GB2207086A

GB2207086A - Fixing of components relative to each other

Info

Publication number: GB2207086A
Application number: GB08717611A
Authority: GB
Inventors: Frederick Arthur Randle
Original assignee: Plessey Co Ltd
Current assignee: Plessey Co Ltd
Priority date: 1987-07-24
Filing date: 1987-07-24
Publication date: 1989-01-25
Anticipated expiration: 2007-07-24
Also published as: EP0326593A1; JPH02500985A; GB8717611D0; WO1989001019A1; GB2207086B

Abstract

The invention provides an improved method of fixing components relative to one another in which a thermoplastic cement arranged to be electrically heatable is used for joining the two components together. Electrical heating of the joining cement enables final positioning or re-positioning of the components. Particularly the method is used in mounting of a fibre optic light conductor (10) relative to a base (12).

Description

IMPROVEMENTS IN OR RELATING TO THE FIXING OF COMPONENTS.

This invention relates to the fixing of components together and is particularly, but not exclusively concerned with the fixing of small dimension components which require, during fixing, positioning accurately relative to one another. An example of such micropositioning would be the mounting of a diode laser and fibre optic light conductor relative to one another to achieve maximum transfer of energy.

It is an object of the present invention to provide a novel method of relatively fixing components, and devices including such relatively fixed components.

According to the present invention, there is provided a method of rigidly fixing components relative to one another comprising the steps of mounting a first component in a thermo-plastic cement, providing electrical heating within the cement, positioning the first component to its desired position and reducing the electrical heating in the cement to solidify the same whilst maintaining the position of the first component.

The invention also includes a plurality of relatively fixed components wherein the fixing has been effected by the aforesaid method.

The invention will be described further, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a diagram illustrating the method of fixing a component in accordance with the present invention; Figure 2 is a perspective diagrammatic view of a component fixed at two points in accordance with the method of the present invention; and Figure 3 is a perspective diagrammatic view of two components fixed together at a plurality of fixing points in accordance with the method of the invention.

Referring firstly to Figure 1, there is shown a fibre optic cable whose end 10 is mounted relative to and projects from a base 12.

For the purpose of this description, the base 12 may be considered as a second component but it will be realised that the base 10, in use, supports a second component (not shown) in fixed relationship thereto and the end 10 of the fibre optic cable is to be adjusted relative to the supported second component.

The end 10 is rigidly fixed in an aperture 14 of the base 12 by means of a thermo-plastic cement 16 such as glass. The base 12 is conductive as also is the surface of the cable end 10. This conduction on the surface of the cable end 10 may be achieved by appropriate metallization as by plating or vapour deposition. Embedded in the cement 16 is an electrically conductive heating element 18 which may take the form of a watch spring. The spirally outer end of the element 18 is electrically connected to the base 12 whilst the other end is electrically connected to the surface coating of the cable end 10.

Considering the point at which the cable end 10 passes through the cement 16 as the origin, it will be appreciated that, on melting of the cement 18, the cable end 10 is allowed six degrees of freedom as indicated by the arrows 20 in the diagram.

Thus, an electrical current from a source 22 is passed between the base 12 and the cable end 10 sufficient to melt the cement 16.

The cable end 10 is then repositioned to its optimum position relative to a second component as above mentioned (which may be a diode laser or a photo-diode for example). The electrical current is then reduced. If this is effected slowly, the cement solidifies radially inwardly towards the cable end 10 in a stress free manner giving subsequent high mechanical strength against, for example, shock failure. Depending on the cement used, the rate of reduction of the heating current can vary up to an instantaneous termination. It will be appreciated that the cable end 10 is held in the desired optimum position by its positioning means, until the cement is completely solidified.

