Hook and loop lock stitch and method and apparatus therefor

Details Hook and loop lock stitch and method and apparatus therefor Hook and loop lock stitch and method and apparatus therefor

2000-08-29

2001-11-13

Izaguirre, Ismael (Department: 3765)

Sewing

Method of sewing

Stitch forming

Reexamination Certificate

active

06314899

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to methods and apparatus of sewing and stitching. More specifically, this invention relates to a lock stitch, wherein a novel “hook and loop” style lower thread is interlocked with a conventional upper thread.
2. Description of the Prior Art
Until now, the two-thread lock stitch has been among the most widely used methods of joining fabric. Conventionally, and as shown in
FIGS. 1 and 2
, a two-thread lock stitch
32
P includes two threads: a needle or upper thread
24
, and a bobbin or lower thread
50
P. The upper thread is typically wound on a spool system (not shown) to provide a continuous feed of thread. In contrast, the lower thread
50
P is typically wound on a bobbin
54
P to provide a predetermined feed of thread. The two-thread lock stitch
32
P is considered an efficient stitch that does not unravel easily and has a “both-sides equal” aesthetic appearance. In order to maintain the aesthetic appearance, the upper and lower threads
24
and
50
P must typically be composed of nearly identical size and strength material to enable stitch conformance.
Stitch conformance relates to the relative position of the upper and lower threads
24
and
50
P in the stitch as shown in
FIGS. 1 and 2
. Conventional lock stitch practice requires a balance of stitching force on either side of a workpiece
10
P being sewn, so that the lower thread
50
P is not completely pulled up through the workpiece
10
P.
FIGS. 1 and 2
illustrate how the upper thread
24
and lower thread
50
P must properly entwine at a midpoint
16
P of the workpiece
10
P.
Referring to
FIG. 1
, in operation, a needle
20
penetrates the workpiece
10
P from a front side
12
P thereof, carrying with it the upper thread
24
that is fed through an eyelet
22
of the needle
20
. The needle
20
reaches the bottom of its stroke on a back side
14
P of the workpiece
10
P and starts to retract, thus forming a loop
26
from the slack upper thread
24
. Referring now to
FIGS. 1 and 2
, and as is well known in the art, the bobbin
54
P and the entire supply of lower thread
50
P is encircled by the loop
26
in order to interlock the upper and lower threads
24
and
50
P, thus forming the locking portion of the lock stitch
32
P. The size of the bobbin
54
P and quantity of lower thread
50
P is necessarily relatively small to enable them to be encircled by the loop
26
. Therefore, the bobbin
54
P is exhausted of its lower thread
50
P at extremely frequent intervals, resulting in downtime of the sewing operation, and, often, stopping and restarting of the sewing operation in the middle of the workpiece
10
P.
Several alternative methods and associated devices of the prior art have been directed at mitigating the problem of the limited supply of lower thread. For example, U.S. Pat. No. 4,117,789 to Rovin et al. teaches a method of automatically loading a bobbin in situ. Rovin et al. disclose a highly complex apparatus that is capable of reloading an empty bobbin in between workpiece cycles and as an operator positions a new workpiece to the sewing machine. The apparatus refills the empty bobbin, in situ, with a precisely measured length of thread.
U.S. Pat. No. 4,140,069 to Laursen teaches a sewing method and associated apparatus for forming a double backstitch seam. The double backstitch seam is formed similarly to previous versions of two-thread lock stitches with one exception. The upper thread is fed through the workpiece and a loop thereof is formed as usual. The lower thread, however, is processed much differently than those of the prior art. The supply of lower thread is not passed entirely through the loop as usual, but instead is passed through the loop in individual thread sections equal in length to several stitches. The lower thread is fed from a relatively large continuous spool, similar to the upper thread. As the loop is formed, a free end of the lower thread is fed and sucked through the loop by a suction nozzle. As the loop is tightened by the needle retracting back through the workpiece, a looper simultaneously grabs the lower thread section near its middle and a free end of a previous lower thread section. The looper then pulls back and tightens the lower thread sections against the loop, thus completing a lock stitch.
Finally, U.S. Pat. No. 4,366,765 to Hoekstra teaches use of a combination single thread chain and lock stitch. Hoekstra discloses a stitch formation having a first loop passing through the workpiece thus forming the first half of a chain stitch. A second loop passes through the workpiece and, with the first loop, forms the second half of the chain stitch. A locking thread passes through the closed end of the second loop to form a lock stitch. The chain and lock stitches thus formed are continuously alternated for the entire length of the stitch.
In addition to the problem of a limited supply of lower thread, thread breakage is a frequent problem when generating the conventional lock stitch. If either the upper or lower thread breaks during a stitch cycle, the entire process must be stopped and the sewing machine re-threaded. Additionally, the article being sewn must be scrapped, or the stitch removed and restarted, since the stitch cannot be stopped and restarted in mid-stitch.
Therefore, what is needed is a lock stitch, method, and related apparatus that is inexpensive, efficient, does not require a bobbin having a limited supply of lower thread, that uses a method and apparatus that are relatively simple compared to the prior art, and that is not so susceptible or sensitive to thread breakage.
SUMMARY OF THE INVENTION
According to the present invention there is provided a novel lock stitch that does not require use of a bobbin nor other complex thread feeding mechanisms, thereby avoiding the shortcomings of the prior art—particularly that of thread breakage and a limited supply of lower thread.
In one form of the invention, an article is provided in the form of a workpiece having a novel lock stitch. Preferably, the stitched article includes the workpiece having upper and lower layers or plies, and a series of needle-made stitch holes extending from a front side through to a back side thereof. A stitch is provided through each stitch hole, and includes an upper thread and a lower thread. The upper thread extends down through each stitch hole, forms a loop underneath the workpiece, and extends back up through each stitch hole. The lower thread is composed of discrete cut-off segments of a hook material, having hooks therein, wherein the lower thread interlocks with the upper thread, and extends transversely through the loop and is entrapped between the loop and the back side surface of the workpiece.
Alternatively, the lower thread can take the form of a hook material composed of discrete cut-off segments that are each aligned with a respective stitch hole. The upper thread extends down through the workpiece and the hook material. The upper thread forms a loop underneath the workpiece and the loop is interlocked with the hooks. Optionally, the workpiece can include the back side surface that is composed of a loop material having loops therein for interlocking with the hooks of the lower thread. Further still, the stitched article can also include an underlining applied to the back side of the workpiece and over the lower thread. The underlining can be composed of a loop material having loops therein interlocking with the hooks of the hook material of the lower thread to retain the underlining to the workpiece.
An apparatus is provided for producing the lock stitch of the present invention wherein the apparatus includes a needle, with an eyelet therethrough, for penetrating the workpiece to a back side thereof. A loop spreader mechanism is provided on the back side of the workpiece for spreading a loop of the upper thread, as is well known in the art. A feeder mechanism and conduit is provided for feeding a portion of the lower thread through the loop of the upper thread, wherein a po

Affiliated with

Also associated with

Rating

Hook and loop lock stitch and method and apparatus therefor does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Hook and loop lock stitch and method and apparatus therefor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Hook and loop lock stitch and method and apparatus therefor will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2603802