Patent Application
20050161892
The present invention relates generally to skates and, in particular, to a skate frame having a core of lightweight material to increase structural strength-to-weight and stiffness-to-weight ratio of the frame.
In-line roller skates generally include an upper shoe portion having a base secured to a frame that carries a plurality of longitudinally aligned wheels. The upper shoe portion provides the support for the skater's foot, while the frame attaches the wheels to the upper shoe portion. Because in-line skates are designed to accommodate a variety of skating styles, including high-performance competitions, it is desirable for such skate frames to be lightweight, stiff, and strong. Skate frames may be constructed from a variety of materials, including aluminum, injection molded plastic, and composites. Although aluminum skate frames are structurally strong and stiff, they are expensive. Skate frames constructed from an injection-molded plastic are often reinforced with short, discontinuous fibers. Although such skate frames are lower in cost than aluminum frames, they lack the specific strength and stiffness performance characteristics associated with continuous fiber-reinforced composite frames.
Currently, fibers of glass or carbon are preferred to reinforce composite frames. Glass reinforced composite skate frames are both structurally stiff and strong, but they are heavier than composite frames reinforced with carbon fibers. Although carbon fiber reinforced skate frames are lightweight, strong, and stiff, they are expensive.
Frames constructed from composites reinforced with glass, carbon fibers, or other high performance fibers, may be improved by sandwiching a core material between face sheets or skins of reinforced composite material. The core is a lighter, less expensive material with moderate structural properties in terms of strength and stiffness.
Prior in-line skate frames having a core construction include inverted U-shaped skate frames having a polymer core bonded within the concave portion of the skate frame. In such skate frames, the core is positioned between the frame's arcuate portion and the wheels. Although such skate frames provide increased structural stiffness, the core is subjected to accelerated wear and damage because it is exposed directly to the wheels and road debris. Therefore, such a skate frame may have a shortened useful life.
Other attempts of providing an in-line skate frame with a core include inverted U-shaped skate frames with core material sandwiched between two composite face sheets. In this type of frame, the core extends from below the wheel attachment points upwardly and across the upper surface of the frame. The wheels and shoe portion of the skate are attached to the frame by drilling or molding their respective attachment points through the sandwich construction, thereby subjecting the core material directly to the loads of both the wheel axle and shoe portion attachment bolts. This construction is undesirable because the core material is in direct contact with the wheel and shoe attachment hardware and, therefore, is susceptible to breakage.
Still other attempts of providing in-line skate frames with a core have included a core inserted within the junction between the sole of the shoe portion and the skate frame. Such skate frames have a flange extending laterally from both sides of the upper end of the skate frame, such that the lateral and medial sides of the upper surface span outwardly to cup the sole of the shoe portion therein. The interior of the flange portion is filled with a core material to absorb a portion of the loads associated with traversing a surface. The location of the flanges relative to the frame is custom made to accommodate a particular skater's foot and shoe width. Because the flange portion is sized to cup a specific shoe width, there is limited adjustment of the location of the shoe portion relative to the frame. Therefore, such a skate frame is not very robust in accommodating different skating styles, even for the skater for whom the skate was custom made. Moreover, because the skate is custom made and designed for a particular skater, it is expensive to manufacture.
Thus, there exists a need for a composite in-line skate frame having a lightweight core that not only maintains the frame's strength and stiffness, but also is economical to manufacture, and meets the performance expectations of a skater.
The present invention provides both a skate frame for an in-line skate having an increased structural strength-to-weight ratio, and a method of constructing such a frame. The in-line skate has a shoe portion and a plurality of longitudinally aligned wheels capable of traversing a surface. The skate frame includes first and second sidewalls and a shoe-mounting portion. Preferably, the sidewalls and shoe-mounting portion include skins constructed from a material having a first average density. Each of the sidewalls has an upper end and a lower end. The lower ends of the sidewalls include wheel load introduction portions, wherein loads associated with the wheels are transferred to the sidewalls. The upper ends of the sidewalls are held in spaced parallel disposition by the shoe-mounting portion spanning therebetween. The shoe-mounting portion includes a shoe load introduction portion, wherein loads associated with the shoe portion are transferred to the shoe-mounting portion. The skate frame also includes core material disposed within at least the first and second sidewalls, or within the shoe-mounting portion. The core material is removed from at least the wheel and shoe load introduction portions.
