U.S. patent application number 10/223410 was filed with the patent office on 2004-02-19 for injection molded bobbin basket.
Invention is credited to Kronenberger, Ronald.
Application Number | 20040031426 10/223410 |
Document ID | / |
Family ID | 31715152 |
Filed Date | 2004-02-19 |
United States Patent
Application |
20040031426 |
Kind Code |
A1 |
Kronenberger, Ronald |
February 19, 2004 |
Injection molded bobbin basket
Abstract
A bobbin basket for use with a lock-stitch sewing machine. The
bobbin basket defines a receptacle for a thread-carrying bobbin
case. The bobbin basket has a wall extending around a central axis
and a rib projecting radially from the wall for reception in a
raceway of a rotary loop taker, to which the bobbin basket can be
operably connected. The bobbin basket is molded from a
TORLON.RTM.-based material commercially sold under the designation
PXM01017.
Inventors: |
Kronenberger, Ronald;
(Riverwoods, IL) |
Correspondence
Address: |
WOOD, PHILLIPS, KATZ, CLARK & MORTIMER
500 W. MADISON STREET
SUITE 3800
CHICAGO
IL
60661
US
|
Family ID: |
31715152 |
Appl. No.: |
10/223410 |
Filed: |
August 19, 2002 |
Current U.S.
Class: |
112/231 |
Current CPC
Class: |
D05D 2209/10 20130101;
D05B 57/265 20130101 |
Class at
Publication: |
112/231 |
International
Class: |
D05B 057/14 |
Claims
1. A bobbin basket for use with a lock-stitch sewing machine, the
bobbin basket defining a receptacle for a thread-carrying bobbin
case, the bobbin basket comprising a wall extending around a
central axis and a rib projecting radially from the wall for
reception in a raceway of a rotary loop taker to which the bobbin
basket can be operably connected, wherein the bobbin basket is
molded from a TORLON.RTM.-based material commercially sold under
the designation PXM 01017.
2. The bobbin basket for use with a lock-stitch sewing machine
according to claim 1 wherein the bobbin basket comprises a center
post extending along the central axis in the receptacle for
supporting a thread-carrying bobbin case.
3. The bobbin basket for use with a lock-stitch sewing machine
according to claim 1 wherein at least the rib is made from the
TORLON.RTM.-based material.
4. The bobbin basket for use with a lock-stitch sewing machine
according to claim 1 wherein at least the wall is made from the
TORLON.RTM.-based material.
5. The bobbin basket for use with a lock-stitch sewing machine
according to claim 1 wherein at least the rib and wall are made
from the TORLON.RTM.-based material.
6. In combination: a) a bobbin basket defining a receptacle for a
thread-carrying bobbin case and comprising a wall extending around
a central axis and a rib projecting radially from the wall; and b)
a rotary loop taker comprising a raceway, the rib residing in the
raceway and guided within the raceway as relative movement of the
bobbin basket and rotary loop taker around the center axis takes
place with the bobbin basket and rotary loop taker operably
connected, wherein the bobbin basket is molded from a
TORLON.RTM.-based material commercially sold under the designation
PXM 01017.
7. The combination according to claim 6 wherein the bobbin basket
comprises a center post extending along the central axis in the
receptacle for supporting a thread-carrying bobbin case.
8. The combination according to claim 6 wherein at least the rib is
made from the TORLON.RTM.-based material.
9. The combination according to claim 6 wherein at least the wall
is made from the TORLON.RTM.-based material.
10. The combination according to claim 6 wherein at least the rib
and wall are made from the TORLON.RTM.-based material.
11. The combination according to claim 6 further in combination
with a thread-carrying bobbin case in the bobbin basket receptacle.
Description
FIELD OF THE INVENTION
[0001] This invention relates to a bobbin basket for a lock-stitch
sewing machine and, more particularly, to a molded bobbin basket
made from a polymer material.
BACKGROUND OF THE INVENTION
[0002] This invention supplements the inventions disclosed and
claimed in applicant's U.S. Pat. No. 4,858,543, issued Aug. 22,
1989, and U.S. Pat. No. 5,188,046, issued on Feb. 23, 1993, both
assigned to the assignee of the present invention. The bobbin
basket covered by U.S. Pat. No. 4,848,543 is adapted for use with a
horizontal rotary loop taker (or "hook"). The invention in U.S.
