US 3229978 A
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Description (OCR text may contain errors)
Jan. 18, 1966 R. J. GUGLIELMO, SR 3,229,978
SYNTHETIC MATERIAL BOWLING PIN WITH UNIFORM DENSITY Filed Nov. 29, 1961 INVENTOR Rm-mu I. Go QHSLMQ ,SIL,
ATTORNEY United States Patent 3,229,978 SYNTHETIC MATERIAL BOWLING PIN WITH UNIFORM DENSITY Richard J. Guglielmo, Sn, Cresskill, N.J., assignor, by
mesne assignments, to Poly-Chem Development Corp., Passaic, NJ., a corporation of New Jersey Filed Nov. 29, 1961, Ser. No. 155,607
4 Claims. (Cl. 273-82) This invention relates to bowling pins 'and more particularly to plastic bowling pins having improved life characteristics while duplicating all desirable physical characteristics of the wooden bowling pins traditionally utilized throughout the bowling industry including rebound and sound as well as comparable weight.
It has been customary in the bowling industry to use bowling pins manufactured of wood. Such wooden pins have normally been made of a single solid piece of silver maple wood or laminated pieces of silver maple wood which has been aged for a number of years and then kiln dried. The single piece of laminated wooden preforms are carefully turned to near specification diameters throughout their length and then finely polished and accurately finished. Because of variation in grain and wood density from point to point, the finished laminated pin structure may be unbalanced in that its center of gravity may not coincide with the pin axis and/or may be located at an inappropriate distance above the pin base. Moreover, because of grain and density differences, no two wooden pins can possibly be exactly alike.
' While uniformity of pin weight is highly desirable, the aforementioned grain and density variations in the woods utilized in pin manufacture has forced pin certifying organizations to establish pin standards with substantial tolerances. For instance, the classic wooden pin of the bowling industry weighs between three pounds, two ounces and three pounds, ten ounces. Further tolerance is given in the location of the center of gravity, being specified at a maximum of 5 inches and minimum of 5 inches above the base of the pin.
' Inasmuch as the pins are struck by bowling balls which are traveling at a highrate of speed, and since the striking area between the ball and the pin is relatively small, each time a pin is struck by a bowling ball it is damaged to some extent. Furthermore, the bowling pins fly when struck by the bowling balls and strike each other or components in the alley pit. This results in further damage to the pins.
Numerous attempts have been made to provide a bowling pin which will withstand the shock of the impact of an eleven to sixteen pound bowling ball and yet have proper rebound and sound. Many pin reinforcing schemes have been proposed to increase the impact strength of pins with the result that the reinforced pin does not react or rebound in the same manner as the conventional maple bowling pin. Reinforced pins have likewise failed to yield the usual sound of bowling balls striking the maple pin. Also, much experimentation has been carried out in the area of coating wooden cores with various high impact strength materials including vulcanized rubbers and synthetic plastics such as cellulose acetate butyrate, polyvinyl chloride and ethyl cellulose. Other pins have been molded in their entirety of hard rubbers, plastics and composition materials. In general, the well known plastics, which have in many applications replaced wood, have not proved to be suitable for manufacturing bowling pins because of inherent inabilities to absorb the high shock forces encountered and their deficiences in bounce characteristics and because of molding difficulties resulting in a majority of reject pins.
Recently, efforts have been made to increase the mini- Patented Jan. 18, 1966 mum life expectancy of one thousand games for wooden bowling pins. One method of treatment, which has been found to increase pin life by approximately fifty percent, involves applying an initial impregnating coating of nylon to the pin followed by successive coatings of ethyl cellulose and polyurethane. Another manufacturer has merely applied an impregnating coating of nylon over the central high impact area around the pin. While such coated pins have a longer life than ordinary wooden pins, failure eventually occurs as a result of the formation of blisters or pockets between the covering and the Wooden core.
It is an object of the present invention to provide a relatively inexpensive bowling pin made of synthetic plastic materials.
It is another object of the invention to provide a molded plastic bowling pin having improved strength and performance characteristics and which can be manufactured in quantity with extreme uniformity of weight and accurate positioning of the center of gravity.
It is still another object of this invention to provide a molded plastic bowling pin having superior impact strength and shock absorbency together with proper rebound characteristics.
It is another object of the invention to provide an improved bowling pin which is more resistant to breakage and more capable of retaining its liveliness or ability to rebound after an extended period of service.
It is yet another object of the present invention to provide a relatively inexpensive molded plastic bowling pin having improved strength and performance characteristics and which sounds like a wooden pin upon being struck by regulation bowling balls.
These and other objects and advantages of the present invention will hereinafter appear and for purposes of illustration, but not of limitation, an embodiment of this invention is shown in the accompanying drawing, in which the figure is a longitudinal sectional view of a bowling pin embodying the features of this invention with the elements designated by number therein.
