Voluntary Closing and Locking is Superior.

The ProHensor RCS is a voluntary closing and locking terminal device. The locking action makes it unique and functionally superior. Although it is a mechanical device, the voluntary closing modality gives the user fine grasp control, and when coupled with automatic locking, unparalleled operation. By design, it outperforms all other body powered terminal devices — voluntary opening, or voluntary closing.

Using a wearable cable and harness system, the user initiates a grasp by applying force to the lever arm of the ProHensor RCS terminal device. The cable force overcomes an opposite internal torsion spring force, closing the device fingers. During the process of closing, a clutch mechanism with a wedge cam, slides along a semi-circular frictional surface. When the user releases tension on the cable, a small spring forces the wedge cam between the mechanism and the frictional surface impeding the device and locking it closed. This action is automatic and can happen anywhere along the path from fully open to fully closed. To unlock and open from any closed position, the user must apply a momentary force, on the cable. This actuates a cam release within the device. After the burst of applied force, the user releases tension on the cable allowing the torsion springs to return the device to its default open position. Once the device fully opens, the clutch cam resets into position for locking again on the next closure. 

There are three main reasons why the APRL voluntary closing and locking terminal device is superior to any other type of device. 

First, the device is voluntary closing. The user is capable of applying variable force to grasp an object, from a light grasp for holding an egg, to one where enough force is required to hold a chisel. This prehensor action allows the user to “feel” the amount of force applied and therefore a connection with the grasping process. 

Second, the action of reaching out to close the device for grasp, more closely relates to the process used by a biological hand when grasping objects. Human hands are normally “open” and therefore prepared for grasping. 

Third, and most importantly, once force is applied to the object, the locking system will maintain grip force on that object until the user releases the device. This is the greatest advantage for users. They can apply enormous force through the cable system when a tight grip is necessary, but, are free to release tension on the cable without releasing their grip. This lessens user fatigue when holding objects for long periods of time.