Method of continuously processing wire material and device therefor

The present invention relates to a processing method of wire material and a processing device therefor at the times of intending to make the tip of wire materials such as guide wire for catheter thin and flexible by tapering. When the wire material passes through the electrolytic tub, the wire speed is made constant and the current value is controlled, or the current value is made constant and the wire speed is controlled to give the processings such as tapering. For the electrolytic polishing bath, it is desirable to use a mixed bath comprising trivalent alcohol, perchloric acid and monovalent alcohol. The inventive method exerts an effect that the tapering can be given efficiently and yet with high precision compared with the traditional method of mechanical polishing or the method of dipping one by one batchwise into the electrolytic polishing bath.

TECHNICAL FIELD 
The present invention relates to a method of processing wire material and a 
processing device therefor at the times of intending to make the tip of 
wire materials such as guide wire for catheter thin and flexible by 
tapering, and the like. 
BACKGROUND TECHNIQUES 
For the guide wire for a catheter used for interposing into a human body, 
etc., it is required to be interposed easily making the tip portion of 
wire material thin and flexible by tapering. As an example, a portion of 
100 to 200 mm at the tip of wire material of around 0.5 mm.phi. is tapered 
so that the diameter of the utmost tip portion is around 0.12 mm.phi. is 
used. 
Traditionally, this tapering has been made first by mechanical polishing, 
but the mechanical polishing has a drawback of losing the superelasticity 
for the Ni-Ti superelastic alloy used usually as a guide wire for a 
catheter. Recently, therefore, an electrolytic polishing method by batch 
process is adopted, wherein the tip portion of a wire material is dipped, 
for example , into a polishing solution having a composition comprising 
92% of CH.sub.3 COOH and 8% of HClO.sub.4, into a polishing solution 
having a composition comprising 20% of HF and 80% of HNO.sub.3, or into a 
polishing solution having a composition comprising 60% of H.sub.2 
SO.sub.4, 30% of HF and 10% of glycerine. 
This traditional electrolytic polishing method is however a method of 
polishing batch wise by dipping one by one into the electrolytic polishing 
bath while moving up and down manually. Hence, there arise the problems 
that the shape of the tapered portion varies widely and many workers are 
required, thus resulting in a high cost. 
Moreover, traditional electrolytic polishing baths have the following 
problems. Namely, the acetic acid-perchloric acid bath has a strong bad 
smell and gives somewhat poor surface gloss after polishing, and the 
fluoric acid-nitric acid bath has a strong bad smell, gives poor surface 
gloss after polishing and requires high cost for effluent treatment to 
avoid a pollution problem. The sulfuric acid-fluoric acid-glycerine bath 
has no bad smell, but it gives poor surface gloss and requires high cost 
for effluent treatment. 
DISCLOSURE OF THE INVENTION 
The invention has been made as a result of diligent investigations to solve 
such problems and is concerned with a method of continuously processing 
wire material characterized in that, in the method of processing part of 
the wire material by electrolytic polishing, a long wire material is 
passed continuously through the electrolytic polishing bath with a cathode 
installed therein and electricity is turned on only when the processing 
portion passes through said electrolytic polishing bath. 
Here, it is preferable from the point of efficiency that, when the 
nonprocessing portion passes through the electrolytic polishing bath, the 
wire speed is made high. 
Further, the invention is concerned with a device for continuously 
processing wire material characterized in that an electrolytic tub having 
the same length as that of a processing portion of wire material, a wire 
material-advancing device for allowing the wire material to pass through 
the electrolytic tub, a cathode provided in the electrolytic tub, an 
anodic electricity-supply device for wire material and a power source 
generating device are equipped. 
Here, as the shapes of processing portion, for example, tapered portion, 
grooved portion, etc. are intended, and, in order to make this tapered 
shape, grooved shape or the like arbitrarily variable the feeding speed of 
wire material-advancing device is desirable to be variable and the 
generating current of power source-generating device is also desirable to 
be variable. 
