July 1, 1911.] 



THE INDIA RUBBER WORLD 



351 



The Manufacture of Insulated Wire — II 



By a Practical Man. 



STRIP MACHINE INSULATION. 



THE application of rubber for insulation by this method differs 

 materially from the one just described. The rubber in its 

 preparation goes through precisely the same process. But 

 instead of passing from the mi.xing mills to the insulating machine, 

 it first goes to the calender. Here it is sheeted to specified thick- 

 nesses and wound between sheeting upon mandrels. These sheets 

 are afterward cut into strips by a machine devised for that pur- 

 pose, and automatically wound, or wound by hand, upon bobbins 

 or reels for use in the strip machine. An advantage in this 

 method is found in that the insulation material can be used hot 

 or cold. Cut into strips it can be held at the convenience of 

 the operator. A disadvantage develops in the necessity for splic- 

 ing strips (their length depending on the size of the roll pro- 

 duced from the calender) ; during which the machine for apply- 

 ing this form of insulation must of necessity stand idle. An- 

 other advantage is seen in less time being required in prepara- 

 tion of insulation material. Rubber, for example, can be used 

 with less care in its washing, and the compound stocks are not 

 passed through a refiner. 



A machine for the aplication of rubber strip to wire is in 

 marked contrast to a spewing m 'chine. Its body resembles that 

 of an ordinary machine shop lathe ; is of iron and stands about 

 hip high. These stands are equipped with one or more frames 

 for holding grooved wheels. The grooves in these wheels corre- 

 spond to the size of insulation it is desired to apply, consequently 

 there are many such wheels. If, for example, a heavy coat of 

 insulation material is to be applied, experience may dictate that 

 the proper thickness can be secured by use of five strips. This 

 would mean the use of five sets of two wheels each, the groove 

 in each set nicely graduated to match the growing diameter as 

 each strip is added. To illustrate: The wire or cable is un- 

 coiled from the holding reel and one end passed through the first 

 set of wheels. Above and below these wheels are bobbins hold- 

 ing the supply of strip insulation. Strips from these bobbins have 

 been passed through a guide, and coming in contact with the 

 cable are enfolded upon it in such a manner as to leave a seam 

 on one side. Passing immediately between the grooved wheels 

 their pressure closes the seam and trims away the surplus in- 

 sulation material, leaving, however, a bead. This shows the 

 wire with the first layer applied, and it passes swiftly through 

 the length of the machine, receiving from each set of bobbins 

 successive plies of material. As most cables, small as well as 

 large, call for a layer of rubber coated tape, it is wrapped upon it 

 as it leaves this machine, and is then wound on the receiving 

 drum. The value peculiar to this method is now evident: In- 

 sulation material, in preparation of which no especial pains has 

 been taken to free it from foreign substances, is applied to a 

 wire or cable in successive layers. These layers calendered to 

 an exact thickness, and applied as shown, must, of mechanical 

 necessity, hold the cable in center, and the chances are worth 

 taking that each layer of insulation material will close most, if 

 not all, defects in the layer immediately preceding. A cable of 

 this sort can be produced at the rate of 15,000 feet per day, and 

 six to eight men are required to handle the machine. For the 

 production of lighter insulation, smaller machines are used, and 

 a single workman can handle a job calling for one or two layers. 

 These machines are used in conjunction with the spewing ma- 

 chine, where the latter applies a seamless "core," and the other 

 one or more layers of strip. While for single wire and small 

 strands less men are required in the strip method than for the 



seamless, they are handicapped by the necessity for stopping 

 when bobbins are empty, while a spewing machine may be 

 operated continuously. 



The ten-strand machine is one that covers ten 14 B & S, or 

 other size wires at one operation with two layers: a core of 

 red or white, and a cover of black. A spewing machine is used 

 for the core material. The machine head is bored for ten wires 

 which pass thence to the "stripper." Two bobbins, one above 

 and the other below, apply to each side of the strands a broad 

 strip of black insulation material, which, in contact with the 

 wires, passes between grooved wheels which compress the stock 

 about each wire, although not completely covering them. These 

 ten strands m form of a wide band are wrapped about steel 

 drums holding from 10,000 to 15,000 feet each. Such a machine, 

 properly handled, should produce 200,000 feet per day. 



Vulcanizing of insulation applied in this manner differs in 

 no essential particular from that employed for seamless. Open 

 steam vulcanizers of various sizes are used. The drums or pans 

 are placed upon a truck that slides into the curing chamber and 

 remains there during the process. Once vulcanized the insulated 

 wire or cable is transferred to reels of convenient size for the 

 next operation — usually that of braiding, to pass therefrom 

 through the various successive steps of the process — waxing, 

 finishing, testing, to the stock or shipping rooms. 



As noted above, 14 B & S is produced ten strands at one 

 operation. After vulcanization these strands are split apart on 

 a machine that coils the ten strands upon ten small reels, and 

 ready for the braiding machines. 



The testing department of an insulated wire factory is its 

 most interesting and important division. It occupies the position 

 of inspector and final judge of all the work of all the processes. 

 It is the repository of those heartless things the "specifications," 

 and there must be decided the fine points of fitness. Doubtless 

 the fact that insulation must conform to certain rigid exactions, 

 has a lot to do with the careful supervision demanded of all 

 branches of the manufacture of insulation. After the expendi- 

 ture of time and money in carrying, say, a 19-conductor cable, 

 through the elaborate steps of its production in lengths of 5,280 

 feet each, to have it "break down" in the electrical testing, is 

 humiliating not to say demoralizing; time is lost, profits dis- 

 appear. There are several factors that contribute to such a 

 result: 



1. Lack of care (proper apparatus) in preparing rubber and 

 compounding ingredients. 



2. Careless workmanship, and inexpert handling of the wire 

 covered by unvulcanized insulation material. 



3. Sacrifice of quality to the demands for "greater produc- 

 tion." 



In short, it is susceptible of easy demonstration that intelligent 

 care distributed through all steps of every process in the manu- 

 facture of insulated wire, pays. 



A diagram or profile of these two methods can be shown thus, 

 indicating steps in process and apparatus: 



Spewing Machine : 



1. Coil of wire or cable to be covered on reel stand, to 



2. Spewing machine (production 10 hours, 75,CKX) feet.) 



3. Hot closet for insulation stock. 



4. Narrow table and soapstone box. ! 



5. Receiving drum or pan. 



6. Taping machine. 



7. Vulcanizer. 



