U.S. patent application number 09/783486 was filed with the patent office on 2002-04-25 for friction feed wheel mechanism with vibration excitation.
Invention is credited to Schmodde, Hermann, Worner, Christoph.
Application Number | 20020047034 09/783486 |
Document ID | / |
Family ID | 7630917 |
Filed Date | 2002-04-25 |
United States Patent
Application |
20020047034 |
Kind Code |
A1 |
Schmodde, Hermann ; et
al. |
April 25, 2002 |
Friction feed wheel mechanism with vibration excitation
Abstract
In connection with a vibration friction feed wheel mechanism,
having a thread guide lever for inserting and removing a thread,
the application of vibrations to the thread guide elements, or the
application of vibrations to the thread feed wheel, is used to
improve the removal properties of the friction feed wheel
mechanism.
Inventors: |
Schmodde, Hermann;
(Horb-Dettlingen, DE) ; Worner, Christoph;
(Baiersbronn, DE) |
Correspondence
Address: |
LEYDIG VOIT & MAYER, LTD
TWO PRUDENTIAL PLAZA, SUITE 4900
180 NORTH STETSON AVENUE
CHICAGO
IL
60601-6780
US
|
Family ID: |
7630917 |
Appl. No.: |
09/783486 |
Filed: |
February 14, 2001 |
Current U.S.
Class: |
226/34 ; 226/174;
242/364.9 |
Current CPC
Class: |
D04B 15/48 20130101 |
Class at
Publication: |
226/34 ; 226/174;
242/364.9 |
International
Class: |
B65H 023/16; B65H
020/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 15, 2000 |
DE |
10006599.6 |
Claims
1. A friction feed wheel mechanism (1) for feeding in at least one
thread (21), having at least one thread guide element (22), through
which or against which the thread (21) rests during operations, or
along which the thread (21) runs during operations, having at least
one thread feed wheel (6), which is seated so that it is rotatable
around a predetermined axis (29) of rotation by means of a support
arrangement (8) on a support (9), which is designed to be connected
with a machine which processes threads (21), wherein the thread
feed wheel (6) has a contact surface (38) for the frictionally
connected conveyance of the thread (21), having a thread guide
lever (5), which is seated on the support (9) by means of a bearing
device (41) and which supports a yarn guide element (33), whose
position affects the frictional connection between the thread (21)
and the contact surface (38), characterized in that a vibration
generating arrangement (28) is provided in order to apply a
vibrational movement to the thread (21).
2. The friction feed wheel mechanism in accordance with claim 1,
characterized in that the vibration generating arrangement (28) is
connected with the bearing device (41) and/or the support
arrangement (8) and/or a thread guide element (22) in order to
impart a vibrational movement to the thread guide lever (5) and/or
the thread feed wheel (6) or the thread guide element (22).
3. The friction feed wheel mechanism in accordance with claim 1,
characterized in that the thread guide lever (5) is a pivot lever,
which supports the thread guide element (33) on its free end, so
that the thread guide element (33) can be moved toward or away from
the thread feed wheel (6) by pivoting the thread guide lever (5),
and that the thread guide lever (5) is pivotably seated by means of
the bearing device (41), preferably around a pivot axis (35) which
extends essentially parallel with the axis (29) of rotation.
4. The friction feed wheel mechanism in accordance with claim 1,
characterized in that the thread guide lever (5) is embodied to be
resilient.
5. The friction feed wheel mechanism in accordance with claim 1,
characterized in that the vibration generating device (28) is
connected with the bearing device (41) of the pivot lever (5) in
order to impart to the latter a vibrational movement which is
oriented transversely to its pivot axis (35).
6. The friction feed wheel mechanism in accordance with claim 1,
characterized in that the friction feed wheel mechanism has a
thread brake (3), which checks the thread (21) running to the
thread feed wheel (6), and that the vibration generating device
(28) is connected with an element (4), which is arranged between
the thread brake (3) and the thread feed wheel (6) and is in
contact with the thread (21) at least over a short period of time
in order to impart a vibrational movement to the latter.
