Stock material or miscellaneous articles – Hollow or container type article – Nonself-supporting tubular film or bag
Reexamination Certificate
1999-06-15
2002-03-26
Dye, Rena L. (Department: 1772)
Stock material or miscellaneous articles
Hollow or container type article
Nonself-supporting tubular film or bag
C428S035500, C156S156000, C156S285000, C264S314000, C473S316000, C473S323000
Reexamination Certificate
active
06361840
ABSTRACT:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
(Not applicable)
FIELD OF THE INVENTION
This invention relates to the manufacture of golf club shafts and other shafts and poles from fiber/resin composite material.
BACKGROUND OF THE INVENTION
A common method for forming golf shafts from fiber/resin composite materials is to wrap fiber impregnated fiber around hard tooling in the form of a mandrel which defines the interior dimensions of the shaft. The fiber is compacted during the winding, by using, for example, rolling tables, and pressure may also be applied by a shrinkable tape wrapped around the mandrel. The advantage of these systems is that the shape and dimensions of uncured resin/fiber preform as it is wound or formed on the mandrel closely approximate the final product. There is little movement of the fiber during cure of the composite, thus the positions of the reinforcing fibers can well be controlled. However, these methods have the disadvantage that only low compaction pressures can only be applied if oven cure of the composite is used. Pressures can be applied using autoclave equipment, but this is not economically feasible for most applications. High compaction pressures are required to form high performance composites that are of light weight but have high strength. In addition, since the tooling must be removable after curing of the part, complex profiles which would trap the rigid interior mandrel pieces cannot be made with this method. Accordingly, this method is limits the shafts to lower structural performance, since the composite is made with low compaction pressure, and this method is also limited to relatively simple tapered shapes.
Another approach is disclosed in French patent applications 90 15387 and 90 15388. In this method a bladder is formed upon a hard metal mandrel. Resin impregnated fiber is formed around the bladder and the assembly placed into female tooling. The bladder is inflated at the base of the mandrel to expand the impregnated fiber into the tooling. This method has several disadvantages. The method disclosed is limited to shapes where the rigid mandrel can be removed from the cured part, i.e., is not trapped by the profile of shape of the part. Conversely, the impregnated fiber material in the preform would have to move substantially from its initial as formed or rolled shape to form a complex shape, which would likely displace the fibers and possibly compromise the properties of the final part. In addition, creation of a complex shape with, for example, a bulge would have entrances precluding removal of a rigid mandrel. Furthermore, the bladder used in this process is a thin walled latex rubber material formed by dipping the mandrel. Accordingly, the bladder necessarily is thin walled and has essentially the shape of the mandrel. In addition, the bladder such a bladder would not be durable and be capable of repeated use. The process of the French patent application also necessarily leaves the rigid metal mandrel inside the part during cure. This has the disadvantage of substantially slowing the rates of heat up and cool down during cure, because the large thermal mass of the metallic mandrel is thermally insulated by the relatively low conductivity composite material. Also, a large number of rigid mandrels are needed to flow through the entire bladder fabrication, shaft fabrication process, substantially increasing capital equipment costs.
BRIEF SUMMARY OF THE INVENTION
The present process involves an improvement of the process disclosed in U.S. Pat. No. 5,534,203, issued Jul. 9, 1996, which is hereby incorporated by reference. In this method plastic laminates are laid up around an inflatable bladder and placed in a female mold. The bladder inflates to compact the laminates to substantially eliminate voids and form a smooth, hollow shaft with a structurally strong and stiff skin. The outer dimensions of the shaft are defined by the dimensions of the female mold. This manufacturing process can generally be referred to as a “molding process” or the shafts can be referred to as “molded shafts”. A particular advantage of this system is that since there is no internal mandrel that must be removed, complex shapes can be formed. In addition, the compression from the bladder is significantly higher that in fixed mandrel processes, which significantly improves the properties of the final part. However, a problem with this process, particular in the formation of golf shafts, is that the movement of the impregnated fiber from inflation of the bladder can displace the fiber sufficiently to compromise the properties of the cured part.
In the present process, the advantages of the molding process are retained while minimizing the movement of impregnated fiber during inflation of the bladder. Thus, the advantages of the molding process are combined with the advantages of fixed internal mandrel processes.
The advantages of the present invention are provided by providing an inflatable bladder that functions as a mandrel in that it is used to form a preform with the same approximate dimensions of the final part. The bladder is dimensioned so that any expansion of the bladder and the preform is minimized when the bladder is pressurized to compress the preform against the female tooling. The preform must only be slightly smaller than the inner dimensions of the female tooling to permit insertion of the bladder and preform into the tooling.
By forming the preform around a bladder that closely defines the shape of the final part, the advantages of the fixed mandrel process is achieved, since there is little movement of the fiber during the subsequent curing process. Since, there is no hard mandrel that has to be removed, but a flexible bladder, complex profiles of the shaft can be achieved and the shafts of the invention are not limited to simple tapers.
The invention can be viewed as the formation of a preform around a pressurizable rubber mandrel, the mandrel providing both the way to closely defined the shape of the preform to the final shape as well as provide the way for compressing the preform against female tooling that defines the outer dimensions of the part. Thus, the bladder, functioning as a mandrel, provides the advantage avoiding material fiber displacement by defining the preform shape to closely correspond to the final shape, but since the bladder is of a flexible material it can be removed from shafts having complex profiles. The bladder also has the function of providing a compressive force to compress the preform during curing, by pressing the preform against female tooling. Since the preform need only be slightly smaller to enable placement of the preform in the female tooling, only minimum expansion of the preform results from the pressurization, with little or no displacement of fiber. In preferred practice, a rigidizer, in the form of metal mandrel is inserted in the shaped elastomeric bladder of nonuniform wall thickness, to provide a more or less rigid substrate for preform construction. The rigid interior mandrel has conical shape with gradual, continuous, and perhaps varying rates of taper down its length, which allow it to be easily extracted after preformed construction and before cure.
The invention is basically a dual function molding tool, a shaped bladder of nonuniform wall thickness which (1) serves as a dimensional template like a mandrel in the formation of the preform, and (2) a systems for compressing the preform to provide for a high-performance composite material. Furthermore, the shaped elastomeric bladder with non-uniform wall thickness can be easily removed from interior spaces which would trap a rigid mandrel. The removal of the shaped elastomeric bladder from a trapped shape is achieved by pulling on, and thereby stretching the bladder to a smaller diameter. In contrast, rigid tooling that would be removable would be of a segmented multipiece design, which would not be economical or practical.
The invention allows for manufacture of shafts of varying diameter where, (1) the preform is dimensio
Milovich Dimitrije
Nelson Ronald H.
Dye Rena L.
Sonntag James L.
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