U.S. patent application number 10/514554 was filed with the patent office on 2006-03-16 for device and method for severing a thread.
Invention is credited to Joost Carpantier, Dirk Willemot.
Application Number | 20060053602 10/514554 |
Document ID | / |
Family ID | 29588510 |
Filed Date | 2006-03-16 |
United States Patent
Application |
20060053602 |
Kind Code |
A1 |
Willemot; Dirk ; et
al. |
March 16, 2006 |
Device and method for severing a thread
Abstract
The invention relates to a device (1) for severing a thread that
comprises two blades (2, 3). An electric drive (4) enables said
blades to be moved counter to the action of leaf springs (6, 7; 9,
10) and into a ready position, from which the blades can be moved
back by means of the force of the leaf springs in order to execute
a severing process.
Inventors: |
Willemot; Dirk; (Rekkem,
BE) ; Carpantier; Joost; (Moorslede, BE) |
Correspondence
Address: |
BACON & THOMAS, PLLC
625 SLATERS LANE
FOURTH FLOOR
ALEXANDRIA
VA
22314
US
|
Family ID: |
29588510 |
Appl. No.: |
10/514554 |
Filed: |
May 27, 2003 |
PCT Filed: |
May 27, 2003 |
PCT NO: |
PCT/EP03/05537 |
371 Date: |
November 30, 2004 |
Current U.S.
Class: |
26/10.4 |
Current CPC
Class: |
B65H 2701/31 20130101;
B65H 54/71 20130101; D03D 49/70 20130101 |
Class at
Publication: |
026/010.4 |
International
Class: |
D06C 13/00 20060101
D06C013/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 31, 2002 |
BE |
202/0357 |
Claims
1. A device (1) for severing a thread (A), which has two blades (2,
3) at least one of which is movable relative to the other by means
of an electric drive (4), characterized in that the at least one
movable blade (2, 3) is movable by the drive (4) counter to the
action of at least one spring element (6, 7; 9, 10) into a ready
position from which, by means of the force of the at least one
spring element, it can be moved back again for executing a severing
operation.
2. The device of claim 1, characterized in that both blades (2, 3)
can be moved into a ready position with contrary motion by means of
electric drives (4) and can be moved back again by means of spring
elements (6, 7; 9, 10).
3. The device of claim 1, characterized in that the blade or blades
(2, 3) are each retained by respective pairs of leaf springs (6, 7;
9, 10), which are oriented transversely to the direction of motion
of the associated blade (2, 3) and are disposed spaced apart from
and parallel to one another.
4. The device of claim 1, characterized in that the blade or blades
(2, 3) are connected to an armature (5, 8) which contains at least
one permanent magnet (24, 25; 26, 27) and with which an
electromagnet (19, 20, 21) is associated.
5. The device of claim 4, characterized in that the armature (5, 8)
includes two permanent magnets (24, 25; 26, 27), which contact one
another with unlike poles.
6. The device of claim 4, characterized in that both blades (2, 3)
are provided with armatures (5, 8), whose permanent magnets (24,
25; 26, 27) are disposed such that they face one another with like
poles in the ready position and with unlike poles in the severing
position.
7. The device of claim 1, characterized in that the length of the
permanent magnets (24, 25; 26, 27) of the armatures (5, 8) in the
direction of motion of the blades (2, 3) approximately equals to
the magnitude of the relative motion between the blades.
8. The device of claim 1, characterized in that one common
electromagnet (19, 20, 21) is provided for the armatures (5, 8) of
both blades (2, 3); and that the permanent magnets (24, 25; 26, 27)
of the two armatures (5, 8) are oriented in opposite
directions.
9. The device of claim 1, characterized in that the two units
comprising a blade (2, 3), an armature (5, 8), and leaf springs (6,
7; 9, 10) are designed for different natural frequencies.
10. The device of claim 1, characterized in that for a control unit
(17) of the electric drive or drives (4), a CAN bus system is
provided.
11. A method for severing a thread (A) by means of two blades (2,
3), at least one of which is moved relative to the other by means
of an electric drive (4), characterized in that the electric drive
(4) moves the at least one blade (2, 3) into a ready position
counter to spring force; and that this blade (2, 3), for executing
a severing operation, is moved back again from the ready position
at least by means of the spring force.
