PYROTECHNIC DRIVETABLE

Description

[0001] The invention relates to a driving tool.

[0002] Hand-held driving tools with propellant charges are known from the prior art. After the ignition of a pyrotechnic charge, the resulting combustion gases expand in a combustion chamber. This accelerates a piston, which acts as an energy transfer medium and drives a fastener into a workpiece. Combustion residues can contaminate the combustion chamber.

[0003] US 6,321,968 B1 describes a driving tool with a propellant charge, in which the combustion chamber is separated into an upper and a lower chamber by a perforated disc. The driving tool has an adjustable dead space volume to adjust the driving energy of the tool. For this purpose, a valve-like slide can be adjusted in a direction perpendicular to a driving axis. Even when the slide is in the closed position, the combustion chamber has a dead space formed as a recess in a side wall of the combustion chamber. A driving tool according to the preamble of claim 1 is known from EP 2 923 797 A1.

[0004] It is the object of the invention to provide a driving tool which enables a simple adjustment of a driving energy, if necessary over the widest possible range for a given propellant charge.

[0005] According to one aspect, a driving tool comprises a hand-held housing with a piston member arranged therein for transmitting energy to a fastening element to be driven in a driving direction, a propellant charge, in particular an exchangeable propellant charge, and a combustion chamber arranged between the propellant charge and the piston member, which extends around a central axis, and an actuator, by means of which the energy to be transmitted from the propellant charge to the piston member can be adjustably changed, wherein a blow-off channel connected to the combustion chamber can be released by means of a movable slide of the actuator, wherein the blow-off channel opens into the combustion chamber with a blow-off opening, which can be partially or completely covered by the slide, and wherein a cross-sectional area of ​​the blow-off opening widens in the driving direction.As a result, during a slide movement, initially only a very narrow section of the blow-off opening is exposed, followed later by a wider section. This enables a largely linear dependence of the set energy to be transferred to the piston member on the slide's displacement. The blow-off opening is preferably arranged in a cylindrical, particularly preferably circular-cylindrical, section of the combustion chamber.

[0006] An advantageous embodiment is characterized in that the driving device has a plurality of blow-off channels, each of which opens into the combustion chamber with a blow-off opening and each has a cross-sectional area that widens in the driving direction.

[0007] According to a further aspect, a driving tool comprises a hand-held housing with a piston member arranged therein for transmitting energy to a fastening element to be driven in a driving direction, a preferably exchangeable propellant charge and a combustion chamber arranged between the propellant charge and the piston member, which extends around a central axis, and an actuator, by means of which the energy to be transmitted from the propellant charge to the piston member can be adjustably changed, wherein the combustion chamber has an internal thread and a preferably cylindrical guide section, wherein the actuator is arranged in the combustion chamber and has an external thread engaging with the internal thread and a bearing for mounting the actuator in the guide section, wherein a thread gap distance between the external thread and the internal thread is greater than a bearing gap distance between the bearing and the guide section.As a result, forces and torques acting on the actuator during combustion in the combustion chamber are transferred via the bearing to the guide section, thus relieving the external and internal threads. Combustion residues resulting from combustion in the combustion chamber may contribute less to jamming of the actuator, allowing the actuator to remain smoothly adjustable. The thread gap spacing is preferably at least twice as large, and particularly preferably at least three times as large, as the bearing gap spacing.

[0008] An advantageous embodiment is characterized in that the combustion chamber has a preferably cylindrical additional guide section, wherein the actuator has an additional bearing for mounting the actuator in the additional guide section, wherein a thread gap distance between the external thread and the internal thread is greater than a further bearing gap distance between the additional bearing and the additional guide section. Preferably, the external thread is arranged along the central axis between the bearing and the additional bearing. Likewise, the additional bearing gap distance is preferably substantially as large as the bearing gap distance.

[0009] An advantageous embodiment is characterized in that the internal thread and / or the external thread has no thread runout.

[0010] An advantageous embodiment is characterized in that the internal thread and / or the external thread has one or more transport grooves, which run in particular parallel to the driving direction. A further advantageous embodiment is characterized in that the actuator has one or more transport bores, which run in particular parallel to the driving direction.

[0011] An advantageous embodiment is characterized in that a blow-off channel connected to the combustion chamber can be opened by means of a movable slide of the actuator. A further advantageous embodiment is characterized in that a starting position of the piston member relative to the combustion chamber can be adjusted by means of the actuator.

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

[0013] Generally, the piston member is preferably guided in the slide at least over a first portion of its movement. Depending on the detailed design, variable opening of the blow-off channel or multiple blow-off channels can be achieved by adjusting the slide in an axial direction and / or in a circumferential direction.

[0014] A blow-off duct within the meaning of the invention is any space that can be selectively added to the combustion chamber volume by the adjusting element in order to define a change in the driving energy via the additional expansion space. Preferably, but not necessarily, the blow-off duct can be connected to an external space. Alternatively or additionally, the blow-off duct can also be a dead space volume that is not connected to an external space.

