A DRIVE UNIT

Abstract: An electric drive unit for driving the adjusting mechanism of an adjustable piece of furniture, in particular for driving the adjusting mechanism of a desk comprising a vertically adjustable desktop. The drive unit comprises the following components: an electric motor with an integrated reduction unit, a control unit for controlling the drive unit, a position sensor for determining the angular displacement provided by the drive unit, and at least one low-speed outgoing shaft, which is coupled to the reduction unit. The drive unit is characterized in that the components are mounted as a unit within a separate housing which encases the components, in such a manner that part of the low-speed outgoing shaft is positioned within said housing.

Description: A DRIVE UNIT The invention relates to an electric drive unit for driving the adjusting mechanism of an adjustable piece of furniture, in particular for driving the adjusting mechanism of a desk comprising a vertically adjustable desktop. Drive units of this type are known, they are used for centrally driving an adjusting mechanism of a desk which is adjustable for height. In many cases, the drive unit is thereby mounted and coupled to the adjusting mechanism near the underside of the desktop. Such electrically adjustable desks are in particular used in a flexible office environment, wherein various persons work alternately at the desk, so that it must be possible to carry out the adjustment quickly and efficiently. The known electric drive unit comprises the following components: a low- voltage DC electric motor with a reduction unit, a control unit for controlling the drive unit, a position sensor for determining the angular displacement provided by the drive unit, and at least one low-speed outgoing shaft. A drawback of the known device is the fact that it adds considerably to the purchasing costs of an adjustable piece of furniture. Not only is it necessary to use expensive electronic components in the known drive units, because heavy demands are made on the drive unit as regards positioning accuracy, electromagnetic shielding and noise production level, but also the mounting of the drive unit and the attuning of the respective various components to each other is a time-consuming and costly affair. This is the case in particular because the mounting of the drive unit on a piece of furniture must be carried out by skilled electricians, who are often not available in a furniture assembly environment. The object of the invention is to eliminate this drawback. In order to accomplish that objective, the invention provides a drive unit for driving the adjusting mechanism of an adjustable piece of furniture, in particular for driving the adjusting mechanism of a desk comprising a vertically adjustable desktop, which comprises the following components: an electric motor with an integrated reduction unit, a control unit for controlling the drive unit, a position sensor for determining the angular displacement provided by the drive unit, and at least one low-speed outgoing shaft, which is coupled to the reduction unit, wherein said components are mounted as a unit within a separate housing which encases the components, in such a manner that part of the low-speed outgoing shaft is positioned within said housing. This makes it possible to couple the low-speed shaft to a position sensor within said housing, so that it will suffice to use an inexpensive position sensor having a low resolution. Moreover, the housing now shields all the components of the drive unit, at least partially so, both as regards electromagnetic radiation and as regards noise. This makes it possible to use an inexpensive, relatively noisy electric motor with an integrated reduction unit. Furthermore it is possible to use cheaper electronic components, because the shielding function of the housing makes it possible to make less heavy demands as regards the generation of electromagnetic radiation. Since all the components are provided as a unit within a separate housing, the drive unit can be supplied as one module. As a result of this, the electronic components are already attuned to each other and interconnected upon assembly of the drive unit, so that the installation of the drive unit can be carried out quickly and effectively by personnel who are not electrically skilled. In one embodiment, the drive unit according to the invention is characterized in that the housing is provided with pre-formed compartments for mounting an electric motor with an integrated reduction unit, a printed circuit board and a coupling. As a result of this, the mounting, connecting and attuning of the various components of the drive unit to each other can be carried out quickly and effectively. Preferably, all the electronic components are mounted on one printed circuit board, so that only a small number of wire connections need to be made. In another embodiment, the drive unit according to the invention is characterized in that the housing is provided with rubber damping means for mounting the electric motor with the integrated reduction unit in such a manner that a damping effect is achieved. This makes it possible to use a relatively inexpensive, poorly balanced low-voltage DC electric motor with an integrated reduction unit, for example. In yet another embodiment, the drive unit according to the invention is characterized in that the housing is provided with a compartment comprising a mechanical indicator fitted with limit switches for controlling the maximum angular displacement to be provided by the drive unit. In another embodiment, the drive unit according to the invention is characterized in that the drive unit comprises a coupling positioned within the housing, which coupling is provided with a right-angled transmission as