Cutting by use of rotating axially moving tool – Tool or tool with support – Including detailed shank
Reexamination Certificate
1999-05-07
2001-01-16
Bishop, Steven C. (Department: 3722)
Cutting by use of rotating axially moving tool
Tool or tool with support
Including detailed shank
C279S019400
Reexamination Certificate
active
06174112
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a tool for a hand-held equipment and including a shank having, in its clamping region, at least one looking groove and at least one drive groove which opens toward the rear end of the shank.
2. Description of the Prior Art
The prior art discloses a number of tools the shanks of which are specifically adapted for insertion in a chuck of a hand-held equipment. Such tools are disclosed, e.g., in European Publications EP-A-0 433 876, EP-B-0 550 489, EP-A-0 584 706 and German Publications DE-A-43 03 545 and DE-U-093 19 009. The tools described in these publications differ from each other by the arrangement and shape of the drive grooves provided on the tool shank or of the driving elements provided in the chuck of the hand-held equipment. In addition to drive grooves, locking grooves are provided on the shank which, in distinction from the drive grooves, are generally axially closed. The locking grooves should prevent a tool from out of the chuck of the hand-held equipment. They also contribute to the torque transmission.
An object of the present invention is a tool for hand-held equipment and having drive grooves and locking grooves the shape and dimensions of which are so selected that the torque transmission and retaining of the tool in the chuck are optimized.
Another object of the present invention is a tool having a sufficiently large, non-weakened remnant cross-section of the shank which is adequate for an optimal transmission of a large energy of a single blow of modern percussion hand-held equipments, and which has an adequate fracture resistance.
SUMMARY OF THE INVENTION
These and other objects of the present invention, which will become apparent hereinafter, are achieved by providing a tool with a shank in a clamping region of which there are provided at least one drive groove and at least one locking groove. The clamping region has a diameter equal to or greater than 12 mm. The at least one locking groove and the at least one drive groove have each a depth equal to or greater than 2.5 mm. Opposite edges of the at least one locking groove and the at least one drive groove, which lie on the shank circumference, form, respectively, an aperture angle equal to or greater than 50°.
The selected diameter of the clamping region of the shank and of the depth of the locking and drive grooves insure that an adequately large solid cross-section of the shank remains after the grooves are formed. Advantageously, the largest depth of the locking and drive grooves is smaller than 3.5 mm. The aperture angle is defined as an angle between the radii which connect the edges of the side surfaces of the locking groove or the drive groove with the shank axis. The chamfers of the transition regions are not taken into account. In case when there are provided several locking and/or drive grooves, it is sufficient when at least one locking groove and at least one drive groove have an aperture angle equal to or greater than 50°. A further locking groove and a further drive groove can have a smaller aperture angle.
The depth and the aperture angle of the drive groove provide a sufficiently large entrained surface which insures a transmission of a torque from the driving means of the chuck to the inserted tool. Advantageously, the diameter of the clamping region of the chuck is equal to about 14 mm, and the depth of the drive groove is equal to about 2.6 mm. The aperture angles of the locking and drive grooves are advantageously so selected that the smallest angular distance between them is larger than 15° and, preferably, at least 20°. Thereby, a sufficiently wide, non-weakened material web remains between the locking groove and the drive groove, which advantageously increases the service life of the tool.
A balanced ratio exists between the surface of the drive groove and the depth of the locking groove. As a result, an adequately large, non-weakened, remnant cross-section of the tool shank is obtained. Advantageously, the depths of the locking and drive grooves are so selected that a region of a respective groove, which is closest to the axis of the shank, is radially spaced form the shank axis by a distance which is smaller than 0.65 of the shank radius in the clamping region.
According to an advantageous embodiment of the present invention, the aperture angles of the locking groove and of the drive groove differ from each other by less than ±10°, preferably, by ±6°. When the locking and drive grooves have approximately the same aperture angles, the clamping region of the shank is weakened over the same angular regions of its circumference. This permits to obtain, even at smaller diameters of the shank, a sufficiently large, non-weakened cross-section.
An advantageous relationship between the size of the entrained surface and the remnant, non-weakened cross-section of the shank is obtained with an aperture angle of the drive groove smaller than 75° and, preferably, smaller than 60°.
A uniform guidance of the tool in a chuck is advantageously obtained when there are provided two locking grooves located diametrically opposite each other. At that, the two locking grooves have the same aperture angle.
In order to obtain a sufficiently large remnant cross-section of the shank when two locking grooves are provided, the distance between the closest to each other regions of the two locking grooves is so selected that it amounts to from about 0.6 to 0.7 of the shank diameter.
Advantageously, the locking groove has an arcuate cross-section. Advantageously, when two locking grooves located diametrically opposite each other are provided, a ratio of the radius of the locking groove arc to the shank radius is selected in a range from about 0.54 to about 0.6. This insures that an adequate remnant cross-section of the shank in the clamping region is obtained.
For increasing the entrained surface, advantageously two, located diametrically opposite each other, drive grooves are provided. To provide for a symmetrical loading of the tool during an operation, both drive grooves have the same aperture angle. In this case, advantageously all of the locking and drive grooves have an aperture angle equal to or greater than 50°.
In accordance with a further advantageous embodiment of the present invention, the edges of the drive grooves, which are remote from the respective edges of the respective locking grooves which follow, along the circumference of the shank, the respective drive grooves, are spaced from the respective remote edges of the respective locking grooves by a minimum angular distance of about 90°. During the tool operation, in particular, when the tool is a drill and/or chisel, the driving element and the locking means of the chuck almost simultaneously engage the side surfaces of the locking and drive grooves. Therefore, the locking grooves also contribute to the transmission of the torque over a certain portion of the circumference, with the load on drive grooves being reduced. This favorably influences the service life of the tool.
REFERENCES:
patent: 3637225 (1972-01-01), Schmuck
patent: 4123074 (1978-10-01), Wanner
patent: 4717292 (1988-01-01), Phillips
patent: 5346340 (1994-09-01), Runge
patent: 5421628 (1995-06-01), Obermeier et al.
patent: 4338818 (1995-05-01), None
patent: 0181093 (1986-05-01), None
Bongers-Ambrosius Hans-Werner
Kleine Werner
Bishop Steven C.
Brown & Wood LLP
Hilti Aktiengesellschaft
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