US3885509A

US3885509A - Overedge seaming

Info

Publication number: US3885509A
Application number: US401417A
Authority: US
Inventors: Roy B Cox
Original assignee: Burlington Industries Inc
Current assignee: Kayser-Roth Corp
Priority date: 1971-08-04
Filing date: 1973-09-27
Publication date: 1975-05-27
Anticipated expiration: 1992-05-27

Abstract

A flat overedge seam joining together the edge portions of two superimposed fabric layers, such as are present at the toe of knitted hosiery, is formed with a looper-type sewing machine having three needles two of which form two separate series of loops spaced from the edge and a third of which forms a series of loops at a raw edge formed by trimming away an edge portion of the layers just prior to stitching.

Description

United States Patent 11 1 Cox 1111 3,885,509 1451 May 27, 1975 1 1 OVEREDGE SEAMING 1,983,631 12/1934 Merrow 112/162 2,903,872 9/1959 Ledwel] 1 1 112/269 X [75] Inventor: 2,980,917 4/1961 Slane 1 112/262 x [73] Assignee; Burlington lndusries Inc" 3,254,617 6/1966 Michaud 1 1 1 112/126 Greensboro N C 3,590,757 7/197] Armstead,Jr. 1, 112/162 {22] Filed, Sept 27 1973 FOREIGN PATENTS OR APPLICATIONS 82,845 8/1895 Germany 112/162 [21] Appl. N0.: 401,417

R d US Application Data Primary Examiner-Werner H. Schroeder [63] Continuation of Ser. NO. 169,035, Aug. 4, 1971, Darby abandoned. Cushman 52 us. c1. 112/441; 112/162; 112/166; 1571 ABSTRACT 112/269 A flat overedge seam joining together the edge por- [51] Int. Cl DOSb 1/22 tions of two superimposed fabric layers, such as are [58] Field of Search 1 12/162, 262, 268, 269, present at the toe of knitted hosiery, is formed with a 112/163, 164, 165, 166, 167, 126, 177, 122, iooper-type sewing machine having three needles two 438, 440, 441 of which form two separate series of loops spaced from the edge and a third of which forms a series of [56] References Cited loops at a raw edge formed by trimming away an edge UNITED STATES PATENTS portion of the iayers just prior to stitching. 1,083,967 [/1914 Weis et a1 1. 112/162 5 Claims, 6 Drawing Figures OVEREDGE SEAMING This is a continuation, of application Ser. No, [69,035 filed Aug, 4, 197i, now abandoned.

This invention relates to the construction of overedge sewing machines, to improved overedge seams produced thereby and to methods of modifying existing overedge sewing machines so as to produce the improved seams,

BACKGROUND OF THE INVENTION In the formation of certain types of overedge seams two piles of fabric are joined by the scam in edge to edge abutment. In the formation of such seams the two plies of fabric to be joined are fed through an appropri ate type of sewing machine with one ply of fabric overlying the other and with the edges of the plies along which the seam is to extend in vertical alignment with each other. The machine, an overedge seamer, passes a loop of thread downwardly through both plies of fabric, Elements of the machine manipulate the loop to draw the loop outwardly beneath the lowermost ply to the fabric edge. This loop may be then drawn upwardly around the edges of both plies and brought to a point overlying the uppermost ply of fabric at which the loop is then pierced by a subsequent fabric penetrating loop or, in other types of seams, a covering thread loop may be passed through the fabric penetrating loop, brought upwardly around the edge and over the upper surface of upper ply to be pierced by a subsequent fabric penetrating loop. In either case, the seam, as completed by the machine, finds the two plies of fabric in overlying relationship with the seam extending along a common edge ofthe two plies. In many cases, after the fabric has been seamed, it is desirable to open out the two plies about the seam so that when the two plies are placed on a flat surface, the seamed edges of the two plies are in edge abutment. rather than the overlapping relationship in which the seam was formed by the machine.

