Patent GB-815065-A (GB)
Title: Method and apparatus for treating nylon and polyester fiber cords
IPC: B29B9/00
Filed: 1955-07-05
Abstract: 815,065. Coating cords. GENERAL TIRE & RUBBER CO. July 5, 1955 [July 9, 1954], No. 19447/55. Class 140. [Also in Groups XXXV and XXXVII] Nylon or polyester cords are coated with a rubber-to fabric adhesive by passage through a dipping solution whilst applying a primary tension to the cords, and then passed while applying a secondary tension at least three times greater than said primary tension through a number of fixed heating zones to which heated gases are supplied while varying the number of zones being heated during heating of the tensioned cords by supplying heating or cooling gases to chosen zones and correlating the speed of the cords and the number of zones heated so as to maintain the heating time within a fixed range, cooling gases being supplied to each zone whenever the supply of heating gases ceases, whereafter the cords are cooled while still under said secondary tension. By this hot-stretching method cords are obtained with a reduced tendency to stretch when used in rubber tyres or other reinforced rubber products. To permit changes in molecular orientation to occur the secondary tension may be reduced during part of the heating and then re-increased to a value such as to minimize shrinkage of the cords. Preferably excess adhesive material is removed before heating and stretching is started. The adhesive may be a latex adhesive containing for example a copolymer of 2-vinyl pyridine, styrene and a diolefine having up to 7 carbon atoms, e.g. butadiene, in which case the coating step is preceded by a water dip to reduce the penetration of the adhesive as in Specification 805,708, [Group IV (c)], or a solvent dip containing an adhesive may be used. As shown, a weak-weft fabric web W composed of parallel nylon cords fed from a spool 1 is wetted in a bath 4 and then coated by adhesive in a latex bath 8, and is drawn through calender rollers 28 by a driven roller 29 to remove excess adhesive. The coated cords are then passed into an oven 19 comprising heating zones separated by a partition 22 from cooling zones and withdrawn by a roller 25 and passed through an accumulator 30, either to storage or to other rubber working machinery for use as reinforcement, for example in tyres. The larger oven 14 is used when the apparatus is used for treating rayon cords which follow the path shown in dotted lines in Fig. 2. During drying the nylon cords are held under tension by driving the roller 25 more quickly than the roller 28, an hydraulic dashpot controlled jockey roller 31 altering the setting of the rheostat 37 in the field coil of the generator 35 and so controlling the speed of motor 26 driving the roller 25 and applying selected tension to the cords. To avoid slipping, the rollers may be rubber covered. The oven is divided into eight zones each fed by five tapering nozzles 47 of rectangular cross-section and by an appropriate positioning of flap valves 59 to 64, zones 1 to 6 may be supplied in pairs either with hot gas from combustion chambers 15 to 17 or with a cooling air blast from fans 56 to 58, while zones 7 and 8 are fed with cooling air from a combustion chamber 18 which is lit only for treatment of rayon and is extinguished when desired to provide cooling air. To operate the machine, a three-pole switch 147 is closed and exciting the motors 112 to 114 for the fans 56 to 58 and generator motor 36 without starting the web driving motors 11, 26 so that the stationary web is flooded with cooling air, the valves 59 to 64, which are operated by air cylinders as 65 controlled by split winding relays 71 to 76, being in their upper rest positions closing the gas ducts 89. Two-pole switch 152 and single-pole switch 153 having been closed, thereby energizing relay RB, closing of push-button 158 operates a relay R1 having hold-on contacts which (i) opens the normally closed switch r1 de-energizing the solenoid 343 so that the by-pass valve 342 for the hydraulic fluid supplied to the dash-pot is closed and the web is tensioned, and (ii) also opens the fuel supply pipe 106 to a burner 99 having a pilot burner 100 in the combustion chamber. When the required gas temperature is reached the thermostat 103 regulates the fuel supply by means of a valve 102 while a thermopneumatic switch comprising thermal element 171, bellows and switch contact 165 energizes relay RA and lights the " ready " lamp 188. Switch 189 is then manually closed, energizing relay RM, which closes the circuits through rheostats 38, 40 to the field coils of the generator 34, 35. By now pressing push-button 190, a rheostat motor 191 reduces the resistance included by the rheostat 39 and so speeds up the motors 11 and 26. When motor 11 has run up to speed, coil 177 across the generator operates switch 182 to energize relay R2 and de-energize relay RB preventing further increase in generator and motor speed irrespective of the operation of the push-button 190 and extinguishing the " ready " lamp 188. Closure of relay contacts r2 closes the by-pass 83 to prevent gas escape to the exhaust 122 and operates the flap valve 60, so that hot gas is fed to zone 2 and also shuts off the fan 56. When the gas fed to zone 2 operates the thermal element 172 to close switch 166, relay RB is re-energized lighting the " ready " lamp 188. By pressing push-button 190 the generator voltages may then be raised so that the web speed is further increased and the solenoid 178 closes the switch 183 de-energizing relay RB and so extinguishing lamp 188, while energizing relay R3. In this way, zones 3, 4, 5, 6 are heated in succession and the web speed is increased up to a maximum. If at any stage it is desired to slow the web, push-button 194 is pressed so that rheostat motor 191 operates the rheostat 39 to decrease the excitations of the generators. Slowing of the web will result in shutting down the hot gas supply to the heating zones and the substitution of cooling air blasts. Push-buttons 194,190 may be replaced by manual switches in which case if these are kept closed the operations are effected automatically. Hot gas or air after contact with the web is fed on a semiclosed circuit 134 back to the main circulating fans, 10 per cent being bled off by fans 126, 129 into the exhaust 128, 131 and fresh air being drawn in through ducts 125 downstream of the exhausts. To equalize the transfer to the cords over the width of the web, the rollers may be curved or curved locating bars used so as to spread the cords at the margins of the web as in Specification 690,165; radiant heaters may be located to heat the margins only; or the oven be divided into central and marginal compartments and the margins may be supplied with hotter gas. Hot gas may be directed at both sides of the web. In a modification, the oven is longitudinally divided into separate heating zones and the web is fed through narrow slits in the end walls of each zone which may be a sinuous form as in Fig. 14, so that the heating gas is passed repeatedly through the web. Instead of the heating gas flowing counter to the web movement it may flow in the same direction. High nip pressure during initial drying should be avoided especially when treating polyester cord, since it increases penetration of adhesive into the cords, reducing flexibility and fatigue life. Omission of the water dip prior to coating has similar results and gives thicker coatings. Accordingly, tension may be applied only after passage through the first heating zone, surplus adhesive-removing squeeze rollers being driven at the same speed as the first main driving roller which is located between the zones 1 and 2. Instead of the squeeze rollers excess adhesive may be removed by beater bars, scrapers, or air jets. In a further modification, for avoiding stretching of the coated cords while wet which deteriorates them, particularly if of polyester, the cords are coated by dipping and then pass successively between stationary scrapers and past a motorvibrated beater bar to a vertical festoon drying unit and then are fed by a driving roller into the first of three heating units followed by a cooling unit before being wound to store or other operations, the drying unit at least and the other units also if desired being supplied with a hot inert gas such as nitrogen to avoid explosion dangers and cord deterioration due to hot oxygen. The dried coated cords are stretched in the first heating unit, the tension is relieved in the second heating unit, and an increased tensioning is applied in the third heating and the cooling units. For this purpose dashpot-operated jockey rollers are located in each of the heating units to control the speed of downstream driving rollers, those on each side of the second heating unit being preferably mechanically locked together.