Flexible protective sleeves are commonly used to protect bundles of wires and pipes in environments where abrasion, heat, corrosive materials etc may cause damage. Such sleeves are also used widely for reducing undesirable noise such as may be caused by vibration between wires or pipes and adjacent components. Such sleeves may also be used to bundle wires together for aesthetic reasons. Such sleeves are used in the engine compartments of vehicles driven by internal combustion engines. Such sleeves need to be flexible enough to follow the bends in such wires or pipes. In other words, such sleeves need to be able to turn through relatively tight bends without deforming in such a way that their internal cross-section reduces, ie without kinking. This is achieved by portions of the sleeve on the inside of the bend moving together while portions on the outside of the bend move apart.

Flexible protective sleeves usually comprise a generally tubular wall, eg of generally circular transverse cross-section, and the member to be protected is positioned within the space enclosed by the wall. For the sleeve to function correctly, the wall must retain its tubular form. In some such sleeves, the wall is made from an extruded plastics tube which is convoluted to give the required flexibility. In this case, the wall retains its tubular form because the shape is set into the plastics material. The tubular shape is retained even when the sleeve has a longitudinally-extending slit in its wall to give access to its interior to allow the sleeve to be installed over an in situ bundle or pipe. In other flexible protective sleeves, the wall is made by braiding or weaving together plastics monofilaments. The monofilaments forming the wall can be heat-set into a tubular form so that the wall retains a tubular form even when the sleeve has a longitudinally-extending slit often with overlapping edges. The slit allows the sleeve to be fitted over a bundle of wires or a pipe and allows wire to enter or leave the sleeve. For the avoidance of doubt, the word"slit"is used herein to mean both a gap caused by slitting a previously tubular sleeve and a gap caused by bending a sleeve into a tubular form, the gap being the edges of the sheet. Such a slit may have an overlap which gives all-round protection and prevents, e. g, wires from falling out of the sleeve. However, the requirement that the tubular form be retained around a space means that many otherwise suitable materials cannot be used to form the walls of flexible protective sleeves and the presence of a s) it reduces the possibilities still further.

It is an object of the present invention to provide an improved flexible protective sleeve which enables a greater range of materials to be used.

The invention provides a flexible protective sleeve which comprises a generally tubular wall having a slit therein extending for at least part of the length of the sleeve and giving access to the interior of the sleeve, characterised in that the wall comprises a layer of flexible sheet material extending from one edge of said slit to the other, and a plurality of generally parallel ribs secured to said flexible sheet material at longitudinal intervals, each rib having a pre-set curvature circumferientially of the sleeve so that said ribs hold the flexible sheet material in the tubular form A sleeve according to the invention can utilise flexible sheet materials which are unable to support themselves in a tubular form. The flexible sheet material is held in a tubular form by said ribs.

The ribs may extend generally parallel to one another. Said ribs may be straight and normal to the longitudinal direction of the sleeve or may be straight and inclined relative to the longitudinal direction of the sleeve. The ribs may, however, not be straight, e. g they may follow helical, sinusoidal or zig-sag paths.

Said'ribs may be generally rectangular in transverse cross-section. Said ribs may suitably be made of plastics material such as polyester or polypropylene and are preferably heat-set into the required curvature.

Each set of ribs may have a width which is at least three times its thickness.

Preferably, the width of the strip is at least five times its thickness.

Preferably, the width of each rib is at least equal to that of the gap between adjacent ribs.

The ribs may be positioned between the layer of flexible sheet material and another layer of the wall of the sleeve. For example, the wall may compromise an inner cushioning or thermally-insulating layer, eg made of felt or foam, and the ribs may be positioned between this layer and the layer of flexible sheet material.

The flexible sheet material may comprise two or more layers bonded to one another, eg a layer of polyester fibre felt may be bonded to a layer of aluminised polyester fibre film. One layer may be a textile or non-woven layer (e. g. of Tyvek-trademark of Du Pont).