In an aspect of a skate frame constructed in accordance with the present invention, the core material has a second average density that is less than the material density of the skins of both the sidewalls and shoe-mounting portion by a predetermined amount and has predetermined structural properties. The core material occupies a volume within the skate frame to provide the skate frame with an increased structural strength-to-weight ratio.
In an aspect of the first preferred embodiment of the present invention, the core material is positioned within sidewalls. The core material is chosen from a group of materials that includes both reinforced and unreinforced polymers and natural materials.
In another aspect of the first preferred embodiment of the present invention, the skate frame also includes a plug of filler material disposed between the core material and the load introduction portions to absorb at least a portion of the loads associated with the wheels and shoe portion.
In yet another aspect of the present invention, the core material defines a varying height along a longitudinal axis extending between the ends of the skate frame.
In an alternate embodiment of the present invention, core material is disposed within the shoe mounting portion.
In yet another alternate embodiment of the present invention, core material is disposed within both the first and second sidewalls and the shoe-mounting portion.
A method of constructing a skate frame for an in-line skate is also provided. The method includes the steps of forming a U-shaped first skin and positioning core material at a predetermined location on the first skin. The method further includes the step of forming a U-shaped second skin over the first skin, such that the core material is positioned and sealed between the first and second skins. A plug of filler material is disposed between the first and second skins to absorb at least a portion of the loads associated with at least the wheels or shoe portion of the skate. Finally, the method includes the step of curing the frame.
The skate frame of the present invention provides several advantages over skate frames currently available in the art. The skate frame of the present invention is lighter than solid composite or aluminum frames because a lightweight core material occupies a substantial volume within the frame. Also, because the core material is lightweight and provides a distance of separation between the skins of the sidewall, the strength-to-weight ratio of the frame is increased. Further, because the skate frame utilizes a core material that is less expensive than the reinforced composite material it replaces, it is more cost efficient than skate frames having an all-composite construction. Finally, because the core material is removed from the load introduction points associated with the wheels and shoe portion, the skate frame has a longer useful life than skate frames having a core that is in direct contact with the load introduction points. Thus, a skate frame constructed in accordance with the present invention has an increased strength-to-weight ratio and is less expensive than those currently available in the art.
In another embodiment, for each wheel a threaded insert is embedded in the core material in the lateral sidewall with the threaded portion extending into the channel between the first and second sidewall. A tubular insert is installed in the medial sidewall, in axial alignment with the threaded insert, such that a threaded axle can be inserted through the threaded insert and the wheel, to engage the threaded insert, thereby rotatably attaching the wheel to the frame.
In another embodiment of the invention, the first and second sidewalls of the skate frame include a affixed to the outwardly facing surface of each sidewall that wraps around the peripheral edges of the sidewall.
In an embodiment of the invention a polymeric cap film sheet is placed over a frame mold, a composite layer is layed up over the film sheet, substantially filling the mold, and a mold cover is placed over the composite layer and the composite layer is cured.
In an embodiment of the invention a polymeric cap film sheet is placed over a frame mold, a first composite layer is layed up over the film sheet, a polymeric foam core is placed over the composite layer and a second composite layer is layed up over the foam core, substantially encapsulating the foam core. The composite layers are then allowed to cure.
The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:
The shoe portion 22 has an upper portion 30 and a base 32. The upper shoe portion 30 is preferably constructed from a flexible and durable natural or man-made material, such as leather, nylon fabric, or canvas. The upper shoe portion 30 also includes a conventional vamp 40 and vamp closure, including a lace 42, extending along the top of the foot from the toe area of the foot to the base of the shin of the skater. Preferably, the upper shoe portion 30 is fixedly attached to the base 32 by being secured beneath a last board (not shown) by means well-known in the art, such as adhesive, riveting, or stitching. Alternatively, any skate footwear may be used with frame of present invention.
