CABINET

The invention relates to a safety clutch connected to a pull-down unit for a cabinet, which pull-down unit is connected movable to the cabinet by a linear actuator.

BACKGROUND

When parts of furniture are made movable for example by a linear actuator, it is important that moving of the furniture part can be stopped in order to avoid that objects and in particular hands, fingers or other body parts of a person will get jammed between the movable furniture part and a solid surface in shape of a table top, a floor, a shelf or other solid objects. Such jamming can cause that the objects jammed, the furniture part and the surface may be damaged. In case of jammed body parts, the body parts could be injured.

Most often, items placed in a cabinet will block for each other in such a way that if you want to get hold of items stored in the back of the cabinet, it is difficult to locate the item or to get an overview of the items stored in the back of the cabinet, without removing the items stored in front of the cabinet first.

It is possible to utilise the space in the back of the cabinet if for example shelves in the cabinet are made shorter and a dividing wall is positioned parallel in relation to a back wall of the cabinet in order to create a space between the dividing wall and the back wall.

Here a vertical moving furniture part or a pull down unit can be positioned. The pull down unit can be used for storing items in the back of a cabinet and when lowering the pull down unit, the user will have easy access to the items. Moreover, the items in the not movable part of the cabinet will also be easier to access and to overview.

Such a piece of furniture is known from EP 2 31 1 346 A1 , where the piece of furniture has a horizontally arranged closing plate i.e. table board, and a pull- out or pull-down unit. The pull-out unit is closed using the closing plate in a closed condition, and protruded over the closing plate in a vertical manner in an opened condition. A separation wall is provided between an inner region of the piece of furniture and the pull-out unit. The closing plate is a bottom of a wall cupboard or a wall shelf. The pull-out unit is arranged at a side of the piece of furniture facing the wall and parallel to the wall. The pull down unit is conveniently provided with a linear actuator, to move the pull down unit down for access of stored items and up to hide the stored items and to bring the pull down unit into storing position, thereby hiding the pull down unit in the rear of the cabinet. From WO 201 1/072686 a cabinet with a pull-down unit is known. Here the pull-down unit is provided with a linear actuator for moving the unit up and down in relation to the cabinet. The linear actuator comprising a housing with a reversible low voltage DC-motor and a transmission. At the end of the housing there is a spindle. On the spindle there is a spindle nut to which is connected a tube shaped rod 7 with a square cross section.

The linear actuator is provided with a squeeze protection based on a piezo element. Using a piezo element as the only squeeze protection can have some drawbacks. If the element somehow gets prevented from stopping the movement of the pull-down unit there is a risk for squeezing. Therefore a simple safety clutch alone or in combination with an electronic squeeze protection will provide more protection against squeezing.

SUMMARY OF THE INVENTION

The purpose of the invention is to provide a simple and safe squeeze protection for a piece of furniture as mentioned above.

A linear actuator used for movement in the pull-down unit is more or less a standard component and comprises an electric motor, which motor through a gear or transmission drives a spindle in shape of a threaded rod to rotate around its longitudinal axis. The spindle having an external threading is rotated in a nut or bushing, having a complementary internal threading. The nut or bushing is mounted securely in a tube in such a way that the nut or bushing will not move or rotate in relation to the tube. The spindle is positioned substantially concentric in the tube.

When the spindle rotates in the nut or bushing, the nut or bushing will be moved towards one end of the spindle and in the direction of the rotation of the spindle is reversed, the nut or bushing will be moved towards the opposite end of the spindle.

Therefore if the tube is fixed in relation to rotation relative to the spindle, the tube will be moved in a longitudinal direction in relation to the spindle. By having a clutch according to the invention connected to an end of the tube, which clutch in engaged position prevents the tube from rotating, and thereby the nut, in relation to the rotating spindle, the clutch will be moved together with the tube.

A simple and safe squeeze protection is therefore provided by a safety clutch connected to a pull-down unit for a cabinet, which pull-down unit is connected movable to the cabinet by a linear actuator, where the safety clutch is provided between the linear actuator and the pull-down unit, which clutch comprises a rotatable part, which rotatable part is rotatable in relation to a housing fixed to the pull-down unit, and that the rotatable part is arranged axially movably in relation to the housing.

