EP2015884A1

EP2015884A1 - Tool holder spindles

Info

Publication number: EP2015884A1
Application number: EP07732694A
Authority: EP
Inventors: John David Stratton; Thomas Retzbach
Original assignee: GSI Group Ltd
Current assignee: Novanta Technologies UK Ltd
Priority date: 2006-05-09
Filing date: 2007-05-08
Publication date: 2009-01-21
Also published as: JP2009536103A; TW200808472A; JP5220727B2; GB0609180D0; WO2007129073A1

Abstract

A tool holder spindle (1) comprising a shaft (4), a spindle body (2) comprising at least one bearing (3) within which the shaft (4) is journalled for rotation relative to the spindle body (2), a tool holder (5) for holding a tool, and an axially moveable actuator portion (6) disposed within the shaft for actuating the tool holder. The tool holder (5) being mounted within the shaft (4) and comprising: a tool receiving portion (B) having at least one deformable tool gripping portion (55); and at least one wedge portion (58) arranged to act on the deformable tool gripping portion (55) and arranged for axial movement relative to the tool receiving portion under action of the axially moveable actuator portion (6), wherein axial movement of the actuator portion (6) in a first direction causes axial movement, relative to the tool receiving portion (B), of the wedge portion (58) in a first direction so deforming the tool gripping portion inwards towards the axis of the spindle for gripping a received tool.

Description

TOOL HOLDER SPINDLES

This invention relates to tool holder spindles. Such spindles may be used for holding tools for various purposes. One example, is for drilling material, for example, for PCB drilling operations.

In some applications, and PCB drilling is one of these, it is necessary to be able to hold tools securely whilst they are rotated at high speed. In some applications, such as PCB drilling, the tool may be rotated at speeds of in the order of, or in excess of, 300,000 rpm. At the same time it is desirable, and for most practical purposes essential, to provide for the replacement of a tool held by a tool holding spindle such as a high speed drilling spindle. Replacement of the tool may be necessary due to the tool having become worn or broken, or because a different size of tool is required. In some applications, such as high speed PCB drilling, so called "tool change" operations have to be carried out relatively frequently.

It is therefore desirable to provide tool holder spindles which cannot only securely hold a tool, for example during high speed rotation, but which also facilitate the changing of the tool which the tool holder is holding. It is furthermore desirable if the tool changing operation can be one which is automatic and one which is operable by way of an actuator which is internal to the spindle.

It is an object of the present invention to provide tool holding spindles which can deliver some or all of the above mentioned desirable features. According to a first aspect of the present invention there is provided a tool holder spindle comprising a shaft, a spindle body comprising at least one bearing within which the shaft is journalled for rotation relative to the spindle body, a tool holder for holding a tool, and an axially moveable actuator portion disposed within the shaft for actuating the tool holder; the tool holder being mounted within the shaft and comprising: a tool receiving portion having at least one deformable tool gripping portion; and at least one wedge portion arranged to act on the deformable tool gripping portion and arranged for axial movement relative to the tool receiving portion under action of the axially moveable actuator portion, wherein axial movement of the actuator portion in a first direction causes axial movement, relative to the tool receiving portion, of the wedge portion in a first direction so deforming the tool gripping portion inwards towards the axis of the spindle for gripping a received tool.

The tool receiving portion may be held against axial movement relative to the shaft. The wedge portion may be arranged for axial movement relative to the shaft.

The tool holder may comprise a tool holder body. The tool holder body may comprise a deformable sleeve of material. The sleeve of material may comprise the deformable tool gripping portion. The tool holder body may comprise at least one arcuate deformable sleeve portion. The arcuate deformable sleeve portion may comprise the deformable tool gripping portion.

The tool receiving portion may comprise a plurality of deformable tool gripping portions. The tool holder body may comprise a plurality of arcuate deformable sleeve portions which are spaced from one another around an inner periphery of the tool receiving portion. Each sleeve portion may comprise at least a respective one of the deformable tool gripping portions.

The arcuate sleeve portions may be arranged in a ring, with circumferential spacings therebetween, around the axis of the spindle, providing an inward facing generally cylindrical tool contacting surface.

The or each sleeve portion may be connected to a main part of the tool holder body via a respective stem.

The or each tool gripping portion may comprise at least one tool engaging edge. The or each sleeve portion may comprise a respective tool engaging edge. Preferably each sleeve portion comprises a pair of tool gripping portions.

