CA1101170A - Heat-recoverable article - Google Patents
Heat-recoverable articleInfo
- Publication number
- CA1101170A CA1101170A CA290,333A CA290333A CA1101170A CA 1101170 A CA1101170 A CA 1101170A CA 290333 A CA290333 A CA 290333A CA 1101170 A CA1101170 A CA 1101170A
- Authority
- CA
- Canada
- Prior art keywords
- heat
- expansion ratio
- tubular cap
- shrinkable tubular
- section
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Abstract
ABSTRACT
Heat-recoverable articles, especially heat-shrinkable tubular articles, having an open end are formed so that the section adjacent said open end has a lower recovery ratio than a section adjacent thereto, thereby substantially reducing the risk of splitting when the degree of recovery is high or in applications where a high degree of unrecovered strain remains after recovery about a substrate such as a supply line. A
preferred article is a tubular end cap in which the open end section has a larger circumference after unrestrained recovery than the adjacent intermediate section. Such a cap is especially useful for encapsulating the termination of a multi-wire telephone cable.
Heat-recoverable articles, especially heat-shrinkable tubular articles, having an open end are formed so that the section adjacent said open end has a lower recovery ratio than a section adjacent thereto, thereby substantially reducing the risk of splitting when the degree of recovery is high or in applications where a high degree of unrecovered strain remains after recovery about a substrate such as a supply line. A
preferred article is a tubular end cap in which the open end section has a larger circumference after unrestrained recovery than the adjacent intermediate section. Such a cap is especially useful for encapsulating the termination of a multi-wire telephone cable.
Description
B~CKGROUND TO THE INVENTION
This invention relates to heat-recoverable articles.
Heat-recoverable articles, especially heat-shrinkable articles, are now widely used in many areas where insulation, sealing and encapsulation are required. Usually these articles recover, on heating, towards an original shape from which they have been previously deformed, but the term "heat-recoverable" as used herein also includes an article which, on heating, adopts a new configuration, even if it has not been previously deformed.
Heat-recoverahle articles are typically made from polymeric materials exhibiting the property of plastic or elastic memory as described, for example, in U.S. Patents
This invention relates to heat-recoverable articles.
Heat-recoverable articles, especially heat-shrinkable articles, are now widely used in many areas where insulation, sealing and encapsulation are required. Usually these articles recover, on heating, towards an original shape from which they have been previously deformed, but the term "heat-recoverable" as used herein also includes an article which, on heating, adopts a new configuration, even if it has not been previously deformed.
Heat-recoverahle articles are typically made from polymeric materials exhibiting the property of plastic or elastic memory as described, for example, in U.S. Patents
2,027,962, 3,086,242 and 3,957,372. In other articles, as described, for example, in British Patent No. 1,440,524, an elastomeric member such as an outer tubular member is held in a stretched state by a second member, such as an inner tubular member, which, upon heating, weakens and thus allows the elastomeric member to recover.
Such heat-recoverable articles are frequently in the form of heat-shrinkable tubes, caps or boots or other articles having a closed cross-section and one or more open ends. One wi~ely used method of making such articles is to mould a molten, crystalline, thermoplastic polymer into a shape which approx-imates to the shape of the final covering required, cross-link the shaped polymer, heat the cross-linked, shaped polymer to a temperature above its crystalline melting point, expand the hot, cross-linked, shaped polymer, e.g. by a mandrel or ,~
. ~.
.
internal pressure, and cool the polymer in its expanded shape.
The present invention especially relates to such heat-shrinkable articles, including in particular (but not limited to) those made by the process described above.
One serious limitation of such heat-shrinkable articles has been that if too high an expansion ratio (i.e. the ratio of the dimension of the article after expansion to the corres-ponding dimension before expansion) is used in making the article, the article tends to split on expansion or during shrinkage, and we have observed that this problem is partic-ularly noticeable at the open ends of such articles. The problem is especially acute if the article has been cut so as to leave a notch or nick which may propagate on recovery and/
or when the article is caused to recover about a large substrate leaving a large degree of unresolved recovery. In accordance with the present invention, we have discovered that it is advantageous if the or each open end of the article is formed by a section such that, when the article is fully shrunk, the open end is larger than the adjacent portion of the article. In particular we have found that the adjacent portion can then be given a higher expansion ratio than would otherwise be possible without danger of splitting.
