GB2103126A - Machining tool, e.g. drill, positioning devices - Google Patents

Abstract

A drill positioning device for maintaining the operating axis of a drill normal to the surface region of a work piece having a curved profile includes a platform member having a fixed location bush 25 defining the operating axis, an adjustable foot 32' and an expandable collet clamping arrangement 39/40 for entering a previously formed hole and clamping the device 20 to the work piece. The foot 32' is adjustable to suit various curvatures of work piece to ensure that the operating axis is maintained normal to the region to be drilled. <IMAGE>

Description

SPECIFICATION Machining tool positioning devices This invention relates to machining tool positioning devices which positively locate a machining tool with its operating axis substantially normal to the surface of a work piece having a planar or curved profile, prior to the machining operation. By the term "machining tool" is meant a tool which performs a machining operation on a work piece, for example a drilling, countersinking, reaming or boring operation along a predetermined operating axis.

According to this invention, there is provided a machining tool positioning device for positioning a machining tool with its operating axis substantially normal to the surface of a work piece having a profile of generally circular arcuate form, which device comprises a platform member including first location means having foot means adapted in use to bear against the surface of the work piece adjacent that region of the surface through which the operating axis passes, and second location means spaced from said first location means and having foot means adapted in use to bear against the surface of the work piece, so that the platform member is supported by said first and second location means, said second location means being adjustable to suit various curvatures of work piece surface by adjusting the separation of the foot means of the second location means from the platform member.

In order to maintain the operating axis of the machining tool normal to the surface, the separation is increased as the local radius of curvature of the work piece decreases.

Preferably, the device includes a clamping arrangement operable to draw the platform member towards the work piece.

Preferably, the second location means comprises a shaft member attached to the foot means, said shaft member being slidably received in a bore in said platform member. The shaft member conveniently includes an abutment surface adapted to engage the ramp surface of an adjusting wedge, said adjusting wedge being movable with respect to the shaft member to effect displacement of the foot means with respect to the platform member.

The adjustment wedge is preferably movable to a plurality of discrete positions, each of the positions corresponding to a particular curvature of the work piece to be drilled.

In a case where a device according to the invention is employed to form a series of holes in a work piece, the clamping arrangement conveniently includes a collet/mandrel device which may be passed through a previousiy-formed hole and then operated to draw the platform member towards the work piece.

In this case, the separation between the operating axis and the collet/mandrel device is adjustable to suit the desired pitch of the holes to be formed.

By way of example only, one specific embodiment of machining tool positioning device will be described in detail, reference being made to the accompanying drawings, in which: Figure 1 is a side view of a drill having fitted thereto a machining tool positioning device; Figure 2 is an under plan view of the arrangement of Figure 1; Figure 3 is a partial view of the arrangement of Figure 1 attached to a work piece prior to a drilling operation; Figure 4 is an under plan view of part of a machining tool positioning device of this invention with certain parts removed for clarity; Figure 5 is a section view on lines V-V of Figure 4; Figure 6 is an end view on arrows VI--VI of figure 4; and Figure 7 is a section view on an enlarged scale through a part of a collet/mandrel device for use in this invention.

Referring to the drawings, there is shown a drill 10 to which a machining tool positioning device 20 of this invention is fitted. The drill 1 0 comprises a drill main body 11 from which project a clamp/feed cylinder 1 2 movable between a retracted position and an extended position, and a drill spindle housing 13 retractable into the drill main body. The clamp/feed cylinder 12 has concentrically mounted therewithin a damper cylinder 14 retractable into the clamp/feed cylinder 12 against a predetermined bias. The drill spindle housing 1 3 houses a drill spindle 1 6 designed to drill and countersink a hole of predetermined dimensions.On operation of the drill by trigger or other suitable means, the drill spindle is rotated and the clamp/feed cylinder 12 is retracted into the drill body 11, an example of such a drill is the Spacematic M62 type drill.

The machining tool positioning device 20 includes a platform 21, an adjustable foot 22, and a clamping arrangement in the form of a collet/mandrel device 23. The platform 21 includes a tubular sleeve portion 24 fitting around the end of the drill spindle housing 13, and through which the drill spindle may project. At the lower end of the sleeve portion 24 is provided a location bush 25. At the end of the platform 21 remote from the sleeve portion 24 there is provided a foot housing 26, having a bore 27 and including an adjusting slot 28 transverse thereto and communicating therewith. Intermediate the sleeve portion 24 and the foot housing 26 there is provided a guide slot 29 which receives a part of the collet/mandrel device 23, and which includes at one end a stop bolt 30.At a position remote from the sleeve portion 24 and the foot housing 26 there is provided a bore 31 which in use is secured around the end of the damper cylinder 14.

The adjustable foot 22 includes a cylindrical shaft 32, and a location member 32'. The shaft 32 is slidably received in the bore 27 of the foot housing 26 and is urged upwardly by means of a spring 33. The shaft 32 is cut away to form a horizontal channel 34, the lower side of which is urged against the ramp surface of an adjustment wedge 35, slidably located in adjusting slot 28.

The separation between the location member 32' and the platform 21 may be varied by sliding adjustment wedge 35 in adjusting slot 28. The wedge 35 includes a plurality of hemispherical indents 36 which engage a sprung biassed pin in the foot housing 26 to locate the wedge 35 in a desired position. The wedge 35 may include symbols to identify the position of the wedge with respect to the slot 28, thereby to identify the particular curvature of work piece for which the device is set. The collet/mandrel device 23 includes a crank arm 37 mounted on the clamp/feed cylinder 1 2 for relative turning movement but axially fixed with respect thereto.

