Method and apparatus of forming one-piece core cap stamping with keyway

A core cap is formed from a one-piece sheet metal blank in which an inner cylindrical sleeve is formed and a reverse-fold outer sleeve determining a bight therebetween, and a recess is gradually formed by stamping in the bight and the inner sleeve so as to provide a keyway with parallel side walls symmetrically parallel with the axis of the inner sleeve.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to core caps, and more particularly, to a 
method of making a core cap with an integral keyway. 
2. Description of the Prior Art 
Core caps typically require a strong rigid inner sleeve for inserting into 
the end of a tubular core. The core may be a lightweight fiberboard or 
plastic cylindrical tube for a large paper roll or the like. It is 
important that the cap have a keyway formed in the rigid sleeve in order 
to receive and transmit torque to the otherwise easily deformed core. The 
cap must also be shaped about the end of the core in order to present a 
wear and impact-resistant end to the core. Such core caps have been made 
either as a one-piece stamping or, when a keyway is required, in two 
pieces. That is, a keyway insert is welded to the stamping. 
SUMMARY OF THE INVENTION 
It is an aim of the present invention to provide an improved core cap, and 
in particular, a one-piece stamped metal core cap with a keyway formed 
therein. 
A construction in accordance with the present invention comprises a 
one-piece stamped metal core cap having an inner sleeve of circular 
cylindrical cross-section and a reverse-fold outer sleeve of circular 
cylindrical cross-section concentric with the inner sleeve with a bight 
formed therebetween, and a keyway defined partly in the inner sleeve and 
in the bight portion, the keyway having planar parallel side walls 
symmetrically parallel to the axis of the inner sleeve. 
An important aspect of the present invention is the method of forming the 
core cap. It is clear that a keyway of the type required, that is, where 
the walls are planar and parallel and the corners are at right angles, is 
not easily formed by stamping. Given the reverse fold formed in the 
stamping, the stresses in the metal would not allow the walls forming the 
recess to be readily formed at the intersection of the bight and the inner 
sleeve. 
It is, therefore, an aim of the present invention to provide a method of 
forming a core cap formed from a one-piece metal stamping having a 
suitable keyway formed therein. 
It is a further aim of the present invention to provide a method of forming 
a one-piece metal stamping of a core cap with a reverse fold and a keyway 
recess formed partly in the bight. 
A method of forming a core cap in accordance with the present invention 
comprises the steps of first, selecting a blank of suitable sheet metal, 
second, forming a shallow U-shaped cup by stamping, third, drawing the cup 
in a plurality of successive stamping procedures to provide a deeper cup 
of smaller diametric dimensions having a bottom wall and a cylindrical 
wall, fourth, reverse stamping the bottom wall in order to form a reverse 
fold inwardly of the cylindrical wall with the bottom parallel and 
adjacent a plane containing the rim of the cup, fifth, causing a further 
step of drawing the bottom wall past the plane containing the rim of the 
cup such that an inner cylindrical wall is formed having an axial extent 
thereof which is greater than the axial extent of the outer cylindrical 
wall, sixth, forming a recess in the inner cylindrical wall at the 
intersection with the reverse fold in at least two successive stamping 
steps wherein the depth of the recess is gradually increased, and the 
recess includes parallel planar side walls symmetrically parallel to the 
axis of the inner cylinder, and seventh, punching out the bottom wall at 
any time from the end of the third step of drawing the inner cylindrical 
wall to the end of the sixth step of forming the recess. 
In a more specific embodiment the second to seventh steps are done 
simultaneously on a succession of individual blanks in different stages of 
formation, by using a ganged metal stamping means while the blanks advance 
intermittently on a linear conveyor. 
The advantage of the above process is that the core cap can be stamped from 
a single blank of sheet metal and a keyway in the form of a recess can be 
formed in the inner wall at the reverse fold in order to avoid the 
necessity of fabricating a two-piece core cap in order to provide the 
keyway.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to the drawings, FIG. 1 shows a typical core 12 to which a 
core cap 10 has been mounted on each end thereof. 
