US 3248115 A
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Description (OCR text may contain errors)
April 26, 1955 R. M. CONKLIN ETAL 3,248 ,115
TENDENCIES BOWLING PIN HAVING DECREASED NECK CHECKING Filed March 27, 1963 INVENTORS: Ma
United States Patent 3,248,115 BOWLING PIN HAVING DECREASED NECK CHECKING TENDENCIES Robert M. Conklin, Muskegon, Fred E. Satchel], Grand Haven, and Foster W. Berry, Muskegon, Micln, assignors to Brunswick Corporation, a corporation of Delaware Filed Mar. 27, 1963, Ser. No. 268,301 6 Claims. (Cl. 27382) This invention relates tobowling pins and more particularly relates to decreasing neck checking tendencies in bowling pins.
Bowling pins usedin such games as ten pins and duck pins are subjected during use to high stresses generated at or just below the minimum section in the neck of the pin. Such high stresses, together with the natural configuration of the tissue elements of a wood core, may often result in'checking or failure in the wood core parallel to the wood grains. Such checking is engendered by repeated impacts during use of the pin and/or by a single blow of sufliciently high magnitude to initiate check type failures. Once the checks or splitting failures have been started in a pin, their growth or extension into the body of the pin or into the head section of the pin results in complete failure of the pin. Failure of pins due a prominent cause of shortened pin life.
In games in which bowling pins are used, the action of a pin is appreciably affected by the continuity of the structure of the pin. When neck check failures have progressed sufficiently, the sound or ring of the pin is adversely affected. Such deterioration in sound is well recognized by the bowler as being symptomatic of checked or failed pins in which the reaction of the pin has deteriorated. As a consequence bowlers rightly refuse toplay such pins knowing that checked or failed pins givelower scores. Thus, the proprietor of a bowling establishment must replace such pins, at some expense.
It is a general object of this invention to provide a new and useful bowling pin having markedly reduced neck checking tendencies.
It is a further object of this invention to decrease the neck checking tendencies in wood core bowling pins by providing an increased amount of vertical wood fiber adjacent the pin surface at the neck portion or region of the P Another object of this invention is to provide increased amounts of vertical wood fiber adjacent the surface of the neck of a wood core bowling pin by oversizing the neck portion of the pin core; a more particular object is to provide densified vertical wood peripheral fibers at the neck of the core.
A further object of this invention is to provide a regulation size coated wood core bowling pin wherein the wood core is the primary stress carrying element, having an increased amount of vertical wood fiber adjacent the core surface in the neck portion. I
It is still another object of this invention to improve the manufacture of bowling pins by increasing the section modulus of the neck portion of the pin by providing a greater than normal diameter in the neck portion and normal diameters in other portions of the core, and especially by providing a neck core diameter which is between .100 and .125 inch oversized in diameter compared with the normal core neck diameter and relative to the diameters of other portions of the core.
It is yet another object to improve the manufacture of plasticcoated hardwood ten. pins bowling pins by 'to checking is currently a serious problem and constitutes Patented Apr. 26, 1966 neck portion of the pin to density the vertical wood fibers adjacent the surface, and especially to a maximum depth at and/or subjacent the minimum diameter of the neck portion to give densification of a maximum depth in the range of to A inch from the surface within an area in the neck portion lying between 3 and 8 inches from the top of the pin.
Further objects include the oversizing of the neck portion of a pin followed by coating processes such as include coating to a uniform thickness followed by removal of excess coating material in neck portion or applying a thinner coating at the neck portion of the core relative to other portions of the core, whereby a pin of regulation size is produced having an oversized core neck.
Additional objects will be apparent to those in the art from the following descriptions and drawings in which:
FIG. 1 is a vertical cross-section through an embodiment of a regulation size plastic coated bowling pin of this invention showing an oversized neck portion;
FIG. 2 is a vertical cross-section through another embodimentof a regulation size plastic coated bowling pin of this invention showing a densified neck portion;
FIG. 3 is a cross-section of an embodiment of a regulation size plastic coated bowling pin of this invention with an oversized densified neck;-FIG. 3A is an enlarged portion of the cross-section'of FIG. 3 showing a stepped coating; and
FIG. 4 is a vertical cross-section through a regulation size plastic coated hardwood core bowling pin. While this invention is susceptible of embodiment in many different forms, there is shown in the drawings and will herein be described in detail an embodiment of the invention together with a modification thereof with the "oversizing the neck portion of a pin and thereafter applying sufiicient pressure to the exterior of the oversized understanding that the present disclosure is to be construed as an exemplification of the principles of the invention'and is not intended to limit the invention to the embodiments illustrated. The scope of the invention will be pointed out in the appended claims.
