Ball Bat System

Abstract

The hollow metal body for a ball bat is made by machining a tapered surface on most of the length of hollow cylindrical metal extruded workpiece, and swaging the machined portion of the workpiece to form the desired outside contour of a ball bat, the wall thickness along the length of the metal body being determined by the balance of the thinning effect of the machining against the thickening effect of the swaging.

Description

BACKGROUND

Bats for hitting balls vary with the particular game being played, but have the common characteristic of comprising a handle at one end for grasping the bat, and a portion at the other end for hitting the ball. In the case of the American baseball, for example, there are differences between bats used for professional hard ball, bats used for the soft ball, and bats used for Little Leaque games, but in general a design good for one of these uses can be adapted to the other two uses.

Wooden ball bats have been conventional for years in all three types of American baseball mentioned above. However, the combination of population increase and lumber resources decrease has led to a search for other materials for making such bats. While all sorts of metals might be used, aluminum and aluminum base alloys are especially well suited for the purpose, considering strength to weight ratio, surface characteristics, formability and cost. While aluminum bats presently cost more than wood bats, they have the great advantage of lasting longer, and hence of costing less in the long run.

Early efforts to develop aluminum bats comprised the approach of mounting a cylindrical tube of extruded aluminum in a lathe and turning it down by pressure of a blunt instrument against the outside of the workpiece as it was rotated with a shaping mandrel inside. The resultant shaped metal bat stock had its original extruded form along one end, where it was designed to hit balls, and had a reduced diameter at its other end, where it was designed to be gripped. A bat made in this way had generally uniform thickness of its metal wall from one end to the other. The metal at the tapered end was forced longitudinally away from the center of the bat, thus lengthening the original cylindrical extrusion. There was less metal per unit length at the tapered handle end of the bat, because of the uniformity of wall thickness in conjunction with decreased diameter at the handle end. As a result, the center of gravity of the bat was displaced from the geometric center of length of the bat in the direction of the hitting end of the bat. A bat made in this way thus had its metal weight concentrated toward the hitting end, where it should be for best results, and where it exists inherently in conventional solid wooden bats. Unfortunately, the turning down step was relatively expensive, and this system of bat manufacture was apparently never employed on a large commercial scale in spite of successful tests of the product.

An improvement over the earlier aluminum bat is disclosed in Merola U.S. Pat. No. 3,479,030, issued Nov. 18, 1969. In accordance with the teaching of that patent, a length of cylindrical aluminum extrusion is swaged down in a rotating die having a tapered throat into which one end of the extrusion is pressed. As the die rotates, the metal is radially compressed, without substantial lengthwise displacement. As compression occurs, the metal stock is thrust further into the die, until the workpiece has completed a predetermined movement into the die. As explained in the patent, metal bat stock formed in this way has equal weight along its length from one end to the other. A minimum counterbore is made in the thickened reduced end, to facilitate insertion of a wooden plug, but this has no substantial influence on the weight distribution of the metal in the bat. Although the hitting end of the bat is plugged with a realtively large piece of material having a substantial weight, the fact remains that the handle end has more metal in it than is desirable from the point of view of weight distribution for purposes of good hitting characteristics. In spite of this, however, bats can be made by this method at a relatively low cost, and they have proved commercially successful on a substantial scale.

A further improvement is disclosed in Swenck U.S. Pat. No. 3,691,625 which issued Sept. 19, 1972. In accordance with the teaching of that patent, the swaging operation described above in connection with the Merola patent is followed by a drilling operation to remove excess metal from the thickened handle end of the work piece. This gives better weight balance in the bat for hitting purposes, and has in turn proved commercially successful on a substantial scale. It is believed to be still the best method of making a metal ball bat having the relatively short tapered portion shown in the drawings of the two said patents.

