JUN-E 1, 1921 



THE INDIA RUBBER WORLD 



6+9 



Manufacture of Hard Rubber Combs* 



By 'William Roberts" 



THERE are thousands of different styles of combs, the stand- 

 ardization of which is quite impossible, as the consumer is al- 

 ways looking for something new and the manufacturer has to 

 cater to the fancies of the trade. Every customer has his own 

 specifications and ideas. Even the United States War Depart- 

 ment prescribes specifications for the combs to be supplied to 

 the Government. There are dressing combs for men and women ; 

 special combs for barbers ; pocket combs and fine-toothed combs 

 in a great variety of styles. Hard rubber comb making is a 

 highly specialized industry, requiring expert knowledge and spe- 

 cial machinery. 



PREPARING AND ROLLING THE STOCK 

 The compounded stock is first warmed on a mill and then cal- 

 endered, after which the rubber sheets are plied up nn a drum 



CoxsTRUcrioN OF Government Rubber Comb 



to obtain the proper thickness and eliminate air pockets or 

 blisters. The warm stock is next rolled in pieces approximately 

 one yard square, between two sheets of tin foil approximately 

 .015-inch thick. This requires a great deal of care and attention. 

 -An iron-top, steam-heated tabic is necessary for this work, with 

 a large iron roller ranging in weight from 1,200 to 2,000 pounds, 

 depending on the thickness of material and the finish that is 

 required in polishing the comb. First, one sheet of tin-foil is 

 applied and then the other, care being taken not to let the roller 

 rest too long at any one place, as it is likely to make ripples or 

 slight grooves. This will cause trapped air between the tin- 



St.\nd.\rd Rubber Combs 



foil and the material and may mean a blemished coiub. It also 

 results in unevcnness in the gage of the stock and will undoubt- 

 edly be the cause of scrapped finished material. 



Mechanical devices are used by some manufacturers but the 

 principal manufacturers still use the hand method which requires 

 two men to operate the rollers and through experience they be- 

 come very skilful in this work. The sheets of tin-foil with the 

 rubber stock between are then cut into rectangular blanks of the 

 proper size. This operation is done on a special cutting and 

 shearing machine, after which the pieces are ready to be formed 

 into the shape of comb required. 



THE COMB MOLD— FORMING AND CURING 



The forming die is made a little larger than the required size 

 and shape of the finished comb. Hydraulic power-presses are 



Hole for Hook 



^^^-^^ 



Comb Mold and Hook 



generally used. The blanks of compound with layers of tin-foil 

 on the outside are then placed in the die and formed, the tin- 

 foil taking on the shape and form of a comb and acting as a 

 mold. Holes are pierced in one corner of these comb molds 

 through which hooks are placed and the molds are hung on a 

 frame built inside a rectangular tank-truck made of boiler plate. 

 The tank-truck is next filled with water and rolled into the heater 

 where the combs are cured or vulcanized for about 12 hours 

 under 75 pounds steam pressure. 



TRIMMING THE FLASH 

 After vulcanization the tank is drained and the tin-foil stripped 

 from the hard rubber comb blanks. The thin flash of hard rubber 



>This article may not be reprinted without permission of the .lulhor. who 

 reserves all pnblicaticn rishls. 



^Enjjineerinl? School of JJrawing, SpringfieUl. Massachusetts. 



Curing Truck-Tank 



iriiiiiiil the form is then removed, various devices being employed 

 for this purpose. The three principal inethods are: (1) Stacking 

 a dozen combs together and whacking them with a flat wood 

 stick, the flash being so tliin that it readily breaks off; (2) Grind- 

 ing off the flash on a disk grinder; (3) Grinding tlie two long 

 sides at once between two grinding wheels. The centrifugal 

 force of the wheels carries the blanks through a specially formed 

 chute into a box. The ends are then finished off individually 

 on a di'k grinder, and the comb is ready to have the teeth cut. 