The crank arm 37 is pivotally connected to a collet/mandrel housing 38 (Figure 6). At its end remote from the crank arm 37 the housing 38 receives the end of a collet/mandrel 39/40 combination for pivotal movement. The collet 39 is received in a collet location sleeve 41 for limited pivotal movement. The mandrel 40 extends through the collet 39 and is attached to the collet/mandrel housing 38 by means of a spherical bearing arrangement. The position of the collet/mandrel 39/40 with respect to the guide slot 29 and thus the separation between location bush 25 and the collet/mandrel may be adjusted by adjusting the angular position of crank arm 36.

The collet is of such a size as to fit through a hole previously drilled by the drill spindle, when the collet is relaxed.

The collet/mandrel device 23 which has the spherical bearing arrangement may be found to be necessary only for worl < pieces of small radius. For work pieces of larger radius the mandrel 40 may be secured directly to the collet/mandrel housing 38.

The collet/mandrel device 23 may be replaced by other forms of location and clamping device which can be inserted from one side of a work piece for example the form of clip marketed under the trade name "Avdel" by Aviation Developments Ltd.

In use, the component to be drilled is overlaid with a template which is provided with holes at the required pitch and adapted closely to receive the location bush 25. The adjustable foot is adjusted by moving adjustment wedge 34, to suit the local curvature of the surface to be drilled. The collet/mandrel 39/40 is passed through a pilot- or previously drilled -- hole, and the location bush positioned in an adjacent hole in the template, the separation between the collet/mandrel 30/40 and the location bush 25 being adjusted to suit the local pitch by sliding the collet/mandrel 39/40 with respect to guide slot 29 as necessary.

The drill 10 is then operated, causing the drill spindle 1 6 to rotate and to retract the clamp/feed cylinder 12 causing the collet/mandrel device 23 to be drawn towards the main drill body, whilst the clamping cylinder 14 remains extended. As this occurs, the collet 39 is expanded to clamp in its surrounding hole and the platform 21 is drawn towards the component to be drilled, urging location bush 25 to its location position. This action is continued untii the platform 21 is securely clamped to the component, supported by location bush 25 and adjustable foot 22. When the platform 21 is clamped to the work piece the drawing up action of the clamp/feed cylinder 12 continues, overcoming the bias of clamping cylinder 14 thus drawing the drill body towards the work piece to drill and countersink a hole.On completion of drilling, the clamp/feed cylinder 12 and the clamping cylinder 1 4 are returned to their initial positions, thereby allowing the positioning device to be moved to drill the next successive hole in the series.

It will be appreciated that when the device of this invention is used to drill a hole through two adjacent members, for example an aircraft skin and a former element, the device further serves to clamp the two members together during the drilling operation. It is envisaged that each hole in the template will have an identification symbol which relates to the local curvature of the work piece. Corresponding symbols will be provided on the adjustment wedge thereby allowing the operator readily to select the appropriate adjustment of the location member 32'.

The above-described embodiment may be employed to drill and countersink holes in planar, conic, double curvature, concave and convex surfaces.

Claims (9)

1. A machining tool positioning device for positioning a machining tool with its operating axis substantially normal to the surface of a work piece having a profile of generally circular arcuate form, which device comprises a platform member including first location means having foot means adapted in use to bear against the surface of the work piece adjacent that region of the surface through which the operating axis passes, and second location means spaced from said first location means and having foot means adapted in use to bear against the surface of the work piece, so that the platform member is supported by said first and second location means, said second location means being adjustable to suit various curvatures of work piece surface by adjusting the separation of the foot means from the platform member.

2. A device according to Claim 1 which includes a clamping arrangement operable to draw the platform member towards the work piece.

3. A device according to Claim 1 or Claim 2, wherein the second location means includes a shaft member attached to said foot means, said shaft member being slidably received in a bore in said platform member.

4. A device according to Claim 3, wherein said shaft member includes an abutment surface adapted to engage the ramp surface of a generally wedge-shaped adjustment member, said adjustment member being movable with respect to the shaft member thereby to adjust the separation of the foot means from the platform.

5. A drill positioning device for positioning a drill with its operating axis substantially normal to the surface of a work piece having a profile of generally circular arcuate form, which device includes a platform member having means for maintaining the operating axis of the drill in a fixed orientation with respect to the platform member, first location means having foot means adapted in use to bear against the surface of the work piece adjacent the surface of the region to be drilled, and second location means spaced from said first location means and having foot means adapted in use to bear against the surface of the work piece, so that the platform member is supported by said first and second location means, said second location means being adjustable to suit various curvatures of work piece by adjusting the separation of the foot means of the second location means from the platform member.

6. A drill positioning device according to Claim 5 which includes a clamping arrangement operable to draw the platform towards the work piece.

7. A drill positioning device according to Claim 6 and adapted for use in applications where a series of holes are drilled in a work piece, wherein the clamping device includes a clamping member which in use is inserted in a previously drilled hole subsequently to effect clamping.

8. A drill positioning device according to Claim 5, wherein the separation between the clamping member and the first location means is adjustable.

9. A machining tool positioning device substantially as hereinbefore described with reference to and as illustrated in any of the accompanying drawings.