208 



THE INDIA RUBBER WORLD 



1 the field before the signing of the armistice was 

 FLEXIBLE HOSE. 

 The flexible hose, shown in figure 9, was used to 



canister to the facepii 



It was originally made of 3/32-gage 



Fig. is.— .Aluminum A, T. Mask Forms. Two Curing Forms 

 .\T Left. Building Form .\t Right. 



rubber with spiral corrugations and covered with S-ounce 

 stockinet. It was made by placing tubed stock on a spiral cor- 

 rugated mandrel, covering with stockinet, and wrapping with a 

 cord. The make-ups were mounted upon racks and cured in 

 open steam. This method yielded a product that was unsatis- 

 factory from several standpoints. Rejections were high on 

 account of interior folds or buckles and poor adhesion. The 

 hose was not flexible enough. The English had used circular 

 instead of spiral corrugations, and had secured greater flexibility. 

 The early manufacturers tried several methods to make this hose 

 and finally a molded method worked out by E. L. Stimson of the 

 Mechanical Rubber Co., Cleveland, Ohio, was adopted. It con- 

 sisted of a semi-cured rubber part which was covered with rub- 

 ber-coated or cemented stockinet and then given a final cure 

 to produce the necessary adhesion. First-cure and second-cure 

 molds were therefore required and mandrels had to remain with 

 their cavity. This process with the later use of stockinet knitted 

 ill a tube of proper size, was standard throughout the manufac- 

 ture of the hose. Individual manufacturers worked out many 

 clever labor-saving methods of applying stockinet, trimming 

 ends, etc. 



Many early troubles were encountered in the manufacture of 

 hose involving correct corrugation design to produce flexibility, 

 proper registration of molds and mandrels, pinching in final cure, 

 and adhesion of stockinet. The hose was tested under water 

 with five pounds' air pressure (Figure 10) and had to pass a 

 flexibility test (Figure 9). The fabric adhesion on a two-corru- 

 gation section had to be at least four pounds at one inch per 

 minute separation. It was necessary that the hose should not 

 kink when bent double on thumb and forefinger. 

 MOUTH-PIECE. 

 The rubber mouth-piece (Figure 5) had to be designed to be 

 as comfortable as possible in the mouth, to cause the minimum 

 amount of salivation and to be tough enough to resist biting 

 and chewing. Several improvements were made in the earlier 

 design, involving a decrease in the flange which went between 

 the lips and gums and the introduction of two corrugations in 

 the neck to make greater flexibility and consequently less irri- 

 tation to the mouth when running or walking. 



The compound was similar to tread compound and called for 

 35 per cent plantation rubber and the balance sulphur and inor- 

 ganic filler. The gravity was placed so high that it was necessary 

 to make most of the balance of zinc oxide. No organic accel- 

 erator was permitted on account of the use of the mouthpiece. 



Little difficulty was encountered in manufacture, once require- 

 ments were appreciated and mold equipment lined up and watched. 

 It was necessary to use the same mandrel in the same cavity each 



time 10 insure even wall tliickncss. Greater smoothness was 

 iibtained by tum))ling', 



NOSE PAD. 

 This was a small molded button provided with corrugations 

 for fastening to the wire nose clip, and with concentric rings 

 molded into the surface to come in contact with the nose in 

 order to make the clip stay in place. The part contracted at 

 the middle to a small diameter neck. This provided easy motion 

 of the face of the pad to accommodate noses of different shapes. 

 Two were furnished for each mask. The manufacture of this 

 article was no different from that of any simple molded article. 

 DIAPHRAGM VALVE. 

 The diaphragm valve is a thin rubber disk designed to rest on 

 a metal fitting in the bottom of the canister. Its use was to pre- 

 vent exhaled air from passing out through the canister. This 

 part was molded and little trouble was encountered in its manu- 

 facture. Some rejections were necessary on account of warpage 

 and poor packing. 



Eye-piece washers were made by the usual jar-ring processes, 

 but a better composition was required. Thirty-five per cent 

 plantation rubber was used, the remainder consisting of sulphur 

 and dry inorganic fillers. 



ELASTIC TAPE. 

 Elastic tape was used in enormous quantities for the head 

 harness. Little trouble was encountered in the manufacture, but 

 numerous changes in specifications were made necessary by 

 changing conditions of gas warfare. At first it was necessary 

 to wear the masks only a few minutes at a time. As soon as 

 it became necessary to wear them for a longer period, it was 

 found that the elastic was too strong in tension. This elastic 

 had been made up in one-inch widths and each strand of rubber 

 was protected against 

 aging by a double thread 

 winding. The tension 

 was first reduced by us- 

 ing narrower tape and 

 looser weaving and final- 

 by omitting the wind- 

 ing of the original 

 strands. A great many 

 experiments on many 

 heads revealed the fact 

 that there was a very 

 narrow limit in the stress 

 strain properties of an 

 elastic between comfort 

 on one hand and safety 

 on the other. 



The purpose of the 

 winding of the strand 

 to protect from aging, 

 caused an investigation 

 of the properties of so- 

 called black elastic thread 

 as against the usual pure 

 Fig. 16.-OXYGEN Inh-nl.^or for S""'- All tests served to 

 TRE..TMENT OF Gassed Soldiers. '^""fi™ '^at the black 

 was more satisfactory, 

 but none was used up to the time of the armistice. 



The specifications provided for twelve strands of No. 26 

 thread with a tension of 18 ounces at 5 per cent stretch and 36 

 ounces at 40 per cent stretch. 



Elastic tape to the amount of 14,666,500 yards was delivered 

 to the Gas Defense Division. 



In the quantity handling of elastic tape for harness, an inge- 

 nious machine shown in I'igure 11 was developed at the Gas 



