Note: Descriptions are shown in the official language in which they were submitted.
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CON~INUOUS ~XTRUSION 0~ M~TALS
TECHNICA~ D
This invention relates to an apparatus for
effecting continuous extrusion of metal from a
feedstock in particulate, comminuted or solid form,
which apparatus includes:-
(a) a rotatable wheel member arranged for
rotation when in operation by a driving means, said
wheel member having formed peripherally thereon a
continuous circumferential groove;
(b) a cooperating shoe member which extends
circumferentially around a substantial part of the
periphery of said wheel member and which has a
portion which projects in a radial direction partly
into said groove with small working clearance from
the side walls of said groove, said shoe member
portion defining with the walls of said groove an
enclosed passageway extending circum*erentially of
said wheel member;
(c) feedstock inlet means disposed at an
inlet end of said passageway for enabling feedstock
to enter said passageway at said inlet end whereby to
be engaged and carried frictionally by said wheel
member, when rotating, towards the opposite, outlet
end of said passageway;
(d) an abutment member carried on said shoe
member and projecting radially into said passageway
at said outlet end thereof so as to substantially
close said passagewa~ at that end and thereby impede
the passage of feedstock frictionally carried in said
groove by said wheel member, thus creating an
ex-trusion pressure in said passageway at said outlet
end thereof; and
(e) a die member carried on said shoe
member and having a die orifice opening from said
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passageway at said outlet end thereof, through which
orifice feedstock carried in said groove and
frictionally compressed by rotation of said wheel
member, when driven, is compressed and extruded in
continuous form, to exit from said shoe member via an
outlet aperture.
The invention is particularly concerned
with a method o~ producing a said rotatable ~heel
member for use in such a rotary, friction--type,
continuous extrusion apparatus.
BA~KGROU~D AR~
In operating such an extrusion apparatus,
the parts defining said passageway adjacent said
outlet end thereof su~fer very great working loads
and very high operating temperatures. Of such highly
stressed (mechanically and thermally) parts, those
that suffer greatest wear or damage are the
stationary, feedstock-engaging parts of, or
associated with, said stationary shoe member,
particularly on said abutment member, said die member
and the stationary parts that support those items.
~ or the convenience of readily making good
worn or damaged surfaces or parts, the abutment
member, and the die member and its supporting parts
are made as separate replaceable items ~hich are
rigidly but removably secured in the stationary shoe
member.
In order to reduce the temperatures at
which those replaceable items operate, such items
have been provided with internal cooling passages
through which cooling water has been circulated.
~owever, such cooling measures have not been very
effective, for the reasons that
(a) the small sizes of those items and the
high ~echanical loads to which they are subjected
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have severely restricted both the si~es of the
internal cooling passages and their proximity to the
source of heat, so that the cooling water has been
unable to extract heat at an adequate rate, and
(b) the materials used for such small items
(e.g. high-speed tool steels) have relatively poor
heat transmission properties.
As a consequence of the low dissipation of
heat by the cooling water, plastic flow of the tip of
the abutment member, at its free end adjoining the
bottom of the groove in the wheel member, has been
experienced, due to the excessive tip temperature~
reached. This has severely limited the life of the
abutment member, and the running time of the
apparatus between successive occasions when the
abutment member has to be replaced. ~his in turn has
led to a reduction in the quantity of the output
extrusion product produced, due to the down-time
during which the apparatus cannot be operated.
Also, with prolonged use, there has been
the risk that the extrusion die may overheat to a
temperature at which its mechanical strength is
impaired, with the consequent risk of deformation
and/or increased wear of the die.
After experimentation with various
different arrangemen-ts of internal cooling passages~
particularly in the abutment member, highly
satisfactory results have now been achieved by means
of an entirely different arrangement for cooling the
abutment member. Such different arrangement, and
various modifications thereof, have been described
and claimed in the copending, parent patent
application No. , filed , 1983, from
which application this present application has been
divided.
