Note: Descriptions are shown in the official language in which they were submitted.
This invention relates ~o metal forming machines, and
particularly to machines ~or the co:Ld forming of metal employing
baclcward and/or forward extrusion of the metal.
Backward and/or forward extrus.ion of metals, without
heating the metal prior to its being formed, are well known in
the art. Such metal forming operations, however, suffer from
several disadvantages, among which are the problems of tool
breakage and lLmitations upon the cross-sectional dimensions
' of the part which can be formed from a given metal billet.
... i 10
~; In a typical extrusion operation, a metal billet is
held within a die cavity. A punch or anvil is inserted in the
die cavity to define an annular space therebetween and held
stationary while the billet is forced to extrude over and about
the anvil, resulting in extrusion of the billet into and then
~, 15
out of the annular space between the die cavity and the anvil.
In other embodiments, the anvil is itself moved relative to
a stationary die cavity with resultant extrusion of the billet
: i! ',.
; out of the die cavity through the annular space bletween the
anvil and the die cavity wall.
- It has been recognized heretofore that tool breakage,
particularly breakage of the anvil, is likely if there is mis-
~ alignment of the anvil with respect to the die cavity by as
; much as 0.0005 inch, per inch, for example. Such misalignment
i
can occur due to "wobble" of the anvil and/or can be caused
25 by defects in the metal billet, etc. For example, hard spots
in the billet and/or air inclusions can result in anvil
misalignment sufficient to cause breaking of the anvil. As
~ !
~/ a conse~uence of these and other factors, it has been
commonly acoepted in the art that a reduction~of greater
than about seventy ~70%) percent is not practical ln an
extrusion operation, such as a backward extrusion. "Reduction"
~. ~
~ (expressed in percentage) is defined in the following equation:
- ~'
Reduction = B X l00 Eq. l
whexe:
B = the cross-sectional area of the bore formed
in the extruded product, in s~uare inches, and
- 5 A = the cross-sectional area of the billet prior to
the commencement of the extrusion operation, in
square inches.
: Thus, it will be seen that the term "reduction" is a
. , ;
r~ measure of the size of the bore in the e~truded product that
can be expected from a billet of given cross-sectional area.
Accordinglv, it has been the practice in the art heretofore
when desiring a product having the relatively large bore,
, ;, . .
to utilize a billet which has a correspondingly, relatively
large cross-sectional area.
One of the considerations in using an extrusion
operation to form a product, as opposed to machining the product,
~ etc., is the conservation of metal. It is recognized in the
;~; art that the production of billets from which the parts are
to be formed must be econ~omical both as to the process
involved and as to the conservation of the metal. ~o this end
. it is desirable that the billet in any particular operation be
of a minimum diameter so that, for example, the billet may be
sheared from standard size metal wire by conventional shearing
; operations that minimize any metal loss~ This is to be
~ 25 contrasted with a sawing operation or a milling or other
;~ ~ cutoff operation, these operations resulting in a substantial
~_ waste of metal. It will be recognized that the desire to use
a minimum diameter billet is in immediate conflict with ~he
commonly accepted rule that a billet cannot be reduced by
more than about seventy (70%) percent of its original
cross-sectional area.
In certain prior art extru~ion operations, in order
to utilize a starting billet that has a minimum cross-
sectional area (thereby realizing the necessary economies
associated with the choice of extrusion as the forming method),
the extrusion process has included multiple steps wherein the
billet is reduced, i.e. extruded, a multiplicity of times,
each successive extrusion enlarging the diameter of the
product by an amount that is within the heretofore acceptable
reduction limit. Obviously, these multiple "hit" operations
~ ; increase the cost of the process, thereby increasing the cost
; , 10 of the resultant product.
~n accordance with the present invention, it has been
~; found that reductions in excess of one hundred twelve (112%~
, ~ .. .
percent can be obtained, using only a single "hitl', thereby
~ : opening up the availability of the less expensive cold
;~ ; 15 extrusion forming process to the manufacture of products not
heretofore possible. This is accomplished in accordance with
. the concepts of the present inventors, in a single "hit"
~ ~- operation, by establishing and maintaining a force against
r the extruding ~illet which is in opposition to the extruding
force, thereby controlling the flow of the metal in the course
- . of the extrusion. It has been found that the opposing force
applied to the extruding product appears to rigidify the
~ product with respect to the extrusion apparatus such that the
; extruding product which is relatively rigidly held at one end
within the annular space between the anvil and the die cavity
~;~ and at its opposite outboard end by a member which is applying
the extrusion-opposition force to the product as it is being
;~ ~ formed, appears to function as a lateral support sleeve for
the anvil about which the billet is extruding. Tool breakage
~has been reduced by the present inventors to a negligible
factor, even at production rates of between 30 and 40 products
- per minute. Further, the product exhibits excellent physical
'':
. .
properties including good dimensional tolerances.
It is therefore an object of the present invention
to provide an improved method or the cold forming of a metal
billet. It is another object to provide a method for the
cold extrusion of a metal billet wherein the extrusion force
is opposed by a controlled further foxce that is of a
magnitude less than the extrusion foroe. It is another
object to provide a method for the cold extrusion of a
rl me~al billet in which the extruded portion of the metal billet
, 10 is initially confined in an annular space defined between the
wall of a die cavity and a concentricalLy disposecl and axially
.
aligned anvil means~ while applying a force to the outboard
, end of the extruding product that i5 in opposition to the
extrusion force and which rigidifies the extrusion product
relative to the extrusion apparatus. It is another object to
provide a method for the cold extrusion of a metal billet in
~ which a reduction in excess of one hundred ~100~) percent is
`~ obtained in a single extrusion operation. It is another object
` .1 ,
- to provide a method for the cold extrusion o a metal billet
wherein the cross-sectional area of the bore of the extruded
product is maximized. It is another object to provide an
improved apparatus for the cold extrusion of a metal billet
including means for rigidifying the extruded product in the
' course of the extrusion operations. It is another object to
provide an apparatus for the cold extrusion of a metal billet
including means for establishing a force that opposes the
extrusion force but which is less than the extrusion force.