Preferably each sleeve portion comprises a pair of tool engaging edges. The tool engaging edges may be on opposing edges of the sleeve portion. Where there are a plurality of spaced sleeve portions separated by circumferential gaps, respective tool engaging edges of adjacent sleeve portions may face one another across the respective gap.

The or each tool gripping portion may be arranged so that inward deformation of the tool gripping portion causes inward movement of the tool engaging edge. The tool holder may comprise a plurality of wedge portions. The or each wedge portion may be tapered along its axial length.

The tool holder may comprise a wedge assembly comprising the or each wedge portion and an engagement portion for engagement with the actuator portion.

The tool holder body may comprise an annular wedge receiving portion. The tool holder body may comprise a plurality of part annular wedge receiving portions.

The annular receiving portion or each part annular receiving portion may be tapered along its axial length. The taper of the or each receiving portion may complement the taper of the or each wedge. This can help to ensure that axial movement of the wedge within the respective receiving portion generates a radial deforming force over an extended portion of the respective tool gripping portion rather than at a single point/circumferential line.

The or each wedge portion may be arranged to act on a plurality of tool gripping portions. The tool receiving portion may be disposed within the axial extent of the shaft directly supported by the bearing. The tool holder may be disposed substantially within the axial extent of the shaft directly supported by the bearing.

The tool holder may be supported along substantially its whole length by virtue of being mounted within the shaft.

The external diameter of the shaft may be substantially constant throughout the spindle. The external diameter of the shaft in the region of the bearing may be substantially the same as the external diameter of the shaft in the region of the tool holder.

The external diameter of at least the main part of tool holder may be less than the internal diameter of the bearing. The external diameter of the main part of the tool holder may be less than the internal diameter of the shaft.

The axially moveable actuator portion and tool holder may be arranged to allow relative rotation therebetween. This can allow the actuator portion to remain static as the shaft and tool holder rotate within the spindle body.

The moveable actuator portion may comprise a head for engagement with the engagement portion.

The engagement portion may be arranged as a male projecting portion for capture by the head of the actuator portion. This is the simplest and most likely route to take without further thought. However this can generate a problem in that the projecting portion will rotate with the tool holder and shaft, and where high speeds are involved this can generate instabilities, such as wobble or high vibration.

The engagement portion may be arranged as a female receiving portion for receiving the head of the actuator portion.

The female receiving portion may be supported against centrifugal effects by an internal wall of the shaft.

The female receiving portion may have an external surface which is in contact with the internal surface of the shaft.

The female receiving portion may comprise a receiving chamber in which the head of the actuator portion is disposed in use. The female receiving portion may comprise an entrance aperture through which the head of the actuator portion may be introduced into the chamber during assembly.

The actuator portion may comprise a spilt stud terminating in the head, the stud comprising a plurality of legs each of which terminates in a respective portion of the head and which may be splayed apart from one another to alter the effective outer diameter of the head. The actuator portion may comprise a splaying pin which arranged for splaying the legs and which is axially moveable relative to the split stud between a first position in which the effective outer diameter of the head is smaller than the diameter of the entrance aperture and a second position in which the effective outer diameter of the head is larger than the diameter of the entrance aperture. This can allow the introduction of the head into the receiving chamber when the pin is in the first position for assembly and allow the head to be engaged in the chamber when the pin is in the second position for actuation. The actuator portion and wedge assembly may be arranged so that contact between the head and the engagement portion is used to move the at least one wedge portion in one axial direction or in both axial directions.

The actuator portion may comprise a shoulder for contacting with the wedge assembly for movement of the at least one wedge portion in one axial direction. This direction may be said first direction which causes inward deformation of the tool gripping portion.

In such a case, the actuator portion and wedge assembly may be arranged so that contact between the head and the engagement portion is used to move the at least one wedge portion in the opposite axial direction.

There may be a pair of radial bearings in which the shaft is journalled. The tool holder may be disposed substantially wholly within a region of the shaft which is between the outermost ends of the pair of bearings. The bearing or each bearing may be a gas bearing, typically an air bearing.

