US3808991A

US3808991A - Apparatus for forming normal stitches

Info

Publication number: US3808991A
Application number: US00192288A
Authority: US
Inventors: H Schaefer
Original assignee: USM Corp
Current assignee: USM Corp
Priority date: 1971-10-26
Filing date: 1971-10-26
Publication date: 1974-05-07
Anticipated expiration: 1991-05-07
Also published as: ES408198A1; CA980175A; FR2158972A5; JPS4851749A; IT969941B; GB1405480A; DE2252577A1

Abstract

A method and apparatus for forming only normal stitches between threads. Normal stitches are those usually formed by sewing machines such as lockstitch or single or double thread chain stitch machines that do not have half-hitches or extra twists between the threads. The method comprises the steps of positioning the threads in a predetermined relation to stitch forming instrumentalities and then forming a stitch. The apparatus comprises means for adjusting the relative position of the threads prior to stitch formation and means for forming stitches between the threads.

Description

PAFENTED W 7 SHKU 1 OF 6 PATENIEDIAY 1 19m SHEEI 2 0F 6 PATENTEU HAY 71974 SHEEI 3 OF 6 PATENTEDHAY 7 m4 SHEET 8 BF 6 FLyZO I APPARATUS FOR FORMING NORMAL STITCHES BACKGROUND OF THE INVENTION This invention relates to a method and apparatus for forming only normal stitches between threads.

Efforts to automate sewing machines and other stitch forming instrumentalities have increased in recent years as the cost and difficulty of obtaining skilled machine operators has increased. Many of these attempts at automating sewing operations such as that described in co-pending U.S. Pat. application Ser. No. 94,772 filed Dec. 3, 1970, in the names of Hans F. Schaefer, Jr. and Reade Williams have included means for automatically moving a workpiece in relation to stitch forming instrumentalities. The means for moving a workpiece described in the above application differ from those traditionally employed in sewing machines in that the unidirectional reciprocating workpiece moving method or feed dogs traditionally employed are' replaced by means for moving the workpiece in multiple directions, usually along substantially orthogonal coordinates designated X and Y. These new moving means are appropriately controlled by automatic control means such as a numerical control to cause relative motion between the workpiece and stitch forming instrumentalities along a predetermined path which may include all vector directions relative to the instrumentalities within the plane defined by the orthogonal coordinates. In contrast, the feed dogs and manual control traditionally employed in sewing machines produced relative movement between a workpiece and the stitch forming instrumentalities having vector directions within a few degrees of the direction of motion of the feed dogs or essentially tangential to the path being sewn.

Movement of the workpiece relative to the stitch forming instrumentalities along a wide range of vector directions produced two unexpected problems. As the workpiece is moved relative to the stitch forming instrumentalities, the stitch last formed in the workpiece by the instrumentalities draws thread from storage spools associated with the instrumentalities in a direction having a vector component in the direction in which the material has carried the last formed stitch. The thread may thus assume a range of vector component directions as wide as the workpiece movement. In certain of these directions, it has been found that the stitch forming instrumentalities then form a next stitch with an extra twist or half-hitch. For this reason this problem is called half-hitching.

A second problem is created by the multidirectional movement of workpieces relative to common stitch forming instrumentalities. In common instrumentalities neither thread is coaxial with a reciprocating needle of the instrumentalities used to periodically pass thread through workpieces to form stitches. Certain directions of workpiece movement may thus draw thread, as above described, into the path of reciprocating needle motion while the needle is out of the workpiece. Stitch forming movement of theneedle through the workpiece will then intersect the thread in the path of the needle. During such intersection the needle may cut or part the thread, resulting in an abnormal stitch. This problem is thus called thread cutting.

The inventor has discovered that half-hitching results from the position 'of the threads relative to the stitch forming instrumentalities just prior to forming a stitch. These positions are effected by the vector direction in which the threads have been moved as the last formed stitch in the workpiece draws these threads in the direction of workpiece movement. The inventor has also discovered that thread cutting also results from thread position produced by workpiece movement. Both half-,

hitching and thread cutting result in abnormal stitches.