Other objects and/or advantages of the invention will be
recognized from the following description and claims, including
the drawings in which:
Thus in one aspect the present invention provides
an apparatus for controlling the movement of a reciprocatory
. hydraulically driven element of a metal forming machine between
. extended and retracted positions including first piston means
: defined by said element, first reservoir means slidably receiving
said first piston means therein, said first piston means having
. a face disposed in fluid communication with said first
reservoir means, second reservoir means, second piston means
secured to and projecting from said face of said first piston
means, said second piston means being slidably received within
:~ said second reservoir when said first piston means is
;~ substantially retracted and being disposed wholly outside said
:~ second reservoir when said first piston is essentially fully
extended, said face of said first piston means having a
substantially larger working area exposed to said fluid in
said first reservoir than the working surface area of said
..''~: . .;
~ second piston means which is exposed to said fluid in said
- .; second reservoir, a source of pressurized hydraulic fluid,
means connecting said source of pressurized hydraulic fluid in
~ 20 ~luid communication with said first reservoir, means connecting
::~ said source of pressurized hydraulic fluid in fluid communica-
tion with said second reservoir, a third reservoir, conduit
; means connecting said third reservoir in fluid communication
: with said first reservoir, and valve means interposed in said
: . .
: conduit means for controlling the flow of hydraulic fluid
between said first and third reservoirs.
: ::
~ ; In another aspect the present invention provides a
:i :
~i method for providing two-speed movement of a rec.iprocatory
. . :
:: ~ hydraulically driven element of a metal working machine
comprising the s~eps~of introducing at respective inlets
: hydraulic fluid at a first pressure substantially simultaneously
~ , .
9~3
into first and second chambers of different cross sectional
areas as viewed in a plane that is substantiall~ perpendicular
to the direction of reciprocatory motion of said element and
which receive therein respective first and second working
faces of said element and thereupon cause said chambers to be
in fluid communication with one another at a location other
than their respective inlets to thereby exert a force against
said element to move the same in a direction that tends to move
one of said faces out of its respective chamber, while
continuing the aforesaid introduction of hydraulic fluid
introducing at a separate and larger inlet hydxaulic fluid o:~
a second and lesser pressure into that chamber haviny the
larger cross sectional area under flow conditions that tend
to e~ualize the pressure within said chambers when said chambers
are not in fluid communication with one another.
FIGURES 1-3 are fragmentary representations, partly
in section, of the sequence of operation of one embodinent of
~ .
~.
,~
~: .
"::
, ~
,. ~
- 4(b) -
. . .
~ ' -
. ~.
6~3
apparatus embodying various features of the invention;
FIGURES 4a, 4b and 4c, collectively, comprise a frag-
mentary top view, part in section and part cutaway, of one
embodiment of ap~aratus ~lbodying various features of the
invention and showing the apparatus in its o~en position or
tool chan~e;
FIGURE 5 is a fragmentary top view, part in section
and part cutaway, of the right hand end of the apparatus shown
~.. ~ . .
- in FIGURE 4c;
~ , 10 FIGURE 6 is a fragmentary top view, partly cutaway and
''' : -
paxtly in section, showing the apparatus depicted in FIGURE 4b
in a closed position for carrying out an extrusion operation;
FIGURE 7 i5 a sectional view taken generally along the
line 7-7 of FIGURE 4a;
~; 15 FIGU~E 8 is a schematic representation of a hydraulic
control system fox controlling the apparatus of the present
invention; ~
~;~' FIGURE 9 is a detailed schematic representation of a
portion of the control system shown in FIGURE 8; and
. ~ :
FIGURE 10 is a block diagram of an electrical control
; system for use in controlling the operation of the apparatus of
~ this invention.
,;
Referring now to the Figures, in FIGURES 1-3, there
is schematically depicted the sequence of operation of one
embodiment of the apparatus of the present invention. The
representations in these Figures also schematically depict
the steps of the method employed. Specificallyt in the
embodiment depicted in FIGURES 1-3, there is provided a
tool stack 9 comprising a die nib lO surrounded by a shrink
;~ r~ing 12. The die nib lO deflnes a cavity 14 within one
end 16 of which there is reciprocatably dispo~;ecl a ram 18
which closes the end l~ of the CAVity 14. A metal billet 20
is disposed within the cavity 14 and the opposite end 22 of
the cavity is closed by a power pad ~eans 24 comprising a
sleeve defining an axial bore 26. W:ithin the bore 26 there
is reciprocatably disposed an anvil 28. The power pad 24 is
provided with an annular shoulder 32 adapted to be received
within the end 22 of the cavity such that this shoulder 32
and the leading end 30 o~ the anvil 28 close the end 22 of
~-, the die cavity 14. Collar means 34 is provided in surroundin~
relationship to the power pad 24 and as will be further,seen
, 10 hereinafter provides for the controlled application of pressure
to the power pad to selectively adjust its position relative to
:, ~ . the die nib 10 and the engagement of the shoulder 32 with the
extrusion product.
~ In FIGURE 1 there is schematically depicted a
:~, 15 magazine 36 within which there is received a plurality of
. metal billets 20' in position to be disposed successively
within the die cavity 14 as will be further described
'~'' hereinafter.
In the embodiment of FIGURE 1, the anvil 28 is
,,, : 20 positioned and maintained stationary by a first force
'' represented by the arrow A. Further, the power pad 24 is
moved into its position closing the annular space 40 between
the anvil 28 and the internal wall 42 of the die cavity 14
.' by a force represented by the arrow B. Further, in FIGU~E
~ 25 1, the ram is shown as having commenced an extrusion
'' operation by reason of a force, represented by the arrow C,
being applied to the ram to urge the biIlet into the annular
' space 40 between the anvil 28 and the die cavity wall 42.
In FIGU~E 2, the ram 18 has been moved further
:
into~the die cavity 14 such that the billet has been
extruded partly a~out the anvil 28. It is natecl that the
:~
~ annular shoulder 32 of the power pad 24 is mai.nt:ained in
~6~9~3
contact with, and urged against, the outboard end 44 of the
extruded billet, the engagement between the shoulder 32 and
the end 44 of the billet being maintained by a force,
represented by the arrow B', applied to the collar 34 which
in turn transmits the force to th~ power pad 24. In the course
~: of the extrusion the force upon the power pad is adjusted
; : to a value less than the extrusion pressure, but kept to a
: relatively high value and in opposition to the extrusion
..
~: ~, pressureO
.~ r~ 10 Upon completion of the extrusion operation, as
~:~ seen in FIGURE 3, the power pad 24 is in a retracted position
,~ .
relative to the die nib 10, the ram 18 is retracted, and the
anvil 28 is retracted to cause the extruded product 48 to
~: drop by gravity through a detector 46 whose function will be
referred to hereinafter. Thereafter/ the apparatus is ready
,; , ,,
: : to commence a further operational cycle.
