Classifications

• • A—HUMAN NECESSITIES
  • A47—FURNITURE; DOMESTIC ARTICLES OR APPLIANCES; COFFEE MILLS; SPICE MILLS; SUCTION CLEANERS IN GENERAL
  • A47B—TABLES; DESKS; OFFICE FURNITURE; CABINETS; DRAWERS; GENERAL DETAILS OF FURNITURE
  • A47B9/00—Tables with tops of variable height
  • A47B9/04—Tables with tops of variable height with vertical spindle
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16H—GEARING
  • F16H25/00—Gearings comprising primarily only cams, cam-followers and screw-and-nut mechanisms
  • F16H25/18—Gearings comprising primarily only cams, cam-followers and screw-and-nut mechanisms for conveying or interconverting oscillating or reciprocating motions
  • F16H25/20—Screw mechanisms
• • A—HUMAN NECESSITIES
  • A47—FURNITURE; DOMESTIC ARTICLES OR APPLIANCES; COFFEE MILLS; SPICE MILLS; SUCTION CLEANERS IN GENERAL
  • A47B—TABLES; DESKS; OFFICE FURNITURE; CABINETS; DRAWERS; GENERAL DETAILS OF FURNITURE
  • A47B2200/00—General construction of tables or desks
  • A47B2200/0035—Tables or desks with features relating to adjustability or folding
  • A47B2200/005—Leg adjustment
  • A47B2200/0051—Telescopic
  • A47B2200/0054—Telescopic with three telescopic parts
• • A—HUMAN NECESSITIES
  • A47—FURNITURE; DOMESTIC ARTICLES OR APPLIANCES; COFFEE MILLS; SPICE MILLS; SUCTION CLEANERS IN GENERAL
  • A47B—TABLES; DESKS; OFFICE FURNITURE; CABINETS; DRAWERS; GENERAL DETAILS OF FURNITURE
  • A47B2200/00—General construction of tables or desks
  • A47B2200/0035—Tables or desks with features relating to adjustability or folding
  • A47B2200/005—Leg adjustment
  • A47B2200/0056—Leg adjustment with a motor, e.g. an electric motor
  • A47B2200/006—Leg adjustment with a motor, e.g. an electric motor with table or desk equipped with limit switches
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16H—GEARING
  • F16H25/00—Gearings comprising primarily only cams, cam-followers and screw-and-nut mechanisms
  • F16H25/18—Gearings comprising primarily only cams, cam-followers and screw-and-nut mechanisms for conveying or interconverting oscillating or reciprocating motions
  • F16H25/20—Screw mechanisms
  • F16H2025/2062—Arrangements for driving the actuator
  • F16H2025/2084—Perpendicular arrangement of drive motor to screw axis
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16H—GEARING
  • F16H25/00—Gearings comprising primarily only cams, cam-followers and screw-and-nut mechanisms
  • F16H25/18—Gearings comprising primarily only cams, cam-followers and screw-and-nut mechanisms for conveying or interconverting oscillating or reciprocating motions
  • F16H25/20—Screw mechanisms
  • F16H2025/2062—Arrangements for driving the actuator
  • F16H2025/209—Arrangements for driving the actuator using worm gears
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16H—GEARING
  • F16H25/00—Gearings comprising primarily only cams, cam-followers and screw-and-nut mechanisms
  • F16H25/18—Gearings comprising primarily only cams, cam-followers and screw-and-nut mechanisms for conveying or interconverting oscillating or reciprocating motions
  • F16H25/20—Screw mechanisms
  • F16H25/2015—Means specially adapted for stopping actuators in the end position; Position sensing means

