METHOD AND APPARATUS FOR POSITIONING A WORKPIECE WITHIN A SEWING STATION

Background of the Invention

1. Field of the Invention This invention relates to a sewing machine, and more particularly to a method and apparatus for positioning a workpiece within a sewing station of a sewing machine.

2. Description of the Related Art In the sewing industry, it is common to use a clamp to hold or clamp a portion of a first workpiece such as a label, patch or emblem to a receiving workpiece, such as a garment, so that the first workpiece can be subsequently sewn to the garment. The first workpiece is typically manually positioned below the clamp and registered such that the clamp contacts a central inner portion of the first workpiece thereby leaving a periphery of the first workpiece available for receiving a stitch pattern. From a quality control point of view, it is important that the stitch pattern be substantially centered on the first workpiece with even margins around the periphery thereof.

Thus, an operator is often faced with the tedious, time consuming and inaccurate task of manually registering the first workpiece with the clamp in two different directions, namely, the X and Y directions. The registration of the first workpiece to the clamp is typically accomplished near or in a sewing station of a sewing machine, which sewing station is often compact and contains numerous sewing machine components, such as a 360° device, needle holder and sewing needle, which make the task of registering the first workpiece difficult.

To alleviate having to register the first workpiece with the clamp in the sewing station, known workpiece feeder mechanisms drive the first workpiece into the sewing station from a position spaced apart from the sewing station. Unfortunately, when using the known feeder mechanisms, an operator is still faced with the tedious, time consuming and inaccurate task of registering the first workpiece on the feeder mechanism in the X and Y directions so that the feeder mechanism can then deliver a properly registered first workpiece to the sewing station.

Summary of the Invention

There is, therefore, a present need to provide an new and improved method and apparatus for positioning a workpiece in a sewing station.

In one aspect, this invention comprises a method of positioning a workpiece relative to a predetermined position associated with a sewing station including the steps of sensing a position of the workpiece relative to the predetermined position, and advancing the workpiece a distance based upon the sensed position.

In a second aspect, this invention comprises an apparatus for positioning a workpiece relative to a predetermined position associated with a sewing station. The apparatus includes a sensing circuit which senses a parameter of the workpiece, and a transport which advances the workpiece a distance based on the sensed parameter. In a third aspect, this invention comprises an apparatus for positioning a workpiece relative to a predetermined position associated with a sewing station. The apparatus includes a mechanism for measuring a

dimension of the workpiece during advancement thereof, and a mechanism for locating the workpiece within the sewing station based on the measured dimension.

In a fourth aspect, this invention comprises a method of sewing a first workpiece to a second workpiece, including the steps of determining a position of the first workpiece relative to a predetermined position associated with a sewing station, advancing the first workpiece a distance based on the sensed position of the first workpiece so that the first workpiece is located within the sewing station, positioning the second workpiece within the sewing station, moving the first workpiece into contact with the second workpiece, and sewing the first workpiece and the second workpiece together.

In a fifth aspect, this invention comprises an apparatus for sewing a first workpiece to a second workpiece. The apparatus includes a sensing circuit adapted to measure a size parameter of the first workpiece, a transport for transporting the first workpiece a distance based on the sensed size parameter of the first workpiece, and a sewing station adapted to receive the first workpiece and the second workpiece, the sewing station including a sewing mechanism adapted to sew the first workpiece and the second workpiece together.

In a sixth aspect, this invention comprises a method of positioning a workpiece relative to a predetermined position associated with a sewing station, including the steps of providing a transport for the workpiece having a registration stop, placing the workpiece onto the transport so that an edge of the first workpiece is aligned with the registration stop, sensing a leading edge of the workpiece during advancement

thereof and generating a leading edge signal in response thereto, sensing a trailing edge of the workpiece during advancement thereof and generating a trailing edge signal in response thereto, determining a position of the workpiece relative to the predetermined position based upon the leading edge signal and the trailing edge signal, and transporting the workpiece a distance based on the determined position of the first workpiece.

An object of the present invention to provide a new and useful method for positioning a workpiece in a sewing station.