12. The method of claim 11, characterized in that the electric
drive (4) is activated while the associated blade (2, 3) is being
moved back from the ready position by means of spring force.
13. The method of claim 11, characterized in that the electric
drive (4) brakes the associated blade (2, 3) during the motion back
from the ready position, particularly after the severing operation
has been performed.
14. The method of claim 11, characterized in that a signal
dependent on the motion of an armature (5, 8) of the electric drive
(4) is formed, by means of which the course of motion of the
associated blade (2, 3) is monitored.
Description
[0001] The invention relates to a device for severing a thread that
has two blades, at least one of which is movable relative to the
other by means of an electric drive, and to a method for severing a
thread.
[0002] A device for severing a weft thread for a weaving loom is
known (German Patent Disclosure DE 2230099), which has two blades
that are movable relative to one another. This device is located in
the vicinity of the fabric edge, in order to cut off a weft thread
that is picked up by a gripper and transported into the shed. To
improve the cutting operation, the blades are pressed against one
another by spring force. One of the blades is driven via a cam
system, which in turn is driven by the weaving loom. Such a device
has the disadvantage that the speed of motion of the blades in
cutting off the thread is determined by the speed of the drive
means, whose speed is determined by the speed of the weaving
loom.
[0003] A device of the type defined at the outset is also known
(European Patent Disclosure EP 0284766 A1), which as its drive
includes an electric drive motor. In this known device, one problem
is that the relative speed of the blades upon severing a thread is
determined by the activating and properties of the electric drive
means.
[0004] The object of the invention is to create a device of the
type defined at the outset in which the speed of motion of the
blades during the severing operation is independent of the speed of
the weaving loom or of properties of an electric drive.
[0005] This object is attained in that the at least one movable
blade is movable by the drive counter to the action of at least one
spring element into a ready position from which, by means of the
force of the at least one spring element, it can be moved back
again for executing a severing operation.
[0006] The invention offers the advantage that the speed of motion
of the blades is independent of the drive means and can thus be
selected as a function of the thread to be severed, in particular a
weft thread of a weaving loom. The speed of the relative motion
between the blades is determined essentially by the natural
frequency of the means that retain the movable blade and that move
with the blade.
[0007] The application of the device according to the invention to
weaving looms leads to the advantage that the speed of severing is
independent of the weaving speed of the weaving loom and
independent of the response times and reaction times of the
electric drive means. The speed for the cutting can be set
adequately high in all cases to enable satisfactory severing of a
weft thread. This is advantageous above all whenever the power loom
is operated at slow speed, and a weft thread has to be severed or
cut.
[0008] According to an embodiment of the invention, it is provided
that both blades can be moved into a ready position with contrary
motion by means of electric drives and can be moved back again by
means of spring elements. Thus substantially higher cutting speeds
can be attained than with one stationary blade and only one moving
blade. In a further embodiment of the invention, it is provided
that the blade or blades are each retained by respective pairs of
leaf springs, which are oriented transversely to the direction of
motion of the associated blade and are disposed spaced apart from
and parallel to one another. Since the blades need not execute
excessively great motions, and since the leaf springs in turn can
have a relatively great length, it is possible in this way to move
the blades substantially rectilinearly, without having to provide
guides for the purpose.
[0009] In an embodiment of the invention, it is provided that the
blade or blades are connected to an armature which contains at
least one permanent magnet and with which an electromagnet is
associated. In further embodiment both blades are provided with
armatures in which the permanent magnets are arranged such that
like poles face each other in the ready position and unlike poles
face each other in the severing position. In this arrangement, the
armatures and thus the blades attract one another while they are in
the region in which the severing operation takes place. The cutting
operation is thus improved. The armatures and hence also the blades
repel one another, however, while they are in the region of the
ready position, and as a result wear to the blades moving relative
to one another is reduced.
[0010] As an embodiment of the invention, one common electromagnet
is provided for the armatures of both blades; and the permanent
magnets of the armatures are oriented in opposite directions. The
common electromagnet has the effect that upon its excitation, the
two armatures are moved with their blades in opposite
directions.