In an embodiment the rotatable part comprises an upper rotatable part, a lower rotatable part, which upper and lower rotatable part is connected by a cylindrical axle part.

In an embodiment the housing on its lower side is provided with a number of engagement parts and that the lower rotatable part on its upper side is provided with a number of complementary engagements parts.

In an embodiment the engagements parts are formed by teeth or ridges and grooves. To ensure that the engagement parts easily will engage, when the upper side of the lower rotatable part is moved towards the lower side of the housing a groove in the housing is more than 1 mm wider than a tooth or ridge on the upper side of the lower rotatable part. In an embodiment a groove on the upper side of the lower rotatable part is more than 1 mm wider than a tooth or ridge in the housing. In another embodiment a groove in the housing is more than 4mm wider than a tooth or ridge on the upper side of the lower rotatable part.

In yet an embodiment a groove on the upper side of the lower rotatable part is more than 4mm wider than a tooth or ridge in the housing.

In an embodiment the upper rotatable part or the lower rotatable part is formed integral with the cylindrical axle. In an embodiment the cylindrical axle is connected and fixed unrotatably in relation to the upper rotatable part or to the lower rotatable part by a spline and groove connection.

The clutch is provided with a rotating part, configured to rotate in a housing, which housing is attached to or integral with a bracket. The bracket is provided with common fastening means, for example the bracket can be provided with holes through which screws or other common fastening means can be inserted when fastening the bracket to a part of the pull down unit or to another part, which is fastened in relation to the pull down unit.

The pull down unit can advantageously be guided by one or more substantially vertical guide rails, grooves or the like provided at the sides of the pull-down unit and/or at the back of the pull-down unit in the space between the cabinet and the pull-down unit..

The linear actuator is positioned in order to let the movement take place in a substantial vertical direction. It should be understood that optimally the movement should be in a vertical direction, but tolerances within building industry should be able to be accepted. At a lower side of the housing, the housing is provided with a number of engagement parts in shape of for example grooves and teeth or ridges for engagement with complementary engagement parts, for example teeth or ridges and grooves on the rotatable part.

When the engagement parts from the housing and complementary engagement parts from the rotatable part are engaged, the rotatable part is prevented from rotating. A slight movement or rotation is possible, but when moving in either direction, the engagement parts will meet a stop and the movement or the rotation will stop.

The rotatable part, which is placed in a bore in shape of a drilled or in other common way provided hole, is provided with a cylindrical axle, which axle connects an upper part of the rotatable part with a lower part of the rotatable part. The axle and the rotatable part can be secured to each other by a fastening screw and a spline/groove connection in such a way that the upper and the lower rotatable part is fixed in relation to each other and, at the same time, able to rotate in the bore, if not prevented by the engagement parts.

The axle is longer than the bore and the axle is able to be moved in relation to the bore in axial direction, thereby being able to let the lower rotatable part rotate when the rotatable part is displaced in axial direction in relation to the bore and the housing in such a way that the engagement parts are not engaged.

When the pull down unit is secured to the clutch by the bracket, weight of the unit itself or from items stored in the unit in addition, will force the pull-down unit and its content in a downwards direction. Thereby the bracket and the housing are forced downwards. The upper rotatable part of the clutch, which is firmly connected to the tube of the linear actuator, will then cause that the clutch will act against the downward forces and hold the weight of the pull-down unit. Hereby the engagement means are pulled together limiting or preventing the rotatable part from rotating in relation to the housing. This will also limit or prevent rotation of the tube of the linear actuator and the linear actuator will move the pull-down unit upwards or downwards, depending on the direction or rotation of the spindle.

If the pull-down unit meets an obstruction on its way down, then the rotatable part will continue its downwards motion together with the tube and spindle, until the engagement parts of the lower rotatable part and the housing is no longer engaged.

Then the rotatable part can rotate freely, and the tube will therefore also rotate, which means that the nut within the tube will not rotate in relation to the spindle and the downwards movement is stopped and the only weight on the obstruction will be the weight from the pull-down unit and its content.

