| 摘要 |
PCT No. PCT/AU86/00155 Sec. 371 Date Jan. 29, 1987 Sec. 102(e) Date Jan. 29, 1987 PCT Filed May 29, 1986 PCT Pub. No. WO86/07113 PCT Pub. Date Dec. 4, 1986.A leveller for a ladder has a pair of sliding legs telescopically engagable in respective up-right tubes (which may constitute the stiles of the ladder or separate tubes to be fixed to the stile of a ladder), and a substantially uniform continuous flexible ligament such as a wire rope fixed to upper regions of the legs and extending between the tubes and engaging with a support guide means which is fixed relative to the ladder structure or relative to the other apparatus on which the levelling device is mounted. When loaded, the ladder transmits its load through the support guide means to tension the ligament but when the load is removed (for example by subsidence of the ground beneath one of the legs) tension is released from the ligament allowing it to slide over the support guide means to cause rapid readjustment of the relative vertical positions of the ladder to compensate for variations in ground level, whereby the ladder is maintained in its desired attitude. |