In accordance with the present invention, bat design can be improved for better performance, particularly in terms of improved capability for power hitters of hard balls, by the combination of machining a tapered surface along most of the length of the initial hollow cylindrical work piece, and then swaging the machined portion of the work piece to produce the desired configuration. The resultant gradual taper preferably begins relatively close to the handle end of the completed metal body, so that the gradually increasing outer diameter will provide increasing strength to resist excessive bending adjacent the grasped portion of the bat when a strong hitter connects with a hard thrown professional baseball, as in a professional or collegiate game. Since there is no internal drilling, there is no problem of excessive thickening of the wall at the point where tapering of the body begins, as described in Column 3, Lines 36-37 of Swenck U.S. Pat. No. 3,691,625. Consequently, it is now made feasible to begin the taper of the bat as far back toward the handle as desired. The wall thickness along the length of the swaged portion of the body can be controlled by the amount of initial machining at each point along the length of the bat, and preferably this is done so that the final wall thickness is substantially uniform from one end of the body to the other.

FIG. 1 shows diagrammatically in section a hollow cylindrical metal work piece;

FIG. 2 shows diagrammatically in section the work piece of FIG. 1 after it has been machined on the outside along most of its length;

FIG. 3 shows diagrammatically in section the work piece of FIG. 2 after it has been swaged along its machined portion;

FIG. 4 shows diagrammatically in section the work piece of FIG. 3 after it has been further swaged;

FIG. 5 shows diagrammatically a completed ball bat incorporating the work piece of FIG. 4;

FIG. 6 is a fragmentary, front elevational view, partially in section and drawn to an enlarged scale, illustrating the hitting end of the bat prior to the insertion of an end plug; and,

FIG. 7 is a fragmentary, front elevational view, partially in section illustrating the bat of FIG. 6 after inserting an end plug.

Referring now more particularly to the drawings, a metal work piece indicated generally at 10 is shown in FIG. 1 to have a hollow metal body with cylindrical inside and outside surfaces. The work piece 10 is made of a light metal, such as aluminum or magnesium and alloys based on either of them. The present preferred example of work piece 10 is an aluminum alloy extruded, drawn, and heat treated.

The work piece 10 is initially machined to the form 10a illustrated in FIG. 2. This machining is done so that what is to become the handle end of the completed bat is machined on the outside to produce a cylindrical outer surface 11 extending along the length of the work piece 10a shown as dimension C in FIG. 2. The opposite end of the work piece 10a, which is to become the hitting end of the completed bat, is left with an unmachined cylindrical outer surface 14 along the length B shown in FIG. 2. The intermediate portion of the work piece 10a, extending along the length D in FIG. 2, between planes 20 and 21, is machined on the outside to produce a conical outer surface 12 which tapers between the reduced outer diameter of the surface 11 and the unreduced outer diameter of the surface 14. The whole length of the inner surface 16 of the work piece 10a remains unmachined, with the same cylindrical surface 16 that was in the original work piece 10. Although the taper of the surface 12 has been described as conical, so that the taper varies linearly, the machining can be adjusted to achieve any other desired curvature for purposes of achieving the ultimate desired purpose.

After said machining, the work piece 10a is subjected to an initial swaging operation to form the work piece 10b shown in FIG. 3. Such swaging may be of the conventional kind, in which a rotating swaging die is used. A conventional swaging die has an opening therethrough which is relatively small at one end, and relatively large at the other, with a conical or other tapered surface between the ends of the opening. The handle end of the work piece 10a is inserted into the large end of the first rotating swaging die, and the work piece 10a is pressed endwise against the die until all of the length C and a minor part of the length D have passed entirely through the small end of the first swaging die, leaving part of the remainder of the work piece 10a in the tapered portion of the die between its small and large end openings.

This produces an untapered, swaged end 26 adjacent the handle end and a tapered, swaged portion 18 between planes 28 and 45.