BRIEF SUMMARY OF THE INVENTION
The present invention provides a heat-shrinkable tubular cap which comprises an open end section having a first expansion ratio, an intermediate section having a second expansion ratio and an unexpanded closed end section, the second expansion ratio being greater than the first expansion ratio by at least 0.5~
DETAILED DESCRIPTION OF THE INVENTION
As mentioned above, the present invention is espec-ially applicable to heat-shrinkable articles made from materials, especially plastics materials, possessing the property of elastic or plastic memory.
Amongst such heat-shrinkable articles there may especially be mentioned those with a closed cross-section.
The articles are commonly tubular, the term "tubular"
including both hollow cylindrical members and members of irregular and/or varying cross-section as well as those of more cornplex configuration such as ~-shaped, T-shaped and X-shaped members having 3 or 4 ends.
In most cases the open end section will have a larger cross-section after recovery than the adjacent intermediate section which has a substantially greater degree of recovery.
The open end section may have a finite length, for example it may extend over a length of from 1 to 10cm., but, in some cases the article may be given a differential expansion so as to produce an increasing expansion ratio along its length away from the open end and the present invention is, therefore, not limited to heat-recoverable articles having a discrete end region.
It will be appreciated that the end region may be non-recoverable, i.e. it may have an expansion ratio of 1, , 11~11~70 but, in many applications, it will be advantageous for it to exhibit a small degree of heat-recovery. However, in such cases the recovery is preferably less than 100%, more preferably less than 25% (corresponding to expansion ratios of 2 and 1.25, respectively).
On the other hand, in order fully to utilise the advantages of the present invention, the intermediate region generally exhibits a high degree of available recovery.
The expansicn ratios which will, in the absence of end sections as required by the present invention lead to splitting on shrinkage are dependent inter alia on the polymer employed and the thickness. There is seldom a problem with expansion ratios below 2.5, and usually expansion ratios of up to 3.0 can safely be used. Howevever, at expansion ratios of 3.5 or higher splitting is usually a problem and this applies more so at ratios of 4.0, 4.5 and 5Ø Thus the present invention is especially applicable at ratios of from 4 to 6 and above, for example up to 10, i.e. where the amount of avaiLable recovery is from 400% to 1000%, usually from 400% to 600%, especially when the percentage of unresolved recovery after shrinkage is high.
Another factor which is relevant to the problem is the difference between the expansion ratios of the open end region and the intermediate region. Generally speaking, the higher the expansion ratios, the greater should this difference be, but in most cases a difference of at least 1.0 and, most preferably, at least 1.5, will be desirable. The difference should preferably be at least 0.~ times, especially at least 0.5 times, the expansion ratio of the lntermediate region.
It will be appreciated that the heat-shrinkable articles of the present invention may have one or more ends which are closed but which are intended to be opened, for example, by cutting, at a later stage, the invention may also advantageously be applied to such temporarily closed ends.
The preferred articles of the present invention may be prepared from any of the polymers and mixtures of polymers known from the prior art to be useful for the production of heat-shrinkable articles. Generally the articles will be monolithic and of constant com-position throughout, however, laminates of two heat-shrinkable polymers can be used, and the articles can be constructed by joining together, e.g. with adhesive, two or more different parts. Suitable polymers include polyolefins, especially polyethylene, copolymers of ethylene and vinyl acetate, (which are particularly valuable when flexibility is required), copolymers of ethylene and ethyl acrylate, chlorinated or fluorinated polymers, especially polyvinyl chloride, polyvinylidene fluoride and polymers incorporating units derived from polyvinylidene fluoride, hexafluoro-ethyIene and chlorotrifluoroethylene, and rubbers such 7~
such as ethylenepropylerle rubber, chlorinated rubbers (~eoprene) and silicone rubbers which may be used in a blend with a crystalline or glassy polymer such as an olefin polymer~
The internal surface of the articles may be provided with a sealant such as a hot-melt adhesive or a mastic. Especially suitable hot-melt adhesives include for example polyamide materials, ethylene/vinyl acetate copolymers and terpolymers (with or without incorporated waxes) and polyesters. Such materials are described, for example, in British Patent ~o. 1,440,810 and German OS 2,709,717. Also suitable are curable adhesives which also melt and flow upon heating, but which will not afterwards be hot-meltable. There may also be mentioned epoxy resins and conventional mastics such as, for example, those based on butyl and isobutylene rubbers modified with suitable materials known in the art. Obviously the type of sealant employed and the method of its application will depend on the particular requirements in any given case.
