Shell forming apparatus and process

Apparatus and process of manufacture for forming a generally cylindrical shell having an interior surface, an opened end with a first internal diameter, a generally closed opposite end, a first internal portion intermediate the ends with a second internal diameter larger than the first internal diameter, and a second internal portion intermediate the first internal portion and the closed end with a third internal diameter larger than the second internal diameter, wherein such apparatus and process of manufacture include a mandrel having an outer surface for forming the interior surface of the shell and having an expandable and contractable intermediate portion, the mandrel intermediate portion expandable outwardly to form its second internal portion and upon the shell being formed the mandrel intermediate portion contractable inwardly sufficiently to permit the mandrel to be moved relatively away from the formed shell through the open end to permit the formed shell and the mandrel to be separated.

FIELD OF THE INVENTION 
This invention relates generally to improved shell forming apparatus 
generally of the type disclosed in U.S. Pat. Nos. 3,459,021 issued Aug. 5, 
1969; 3,495,433 issued Feb. 17, 1970; and 3,509,785 issued May 5, 1970; 
all issued to F. J. Fuchs, Jr., the inventor of the present invention. 
More particularly this invention relates to improved shell forming or 
extruding apparatus for forming a generally cylindrical shell having an 
interior surface, a first end with a first internal diameter, a generally 
closed opposite end, a first internal portion intermediate said ends with 
a second internal diameter smaller than said first internal diameter, and 
a second internal portion intermediate said first internal portion and 
said closed end with a third internal diameter larger than said second 
internal diameter 
BACKGROUND OF THE INVENTION 
Referring now to FIG. 1, there is shown a closed shell indicated by general 
numerical designation 10 and which shell may be formed advantageously by 
the apparatus and process of the present invention. The shell 10, in 
accordance with the teachings of the present invention set forth below, is 
for being formed, such as by being extruded or drawn, in a forming die 12 
and with a reciprocably mounted mandrel 14. The exterior surface of the 
mandrel 14 forms the interior surface of the shell 10 and the interior 
surface of the forming die 12 forms the exterior shell surface. It will be 
noted from FIG. 1 that the shell 10 has an open end 16 having an internal 
diameter ID.sub.1, a closed end 17, a first internal portion 18 
intermediate the open and closed ends having an internal diameter ID.sub.2 
smaller than ID.sub.1, a second internal portion 19 intermediate the first 
internal portion 18 and the closed end 17 having an internal diameter 
ID.sub.3 larger than ID.sub.2, and internal lower portions as shown (e.g. 
lower internal portion 20 having internal diameter ID.sub.4) each having 
an internal diameter not larger than ID.sub.2. To form the interior 
surface of the shell 10, the mandrel 14, of course, must be provided with 
portions of complementary shape to the opposed portions of the interior 
surface of the shell as shown, such portions 21-25 from top to bottom 
having, respectively, outer diameter OD.sub.1, outer diameter OD.sub.2, 
outer diameter OD.sub.3, and outer diameter OD.sub.4. After forming, the 
mandrel 14 is retracted or moved away from the formed shell 10, but it 
will be noted that since mandrel portion 23 having outer diameter OD.sub.3 
is larger than the internal portion 18 of the formed shell having internal 
diameter ID.sub.2, it is not possible to retract the mandrel 14 as shown 
from the formed shell 10, or it is not possible to so retract the mandrel 
14 without damage to or destruction of the internal portion 18 of the 
formed shell 10. Shell 10 may be a grenade body of the type broadcast by a 
large projectile or shell (such as a howitzer shell) over a general area 
and which grenade body typically contains a shaped charge and upon the 
grenade body striking an object, such as an enemy tank, explodes. 
