Patent GB-1056379-A (GB)
Title: Instrument tables
IPC: A61G15/14
Filed: 1965-09-07
Abstract: 1,056,379. Dental instrument tables. EMDA FABRIK ELEKTRO - MEDIZINISCHER UND DENTALER APPARATE GEORG HARTMANN. Sept. 7, 1965 [Sept. 7, 1964], No. 38274/65. Heading A5R. [Also in Division A4] A dental instrument table adjustable for height comprises a table part mounted for vertical movement by a parallelogram linkage, a piston connected to a first side of the linkage, a hydraulic cylinder containing the piston and connected to a second side of the linkage, a conduit System connecting the cylinder chamber with an accumulator space, and a valve mechanism in the conduit system operable to permit movement of the table. The piston is preferably a double-acting piston, the cylinder chambers on both sides of the piston being connected by the conduit system and one of the chambers acting as the accumulator space. As illustrated in Fig. 1, stand 1 has a mount 2 connected by pin 3 to horizontally pivotable short arm 4 at the other end of which link 6 is horizontally pivotably mounted by pin 5. Parallel arms 9 and 10 are articulated at joints 7 and 8 to this link and at joints 11 and 12 to a second link 13 to which dental instrument table 15 is horizontally pivotably mounted by pin 14. The links 6 and 13 and the arms 9 and 10 form the parallelogram linkage, a tension spring 16 is mounted between the diagonal points 7 and 12. Link 6 carries jib 17 to which extension arm 26 of end cover 25 of cylinder 19 is pivotally connected by pin 18. The lower parallel arm 10 carries two flanges 20 to which a piston mounted in the cylinder is connected by pin 21; this pin passes through two diametrically opposed axial slots 23 in the side wall of the cylinder. The cylinder may also have at least one axially extending slot through which projects a socket or sockets connecting the conduit system with one or both cylinder chambers by means of a bore or bores extending through the piston; as illustrated in Fig. 2 (not shown), the conduit system comprises a single conduit which contains a single valve, an axial bore extending from each cylinder chamber through the piston to a lateral bore leading through an axially extending slot in the side wall of the cylinder to connecting sockets 35, Fig. 1, which communicate with hydraulic conduits 36 and 37 leading to a valve 38. The valve may be an electrically operable valve and, as shown, may be connected by electric cable 40 to operating push button 39 mounted adjacent handle 41 at the front edge 42 of table 15. The valve may be so mounted in the conduit system that its closing member is pressed against its seat by the hydraulic fluid when the table is loaded and is lifted off its seat by the fluid when the table is raised. Alternatively, the conduit system may comprise two conduits each of which contains a non-return valve which opens in a direction opposite to the direction of opening of the other valve. These valves may be spring loaded and the valve responding under load in the direction of the force of gravity may have a stronger spring than the other valve. As illustrated in Fig. 5 (not shown), two axial bores, each containing a non-return valve, extend through the length of the piston, conduits and valves external to the cylinder not being required.