Abstract:
Molded plastic yo-yo halves are connectible to each other by an axial having threaded ends that are adapted to threadably engage threaded inserts press fitted into a specially designed socket. The inserts are polygonal as are the sockets with the insertion end of the socket being provided with a shallow registration socket adapted to orient the threaded insert with respect to the socket. The yo-yo halves are molded separately and the inserts are press fitted into the sockets into a subsequent operation, resulting in manufacturing efficiencies as well as a strong properly aligned yo-yo construction.

Description:
CROSS-REFERENCE TO EARLIER APPLICATIONS 
     This application claims priority of U.S. provisional patent application No. 60/061,493, filed Oct. 9, 1997 and entitled “YO-YO AND METHOD FOR ITS MANUFACTURE”. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to improvements in yo-yos and methods for their manufacture. 
     BACKGROUND OF THE INVENTION 
     This invention relates to yo-yos, including, but not limited to high performance yo-yos as described in my U.S. Pat. No. 4,895,547 entitled Superior Performance Yo-Yo. Such high performance yo-yos are adapted to spin or “sleep” for extended periods of time, to permit lengthy and extended tricks to be performed before the yo-yo is wound up on its string. 
     Although the yo-yo construction described in my &#39;547 patent achieves its intended objects, it would be desirable to make further improvements in its construction as well as to achieve further assembly and manufacturing efficiencies. The yo-yo is formed from a pair of injection molded plastic yo-yo halves in a conventional insert molding process in which a HeliCoil internally threaded insert, to which the yo-yo axle will attach, is placed in the mold. The mold then is closed and the plastic is injected into the mold to form the yo-yo half with the threaded insert embedded within the yo-yo half. Such conventional insert molding techniques include the use of core pins within the mold on which the inserts can be placed so that they will be located properly and in registry within the mold during the injection process. The inserts are selected from materials that are softer than those of the mold to avoid the possibility of the mold becoming damaged should an insert be improperly loaded or misaligned and the mold closed under such circumstances. Yo-yos that have been manufactured incorporating the invention described in my &#39;547 patent are commercially available from Yomega Corporation typically have used relatively soft inserts such as those formed from brass. Another inefficient result of making such yo-yos with conventional insert molding techniques is that in the event that a molded plastic yo-yo half is not properly formed it cannot, as a practical matter, be recycled and remolded because of presence of the embedded brass insert. The rejected yo-yo half must be discarded together with the insert. Even with a moderate rejection rate, when such yo-yos are manufactured in very large quantities, the aggregate cost of the lost plastic and insert can become a significant cost factor. 
     Also among the difficulties that may be encountered with the prior yo-yos is that where the threaded inserts are relatively soft as compared to the steel from which the axle of the yo-yo is formed, there may be some tendency for the threads between the axle and the insert to become stripped should the yo-yo be overtightened by the user. Should the threads become stripped, the yo-yo is no longer usable. 
     The yo-yo construction described in my &#39;547 patent, made with insert molding techniques, typically requires that the mold be operated manually by an operator. The inserts are loaded manually onto the core pins. The mold then is closed and locked. The injection step then is performed and monitored. The mold then is opened to remove the molded products, at which time the process is repeated. The procedure necessarily is subject to human error and, also necessarily results in substantial unused mold time when the mold is opened, re-loaded with inserts and closed during the insert loading process. 
     It would be desirable to provide a yo-yo construction and technique for its manufacture that avoids the above difficulties. 
     SUMMARY OF THE INVENTION 
     In the present invention, the yo-yo halves are molded without placing inserts in a mold cavity. The use of insert molding is made unnecessary. Consequently, the yo-yo halves can be made on continuous automated injection molding machinery with substantial higher production capability and operator efficiency than with insert molding. The yo-yo halves are molded to include a socket aligned with the central axis of the yo-yo half. The socket is open at a face of the yo-yo half, defining an insertion end, and is polygonal in cross section. The socket is relatively deep and is adapted to receive, in an interference fit, a similarly shaped threaded insert, by press fitting the insert into the socket. The socket is formed with a shallow registration socket adjacent its insertion end that is slightly larger in cross-section than the socket but having a shape to facilitate orientation and alignment of the nut with the polygonal socket. With the nut being properly aligned with the socket, the nut then can be press fitted into the socket. The polygonal configuration of the socket and nut assure that the nut cannot become loosened within the plastic. Additionally, by attaching the nut to the yo-yo half in a separate procedure, after the yo-yo half has been molded, the nut can be formed from the same material as the yo-yo axle, e.g., steel, so that there is less risk of the connecting threads being stripped. 
