Page:The American Cyclopædia (1879) Volume III.djvu/748

738 CAOUTCHOUC small pieces, and washed by streams of hot water which fall upon it from a perforated horizontal pipe. After being passed several times through this machine, it ia taken to another, standing FIG. 4. Washing and Compreuing Mill. beside it, similar in construction, but having a pair of smooth cylinders in place of the fluted ones. These produce an enormous pressure, which packs the pieces together in the form of a mat ; this is also passed several times in succes- sion through the machine and washed by the dripping of hot water, as in the preceding ope- ration. These machines are called washing, masticating, and compressing machines. When the mat is sufficiently compacted and washed, it is taken to a drying room, a warm chamber heated by steam, where it is allowed to remain from four to six weeks, until it is thoroughly dry; for if it were attempted to work the ma- terial while it contained any moisture, an in- ferior fabric would be the result. When per- fectly dry the rubber is taken to the mill room and passed successively through three mills. All the mills are of similar construction to the one already represented, except that in each machine one cylinder is made to revolve twice as rapidly as the other, in consequence of which the material is thoroughly ground and mixed. But while undergoing the process the conti- nuity of the mat is not destroyed, for it retains its form, although a careful scrutiny will show that a constant and rapid change of position is going on among the particles. The cylinders are hollow and are supplied with steam, which keeps them at about 220 F. in the first mill, and at a little lower temperature in the other two. The first mill merely works and com- presses the material into a firm thick sheet of a homogeneous texture, preparatory to the in- corporation of die sulphur and whatever other ingredients are to be added, which operation is performed entirely in the second mill. Taking as an example the manufacture of India-rubber hose for steam fire engines, as curried on at a large establishment in New York, the subse- quent steps are as follows: After leaving the' first mill, about 5 per cent, of sulphur (and in some cases certain mineral matters, as white lead) is thrown upon the sheet while it is pass- ing down between the cylinders. The mixing at first causes disintegration and the separation of the material into shreds ; but union is speed- ily reestablished, and the mass again becomes homogeneous, and will retain its pliability and elasticity after cooling. This, however, is not allowed to take place until it is passed through the third or finishing mill. Here the sheet is passed between the cylinders over and over again, until its pliability and working qualities are perfected, and as far as possible adapted to being spread upon canvas. This operation is performed in an adjoining room upon a calen- der (fig. 5), a machine somewhat similar to that used in cotton-bleaching establishments. The rubber is first of all again passed through a pair of cylinders in a machine called a feeder, which is also similar to the mills through which it has already passed. This feeder stands near the calender, and its purpose is to knead and tem- per the India rubber to the exact condition in which it can be best applied to the cloth. It is taken in handful s at a time and fed to the calender between the two upper cylinders rep- resented in the figure, but upon the opposite side to that which is shown. The surfaces of the two cylinders are so prepared that the rubber adheres in a thin sheet to the lower one of the two, which in its revolution brings it FIG. B. Calender. in contact with the third or next lower cylin- der, over which the cloth is being passed, for- cing it thoroughly into the meshes of the fabric. After one side of the canvas has been coated it is turned, and the rubber is applied to the other side. It is then taken to a larger calender, where another coating is applied to one side, | the whole sheet being well consolidated under powerful pressure. The cloth is now ready to bo made into hose, and the operation is com- menced by cutting it into strips diagonally, so that both warp and weft may receive the strain to which the hose may be subjected, thus great- | ly increasing the strength of the fabric. The strips are cut in width a little more than twice j the intended circumference of the hose, so that ! one sheet will form two thicknesses of its walls.