Shown in FIG. 2 is another closed shell which is indicated by general 
numerical designation 30 and which closed shell may be also a grenade body 
of the same type as closed shell 10 of FIG. 1. The grenade body 30 is a 
generally cylindrical shell having an open end 31 with a first internal 
diameter ID.sub.6, a generally closed opposite end 32, a first internal 
portion 33 intermediate the ends and having an internal diameter ID.sub.7 
smaller than internal diameter ID.sub.6 and a second internal portion 34 
intermediate the first internal portion 33 and the closed end 32 with an 
internal diameter ID.sub.8 larger than the internal diameter ID.sub.7 of 
the first internal portion 33. Further, as may be noted from FIG. 2, the 
grenade body 30 may have its lower interior portion embossed as indicated 
by the area identified by numerical designation 35. Such embossing is 
produced by indentations, e.g. 36, 37 and 38, having internal diameters 
ID.sub.9, ID.sub.10, and ID.sub.11 larger than internal diameter ID.sub.7 
of internal portion 33; in the closed shell 30 internal diameters ID.sub.8 
-ID.sub.11 are equal. In addition, the shell 30 may be provided at its 
lower or closed end portion with a shoulder 39 for facilitating stacking, 
or axial alignment, of a plurality of such shells. 
To form the interior surface of the grenade body 30 as shown, the outer 
surface of the mandrel (not shown for clarity of presentation) must, of 
course, be of complementary shape to the interior surface of the grenade 
body, and must be provided with outwardly extending ridges for forming the 
internal portion 34 and the indentations 36, 37 and 38, and hence if solid 
such a mandrel could not be retracted from the formed shell (or at least 
not so without damage to the formed shell) since the mandrel portions 
forming the shell portions having internal diameters ID.sub.8 -ID.sub.11 
would be larger than internal diameter ID.sub.7 of shell internal portion 
33; thus, the solid mandrel could not be retracted past internal portion 
33 of the shell (without shell damage) to separate the formed shell and 
the solid mandrel. 
Accordingly, there exists a need in the art for apparatus including a 
mandrel for forming a closed shell (e.g. shell 10 or 30) and a process for 
using the same, wherein the mandrel is provided with an expandable and a 
contractable intermediate portion for being expanded to form a second 
internal portion (e.g. 19 or 34) of the closed shell intermediate a first 
internal portion (e.g. 18 or 33) of the shell and the closed end of the 
shell wherein the second internal portion (e.g. 19 or 34) of the shell has 
an inner diameter (ID.sub.3 or ID.sub.8 -ID.sub.11) larger than the 
internal diameter (ID.sub.2 or ID.sub.7) of the first internal portion of 
the shell, and wherein the mandrel intermediate portion is contractable to 
permit the mandrel to be withdrawn past the first internal portion (e.g. 
18 or 33) of the formed shell and through the open end of the formed shell 
to separate the mandrel and shell after forming. 
Preferably, as is known to those skilled in the art, for shell forming such 
as shell 10 of FIG. 1 or shell 30 of FIG. 2, the mandrel must be solid or 
at least must be solid, or substantially solid, during shell forming. 
Accordingly, there exists a need in the art for a mandrel, and process for 
using the same, where the mandrel is comprised of a plurality of parts so 
as to be expandable and contractable for the reasons described above but 
which plurality of mandrel parts are formed into a solid, or a 
substantially solid, mandrel during shell forming. 
SUMMARY OF THE INVENTION 
The object of the present invention is to provide apparatus and process of 
manufacture for forming a generally cylindrical shell having an exterior 
surface, an open end with a first internal diameter, a generally closed 
opposite end, a first internal portion intermediate said ends with a 
second internal diameter smaller than the first internal diameter and a 
second internal portion intermediate the first internal portion and the 
closed end with a third internal diameter larger than the second internal 
diameter. 
The foregoing object is accomplished by apparatus and process of 
manufacture of the present invention including a mandrel having an outer 
surface for forming the interior surface of the shell and having an 
expandable and contractable intermediate portion, the mandrel intermediate 
portion expandable outwardly to form the second internal portion and upon 
the shell being formed the mandrel intermediate portion contractable 
inwardly sufficiently to permit the mandrel to be moved relatively away 
from the formed shell through the open end to permit the formed shell and 
the mandrel to be separated.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to FIGS. 3-7, there is shown apparatus embodying the present 
invention, and for practicing the process of manufacture of the present 
invention, indicated by general numerical designation 40. Generally, such 
apparatus 40 is for forming a shell of the type illustrated in FIGS. 1 and 
2, from a shell blank cut or sheared from blank material strip stock 42. 
