THERMALLY-INSULATING SLEEVE

Abstract: A thermally insulating sleeve (10; 30) comprises a generally-tubular wall portion (12; 32) formed from heat resistant material. The sleeve also comprises a heat-activatable layer (16; 36) on the interior surface (18; 38) of said wall portion (12; 32). The heat-activatable layer (16; 36) is such that, when subjected to heat, the layer increases in thickness, thereby improving thermal insulation.

Description: THERMALLY-INSULATING SLEEVE This invention is concerned with a thermally- insulating flexible protective sleeve for use in protecting an elongated member, such as a flexible pipe or a bundle of electrical wires. The sleeve may also provide abrasion protection and/or noise reduction . It is common practice to protect elongated members such as pipes and bundles of electrical wires by enclosing them in a sleeve. For example, such sleeves are utilised in the engine compartments of vehicles powered by internal combustion engines to give abrasion protection, reduced noise, and thermal insulation. Such sleeves have to be flexible enough to follow bends in the member being protected and have to be made of materials which are suitable to give the protection required. Some such sleeves need to be resistant to the fluids found in engine compartments such as water, fuel and anti-freeze. Some such sleeves have generally tubular wall portions which are formed from sheet-like plastics materials, such as nylon 6 and polyester, the wall portions being convoluted to give them the necessary flexibility. Some convoluted sleeves have a longitudinally extending slit therein to allow access to the interior thereof. Other such sleeves have generally tubular wall portions formed from plastics monofilaments or yarns by a braiding or weaving process. This invention is applicable to sleeves of all the aforementioned types which are intended to provide thermal insulation. However, the type of thermally-insulating material utilised has to be selected to be compatible with the particular formation of the generally tubular wall portion. Clearly, the thermal insulation properties of a protective sleeve can be improved by providing a thermally- insulating material between the wall portion of the sleeve and the member being protected. Such thermally-insulating material can be provided by a layer of foam or other suitable material covering the interior surface of the wall portion. Although such a layer provides equal thermal insulation in all radial directions, it is likely that the sleeve will be used in a situation where heat is only received from one or a small range of radial directions. In this case, thermal insulation in other directions is actually harmful since it prevents heat from leaving in those directions. It is not practical to pre-form a sleeve with asymmetric thermal insulation to avoid this problem since orientation of the sleeve so that the insulation faces in a particular direction is too difficult. It is an object of the present invention to provide a thermally-insulating sleeve having more efficient insulation. The invention provides a thermally-insulating flexible protective sleeve comprising a generally-tubular wall portion formed from heat resistant material, characterised in that the sleeve also comprises a layer on at least part of the interior surface of said wall portion, the layer being heat-activatable so that, when the sleeve receives heat from an external source, a portion of the layer nearest to said source increases in thickness in a direction towards the centre of the sleeve, thereby improving the thermal insulation properties of the sleeve across said portion. In a sleeve according to the invention, the insulation is created in situ by the influence of the heat source itself so that the insulation can be formed only where it is needed, ie on one side of the member being protected. The member may also be pressed away from the heat source against a relatively cold part of the wall portion, thereby assisting the removal of heat. In a sleeve according to the invention, the heat- activatable layer may comprise a compressed thermally- insulating material and retaining means operative to retain said thermally insulating material in its compressed state, said retaining means acting to release said thermally- insulating material on being subjected to heat. Such compressed thermally-insulating material may be, for example, a thermally-insulating resilient foam or a plurality of fibres. The retaining means may be for example, a meltable wax, a thermoplastic polymer, or meltable or burnable stitching. In another alternative, the heat-activatable layer may comprise a material which expands on the application of heat thereto. Such a material may be, for example, a precursor of a foam. Such a precursor of a foam may comprise a thermally-activated blowing agent or hollow microspheres which expand when heated. The material may, alternatively, be an intumescent material. In a sleeve according to the invention, said layer may be arranged so that, on cooling, said portion of the layer reduces in thickness. For example, such a layer may comprise resiliently expandable bags containing a volatile liquid which, on heating, becomes a gas and, on cooling, returns to a liquid state. This type of layer is advantageous in circumstances in which the direction from which heat reaches the sleeve varies. Said layer may be provided as discrete patches distributed over said interior surface of said wall portion. This arrangement allows more space for expansion towards the centre of the sleeve. For example, such patches may be in the form