Another object of the present invention to provide a new and useful apparatus for positioning a workpiece in a sewing station. A further object of the present invention to provide a method of positioning a workpiece in a sewing station which reduces the effort required for an operator to appropriately position a workpiece on a carriage arm. It is yet another object of this invention to provide a new and useful apparatus that enables an operator to quickly position a workpiece on a carriage arm.

It is still another object of this invention to provide a method and apparatus for positioning a workpiece which provides for convenient adjustment of a workpiece destination position in a sewing station.

It is still another object of this invention to provide a method and apparatus for positioning a workpiece within a sewing station which is able to determine defective workpieces during a workpiece positioning operation.

The above and other objects, features, and advantages of the present invention will become apparent from the following description and the attached drawings.

Brief Description of the Drawing

FIG. 1 is a front elevation view of a sewing machine and carriage assembly which incorporates the features of the present invention therein; FIG. 2A is an elevation view of a first workpiece interrupting a light beam to determine a step address for a leading edge of the first workpiece;

FIG. 2B is an elevation view of the first workpiece passing through the light beam to determine a step address for a trailing edge of the first workpiece;

FIG. 3A is a perspective view of the workpiece after being loaded onto a carriage arm;

FIG. 3B is a perspective view of the workpiece positioned at a predetermined location in a sewing station by the carriage arm;

FIG. 3C is a perspective view of the workpiece being lifted from the carriage arm by a lift device;

FIG. 3D is a perspective view of the carriage arm in a retracted position; FIG. 3E is a perspective view of a second workpiece being positioned in the sewing station under the suspended workpiece;

FIG. 3F is a perspective view of the first workpiece being clamped to the second workpiece by a first workpiece clamp;

FIG. 3G is a perspective view the lift device in a retracted position;

FIG. 3H is a perspective view of the first workpiece being sewn to the second workpiece; and FIG. 4 is a perspective view of a sensor assembly for use in determining a centerline of the first workpiece.

Description of the Preferred Embodiment While the invention is susceptible to various modifications and alternative forms, a specific embodiment thereof has been shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that there is no intent to limit the invention to the particular form disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims .

Referring now to FIG. 1, there is shown a sewing system or sewing machine 10 and an adjacent carriage assembly or workpiece feeder system 12 which incorporates the features of the present invention therein. The function of the sewing machine 10 is to sew a first workpiece 14, such as a label, onto a receiving workpiece 16 (FIG. 3E) , such as a garment, at a sewing station 18 of the sewing machine 10. The workpiece 14 is sewn in a conventional manner onto the receiving workpiece 16 with a predetermined stitch or sew pattern 20 (FIG. 3H) in accordance with a computer program (not shown) which is controlled by a master controller 22 of the sewing machine 10. The first workpiece 14 is clamped against a cloth plate 24 (in a manner discussed further below) which provides a clamping or sewing surface 26. The sewing machine 10 may be a programmable sewing machine, such as Brother BAS Models 304 or 340 which are manufactured by Brother Industries of Japan. It should be appreciated that the predetermined stitch pattern 20 (FIG. 3H) is fixed, in the sense that the master controller 22, upon execution of the computer program, causes sewing needle components to be driven in a predetermined pattern. Thus, the first workpiece 14,

prior to being sewn, must be properly positioned relative to the fixed stitch pattern 20 so that the stitch pattern 20 will be sewn on the workpiece 14 a desired or predetermined location such that, for example, even margins will be sewn around the periphery thereof.

