IV The Centre Tie-up
The centre tie-up, also called the point tie-up, has for its purpose the enlargement of the design in fabrics such as table-covers, dressgoods, etc. This tie-up resembles in its principle that of a common point-draw on the harness-loom. After drawing from front to rear once straight through the entire set of harness, draw from rear to front and repeat. The only difference between harness-work and Jacquard work is in the fact, that with harness we commence to draw in from the first harness straight through to the last, A to B, and back again, B to C; but with the Jacquard tie-up on this method this is arranged through the threading of the comber-board, having a straight-through leasing of the heddles and drawing in of the warp.
In Fig. XXXV. there is a clear illustration given of the principle of the centre tie-up on an 8-row comber-board A, A´, B, B´. In laying out the comber board, it must be divided by the line C, C´, into two equal parts, D, C, and C, D´. In the part A, A´, C, C´, of the comber-board, we commence threading with leash 1 at the left-hand rear corner, running in succession towards the centre, as indicated by the arrow on this part of the comber-board.
In part B, B´, C, C´, the threading begins in the opposite corner, to the right-hand in front, with number 1 leash, threading in rotation the number of leashes from the front towards the rear, as again indicated on the figure by an arrow. After leasing and threading the harness, No. 1 leash will contain in its two mails the first and the last of the warp-threads, as indicated in Fig. XXXV. by the numbers, and the rotation by the arrows, S and S´.
Fig. XXXVI. represents this centre or point tie-up applied to a 200 Jacquard machine; comber-board, 8 rows deep; two full divisions; A, B, the first division; B, D, the second division; C and C´ forming the centre in each division. This machine will, if tied-up in this manner, produce a design requiring 400 warp-threads. We must arrange the design for this tie-up so as to repeat forwards and backwards respectively in the centre. Such a design will run upwards at a given angle to a definite point, then it will return by the same angle in an opposite direction until it reaches the base from which it originally started.
In this manner design, Fig. XXXVII., is constructed. A, B, C, C´, D, correspond with the same letters used in Fig. XXXVI.; hence, it will readily explain itself, as well as the method to be observed in designing for this kind of tie-up. The design runs straight through from A to C, and repeats itself backwards from C to B, finishing at B the first full division.
B-C´ equal A-C,}
C´-D equal C-B,} forming the second division.
Any changes as to different sizes of machines, rows deep of comber-board, or number of divisions, must be executed upon the principle explained in this article.