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The use o~ the invention of that parent
application enables such a rotary, friction-type,
continuous extrusion apparatus to operate at lower
temperatures, for longer periods of time, and ~ith
longer operating lives for those parts of the
apparatus that are subjected to high mechanical and
; thermal stresses.
The beneficial results obtained by the use
of that invention can be enhanced by the use in
conjunction therewith of the invention of this
divisional application.
By way of introduction to the present
invention, reference should be made to the passage in
the specification of that parent application, which
begins - "It is believed that the highly beneficial
..." and ends - "... at which heat will be conveyed
to the cooling zone by the wheel member."
That passage appears later in this
specification, since the description given later with
reference to the drawing figures is the same as that
given in said parent application.
DISC~OSUR~ OF INVE~TION
According to the present invention, a
method of producing a rotary wheel member adapted for
use, in a rotary, friction type, continuous extrusion
apparatus comprises the steps o~:
(a) producing a rotary wheel having formed
in its cylindrical peripheral parts a continuous 9
radially-extending groove, and secured in that groove
for movement with said peripheral parts of said
wheelan annular metal mass;
(b) rotating said wheel about its rotary
axis; and
(c) applying to the periphery of said
annular metal mass secured in said wheel a tool of
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predetermined end shape, and progressively advancing
said tool in a radial direction as said wheel
continues to rotate whereby to machine in the
peripheral parts of said annular metal mass a working
groove of predetermined desired transverse cross
sectional shape;
said peripheral parts of said annular metal
mass which define said working groove being of a
composition which is substantially the same as that
of a predetermined feedstock metal that is to be
extruded in a said apparatus when equipped with the
wheel member so produced; and said predetermined end
shape of said tool being substantially the same as
that of a predetermined abutment member which is to
be used in that apparatus to close the end of an
arcuate passageway which is formed in said working
groove by a shoe member which when the apparatus is
in operation co-operates with said cylindrical
peripheral parts of said wheel member.
Preferably, said annular metal mass secured
in said wheel groove i9 in good thermal relationship
with said wheel.
Said annular metal mass secured in said
wheel groove may comprise an annulus of a first
predetermined metal lying concentrically with said
wheel in 3aid wheel groove and being enveloped within
a sheath of a second predetermined metal, said second
predetermined metal defining said working groove and
being in good thermal relationship with said first
predetermined metal.
Said annular metal mass secured in said
wheel groove may alternatively comprise an annulus of
a first predetermined metal lying concentric with
said wheel in the bottom o~ said wheel groove and
being overlaid by a second annulus of a second
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predetermined metal, said first predetermined metal
being in good thermal relationship with ~aid second
predetermined metal, and said second predetermined
metal defining said working groove.
Preferably, said first and second
predetermined metals each have a product of thermal
conductivity and specific heat per unit volume that
is greater than that of the material of the wheel.
Advantageously, said product for said first
predetermined metal is greater than that for said
second predetermined metal.
In carrying out the methods of the present
invention, said wheel is preferably mounted for
rotation in a said rotary extrusion apparatus, and is
rotated therein, and said tool comprises a said
abutment member of said apparatus, which abutment
member is advanced radially into said annular metal
mass as said wheel is rotated, whereby to form said
wor~ing groove.
The present invention also provides wheel
members prepared by methods according -to the present
invention.
Other features and advantages of the
present invention will appear from a reading of the
description that follows hereafter, and from the
claims appended at the end of that description.
BRIE~ DESCRIPTION 0~ DRAWI~GS
One continuous extrusion apparatus
embodying the present invention will now be described
~0 by way of example and with reference to the
accompanying diagrammatic drawings in which:
~igure 1 shows a medial, vertical cross-
section taken through the essential working parts of
the apparatus~ the plane of that section being
~5 indicated in ~igure 2 at I-I;
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~igure 2 shows a transverse sectional view
taken on the section indicated in ~igure 1 at II-II;
~igures 3 and 4 show in sectional views
similar -to that of ~igure 2 two arrangemen-ts which
are alterna-tives to that of ~igure 2;
~igure 5 shows a schematic block diagram of
a ~ystem embodying the apparatus of the ~igures 1
and 2;
~igure 6 shows a graph depicting the
variation of a heat extraction rate with variation of
a cooling water. ~low rate, as obtained from tests on
one apparatus according to the present invention;
~igures 7 to 9 show, in views similar to
that of ~igure 2, various modified forms of a wheel
member incorporated in 3aid apparatus; and
~igure 10 shows, in a view similar to that
of ~igure 1, a modified form o~ the apparatus shown
in the ~igures 1 and 2.
