Handloom provided with a mechanism for variation of the distance between breastbeam and back beam

A handloom provided with a warp beam for the supply of warp threads, a back beam for guiding the wrap to the weaving plane and a cloth beam for advancing the fabric. There are means provided for variation of the distance between the back beam and the breastbeam. The breastbeam is moveable substantially in the direction of the back beam and parallel to its starting position. Resilient members are present which exert a force away from the back beam on the breastbeam.

The invention relates to a handloom, provided with a warp beam for the 
storage and supply of warp threads, a back beam for guiding the warp 
threads to the weaving plane, a breastbeam for guiding the fabric from the 
weaving plane and a cloth beam for advancing the fabric, in which means 
are provided for variation of the distance between the back beam and the 
breastbeam. 
In weaving, every warp thread which has been tensioned in the loom is led 
through a heddle. These heddles are fastened group by group in harnesses. 
The harnesses can be moved substantially crosswise to the direction of the 
weaving plane. This arrangement results in the formation of a clearance 
between the warp threads, called shed, through which the weft thread is 
caused to impinge on the already formed fabric by means of an impact 
member, called reed. The harnesses are worked with the aid of handles or 
treadles. To enable a large amount of weft thread to be passed through, it 
is important that the movements of the harnesses create a wide clearance 
between the warp threads without any undue increase in the warp tension 
and/or adverse effects on operation. 
In virtually all types of handloom the back beam and the breastbeam are 
fixed, in consequence whereof the warp tension increases considerably 
during the formation of the shed. The use of an inelastic warp material in 
particular severely limits the height of the shed and involves the danger 
of the warp threads being ruptured or damaged. The force required to 
operate the harnesses increases according as the warp tension is higher 
and rises during the formation of the shed. In addition, the requisite 
operation force is increased during the shed formation by the angle at 
which the harness is exposed to the warp tension. Systems designed to 
solve this problem by regulation of the tension during shed formation are 
called compensation devices. 
In the present state of the art there are compensation devices of a 
mechanical and a hydropneumatic nature. The desired effect is attained by 
moving the breastbeam and the back beam towards each other during shed 
formation, so that the length of the warp stretched in between need not, 
or hardly, change. Only mechanical compensation devices can be adapted for 
use in a handloom. A known mechanical compensation device has a back beam 
moving towards the breastbeam during shed formation. The movement of the 
back beam is induced by a mechanism that is linked to the drive of the 
harnesses. This mechanism can be designed such that the length of the warp 
between breastbeam and back beam, and hence the warp tension, remains 
virtually constant during shed formation. It has been developed 
specifically for industrial looms, but when applied to a handloom it has 
the following disadvantage, among other things. The harnesses of a 
handloom are driven by a number of treadles or handles, generally four, 
six, eight or ten, but sometimes even more. As every handle or treadle has 
to move not only the harnesses but also the back beam, every handle or 
treadle requires a mechanism which actuates the back beam. When used for a 
handloom, the existing system will thereby become complex and expensive. 
This disadvantage will worsen when the handloom is to be extended so as to 
include more treadles or handles than the number provided in its simplest 
design. 
During shed formation in a handloom, it is desirable for the warp tension 
to increase somewhat, since this will facilitate the return of the warp 
threads in the weaving plane when the harnesses are no longer operated. 
It is an object of the present invention to provide a handloom having a 
simple mechanism for regulating the distance between back beam and 
breastbeam in such a fashion that the warp tension increases only slightly 
during the formation of the shed. To this end, the breastbeam is disposed 
in the loom according to the invention so as to be movable substantially 
in the direction of the back beam and parallel to its starting position, 
while resilient members are present which exert a force away from the back 
beam on the breastbeam. In order to guide the movement of the breastbeam, 
the latter may, according to a feature of the invention, form part of a 
pivoting frame whose axis of swivel runs parallel to and below the 
breastbeam. 
During the movement of the breastbeam, the tension in the fabric located 
between breastbeam and cloth beam is subject to changes. Any great change 
in this tension is undesirable, however. This problem can be solved 
according to a further feature of the invention by the provision of a 
guide for the fabric near the axis of swivel of the pivoting frame, so 
that the movement of the pivoting frame with the associated breastbeam 
causes very little change to the length, and hence to the tension, of the 
fabric between breastbeam and cloth beam. 
The resilient members can exert their force on the breastbeam through the 
pivoting frame. To achieve this, they have been disposed between the 
pivoting frame and the fixed part of the loom. At a certain desired warp 
tension, the requisite force of the resilient members depends upon the 
length of the actuating arm of the said members relative to the axis of 
swivel and on the distance between the axis of swivel and the breastbeam. 
The resilient members are preferably of a light construction as commonly 
known in domestic use. According to a feature of the invention, the 
actuating arm of the resilient members relative to the axis of swivel may 
therefore be considerably longer than the distance between the axis of 
swivel and the breastbeam. 
As a handloom must be capable of weaving different types of fabric in 
different widths and from different materials, it is desirable that the 
force of the resilient members admits of variation. Accordingly, it is a 
feature of the invention that the resilient members may be given a 
desirable initial tension. In order to render the tension even more 
variable, according to a further feature of the invention the resilient 
members may consist of a variable number of springs. This arrangement also 
has the advantage that a relatively small resilience per spring will 
suffice, so that the springs can be readily mounted and/or subjected to 
the desired tension.

The FIGURE is a simplified diagram of an embodiment in which the warp (1) 
is held in stock on the warp beam (2), guided through the back beam (3) 
and then passed through the heddles which have been grouped in harnesses 
(4). Between the harnesses (4) and the breastbeam (6) the warp (1) is 
turned into fabric (5) during the weaving process. The resultant fabric 
(5) is passed via the breastbeam (6) to the cloth beam (7). Breastbeam (6) 
forms part of a pivoting frame (11) whose axis of swivel (10) is located 
parallel to and underneath the breastbeam (6). Fabric (5) is passed 
between breastbeam (6) and cloth beam (7) through a guide (9) disposed 
near the axis of swivel (10). Resilient members (12) are attached between 
the pivoting frame (11) and a longitudinally adjustable link (13) which is 
in its turn attached to the frame of the loom (8). When the harnesses (4) 
are worked in the direction indicated by the arrows, the increasing 
tension on the warp (1) will be compensated by the displacement of the 
breastbeam (6) in the direction of the arrow. At the same time the 
bottommost part of the pivoting frame (11) will move in the direction of 
the appropriate arrow. The resilient members (12) will be stretched such 
that their elongation is substantially equal to the displacement of the 
bottommost part of the pivoting frame (11). The degree to which the 
tension of the warp (1) changes during the movement of the harnesses (4) 
bears a certain ratio to the degree to which the tension of the resilient 
members (12) changes during their elongation. This ratio is governed by 
the length of the actuating arm of the resilient members (12) relative to 
the axis of swivel (10) and the distance between breastbeam (6) and axis 
of swivel (10). Changes in tension on the warp (1) will be relatively 
slight when the resilient members (12) are chosen such that they undergo 
relatively little change in tension upon a variation of their length. The 
provision of a longitudinally adjustable link (13) makes it possible to 
impart a desirable initial tension to the resilient members (12).