| 摘要 |
1332664 Mobile gantry cranes B E WALLACE PRODUCTS CORP 6 Oct 1970 [8 Oct 1969] 47536/70 Heading B8B A gantry comprises an I-beam 14 supported by pairs of legs 17 each of which is pivoted above and offset from the longitudinal centreline of the beam 14 on pivots 18. The legs 17 are braced by braces 25 pivoted on pivots 27 coaxial with the pivots 18. The legs 17 are telescopic and their angular separation may be adjusted by a telescopic tie-bar 34, 35. The legs 17 are pivoted at 41 on the respective ends of the tie-bar 34, 35, these ends also carrying castors 45 whose castoring areas remain parallel for all settings of the tie-bar 34, 35. In the unloaded or lightly loaded condition the gantry is unstable laterally, the beam 14 being held away from contact with the legs 17 by springs 32. The offset of the pivots 18 from the centre of the beam 14 is sufficiently small so that the gantry is self-stabilizing under loaded conditions. |
