Note: Descriptions are shown in the official language in which they were submitted.
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' The invention relates to slide fasteners and
particularly to a method of forming coupling elements Eor
slide fasteners.
One common slide fastener employs metal scoops ~r
S coupling elements wherein each of the metal scoops has a
tapered projection from the front thereof and a similarly
shaped recess in the rear thereof for receiving the projection
of a mating scoop; the tapered projection and the recess being
in alignment parellel to the tape to which the metal scoop is
secured. The bottom surface of the tapered projection on the
scoop is thus substantially closer to the edge of the tape
than the top of the recess such that the crosswise ~orces on
the slide fastener tend to pivot the coupling element causing
longitudinal stress on the edge of the tape.
According to the present invention there is provided
a method of forming a coupling element for a slide fastener
comprising forming a coupling element blank of flowable
synthetic polymer resin wherein one of a head portion and a
pair of 12g portions of the blank has an excess of the polymer
resin, and molding the blank to extrude the excess polymer
resin by laminar flow through the neck sections of the leg
portions adjacent the head portion to orient the polymer in
the neck sections and to form a head and a pair of legs for
the coupling element.
An object of the invention is to provide a method
of forming a coupling element for a slide fastener having an
improved uniformity of stress loading of the element.
Another object of the invention is to provide a
method of forming a coupling element aesthetically similar
to metal scoops but having a specific geometry to permit
manufacture with synthetic resins as well as requiring less
material.
It is preferably also an object of the invention
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to form a coupling element with a front locking projection
and a back locking recess or pocket wherein the front and back
coupling or loading surfaces are equidistant from the edge of a
supporting tape.
An additional preferred feature is an open pocket in
the coupling element.
Another feature of the invention is the orientation
of a polymer resin in leg sections adjacent the head of the
coupling element producing increased strength.
Other objects, advantages and features of the inven-
tion will be apparent from the following description of the
preferred embodiment taken in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a plan view of a slide fastener formed by
a method in accordance with the invention.
Fig. 2 is a perspective view of a coupling element of
the slide fastener of Fig. 1. -
Fig. 3 is a perspective view of the element of Fig. 2
taken from a different angle.
Fig. 4 is a back view of the element of Figs. 2 and 3.
Fig. 5 is a bottom view of the element of Figs. 2,
3 and 4.
Fig. 6 is an enlarged plan view, partially in cross
section, of a broken away portion of the fastener of Fig. 1 in
an unloaded state.
Fig. 7 is a view similar to Fig. 6, but with the
fastener in a loaded state.
Fig. 8 is a side cross section view taken along line
8-8 in Fig. 4.
~ Fig. 9 is a side cross section view of a blank used
i in forming the coupling element of Figs. 2-5 and 8.
~ ~ Fig. 10 is a side cross section view of a variation
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of the coupling element.
Fig. 11 is a side cross section view of another
variation of the coupling element.
DESCRIPTION OF THE PREFERRED EMBODIMENT
As illustrated in Fig. 1, a slide fastener manu-
factured in accordance with the invention includes a pair of
carrier tapes 20 and 22 with rows of respective pluralities of
interlocking coupling eiements 24 and 26 secured to the inner
e~ges of the tapes 20 and 22. A slider 28 is slidably mounted
on the coupling elements 24 and 26 for opening and closing the
coupling elements. The tape 20 and coupling elements 24 form
a left stringer, while the tape 22 and the coupling elements
26 form a right stringer. The left and right stringers are
substantially mirror images of each other and together form a
slide fastener chain.
As shown in Figs. 2-5, each of the coupling elements
24 (and the coupling elements 26, Figs.6 and 7) has a head 30
and a pair of parallel spaced legs 32 and 34 extending down-
ward from opposite sides of the head 30. A tapered locking
protrusion or projection 36 is formed on the front of the head
- 30 and is defined by a generally horizontal top surface 38 of
the element 24, a bottom surface 40 on the head 30 sloping
upward from the front of the legs 32 and 34, and a pair of con-
verging side surfaces 42 and 44 extending from about midway of
the sides of the respective legs 32 and 34. A locking recess
or pocket indicated generally at 46 in the back of the element
24 is bordered by a bottom inside surface 48 of the head 30
sloping downwardly from the rear of the element 24, and a pair
of inside vertical surfaces 50 and 52 converging inwardly from
the rear of the element 24. The bottom of the recess 46 opens
into a slit 54 between the legs 32 and 34. As viewed in Fig.8,
~ the head 30 has a side cross section which is generally tri-
; angular and bounded by the surfaces 38, 40 and 48; the surfaces
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40 and 48 converging downwardly at substantially the same angle
relative to the horizontal or to the legs 32 and 34. Also mid-
points of the surfaces 40 and 48 define a straight line 55,
Figs. 6 and 7, generally perpendicular to the legs 32 and 34.