~ . In FIGURES 4a, 4b and 4c, there is depicted one
~ ~ embodiment of apparatus for carrying out the disclosed
:: ; method. The view of FIGU~ES 4a, 4b and 4c is looking down
.: ~
~ . 20 on the top of the apparatus and shows a plurality of plates
,
50, 52, 54 and 56 adapted to be supported on a suitable
means such as a frame means 57 (See FIGURE 71. The plates
. 50, 52, 54 and 56 preferably are rectangular in form and
are oriented in upright planes that are substantially
parallel one to another, with the interconnection between
': .
the plates established and maintained by a plurality of
. rod members 58, 59, 61 and 63 (See FIGURE 7) that are
.
received in registered openings through the thickness of
the respective corners of the plates. Only rod 58 is
shown in FIGURES 4a-4c but it will be immediately recognized
from FIGURE 7 that substantially identical rods 59, 61 and
63 are provided at each of the opposite corner~ of the
.
. , ,
i
--7--
~6~3
rectangular plates. Rod 58 is typical of each such rod and
; a description of rod 58 will suffice for an understanding
of the construction and function of each of the rods. In
the depicted embodiment the end 60 of the rod 58 projects
through the end plate 56 and is externally threaded for
receipt of an appropriate nut 62 thereonO The rod 58 is
; provided with a first concentric bearing member 64 that
; . extends substantially the full length of the rod 58 between
~,, the end plates 50 and 56, these concentric members passing
r~' 10 through the thickness of the intermediate plates 52 and 54.
The end of the rod 58 opposite the end 60 (.such opposite
,~, ';., end not being shownl projects through plate 50 in like
'~-';, manner as the end 60 projects through the plate 56, and i6
: threaded to receive a nut like the nut 62 on end 60 of the
'. rod 58.
.
. '.: The apparatus is assembled by inserting rods 58 ! 59~
~ ~ .
61 and 63 through the four corners of the rectangular plates
50, 52, 54 and 56 with the concentric tubular member 64
~' ' passinq through the plates 52 and 54 and having its respective
, 20 opposite ends terminating ad~acent the inboard side 72 of the
.:,
: ~' plate 56 and the inboard side 74 of the plate 50 to thereby
. . .
establish and fix the minimum lateral spatial relationship
' between the end plates 50 and 56. With the rod 58 and it~
.', concentric member 64 in position, the nuts on the opposite
:' ' 25 ends of the rod 58 are tightened to force the end plates 50
and 56 against the ends of the member 64 to place the rods
~,' 58, 59~ 61 and 63 in tension to lock the assemblage together.
A tubular sleeve 66 is disposed about the bearing
member 64 in the space between the plates 54 and 56 ~ith
washers 68 and 78 being interposed between the ends of the
~ sleeve: 66 and the plates 54 and 56. This sleeve 66,,and its
,; ~ counterparts associated with the rods 59, 61 and 63,
establish the minimum spacing hetween the plates 54 and 56.
6~3
The plate 52 is slidable on the member 64. The
right hand limit of movement of the plate 52 along the member
^ 64 is limited by a tu~ular sleeve 96 that encompasses the
bearing member 64 in the space between the plates 52 and
~- 5 54. Washers 70 and 76 are interposed between the ends of the
sleeve 96 and the plates 52 and 54.
As noted, the plate 52 is slidable alony the tubular
bearing member 64 relative to the fixed end plate 50. To this
end, a sliding tubular bushing 102 is provided on the bearing
member 64 and receives the plate 52 at one of its corners as
noted above. Like sliding bushings are provided at the other
. . .
- corners o the plate 52 (see FIGURE 7). This sliding movement
of the plate 52 provides for opening of the means which holds
the tool stack 9 in position and is accomplished in the
depicted embodiment by piston cylinder devices 82 and 83,
; only 82 being shown in FIGURE 4a. The cylinder portion 84
g ~ of the Piston cylinder device 82 is attached to the inboard
~; ~
side 74 of the plate 5~ by a rod eye 88 attached at one of
its ends to the cylinder 84 and pivotally secured at its
opposite end to a clevis 86 mounted on the end plate 50.
The piston rod 90 of the piston cylinder device 82 is
pivotally connected through a clevis 92 to one side 94
~ ~ of the plate 52. Preferably, the second piston cylinder
; unit 83 is provided on the opposite side of the apparatus
so that an evenly applied force is available to change the
position of the plate 52 relative to plate 50. As noted,
. this movement of plate 52 provides for opening of the apparatus
for tool change and/or maintenance purposes. When plate 52
is moved to the right as viewed in FIGURE 6, the tool stack
; 30 is clamped in position for an ex~rusion operation,
When the plate 52 is moved to its extreme right
hand position (i.e. the apparatus is closed ~or an extrusion
,., ~
~6~3
operation) there is provided one or more spacer sleeves 100
in encompassing relationship with the tubular member 64 in
the space between the plates 50 and 52. One or more of these
spacer sleeves, or additional ones, as required, is made
removable so that when it is desired to move ~he plate 52 to
the open pOSitiOII, i.e. in the left hand direction in
; FIGURES 4a and 4b, there is provided available space alongthe member 64 within which the plate 52 can be moved. The
: r'~ s2~e detachable sleeve is replaced when the plate 52 is in the closed position.
As seen in FIGURE 4b, the intermediate plate 54 is
; ;;~ provided with a detachable first die stack holder 108 on its
face llU, the holder being releasably secured to the face 110
as by bolts 112. This holder 108 is provided with a recess 114
- 15 on its exposed face 113. On the facell6 of the plate 52 and
: in facing relationship to the holder 108, there is provided a
- second die stack holder 118 which is releasably secured to the
plate 52 as by bolts 120. The exposed face 113 of the second
..
holder 118 is provided with a recess 122 that faces the rPcess
114 in the holder 108. The tool stack 9 comprising the die
nib 10 and shrink rings 12 and 126 (see FIGURES 1 and 6) is
removably received between the holders 108 and lla. To this
end, the outermost surface of the shrink ring 126 is provided
with angled lands 128 and 130 adapted to be received in mating
engagement within the recesses 114 and 122, respectively.
~otably, the land 128 is of a different angular construction as
land 130 and the geometr~ of the recesses 11~ and 122 are
selected to receive only their specifically angled land, so
that it is virtually impossible to insert the tool stack in
the apparatus in an incorrect or reverse positio~. Still
furtherl the angled relationship between the recess 114 2md
the cooperating land 128 r and the recess 122 2md the
. .
~ln_
~6~3
,
cooperating land 130 provide for accurate aligmnent o~ the
tool stack within the recesses, hence accurate parallel
alignment of the tool stack with respect to the plates 52
and 54. Still further, the angular relationships between
the recesses and the respective l~nds on the die assembly
establish precise concentricity of the tool stack with
respect to the remaining elements of the tooling as will
appear further hereinafter.
