In some looms a letting-off motion works in conjunction with the take-up, to release the yarn on the beam at a fixed rate.
The Weft Stop Motion.
A reference to the invention of this very ingenious and useful apparatus is made in Chapter I. Its object is to stop the loom on the breakage of the weft, or when the cop is finished. Unsightly gaws or goals in the fabric are thus prevented, and the weaver enabled to attend to more looms. A lever is fixed to the breast beam ([Fig. 27]), hinged at one end, and arranged so as to rest against the starting handle E. The lever carries a bent fork C, which projects into a grid D in the slay at the moment that the crank is at the fore centre. The grid is let into the back board of the slay between the reed and the shuttle box at the starting side of the loom. On the tappet shaft is fixed a projecting cam or sector, raising one end of a bent lever C, the lower part of which is called the greyhound tail, and the upper part, which ends above the breast-plate, from its peculiar form is dubbed the hammer. The fork before referred to is balanced, and its back end hooked and resting on the hammer.
FIG. 27.
When there is weft in the loom the fork is prevented by the thread from passing through the grid, and its back part is thus lifted clear of the hammer. Should the weft be broken, the loom is stopped thus: The sector raises the greyhound tail at the moment that the slay is at the fore centre, and there being no weft to raise the fork, it is caught by the hammer, and the lever to which the fork is attached pulled forward, when, as previously referred to, the spring handle is released and the loom stops. Manifestly the motion must be set so as to act when the shuttle is at the fork side of the loom.
The Brake.
A good brake contributes greatly to the manufacture of even cloth; should the stopping arrangements be ineffective, thin places and cracks will be inconveniently numerous. Usually the brake is a simple lever acting on a brake pulley at one end, whilst at the other it is regulated by an inclined bracket connected with the starting handle. When the handle is pushed forward, the brake lever is lifted; when the knocking-off takes place the end of the brake lever drops and the leathers come in contact with the pulley, stopping the loom. Additional brake power may be made by altering the leathers or weighting the brake lever.