GB2154479A - Machine tool - Google Patents

Abstract

A machine tool head allows quick changing between the tool (12) and a tool body (10) and comprises an annular array of balls (70), a bar with a conical portion (42) for increasing and decreasing the radius of the annulus of the balls (70); and an annular groove (86) in tool 12 for receiving the balls (70) on outward radial movement thereof to thereby lock the tool (12) in position in the socket of body (10).

Description

SPECIFICATION Machine Tool The present invention relates to a machine tool and in particular a head for a machine tool.

In the present day and age, efficient production on machine tools requires quick and easy tool changing. In addition to quick and easy tool changing, it is an absolute requirement that the tool holder and tool head are rigidly connected to provide accurate location and positive engagement.

Positive engagement allows transmission of the forces from the tool holder to the tool head without any loss through the coupling arrangement.

According to the present invention, there is provided a machine tool allowing quick changing between a tool head and a tool body comprising a tool head capable of positive engagement with the tool body having an open bore, a tool body having a locking means capable of being received within the open bore of the tool head, the locking means comprising an annulus of spheres, means for increasing and decreasing the radius of the annulus of spheres, the tool head including an annular groove for receiving the spheres on increase of the radius of the annulus of spheres to thereby lock the tool head in position.

In a preferred embodiment the annulus of spheres is retained around a central shaft. It is preferred that the central shaft has a conical portion, longitudinal movement of which causes the conical portion to adjust the radius of the annulus of spheres. Thus, the central shaft when moved in one direction causes the conical portions to engage the spheres such that they are forced outwards from the central shaft. Movement in the opposite direction by the central shaft allows the spheres to be drawn inwards until they substantially surround the central shaft.

In order to retain the spheres around the central shaft, it is preferred to provide a cage within a sleeve slidable upon the central shaft. Another function of the cage is to prevent extreme longitudinal motion of the sphere on longitudinal movement of the central shaft. To prevent the spheres from falling from the cage when the tool body is separated from the tool head, a retaining sleeve may be provided which is slidable about the cage sleeve. When the tool head is separated from the body, spring means urge the retaining means to cover the cage.

The tool head has a head shaped such that it is capable of positive engagement with the tool body.

The external shape of the head may be of any suitable shape for such positive engagement such as, in cross-section square, rectangular, or circular.

The tool head and tool body preferably have interconnecting keys such that on connection the tool head and tool body are provided preferably in the form of a castellated projections on both the tool head and the tool body. During the longitudinal locking of the tool head on the tool body, the castellated projection interconnects to prevent rotational movement of the tool head with respect to the tool body.

It is preferred that the tool head has a frustoconical portion, the frustoconical portion having the open bore. The frustoconical portion is preferably receivable within a corresponding tapered jaw to provide positive engagement between the tool head and the tool body. The open bore includes an internal annular groove for receiving the spheres on increase of the radius of the annulus of the spheres, such that it locks the tool head in position.

On engagement with the tapered jaw, the frustoconical portion of the tool head causes the retaining sleeve to slide longitudinally to uncover the cage releasing the balls to allow them to position themselves within the annular groove and to be locked in position therein by longitudinal motion of the central shaft causing the conical portion to increase the radius of annulus of the spheres.

The present invention will be further described by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a side view of the quick change tool of the present invention; Figure 2 is a side view of a tool head disconnected from the quick change tool; Figure 3 is a cross-section of the quick change tool of the present invention, showing the tool head; Figure 4 is a cross-section of the quick change tool of the present invention showing the position of the internal parts of the tool when disconnected from the tool head; and Figure 5 is a schematic view of the quick change tool of the present invention in a machine tool.

Referring to Figures 1 and 2, a tool body 10 is connected to a tool head 12 through an internal coupling device. The tool body 10 is generally cylindrical in shape and is connected to the generally cylindrical tool head. Keys 14 on the tool body and keys 16 on the tool head interconnect with one another to provide positive engagement between the tool body and the tool head and prevent rotational slippage of the tool head. The keys are preferably arranged in a castellated cylindrical arrangement around the end of the cylindrical portions of the respective tool body 10 and the tool head 12 and are made to interfit with one another to provide secure driving arrangement for the tool head when the tool is used under load.

The tool head 12 can be of any well-known tool, such as a cut-off blade holder, a tapping head, a drill, a turning tool, or a boring bar. As shown in Figures 1 and 2, the tool head 12 is a boring head which has a pocket 17 for a cutting insert to be mounted therein. The cylindrical shank 18 of the tool head 12 flattens into a spade-like arrangement 20 (as is well-known) to allow suitable positioning for the pocket 16. As is shown in Figure 2, the connecting end of the tool head 12 is a frustoconical head 22 which generally tapers away from the working end of the tool head 12, i.e. from the pocket 16. The frustoconical head 22 is capable of being received into the cylindrical casing of the tool body 10 and is locked in position by means to be described.

Figure 3 shows the position of the internal components when connected to the tool head 12.

Figure 4 shows the position of the internal components of the tool body 10 when disconnected from the tool head 12.