The holder 118 is further provided with a channel
; 10 132 defining a magazine for receiving a plurality of billets
20' in position for feeding into the die 10. These billets
may be fed into the magazine hy any suitable means such as
.1''
r are well known in the art.
As referred to hereinabove, the depicted die nib
.
~ ; 15 10 is provided with a cavity extending through the thickness
::,
~ of the die nib and open at both of its ends. In accordance
~; ~
with the present disclosure, the cavity is provided with a first
; - cylindrical section 136 of substantially uniform cross-section
.~ .,
~ ~ along its length and a second section 138 having a cross-
;
;~ 20 section larger than the cross-section of the section 136.
; In the preferr~d embodiment, the section 138 is of relatively
short length compared to the length of the section 136.
In the embodiment depicted in FIGURES 4b and 6, the
; apparatus is provided with a ram 140 having its outboard end
142 reciprocatably received within the die cavity section 136.
The ram 140 is supported outside the die cavity by a sleeve
_ 144 mounted in the annular plate 118 and extending therefrom
to be received in an opening 148 extending through the
thickness of the plate 52. Within the plate 52, the sleeve
144 is received in a further sleeve 146 which in turn fits
; in an opening 148 that extends through the thicXness of the
~-~ plate 52. Thus, the concentricity of the ram 140 .is
.,i i
l3
maintained with respect to the annular plate 118, the tool
: stack 9, and the plate 52. The exposed end of the ram 140
. is formed to an enlarged piston head 150 which is in turn
substantially surrounded by a collet 152 whi~h is in turn
housed within the externally threaded end 153 of a tool
holder 154. The end 153 of the tool holder 154 is capped
by an internally threaded cap 156 that is slidably received
.: within a hollow cylindrical ram support 158 that is in turn
;; detachably secured to the plate 52 as by bolts 160. By
;~ 10 this means, the piston head 150 of the ram 18 is slidably
; supported in axial alignment with the die cavity 14. The
, ~ support 158 is externally threaded on its outboard end to
~ . .. .
t~ .~ ,, ,, receive a threaded cap 162 having a rear face 159 that
~ serves as an abutment for selectively adjusting the limit
h' - ~ 15 of travel of the r~m 18 toward its retracted position, i.e.
to the left as viewed in FIGURE 4a~
. The enlarged section 138 of the die cavity 10 is
adapted to matingly receive therein the reduced diameter
: : annular shoulder 32 on the end o the power pad bushing 24
facing the die cavity. As noted above, the power pad 24
is provided with an internal bore 26 within which there is
reciprocatably received the anvil 28. In the depicted embodiment,
. when the leading end 30 of the anvil is in its forward position
:~ (to the left as viewed in FIGURE 6), the end 30 of the anvil
~ 25 projects from the power pad 24 into the cavity section 138.
),; , . .
~; In this position, there is defined between the end 30 of the
$~ anvil and the wall of the cavity section 138, an annular
; space 42.
~ Also, as noted before, the power pad 24 is carried
.~ 30 in an annular collar 34 which, as shown in FIGURE 4b, is
: threadably mounted in the end 166 of a hollow cylindric al
~ piston 168 which is in turn reciprocatably rec:eived within
i' "~:
' ~;
a housing 170 having a reduced diameter end 172 mounted in
the plate 54. The internal diameter of the reduced dia~eter
end 172 of the housing 170 is in axial alignment with, a
central bore 173 through the thickness of the plate 54, and
a central bore 175 through the tool stack holder 108 so that
the piston 158 is reciprocatable with these aligned bores.
The opposite end of the housing 170 is closed by a cap 174.
Ports 176 and 178 in the housing 170 are provided for
the movement of hydraulic fluid into annular spaces 180
and 182, respectively, on opposite sides of an enlarged
section 184 of the anvil 168, such enlarged section bein~
sealed with respect to the housing 170 as by a seal 186.
The end 166 of the piston 168 is sLmilarly sealed by seal
188 with respect to the end 172 of the housing 170. The
.,
~ i 15 opposite end 190 o~ the piston 168 is sealed with respect
,.:: ,, ^
. . to the cap 174 by a seal 192.
The cap 174 is further provided on its exposed end
with a fIange nut 194 which in turn receives an internally
threaded annular abutment member 196 that serves as an
;.,
;~ 20 adjustable limit for the retraction movement of the anvil
28 as will appear further hereinafter.
. The outboard end of the anvil 28 is enlarged to
define a piston head 198. This piston head is mounted in
a collett 200 which is in turn received in an externally
: ~ 25 threaded end 201 of a cylindrical tool holder 202. The end
~ 201 of the tool holder 202 is encircled bv an internally
'-~ threaded sleeve member 203~hich is in turn slidably received
,~
:~ within an axial bore 204 provided in the piston 168 such
~:~ that the anvil 28 is axially movable relative to the piston
168, and to the power pad 24 which aids in maintaining the
end 30 of the piston 28 concentrically of the ~iston
168.
,. ~
~69t~L3
The tool holde~ 202 comprises a generally cylindrical
hollow central section 216 which projects out of the rear end
205 of the hollow piston 168 to be detachably received on the
forward end 218 of a piston 220. The tool holder is further
provided with an elongated slot 224 along one of its sides.
A cover 222 for the tool holder is slidably positioned in
, encircling relationship with the central section 216 of the
tool holder 202. This cover 222 is provided with an appropriate
~ .
opening such that upon rotation of the cover, the opening in
the cover can be caused to come into register with the slot
224 to expose the interior of the hollow tool holder. Within
~ : .
the hollow interior of the tool holder 202, there is provided
a pluralit~ of spacers 226, 228 and 230. When it is desired
to remove the anvil or exchange it for a different size
tooling or to change the relative position of the anvil
with respect to the piston 220, the spacers 226, 228 and
230 or selected ones of these may be removed and a spacer
of different l~ngth substituted therefore, these spacers
being removed throuqh the slot 224 and the registered opening
in the cover 222.
