WO2011001421A1

WO2011001421A1 - Turbine driven rotary cutting tool

Info

Publication number: WO2011001421A1
Application number: PCT/IL2010/000443
Authority: WO
Inventors: Oz Yitzhak
Original assignee: Colibri Spindles Ltd.
Priority date: 2009-06-28
Filing date: 2010-06-06
Publication date: 2011-01-06

Abstract

A turbine driven rotary cutting tool is adapted for replaceable mounting on a tool holder that is part of for example a manual tool or a low speed machine tool such as a lathe, milling machine of drill head. The cutting tool has a one piece unitary cutting bit for performing a cutting operation and at least one bearing for supporting rotation of the cutting bit. At least a first part of the bearing is fitted integrally to the cutting bit so that replacement of the cutting tool includes replacing the cutting bit and bearing as a set. The cutting tool may perform various machining operations such as, for example, milling, drilling, deburring, polishing and grinding operations.

Description

TURBINE DRIVEN ROTARY CUTTING TOOL

FIELD OF THE INVENTION

The present invention relates to rotary cutting tools for performing various rotary machining operations, and more particularly, to turbine driven rotary cutting tools that are detachably mounted on a tool holder.

BACKGROUND OF THE INVENTION

Machine tools such as lathes, milling machines or drill heads that are used in manufacturing to mechanically remove material from a workpiece normally operate at a relatively low speed and high output power. In some cases, a workpiece being machined by such machine tools may require additional machining by other types of tools that are suitable for example for performing more accurate machining. This additional machining may require additional setup and machining time.

Turbine driven rotor maching tools that operate at relatively higher speeds may be suitable for performing for example the above mentioned accurate machining. These tools typically have a spindle that is supported for rotation by accurate and often expensive bearings and a replaceable machining bit that is detachable secured to the spindle. US Patent No. 7,192,248 describes a turbine driven rotary cutting tool that has a tool support for attaching the turbine cutting tool to a conventional machine tool holder. The turbine cutting tool has a spindle which is supported by bearings and the spindle is provided with a tool holder that is adapted to grip a cutting bit. PCT Patent publication No. 2008139472 describes a dual spindle system having a low speed spindle head that may alternately receive at a forward end thereof a drill bit for performing a low speed drilling action and a high speed spindle head with a drill bit for performing a high speed drilling action.

SUMMARY OF THE INVENTION

In accordance with the present invention there is provided a rotary cutting tool for performing a cutting operation, the rotary cutting tool comprises a one piece unitary cutting bit and at least a first part of a bearing for supporting rotation of the cutting bit about a cutting axis, wherein the at least a first part of the bearing is fitted integrally to the cutting bit forming an integral cutting bit module. The rotary cutting tool is adapted for replaceable mounting on a tool holder or for mounting on an adaptor which is replaceably mountable on the tool holder. In other words, the cutting bit and the at least a first part of the bearing form an integral cutting bit module. Forming such an integral cutting bit module has an advantage in that when either or both of the cutting bit and the first part of the bearing become worn the integral cutting bit module as a whole can be disposed of and replaced thereby maintaining accuracy of the tool and saving setup time. The tool holder may be part of a manually held tool or a machine tool such as a lathe, milling machine or drill head that typically operates at a relatively low speed. The term "cutting" does not have a limiting meaning where this term appears in the description and claims but is understood to mean machining in general. Hence, cutting operations may include, for example, such machining operations as a milling, drilling, deburring, polishing, grinding, etc. Similarly, the cutting bit is understood to be a machining bit that may be adapted to perform such machining operations.

Typically, the rotary cutting tool further comprises a turbine coupled to the cutting bit.

Quite generally, the turbine is driven by a medium for imparting rotation to the rotary cutting tool about the cutting axis. In some embodiments, the rotary cutting tool further comprises a housing and a second part of the bearing, wherein the first and second parts of the bearing comprising the bearing.

In accordance with other embodiments, the cutting tool further comprises a housing and at least a second part of the bearing, wherein the second part of the bearing is coupled to the housing.