of beads extending longitudinally of the sleeve. Preferably, the patches are distributed uniformly circumferentially of the sleeve. It is desirable, in some cases, if the heat-activated layer forms a relatively rigid material on expansion, eg by cross-linking of a thermosetting material. Such a rigid material can resist expansion of other portions of the layer which may reach the activation temperature later. The invention also provides an assembly comprising a thermally-insulating flexible protective sleeve and an elongated member contained within said sleeve, the sleeve comprising a generally-tubular wall portion formed from heat resistant material, characterised in that the sleeve also comprises a layer on at least part of the interior surface of said wall portion, the layer being heat- activatable so that, when the sleeve receives heat from an external source, a portion of the layer nearest to said source increases in thickness in a direction towards the centre of the sleeve, thereby improving the thermal insulation properties of the sleeve across said portion, said portion of the layer being in a condition of increased thickness and acting to press said elongated member against unexpanded portions of said layer on the wall portion of the sleeve, other portions of said layer being in an as- installed condition thereof in which their thickness has not increased. In an assembly according to the invention, the protected member is pressed away from the heat source giving maximum insulation on the side from which heat is received and maximum opportunity for heat to leave in the opposite direction. Furthermore, the member is gripped by the sleeve preventing displacement of the sleeve along the member and also preventing rattling. The invention also provides a method of protecting an elongated member from a heat source located to one side thereof, the method comprising enclosing the elongated member in a thermally-insulating flexible protective sleeve, the sleeve comprising a generally-tubular wall portion formed from heat resistant material, characterised in that the sleeve also comprises a layer on at least part of the interior surface of said wall portion, the layer being heat-activatable so that, when the sleeve receives heat from said source, a portion of the layer nearest to said source increases in thickness in a direction towards the centre of the sleeve, thereby improving the thermal insulation properties of the sleeve across said portion. There now follow two detailed descriptions, to be read with reference to the accompanying drawings, of two thermally-insulating sleeves which are illustrative of the invention. In the drawings: Figure 1 is a transverse cross-sectional view taken through an assembly which includes an elongated member and the first illustrative sleeve showing the sleeve in a newly-installed condition; Figure 2 is a similar view to Figure 1 but showing the first illustrative sleeve in a final condition; and Figures 3 and 4 are similar views to Figures 1 and 2, respectively, but showing the second illustrative sleeve and including a detailed view of a portion of the sleeve in a circle. The first illustrative thermally-insulating flexible protective sleeve 10 comprises a generally-tubular wall portion 12 formed from heat resistant plastics material. Specifically, the wall portion 12 is formed from nylon 6 as a convoluted sleeve having a sheet-like wall. Such convoluted plastics tubes are well-known. The wall portion has a longitudinal slit 14 therein which allows access to the interior thereof. The sleeve 10 also comprises a layer 16 covering to the interior surface 18 of the wall portion 12. The layer 16 is heat-activatable so that, when the sleeve 10 receives heat from an external source (not shown) , a portion 20 (see Figure 2) of the layer 16 nearest to said source increases in thickness in a direction towards the centre of the sleeve 10, thereby improving the thermal insulation properties of the sleeve across said portion. The layer 16 comprises a material which expands on the application of heat thereto. Specifically, this material is the precursor of a foam, being a mixture of 15 weight percent of expandable hollow microspheres with 85 weight percent of water-based acrylic adhesive. The adhesive serves to secure the material to the surface 18 to which it is applied by a spreading process. The microspheres are arranged to expand when heated to 75-80°C. In a modification of the illustrative sleeve 10, the material 16 may be a precursor of a foam formed by a heat-activatable blowing agent. In this case, the layer 16 uniformly covers the surface 18. Figure 1 shows the sleeve 10 in an as-installed condition in an assembly with an elongated member, specifically, a wire bundle 22 contained within the sleeve 10. Figure 2 shows the sleeve 10 after it has been subjected to heat from a heat source located to the left of Figure 2. The material of the layer 16 nearest to the heat source has been caused to expand by heat from the heat source to form foam 20 but the material on the other side of the sleeve 10 has not expanded. The expansion of the foam 20 has resulted in the wire bundle 22 being pressed against a portion of the interior surface 18 by the foam. Hence, the foam 20 is formed between the heat source and the bundle 22 but not on the opposite side of the bundle 22. This means that the bundle 22 is well insulated from heat on one side but not insulated as well on the other side, allowing heat to escape. Thus, in the assembly formed by the sleeve 10 and the bundle 22, said portion 20 of the layer 16 is in a condition of increased