Method Of Making Ball Bat Metal Body System

Abstract

The hollow metal body for a ball bat is made by swaging one end of a cylindrical metal extrusion to form the handle portion of reduced diameter, and the swaged end is then drilled out to reduce the wall thickness and thereby put more of the metal weight at the large diameter end, where balls are hit.

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 League 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 relatively 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.

IMPROVEMENT

In accordance with the present invention, the good hitting characteristics of the earlier lathe-turned metal bats are combined with the low cost production characteristics of the swaged-down bat. This is accomplished by first swaging down the bat stock, and subsequently hollowing out the thickened tapered end to enlarge the internal diameter of most or all of the thickened end until the residual walls have a thickness not substantially greater than the thickness of the walls at the hitting end of the bat. The result is a metal bat element which has good weight distribution for hitting, and yet is not too expensive for commercial production.

DRAWINGS

The accompanying drawings show, for purposes of illustration only, a present preferred embodiment of the invention. In the drawings:

FIG. 1 shows in section a cylindrical metal workpiece entering a rotating swaging die;

FIG. 2 shows in section the workpiece of FIG. 1 after it has been swaged down at one end, and also shows a drill approaching the thick end to drill out the thickened handle;

FIG. 3 shows in section the drilled out workpiece after the drill of FIG. 2 has been used and withdrawn; and

FIG. 4 shows in section a completed bat in accordance with the invention.

DESCRIPTION

Referring now more particularly to the drawings, the illustrated metal workpiece 10 is in the form of an extruded hollow cylinder of uniform cross-section along its length, preferably made of a heat treatable aluminum alloy. The illustrated rotating swaging die 12 has a tapered throat 14, suitable for swaging down one end of the workpiece 10. The throat 14 has the effect of progressively pressing against the end of the workpiece 10 thrust into it, and thereby causing the metal compressed against the die to be displaced radially inwardly. This reduces the outside diameter of the swaged end of workpiece 10 while reducing the adjacent inside diameter even more, thus progressively thickening the wall of the swaged end of the workpiece.

The workpiece 10 is thrust a predetermined distance into the die 12, and is removed with the shape illustrated in FIG. 2. As can be seen in FIG. 2, the unswaged end 16 of the workpiece has its original inner and outer diameter and original wall thickness. At the swaged end, the outer wall is progressively tapered down along an intermediate portion 18 of the workpiece, and is given a generally uniform outside diameter at the handle end 20 of the bat. This simulates the general exterior shape and proportions of a conventional wooden bat.

As further shown in FIG. 2, a long drill bit 22 is mounted in coaxial relation with the workpiece 10, for endwise movement toward the handle end 20. The drill is held in a chuck 24 rotated by a motor 26, and the rotating drill bit 22 is thrust coaxially into the thickened end 20 of the workpiece until at least most of the thickened end of the workpiece has been drilled out to leave metal walls having a thickness not substantially greater than the thickness of the ball hitting end 16 of the workpiece. Preferably, the bit is thrust as far as it will do any drilling in the workpiece, leaving the workpiece in the form shown in FIG. 3. Instead of drilling out the reduced end, the excess metal may be removed by broaching, reaming, grinding, chemical milling or other hollowing out operations.

In a typical example of metal bat stock made in accordance with the invention, the body has three major components along its length. The hitting end has smooth cylindrical surfaces inside and out. A central transitional portion has a smooth conical exterior surface and is progressively thicker and more rough surface on the inside away from the hitting end, until the interior drilled out surface is reached. The remaining portion is the handle, which has smooth cylindrical surfaces inside and out.

As shown in FIG. 3, the drilled out portion of the workpiece extends through the handle end 20 and through part of the tapered intermediate portion 18 of the workpiece. The drill hole 27 terminates at an annular line of intersection 28 with the place where the internal taper 30 begins to have a greater diameter than the drill hole 27. As a result, there is a slight thickening of the wall which is greatest at the annular line of intersection 28, and which diminishes on both sides of line 28. This does not significantly alter the fact that the metal bat stock thus produced has substantially equal wall thickness from end to end, and hence has substantially more metal weight concentrated at the ball hitting end than would be the case if the drilling operation had not been carried out as described.

In some cases the metal bat stock may be improved by reducing the handle wall thickness to less than that at the hitting end of the bat; for example, down to about half of the hitting end wall thickness. As shown in FIG. 4, the bat stock of FIG. 3 is preferably completed by inserting a rubber-like plug at the open end 16. This may be secured by any suitable means, such as by gluing, and also by swaging in the tip of the hitting end 16 of the metal bat stock after the plug 34 has been put in place. The handle end 20 can be finished in any suitable manner. For example, the handle 20 can be inserted in a cap 36 which provides a knob and hand gripping surface for the handle end.

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

Claims

What is claimed is:

1. The method of making the metal body of a ball bat, comprising the steps of radially compressing one end of a tubular metal workpiece so that its outer diameter is reduced substantially uniformly along said end to form the bat handle, radially compressing an intermediate portion of the workpiece adjacent said end so that its outer diameter tapers between the outer diameter of the compressed end and the outer diameter of the remaining uncompressed portion of the workpiece, and removing metal from the interior of the workpiece to enlarge the bore through at least most of the length of said end and thereby to reduce the wall thickness of said end so that it does not substantially exceed the wall thickness of the radially uncompressed portion of the bat body.

2. The method of claim 1, in which the outer diameter is reduced by swaging, and the metal is removed from the bore by drilling.

3. The method of claim 1, in which the bore is of uniform diameter and is extended through as much of the intermediate tapered portion of the workpiece as would otherwise have a smaller bore.

4. The method of claim 1 in which the metal is removed until the wall thickness of said end is substantially equal to the wall thickness of the radially uncompressed portion of the bat body.

5. The method of claim 1, in which metal is removed until the wall thickness of said end is not substantially greater than, and not less that substantially half of, the wall thickness of the radially uncompressed portion of the bat body.