7. The friction feed wheel mechanism in accordance with claim 1,
characterized in that the contact surface (38) of the thread feed
wheel (5) is an interrupted surface.
8. The friction feed wheel mechanism in accordance with claim 1,
characterized in that the contact surface (38) of the thread feed
wheel (5) is defined by strips (31, 32).
9. The friction feed wheel mechanism in accordance with claim 8,
characterized in that pairs of adjoining strips (31, 32) together
enclose an angle.
10. The friction feed wheel mechanism in accordance with claim 1,
characterized in that an inlet thread guide element (22) is located
upstream of the thread feed wheel (6), and an outlet thread guide
element (7) is arranged downstream of it, wherein the inlet thread
guide element (22), as well as the outlet thread guide element (7)
are accessible from a defined operating side of the thread feed
device (1), and that the thread track at the thread feed wheel (6)
is fixed on a circumferential section facing the operating side.
Description
[0001] The invention relates to a friction feed wheel mechanism
with vibration excitation, having the characteristics of claim
1.
[0002] So-called friction feed wheel mechanisms are often employed
for feeding thread to thread-processing machines, in particular
those, which have a chronologically fluctuating or intermittent
thread requirement. These have a thread feed wheel, which is driven
at a constant number of revolutions and has a contact surface for
the thread. The thread is wrapped around the thread feed wheel at a
wrap angle which is mostly less than 360.degree.. The thread is
moreover conducted through the eye of a thread guide lever, wherein
the position of the lever affects the wrap angle. The thread guide
lever is usually pre-stressed away from the thread feed wheel by
means of a spring force. When the use of thread by the
thread-processing machine ends, the thread guide lever slightly
lifts the thread off the thread feed wheel or reduces the wrap
angle, so that the thread feeding is stopped. Thus, the thread
usage controls the thread feeding.
[0003] The coefficient of friction which prevails between the
thread and the contact surface is important for the functioning of
such a friction feed wheel mechanism. In actual use, the
coefficient of friction changes because of matter being carried
along by the thread, such as oil, wax or other materials and being
deposited on the contact surface. Because of this, as well as
because of the aging of a possible friction lining, for example a
plastic material or rubber, the feeding properties of the device
slowly change. If the coefficient of friction between the friction
lining and the thread is large, the thread tends to adhere to the
friction lining. The result of this can be that the
friction-controlled switch-off, i.e. the stoppage of feeding by the
friction feed wheel mechanism, does not take place correctly. For
example, the thread is not detached from the drum when the thread
guide lever is pivoted out and its feeding is therefore continued.
Even if the thread is detached from the friction lining, damage of
the thread and/or of the friction lining can occur because of the
remaining contact between the thread and the thread lining of the
rotating drum during extended periods of stoppage of the thread.
Rubber linings are particularly endangered. Too low a coefficient
of friction, however, can interfere with the reaction properties of
the friction feed wheel mechanism, if a thread feed suddenly occurs
and thread must again be fed in following a feeding stop.
[0004] A friction feed wheel mechanism is known from U.S. Pat. No.
4,058 245 which, in view of the above mentioned problems, is
provided with a special thread feed wheel. The thread feed wheel
has a contact surface which is designed, for example, as a
meander-shaped annular groove. In another embodiment, the contact
surface is constituted by spokes of a wheel or by pins attached to
a wheel, which are arranged crosswise, viewed in the
circumferential direction, and are inclined at an acute angle in
respect to the radial direction. A thread placed around the wheel
lies in a zig-zag shape between the pins or spokes.
[0005] The division of the contact surface into individual surfaces
and the zig-zag-shaped thread placement lead to conditions which
differ from those occurring in connection with thread feed wheels
which are coated with a plastic material or rubber and are
essentially cylinder-shaped. Such friction feed wheel mechanisms
are also dependent on the friction between the contact surface and
the thread in regard to their reaction properties. The friction, in
turn, is a function of the yarn type and the thread type.
