On a rigid-rapier loom when the rapiers are withdrawn from
the shed they must project outside the working width by amounts totalling at
least W. For any given W,rigid-rapier looms generally have a greater overall
width than flexible -rapier looms; the exceptions near the narrow end of the
range of W could be expected from the values of Kf Continuously
moving rigid rapiers would be expected to lead to large val use of A and looms
with this kind of rigid- rapier drive are normally available over only a small
range of widths, up to about 2m. Looms using cam-driven rapiers are available over
a wider range of widths, although this usually extends to only slightly above
the range for the first group. The rei tion between A and W in this second case
depends on whether-or not the rapier housings extend further outside the
working width than other parts of the loom. The other loom components may be
asymmetrically disposed, due to the location of the weft creel in particular,
and on narrow looms the rapier housing may extend further on one side only (as
in Fig. 6b)
Then A = 1.5W + Kr1 (2) When the housing extends
further on both sides A = 2W + Kr2
(Eqn. 3 has been given previously for rigid-rapier 100ms5).
Kr1 and Kr; are both constants, and whichever equation applies A
increases with W more rapidly than on a flexible loom. For a given range of looms
Eqns. 2 and 3 may both apply, each over a different part of the width range? It
should ne noted that if in such cases Eqn. 3 is fitted to the data for the
wider looms, it will underestimate A if used in the width range where Eqn. 2
applies, Also the deviations from Eqn. 3 are particularly marked in the
important case of the Dornier loom; Eqn. 3 this over only part of the width
range and if this fitted line in extrapolated to smaller val use of W it under
-estimates A by up to Similarly for two -component telescopic-rapier looms,
graphs of A against W with gradients of 1.5, 1.25, and (possibly)1.0 can be
expected.
Discussion
So far an account has been. given of the more conventional
rapier-loom design strategies. In this final section some other uses of rapiers
are briefly mentioned, and attention is drawn both to some of the aspects of
rapier motion not considered here, and to a number of other accounts of rapier
looms.
It has been implicit in the present article that the purpose
of the rapier (S) is to insert weft from a supply package outside the shed.
However, occasionally. This is not all, or it may be only one of the functions
of the rapiers. Thus on wire us paving looms rapiers are sometimes used to pass
a weft package positively through the shed6, as was envisaged in a
number of the early attempts to devise a full-width power loom? In one recently
exhibited loom small weft packages are passed in turn through the two shed on
either side of a central rapier-driving unit; it has a single rigid rapier each
end of which is used to insert weft into one sheds. Again, in the ATPR shuttle
less loom, which is widely used in the USSR, the tubular rapiers are not used
directly for weft insertion, but to channel the air flow of the pneumatic weft
insertion system.
Another less radical use of a tubular rapier may be noted on
the Gardella T egard loom, which is an elaboration of the single rigid-rapier
method of inserting double picks. The weft is threaded through the full length
of the rapier, and is supplied to it from a location such that yarn is
withdrawn from the package during the rapier movement in both directions9
Lastly, the use of rapiers for additional operations occurs on the various
models of Mackie Tumack and Onemack looms, where the rapiers are involved in
best-up as well as
weft insertion.
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