well as with a linear transmission. This makes it possible to provide the drive unit with one, two or three outgoing shafts upon assembly, according to which is desired, so that the drive unit can be coupled to an adjusting mechanism in various ways. The invention will be explained in more detail with reference to the drawing, which shows a preferred embodiment of the invention. In the drawing: Figure 1 is a schematic cross-sectional view of a desk comprising a vertically adjustable desktop; Figure 2 is a partially cut-away plan view of a drive unit; Figure 3 is a partially cut-away side view of the longitudinal side of the drive unit of Figure 2; and Figure 4 is a partially cut-away side view of the transverse side of the drive unit of Figure 2. The figures are merely diagrammatic representations of the embodiments, wherein like parts are numbered alike. Referring to Figure 1, a desk 1 is shown, which desk comprises a desktop 2 which is supported by two standards 3, 4 in such a manner that it can be adjusted for height. A drive unit 5 is mounted on the underside of desktop 2 by means of dampers 6. Drive unit 5 has an outgoing, low-speed shaft 7, 8 on either side thereof. Shafts 7, 8 are each coupled to a drive rod 11, 12 via a coupling 9, 10. It is preferred to use drive rods and shafts of hexagonal section, which have a diameter which corresponds with a width 6 spanner, because standard rods, couplings and transmissions are commercially available in that size. The drive unit 5 of Figure 1 may also be provided with an outgoing shaft extending perpendicularly to the plane of the drawing upon assembly, which shaft is coupled to drive rods 11, 12, for example by means of a right-angled transmission positioned outside housing 39. Drive rods 11, 12 are each coupled to a right-angled gear transmission 13, 14, which transmissions 13, 14 are mounted in the upper parts 15, 16 of the respective standards 3, 4. The upper parts 15, 16 are fixed to the desktop 2 of desk 1. The right-angled transmissions 13, 14 are each connected, via a shaft 17, 18, to a screwed spindle 19, 20 positioned within the respective standards 3, 4. Screwed spindles 19, 20 each support a nut 21, 22, which nuts 21, 22 are fixedly connected to the lower parts 23, 24 of the respective standards 3, 4. The lower parts 23, 24 of standards 3, 4 are each supported on the floor, and they are capable of telescoping movement with respect to the upper parts 15, 16 of the respective standards 3, 4. The screwed spindles 19, 20 are rotated by means of drive unit 5 via the aforesaid drive rods, couplings and transmissions. Rotation of screwed spindles 19, 20 causes nuts 21, 22 to translate along screwed spindles 19, 20, carrying along the lower parts of standards 23, 24 thereby. This causes the lower parts 23, 24 of the respective standards 3, 4 to telescope with respect to the upper parts 15, 16, thus adjusting desktop 2 of desk 1 for height. The maximum load of the desktop is 150 kg, for example. The maximum adjusting speed is 6 mm per second, for example, whilst the maximum range of adjustment is about 200 mm, for example. Screwed spindles 19, 20 are self-braking, and they have a pitch of 3 mm per revolution, for example. It is noted that in particular the maximum load, the adjusting speed and the maximum range of adjustment are design parameters which can be selected at will. Referring to Figure 2, the drive unit is shown to comprise an electric motor 25 with an integrated reduction unit 26 comprising a low-speed outgoing shaft 27, whose axis extends at right angles to the axis of motor 25. The motor is preferably a low- voltage DC motor, which has a supply voltage of 24V and a power input of about 75W. The outgoing shaft 27 of the reduction unit preferably has a speed of revolution of about 2 revolutions per second. Figure 2 furthermore shows a printed circuit board 28 provided with a transformer 29, control electronics 30 and a position sensor 31 for determining the angular displacement provided by the drive unit. The control electronics 30 also comprise a programmable IC 32 for controlling the drive unit. Position sensor 31, which is a low-resolution type sensor, is connected to the low-speed outgoing shaft 27. Position sensor 31 comprises an encoding disc, by means of which the velocity of angular displacement, the direction of angular displacement and the total angular displacement of outgoing shaft 27 can be determined. In the present embodiment, the drive unit is also provided with a mechanical indicator 33 comprising limit switches 34 for controlling the maximum angular displacement/range to be provided by the drive unit. The mechanical indicator 33 is coupled to the low-speed outgoing shaft 27 of reduction unit 26 by means of gears 35. The maximum angular displacement/range of adjustment can be set by means of stops 36. Also software control of the maximum range of adjustment is possible, in that a maximum angular displacement for each direction of rotation is programmed in the programmable IC 32. Figure 2 furthermore shows the low-speed outgoing shaft 27 of reduction unit 26 to be coupled, via a coupling 37 comprising a linear transmission, to a low-speed outgoing shaft 38 of the drive unit. Coupling 37 is also provided with a right- angled transmission. It is possible to connect other, likewise low-speed, outgoing shafts to this transmission, for example the low-speed outgoing shafts 7 and 8 of the drive unit 5 as shown in Figure 1. Referring to Figures 2, 3 and 4, the components are shown to form a unit which is provided within the separate housing 39, and part of the low-speed, outgoing shaft 38 of the drive unit (and/or shafts 7 and 8, if a right-angled transmission is used) to be positioned within housing 39. Housing 39 comprises two parts 40 and 41, which are interconnected by