[0006] Based upon the foregoing, it is the object of the invention
to produce an improved friction feed wheel mechanism.
[0007] This object is attained by means of the friction feed wheel
mechanism in accordance with the invention having the
characteristics of claim 1.
[0008] The friction feed wheel mechanism in accordance with the
invention has a vibration generating device, which acts on the
thread. This is accomplished, for example, in that it is connected
with the thread guide lever, the thread feed wheel, a thread guide
element or any other element touching the thread.
[0009] In this way the detachment of the thread from the contact
surface of the thread feed wheel is made considerably more easy, in
particular in case of a feed stop, and the remaining contact
between the thread and the thread feed wheel is minimized.
[0010] If the thread adheres to the contact surface, it is possible
to overcome the static friction by means of the vibration applied
to the thread, the thread guide element, the thread feed wheel or
the thread guide lever or other element, which considerably
improves the removal properties (switching the thread feed off).
This applies in particular, but not exclusively, to thread feed
wheels having a coating with a large coefficient of friction or a
structured surface, which permits good thread feeding. Moreover,
this applies in particular to threads having a large coefficient of
friction. A further advantage lies in that deposited dirt, which
possibly can lead to adherence, such as sizing, oil or the like,
does not lead, or leads less, to adherence of the thread. The step
of exposing the contact between the thread and the thread feed
wheel to a certain vibration, therefore drastically improves the
thread removal, i.e. the disruption of the thread feed wheel which
takes the thread along.
[0011] Because of the application of vibration to the thread it is
possible for the latter to be lifted off the thread feed wheel
almost completely when the thread is standing still, wherein at
most a small area of contact between the thread and the thread feed
wheel remains, in which the thread then rests against the thread
feed wheel without or under only little tension. Because of this,
long thread idle times are possible without damage to the thread or
to the thread feed wheel.
[0012] The feed wheel mechanism in accordance with the invention
can be employed for various threads with differing frictional
properties. Because of the vibrational reinforcement, the correct
functioning is not sensitive to changes in the coefficient of
friction.
[0013] In the embodiment of the invention, the thread guide lever
can be designed as a pivot lever, as well as a resilient hoop, or
as any other shape. It is essential that it supports a thread guide
element, whose position in respect to the thread feed wheel can be
affected by the thread tension. In a simple manner, rigid levers
permit the setting of a force which pre-stresses the lever, for
example by means of a tension spring, whose point of suspension is
adjustable. The setting of the force permits the matching to
different thread tensions and thread qualities. Resiliently
designed levers, however, lead to particularly simple structures.
In both embodiments, the respective lever is attached to a seating
device ("second seating device") at its end remote from the thread
guide element. If the lever is rigid, the second seating device
allows a movable, for example pivotable, seating. Independently
thereof, the seating arrangement (pivot bearing or a rigid version)
can be connected with the vibration generating device, which causes
the thread guide lever, and therefore also the thread guide element
supported by the thread guide lever, to vibrate. These vibrations
can be transferred to a larger or lesser degree to the thread via
the thread guide element.
[0014] Alternatively or additionally, the first seating device for
the thread feed wheel and/or a thread guide element, which is
arranged upstream or downstream of the thread feed wheel, can be
connected with the vibration generating device. A vibrational
movement is respectively caused, which can be transmitted to the
thread. In this connection the vibrating movement can be directed
as needed. Possible are, for example, oscillations transversely in
respect to the respective axis of rotation, linearly in respect to
the respective axis of rotation or pivot axis, or obliquely in
respect to it. If the vibration generating device acts on the
thread guide element, which is arranged upstream or downstream of
the thread feed wheel, the direction of vibration can be directed
transversely in respect to the thread and parallel with the axis of
rotation of the thread feed wheel, or transversely to the latter.
The vibration generator can basically also perform a superimposed
oscillation, so that the respective vibrating element is not only
guided (swings) on a linear, but also an elliptical or circular
path. In this case the vibrating movement becomes an orbital
movement with a small radius.
