GB2089251A

GB2089251A - Centre finders

Info

Publication number: GB2089251A
Application number: GB8039403A
Authority: GB
Original assignee: ACORN SPRING WORKS Ltd
Current assignee: ACORN SPRING WORKS Ltd
Priority date: 1980-12-09
Filing date: 1980-12-09
Publication date: 1982-06-23

Abstract

A "centre finder" for centering a workpiece relating to a workmember comprises an electrically conductive contact probe 5 having a free end and an end mounted on a base member 9 which allows movement of the free end in at least one plane, the base member being electrically insulated from the workmember on which, in use, it is mounted. An electrical indicating means 16 is provided which is electrically connected to the probe and has means 19 for connecting it to the workpiece so that a circuit is formed when the probe touches the workpiece, the circuit altering the state of the indicating means. The indicating means is preferably an audible and/or visual indicator such as a noise generator and/or light. <IMAGE>

Description

SPECIFICATION Improvements relating to "Centre Finders" The present invention relates to a "centre finder" for centering a workpiece relative to a workmember.

"Centre finders", otherwise known as wrigglers or wobblers, are well known and are used in such applications as centering workpieces on lathes or centering workpieces relative to drill chucks. Known centre finders generally comprise a shaft or probe having a free end and a ball at the other end which is received into a socket of a holder.

In use of known "centre finders", where for example one is trying to centre a rod for rotation in a lathe, the free end is placed against the rod and the rod rotated. If the position of the rod is not "dead centre" the rod will describe a circular path of larger diameter than the rod touching the probe end only once every revolution. If the position of the rod is dead centre, the probe will remain in contact for the complete rotation of the rod. The user of known centre finders must be trained to centre the rod visually on the lathe which can be a skilled and somewhat lengthy job, and which is not always particularly accurate due to the limitation of visual alignment.

The present invention seeks to avoid the above disadvantages of visual "centre finders" and to enable the quick centering of workpieces on workmembers without the need for skilled persons.

According to the present invention there is provided a "centre finder" for centering a workpiece relative to a workmember comprising: a) an electrically conductive contact probe having a free end and an end mounted on a base member which allows movement of said free end in at least one plane, said base member being adapted to be mounted on said workmember so as to be electrically insulated therefrom, and b) electrical indicating means connected to said probe and having means for connecting itto said workpiece, whereby a circuit is formed when said probe touches said workpiece which circuit alters the state of said indicating means.

Preferably the electrically conductive probe is attached to said base member by means of a spring loaded ball and socket joint, said ball preferably being located on said probe and the socket in said base member. The base member may be divided into a first portion connected to the probe and a second portion for connection to the workmember, and said first and second portions may be electrically insulated from one another by means of an insulating connector. The first portion may comprise the socket for receiving the ball of the probe and a collar, said socket being rotatable relative to the collar, and a torque bar may be connected to the collar. The first portion of the base and the probe are preferably inter-electrically conductive.

The indicating means is preferably an audible and/or visual indicator such as a noise generator and/or light which is normally off (or in the off state), and which switches on when the probe touches the workpiece and subsequently switches off when the probe departs from contact with the workpiece.

The present invention is now described with reference to the accompanying drawing which shows one application of its use.

Referring to the drawing, the head of a drill chuck 1 is shown having a plurality of jaws 2 for gripping a drill bit (not shown). In this example of the application of the invention, a circular aperture 3 in a sheet of metal 4 needs to be enlarged by lowering a drill bit of larger diameter than aperture 3 onto the sheet of metal 4. In order that the centre of the aperture be maintained in the same position in the sheet of metal 4, the rotational axis of drill chuck 1 must be in line with the centre of the aperture 3 before the drill bit can be lowered down to drill into the sheet of metal 4. The centre finder of this invention may be employed for this purpose.

The centre finder comprises an electrically conductive contact probe in the form of a tapering metal shaft 5. Shaft 5 has a free end having an integrally mounted ball 6 thereon, and a balled end 7 is mounted in a socket 8 of a base member 9 to enable free universal movement of shaft 5. A spring 10 urges balled end 7 against wall of socket 8 and maintains the shaft 5 in a position into which it is moved. Base member 9 further includes a rod 11 integral with socket 8, a collar 12, all of which comprise a first portion, an insulated connector 13 and chuck attachment shaft 14 comprising a second portion. Socket 8, rod 11, insulated connector 13 and chuck attachment shaft 14 are all fixed to one another and rotate within collar 12.A torque bar 15 is supported on the collar 12 and is fixed to the drill machinery (not shown) to prevent rotation of collar 12 when the remaining components of base member 9 are rotated. Shaft 5, socket 8, rod 11, collar 12 and torque bar 15 are all electrically conductive and hence inter-electrically conductive.