[0011] In a preferred embodiment, it is provided that the two units
comprising a blade, an armature, and leaf springs are designed for
different natural frequencies. By the choice of the mass of the
unit comprising the leaf springs, armature and blade, and the
choice of the spring characteristic curve for the leaf spring, the
natural frequency can be defined. It is advantageous if the speeds
of motion, selected by means of the natural frequency, are set so
differently that the position in which the cutting is done differs
from the position of repose when the electromagnet is not excited.
It can thus be attained that in gripper looms, in a position of
repose assumed when the electric drive means are not excited, the
device is located above the fabric, so that upon beating up, the
weft threads can pass underneath the device. Nevertheless, the weft
threads can be severed at the level of the plane of the fabric.
This mode of operation is made possible whenever the blade that is
moving downward is faster than the blade that is moving upward. The
different speed and hence a different course of motion can be
attained by providing that leaf springs of different stiffness or
with a different spring characteristic curve, and/or armatures of
different mass, and/or blades of different mass are used. Each of
these provisions contributes alone or in combination with other
provisions to a change in the natural frequency.
[0012] In a preferred embodiment, for a control unit of the
electric drive or drives, a CAN bus system is provided.
[0013] The object is attained by a method in which the electric
drive moves the at least one blade into a ready position counter to
spring force, and for executing a severing operation, this blade is
moved back again from the ready position at least by means of the
spring force.
[0014] In a refinement, the electric drive is activated while the
associated blade is being moved back from the ready position by
means of spring force. Thus the speed and the course of motion
during the severing can both be varied. In particular, it is
provided that the electric drive brakes the associated blade during
the motion back from the ready position, particularly after the
severing operation has been performed.
[0015] In a further embodiment of the invention, a signal dependent
on the motion of an armature of the electric drive is formed, by
means of which the course of motion of the associated blade is
monitored. This signal, which comprises a voltage, for instance,
serves as feedback for controlling the device of the invention.
[0016] Further characteristics and advantages of the invention will
become apparent from the ensuing description of the exemplary
embodiments shown in the drawings.
[0017] FIG. 1 shows a device according to the invention in a
position of repose;
[0018] FIG. 2 shows the device of FIG. 1, with a few components
having been left out to increase the clarity;
[0019] FIG. 3 is a vertical section through FIG. 2;
[0020] FIG. 4 shows the device of FIG. 1 (leaving out additional
components) in a ready position;
[0021] FIG. 5 shows the device of FIG. 1 in a severing position;
and
[0022] FIG. 6 is a fragmentary view in the direction of the arrow
F6 of FIG. 1.
[0023] The device according to the invention shown in FIG. 1 has
two blades 2 and 3, movable relative to one another, and electric
drive means for moving these blades 2, 3 relative to one another.
The blade 2 is connected to an armature 5, which is retained
movably by means of leaf springs 6, 7. The blade 3 is connected to
an armature 8, which is retained movably by means of leaf springs
9, 10. The leaf springs 6, 7 and 9, 10 are oriented transversely to
the direction of motion of the blades 2, 3 and are disposed
parallel to and spaced apart from one another. Each of two leaf
springs 6, 7; 9, 10 are located directly one above the other, so
that thin leaf springs, which are advantageous with respect to the
service life, can be used. The armatures 5, 8 are each retained on
both ends by relatively long leaf springs 6, 7; 9, 10, so that the
armatures 5, 8 move essentially linearly. The ends of the leaf
springs 6, 7; 9, 10 remote from the armatures 5, 8 are retained by
means of a holder 11 in which they are fastened. The leaf springs
6, 7 and 9, 10 are embodied in one piece in the region of the
holder 11, in this exemplary embodiment. The holder 11 has a shaft
12, which is mounted for instance by means of an arm 13 on a frame
of a textile machine. The shaft 12 is fastened between the arm 13
and a clamping element 14 and as a result can be disposed at an
arbitrary axial or radial point. As a result, the device according
to the invention can be positioned relative to a textile machine in
such a way that a thread can be severed or cut off. In this way,
the device according to the invention can be disposed in a gripper
weaving loom in the direction of the weft thread in a predetermined
position relative to the fabric. In addition, holder elements 15
are secured to the holder 11; they carry an electromagnet 16,
cooperating with the armatures 5 and 8, and a control unit 17. The
control unit 17 is connected to a control unit of the textile
machine via a cable 18. The control unit of the textile machine
sends signals to the control unit 17 for actuating the device 1
according to the invention synchronously with the textile
machine.
