414 



THE INDIA RUBBER WORLD 



[September i, 1904. 



THE MANUFACTURE OF RUBBER HEELS. 



BY J. W. C. 



RUBBER heels are now made by the ton. Millions of pairs 

 are sold and used, and the demand seems constantly to 

 grow, so that the production of this class of goods has become 

 an item of no small importance to the rubber industry. Hence 

 it has occurred to the writer to offer these few suggestions, in 

 the hope that they may prove of some practical value. 



The compounds used range in cost from 10 cents to 40 cents 

 a pound. For heels not over ', inch in thickness it saves time 

 to use stock " slabbed out " on the mixing mills. Many heels, 

 however, are made from two separately mixed stocks, a cheap 

 grade being used for the top of the heel {i.e., next the foot), 

 and another, with superior wearing qualities, for the tread. Such 

 a combination is commonly "plied up"on the calender, for 

 when thus joined there is less liability of the component stocks 

 splitting apart when in use as heels. To cut up slabs of stock 

 preparatory for mold work steel dies are used, closely copying 

 the size and shape of the heel. A power press controlled by a 

 foot lever is frequently used, and one in which slabs 36 to 40 

 inches wide can be handled, is preferable, as it admits of rapid 

 dieing-out across the width of the slab. 



In some shops great pains is taken to trim the stock thus 

 died-out to a specific weight, thus adding a large and unneces- 

 sary item to the cost of production. Assuming that there are 

 no wide variations in the specific gravity of a given stock, and 

 it is furnished in slabs of a specified and uniform thickness, as 

 it should be, then with a proper assortment of cutting dies 

 trimming to weight becomes a superfluous operation. Work 

 in mill room and calender room has, however, an important 

 bearing, as careless or imperfect work there will make weigh- 

 ing and trimming a necessity. This is especially true where 

 " plunger " molds are used, as a heel or two heavier than the 

 rest will prevent the other heels in the mold from " filling out." 

 Uniformity in thickness and weight of heels before curing nec- 

 essarily effects percentages in cured waste. In figuring cost 5 

 percent, is generally specified, although some shops allow 10 per 

 cent. Care regarding this item will show, however, that cured 

 waste need not exceed an average of 3 per cent. There is, it ap- 

 pears, such a thing as figuring this item of cured waste to too 

 fine a point, as it is susceptible of demonstration that a heel 

 cured with an abundant overflow, has a closer grain and will 

 outwear one produced with barely enough stock to fill the mold 

 cavity. 



In the press room, as in other departments, production is 

 the keynote. Each press should be so handled that its maxi- 

 mum capacity is attained. Heel molds are made containing 

 from 12 to 16 cavities. A capable pressman should handle two to 

 four such molds per heat. There is " no money " in the use of 

 single-platen presses for curing heels. The two-platen press is 

 proportionately better and the four platen press the best of all, 

 for it will accommodate the work of two men handling 16 

 molds between them. This is an important item where floor 

 space and the number of presses that can be used is limited. 

 A factory that had floor space lor but 10 presses, could, with 

 the single-platen style produce 3500 pairs of heels in ten hours; 

 with 10 four platen presses, 14,000 pairs. 



Superintendents generally have to make the most of their 

 factory equipment as it stands, and where this includes an open- 

 steam vulcanizer, the output of the press room in heels may be 

 substantially increased by beginning the cure in presses and 

 finishing it in the vulcanizer. Let us suppose, for illustration, 

 that the proper cure for a particular heel stock is 15 or 20 min- 

 utes. Ten minutes in the mold is probably all the time neces- 



sary to perfectly mold the heel, although not to thoroughly 

 cure it. At that time, however, it can safely be removed from 

 mold and the cure completed in open steam, to the distinct bet- 

 terment of the product, and a material increase in the number 

 of heels turned out during the day. 



There is just now a demand for a heel that will not bloom, 

 and if the compounds give trouble in this particular, a cure of 

 30 minutes at 50 pounds in the open steam vulcanizer, as above 

 suggested, will effectually dispose of the bloom. After trim- 

 ming, all heels should be cleaned by washing in a hot solution 

 of potash, then rubbed with a cloth moistened with naphtha or 

 a small quantity of glycerine. This results in a black heel of 

 very attractive appearance. The introduction of a heel with a 

 piece of duck vulcanized into the wearing surface has added 

 another item to the burden of worries carried by the factory 

 superintendent. It can be made successfully, although at a 

 considerable advance in cost over the plain article. 



The production of a perfect heel is contingent largely upon 

 the class of work demanded of the press room. As in all press- 

 work, the greatest care must be taken to keep the molds clean. 

 The pressman can accomplish this in large part, and nothing 

 sharpens his senses so rapidly as charging him with the value 

 of heels that are defective owing to some neglect on his part. 

 In spite of the best oversight, however, molds will gradually 

 accumulate a thin scale, especially in those parts bearing the 

 name or trade mark or ornamental design. Boiling in strong 

 potash, followed by a few minutes in a sand blast, will clean a 

 mold thoroughly. A thin solution of castile soap (say 5^ 

 ounces to a pail of hot water) makes a good solution, and is in 

 common use, and where a stock gives trouble by sticking to the 

 mold, 1 or 2 ounces of carbolic acid will be found of advantage. 

 Two points are to be observed if the heels are practically to fall 

 out of the mold as soon as it is opened : Cleanliness and proper 

 soaping. It is easy to put on too much soap. Heels have a 

 very aggravating way of not " filling-out," although plenty of 

 stock has been used. This should be looked for in a stock that 

 is too dry, and in the more expensive stocks. This trouble can 

 be overcome by placing the loaded mold in the press and allow- 

 ing the stock to become softened by the heat, before actually 

 closing the press upon it. Increasing the length of cure two 

 or three minutes has also been tried, with good results. 



A TARIFF DECISION ON RUBBER TOYS. 



IN the matter of a protest by George Borgfeldt & Co. against 

 the assessment of duties by the collector of customs at 

 New York, the United States general appraisers decided, on 

 July 30, that rubber dolls and doll heads are dutiable at 35 per 

 cent, ad valorem under paragraph 418 of the tariff act. Kin- 

 dred articles of rubber, such as figures of children with elastic 

 cords attached thereto; grotesque, military, and other figures 

 such as clowns, horseback riders, animals, etc., although toys, 

 are expressly excluded from classification under this paragraph, 

 and are dutiable as manufactures of rubber under paragraph 

 449, at 30 per cent, ad valorem. The importers contended 

 that the articles were rubber toys, not dolls, and that, inasmuch 

 as toys composed of rubber are expressly excluded from the 

 provisions of paragraph 418, they are properly dutiable at 30 

 per cent., as manufactures of rubber. " Dolls and doll heads of 

 whatever material " being provided for by paragraph 418, the 

 board of appraisers undertook to decide what are dolls, and it 

 was set forth that "rubber articles representing children, 

 dressed or undressed, whether the arms and legs thereof are 

 partly detached from the body or otherwise, were universally 

 and generally known as dolls," and were dutiable as such. 