SUMMARY OF THE INVENTION Accordingly, it is an object of the invention to provide a method and apparatus for forming only normal stitches without half-hitches.

To this end, the method provides an additional step to those traditionally employed to form stitches. The additional step comprises positioning the threads in a predetermined position relative to the stitch forming instrumentalities which position is known to permit the stitch forming instrumentalities to form a normal stitch. Since the position 'of the threads prior to forming a stitch has now been found to be affected by the vector direction of workpiece movement between stitches, a preferred form of the method provides adjustment of the thread positions by adjusting the vector direction of workpiece movement from the last formed stitch to the next formed stitch.

The apparatus for carrying out the method of the invention comprises means operative on one of the threads to cause the stitch forming instrumentalities to form only normal stitches. A preferred embodiment of the apparatus has means for adjusting the position of the threads relative to the stitch forming instrumentalities prior to forming a stitch. In the preferred embodiment the adjustment of thread position is provided by means for adjusting the direction of workpiece movement since the last formed stitch was made which, in turn, adjusts the position of the threads.

It should be clearly understood that embodiments other than those described as preferred are contemplated within the scope of the invention. The embodiment hereinafter described to be preferred includes lockstitch forming instrumentalities. However, it is contemplated that the invention is applicable to other types of stitch forming instrumentalities. For example, when the invention is employed with single thread chain stitch forming instrumentalities the threads referred to herein are actually different portions of a single thread. It should therefore by understood that it is not intended. to limit the invention to an embodiment described.

BRIEF DESCRIPTION OF THE DRAWINGS There is hereinafter described a preferred embodiment of the invention which is intended to illustrate and not limit the invention and which is further described hereafter in relation to the drawings, in which:

FIG. 1 is a perspective view of an automatically con trolled sewing machine for practicing the invention;

FIG. 2 is a view of normal stitches;

FIG. 3 is a view of stitches having half-hitches;

FIGS. 4 through 7 are partial views of lockstitch forming instrumentalities showing the progressive formation of a normal stitch when threads are oriented in a conventional direction;

FIGS. 8 through 11 are views similar to FIGS. 4 7 but showing the progressive formation of an abnormal stitch when the threads are in a different direction;

FIGS. 12 through 15 are further progressive views showing the formation of a normal stitch when the threads arrive at the same direction as FIGS. 8 11 via a different direction;

FIGS. 16 through 19 are still further progressive views showing the formation of anabnormal stitch when the threads are in a still different direction; and

FIG. 20 is a partial view of the machine in FIG. 1 showing particular means for carrying out the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows a lockstitch sewing machine of a type long known in the art upon which the workpiece moving means have been replacedby motor operated means generally indicated at 12 The workpiece moving means include means for moving the workpiece along an-X axis 14 and an orthogonal Y axis 16. A control 18 simultaneously and coordinately operates the moving means associated with each axis to' move a workpiece along a predetermined path which may include any vector direction relative to the machine within the plane defined by the coordinate X and Y axes.

The X and Y axes and the workpiece moving means associated with the axes are additionally mounted on a pivot 20 secured to the machine along a longitudinal center line of a needle 22 of stitch forming instrumentalities, generally at 24, of the machine. Thus, although the workpiece may rotate relative to the machine, the workpiece does not rotate relative to the X and Y axes; so that a particular path of workpiece movement rela- V tive to the machine 10 may be accomplished by a single set of control instructions from the control 118 to the moving means associated with the X and Y axes irrespective of the rotational orientation of the axes relative to the machine. The direction of workpiece movement relative-to the machine, however, is alteredby rotation of the workpiece moving means 12. As used herein, the .vector direction of workpiece movement will always refer to workpiece movement relative to the machine 10 unless specifically recited to refer to workpiece movement relative to the X and Y coordinate axes l4 and 16 of the workpiece moving means.