The portion of the work piece 10b which is passed entirely through the small opening of the first swaging die is shown as dimension E in FIG. 3, and the portion remaining in the tapered portion of the die is shown as dimension F in FIG. 3. The length F of FIG. 3 extends along the balance of the length D of work piece 10a shown in FIG. 2, and slightly into the unmachined length B shown in FIG. 2. This leaves an unmachined and unswaged surface 22 extending along the length G shown in FIG. 3 or to the right of plane 45 in that figure. The interior surface at 24 remains cylindrical. This first swaging operation has the effect of forming a cylindrical inner surface along the inside of the length E shown in FIG. 3, and the wall of the work piece 10b along that portion of the length E corresponding to length C in FIG. 2 is uniformly thickened compared to the thickness of the wall of the work piece 10a along the length C shown in FIG. 2. This increase in thickness may be predetermined to offset to any desired degree the reduction of thickness caused by the initial machining along the length C shown in FIG. 2. The portion of the length E shown in FIG. 3 extending into one end of the length D shown in FIG. 2 has a wall thickness which may be slightly thicker than the wall thickness of the rest of the length E shown in FIG. 3 because the effect of the initial machining is to increase the wall thickness along the length D shown in FIG. 2 away from the handle end, while the effect of the first swaging operation is to progressively diminish the thickening effect of swaging along the length D toward the handle end. As to the portion of the work piece 10b along the length F, the offsetting effects of the machining operation in the first swaging operation likewise can be predetermined to give a substantially uniform wall thickness along the length F shown in FIG. 3, or to permit a gradual increase of wall thickness from left to right in FIG. 3, depending on the predetermined thickness of adjacent portions of the bat.

The entire swaging operation could be done in one operation, if swaging dies were available which were of the proper dimensions to do so. However, conventional swaging dies have a relatively short length, usually up to about 13 inches, between the large and small ends of the die, and this limitation can be overcome in accordance with the invention by a second swaging operation, on the intermediate work piece 10b shown in FIG. 3. The second swaging die has a small end of less diameter than that of the first swaging die, and a large end of a less diameter than the large end of the first swaging die. The handle end of the work piece 10b is pressed against the large opening of the second swaging die while it is rotating, and this action is continued until the extreme end of the handle extends through the small end of the second swaging die, along the length H shown in FIG. 4 leaving the length I shown in FIG. 4 in the tapered portion of the second swaging die. Thus the second swaging operation produces an untapered swaged end 30 and a tapered portion 34 which extends between planes 32 and 28. The second swaging die may have the same but preferably has a lesser degree of taper than the first swaging die, and this change of taper closely simulates that of conventional wooden baseball bats. The differing degrees of taper are in contiguous and abutting relationship. The lengths H and I shown in FIG. 4 together correspond substantially to the length E shown in FIG. 3, (this being the total second swaging operation), while the lengths J and K shown in FIG. 4 correspond to the lengths F and G shown in FIG. 3. The wall thicknesses along the lengths H and I may be predetermined by the amount of initial machining balanced against the amount of swaging, to provide a uniform wall thickness along H, I, J, and K, but preferably H has a uniform small wall thickness, and the thickness progressively increases along I and J until reaching a maximum uniform thickness along K.

Both swaging operations are preferably carried out without the use of an internal mandrel, and in that case the swaging operation tends to thicken the wall without lengthening the work piece substantially (i.e., an increase of about 2 inches in a total of 28-inch original swaged length). However, an internal mandrel might be used, if its tendency to limit wall thickening and increase lengthening is taken into account in the choice of dimensions specified for the various steps.

After the two swaging operations, the work piece 10c shown in FIG. 4 is preferably trimmed at the handle end to the desired dimensions, and the large end is internally machined at 42 as shown in FIG. 6. The machined end is "bullnosed" and a suitable end plug 40 is inserted and locked in place by folded over portion 44. A handle grip 38 is also added to complete the bat.

