GB2106073A

GB2106073A - Protective tubing

Info

Publication number: GB2106073A
Application number: GB08216517A
Authority: GB
Inventors: Giovanni Schiapparelli
Original assignee: Individual
Current assignee: Individual
Priority date: 1981-09-10
Filing date: 1982-06-07
Publication date: 1983-04-07
Also published as: FR2512577A1; CS253705B2; CS624882A2; BE894341A; CH655597B; NL8203536A; JPS5851712A; PL130653B1; GB2106073B; IT8112620A0; ES8306848A1; ES512901A0; DE3221168A1; PL238188A1; DD206863A5; IT1146803B; FR2512577B1

Abstract

Protective tubing, such as insulation for electrical cables, is made by assembling non-woven yarns (2) in a longitudinal and mutually-parallel arrangement of tubular form, surrounding them with one or more helically- wound yarns (3) and impregnating the resultant assembly with a resin which is then dried to form the desired tubing (1). Yarns (2), Figure 3, are laid on mandrel 10, wound with yarn 3 from rotating bobbin 12, and impregnated with resin at 14 which is dried at 17. <IMAGE>

Description

SPECIFICATION Protective tubing This invention relates to protective tubing in general, and is particularly, but by no means exclusively, concerned with insulating tubing, e.g. for electrical use; the invention also relates to a simplified system for manufacturing such tubing, comprising both the relevant method and apparatus for making the tubing. The tubing of the invention can advantageously replace known insulating and other protective tubing, used especially in the electrical art, which tubing is generally formed as a tubular structure from various types of woven yarn, saturated with resinous material and arranged to form a flexible casing.Such tubing as now on the market is manufactured by a method mainly comprising three steps, namely (a) preparation of the woven yarn and its transfer from reels to bobbins, (b) location of the bobbins on a machine for forming a tubular woven structure and (c) arrangement of the latter in the form of large rolls, which are then transferred to the final apparatus for carrying out continuous impregnation and oven-drying.

Conventional protective tubing, called sometimes "sterling tubing", fully complies with current requirements of the art, but is very expensive, due to the complexity of its manufacturing process. An improved manufacturing process has been sought, therefore, in order to ensure a substantial reduction of costs. After long research, a complete solution of the problem has been achieved, which ensures a reduction of costs of over 70%.

According to one aspect of this invention, a method of manufacture of protective tubing is provided, in which a plurality of non-woven yarns are supplied from reels in a feeding creel by way of a felted roller arranged to equalize the tension of the yarns and a divider reed to a yarn-guide assembly comprising stationary means for distributing the yarns about a matrix rod in a longitudinal and mutually-parallel arrangement, a rotating drum carrying one or more bobbins of a winding yarn and one or more helix-forming needles being provided so as to wind one or more strands of the winding yarn about the parallel assembly of non-woven yarns, prior to impregnation oftheyarn assembly with a resin and drying to form the desired protective tubing.

In one preferred form of the invention, the nonwoven yarns comprise one or more animal, vegetable or synthetic fibre materials.

In a preferred embodiment of the method of the invention, the matrix rod is of uniform diameter, while in another preferred embodiment the matrix rod is of reduced diameter at one or more spaced locations where friction generated by the bundle of yarns is to be reduced.

The non-woven yarns are preferably distributed by passage through a stationary divider cylinder associated with a divider disc and having the matrix rod attached to its base. However, it will be apparent that other means for effecting this step in the method can be employed, if desired.

The resultant yarn assembly preferably is impregnated with the resin by being passed under the guidance of the matrix rod and after being helically bound together by the one or more strands of winding yarn, through a container for a supply of the impregnating material, such container including an inlet die-plate and an outlet or shaving die-plate, and the resultant resin-impregnated assembly is then dried by being passed through a drying or baking oven.