The sewing machine 10 also includes a base 28 having a horizontal arm 30 secured thereto. The horizontal arm 30 extends above the sewing surface 26 and has a needle holder 32 which supports a needle 34 for reciprocating motion in a fixed path which is generally vertical and perpendicular to the sewing surface 26 and which defines a needle centerline position 36. The needle 34 moves down through a hole 38 (FIG. 3A) in a throat plate 40 (FIG. 3A) at the bottom of its stroke to transfer a loop of thread (not shown) to a loop taker (not shown) under the sewing surface 26 at the sewing station 18. The loop taker and needle holder 32 are both connected to a motor (not shown) which is controlled by the master controller 22. The sewing machine 10 further includes a workpiece transfer assembly 42 which transfers the first workpiece 14 from the carriage assembly 12 to the receiving workpiece 16 as described further below. In the embodiment being described, the workpiece transfer assembly 42 is a vacuum pick-up assembly comprising a multi-position pneumatic cylinder 44 having a movable output shaft 46 connected to a number of vacuum pick-up tubes or hoses 48. The vacuum pick-up assembly 42 also includes a number of conventional solenoid air valves (not shown) which cause the stroke of the output shaft 46 to vary in magnitude and direction along a fixed path that is generally vertical and perpendicular to the sewing surface 26. In the embodiment being described, the pneumatic cylinder 44 is a three-position pneumatic

cylinder which causes two vacuum pick-up tubes 48 to be driven toward and away from the sewing surface 26 as described further below. A suitable three-position pneumatic cylinder 44 is available from BIMBA Corporation.

The sewing machine 10 also includes a clamping assembly 50 for urging the first workpiece 14 against the receiving workpiece 16 during a sewing operation as described further below. In the embodiment being described, the clamp assembly 50 includes an inner clamp 52 for clamping an interior portion of the workpiece 14, and a 360° device 54 which causes a crank 55 (FIGS. 3A and 3B) associated with the inner clamp 52 to flip-flop in a conventional manner so that the sewing machine 10 can sew stitch patterns which are endless or continuous. The clamp assembly 50 is urged along a fixed path that is generally vertical and perpendicular to the sewing surface 26 by a conventional drive means (not shown) which operates in accordance with the computer program executed by the master controller 22.

In the embodiment being described, the inner clamp 52 includes two apertures 56 (FIG. 3A) for receiving the vacuum pick-up tubes 48 as shown in FIG. 3C. Alternatively, the inner clamp 52 may be provided with recesses or notches for accommodating the vacuum pick-up tubes 48. The inner clamp 52 has a peripheral or exterior edge 58 (FIG. 3A) which defines a predefined clamping area generally corresponding to an inner portion of the workpiece 14. The sewing machine 10 may additionally include an outer or garment clamp or peripheral (not shown) that at least partially surrounds the inner clamp 52 for independently clamping the receiving workpiece 16 during a sewing operation described further below. For example, features of the

peripheral clamp shown and disclosed in U. S. Patent No. 5,377,605 (which is assigned to the same assignee as the present invention and which is incorporated herein by reference and made a part hereof) may be used with the invention described herein.

Referring again to FIG. 1, the carriage assembly 12 includes a platen 60, a carriage or feeder arm 62 slidably mounted on the platen 60, and a linear stepper motor 64 for driving the carriage arm 62 along an axis X that defines a fixed path of travel that is generally horizontal and parallel to the sewing surface 26. The carriage assembly 12 further includes a sensor assembly 66 which is used for positioning the workpiece 14 at a predetermined location within the sewing station 18 as described further below.

As best shown in FIGS. 3A-3H, a free end portion of the carriage arm 62 defines a recessed workpiece loading portion 68. The workpiece loading portion 68 includes a carrier surface 70, a slot 72 extending longitudinally through the carrier surface 70 substantially parallel with the axis X, a flanged edge 74 defining a reference stop or alignment guide for the workpiece 14, and a number of vacuum ports 76 communicating with the carrier surface 70. The vacuum ports 76 supply a vacuum or negative pressure source via a vacuum hose 78 (FIG. 1) to pull the workpiece 14 against the carrier surface 70 thus preventing relative movement between the workpiece 14 and the carrier surface 70 during acceleration and deceleration of the carriage arm 62 as described further below.

The stepper motor 64 has an output shaft (not shown) mechanically coupled to the carriage arm 62 which conventionally drives the carriage arm 62 in either direction along the axis X in approximately 0.0001 (one

ten-thousandth) inch increments or steps. In the embodiment being described, the master controller 22 increases the resolution of the stepper motor 64 by driving the output shaft of the stepper motor in micro- step increments of approximately 0.0000062 inch (1/16 of a 0.0001 step) . A zero reference or home position 79 (FIG. 1) of the carriage arm 62 is defined as the carriage arm position most remote from the sewing station 18 along the axis X (the rightmost position as shown in FIG. 1) . A proximity sensor (not shown) coupled to the master controller 22 detects the presence and/or absence of the carriage arm 62 in the home position 79.