MODES 0~ CARRYI~G OUT ~HE I~VE~TION
Referring now to Figures 1 and 2, the
apparatus there shown includes a rotatable wheel
member 10 which is carried in bearings (not shown)
and coupled through gearing (not shown) to an
electric driving motor (not shown) so as to be driven
when in operation at a ~elected speed within the
range O to 20 RPM (though greater speeds are
possible).
The wheel member has formed around its
periphery a groove 12 whose radial cross-~ection is
depicted in ~igure 2. The deeper par-t o~ the groove
has parallel annular sides 14 which merge with a
radiused bottom surface 16 of the groove. A
convergent mouth part 18 of said groove i~ de~ined by
oppositely-directed frusto-conical surfaces 20, 22.
A stationary shoe member 24 carried on a
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lower pivot pin 26 extends around and coopera-tes
closely with approximately one quarter of the
periphery of the wheel member 10. The shoe member is
retained in its operating position as shown in
5 ~igure 1 by a withdrawable stop member 28.
The shoe member includes centrally (in an
axial direction) a circumferentially-extending
projecting portion 30 which projects partly into the
groove 12 in the wheel member 10 with small axial or
10 transverse clearance gaps 32, 34 on either side.
~hat projecting, portion 30 is constituted in part by
a series of replaceable inserts, and comprises a
radially-directed abutment member 36, an abutment
support 38 downstream of the abutment member, a die
15 block 40 (incorporating an extrusion die 42) upstream
of the abutment member, and an arcuate wear-resisting
member 44 upstream of ~aid die block. Upstream of
the member 44 an integral entry part 46 of the shoe
member completes an arcuate passageway 48 which
20 extend~ around the wheel member from a vertically-
oriented feedstock inlet passage 50 disposed below a
feedstock hopper 52, downstream as far as the front
face 54 of the abutment member 36. ~hat passageway
ha~ a radial cross-section which in the ~igure 2 is
25 defined by the annular side wall~ 14 and bottom
surface 16 of the groove 12, and the inner surface 56
of the said central portion 30 of the shoe
member 24.
~he said abutment member 36, die block 40,
30 die 42 and arcuate member 44 are all made of suitably
hard, wear-resistant metals, e.g. high-speed tool
steels.
~ he shoe member is provided with an outlet
aperture 58 which is aligned with a corresponding
35 aperture 60 formed in the die block 40 and through
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which ~he extruded output metal product 61 (e.g. a
round wire) from the orifice of the die 42 emerges.
On rotation of the wheel member 10,
comminuted feedstock admitted to the inlet end of the
said arcuate passageway 48 from the hopper 52 via the
inlet passage 50 is carried by the moving groove
surfaces of the wheel member in an anti-clockwise
direction as seen in ~igure 1 along the length of
said arcuate passageway 48, and is agglomerated and
compacted to form a solid slug of metal devoid of
inter~tices in the lower section of the passageway
adjacent said die block 40. ~hat slug of metal is
continuously urged under great pressure against the
abutment member by the ~rictional drag of the moving
groove surfaces. ~hat pressure is sufficient to
ex-trude the metal of said slug through the orifice of
the extrusion die and thereby provide an extruded
output product which issues through the apertures 58
and 60 in the shoe member and die block. In the
particular case, the output produc-t compri~es a
bright copper wire produced from small chopped pieces
of wire which constitute the said feedstock.
