1.  Technical Field
The present invention is directed toward bowling pins, and specifically to an improved bowling pin base. 
2.  Background Art
Bowling pins typically have a wooden core, with a plastic coating for impact protection and durability.  A bowling pin base insert is connected to the bottom of the wooden core and serves to reinforce the plastic cover.  The bowling pin base is connected by forming an undercut in a groove in the wood and then heating one end of the insert to cause the plastic to flow into the undercut to bond the two parts together.  This has the inherent disadvantage of being mechanically a cumbersome application and one which is difficult to monitor from a quality control point of view.  Longevity of the pin is also a consideration as the use of two parts bonded together represents a point prone to later separation. 
One proposed solution to this problem has been to bond or fuse the reinforcement base insert or ring into the encapsulating plastic cover instead of the wood.  U.S. Pat.  Nos.  4,332,078 to Mallette and 4,865,320 to Unterberger illustrate devices embodying this general concept.  The base insert has a generally L-shaped perimeter seated into an undercut annular opening of the wooden core at the bottom of the pin prior to applying the plastic coating to the pin.  The base insert is locked to the outer plastic coating or cover during the process of encapsulating the wooden pin with its outer plastic cover.  During the covering process, the heated coating material flows into the undercut of the L-shaped perimeter of the base insert and forms a locking lip which bonds the base insert to the cover. 
This type of base insert for interengaging the wooden core and the outer coating has inherent disadvantages.  The base is held in place only by the molded plastic locking lips formed by the outer coating.  In the high impact bowling environment, it is likely for the molded lips to fracture, resulting in the loosening of the base insert.  Because of the geometry of the base, it is possible for the base to completely disengage the pin. 
In the Unterberger U.S. Pat.  No.  4,865,320, an expansion gap is provided between the base ring and the wood core and plural blind openings are formed in the bottom of the undercut groove.  The covering material sometimes will and sometimes will not fill the blind openings so that the intended relative rotational anchoring between the cover and the base ring does not always occur so that the base ring breaks loose and starts the deterioration of the pin.  The present invention is directed toward overcoming these problem.