Bearing in mind the above discussion it will be appreciated that the shape and design characteristics of the heat-recoverable articles of the present invention will depend on the use intended for them. In some cases, it may be preferable for the open end regions to be thicker than the intermediate high-recovery regions in which case it may be convenient to prepare a moulded article which has (prior to expansion) the same wall thickness throughout so that the ratio of the thickness of the open end section(s) to the thickness of the intermediate section(s) after expansion will be 7~11 substantially the same as the inverse ra-tio of their expansion ratios.
Similarly, the shape, after shrinkage, of the open end region and the intermediate region will be dependent of the relative sizes of the article and of the substrate as well as the expansion ratios of the two regions. Thus both regions may shrink into contact with the substrate along their entire length. More usually, however, the open end section will spontaneously recover on heating to a size larger than the substrate and will, therefore, form a collar at the end of the article which flares out of contact with the substrate.
Depending upon the application concerned, this collar may be left in place or may subsequently cut off.
In general, the tubular cap will be of circular cross-section, although it may have another cross-section, and it is often preferable that it should have a substantially constant cross-section.
The articles are preferably monolithic, i.e. are moulded or otherwise formed as one part, but they may be made from two or more parts bonded together, for example with an adhesive, or otherwise attached on to the other~
The heat-recoverable articles of the present invention are especially useful when the degree of recovery required in a given application is, or may be, very high because the articles are capable of providing a high degree of recovery or accommodating a high degree of unrecovered strain without splitting, ~r --8--7(;) A tubular cap according to the present invention is particularly useful for providing a sealed end closure of an elongate substrate having a terminal portion of size greater than the main part of the substrates, especially a telephone cable comprising a plurality of wires to which connectors have been attached. To an ever increasing extent, connectors are being installed on telephone cables in the factory, in order to avoid some of the expense and incon venience of working at the installation site, and it is vitally important to protect the end section, having the connectors attached thereto, while the cable is taken from factory to site. To install the cap, it is placed over the substrate so that the closed end section extends over terminal portion as far as the main part of the substrate, and the intermediate section of the article is then heated to cause shrinkage thereof into contact with the main part of the cable, but not into contact with the terminal portion of the substrate. It is to be noted that the presence of the open end section of lower expansion ratio means that the inter-mediate section can be given a higher expansion ratio, andcan therefore pass over a larger terminal portion, than would otherwise be the case. This improvement is of particular importance in the case of telephone cables as described above, since the multitude of connectors which must be attached to the individual wires (often 400 or more in number) occupy a considerable space, whose circumference is often .;. ~
17~D
at least 4 times, for example about 6 times, the circum-ference of the main part of the cable, to which the inter-mediate section of the cap must shrink and seal.
The dimensions and expansion ratios of a cap according to this second embodiment of the invention will of course be dependent on the substrate, but typically the open end section is 1 to 7.5 cm., preferably l.to 5 cm. long, the intermediate section is 2 to 15 cm., preferably 7 to 12 cm., long and the closed end section is 20 to 100 cm. long, and the cap has a diameter of 10 to 25 cm~
It will be appreciated that the heat-recoverable articles of the invention may be made by various methods and that the invention is not limited to any particular method for their manufacture. However, in a preferred embodiment, the present invention also provides a method of making a heat-shrinkable tubular cap which comprises the steps of (a) moulding a molten, thermoplastic, crystalline polymer into a shaped article having an open end, an intermediate section and a closed end, the open end being defined by an end section whose circumference is greater than the intermediate section of the article adjacent thereto, (b) cross-linking the moulded article;
(c) heating the cross-linked article above the crystalline melting point of the polymer, (d) expanding at least the intermediate section of the heated article, and . ~ ' .
7~
(e) cooling the article whilst maintaining it in the expanded condition.
