In laparoscopic surgery large instruments cannot be used because they cannot pass through trocars which are typically smaller than 12mm in diameter. For example, retracting an internal organ with a slender instrument is often a difficult task. To remove this limitation, we have proposed “assemblable instruments”, that is, parts are inserted through trocars and assembled inside the abdominal cavity to become a large instrument and we have developed assemblable hands. However they use two trocars for assembling, which require positioning and alignment of two assembled parts. This paper presents a simple three fingered hand whose function is limited to retracting. We propose a much simpler assembling method “single trocar assembling” for the hand. Experimental results verify that the hand can be assembled easily and that it can withstand a force of 25N enough to rectract a pancreas.

This paper proposes an assemblable hand that can be inserted through trocars for robotic hand assisted laparoscopic surgery (HALS). When it is difficult to perform surgery using only slender laparoscopic surgery instruments, surgeons often apply HALS, which makes an incision about 7-8 cm through which their hand is inserted. This is invasive compared with complete laparoscopic surgery. We proposed robotic HALS to replace a human hand with a robotic hand. We previously developed a three-fingered five-degree of freedom assemblable hand. It is challenging to an assemblable hand with more degrees of freedom (DOF) that can be assembled with a simple assembly procedure. This paper presents an assemblable hand with three fingers and nine degrees of freedom-the 3f9d-hand. Its power transmission mechanisms and assembly procedure are completely different from those of our previous 3f5d-hand. The new hand consists of center, right, and left finger units. The center finger unit connects the operational part at its end and the right and left finger units connect to the operational part outside the abdominal cavity. This facilitates assembly and improves safety, which is a significant improvement compared with the previous hand. Although the hand has no wrist joint, its three finger joints play the role of a wrist joint. A preliminary experiment with a plastic model verified that the proposed assembly procedure was feasible and the hand was easily assembled and disassembled.

In laparoscopic surgery, surgeons perform surgery in the abdominal cavity by using only slender instruments that can be inserted through small diameter trocars. When it is difficult to perform surgery by using only instruments for laparoscopic surgery, they often make a 7–8 cm incision through which their hand can be inserted. Clearly this is invasive compared with complete laparoscopic surgery. This paper proposes an assemblable mechanical hand like a human hand that can be inserted through trocars. We already developed a three-fingered three-degree of freedom assemblable hand. The purpose of this paper is to develop an assemblable hand with more degrees of freedom that can grasp/push aside large internal organs and open membranes. The developed hand has three fingers with a total of five degrees of freedom. Its power transmission mechanisms and assembling method are completely different from those of the previous hand. The hand is assembled from body and finger units with an installation tool. The finger unit is fixed to the body unit with only one screw by using the installation tool. To drive the fingers, power is transmitted with cables, gears and shafts. Experimental results verify that the hand can be assembled in a closed space and that it can grasp and push aside various objects.

In laparoscopic surgery, surgeons can use only rod-shaped instruments that can be inserted through a trocar and therefore high technique is required. To overcome this problem, much work has been done to develop multi-degree-of-freedom forceps. However they are still inadequate to grasp, manipulate or push aside large internal organs, like a spleen, pancreas, and liver. This paper proposes mechanical hands with detachable fingers that can be assembled in the abdominal cavity, each of whose parts can be inserted through a trocar. Two types of such three-fingered hands are developed. The three fingers of one are dependently driven and those of the other are independently driven. For each hand, we show fixing and power transmission mechanisms. Power of each hand is transmitted from operator's hand to its fingers by connecting wires with a ball and socket. Experimental results verify that both hands can grasp large and oily objects like internal organs. One goal of this study is to develop simple hands that can be used as a retractor. The other goal is to develop skillful hands that can replace surgeons' hands in hand assisted laparoscopic surgery which is still invasive by making a 7-8cm incision to insert a human hand into the abdominal cavity.