Endoscopic biopsy forceps instrument having a constant force spring

Abstract

A biopsy forceps instrument includes a flexible coil having one or more pull wires extending therethrough, a clevis coupled to the distal end of the coil, a pair of forceps jaws mounted in the clevis and coupled to the distal end of the pull wire(s), and a proximal handle coupled to the proximal ends of the coil and the pull wires. The handle includes a slotted shaft and a displaceable spool having a cross member which extends through the slot. The shaft is coupled to the coil and the cross member is coupled to the pull wire(s). According to the invention, at least one constant force spring is provided between the shaft and the spool and biases the spool in the proximal direction in order to maintain the jaws in a closed position. According to a presently preferred embodiment of the invention, a pair of flat wound spiral springs are provided with the free flat ends of the springs being coupled to a proximal portion of the shaft. The distal portion of the spool is provided with a pair of cavities in which the spiral portions of the springs reside and a pair of grooves are provided on the interior of the spool through which the flattened spring extends. Alternative embodiments of the invention include one or two springs with the free flat end(s) coupled to either the spool or the shaft and the wound spiral end captured in a cavity or mounted on an axle.