WO1994016884A1

WO1994016884A1 - Double reticulate tape

Info

Publication number: WO1994016884A1
Application number: PCT/US1994/000555
Authority: WO
Inventors: John Stewart
Original assignee: Raychem Corporation
Priority date: 1993-01-28
Filing date: 1994-01-20
Publication date: 1994-08-04
Also published as: EP0695235A1; CA2151480A1; JPH08505824A

Abstract

A sealing delivery system including a layer of sealing material juxtaposed with at least one layer of open cell material, typically in the form of an elongate tape. Application of a force along the longitudinal axis of the tape produces a longitudinal component of tension and a perpendicular component of compression such that the sealing material penetrates through interstices of the open cell layers to form a tacky surface for sealing. Upon release of the force, the sealing material reenters back through the interstices of the open cell layer, resulting in a relatively non-tacky, easily handleable surface.

Description

DOUBLE RETICUIATE TAPE

Field of Invention

5 This invention relates to a system for delivering a sealing material, a tape, an article for providing protection against moisture and a method of protecting a wire bundle from moisture.

Background of the Invention

10

In autos, light trucks, airplanes, boats, and telephone systems, many wire bundles traverse from a compartment, such as the passenger compartment of a vehicle, to unprotected areas, such as under the hood. A rubber grommet typically seals the outside of the wire bundle to the Έ sheet metal. Under the grommet, the wire bundle must be sealed in order to prevent water from wicking along the wires into the passenger compartment. Until now, no effective and economical method to seal the wire bundle has been found.

2) The automotive industry has attempted a number of solutions to this problem. The most common attempt is mastic and tape. Mastic pads are pushed into the wire bundle and then massaged in an attempt to seal each wire. A tight wrap is then applied. When done properly, this method can seal a wire bundle effectively, but it is messy and can flow at

25 elevated temperatures. Its primary drawback is that it is extremely craft sensitive and permits no quality control for the seal. Additionally, the seal often deteriorates over time under flexing and vibration.

A second attempt at solving this problem for smaller wire bundles 3D is a drip loop formed before the bulkhead penetration. The drip loop takes up considerable space and can be formed only on small bundles.

Often, the location of the wire bundle will be moved to a protected area to prevent water from splashing directly on the bundle. This 35 location is usually not optimal from a routing perspective. Alternatively, a sealed connector can be used instead of penetrating the bulkhead with the wire bundle. This method is particularly expensive.

An additional alternative includes a two-piece plastic box in the form of a hardshell grommet. The bottom piece is used to fix in place an engineering plastic comb. The individual wires are fed through the comb during harness assembly. The top of the box is then snapped in place and the box, with harness, is transported to a water cooled "nest." Hot melt adhesive is injected into the box. This method is cumbersome and bulky, but provides a reasonably effective seal and is relatively inexpensive.

Articles and/or compositions are known that may be used as a sealant and void-filler to protect a substrate in a corrosive, moist and adverse environment. These articles and/or compositions include simple tape wrappings as well as heat recoverable materials. One example is disclosed in U.S. Patent No. 3,086,242 by Cook, assigned to the assignee of the present invention, which is completely hereby incorporated by reference for all purposes. Other articles and/or compositions that are advantageously employed under appropriate conditions are oils, greases and adhesives.

Gels have also been used as sealing members in compression, such as described in U.S. Patent Application No. 07/762,533 filed on January 14, 1992 entitled "Sealing Member and Methods of Sealing" by Collins et al which is a continuation-in-part of U.S. Patent Application No. 07/584,320 filed on September 18, 1990, assigned to the assignee of the present invention, and which is completely hereby incorporated by reference for all purposes. A layer of encapsulant or gel is sandwiched between two constraining layers of closed cell foam. The entire member is disposed within a hollow member for applying the compressive force. This compressive force must be applied subsequent to positioning the member for sealing.

One additional such article for protection of a substrate is described in U.S. Patent No. 4,865,905 by Uken, assigned to the assignee of the present invention, which is completely hereby incorporated by reference for all purposes. This article includes a flexible matrix which is impregnated with gel. Exposed surfaces are covered by a release paper which is removed before the article is applied. This provides an effective seal. However, the tacky surface of the impregnated gel sticks to itself and the hands of the operator, resulting in messy application.

