Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
' ~ 21~1260 23792-120
The present invention relates to a cutting tool for
loop-forming textile machines, in particular for the production
of plush goods, comprising a shank having a longitudinal axis,
and at least one cutting section formed on the shank. The
cutting section includes a wedge-shaped region defining a
razor-sharp cutting edge having a length.
As disclosed in German Patent No. 1 153 482, which
describes a circular knitting machine for the production of
plush goods, it is known to directly cut open the plush loops,
which are stretched out in a looped shape, on the machine
using corresponding cutting tools.
This known circular knitting machine includes a dial
having guiding grooves. Latch needlels guided in a needle
cylinder are used to form the loops in the plush thread. Plush
sinkers in the guiding grooves are each provided with a control
butt cooperating with a dial cam.
The plush sinkers are respectively provided with a
projecting cutting section. The cutting section is provided
with an inwardly oriented cutting edge that cooperates, as in
scissors, with an outwardly oriented cutting edge of an
associated fixedly arranged-cutting sinker, to cut the plush
thread after the plush loops have been stretched out.
Such plush-cutting blades as well as plush-cutting
needles are kno~n in several embodiments. Typically, the
known needles are provided with a needle head in addition to
the cutting section.
Occasionally, it is also necessary to cut through
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individual threads during a knitting process. As disclosed in
German Un~Am;ned Published Patent Application DE-OS 2 003 301,
a circular knitting machine for hosiery or the like is known
for producing a longitudinal cut in a tube-shaped section of
the goods. This known machine operates with cutting needles
that are inserted into the guiding grooves of the needle
cylinder. In a region behind the needle head, the shank of
the cutting needles (which are typically latch needles) is
provided with a cutting section having a ground, razor-sharp
cutting edge for cutting through a loop hanging on the shank.
The cutting of the loop occurs when the needle is moved into a
cutting position, which corresponds to a portion of the goods
to be cut along a row of loops.
Further applications for these known cutting tools
are in jacquard machines and yarn stripping devices and the
like, i.e., in all cases where individual threads must be cut
through during the knitting process.
To ensure the flawless quality of the goods produced,
it is important that the threads be perfectly and cleanly cut
through at the cutting points. If, for example, in filament
yarns, individual filaments rema-in uncut, knitting errors may
occur.
Since the cutting edges are heavily stressed, for
example, when cutting threads of synthetic fiber materials,
the service life of the known cutting tools is undesirably
limited. However, replacement of cutting sinkers and cutting
needles in a knitting machine requires a considerable amount of
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time, which results in corresponding production losses.
The invention provides a cutting tool for loop-forming
textile machines, comprising: a shank having a longitudinal
axis; and at least one cutting section formed on the shank, the
cutting section including a wedge-shaped region defining a
razor-sharp cutting edge having a length, the cutting edge
being wave-shaped over at least a part of the length.
Compared to the known plush-cutting blades and
plush-cutting needles, which have a cutting section with a
straight, line-shaped cutting edge alcng the entire length, a
waved cutting edge increases the blade length. Because of the
periodic rise and fall of the cutting point due to the wave
form, a significant improvement in the cutting conditions is
achieved. Further, the service life of the cutting blade may
be increased from six to ten times compared to the conventional,
known cutting tools with straight cutting edges.
Of course, hand-held knives or scissors, etc., with a
waved finish are known. However, the teachings from such tools
cannot simply be transferred to cutting sinkers or cutting
needles for the production of plush goods, since cutting
sinkers and cutting needles have small dimensions and a limited
lateral stability. Moreover, the fibers of the threads or yarns
to be cut are always extremely thin.
Preferably, the wedge-shaped region of the cutting
section of a cutting tool according to the present invention
is provided, at least on one side, with a waved surface having
recesses parallel to each other, and that extend essentially
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transversely to the wave-shaped cutting edge. The recesses
help protect the sharp cutting edge from outside mechanical
influences. Further, preferably, the recesses each have a
base arranged to form an acute angle with a plane extending
through the cutting edge and through the longitudinal axis of
the shank, or alternatively, extending parallel to the
longitudinal axis of the shank. Typically, the acute angle is
between 10~ to 30~, and is preferably 15~.
The wedge-shaped region of the cutting section may
be provided with the waved surface on koth sides of the cutting
edge. However, it may occasionally be advisable to provide the
wedge-shaped region on one side with an essentially planar,
smooth surface. Preferably, the smooth surface forms an acute
angle with a plane extending through the cutting edge, and
extending through the longitudinal axis of the shank or extend-
ing parallel to the longitudinal axis of the shank. The acute
angle is approximately between 10~ to 30~, and is preferably
between 13~ to 15~. Thus, the cutting needle may have a wedge-
shaped cutting section with a waved surface on one side, and
with a straight, planar surface on the other side to form a
wedge angle, for example, of approximately 28~.
