CLIAMS:1. A zip slide fastener having a pair of coplanar stringer tapes (41,41) longitudinally abutting each other along the plane, a pair of interlocking coupling elements each disposed between a common top stop station and a common bottom stop station and a movable slider slidably mounted for engaging and disengaging the stringers for correspondingly engaging and disengaging the coupling elements, characterized in the pair of stringer tapes (41,41) of substantial length each contoured with an inward bent gap (48) to form a folded edge (47) and a lip (49), and having the series of interlocking coupling elements (43,43) matingly coupled along their longitudinal edges forming a fastener chain, and also in the coupling elements each ending securedly at an end point which is the folded edge (47) of the stringer tape and wherein the said stringers are encapsulated with an encapsulation on top, side and inward bent gap (48), with an openable slit along the length such that the slit is in closed state when the said slide is at closed position and said slit progressively changing to open state in response to movement of said slider towards open position of the zipper.

2. The zip slide fastener as claimed in claim 1, wherein the two stringers may be encapsulated together wholly but beyond the complimentary mating / interlocking portion of the coupling elements.

3. The zip slide fastener as claimed in claim 1, wherein each string may be encapsulated separately.

4. The zip slide fastener as claimed in claim 1, wherein slider may be supported with a bottom backing strengthener member disposed at top stop station.

5. The zip slide fastener as claimed in claim 1, wherein fastener coupling elements are formed by a continuous coil.

6. The zip slide fastener as claimed in claim 1, wherein the stringer tapes may be coated with thermoplastic resin on one of the sides or on both sides.

7. The zip slide fastener as claimed in claim 1, wherein the encapsulation is made with materials selected from a group of thermoplastic resins.

8. The zip slide fastener as claimed in claim 1, wherein the slider may be of metal or non-metal. ,TagSPECI:FIELD OF THE INVENTION

The present invention relates to Airtight / fluid tight nonmetallic slide fastener fully encapsulated by thermoplastic resin for providing hermetical seal to the products, in which this fastener is used.

BACKGROUND OF PRIOR ART

Airtight and fluid tight Slide fasteners are known in the prior art. The first embodiment as shown in fig.1 - consists of coupling mechanism in stringers, composed of U shaped clamps (13) which fold the polymer coated textile support tape (12) around inner metal coupling elements (14). When the coupling elements in the stringer joined together a seal is formed by the coated textile tape (11) that prevents air or fluid getting in from the top or bottom surface of the slide fastener. This fastener being metal is heavy and has a very poor life when subjected to load. Also as the coupling elements are made of individual metal components, even if one coupling element damaged the slide fastener becomes inoperable. As individual elements are formed, clamped in the support tape and then riveted leads to poor productivity and high cost of production.

The embodiment as shown in fig.2 – consists of a continuous coil slide fastener which is encapsulated with a thermo plastic resin except the heads of coupling coil (23). We can note in the cross section, the entire area of joined coil is covered by thermoplastic resin except mating coil heads (24) . The tape (21) also coated with thermoplastic resin (22). As the chain is encapsulated when it is joined, a seal is formed by the encapsulated chain coated and tape (22) that prevents air or fluid getting in from top or bottom surface of the slide fastener. This gives higher cross wise strength and also higher Airtight and fluid tightness. But this has limitation of flexibility and thus cannot be fixed for a garment that needs bending or in a garment where needs curved operation of zip fasteners. As this has rectangular cross section, this slider rubs over encapsulated surface and hence the life of the fastener is less.

Further this fastener has a poor sealing property in the region of top end when the fastener is closed, as the profile of slider (34) has to completely match the top stop (36) profile and when docked at this region it should be completely sealed. But when it is subjected to pressure, the stress makes slider to deflect from its position for which reinforcement is to be provided with cross suspension (31) as shown in Fig 3. As the slider (34) bottom flange (33) has also move in and out of the cross suspension, a gap (35) has to be provided to facilitate this movement. Due to this cross suspension is ineffective and the sealing gets affected.

