Despite the advantages of mobility
and ease of use, current conventional
hydraulic foot pumps have
a number of real limitations. For
example, these pumps are fitted
with an inclined pedal, and the user
has to lift his foot fully to operate them.
This has the ergonomic disadvantage that the
whole body weight rests on one leg, which is tiring
and unstable.
Moreover, the small hydraulic delivery
means that it takes quite a long time before
the cylinder is fully extended and the maximum operating
pressure is reached. For example, it takes
on average more than 20 seconds to let a 10-ton
cylinder with a stroke length of 152mm fully extend
and then build up to 700bar operating pressure.
Another typical disadvantage of air/hydraulic
pumps is the poor controllability. This is simply
because the maximum pump delivery is reached as
soon as the pedal is depressed. After all, the minimum
oil delivery per pump stroke is determined
by a single stroke of the linear air motor; fractions
are not possible. Reversely, the oil is pressed back
unhindered into the reservoir by the fast-working
release valve and the spring force of the cylinder.
Here also, the return flow cannot be accurately
controlled. These limitations are especially important
with car repair companies, for example,
where accurate metering of the oil flow and thus
the cylinder movement is a requirement.
Furthermore, the efficiency of the pump is fairly low,
namely approx. 5 percent. Additionally, this is a physical
limitation caused by the ratio between the diameter
of the air piston and the hydraulic piston,
as well as by the efficiency of the internal air
control technology.
Finally, most conventional air/hydraulic pumps
have an open oil reservoir with vent screw. This gives
a risk that oil will run out of the reservoir if it tilts
or falls over. The pump must therefore always be
horizontal. An open oil reservoir naturally also
leads to internal pollution (from dust and fluids etc.)
which can cause the hydraulic system to fail. These
are however technical limitations with which the
industry has learned to live, partly as a result of the
favourable price compared to the more expensive
electric pumps.
To tackle these limitations optimally, Enerpac has
developed a whole new technology. As a result of
the interviews with end-users, the design was
based on the following three main objectives: ergonomically
better product, optimum controllability
of the oil flow, or fine metering and higher oil
flow. Additionally, to prevent possible leakage
with tilting and to prevent internal pollution, a
closed oil reservoir was assumed, as well as a
slightly larger base area for the stability of the pump.
The development has resulted in a pump with not
only a totally different appearance, but also with
a totally different technology ‘under the cover’.
With the XVARI Technology, Enerpac has again
set a new industrial standard for the 50-year old
technology of conventional air-driven hydraulic
foot pumps. This technology replaces the popular
and widely-used linear air motor technology and,
besides strongly improved ergonomics and a more
accurate metering of the hydraulic oil flow, also
offers a higher delivery and higher efficiency. The
popular air-driven foot-operated hydraulic pump
is undoubtedly one of the most used industrial
pumps for working with high-pressure hydraulics.
We find them in such places as machine factories,
production companies, mechanical workshops,
maintenance companies and car repair companies.
The pumps are mainly used to drive small single-
acting (spring return) cylinders and other hydraulic
tools. The technology was developed by Enerpac
at the end of the 1950s, and Enerpac was
therefore the first manufacturer to introduce hydraulic
foot pumps based on this technology worldwide.
In the following decennia, Enerpac and numerous
competitors have admittedly brought various
new generations of this type of pump on to
the market. However, the technological principle
has in fact remained unchanged in the past 50
years. These air-driven hydraulic pumps have an average
hydraulic delivery of 0.16 litres/minute with
a pressure of 700 bar. The principle is simple: the
pump is driven with (workshop) compressed air from
5 to 8 bar and a linear air motor (pneumatic cylinder)
in the pump operates a small hydraulic piston,
with which the oil is fed from the reservoir, and the
hydraulic pressure is built up. The pump unit is small
and therefore has the important advantage that
it is easy to move.
Admittedly, the new pump has the same functions
as the conventional air/hydraulic pump technology,
but offers the user several unique advantages.
For example, with the ergonomic design
an important advantage has been achieved with respect
to the conventional models. Furthermore, an
optimally controllable oil flow is possible for the
first time, so that the cylinder movement can be controlled
more accurately, both during advance and
retraction. And thirdly, with the higher hydraulic
delivery, the operator can work considerably faster.
In brief, the new pump means the end of the
more than 50 years hegemony of the time-honoured
hydraulic pumps with linear air motors.
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