The invention relates to a tool clamping system having a rotationally drivable tool holder for clamping a cutting tool.
Tool clamping systems of this type have been known for decades and are used in many ways when machining workpieces.
For some years, it has been required in some machining centers with rotating tools, in addition to the conventional cutting tools, to also provide for measurement-based applications or monitoring operations of the cutting or machining tool. These are generally applications in which a measurement system, usually based on electromechanical principles, is mounted on a spindle interface. On the one hand the connection and guidance is to be ensured by the machine kinematics, and on the other hand the sensing of the measured values and transfer thereof to the controller are to be made possible. Here, the energy supply of the measurement system must be provided usually by batteries or accumulators. The data transfer to a fixed evaluation station takes place as standard via infrared transmitters and receivers, and increasingly also via radio.
However, the supply by means of battery or accumulator is usually a limiting variable, since the assurance of the energy supply thus leads to additional maintenance and supervision effort. The charging station is normally located outside the machine tool, or the application in question must be removed from the machine tool in order to change the battery. In addition, the energy supply in the case of sensor systems or possibly also actively operating, actuator systems generally constitutes a limitation. As a result, and due to the extremely harsh environment in the working area of machine tools, the equipping of tools known per se with additional intelligence is not successful in principle.
In view of this, there is a need for tool monitoring systems that can operate with machine tools without external energy supply.
It is a first object of the invention to disclose a tool clamping system having a tool holder for clamping a cutting tool, which system allows an energy supply for generating electrical energy without an external voltage supply in the form of a battery or an accumulator.
It is a second object of the invention to disclose a tool clamping system allowing to monitor at least one operating parameter of the tool clamping system.
It is a third object of the invention to disclose a tool clamping system allowing to transmit a signal from a cutting tool wirelessly to an external receiver.
According to one aspect of the invention these and other objects are solved by a tool clamping system comprising:
The object of the invention is fully achieved in this way.
In accordance with the invention thermal energy provided in any case with the tool clamping system is used to generate electrical energy therefrom. The thermal energy may result from the heating of the tool in the region of the cutting edge(s) by the cutting process during use.
In accordance with an advantageous embodiment of the invention the device has at least one Seebeck element for generating a voltage from thermal energy of the tool clamping system.
With Seebeck elements temperature differences can be converted directly into electrical energy. The thermal energy released by the machining as a result of the heating of the cutting edge(s) can thus be converted directly into electrical energy.
In an advantageous development of this embodiment the at least one Seebeck element is arranged in the tool in a region between a cutting edge or a cutting edge support and a cooling channel of the tool.
The maximum temperature difference between the hot cutting edge and the cooling channel is typically provided in this region. A maximum yield in the case of the voltage generation is thus provided.
In accordance with a further embodiment of the invention the at least one Seebeck element is arranged in the region of the cutting edge support, preferably in contact with a cutting edge plate.
In this way, the thermal energy produced in particular at the cutting edge or the cutting edge plate as a result of the heating can be utilized particularly advantageously.
In an advantageous development of the invention the at least one
Seebeck element is applied resiliently against the cutting edge or the cutting edge plate.
Particularly good contact can be produced in this way.
In an additional development of the invention the at least one Seebeck element is fastened by means of thermal contact gel.
In this way, it is possible to compensate for unevennesses on the contact face between the Seebeck element and the cutting plate, such that an optimal heat transfer is enabled.
In a further advantageous embodiment of the invention a plurality of Seebeck elements are provided, which are preferably connected to one another in parallel.
In this way, the energy yield can be improved; as a result of a temperature monitoring at different locations, a process monitoring can additionally take place at the same time.
In a further advantageous embodiment of the invention the Seebeck elements connected in parallel are coupled to one another via threshold switches and are preferably short-circuited in each case via high resistances.
Provided the individual Seebeck elements deliver different output voltages, internal losses are prevented by the threshold switches. Below the threshold value, the voltage of the respective Seebeck element is short-circuited via a high resistance.
A robust voltage supply can be provided in this way.
The high resistances are in any case greater than the resistance of a consumer supplied by the circuit. Since, if the temperature gradient reverses, there is a polarity reversal in the case of a Seebeck element, the output voltage of a plurality of Seebeck elements connected in parallel, which are preferably coupled to one another via threshold switches, is fed to a rectifier, preferably a bridge rectifier, in accordance with a further advantageous embodiment of the invention.