5

Summary of the Invention

Juxtaposition of a layer of sealing material and a layer of open cell material provides an improved arrangement for sealing wire bundles. ιo Application of tension to the layered article when wrapped around a bundle of wires causes the encapsulant to move through the layer of open cell material, providing a tacky surface. The terms sealing material and encapsulant refer to the layer of material forming a tacky surface and are used interchangeably hereinafter. A compressive force results from this

15 application of tension combined with a compressive force caused by contact with the wire bundle. This arrangement provides an improved seal for wire bundles; however, one surface of the article remains tacky to the touch. Furthermore, the article must be wrapped about a surface to enable the sealing material to move through the layer of open cell

2) material.

The present invention is directed to a sealing means which allows simple and economical application. The sealing means of the present invention provides a non-tacky surface to the touch, is resealable,

25 reuseable, and can be easily handled. All of the desired sealing attributes of previous encapsulant seals are achieved, with improved results.

A layer of sealing material is disposed between two layers of open cell material. In its relaxed state, the sealing assembly provides a non-

3D tacky surface. Upon application of a force, preferably including a substantially perpendicular component of compression and a substantially longitudinal component of tension, the layer of sealing material moves through the layers of open cell material, resulting in a tacky, easily handleable surface having sufficient volume of sealing εε material to penetrate through the open cell layer and thereby provide the desired sealing effect. The open cell material can be any stretchable material. It is preferably an open cell foam, but can also be any fabric or material having interstices in an open cell arrangement. For example, any lattice structure which can be elongated, whereby an appropriate force would 5 allow the sealing material to move through the interstices to the outer edge to provide a tacky surface at application would be acceptable.

The sealing material is also preferably formed of a stretchable, elongatable material. The open cell layers are preferably stretchable to an 10 extent greater than the extent of stretching of the layer of sealing material. The thickness of the sealing material is preferably between about one and two times the thickness of each layer of open cell material. More preferably, the sealing material is about two times the thickness of each layer of open cell material.

15

Upon release of the force, the sealing material reenters the interstices of the open cell layers, returning to its original location therebetween. The article thus returns to its relatively non-tacky, easily handleable form. In this way, the device of the present invention can be

2) resealed or reused.

The sealing material is preferably a silicone based gel, although various polyurethane or thermoplastic based gel materials can also be used. The sealing material may also be a layer of material impregnated 25 with gel.

In the preferred embodiment, the sealing means is in the form of a tape, the intended application of which is to provide protection against moisture wicking about a substrate. The thickness of the layer of sealing

3D material is sufficient to fill gaps surrounding the substrate. However, the present invention may be used for any sealing application.

The present invention is also directed to a method of protecting a wire bundle from moisture comprising:

35

(a) providing a section of tape, wherein the tape comprises at least one layer of encapsulant disposed between at least two layers of open cell material; (b) selecting two individual wires of the wire bundle;

(c) pinching the end of the tape between the wires;

(d) wrapping the tape around both wires;

(e) applying a force to the tape such that the encapsulant 5 penetrates through the open cell layers, thereby providing a moisture seal around the wires;

(f) selecting an additional wire from the bundle;

(g) wrapping a layer of tape around the additionally selected wire; (h) continuing to apply a force to the tape;

10 (i) selecting additional wires from the bundle and repeating steps

(f) through (h) until all wires from the bundle are wrapped.

As described above, the force applied is most preferably a substantially perpendicular component of compression and also -5 preferably includes a substantially longitudinal component of tension. However, the longitudinal component of tension is not required in the present invention. The section of tape wrapped around the protected wire bundle is sufficient to ensure enough encapsulant on the outside of the wire bundle to seal against moisture.

2D

In one form of the particularly preferred embodiment of the invention, a wrap of vinyl tape may be applied to the protected wire bundle to maintain it sealed with encapsulant and to prevent the novel sealing tape from unwrapping. Additionally or alternatively, a compressive force

25 may be applied over the sealed wire bundle to maintain the wire bundle in its sealed condition.

The wires may be positioned in an optimal arrangement so as to prevent wicking thereon.

30

Other features and advantages of the present invention will appear from the following description in which the preferred embodiment has been set forth in detail in conjunction with the accompanying drawings. Brief Description of the Drawings

Fig. 1 is a cross sectional view of the preferred embodiment of a sealing delivery system constructed in accordance with the present 5 invention.

Fig. 2 is a cross sectional view of the invention of Fig. 1 upon application of force.

o Figs. 3A - 3C are schematic cross sectional views of the invention in its preferred application.