thickness and acts to press the bundle 22 against the wall portion 12. Other portions of said layer 16 are in an as-installed condition thereof in which their thickness has not increased. The second illustrative sleeve 30 is shown in Figures 3 and 4. The sleeve 30 has a wall portion 32 which is identical to the wall portion 12 of the sleeve 10. The sleeve 30 also comprises a heat-activatable layer 36 on its interior surface 38. The heat-activatable layer 36 comprises a plurality of plastics monofilaments 37 (see detailed view) . One end of each of the monofilaments 37 is adhered to the surface 38. The monofilaments 37, when not distorted, extend normally of the surface 38 and provide thermal insulation. However, in the as-installed condition of the sleeve 30, the monofilaments 37 are retained in a compressed condition by retaining means in the form of meltable wax 40. On being subjected to heat, the wax 40 releases the monofilaments 37 which spring back into their uncompressed condition, increasing the thickness of the layer 36 in a direction towards the centre of the sleeve 36. In their compressed condition, the monofilaments 37 lie close to the surface 38, ie they extend generally circumferentially of the sleeve 30. The wax 40 adheres the monofilaments 37 to the surface 38 or to adjacent monofilaments 37 along the length of the monofilaments. Figure 4 shows the effect of heat received from a heat source to the left of Figure 4. A portion of the layer 36 has been activated by melting of the wax 40 in that portion. Specifically, the wax 40 on one side of the sleeve 30 has melted, releasing the monofilaments 37 which spring into a radial orientation in which they provide insulation for a bundle 42 within the sleeve 30. Thus, in the assembly formed by the sleeve 30 and the bundle 42, the left-hand portion of the layer 36 is in a condition of increased thickness, with the monofilaments 37 extending normally of the surface 38, and acts to press the bundle 42 against the wall portion 32. Other portions of said layer 36 are in an as-installed condition thereof in which their thickness has not increased.

Claims: CLAIMS A thermally-insulating flexible protective sleeve (10; 30) comprising a generally-tubular wall portion (12; 32) formed from heat resistant material, characterised in that the sleeve also comprises a layer (16; 36) on at least part of the interior surface (18; 38) of said wall portion, the layer (16; 36) being heat- activatable so that, when the sleeve receives heat from an external source, a portion (20) of the layer nearest to said source increases in thickness in a direction towards the centre of the sleeve, thereby improving the thermal insulation properties of the sleeve across said portion. A sleeve according to claim 1, characterised in that the heat-activatable layer (36) comprises a compressed thermally-insulating material (37) and retaining means (40) operative to retain said thermally insulating material in its compressed state, said retaining means (40) acting to release said thermally-insulating material (37) on being subjected to heat. A sleeve according to claim 1, characterised in that the heat-activatable layer (16) comprises a material which expands on the application of heat thereto. A sleeve according to claim 1, characterised in that said layer is arranged so that, on cooling, said portion of the layer reduces in thickness. A sleeve according to any one of claims 1 to 4, characterised in that said layer (16; 36) is provided as discrete patches distributed over said interior surface (18; 38) of said wall portion (12; 32). An assembly comprising a thermally-insulating flexible protective sleeve (10; 30) and an elongated member (22; 42) contained within said sleeve, the sleeve comprising a generally-tubular wall portion (12; 32) formed from heat resistant material, characterised in that the sleeve also comprises a layer (16; 36) on at least part of the interior surface (18; 38) of said wall portion, the layer (16; 36) being heat- activatable so that, when the sleeve receives heat from an external source, a portion (20) of the layer nearest to said source increases in thickness in a direction towards the centre of the sleeve, thereby improving the thermal insulation properties of the sleeve across said portion, said portion (20) of the layer (16; 36) being in a condition of increased thickness and acting to press said elongated member (22; 42) against unexpanded portions of said layer on the wall portion of the sleeve, other portions of said layer being in an as-installed condition thereof in which their thickness has not increased. A method of protecting an elongated member (22; 42) from a heat source located to one side thereof, the method comprising enclosing the elongated member in a thermally-insulating flexible protective sleeve (10; 30) , the sleeve comprising a generally-tubular wall portion (12; 32) formed from heat resistant material, characterised in that the sleeve also comprises a layer (16; 36) on at least part of the interior surface (18; 38) of said wall portion, the layer being heat-activatable so that, when the sleeve receives heat from said source, a portion (20) of the layer nearest to said source increases in thickness in a direction towards the centre of the sleeve, thereby improving the thermal insulation properties of the sleeve across said portion.

Inventors: ATKINSON ALAN WILLIAM, ATKINSON, ALAN, WILLIAM
Applicants: ATKINSON ALAN WILLIAM, FEDERAL MOGUL TECHNOLOGY LTD, ATKINSON, ALAN, WILLIAM, FEDERAL-MOGUL TECHNOLOGY LIMITED
Application year: 2000
Main classification: F16L59
IPC codes: F16L59