As seen in FIG. 4 the stitch forming instrumentalities 24 include a needle thread 26 running along the needle from a storage spool (not shown) through an eye 28 of the needle and then along a vector direction 30 of workpiece movement. The instrumentalities also include a bobbin thread 32 running below the workpiece from a bobbin (not shown) through a rotating sewing hook 34 and then along the vector direction of workpiece movement 30. Both threads move in the vector direction of workpiece movement because a last formed stitch (not shown) secures the threads to the workpiece for movement therewith. The stitch forming instrumentalities above described correspond to a portion of stitch forming instrumentalities well known in the art as lockstitch forming instrumentalities.

A portion 36 of the bobbin thread 32 which emerges from the sewing hook 34 is seennot to be in coaxial relation with a longitudinal center line of the needle 22.

Such out of alignment arrangement of the thread portion 36 is typical of lockstitch forming instrumentalities because the sewing hook 34 has a hook portion 38 which rotates about the sewing hook to engage only the needle thread as seen in FIG. 3 to form a stitch. Alignment of the bobbin thread portion 36 and the needle is thus difiicult or impossible to accomplish. Without such alignment, the direction of workpiece and thread movement 30 will affect the position of the threads relative to the needle. As hereafter more fully described, the direction 30 of workpiece movement may thus be adjusted to adjust the position of the threads relative to e the needle to cause the stitch forming instrumentalities to form only normal stitches. The direction of workpiece movement may similarly be adjusted to adjust the position of the threads relative to the needle to prevent the needle from penetrating and cutting the threads.

The formation of normal. stitches shown in FIG. 2 and abnormal, half-hitched stitches shown in FIG. 3 will now be more particularly described with relation to the drawings. FIGS. 4 through 7 show the formation of a normal stitch with workpiece movement 30 substantially in the direction employed with traditional sewing machines having feed dogs, which direction is also substantially along the X axis 14. The workpiece 40 is preferably stationary during stitch formation having moved in the direction 30 between the formation of stitches but may also continue to have a component of motion I in the direction 30. However, motion of the workpiece during stitch forming penetration of the workpiece by the needle must not be such as to break the needle while the needle is inserted in the workpiece. During stitch formation the needle 22 penetrates the workpiece 40 carrying with it the needle thread 26 in the eye 28 of the needle. The needle thread below the workpiece is engaged by the hook 38 of the sewing hook as seen in FIG. 5 and carried around the sewing hook 34 by rotation of the sewing hook as seen in FIG. 6. The needle. thread is drawn out of engagement with the hook 38as the hook again approaches the needle by further workpiece movement drawing the thread in the direction 30. A normal stitch 39 is thus formed as seen in FIG. 7.

Referring now to FIGS. 8 through 11 a new direction of workpiece movement 42 has been obtained by rotating the workpiece approximately clockwise of the direction 30 or slightly past the Y axis 16. The needle thread 26 has thus been carried behind the needle as seen in FIG. 8 while the bobbin thread 32 is in front of the needle as seen in FIG. 8. The. needle 22'then carries the needle thread through the workpiece and into engagement with the-hook 38 of the rotating sewing hook 34 which carries the thread around the sewing hook. As the needle 22 withdraws from the workpiece, renewed workpiece movement in the direction 42 draws the thread 26 out of engagement with the hook 38 and into stitch formation. The stitch, however, has an extra twist or half-hitch 44 and is thus an abnormal stitch.

Referring now to FIGS. 12 through 15 the direction of workpiece movement 42 is the same as that shown in FIG. 8 but having in FIG. 12 been reached by rotation of the workpiece 265 counterclockwise from the direction 30. The needle thread 26 and the bobbin thread 32 are thus both in front of the needle as seen in FIG. 12. The needle thread is carried through the workpiece by the needle, engaged by and carried around the sewing hook 34 and drawn away from the stitch 39.