As shown in FIGURE 4c and FIGURE 5, the power for
, .
advancing or retracting the anvil 28 is provided by means of
a piston-cylinder assernbly 219 mounted in the plate 56. As
seen in FIGURE 5, the plate 56 is provided with a central
; 25 opening 232 through the central thickness thereof~ This
opening is further provided with a bushing 234 that encircles
a piston 220 which extends through the opening 232. Chevron
seals 236 provide an appropriate seal for slidlng action o
- the piston through the plate 56. A seal ring 238 is provided
3~ on the face 72 of the plate 56 in encircling relationship
~; ~ with the piston 220. The rear end 240 of the piston 220 is
I provided with piston head member 2q2 which is slidably mounted
6~:~L3
within a hollow cylinder ~44 with a sliding se~l therebetween
being affected by seals 246 and 248. In this manner, the
hollow cylinder 244 is divided into two expandable chambers
245 and 247, one on each of the opposite sides of the piston
. 5 head 242.
The cylinder 244 comprises a cylindrical housing
250 which has one of its ends 252 mounted in the plate 56.
The housing 250 extends from the plate 56 rearwardly ~to the
~, right in FIGURE 5~ and is closed at its rear end 254 by a
plate 256. Internally of the end 254 of the cylinder 244,
there is provided a further hollow cylinder 258 disposed
. concentrically of and in axial alignment with the cylinder
r
244 and defining a chamber 259. This cylinder 258 i5 further
provided with a cylindrical bushing 260 within which there is
~; 15 received a reduced diameter piston section 262 that projects
- rearwardly from the piston 220 to be slidably received within
: ~ .
. the bushing 260. Seals 264 encircle the piston section 262
~:- and provide for sealing engagement bet~e~n the outer surface
: .; .. .~
:. of the piston section 262 and the bushin~ 260.
.20 The plate 256 is provided with a first port 266
which is in fluid communication with the chamber 259 such
that hydraulic pressure applied through port 266 serves to
pressurize the chamber 259 and urge the piston section 262
; . to the left of FIGURE 5. The plate 256 is provided with a
further port 268 which is in fluid communication through
~ passageway 270, conduit 272, and passageway 274 to the chamber
I~ ~. 245 of cylinder 244 on the left hand side of the piston head'~ 242 as is seen in FIGURE 5. A further port 276 of substantially
i~f ~' enlarged opening is provided in the wall of the cylinder 244at a location rearwardly (to the right in FIGURE 5) of the
~;~ most rearward position of ~he piston head 242 and in fluid
:. communication with the chamber 247 of the cylinder 244
15-
. -
~6~:~3
Power for reciprocating movement of the ram 18 ~on
: the end of the apparatus opposite anvil 28~ is proYided b~
apparatus substantially identical to the apparatus hereinabove
described in connection with the rec:iprocating movement of the
. 5 anvil 28 so that the foregoing description of the piston-
cylinder apparatus that accomplishes reciprocating movement
- of the anvil 28 is sufficient for an understanding of the
apparatus that provides for reciprocating movement of the
:~ ram 18. In FIGURE 4a, that portion of the apparatus shown
; 10 which corresponds to equivalent apparatus in FIGURES 4c and
FIGURE 5 is indicated by numerals having a prime.
: A schematic representation of a hydraulic control
.~
. circuit for providing programmed power for actuation of the
- various working elements of the present apparatus is shown in
; 15 FIGU~E 8. Generally, the several working components of the
:. present apparatus are powered by pressurized hydraulic fluid
~;. supplied by way of a main hydraulic circuit that provides
; ~ relatively high pressure, and a secondary hydraulic circuit
: ~ -
:; ~ that provides relatively low pressure. In the main hydrauliccircuit of the depicted embodiment, pumps 300 and 302, which
. are driven by a motor 304, provide pressurized hydraulic fluid
; that is conveyed through respective filters 306 and 314,
through respective check valves 308 and 310 to a manifold
conduit 309. The conduit 309 is connected in fluid communi-
cation with a first directional control valve 312 associ~ted
~ .
with the piston cylinder apparatus 219 which provides motive
. power for the anvil 28. The conduit 309 is further connected
~,,
to a second directional control valve 312' that is associated
with the piston cylinder assembly 219l which provides motive
power for reciprocating movement of the ram 18.
.~ ~
The hydraulic fluid in the main cixcuit is returned
to a reservoir 311 via a conventional pressure relief valve
~;
',' ',
- _1 ~_
~69:~3
and check valve assembly 316. The pumps 300 and 302 draw
hydraulic fluid from the reservoir 311 through respective
conduits 315 and 317. The pressurized hydraulic fluid in
the main circuit provides driving force for the pistons
220 and 220' to advance the ram 18 and/or the anvil 28 and/or
hold either stationary against an extrusion pressure.
In the automatic operation mode, it is desired
that the piston 220 be provided with a fast forward travel
.
until the anvil 28 has approached its position for the
extrusion operation. As the anvil 28 approaches its extrusion
position, it is desired that the forward motion be slowed
considerably and that the movemen~ of the anvil 28 into its
; ~ final extrusion position be at a relatively slow rate. In
the depicted embodiment, this dual rate of movement of the
piston 220 is accomplished by first introducing pressurized
hydraulic fluid into the chamber 259 to the rear of the
l; , ~- .,.
'~ reduced diameter piston section 262. The application of
this pressurized fluid to the rear face 257 of the piston
! l
section 262 provides for fast forward movement of the piston
220, until the piston section 262 has moved completely out
~i~
of the chamber 259. Thereupon, the pressurized fluid is
released into the much larger interior chamber 247 within
,.,
the cylinder 244 on the rear side of the piston head 242. At
this point in time, the anvil 28 is approachlng its extrusion
;!; 25 position. By reason of the relatively larger surface area
Y~ on the rear face 241 of the piston head 242, the pressurized
~ r hydraulic fluid admitted to the chamber 247 causes the piston
r 220 to move forward relatively slowly until the anvil has
~; achieved it9 extrusion position. The forward movement of the
anvil is halted by the forward face 311 of the tool holder
,~ 216, which is attached to the piston 220, engaging ~he rear
,.~:
~ face 313 of the anvil stop 19~ (see FIGUR~ 4c).
.:-~ -
~ --17--
L3
The pressure developed by the pumps 300 and 302 is
deemed the high pressure portion of the hydraulic system, the
pressure anticipated being approximately 3000 pounds per square
; inch ~psil which develops a working pressure of about 75 tons.
It will be recognized that other similar re~atively high pressures
may be utilized depending upon the circumstances of the extrusion
operation.
: '
The secondary hydraulic circuit comprising a lesser
- pressure, i.e. to about 1500 psi, is also shown in FIGURE 8.
This secondary hydraulic circuit comprises a motor 322 which
, ~.
drives a pump 324 from which hydraulic fluid is conveyed through
- a filter 326 to a manifold 328.
~' '.;
The pressure in the secondary hydraulic circuit serves
multiple functions including providing a pilot pressure utilized
~- Z~ .
