VARIABLE DELIVERY PUMP :-
Variable delivery pumps can run continuously in one direction but have the capability of an infinitely variable discharge from zero to maximum either way. The principle of operation is based on altering the stroke of the pump pistons in radial or axial cylinders,
Non-reverse locking gear to stop pump idling (Dean)
by means of a floating ring or swash plate respectively, to change the amount of oil displaced . There is very little shock to the hydraulic system as the pump commences delivery , because the piston stroke increases gradually from zero.
HELE-SHAW PUMP :-
The shaft is stationery and the cylinder body forming the cylinders rotates around the shaft, being driven by a constant speed electric motor. The plungers are connected to slippers which run in annular groves inside two circular rings on each side of the plungers, when the center of the rings coincides with the shaft center(O), the pump travel is at mid-position . At this position, the plungers rotate at a fixed radius distance from the shaft center (distance OC) . This means there is no relative motion between the plungers and the shaft, and no pumping action taken place. It now the circular slipper rings are moved to the right by the operating rod , through the casing from the telemotor rod , then the centre of rotation of the slippers and plungers is at B which is eccentric to the centre of the shaft 'O'. This means the greatest distance the plunger gudgeons are from '0' is OG and the shortest distance is OF. With the direction of rotation as shown, in travelling round from G to F the plungers are moving in relative to the fixed central shaft and ports and hence the top port 'T' acts as a discharge. In completing the circular route from F back to G, the plungers are moving out relative to the central shaft and ports and the bottom port 'B' acts as suction. Similarly if the circular rings are moved to the left, reverse action takes place and top port'T' acts as suction and bottom port 'B' acts as discharge. As the stroke of the plungers depends on the movement of the slipper path horizontally and hence the eccentricity, so the pump is of variable delivery pump type. Also direction of flow depends on movement left or right of central position so that for unidirection rotation, the direction of flow reversible.
HELE-SHAW PUMP DETAIL (1\4 PLAN)
position I
HELE-SHAW PRINCIPLE
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