The tubing according to the invention may be generally characterised as comprising a yarn structure which is not formed by woven yarns, but by a plurality of longitudinal non-woven yarns which are assembled in a parallel and side-by-side arrangement and are peripherally bound together by a yarn or several yarns helically wound therearound, the assembly then being resin-impregnated as known in the art. Therefore, manufacture requires apparatus which is much simplified and which can be supplied directly from reels having a suitable yarn wound on them, while the continuous linear grouping of the yarns and their helical binding and the successive impregnation, feeding and oven-drying are effected in a single cycle which can be completed very quickly, since it is not slowed down by any weaving operation.The tubing made according to the method of tuhe invention is technically equivalent to the tubing marketed heretofore.

The tubing of the invention, broadly stated, comprises a protective tubing comprising a plurality of mutually-parallel non-woven yarns extending iongitudinally of the tubing and at least one other yarn helically wound around the non-woven yarns, the assembly of yarns being impregnated with a resin material.

The accompanying drawing shows, as a nonlimiting example, a length of tubing according to the invention and, diagrammatically, the general form of an apparatus for manufacturing it. In the drawing: Figure 1 shows a side elevational view of a length of tubing according to the invention; Figure 2 shows a cross-sectional view of the tubing of Figure 1; Figure 3 shows diagrammatically a general view of a form of apparatus for the continuous production of the tubing, the apparatus being shown arranged vertically, although it may also be either horizontal or of the inclined type.

As shown in Figures 1 and 2, the tubing 1 according to the invention comprises a structure of longitudinal parallel yarns 2 arranged in a side-byside relationship around the circumference of the tube and bound together by a yarn 3 (or several yarns), helically wound therearound with any desired pitch, the resultant assembly then being impregnated with a resinous material, as known in the art.

The apparatus for manufacturing the tubing comprises, as shown in Figure 3, the following components: a feeding creel 4 with a plurality of yarn reels, a felted roller 5 arranged to equalize the tension of the yarns 2, a divider reed 6, yarn guides 7, a divider cylinder 8 and associated divider disc 9, a matrix rod 10, a rotating drum 11 carrying at least one bobbin 12 of the winding yarn 3, a helix-forming needle 13 for guiding the yarn 3 from the bottom 12, a container of impregnating material, e.g. a bottle 14, an inlet die-plate 15 at the lower end of the container 14, an outlet or shaving die-plate 16 at its upper end and a drying oven 17; the finished tubing 1 is indicated at the top of Figure 3.

The apparatus operates as follows: the yarns 2, coming from the common feeding creel 4 on which the yarn reels are mounted, are grouped so as to pass the felted roller 5, arranged to as to equalize the tension of the yarns which, then divided in an orderly manner by the reed 6, are directed by the conventional yarn guides 7 to the inlet holes of the divider cylinder 8. These holes are formed radially in the cylinder 8, which is suitably supported on a fixed base. The yarns 2 are therefore obliged to enter the cylinder 8 around its circumference, i.e. they are distributed regularly and peripherally around it at equally-spaced intervals. Within the cylinder 8, the yarns converge towards the centre and pass into the holes of the divider disc 9, which arranges all the yarns around the circumference of the matrix rod 10.

This is fixed to the base of the drum 11 and passes through the divider disc 9 and extends along the vertical axis. The divider disc 9 comprises as many holes as there are yarns in the tubing 1 and is interchangeably mounted on the cover of the divider cylinder 8, so as to permit the mounting of other discs having a different number of holes, depending upon the diameter of the tubing 1 which is to be made. Mounted on the cylinder 8 is also the rotating drum 11 having a central opening and driven by a toothed belt 1 lea in a clockwise or anticlockwise direction, while the cylinder 8 remains stationary.

