Prosthetic Arm Force Reducer Team 1 – Halliday's ... - Ohio University

Fig. 4.1.6 – Utah Arm 3
MAGNUM Parallel Grippers are used in the robotics industry. They utilize third-generation
Zaytran technology and are made of tough, corrosive resistant materials. The MAGNUM
parallel grippers are used in a variety of environments from welding, grinding, machining, clean
room, disk fabrication, and food processing. The force to weight ratio of these grippers is in
excess of 200. The gripper consists of two independent systems; force and synchronizing double
helix. The MAGNUM Parallel Gripper mechanism is double sealed to ensure isolation from the
environment. In harsh environments the double seals protect the parallel gripper from
contamination that could lead to failure. The MAGNUM Parallel Grippers are shown in use in
Fig. 4.1.7.
Figure 4.1.7– Zaytran: MAGNUM Parallel Grippers
A vector is described by its magnitude and direction. Vector prehensors (Fig. 4.1.8) yield a
variable gripping force by varying the direction of the rubber band closing force yet keeping its
magnitude constant. When the rubber band angle is 90 degrees, grip force is maximized. As the
band angle decreases, the torque applied by the band about the pivot decreases. Currently, the
best design to date uses elastomer bands will last for more than 70,000 cycles at the highest grip
force setting. Bands are contained within the casing to shield the elements. With the current
design, the elastomer bands can be replaced by an individual with Phillips’ head and flathead
screwdrivers in about 10 minutes. At the highest setting, grip force begins at about 11 lbs and
gradually rises to nearly 20 lbs as the hooks are opened. There are 11 intermediate settings that
provide a choice of grip force levels between these two extremes.
11