The external shape of the tool body 10 is preferably a cylinder although it may be square or rectangular in cross-section. The central internal portion has an internal collar 24 with a further extending collar 26 thereon. The internal extending collar 26 is positioned towards the connecting portion of the tool body 10, which receives the frustoconical head 22 of the tool head 12. This is a tapered jaw 28 machined to accurately receive the frustoconical head 22 of the tool head 12.

A central shaft 30 extends longitudinally within the tool body 10 around the centre line. The shaft 30 is screw4hreaded into a second shaft 32 of slightly greater diameter. The second shaft 32 is connected by means of a screw thread to a domed capped plunger 34 which has a diameter substantially the same diameter as the bore of the tool body 10 such that it is slideable within the bore of the tool body.

The domed plunger 34, plus the second shaft 32 extends longitudinally within the bore of the tool body 10 such that they are adjacent the internal collar 24 which forms a shoulder 36. Attached to the other end of the central shaft 30 by means of a bolt 38 and washer 40 is a cone 42. Surrounding the second shaft 32, is a series of disc springs 44 such as Belville washers, preferably arranged in pairs or threes, and arranged in opposed relationship with further disc springs 46 also preferably Belville washers to provide a compressible spring arrangement. The arrangement of disc springs 44, 46 is such that they extend around the shaft 32 between the shoulder 36 and the domed capped plunger 34. The shoulder 36 provides a stop for the disc springs 44,46.Positioned around the central shaft 30 is a counterbored slidable ring 48 having a first internal bore 50 such that it is slidable about the central axis 30 and closely slidable on the central shaft 30. A second larger diameter bore 52 within the ring 48 allows the second central shaft 32 to slide to about an inner shoulder 53 separating the bores 50 and 52 and allowing outer shoulder 55 to abut the external extending collar 26 to cause itto act as a stop. Thus the central shaft 32 is slidable within the bore 52, and the shoulder 53 abuts the shoulder 54 of central shaft 32, as shown in Figure 4.

A counterbored sleeve 56 is provided having a diameter such that it is longitudinally slidable upon but abuts the central shaft 30. The counterbored sleeve also has a thread 58 to receive and engage thread 60 of the ring 48. A collar 62 surrounds the neck of the sleeve 56 and acts as a washer between interconnected sleeve 58 and ring 48. The collar 62 abuts against the inner extending collar 26 when tool head 12 is connected. The sleeve 56, as has been stated, is longitudinally slidable on the central shaft 30 and has a tapered mouth 66 to receive the cone 42 with some clearance space 68 between the cone 42 and the tapered mouth 66. The tapered mouth 66 of the sleeve also provides a cage 67 for a spherical steel ball 70.The tapered mouth 66 allows a plurality of balls 70 to be positioned around its circumference in the form of an annulus, with preferably at least five balls being used. Afurther retaining sleeve 72 surrounds the sleeve 56 such that it is slidable upon it and slidable within the tool body 10. The retaining sleeve 72 has the function of retaining the balls 70 around the shaft 30 as well as acting as an outer shoulder against which a compression spring 74 abuts forming a retaining shoulder 76. As shown in figure 4, the compression spring 74 is extended such that the retaining sleeve 72 abuts the shoulder 78 on the sleeve 56. The retaining sleeve 72 covers the cage 67 retaining the steel ball 70.

As shown in Figure 3, the frustoconical head 22 engages with the tapered jaw 28. The internal portion ofthefrustonical head 22 forms substantially cylindrical bore 80 in the frustonical head 22. The cylindrical bore 80 has an open end 82 and a closed end 84 within the tool head 12.

Towards the open end 82 of the cylindrical bore 80 is provided an annular depression or groove capable of receiving the steel balls 70 when the frustoconical head is fitted into the tool body. The annular depression or groove 86 is preferably chamfered to allow easy positioning of the steel ball 70 when the frustoconical head 22 is inserted into the tool body 10. The diameter of the tool body 10 can be of any suitable measurement required according to the use of the tool. However, it is preferred to provide it of a diameter such that it can be adapted to existing machine tools.

The tool body 10 is mounted in a machine tool.

The present invention is particularly suited to machine tools having rotating turrets, to bring the tool body into the operating axis of the machine tool. Figure 5 shows a schematic representation of such a machine tool 89 which may be used. Aturret 90 which is cylindrical and rotatable around axis 92 may have a plurality of receiving and clamping postions 94 preferably up to 12 positions arranged circumferentially around the turret. A tool body 96 is clamped in each of the clamping positions 94. At the operating station 98, the tool body 96 and tool head 100 are in line with operating axis 102 of the machine tool. When rotated, the tool body 96 and tool head 100 reach disconnection station 104. At this point an operating mechanism acts on the domed capped plunger 34 (see Figures 3 and 4) to disconnect the tool head from the tool body as described hereinafter.