Further embodiments and advantages are disclosed below in the description and in the claims. BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described more fully below, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows schematically a clutch secured to an end of a linear actuator and to a pull-down unit, with the clutch in engaged position; Figure 2 shows schematically the clutch secured to the end of a linear actuator and to a pull-down unit, with the clutch in disengaged position;

Figure 3 shows schematically a perspective view of the clutch in engaged position;

Figure 4 shows schematically an exploded view of the clutch showing an embodiment of the rotatable part separated from each other; and Figure 5 shows schematically an exploded side view of the clutch.

DETAILED DESCRIPTION

Now convenient embodiments of the invention will be described. The safety clutch 1 comprises a bracket 2, which bracket 2 can be secured or fastened to a moveable furniture part 3 of a cabinet (not shown) by common means for fastening such as screws or bolts or by other fastening methods. Such a movable furniture part 3 can be called a pull down unit. A linear actuator is used for movement of the pull-down unit 3 in the cabinet.

The linear actuator (not shown) is more or less a standard component and comprises an electric motor, which motor through a gear or transmission drives a spindle in shape of a threaded rod to rotate around its longitudinal axis. The spindle having an external threading is rotated in a nut or bushing, having a complementary internal threading.

The nut or bushing is mounted securely in a tube 10 in such a way that the nut or bushing will not move or rotate in relation to the tube 10. The spindle is positioned substantially concentric in the tube 10. When the spindle rotates in the nut or bushing, the nut or bushing will be moved towards one end of the spindle and in the direction of the rotation of the spindle is reversed, the nut or bushing will be moved towards the opposite end of the spindle.

Therefore if the tube 10 is fixed in relation to rotation relative to the spindle, the tube 10 will be moved in a longitudinal direction in relation to the spindle.

The clutch 1 is provided with a rotatable part 4, 5, 6, configured to rotate in a housing 7, which housing 7 is attached to or integral with the bracket 2. The bracket 2 is provided with common fastening means 8, 9, for example the bracket 2 can be provided with holes 8 through which screws or other common fastening means 9 can be inserted when fastening the bracket 2 to a part of the pull down unit 3 or to another part, which is fastened in relation to the pull down unit 3.

The rotatable part 4, 5, 6 is by its upper rotatable part 4 is firmly connected to the tube 10 of the linear actuator. The upper rotatable part 4 is normally part of the linear actuator together with the tube 10.

The pull down unit 3 can advantageously be guided by one or more substantially vertical guide rails, grooves or the like (not shown) provided at the sides of the pull-down unit 3 and/or at the back of the pull-down unit 3 in the space between the cabinet and the pull-down unit 3.

A linear actuator 10 is positioned in order to let the movement take place in a substantial vertical direction. It should be understood that optimally the movement should be in a vertical direction, but tolerances within building industry should be able to be accepted. At a lower side 1 1 of the housing 7, the housing 7 is provided with a number of engagement parts 12 in shape of for example grooves and teeth or ridges for engagement with complementary engagement parts 12, for example teeth or ridges and grooves on the rotatable part 4, 5, 6..

When the engagement parts 12 from the housing 7 and complementary engagement parts 12 from the rotatable part 4, 5, 6 are engaged, the rotatable part 4, 5, 6 is prevented from rotating. A slight movement or rotation of the rotatable part 4, 5, 6 around an axis in a longitudinal direction of a bore 13 provided in the housing 7 is possible, but when moving in either direction of rotation, the engagement parts 12 will meet a stop due to engagements parts 12 blocking the rotation. The rotatable part 4, 5, 6, which is placed in the bore 13 in the housing 7 in shape of a drilled or in other common way provided hole, is provided with a cylindrical axle 5, which axle 5 connects an upper part 4 of the rotatable part with a lower part 6 of the rotatable part. The axle 5 and the rotatable part can be secured to each other by a fastening screw and a spline/groove connection 14 in such a way that the upper 4 and the lower rotatable part 6 is fixed in relation to each other and, at the same time, able to rotate in the bore 13, if not prevented by the engagement parts 12.