There has been therefore a need for a nonmetallic continuous filament Airtight / Fluidtight slide fastener that would give high cross wise breaking strength, better flexibility, higher hermetical seal along the chain and also at the ends of the fastener.

There are many patents relating to prior art. Some of them are pasted below: -

US 8112848
A slider for a fluid tight slide fastener that has upper and lower plates joined together by a guide post. A guide plate is formed on the guide post to cooperate with the upper and lower plates, to guide the coupling elements and sealing lips of the slide fastener into engagement in conjunction with side flanges on the upper and lower plates. The slider is integrally formed; such as by die casting or moulding. To facilitate moulding the guide plate may be thickened at its leading end and provided with a tapered edge, and connected to the upper plate by a web at its trailing end.

US 4580321
A fluid-tight slide fastener comprises a pair of slide fastener halves each including a support tape, a row of continuous coupling elements extending longitudinally along the inner edge of the tape on one side thereof, and an elastomeric sealing member overlying the other side of the tape. The tape has a longitudinal ridge substantially defining the inner edge and supporting the row of coupling elements laterally longitudinally by means of stitching threads. A portion of the threads is disposed adjacent to the ridge to prevent the latter from moving remotely from the coupling elements row for thereby supporting the ridge intimately enough to ensure the abuttment of opposed sealing edges of the tapes when the fastener halves are coupled together.

US 4823446
A fluid-tight slide fastener stringer has a fluid-tight tape including a longitudinally non-stretchable and transversely stretchable woven or knit fabric wholly covered with a layer of elastic rubber or synthetic resin. The tape has non-stretchable warp inlaid threads and stretchable weft inlaid threads. The laterally stretchable tape serves as a shock absorber for reducing the intensity of external lateral pulling forces exerted on the tape.

US 4780937
A fluid-tight slide fastener comprises a pair of stringers each having a water-proof support tape and a row of coupling elements mounted on and along a bent inner longitudinal edge of the support tape, a slider slidably mounted on the two rows of coupling elements to take the latter into and out of coupling engagement with each other to close and open the slide fastener, and a top end stop mounted on upper ends of the support tapes and having embedded therein a length of the folded edges. The bent inner longitudinal edge has throughout the length thereof a pair of upper and lower sealing abutments disposed on opposite sides of an intermediate portion folded around the row of coupling elements. The upper sealing abutments are spaced from one another by a first distance substantially equal to the width of a diamond of the slider while the lower sealing abutments are spaced from one another by a second distance smaller than the width of the slider diamond. With these spacings between the sealing abutments, the slider is allowed to move in the fastener closing direction to assure full closure of the slide fastener without affecting the fluid-tight property of the slide fastener.

US 4888859
A water-tight slide fastener is disclosed, which comprises a pair of support tapes each coated on one surface with a water-resistant material and a row of coupling elements mounted on each of the tapes along its longitudinal edge. The spaces or gaps defined in the row of elements being completely filled by a filling core when the latter swells in contact with a liquid to prevent entry of the liquid into a garment to which the fastener is applied.

US 5438744

An automatic finishing method for an airtight and waterproof slide fastener, comprising the steps of: supplying each of a pair of slide fastener chains, which has coupling elements attached to a waterproof fastener tape by clamp elements, by a pair of toothed supply rollers meshing with the clamp elements of the respective slide fastener chain; and threading the slide fastener chains through a slider situated on a travelling path of the slide fastener chains for interengaging the slide fastener chains and then discharging the interengaged slide fastener chains from the slider.

US 4607416

A fluid-tight slide fastener comprises a pair of stringer tapes each having an inner edge region, an outer edge region and a stretchable region intermediate between the two edge regions which are non-stretchable. The intermediate stretchable region yieldingly takes up any transverse stresses which would otherwise act upon the inner edge region to split apart the fastener halves and produce leakage therethrough.

