Abstract:
Electromotive furniture drive for displacing parts of a piece of furniture relative to one another. The drive includes a drive element that can linearly move along a linear motion axis. This drive is provided for pivoting a pivotal element, which can pivot about a pivot axis and which, when the furniture drive is in a mounted position, is actively connected to a part of the piece of furniture to be displaced. An element may be provided that, during the displacing motion, maintains the engagement between the drive and the pivotal element at a point P that is essentially fixed along the linear motion axis. The furniture drive can be easily and economically produced and has a sturdy design.

Description:
CROSS-REFENCE TO RELATED APPLICATIONS  
       [0001]     This application is a continuation of international application no. PCT/EP2003/006548, filed 20 Jun. 2003, which claims priority of German patent application no. 102 31 290.7, filed Jul. 10, 2002, and each of which is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION  
       [0002]     This invention relates to a electromechanical furniture drive mechanism for moving sections of a piece of furniture relative to one another. More particularly the invention relates to a furniture drive mechanism configured for exerting substantially consistent adjustment forces during movement of sections of a piece of furniture relative to one another.  
       BACKGROUND OF THE INVENTION  
       [0003]     Furniture drive mechanisms of that type have been widely known and are used for instance as adjustment drives for adjusting the parts of a lattice array relative to one another.  
         [0004]     EP 0 372 032 B1 describes a furniture drive mechanism of the type referred to above, comprising a pivot-mounted, pivotable swivel unit which is functionally connected to a positionally adjustable part of the furniture via a drive unit that is linked to the furniture drive mechanism in its operating state and can be moved in an axial direction along a linear axis of travel. In that earlier furniture drive mechanism the axially movable drive unit includes the nut of a spindle drive while the swivel unit is a pivot lever that is rigidly connected to a pivot shaft which in turn is functionally connected to the adjustable section of the furniture item. The spindle drive nut is in freely moving contact with the end of the pivot lever facing away from the pivot shaft.  
         [0005]     Similar furniture drive mechanisms have also been described in DE 38 42 078 C2, EP 0 583 660 B1, DE 100 46 750 C1 and DE 100 46 752 C1.  
         [0006]     In these earlier furniture drive designs the adjustment movement is accompanied by a change in the angular position of the pivot lever relative to the linear axis of travel of the drive unit. The resulting drawback is that the effective length of the lever arm that engages in the pivot shaft, meaning the length of the lever-arm component that extends perpendicular to the linear axis of travel of the drive unit, keeps changing during the adjustment movement, which in turn causes the force that bears on the pivot shaft and thus on the adjustable part of the furniture item during the adjustment movement to change continuously and to diminish as the effective length of the lever arm decreases. As the angle between the linear axis of travel of the drive unit and the longitudinal axis of the pivot lever grows more acute, the adjustment force exerted by the furniture drive mechanism on the adjustable part of the furniture item decreases at a correspondingly steep rate. A particular disadvantage lies in the fact that the angle grows more acute as the furniture drive mechanism approaches the end position of its adjustment movement even though that is where the force of the furniture acting on the drive mechanism, and thus the necessary adjustment force, is usually the highest.  
         [0007]     DE 100 17 978 A1 and DE 100 17 979 A1 each describe similar furniture drive mechanisms in which, however, the drive unit is in the form of a flexible tension element such as a pull strip.  
         [0008]     It is an object of this invention to introduce a furniture drive mechanism configured for displacing parts of a piece of furniture relative to each other, and in which the stated drawback of the conventional furniture drive mechanisms is eliminated by substantially avoiding any decrease of the adjustment force provided by the furniture drive mechanism during the adjustment movement, yet which can be produced by a simple process and thus at low cost.  
         [0009]     This object is achieved by an electromechanical furniture drive configured during an adjustment movement, for adjusting sections of a piece of furniture relative to one another, comprising a drive unit, the drive unit being axially movable along a linear axis of travel for tilting a swivel unit, which in an operational position of the furniture drive mechanism is functionally connected to an adjustable section of the piece of furniture and can be rotated around a swivel axis, and the drive unit including an element configured for causing the drive unit to remain engaged in the swivel unit at substantially fixed point P along a linear axis of travel ( 30 ) throughout the adjustment movement.  