[0015] It is considered to be particularly practical to design the
contact surface of the thread feed wheel in an interrupted fashion.
The contact surface can be defined by several strips, spokes, teeth
or pins, which determine a zig-zag-shaped thread course, for
example. This embodiment not only has good reaction properties, but
also good removal properties. This applies to a great extent
independently of the type of the thread used.
[0016] A particularly operator-friendly structure results if both
the inlet thread guide element, placed upstream of the thread feed
wheel, and the outlet thread guide element, placed downstream of
the thread feed wheel, are arranged to be accessible from the
direction of the operating side of the thread feed device, and if
both the thread guide element of the thread guide lever and the
thread travel path on the thread feed wheel are fixed on a section
of the circumference of the thread feed wheel which faces the
operating side. Therefore the thread need not be conducted behind
the thread feed device in the course of being threaded, which makes
the operation considerably easier.
[0017] Advantageous details of the embodiments of the invention can
be seen in the drawings or taken from the description, or are the
subject of dependent claims. Exemplary embodiments of the invention
are represented in the drawings. Shown are in:
[0018] FIG. 1, a perspective representation of a vibration feed
wheel mechanism for eight threads,
[0019] FIG. 2, a schematic lateral view of the vibration feed wheel
mechanism of FIG. 1 during the thread feeding process,
[0020] FIG. 3, a schematic lateral view of the vibration feed wheel
mechanism of FIGS. 1 and 2 during the removal of the thread,
[0021] FIG. 4, a schematic lateral view of the vibration feed wheel
mechanism of FIGS. 1 to 3 with a removed thread,
[0022] FIG. 5, a perspective and partial representation of the
vibration feed wheel mechanism of FIGS. 1 to 4,
[0023] FIGS. 6 to 9, vibration feed wheel mechanisms in different
embodiments and each in a schematic representation, and
[0024] FIGS. 10 to 12, vibration generating devices in different
embodiments and each in a schematic representation.
[0025] A vibration feed wheel mechanism 1 is represented in FIG. 1,
which has a total of eight thread feed tracks and therefore eight
thread feed systems 2a to 2h, which are basically designed
identical, and each of which has a thread brake 3, a thread guide
eye 4, a thread guide lever 5, a thread feed wheel 6 and thread
guide eyes 7 on the outlet side. To distinguish them, the
respective elements are identified by letter indices in FIG. 1.
[0026] The thread feed wheels 6a to 6h are supported on a common
shaft 8, with which they are connected, fixed against relative
rotation. The shaft 8 is rotatably seated by means of a bearing
device, not shown in detail, held in a housing 9, and constitutes a
support device for the thread feed wheel 6. In addition, the
housing 9 contains an angular gear, whose power take-off side is
the shaft 8, and whose input shaft supports pulleys 11 for driving
the thread feed wheels 6a to 6h.
[0027] As FIG. 2 shows, the housing 9 is provided on one side with
a clamping device 12 for fastening the vibration feed wheel
mechanism 1 on a thread-processing machine, for example a circular
knitting machine or other knitting machine. The same as the
respective pulleys of further feed wheel mechanisms, the pulleys 11
are in connection with a circulating belt and are driven by it. The
thread feed systems 2 of the vibration feed wheel mechanism 1 are
identical with each other. Therefore the following description of
the thread feed system 2h represented in FIG. 2 correspondingly
applies to all thread feed systems 2a, b, c, d, e, f, g, for which
reason the letter indices have been left out to a great extent in
the description which follows.
[0028] A brake support 14 is fastened on the housing 9 in an area
of the operating side of the housing 9 which is remote from the
clamping device 12. This support holds the thread brake 3. The
latter is a disk brake with two brake disks 15, 16 seated on a
common pin or peg 17. The brake disks 15, 16 are adjustably
pre-stressed by means of a tension spring 18, which is supported on
a knurled nut 19. However, other types of brakes, for example
magnetically pre-stressed brakes, brakes acted upon by vibration,
wrap-around brakes, or other devices braking the thread movement,
can also be used.
