Patent Publication Number: US-2021170559-A1

Title: Setting tool

Description:
The present invention relates to a setting tool for driving fastening elements into a substrate. 
     Such setting tools usually have a holder for a fastening element, from which a fastening element held therein is transferred into the substrate along a setting axis. For this, a drive-in element is driven toward the fastening element along the setting axis by a drive. 
     U.S. Pat. No. 6,830,173 B2 discloses a setting tool with a drive for a drive-in element. The drive has an electrical capacitor and a coil. For driving the drive-in element, the capacitor is discharged via the coil, whereby a Lorentz force acts on the drive-in element, so that the drive-in element is moved toward a nail. 
     The object of the present invention is to provide a setting tool of the aforementioned type with which high efficiency and/or good setting quality are ensured. 
     The object is achieved by a setting tool for driving fastening elements into a substrate, comprising a holder, which is provided for holding a fastening element, a drive-in element, which is provided for transferring a fastening element held in the holder into the substrate along a setting axis, and a drive, which is provided for driving the drive-in element toward the fastening element along the setting axis, wherein the drive comprises an electrical capacitor, a squirrel-cage rotor arranged on the drive-in element and an excitation coil, which during rapid discharge of the capacitor is flowed through by current and generates a magnetic field that accelerates the drive-in element toward the fastening element, and wherein the setting tool has a means for detecting a temperature of the excitation coil and a control unit which is suitable for controlling an operating sequence of the setting tool in dependence on the detected temperature of the excitation coil. The setting tool can in this case preferably be used in a hand-held manner. Alternatively, the setting tool can be used in a stationary or semi-stationary manner. 
     In the context of the invention, a capacitor should be understood as meaning an electrical component that stores electrical charge and the associated energy in an electrical field. In particular, the capacitor has two electrically conducting electrodes, between which the electrical field builds up when the electrodes are electrically charged differently. In the context of the invention, a fastening element should be understood as meaning for example a nail, a pin, a clamp, a clip, a stud, in particular a threaded bolt, or the like. 
     An advantageous embodiment is characterized in that the means for detecting a temperature of the excitation coil comprises a temperature sensor which is arranged on the excitation coil and/or a frame holding the excitation coil. 
     An advantageous embodiment is characterized in that the means for detecting a temperature of the excitation coil comprises a means for detecting an ohmic resistance of the excitation coil. 
     An advantageous embodiment is characterized in that the means for detecting a temperature of the excitation coil comprises a means for detecting a time, a means for detecting a process which causes the temperature of the excitation coil to rise, a data memory, in which a standard cooling rate of the excitation coil and the temperature rise caused by the process are stored, and a program for calculating the temperature of the excitation coil, starting from a starting temperature at a starting time, on the basis of the recorded process and the stored temperature rise as well as the recorded time and the stored standard cooling rate. The means for detecting a temperature of the excitation coil preferably comprises an ambient temperature sensor, the starting temperature being a temperature of a surrounding area of the setting tool detected by the ambient temperature sensor. The setting tool also preferably has a means for cooling the excitation coil, an increased cooling rate of the excitation coil being stored in the data memory, and the program for calculating the temperature of the excitation coil using the standard cooling rate in periods in which the means for cooling the excitation coil is not in operation and using the increased cooling rate in periods in which the means for cooling the excitation coil is in operation. 
     An advantageous embodiment is characterized in that the setting tool has a means for cooling the excitation coil, and the control unit being intended to control the means for cooling the excitation coil in dependence on the detected temperature of the excitation coil. As a result, more driving-in operations are possible before the excitation coil and/or other components of the setting tool overheat In addition, an increase in ohmic resistance of the excitation coil associated with an increase in temperature and an associated drop in efficiency of the drive are reduced or avoided. The means for cooling the excitation coil preferably comprises a rotor, the control unit being intended to control a running time and/or a rotational speed of the rotor in dependence on the detected temperature of the excitation coil. The control unit is particularly preferably intended to increase the running time and/or the speed of the rotor, the higher the temperature of the excitation coil detected. 
