Spring devices – Resilient shock or vibration absorber – Nonmetallic – resilient element
Reexamination Certificate
2000-05-30
2001-09-11
Schwartz, Christopher P. (Department: 3613)
Spring devices
Resilient shock or vibration absorber
Nonmetallic, resilient element
C267S141100
Reexamination Certificate
active
06286821
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a pivot for a stabilizer bar in a suspension system of an automotive vehicle and a method of making a bushing used in the pivot.
2. Background Information
A purpose of a stabilizer bar in a suspension system of an automotive vehicle is to resist rolling of the vehicle body in relation to wheels of the vehicle when the vehicle is making a maneuver such as a turn. A known device for mounting a stabilizer bar with respect to a vehicle body is an elastomeric pivot bushing. The bushing is annular in shape and captured in a metal bracket that is fastened to a part of the vehicle undercarriage that is in fixed relation to the body. Such a part may be a frame or sub-frame of the vehicle for example. A free end of the stabilizer bar is associated in a suitable manner with a portion of the vehicle that is associated with the vehicle undercarriage through a suspension system. The stabilizer bar is arranged to resist certain types of relative motion so the vehicle body will tend to remain more stable during certain driving maneuvers such as turns.
It is known to fabricate such bushings by injection molding and to include inserts in such bushings. It is believed that injection molding is relatively expensive because it requires injection molding capital equipment and a die that has one or more mold cavities. Where a bushing includes one or more inserts, they must also be loaded into the die before the elastomer is injected. The cycle time must be long enough to allow the injected elastomer to cure sufficiently before it is removed from the die.
SUMMARY OF THE INVENTION
The present invention relates to what is believed to be a less expensive, more efficient method for making a stabilizer bar bushing. The method can be practiced without injection molding in a molding die, free of factors that may complicate that type of process.
Generally speaking, the present invention relates to a method of making a stabilizer bar bushing that employs extrusion of elastomeric material rather than injection molding of such material. The invention also relates to the resulting bushing.
Because shear plates embedded in the elastomeric body of a stabilizer bar bushing impart certain characteristics that are desirable from a performance standpoint, the inventive method provides an efficient way to incorporate them during the extrusion process. One or more shear plates are run lengthwise through an extrusion die where the elastomeric material is extruded around the plate or plates in proper manner to produce the desired transverse cross sectional shape for the finished bushing. Finished bushings are severed from the extruded material by transversely cutting the extruded material into individual pieces of desired length at successive intervals.
It is believed that the method is beneficially conducive to the use of shear plates fabricated from certain plastic material. Compared to metal shear plates, the material characteristics of substantially plastic shear plates are believed more consistent with those of the elastomeric materials in which they are embedded. For example, elastomerics may bond better to plastics than to metal. Substantially plastic shear plates may be cut with less difficulty than metal ones, a desirable attribute for the inventive method when individual bushings are being severed from an extrusion.
Accordingly, a general aspect of the invention relates to a method of making pivot bushings comprising: providing at least one length of insert material having a transverse cross section that in the individual pivot bushings is arcuate about a central axis; moving the insert material lengthwise through an extrusion die; at the die, creating an annular elastomeric body within which the insert material is embedded by extruding elastomeric material in covering relation to the insert material as the insert material moves through the die; and then transversely cutting through the annular elastomeric body, including cutting through the insert material, at locations along the length of the insert material, thereby creating individual bushings.
Another general aspect of the invention relates to a bushing for mounting a stabilizer bar in association with a suspension system on the undercarriage of a motor vehicle comprising: an elastomeric body that is annular about a central axis and comprises a central through-hole adapted to receive a portion of the stabilizer bar and an outer perimeter adapted to be received in a bracket for attachment to the undercarriage; and at least one shear plate of substantially plastic material that in transverse cross section has a shape which is arcuate about the central axis and that is embedded within the elastomeric body.
Still another general aspect relates to a suspension system of a motor vehicle comprising: a stabilizer bar; a bushing for associating a portion of the stabilizer bar with an undercarriage of the vehicle; and a bracket which is attached to the vehicle undercarriage and within which the bushing is received; the bushing comprising an elastomeric body that is annular about a central axis and comprises a central through-hole within which the portion of the stabilizer bar is received and an outer perimeter which is received in the bracket, and at least one shear plate of substantially plastic material that in transverse cross section has a shape which is arcuate about the central axis and that is embedded within the elastomeric body.
Further aspects will be seen in various features of a presently preferred embodiment of the invention that will be described in detail and in principles of the invention as set forth in various claims.
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Brown Gregory P.
Coughlin William J.
Ford Global Technologies Inc.
Schwartz Christopher P.
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