In the embodiment being described, the sensor assembly 66 is a photo-electric sensor assembly 66 mounted to the platen 60. The function of the sensor assembly 66 or sensing means is to sense a predetermined parameter or characteristic of the workpiece. In the embodiment being described, the parameter corresponds to the length of the workpiece 14 , but it should be appreciated that it could be any characteristic capable of being sensed, such as texture, width, size, shape, color, weight and the like. The photo-electric sensor assembly 66 includes a transmitter or sender unit 80 (FIG. 1) , and a receiver unit 82 operatively connected to the master controller 22. As shown in FIG. 4, the photo¬ electric sensor assembly 66 also includes an adjustment device 84 comprising two threaded adjusters 86a and 86b for adjusting the position of the receiver unit 82 in either direction along the axis X relative to the sender unit 80 as discussed further below. In operation, the sender unit 80 transmits a light beam 88 along a light beam centerline position 89, which light beam 88 is detected by the receiver unit 82 unless the light beam 88

is at least partially interrupted or broken by an object intersecting the path of travel of the light beam 88. Referring to FIGS. 3A-3H, the operation and method for positioning the first workpiece 14 at the predetermined location at the sewing station 18 will now be described. With the carriage arm 62 initially positioned in the home position 79, an operator manually places the first workpiece 14 on the carrier surface 70 and urges the first workpiece 14 against the flanged edge 74 as shown in FIG. 3A. It should be noted that the first workpiece 14 need only be placed against the flanged edge 74 without regard for the position of the workpiece 14 relative to the needle centerline position 36 along the axis X. Once positioned on the carrier surface 70, the workpiece 14 is held in place by the vacuum ports 76.

In the embodiment being described, the stepper motor 64 outputs a step number or address of zero (0) when the carriage arm 62 is in the home position 79. Referring to FIG. 1, a fixed distance separates the needle centerline position 36 from the home position 79 of the carriage arm 62, thus a predetermined destination or step address (A) representing the needle centerline position 36 is programmed into the master controller 22. Likewise, a predetermined distance separates the light beam centerline position 89 from the home position 79 of the carriage arm 62, thus a predetermined step address (B) representing the light beam centerline position 89 is programmed into the master controller 22. The step addresses (A) and (B) for the needle centerline position 36 and light beam centerline position 89, respectively, are used to determine a distance between the needle centerline position 36 and the centerline of the workpiece 14 as described further below.

As shown in FIG. 3B, the stepper motor 64 is actuated to drive the carriage arm along the axis X in a direction toward the sewing station 18. As the leading edge of the carriage arm 62 passes between the sender unit 80 and receiver unit 82, the light beam 88 passes through the slot 72 to remain unbroken until a leading edge 90 of the first workpiece 14 interrupts the light beam 88.

Referring now to FIGS. 2A and 2B, there is shown an elevation view of the first workpiece 14 interrupting the light beam 88 for determining a centerline 94 of the workpiece 14, and for determining a distance of travel (F) , measured in stepper motor steps, from the workpiece centerline 94 to the needle centerline position 36. As shown in FIG. 2A, when the workpiece leading edge 90 breaks the light beam 88, the receiver unit 82, upon detecting the interruption, signals the master controller 22 to thereby establish a step address (C) for the workpiece leading edge 90. That is, as the stepper motor 64 drives the carriage arm 62, the master controller 22 maintains a count of the step signals generated by the stepper motor 64. Thus, the step address (C) for the workpiece leading edge 90 is defined as the step count value at the time the receiver unit 82 detects the interruption of the light beam 88 by the workpiece leading edge 90.

