Hydraulic Transmission
In a usual hydraulic
system, there are two networks of tubes; one contains high pressure hydraulic fluid
and the other low pressure.
One or a few engines drive pumps,
which move hydraulic fluid from low pressure network of tubes to high pressure
network of tubes. Hydraulic machines as motors, pumps, compressors, presses, electric
generators, etc. take fluid in high pressure network and pass it to low
pressure network and use pressure difference to perform their work.
When hydraulic machines change
speed of their operation, conflict arises between volume of fluid movement
through them and volume of fluid movement through pumps driven by engines.
Often, engines cannot adjust quickly enough and this could lead to pressure
waves in the system of tubes.
To protect the system, special
compensating elements should be included into it. There are two types of
candidates for such compensators and it is desirable to use them both, because
they offer complementary capabilities.
One is a reciprocating electric
generator combined with electric battery, which it feeds. Energy stored in the
battery could be used, as needed, particularly to start the system. The
generator starts automatically, when pressure in the system exceeds some high level
and stops, when it drops below some low level. Unfortunately, when battery is
full, this “safety valve” cannot be used.
The other is a reciprocating pump used
to pump air into a special tank, where compressed air is kept – an air
compressor. It starts and stops the same way electric generator does. However,
compressed air from the tank could be vented, when pressure in it exceeds
safety limit. Compressed air has its own uses, for example for air conditioning.
There are a few types of machines especially
suitable to be used with hydraulic transmission.
One is various reciprocating pumps
pumping liquid, gas (compressors), etc., which are driven by reciprocating
hydraulic motors (pumps in reverse, hydraulic motors takes energy from the
Transmission). Hydraulic presses are another example. Turbines could be used,
where rotation is needed.
Energy producers (engines driving
pumps) are turned on and off as needed. Speed of pumping of the transmission
fluid is controllable. Cost of reciprocating pumps, compressors and motors is
low. They are quiet, reliable and cost of their maintenance is low.
When tubes of transmission are not
movable after they are installed, the system could be made leak proof. This
could be achieved in a building, in a settlement, in an airplane or in a ship.
Alexander Liss 7/9/2019; 7/16/2019