[0024] As can be seen from FIGS. 1 through 3, each electromagnet
16, cooperating with a respective armature 5 or 8, has two
mirror-symmetrically disposed iron cores for the armatures 5 and 8;
that is, two iron cores 19 for the armature 5, and two iron cores
20 for the armature 8. The iron cores 19, 20 are formed from
plates. In the exemplary embodiment shown, a pair of coils 21 for
the iron cores 19, 20 is provided, so that both electromagnets 16
can be controlled by the same pair of coils 21. The coils 21 are
each disposed around a middle part 22 of the iron cores 19, 20 in
the region of the armatures 5, 8. The iron cores 19, 20 are secured
to the holder elements 15 by means of screws. In a modified
embodiment, the iron cores 19, 20 are embodied in one piece; that
is, they comprise only one set of plates fastened together. As
shown in FIG. 1, a housing 23 of nonmagnetizable material is
disposed around the electromagnets 16.
[0025] In a modified embodiment, only one coil 21 is provided,
which performs the function of the two coils 21 that are connected
in series. Instead of two mirror-symmetrically disposed iron cores
19, 20 for the armature 5 and for the armature 8, it is also
possible for a single iron core to be used, while the other is
replaced by a beam that is either disposed in stationary fashion or
is connected to the associated armature. In another modified
embodiment, each electromagnet 16 that cooperates with one of the
armatures 5 or 8 is controlled by its own coil.
[0026] As can be seen in FIG. 2, two permanent magnets 24, 25 are
accommodated in the armature 5 and two permanent magnets 26, 27 are
accommodated in the armature 8. These permanent magnets 24 through
27 have a rodlike shape and have two poles. The north-south
direction of the permanent magnets 24 through 27 extend vertically
to the direction of motion of the armatures 5 and 8. The permanent
magnets 24, 25 on the one hand and the permanent magnets 26, 27 on
the other are each disposed such that the unlike poles border one
another. Each of the permanent magnets 24 through 27 has a length
equivalent to approximately the magnitude of the motion of the
associated armature 5 or 8 between a position of repose, with the
coil not excited, and a position with the coil 21 excited. The
permanent magnets 24, 25 are oriented with their poles oppositely
to the poles of the permanent magnets 26, 27, so that upon
excitation of the coil 21, the armatures 5, 8 are each moved in
opposite directions. Because of this embodiment, it is possible for
both armatures 5, 8 to be actuated with either the same coil 21 or
with one coil set 21.
[0027] In FIG. 2, the blades 2, 3 are in a position of repose, in
which the coil 21 is not excited. When the coil 21 of the electric
drive means 4 is excited, the armatures 5, 8 move in opposite
directions as far as a position that is shown in FIG. 4. This
position is called the open position or ready position. In this
position, the armatures 5, 8 and thus also the blades 2, 3 are
moved counter to the force of the leaf springs 6, 7; 9, 10. The
electromagnets 16 and the exciter current for the electromagnets 16
are understood to be adapted to the strength of the leaf springs 6,
7; 9, 10, or else the leaf springs 6, 7; 9, 10 are adapted to the
electromagnets 16 and to the exciter current. Since the like poles
of the permanent magnets 24, 26 on the one hand and the permanent
magnets 25, 27 on the other rest side by side in the ready
position, the armatures 5, 8 are pressed apart somewhat, so that
the blades 2, 3 are pressed against one another with only slight
force. In this position, a thread A to be severed or to be cut, for
instance a weft thread in the case of a gripper weaving loom, is
placed between the blades 2 and 3. This can be done for instance in
the way described in DE 2230099. Once the excitation of the coil 21
is ended, the armatures 5, 8 are moved back again out of the ready
position by the force of the prestressed leaf springs 6, 7; 9, 10,
so that they sever the thread A located between the blades 2, 3, in
a cutting position that is shown in FIG. 5. In this cutting
position, the unlike poles of the permanent magnets 24 through 27
face one another, so that the armatures 5, 8 attract one another,
which reinforces the cutting operation.
