Plastic and nonmetallic article shaping or treating: processes – With printing or coating of workpiece – Anti-stick or adhesion preventing coating
Reexamination Certificate
1996-04-02
2003-02-04
Eashoo, Mark (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
With printing or coating of workpiece
Anti-stick or adhesion preventing coating
C264S242000, C264S264000
Reexamination Certificate
active
06514443
ABSTRACT:
The invention pertains to a method for manufacturing a ball joint consisting of a ball-ended spindle and a socket, in particular a ball joint for motor vehicles.
Ball joints, in particular ball joints for motor vehicles, are known in numerous variations. These ball joints consist of a ball-ended spindle and a socket, inside of which the ball of the ball-ended spindle is arranged such that it can be pivoted and turned to a limited extent. A bearing shell is usually arranged between the socket and the ball of the ball-ended spindle in order to attain the desired mating of material and quality of the ball seat independent of the preferably metallic material of the socket.
These known ball joints which comprise a bearing shell have the disadvantage that a plastic deformation of the bearing shell and, if necessary, the socket is required during the insertion of the ball-ended spindle into the socket so as to attain the required overlap between the bearing shell and the equator of the ball. This overlap is necessary for preventing the ball-ended spindle from being torn out of the socket if loads are exerted in the longitudinal direction of the ball-ended spindle.
Since the assembly of these known ball joints requires a relatively high expenditure, it was already proposed to manufacture the socket by coating a ball-ended spindle by means of injection molding in an injection molding tool, wherein the ball is provided with a bearing shell that is manufactured separately prior to the injection molding process. Although this bearing shell is attached to the ball in the form of a press fit, it is difficult to prevent the plastic which is supplied under pressure from being admitted between the ball and the bearing shell during the manufacture of the socket such that the ball joint is rendered unusable due to the fact that the hollow spaces, in particular the flattened pole surface of the ball, are filled with said plastic material. If a fiber-reinforced plastic material is used for manufacturing a housing that is able to withstand high loads, the bearing shell would remain ineffective and consequently become unnecessary.
The present invention is based on the objective of developing a method and a device for manufacturing a ball joint consisting of a ball-ended spindle and a plastic socket which allow the inexpensive manufacture of ball joints that are able to withstand high loads while eliminating the aforementioned disadvantages.
According to the invention, this objective is attained by placing the ball-ended spindle that comprises a ball without a pole surface into an injection molding tool and retaining said ball-ended spindle by a core puller that seals the hollow spaces of the injection molding tool relative to the ball and simultaneously forms a clearance for realizing the maximum pivoting angle of the ball-ended spindle relative to the socket, whereafter the ball is directly coated with plastic, preferably a fiber-reinforced plastic, by means of injection molding so as to form the socket.
The method according to the invention makes it possible to manufacture a ball joint consisting of a ball-ended spindle and a socket in which not only the complicated assembly, but also the entire bearing shell is eliminated. In this way, the risk of creating tolerances with respect to the ball seat, in particular dimensional deviations from the spherical shape, is simultaneously eliminated. The direct coating of the ball by means of injection molding so as to form the socket consequently results in a superior contact pattern and a high-percentage contact area of the ball joint. Since a sufficient overlap between the high-strength socket material and the equator of the ball can be attained despite the elimination of the bearing shell, the ball joint manufactured in accordance with the invention provides a high stability against tearing if the ball-ended spindle out of the socket, i.e., a significant advantage as compared to known ball joints with plastic bearing shells that consequently have a lesser stability against tearing of the ball-ended spindle out of the socket is attained. Since the ball joint manufactured in accordance with the invention also has a low radial and axial elasticity, said ball joint can be utilized as an axial as well as a radial joint. Due to the fact that the bearing shell is eliminated, the ball joint according to the invention can also be realized with smaller external dimensions of the socket.
According to one additional characteristic of the invention, the connection piece of the socket or a complete chassis strut can be manufactured in the injection molding tool simultaneously with the socket. The invention additionally proposes producing a groove that surrounds the opening of the socket and serves for holding a sealing bellows simultaneously with the manufacture of the socket.
According to one additional characteristic of the invention, the ball-ended spindle that is provided with a ball without a pole surface is manufactured by welding a ball onto the recessed surface of the spindle part. The preferred welding method utilized for this purpose is either the pulsed-current arc welding method or the friction welding method. According to the invention, the ball can be provided with an antifriction coating before the injection molding process.
The device for implementing the method according to the invention consists of an injection molding tool that comprises a hollow space which corresponds with the socket including its connection piece or chassis strut and forms a guide for a core puller. One embodiment of the device according to the invention is characterized by the fact that the core puller which is guided in a sealed fashion relative to the injection molding tool is provided with an annular sealing surface that adjoins the underside of the ball in a sealed fashion, with said sealing surface being formed at the end of the core puller that has the shape of a truncated cone and forms the clearance for realizing the maximum pivoting angle of the ball-ended spindle relative to the socket.
With this design according to the invention, one obtains a simple and functionally safe injection molding tool that not only allows the manufacture of the socket that directly surrounds the ball, but also the simultaneous manufacture of the clearance required for moving the ball-ended spindle relative to the socket by the maximum pivoting angle.
According to one preferred embodiment of the device according to the invention, the injection molding tool can be divided along the longitudinal center of the socket and the core puller, wherein the core lies in the tool partition plane such that one half cylinder is situated in each respective tool half. Consequently, the ball joint with an integrally formed groove for the sealing bellows and an open strut profile of the connection piece can be removed from the mold without additional core pullers or slides.
According to one additional characteristic of the invention, holding pins can be arranged in one of the injection molding tool halves as contact surfaces for the spindle part of the ball-ended spindle in order to generate the required force for counteracting that particular force with which the annular sealing surface is pressed against the underside of the ball and prevent the plastic material from being admitted into the clearance during the injection molding of the socket. Alternatively, this counter force can also be generated by a core via the threaded section of the ball-ended spindle.
One embodiment of the device according to the invention is illustrated in the figure in the form of a vertical section through the tool partition plane. This illustration also serves for the following description of the method according to the invention.
The figure schematically shows part of an injection molding tool
1
that serves for manufacturing a ball joint
2
that, in particular, is intended for motor vehicles.
This ball joint
2
consists of a ball-ended spindle
21
that is composed of a spindle part
22
and a ball
23
. The ball
23
is fo
Eashoo Mark
Tarolli, Sundheim, Covell Tummino & Szabo L.L.P.
TRW Fahrwerksysteme GmbH & Co. KG
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