Pyrotechnic drive device

Abstract

A drive device, comprising a hand-held housing, in which a piston element is arranged for delivering energy to a fastening element to be driven in a drive direction, a propellant charge, in particular a replaceable propellant charge, a combustion chamber arranged between the propellant charge and the piston element and extending around a central axis, and an actuator by means of which the energy to be transferred from the propellant charge to the piston element can be varied in such a way that the energy can be set, wherein the combustion chamber has an internal thread and a particularly cylindrical guide portion, wherein the actuator is arranged in the combustion chamber and has an external thread engaging with the internal thread and a bearing portion for mounting the actuator in the guide portion, wherein the thread gap spacing between the external thread and the internal thread is greater than the bearing gap spacing between the bearing portion and the guide portion.

Description

TECHNICAL FIELD

[0001] The invention relates to a drive device. BACKGROUND

[0002] The prior art discloses handheld drive devices with a propellant charge, wherein combustion gases generated after ignition of the pyrotechnic charge expand in a combustion chamber. The effect is that a piston is accelerated as an energy transmission means and drives a fastening element into a workpiece. Combustion residues can contaminate the combustion chamber.

[0003] US 6,321,968 B1 describes a drive device with a propellant charge, wherein the combustion chamber is divided into an upper sub-chamber and a lower sub-chamber by means of a perforated plate. The dead volume of the drive device can be adjusted in order to adjustably change the drive energy of the device. For this purpose, a slide similar to a valve can be adjusted in a direction perpendicular to the drive axis. In this case, the combustion chamber also has a dead volume when the slide is in the closed position, which dead volume is formed as a recess in the side wall of the combustion chamber. SUMMARY

[0004] The object of the invention is to provide a drive device which allows the drive energy to be easily set, if necessary over a wide range, with a given propellant charge.

[0005] According to one aspect, a drive device comprises a handheld housing, in which a piston element is arranged for delivering energy to a fastening element to be driven in a drive direction, a propellant charge, in particular a replaceable propellant charge, a combustion chamber arranged between the propellant charge and the piston element and extending around a central axis, and an actuator by means of which the energy to be transmitted from the propellant charge to the piston element can be changed in such a way that it can be set, wherein a ventilation channel connected to the combustion chamber can be exposed by means of a movable slide of the actuator, wherein the ventilation channel opens into the combustion chamber through a ventilation opening which can be partially or completely covered by the slide, and wherein the cross-sectional area of the ventilation opening increases in the drive direction. As a result, during displacement of the slide, first only a very narrow part of the ventilation opening is exposed, and then a wider part of the ventilation opening is exposed. This allows the set energy transmitted to the piston element to largely depend linearly on the displacement distance of the slide. Preferably, the ventilation opening is arranged in a cylindrical, in particular preferably circular cylindrical, portion of the combustion chamber.

[0006] An advantageous embodiment is characterized in that the drive device has a plurality of ventilation channels which each open into the combustion chamber through a ventilation opening and whose respective cross-sectional area increases in the drive direction.

[0007] According to a further aspect, a drive device comprises a hand-held housing, arranged in which is a piston element for delivering energy to a fastening element to be driven in a drive direction, a propellant charge, in particular a replaceable propellant charge, a combustion chamber arranged between the propellant charge and the piston element and extending around a central axis, and an actuator by means of which the energy to be transferred from the propellant charge to the piston element can be varied in such a way that it can be set, wherein the combustion chamber has an internal thread and a preferably cylindrical guide portion, wherein the actuator is arranged in the combustion chamber and has an external thread engaging with the internal thread and a bearing portion for mounting the actuator in the guide portion, wherein the thread gap spacing between the external thread and the internal thread is greater than the bearing gap spacing between the bearing portion and the guide portion. As a result, the forces and torques acting on the actuator during combustion in the combustion chamber are transmitted via the bearing portion to the guide portion, so that the external thread and the internal thread are relieved. The situation in which combustion residues resulting from combustion in the combustion chamber jam the actuator can be reduced, so that the actuator can still be adjusted relatively easily. Preferably, the thread gap spacing is at least twice, particularly preferably at least three times, the bearing gap spacing.

[0008] An advantageous embodiment is characterized in that the combustion chamber has a further guide portion which is preferably cylindrical, wherein the actuator has a further bearing portion for mounting the actuator in the further guide portion, wherein the thread gap spacing between the external thread and the internal thread is greater than a further bearing gap spacing between the further bearing portion and the further guide portion. Preferably, the external thread is arranged between the bearing portion and the further bearing portion along the central axis. Also preferably, the further bearing gap spacing is approximately the same size as the bearing gap spacing.

