GB2207970A

GB2207970A - Articulated joint

Info

Publication number: GB2207970A
Application number: GB08719155A
Authority: GB
Inventors: Andrew Damien Macgregor; Michael Dennis Simmons
Original assignee: Coal Industry Patents Ltd
Current assignee: Coal Industry Patents Ltd
Priority date: 1987-08-13
Filing date: 1987-08-13
Publication date: 1989-02-15
Also published as: GB8719155D0

Abstract

An articulated joint of the ball and socket construction, used in an optical measuring device, includes on the ball (3) a mirror (10) in a recess which can receive light from a light source (8) located internally of one of the members. The joint is limited in its rotation and is sealed so that it can be used in an environment which is hostile. <IMAGE>

Description

ARTICUL~TED JOINT This invention relates to an articulated joint and deals specifically with an improved form of joint suitable for use with optical measuring devices. The joint is of the kind using a ball and socket configuration.

In our co-pending patent application number

there is described and claimed a method of measuring the deviation of a borehole using an optical device which is passed along the borehole and which relies on deflections of light fran an optical source onto a detector array to give an indication of the inclination of the two elements of the detector. Since the device is being used in a situation where environmental conditions are rOugh it is essential that the optical parts of the system are kept clean and that the moving parts are robust. This is a very difficult requirement and has required a special type of joint.

Such a special joint is the subject of the present invention and although it has its particular application or the method is as described in the co-pending application it clearly has wider applications Wherever an optical deviation is to be measured at a joint.

According to the present invention an articulated joint for an optical measuring device includes a ball arranged to be connected to a first element and a socket engaging the ball and arranged to be connected to a second element, the ball being provided with a mirror area on a part presented to the second element and the second element being apertured in the area of the socket to allow a light beam fran a light source within the second element to impinge on the mirror.

The mirror may be carried on the exterior of the ball of the joint but preferably the ball is recessed and the mirror is set into this recess.

Generally the two elements would be expected to have restricted movement relative to each other and this may be arranged by providing the joint with suitable limiting means such as dowels engaging with the ball and slots in the socket or external lips engaging with the socket end.

The joint may have associated with it lens arrangements for directing the light onto the mirror.

In order that the invention may be readily understood one example of an articulated joint in accordance therewith will now be described with reference to the two figures of the acccmpanying drawings.

The drawings show in figure 1 the joint between two tubular elements of a measuring device. Figure 2 shows in detail the construction of the ball part of the joint.

Referring now particularly to figure 1 the joint here is used in a measuring device for determining the deviation of a long drilled hole and comprises two tubular elements 1, 2. The element 1 is a leading passive element and contains no active components whereas the element 2 contains a number of active ocEponents including measuring devices and has a trailing wire (not shown) which feeds electrical information and signals to and fran the element 2. The tubes 1 and 2 are made fran stainless steel and are joined by the articulated joint of the invention. This canprises basically a spherical ball 3 surrounded by a cap 4 of a configuration corresponding to the spherical ball 3.The end of the element 2 has an insert 5 which has a spherical seating 6 for the ball 3.

Adjacent to insert 5 a lens arrangement 7 is positioned in the element 2 and this receives light fran a source 8 which is an LED.

The cap 4 is screwed onto the end of the insert 5 and has a knurled outer portion 9. To ensure the correct degree of 'play' in the ball joint, a shim will be inserted between the ball cap 4 and the insert 5 and the ball cap 4 will then be tightened. Once the correct degree of 'play' has been achieved, the ball cap may be screwed or swelled into the insert.

The element 1 has an insert 11 at its end which has an inwardly radial projection 12 which secures the ball 3 against rotation relative to the element 1 by use of a key 13. The end of the ball 3 is held against the insert 12 by a nut and washer assembly 14. The insert itself is secured to the element 1 by suitable screws 15. At its end the insert 11 has a radial flange 16 which surrounds the cap 4 although there is a short distance 17 between the edge of the flange 16 and the cap 4. Ihe effect of the flange 16 is to limit relative movement between the two elements 1 and 2.

Referring now also to figure 2, it can be seen here that the ball 3 has a recess 18 cut into it which gives a flat face 19 along the vertical axis as shown. This face is fitted with a mirror 10 which is vertical to the horizontal axis of the elements 1 and 2 when in their aligned position. The ball 3 on its stem 20 is provided with a key way 21 which receives the key 13 and an external circular groove 30 is provided in which a seal 22 is inserted to ensure that the atmosphere within the element 2 is kept uncontaminated. As can be seen fran figure 1 a dowel stud 23 is fixed into the outer surface of the ball 3 so that there is only limited movement of the ball relative to the cap 4.

In use light fran the source 8 is reflected through a mask 24 onto a mirror 25 through the lens arrangement 7 and onto the mirror 10 on surface 19 within the ball 3. Light is reflected fran this mirror 10 onto a detector array 26 and when there is relative movement between the elements 1 and 2 the reflected light illuminates different detectors in the array. This is explained in our co-pending application

The e use of the mirror 10 enables the length of the light path to be doubled over the length of light path that would be available if the light source was incorporated into the ball itself and therefore makes the arrangement more sensitive than would otherwise be the case.

In order to ensure the device is environmentally secure further sealing is provided by 0 ring seals 27, 28 and further sealing can be achieved by the provision of a bulkhead 29 welded into the tube 1.

the design of the articulated joint enables a highly sensitive practical and secure means to be provided for measuring deviation between the two elements 1 and 2.

Claims

1. An articulated joint for an optical measuring device ccmprising a ball arranged to be connected to a first element and a socket surrounding the ball and arranged to be connected to a second element, wherein the ball is provided with a mirror area on a part presented to the second element and an aperture in the socket end of the second element provides a path for light fran a light source in the second element to impinge on the mirror.

2. An articulated joint as claimed in claim 1 in which the mirror is located in a recess in the ball.

3. An articulated joint as claimed in claim 1 or 2 wherein the joint includes means for restricting the movement of the elements connected to the joint.

4. An articulated joint as claimed in claim 3 wherein the means canprises dowels carried by the ball and engaging with part of the socket.

5. An articulated joint as claimed in claim 3 wherein the means canprises an external flange spaced from the socket but permitting limited articulated movement thereof.

6. An articulated joint substantially as hereinbefore described with reference to figures 1 and 2 of the aocanpanying drawings.