GB1271677A - Gear pumps - Google Patents

Abstract

1,271,677. Gear pumps. DANFOSS A. S. July 10, 1969 [July 12, 1968], No.34768/69. Heading F1F. In a gear pump of the internally-meshing n and n+1 tooth type, having the end-faces of the gears covered by end-face members to close the chambers formed by the tooth spaces and in which at least one of the end-face members is provided with an arcuate suction groove 12, Fig. 2, and an arcuate pressure groove 13 disposed on either side of a line 15, joining the axes 10, 11 of the internallytoothed gear ring 8 and externally-toothed gear 6, the end 21 of the pressure groove in the zone 20 where the chambers between the tooth spaces are at maximum volume is further from the line 15 than the associated end 22 of the suction groove and a throttle passage 23 extends from that end 21 of the pressure groove to the vicinity of the line 15. The throttle passage 23 which is of very small cross-section, see Fig. 4, permits the admittance of hydraulic pressure fluid to a chamber 9a in the maximum volume zone 20 which is beginning to diminish in volume at a slow rate to reduce pump noise and also maintain pressure in this chamber at a sufficiently high value to counteract the pressure acting in the chambers in the minimum volume zone 17 to reduce the wear that occurs between the crests 18, 19 of the teeth as the teeth pass through the maximum volume zone 20. In the vicinity of the minimum volume zone 17, the end of the suction groove 12 may be farther from the line 15 then the end of the suction groove 13 and include a throttle passage 26. Any pressure in the chambers as they increase in volume can be rapidly reduced by this throttle passage and any entrained air bubbles, gradually dispersed to again reduce noise.