US 3990130

Two paralleled fastener tapes are provided on their front and back surfaces with engagement pieces to close and open the tapes, as well as a locking device to fix the slider having inversed V shaped arms at one end. On both sides of the slider are provided hooks to close the arms by engaging the tips of the arms of the locking device, so that a complete airtightness is maintained in the airtight slide fastener when the fastener is closed against any of the pressures applied from the directions of the back or the front of the tapes.

US 4513482

A fluid-tight slide fastener stringer comprising a support tape made of a fluid-tight soft material, and a row of discrete coupling elements mounted on the tape along an inner longitudinal edge portion thereof. Such tape margin is folded so as to provide therealong a contact portion engageable with a corresponding contact portion of a like companion stringer to effect a fluid-tightness between the two stringers. In order to absorb or reduce undue stress exerted on the individual coupling elements, each coupling element has a slot extending parallel to the general plane of the stringer transversely through the whole width of a coupling head portion and also extending longitudinally of the same coupling element through the coupling head portion into a base portion.

US 3501816

A slide-fastener assembly having a pair of interengageable elastomeric sealing strips encapsulating respective helicoidal or meandering coupling elements with a coating on the stringer tapes wherein the slide-fastener halves are originally laterally reversed with respect to one an other (and their normal positions) and interconnected for extrusion of the elastomeric material therearound, then separated and reconnected in their normal orientation whereby overhanging portions of the strips of high sealing effectiveness, are formed. The sealing strips include wedge-shaped formations on opposite sides of the assembly.

US 2615224

A self-contained closure unit for garments and the like comprising two slide fasteners assembled one on the other, each fastener comprising a pair of companion stringer tapes carrying rows of fastener elements along their adjacent edges which define the fastener opening and a slider for engaging and disengaging elements, a tape of one fastener and ‘the opposite tape of the other fastener having greater width than their companion tapes whereby fastener openings are offset laterally from the longitudinal center line of the closure unit and the opening of each fastener is covered by the wider tape of the other fastener, and sealing means completely filling the space between the two fasteners, sealing means comprising two strips of resilient sealing material whose adjacent edges are complementally formed so as to sealingly engage one with the other generally: along longitudinal center line, each strip being carried by the wider tape of one fastener element and having width not substantially less than the width of wider tape whereby it also covers ‘the opening ‘ of the other fastener, the faces of the sealing‘ strips adjacent the fastener openings having channels for accommodating the fastener elements and sliders of the respective fasteners.

US 3389441

A water-tight slide fastener in which helicoidal or meandering continuous coupling elements have spaced con vex heads engaging respective continuous strips of elastomeric material along the other coupling element having outwardly concave portions between the heads and dished sockets complementarily engaging the heads of the other coupling element and resiliently compressible thereby.

OBJECTS OF THE INVENTION:

The basic object of present invention is thus directed to provide continuous coil type Air and Fluid tight slide fastener that would on one hand provide higher breaking strength, higher Air and fluid tightness, flexible and also provide long life.

Another object of the invention to provide non metallic Air and fluid tight that would be corrosion proof, work in higher temperature range both in hot and cold.

A still further object of the invention is directed to provide fire retardant Air and fluid tight fastener that would meet industrial safety requirements.

Yet further object of the invention is to provide high seal on top ends of the fastener with cross suspension, so that sealing property is improved.

Various modifications of the disclosed objects, as well as alternate objects of the subject matter, will become apparent to persons skilled in the art upon reference to the description of the subject matter, It is therefore contemplated that such modifications can be made without departing from the spirit and scope of the present subject matter as defined.