It is frequently desirable to form an overedge seam by forming two series of fabric penetrating loops by employing a pair of needles in side by side relationship, the fabric penetrating loops formed by one needle penetrating the fabric at points lying along a first line extending parallel to the edge of the fabric and the loops formed by the second needle penetrating the fabric at points lying along a second line spaced at a greater distance from the fabric edge than the line of penetrating points of the first needle. I

In the manufacture of hosiery it is common practice to knit the hosiery on a circular knitting machine, leaving an elongated opening across the toe. This opening is subsequently closed by superimposing the edge portions of each individual hose and passing the superimposed edge portions through the overedge seaming machine which first trims off a thin strip of the superimposed edges. The seam is produced by loosely overseaming the two layers and then opening out the layers flat as though hinged together by the seam, using a vanety of overseam stitching that will permit such hinging action to bring the two edges of the material practically end-to-end to flatten the seam. In the conventional formation of these types of seams, two rows of needle thread loops are placed in the work material along lines parallel to and spaced from the edges to be joined, and a third thread is manipulated by a looper mechanism of the machine to be interlooped with both series of needle thread loops. The resulting seam, when opened out,

is relatively flat but still exhibits undesirable bulk, the bulk being necessitated because the two needles require a relatively wide span of fabric in order to make a complete solid seam. If the needles are moved closer to the trimmed edge (or if more material is trimmed off to place the trimmed edge nearer to the needles), one or possibly both needles would miss the edge of the work piece intermittently along the length of the seam, thus resulting in the formation of holes in the areas where misses occurred.

SUMMARY OF THE INVENTION It is the broad object of the present invention to make possible a flatter, less bulky overedge seam using the principles of known overedge stitching operations. This is accomplished, broadly, by providing in addition to the conventional two rows of thread loops through the work piece, as summarized above, a third row of thread loops through the raw edge of the work piece and by manipulating a looper thread to be interlooped with all three series of needle thread loops to form overedge stitches. In the preferred embodiment the raw edge is the edge resulting from trimming off a thin strip of the superimposed layers just prior to the stitching operation, the trimming operation being carried out automatically and continuously by a conventional trimming mechanism. This raw edge is inherently uneven or ragged in a knitted article due to the cutting of the knitted loops by the trimmer, and this is particularly true in the case of mens socks which are often loosely knitted from heavy yarn.

The third needle provides an additional stitching motion through the ragged edge thereby stitching down the projecting yarns. This serves both to make the seam much smoother when the seam is pulled out after sewing and to prevent the double needle stitches from overseaming or overstitching on the raw edge, thereby eliminating the possibility of producing holes in the seam somewhere along its length due to missed stitches by one of the outside needles. The bulk of the seam is reduced because a greater width of material can be trimmed off prior to the seaming operation whereby there is less material to be abutted when the seam is opened up. The same result can be obtained by making equivalent adjustments to the machine to bring the needle loops closer to the raw edge.

The stitch formation of the present invention is particularly adapted to be produced on a Merrow overedge sewing machine, for example the class M ma chine, manufactured by the The Merrow Machine Company, Hartford, Conn, although the invention is not limited by the structure and operations of those machines. It is, nevertheless, a further feature of the present invention to provide modifications to the Merrow type of machine which render the machine capable of producing a flatter smoother overedge seam. The illustrative embodiment is therefore described hereinafter in terms ofa Merrow machine, and to this end the disclosures in the following US. Pats. are incorporated in this specification by reference: Nos. 2,5 80,953; 2,755,757; 2,827,869; 2,879,733; 2,931,328; 3,034,460; 3,079,882; 3,082,724; 3,373,706; and 3,450,078. Also incorporated by reference is the publication Instructions for Setting Up and Operating Class M Merrow Machines," copyright [955 by The Merrow Machine Company.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a perspective view of the sewing portion of a Merrow overedge machine modified in accordance with the principles of the present invention;

FIG. 2 is a front view. partly in section with certain parts broken away or omitted. of the machine of FIG. 1;

FIG. 3 is a sectional view of the looper drive mechanism of FIG. 1;

FIG. 4 is a plan view of the throat plate of the machine of FIG. 1 showing the relationship of the work piece to the needles;

FIG. 5 is a sectional view on the line 4-4 of FIG. 3;

FIG. 6 is an enlarged front view of the needle carrier of FIG. 1;

Referring to FIG. 1 the illustrated machine 10 is a typical Merrow machine modified in accordance with the principles of the present invention, although the modifications are best shown in some of the other views. The machine includes a presser foot arm 12 which is pivotally mounted on the body ofthe machine at 14 so that it may be swung out about a vertical axis. The presser foot arm is normally engaged by a spring urged plunger assembly 16 comprising a lever 18 for raising the plunger 20 out of engagement with the presser foot arm whenever it is desired to swing the latter out of the way. The arm has a horizontal projection 22 at its end resting in a surface depression of a presser foot 24 which may pivot about the projection 22 and is attached to the presser foot arm by means of a hinge spring plate 26 secured to the foot 24 by a screw 28. A portion ofthe plate 26 bears down on the projection 22 from above.

