:: Literature ::

Schold Machine mixes with Rexroth

by Michael A. Hanley,
Circuit Engineering, Inc.,
Tampa, Florida, U.S.A.
Rexroth Representative

Mixing the unmixable has always been the challenge at Schold Machine Co. in St. Petersburg, Florida, USA. Rapidly changing technologies in the chemical industries create new demands for industrial mixers. The need for larger and more efficient methods of blending these chemicals requires strict control of input horsepower.

Schold Machine builds mixers for everything from glue to gunpowder. One of their most popular machines has been a 'coaxial' mixer. In this design, two concentric shafts operate at various speeds and torques depending upon the material. A low speed hollow shaft hydraulic motor turns the outside shaft to auger the material into the center. The inside shaft turns a high speed shearing blade which does the actual mixing.

Since each material requires a different speed and torque for proper mixing, a variable displacement hydraulic motor was desirable. A Rexroth bent axis piston motor type AA6V55EL was selected for its high efficiencies and ability to be remotely controlled. The proportional solenoid control is integral to the hydraulic motor.

Operator control and flexibility was further enhanced by the use of electronic proportional flow control valves type 2FRE16 to regulate flow from the pumps. Load sensing controls on the double pump type AIOVS63/40, together with the proportional flow control valves, provided an extremely accurate and energy efficient system. The operator can now 'dial in' the required speed and torque.

Rexroth's worldwide capabilities have enhanced Schold Machine's ability to sell their newly patented mixers all over the world.

Fig. 1 shows the complete mixer drive and auger powered by a Rexroth hydraulic motor (on top).

Fig. 2 Hydraulic power station equipped with the Rexroth AIOVS double pump, load sensing controlled.

Fig. 3 A close-up of the Rexroth bent axis piston motor type AA6V 55EL.

Fig. 4 The piggyback version of the Rexroth bent axis piston pump saves space.