The base 32 is constructed in a manner well known in the art from a resilient composite polymeric or natural material. The base 32 includes a toe end 34, a heel end 36 and a toe cap 44. Suitable materials for the base 32 includes semi-rigid thermoplastic or thermosetting resins, which may be reinforced with structural fibers, such as carbon reinforced epoxy, or other materials, such as leather, wood, or metal. The toe cap 44 surrounds the toe end of the upper shoe portion 30 and is suitably bonded to the base 32. Alternatively, the toe cap 44 may not be used or may be formed of a different material from the rest of the base 32, such as rubber. Because the upper shoe portion 30 is preferably constructed from nylon or other flexible, natural, or man-made materials, the function of the toe cap 44 is to protect the toe end of the upper shoe portion 30 from impact, wear, and water. The toe cap 44 also extends around the lateral and medial sides of the toe end of the upper shoe portion 30 to provide additional support to the foot of the skater.
Referring to
The wheels 24 are conventional roller skate wheels well known in the art. Each wheel 24 has an elastomeric tire 54 mounted on a hub 56. Each wheel 24 is journaled on bearings and is rotatably fastened between the first and second sidewalls 52 and 53 on an axle bolt 58. The axle bolt 58 extends between laterally aligned first and second axle mounting holes 60 and 61 (
The base 32 of the shoe portion 22 may be rigidly fastened to the shoe mounting portion 50 of the frame 20 by well-known fasteners (not shown), such as bolts or rivets. The fasteners extend vertically through the toe and heel ends 34 and 36 of the base 32 and into corresponding holes extending vertically through the shoe mounting portion 50. Although it is preferred that the shoe portion 22 be rigidly fastened to the frame 20, other configurations, such as detachably or hingedly attaching the shoe portion to the skate frame, are also within the scope of the present invention.
The frame 20 includes an inner skin 62, core material 64, structural filler material 66, and an outer skin 68. Within the meaning of this specification, skins are used to designate layer or layers of material. The inner and outer skins 62 and 68 are preferably constructed in a manner well known in the art from a lightweight and high strength material, such as a carbon fiber reinforced thermosetting polymer or a fiber reinforced thermoplastic. Preferably, the filler material 66 is also a lightweight and high strength material having structural properties, such as strength and stiffness, greater than the core material 64. In particular, the filler material 66 can be the same composite material used to construct the inner and outer skins 62 and 68, or the filler material 66 can be some other material that is more structural and dense than the core material 64. Thus, while the type of material used as filler material 66 is not important to the invention, it is important that the filler material 66 is more structural in terms of stiffness, density, and strength than the core material 64. Furthermore, although the preferred embodiment is illustrated and described as having a separate plug of filler material 66, other configurations, such as a frame without filler material, are also within the scope of the present invention and are described in greater detail below.
Still referring to
Although it is preferred to have a plug of filler material 66 surrounding the axle mounting holes 60 and 61, other configurations are also within scope of the invention. As seen in the nonlimiting example of
As may be seen better by referring back to the preferred embodiment of
As configured, the risk of damage to the core material 64 from the shoe portion 22, the wheels 24 and direct exposure to the environment is minimized by utilizing an enclosed torsion box construction, wherein the core material 64 is sealed within the frame 20. Damage to the core material 64 is also minimized by removing core material from at least the load introduction portions of the frame 20, wherein loads associated with the wheels 24 and shoe portion 22 are transferred to the frame 20. Furthermore, because the core material 64 has a density that is less than that of either the filler material 66 or the material used to construct the inner and outer skins 62 and 68, and because it occupies a substantial volume within the sidewalls 52 and 53, the frame 20 is lighter than a comparable frame without the core.
Although it is preferred to dispose core material 64 within the first and second sidewalls 52 and 53 of a U-shaped frame, other locations of the core material 64 are also within the scope of the present invention. As seen in the first alternate embodiment of
As configured within the shoe mounting portion 150 of the skate frame 120, the core material 164 has a variable depth along the longitudinal direction of the skate frame 120. As seen better in
Preferably, the upper shoe mounting portion 150 also includes a pair of vertically extending shoe attachment bores 151a and 151b. The shoe attachment bores 151a and 151b are each sized to receive a shoe attachment fastener (not shown) vertically therethrough. The fasteners are adapted to attach the toe and heel ends of the shoe portion 22 (
As seen in the second alternate embodiment of
Although a single piece frame having first and second sidewalls integrally formed with the shoe mounting portion is the preferred embodiment of the present invention, other configurations are also within the scope of the present invention. As seen in a first nonlimiting example of
As a second nonlimiting example, the frame 420 may be a two-piece frame. Referring to
In a preferred method of constructing a frame 20, core material 64 may be sealed within the sidewalls 52 and 53 of the frame 20. First, uncured inner skin composite material reinforced with fibers is laid up on a male mold until the desired thickness is achieved. The mold is substantially U-shaped in configuration. Then, core material 64 is disposed within the mold in the desired location. In the preferred embodiment, core material is disposed along the sides of the sidewalls of the inner skin. Although it is preferred that core material is positioned along the arms of the inner skin, core material may be disposed along other portions of the inner skin, such as along the arcuate portion or along both the arcuate portion and the arms of the inner skin.
