Abstract:
Cylindrical bobbin cores have at least one radially oriented slot formed in at least one end thereof. The slot is sized and configured to mate with a radially extending blade associated with the drive head of the winder so as to achieve positive rotational drive therebetween. In view of this interconnection between the core and the drive head, significantly less spring pressure needs to be exerted against the core by the tail stock of the winder.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to bobbin cores, especially those for use as cores for sideless bobbins pre-wound with sewing thread. 
     BACKGROUND AND SUMMARY OF THE INVENTION 
     The conventional technique to drive bobbin cores during a thread-winding operation involves providing a “knifed” or “serrated” drive head associated with the winder which physically digs into the bobbin core. The serrated drive head spins at high speeds and is intended to prevent the core from slipping during the thread-winding operation. In this regard, even small amounts of core slippage during thread-winding causes the bobbin to be out-of-specification due to incorrect thread tensions. 
     There are several disadvantages associated with the use of conventional serrated drive heads. Specifically, over time the serrations on the drive head become dull due to wear and tear. As they dull, small amounts of slippage may occur which is evidenced by incorrect thread tensions resulting in out-of-specification bobbins. In addition, small amounts of debris or other material may become trapped in the serrations which again might lead to relative slippage between the drive head and the bobbin core. Needless to say, the ends of the cores become scarred due to the frictional engagement with the serrated drive head—a possibility that can lead to structural weakness in the bobbin core and/or a core which becomes out-of-round. 
     The amount of spring pressure required to hold the drive heads against the bobbin core to prevent slippage can also cause operator difficulty during doffing of the wound bobbins and replacement with fresh bobbin cores. That is, as the serrated drive head becomes worn, greater spring pressures are needed in order to overcome the tendency of the bobbin core to slip. 
     Recently, novel magnetic bobbin cores and sideless pre-wound bobbins employing the same are disclosed in copending U.S. patent application Ser. No. 09/447,740 filed concurrently herewith, the entire content of which is expressly incorporated hereinto by reference. In general, such bobbin cores include a cylindrical core with at least one end thereof being permanently magnetized. In preferred forms, the bobbin cores are formed from a thermoplastic or thermoset resin in which magnetized particles are dispersed. The problems noted above, can sometimes be exacerbated by the permanent magnetism exhibited by such bobbin cores. 
     It would therefore be highly desirable if bobbin cores, especially magnetized bobbin cores, could be provided which overcome these difficulties. It is toward providing solutions to such problems that the present invention is directed. 
     Broadly, the present invention is embodied in cylindrical bobbin cores which have at least one radially oriented slot formed in at least one end thereof. The slot is sized and configured to mate with a radially extending blade associated with the drive head of the winder so as to achieve positive rotational drive therebetween. In view of this interconnection between the core and the drive head, significantly less spring pressure needs to be exerted against the core by the tail stock of the winder. 
     These, and other, aspects and advantages of the present invention will become more clear after careful consideration is given to the following detailed description of the preferred exemplary embodiments thereof. 
    
    
     BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS 
     Reference will hereinafter be made to the accompanying drawings wherein like reference numerals throughout the various FIGURES denote like structural elements, and wherein, 
     FIG. 1 is a perspective view of a sideless pre-wound bobbin employing a notched bobbin core in accordance with the present invention; 
     FIG. 2 is perspective view of another embodiment of a notched bobbin core in accordance with the present invention; 
     FIG. 3 is schematic side elevational view, partly in section, of a bobbin winder system in accordance with the present invention; 
     FIG. 4 is an enlarged front end view as taken along line  4 — 4  in FIG. 3 of the drive head employed in the winder system therein; and 
     FIG. 5 is an enlarged side elevational view as taken along line  5 — 5  in FIG. 4 showing the mated relationship between the bobbin and the drive head during a bobbin winding process. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Accompanying FIG. 1 shows a sideless bobbin B which includes a core  10  around which a continuous length of thread  11  is wound. The core  10  is cylindrical and most preferably has a diameter which is substantially the same as its lengthwise dimension. The thread  11  is thus wound upon the bobbin  10  to form a cylindrical bobbin structure B whose diameter is about three times its lengthwise dimension. 
     As shown, the core  10  includes a radially oriented slot  12  formed in end face  10 - 1 . The slot  12  is oriented radially along a lengthwise bisecting plane of the core  10 . Most preferably, the core  10  also has a radially oriented slot  14  defined in its opposite end face  10 - 2 . In this regard, the slot  14  is oriented along the same lengthwise bisecting plane of the core  10 , but is 180° out of phase with the slot  12 . 