Pat. No. 5,188,046, and the present invention, are both useful with
bobbin baskets adapted for use with a horizontal hook, a vertical
hook, or a zigzag hook.
[0003] Sewing machine bobbin baskets are often made of metal,
typically steel. The inventions covered by Patent Nos. 4,858,543
and 5,188,06 went long way toward providing a bobbin basket that
avoids the problems long associated with steel bobbin baskets.
[0004] There are many advantages that a plastic bobbin basket has
over a conventional all-steel basket. Molding of the basic plastic
piece is far more convenient and less expensive than the casting or
forging--followed by various machining, polishing and hardening
steps--that is involved in the production of an all-steel bobbin
basket. Chattering of the bearing rib in its raceway--which
produces chipping and burring, with resulting thread breakage--is
avoided with a plastic bobbin basket. The low coefficient of
friction between the bearing rib, and a raceway in which it moves,
accounts for potentially a longer life for the plastic bobbin
basket, and may avoid the problems of messy lubrication, galling,
bluing of a rotary loop taker, and puckering of the goods being
sewn that accompany the use of an all-steel basket.
[0005] There are several plastic materials of a high wear and
self-lubricating type that may be considered as being more or less
suitable for the manufacture of a bobbin basket. Of these, the most
suitable are the poly(amide-imide) resins, in which the polymer
chain comprises amide linkages alternating with imide linkages.
Poly(amide-imide) resins have exceptional mechanical strength and
dimensional stability, and a low coefficient of thermal expansion.
Furthermore, they maintain these properties at very high
temperatures.
[0006] It was generally believed by skilled workers in this art in
the early 1990's that the high melt viscosity of poly (amide-imide)
resins, combined with the extremely complicated structure of bobbin
baskets, made it impossible to use these polymers in producing such
baskets by injection molding. However, the applicant successfully
engineered and successfully commercially marketed, and continues to
successfully market, injection molded bobbin baskets using
poly(amide-imide) resins, and particularly ones incorporating
resins sold commercially under the trademark TORLON.RTM., owned by
Amoco Performance Products, Inc.
[0007] While bobbin baskets using poly(amide-imide) resins have
performed very well in the industry, designers of sewing equipment
are constantly seeking ways to improve bobbin baskets by
maintaining the desirable operating characteristics of the resin
materials, while at the same time increasing the useful life of
these baskets, primarily by reducing wear during use. As bobbin
baskets wear, their operating characteristics may be altered. At
the point that replacement becomes necessary, equipment must be
shut down to allow the removal of the spent basket and installation
of a new basket. Aside from the expense associated with a new
basket and the labor costs associated with basket replacement,
system down time may account for further significant, economic
loss. Heretofore, to the knowledge of the applicant, while the call
for improved wear characteristics for plastic bobbin baskets has
been made by the industry, no significant, viable improvements in
the baskets, over those made from currently used poly (amide-imide)
resin baskets, have evolved over the last decade that afford better
wear properties which translates into longer basket life.
SUMMARY OF THE INVENTION
[0008] In one form, the invention is directed to a bobbin basket
for use with lock-stitch sewing machine. The bobbin basket defines
a receptacle for a thread-carrying bobbin case. The bobbin basket
has a wall extending around a central axis and a rib projecting
radially from the wall for reception in a raceway of a rotary loop
taker, to which the bobbin basket can be operably connected. The
bobbin basket is molded from a TORLON.RTM.-based material
commercially sold under the designation PXM01017.
[0009] In one form, the bobbin basket has a center post extending
along the central axis in the receptacle for supporting a
thread-carrying bobbin case.
[0010] In one form, at least the rib is made from the
TORLON.RTM.-based material.
[0011] In one form, at least the wall is made from the
TORLON.RTM.-based material.
[0012] The rib and wall may both be made from the TORLON.RTM.-based
material.
[0013] The invention is further directed to the combination of a
bobbin basket and a rotary loop taker with a raceway. The bobbin
basket has a receptacle for a thread-carrying bobbin case, a wall
extending around a central axis, and a rib projecting radially from
the wall. The rib resides in the raceway and is guided within the
raceway as relative movement of the bobbin basket and rotary loop
taker around the central axis takes place with the bobbin basket
and rotary loop taker operably connected. The bobbin basket is
molded from a TORLON.RTM.-based material commercially sold under
the designation PXM01017.