A trimming mechanism located on the machine side of the presser foot includes an upper trimmer blade 30 which is of substantially L-shaped cross section and disposed at a downward slant with its lower cutting end ground substantially vertical The blade 30 is clamped to an upper cutter holder 32 which is driven with an up and down motion by the main gearing (not shown) of the machine. A clamp 34 and screw 36 are provided for tightening the blade 30 against an inner part 38 of the holder, the part 38 being horizontally slidable within a slot in the main part 32 of the holder in order to provide for horizontal adjustment of the blade 30 toward and away from the presser foot 24. A set screw (not shown) is provided for locking the part 38 in a selected position within the slot in the part 32. The lower cutting edge of the blade cooperates with a fixed lower blade 40 to trim off a strip of material from the edge of a work piece passing under the presser foot 24. The lower blade 40 is mounted to the frame of the machine 10 for both vertical and horizontal adjustment by any suitable means (not shown).

A horizontal plate 30, or needle plate, is disposed below the presser foot 24 and is secured to the machine frame by a screw 32. Feed dogs 34 project through an aperture in the plate 30 to cooperate with the presser foot 24 in a well known manner to effect feeding of a work piece into the machine.

The machine 10 also includes an oscillating needle carrier (not shown in FIG. I) and a looper mechanism of which an upper looper arm 36 appears in FIG.

All of the above, as so far described, is conventional in a Merrow machine and has been presented in order to define the environment of the present invention. The

modifications made in the machine are described more in detail below together with further conventional features.

Referring to FIG. 2 it will be seen that the machine 10 includes upper and

lower shafts

38 and 40 journalled in the machine frame for rotation and rotatably driven in synchronization by the machine gearing (not shown) the input to the machine usually being by means of a motordriven belt (not shown). A needle carrier 42 is driven in rotary oscillation about the horizontal axis of a pivot support designated generally at 44. The carrier 42 is oscillated in a conventional manner by an eccentric pin and crank assembly 46 at the outer end of the upper shaft 38. The carrier 42 supports three

curved needles

48, 50 and 52 in side-by-side relationship, the lower limit of the needles locating their points below the path of a lower looper 54 while the upper limit of movement locates the needle points somewhat above the upper looper 36. As is well known in the art the

loopers

36 and 54 cooperate with needle threads to form overedge stitches.

The upper looper 36 is secured in a looper carrier 56 which is designed to be actuated to impart to the looper 36 a compound motion effective to pass the thread engaging end of the looper in a required path. For this purpose the looper carrier has a hub 58 pivoted on a stud 60 extending from a sleeve 62 which is reciprocated on a rod 64 carried by a frame cap 66. With this mounting the looper carrier 56 may oscillate on the axis of its hub while it is shifted bodily back and forth as in a rectilinear path.

A cam mechanism for actuating the looper carrier 56 includes a pair of

rotary cylinders

68 and 70 arranged to be rotated in unison and provided at their respective peripheries with endless wave-shaped

cam grooves

72 and 74. A pair of motion-receiving

arms

76 and 78 extend in opposite directions from the hub 58. The ends of arm 76 and arm 78 are provided with

cam followers

80 and 82 in the form of rollers positioned in the

grooves

72 and 74 for engagement with the sidewalls of the respective groove. The sidewalls serve as cam sur faces and impart movement to the looper carrier 56 upon rotation of the

cylinders

68 and 70.

The lower looper 54 projects from a lower looper carrier 84 which is connected to a link 86. The link 86 is pivoted on a pin 88 about which it is caused to oscillate by a cam roll 90 carried by the link 86 and engaged in a wave-shaped cam groove 92 in the periphery of the forward end portion of the cylinder 70. The rear ends of the

cylinders

68 and 70 carry meshing

gears

94 and 96 which synchronize the rotation of the cylinders. The lower shaft 40 is driven from the power input to the ma chine l0 and thereby rotatably drives the cylinder 70, the cylinder 68 and the pin and crank 46.

