| 摘要 |
A jib crane comprises a fixed support pillar pivotally mounting a jib arm and a support leg 5 fixedly attached to the jib arm remote from the pillar. The base of the support leg 5 mounts a shoe 6 on the underside of which two removable tray assemblies 7 are slidably received. Each tray assembly 7 carries an air bearing pad 23 having apertures 28 through which air supplied to the pad 23 via a coupling 30 egresses to form an air film f at the base of the support leg 5 which permits movement of the support leg 5 relative to the ground 31 without friction. As a result, pivotal movement of the jib arm 3 relative to the support pillar 1 is facilitated. <IMAGE> |