[0028] As can be seen from FIG. 5, the cutting position is located
somewhat lower than the position of repose shown in FIG. 2. This is
due to the fact that the blade 3 moves downward at a higher speed
than the speed at which the blade 2 moves upward. This difference
in speed is due, in the embodiment shown, to a difference in the
natural frequency between the unit comprising the blade 2, armature
5 and leaf springs 6, 7 and the unit comprising the blade 3,
armature 8 and leaf springs 9, 10. In the embodiment shown, the
difference in the speed of motion is caused for instance by the
fact that the unit having the blade 2 is heavier and thus moves
more sluggishly than the unit having the blade 3. It is understood
also to be possible to attain a different speed of motion by means
of varying the natural frequency of the applicable unit in some
other way, in particular by varying the mass of the unit or the
spring stiffness of the leaf springs 6, 7; 9, 10.
[0029] In order to vary the speed of motion of the blades 2 and 3,
the coil 21 may also be activated. To reduce the speed of motion,
it can be provided that the excitation of the coil 21 not be
interrupted, but instead that a relatively low current be made to
flow through the coil. As a rule, however, the latter is unwanted,
since in most cases as high a speed as possible is advantageous for
cutting. Therefore, to increase the speed of the motion, a current
is passed through the coil 21 that is opposite the current that
flows through the coil 21 for putting the blades 2 and 3 into the
ready position shown in FIG. 4. In that case, the blades 2, 3,
during their motion out of the ready position, are likewise
controlled by the electric drive means 4. However, since the
acceleration and the speed reached by the leaf springs 6, 7; 9, 10
are relatively high, in most cases activated the coil 21 with an
oppositely oriented current affects the speed of the motion during
cutting only slightly. To limit the speed of the blades 2, 3, it is
advantageous to activated the electric drive means 4 briefly,
directly after the cutting, in such a way that the blades 2, 3 are
forced back into the direction to the position shown in FIG. 4, or
in other words are braked after the cutting.
[0030] If the device of the invention is used in a gripper weaving
loom, the coil 21 is briefly excited after the cutting--for
instance as described above--in other to brake the blades 2, 3.
After that, the unit can settle freely until the position of repose
of FIG. 2 has been resumed. The settling process is damped since
the blades 2, 3 rest on one another and rub against one another. In
a modified version, damping is accomplished by the drive means 4.
To that end, the coils 21 can be short-circuited after the severing
operation. The motion of the permanent magnets 24 through 27
generates a voltage which, with short-circuited coils 21, generates
a current through the coils 21. As a result, some of the energy of
motion into the coils 21 is converted into heat. Because of this,
moreover, the frequency of the operation can be increased further.
In the position of repose of FIG. 2, a beaten-up weft thread can
travel beneath the blade 2. In gripper weaving looms, it is also
important for the instant at which the drive means are no longer
activated and the severing operation takes place to be synchronized
with the weaving cycle.
[0031] The control unit 17 of the device of the invention is
connected via a cable 18 to a CAN bus system, so that the electric
drive means, and in particular the coil 21, can be activated via
this CAN bus system. As a result, it is possible to use the device
according to the invention in any already-existing textile machine
that is equipped with a CAN bus system.
[0032] In a modified embodiment, the control unit 17 is provided
with means for detecting the course of motion of the blades 2, 3
during the motion and in particular the cutting motion. This can be
done for instance by measuring an electrical signal that occurs in
the coil 21 as a result of the permanent magnets 24 through 27,
moving relative to the coil 21, of the armatures 5, 8. On the basis
of this signal, the instant of cutting can be determined. The
determination of the instant of cutting can also be done in some
other way, such as with the aid of optical sensors, or as known
from International Patent Disclosure WO 99/29946.