Definitions

• This invention concerns a linear actuator, in particular as a drive unit for lifting columns, comprising a reversible electric motor with a drive shaft connected to a transmission and where the electric motor and transmission are contained in a housing, a spindle unit, the one end of which is connected to the transmission, a spindle nut on the spindle unit, which spindle nut moves longitudinally on the spindle unit, when this is rotated by the motor, a tube shaped actuation rod connected to the spindle nut and which moves respectively longitudinally out and in depending on the spindle nuts movement and where the actuation rod has an internal cross section larger than the spindles outer cross section so that the actuation rod can sit in over the spindle and which with its other end is designed to be fixed to the construction in which the actuator is to be built .
• the invention is based upon the type of lifting columns that are used with height adjustable desks, and are based on an electrically driven linear actuator as drive unit.
• the columns comprises two or three telescopically adjustable tubes.
• the actuator is in its entirety placed so that it is hidden inside the column, which requires a large cross section of the column. The construction is therefore not suitable for slim legs for desks.
• the actuators length of stroke is proportional with its installation dimension which causes a contrast between the installation dimensions of the column and the desired minimum and maximum height of the column.
• the achievable maximum and minimum heights with a linear actuator are in reality a compromise where each millimeter of the installation dimension and the stroke length counts.
• the internal placement of the actuator contributes negatively to the relationship between the minimum and maximum heights.
• the purpose of the invention is to provide an actuator, which can also be used in connection with slim lifting columns .
• the actuator is characterized in that the housing has a bearing surface which stretches at right angles to the longitudinal axis of the spindle unit and is designed to rest against the construction, preferably the top of a lifting column in which the actuator is to be fitted.
• the actuator is fitted above the column with only the actuation rod and perhaps the outer tube belonging to it led down into the inside of the column. In this way the actuator can be used in connection with very slim lifting columns.
• the height of the actuator in the area over the end of the column can be made low.
• the motor can either be placed so that it sits parallel with the outer tube or at a right angles to it.
• the column can always be turned such that the motor sits under the desktop. However it is preferred that the motor is placed such that it sits at a right angle away from the actuation rod and therewith the column, in this way the motor is least visible but also takes up the least room with regard to height.
• the height over the column can be further reduced by the actuator being so designed such that in this area the transmission is in one plane only i.e.
• the bearing surface can be made relatively large or put another way the motor can be moved a relatively long distance from the longitudinal axis of the spindle unit. This means that it is not necessary to make cut outs in the side of the column in order to give room to the motor housing. Furthermore it is important in relation to that there in the areas in which the lifting columns are usually placed often is a closed frame or another bearing profile under the desk surface .
• a special problem is stopping the actuator in the end positions, which is typically done with end stop switches.
• the problem is to establish a clear activation and to find room for the contacts in the construction.
• the invention solves this by the activating organ for the switches being held in a neutral position between two spring elements and where the activating organ is activated either directly or indirectly in the spindle nuts end positions.
• Fig. 1 shows in the perspective
• Fig. 2 shows a longitudinal cross section of the actuator
• Fig. 3 shows a close up picture of the end stop switches seen from the bearing surface
• Fig. 4 shows the same as fig. 3 seen from the side
• Fig. 5 shows an embodiment of the actuator with a larger stroke length
• Fig. 6 shows a longitudinal cross section of the actuator in a retracted condition.
• Fig. 7 shows a detailed view of the end of the actuator, and
• Fig. 8 a detailed view of the fixing of the actuation rod in the housing.
• the actuator has a housing 1, which in this case comprises two shells la, lb and a lid lc.
• the two shells la, lb have an assembly plan which runs through the longditudinal axis of the actuators outer tube 2.
• the two shells la, lb forms two chambers Id, le, one of which, the motor chamber Id containing the motor unit is cylindrical in shape and externally closed.
• the other chamber le, the assembly chamber appears as a rectangular box which is open from above and can be closed with the lid lc.
• the underside of the assembly chamber le forms a bearing surface If upon which the actuator can rest on the end of a column.
• Screw holes lg extends from the bearing surface up through the assembly chamber and up onto the upper side of the lid for securing the actuator to the column with screws. Inside the housing the screw holes are shaped as ducts.
• the outer tube 2 rests wit one end in the assembly chamber.
• the tube is fixed with cams in the bearing surface of the chamber, these cams rest in recesses in the tube.
• Inside the outer tube there is a spindle 3, upon which there is a spindle nut 4.
• a tube shaped actuation rod 5 is with one end fixed to the spindle nut 4.