A water pipe 62 secured around the lower
end of the shoe member 24 has an exit nozzle 64
positioned and secured on the side of the shoe member
that lie~ adjacent the wheel member 10. ~he nozæle
is aligned so as, when the pipe is ~upplied with
cooling water, to direct a jet of water directly at
the downstream parts of the abutment member where it
lies in and abuts the groove 12 in the wheel
member 10. ~hus, the tip of the free end of the
abutment member (where in operation most of the heat
is genera-ted) and the adjoining surfaces of the wheel
member and groove are directly cooled by the flow
thereover of water from the jet directed towards
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them.
The die block 40 is provided with internal
water passages (not shown) and a supply o~ cooling
water for enveloping the output product leaving the
die and extracting some of the heat being carried
away in that product. But no such internal passages
are ~ormed in the abutment member. Thus, the
s-trength of that member is not reduced in the
interests of providing internal water cooling for
cooling that member.
If desired, the cooling of the apparatus
may be enhanced by providing cooling water
sprinklers 65 over the hopper 52 so a~ to feed ~ome
cooling water into the said arcuate passageway 48
with the comminuted feedstock.
In the ~igure 2, the slug of compacted
metal in the extrusion zone adjacent the die block 40
i3 indicated at 66. ~rom that metal slug, the output
product i3 extruded through the extrusion die 42 by
the pressure in that zone. That pressure also acts
to extrude some o~ the metal through the said axial
clearance gaps 32 and 34 between the side walls of
the groove and the respective opposing sur~aces o~
the die block and abutment member. That extruded
metal gradually builds up in a radial direction to
form 3trips 68 o~ waste metal or "~lash". In order
to prevent those waste strips growing too large to
handle and control, a plurality of transversely-
directed teeth 70 are secured on the divergent
walls 20, 22 which constitute the said mouth 18 o~
the groove l2. Those teeth are uniformly spaced
around the wheel member, the teeth on one o~ the
walls being disposed opposite the corresponding teeth
on the opposite wall. I~ desired, the teeth on one
wall may alternatively be staggered relative to
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corresponding teeth on the other wall.
In operation, the inclined surfaces 72 of
the die block 40 deflect the extruded waste strips 68
obliquely into the paths of the respective sets of
moving teeth 70. Interception of such a waste
strip 68 by a moving tooth causes a piece of that
strip to be cut or otherwise torn away from the
extruded metal in the clearance gap. ~hus, ~uch
waste extruded strips are removed as soon as they
extend radially far enough to be intercepted by a
moving tooth. In this way the "flash" is prevented
from reaching unmanageable proportions.
The said teeth do not need to be sharp, and
can be secured in any satisfactory manner on the
wheel member 10, e.g. by welding.
In the Figures 3 and 4 are shown other
teeth Pitted in analogous manners to appropriate
surface~ of other forms of said wheel member 10.
In those alternative arrangements, the
external surfaces of the wheel member 10 cooperate
with correspondingly shaped surfaces of the
cooperating shoe member 24 whereby to effect control
of the flash in a particular desired way. In
Figure 3, the flash i9 cau~ed to grow in a purely
tranverse or axial direction, until it is intercepted
by a radially projecting tooth, whereupon that piece
of flash is torn away ~rom the extruded metal in the
associated clearance gap.
In Figure 4, the flash is cau~ed to grow in
an oblique direction (as in the case of Figure 2),
but is intercepted by teeth which project radially
from the surface of the wheel member 10.
For various reasons that will appear later,
it may be desirable, or even necessary, to treat the
extrusion product (wire 61) issuing from
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the continuous extrusion apparatus described above in
an extrusion product treatment apparatus before
passing it to a product collection and storage means.
Moreover, it may be desirable or advantageous to
treat the extrusion product whilst it still remains
hot from the continuous extrusion process in which it
was produced.
Such a treatment apparatus may, for
example, be arranged to provide the extrusion product
with a better or different surface finish (for
example, a drawn finish), and/or a more uniform
external diameter or gauge. Such a treatment
apparatus may also be used to provide, at different
times, ~rom the same continuous extrusion product,
finished products of various different gauges and/or
tolerances. ~or such purposes, the said treatment
apparatus may comprise a simple drawing die through
which said extrusion product is first threaded and
then drawn under tension, to provide a said finished
product of desired size, tolerance, and/or quality.
