Reciprocating Pumps


Following is an outline of a few variants of reciprocating pumps (including pumps moving gasses – compressors) driven either by hydraulic fluid, or by compressed air, or by reciprocating electric motor.



General Schema


Following is a general schema of a Pump:


     PL         RL         PB         RR         PR





     AL        CL           B         CR        AR


It is a large tube divided by 4 walls into 5 compartments, from left to right:

AL, CL, B, CR and AR

It contains one movable part – a piston-rod assembly, consisting of 3 pistons

PL, PB and PR

connected with two “rods”:

RL and RR

“Rods” could be implemented as tubes to better resist bending forces on them, when they are under pressure.

Walls between chambers have tight openings for “rods”. They also help resisting bending forces, when “rods” are under compression.

Chambers AL and AR operate as single acting pumps and a chamber B operates as a double acting pump (when they are not used as motors).


Valves Control

Chambers CL and CR do not contain liquid or compressed gas, each one has opening, through which a “hand” connected to the “rod” is extended outside the main tube. These two “hands” reach to a Valve Control Box and this allows synchronization between opening/closing of valves and position of the movable piston-rod assembly.

Note that one joint Valve Control Box could synchronize operations of two or even more such pumps. For example, piston-rod assemblies of different pumps could move in opposite directions and this should minimize vibration caused by pumps operations.

We could prevent hydraulic shocks through smooth and slow opening and closing of valves.


Protective Chambers

To minimize leaks and facilitate lubrication of “rods”, additional narrow chambers could be “carved out” from chambers CL and CR next to walls of adjacent chambers. These chambers could be filled with lubricant.


Pump driven with reciprocating electric motor

    We could place in the chamber B a reciprocating linear electric motor instead of a piston PB, and this gives us an electric pump or electric compressor. Electric controls we would place in the same box, where we have valve controls and synchronize them with valves operations.


Pump driven via hydraulic transmission

    Similar to electric pump, we would use hydraulic fluid in the chamber B to move piston PB back and forth. Valve controls of such hydraulic motor we would place in the same box, where other controls are.


Output Pressure

    Let us look at the pump driven via hydraulic transmission. Most likely, we would want output pressure of the pump differ from one we get from pump driving fluid. This is achieved with chambers of different diameters. This could be done because pistons are confined to their respective chambers. In such case, the shape of chambers CL and CR would be defined only by demands of structural soundness of the pump.

    Obviously, in such case, we would not be able to use one tube to house all assembly, but would need to combine the pump from a few cylindrical components of different diameter. They could be welded or joined some other way.

Alexander Liss 7/22/2019