinder and the mechanism includes means for feeding fluid to the cylinder, a valve controlling the discharge of fluid from the cylinder and means for automatically moving the valve to closed position as the moving part completes a descending movement to its lowest position, the valve being so positioned that when closed it maintains that supply of fluid in the feed to the cylinder which is necessary to ensure correct starting on the next upward movement. A base section 30, Figs. 3 and 4, carries a section 32 which rotates on rollers 34. The section 32 carries a sliding cylindrical section 40 which has at its lower end ears 42, Fig. 4, sliding on guide rods 44, and is also provided with vertical rails engaged by rollers 46, Fig. 3. Within the section 40 is a second tubular section 50 similarly guided by rods 54 and rollers 56. The inner section 50 is raised relatively to the outer section 40 and simultaneously therewith by chains or the like fixed to the base 32 and to the section 50 and passing over pulleys 60 on the section 40. The chair seat 98 or operating table is carried on the inner section 50. Fluid under pressure is admitted to a cylinder 104, Fig. 4, which is connected to the section 40 by brackets 106, through a stand pipe 102 from the upper end of which liquid passes into the part of the cylinder above the packing rings 110. The liquid is supplied by a pump 134, Fig. 3, driven by an electric motor 190 and provided on the outlet side with an air bell 170. The pump and motor are constructed and mounted as described in Specification 1516/38. Liquid flows from the delivery pipe 178 to the standpipe through a non-return valve 182. The motor is controlled by two switches, preferably mercury switches, a main switch 220, Fig. 11, and a second switch 222 which serves to short-circuit a resistance in the lead to the motor. The switches are mounted on pivoted platforms 250, 252, which are spring urged to the position in which the switches are closed. A pedal 266 is mounted below the platforms, and has an upstanding arm 270 which when the pedal is not depressed holds both platforms up and the switches open. Other arms on the pedal 266 carry springs connected to the platforms which tend to pull the platforms down and so close the switches. When the pedal 266 is depressed the switches are thus closed, but the movement of the platform 252 carrying the switch 222 is controlled by a dash-pot 284 so that closing of this switch, which cuts out the starting resistance, is delayed. Lowering of the chair is effected by gravity as fluid is allowed to escape from the cylinder 104, Fig. 3, through a passage 302 into a chamber 304, Fig. 18, the exit from which is controlled by a valve 330 having two conical faces 332, 334 co-operating with seats 312 and 310 respectively, and normally held closed by a spring 336. When the valve is open, fluid passes through the passage 318 to a second valve 402, Fig. 8. The valve 330 is operated both at the will of the operator and automatically in case of excessive elevation of the chair. In the first case, one of a pair of pedals 340, Fig. 3, is depressed and operates a lever 352, Fig. 8, which presses the valve 330 down through the rod 354. In the second case, a lug 360, Fig. 3, carried by the member 40 engages a washer 362 on a rod 364, Fig. 8, and operates the valve 330 through a lever 370. The lug 368 on the lower end of the rod 364 is also arranged to raise the platforms carrying the switches and so stop the motor before the valve 330 is opened. The valve 402 operates to regulate the rate of fluid flow and consequently the rate of descent of the chair. It is normally held open by a spring 406, but its open position is limited by a rod 408 adjustable by a screw 410. This valve also brings the chair to a smooth stop at the lower end of the travel of the member 40, when a lug 416 on the latter makes contact with the valve 402 and shuts the passage gradually.