Apparatus 40 may include a draw punch or mandrel 44 including an 
expandable and contractable intermediate portion 43, a blanking punch or 
ram 46, blanking die and cover plate 48, iris die indicated by general 
numerical designation 50 including a plurality of edge punches or iris 
forming members 51a and 51d (better seen in FIG. 8 as edge punches or iris 
forming members 51a-51f), forming die 52, shoulder punch or ram 54, and 
back-up die ram and knock-out punch 56; it will be noted that the iris die 
50 is mounted circumferentially around the top of the forming die 52, note 
FIG. 8. 
It will be understood by those skilled in the art, and referring to FIGS. 
3-7, that the draw punch or mandrel 44, blanking punch or ram 46, edge 
punches or iris forming members 51, shoulder punch or ram 54 and back-up 
die ram and knock-out punch 56 are mounted reciprocably and as double 
acting pistons as shown; the draw punch or mandrel 44 and blanking punch 
or ram 46 are mounted concentrically and telescopically as shown and the 
forming die 52, shoulder punch or ram 54 and back-up die ram and knock-out 
punch 56 are mounted concentrically and telescopically as shown. It will 
be further understood that the associated entrance and exit pressurized 
fluid ports are not shown for clarity of presentation. 
It will still be further understood by those skilled in the art that the 
pressurized fluid or hydraulic control circuitry for operating the 
structural elements of apparatus 40, although not shown, may be any one of 
several suitable pressurized fluid or hydraulic circuitry systems known to 
the art which, as will be further understood by those skilled in the art, 
may be operated in the manner known to the art for controlling the 
operation and sequence of operation of such structural elements as 
described below. 
Referring now generally to the operation of apparatus 40 embodying the 
present invention, and for practicing the process of manufacture of the 
present invention, as noted above, such is for forming a closed shell 60 
(FIGS. 6 and 7) of the type described above and illustrated in FIGS. 1 and 
2, from a shell blank cut or sheared from shell material strip stock 42, 
FIG. 3. Referring now to FIG. 3, it will be understood that the 
above-described structural elements comprising the apparatus 40 will 
initially occupy the positions shown with the shell material strip stock 
42 having been advanced, by suitable means not shown but known to those 
skilled in the art, into the position shown in FIG. 3. As illustrated in 
FIG. 4, the blanking punch or ram 46 is advanced downwardly to shear or 
cut a shell blank 62 from the strip 42; as shown in FIG. 8 the shell blank 
62 may be suitably shaped for having its circumferential edges engaged 
complementarily by the forming edges 53a-53f of the edge punches or iris 
forming members 51a-51f, for example, the shell blank 62 may be cut or 
sheared into a hexagonal shape as shown in FIG. 8, and it will be 
understood that for such hexagonal shaping the blanking punch or ram 46 
and blanking die and cover plate 48 would be of complementary shape or 
cross-sectional configuration. The draw punch or mandrel 44 is then 
advanced downwardly at a constant rate and the edge punches or iris 
forming members 51a-51f are advanced radially inwardly in the directions 
of the arrows 71-76 in FIG. 8 to apply radially inward force to the 
circumferential edge of the blank 62 to force or extrude the shell blank 
52 towards the downwardly moving draw punch or mandrel 44 to form the 
shell 60 between the lower portion of the mandrel 44 and the forming die 
52 with the exterior surface of the mandrel defining or forming the 
interior surface of the shell 60 and with the interior surface of the 
forming die 52 defining or forming the exterior surface of the shell 60. 
It will be understood that at each increment of downward movement of the 
draw punch or mandrel 44, the radially inwardly advancing or moving edge 
punches or iris forming members 51a-51f supply the proper volume of blank 
material to provide the proper wall thickness of the formed shell 60. 
