US 3404885 A
Description (OCR text may contain errors)
oct. 8, 1968 R. A. SMITH 3,404,885
BowL'ING PIN Filed March so, 1966 ATTORNEY 3,404,885 BOWLING PIN Richard A. Smith, Cornwall on the Hudson, N.Y., as-
signor to American Machine & Foundry Company, a corporation of New Jersey Filed Mar. 30, 1966, Ser. No. 538,678 Claims priority, application Great Britain, Apr. 5, 1965, 14,333/ 65 2 Claims. (Cl. 273-82) The invention relates to bowling pins and more particularly to an improved method for manufacturing plastic-coated bowling pins and to the pins so produced.
It has been the conventional practice in preparing plastic-coated wood pins to apply to the wood core a plurality of layers until a plastic coating of suiicient depth has ben provided. This procedure of applying the several layers and generally drying each layer before applying the subsequent layers, is time consuming, cumbersome and expensive .and often results in a plastic coating which delaminates from the pin core under the rigorous impact conditions of use.
The present invention is concerned with an improvement in the art of manufacturing plastic-coated bowling pins wherein the surface cladding comprises a single polymeric composition. Specifically the invention is directed to a novel synthetic plastic cladding comprising a caprolactam or nylon composition. More particularly the composition comprises a preferred copolymer of caprolactam and an alkyl ester of an acrylic acid. The resultingbowling pin is attractive as molded .and requires no additional finishing to make it acceptable commercially, and it has a marked increase in durability which makes it superior to any known plastic coated wood pin.
The present invention summarized in essence, is concerned with the manufacture of plastic-coated wood core bowling pins in which a single plastic comprising caprolactam is applied to the wood core thereby avoiding the need for an impregnant or prime coating for the wood, for sealer coats, and for top coats all of which heretofore were considered necessary, in addition t-o the main protective coating, in order to provide a commercially acceptable bowling pin. Although the present invention involves primarily encasing wood bowling pin cores, the invention also has advantageous applications to other bowling pin cores of other materials, eg., plastic, including foamed plastic, and metal. The invention may also be employed in conjunction with reinforced cores such as those utilizing mesh fabric envelopes, e.g., nylon webbing, over the pin core.
It is an object of the present invention to provide a relatively less costly plastic-coated bowling pin of substantially increased useful life and resistance to soilage and at less cost in which a single composition is utilized as the plastic layer.
It is a further and more specific object of the present invention to provide a bowling pin containing as the sole surface cladding a single layer of synthetic resin comprising a copolymer of caprolactam and an alkyl ester of acrylic acid on the bowling pin core.
Additional objects and advantages will become apparent as the description of the invention progresses.
In order that the manner in which these and other objects are attained, in accordance with the invention, can be better understood, reference is made to the .accompanying drawing wherein:
' United States Patent Oce Patented Oct. 8, 1968 FIG. 1 is vertical elevational view partly in section, of a bowling pin having a wooden body on which, in accordance with the invention, a protective cladding comprising caprolactam is molded.
In order that the method of the invention can be best understood, the general structure of the finished bowling pin will first be described with reference to the drawing. It will be understood that the present invention is concerned essentially with the improvement comprising a bowling pin with a plastic cladding in which essentially, a single synthetic resinous composition is applied over the core; said composition comprising a caprolactam resin.
