Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Wire drawing method and apparatus
This invention rela~es to an improved method o~ draw-
ing wire, in particular ferrous wire, which is a combination
of the known dry drawing technique for ferrous wires and
the wet drawing technique known for non-~errous wires. The
method has advantages in simplifying the conskruction and
use of a wire drawing machine.
It is conventional practice to draw wire through a siz-
ing opening by wrapping the wire many times around a rotat-
able drawing block downstream of the sizing opening and
using the engagement of the wire around the block to gener-
ate the drafting tension required for pulling the wire
through the sizing opening. This method of drawin~ wire
(hereina~ter referred to as the capstan block method) has
been widely used for many years and many di~ferent designs
o~ apparatus for operating the method ha~e been developed.
To get adequate tension for drawing the wire through the
sizing opening it is necessary to wrap the wire several times
around the block and it has become conventional practice to
extract from the wire the heat generated by the drawing
process by cooling the wire while it is on the capstan block.
The longer the~dwell time of the wire on the block surface,
the more efficient the cooling can be and there has thus been
a trend towards increasing the number of turns on the block
beyond khat necessary for traction purposes to meet the
cooling requirement as drafting speeds increased. However,
a large number of turns on each capstan block of a multi-
stage machine increases the complexity and cost of the mach-
ine and makes the threading up of the machine complicated
and time-consuming.
In U.K. Patent Specification No. 1,249,926 (BISRA) it
has been proposed to cool the wire whilst it is on the cap-
stan block, by directly contacting it with liquid coolant
sprays and in U.X. Patent Specification No. 1,428,889 (Kobe)
it has been proposed to cool the wire as it leaves the siz-
ing opening by surrounding the wire with liquid coolant
between the opening and the capstan block.
In European Patent Application 0012592 we describe a
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wire drawing method which comprises pulling the wire through
a sizing opening by engaging the wire in an endless groove
of a rotating drawing wheel through an arc of less than 360
and directly contacting the wire between the opening and the
5 wheel with liquid coo]ant flows.
According to one aspect of the present invention a method
of drawing wire which comprises pulling the wire through a
wire lubricant and then through a sizing opening by wrapping
;the wire for at leas~ part of a turn around a rotating draw-
lO ing block to generate the necessary drafting tension for
drawing the wire through the sizing opening, contacting the
wire leaving the sizing opening with a liquid coolant
different from said lubricant and removing coolant from
the wire downstream of the block, is characterised in that
15 at least one complete turn of wire is wrapped around the block
and the wire on the block passes -through a bath of said
liquid coolant supported against the block.
Preferably ~he liquid eoolant forms a movin~ eolumn
~which surrounds the wire leaving the sizing openlng and re-
;20 mains around the wire as it contacts the bloek. Suitably the
iliquid eoolant forming the eolumn also eools the member de-
~ining the sizing opening. Suitably the apparatus for form-
ing the eolumn of eooling liquid around the wire as it is
drawn, generates helieal~flows in the eolumn to improve the
25 eooling effect and eneourage the maintenanee of the eolumn
downstream of the sizing opening and onto the ~urfaee of the
rotating block.
The ro-tary drawing block can be a flanged capstan block
supporting a few complete turns of wire. '~
The liquid coolant is normally water or a water-based J
solution and preferably the bath of coolant is supported
against the block by a eowl closely surrounding the block
for a substantial part of the cireumference of the block
downstream of the point of first contact of the wire on
35 the block.
Surprisingly we find we can dissipate the heat generated
by the heaviest drafting schedules in the short time in which
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the wire is passing to the block an~ is retained on the
block. With conventional prior art capstan blocks (e.g.
with typically 20 - 100 turns of wire on the block) transit
times in which the wire was on the block ranged ~rom say
10 to 100 seconds. At comparable drawing speeds and with a
block of com~arable diameter, the time available for cooling
the wire in a method according to the invention is very much
reduced, the entire cooling being effected in times of say
0.5 to 5 seconds.
The liquid coolant is suitably removed from the wire by
means of an air wipe in which compressed air is fed into
a chamber surrounding the wire, the chamber being limited
in both upstream and downstream directions of the wire path
therethrough by apertured plates whose wire-receiving aper-
tures are only slightly larger than the cross-section of the
wire passing therethrough.
