U.S. patent number 3,860,187 [Application Number 05/352,268] was granted by the patent office on 1975-01-14 for circuit for controlling the thread velocity in winding equipment with a traversing mechanism.
This patent grant is currently assigned to Siemens Aktiengesellschaft. Invention is credited to Manfred Liska, Jurgen Metzger.
United States Patent |
3,860,187 |
Liska , et al. |
January 14, 1975 |
CIRCUIT FOR CONTROLLING THE THREAD VELOCITY IN WINDING EQUIPMENT
WITH A TRAVERSING MECHANISM
Abstract
A circuit for controlling the thread velocity in universal
winding machines having a traversing mechanism is disclosed. The
circuit develops a correction factor, derived from the diameter of
the winding on the spindle or the speed of the motor driving the
spindle. This correction factor is then used as an input to the
thread velocity control circuit to maintain a constant velocity for
the thread being fed to a spindle.
Inventors: |
Liska; Manfred (Nurnberg,
DT), Metzger; Jurgen (Erlangen, DT) |
Assignee: |
Siemens Aktiengesellschaft
(Munchen, DT)
|
Family
ID: |
5842907 |
Appl.
No.: |
05/352,268 |
Filed: |
April 18, 1973 |
Foreign Application Priority Data
|
|
|
|
|
Apr 21, 1972 [DT] |
|
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2219755 |
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Current U.S.
Class: |
242/413.9; 318/6;
242/414.1 |
Current CPC
Class: |
B65H
59/385 (20130101); B65H 2701/31 (20130101) |
Current International
Class: |
B65H
59/00 (20060101); B65H 59/38 (20060101); B65h
059/38 () |
Field of
Search: |
;242/45,75.5,75.51,186
;318/6 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Gilreath; Stanley N.
Attorney, Agent or Firm: Kenyon & Kenyon Reilly Carr
& Chapin
Claims
What is claimed is:
1. A circuit for controlling the thread velocity in a universal
winding machine having a traversing mechanism, said machine
including a spool drive operated by a speed control, said circuit
providing compensation for inaccuracies resulting from said
traversing mechanism comprising:
a. means to measure the tangential velocity of the spool and to
provide a first output signal proportional thereto;
b. means to provide a second signal representing a desired
tangential velocity;
c. means having said first and second signals as inputs to develop
a speed control signal;
d. means to develop a third signal proportional to the actual spool
drive speed;
e. means to couple said speed control signal and said third signal
to said speed control;
f. means to develop from said actual spool drive speed a correction
factor signal proportional to the diameter of the winding on the
spool; and
g. means to add said correction factor signal to said speed control
signal.
2. A circuit for controlling the thread velocity in a winding
machine as in claim 1 in which the spool winder drive is a d-c
motor without a commutator and having a permanent magnet rotor and
in which the e.m.f. inducted in the stator windings by the
permanent-magnet rotor is used to represent the actual value of the
speed of rotation of the spindle winder.
3. A circuit for controlling the thread velocity in a winding
machine as in claim 2 wherein said means to develop a correction
factor signal comprises an amplifier having as an input said e.m.f.
induced in the stator windings.
4. A circuit for controlling the thread velocity in a winding
machine as in claim 3, in which the amplifier has adjustable
feedback.
5. A circuit for controlling the thread velocity in a winding
machine as in claim 4, in which the adjustable feedback is made
non-linear.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention is concerned with a circuit for controlling the
thread velocity in a universal winding machine, in which a
traversing mechanism is employed. More particularly, it is
concerned with a means for measuring the velocity of the thread
winding to thereby supply a reference value for a thread velocity
control means in a spindle winder drive in which speed control is
used.
In order to insure that the properties of thread-like materials
such as yarns are not changed during winding operations, it is
necessary to maintain the thread tension constant during the entire
winding procedure. With extremely thin yarns the commonly used
method of controlling the tension in heavier yarn thread by means
of a feeler roll is not technically possible. Therefore, one must
resort to some form of thread velocity measurement.
