Abstract
A tool received in a tool holding fixture of a tool holder includes a tool shank defining a recess and a force sensor arranged in the recess. During operation of the tool, the force sensor measures a tool force exerted by the tool shank onto the tool holder. A method for measuring a tool force by using the tool includes the steps of: arranging the force sensor between the tool shank and the tool holding fixture; clamping the force sensor by means of a clamping device of the tool holding fixture; operating the tool; and using the force sensor to measure the tool force exerted by the tool shank onto the tool holder.
Claims
1. A tool comprising: a tool holder that includes a tool holding fixture that is configured to receive a tool shank; a tool shank received by the tool holding fixture; a recess disposed at the tool shank; a force sensor arranged in the recess at the tool shank; and wherein the force sensor is configured to measure a tool force exerted by the tool shank onto the tool holder during operation of the tool.
2. The tool according to claim 1, wherein the recess is manufactured in the tool shank.
3. The tool according to claim 1, wherein the recess is manufactured in the tool holder.
4. The tool according to claim 1, wherein the tool comprises an intermediate piece which is received in the tool holding fixture; in that the recess is manufactured in the intermediate piece; and in that the force sensor measures a tool force exerted by the tool shank onto the intermediate piece during operation of the tool.
5. The tool according to claim 1, wherein the force sensor is not completely accommodated within the recess.
6. The tool according to claim 1, wherein the tool is a cutting tool.
7. The tool according to claim 1, wherein the tool holding fixture comprises a clamping device for clamping a tool shank; and wherein the clamping device comprises a wedge.
8. The tool according to claim 1, wherein the force sensor is a piezoelectric force sensor.
9. The tool according to claim 1, wherein the force sensor is pretensioned by a pretensioning force or in that the force sensor is pretensioned by an adjustable pretensioning force.
10. The tool according to claim 9, wherein the pretensioning force is equal to a clamping force exerted onto the force sensor by a clamping device of the tool holding fixture.
11. The tool according to claim 1, wherein there is a form fit between the force sensor and the tool shank or between the force sensor and the tool holding fixture.
12. The tool according to claim 11, wherein said form fit is reversible.
13. The tool according to claim 1, wherein the force sensor is configured to transmit signals measured by the force sensor to an evaluation device.
14. The tool according to claim 1, wherein the force sensor is configured to enable the monitoring of signals measured by the force sensor in real time.
15. A method for measuring a tool force by using a tool according to claim 1, said method comprising the steps of: arranging a force sensor between a tool shank of the tool and a tool holding fixture of a tool holder; and clamping the force sensor by means of a clamping device of the tool holding fixture.
16. The tool according to claim 1, wherein the force sensor is completely accommodated within the recess.
17. The tool according to claim 1, wherein the force sensor is a multi-axis force sensor.
18. The tool according to claim 1, wherein the force sensor is pretensioned by an adjustable pretensioning force.
19. The tool according to claim 1, wherein there is a force fit between the force sensor and the tool shank or between the force sensor and the tool holding fixture.
