Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates to powder material com-
pacting apparatus and methods and, more part~cularly, to an im-
proved apparatus and method for compacting powder material into
spherical and similar shapes.
The present invention is concerned with improved tooling
for use in powder-compacting presses such as are disclosed in U. S.
patents 3,826,599; 3,775,032; 3,730;659; 3,726,622; 3,~45,658;
3,574,892; 3,561,056; 3,415,142; 3,344,213; and 3,328,840, all of
which are assigned to the same assignee as the present application.
In the powder-compacting presses disclosed in the afore-
mentioned U. S. patents, the articles are compacted and formed
in a multi-cavity die forming part of a punch and die set, with
the finished articles being automatically ejected from the die
cavities, picked up by a vacuum pick-up head, and conveyed into
suitable receptacles. The work station positioner assembly, which
is part of the press, is mounted angularly movable transversely
over the die plate and carries a powder dispenser, an anvil and
the pick-up head. The powder dispenser, which is supplied with
powder from a primary powder supply means connected thereto by
means of a flexible tubing or the like, is first positioned over
the die cavity or cavities which are thus filled with powder as
the punches are displaced downwardly so as to draw a predeter-
mined amount of powder into the die cavity or cavities. The
dispenser is then removed from above the die cavity or cavities
by the subsequent angular motion of the station positioner assem-
bly, and the anvil is, in turn, positioned over the die cavities.
The anvil is clamped over the die cavity by means of a pivotable
clamp supported above the anvil and actuated in timed relation
with the movement of the punches. The anvil is held down with
sufficient pressure to perm~t the compaction of the powder against
the anv~l as a result of an up~ard motion of the punches into the
die cavit~ or cavit~e~. The anv~1 i5` then removed from its
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position over the die cavity or cavities and is replaced by the
pick-up head by a further angular motion of the work station posi-
tionex transversely across the face of the die plate. The punches
are d:isplaced upwardly so as to bring their upper ends in sub-
stantial flush alignment with the upper surface of the die plate,
such that the finished compacted articles are ejected from the
die cavities and picked up by the pick-up head. As the result
of a return angular motion of the work station positioner to the
initial fill position, the pick-up head is removed from over the
die cavity and is disposed over one or, if a plurality of die cav-
ities are employed, a series of discharge apertures arranged in
a disposition similar to the arrangement of the die cavities in
the die plate, and the finished compacted article or articles are
drawn, as by vacuum, through the discharge aperture or apertures
into a container or separate containers.
The tooling used in the prior art in compacting powder
materials into spherical forms consists of a die having a center
bore, and upper and lower punches the faces of which define a
spherical cavity. Typically, powder material is charged in a
measured quantity into the die bore and hemispherical cavity of
the lower punch. The upper punch is then moved through the bore
and compacts the powder material in the spherical cavity defined
by the end faces of upper and lower punches. It is necessary to
make the ends of the walls of the punch members thick enough at
the equator of the spherical cavity to prevent distortion or
breakage of the walls by the compacting forces. As a result, a
portion of the powder material is squeezed in the equatorial space
and the end faces of the punches do not make contact with each
other. The compacted material then has an equatorial ring or
bulge of greater diameter than the d~ameter of the spherical cav-
it~, T~e excess m~ter~al ~:n t~is ring has to be removed by a
tum~ling or similar proce~ i~ order to obtal'n a spher~cal article.
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The present invention provides a method and apparatus
for producing a compacted spherical article without an equatorial
ring or bulge.
In accordance with the present invention, a spherical
mold cavity is defined primarily by an upper punch member and
a die with a center bore. These members are brought into
engagement prior to the time a compaction stroke is started.
The compaction stroke then takes place by reciprocation of the
lower punch through the die bore which has a diameter less than
the diameter of the spherical cavity.
One aspect of the present invention relates to an
apparatus for compacting powder material into ~enerally spherical
articles, the apparatus comprising a punch and die assembly
comprising a die plate, a bore in the die plate, a punch disposed
reciprocably in the bore, a compacting face on the end of the
punch, a progressively enlarged end portion in the bore, the
enlarged end portion forming with the compacting face a first
half-mold cavity, a counterpunch having a flat end face
engageable with the die plate, a second half-mold cavity
disposed in the counterpunch end face, the second half-mold
cavity being alignable with the bore, and means for reciprocating
the punch to a position whereby the face of the punch forms with
the enlarged end portion of the bore the first half-mold cavity
for compacting the powder material in a molding cavity formed
by the first and second half-mold cavities.