~he use of such a treatment apparatus to treat the
extrusion product would enable the continuous
extrusion die 42 of the continuous extrusion
apparatus to be retained in service for a longer
period before having to be discarded because o~ the
excessive enlargement of its die aperture caused by
: wear in service. Moreover, such a treatment
apparatus may have its die readily and speedily
interchanged, whereby to enable an output product of
a different gauge, tolerance and/or quality to be
produced instead.
One example of a continuous extrusion
system incorporating a continuous extrusion apparatus
and an extrusion product treatment apparatus will now
be described with reference to the igure 5.
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Referring now to the ~igure 5, the system
there shown includes at reference 100 a continuous
extrusion apparatus as just described above and, if
desired, modified as described below, the output
copper ~ire produced by that apparatus being
indicated at 102, and being drawn through a sizing
die 104 (for reducing its gauge to a desired lower
value) by a tensioning pulley device 106 around which
the wire passes a plurality of times before passing
via an accummulator 108 to a coiler 11 O.
The pulley device 106 is coupled to the
output ~haft o:e an electrical torque mo-tor 112 whose
energisation is provided and controlled by a control
apparatus 114. The latter is responsive to (a) a
15 first electrical signal 116 derived from a wire
tension sensor 118 which engages the wire 102 at a
position between the extru~ion apparatus 100 and the
sizing die 104, and which provides as said first
signal an electrical signal dependent on the tension
20 in the wire 102 at the output of the extrusion
apparatus 100; and to (b) a second electrical
signal 120 derived from a temperature sensor 122
which measures the temperature OI the wire 102 as it
leaves the extrusion apparatus 100.
The control apparatus 114 incorporates a
function generator 124 which is responsive to said
second (temperature) signal 120 and provides at its
output circuit a third electrical signal
representative of the yield stress tension for the
particular wire 102 when at the particular
temperature represented by the said second
(temperature) signal. That third electrical signal
126 is supplied as a reference signal to a comparator
128 (also part of said control apparatus) in which
the said first (tension) signal 116 is compared with
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said third signal (yield stress tension). The output
signal o~ the comparator constitutes the signal for
controlling the energisation of the torque motor.
In operation, the torque motor is energised
to an extent su~ficient to maintain the tension in
the wire leaving the extrusion apparatus 100 at a
value ~hich lies a predetermined amount below the
yield stress tension for the particular wire at the
particular temperature at which it leaves the
extru~ion apparatus.
Wherea3 in the description above re~erence
has been made to the use of a water jet for cooling
the abutment member tip, jets o~ other cooling
liquids (or even cooling gases) could be u~ed
instead. Even jets of appropriate liquified gase~
may be used~
Regarding the flash-removing teeth 70
referred to in the above description, it should be
noted that:-
(a) the shaping of the leading edge
(i.e. the cutting or tearing edge) of each tooth is
not critical, as long as the desired ~lash removal
function is ful~illed;
(b) the working clearance between the tip
f each tooth 70 and the adjacent opposing sur~ace of
the stationary shoe member 24 i9 not critical, and is
typically not greater than 1 to 2 mm, according to
the speci~ic design of the apparatu~;
(c) the greater the number o~ teeth 3paced
around each side of the wheel member 10, the smaller
will be the lengths o~ "~lash" removed by each
tooth;
(d) the teeth may be made o~ any 3uitable
material, such a~ for example, tool steel; and
(e) an~ convenient method o~ securing the
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teeth on the wheel member ma~y be used.
~ he ability of the apparatus to deliver an
acceptable output extrusion product from feedstock in
loose particulate or communited form is considerably
enhanced by causing the radial depth (or height) of
the arcuate passageway 48, in a pressure-building
zone which lies immediately ahead (i.e. upstream) of
the front face 54 of the abutment member 36, to
diminish relatively rapidly in a preferred manner in
the direction of rotation of the wheel member 10, for
example in the manner illustrated in the drawings.
