GB2315702A - Integral tube having strands - Google Patents

Abstract

In order to make an integral plastics material tube which has a wide range of diameter change and is suitable for the use for protecting or collating cables, a bi-planar diamond net tube 1 is extruded and the angle between one set of strands 2 and the other set of strands 3 is changed to cause the portions of the strands 2, 3 at their interconnections to rotate with respect to each other and cause the plastics material at the interconnections to be molecularly oriented into oriented joints that allow the angles between the sets of strands 2, 3 to be readily changed.

Description

Integral Tube Background Extruded, polymeric diamond integral net tubes manufactured using the process of GB 836 555, GB 928 954, or other extruded net processes, and also woven, braided tubes, are used as protective sleeves for a wide range of components and applications, because of their ability to be expanded and contracted over a range of diameters. Similar tubes can be used for collation, to hold a number of components together. The components can be for instance electric cables or tubes or hoses. The "protection" may be to protect the components inside the sleeve or to protect external components, materials or persons from the components inside the sleeve.

The extruded, integral tubes can be manufactured on relatively simple machinery, but are limited in the range of diameters over which a single tube can be applied, typically 2.5:1 or less.

The woven braided tubes can have a wide range of diameter change, with greater flexibility but need complex, small diameter, circular weaving machines for their manufacture.

It is desirable to combine the ease of manufacture of the extruded net tubes with the wide range of applications of the woven braided tubes.

A "swivel joint" was used in a Netlon Limited hat moulding net in the 1960's to provide ease of moulding hat forms and heat-setting to shape, so that the strands could swivel easily during moulding, but then retain shape after heat-setting. After yielding in one direction during the moulding operation, the joint was then heat-set at its new angle.

The Invention The present invention provides methods as set forth in Claims 1 or 3, integral tubes as set forth in Claims 4, 5 or 7, and the tube in use, positioned around one or more components to protect and/or collate the component(s).

The invention provides rotational integral hinges as swivel joints between the strands of one set and the strands of the other set. When initially changing the angle, the material that is oriented may originate in the strand, and it is possible that both the for instance infinitesimally thin layers forming the original interconnection between the strands and the adjacent material from the strands orient to form ajoint in the finished product. The mechanism will depend on the form of the interconnection between the strands in the as-cast material.

In general, there is a very small intersection area between the strands, and the molecular orientation of the joints causes the joints to act like pivots so that the angle between the sets of strands can be readily changed. When the tube is expanded to pull it over one or more components, the strands do not flex or bend significantly at the joints, their stiffness being sufficient to apply sufficient torque to the joints to cause the joints to swivd; in other words, the tube on expansion yields by rotation at the joints more than by significant bending of the strands. In this way, the inner and outer strands act like two helical springs; they can be expanded until their turns are in contact almost along the whole of their lengths, and their resilience can provide some clamping as the strands tend to return to their as-cast configuration.

In general terms, the as-cast material (for instance the material after extrusion and passing over the sizing mandrel, if used) should exhibit some bi-planarity, but it is not required that there should be no or substantially no overlap between the inner and outer strands as it may be possible to make the product even if there is a large overlap of strand cross-sections. Furthermore, the product can be made from as-cast materials which are beyond bi-planar, for instance by extruding the inner strands into spiral grooves in a rotating sizing mandrel which are deeper than the inner strands, so that the sizing mandrel causes the outer strands to be pulled away somewhat from the inner strands; in any case, some separation can be obtained with normal extrusion techniques, eg a separation of not less than about 1:30, or of not more than about 1:10, preferably about 1:20, as a ratio of the thickness of the tube wall.

The sections of extruded strands vary somewhat along the lengths of the strands and only approximate to geometrical shapes. However, the strands preferably are of generally rectangular shape, taller than they are wide (though they may be considerably canted over), with a height to width ratio eg not less than about 1.3:1 or 1.4:1 and eg not greater than about 1.8:1 or 2:1. The strand sections could alternatively be of a special profile, eg as in GB 1 210 354.

The temperature at which the oriented joints are formed can be any temperature at which the plastics material is sufficiently solid for the joints to be mechanically swivelled; the relationship of the joint-pivoting modulus to the strand-bending modulus is not very temperature dependent, and the lower limit is determined by the particular products and polymer. With a suitable plastics material, the temperature could be room temperature and the orientation could be effected immediately before or during braiding or collating. Once the oriented swivel joint is formed, it is preferably not subsequently heat set, ie it is preferably not heated above a temperature at which it de-orients (heat setting an oriented plastics material requires constraining the plastics material to prevent any shrink back, heating to a temperature significantly above the orientation temperature, and cooling). Nonetheless, the tube could be heat set if desired, for instance in its flilly-extended configuration.

The plastics material can be any suitable molecularly orientable material, preferred materials being polyamides, polyesters and polyolefins.

