CA1228835A - Continuous extrusion of metals - Google Patents
Continuous extrusion of metalsInfo
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- CA1228835A CA1228835A CA000529954A CA529954A CA1228835A CA 1228835 A CA1228835 A CA 1228835A CA 000529954 A CA000529954 A CA 000529954A CA 529954 A CA529954 A CA 529954A CA 1228835 A CA1228835 A CA 1228835A
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Abstract
ABSTRACT
CONTINUOUS EXTRUSION OF METALS
A continuous extrusion machine in which feedstock is admitted (at 50) to a peripheral groove (12) in a rotating wheel (10), is enclosed in that groove by a cooperating shoe (24), and is frictionally dragged along the arcuate passageway (48) formed by said groove and a projecting portion (30) of said shoe towards an abutment (36) carried by the shoe. The pressure in the metal in front of the abutment continuously extrudes a metal product through a die (42). The abutment tip and adjacent wheel parts disposed downstream of the abutment are cooled directly by a jet of cooling fluid issuing from a nozzle (64) carried downstream on the shoe. An annular band (Figure 2, 74) of a good thermally-conductive metal embedded concentrically in the wheel enhances the cooling obtained. Flash (68) extruded through clearance gaps (32, 34) between cooperating wheel and shoe surfaces is intercepted and broken off periodically, in short lengths, by teeth 70 projecting from the wheel. The radial depth of the passageway (48) progressively decreases in the direction of wheel rotation in a zone extending upstream from the abutment (36), so as to improve in that zone, in the case of particulate or comminuted feedstock, the metal flow pattern adjacent the abutment, such feedstock in that zone being in a fully compacted condition without voids.
This is achieved by the shaping of a surface (40A) of a die block (40) which adjoins the abutment (36) and incorporates the die member (42). That shaping produces with particulate or comminuted feedstock a metal flow pattern closely resembling that achievable with feedstock in solid form. A continuous extrusion product (Fig. 5, 102) issuing from a continuous extrusion apparatus (Fig.
1, 10; Fig. 5, 100) is threaded through e treatment die (104) whereby to change its cross-section and is continuously drawn there through by a tensioning device (106,112) under the control of a system which (a) senses the temperature of the product (102) as it leaves the extrusion apparatus (100); (b) converts a temperature signal (120) so produced, in a function generator (124), into a tension reference signal (126): (c) compares with that tension reference signal a tension feedback signal (116) derived from a sensor (118) adjacent the extrusion apparatus; and (d) controls the tensioning device in accordance with the difference of the tension reference and feedback signals so as to prevent the sensed tension in the product extending between the extrusion apparatus (100) and the treatment die (104) from exceeding a safe value which is less than the yield stress tension of that product at the sensed temperature.
CONTINUOUS EXTRUSION OF METALS
A continuous extrusion machine in which feedstock is admitted (at 50) to a peripheral groove (12) in a rotating wheel (10), is enclosed in that groove by a cooperating shoe (24), and is frictionally dragged along the arcuate passageway (48) formed by said groove and a projecting portion (30) of said shoe towards an abutment (36) carried by the shoe. The pressure in the metal in front of the abutment continuously extrudes a metal product through a die (42). The abutment tip and adjacent wheel parts disposed downstream of the abutment are cooled directly by a jet of cooling fluid issuing from a nozzle (64) carried downstream on the shoe. An annular band (Figure 2, 74) of a good thermally-conductive metal embedded concentrically in the wheel enhances the cooling obtained. Flash (68) extruded through clearance gaps (32, 34) between cooperating wheel and shoe surfaces is intercepted and broken off periodically, in short lengths, by teeth 70 projecting from the wheel. The radial depth of the passageway (48) progressively decreases in the direction of wheel rotation in a zone extending upstream from the abutment (36), so as to improve in that zone, in the case of particulate or comminuted feedstock, the metal flow pattern adjacent the abutment, such feedstock in that zone being in a fully compacted condition without voids.
This is achieved by the shaping of a surface (40A) of a die block (40) which adjoins the abutment (36) and incorporates the die member (42). That shaping produces with particulate or comminuted feedstock a metal flow pattern closely resembling that achievable with feedstock in solid form. A continuous extrusion product (Fig. 5, 102) issuing from a continuous extrusion apparatus (Fig.
1, 10; Fig. 5, 100) is threaded through e treatment die (104) whereby to change its cross-section and is continuously drawn there through by a tensioning device (106,112) under the control of a system which (a) senses the temperature of the product (102) as it leaves the extrusion apparatus (100); (b) converts a temperature signal (120) so produced, in a function generator (124), into a tension reference signal (126): (c) compares with that tension reference signal a tension feedback signal (116) derived from a sensor (118) adjacent the extrusion apparatus; and (d) controls the tensioning device in accordance with the difference of the tension reference and feedback signals so as to prevent the sensed tension in the product extending between the extrusion apparatus (100) and the treatment die (104) from exceeding a safe value which is less than the yield stress tension of that product at the sensed temperature.
Description
US
Continuous EXTRUSION OF METALS
. . . _ _ .
TECHNICAL FIELD
This invention relates to a continuous extrusion system, that is to say a system which includes (a) a continuous extrusion apparatus for producing a continuous metal extrusion product, and (b) an extrusion product treatment apparatus for receiving that extrusion product from said extrusion apparatus and for treating it as it issues from said extrusion apparatus so as to change one or more predetermined characteristics thereof (e.g. its transverse cross-sectional size or shape) in a desired way before said product is passed to a product collection and storage means. The extrusion product may be treated in said treatment apparatus whilst it is still hot from the extrusion process in which it was produced.
Such a treatment apparatus may comprise an extrusion product treatment means through which said extrusion product is to be threaded and drawn under tension from said extrusion apparatus, and tensioning means for drawing said extrusion product continuously through said treatment means from said extrusion apparatus as it emerges therefrom. Said treatment means may comprise, for example, a die or other means for changing the size and/or shape of the transverse cross-section of the extrusion product, and/or the surface finish of that product.
BACKGROUND ART
In operating such a product treatment apparatus, great care has to be exercised so as to ensure that the tension applied to the treated product emerging from the treatment means does not increase to a level at which the tension consequently induced in the extrusion product as it emerges from the extrusion apparatus is sufficient to break or otherwise impair the properties of the extrusion product entering the treatment means. Control difficulties can arise since, in particular, the yield stress of the hot extrusion ~>'~ 35 product is variable in dependence upon the temperature at which the extrusion product emerges from the extrusion apparatus, which temperature is itself dependent upon the rate at which the extrusion product issues from the extrusion apparatus, and the general operating temperature of the extrusion apparatus.