means of fastening screws (not shown). If desired, housing 39 may be provided with extra sound-absorbing material or with an extra coating so as to reduce the emission of electromagnetic radiation. This may be advantageous in particular if a PC is placed near drive unit 5 on desk 1. Housing 39 is provided with pre-formed compartments for mounting the components of the drive unit, such as the electric motor 25 with integrated reduction unit 26, printed circuit board 28 and coupling 37. The compartments are essentially formed by varying the thickness of wall 42 of housing 39, as a result of which projections and ridges are formed. Preferably, housing 39 is provided with rubber damping means (not shown for easy reference) for mounting the electric motor so that a damping effect is achieved. The drive unit is furthermore provided with a terminal connecting point (not shown) for an external voltage supply, for example a power socket for a 230 V, 50 Hz DC voltage. The drive unit is also provided with a terminal connecting point (likewise not shown) for a remote control device, for example a telephone socket. The remote control device may be a control box provided with pushbuttons and/or a display and with a three-position quick-break switch mounted under the desk, which springs back to a neutral position, whilst it is also possible to use a PC which is present on desk 1. The remote control device can be used for controlling drive unit 5 and for selectively adjusting the height of desktop 2 with respect to the floor. If the control box comprising the display is used as the remote control device, either the "up" button or the "down" button is depressed until the display indicates the desired height. The display can also show status indications, such as "hot", "overload" or "end position". If the drive unit is connected to a three-position switch, the switch is held in the "up" position or in the "down" position by hand until the desired height is reached. If the drive unit is connected to a PC, the display unit thereof can function as a display, and drive unit 5 can be controlled, by depressing one of the keys of the keyboard, to move desk 1 to a desired position which is stored in the computer memory. The control electronics 30 are programmed upon assembly of drive unit 5 already, whilst also the limit switches 34 of mechanical indicator 33 are pre-set. In the furniture factory, the drive unit 5 is mounted on desktop 2 as a separate unit. Then the drive unit 5 is set to calibration mode, for example by depressing the "up" and "down" buttons of the control box simultaneously when the power is turned on. The drive unit will then move to an extreme position, for example to a "high" mechanical or software-controlled limit switch. Following that, the standards of the desk are moved to an extreme position by hand, the highest position in this example. Finally, the drive unit and the adjusting mechanism are coupled, for example by coupling drive rods 11 and 12 to the low-speed outgoing shafts 7, 8 of drive unit 5 by means of couplings 9, 10. The programmable IC 32 is preferably programmed with a communication protocol, by means of which it is automatically detected what type of remote control device is connected to the drive unit, whereby the protocol is for example carried out each time the drive unit is moved to the calibration position. Preferably, the control electronics 30 are furthermore provided with a non- volatile memory, so that the changing position during the running out of the drive unit will still be registered in the case of a power failure. It is noted that the invention is not limited to the illustrated preferred embodiment. Other embodiments are possible within the scope of the invention.

Claims: CLAIMS 1. An electric drive unit for driving the adjusting mechanism of an adjustable piece of furniture, in particular for driving the adjusting mechanism of a desk comprising a vertically adjustable desktop, which drive unit comprises the following components: an electric motor with an integrated reduction unit, a control unit for controlling the drive unit, a position sensor for determining the angular displacement provided by the drive unit, and at least one low-speed outgoing shaft, which is coupled to the reduction unit, wherein said components are mounted as a unit within a separate housing which encases the components, in such a manner that part of the low-speed outgoing shaft is positioned within said housing. 2. A drive unit according to claim 1, characterized in that the housing is provided with pre-formed compartments for mounting an electric motor with an integrated reduction unit, a printed circuit board and a coupling. 3. A drive unit according to claim 2, characterized in that the housing is provided with rubber damping means for mounting the electric motor with the integrated reduction unit in such a manner that a damping effect is achieved. 4. A drive unit according to any one of the preceding claims, characterized in that the housing is provided with a compartment comprising a mechanical indicator fitted with limit switches for controlling the maximum angular displacement to be provided by the drive unit. 5. A drive unit according to any one of the preceding claims, characterized in that the drive unit comprises a coupling positioned within the housing, which coupling is provided with a right-angled transmission as well as with a linear transmission. 6. A piece of furniture provided with a drive unit according to any one of the preceding claims 1 - 5.

Inventors: VAN DER MEER FRANCISCUS HENRIC, VAN DER MEER, FRANCISCUS, HENRICUS, JOZEF
Applicants: ELMEQ NEDERLAND B V, MEER FRANCISCUS HENRICUS JOZEF, ELMEQ NEDERLAND B.V., VAN DER MEER, FRANCISCUS, HENRICUS, JOZEF
Application year: 1998
Main classification: A47B9
IPC codes: A47B9