PRINCIPLES OF CONSTRUCTION. 99 



machines, and several welders may be worked off one generator. 

 In connection with the latter, a very simple method of signal- 

 ling has been devised for the purpose of preventing two or more 

 welders being used simultaneously, consisting of a number of 

 incandescent lamps which are connected to the welding circuit, 

 three 100 volt lamps in series generally being arranged close to 

 the various plug attachments. When the lamps are glowing 

 at their normal brightness the operator knows that no welder 

 is in use, and connects his machine to the circuit. During 

 the operation of welding, the voltage falls slightly on the 

 lamps, and indicates to the other operators that the alternator 

 js being used. Of course, when the supply is taken from a 

 large constant-potential dynamo, or from the public mains, 

 there is no need of any such system of signalling. 



There can be no doubt of the advantage of electric welding 

 over hand welding and brazing. Its cleanliness, quickness and 

 portability should recommend it to the table manufacturer ; the 

 increased strength of cable and freedom from liability of electro- 

 lytic troubles to the cable owner. The extensive submarine 

 cable factory of the Telegraph Construction and Maintenance 

 Co. (Ltd.), at East Greenwich, is fitted out exclusively for electric 

 welding ; and many minor improvements in the machines and 

 system have been introduced by this company. 



Mr. Reginald J. Wallis-Jones (engineer of the Electric 

 Welding Co., Ltd.) and Mr. A. F. Berry have recently patented 

 an improved form of transformer for use in electric welding 

 machines of the type just described, whereby a more efficient 

 apparatus is obtained, while the weight, size and cost of the 

 machine are reduced. Fig. 47 shows in part section an auto- 

 matic wire welder fitted with this improved transformer, a is 

 the secondary winding, consisting of a number of flat copper 

 strips arranged side by side, bent to a circular shape, and 

 enclosing the primary winding h. The ends of the secondary 

 winding at h and c are connected together in parallel, and 

 secured to the blocks / and g^ on which are mounted the 

 platens d and e. The primary coil is of hollow cylindrical 

 shape, and is arranged horizontally and co-axially within the 

 secondary coils a. The iron core of the transformer is made up 

 of a number of laminated plates, i, of straight strips of soft iron, 

 arranged radially around the primary and secondary coils. 



Electric welding is such a simple process that a great saving 



h2 



