U.S. patent application number 10/605781 was filed with the patent office on 2005-07-07 for electronic stitch length regulator for home sewing machines.
This patent application is currently assigned to Hooke, David Andrew. Invention is credited to Hooke, David Andrew.
Application Number | 20050145149 10/605781 |
Document ID | / |
Family ID | 34710286 |
Filed Date | 2005-07-07 |
United States Patent
Application |
20050145149 |
Kind Code |
A1 |
Hooke, David Andrew |
July 7, 2005 |
Electronic Stitch Length Regulator for Home Sewing Machines
Abstract
This invention comprises a means to control stitch length of
household sewing machines when used on free-motion quilting frames.
A sensor in the form of a computer mouse or a pair of sensors in
the form of optical encoders is used to determine the translational
speed of the set of carriages that hold the sewing machine. This
information is sent to electronic circuitry that converts this
information to an electrical resistance which is applied to the
foot pedal control electrical connector on the sewing machine. When
thusly applied, this resistance sets the rotational speed of the
sewing machine. This invention achieves stitch length uniformity by
maintaining the proper relationship between the input signal from
the sensor or sensors caused by carriage translation and the output
resistance to the sewing machine which controls its rotational
speed.
Inventors: |
Hooke, David Andrew;
(Palmdale, CA) |
Correspondence
Address: |
DAVID ANDREW HOOKE
39748 GORHAM LANE
PALMDALE
CA
93551
US
|
Assignee: |
Hooke, David Andrew
39748 Gorham Lane
Palmdale
CA
|
Family ID: |
34710286 |
Appl. No.: |
10/605781 |
Filed: |
October 26, 2003 |
Current U.S.
Class: |
112/315 ;
112/470.01 |
Current CPC
Class: |
D05B 69/18 20130101;
D05B 11/00 20130101 |
Class at
Publication: |
112/315 ;
112/470.01 |
International
Class: |
D05B 027/22; D05B
019/00 |
Claims
1. An electronic stitch length regulator comprising: a position
sensor; a sensor arm; a base plate; an electronic circuit; an
electrical output connector.
2. The electronic stitch length regulator of claim 1, wherein the
sensor arm is pivotally mounted in the base plate.
3. The electronic stitch length regulator of claim 2, wherein the
sensor arm is preloaded longitudinally with a spring element.
4. The electronic stitch length regulator of claim 1, wherein the
base plate is mounted below the sewing machine.
5. The electronic stitch length regulator of claim 1, wherein the
electronic circuit converts speed of position sensor to electrical
resistance measured in Ohms.
6. The electronic stitch length regulator of claim 5, wherein the
frequency output of the sensor comprises two channels.
7. The electronic stitch length regulator of claim 6, wherein each
channel of frequency signal is converted to a voltage
respectively.
8. The electronic stitch length regulator of claim 7, wherein the
two channels of voltage are added to form a composite total
voltage.
9. The electronic stitch length regulator of claim 8, wherein the
composite total voltage is used as an input signal to a comparator
circuit.
10. The electronic stitch length regulator of claim 9, wherein the
comparator output is dependent on the composite total voltage.
11. The electronic stitch length regulator of claim 10, wherein the
comparator output controls an opto-isolator integrated circuit.
12. The electronic stitch length regulator of claim 11, wherein the
output of the optoisolator circuit is connected to a plurality of
fixed electrical resistors.
13. The electronic stitch length regulator of claim 12, wherein the
plurality of fixed electrical resistors are connected to an
electrical output connector.
14. The electronic stitch length regulator of claim 13, wherein the
electrical output connector plugs into the sewing machine foot
pedal connector port.
Description
BACKGROUND OF INVENTION
[0001] Typically machine quilting is performed by using a sewing
machine which uses a mechanical means to control stitch length.
Consistent stitch length is accomplished by a set of feed dogs
located under the throat plate of the sewing machine that are in
contact with the fabric being sewn which, in turn, is in contact
with the presser foot of the sewing machine. As the machine runs,
the feed dogs alternately grab and release the fabric in precise
timing with the up and down motion of the needle. The result is an
even stitch based on a mechanical means. However, free motion
quilting, as it is called in the art, does not use the sewing
machine feed dogs to move the fabric through the sewing machine. In
free motion quilting, the quilter controls the rate at which the
fabric is moved through the machine independently from the up and
down rate of the needle. The result is uneven stitching. For
instance if the needle is moving up and down quickly, but the
fabric is moving slowly, the result is a very short stitch length.