Filler material 66 is then placed in the desired location within the mold. Uncured outer skin composite material is then applied to the mold, such that the core material and filler material are sandwiched between the inner and outer skins. A female mold is placed over the lay-up and the entire lay-up is permitted to cure. Although a plug of filler material is preferred, other configurations, such as eliminating the plug of filler material and laying the inner and outer skins to seal the core material therein, are also within the scope of the method of the present invention.
An alternate method of constructing a frame 20 in accordance with the present invention is identical to the preferred method, as described above, with the following exceptions. In place of the outer skin composite material, a decorative sheet 500 may be applied to the mold, such that the core material and the filler material are sandwiched between the inner skin and the decorative sheet 500. In still yet another alternate method of constructing a frame in accordance with the present invention includes the steps as outlined above for the preferred method with the following exception. As seen in
Another embodiment of the present invention is shown in
In the preferred embodiment, the transverse member 626 is formed continuously with the sidewalls, and has an arch shaped configuration. The foam core 664 extends from near the lowermost edges of the sidewalls 622, 624 to the upper end portions of the sidewalls, adjacent the beginning of the curvature of the arch shaped transverse member 626.
Referring still to
The tubular insert 610 extends all the way through the medial sidewall 624, in axial alignment with the threaded insert 602, providing an aperture therethrough having a diameter approximately equal to the diameter of the axial aperture 25 through the wheel 24. In the disclosed embodiment, the tubular insert 610 includes an outwardly-extending circumferential ridge 611, which is embedded in and surrounded by the foam core 664 of the medial sidewall 624. The circumferential ridge 611 secures the tubular insert 610 in the frame 620. It will be apparent to one of skill in the art that the present invention could be practiced without the circumferential ridge 611, by securing the tubular insert by any other suitable means, for example with a friction fit, an epoxy, or with outer flange portions. The axle 612 includes a head portion 614, including a keyed engagement aperture 613, an axle shaft 616 having a diameter slightly smaller than the aperture provided by the tubular insert 610, and a threaded end portion 615 that is adapted to engage the threaded insert 602.
The wheels 24 can therefore be easily installed in the frame 620 by aligning the axial aperture 25 of each wheel 24 between the threaded insert 602 and the tubular insert 610, inserting the axle 612 through the tubular insert 610 and the wheel aperture 25 to the threaded aperture 605, and screwing the axle 612 in place using a suitable tool keyed to the engagement aperture 613. It will be appreciated that the axle 612 can easily be installed with one hand, and that the imbedded threaded insert 602 precludes the possibility of dropped and/or lost attachment hardware that might occur in a conventional “nut and bolt” design. Moreover, it will be appreciated that in the human anatomy, the medial side of the foot is generally more easily accessible, and therefore, because the axle 612 is inserted through the medial sidewall 624, it will be relatively easy for the user to tighten and/or rotate (i.e., change the order of) the in-line wheels 24 when the in-line skates 618 are on the user's feet. It should be readily apparent to one of skill in the art, however, that the present invention could be practiced with the positions of the threaded inserts 602 and the tubular inserts 610 reversed.
