System and method for sealing electrical terminals
10103458 ยท 2018-10-16
Assignee
Inventors
- Sunny Sethi (Castro Valley, CA, US)
- Vijay Daga (Sunnyvale, CA, US)
- Kavitha Bharadwaj (Fremont, CA, US)
- Ting GAO (Palo Alto, CA, US)
Cpc classification
H01R4/723
ELECTRICITY
International classification
Abstract
A system and device for sealing a plurality of electrical wires to a wire attachment portion of an electrical terminal, wherein a shrinkable tubing is placed over the plurality of electrical wires such that one end thereof extends over the wire attachment portion of the electrical terminal. A band of the high viscosity sealant/adhesive is placed within the heat shrink tubing adjacent to the edge of heat shrink tubing. A band of the low viscosity sealant/adhesive is placed within the heat shrink tubing. Upon the application of heat to the device, the shrinkable tubing starts to recover, the high viscosity sealant/adhesive seals the edge of the shrinkable tubing and the low-viscosity sealant/adhesive flows across and through the plurality of electrical wires to create a seal. The high viscosity sealant/adhesive prevents flow of the low-viscosity sealant/adhesive from contaminating the electrical terminal.
Claims
1. A system for sealing an electrical terminal, comprising: (a) a device for sealing a plurality of electrical wires to a wire attachment portion of the electrical terminal, wherein the device further includes: (i) a shrinkable tubing having a predetermined length, wherein the shrinkable tubing has been placed over the plurality of electrical wires such that one end thereof extends over the wire attachment portion of the electrical terminal; (ii) a band of a high viscosity sealant/adhesive, placed within the shrinkable tubing adjacent to an edge of the shrinkable tubing, (iii) a band of a low viscosity sealant/adhesive placed within the shrinkable tubing and adjacent to the high viscosity sealant/adhesive such that low viscosity sealant/adhesive is further away from the edge of the shrinkable tubing, (b) wherein upon an application of heat to the device after installation of the device over the electrical terminal, the shrinkable tubing starts to recover, the high viscosity sealant/adhesive seals the edge of the shrinkable tubing and the low-viscosity sealant/adhesive flows across and through the plurality of electrical wires creating a seal, wherein the high viscosity sealant/adhesive prevents flow of the low-viscosity sealant/adhesive from contaminating the electrical terminal.
2. The system of claim 1, wherein the band of the high viscosity sealant/adhesive is a circular ring.
3. The system of claim 1, wherein the band of the low viscosity sealant/adhesive is a circular ring.
4. The system of claim 1, wherein the band of the high viscosity sealant/adhesive and the band of the low viscosity sealant/adhesive are circular rings.
5. The system of claim 1, wherein the shrinkable tubing is either single-walled tubing or double-walled tubing.
6. The system of claim 1, wherein the high-viscosity sealant/adhesive has a viscosity that is greater than 20 Pa.Math.s at 120 C.
7. The system of claim 1, wherein the low-viscosity sealant/adhesive is a cross-linkable low-viscosity sealant/adhesive.
8. The system of claim 1, wherein the high viscosity sealant/adhesive includes a hot melt thermoplastic sealant; a polyolefin copolymer-based sealant; a polyamide-based sealant; a thermoplastic elastomer-based sealant; a polyolefin and polyamide mixture-based sealant; a polyolefin and polyolefin copolymer mixture-based sealant; a polyolefin copolymer and polyamide mixture-based sealant; a fluoropolymer sealant, or combinations thereof.
9. The system of claim 1, wherein the low viscosity sealant/adhesive includes a hot melt thermoplastic sealant; a polyolefin copolymer-based sealant; a polyamide-based sealant; a thermoplastic elastomer-based sealant; a polyolefin and polyamide mixture-based sealant; a polyolefin and polyolefin copolymer mixture-based sealant; a polyolefin copolymer and polyamide mixture-based sealant; a fluoropolymer sealant, or combinations thereof.
10. The system of claim 1, wherein the shrinkable tubing, the high-viscosity sealant/adhesive and the low-viscosity sealant/adhesive are assembled prior to placement of the device over the electrical terminal.
11. The system of claim 1, wherein the shrinkable tubing, the high-viscosity sealant/adhesive and the low-viscosity sealant/adhesive are assembled after placement of the device over the electrical terminal.