     An advantageous embodiment is characterized in that the capacitor is charged with a charging voltage at the beginning of the rapid discharge, the control unit being suitable for controlling the charging voltage in dependence on the detected temperature of the excitation coil. The charging voltage is preferably all the greater the higher the detected temperature of the excitation coil. This makes it possible to compensate for an increasing ohmic resistance of the excitation coil with increasing temperature. 
     An advantageous embodiment is characterized in that the control unit is intended to enable a driving-in process in which the drive-in element is accelerated onto the fastening element if the detected temperature of the excitation coil is less than a predetermined maximum temperature and to inhibit the driving-in process if the detected temperature of the excitation coil is greater than the specified maximum temperature. This prevents damage to the excitation coil and/or the soft magnetic frame and/or other components of the drive or the setting tool due to overheating. 
     An advantageous embodiment is characterized in that the capacitor is charged with a charging voltage at the beginning of the rapid discharge, the control unit being suitable for controlling the charging voltage. The capacitor is preferably charged in a charging process before the rapid discharge, the charging process being controlled by the control unit. 
    
    
     
       The invention is represented in a number of exemplary embodiments in the drawings, 
       in which: 
         FIG. 1  shows a longitudinal section through a setting tool, 
         FIG. 2  shows a circuit diagram of a setting tool and 
         FIG. 3  shows a longitudinal section through an excitation coil. 
     
    
    
       FIG. 1  illustrates a hand-held setting tool  10  for driving fastening elements into a substrate that is not shown. The setting tool  10  has a holder  20  formed as a stud guide, in which a fastening element  30 , which is formed as a nail, is held in order to be driven into the substrate along a setting axis A (to the left in  FIG. 1 ). For the purpose of supplying fastening elements to the holder, the setting tool  10  comprises a magazine  40  in which the fastening elements are held in store individually or in the form of a fastening element strip  50  and are transported to the holder  20  one by one. To this end, the magazine  40  has a spring-loaded feed element, not specifically denoted. The setting tool  10  has a drive-in element  60 , which comprises a piston plate  70  and a piston rod  80 . The drive-in element  60  is provided for transferring the fastening element  30  out of the holder  20  along the setting axis A into the substrate. In the process, the drive-in element  60  is guided with its piston plate  70  in a guide cylinder  95  along the setting axis A. 
     The drive-in element  60  is, for its part, driven by a drive, which comprises a squirrel-cage rotor  90  arranged on the piston plate  70 , an excitation coil  100 , a soft-magnetic frame  105 , a switching circuit  200  and a capacitor  300  with an internal resistance of 5 mOhms. The squirrel-cage rotor  90  consists of a preferably ring-like, particularly preferably circular ring-like, element with a low electrical resistance, for example made of copper, and is fastened, for example soldered, welded, adhesively bonded, clamped or connected in a form-fitting manner, to the piston plate  70  on the side of the piston plate  70  that faces away from the holder  20 . In exemplary embodiments which are not shown, the piston plate itself is formed as a squirrel-cage rotor. The switching circuit  200  is provided for causing rapid electrical discharging of the previously charged capacitor  300  and conducting the thereby flowing discharge current through the excitation coil  100 , which is embedded in the frame  105 . The frame preferably has a saturation flux density of at least 1.0 T and/or an effective specific electrical conductivity of at most 10 6  S/m, so that a magnetic field generated by the excitation coil  100  is intensified by the frame  105  and eddy currents in the frame  105  are suppressed. 
     In a ready-to-set position of the drive-in element  60  ( FIG. 1 ), the drive-in element  60  enters with the piston plate  70  a ring-like recess, not specifically denoted, of the frame  105  such that the squirrel-cage rotor  90  is arranged at a small distance from the excitation coil  100 . As a result, an excitation magnetic field, which is generated by a change in an electrical excitation current flowing through the excitation coil, passes through the squirrel-cage rotor  90  and, for its part, induces in the squirrel-cage rotor  90  a secondary electrical current, which circulates in a ring-like manner. This secondary current, which builds up and therefore changes, in turn generates a secondary magnetic field, which opposes the excitation magnetic field, as a result of which the squirrel-cage rotor  90  is subject to a Lorentz force, which is repelled by the excitation coil  100  and drives the drive-in element  60  toward the holder  20  and also the fastening element  30  held therein. 