In its third aspect the invention provides a method of covering a part of an elongate substrate which comprises placing around said part of the substrate at least part of a heat-shrinkable tubular cap as described above and heating at least part of the article to cause shrinkage thereof into contact with the substrate.
BRIEF DESCRIPTION OF THE DRAWINGS
1~ Figure 1 is a cross-section through a heat-recoverable article according to the present invention formed as an end cap, and Figure 2 is a cross-section showing the end cap of Figure ~ installed about a telephone cable having connectors attached to the individual wires thereof.
DETAILED DESCRIPTION OF THE DRAWINGS
Referring now to the drawings, in Figure 1 there is shown a tubular end cap 31 which has an open end section 32 having an expansion ratio of about 2 at the open end thereof, an intermediate section 33 which has an expansion ratio of about 5, and a closed end portion 34 which is not heat-shrin~able. The cap is made from high density polyethylene.
The dotted lines in Figure 1 show sections 32' and 33' of the article prior to expansion which become sections 32 and 33. Typical dimensions, in inches, of three such end caps are as follows:
,~ - 11 -a b c d e f g h 1st 0.80 4.0 0.075 2.80 0.15 1 3 4 2nd 1.50 6.0 0.105 3.50 0.15 1 3 4 3rd 2.50 8.0 0.135 4.50 0.15 1 3 4 All three caps have a total length of 34 inches and the cap of Figure 1 is shown in truncated form for convenience.
Referring now to Figure 2, telephone cable 40 comprises a plurality of wires 41 encased by a protective sheath 42 which has been removed from the end of the cable. Connectors have been attached to the ends of the wires 41, and the mass of wires and connectors is designated generally by 43. An end cap 31 as shown in Figure 1 has been passed over the mass of wires and connectors 43 and the sections 32 and 33 have been heated so that they shrink to provide shrunken sections 32a and 33a respectively. Section 33a is in contact with the cable while section 32a, having a lower expansion ratio, forms a flared collar.
Attention is drawn to copending Application Serial No.
290,309, title "Heat-Recoverable Article", inventors Francis De Blauwe and Frank Selleslags, filed 7th ~ovember 1977 ~ , .
.f`'~"
Such heat-recoverable articles are frequently in the form of heat-shrinkable tubes, caps or boots or other articles having a closed cross-section and one or more open ends. One wi~ely used method of making such articles is to mould a molten, crystalline, thermoplastic polymer into a shape which approx-imates to the shape of the final covering required, cross-link the shaped polymer, heat the cross-linked, shaped polymer to a temperature above its crystalline melting point, expand the hot, cross-linked, shaped polymer, e.g. by a mandrel or ,~
. ~.
.
internal pressure, and cool the polymer in its expanded shape.
The present invention especially relates to such heat-shrinkable articles, including in particular (but not limited to) those made by the process described above.
One serious limitation of such heat-shrinkable articles has been that if too high an expansion ratio (i.e. the ratio of the dimension of the article after expansion to the corres-ponding dimension before expansion) is used in making the article, the article tends to split on expansion or during shrinkage, and we have observed that this problem is partic-ularly noticeable at the open ends of such articles. The problem is especially acute if the article has been cut so as to leave a notch or nick which may propagate on recovery and/
or when the article is caused to recover about a large substrate leaving a large degree of unresolved recovery. In accordance with the present invention, we have discovered that it is advantageous if the or each open end of the article is formed by a section such that, when the article is fully shrunk, the open end is larger than the adjacent portion of the article. In particular we have found that the adjacent portion can then be given a higher expansion ratio than would otherwise be possible without danger of splitting.
BRIEF SUMMARY OF THE INVENTION
The present invention provides a heat-shrinkable tubular cap which comprises an open end section having a first expansion ratio, an intermediate section having a second expansion ratio and an unexpanded closed end section, the second expansion ratio being greater than the first expansion ratio by at least 0.5~
DETAILED DESCRIPTION OF THE INVENTION
As mentioned above, the present invention is espec-ially applicable to heat-shrinkable articles made from materials, especially plastics materials, possessing the property of elastic or plastic memory.
Amongst such heat-shrinkable articles there may especially be mentioned those with a closed cross-section.
The articles are commonly tubular, the term "tubular"
including both hollow cylindrical members and members of irregular and/or varying cross-section as well as those of more cornplex configuration such as ~-shaped, T-shaped and X-shaped members having 3 or 4 ends.
