Patent ID: 12202110

InFIG.1, a tool10for working a substrate (not shown), which is designed as a hand-held setting device for driving fastening elements into the substrate, is shown in a longitudinal section. The tool10has a receptacle20which is formed as a stud guide and in which a fastening element30formed as a nail is received in order to be driven into the substrate along a working axis A (to the left inFIG.1). For feeding fastening elements to the receptacle, the tool10comprises a magazine40in which the fastening elements are received individually or collectively in the form of a fastening element strip50and are transported one by one into the receptacle20. To this end, the magazine40has a spring-loaded feed element, not specifically denoted.

The tool10has a working piston60, which comprises a piston body70and a piston rod80. The working piston60is intended to transfer the fastening element30out of the receptacle20along the working axis A into the substrate. In this case, the working piston60is guided with its piston body70in a guide cylinder95along the working axis A. In exemplary embodiments that are not shown, the working piston is guided along the working axis by two, three or more guide elements, for example guide rods. The working piston60is in turn driven by a drive65, which comprises a switching circuit200and a capacitor300. The switching circuit200is intended to bring about a rapid electrical discharge of the previously charged capacitor300and to feed the discharge current thereby flowing to the drive65.

The tool10also comprises a housing110, in which the drive65is received, a handle120with an actuating element130formed as a trigger, an electrical energy store140formed as a storage battery, a control unit150, a trigger switch160, a pressure switch170, a temperature sensor180arranged on the drive65and electrical connecting lines141,161,171,181,201,301, which connect the control unit150to the electrical energy storage140, the trigger switch160, the pressure switch170, the temperature sensor180, the switching circuit200and the capacitor300. In exemplary embodiments that are not shown, the tool10is supplied with electrical energy by means of a power cable instead of the electrical energy store140or in addition to the electrical energy store140. 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 tool10is pressed against a substrate that is not shown (to the left inFIG.1), a contact-pressure element, not specifically denoted, operates the contact-pressure switch170, which as a result transmits a contact-pressure signal to the control unit150by means of the connecting line171. Triggered by this, the control unit150initiates a capacitor charging process in which electrical energy is conducted by means of the connecting line141from the electrical energy store140to the control unit150and by means of the connecting lines301from the control unit150to the capacitor300in order to electrically charge the capacitor300. To this end, the control unit150comprises a switching converter, not specifically denoted, which converts the electrical current from the electrical energy store140into a suitable charge current for the capacitor300. When the capacitor300is charged and the working piston60is in its ready-to-set position shown inFIG.1, the tool10is in a ready-to-set state. Since the charging of the capacitor300is only brought about by the tool10pressing against the substrate, to increase the safety of bystanders a setting process is only made possible when the setting tool10is pressed against the substrate. In exemplary embodiments that are not shown, the control unit already initiates the capacitor charging process when the tool is switched on or when the tool is lifted off the substrate or when a preceding driving-in process is completed.

When the actuating element130is actuated, for example by being pulled using the index finger of the hand holding the handle120, with the tool10in the ready-to-set state, the actuating element130actuates the trigger switch160, which as a result transmits a trigger signal to the control unit150by means of the connecting line161. Triggered by this, the control unit150initiates a capacitor discharging process, in which electrical energy stored in the capacitor300is conducted by means of the switching circuit200from the capacitor300to the drive65, in that the capacitor300is electrically discharged.

For this purpose, the switching circuit200schematically illustrated inFIG.1comprises two discharge lines210,220, which connect the capacitor300to the drive65and of which at least one discharge line210is interrupted by a normally open discharge switch230. The switching circuit200with the drive65and the capacitor300may form an electrical oscillating circuit. Oscillation of this oscillating circuit back and forth and/or negative charging of the capacitor300may potentially have an adverse effect on the efficiency of the drive65, but can be suppressed with the aid of a free-wheeling diode240. The discharge lines210,220are electrically connected in each case to an electrode310,320of the capacitor300arranged on a carrier film330by means of electrical contacts370,380of the capacitor300arranged on an end face360of the capacitor300facing the receptacle20, for example by soldering, welding, screwing, clamping or a form fit. The discharge switch230is preferably suitable for switching a discharge current with a high current intensity and is formed for example as a thyristor. In addition, the discharge lines210,220are at a small distance from one another, so that a parasitic magnetic field induced by them is as low as possible. By way of example, the discharge lines210,220are combined to form a busbar and are held together by a suitable means, for example a retaining device or a clip. 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.

