TECHNICAL FIELD
The present invention relates to fire retardant zippers and in particular to plastic fire
retardant zippers.
BACKGROUND OF THE INVENTION
Zippers are the most essential part of our daily life and find a wide variety of application
in clothings, sports garments, stationary pouches, shoes, luggage and several other applications.
One such application of zippers is in the military where fire retardant zippers are essentially
required by the industry for workmen as protective wear.
The currently available zippers for fire retardant applications such as in firemen’s suits
are made of aramid tapes or cotton tapes coated with fire retardant chemicals, on which either
brass or plastic molded elements are fixed. Also, these zippers use sliders made entirely from
metals such as zinc or brass. CN 10169204 provides zippers that utilize cotton tapes made of the
aramid fiber materials or the carbon fiber materials that greatly improve the fire resistance and
usage performance of the zipper.
Fire retardant zippers can also be prepared by chemically coating synthetic or cotton
tapes with fire retardant chemicals by the processes of adding flame retardants to raw materials
and carrying out carrier dyeing in the production process or by padding process. Though this
reduces the cost of the zipper, such coatings are not wash resistant and lose their efficacy after
multiple washes of the garments. Such zippers use sliders made from metals such as zinc or
brass, leading to possibilities of burns.
Fire retardant zippers using metal elements, usually brass alloys or molded elements
made from fire retardant grade plastic resins are known to exist. Zippers made using metal
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elements suffer from a major drawback that when exposed to fire or heat, the elements, being
good conductors of heat, become hot causing burns to the wearer. These metal elements are heat
conducting, exposing the wearer of the garment to burn hazard. This needs to be circumvented
by providing a flap to cover the zipper, adding a manufacturing and operation cost.
Similarly, zippers made from molded elements have very poor lateral strength and also
the elements need to be protected from direct exposure to heat as the plastic used have a low
melting point, which can cause failure in actual use in light of the possibility of melting of the
elements when exposed to direct heat. This again requires provision of a flap over the zipper,
adding to an extra operation and cost.
Additionally, both the fire retardant zippers made using metal elements and those made
from molded elements use sliders which are made from metals such as zinc or brass, which can
also cause burns when exposed to heat, being good thermal conductors. Again, to prevent burn
injury to exposure of the metal slider to direct heat, a protective flap has to be provided.
From the above it is clear that the presently available fire retardant zippers require
additional cost of the protective flap as well as additional time to operate the zipper and take off
the garment due to obstruction by the protective flap. Till date, since there was no solution to the
aforementioned drawbacks, the use of such sub-optimal zippers was unavoidable
To overcome the difficulties of current designs of Fire retardant zippers, a special allplastic
zipper has been developed, which eliminates all the above referred problems.
OBJECT AND SUMMARY
The principal object of the present invention is to provide an all plastic zipper.
Another object of the present invention is to provide a zipper which is cost effective.
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The present invention provides a zipper comprising
 a pair of carrier tapes having an outer and inner edge
 engaging elements stitched to the carrier tape on the inner edge
 a knitted lace covering the engaging elements on both faces and stitched all along
the length of the carrier tape
 a slider centrally disposed on the inner edges of the said carrier tape
wherein the engaging elements are made from fire retardant grade polyester
monofilaments; the carrier tapes and knitted lace are made from aramid yarns and
the slider is made from fire retardant plastic resins
BRIEF DESCRIPTION OF DRAWINGS
The aforementioned aspects and other features of the present disclosure will be
explained in the following description, taken in conjunction with the accompanying drawings,
wherein:
Figure 1 illustrates cross sectional view of the ladder type zipper.
Figure 2 illustrates the closed end construction according to an embodiment of the present
disclosure.
Figure 3 illustrates the open end construction according to an embodiment of the present
disclosure.
While the disclosure will be described in conjunction with the illustrated
embodiment, it will be understood that it is not intended to limit the disclosure to such
embodiment. On the contrary, it is intended to cover all alternatives, modifications and
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equivalents as may be included within the spirit and scope of the disclosure as defined by the
appended claims.
DETAILED DESCRIPTION
The subject matter describes a zipper which can effectively improve the heat resistance
and flame resistance of the garment, simultaneously enhancing the performance of the fastener
itself, while greatly improving the ease of use.
The fire retardant zipper of the subject matter is made entirely of plastic raw materials.