The end of torque bar 15 remote from collar 12 is connected to an indicating means 16 by means of wire 17. Indicating means 16 may be an audible and/or visual indicating means such as electric light and/or electric noise generator. Indicating means 16 has two electrical terminals, 18 (connected to wire 17) and 19. Terminal 19 is in the form of a metal plate which in use, is placed on sheet of metal 4. Indicating means 16 is so designed that when terminals 18 and 19 are electrically connected, the state of indicating means 16 is altered, e.g. if indicating means is "off" it is turned on (or vice versa), and when terminals 18 and 19 are subsequently electrically disconnected its state is again altered.

In order to line up the rotational axis of chuck 1 with centre of hole 3, probe 5 is placed in contact with sheet of metal 4. This consequently connects terminals 18 and 19 whereby the state of indicating means 16 is changed e.g. noise generator and/or light will come on. Chuck 1 is then rotated manually by an operator or by turning on the drilling machine and if the rotational axis of the chuck is dead centre with the centre of aperture 3, ball 6 will remain in contact with the periphery of aperture 3, and hence noise generator and/or light will remain on. If the rotational axis of chuck is not dead centre with aperture 3, ball 6 will not remain in contact with the periphery of aperture 3 and the noise generator and/or light will only be on intermittently when ball 6 comes in contact with the periphery of aperture 3.

Accordingly, the operator will move the sheet of metal 4 relative to chuck 1 (or vice versa) until ball 6 continuously remains in contact with the periphery of aperture 3 and noise generator and/or light is permanently on in the indicating means.

Instead of indicating means 16 showing a light or generating a noise, it could be in the form of other types of indicators such as a meter. Furthermore, the indicating means 16 could be arranged such that its audible or visual signal is normally active but when probe 5 contacts metal sheet 4, the audible or visual signal is turned off.

As shown in the drawing, probe 5 is attached to the base 8 by means of a ball and socket joint which allows movement of probe 5 in three planes. It will be appreciated however that it would only be necessaryforthe probe to move in one plane if one was centering a rod for rotation on a lathe.

Further more, the centre finder of the invention may be used in all other applications known centre finders are used for, such as locating datum positions or datum faces on workpieces.

CLAIMS (Filed 1 Dex.81) 1. A "centre finder" for centering a workpiece relative to a workmember comprising an electrically conductive contact probe having a free end and an end mounted on a base member which allows movement of said free end in at least one plane, said base member being adapted to be mounted on said workmember so as to be electrically insulated therefrom, and electrical indicating means connected to said probe and having means for connecting itto said workpiece, whereby an electrical circuit is formed when said probe touches said workpiece to alter the state of said indicating means.

2. A "centre finder" according to claim 1 and in which the electrically conductive probe is attached to said base member by means of a spring loaded ball and socket joint, said ball being located on said probe and the socket in said base member.

3. A "centre finder" according to claim 2 and in which a first portion of the base member which is connected to the probe and a second portion for connection to the workmember are electrically insulated from one another by means of an insulating connector.

4. A "centre finder" according to claim 3 and in which the first portion of the base member comprises the socket for receiving the ball of the probe and a collar, said socket being rotatable relative to the collar, and in which a torque bar is connected to the collar.

5. A "centre finder" according to claim 4 and in which the first portion of the base member and the probe are inter-electrically conductive.

6. A "centre finder" according to any of claims 1 to 5 and in which the indicating means is an audible and/or visual indicator such as a noise generator and/or light.

7. A "centre finder" substantially as hereinbefore described and as illustrated in the accompanying drawing.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. and/or light will only be on intermittently when ball 6 comes in contact with the periphery of aperture 3. Accordingly, the operator will move the sheet of metal 4 relative to chuck 1 (or vice versa) until ball 6 continuously remains in contact with the periphery of aperture 3 and noise generator and/or light is permanently on in the indicating means. Instead of indicating means 16 showing a light or generating a noise, it could be in the form of other types of indicators such as a meter. Furthermore, the indicating means 16 could be arranged such that its audible or visual signal is normally active but when probe 5 contacts metal sheet 4, the audible or visual signal is turned off. As shown in the drawing, probe 5 is attached to the base 8 by means of a ball and socket joint which allows movement of probe 5 in three planes. It will be appreciated however that it would only be necessaryforthe probe to move in one plane if one was centering a rod for rotation on a lathe. Further more, the centre finder of the invention may be used in all other applications known centre finders are used for, such as locating datum positions or datum faces on workpieces. CLAIMS (Filed 1 Dex.81)

1. A "centre finder" for centering a workpiece relative to a workmember comprising an electrically conductive contact probe having a free end and an end mounted on a base member which allows movement of said free end in at least one plane, said base member being adapted to be mounted on said workmember so as to be electrically insulated therefrom, and electrical indicating means connected to said probe and having means for connecting itto said workpiece, whereby an electrical circuit is formed when said probe touches said workpiece to alter the state of said indicating means.