To initiate the capacitor discharge process, the control unit150closes the discharge switch230by means of the connecting line201, whereby a high-intensity discharge current of the capacitor300flows through the drive65, which drives the working piston60toward the receptacle20and the fastening element30received therein. As soon as the piston rod80of the working piston60meets a head, not specifically denoted, of the fastening element30, the fastening element30is driven into the substrate by the working piston60. Excess kinetic energy of the working piston60is absorbed by a braking element85of a spring-elastic and/or damping material, for example rubber or an elastomer, by the working piston60moving with the piston body thereof70against the braking element85and being braked by the latter until it comes to a standstill. The working piston60is then reset to the ready-to-set position by a resetting device that is not specifically denoted.

InFIG.2-3, a drive/working-piston unit400of a tool, for example the tool10shown inFIG.1, is illustrated from different angles. The drive/working-piston unit400comprises a partly shown drive410, a working piston420and a stator430. The working piston420has a piston body421and a piston rod422and is intended to move relative to the stator430along a working axis401. The drive410is intended to drive the working piston420along the working axis401. For this purpose, the drive410comprises a capacitor (not shown) and a piston coil440arranged on the working piston420. The piston coil440can be electrically connected to the capacitor in order during rapid discharge of the capacitor to have a current flowing through it and to generate a magnetic field that brings about a repulsive force between the piston coil440and the stator430and accelerates the working piston420relative to the stator430.

In addition, the drive410comprises a first stator coil450arranged on the stator430and a second stator coil455arranged on the stator430. The stator coils450,455can be electrically connected to the capacitor in order during rapid discharge of the capacitor to have a current flowing through them and to generate a magnetic field that brings about a repulsive force between the stator coils450,455and the working piston420and accelerates the working piston420away from the stator430. The repulsive force between the stator coil450and the working piston420is brought about for example by the magnetic field generated by the stator coils450,455being opposite to the magnetic field generated by the piston coil440. For this purpose, the first stator coil450and the second stator coil455are supplied with electrical current in the same direction, while the piston coil440is supplied with electrical current in the opposite direction and at the same time, by the capacitor being discharged.

The stator coils450,455are arranged opposite one another on two sides of the working axis401and the piston coil440is arranged between the stator coils450,455on the working axis401. The piston coil440and the stator coils450,455respectively have a piston coil axis and a stator coil axis, which are inclined perpendicularly relative to the working axis401and are oriented parallel to one another.

InFIG.3, a drive510of a tool, for example the tool10shown inFIG.1, is illustrated. The drive510is shown cut away along a working axis501and is intended to drive a working piston520with a piston body521and a piston rod522along the working axis501and to move it relative to a stator530. The drive510comprises a capacitor560, a switching circuit570with a switch571and a current control element572designed as a diode, in particular a free-wheeling diode, a piston coil540arranged on the working piston520, a first stator coil550arranged on the stator530and a second stator coil550arranged on the stator530. The piston coil540and the stator coils550,555can be electrically connected to the capacitor560in order during rapid discharge of the capacitor560to have a current flowing through them. A current flowing through the piston coil540generates a first magnetic field, while a current flow through the stator coils550,555generates a second magnetic field.

One electrode of the capacitor560is electrically connected to an input of the switch571and can be charged with respect to a counter electrode of the capacitor560, which is electrically connected to a ground potential (not shown), for example the negative terminal of an electrical rechargeable battery or a battery. An output of the switch571is electrically connected, preferably permanently wired, to an input of the first stator coil550. An output of the first stator coil550is electrically connected, preferably permanently wired, to a first electrical stator contact531, which is formed as a contact brush and which the stator530has. An input of the piston coil540is electrically connected, preferably permanently wired, to a first piston contact541, which is formed as a contact rail and which the working piston520has. The first piston contact541slides in an electrically conducting manner along the first stator contact531when the working piston520moves along the working axis501. A first spring (not shown) loads the first stator contact531toward the first piston contact541. In exemplary embodiments that are not shown, a spring additionally or alternatively loads the first piston contact toward the first stator contact.

An output of the piston coil540is electrically connected, preferably permanently wired, to a second piston contact542, which is formed as a contact rail and which the working piston520has. The second piston contact542slides in an electrically conducting manner along a second stator contact532when the working piston520moves along the working axis501. The stator530has the second stator contact532, which is formed as a contact brush and is electrically connected to an input of the second stator coil555. An output of the second stator coil555is finally electrically connected to ground potential. A second spring (not shown) loads the second stator contact532toward the second piston contact542. In exemplary embodiments that are not shown, a spring additionally or alternatively loads the second piston contact toward the first stator contact. The piston contacts541,542do not necessarily contact the stator contacts531,532during the entire movement of the working piston. In some applications, contacting during the first 0.5 ms to 1 ms, in particular during the first 0.6 ms, is sufficient. The piston contacts541,542have a length in the direction of the working axis501which for some areas of application is approximately 10 mm to 30 mm.