     The setting tool  10  further comprises a housing  110 , in which the drive is held, a handle  120  with an operating element  130  formed as a trigger, an electrical energy store  140  formed as a rechargeable battery, a control unit  150 , a tripping switch  160 , a contact-pressure switch  170 , a means for detecting a temperature of the excitation coil  100 , formed as a temperature sensor  180  arranged on the frame  105 , and electrical connecting lines  141 ,  161 ,  171 ,  181 ,  201 ,  301 , which connect the control unit  150  to the electrical energy store  140 , to the tripping switch  160 , to the contact-pressure switch  170 , to the temperature sensor  180 , to the switching circuit  200  and, respectively, to the capacitor  300 . In exemplary embodiments which are not shown, the setting tool  10  is supplied with electrical energy by means of a power cable instead of the electrical energy store  140  or in addition to the electrical energy store  140 . The control unit comprises electronic components, preferably interconnected on a printed circuit board to form one or more electrical control circuits, in particular one or more microprocessors. 
     When the setting tool  10  is pressed against a substrate that is not shown (on the left in  FIG. 1 ), a contact-pressure element, not specifically denoted, operates the contact-pressure switch  170 , which as a result transmits a contact-pressure signal to the control unit  150  by means of the connecting line  171 . This triggers the control unit  150  to initiate a capacitor charging process, in which electrical energy is conducted from the electrical energy store  140  to the control unit  150  by means of the connecting line  141  and from the control unit  150  to the capacitor  300  by means of the connecting lines  301 , in order to charge the capacitor  300 . To this end, the control unit  150  comprises a switching converter, not specifically denoted, which converts the electric current from the electrical energy store  140  into a suitable charge current for the capacitor  300 . When the capacitor  300  is charged and the drive-in element  60  is in its ready-to-set position illustrated in  FIG. 1 , the setting tool  10  is in a ready-to-set state. Since charging of the capacitor  300  is only implemented by the setting tool  10  pressing against the substrate, to increase the safety of people in the area a setting process is only made possible when the setting tool  10  is pressed against the substrate. In exemplary embodiments which are not shown, the control unit already initiates the capacitor charging process when the setting tool is switched on or when the setting tool is lifted off the substrate or when a preceding driving-in process is completed. 
     When the operating element  130  is operated, for example by being pulled using the index finger of the hand which is holding the handle  120 , with the setting tool  10  in the ready-to-set state, the operating element  130  operates the tripping switch  160 , which as a result transmits a tripping signal to the control unit  150  by means of the connecting line  161 . This triggers the control unit  150  to initiate a capacitor discharging process, in which electrical energy stored in the capacitor  300  is conducted from the capacitor  300  to the excitation coil  100  by means of the switching circuit  200  by way of the capacitor  300  being discharged. 
     To this end, the switching circuit  200  schematically illustrated in  FIG. 1  comprises two discharge lines  210 ,  220 , which connect the capacitor  300  to the excitation coil  200  and at least one discharge line  210  of these is interrupted by a normally open discharge switch  230 . The switching circuit  200  forms an electrical oscillating circuit with the excitation coil  100  and the capacitor  300 . Oscillation of this oscillating circuit back and forth and/or negative charging of the capacitor  300  may potentially have an adverse effect on the efficiency of the drive, but can be suppressed with the aid of a free-wheeling diode  240 . The discharge lines  210 ,  220  are electrically connected, for example by soldering, welding, screwing, clamping or form-fitting connection, to in each case one electrode  310 ,  320  of the capacitor  300  by means of electrical contacts  370 ,  380  of the capacitor  300  which are arranged on an end side  360  of the capacitor  300  that faces the holder. The discharge switch  230  is preferably suitable for switching a discharge current with a high current intensity and is formed for example as a thyristor. In addition, the discharge lines  210 ,  220  are at a small distance from one another, so that a parasitic magnetic field induced by them is as low as possible. For example, the discharge lines  210 ,  220  are combined to form a busbar and are held together by a suitable means, for example a retaining device or a clamp. In exemplary embodiments which are not shown, the free-wheeling diode is connected electrically in parallel with the discharge switch. In further exemplary embodiments which are not shown, there is no free-wheeling diode provided in the circuit. 
