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.
Fig. XXXV.
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.
[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.
Fig. XXXVII.
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.