GB816217A - Improvements in welding positioners - Google Patents

Abstract

816,217. Work-holders. QUASI-ARC Ltd. Sept. 20, 1956 [Sept. 20, 1955], No. 26815/55. Class 83 (3). A welding-positioner comprises a turntable 1 tiltable from the horizontal to the vertical plane, the table being in its lowest position when horizontal and raised to higher levels during tilting. The table 1, table-rotating electric motor 16, and gearing 17 are mounted on the parallel bars 10 of a pair of four-bar kinematicchains 5, 8-10 arranged side-by-side, the bars 5 forming part of the stationary framework 3, 4 of the positioner to which the bars 8, 9 are pivoted at 11, 12. Screw-jacks or, as illustrated, one or more fluid-pressure jacks 19, 23 simultaneously raise and tilt the table from the horizontal, through the outer dead-centre position of the bars 9, 10, to the vertical and then to the 135-degree face-down position depicted in broken lines. A single-acting jack 23 is connected to each pivot 12 and the adjacent bar 8, and the double-acting jack 19 is pivoted at 21 between the frames 3, 4 and at 22 to a member connecting the bars 9, the jacks 19, 23 acting together to raise the table, but the jacks 23, acting as dash-pots, opposing the jack 19 as the table is lowered to the horizontal, or passes beyond the dead centre of bars 9, 10. Fluid-pressure control.-Fluid, drawn from a reservoir 32, Fig. 4, by a pump 30 driven by an electric motor 31, Fig. 1, is delivered through a relief valve 40 to three three-position valves 34, 36, 35, valves 34, 36 being hand-operated and linked mechanically, and valve 35 being returned by spring pressure to the central setting, in which the jacks 23 are locked. Setting of the valve 35 in its other two positions is controlled by the valve 36 and a two-position valve 37 which crosses the pressure and return control lines from the valve 36 to valve 35, and thus changes the setting of valve 35, when the bars 9, 10 are passing through the dead-centre position. The two ends of valve 37 are connected to spring-return valves 38, 39, operated by cams, (not shown) on the linkage as the bars 9, 10 pass through the dead-centre position, the valves 38, 39 being connected to the feed-lines for the jack 19 so that although both are actuated at top-dead-centre, the impulse received at valve 37 is that from valve 38 or 39, corresponding to the direction of movement of the ram 19. Exhaust lines are shown in broken lines and that from the jacks 23, through valve 35, passes through an adjustable metering-valve 33 to control the rate of descent of the table. The Provisional Specification describes also a construction in which only two fluid-pressure jacks are used, the double-acting jack being connected to one side of the base and the single-acting jack to the other.