The lifting column is a single drive with a robust linear guidance which is often equipped with special design features. This type of drive is able to deal reliably with lateral forces and bending moments and also to guarantee the necessary stability when fully extended. In many cases, more than one synchronously-controlled lifting column is used in a single application.
A technically perfect final switch-off process is vital for the safe operation of a drive system. Three basic systems are used for furniture drive systems:
The current to the motor is interrupted via electromechanical limit switches, which stops the drive working.
Safety limit switches:
In situations in which safety is relevant, an additional limit switch can be fitted. In the event that the regular limit switch fails, the additional limit switch can be used to switch the drive off safely.
Electronic (virtual) limit switches:
In many cases restrictions on space in the application mean that it is not possible to fit electromechanical limit switches. In this case, memory drives with a position feedback system are used. The control unit recognises the relevant end positions and stops the drive.
In some cases, for reasons of cost, no electromechanical and virtual limit switches are fitted, and the drive is stopped by means of mechanical end stops. An overcurrent switch-off recognises that the power to the motor has increased sharply and switches off the power.
The drive carries out a straight (linear) movement.
Each drive type is designed to deal with an individual load capacity which defines the maximum pull or push force (with linear actuators and double drives) or the maximum torque which is available (with rotation actuators) from the drive.
The load capacity of a DEWERT drive is always a so-called dynamic load – even under this maximum load, the drive carries out a reliable adjustment movement. The load capacity is stated as a force (in the case of linear actuators) in newtons [N], and (in the case of rotation actuators) in newton meters [Nm]. 1 kg ≈ 10 N.
These additional devices block certain drive functions, in particular in respect of patient care and hospital applications.
Simple locking device with locking function for more than one drive and, depending on the type, additional keys for activating drive functions.
In addition to locking elements for several drives, the “central command unit” also incorporates comprehensive control functions for patient care and hospital beds.