WO2002091539A1

WO2002091539A1 - A device for drive equipment for adjustable furniture

Info

Publication number: WO2002091539A1
Application number: PCT/DK2002/000265
Authority: WO
Inventors: Kjeld Kristiansen
Original assignee: Linak AS
Current assignee: Linak AS
Priority date: 2001-04-24
Filing date: 2002-04-24
Publication date: 2002-11-14
Anticipated expiration: 2003-10-24
Also published as: EP1389355A1

Abstract

A drive arrangement for adjustable articles of furniture, said arrangement comprising at least a drive unit intended for mounting in the article of furniture to adjust a movable part thereof, as well as a control box containing a mains-based power supply. Such a structure may involve a risk of fire by unintentional sparking because of defective cables and wires as well as their connections. To counteract this, the drive arrangement comprises a circuit for detecting the power consumption, connected to a switch relay in the mains cable for interrupting the mains voltage if a power consumption outside a predetermined level is detected or no consumption is detected.

Description

device for drive equipment for adjustable furniture

The present invention relates to a device in a drive arrangement for adjustable articles of furniture, said arrangement comprising at least an electrical drive unit intended for mounting in the article of furniture to adjust a movable part thereof, a control box containing a mains-based power supply as well as control electronics, a mains cable for connecting the control box to a plug, a wire for each drive unit for connecting it to the control box, and a manual control and/or operating panel for activating the drive unit(s).

In such drive arrangements, it has been found that there is a risk, although quite small, then nevertheless real, that fire and personal injuries may occur because of failure of and damage to the electrical installation. The mains cable is particularly prone to damage inter alia because of failure to remove it when the article of furniture is moved.

WO 93/11593 to Okin relates to an off-mains switching device for such a drive arrangement, but this does not protect completely against the above- mentioned conditions. A not very great, but nevertheless real risk is in- volved by the mains voltage on the manual control if, the mains cable is damaged, since, in practice, this contains conductors for the mains voltage as well conductors for the cut-off relay. If a separate cable is run to the plug and a separate wire is run to the disconnection relay, the relay may be activated even though the cable has been torn completely apart, since the relay is activated by an auxiliary voltage source. Further, the mains disconnection device does not take any overloading of the drive arrangement into account.

The invention focuses on the above-mentioned problems in order to provide a solution intended to diminish and preferably entirely avoid these. The invention provides a solution which is characterised in that the device comprises a circuit for monitoring the power consumption, and a relay connected to the device and arranged in the connection to the mains to interrupt the mains voltage if a power consumption outside a predetermined permissible level is detected. It is ensured hereby with almost absolute certainty that the current to the drive arrangement is interrupted if damage or a defect occurs in the drive arrangement that might cause a fire or result in personal injury because of an electric shock. The device may be incorporated in the plug on the mains cable, or be constructed as a separate unit to be arranged between a plug and the mains cable, whereby the device may be made universally useful and be used in connection with existing drive arrangements.

According to the invention, the level within which the power is to be kept is divided into three levels, which may be called a start phase, an operating phase and a standby phase. In the start phase, a great current is allowed quite briefly to obviate drop-out because of an instantaneous, great draw of power at the start of the drive arrangement. In the standby phase, a quite small draw of power is required and allowed to cover no-load losses in the system, which are essentially constituted by no-load losses in the transformer. If such a small draw of power is not observed, this is indicative of an unauthorised interruption, e.g. a mains cable rupture, a blown fuse, etc. The operating phase may be graduated according to the current loading conditions of the drive arrangement, e.g. a great draw of power may be allowed for a short period corresponding to a severe load of the drive arrangement, and a smaller draw of power for an extended period of time corresponding to a normal load. Heat is generated in the drive arrangement during operation, and the generation of heat is particularly great at extreme loads. However, the drive arrangement cools during standstill. The periods of a high and a smaller draw of power are expediently determined as an integration over a certain period of time in view of the thermal conditions in the drive arrangement.

The invention will be explained more fully below with reference to the embodiment illustrated in the accompanying drawing. In the drawing:

Fig. 1 shows a hospital bed,

fig. 2 shows a schematic diagram of the drive arrangement for adjustment of the bed,

fig. 3 shows a curve of energy consumption, and

fig. 4 shows a block diagram of the device according to the invention.

The bed shown in fig. 1 is a typical hospital bed, but the drive arrangement in a sickbed and a domestic bed is basically the same, except that a domestic bed is usually not adjustable in the height.

The bed comprises a frame 1 which accommodates a support for a mat- tress, said support consisting of a pivotable back section 2, a fixed central section 3 and a pivotable leg section 4 which is articulated. The back and leg sections 2, 4 may be adjusted by means of their respective linear actuators 5, 6. The support as a whole is adjustable in the height, just as it may be tilted about its transverse axis with two linear actuators 7, 8.