Although said angle need be changed in only one direction, it is preferably changed in one direction relative to the as-extruded configuration and is then changed in the opposite direction. The amount by which the angle need be changed will vary according to the plastics material, the temperature and the rate of change. However in general, the angle change is preferably greater than about 15 , about 20 , about 30 , about 40 , or about 50 ; the angle change is the total angle through which the angle is changed, as measured from one extreme position to the opposite extreme position (one of which extreme positions would be the starting position if the angle is changed in one direction only).

Preferably, the net formed by the sets of strands is a diamond net in which each set of strands makes approximately the same (but opposite) angle with the machine direction.

However, this is not essential, and the angles can be different or one set of strands can extend in the longitudinal direction.

Preferred Embodiments The invention will be further described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a plan view of an as-cast tube for forming a braided tube in accordance with the invention; Figure 2 is a plan view of the tube of Figure 1 extended to its maximum length; Figure 3 is a plan view of the tube of Figure 1 compressed to its minimum length; Figure 4 is a schematic isometric view of a typical interconnection between two strands in an as-cast tube; Figure 5 is a schematic elevation of the interconnection of Figure 4; Figure 6 is an elevation showing the oriented joint after swivelling the interconnection of Figure 4; Figure 7 is a partly schematic plan view of a typical interconnection between two strands in a second as-cast tube; Figures 8 and 9 are vertical sections along the planes VIII-VIII and IX-IX in Figure 7; Figure 10 is an isometric view of the interconnection of Figure 7 but taken from a photograph of an actual interconnection; Figures 11 and 12 correspond to Figures 8 and 9, but show the oriented joint after swivelling the interconnection; Figure 13 is an isometric view of the oriented joint of Figures 11 and 12 but taken from a photograph of an actual joint; Figure 14 is a schematic elevation of a first production machine; Figure 15 is a schematic elevation, showing a variation of Figure 14; Figure 16 is a schematic elevation of another production machine; and Figures 17 and 18 illustrate two uses of the braided tube of the invention.

Figures 1 to 3 Figures 1 to 3 illustrate the invention as applied to a tubular diamond form integral net.

An integral diamond net tube 1 as cast by the extrusion process is shown in Figure 1. It consists of two sets of strands runing in opposite helical directions, outer strands 2 and inner strands 3. If, at each crossing point of the inner and outer strands 2, 3, there is formed between the strands 2,3 an integral rotational hinge joint, the tube shown in Figure 1 can be readily expanded in length to the form shown in Figure 2, at which point its turns are in contact and it has its minimum diameter, or contracted in length to the form shown in Figure 3, at which point its turns are again in contact and it has its maximum diameter.

Figures 4 to 6 Figure 4 shows the strands 2, 3 connected at an interconnection 4 in the as-cast form.

The machine direction is indicated as MD, and e is the strand angle. If the strands 2, 3 are rotated in the direction of the arrows A or B, the interconnection 4 is subjected to rotational shear. If the rotational shear yield moment of the intersection 4 is less than the bending yield moment for the strands 2, 3, forces applied in directions of arrows A or B will cause the intersection 4 to yield in rotational shear before the strands 2, 3 yield in bending. If the intersection 4 is yielded first in one direction then optionally in the other, the intersection becomes oriented into an integral rotational hingejoint 5 as shown in Figure 6, forming a tubular net or braided tube 6 in accordance with the invention.

Figures 7 to 13 The same references used as in Figures 1 to 6. The strand 2 is of generally rectangular section and has a height:width ratio of about 1.6:1 but is somewhat canted over; the strand 3 is of similar section with a height:width ratio of about 1.5:1 but is very canted over. In this canted situation, height is measured in directions h and width is measured in directions w. In this case, there was some tearing of the material in the area 7 (Figures 11 and 13) during the orientation of the hinge joint 5. After formation of the integral hinge joint 5, the strands 2 and 3 are substantially further apart. In the as-cast net 1 of Figures 7 to 10, the distance apart of the strands 2 and 3 was about 1/20 of the net thickness; in the braided tube 6 of Figures 11 to 13, the distance apart was about 1/8 of the net thickness.

Figure 14 Suitable equipment for manufacturing braided tubes 6 according to this invention is illustrated in Figure 14. The equipment comprises a suitable diehead 8 for manufacturing an integral bi-planar diamond net in accordance with GB 836 555 or GB 928 954, a sizing mandrel 9 over which the diamond net (1) is cast, and spray nozzles or water jets 10 to cool and solidify the diamond net (1). The sizing mandrel 9 is fastened to the diehead 8. Downstream of the sizing mandrel 9 an expanding mandrel 11 is fastened to the sizing mandrel 9 by a towing wire or rod 12. A caterpillar haul-off 13 pulls the diamond net (1) over the sizing mandrel 9 and along a smaller diameter portion of the expanding mandrel 11 and then pushes the diamond net on to a larger diameter portion of the expanding mandrel 11. This causes the joints in the diamond net to rotate in the direction necessary to move from the form of Figure 1 towards the form of Figure 3. The smaller diameter portion of the expanding mandrel 11 may be of a similar diameter to the sizing mandrel 9 or it may be significantly smaller than the sizing mandrel 9. In this latter case, the tension generated in the diamond net by the caterpillar haul-off 13 to pull the diamond net off the sizing mandrel 9 may cause rotation of the interconnections 4 in the diamond net 1 from the form of Figure 1 towards the form of Figure 2. The diamond net (6) is then pulled off the expanding mandrel 11 by equipment 14 which may be a haul-off nip or a wind-up mechanism.