     It is among the objects of the invention to provide an improved yo-yo construction that avoids the limitations of insert molding techniques; to provide a yo-yo construction in which the axle of the yo-yo is threaded into an insert in each of the yo-yo halves where the inserts are formed from the same or like materials, and to provide an improved process for manufacturing such yo-yos. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     The foregoing and other objects and advantages of the invention will be appreciated more fully, from the following further description thereof, with reference to the accompanying drawings wherein: 
     FIG. 1 is a sectional, fragmented illustration of the yo-yo taken in part through the diameter of the yo-yo; 
     FIG. 2 is an illustration of an internal face of a yo-yo half as seen along the plane  2 — 2  of FIG. 1; 
     FIG. 3 is an end view of the socket of the yo-yo half as seen from the exterior of the yo-yo along the line  3 — 3  of FIG.1; 
     FIG. 4 is an enlarged section taken through the region of the spool and the yo-yo half, showing the structure for attaching the yo-yo axle to the yo-yo half; 
     FIG. 5 is a sectional illustration of the region of a yo-yo half in which the nut and axle are received; 
     FIG. 6 is a further enlarged diagrammatic illustration of the manner in which the nut insert is aligned with the yo-yo half in readiness for the nut to be press-fitted into its receptive socket; 
     FIG. 7 is a flow chart of a prior art process for forming a yo-yo half; 
     FIG. 8 is a flow chart of the process for forming a yo-yo half in accordance with the invention; and 
     FIG. 9 is an exploded, sectional illustration of a hollow yo-yo half made in accordance with the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     As shown in the drawings, the yo-yo includes a pair of yo-yo halves  10 ,  12  which preferably are formed from a suitable plastic made in an injection molded process. Preferably the yo-yo halves are molded from high strength polycarbonate, although other materials may be used. The yo-yo halves may be about 2 ¼ inch in diameter. When the invention is used with the high performance yo-yo described in my &#39;547 patent, the inwardly facing surface  14  of each yo-yo half is formed with a cylindrical socket  16  that, in turn, communicates with a smaller diameter inner bore  18 . The socket  16  and bore  18  are aligned with the axis of rotation of the yo-yo. The socket  16  is adapted to receive part of a spool  17  that is rotatably mounted about the axle  30  of the yo-yo. The yo-yo halves are essentially identical. The inner bore  18  communicates with a socket  20  that, in the illustrative embodiment, is open toward the outwardly facing surface  15  of the yo-yo half. In accordance with the invention, the cross sectional configuration of the socket  20  preferably is polygonal, desirably hexagonal. It should be understood, however, that other polygonal shapes may be used. The socket  20  is adapted to receive an internally threaded nut  22  having a polygonal shape adapted to fit, in an interference fit, within the socket  20 . Preferably the nut  22  has the same polygonal cross sectional shape as the socket  20 . The relative cross sectional dimensions between the nut  22  and the socket  20  should be such as to permit a press fit of the nut in the socket without unduly stressing the plastic of the yo-yo half while also effecting the secure connection. An interference fit of a few thousands of an inch has been found to be satisfactory. 
     In order to facilitate assembly of the polygonal nut  22  with the yo-yo half, the outer end of the socket  20  is provided with an alignment socket  24  into which an end of the nut  22  can be inserted and which is contoured to engage the inserted end of the nut to align the polygonal shape of the nut  22  with that of the socket  20 . The alignment socket may be the identical polygonal shape as the nut  22  and the socket  20 . It need be only very slightly wider than the socket  20  and should be sufficiently wide to enable an end of the nut  22  to be inserted without interference. During the press fifting operation, suggested by the arrow  21  in FIG. 6, the assembler need only bring the nut  22  against the alignment socket  24  while rotating the nut  22  until the end of the nut drops into the alignment socket  24 . So aligned, the nut then can be pressed fitted into the socket  20 . Because the nut is pressed into the yo-yo half in a separate operation, it is not necessary to use the relatively inefficient, labor intensive insert molding techniques described above. Consequently, it is not necessary to form the nut  22  from a softer material than that of the axle  30 . Both the nut  22  and the axle  30  can be formed from the same material, such as steel, thereby reducing the risk of threads becoming stripped by firm tightening of the yo-yo halves. 
     The axle  30  has threaded ends  32 ,  34  adapted to be screwed into the nuts  22  as shown in FIGS. 1 and 4. The junctures of the unthreaded portion of the axial  30  with  20  the threaded ends  32 ,  34 , define shoulders that abut the inner ends of the nuts  22 . 
     The cylindrical spool  17  is rotatably mounted on the axle  30 , the ends of the spool being received, symmetrically, within the sockets  18  in the yo-yo halves. Details concerning the dimensions and other aspects of the spool  17  are disclosed in further detail U.S. Pat. No. 4,895,597, the disclosure of which is incorporated by reference herein, in its entirety. 
     The nut  22  preferably is made relatively long, longer than the width of the nut  22 , and is intended to mate with a similarly long threaded end  32 ,  34  of the axle  30 . The relatively long length of the nut and its secure press fit into the preformed polygonal socket provides a self-registering arrangement in which coaxial alignment of the axis of the nut and of the molded yo-yo half is assured. Consequently, the resulting yo-yo will be well balanced and will maintain uniform spacing between the yo-yo halves, fully about the circumference of the yo-yo. For example, the nut  22  may be about ¼ inch long. In illustrative example, in which the socket  20  is hexagonal, a hexagonal nut can be press fitted into a socket  20  about 0.001 inch smaller in cross section than the socket  20 . The depth of the socket  20  may be of the order of ¼ inch with the alignment socket  24  being of the order of 0.020 inches in depth. The cross sectional dimension of the alignment socket may be of the order of 0.190 inches, just slightly larger than that of the nut  22  to permit the nut  22  to be inserted and rested on the shoulder  36  defined between the junctures of the socket  20  and the alignment socket. 
     Although the invention has been described, for convenience, in connection with solid yo-yo halves, yo-yos often include yo-yo halves that are hollow. FIG. 9 is an illustration of one such yo-yo half and related components, in exploded view, including a cover  36  for the outwardly facing surface of the yo-yo half, the axle  30  and nut  22 . The sockets and bore may be formed in a boss  38  that protrudes outwardly into the hollow  40  of the yo-yo half. 
     From the foregoing, it will be appreciated that the invention provides an improved structure for a yo-yo as well as an improved method for making the yo-yo. The construction avoids the use of insert molding techniques and results in substantial efficiencies. With the invention, yo-yos may be made with improved alignment. 
     It should be understood that the foregoing description of the invention is intended merely to be illustrative thereof and that other embodiments, modifications and equivalents may be apparent to those skilled in the art without departing from its spirit and scope.