     Another embodiment of a bobbin core  20  is depicted in accompanying FIG.  2 . Most preferably, the bobbin core  20  is similarly sized as compared to the bobbin core  10  described above. However, according to this embodiment of the invention, the bobbin core  20  includes a pair of diametrically opposed slots  22  formed on end face  20 - 1  and a pair of diametrically opposed slots  24  formed on the opposite end face  202 . These pairs of slots  22 ,  24  are oriented relative to respective lengthwise bisecting planes of the core  20  so as to be mutually orthogonally disposed relative to one another. That is, each of the slots  22  is disposed radially at an orientation that is substantially 90° relative to the slots  24 , and vice versa. 
     The bobbin cores  10  and  20  are most preferably magnetized as described more fully in the co-pending patent application Ser. No. 09/447,740 filed on Nov. 23, 1999 cited above. In this regard, the bobbin cores  10  and  20  are most preferably a flangeless, sideless bobbin having at least one end which is permanently magnetized. However, the cores may be non-magnetic, if desired. 
     A thread-winding system  30  in which the bobbin cores  10  and/or  20  may be used is shown in FIG.  3 . The discussion which follows will refer to core  10  as depicted in FIG. 1, but it will be understood that the discussion is equally applicable to core  20  depicted in FIG.  2 . In this regard, the core  10  is positioned between coaxially opposed drive head  32  and tail stock  34 . The tail stock  34  is biased by means of spring  34 - 2  toward the drive head  32 . Spring pressure is adjustable by means of the threaded shaft  36  which is threadably engaged with the slide block  34 - 1  of the tail stock  34 . Thus, turning movements applied to the knob  36 - 1  of the shaft  36  will cause the block  34 - 1  to reciprocally move within guides  38  thereby increasing or decreasing the spring pressure exerted against the core  10 . 
     The terminal end  32 - 1  of the drive head  32  is shown in greater detail in accompanying FIGS. 4 and 5. As seen therein, the terminal end  32 - 1  of the drive head  32  is generally conically shaped so as to be insertable within the interior space of the cylindrical core  10 . The terminal end  32 - 1  carries a rigid radially projecting blade  32 - 2  which is mated within the slot  12  of core  10 . Thus, this mated relationship between the terminal end  32 - 1  of the drive head  32  and the slot  12  of core  10  provides for positive drive of the latter by the former. 
     In use, the drive head  32  is rotated by means of a drive motor  40  (see FIG.  3 ). During winding operation, therefore, the core  10  is frictionally engaged between the drive head  32  and tail stock  34  and is rotated by the drive head  32  by virtue of the positive mated drive relationship between the radially extending blade  32 - 2  and the slot  12 . Simultaneously during such rotation, the thread  11  is directed to the core  10  by a traversing arm  42  which reciprocates by traverse cam  44 . The traversing arm  42  reciprocally causes the thread  11  to traverse from one end of the core  10  to the other. After a period of time, therefore, a quantity of the thread  11  will be wound upon the core  10 . 
     When sufficient amount of the thread  11  has been built up on the core  10  to form the bobbin B, the winding operation is stopped to allow  10  automatic doffing of the bobbin B. At that time, a fresh bobbin is placed between the drive head  32  and tail stock  34  and the process repeated. It should be noted here that the operator does not need to align the slot  12  and blade  32 - 2  when a fresh core  10  is initially coaxially placed between the drive head  32  and tail stock  34 . Instead, the spring pressure exerted by the tail stock  34  is sufficient to maintain the core  10  positionally therebetween. On rotation of the drive head  32 , therefore, relative slippage occurs between the terminal end  32 - 1  of the drive head  32  and the adjacent end  10 - 1  of the core  10  until such time as the blade  32 - 2  is rotated into alignment with the slot  12 . At the moment of such alignment, then, the spring pressure will urge the blade  32 - 2  to be seated within the slot  12  so that thereafter, positive rotational drive may be transferred to the core  10  by the drive head  32 . 
     As can be appreciated, the mated relationship between the blade  32 - 2  and the slot  12  of the core  10  prevents relative slippage from occurring therebetween. Moreover, because of this positive drive arrangement, minimal spring tension needs to be applied against the core  10  by mans of the tail stock  34 . As such, if manual doffing of the bobbin B and replacement with a fresh core  10  is required, then it is an easier task for the operator. 
     While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.