Machine element or mechanism – Elements – Cranks and wrist pins
Patent
1992-02-05
1992-09-01
Luong, Vinh T.
Machine element or mechanism
Elements
Cranks and wrist pins
403274, 74 42, F16C 304, F16H 2118, B25G 328
Patent
active
051429390
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a drive unit for a wiper system of motor vehicles having a wiper shaft or pivot pin with a fastening section for connecting to a crank arm.
DESCRIPTION OF THE PRIOR ART
In wiper systems of motor vehicles several drive units are needed to transform the rotary motion of an electric motor into a pendular motion of a wiper. A problem generally experienced is how to fix a first element onto a crank arm or onto a crank, whereby the fastening area of the first element is anchored in a respective aperture of the crank arm. The first element could be, for instance, a wiper shaft or a pivot pin, especially a ball pivot pin.
A drive unit for wiper systems in which a crank arm is fixed in a middle fastening area of a wiper shaft is already known. The fastening section of the wiper shaft to which the wiper arm is connected is disposed on one side of this crank arm and is usually provided with a threaded section and a knurl. On the other side of the crank arm, a bearing section of the wiper shaft is rotatively located in a bearing bushing. In order to provide an unrotatable connection stable inform between the crank arm and the wiper shaft, the typical wiper shaft comprises an extending profiled section that is pressed into the respective aperture in the crank arm. In order to secure the crank arm in the axial direction of the wiper shaft arresting shoulders serving as holding elements for the crank arm are punched out of this profiled section. Because of this profiled section in the middle of the wiper shaft it is relatively expensive to manufacture such a drive unit.
Drive units with a double ball pin anchored at a crank arm for being linked to further drive units which, for instance push rods, are also known. So far this pivot pin has been soldered to the crank arm in the fastening area.
SUMMARY OF THE INVENTION
The object of the present invention is to reduce the manufacturing costs of such a drive unit while at the same time guaranteeing sufficient stability of the connection between the wiper shaft or the pivot pin and the crank arm.
According to the invention this object is achieved by having a drive unit with a first element which has a ring groove in a fastening area which engages a holding element formed out of the crank arm.
The invention is based on the idea that sufficiently stable security of position in the axial direction of the wiper shaft is achieved when the wiper shaft or the pivot pin is provided with a ring-groove and the holding element is formed out of the crank arm. Thus, as to embodiments in which the crank arm has to be fixed onto the first element approximately midway, i.e. onto the wiper shaft or a double pivot pin, this first element can be manufactured as a turned piece at low costs.
The basic idea of the present invention could be implemented in such a way that separate lugs acting as holding elements are formed out of the front sides of the crank arm. However, with the holding elements at the front sides of the crank arm the adjacent knurled section of the wiper shaft could be damaged. Therefore one preferred embodiment is provided with the holding element formed out of the surface area of the aperture of the crank arm at a distance from the front sides of the crank arm. When the drive unit is finally assembled, the means by which the crank arm is axially secured is not visible.
Thus an especially stable connection is achieved when instead of separate holding elements, a surrounding bulge is formed which engages approximately radially into a ring-groove of the wiper shaft or pivot pin. Such a ring-like bulge can be formed by a so-called "ring wedging operation", in which a ring-like recess is worked into the front side of the crank arm by means of a ring-like die, which pushes material out of the surface area at the border of the recess. Then, the material pushed out of the surface area enters the ring-groove, which preferably has a cross-section in the shape of a half-circle so that stability is not reduced because of a grooving eff
REFERENCES:
patent: 2067967 (1937-01-01), Kniepen
patent: 4249298 (1981-02-01), Kanamaru et al.
patent: 4335496 (1982-06-01), Kanamaru et al.
patent: 4848171 (1989-07-01), Steijger et al.
patent: 4878398 (1989-11-01), Heinrich
Bauer Kurt
Dorr Wilhelm
Edele Reinhard
Pfitzenmaier Werner
Roth Christian
Lewis J. Gordon
Luong Vinh T.
Seitter Robert P.
SWF Auto-Electric GmbH
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