GB2073620A

GB2073620A - Apparatus for applying powder to a flexible elongate element

Info

Publication number: GB2073620A
Application number: GB8111997A
Authority: GB
Original assignee: BICC PLC
Current assignee: Balfour Beatty PLC
Priority date: 1980-04-16
Filing date: 1981-04-15
Publication date: 1981-10-21

Abstract

Apparatus for applying dusting powder to an advancing optical fibre F or other flexible elongate conductor comprises a cylindrical container 1 having in its end walls 2, an inlet port 5 and an outlet port 6 through which the fibre advances. The end walls 2 are secured together and spaced apart by circumferentially spaced rods 3. When the container 1 is rotatably driven about an axis passing through the inlet and outlet ports 5 and 6, powder partly filling the container is caught by the rods 3 and is caused to drip prior to reaching its zenith, thereby creating a cloud of powder through which the fibre F passes. <IMAGE>

Description

SPECIFICATION Improved apparatus for applying powder to a flexible elongate element This invention relates to apparatus for applying powder to a flexible elongate element as the element travels in the direction of its length through the apparatus and is especially, but not exclusively, concerned with apparatus for applying powdered French chalk, talc, or other dusting powder, to an advancing flexible elongate conductor. For convenience, such apparatus will hereinafter be referred to as dusting apparatus.

It is an object of the present invention to provide simple and inexpensive dusting apparatus which is especially, but not exclusiVely, suitable for applying dusting powder to a flexible elongate conductor in the form of an optical fibre advancing in the direction of its length.

According to the invention, the dusting apparatus comprises a container partly filled with dusting powder and having inlet and outlet ports for passage through the container in a substantially horizontal plane and in a rectilinear direction of a flexible elongate element advancing in the direction of its length, and means for rotatably driving the container about an axis extending through the inlet and outlet ports of the container, the arrangement being such that, as the container is rotatably driven about said axis, a flexible elongate element advancing through the container passes through a cloud of dusting powder.

Since the flexible elongate element is not caused to pass through a body or pile of dusting powder but passes through a cloud of dusting powder, the advancing element is subjected to substantially no drag and, as a consequence, the dusting apparatus is especially suitable for applying dusting powder to an advancing optical fibre or other advancing relatively fragile filament.

Preferably, the container is of substantially cylindrical shape with the inlet and outlet ports in the end walls of the cylindrical container.

Preferably, also, extending between the end walls is a plurality of substantially rigid elongate members which are circumferentially spaced around the container and which serve to catch powder and cause it to drop prior to powder reaching its zenith, thereby creating the desired cloud of dusting powder through which a flexible elongate element is caused to pass and limiting the quantity of powder which drops directly on to the flexible elongate element. In-a preferred embodiment, the cylindrical container is of substantially circular cross-section with the inlet and outlet ports at the centres of the circular end walls. In order that the operation of the dusting apparatus can be readily monitored, the circumferential wall of the cylindrical container is preferably of transparent material.

The means by which the container is rotatably driven about an axis extending through the inlet and outlet ports may take any convenient form but, where the container is a cylinder of circular cross-section, said means preferably comprises a pair of rollers arranged with their axes parallel and so transversely spaced apart that the cylindrical container can be supported on and between the rollers with its axis parallel to the axes of the rollers, at least one of the rollers being rotatably driven to impart rotational motion to the cylindrical container. The use of a pair of transversely spaced rollers for supporting and rotatably driving the container has the advantage that the container can be readily disengaged from the drive means for the introduction of dusting powder into the container.

To enable dusting powder to be introduced into the container, the container may have in one or each of its end walls, a filler hole with a detachable cap or plug; alternatively, one or other of the inlet and outlet ports may be employed for this purpose.

The dusting apparatus of the present invention is especially suitable for use in a method of sheathing an optical fibre which comprises forming by extrusion a sleeve of plastics material and feeding an optical fibre into the sleeve as the sleeve is extruded, the diameter of the sleeve being substantially greater than the diameter of the fibre, the optical fibre passing through the dusting apparatus-which applies dusting powder to the optical fibre prior to being fed into the extruded sleeve.

An example of dusting apparatus in accordance with the invention for applying powdered French chalk to an optical fibre travelling in the direction of its length will now be described with reference to the accompanying drawing, in which: Figure 1 is a diagrammatic isometric view of the apparatus' and Figure 2 is a transverse cross-sectional view of the container of the apparatus.

