Background of the Invention

Recreational skateboards are made of wood or molded plastic material. High quality wood boards are usually finished with a varnish or synthetic material which may peel or crack, leaving the board or its finish subject to water damage. Nonskid surfaces are added to wooden boards by bonding nonskid tapes which stick to the top of the board but which may peel off in use. The desired curvatures are difficult to form in the- wooden boards.

Known plastic boards may be less strong than wooden boards and may have surfaces which are less attractive and less amenable to design.

While the curvature of plastic boards may be controlled by molds, thick¬ ness and weight may cause problems.

Summary of the Invention

The present invention overcomes problems existing in the prior art in unique manners.

The decorative lower sheet rigidifies the reaction molded upper body member. Reinforcement bars extending through the upper body member and held in precise position by clips which become part of the body member cooperate with the lower rigidifying sheet to provide rigidity to the skateboard.

The curvatures of the upper and lower surfaces are controlled to provide a relatively thick central portion and relatively thin edge portions. The thickness differential provides wheel clearance for the flexible trucks when turning, provides maximum strength to weight ratio, and provides a highly desirable thin-appearing board.

The mold-shaped reinforcing sheet provides maximum rigidity, auto bonding at maximum and uniform pressure and facility of manufacture. The reinforcing sheet with preformed wheel wells provides optimum strength when, the wheel wells are required for turning.

The unique manufacturing steps provide a structural bottom which may be predecorated in a flat shape before final compound bending. The upper surface is formed with a permanent finish which is waterproof and which provides a permanent nonskid finish.

Reinforcing elements are placed in clips and the assemblies are placed on a convex inner surface of a first cavity of a first mold half. A recrea¬ tional skateboard apparatus is made by placing a reinforcing sheet having a decorative outer surface against a rim of the first cavity on the first mold half. A second mold half having a second cavity with a concave inner surface is placed over the sheet. The mold halves are placed together and the first cavity is filled with reaction injection molding material. Pressure of the

reaction material bonds the material to an inner face of the sheet and forms the sheet on the curved inner face of the second cavity. The convex curved inner face of the first cavity has a nonslip pattern which forms a nonslip pattern in the upper surface of the skateboard which is molded upside down. After the mold halves are separated and the skateboard is removed, edges of the sheet are trimmed. The concave inner surface of the second cavity has flat central areas for forming truck mounting areas on the surface of the sheet. One sheet is formed with prepressed wheel wells along side edge por¬ tions adjacent the flat truck mounting areas. Skateboards made according to the present invention have concave and convex curved upper and lower surfaces with relatively thick central portions and relatively thin lateral edge por¬ tions. Upper surfaces are self-formed nonskid surfaces with self-formed design patterns. Other upper surfaces are formed smooth to accept grip tape. Lower surfaces are formed of the decorative plates which are permanently self- bonded to the molded upper main bodies. Reinforcing rods and supporting clips are permanently encased in the upper bodies.

Recreational board apparatus of the present invention comprises an elon¬ gated body having upper and lower surfaces and having longitudinally extending opposite curved side edges and having relatively short forward and rearward edges interconnecting respective forward and rearward ends of the side edges. The body has an upper body member extending between the opposite side edges and forward and rearward end edges. An upper surface of the body member forms the upper surface of the board apparatus, and a bottom curved structural sheet member is connected to a lower surface of the upper body member for rigidify- ing the upper body member and the recreational board apparatus. A lower surface of the bottom sheet member forms the bottom surface of the recreational b apparatus.

Preferably, the lower surface of the bottom plate member comprises a

decorative outer bottom surface of the recreational board apparatus.

Preferably, the upper surface of the upper body member has integrally formed nonskid surface patterns therein.

In a preferred embodiment, the upper body member is a reaction injection molded body member.

Preferably, the bottom sheet member is attached to the upper body member during reaction injection molding of the upper body member.

In a preferred embodiment plural longitudinal reinforcement elements extend from near the forward edge to near the rearward edge of the apparatus in the upper body member. Preferably, the plural reinforcement elements extend through the upper body member in positions nearer to the upper surface thereof than to the lower surface of the body member.