20. The tool according to claim 11, wherein said form fit is reproducible.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0063] Exemplary embodiments are explained in the drawings in which:
[0064] FIG. 1 shows a cross-section taken in the direction of the arrows A-A in FIG. 2 of the first embodiment of the tool according to the invention having a recess for the pressure sensor located in the tool shank wherein solely a contact surface of the pressure sensor abuts on the tool holder,
[0065] FIG. 2 shows a top view of the first embodiment of the tool of the invention according to FIG. 1,
[0066] FIG. 3 shows a cross-section taken in the direction of the arrows B-B in FIG. 4 of a second embodiment of the tool according to the invention having a recess for the pressure sensor located in an intermediate piece wherein solely a contact surface of the pressure sensor abuts on the tool shank,
[0067] FIG. 4 shows a top view of the second embodiment of the tool of the invention according to FIG. 3,
[0068] FIG. 5 shows a cross-section of a third embodiment of the tool according to the invention having a recess for the pressure sensor located in the tool holder wherein solely a contact surface of the pressure sensor abuts on the tool shank,
[0069] FIG. 6 shows a cross-section of a fourth embodiment of the tool according to the invention having a recess for the pressure sensor located in the tool holder wherein solely a contact surface of the pressure sensor abuts on an intermediate piece,
[0070] FIG. 7 shows a cross-section of a fifth embodiment of the tool according to the invention having a recess for the pressure sensor located in the tool shank wherein a common contact surface formed by the pressure sensor and the tool shank abuts on the tool holder,
[0071] FIG. 8 shows a cross-section of a sixth embodiment of the tool according to the invention having a recess for the pressure sensor located in an intermediate piece wherein a common contact surface formed by the pressure sensor and the intermediate piece abuts on the tool shank,
[0072] FIG. 9 shows a cross-section of a seventh embodiment of the tool according to the invention having a recess for the pressure sensor located in the tool holder wherein a common contact surface formed by the pressure sensor and the tool holder abuts on the tool shank, and
[0073] FIG. 10 shows a cross-section of an eighth embodiment of the tool according to the invention having a recess for the pressure sensor located in the tool holder wherein a common contact surface formed by the pressure sensor and the tool holder abuts on an intermediate piece.
[0074] Throughout the figures, the same parts are principally designated by the same reference numbers.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0075] FIGS. 1 to 10 show a plurality of embodiments of a tool 10 comprising a force sensor 30.
[0076] Preferably, the force sensor 30 is a piezoelectric force sensor. A piezoelectric force sensor comprises a piezoelectric element, an electrode, an electrical conductor and a contact surface. Force sensor 30 measures a tool force acting onto the contact surface. The contact surface is made of mechanically resistant material and is cylindrical or hollow cylindrical in shape. The piezoelectric element is cylindrical or hollow cylindrical in shape and consists of piezoelectric material such as quartz (SiO.sub.2 monocrystal), calcium gallo-germanate (Ca.sub.3Ga.sub.2Ge.sub.4O.sub.14 or CGG), langasite (La.sub.3Ga.sub.5SiO.sub.14 or LGS), tourmaline, gallium orthophosphate, piezo ceramics, etc. The piezoelectric element is oriented to be highly sensitive for the tool force to be absorbed. Preferably, the piezoelectric element is oriented in a way that electrical polarization charges are generated on those surfaces onto which the tool force acts. The electrode is also cylindrical or hollow cylindrical in shape and is preferably arranged on the surface of the piezoelectric element onto which the tool force acts. The electrode picks up the electrical polarization charges as signals. The signals are proportional to the amount of the tool force. Preferably, the electrode is electrically insulated from the tool or tool holder or contact surface. Preferably, the electrode is an electrically insulating film coated with an electrically conductive material on one or both sides thereof. The electrical conductor is connected to the electrode and transmits the signals from the electrode to a plug connection for a signal cable, which signal cable in turn conducts the signals to an evaluation device. Alternatively, the electrical conductor connected to the electrode conducts the signals to a radio device, which radio device in turn transmits the signals to an evaluation device via a radio link.
[0077] Tool 10 comprises a tool holder 20 and a tool shank 11. Tool holder 20 comprises a tool holding fixture 21. Tool holding fixture 21 is adapted to accommodate the tool shank 11. For this purpose, the tool holding fixture 21 has an indentation 22 and a wedge 23 which may be adjusted by means of a clamping screw 24 to exert a clamping force onto the tool shank 11 when the tool shank 11 is accommodated in the indentation 22. The tool holder 20 may be secured to a tool slide (not shown) by means of securing screws 25.
[0078] The force sensor 30 is arranged in a recess 12 at the tool shank 11. Recess 12 is manufactured in a mechanically resistant material. The material is either the tool shank 11 (FIGS. 1, 2, 7) or a tool holder 20 (FIGS. 5, 6, 9, 10) or an intermediate piece 26 (FIGS. 3, 4, 8).