In most cases the open end section will have a larger cross-section after recovery than the adjacent intermediate section which has a substantially greater degree of recovery.
The open end section may have a finite length, for example it may extend over a length of from 1 to 10cm., but, in some cases the article may be given a differential expansion so as to produce an increasing expansion ratio along its length away from the open end and the present invention is, therefore, not limited to heat-recoverable articles having a discrete end region.
It will be appreciated that the end region may be non-recoverable, i.e. it may have an expansion ratio of 1, , 11~11~70 but, in many applications, it will be advantageous for it to exhibit a small degree of heat-recovery. However, in such cases the recovery is preferably less than 100%, more preferably less than 25% (corresponding to expansion ratios of 2 and 1.25, respectively).
On the other hand, in order fully to utilise the advantages of the present invention, the intermediate region generally exhibits a high degree of available recovery.
The expansicn ratios which will, in the absence of end sections as required by the present invention lead to splitting on shrinkage are dependent inter alia on the polymer employed and the thickness. There is seldom a problem with expansion ratios below 2.5, and usually expansion ratios of up to 3.0 can safely be used. Howevever, at expansion ratios of 3.5 or higher splitting is usually a problem and this applies more so at ratios of 4.0, 4.5 and 5Ø Thus the present invention is especially applicable at ratios of from 4 to 6 and above, for example up to 10, i.e. where the amount of avaiLable recovery is from 400% to 1000%, usually from 400% to 600%, especially when the percentage of unresolved recovery after shrinkage is high.
Another factor which is relevant to the problem is the difference between the expansion ratios of the open end region and the intermediate region. Generally speaking, the higher the expansion ratios, the greater should this difference be, but in most cases a difference of at least 1.0 and, most preferably, at least 1.5, will be desirable. The difference should preferably be at least 0.~ times, especially at least 0.5 times, the expansion ratio of the lntermediate region.
It will be appreciated that the heat-shrinkable articles of the present invention may have one or more ends which are closed but which are intended to be opened, for example, by cutting, at a later stage, the invention may also advantageously be applied to such temporarily closed ends.
The preferred articles of the present invention may be prepared from any of the polymers and mixtures of polymers known from the prior art to be useful for the production of heat-shrinkable articles. Generally the articles will be monolithic and of constant com-position throughout, however, laminates of two heat-shrinkable polymers can be used, and the articles can be constructed by joining together, e.g. with adhesive, two or more different parts. Suitable polymers include polyolefins, especially polyethylene, copolymers of ethylene and vinyl acetate, (which are particularly valuable when flexibility is required), copolymers of ethylene and ethyl acrylate, chlorinated or fluorinated polymers, especially polyvinyl chloride, polyvinylidene fluoride and polymers incorporating units derived from polyvinylidene fluoride, hexafluoro-ethyIene and chlorotrifluoroethylene, and rubbers such 7~
such as ethylenepropylerle rubber, chlorinated rubbers (~eoprene) and silicone rubbers which may be used in a blend with a crystalline or glassy polymer such as an olefin polymer~
The internal surface of the articles may be provided with a sealant such as a hot-melt adhesive or a mastic. Especially suitable hot-melt adhesives include for example polyamide materials, ethylene/vinyl acetate copolymers and terpolymers (with or without incorporated waxes) and polyesters. Such materials are described, for example, in British Patent ~o. 1,440,810 and German OS 2,709,717. Also suitable are curable adhesives which also melt and flow upon heating, but which will not afterwards be hot-meltable. There may also be mentioned epoxy resins and conventional mastics such as, for example, those based on butyl and isobutylene rubbers modified with suitable materials known in the art. Obviously the type of sealant employed and the method of its application will depend on the particular requirements in any given case.
Bearing in mind the above discussion it will be appreciated that the shape and design characteristics of the heat-recoverable articles of the present invention will depend on the use intended for them. In some cases, it may be preferable for the open end regions to be thicker than the intermediate high-recovery regions in which case it may be convenient to prepare a moulded article which has (prior to expansion) the same wall thickness throughout so that the ratio of the thickness of the open end section(s) to the thickness of the intermediate section(s) after expansion will be 7~11 substantially the same as the inverse ra-tio of their expansion ratios.
