The present invention relates to clamping device for a saw, in particular a jigsaw, for releasably clamping and releasing a machining tool, in particular a saw blade, comprising a blocking element, a clamping element, a holding sleeve and an ejection element, wherein the clamping element comprises a recess on an inner surface area, the holding sleeve comprises a cannulation and the ejection element comprises a recess on an outer surface area.

A tool clamping device, in particular a saw-tool clamping device, for a portable power tool is already known from the European patent EP 0 814 934 B1. The tool clamping device in this case has a clamping unit for clamping-in a machining tool, which comprises at least one movably mounted release element, at least for transferring the clamping unit into a release position, at least one clamping element, for generating a clamping-in force acting on the machining tool, at least when the machining tool is in a state in which it is connected to the clamping unit, and at least one movement-arresting element, for arresting at least one movement capability of the release element in at least one state.

It is one objective of the present invention to provide an improved clamping device for a saw, in particular a jigsaw, for releasably clamping and releasing a saw blade.

There is proposed a clamping device for a saw, in particular a jigsaw, for releasably clamping and releasing a machining tool, in particular a saw blade, comprising a blocking element, a clamping element, a holding sleeve and an ejection element, wherein the clamping element comprises a recess on an inner surface area, the holding sleeve comprises a cannulation and the ejection element comprises a recess on an outer surface area.

According to the invention it is provided that the ejection element can be reversibly set in a first or second position relative to the clamping element and holding sleeve, whereby when the ejection element is arranged in the first position the clamping device is set in a locking state, in which the blocking element is arranged at least partially within the cannulation and the recess of the ejection element and thereby clamping the saw blade within in the clamping device, and when the ejection element is arranged in the second position the clamping device is set in a release state, in which the blocking element is arranged at least partially within the cannulation and the recess of the clamping element allowing the saw blade to be removed from the clamping device. It is thereby possible, that the ejection element is positioned inside the holding sleeve and the holding sleeve is positioned inside the clamping element. The holding sleeve is rotatable relative to the ejection element and rotatable relative to the clamping element.

In an advantageous configuration of the clamping device according to the invention it is provided that the clamping device comprises a torsion spring for applying a spring force to keep the ejection element in the first position. Hereby, a certain force has to be applied by an user of the clamping device to the torsion spring, in order to overcome the retention force of the torsion spring and to bring the ejection element from the first to the second position, so that an accidental and unwilling release of the saw blade can be avoided.

In another advantageous configuration of the clamping device according to the invention it is provided that the clamping device comprises an ejector spring for applying a spring force to the ejection element. Hereby, the ejection of the saw blade can be made easier, as the spring force of the ejector spring is pressing down onto the ejection element and forcing the saw blade out of the clamping device.

In yet another advantageous configuration of the clamping device according to the invention it is provided that that the blocking element is formed as a sphere. Due to the spherical form of the blocking element the correct orientation of the blocking element is always given. The blocking element can also be formed as a cylinder.

Further features and advantages of the invention are described in greater detail hereinafter by means of an embodiment by way of example with reference to the drawings. The terms "left",

"right", "top" and "bottom" used throughout the description relate to the drawings in an orientation with the references and Figure identifications being normally readable. In the Figures:

Fig. 1 a perspective view on a power tool in form of jig saw;

Fig. 2a a sectional side view on an inventive clamping device with a blocking element, a clamping element, a holding sleeve and an ejection element, whereby the ejection element is in a first position so that the clamping device is in a locking state;

Fig. 2b a sectional top view on an inventive clamping device with the blocking element, the clamping element, the holding sleeve and the ejection element, whereby the ejection element is in a first position so that the clamping device is in a locking state;

Fig. 3a a sectional side view on an inventive clamping device with the blocking element, the clamping element, the holding sleeve and the ejection element, whereby the ejection element is in a first position so that the clamping device is in a release state;

Fig. 3b a sectional top view on an inventive clamping device with the blocking element, the clamping element, the holding sleeve and the ejection element, whereby the ejection element is in a first position so that the clamping device is in a release state;

Fig. 4 a first end of a machining tool in form of a saw blade for inserting in the inventive clamping device;

Fig. 5 the clamping element in a side view;

Fig. 6 the clamping device in a top view with various section planes E-E, F-F and G-G;

Fig. 7 a sectional side view of the clamping element within the section plane E-E of Fig.