The operation of the iris die 50 as described above may be better 
understood by reference to FIGS. 8-10 wherein, it will be noted, as stated 
above, the edge punches or iris forming members 51a-51f, are mounted 
reciprocably as double-acting pistons and in forming the shell 60, 
particularly as illustrated in FIG. 5, the iris forming members 51a-51f 
are advanced inwardly in the directions of the arrows 71-76 to cause the 
forming edges 53a-53f of the iris forming members 51a-51f to apply 
radially inwardly acting force to the circumferential edge, or edges, of 
the blank 62 as indicated in FIG. 8 by the arrows 81-86. A better 
understanding of the individual structure or shape of each iris forming 
member 51 may be better understood by reference to FIG. 9 where there is 
illustrated individually edge punch or iris forming member 51a. 
In accordance with the further teachings of the present invention, 
particularly with regard to the iris die 50 and as may be best seen in 
FIGS. 8 and 9, a hydrostatic bearing may be provided for each iris forming 
member (the hydrostatic bearings being indicated by numerical designations 
81-86 with one associated with each iris forming member as shown) for 
applying inwardly acting hydrostatic force, as indicated by arrows 88 and 
89, the iris forming members 51a-51f as shown in FIG. 8, to compensate for 
the edge punch or iris forming member load, or reaction force, produced in 
opposition to the radially inwardly acting forces indicated by arrows 
81-86. Thus, it will be understood that the hydrostatic bearings 81-86 
assist in facilitating the edge punches or iris forming members 51a-51f in 
applying the radially inward force indicated by arrows 81-85 to the 
circumferential edge or edges of the blank 62 in extruding the blank 
radially inwardly as described above to form the shell 60. The hydrostatic 
bearings 81-86 may be provided with suitable seals as shown in FIG. 8 and 
may be supplied with suitable pressurized fluid or hydraulic pressure 
through suitable inlet ports as indicated in dashed outline in FIG. 8. 
Referring again to FIGS. 4 and 5, it will be further understood and in 
accordance with the further teachings of the present invention that at 
each increment of draw punch or mandrel 44 downward movement, and upon 
each increment of radially inward movement of the edge punches or iris 
forming members 51a-51f, the back-up die ram and knock-out punch 56 is 
moved downwardly to provide back-up force or pressure to the blank 62 
during forming of the shell 60. Upon the blank 60 being formed into the 
shell configuration shown in FIG. 5, the shoulder punch or ram 54 is 
advanced upwardly as shown in FIG. 6 to form a shoulder on the bottom of 
the shell 60 such as the shoulder 39 of shell 30 of FIG. 2. 
It will be generally understood, in accordance with the teachings of the 
present invention, that during the forming of the shell blank 62 into the 
shell 60, particularly as illustrated in FIG. 5, the expandable and 
contractable intermediate portion 43 of the draw punch or mandrel 44 is 
expanded radially outwardly to provide the shell 60 with an internal 
portion such as internal portion 19 of FIG. 1 or 34 of FIG. 2 having an 
internal diameter such as internal diameter ID.sub.3 of FIG. 1 or ID.sub.8 
-ID.sub.11 of FIG. 2, larger than the internal diameter ID.sub.2 of 
internal portion 18 of FIG. 1 or ID.sub.7 of internal portion 33 of FIG. 
2; the specific structure and function of the mandrel expandable and 
contractable intermediate portion 43 embodying the present invention is 
described in detail below and illustrated in alternative embodiments in 
FIGS. 11-16 and FIGS. 17-19. At this time, as illustrated in FIG. 6, the 
shell 60 is fully formed. 
