Abstract:
An improvement in the manufacture of golf ball cores utilizing a three plate mold to form the cores therein providing the cores with dual parting lines.  
     The apparatus comprises top, center and bottom plates, each having at least one mold insert. Each insert having a cavity therein. The three cavities collectively forming a spherical shape for molding a golf ball core. Upon the cores being formed, the center plate holding the cores, is lifted and rotated to a juxtaposed position against a stripping plate, whereby the cores are mechanically separated from both the mold and overflow flashing. The dual parting lines of different distances from their respective polar ends.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application is a divisional of co-pending U.S. application Ser. No. 10/111,830 which was filed Dec. 4, 2001 which is a continuation-in-part of U.S. patent application Ser. No. 09/973,344 which was filed on Oct. 9, 2001 and is incorporated herein in its entirety by express reference thereto. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates to the manufacture of golf balls and golf ball cores. More specifically, golf balls and cores made by a three-mold plate system to produce golf ball cores with dual parting lines.  
         BACKGROUND OF THE INVENTION  
         [0003]    Rubber balls are frequently molded by compression. In compression molding there are usually two mold plates, bottom and top, each of which has a plurality of insert cavities of hemispherical dimension. The composition to be molded is distributed in cylindrical slugs to the bottom mold cavities. Usually the bottom mold plates have cavities that are truncated spheres of greater than hemispherical dimension, while the cavities of the top mold plate are truncated spheres of less than hemispherical dimension as seen in U.S. Pat. No. 4,389,365. The molds are generally aligned in rows as in a muffin tin with from 200 to 400 or more being a typical number of molds per press. The cavities of the bottom mold generally have cross-sections at their top section, which are smaller in dimension than the greatest cross-section of the ball. When the mold plates are parted, the balls will all remain in the cavities in the bottom mold plate, where they are subsequently removed by a pop-up pin design coupled with a stripping fixture plate which is manually operated. A consistent problem is that the pins in their normal operation do generate a high force, which often distorts some of the ball cores in their South Pole area. The mold plates are brought together under heat and pressure as a result of which the rubber expands and fills the spherical cavities of the opposed mold plates. Since it is undesirable to have any voids in the balls, there is usually employed a slight excess of material which exits out of the mold during the ball formation into an overflow area. This excess material cures into scrap or “flash.” The scrap is typically ground up and reincorporated into future core material without degrading the properties of the cores, and disposing of scrap adds costs to the making of cores. Another factor influences scrap formation during core molding. Typically, the half-molds are fixed within mold frames so that they cannot move during molding. Differential thermal effects and mechanical mismatches of the half-molds can cause dimensional errors within the molds. As a result, the half-molds can be misaligned during molding. This allows excess pre-form material to escape the cavity. This excess material contributes to the undesirable formation of scrap. These errors can also cause the cores to be out of round. Out-of-round cores can form unplayable golf balls. When the mold plates are parted, the balls all remain in the cavities in the bottom mold plate, where they are subsequently removed along with the flashing by action of the pop-up pins that are located in a base of which the bottom mold plate rests upon.  
           [0004]    A manually operated stripping plate is generally used to separate the ball cores from the flashing. This is a very labor intensive procedure which assumes that the ball cores will be held by the flashing long enough to have the stripper plate pass underneath to separate ball core from flashing.  
           [0005]    The instant invention presents a method and apparatus to address the above problems, particularly as to providing a means for reducing product defects and reducing the amount of excess flash or scrap.  
         SUMMARY OF THE INVENTION  
         [0006]    The present invention is directed towards golf ball cores made from an improved method for stripping a plurality of golf ball cores from a mold plate and the flashing that engulfs the cores. The instant invention utilizes a three-plate mold with improved positive retention of the cores in the center of the three plates, thereby allowing for efficient handling by an automated or semi-automated ball core removal system. The improvement in handling the ball cores will reduce product defects.  