The tension generated to pull the net off the expanding mandrel 11 will cause rotation of the joints within the net 6 towards the form of Figure 2.

Figure 15 As an alternative to the "towed" expanding mandrel 11 shown in Figure 14, a freefloating expanding mandrel 15 as illustrated in Figure 15 may be employed. This freefloating mandrel 15 is trapped between haul-off rollers 16 and a stop mechanism 17 which is formed by a stationary guide or by stationary rollers.

The caterpillar haul-off 13 as shown in Figure 14 and the driven haul-off rollers 16 shown in Figure 15 are interchangeable.

Figure 16 Figure 16 shows an arrangement in which the machine direction is vertical, and in which, in place of the expanding mandrel 11 or 15 of Figures 14 and 15, a smooth expanding ball 18 is used, trapped between haul-off rollers 16 and a stop mechanism 19 which may be a stationary ring. The net (1) is extruded into a water tank 20 and is turned around a roller 21 by the haul-off rollers 16.

Example A protective sleeve was formed as set out below. The equipment was as in Figure 16.

Material: polyamide (Nylon) Grade: high viscosity stabilized extrusion grade.

Die diameter: 31.75 mm.

Slot type: straight cut.

Slot width: 0.61 mm.

Slot depth: 0.91 mm.

No. ofouter slots: 17.

No. of inner slots: 17.

Strand (filament) cross-sectional shape: generally rectangular with radiussed corners, as in Figures 8 and 9.

Outer strand maximum cross-section dimension: 0.83 mm.

Outer strand minimum cross-section dimension: 0.59 mm.

Inner strand maximum cross-section dimension: 1.00 mm.

inner strand minimum cross-section dimension: 0.57 mm Sizing mandrel diameter: 24.2 mm.

Expanding ball diameter: 40 mm.

Running speed; 4 mlmin.

Die rotation speed: 30 rpm.

Processing temperatures: Die head 8 295"C Water tank 20 10"C nominal Mean diameter of as cast product on reaching expanding ball 18: 24 mm.

9 on leaving sizing mandrel 9: 60c.

9 on reaching expanding ball 18: 60".

O on reaching maximum distortion over expanding ball 18: 120 .

o on reaching haul-off equipment 14: 60".

Product linear mass: 20 gJm.

Product inner diameter (as cast): 20 mm.

Maximum product inner diameter (flexed): 42 mm.

Minimum product inner diameter (flexed): 4 mm.

0 of product at maximum diameter: 165".

Figures 17 and 18 A braided tube 6 of the invention is shown protecting a cable 22 in Figure 17 and collating three cables 23 in Figure 18.

* * * The present invention has been described above purely by way of example, and modifications can be made within the spirit of the invention. The invention also consists in any individual features described or implicit herein or shown or implicit in the drawings or any combination of any such features or any generalisation of any such features or combination.

Claims (8)

CLAIMS:

1. A method of making an integral tube, comprising: integrally extruding a plastics material tube formed of at least two sets of strands with the strands of one set at an angle to the strands of the other set, respective strands at an angle to each other being interconnected where the strands cross; and at a temperature below the melt temperature of the plastics material, changing the angle between one set of strands and the other set of strands, to cause the portions of the strands at the interconnections to rotate with respect to each other and cause the plastics material in the interconnections of the strands to be molecularly oriented.

2. The method of Claim 1, in which, at a temperature below the melt temperature of the plastics material, said angle is changed in one direction relative to the as-cast configuration and is then changed in the opposite direction relative to the as-cast configuration.

3. A method of making an integral tube, substantially as herein described with reference to Figure 14 or Figure 15 or Figure 16 of the accompanying drawings or in the foregoing Example.

4. An integral tube made by the method of the preceding Claims.

5. An integral plastics material tube comprising an outer set of strands in a helical configuration, an inner set of strands in a helical configuration with the strands of the inner set at an angle to the strands of the outer set, respective strands of the outer and inner sets being interconnected where the strands cross by molecularly-oriented joints which act like pivots to enable the angles between the portions of the strands at the joints to be changed, whereby the tube can be expanded in diameter by decreasing the length of the tube, passed over one or more components, and have its diameter reduced by increasing the length of the tube to fit more closely on the component(s).

6. The tube of Claim 5, wherein the helix angles of the outer and inner sets of strands are in opposite directions.

7. An integral tube, substantially as herein described with reference to Figures 4 to 6 or Figures 7 to 13 of the accompanying drawings or in the foregoing Example.

8. The tube of any of Claims 4 to 7, positioned around one or more components to protect and/or collate the components and/or protect other components, materials or persons from the components inside the tube.