DISCUSSER OF THE Invention According to one aspect of the present invention, there is provided in such a continuous extrusion system:-(a) a temperature sensing means arranged to sense the temperature of the extrusion product as it leaves the continuous extrusion apparatus and to provide a temperature reference signal dependent upon the sensed temperature of the extrusion product;
(b) a tension sensing means arranged to sense the tension in the length of the extrusion product extending between the extrusion apparatus and the treatment means, and to provide a tension feedback signal dependent upon the sensed tension in that length of the extrusion product: and (c) a control apparatus arranged for controlling the said tensioning means, which control apparatus is responsive to said temperature reference signal and said tension feedback signal and is arranged to control said tensioning means automatically in a manner such that the sensed tension in said length of said extrusion product does not exceed a predetermined safe value which is less than the yield stress tension of said extrusion product at the sensed temperature at which the extrusion product leaves the extrusion apparatus.
Preferably, said control apparatus includes:-(i) a function generator responsive to said temperature reference signal and arranged to produce in response thereto tension reference signal representative of the yield stress tension for said extrusion product at said sensed temperature;
and (ii) comparison means responsive differentially to said tension reference and feed back signals, and arranged to produce in response thereto a control signal for controlling I ', said tensioning means in dependence upon the difference of said tension reference and feedback signals.
According to a second aspect of the present invention, there is provided a method of treating a continuous metal extrusion product issuing from a continuous extrusion apparatus, which method includes the steps of:-(i) threading said extrusion product issuing from a said extrusion Apparatus through an extrusion product treatment means;
(ii) continuously applying a tension to said extrusion product as it emerges from said treatment means whereby to draw said extrusion product through said treatment means, and thereby to induce a tension in the length of said extrusion product currently extending between said extrusion apparatus and said treatment means;
(iii) sensing the temperature of said extrusion product as it leaves said extrusion apparatus, and producing a temperature reference signal which is dependent on the sensed temperature;
(iv) sensing the tension in the said length of said extrusion product, and producing a tension feedback signal which is dependent on the sensed tension; and (v) controlling said tension applied to said extrusion product emerging from said treatment means in dependence upon said temperature reference signal and said tension feedback signal automatically in a manner such that the sensed tension in said length of said extrusion product does not exceed a predetermined safe value which is less than the yield stress tension of said extrusion product at the sensed temperature at which the extrusion product leaves the extrusion apparatus.
Preferably, said step (v) comprises the steps of:
(vi) converting said temperature reference signal into a tension reference signal in accordance with a predetermined function relating the value of the said sensed temperature and the value of a safe tension which can be induced in said length of said extrusion product without exceeding the yield stress for said product at the sensed temperature;
~.~.Z~3.S
(vii) comparing said tension feedback signal with said tension reference signal, and producing therefrom a difference signal dependent on the deviation of said tension feedback signal from a value determined by said tension reference signal:
and (viii) controlling said tension applied to said extrusion product emerging from said treatment means in dependence upon said difference signal in a manner such as to prevent said sensed tension exceeding a said safe tension value.
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.
BRIEF DESCRIPTION OF DRAWINGS
One continuous extrusion apparatus embodying the present invention will now be described by way of example and with reference to the accompanying diagrammatic drawings in which:-Figure 1 shows a medial, vertical cross-section taken through the essential working parts of the apparatus, the plane of that section being indicated in Figure 2 at I-I;
Figure 2 shows a transverse sectional view taxes on the section indicated in Figure 1 at II-II;
Figures 3 and 4 show in sectional views similar to that of Figure 2 two arrangements which are alternatives to that of Figure 2:
Figure shows a schematic block diagram of a system embodying the apparatus of the Figures 1 and US
Figure 6 shows a graph depicting the variation of a heat extraction rate with variation of a cooling water flow rate, as obtained from tests on one apparatus according to the present invention;
Figures 7 to 9 show, in views similar to that of Figure 2, various modified forms of Allah member incorporated in said apparatus; and A
Figure 10 show, in a view similar to that ox Figure 1, a modified form of the apparatus shown in the Figures 1 and 2.
MODES OF CARRYING OUT THE INVENT
Referring now to Figures 1 and 2, the apparatus there shown includes a rotatable wheel member 10 which it 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 selected speed within the range 0 to 20 RPM (though greater speeds are possible).
- The wheel member has formed around its periphery a groove 12 whose radial cross-section is depicted in Figure 2. The deeper part of the groove has parallel annular sides 14 which merge with a radiuses bottom fiurface 16 of the groove. A convergent mouth part lo of said groove is defined by oppositely-directed frusto-conical surfaces 20, 22.
. A stationary shoe member 24 carried on a lower pivot pin 26 extends around and cooperates 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 Figure 1 by a with drawable fitOp 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 transverse clearance gaps 32, 34 on either side. That projections portion 30 it constituted in part by a series of replaceable insert, and comprises a radially-directed abutment member 36, an abutment support 38 downstream of the abutment member, a die bloc I (incorporating an extrusion die 42) upstream of the abutment member, and an arcuate wear-resisting US member 44 upstream of field die bloc. Upstream of the member 44 an integral entry part 46 of the shoe member UP:
completes an arcuate passageway 48 which extends around the wheel member from a vertically-oriented feed stock inlet passage 50 disposed below a feed stock hopper I
downstream as far as the front face 54 of the abutment member 36. That passageway has a radial cross-oection which in the Figure 2 it defined by the annular elide 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.
The said abutment member 36~ die block 40, die 42 and arcuate member 44 are all made of suitably hard, wear-resistant metals, e.g. whopped tool steels.
The shoe member it provided with an outlet aperture 58 which is aligned with a corresponding aperture 60 formed in the die block 40 and through which the extruded output metal product 61 (e.g. a rounder) from the orifice of the die 42 emerges.
On rotation of the wheel member 10, commented feed stock 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 Figure 1 along the length of said arcuate passageway 48, and is agglomerated and compacted to form a solid slug of metal devoid of interstices in the lower section of the passageway adjacent said die block 40. That slug of metal is continuously urged under great pressure against the - abutment member by the frictional drag of the moving groove surfaces. That pressure is efficient to extrude the petal 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 product comprise a bright copper wire produced from small chopped pieces of wire which constitute the said feed stock.
A
US
A water pipe 62 secured around the lower end of the shoe member 24 has an exit nozzle 64 positioned and secured on the wide of the shoe member that lie adjacent the wheel member 10. The nozzle it aligned 80 as, when the pipe is supplied 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. Thus, the tip of the free end of the abutment member (where in operation most of the heat it generated) and the adjoining surfaces of the wheel member and groove are directly cooled by the flow there over of water from the jet directed towards them.