Turning now to FIGS. 1 through 4, there are illustrated three embodiments (FIGS. 13) of regulation size ten pins bowling pins of the present invention and a conventional regulation size wood core plastic coated bowling pin (FIG. 4) for purpose of comparison. In FIG. 1, the various sections or portions of a bowling pin are identified generally as head 15, neck 16, shoulders 17, belly 18 and base 19. FIG. 1 illustrates a pin having an oversized core neck section. The pin includes a hardwood, e.g., maple, core 10 and a plastic coating 11, such as ethylcellulose laid down in layers. Coating 11 is generally from 0.050 to 0.095 inch thick over the surface of the pin except in the neck area, where the neck area portion of the coating, as indicated at 11a, decreases to as thin as 0.008 to 0.015 inch thick. Reference numeral 1012 refers to dotted lines showing normal core configuration, the portion outside of the dotted lines being the amount of the oversizing in the neck, i.e., excess hardwood at the periphery of the neck.
FIG. 2 illustrates another embodiment where the neck portion is densified. Again, the illustrated bowling pin includes a hardwood core 20 having a plastic coating 21, which is uniform over the pin. Reference numeral 20a indicates the densified portion of the neck which decreases The oversized and densified neck region is indicated by reference numeral 30a and the coating of decreased thickness, substantially as illustrated in FIG. 1, is indicated by reference numeral 31a. The coating 31a in the neck region is a stepped layer coating which will be more fully discussed herein below.
FIG. 4 illustrates a conventional regulation size bowling pin having a hardwood core 40 and a plastic coating 41. The exterior dimension of coating 41 in FIG. 4 is of regulation size, as are the exterior dimensions of coatings 11, 21 and 31 in FIGS. 1, 2 and 3 respectively. Thus, the pins of FIGS. 1, 2 and 3, although of regulation exterior size, include additional wood in the neck area by substantially oversizing or oversizing and densifyingthe neck region.
In a plastic coated wood core bowling pin the wood core is the primary stress carrying element. The plastic coating, because of its physical properties, has practically no effect on carrying stresses or inhibiting neck checking since it carries or absorbs only a minute percentage of the longitudinal and shear stresses generated in the geometry of a pin. V
In accordance herewith, an improved pin is provided by niques as well as by solvent washing the neck to remove increasing the amount of vertical wood fiber adjacent the 7 surface in the neck region. This is accomplished by oversizing the neck region. The oversized neck region may subsequently be densified, if desired, to provide a further increase in the amount of wood fiber in the neck region or to compress the neck to normal core size so that a relatively uniform plastic coating can be applied over the pin core without having to subsequently remove part of w p to head of the pin. a It is known that fiber stress is a func tion of the section modulus for a given moment. Thus,
increasing the size of the core neck diameter, in accord-v ance herewith, reduces fiber stress. However, the increase in size of the core neck diameter is limited in that it is necessary to maintain the pin within the dimensions as established by governing bodies for bowling games. The larger radius of transition from the neckto shoulder and head reduces the stress concentration in the neck.
As indicated above, the oversized neck may be densified prior to applying the plastic coating to the pin. Densification may advantageously be used to decrease the diameter of the oversized neck portion so that a plastic coating may be applied to the neck portion in the same thickness as applied to other portions, thereby simplifying the coating operation. In such instance, the core neck diameter may be decreased by densification to the normal diameter of a core neck while maintaining the effective section modulus of the oversized neck, although the larger radius of transition would be lost. Alternatively, the wood core could be shaped to provide sufficient over sizing so that after densification the neck wouldremain of greater than normal'diameter, but less than the regulation diameter for a finished pin, thereby retaining the larger radius of transition and acquiring a still greater effective section modulus. V 7
Where the wood core of the pin is to be coated with plastic material, if the neck has beendensified sufiiciently to provide a normal neck diameter, the usual coating methods may be employed. Accordingly a coating of rather uniform thickness, e.g., varying from about..050 to .095 or more preferably .060 to .065 inch in thickness may be provided on the pin with thickness varying slightly over the core surface. dipping, flow-coating, and the like.
However, where the core having a larger diameter than normal is coated, the plastic coating must be correspondingly thinner at the neck region with increased core thick- Such coatings are applied by A variety of techniques may be used for providing coat-.
ings of reduced thickness in the neck regions. Such techniques include the coating of the pin to a normally rela tively uniform thickness followed by removal of excess plastic material to restore proper dimensions to the pin:
by shaping, sanding, grinding, or other machining techundesired thicknesses of coating. Another technique tor providing reduced coating thickness at the neck is by placing only that amount of coating material on the neck region as is desired. .This maybe done by stepped .coat- I ing or other methods for providing a lesser number of coating layer in the neck region,- minimizing the coating build up in the neck region. niques usually provide a smooth coating in the neck area with a gentle transition into the coating above and below the neck, especially after turning to remove irregularities in the coating.
