Corby

Corby was a relatively short-lived lamp factory, having made sealed beam reflector lamps over a period of just 17 years. At first these were produced primarily for automotive headlamps, but later a number of types for general lighting as well as different specialised applications were introduced. After a decade of prosperity the automotive side of the business declined and made continued operation of the site unrealistic. Some of the other lamp types were transferred to the nearby factory of Thorn Lighting at Leicester, and it was closed in 1976.

Just one year after the 1938 invention of the Sealed Beam Reflector lamp by Daniel Wright at General Electric in the USA, this novel light source was adapted for automotive headlamps and grew rapidly in popularity. It offered the advantage of being a completely sealed system, excluding water and grime from the optical system, which had until then been responsible for a continual decline in headlamp performance over the life of a vehicle. Pre-focussing of the filament in the reflector and lens also reduced the time needed to align the headlights after a lamp replacement.

The process of manufacturing a sealed beam lamp is entirely different from any other light source that was in existence at the time, and required the use of dedicated manufacturing equipment. At first the majority of new vehicles were being manufactured in North America, and overseas manufacturers did not have sufficient volume to justify the investment needed to produce sealead beam lamps competitively. All demand was therefore supplied by the American manufacturers - first GE, and followed soon afterwards by Westinghouse and Sylvania. It took two decades for the British automobile business to grow large enough to began to change this situation, and plans were then made for local production. This was facilitated by a parallel growth in demand for sealed beam lamps of the PAR38 and PAR56 varieties for general lighting applications.

Because no one lighting company had sufficient volume to justify the major investment on its own, three of the UK manufacturers clubbed together and formed the joint company 'British Sealed Beams Limited'. The shareholding was divided 40% AEI-Mazda, 20% Osram-GEC, and 40% Joseph Lucas (automotive equipment manufacturers). The location chosen for the new factory was at the AEI's existing site in Corby, which had originally been built as a wire-drawing facility and which was no longer required for that activity.

During the 1970s, sealed beam automotive headlamps began to fall out of fashion for a number of reasons. Firstly they were available only in round shapes and automotive designers were becoming more interested in exploring rectangular and other profiles for their headlamps. This hit the factory hard because the automatic production equipment could not realistically be adjusted to handle the wide variety of different shapes and sizes that car manufacturers desired. A sixth production group, Line F, was eventually set up to produce rectangular shape lamps, but the production of these types was technically challenging and only a limited range of shapes and sizes could be produced.

Secondly, great improvements had taken place in the design of the rubber sealing gaskets on conventional headlamp assemblies, to reduce the ingress of moisture and dirt, and this presented a lower cost solution than the flame-fused sealed beam lamps. Thirdly, tungsten halogen lamps of compact dimensions were beginning to take over the headlighting market, and these were introduced with various pre-focussed caps which also made headlamp alignment a thing of the past.

Thus the advantages of the sealed beam lamp, at least for automotive applications, had been entirely eliminated and it only brought drawbacks of inflexibility and relatively high cost. Some types were produced with tungsten halogen capsules inside, but those could be produced still more cost competively by glueing the reflector and lens together instead of the flame-sealing process. Demand for Corby's lamps rapidly declined, and the factory was closed in April 1976 with the loss of over 500 jobs. As the market continued to dwindle, the British manufacturers once again reverted to sourcing in their requirements from the Americans, who were able to sustain their own automotive sealed beam production for many years longer owing to the much larger size of that market.

Meanwhile, demand was still high and in fact growing for the general lighting PAR38 lamp, and the high speed automatic production line for these types was saved and relocated to Thorn's Leicester factory, along with some smaller single-head type machines that produced PAR36 and PAR64 lamps for aircraft and stage/studio applications. Thorn later gave up the PAR38 operations and once again sourced in its requirements, primarily from GE's Canadian factory but occasionally also from Osram Germany and Philips of the Netherlands, which had become more cost-effective due to their faster equipment which operated with lower scrap levels. The PAR64 production still survives today, having been re-located once again to the GE-Tungsram operations in Hungary.

As of 2015 the building still exists, and is in use for the production of Weetabix breakfast cereals.