PYROTECHNIC DRIVING TOOL

Abstract

A driving tool, comprising a handheld housing with a piston accommodated therein for transmitting energy to a fastening element to be driven in, a propellant charge for generating a gas pressure, a placing member that is able to be pressed against a workpiece, an in particular movable breech face for absorbing a recoil, and an ignition hammer that is movable relative to the breech face, wherein the ignition hammer is accelerated by means of at least one first spring against an igniter of the propellant charge, and wherein the spring is held in a tensioned state by a controllable holding member before the ignition hammer is accelerated, wherein the first spring is moved back into the held and tensioned state by the gas pressure after an ignition operation.

Claims

1. A driving tool, comprising a handheld housing with a piston accommodated therein, for transmitting energy to a fastener being driven-in in a driving direction; a propellant charge for generating gas pressure; pressure a contact element which can be pressed against a workpiece; a movable impact base for supporting a recoil; and a firing hammer which can be moved relative to the impact base, wherein the firing hammer is accelerated by at least one first spring against an igniter of the propellant charge, wherein the at least one first spring is retained in a tensioned state by a controllable retaining element before the acceleration of the firing hammer; and wherein the first spring is returned by the gas pressure to the retained and tensioned state after an ignition procedure.

2. The driving tool according to claim 1, wherein the impact base is moved counter to the driving direction by the gas pressure, and tensions the at least one first spring as a result.

3. The driving tool according to claim 1, wherein the tool has an impact base spring and force is applied to the impact base in the driving direction by the impact base spring.

4. The driving tool according to claim 1, wherein the retaining element comprises a spring-loaded locking catch.

5. The driving tool according to claim 1, wherein the at least one first spring is alternatively brought into the retained and tensioned state by the contact element being pressed.

6. The driving tool according to claim 1, wherein force is applied to the firing hammer in a direction of the igniter by a second spring.

7. The driving tool according to claim 6, wherein the second spring is moved into a tensioned state exclusively by the pressing of the contact element.

8. The driving tool according to claim 1, wherein movement of the firing hammer between an untensioned stop of the at least one first spring and a contact with the igniter comprises a free travel path.

9. The driving tool according to claim 6, wherein the second spring has a smaller spring constant than the at least one first spring.

10. The driving tool according to claim 2, wherein the tool has an impact base spring and force is applied to the impact base in the driving direction by the impact base spring.

11. The driving tool according to claim 2, wherein the retaining element comprises a spring-loaded locking catch.

12. The driving tool according to claim 3, wherein the retaining element comprises a spring-loaded locking catch.

13. The driving tool according to claim 2, wherein the at least one first spring is alternatively brought into the retained and tensioned state by the contact element being pressed.

14. The driving tool according to claim 3, wherein the at least one first spring is alternatively brought into the retained and tensioned state by the contact element being pressed.

15. The driving tool according to claim 4, wherein the at least one first spring is alternatively brought into the retained and tensioned state by the contact element being pressed.

16. The driving tool according to claim 2, wherein force is applied to the firing hammer in a direction of the igniter by a second spring.

17. The driving tool according to claim 3, wherein force is applied to the firing hammer in a direction of the igniter by a second spring.

18. The driving tool according to claim 4, wherein force is applied to the firing hammer in a direction of the igniter by a second spring.

19. The driving tool according to claim 5, wherein force is applied to the firing hammer in a direction of the igniter by a second spring.

20. The driving tool according to claim 6, wherein the second spring is moved into a tensioned state exclusively by the pressing of the contact element.

Description

[0020] Two embodiments of the invention are described and explained below in more detail with reference to the accompanying drawings.

[0021] FIG. 1 shows a schematic overall view of a driving tool according to the invention.

[0022] FIG. 2 shows a partial sectional view of a first embodiment of the invention in an untensioned state.

[0023] FIG. 3 shows the embodiment of FIG. 2 in a tensioned state with no workpiece contact.

[0024] FIG. 4 shows the embodiment of FIG. 2 in a tensioned state with workpiece contact.

[0025] FIG. 5 shows a partial sectional view of a second embodiment of the invention in an untensioned state.

[0026] FIG. 6 shows the embodiment of FIG. 5 in a tensioned state with no workpiece contact.

[0027] A driving tool according to the invention comprises a hand-held housing 1 in which a piston element in the form of a piston 2 is accommodated. A rear surface of the piston 2 defines a combustion chamber 3 in which the combustion gases of a pyrotechnic propellant charge 4 expand to accelerate the piston 2.

[0028] The piston 2 provided with kinetic energy in this manner strikes, with a ram on the end-face thereof, a fastener element (not shown), which is thereby driven into a workpiece.

[0029] The propellant charge 4 in this case is accommodated on a charge strip 5 with a plurality of cartridge-shaped charges (FIG. 3). The propellant charge 4 has an impact-sensitive igniter 4a in an edge region. Prior to ignition, a charge chamber 6 which adjoins the combustion chamber 3 is driven against the propellant charge 4 via a corresponding mechanism (see ignition-ready state in FIG. 4).

[0030] A contact element 7 which can slide relative to the housing 1 is arranged on the front end of the device and connected to the charge chamber 6. The contact element 7 is placed on the workpiece in the course of a driving operation and pushed-in a defined stroke H distance (see FIG. 5) against a spring force. As a result, inter alia, the charge chamber 6 is pushed back against the propellant charge 4.