In the embodiment illustrated, the pin 5 comprises a pin body 6 of maple or other hardwood, however, although metal such as magnesium or aluminum or plastic foam cores may also suitably be employed. The core is encased in accordance with the invention with a cladding or cover 7. In utilizing the single composition layer as taught by the present inventive concept, it is unnecessary to follow the prior art technique of pretreating the core with a plurality of layers including a primer impregnant composition to permeate the surface of the Wood and a sealer coat in addition to the thick cushioning coat which generally consisted of ethyl cellulose and thereafter followed with a top coat or finishing coat. A single layer of caprolactam preferably a copolymer of caprolactam and ester of acrylic acid is used in lieu of the multiple coat system heretofore required. The term an acrylic acid includes acrylic acid itself, methacrylic acid, ethacrylic acid and the like. Such esters include, for example, the alkyl, ammo alkyl hydroxyalkyl and the like esters of acylic acid. Specific illustrative compounds are ethylacrylate, butyl acrylate, Z-ethylhexyl acrylate, methylacrylate, methyl-methacrylate, ethylmethacrylate, butyl methacrylate isobutyl methacrylate, lauryl methacrylate, stearylmethacrylate, dmethylaminoethyl methacrylate, t-butylaminoethyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, butylene dimethacrylate and the like. Particularly good results appear from the use of the caprolactam-ethyl acrylate copolymer.
In the preferred embodiment of the invention, the caprolactam-acrylate ester copolymer is cast or injection molded directly over the core; no primer layer or mpregnant is employed nor is desirable. The coating produces a smooth, glossy, attractive appearance so that a finish or top coat is not required, although for some applications, it may be optionally desirable to apply a thin top coat film, e.g., for extra gloss or to modify friction characteristics. If desired, the resin layer may be contoured so that a thicker layer is formed at the head and belly regions, 8 and 9, respectively, where abuse and wear is most severe, although preferably, the peripheral layer is made uniform because it does not add appreciably to the amount of needed resin and a uniform layer aids in promoting balance.
The caprolactam copolymers which may be employed in providing the cladding for the bowling pins, in accordance with the invention, :are available commercially and may be obtained, for example, from Allied Chemical Corporation, New York.
The polycaprolactam copolymers contemplated are preferably those having an ester proportion of from about 10 percen-t to about 25 .percent with a corresponding proportion of from about percent to about 75 percent caprolactam.
In applying the coating to the pin cores, any of various suitable procedures such as casting the synthetic resinous liquid around the core in commercially available molding machines may be employed. The following preferred procedure has been successfully utilized:
(1) Metal support pins are positioned at each end of the wood core at 10 and 1l.
(2) The wood core with support pins is placed in a suitable mold.
(3) The copolymer is injection molded over the wood core.
(4) The copolymer-clad core is removed from the mold or press. At this time, the metal -support end pins may be removed automatically or manually.
(5) The sprue and any polymer ash are removed.
(6) A top plug, preferably molded of the same copolymer as the cladding, is cemented in the hole at at the top of the pin using a suitable adhesive eg., nylon adhesive CPA 619A (Goodrich Tire & Rubber Co., Chemical Division, Akron 16, Ohio) may be used to -achieve adhesion.
(7) The base of the bowling pin may be finished either by:
(a) A groove is cut in the base, as is standard practice with commercial bowling pins, and a molded plastic base is cemented in place; or
(b) The base can be molded as an integral part of the cladding as shown at 12, by using a properly contoured modified metal support pin during the molding opera tion. In this case, the only operation would be removal of flash.
(8) When the molded copolymer cladding has a commercially acceptable color and dirt repellency, the usual neck bands and insignia are placed on the pin. A durable, red pigmented, moisture curable polyurethane coating system may be used for this purpose, A solvent system to promote adequate adhesion contributes to durability of the markings.
When it is desired to utilize a topcoat for added soil repellency and/or intensity of color, for example, the copolymer cladding may be given la suitable topcoat, e.g., a white pigmented, moisture curing polyurethane film which utilizes a proper solvent system to promote adhesion. Red neck stripes and the insignia may be then added, as described above.
The following examples, in which the parts recited are parts by weight, are provided in order that the invention may be better understood. The examples are illustrative only and should not be interpreted as indicative of limitation on compounds or conditions stated. In each example, unless otherwise stated. a plastic cladding of 50 mils is applied to the bowling pin cores. The over all cycle time generally can vary from about 75 seconds to two minutes.
