Sealing system for a tool holder

Abstract

The present invention concerns a sealing system for a tool holder of a fluid-assisted axial machining or milling machine, including:—at least first and second seals contributing to define a space for the flow of fluid to at least one inner channel of the tool, one of the seals being applied to the tool or an optional adapter carrying the tool and the other seal a) being applied to the tool or to the adapter carrying the tool or b) being applied to a surface spaced apart from the tool and rotating with same, with 0.3≦Do/Dj.sub.max for Do in the interval [1; 3] in mm and 0.5≦Do/Djmax for Do in the interval [3; 20] in mm, where Do is the diameter of the tool facing this other seal and Djmax is the internal diameter of this seal.

Claims

1. A sealing system for a tool holder of a fluid-assisted milling or axial machining machine tool, comprising: at least a first and a second seal contributing to delimiting a space for the circulation of the fluid toward at least one internal passage of the tool, one of the seals pressing against the tool or a tool-bearing adapter there may be, and the other seal pressing against a surface spaced away from the tool and rotating with the latter, with 0.3≦Do/Dj.sub.max for Do in the range of 1 mm to 3 mm and 0.5≦Do/Dj.sub.max for Do in the range of 3 mm to 20 mm, where Do is the diameter of the tool facing this other seal and Dj.sub.max is the internal diameter of this seal.

2. The system as claimed in claim 1, comprising a collet nut for tightening an expanding collet that holds the tool or the adapter, fixed to a body of the tool holder.

3. The system as claimed in claim 1, the surface being defined by an adapter ring.

4. The system as claimed in claim 1, the seals being borne by a ring adapted to the diameter of the tool or of the adapter, arranged in contact with a stator body.

5. The system as claimed in claim 1, the surface being defined by a deformable, adapter sleeve.

6. The system as claimed in claim 5, the adapter sleeve comprising at least one longitudinal groove extending over its internal surface and over the entire length.

7. The system as claimed in claim 5, comprising an O-ring seal positioned between a plug and the adapter sleeve, the plug being held against the seal by the pressure of the cutting fluid present in the adapter sleeve.

8. The system as claimed in claim 1, the axial or milling machining operation being a machining operation of drilling or of countersinking.

9. A range of at least a first and a second sealing system as claimed in claim 1, the two sealing systems being intended for one and the same tool holder of a cutting fluid-assisted machine tool, adapted to different diameters D1 and D2 of tool or adapter, where D2 is greater than D1, each sealing system comprising at least a first seal contributing to delimiting a space for the circulation of the fluid toward at least one internal passage of the tool, the seal being interposed between surfaces to which a relative rotational movement is imparted, as the tool rotates, the inside diameter of the first seal of the first sealing system being intended to collaborate with the tool or adapter of diameter D1, and the inside diameter of the first seal of the second sealing system being intended to collaborate with the tool or adapter of diameter D2, each sealing system also comprising a second seal likewise contributing to delimiting the space for the circulation of the fluid, the second seal of the first sealing system being intended to collaborate with the tool or adapter of diameter D1, the second seal of the first sealing system being of an inside diameter less than the inside diameter of the second seal of the second sealing system, intended to collaborate with the tool or adapter of diameter D2.

10. A range of at least a first and a second sealing system as claimed in claim 5, the two sealing systems being intended for one and the same tool holder of a cutting fluid-assisted machine tool, adapted to different diameters D1 and D2 of tool or adapter, and to different diameters D3 and D4 of adapter rings or adapter sleeves mounted on the tools or adapters, where D2 is greater than D1, and D4 greater than D3 each sealing system comprising at least a first seal contributing to delimiting a space for the circulation of the fluid toward at least one internal passage of the tool, the seal being interposed between surfaces to which a relative rotational movement is imparted, as the tool rotates, the first seal of the first sealing system being intended to press against the adapter ring or the adapter sleeve of diameter D3, and the first seal of the second sealing system being intended to press against the adapter ring or the adapter sleeve of diameter D4, each sealing system also comprising a second seal likewise contributing to delimiting the space for the circulation of the fluid, the second seal of the first sealing system being intended to collaborate with the tool or adapter of diameter D1, the second seal of the first sealing system being of an inside diameter less than the inside diameter of the second seal of the second sealing system, intended to collaborate with the tool or adapter of diameter D2.