12. The system of claim 1, wherein an additional band of a sealant/adhesive is positioned on the shrinkable tubing and is spaced from the band of the low viscosity sealant/adhesive, wherein the band of the low viscosity sealant/adhesive is positioned between the band of the high viscosity sealant/adhesive and the additional band of the sealant/adhesive.
13. A system for sealing an electrical terminal, comprising: (a) a device for sealing a plurality of electrical wires to a wire attachment portion of the electrical terminal, wherein the device further includes: (i) a shrinkable tubing having a predetermined length, wherein the shrinkable tubing has been placed over the plurality of electrical wires such that one end thereof extends over the wire attachment portion of the electrical terminal; (ii) a high viscosity sealant/adhesive sleeve having high viscosity sealant/adhesive, the high viscosity sealant/adhesive sleeve positioned proximate to an edge of the shrinkable tubing, (iii) a low viscosity sealant/adhesive sleeve having a low viscosity sealant/adhesive, the low viscosity sealant/adhesive sleeve positioned further away from the edge of the shrinkable tubing than the high viscosity sealant/adhesive sleeve, (b) wherein upon an application of heat to the device, the high viscosity sealant/adhesive melts and flows forming a barrier, the low viscosity sealant/adhesive melts and flows across the plurality of wires filling any present air voids, and the shrinkable tubing encapsulates the plurality of electrical wires, substantially sealing the melted low viscosity sealant/adhesive and the high viscosity sealant/adhesive in the shrinkable tubing.
14. The system of claim 13, wherein the high viscosity sealant/adhesive sleeve is a slit sealant/adhesive sleeve.
15. The system of claim 13, wherein the low viscosity sealant/adhesive sleeve is a slit sealant/adhesive sleeve.
16. The system of claim 13, wherein the high viscosity sealant/adhesive sleeve and the low viscosity sealant/adhesive sleeve are installed in situ.
17. The system of claim 13, wherein the shrinkable tubing is either single-walled tubing or double-walled tubing.
18. The system of claim 13, wherein the high-viscosity sealant/adhesive has a viscosity that is greater than 20 Pa.Math.s at 120 C.
19. The system of claim 13, wherein the low-viscosity sealant/adhesive is a cross-linkable low-viscosity sealant/adhesive.
20. The system of claim 13, wherein the high viscosity sealant/adhesive includes a hot melt thermoplastic sealant; a polyolefin copolymer-based sealant; a polyamide-based sealant; a thermoplastic elastomer-based sealant; a polyolefin and polyamide mixture-based sealant; a polyolefin and polyolefin copolymer mixture-based sealant; a polyolefin copolymer and polyamide mixture-based sealant; a fluoropolymer sealant, or combinations thereof.
21. The system of claim 20, wherein the low viscosity sealant/adhesive includes a hot melt thermoplastic sealant; a polyolefin copolymer-based sealant; a polyamide-based sealant; a thermoplastic elastomer-based sealant; a polyolefin and polyamide mixture-based sealant; a polyolefin and polyolefin copolymer mixture-based sealant; a polyolefin copolymer and polyamide mixture-based sealant; a fluoropolymer sealant, or combinations thereof.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) The accompanying drawings, which are incorporated into and form a part of the specification, schematically illustrate one or more exemplary embodiments of the invention and, together with the general description given above and detailed description given below, serve to explain the principles of the invention, and wherein:
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DETAILED DESCRIPTION OF THE INVENTION
(23) The description of illustrative embodiments according to principles of the present invention is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description. In the description of embodiments of the invention disclosed herein, any reference to direction or orientation is merely intended for convenience of description and is not intended in any way to limit the scope of the present invention. Relative terms such as lower, upper, horizontal, vertical, above, below, up, down, top and bottom as well as derivative thereof (e.g., horizontally, downwardly, upwardly, etc.) should be construed to refer to the orientation as then described or as shown in the drawing under discussion. These relative terms are for convenience of description only and do not require that the apparatus be constructed or operated in a particular orientation unless explicitly indicated as such. Terms such as attached, affixed, connected, coupled, interconnected, and similar refer to a relationship wherein structures are secured or attached to one another either directly or indirectly through intervening structures, as well as both movable or rigid attachments or relationships, unless expressly described otherwise. Moreover, the features and benefits of the invention are illustrated by reference to the preferred embodiments. Accordingly, the invention expressly should not be limited to such preferred embodiments illustrating some possible non-limiting combination of features that may exist alone or in other combinations of features, the scope of the invention being defined by the claims appended hereto.
