Joints and connections – Interfitted members – Clamped members
Reexamination Certificate
2000-10-27
2003-05-06
Browne, Lynne H. (Department: 3679)
Joints and connections
Interfitted members
Clamped members
C403S374100, C403S373000, C403S409100
Reexamination Certificate
active
06558066
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention is based on an apparatus for securing a component to a drive shaft of a wiper system.
Wiper systems with a plurality of windshield wipers for motor vehicles are secured with their wiper bearings directly or indirectly via a mounting tube to the body of the motor vehicle. The mounting tube carries a wiper drive mechanism with a wiper motor, whose motor shaft, via a rod assembly, drives cranks that are solidly connected to one end of a drive shaft for each windshield wiper. It is also possible for only the drive shaft of one windshield wiper to be driven by the wiper motor, while another windshield wiper is connected to the first windshield wiper via a four-bar lever mechanism and has a bearing shaft. The drive shaft or a bearing shaft is supported in a wiper bearing. The remarks below pertain logically to a drive shaft for a bearing shaft as well, although it will no longer be expressly mentioned.
At least one radial bearing is provided in the bearing housing, and an axial bearing is provided between the bearing housing and a part solidly joined to the drive shaft. The drive shaft protrudes from the body and moves a wiper arm, secured to its free end, with a wiper blade over the windshield. The wiper arm has a fastening part, connected to the drive shaft in a manner fixed against relative rotation, that is pivotably connected to a hinge element, which is adjoined rigidly by a wiper rod. It is also possible for the wiper arm not to be directly connected to the drive shaft but instead to be driven via a lever mechanism with a drive lever connected to the drive shaft in a manner fixed against relative rotation. The remarks below on connecting the fastening part to the drive shaft also apply to a drive lever, which will no longer be expressly mentioned.
In known windshield wipers, the end of the shaft has an outer cone, onto which the fastening part is pressed with a fitting inner cone and firmly clamped by means of a nut. With this type of connection, production-dictated variations can unfavorably add up, so that accurate positioning of the fastening part relative to the drive shaft can be assured only with difficulty. Furthermore, the tightening moment of the nut affects the position of the wiper arm.
From German Patent Disclosure DE 44 28 371 A1, a shaft hub connection of a wiper is known, in which the drive shaft has a cross-sectional region that deviates from circular symmetry and also has a bearing shoulder. Placed between the drive shaft and the fastening part is a pressure piece, which has an opening that even before assembly is embodied to suit the cross-sectional region deviating from circular symmetry and which positively surrounds the drive shaft. The pressure piece also has an outer cone, with which it is pressed via a separable fastening element on the drive shaft into a suitably shaped inner cone of the fastening part. The fastening part is pressed onto the bearing shoulder by the fastening element via the pressure piece and fixed in the longitudinal direction of the shaft.
In the proposed embodiment, production variations have only slight influence on the precision of positioning of the wiper arm. The wiper arm can be secured with a high tightening moment, without influencing the positioning precision of the wiper arm.
From U.S. Pat. No. 3,085,821, a shaft hub connection is known in which a fastening part has an inner cone with a knurled or zigzag surface. The drive shaft also has a cylindrical or conical region with a knurled or zigzag surface. Upon installation, via a nut, a deformable pressure piece is pressed with an outer cone between the fastening part and the drive shaft. As a result of the conical connection between the fastening part and the pressure piece and optionally the conical connection between the pressure piece and the drive shaft, the zigzag surface of the fastening part and of the drive shaft is pressed into what until then are largely smooth surfaces of the pressure piece and permanently deform them. Along with a nonpositive engagement, many small side faces of the zigzags create a reinforcing positive engagement.
The fastening part transmits the drive moment from the drive shaft to the wiper blade, via the hinge element and the wiper system. It also forms part of the toggle joint by way of which the fastening part is tensed together with the hinge element with a tension spring and pressed in the direction of the vehicle window. The greatest forces or moments arise in the fastening part parallel and perpendicular to the vehicle window. Deformation and play in the lower region of the windsheild wiper also have an especially pronounced effect over the entire length and because of a spring effect can lead to uneven wiping speeds. The drive shaft and the fastening part should therefore be permanently joined without play. Furthermore, the wiper arm should be easy to install and disassemble together with the fastening part and the pressure piece.
SUMMARY OF THE INVENTION
The apparatus according to the invention has a drive shaft with a cross-sectional region deviating from circular symmetry, on which region a pressure piece is supported positively with an opening that even before assembly is embodied to suit the cross-sectional region deviating from circular symmetry. The cross-sectional region deviating from circular symmetry of the drive shaft, at least in one region, has an increasing diameter in the mounting direction or is embodied conically, as a result of which the pressure piece, in addition to a positive engagement that transmits the drive moment, is connected nonpositively and without play to the drive shaft. Furthermore when the pressure piece is slipped on, a greater inside diameter of the pressure piece initially meets a smaller outside diameter of the drive shaft, as a result of which the pressure piece canteasily be installed.
The pressure piece can be made from hard material, which maintains its shape during operation and can be secured permanently without play plastic deformation for the positive engagement is avoided, and the pressure piece can be used more than once. The opening of the pressure piece can be embodied with a constant diameter or advantageously with a diameter that corresponds to the drive shaft, that is, a diameter that increases in the mounting direction. Pressure pieces produced by an injection molding process, if they have a conical opening, are easy to release from a casting mold, especially pressure pieces of aluminum and an aluminum alloy. The bearing faces require little if any remachining, and the casting mold is not tattered as much in the unmolding process. The service lives are longer, and production costs drop.
The positive engagement between the drive shaft and the pressure piece is advantageously created with a few large, load-bearing faces, preferably from one to twelve faces. The pressure piece, with a suitably shaped opening given slight elastic deformation and tensing, can be made to rest on the faces without play, with a largely constant pressure per unit of surface area, as a result of the conical connection. Despite a play-free support of the pressure piece on the drive shaft, the pressure piece and a fastening part can be pulled off the drive shaft axially, or disassembled in the axial direction, using only slight force. Furthermore, a few load-bearing faces in the pressure piece and on the drive shaft can be manufactured inexpensively with low tolerances. The drive shaft can be embodied with a polygonal or nonround, for instance arbitrarily elliptical outer cone, and the pressure piece can be embodied with an inner cone to suit. Two-, four- or six-sided cross-sectional faces can be achieved easily by milling. However, it is more economical to provide a nonround or elliptical outer cone that is produced simultaneously in turning the drive shaft on a lathe. This reduces the production cost and retooling times.
On the cross-sectional region deviating from circular symmetry, the fastening part can also be braced directly by the increasing diameter on a bear
Browne Lynne H.
Dunwoody Aaron
Robert & Bosch GmbH
Striker Michael J.
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