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THE INDIA RUBBER WORLD 



lAi-KiL 1, 1917. 



The Manufacture of Jar Rings. 



THE production of jar rings has assumed such proportions 

 as to make it a most important branch of the rubber in- 

 dustry. The compounded stock from which the rings are 

 made is generally run through a tubing machine, the outside 

 diameter of the resultant tube being slightly larger than is re- 

 quired to offset the reduction in size when the tube is wrapped 

 for curing. As the stock is run from the tubing machine it is 

 cut off in lengths of about 30 inches. These are placed on steel 

 mandrels and wrapped tightly with strips of wet cloth, after 

 which the tubes are vulcanized in open steam for 30 minutes at 

 SO pounds pressure. 



After curing, the tubes are removed from the mandrels by 

 compressed air and at the same time each tube is forced by the 

 same means over a special mandrel upon which the rings are 

 cut. Tliis mandrel, upon which the tube is mounted, is revolved 

 in the lathe at a high rate of speed and the cutting is done by 

 sharp steel blades mounted on a traveling carriage provided 

 with a longitudinal feeding mechanism, the cutting blades being 

 pressed against the revolving tube by a cam or other mechanism. 

 The cut rings are stripped from the mandrel by compressed air 

 and then inspected, counted and packed. 



An important item in the successful cutting of jar rings is 

 the cover for the cutting mandrels. This is usually made of 

 brass that will not injure the cutter when it passes through the 



Fig. 1. — McGeouch Lathe. 



rubber. This covering was formerly a cheap grade of rubber 

 compound, rolled on the mandrel by hand and cured in the usual 

 manner, after which it was dressed down to size on a speed 

 lathe. Such, a covering, however, becomes so badly cut after a 

 short time as to be rendered useless, A substitute for this cover- 

 ing is one of tough stock, sheeted very thin on a calender and 

 built up to 'the exact diameter on the mandrel. The uncured 

 stock will stand more cutting than when cured, and when worn 

 out it may be stripped from the mandrel, sent to the mill room 

 and sheeted for further use. Paper tubes are also used. 



There are several types of jar ring lathes and the principle 

 is about the same in all. However, the more recent machines 

 show marked improvement in design and construction that 

 makes for greater production. Descriptions of the most impor- 

 tant machines follow : 



THE McGEOUCH LATUR. 

 The machine shown in Fig. 1 is designed lor cutting two rings 

 simultaneously. A represents the mandrel upon which is placed 

 the rubber tube B, and C and D are circular knives mounted on 

 shafts which are journaled in the swinging arms E and f. The 

 knives are moved into engagement with the tube B by a cam on 

 the shaft G. After the two rings are cut, the cutters are held 

 in operative position while the knife carriage is moved longi- 

 tudinally a distance equal to the thickness of the rings. Pro- 



vision is made for stopping the feed shaft to prevent over-feed- 

 ing of the cutter carriage, and for shutting off the power when 

 the carriage has reached the end of its forward travel. 



COFFEY'S LATHE. 



In Fig. 2 are shown the front and end elevations of this 



Fig. 2. — Coffey's Lathe. 



machine. A is the lathe bed and B the cam shaft that moves 

 the knife carriage to and from the work. Mounted on the bed 

 A is the carriage F, which is moved longitudinally by a lead 

 screw G driven from the spindle by change gears H. The rotary 

 knife / is mounted on a short belt-driven shaft, that is journaled 

 in the cross slide L, which is attached to the auxiliary slide / 

 and the carriage F. 



After the knife has been set in proper relation to the surface 

 of the rubber tube to be cut, and the lathe started, one half a 

 revolution of the cam will feed the knife to the required depth, 

 while during the other half revolution the knife is withdrawn 

 by the cam. The moment the knife has cleared the surface 



Pianarosa's Original Lathe. 



of the rubber, the carriage is moved longitudinally the required 

 distance to bring the knife in position for the next cut. 

 THE ORIGIN-\I. PTWAROS.V JAR RING LATHE. 

 The jar ring cutting lathe, shown in Fig. 3, differs in design 

 from the usual type. The feature of this lathe is an elliptical 

 rotary cutter by means of which the rings are cut with very 

 smooth surfaces. The drawing shows a front elevation of the 

 machine. Secured to the bed A are the stands B and C. In 