The direct measurement of the thread velocity for moving material,
however, causes difficulties, and it is therefore advisable to
measure the tangential velocity of the winding by means of a feeler
roll. A system which operates in this manner is described in U.S.
application Ser. No. 334,933, filed by M. Liska and H. Grunleitner
on Feb. 22, 1973 and assigned to the same assignee as the present
invention. However, sufficient accuracy is obtained by this method
only if the thread velocity is proportional to the tangential
velocity of the winding. Modern winding machines, however, are
always equipped with a traversing mechanism which, by means of a
thread guide, moves the thread along the axis of the reel once or
several times during the revolution of the reel. The subsequent
trouble free unwinding of spools can be accomplished only if the
spools were originally wound in the same manner.
2. Summary of the Invention
It is therefore an object of this invention to use a relatively
simple circuit to compensate for changes in thread velocity created
during the winding process by the motion of the traversing
mechanism.
According to the invention, the problem is solved by introducing
into the thread velocity control circuit a correction factor
derived from a quantity which is a function of the diameter of the
winding such as from the speed of rotation of the spool winder. It
is particularly advantageous if the correction fator is derived
from the actual value of the speed of rotation of the spool winder
drive, because it is usually very complicated to sense the diameter
of the winding. The illustrated embodiment uses a d-c motor without
a commutator as the spool winder drive with the e.m.f. induced in
the stator winding by the permanent-magnet rotor utilized as a
measure of the actual value of the speed of ratation. The e.m.f. is
advantageously fed to an amplifier whose output signal is used as
the correction factor for the reference value transmitter.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention, as well as its objects and features will be better
understood by reference to the following detailed description of
the preferred embodiment of this invention taken in conjunction
with the accompanying drawings in which:
FIG. 1 is a diagrammatic illustration of the apparent movement of
the thread guide over the surface of the winding for a crossing
ratio k = 1. The crossing ratio is defined as the number of double
throws per revolution of the winding. As shown in FIG. 1, the
winding diameter d is apparently increased to d' during one
traversing motion.
FIGS. 2 and 3 illustrate side views of the winding shown in FIG. 1,
with different diameters.
FIG. 4 is the block diagram of a thread velocity control circuit
constructed according to the invention for a winding machine drive
having subordinated speed control and a correction for the
influence of the traversing motion.
DESCRIPTION OF THE PREFERRED EMBODIMENT
FIG. 1 is a perspective view showing the manner in which the thread
is wound on a spool. The actual diameter d' of a loop of thread
will be greater than the diameter d of the total winding which is
the diameter at which the tangential velocity is sensed. If the
ratio of d:d' remained constant, no problems would arise. However,
as will be seen by comparing FIGS. 2 and 3, the diameter ratio,
d:d', changes with increasing diameter as a result of the fixed
spool length 1. Thus, even with an exactly constant tangential
velocity of the winding, as measured by a roller tangent to the
diameter d, a thread velocity is obtained which decreases with the
increasing diameter of the winding. The change in magnitude
essentially depends on the change in the diameter of the winding
and the crossing ratio. Practical investigations have shown that
the velocity deviation can be 10 percent or more. Deviations of
such an order of magnitude are no longer permissible in many cases,
particularly in precision winding machines. With little thread on
the spool, as shown on FIG. 2, the difference between d and d' will
be great. As more thread is wound on the spool, as shown on FIG. 3,
the difference becomes smaller. To maintain a constant tangential
velocity the angular velocity of the motor will be higher when
there is little thread on the spool and lower when more thread is
on the spool. Thus, the velocity of the motor is directly related
to the diameter error. The present invention makes use of this fact
in providing the needed correction.
As shown in FIG. 4, a commutatorless d-c motor 1 drives the shaft
of a winding 2 on which thread-like material is to be wound. The
winding equipment comprises a traversing mechanism, not shown in
the drawing. The motor 1 has a permanent-magnetic rotor which
interacts with four windings arranged in the stator. The stator
windings are connected with each other at one end and the neutral
point formed in this manner is connected with one terminal of a d-c
source. The other ends of the windings are sequentially connected
through an electronic commutator 3 and the other terminal of the
d-c source in such a manner that a rotating field is produced in
the stator. The electronic commutator 3 is controlled by a speed
control means 4. Similarly a conventional d-c motor such as that
described in the above referenced application may be used.
