Wide needle swing oscillating hook system for sewing machines

Details Wide needle swing oscillating hook system for sewing machines Wide needle swing oscillating hook system for sewing machines

2000-10-10

2001-08-07

Izaguirre, Ismael (Department: 3765)

Sewing

Elements

Driving mechanisms

C112S192000

Reexamination Certificate

active

06269760

ABSTRACT:

FIELD OF THE INVENTION
This invention pertains to an oscillating hook system for a zigzag sewing machine for sewing seams and designs in a fabric. More particularly, the invention relates to a mechanism providing increased amplitude transverse needle swing in a zigzag sewing machine utilizing an oscillating hook system.
BACKGROUND OF THE INVENTION
Several mechanical systems provide for transverse needle swing in zigzag sewing machines. The transverse needle swing, i.e., from side to side, in the course of sewing a fabric, aids in sewing, particularly in sewing a seam or design in a fabric. The term fabric is used here to refer to any material that may sewn on a sewing machine and is not limited to a woven material including a warp and weft. Non-woven fabrics and sewable goods that are not fabrics at all, for example, plastics and leather, are within the scope of the term “fabric” as used here.
Conventional sewing machines produce zigzag stitching by using either a rotary hook system that provides a relatively wide transverse needle swing, for example, an amplitude of 9 millimeters between the extreme transverse positions of needle swing, or an oscillating hook system. In the oscillating hook system, the transverse swing has been limited, particularly in free-aim consumer sewing machines, to an amplitude of about five millimeters. The invention described below particularly pertains to oscillating hook system sewing machines providing a wider traverse needle swing without loss of the higher stitch quality produced by the oscillating hook mechanism.
FIGS.
1
(
a
) and
1
(
b
) are schematic front and rear views of a conventional oscillating hook sewing machine drive system in a free-arm sewing machine. The front view of
FIG. 1
(
a
) is cut away to show thread, needle, and bobbin relationships and is the view that a person operating the sewing machine would see if the free arm covering were transparent. FIG.
1
(
b
) is a rear view of the oscillating hook system showing a driving mechanism for driving the oscillating hook. FIG.
1
(
a
) illustrates a “front loading” configuration in which a bobbin is inserted into the sewing machine along a direction perpendicular to the plane of
FIG. 1
(
a
). However, other arrangements, to which the invention likewise applies, are known. For example, the bobbin may be loaded from the side, i.e., along a direction parallel to the plane of FIG.
1
(
a
). Still other bobbin loading positions may be employed. Although the invention, described below, is not limited to a particular bobbin loading configuration, the illustrated front loading bobbin arrangement is preferred.
In all figures, like elements are given the same reference number. In FIG.
1
(
a
), a needle
1
engages a needle thread
2
. Thread is used in a general sense here and means any multiple strand or single strand filament that can be used to join two pieces of fabric or to decorate a fabric. The needle thread
2
passes through a hole or eye of the needle
1
. The needle
1
is driven by a motor, not shown, in an oscillating motion in a generally linear direction, usually vertical, subject to the transverse swing of the zigzag stitch. The drive from the motor may be indirect, through gears, belts, or the like. The needle, in its linear, up and down motion, passes through a hole
3
in a needle plate
4
that supports a fabric (not shown) being sewn. The needle thread
2
is maneuvered, as described below, by an oscillating hook
5
. A second thread, a bobbin thread
6
is supplied from a bobbin
7
that is coaxial with the hook
5
.
As shown in FIG.
1
(
b
), the oscillating hook
5
includes a shaft with a toothed gear, i.e., a pinion,
20
that is driven by a rack
21
having teeth that engage the teeth of the gear
20
. The rack
21
is pivotally connected to a link
22
at a pin
23
that permits rotational movement of the rack
21
relative to the link
22
. The opposite end of the link
22
is pivotally pinned by a pin
25
to a driven rotating wheel
24
near the periphery of the wheel. The wheel
24
is rotationally driven by a motor (not shown), directly or through gears, belts, or another transmission mechanism. Preferably, the same motor drives the wheel
24
and the needle
1
. Separate motor drives may be used provided they are maintained in synchronization.
In the conventional mechanism shown in FIG.
1
(
b
), as the wheel
24
rotates, the link
22
is caused to move transversely, i.e., from left to right, in, essentially, simple harmonic motion. The rack
21
likewise, to the extent its motion is only planar, moves in nearly simple harmonic motion. Because of the presence of the two separate elements, the link
22
and the rack
21
connected at the pin
23
, the actual motion of the rack
21
deviates from simple harmonic motion. The deviation is relatively small and of the second order. For purposes of this disclosure, that minor deviation is considered to be insignificant and the term “simple harmonic motion” is used to encompass the repetitive cyclic transverse movement of the rack
21
between extreme left and extreme right positions. As understood from the basic definition of simple harmonic motion, at two points in each cycle, a moving element has a zero velocity. The speed of the element increases from the two zero velocity points, e.g., the most extreme right and left positions of the rack
21
in FIG.
1
(
a
), to a maximum velocity at a position intermediate the two extreme positions.
The stitching produced by the rotation of the wheel
24
in driving the hook
5
through the engagement of the gear
20
and the rack
21
is described with respect to FIGS.
2
(
a
)-
2
(
d
). FIGS.
2
(
a
)-
2
(
d
) show four sequential positions of the oscillating hook
5
. In FIG.
2
(
a
), the oscillating hook
5
is in an extreme position after rotating counterclockwise and is at zero velocity. This extreme position is approximately synchronized with the lowest position of the needle
1
. The needle thread
2
extends from a source of thread, e.g., a spool, and other mechanisms (not shown), downward and through the eye of the needle
2
. The other mechanisms include a means of adjusting the tension of the thread and a take-up lever, known elements of conventional sewing machines located above the needle plate
4
. The thread
2
extends beneath the needle plate
4
, through the hole
3
, loops, and extends back and out through the hole
3
in the needle plate
4
on the top side of the needle plate
4
. A needle thread loop
8
is located beneath the needle plate
4
. The bobbin thread
6
extending from the bobbin
7
underneath the needle plate
4
also passes through the hole
3
and extends on the top side of the needle plate
4
.
As shown in FIG.
2
(
b
), as the needle
1
begins to rise, the hook
5
begins to turn clockwise, a hook finger
9
on the end of the hook
5
passes through and engages the needle thread loop
8
at a position spaced from the needle
1
. The hook
5
continues to rotate in a clockwise direction, as shown in FIG.
2
(
c
), increasing the size of the needle thread loop
8
as the hook finger
9
pulls on the needle thread
2
. The needle thread look
8
is pulled almost completely around the bobbin
7
. The needle
1
is in approximately its highest position in FIG.
2
(
c
). At that position, the take-up lever (not shown) above the needle plate
4
is beginning to rise, pulling on the needle thread
6
.
The take-up lever continues to rise and, as shown in FIG.
2
(
d
), the needle thread
2
, formerly wrapped around the bobbin
7
, slips off the hook finger
9
, surrounding the bobbin thread
6
. The needle thread loop
8
is pulled closed, gripping the bobbin thread
6
, and brought tight against the bottom surface of the fabric being sewn, so that a locked stitch is formed. The needle
1
finishes its rise and then moves downward to form another needle thread loop
8
for the next stitch. In the meantime, the hook
5
rotates counterclockwise, starting from a zero velocity at the maximum clockwise position, moving to its maximum co

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