[0029] In the immediate vicinity of the thread brake 3, the brake
support 14 holds the thread guide eye 4, starting at which a thread
21, which is to be fed in, is conducted to a further eye 22. The
latter is, as represented in particular in FIG. 5, embodied as an
open hook with a ceramic insert 23. The eye 22 is maintained on a
pivot arm 24, which is seated on the housing 9 and is pivotable
around a pivot axis 25. The pivot arm 24 is connected via a journal
26 and a connecting rod with an eccentric 27, which is connected
with the thread feed wheel 6 in a manner fixed against relative
rotation. During each rotation of the thread feed wheel 6, the eye
22 therefore performs a short-stroke oscillating movement in the
direction of the arrow P represented in FIG. 5.
[0030] The pivot arm 24, the connecting rod and the eccentric
constitute a vibration generator 28. The pivot axis 25 is indicated
parallel with the axis of rotation of the thread feed wheel 6,
which is indicated by a dash-dotted line 29 in FIG. 6. The
direction of the oscillating movement approximately corresponds to
the direction of the thread 21 running to the thread feed wheel
6.
[0031] Alternatively or additionally, the thread guide eye 4, or
another element which is in total or partial connection with the
thread, can be connected with an electrical, electromagnetic or
mechanical vibration generator, which operates continuously or when
needed. With both embodiments (vibration of the eye 22 or vibration
of the eye 4), vibration acts on the thread between the thread
brake 3 and the thread feed wheel 6.
[0032] In principle, the thread feed wheel 6 can be designed in any
arbitrary manner. For example, it can be constituted by a
disk-shaped drum, on whose outer circumference an appropriate
coating, for example a plastic material or a rubber coating, is
provided. However, a spoked wheel is preferred, which is
represented in part and somewhat simplified in FIG. 5a. On its
outer circumference, this thread feed wheel 6 has a circumferential
and groove-like depression, in which strips 31, 32 have been
arranged, which alternate with each other and cross each other in
the circumferential direction. In this case the strips 31, 32 are
essentially arranged inclined in the radial direction, but toward
the axis of rotation, and are spaced apart from each other.
Adjoining strips 31, 32 do not touch, and enclose an angle with
each other. This angle preferably is an acute angle, independently
thereof the thread 21 resting on the thread feed wheel 8 follows a
zig-zag-shaped course. The pins or strips 31, 32 define a
repeatedly interrupted contact surface 38 for the thread 21.
[0033] As FIG. 2 shows, the thread 21 is additionally conducted
through an eye 33, which is arranged at the free end of the thread
guide lever 5. Here, the eye 33, or another thread guide element
supported on the thread guide lever 5, is arranged at some radial
distance from the axis of rotation 29 of the thread feed wheel 6,
wherein the radial distance can be changed or adjusted by pivoting
the thread guide lever 5.
[0034] As shown in particular in FIG. 5, the thread guide lever 5
is pivotably seated around a pivot axis 35, which is oriented
parallel with the axis of rotation 29 of the thread feed wheel 6. A
spring mechanism 36 indicated in FIG. 5 here pre-stresses the
thread guide lever 5 in a position, wherein its eye 33 is at the
farthest possible distance from the thread feed wheel 6. The spring
force is of such a size that the thread 21, when it is pulled in by
the knitting machine, can pull the thread guide lever 5 to the
thread feed wheel. The spring force and/or the pivot travel of the
thread guide lever 5 can be adjustable for varying the thread
outlet tension and/or for setting the vibration friction feed wheel
mechanism for various types of thread.
[0035] The further thread track downstream of the thread feed wheel
6 is determined by the thread guide eye 7 and, if required,
additional thread guide eyes 37a, 37b, through which the thread 21
is conducted. As can be seen in FIG. 5, a return safety device is
embodied between the two thread guide eyes 37a, 37b, part of which
are a pivotable switch-off lever 40 and a brake element 43, which
has a V-shaped cut in a flat area, and which is arranged at an
acute angle against the thread. Next to the brake element, a
hook-shaped end of the switch-off lever, which protrudes out of the
housing 9, rests on the thread 21. It other end is arranged in the
housing and assigned to a switch-off contact K. The machine is
turned off if the switch-off lever touches the switch-off contact
K.