     For the purpose of initiating the capacitor discharging process, the control unit  150  closes the discharge switch  230  by means of the connecting line  201 , as a result of which a discharge current of the capacitor  300  with a high current intensity flows through the excitation coil  100 . The rapidly rising discharge current induces an excitation magnetic field, which passes through the squirrel-cage rotor  90  and, for its part, induces in the squirrel-cage rotor  90  a secondary electric current, which circulates in a ring-like manner. This secondary current which builds up in turn generates a secondary magnetic field, which opposes the excitation magnetic field, as a result of which the squirrel-cage rotor  90  is subject to a Lorentz force, which is repelled by the excitation coil  100  and drives the drive-in element  60  toward the holder  20  and also the fastening element  30  held therein. As soon as the piston rod  80  of the drive-in element  60  meets a head, not specifically denoted, of the fastening element  30 , the fastening element  30  is driven into the substrate by the drive-in element  60 . Excess kinetic energy of the drive-in element  60  is absorbed by a braking element  85  made of a spring-elastic and/or damping material, for example rubber, by way of the drive-in element  60  moving with the piston plate  70  against the braking element  85  and being braked by the latter until it comes to a standstill. The drive-in element  60  is then reset to the ready-to-set position by a resetting tool that is not specifically denoted. 
     The capacitor  300 , in particular its center of gravity, is arranged behind the drive-in element  60  on the setting axis A, whereas the holder  20  is arranged in front of the drive-in element  60 . Therefore, with respect to the setting axis A, the capacitor  300  is arranged in an axially offset manner in relation to the drive-in element  60  and in a radially overlapping manner with the drive-in element  60 . As a result, on the one hand a small length of the discharge lines  210 ,  220  can be realized, as a result of which their resistances can be reduced, and therefore an efficiency of the drive can be increased. On the other hand, a small distance between a center of gravity of the setting tool  10  and the setting axis A can be realized. As a result, tilting moments in the event of recoil of the setting tool  10  during a driving-in process are small. In an exemplary embodiment which is not shown, the capacitor is arranged around the drive-in element. 
     The electrodes  310 ,  320  are arranged on opposite sides of a carrier film  330  which is wound around a winding axis, for example by metallization of the carrier film  330 , in particular by being vapor-deposited, wherein the winding axis coincides with the setting axis A. In exemplary embodiments which are not shown, the carrier film with the electrodes is wound around the winding axis such that a passage along the winding axis remains. In particular, in this case the capacitor is for example arranged around the setting axis. The carrier film  330  has at a charging voltage of the capacitor  300  of 1500 V a film thickness of between 2.5 μm and 4.8 μm and at a charging voltage of the capacitor  300  of 3000 V a film thickness of for example 9.6 μm. In exemplary embodiments which are not shown, the carrier film is for its part made up of two or more individual films which are arranged as layers one on top of the other. The electrodes  310 ,  320  have a sheet resistance of 50 ohms/□. 
     A surface of the capacitor  300  has the form of a cylinder, in particular a circular cylinder, the cylinder axis of which coincides with the setting axis A. A height of this cylinder in the direction of the winding axis is substantially the same size as its diameter, measured perpendicularly to the winding axis. On account of a small ratio of height to diameter of the cylinder, a low internal resistance for a relatively high capacitance of the capacitor  300  and, not least, a compact construction of the setting tool  10  are achieved. A low internal resistance of the capacitor  300  is also achieved by a large line cross section of the electrodes  310 ,  320 , in particular by a high layer thickness of the electrodes  310 ,  320 , wherein the effects of the layer thickness on a self-healing effect and/or on a service life of the capacitor  300  should be taken into consideration. 