With the exception of the three

needles

48, 50 and 52 the above elements, as broadly described. are known. However, certain changes have been made in some of the parts, and reference is now made to FIG. 6 which illustrates in more detail the needle carrier and its three needles. As shown, the needle carrier includes a hub 98, a web portion 100 and a head [02 having a threaded stud 104 projecting therefrom. A washer 106 is keyed to the head 102 to prevent relative turning movement. A nut I08 is threaded on the stub 104 and urges the washer I06 toward the head to thereby clamp the shanks ol' the three

needles

48, 50 and S2. The needle shanks are disposed in and are accurately positioned by a groove 110 in the head. In the conventional two-needle Merrow machine the groove 110 is sufficiently deep to receive the shanks of two needles; in the modified machine the groove has been deepened by about 0.04 of an inch so as to receive the third needle 52 which is placed on the machine side of the

needles

48 and 50. The third needle 52 may be identical to the other two in size and shape, or it may be shorter. However, in both cases it is necessary to modify the motion of the upper looper 36 to assure that the latter will clear the needle 52.

FIG. 4 illustrates in plan view the throat plate 30 which has been modified to cooperate with the three needle feature. The plate 30 has an elongated opening 112 within which the feed dogs are located to feed a work piece across the plate 30. Two

stitch fingers

114 and 116 extend in spaced apart parallel relationship from a projection 118 in the direction F of work piece feed. The needle 48 passes through the plate between the finger 114 and a side edge 120 at a location adjacent the base of the finger 114, while the needle 50 passes between the

fingers

114 and 116 adjacent their bases. The needle 52 also passes between the

fingers

114 and 116. To provide for this groove, which accommodates only a single needle in the conventional machine, is widened by cutting away part of the left edge of the finger 116. It will be seen that the space between the needles S0 and 52 is purposely somewhat less than the space between the

needles

48 and 50, this relationship being obtainable with conventional needles due to the fact that the curved needle portion of a needle is not coaxial with its shank. FIG. 4 also shows the upper and

lower trimmer blades

38 and 40, and it will be seen that a trimmed edge 122 ofa work piece 124 is substantially in line with the needle 52. The trimmed-off strip is shown at 126.

Still referring to the third needle 52 it will be realized that the addition of this needle increases the width of the sewing area of the machine. The compound motion of the upper looper 36 in the conventional machine is such that the looper 36 would strike the needle 52. It has been found, however, that the path of travel of the looper 36 can be modified so that the latter misses the needle 52, without adversely affecting its normal looping function. The preferred manner of changing the motion of the looper is to rotatably adjust one of the

cylinders

68 or 70 with respect to the other and then reestablish synchronization, it having been found that an adjustment of about is appropriate. In one commercial form of the machine it was found that rotating one of the cylinders a distance of one tooth on the

gears

94,96 was appropriate.

The provision of the third needle 52 also requires several other modifications to an existing two-needle machine, but these changes flow naturally from the fact that there are three-needle threads to be handled. Thus, a three-hole thread guide (not shown). a third thread-tensioning post (not shown) and a third needlethread supply (not shown) must be provided. It is also desirable to make some minor changes in the presser foot 24, but these are not critical.

The operation of the structural elements of the machine 10 is well known and need not be described in detail. In summary it may be said that the power input to the machine 10 is usually by a belt drive connection to the shaft 40, rotation of which moves the upper trim ming blade up and down. rotates the cylinder 70 which in turn rotates the cylinder 68 and shaft 38 through the

gears

94,96. The oscillating movement of the needle carrier 42 results from rotation of the shaft 38. The compound movement of the upper looper 36 results from the reaction of the cam rollers and 82 on the sidewalls of the

grooves

72 and 74, and the oscillating movement of the lower looper 54 results from the reaction of the cam roller on the side walls of the groove 92.

The overall result of these movements is that c0ntinuous needle threads carried by the

needles

48,50 are passed through the work piece 124 at points spaced along two parallel lines which are parallel to and spaced from the trimmed edge 122 of the work piece to form first and second rows of needle thread loops in the work piece. Simultaneously the third needle 52 passes a third thread through or very close to the raw trimmed edge 122 to form a third series of loops. A fourth thread, a looper thread, is manipulated first by the lower looper 54 to be interlooped with all three series of loops to form overedge stitches of the type which permit the layers ofa two layer work piece to be rotated relative to each other about a common axis to bring the edges of the layers into generally abutting relationship.