Similarly, the shape, after shrinkage, of the open end region and the intermediate region will be dependent of the relative sizes of the article and of the substrate as well as the expansion ratios of the two regions. Thus both regions may shrink into contact with the substrate along their entire length. More usually, however, the open end section will spontaneously recover on heating to a size larger than the substrate and will, therefore, form a collar at the end of the article which flares out of contact with the substrate.
Depending upon the application concerned, this collar may be left in place or may subsequently cut off.
In general, the tubular cap will be of circular cross-section, although it may have another cross-section, and it is often preferable that it should have a substantially constant cross-section.
The articles are preferably monolithic, i.e. are moulded or otherwise formed as one part, but they may be made from two or more parts bonded together, for example with an adhesive, or otherwise attached on to the other~
The heat-recoverable articles of the present invention are especially useful when the degree of recovery required in a given application is, or may be, very high because the articles are capable of providing a high degree of recovery or accommodating a high degree of unrecovered strain without splitting, ~r --8--7(;) A tubular cap according to the present invention is particularly useful for providing a sealed end closure of an elongate substrate having a terminal portion of size greater than the main part of the substrates, especially a telephone cable comprising a plurality of wires to which connectors have been attached. To an ever increasing extent, connectors are being installed on telephone cables in the factory, in order to avoid some of the expense and incon venience of working at the installation site, and it is vitally important to protect the end section, having the connectors attached thereto, while the cable is taken from factory to site. To install the cap, it is placed over the substrate so that the closed end section extends over terminal portion as far as the main part of the substrate, and the intermediate section of the article is then heated to cause shrinkage thereof into contact with the main part of the cable, but not into contact with the terminal portion of the substrate. It is to be noted that the presence of the open end section of lower expansion ratio means that the inter-mediate section can be given a higher expansion ratio, andcan therefore pass over a larger terminal portion, than would otherwise be the case. This improvement is of particular importance in the case of telephone cables as described above, since the multitude of connectors which must be attached to the individual wires (often 400 or more in number) occupy a considerable space, whose circumference is often .;. ~
17~D
at least 4 times, for example about 6 times, the circum-ference of the main part of the cable, to which the inter-mediate section of the cap must shrink and seal.
The dimensions and expansion ratios of a cap according to this second embodiment of the invention will of course be dependent on the substrate, but typically the open end section is 1 to 7.5 cm., preferably l.to 5 cm. long, the intermediate section is 2 to 15 cm., preferably 7 to 12 cm., long and the closed end section is 20 to 100 cm. long, and the cap has a diameter of 10 to 25 cm~
It will be appreciated that the heat-recoverable articles of the invention may be made by various methods and that the invention is not limited to any particular method for their manufacture. However, in a preferred embodiment, the present invention also provides a method of making a heat-shrinkable tubular cap which comprises the steps of (a) moulding a molten, thermoplastic, crystalline polymer into a shaped article having an open end, an intermediate section and a closed end, the open end being defined by an end section whose circumference is greater than the intermediate section of the article adjacent thereto, (b) cross-linking the moulded article;
(c) heating the cross-linked article above the crystalline melting point of the polymer, (d) expanding at least the intermediate section of the heated article, and . ~ ' .
7~
(e) cooling the article whilst maintaining it in the expanded condition.
In its third aspect the invention provides a method of covering a part of an elongate substrate which comprises placing around said part of the substrate at least part of a heat-shrinkable tubular cap as described above and heating at least part of the article to cause shrinkage thereof into contact with the substrate.
BRIEF DESCRIPTION OF THE DRAWINGS
1~ Figure 1 is a cross-section through a heat-recoverable article according to the present invention formed as an end cap, and Figure 2 is a cross-section showing the end cap of Figure ~ installed about a telephone cable having connectors attached to the individual wires thereof.
DETAILED DESCRIPTION OF THE DRAWINGS
Referring now to the drawings, in Figure 1 there is shown a tubular end cap 31 which has an open end section 32 having an expansion ratio of about 2 at the open end thereof, an intermediate section 33 which has an expansion ratio of about 5, and a closed end portion 34 which is not heat-shrin~able. The cap is made from high density polyethylene.