[0031] The ignition occurs due to the impact of a firing hammer 8 accelerated against the igniter 4a of a propellant charge 4. In the present case, the firing hammer 8 is substantially formed as a pin which is mounted to allow movement parallel to a driving direction.

[0032] The firing hammer 8 is arranged in a central recess of an impact base 9 which is likewise movable parallel to the driving direction, wherein the firing hammer 8 is also movable relative to the impact base 9. A tip 8a of the firing hammer 8 can pass through a front opening of the impact base 9 and strike the igniter 4a.

[0033] The firing hammer 8 is supported with respect to the housing 1 by means of a first spring 10, and subjected to a force in the direction of the propellant charge 4. The first spring 10 is mounted on the front side in a sleeve 11, wherein the sleeve 11 is slidably guided on the impact base 9. A front stop 12 of the sleeve 11 on the impact base 9 defines a maximum untensioned position of the first spring 10. The stop 12 is positioned in such a manner that the firing hammer 8 still has a free travel path of about 2 mm until contact with the igniter 4a when the sleeve 11 comes to rest against the stop 12.

[0034] The impact base 9, in turn, is supported by an impact base spring 13 with respect to the housing 1. The first spring 10 is expediently arranged, from a structural point of view, concentrically within the impact base spring 13. A damper 14 made of elastic material is attached to a rear stop of the impact base 9.

[0035] The first spring 10 can be held in a tensioned position by means of a schematically-illustrated retaining element 15. The retaining element in the present case is designed as a spring retainer, wherein a detent 15a which can be moved perpendicular to the driving direction is subjected to force by means of a detent spring 15b. When the sleeve 11 of the spring 10 travels over a ramp of the detent 15a in the course of a tensioning movement, the detent 15a snaps over the edge of the sleeve 11 and holds the first spring 10 in the tensioned state.

[0036] The first spring 10 is released when the catch 15a is lifted. This can be done by a corresponding mechanism (not shown) by operating a trigger 16 of the driving tool, by an electromechanical actuator, or in another manner.

[0037] The invention works as follows:

[0038] Starting from an untensioned state of the first spring 10 (see FIG. 2), a first tensioning of the first spring 10 must be performed initially. In the present case, this is achieved by pressing-in the contact element 7 the distance of the stroke H. Accordingly, an increased force must be applied by the operator for the first setting operation and/or for the first spring tensioning.

[0039] FIG. 3 shows a position of the driving tool with tensioned first spring 10 and no contact with the workpiece. In the case of the first embodiment, with the first spring 10 tensioned, the firing hammer 8 is also held in a rear position together with the spring 10. The device is usually in this state during its use and between the setting operation.

[0040] To trigger a setting operation, the device is pressed against a workpiece and the contact element 7 is pushed in the distance of the stroke H, such that the propellant charge 4 and charge chamber 6 are brought together. This condition is shown in FIG. 4.

[0041] If the trigger 16 is then actuated, the retaining element 15 releases the first spring 10. This accelerates the firing hammer 8 forward in the direction of the igniter 4a, until the sleeve 11 reaches the stop 12 on the impact base 9. The firing hammer 8 then travels the last free distance without further acceleration and strikes the igniter 4a. A reliable ignition occurs according to the appropriate design of mass and speed of the firing hammer 8.

[0042] During the expansion of the combustion gases, the piston 2 is accelerated forward and the impact base 9 supporting the gas pressure is moved back against the impact base spring 13. The impact base 9 in this case carries the sleeve 11 with it, and tensions the first spring 10. By passing over the spring-loaded detent 15a, the first spring is returned to a tensioned and retained state without the operator needing to expend any force before the subsequent setting operation.

[0043] Depending on requirements, the first spring can be untensioned after completion of the work, for storage of the devicefor example, by firing a blank shot without a propellant charge.

[0044] In a second embodiment according to FIGS. 5 and 6, additional measures are taken to prevent an unintended activation of the propellant charge. For this purpose, a further, second spring 17 is configured on the firing hammer 8, which presses the firing hammer 8 forward, like the first spring 10. This ensures that the firing hammer is permanently held in its forward position even when the first spring is tensioned when the device is not in contact with a workpiece. Because the stop 12 is reached before the igniter 8 is struck, an unintentional release of the first spring would therefore not lead to an acceleration of the firing hammer or any other effect on the propellant charge 4.

[0045] FIG. 5 shows the second embodiment with the first spring 10 untensioned, and with no contact with a workpiece. FIG. 6 shows the state with no workpiece contact, when the first spring 10 is tensionedthat is, the typical state of use between two setting operations.

[0046] The second spring 17 is arranged concentrically within the first spring 10, and has a significantly smaller spring constant. As a result, it represents a negligible resistance to the operator when the device is pressed against a workpiece. The contribution of the second spring 12 to the acceleration of the firing hammer 8 is accordingly negligible, such that the second spring 17 only serves to position the firing hammer for safety reasons.

[0047] When the driving tool is pressed against a workpiece, the firing hammer is pushed backward against the second spring 17 via a mechanism (not shown) connected to the contact element. This state is not shown, but corresponds to the state of FIG. 4 with respect to the position of the components.

[0048] When the setting operation is initiated, the retaining element 15 releases the first spring 10, as in the first example. Via a mechanism which is not shown, the second spring 17 is released at the same time, such that the firing hammer 8 is accelerated forward by the springs 10, 17. As in the first example, the acceleration effected by the first spring 10 and the second spring 17 ends at the stop 12. The igniter is not subjected to acceleration over the subsequent free travel path of approx. 2 mm. Rather, it continues its movement only due to its inertia.