A.T.I.s Crescent Gear Pump (Crescent Pump on Aerospace Steroids)

THIS DOCUMENT IS THE PROPERTY OF A.T.I. AND IS DELIVERED ON THE EXPRESS CONDITION THAT IT IS NOT TO BE DISCLOSED, REPRODUCED IN WHOLE OR IN PART, WITHOUT THE WRITTEN CONSENT OF A.T.I.

8,000 RPM APU Size to 30,000 RPM Miniature, Aerospace Applications.

2.75 gpm @ 43Kft altitude inlet, 8,300 rpm

.5 gpm @ 30Kft altitude inlet, 30,000 rpm

A.T.I.s Internal Gear Crescent Pump (Crescent Pump on Aerospace Steroids)

Up to

Introduction Armstrong Technology Inc. has developed a Crescent Gear Pump to

operate at high speeds and ultra low inlet pressures for use in Air Turbine Starter and Gas Turbine lubrication systems.

Design ConceptAerospace Crescent Gear Pump;

This design uses a gear profile optimized for a very small envelope to perform at extreme speeds with a cavitating inlet.

Gear Form is a true involute ON BOTH parts. The involute form provides a positive rolling action and does not require post surface treatments (carburizing, nitriding or induction hardening)

Gears ARE NOT a matched set. Centered drive shaft and pump element stacking and/or Gear/Shaft

combinations. The multi-toothed gear elements also produce relatively high

frequency, low amplitude pressure pulsations. The serious housing fretting problems encountered with lobe-type

pump designs will also be abated with this concept. Gear Material, 4340 per AMS 6415, 38-42 HRc, NO surface

Treatment, has been the standard material selection for Aerospace Gear Pumps for the last 40 years.

Note: the Inner Gear/Shaft is Heat Treated to 50 55 HRc. On the ATS application, the shaft is acting as a bearing journal and requires the increased hardness.

Positive displacement pumps

Internal gear (Crescent) pump design.

Internal gear (Gerotor) pump design.

External gear pump design.

INTERNAL GEAR PUMP has only two moving parts a "gear-within-a-gear." Power is on the rotor gear. As the gears mesh, liquid is drawn into the pump, filling the spaces between the gear teeth. Liquid moves smoothly around the crescent and is forced out at the

discharge port by the meshing of the gear teeth, as indicated by direction arrows in diagram.

Standard (older technology) Gear Pumps

Sealing between the Inlet & Outlet is achieved by the Gerotor Form Clearance.

GEROTOR:

PROPRIETARY GEAR GEOMETRY, UNABLE TO USE STANDARD GEAR INSPECTION, ONLY A FEWSUPPLIERS. GEARS ARE A MATCHED SET.

STANDARD GEAR GEOMETRY, STANDARD GEAR INSPECTION, MULTIPLE SUPPLIERS. GEARS ARE NOTA MATCHED SET.

Sealing between the Inlet & Outlet is achieved by the CrescentCRESCENT:(NOTE: USES SAME GEAR FORM AS GEAR PUMP.