The flexible sheet material may comprise at least a surface layer of infrared radiation reflective material. For example, the flexible sheet material may be a thin metal foil, or a plastics film or textile with a thin metallic layer deposited thereon. Aluminium is a suitable metal for these purposes.

The slit of a flexible protective sleeve according to the invention may overlapping edges.

In one method of manufacturing a flexible protective sleeve according to the invention, the method comprises forming the tubular wall by forming an elongated strip into the general shape of a helix of substantially constant diameter, setting the strip in the curvature of the helix, securing a layer of flexible sheet material to the outer surface of the helix so that the flexible sheet material covers at least the gap between the coils of the helix, and forming a slit through said flexible sheet material and said strip, the slit extending longitudinally of the helix and dividing the strip into a plurality of generally parallel ribs secured to said flexible sheet material at longitudinal intervals, each rib having a pre set curvature circumferientially of the sleeve so that said ribs hold the flexible sheet material in the tubular form.

In a method described in the last preceding paragraph, a further strip may be wound into a helix in the gap between the coils of the first-mentioned helix. In other words a multi-start helix is utilised with adjacent ribs being formed from different strips.

In order to provide a sleeve having overlapping edges in the region of the slit, the flexible sheet material may be secured to the outer surface of the helix when the helix is in a radially expanded condition, ie when the strip forming the helix is wound at a greater diameter then its pre-set or relaxed condition curvature. For example, after being heat-set in the shape of said helix, the strip may be wound onto a mandrel having a great diameter than the helix and the flexible sheet material may then be secured to the strip.

In an alternative method of manufacturing a flexible protective sleeve according to the invention, the method comprises securing a plurality of ribs to a strip of flexible sheet material, bending the sheet material into a generally tubular form, and setting the ribs into the curvature of said tubular form. For example, said ribs may be provided as a unit joined together by relatively thin joining members. Such a unit can be formed by cutting slits in a sheet and stretching the sheet. The tubular form may have overlapping edges.

There now follow detailed descriptions, to be read with reference to the accompanying drawings, of five flexible protective sleeves which are illustrative of the invention.

In the drawings: Figure 1 is a diagrammatic longitudinal cross-sectional views of a portion of a first illustrative sleeve ; Figure 2 is a diagrammatic view of the first illustrative sleeve, showing the sleeve opened out into a flat condition; Figure 3 is a diagrammatic perspective view of the first illustrative sleeve ; Figure 4 is a diagrammatic view of a sheet used in the manufacture of the second illustrative sleeve ; Figure 5 is a similar view to Figure 2 but of the second illustrative sleeve ; Figures 6 and 7 are similar views to Figures 4 and 5 but of the third illustrative sleeve ; Figure 8 is a diagrammatic view illustrating a stage in the manufacture of the second illustrative sleeve ; Figures 9 and 10 are diagrammatic views of a sheet used in the manufacture if the fourth illustrative sleeve, Figure 10 showing the strip in a stretched condition; Figure 11 is a diagrammatic perspective view of a sheet used in the manufacture of the fourth illustrative sleeve ; and Figure 12 is a similar view to Figure 1 but of the fifth illustrative sleeve.

The first illustrative flexible protective sleeve 10 (see Figures 1 to 3) has a generally tubular wall 12 having a slit 145 therein extending for the length of the sleeve 10 and giving access to the interior of the sleeve. The edges of the wall 12 overlap one another in the region of the slit 14. The sleeve 10 has an internal diameter of 15mm and is for use in protecting a bundle of wires in the engine compartment of a vehicle.

The wall 12 comprises a layer of flexible sheet material 12a made of polyester film with a thin surface layer (less than 1 micron in thickness) of infrared radiation-reflecting metal, specifically aluminium deposited thereon. The metal layer faces outwardly of the sleeve 10, although it could face inwardly or there could be two such layers, one facing inwardly and the other facing outwardly.

The layer of flexible sheet material 12a extends continuously from one edge of the slit 13 to the other edge thereof.

