NoVEMIiER I, 1904.] 



THE INDIA RUBBER V/ORLD 



45 



VULCANIZATION OF RUBBER BY ELECTRICITY. 



ONE of the most interesting recent developments in 

 the line of rubber manufacture is the Riddle process 

 for the vulcanization of rubber by electric heat, gener- 

 ated either in press, vulcanizer, mold, support, or 

 former. The inventor and patentee of tlie processes and ma- 

 chinery is Mr. Howard S. Riddle, for six years mechanical 



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That this process has an almost infinite number of applica- 

 tions in the manipulation of rubber is at once apparent. Those 

 cited by the inventor relate chiefly to the closing of the mold 

 and the curing of t he rubberin molds for tires of the single tube 

 and clincher variety, in curing hose by sending a current through 

 the mandrel on which it is made, in closing the platens of a 

 press for regular mold work, in heating the platens, and in 

 closing tl'.e door of a vulcanizer and holding it tightly while the 



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I-'IG. I.— Mold for curiiiK Single Tube Tires. Desctiption: 10, II. upper and 

 lower halves of mold ; 12, rubber tire ; 13, valve stem ; 14, 15, coils for magnetiz- 

 ing and heating upper half of mold; 16, 17, coils for magnetizing and heating 

 lower half of molds. 



engineer for The Diamond Rubber Co. (Akron, Ohio), and an 

 expert both in mechanics and electricity. Patents have been 

 secured by him in Great Britain, France, Germany, Belgium. 

 Holland, Italy, Switzerland, Russia, 

 Finland, Japan, Australia, Mexico, 

 Canada, the United States, and 

 some South American countries. 



The inventions consist, broadly 

 stated, in making use of an electric 

 current, to close the parts of a 

 mold, or the platens of a press, 

 and also to heat electrically the 

 molds or the platens and thus eflect 

 vulcanization. 



The currents used are preferably 

 the direct, for closing, and the 

 alternating, for heating. While 

 neither current is strong enough to be in the slightest degree 

 dangerous, any degree of heat up to 400° F. is easily obtained, 

 and may be controlled with absolute accuracy for any length of 



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FIG 2 —Mold for curiiigClincher Tires. Description : i8, 19, upper 

 and lower halves of mold ; 20, clincher lire; 21, key piece; 2a, infiat- 

 iiig ha^ ; 23, valve stem; 24. single magnetizing antl he.iting coil, 

 with wires running through valve stem. 



I'"Ki 4. — Curing Hose. J >r'5cyiption : 4g, mandni connected at ends for electric 

 heating by direct current ; 48, rubber covering to be vulcanized. 



whole interior is electrically heated and vulcanization goes on. 

 Of plans for heating mixing and calender rolls, of curing dry 

 heat goods such as shoes, clothing, dress shields, etc., no 

 specific mention is made, although they all come under the 



broad claims that are allowed. 

 No adaptation of the new process 

 however, seems to fit the curing of 

 dipped goods, and that seems to be 

 the only exception as far as gen- 

 eral lines go. 



The electric heat is developed 

 by placing magnet coils in re- 

 cesses or grooves in the faces of 

 the platens or molds, connecting 

 with an alternating current, which 

 establishes rapidly alternating 

 magnetic fields with the attend- 

 ing hysteresis effects, and foucault 

 or eddy currents. The mold is closed by the magnetic attrac- 

 tion of its parts induced by an electric current passing through 

 coils imbedded in the parts of the mold. 



A magnetic press is also used to perform the work of the old 

 hydraulic presses, and is operated by a solenoid — and a series 

 of toggles and bell crank levers. 



There are many obvious advantages to the new process. It 

 does away with bolts and clamps for molds, steam chambers 

 for presses and tubing machines, leaky valves, and new pack- 

 ing, and it is claimed that the actual cost of operation is about 

 one-half of that of steam. 



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CONCESSIONS FOR "ALMEiDINA" GUM. 



FIG. 3. -Closing Device for Molds or Presses. Desct iption : 25, 26, tire mold ; 

 27, electro-magnet or solenoid; 28. toggle levers; 29. bell crank levers; 30, 

 pivotally fulcrumed arms ; 31, 32. coils for heating ; 33, tire. 



time, while by the direct current the mold or press may be 

 closed, and any pressure needed for rubber work be exerted 

 and continued until the current is turned off. 



The molds, platens, or formers — that 

 is, the heating surfaces — must be 

 made of a magnetizable metal, either 

 soft steel or cast iron being the best. 

 Soft metal molds such as are used 

 in hard rubber work could not be 

 magnetized and heated, although they 

 could doubtless be used in a press 

 or vulcanizer that was itself electri- 

 cally heated. 



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FIG. 5. Description : 5.', \ulcanizer ; 53, door; 54, 55. mag 

 net coils for closing docjr^; ^6, coil for heating the vulcanizer 

 57, protective casing. 



WHILE not much has been heard recently in regard to the 

 grade of rubber known as "Almeidina," it appears that 



interest in it has not died out in the country of its production. 



The Portuguese Diariodo Governo of September 24 contains a 

 royal decree authorizing the govern- 

 ment to grant to Portuguese compa- 

 nies legally constituted, to Portuguese 

 subjects, or to foreigners who under- 

 take to establish Portuguese companies, 

 concessions for the exploitation of the 

 "Almeidina" rubber plant {Euphorbia 

 tirucalH) in Angola, on certain condi- 

 tions, the details of which we hope to 

 present later. 