The removable die block 40 is arranged to
be circumferentially co-extensive with that zone, and
the said progressive reduction of the radial depth of
the arcuate passageway is achieved by appropriately
shaping the surface 40A of the die block that faces
the bottom of the groove 12 in the wheel member 10.
That surface 40A of the die block is
preferably shaped in a manner such as to achieve in
the said zone, when the apparatus is operating, a
feedstock metal flow pattern that closely resembles
that which is achieved when using instead feedstock
in solid form. In the preferred embodiment
illustrated in the drawings, that surface 40A
comprises a plane surface which is inclined at a
suitable small angle to a tangent to the bottom of
the groove 12 at its point of contact with the
abutment member 36 at its front face 54.
That angle is ideally set at a value such
that the ratio of (a) the area of the abutment member
36 that i3 exposed to feedstock metal at the
extrusion pressure, to (b) the radial cross-sectional
area of the passageway 48 at the entry end of said
zone (i.e. at the radial cross-section adjacent the
upstream end of the die block 40) is equal to the
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ratio of (i) the apparent density of the feedstock
entering that zone at said entry end thereof, to (ii)
the density of the ~ully-compacted feedstock lying
adjacent the front face 54 of the abutment member
36.
In one satisfactory arrangement, the said
plane surface 40A of the die block was inclined at an
angle such that the said area of the abutment member
that is exposed to feedstock metal at the extrusion
pressure is equal to one half of the said radial
cross-sectional area of the passageway 48 at the
en-try end of said zone (i.e. at the upstream end of
the die block).
If desired, in an alternative embodiment
the surface of the die block facing the bottom of the
groove 12 may be inclined in the manner referred to
above over only a greater part of it~ circumferential
length which extends from the said upstream end of
the die block, the part of the die block lying
immediately adjacent the front face 54 of the
abutment member being provided with a surface that
lies parallel (or substantially parallel) with the
bottom of the groove 12.
The greater penetration of the die block 40
into the groove 12, which resul-ts from the said
shaping of the surface 40A referred to above, serves
al~o to offer increa~ed phy~ical resistance to the
unwanted extrusion o~ flash-forming metal through the
clearance gaps 32 and 34, so that the amount of
feedstock metal going to the formation of such flash
is greatl~ reduced. Moreover, that penetration of
the die block into the groove 12 results in
reductions in (a) the redundant work done on the
~eedstock, (b) in the amount of flash produced, and
(c) the bending moment imposed on the abutment member
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by the metal under ~res~ure. ~urthermore, the choice
of a plane working surface 40A for the die block
reduces the cost of producing that die block.
Whereas in the above description, the wheel
member 10 is driven by an electric driving motor, at
speeds within the stated range, other like-operating
continuous extrusion machines may utilise hydraulic
driving means and operate at appropriate running
speeds.
As an alternative to introducing additional
cooling water into the passageway 48 via the
~prinklers 65, hopper 52 and passage 50, such
additional cooling water may be introduced into that
pa~sageway (for example, via a pas3age 67 formed in
the shoe member 24) at a position at which ~aid
pa3~ageway i~ filled with particulate feedstock, bu-t
at which said particulate feedstock therein is not
yet fully compacted.
It is believed that the highly beneficial
cooling effects provided by the present invention
arise very largely from the fact that the heat
absorbed by a part of the wheel member lying
temporarily adjacent the hot metal in the confined
extrusion zone upstream of the abutment member is
conveyed (both by thermal conduction and rotation of
the wheel member) from that hot zone to a cooling
zone situated downstream of the abutment member, in
which cooling zone a copious ~upply of cooling fluid
is caused to flow over relatively large areas of the
wheel member pas~ing through that cooling zone ~o as
to extract therefrom a high proportion o~ the heat
absorbed by the wheel member in the ho-t extrusion
zone.
