Molitech hydraulic motor design

Introduction

The MOLITECH Hydraulic Motor design was patented by Joseph Molitorisz June 27, 1993 under US Patent Number 5,222,427 and further protected by current and subsequent patents pending.

The interactive twin-rotor angular-piston concept of the MOLITECH hydraulic motor design provides practical technological solution to medium pressure, high torque, high efficiency drive for general industrial, marine and aircraft hydraulics. The performance capabilities of the hydraulic motor were proven in extensive testing under laboratory conditions.

Technical description

The motor employs two interacting rotors, contained and bearing-mounted in a common housing. The axes of rotation of the rotors intersect at 90° angle. The rotors have a plurality of piston holes in equal angular distribution on identical radii and parallel to their axes of rotation. The pistons are angular, and are inserted into corresponding holes of both rotors, mechanically interconnecting them

When the pistons are subjected to fluid pressure they are displaced axially within the piston holes. Due to the angularity of relative axial position of the rotors the linear axial displacement of the pistons in one of the rotors is directly converted into rotational motion of the other rotor. The action of the angular pistons on both rotors may be considered as a "wedge effect" producing simultaneous synchronous rotation of both rotors. For proper operation at least three pistons are necessary, pressurized and released sequentially within two opposite 180° rotational phases of the rotors.

As the rotors turn, the position of the longitudinal axes of the piston holes changes relative to the plane of intersection of the rotational axes of the rotors, resulting in changing length of the torque arm on which the linear displacement of the pistons in one of the rotors produces the rotation of the other rotor.

For optimum utilization of the hydraulic motor capabilities nine pistons are applied. The torque arm has a minimal length next to the plane of intersection, reaching maximum at the mid-point of the 180° phase. This geometrical and mechanical relationship between the two rotors provides optimum conditions for direct conversion of the linear displacement of the pistons into the rotational displacement of the rotors.

Not considering the frictional losses, which under the pressurized lubrication of the pistons is minimal, the conversion at the mid-point where the length of the torque arm is equal to the radius on which the piston holes are arranged on the rotors, and where the forces from the pressurized piston act perpendicular to the torque arm, is 100% efficient.

None of the commercially available axial piston hydraulic motors have such direct and efficient means for converting the linear displacement of the reciprocation pistons into continuous rotational motion of the rotor. The axial position of the pistons in the rotor holes changes with the rotational position of the rotors. In the 180° pressurized phase the displacement of the pistons is generated by the fluid flow under pressure. In the opposite 180° rotational phase the displacement of the pistons is in the opposite direction, expelling the fluid from the piston holes. A stationary valve controls the flow of the pressurized and expelled fluid.

To achieve the desired volumetric efficiency in axial-piston type hydraulic motors the typical diametrical tolerance between the pistons and rotor holes is at or less than 0.001 inch. Maintaining such close tolerance in an angled-axis type motor requires highly exact manufacturing precision. The Molitech design overcomes that requirement by applying temperature and pressure-responsive sealing plugs.

The Molitech hydraulic motor was originally developed for marine propulsion applications, including bow-thruster. This application allows a single power source to operate several output motors without mechanical power transmission. There is a tube-encased, dual-propeller design with two motors connected parallel in a hydraulic circuit that provide dual-stage, high energy, high water velocity output, producing water-jet type propulsion.

Another unique design and operational feature of the Molitech hydraulic motor in industrial application is the availability of two output shafts, delivering identical speed and torque. Such a feature is significant in applications where fully synchronized drive with identical speed and torque are desired. With its high starting and running torque the motor has numerous industrial applications. The twin rotor design provides dual speed and torque operation. Pressurizing both rotors delivers high torque, pressurizing only one rotor at the same flow rate delivers high speed.

Comparative analysis

Comparative analysis of the axial piston hydraulic motors proves significant advantages of the twin-rotor MOLITECH design. With the interactive angular piston design the swash plates are eliminated. The 14° to 40° angularity of the swash plates brings inherent inefficiency to the conversion of the linear displacement of the pistons to continuous rotation of the rotors. In the MOLITECH hydraulic motors the equivalent angle is 90°, providing the highest possible mechanical efficiency. With the elimination of the swash plates, sliding shoes and the related components significant mechanical simplification is achieved.

For further in formation, contact Phillip K. Parson at Hydraulic Concepts Inc.
Telephone: 360-779-0915
Email: phillip_k_parson at attbi dot com

"This book has the potential to save many organizations lots of money. It should be on the bookshelf of every engineer, supervisor, planner and technician that deals with hydraulic equipment... it's worth its weight in gold." Find out more Alexander (Sandy) Dunn Plant Maintenance Resource Center

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