192 clutches and power-stop control – Clutches – Transversely engaged
Reexamination Certificate
1998-08-05
2001-04-24
Bucci, David A. (Department: 3682)
192 clutches and power-stop control
Clutches
Transversely engaged
C192S1050BA, C384S439000, C403S279000
Reexamination Certificate
active
06220417
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a clutch cup for a centrifugal clutch of a hand-held working tool, especially a trimmer, driven by an internal combustion engine whereby the clutch cup is comprised of a clutch drum, a hub coaxially fastened thereto with a bearing bushing arranged therein and with a coaxially fastened receiving element for receiving the end of a drive shaft.
Hand-held working tools driven by a internal combustion engine often include a centrifugal clutch by which the driven working tool at low rpm of the internal combustion engine is turned off and with increasing rpm is automatically switched on due to the centrifugal forces. Thus, the operation of the working tool is simplified and operational safety increased.
In hand-held working tools, especially trimmers, the centrifugal member of the centrifugal clutch is fixedly connected to the crank shaft of the combustion engine while the clutch cup that encloses the centrifugal member is rotatably supported on the crankshaft end in a bearing bushing or in a separate clutch housing.
In the case of support on the crankshaft, the bearing bushing is inserted into the hub of the clutch cup. The connection bearing bushing/hub is mechanically greatly stressed so that securing against loosening and axial movement of the bearing bushing is required.
In order to axially secure the bearing bushing in the hub, the inner side of the clutch drum is provided with a disc welded thereto having an inner diameter that is slightly smaller than the outer diameter of the bearing bushing. This type of axial securing is complicated because an additional part and a welding connection as well as an additional working step are required.
It is therefore an object of the present invention to provide a reliable and inexpensive axial securing of a bearing bushing inserted into the hub of the clutch cup of a centrifugal clutch.
SUMMARY OF THE INVENTION
The clutch cup for a centrifugal clutch of a hand-held working tool according to the present invention is primarily characterized by:
a clutch drum;
a hub coaxially fastened to the clutch drum;
a bearing bushing arranged in the hub and fastened to the hub by a frictional and positive-locking connection;
a receiving member, coaxially fastened to the hub, for receiving the drive shaft.
The combined use of a frictional and positive-locking connection provides a maximum of positioning securing action of the bearing bushing.
By providing radially extending, circumferentially arranged impressions at the hub that are pressed into the bearing bushing for realizing the positive-locking connection, a very effective and very secure axial securing action is provided. Furthermore, this type of securing is inexpensive because there is no need for additional parts or a welding connection with additional working steps.
The wide range of possible shapes and positioning of the impressions at the hub allow for an adaptation to respective manufacturing specifications and application requirements of the different types of hand-held working tools.
It is advantageous to use the pressing device for the bearing bushing also for the pressing step for providing the impressions. The pressing device thus serves as a pressure relief device thus ensuring the shape stability of the hub, especially when the impressions are provided in pairs on opposite sides of the hub and when the bearing bushing is supported by a calibrating mandril. It may be expedient to arrange a plurality of impressions over the circumference so as to be staggered by an angular distance of 120°.
When the clutch drum, the hub, and the receiving member are provided as a monolithic (unitary) deep-drawn part, considerable cost savings are achieved. The redressing as well as calibration option provided by the redressing device and calibrating device of the pressing device increases the service life and improves running trueness of the hand-held working tool.
REFERENCES:
patent: 3635529 (1972-01-01), Nass
patent: 3954311 (1976-05-01), Pike
patent: 4984669 (1991-01-01), Hoffman
patent: 5845757 (1998-12-01), Csonka
Andreas Stihl AG & Co.
Bucci David A.
Joyce William C.
Robert W. Becker & Associates
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