114 



THE INDIA RUBBER WORLD 



[January i, 1904. 



changed to prismatic Sulphur and that it will become melted 

 at 248°. The extremely fine particles will assume the globular 

 form as their surface tension must be very great. In the mean 

 time vulcanization has commenced, attended with absorption 

 of the Sulphur vapor, which is presented to the rubber in the 

 smallest possible amounts and therefore to the largest possible 

 surface of rubber. As the temperature of 248° is passed the 

 rate of vulcanization rapidly increases, until the highest tem- 

 perature adapted to the compound and the goods to be made 

 is reached. 



MAKING MOLDED GOODS IN RUBBER. 



A GREAT variety of small molded articles in a rubber fac- 

 tory brings forward the necessity for rapid and inexpen- 

 sive means for preparing the stock, and pressing and trimming 

 the goods. The methods employed are not always well con- 

 sidered from an economical standpoint, notwithstanding their 

 importance. A few notes on some methods actually employed 

 may be of interest, and afford a clue for further study and de- 

 velopment where new problems of this kind need to be worked 

 out. 



In the preparation of stock (or mold work a good tubing ma- 

 chine is essential. By providing suitable dies stock may be 

 rapidly run for an endless variety of shapes ready to cut into 

 pieces of suitable size to fit the molds. One of the most satis- 

 factory stock cutters for this purpose is a small semi circular 

 or cam shaped blade, attached to a spindle operated by power 

 at a lively speed. The blade is arranged to pass with a shear- 

 ing action across an opening in a metal face through which the 

 stock from the tubing machine is fed against an adjustable 

 guide to regulate the length of the piece. In this way thou- 

 sands of pieces an hour may be cut ready for the molds. 



Washers and similar thin articles may be punched from a nar- 



TOP AND BOTTOM VIEWS OF A SIMPLE QAQE KNIFE. 



row strip with great exactness of weight, and with considerable 

 speed if power is used, or a fair rate if cut by hand die. An ex- 

 cellent arrangement for this sort of work consists of a power 

 press, cutting several pieces at a stroke ; or with a die making 

 one part of the cut as a hole, and the next the outside of the 

 circle. Boot heels are easily cut by a press of this kind at the 

 rate of 3000 per hour. 



Valves and large circular work, such as gaskets, are cut by 

 knives attached to a cross bar at the end of a vertical shaft. 

 The stock is brought upward into contact with the knives by 

 raising the table of the machine by foot power. Calendered 

 slab stock : \ inch or more in thickness may be rapidly cut in 

 strips of any desired width by a simple gage knife made of J 

 inch spruce or pine, as shown in the figure. The wood portion 

 consists of a board about 5 inches wide by 10 inches long ; on 

 one edge of this is fastened a strip of J inch wood about 2 X 10 

 inches. On the opposite side a strip of -J inch iron £ inch 

 by 10 inches is attached by three or four screws. This iron 

 strip is adjustable by means of the screws to any desired dis- 

 tance from the point of the blade which is pushed through the 

 joint of the main board and wooden back strip. The knife is 

 held to its work by a nail or screw driven in behind it. With 



such a simple tool rapid and accurate work is possible in cut- 

 ting strips for gaskets and similar work. 



In the curing of goods it should be noted that the object of 

 press work should be merely to shape and " set " or partly vul- 

 canize the goods, in order to economize the time of the 

 presses. From 10 to 20 minutes at 40 to 60 pounds of steam, 

 according to the stock employed, is long enough in the press. 

 The subsequent final curing can be effected by a wholesale heat 

 in open steam. By this method the stock will have the feel of 

 much better quality than if fully cured in the molds. 



The weight of stock to make any given object should be reg- 

 ulated as nearly as possible to the capacity of the mold, that 

 there may be produced the minimum amount of cured trim- 

 mings. With some very low grade goods trimming and finish- 

 ing are most cheaply done by tumbling the articles in a barrel. 

 This treatment removes all traces of the " fin " from the parting 

 of the mold ; but, of course, is only adapted to special cases. 

 Such goods as Fuller balls and others of circular cross section 

 are most economically trimmed by means of a small power 

 punch forcing single pieces through a die which trims them 

 clean as they pass rapidly through to a receptacle below. With 

 such a trimming machine, operated by a boy, the expense of 

 trimming need not exceed 10 cents per 1000 pieces. 



In valve making it is often necessary to procure a mold 

 quickly to fit certain odd dimensions for which no mold is at 

 hand. This is most easily effected by springing into the circular 

 recess of the base plate of a larger valve mold than is required, 

 one or more rings of thin iron rolled to circular form by hand 

 power rollers and filed on the ends to make a neat driving fit. 

 In this way the size of a valve mold as regards both depth and 

 diameter, may be quickly altered, and the rings if kept and 

 properly marked, are always available for making the same 

 size again. 



Rubber molds are frequently useful, inexpensive, and durable 

 when properly made. They are especially adapted to such 

 goods as stair treads, door mats of corrugated design, and a 

 variety of small mats. If carefully handled, such molds give 

 surprisingly long service. They are generally made on a foun- 

 dation of belt duck built up }i inch or so thick, like a slab of 

 packing. This is well cured in the hydraulic press and then 

 one ply is stripped out of the face the size and shape of the 

 molded surface desired. The mat or tread pattern is cut in 

 strips or blocks from j4 thick cured rubber packing or cor- 

 rugated matting. These shapes are carefully cemented in place 

 where the ply has been removed. Care is always taken to 

 leave a supporting margin of 4 or 5 inches of duck around 

 the design. This is necessary to prevent spreading under the 

 molding pressure. If such a mat mold is mounted on an iron 

 plate with supporting edges, it is practically indestructible. 



One of the leading concerns in the world for the produc- 

 tion of apparatus for the extinction of fires is that of Merry- 

 weather & Sons, at Greenwich, in England. The founder of 

 the' present head of the business was the inventor of the fire 

 engine which won the first prize of the Great Exhibition of 1851 

 in London. The works turn out practically every type of fire 

 engine and accessory machines, and the disposition of the firm 

 to keep up with the times is indicated by their manufacture of 

 a hose tender and chief officer's buggy driven by a 12 HP. mo- 

 tor. The products of this establishment are shipped to every 

 continent. Messrs. Merryweather & Sons continue the manu- 

 facture, on an extensive scale, of. leather fire hose, which is 

 made up to a diameter of 9 inches. They also make canvas 

 hose and rubber lined hose, the rubber being supplied by rub- 

 ber manufacturers. 