• an eye 6 is fixed, by means of the actuation rod can be fixed to the column into which the actuator is to be built. Instead of an eye the actuation rod can be restrained from rotating in another way, such as matching cams and recesses or fins and slits.
• a bushing 24 which functions as a guide for the actuation rod.
• the bushing is fixed with a set of spring legs, which with a barb engages a cut out slit 25 in the outer tube.
• a ball bearing 7 On the end of the spindle there is a ball bearing 7, which is nested in the housing.
• a large gear wheel 8 is mounted on the spindle. This is fixed against rotation by means of a spline connection as on the end of the spindle there is by riveting mounted a bushing 9 on the outer surface of which one part of the spline connection is shaped whilst the corresponding part is shaped in a cut out in the gear wheel.
• the spindle is driven by a reversible electric motor 10.
• An extension of the motor shaft is shaped as a worm which drives a worm gear 11.
• One end of the screw is fixed in the actuator and the coils run such that they create a braking effect on the cylinder and therewith the worm gear, when the actuation rod pulls inwards and thereby contributes to the self locking effect of the actuator.
• the spring has no braking effect, cp. the applicants EP 662 573.
• the worm gear with corresponding spring is fitted to a console 14 on the motors front cover.
• a short transmission axle 22, which with it's middle part is resting in the housing is with it's one end received in the cylinder 12 on the side of the worm wheel 11 and is therefore rotation inhibited via a splines connection.
• the other end of the axle is by means of a spline joint connected with a gear wheel 16, which engages the gear wheel 8 on the end of the spindle 3.
• the two gear wheels 8, 16, are thus located in the same plane and are also identical and as such neutral in their exchange ratio.
• a contact set of two switches 15a, 15b In the outer tube 1 there is in a groove a slider 23 made of a metal strip. The end nearest the free end of the outer tube is bent inwards so that it is pushed by the end of the spindle nut 4. On the other end of the slider there is a plastic means 17 with two contact surfaces 18a, 18b, that can activate the respective switches 15a, 15b. the plastic means 17 has a further contact surface 19, which sits inside the outer tube and which is pushed by the other end of the nut.
• the plastic means 17 has a cam 27, which rests between the ends of two coil springs 20a,20b mounted in the assembly chamber.
• the ends of the two coil springs are held at a distance from each other by a small wall 21 as a distance keeper.
• the spring effect will also here ensure that the plastic means and the slider return to the neutral position when the actuation rod again moves outwards.
• the construction ensures that the switches are in the correct position when the actuation rod leaves the end positions also that the slider cannot by accident between the end positions be displaced and activate the end stop switches. It is to be understood that the switches either directly cut off the current to the motor or that they are part of a control circuit with relays cutting off the motor current.
• the usual solutions with optical or magnetic encoders or potentiometers can be used.
• the actuator can be connected to a control box containing a control and current supply.
• the control box can be connected to the mains and a control panel to activate the actuator.
• FIG. 5-8 an embodiment of the actuator is shown according to the invention with a greater stroke length than the previous embodiment.
• the motor unit with transmission and housing is as described above, the difference is entirely in the telescopic movement.
• This is based on a telescopic spindle with an inner and outer part 30a, 30b.
• the outer part 30b is via a spindle nut 32 in connection with the tube shaped actuation rod 31.
• the outer part 30b will move outwards on the inner part 30a of the telescope spindle, whilst the actuation rod 31 will move outwards on the outerpart 30b. In this way an almost doubling of the stroke length can be achieved in comparison to the previously described embodiment.
• an actuator is provided that is suitable as a drive unit to slim lifting columns for tables. It is to be understood that the use of the actuator is not limited to this. Even though in the first instance it is considered that the actuator is turned so that the motor is at the top, there is of course no reason why it cannot be turned so that the motor sits at the bottom. In such cases the motor can be built into the foot of the column.
• An alternative to the bearing surface If is the upper surface of the housing, in the actual embodiment the lid lc, being designed as bearing surface, i.e. the actuator can be secured with the lid abutting to an overhead part, there could be clamps rising up from below or the column could be secured to the underneath of a frame or tabletop and the actuator could itself in a similar manner be secured to the frame or tabletop.

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• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Transmission Devices (AREA)

Applications Claiming Priority (5)

Publications (1)

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ID=26068913

Family Applications (1)

Country Status (3)

Families Citing this family (7)

Family Cites Families (12)

• 2001
  • 2001-11-16 EP EP01996319A patent/EP1339302A1/de not_active Withdrawn
  • 2001-11-16 WO PCT/DK2001/000767 patent/WO2002039848A1/en not_active Application Discontinuation
  • 2001-11-16 AU AU2002223508A patent/AU2002223508A1/en not_active Abandoned

Non-Patent Citations (1)

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