Thereafter, blanking punch or ram 46, shoulder punch or ram 54, and edge 
punches or iris forming members 51a-51f are retracted to the positions 
shown in FIG. 7. Then, the draw punch or mandrel 44 is retracted upwardly 
and the back-up die ram and knock-out punch 56 is advanced upwardly 
following the mandrel 44 to remove or extract the formed shell 60 from the 
forming die 52 with the formed shell 60 remaining attached to the lower 
end of the mandrel 44, this continues until the back-up die ram and 
knock-out punch 56 has reached its position shown in FIG. 7. Thereafter, 
the draw punch or mandrel 44 continues to be retracted upwardly with the 
formed shell 60 attached to its lower end as shown in FIG. 7 until the 
upper end of the formed shell 60 strikes the blanking punch or ram 46 
which causes, as will be described in detail below and as shown in the 
alternate embodiments of FIGS. 11-16 and 17-19, the expandable and 
contractable intermediate portion 43 of the mandrel 44 to contract 
inwardly to permit the portions of the mandrel forming the internal 
portions, such as internal portions 19 of FIG. 1 and 34 of FIG. 2 having 
respectively internal diameters ID.sub.3 and ID.sub.8 -ID.sub.11 larger 
than internal diameter of internal portions 18 of FIG. 1 and 33 of FIG. 2, 
to contract and permit the mandrel to be moved or retracted past the 
internal portions, such as internal portion 18 of FIG. 1 and internal 
portion 33 of FIG. 2, and permit the mandrel to be pulled out or separated 
from the formed shell passing through the open end of the formed shell 
thereby permitting the mandrel and formed shell to be separated. 
Subsequently, the formed shell 60 may be transferred by suitable means 
known to the art from the apparatus 40 for a possible trimming operation 
to provide the formed shell with a further or better defined upper end as 
shown with regard to the shells 10 and 30 illustrated in FIGS. 1 and 2. 
Detailed structure of a preferred embodiment of a draw punch or mandrel 44A 
in accordance with the teachings of the present invention is illustrated 
in FIGS. 11-16 and which is particularly useful for forming shell 10 of 
FIG. 1. The mandrel 44A of FIGS. 11-16 has an axis 41 and, as described 
above, is provided with an outer surface indicated by general numerical 
designation 90 for defining or forming the interior surface of a shell, 
such as shell 10 of FIG. 1. The lower end of the draw punch or mandrel 
44A, as shown in FIGS. 11, 12 and 16, may include an upper portion 92 
secured to the mandrel 44A by suitable threaded members 91A and 91B as 
shown and may include a lower portion 94 connected (FIG. 16) to a 
cylindrical portion 94A, surrounding upper portion 92, by a rod 95 
extending through a passageway 95A formed centrally of the mandrel upper 
portion 92 and a cross member 96; threaded members 97A and 97B 
interconnect the cross member 96 and portions 94A as may be best seen in 
FIG. 16. Lower portion 94 hangs or depends below upper portion 92 being 
supported by the rod 95 and the cross member 96 residing in an axially 
(vis-a-vis mandrel axis 41) oversized slot 97 formed at the top of upper 
portion 92. It will be understood that the upper portion 92 and lower 
portion 94 are movable relatively towards and away from each other, with 
the upper portion 92 sliding within portion 94A, upon the mandrel 44A 
being advanced downwardly and retracted upwardly as described above with 
regard to mandrel 44; as shown in FIG. 11, the upper portion 92 is moved 
upwardly or away from the lower portion 94 and in FIGS. 12 and 16 the 
upper portion 92 is shown moved downwardly towards lower portion 94. As 
may be best understood by reference to FIGS. 11B, 13A and 13B, the upper 
portion 92 of mandrel 44A is provided at its lower end with a conical 
portion 98 tapering toward the lower portion 94 and radially inwardly at a 
first angle .beta..sub.1 with respect to the mandrel axis 41 (note 
particularly FIG. 13B). The conical portion 98, as may be best seen in 
FIG. 13A, is provided with a radial slot 99 partially defined by a surface 
101 inclined inwards toward the lower mandrel portion 94 and radially 
inwardly at a second angle .beta..sub.2 with respect to the mandrel axis 
41 (best seen in FIG. 13B), with it being understood that angle 
.beta..sub.1 is less than angle .alpha..sub.2 and vice versa. 