           [0007]    The present invention provides for forming ball cores using three mold plates. A top mold plate contains cavity inserts that consist of core geometry above the core equator. A center mold plate contains cavity inserts having geometry below the core equator and is placed in an intermediate position relative to the core equator and the South Pole of the core. Finally, the inserts of a bottom mold plate contain the remaining core geometry to complete the sphere.  
           [0008]    The method of removing the cores comprises first, lifting the top plate immediately upon the mold exiting the press, thereby exposing the center plate containing the molded ball cores. Then lifting while simultaneously rotating the center plate to an angle beyond 90° where it is juxtaposed against a stripping fixture plate with the South Pole area of the cores exposed. And finally, pushing out the remaining cores with a low force from behind the center plate wherein the cores are passed through openings of the fixture plate. The flashing remains in the molding fixture for further handling. The plate handling procedure is automated.  
           [0009]    The present invention also provides for the production of golf ball cores having dual parting lines. A first parting line being spaced from a first pole (North Pole) by a first distance, and a second parting line being spaced from an opposite second pole (South pole) which of the core by a second distance less than the first distance.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    [0010]FIG. 1 is a cross-sectional view of the three-plate mold and a ball core formed therein.  
         [0011]    [0011]FIG. 2 is a cross-sectional of the three inserts.  
         [0012]    [0012]FIG. 3 is a front view showing the relationship of the three plates when the mold is in position for stripping the cores from the mold and flashing.  
         [0013]    [0013]FIG. 4 shows the ball core/flashing complex.  
         [0014]    [0014]FIG. 5 is a symmetrical view of the parting lines of the core.  
         [0015]    [0015]FIG. 6 is a flow chart illustrating a method of making golf ball cores according to the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0016]    The present invention is directed towards making golf ball cores. These cores are substantially solid and form a center of a golf ball. To form the balls the cores of the present invention can be painted or surrounded by a single-layer or multiple-layer cover then painted. These balls may also include intermediate layers of molded or wound material as known by those of ordinary skill in the art. The present invention is therefore not limited to incorporating the cores into any particular golf ball construction and the present cores can be used in any constructions.  
         [0017]    Referring to FIGS. 1 and 2, a three-plate mold  10  is shown having a top mold plate  11 , a center mold plate  12  and a bottom mold plate  13 . Each of the mold plates  11 ,  12 , and  13  define at least one cavity  14 ,  15 , and  16 , respectively therein. It will be appreciated that preferably there are a number of cavities in each mold plate  11 ,  12 , and  13  with only one thereof being shown of each in FIG. 1. The cavities of typical mold plates are generally aligned in rows as in a muffin tin.  
         [0018]    The cavity  14  in the top mold plate  11  receives a top mold insert  30 . The top mold insert  30  includes an exterior surface  31  (best seen in FIG. 2) with an extension  32  extending outwardly therefrom and an opposite interior surface  33 . The extension  32  further includes a circumferentially extending groove  34  for receiving a retaining ring  35  therein. The retaining ring  35  is formed separately from the extension  32 . In another embodiment, the top mold insert  30  can be pressed-fit into the top cavity  14 .  
         [0019]    The interior surface  33  is a section within a circumscribed alignment ridge  38  which extend downwardly away from the top mold insert  30 , and includes a central-truncated-spherical cavity  36  and an overflow semi-hemispherical channel  37  spaced from and circumscribing the truncated-spherical cavity  36 . The cavity  14  includes a central axis Cl extending through a first pole P 1  of the cavity  14 .  
         [0020]    The cavity  15  in the center mold plate  12  receives a center mold insert  40 . The center mold insert  40  includes an exterior surface  41  and a pair of opposite interior surfaces, an upper interior surface  42  and a lower interior surface  43 . The upper interior surface  42  includes a first portion  52  and a second portion  53 . The first portion  52  includes a pair of opposite spherical sections  46  and  47  defining a central-truncated-spherical cavity  48  with a slot  45  defined on the lower segment of the cavity  48 . The second portion  53  includes a circumferential recess  54  for receiving the alignment ridge  38 . The lower interior surface  43  includes a first portion  49  and a second portion  50 . The first portion  49  includes the slot  45  defined therein. The second portion  50  circumscribes and is angularly offset from the first portion  49  by an angle α. Preferably, the angle α is between about 105° and about 145° and more preferably the angle α is about 120°. The exterior surface  41  includes a circumferential retaining ring member  54  that is formed separately from the insert  40 . The ring member  54  is placed into a friction fit with a circumferential orifice  55  defined in the surface of the center mold plate cavity  15 .  