As shown in FIG. 2B, the light beam 88 is restored when a trailing edge 92 of the workpiece 14 is driven through the light path 88 toward the sewing needle 34. The receiver unit 82, upon detecting the restoration of the light beam 88, signals the master controller 22 to thereby establish a step address (D) for the workpiece trailing edge 92. Thus, the step address (D) for the workpiece trailing edge 92 is defined as the step count

value at the time the receiver unit 82 detects the restoration of the light beam 88.

Once the leading edge and trailing edge step addresses (C) and (D) are determined, the master controller 22 then determines a step address (E) for the workpiece centerline 94 according to equation (1) :

(1) E = (D - C)/2 + B; where (B) is the predetermined step address for the light beam centerline position 89; (C) is the step address for the workpiece leading edge 90; (D) is the step address for the workpiece trailing edge 92; and (E) is the step address for the workpiece centerline 94.

In order to position the workpiece 14 substantially exactly in the center of the fixed stitch pattern 20 as described above, the workpiece centerline 94 must be substantially exactly aligned with the needle centerline position 36. Since the step address (A) for the needle centerline position 36 is known, the master controller 22 can determine the number of additional stepper motor steps (F) that are required to drive the workpiece centerline 94 into substantial alignment with the needle centerline position 36 according to equation (2) :

(2) F = A - E; where (A) is the step address for the needle centerline position 36; (E) is the step address for the workpiece centerline 94 calculated from equation (1) above; and (F) is the number of additional stepper motor steps that are required to drive the workpiece centerline 94 into substantial alignment with the needle centerline position 36. That is, (F) is the number of stepper motor steps required to drive the workpiece centerline 94 from the step address (E) to the step address (A) .

It should be appreciated that in the loading step shown in FIG. 3A, the position of the first workpiece 14 along the axis X relative to the needle 34 is of no consequence in aligning the first workpiece 14 with the fixed sew pattern 18, thus eliminating the often tedious, time consuming and inaccurate manual alignment methods previously used. In addition, the length (relative to the axis X) of the first workpiece 14 is of no consequence in aligning the first workpiece 14 with the fixed sew pattern 18. Thus, the presently disclosed aligning method and apparatus can be used for positioning workpieces 14 of varying size and/or dimension without having to adjust the carriage assembly 12 to accommodate varying workpiece sizes. By defining minimum and maximum workpiece 14 length thresholds, the master controller 22 can use the workpiece leading edge and trailing edge step addresses (C) and (D) to determine a length or threshold and then accept or reject a particular workpiece 14 if a particular workpiece 14 falls outside the minimum or maximum length thresholds. Thereafter, the carriage arm 62 can be returned to the home position so that an operator can replace the defective workpiece, thus preventing the defective workpiece from subsequently being sewn to the receiving workpiece 16. If the length of the particular workpiece 14 falls within the predefined thresholds, then the workpiece is acceptable and the carriage arm 62 continues to drive the workpiece 14 until the workpiece centerline 94 is substantially exactly aligned with the needle centerline position 36 precisely under the inner clamp 52 as shown in a fragmentary view in FIG. 3B.

Referring now to FIG. 3C, a first stage of the pneumatic cylinder 44 (FIG.1) is actuated to drive the

free ends of the pick-up tubes 48 downwardly through the apertures 56 of the inner clamp 52 and into contact with the upper surface of the workpiece 14. The workpiece 14 adheres to the pick-up tubes 48 when a source of negative air pressure (as shown by arrows Y in FIG. 1) is applied to remote ends of the pick-up tubes 48. The pick-up tubes 48 and workpiece 14 are raised substantially vertically from the carriage arm 62 when a second stage of the pneumatic cylinder 44 is actuated. In the embodiment being described, the pick-up tubes are lowered and raised approximately 1/4 inch by the pneumatic cylinder 44.