FIG. 5 illustrates the relationship of the three-needle threads to the throat plate 30 and to a two-layer work piece 124 during the seaming operation. The

needles

48 and 50 and their respective threads 128 ad 130 pass downwardly through the throat plate 30 to a point where the thread loops are located in the path of travel of the lower looper 54 (not shown in FIG. 5). At this time the lower looper 54 moves to the right from its position in FIG. 2, and the point of the lower looper 54 between the

threads

128 and 130 and their respective needles. A loop of each thread 128,130 is thus retained on the lower looper to the left and below the eye. This movement of the looper 54 also projects a loop of looper thread 132 through the respective retained loops in the

threads

128 and 130.

The loop of thread 132 is carried to the right by the eye of lower looper 54 outwardly beyond edge of throat plate 30 at the time upper looper 36 moves to a position below and to the left of the eye of the lower looper 54, and the point of the upper looper 36 passes upwardly between the back side of lower looper 54 and the thread 132, thus placing a loop of thread 132 in the throat of upper looper 36. The upper looper 36 carries this loop of thread 132 upward and over the plies of material suppported by the throat plate 40 to a point where the next downward movement of

needles

48 and 50 pass through the loop of covering thread 132.

Tension on the thread 132 retains the respective loops of

threads

128 and 130 as the lower looper 54 returns to the position shown in FIG. 2.

The looper thread 132 is manipulated by the

loopers

36 and 54 to loop with the third-needle thread 134 in just the same manner as with the

threads

128 and 130.

What is claimed is:

1. In a sewing machine for overedge stitching of a plurality of layers of material in a manner such that the layers can be hinged about a common axis to form a relatively flat seam, said machine being of the type having means for feeding a plural layered workpiece past a seaming area on a throat plate. a needle carrier mounting two curved needles and adapted to reciprocate the curved needles in arcuate paths through the throat plate and through the superimposed layers of material along two different lines parallel to and spaced from the edge of the layers of material, a looper mechanism for cooperating with both needle threads to effect overedge stitches, said looper mechanism including an upper looper arm and a lower looper arm, said looper arms being driven by cam cylinders having endless cam grooves, a trimming mechanism disposed in advance of the seaming area for trimming off the edge of superimposed layers of material along a straight trim line just prior to arrival of the superimposed layers at the scam ing area, and a drive mechansim for driving the needle carrier and looper arms in synchronization, the im' provement comprising an auxiliary needle carried by the needle carrier in a position transversely spaced from the aforesaid needles with respect to the direction of feed such that the third needle moves in a path substantially coextensive with the trim line and through the raw edges of the freshly trimmed material, said looper arms cooperating with the thread carried by said auxi1iary needle in the same manner as with the thread carried by the first-mentioned needles to form an overedge stitch.

2. A sewing machine as in claim 1 wherein said throat plate comprises two parallel stitch fingers extending in the direction of feed and defining between them a slot which receives both said auxiliary needle and the next adjacent needle.

3. A method of overedge seaming a plurality of layers of work material comprising: superimposing the edge portions of the layers trimming off a thin strip of the superimposed layers, passing first and second continuous needle threads through the work material at points spaced along two parallel lines which are parallel to and spaced from the trimmed edge of the work material to form first and second rows of needle thread loops in the material, simultaneously passing a third thread through the raw, freshly trimmed edge of the work material to form a third series of loops, manipulating a looper thread to be interlooped with all three series of loops to form overedge stitches of the type which permit the layers of the work material to be rotated relative to each other about a common axis to bring the edges of the layers into generally abutting relationship,

and rotating layers about said common axis to bring the edges into generally abutting relationship whereby the resulting seam is smooth and flat and free from holes,

4. An overedge seam connecting a plural layered work piece in a manner such that the layers can be rotated relative to each other about a common axis to bring the edges of the layers into generally abutting relationship. said seam comprising first and second nee dle threads formed into two series of loops penetrating the work piece at spaced points along two spaced-apart lines extending parallel to the edge of the work piece, a third continuous needle thread formed into a series of loops penetrating the edge of the work piece and a looper thread interlooped with all three series of needle thread loops to form overedge stitches.