Figure 2 shows one method of mounting a fibre optic cable end 10 in a terminator 24 for optimal positioning the end 10a relative to a light emitting or receiving device 26. The device 26, in use, is located in a fixed position relative to the terminator 24 and it is necessary that the relationship between the cable end 10a and the terminator 24 be accurately pre-established.To this end, the terminator 24 includes two bushes 28, 30 (each corresponding to the base 12 of Figure 1) wherein the cable end 10a is concentrically mounted in a thermo-plastic cement plug 16a incorporating an electrical heating element 18ffi. As in the previous embodiment, the bushes 28, 30 are electrically conductive and the cable end 10a is metallized to render it conductive. The heating elements 18a are connected by their spirally outer end to the bush 28 or 30 and by their other ends to the metallized surface of the cable end 10#. The heating elements 18 are connected to respective current sources 32, 34 so that they may be differently energised.

Both heating elements 18# are initially energised to melt the cement plugs 16a permitting the six degrees of freedom in positioning the free end of the cable end 16a relative to the device 26. Thereafter the current supplied by the current source 32 is reduced so that the annulus of molten cement in the bush 28 is reduced in size to approximately the radius of the cable end 10a. In this way, the first fixing location (in the bush 28) acts as a pivot point and final, very fine adjustment of the free end of the cable end 10a relative to the device 26, can be effected.

Figure 3 shows an arrangement wherein a three-point fixing of a movable plate 36, for example a mirror, relative to a fixed plate 38, is effected. Each of the fixing locations is as described in relation to Figures 1 and 2 above with the exception that metal pins 40 are used for mounting the plate 36 rather than the ends of a fibre optic cable.

Respective heating elements 18b are provided in the thermo-plastic cement plugs 16b and are connected to respective current sources 42, 44, and 46.

The arrangement shown permits manufacturing to be effected with less regard for positional tolerances and for subsequent micropositioning of the mirror (the movable plate 36) to within very small tolerances, in the apparatus wherein it is to be employed.

The invention has been described in detail with reference to particular examples but it will be appreciated that many variations are possible. For example, the thermo-plastic cement may itself be conductive. Conductive glasses, for example, are well known in the art. Using such conductive cement would eliminate the need for incorporation of a heating element in the cement, facilitating manufacture.

Thermo-plastic cements other than glass may be used.

The method according to the present invention greatly facilitates the micro-positioning of components used in fibre optic technology but it is not to be considered limited thereto. However, as described, it enables the positioning of such components in a stress free cement thereby minimising adverse effects of shock on the fixed components. It will be appreciated that fixing, according to the present invention, readily permits re-fixing of components relative to one another if, at any subsequent time, this becomes necessary.

Other variations are possible within the scope of the present invention.

Claims

CLAIMS:

1. A method of rigidly fixing components relative to one another comprising the steps of mounting a first component in a thermoplastic cement, providing electrical heating within the cement, positioning the first component to its desired position and reducing, the electrical heating in the cement to solidify the same whilst maintaining the position of the first component.

2. A method as claimed in claim 1 comprising the steps cementing the first component using the thermo-plastic cement relative to a conductive base, simultaneously inserting an electrical heating element in the cement around the first component, and passing an electrical current through the element' to melt the cement around the first component.

3. A method is claimed in claim 1 comprising the steps of cementing the first component using a thermo-plastic conductive cement relative to a conductive base, making electrical contact with the cement adjacent the first component, passing an electrical current through the cement between the base and the electrical contact to melt the cement around the first component.

4. A method as claimed in any of claims 1 to 3 wherein the thermo-plastic cement is glass.

5. A method as claimed in any of claims 1 to 4 wherein the first component is electrically conductive or has an electrically conductive contact thereon and constitutes a terminal for effecting electrical heating of the cement.

6. A method as claimed in any preceding claim comprising the step of similarly fixing the first component at a second spaced location, and effecting limited electrical heating at the first fixing location relative to the electrical heating at the second spaced location whereby the component may be pivoted about its first fixing location.

7. A method of securing a first component relative to a second component at a plurality of locations, each fixing location being effected by the method as claimed in any preceding claim.

8. A method of securing a plurality of components relative to one another substantially as hereinbefore described.

9. A plurality of components rigidly fixed relative to one another by the method as claimed in any preceding claim.