(24) Exemplary embodiments of the present invention are now described with reference to the Figures. Reference numerals are used throughout the detailed description to refer to the various elements and structures. Although the following detailed description contains many specifics for the purposes of illustration, a person of ordinary skill in the art will appreciate that many variations and alterations to the following details are within the scope of the invention. Accordingly, the following embodiments of the invention are set forth without any loss of generality to, and without imposing limitations upon, the claimed invention.
(25) With reference to the Figures,
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(28) With regard to testing device 200, no adhesive was observed to have migrated onto terminal attachment portion 12 after recovery of the device from an infrared oven. Device 200 passed forced-air leak tests and adhesive drip tests wherein device 200 was kept in an oven at 125 C. for more than 24 hours. Second piece of heat shrink tubing 204 was determined to be capable of recovery in as few as 15 seconds in an infrared oven, thereby effectively creating blockage to any significant adhesive flow out of the device.
(29) The sealants/adhesives used with the present invention are designed to exhibit a low-melt viscosity so that these materials are capable of flowing between and around multiple electrical wires and providing robust sealing of an electrical terminal. The sealants/adhesives are also capable of being reheated to temperatures of up to 125 C. without running or dripping. These characteristics may be achieved through the use of high-speed cross-linking materials, high-temperature melting polymers, or a combination of both. Regarding cross-linking materials, the adhesives are capable of sufficiently cross-linking under predetermined cure conditions and upon reheating, the resultant cross-linked geometry provides seal stability. Regarding high-temperature melting polymers, the adhesives typically include a base system that melts at temperatures above 125 C. or show very little flow below 125 C. In general, the adhesive system exhibits low viscosity once molten, but maintains its form factor at temperatures below 125 C. An example of a suitable high-temperature melting adhesive is Technomelt PA 7901 (Loctite 7901 Hysol Hot Melt Adhesive; Henkel) with 0-1% CB (carbon black), which is a low viscosity polyamide used extensively for potting and encapsulating. An example of a suitable cross-linking sealant appears in TABLE 1, below. Three examples of suitable high-temperature melting systems appear in TABLES 2-4 below. The following adhesives/sealants are also compatible with this invention: hot melt thermoplastic sealants such as polyolefin-based sealants (e.g., wherein the base polymer is polyethylene (PE) metallocene-formed PE, maleic anhydride functionalized PE, glycidyl methacrylate functionalized PE, or combinations thereof); polyolefin copolymer-based sealants (e.g., wherein the base polymer is ethylene-vinyl acetate copolymer (EVA)); polyamide-based sealants; thermoplastic elastomer (TPE)-based sealants; a polyolefin and polyamide (PA) mixture-based sealant; a polyolefin and polyolefin copolymer mixture-based sealant (e.g., PE:EVA in weight ratios 95:5, 90:10, 75:25, or 50:50); a polyolefin copolymer and polyamide mixture-based sealant (e.g., EVA:PA in weight ratios of 95:5, 90:10, 75:25, or 50:50); a fluoropolymer or combinations thereof. Different sealants or sealant mixtures with similar characteristics may be also utilized with this invention. In the context of this invention, the term sealant includes and encompasses adhesives such as hot melt adhesives and other types of adhesives. In the context of this invention, sealant or adhesive melt refers to the state of a semi-crystalline polymer or material over its melting point and/or the state of an amorphous material above its softening point, as determined by tools and techniques such as a rheometer.