[0079] The recess 12 is cylindrical or hollow-cylindrical in shape. The force sensor 30 may comprise a cylindrical or hollow cylindrical housing that is made of mechanically stable material, which housing accommodates the piezoelectric element, the electrode and the electrical conductor. Preferably, the housing is sealed by the contact surface via a material bond. The force sensor 30 is arranged in the recess 12 with the housing. The plug connection is arranged at the housing so that the signal cable is connected to the electrical conductor by the plug connection in the recess 12. Alternatively, the radio device is arranged in the housing so that the electrical conductor is connected to the radio device in the housing. However, the force sensor 30 may have no housing in which case the recess 12 accommodates the piezoelectric element, the electrode and the electrical conductor. In this case, the plug connection is arranged in the material surrounding the recess 12 so that the signal cable is connected to the electrical conductor by the plug connection in the material surrounding the recess 12. Alternatively, the radio device is arranged in the material surrounding the recess 12 so that the electrical conductor is connected to the radio device. Preferably, the recess 12 is then sealed by the contact surface via a material bond.
[0080] In the first embodiment of the tool 10 as shown in FIGS. 1 and 2, the force sensor 30 is not completely accommodated within the recess 12 in the tool shank 11. In the context of the present invention, not completely accommodated within the recess 12 in the tool shank 11 means that in some areas the contact surface of the force sensor 30 projects beyond the tool shank 11. A contact surface of the tool holder 20 and the contact surface of the force sensor 30 abut against one another in a contact plane 31, which is schematically indicated by the dashed line in FIG. 1 and FIG. 2. In the contact plane 31, a mechanical contact between the tool shank 11 and the contact surface of the tool holder 20 is made solely by the contact surface of the force sensor 30. In this first embodiment of the tool 10 shown in FIG. 1 and FIG. 2 for example, the force sensor 30 measures 100% of the tool force exerted onto the contact surface of the force sensor 30 by the contact surface of the tool holder 11. A force component of the tool force measured is 100%. This has the advantage that the force is measured with maximum sensitivity since no force component acts in a force shunt outside of the force sensor 30. Preferably, the tool shank 11 has a square cross-section. It can be seen in the top view according to FIG. 2 that the tool 10 may also comprise two force sensors 30.
[0081] In the second embodiment of the tool 10 as shown in FIGS. 3 and 4 the force sensor 30 is not completely accommodated within the recess 12 in the intermediate piece 26.
[0082] As compared to the first embodiment of the tool 10, the second embodiment of the tool 10 comprises a tool holding fixture 21 having a wider indentation 22. This wider indentation 22 not only provides space for the tool shank 11 but also for the intermediate piece 26. In this case, the force sensor 30 is not completely accommodated within the recess 12 in the intermediate piece 26. In the context of the present invention, not completely accommodated within the recess 12 in the intermediate piece 26 is intended to mean that some portion of the force sensor 30 protrudes beyond the intermediate piece 26. A contact surface of the tool shank 11 and the contact surface of the force sensor 30 abut against one another in a contact plane 31. In the contact plane 31, a mechanical contact between the intermediate piece 26 and a contact surface of the tool shank 11 is made solely over the contact surface of the force sensor 30. In this second embodiment of the tool 10, the force sensor 30 measures 100% of the tool force exerted by the contact surface of the tool shank 11 onto the contact surface of the force sensor 30. A force component of the tool force measured is 100%. This has the advantage that the force measurement is performed with maximum sensitivity since no force component acts in a force shunt outside of the force sensor 30. In the top view according to FIG. 4 the wider indentation 22 is partially hidden by the intermediate piece 26. However, it can be clearly seen that two force sensors 30 arranged in the intermediate piece 26 are in operative connection with the tool shank 11.