The piston contacts541,542are rigidly connected to the rest of the working piston520and move with the rest of the working piston520. In exemplary embodiments that are not shown, the first and/or the second stator contact is formed as a slip ring. In further exemplary embodiments that are not shown, the first and/or the second stator contact is formed as a contact rail and the first or the second piston contact is formed as a contact brush or a slip ring. The second piston contact542and the second stator contact532are arranged radially within the stator coils550,555and the piston coil540with respect to the coils540,550,555.

The rapid discharge of the capacitor560via the piston coil540and the stator coil550can be triggered by means of the switching circuit570, by the switch571being closed when the capacitor560is electrically charged and the piston coil540and the stator coils550,555being electrically connected to the capacitor560. The electrical current then flows from the capacitor560through the switch571, through the first stator coil550, through the first stator contact531and the first piston contact541, through the piston coil540, through the second piston contact542and the second stator contact532and finally through the second stator coil555to the capacitor560or to ground potential.

The piston coil540and the stator coil550respectively have a piston coil axis (540′) and a stator coil axis (550′), which are oriented perpendicularly to the working axis501and parallel to one another. The piston coil540and the stator coils550,555(the stator coils550,555having respective stator core axes550′,555′) are wound in the same direction and the electrical current flows through them in opposite directions, so that the first magnetic field generated by the piston coil540and the second magnetic field generated by the stator coils550,555are opposite to one another. In exemplary embodiments that are not shown, the coils are wound in opposite directions and the electrical current flows through them in the same direction. This brings about a repulsive force between the stator coils550,555and the piston coil540, and thus between the stator530and the working piston520, so that the working piston520is accelerated relative to the stator530. The piston coil540and the stator coils550,555are electrically connected in series with one another, that is to say that electrical current flows through them at the same time, a current intensity of the current flowing through the coils540,550,555being the same for the piston coil540and the stator coil550. In addition, the piston coil540and the stator coils550,555preferably have in each case the same number of coil turns, so that the magnetic fields generated by the coils540,550,555are equally strong.

The working piston520has a piston frame525, which preferably consists of a soft magnetic material, such as for example iron or an alloy thereof, for example steel. The piston frame525surrounds the piston coil540. As a result, the first magnetic field generated by the piston coil540is intensified in the area of the stator coils550,555and the repulsive force between the stator530and the working piston520is increased. The piston body521preferably consists of the soft magnetic material and particularly preferably forms the piston frame. The piston rod522also preferably consists of the soft magnetic material and is particularly preferably connected in one piece to the piston body521, which may increase a stiffness and/or mechanical robustness of the working piston520. The stator530has a stator frame535, which preferably consists of a soft magnetic material, such as for example iron or an alloy thereof, for example steel. The stator frame535surrounds the stator coils550,555. As a result, the second magnetic field generated by the stator coils550,555is intensified in the area of the piston coil540and the repulsive force between the stator530and the working piston520is increased.

In the starting position shown inFIG.4, the piston coil axis (540′) is arranged offset (598) relative to the stator coil axes (550′,555′) in the direction of the working axis501. This improves repulsion in the direction of the working axis501. For guiding the working piston520along the working axis501, the tool has a guide599, for example formed as a guide rail.

Wherein the drive has a diode which is arranged on the working piston and is electrically connected to the piston coil. An advantageous embodiment is characterized in that the drive has a switching circuit comprising the diode, by means of which the rapid discharge is triggered and/or the piston coil is electrically connected to the capacitor.

InFIG.5, an electrical circuit diagram of the drive510shown inFIG.4is illustrated. In addition to the capacitor560, the switch571, the piston coil541, the first stator coil550and the second stator coil555, the drive510comprises a first diode591assigned to the first stator coil550, a second diode592assigned to the second stator coil and a piston diode593assigned to the piston coil541. The piston diode593is an exemplary embodiment of a current control element for controlling the electrical current flowing through the piston coil541. The coils541,550,555form an oscillating circuit with the capacitor560. The current control element593then serves the purpose of preventing this oscillating circuit from oscillating back after the capacitor560has discharged. The piston contacts shown inFIG.4are thereby de-energized, so that the risk of electrical flashovers between the piston contacts and the stator contacts is reduced. This can be used to shorten the contact rails involved, in particular to a sliding length that is shorter than a movement path of the working piston520along the working axis. This is made possible by an arrangement, in particular fastening, of the current control element593on the working piston520. In the embodiment shown in FIG.5as a freewheeling diode, the diode593is electrically connected in parallel with the piston coil541.

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 is pointed out that the tool according to the invention can also be used for other applications, for example as a hammer drill or the like.