ELASTIC BANDS

( Ti us Elastiques , Fr.; Federharz-zeige , Germ.) The manufacture of braces and garters, with threads of caoutchouc, either naked or covered, seems to have originated, some time ago, in Vienna, whence it was a few years since imported into Paris, and thence into this country. At first the pear-shaped bottle of Indian rubber was cut into long narrow strips by the sci ors; a single operative turning off only about 100 yards in a day, by cutting the pear in a spiral direction. He succeeded next in separating with a pair of pincers the several layers of which the bottle was composed. Another mode of obtaining fine threads was to cut them out of a bottle which had been rendered thin by inflation with a forcing pump. All these operations are facilitated by previously steeping the caoutchouc in boiling water, in its moderately inflated state. More recently, machines have been succe fully employed for cutting out these filaments, but for this purpose the bottle of caoutchouc is transformed into a disc of equal thickne in all its parts, and perfectly circular. This preliminary operation is executed as follows: 1. the bottle, softened in hot water, is squeezed between the two plates of a pre , the neck having been removed beforehand, as usele in this point of view; 2. the bottle is then cut into two equal parts, and is allowed to consolidate by cooling before subjecting it to the cutting instrument. When the bottle is strong enough, and of variable thickne in its different points, each half is submitted to powerful pre ure in a very strong cylindrical mould of metal, into which a metallic plunger descends, which forces the caoutchouc to take the form of a flat cylinder with a circular base. The mould is plunged into hot water during the compre ion. A stem or rod of iron, which goes acro the hollow mould and piston, retains the latter in its place, notwithstanding the resilience of the caoutchouc, when the mould is taken from the pre . The mould being then cooled in water, the caoutchouc is withdrawn. The transformation of the disc of caoutchouc into fine threads is performed by two machines; the first of which cuts it into a riband of equal thickne in its whole extent, running in a spiral direction from the circumference to the centre; the second subdivides this riband lengthwise into several parallel filaments much narrower but equally thick. The following figs. 366 , 367 , 368. represent the machine for cutting the spiral riband. The disc D , placed horizontally, turns round its vertical axis, so as to present its periphery to the edge of a knife C , formed like a circular blade, whose plane is perpendicular to that of the bases of the disc. This knife turns round its centre, which is fixed. The rotatory motion of the disc forces the knife to penetrate further and further into its ma , and the motion of the knife itself makes it cut the riband more easily. It is obvious, that if the disc alone revolved, the motionle knife could act only by pre ure, and would meet with an enormous resistance. A third movement becomes nece ary. In proportion as the disc is diminished by the removal of the spiral band, the centre of this disc must advance upon the knife, in order that the riband may have always the same breadth. The inspection of fig. 368. will make the accordance of the three motions intelligible. IMG:4147767755307473660_illo0425.png:Spiral riband cutter The knife C is placed upon a shaft or axis A , which carries a pulley, round which a belt or cord runs which drives the whole machine. This knife is six inches in diameter. In order that by being kept cool it may cut the caoutchouc better, it is plunged at its lower part into a trough B , full of water; a stopcock R , serves to empty this trough. The shaft A bears a pinion p, which takes into a wheel R , placed upon the shaft A ′; upon which there is cut a worm or endle screw, V , V . This worm bears a nut E , which advances as the screw turns, and carries with it a tie L , which in its turn pushes the disc D , carried upon a shoulder constantly towards the knife. This shoulder is guided by two ears which slide in two grooves cut in the thickne of the table. The diameter of the pinion p is about one fifth of that of the wheel R ; so that the arbour A turns five times le quickly than the arbour A ; and the finene of the screw V contributes further to slacken the movement of translation of the disc. When the disc is all cut down, the shoulder, the tie, and the nut, are brought back to their original position by lifting the nut, which is hinged on. The disc is fixed upon the shoulder by means of sharp points, and an upper washer. The shoulder and the washer have a very small diameter, in order that the knife may, in cutting down the disc, advance as near as po ible to the centre. The rotatory movement of the disc and its shoulder, is given by an endle screw W , W , which governs a pinion p′ , provided with 10 teeth, and carried by the shaft A , upon which the shoulder is mounted. The arbour A ′ of this endle screw receives its motion from the first shaft A , by means of the wheels S and S ′ mounted upon these shafts, and of an intermediate wheel S ′′. This wheel, of a diameter equal to that of the shaft A ′′, is intended merely to allow this shaft to recede from the shaft A . The diameter of the wheel of this last shaft is to that of the two others in the ratio of 10 to 8. IMG:4147767755307473660_illo0426.png:Riband cutter