Design of a Rotating Assembly Fixture for Power Take-Off Units

Power Take-Off (PTO) units are widely used in the industry to transmit power from a prime mover such as a running engine to another equipment or machine. As a power transfer equipment, PTOs find applications in various industries ranging from agriculture to aviation. A typical PTO unit encompasses various machine elements such as shafts, bearings, clutch disks, springs and flanges, and could weigh around 500 lbs. or more. In this work, a rotary assembly fixture is proposed by the Midwestern State University (MSU) Senior Design team to aid in the assembly of the PTO units produced by the WPT Power Corporation, a local manufacturer for power transmission equipment in Wichita Falls, TX. In their current manufacturing processes of PTO units, WPT Power employees must repeatedly lift units onto an elevated stand with an overhead hoist lift, work on one side of the unit, lift it off of the stand and onto the floor, and manually roll the units over to then lift them back onto the stand to work on the opposite side. This process is slow and poses safety risks to workers. Inspired by the commercially available products, patents, and the relevant technology, a conceptual design idea has been proposed to WPT. The proposed fixture allows for the machine to stop at numerous angles, rotate smoothly, and withhold the weight and forces of three PTO units at all angles without complicating the assembly. Following the approval of the conceptual design by the WPT Team, the detailed design of the parts have been made to prevent failure under combined loading scenarios such as shear, torsion, buckling, and bending. Structural safety simulations are also performed in ANSYS software to validate the theoretical design calculations to provide evidence that the calculations performed were correct and satisfied the safety factor of 8, which is the criterion set by the WPT Power Team. A two-handed operation pneumatic system has been designed to ensure the operator is a safe distance from moving parts to maintain safety for use of this fixture. A 5 port 3 position exhaust center spring centered directional control valve used in series with a 3 port 2 position spring offset normally closed push button valve creates the two-hand circuit that controls the direction and motion of the pneumatic motor. The pneumatic circuit also contains manifolds for connecting various air powered tools that will be used during the assembly of PTO’s, as well as a regulator-dryer to keep the appropriate air pressure needed for the air motor. The exhaust port of the air motor includes a combination flow control valve and exhaust muffler to control both the speed of the rotation as well as reducing the ambient noise created by the motor during use. The fabricated product has been delivered to WPT Power by the end of April 2020.