1. Field of the Invention
The present invention relates to a medical instrument such, for example, as a forceps, a scissor-type instrument or needle holder, with a pair of distal jaws, a proximal handle which actuates gripping motion to the jaws, and a means for limiting the holding force of the jaws to a predetermined maximum value.
2. Description of the Prior Art
German Patent document DE-A 36 01 166 discloses a forceps for gripping tissue of a patient. The forceps has a fixed jaw and a movable jaw, the fixed jaw being connected to a fixed grip and the movable jaw being connected to a pivotable grip. To limit the compressive force that the jaws can exert on the tissue, the pivotable grip is divided into two pieces --an upper and a lower piece. The two pieces are articulated or joined to one another and supported against each other by a spring member. In operation, when the applied pressure exceeds a predetermined value, the lower piece becomes deflected relative to the upper piece so that the pivotable grip can no longer pivot. However, upon further movement of the pieces towards each other, the holding force of the jaws increases, depending on the stiffness of the spring member. Consequently, this increased holding force could ultimately damage, perforate or sever the tissue held between the jaws.
German Patent document DE-A 40 10 775 discloses a surgical forceps having a fixed jaw and a movable jaw, which are connected to a fixed grip and a pivotable grip, respectively. The pivotable grip consists of two parts in alignment with each other. The two parts are unreleasably connected to each other by a spiral spring element. Detent elements or pawls are provided on the two parts of the pivotable grip, which are releasably engaged with each other. The holding force applied by the pivotable grip cannot be limited to a predetermined value. Consequently, the surgical forceps can damage blood vessels, tissue, or organs if a user inadvertently applies an excessive force during a surgical operation or procedure.