The present invention relates to an improved thread guide particularly
for guiding elastic threads in knitting machines for manufacturing socks, stockings,
or the like, and particularly for medium-diameter circular knitting machines such
as machines for manufacturing underpants, undershirts, body stockings, etc.
As known, in small- and medium-diameter single-cylinder circular
machines for knitting which requires the cutting of threads at the end of a portion
of knitting, there is a cutter arranged above the needle cylinder and coaxially
thereto. More particularly, said cutter is substantially constituted by a disk
which is rigidly associated with the needle cylinder in its rotation about its
axis, in rotating-cylinder machines, and is peripherally provided with small teeth
which engage the thread to be cut when said thread is no longer engaged by the
In fact, at the end of the knitting of a portion of knitting, the
thread guide or guides which supplied the thread or threads to the needles which
knitted said portion are raised so that the subsequent needles can no longer engage
said thread which, by being engaged with the last needle, and which in the meantime
has retracted into the related groove of the needle cylinder, passes, due to the
rotation of the needle cylinder with respect to the thread guides, on the side
of the tip of the following needles which is directed toward the axis of the needle
cylinder. The thread becomes arranged along a chord above the cutter and is engaged
by the teeth thereof which face the inner side of the needle cylinder.
A counterblade is arranged downstream of the feed being considered
and is constituted by a plate which rests above the cutter in the region of the
teeth and cuts the thread when the tooth which has engaged said thread arrives
at said plate.
A suction nozzle is arranged between the counterblade and the thread
feed and is directed toward the upper face of the cutter; by means of a continuous
stream of air, the nozzle retains the end of the thread fed by the related thread
guide when said thread is cut, in order to prevent it from returning towards the
thread guide and to consequently prevent interference with the other threads being
fed. The suction nozzle is arranged proximate to the thread feed so as to keep
said thread orientated along a direction which is radial with respect to the needle
cylinder in order to facilitate the engagement of said thread by the needles when
the related thread guide is lowered again, i.e. at the beginning of a new row
or knitting portion for which the use of that thread is required.
In the use of elastic threads, problems are encountered in retaining
the thread by means of suction nozzles, particularly when the thread is subjected
to tensing during knitting. In this case, in fact, after the cutting operation
has been performed by the cutter, the thread elastically shortens and returns
towards the thread guide, since the suction nozzle does not exert on the thread
a force sufficient to overcome the elastic reaction of the thread.
With threads having a high degree of elasticity, the shortening of
the thread can be such as to cause the complete escape of the thread from the related
thread guide, thus compulsorily requiring the halting of the machine and the intervention
of an operator to restore the correct feed of the thread.
Thread cutting and clamping units are used in order to solve this
problem; said units are arranged above the cutter and operate alternatively with
respect to said cutter when it is necessary to cut an elastic thread. Although
they solve the problem of the possible escape of the elastic thread from the related
thread guide, said cutting and clamping units have the disadvantage of requiring,
for their operation, appropriate actuation elements which must be controlled by
a control unit of the machine, generally a microprocessor, making the programming
of said machine complicated.
Since the cutting and clamping units are arranged above the cutter,
they can also create problems in design, since they cause problems in arranging
other elements required for the operation of the machine in this region, which
in turn creates problems during maintenance interventions on the machine.
The aim of the present invention is to obviate the above described
disadvantages by providing an improved thread guide which effectively avoids the
escape of the thread when it is cut without requiring the use of thread cutting
and clamping units arranged above the cutter.
Within the scope of this aim, an object of the invention is to provide
a thread guide which allows to use the cutter to cut elastic threads as well as
Another object of the invention is to provide a thread guide which,
since it does not require thread cutting and clamping units, simplifies the design
of the machine and the programming of the electronic control unit which controls
A further object of the invention is to provide a thread guide which
allows to maintain low costs for the elements required for thread feeding.
This aim, these objects and others which will become apparent hereinafter
are achieved by an improved thread guide particularly for elastic threads in knitting
machines for manufacturing socks, stockings, or the like, which comprises a rod
having at least one passage defined therein for a thread, said passage leading
out proximate to a longitudinal end of said rod which is arrangeable proximate
to a workspace of needles of a knitting machine or the like, characterized in
that thread locking means are provided along the path followed by a thread on said
rod and can be activated upon a return of a thread fed through said passage.
Further characteristics and advantages of the invention will become
apparent from the description of two preferred but not exclusive embodiments of
the thread guide according to the invention, illustrated only by way of non-limitative
example in the accompanying drawings, wherein:
- figure 1 is a lateral elevation view of two thread guides according to the
invention in the first embodiment;
- figure 2 is a perspective view of a thread guide in the first embodiment;
- figures 3 and 4 are lateral elevation views of a thread guide in the first
embodiment, illustrating its operation;
- figure 5 is a perspective view of a thread guide according to the invention
in a second embodiment;
- figures 6 and 7 are lateral elevation views of the thread guide illustrated
in figure 5, illustrating its operation.