The die block 40 is provided with internal water passages (not shown) and a supply of 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 formed in the abutment member. Thus, the strength 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 sprinkler 65 over the hopper 52 80 as to feed some cooling water into the said arcuate passageway 48 with the commented feed stock.
In the Figure 2, the 61ug of compacted metal in the extrusion zone adjacent the die block 40 is indicated at 66. From that metal 61ug, the output product is extruded through the extrusion die 42 by the pressure in that zone. That pressure also acts to extrude some of the metal through the said axial clearance gaps 32 and 34 between the side walls of the groove and the respective opposing surfaces of the die block and abutment member.
That extruded metal gradually builds up in a radial direction to form strips 68 of waste metal or flash". In I order to prevent those waste strip growing too large to handle and control, a plurality of transversely-directed Pi teeth 70 are secured on the divergent walls 20, 22 which Constitute the said mouth 18 of the groove 12. Those teeth are uniformly spaced around the wheel member, the teeth on one of the walls being disposed opposite the corresponding teeth on the opposite wall. If desired, the teeth on one wall may alternatively be staggered relative to corresponding teeth on the other wall.
In operation, the inclined surface 72 of the die block 40 deflect the extruded waste strips 68 obliquely into the paths of the respective jets 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. Thus, such waste extruded trips 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 fitted in analogous manners to appropriate surfaces 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 it caused to grow in a purely transverse or axial direction, until it is intercepted by a radially projecting tooth, whereupon that piece of flash it torn away from the extruded metal in the associated clearance gap.
In Figure 4, the flash it caused to grow in an oblique direction (a in the case of Figure 2), but is intercepted by teeth which project radially from the surface of the wheel member 10.
A
~1.2~ I
g For various reason that will appear later, it Jay be desirable, or even necessary, to treat the extrusion product (wire 61) issuing from the continuous extrusion apparatus described above in an extrusion product treatment apparatus before pausing it to a product collection and storage means. Moreover, it Jay be desirable or advantageous to treat the extrusion product whilst it till remain 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, from the same continuous extrusion product, finished products of various different gauges and/or tolerances. For 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. The 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 of 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 Figure I.
Referring now to the Figure 5, the system there shown includes at reference 100 a continuous extrusion US
apparatus as just described above and, if desired, modified as described below, the output copper wire produced by that apparatus being indicated at 102, and being drawn through a sizing die 104 (for reducing it 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 accumulator 108 to a goiter 110.
The pulley device 106 is coupled to the output shaft of an electrical torque motor 112 whose energisation is provided and controlled by a control apparatus 114.
The latter is responsive to (a) a first electrical signal 116 derived from a wire tension tensor 118 which engages the wire 102 at a position between the extrusion apparatus 100 and the sizing die 104, and which provides as said first signal an electrical signal dependent on the tension 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 of the wire 102 a 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 fiignal 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 said third signal (yield stress tension). The output signal of the comparator constitutes the signal for controlling the energisation of the torque motor.
In operation, the torque motor is energized to an extent sufficient to maintain the tension in the wire I
leaving the extrusion apparatus 100 at a value which lies a predetermined amount below the yield strews tension for the particular wire at the particular temperature at which it leaves the extrusion apparatus.
Whereas in the description above reference has been made to the use of a water jet for cooling the abutment member tip, jets of other cooling liquids (or even cooling gases) could be used instead. Even jets of appropriate liquefied gases 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, long as the desired flash removal function is fulfilled;
(b) the working clearance between the tip of each tooth 70 and the adjacent opposing surface of the stationary shoe member 24 it not critical, and it typically not greater than 1 to 2 mm, according to the specific design of the apparatus;
(c) the greater the number of teeth spaced around each side of the wheel member 10, the smaller will be the lengths of "flash" removed by each tooth;
Ed) the teeth may be made of any suitable material, such as for example, tool steel; and (e) any convenient method of securing the teeth on the wheel member may be used.
The ability of the apparatus to deliver an acceptable output extrusion product from feed stock on loose particulate or commented form is considerably enhanced by causing the radial depth (or height) of the arcuate passageway 48, in a pres~ure-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.
A
US
The removable die block 40 it arranged to be circumferential 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 AYE of the die block that faces the bottom of the groove 12 in the wheel member 10.
That surface AYE of the die block ill preferably shaped in a manner such as to achieve in the said zone, when the apparatus it operating, a feed stock metal flow pattern that closely resembles that which is achieved when using instead feedstocX in idea form. In the preferred embodiment illustrated in the drawing, that surface AYE
comprises a plane surface which it 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 it ideally jet at a value such that the ratio of (a) the area of the abutment member 36 that is exposed to feed stock metal at the extrusion pressure, to tub) 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 ratio of (i) the apparent density of the feed stock entering that zone at said entry end thereof, to (ii) the density of the fully-compacted feed stock lying adjacent the front face 54 of the abutment member 36.
In one satisfactory arrangement, the said plane surface AYE of the die block was inclined at an angle such that the said area of the abutment member that is exposed to feed stock metal at the extrusion pressure it equal to one half of the said radial cro6s-sectional area of the passageway 48 at the entry 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 A
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 results from the said shaping of the surface AYE referred to above, serves also to offer lo increased physical resistance to the unwanted extrusion of flash-forming metal through the clearance gaps 32 and 44, 80 that the amount of feed stock metal going to the formation of such flash it greatly reduced. Moreover, that penetration of the die block into the groove 12 results in reductions in (a the redundant work done on the feed stock, (b) the amount of flash produced, and (c) the bending moment imposed on the abutment member by the metal under pressure. Furthermore, the choice of a plane working surface AYE 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 utilize hydraulic driving jeans and operate at appropriate running speeds.
As an alternative to introducing additional cooling water into the passageway 48 via the sprinkler 65, hopper 52 and passage 50, such additional cowling water may be introduced into that passageway (for example, via a passage 67 formed it the shoe member 24~ at a position at which said passageway B filled with particulate feed stock, but at which said particulate feed stock therein it not yet fully compacted.
It it 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 Jo t I
the wheel member lying temporarily adjacent toe hot petal in the confined extrusion zone upstream of the abutment member it 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 supply of cooling fluid us caused to flow over relatively large areas of the wheel member passing through that cooling zone 80 as to extract therefrom 8 high proportion of the heat absorbed by the wheel member in the hot extrusion zone.
