IE47645B1

IE47645B1 - Heat-recoverable metallic coupling members

Info

Publication number: IE47645B1
Application number: IE69/79A
Authority: IE
Original assignee: Raychem Corp
Priority date: 1978-01-16
Filing date: 1979-01-16
Publication date: 1984-05-16
Also published as: NO144078B; GB2012384A; BR7900242A; NO144078C; JPS54148960A; DE2901536A1; FR2414677A1; IT1110021B; CA1101463A; IE790069L; GB2012384B; FR2414677B1; NO790120L; NL7900096A; JPS6222002B2; IT7919347A0

Abstract

A coupling member comprises a tubular memory metal member which is heat-shrinkable or can be rendered heat-shrinkable in the radial direction, and which is provided on its inner surface with at least three teeth in the form of radially extending rings, the distance (t) between any pair of adjacent teeth being less than 0.95 d and less than 4 w, where d is the internal diameter of the tubular member, and w is the wall thickness of the tubular member, there being at least one tooth either side of the tooth nearest the center of the tubular member the distance from the center of the member to the tooth nearest the center of the member being from 0 to 0.3 d and the distance between the two teeth adjacent the tooth nearest the center of the member being more than the smaller of 0.4 d and 3 w. Such a coupling member can be expanded by mandrel expansion methods without danger of damaging the teeth.

Description

This invention relates to heat-recoverable metallic couplings as described in, for example, O.S. Patents Nos. 4,035,007 and 3,805,567 and German Offenlegungschrift· No. 2,448,160, the disclosures of which are incorporated herein by reference. The known monolithic couplings comprise a heat-recoverable tubular member which recovers directly onto the substrates to be coupled. The member is preferably provided on its inner surface with at least two teeth which are in the form of radially extending rings. The function of these teeth is to grip and/or seal to the substrates when the member is recovered, and they are therefore spaced away from the center of the member, leaving the center section of the inner surface free of teeth (indeed the center section has often been provided with a recess such that the ends of the tubings being coupled do not touch the coupling at any point).

The conventional method of preparing such monolithic couplings is to drive a tempered mandrel through the coupling while the metal is in the martensitic state. However, a disadvantage of this method is that the mandrel can score or otherwise damage one or more of the teeth in a way which allows the installed coupling to leak. We have now discovered a novel coupling member in which teeth are so disposed on the inner surface of the member that the likelihood of damage to the teeth by the mandrel is substantially reduced. In particular we have discovered that, contrary to the accepted teaching in the art as represented bv u.S. Patent No. 4,035,007, it is advantageous that the center section of the coupling member should be provided with a tooth, especially when the distance between the innermost gripping teeth defining the center section is relatively large. -247645 In one aspect, the invention provides a coupling member which comprises a hollow, generally tubular member composed of a memory metal, which member is heat-shrinkable in the radial direction or can be rendered heat-shrinkable in the radial direction, and which is provided on its inner surface with at least three teeth in the form of radially extending rings, the distance (t) between any pair of adjacent teeth having a value which is less than 0.95 d and less than 4 w, where d is the internal diameter of the tubular member and w is the wall thickness of the tubular member, there being at least one tooth either side of the tooth nearest the center of the tubular member, the distance from the center of the member to the tooth nearest the center of the member being from 0 to 0.3 d, and the distance (p) between the two teeth adjacent the tooth nearest the center of the member being more than the smaller of 0.4 d and 3 w (i.e. p is greater than 0.4 d if 0.4 d is less than 3 w, and p is greater than 3 w if 0.4 d is more than 3 w).

The term memory metal is used herein to denote a metallic material which exists in an austenitic phase at a first temperature and in a martensitic phase at a second temperature lower that the first temperature, which material, when cooled from a first temperature at which it is in a first configuration and is in the austenitic phase to a temperature at which it is in the martensitic phase, can be deformed to a second configuration which it will maintain until it is reheated to a temperature at which it is in the austenitic phase, whereupon it will recover towards the first configuration. The memory metals used in the present invention are preferably alloys comprising nickel and titanium. -347645 Xn another aspect, the invention provides a method of preparing a heat-shrinkable coupling member as defined above, which method comprises driving a tapered mandrel through a coupling member as defined above which can be rendered heat-shrinkable, thereby effecting radial expansion of the member while the memory metal thereof is in the martensitic phase.