With reference to the above figures, the thread guide according to
the invention, indicated by the reference numerals 1, 1a in the two embodiments,
comprises a rod 2, 2a which is intended to be pivoted, at an intermediate portion
3, 3a thereof, to a supporting structure 4 which is arranged laterally with respect
to the needle cylinder 5 of a circular knitting machine for manufacturing socks,
stockings, or the like.
A passage 8, 8a for a thread 9 to be fed to the needles 7 is defined
proximate to the longitudinal end 6, 6a of the rod which is intended to be directed
toward the needle cylinder 5 in the workspace of the needles 7.
According to the invention, locking means 10, 10a are provided along
the path followed by the thread 9 on the rod 2, 2a and are activated when a return
of the thread 9 fed through the passage 8, 8a occurs.
More particularly, the rod 2 of the thread guide in its first embodiment
has guiding means for the thread 9 which are substantially constituted by channels
11 and 12 defined in the body of the rod 2 and are aligned with respect to the
passage 8. Said channels 11 and 12, together with the passage 8, define a sliding
path for the thread which is fed through the passage 8.
Along said sliding path, the thread 9 passes above a supporting surface
or plane 13 which is arranged directly ahead of the passage 8 along the sliding
direction of the thread indicated by the arrow 14.
In this first embodiment, the locking means comprise an element 15
which is pivoted, at its upper end, to a portion 16 of the rod 2 which is arranged
above the supporting plane 13. The lower end of the element 15 extends toward the
supporting plane 13. The element 15 can oscillate about an axis 17, arranged parallel
to and spaced upward with respect to the supporting plane 13 and perpendicular
to the sliding direction 14 of the thread 9.
In this manner, the lower end of the element 15 can move toward or
away from the supporting plane 13 by oscillating about the axis 17.
The oscillation of the element 15 in the opposite direction with
respect to the delivery end 6 of the thread guide is limited by the presence of
the portion 16, and return means act on the element 15 and bias the oscillation
thereof toward the thread delivery end 6.
If the element 15 is made of ferromagnetic material, said return
means can be conveniently constituted, as in the illustrated case, by a permanent
magnet 18 associated with the portion 16 of the rod 2 and orientated toward the
The lower end of the element 15 has, on the opposite side with respect
to the end 6, a level or chamfer 19 which forms an acute angle with respect to
the sliding direction 14 of the thread on the supporting plane 13.
In this manner, when the thread 9 is fed, by means of the traction
performed by the needles which engage it, the contact itself of the thread keeps
the lower end of the element 15 at a distance from the supporting plane 13 which
is sufficient to ensure the correct sliding of the thread 9. A return of the thread
9 in the direction opposite to the feed direction causes the oscillation of the
element 15 in the opposite direction, i.e. it causes the lower end of the element
15 to move closer to the supporting plane 13, and the thread 9 is pressed and thus
locked between the element 15 and the supporting plane 13. The oscillation of the
element 15 during the return of the thread 9 is caused not only by contact with
said thread but also by the action of the magnet 18.
Said magnet 18 can be replaced with a simple return spring which
is not illustrated for the sake of simplicity.
In the second embodiment, channels 11a and 12a and a supporting plane
13a are defined in the rod 2a similarly to what has already been described with
reference to the first embodiment.
In this second embodiment, the locking means comprise an elastically
flexible lamina 15a which is fixed, at its upper end, to a portion 16a of the rod
2a, arranged above the supporting plane 13a and upstream of the supporting plane
13a along the sliding direction 14 of the thread 9.
The lower end of the lamina 15a rests on the plane 13a, forming an
acute angle with respect to the sliding direction 14 of the thread 9.
In this manner, an advancement of the thread 9 along the sliding
direction 14 is allowed by the elastic oscillation of the lamina 15a caused by
the contact itself of the thread 9, whereas a return of the thread 9 in the opposite
direction causes the locking of the thread 9, which is pressed by the lamina 15a
against the supporting plane 13.
The thread guide according to the invention can be adopted in replacement
of conventional thread guides and can be actuated in the same way as conventional
thread guides, for example by means of electromagnetic actuators 20 and springs
The operation of the thread guide according to the invention is evident
from the above description and from the drawings, and in particular it is evident
that by cutting the thread 9 on the machine it is not necessary to provide a device
for clamping the cut thread 9, since its return toward the thread guide is blocked
by the element 15 or by the lamina 15a directly on the thread guide. Even in the
case of very elastic threads, in view of the small distance between the thread
locking point and the delivery end of the thread guide, the portion of thread 9
which remains protruding from the thread guide is long enough to be engaged by
the needles at the beginning of a new knitting.
In practice it has been observed that the thread guide according
to the invention fully achieves the intended aim, since it avoids the use of the
cutting and clamping units used so far for elastic threads, while effectively
preventing the escape of the thread from the thread guide.
The thread guide thus conceived is susceptible to numerous modifications
and variations, all of which are within the scope of the inventive concept; all
the details may furthermore be replaced with technically equivalent elements.
In practice, the materials employed, as well as the dimensions, may
be any according to the requirements and to the state of the art.
Where technical features mentioned in any claim are followed by reference
signs, those reference signs have been included for the sole purpose of increasing
the intelligibility of the claims and accordingly such reference signs do not
have any limiting effect on the scope of each element identified by way of example
by such reference signs.