DRIVE-IN DEVICE WITH ADJUSTABLE COMBUSTION CHAMBER

Abstract

The invention relates to a drive-in device, comprising a drive-in piston which is guided in a cylinder for driving a nail element into a workpiece and comprising a combustion chamber which is arranged over the drive-in piston and which can be filled with a combustion gas, said combustion chamber comprising a cylindrical portion which is symmetrical about a central axis (A). A movable combustion chamber wall of the combustion chamber can be adjusted along the central axis (A), and a spring is supported between the movable combustion chamber wall and a housing. A force vector (F) of the spring has a lateral offset (V) with respect to the central axis (A).

Claims

1. A drive-in device, comprising a housing having a rear wall; a drive-in piston which is guided in a cylinder for driving a nail element into a workpiece; and a combustion chamber which is arranged over the drive-in piston and which can be filled with a combustion gas; the combustion chamber comprising a cylindrical portion which is symmetrical about a central axis (A), and a movable combustion chamber wall; wherein the movable combustion chamber wall of the combustion chamber can be adjusted along the central axis (A); and, a spring supported between the movable combustion chamber wall and the rear wall of the housing; the spring having a force vector (F) having a lateral offset (V) with respect to the central axis (A).

2. The drive-in device of claim 1, wherein the movable combustion chamber wall has a radius and the lateral offset (V) is at least equal to one tenth of the radius of the movable combustion chamber wall.

3. The drive-in device of claim 1, further comprising a mounting element, which is spring loaded and can be pushed in a direction of the central axis (A), arranged on the drive-in device, wherein the mounting element is connected to the movable combustion chamber wall by a linkage.

4. The drive-in device of claim 3, wherein the linkage is force decoupled in a direction perpendicular to the central axis (A).

5. The drive-in device of claim 4, wherein a force transmission point near the force decoupling is essentially arranged in line with the force vector (F) of the spring.

6. The drive-in device of claim 3, wherein the linkage comprises a movable adjusting rod, which passes through a passage in the combustion chamber and which is connected to the movable combustion chamber wall.

7. The drive-in device of claim 2, further comprising a mounting element, which is spring loaded and can be pushed in a direction of the central axis (A), arranged on the drive-in device, wherein the mounting element is connected to the movable combustion chamber wall by a linkage.

8. The drive-in device of claim 7, wherein the linkage is force decoupled in a direction perpendicular to the central axis (A).

9. The drive-in device of claim 8, wherein a force transmission point near the force decoupling is essentially arranged in line with the force vector (F) of the spring.

10. The drive-in device of claim 4, wherein the linkage comprises a movable adjusting rod, which passes through a passage in the combustion chamber and which is connected to the movable combustion chamber wall.

11. The drive-in device of claim 5, wherein the linkage comprises a movable adjusting rod, which passes through a passage in the combustion chamber and which is connected to the movable combustion chamber wall.

12. The drive-in device of claim 8, wherein the linkage comprises a movable adjusting rod, which passes through a passage in the combustion chamber and which is connected to the movable combustion chamber wall.

13. The drive-in device of claim 9, wherein the linkage comprises a movable adjusting rod, which passes through a passage in the combustion chamber and which is connected to the movable combustion chamber wall.

Description

[0013] In the following, a preferred exemplary embodiment of the invention is described and explained in detail by means of the attached drawings.

[0014] FIG. 1 shows a spatial global view of a drive-in device according to the invention with a section of the combustion chamber,

[0015] FIG. 2 shows a top view of components of the device of FIG. 1 from the side,

[0016] FIG. 3 shows a top view of components of the device of FIG. 1 from above,

[0017] FIG. 4 shows a sectional view of the combustion chamber of the device of FIG. 1 from the side, in a collapsed state,

[0018] FIG. 5 shows a sectional view of the combustion chamber of the device of FIG. 1 from the side, in a tensioned state.

[0019] The drive-in device of FIG. 1 is a handheld device, comprising a housing 1 and a combustion chamber 2 which is contained in the same, with a partially cylindrical combustion chamber wall. The combustion chamber 2 is adjoined by a cylinder 3 with a drive-in piston 4 which is guided in the same.