The wave-shaped cutting edge defines a plurality of
crests arranged in a line, i.e., a line which extends along
and touches the crests of the waved cutting edge. In the most
simple arrangement, this line is straight, but it may also be
arcuate, i.e., concave (sickle-shaped) or convex. Preferably,
the line forms an acute angle with the longitudinal axis of the
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237~2-120
shank so that the cutting tool is suited for a pulling cut.
Generally, the thread to be cut is held under
tension. The cut is obtained by causing a relative motion
between the thread and the cutting edge of the cutting tool.
Depending on the construction of the knitting machine, however,
it is also possible to provide an arrangement wherein the
cutting section of the cutting tool cooperates with a fixedly
arranged opposing blade. The opposing blade may be provided
with a straight surface to form a straight opposing cutting
edge. Alternatively, the opposing blade may be provided with
a waved surface to form a waved opposing cutting edge. The
cutting edge of the cutting tool and the opposing cutting edge
of the opposing blade cooperate with each other to form a
scissors-like arrangement.
The invention will be described below in greater
detail in connection with exemplary embodiments thereof that
are illustrated in the drawing figures, wherein:
Figure 1 illustrates a side view of a cutting tool
comprising a cutting needle according to the invention;
Figure 2 is a plan view of the cutting needle of
Figure l;
Figure 3 is an enlarged, partial side view of the
cutting section and the needle head of the cutting needle of
Figure l;
Figure 4 is an enlarged, sectional view of the
cutting needle taken along the line IV-IV in Figure 3;
Figure 5 is an enlarged, partial side view of a
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cutting arrangement according to the invention, including a
cutting tool cooperating with an opposing blade;
Figure 6 is an enlarged, sectional view taken along
the line VI-VI of Figure 5.
Referring to Figures 1 through 3, a cutting needle
is illustrated which is typically used to produce cut plush
fabric on a circular knitting machine. The cutting needle
includes a punched needle shank 1 having three control butts
2, 3, and 4 that are spaced apart from each other on the
shank's upper side. The three control butts cooperate with cam
assembly elements (not shown) in a known manner.
A front end of shank 1 includes a round, plating hook
5 of circular cross-section. Alternatively, hook 5 can have a
laterally and/or inwardly pressed cross-section, or be tapered
toward a truncated cone-shaped tip of the hook.
A typically triangular-shaped cutting section 7 is
formed on shank 1, adjoining hook 5. Hook 5 has a root 8,
from which a cutting edge 9 originates. Cutting section 7 is
delimited on its upper side by cutting edge 9, which ascends
obliquely in a direction toward the end of shank 1. Cutting
edge 9 forms an acute angle with the longitudinal axis 10 of
shank 1. Typically, the acute angle is about 20~, as shown in
Figure 3.
As shown in Figure 4, cutting section 7 is provided
at its upper portion with a wedge-shaped region 11 that is
tapered toward the razor-sharp cutting edge 9. As best
illustrated in Figure 3, region 11 extends from a rearward end
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12 of cutting section 7 to about the back (i.e., the lower side)
of shank 1 near the hook root 8.
The cutting edge 9 is provided with a waved cutting
edge 9' along most of its length, typically beginning at a
level slightly below an upper edge of shank 1. Cutting edge 9
further includes a straight cutting edge 9" that adjoins waved
cutting edge 9'. Straight cutting edge 9" extends to rearward
end 12 of cutting section 7.
Waved cutting edge 9' is formed by providing one side
of wedge-shaped region 11, i.e., on the side facing the viewer
in Figure 3, with a waved surface 13 having parallel, groove-
like recesses 13' that extend essentially transversely to
waved cutting edge 9'. Recesses 13', together with the
elevations or crests 13" formed between adjacent recesses, form
an approximately sinusoidal profile.
On the opposite side, region 11 is provided with a
smooth, straight, essentially planar surface 14, which,
together with waved surface 13 defin-es waved cutting edge 9'.
Of course, instead of planar surface 14, it is also possible
to provide region 11 with waved surfaces on both sides of the
wedge, i.e., each side of region 11 would be provided with
recesses 13'. If this arrangement is used, the recesses of
the respective sides could be offset relative to each other in
the longitudinal direction of cutting edge 9.
