Background of the Invention Construction toy sets have proven to be a long lasting and popular type of toy due in no small part to the full endorsement of educators and child development experts. Such experts appreciate the skill development that occurs as children construct various items of complexity from relatively simple components. Early playsets utilize various stamped metal links together with plates all defining a plurality of apertures therein. The links and plates were variously configured and were joined using conventional fasteners such as screws and nuts.

Another early type of construction toy set utilized wood in fabricating complex structures. The most popular of such sets utilized a plurality of elongated dowels together with pluralities of junction blocks having passages formed therein at various angles for joining the end portions of the dowels to each other.

In recent years the advent of construction toy sets which employ elements fabricated of molded

plastic have become the most popular and widely used type of toy set. Molded plastic processes have several inherent advantages which toy practitioners were quick to realize in shifting from metal and wooden playsets. For example, plastic components may be molded at a relatively low cost notwithstanding complex shapes which would be impractical in other processes. Further plastic molded components can be fabricated of lightweight material in a variety of shapes, colors, and sizes. In addition, plastic elements are uniquely qualified to provide snap-fit attachment and removal of interlocking elements.

Snap-fit attachment is highly desirable in such construction toy sets due to the ease of use and the fact that no tools are required making the set highly desirable for younger children. In addition, the degree of fit, that is the insertion/withdrawal force, for snap-fit members may be adjusted to suit children of a selected age bracket.

In most construction toy sets mechanical apparatus is provided for supporting rolling wheels to allow the fabrication of toy vehicles. Unfortunately, however, these mechanisms are often complex and costly to a degree which is disproportionate to the total cost of the playsets. For example, such wheel supporting mechanisms often utilize axles and axle supports or the like. In providing wheels and wheel supporting structures for construction toy sets, practitioners have found that molding the wheels themselves is difficult to do in a simple injection molding process. Often the need to make larger volume tires proves impractical in the process of molding large volume solid masses for the tires. As a result, practitioners often must resort to a plurality of

parts to allow them to make the hollow tire and wheel assembly in sufficiently light weight to be processed in a simple injection mold.

U. S. Patent 4, 690, 656 issued to Friedman et al sets forth WHEEL AND WENCH ASSEMBLIES UTILIZING IDENTICAL HUBS AND AXLES IN A TOY CONSTRUCTION SET which includes a special block having an axle projecting therefrom, the axle having a slot providing a pair of resilient legs with a groove formed near the free end of each leg. A hub has a bore for receiving the axle and a releasable snap action retention. A resilient tire is provided for mounting upon the hub.

U. S. Patent 3, 638, 352 issued to Christiansen sets forth a SPLINED SHAFT AND WHEEL RETAINED THEREON BY SPRING AND HUB ELEMENT includes a splined shaft and a wheel element nonrotatably fitting thereon and retained by a spring ring which grips the shaft. The hub element is detachably secured to the wheel with the spring occupying a recess between the wheel and hub elements.

U. S. Patent 3, 651, 597 issued to Daenen sets forth an INTERCONNECTING TOY BLOCK SET having generally cubic modules defining various combinations of outwardly extending posts and cylindrical concave recesses to permit joining of the elements. A plurality of disk-like elements having center holes are receivable upon the modules and may engage other similar disks to provide rotatable elements.

U. S. Patent 5, 022, 885 issued to Lyman sets forth a TOY CONSTRUCTION SET FEATURING RADIATING FACE AND COMPLEMENTARY EDGE CONNECTORS having variously

configured interconnecting building blocks with their facets defining structure for attachment to other facets of other blocks.

U. S. Patent 5, 310, 376 issued to Mayuzumi et al sets forth a TOY THAT CAN BE ASSEMBLED INDEPENDENTLY BY A CHILD having a multiply apertured generally flat frame and a set of rolling wheels for support thereof.

Various elongated bendable elements having fittings at their respective ends are securable to the flat elements to build complex shapes.

U. S. Patent 4, 861, 307 issued to Larws sets forth a WHEEL FOR A MODULAR ASSEMBLY SYSTEM operable with plug-in elements. The dimensioning of all elements is based on a basic length and the wheel defines a square central axle hole with rectangular slots radially cut from the center hold.

U. S. Patent 3, 654, 726 issued to Witte sets forth a TOY BUILDING SET AND DISK-LIKE UNITS THEREFOR having spaced flexible rims defining a peripheral slotted portion therein. The rims are undercut along their walls and terminate in an inner peripheral concave wall on the hub of the toy. The toy unit serves as a female connector for other toy members sized for a releasable fitted connection thereto or may operate as a wheel gear or sprocket in a complex structure.