[0020] A safety mechanism of device comprises a mounting element provided by a mounting sleeve 5, which is mounted on a workpiece (not shown) and which is pushed against the pressure of a spring 8. Only in this state, the drive-in process may be activated by ignition of a combustion gas in the combustion chamber 2.

[0021] A swirl plate 6 is also arranged in the combustion chamber, which may be moved before an ignition by an adjusting rod 6a through the combustion chamber 2.

[0022] A movable combustion chamber wall 7 of the combustion chamber 2 is movable along an axis A coinciding with the drive-in direction, so that the volume of the combustion chamber is variable. The bottom 7 rests, to this end, with the spring 8, against a rear wall la of the outer housing 1. The spring 8 applies a force vector F upon the movable combustion chamber wall 7. The spring 8, which is a helical spring, is not concentric with respect to the axis A. The force vector F of spring 8 is parallel to axis A, although it radially acts, with an offset V with respect to central axis A, on the movable combustion chamber wall 7. The value of offset V in this case is equal to about 23% of the radius of movable combustion chamber wall 7 or combustion chamber 2.

[0023] The length of force vector F varies according to the respective tension of spring 8. The force vector F does not run beside the combustion chamber, but overlaps instead the cross section of combustion chamber 2 in the plane perpendicular to the central axis. The spring 8 rests directly against the rear side of the movable combustion chamber wall 7.

[0024] The movable combustion chamber wall 7 may be moved through the linkage 10 in the direction of axis, wherein both the linkage 10 and the adjusting rod 9 pass through a passage 10a or 9a in a second anterior bottom of the combustion chamber. The pushing in of the mounting sleeve 5 acts upon the linkage 10, which in turn displaces the movable combustion chamber wall 7 against the force of spring 8. In this way, a volume sufficient for ignition is formed in the combustion chamber. The linkage 10 and the adjusting rod 9 inside the combustion chamber run parallel to axis A, although laterally offset. The linkage 10 and the adjusting rod 9 are also laterally offset with respect to force vector F.

[0025] The adjusting rod 9 is part of the pressing system, which is connected from the movable combustion chamber wall 7 to the linkage 10, which in turn is connected to the mounting element. The mounting element 5 has a sleeve-like shape near its application point on the workpiece, and is concentric with respect to axis A. An integrally formed extension 5a laterally protrudes and supports the mounting element 5 in a force transmission point 11 against the linkage 10. In this force transmission point 11, a force of the mounting sleeve is transmitted, on one hand, only in a direction parallel to the central axis, and on the other hand, only in a direction towards the linkage. A clearance is present in the perpendicular direction in the force transmission point 11, so that in these directions, a force decoupling is present. The further linkage 10 has no force decoupling, and therefore transmits also moments.

[0026] The decoupling in the force transmission point 11 in particular allows the bolt guide to remain on the workpiece when the device recoils due to combustion. It also facilitates a simple construction of an adjusting element 12 in the area of the mounting element 5. By means of the adjusting element 12, the striking depth of the mounting element 5 may be adjusted.

[0027] In order to simplify the illustration, parts of linkage 10 are not shown in drawings. In particular, the adjusting rod 9 is connected to the bottom 7 in a torque-fixed way. The linkage 10 is connected, in turn, in a torque-fixed way, to the bottom 7. In order to have a low-torque support of the movable combustion chamber wall 7 by the spring 8 or the force vector F, the force vector is approximately or essentially positioned on a line with the force transmission point 11, which is parallel to the central axis.

[0028] In order to further reduce a maximum tilting moment acting on the movable combustion chamber wall 7, the position of the force vector F or spring 8 may also be finely tuned. This is performed considering further forces, which exert a moment on the movable combustion chamber wall 7.

[0029] Such further forces may be generated, for example, by an inlet and outlet valve 13, which is mechanically connected to the movable combustion chamber wall 7, a safety switch (not shown) or the spring of the swirl plate 6, which is preloaded by the linkage 10.

[0030] Normally, the various forces which generate a tilting moment on the movable combustion chamber wall 7, depend on the position of the movable combustion chamber wall 7 or on the respective operating condition. Therefore, in general, it is not always possible to obtain a complete compensation of all moments. In the invention, the position of the force vector F may however be selected so that the maximum tilting moments acting on the bottom are reduced during operation. In this way, a locking or friction of the movable combustion chamber wall 7 during its adjustment may be effectively reduced.