[0009] An advantageous embodiment is characterized in that the internal thread and / or the external thread do not have any thread tail.

[0010] An advantageous embodiment is characterized in that the internal thread and / or the external thread have one or more delivery grooves, in particular which extend parallel to the drive direction. A further advantageous embodiment is characterized in that the actuator has one or more delivery holes, in particular which extend parallel to the drive direction.

[0011] An advantageous embodiment is characterized in that a ventilation channel connected to the combustion chamber can be exposed by means of a movable slide of the actuator. A further advantageous embodiment is characterized in that a starting position of the piston element relative to the combustion chamber can be set by means of the actuator.

[0012] An advantageous embodiment is characterized in that the actuator comprises a threaded sleeve, preferably having a cylindrical inner wall.

[0013] It is generally preferred that the piston element is guided in a slide at least over a first portion of its movement. Depending on the detail design, the degree of exposure of the venting channel or the number of venting channels can be changed by adjusting the slide in axial direction and / or in circumferential direction.

[0014] For the purposes of the present invention, a venting channel is any space which can be selectively added to the volume of the combustion chamber by means of the setting element in order to change the drive energy in a defined manner by means of the additional expansion space. Preferably, but not necessarily, in this case the venting channel can be connected to an external space. As an alternative or in addition thereto, the venting channel can also have a dead volume which is not connected to an external space.

[0015] For the purposes of the present invention, drive energy is understood to mean the energy which is transferred to a given fastening element in the case of a given propellant charge. If these boundary conditions are specified, the resulting drive energy of the fastening element can be changed by means of the actuator in such a way that it can be set.

[0016] For the purposes of the present invention, a piston element is any device which is imparted kinetic energy by means of ignition of a charge, wherein the kinetic energy is ultimately transferred to a fastening element. The piston element usually takes the form of a piston, in particular a cylindrical piston. The piston head can be provided with recesses or other structures which further promote the turbulent flow and uniform expansion of the combustion gases.

[0017] For the purposes of the present invention, a central axis is an axis which is at least parallel to the movement of the fastening element and which passes through the centre of the combustion chamber. Preferably, the central axis passes both through the centre of the combustion chamber and through the centre of the fastening element.

[0018] For the purposes of the present invention, a fastening element is generally any fixture which can be driven in, such as a nail, a bolt or a screw.

[0019] It is generally advantageous for the slide to have an inner wall which is preferably cylindrical and which is formed as part of the combustion chamber. In the case of this arrangement, it is expedient for the slide also to serve to guide the piston element in the first portion of the movement of the piston.

[0020] In order to achieve easy and intuitive adjustment of the drive energy, the actuator has an operating part which can be pivoted about the central axis. The operating part can be any suitable means for manual adjustment, such as a rotatable sleeve, a pivotable knob or the like as particularly preferred variants. The pivotability of the operating part about the central axis has the effect that easy adjustment is achieved and at the same time effective visual monitoring of the set value is achieved. This arrangement allows easy adjustment even under adverse conditions such as wearing work gloves.

[0021] Pivoting the operating part about the central axis in this case means deflecting the operating part from the previous position and approximately perpendicular to the axis. The radius of curvature of the moment line or trajectory of the operating part in this case is preferably not smaller than the distance of the operating part from the central axis. Preferably, but not necessarily, the pivoting is a rotation about the central axis. In this case, the operating part and the slider are preferably connected together for common rotation, so that turning the operating part also turns and adjusts the slider at the same time, thereby adjusting the drive energy.

[0022] It is generally advantageous for the slider to have a collar which extends about the central axis and engages in the recess of the combustion chamber housing in an overlapping manner, wherein at least a portion of the ventilation channel is formed as a gap which extends axially between the collar and the combustion chamber housing. In this way, the result of the overlap is that a tight seal can be achieved even at greater gas pressures. In addition, the connection between the ventilation channel and the combustion chamber can be exposed directly at the charge-side end of the combustion chamber in such a way that the degree of exposure can be set, thereby allowing the drive energy to be adjusted over a greater range.

[0023] Further features and advantages of the present application will become apparent from the exemplary embodiments and from the dependent claims. Preferred exemplary embodiments of the present application are described below and explained in detail with reference to the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 An overall space view of a drive device according to the present application is shown.

[0025] Figure 2 A longitudinal section of a combustion chamber is shown.

[0026] Figure 3 A longitudinal section of a combustion chamber is shown when the actuator is in a low drive energy position.

[0027] Figure 4 A longitudinal section of a combustion chamber is shown when the actuator is in a high drive energy position.

