COMBUSTION GAS-DRIVEN DRIVING-IN DEVICE

Abstract

The invention relates to a driving-in device comprising a driving-in piston which is guided in a cylinder for driving a nail element into a workpiece and comprising a combustion chamber which is arranged on the driving-in piston and which can be filled with an ignitable combustion gas mixture. An overpressure of the combustion gas mixture can be generated in the combustion chamber by a charging element, and the driving-in piston is sealed against an inner wall of the cylinder by a first seal during the driving-in movement. The driving-in piston is sealed from the combustion chamber by a second seal, which is loaded axially to a piston axis (A), in a starting position.

Claims

1. A driving-in device, comprising a driving-in piston guided in a cylinder for driving a nail element into a workpiece, the cylinder having an inner wall; and a combustion chamber, which is fillable with an ignitable combustion gas mixture, arranged on the driving-in piston; wherein an overpressure of the ignitable combustion gas mixture can be generated in the combustion chamber wherein the driving-in piston is sealed on the inner wall of the cylinder by a first seal during a driving-in movement, and the driving-in piston is sealed in a starting position in relation to the combustion chamber by a second seal, which is loaded axially in relation to a piston axis (A).

2. The driving-in device as claimed in claim 1, wherein the second seal consists of a polymer.

3. The driving-in device as claimed in claim 1, wherein the driving-in piston is held in the starting position by a piston holder.

4. The driving-in device as claimed in claim 3, wherein the piston holder comprises a magnetic holding element.

5. The driving-in device as claimed in claim 1, wherein the second seal presses against a spring-elastic screen on a combustion chamber side.

6. The driving-in device as claimed in claim 1, wherein the second seal is fixed in place in relation to the combustion chamber.

7. The driving-in device as claimed in claim 1, wherein the second seal is fixed in place in relation to the driving-in piston.

8. The driving-in device as claimed in claim 1, wherein the second seal is arranged in a dovetail guide of the piston.

9. The driving-in device of claim 1, wherein the overpressure of the ignitable gas mixture is generated in the combustion chamber by a charging element.

10. The driving-in device of claim 3, wherein the piston holder exerts a defined minimum holding force in the direction of the piston axis (A) on the driving-in piston.

11. The driving-in device as claimed in claim 2, wherein the driving-in piston is held in the starting position by a piston holder.

12. The driving-in device as claimed in claim 11, wherein the piston holder comprises a magnetic holding element.

13. The driving-in device as claimed in claim 2, wherein the second seal presses against a spring-elastic screen on a combustion chamber side.

14. The driving-in device as claimed in claim 3, wherein the second seal presses against a spring-elastic screen on a combustion chamber side.

15. The driving-in device as claimed in claim 4, wherein the second seal presses against a spring-elastic screen on a combustion chamber side.

16. The driving-in device as claimed in claim 2, wherein the second seal is fixed in place in relation to the combustion chamber.

17. The driving-in device as claimed in claim 3, wherein the second seal is fixed in place in relation to the combustion chamber.

18. The driving-in device as claimed in claim 4, wherein the second seal is fixed in place in relation to the combustion chamber.

19. The driving-in device as claimed in claim 5, wherein the second seal is fixed in place in relation to the combustion chamber.

20. The driving-in device as claimed in claim 2, wherein the second seal is fixed in place in relation to the driving-in piston.

Description

[0015] Several preferred exemplary embodiments of the invention are described hereafter and explained in greater detail on the basis of the appended drawings.

[0016] FIG. 1 shows a schematic sectional view of a driving-in device according to the invention of a first exemplary embodiment of the invention.

[0017] FIG. 2 shows a detail view of the driving-in device from FIG. 1 before the triggering of a driving-in procedure.

[0018] FIG. 3 shows the driving-in device from FIG. 2 during a driving-in procedure.

[0019] FIG. 4 shows a detail view of a driving-in device according to a second exemplary embodiment of the invention during a driving-in procedure.

[0020] The driving-in device from FIG. 1 is a handheld device, comprising a housing 1 and a combustion chamber 2 accommodated therein having a combustion chamber wall. A cylinder 3 having a driving-in piston 4 guided therein adjoins the combustion chamber 2. The driving-in piston 4 comprises a driving-in tappet 5 for driving a nail element (not shown) into a workpiece.

