Abstract:
A plastic pin, such as a bowling pin, for bowling lanes. The pin has a hard shell that surrounds a core of cellular and/or porous material, preferably a thermoplastic material. The interior of the shell has at least one partition that divides the hollow interior of the shell.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a plastic pin, including a so-called bowling pin, for bowling lanes. The pin has a hard shell that surrounds a core of cellular and/or porous material, preferably a thermoplastic material. 
     During the manufacture of such pins, the shell is first produced, for example by blow molding. The material for the core, to which has been added an expanding agent, is then introduced into the shell, and in particular from below, i.e. from the base of the shell, in order in this manner to fill the shell with expanded material. Although such pins can be made true to shape, difficulties often arise with respect to the level of the center of gravity, which is significant with respect to the tipping characteristic of the pin. 
     It is therefore an object of the present invention to improve a pin of the aforementioned general type in such a way that the level of the center of gravity of the pin body can be affected in a simple manner. 
     This object, and other objects and advantages of the present invention, will appear more clearly from the following specification in conjunction with the accompanying schematic drawing, which is a partially broken away view of one exemplary embodiment of the inventive pin. 
     SUMMARY OF THE INVENTION 
     The pin of the present invention is characterized primarily in that the interior of the shell is provided with at least one transverse wall or partition such that at least two chambers are formed above one another within the shell. These chambers can then be filled as desired with porous and/or cellular material or even with other materials, with it being expedient to use materials having different specific weights. It would also be possible to fill, for example, one chamber while leaving a second chamber unfilled. 
     Preferably merely a single partition is provided, and in particular in the vicinity of the head of the pin, so that, for example, by filling the upper chamber with a material having a lighter specific weight, it is possible to affect the tendency of the pin to tip, i.e. the level of its center of gravity. 
     Although the partitions can be continuous to thereby provide for complete partitioning, it is nonetheless preferable to provide the partitions with small holes that can then serve as venting means when the pertaining chambers are filled with a material that forms a cellular and/or porous core. 
     Further specific features of the present invention will be described in detail subsequently. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cut away view of the bowling pin in accordance with the present invention. 
     FIG. 2 shows an alternate embodiment of the instant invention with an unfilled head portion. 
     FIG. 3 shows another embodiment where the material in the head portion is of different specific weight. 
     FIG. 4 shows the pin filled with reinforcing fiber. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring now to the drawing in detail, the illustrated pin, in a customary manner, is provided above a base 1 with a barrel portion 2, a neck 3 and a head 4. In other words, in the region of the neck 3 the outer diameter of the pin is reduced. 
     The contour of the pin is determined by its shell 5, which is made of a hard, impact resistant plastic, for example one having a polyamide base. The shell 5 is made, for example, by blow molding and has a wall thickness of about 3 to 6 mm. 
     In the neck region, and in particular in the region between the head 4 and the neck 3, the shell 5 has a horizontal transverse wall or partition 6 that extends through the hollow interior of the shell 5 such that it divides the interior of the shell 5 into an upper chamber 7 and a lower chamber 8. However, the partition 6 is not continuous, but rather is provided with a central hole 9 having a diameter of about 5 mm. Similarly, a hole 10 is provided in the middle of the upper end of the head 4; the hole 10 can have a diameter of about 5 mm. 
     The partition 6 is disposed at such a level that the chamber 7 has a volume of about 50-100 cm 3 . It is therefore also possible to dispose the partition 6 at the level indicated by the dot-dash line &#34;a&#34;. 
     After the shell 5 has been produced, a plastic to which has been added expanding agent and which has a specific weight of about 0.4-0.8 kg/dm 3 , preferably having a polypropylene base, is introduced into the chamber 8 via the base 1 through a hole provided there. The expansion of the material then takes place in the chamber 8. In so doing, the air that is displaced can escape upwardly through the holes 9 and 10. Glass fibers or other reinforcing fibers can be mixed with the plastic. 
     Under these conditions, the chamber 7 can remain unfilled. However, it is also possible to fill this additional chamber at the upper end of the pin with a material that forms expanded material and cells but that generally has a specific weight of only 0.1-0.2 kg/dm 3 , in other words, a specific weight that is only about 1/4 that of the material that fills the chamber 8. 
     Although generally only one partition 6 is provided, it would also be possible to provide a further partition in order to divide the shell 5 into three chambers. These chambers should also communicate with one another by small holes provided in the partitions for venting reasons. 
     It should be noted that the aforementioned holes 9, 10 do not, with the diameter values that are provided, allow for any significant amount of the expanding material to pass therethrough. Rather, these holes restrict the passage of the expanding material from one chamber to the other while at the same time allowing air to escape in an unobstructed manner. 
     The present invention is, of course, in no way restricted to the specific disclosure of the specification and drawing, but also encompasses any modifications within the scope of the appended claims.