Preferably, the reinforcement elements are held in clips having inward openings.

The preferred board apparatus is a skateboard.

In preferred embodiments the board apparatus is relatively thick between upper and lower surfaces in a middle portion and is relatively thin between upper and lower surfaces at lateral edges thereof. The upper surface of the board is concave and the lower surface of the board is convex.

Preferably, the concave upper surface has relatively large radii of curvature and the lower surface has relatively short corresponding radii of curvature.

Preferably a central portion of the lower surface is flattened.

Gross sections of the board apparatus have upper surface sections of generally uniform radii of curvature.

Gross sections of the board member have lower surfaces with generally flat central portions and generally uniform radii of curvature at opposite edge portions extending between the lateral edges and the central portion.

Preferably, areas of the bottom surface near the forward and rearward edges are substantially flat for receiving skate trucks.

In one embodiment the bottom sheet member has prepressed wheel wells at lateral edge portions thereof near the forward and rearward edges. The remainder of the sheet is formed during molding and joining of the top member.

A preferred skateboard apparatus has a relatively thick upper body member and a relatively thin bottom rigidifying member permanently attached to a lower surface of the upper body member.

Preferably, the upper body member is a die formed reaction injection molded member, and the bottom sheet member is formed with compound curves and is secured to the upper body member by the reaction injection molding of the upper body member.

The preferred method of manufacturing a skateboard comprises placing a sheet of material across a rim of a first mold half having a first cavity with a convex inner surface, placing a second mold half having a concave cavity against the first mold half with a rim of the second mold ^"~ half in contact with the sheet, filling the first mold half with reaction injection molding product and expanding the product within the mold cavity and against the sheet, permanently shaping the sheet against the cavity in the second half and bonding the reaction injection molding material to an inner side of the permanently formed sheet, separating the mold halves and removing the skate¬ board product from the mold cavity.

These and further and other objects and features of the invention are apparent in the disclosure which includes the above and ongoing specification with the claims and the drawings.

Brief Description of the Drawings

Figure 1 is a bottom plan view of the skateboard constructed according to the present invention.

Figure 2 is a side elevation of the skateboard shown in Figure 1.

Figure 3 is a top plan view of the skateboard shown in Figures 1 and 2.

Figures 4, 5 and 6 are sections taken along lines 4-4, 5-5 and 6-6 of Figure 3 *

Figure 7 is a longitudinal cross section taken along line 7-7 of Figure 3-

Figure 8 is a cross-sectional view of the first and second mold halves used to construct the skateboard shown in Figures 1-7.

Figure 9 is an end elevation of the clips used to support longitudinally extending reinforcement elements in the mold cavities.

Figure 10 is a detail of the flat reinforcing sheet before being inserted in the mold. _

Figure 11 is a plan view of the mold shown in Figure 8.

Figure 12 is a top plan view of an alternate form of the invention in which the bottom plate is provided with wheel wells.

Figure 13 is a bottom plan view of the skateboard shown in Figure 12.

Figure 14 is a side elevation of the skateboard shown in Figure 12.

Figures 15, 16, and 17 are cross-sectional details of the skateboard shown in Figure 12 taken along lines 15-15, 16-16 and 17-17, respectively.

Figure 18 is a longitudinal cross-sectional detail of the skateboard shown in Figure 12.

Detailed Description of the Drawings

Referring to Figures 1-7, a skateboard is generally indicated by the numeral 1. The skateboard has curved upper and lower surfaces 2 and 4 and curved opposite longitudinally extending lateral edges 6 and 8. A curved front edge 10 and a curved rear edge 12 interconnect the side edges. The lower surface 4 is a highly polished, smooth surface which carries surface decoration in a preferred embodiment. The upper surface 2 shown in Figure 3 has a general overall nonskid surface 14 as well as an integrally formed pattern 16.

As shown in Figures 4-7, the skateboard is made of an upper body portion 20 and a reinforcing lower sheet 22. The reinforcing lower sheet 22 has an upper surface which is permanently bonded to .the lower surface of the upper body portion 20. Reinforcing bars 24 spaced slightly downward from the upper surface 2 extend through the upper body 20 in a direction generally parallel to the lateral edges 6 and 8.