[0014] The bobbin basket may have a center post, as described
above.
[0015] A part, or all, of the bobbin basket may be made from the
TORLON.RTM.-based material, as described above.
[0016] The combination may further include a thread-carrying bobbin
case in the bobbin basket receptacle.
BRIEF DESCRIPTION OF THE DRAWING
[0017] The present invention is described in detail below with
reference to the accompanying drawing, in which:
[0018] FIG. 1 is a top plan view of one embodiment of the bobbin
basket of this invention adapted for use with a horizontal rotary
loop taker in a sewing machine that is equipped with an
undertrimmer;
[0019] FIG. 2 is a front elevation view of the embodiment of FIG.
1, as seen from the top of FIG. 1;
[0020] FIG. 3 is a cross-sectional view of the embodiment of FIG. 1
taken along line 3-3 in FIG. 1;
[0021] FIG. 4 is a similar view of the embodiment of FIG. 1 taken
along line 4-4 in FIG. 1; and
[0022] FIG. 5 is a similar view of the embodiment of FIG. 1 taken
along line 5-5 in FIG. 1.
DETAILED DESCRIPTION OF BEST MODES OF PRODUCT AND PROCESS
[0023] A detailed description of the best modes of practicing the
present product and process inventions will now be provided by
reference to the accompanying drawings.
General Configuration Of Bobbin Basket
[0024] Plastic bobbin basket 20, seen in top plan view in FIG. 1,
includes cylindrical side wall 22 extending around a central axis
23, crosswise support member 24 extending across the bottom of the
bobbin basket, center bobbin spool support post 25 extending
axially from crosswise support member 24 into a space/receptacle
defined by side wall 22, and flange 28 extending radially outward
from the top portion of the side wall. Center post 25 carries notch
27 near its upper end to receive a latch for retaining a bobbin
case 29 in which the bobbin thread spool is contained. Apertures
25, which are smaller in area than the corresponding apertures of a
conventional steel bobbin basket, help to define crosswise support
member 24.
[0025] Portions 28a and 28b of flange 28 form oppositely facing
side walls 30a and 30b that are positioned generally radially to
form rotation-restraining notch 32 in the top surface of flange 28.
First notch side wall 30a forms the downstream side of
rotation-restraining notch 32, relative to the direction of
rotation D1 (in FIG. 1, counterclockwise) of the rotary loop taker
31 with which bobbin basket 20 is adapted to be used. Second notch
side wall 30b forms the upstream side, relative to the direction of
hook rotation, of rotation-restraining notch 32. Notch 32 is
adapted to receive the stud portion of a conventional stationary
positioning finger (not shown) with a secure but sufficiently loose
fit to permit limited back-and-forth rotational movement of the
bobbin basket.
[0026] A second notch 33 is provided at the inside perimeter of
flange 28, on the right-hand side of FIG. 1. In use, a projection
from the bobbin case that contains the bobbin spool is seated in
this notch to align the case properly and to keep the case from
rotating on post 25.
[0027] Annular bearing rib 34 extends radially outward from
cylindrical sidewall 22.
[0028] The rib 34 extends substantially around the perimeter of the
bobbin basket except for a portion of the rib that is omitted at 36
to provide two oppositely facing rib end portions 38 and 40 that
define a needle thread pick-up and release area. The rib 34 is
guided in the raceway on the rotary loop taker 31 as the rotary
loop taker 31 moves relative to the basket 20 around the axis
23.
[0029] Rib end portion 38 forms "T"-shaped pick-up notch 42 at the
downstream end, relative to the direction of hook rotation D1, of
needle thread pick-up and release area 36 (FIGS. 1 and 2). Rib end
portion 40, located adjacent rotation-restraining notch 32, forms a
needle thread stop at the upstream end, again relative to the
direction of hook rotation, of needle thread pick-up and release
area 36 (FIGS. 1 and 2). Needle thread loop 41 comes into contact
with stop 40 as the loop is pulled around the bobbin basket and
tightened around the bobbin thread (FIG. 2).