The core cap includes an outer sleeve 14 of circular cylindrical 
configuration, an inner sleeve 18 of cylindrical configuration concentric 
with the outer sleeve 14, and a bight 16 extends between the inner sleeve 
18 and the outer sleeve 14 and is integral therewith. As shown in FIGS. 1, 
2, and 3, a keyway in the form of a recess 20 is formed in the inner 
sleeve 18 and the bight 16. The keyway includes side walls 24 and 26 which 
are in planes parallel to each other and to the axis of the concentric 
sleeves. The recess is also provided with a rear wall 22 and a bottom wall 
28. The bottom of sleeve 18 is formed by a rim 28 which can be slightly 
tapered in order to allow better insertion on the end of the core 12. 
The core cap 10 is formed from a steel sheet stamped into the form shown in 
FIGS. 2 and 3. The stamping process is illustrated in FIGS. 4a to 4j in 
successive steps starting with a blank of sheet metal 8 as shown in FIG. 
4a. 
As will be described the stamping steps shown in FIGS. 4b to 4j can be done 
by a ganged stamping apparatus having a separate stamping die for each 
step acting in unison on successive blanks in different stages of 
formation over a linear conveyor (not shown). The successive blanks are 
advanced on the linear conveyor by a shuttle means (not shown), from one 
stamping position to the other. 
FIGS. 4b and 5 illustrate the formation of the blank 8 into a cup-shaped 
member having the beginning of an outer sleeve 14 and a bottom wall 34. As 
shown in FIG. 5, the stamping dies could typically include a female die 
member 36 and a mating male die member 38. 
FIGS. 4c and 6 illustrate the succeeding step of forming the core cap by 
drawing out the bottom wall and thus extending the outer sleeve 14. As 
shown in FIG. 6, this is accomplished by using a male die member 40, a 
guide member 44, and a hollow cylindrical female die member 42 which 
slides on guide member 44 and draws the material of the walls 14 and 34 to 
reduce the diameter of the cup and to draw out the 30 outer wall or sleeve 
14. 
FIGS. 4d and 4e show successive steps using die members similar to that 
shown in FIG. 6 to further draw the outer sleeve 14. 
FIGS. 4f and 7 illustrate the next step of reverse folding the inner sleeve 
18 by using a cylinder 46 to retain the outer sleeve 14. A male die member 
48 slides within the cylinder 46 and engages the bottom wall 34 to draw it 
into the female die member 50. The result of this step is that the bottom 
wall 34 is still within the confines of the outer sleeve 14 and is 
slightly spaced from the bottom rim of the outer sleeve 14. An inner 
sleeve 18 is now formed and a reverse fold or bight 16 as well. 
The next step, as illustrated in FIGS. 4g, 8, and 9, requires a further 
drawing of the inner sleeve 18, and this is accomplished by the male die 
52 sliding within cylinder 56 and engaging the bottom wall 34 to draw it 
further into a female die 54. 
The steps shown in FIGS. 4h to 4j provide for a successive forming of the 
recess 20 to form the keyway as well as the punching out of the bottom 
wall 34. FIG. 10 shows the die cylinder 66 retaining the outer sleeve 14 
and a male die member 64 which is suitable to punch out the bottom wall 34 
through an opening 70 in the female die 68. Successive male dies 64 would 
have larger projections 64a to accomplish the successive forming of the 
recess 20. The progressive forming of the recess 20 by means of the male 
die 64 reduces the stresses on the wall material allowing the recess 20 to 
be fully formed with relatively right angular corners and parallel side 
walls 24 and 26. The recess 20 serves as the keyway in the finished core 
cap 10. 
It is contemplated that different outer diameter core caps can be provided. 
Depending on the thickness of the wall of the core, at least two sizes of 
core caps may be required. By keeping the internal diameter of the inner 
sleeve 18 of the core cap 10 constant, the outer sleeve 14 can vary in 
diameter. The recess 20 formed in the bight portion 16 and the inner 
sleeve 18 will be of constant dimension regardless of the diameter of the 
outer sleeve 14. 
In an example of a particular core cap 10, the inner sleeve 18 had a 
diameter of 3.034 inches and the outer diameter of the outer sleeve 14, 
4.0 inches. The recess 20 had a width tangential to the inner sleeve 18 of 
0.78 inches and a depth of 0.796 inches. The overall axial length of the 
inner sleeve 18 was 3 inches, and the axial length of the outer sleeve 14 
was 1.5 inches. 
In another example of a core cap 10, the dimensions of the inner sleeve 18 
and the recess 20 remained the same, but the diameter of the outer sleeve 
14 was 4.375 inches and its axial length remained at 1.5 inches.