[0083] In the third embodiment of the tool 10 as shown in FIG. 5, the force sensor 30 is not completely accommodated within the recess 12 in the tool holder 20. In the context of the present invention, not completely accommodated within the recess 12 in the tool holder 20 means that some portion of the force sensor 30 protrudes beyond the tool holder 20. A contact surface of the tool shank 11 and the contact surface of the force sensor 30 abut against one another in a contact plane 31. In the contact plane 31, a mechanical contact between the tool holder 20 and the contact surface of the tool shank 11 is made solely by the contact surface of the force sensor 30. In this third embodiment of the tool 10, the force sensor 30 measures 100% of the tool force exerted by the contact surface of the tool shank 11 onto the contact surface of the force sensor 30. A force component of the tool force measured is 100%. This has the advantage that the force measurement is carried out with maximum sensitivity since no force component acts in a force shunt outside of the force sensor 30.
[0084] In the fourth embodiment of the tool 10 as shown in FIG. 6, the force sensor 30 is not completely accommodated within the recess 12 in the tool holder 20. In the context of the present invention, not completely accommodated within the recess 12 in the tool holder 20 is intended to mean that some portion of the force sensor 30 protrudes beyond the tool holder 20. A contact surface of an intermediate piece 26 and the contact surface of the force sensor 30 abut against one another in a contact plane 31. In the contact plane 31, a mechanical contact between the tool holder 20 and the contact surface of the intermediate piece 26 is made solely by the contact surface of the force sensor 30. In this fourth embodiment of the tool 20, the force sensor 30 measures 100% of the tool force exerted by the contact surface of the intermediate piece 26 onto the contact surface of the force sensor 30. A force component of the tool force measured is 100%. This has the advantage that the force measurement is carried out with maximum sensitivity since no force component acts in a force shunt outside of the force sensor 30.
[0085] In the fifth embodiment of the tool 10 according to FIG. 7, the force sensor 30 is completely accommodated within the recess 12 in the tool shank 11. In the context of the present invention, completely accommodated within the recess 12 in the tool shank 11 is intended to mean that the force sensor 30 does not protrude beyond the tool shank 11. The tool shank 11 and the force sensor 30 completely accommodated therein form a common contact surface. A first portion of the common contact surface is a contact surface of the tool shank 11 and a second portion of the common contact surface is the contact surface of the force sensor 30. The common contact surface is ground flat, for example. The common contact surface formed by the tool shank 11 and the force sensor 30 and a contact surface of the tool holder 20 abut against one another in a contact plane 31. In the contact plane 31, a mechanical contact between the tool shank 11 and the contact surface of the tool holder 20 is made by the common contact surface formed by the tool shank 11 and the force sensor 30. In the fifth embodiment of the tool holder 20 shown in FIG. 7 for example, the force sensor 30 measures less than 100% of the tool force acting on the common contact surface because there is a force shunt outside of the force sensor 30 acting from the contact surface of the tool shank 11 onto the contact surface of the tool holder 20. A force component of the tool force measured is less than 100%. This has the advantage that the force measurement is performed with high mechanical stability and high natural frequency because mechanical bending of the tool holder 20 is not possible since, advantageously, the common contact surface formed by the tool shank 11 and the force sensor 30 substantially has the same dimensions as the contact surface of the tool holder 20.
[0086] In the sixth embodiment of the tool 10 according to FIG. 8, the force sensor 30 is completely accommodated within the recess 12 in the intermediate piece 26. In the context of the present invention, completely accommodated within the recess 12 in the intermediate piece 26 means that the force sensor 30 does not protrude beyond the intermediate piece 26. The intermediate piece 26 and the force sensor 30 accommodated therein form a common contact surface. A first portion of the common contact surface is a contact surface of the intermediate piece 26 and a second portion of the common contact surface is the contact surface of the force sensor 30. The contact surface is ground flat, for example. The common contact surface formed by the intermediate piece 26 and the force sensor 30 and the contact surface of the tool shank 11 abut against one another in a contact plane 31. In the contact plane 31, a mechanical contact between the intermediate piece 26 and the contact surface of the tool shank 11 is made over the common contact surface formed by the intermediate piece 26 and the force sensor 30. In the sixth embodiment of the tool holder 20 shown in FIG. 8 for example, the force sensor 30 measures less than 100% of the tool force acting from the contact surface of the tool shank 11 onto the common contact surface because there is a force shunt outside the force sensor 30 acting from the contact surface of the tool shank 11 onto the contact surface of the intermediate piece 26. A force component of the tool force measured is less than 100%. This has the advantage that the force measurement is carried out with high mechanical stability and high natural frequency because mechanical bending of the tool shank 11 is not possible since, advantageously, the common contact surface formed by the intermediate piece 26 and the force sensor 30 has substantially the same dimensions as the contact surface of the tool shank 11.