DETAILED DESCRIPTION OF THE INVENTION:

Thus according to the basic aspect of the present Invention, the Air and Fluid tight Slide fastener as shown in Fig 4,comprises of coupling elements(43) of continuous coil type secured to the folded edge(47) of the opposed support tapes ,the joined chain of the fastener fully encapsulated(42) with thermoplastic resin with the support tapes(41) coated with thermoplastic .The thermoplastic resin masses gets filled fully in between the respective mating coupling elements of the stringers and when joined the both the mating heads of coupling elements in the stringers mate tightly to one another when brought together by the slider. This joined chain is encapsulated on top, side and inward bent gap (48)of both the stringers. After encapsulation a hair line trim is made so that the stringers are separated to facilitate opening and closing of chain through a slider and at the same time due to property of thermoplastic resin when closed seal tightness is established in spite of slit. .The trimmed area becomes a seal once the stringers are joined due to resilient property of thermoplastic resin. As this profile at the bottom where the slider (65) moves is bent inside, the slider does not rub over all the surface. Additional seal is provided by the thin mating cross section, gives more flexibility without compromising quality of seal. The stringers with coupling elements can also be coated with thermoplastic resin individually (Fig.5) and then joined together to form chain, the lips (49) formed while coating stringers provide seal function.

The slide fastener structure in which sealing strips formed either by hair line slit in the fully encapsulated chain or by encapsulating individual stringers, mate with one another with considerable force to provide a good seal to provide the necessary air and fluid tightness.

According to another aspect of the invention, the encapsulation is done either in the joined chain or in the individual stringer by means of extrusion process with properly designed dies so that that complete chain or stringer is excepting the heads of mating elements are filled with masses of thermoplastic so that opening and closing of chain can be facilitated.

Another feature of this invention is it would facilitate improvement in the seal strength at the end part where slider is seated as shown in the figure 6. Top ends can extend further to operating opening of fastener and the length this extended can be hermetically sealed by providing a reinforcement with a rigid fabric in the extended width of slide fastener.

BRIEF DESCRIPTION OF ACCOMPANYING FIGURES

The above and other features, aspects and advantages would be better understood with the accompanying figures where:

Fig 1 illustrates the design of an existing Air and Fluid tight fasteners with individual metal coupling elements available in prior art as explained in section 1.
PART NUMBER PART NAME
11 Textile Tape
12 Coated Textile support tape
13 U shaped clamps
14 Metal Coupling elements

Fig 2 illustrates the design of an existing Air and Fluid tight slide fastener with continuous coil coupling elements available in prior art as explained in section 1

PART NUMBER PART NAME
21 Textile Tape
22 Thermoplastic resin
23 Coupling coil
24 Mating coil heads

Fig 3 illustrates the defect in the present prior art as shown Fig 2 where in the seal strength at the slider seating end is poor due to the opening given in backing member as explained in section 1

PART NUMBER PART NAME
21 Textile Tape
22 Thermoplastic resin
23 Coupling coil
31 Cross suspension
33 Bottom flange of slider
34 Slider
35 Gap in cross suspension
36 Top stop end

Fig 4 illustrates the proposed design of Air and Fluid tight fastener which overcomes the disadvantages in prior art 1 and 2.

PART NUMBER PART NAME
41 Coated textile support tapes
42 Encapsulated chain of fastener
43 Coupling elements of continuous coil
47 Folded edge of coated textile tape
49 Lips

Fig 5 illustrated details of expanded view of individual stringers to show filling of thermoplastic resin inside the coupling elements to establish the sealing function.

PART NUMBER PART NAME
41 Coated textile support tapes
42 Encapsulated chain of fastener
43 Coupling elements of continuous coil
47 Folded edge of coated textile tape
48 Inward bent gap
49 Lips
51 Stringers

Fig 6 illustrates details of the design of strength improvement achieved in the proposed design.

PART NUMBER PART NAME
41 Coated textile support tapes
42 Encapsulated chain of fastener
43 Coupling elements of continuous coil
64 Cross suspension seal
65 Slider
66 Cross suspension support

The invention has been described and illustrated with few embodiments and plurality of aspects. However these embodiments shall not restrict the scope of the invention. All modifications and variations as obvious to skilled persons shall be within the sport and scope of the invention.