Stitch bonded fabric

A stitch knitted fabric, for example a stitch bonded web of fibres, is made on a two guide bar machine with the front bar (which may exhibit missed thread patterning) knitting pillar stitches and the back bar (which may have part, for example, half set threading) forming stitches and/or laid-in sections and/or floats of thread extending over at least two wales of the front bar system and repeating over not less than four courses, the back bar system distorting, through thread tension, the front bar system and/or filling to give a pattern or texture effect.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to stitch knitted fabric in which a filling is 
knitted through with front and back guide bar warp thread systems. 
The invention has particular reference to stitch bonded fabrics in which 
the filling is a fibre fleece, usually a cross-folded card web. Other 
types of filling, of course, include for example a sheet of weft threads 
or a sheet of foamed plastics material. 
2. Description of the Prior Art 
Two guide bar fabrics have been manufactured in which the front and back 
bars knit with different stitch systems. Reasons for using two independent 
thread systems in stitch bonded production include the production of more 
interesting surface texture or pattern effects, improved weft-way 
strength, and the avoidance of laddering. In a well known arrangement, one 
bar knits pillar stitch while the other bar knits tricot stitch. In 
another arrangement, both bars knit mirror-image systems extending over 
two or more needles. 
Pattern effects are also achieved--even in single guide bar stitch bonding 
machinery--by the use of half set or otherwise incomplete threading. 
Missing out a single thread occasionally from a ground of pillar stitch 
gives rise to a lengthwise stripe or rib. Pattern effects have also been 
produced by the incorporation of a laid-in effect thread substantially 
without tension in a ground of pillar stitch, which shows up for example 
as a zig-zag line or a wavy stripe, if several such threads are laid-in in 
a block. 
However, stitch bonded fleece fabrics, even with these various pattern or 
texture effects, have always had a relatively flat surface or an 
essentially lengthwise ribbed texture somewhat resembling a cord cloth. 
Lengthwise ribbiness can to some extent be reduced by avoiding the pillar 
stitch and knitting tricot stitch formation on both bars--or perhaps more 
complicated zig-zag patterns--but the physical properties of such fabrics, 
particularly as regards lengthwise stability, are considerably inferior to 
those of fabrics that have pillar stitch on one bar. 
SUMMARY OF THE INVENTION 
The present invention provides two guide bar stitch knitted fabrics having 
novel pattern or texture effects and good physical properties, in 
particular, lengthwise stability. 
The invention comprises a two guide bar stitch knitted fabric comprising a 
filling and front and back bar warp thread systems of which the front bar 
system comprises pillar stitches and the back bar system repeats over not 
less than four courses, its threads passing between at least two wales of 
the front bar system and comprising fewer stitches in a repeat than the 
number of courses in the repeat, the back bar system distorting, through 
tension in its threads, the front bar system and/or filling, to give a 
pattern or texture effect. By `stitch` is meant the result of an overlap, 
where the thread is laid into the hook of the needle. 
The back bar system may comprise laid in sections of thread, or stitches 
and laid in sections, or stitches and floats, or stitches and both laid in 
sections and floats. 
A `laid in` section is a section of back bar thread that is not formed into 
a stitch but which is trapped between the filling and the underlays of the 
front bar thread. A `float` is a section of back bar thread that is not 
formed into a stitch and is not trapped by the front bar thread but floats 
on the technical back, i.e. the underlap side of the fabric. The pillar 
stitch on the front bar gives the fabric desired lengthwise stability, 
while the distorting effect of the back bar system can be used to produce 
a wide variety of patterning or texture effects. 
The front bar system may exhibit missed thread patterning, in which one 
thread, or, in finer gauges, two adjacent threads, can be omitted, usually 
to a predetermined pattern. The back bar system may, and in most cases 
will, exhibit part set threading, such as half set threading, or a missed 
thread every third or fourth wale. 
One effect that can be produced in accordance with the invention is a 
simulated raised cable stitch formation. A single, or preferably a double 
missed thread wale on the front bar system is crossed by floats of the 
back bar system. Tension in the floats pulls in the front bar pillar 
stitch wales either side of the missed thread wale, which bunches up the 
filling in between to stand proud of the adjacent pillar stitched regions, 
while the floats extending diagonally across the raised filling impart a 
cabled or twisted appearance. 
A waffle effect is produced when the back bar system comprises a system of 
laid in sections extending alternatively between first and second pairs of 
wales of the front bar system. 
A hopsack fabric is simulated when the back bar system comprises three or 
more courses of tricot stitch followed by one or more course of float 
and/or laid in sections in the repeat. This effect is enhanced by half set 
threading of the back bar system or by other part set threading systems. 