[0087] In the seventh embodiment of the tool 10 according to FIG. 9, the force sensor 30 is completely accommodated within the recess 12 in the tool holder 20. In the context of the present invention, completely accommodated within the recess 12 in the tool holder 20 means that the force sensor 30 does not protrude beyond the tool holder 20. The tool holder 20 and the force sensor 30 completely accommodated therein form a common contact surface. A first portion of the common contact surface is a contact surface of the tool holder 20 and a second portion of the common contact surface is the contact surface of the force sensor 30. The common contact surface is ground flat, for example. The common contact surface formed by the tool holder 20 and the force sensor 30 and a contact surface of the tool shank 11 abut against one another in a contact plane 31. In the contact plane 31, a mechanical contact between the tool holder 20 and the contact surface of the tool shank 11 is made over the common contact surface formed by the tool holder 20 and the force sensor 30. In the seventh embodiment of the tool holder 20 shown in FIG. 9 for example, the force sensor 30 measures less than 100% of the tool force that acts onto the common contact surface because there is a force shunt outside of the force sensor 30 acting from the contact surface of the tool shank 11 onto the contact surface of the tool holder 20. A force component of the tool force measured is less than 100%. This has the advantage that the force measurement is carried out with high mechanical stability and high natural frequency because mechanical bending of the tool shank 11 is not possible since, advantageously, the common contact surface formed by the tool holder 20 and the force sensor 30 substantially has the same dimensions as the contact surface of the tool shank 11.
[0088] In the eighth embodiment of the tool 10 according to FIG. 10, the force sensor 30 is completely accommodated within the recess 12 in the tool holder 20. In the context of the present invention, completely accommodated within the recess 12 in the tool holder 20 means that the force sensor 30 does not protrude beyond the tool holder 20. The tool holder 20 and the force sensor 30 completely accommodated therein form a common contact surface. A first portion of the common contact surface is a contact surface of the tool holder 20 and a second portion of the common contact surface is the contact surface of the force sensor 30. The common contact surface is ground flat, for example. The common contact surface formed by the tool holder 20 and the force sensor 30 and a contact surface of an intermediate piece 26 abut against one another in a contact plane 31. In the contact plane 31, a mechanical contact between the tool holder 20 and the contact surface of the intermediate piece 26 is made over the common contact surface formed by the tool holder 20 and the force sensor 30. In the eighth embodiment of the tool holder 20 shown in FIG. 10 for example, the force sensor 30 measures less than 100% of the tool force that acts onto the common contact surface because there is a force shunt outside of the force sensor 30 acting from the contact surface of the intermediate piece 26 onto the contact surface of the tool holder 20. A force component of the tool force measured is less than 100%. This has the advantage that the force measurement is performed with high mechanical stability and high natural frequency because mechanical bending of the intermediate piece 26 is not possible since, advantageously, the common contact surface formed by the tool holder 20 and the force sensor 30 substantially has the same dimensions as the contact surface of the intermediate piece 26.
LIST OF REFERENCE NUMERALS
[0089] 10 tool [0090] 11 tool shank [0091] 12 recess [0092] 20 tool holder [0093] 21 tool holding fixture [0094] 22 indentation [0095] 23 wedge [0096] 24 clamping screw [0097] 25 securing screws [0098] 26 intermediate piece [0099] 30 force sensor [0100] 31 contact plane