The tool holder spindle may be a machining spindle. The tool holder spindle may be a drilling spindle, for example a high speed PCB drilling spindle. The tool holder spindle may be a rotary paint spraying spindle. The tool holder spindle may be a grinding spindle. The tool holder spindle may be a routing spindle

According to a further aspect of the present invention there is provided a tool holder spindle comprising a shaft, a spindle body comprising at least one gas bearing within which the shaft is journalled for rotation relative to the spindle body, and a tool holder for holding a tool; the tool holder being mounted within the shaft and comprising: a tool receiving portion having at least one deformable tool gripping portion; and at least one wedge portion arranged to act on the deformable tool gripping portion and arranged for axial movement relative to the tool receiving portion under action of an actuator, wherein axial movement of the wedge portion, relative to the tool receiving portion and under action of an actuator, in a first direction deforms the tool gripping portion inwards towards the axis of the spindle for gripping a received tool. The actuator may comprise an axially moveable actuator portion disposed within the shaft. The actuator may comprise an external actuator, which may be separate from the spindle. The external actuator may operate on the wedge portion from a front, tool receiving, end of the spindle or from a rear end of the spindle.

According to yet a further aspect of the present invention there is provided tool holder apparatus comprising a tool holder spindle according to said further aspect of the invention and an external actuator for acting on the wedge portion in the tool holder spindle.

According to another aspect of the present invention there is provided a drilling spindle comprising a shaft, a spindle body comprising at least one gas bearing within which the shaft is journalled for rotation relative to the spindle body, a tool holder for holding a tool, and an axially moveable actuator portion disposed within the shaft for actuating the tool holder; the tool holder being mounted within the shaft and comprising: a tool receiving portion having at least one deformable tool gripping portion; and at least one wedge portion arranged to act on the deformable tool gripping portion and arranged for axial movement relative to the tool receiving portion under action of the axially moveable actuator portion, wherein axial movement of the actuator portion in a first direction causes axial movement, relative to the tool receiving portion, of the wedge portion in a first direction so deforming the tool gripping portion inwards towards the axis of the spindle for gripping a received tool.

According to yet another aspect of the present invention there is provided a tool holder for a spindle of the type defined above.

It will be appreciated that the optional features mentioned in respect of the first aspect of the invention may also be optional features of the other aspects of the invention where context allows.

Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which:

Figure 1 is a schematic sectional view of a tool holder spindle;

Figure 2 is an end view of a sub-assembly of the tool holder spindle shown in Figure 1 ;

Figure 3 is a section on line HI-III of the sub-assembly shown in Figure 2;

Figure 4 is a perspective view of a tool holder body of a tool holder of the spindle shown in Figure 1 ;

Figure 5 is an end view of the tool holder body shown in Figure 4; Figure 6 is a section on line VI-VI of the tool holder body shown in Figure 5;

Figure 7 is a perspective view of a wedge assembly of the tool holder of the spindle shown in Figure 1 ;

Figure 8 is an end view of the wedge assembly shown in Figure 7;

Figure 9 is a section on line IX-IX of the wedge assembly shown in Figure 8;

Figure 10 is an end view of a split stud of an actuator portion of the spindle shown in Figure 1 ;

Figure 11 is a section on line XI-XI of the split stud shown in Figure 10;

Figure 12 is a 3 -dimensional view of part of the tool holder body shown in Figures 4 to 6; and

Figure 13 is a 3-dimensional view of the wedge assembly shown in Figures 7 to 9.

Figure 1 shows a tool holder spindle 1 which generally comprises a spindle body 2 within which are mounted a pair of air bearings 3. A shaft 4 is journalled for rotation about the axis of the spindle 1 within the pair of air bearings 3. The shaft 4 is hollow. Within the shaft 4 is mounted a tool holder 5 for holding a tool (not shown). In the present embodiment the tool holder spindle 1 is a drilling spindle and the tool holder 5 is arranged for holding a drill bit.

The tool holder spindle 1 is arranged to rotatingly drive the shaft 4 and hence tool holder 5 and a carried tool about the axis of the spindle 1. In the present embodiment, rotational drive is provided by a motor M comprising a stator Ml which surrounds the shaft 4 and is provided between the two air bearings 3 and rotor windings M2 which are plated onto the external surface of the shaft 4. Such AC motor drive arrangements are well known for use in air bearing spindles and are not of particular pertinence in the case of the present invention. Therefore no further description of the structure or operation of the motor M will be given.

Also provided within the shaft 4 is a tool actuator portion 6 for actuating the tool holder 5 so as to allow gripping and release of carried tools.