All prior attempts to fabricate a suitable plastic bowling pin have failed because of the inability of the plastics employed to meet in total the criteria established by the classic wooden pin. The common plastics including polyethylenes, vinyls, polystyrenes, urethanes, etc. in rigid form (when cast in the shape of bowling pins) have been unable to withstand the high impact forces or absorb the shock stresses encountered during normal pin usage. The foam plastics, while in some cases evidencing adequate shock absorbing qualities, do not have suflicient weight and rebound. Another failing has been the inability of plastics in bowling pin form to sound like a wooden pin upon being struck under game conditions with a regulation bowling ball.
It has been found in accordance with the practice of this invention that an improved bowling pin can be fabricated so as to exhibit excellent shock absorbing characteristics while possessing extremely high longitudinally oriented impact strength.
Referring now to the drawing, the bowling pin of this invention comprises a lower body portion 10, a neck portion 12 and a head portion 14 of main pin form 16 hearing outer shell or skin portion 18.
The main pin form 16 may be comprised of a cast plastic material formed by the polymerization of a suitable thermosetting resin. The pin form 16 must be strong, tough and rigid and, during curing, must exhibit controllable shrinkage.
It has been found that the high impact stresses experienced by bowling pins are primarily longitudinally oriented with'the most critical area for breakage located in the reduced diameter neck portion. To increase the impact strength of the pin of this invention, there may be provided an outer skin 18 also formed of a thermosetting resin and preferably the same resin as the thermosetting resin of the cast pin form 16 or a resin compound physically and chemically compatible with said cast pin form. This outer skin is reinforced, particularly in a longitudinal or axial direction, by fibrous filling material such as discontinuous or staple glass fibers. Continuous glass fibers may be employed in the form of mats fabricated as by swirling the endless filaments or strands of continuous fibers, or they may be chopped or cut to shorter lengths for mat or batt formation.
The specific gravity of the pin form material, in accordance with the invention, is important in establish ing (for given thermosetting materials), the finished weight of the pin. As heretofore mentioned, regulation bowling pins weight between three pounds, two ounces and three pounds, ten ounces. For example, to duplicate the weight characteristics of a three pound, eight ounce regulation wooden pin (specific gravity of 0.765) using a thermosetting resin having a normal specific gravity of 1.17; fillers, having for example a specific gravity of .25 to .30, are added to the resin pin form mix to the extent necessary to reduce the effective resin volume 'to the point (55% of the total volume) whereby the effective pin form specific gravity of 0.523 is obtained. In the foregoing example, the specific gravity of the outer skin (18% of total pin volume) approximated the 1.17 specific gravity of the thermosetting resin without filler, yielding a desired overall specific gravity for the pin of 0.765.
Investigations relative to the suitability of the wellknown synthetic plastics for manufacturing bowling pins.
has yielded the following observations. The common thermoplastics, which can normally be molded by blow molding, injection molding and slush molding techniques, are difficult to utilize in the context of the heavy molded section of a bowling pin. For heavy objects, such as bowling pins, molding reproducibility with thermoplastics is poor and heat control is critical and difiicult to maintain and control. Too much heat results in charring While too little heat results in poor flow characteristics.
Of the common thermosetting resins, olyesters have shown good flexibility and hardness characteristics and good moldability in the context of bowling pin manufacture but such plastics exhibit relatively poor bounce and sound characteristics as compared to the classic wooden pin. The epoxy resins have generally poor molding and finishing characteristics and, without modifiers, become extremely brittle. Further, the epoxies have good bounce characteristics but have high specific gravities and poor sound characteristics. Phenolics, like epoxies, are normally too brittle for high impact applications and for absorbing shock.
Through the present invention a bowling pin can be economically manufactured of any desired weight and reaction to impact by the bowling ball depending upon the choice of resin and filler materials employed in pin form 16. As heretofore mentioned, in accordance with the invention pin form 16 is formed of a thermosetting resin. It is essential that the exotherm of this material be relatively low and controllable whereby the molding of the thick pin portions can be successfully carried out without improper material flow, heat patterns or material charring. Thermosetting materials which have been found to be exceptionally suitable for fabricating the pin form and coating of the bowling pin of the present invention are the resins formed as a result of catalytic plymerization of unsaturated cyclic acetal monomers. Such monomers include (but are not limited to): 3,9-dialkenylspirobi (meta-dioxane) including 3,9-divinyl-spirobi (meta-dioxane) or diallylidene-pentaerythritol and 3,9- dipropenyl-spirobi (meta-dioxane) or dicrotonylidenepentaerythritol; and -ethyl S-hydroxymethyl 2-propenyl omers are the condensation derivatives of crotonaldehyde and pentaerythritol.