     The capacitor  300  is mounted on the rest of the setting tool  10  in a manner damped by means of a damping element  350 . The damping element  350  damps movements of the capacitor  300  relative to the rest of the setting tool  10  along the setting axis A. The damping element  350  is arranged on the end side  360  of the capacitor  300  and completely covers the end side  360 . As a result, the individual windings of the carrier film  330  are subject to uniform loading by recoil of the setting tool  10 . In this case, the electrical contacts  370 ,  380  protrude from the end surface  360  and pass through the damping element  350 . For this purpose, the damping element  350  in each case has a clearance through which the electrical contacts  370 ,  380  protrude. The connecting lines  301  respectively have a strain-relief and/or expansion loop, not illustrated in any detail, for compensating for relative movements between the capacitor  300  and the rest of the setting tool  10 . In exemplary embodiments which are not shown, a further damping element is arranged on the capacitor, for example on the end side of the capacitor that faces away from the holder. The capacitor is then preferably clamped between two damping elements, that is to say the damping elements bear against the capacitor with prestress. In further exemplary embodiments which are not shown, the connecting lines have a rigidity which continuously decreases as the distance from the capacitor increases. 
       FIG. 2  illustrates an electrical circuit diagram  400  of a setting tool that is not shown any further, for driving fastening elements into a substrate that is not shown. The setting tool has a housing, not shown, a handle, not shown, with an operating element, a holder, not shown, a magazine, not shown, a drive-in element, not shown, and a drive for the drive-in element. The drive comprises a squirrel-cage rotor, not shown, arranged on the drive-in element, an excitation coil  410 , a soft-magnetic frame, not shown, a switching circuit  420 , a capacitor  430 , an electrical energy store  440  designed as a rechargeable battery, and a control unit  450  with a switching converter  451  designed for example as a DC/DC converter. The switching converter  451  has a low-voltage side U LV , electrically connected to the electrical energy store  440 , and a high-voltage side U HV , electrically connected to the capacitor  430 . 
     The switching circuit  420  is provided for causing rapid electrical discharging of the previously charged capacitor  430  and conducting the thereby flowing discharge current through the excitation coil  410 . To this end, the switching circuit  420  comprises two discharge lines  421 ,  422 , which connect the capacitor  430  to the excitation coil  420  and at least one discharge line  421  of which is interrupted by a normally open discharge switch  423 . A free-wheeling diode  424  suppresses excessive oscillation back and forth of an oscillating circuit which is formed by the switching circuit  420  with the excitation current  410  and the capacitor  430 . 
     When the setting tool is pressed against the substrate, the control unit  450  initiates a capacitor charging process, in which electrical energy is conducted from the electrical energy store  440  to the switching converter  451  of the control unit  450  and from the switching converter  451  to the capacitor  430  in order to charge the capacitor  430 . In the process, the switching converter  451  converts the electric current from the electrical energy store  440 , at an electrical voltage of for example 22 V, into a suitable charging current for the capacitor  430 , at an electrical voltage of for example 1500 V. 
     Triggered by an actuation of the actuating element that is not shown, the control unit  450  initiates a capacitor discharging process, in which electrical energy stored in the capacitor  430  is conducted from the capacitor  430  to the excitation coil  410  by means of the switching circuit  420  by the capacitor  430  being discharged. For the purpose of initiating the capacitor discharging process, the control unit  450  closes the discharge switch  430 , as a result of which a discharge current of the capacitor  430  with a high current intensity flows through the excitation coil  410 . As a result, the squirrel-cage rotor, not shown, is subject to a Lorentz force, which is repelled by the excitation coil  410  and drives the drive-in element. The drive-in element is reset to a ready-to-set position by a resetting device that is not shown. 