(30) TABLE-US-00001 TABLE 1 Formulation I: Cross-Linkable Adhesive Chemical Description Wt % Polyolefins (e.g., HDPE, ethylene 63%-90% vinyl acetate) Viscosity modifiers 0-20% Organic peroxide 1-9% Cross-linking promoters (e.g., 0-10% Trimethallyl isocyanurate (TAIC) or Trimethylolpropane Trimethacrylate (TMPTMA)) IR absorbing pigments (e.g., carbon 0-2% black) Stabilizers and antioxidants 0-4% (e.g., sterically hindered phenolic antioxidants) Metal deactivators 0-2%
(31) TABLE-US-00002 TABLE 2 Formulation II. High-Temperature Resistance Adhesive Chemical Description Wt % EVA/PO/Waxes 89%-95% untreated and synthetic 0-10% fumed silica IR absorbing pigments (e.g., 0-2% carbon black) Stabilizers and antioxidants 0-4% (e.g., sterically hindered phenolic antioxidants) Metal deactivators 0-2%
(32) TABLE-US-00003 TABLE 3 Formulation III. High-Temperature Resistance Adhesive Chemical Description Wt % Polyamide 89%-95% Fumed silica 0-10% IR absorbing pigments (e.g., 0-2% carbon black) Stabilizers and antioxidants 0-4% (e.g., sterically hindered phenolic antioxidants) Metal deactivators 0-2%
(33) TABLE-US-00004 TABLE 4 Formulation IV: High-Temperature Resistance Adhesive Chemical Description Wt % Acrylate polymer 89%-95% Fumed silica 0-10% IR absorbing pigments (e.g., 0-2% carbon black) Stabilizers and antioxidants 0-4% such as sterically hindered phenolic antioxidant Metal deactivators 0-2%
(34) In addition to the embodiments described above, other geometric variations for the terminal sealing device of the present invention are possible. In one alternate embodiment, a dual-component tape is wrapped around the wire attachment portion of the electrical terminal. This system also includes a layer of pressure-sensitive adhesive (PSA), which allows installation of the tape on an electrical terminal before heat shrink tubing is placed over electrical wires that are attached to the electrical terminal. The dual-component tape includes a non-melting profile, which may be heat-shrinkable tape that is oriented toward the terminal attachment portion of the assembly and an adhesive ring that is positioned over the wire attachment portion of the assembly. One edge of the adhesive may be low flow (high viscosity), which is attained by partially cross-linking one edge of the adhesive system or through the use of a different adhesive having a higher viscosity (e.g., greater than 500 Pa.Math.s at 120 C.). The viscosity of the sealant/adhesive materials described herein was measured using a rotation rheometer. In this method, a small disk of sealant material (e.g., 1.5 mm-1.8 mm thick, 25 mm diameter disk) is placed between plates of the rotation rheometer and sheared (oscillatory mode) by means of a rotational motion frequency of 6.28 rad/sec. The temperature of the sealant material is gradually increased from 60 C. to 140 C. at a rate of 5 C./min and 5% strain and the complex viscosity is measured as a function of temperature.
(35) In still another embodiment, the low-temperature heat shrinkable edge tubing (see, for example, item 204 in
(36) In still other embodiments of this invention, the device includes only a single piece of heat shrinkable tubing, an adhesive ring, and the heat source (e.g., an infrared oven) used to shrink the tubing includes multiple heating elements, wherein a first heating element (operating at a first temperature) is placed in close proximity to the terminal attachment portion of the electrical terminal and a second heating element (operating at a second temperature lower than the temperature of first heating element), is placed at a predetermined distance away from the terminal attachment portion of the electrical terminal and further away from the tubing itself. The tubing closer to the ring portion shrinks more quickly than the tubing further away from the ring terminal due to the different temperature profile of the heating system. In still another embodiment, the device includes only a single piece of heat shrinkable tubing and is passed through a heating system (e.g., an infrared oven) on a conveyer, with the terminal attachment portion entering first, causing the tubing near the ring portion to shrink first and the following length of tubing to shrink secondarily. The speed of the conveyor can be tuned for desired recovery at the ring terminal end to prevent the adhesive from oozing out of the device.
(37) With reference to
(38) With reference to
(39) With reference to
(40) The high viscosity sealant/adhesive on the high viscosity sealant/adhesive sleeve 504 has a flow behavior such that it conforms to the surface of the wire attachment portion and the surface of the plurality of wires without significantly flowing out of the desired region. This is achieved by using a sealant/adhesive which has a high inherent viscosity or which could attain high viscosity by methods like cross-linking (where the cross-linking induces viscosity increase at a higher rate than an ooze out rate). Ooze out refers to a phenomenon wherein excess sealant/adhesive flows out of the sealing zone onto the electrical terminal, thus contaminating the electrical terminal. The high viscosity sealant/adhesive sleeve 504 creates a barrier and prevents ooze out of the low viscosity sealant/adhesive of the low viscosity sealant/adhesive sleeve 506. The low viscosity sealant/adhesive of the low viscosity sealant/adhesive sleeve 506 has a low viscosity which allows it to displace air efficiently inside the substrate intended to be sealed. The low viscosity sealant/adhesive sleeve 506 creates a robust seal. A robust seal includes seals which provide an impermeable barrier between two environments. In the current case, robust sealing deters fluid flow across the barrier.