The unsaturated cyclic acetal based A-stage resins or polymerized unsaturated cyclic acetal monomers mentioned above together with appropriate fillers and catalyst (such as diethyl sulfate), when brought to proper temperature C. to 150 C. and preferably 95 C. to
105 C.), yield a moldable thermosetting plastic composition having: ideal bounce and wood sound characteristics together with exceptional impact strength and long life; and the proper degree of hardness as specified by pin certifying agencies. The weightcompensating resin filler should be a material of substantially lower specific gravity which will not in any way interfere with or affect the superior strength, rebound and sound characteristics of the resin. The preferred filler material is a particulate phenolic resin supplied in the form of minute hollow spheres. Such spheres, termed Microballoons (trademark), may have a specific gravity of about 0.25 to about 0.30 and are incorporated directly into the liquid resin whereby (when the resin-Microballoon materials are in proper proportion) the composition yields. a pin of suitable physical characteristics and which meets the weight requirements of the American Bowling Congress. Proper weight may be derived from a resin mixture as set forth in the following example:
It has been found that Microballoon filler material in amounts of between about 15 parts by weight to about 40 parts by wei ht for parts by weight of A-stage resin yield pin forming compositions of proper weight.
Weight compensating filler spheres, similar to Micro- 'balloon spheres, may also be formed of glass.
As previously mentioned, the bowling pin of this invention may be fabricated with an outer shell 18 for added impact strength, particularly in the neck area 12 and the. high impact band about the pin body portion 10. Such shell is preferably composed of the same thermosetting resin material utilized in the pin form 16, but without weight reducing fillers and appropriately reinforced by strong longitudinally oriented fibrous material such as glass fibers. The outer shell or skin 18 may be 80 to 300 mils thick or more or less as desired and is also intimately united with the pin form 16 at the interface of such shell and pin form. Titanium dioxide may be added to adjust the final whiteness of the pin. Other coloring agents may be utilized as desired. Proper coloring of the outer shell or skin 18 has been derived from a resin mixture as set forth in the following example:
Constituent: Parts by weight A-stage resin (Spirobi) 100.0
Diethyl-sulfate (Catalyst) 0.5 Titanium dioxide (Color agent) 1.0
Total parts 101.5
It is contemplated in accordance with the present invention that a relatively thin final protective coating of urethane may be applied to pin shell 18. The urethane coating reacts with any free hydroxyl groups that arepresent on the cured cross-linked A-stage resin to form a truly intimate chemical-mechanical bond therewith.
Although not illustrated, the base of the pin of this invention may be provided with a recess of appropriate character and dimensions so that the pin will receive the pin or peg of the well-known pin setting devices.
While the invention has been described in its preferred form, other modifications may be resorted to without departing from the spiirt thereof, and the scope of the invention will be best defined in the appended claims.
1. A synthetic bowling pin of standard size and shape having improved rebound, impact and sound characteristics comprising a molded body defining said pin and formed of the cured condensation product of a liquid cyclic acetal based A-stage thermosetting resin in which there is uniformly dispersed a quantity of weight compensating relatively low specific gravity discrete, hollow, spherical particles, said pin having a substantially uniform density throughout and a specific gravity Within certified bowling pin specifications.
2. A synthetic bowling pin of standard size and shape having improved rebound, impact and sound characteristics comprising: a molded body portion defining said pin including a substantially uniform dispersion of discrete, hollow, spherical particles in a quantity of the cured condensation product of a liquid cyclic acetal base-d A-stage thermosetting resin having a higher specific gravity than the particles, said body portion having a substantially uniform density throughout and a specific gravity within certified bowling pin specifications; and a relatively thin shell portion intimately surrounding and bonded to said body portion and formed of said cured cyclic acetal based A-stage thermosetting resin.
3. A synthetic bowling pin as claimed in claim 2 wherein the weight compensating particles are formed of a phenolic resin.
4. A synthetic bowling pin of standard size and shape having improved rebound, impact and sound characteristics comprising a molded body defining said pin including a substantially uniform dispersion of discrete, hollow, spherical phenolic particles having a specific gravity of between 0.25 and 0.30 in the cured condensation product of a liquid cyclic acetal based A-stage thermosetting resin, said resin having a specific gravity greater than the specific gravity of said pin, said pin being of substantially uniform density, and said particles being dispersed in said cured resin in an amount sufficient whereby said pin has a specific gravity of between 0.68 and 0.79.
References Cited by the Examiner UNITED STATES PATENTS 1,620,310 3/1927 Whelan 273-82 2,909,506 10/1959 Guest et a1 2606'7 2,944,821 7/1960 Mason 273-82 3,012,987 12/1961 Ansul.
3,022,273 2/1962 Guest et a1. 26067 X 3,037,771 6/1962 Gambino 273-82 3,147,975 9/1964 Gruss et -al 2'73-8Z RICHARD C. PINKHAM, Primary Examiner.
F. BARRY SHAY, Assistant Examiner.