[0036] The brake element 43 is arranged in the immediate vicinity
of the thread guide eye 37a in such a way that the thread 21, which
is stretched tight between the thread guide eyes 37a, 37b, runs
through the V-shaped cut without touching it. If the thread 21 is
no longer tightly held between the thread guide eyes 37a, 37b, the
switch-off lever 40 drops slightly downward and pushes the thread
21 into the V-shaped cut of the brake element 43. The thread 21 is
clamped by this and prevented from running back. However, the
switch-off lever 40 is not in any way touching the contact K. The
machine is not switched off. The switch-off device only reacts if
the switch-off lever 40 drops all the way down, which is the case
with a completely detached thread or a ripped thread.
[0037] The vibration friction feed wheel mechanism 1 described so
far operates as follows:
[0038] During operation, a circulating toothed belt, which is in
contact with at least one of the pulleys 11, rotates the respective
pulley 11 and in this way drives the shaft 8 with the thread feed
wheels 6 via a gear, not represented in further detail. The thread
21 is conducted between the brake disks 15, 16 of the thread brake
3 and runs through the thread guide eye 4 to the eye 22. It will
now be assumed that the thread-processing machine arranged
downstream of the vibration friction feed wheel mechanism 1, i.e. a
knitting machine, for example, requires thread and therefore
maintains the thread 21, running from the thread guide eye 37b to
the machine, tensed. The thread 21 is thus kept in contact with the
repeatedly interrupted contact surface 38 of the thread feed wheel
6, and therefore in engagement with the thread feed wheel 6. In the
course of this, the eye 33 is subjected to a (small) force,
represented by an arrow 39 in FIG. 2, which attempts to lift the
thread 21 off the thread feed wheel 6. However, as long as there is
a sufficient consumption of thread by the downstream-connected
machine, the thread guide lever 5 cannot do this--the thread 21
remains in engagement with the thread feed wheel 6 and is
positively conveyed by the latter. This is represented in FIG. 2.
The thread 21 is in engagement with the thread feed wheel 6 over a
wrap angle of approximately 270.degree.. The thread guide lever 5
is maintained by the thread 21 against the comparatively weaker
force of the spring mechanism 36 (only schematically indicated in
FIG. 5) in such a way that the eye 33 is located close to the
circumference of the thread feed wheel 6.
[0039] If the thread consumption of the downstream-connected
machine is reduced, or is even stopped, the thread feed wheel 6
initially feeds in more thread than what runs through the thread
guide eyes 7 and the thread guide eyes 36, 37 to the machine.
Therefore the thread guide lever 5 can pivot out because of the
tension of its pre-stressing spring and can lift the thread 21 off
the thread feed wheel 6, as illustrated in FIG. 3. The wrap angle
of the thread 21 at the thread feed wheel 6 is clearly reduced.
However, it is still possible to deliver a small amount of thread
because of the frictional connection. In the intermediate pivot
position represented in FIG. 3, the thread 21 touches the thread
feed wheel 6, before running to the eye 33 of the thread guide
lever 5. From there, the thread 21 reaches the thread guide eye 7
essentially without touching the thread feed wheel 6. The contact
between the thread 21 and the thread feed wheel is small, without
pressing the thread 21 against the thread feed wheel 6. With an
appropriate arrangement of the eye 22 and the thread guide eye 7,
the thread 21 can also be lifted completely off the thread feed
wheel 6, so that in the removed state it no longer touches the
latter. In both cases the thread 21 comes through even extended
periods of stoppage without damage.