Referring now to FIGS. 16 through 19 the direction of workpiece movement 46 is shown to be substantially along the Y axis 16 reached by rotating the workpiece 270 from the direction of workpiece movement 30 along the X axis 14. The needle. thread 26 is thus in front of the needle 22 while the bobbin thread 32 is behind the needle as seen in FIG. 16. The hook 38 of the sewing hook engages the thread 26 and carries it around the rotating sewing hook 34 until the thread 26 is drawn out of engagement with the hook 38 by renewed workpiece movement in the direction 46. A stitch 44 having an extra twist or half-hitch is again formed in the threads.

As illustrated in FIGS. 4 through 19, the formation of normal or abnormal stitches is dependent upon the orientation of the sewing threads relative to the needle 22, particularly, the threads must be on a common side of the needle. Thread cutting is similarly dependent. Thus, orientation of the threads on opposite sides of the needle resulting in formation of abnormal stitches is seen to be dependent upon certain direction of workpiece movement and the rotation of the workpiece undertaken to achieve that direction of movement, hereafter referred to as forbidden directions.

The apparatus for carrying out the method of the invention is thus provided withmeans generally at 48 to 1 rotate the workpiece out of the forbidden directions.

The means comprise a pivot 20 rotatably supporting the conventional X Y workpiece moving means 12. A cylinder 51 is secured to a frame of machine and a piston rod 42 of the cylinder is connected through pivot 54 to an arm 56 of a sleeve 53 on pivot and secured to the workpiece moving means 12. Actuation of the cylinder 51 is thus effective to rotate the workpiece moving means 12 about pivot 20. The extent of movement of the piston relative to the cylinder to produce rotation of the workpiece moving means sufficient to orient both threads on the same side of the needle is determined by the particular construction of the sewing machine 10 employed. However, the workpiece moving means 12 must rotate a number of degrees at least equal to the maximum number of consecutive degrees constituting a zone of forbidden directions. In this way actuation of the cylinder will always rotate the workpiece moving means out of a zone of forbidden directions. In a-preferred embodiment of the invention the control 18 provides means (not shown) for automatically actuating the piston and cylinder. However, in another embodiment a manually operated switch may be provided for this purpose.

In correspondence with the apparatus, a preferred form of the method of the invention comprises adjusting the position of the threads prior to forming stitches to permit stitch forming instrumentalities to form only normal stitches. The adjustment may be accomplished by rotating the direction of workpiece movement out of a zone of forbidden directions.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

1. A stitching machine comprising:

A. an automatically controlled support for moving a workpiece in relation to stitching instruments, said support being capable of moving said workpiece in directions in which abnormal stitching will occur; and

B. means operatively connected to the automatically controlled support to move the workpiece away from directions of abnormal stitching.

2. A stitching machine as described in claim .1 wherein the automatically controlled support is pivotally mounted on the stitching machine and the means are operative on said support to cause pivotal movement thereof.

3. A stitching machine comprising:

A. an automatically controlled support for moving a workpiece in relation to stitching instruments pivotally mounted on the stitching machine, said support being capable of moving said workpiece in directions in which abnormal stitching will occur;

B. piston and cylinder means operatively connected to the automatically controlled support to pivot the workpiece away from the directions of abnormal stitching; and

C. switching means operative to energize the piston and cylinder means when directions of abnormal stitching are called for by the automatic control.

Claims

1. A stitching machine comprising: A. an automatically controlled support for moving a workpiece in relation to stitching instruments, said support being capable of moving said workpiece in directions in which abnormal stitching will occur; and B. means operatively connected to the automatically controlled support to move the workpiece away from directions of abnormal stitching.

2. A stitching machine as described in claim 1 wherein the automatically controlled support is pivotally mounted on the stitching machine and the means are operative on said support to cause pivotal movement thereof.

3. A stitching machine comprising: A. an automatically controlled support for moving a workpiece in relation to stitching instruments pivotally mounted on the stitching machine, said support being capable of moving said workpiece in directions in which abnormal stitching will occur; B. piston and cylinder means operatively connected to the automatically controlled support to pivot the workpiece away from the directions of abnormal stitching; and C. switching means operative to energize the piston and cylinder means when directions of abnormal stitching are called for by the automatic control.