         [0021]    The cavity  16  in the bottom mold plate  13  receives a bottom mold insert  60 . The bottom mold insert  60  includes an exterior surface  61  with an extension  62  extending outwardly therefrom and an opposite interior surface  63 . The extension  62  further includes a circumferentially extending groove  64  for receiving a retaining ring  65  therein. The retaining ring  65  is formed separately from the extension  62 . In another embodiment, the bottom mold insert  60  can be pressed-fit into the bottom cavity  16 .  
         [0022]    The interior surface  63  includes a first portion  67  and a second portion  66 . The first portion  67  includes a central-truncated-spherical cavity  68 . The cavity  16  includes a central axis C 2  extending through a second pole P 2  of the cavity  68 . The second portion  67  circumscribes and is angularly offset from the first portion  66  by an angle β. Preferably, the angle β is between about 105° and about 145° and more preferably the angle β is about 120°. It will be appreciated that preferably there are a number of three mold inserts  30 ,  40 , and  60  in each mold plate  11 ,  12  and  13  with only one thereof being shown in FIG. 2.  
         [0023]    The spherical cavity  48  of the center mold insert  40 , when combined with the spherical cavity  68  of the bottom mold insert  60 , creates a truncated sphere cavity of preferably greater than hemispherical dimension. And the spherical cavity  36  of the top mold insert  30  is a truncated sphere of preferably less than hemispherical dimension, as disclosed in U.S. Pat. No. 4,389,365, which is incorporated by reference herein in its entirety. This configuration and dimension of the cavity allows cores to be retained in the center mold insert  40  after molding.  
         [0024]    Preferably, each of the three mold inserts  30 ,  40  and  60  are formed as a single piece including the extensions  32  and  62  of mold inserts  30  and  60  respectively, and the cavities  36 ,  48  and  68  by machined casting. The overflow channel  37  is optional and preferably machined into the mold insert  30 . The second portions  50  and  66  of the upper surface of the center and bottom mold inserts  40  and  60  are machined with a precise mating angle within about 0.5%. One preferred material for forming the mold inserts is hardened steel with chrome plating. Alternatively, the mold inserts can be formed of beryllium, copper or aluminum but are not limited to these materials. The retaining rings are preferably formed of commercially available materials such as carbon or stainless steel.  
         [0025]    Referring again to FIG. 1, the top, center and bottom mold plates  11 - 13  each include a bore  70 . The bore  70  includes a narrow portion  71  and an enlarged portion  72 . Each narrow portion  71  receives the extensions  32  and  62  of the top and bottom mold inserts  30  and  60  respectively. Each enlarged portion  72  receives the retainer rings  35  and  65  of the top and bottom mold inserts  30  and  60  respectively. The retainer rings  35  and  65  and the configuration of the bore  70  and cavities  14 ,  15  and  16  of the mold plates  11 ,  12  and  13  allow the three mold inserts  30 ,  40  and  60  to move vertically in the directions D 1  and D 2  and the opposites thereof. Preferably, less than about 0.030 inches of vertical movement is allowable and more preferably less than about 0.020 inches of vertical movement is allowable. Alternatively, the mold can be formed so that vertical movement of the mold inserts  30 ,  40  and  60  is prevented.  
         [0026]    The three mold inserts  30 ,  40  and  60  and the respective cavities  14 ,  15  and  16  are configured and dimensioned such that a gap g 1  is formed there between. The extensions  32  and  62  and the narrow portion  71  of each bore  70  are configured and dimensioned such that a gap g 2  is formed there between. The retainer rings  35  and  65  and the enlarged portion  72  of each bore  70  and cavities  14  and  16  of the top and bottom mold plates  11  and  13  are configured and dimensioned such that gaps g 3  and g 4  are formed.  
