GB1239110A - - Google Patents

Abstract

1,239,110. Gear pumps. ZAHNRADFABRIK FRIEDRICHSHAFEN A. G. Dec.22, 1969 [Dec. 21, 1968], No. 62248/69. Heading F1F. An externally meshing gear pump comprises a fixed casing 4 housing a movable casing 3 pivotable in either direction through 180 degrees about the axis of rotation of the drive-shaft 12, the movement being effected by frictional engagement of a pair of clutch pads 5, connected to the casing 3, with the drive-shaft, and controlled in dependence on the pump output pressure, so that the pump has a constant delivery direction for both directions of shaft rotation. The clutch pads 5 pivoted together by a pin 11 are urged into engagement with the drive-shaft 12 by a spring 7, and are held out of engagement with the shaft during normal pumping by a pair of coaxial pistons 6 mounted in a cylinder 22, the space between the pistons being connected via an axial channel 23, 24, a radial channel 25 and a passage 26 or 27 in the fixed casing 4, with the outlet side of the pump. When the direction of rotation of the shaft 12 is reversed, the output pressure drops until spring 7 overcomes the force of the pistons 6 urging the pads 5 into engagement with the shaft. The inner casing 3 then rotates with the shaft 12 through 180 degrees, the rotation being limited by a pin 8 mounted in the casing 4 engaging in a semi-circular slot 18 in the casing 3. The pads 5 remain in frictional engagement with the shaft 12 until the outlet pressure builds up and pistons 6 overcome the force of spring 7. Figs. 5, 6, 7 (not shown) show a similar arrangement applied to an internally meshing pump.