External gear pumps are the most popular pumps used in modern hydraulic systems. They feature versatility, strength and long life. Their simple construction ensures cost effective purchasing and service. Thanks to these basic concepts, coupled with ever improving product design and features, result in a quality product manufactured to the very highest standards. Due to the many years of research and experience, accurate material selection, rigid production process and rigorous testing on all aspects of the product range, enables Marzocchi gear pumps to operate under extreme working conditions and transmit high hydraulic power. In addition Marzocchi pumps are produced with good mechanical and hydraulic efficiency, low noise level and their compact dimensions give a low weight too power ratio. A gear pump usually consists of a gear pair supported by two aluminium bushes for groups 0.25, 0.5 and 1P, or bushes with plain bearings coated with anti-friction material for groups 1, 2, 3 and 4, a body, a securing flange and a cover. Shaft of the driving gear projecting beyond the flange mounts a twin-lip seal ring (the inner lip being a seal, the outer lip being a dust seal) for groups 0.25, 0.5 and 1P, or two opposed single-lip seal rings (the outer being a dust seal) for groups 1, 2, 3 and 4. Pump body, flange and cover are made of special high-resistant aluminium alloys for minimized deformation even when subject to high pressure, be it continuous or intermittent or peak pressure. The body is profiled by means of extrusion, whereas flange and cover are obtained by means of die-casting (gravity die-casting for some models). Gears are made of special steel. Their manufacturing process includes case-hardening and quench hardening. The gears are ground and fine finished so as to have a high degree of surface finishing. Proper tooth profile design and geometric proportions ensure low pulsation levels and low noise levels during pump operation. Bushes are made of special low-friction and high-resistant aluminium alloy and manufactured from die-casting. Special compensation zones onto flange and cover, insulated by special seals with anti-extrusion rings, allow fully free axial and radial movement to the bushes, which is proportional to pump operating pressure. In this way, internal leakage is dramatically reduced, thus ensuring very high pump performance (both in terms of flow and overall) and proper lubrication to the moving pump parts. Gear Pump Basic Design - simple construction, long and useful life. Basic pump parts 1 - Drive gear 2 - Driven gear 3 - Bushings 4 - Body 5 - Flange 6 - Cover 7 - Rotary shaft seal 8 - Compensation seals 9 - Anti-extrusion seals 10 - Circlip
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