In accordance with some embodiments, the bearing is a ball bearing and the cutting operation of the cutting tool is adapted to take place at an axial forward end of the cutting tool, and wherein at least part of the medium applied to drive the turbine is adapted to urge the turbine axially forwardly. The turbine may be attached to an inner part of the bearing via the cutting bit, so that when urged axially forwards it causes the inner part of the bearing to move axially relative to an outer part of the bearing that remains in place fixed to the housing. This relative movement between the inner and outer parts of the bearing forms a dynamic pre- load of the bearing that may increase the over all accuracy of the cutting tool. Optionally, the axial movement of the turbine may be in an axially rearward direction.

Typically, the first and second parts of the ball bearing are respectively the inner and outer races of the ball bearing.

In accordance with some embodiments, the medium comprises one of the group of a fluid, a coolant fluid, water or air.

In accordance with some embodiments of the invention, the bearing is an air bearing and the first part of the bearing is in the form of a groove pattern, and at least part of the air applied to drive the turbine is adapted to communicate with the groove pattern.

Typically, the air communicating with the groove pattern forms a thin film interface of pressurized air between the cutting bit and the housing.

Preferably, the air communicates with the groove pattern via at least one hole formed in the turbine. BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention and to show how the same may be carried out in practice, reference will now be made to the accompanying drawings, in which:

Fig. IA is a perspective top view of a machine tool incorporating a turbine driven rotary cutting tool in accordance with embodiments of the present invention;

Fig. IB is a detail of Fig. IA;

Fig. 2A is a perspective bottom view of a manual tool incorporating a turbine driven rotary cutting tool in accordance with embodiments of the present invention;

Fig. 2B is an exploded view of the manual tool and turbine driven rotary cutting tool of Fig. 2 A;

Fig. 3 is a perspective bottom view of a turbine driven rotary cutting tool in accordance with a first embodiment of the present invention attached to an adaptor;

Fig. 4 is an exploded view of the turbine driven rotary cutting tool and adaptor of Fig. 3;

Fig. 5 is a cross sectional view of the turbine driven rotary cutting tool and adaptor taken in plane V-V in Fig. 3;

Fig. 6 is a cross sectional view of the turbine driven rotary cutting tool and adaptor taken in plane VI-VI in Fig. 4;

Fig. 6' is a cross sectional view of the integral cutting bit module formed by the cutting bit and bearings fitted integrally to the cutting bit;

Fig. 7A is a perspective top view of a turbine driven rotary cutting tool in accordance with a second embodiment of the present invention;

Fig. 7B is a partial cross sectional view of the turbine driven rotary cutting tool as seen in Fig. 7A;

Fig. 8 is a cross sectional view of the turbine driven rotary cutting tool taken in plane VIII-VIII of Fig. 7A. Fig. 9 is a partial cross sectional perspective top view of a turbine driven rotary cutting tool in accordance with a third embodiment of the present invention;

Fig. 10 is a perspective top view of a cutting bit of the turbine driven rotary cutting tool shown in Fig. 9;

Fig. 11 is a detail of Fig. 9;

Fig. 12 is a perspective top view of a turbine driven rotary cutting tool in accordance with a fourth embodiment of the present invention; and

Fig. 13 is a cross sectional view of the turbine driven rotary cutting tool taken in plane XIII-XIII of Fig. 12.

The drawings taken with description make apparent to those skilled in the art how the invention may be embodied in practice.

It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals may be repeated among the figures to indicate similar elements.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Attention is first drawn to Figs. IA and IB. A machine tool 7 such as a lathe is adapted to perform a relatively low speed machining operation in order to remove material from a workpiece (not shown). Other non binding examples of such relatively low speed machine tools 7 may be milling machines or drilling heads. Cutting tools used to perform such a low speed machining opetrations are typically detachably secured to a tool holder 8 of the machine tool 7. In cases where for example more accurate machining is required, relatively high speed turbine driven rotary cutting tools 100 may be secured to the tool holder 8. Such turbine driven rotary cutting tools 100 may perform various machining operations such as, for example, milling, drilling, deburring, polishing and grinding operations. Attention is additionally drawn to Figs. 2 A and 2B showing a manual tool 9 having a tool holder 8 at one of its ends in which such a turbine driven rotary cutting tool 100 may also be detachably secured. Such a manual tool 9 may be used to manualy perform metal working operations such as deburring.

