Plastic article or earthenware shaping or treating: apparatus – Press forming apparatus having opposed press members – Male shaping member and female mold
Reexamination Certificate
2000-06-29
2001-07-17
Davis, Robert (Department: 1722)
Plastic article or earthenware shaping or treating: apparatus
Press forming apparatus having opposed press members
Male shaping member and female mold
C264S003400, C425SDIG001
Reexamination Certificate
active
06261082
ABSTRACT:
STATEMENT OF GOVERNMENT INTEREST
The invention described herein may be manufactured and used by or for the Government of the United States of America for government purposes without the payment of any royalties therefor.
BACKGROUND OF THE INVENTION
The invention relates in general to manual die sets for pressing explosive powder and in particular to a self-aligning manual die set for pressing explosive powder into pellets.
Manual die sets for pressing explosive powder into pellets are known. The explosive powder is a highly sensitive explosive molding powder, for example, PBXN-9 or PBXW-11. The manual die set, in combination with a press for supplying the pressing force, presses the explosive powder into solid cylindrical pellets.
FIG. 1
is an elevation view, partially in cross-section, of a known manual die set
10
in a press configuration and
FIG. 2
is an elevation view, partially in cross-section, of the known manual die set
10
of
FIG. 1
in a knockout configuration. Manual die set
10
includes a die
12
with an opening
14
therethrough, a ram
16
having a head
18
, a baseplate
22
that fits in the bottom of the opening
14
in die
12
and a knockout ring
24
.
Manual die set
10
is used to press highly sensitive explosive molding powder
20
into a pressed pellet
26
in the following manner. First, the baseplate
22
is fitted into the opening
14
in the bottom of the die
12
. The required amount of molding powder
20
is poured into the die opening
14
. Next, the ram
16
is inserted into the top of the die opening
14
and allowed to “float” down as its weight forces air out of opening
14
. Air escapes through the limited clearance between the ram
16
and the die wall until the ram
16
rests on the surface of the powder
20
.
Next, the die set
10
is placed under a pressing mechanism (not shown), such as a hydraulic ram, and press force is applied to the ram head
18
for a required dwell time. After pressing, the die set
10
is lifted and placed on top of the knockout ring
24
. If the baseplate
22
is loose, it is usually removed before the die is placed on the knockout ring
24
. Finally, the ram
16
is pressed completely down, ejecting the baseplate
22
(if not previously removed) and the pressed pellet
26
into the cavity in the knockout ring
24
. Usually, a small piece of wadding or foam rubber (not shown) is inserted in the bottom of the knockout ring
24
to cushion the landing of the baseplate
22
and/or pellet
26
.
FIG. 3
is an elevation view, partially in cross-section, of the manual die set
10
of
FIG. 1
showing an alignment problem. The amount of misalignment shown in
FIG. 3
is somewhat exaggerated to illustrate the problem. While pressing pellets using the manual die set
10
, it is difficult to align the ram
16
vertically in the die
12
. Also, the ram
16
may become cocked in the die
12
when the pressing pressure builds up. The lack of vertical alignment causes a high shear stress area
17
with safety problems where the edge of the ram
16
touches the die wall. First, the ram
16
may cause galling of the interior wall of the die
12
, requiring replacement of the die. Second, the ram
16
may pinch some of the powder
20
against the die, which may cause an explosion. Third, as the pellet
26
is ejected, the ram
16
can shear off the explosive residue on the inside surface of the die
12
, resulting in an explosion. These are serious safety problems when pressing highly sensitivity explosive molding powder.
Thus, a need exists for a manual die set that overcomes the problems of the manual die set of
FIGS. 1-3
.
SUMMARY OF THE INVENTION
The present invention provides a manual die set, comprising a ram, the ram having a head, a large diameter portion, a tapered portion, a small diameter portion and a pressing portion; a die defining an opening therethrough for receiving the ram, the opening including a large diameter portion, a tapered portion and a small diameter portion, the large diameter portion of the opening having a diameter less than or equal to about 0.002 inches larger than a diameter of the large diameter portion of the ram; a baseplate disposed in a bottom of the opening in the die; and a die holder for supporting the die and the baseplate when the manual die set is in a pressing configuration; wherein vertical alignment of the ram is maintained by insertion of the large diameter portion of the ram in the large diameter portion of the opening in the die.
Explosive molding powder is disposed in the opening in the die between the pressing portion of the ram and the baseplate.
The manual die set further comprises a knockout ring for supporting the die when the manual die set is in a knockout configuration.
When the manual die set is in the knockout configuration and the ram is fully inserted in the opening in the die, the tapered portion of the ram and the tapered portion of the die define a gap therebetween.
Preferably, the die includes a bottom surface and an external surface, the bottom surface including at least one groove extending from the opening in the die to the external surface of the die, for passage of air therethrough. The die holder includes a base portion and an upwardly extending portion, the upwardly extending portion preferably includes at least one opening therethrough for passage of air.
More preferably, the large diameter portion of the ram includes a groove formed therein and the external surface of the die includes a groove formed therein, the manual die set further comprising an O-ring disposed in the groove in the large diameter portion of the ram and a second O-ring disposed in the groove in the external surface of the die.
Further objects, features and advantages of the invention will become apparent from the following detailed description taken in conjunction with the following drawing.
REFERENCES:
patent: 3156011 (1964-11-01), Olson
patent: 3597796 (1971-08-01), Erlich
patent: 3606637 (1971-09-01), Lawless
patent: 3619861 (1971-11-01), Lumby
patent: 3790330 (1974-02-01), Roland
patent: 4061453 (1977-12-01), DeSantis
patent: 4573895 (1986-03-01), DeSantis et al.
patent: 4759886 (1988-07-01), Daugherity
patent: 4987818 (1991-01-01), Alford
patent: 5277570 (1994-01-01), Siggers
Mark D. Lowell, Manual Hydraulic Press Die Set Design, IHTR 1363, Mar. 15, 1991.
Davis Robert
Homer Mark
The United States of America as represented by the Secretary of
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