The dotted lines in Figure 1 show sections 32' and 33' of the article prior to expansion which become sections 32 and 33. Typical dimensions, in inches, of three such end caps are as follows:
,~ - 11 -a b c d e f g h 1st 0.80 4.0 0.075 2.80 0.15 1 3 4 2nd 1.50 6.0 0.105 3.50 0.15 1 3 4 3rd 2.50 8.0 0.135 4.50 0.15 1 3 4 All three caps have a total length of 34 inches and the cap of Figure 1 is shown in truncated form for convenience.
Referring now to Figure 2, telephone cable 40 comprises a plurality of wires 41 encased by a protective sheath 42 which has been removed from the end of the cable. Connectors have been attached to the ends of the wires 41, and the mass of wires and connectors is designated generally by 43. An end cap 31 as shown in Figure 1 has been passed over the mass of wires and connectors 43 and the sections 32 and 33 have been heated so that they shrink to provide shrunken sections 32a and 33a respectively. Section 33a is in contact with the cable while section 32a, having a lower expansion ratio, forms a flared collar.
Attention is drawn to copending Application Serial No.
290,309, title "Heat-Recoverable Article", inventors Francis De Blauwe and Frank Selleslags, filed 7th ~ovember 1977 ~ , .
.f`'~"
Claims (18)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A heat-shrinkable tubular cap which comprises an open end section having a first expansion ratio, an intermediate section having a second expansion ratio and an unexpanded closed end section, the second expansion ratio being greater than the first expansion ratio by at least 0.5.
2. A heat-shrinkable tubular cap as claimed in claim 1, wherein the difference between the first and second expansion ratios is at least 1Ø
3. A heat-shrinkable tubular cap as claimed in claim 2, wherein said difference is at least 1.5
4. A heat-shrinkable tubular cap as claimed in claim 1, wherein the difference between the first and second expansion ratio is at least 0.4 of the second expansion ratio.
5. A heat-shrinkable tubular cap as claimed in claim 4, wherein the difference between the first and second expansion ratios is at least 0.5 of the second expansion ratio.
6. A heat-shrinkable tubular cap as claimed in claim 1, wherein the second expansion ratio is at least 2.5.
7. A heat-shrinkable tubular cap as claimed in claim 6, wherein the second expansion ratio is at least 3Ø
8. A heat-shrinkable tubular cap as claimed in claim 7, wherein the second expansion ratio is at least 3.5.
9. A heat-shrinkable tubular cap as claimed in claim 8, wherein the second expansion ratio is at least 4Ø
10. A heat-shrinkable tubular cap as claimed in claim 9, wherein the second expansion ratio is at least 5Ø
11. A heat-shrinkable tubular cap as claimed in claim 1, wherein the expansion ratio of the open end section is less than 2.
12. A heat-shrinkable tubular cap as claimed in claim 11, wherein the expansion ratio of the open end section is less than 1.25.
13. A heat-shrinkable tubular cap as claimed in claim 1, wherein the closed end section has a substantially constant cross-section except at the closed end thereof.
14. A heat-shrinkable tubular cap as claimed in claim 1, made from high density polyethylene.
15. A heat-shrinkable tubular cap as claimed in claim 1, provided with a coating of a hot melt adhesive on at least part of the interior surface thereof.
16. A heat-shrinkable tubular cap as claimed in claim 1, wherein the open end section is from 1 to 7.5 cm. long, the intermediate section is from 2 to 15 cm. long and the closed end section is from 20 to 100 cm. long.
17. A heat-shrinkable tubular cap as claimed in claim 16, wherein the internal diameter of the closed end section is from 10 to 25 cm.
18. A heat-shrinkable tubular cap as claimed in claim 1, wherein the circumference of the open end section after unrestrained recovery is greater than that of the intermediate section.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB36246/77 | 1977-08-30 | ||
| GB3624677 | 1977-08-30 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1101170A true CA1101170A (en) | 1981-05-19 |
Family
ID=10386340
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA290,333A Expired CA1101170A (en) | 1977-08-30 | 1977-11-07 | Heat-recoverable article |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1101170A (en) |
-
1977
- 1977-11-07 CA CA290,333A patent/CA1101170A/en not_active Expired
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| Date | Code | Title | Description |
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| MKEX | Expiry |