Mounted on the drum 11 are a suitably-braked yarn bobbin 12 and a helix-forming needle 13,through the free end of which passes the yarn 3 coming from the bobbin 12. When the apparatus is operating, that is when the vertically-disposed yarns 2 along the matrix rod 10 advance upwards due to the traction exerted thereon, the drum 11 rotates at a speed related to the linear extrusion speed according to the number of winding turns to the obtained. Therefore, the helix-forming needle 13 lays the winding yarn 3 around the vertical yarns 2 with the desired helixpitch and fastens them around the matrix rod 10. The resultant assembly is then introduced in this condition into the impregnation bottle 14 through the inlet die-plate 15.Within the bottle or other container 14, the assembly is impregnated with the material therein and then emerges through the outlet or shaving die-plate 16, which limits as desired the amount of impregnating material remaining on the surface of the tubing. Upon leaving the bottle 14 and the matrix rod 10, which ends at this point, the tubing is introduced into the baking oven 17, where it is dried and baked according to conventional procedure, and then emerges therefrom as the finished tubing 1.

Obviously, many changes can be made to the above system within the scope of the invention. The yarns forming the tubing 1 can be of any nature and this is also true of the impregnating material, depending on practical requirements. The matrix rod 10, which extends from the bottom of the divider cylinder, to which is is screwed or otherwise fixed, to beyond the outlet from the impregnation bottle 14, can be either of uniform diameter or of reduced diameter at one or more spaced locations, so as to reduce at these locations the friction generated by the yarn assembly, such friction depending upon the nature of the yarns. The cylinder 8 can be replaced by a single member having a hole of suitable diameter, whilst a curved tube can be used to guide the yarns to the holes in the divider disc 9. Moreover, the rotating drum 11 can support a plurality of yarn bobbins 12, so as to obtain different helix patterns on the tubing 1. Finally, it is to be noted that the system, which can be of the vertical, horizontal or inclined type, by replacing suitable members (which are all interchangeable to produce tubing of any desired diameter), can also extrude tubing of any section other than circular, for example square, hexagonal or the like, and always with a structure of multiple yarns of variable number, arranged in a longitudinal and parallel side-by-side relationship, assembled and bound together by one or more helically-wound yarns and then impregnated with a resinous material forming a casing film.

Claims

1. A method of manufacture of protective tubing, such as electrically insulating tubing, in which a plurality of non-woven yarns are supplied from reels in a feeding creel by way of a felted roller arranged to equalize the tension of the yarns and a divider reed to a yarn-guide assembly comprising stationary means for distributing the yarns about a matrix rod in a longitudinal and mutually-parallel arrangement, a rotating drum carrying one or more bobbins of a winding yarn and one or more helix-forming needles being provided so as to wind one or more strands of the winding yarns about the parallel assembly of non-woven yarns, prior to impregnation of the yarn assembly with a resin and drying to form the desired protective tubing.

2. A method according to claim 1, in which the non-woven yarns comprise one or more animal, vegetable or synthetic fibre materials.

3. A method according to claim 1 or 2, in which the matrix rod is of uniform diameter.

4. A method according to claim 1 or 2, in which the matrix rod is of reduced diameter at one or more spaced locations where friction generated by the bundle of yarns is to be reduced.

5. A method according to any preceding claim, in which the non-woven yarns are distributed by passage through a stationary divider cylinder associated with a divider disc and having the matrix rod attached to its base.

6. A method according to any preceding claim, in which the yarn assembly is impregnated with the resin by being passed under the guidance of the matrix rod and after being helically bound together by the one or more strands of winding yarn, through a container for a supply of the impregnating material, such container including an inlet die-plate and an outlet or shaving die-plate, and the resultant resin-impregnated assembly is then dried by being passed through a drying or baking oven.

7. A method according to any preceding claim, in which the yarn assembly is subjected to the respective treatment steps while passing vertically upwards.

8. A method according to claim 1, substantially as described with reference to Figure 3 of the accompanying drawing.

9. A protective tubing comprising a plurality of mutually-parallel non-woven yarns extending longitudinally of the tubing and at least one other yarn helically wound around the non-woven yarns, the assembly of yarns being impregnated with a resin material.

10. A protective tubing, when made by a method according to any of claims 1 to 8.

11. An electrical cable having a protective tubing according to claim 9 or 10.