Smith Precision Products
1299 Lawrence Drive
Newbury Park, CA 91320

Phone: (805) 498-6616
Fax: (805) 499-2867
Product Design - Balanced-LoadingFebruary 22 2017

How Does Balanced-Loading
in the Smith 3-Gear Pump Work?

  1. Liquid first enters the inlet of the pump, shown as blue in the upper left corner of the pump main housing. It is also directed within the pump to the bottom right port, also shown as blue.
  2. As the drive gear in the center rotates in a counterclockwise direction, the low pressure blue liquid is directed into the spaces between the gear teeth and transferred to the red ports, as shown. The velocity of the liquid entering the gear teeth spaces is carefully matched with the speed of the gear set to minimize changes in velocity and directional changes of the liquid, thus minimizing the pressure drop in the pump. Gear pockets are designed to insure a pressure gradient is present around the outside diameter of the idler gears to suppress cavitation and maximize the transfer rate of the pump.
  3. It is the design and efficiency of the non-contacting side of the gear teeth (in the Red Zones) that largely determines the ability of the pump to develop pressure. Permissible wear on the leading side of the gear teeth does not compromise this performance characteristic of the Smith 3-gear pump. The red ports are also integrated within the pump (high pressure).
  4. It is important from a loading standpoint that the drive gear is exposed to a neutral load, eliminating the necessity for another ball bearing to support the other end of the drive shaft (which would also add another mechanical seal). Given that the schematic uses color to indicate pressure, the symmetric colors surrounding the drive gear illustrate that the drive gear is balanced.
  5. As high pressure develops in the red ports, liquid maintains velocity and flows out of the pump through the outlet port shown as red in the upper right corner.
  6. Secondary gear housings can be added to the main housing shown and are internally ported to match those of the main housing. The addition of a secondary gear housing is not to boost the pressure capability of the pump, but rather to increase the volumetric flow rate of the pump.

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