Attention is now drawn to Figs. 3 and 4. A turbine driven rotary cutting tool 110 in accordance with a first embodiment of the present invention is shown attached and detached in relation to an adaptor 12. The rotary cutting tool 110 extends along an axis of rotation R and is adapted to perform a high speed cutting operation about said axis R. The adaptor 12 has a shank 14 at an axially rear end thereof for optional replaceable mounting of the cutting tool 110 with the adaptor 12 on the tool holder 8 of for example the machine tool 7 or manual tool 9.

The embodiments of the turbine driven rotary cutting tools presented herein will all be described in relation to the axis of rotation R about which they are adapted to perform their relatively high speed rotary cutting motions. Axis R will also be defining herein an axially forward direction pointing to the direction where cutting occurs and an opposing rear direction. It should be noted that directional terms appearing throughout the specification and claims, e.g. "forward", "rear", etc., (and derivatives thereof) are for illustrative purposes only, and are not intended to limit the scope of the appended claims.

Attention is now drawn to Figs. 5 and 6. The turbine driven rotary cutting tool 110 has a housing 16 and a cutting bit 18. The cutting bit 18 extends axially through the housing 16 and has a rear shaft 20 and a forward cutting head 22 that are integrally formed of optionally the same material and have a unitary one-piece construction. An air driven turbine 24 of the turbine driven rotary cutting tool 110 is attached by for example heat shrinking, bonding or mechanical means to a rear end of the shaft 20 and the shaft 20 is supported for rotation within the housing 16 by rear and forward ball bearings 26, 28.

In accordance with some embodiments, each ball bearing 26, 28 is integrally fitted at its outer and inner races 30, 32 respectively to the housing 16 and to the shaft 20 of the cutting bit 18 by, for example, heat shrinking, bonding or mechanical means. In accordance with such embodiments, the outer and inner races 30, 32 are removably fitted to each other. In accordance with such embodiments, the cutting bit 18 and the inner race 32 of each ball bearing 26, 28, for an integral cutting bit module 19.

In accordance with some embodiments, each ball bearing 26, 28 is integrally fitted at its inner race 32 to the shaft 20 of the cutting bit 18 by, for example, heat shrinking, bonding or mechanical means. In accordance with such embodiments, the outer and inner races 30, 32 are integrally fitted to each other and each ball bearing 26, 28 is removably fitted at its the outer race 30 to the housing 16. In according with such embodiments, the cutting bit 18 and outer and inner races 30, 32 of each ball bearing 26, 28, for an cutting bit module 19.

Fig. 6' shows a cutting bit module 19 in accordance with embodiments of the present invention.

The turbine driven cutting tool 110 is detachably mounted to the adaptor 12 so that it may be easily removed or replaced when needed from the adaptor 12. When mounted in the adaptor 12 , air passages 34 that are formed in the adaptor 12 communicate with the turbine 24 to provide a flow path for pressurized air or gas that drives the turbine 24 to rotate the cutting bit 18 to perform the high speed rotational cutting or drilling movement about axis R.

Attention is now drawn to Figs. 7 A, 7B and 8. A turbine driven rotary cutting tool 120 in accordance with a second embodiment of the present invention has a housing 16 and a cutting bit 18 that extends axially through the housing 16 and has a rear shaft 20 and a forward cutting head 22 that are integrally formed of optionally the same material and have a unitary one-piece construction. As in the first embodiment, an air driven turbine 36 of the turbine driven rotary cutting tool 120 is attached to a rear end of the shaft 20 and the shaft 20 is supported for rotation within the housing 16 by rear and forward ball bearings 26, 28 that are integrally fitted at their outer an inner races 30, 32 respectively to the housing 16 and to the shaft 20 of the cutting bit 18 by for example heat shrinking, bonding or mechanical means. In this embodiment, the air passages 34 that provide the flow path for pressurized air or gas jet that drives the high speed rotational movement of the cutting bit 18 are formed in the housing 16 and the housing 16 has optional attachment planes 38 formed on its peripheral outer face for replaceable mounting of the turbine driven rotary cutting tool 120 on the tool holder 8 of for example the machine tool 7 or manual tool 9.