Referring to the drawing, the dusting apparatus comprises a cylindrical container 1 of circular cross-section having end walls 2 secured together and spaced apart by twelve circumferentially spaced rods 3, and a transparent circumferential wall 4. Centrally positioned in one end wall 2 is a circular inlet port 5 and centrally positioned in the other end wall is a circular outlet port 6. One end wall 2 has a filler hole closed by a removabie plug 7. The cylindrical container 1 is supported with its axis lying in a substantially horizontal plane on and between two rollers 8, one of which is rotatably driven by a motor (not shown) to impart rotational motion to the container about an axis passing through the inlet and outlet ports 5 and 6.The cylinder 1 has an overall length of 7.75 inches, an overall diameter of 3.5 inches and each inlet and outlet port 5 and 6 has a diameter of 0.5 inches.

Each rod 3 has a diameter of 0.2 inches.

In use, with the cylinder 1 approximately halffilled with powdered French chalk, an optical fibre F travelling in the direction of its length towards an extrusion machine where a loose sleeve of polymeric material is to be extruded around the fibre, passes into the cylinder 1 through the inlet port 5 and out of the cylinder via the inlet port 6.

Whilst the fibre F is travelling through the container 1, the container is rotatably driven about its axis at a rotational speed of approximately 30 revolutions per minute. As the container 1 rotates, the rods 3 catch powdered French chalk and cause it to drop prior to it reaching its zenith, thereby creating a cloud of powdered French chalk through which the fibre F passes. On emerging from the container 1, the fibre F has an overall coating of powdered French chalk which serves to reduce any effects of friction between the fibre and the surrounding sleeve during subsequent annealing of the sleeve.

Although the dusting apparatus of the present invention is especially suitable for applying dusting powder to an optical fibre or other fragile flexible filament, it is to be understood that the apparatus can also be used for applying dusting powder to other flexible elongate conductors, such as an insulated conductor or cable.

Claims

1. Dusting apparatus comprising a container partly filled with dusting powder and having inlet and outlet ports for passage through the container in a substantially horizontal plane and in a rectilinear direction of a flexible elongate element advancing in the direction of its length, and means for rotatably driving the container about an axis extending through the inlet and outlet ports of the container, the arrangement being such that, as the container is rotatably driven about said axis, a flexible elongate element advancing through the container passes through a cloud of dusting powder.

2. Dusting apparatus as claimed in Claim 1, wherein the container is of substantially cylindrical shape with the inlet and outlet ports in the end walls of the cylindrical container.

3. Dusting apparatus comprising a-container of substantially cylindrical shape partly filled- with dusting powder and having in its end walls inlet and outlet ports for passage through the container in a substantially horizontal plane and in a rectilinear direction of a flexible elongate element advancing in the direction of its length, a plurality of substantially rigid elongate members which extend within the container between the end walls and which are circumferentially spaced around the container, and means for rotatably driving the container about an axis extending through the inlet and outlet ports of the container, the arrangement being such that, as the container is rotatably driven about said axis and a flexible elongate element is caused to advance through the container, the rigid elongate members catch powder and cause it to drop prior to powder reaching its zenith, thereby creating a cloud of dusting powder through which the flexible elongate element passes and limiting the quantity of powder which drops directly onto the flexible elongate element.

4. Dusting apparatus as claimed in Claim 2 or 3, wherein the cylindrical container is of substantially circular cross-section with the inlet and outlet ports at the centres of the circular end walls.

5. Dusting apparatus as claimed in Claim 4, wherein the means by which the container is rotatably driven comprises-a pair of rollers arranged with their axes parallel and so transverseiy spaced apart that the cylindrical container is supported on andbetween the rollers with its axis parallel to the axes of the rollers, at least one of the rollers being rotatably driven to impart rotational motion to the cylindrical container.

6. Dusting apparatus as claimed in any one of Claims 2 to 5, wherein the circumferential wall of the cylindrical container is of transparent material.

7. Dusting apparatus as claimed in any one of Claims 2 to 6, wherein the container has in one or each of its end walls, a filler hole with a detachable cap or plug.

8. Dusting apparatus substantially as hereinbefore described with reference to and as shown in the accompanying drawing.