Conveniently the method of the invention i9 used for
the stages of a multi-stage wire drawing operation in which
the cross-section of the wire is progressively reduced stage
by stage from an input feedstock to the final drawn wire.
The wire can be lubricated with a water-insoluble (e.g. a
calcium-based) powder or, i~ electrostatic coating techniques
are used to ensure powder coating~of clean metal, a water-
soluble lubricant powder (e.g. a sodium-based material).
The sizing openings can be fixed dies which are pro-
vided with li~uid cooling on their downstream faces.
Drafting pulls of 25,000 Kg are obtainable with area
reductions per stage in excess o~ 40% easily realisable.
Although cooling has to be accomplished in a much shorter
time than with a prior art capstan machine, we have success-
~ully dissipated 33 KW of power in one stage of a multi-
stage apparatus with an output wire temperature from that
stage of less than 90C (representing a temperature increase
of less than 75C). Drafting speeds in excess o~ 22 m/sec
have also been achieved and it is expected that drawing
speeds at least equal to the best obtainable in prior art
capstan machines can be obtained. Galvanlsed and ungalvan-
ised ferrous wires can be drawn by the method of the invention.
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According to a further aspect of the invention, wire
drawing apparatus comprising a container for wire lubricant 7
a sizing opening for the wire, means to supply a liquid cool-
ant to surround the wire leaving the-opening, a rotatable
5 drawing block downstream of the opening with means to rotate
the block in a direction to draw wire, wrapped in at least a
part turn around the block, through the container, a lubri-
cant di~ferent from said coolant in the container and the
sizing opening, means to keep the wire wet with said liquid
10 coolant on the block and means downstream of the block to
remove said liquid coolant from the wire, is characterised
in that a cowl closely confronts the wire-engaging surface
of the block for at least a part turn therearound from the
initial point of contact of wire on the block to ensure the
15 wire is immersed in a bath of said liquid coolant for at
least an initial part of each turn of the wire on the block.
The rotating block can contain a single endless ~-groove
irl which the wire is located for a few turns (say three to
f'ive) preferably on a slightly tapering cylindrical surface
20 formed between side flanges of the block. If the cowl is
located very close to the outer peripheral edges of both
the side flanges it will define a volume, limited on the
radially inward side by the wire-engaging surface o~ the
block, which can be filled with liquid coolant during use
25 of the block, to form the coolan-t bath through which the
initial part turn of wire on the block will pass.
The cowl can be movable away from the block~to facili-
tate threading-up of the machine.
Since the wire need make at most only a few turns a-
30 round the block in apparatus according to this invention,
threading-up of a multi-stage apparatus according to the in- ^`~
vention is much easier to achieve than would be the case in a
conventional multi-stage capstan block machine. Further, where
only a few turns of wire engage each block; the wire paths to
35 and from each block need be displaced by little more than a
few diameters of the wire and this means that there need be
little displacement of the wire out of a single plane from
the inlet end of a multi-stage apparatus to the outlet end.
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An air wipe is preferred to remove resldual liquid coolant
from the wire prior to i~s entering the next lubricant
container (soap box), this using axially directed compressed
air streams which surround the wire to blow the coolant
5 from the wire surface. To improve lubricant (soap) utili-
sation, it is advantageous to use constantly circulating
lubricant supplies for each soap box. The lubricant powder
can be drained from each soap box, to facilitate threading-
up .
Conveniently the blocks in a multi-stage apparatus are
10 disposed with their ro~ating axes lying in parallel planes
and suitably with their rotating axes disposed horizontally.
Suitably each block is located within a casing so that
although the wire on the block is flowing through a coolant
bath, coolant can be prevented from impinging on coolant-
15 free parts of the wire path. The coolant used can collect
in a trough (suitably ~orming part o~ the base of the appara-
tus) and be filtered and optionally cooled before being
returned to the casings. A recirculating coolant system can
be provided in this way.
Gonveniently the control of the torque applied to the
blocks in a multi-stage apparatus, and hence their relative
rotational speeds, is effected either by sensing the posi-
tion of a dancer pulley between each block and its respective
downstream sizing opening or by sensing the tension gener~
25 ated by the wire on a fixed guide pulley disposed between -
each block and its respective downstream sizing opening.