[0028] Figure 5 A detail of a longitudinal section in Figure 4 is shown.

[0029] Figure 6 A space view of a detail of an actuator is shown. DETAILED DESCRIPTION

[0030] Figure 1 A drive device is shown in Fig. 1. The drive device comprises a hand-held housing 1 in which a piston element in the form of a piston is held. The 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 kinetically applied piston acts together with the end tappet on a fastening element (not shown), thereby driving the fastening element into the workpiece (to the right in the figure). In particular, the fastening element can be held in a magazine or cartridge (not shown), which is exchangeably attached in the forward holding area la of the drive device 1. Figure 1

[0032] In the present case, the charge is held in a sheet metal cartridge 4a. The cartridge 4a has an impact detonator, which is inserted into the cartridge support by a corresponding charge mechanism (in the present case by means of a cartridge strip 4) before ignition. The cartridge 4a and the cartridge support are then arranged rotationally symmetrical around a central axis A. In the present example, the central axis A is at the same time the central axis of the combustion chamber and the piston element.

[0033] Figure 2 The combustion chamber 20 is shown in Figures 1 to 3, which is formed by a combustion chamber housing 21. The combustion chamber 20 is arranged between the circular opening 22 of the cartridge support 23 and the surface of the piston (not shown). During combustion, the cartridge rests on the cartridge support and is closed there. In the combustion chamber housing 21, there is a multi-start internal thread 24 in the region of the combustion chamber 20. The combustion chamber 20 is connected to a plurality of ventilation channels 25, in particular two or three ventilation channels, which each open into the combustion chamber 20 by means of a ventilation opening 26. The cross-sectional area of each ventilation opening 26 increases in the drive direction 27. The ventilation openings 26 are arranged in a cylindrical portion of the combustion chamber 20. Furthermore, the combustion chamber 20 has a cylindrical guide portion 33 and a further guide portion 32. The internal thread 24 is arranged between the guide portion 33 and the further guide portion 32 along the central axis A.

[0034] In Figures 1 to 3, 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 a piston guide 28a. The energy to be transferred from the propellant charge to the piston element 34 is set by means of the actuator 28 in such a way that the ventilation channels 25 can be gradually exposed by means of the actuator 28 and additionally or alternatively by setting the starting position of the piston element 24 relative to the combustion chamber 20 by means of the actuator 28. The fact that the cross-sectional area of the ventilation openings 26 increases in the drive direction 27 means that, during displacement of the actuator 28, only a very narrow part of the ventilation openings 26 is initially exposed, and then a wider part of the ventilation openings 26 is exposed. As a result, the energy to be transferred to the piston element 34 has a linear relationship with the displacement distance of the actuator 28. Figure 3 Figure 4 Figure 5 In Figures 1 to 3, 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 a piston guide 28a. The energy to be transferred from the propellant charge to the piston element 34 is set by means of the actuator 28 in such a way that the ventilation channels 25 can be gradually exposed by means of the actuator 28 and additionally or alternatively by setting the starting position of the piston element 24 relative to the combustion chamber 20 by means of the actuator 28. The fact that the cross-sectional area of the ventilation openings 26 increases in the drive direction 27 means that, during displacement of the actuator 28, only a very narrow part of the ventilation openings 26 is initially exposed, and then a wider part of the ventilation openings 26 is exposed. As a result, the energy to be transferred to the piston element 34 has a linear relationship with the displacement distance of the actuator 28.

[0035] ​​​The actuator 28 has an outer thread 29 engaging the inner thread 24, a bearing portion 30 for mounting the actuator 28 in the guide portion 33, and a further bearing portion 31 for mounting the actuator 28 in the further guide portion 32. The outer thread 29 is arranged between the bearing portion 30 and the further bearing portion 31 along the central axis A. The thread clearance spacing between the outer thread 29 and the inner thread 24 is about four times the bearing clearance spacing between the bearing portion 30 and the guide portion 33 and / or the bearing clearance spacing between the further bearing portion 31 and the further guide portion 32. As a result, the outer thread 29 and the inner thread 24 are subjected to less force and torque loading during combustion.

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

[0037] In Figure 6 , details of the actuator 60 are depicted in a spatial view. The actuator 60 comprises a piston guide 61 and a slider 62, which is axially displaceable relative to the piston guide 61 but turns together with it during a rotation of the piston guide 61 about the central axis A'. For this purpose, the piston guide 61 has two claws 63, which engage in two corresponding recesses 64 in the slider 62 for co-rotation but axial displacement. In an exemplary embodiment not shown, the piston guide is coupled with the slider by one, three, four, five or more claws. Advantageously, all claws engage with the respective recesses at the same time, so that lateral forces on the slider are reduced. This simultaneous engagement is improved by designing the claws as curved springs.