11. A machining method, comprising: selecting a tool from a number of tools of different diameters, depending on the tool chosen, selecting a sealing system as claimed in of claim 1 or components that allow the sealing system to be modified to adapt it to the diameter of the tool or of an adapter there may be, this sealing system being chosen from at least two sealing systems adapted to tools of different diameters or the components being chosen from ranges of components adapted to different diameters of tool, fitting the tool and the adapted sealing system or the components allowing the sealing system in place to be modified to adapt it to the diameter of the tool or of the adapter there may be, proceeding to machine using the tool and the sealing system thus fitted.

12. The method as claimed in claim 11, the choice of components being restricted, aside from the choice of an adapted clamping means such as an expanding collet, to the choice of a seal-bearing ring, with the seals, that is adapted to the diameter of the tool or of the adapter bearing the tool, or to the choice of a seal-bearing ring, with the seals, and of an adapter ring, when just one of the seals presses directly against the tool and the other presses against the adapter ring.

13. The method as claimed in claim 11, the choice of components comprising that of an adapter sleeve adapted to the diameter of the tool against which the first seal presses.

Description

(1) The invention may be better understood from reading the following detailed description of some nonlimiting exemplary embodiments thereof and from studying the attached drawing in which:

(2) FIG. 1 is a simplified diagram of one variant of the invention, given by way of introduction,

(3) FIGS. 2A, 3A, 4A, 5A, 6A are end-on views of tool holders according to the invention, with adapted tools and sealing systems,

(4) FIGS. 2B, 3B, 4B, 5B, 6B are views in longitudinal section, on IIB-IIB, IIIB-IIIB, IVB-IVB, VB-VB, VIB-VIB of FIGS. 2A, 3A, 4A, 5A, 6A, respectively, and

(5) FIGS. 2C, 3C, 4C, 5C, 6C are side views of the tool holders of FIGS. 2A, 3A, 4A, 5A, 6A, respectively, and

(6) FIGS. 7 and 8 are longitudinal sections of variants of tool-holder according to the invention.

(7) The tool has been depicted schematically in the figures. The invention is not restricted to one particular tool, and this tool may be something other than a drill bit.

(8) FIG. 1 is a simplified depiction of a tool-holder 10 produced in accordance with the invention, notably in accordance with variant b) defined above, in which one of the seals presses against a surface of the tool holder and the other presses directly against the tool.

(9) The tool holder 10 takes a tool 20, depicted schematically, comprising an internal passage 21 that allows fluid to be conveyed from an inlet 22, situated for example as illustrated at the proximal (shank) end of the tool, toward one or more outlets 23 situated near a cutting edge 24 of the tool. This fluid is typically a lubricant.

(10) The tool is held by the tool holder in such a way as to allow the transmission of torque and circulation of fluid to the inlet 22 and comprises a structure which defines a circulation space 41. The latter is delimited notably by two seals 50 and 60 which press against respective surfaces 51 and 61 formed respectively on the structure and on the tool 20.

(11) The seals 50 and 60 are borne by a stator 70, depicted schematically.

(12) The surface 51 against which the seal 50 presses is of diameter D.sub.jmax and that 61 of the tool 20 on which the seal 60 presses is of diameter Do.

(13) In the schematic FIG. 1, any guiding rolling bearing or bearings there may be have not been depicted.

(14) According to the invention, Do and D.sub.jmax satisfy the relationship 0.3≦Do/Dj.sub.max for Do in the range [1; 3] in mm and 0.5≦Do/Dj.sub.max for Do in the range [3; 20] in mm, where Dj.sub.max is the internal diameter of the larger of the two seals, namely the seal referenced 50.

