Patent Grant
8021214
1. Field of the Invention
The present invention relates to a hand-held power tool with a locking nut for securing a disc-shaped tool and, in particular, to angle grinder, hand-held jointer saw, or hand-held circular saw.
2. Description of the Prior Art
Conventional tool holders for a disc-shaped tool (under which in addition to flat discs, also plate-shaped tools are understood) frictionally secure the disc-shaped tool on the rotatable drive spindle between a clamping flange provided on the drive spindle and a locking nut that is screwed onto the drive spindle. The thread direction of the locking thread provided on the drive spindle is usually so selected that the locking nut automatically tightens upon actuation of the power tool or start up of the operation.
Contemporary hand-held power tools with safety routines provide for sudden braking of the drive spindle up to a complete stop. In order to reliably prevent an inadvertent loosening of the locking nut and/or of the disc-shaped tool in case when the locking nut becomes loose due to its inertia upon a sudden stop of the spindle, German Publication DE 42 38 466 discloses locking means that in addition to a locking nut, includes additional clamping means that applies pressure to the disc-shaped tool and is preloaded against a locking nut with a plate spring.
German Publication DE 42 43 328 discloses additional locking means that is connected with the drive spindle for joint rotation therewith and brakes, as a result, the inertia-induced relative rotation of the locking rut.
According to German Publication DE 43 05 317, the locking nut braking means is formed as a steel spring ring located in the locking nut and frictionally engaging the locking thread of the drive spindle.
An object of the present invention is to provide a reliable tool holder for a disc-shaped tool and that includes a locking nut.
This and other objects of the present invention, which will become apparent hereinafter are achieved by providing a hand-held power tool including a drive spindle rotatable about a rotational axis and provided at its free end with a clamping flange and a locking thread, a locking nut having a clamping surface and tightenable on the locking thread for securing a disc-shaped tool between the clamping flange of the drive spindle and the clamping surface of the locking nut, and a safety spring located between the disc-shaped tool and an inner recess formed in the clamping surface of the locking nut, radially preloaded against the locking thread, and having at least one radial, outwardly projecting nose, with the disc-shaped tool having at least one, opening radially inwardly and axially extending groove associated with the at least one nose of the safety spring.
With the radially projecting nose of a safety spring, which is frictionally secured on the locking thread of the drive spindle, the disc-shaped tool can be removed from the drive spindle only in associated circumferential positions, and in particular, not in an inertia-induced rotational condition relative to the drivespindle. Thus, the disc-shaped tool is axially secured on the drive spindle even in the case when the locking nut would have become loose on the drive spindle due to inertia.
Advantageously, the safety spring is formed of spring steel, which provides for a high elasticity of the safety spring.
Advantageously, the safety spring is formed of wire, which insures its technically simple manufacturing.
Advantageously, the safety spring is formed as almost completely annular spring ring, which permits to achieve a high static friction.
Advantageously, the safety spring has two opposite, projecting radially outwardly noses. Thereby, the associated disc-shaped tool can be ergonomically mounted/dismounted in at least two circumferential positions.
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 1, which schematically shown in
The safety spring 9, which is shown in
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 055 778 | Dec 2007 | DE | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 2331861 | Smith | Oct 1943 | A |
| 20060172668 | Hofmann et al. | Aug 2006 | A1 |
| Number | Date | Country |
|---|---|---|
| 42 38 466 | Jan 1994 | DE |
| 42 43 328 | Jun 1994 | DE |
| 43 05 317 | Sep 1994 | DE |
| Number | Date | Country | |
|---|---|---|---|
| 20090156106 A1 | Jun 2009 | US |