Preferably, in the latter case, the journals mounting the
guide pulley are connected to a force transducer (e.g. a
load cell) which associates an electrical signal with the
3~ magnitude of the back tension generated in the wire at each
sizing opening.
Conventional electrical control circuits can be used
to convert the outputs of the force transducers into torque
control signals for the respective motors.
As an alternative to forming a shallow coolant bath
against the wire-engagin~ surface of the or each block by
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means of a cowl, the block can be immersed in a deep batn
of liquid coolant,wire leaving the bath when it has le~t the
block.
The method and apparatus of the invention can be used
with both ferrous and non-ferrous wires of both circular
and non-circular cross-section.
The sizing openings can be of any conventional kind
(e.g. fixed dies or roller dies) but fixed dies would be
the normal choice.
The invention will now be further described, by way of
example, with reference to the accompanying drawings,in
which:-
Figure 1 is a general view of one stage of a prior art
multi-stage wire drawing apparatus in which wire is wedged
lS in a V-groove in the block,
Figure 2 is an enlarged view of part of the periphery
- of the block in Figure 1 showing the cowl used to enhance
the cooling effect on the wire being drawn,
Figure 3 is a general view of one stage of a first
embodiment of multi-stage wire drawing apparatus in accord-
ance with the invention,
Figure 4 is a schematic cross-section taken on the line
IV-IV of Figure 3, and ~ ~ ~
Figure 5 shows two stages of a multi-stage drawing
25 apparatus according to~the invention using a deep coolant
bath for the drawing block ln each stage.
; ~ Figure~l shows the wire path for one stage of a multi-
stage wire-drawing apparatus of the kind described in European
Patent Application ooi2592 w~ith the wire entering the
stage illustrated from the left in the direction of the
arrow Y either from a spool of input material or from a
preceding stage. A drawing~block 1 provided with a V-groove
2 indenting its circumferential surface is rotatably mounted
about a horizontal axis 3 for rotation~in the~direction of
the arrow A and by virtue of trapping of the wire in the
groove 2 draws the wire khrough a guide die 4~ a soap box
5 and a sizing die 6. Downstream of the die 6 there is
provided a shroud 7 which forms a coherent column of liquid
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coolant around the wire which column is shown at 8 issu-
ing onto the cylindrical surface of the block 1.
The column of coolant 8 is trapped against the surface
of the block 1 to form a coolant bath (through which the
wire on the block surface passes) by the provision of a
cowl 13 closely surrounding the periphery of the block 1
around an arc of approximately 180. The narrow gap 14 be-
tween the cowl 13 and the block 1 has been shown exaggerated
in Figure 1 and in practice would be of the order of a
tenth of a mm. ~he cowl 13 is pi~oted at 15 to permit it
to be swung away from the block 1 to facilitate the thread-
ing up operation of the apparatus. The downstream end 16
of the cowl i3 closely confronts the upstream end of an open-
topped trough 17 having a drain connection 18. Coolant
leavin~ the cowl 13 fills this trough above the level of the
wire passing through it and ensures that the wire is located
in a ooolant bath all the while the wire is trapped in the
groove 2. A vertical slot is provided in the downstream end
wall 19 o~ the trough 17 to receive the wire and the trough
is pivoted about a turning axis 20 to enable it to be moved
away-from the block 1 on the occasion of threading-up. A
stationary baffle 21 prevents splashes of coolant from the
block 1 contacting wire downstream of an air wipe 9.
After passing through the air wipe 9,the wire passes
around guide pulleys 10 and 11 into an upper wire path 12
which leads on to the next stage of the apparatus, or to a
spooler for finished wire.
The gulde pulley 11 can form part of a speed control
system for one stage of the apparatus and is mounted for
limited movement in the directions of the arrows B.
At the point X where the wire paths cross, a small
clearance is provided between the wires (e.g. a clearance
of 3 centimetres) and this clearance can easily be provided
by slightly angling either or both the guide pulleys 10 and
11.
