| 摘要 |
1, 173, 291. Hydraulic jacking-systems; tunnelling supports. LANCER MACHINERY Ltd. and P.J. PRESTON. Dec. 6, 1966 [Jan. 21, 1966], No. 2905/ 66. Heading F1P. A hydraulic jacking-system for a side-loading fork-lift truck includes a pair of jacks 12, Fig. 1, which extend between the chassis and the axles 2 of the road-wheels 3 on the loading-side of the truck, and a further pair of jacks 17 attached to the chassis on said side and having feet 19 that can be brought into contact with the ground to stabilize the truck when the lifting fork 7 is to carry a heavy load, the two pairs of jacks being independently connectable to a source of hydraulic fluid 25, Fig.3, through associated control valves of conventional kind and hydraulically connected to each other through non-return valves 21, 23 when the jacks 17 are brought into use and when the pressure in working chambers 15 thereof becomes at least equal to that in the corresponding chambers of the jacks 12 so that the jacks are uniformly loaded. Each of the axles 2 is pivotally attached at one end thereof to the chassis, Fig. 2 (not shown), the opposite end being pivotally connected to the piston rod 11 of the corresponding jack 12. The valve 23 has a sense of direction opposite to that of the valve 21 and opens simultaneously with the latter to effect equalization of pressures in the lowermost working chambers 16 of the two pairs of jacks, from which chambers hydraulic fluid is expelled when the jacks are being loaded, these chambers being used to effect retraction of the pistons 13 when required. Alternatively, the pairs of jacks may be replaced by single jacks, the valve 23 and the conduits associated therewith being dispensed with each jack may single acting instead of double acting as shown and more than two jacks may be hydraulically connected in parallel in the manner shown in Fig. 3. It is stated that the jacking system is applicable to progressive jacking of tunnelling supports, a plurality of jacks for said supports being hydraulically connected with one another through non- return valves in the manner described so as to permit the introduction of additional supports without interruption of the supply of hydraulic fluid to the jacks of the existing supports. The invention is not restricted to the use of a hydraulic fluid in the system. |