[0030] Needle guard plate 46 (shown in FIG. 2) is of the type
disclosed and claimed in Applicant's U.S. Pat. No. 4,858,543
referred to above. It is included in the plastic bobbin basket to
prevent damage to cylindrical wall 22 if a needle used with the
horizontal hook with which this basket is adapted to be employed
should be accidentally deflected as it moves toward and into
needle-receiving space 48. Plate 46 is omitted from FIG. 1 for
clarity.
Damage Resistant Members
[0031] Damage resistant members such as are disclosed and claimed
in Applicant's U.S. Pat. No. 5,188,046 are shown in FIG. 1, but are
omitted for clarity from FIG. 2. Wear resistant pin 50 protects rib
end portion 38, which forms "V"-shaped pick-up notch 42 at the
downstream end of the needle thread pick-up and release area. Pin
54 minimizes wear that tends to occur on bearing rib end portion 40
adjacent the upstream end of the pick-up and release area.
[0032] Insert 56 is provided at the upstream side wall 30b of
rotation-restraining notch 32 to minimize impact damage to that
wall that would otherwise be caused by the stud portion of the
stationary positioning finger referred to above. Pin 60, together
with pins 50 and 54, helps prevent wear on the body of bearing rib
34 as the raceway of the associated rotary loop taker 31 slides
around the rib at the high rotational speeds at which sewing
machines, especially industrial sewing machines, are operated.
Complicated Structure Of Bobbin Basket
[0033] There are hundreds of different types of bobbin baskets
employed with industrial sewing machines. Many are used with
horizontal hooks, many with vertical hooks and some with zigzag
hooks. Each one has a complicated form that is dictated by the
functions that are performed by the bobbin basket and by the
basket's relationship with the rest of the sewing machine,
especially the rotary loop taker (or "hook") that is used in the
machine.
[0034] Some bobbin baskets have even more complicated forms than
the basket shown in the accompanying drawing, and others have a
somewhat less complicated form. As regards molding problems,
however, practically all bobbin baskets have very complicated
structures. This is discussed further below.
[0035] As mentioned above, FIGS. 3-5 are cross-sectional views of
the bobbin basket of FIG. 1 taken along the respective lines
indicated in that Figure. Each of these is shown in an inverted
position, to illustrate how the inner and outer portions of a mold,
together with various inserts and slides, as required, can be used
to produce a plastic bobbin basket by the injection molding process
if the polymeric material is in fact moldable. These three Figures
also illustrate how complicated the structure of the typical bobbin
basket of FIG. 1 is.
[0036] Flange 28, which extends outwardly from the top of
cylindrical wall 22 in the lower right-hand corner of FIG. 1, is
seen extending from the side wall in the lower left-hand portion of
FIG. 3. Bearing rib 34 is shown extending outward from the side
wall. Needle thread pickup and release area 36 is not indicated in
FIG. 3, but is located on the far side of cylindrical wall 22.
[0037] Rotation-restraining notch 32, with downstream wall 30a
undercut at 62, is seen at the bottom of FIG. 3. Needle-receiving
space 48 is located a short distance above notch 32 as seen in this
inverted Figure. Aperture 70 is located adjacent the
needle-receiving space, and apertures 72 are provided at each end
of that space, to receive attaching means for securing metal needle
guard plate 46 (seen in FIG. 2) to the plastic bobbin basket.
[0038] Holes are provided for each of the damage resistant members
referred to above. Hole 50a in side wall 22 is adapted to receive
wear-resisting insert 50, and hole 54a is adapted to receive
wear-resisting insert 54. A hole is provided in bearing rib 34 and
side wall 22 to receive wear resistant member 60 at the location
indicated in FIG. 1. (Pin 60 is of course not visible in the
cross-sectional views of FIGS. 3-5.) The holes for these three pins
just mentioned--50, 54 and 60--preferably extend through both
bearing rib 34 and side wall 22. They are preferably insert molded,
both for accuracy and to reduce the number of separate mechanical
steps required. If the holes are drilled after the basic molding is
completed, a diamond or carbide drill must be used.
[0039] The sectional views seen in FIGS. 3-5 are considerably
larger than the actual size of the bobbin basket. In the actual
life-size basket, the dimensions are very much smaller than they
appear in the drawing. In addition to this, a number of thin walls,
small ridges, narrow undercuts, small holes and sharp corners are
present in the structure of this basket. As will be discussed
below, these complexities make for an extremely difficult molding
problem at best.
