When laparoscopic surgery is performed, polymer clip blood vessel ligators are widely used to prevent bleeding and secure surgical vision. However, long-term use of such ligators can cause many structural problems, especially in the jaw part where the clip is mounted directly to the blood vessel. For example, jaws of the ligation device might be opened above the design value and upper and lower jaws might be twisted against each other. In addition, buckling or bending deformation can easily occur at the tip of the inner shaft. Due to these problems, the ligation machine cannot ligate the clip properly, which might lead to a medical accident. Therefore, in this study, the design was changed to improve these problems by increasing the pin diameter and contact surface, applying a double pin structure, and changing the structure of the shaft tip. As a result, the modified model showed 12.5% and 10.2% improvements in opening and twisting stiffness compared to the initial model with 7.2% and 58% improvements in critical buckling load and bending stiffness, respectively.

Laparoscopic surgical instruments have been used widely since 1980s and they are still important tool to the medical field as the surgical robot systems spread. In this study we devised three types of motorized mechanism to reduce the user hand fatigue. We detailed the mechanism of each type and compared the performances with several indices such as a bending angle, response time and number of mechanical components. And also we show the movement relationships among the jaw joint, passive gimbal set and motors in the case of MPDG (Motor Drive with a Push Disk and Driven Disk of Gimbal Mechanism) type during the typical jaw joint motions. MTPS (Modified Two Parallel Semicircle Guide Mechanism) type excels others in response time and number of components while showing the increase of load and kinematic occlusion during the diagonal movement. MBDG (Motor Drive with a Ball-Screw, Link and Disk Type Gimbal Mechanism) type shows the medium level bending performance with slow response time and large number of components. Lastly MPDG type excels in jaw joint bending performance with an unstable rotation motion transfer between pushing disk and driven disk at the large disk rotation angle.