The tangential velocity of the winding is converted into a pulse
train x.sub.f, by means of a non-contacting transducer means 6.
(Such means along with the other basic elements of the control
circuit are described in detail in the above referenced U.S.
application Ser. No. 334,933, and will only be briefly described
herein). The voltage-time area of the pulse train x.sub.f
representing the tangential velocity is compared with an average
d-c voltage value x.sub.s representing a desired velocity, produced
by a reference value transmitter 5. The deviation, x, the error
between the actual and desired velocities, between x.sub.f and
x.sub.s is fed to an integrator 7, which may be a
differentiating-feedback amplifier i.e., it has a capacitor in its
feedback path. As long as the deviation x remains at zero the
output of the integrator will remain fixed. An error in either
direction will cause a charging or discharging of the feed back
capacitor to adjust the integrator output until the proper velocity
is reached. The output quantity x.sub.a of integrator 7 is picked
off by a potentiometer 8 used to provide coarse control of motor
speed. This is the speed control value fed to the speed control
means 4.
The actual value x.sub.n of the speed of rotation of the motor 1 is
determined in a known manner from the e.m.f. of the motor by means
of the plurality of diodes 12. Voltages corresponding to the e.m.f.
of the motor are induced in the windings of the stator by the
revolving permanent-magnet rotor. A tachometer may also be used to
develop this signal as described in the above referenced
application. The entire circuit for the speed control circuit 11 is
indicated by the dashed lines in FIG. 4. Here in well known fashion
the output of potentiometer 8 is summed with the value x.sub.n to
provide outputs to maintain the required motor speed. The portion
of the circuit thus far described is conventional and as noted may
be constructed in the manner described in application Ser. No.
334,933. However, it will exhibit the inaccuracies described
above.
To correct for these inaccuracies, the present invention uses the
e.m.f. of the motor which is proportional to the angular velocity
to derive a correction factor for the thread velocity control
circuit 11. This is accomplished by feeding the coupled output of
diodes 12 to an amplifier 9, whose output signal x.sub.k is summed
with the input x.sub.a at the input to potentiometer 8 to provide a
correction factor. Although shown as a potentiometer, block 8 may
also contain a summing amplifier to sum these signals. The
resulting output is then fed to the thread velocity control circuit
11. In order to obtain compensation for different crossing ratios
and different reel sizes amplifier 9 has a variable feedback means
10 which, to provide better compensation, can be made non-linear.
In this manner, the correction quantity is no longer directly
proportional to the angular speed of rotation of the spool and by
proper selection of feedback elements the deviation of the thread
velocity from the ideal value can be made approximately zero. As
illustrated schematically by the block 10, the variable feedback
means can comprise a variable resistor in a feedback path which
resistor may be setup at the beginning of a winding operation to
give the desired gain. Similarly, the resistor may be replaced by
non-linear networks comprising for example, diodes resistors,
variable resistors, etc., which also will be initially set up prior
to a winding operation.
The invention thus permits the application of thread velocity
control to precision winding machines. In addition it permits
adding improved accuacy to a normal thread velocity control with no
additional mechanical components and only a minimum amount of
additional circuitry. In addition, one obtains the ability to adapt
and use the correction factor produced by the circuit to different
designs of spools such as those having different crossing ratios
and different ratios of length to diameter. A further advantage
consists, moreover, in the fact that the dynamic behavior of the
thread velocity does not influence the control circuit because the
correction factor only influences the reference value. By
introducing non-linear feedback in the correction factor amplifier
the deviation of the thread velocity from the ideal value can
thereby be reduced to almost zero.
In the foregoing, the invention has been described in reference to
specific exemplary embodiments. It will be evident, however, that
variations and modifications, as well as the substitution of
equivalent constructions and arrangements for those shown for
illustration, may be made without deparing from the broader scope
and spirit of the invention as set forth in the appended claims.
The specification and drawings are accordingly to be regarded in an
illustrative rather than in a restrictive sense.
* * * * *