As seen most clearly in
In a preferred method of construction, the inserts 602 and 610 are placed and held in a desired position in a mold, and a foam core material such as a polymeric foam, which may include reinforcing materials, is either injected or poured into the mold and permitted to set, thereby substantially embedding the inserts 602 and 610 in the foam core 664, preferably with a narrow portion of the inserts extending out from the surface of the foam, for example, with the threaded insert 602 extending from the inside surface of the foam and the tubular insert 610 extending slightly from both the inside and outside surface of the foam (where inside surface refers to the side that will be facing the opposite sidewall and outside surface refers to the side that will face away from the opposite sidewall). Fiberglass is then placed into a mold around the foam core 664 and the assembly is pressed together under heat and pressure to form the structural frame member. In the disclosed embodiment both sidewalls 622, 624 of the frame 620 are formed as a single, integral piece with the transverse member 626. In the alternative embodiments discussed above the sidewalls and transverse member may be formed as separate pieces, or in various combination, and then assembled into the desired frame. It will be appreciated that although fiberglass is used in this preferred embodiment, other outer sidewall materials are also possible, including various structural polymers, and pre-formed or pressed metals such as aluminum sheets.
In another preferred method of construction, the inner and outer layers 662 and 668 respectively, may first be formed and joined to form a hollow frame shell. For example if the frame shell is made from stamped metal, such as aluminum sheet, or reinforced fiberglass, the shell may be formed in two parts that are then joined together. The inserts 302 and 310 may be positioned in the frame shell, and suitable foam core material injected into the shell to form the foam core 664 with the inserts embedded therein.
The inner and outer layers, 762 and 768 respectively may be constructed in a manner well known in the art from a lightweight and high strength material, such as a carbon fiber reinforced thermosetting polymer or a fiber reinforced thermoplastic. The core material 764 is preferably an unreinforced or reinforced polymer, such as a structural foam or a syntactic foam, having an average density that is less than the density of the inner and outer layers 762, 768. The core material 764 may alternatively comprise a natural material such as wood, or a low-density viscoelastic material. In the preferred embodiment the core material 764 is encased between the inner layer 762 and the outer layer 768, and extends longitudinally for a substantial portion of the length of the sidewalls 722 and 724. As shown in
In the present embodiment the outer layer 768 of each sidewall 722, 724 is covered with a protective and/or decorative cap 770 that conforms and adheres to the outer layer 768. The protective cap 770 includes a main body portion 772 and a peripheral lip portion 774 extending from the body portion 772. The lip portion 774 extends generally over the edge of the sidewalls 722, 724 to protect and/or improve the aesthetic aspects of the sidewalls 722 and 724.
The protective cap 770 is preferably made from a relatively elastic, abrasion-resistant material, for example a tough polymer such as nylon, urethane, acrylic, polycarbonate or blends thereof that will not splinter or fray when abraded. The preferred cap material is a blend of acrylic and urethane. It will be appreciated from
It will also be appreciated that in particular for frames utilizing a fiber-type composite material such as a carbon fiber reinforced composite, the composite material can have a tendency to fray at the edges when subjected to external stressors such as abrasions and the like. By providing a flexible cap over the edges, the fiber composite portion of the frame is protected from such wear and tear, and the durability of the skate frame's appearance is improved. The portion of the frame 720 facing the channel between sidewalls 722, 724 is substantially hidden from view by the skate wheels and the opposite sidewall.
Although the protective cap construction is shown in
In a preferred method of constructing the sidewalls, a first mold piece having an indented portion corresponding to the desired frame sidewall shape is provided. A sheet of protective film, which may be partially pre-formed to correspond to the desired skate shape, is placed into or over the first mold piece indented portion. The protective film may be provided with a decorative design, preferably on the inner surface of the film. A first layer of fiber reinforced resin is then pressed into the mold depression, over the protective film. A pre-shaped core material, such as a polymeric foam is then placed over a portion of the first layer of fiber reinforced resin, and a second layer of fiber reinforced resin is layed up over the core material and the first layer. A second mold piece is then placed over the mold, and the mold is heated and pressed to facilitate setting of the resin. After sufficient time for setting has been allowed, the sidewall is removed from the mold, and excess materials are removed, to produce the desired frame. It will be appreciated that additional mold pieces may be utilized, depending on the complexity of the sidewall shape.
Similarly, in a preferred method of constructing a skate frame, wherein the skate frame is made unitarily, such as that shown in
Although a preferred method of construction has been described, it will be apparent that other methods of construction are possible and contemplated by this invention. For example, the layer materials or foam core may be injected into an assembled mold that is adapted to receive an injection of foam or resin material. Alternatively, the cap may be preformed to conform to the outer shape of the sidewalls, placed over the finished sidewalls and affixed thereto, for example with an adhesive. Other methods of construction will be apparent to one of skill in the art.