In this cooling zone access to the wheel
~5 member is less restricted 9 and relatively large
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~urfaces of that member are freely available for
cooling purposes. This is in direct contrast to the
extremely small and con~ined cooling surfaces that
can be provided directly adjacent the extrusion zone
in the parts of the said shoe member (i.e. the die
block and abutment member) that bound that extrusion
zone. As has been mentioned above, the cooling
surfaces that can be provided in those parts are
severely limited in size by the need to conserve the
mechanical strengths of those parts and so enable
them to sa~ely withstand the extrusion pressure
exerted on them.
The conveying o~ heat absorbed by the wheel
member to the said cooling zone can be greatly
enhanced by the incorporation in said wheel member of
metals having good thermal conductivities and good
specific heats (per unit volume). However, since the
said wheel member, for reasons o~ providing adequate
mechanical strength, is made of physically strong
metals, (e.g. tool steels), it has relatively poor
heat transmission properties. Thus, the ability of
the wheel member to convey heat to said cooling zone
can be greatly enhanced by incorporating intimately
in said wheel member an annular band of a metal
having good thermal absorption and transmission
properties, for example, a band of copper.
Such a thermally conductive band may
conveniently be constituted by an annular band
secured in the periphery of the said wheel member and
preferably constituting, at least in part, the part
of said wheel member in which the said
circumferential groove is formed to provide (with the
shoe member) the said passageway (48).
In cases where the e~trusion product o~ the
machine is o~ a metal having suitably good thermal
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properties, the said thermally conductive band may be
composed of the same metal as the extrusion product
(e.g. copper).
In other cases, said thermally~conductive
band may be embedded in, or be overlaid by, a second
annular band, which second band is of the same metal
as the extrusion product o~ the machine and is in
contact with the tip portion of the said abutment
member, the two bands being of different metals.
Metals which may be used for the said
thermally-conductive band are selected to have a
higher product of thermal conduc-tivity and specific
heat per unit volume than tool stee1, and include the
~ollowing (in decreasing order of said higher
product):-
Copper, silver, beryllium, gold, aluminium,tung~ten, rhodium, iridium, molybdenum, ru-thenium,
zinc and iron.
~ he rate at which heat can be conveyed by
such a thermally-conductive band from the extrusion
zone to the cooling zone i9 dependent on the radial
cross-sectional area of the band, and is increased by
increasing that cross-sectional area. ~hus, for a
given cross-sectional dimension measured transversely
of the circumference o~ the wheel member, the greater
the radial depth of a said band, the greater the rate
at which heat will be conveyed to the cooling zone by
the wheel member.
Calculations have shown that for a said
wheel member having an ef~ective diameter o~ 233 mm,
and a speed of rotation of 10 RPM, and a said
thermally-conductive band of copper having a radial
cross-section o~ U-shape, the rate "R" of conveying
heat from the extrusion zone to the said cooling zone
by the wheel member, by virtue of its rotation alone,
2 ~ Z 6 ~ Z
2020~0RDIV
-20-
varies in the manner shown below with variation of
the radial depth or extent to which a said abutment
(36) cooperating with the wheel member penetrates
into that copper band, that is to sa~, with variation
of the radial thickness "~" of the copper band that
remains at the bottom of the said circumferential
groove (12). The~e calculations were based on a said
copper band having with the adjacent parts (tool
steel) o~ the wheel member an inter~ace of generally
circular configuration as seen in a radial cross
section. ~ence, the radial cross-sectional area "A"
o~ the copper band varies in a non-linear manner with
the ~aid radial thickne~s "~" o-~ copper at the bottom
o~ ~aid groove (12).
~ (mm) A (sq. mm) R (kW)
1.0 18.0 5.1
1.5 22.7 6~4
2.0 27-4 7.7
2-5 32.1 9,1
3- 36.8 10.4
In one practical arrangement having such a
wheel member and a 2 mm radial thickness ~ of said
copper band at the bottom of said groove (12), when
operating at said wheel member speed and extruding
copper wire of 1.4 mm diameter at a speed of 150
metres per minute, heat wa~ extracted ~rom the wheel
member and abutment member in said cooling zone at a
rate of 10 kW b~ cooling water ~lowing at as low a
rate o~ 4 litres per minute and providing at the
sur~aces to be cooled in said cooling zone a jet
velocity of approximately 800 metres per minute.