Besides, as the composition of wire material, a super-elastic alloy 
comprising 50.5 to 53.0 at % of Ni and the balance of Ti, or a 
superelastic alloy substituted part of Ni and/or Ti in 50.5 to 53.0 at % 
of Ni and 49.5 to 47.0 at % of Ti with any one kind or two or more kinds 
of Cr, Fe, Co, Mo, V, Pd, W and Cu within a range of 0.01 to 5.0 at % of 
each can be used. 
Moreover, as the electrolytic polishing bath to be used for said 
continuously processing device, it is effective to use a bath comprising 
10 to 50 vol. % of trivalent alcohol, 5 to 20 vol. % of perchloric acid 
and the balance of monovalent alcohol. 
And, as the monovalent alcohol, ethanol or methanol is desirable and, as 
the trivalent alcohol, glycerine is desirable. 
Besides, if the investigation is made from the aspects of installation, a 
bath of 80 to 95 vol. % acetic acid-20 to 5 vol. % perchloric acid can 
also be used. 
In the following, the invention will be illustrated in more detail using 
diagrams. 
As shown in FIG. 1, when tapering a wire material 1 while passing it 
through the electrolytic polishing bath, electricity is turned on between 
cathode 3 and electricity-supply roll 4 at the time of point A of wire 
material having reached the inlet of bath and said electricity is turned 
off at the time of point A having reached the outlet of bath (FIG. 2). By 
this procedure, the wire material is tapered in such a shape that the wire 
diameter increases gradually towards both ends making point A as a center 
as shown in FIG. 3. And, the length of the portion to be tapered AC is 
approximately equal to the length of electrolytic polishing bath AB (i.e. 
the length of wire material existed initially in the bath) and the 
distance between A and C and that between A and B are processed almost 
symmetrically. Besides, the diameter of point A becoming the minimum 
diameter of wire material is determined depending on the current to be 
turned on. 
Moreover, by periodically turning on-off the current at a fixed period, a 
long processed material (FIG. 4) can be obtained. Hence, if cutting at 
point A and point A', tapered material at both ends is obtained and, if 
cutting at point A and point D, tapered material at one end is obtained. 
The turning on-off of power source may be performed manually, but it goes 
without saying that it can be automated briefly by using a feedback 
circuit through the detection of winding length. 
It is extremely effective from the point of cost reduction that, when 
passing the portion not to be tapered through the electrolytic polishing 
bath, the wire speed is made high, thus enhancing the productivity. 
Further, the processing device will be illustrated in detail. FIG. 6 shows 
an outline diagram of the inventive device and FIG. 7 shows a partially 
magnified diagram. In FIG. 6 and FIG. 7, numeral 11 is a supply reel, 
numeral 12 is a wire material, numeral 13 is an anodic electricity-supply 
device (diagram shows electricity-supply roll), numeral 14 is an 
electrolytic tub, numeral 15 is an electrolytic polishing bath, numeral 16 
is a cathode, numeral 17 is a wash tub, numeral 18 is a drying device, 
numeral 19 is a wire material-advancing device, numeral 20 is a power 
source-generating device, and numeral 21 is a winding reel, respectively. 
The electrolytic polishing by the inventive device is performed, as shown 
in FIG. 7, in a way that electricity is supplied to anode by anodic 
electricity-supply device 13 provided outside the electrolytic tub, on the 
other hand, a cylindrical electrode formed so as to locate at both sides 
or to envelop the whole circumference of wire material securing a fixed 
distance from the wire material in electrolytic solution (i.e. 
electrolytic polishing bath) is provided to make this the cathode 16, and 
a variable fixed current is turned on by means of power source-generating 
device while allowing the wire material to run at a constant or variable 
appropriate speed by means of wire material-advancing device 19. Thereby, 
the tapering in an arbitrary shape can be achieved. 
Since the tapering length is a contacting length of electrolytic solution 
with wire material, the length of the electrolytic tub is altered for 
fitting to the desired tapering length. For Controlling the shape of 
taper, it is only necessary to experimentally determine beforehand through 
the change in said feeding speed of wire material or the change in 
electrolytic current so that the desired shape can be achieved. 
Next, the explanation will be made in detail about the electrolytic bath. 