6;

Fig. 8 a sectional side view of the clamping element within the section plane F-F of Fig.

6;

Fig. 9 a sectional side view of the clamping element within the section plane G-G of Fig.

4; Fig. 10a a perspective view of a holding sleeve;

Fig. 10b another perspective view of the holding sleeve; Fig. 1 1 a sectional side view of the holding sleeve;

Fig. 12 another sectional side view of the holding sleeve; Fig. 13 another sectional side view of the holding sleeve; Fig. 14 a perspective view of an ejection element;

Fig. 15 a top view of the ejection element;

Fig. 16 a side view of the ejection element;

Fig. 17 another side view of the ejection element; and Fig. 18 another side view of the ejection element.

DETAILED DESCRIPTION OF THE INVENTION:

Figure. 1 shows a portable power tool, realized as a jigsaw, comprising an inventive clamping device. The portable power tool has a power-tool housing.

The power-tool housing encloses a drive unit of the portable power tool and a transmission unit of the portable power tool. The drive unit is in form of an electric motor. The transmission unit is in form of a gear box.

The drive unit and the transmission unit are provided to drive a machining tool, which is clamped-in in the clamping device, in an oscillatory manner. The clamping device is illustrated in figure 2a and 2b as well as in figure 3a and 3b.

The machining tool in this case is driven in an oscillatory manner substantially perpendicularly in relation to a machining movement direction of the portable power tool. The machining tool is realized as a saw blade, in particular a jigsaw blade. Figure 4 shows a connecting end of the machining tool. This connecting end of the machining tool can be clamped into the clamping device. It is also conceivable, however, for the machining tool to be constituted by a different machining tool, considered appropriate by persons skilled in the art.

The transmission unit has a driving-force-transmission element, realized as a lift rod, for driving the machining tool fixedly clamped by means of the clamping device. The clamping device in this case is arranged on the lift rod, or connected in respect of drive to the lift rod, in a manner already known to persons skilled in the art. The clamping device is thus provided to couple the machining tool to the lift rod for the purpose of oscillating drive. The machining tool thus executes a stroke motion along a stroke axis of the lift rod. In addition, the drive unit and/or the transmission unit are/is provided, in at least one operating mode of the portable power tool, to drive the machining tool with a pendulum action along a direction transverse to the stroke axis, in a manner already known to persons skilled in the art. In one operating state, therefore, the machining tool executes a pendulum-action stroke.

Figure 2a and 2b as well as in figure 3a and 3b show a detailed sectional side view of the clamping device. The clamping device comprises a clamping element, a holding sleeve and an ejection element.

Details of the clamping element are shown in the figures 5 to 9. The clamping element is basically formed as a conical sleeve with a first and second end. As seen in figure 5, a release lever is fixed to an outer surface of the clamping element. The release lever is projecting from the outer surface of the clamping element and serves for operating the clamping device and in particular the clamping element. Figure 7, 8 and 9 are showing several sectional views of the clamping element. The first end of the clamping element comprises an internal screw thread and serves to connect, i.e. screw, the clamping device to the holding sleeve. The second end of the clamping element comprises a receiving recess for receiving the connecting end of the machining tool. For this purpose, the second end of the clamping element is formed as a slot. Beyond that, the clamping element comprises a recess on an inner surface area. The recess on the inner surface of the clamping element could also be described as a cavity, a pit or a groove. As described later in more detail, this recess serves for partially holding a blocking element

Figure 10a to 13 illustrate details of the holding sleeve. The holding sleeve is in form of a graded cylinder with a first and second section and serves to hold the connecting end of the machining tool. The first section comprises an external thread and serves to be screwed onto the internal screw thread of the clamping element. Figure 2a to 3b show constellations wherein the holding sleeve and the clamping element are screwed to each other. The holding sleeve is thereby positioned inside the clamping element. The free end of the second section comprises two cavities positioned opposite to each other. These two cavities border on the machining tool, when the machining tool is clamped inside the clamping device. Also, the holding sleeve contains a longitudinal fillet projecting from an inner surface (cf. figure 10b). The fillet serves to fit into a slot-shaped cavity of the ejection element, when the ejection element is positioned inside the holding sleeve, in order to keep the ejection element orientated relative to the holding sleeve. Moreover, the holding sleeve contains a cannulation for partially receiving the blocking element.