Yet another embodiment of a skate frame 820 according to the present invention is shown in
The frame 820 is covered with a protective and/or decorative cap 870 that conforms and adheres to the outer layer 864, extending over the connecting transverse portion 826. The protective cap 870 includes a main body portion 872 and a peripheral lip portion 874 extending from the body portion 872. The lip portion 874 extends generally over the edge of the frame 820 to protect and/or improve the aesthetic aspects of the sidewalls 822 and 824.
The protective cap 870 is preferably made from a relatively elastic, abrasion-resistant material, for example a tough polymer such as nylon or urethane, that will not splinter or fray when abraded.
Another embodiment of a skate frame 920 according to the present invention is shown in
A threaded insert 602 having a head portion 604 embedded in the foam core 964 of the lateral sidewall 922, and a threaded tubular portion 603 extending through the inner layer 962 of the lateral sidewall 922. An axle 612 including a shaft 616 with a head 614 at one end and a threaded portion 615 at the other end is inserted through an aperture in the medial sidewall 924, to threadably engage the threaded insert 602. The outer layers 968 are covered with a protective and/or decorative cap 970 that conforms and adheres to the outer layer 968. The protective cap 970 includes a main body portion 972 and a peripheral lip portion 974 extending from the body portion 972. The lip portion 974 extends generally over the edges to protect and/or improve the aesthetic aspects of the sidewalls 922 and 924.
In this embodiment the foam core of the medial sidewall 924 comprises an upper portion 964a and a lower portion 964b. The outer layer 968 of the medial sidewall 924 curves inwardly to engage the inner sidewall 962 between the foam core portions 964a and 964b, providing structural support at the aperture 25 for the axle 612. Another advantage of the protective cap construction is apparent from
Although this embodiment is shown with an embedded, threaded insert 604 in the lateral sidewall 922, it will be readily apparent that the lateral sidewall could alternatively be formed with a foam core similar to that shown for the medial sidewall 924, and a conventional axle nut could be utilized to attach the axle 612 to the frame 920.
The previously described versions of the present invention have several advantages over skate frames currently available in the art. The skate frame of the present invention is lighter than solid composite or aluminum frames because a lightweight core material occupies a substantial volume within the frame. Also, because the core material is lightweight and has moderate structural properties in terms of strength and stiffness, the strength-to-weight ratio of the frame is increased. Further, because the skate frame of the present invention utilizes a core material that is less expensive than the reinforced composite material it replaces, it is more cost efficient than skate frames having an all composite construction. Finally, because core material is removed from the load introduction points associated with the wheels and shoe portion, the skate frame has a longer useful life than skate frames having a core that is in direct contact with the load introduction points. Thus, a skate frame constructed in accordance with the present invention has an increased strength-to-weight ratio and is less expensive than those currently available in the art.
From the foregoing description, it may be seen that the skate of the present invention incorporates many novel features and offers significant advantages over the prior art. It will be apparent to those of ordinary skill that the embodiments of the invention illustrated and described herein are exemplary only and, therefore, changes may be made to the foregoing embodiments. As a nonlimiting example, core material located within the sidewalls or upper surface of the skate frame may bulge outwardly, such that the sidewalls have a bubble contour to accommodate the core. Thus, it may be appreciated that various changes can be made to the preferred embodiment of the invention without departing from the spirit and scope of the invention.
While the preferred embodiment of the invention has been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the invention.
This application is a continuation of application Ser. No. 10/421,003, filed Apr. 21, 2003, which is a continuation of application Ser. No. 09/861,170, filed May 18, 2001, which is a continuation in part of application Ser. No. 09/199,398, filed Nov. 24, 1998, now U.S. Pat. No. 6,422,577, priority from the filing date of which is hereby claimed under 35 U.S.C. § 120.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10421003 | Apr 2003 | US |
| Child | 11029152 | Jan 2005 | US |
| Parent | 09861170 | May 2001 | US |
| Child | 10421003 | Apr 2003 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 09199398 | Nov 1998 | US |
| Child | 09861170 | May 2001 | US |