1 Case of electrolytic polishing bath comprising perchloric acid-trivalent 
alcohol and monovalent alcohol 
The reason why perchloric acid was restricted to 5 to 20 vol. % is because, 
in the case of being under 5 vol. %, the stability of solution is damaged 
due to the consumption during electrolytic polishing. And, if being over 
20 vol. %, safety becomes problematic and the surface gloss is damaged. 
Moreover, the reason why trivalent alcohol was restricted to 10 to 50 vol. 
% is because of that, in the case of being under 10 vol. %, the viscosity 
of both is low and the smoothness of surface is poor and, if being over 50 
vol. %, the viscosity is too high resulting in difficult agitation of bath 
and generation of color unevenness. 
As the monovalent alcohol, methanol or ethanol is excellent from the points 
of availability and viscosity. 
As the trivalent alcohol, glycerine is excellent from the points of cost 
and availability. 
2 Case of electrolytic polishing bath comprising acetic acid and perchloric 
acid 
The reason why perchloric acid was restricted to 5 to 20 vol. % is because, 
in the case of being under 5 vol. %, the stability of solution is damaged 
due to the consumption in electrolytic polishing bath and, if being over 
20 vol. %, the safety becomes problematic and the surface gloss is injured 
.

BEST EMBODIMENT TO PUT THE INVENTION INTO PRACTICE 
For illustrating the invention in more detail, it will be described based 
on the following examples. 
Example 1 
Using a 0.48 mm.phi. NiTi alloy wire (Ni:Ti=50 9:49.1 at %), the 
electrolytic polishing was conducted under following conditions: 
______________________________________ 
(1) Composition of electrolytic 
Ethanol 72% 
polishing bath Glycerine 20% 
Perchloric acid 8% 
(2) Bath temperature 
25.degree. C.-30.degree. C. 
(3) Electrolytic tub 
Length 125 mm 
(4) Wire speed Constant speed of 33 mm/min 
(5) Total current turned on 
1.2 A 
(6) On-off timing 
According to FIG. 1 and FIG. 
2 
______________________________________ 
The shape of wire material thus obtained is shown in FIG. 5. As evident 
from FIG. 5, smooth tapering is given for the shape of taper obtained 
according to the invention. 
Example 2 
Using a 0.48 mm.phi. NiTi alloy wire (Ni:Ti=50.9:49.1 at %), the 
electrolytic polishing was conducted under following conditions: 
______________________________________ 
(1) Composition of electrolytic 
CH.sub.3 COOH 92% 
polishing bath HClO.sub.4 8% 
(2) Bath temperature 
25.degree. C.-30.degree. C. 
(3) Electrolytic tub 
Length 125 mm 
(4) Wire speed Constant speed of 33 mm/min 
(5) Total current turned on 
1.2 A 
(6) On-off timing 
According to FIG. 1 and FIG. 
2 
______________________________________ 
The shape of wire material thus obtained is shown in FIG. 5. As evident 
from FIG. 5, smooth tapering is given to the tapered wire material 
obtained according to the invention. 
Example 3 
Employing a continuous tapering device shown in FIG. 6, the tapering of 
Ni-Ti alloy (Ni:Ti=50:50 at %) superelastic wire material was conducted. 
Said 0.48 mm.phi. NiTi alloy wire material was wound around supply reel 11 
and it was rewound around winding reel 21 changing the feeding speed of 
wire material by wire material-advancing device 19 as shown in FIG. 8. The 
turning-on of electricity was made by anodic electricity-supply device 13 
and cathode 16. The electrolytic polishing conditions are as follows: 
______________________________________ 
(1) Composition of electrolytic polishing 
Ethanol 72% 
bath Glycerine 20% 
Perchloric acid 8% 
(2) Bath temperature 25.degree. C.-30.degree. C. 
(3) Electrolytic tub Length 125 mm 
(4) Wire speed 0.28 m/min-0.47 m/min 
(5) Total current turned on 
2A 
______________________________________ 
The shape of wire material thus obtained is shown in FIG. 9. 
Example 4 
Similarly to Example 3, however, making the feeding speed of wire material 
constant, the turned-on current was increased gradually as shown in FIG. 
10. 
