Patent GB-788317-A (GB)
Abstract: 788,317. Miners' cap lamps. OLDHAM & SON, Ltd., and PROUT, L. R. Jan. 9, 1956 [Jan. 20, 1955], No. 1824/55. Classes 39(2), 75(2) and 75(4) [Also in Group XXXVII] A portable electric lamp comprises a body 4 formed as a single moulding having a reflector shape, a light reflecting surface 2 on the reflector shape, a lens 5 attached to the body in front of the reflector shape, a bulb holder 11 behind the lens 5 and electric conducting elements connected to the bulb holder and having portions disposed for connection into an external circuit including an electric supply, either both the bulb holder and the conducting elements being at least partially insert moulded into the body during the moulding operation or the body being formed during moulding with recesses into which bulb holders are subsequently secured as push fits or by screwing them into threads in the recesses and the conducting elements being insert moulded into the body and having portions exposed in the recesses to make contact with the bulbs. The' body is made of electrically insulating plastic material. The reflecting surface 2 is formed by vacuum deposition of aluminium or rhodium or silver, and may vary from highly polished to matt. Before deposition of the reflecting material the surface may be coated with lacquer. The diffusion of the reflecting surface is varied by using moulding tools having different' finishes. The lens 5 may be etched on both faces and is secured by a threaded bezel 6 to the front of the body, the joint being made gastight by a sealing ring 9. The bulb holder 11 is screwthreaded to receive a main bulb 3 and is arranged in a cylindrical recess at the centre of the reflector. A contact member 17 moulded into the bottom of the recess carries a coiled spring 18 having at its centre a contact 19 adapted to engage the central contact of the main bulb 3. The coiled spring 18 holds the bulb in adjusted position in the bulb holder. Another bulb holder 12 for a pilot bulb 13 is similar to the main bulb holder 11 and is moulded into the body to one side of the main bulb holder 11. A switch unit 22 moulded into the body consists of four contacts 22...26 arranged in a circle and a rotary conducting switch member 30 rotatably mounted on a conducting bearing member 28. The contacts 23, 24 are connected together by a bar 63 and the contact 23 is connected by a strip conduit 62, Fig. 4, to a pin 46 extending out of the side of the body opposite the switch unit for connection with one of two sockets of a connector 55, Fig. 2, on the end of a cable 58 extending from a battery. The other two contacts 25, 26 are connected separately to the contacts 19 engaging the central contacts of the bulbs by strip conduits 65, 64 moulded into the body. The switch member 30 is adapted to bridge contacts 23, 25 and 24, 26 and has bows 31 engaged in a slot on the underside of a rotary element 33 secured to an operating handle 38, Fig. 5, having a spring pressed plunger 39 engaging in three dimples on the body to locate the switch in selected positions. The bulb holders 11, 12 are connected by a strip conduit 52 in the body to an insert 53 having a pin 54, Fig. 2, extending out of the body adjacent to the pin 46 and adapted to engage with the second socket of the connector 55. A spring charging terminal 43 is fixed to an insert 45 connected to the contact pin 46 and a second charging terminal 51 is riveted to the exposed end of the strip conduit 52. The chamber 1 between the lens 5 and the body 4 is filled with nitrogen, carbon dioxide, argon, neon or air under pressure and a pressure sensitive switch 66, Fig. 5, operates to cut off electric current to the bulbs upon a predetermined fall of pressure. The switch comprises a chamber 67 in the body 4 connected to the chamber 1 by a passage 68 and closed by a resilient metal diaphragm 70 having a lobe 71, Fig. 2, through which the contact pin 54 passes in electrical contact therewith. A contact 72 secured to the diaphragm centre is disposed to engage a nipple 73 on the conducting bearing member 28 of the rotary switch unit 22. Should the pressure in the lamp drop the diaphragm will flex to connect the contact 74 and the nipple 73 so that a fuse 50 connected in one of the battery leads and mounted on the battery blows. The pressure gas is introduced into the lamp through a plug 74, Fig. 4, screwed into the base contact member 21 of the pilot bulb holder 12. A valve 80 in the plug is urged by a spring 82 against a seating 83 in the plug. When a high pressure gas connector is attached to the plug the pressure unseats the valve and the gas passes through the plug, through an aperture in the base contact member 21 into the pilot bulb holder 12. It then passes between the threads of the pilot bulb and its holder into the chamber 1 and between the threads of the main bulb and its holder into the main bulb holder and along the passage 68 into the diaphragm chamber 67. Specification 548,223 is referred to.