U. S. Patent 4, 164, 090 issued to Fischer sets forth an ASSEMBLY KIT FOR ASSEMBLING A TOY VEHICLE having a chassis supporting modules which are secured to the chassis in a releasable fashion and which together form various types of toy vehicles.

U. S. Patent 5, 186, 672 issued to Tung sets forth a MULTIPURPOSE BLOCK TOY having a set of blocks, a set of connecting rods, and a set of rollers in which the blocks may be separately used in playing the game of Domino or may be interconnecting with rods and rollers to form a more complex structure.

U. S. Patent 2, 649, 803 issued to Andre sets forth a SNAP-FASTENER TOY BLOCKS in which a plurality of differently shaped blocks are provided with male and female snap elements on their outer surfaces whereby complex structures may be formed by snap-fitting the blocks together.

U. S. Patent 5, 667, 326 issued to McGaffigan sets forth a FLEXIBLE TIE STRUT for supporting both compressive and tensile forces which includes a tension member and a coaxially mounted compression member.

While the foregoing described prior art devices have improved the art, and in many instances enjoyed commercial success, there remains nonetheless a continuing need in the art for a rotatable wheel for a construction toy set which is more suited to modern, low cost, high volume injection molding processes and which avoids the need for costly wheel mounting apparatus.

Summary of the Invention Accordingly, it is a general object of the present invention to provide an improved rotatable wheel for toy construction set. It is a more particular object of the present invention to provide an improved rotatable wheel for toy construction set

which is readily fabricated using simple injection molding processes and which is easy to secure and remove from other cooperating construction toy elements without additional apparatus.

In accordance with the present invention, there is provided a wheel in combination with a toy construction set, the toy construction set including a plurality of couplers each having at least one spacer supporting an enlarged flange, the wheel comprising : a generally cylindrical tire having a tread surface defining a plurality of interleaved ribs and grooves, a hub supporting the tire and defining an inner face, and a wheel connector defining a receptacle and front face generally parallel to the inner face, the front face defining a slot and cylindrical portion for receiving a flange of a coupler in a rotatable attachment, the receptacle being of sufficient size to allow the flange of a joined coupler to rotate within the receptacle.

Brief Description of the Drawings The features of the present invention, which are believed to be novel, are set forth with particularity in the appended claims. The invention, together with further objects and advantages thereof, may best be understood by reference to the following description taken in conjunction with the accompanying drawings, and in which : Figure 1 sets forth a perspective view of a pair of prior art construction toy set coupling elements ;

Figure 2 sets forth a perspective view of a rotatable wheel constructed in accordance with the present invention ; Figure 3 sets forth the present invention rotatable wheel joined to an exemplary combination of conventional construction toy elements ; and Figure 4 sets forth a section view of the present invention rotatable wheel taken along section lines 4- 4 in Figure 3.

Description of the Preferred Embodiment Figure 1 sets forth a pair of prior art conventional coupling elements utilized in construction toy sets of the type to which the present invention rotatable wheel is particularly suited.

Such coupling elements are well known in the art and provide the highly beneficial above-described snap-fit attachment to other plastic toy construction set elements.

With specific attention to Figure 1 and the prior art structure shown therein, a coupler 10 includes a generally cubic six-sided body having a plurality of outwardly extending snap-fit connectors 12,16, 17, 30, and 33 facing outwardly in different directions.

Each snap-fit connector shown in Figure 1 is substantially identical in structure to snap-fit connector 12. Thus snap-fit connector 12 is exemplary and the descriptions thereof apply equally well to the remaining snap-fit connectors in the elements shown.

Snap-fit connector 12 includes a generally cylindrical spacer 14 supporting an enlarged flange 13. The latter defines a passage 15 extending therethrough

which, in the most typical prior art structures, is a continuous bore extending entirely through cubic body 11 and the oppositely positioned snap-fit connector (connector 17 in this case). Flange 13 is substantially square with the corner portions being faceted to provide the above-described rotatable attachment capability.

A nonrotatable coupler 40 defines a receptacle 41 having inwardly extending frontal walls to form a slot 42. Nonrotatable coupler 40 further includes a pair of lock surfaces 43 and 44 which extend toward slot 42 but which define a greater distance therebetween than the distance across slot 42. In the typical fabrication of the prior art devices, slot 42 is slightly larger than the spacer and somewhat smaller than the flange of a standard snap-fit connector.

