Device for clamping weft threads in a warp knitting machine

The weft threads (10) are clamped in weft thread hooks (12) supported on longitudinal conveyors (43, 44) extending perpendicular to and adjacent opposite ends of a row of knitting needles (42) by means of clamping slides (20) mounted on the longitudinal conveyors (43, 44). The clamping slides (20) are supported for sliding movement in a perpendicular direction relative to the movement of the longitudinal conveyors (43, 44) and are movable between an inactive, retracted position away from the hooks (12) through a placement zone (E) and an active position pressed against the hooks (12) and the weft threads (10) as the longitudinal conveyors (43, 44) move through a clamping zone (K) extending both upstream and downstream of the row of knitting needles (42).

FIELD OF THE INVENTION 
This invention relates generally to a device for clamping weft threads in a 
warp knitting machine, and more particularly to such a device which 
includes thread clamping slides mounted on longitudinal conveyors 
extending perpendicular to and adjacent opposite ends of the row of 
knitting needles and including operating means for selectively moving the 
slides between a retracted position and an active position in which the 
slides are pressed against the weft thread hooks. 
BACKGROUND OF THE INVENTION 
One type of device for clamping weft threads in a warp knitting machine is 
disclosed in DE-OS No. 20 12 114. In this type of device the clamping part 
includes a pressure wheel which is formed of elastic material and its 
circumference engages the weft thread hooks to hold in position the weft 
threads placed around the hooks. It is necessary to retain the weft 
threads against the hooks because weft thread waste pieces extend around 
the hooks after the weft threads have been incorporated and cut off. 
Unless the weft thread waste pieces are retained on the weft thread hooks, 
the weft threads will not remain under tension and may become loose. The 
pressure wheel is positioned at the same position as the weft thread 
cutting location and is rotated by the weft thread hooks as they move 
forwardly so that the inward pressure of the pressure wheel engages and 
presses against at least two hooks during its rotation, because of the 
diameter and elasticity of the pressure wheel. The pressure wheel thus 
acts only with a relatively short clamping zone as the longitudinal 
conveyors are advanced so that the clamping of the weft threads by the 
pressure wheel takes place over a short weft thread racking zone as the 
weft threads extend back and forth between the opposite longitudinal 
conveyors. As a greater number of weft threads are placed on the hooks by 
the thread guide, the weft threads will be laid on top of one another in 
certain hooks and must be clamped in this position by the pressure wheel. 
This may lead to the release of certain of the weft yarns, particularly 
when very smooth and slick yarns are employed, so that the tension in the 
weft threads can be released and allow the yarns to slip back in relation 
to the hooks and the pressure wheel. 
In an attempt to overcome this problem of the short clamping zone provided 
by the pressure wheel, it has been proposed that the pressure wheel be 
elongated to form a kind of revolving caterpillar so that a pressure belt 
is pressed against the hooks by sequentially arranged pressure rolls. With 
this arrangement, the weft thread clamping zone is lengthened, in 
accordance with the length of the caterpillar pressure belt. In this 
arrangement, the pressure belt is moved along by friction against the 
hooks and the weft threads, in a similar manner as described above for the 
pressure wheel. This pressure belt arrangement also does not always 
operate satisfactorily, especially when weft thread arrays including a 
large number of threads, for example 20 weft threads, are fed to the hooks 
so that the hooks in the center of the array have large bunches of threads 
being pressed against the hooks by the pressure belt. The thickness of the 
bunch of weft threads is not evenly distributed throughout the weft thread 
waste pieces, but tapers evenly from the center to both sides and thus has 
to be compensated by the caterpillar pressure belt. It has been found that 
an even contact pressure function of the caterpillar pressure belt cannot 
be achieved across a large clamping zone so that, especially with warp 
threads having a low frictional contact with the hooks, the same problems 
occur as with the contact pressure wheel described above. Also, the 
contact pressure wheel and the contact pressure belt are each subject to a 
high degree of wear. 
SUMMARY OF THE INVENTION 
With the foregoing in mind, it is an object of the present invention to 
provide a device for clamping weft threads in a warp knitting machine 
which provides a secure clamping of the weft threads against the hooks, 
regardless of the number of threads to be held in each instance, which has 
a long wear life, and may be utilized to maintain the warp threads in 
pressure engagement with the hooks throughout a relatively long clamping 
zone. 