The wall 12 also comprises a plurality of ribs 12b secured to the flexible sheet material 12a, specifically to the inwardly face surface of the material 12a which i,. faces the interior of the sleeve 10. The ribs 12b are formed of strips of polyester which are of rectangular transverse cross-section, having a width of 10mm and a thickness of 0.5mm. The ribs 12b extend parallel to one another and are inclined relative to the longitudinal direction of the sleeve 10. Each rib 12b has a pre-set curvature circumferentially of the sleeve 10 so that the ribs 12b hold the sheet material 12a in the tubular form.

The first illustrative sleeve 10 is manufactured by the first illustrative method which comprises forming the tubular wall 12 by taking an elongated strip of polyester having the same transverse cross-sectional shape as the ribs 12b and winding it around a mandrel having a diameter of 15mm. This forms the strip into the general shape of a helix of substantially constant diameter. Next, while, the strip is still, on said mandrel, it is set into the curvature of the helix by heating it and subsequently allowing it to cool. Next, the elongated strip is removed from said mandrel and re-wound onto a mandrel of greater diameter.

Next, the layer of flexible sheet material 12a is secured by adhesive to the outer surface of the helix so that the material 12a covers the gap between the coils of the helix. This is achieved by taking a strip of the material 12b which is 25mm wide and 50 microns thick and helicaly winding it on to the elongated strip so that overlapping joints are formed between successive coils of the material 12a.

The wall 12 is then removed from the mandrel and the longitudinal strip 14 is cut through the wall so that it extends the length of the helix. Cutting the slit divides the helical polyester into parallel ribs 12b which are secured by the' adhesive to the sheet material 12a at longitudinal intervals. Because the ribs 12b have a pre-set curvature which is of smaller diameter than the diameter at which the material 12a was secured to the ribs 12b, the ribs cause the wall 12 to adopt a tubular form with the edges of the slit 14 overlapping one another.

The second illustrative sleeve 20 (see Figures 4,5 and 8) is similar to the first illustrative sleeve 10 but is constructed by a different method. The generally tubular wall 22 of the sleeve 20 comprises a layer of flexible sheet material 22a and a plurality of ribs 22b secured to the sheet material 22a at longitudinal intervals. The sleeve 20 also has a longitudinal slit 24.

The second illustrative sleeve 20 is manufactured by a method which comprises taking a strip of flexible sheet material 22a which is of constant width, this width being equal to the distance from one edge of the slit 24 to the other edge thereof measured around the sleeve 20 circumferentially. The flexible sheet material 22a is the same as that used in the first illustrative sleeve 10. The method also comprises taking an elongated sheet 26 of polyester (shown in Figure 4) which is thicker and stiffer than the material 22a. This sheet 26 has a width equal to the width of the sheet material 22a and is provided with slits 28 from opposite edges thereof. The slits 28 in a pair are close together to define a narrow portion 26a of the sheet 26 and the pairs of slits 28 are more widely spaced from one another to define a wider portion 26b of the sheet 26. The wider portions 26b are to form the ribs 22b and the narrow portions 26a joint the ribs together.

Next, in the manufacture of the sleeve 20, the sheet 26 us stretched longitudinally so that the spaces between the individual wide portions 26b are increased in width while the narrow portions 26a are deformed as shown in Figure 5. In the extended condition thereof, the sheet 26 is secured to the material 22a by adhesive. Thus, the ribs 22b are provided as a unit joined by the relatively narrow joining portions 26a. Next, as illustrated in Figure 8, the wall 22 made up of the material 22a and the ribs 22b is bent into the generally tubular form required for the sleeve 20 by bringing opposite edge portions of the wall 22 into an overlapping relationship and thereby defining. the slit 24 between said edge portions. Once the wall 22 is in its tubular form, the polyester of the ribs 22b is heat-set into the curvature which it has adopted.

The ribs 22b extend parallel to one another and are inclined to the longitudinal direction of the sleeve 20. The narrow portions 26a have been omitted from Figures 8 but remain in position in the sleeve 20.