Conversely, if the needle is moving slowly and the fabric is moving
quickly, the result is a very long stitch length. Alternatively,
there are quilting frames in the art in which the fabric layers of
the quilt are held stationary while the sewing machine, placed on a
carriage is moved to create the quilting design. Stitch length is
based on the user's ability to regulate the rotational (or
stitching) speed of the sewing machine independently of the
traveling speed of the sewing machine atop the carriage. This is a
difficult if not impossible procedure to master. Thus, there exists
a need for an improved method of stitch length regulation for the
quilter. Such a means to control stitch length should relate the
relative translational speed between the sewing machine and fabric
to the rotational speed of the sewing machine to maintain constant
stitch length. It is to the provision of such an apparatus that the
present invention is primarily directed.
SUMMARY OF INVENTION
[0002] The present invention, in one embodiment thereof, comprises
a sensor to measure translational speed of a sewing machine
carriage electrically connected to electronic circuitry which takes
the signal generated by the sensor as input and outputs an
electrical resistance value in Ohms. This electrical resistance,
when applied to the foot pedal control electrical connector of the
sewing machine, sets the sewing machine rotational speed. As the
sensor detects varying translational speed, the output resistance
varies in concert which, in turn, varies the sewing machine
rotational speed. In the present embodiment of the invention, the
sensor is mounted on the end of a rod, which pivots in a base plate
placed on top of a carriage and under the sewing machine. The
sensor outputs two signals. The first signal is an alternating
voltage with a frequency proportional to the rate of position
change, or speed, of the longitudinal axis. The second signal is an
alternating voltage with a frequency proportional to the rate of
position change, or speed, of the transverse axis. The electronic
circuitry of the present invention takes each of the aforementioned
signals and converts the respective frequencies to voltages
proportional to the frequencies. Furthermore, the voltages from
each of the channels are then added together to form a composite
voltage proportional to the speed of the carriage. This voltage is
then measured with a multi-step comparator circuit, the output of
which controls a multi-step optical-isolator, or opto-isolator,
circuit which contains a different resistance value for each step.
The output of the circuitry is therefore a resistance that is
dependent on the speed of carriage movement. This resistance mimics
the resistance of a foot pedal control for the sewing machine.
These and other aspects of the present invention will be more
apparent from the following description.
BRIEF DESCRIPTION OF DRAWINGS
[0003] FIG. 1 is an isometric view of the basic components of a
commercially available quilting apparatus containing the addition
of an embodiment of the present invention.
[0004] FIG. 2 is an isometric view of a base plate and sensor
placement in accordance with embodiments of the present
invention.
[0005] FIG. 3 is a block diagram of the methodology by which sensor
input is converted to an output resistance which controls sewing
machine speed as used in an embodiment of the present
invention.
[0006] FIG. 4 is a block diagram of the fundamental stages and
components of the electronic circuitry of the invention.
[0007] FIG. 5 is a block diagram of the final stage of circuitry
showing the connection to the sewing machine.
DETAILED DESCRIPTION
[0008] FIG. 1 illustrates a quilting frame 1 and its components
used for reference in this patent. The frame 1 is described in
detail in U.S. Pat. No. 6,615,756. The components of frame 1 of
interest in this invention are the longitudinal carriage 2 and the
transverse carriage 3 with reference to the coordinate system 29.
The sewing machine 4 is placed on top of the base plate 5 which is
placed on the transverse carriage 3 which is placed on top of the
longitudinal carriage 2 which rides on rails 6. The transverse
carriage 3 has guide wheels suitably fixed such that only movement
in the transverse direction is possible. Similarly, the
longitudinal carriage 2 has guide wheels suitably fixed to it such
that only longitudinal movement is possible. The sewing machine 4
can move in both the transverse and longitudinal directions using
this arrangement. FIG. 2 illustrates the mounting of the position
sensor 7 to the sensor arm 8 in one embodiment. The sensor 7 is
pivotally mounted to the sensor arm 8 such that the sensor is free
to rotate about an axis parallel to the longitudinal axis. The
sensor 7 rests on the table top 13 or other suitable flat surface.