The above-described expandable and contractable intermediate portion 43 of 
draw punch or mandrel 44 may be embodied as the annular member 104 and 
wedge member 106, best seen in FIGS. 14 and 15. The annular member 104 is 
provided with a peripheral or radial interruption 108 in which is mounted 
the wedge member 106 and it will be noted, also best seen in FIGS. 14 and 
15, that the wedge member 106 tapers radially outwardly with respect to 
the mandrel axis 41. As may be best understood from FIGS. 11, 12 and 16, 
the interrupted annular member 104 surrounds the conical portion 98 of 
upper mandrel portion 92 with its inner surface residing slidably against 
the conical portion 98 and the inner surface of wedge member 106 resides 
slidably against the inclined surface 101. The annular member 104 (FIGS. 
14 and 15) is provided with a radially or peripherally interrupted, 
radially outwardly extending (with respect to mandrel axis 41) ridge 110 
and the wedge member 106 is provided with a radially outwardly extending 
ridge 112; as will be explained in detail below, the ridges 110 and 112 
are for forming the internal portion 19 of shell 10 of FIG. 1 having 
internal diameter ID.sub.3. 
It will now be assumed that mandrel 44A of FIGS. 11-16 is substituted for 
mandrel 44 of FIGS. 3-7, that mandrel 44A is occupying the position shown 
for mandrel 44 in FIG. 3, i.e. mandrel 44A is in its initial position, and 
that mandrel 44A and the forming die 52 (FIGS. 3-7) are for forming the 
shell 10 of FIG. 1 from shell blank 62 (FIG. 4). In this initial position, 
the upper portion 92 of mandrel 44A will be retracted and moved upwardly 
away from the lower mandrel portion 94 and the annular member 104 and 
wedge member 106 will occupy the contracted or radially inward positions 
shown in FIGS. 11, 11B, 14 and 15A with the wedge member 106 residing 
radially inwardly of the annular member 104 and with the interrupted ridge 
110 of annular member 104 having an outer diameter OD.sub.6 (also note 
FIGS. 11A and 11B) slightly less than, by a predetermined amount as 
understood by those skilled in the art, the internal diameter ID.sub.2 
(FIG. 1) of internal portion 18 of shell 10. Upon downward movement of the 
mandrel 43A, the lower portion 94 of the mandrel 44A will first engage and 
temporarily come to a stop against the shell blank 62 and upon continued 
downward movement of the mandrel 44A, the upper portion of the mandrel 92 
will move downwardly until it engages the mandrel lower portion 94. As the 
upper mandrel portion 92 moves into engagement with the lower mandrel 
portion 94, and since angle .beta..sub.1 (FIG. 13B) of the conical surface 
98 is less than angle .beta..sub.2 of the surface 101 against which the 
wedge member 106 resides, the conical surface 98 of upper mandrel portion 
92 will first cam and expand annular member 104 radially outwardly and 
thereafter, since angle .beta..sub.2 is larger than angle .beta..sub.1, 
the inclined surface 101 will cam wedge member 106 radially outwardly to 
fill the radial interruption 108 (FIG. 14) of the annular member 104 with 
the wedge member 106 and the expanded annular member 104 forming a 
complete annulus as shown in FIGS. 12 and 15B and with the interrupted 
annular ridge 110 of the annular member 104 and the ridge 112 of the wedge 
member 108 forming a complete annular ridge having an outer diameter 
OD.sub.7 (also note FIG. 12A), substantially equal to, or slightly less 
than by a predetermined amount as understood by those skilled in the art, 
the inner diameter ID.sub.3 of internal portion 19 of the shell 10 of FIG. 