         [0010]     The invention is based on the realization that the effective length of the swivel-unit lever arm changes because during the adjustment movement the point at which the drive unit engages in the swivel unit keeps shifting along the linear axis of travel of the drive unit. Accordingly, the invention is based on a concept whereby an element is provided that keep the drive unit engaged in the swivel unit at an substantially fixed point along the linear axis of travel. In that fashion, the effective length of the lever arm remains substantially unchanged during the adjustment movement and, consequently, the adjustment force exertable on the adjustable section of the furniture item by the furniture drive mechanism will remain substantially constant throughout the adjustment movement. It follows that, throughout that adjustment movement, forces of an substantially uniform order of magnitude are applied on the adjustable part of the furniture item, and most significantly in the end positions of the adjustment movement as well.  
         [0011]     The furniture drive mechanism according to this invention is of a simple design, consequently inexpensive to produce, and rugged. It lends itself well to the adjustment of any given sections of a piece of furniture but especially to the adjustment of movable parts of a support system such as supports the slats of a lattice supporting the cushions of a chair and/or chaise longue.  
         [0012]     To keep the drive unit engaged in the swivel unit at an substantially fixed point along the linear axis of travel throughout the adjustment movement, the swivel unit, or a component attached to the swivel unit, is provided in the direction of rotation with an extension which is so configured that during the adjustment movement the drive unit remains constantly engaged in the swivel unit at an substantially fixed point. To that effect, the swivel unit may be provided for instance with several lever arms consecutively positioned in the direction of rotation and sequentially engaging the drive unit in such fashion that over the course of the adjustment movement the drive unit remains engaged in the swivel unit at an substantially fixed point along the linear axis of travel. In an implementation of the inventive concept that is particularly simple and thus manufacturable at low cost, the element or provisions that keep the drive unit engaged in the swivel unit during the adjustment movement at an substantially fixed point along the linear axis of travel encompass a cam-shaped guide element for the drive unit which guide element is linked to the furniture drive mechanism in its operating position. Cams of that type are particularly simple in design and correspondingly inexpensive to make, meaning that the overall furniture drive mechanism according to the invention is particularly uncomplicated and can be produced at low cost.  
         [0013]     In another embodiment of the invention, the guide element has an substantially circular-arc profile. The guide element in that configuration is particularly simple and thus inexpensive to make.  
         [0014]     In the aforementioned embodiment, the guide element can extend over an angle of 360°, or approximately 360°, relative to the swivel axis, with the guide element substantially having a fully circular profile. In another embodiment, of the invention, the guide element substantially constitutes the segment of a circle and, in particular, a quarter circle. For the guide element, this much of an extension in the direction of rotation is usually sufficient to ensure the engagement of the drive unit in the swivel element during the adjustment movement at an substantially fixed point along the linear axis of travel.  
         [0015]     In another embodiment employing a guide element configured as a cam, the guide element has an substantially curved profile whereby, in the circumferential direction of the guide element, at least certain sections vary in their distance between the periphery of the profile and the swivel axis. In this embodiment the guide element and the drive unit jointly constitute a cam drive mechanism. As the curvature of the guide element changes in during constant speed of the drive unit along the linear axis of travel, the angular at which the swivel unit is rotated will change correspondingly.  
         [0016]     Depending on individual requirements, the drive unit may be a traction or a pressure element as provided for in other embodiments.  
         [0017]     In other embodiments of the invention, the drive unit may be flexible or substantially rigid.  
         [0018]     In an extraordinarily advantageous embodiment according to this invention, the drive unit that engages in the guide element in the operating position of the furniture drive mechanism is provided with a toothed surface that substantially meshes with a corresponding toothed surface of the guide element. Configured that way, the guide element and the drive unit interact like a gear system. This embodiment is particularly simple and thus inexpensive to make. Moreover, it is especially sturdy and permits the application of considerable force.  
         [0019]     In this embodiment the guide element may be in the form of a gear wheel or of a toothed quadrant as provided for in another embodiment. Gear wheels are commercially available as simple and therefore inexpensive standard products, which further simplifies the design of the furniture drive mechanism according to the invention.  
         [0020]     In another embodiment of the above-described concept, the drive unit encompasses a chain, the combination constituting a chain drive. This embodiment as well is particularly simple and thus inexpensive to make and permits the application of considerable force.  