[0040] If the thread-processing machine continues to take up no or
insufficient amounts of thread 21, the thread guide lever 5 can
pivot out more and remove the eye 33 farther from the thread feed
wheel 6 and its axis of rotation 29, as can be seen in FIG. 4 in
particular. The eye 33 is then in a position in which the thread 21
runs from the eye 22 to the eye 33 without touching the thread feed
wheel 6 in the process. Thus, conveyance of the thread 21 is
completely stopped and the thread 21 is "removed". No thread
conveyance takes place. The thread 21 runs from the eye 33 over the
thread feed wheel 6 to the thread guide eye 7 and through the
further thread guide eyes 37a and 37b to the machine. But the wrap
angle at the thread feed wheel 6 is so small that the friction
between the thread 21 and the thread feed wheel 6 is not sufficient
to pull the thread 21 along and thereby to pull the pivot lever 5
against the thread feed wheel. This lasts at least as long as the
thread 21 is not under tension.
[0041] The eye 22 is maintained in continuous vibration by the
eccentric mechanism (vibration generator 28) illustrated in FIG. 5.
This is of special importance, in particular when removing the
thread 21, i.e. in the course of the abrupt change between the
operating position in accordance with FIG. 2, in which the thread
21 is conveyed, and the operating position in accordance with FIG.
4, in which no thread is conveyed. If the thread consumption is
suddenly stopped in the downstream-connected machine, the thread 21
initially still rests against the thread feed wheel 6. Because of
its adhesion to the thread feed wheel 6, there can be a certain
tendency of the thread feed wheel 6 to take along the thread not
accepted by the downstream-connected machine in the direction 39 of
rotation, so that the thread guide lever 5 would be prevented from
removing the thread 21. But the vibration of the thread guide eye
22 is transmitted to the thread 21 and prevents the latter from
adhering to the thread feed wheel 6. Because of this, the thread 21
can be immediately detached from the thread feed wheel 6 when the
thread consumption is reduced. By means of this step in particular
it is possible to make do with comparatively low forces at the
thread guide lever 5 and therefore to deliver threads 21 which are
and should be under only little tension. It is moreover possible to
process critical threads, which otherwise would tend to strongly
adhere to the thread feed wheel 6. This also applies to thread feed
wheels 6 which, in place of the structure shown, have a
cylindrical, plastic- or rubber-coated surface. The vibration of
the thread aids the feeding of the thread against the checking
force of the thread brake 3, and therefore the removal process.
[0042] Deviating from the above described embodiments, vibrations
can also be transmitted to the vibration friction feed wheel
mechanism 1. For example, the thread can be briefly deflected by
means of a pin or other element, or vibration can be applied to it,
wherein it is immaterial in most cases at which location between
the thread brake 3 and the thread feed wheel the vibrational
movement is imparted to the thread 21.
[0043] As schematically represented in FIG. 6, the vibration can
also be introduced to the thread guide lever 5. To this end it is
possible, for example, to initially seat the thread guide lever 5
on a hinge point 41, which is seated fixed in place, wherein the
thread guide lever 5 is connected to a pre-stressing spring 42. The
latter can be suspended from the vibration generator 28, so that
the vibrations reach the eye 33 of the thread guide lever 5 in the
end. The vibration-capable system constituted by the pre-stressing
spring 42 and the thread guide lever 5 can be tuned to resonance or
outside of the latter. In this embodiment, the thread feed wheel 6
is rotatably seated on a seating device, which is seated fixed in
place. The thread guide eyes 7 and the eyes 22 are also seated
fixed in place.
[0044] The same applies to the embodiment in accordance with FIG.
7, wherein again the thread guide lever 5 is subjected to
vibrations. The vibration generator 28 is again used for this
purpose and acts on the hinge point 41 of the thread guide lever.
But in contrast thereto, the pre-stressing spring 42 is supported
at a suspension point which is fixed in place. Here, again,
resonance tuning is possible, as well as an operation of the
vibration generator 28 at a frequency different from the resonance
frequency which the thread guide lever 5 determines by means of the
pre-stressing spring 42.