The external diameter of the shaft 4 is the same throughout substantially the whole of the spindle 1; a larger diameter thrust runner (not shown) will typically be provided at some point along the length of the shaft 4. Furthermore it will be noted that the tool holder 5 has a maximum external diameter which is smaller than the internal diameter of the air bearing 3. In fact a majority of the length of the tool holder 5 is fitted within the shaft 4. Where, as in the present embodiment, the shaft 4 is of steel, the tool holder 5 is an interference fit into the bore of the shaft 4. Where, in alternatives, the shaft 4 is of composite or ceramic material, the tool holder 5 is a sliding fit in the bore of the shaft and held in place with adhesive. The only part of the tool holder which projects radially outwards of the internal diameter of the shaft 4 is an end support flange 5F which is used in connecting the tool holder 5 to the shaft 4 via welds, adhesives, and/or bolts.

The shaft 4, spindle 1, and tool holder 5 are co-axially arranged. The tool holder 5 is disposed within the shaft 4 which in turn is within the bearings 3. The axial position of the tool holder 5 coincides with the axial position of one of the bearings 3 - the "front bearing" 3.

In the present application, it is the structure and operation of the tool holder 5 and the actuator portion 6 which are of particular interest. These aspects of the spindle will now be described in more detail below with reference to Figures 2 to 11.

Figures 2 and 3 show a sub-assembly of the tool holder spindle 1. This sub- assembly comprises the tool holder 5 and the actuator portion 6. In the complete spindle 1, as shown in Figure 1, this sub-assembly is mounted in the hollow shaft 4. The tool holder 5 comprises a tool holder body 51 and a wedge assembly 52.

Figures 4, 5, 6 and 12 show the tool holder body portion 51 in isolation. The tool holder body 51 is generally cylindrical and has a central bore B which is arranged for receiving the tool which is to be held by the spindle 1. In this embodiment the tool holder body 51 is of a single piece of material. The central bore B is defined by a tool receiving portion B'. The tool receiving portion B' comprises a plurality of arcuate deformable, resilient, sleeve portions 53. In the present embodiment there are three such sleeve portions 53. As is best seen in Figure 2 and Figure 5, the arcuate sleeve portions 53 are arranged in a ring around the axis of the tool holder body 51 which means they are arranged in a ring around the axis of the spindle 1 as a whole and indeed around the axis of the shaft 4.

Again, as most clearly seen in Figures 2 and 5, each of the arcuate sleeve portions 53 is joined by a respective stem 54 to the remainder of the tool holder body portion 51. Each stem portion 54 is joined to the respective arcuate sleeve portion 53 towards its centre. The material of each arcuate sleeve portion 53 is elastically deformable and this means that the portion of the sleeve portion 53 on each side of the stem 54 may be deformed away from the rest position shown in Figure 2 and Figure 5. The two parts of each arcuate sleeve portion 53 on either side of the stem 54 can act as tool gripping portions 55. Thus in the present embodiment there are 6 tool gripping portions 55 which are arranged in a ring around the central bore B. Each of the tool gripping portions 55 is spaced at each end from the adjacent tool gripping portion 55 by a circumferential gap G. Furthermore, each tool gripping portion 55 has a tool engaging edge 55a at the end of the innermost surface of the arcuate sleeve portion 53. It will be seen that if the deformable tool gripping portions 55 are deformed inwards then the tool engaging edges 55a of the tool gripping portions 55 will extend into the central bore B and thus contact with, and engage, a tool shank if disposed within that bore B. The tool holder body 51 also comprises a plurality of wedge receiving portions

56. hi the present embodiment there are three wedge receiving portions 56. The wedge receiving portions 56 are again arcuate and may be described as semi- annular. The wedge receiving portions 56 are disposed between the tool gripping portions 55 and an outer wall 57 of the tool holder body portion 51. Adjacent wedge receiving portions 56 are separated from each other by respective ones of the stems 54. As is most easily seen in Figure 6, the wedge receiving portions 56 are tapered from one end of the tool holder body portion 51 to the other. That is to say the radial spacing between the facing surfaces of the tool gripping portions 55 and outer wall portions 57 are greater at one end of the tool holder body portion 51 than at the other end of the tool holder body portion 51. This radial spacing is smallest at the end of the tool holder body portion 51 that is closest to the open end of the bore B through which a tool may be introduced into the bore B.