In this cooling zone access to the wheel member is less restricted, and relatively large surfaces of that member are freely available for cooling purposes. This it in direct contrast to the extremely small and confined cooling ~urface6 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 I limited in size by the need to conserve the mechanical strengths of those parts and 80 enable them to safely withstand the extrusion pressure exerted on them.
he conveying of 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 conductivitie6 and good specific heats (per unit volume). However, wince the said wheel member, for reasons of providing adequate mechanical strength, it made of physically strong metal, (e.g. tool steels), it ha 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 tran6mi~sion properties, for example, a band of copper.
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I
Such a thermally conductive band Jay 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 extrusion product of the machine is of a metal having suitably good thermal 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 it of the same metal as the extrusion product of the machine and it 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 conductivity and specific heat per unit volume than tool steel, and include the following (in decreasing order of said higher product):-Copper, Culver, beryllium, gold, aluminum, tungsten, rhodium, iridium, molybdenum, ruthenium, zinc and iron.
The rate at which heat can be conveyed by such a thermally-conductive band from the extrusion zone to the cooling zone is dependent on the radial cross-sectional area of the band, and is increased by increasing that cross-sectional area. Thus, for a given cros6-sectional dimension measured transversely of the circumference of 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 effective diameter of 233 mm, and a speed ~"~
3.5 of rotation of 10 RPM, and a said thermally-condu~ti~e band of copper having a radial cross-section of U-shape, the rate OR" of conveying heat from the extrusion zone to the said cooling zone by the wheel member, by virtue of it rotation alone, varies in the wanner 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 it to say, with variation of the radial thickness "T" of the copper band that remains at the bottom of the said circumferential groove (12).
These calculations were based on a said copper band having with the adjacent parts (tool steel) of the wheel member an interface of generally circular configuration as seen in a radial cross section Hence, the radial cross-sectional area "A" of the copper band varies in a non-linear manner with the said radial thickness IT" of copper at the bottom of said groove (12).
T (mm) A (so. mm) R (ow) 1.0 18.0 5.1 1.5 22.7 6.4
Continuous EXTRUSION OF METALS
. . . _ _ .
TECHNICAL FIELD
This invention relates to a continuous extrusion system, that is to say a system which includes (a) a continuous extrusion apparatus for producing a continuous metal extrusion product, and (b) an extrusion product treatment apparatus for receiving that extrusion product from said extrusion apparatus and for treating it as it issues from said extrusion apparatus so as to change one or more predetermined characteristics thereof (e.g. its transverse cross-sectional size or shape) in a desired way before said product is passed to a product collection and storage means. The extrusion product may be treated in said treatment apparatus whilst it is still hot from the extrusion process in which it was produced.
Such a treatment apparatus may comprise an extrusion product treatment means through which said extrusion product is to be threaded and drawn under tension from said extrusion apparatus, and tensioning means for drawing said extrusion product continuously through said treatment means from said extrusion apparatus as it emerges therefrom. Said treatment means may comprise, for example, a die or other means for changing the size and/or shape of the transverse cross-section of the extrusion product, and/or the surface finish of that product.
BACKGROUND ART
In operating such a product treatment apparatus, great care has to be exercised so as to ensure that the tension applied to the treated product emerging from the treatment means does not increase to a level at which the tension consequently induced in the extrusion product as it emerges from the extrusion apparatus is sufficient to break or otherwise impair the properties of the extrusion product entering the treatment means. Control difficulties can arise since, in particular, the yield stress of the hot extrusion ~>'~ 35 product is variable in dependence upon the temperature at which the extrusion product emerges from the extrusion apparatus, which temperature is itself dependent upon the rate at which the extrusion product issues from the extrusion apparatus, and the general operating temperature of the extrusion apparatus.
DISCUSSER OF THE Invention According to one aspect of the present invention, there is provided in such a continuous extrusion system:-(a) a temperature sensing means arranged to sense the temperature of the extrusion product as it leaves the continuous extrusion apparatus and to provide a temperature reference signal dependent upon the sensed temperature of the extrusion product;
(b) a tension sensing means arranged to sense the tension in the length of the extrusion product extending between the extrusion apparatus and the treatment means, and to provide a tension feedback signal dependent upon the sensed tension in that length of the extrusion product: and (c) a control apparatus arranged for controlling the said tensioning means, which control apparatus is responsive to said temperature reference signal and said tension feedback signal and is arranged to control said tensioning means automatically in a manner such that the sensed tension in said length of said extrusion product does not exceed a predetermined safe value which is less than the yield stress tension of said extrusion product at the sensed temperature at which the extrusion product leaves the extrusion apparatus.
Preferably, said control apparatus includes:-(i) a function generator responsive to said temperature reference signal and arranged to produce in response thereto tension reference signal representative of the yield stress tension for said extrusion product at said sensed temperature;
and (ii) comparison means responsive differentially to said tension reference and feed back signals, and arranged to produce in response thereto a control signal for controlling I ', said tensioning means in dependence upon the difference of said tension reference and feedback signals.
According to a second aspect of the present invention, there is provided a method of treating a continuous metal extrusion product issuing from a continuous extrusion apparatus, which method includes the steps of:-(i) threading said extrusion product issuing from a said extrusion Apparatus through an extrusion product treatment means;
(ii) continuously applying a tension to said extrusion product as it emerges from said treatment means whereby to draw said extrusion product through said treatment means, and thereby to induce a tension in the length of said extrusion product currently extending between said extrusion apparatus and said treatment means;
(iii) sensing the temperature of said extrusion product as it leaves said extrusion apparatus, and producing a temperature reference signal which is dependent on the sensed temperature;
(iv) sensing the tension in the said length of said extrusion product, and producing a tension feedback signal which is dependent on the sensed tension; and (v) controlling said tension applied to said extrusion product emerging from said treatment means in dependence upon said temperature reference signal and said tension feedback signal automatically in a manner such that the sensed tension in said length of said extrusion product does not exceed a predetermined safe value which is less than the yield stress tension of said extrusion product at the sensed temperature at which the extrusion product leaves the extrusion apparatus.
Preferably, said step (v) comprises the steps of:
(vi) converting said temperature reference signal into a tension reference signal in accordance with a predetermined function relating the value of the said sensed temperature and the value of a safe tension which can be induced in said length of said extrusion product without exceeding the yield stress for said product at the sensed temperature;
~.~.Z~3.S
(vii) comparing said tension feedback signal with said tension reference signal, and producing therefrom a difference signal dependent on the deviation of said tension feedback signal from a value determined by said tension reference signal:
and (viii) controlling said tension applied to said extrusion product emerging from said treatment means in dependence upon said difference signal in a manner such as to prevent said sensed tension exceeding a said safe tension value.