Below the support there is mounted a control box 9 (not shown in fig. 1) which accommodates a 24V power supply based on a transformer, and which also contains control electronics and a battery pack. The control box is connected by a cable 10 to the mains voltage. Each actuator 5-8 is also connected to the control box by a multi-membered wire, in which supply voltage as well as control signals are conveyed. A manual control 11 is pro- vided for the control of the actuators and is connected to the control box by a wire. In certain cases, the bed may be equipped with an additional control panel 12, which may exclusively be operated by authorised hospital staff.

The plug 13 of the mains cable 10 is provided with a circuit which monitors the power consumption of the control box. The monitoring circuit is connected to a switch relay likewise disposed in the plug 13 for interruption of the mains voltage if a power consumption outside a predetermined level is detected.

An example of a predetermined power consumption appears from the curve in fig. 3. Quite briefly, here 47 ms, a great current is allowed that covers a great draw of power at start. However, if the great draw of power continues, e.g. because of a blocked actuator, electrical defect, etc., the relay inter- rupts the mains connection.

There are three stages on the curve for the operation of the actuators, viz. one stage at a high load which is allowed in 2 out of 20 minutes, which corresponds to a brief, extremely severe load of the actuators, e.g. because of emergencies or lack of care. There is a subsequent stage of lower load corresponding to ordinary daily load of the actuators, which is allowed for 6 out of 60 minutes. This corresponds to raising the bed or adjusting the back and/or leg section with ordinary load. The last stage of a low load is allowed for 15 out of 60 minutes. This corresponds e.g. to lowering of the bed or lowering of the back and/or leg section.

The last stage on the curve is a small permanent consumption, which, with a certain small overmargin, covers a standby consumption, which is essentially constituted by the no-load consumption of the transformer. If this small permanent consumption is not detected, the relay interrupts the mains connection, since this is indicative of a defect in the connection to the primary side of the transformer.

A more specific realisation of the invention appears from the block diagram, fig. 3, where 14A, 14B indicates the switch relay in the mains connection. The relay is coupled so that in a position of rest it interrupts the mains voltage, while in an excited state it connects the mains voltage, which protects against defects. The necessary voltage is supplied by an internal power supply 15 based on the mains voltage. The relay is activated by a single FET transistor 16.

A first measuring circuit 19A for measuring the power consumption is inserted into one conductor in the mains connection. The measuring circuit is connected to the FET 16 via a recording unit 17, which is in turn connected to a starter logic 18. If no power in the mains connection is detected, the relay is deactivated and the mains connection is interrupted. This measuring circuit 19A is based on diodes, since the power at idle load is very small.

A second measuring circuit 19B is likewise connected to the FET via the starter logic 18, but this is made via four integrators 20-23 which control the relay in accordance with what has been described previously, e.g. a power equivalent to a consumption of 350W for more than 47 ms will turn off the FET via the starter logic and thereby deactivate the relay, and the mains connection will be interrupted. The measuring circuit 19 is based on a measurement resistance, since the power consumption in the situations concerned is considerably greater than at standby.

The invention thus provides a simple and reliable protection against damage resulting from electrical defects in the drive arrangement and moreover allows for blockages of it.

Claims

Patent Claims

1. A device in a drive arrangement for adjustable articles of furniture, said arrangement comprising a least a drive unit intended for mounting in the article of furniture to adjust the movable part thereof, a control box containing a mains-based power supply as well as control electronics, a mains cable for connecting the control box to a plug, a wire for each actuator for connecting it to the control box, and a remote control and/or operating panel for activating the drive unit(s), cha racterized in that the device comprises a circuit for monitoring the power consumption, and a switch connected to the circuit, preferably a relay arranged in the connection to the mains for interrupting the mains voltage if a power consumption outside a predetermined permissible level is detected.

2. A device according to claim 1, c h a ra cte r i z e d in that it is designed as a separate unit for insertion between a plug and the mains cable.

3. A device according to claim ^ cha racterized in that the monitoring of the power consumption comprises three levels, viz. a first level where a great power corresponding to start of the drive arrangement is allowed briefly, a second level where a small draw of power corresponding to standby of the drive arrangement is constantly required, and finally a third level for a period of time adapted to the drive arrangement and its conditions of load.

4. A device according to claim 3, cha racterized in that the third level is subdivided into two levels, where a great draw of power is allowed for a short period of time at the first sublevel, corresponding to a severe load of the drive arrangement, and a smaller draw of power for an extended period of time corresponding to a normal load.

5. A device according to claim 3 or 4, characterized in that the period of time for the third level is an integration over a predetermined period of time.

6. A device according to one of claims 1 and 3, characterized in that it comprises a separate measuring circuit for the detection of power consumption at standby.