Additionally, the in core can be partially di ped from eachend, e.g., alternatingly, omittingvthe dipping of'the neck portion' for a sufficient number of dippingsqto i provide a thinner-coating as desired. As another technique the neck area can be masked with tapes or strippable coatings, which are insoluble in the plastic .coating material.
lying coats. These techniques usually provide a stepped coating in the neck area, which may be suflicient as produced or may be machined to provide a smoother transition in, the neck coating, especially where the 7 steps are steep. The stepped layers of coating, ma-
terial are illustrated by reference numbers 32 through 36 in FIG. 3A.. As another technique, when using coating systems of lower viscosity, after the desired thickness or number of layers of coating has been .attainedin neck region.
the art. a Coating material compositions for use in coating bowling pins are well known and any such compositions: are usable in accordance herewith. For example thef coating may be a lacquer of ethylcellulose, nitrocellulose, cellulose acetate, epoxies, urethanes or the like Multilayer coatings of difiering materials may be used if de-. sired. Reinforcingfabrics or other materials may be embedded within the coating, e.g., by placing between coating layers during the coating of the pin. Additionally,
or alternatively, in order to further strengthen the neck of the pin again'stchecking, a thin layer of reinforcing material may be laid directly against the wood fibers of the oversized or oversized and den'sified portionof" the neck prior to application of the coating materiaL-as is disclosed in copendingapplication Serial No. 268,300,
filed on March 27, 1963, and entitled, Pin Having 15E creased Neck Checking Tendencies.
The thinner coating in the neck region does not apprecia-bly detract from the appearance of the pin, so long as sufficient plastic coating is left in the neck area to give a pleasing appearance and maintain physical con- The above coating tech Such masking compositions are applied at the proper level of film build up during the coating process, and upon completion of the coating process. the masks are removed from the pin thereby removing oven 7 present bowling pins. Such coatings readily permit a preferred increase in core diameter of between .100 and .125 inch in the area of maximum oversizing. This increase appreciably reduces the neck checking in pins, being equivalent to approximately a ten to fifteen percent increase in cross-sectional area in the neck;
Turning now to the densification of the wood fibers in the neck region, a concentration of peripheral fibrous material, i.e., at an adjacent outer surface of the neck,
is achieved by densification. The outer surface of the neck (slightly below the minimum diameter) usually carries the maximum-flexural strength resulting from impact of the pin; The ultimate strength of wood in tension compression and flexureis a function of density.
'Ihus, densification of the outer surface provides more material or fibers to reduce stress to a higher degree before checking occurs. When the neck region is densified, 'the density of the fiber varies radially from inside 'the pin to the surface of the pin. The variation of density increase is from practically zero increase, i.e., any increase above normal densitiy being barely apparent,
to a maximum at the surface of the core. Thus, the concentration or densification of the fibers in the pin is provided in a manner which affords the maximum increase in density at the surface, gradually diminishing to .to improve the densification results by application of glycerin, urea, phenols, various inorganic salts, minerals,
animal and vegetable oils, resins forming systems, or other compositions.
More particularly, the densification of the neck section can be efiected by placing a turned bowling pin body within die sections contoured to give densifica tion as desired. Twoor more die sections can be provided to act radially on the pin body, preferably with maximum pressure just below the minimum diameter. Either the pin or die can be rotated, if desired, during the densification process. Alternatively a hydraulic apparatus can be used for applying pressure to the neck section of the pin surface by injecting air or other fluid into a chamber having a flexible wall, e.g., rubber or leather, which transmits pressure from the chamber to the pin surface. In still another densification procedure, the pin is inserted between spaced roll form wheels and the pin is rotated with the spaced wheels pressing against the desired length and depth of densification. After densification of the neck region, it is preferred that the neck be reshaped to remove irregularities in the surface which may be created by compression of the fibers and to assure smooth transition of the neck into the head and shoulder portions of the pin.
The oversizing and oversizing and densifyingof the wood portion of the neck of a pin in accordance herewith is provided somewhere between 3 and 8 inches, and preferably between 4 and 7 inches, from the top of a regulation ten pins bowling pin. Preferably, the neck has a 6 maximum oversizing and/ or maximum density at or slightly below the minimum diameter of the neck, i.e., about 5 to 6 inches from the top of the pin and the oversizing and density respectively each decrease gradually above and below the area of maximum oversizing or density. The length of the oversized and densified portions of the neck can be varied but is usually within the range of about 2 to 5 inches, although an actual length of from 2 to 3 inches would be normally sufficient.
