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September, 1936

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Some outstanding design features are to be found in two new electric lamps — a cap lamp and a hand lamp — which have recently been developed by Ceag Limited, Barnsley. Both have been designed with a practical eye to economy in maintenance and in lamproom handling as well as with a view to safety, high illumination and high illumination-to-weight ratio.

The Ceag 4 V Major acid hand lamp, depicted in Fig. 1, is of higher capacity than the existing Ceag 4 V. lamps, of which more than 50,000 are in service. The bulb is rated at 4 V. 4 W., which is the highest candlepower Schedule A bulb approved, and the battery is rated to give 16 hours continuous burning.

A noteworthy feature of the lamp is its two-piece construction, incorporating a hard-rubber battery container, a method of construction which greatly economises work in the lamproom. Two difficulties in developing such a design have been sealing the container and checking the acid level, but the former has been overcome by the use of a monel-metal sealing ring, and the latter by an electrical topping-up device similar to that in use for alkaline lamps. The view of the battery, Fig. 2, and the section, Fig. 3, show the battery construction and the method of sealing. A lip is moulded on the hard-rubber container, and over this is fitted a joint ring of genuine monel metal. A monel-metal lock ring screws inside the joint ring and secures the battery lid, which is also of moulded rubber. The battery chambers are filled through valve-type stops such as are generally fitted to an alkaline battery, the container being sufficiently strong to withstand the gas pressure. A moulded-rubber plate is fitted on top of the lid to prevent spray reaching the lamp top. The battery is of the flat-plate type, and has ample mud space to avoid frequent washing out. As the battery has no metal case, but is put on charge as it stands, it is fitted with a monel-metal bottom plate which imparts mechanical strength without suffering from corrosion due to standing in acid.

In the lamp top the number of rubbing contacts has been reduced to the minimum, and consists only of two between the battery and lamp top and one between the bulb and bulb holder. Furthermore, springs are used merely to ensure contact, and do not carry current. This is claimed to minimise resistance losses and to give unfailing current supply to the bulb throughout the shift. In accordance with Ceag practice a safety fuse is incorporated which blows in the event of well-glass breakage or of short circuit. This is considered to be an essential fitment with high-capacity lead-acid batteries.

The Ceag "Twin-lite" one piece cap lamp, depicted in Fig. 4, also possesses many features meriting attention. An alkaline battery is employed, having tubular positive electrodes to give maximum capacity and long life, and is contained in a moulded rubber sheath within a monel-metal container. No annual battery replating is necessary, as the battery is guaranteed by Ceag Limited to have a life of 6 years, and the maintenance cost is guaranteed not to exceed ½d. per lamp week. The battery is hermetically sealed when in service by a cover plate over the vents, and two fuses are included to give complete protection. The headpiece is of hard moulded rubber, and has an elliptical reflector giving a beam broader than it is high, so as to conform to the natural field of vision. Twin bulbs within the reflector spread the light evenly over the field, and act as a safeguard against leaving the miner in darkness in the event of one lamp burning out.

Charging arrangements in the case of both the hand and the cap lamps are designed to minimise lamproom labour. A combined charging and hanging rack has been designed in which, after charge, the lamp is closed and placed on a blank position next to the charging position. The collier himself takes his lamp away from either the front or the back of the stand, and when he comes from the pit returns the lamp to the same position. All the lampman has to do is to open the lamp and put it in the charging position, and when charged put it back again for the collier to collect. Both these lamps lend themselves to this method, as the 4 V. lamp is a two-piece lamp, and the top only has to be removed, and the cap lamp is a one-piece lamp, and all that has to be done is to swing over the lid. Fig. 5 shows the arrangement as applied to the cap lamp. This system reduces lamproom handling to the minimum, but ensures that every lamp passes through the lampman's hands when being placed on charge, so that any damage can be detected.

Drawings and Photographs accompanying the article