Patent Publication Number: US-2021178561-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, a drive, which is provided for driving the drive-in element toward the fastening element along the setting axis, wherein the drive comprises an excitation coil which is flowed through by current and generates a magnetic field which accelerates the drive-in element onto the fastening element, and a stop element, which supports the drive-in element against movement toward the excitation coil when the drive-in element is in a ready-to-set position, the drive-in element being spaced apart from the excitation coil in the ready-to-set position. 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. 
     A preferred embodiment is characterized in that an air gap is formed between the drive-in element and the excitation coil when the drive-in element is in a ready-to-set position. The air gap preferably has a gap width which is between 0 and 0.5 mm, particularly preferably between 0.01 mm and 0.2 mm, for example between 0.02 mm and 0.1 mm. 
     A preferred embodiment is characterized in that the stop element has a stop surface that faces the holder and the drive-in element has a counter surface that faces away from the holder, and the stop surface and the counter surface lie against one another when the drive-in element is in a ready-to-set position. The stop surface and/or the counter surface is preferably arranged on the setting axis or around the setting axis. Likewise preferably, the stop surface and/or the counter surface is convex, particularly preferably spherical. 
     A preferred embodiment is characterized in that a projection of the stop element in the direction of the setting axis is arranged radially inside a projection of the excitation coil in the direction of the setting axis. The stop element is preferably arranged radially inside the excitation coil with respect to the setting axis. 
     A preferred embodiment is characterized in that the drive comprises a soft-magnetic frame on which the excitation coil is arranged. The excitation coil is preferably embedded in the soft-magnetic frame. The drive-in element is preferably spaced apart from the soft-magnetic frame in the ready-to-set position. Particularly preferably, a further air gap is formed between the drive-in element and the soft-magnetic frame when the drive-in element is in the ready-to-set position. 
     A preferred embodiment is characterized in that the soft-magnetic frame is formed in a ring shape, wherein a projection of the stop element in the direction of the setting axis is arranged radially inside a projection of the soft-magnetic frame in the direction of the setting axis. The stop element is preferably arranged radially inside the soft-magnetic frame with respect to the setting axis. 
     A preferred embodiment is characterized in that the stop element and/or the drive-in element comprises a damper which has the stop surface or the counter surface. The damper preferably dampens striking of the drive-in element against the stop element. 
     A preferred embodiment is characterized in that the drive comprises an electrical capacitor, which is preferably arranged on the setting axis or around the setting axis, and, when the excitation coil is discharged, current flows through it in order to generate the magnetic field. A further embodiment is characterized in that the drive has arranged on the drive-in element a squirrel-cage rotor, which is permeated by the magnetic field generated by the excitation coil. 
    
    
     
       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 and 
         FIG. 2  shows a longitudinal section through a setting tool. 
     
    
    
       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 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 which 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  20 . 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 electrical 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 pretension. 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 a further exemplary embodiment of a hand-held setting tool  410  for driving fastening elements along a setting axis A′ into a substrate that is not shown. Analogously to the setting tool  10  illustrated in  FIG. 1 , the setting tool  410  comprises a holder  420  formed as a stud guide, in which a fastening element  430 , which is formed as a nail, is held, a magazine  440 , in which the fastening elements are held in store individually or in the form of a fastening element strip  450 , a drive-in element  460 , which comprises a piston plate  470  and a piston rod  480 , a guide cylinder  495 , in which the piston plate  470  is guided, a braking element  485  and a stop element  580 . 
     The drive-in element  460  is driven by a drive, which comprises a squirrel-cage rotor  490  arranged on the piston plate  470 , an excitation coil  500 , a ring-like soft-magnetic frame  505 , a switching circuit that is not shown and a capacitor that is likewise not shown. The setting tool  410  further comprises a housing  510 , in which the drive is held, a handle  520  with an operating element  530  formed as a trigger and further components that are not shown, such as an electrical energy store or a power cable, a control unit, a tripping switch, a contact-pressure switch and electrical connecting lines, which connect the control unit to the electrical energy store, to the tripping switch, to the contact-pressure switch, to the switching circuit and, respectively, to the capacitor, and a resetting device. 
     In the ready-to-set position of the drive-in element  460  illustrated in  FIG. 2 , the stop element  580  supports the drive-in element  460  against movement toward the excitation coil  500 . In this case, the drive-in element  460  is spaced apart from the excitation coil  500  to form an air gap  590  with a gap width of 0.05 mm and from the soft-magnetic frame  505  to form a further air gap  595  with a gap width of for example 0.5 mm. This has the effect of preventing or mitigating impact of the drive-in element  460  on the excitation coil  500 , which may be additionally dampened with the aid of an air cushion between the drive-in element  460  and the excitation coil  500 . With the aid of the stop element  580 , a small gap width, and thus a large repulsive force, between the excitation coil  500  and the squirrel-cage rotor  490  is ensured. The stop element  580  has facing the holder  420  a convex stop surface  585 , which is arranged on the setting axis A′. The drive-in element  460  has facing away from the holder  420  a flat counter surface  465 , which is likewise arranged on the setting axis A′. In exemplary embodiments which are not shown, instead of or in addition to the stop surface, the counter surface is convex, in particular spherical. In the ready-to-set position of the drive-in element  460  illustrated in  FIG. 2 , the stop surface  585  and the counter surface  465  lie against one another. With respect to the setting axis A′, the stop element  580  is arranged radially inside the excitation coil  500  and radially inside the soft-magnetic frame  505 . The stop element  580  comprises a damper  581 , which has the stop surface  585  and dampens striking of the drive-in element  460  against the stop element  580 . 
     The setting tool  410  functions substantially in just the same way as the setting tool  10  illustrated in  FIG. 1 . When the drive-in element  60  is returned to the ready-to-set position by the resetting device, the counter surface  465  comes to lie against or strikes the stop surface  585 . A mechanical stressing of the excitation coil  500  and/or the soft-magnetic frame  505  is reduced due to the respective distance of the excitation coil  500  or the soft-magnetic frame from the drive-in element  460 . 
     The piston rod  480  preferably passes through the piston plate  470  and has the counter surface  465 . The piston rod  480  is made of an impact-resistant material, such as for example steel, with the effect of reducing wear of the piston rod  480  when the fastening elements  430  are repeatedly hit and/or likewise when the stop element  580  is repeatedly hit. The piston plate  470  is protected from impact by the arrangement according to the invention and consists of a low-density material, for example aluminum, so that a total mass of the drive-in element  460 , and thus energy required to accelerate it, is reduced. The stop element  580  is preferably rod-shaped and preferably consists of an impact-resistant material, such as for example steel, and is supported, in particular fastened, on the housing  510  directly or indirectly, for example by means of a reinforcement  506  of the soft-magnetic frame  505  and/or a fastening element  507 , for example a screw or nut. 
     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.