[0033] In gripper weaving looms, this method can for instance be
employed to compare the correct instant of cutting with the instant
when the coil 21 is no longer excited. The instant when the drive
means 4 are no longer excited is synchronized with the weaving
cycle by setting or adjusting the instant of the end of excitation
within the weaving cycle such that cutting is done at the correct
instant within the weaving cycle. Hence a correct setting of the
instant of the end of excitation can be defined for every device
for cutting, without there being any influence by the properties of
the leaf springs, armatures or blades on the synchronization of the
instant of cutting with the weaving cycle. Such a setting can be
achieved for instance by providing that the instant of the end of
excitation of the coils 21 is set relative to the position of the
drive shaft of the gripper weaving loom such that the armatures 5
and 8, which are restrained firmly in their ready position, are
released at that instant. The relative instant of thread cutting
relatively to the instant of the end of excitation can then be used
as a feedback value for setting or adjusting the instant of the end
of excitation relative to the position of the drive shaft of the
gripper weaving loom. By shifting the instant of the end of
excitation of the coil set 21 to a greater or lesser extent
relative to a previously determined position of the drive shaft,
the instant of cutting can be set precisely or changed by the
control of the end of excitation as a function of the
aforementioned, previously determined position relative to the
position of the drive shaft and thus relative to the weaving
cycle.
[0034] In FIGS. 1, 3 and 6, details are also shown for how the
blades 2 and 3 are connected to the armatures 5 and 8. On the
underside of the armature 5, the leaf springs 7 are secured to the
armature by means of a clamping element 28. A T-element 30 is
secured to this clamping element 28 by means of a screw. The blade
2 is secured to this T-element 30 by fastening means 31. The leaf
springs 10 are secured to the underside of the armature 8 by means
of a clamping element 29. By means of a screw, a T-element 32 is
secured to this clamping element 29. A leaf spring 33 is secured to
this T-element 32 by a fastening means 34. The blade 3 is secured
to this leaf spring 33 by adhesive bonding, soldering, or welding,
or the like, for instance. By means of the fastening of the
T-elements 30 and 32 relative to one another and the deformation of
the leaf spring 33, the force with which the blades 2, 3 are
pressed against one another can be adjusted. By the fastening means
31 and 34, the relative height of the blades 2 and 3 with respect
to one another can also be adjusted. The blades 2 and 3 are ground
in a known manner so that they will cut optimally.
[0035] In a modified embodiment, the armatures 5 and 8 each have
only one permanent magnet, for instance the permanent magnets 25
and 26, respectively. For cutting and to avoid wear of the blades
2, 3, however, it is more advantageous to use two permanent magnets
24, 25; 26, 27 each, respectively.
[0036] Different speeds for the motion of the blades 2 and 3 can
also be attained by providing that in the motion toward the cutting
position, the blades 2, 3 are controlled differently by the
electric drive means 4, by using permanent magnets of different
strengths for the two armatures 5, 8, by activating the
electromagnets 21 differently, by activating each armature 5, 8 by
a different electromagnet, or by a combination of these provisions.
Moreover, an auxiliary coil may be provided for each armature 5, 8,
in order to speed up or slow down the motion of the armature 5, 8
during cutting.
[0037] In the embodiment shown, the ready position is determined
essentially by the longitudinal dimensions of the permanent magnets
24 through 27. In a modified embodiment, this position can be
determined with the aid of sensors, for instance optical sensors,
that cooperate with the control unit 17. The control unit 17 may
for instance control the current delivered to the coil 21 such that
the armatures 5, 8 assume a previously defined ready position.
[0038] It is understood that the device of the invention is not
limited to use in a gripper weaving loom. It can readily be
employed in any other textile machine in which threads must be
severed, such as air jet looms, gripper shuttle looms, water jet
looms, projectile looms, other types of weaving looms, knitting
machines, sewing machines, and other textile machines. The device
of the invention offers the advantage that it can be built into any
existing textile machine without problems. A particular advantage
is that a thread can be severed at a relatively high cutting speed,
which can be adjusted independently of the speed of the textile
machine and independently or at least largely independently of the
electric drive means. Because the two blades 2, 3 move relative to
one another upon cutting, a higher cutting speed is obtained
compared to the case in which one of the blades is stationary.
[0039] The device according to the invention and the method
according to the invention are not limited to the embodiments
described here as examples and shown in the drawings. On the
contrary, they may be realized in various variants.
* * * * *