The present invention relates to an electrical actuator system for adjustable articles of furniture, such as beds and chairs as well as patient lifters, as stated in the introductory portion of claim 1.

Actuator systems are widely used today for the adjustment of hospital and nursing beds as well as domestic beds. As an arbitrary example, reference may be made to EP 488 552 A1 to Huntleigh Technology pic, which relates to a hospital bed. These actuator systems are traditionally composed of a control box which typically consists of a power supply part, which converts the mains voltage, e.g. 110V/240V, down to an operating voltage, typically 24V, and a control part determining whether the actuator runs in the one or the other direction or runs according to a specific pattern, e.g. for mutual adjustment of the backrest and legrest sections of the bed relative to each other. At least typically for hospital beds, the control box is moreover pro¬ vided with rechargeable batteries so that the actuator system is capable of serving the desired functions without being connected to the mains voltage.

The mains voltage cable constitutes a special danger because of the risk that the cable is cut/torn completely or partly in the movable parts of the bed, or because the bed is moved thoughtlessly so that the cable is torn out of the socket.

The object of the invention is to provide an electrical actuator system with a high degree of safety against electrical malfunction.

This is achieved according to the invention by integrating the control or at least the H-bridge of the control in the individual actuators and, at the same time, placing the power supply outside the article of furniture in which trie actuators are incorporated. This provides unique advantages, as the elec-

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trical safety of the article of furniture is enhanced significantly, since there is no longer mains voltage in the vicinity of the movable parts of the articles of furniture. Further, it is not necessary to place/mount a separate control unit in the article of furniture.

The externally arranged power supply may be, but is not limited to, a transformer and rectifier or e.g. a switch mode power supply arranged directly in the mains socket.

Additional safety is achieved in that a switch is provided in the power supply in the power circuit to the actuators, said switch being controlled via the hand control so that, normally, the power circuit is interrupted and is closed only when one of the keys of the control is activated. Hereby, the cable between the power supply and the actuators carries current only when one of the actuators is in operation. Here, such a great power may be present in the cable, and the level of energy may be so high that this may be a con¬ tributory factor in causing a fire. The current per se, however, is not dan¬ gerous to people, as the voltage is low. Even if the cable is cut in the structure, no short-circuit can take place, since the power circuit is thereby interrupted in the separate power supply. In an embodiment, the switch is a FET transistor, expediently arranged on the earth side.

An embodiment of the invention will be explained more fully below with ref¬ erence to the accompanying drawing, in which:

Fig. 1 shows an electrical actuator system for beds, shown with the incorpo¬ rated devices and diagram.

As mentioned, the drawing shows an electrical actuator system for beds for adjustment of the backrest section and the legrest section of the bed. The bed per se is not shown, and only the parts necessary for the understand-

ing of the invention are shown.

The drawing, farthest to the left, shows a power supply TR based on a transformer and rectifier. The power supply is connected to the mains by a mains cable and supplies an operating voltage of 24V. Two linear actuators LA1, LA2 having a reversible DC motor are connected to the power supply, which is arranged outside the bed. These two actuators LA1 and LA2 are intended to adjust the backrest section and the iegrest section, respectively, of the bed. The actuators have incorporated a control in the form of an H- bridge H1, H2 for reversing the direction of the current and thereby the di¬ rection of rotation of the motor. The actuators are controlled by a hand con¬ trol HB, from which signal wires are run to the control in the actuators as well as to a switch in the form of a FET transistor T1 in the power supply. This FET transistor, which is provided on the earth side, interrupts the cur- rent in the cable from the power supply TR to the actuators LA1, LA2. This means that even if the cable from the power supply and the actuators should be damaged, no dangerous situations can occur, since earth is in¬ terrupted in the power supply.

Activation of one of the keys HB1-HB4 of the hand control causes activation of the FET transistor T1 to establish the earth connection to the actuators LA1 , LA2, at the same time as the control of the actuator concerned is acti¬ vated. The actuator can hereby run. When the hand control key is released, the signal voltage to the FET transistor T1 is interrupted, which falls and interrupts the power to the actuator. Under normal conditions, the wiring to and in the bed is free of voltage, as it is interrupted at the transformer, and the power is switched on only when the hand control is activated. In other words, there is power to the bed only in the short intervals where the ac¬ tuators run.

A concrete embodiment is described above, but it is evident to a person

skilled in the art that the invention may be realized in many ways, e.g. the +connection may be interrupted instead of earth, and a relay may be used as a switch instead of a FET transistor, just as the invention does not de¬ pend on a wired hand control, it being possible, in the alternative, to use a wireless hand control. Not to mention that it might be a fixed control panel.

As for examples of actuators, reference is made to WO 98/30816 A1 to Li- nak A/S, which relates to an actuator with an actuator rod, and DK 174457 B1 to Linak A/S, where the spindle nut is intended for direct attachment to the application. A special embodiment of actuators for domestic beds with two spindles is known from EP 372 032 B2 to Dewert Antriebs- und Sys- temtechnik GmbH & CO. KG. All these are linear actuators. An example of a rotary actuator is known from EP 1 217 922 B1 to Linak A/S.