Metallic mold for injection-molding of golf balls

Abstract: The invention relates to a mold for injection-molding golf balls. A plurality of small-sized recesses (10) are provided along outer peripheral edges (3a) of the openings of semispheric recessed portions (3) in which a golf ball is injection-molded. These small-sized recesses (10) form small-sized positioning juts along the parting line of a golf ball intended to be injection-molded.

Description: BACKGROUND AND SUMMARY OF THE INVENTION The present invention relates to a metallic mold for injection-molding of golf balls. In molding operation in which golf balls are produced by using a metallic mold, molding flashes at the injection gate portion of the metallic mold inevitably adheres to the golf balls, and immediately after their molding operation is completed, they have molding flashes still left on their surfaces. In a conventional method of removing molding flashes from the golf balls, the molding flashes are removed by hand from them. However, the manual removal of the molding flashes are inefficient. For this reason, a proposal for overcoming this disadvantage is recently made such as, for example, a golf ball with molding flashes after being subjected to injection-molding operation is rectified in the position thereof by means of a position rectifying machine for balls, such as disclosed in the Japanese Patent-Application Gazette to Public Inspection No. 81059-1984 (See Figure 11 of the accompanying drawings which is hereinafter described.), to thereby locate all the molding flashes in a horizontal plane for their easy removal, and thereafter, the golf ball rectified in the position thereof is automatically rid of the molding flashes by using a method and a machine for removing molding flashes from golf balls, which is disclosed in the Japanese Patent Publication Gazette No. 25911-1988. However, it has proved that in the foregoing conventional method, the following problem remains unsolved when in a ball-position rectifying machine such as shown in Figure 11, molding flashes b which adhere to the equatorial position (the parting line) of a golf ball e at the injection gate portion of a metallic mold used to mold it is engaged with stoppers c, c of the rectifying machine, and the golf ball e is rectified in the position thereof by rotating it, so that the molding flashes b are horizontally located to remove them. That is to say, the injection-gate portions arranged for a single golf ball in the metallic mold are limited in number, depending upon an arrangement of dimples on the surface of the golf ball. Also, the molding flashes b which adhere to a golf ball intended to be produced, at the injection-gate portions of the metallic mold are smaller in their size as they jut from the metallic mold, owing to a surface dimple arrangement of the golf ball. Moreover, all the molding flashes b are not detached at the same positions from the metallic mold, and therefore, they do not remain constant in their size. For these reasons, the probability is low that the molding flashes b of the golf ball e are engaged with the stoppers c, c shown in Figure 11. Therefore, a positional rectification of the golf ball mounted in the ball-position rectifying machine is extremely difficult of practice, because the molding flashes have the foregoing dimensional characteristics. As a result, it is substantially impossible to apply the flash removing machine of Figure 11 to the golf balls intended to be completed. A method and apparatus for producing a game ball such as a billard or pool ball is known from US-A-4 116 439. The ball is produced in a mold provided with recesses for positioning a weighted object centered within the outer covering of the finally produced ball, and an opening for pouring in the outer covering. Those parts of the weighted object supported in these recesses of the mold and projecting beyond the outer surface of the ball after the pouring process or the entire outer surface of the poured ball are uniformly ground to provide a smooth spherical surface of the final product. It is therefore an object of the present invention to provide for a metallic mold which constantly ensures positional rectification of a golf ball with molding flashes therewith when it is mounted in a ball-position rectifying machine, before it is ground by means of a flash removing apparatus, to thereby achieve the complete removal of molding flashes from the golf balls. Also, it is another object of the present invention to provide for a metallic mold which produces golf balls good in their surface appearance and