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.
BRIEF DESCRIPTION OF DRAWINGS
One continuous extrusion apparatus embodying the present invention will now be described by way of example and with reference to the accompanying diagrammatic drawings in which:-Figure 1 shows a medial, vertical cross-section taken through the essential working parts of the apparatus, the plane of that section being indicated in Figure 2 at I-I;
Figure 2 shows a transverse sectional view taxes on the section indicated in Figure 1 at II-II;
Figures 3 and 4 show in sectional views similar to that of Figure 2 two arrangements which are alternatives to that of Figure 2:
Figure shows a schematic block diagram of a system embodying the apparatus of the Figures 1 and US
Figure 6 shows a graph depicting the variation of a heat extraction rate with variation of a cooling water flow rate, as obtained from tests on one apparatus according to the present invention;
Figures 7 to 9 show, in views similar to that of Figure 2, various modified forms of Allah member incorporated in said apparatus; and A
Figure 10 show, in a view similar to that ox Figure 1, a modified form of the apparatus shown in the Figures 1 and 2.
MODES OF CARRYING OUT THE INVENT
Referring now to Figures 1 and 2, the apparatus there shown includes a rotatable wheel member 10 which it 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 selected speed within the range 0 to 20 RPM (though greater speeds are possible).
- The wheel member has formed around its periphery a groove 12 whose radial cross-section is depicted in Figure 2. The deeper part of the groove has parallel annular sides 14 which merge with a radiuses bottom fiurface 16 of the groove. A convergent mouth part lo of said groove is defined by oppositely-directed frusto-conical surfaces 20, 22.
. A stationary shoe member 24 carried on a lower pivot pin 26 extends around and cooperates 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 Figure 1 by a with drawable fitOp 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 transverse clearance gaps 32, 34 on either side. That projections portion 30 it constituted in part by a series of replaceable insert, and comprises a radially-directed abutment member 36, an abutment support 38 downstream of the abutment member, a die bloc I (incorporating an extrusion die 42) upstream of the abutment member, and an arcuate wear-resisting US member 44 upstream of field die bloc. Upstream of the member 44 an integral entry part 46 of the shoe member UP:
completes an arcuate passageway 48 which extends around the wheel member from a vertically-oriented feed stock inlet passage 50 disposed below a feed stock hopper I
downstream as far as the front face 54 of the abutment member 36. That passageway has a radial cross-oection which in the Figure 2 it defined by the annular elide 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.
The said abutment member 36~ die block 40, die 42 and arcuate member 44 are all made of suitably hard, wear-resistant metals, e.g. whopped tool steels.
The shoe member it provided with an outlet aperture 58 which is aligned with a corresponding aperture 60 formed in the die block 40 and through which the extruded output metal product 61 (e.g. a rounder) from the orifice of the die 42 emerges.
On rotation of the wheel member 10, commented feed stock 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 Figure 1 along the length of said arcuate passageway 48, and is agglomerated and compacted to form a solid slug of metal devoid of interstices in the lower section of the passageway adjacent said die block 40. That slug of metal is continuously urged under great pressure against the - abutment member by the frictional drag of the moving groove surfaces. That pressure is efficient to extrude the petal 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 product comprise a bright copper wire produced from small chopped pieces of wire which constitute the said feed stock.
A
US
A water pipe 62 secured around the lower end of the shoe member 24 has an exit nozzle 64 positioned and secured on the wide of the shoe member that lie adjacent the wheel member 10. The nozzle it aligned 80 as, when the pipe is supplied 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. Thus, the tip of the free end of the abutment member (where in operation most of the heat it generated) and the adjoining surfaces of the wheel member and groove are directly cooled by the flow there over of water from the jet directed towards them.
The die block 40 is provided with internal water passages (not shown) and a supply of 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 formed in the abutment member. Thus, the strength 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 sprinkler 65 over the hopper 52 80 as to feed some cooling water into the said arcuate passageway 48 with the commented feed stock.
In the Figure 2, the 61ug of compacted metal in the extrusion zone adjacent the die block 40 is indicated at 66. From that metal 61ug, the output product is extruded through the extrusion die 42 by the pressure in that zone. That pressure also acts to extrude some of the metal through the said axial clearance gaps 32 and 34 between the side walls of the groove and the respective opposing surfaces of the die block and abutment member.
That extruded metal gradually builds up in a radial direction to form strips 68 of waste metal or flash". In I order to prevent those waste strip growing too large to handle and control, a plurality of transversely-directed Pi teeth 70 are secured on the divergent walls 20, 22 which Constitute the said mouth 18 of the groove 12. Those teeth are uniformly spaced around the wheel member, the teeth on one of the walls being disposed opposite the corresponding teeth on the opposite wall. If desired, the teeth on one wall may alternatively be staggered relative to corresponding teeth on the other wall.
In operation, the inclined surface 72 of the die block 40 deflect the extruded waste strips 68 obliquely into the paths of the respective jets 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. Thus, such waste extruded trips 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 fitted in analogous manners to appropriate surfaces 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 it caused to grow in a purely transverse or axial direction, until it is intercepted by a radially projecting tooth, whereupon that piece of flash it torn away from the extruded metal in the associated clearance gap.
In Figure 4, the flash it caused to grow in an oblique direction (a in the case of Figure 2), but is intercepted by teeth which project radially from the surface of the wheel member 10.
A
~1.2~ I
g For various reason that will appear later, it Jay be desirable, or even necessary, to treat the extrusion product (wire 61) issuing from the continuous extrusion apparatus described above in an extrusion product treatment apparatus before pausing it to a product collection and storage means. Moreover, it Jay be desirable or advantageous to treat the extrusion product whilst it till remain 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, from the same continuous extrusion product, finished products of various different gauges and/or tolerances. For 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. The 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 of 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 Figure I.
Referring now to the Figure 5, the system there shown includes at reference 100 a continuous extrusion US
apparatus as just described above and, if desired, modified as described below, the output copper wire produced by that apparatus being indicated at 102, and being drawn through a sizing die 104 (for reducing it 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 accumulator 108 to a goiter 110.
The pulley device 106 is coupled to the output shaft of an electrical torque motor 112 whose energisation is provided and controlled by a control apparatus 114.
The latter is responsive to (a) a first electrical signal 116 derived from a wire tension tensor 118 which engages the wire 102 at a position between the extrusion apparatus 100 and the sizing die 104, and which provides as said first signal an electrical signal dependent on the tension 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 of the wire 102 a 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 fiignal 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 said third signal (yield stress tension). The output signal of the comparator constitutes the signal for controlling the energisation of the torque motor.