[0021] An ignitable combustion gas mixture is introduced in the present case by means of a combustion gas store 6 and in particular a fresh air inlet (not shown) into the combustion chamber 2. The combustion gas mixture is compressed to an overpressure in this case by means of a charging element 7. The charging element is, for example, designed as an electrically driven compressor supplied via a rechargeable battery 8, which is arranged as an integral component of the driving-in device inside the housing 1. In further embodiments, the charging element is a device separate from the driving-in device. In other embodiments, a charging can also take place by means of a reset of the driving-in piston 4, which is driven in particular by combustion, or in another manner.

[0022] The combustion gas is introduced via a metering valve 9 from the combustion gas store 6 into the air of the combustion chamber 2. The combustion gas injection can take place depending on the requirements into the still uncompressed, partially compressed, or also completely compressed air. In the completely reset state (see FIG. 2), the driving-in piston 4 is held by a piston holder in the form of a magnetic holder 10 against the overpressure in the combustion chamber.

[0023] With charged combustion chamber, via a hand-actuated trigger 11, an ignition of the combustion gas mixture can be triggered, for example, via a spark plug, and therefore the driving-in piston 4 is driven forward and drives the nail element (not shown) from a magazine 12 into the workpiece via the driving-in tappet 5. The exhaust gases of the ignited and expanded combustion gas can enter the exterior at the end of the path of the driving-in piston via outlet openings 13.

[0024] To ensure a sufficient seal of the system, a first seal 14 is provided on the driving-in piston 4, which is supported radially in relation to a piston axis A of the driving-in piston against the inner wall of the cylinder 3. This first seal 14 can consist, for example, of a metal or a hard, thermally and mechanically high-strength plastic such as Torlon (polyamide imide). During the driving-in movement of the driving-in piston 4, the seal slides on the cylinder wall. Because of the short duration of the driving-in procedure, only a relatively moderate leak-tightness of the first seal is required to ensure a sufficiently small pressure loss during the acceleration of the driving-in piston.

[0025] To additionally ensure a sufficient sealing of the combustion chamber volume under overpressure before an ignition of the combustion gas mixture, a second seal 15 is moreover provided between the driving-in piston 4 and an outlet opening 16 of the combustion chamber 2.

[0026] The second seal 15 is preferably formed as an O-ring made of an elastomer and is loaded in the axial direction with respect to the piston axis A by the driving-in piston 4. The second seal 4 is accommodated on a bottom of the driving-in piston 4, for example, in a ring groove.

[0027] A sealing surface for the second seal 15 opposite to the bottom of the driving-in piston 4 is formed in the present case by a screen 16, which forms an outlet opening 17 of the combustion chamber 2. The outlet opening 17 has a smaller diameter than the cylinder 3, and the second seal 15 has a smaller diameter than the first seal 14.

[0028] The screen 16 is formed from a defined spring-elastic plate, which is connected in a fixed manner to an extension of the combustion chamber wall. Permanent magnets 10, which form the piston holder for the driving-in piston in the form of a magnetic holder, are arranged on the side of the screen 16 opposite to the driving-in piston 4.

[0029] The invention functions as follows:

[0030] In the starting position of the driving-in piston 4 according to FIG. 2, an axially oriented holding force is exerted on the driving-in piston 4 by the magnets 10, which is substantially greater than an opposing force exerted by the overpressure in the combustion chamber. In this case, the second seal 15 is pressed by the driving-in piston 4 against the spring-elastic screen 16. The elasticity and/or deformability of the screen 16 improves a secure hold by the magnetic forces and simultaneously prevents an overload of the seal 15.

[0031] In this state, an overpressure can be applied to the combustion chamber, wherein a reliable sealing in relation to the exterior is provided by the second seal 15. An arbitrarily long time can pass in principle between the charging and the ignition, in which an operator optimizes the driving-in device in its position or waits for other reasons.

[0032] After triggering of the ignition, the holding force of the magnetic holder 10 is overcome by the rising pressure and the driving-in piston is accelerated in the direction of the nail element (see FIG. 3). During this procedure, the expanding combustion gas is only sealed via the first seal 14 in relation to the exterior. In the present example, the second seal 15 is moved along with the driving-in piston, since it is arranged fixed in place thereon. This enables easy maintenance of the seal after removal of the driving-in piston. Under certain circumstances, the achievable energy and thus the driving-in energy of the driving-in piston are increased by the holding back thereof.

[0033] In the second exemplary embodiment of the invention shown in FIG. 4, the second seal 15, in contrast to the first exemplary embodiment, is located fixed in place on the cylinder side of the screen 16. This has the advantage, inter alia, that the seal is subjected less to the hot combustion gas stream.