         [0027]    The mold  10  further includes a top back-up plate  80  adjacent to the top mold plate  11  and a bottom back-up plate  82  adjacent the bottom mold plate  13 . The top and bottom back-up plates  80  and  82  are optional. The mold plates  11 ,  12  and  13  and back-up plates  80  and  82  are preferably formed of steel.  
         [0028]    Referring to FIGS. 2 and 6, in step  6   a  the method of the present invention includes providing a three plate mold  10  with at least one set of mold plates  11 ,  12  and  13  to form a spherical cavity. In step  6   b , recall that preferably conforming pre-forms are disposed into the cavity  48  of the center mold insert  40 . The set of mold inserts  30 ,  40  and  60  are advanced toward each other in the directions D 1  and D 2  or closed using a conventional molding press. The bores  70  of the mold plates  11 ,  12  and  13  align the mold plates with respect to one another. When the second portions  50  and  66  (as best seen in FIG. 2) of the center and bottom mold inserts  40  and  60  contact each other, the gaps g 1 , g 2  and g 3 , allow for the three mold inserts  30 ,  40  and  60  to move (in the directions illustrated by the arrow D 3 ) into alignment with respect to one another. As compared to the closing directions D 1  and D 2 , the mold inserts  30 ,  40  and  60  move along direction D 3 , which is angularly offset from the closing directions. More preferably, the mold inserts  30 ,  40  and  60  move substantially horizontally with respect to one another in the directions illustrated by the arrow D 3  into alignment. Thus, during closing the mold inserts  30 ,  40  and  60  align such that the central axis Cl and central axis C 2  are coaxial. When the second portions  50  and  67  of the mold inserts, respectively, contact each other, the gaps g 4  allow the mold inserts to move vertically with respect to one another in the directions illustrated by the arrows D 1  and D 2  or in directions opposite thereto.  
         [0029]    Once the mold  10  is completely closed, step  6   c  of compression molding occurs at a predetermined time, temperature, and pressure to cross-link the pre-form material. For example, compression molding can occur at about 160° C. (320° F.) for about 15 minutes at a cavity pressure of 3000 psi to form the cores. After compression molding, the cores can remain in the molds until the material is completely or partially cured.  
         [0030]    Passing about the top mold insert  30  are semi-hemispherical flash overflow grooves  37  for release of excess ball material that makes up the flashing  85  which is interconnected throughout the mold plates and is shown in FIG. 4 herein. The shape of the grooves is optional, as many various shapes will perform equally as well.  
         [0031]    The golf ball core  88  has a center line  89 , however, for the present invention this is not the mold parting line between the top mold plate  11  and the center mold plate  12 . For the present invention a pair of parting lines, an upper parting line  86  and a lower parting line  87 , are created as shown in FIGS. 2 and 5. The upper parting line  86  is spaced from the first pole P1 by a first distance T1 and the second parting line is spaced from the second pole P2 by a second distance T2. The second distance T2 being less than the first distance T1. Preferably, the first distance is between about 30 to 49 percent of the length of the diameter of the core and more preferably about 45 percent. Preferably, the second distance is between about 3 to 20 percent of the length of the core diameter and more preferably about 10 percent.  
         [0032]    The center and bottom spherical cavities  48  and  68  form a truncated sphere of greater than hemispherical dimensions, while the top spherical cavity  36  is a truncated sphere of less than hemispherical dimension. The cavity formed by the center spherical cavity  48  thus has a cross-section at its top that is smaller in dimension than the greatest cross-section of the ball core  21  as described in U.S. Pat. No. 4,389,365. When the mold plate  11  is parted from the center mold plate  12 , the ball cores  88  all remain in the cavity inserts  40  and  60  of the center and bottom mold plates  12  and  13 . The ball cores  88  can be removed by activation of the method shown in FIG. 3, to be described in detail below.  
