Stepper motor driven pump description

The Lee Company Variable Volume pumps are designed to provide a convenient and reliable means of moving and metering fluids in precision systems. Compact in size, LPV pumps are ideal for replacing syringe and peristaltic pumps in most applications. The variable dispense volume provided by the LPV pumps also offers greater system design flexibility. The LPV pump is actuated by a stepper motor, which is directly connected to a precision piston by means of a precision screw. Conventional motor controllers available from a variety of sources can be used to control the stepper. The pump itself is an open-loop device. A typical configuration of an LPV pump is depicted below.

Product Description & Operation
The LPV pump is operated through actuation of the stepper motor. Upon actuation, the stepper motor armature rotates in finite angular steps. This rotation is converted to linear motion through a threaded nut at the central axis of the motor armature. The nut engages a threaded shaft, which is splined to preclude rotation. As the armature turns, the shaft is moved in and out, depending upon the direction of rotation. The shaft is connected to a piston made of yttrium-stabilized tetragonal zirconia polycrystal ceramic (YTZP). Ground and polished to be extremely precise and smooth, the YTZP piston is an important key to the reliability of the LPV pumps. Moving in and out of a chamber, the piston displaces fluid at a rate determined by the motor controller.

Leakage and contamination of the motor are prevented by a ring seal around the piston and chamber. The ring seal is made of ultra-high molecular weight polyethylene (UHMWPE). This material possesses a superb balance of inertness, wear resistance, and lubricity, making it ideal as a seal material. In addition, the ring seal is backed up by a non-wetted radial spring, to compensate for any wear or thermal changes that may occur.

The combination of mechanical simplicity, engineered materials, and quality manufacturing make the LPV pump accurate, precise and reliable.

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For more information, please send us your application information via our ASK LEE service. Or contact our application engineers in the USA at 1-800-LEE-PLUG or our representatives around the world.
Copyright 07/2002 by The Lee Company, USA
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