Figures 7, 8, 9 and 13 show the wedge assembly 52 in isolation. The wedge assembly 52 comprises a plurality of taper wedges 58. hi the present embodiment there are three taper wedges 58. The wedge assembly 52 is generally cylindrical with the taper wedges 58 being circumferentially spaced from one another and projecting from an engagement portion 59. In the present embodiment the wedge assembly 52 is of a single piece of material. The inner surface of each of the taper wedges 58 extends generally axially and circumferentially so that together the internal surfaces of the taper wedges 58 lie on the surface of a cylinder. On the other hand, the outer surfaces of the taper wedges 58 taper inwards from one axial end of the wedge 58 to the other. Thus, the outer surfaces of the tapered wedges

58 lie on a conic surface. The tapering of the taper wedges 58 is such that the cross-sectional thickness in a radial direction of each of the wedges 58 is smallest at their end which is closest to the open end of the bore B. The taper of each of the taper wedges 58 is complimentary to the taper of the wedge receiving portions 56 in the tool holder body portion 51.

The taper wedges 58 are arranged to be received in respective ones of the wedge receiving portions 56 in the tool holder body portion 51. In the sub-assembly shown in Figures 2 and 3, and in Figure 1, the taper wedges 58 are shown inserted in the receiving portions 56.

The engagement portion 59 of the wedge assembly 52 comprises a receiving chamber 59a for receiving a head 61 of the actuator portion 6 and an entrance aperture 59b through which the head 61 may be introduced into the chamber 59a.

At the inner end of the entrance aperture 59b, the chamber 59a is provided with an abutment surface 59c which in this embodiment is in the form of a annular ledge against which the head 61 of the actuator portion can abut.

Thus the annular ledge 59c is provided around the periphery of the inner end of the entrance aperture 59b. However, it will be noted that the head 61 is to be introduced through the entrance aperture 59b during assembly. The ability to introduce the head 61 through the entrance aperture 59b during assembly yet allow the head 61 to abut with the abutment surface 59c during actuation is achieved by the structure of the actuator portion 6 which will be explained in more detail below.

The actuator portion 6 comprises a split stud 62 which terminates in the head 61. Around the split stud 62 there is provided a outer portion 63 which terminates in a shoulder 63a which is also arranged to act on the engagement portion 59 of the wedge assembly 52.

Figures 10 and 11 show the split stud 62 in isolation. The split stud 62 comprises a plurality of legs 62a. In the present embodiment there are four legs 62a. Each of the legs 62a terminates in a respective portion 61a of the head 61. The legs 62a are arranged to be splayable relative to one another in order to change the effective external diameter of the head 61. The legs 62a are also arranged to be collapsible relative to one another in order to minimise the effective external diameter of the head 61.

As can be seen in Figure 3, a splaying pin 64 with a tapered end 65 is provided within the split stud 62. The internal surfaces of the legs 62a as they meet the respective portions 61a of the head 61 are also tapered with a taper which is complimentary to that of the tapered end 65 of the splaying pin 64. If the splaying pin 64 is retracted axially such that the tapered end 65 moves away from the head 61 , the portions of the head 61a may be collapsed together to enable them to be inserted through the entrance aperture 59b. Once the head 61 is within the chamber 59a and the collapsing forces are removed, the head will obtain a rest diameter. However, in order to ensure that there is good abutment between the head 61 and the abutment surface 59c during actuation, the tapered pin 64 is driven into an extended position where the tapered end 65 tends to splay out the legs 62a and hence increase the outer diameter of the head 61.

The actuator portion 6 and engagement portion 59 are arranged to allow relative rotation therebetween. The tool holder 5 comprising both the tool holder body 51 and wedge assembly 52 is mounted in the shaft 4 in such a way that they rotate with the shaft 4. However, the actuator portion may remain static. The actuator portion 6 may be driven to move in the axial direction by a component external to the spindle 1 (introduced from the rear) or in other alternatives by an axial drive means provided within the spindle.

The engagement portion 59 is arranged as a female receiving portion rather than as a male projecting portion such as a bolt head. The engagement portion 59 has a cylindrical outer surface 59d, which as can be seen in Figure 1, contacts with the internal wall of the hollow shaft 4. This provides support to the engagement portion 59 against centrifugal effects as the tool holder 5 rotates with the shaft 4. This can be useful in alleviating instabilities such as wobble and vibration which might otherwise occur in high speed applications. It should also be noted that the tool holder 5 is supported along its whole, or substantially its whole, length by the shaft 4. Again this can help prevent instability at high speed.