The bowling pins illustrated in FIGURES l and 2 and a control pin (as illustrated in FIGURE 4) of the same construction but without oversizing for densification in the neck were tested in accordance with a rotating beam fatigue test technique adapted to test pin neck fatigue life. The test determines failure in a bowling pin by neck checking due to stresses set up in the pin. Briefly, in accordance with the test procedure, the pin tested is rotated on its longitudinal axis while maintaining a fixed. moment (relative to the rotating pin) of 2400 in. lb. so that as the pin rotates, the tension and compression shifts in such a manner to in effect rotate through the pin so that each portion of the neck surface is exposed to tension and compression in each cycle of pin rotation. The number of cycles before neck checking, i.e., failure of the pin, is taken as the test result, indicative of ability of the pin to withstand stresses in the direction of the longitudinal axis. The results of the test were as follows:
Cycles Pin sample tested: before failure Control (FIGURE 4) 1,900 FIGURE 1 100,000 FIGURE 2 4,400
The above data indicates marked improvement in the present bowling pins, and especially oversized pins, to withstand tension and compression.
In further testing, a set of each of the pins of FIGURES '1 and 2 and a set of control pins (as illustrated in FIG- URE 4) of the same construction with the exception that the neck portion of the core was neither oversized nor densified, were subjected to an accelerated bowling test. Briefly, the test is cyclic and employs an automatic pinsetter, a ball throwing machine and a short length of bowling alley. In. each cycle the ball throwing machine ejects a ball at a preselected speed in a fixed direction into the set of bowling pins at the strike zone. Between hits, the automatic pinsetter resets the pins with random orientation and random position of pins. The pinsetter automatically returns the ball to the throwing machine after each hit to complete the cycle. The number of cycles before failure of all pins of the set is recorded. The results are as follows: 1
Set of pins tested: Number of cycles Control (FIGURE 4 28,000 FIGURE 1 68,000 FIGURE 2 63,000
In view of failures of other portions of the pins, e.g., the belly, especially in the pin that was produced in accordance with the present invention, it was not possible to determine the true neck life on every pin of the set.
However, it is believed that the comparative results are indicative of the improvement in the present invention in the prevention of neck checking during use.
As a more particular identification of a typical suitable oversize pin core configuration, e.g., as illustrated in FIG- URE 1, the following table gives dimensions of such a pin compared with dimensions of a standard core as illustrated in FIGURE 4. The core plus coating diameters given were the same for both pins.
Distance from Top Oversize Core Standard Core Core Plus Coatof15" High Core, Diameter (Fig. Diameter (Fig. mg Overall in. 1), in. 4), in. Diameter, in.
The above dimensions were the general dimensions of the cores of the pins comparatively tested with results reported hereinabove.
It is an advantage of the present invention that there has been provided a new and useful bowling pin having having the prescribed external configuration, said coating having a thickness in the neck area of the pin less than at other areas of the pin, and the ,core having peripheral densified stress absorbing wood fibers in the neck area, said coating bringing the external pin configuration to prescribed dimensions.
2. A regulation size plastic coated hardwood bowling pin comprising a hardwood core as the primary stress carrying element,'said hardwood core being smaller than the regulation size bowling pin and having an enlargement in the-neck section otthe core relative to other portions of the core defining a substantially greater amount of vertical Wood fiber adjacent the pin surface in the neck section of the core than in the neck section of the core 8 of .the corresponding uniformly plastic coated wood core regulation size bowling pin and a generally uniform density plastic coating covering and bringing said core ing element and a plastic coating of generally uniform density on said core, said hardwood cone having an ex-, 'terna'l shape generally corresponding to that of the com- 1 plete pin butrof a smaller size suflicient to permit applica- -tion of a' coating thereto, an excess of integral hardwood in the core in neck section of said pin, said. excess hard- 7 wood providing an oversized neck portion between three and eight inches from the top or said pirysaid. oversized i neck portion gradually tapering to normal configuration at its upper and'iower ends, said coating comprising a coating of less than normal thickness over said oversized neck portion and a coating of normal thickness over there! mainder of said pin.
5. The bowling pin of claim 4 wherein said coating of normal thickness is in the range of from about 0.50 to 0.95 inch in thickness and said coating of less than normal thickness is in the range of from about .008 to .015 .inch' density at the upper and lower ends of the neck section and gradually decreases .to normal density interior-1y irom the surface of the neck section.
References Cited hythe Examiner.
UNITED STATES PATENTS 2,562,801 7/1951 McKenzie.
2.944321 7/1960 Mason 273-8.2. 3,024,819 '3/1962 Dosker 273-42 3,065,966 11/1962 Egbert 273- 821 3,098,655 7/1963 Martin 27,3 82
RICHARD c. PINKHAM, Primary Examiner. DELBERT B. LOWE, Examiner.