As shown in FIG. 3D, once the workpiece 14 is lifted from the carrier surface 70, the carriage arm 62 is driven back to the home position by the stepper motor 64 under control of the master controller 22. While in the home position, the operator can load another workpiece 96 onto the carrier surface 70 as described above with regard to FIG. 3A. If the operator has not previously positioned the receiving workpiece or garment 16 on the cloth plate 24, then the garment 16 is placed under the inner workpiece clamp 52 in such a manner so as not to disturb the suspended workpiece 14 as shown in FIG. 3E. Referring now to FIG. 3F, a third stage of the pneumatic cylinder 44 is actuated to drive the pick-up tubes 48 and the workpiece 14 substantially vertically downward directly into contact with an upper surface of the receiving workpiece 16. The inner workpiece clamp 52 is subsequently driven downwardly around the pick-up tubes 48 into contact with the upper surface of the workpiece 14 to thereby clamp the workpiece 14 to the receiving workpiece 16. As shown in FIG. 3G, the pneumatic cylinder 44 is then actuated to raise or

retract the pick-up tubes 48 from the workpiece 14. With the carriage arm 62 in the home position and the pick-up tubes 48 retracted, the first workpiece 14 is sewn to the receiving workpiece 16 in accordance with the fixed stitch pattern 20 as shown in FIG. 3H. After the sewing operation is complete, the receiving workpiece 16 is removed with the first workpiece 14 sewn thereto, and the next sewing operation can begin with the workpiece 96 all ready in place against the flanged edge 74 of the carriage arm 62.

Referring now to FIG. 4, if it is determined that the destination step address (A) is not properly aligned with the fixed needle centerline position 36 (thus, the workpiece centerline 94 does not substantially exactly aligned with the needle centerline position 36) , the adjustment device 84 can be used to skew the workpiece centerline 94 in either direction along the axis X relative to the destination step address (A) , rather than determine and reprogram the master controller 22 with a new destination step address (A) .

More specifically, by adjusting the thread adjusters 86a, 86b, the position of the receiver unit 82 can be varied relative to the sender unit 80 along the axis X. If the value of the step address (A) causes the workpiece centerline 94 to be misaligned with the needle centerline position 36, the adjustment device 84 can be used to realign the workpiece centerline 94 with the needle centerline position 36 without having to reprogram the master controller 22 with a different value for the step address (A) .

For example, if the workpiece centerline 94 is driven short of the needle centerline position 36, then the receiver unit 82 can be shifted toward the needle centerline position 36 to compensate for the

misalignment . When the receiver unit 82 is shifted toward the needle centerline position 36, the step address (E) for the workpiece centerline 94 will be greater than if the receiver unit 82 was not shifted, because the workpiece 14 had to travel farther before the master controller 22 could determine the step address (E) for the workpiece centerline 94.

Since the step address (B) for the light beam centerline position 89 is pre-programmed into the master controller 22, the number of additional stepper motor steps (F) determined in equation (2) will remain the same (assuming that workpieces 14 having the same length are used) . Thus, the stepper motor 64 will drive the workpiece centerline 94 the same number of additional stepper motor steps from a step address (E) which is greater than if the receiver unit 82 was not shifted. This results in driving the workpiece centerline 94 past the step address (A) .

Likewise, if the workpiece centerline 94 is driven past the needle centerline position 36, then the receiver unit 82 can be shifted away from the needle centerline position 36 to compensate for the misalignment. When the receiver unit 82 is shifted away from the needle centerline position 36, the step address (E) for the workpiece centerline 94 will be less than if the receiver unit 82 was not shifted, because the workpiece 14 did not have to travel as far before the master controller 22 could determine the step address (E) for the workpiece centerline 94. Since the step address (B) for the light beam centerline position 89 is pre-programmed into the master controller 22, the number of additional stepper motor steps (F) determined in equation (2) will remain the same. Thus, the stepper motor 64 will drive the workpiece

centerline 94 the same number of additional stepper motor steps from a step address (E) which is less than if the receiver unit 82 was not shifted. This results in driving the workpiece centerline 94 to a destination point before the step address (A) .

Advantageously, this invention provides an improved method and apparatus for sewing a label onto a garment by sensing a predetermined parameter or characteristic of the label, such as label length, and then using that sensed characteristic to accurately position he label at a predetermined position at the sewing station 18.

While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description is to be considered as exemplary and not restrictive in character, it being understood that only the preferred embodiment has been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected. For example, the parameter or characteristic which is being sensed could be weight, shape, width, color, texture, material, opaqueness and the like.

What is claimed is: