GB2256381A

GB2256381A - Fixing arrangement

Info

Publication number: GB2256381A
Application number: GB9111939A
Authority: GB
Inventors: Anthony Paul Wyatt
Original assignee: Crawford Collets Ltd
Current assignee: Crawford Collets Ltd
Priority date: 1991-06-04
Filing date: 1991-06-04
Publication date: 1992-12-09
Anticipated expiration: 2011-06-04
Also published as: GB9111939D0; GB2256381B

Abstract

A fixing arrangement for releasably fixing different collets (12) to a chuck body (10) of a machine tool comprises an outer body (14), bolted permanently to the chuck body, and a ring-shaped insert (16). The outer body (14) has three radially inwardly directed shoulders (e.g. 30) spaced angularly by 60 DEG while the insert 16 has three radially outwardly directed lugs (e.g. 70) also spaced angularly by 60 DEG . The collet is attached to the insert (16), having a shallow groove (100). The collet and the insert may be supported by a handle (not shown) which has pins temporarily locating in bores (e.g. 62) in the insert. Using this handle, the operator feeds the collet through the aperture of the outer body (14), angularly positioning the insert (16) so that its lugs pass between the shoulders of the outer body. The operator then rotates the insert through 60 DEG that the lugs interlock with pockets in the shoulders to secure the two parts together, aided by axial spring pressure developed by spring-biassed ball bearings (26, Fig 3, not shown) acting on the rim of the insert (16). <IMAGE>

Description

IMPROVEMENTS IN AND RELATING TO MACHINE TOOLS The invention relates to machine tools. Embodiments of the invention to be described relate to arrangements for attaching holding devices, such as work holding devices in the form of collets, to machine tools.

According to the invention, there is provided a fixing arrangement for releasably fixing a rotatable holder to receiving means of a machine tool, comprising an annular mount adapted to be secured to the receiving means, a member adapted to hold and radially to locate the holder, the mount and the member being mutually sized and shaped so as to fit together in a manner axially and radially locating the holder with respect to the receiving means, and bayonet-type fixing means for securing the member and the mount together.

According to the invention, there is further provided a fixing arrangement for releasably and selectively fitting a plurality of collets, of respectively different internal bore size, to a chuck body of a machine tool, comprising an annularly shaped mount secured to the chuck body around a circular opening therein for receipt of each of the collets and defining a plurality of formations directed radially inwardly of its annulus so as to define angularly spaced gaps between them, an insert body defining a circular periphery sized to be a close fit with the interior of the annulus of the mount and defining, within that periphery, a plurality of angularly spaced radially outwardly directed formations, means on the insert body for releasably securing each of the collets in turn to it whereby to enable a collet secured to the insert body to be inserted into the circular aperture in the chuck body when the insert body and the mount are so relatively angularly oriented that the formations on the insert body pass through the angularly spaced gaps on the mount, whereafter relative angular movement between the insert body and the mount brings the formations on the mount into locking engagement with the formations on the insert body, and resilient biassing means acting between the mount and the insert body for releasably holding the formations in the said locking~engagement.

Fixing arrangements embodying the invention for removably fixing different sized collets to machine tools will now be described, by way of example only, with reference to the accompanying diagrammatic drawings in which: Figure 1 is a cross-section through part of a machine tool chuck showing a collet held in position by one of the arrangements to be described; Figure 2 is an end view of an outer body forming part of the arrangement shown in Figure 1; Figure 3 is a cross-section on the line III-III of Figure 2; Figure 4 is an end view of an insert forming part of the arrangement shown in Figure 1; Figure 5 is a cross-section on the line V-V of Figure 4; and Figure 6 is a cross-section through the insert of Figure 1 supported by an insert loader forming part of the arrangement.

Figure 1 shows part of the chuck body 10 of a machine tool to which is secured (in a manner to be described) a collet 12. The collet 12 is secured in position in the chuck by the fixing arrangement to be described and which comprises two main parts, an outer body 14 and an insert 16. The collet 12 does not form part of the invention and may be of any conventional type, such as a dedicated spring collet or a wide range multi-bore collet, for example.

Collets will be of a variety of different sizes (different internal diameters) to receive and hold differently sized tools in use. During use of the machine tool, it will therefore be necessary, at intervals of greater or less frequency, to change the collet for one of a different size - so as to suit the requirements of the particular manufacturing process being carried out. The mounting arrangement to be described in detail below enables collets to be changed simply and rapidly, so as to maximise useful production time from the machine tool.

The outer body 14 of the fixing arrangement is shown in Figures 2 and 3. It comprises a circular ring 18 defining a generally circular aperture 20. The ring is provided with six through bores 22 for receiving fixing bolts for a purpose to be described. The ring 18 is machined to produce a rim 24 around one of its axial ends and has three radially directed bores 26,28 and 30 arranged with 0 an angular spacing of 600. Each of these bores houses a spring-loaded ball bearing which projects radially inwardly of the aperture 20 adjacent the rim 24.

In addition, the ring 18 is machined to provide three shoulders 30,32 and 34 arranged with an angular separation of 600 so as to define corresponding gaps 36,38 and 40.

Each of the shoulders 30,32,34 extends between a wall 42,46,48 having a depth extending partway through the ring 18 and a respective land 44,48,52 which stands one millimetre proud of the axially directed face of the surface of the associated shoulder. On each shoulder 30,32,34, there is therefore formed a "pocket" extending between wall 42 and land 44 for shoulder 30, between wall 46 and land 48 for shoulder 32, and between wall 50 and land 52 for shoulder 34.

The insert (Figures 4 and 5) is in the form of a ring 60 which is provided with three blind bores 62, 64 and 66 arranged with an angular spacing of 600. The ring 60 is machined to provide a rim 68 on one of its axial faces and three lugs 70,72,74 on its opposite axial face, each lug having an outwardly facing chamfer and defining a part annular gap between itself and the rim 68 - as shown at 76 in Figure 5.

In use of the fixing arrangement, the outer body 14 (Figs. 2 and 3) is fixed to the chuck body 10 (see Fig. 1) by means of bolts passing through the bores 22 (Fig. 2), as shown at 80 in Fig. 1.

The collet 12 is secured in position on the chuck body in the following manner. For this purpose, an insert loader 90 (Fig. 6) is used. The insert loader 90 is advantageously made of plastics or similar material and comprises a handle portion 92 integral with an annular shoulder 94 from which project three pins arranged with a 600 annular spacing, only one of these pins, 96, being shown in Figure 6. Each pin has an O-ring near its free end as shown at 98 in Figure 6. The first stage in the assembly process is the fitting of the insert 16 to the insert loader 90. This is achieved by positioning the two parts relative to each other so that the pin 96, and the other two corresponding pins of the insert loader, engage the blind bores 62,64 and 66 of the insert (see Fig. 4).

The O-rings carried by the pins provide frictional grip sufficient to hold the two parts together during the assembly process.

The particular collet to be assembled to the chuck body is then placed in the insert 16, inserting it in the direction of the arrow A (Fig. 6). The interior bore of the ring 60 of the insert 16 is provided with a small circular step as indicated at 100, and an annular step 102 (Fig. 1) on the nose of the collet engages behind this, the collet being compressed slightly against its spring pressure in a radial direction to accommodate this. The collet is thus temporarily held in the insert 16 and the two parts held together in this way are in turn secured to the insert holder 90. Holding the assembly thus formed, the operator offers it up to the chuck body 10, inserting the collet 12 through the aperture 20 of the outer body 14 (Fig. 2). The operator angularly aligns the assembly so that the lugs 70 of the insert 16 pass through the gaps 36,38 and 40 of the outer body 14.Eventually, resistance to further axial movement of the assembly into the chuck body arises, when the rim 68 of the insert engages the ball bearings of the spring plunger units in the radial bores 26,28 and 30 of the outer body, as shown in Figure 1. The operator maintains axial pressure so as partly to depress the ball bearings into their respective radial bores. This provides sufficient axial clearance to enable 0 the assembly to be rotated approximately 60 in an anti-clockwise direction (with reference to Figure 2), so that the lugs 70,72 and 74 pass over the lands 44,48 and 52 (Fig. 2).The operator now relaxes axial pressure, and the depressed ball bearings of the spring plunger units force the assembly axially away from the chuck body so that the lugs 70,72 and 74 are now located in the three one millimetre deep pockets respectively formed on the shoulders 30,32 and 34 (Fig. 2). Further rotation of the insert is thus prevented, and the insert is thus held in position.

Assembly is completed by pulling the insert holder 90 away from the chuck body so as to disconnect it.

The procedure for removal of the collet is the reverse of that described above.

The fixing arrangement enables a second insert, similar to the insert 16, to be pre-assembled with a collet of different bore size in readiness for the next change-over.

The fixing arrangement described is clearly advantageous compared with fixing arrangements in which collets are secured in position using a single piece securing cap which has to be attached to the collet and the resultant assembly then bolted to the chuck body. It is found that, with fixing arrangements of the type described and illustrated, change over times of the order of 30 seconds are possible.

The rim 24 and the rim 68 cooperate to locate the collet radially and are a sufficiently close fit to exclude the entry of swarf and the like.

