A New Hydraulic
Page 48
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Tipping Gear THE merits of hydraulically operated tipping gear are already well known in connection with power operation. Where circumstances demand that the tipping shall be done by hand, these advantages should be equally or, perhaps, more noticeable.
With this in mind, Edwards Bros. (Tippers), Ltd., Bradford Street, Bolton, has produced a hand-operated hydraulic tipper for which it is claimed that a boy—" the smallest in the shop "—can tip a 50-cwt. load in 45 secs. In that connection it should be mentioned that the angle of tip is approximately 50 degrees from the horizontal.
Mounted on simple trunnions between the chassis side members, just behind the driver's cab, is a box containing the supply of oil, the pump unit and the base of the ram. An iron casting carries the last-named as well as the two pump barrels, the release valve and the fulcrum standard for the pump lever. Consequently, no pipework is employed, the necessary passages being drilled in this base casting.
The two pumps are of a straightforward plunger type arranged one on each side of the lever fulcrum. It is noteworthy that a smaller capacity is employed for the pump which discharges during the upward stroke of the lever, so as to make even the energy required in operation.
Arranged transversely across the chassis, the opertiting. lever protrudes on the near side and is detachable. Alongside it is a pull-rod which unseats a ball valve and thus allows the oil to escape from the ram into the tank, so that the body can descend to its normal position.
Turning to the ram itself, the cylinder is attached rigidly to the base casting already mentioned, and within it is a conventional plunger. Surrounding it and the working cylinder is a second cylinder which excludes dirt from the working parts of the ram and takes the place of the usual link mechanism.
On the example that we examined, this outer cylinder is attached to the lorry body by a simple trunnion, but it is understood that later products will have a spherical bearing so as to eliminate twisting or binding due to distortion of the body.
The same concern has developed an alternative form of pump which has several novel and interesting features. In this the up-and-down motion required with the gear just described is exchanged for ordinary rotary motion.
A horizontal shaft carries four " square " cams, each of which operates a spring-loaded plunger pump. To relieve the plungers of any side thrust, a roller-ended rocker arm is provided between the cam and the plunger. This pump is mounted in a welded-steel tank similar to that used in the simpler design and the remaining features of the design are unaltered.
Owing to the shape of the cam it will be realized that each pump is operatedaour times per revolution of the handle. As there are four such pumps, the turning resistance is even, and it is stated that a gallon of oil can be displaced in less than a minute against a pressure of 700 lb. per sq. in.