In a preferred embodiment the reinforcing elements are steel bars and the reinforcing sheet 22 is an aluminum sheet. Alternatively, the reinforcing elements 24 may be made of some other high tensile strength material which is compatible with the material of the body 20. The reinforcement sheet 22 may be made of some material other than aluminum, for example fiber -reinforced plastic. The aluminum sheet is preferred since it provides the requisite strength in conjunction with the reinforcing bars 24, and the aluminum pro¬ vides a surface which may be bent in the compound curves as required of the lower surface and which may provide a surface for decoration.

As shown in Figures 4, 5 and 6, curvature of the upper surface 2 and the lower surface 4 varies according to the particular spacing between front edge 10 and rear edge 12.

Throughout the figures it can be seen that the center of the board is thicker than the corresponding edge portions. This is particularly pronounced in the areas near edges 6 and 8 to provide wheel clearance at the edge por¬ tions.

As shown in Figure 7, besides being curved across the board, the board is also curved upward' at its forward and rearward portions.

In the preferred method of construction shown in Figure 8, the board is formed in two mold halves 30 and 32. The upper mold half has a relatively shallow concave cavity 34« The lower mold half has a relatively deep cavity 36 with a convex lower surface 38. Pins 40 on the lower mold half extend into openings 42 on a upper mold half to positively locate the mold halves.

Clips 44, such as shown in Figure 9, hold the reinforcement elements 24 in position during the molding. The clips 44 become part of the upper body 20.

Three or more of the clips may be used.

First the rods 4-6 are snapped through openings 48 into the holders 50 in the clips. The openings 50 have edges 52 which prevent outward movement of the rods 24 through the openings 48 during the molding operations.

Knobs 54 at the bottoms of the holders 50 space the holders and rein¬ forcing elements 4 a precise distance above the convex surface 38 of mold cavity 36. Connectors 56 space the holders 50 and rods 46 a precise distance apart and spring levers 58 push the connectors 56 and holders 50 downward in the mold during the reaction injection and hardening process.

A previously decorated reinforcing sheet 60, as shown in Figure 10, is placed on a rim of the mold cavity 36, with the hole 62 engaging one pin 40 and the slot 64 engaging another pin. The slot 64 permits slight longitudinal movement of the sheet while preventing lateral movement of the sheet.

After the sheet 60 is placed on the pins 40j ^" the mold halves are closed.

The sheet presses downward against elements 58 of the clips 44, pushing the clips against surface 38.

The reaction injection molding products are injected into cavity 36, and expansion of products rapidly presses the sheet 60 upward against the concave surface of cavity 34 in mold half 30. Springs 58 continue to push the clips 44 downward. The high pressure in the mold cavity permanently bonds the reaction injected material to the inner surface of the sheet 60. After the mold halves are separated and the skateboard blank is removed, the sheet 60 is trimmed to the final skateboard shape.

In an alternate embodiment, as shown in Figures 12-18, the skateboard embodiment 70 has upper and lower curved surfaces 72 and 74 similar to the curved surfaces 2 and 4 of skateboard 1. Lateral edges 76 and 78 are con¬ nected by front and rear edges 80 and 82. Wheel wells 84 and 86 are provided in the lower surface of the board. The central portion 88 of the board is without indentations, as shown in Figures 15 and 17.

The board is made of an upper main ^" body portion 90-and a lower reinforc¬ ing sheet 92 and reinforcing bars similar to the bars 24 used in the first embodiment. The major distinction between the second embodiment and the first embodiment is that the wheel wells 84 and 86 are preformed in the decorative sheet before the otherwise flat decorative sheet is placed in the mold for forming against the concave surface of the smaller cavity which has convex wheel well shaped portions on its generally concave surface.

While the invention has been described with reference to specific embodi¬ ments, modifications and variations of the invention may be constructed with¬ out departing from the scope of the invention.

The scope of the invention is defined in the following claims.