The chuck body incorporates means 104 (Fig. 1) for exerting axial pressure on the collet 12 (to hold in place therein the tool, not shown, clamped in the collet) and this axial pressure holds the collet in position.

Claims

1. A fixing arrangement for releasably fixing a rotatable holder to receiving means of a machine tool, comprising an annular mount adapted to be secured to the receiving means, a member adapted to hold and radially to locate the holder, the mount and the member being mutually sized and shaped so as to fit together in a manner axially and radially locating the tool holder with respect to the receiving means, and bayonet-type fixing means for securing the member and the mount together.

2. An arrangement according to claim 1, including handle means adapted to be temporarily attached to the member to enable the operator to fit the member, with the tool holder secured thereto, to the mount.

3. An arrangement according to claim 1 or 2, in which the bayonet-type fixing means comprises a plurality of angularly spaced formations on the mount and extending radially inwardly of the aperture defined by the annulus thereof so as to define angularly spaced gaps between them, and a plurality of matching angularly spaced formations around the periphery of the member and directed radially outwardly thereof, whereby to permit the member to be inserted axially within the mount so that its formations pass through the angularly spaced gaps of the mount and whereby subsequent relative angular movement between the mount and the member locks the angular formations of the mount to the angular formations of the member.

4. An arrangement according to claim 3, including resilient means providing an axially directed force for holding the formations in locking engagement.

5. An arrangement according to any preceding claim, in which the holder is a work holder such as a collet.

6. A fixing arrangement for releasably and selectively fitting a plurality of collets, of respectively different internal bore size, to a chuck body of a machine tool, comprising an annularly shaped mount secured to the chuck body around a circular opening therein for receipt of each of the collets and defining a plurality of formations directed radially inwardly of its annulus so as to define angularly spaced gaps between them, an insert body defining a circular periphery sized to be a close fit with the interior of the annulus of the mount and defining, within that periphery, a plurality of angularly spaced radially outwardly directed formations, means on the insert body for releasably securing each of the collets in t urn to it whereby to enable a collet secured to the insert body to be inserted into the circular aperture in the chuck body when the insert body and the mount are so relatively angularly oriented that the formations on the insert body pass through the angularly spaced gaps on the mount, whereafter relative angular movement between the insert body and the mount brings the formations on the mount into locking engagement with the formations on the insert body, and resilient biassing means acting between the mount and the insert body for releasably holding the formations in the said locking engagement.

7. An arrangement according to claim 6, in which the resilient biassing means comprises plunger means mounted on one of the mount and the insert body and spring-biassed in a radial direction so as to contact an edge of the other of the mount and the insert body to produce a component force acting perpendicularly to the radial direction.

8. An arrangement according to claim 7, in which the plunger means comprises a plurality of angularly arranged plungers on the mount and spring-biassed radially inwardly into contact with a peripheral edge on the insert body.

9. An arrangement according to any one of claims 6 to 8, in which one of the two pluralities of formations comprises a plurality of recessed surfaces each for receiving one of the other plurality of formations, such that the latter formations are respectively held within the recesses by the resilient biassing means.

10. An arrangement according to any one of claims 6 to 9, including handle means adapted to be temporarily secured to the insert body for enabling an operator to insert the latter, with a collet held in position, into the said mount.

11. A fixing arrangement for fixing collets to a machine tool, substantially as described with reference to the accompanying drawings.

Amendments to the claims have been filed as follows 1. A fixing arrangement for releasably fixing a rotatable holder to receiving means of a machine tool, comprising an annular mount adapted to be secured to the receiving means, a member adapted to hold and radially to locate the holder, the mount and the member being mutually sized and shaped so as to fit together in a manner axially and radially locating the tool holder with respect to the receiving means, and bayonet-type fixing means for securing the member and the mount together.

6. A fixing arrangement for releasably and selectively fitting a plurality of collets, of respectively different internal bore size, to a chuck body of a machine tool, comprising an annularly shaped mount secured to the chuck body around a circular opening therein for receipt of each of the collets and defining a plurality of formations directed radially inwardly of its annulus so as to define angularly spaced gaps between them, an insert body defining à circular periphery sized to be a close fit with the interior of the annulus of the mount and defining, within that periphery, a plurality of angularly spaced radially outwardly directed formations, means on the insert body for releasably securing each of the collets in turn to it whereby to enable a collet secured to the insert body to be inserted into the circular aperture in the chuck body when the insert body and the mount are so relatively angularly oriented that the formations on the insert body pass through the angularly spaced gaps on the mount, whereafter relative angular movement between the insert body and the mount brings the formations on the mount into locking engagement with the formations on the insert body, and resilient biassing means acting between the mount and the insert body for releasably holding the formations in the said locking engagement.