~his heat extraction rate indicates that
heat was reaching the cooling zone at a rate o~ some
2.3 kW as a result of the conduction of heat through
the said conductive band, the adjacent wheel member
7;~
2020~0RDIV
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parts, and the abutment member, induced by the
temperature gradient existing between the extrusion
zone and the cooling zone.
This measured rate of extracting heat by
the cooling water flowing in the cooling zone
compares very favourably with a maximum rate o~ heat
extraction o~ some 1.9 k~ that has been found to be
achievable by flowing cooling water in the prior art
manner through internal cooling passages formed in
the abutment member.
Figure 6 shows the way in which the rate o~
extracting heat from the wheel member and abutment
member in said cooling zone was found to vary with
variation of the rate of flow of -the cooling water
supplied to that zone.
The extrusion machine described above with
reference to the drawings was equipped for the
practical tests with a said thermally-conductive band
of copper, which band is shown at reference 74 in
~igure 10, and indicated, for convenience only, in
dotted-line form in Figure 2. ,(It should be noted
that Figure 2 also depicts, when the copper band 74
is repre~ented in full-line ~orm, the transverse
sectional view taken on the section indicated in
Figure 10 at II-II.) As will be understood from
reference 74 in ~igure 2, the said copper band had a
radial cross section of U-shape, which band lined the
rounded bottom 16 of the circum~erential groove 12
and extended part-way up the parallel side walls o~
that groove.
Figure 7 shows in a view similar to that o~
Figure 2 a modification of the wheel member 10. In
that modification, a solid annular band 76 of copper
having a substantially rectangular radial cross-
section i~ mounted in and clamped securely between
`"` 124;267Z
2020FORDI~J-22-
cooperating steel cheek members 78 of said wheel
member, so as to be driven by said cheek members when
a driving shaft on which said cheek members are
carried is driven by said driving motor. ~he band 76
has, at least intially, a small internal groove 76A
spanning the tight joint 78A between the two cheek
member3 78. That groove prevents the entry between
those cheek members of any of the metal of said band
76 during assembly of the wheel member 10.
Complementary frusto-conical surfaces 76~ and 78~ on
said band and cheek members re~pectively permit
easier assembly and disassembly of those parts of the
wheel member 10.
The circumferential groove 12, iæ formed in
15 the copper band by pivotally advancing the shoe
member 24 about its pivot pin 26 towards the
periphery of the rotating wheel member 10, so as to
bring the tip of the abutment member 36 into contact
with the copper band, and thereby cause it to machine
the copper band progressively deeper to form said
groove 12 therein.
Figure 8 shows an alternative form of said
modification of Figure 7, in which alternative the
thermally-conductive band comprises instead a
25 composite annular band 80 in which an inner core 82
of a metal (such as copper) having good thermal
properties is encased in and in good thermal
relationship with a sheath 84 of a metal (for
example, zinc) which is the same as that to be
extruded by the machine.
Figure 9 shows a further alternative form
of said modification of Figure 7, in which
alternative the thermally-conductive band comprises
instead a composite band 86 in which a radially-inner
35 annular part 88 thereof is made of a metal (such as
` ` lZ~2~7~
2020~0RDIV
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copper) having good thermal properties and is
encircled, in good thermal relationship, by a
radially-outer annular part 90 o~ a metal which is
the same as that to be extruded by the machine. Said
circumferential groove is machined by said abutment
member wholly within said radially-outer part 90 of
said band.
Metals which can be extruded by extrusion
machines as described above include:-
Copper and its alloys, aluminium and its
alloys, zinc, silver, and gold.
It should be noted that various aspects ofthe present disclosure which are not re~erred to in
the claims below have been made the subjects of the
respective sets of claims o~ other patent
applications all of which likewise claim priority
from the same two UK patent applications,
Nos. 8309836 (filed 12th April, 1983) and 8302951
(filed 3rd ~ebruary, 1983).
