Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
2000-02-03
2001-08-28
Ball, Michael W. (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S085000, C156S086000, C156S381000, C604S264000, C604S523000, C604S509000, C604S096010, C604S101050, C606S194000
Reexamination Certificate
active
06280545
ABSTRACT:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT
The present invention relates to a method of forming a balloon catheter to be used in a percutaneous transluminal coronary angioplasty (PTCA) procedure and/or in a stent implantation into a patient's body lumen.
A balloon catheter has been widely used for vascularization of a coronary artery. In this case, a balloon attached to a catheter is delivered into a coronary artery to enlarge a stenosis, i.e. constriction in the coronary artery. Since a large pressure is applied to the balloon to enlarge the stenosis, the balloon is required to withstand high inner pressure.
Conventionally, a balloon used for a balloon catheter has been made by blow molding method. When the blow molding method is used, as shown in
FIG. 13
, a balloon member
102
having a diameter substantially the same as that of an inner tube member
101
is disposed over the inner tube member
101
. Then, as shown in
FIG. 14
, the inner tube member
101
with the balloon member
102
thereon is placed in a mold
104
, which includes an inner chamber
105
in a shape of an inflated balloon and heating elements
106
.
Thereafter, the mold
104
is heated by the heating elements
106
in the mold
104
, and a gas for blowing the balloon member
102
is supplied from the inner tube
101
. The balloon member
102
is inflated by the gas supplied from the inner tube
101
and entered inside the balloon member
102
through a communication hole
103
in the inner tube member
101
. The balloon member
102
is inflated to abut against the wall portion of the mold
104
as shown in FIG.
15
. Then, end portions
107
,
108
of the balloon member
102
are adhered to the inner tube member
101
by an adhesive or the like. The end portions
107
,
108
of the balloon member
102
may be fixed to the inner tube member
101
before blow molding the balloon member.
In the conventional blow molding method, however, there is a problem. Namely, since the balloon member, which has a shape of a tube member with the small diameter before blow molding, is blown by the gas supplied thereinto to have a shape of the inflated balloon, degree of inflation of the balloon member is different according to the portions of the balloon member, resulting in uneven thickness. Namely, although the thickness of the balloon member before blow molding is substantially constant, the thickness of the inflated balloon member may be partly different. As a result, if high pressure is applied to the balloon member in use, the balloon member may be torn or broken.
Also, in the conventional balloon catheter, the quality of the balloon catheter can be checked only after the balloon member is formed.
The present invention has been made in view of the above problems, and an object of the present invention is to provide a method of forming a balloon catheter, wherein the high quality balloon catheter can be formed easily at a low cost.
Another object of the invention is to provide a method of forming a balloon catheter as stated above, wherein a balloon portion with a constant thickness can be formed without fail.
Further objects and advantages of the invention will be apparent from the following description of the invention.
SUMMARY OF THE INVENTION
In the method of forming a balloon catheter of the invention, a heat shrinkable tube is used. The heat shrinkable tube used in the invention has a predetermined diameter in a normal condition i,e. normal pressure and temperature, and a thickness substantially constant throughout the entire length thereof. When heat is applied to the heat shrinkable tube, a portion where the heat is applied shrinks. The heat shrinkable tube is made of a material same as or similar to a regular material for making a balloon portion of the balloon catheter. Since the process for making the heat shrinkable tube is known in the art, the explanation thereof is omitted herein.
In the invention, the heat shrinkable tube has a first diameter in the normal condition, which is substantially the same as the diameter of a balloon portion of the balloon catheter when it is expanded.
In the method of the invention, a rod member, preferably a metal rod member so that the shrinkable tube when heated does not stick to the rod member, is inserted into the shrinkable tube. Then, at least one part of the shrinkable tube is heated so that the part of the shrinkable tube shrinks to have a second diameter to thereby form an end portion of one balloon portion while a portion away from the end portion has the first diameter as it is. Namely, when the shrinkable tube is heated, a part of the shrinkable tube close to the non-heating portion does not shrink too much, but an end portion of the tube shrinks largely and is disposed onto the rod.
In the invention, two end portions of the shrinkable tube are processed at the same time or different time to have the second diameter by heat shrinking.
Then, the rod member is removed from the balloon portion, and a catheter shaft is inserted into the balloon portion to completely pass therethrough. Thereafter, the two end portions of the balloon portion are fixed onto the catheter shaft, so that the balloon catheter is formed.
In the method of the invention, since the heat shrinkable tube formed already is used, the quality of the balloon portion is assured. Namely, the quality of the shrinkable tube is generally good, i.e. the thickness and strength are substantially constant throughout the entire length thereof. Nevertheless, in case the quality of the shrinkable tube is questionable, the quality thereof can be checked before forming the balloon portion. Thus, in the method of the invention, the high quality heat shrinkable tube can only be used in forming the balloon catheter.
In this respect, in the conventional method, i.e. blow molding method, the balloon portion is expanded in a mold each time. Thus, although the good quality member is used, the quality of the balloon portion formed by blow molding is slightly different in each blow molding. The quality of the balloon can be checked after completion of the balloon. If the quality of the balloon portion is not good, the balloon catheter must be discarded. In the method of the invention, however, since blow molding is not used and the end portions are simply processed to shrink by heating, the balloon portion with high quality can be formed constantly. Thus, the productivity used in the method of the invention is high.
In one embodiment of the invention, two end portions of the balloon portion are formed by heat-shrinking the shrinkable tube. In this case, an outer periphery of a middle portion between the two end portions is insulated from the two end portions, and then, heat is applied so that the two end portions are heated to shrink while the middle portion is insulated from being heated. In this case, a gas may be supplied inside the shrinkable tube before heating to keep a shape of the shrinkable tube.
In another embodiment, after the rod member is inserted into the shrinkable tube, the diameter of one end of the shrinkable tube is reduced or the one end is heat-shrunk. The one end of the shrinkable tube may be fixed onto the rod member by string, tape or other means. Then, a gas is provided inside the shrinkable tube to keep the shape of the shrinkable tube in an inflated condition. Thereafter, a part of the shrinkable tube is heated so that one end portion of one balloon portion and one end portion of another balloon portion are formed at the same time. Namely, a plurality of parts of the shrinkable tube is heated at substantially the same time to form a plurality of balloon portions at substantially the same time.
In this case, heat is allied by heat pads formed of a plurality of heat segments. Namely, the heat segments are disposed onto the rod member through the shrinkable tube while shrinking the shrinkable tube. Preferably, the heat segments are pressed against the rod member to thereby cut the balloon portions away from each other at the same time.
REFERENCES:
patent: 5549552 (1996-08-01),
Ball Michael W.
Kanesaka & Takeuchi
Rossi Jessica
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