April i, 1901.] 



THE INDIA RUBBER WORLD 



199 



THE MANUFACTURE OF RUBBER PACKINGS. 



By John S. McClurg, AT. S. 



T T THENEVER a large number of the operators of the 



\/\ manufacturing industries become compelled to use 



any certain article in the operation of their respect- 

 ive plants, that article naturally becomes an object 

 of interest to them. Is there a mill or a factory which can be 

 operated without rubber packing being used somewhere with- 

 in its confines ? No. 



Every engine and every pump must have its joints made 

 tight by an application of rubber packing. Rubber packing 

 is, therefore, an interesting article to the whole of the indus- 

 trial world. 



In this connection it may be interesting to state that just in 

 proportion as rubber packing is so universally used and useful 

 the details of its manufacture and construction are as little 

 known to the great multitude of consumers. There is no man- 

 ufactured line to-day about which so little is known by the 

 general public — and even the consumers — as the rubber line. 



As in the case of most products of the manufacturers' skill 

 and enterprise, there is an almost endless variety of rubber 

 packings on the market. These varieties naturally range in 

 quality from the cheapest shoddy packings to the medium and 

 best grades. Every manufacturer of mechanical rubber goods 

 turns out his own brands of packing and claims for them such 

 merits as will have the greatest weight in influencing a pros- 

 pective customer. 



In purchasing a rubber packing which will best meet his 

 needs the consumer must rely, more or less, upon his own 

 knowledge of the quality, based either upon experience or else 

 on the appearance of the goods. It is not the purpose of this 

 article to praise or to recommend any particular brand of pack- 

 ing, but to give to the readers of The India Rubber World 

 considerations on the methods of manufacture of this most use- 

 ful class of goods. 



A question of vital import to every manufacturer is : " What 

 disposition can be made of the scrap waste and trimmings 

 which accumulate about every factory ?" To no class of manu- 

 facturers IS this question more important than to the manufac- 

 turer of rubber goods. The proper solution of this important 

 problem has meant to many industries a vast increase in 

 wealth. In many cases this waste product — which formerly 

 went to the sewer or scrap pile — is now converted into useful 

 merchandise, and in many instances the revenue derived from 

 this source has proved sufficient to defray all the expense of 

 operating the factory. In the mechanical rubber industry rub- 

 ber packing is one of the principal products obtained from the 

 scrap and trimmings collected from the various departments. 



To the class of goods commonly known as rubber packing, 

 the various kinds of corrugated and embossed mattings also 

 really belong. They are so nearly identical in conformation, 

 construction, and manufacture that they cannot conveniently 

 be separated into different classes. We will begin, for conven- 

 ience, with the cheaper grades, and take up each succeeding 

 kind according to grade. 



It is essential first of all that every factory, in order to be 

 economically operated, should provide each department with 

 suitable receptacles to receive all the waste and trimmings 

 which accumulate in the manufacture of the different products. 

 These receptacles can be easily removed each day and carried 

 to the mill room, where their contents can be sorted over. 



Pieces which cannot be worked over again into the original 

 compound are piled away separately to be milled and ground 

 together. This is not only economical, but it also keeps the 

 factory clean and in good order. 



The waste having been sorted, it is ready to be milled. The 

 mill should be warmed up to a moderate temperature and the 

 scraps and trimmings worked through it until they become 

 thoroughly ground and mixed in batches of about 50 pounds. 

 It is important that the batch should become well ground and 

 perfectly smooth, to insure a packing free from lumps and 

 other defects. These batches are piled away and are ready to 

 be mixed with other compounds. 



The very cheap grades of packing consist of three kinds: 

 C.O.S. (cloth one side), C.B.S. (cloth both sides), and C.I. 

 (cloth insertion). In most cases the two former kinds have a 

 combination of the latter ; as, C.O.S. and C.I. The reason 

 for using these insertions and outside coverings of cloth is that, 

 in view of the fact that the quality of rubber entering into 

 the construction of cheap packings is so poor, it must be 

 strengthened. To use rubber alone for this purpose would be 

 too expensive; hence cloth is inserted to make the packing 

 strong and prolong its wearing qualities. 



The method of preparing the cloth, by the way, is the same 

 for all kinds used in packing ; hence this description will cover 

 all the different uses it may be put to. The cloth comes in 

 rolls about 38 inches wide and usually about 110-120 yards 

 long and is a good heavy sheeting. It is passed over a series 

 of heated iron rolls to eliminate all the moisture which the 

 sheeting absorbs in transportation and storage. 



The sheeting is then taken to the friction calender and 

 coated, that for use in insertion on both sides, and that for the 

 outsides on one side only — that side which is placed next to 

 the gum. The reason for covering this sheeting is to cause it 

 to vulcanize securely to the center and facing of the packing. 



The center is next prepared. This part of the packing is 

 made from the batches composed of the scrap and trimmings, 

 and should have some shoddy and compound mixed with it to 

 give it the proper body and firmness. These batches are now 

 warmed up on a mill. The calender isalso heated and the rolls 

 adjusted to make the sheet the thickness desired. 



Suppose it is desired to make a roll of C. O. S. packing. 

 Hang up a roll of sheeting which has been frictioned on one 

 side, so it will run evenly through the calender, and begin 

 running the warm scrap compound into it. When the com- 

 pound has reached the proper heat, start the sheeting between 

 the rolls and a smooth even coat of gum is thus spread over 

 the surface of the sheeting. 



During this process care should be exercised that all bubbles 

 are pricked to permit the air to escape and to allow the gum 

 to spread evenly over the sheeting. This will prevent blisters 

 and blemishes in vulcanization. Next comes the outer cover- 

 ing which — for convenience — we will call facing. This should 

 be of a better quality than the center, as it is the point of con- 

 tact when in use, and requires a better compound to give it 

 more strength and longer life. This compound is mixed and 

 milled and laid aside a few days to dry and harden before us- 

 ing. As soon as it is ready, warm up the batches on a warm 

 mill and then feed it into the calender. 



Again hang up the partially completed roll of packing and 