[0015] For the purposes of the invention, driving energy is understood to be the energy transferred to a given fastener with a given propellant charge. By specifying these boundary conditions, the actuator allows the resulting driving energy of the fastener to be adjusted.

[0016] A piston element, within the meaning of the invention, is any element that is imparted with kinetic energy by the ignition of the charge, with the kinetic energy ultimately being transferred to the fastening element. The piston element is often designed as a cylindrical piston. Recesses or other structures can be provided in the piston crown to further promote swirling and uniform expansion of the combustion gases.

[0017] A central axis within the meaning of the invention is an axis that is at least parallel to the movement of the fastening element and that runs through a center of the combustion chamber. Preferably, the central axis runs through both the center of the combustion chamber and a center of the fastening element.

[0018] A fastening element within the meaning of the invention is generally understood to mean any drivable anchor, such as a nail, bolt or screw.

[0019] Generally advantageously, the slide has a preferably cylindrical inner wall, which is formed as part of the combustion chamber. With such an arrangement, the slide also expediently serves to guide the piston member during a first section of the piston movement.

[0020] To achieve simple and intuitive adjustment of the driving energy, the actuator has an operating element that can be pivoted around its central axis. The operating element can be any suitable means for manual adjustment, such as a rotatable sleeve (the particularly preferred variant), a pivoting knob, or similar. The pivoting of the operating element around its central axis allows for simple adjustment while simultaneously allowing effective visual control of the set value. This arrangement also enables easy adjustment even under adverse conditions, such as when wearing work gloves.

[0021] Pivoting the control element around the central axis means deflecting the control element from a previous position, essentially perpendicular to the axis. A line of movement or trajectory of the control element has a radius of curvature that is preferably no smaller than the distance of the control element from the central axis. Preferably, but not necessarily, the pivoting is a rotation around the central axis. The control element and the slider are preferably connected in a rotationally fixed manner, so that rotating the control element simultaneously rotates and adjusts the slider to regulate the driving energy.

[0022] It is generally advantageous for the slide to have a collar surrounding the central axis, which overlaps and engages a recess in a combustion chamber housing, with at least part of the blow-off channel being designed as an axially extending recess between the collar and the combustion chamber housing. Due to the overlap, a high degree of tightness can be achieved, even against high gas pressures. Furthermore, a connection between the blow-off channel and the combustion chamber can be opened in an adjustable manner directly at a charge-side end of the combustion chamber, which enables adjustability over a wide range of driving energy.

[0023] Further features and advantages of the invention will become apparent from the exemplary embodiment and the dependent claims. A preferred embodiment of the invention is described below and explained in more detail with reference to the accompanying drawings. Fig. 1 shows a spatial overall view of a driving tool according to the invention. Fig. 2 shows a longitudinal section of a combustion chamber. Fig. 3 shows a longitudinal section of a combustion chamber with an actuator in a position for a low driving energy. Fig. 4 shows a longitudinal section of a combustion chamber with an actuator in a position for a high driving energy. Fig. 5 shows a detail of the longitudinal section in Fig. 4 . Fig. 6 shows a spatial detailed view of an actuator.

[0024] In Fig. 1 A driving device is shown. The driving device comprises a hand-held housing 1 in which a piston member in the form of a piston is housed. A surface of the piston defines a combustion chamber in which the combustion gases of a pyrotechnic charge expand to accelerate the piston.

[0025] The piston, thus subjected to kinetic energy, hits a fastening element (not shown) with a tappet at its end, which is thereby driven into a workpiece (in Fig. 1 to the right). The fastening element can in particular be accommodated in a module or magazine (not shown) that is replaceably attached in a front holding area 1a of the driving tool 1.

[0026] In this case, the charge is contained in a cartridge 4a made of sheet metal. The cartridge 4a has an impact igniter and, before ignition, is inserted into a cartridge chamber via a corresponding loading mechanism, in this case by means of a magazine strip 4. The cartridge 4a and the cartridge chamber are then arranged rotationally symmetrically around a central axis A. In the present examples, the central axis A is also a central axis of the combustion chamber and the piston member.

[0027] In Fig. 2 a combustion chamber 20 is shown, 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 combustion, the cartridge rests against the cartridge bearing and is chambered there. In the combustion chamber housing 21, in the area of ​​the combustion chamber 20, there is a multi-start internal thread 24. Connected to the combustion chamber 20 are several, in particular two or three, blow-off channels 25, each of which opens into the combustion chamber 20 via a blow-off opening 26. A cross-sectional area of ​​each blow-off opening 26 widens in the driving direction 27. The blow-off openings 26 are arranged in a circular-cylindrical section of the combustion chamber 20. Furthermore, the combustion chamber 20 has a circular-cylindrical guide section 33 and a further guide section 32.The internal thread 24 is arranged along the central axis A between the guide section 33 and the further guide section 32.