inconspicuous in marks remaining after their molding flashes have been ground by means of a flash removing apparatus. BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be described with reference to the accompanying drawings, in which: Figure 1 is a schematic longitudinal-sectional view of a principal portion of the metallic mold of the present invention according to a preferred embodiment thereof; Figure 2 is a plan view of a lower cavity, or a bottom part of the metallic mold shown in Figure 1; Figure 3 is a longitudinal-sectional view taken along the line III - III of Figure 2; Figure 4 is an enlarged sectional view of a principal portion of the metallic mold shown in Figure 1; Figure 5 is an enlarged plan view of a principal portion of the bottom part of the metallic mold shown in Figure 2; Figure 6 is a bottom view of an upper cavity, a top part of a metallic mold according to a second preferred embodiment of the present invention; Figure 7 is an enlarged sectional view of a principal portion of the metallic mold of the present invention according to a third preferred embodiment of the present invention; Figure 8 is an elevational view of a golf ball immediately after and as being injection-molded by using the metallic mold of the present invention; Figure 9 is a plan view of a golf ball immediately after and as being injection-molded by means of the metallic mold of the present invention; Figure 10 is an explanatory view of a principal portion of a position rectifying means for a ball with molding flashes; Figure 11 is an explanatory view of a principal portion of a position rectifying means which is mounted with a golf ball produced by means of a conventional metallic mold. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the metallic mold according to the present invention will be described with reference to the accompanying drawings. Figure 1 is a schematic longitudinal-sectional view of a principal portion of a metallic mold for injection-molding of golf balls, and this metallic mold comprises an upper cavity, or a top part 4 and a lower cavity, or a bottom part 5. The top part 4 and the bottom part 5 are respectively provided with a semispherical recessed portion 3 of a radius R. As shown in Figures 1 to 3, in one of two jointing surfaces 7 and 8 on which the top part 4 and the bottom part 5 are brought into separable contact with each other, for example, the jointing surface 8 in this embodiment of the invention, grooves 9 for the injection gates of, for example, eight in number are arranged at substantially equal or identical central angles along an outer peripheral edge 3a of the opening of the semispherical recessed portion 3. Moreover, small-sized recesses 10, 10 of, for example, two in number are disposed between every two neighboring injection gate grooves 9, 9 to form projections. Figure 2 gives an illustrative example of arrangements of the injection gate grooves 9 and the small-sized recesses 10 for the formation of the projections. In this illustrative example, the central angles at which the grooves 9 and recesses 10 are arranged are such as to be substantially identical. However, such central angles are occasionally unequal, depending upon a surface dimple arrangement of a golf ball to be produced by using the metallic mold of the present invention. Also, the number of the injection gate grooves 9 is limited in accordance with the surface dimple arrangement of a golf ball to be produced by using the metallic mold of the present invention, the kind of the material resin which is to be used for injection molding, the injection-molding conditions, and the like. The projection forming small-sized recesses 10 are located at substantially regular intervals of place over the entire circumference of the peripheral edge of the opening of the semispherical recessed portion 3. The number of the small-sized recesses 10 are three to thirty, and preferably four to twenty. In Figure 4 which is an enlarged view of a principal portion of the metallic mold shown in Figure 1, and in Figure 5 which is an enlarged view of a principal portion of the bottom part shown in Figure 2, the small-sized recesses 10 are sized such as to range between 0.02 mm and 3.0 mm (preferably between 0.1 mm and 2.0 mm) in their depth H, while at the same time, they are formed such as to be 0.3 mm to 5.0 mm (preferably 0.5 mm to 3.0 mm) in their diametrical dimensions L, and to be 0.5 mm to 5.0 mm (preferably 0.6 mm to 3.0 mm) in their width W. The cross-sectional configurations of the small-sized recesses 10, which are in effect their shapes as viewed from