In operation, the torque motor is energized to an extent sufficient to maintain the tension in the wire I
leaving the extrusion apparatus 100 at a value which lies a predetermined amount below the yield strews tension for the particular wire at the particular temperature at which it leaves the extrusion apparatus.
Whereas in the description above reference has been made to the use of a water jet for cooling the abutment member tip, jets of other cooling liquids (or even cooling gases) could be used instead. Even jets of appropriate liquefied gases 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, long as the desired flash removal function is fulfilled;
(b) the working clearance between the tip of each tooth 70 and the adjacent opposing surface of the stationary shoe member 24 it not critical, and it typically not greater than 1 to 2 mm, according to the specific design of the apparatus;
(c) the greater the number of teeth spaced around each side of the wheel member 10, the smaller will be the lengths of "flash" removed by each tooth;
Ed) the teeth may be made of any suitable material, such as for example, tool steel; and (e) any convenient method of securing the teeth on the wheel member may be used.
The ability of the apparatus to deliver an acceptable output extrusion product from feed stock on loose particulate or commented form is considerably enhanced by causing the radial depth (or height) of the arcuate passageway 48, in a pres~ure-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.
A
US
The removable die block 40 it arranged to be circumferential 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 AYE of the die block that faces the bottom of the groove 12 in the wheel member 10.
That surface AYE of the die block ill preferably shaped in a manner such as to achieve in the said zone, when the apparatus it operating, a feed stock metal flow pattern that closely resembles that which is achieved when using instead feedstocX in idea form. In the preferred embodiment illustrated in the drawing, that surface AYE
comprises a plane surface which it 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 it ideally jet at a value such that the ratio of (a) the area of the abutment member 36 that is exposed to feed stock metal at the extrusion pressure, to tub) 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 ratio of (i) the apparent density of the feed stock entering that zone at said entry end thereof, to (ii) the density of the fully-compacted feed stock lying adjacent the front face 54 of the abutment member 36.
In one satisfactory arrangement, the said plane surface AYE of the die block was inclined at an angle such that the said area of the abutment member that is exposed to feed stock metal at the extrusion pressure it equal to one half of the said radial cro6s-sectional area of the passageway 48 at the entry 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 A
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 results from the said shaping of the surface AYE referred to above, serves also to offer lo increased physical resistance to the unwanted extrusion of flash-forming metal through the clearance gaps 32 and 44, 80 that the amount of feed stock metal going to the formation of such flash it greatly reduced. Moreover, that penetration of the die block into the groove 12 results in reductions in (a the redundant work done on the feed stock, (b) the amount of flash produced, and (c) the bending moment imposed on the abutment member by the metal under pressure. Furthermore, the choice of a plane working surface AYE 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 utilize hydraulic driving jeans and operate at appropriate running speeds.
As an alternative to introducing additional cooling water into the passageway 48 via the sprinkler 65, hopper 52 and passage 50, such additional cowling water may be introduced into that passageway (for example, via a passage 67 formed it the shoe member 24~ at a position at which said passageway B filled with particulate feed stock, but at which said particulate feed stock therein it not yet fully compacted.
It it 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 Jo t I
the wheel member lying temporarily adjacent toe hot petal in the confined extrusion zone upstream of the abutment member it 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 supply of cooling fluid us caused to flow over relatively large areas of the wheel member passing through that cooling zone 80 as to extract therefrom 8 high proportion of the heat absorbed by the wheel member in the hot extrusion zone.
In this cooling zone access to the wheel member is less restricted, and relatively large surfaces of that member are freely available for cooling purposes. This it in direct contrast to the extremely small and confined cooling ~urface6 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 I limited in size by the need to conserve the mechanical strengths of those parts and 80 enable them to safely withstand the extrusion pressure exerted on them.
he conveying of 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 conductivitie6 and good specific heats (per unit volume). However, wince the said wheel member, for reasons of providing adequate mechanical strength, it made of physically strong metal, (e.g. tool steels), it ha 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 tran6mi~sion properties, for example, a band of copper.
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I
Such a thermally conductive band Jay 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 extrusion product of the machine is of a metal having suitably good thermal 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 it of the same metal as the extrusion product of the machine and it 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 conductivity and specific heat per unit volume than tool steel, and include the following (in decreasing order of said higher product):-Copper, Culver, beryllium, gold, aluminum, tungsten, rhodium, iridium, molybdenum, ruthenium, zinc and iron.
The rate at which heat can be conveyed by such a thermally-conductive band from the extrusion zone to the cooling zone is dependent on the radial cross-sectional area of the band, and is increased by increasing that cross-sectional area. Thus, for a given cros6-sectional dimension measured transversely of the circumference of 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 effective diameter of 233 mm, and a speed ~"~
3.5 of rotation of 10 RPM, and a said thermally-condu~ti~e band of copper having a radial cross-section of U-shape, the rate OR" of conveying heat from the extrusion zone to the said cooling zone by the wheel member, by virtue of it rotation alone, varies in the wanner 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 it to say, with variation of the radial thickness "T" of the copper band that remains at the bottom of the said circumferential groove (12).
These calculations were based on a said copper band having with the adjacent parts (tool steel) of the wheel member an interface of generally circular configuration as seen in a radial cross section Hence, the radial cross-sectional area "A" of the copper band varies in a non-linear manner with the said radial thickness IT" of copper at the bottom of said groove (12).
T (mm) A (so. mm) R (ow) 1.0 18.0 5.1 1.5 22.7 6.4
2.0 27.4 7.7 2.5 32.1 9.1
3.0 36.B 10.4 In one practical arrangement having such a wheel member and a 2 mm radial thickness T 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 metros per minute, heat was extracted from the wheel member and abutment member in said cooling zone at a rate of 10 ow by cooling water flowing at as low a rate of 4 liters per minute and providing at the surfaces to be cooled in said cooling zone a jet velocity of approximately 800 metros per minute.
This heat extraction rate indicates that heat was reaching the cooling zone at a rate of some 2.3 ow as a result of the conduction of heat through the said .' ~'2~3.S
conductive band, the adjacent wheel member 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 S cooling water flowing in the cooling zone Cooper very favorably with a maximum rate of heat extraction of fume 1.9 ow 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 of 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-conductiYe band of copper, which band it shown at reference 74 in Figure 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 represented in full-line form, the transverse sectional view taken on the section indicated in Figure 10 at II-II.) As will be understood from reference 74 in Figure 2, the said copper band had a radial cross section of U-shape, which band lined the rounded bottom 16 of the circumferential groove 12 and extended part-way up the parallel wide walls of that groove.