Thus nonrotatable coupler 40 is snap-fitted to a snap- fit connector such as connector 30 by forcing the spacer thereof through slot 42 such that flange 31 thereof is captivated behind slot 42. Locks 43 and 44 extend inwardly to form a channel therebetween which is slightly larger than the dimensions of flange 31.

Thus a snap-fit connection is made in which the interaction of the spacer and slot 42 secure coupler 40 to coupler 10 while the presence of lock portions 43 and 44 prohibit rotation of flange 31 within receptacle 41. The resulting connection is a nonrotatable connection which virtually joins couplers 10 and 40 to form a single structure.

A rotatable coupler 20 also of conventional fabrication includes a rectangular body 21 supporting a plurality of snap-fit connectors 22 through 26 which are substantially identical to snap-fit connector 12.

Rotatable coupler 20 further includes a receptacle 27

defining a slot 28 in the connecting wall thereof. In a similar fashion to the above-described coupling of couplers 10 and 40, a snap-fit connector such as connector 33 of coupler 10 is positioned such that spacer 35 is aligned with slot 28 and thereafter coupler 10 is forced downwardly to insert spacer 35 through slot 28 and captivate flange 34 within receptacle 27. Typically rotatable couplers such as coupler 20 utilize a slot configured to define an enlarged cylindrical portion for receiving the coupler spacer and for better facilitating rotation.

Comparison of receptacles 41 and 27 reveals that both receptacles define a slot (slots 42 and 28, respectively) for receiving a spacer and captivating a flange of a snap-fit connector. The difference, however, is found in the use of lock portions such as portions 43 and 44 in a nonrotatable coupler such as coupler 40 and the absence of such lock portions in a rotatable coupler such as coupler 20. Thus it will be apparent that rotation of nonrotatable coupler 40 correspondingly rotates coupler 10 due to the engagement of lock portions 43 and 44 with flange 31 while rotation of coupler 20 is freely accomplished without moving coupler 10 due to the absence of locking portions leaving flange 34 free to rotate within receptacle 12. Thus the prior art device shown in Figure 1 exemplifies rotatable and nonrotatable couplers having various other elements of the type typically found in such snap-fit construction toy sets.

Figure 2 sets forth a perspective view of a rotatable wheel for toy construction set which enjoys particular advantage when utilized in combination with the above-described type of toy construction set and

in which is generally referenced by numeral 50. Wheel 50 defines a generally cylindrical tire 51 having a tread surface 54 defining a plurality of inwardly extending grooves 55,56, 57, and 58. Between grooves 55 through 58 a plurality of ribs 65,66, 67,68, and 69 are formed which combine to form a tread surface 54 upon which wheel 50 rolls. Wheel 40 further defines an inner face 52 which, in accordance with the present invention, supports a wheel connector 70. By way of overview, wheel connector 70 is substantially the same as receptacle 27 of rotatable coupler 20 shown in Figure 1. Thus wheel connector 70 includes a pair of side walls 71 and 72 together with a bottom 74 and a front face 73. The combination of side walls 71 and 72 together with bottom 74 and front face 73 define a receptacle 78 positioned against inner face 52.

Front face 73 defines a slot 75, a cylindrical portion 76, and an expansion indent 77.

In the preferred fabrication of the present invention, wheel 50 together with wheel connector 70 is formed as a single integral molded plastic unit suitable for conventional high volume injection molding processes. The function of wheel connector 70 is the provision of a snap-fit attachment to a snap- fit connector such as connector 12 shown in Figure 1.

In further accordance with the present invention, the combination of cylindrical portion 76 being sized slightly larger than the standard size of the spacer within the snap-fit connectors (such as spacer 14 on snap-fit connector 12 shown in Figure 1). The size of cylindrical portion 76 is able to receive a spacer from a snap-fit connector in a sufficiently loose captivity to facilitate rotation of wheel 50 upon the coupling snap-fit connector. In addition, it will be

noted that the structure of wheel connector 70 eliminates flange lock portions such as lock portions 43 and 44 of coupler 40 shown in Figure 1. This facilitates the rotation of a connector flange within receptacle 78. As a result, wheel 50 is easily secured to a conventional coupler and is freely rotatable thereon. This quality of wheel 50 gives substantial ease of use in combination with more complex structures formed of the prior art couplers.

The structure of tire 51 provides an additional substantial advantage of wheel 50 which by facilitating the use of large size tires upon the wheel without the typical difficulties encountered in injection molding such large size wheels in a solid fabrication. The presence of grooves 55 through 58 and interleaved ribs 65 through 69 combine to provide a tire portion which is large in diameter and wide in tread surface but which does not require either the formation of a large volume tire or a separate tire to be secured to a cooperating hub as provided in prior art structures where large size tires are utilized.