The air wipe 9 can comprise a chamber surrounding the
wire which is limited at its ends by apertured plates whose
wire-receiving apertures are only slightly larger than the
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cross-section of ~he wire. The ehamber can be fed with
compressed air (e.g. at a pressure of about 30 psig), the
air streams leaving the chamber through the end plates (and
particularly the upstream end plate) removing water from the
surface of the wire.
Figure 2 shows in detail part of the cowl 13 and the
coolant flows arising during a drawing operation. Baffle
plates 22 are disposed within the channel defined by the
cowl 13 and provide spaced-apart weirs to dam back the cool-
ant attempting to be flung radiaIly outwards from the surfaceof the block 1. The baffles slow down the flow of eoolant
within the cowl forcing it back against the block as it
drains past each baffle. In this way a coherent coolant
bath is formed against the surface of the block 1. Flgure
2 also shows the cooIant (indicated at 23) which is trapped
by the wire in the groove 2.
Figure~3 and 4 show one stage in a first embodiment
of apparatus in accordanee with the invention, similar refer-
enee nurnbers 7 but with a prime~ having been used in these
Figures to those used in Figures 1 and 2, where similar
integers are involved.
The main difference between the arrangement in Figures
1 and 3, is that the block 1' in Figure 3 is a narrow capstan
bloek aeeommodating four turns of wire. The groove 2 7 formed
in the block 1' has a tapered side wall 24 onto which the
wire W is led as it leaves the shroud 7'. The inclination
of the side wall 24 and the slight taper of the base 26 of
the groove 2' (mueh exaggerated in Figure 4 and of the
order of ~ in practiee) eause the turns of wire on the
block 1 to progress to the right in Figure 4 as drawing
proeeeds.
The eowl 13' whieh traps the bath of liquid eoolant
against the periphery of the bloek 1' is shown in Figure 4
as a plane areuate plate whieh is elose to the cireumference
of the bloek 1. Upstream of the point seetioned in Figure
4, the eowl diverges from the peripheral surfaee of the block
1' to meet with generall~ triangular side walls to form a
elosed volume 27 whieh beeomes filled with eoolant during
use of the apparatus.
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Since the wire makes four complete turns around the
block 1'~ its lead-off direction is substantially coplanar
with its lead-on direction, so tha~ the air wipe g' is
located to one side of the coolant-filled closed volume 27
in the inlet region of the block 1'.
A coolant drain 28 is located in the lowest point of the
cowl 13' and this drain can be provided with a valve 2g to
set the outflow rate of coolant and ensure adequate filling
of the volume 27 with coolant.
The cowl 13' can be moved in the direction of the arrows
C in Figure 4 to faciliate threading-up of the apparatus.
In the arrangement of Figures ~ and 4, a load cell can
be located at the position marked L, just upstream of the
guide die 4', to control the-speed of the block 1' in known
manner,
Referring now to Figure 5, there is shown two stages ofa
second ~mbodiment of apparatus in accordance with the inven-
tlon. Again similar reference numerals, this time with a
double prime,have been used to designate similar integers.
~eferring to Figure 5, wire W" enters the upstream
stage from the left and passes through a guide die 4", a
soap box 5" and a sizing die 6" before passing into an end-
less groove 2" in a drawing block 1" rotating in the direc-
tion of the arrow. The block 1" is submerged in a bath 29
of water and after making almost three turns around the
block 1", the wire leaves the groove 2" and passes up out
of the bath to an air wipe 9" and over a pulley 11". The
air wlpe 9" completely dries the wire W" in preparation for
its passage through the guide die~ soap box and sizing die
of the next upstream stage.
A shroud 7" is employed on the downstream side of the
die 4", the sleeve being fed with water at its upstream end
so that a moving column 8" of water surrounds the wire as it
leaves the die and travels with the wire into the bath 29.
The column 8" may be induced to turn helically around the
wire to ensure the coherence of the column 8" and to increase
the relative speed between the wire and the coolant in the
column.
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The pulley 11" can be mounted to move in the directions
of the arrows D for speed control purposes in the manner
well known in the wire drawing art. A drain 30 is provided
to permit the bath to be emptied Or water and optionally to
allow continuous circulation Or water throu~h the bath as
wire drawing proceeds.
The bath 29 can be divided (e.g. as shown dotted at 31)
so that each block has its own coolant bath.