     An amount of energy of the current flowing through the excitation coil  410  during the rapid discharge of the capacitor  430  is controlled, in particular steplessly, by the control unit  450 , in that a charging voltage (U HV ) applied to the capacitor  430  is set during and/or at the end of the capacitor charging process and before the beginning of the rapid discharge. An electrical energy stored in the charged capacitor  430 , and thus also the amount of energy of the current flowing through the excitation coil  410  during the rapid discharge of the capacitor  430 , can be controlled in proportion to the charging voltage and thus by means of the charging voltage. The capacitor is charged during the capacitor charging process until the charging voltage U HV  has reached a setpoint value. The charging current is then switched off. If the charging voltage decreases before the rapid discharge, for example due to parasitic effects, the charging current is switched on again until the charging voltage U HV  has reached the setpoint value again. 
     The control unit  450  controls the amount of energy of the current flowing through the excitation coil  410  during the rapid discharge of the capacitor  430  in dependence on a number of control variables. For this purpose, the setting tool comprises a means formed as a temperature sensor  460  for detecting a temperature of the excitation coil  410  and a means for detecting a capacitance of the capacitor, which is designed for example as a calculation program  470  and calculates the capacitance of the capacitor from a profile of a current intensity and an electrical voltage of the charging current during the capacitor charging process. Furthermore, the setting tool comprises a means designed as an acceleration sensor  480  for detecting a mechanical load variable of the setting tool. The setting tool further comprises a means for detecting a driving depth of the fastening element into the substrate, which comprises a proximity sensor  490 , for example an optical, capacitive or inductive proximity sensor  490 , which comprises a reversing position of the drive-in element that is not shown. The setting tool further comprises a means for detecting a speed of the drive-in element, which has a means designed as a first proximity sensor  500  for detecting a first point in time, at which the drive-in element passes a first position during its movement toward the fastening element, a means designed as a second proximity sensor  510  for detecting a second point in time, at which the drive-in element passes a second position during its movement toward the fastening element, and a means designed as a calculation program  520  for detecting a time difference between the first point in time and the second point in time. The setting tool further comprises an operating element  530 , which can be adjusted by a user, and a means designed as a barcode reader  540  for detecting a characteristic variable of a fastening element to be driven in. 
     The control variables in dependence on which the control unit  450  controls the amount of energy of the current flowing through the excitation coil  410  during the rapid discharge of the capacitor  430  comprise the temperature detected by the temperature sensor  460  and/or the capacitance of the capacitor calculated by the calculation program  470  and/or the load variable of the setting tool detected by the acceleration sensor  480  and/or the driving-in depth of the fastening element detected by the proximity sensor  490  and/or the speed of the drive-in element calculated by the calculation program  520  and/or the adjustment of the operating element  530  adjusted by the user and/or the characteristic variable of the fastening element detected by the barcode reader  540 . 
     Furthermore, the setting tool, preferably the control unit  450 , comprises a means  550  for detecting a temperature of the excitation coil. In one exemplary embodiment, the means  550  is a program which processes a signal that the control unit  450  receives from the temperature sensor  460 . In a further exemplary embodiment, the means  550  comprises a means for detecting an ohmic resistance of the excitation coil, which has a signal transmitter and a voltmeter. The signal generator generates a measuring current flowing through the excitation coil  410  and the voltmeter measures an electrical voltage thereby dropping across the excitation coil  410 . A calculation program calculates the ohmic resistance of the excitation coil  410  from the measurement current and the voltage drop across the excitation coil  410 . The means  550  then calculates a difference between the ohmic resistance of the excitation coil  410  thus obtained and a reference resistance, which was recorded in the same way after a relatively long time without setting operation, that is to say at ambient temperature. The means  550  finally calculates from this difference the temperature of the excitation coil  410 . 