5. A method of modifying an overedge sewing machine of the type having a horizontal throat plate provided with first and second parallel needle slots separated by a stitching finger. said second slot being on the machine side of said first slot, means for feeding a work piece over the upper surface of the throat plate in a direction parallel to the slots, a needle carrier having a groove therein of sufficient depth to receive the shanks of first and second side-by-side curved needles, said needle carrier being adapted to reciprocate the two needles in an arcuate path through the needle slots, each needle passing through a different one of said slots, a looper mechanism including an upper looper arm and a lower looper arm adapted to cooperate with needle threads to effect overedge stitches in a work piece, and a trimming mechanism for trimming an edge from a work piece just in advance of the seaming area and along a line which is parallel to said slots and which is disposed to the machine side of the second needle, said method comprising: providing said needle carrier with a third curved needle positioned in side-by-side relationship to said second needle on the machine side thereof, enlarging the width of said second slot to receive said third needle during reciprocation thereof and adjusting the position of said trimming mechanism to effect trimming of the work piece substantially along a line which is penetrated by said third needle.

Claims

1. In a sewing machine for overedge stitching of a plurality of layers of material in a manner such that the layers can be hinged about a common axis to form a relatively flat seam, said machine being of the type having means for feeding a plural layered workpiece past a seaming area on a throat plate, a needle carrier mounting two curved needles and adapted to reciprocate the curved needles in arcuate paths through the throat plate and through the superimposed layers of material along two different lines parallel to and spaced from the edge of the layers of material, a looper mechanism for cooperating with both needle threads to effect overedge stitches, said looper mechanism including an upper looper arm and a lower looper arm, said looper arms being driven by cam cylinders having endless cam grooves, a trimming mechanism disposed in advance of the seaming area for trimming off the edge of superimposed layers of material along a straight trim line just prior to arrival of the superimposed layers at the seaming area, and a drive mechansim for driving the needle carrier and looper arms in synchronization, the improvement comprising an auxiliary needle carried by the needle carrier in a position transversely spaced from the aforesaid needles with respect to the direction of feed such that the third needle moves in a path substantially coextensive with the trim line and through the raw edges of the freshly trimmed material, said looper arms cooperating with the thread carried by said auxiliary needle in the same manner as with the thread carried by the first-mentioned needles to form an overedge stitch.

3. A method of overedge seaming a plurality of layers of work material comprising: superimposing the edge portions of the layers trimming off a thin strip of the superimposed layers, passing first and second continuous needle threads through the work material at points spaced along two parallel lines which are parallel to and spaced from the trimmed edge of the work material to form first and second rows of needle thread loops in the material, simultaneously passing a third thread through the raw, freshly trimmed edge of the work material to form a third series of loops, manipulating a looper thread to be interlooped with all three series of loops to form overedge stitches of the type which permit the layers of the work material to be rotated relative to each other about a common axis to bring the edges of the layers into Generally abutting relationship, and rotating layers about said common axis to bring the edges into generally abutting relationship whereby the resulting seam is smooth and flat and free from holes.

4. An overedge seam connecting a plural layered work piece in a manner such that the layers can be rotated relative to each other about a common axis to bring the edges of the layers into generally abutting relationship, said seam comprising first and second needle threads formed into two series of loops penetrating the work piece at spaced points along two spaced-apart lines extending parallel to the edge of the work piece, a third continuous needle thread formed into a series of loops penetrating the edge of the work piece and a looper thread interlooped with all three series of needle thread loops to form overedge stitches.

5. A method of modifying an overedge sewing machine of the type having a horizontal throat plate provided with first and second parallel needle slots separated by a stitching finger, said second slot being on the machine side of said first slot, means for feeding a work piece over the upper surface of the throat plate in a direction parallel to the slots, a needle carrier having a groove therein of sufficient depth to receive the shanks of first and second side-by-side curved needles, said needle carrier being adapted to reciprocate the two needles in an arcuate path through the needle slots, each needle passing through a different one of said slots, a looper mechanism including an upper looper arm and a lower looper arm adapted to cooperate with needle threads to effect overedge stitches in a work piece, and a trimming mechanism for trimming an edge from a work piece just in advance of the seaming area and along a line which is parallel to said slots and which is disposed to the machine side of the second needle, said method comprising: providing said needle carrier with a third curved needle positioned in side-by-side relationship to said second needle on the machine side thereof, enlarging the width of said second slot to receive said third needle during reciprocation thereof and adjusting the position of said trimming mechanism to effect trimming of the work piece substantially along a line which is penetrated by said third needle.