Tappet and dobby looms : their mechanism and management by Roberts Thomas

Author:Roberts, Thomas
Language: eng
Format: epub, pdf
Tags: Looms
Publisher: Manchester [Greater Manchester] : Emmott & Co., Ltd.
Published: 1912-03-25T05:00:00+00:00

110 TAPPET AND DOBBY LOOMS

either in front of or behind the boxes. When in front the box is formed by turning the box shelf up or down to form the shuttle-box front. In this instance the shuttle is only gripped on about one-third of its depth, the remaining space being required for the working of the picker. Where the picker is placed behind, the back of the box is made with an aperture to accommodate the picker. The box swell in this instance is at the front of the box, and practically takes the place of the box front. Long shuttle-boxes are much better than short boxes in their influence on the picking and checking of the shuttle, though faulty construction may be the cause of that ever-recurring defect, " weft cutting."

The Pick. —The nature of the blow to be imparted to the shuttle should be such as will cause the minimum of vibration on the parts affected. There is no possible means of calculating the actual force required, owing to the many variable circumstances attendant on picking —viz., the frictional resistance between the warp and the shuttle; the pressure exerted on the shuttle when leaving and entering the box; and the friction of the picker on the spindle when newly oiled or when requiring oil. With careful and judicious setting of the parts, however, the picking motion may be adapted to cover a wide range of requirements.

Picking Motions. —Fig. 29 illustrates the most common method of developing the force by which the shuttle is driven across the race. This is a type of an over - pick motion invariably adopted on plain looms giving alternate picking. It is also applied in a modified form to looms in which the pick is required to take place from either side a number of times in succession. The mechanism consists of the upright shaft A supported by the footstep bearing B, and held in position at the top by means of a bottle-neck pedestal C. At the bottom

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