~ ; 15 in operating certain of the control valves employed in the
, ~, . .
hydraulic circuits of the control system. The pressurized
hydraulic fluid from the secondary system is also utilized
in operating the power pad assembly, and for opening and
~, .
closing the tool stack clamping mechanism.
SpecificalIy, the pressurized hydraulic fluid from the
pump 324 is conveyed through a filter 326, and through a conduit
,.
350 to the manifold 328 which includes a return line 352 from
which the hydraulic fluid returns to the reservoir 311 hence
to the pump 324 to complete the circuit. Within the manifold
.,., ~
328, there is provided a pressure relief valve 354 connected
across the conduits 350 and 352 and by means of which the
maximum pressure obtaining within the secondary circuit is
regulated.
Referring to FIGURE 9, to supply pressurized
hydraulic fluid to the chambers 180 and 182 of the cylinder
170 for reciprocating movement~of the power pad 24, the~e
... ~ :
~ is pro~ided in the manifold 328 a directional control valve
iffl~3
356 having its inlet 358 connected to the conduit 350. The
outlet 360 of this directional control valve is fed through
a conduit 362 to a pressure relief valve 364. The outlet
368 from this pressure relief valve 364 is fed through a
conduit 370 to the port 178 in the cylinder 170 for providing
a force urging the power pad toward its position of engagement
with the die nib 10. It is noted that the pressure relief
valve 364 is manually regulated and includes a bypass 372 that
incorporates a check valve 374. Importantly, when during an
extrusion operation there is a force applied against the power
pad by reason of the extrusion, th~re occurs a pressure
buildup within the chamber lB2 on the rear side of the piston
168. This buildup in pressure is transmitted by the conduit 370
to the pressure relief valve 364. Inasmuch as the check valve
. . . I
374 prevents reverse:flow of hydraulic fluid around the bypass
~:. 372, the flow of hydraulic fluid out of the chamber 182 behind
, .
.r, the piston 168 is regulated by the set~ing of the pressure
relief valve 36a. Thus, by choosing the setting of the pressure
relief valve, one lS able to establish that pressure which wlll
~-. 20 be developed to maintain the power pad against the force of the
.,
extrusion operation. As will be recognized hereinafter, this
pressure is chosen to ~e sufficient to exert an opposing force
~ against the extruding part that will riyidify the extruding
;~ . part relative to the tool stack, the plate 54, etc., such that
. ~ 25 the part provides lateral support for the anvil 28 as the power
.,
-~l pad 24 is moved rearwardly with the extruding metal. Power for
. i
. returning the po~er pad to its rearward position upon the
completion of an extrusion operation is providecl by pressurized
i
hydraulic fluid introduced to the:forward chamber 180 of the
cylinder 170:through~ conduit;376 which is valved into fluid
communication with the condult 350 by the directional control
. valve 356. A solenoid 378 provides the means for ad~usting
, ~
valve 356 in selecting the direction of flow of fluid through
the valve 356.
Whereas the specific embodiment of the apparatus
shown in FIGURES 4a, b, and c does not include a power pad
~ 5 on the ram side of the die nib 10, it is noted that FI~URES
!~ ~ 8 and 9 show the manner in which such a power pad 24' can be
~- provided and controlled. Basically, the control of the power
9'
j; pad on the ram side is substantially identical to the control
-i of the power pad on the anvil side so that the description of
~( . j. . .
the hydraulic circuitry for controlling the power pad on the
anvil side will be sufficient for an understanding of the
manner in which the power pad on the ram side is controlled.
Equivalent elements of the control system for the power pad on
the ram side are identified by prLmed numerals.
~; 15 As noted above, openinq and closing of the tool stack
clamping mechanism is also controlled from the secondary
hydraulic circuit. Referring specifically to FIGURE 9~ the
- input port 379 of a directional control valve 380 is connected
:.. : .
by way of a conduit 382 to the manifold conduit 350. The output
384 of this directional control valve is connected through
a regulated check valve 386 and conduit 388 to the rear chambers
~-~ 390 and 392 of the piston-cylinder members 82 and 83 which,
as referred to above, provide for movement of plate 52 to
open and close the tool stack clamping assembly. The output
, 25 port 394 of the directional control valve 380 is connected
in fluid communication through a regulated check valve 396 and
conduit 398 to the forward chambers 400 and 402 of the piston
cylinde~r members 82 and 83.~ Thus, by~means of the directional
control valve 380~, the opening and closing of the tool stack
clamping assembly is accomplished by selecting the directional
flow of the pressurized hydraulic fluid through the valve 380.
Solenoids 404 and 405 provided on the valve 380 serve to control
~',:, ~ : :
. .
~6~:~3
the functioning of the ~alve 380. To complete the circuit,
the directional control valve 380 is connected through an
output conduit 406 to the return line 352.
As noted hereinbefore, in the movement of the anvil
28, it is desired that the anvil 28 initially be moved rapidly
forwardly toward its extrusion position but that the movement
of the anvil 28 be slowed ~ust prior to its reaching its final
position for the extrusion operation. As further noted
above, the rapid forward movement of the anvil 28 is provided
by the introduction of pressurized hydraulic fluid, for
example, 3000 psi to the chamber 259 within the cylinder 258
by way of the valve 312. This latter valve 312 is of the
~ r
double solenoid, spring centered, blocked port type and by
- reason of its size is relatively slow in its operation. For
example, after the anvil 28 has reached its forward limit of
travel, it is desired that the valve 312 be closed, i.e.
shifted to its "blocked port" stage, to hold the pressure
...
~ in the cham~er 247 and thus hold the anvil in a
~ .. ..
stationary position during an extrusion. However, the
relatively slow operation of the valve 312 results in a
slight, but undesirable delay between the time the anvil
is positioned and the commencement of an extrusion.
Moreover, any leakage past the valve 312 can result in
rearward movement of the anvil and disruption of the extrusion.