In use, the tool body is inserted into a machine tool such that an operating system, for example a piston 104, can move in or out of the machine tool to operate the domed capped plunger 34. When disconnecting the tool head, a piston extends from the machine tool to force the domed capped plunger longitudinally within the bore of the tool body 10 causing the shafts 32 and 30 urging the frustoconical head 22 from the tool body 10 as shown in Figure 4. Because the shaft 30 is of a smaller outer diameter than the shaft 32, the shoulder 54 abuts a shoulder 53 on the counterbored ring 48 causing the outer shoulder 55 on the counterbored ring 48 to abut the extending collar 26 stopping the ring 48 from further movement to the left as shown in the drawing.

Compression spring 74 urges the retaining sleeve 78 away from extending collar 26 causing the retaining sleeve to entrap the balls 70. The sleeve 56 with the cage 67 containing annulus of the balls 70 are retained at the base of the cone 42. When the domed capped plunger 34 is depressed the cone 42 is urged away from the dome capped plunger 34 as it is attached via shaft 30, second shaft 32 as the disc spring washers are compressed. In this way the retaining sleeve 72 entraps the balls 70 on the shaft 30 at the base of the cone 42. A clearance space is provided between the sleeve 56 and ring 48.

Insertion of the tool head 12 with itsfrustoconical head 22 into the tapered jaw 28 causes abutment between the frustoconical head 22 and the retaining sleeve 72. Insertion of the frustoconical head into close fitting and positive engagement with the tool body 10 forces the retaining sleeve 72 to compress the compression spring 74 against the extending collar 26. The retaining sleeve 72 is slidable about the sleeve 56. The balls 70 are received in the annular depression or groove 86 to locate and ultimately lock the frustoconical head 22 in position.

Once the frustoconical head 22 is accurately located within the tapered jaw 28 locking pressure is removed from the domed capped plunger 34 causing itto be urged towards the right as shown in Figure 4, on decompression of the disc springs 44, 46. Release of the domed capped plunger 34 causes movement in the second central shaft 32, the central shaft 30 and ultimately the cone 42, causing the balls 70 to move both longitudinally in the same direction as the central shaft 30 and radially outwardly to increase the radius of the annulus of balls and to lock the balls 70 within the annular depression or groove 86. The balls 70 are prevented from moving longitudinally with the shaft 30 by means of the sleeve 56 which abuts the extending collar 26. At the same time the ring 48 is urged longitudinally such that it lies freely on the shaft 30.

To release the tool head, the domed capped plunger 34 is moved longitudinally towards the left as shown in the drawings with compression of the disc springs 44, 46. The shoulder 54 causes ring 48 and consequently interconnected ring 56 to move to the left longitudinally as shown in the drawings. The shoulder 64 abuts the collar 62 causing the sleeve 56 to move to the left allowing inward radial movement of the balls 70 as the cone 42 moves also to the left.

As soon as the balls 70 move radilly inwards such that the radius of the annulus is decreased, they disengage the annular depression or groove 86 unlocking the tool head and allowing the frustoconical head 22 to be withdrawn from the tapered jaw 28.

The frustoconical head and the tapered jaw allow accurate and positive engagement of the tool head 12 within the tool body 10. The balls 70 allow positive locking within the annular depression or groove 86. Thus, transmission of the forces from the tool holder to the tool head occur successfully without any loss through the coupling arrangement.

Claims (10)

1. A machine tool head allowing quick changing between the tool head and a tool body comprising: a tool head capable of positive engagement with a tool body having an open bore; a tool body include a locking means within the open bore of the tool head; the locking means comprising an annulus of spheres, means for increasing and decreasing the radius of the annulus of the spheres; and the tool head including an annular groove for receiving the spheres on increase of the radius of the annulus of the annulus of the spheres to thereby lock the tool head in position.

2. A machine tool as claimed in claim 1 wherein the annulus of spheres is retained around a central shaft having a conical portion, longitudinal movement of which causes the conical portion to adjust the radius of the annulus of spheres.

3. A machine tool as claimed in claim 2 wherein the annulus of spheres is retained around the central shaft by means of a cage within a sleeve slidable on the central shaft.

4. A machine tool as claimed in claim 3 wherein the cage is covered by a retaining sleeve slidable on the cage sleeve when separated from the tool head.

5. A machine tool as claimed in claim 4 wherein the tool head has a frustoconical portion which is receivable within a corresponding tapered jaw to provide positive engagement between the tool head and the tool body.

6. A machine tool head as claimed in claim 5 wherein the frustoconical portion of the tool head on insertion and engagement with the tapered jaw causes the retaining sleeve to slide longitudinally to uncover the cage.

7. A machine tool head as claimed in any one of claims 2 to 6 wherein the annulus of spheres is capable of being retained in a locked position by at least a cluster of disc springs around the central shaft urging it longitudinally such that the conical portion causes the annulus of spheres to be recovered in the annular groove.

8. A machine tool head as claimed in any one of the preceding claims wherein the tool head and tool body have interconnectable keys to provide positive engagement between the tool head and tool body.

9. A machine tool as claimed in claim 8 wherein the keys are external castellated projections of the tool head and the tool body.

10. A machine tool head as claimed in claim 1 substantially as hereinbefore described.