(15) The rubbing speed is thus reduced and a higher rotational frequency, notably one greater than or equal to 5000 rpm, can be tolerated.

(16) For preference, the tool holder is produced in such a way as to minimize D.sub.jmax while at the same time leaving a sufficient passage for the fluid to pass as far as the inlet 22 into the tool 20.

(17) It thus may prove beneficial to reduce the thickness of the wall defining the surface 51 as far as possible, depending on the nature and treatment of the material of which it is made, on the rubbing speed of the seal, on the ability to remove the heat generated by the rubbing of the seal and the mechanical stresses applied to the tool holder.

(18) FIGS. 2A to 2C on the one hand, and 3A to 3C on the other, depict two examples of a tool holder equipped with two sealing systems adapted to different respective tool diameters, according to variant b) of the invention.

(19) The tool holder comprises a body 40 provided with a conical recess 49 collaborating with a collet 30 and a collet nut 47 that tightens the collet 30 is screwed onto a screw thread 45 of the body 40.

(20) The body 40 rotates with the tool 20 guiding a rolling bearing 80 of which one of the rings, referenced 81, the radially outermost one, is fixed with respect to the stator 70.

(21) The tool holder comprises an adapter ring 101 having a thinned wall 100 against which the rubbing surface 51 of the seal 50 presses.

(22) This wall 100 extends a small distance away from the surface of the tool 20, so as to minimize the internal diameter of the seal 50.

(23) The adapter ring 101 is assembled with the collet nut 47 with the interposition of an O-ring seal 103, in order to seal the assembly.

(24) The adapter ring 101 comes into contact with the end of the collet 30, in the example being considered, and this ensures that it is completely immobilized in the tool holder.

(25) The seals 50 and 60 are borne by a seal-bearing ring 73 mounted on a body 78 of the stator 70, the ring 73 defining, with the seals 50 and 60, a chamber 74 into which the fluid from a coupling end fitting 75 is injected via orifices 130.

(26) The seal-bearing ring 73 is held on the body 78 of the stator 70 with the interposition of O-ring seals 79, in order to seal the assembly.

(27) Set screws 110 hold the rolling bearing 80 by collaborating with an outside ring 113 mounted on the body 78 of the stator 70.

(28) In the example illustrated in FIGS. 3A to 3C, the tool 20 is of a smaller diameter than in the example of FIGS. 2A to 2C, for example 16 mm instead of 20 mm.

(29) The collet 30 is different, being adapted to the new diameter of tool 20.

(30) The body 40 is unchanged, as is the collet nut 47. The adapter ring 101 is replaced by a new ring of smaller inside diameter, so as to compensate for the reduction in the diameter of the tool 20. Replacing the adapter ring 101 means that the smallest possible clearance suited to the circulation of the fluid can be maintained between the thinned wall 100 and the surface of the tool 20.

(31) In the example of FIGS. 3A to 3C, the seal-bearing ring 73 is also replaced by a ring adapted to the seals that it is to hold and has bores of different diameters.

(32) The other components of the tool holder remain unchanged. Thus, the user has available several components adapted to different diameters of tool, such as a range of seal-bearing rings 73 (with their seals) and of adapter rings 101 which are adapted to specific diameters of tool.

(33) As an alternative, as illustrated in FIGS. 7 and 8, the tool holder comprises an adapter sleeve 140 against which the seal 50 presses. The adapter sleeve 140 fits around the tool 20 and is arranged radially between the collet 30 and the tool 20. The adapter sleeve 140 extends longitudinally between the chamber 74 into which the fluid is injected by the coupling end piece 75 and the internal end of the tool holder. The adapter sleeve 140 is deformable and as the collet 30 is tightened, it can transmit the clamping force to the tool 20 in order to hold the latter in place. As the collet is loosened, the adapter sleeve 140 relaxes and frees the tool 20. The adapter sleeve 140 comprises, as illustrated in FIG. 7, at least one longitudinal groove 143, better a plurality of longitudinal grooves 143, extending over its internal surface over its entire length.