In operation, the amount of gripping force exerted on a tool shank disposed in the central bore B is dependent on the axial position of the taper wedges 58 in the receiving portions 56. Thus, a tool is inserted into the central bore B with the taper wedges 58 in a first position such that the tool gripping portions 55 in the tool holder body 51 are in the rest position as shown in Figure 5. In this state, the central bore B and tool receiving portion B' have their maximum internal diameter. Once a tool shank has been inserted into the receiving bore B, the wedge assembly 52 may be moved relative to the tool holder body 51 so driving the taper wedges 58 further into the receiving portions 56. The result of such movement of the wedges 58 into the receiving portions 56 is inward deformation of the tool gripping portions 55 into the central bore B towards the axis of the spindle 1. This gives rise to gripping of the tool shank by virtue of a decrease in the overall effective diameter of the central bore B. Furthermore, the tool engaging edges 55a of the tool gripping portions 55 will tend to bite into the tool shank.

In operation the taper wedges 58 are driven into the receiving portions 56 by the shoulder 63 a of the actuator portion 6 contacting with the end of the engagement portion 59 of the wedge assembly 52 and driving the wedge assembly 52 towards the tool holder body portion 51. When it is desired to release a gripped tool then the actuator portion 6 is moved in the opposite direction so that the shoulder 63 a does not contact with the engagement portion 59, but rather the head 61 of the actuator portion contacts with the abutment surface 59c provided at the inner surface of the entrance aperture 59. As mentioned above, good abutment between the head 61 and abutment surface 59c is achieved by splaying the head portion 61a apart using the splaying pin 64. That is to say, the splaying pin 64 is moved in an axial direction towards the open end of the central bore B splaying out the portions 61a of the head 61 and then the actuator portion 6 as a whole may be moved in a direction away from the open end of the central bore B. This causes the head 61 to contact with the abutment surface 59c in the engagement portion 59 and hence pulls the wedge assembly 52 away from the tool holder body portion 51. As the wedge assembly 52 is pulled away from the tool holder body portion 51, the taper wedges 58 move axially within the receiving portions 56 in such a way that the radial force on the tool gripping portions 55 is removed and the tool gripping portions 55 can relax to their original state. Of course, as this occurs, the central bore B returns to its original diameter and the gripping force on the tool shank is released.

The tool holder body 51 and wedge assembly will typically be of steel. In the present embodiment the shaft 4 is of steel. In other embodiments however, the shaft 4 may be of ceramic material or of composite material - in such a case a different, and probably dc, type of motor will most likely be used. In alternatives the head 61 may act on the wedge assembly 52 to move it in both axial directions.

The tool holder body 51 may be made by electrical discharge machining (EDM) of a single piece of material to give the required shape. In particular the sleeve portions 53 and hence the gripping portions 55 may be made by electrical discharge machining. The gripping portions 55 and receiving bore B surface may be machined in a single process, which may be an EDM process.

The gripping portions 55 are shaped and dimensioned so as to minimize weight. The gripping portions 55 are shaped and dimensioned so as to minimize their radius. They are disposed as close as possible to the axis of the tool holder. They are radially thin. They have minimum outer radius and inner radius. Each gripping portion 55 has a substantially constant radial thickness along its axial length. Each gripping portion 55 has a substantially constant radial thickness along its circumferential extent. A cross-section taken perpendicularly to the axis of the tool holder through any one of the gripping portions 55 is invariant along the axial length of the gripping portion 55. That is to say a cross-section taken at one point along the length of the gripping portion 55/tool holder 51 is the same as one taken at any other point along the length of the gripping portion.

The mass of the gripping portions 55 is small compared with the mass of the tool holder body 51 as a whole. The combined mass of the gripping portions 55 may be less than 50% of the mass of the tool holder body 51. The combined mass of the gripping portions 55 may be less than 10% of the mass of the tool holder body

51.

These features in isolation or in combination can help give good performance at high speed and can help minimize centrifugal effects.

The above described features of the gripping portions 55 also apply in respect of the sleeve portions 53, in this embodiment.