In this way, an optimal voltage yield is ensured and internal compensating currents are avoided.
In accordance with a further embodiment of the invention the output voltage of the least one Seebeck element is fed to a device for voltage stabilization, which preferably has at least one Zener diode and/or a capacitor.
A stable voltage supply can be obtained with an embodiment of this type.
In accordance with a further embodiment of the invention the output voltage of the Seebeck elements is fed to a differential amplifier or comparator.
In this way, the Seebeck elements themselves can be used as sensor for monitoring an operating parameter, since conclusions can be made regarding the state of the overall system on the basis of the output voltage of the Seebeck elements.
If, for example in the case of a drill having two cutting edges, two Seebeck elements are received symmetrically, it is assumed in the normal state that both Seebeck elements deliver the same compensating voltage. If the differential amplifier thus generates an output voltage of approximately 0, it is to be assumed that the process is in equilibrium. This means that both cutting edges are intact and that the associated cooling channels are functioning correctly.
If, however, an output voltage that is different from 0 is generated, either one of the two cutting edges is worn or the associated cooling channel is blocked. Here, depending on the polarity of the output voltage, either the cutting edge 1 or the cooling channel 1 is affected, or the cutting edge 2 or the cooling channel 2 is affected.
In this way, low-loss monitoring can be performed during operation using particularly simple means. Such information is helpful, particularly in the implementation of minimal lubrication (ML) of tools having a plurality of cutting edges, in order to ensure uniform wetting of all cutting edges.
In accordance with a further embodiment of the invention the output voltage of the at least one Seebeck element is fed to a consumer in the form of a sensor and/or a transmitter for the wireless transfer of a useful signal to a stationary evaluation circuit.
The voltage generated by the at least one Seebeck element may preferably be used, following suitable stabilization and smoothing, for the wireless transfer of a useful signal to a stationary evaluation circuit. Here, the transfer may be performed for example via radio, via RFID, or via WIFI, etc. On the one hand the output voltages of different Seebeck elements can be used themselves as a useful signal for monitoring an operating parameter. On the other hand, one or more sensors can be operated with the aid of the generated voltage, said sensors being used for the monitoring of certain operating parameters.
Here, the operating parameter may be, for example, the temperature of the tool, the temperature of the coolant, the cutting force, or acceleration or cutting integrity of the tool. If a separate sensor is used, this is preferably received in the tool and is supplied with voltage by the at least one Seebeck element. The output signal is preferably transferred wirelessly to a stationary evaluation circuit by means of a transmitting device.
Since the space in the tool itself is extremely limited, the tool in accordance with a further embodiment of the invention is to be coupled to the tool holder via an electric interface for the transfer of an electric signal.
In this way, merely the at least one Seebeck element for example may be arranged in the tool, whereas all further elements are provided in the tool holder. For example, a transmitting device for the wireless transfer of a signal may thus be provided.
If a sensor is to be provided with voltage by the at least one Seebeck element, it is expedient to integrate this Seebeck element in the tool in order to enable the most sensitive possible parameter detection.
Depending on dimensions and installation conditions, however, it may be necessary to also provide the sensor in the tool holder.
It is also conceivable to accommodate the Seebeck element also in a pocket in the cutting edge (indexable insert) itself, said pocket being formed by sintering or by means of other suitable methods.
In this case the cutting edge and the Seebeck element form a unit, and only the thermal contact with the cooling channels or the other available temperature pole is also provided in the cutting edge support.
In accordance with a further embodiment of the invention the output signal of the at least one piezo element is fed back to a controller of the drive machine as control variable.
The fed-back signal may be used advantageously for process adaptation.
It goes without saying that the features mentioned above and the features yet to be explained hereinafter can be used not only in the specified combinations, but also in other combinations or independently, without departing from the scope of the invention.