Another aspect of the present invention relates to
the method of compacting powder material in a mold into
generally spherical articles which comprises filling by
gravity with said powder material a first partial mold having
an open upper end, displacing a movable portion of said first
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partial mold during filling in a direction and to a prede-
termined position increasing the volume of said first partial
mold, leveling said powder material in said first partial
mold to a level corresponding to the level of said open end,
placing over the open end of the first partial mold a second
partial mold having an open cavity therein, the first and
second partial molds having correspondingly engageable
interferring faces preventing one of the partial molds from
penetrating into the other, displacing in an opposite
direction the movable portion for transferring part of the
powder material from the first partial mold through the
open end into the cavity in the second partial mold and
for compacting the powder material in a mold defined by the
first and second partial molds for forming one of the
articles, removing the second partial mold from over the open
end of the first partial mold, and further displacing the
movable portion in the opposite direction for ejecting the
article from the first partial mold through the open end.
FIG. 1 is a broken sectional view of a die with upper
and lower punches illustrating the prior art apparatus and
method of forming spherical articles from powder material;
FIG. 2 is a view of a spherical article produced by
the prior art apparatus and process illustrated in FIG. l;
FI~. 3 is a broken sectional view of a die and lower
punch according to the present invention showing the charging of
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powder material to the die cavity;
FIG. 4 is a broken sect~onal view of the apparatus in
accordance with the present invention showing the upper punch
clamped over the die cavity prior to the powder material compac-
tion step;
FIG. 5 is a broken sectional view similar to FIG. 4 but
with the lower punch in the position it occupies after compaction
of the material;
FIG. ~ is a broken sectional view similar to FIG. 5 but
with the upper punch withdrawn after compaction of the material;
FIG. 7 is a broken sectional view of the die and lower
punch with the lower punch in ejection position and pick-up head
in place;
FIG. 8 is a broken sectional view of a vacuum-powered
system for collecting spherical articles in a receptacle;
FIG. 9 is a schematic partial elevation view of means
for cleaning the end face of the upper punch; and
FIGS. 10 and 11 are schematic representations of modi-
fications of lower punch shapes and corresponding articles made
thereby.
Referring to FIG. 1, which illustrates the prior art,
a die 10 of cylindrical configuration has an axial bore 11. The
die 10, which is sometimes referred to as a "die bushing", is nor-
mally composed of a very hard material such as cemented tungsten
carbide. The die bushing 10 is supported by being press-fitted
or otherwise fastened in a bore of a die plate 12 which may be
made of carbide but which is normally made of a less costly
material than tungsten carbide, such as steel or the like. The
die plate is mounted in the table or bed of a press apparatus
(not shown~.
The die bore 11 accommodates an upper punch 13 and a
lower punch 14 which are rec~procally mova~Ie therein. The end
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faces of the punches 13 and 14 define a hemispherical cavity.
With the upper punch 13 out of engagement from within the die 10,
a measured portion of powder material is poured in the hemispher-
ical cavity of the lower punch 14 and in the bore 11 of the die
10. The upper punch 13 is then moved into the die bore 11 and
the lower punch is moved upwardly into compacting engagement with
the powder material to compact it into a spherical form as shown
at 15. During the compacting stroke, a portion of the powder is
caused to project between the flat portions of the end faces of
the upper punch 13 and lower punch 14, thus forming an equatorial
bulge 16 which prevents engagement of the surfaces of the punches
13 and 14. This equatorial bulge must be factored into the design
in order to provide a uniform diameter in a longitudinal direction
of the sphere. The product removed from the press is as shown in
FIG. 2. It is necessary to remove the bulge 16 by a tumbling or
similar process, in order to obtain a generally spherical article.
