January 1, 1921 



THE INDIA RUBBER WORLD 



243 



The Manufacture of Tire Flaps 



Cameron Slitting and 

 Machine, 



Rewinding 



TIRE flaps were originated to meet the necessity of protecting 

 the inner tube of a pneumatic tire against injury in service, 

 from chafing on rim, tread or beads and from pinching 

 caused by flexing of the tire walls. 



Reliners are similar to tire flaps in construction, but generally 

 are wider and thicker. They are formed to fit between the casing 

 and inner tube against the tread side instead of the rim side. 



CONSTRUCTION 



Tire flaps and reliners are of laminated construction consisting 

 of rubberized plies of fabric built up in stepped widths. Thus 

 the flap is thick at the 

 center and thin at the 

 edges, which permits 

 it to be readily molded 

 with crescent-shaped 

 cross-section. 



Referring especially 

 to tire flaps, the con- 

 cave side practically 

 affords a continuation 

 of the inner wall of 

 the tire casing and ac- 

 commodates the shape 

 of the inflated tube, 

 while its opposite con- 

 vex surface is molded 

 to seat comfortably 

 on the tread surface 

 of the rim between the 



tire beads. The edges of the flap or reliner are sufficiently thin 

 and pliable to prevent injury to the tube by chafing. 



MATERIAL FOR FLAPS 



The material commonly used in the construction of tire flaps 

 is light-weight flat duck, osnaburg, sheeting or combinations of 

 ihese. Sometimes cotton flannel is employed as a facing on the 

 inner-tube side. The number of plies is usually four or five. 

 The inner plies are, of course, friction-coated on both sides, while 

 those forming the outer surfaces are frictioned on one side only. 

 The edges of the flaps are ordinarily two-ply by the union of 

 the fabric layers of the outer surfaces. In such case the flap 

 has a plain cut edge. Better grades are finished on the edges 

 by folding about one-quarter of an inch of the ply from the inner 

 lube side onto the opposite side. 



HAND-MADE FLAPS 



Flap production has probably advanced more rapidly during the 

 past two or three years than any other feature in tire manufac- 

 turing. Previously it was thought necessary to build flaps singly 

 on a concave drum, laying up the plies in rotation by hand. This 

 construction was known as the "endless type." The method was 

 gradually improved by home-made devices, making use of 

 wringer rollers to pull the several plies from spindles. The 

 wringer rollers also pressed the plies together, uniting them by 

 the adhesive quality of the friction. The hand-built flap was gen- 

 erally cured in a press of the general design of ordinary platen 

 presses, except that the face plates were so shaped as to give the 

 cross-sectional curve to the flap. The defects of this method of 

 curing were high cost per flap, due to slowness of production, 

 and failure to impart to the flap the transsectional curve needed 

 to perfect the proper shape of the finished goods. 



MACHINE-MADE FLAPS 



Machine processes have generally superseded hand methods in 

 flap production, permitting them to be run off in continuous 



lengths at high speed. Various machines are employed for the 

 purpose, namely: slitting and rewinding, flap building, flap meas- 

 uring and cutting, and drum filling machines. 



Rolls of adhesive friction-coated fabric in liners as received 

 from the friction calender, with intcrliner of plain separating 

 sheeting, are delivered to a slitting and rewinding machine. This 

 is provided with adjustable circular knives by which the fabric is 

 cut to precise widths, thence passing on through the rewinding 

 device which separates and accurately winds the strips into in- 

 dividual rolls ready for making up in the flap-building machine. 



FLAP-BUILDING MACHINE 



In general design the flap-building machine is similar to a belt- 

 folding machine. It consists of two small calenders, the first of 

 which strips tlie fabric from the rolls mounted on spindles at the 

 rear of the machine as shown in the illustration. 



The rolls of ply stock are arranged on the spindles so that the 

 different widths are delivered for lamination in proper sequence 

 and are faced on both sides by single-coated plies. 



PROCESS OF BUILDING FLAPS 



.^s the plies leave the spindles they run through a set of guides, 

 each ply of the flap passing through a separate guide in order that 

 all may register accurately as they unite in the laminated strip. 

 From the guides the flap enters the first set of pressing rollers. 

 This set of rollers also pulls the various plies from the stock 

 rolls. Between the first set and second set of rollers is placed a 

 folding device that turns over the edges of the flap. The ad- 

 vantage of a folded-edge flap is that the rough edges of the nar- 

 rower plies are covered and thus do not come in contact with the 

 inner tube. It also improves the appearance of the flap. 



From the folding device the flap enters the second set of press- 

 ing rollers which rolls down the fold. The top roller is rubber- 



Ue-\ter Flap Building Machine. 



covered to accommodate the various thicknesses due to the plies 

 varying in width and equalize the pressure across the flap. 



From the second set of rollers the flap is drawn over a breaker 

 drum, and wound on the detachable curing drum underneath ths 

 machine. The curing drum is friction-driven, so that its speed is 

 much faster than that of the machine. This allows the flap to 

 be pulled into the drums very tightly and conform closely to the 

 curvature of the drum. Each drum as it fills up with stock is 



