U.S. patent number 3,841,130 [Application Number 05/417,695] was granted by the patent office on 1974-10-15 for ball bat system.
This patent grant is currently assigned to Reynolds Metals Company. Invention is credited to Irvin C. Scott, Jr., George F. Swenck.
United States Patent |
3,841,130 |
Scott, Jr. , et al. |
October 15, 1974 |
**Please see images for:
( Certificate of Correction ) ** |
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.
Inventors: |
Scott, Jr.; Irvin C. (Richmond,
VA), Swenck; George F. (Richmond, VA) |
Assignee: |
Reynolds Metals Company
(Richmond, VA)
|
Family
ID: |
23655038 |
Appl.
No.: |
05/417,695 |
Filed: |
November 20, 1973 |
Current U.S.
Class: |
72/70; 473/566;
72/370.24 |
Current CPC
Class: |
B21D
51/16 (20130101) |
Current International
Class: |
B21D
51/16 (20060101); B21d 051/16 () |
Field of
Search: |
;72/367,70,76
;273/72A |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Larson; Lowell A.
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.
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.
* * * * *