Referring now to FIGS. 3-7, there is shown, in a sche-
matic manner, an apparatus according to the present invention for
molding a generally spherical or partly spherical article without
an equatorial bulge. The molding apparatus comprises a die con-
sisting of a die bushing 20 press-fitted, cemented or otherwise
disposed in a bore 22 in a die plate 24. The die bushing 20 is
preferably made of a hard material, such as tungsten carbide or
the like, and the die plate 24 may be made of a tool steel, but
is preferably also made of carbide with a highly polished upper
sur~ace 25. The die bushing 20 is provided with a longitudinal
bore 26 accepting for reciprocation therein a lower punch 28.
In the example of structure illustrated, the lower punch 28 has
a concave end face 3Q shaped substantially as a spherical seg-
ment, and the upper end of the die bushing bore 26 is provided
with an enlarged portion shaped ~u~stantially as a complementary
spherical zone, as- s~own at 3I, such that together they define a
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first half-mold cavity.
The lower punch 28 is reciproca~le by means of an
appropriate ram 29 forming a part of the press apparatus, not shown,
as di.sclosed in detail in the aforementioned patents, and an upper
punch member 32, or counterpunch, (FIGS. 4-6) is provided recipro-
cable towards, and away from, the die plate 24 and die bushing
20 by being mounted on the end of a ram 33 ~FIG. 4), reciprocated
by appropriate means by the press mechanism, not shown, as dis-
closed, for example, in aforementioned Patent No. 3,826,599. The
end face of the upper punch 32 is provided with a hemispherical
cavity 34, defining the second half-mold cavity, surrounded by an
annular flat surface 36. When reciprocated towards and away from
the die plate 24, the upper punch 32 is guided by an anvil member
38, having a lower surface 39 at all times in engagement with the
upper surface 25 of the die plate 24, but displaceable from posi-
tions away from over the die cavity to a position over the die
cavity, the latter position being illustrated at FIGS. 4-6. The
upper punch 32 is reciprocable through a vertically disposed bore
40 in the anvil member 38, and has an abutment surface 42 engage-
able with the top end surface 44 of a coil spring 46, or other
biasing means such as superimposed Belleville springs or the like,
disposed over a reduced diameter portion 48 of the anvil member
38.
A radial slot 50 is disposed through the wall of the
anvil member 38 to provide appropriate clearance for the finished
part, when the anvil member 38 is laterally displaced from above
the die cavity by means of the operation of the station positioner
of the press apparatus as disclosed and explained in detail in the
hereinbefore referred-to patents, and more particularly Patent
Nos. 3,726,622; 3,645,658; 3,574,892; 3,561,056 and 3,145,142.
In operation, the die cavity is gravity filled with
powder material 52 as illustrated at FrG. 3 by means of a powder
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hopper 54 disposed over the die cavity. During filling of the
die cavity with powder material, the lower punch 28 is retracted
so as to draw into the die cavity an appropriate amount of powder
materi.al 52.
Subsequent to filling of the die cavity with powder
material, the powder hopper 54 is laterally displaced, with the
result that the edge of the powder hopper 54, in contact with the
upper surface 25 of the die plate 24 and the end face 21 of the
die bushing 20, wipes the surfaces clean of any powder particles
and at the same time levels the charge of powder material 52
evenly flush with the end face 21 of the die bushing 20. The
anvil member 38, supported and driven by the station positioner
of the press apparatus, is then displaced to its position over
the die cavity, and the upper punch 32 is advanced by the ram 33
into the guiding bore 40 of the anvil member 38, thus compressing
the spring 46 and forcing firmly the anvil member against the die
plate 24 until the annular face 36 of the upper punch 32 engages
the end face 21 of the die bushing 20, as represented at FIG. 4.
Although not absolutely necessary for successful opera-
tion of the apparatus of the invention, the height of the anvil
member 38 and the length of the upper punch 32 are preferably
e~ual, such that, in the position shown at FIG. 4, the punch
abutment surface 42 engages the top end surface of the anvil mem-
ber, therefore apply.ing the anvil member lower face 39 with great
pressure against the die plate upper surface 25.