As shown in Figure 4, region 11 is machined, i.e.,
ground, so that a base of each respective recess 13' and/or
crests 13" disposed between adjacent recesses are arranged to
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form with a plane 15 an acute angle 16. Plane 15 extends
through cutting edges 9' and 9"j and through longitudinal axis
10 of shank 1. Alternatively, plane 15 can extend through
cutting edges 9' and 9", and parallel to longitudinal axis 10
of shank 1. Typically, acute angle 16 is between 10~ to 30~,
and is preferably about 15~.
Planar surface 14 forms an acute angle 17 with plane
15. Acute angle 17 is typically between 10~ to 30~, and is
preferably about 13~. Thus, using the preferred acute angles,
region 11 will have a wedge angle of about 28~, with the angle
point of the wedge angle being disposed on cutting edges 9'
and 9".
However, if the plush loops are to be cut open
symmetrically into two parts having precisely identical lengths,
cutting edges 9' and 9" will be disposed in a centrally located
plane 15, i.e., the acute angles 16 and 17 will be essentially
equal.
In the embodiment illustrated, a straight line _
extends along crests 13" of waved cutting edge 9', and
continues along straight cutting edge 9". Straight line A is
inclined with respect to longitudinal axis 10 to form an angle
of about 20~. However, line _ may also be arcuately shaped,
for example, concave or convex (not shown). Further, straight
line A (and therefore cutting edges 9' and 9") may be
oriented parallel to, or at a near right angle to, longitudinal
axis 10, depending on the configuration of the cutting tool.
In the embodiments according to Figures 1 through 4,
2141260 - 23792-120
the cutting needle cuts through a thread (held under tension)
by using relative motion between the thread and cutting edge 9
of the cutting needle. However, it is also possible, depend-
ing on the construction of the machine, to provide a cutting
device that includes a cutting tool that cooperates with an
opposing blade, in a scissors-like arrangement. In such a
configuration, the cutting tool may be configured similar to
the cutting needle previously described in conjunction with
Figures 1 through 3, i.e., a cutting needle having a hook 5.
Alternatively, as illustrated in Figures 5 and 6, the cutting
needle may be configured as a cutting sinker, i.e., as a
cutting tool 19 without a hook. In Fi-gures 5 and 6, parts
identical to those already described in conjunction with
Figures 1 through 3 are provided with a supplemental
designation "a", and will not be described in any further
detail.
An opposing blade 20 is associated with the cutting
tool 19. Cutting tool 19 includes a shank la, and opposing
blade 20 has a wedge-shaped region 21 facing cutting edge 9a
of cutting tool 19 and extending at least over a length of
opposing blade 20 corresponding to the length of waved cutting
edge 9a'. Region 21 is provided with groove-like, parallel
recesses 22 that extend essentially transversely to a waved-
shaped cutting edge 23. Recesses 22, together with the crests
located between adjacent recesses, form a waved surface.
Cutting section 7a and opposing blade 20 each have facing,
adjacent sides having respective parallel, planar surfaces 24
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and 25. Surfaces 24 and 25 adjoin each other under elastic
initial tension, similar to a pair of scissors.
Preferably, cutting tool 19 operates in a back and
forth motion, i.e., cutting tool 19 moves in a horizontal
direction. However, cutting tool 19 may also be fixedly
arranged. Further, opposing blade 20 may also be moved in a
back and forth motion relative to cutting tool 19. Alterna-
tively, opposing blade 20 may be movable in a tilting motion
or in a combined tilting and back and forth motion. Further,
it may be desirable to fixedly arrange opposing blade 20, and
to only move cutting tool 19. However, regardless of the
relative motion of opposing blade 20 and cutting tool 19, the
respective cutting edges cooperate with one another to generate
a scissors-like cutting action between cutting edge 9a' (and
possibly 9a") and cutting edge 23.
Of course, if desired, opposing blade 20 may be
provided with a straight cutting edge (not shown).
The angles defined by wedge shaped region lla and by
wedge shaped region 21 are typically about 28~. However,
these angles may be considerably larger, for example, 70~ to
a maximum of about 90~. Moreover, it is not required that the
angle defined by wedge shaped region lla be identical to the
angle defined by wedge shaped region 21.
The cutting tool, and possibly the opposing blade, is
preferably composed of a suitable resilient steel. Cutting
sections 7 and 7a may be hardened in a region of the cutting
edges, and/or treated by providing the cutting edge with a
wear-resistant coating.
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The invention now being fully described, it will be
apparent to one of ordinary skill in the art that many changes
and modifications can be made thereto without departing from
the spirit or scope of the invention as set forth herein.