, 25 Therefore, in the hydraulic circuitry shown in FIGURE 8~ there
is also provided a slow forward control circuit which at all
times durlng an extrusion cycle, maintains the pressure ~using
lower flow rates) within the chamber 247. This circuitry
includes a directional control throttle~valve 410 having its
inlet 412 connected to the main hydraulic circuit yia a
conduit 414. This directional control valve lS actuated as
; ~ by a solenoid 416. The output 417 of the directional control''~'
:
valve 410 is connected through a throttle valve 418 and
conduit 421 and to port 423 to the interior of the chamber
- 247 on the reverse side of the piston head 242. A check
valve 425 interposed in the conduit 42~ prevents reverse
flow of fluid through this conduit. In the disclosed
..
system, the directional control valve 410 is activated
; ' initially with the introduction of pressurized fluid through
the port 266 to the chamber 259 of cylinder 258 and remains
,, activated until the end of a cycle. In this manner, there is
~,, 10 continually supplied to the chamber 247 pressuri2,ed ~luid
adequate to effect slow forward movement of the 2~vil 28 and
;;- and to maintain anvil 28 in its position, regardless of the
; speed of operation of valve 312. It will be recognized,
however, that this slow forward movement of the anvil 28 is
, 15 overridden initially by the effect of the pressurized fluid
~; within the chamber 259 of the cylinder 258 until the piston
section 262 has cleared chamber 259.
,' In connection with the fast forward movement of the
piston 220, it~is noted that as the piston 220 is moved rapidly
forwardly by the pressurized fluid in the chamber 259, there is
a rapidly increasing volume change within the chamber 247.
-
This rapid change in volume size of the chamber 247 develops a
,, .
~l "vacuum" which would ne~ate the desired rapid forward movement
-
of the piston 220 in the absence of provision for accommodating
' 25 such volume change. The present inventors accommodate this
, volume change by connecting the chamber 247 through the port
~'- 276 to a reserve hydraulic fluid tank 420 which provides-a
l, ~supply of hydraulic fluid for flooding the chamber 247 without
; significant resistance to forward movement o~ the piston 220.
~; ; 30 To this end, the port 226 is relatively large. The connection
between the port 226 and the tank 420 is effected as ~y a
~ conduit 422 having a check valve 424 interposed therein which
,, '' '
,6~
permits flow of hydraulic fluid toward the chamber 247 and only
allows flow outwardly from the chamber 247 when the check valve
is overridden. It will be further recognized that such outward
flow of hydraulic fluid from the chamber 247 is desired when
the piston 220 is to be moved in a rearwardly direction.
Override of the check valve 424 to permit such outflow is
accomplished by hydraulic pressure applied to the check valve
. through a conduit 426 connected through a directional control
., valve 428 connected across the conduits 350 and 352 of the
~; ;, 10 manifold 328. This directional control valve 428 is activated
by a solenoid ~30 such that upon an appropriate ~ignal, the
; directional control valve 428 admits hydraulic fluid through
the conduit 426 to the check valve 424 to override the check
valve and permit the flow of hydraulic fluid outwardly from
the chamber 247 to the ~ank 420.
. ~ .
Fast forward movement of the ram 18 is accomplished
in like manner as fast forward movement of the anvil 28. This
is accomplished hy the directional control valve 312' which is
. ~ . .,
identical in construction and operation to~the directional
; 20 control valve 312 described above. In addition, there is
provided a check valve 424' connected in fluid communication
bet~een the chamber 247' on the revexse side of the piston
- 220' and a hydraulic reservoir 420'. Overriding of the check
'? valve 424' is accomplished by pressurized hydraulic fluid
admitted thereto by way of conduit 426' connected to a
directional control valve 428' that is activated by a solenoid
.:
~ ' 430'. The function and operation of the correspondin~ elements
,. :
~ described above as will be recognized by a person skilled in
,~ ~ the art.
~ In a preferred embodiment, the hydraulic control
circuit is provided with a visual pressure indicator having
::
~ multiple positions for providinJ a visual inclication of the
..~ ,.
6~3
pressure at various points in the system. As shown in FIGURE
9, position No. 2 is connected by conduit 440 to the conduit
370 to provide an indication of pressure within the chamber
182 of the cylinder 270, thereby indicating the pressure
being exerted against an extruding product. Position No. 6
.
is connected by way of conduit 442 to the output of the
directional control valve 428 to provide an indication of
the pressure within the secondary hydraulic circuit. Posi~ion
No. 5 is connected by conduit 444 to the forward chamber 180
,~, 10 in the cylinder 170 to provide an indication of the rearward
~ , pressure being applied to the power pad 24. Position No. 4-~l is connected by conduit 446 to the conduit 376' to provide an
:. ~ ,1' '
, indication of the pressure being applied by a power pad on the
ram side of the die nib 10 in the event such a power pad is
employed. Position No. 3 is connected by conduit 448 to the
: main hydraulic circuit.
: ~
In an operation of the apparatus depicted in the
several Fiaures, a plurality of relatively slender cylindrical
billets 20 are loaded into the maga~ine 132. Upon an
.
appropriate electrical signal, the solenoid 404 is activated
to open valve 380 to admit pressurized hydraulic fluid to
,. ~
the chambers 390 and 392 of the piston-cylinder devices 82
and 83 to clamp the die assembly in position between the
plates 52 and 54. The tool stack is held in this position
. 25 until a further signal is directed to solenoid 405 to activate
the valve 380 to change the direction of flow of hydraulic
; '~ fluid through the valve 380 and into the chambers 400 and
402 of the piston cylinder devices 82 and 83 to open the
tool stack~ clamping assembly.
Once the tool stack is clamped into position, an
electrical signal is directed simultaneously to the solenoids
416 and 44Q. The solenoid 440 opens t~e valve 312 and admits
~6~3
the pressurized hydraulic fluid through the port 266 to the
chamber 259 in cylinder 258, thereby commencing fast forward
movement of the anvil 28. As the p:iston 220 moves forward~
the "vacuum" created in the chamber 247 pulls hydraulic fluid
from tank 420 and check valve 424 into the chamber 247.
Simultaneously, with the opening of valve 312, solenoid 416
open valve 410 to start the flow of pressurized hydraulic
fluid from the main hydraulic circuit through valve 410 to
the chamber 247. This valve 410 remains open until the anvil
,'. 10
bottoms out as noted above. Also, simultaneously with the
commencement of the forward movement of the anvil 28, solenoid
378 is activated to open valve 356 to admit pressurized hydraulic
fluid through conduit 370 to the chamber 182 on the reverse side
of ~he piston 168 thereby commencing forward movement of the
:l .; 15
power pad 24. This power pad moves forwardly into contact
with the die nib 10 and is held thereagainst by the pressure
from the secondary hydraulic circuit as controlled by the valve
. ..