Ball bearings used in turbine driven rotary cutting tools in accordance with some embodiments of the present invention should preferably have "zero" clearance when load due to for example a cutting action is applied thereupon. Such "zero" clearance limits vibration and thereby increases the cutting accuracy. A force that is applied to a ball bearing to achieve such "zero" clearance is known as preload (static preload). In accordance with an aspect of the present invention, the turbine 36 has blades 40 that are spaced apart by cavities 42 wherein each cavity 42 is closed at its rear side by a roof 44 of the turbine 36 while remaining open at its forward side. Air or gas indicated by wavy arrow 37 driving the rotational movement of the turbine 36 about axis R bears, inter alia, against the roof 44 bounding in each cavity 42 to thereby provide rearwadly directed forces F that act upon the turbine 36. These forces F urge the cutting bit 18 that is attached to the turbine 36 slightly rearwardly and as a result the inner races 32 of the ball bearings 26, 28 that are integrally fitted to the cutting bit 18 are also urged slightly rearwardly. The outer races 30 of the ball bearings 26, 28 on the other hand remain substantially in place attached to the housing 16. This results in a dynamic preload force being applied upon the ball bearings 26, 28 that improves the overall cutting accuracy of such turbine driven rotary cutting tools.

Attention is now drawn to Figs. 9 to 11. A turbine driven rotary cutting tool

130 in accordance with a third embodiment of the present invention has a housing 16 and a cutting bit 18 that extends axially through the housing 16 and has a rear shaft 20 and a forward cutting head 22 that are integrally formed of optionally the same material and have a unitary one-piece construction. An air driven turbine 46 of the cutting tool 130 is attached to a middle section 48 of the shaft 20 and the shaft 20 is supported for rotation within the housing 16 by air bearings 50 that have herringbone and spiral groove patterns 52, 54 and by rear and forward bearings 26, 28 of the housing 16. The herringbone groove pattern 52 is integrally fitted to the shaft 20 of the cutting bit 18 by being formed thereupon and the spiral groove pattern 54 is integrally fitted to the axially directed faces of the turbine 46. These grooves 52, 54 contribute to the formation a thin film interface of pressurized air between the cutting bit 18 and turbine 46 on the one hand and the housing 16 on the other hand when the cutting tool 130 is performing a rotary cutting action about axis R.

The turbine 46 of the turbine driven rotary cutting tool 130 has inner and outer peripheral faces 56, 58 respectively proximal and distal to the shaft 20 of the cutting bit 18. Cavities 42 formed about axis R in the outer face 58 of the turbine 46 define blades 40 there between. In accordance with an aspect of the present invention, holes 60 formed in the turbine 46 communicate each between a given cavity 42 and the turbine's inner face 56; and the middle section 48 of the shaft 20 has raised bases 62 that are attached to the turbine's inner face 56 and an array of un obstructed channels 64 that are formed between those bases 62. Air or gas flowing via air passages 34 in the housing 16 to drive the turbine 46 flows, inter alia, through the holes 60 into the channels 64 of the middle section 48. These air flows, indicated in Fig. 11 by small arrows, communicate via the channels 64 with the grooves 52, 54 of the air bearings 50 of the cutting tool 130 to form the thin film interface of pressurized air that supports the rotational movement of the turbine driven rotary cutting tool 130. Notably, the provision of air to the air bearings 50 of the turbine driven rotary cutting tool 130 via the holes 60 and channels 64 simplifies the construction of the turbine driven rotary cutting tool 130 which otherwise might require additional air passages formed for example in the cutting tool's housing 16 for the provision of pressurized air to the air bearings 50. The turbine driven rotary cutting tool 130 has a shank 14 at an axially rear end thereof for optional replaceable mounting of the turbine driven rotary cutting tool 130 on the tool holder 8 of for example the machine tool 7 or manual tool 9.