[0028] In the Fig. 3, 4 and 5The 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. By means of the actuator 28, the energy to be transferred from the propellant charge to a piston member 34 can be adjusted by gradually opening the blow-off channels 25 by means of the actuator 28 and by additionally or alternatively adjusting a starting position of the piston member 34 relative to the combustion chamber 20 by means of the actuator 28. Because the cross-sectional areas of the blow-off openings 26 widen in the driving direction 27, during a displacement of the actuator 28, initially only a very narrow section of the blow-off openings 26 is opened, and later a wider section of the blow-off openings 26 is opened. The energy to be transferred to the piston member 34 is thus linearly related to the displacement path of the actuator 28.

[0029] The actuator 28 has an external thread 29 engaging with the internal thread 24 and a bearing 30 for supporting the actuator 28 in the guide section 33, as well as a further bearing 31 for supporting the actuator 28 in the further guide section 32. The external thread 29 is arranged along the central axis A between the bearing 30 and the further bearing 31. A thread gap distance between the external thread 29 and the internal thread 24 is approximately four times as large as a bearing gap distance between the bearing 30 and the guide section 33 and / or a bearing gap distance between the further bearing 31 and the further guide section 32. As a result, the external thread 29 and the internal thread 24 are less stressed by forces and torques occurring during combustion.

[0030] 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 root of the external thread 29 or to a thread ridge of the internal thread 24 is advantageously provided with a tree root fillet.

[0031] In Fig. 6 an actuator 60 is depicted in a three-dimensional detailed view. The actuator 60 comprises a piston guide 61 and a slide 62, which is axially displaceable relative to the piston guide 61, but is rotated when the piston guide 61 rotates about a central axis A'. For this purpose, the piston guide 61 has two claws 63, which engage in two corresponding recesses 64 in the slide 62 in a rotationally fixed but axially displaceable manner. In embodiments not shown, the piston guide is coupled to the slide by means of one, three, four, five or more claws. Advantageously, all claws engage with the respective recesses simultaneously, so that lateral forces on the slide are reduced. This simultaneous engagement is improved by designing the claws as spiral springs.

[0032] The piston guide 61 is in turn connected to an operating part 10 ( Fig. 1 ) are connected in a rotationally fixed manner, so that the piston guide 61 simultaneously forms a mechanical connection between the operating part 10 and the slide 62. The operating part 10, together with the piston guide 61 and the slide 62, forms the actuator 60 for changing the driving energy of the tacker.

[0033] The slide 62 has an external thread 65 which is complementary to an internal thread of a combustion chamber housing (not shown), for example to 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 may contribute to cleaning the combustion chamber of combustion residues. To enable or facilitate the removal of such combustion residues, the external thread 65 has several transport grooves 67 and several transport bores 68, each of which runs essentially parallel to the driving direction. This allows the actuator 60 to remain smoothly adjustable under certain circumstances.

[0034] The adjustment of the driving energy works, for example, as follows: The slide 62 is screwed with its external thread 65 into the internal thread of the combustion chamber housing. A rotation of the operating part, and thus of the piston guide 61 and the slide 62, about the central axis A, causes a positively controlled axial displacement of the slide 62. In preparation for a driving operation, the desired driving energy is set as an energy level marked on the operating part by rotating the operating part. This leads, via the positive control described above, to a corresponding axial positioning of the slide 62 relative to the combustion chamber housing. This partially opens any blow-off channels that may be present via the passage (low driving energy, Fig. 3 ) or closed (maximum driving energy, Fig. 4 ).

[0035] The invention has been described using several exemplary embodiments of a setting tool. It is understood that all features of the individual exemplary embodiments can also be implemented in a single device in any combination, provided they do not contradict each other.

Claims

1. Driving device, comprising a hand-held housing (1) with a piston element (34) arranged therein for the transmission of energy to a fastening element to be driven in a driving direction (27), a propellant charge, in particular an exchangeable propellant charge, and a combustion chamber (20), which is arranged between the propellant charge and the piston element (34) and extends around a central axis (A), and an actuator (60), by means of which the energy to be transmitted from the propellant charge to the piston element (34) can be varied in such a way that it can be set, wherein a venting channel (25) connected to the combustion chamber (20) can be exposed by means of a movable slide (62) of the actuator (60), characterized in that the venting channel (25) opens out into the combustion chamber (20) by way of a vent opening (26), which can be partially or completely covered by the slide (62), and wherein a cross-sectional area of the vent opening (26) increases in the driving direction (27).

2. Driving device according to Claim 1, wherein the driving device has a number of venting channels (25), which respectively open out into the combustion chamber (20) by way of a vent opening (26) and have in each case a cross-sectional area which increases in the driving direction (27).

3. Driving device according to either of the preceding claims, wherein the vent opening (26) is arranged in a cylindrical, in particular circular-cylindrical, portion of the combustion chamber (20).