Valve Factory Virtual Tour AWV Ashfield

Forming of Miniature Valve Stem Leads

The intricate mechanism used in forming the stem leads of a miniature type valve. Wholly designed and constructed at the Ashfield works of the Amalgamated Wireless Valve Co., this octopus -like device automatically forms all seven pins into pre-determined positions through the action of air-operated rams.

It is necessary to look very closely at a miniature Radiotron to trace the various connections from the valve pins to their respective elements within the glass bulb.

Unfortunately the valve electrodes cannot be placed conveniently with respect to the pins, thus the lead wires have to be bent or shaped into some peculiar forms to avoid short circuits. At the same time this allows the assembly operator to weld the parts quickly.

To maintain the high standard of quality and performance required of the miniature Radiotron, all parts must be consistent. In this instance, it means when the correct shape has been found for each wire that shape must be the same in all valves of that particular type.

The design of a tool which will do this rapidly enough to satisfy the daily quota and at the same time be simple and foolproof to operate, presents several problems. The small space available for the various supporting and forming tools and the fact that the wires frequently lie one above the other are difficulties that have to be contended with.

A costly hand operated piece of equipment was first tried but it was found in practice to give continuous trouble owing to small fragments of glass finding their way amongst the sliding tools.

These tools were operated by a series of circular internal cams which were expensive to make and the entire equipment was only suitable for one type of valve.

The present procedure is to bend the wires with small tools fixed to the ends of air operated piston rods. These are in turn operated by valves controlled by extremely simple cams which are secured in a rack and screwed to the main fixture. An entirely different type of valve stem can be formed by merely changing the cam rack and piston units.

The latter, which vary in number according to the particular valve, are secured to a flat steel plate by a screw and two dowels. This whole plate assembly is removable when it is desired to change the valve type.

The operator places the unformed stem in the correct location and presses down a foot pedal until the cams reach the bottom of the stroke when the pedal is released returning the cams into position for the next cycle.

As there is no metal supporting structure around the ends of the forming tools any pieces of wire or broken glass will fall clear. It is also possible to watch each tool perform its task by operating the unit slowly. This is of particular assistance during construction. The whole equipment was designed and built at the Ashfield works of Amalgamated Wireless Valve Company.

Valve Factory Virtual Tour AWV Ashfield

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Acknowledgment: This page contains text and images from Radiotronics number 136, March-April 1949. A Radiotron technical release published in Sydney, N.S.W., by Amalgamated Wireless Valve Company Pty. Ltd.

Retrovox/R136/Valve Factory