Attention is now drawn to Figs. 12 and 13. A turbine driven rotary cutting tool 140 in accordance with a fourth embodiment of the present invention has a housing 16 having rear and forward parts that are attached by screws 70. A cutting bit 18 of the turbine driven rotary cutting tool 140 extends axially through the forward part of the housing 16 and has a rear shaft 20 and a forward cutting head 22 that are integrally formed of optionally the same material and have a unitary one-piece construction. An air driven turbine 66 of the cutting tool 140 integrally formed with a sleeve 68 is attached to the shaft 20 of the cutting bit 18. The cutting bit 18 via the sleeve 68 is supported for rotation within the housing 16 by rear and forward ball bearings 26, 28 that are integrally fitted at their outer races 30 to the housing 16 and at their inner races 32 via the sleeve 68 to the cutting bit's shaft 20 by for example heat shrinking, bonding and/or mechanical means.

Air passages 34 that provide a flow path for pressurized air or gas that drives the high speed rotational movement of the cutting bit 18 are formed in the rear and forward parts of the housing 16 and the rear part of the housing 16 has a shank 14 at an axially rear end thereof for optional replaceable mounting of the rotary cutting tool 140 on the tool holder 8 of for example the machine tool 7 or manual tool 9. When replacement of the cutting bit 18 is required, the forward part of housing 16 may be detached from the rear part and replaced by a new forward part incorporating a new cutting bit 18 and bearings 26, 28.

It should be understood that other types of bearings such as hydrodynamic bearings, hydrostatic bearings, aerostatic bearings, needle bearings and cone bearings, may be used in embodiments of the turbine driven rotary cutting tools described hereinabove. In addition it is noted prior art turbine driven rotary cutting tools typically utilize replaceable cutting bits that are typically gripped in such prior art turbine driven rotary cutting tools. As a result, such prior art turbine driven rotary cutting tools typically have "high end" and often expensive bearings that are adapted to support a required cutting accuracy for a relatively long period of time.

In the present invention on the other hand the bearings are integrally fitted to the cutting bit 18 and are therefore replaceable together with the cutting bit 18 as a set.

As a result, bearings used in a turbine driven rotary cutting tool in accordance with the present invention may be adapted to support a required cutting accuracy for a relatively shorter period of time that is generally similar to the usage time of the cutting bit 18 and therefore may be of a cheaper type.

Although the present invention has been described to a certain degree of particularity, it should be understood that various alterations and modifications could be made without departing from the scope of the invention as hereinafter claimed.

Claims

CLAIMS:

1. A rotary cutting tool for performing a cutting operation, the rotary cutting tool comprising a one piece unitary cutting bit and at least a first part of a bearing for supporting rotation of the cutting bit about a cutting axis, wherein the at least a first part of the bearing is fitted integrally to the cutting bit forming a cutting bit module.

2. The rotary cutting tool according to claim 1 comprising a turbine coupled to the cutting bit.

3. The rotary cutting tool according to claim 2, wherein the turbine is driven by a medium for imparting rotation to the rotary cutting tool about the cutting axis.

4. The rotary cutting tool according to claims 2 or 3, further comprising a housing and a second part of the bearing, wherein the first and second parts of the bearing comprising the bearing.

5. The rotary cutting tool according to claims 2 or 3, further comprising a housing and at least a second part of the bearing, wherein the second part of the bearing is coupled to the housing.

6. The rotary cutting tool according to claims 4 or 5, wherein the bearing is a ball bearing and the cutting operation is adapted to take place at an axial forward end of the cutting tool, and wherein at least part of the medium applied to drive the turbine is adapted to urge the turbine axially forwardly.

7. The rotary cutting tool according to claim 6, wherein the first and second parts of the ball bearing are respectively inner and outer races of the ball bearing.

8. The rotary cutting tool according to any one of claims 3-7, wherein the medium comprises one of the group of a fluid, a coolant fluid, water or air.

9. The rotary cutting tool according to any one of claims 3- 5, wherein the medium is air and the bearing is an air bearing and the first part of the bearing is in the form of a groove pattern, and at least part of the air applied to drive the turbine is adapted to communicate with the groove pattern.

10. The rotary cutting tool according to claim 9, wherein the air communicating with the groove pattern forms a thin film interface of pressurized air between the cutting bit and the housing.

11. The rotary cutting tool according to any one of claims 9- 10, wherein the air communicates with the groove pattern via at least one hole formed in the turbine.