[0038] The piston guide 61 itself is connected to the operating portion 10 Figure 1 in a co-rotating manner for co-rotation, so that the piston guide 61 simultaneously forms a mechanical connection between the operating portion 10 and the slider 62. The operating portion 10 together with the piston guide 61 and the slider 62 forms the actuator 60 for changing the drive energy of the drive device.

[0039] The slider 62 has an outer thread 65, which is formed as an inner thread, for example the inner thread 24 Figure 2) complementary. The outer thread 65 does not have a thread tail, but ends abruptly with a scraping edge 66, which facilitates cleaning of combustion residues from the combustion chamber if required. In order to allow or assist in the transport of such combustion residues away, the outer thread 65 has a plurality of transport grooves 67 and a plurality of transport holes 68, which in each case extend approximately parallel to the drive. As a result, the actuator 60 can still be easily adjusted if required.

[0040] The adjustment of the drive energy takes place, for example, as follows:

[0041] The outer thread 65 of the slider 62 is screwed into the inner thread of the combustion chamber housing. Rotating the operating part about the central axis A and thus the piston guide 61 and the slider 62 forces a controlled axial displacement of the slider 62, respectively. In preparation for a drive operation, the desired drive energy is set by rotating the operating part to the energy level marked on the operating part. This forces the slider 62 into the corresponding axial positioning relative to the combustion chamber housing by the forced control described above. As a result, any ventilation channels here can be partially exposed to the through opening (low drive energy, Figure 3 ) or closed (maximum drive energy, Figure 4 ).

[0042] The application has been described with reference to a number of exemplary embodiments of the installation tool. It goes without saying that all features of the individual exemplary embodiments can also be implemented in a single device in any desired combination, provided that the features do not contradict one another. It should be noted that the application is also applicable to other applications.

Claims

1. A drive apparatus, the drive apparatus comprising: a hand-held housing, in which a piston element is arranged for delivering energy to a fastening element to be driven in a drive 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 means of which the energy to be transferred from the propellant charge to the piston element can be changed in such a way that the energy can be set, wherein the combustion chamber has an inner thread and a guide portion, wherein the actuator is arranged in the combustion chamber and has an outer thread engaging with the inner thread and a bearing portion for mounting the actuator in the guide portion, wherein a thread gap spacing between the outer thread and the inner thread is greater than a bearing gap spacing between the bearing portion and the guide portion.

2. The drive apparatus of claim 1, wherein The thread gap spacing is at least twice as large as the bearing gap spacing.

3. The drive apparatus of claim 2, wherein The thread gap spacing is at least three times as large as the bearing gap spacing.

4. The drive apparatus of claim 1, wherein The propellant charge is a replaceable propellant charge.

5. The drive apparatus of claim 1, wherein The guide portion is cylindrical.

6. The drive apparatus of any one of claims 1 to 5, wherein, The combustion chamber has a further guide portion, wherein the actuator has a further bearing portion for mounting the actuator in the further guide portion, wherein a thread gap spacing between the outer thread and the inner thread is greater than a further bearing gap spacing between the further bearing portion and the further guide portion.

7. The drive apparatus of claim 6, wherein, The further guide portion is cylindrical.

8. The drive apparatus of claim 6, wherein The further bearing gap spacing is approximately the same size as the bearing gap spacing.

9. The drive apparatus of any one of claims 1 to 5, wherein, The inner thread and / or the outer thread has no thread tail.

10. The drive apparatus of any one of claims 1 to 5, wherein, The inner thread and / or the outer thread has one or more delivery grooves.

11. The drive apparatus of claim 10, wherein, The one or more delivery grooves extend parallel to the drive direction.

12. The drive apparatus of any one of claims 1 to 5, wherein, The actuator has one or more delivery holes.

13. The drive apparatus of claim 12, wherein, The one or more delivery holes extend parallel to the drive direction.

14. The drive apparatus of any one of claims 1 to 5, wherein, A ventilation channel connected to the combustion chamber can be exposed by a movable slide of the actuator.

15. The drive apparatus of any one of claims 1 to 5, wherein, The starting position of the piston element relative to the combustion chamber can be set by the actuator.

16. The drive apparatus of any one of claims 1 to 5, wherein, The actuator comprises a threaded sleeve.

17. The drive apparatus of claim 16, wherein, The threaded sleeve has a cylindrical inner wall.

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