The weft thread clamping device of the present invention includes clamping 
slides mounted on the longitudinal conveyors supporting the weft thread 
hooks and extending perpendicular to and adjacent opposite ends of the row 
of knitting needles. The clamping slides are mounted for sliding movement 
in a perpendicular direction relative to the movement of the longitudinal 
conveyors. Control means is provided for maintaining the slides in a 
retracted position away from the hooks through a placement zone and for 
maintaining the slides pressed against the hooks and the weft threads as 
the longitudinal conveyors move through a clamping zone extending both 
upstream and downstream of the row of knitting needles. 
The configuration of the clamping slides on the longitudinal conveyor 
eliminates the necessity of the clamping parts to be rotated by the 
threads and the hooks. The clamping slides operate to press the weft 
threads against the hooks without any relative movement between the 
clamping slides and the hooks. The clamping slides are thus subjected only 
to static friction and, because they do not roll as a result of being 
carried along, no sliding friction can occur, which is largely responsible 
for the wear experienced when using a pressure wheel or a pressure belt. 
Since the clamping slides are supported for inward and outward sliding 
movement on the longitudinal conveyors, considerable pressure can be 
easily exerted by the slides on the hooks so that a high degree of 
efficiency can be achieved with regard to clamping the weft threads which 
are placed in the hooks. 
The inner end portions of the clamping slides which face the hooks are 
preferably provided with an elastic pressure piece shaped on its outer 
free end to conform to the shape of the corresponding weft thread hook 
against which it is pressed. The shaping of the outer end of the elastic 
pressure piece insures that the pressure piece fits snugly against the 
outer surface of the hook and also insures that the pressure surface 
engages the hook and any weft threads which are passed between the hook 
and the clamping slide. 
In order to impart the required inward and outward movement to the clamping 
slides, a guide piece is supported on the outer end portions of the slide 
to cooperate with a guide rail. The guide rail applies pressure on the 
guide piece to move the clamping slide inwardly or outwardly, depending 
upon the position of the guide rail, relative to the longitudinal 
conveyor. The guide rail can be provided with a curved cam groove or 
trackway into which the guide piece is mounted. In this instance, the 
position of the clamping slide in relation to the hooks is defined by the 
curved configuration of the cam groove. 
It is also possible to press the clamping slides against the hooks by the 
tension of a spring and to hold the slide clamps in the retracted position 
in the placing zone by means of a guide rail so that the hooks are free to 
allow the weft threads to be placed therein by the weft thread carriage 
and thread guides. In this embodiment, the guide rail acts to withdraw or 
retract the clamping slide during the passage through the weft thread 
placing zone while the tension spring operates to move the clamping slide 
inwardly with the elastic pressure piece being pressed against the weft 
threads and the hooks in the clamping zone. Applying the contact pressure 
of the clamping slides by means of a tension spring has the advantage that 
the spring can easily compensate for various thicknesses of weft threads, 
or a changing number of weft threads, which are placed in the hooks. 
The clamping slides are supported for perpendicular sliding movement on the 
longitudinal conveyors by the same parts which are used for fastening the 
hooks to the longitudinal conveyor to insure that the clamping slides 
remain in proper relationship to the hooks as they are moved inwardly to 
the clamping position and moved outwardly to the weft thread placing 
position. In particular, the hooks are attached to the inner ends of hook 
plates which are maintained on the longitudinal conveyor by shoulder 
screws and these shoulder screws also serve to support the clamp slides 
for sliding movement on the longitudinal conveyor. 
When the warp knitting machine is being used merely for incorporating cross 
weft threads when a single weft thread is placed around each hook, it is 
possible to associate all of the hooks of one longitudinal conveyor to one 
slide clamp. This arrangement can also be used in cases where each weft 
thread includes either multiple or individual weft threads. 
In instances where parallel weft threads are being incorporated in the warp 
knitting machine, the number of hooks can be reduced. This can occur in a 
weft knitting machine with a weft carriage that places one array of weft 
threads at a time so that the weft threads are placed after the forward 
movement in a parallel position to and at the same distance from the weft 
threads placed after the return movement. In this instance, the relevant 
neighboring parallel weft thread, and the two adjacent weft thread arrays 
form a recurring racking section in relation to the relevant longitudinal 
conveyor, are linked by a weft thread racking outside of the longitudinal 
conveyor so that the length of the longitudinal conveyor represents a 
multiple of the racking section. In this case, the clamping slides can be 
spaced along the longitudinal conveyor in such a way that each of them 
only operates across a limited range in the center of the racking section. 
