Plastics for Tipping-gear Pump
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SIGNIFICANCE is attached to a new departure by one of this country's foremost tipping-gear makers. It displays, on the one hand, how an important industrial development of the present era is further extending its field of application into the commercialmotor world, and, on the other, commendable enterprise on the part of the concern responsible for the venture represented.
We refer to an innovation of 13romilow and Edwards, Ltd., Foundry Street, Bolton, which takes the form of employing " plastic " material for a number of parts of a piston-type hydraulic pump for operating its tipping bodies.•
Certain parts of the unit, which are not highly stressed, are made, by moulding, of thermo-setting Material, such as formaldehyde compositions, or any known like substance having a synthetic resin base. According to the specification (No. 543,619) detailing this patent, which bears, in addition to that of the company, the name H. W. Swift, the plastic moulding may, if preferred, be metal reinforced,.
This material forms the pump body, pistons, valves and cylinder head, whilst among the advantages claimed are decrease in weight, simplification of manufacture, and reduction in cost.
The specified application of the invention is to an hydraulic pump of the three-cylinclercd type designed for direct attachment to the vehicle gear box power take-off. One moulding forms the casing of the eccentric shaft, carries the bearings, and is provided with a flange for bolting to the gearbox extension piece. Another moulding forms the cylinder block, with which, in this case, the cylinder head is integral. A wearing surface for the pistons is provided by metal cylinder liners.
For the pistons, thermo-setting material, such as Bakelite, is mentioned. Into this the gudgeon pins are fitted direct, whilst sealing is effected by cup-leathers secured by centre screws to the piston crowns. Plugs, incorporating blind valve guides, are screwed into the head, in line with the valve seats. Metal, it is stated, is the preferred substance for these plugs, but thermo-setting mouldings may also be used here.
Plastic material, with integral metal reinforcement, is employed for the poppet valves, largely, we understand, for the sake of its lightness. Metal, or " other appropriate material," forms the valve seats, which are countersunk into the cylinder heads, In units such as the cylinder block and head, in which there are somewhat complex passages, the advantages of employing a moulding process are readily appreciated.