Figure 7 shows in a view similar to that of 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 it mounted in and clamped securely between cooperating Steel cheek members 78 of said wheel member, Jo as to be driven by said cheek members when a driving shaft on which said cheek member are carried is driven by said driving D
motor. The band 76 ha, at least initially, a small internal groove AYE spanning the tight joint AYE between the two cheek members 78. That groove prevent the entry between those cheer members of any of the metal of said band 76 during assembly of the wheel member 10.
Complementary fru6to-conical surfaces 76B and 78B on said band and cheek members respectively permit easier assembly and disassembly of those part of the wheel member 10.
The circumferential groove 12, is formed in the copper band by pivotal advancing the shoe member 24 about its pivot pin 26 towards the periphery of the rotating wheel member 10, 80 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 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 it 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 annular part 8B thereof is made of a metal (such as copper) having good thermal properties and is encircle, in good thermal relationship, by a radially-outer annular part 90 of a metal which it the same a 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:-I.
I
Copper and its alloys, aluminum and itfi allying silver, and gold.
It should be noted that various aspect of the present disclosure which are not referred to in the claims -below have been made the subjects of the respective claims of other, concurrently-filed patent application which likewise claim priority from the tame two UK patent applications Nos. 8309836 (filed 12 April 1983) and 8302951 filed 3 February 1983).
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This heat extraction rate indicates that heat was reaching the cooling zone at a rate of some 2.3 ow as a result of the conduction of heat through the said .' ~'2~3.S
conductive band, the adjacent wheel member 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 S cooling water flowing in the cooling zone Cooper very favorably with a maximum rate of heat extraction of fume 1.9 ow 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 of 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-conductiYe band of copper, which band it shown at reference 74 in Figure 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 represented in full-line form, the transverse sectional view taken on the section indicated in Figure 10 at II-II.) As will be understood from reference 74 in Figure 2, the said copper band had a radial cross section of U-shape, which band lined the rounded bottom 16 of the circumferential groove 12 and extended part-way up the parallel wide walls of that groove.
Figure 7 shows in a view similar to that of 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 it mounted in and clamped securely between cooperating Steel cheek members 78 of said wheel member, Jo as to be driven by said cheek members when a driving shaft on which said cheek member are carried is driven by said driving D
motor. The band 76 ha, at least initially, a small internal groove AYE spanning the tight joint AYE between the two cheek members 78. That groove prevent the entry between those cheer members of any of the metal of said band 76 during assembly of the wheel member 10.
Complementary fru6to-conical surfaces 76B and 78B on said band and cheek members respectively permit easier assembly and disassembly of those part of the wheel member 10.
The circumferential groove 12, is formed in the copper band by pivotal advancing the shoe member 24 about its pivot pin 26 towards the periphery of the rotating wheel member 10, 80 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 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 it 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 annular part 8B thereof is made of a metal (such as copper) having good thermal properties and is encircle, in good thermal relationship, by a radially-outer annular part 90 of a metal which it the same a 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:-I.
I
Copper and its alloys, aluminum and itfi allying silver, and gold.
It should be noted that various aspect of the present disclosure which are not referred to in the claims -below have been made the subjects of the respective claims of other, concurrently-filed patent application which likewise claim priority from the tame two UK patent applications Nos. 8309836 (filed 12 April 1983) and 8302951 filed 3 February 1983).
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Claims (9)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A continuous extrusion system comprising:-(a) a continuous extrusion apparatus for pro-ducing a continuous metal extrusion product;
(b) an extrusion product treatment means through which said extrusion product is to be threaded and drawn under tension from said extrusion apparatus, whereby to effect a desired change in one or more predetermined characteristics of said extrusion product;
(c) a tensioning means arranged to apply, when the system is in operation, a tension to said extrusion product leaving said treatment means whereby to continuously draw said extrusion product through said treatment means;
(d) a temperature sensing means arranged to sense the temperature of the extrusion product as it leaves the continuous extrusion apparatus and to provide a temperature reference signal dependent upon the sensed temperature of the extrusion product;
(e) a tension sensing means arranged to sense the tension in the length of the extrusion product ex-tending between the extrusion apparatus and the treatment means, and to provide a tension feedback signal dependent upon the sensed tension in that length of the extrusion product; and (f) a control apparatus arranged for controlling the tensioning means, which control apparatus is respon-sive to said temperature reference signal and said tension feedback signal and is arranged to control said tensioning means automatically in a manner such that the sensed tension in said length of said extrusion product does not exceed a predetermined safe value which is less than the yield stress tension of said extrusion product at the sensed temperature at which the extrusion product leaves the extrusion apparatus.
(b) an extrusion product treatment means through which said extrusion product is to be threaded and drawn under tension from said extrusion apparatus, whereby to effect a desired change in one or more predetermined characteristics of said extrusion product;
(c) a tensioning means arranged to apply, when the system is in operation, a tension to said extrusion product leaving said treatment means whereby to continuously draw said extrusion product through said treatment means;
(d) a temperature sensing means arranged to sense the temperature of the extrusion product as it leaves the continuous extrusion apparatus and to provide a temperature reference signal dependent upon the sensed temperature of the extrusion product;
(e) a tension sensing means arranged to sense the tension in the length of the extrusion product ex-tending between the extrusion apparatus and the treatment means, and to provide a tension feedback signal dependent upon the sensed tension in that length of the extrusion product; and (f) a control apparatus arranged for controlling the tensioning means, which control apparatus is respon-sive to said temperature reference signal and said tension feedback signal and is arranged to control said tensioning means automatically in a manner such that the sensed tension in said length of said extrusion product does not exceed a predetermined safe value which is less than the yield stress tension of said extrusion product at the sensed temperature at which the extrusion product leaves the extrusion apparatus.
2. A system according to Claim 1, wherein said control apparatus includes:-(i) a function generator responsive to said temperature reference signal and arranged to produce in response thereto a tension reference signal representative of the yield stress tension for said extrusion product at said sensed temperature; and (ii) comparison means responsive differentially to said tension reference and feedback signals, and arranged to produce in response thereto a control signal for controlling said tensioning means in dependence upon the difference of said tension reference and feedback signals.
3. A system according to Claim 1 or Claim 2, wherein said tensioning means incorporates an electrically energised torque motor, and said control apparatus is arranged to vary the electrical energisation of said torque motor.
