Elastic and non-elastic narrow fabrics : $b and a chapter on narrow fabrics made on knitting machinesBrown, Samuel
History
Elastic and non-elastic narrow fabrics : $b and a chapter on narrow fabrics made on knitting machines
Brown, Samuel
Elastic fabrics; Looms; Rubber industry and trade; Textile fabrics; Weaving
Another type of loom employed in the making of fancy goods is what
is known as the overshot loom. It is used for the introduction of a
silk weft figure effect, and is probably the most pronounced form of
elaboration introduced. It differs from the old rise and fall method in
the economy of operation. The overshot continues to weave the body of the
goods right along while the auxiliary shuttle is putting the silk figure
in at the same time. Not only is it economical in the respect of greater
yardage, but the method employed in binding the figure limits the use of
silk to the actual figure displayed, and does not carry the silk, which
is the most expensive material in the fabric, to the extreme selvage at
every pick, as is the case where the rise and fall method is employed.
In the overshot system a specially designed dobby, shown at Fig. 3, is
used for operating the lightly weighted threads of the binder warps. Two
pairs of knives are employed, one of each pair operating far enough to
raise the threads used in the binder warp to the level of the top main
shed, while the other one of each pair carries the threads which are used
for figure purposes to a higher level, so that the overshot shuttle may
pass under them. This occurs every alternate pick of the loom, the body
shuttle making two picks while the upper or overshot shuttle makes only
one.
In levelling the harness, setting or timing of the loom, and making the
shed for overshot work, the plans followed are identically the same as
in ordinary single shuttle work, as the upper shuttle and upper shed are
distinctly auxiliary and subordinate to the main shed. The binder warp,
being necessarily but lightly weighted in its relationship to the upper
and lower cloths it is binding together, allows for the figure threads
to be strained out of their normal position, so that the upper shuttle
may pass under them. In order to conform to this strained position of the
binder figure threads, the upper shuttle must be acutely pitched downward
at the nose so as to get a good clearance, and thus avoid any binding
in its passages through the shed. This peculiar downward pitch of the
shuttle is very important and cannot be over emphasized. It is shown in
Fig. 4.
The overshot dobby is so constructed that a different set of draw knives
operate on each alternate pick of the loom, one on the binder lift and
the other on the rubber lift. This not only allows for a silk figure made
with the shuttle but affords facilities for the introduction of a warp
figure also, a combination which can often be made very effective, as
shown in Fig. 5.
[Illustration: Fig. 4.—Showing Auxiliary Shed and Pitched Shuttle as Used
in Overshot Work]
IMPORTANCE OF DOBBY HARNESS
Public-domain text, read in full here on John Shaqi.
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