Two illustrative examples are given below of baseball bats actually constructed in accordance with this invention with dimensions A-L being listed in Tables I and II wherein:

A = overall length in inches of original tube or work piece 10a of FIG. 2;

b = distance in inches of unmachined area from the hitting end of the work piece to the runout of the machined portion (FIG. 2);

c = distance in inches of machined area of constant O.D. from the handle end of the work piece to the beginning of the machined transition area 12 at plane 21 (FIG. 2);

d = distance in inches of the machined taper or transition area 12 in FIG. 2 between planes 21 and 20. In Tables I and II this distance is a constant 15' for all sizes;

E = (FIG. 3) the constant outer diameter resulting from the first swaging operation;

F = (FIG. 3) the same as J (FIG. 4);

g = (fig. 3) the same as K (FIG. 4);

h = distance in inches after sawing, from the handle end of the work piece having a constant diameter (O.D.) to the beginnning of the transition or tapered portion at plane 32 (FIG. 4) from the second swaging operation;

I = length in inches of the transition or tapered portion (FIG. 4) from the second swaging operation;

J = length in inches of the transition or taper from the first swaging operation (FIG. 4);

k = in inches of the unmachined and unswaged portion at the hitting end of the work piece 10c (FIG. 4);

l = overall length in inches of the finished work piece 10c (FIG. 4) cut to length.

Table I __________________________________________________________________________ NOMINAL BAT SIZE A B C L H I J K D (INCHES) (INCHES) (INCHES) (INCHES) (INCHES) (INCHES) (INCHES) (INCHES) (INCHES) (INCHES) __________________________________________________________________________ 32 31 4 3/16 11 13/16 31 7/16 43/4 11 12 3 11/16 15 33 32 4 3/16 12 13/16 32 7/16 53/4 11 12 3 11/16 15 34 33 5 3/16 12 13/16 33 7/16 53/4 11 12 4 11/16 15 35 34 5 3/16 13 13/16 34 7/16 63/4 11 12 4 11/16 15 __________________________________________________________________________

TABLE II __________________________________________________________________________ NOMINAL BAT SIZE A B C L H I J K D (INCHES) (INCHES) (INCHES) (INCHES) (INCHES) (INCHES) (INCHES) (INCHES) (INCHES) (INCHES) __________________________________________________________________________ 32 31 6 3/16 9 13/16 31 7/16 2 3/4 11 12 5 11/16 15 33 32 6 3/16 10 13/16 32 7/16 3 3/4 11 12 5 11/16 15 34 33 7 3/16 10 13/16 33 7/16 3 3/4 11 12 6 11/16 15 35 34 7 3/16 11 13/16 34 7/16 4 3/4 11 12 6 11/16 15 __________________________________________________________________________

From the foregoing examples, it will be seen that each bat has a relatively long taper area produced by the first and second swaging operations of 23 inches which substantially exceeds the 13-inch stroke capability of available swaging machines.

While presently preferred embodiments of the practice of the invention have been illustrated and described, it will be understood that the description and drawings are for purposes of illustration only, and that the scope of the invention is limited only by the appended claims.

Claims

We claim:

1. The method of making a metal body for a ball bat comprising the steps of

a. providing a cylindrical hollow metal work piece;

b. machining post of the length of the outside of the work piece, thereby reducing its wall thickness to a predetermined extent; and,

c. swaging down most of the machined portion of the work piece in successive swaging operations to form two abutting tapering sections, thereby shaping the work piece and increasing the thickness of the wall of the work piece to a predetermined extent where it had been thinned by machining, the offsetting effects of machining and swaging being such as to provide a tapered metal bat body having a predetermined wall thickness from one end to the other.

2. The method of claim 1, wherein a first swaging operation produces a first degree of taper on the outside of the work piece and a second swaging operation produces a lesser degree of taper on the outside of an abutting portion of said work piece.

3. The method of claim 1, wherein the wall thickness is generally uniform from one end to the other.

4. The method of claim 1 in which the swaged length portion formed by said two abutting tapering sections is substantially greater than 13 inches.