~ ~ 368 and its bypass 372. When the power pad contacts the die
. ..
nib, (or reaches some other point in its motion) an appropriate
signal is generated to activate solenoid 440' to start forward
movement of the ram 18. It will be recognized that the anvil
side of the die cavity 14 is closed by the power pad 24 and
the anvil 28. As the ram moves forwardly, its leading end
contacts a billet 20 and urges the billet into the die cavity
14. Further forward movement of the ram 18 commences extrusion
o~ the billet, such extrusion continuing until the forward
movement of the ram passes an electronic eye, for example
whereupon an appropriate electrical signal is developed
to activate solenoid 441' to reverse the direction of
movement of the ram 18. The signal from the electronic eye
that senses the foxward limit of travel of the ram 18 is
further fed to the solenoid 441, after a time delay of a~out
,.. .. .
9~3
30 to 50 milliseconds, ~o commence reverse movement of the
anvil 28. As the reverse movements of the anvil 28 and the
ram 18 are commenced, the solenoids 430 and 430' are activated
to open the valves 428 and 428' to direct pressurized hydraulic
S fluid to the check valves 424 and 424' for opening these
check valves and allow hydraulic fluid in the chambers 247
and 247' to be dumped into the tanks 420 and 420'~ Also,
; simultaneously with commencement of reverse movement of the
anvil 28, an appropriate electrical signal is directed to
,'f, 10 the solenoid 378 to change the direction of the flow of
; hydraulic fluid through the valve 356 such that the chamber
i 180 in the cylinder 170 is pressurized to commence reverse
movement o~ the power pad 24.
As the power pad 24 and the anvil 28 are retracted,
~. .
the extruded product is withdrawn from the die cavity while
~: still on the anvil 28. The power pad 24 reaches its rear
..; ,: . .
limit of travel when the face 313 on the collar 1~6 contacts
the face 311 ~f the tool holder 216. The anvil 28 continues
its reverse travel, thereby stripping the product from the
anvil. The freed product falls by gravity past the detector
46 to develop a signal for commencement of another cycle of
operation.
In one type of extrusion employing the disclosed
method and apparatus, billets were sheared from AlS1-1~08
cold heading quality steel wire. The individual billets were
cylindrical, 1.27 inches long, and possessed a diameter of
~ 0.625 inch with a weight o~ 50 grams. These billets were
given a conventional pretreatment, including speroidize~annealling
.,
~ and cleaning, and lubricated with phosphate and molyheleum-
~ :, . :
30 ~ sulphide powder. The pretreated billets were extruded about
the end of a cylindrical anvil having a diameter of 0.662
- inch, with the apparatus disclosed herein operating in the
giL3
automatic mode, at rates of between 30 and 40 extrusions
(billets) per minute. This anvil was disposed within a
cylindrical die cavity section having a diameter of .860
inch so that there was an annular space defined ~etween
the anvil of the die cavity of .23668 square inches
cross-sectional area.
The extruded product of this operation was of a
cylindrical cup geometry 2 inches long and having an outside
., diameter of 0.850 inch and an inside diameter o~ 0.662 inch,
; ~ 10 yielding a cross-sectional bore area of 0.344196 square inch
("B" in E~. 1). The cross-sectional area of the billet
: '
before extrusion was 0.306796 square inch (11~11 in Eq. 1).
There~ore, using Eq. 1, there was a reduction of approximately
112%.
~ lS The anvil ~8 in this operation was maintained
; stationary with a pressure of approximately 75 tons while
the ram 18 was advanced with the same applied pressure. The
power pad 24 was initially pos1tioned in closing relation
ship with the die nib 10 with a pressure of to about 1500
psi. The pressure relief valve 356 was regulated, i.e.
manually adjusted, to permit that flow of hydraulic fluid
therepast which under the existing extrusion force resulted
in a back pressure of up to about 7.5 tons psi as the
extrusion took place. This baclc pressure initially increased
to a relatively large value as the ram moved the billet into
contact with the anvil and power pad, and then decreased
as the power pad was pushed toward its retracted position
by the greater pressure exerted by the extruding billet.
In any event, the back pressure exerted by the power pad was
sufficiently great to firmly hold the extruding billet in
concentric alignment with the anvil, so that the extruded
- .
- product provided lateral support and alignment ~or the anvil
g~3
as the power pad retracte~. It will be recognized t~at during
extrusion, the metal of the billet achieves a plastic state
substantially only in the annular space between the end of
the anvil and the die cavity wall, and that at least a portion
; 5 of the extruded product solidifies prior to exiting the die
cavity so that this end of the extruded product is firmly
held in concentric relationship with the die cavity and the
anvil.
.~
, The tensile strength of the billet averaged about
39,000 psi before extrusion and averaged about 80,000 psi
~ in the extruded product. The yield strength in the billet
;~ before extrusion averaged abouk 24,000 psi, and averaged
'' ~; I' ' '
about 64,000 psi in the extruded product.
Other steel alloys such as AlSl 1018, 1020, and
4027 have been extruded successfully in like manner as
described hereinabove.
~ .
; The complete extrusion described above was accomplishedin a single "hit", i.e. one operation cycle of the apparatus in
: which the billet is deformed only once to obtain the extruded
product.
In addition to the usual savings associated with cold
extrusion as compared to machining a product from stock metal,
the present method and apparatus permit the manufacture of a
given product from wire stock, thereby reducing the cost of
billets. Further, the present method and apparatus provides
for the production of a given extruded product in a single
"hit" as compared to the multiple "hits" re~uired heretofore.
Still further, the inventors have found that tool breakage is
~ ~ ~ minimal, and almost nonexistent, when using the disclosed
- ~ ~ method and apparatus.
In addition to the usual forces that: operate on ~he
metal in a conventional extrusion, it is theorized by the
6~3
present inventors that the pressure applied against the metal
in opposition to the extrusion pressure puts additional "work"
into the metal. The exact effect of this on the flow of the
metal is not known, but it appears to be favorable, judging
from the improved product. It appears, in any event, that
the movement, i.e. flow, of the metal during extrusion is
"controlled" in the sense that the metal is not left free to
; be extruded from the die in an uncontrolled manner as in theprior art, but rather, the metal is allowed to extrude from
the die under restraints that have been demonstrated to permit
reductions not heretofore obtainable in a single "hit." Notably,
i the back pressure automatically accommodates for the continually
. changing dimensions of the product in the course of the extrusion
- operation.
While a preferred embodiment has been shown and
. described, it will be understood that there is no intent to
~ ~ .
: ~. limit the invention by such disclosure, but rather, it is
. intended to cover all modifications and alternate constructions
,. ..
- falling within the spirit and scope of the inventlon as
; . 20 defined in the appended claims. For example, sources of energy:~ other than pressurized hydraulic fluid may be employed.
Further, the working pressures employed may be varied to
accommodate the required tonnage for working a specific
metal or alloy.
' '
'
; .
: :
:.
~ 30