The invention also comprises a method for making a two guide bar stitch 
knitted fabric in which the front bar knits pillar stitch and the back bar 
executes a lapping motion which repeats over not less than four courses, 
which extends over at least two needles, and which executes fewer overlaps 
in the repeat than the number of courses in the repeat, the back bar warp 
threads being under tension so as to distort the front bar system and/or 
filling to give a pattern or texture effect. 
The distorting effect will of course depend on the tension in the back bar 
threads, which can be adjusted to produce the exact effect desired. 
Normally, the tension in each back bar thread will be somewhat higher than 
the tension in each front bar thread, and both may be controlled in the 
usual way by positive feed let off from the beam and by the tension rail.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIGS. 1 and 2 illustrate a two guide bar stitch bonded fleece fabric having 
an open pillar stitch warp thread system on the front bar and a back bar 
system which repeats over four courses, the threads passing through four 
wales of the front bar system, and having two stitches in each repeat. 
Between stitches, the back bar threads have laid in sections crossing over 
adjacent wales. 
The front bar exhibits double missed thread wales and in fact has a 
repeated threading pattern 1111111100111100, while the back bar is 
threaded 1010100100100100, where "1" indicates the presence of a thread 
and "0" indicates a missed thread. 
It will be seen that some of the back bar threads, namely B1, B2, B3 and B5 
lie wholly within the regions of front bar pillar stitch wales. Tension in 
these threads has the effect of pulling the front bar wales F1 to F8 into 
pairs (F1,F2), (F3,F4), (F5,F6) and (F7,F8) so as to accentuate lengthwise 
ribbiness by bunching up the fleece fibres in between the wale pairs. It 
also has the effect of accentuating the transverse ribbing of the fleece 
into well defined transverse rib pairs between the courses of back bar 
stitches. This accentuated walewise and coursewise ribbing gives the 
fabric ground between the front bar missed thread wales a woven 
appearance. 
Tension in the back bar thread floats B4, B6 that cross the front bar 
missed thread wales has the effect of pulling together the adjacent front 
bar thread wales which causes the intervening fleece to bunch up and stand 
proud of the ground--there is no stitch in this region to hold the fleece 
down. The fibres bunch up around the floats giving the appearance of a 
raised cable stitch formation. 
FIGS. 3 and 4 illustrate the production of a waffle effect. The front bar 
knits a full set of pillar stitches, while the back bar, with half set 
threading, simply lays in threads over three wales which alternatively 
connect the two right hand wales and the two left hand wales of the three 
wales covered. Tension in the laid in threads pulls the front bar stitch 
wales F together wherever they are connected by the laid in back bar 
threads B. The fleece fibres billow out into small cushion like formations 
between the distorted stitches on the technical back. The technical front 
of the fabric has a different though equally attractive waffle appearance, 
with small ridges of fibre raised up between the stitch chains where they 
are pulled together. 
FIGS. 5 and 6 and FIGS. 7 and 8 illustrate the production of two different 
hopsack effect fabrics. That shown by FIGS. 5 and 6 has a full set of 
pillar stitch on the front bar, and on the back bar, with half set 
threading, a sequence of stitches S first on one needle, then on an 
adjacent needle, then back to the first needle followed by a float F, as a 
repeated pattern. In the conventional notation, the lapping motion would 
be described as the sequence, 1-0/1-2/1-0/0-0/repeat. 
The fabric illustrated by FIGS. 7 and 8 is similarly produced except that 
the back bar is threaded 110110110 etc. 
Tension in the back bar threads pulls the front bar wales of pillar 
stitches into groups of two (FIGS. 5 and 6) or three (FIGS. 7 and 8), 
enhancing the lengthwise ribbed effect of the front bar wales. The 
coursewise alternation of stitches and float on the back bar gives rise to 
a transverse ribbing effect. The combination of effects give an appearance 
characteristic of hopsack weave. 
Although it is of prime importance from the point of view of lengthwise 
stability that there should be a pillar stitch formation maintained 
throughout on the front bar, this is not to say that minor divergences 
from this requirement cannot be made. It would be perfectly possible, for 
example, to achieve some special effect by introducing occasional tricot 
stitches instead of pillar stitches. This would affect the lengthwise 
stability, but perhaps within acceptable limits. 
Open pillar stitch has been shown in the examples illustrated. Closed 
pillar stitch could be used instead if desired. 
Obviously, numerous modifications and variations of the present invention 
are possible in light of the above teachings. It is therefore to be 
understood that within the scope of the appended claims, the invention may 
be practiced otherwise than as specifically described herein.