THE INDIA RUBBER WORLD 



capacity was available and balloons and airplanes themselves 

 were demanding enormous yardage to meet the wartime pro- 

 gram. It was therefore necessary to work cooperatively with 

 various cloth manufacturers in order that they might produce 

 cloth to Gas Defense 

 standards. 



The problem involved 

 more careful methods of 

 yarn preparation, spin- 

 ning, and the equipment 

 of many hundreds of 

 looms with automatic 

 stop motions in connec- 

 tion with warp breakage. 

 One manufacturer went 

 so far as to start a spin- 

 ning frame full-spooled 

 and running through to 

 ihc end, shutting down as 

 tlie lirst spool ran out, 

 and replacing through- 

 out with new full spools. 

 Thus the tied ends were 

 eliminated. The less ex- 

 pensive method usually 

 — .Vmerican a. T. Rf..spir.\tor. employed is to replace 

 the spool and tie in a 

 new end as each one runs out. This made by far the best 

 fabric. 



The No. 4 sail-cloth had a count of 110 in the warp and 116 

 in the fill, and a breaking strength of 50 pounds warp and fill 

 in a one-inch strip. 



Fig. 13.— Interior of A. T. F.\ce-piece, 

 Showing Clarifying Tube and 

 Chin Rest. 



EXHALATION OR FLUTTER VALVE. 

 This valve, see Figure 5, had to fulfil one of the most impor- 

 tant requirements of all the parts of the respirator. It was neces- 

 sary that it should allow the escape of exhaled air without too 

 much resistance, and yet close instantly upon inspiration. It 

 was required to show not over one inch of resistance at 120 liters 

 per minute exhalation and a leakage of not over 10 cc. per 

 minute when dry and at a pressure difference of one inch of 

 water. In use, the valve became immediately wet with saliva 

 which reduced its leakage to 

 zero. 



As originally made, the valve 

 was wider and had a neck 

 formed to fit the metal con- 

 nection. Extensive experimen- 

 tation revealed the fact that it 

 was better to make the valve 

 flat and narrower. When the 

 flat neck was fitted to the oval 

 connection, slight stresses were 

 set up which tended to close 

 the ports more tightly. The 

 flutter valve was a source of 

 great trouble for the manufac- 

 turers. The requirements were 

 severe. Aside from the leak- 

 age test the valve was ex- 

 amined very carefully for holes, 

 foreign material, gaping ports 

 and dimensions. A part of 

 this examination consisted in 



placing a rounded brass knob inside the valve, sliding and 

 stretching the valve over the knob to bring to light any breaks, 

 pits, or foreign material. This examination also showed any 

 weak seams and edges. Seam construction gave a great amount 



Fig. 14 



of early trouble, which was finally overcome by careful handling 

 and adjustment of stocks. This valve had one weakness inherent 

 in the design, which was not overcome during the whole expe- 

 rience. This was a weak edge where the two halves were joined 

 at the sides. The weak 

 edge resulted from the 

 fold at this point and 

 pressure during cure 

 with a consequent loss in 

 grain. It was undesir- 

 able because, when the 

 valve was mounted, the 

 solvent in the cement at- 

 tacked the weakened tis- 

 sue and often broke 

 through. 



The method of manu- 

 facture usually employed 

 was to die out of sheet 

 stock in single or double 

 piece and then by making; 

 one or two seams and a 

 fold, the make-up was 

 ready for cure. Curing 

 was done in soapstone 

 or with slight pressure 

 from plates. After cure, 

 the valves were trimmed 

 at neck and ports to 



diinensions. Specifications required not less than 85 per cent up- 

 river fine Para rubber, the remainder being sulphur and dry 

 niorganic fillers. The use of organic accelerators was per- 

 mitted upon application of manufacturers and upon evidence of 

 satisfactory delivery. Large rejections took place at the manu- 

 facturing and assemldy plants, and while constant eft'ort was 

 made to reduce rejections and much progress was made, yet 

 the manufacturer was always obliged to reject many valves. To 

 illustrate, there was an accepted delivery from all sources of 

 8,500.000 valves and it is estimated that 15,000.000 were made 

 to yield this delivery. 



Numerous attempts were made to replace this valve and many 

 unique and interesting samples were submitted. All of them 

 lacked some property which 

 the standard valve possessed. 

 One of the most promising was 

 submitted by Dr. Geer of The 

 l; F. Goodrich Co. and was 

 made up of two molded rubber 

 parts and a cylindrical metal 

 housing. One was a bell- 

 shaped rubber piece joined to 

 the housing and leading to the 

 mask : the other, a nearly flat 

 fiange w^hich rested against the 

 bcU-shaped part. This flange 

 was mounted upon the base of 

 the housing and contracted 

 and expanded into a bellows, 

 thus furnishing a delicate 

 spring action to provide closure. 

 The frame served to mount the 

 two rubber parts, to protect 

 them from damage, and to pro- 

 vide adjustment. The especially 

 were its compactness and very 



Masks. 



desirable features of this valv 

 low resistance to exhalation, about one-quarter of that of the 

 standard valve. There was not time after the valve had been 

 perfected in design, to determine its durability and dependability 