4. A system according to Claim 1 or 2, wherein said continuous extrusion apparatus comprises an apparatus in which feedstock in comminuted or particulate form (a) is admitted to a passageway that is closed at a remote end thereof, (b) is frictionally driven along that passage-way towards said closed end, and (c) is extruded under high pressure and at a high temperature at said closed end through an orifice of an extrusion die to provide said extrusion product.
5. A system according to Claim 1 or 2, wherein said continuous extrusion apparatus comprises a power-operated driving wheel having a peripheral groove, a shoe member extending circumferentially around and partway radially into a portion of that groove so as to form with said groove portion an arcuate passageway, said shoe member having disposed at an exit end thereof a radial abutment which protrudes into said groove so as to close it, and at an inlet end thereof a feedstock supply means for feeding to that end of said passageway metal feedstock in comminuted or particulate form, said shoe member also having at the closed end of said passageway an extrusion die having an orifice through which feedstock engaged and driven frictionally by surfaces defining said groove on rotation of said driving wheel is extruded at high temperature to provide said continuous metal extru-sion product.
6. A system according to Claim 1 or 2, wherein said treatment apparatus comprises a drawing die through which said extrusion product is to be drawn whereby to change its transverse cross section.
7. A method of treating a continuous metal extrusion product issuing from a continuous extrusion apparatus, which method includes the steps of:
(i) threading said extrusion product issuing from a said extrusion apparatus through an ex-trusion product treatment means;
(ii) continuously applying a tension to said extrusion product as it emerges from said treatment means whereby to draw said extrusion product through said treatment means, and thereby to induce a tension in the length of said extrusion product currently extending between said extrusion apparatus and said treatment means;
(iii) sensing the temperature of said extrusion product as it leaves said extrusion apparatus, and producing a temperature reference signal (120) which is dependent on the sensed temperature;
(iv) sensing the tension in the said length of said extrusion product, and producing a tension feed-back signal (116) which is dependent on the sensed tension;
(v) controlling said tension applied to said extrusion product emerging from said treatment means in dependence upon said temperature reference signal and said tension feedback signal automatically in a manner such that the sensed tension in said length of said extrusion product does not exceed a predetermined safe value which is less than the yield stress tension of said extrusion product at the sensed temperature at which the extrusion product leaves the extrusion apparatus.
(i) threading said extrusion product issuing from a said extrusion apparatus through an ex-trusion product treatment means;
(ii) continuously applying a tension to said extrusion product as it emerges from said treatment means whereby to draw said extrusion product through said treatment means, and thereby to induce a tension in the length of said extrusion product currently extending between said extrusion apparatus and said treatment means;
(iii) sensing the temperature of said extrusion product as it leaves said extrusion apparatus, and producing a temperature reference signal (120) which is dependent on the sensed temperature;
(iv) sensing the tension in the said length of said extrusion product, and producing a tension feed-back signal (116) which is dependent on the sensed tension;
(v) controlling said tension applied to said extrusion product emerging from said treatment means in dependence upon said temperature reference signal and said tension feedback signal automatically in a manner such that the sensed tension in said length of said extrusion product does not exceed a predetermined safe value which is less than the yield stress tension of said extrusion product at the sensed temperature at which the extrusion product leaves the extrusion apparatus.
8. method according to Claim 7, wherein said step (v) comprises the steps of:
(vi) converting said temperature reference signal into a tension reference signal in accordance with a predetermined function relating the value of the said sensed temperature and the value of a safe tension which can be induced in said length of said extrusion product without exceeding the yield stress for said product at the sensed temperature;
(vii) comparing said tension feedback signal with said tension reference signal, and producing there-from a difference signal dependent on the deviation of said tension feedback signal from a value determined by said tension reference signal; and (viii) controlling said tension applied to said extrusion product emerging from said treatment means in dependence upon said difference signal in a manner such as to prevent said sensed tension exceeding a said safe tension value.
(vi) converting said temperature reference signal into a tension reference signal in accordance with a predetermined function relating the value of the said sensed temperature and the value of a safe tension which can be induced in said length of said extrusion product without exceeding the yield stress for said product at the sensed temperature;
(vii) comparing said tension feedback signal with said tension reference signal, and producing there-from a difference signal dependent on the deviation of said tension feedback signal from a value determined by said tension reference signal; and (viii) controlling said tension applied to said extrusion product emerging from said treatment means in dependence upon said difference signal in a manner such as to prevent said sensed tension exceeding a said safe tension value.
9. A method according to Claim 7 or 8, wherein said step (i) comprises threading said extrusion product through a drawing die, which die constitutes said extrusion product treatment means.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000529954A CA1228835A (en) | 1983-02-03 | 1987-02-17 | Continuous extrusion of metals |
Applications Claiming Priority (6)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB838302951A GB8302951D0 (en) | 1983-02-03 | 1983-02-03 | Continuous extrusion of metals |
| GB8302951 | 1983-02-03 | ||
| GB08309836A GB2134428B (en) | 1983-02-03 | 1983-04-12 | Continuous extrusion of metals |
| GB8309836 | 1983-04-12 | ||
| CA000446420A CA1225366A (en) | 1983-02-03 | 1984-01-31 | Continuous extrusion of metals |
| CA000529954A CA1228835A (en) | 1983-02-03 | 1987-02-17 | Continuous extrusion of metals |
Related Parent Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000446420A Division CA1225366A (en) | 1983-02-03 | 1984-01-31 | Continuous extrusion of metals |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1228835A true CA1228835A (en) | 1987-11-03 |
Family
ID=27167411
Family Applications (3)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000519819A Expired CA1242672A (en) | 1983-02-03 | 1986-10-03 | Continuous extrusion of metals |
| CA000529954A Expired CA1228835A (en) | 1983-02-03 | 1987-02-17 | Continuous extrusion of metals |
| CA000529955A Expired CA1228836A (en) | 1983-02-03 | 1987-02-17 | Continuous extrusion of metals |
Family Applications Before (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000519819A Expired CA1242672A (en) | 1983-02-03 | 1986-10-03 | Continuous extrusion of metals |
Family Applications After (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000529955A Expired CA1228836A (en) | 1983-02-03 | 1987-02-17 | Continuous extrusion of metals |
Country Status (1)
| Country | Link |
|---|---|
| CA (3) | CA1242672A (en) |
-
1986
- 1986-10-03 CA CA000519819A patent/CA1242672A/en not_active Expired
-
1987
- 1987-02-17 CA CA000529954A patent/CA1228835A/en not_active Expired
- 1987-02-17 CA CA000529955A patent/CA1228836A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| CA1228836A (en) | 1987-11-03 |
| CA1242672A (en) | 1988-10-04 |
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| MKEX | Expiry |