Fundamentals of Piston Pumps

Blog | June 8th, 2018

Everyone knows how a single piston operates. In a sealed chamber, a metal rod slides forward then back. If there’s fluid in the chamber, the sliding rod generates suction as it moves forward, then the force reverses as the rod moves back. However, that basic linear action doesn’t easily translate to spinning force. Something else is needed here, some other mechanism that bridges linear and rotating mechanics.

Reciprocating Piston Pumps 

The only way to facilitate that force translating feature is to incorporate a reciprocating ring of additional pistons. Now, instead of a single plunger and cylinder, the piston pump is loaded with numerous pistons, which are arranged in a ring inside a cylinder block. So far so good, but there’s still an element missing from the pump, a part that will create a differential charge between the ring of smoothly sliding rods.

Adding the Tilted Swashplate 

The pump is eager to start turning. Nothing’s happening, not without a control element in place. This is where the swashplate enters. It’s a disc, an angled plate that’s fitted in front of the piston array. Spring-loaded, each piston is in a slightly different position because of the plate’s angle. Differing quantities of suction and discharge energy build as the plungers are moved to slightly different positions within their cylinders, and since the cylinders are formed into one large cylinder block, rotating energy develops.

Force-Transforming Reciprocating Action 

One cylinder dips deep while the next doesn’t move forward quite as much. The positions of the plungers are controlled in this manner all around the piston pump, and the reciprocating bridge starts turning the discrete chunks of linear force into accumulated energy. The pump is spinning. Half of the plungers are generating suction while the other half is producing discharge pressure, so the entire block is spinning. Coupled to a drive shaft on the other side of the piston pump housing, the hydraulic energy entering the input side is being transformed into spinning power, courtesy of that reciprocating mechanism.

There are slightly different types of hydraulic piston pumps on the market, including radial and axial variants. Essentially, the pistons and input energy are transformed by ninety-degrees when an axial model is favoured over a radial device. In the end, however, the mechanism still uses an angled plate and a cylinder block filled with pistons. The transformative medium here, the engine that turns linear force into rotational pumping power, is the reciprocating principle that comes into play as the pistons receive their slightly different positional directions from the swashplate.

Mobile Hydraulic Specialties Pty Ltd

Factory 89, 38-40 Popes Road
Keysborough, Victoria, 3173

Phone: (03) 9798-6511

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