(41) Upon the application of heat (e.g., in an infrared oven for 30 seconds or other time period) the high viscosity sealant/adhesive 504 melts and flows across the wire attachment portion 14 and surface of the plurality of wires 16 to form the barrier. The low viscosity sealant/adhesive 506 melts and flows across the plurality of wires 16 filling any present air voids. The shrinkable tubing 502 shrink to encapsulate plurality of electrical wires and wire attachment portion of the electrical terminal, thereby substantially sealing the melted sealant/adhesive within the shrinkable tubing 502. During the heating process, the high viscosity sealant/adhesive sleeve 504 effectively constrains the flow of sealant/adhesive in the direction of the terminal attachment portion 12, thereby reducing or preventing any problematic contamination of the terminal attachment portion 12. While in some instances a small amount of sealant/adhesive may travel onto terminal attachment portion 12, the amount will be insignificant with regard to the functioning of the electrical terminal. In some embodiments, the components of device 500 are provided individually (as opposed to pre-assembled) and are assembled on the electrical terminal and wire assembly just prior to creating the desired seal. For example, the piece of shrinkable tubing 502, the high viscosity sealant/adhesive sleeve 504, and the low viscosity sealant/adhesive sleeve 506 may be installed in situ. The sleeves 504, 506 may be, but are not limited to slit sealant/adhesive sleeves. While the sleeves are shown positioned proximate the wire attachment portion, the sleeves may be positioned at any desired location.
(42) With reference to
(43) The band of the first sealant/adhesive 604 has a flow behavior such that it conforms to the surface of the wire attachment portion or surface of the plurality of wires without significantly flowing out of the desired region. This is achieved by using a sealant/adhesive in the band of the first sealant/adhesive 604 which has a high inherent viscosity or which could attain high viscosity by methods like cross-linking (where the cross-linking induces viscosity increase at a higher rate than an ooze out rate). The band of the first sealant/adhesive 604 creates a barrier and prevent ooze out of the second sealant/adhesive. The band of the second sealant/adhesive 606 has a low initial viscosity which allows it to displace air efficiently inside the substrate intended to be sealed. The band of the second sealant/adhesive 606 creates a robust seal. The band of the first sealant/adhesive 604 has a higher viscosity than the band of the second sealant/adhesive 606 prior to installation.
(44) Upon the application of heat (e.g., in an infrared oven for 30 seconds or other time period) after installation of the shrinkable tubing 602 over the electrical terminal, the band of the first sealant/adhesive 604 melts and flows across the wire attachment portion or surface of the plurality of wires to form the barrier. In addition, the band of the second sealant/adhesive 606 melts and flows across the plurality of wires filling any present air voids. The shrinkable tubing 602 shrinks to encapsulate the plurality of electrical wires and the wire attachment portion of the electrical terminal, thereby substantially sealing the melted sealant/adhesive within the shrinkable tubing. During the heating process, the band of the first sealant/adhesive 604 effectively constrains the flow of sealant/adhesive in the direction of the terminal attachment portion, thereby reducing or preventing any problematic contamination of the terminal attachment portion. While in some instances a small amount of sealant/adhesive may travel onto the terminal attachment portion, the amount will be insignificant with regard to the functioning of the electrical terminal. In some embodiments, the components of device 600 are provided individually (as opposed to pre-assembled) and are assembled on the electrical terminal and wire assembly just prior to creating the desired seal.
(45) With reference to
(46) While the present invention has been illustrated by the description of exemplary embodiments thereof, and while the embodiments have been described in certain detail, there is no intention to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. Therefore, the invention in its broader aspects is not limited to any of the specific details, representative devices and methods, and/or illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of the general inventive concept.