Tlwtøilftrt n- -πri tion of the Preferred Embodiment

5 Referring now to the Figures, Figs. 1 and 2 illustrate a sealing delivery system 2 including a center, sealing material layer or encapsulant 4 sandwiched between reticulate layers of open cell material 6, 8. Upon application of a force, preferably a compressive force, to sealing delivery system 2, the sealing material moves through reticulate D layers 6, 8 in the direction of arrow 12. Sealing material 4 moves through reticulate layers 6, 8 to the outer edges 14, 16 of the open cell material, thereby wetting the tape and providing a tacky surface for sealing, as seen at reference numeral 20 in Fig. 2.

5 In the preferred embodiment, sealing delivery system 2 is in the form of a double reticulate tape having a triple layer construction. Reticulate layers 6, 8 and sealing material 4 are, together, stretched in the direction of arrow 10. Each reticulate layer is stretchable, or elongatable, to an extent at least equal to but preferably greater than the D extent of stretching of the sealing material layer 4. When compressed, reticulate layers 6, 8 allow sealing material 4 to penetrate the open structure of the reticulate layers and, thereby provides the wetting and tack properties of previous gel applications. The relative thicknesses of reticulate layers 6, 8 and sealing material 4 is sufficient to fill gaps 5 surrounding the surface to be sealed. The open cell layers 6, 8 stretch elastically with sealing material 4 to allow the tape to be smoothly applied to an uneven surface and thereby conform to the uneven surface. Force in the direction of arrow 10 applied to sealing delivery system 2 includes a substantially longitudinal component of tension along arrow 10 and a substantially perpendicular component of compression as shown by arrows 18. Upon application of the force to tape 2, sealing material 4 5 penetrates through interstices of open cell layers 6, 8 , forming tacky surface 20 for sealing. Upon release of the force, sealing material 4 reenters back through the interstices of open cell layers 6, 8, again resulting in a relatively non-tacky, easily handleable surface, as shown in Fig. 1. Thus, layers 6, 8 are selected to have an adhesive affinity for o sealing material 4 which is less than the cohesive strength of the sealing material.

Reticulate layers 6, 8 are preferably in the form of an open cell foam, more particularly, a polyester urethane foam. However, it is 5 within the scope of the present invention to utilize a fabric material or lattice structure having interstices through which sealing material 4 can move or "ooze." In either latter case, the adhesive affinity of the fabric material or lattice structure is less important.

D The reticulate layers may also be a woven or nonwoven fabric, the fibers of the fabric being natural or synthetic and composed of organic or inorganic material. The fibers may be glass, metal or organic polymer fibers. The fibers of reticulate layers 6, 8 need not themselves be stretchable, so long as the structure can be elongated. For example, a 5 metal mesh material would be suitable for use as a reticulate layer according to the present invention.

Sealing material 4 is preferably a gel, and more particularly an oil extended triblock copolymer. The most preferred gel of the present D invention is constructed of a silicone based gel. In alternate embodiments, the sealing material may be a polyurethane or thermoplastic gel. Two such examples are oil extended Kraton® (styrene-ethylene-butylene-styrene) triblock polymers and oil extended Septon® (styrene-ethylene-propylene-styrene) triblock copolymers. 5

Preferably, sealing material 4 is selected to have an ultimate elongation of at least 100%, especially at least 150% and more preferably at least 200%. The sealing material is also selected to have a voland hardness of between 7.5 and 40 g, especially between 10 and 20 g, and more particularly between 10 and 15 g.

As is apparent, the wetting characteristics of gels which may be used for the present invention differ. Therefore, the choice of open cell foam must be optimized to permit the particular gel utilized to penetrate the interstices of the open cell structure. For example, a softer sealing material will be used with a reticulate material having a smaller average cell size while a harder sealing material may be used with a reticulate material having a larger average cell size. Additionally, the sealing material may be a center layer of foam impregnated with a gel.

Sealing material 4 is bonded, preferably chemically bonded, between reticulate layers 6, 8. A roll of sealing material is joined with two rolls of reticulated tape, thereby forming sealing material layer 4 interposed between reticulate layers 6, 8. Tension of the sealing material and open cell material is sufficiently matched such that tape 2 cures as the joined rolls are assembled. Optimally, each open cell layer 6, 8 has a thickness of 0.030 inches, and a porosity of 100 pores per square inch with a maximum hole diameter of 0.020 inches. The preferred thickness of sealing material 4 differs depending upon the application. For uniform elements to be sealed, the preferred thickness of sealing material layer 4 is 0.030 inches. Thus, the preferred ratio of relative thickness of layers is 1:1:1. For elements to be sealing having varying configurations, the sealing material layer preferably has a thickness of approximately 0.060 inches. In this case, the preferred ratio of thickness of layers is 1:2:1. The relative thicknesses of reticulate layers 6, 8 and sealing material 4 determine the necessary forces to adequately move through the interstices of reticulate layers 6, 8 and provide a sealing effect.