In fact, it is in the center of the racking section that the number of 
threads placed around the hooks within this range equals the number of 
weft threads contained in a weft thread array. If this accumulation of 
threads is clamped, no problems arise when the weft threads that have just 
been incorporated are cut off, since their continuations into the 
unincorporated area, where the weft thread arrays enter the needle row, 
extend across the clamping point in the center of the racking section and 
are positively retained therein by the clamping slides.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Only those portions of a warp knitting machine are shown in the drawings 
which are necessary to an understanding of the present invention. The warp 
knitting machine can be of the type illustrated in the above-mentioned 
DE-OS No. 20 12 114 (see particularly FIGS. 2 and 6) which is incorporated 
herein by reference. As best illustrated in FIGS. 2 and 3, a conveyor 
chain guide plate 1 supports spaced-apart longitudinal conveyors 43, 44 
(FIG. 4) which extend perpendicular to and adjacent opposite ends of a row 
of knitting needles 42. The conveyors 43, 44 are moved forwardly in timed 
relationship to operation of the warp knitting machine. 
The details of only the longitudinal conveyor 44 are shown in FIGS. 1-3 
with each chain link 2 of the longitudinal conveyor including a pair of 
rollers 3, 4 which are adapted to roll along on the upwardly extending 
projections of the guide plate 1. The individual chain links 2 are 
interlinked in longitudinal direction of the longitudinal conveyor by 
shackles or links 5, 6, 7, 8 and 9 in the conventional manner of conveyor 
chain construction. The tension exerted by the weft threads 10 on the 
individual chain links 2 applies inward pressure on the longitudinal 
conveyors 43, 44 to maintain a downwardly depending guide plate 11 (FIGS. 
2 and 3) in sliding contact with the outer edge of the guide plate 1 as 
the longitudinal conveyor slides along in its forward motion. 
Hooks 12 extend upwardly from the inner end of a hook plate 13 having a 
horizontal leg extending across and secured to the longitudinal conveyor 
by shoulder screws 14, 15 having their lower ends fixed in nuts 16, 17 
carried by the chain link 2. The shoulder screws 14, 15 include respective 
shoulders 18, 19 which bear against the hook plate 13, thus clamping the 
same to the chain link 2. The screws 14, 15 pass through a clamping slide 
20 to fasten the slide 20 to the chain link 2 in a manner permitting the 
slide to move inwardly and outwardly. The slide 20 includes two elongated 
holes or slots 21, 22 in which the shoulders 18, 19 are positioned. The 
height of the shoulders 18, 19 is sufficient to insure that the clamping 
slide 20 will have sufficient play for longitudinal movement when the 
screws 14, 15 are tightened. 
The outer end of the clamping slide 20 is provided with a guide roller 23 
which moves along a cam groove 24 in the lower surface of a guide rail 25 
so that the roller 23 and the slide 20 are moved inwardly and outwardly by 
the cam groove 24. The roller 23 is supported for rotational movement on 
the outer end of the slide 20 by means of a screw 26. A pressure piece 27 
is attached to the inner end of the slide 20 and is made of elastic 
material, such as rubber, and is adapted to the shape of the pair of hooks 
12 on the inner end of the hook plate 13. 
FIG. 2 illustrates the pressure piece 27 spaced outwardly from the hooks 12 
while FIG. 3 illustrates the pressure piece 27 moved inwardly and pressed 
against the hooks 12. The inward and outward movement of the clamping 
slide 20 is controlled by the cam groove 24 in the guide rail 25. The 
inward and outward movement of the slide 20 is indicated by the dotted 
line illustration of the cam groove 24 in FIG. 1. When the clamping slide 
20 is moved inwardly, the weft thread 10, placed in the hooks 12, is 
firmly pressed into the hooks 12 and clamped by the pressure piece 27. 
A fragmentary plan view of one portion of one of the longitudinal conveyors 
is shown in FIG. 1 with the hooks 12 being supported on the inner ends of 
adjacent hook plates 13. Each clamping slide 20 interacts with a pair of 
hooks 12 so that all of the hooks 12 of the longitudinal conveyor are 
acted upon by the corresponding pressure pieces 27 on the inner ends of 
the clamping slides 20. The rollers 23 of the slides 20 are guided by the 
cam groove 24 extending inwardly beneath the guide rail 25. As shown in 
dotted lines, the cam groove 24 includes an outwardly directed cam surface 
28 and an inwardly directed cam surface 29 to define a clamping zone K 
therebetween. In this clamping zone K the slides 20, with their pressure 
pieces 27, press against the hooks 12. The clamping zone K extends both 
upstream and downstream of the row of knitting needles 42. In the areas 
above and below the clamping zone K the slides 20 are moved outwardly and 
retained in retracted position so that the pressure pieces 27 move 
outwardly away from the hooks 12 to provide placement zones E. 