1. Thereafter, as described above with regard to the forming of shell 60 
and as illustrated in FIGS. 4 and 5, the shell 60 is formed between the 
outer surface 90 of the mandrel 44A and the inner surface of the forming 
die 52 of FIGS. 4 and 5 and with the completed annular ridge comprised of 
interrupted ridge 110 of the annular member 104 and the ridge 112 of the 
wedge member 106 forming the internal portion 19 of shell 10 (FIG. 1) 
having internal diameter ID.sub.3. Upon the shell 10 being formed as 
illustrated in FIG. 6 with regard to shell 60, the mandrel 44A is 
retracted upwardly with the formed shell 10 residing on the lower portion 
thereof as shown in FIG. 7 with regard to mandrel 44, and upon the shell 
10 engaging the blanking punch or ram 46 as shown in FIG. 7 and described 
above, the upward movement of the lower portion 94 of the mandrel 44A will 
stop its upward movement, but the upper portion 92 of the mandrel 44A will 
continue to move or be retracted upwardly away from the lower portion 94 
until the mandrel upper portion 92 occupies the position shown in FIG. 11; 
as the upper mandrel portion 92 is retracted upwardly away from the lower 
mandrel portion 94, since angle .beta..sub.2 is larger than angle 
.beta..sub.1 (FIG. 13B), the wedge member 106 first moves radially 
inwardly of the annular member 104 sliding against inclined surface 101 
whereafter, since angle .beta..sub.1 is less than angle .beta..sub.2, the 
annular member 106 contracts radially inwardly sliding against the conical 
surface 98 (FIGS. 13A and 13B) and occupying the position shown in FIGS. 
11, 11B, 14 and 15 with the ridges 110 and 112 of the annular member and 
wedge member being contracted radially inwardly such that the interrupted 
annular ridge 110 now has outer diameter OD.sub.6 of FIG. 15A 
substantially equal to or slightly less than the internal diameter 
ID.sub.2 of internal portion 18 of shell 10 (FIG. 1) thereby permitting 
the mandrel 44A to continue to be moved or retracted upwardly, with the 
contracted annular member 104 and the lower portion of the mandrel 44A 
sliding past internal portion 18 of the formed shell having ID.sub.2 
without damage to the formed shell and thereby permitting the formed shell 
10 and mandrel 44A to be separated. 
Referring again to FIGS. 11, 11A, 11B and 12, and the positions occupied by 
the annular member 104, wedge member 106, and upper and lower mandrel 
portions 92 and 94 during shell forming, it will be noted that the annular 
member 104, wedge member 106, and upper and lower mandrel portions 92 and 
94 are provided with a plurality of contiguous, internal surfaces (not 
individually numbered to reduce the amount of numerals used for the sake 
of clarity) of complementary shape, which internal surfaces during shell 
forming are engageable to form the mandrel 44A into a solid, or 
substantially solid, mandrel to enhance forming of the shell. 
As may be best understood from FIGS. 11A and 11B, mandrel portions 94A and 
94 are provided with opposed surfaces 122 and 124, respectively, spaced 
apart a distance substantially equal to the axial length, or height, of 
the annular member 104 and wedge member 106 with such members slidable 
thereagainst. The opposed surfaces 122 and 124 are for preventing relative 
axial movement (vis-a-vis mandrel axis 41) between the annular member 104 
and wedge member 106 thereby restricting their movements during radial 
expansion and contraction to radial movement. 
Detailed structure of an alternate preferred embodiment of a draw punch or 
mandrel 44B in accordance with the teachings of the present invention is 
illustrated in FIGS. 17-19 and which is particularly useful for forming 
shell 30 of FIG. 2. The mandrel 44B has an axis 41B and is provided with 
an outer surface indicated by general numerical designation 190 for 
defining or forming the interior surface of a shell, such as shell 30 of 
FIG. 2. The lower end of draw punch or mandrel 44B, as shown in FIGS. 17 
and 18 may include an upper portion 192 secured to the mandrel 44B by 
suitable threaded members as shown and may include a lower portion 194 
connected to a cylindrical portion 194A, surrounding upper portion 192, by 
a rod 195 formed integrally with lower portion 194 and which rod extends 
through a passageway 195 formed centrally of the mandrel upper portion 192 
and a cross member 196 residing in an axially oversized slot 197 formed at 
the top of upper portion 192. Lower mandrel portion 194 hangs or depends 
below the upper mandrel portion 192 being supported by the rod 195 and 
cross member 196. It will be understood that the upper portion 192 and 
lower portion 194 are movable relatively towards and away from each other 
with the upper mandrel portion 192 sliding within the lower portion 194 
upon the mandrel 44B being advanced downwardly and retracted upwardly as 
described above with regard to mandrel 44A; in FIG. 17, the upper mandrel 
portion 192 is shown moved upwardly or away from the lower mandrel portion 
194 and in FIG. 18 the upper mandrel portion 192 is shown moved downwardly 
towards lower mandrel portion 194. As may be understood by reference to 
FIG. 17, the upper mandrel portion 192 is provided at its lower end with a 
conical portion 198 tapering toward the lower portion 194 and radially 
inward at a first angle .beta..sub.3 with respect to the mandrel axis 41B. 
