[Illustration: Fig. XXXV.]
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´_.
[Illustration: 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.
[Illustration: 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_ " _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.