The present invention is directed to a combustion-operated setting device for driving fastening elements into a substrate, with a combustion chamber which has at least one combustion chamber outlet and in which a fuel gas mixture can be ignited for driving a driving piston guided in a piston guide, and with a locking and unlocking mechanism for unlocking the at least one combustion chamber outlet in the starting position of the driving piston and for locking the at least one combustion chamber outlet outside of the starting position of the driving piston. Setting devices of this kind can be operated by gaseous or liquid fuels that are burned in a combustion chamber and drive a driving piston for fastening elements.
In fuel-operated setting devices, e.g., with liquid-gas driving means, the piston is guided back to its initial or starting position at the combustion chamber after the ignition of the air-fuel mixture in the combustion chamber and the process triggered by this ignition for driving in the fastening element, during which the piston runs forward due to the combustion pressure. The setting device is ready to be used again for the next setting process only when the piston has returned to its starting position.
Conventionally, the piston is guided back by a thermal piston return. Shortly after combustion has taken place in the combustion chamber, the advancing piston runs past an exhaust port so that the combustion chamber pressure drops to atmospheric pressure. The pressure drops further due to the cooling of the combustion gases at the cylinder walls and a vacuum occurs in the combustion chamber which draws the piston back into its starting position. It is important that the combustion chamber remains tightly closed until the starting position of the piston to enable trouble-free functioning and for the piston to be drawn back into its starting position at the rear of the combustion chamber. If this is not the case and the combustion chamber opens before the piston has moved back completely, the vacuum is immediately canceled and the piston remains in an incorrect position. However, an opening of the combustion chamber after the setting process is also necessary to purge the exhaust gases from the combustion chamber.
DE10032310A1 provides a locking and unlocking mechanism which interrogates the displacement position of the piston to determine when it has reached its starting position again and to prevent premature opening of the combustion chamber. As soon as the locking and unlocking mechanism determines that the piston has reached its starting position again, an unlocking of the outlet valve is carried out to open and vent the combustion chamber.
The locking and unlocking mechanism is constructed as a piston feeler which senses the piston rod and can drop into the movement path of the piston rod when the piston is in its starting position at the combustion chamber. However, this is disadvantageous in that the piston feeler rubs against the piston rod during the return of the piston and accordingly impedes the return of the piston to its starting position.
In the setting device disclosed in U.S. Pat. No. 5,909,836, an opening of the combustion chamber is mechanically blocked by the actuation of the trigger switch (for triggering the setting device). Accordingly, the combustion chamber cannot be opened until the trigger switch is in its inoperative position again. The return movement of the trigger switch to the inoperative position and, therefore, the opening of the combustion chamber are delayed by a delay device until the piston has returned to its starting position completely within the delay time period. However, this solution is disadvantageous in that rapid operation is impossible because after every setting process it is necessary to wait until the delay time of the trigger switch expires before another setting process can be carried out.
It is the object of the present invention to develop a setting device which overcomes the aforementioned disadvantages. According to the invention, this object is met by a combustion-operated setting device for driving fastening elements into a substrate, with a combustion chamber which has at least one combustion chamber outlet and in which a fuel gas mixture can be ignited for driving a driving piston guided in a piston guide, and with a locking and unlocking mechanism for unlocking the at least one combustion chamber outlet in the starting position of the driving piston and for locking the at least one combustion chamber outlet outside of the starting position of the driving piston.
The locking and unlocking mechanism for unlocking the at least one combustion chamber outlet in the starting position of the driving piston has a magnet for detecting the driving piston in the starting position. By using a magnet in accordance with the invention for detecting the presence of the driving piston in its starting position, mechanical contact with the driving piston or its piston rod during the return of the piston can be prevented so that incorrect positions of the piston seldom occur.
In an advantageous embodiment of the invention, the locking and unlocking mechanism has a swivelable locking device cooperating with the magnet. In the starting position of the driving piston, the locking device is swiveled by the magnet into an unlocked position for the combustion chamber outlet, while it is in a locked position when the piston is not in its starting position. Through the use of a swivelable locking with a magnet, the locking and unlocking mechanism according to the invention can be constructed from very few parts (e.g., only two parts). A setting device according to the invention is therefore economical to produce.
The magnet is advantageously arranged directly at the locking device, cooperating with and magnetically attracting the head of the driving piston in the starting position of the driving piston. The magnetic attractive force on the head of the piston results in the advantage that the magnetic attractive force of the magnet acts in the direction of the piston return and therefore assists in a complete return.
An armature for the magnet is advantageously arranged at the side of the driving piston facing the combustion chamber; the magnet draws toward the armature in the starting position of the driving piston.
