Chucks or sockets – Socket type – Spring biased jaws
Reexamination Certificate
2001-11-15
2003-06-03
Bishop, Steven C. (Department: 3722)
Chucks or sockets
Socket type
Spring biased jaws
C279S053000, C279S156000, C279S157000, C409S234000
Reexamination Certificate
active
06572119
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
This application claims the priority of German Patent Application No. 100 56 729.0 filed Nov. 15, 2000 which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
The invention relates to a chuck for clamping in shafts, in particular to a chuck for the frictional clamping of tool shafts.
Axial chucks for clamping in rotating tools or their shafts are known. These chucks are provided with clamping jaws or clamping sleeves for clamping a cylindrical section (shaft) of a tool. The tightening or releasing of the clamping sleeves requires access to a corresponding actuation device. The goal is to be able to actuate this clamping sleeve even if the chuck is connected to the spindle of a machine tool or if the chuck is connected to a tool-presetting device. In addition, a manual operation of the chuck should be possible without mounting device.
A high torsional moment or torque that can be transmitted is also frequently desired. Due to the frictional clamping of the tool shafts, this torsional moment requires high radial pressure forces that must be generated by the chuck.
Chucks with clamping sleeves are frequently used to clamp tools with varied shaft diameters. For this, the inside diameter of the clamping sleeve must always coincide with the shaft diameter. Intermediate layers between the tool shaft and the clamping sleeve are not practical because they worsen the rotational accuracy. Thus, it is necessary or desirable to be able to change the clamping sleeves.
A chuck is known from German patent reference No. DE 44 05 242 A1, which has a basic body with an approximately cylindrical front and a cone-shaped shaft. The basic body has an essentially rotation symmetrical design and is provided with an axially aligned through bore with a cone-shaped clamping surface region in the cylindrical section of the basic body. A clamping sleeve is arranged in this region, which is provided with an extension having an external thread that extends into the through bore. The clamping sleeve is arranged, via a pin installed on the side, such that it is axially displaceable but rotationally connected inside the through bore by the side pin. The clamping sleeve is tensioned by applying a tensile force to its extension. For this, a screw sleeve is arranged inside the through bore and is provided with an internal thread. The through bore is connected to the extension provided with an external thread. The screw sleeve is also provided with an external thread, having a different pitch than the internal thread and engages in a section of an internal thread of the through bore. As a result of the difference in pitch between the thread couplings screw sleeve/clamping jaws and screw sleeve/basic body, a tensioning movement of the clamping jaws is generated by turning the screw sleeve.
With this type of chuck, the threaded sleeve can be actuated only if the clamping device is separate from a tool spindle, meaning if the through bore that ends at the cone-shaped basic body is empty. In addition, it must be partially integrated into a mounting device to be able to generate the coaxial moment of torsion.
A chuck with a clamping sleeve that is operated via a worm is also known from the European patent reference No. EP 0 304 558. The clamping sleeve is used for holding a tool holder and is provided at its back end with an extension having an external thread. A sleeve is fitted with radial play onto this extension. The sleeve is provided with a ring or annual flange on its end and supports itself on a threaded ring nut that is screwed onto the extension. Via a groove and tongue connection, the ring nut and the sleeve are positioned rotationally connected inside the basic body. The sleeve is provided with a tensioning thread on the outside, on which a ring nut is positioned. This ring nut is positioned in the basic body, such that it cannot be displaced axially and can be rotated. On its outside, it is provided with a toothing that is connected to a worm.
In order to increase torsional moments that can be transmitted, the basic body is provided with projections that engage in corresponding recesses of a disk-shaped flange that is connected to the tool. A chuck of this type requires a special tool adaptation in the shape of a form-locking flange for coupling. A replacement of the clamping sleeve is furthermore not planned. Moreover, the tool holder is centered with the clamping sleeve inside its relatively steep conical seat. To keep radial forces away from the clamping sleeve, this clamping sleeve is connected to an uncoupling sleeve, which in turn is connected to a chucking mechanism.
A chuck is furthermore known from practical operations, which uses a helical gear to pull clamping sleeves with a steep cone into a tensioning opening. In order to center the clamping sleeve, it is provided with a cylindrical section that is guided inside a cylindrical bore section in the chuck. The helical gear engages the clamping sleeve behind the cylindrical section and is provided with an angular mechanism (bevel gear) for the actuation.
Starting with this prior art, it is the object of the invention to create a chuck, which can tension traditional, cylindrical shafts and can transmit high torsional moments with high tensioning accuracy.
SUMMARY OF THE INVENTIION
The above object generally is achieved by a according to the invention by a chuck comprising: a clamping element with an axial opening and a cone-shaped outer surface, which is formed onto a shaft or is connected to a shaft and is provided with a tensioning thread, with the outer surface determining a conical angle <3.5°; a housing body provided with a conically extending tapered centering opening for holding the clamping element and a holding chamber for a chucking mechanism, with the centering opening leading to the holding chamber; and the chucking mechanism comprises a rotational body that is disposed inside the holding chamber coaxial to the centering opening and is positioned such that it can rotate and essentially cannot be displaced axially, and that has a thread that directly engages in the tensioning thread, and an activation means that is connected to the rotational body for selectively rotating the rotational body to cause axial displacement of the clamping element within the centering opening.
The chuck according to the invention is provided with a clamping element with conical outside shape, for example in the form of a clamping sleeve or clamping jaws, which is equipped to hold a shaft or is designed to be part of a shaft. The conical outside engages in a conical inside of a central opening in the housing body. During the axial movement of the clamping sleeve, a wedge-type effect is thus created between the conical surfaces, as a result of which the clamping sleeve is compressed in the radial direction. The clamping sleeve is provided with several, for example, three or four, longitudinal slots for this purpose.
With the chuck according to the invention, clamping sleeves or tool shafts with an extremely narrow wedge angle (preferably less than 3.5°) are tensioned. Narrow wedge angles of this type permit high tensioning forces, particularly in connection with high reduction chucking mechanisms such as worm gears or even bevel gears, but generally require additional centering. The chuck according to the invention does not require additional centering. The narrow cone is centered solely with the aid of the centering opening with its corresponding cone-shaped inside surface (wall). It has turned out that narrow centering openings that cause a self-locking of the clamping element provide excellent centering and thus a good rotational movement without requiring additional measures such as cylindrical guides or the like, despite the tilting moments, which act upon the clamping sleeve or the clamping shaft and may be caused by the angular mechanism. Surprisingly, this is true even though the clamping element can no longer “straighten itself out” once it is in a slanted position due to the self-locking feature.
Bishop Steven C.
Josef Albrecht Bohrfutterfabrick GmbH & Co.
Kunitz Norman N.
Venable LLP
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