FIGS. 5 and 6 illustrate a modified form of clamping slide 20' which is 
similar to the slide illustrated in FIGS. 2 and 3. However, the slide 20' 
of FIGS. 5 and 6 operates in a different manner from the slide 20 of FIGS. 
2 and 3. In the embodiment shown in FIGS. 5 and 6, the screw 15 has been 
replaced by a shoulder screw 30 provided with an upstanding portion having 
a groove therein providing a spring perch for the bent end 31 of a tension 
spring 32. The other end of the spring 32 is fixed on a bolt 33 on which a 
cam roller 34 is rotatably supported beneath the outer end of the slide 
20'. The cam roller 34 is adapted to ride against the outer surface of a 
guide rail 35. The tension of the tension spring 32 insures that the cam 
roller 34, and thus the pressure piece 27', is constantly pulled toward 
the hooks 12'. 
The outer surface of the guide rail 35, against which the roller 34 rolls, 
corresponds in shape with the corresponding side of the cam groove 24, as 
shown in FIG. 1. As the longitudinal conveyor advances forwardly, the 
roller 34, carried by the outer end of the slide 20', is moved along in 
accordance with the configuration of the outer surface of the guide rail 
35. In the position shown in FIG. 5, the guide rail 35 pulls the cam 
roller 34 and the slide 20' away from the hooks 12'. When the cam roller 
34 reaches that area of the guide rail 35 that corresponds with the 
clamping zone K, the pull of the spring 32 moves the slide 20' toward the 
hooks 12' until the pressure piece 27' is pressed into the hooks 12'. In 
order to achieve a secure contact pressure between the pressure piece 2' 
and the hooks 12' and against the several weft threads 10' being placed in 
the hooks 1', the cam roller 34 is spaced from the cam surface of the 
guide rail 35, as indicated by the space 36 in FIG. 6. 
FIG. 4 schematically illustrates the hooks 12 of the two longitudinal 
conveyors 43, 44 supporting arrays 38 of weft threads 10 which are placed 
into each of the hooks 12 by a thread guide 37 of a weft carriage, not 
shown. Racking rakes, not shown, but illustrated in DE-OS No. 20 12 114 
(see particularly rakes 52, 160 of FIGS. 7 and 8), are utilized to rack 
each weft thread array 38 outside of the longitudinal conveyors 33, 34 by 
the width of the weft thread array 38 so that the usual type parallel weft 
is laid in a conventional manner. In this parallel weft arrangement, all 
of the weft threads 10 run parallel to one another and at equal distance 
from the adjacent weft thread. 
This method of laying parallel weft threads results in a recurrence of 
racking section 39 consisting of two adjacent weft thread arrays 38. 
Outside of the hooks 12, the weft threads 10 form weft thread waste pieces 
40 to be cut off after the weft threads 10 move forwardly of the row of 
knitting needles 42. These weft thread waste pieces 40 increase in number 
from the outermost weft thread 10 in a racking section 39 toward the 
center and in the center of each racking section 39, the number of weft 
threads lying outside of the corresponding hooks 12 equals the number of 
weft threads 10 contained in a weft thread array 38. When the clamping of 
the weft threads is effected by a pair of the clamping slides 20 only in 
the range of this maximum accumulation, as illustrated in FIG. 6, the 
placed weft threads 10 are secured even after the cutting point 41, 
downstream of the needle row 42, so that they are securely clamped by the 
pair of clamping slides 20 and the corresponding pressure pieces 27 
carried thereby. 
In the modification shown in FIG. 4, the weft thread arrays 38 repeatedly 
form the racking sections 39 and the length of each longitudinal conveyor 
43, 44, with the hooks 12, forms a multiple of the racking sections 39. 
Under this condition, it is possible to provide only the pairs of adjacent 
clamping slides 20, illustrated in FIG. 4, at the points of maximum 
accumulation of weft thread waste pieces 40. Thus, it is not necessary to 
provide all of the hooks 12 with slides 20. The placing of weft threads 10 
with regularly recurring racking sections thus permits a significant 
savings in the number of clamping slides 20 required. 
In the drawings and specification there have been set forth the best modes 
presently contemplated for the practice of the present invention, and 
although specific terms are employed, they are used in a generic and 
descriptive sense only and not for purposes of limitation, the scope of 
the invention being defined in the claims.