Mechanical Properties of Poly(amide-imide) Resins At High
Temperatures
[0040] Plastics that may be considered acceptable for the
manufacture of a bobbin basket include high-wear, self-lubricating
resins such as ZYTEL 101 (nylon resin) and DELRIN (acetal resin),
both marketed by E. I. du Pont de Nemours and Company, ULTM 4001
(polyether amide resin) marketed by General Electric Company and
TORLON (poly (amide-imide) resin) marketed by Amoco Performance
Products, Inc. Of these plastics, the heat-cured poly(amide-imide)
resins have proven to be better than the other available resins in
those engineering properties that are critical for any part that is
subjected to the extreme conditions under which bobbin baskets are
used.
[0041] In use, a bobbin basket is subjected (1) to severe harmonic
vibrations caused by the needle thread loops that are pulled
forcibly around and along the outer surf ace of the bobbin basket
thousands of times a minute (as a result of the high rotational
speed of the associated rotary loop taker), and (2) to serious
impact forces on the upstream wall of the rotation-restraining
notch that are created by the stud portion of the stationary
positioning finger when the bobbin basket is jerked back and forth
by the needle thread loop as tension is applied to that loop in one
direction and then in the other. For these reasons, among others,
the plastic of which a bobbin basket is formed must have excellent
strength and rigidity.
[0042] The raceway of the rapidly rotating rotary loop taker rubs
against the outwardly extending bearing rib of the bobbin basket
and tends to create very substantial frictional heat and resulting
wear. As the needle thread loop passes around the bobbin basket and
is pulled up tight against it, the pressure of the thread as it
repeatedly rubs across and along certain portions of the bobbin
basket likewise tends to cause frictional heat and resulting wear.
It is believed that the frictional heat produced in these two ways
may raise the temperature imposed on certain narrowly defined
portions of the bobbin basket to several hundred degrees F., or
even higher.
[0043] Applicant, years ago, made the surprising discovery
that--despite the extremely difficult molding parameters
involved--poly(amide-imide) bobbin baskets can in fact be injection
molded. Applicant has successfully made and in past years marketed
a line of poly(amide-imide) bobbin baskets. To the knowledge of the
applicant, while the poly(amide-imide) bobbin baskets have been
successfully used worldwide, the performance of these baskets has
plateaued in spite of ever ongoing efforts in this industry to
still further increase the wear characteristics of these baskets
while retaining the desired properties associated with resin bobbin
baskets.
[0044] Composite Resin
[0045] The thermoplastic resin in the bobbin basket of this
invention is preferably a variation of TORLON.RTM. material Grade
4275, previously sold by Amoco Performance Products, Inc. The
material which the applicant has incorporated into a preferred form
of its bobbin baskets is currently sold by Solway Advanced Polymers
LLC commercially as a TORLON.RTM. based material under the
designation PXM01017.
[0046] Surprisingly, the bobbin baskets made using the
TORLON.RTM.-based PXM01017 material exhibited very significantly
improved wear characteristics compared to bobbin baskets made with
conventional TORLON.RTM. material of Grade 4275, sold by Amoco
Performance Products, Inc. and used by the applicant on a high
volume basis over the past several years. Data from comparative
testing is provided in the following table and demonstrates the
very significant gains made in terms of improved wear.
1 Clearance After 157 h Clearance before test test TORLON .RTM.
Material Axial Radial Axial Radial PXM01017 0.05 mm 0.055 mm 0.065
mm 0.10 mm PXM01017 0.05 mm 0.05 mm 0.065 mm 0.11 mm 4275 0.05 mm
0.04 mm 0.066 mm 0.45 mm
[0047] During the testing procedures, the hooks were operated on a
stop and go basis for 157 hours, with 2 second stops and 4 second
operation at a speed of 4,000 rpm.
[0048] A very significant improvement in radial wear resistance for
the guide ribs was observed. The operating forces in a radial
direction are generally such as to cause significant radial wear
that may necessitate replacement before there is any appreciable
axial wear relative to the basket center axis.
[0049] The potential increase in the life of the bobbin baskets
attributable to this improved wear resistance is very significant.
This increased life not only offers savings in the cost of the
baskets, but also by reason of reduced down time and attendant
labor costs associated with basket replacement.
[0050] The foregoing disclosure of specific embodiments is intended
to be illustrative of the broad concepts comprehended by the
invention.
* * * * *