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After the ”door light” had signaled the operator will
press the “up” key and the solenoid will retract.
At this stage the unlocking operation is completed and
the operator can open the door.
9.3 Piston Lifting Device For 3850/3870/5050/5075 ELV
In order to ensure the stability of the door in the open position and avoid a
sudden jolt downwards of the door which can hurt the operator, a hydro-
pneumatic safety device, is provided to ensure the smooth lifting and
lowering of the door, facilitating the handling of it.
The device is a gas-pressurized spring, which incorporates a cylindrical
barrel filled with oil and nitrogen gas. The spring force, that damps the
door movement, is produced by the compressed nitrogen filling. A piston-
rod is telescopically guided within the cylindrical barrel and fixed by the
side of the door to the rear.
There is one cylinder for the models 3850/3870 and two cylinders for the
models 5050/5075.
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