Claims

CLAIMS:

1. A tool holder spindle comprising a shaft, a spindle body comprising at least one bearing within which the shaft is journalled for rotation relative to the spindle body, a tool holder for holding a tool, and an axially moveable actuator portion disposed within the shaft for actuating the tool holder; the tool holder being mounted within the shaft and comprising: a tool receiving portion having at least one deformable tool gripping portion; and at least one wedge portion arranged to act on the deformable tool gripping portion and arranged for axial movement relative to the tool receiving portion under action of the axially moveable actuator portion, wherein axial movement of the actuator portion in a first direction causes axial movement, relative to the tool receiving portion, of the wedge portion in a first direction so deforming the tool gripping portion inwards towards the axis of the spindle for gripping a received tool.

2. A tool holder spindle according to claim 1 in which a cross-section of the tool gripping portion taken perpendicularly to the axis of the tool holder is invariant along the axial length of the gripping portion.

3. A tool holder spindle according to claim 2 in which the tool receiving portion is held against axial movement relative to the shaft.

4. A tool holder spindle according to claim 2 or claim 3 in which the wedge portion is arranged for axial movement relative to the shaft.

5. A tool holder spindle according to any one of claims 1 to 4 in which the tool holder may comprise a tool holder body.

6. A tool holder spindle according to claim 5 in which the tool holder body comprises at least one arcuate deformable sleeve portion.

7. A tool holder spindle according to claim 6 in which the arcuate deformable sleeve portion comprises the deformable tool gripping portion.

8. A tool holder spindle according to any preceding claim in which the tool receiving portion comprises a plurality of deformable tool gripping portions.

9. A tool holder spindle according to claim 8 when dependent on any one of claims 5 to 7 in which the tool holder body comprises a plurality of arcuate deformable sleeve portions which are spaced from one another around an inner periphery of the tool receiving portion.

10. A tool holder spindle according to claim 9 in which each sleeve portion comprises at least a respective one of the deformable tool gripping portions.

11. A tool holder spindle according to claim 9 or claim 10 in which the arcuate sleeve portions are arranged in a ring, with circumferential spacings therebetween, around the axis of the spindle, providing an inward facing generally cylindrical tool contacting surface.

12. A tool holder spindle according to claim 6 or any one of claims 7 to 11 when dependent on claim 6 in which the or each sleeve portion is connected to a main part of the tool holder body via a respective stem.

13. A tool holder spindle according to any preceding claim in which the, or each tool gripping portion comprises at least one tool engaging edge.

14. A tool holder spindle according to claim 13 when dependent on claim 9, or when dependent on any one of claims 10 to 12 when dependent on claim 9, in which each sleeve portion comprises a pair of tool gripping portions.

15. A tool holder spindle according to claim 14 in which each sleeve portion comprises a pair of tool engaging edges which are on opposing edges of the sleeve portion.

16. A tool holder spindle according to claim 13 or any one of claims 14 and 15 when dependent on claim 13 in which the or each tool gripping portion is arranged so that inward deformation of the tool gripping portion causes inward movement of the tool engaging edge.

17. A tool holder spindle according to any preceding claim in which the tool holder comprises a plurality of wedge portions.

18. A tool holder spindle according to any preceding claim in which the tool holder comprises a wedge assembly comprising the or each wedge portion and an engagement portion for engagement with the actuator portion.

19. A tool holder spindle according to claim 5 or anyone of claims 6 to 18 when dependent on claim 5 in which the tool holder body comprises at least one annular wedge receiving portion, the at least one annular receiving portion being tapered along its axial length and the at least one wedge portion being tapered along its axial length, the taper of the at least one receiving portion complementing the taper of the at least one wedge.

20. A tool holder spindle according to any preceding claim in which the at least one wedge portion is arranged to act on a plurality of tool gripping portions.

21. A tool holder spindle according to any preceding claim in which the tool receiving portion is disposed within the axial extent of the shaft directly supported by the bearing.

22. A tool holder spindle according to any preceding claim in which the tool holder is disposed substantially within the axial extent of the shaft directly supported by the bearing.

23. A tool holder spindle according to any preceding claim in which the tool holder is supported along substantially its whole length by virtue of being mounted within the shaft.

24. A tool holder spindle according to any preceding claim in which the external diameter of the shaft is substantially constant throughout the spindle.

25. A tool holder spindle according to any preceding claim in which the external diameter of the shaft in the region of the bearing is substantially the same as the external diameter of the shaft in the region of the tool holder.

26. A tool holder spindle according to any preceding claim in which the external diameter of at least the main part of tool holder is less than the internal diameter of the bearing.