Further features and advantages of the invention will emerge from the following description of preferred exemplary embodiments with reference to the drawing, in which:
An exemplary embodiment of a tool clamping system according to the invention is illustrated in
The tool clamping system 10 has a tool holder 12, on which a tool 14 is received in the form of the short-hole drill. As can be seen in particular also from the view according to
As is usual in the case of short-hole drills, the two cutting edges 16, 20 are received slightly asymmetrically offset radially with respect to the longitudinal center axis. The cutting edges 16, 20 or indexable inserts are fastened to the associated cutting edge supports 17 in the conventional manner using fastening screws 18. Each cutting edge support 17 is assigned a cooling channel, wherein the two cooling channels are indicated in
A Seebeck element 26, 28 is arranged between each cutting support 17 and the assigned cooling channel 22, 24 (
The Seebeck elements 26, 28 are thus each located in the region of the maximum temperature difference, such that a maximum energy yield is achieved.
A position of installation for the Seebeck element is sketched by way of example in
In
It is also conceivable to accommodate the Seebeck element 26 also in a pocket in the cutting edge (indexable insert) itself, said pocket being formed by sintering or by means of other suitable methods, wherein the cutting edge and Seebeck element 26 then form a unit and only the thermal contact with the cooling channels or the other available temperature pole is also provided in the indexable insert mount 34.
In the case of the tool clamping system designated on the whole by 10a, corresponding reference numerals are used incidentally for corresponding parts. In the outer region of the tool 14 a Seebeck element 26 is indicated schematically in the region of a cutting edge. The tool 14 is clamped via its shaft 36 in an associated recess of the tool holder 12, for example by shrink clamping or in the usual manner by mechanical clamping. An electric interface designated on the whole by 40 is provided at the lower end of the tool shaft 36, via which interface the signal transferred via a line 38 from the Seebeck element 26 is transferred via a contact face 41 with the aid of a contact pin 42 applied thereto to the tool holder 12. The contact face 41 on the tool shaft 36 is electrically insulated with respect to the rest of the tool shaft 36 by means of suitable ceramic faces. The contact pin 42 is likewise received in the tool holder 12 in an electrically insulated manner and is preferably applied resiliently against the contact face 41 by means of a spring element 44 in order to ensure the most secure and reliable contact possible. The signal received by the contact pin 22 is transferred via a line, which is indicated schematically by 46, to a transmitting unit in the tool holder 12, in which the signal is processed and transferred by radio to an associated stationary evaluation circuit 50. It goes without saying that the transmitting unit 48 is provided with a suitable antenna such that the signal can be received and evaluated by a stationary evaluation circuit 50 via an associated antenna 51.
In
The two output signals of the first Seebeck element 26 and of the second Seebeck element 28 are provided at the two inputs of the differential amplifier 73 and 74.
In addition, the two Seebeck elements 26, 28 are loaded by a high resistance R, which allows a voltage breakdown when the respective threshold switches 62, 64 are not interconnected. This resistance R has a sufficiently high impedance, i.e. is in any case much greater than the resistance of a load by which the useful voltage Ug is loaded.
If a voltage Ua of approximately 0 is produced at the output of the differential amplifier, both Seebeck elements 26, 28 thus deliver the same output voltage.
With symmetrical installation and otherwise identical conditions, this shows that the paired cutting edges 16, 20 must be intact and that the associated cooling channels 22, 24 function consistently.
If, however, an output voltage Ua that is different from 0 is produced, this is due to the fact that either one of the two cutting edges 16, 20 is worn unevenly or that one of the two cooling channels 22, 24 is blocked.
Depending on whether the output voltage Ua is greater than 0 or less than 0, either one cutting edge 16 or the other cutting edge 20 or the associated cooling channel 22 or 24 respectively is affected.
An associated evaluation and transmitting unit 23 is additionally also illustrated in
By way of example, a further sensor is also indicated by numeral 78, which sensor is operated with the voltage Ug and of which the output signal 79 can be coupled to an associated input 81 of the evaluation and transmitting unit 80. Other operating parameters can be monitored using a sensor 78 of this type.
Number | Date | Country | Kind |
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10 2013 105 830.2 | Jun 2013 | DE | national |
This application is a continuation of international patent application PCT/EP2014/058061, filed on Apr. 22, 2014 designating the U.S., which international patent application has been published in German language and claims priority from German patent application 10 2013 105 830.2, filed on Jun. 6, 2013. The entire contents of these applications are incorporated herein by reference.
Number | Date | Country | |
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Parent | PCT/EP2014/058061 | Apr 2014 | US |
Child | 14959340 | US |