The present invention relates to medical catheters, and relates more particularly to an integrate-forming silicone formed of an even outside diameter balloon catheter which comprises a shaft having a conical tip, and a sheath made around the shaft and disposed in flush with the conical tip. The sheath has an inflatable section which forms into a balloon that can be inflated to hold down the catheter in position when the catheter is inserted into an organ of the patient's body and deflated to an original even outside diameter after using for a painless in-out operation.
For example, if a patient cannot discharge urine because of a certain disease, an instrument such as a urethral catheter must be used and inserted through the urethral into the urinary bladder to carry urine away from the urinary bladder. In order to hold down the urethral catheter in the urinary bladder, a positioning means is required. FIGS. 1 through 3C-3C show a urethral catheter according to the prior art. The urethral catheter comprises a shaft with a balloon 10, having one end terminating in a plug segment 11 and an opposite end terminating in a three-way drain unit 12, which comprises an intermediate drainage and irrigation hole 22, and a bifurcated funnel 23 and 29. The bifurcated funnel has one end fitted with a valve for balloon inflation and the other end for medicine administration. The drainage and irrigation hole 22 is for urine drainage and irrigation shaft. One branch tube 23 is connected to an inflation lumen 24, which is disposed within the shaft 10. The inflation lumen 24 has an opposite end connected to a valve 19 in the plug segment 11. The plug segment 11 is connected with a conical tip 11'. A balloon 27 is mounted around the shaft 10. The inflation lumen 24 has an outlet communicated with the inside space of the balloon 27. When the urethral catheter is inserted through the urethra into the urinary bladder, a solution can be filled through the branch tube 23 and the inflation lumen 24 to the balloon 27, causing the balloon 27 inflated and stopped against the inside wall of the urethra, and therefore the tip of the urethral catheter is maintained in position for guiding urine out of the urinary bladder. This structure of urethral catheter is complicated to manufacture because the balloon 27 is separately made and then bonded to the shaft. Before the installation of the balloon 27, the shaft 10 must be drilled with a through hole to impart a passage between failure will occur. Because the balloon is bonded to the shaft 10, an enlarged step is formed in the connecting area between the balloon and the shaft. This enlarged step will rub against the inside wall of the urethra to cause pain when the urethral catheter is inseted into the urethra. Furthermore, the complicated manufacturing process of this structure of urethral catheter greatly increases the manufacturing time and cost.
U.S. Pat. No. 5,137,671 (see FIG. 4) discloses a method of making a balloon catheter. This method includes the steps of providing a tube having an outer surface and a plurality of lumens including first and second lumens, the tube including a first lumen access-opening in the outer surface communicating with the first lumen; simultaneously coating a first portion of the outer surface with an amount of a bond preventing agent effective to prevent bonding to the first portion of the outer surface and plugging the first lumen access opening; and subsequently coating a second portion of the outer surface and the coating of bond preventing agent on the first portion of the outer surface with a polymetric bonding composition, wherein a resilient overcoat layer is created which is fixed to and integral with the tube proximate the second portion of the outer surface and free from adherence to the tube proximate overcoat layer is created which is fixed to and integral with the tube proximate the second portion of the outer surface and free from adherence to the tube proximate the first portion of the outer surface. However, a balloon catheter made according to this method still cannot eliminate the aforesaid problem because the balloon portion of the overcoat layer is not disposed in flust with the exterior surface of the shaft of the balloon catheter (see FIG. 4).