The sensor arm 8 is pivotally mounted to the base plate 5 in
journals 9 such that the sensor arm 8 is free to rotate in an axis
parallel to the longitudinal axis, but is restrained in all other
axes. The sensor arm 8 is restrained from sliding in the journals 9
by a preloaded spring 10 and clip 11. Therefore, as the carriage
assembly comprised of 2 and 3 is moved in the longitudinal and
transverse directions, the sensor 7 moves in the same directions
and at the same speed. Also shown is another embodiment where
position sensors are shaft encoders 12 attached to the carriage
wheels or alternatively independent units suitably attached to the
longitudinal and transverse carriages 2 and 3, respectively. The
electrical output of the sensor is sent to the electronic control
via the sensor wire bundle 14. Two signals are present in the
sensor wire bundle 14. The first signal is a voltage with constant
amplitude, but frequency varying with longitudinal speed 15 as
shown in FIG. 3. The second signal is a voltage with constant
amplitude, but frequency varying with transverse speed 16. As shown
in FIG. 3, the signals 15 and 16 are then converted to independent
voltages 17 and 18 proportional to their frequencies 15 and 16
respectively. An estimate of the true speed of the carriage
comprised of 2 and 3 is obtained by adding voltages 17 and 18
together to form a composite sum voltage 19. The composite voltage
19 is proportional to carriage speed. The composite voltage 19 is
then monitored by a comparator circuit 20 which takes as its input
the composite voltage 19, compares it to established lower 21 and
higher 22 bounds, and provides as its output twenty levels of
on-off switches or gates. More clearly, as the voltage 19 is
increased slightly above the lower bound 21 the first gate or
switch allows current to pass through its comparator stage 23. As
the voltage 19 is raised higher, the second gate or switch allows
current to pass through its comparator stage 24. This continues in
a similar fashion until the voltage 19 reaches just above the
higher bound 22 of the comparator circuit, then the final stage,
the twentieth stage 25, of the comparator circuit is energized
allowing current to pass through the final stage 25. As shown in
the block diagram of FIG. 3 and more distinctly in FIG. 4, the
gates in the comparator stages control current through one half of
an opto-isolator integrated circuit 26. The function of the
opto-isolator circuit 26 embodied in this invention is to
electrically separate the voltages and currents of the control
circuitry from the voltages and currents of the sewing machine. As
the gates 30 of the comparator circuit 20 cycle on and off in
accordance with the speed of the sensor 7, they allow current to
pass through light emitting diodes 31, LEDs, embedded within the
opto-isolator 26 integrated circuit causing the LED to illuminate.
The other half of the opto-isolator circuit 26 is a series of
phototransistors 32 which pass electrical current when illuminated
by the light of its matching LED. This is integrated with the
electronics of the sewing machine as shown in FIG. 5. The majority
of sewing machines have a foot pedal speed control which is at its
core a variable resistor 27. The purpose of this invention is to
mimic that variable resistance in a manner such that it varies with
the translational speed of the sensor 7 so that the resulting
stitch length remains constant. The output of the opto-isolator
circuit 26 in conjunction with a plurality of fixed resistors 27
accomplish the task of mimicking the variable resistance. As shown
in FIG. 5, when the first comparator stage 23 allows current to
flow through its gate, illuminating the first stage LED of the
opto-isolator, the matching phototransistor is energized allowing
current to flow. The first resistor 28 in the plurality of
resistors 27 is thusly electrically connected to the sewing
machine. The sewing machine will run at a speed commensurate with
the electrical resistance applied to the foot pedal connector.
Similarly, as the sensor 7 speed changes in direct response to the
change in translational speed of the sewing machine 4, different
stages of the comparator circuit 20 will be energized. As a result,
different stages of the opto-isolator circuit 26 will be energized
causing different phototransistors to be energized which, in turn,
cause different resistance values to be applied to the foot pedal
connector port of the sewing machine 4. With proper circuit tuning
by judicious choice of resistors 27, the rotational speed of the
sewing machine can be controlled such that the stitch length is
constant, independent of the translational speed, until the point
where the translational speed causes the machine to run at its
maximum rotational speed. Above that speed, the machine cannot
physically rotate any faster and stitch length will elongate.
* * * * *