The invention describes a zipper which is made entirely from fire retardant plastic materials,
comprising interlocking elements (commonly known as teeth), the slider which joins and
separates the elements, the carrier tapes, the knitted lace covering the elements, the end stops –
whether top & bottom stops or top stops and box-pin assembly and the sewing threads used to
stitch together the elements to the carrier tapes.
The elements, which can be in any form and particularly in coil form are stitched in a
symmetric wrap-around manner around the inner edge of the carrier tapes with the help of
sewing threads. The carrier tapes are made of aramid yarns, which have fire retardant properties.
The sewing threads pass through the holes in the knitted lace made from aramid yarns placed on
either side of the engaging elements. The aramid yarns can be meta isomer of aromatic
polyamides such as Nomex, Conex and Arawin. The coiled elements are made from fire
retardant grade polyester monofilaments. The fire retardant grade polyester monofilaments can
be modified polyethylene terephthalate thermoplastic materials incorporating fire retardant
additives. The sewing threads are also aramid fiber. The other components such as the slider and
the end stops are made from fire retardant plastic resins. The fire retardant plastic resins can be
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modified glass filled polyamide 66 thermoplastic materials incorporating fire retardant additives.
The fire retardant additives can be aluminium hydroxide, magnesium hydroxide,
organophosphorus or organohalogens.
The subject matter of the present disclosure as depicted by figures 1 and 2 provides a
zipper, including the carrier tape (1), the knitted lace (2), the sewing threads (3) to join the
engaging elements (4) and the knitted lace to the carrier tape made from fire retardant aramid
yarns all these combined to form the zipper chain (5) which also has the slider (6) made from fire
retardant plastic. The zipper also has its end stops – namely the top stops (7) and bottom stops
(8) or the open-end separable zipper construction having top stop with box-pin assembly (9)
fixed over reinforcement tapes (10) at the bottom end, which are also constructed from fire
retardant plastic resins.
It is pertinent to mention here that the zipper does not use any chemical coatings to render
the property of fire retardancy to the zipper or its components. The zipper also does not use
sliders and end stops made from any metals.
In a particular embodiment of the subject matter a particular construction of zipper, called
the L-type or LFC zipper was chosen to be developed as a fire retardant zipper. This zipper has a
coiled element which is stitched onto the carrier tape and covered with lace. Some of the
advantages of the zipper are as follows:
 The elements are symmetric, making them suitable for bi-directional use (opened &
closed in both directions), which is required for a protective work wear
 The elements are wrapped around the edge of the tape, significantly increasing their
strength properties such as lateral strength or fold-over strength
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 The elements are covered with a lace, protecting them from abrasion by the moving slider
and also from direct exposure to heat
 When the zipper elements (teeth) are in the form of continuous coil, the failure of a single
element (tooth) does not affect the performance of the zipper, unlike in the case of metal
or plastic molded elements, where even a single element missing can result in failure of
the zipper.
This particular design had a lot of challenges in the manufacturing processes, which had
to be suitably modified to handle the special fire retardant raw material used. Some of the
challenges are as follows:
 The lace used in covering the elements, is made of very fine aramid yarns. These have
tensile strength typically half that of polyester yarns used in normal zippers. Also, the
aramid yarns have distinct hairiness, requiring use of special binding agents to prevent
filamentation and snarling during the production process. The special binders are so
chosen as to dissolve during the subsequent processing so that the fire retardant property
of the final zipper is not compromised.
 The coiling process used for forming the ladder-shaped coil required re-designing, since
the fire retardant grade of monofilament used has different thermoforming properties,
being softer compared to normal polyester monofilament. The different set-up included
change in feeding mechanism and speed, changed temperature settings and modification
in the shape of the forming mechanism.
 The aramid sewing threads used for stitching the coiled elements and the laces on the
carrier tape have very poor loop forming property, affecting the stitching quality,
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resulting in dropped stitches. This required special machine set-ups and thread feeders to
impart positive feed to the sewing thread to ensure sufficient length of the loops.
 The dyeing process for aramid and polyester being entirely different and requiring
different chemicals, the zipper chain had to be processed for its aramid components (the
carrier tape, the lace and the sewing threads) and its monofilament component. Aramids
typically require lower dyeing temperatures but more than twice the dyeing time
compared to the monofilament used. The process had to be stabilized to accept both sets
of chemicals and dyeing parameters.