It is further advantageous when the locking device is constructed as a springing-elastic clip which is fastened at one of its ends to a structural component part of the setting device and is provided at its other, free end with a lock member which engages in a counter-lock in the locked position of the locking and unlocking mechanism to lock the combustion chamber outlet. The lock member and locking device are pretensioned or biased in a direction of the unlocked position by spring force, which acts counter to the magnetic attractive force of the magnet for the driving piston. A very simple, low-wear construction of the locking and unlocking mechanism can be achieved through this step.
When the combustion chamber outlet is constructed such that the combustion chamber wall can be lifted from the floor of the combustion chamber in the setting direction, a very simple construction of the locking and unlocking mechanism can be achieved such that one end of the locking device or clip is fastened to an end of the piston guide facing the combustion chamber and the counter-lock is arranged on the inside at the combustion chamber wall. By this step, a displacement of the combustion chamber wall relative to the piston guide can be prevented in the locked position of the device, while a displacement of the combustion chamber wall in the setting direction and, therefore, an opening of the combustion chamber outlet is possible when the locking device and lock member are swiveled out of the counter-lock.
It is also advantageous when the locking and unlocking mechanism is provided with means for compulsory unlocking by which the locking and unlocking mechanism can be moved manually into the unlocked position in case of an incorrect position of the piston.
This step is advantageous in that it is possible to vent the combustion chamber even when the incorrect position of the piston cannot be overcome directly.
In an advantageous construction for compulsory unlocking, the latter is carried out in that the combustion chamber wall is at least partly rotatable around the setting axis of the setting device. Due to the partial rotation of the combustion chamber wall around the setting axis, the lock member can be moved manually out of its position in which it engages behind the counter-lock arranged at the combustion chamber wall. In this way, compulsory unlocking is provided in a very simple manner.
Further advantages and steps of the invention are provided with reference to the drawings, wherein:
The setting device 10 according to the invention is shown in its starting or rest position in
In the present embodiment, an ignition unit (not shown in the drawing) is also provided in the combustion chamber 12 for igniting an air/fuel gas mixture introduced into the combustion chamber 12 for a setting process. A switching device, e.g., a trigger switch 32, is provided at a handle 33 of the setting device 10 for triggering a setting process after the setting device 10 is pressed against a substrate.
The combustion chamber 12 is formed by a combustion chamber wall 12.1 which is constructed as a sleeve 15 and which opens at the front into the piston guide 17. A rear wall 14 of the combustion chamber which closes the combustion chamber 12 at the rear is located at the rear end of the sleeve 15. A combustion chamber outlet 13 formed between the combustion chamber rear wall 14 and the sleeve 15, which is pushed forward slightly, is open in the starting position or rest position of the setting device 10, shown in
The combustion chamber 12 can be filled with fresh air and the propellant gas expelled through the combustion chamber outlet 13. The combustion chamber outlet 13 can be connected to an exhaust and/or air inlet of the setting device for this purpose.
Further, a locking and unlocking mechanism, designated in its entirety by 20, which will be described more fully in the following is arranged at the setting device 10. This locking and unlocking mechanism 20 includes a locking device 22, a counter-lock 25 and a magnet 21.
The counter-lock 25 for the locking device 22 which will be described more fully in the following with reference to
In
One end 22.1 of the locking device is fastened to the piston guide 17 at the end of the piston guide 17 facing the combustion chamber 12. As can be seen from
In
In
At the conclusion of the setting process, the setting piston 16 along with its head 16.1 and the armature 16.2 is drawn back again into its starting position 31 shown in
Compulsory unlocking of the combustion chamber outlet 13 is also possible as can be seen from
It remains to be noted that the combustion chamber outlet can also be constructed differently than shown herein. For example, it can be constructed as a valve which can be actuated by actuating means and which can be unlocked or locked by the locking and unlocking mechanism. Further, the locking device and the magnet could also be arranged in the area of the end of the piston or piston rod in the setting direction, for example.
Number | Date | Country | Kind |
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103 08 359 | Feb 2003 | DE | national |
Number | Name | Date | Kind |
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3967771 | Smith | Jul 1976 | A |
4074843 | Oesterle | Feb 1978 | A |
5213247 | Gschwend et al. | May 1993 | A |
5909836 | Shkolnikov et al. | Jun 1999 | A |
6247626 | MacVicar | Jun 2001 | B1 |
6679410 | Wursch et al. | Jan 2004 | B2 |
6843401 | Favre-Bulle | Jan 2005 | B2 |
Number | Date | Country | |
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20040232191 A1 | Nov 2004 | US |