FIG. 24.
The shuttle race is made of hard wood laid on the beam, and in addition to the depression at the centre is also rather wider at the middle of the race—at that point bulging out slightly against the reed, which is kept in contact with it by the slay cap at the top and the reed case at the bottom. Care must be taken to keep the ends of the reed from projecting in front of backboard, or the shuttle will be thrown out.
Loose and Fast Reeds.
To obtain a firm blow at the cloth the reed is made to strike it at right angles, for if the angle were more obtuse or acute a loss of force would be entailed by a consequent downward or upward stroke imparted to the cloth, the line of action not being in the same plane as the line of reaction.
With regard to the firmness of the beating up, we have to consider the merits of fast and loose reed looms.
In weaving, an accident which not infrequently occurs is the stoppage of the shuttle when it has only traversed a portion of the distance across the warp. A case of this shuttle trapping causes the breakage of more or fewer ends, and consequently arrangements are made for preventing much damage, either by arresting the motion of the loom suddenly, in case of a fast reed, or by having a reed hanging loosely behind the shuttle so as to give way in case of a “mash.” The latter arrangement is preferable, as there is not the sudden concussion given to the loom, which causes the vibration and straining of every part, so objectionable in the fast reed loom; the loose reed can, however, only be used for light and medium cloths, as the reed is too lightly fixed to give a strong beat-up. In the case of the loose reed, the slay cap holds the upper part of the reed in a slot, the bottom part being pressed against the shuttle race by a strip of wood (completing the reed case) attached to the stop rod. When at the fell of the cloth, the stop rod is held firmly by a spring, and a fairly strong blow can be given to the cloth; but at all other portions of the slay’s movement nothing holds the reed but a weak spring acting on the casing, and if the shuttle traps, the reed flies out, while a finger on the stop rod knocks the loom handle off, stopping the machine without unnecessary concussion. This latter advantage enables the loose reed loom to be run at a speed of some 30 or 40 revolutions more than the fast reed.