the direction marked X in Figure 5, may be set as rectangles (including a shape of a straight line), semicirculars, ellipses or any other desired shapes which conform to the configuration of the land area around the parting line of the metallic mold. In Figure 1 to 5, the injection gate grooves 9 and the projection forming small-sized recesses 10 are illustrated such that they are both formed in the bottom part 5 of the metallic mold. However, as shown in Figure 6, the grooves 9 and the recesses 10 may be formed on the top part 4 of the metallic mold. Alternatively, preferably, ones of the grooves 9 and the recesses 10 are located in the top part 4, and the others are disposed in the bottom part 5, to thereby achieve a circumferential arrangement of the grooves 9 and the recesses 10 as illustrated in Figure 2 when they are both joined together. In any case, the projection forming small-sized grooves 10 are arranged in one or both of the top part 4 and the bottom part 5. Next, in Figure 7 which shows the other preferred embodiment of the present invention, the projection forming small-sized recesses 10 are made on both of the top part 4 and the bottom part 5 of the metallic mold. In this case, the recesses 10 are formed such that a total of depth of the top part side recesses and the bottom part side recesses, H (H1 + H2) ranges between 0.02 mm and 3.0 mm when the top part 4 and the bottom part 5 are brought into contact with each other in their jointing surfaces 7, 8. In connection with this, when the small-sized recesses 10 are made on both of the top part 4 and the bottom part 5 of the metallic mold as illustrated in Figure 7, the depth H of the small-sized recess is defined here as a total of depth of each top part side recess and each bottom part side recess. As shown in Figures 8 and 9, a golf ball 11 immediately after and as being injection-molded by using the metallic mold described in the foregoing is formed with small-sized positioning juts 12 and protruding injection-gate portions 13 along the parting line P thereof. The shape of the small-sized juts 12 may include a needle-shaped or small bar-shaped configuration. The manner in which the golf ball is formed with the positioning juts 12 and the injection gate portions 13 may be rephrased as the positioning juts 12 and the injection gate portions 13 are provided along the seam thereof such that the juts 12 and the injection-gate portions 13 project from the surface thereof. The thickness, the protruding length and the width of the positioning juts 12 are respectively substantially identical to the depth L, the diametrical size L and the width W of the small-sized recesses. Moreover, the cross-sectional configuration of the positioning juts 12 is a rectangle, a horizontal linear shape, a circle, an ellipse or other similar shape in conformity with that (in the direction of X in Figure 5) of the projection forming small-sized recesses 10. As is apparent from the foregoing description, the metallic mold of the present invention for injection molding of golf balls is provided with the projection forming small-sized recesses 10 in a circumferential row along the outer peripheral edge 3a of the opening of the semispherical recess 3 to form the positioning juts 12 along the parting line P of the golf ball 11. If the foregoing depth H, or (H1 + H2) of the small-sized recess does not exceed a value of 0.02 mm in Figure 4, Figure 5 or Figure 7, the positioning juts 12 are excessively small in their thickness, and as a result, it becomes difficult to engage the juts 12 with the stoppers 15, 15 of the ball-position rectifying means 14, which is shown in Figure 10. To the contrary, if the depth H of the small-sized recesses 10 exceeds 3.0 mm in the value thereof, a golf ball mounted on the metallic mold of the present invention, which is provided with the recesses 10 of such depth H is caused to remain wider in a mark of the seam thereof after molding flashes have been removed from the golf ball, whereby it deteriorates in an outer surface appearance thereof. Moreover, the depth H of 3.0 mm or above makes it impossible, depending upon a surface dimple pattern of the golf ball to arrange the juts 12 in the (narrow and small) land area of the golf ball, and also, to makes it difficult to move the golf ball for positional adjustment thereof in the ball-position rectifying means 14, which is illustrated in Figure 10. Also, if the width W of the small-sized recesses 10 in Figures 4 and 5 does not exceed 0.5 mm in the value thereof, the juts 12 become excessively small in the width thereof, and as a