(34) The longitudinal grooves 143 open out, at one end of the adapter sleeve 140, onto the chamber 74 and, at the other end of the adapter sleeve 140, onto a space 145 communicating with the inlet 22 of the internal passage 21 of the tool 20. The longitudinal grooves 143 allow cutting fluid to circulate from the chamber 74 to the internal passage 21 of the tool in order to be fed to this tool.

(35) The internal end of the adapter sleeve 140 comprises a plug 148 adapted to the diameter of the tool 20 and bears an end seal 150. The latter is positioned between the plug 148 and the adapter sleeve 140 and makes it possible to limit the losses of cutting fluid.

(36) For preference, the end seal 150 is positioned in the adapter sleeve 140 in a groove 151 of the adapter sleeve 140. The plug 148 is inserted into the adapter sleeve 140 via the other end thereof so as to slide into the adapter sleeve 140 and become pressed against the end seal 150 in order to ensure sealed closure of the adapter sleeve 140. The plug 148 comprises a groove 151 intended to accept the end seal 150. The latter may clip into the groove 151. The latter has a cross section slightly exceeding a quadrant, notably of between 90° and 120°. Because the groove 151 is open in the opposite direction to the end via which the plug is introduced into the sleeve, a greater space 149 is created behind the seal 150 between the plug 148 and the internal surface of the sleeve 140.

(37) The end seal 150 restrains the plug 148 against the pressure of the cutting fluid in the adapter sleeve, comprised between 1 bar and 10 bar, better between 1 bar and 7 bar.

(38) The adapter sleeve 140 comprises an annular groove 153 which accepts a snap ring (circlip) 155 positioned between the collet 30 and the seal-bearing ring 73. The snap ring 155 is positioned in the annular groove 153 and immobilizes the adapter sleeve 140 at a predetermined depth of penetration.

(39) As illustrated in FIGS. 7 and 8, the adapter sleeve 140, the plug 148, the end seal 150 and the snap ring 155 are adapted to the diameter of the tool 20.

(40) The example of FIGS. 4A to 4C is similar to that of FIGS. 3A to 3C, for another diameter of tool, which is smaller still, for example 12 mm.

(41) In the example of FIGS. 5A to 5C, the two seals 50 and 60 press directly against the tool 20, making it possible to minimize the rubbing speeds of said seals.

(42) As an alternative, these seals press against an adapter to which the tool is fixed, as described later on.

(43) In the example of FIGS. 5A to 5C, in order to ensure the supply of fluid to the tool 20, the latter is provided with at least one internal passage 27 opening into the fluid circulation space 74, between the seals 50 and 60.

(44) For example, as illustrated, the tool 20 comprises several radial passages 24 communicating with the longitudinal internal passage 21, which is plugged by a plug 28 at its proximal (tool shank) end.

(45) The adapter ring 101 of the examples of FIGS. 3A and 3B is no longer needed because the seals press directly against the tool 20 and because the fluid is no longer inlet via the proximal end thereof.

(46) In the variant of FIGS. 6A to 6C, the tool 20 is borne by an adapter 120.

(47) The tool 20 has, for example, as illustrated, a shank 29 screwed into a tapping 121 of the adapter.

(48) The passage 21 of the tool communicates with a chamber 122 into which there open radial passages 127 of the adapter that perform the same function as the passages 27 described previously. The seals 50 and 60 press against the adapter 120.

(49) Of course, the invention is not restricted to the examples illustrated.

(50) It is notably possible to modify the shape of the tool holder and to create other assemblies that allow the rubbing surface of the seals to be better brought closer to the surface of the tool.

(51) Clamping means other than an expanding collet may be used, for example a shrink-fitted band, mechanical binding band, or radial clamping.

(52) The expression “comprising a” is to be understood as being synonymous with “comprising at least a” and “comprised between” includes end points.