Operation
Slim Jim Idrocompresso User manual
page 8
Brew-lever mechanism
Pulling the brew-lever towards you activates valves, lifts a piston and shortens a spring. The brew-
lever will lock into position when maximum upward-travel of the piston is reached. When the brew-
lever is very close to the locking position, a valve is opened such that water can flow into the cylinder
and pre-infusion starts under incoming water pressure. When the machine is equipped with the
optional pump, the pump will activate at that moment as well. Active-duration of the pump can be
adjusted per individual group in the “water timer” section of the Barista level under “PUMP-ON-TIME”.
In a lever-group, spring force on a piston is used to obtain
elevated water pressure onto the coffee bed. At resting
position the spring is already shortened, pulling the brew-
lever towards you shortens the spring even more. With
the brew-lever returning to resting position, water
pressure onto the coffee-bed thus decreases during the
brew as the piston moves down and the stressed spring
relaxes. Typical lever mechanism brew-pressure profile
from start to end of a brew is approximately 9 to 6 bar.
You would normally perform a short flush (see next), lock
in the prepared portafilter, confidently
2
pull the brew-lever
into locked position, wait until you see the first drop of
coffee in the cup and then release the brew-lever to
extract at elevated pressure.
Pressing the release pin on top of the grip will release the
lock, the stressed spring then forces the piston down
which pressurises the water flowing through the coffee-
bed. Very shortly after the brew lever has left lock-position
a valve in the machine closes such that no more water
can flow from the machine towards the cylinder or vice
versa.
Total down-travel of the piston will result in approximately
60 ml of water being pushed through the coffee-bed,
enough for two single espressos.
When the lever returns to resting position, the electric
circuit is opened, the relief valve will de-activate.
The Bowden cable on the back of the brew-lever
mechanism operates two switches inside the machine.
The first switch will start/stop the shot-timer and close the
relief valve, the second switch will allow water to flow from
the machine to the cylinder and instructs the optional
pump to start.
Figure 8. The brew-lever mechanism.
Danger
Despite the measures taken to reduce the danger, under certain circumstances (obstructed water
flow, no coffee-bed, portafilter not properly locked in) it is possible that the brew-lever returns to
resting position with high velocity, force and momentum. Keep body-parts other than your hand away
from the reach of the brew-lever.
2
If you pull the brew-lever (very) slowly or when the coffee-bed is not prepared properly, it is likely that
air is sucked through the coffee-bed into the cylinder before water enters the cylinder. Upon release,
the brew-lever will not feel firm and the shot volume will be less than expected.
brew
lever
lock
mechanism
release
pin