The lower punch 28;is then advanced to the position in-
dicated at FIG. 5 until the recess 30 at the end of the lower
punch forms with the spherical zone portion 31 of the die bore
wall a complete hemisphere, thus compacting the powder ~aterial
52 into a spherical article 56, The press apparatus i5 adjusted
such that the force applied for reciprocat~ng the lower punch 28
i5 slightly smaller than the force h~ldl~ng the upper`punch 32
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with its annular face 36 in engagement with the die bushing end
face 21. The upper punch 32 is subsequently withdrawn from within
the bore 40 in the anvil member 38, as illustrated at FIG. 6, and
the anvil member 38 is laterally displaced to a position away from
above the die cavity, the slot 50 in the wall of the anvil member
providing appropriate clearance for the spherical article 56 dur-
ing displacement of the anvil member.
A vacuum pickup head 58, also supported by the press
apparatus station posi.~ioner, is subsequently placed above the
die cavity, and the lower punch 28 is advanced upwardly such as
to eject the spherical article 56 from the spherical zone wa~l
31 of the die into the vacuum pickup head 58. ~,~
In the structure illustrated at FIG. 7 and in more de-
tail at FIG. 8, the vacuum pickup head 58 has an orifice 60 placed
in communication by means of a flexible tubing 62 with a recep-
tacle 64 connected by way of a line 66 to a source of vacuum (not
shown). In this manner, the spherical articles 56 ejected from
the die cavity are propelled within the tube 62 to the receptacle
64. It will be appreciated that other means of ejecting the fin-
ished part, such as mechanical wiper means or vacuum pickup heads
provided with a screen to which the finished articles remain ad-
hering until the pickup head is displaced over an appropriate
ejection aperture through the die plate communicating with an
àppropriate receptacle, may also be used in conjunction with the
apparatus of the invention as disclosed in the aforementioned
patents.
It has been d~scoYered that when forming certain types
of powder material into spherical articles, according to the pre-
sent invention, some powder particles ma~ find their way betweén
the upper punch annular ~ux~ace 36 and the end face 21 of the die
hu~fi~ng 2a~ The d~e ~ush~ng end f~ce 21 ~9` ~ept clean by the
~ng act~on of the powder a~penser edge and, in order to pre~
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vent an accumulation and build-up of powder particles on the end
annular face 36 of the upper punch 32, means may be provided, as
illustrated at FIG. 9, for wiping the annular surface 36 of the
punch clean between compacting operations. As illustrated, such
wiping operation is effected by means of a vacuum brush 68, having
a length corresponding substantially to the diameter of the punch
32, mounted on the end of an arm 70 pivotable about a~ipivot point
72 disposed on a side of the upper ram 33. A cam follower 74 sup-
ported on one side of the arm 70 is engageable with a stationary
cam surface 76 when the ram 33 and the punch 32 are reciprocated,
so as to move the vacuum brush 68 from the position shown in phan-
tom line at FIG. 9 when the upper punch 32 is advanced, to the
position shown in full line when the upper punch 32 is retracted.
Appropriate biasing means, such as a spring 78, are provided for
urging the arm 70 and the brush 68 in the position shown in phan-
tom line, such that during reciprocation of the upper punch 32,
the vacuum brush 68 is caused to traverse the face of the punch,
thus removing any powder particles that may remain adhering to
the punch face. Other convenient means, such as the rotary brush
arrangement disclosed in Patent No. 3,328,840, may be used for
wiping clean the end face of the upper punch.
It will be readily appreciated that the compacting
apparatus of the present invention may be modified to provide
compacted articles other than strictly spherical articlesO For
example, as shown at FIG. 10, by using a lower punch having a
flat face an article 56' is obtained of generally spherical shape
but provided with a flat face 80 corresponding to'the f~at end
face of the lower punch. With a lower punch 28 having a convex
end face, a generally spherical article 56" is obtained, as shown
at FIG. 11, having a concave recess 82.
The present invention also contemplates that at least
a portion of the wall of the molding cavity may be coated with an
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adhering layer of elastomeric material. For example, the wall of
the hemispherical cavity 34, FIG. 4, in the upper punch member 32
may be provided with a surface layer varying in thickness from a
few microns to a few millimeters, which is made of a material
such as natural rubber, neoprene, polysiloxane elastomers,
polyurethane, polysulfide rubber, polybutadiene, buna-S or like
material.
It is to be understood that the example of the present
invention as disclosed herein constitutes one preferred form and
that other forms might be adopted. For example, the term "~pheri-
cal" should not be considered unduly limiting, but should include
other shapes within the spirit of the invention and the scope of
the appended claims.
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