27. A tool holder spindle according to any preceding claim in which the external diameter of the main part of the tool holder is less than the internal diameter of the shaft.

28. A tool holder spindle according to any preceding claim in which the axially moveable actuator portion and tool holder are arranged to allow relative rotation therebetween.

29. A tool holder spindle according to claim 18 or any one of claims 19 to 28 when dependent on claim 18 in which the moveable actuator portion comprises a head for engagement with the engagement portion.

30. A tool holder spindle according to claim 29 in which the engagement portion is arranged as a female receiving portion for receiving the head of the actuator portion.

31. A tool holder spindle according to claim 30 in which the female receiving portion is supported against centrifugal effects by an internal wall of the shaft.

32. A tool holder spindle according to claim 30 or claim 31 in which the female receiving portion has an external surface which is in contact with the internal surface of the shaft.

33. A tool holder spindle according to any one of claims 30 to 32 in which the female receiving portion comprises a receiving chamber in which the head of the actuator portion is disposed in use and an entrance aperture through which the head of the actuator portion may be introduced into the chamber during assembly.

34. A tool holder spindle according to any one of claims 29 to 33 in which the actuator portion comprises a spilt stud terminating in the head, the stud comprising a plurality of legs each of which terminates in a respective portion of the head and which may be splayed apart from one another to alter the effective outer diameter of the head.

35. A tool holder spindle according to claim 34 when dependent on claim 33 in which the actuator portion comprises a splaying pin which is arranged for splaying the legs and which is axially moveable relative to the split stud between a first position in which the effective outer diameter of the head is smaller than the diameter of the entrance aperture and a second position in which the effective outer diameter of the head is larger than the diameter of the entrance aperture.

36. A tool holder spindle according to claim 29 or anyone of claims 30 to 35 when dependent on claim 29 in which the actuator portion and wedge assembly are arranged so that contact between the head and the engagement portion is used to move the at least one wedge portion in one axial direction or in both axial directions.

37. A tool holder spindle according to claim 36 in which the actuator portion comprises a shoulder for contacting with the wedge assembly for movement of the at least one wedge portion in one axial direction.

38. A tool holder spindle according to any preceding claim in which there is a pair of radial bearings in which the shaft is journalled, the tool holder being disposed substantially wholly within a region of the shaft which is between the outermost ends of the pair of bearings.

39. A tool holder spindle according to any preceding claim in which the bearing or each bearing is a gas bearing, typically an air bearing.

40. A tool holder spindle comprising a shaft, a spindle body comprising at least one gas bearing within which the shaft is journalled for rotation relative to the spindle body, and a tool holder for holding a tool; the tool holder being mounted within the shaft and comprising: a tool receiving portion having at least one deformable tool gripping portion; and at least one wedge portion arranged to act on the deformable tool gripping portion and arranged for axial movement relative to the tool receiving portion under action of an actuator, wherein axial movement of the wedge portion, relative to the tool receiving portion and under action of an actuator, in a first direction deforms the tool gripping portion inwards towards the axis of the spindle for gripping a received tool.

41. A tool holder spindle according to claim 40 in which the actuator comprises an axially moveable actuator portion disposed within the shaft.

42. A tool holder spindle according to claim 40 in which the actuator comprises an external actuator, which is separate from the spindle.

43. A tool holder spindle according to claim 42 in which the external actuator operates on the wedge portion from one of: a front, tool receiving, end of the spindle, and a rear end of the spindle.

44. Tool holder apparatus comprising a tool holder spindle according to any one of claims 40, 42 and 43 and an external actuator for acting on the wedge portion in the tool holder spindle.

45. A drilling spindle comprising a shaft, a spindle body comprising at least one gas bearing within which the shaft is journalled for rotation relative to the spindle body, a tool holder for holding a tool, and an axially moveable actuator portion disposed within the shaft for actuating the tool holder; the tool holder being mounted within the shaft and comprising: a tool receiving portion having at least one deformable tool gripping portion; and at least one wedge portion arranged to act on the deformable tool gripping portion and arranged for axial movement relative to the tool receiving portion under action of the axially moveable actuator portion, wherein axial movement of the actuator portion in a first direction causes axial movement, relative to the tool receiving portion, of the wedge portion in a first direction so deforming the tool gripping portion inwards towards the axis of the spindle for gripping a received tool.

46. A tool holder for a spindle according to any preceding claim.