 The heat-setting process used in normal zippers cannot be used for fire retardant zippers,
which are inherently heat-resistant. However the coiled elements are required to be heat
set to ensure their dimensional stability. This was done with a special cabinet type stenter
imparting controlled tension to the zipper chain.
 The fire retardant plastic resin used for the slider has significantly lower strength
compared to the normal material. Thus the slider had to be redesigned to improve its
flexural strength and resistance to mouth deformation to ensure that the zipper
performance on reciprocation meets and surpasses various international as well the Indian
standards.
 Specially designed injection molds and molding machine had to be used for
manufacturing the sliders.
Although the disclosure of zipper has been described in connection with the embodiment
of the present disclosure illustrated in the accompanying drawings, it is not limited thereto. It
will be apparent to those skilled in the art that various substitutions, modifications and changes
may be made thereto without departing from the scope and spirit of the disclosure.
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The various embodiments described above can be combined to provide further
embodiments. All of the patents, patent application publications, and non-patent publications
referred to in this specification are incorporated herein by reference, in their entirety. Aspects of
the embodiments can be modified, if necessary to employ concepts of the various patents,
applications and publications to provide yet further embodiments.
These and other changes can be made to the embodiments in light of the above-detailed
description. In general, in the following claims, the terms used should not be construed to limit
the claims to the specific embodiments disclosed in the specification and the claims, but should
be construed to include all possible embodiments along with the full scope of equivalents to
which such claims are entitled. Accordingly, the claims are not limited by the disclosure.

We Claim:
1. A zipper comprising
 A pair of carrier tapes (1) having an outer and inner edge
 Engaging elements (4) stitched to the carrier tape on the inner edge
 A knitted lace (2) covering the engaging elements (4) on both faces and stitched
all along the length of the carrier tape
 A slider (6) centrally disposed on the inner edges of the said carrier tape
wherein the engaging elements are made from fire retardant grade polyester
monofilaments; the carrier tapes and knitted lace are made from aramid yarns and
the slider is made from fire retardant plastic resins
2. The zipper as claimed in claim 1, wherein the engaging elements are coiled elements.
3. The zipper as claimed in claim 1, wherein the zipper comprises end stops.
4. The zipper as claimed in claim 3, wherein the end stops comprise top stops (7) and
bottom stops (8).
5. The zipper as claimed in claim 3, wherein the end stops comprise top stops and box-pin
assembly (9).
6. The zipper as claimed in claim 5, wherein the box-pin assembly comprises separating pin
and retainer box fixed at the bottom end of the zipper.
7. The zipper as claimed in claim 3, wherein the end stops are made of fire retardant plastic
resins.
8. The zipper as claimed in claim 1, wherein the engaging elements are stitched in a
symmetric wrap-around manner around the inner edge of the carrier tapes with sewing
threads (3) made of aramid yarns.
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9. The zipper as claimed in claim 1, wherein the engaging elements are stitched in a
symmetric wrap-around manner around the inner edge of the carrier tapes with sewing
threads made of aramid yarns, such that the sewing threads pass through the holes in the
knitted lace made from aramid yarns placed on either side of the engaging elements.
10. The zipper as claimed in claim 1, wherein the fire retardant grade polyester
monofilaments are selected from the group consisting of modified polyethylene
terephthalate thermoplastic materials incorporating fire retardant additives
11. The zipper as claimed in claims 1 and 3, wherein the aramid yarns are selected from the
group consisting of the meta isomer of aromatic polyamides.
12. The zipper as claimed in claims 1 and 3, wherein the fire retardant plastic resins are
selected from the group consisting of modified glass filled polyamide 66 thermoplastic
materials incorporating fire retardant additives.
13. The zipper as claimed in claim 1 and 3, wherein end stops are made from fire retardant
plastic resins selected from the group consisting of modified polyolefin thermoplastic
materials incorporating the fire retardant additives
14. The zipper as claimed in claims 10, 12 and 13 wherein the fire retardant additives are
selected from the group consisting of aluminium hydroxide, magnesium hydroxide,
organophosphorus or organohalogens
15. The zipper as claimed in claim 11 wherein the meta isomer of aromatic polyamide is
selected from the group consisting of Nomex, Conex and Arawin.