The third illustrative sleeve 30 (see Figures 6 and 7) is similar to the second illustrative sleeve 20 except that its ribs 32b are formed differently. The ribs 32b are formed from a sheet of 36 which is similar to the sheet 26 but differs in the arrangement of slits 38 therein. The slits 38 all extend normally of the longitudinal direction of the sheet 36. The slits 38 all extend normally of the longitudinal direction of the sheet 36. The slits 38 are arranged in groups of three. with the centre slit in each group extending from one edge of the sheet 36 while the other two slits 38 in the group extend from the opposite edge of the sheet 36. The groups of slits 38 separate wide portions 36b which will form ribs 32b of the sleeve 30 while the slits 38 in a group define a narrow portion 36a of the sheet 36 (see Figure 7) causes the narrow portions 36a to be deformed into generally inverted V-shapes while the wider portions 36b are further apart but extend normally of the sheet 36. The stretched sheet 36 provides the ribs 32b (formed by the portions 36b) as a unit joined by the portions 36a. The wall 32 made-up from the material 32a and the ribs 32b is then bent into a tubular form in a similar manner to the wall 22 of the sleeve 20 and the ribs 32b are heat-set to their curvature. Thus, the sleeve 30 has circumferentially-extending ribs 32b which are parallel to one another. The sleeve 30 also has the narrow portions 36a left in position. The edges of the wall 32 define the slit 34.

The fourth illustrative sleeve 40 (see Figures 9,10 and 11) is similar to the sleeves 20 and 30 except in the formation of its ribs 42b. Thus, the sleeve 40 has a wall 42 formed into a tubular shape and defining a longitudinally extending slit 44 which gives access to the interior of the sleeve 40.

The ribs 42b of the sleeve 40 are formed from an elongated sheet 46 of polyester material which is shown in Figure 9. The sheet 46 has a pattern of slits 48 formed therein (only those at the right-hand end of the sheet 46 are shown in Figure 9). The slits 48 do not extend to the edges of the sheet 46 but are aligned normally to the longitudinal direction of the sheet 46. The method of manufacturing the sleeve 40 is similar to the methods by which the sleeves 20 and 30 are manufactured, The longitudinal stretching of the sheet 46 results in it adopting the appearance shown in Figure 10 in which the slits 48 have stretched into leaf-shaped holes 51 separated by portions 46b of the sheet 46.

Each of the portions 46b follow a sinusoidal path from one edge of the sheet 46 to the other edge thereof. These portions 46b form the ribs 42b of the finished sleeve 40. While in its expanded condition, the sheet 46 is rolled into a tubular shape (as shown in Figure 11), the sheet 46 is heat-set in the curvature which it has adopted, and flexible sheet material 42a is secured to the outer surface of the sheet 46.

The fifth illustrative sleeve 50 (see Figure 12) is similar to the sleeve 10, having a tubular wall 52 and a slit (not shown). The wall 52 comprises an outer layer 52a of flexible sheet material and a plurality of ribs 52b secured to the inwardly- facing. surface of-the material 52a. However, unlike the sleeve 10, the wall 52 of the sleeve 50 also comprises a flexible inner cushioning and thermally- insulating layer 52c secured by adhesive to the inwardly facing surfaces of the ribs 52b. Thus, the ribs 52b are positioned between the layers 52a abd 52v.

The layer 52c is formed by helically-winding a strip of polyester felt so that successive turns abut one another (shown spaced for clarity in Figure 12) and winding the other layers 52b and 52a on top.

In sleeves 20,30 and 40, stretching the sheets 26, or 36 or 46 may result in twisting but this can be overcome by heat-setting to a flat form before attachment to the material 22a, or 32a or 42a.

In sleeves according to the invention, the slit which gives access to the interior of the sleeve may not extend in a straight line longitudinally of the sleeve but may, for example, follow a zig-zag or sinusoidal path or even a helical path.