Patent GB-1164155-A (GB)
Title: Support Device, in particular for the Stepless Vertical Adjustment of Table Tops and Chairs
IPC: A47C3/30
Filed: 1966-08-31
Abstract: 1164155 Adjustable support device FICHTEL & SACHS A G 31 Aug 1966 [ 28 March 1966] 38786/66 Index F2S 31 [Also in Divisions A4 and F2] An adjustable resiliently compressible support device, Fig. 1, comprising a cylinder 1 with fixed ends and a piston 3 sealed to the internal walls of the cylinder with a piston rod 2 attached to the piston 3 passing through end 5 and sealed thereto. The device is charged with compressed gas and communication between upper and lower chambers of the cylinder can be established by depressing a rod 7 to open a valve 9. The device then extends under the action of the gas expanding or can be forced to retract by pressure applied to the rod 2. Release of the rod 7 closes the valve 9 under the action of spring 12 and locks the device. The size of the upper and lower chambers may be extended by annular reservoirs surrounding the cylinder, Fig.13 (not shown). The valve may be actuated in a number of ways, such as electrically, pneumatically or hydraulically, Figs.3 and 4 (not shown), or electrothermally. Fig.5 shows a modification wherein a piston 23 is provided with channels 24, 25 and a flexible diaphragm 26. When operating handle 30 is depressed against the action of spring 31 a space 27 is formed under the diaphragm 26 connecting channels 24, 25 as shown in the left-hand-side of the figure. In its rest position, right-hand-side of the figure, the spring 31 causes the diaphragm 26 to interrupt the channels 24, 25 thus locking the device. Fig.6a shows a modification in which valve means are closed automatically if the relative speed between piston 32 and housing 43 is higher or lower than a predetermined speed. For this purpose the piston 32 is axially displaceable on piston-rod 33 between two limit stops 34, 35. Rod 33 has an oblique bore 36. A spring 40 provided which, in the relaxed condition, forces the piston 32 against the stop 34, in which position bore 36 bridges a gasket 38. As shown the piston 32 is in the closed position, bore 36 ending in axial duct 37 in front of the gasket 38. When the piston-rod is pushed in (i.e. down as shown) the bore 36 bridges the gasket 38, spring 40 tends to maintain this condition. As a result the piston 32 will remain in its opened position even if the rod 33 is moved slowly outwards from housing 43. If the outward speed increases a pressure differential is created, depending on the selected setting of the flow cross-section in piston 32, this pressure works against the spring 40 and locks the device. Fig.7 (not shown) illustrates a modification with similar action. Fig.8 shows an embodiment with a self-locking piston which can lock in both directions. Piston 53 has an axial bore 54 which can be closed by a gasket 55. Piston-rod 56 has an annular groove 57 which, in the open position shown, bridges the gasket 55. The piston 53 is mounted axially displaceable between two springs 60, 61 on piston-rod 56 between two stops 58, 59. If the movement is, slow, piston 53 is open for both directions of movement otherwise the pressure differential, in either direction, will lock the device. As shown, applied to an adjustable chair support, the chair will remain at its pre-selected height when the person rises or sits at the normal speed. However, if he sits down deliberately slowly, the chair will become lower. If he rises particularly slowly, the chair seat will also be raised. The total amount of charge in the working space in the cylinder, above and below the piston and including any reservoirs connected thereto, is constant. The charge may be liquid, the piston-rod protruding from both ends of the cylinder and having different diameters at each end (not shown).