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New Edbro Wobble-plate Tipping-gear Pump

16th October 1936
Page 63
Page 63, 16th October 1936 — New Edbro Wobble-plate Tipping-gear Pump
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An Easily Installed Fourcylindered Unit Delivering at a Steady Pressure and Equipped with an Efficient Relief Valve

REQUIRING less than a day's work, by a mechanic and a boy, to install on most machines, a new hydraulic tipper pump, just introduced by Edwards Bros. (Tippers), Ltd., of Bolton, has many attractive features. Among these, smoothness of action, an efficient relief valve and a design that should result in lengthy running without attention, may be enumerated.

In the case of a number of standard chassis, it is possible for the unit to be bolted straight to the gearbox power take-off. This simplicity of fitting makes it unnecessary for vehicles to be sent to the manufacturers, as the work can probably be carried out locally.

The relief valve obviates any possibility of damage when, as occasionally happens, the pump is started with the hinge pins still in place. Instead of the chassis frame or body being distorted or the pins broken, the valve releases the pressure immediately the full working force has been attained ; oil thus released is returned to the reservoir.

At a demonstration given to a representative of The Commercial Motor, a gauge was placed in the ram pipe line and the pump was operated with all body hinges fastened. The figure registered was 900 lb. pressure, which is approximately the same as the ram pressure required in normal work. Although the engine was run for nearly a minute, the figure remained constant.

The pump itself, although small, has a constant flow, resulting in a smooth action, and when demonstrated on a Bedford three-way tipper, the steady pressure rise and absence of jerking were particularly noticeable.

The pump is contained in an outer casing, roughly cylindrical in shape and incorporating four cylinders. Mounted on thrust and journal bearings at the .,take-off end is a shaft driven by a gearwheel which engages with the transmission. At the other end of the shaft is a wobble-plate which

carries a disc mounted on thrust bearings. This is in actual contact with the spherically ended plungers that operate in the four cylinders, these being spring returned.

Within the cover plate, shown on the left in the drawing, there are passages from the cylinders to a central delivery pipe. Oil enters on the right, filling the whole at the wobble-plate chamber. Fluid enters each of the four cylinders via suction valves fed from this chamber. A relief valve, incorporated in the cover plate, but arranged centrally between the cylinders, allows oil to return to the supply reservoir when excess pressure is developed. It is noteworthy that all the wobble-plate bearings are thoroughly lubricated by the oil in this chamber.

The pump is available for 3i tons, tons and 7 tons. On the Bedford machine on which the gear was demonstrated to us, only two short pipe lines were necessary, and with the oil reservoir placed under the near-side scat with the relief valve at the back of the reservoir, the whole mechanism was particularly accessible. A bodylowering lever was fitted at the seat side. Strong hinge pins were provided and the tipping rams were mounted on a rocking cradle.

An interesting feature of standard Edbro tippers generally is the use of the four-tube system, which provides a substantial means for at

tachment. A check valve is incorporated to guard against the possibility of pipe breakage or leakage causing the colla?se of a loaded body in the course of tip pin. Furthermore, a camoperated valve relieves the pressure when a predetermined' angle of tip is reached, thus rendering. it impossible for the gear to he over-stressed.

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Organisations: US Federal Reserve

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