Example l Metal support pins are attached to each end of a wood core of suitable dimensions, as shown in FIG. 1. The support pins have from two to four gates which distribute and control the flow of polymer. The mold is so constructed that polymer can be introduced from the top of the pin, the bottom of the pin, or from both ends. The preferred techniques, and that used in the example provided, it to gate the polymer by means of the top metal support pin. The wood core preformed and suitably finished and with support pins attached is placed in the holding pins of a suitable constructed mold which is mounted in an injection molding press, such as, for example, New Britain, Ankewerke Reciprocating Screw Injection Molding Machine, Model 385, New Britain, Conn.
A copolymer of caprolactam-ethylacrylate 80:20 by weight is injected over a period of about -50 seconds at a temperature of 4about 550 F., extrusion nozzle temperature into the mold at about 1l0120 F. around the wood core applying a substantially uniform layer of about 50 mils.
After a brief cooling period of `about 45 seconds (total cycle time including injection, cooling and empty dwell in 90 seconds), the molded larticle is removed, the metal pins, ash and sprue :are removed and a top plug is inserted at the head. A set of pins made in this manner are tested and found to have an exceptional life exceeding 10,000 lines of play.
Example 1I Example I is repeated except that the copolymer introduced into the extrusion .press is pigmented with a 0.5 percent TiOZ pigment based on the total weight of the polymer.
The product has an excellent white lustre and durability comparable to the pins described in Example I.
Example III The procedure of Example I is repeated except that the resinous composition used is an :20 caprolactamunidecanoic lactam copolymer, i.e., no acrylic acid ester monomer is involved. While the resulting product did not have durability equal to the pins produced according to Example I, the product life at over 7,000 lines was nevertheless far superior to present commercial pins.
Example V The procedure of Example II is repeated with the exception that la caprolactam-methylmethacrylate 80:20 copolymer is used. A product having a life substantially superior to commercial bowling pins was attained.
Example Vl The procedure of Example II is repeated except that a copolymer of 75:25 caprolactam-ethylacrylate is substituted. Exceptional results, even superior to the product of Example I is obtained.
Example VII The procedure of Example II is repeated using instead a copolymer of :10 capro]actam-ethylacylate. The bowling pin was not as durable as that of Example II, nevertheless, has a life exceeding 8,000 lines of play.
Randomly selected, samples of bowling pins containing a plastic cladding over maple cores of compositions having formulations of Examples I-VII were also -tested on a laboratory impact testing apparatus until the pins had been subjected to a number of blows on the impact tester representing actual rough bowling alley service. In each case, the coating was superior to the best commercially available plastic-coated pins prepared by multiple coating systems. The coatings in each case were unusually free of cracks. They had excellent surface appearance and dirt resistance. In each set, scoring is excellent and constant throughout the life of the pin. The pins exhibited no loss of coating material and showed a negligible change in ball-line diameter or loss of adhesion of the cladding from the core.
It will be apparent to those skilled in the art that various modifications may be made in the teaching presented without departing from the scope of the invention. Accordingly, the invention is not to be limited 5 6 except insofar as necessitated by the appended claims. References Cited I claim: P 1. A bowling pin comprising a preformed body encased UNITED STATES ATENTS in a plastic protective cladding composition comprising 2,944,821 7/1960 Mason 273-82 a resinous layer of from yabout 20 to about 200 mils 5 3,138,574 6/1964 Kohan 26Q-78 minimum overall thickness, said composition comprising 3,332,939 7/1967 Detoro 260-78 t ncgoxllyinit caprolac am and a lower alkyl ester of FOREIGN PATENTS 2. A bowling pin in :accordance with claim 1, wherein 6,403,902 10/1964 Netherlands. said lower alkyl ester is ethyl acrylate of about 5 to 10 735,332 5/ 1966 Canada.
25 parts by weight and said caprolactam is of about c 95 to 75 parts Iby weight. RICHARD C. PINKHAM, Primary Examiner.