The conical portion 198, it will be understood, is provided with a radial 
slot (analogous to radial slot 99 of FIG. 13A) partially defined by a 
surface 201 inclined inwardly towards the lower mandrel portion 194 and 
radially inwardly at a second angle .beta. .sub.4 with respect to the 
mandrel axis 41B with it being understood that angle .beta..sub.3 is less 
than angle .beta..sub.4 and vice versa. 
In mandrel embodiment 44B, the annular member 104 and wedge member 106 of 
mandrel embodiment 44A are replaced, respectively, by annular or 
cylindrical member 204 and wedge member 206 as may be best seen in FIG. 
19; annular member 204 resides slidably against conical surface 198 of 
upper mandrel portion 192 and wedge member 206 resides slidably against 
inclined surface 201 partially defining the radial slot formed in the 
upper mandrel portion 192. As also may be best seen in FIG. 19, annular 
member 204 is provided with a radially outwardly extending ridge 210 and 
wedge member 206 is provided with a radially outwardly extending ridge 
212; the ridges 210 and 212 are for forming the internal portion 34 of 
shell 30 (FIG. 2) having internal diameter ID.sub.8. 
It will be further understood that the outer surface of annular member 204 
and wedge member 106 in addition to the ridges 210 and 212 are also 
provided, respectively, with radially outwardly extending ridges indicated 
diagrammatically in FIG. 19 by the crisscross lines and by the respective 
ridges shown in FIGS. 17 and 18 identified by numerical designations 240 
and 241 for engaging and embossing (i.e. by providing ridges 36, 37 and 38 
of FIG. 2) the lower interior portion of the shell 30 (FIG. 2) with a 
predetermined pattern (e.g. area 35 of FIG. 2) to enhance fragmentation of 
the grenade body 30. It will be understood that upon the annular member 
204 and wedge member 206 being contracted radially inwardly the ridges 210 
of annular member 204 will have an outer diameter OD.sub.7 slightly less 
than internal diameter ID.sub.7 of internal portion 33 of shell 30 of FIG. 
2, and upon the annular member 204 and wedge member 206 being expanded 
radially outwardly the ridges 210 and 212, and ridges 240 (formed on 
annular member 204) and 241 (formed on wedge member 206) providing the 
abovenoted embossing, will have an outer diameter OD.sub. 8 slightly less 
than, by a predetermined amount, the internal diameters ID.sub.8 
-ID.sub.11 of FIG. 2. It will now be understood that upon the mandrel 44B 
being substituted for mandrel 44A, mandrel 44B will perform substantially 
the same function as mandrel 44A with the annular member 204 and wedge 
member 206 being expanded and contracted thereby performing substantially 
the same functions as annular member 104 and wedge member 106 of mandrel 
44A. 
It will be understood by those skilled in the art that the above-described 
operation and mounting of the structural elements of apparatus embodying 
the present invention are merely illustrative of the present invention and 
that other structure, structural mountings and relative movements are 
possible within the scope of the present invention, for example instead of 
mounting the forming die stationarily and the mandrel reciprocably for 
movement toward and away from the forming die, the mandrel may be mounted 
stationarily and the forming die may be mounted reciprocably for movement 
toward and away from the mandrel, or both may be mounted reciprocably for 
movement toward and away from each other; the significant movement being 
relative movement toward and away from each other. Further, it will be 
understood that while the apparatus embodying the present invention 
illustrated in the figures is oriented vertically, the present apparatus 
is not so limited and apparatus embodying the present invention may be 
oriented differently, such as for example may be oriented horizontally. 
Further, it will be understood by those skilled in the art that many 
modifications and variations may be made in the present invention without 
departing from the spirit and the scope thereof.