As shown in figures 14 to 18, the ejection element is basically formed as a cylinder with a circular cross section area. The ejection element serves eject the machining tool from the clamping device. The ejection element contains a longitudinal groove extending along the outer surface of the ejection element. The longitudinal groove is formed to fit the fillet of the holding sleeve, when the ejection element is positioned inside the holding sleeve. Besides that, the ejection element also contains a slot-shaped cavity. This slot-shaped cavity serves to receive the connecting end of the machining tool. Also, the ejection element contains comprises a recess on an outer surface area for partially receiving the blocking element.

As shown in figures 2a to 3b, the ejection element is positioned inside the holding sleeve. As mentioned before, the fillet of the holding sleeve is fitted inside the slot-shaped cavity of the ejection element. The holding sleeve with the ejection element inside is again positioned inside the clamping element (cf. figures 2a to 3b). As mentioned before, the external thread of the holding sleeve is screwed onto the internal thread of the clamping element. The holding sleeve can be rotated relative to the clamping element and relative to the ejection element.

The blocking element is formed as a sphere (i.e. a ball) and positioned inside the cannulation of the holding sleeve. The blocking element is either partially positioned inside the recess of the clamping element (of. figure 2a and 2b) or partially inside the recess of the ejection element (of. figure 2a and 2b).

The clamping device also comprises a first spring and a second spring. The first spring is in form of a torsion spring and positioned in a cavity between the clamping element and the holding sleeve (of. figure 2a to 3b). This torsion spring serves to apply a spring force onto the clamping element and the holding sleeve, so that the spring force is to overcome if the clamping element and the holding sleeve are to be rotated relative to each other. The second spring is formed as an ejector spring and positioned between the top end of the ejection element and the lift rod (of. figure 2a to 3b). This ejection spring serves to apply a spring force to the ejection element and thereby forcing the machining tool out of the clamping device.

The clamping device can be reversible positioned in a locking state and a release state. When the clamping device is in the locking state, the machining tool (i.e. the saw blade) is positioned and hold (i.e. clamped) inside the clamping device. When the clamping device is in the release state, the machining tool can be inserted into or removed from the clamping device.

Figure 2a and 2b show the clamping device in the locking state. In the locking state the ejection element is in an upper position inside the holding sleeve. The ejection spring is compressed and the blocking element is partially positioned inside the cannulation of the holding sleeve and partially inside the recess of the ejection element. The inner surface area of the clamping element is pressing the blocking element towards and inside the recess of the ejection element. It is to be noticed that the recess of the clamping element is not in line with the cannulation of the holding sleeve and partially inside the recess of the ejection element. In this locking state the ejection element is not able to move downwards and is being blocked by the clamping element pushing the blocking element towards the ejection element. It is also to be noticed that in the locking state the receiving recess of the clamping element for receiving the connecting end of the machining tool is blocking the machining tool inside the clamping device. The machining tool can therefore not be removed from the clamping device. Also, during the locking state, the torsion spring is not in a compressed condition, so that no spring force is applied onto the clamping element or the holding sleeve. In order to bring the clamping device from the locking state into the release state, a user of the clamping device has to apply a force onto the clamping element and rotate the clamping element relative to the ejection element. The torsion spring positioned between the clamping element and the ejection element is applying a spring force onto the clamping element and the ejection element, so that the user has to overcome the spring force by compressing the torsion spring.

Figure 3a and 3b show the clamping device in the release state. In the release state the ejection element is in a lower position inside the holding sleeve. The ejection spring is relaxed (i.e. unstrung) and the blocking element is partially positioned inside the cannulation of the holding sleeve and partially inside the recess of the clamping element. The outer surface area of the ejection element is now pressing the blocking element towards and inside the recess of the clamping element. The recess of the ejection element is not in line with the cannulation of the holding sleeve and partially inside the recess of the clamping element. In this release state the ejection element is now being pushed by the ejection spring and able to move downwards as the ejection element is no longer blocked by the clamping element. It is also to be noticed that in the release state the receiving recess of the clamping element for receiving the connecting end of the machining tool is not blocking the machining tool inside the clamping device. The machining tool can therefore be removed from the clamping device or machining tool can be inserted into the clamping device. Also, during the release state, the torsion spring is in a compressed condition and applying a force onto the clamping element and the holding sleeve. A user has to overcome the spring force of the torsion spring, in order to keep the clamping device in the release state.