Reticulate tape 2 may be employed in any sealing application. A force applied to the tape, including a substantially perpendicular component of compression 18, causes sealing material or encapsulant 4 to move through the interstices of open cell layers 6, 8, to outer edges 14, 16 of the tape, thereby providing a tacky, sealing surface 20. In the preferred embodiment, the force also includes a substantially longitudinal component of tension, easing movement of the sealing material through the open cell layers. Upon removal of force 10, tape 2 returns to its original configuration shown in Fig. 1. Sealing material 4 reenters back through the interstices of open cell foam layers 6, 8, again resulting in a relatively 5 non-tacky, easily handleable surface.

In the most preferred application, double reticulate tape 2 is used to protect a wire bundle from moisture. A piece of reticulate tape is provided. To seal a bundle of 10 to 15 wires, a piece of tape approximately 0 6 inches is necessary. Referring to Fig. 3, two individual wires, 24, 26 are pulled from the bundle (not shown). The end of the reticulate tape is pinched between the wires, as shown at reference numeral 22. The tape is then wrapped around both wires, as seen in Fig. 3A. Light tension is applied in the direction of arrow 10, causing encapsulant 4 to penetrate 5 reticulate layers 6, 8 , providing a tacky surface at 20 and providing a moisture seal around wires 24, 26. Compressive force 18, as shown in Fig. 2, results from the application of force in the direction of arrow 10. A third wire 28 is selected and pulled from the bundle and placed adjacent outer edge 16 opposite wires 24, 26. The force in the direction of arrow 10 D is maintained. Additional wires, such as wire 30 shown in Fig. 3C, are selected from the bundle and the above steps repeated until all wires from the bundle are wrapped. As the wrapped and sealed bundle grows, multiple wires can be added simultaneously, so long as they are separated by 180 degrees. Once all wires from the bundle are wrapped, 5 an additional turn is made around the wrapped wire bundle to ensure sufficient sealing material on the outside of the bundle to adequately seal, and thereby protect the bundle from moisture.

With large wire bundles, it may be necessary to position the wires D in an optimal arrangement so as to prevent wi eking thereon.

If desired, a member, such as a grommet, for applying a compressive force over the sealed wire bundle maintains the wire bundle sealed with encapsulant. Additionally or alternatively, a wrap of vinyl 5 tape is applied to the bundle to prevent reticulate tape 2 from unwrapping.

Although the preferred embodiment is directed to sealing material sandwiched between two layers of open cell material, it is within the scope of the present invention to provide a sealing material disposed adjacent a single layer of open cell material. The sealing delivery system of the present invention can be employed to address a variety of sealing applications. Variations and modifications can be made to the preferred embodiment without departing from the scope of the present invention, which is limited only by the following claims.

Claims

WHAT IS CLAIMED IS:

1. A sealing delivery system comprising a sealing material sandwiched between layers of open cell material wherein upon application of a force to

5 the system, the sealing material moves through the layers of open cell material for sealing.

2. The system as defined in claim 1 wherein the sealing material and layers of open cell material are stretchable. x>

3. The system as defined in claim 1 wherein each layer of open cell material comprises a layer of foam.

4. The system as defined in claim 1 wherein each layer of open cell 15 material comprises a layer of fabric.

5. The system as defined in claim 1 wherein the sealing material comprises one of a silicone, polyure thane or thermoplastic based gel material.

2D

6. The system as defined in claim 1 for providing protection against moisture about a substrate comprising a tape wherein said sealing material comprises at least one layer of encapsulant, and wherein upon application of said force to the tape, the encapsulant layer moves through

25 the layers of open cell material for sealing about the substrate.

7. The system as defined in claim 6 wherein the thickness of the layer of sealing material is sufficient to fill gaps surrounding the substrate.

3D 8. The system as defined in any one of the preceding claims, wherein said sealing material comprises a gel having a tacky surface, which with said open cell material forms a multi-layer tape having a relatively non- tacky surface, and wherein upon application of said force to the tape, gel of the center layer penetrates through interstices of the open cell layers to

35 form a tacky surface for sealing.

9. The article as defined in claim 8 wherein the open cell sheet layer is selected such that upon release of said force, the gel reenters back through the interstices of the open cell layer, resulting in a relatively non- tacky, easily handleable surface.

10. The article as defined in claim 8 wherein the open cell layers and the center layer are stretchable, the open cell layers being stretchable to an extent greater than the extent of stretching of the center layer.