In a further aspect, the invention provides a method of coupling together a pair of substrates which comprises placing the ends of the substrates within a heatshrinkable coupling member as defined above, and heating the coupling member to cause shrinkage thereof. The substrates should of course be positioned and sized so that when the coupling member has shrunk, at least one of the teeth grips each of the substrates.

The less the distance (t) between any pair of adjacent teeth, the less is the danger that the mandrel will damage the teeth. The distance t is generally at most 0.8 d, preferably at most 0.75 d, especially at most 0.7 d, particularly at most 0.6 d. The internal diameter of the member between the teeth is generally less than 3 inches e.g. 1 to 2.5 inches, but can be much greater. The height of the teeth (h) is generally from 0.015 d to 0.02 d. The wall thickness (w) of the member is generally not more than 0.45 d, for example 0.1 d to 0.4 d, preferably 0.2 d to 0.35 d, e.g. 0.23 d to 0.33 d. -447848 The distance (p) between the two teeth adjacent the tooth nearest the center of the member is usually at least 0.6 <3, preferably at least 0.75 d, for example at least 0.80 d or 0.9 d. The couplings will usually comprise at least two teeth either side of the tooth nearest the center of the member, and will usually be symmetrical about the mid-point thereof (i.e. have a tooth at the center thereof).

The invention is illustrated in the accompanying drawings in which the Figure is a cross-section of a coupling member according to the invention.

Claims

1. A coupling member which comprises a hollow, (as hereinbefore defined) generally tubular member composed of a memory metal,/which member is heat-shrinkable in the radial direction or can be 5 rendered heat-shrinkable in the radial direction, and which is provided on its inner surface with at least three teeth in the form of radially extending rings, characterised in that (i) the distance (t) between any pair of adjacent teeth is less than 0.95 d and less than 4 w, where d is the 10 internal diameter of the tubular member and w is the wall thickness of the tubular member; (ii) there is at least one tooth either side of the tooth nearest the center of the tubular member; (iii) the distance from the center of the member to the tooth nearest the center of the member is from 15 0 to 0.3 d; and (iv) the distance (p) between the two teeth adjacent the tooth nearest the center of the member is more than the smaller of 0.4 d and 3 w.

2. A coupling member according to Claim 1, characterised in that w is 0.1 d to 0.4 d, t is at most 20 0.7 d and p is at least 0.75 d.

3. A coupling member according to Claim 2, characterised in that w is 0.2 d to 0.35 d, t is at most 0.6 d, p is at least 0.8 d and the height of each of the teeth is 0.015 d to 0.02 d. 25

4. A coupling member according to Claim 3^ characterised in that w is 0.23 d to 0.33 d, t is at most 0.6 d and p is at least 0.9 d. -647645

5. A coupling member according to any one of the preceding claims characterised in that it has a tooth at the center thereof and at least two teeth either side of the central tooth. 5

6. A coupling member according to any one of the preceding claims characterised in that said memory metal is an alloy comprising nickel and titanium.

7. A method of making a heat-shrinkable coupling member as defined in any one of the preceding claims

8. 10 characterised by driving a tapered mandrel through a coupling member as defined in any one of the preceding claims which can be rendered heat-shrinkable, thereby effecting radial expansion of the member while the memory metal thereof is in the martensitic state. 15 8. A method of coupling together a pair of substrates which comprises placing the ends of the substrates within a heat-shrinkable coupling member composed of a memory metal and heating the coupling member to cause it to shrink and engage the substrates, characterised by 20 using a heat-shrinkable coupling member as claimed in any one of claims 1 to 6.