     In a further exemplary embodiment, the means  550  comprises a means formed as a timer for recording a time, a means formed as a data receiver for detecting a driving-in process as a process which causes the temperature of the excitation coil to rise, a data memory in which a standard cooling rate of the excitation coil and the temperature rise caused by the process are stored, and a program for calculating the temperature of the excitation coil  410 . The means for detecting a driving-in process is designed as an information receiver, which in each case receives information from the control unit  450  about a driving-in process started by the control unit  450 . The temperature of the excitation coil  410  is calculated as follows. After the setting tool has not been used for a relatively long time, device electronics of the setting tool are woken up by actuating a main switch, a pressure switch, a trigger switch or a motion sensor. The program for calculating the temperature of the excitation coil  410  then reads in a starting temperature detected by the temperature sensor  460  or an ambient temperature sensor as the actual temperature. The timer is also started. As soon as a first driving-in process is recorded, the temperature rise stored in the data memory is added to the actual temperature and the sum is saved as the new actual temperature. As soon as a further driving-in process is detected, first a temperature drop is calculated from a difference between the actual temperature and the ambient temperature detected by the ambient temperature sensor and the time that has elapsed since the last driving-in process, recorded by the timer, using the standard cooling rate stored in the data memory. The temperature drop is then subtracted from the actual temperature and the temperature rise stored in the data memory is added and the sum is saved as the new actual temperature. After a relatively long time without driving-in operations, for example two hours, the timer is set to zero and the electronics of the setting tool are put into a sleep mode or switched off. The ambient temperature sensor is preferably arranged on a circuit board of the electronics, for example the control unit  450 . 
     The setting tool has a means  560  for cooling the excitation coil  410 , which comprises a rotor and is designed for example as a fan or circulation pump for a cooling liquid. The control unit  450  is intended to control the means  560  for cooling the excitation coil  410 , for example a running time and/or speed of the rotor, in dependence on the detected temperature of the excitation coil  410 . In the exemplary embodiment described above, an increased cooling rate of the excitation coil  410  is stored in the data memory, the program for calculating the temperature of the excitation coil  410  using the standard cooling rate during periods of time in which the means  560  for cooling the excitation coil  410  is not operating and using the increased cooling rate during periods in time in which the means  560  is operating. 
     The control unit  450  is suitable for controlling further operating sequences of the setting tool in dependence on the detected temperature of the excitation coil  410 . For example, the setpoint value for the charging voltage of the capacitor  430  is controlled in dependence on the detected temperature of the excitation coil  410 , the setpoint value being all the greater the higher the detected temperature of the excitation coil  410 . Furthermore, the control unit  450  only enables a driving-in process if the detected temperature of the excitation coil  410  is lower than a predetermined maximum temperature. By contrast, if the detected temperature of the excitation coil  410  is greater than the predetermined maximum temperature, the driving-in process is inhibited. The means  560  for cooling the excitation coil  410  preferably remains in operation. 
       FIG. 3  illustrates a longitudinal section through an excitation coil  600 . The excitation coil  600  comprises an electrical conductor, preferably made of copper, with a circular cross section, for example, which is wound in several turns  610  around a setting axis A 2 . Overall, the excitation coil has a substantially cylindrical, in particular circular-cylindrical, outer shape with an outside diameter Ra and a coil length L Sp  in the direction of the setting axis A 2 . In a radially inner region with respect to the setting axis A 2 , the excitation coil  600  has a clearance  620 , which is preferably likewise cylindrical, in particular circular-cylindrical, and defines an inside diameter R i  of the excitation coil. 
     A means formed as a temperature sensor  660  for detecting a temperature of the excitation coil  600  is arranged on an axial end face of the excitation coil  600  with respect to the setting axis A 2  and is connected in a thermally conducting manner to the excitation coil  600 , for example by means of a thermal paste. In exemplary embodiments which are not shown, the temperature sensor is arranged on an inner circumference or outer circumference of the excitation coil. 
     The invention has been described using a series of exemplary embodiments that are illustrated in the drawings and exemplary embodiments that are not illustrated. The individual features of the various exemplary embodiments are applicable individually or in any desired combination with one another, provided that they are not contradictory. It should be noted that the setting tool according to the invention can also be used for other applications.