PYROTECHNIC DRIVING DEVICE

Abstract

A driving device, comprising a hand-held housing with a piston element arranged therein for the transmission of energy to a fastening element to be driven in a driving direction, a propellant charge, and a combustion chamber, which is arranged between the propellant charge and the piston element and extends around a central axis, and an actuator, by which the energy to be transmitted from the propellant charge to the piston element can be varied in such a way that the energy can be set, wherein a venting channel connected to the combustion chamber can be exposed by means of a movable slide of the actuator, wherein the venting channel opens out into the combustion chamber by a vent opening, which can be partially or completely covered by the slide, and wherein a cross-sectional area of the vent opening increases in the driving direction.

Claims

1. A driving device, comprising a hand-held housing with a piston element arranged therein for the transmission of energy to a fastening element to be driven in a driving direction; a propellant charge; a combustion chamber, which is arranged between the propellant charge and the piston element and extends around a central axis; and, an actuator, by which the energy to be transmitted from the propellant charge to the piston element can be varied in such a way that the energy can be set, wherein a venting channel connected to the combustion chamber can be exposed by a movable slide of the actuator, wherein the venting channel opens out into the combustion chamber by a vent opening, which can be partially or completely covered by the slide, and wherein a cross-sectional area of the vent opening increases in the driving direction.

2. The driving device as claimed in claim 1, wherein the driving device has a number of venting channels, which respectively open out into the combustion chamber by a vent opening and have in each case a cross-sectional area which increases in the driving direction.

3. The driving device as claimed in claim 1, wherein the vent opening is arranged in a cylindrical, in particular circular-cylindrical, portion of the combustion chamber.

4. The driving device as claimed in claim 2, wherein the vent opening is arranged in a cylindrical, in particular circular-cylindrical, portion of the combustion chamber.

5. The driving device of claim 1, wherein the propellant charge is an exchangeable propellant charge.

6. The driving device of claim 3, wherein the vent opening is arranged in a circular-cylindrical portion of the combustion chamber.

7. The driving device of claim 4, wherein the vent opening is arranged in a circular-cylindrical portion of the combustion chamber.

Description

[0023] Further features and advantages of the invention are apparent from the exemplary embodiment and from the dependent claims. A preferred exemplary embodiment of the invention is described below and explained in more detail with reference to the appended drawings.

[0024] FIG. 1 shows a spatial overall view of a driving device according to the invention.

[0025] FIG. 2 shows a longitudinal section of a combustion chamber.

[0026] FIG. 3 shows a longitudinal section of a combustion chamber with an actuator in a position for low driving energy.

[0027] FIG. 4 shows a longitudinal section of a combustion chamber with an actuator in a position for high driving energy.

[0028] FIG. 5 shows a detail of the longitudinal section in FIG. 4.

[0029] FIG. 6 shows a spatial view of a detail of an actuator.

[0030] Shown in FIG. 1 is a driving device. The driving device comprises a hand-held housing 1, in which a piston element in the form of a piston is held. A surface of the piston delimits a combustion chamber, in which the combustion gases of a pyrotechnic charge expand in order to accelerate the piston.

[0031] The piston to which kinetic energy is imparted acts with an end tappet on a fastening element (not shown), which is thereby driven into a workpiece (on the right in FIG. 1). The fastening element may be held in particular in a module or magazine (not shown), which is exchangeably attached in a forward holding region 1a of the driving device 1.

[0032] The charge is in the present case held in a sheet-metal cartridge 4a. The cartridge 4a has an impact detonator and, before ignition, is inserted into a cartridge bearing by way of a corresponding charging mechanism, in the present case by means of a magazine strip 4 The cartridge 4a and the cartridge bearing are then arranged rotationally symmetrically around a central axis A. The central axis A is in the present examples at the same time a central axis of the combustion chamber and of the piston element.

[0033] Shown in FIG. 2 is a combustion chamber 20, which is formed by a combustion chamber housing 21. The combustion chamber 20 is arranged between a circular opening 22 of the cartridge bearing 23 and the surface of the piston (not shown). At the time of the combustion, the cartridge lies against the cartridge bearing and is enclosed there. In the combustion chamber housing 21 there is a multi-start internal thread 24 in the region of the combustion chamber 20. Connected to the combustion chamber 20 are a number of venting channels 25, in particular two or three, which in each case open out with a vent opening 26 into the combustion chamber 20. A cross-sectional area of each vent opening 26 increases in the driving direction 27. The vent openings 26 are arranged in a circular-cylindrical portion of the combustion chamber 20. Furthermore, the combustion chamber 20 has a circular-cylindrical guiding portion 33 and a further guiding portion 32. The internal thread 24 is arranged between the guiding portion 33 and the further guiding portion 32 along the central axis A.