The tapered wire material thus obtained was same as one shown in FIG. 9. 
As evident from FIG. 9, smooth tapering is given to the tapered wire 
material obtained by the inventive device. 
Example 5 
Employing a continuous tapering device shown in FIG. 6, the tapering of 
Ni-Ti alloy (Ni:Ti=50.9:49.1 at %) super-elastic wire material was 
conducted. 
Said 0.48 mm.phi. NiTi alloy wire material was wound around supply reel 11 
and it was rewound around winding reel 21 changing the feeding speed of 
wire material by wire material-advancing device 19 as shown in FIG. 8. The 
turning-on of electricity was made by anodic electricity-supply device 13 
and cathode 16. The electrolytic polishing conditions are as follows: 
______________________________________ 
(1) Composition of electrolytic polishing 
CH.sub.3 COOH 92% 
bath HClO.sub.4 8% 
(2) Bath temperature 25.degree. C.-30.degree. C. 
(3) Electrolytic tub Length 125 mm 
(4) Wire speed 0.25 m/min-0.47 m/min 
(5) Total current turned on 
2A 
______________________________________ 
The shape of wire material thus obtained is shown in FIG. 9. 
Example 6 
Similarly to Example 5, however, making the feeding speed of wire material 
constant, the turned-on current was increased gradually as shown in FIG. 
8. 
The tapered wire material thus obtained was same as one shown in FIG. 9. 
As evident from FIG. 9, smooth tapering is given to the tapered wire 
material obtained by the inventive device. 
Moreover, the comparison of electrolytic solutions is as follows: 
Example 7 
Employing a 1 mm.phi. Ni-Ti alloy (50.9-49.1 at %) wire material and using 
a bath comprising 50 vol. % of methanol, 40 vol. % of glycerine and 10 
vol. % of perchloric acid, the electrolytic polishing was conducted for 10 
minutes at ambient temperature applying a voltage of 25 V. 
Example 8 
Employing the same wire material and using a bath comprising 30 vol. % of 
ethanol, 50 vol. % of glycerine and 20 vol. % of perchloric acid, the 
electrolytic polishing was conducted for 10 minutes at ambient temperature 
applying a voltage of 25 V. 
Example 9 
Employing the same wire material and using a bath comprising 8 vol. % 
perchloric acid-92 vol. % acetic acid, the electrolytic polishing was 
conducted for 10 minutes at ambient temperature applying a voltage of 25 
V. 
Comparative example 1 
Similarly, the experiment was conducted in a bath of HF:HNO.sub.3 =1:4 
(molar ratio). 
With respect to above-mentioned Example 7-9 and Comparative example 1, the 
smell of bath and the surface situation were observed and, in addition, 
the dissolution rate of wire material was determined, the results of which 
are put down in Table 1. 
TABLE 1 
______________________________________ 
Surface Dissolution 
Situation 
Smell of bath 
rate 
______________________________________ 
Example 7 .circleincircle. 
No 12 .mu.m/min 
Example 8 .circleincircle. 
No 14 .mu.m/min 
Example 9 .largecircle. 
Yes 10 .mu.m/min 
Comparative 
X Yes 8 .mu.m/min 
example 1 
______________________________________ 
As evident from Table 1, in the examples of the invention, the surface 
situation was good, no smell of bath was felt except Example 9 , and the 
dissolution rate was also as fast as 12 to 14 .mu.m/min . 
Besides, in Example 9, the smell of bath was felt, but the surface 
situation was good, thus it is possible to use, if investigating from the 
aspects of installation such as de dorizing device. 
On the contrary, in comparative example, the surface situation was not 
good, bad smell was felt strongly, and the dissolution rate was slow. 
Utilizability in the industry 
As described above, in accordance with the invention, the change in wire 
diameter in the longitudinal direction of wire material can be controlled 
arbitrarily and the processings such as tapering and joggling can be given 
efficiently and yet with high precision. 
Moreover, for the electrolytic polishing bath of the inventive processing 
device, if using monovalent alcohol and trivalent alcohol, no bad smell is 
felt and they are suitable for efficiently obtaining the polished material 
of Ni-Ti alloy with good surface situation.