GB1331850A - Self regulating gear pump - Google Patents

Abstract

1331850 Gear pumps FIAT SpA 10 Nov 1971 [17 Nov 1970] 52265/71 Heading F1F [Also in Division G3 ] In an hydraulic gear-pump comprising two pairs of gears A 1 , A 2 operating in parallel and having common inlet and outlet conduits 4, 5, co-axial main and pilot spool-type valve-members 21, 42 operate so as to bye-pass the gears A, when the outlet pressure rises to a predetermined value. The valve members are lodged in a fixed casing-part 10 and loaded by compression springs 41, 52. At low pressures the valve members occupy the positions shown in Fig. 2 and the gears A 1 deliver fluid to the conduit 5 by way of conduits 8, 9 and annular chambers 18, 19. When the said value is reached pressure transmitted through openings 29 to an annular chamber 28 lifts the pilot valve-member 42. A chamber 20 is thus connected to the chamber 28 by way of openings 31, 57 and consequently the main valve-member 21 is raised to the position shown in Fig.3. The conduit 8 is thereby shut off from the conduit 9 and connected to a conduit 7 on the inlet side of the gears A 1 through a further annular chamber 17. While the main valve-member is in transit, pressure in the conduit 8 is relieved by a ball valve 61 in a path inter-connecting the chambers 18, 19, Fig. 5. When the valve members are in the Fig. 2 position the pressure in the chamber 20 is equalized with that in the conduit 7 by openings 34, 44, 45, which relieve fluid trapped in said chamber when the valve members descend.