result, the probability is low that the juts 12 are engaged with the stoppers 15, 15 shown in Figure 10. Reversely, if the foregoing width W of the recesses 10 exceeds 5.0 mm in the value thereof, the mark of a seam easily remains as a result of the removal of molding flashes in a golf ball mounted on the metallic mold of the present invention, which is provided with the recesses 10 of such width H, whereby it deteriorates in an outer surface appearance thereof. Moreover, the width W of 5.0 mm or above makes it difficult depending upon the surface dimple pattern of the golf ball to arrange the juts 12 in the (narrow and small) land area of the golf ball. Moreover, if the diametrical length L of the recesses 10 which is described in the foregoing with reference to Figures 4 and 5 does not exceed 0.3 mm in the value thereof, the positioning juts 12 become excessively small in their projecting length, and therefore, the probability is low that the juts 12 are engaged with the stoppers 15, 15 shown in Figure 10. If the diametrical length L of the recesses 10 exceeds 5.0 mm in the value thereof, the golf ball 11 mounted on the metallic mold of the present invention is prevented from the smooth rotational movement thereof owing to the ball-position rectifying means 14, which is illustrated in Figure 10, and as a result, the probability is low that this golf ball 11 is engaged with the stoppers 15, 15. In the present invention, the golf ball 11 as inject ion-molded is formed with the small-sized positioning juts 12 along the parting line P thereof, and therefore, it is infallibly and speedily feasible to allow the ball-position rectifying means 14 (such as illustrated in Figure 10) to position the golf ball 11 precisely for removing molding flashes located along the parting line P thereof. The small-sized positioning juts 12 are not molding flashes of larger size than necessary. Therefore, a grinding operation for the removal of molding flashes located along the parting line P of the golf ball can easily remove the positioning juts 12, to thereby allow the golf ball to have a good surface appearance.

Claims: A metallic injection mold for injection-molding of golf balls, whereby a plurality of small-sized recesses for making substantially identical small-sized positioning juts along the parting line of an injection-molded golf ball and a plurality of injection-molding gate grooves are provided along the outer peripheral edges of the openings of semispheric recessed portions of the mold in which the golf ball is to be injection-molded. The metallic mold for injection-molding of golf balls as set forth in claim 1, wherein a top part thereof is provided with the small-sized recesses. The metallic mold for injection-molding of golf balls, as set forth in claim 1, wherein a bottom part thereof is provided with the small-sized recesses. The metallic mold for injection-molding of golf balls, as set forth in claim 1, wherein the top part and the bottom part thereof are respectively provided with the small-sized recesses which are opposed between the top part and the bottom part if the top part and the bottom part are assembled together. The metallic mold for injection-molding of golf balls, as set forth in claim 2 or 3, wherein the small-sized recesses are set in their depth to a value which ranges between 0.02 mm and 3.0 mm. The metallic mold for injection-molding of golf balls, as set forth in claim 4, wherein the depth of the small-sized recesses in the top part thereof and the depth of the small-sized recesses in the bottom part thereof total to 0.02 mm - 3.0 mm. The metallic mold for injection-molding of golf balls, as set forth in claim 2, 3 or 4, wherein the small-sized recesses are set in their diametrical size to a value which ranges between 0.3 mm and 5.0 mm. The metallic mold for injection-molding of golf balls, as set forth in claim 2, 3 or 4, wherein the small-sized recesses are set in their width to a value which ranges between 0.5 mm and 5.0 mm. The metallic mold for injection-molding of golf balls, as set forth in claim 2, 3 or 4, wherein the small-sized recesses are set in a total of number to 3 - 30.

Inventors: ARAKI NORITAKE, ENDO SEIICHIRO, MIMOTO YOSHIYUKI, MORIYAMA KEIJI, OKIDO YOSHIYUKI, ARAKI, NORITAKE, ENDO, SEIICHIRO, MIMOTO, YOSHIYUKI, MORIYAMA, KEIJI, OKIDO, YOSHIYUKI, ENDO, SEIICHIRO, UOZUMI DORMITORY OF, MORIYAMA, KEIJI, UOZUMI DORMITORY OF, OKIDO, YOSHIYUKI, UOZUMI DORMITORY OF
Applicants: SUMITOMO RUBBER IND, SUMITOMO RUBBER INDUSTRIES LIMITED
Application year: 1993
Main classification: A63B45
IPC codes: B29C45, B24B9, A63B45, B29L31