[0034] In FIGS. 3, 4 and 5, the combustion chamber 20 is shown with an actuator 28 arranged therein. The actuator 28 comprises a threaded sleeve with a cylindrical inner wall and also a piston guide 28a. By means of the actuator 28, the energy to be transmitted from the propellant charge to a piston element 34 is variable in such a way that it can be set, by the venting channels 25 being gradually exposed by means of the actuator 28 and additionally or alternatively by a starting position of the piston element 24 in relation to the combustion chamber 20 being set by means of the actuator 28. The fact that the cross-sectional areas of the vent openings 26 increase in the driving direction 27 means that, during a displacement of the actuator 28, at first only a very narrow portion of the vent openings 26 and later a wider portion of the vent openings 26 is exposed in each case. As a result, the energy to be transmitted to the piston element 34 has a linear relationship with the displacement distance of the actuator 28.

[0035] The actuator 28 has an external thread 29 in engagement with the internal thread 24 and a bearing 30 for mounting the actuator 28 in the guiding portion 33 and also a further bearing 31 for mounting the actuator 28 in the further guiding portion 32. The external thread 29 is arranged between the bearing 30 and the further bearing 31 along the central axis A. A thread gap spacing between the external thread 29 and the internal thread 24 is approximately four times as great as a bearing gap spacing between the bearing 30 and the guiding portion 33 and/or a bearing gap spacing between the further bearing 31 and the further guiding portion 32. As a result, the external thread 29 and the internal thread 24 are subjected to less loading by forces and torques occurring during the combustion.

[0036] A flank angle between a front side 35 of the external thread 29 and/or the internal thread 24 and the central axis A is between 0? and 60?, preferably between 30? and 45?. A transition from the front side 35 to a thread base of the external thread 29 or to a thread back of the internal thread 24 is advantageously provided with a tree-root fillet.

[0037] In FIG. 6, an actuator 60 is depicted in a spatial view of a detail. The actuator 60 comprises a piston guide 61 and a slide 62, which is axially displaceable in relation to the piston guide 61, but during rotation of the piston guide 61 about a central axis A is turned with it. For this purpose, the piston guide 61 has two claws 63, which engage in two corresponding recesses 64 in the slide 62 for conjoint rotation but axially displaceably. In exemplary embodiments that are not shown, the piston guide is coupled with the slide by means of one, three, four, five or more claws. Advantageously, all of the claws come into engagement with the respective recesses at the same time, so that lateral forces on the slide are reduced. This simultaneous engagement is improved by the claws being designed as bending springs.

[0038] The piston guide 61 is for its part connected for conjoint rotation to an operating part 10 (FIG. 1) for conjoint rotation, so that the piston guide 61 at the same time forms a mechanical connection between the operating part 10 and the slide 62. The operating part 10 forms together with the piston guide 61 and the slide 62 the actuator 60 for varying the driving energy of the driving device.

[0039] The slide 62 has an external thread 65, which is formed so as to complement an internal thread of a combustion chamber housing (not shown), for example the internal thread 24 (FIG. 2). The external thread 65 does not have a thread runout, but instead ends abruptly with a scraping edge 66, which contributes to cleaning the combustion chamber of combustion residues when circumstances require. In order to allow or assist such combustion residues to be transported away, the external thread 65 has a number of transporting grooves 67 and also a number of transporting bores 68, which in each case run substantially parallel to the driving device. As a result, the actuator 60 remains easily adjustable when circumstances require.

[0040] The adjustment of the driving energy works for example as follows:

[0041] The slide 62 is screwed with its external thread 61 into the internal thread of the combustion chamber housing. Turning of the operating part, and consequently of the piston guide 61 and the slide 62, about the central axis A accordingly brings about a forcibly controlled axial shift of the slide 62. In preparation for a driving operation, the desired driving energy is set as an energy stage marked on the operating part by turning the operating part. This leads by way of the forced control described above to a corresponding axial positioning of the slide 62 in relation to the combustion chamber housing. As a result, any venting channels there may be are partially exposed over the through-opening (low driving energy, FIG. 3) or closed (maximum driving energy, FIG. 4).

[0042] The invention has been described with reference to a number of exemplary embodiments of a setting tool. It goes without saying that all the features of the individual exemplary embodiments can also be realized in a single device in any desired combination, as long as they are not mutually contradictory. It should also be noted that the invention is also suitable for other applications.