[0045] Deviating from this, it is possible to omit the
pre-stressing spring 42, if the thread guide lever 5 is itself
resiliently embodied and is not pivotably connected with the
vibration generator 28. A rigid connection, for example, can be
provided. Again, the excitation of the natural resonance of the
thread guide lever 5 is possible. In the cases represented, the eye
33 can vibrate in the plane in which the thread 21 runs. This would
be the plane of projection in FIGS. 6 and 7. If needed, the
vibration can also be directed transversely to the direction of
thread travel, or it can be circularly polarized. Chronologically
changing vibration directions can also result. It is important that
the thread 21 be charged with vibrations in such a way that it does
not adhere to the thread feed wheel 6, but that the frictional
adherence is disrupted at least at the detachment point.
[0046] This can also be achieved by the embodiment in accordance
with FIG. 8, wherein the seating device of the thread feed wheel 6,
i.e. the shaft 8 in particular, is acted upon by vibrations. The
remaining elements are again seated fixed in place. The pivotably
seated thread guide lever 5 is also not acted upon by vibrations.
However, the detachment of the thread 21 from the contact surface
38 is aided by the application of vibration, in particular to the
contact place of the thread 21 running off the thread feed wheel
6.
[0047] This also applies to the embodiment in accordance with FIG.
9, wherein the vibration acts on the thread guide eye 7. However,
in this case the detachment of the thread 21 from the thread feed
wheel 6 can be somewhat weaker in respect to the previously
described embodiments. The reason for this can be the reduced
vibration transmission from the thread guide eye 7 via the thread
21 to the contact point between the thread feed wheel 6 and the
thread 21 which occurs, if the thread 21 is not maintained
tight.
[0048] In principle, the vibration generator can be differently
constructed. In accordance with FIG. 5, it can be constituted by
the arrangement of an eccentric device. FIG. 10 illustrates an
alternative embodiment, wherein a driven cam 44 periodically hits a
tappet 45 in order to impart a short stroke on the latter. The
tappet 45 can be pre-stressed by means of a spring 46 against the
cam 44. The cam 44 can rotate synchronously with the thread feed
wheel 6, but if required also at greater or lesser numbers of
revolutions. Moreover, it can generate several strokes per
revolution if, varying from the representation in FIG. 10, it has
several protrusions.
[0049] Further than that, an electrical vibration generation is
possible. FIG. 11 schematically illustrates such a vibration
generator 28, which has a magnetic coil 47, which is seated fixed
in place. Its core 48 is for example magnetically polarized (north
pole N, south pole S), and has been suspended, for example by
resilient strips or diaphragms 50, 51, in an axially displaceable
manner. If an a.c. voltage is applied to the magnetic coil 47, the
armature 48 swings in the direction of the arrow indicated in FIG.
11. The arrangement can be tuned to resonance, as well as outside
of resonance, and can be used for applying vibrations to the
individual elements in accordance with FIGS. 6 to 9, or also FIG.
5. The application of the vibrations can take place permanently or
periodically over time.
[0050] A vibration generator 28 in accordance with FIG. 12 is
designed for generating a rotary vibration. The latter can for
example be used as a bearing device for a thread feed wheel 6.
Here, the shaft 8 is seated in a bearing 52, which is held by means
of an eccentric 53. The eccentric 53 is held on a bearing receiver
55, fixed in place, via a further bearing 54. Independently of the
intrinsic rotation of the shaft 8, a rotation of the eccentric 53
guides it on an orbiting path, such as indicated by an arrow 56
next to it in FIG. 12. The radius of this orbital movement is
preferably relatively short and lies in the range of a vibration
amplitude of approximately 1 mm. In this case the orbital movement
can have a number of orbits which differs from the number of
revolutions of the thread feed wheel. Numbers of orbits which are
larger than the number of revolutions of the thread feed wheel 8
are preferred.
[0051] In connection with a vibration friction feed wheel mechanism
1, having a thread guide lever 5 for inserting and removing a
thread 21, the application of vibrations to the thread guide
elements 22, 33, 7, or the application of vibrations to the thread
feed wheel 6, is used to improve the removal properties of the
friction feed wheel mechanism 1.
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