The axle 5 is longer than the bore 13 and the axle 5 is able to be moved in relation to the bore 13 in axial direction, thereby being able to let the lower rotatable part 6 rotate when the rotatable part 4, 5, 6 is displaced in axial direction in relation to the bore 13 and the housing 7 in such a way that the engagement parts 12 are not engaged. When the pull down unit 3 is secured to the clutch 1 by the bracket 2, weight of the unit 3 itself or from items stored in the unit in addition, will force the pull-down unit 3 and its content (not shown) in a downwards direction. Thereby the bracket 2 and the housing 7 are forced downwards.

The upper rotatable part 4 of the clutch 1 , which is firmly connected to a tube 10 of the linear actuator, will then cause that the clutch 1 will act against the downward forces and hold the weight of the pull-down unit 3.

Hereby the engagement means 12 are pulled together limiting or preventing the rotatable part 4, 5, 6 from rotating in relation to the housing 7. This will also limit or prevent rotation of the tube 10 of the linear actuator and the linear actuator will move the pull-down unit 3 upwards or downwards, depending on the direction or rotation of the spindle in the linear actuator.

If an lower side 15 of the pull-down unit 3 meets an obstruction on its way down, then the rotatable part 4, 5, 6 will continue its downwards motion together with the tube 10 and spindle, until the engagement parts 12 of the lower rotatable part 6 and the housing 7 is no longer engaged.

Then the rotatable part 4, 5, 6 can rotate freely, and the tube 10 will therefore also rotate, which means that the nut within the tube 10 will not rotate in relation to the spindle and the downwards movement is stopped and the only weight on the obstruction will be the weight from the pull-down unit 3 and its content.

In a simple embodiment, the clutch 1 is engaged for further operation by simply removing the obstruction, whereby the pull-down unit 3 moves downwards until the engagement parts 12 re-engages. Then the pull-down unit 3 can be operated normally again.

The upper rotatable part 4 can be assembled to the axle 5 and the lower rotatable part 6 by a screw or bolt through a longitudinal hole in the axle 5. A friction in the bore 13 between the axle 5 and the housing 7 can be provided in order to establish a starting torque. This will ensure that if the pull-down unit 3 is stopped in its downwards movement and a user changes the direction of the unit 3 to be moved upwards by changing direction of rotation of the spindle, then the linear actuator will be activated to move the tube 10 and the rotatable part 4, 5, 6 of the clutch 1 upwards and thereby bring the engagement parts 12 into an engaged position.

It is important that the friction between surfaces of the axle 5 and the bore 13 will be greater than the friction between the threading of the spindle and the nut, but not greater than the friction will be low enough to let the axle 5 rotate in the bore 13 of the housing 7, if the pull-down unit 3 meets an obstruction on its way to a lower or extended position. At an upper side of the housing 16, the housing is provided with a smooth and plane surface in order to let the upper rotatable part 4 rotate in relation to the housing 7 even if the upper rotatable part 4 is in contact with the upper side 16 of the housing 7. In an embodiment a bearing could be provided between the upper side 16 of the housing 7 and the upper rotatable part 4.

In an alternative embodiment the bearing (not shown) can be provided in relation to the bore 13 through the housing 7 in shape of a bushing, in which the rotatable part 4, 5, 6 can rotate in relation to the housing 7.

In an alternative embodiment, a sensor (not shown) can be provided to detect movement of the pull-down unit 3 in relation to the cabinet in order to be able to stop the linear actuator from running in no-load condition. Such a situation can occur if the pull-down unit 3 meets an obstruction on its way down, whereby the clutch 1 is axially displaced to disengage the engagement parts 12 and enable rotation of the rotatable part 4, 5, 6 of the clutch 1 and thereby the tube 10 of the linear actuator, which action will let the actuator rotate without extending further in an axial direction of the linear actuator, more specific in a downwards direction.

If no vertical movement is detected of the pull-down unit 3 in relation to the cabinet, the motor of the linear actuator can be stopped automatically by a timer or another type of switch, in order to stop the spindle from rotating unnecessary until it is activated again.

In addition to the safety clutch, the linear actuator can be provided with a known safety device in order to apply safety when the pull-down unit 3 is activated to be retracted into the cabinet also to avoid that objects and in particular hands, fingers or other body parts of a person will get jammed between the movable furniture part and the cabinet.