In forming the chain in Figs. 1, 6 and 7 the elements
24 and 26 are positioned with the inner edges of the tapes 20
and 22 received within the slots 54, Fig. 4, and between the
leg portions 32 and 34. The heads 30 are spaced from the tapes
20 and 22 with the legs 32 and 34 extending perpendicular to
the edges of the tapes. The coupling elements 24 and 26 are
secured to the tapes 20 and 22 in a suitable manner, such as
by adhesive bonding, ultrasonic bonding, dielectric bonding, or
otherwise securing the legs 32 and 34.
The particular construction of the coupling element
with a front locking projection and a rear locking pocket which
opens into a slit 54 between the legs, thus forming an open
pocket, results in utilization of less material for forming the
coupling element as well as allowing leg to leg flexability and
relatively easy attachment to the tape. The increased flex-
ability allows for distribution of stress between the legs.
- As shown in Figs. 6 and 7, the projections 36 of the
coupling elements 24 mate with the recesses 46 in the rear of
the mating coupling elements 26, and vice versa. The engaging
surfaces 40 and 48 on the front and back of each element are
generally equidistant from the respective inner edges of the
tapes 20 and 22; thus camming forces transverse the elements
due to the crosswise forces on the tapes cancel and pivotal
forces on the elements are substantially reduced. The tri-
angular shape of the head 30 with the surfaces 40 and 48 ex-
tending at substantially the same angle or slope producing in-
line coupling provides a more efficient coupling between the
elements 24 and 26 as well as more uniform stress loading of
~ the elements.
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The coupling elements 24 and 26 are formed from a
synthetic polymer resin, such as one ~f the thermoplastic resins,
nylc,n 6, nylon 6-6, polypropylene, polyethylene, polyester and
acetal. As shown in Fig. 9, the coupling element is initially
formed in a blank indicated generally at 56 which has a head
portion 58 and leg portions (only one leg portion 59 of two leg
portions shown). The blank has in one portion thereof a volume
of resin in excess of that required for the corresponding
portion of the finished product (herein after, simply "excess
of resin"). For example, the blank may have an excess of
synthetic resin in the head portion 58 such as in the area where
the recess 46 is to be formed. Then the blank 56 is reformed,
as indicated by ~he dashed lines, into the configuration of the
coupling element of Figs. 2-7 by molding to extrude the excess
synthetic resin from the head portion 58 downward through neck
sections 60 and 62, Figs. 3,4 and 8, of the legs 32 and 34
adjacent the head 30. As indicated by the arrows 65 the ex-
trusion produces laminar flow (i.e., flow in one direction) of
the resin downward through the neck sections 60 and 62. Further,
the molding die has constrictions in the front and back of the
neck sections 60 and 62 to form indents 64 and 66 which reduce
the cross sectional area of the neck sections 60 and 62 in-
creasing the rate of laminar flow of the flowable resin material
through the neck portions 60 and 62. Alternately the leg
portions of the blank may have an excess of polymer resin while
the head portion is deficient; the laminar flow being upward
rather than downward through the neck portions 60 and 62.
Synthetic polymer resins have long chain molecules
which are believed to be oriented during the laminar flow of
the plastic resin to produce an orientation of the long chain
molecules along the direction of the laminar flow. Additionally
the laminar flow of the synthetic polymer resin may result in
stratification in the crystalline structure of the polymer resin.
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Such orientation or stratification results in substantially in-
creased tensile strength o~ the neck sections 60 and 62 of the
legs 32 and 34 adjacent to the head 30; thus the chance of
breakage of the coupling elements at the neck portions 60 and
62, where the greatest amount of forces are concentrated during
use of the slide fastener, is greatly reduced. The reduced
neck section 60 and 62 also increase the flexibility of the
head 30 making operation of the slide fastener easier than if
such sections were not reduced.
Variations of the coupling elements are illustrated
in Figs. 10 and 11 wherein numbers used to identify parts of the
coupling element in Figs. 2-5 and 8 are used to identify sub-
stantially identical parts of the variations in Figs. 10 and
11. In the coupling element of Figs. 2-5 and 8 excess of
the molded material from the head portion is extruded through
the neck sections 60 and 62 into the leg portions which are then
expanded both forwardly and rearwardly. In the variation of
Fig. 10 the legs are expanded only to the front, while in the
variation of Fig. 11 the legs are expanded downwardly.
Also, the coupling elements can be made by a contin-
uous molding process wherein they are molded in a flat config-
uration joined by connecting threads embedded in the legs of
the coupling elements; the legs subsequently being bent into
the U-shape of the elements illustrated herein.
Since many variations, modifications, and changes in
detail may be made to the described coupling elements and slide
fastener and their method of manufacture, it is intended that
all matter in the foregoing description and shown in the
accompanying drawings be interpreted as illustrative and not
in a limiting sense.
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