         [0033]    The size of the opening of the bottom mold insert  60  is not critical. However, it is preferred that the center mold insert  40  have an opening diameter of at least 0.5% less than the diameter of the widest part of the ball core  88 . And preferably, the center mold insert  40  has an insert opening of at least 1% less than the diameter of the widest part of the ball core  88 . It is further preferred that the center mold insert  40  not have a diameter at its opening which is greater than 10% less than the diameter of the widest part of the ball core  88 . For the range of 0.5%-10% the insert volume ratio will be from about 10:7 to about 5:2 between the center/bottom mold inserts  40 ,  60 , and top insert  30  (not necessarily respectively). The lower limit has been found to yield excellent retention of the ball cores  88  in the center mold plate  12  while diameters above the upper limit frequently result in tearing of the product during removal. Obviously these values will vary depending upon the overall size of the core, the nature of the product being made, the material being molded and its intended use. It is important that the dimension for the upper portion of the mold insert  40  of the center mold plate  12  be small enough in dimension to retain substantially all of the ball cores  88  when the mold plates  11 - 13  are open. And they should be of large enough dimension so that the ball cores  88  are not destroyed when ejected.  
         [0034]    It is well known in the prior art that ball cores have a tendency to stick in both the upper and lower mold plates as a result of which removal is quite difficult. If ejector pins are used for both the upper and lower mold plates, the balls falling from the top have a tendency to bounce around and fall out of the mold where the operator cannot get them easily. Furthermore, the balls will usually have portions of the flash hanging from various parts of the equator of the ball, of which the flash is somewhat difficult to remove. This problem is accentuated when molding relatively small inner cores of about 1 inch or less.  
         [0035]    The creation of a preform slug and its placement into the center mold insert  40  for compression molding into a golf ball core  88  is discussed in the parent application and is part of step  6   b  of the method previously discussed. FIGS. 3 and 6, further shown the method of making a ball core  88  once the preform has been disposed into the mold insert  40 . Steps  6   d ,  6   e ,  6   f  and  6   g  complete the method of removing the cores  88  from the mold  10  while simultaneously stripping the cores  88  from any excess overflow flashing  92 . When the ball cores  88  are sufficiently cured, the three plate mold  10  is removed from the compression machinery, wherein the top mold plate  11  is automatically raised by hydraulic means and turned rearward to an approximately 90° angle relative to the center mold plate  12  as in step  6   d . With the formed ball cores  88  disposed within the center cavity mold inserts  40 , the center mold plate  12  is lifted automatically by hydraulic means as shown in step  6   e . In step  5   f  while the center mold plate  12  is lifted, it is simultaneously rotated away from the bottom mold plate  13  to a position where it is finally juxtaposed against a fixed stripping plate  90 , that is at an angle slightly beyond 90° vertical. The second poles P 2  (South Pole) of ball cores  88 , the bottom core inserts  60  are thereby exposed. The fixed stripping plate  90  has a plurality of holes  91  corresponding to the position of the ball cores  88  in the center mold plate  12 . Holes  91  are preferably made slightly larger (up to about 10% greater diameter is suitable) than the diameter of the ball cores  88 . As the ball cores  88  drop through the holes  91  in the stripping plate  90 , they come out substantially free of overflow flash  82 . In step  6   g  once the center mold plate  12  is in raised position, the ball cores  88  need only to be tapped to separate them from the overflow flashing  92 . The balls cores  88  will fall through the holes  91  of the stripping plate  90  wherein the overflow flashing  92 , which is interconnected throughout the center core plate  12 , will be trapped between the two plates  12  and  90 . The overflow flashing  92  can be therein removed for recycling. This procedure can be automated, but as suggested above, can also be accomplished manually.  
         [0036]    Although the present invention is primarily concerned with spherical objects, such as golf balls, it will be appreciated that it can also be used with other objects, especially those with a smooth surface such as: egg shaped products, and cylindrical products wherein the parting line is along the length.  
         [0037]    It will be understood that the claims are intended to cover all changes and modifications of the preferred embodiments of the invention, herein chosen for the purpose of illustration, which do not constitute a departure from the spirit and scope of the invention.