Patent Application
20090133889
1. Field of the Invention
The present invention relates to a hand-held power tool with an auxiliary handle having a clamping band and, in particular, to a hammer drill.
2. Description of the Prior Art
Usually, an auxiliary handle is secured on a cylindrical locking flange of a power tool with a clamp, a clamping yoke, or a clamping band. Often, on the auxiliary handle, there is also provided a depth stop in form of a rigid, displaceably securable bar.
European Publication EP 0 132 593 discloses an auxiliary handle securable on a locking flange of a hand-held power tool with a loop-shaped clamping band. The clamping band is tensioned by a locking screw upon rotation of a hand grip. The auxiliary handle has a head that is formlockingly adapted to the locking flange and, with the auxiliary handle secured in a predetermined manner, is positioned relative to the rotational axis of the power tool. Additionally, a depth stop is formlockingly and displaceably secured in the auxiliary handle. The clamping band loop is displaced over V-shaped guide surfaces of the head. This can lead to loosening of the locking screw which is formlockingly received in receiving openings provided in the ends of the clamping band which are guided along the head upon a wider opening of the clamping band loop.
German Publication DE 10 2005 057 269 discloses an auxiliary handle with a clamping yoke having a partially circumferential guide web that axially formlockingly engages in a circumferential guide groove provided on the associated cylindrical locking flange of a hand-held power tool. The end surface of the clamping yoke is provided with recesses in which circumferentially distributed noses tangentially formlockingly engage. As a result, the locked auxiliary handle is completely formlockingly secured, in addition to being frictionally secured.
The object of the present invention is to provide a hand-held power tool having an auxiliary handle that can be completely formlockingly secured on the hand-held power tool in a manner suitable for use in constructional industry.
This and other objects of the present invention, which will become apparent hereinafter are achieved by providing a hand-held power tool having an auxiliary handle securable on the locking flange of the power tool and having a head positioned relative to an operational axis, a loop-shaped clamping band located in the head and guided therein, at least one, radially inwardly projecting cam provided on the clamping band and formlockingly engageable in an associated recess formed in the locking flange, and means for manually tensioning the clamping band. The radially inwardly projecting cam provides for a formlocking attachment of the auxiliary handle to the locking flange, in addition to frictional locking.
Advantageously, the auxiliary handle has a plurality of radially inwardly projecting cams offset relative to each other along a clamping band loop. With a plurality of cams, the formlocking connection can absorb large forces.
Advantageously, there are provides at least two different types of cams. The different types of cams can include elongate transverse cams extending transverse to the loop, elongate cams extending along the loop, and spherical cap-shaped cams. These cams permit to achieve (with respect to the locking flange) both axial and tangential formlocking action, without increasing bending stiffness along the loop.
Advantageously, the clamping band is formed of metal, preferably, of spring steel, which permits to achieve high locking forces, together with a high elasticity. In addition, the cams, which are coined from metal, are characterized by a high wear resistance and, therefore, have an extended service life.
Advantageously, the manually tensioning means includes a rotatable hand grip and a locking screw for tensioning the band in response to a respective rotation of the hand grip. Thereby, the locking is easily carried out by rotating the hand grip.
Advantageously, the clamping band has two receiving openings provided in its opposite ends respectively, for formlockingly receiving a head of a locking screw. As a result, the clamping band is locked with a screw.
Advantageously, the clamping band has two, radially outwardly projecting, guide noses provided respectively on its two opposite ends. Thereby, upon releasing the clamping band, the open width of the two ends of the clamping band is determined by the guide surfaces of the locking flange. Thereby, falling of the locking screw off the head upon opening of the receiving openings can be prevented.
The novel features of the present invention, which are considered as characteristic for the invention, are set forth in the appended claims. The invention itself, however, both as to its construction and its mode of operation, together with additional advantages and objects thereof, will be best understood from the following detailed description of preferred embodiment, when read with reference to the accompanying drawings.
The drawings show:
A hand-held power tool 3, which is formed as a hammer drill and is only partially shown in
In the head 4, a loop-shaped clamping band 5, which is formed of spring steel, is displaceably arranged. The clamping band 5 is tensioned by a manual rotation of a hand grip 6, with a head 8 of a locking screw 7 and which engages in receiving openings 9 in both ends 10 of the clamping band 5. On the clamping band 5, on a loop section opposite the handle 6, there are provided a plurality of longitudinally offset, radially inwardly projecting cams 11a, 11b.
The cams 11a, 11b formlockingly engage in associated recesses 12a, 12b in the locking flange 2 of the power tool 3. The locking band 5 has, on both of its ends 10, projecting radially outwardly, guide noses 13, respectively. The guide noses 13 displace, upon locking/unlocking, on respective, substantially parallel to each other guide surfaces 14 of the head 4.
As shown in
Though the present invention was shown and described with references to the preferred embodiment, such is merely illustrative of the present invention and is not to be construed as a limitation thereof and various modifications of the present invention will be apparent to those skilled in the art. It is therefore not intended that the present invention be limited to the disclosed embodiment or details thereof, and the present invention includes all variations and/or alternative embodiments within the spirit and scope of the present invention as defined by the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2007 047 881.1 | Nov 2007 | DE | national |