In this manner, the injection molding of wheel 50 is greatly simplified and the use of a plurality of parts to provide a rotatable wheel usable with elements of a toy construction set is avoided. As a result, the present invention wheel is substantially lower in cost and is substantially simpler for the user to apply to a toy construction set. One of the advantages of the present invention wheel is the absence of an axle pair arrangement of wheels. This provides substantial flexibility in the fabrication of complex wheeled structures in that the wheel does not mandate any particular position with respect to other wheels on the vehicle.

Figure 3 sets forth a section view of wheel 50 rotatably coupled to a standard coupler 10. Coupler 10 is described above and includes a plurality of snap-fit connectors 12,17, 30, and 33, each having a spacer and flange such as spacer 32 and flange 31 of snap-fit connector 30. In accordance with the above- described toy construction set, a pair of elongated elements 45 and 46 are joined to coupler 10 at snap- fit connectors 17 and 33.

In accordance with the present invention, wheel 50 defines a generally cylindrical tire 51. having a plurality of grooves 55,56, 57, and 58 formed therein which defines a plurality of ribs 65,66, 67,68, and 69 interleaved therebetween. Wheel 50 further defines a large hub recess 60 having an interior hub 61. Hub 61 in turn defines an inner face 52 which supports a wheel connector 70. As described above, wheel connector 70 includes sides 71 and 72 together with front face 73 and bottom 74 which combine to form a receptacle 78 against inner face 52. In the preferred fabrication of the present invention, wheel 50 is fabricated as a single integral injection molded article.

As mentioned above, coupler 10 includes a snap- fit connector 30 comprised of a spacer 32 supporting a flange 31. As is better seen in Figure 2, wheel connector 70 includes a slot 75 formed in front face 73. In the couple position shown in Figure 3, snap- fit connector 30 is snap-fitted within wheel connector 70 to place spacer 32 beneath slot 75 and to captivate flange 31 within receptacle 78. Once again it will be noted that the attachment of wheel 50 to coupler 10 is a rotatable attachment similar to the attachment of rotatable coupler 20 to coupler 10 shown in Figure 1.

As a result, the entire structure of wheel 50 which is preferably formed as a single unit is rotatable about spacer 32 and is able to perform the functions of a freely rolling wheel due to the slight oversize of cylindrical portion 76 (seen in Figure 2) which secures spacer 32.

In further accordance with an important aspect of the present invention, tire 51 defines a substantial tire size without a prohibitive volume of solid material due to the formation of grooves 55 through 58. The presence of grooves 55 through 58 facilitates the structure of ribs 65 through 69 to maintain outer tread surface while greatly reducing the volume of material within tire 51 for any given size.

Figure 4 sets forth a section view of wheel 50 and coupler 10 taken along section lines 4-4 in Figure 3. As described above, wheel 50 includes a wheel connector 70 formed of sides 71 and 72 together with a front face 73 and a bottom 74 which combine to form a receptacle 78. As is also described above, front face 73 defines a slot 75, a cylindrical portion 76 and an expansion indent 77. Flange 31 of coupler 10 is received within cylindrical portion 76 by the placement of spacer 32 within cylindrical portion 76.

As is also described above, the fit of spacer 32 within cylindrical portion 76 is a loose fit allowing wheel connector 70 and as a result wheel 50 to rotate about snap-fit connector 30 as indicated by arrows 36.

Thus wheel 50 may be fitted to a snap-fit connector such as snap-fit connector 30 by simply forcing spacer 32 thereof through slot 75 into cylindrical portion 76. Separation is accomplished by the reverse process of forcing snap-fit connector 30 away from cylindrical portion 76 and outwardly through slot 75. The snap-

fit movement to and from coupling for snap-fit connector 30 is indicated by arrows 37.

What has been shown is a rotatable wheel for toy construction set which is fabricated to provide a snap-fit rotational attachment to a standard coupler of the type utilized in a toy construction set. The inventive wheel provides a wheel connector and tire together with an inner face which provides this snap- fit rotatable attachment while minimizing the volume of material which is to be molded for any given tire and wheel size. The formation of a plurality of grooves and ribs in the tread portion of the tire substantially reduces the volume of material and avoids the problems inherent in a solid tire molding process. The inventive structure also avoids the costly need for a separately fabricated tire to be secured to a separately fabricated rim.

While particular embodiments of the invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects. Therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of the invention.