         [0021]     In another embodiment of the inventive concept employing a guide element in the form of a gear wheel or toothed quadrant, the drive unit may include a toothed rack, the combination forming a rack-and-pinion drive mechanism. This configuration is again particularly uncomplicated, correspondingly inexpensive to make, and especially rugged.  
         [0022]     In another embodiment the drive unit encompasses a rope or belt that works with the guide element, in the form of a rope drum or belt pulley, the combination constituting a belt drive mechanism. This embodiment further simplifies the design of the novel furniture drive mechanism.  
         [0023]     The guide element may be a separate component rigidly connected to the swivel unit. However, the configuration of the furniture drive mechanism according to the invention can be further simplified by producing the guide element and the swivel unit in the form of one integral component, or with the swivel unit doubling as the guide element, as provided for in another embodiment of the invention.  
         [0024]     The axially moving drive unit may be of any suitable design. In a desirable implementation of the inventive concept the axially moving drive unit connects to, or is constituted of, a linearly movable drive element of a spindle drive mechanism. Spindle drives of that kind are commercially available as simple, low-cost standard components, they lend themselves well to the transfer of strong forces, and they are sturdy.  
         [0025]     The axially movable drive element of the aforementioned spindle drive mechanism may be a spindle nut which is torsionally locked but axially movable on a rotating drive spindle.  
         [0026]     In a kinematically reversed implementation of this embodiment, the axially movable drive element of the spindle drive mechanism may equally well be an axially movable but torsionally locked spindle on which a stationary, rotationally drivable spindle nut is mounted.  
         [0027]     In another advantageous embodiment of the inventive concept, the drive unit is attached to the swivel unit or to the guide element.  
         [0028]     An electromechanical adjustable support system for the cushions of a chair and/or lounger and especially for the mattress of a bed are provided. Variations and further embodiments of the support system are described herein.  
         [0029]     An inventive adjustment assembly for relatively adjustable parts of a piece of furniture is provided, as set forth herein. Appropriate, advantageous embodiments of the invention are described herein that are particularly suited for different applications and types of furniture.  
         [0030]     Relative terms such as up, down, left, and right are for convenience only and are not intended to be limiting. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0031]     The following will explain this invention in more detail based on embodiment illustrated in the attached drawings in which  
         [0032]      FIG. 1  is a top view of a support system according to this invention, implemented in a slat array and equipped with embodiment of a furniture drive mechanism according to the invention;  
         [0033]      FIG. 2  is a sectional view along the line II-II in  FIG. 1 ;  
         [0034]      FIG. 3  along the same view as in  FIG. 2 , depicts an enlarged-scale detail of  FIG. 2  in the area of the furniture drive mechanism;  
         [0035]      FIG. 4  in similar fashion as  FIG. 3 , shows another embodiment of a furniture drive mechanism according to the invention;  
         [0036]      FIG. 5  on a scale larger than that of  FIG. 4 , is a view from the left of a belt pulley of the furniture drive mechanism per  FIG. 4 ; and  
         [0037]      FIG. 6  is a view, similar to that in  FIG. 3 , of a further embodiment implementation of a furniture drive mechanism according to this invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0038]     In the drawings and description, identical or comparable components bear identical reference numbers.  
         [0039]      FIG. 1  depicts an embodiment of a support device or system  2  according to the invention, which in the case of this embodiment includes a slat system with a frame or base body  4  to which connects a stationary center support part or section  6 . The center support part or section  6  connects in hinged fashion to a leg support part or section  8  which can be tilted around a horizontal swivel axis and which, at its far end away from the center support section  6 , connects in hinged fashion to a lower leg support part or section  10  that can be tilted around a horizontal swivel axis. The end of the center support section  6  facing away from the leg support section  8  connects in hinged fashion to a torso or upper body support section  12  that can be tilted around a horizontal swivel axis and, at its end facing away from the center support section  6 , connects in hinged fashion to a head support section  14  that can be tilted around a horizontal swivel axis. The interconnection between the support sections  6  to  14  may be conventional and therefore need not be discussed here in detail.  
         [0040]     On their top side the support sections  6  to  14  are provided with resilient slats only one of which is identified in the drawing by reference number  16 . These slats  16  provide resilient support, by the support system  2 , of the cushions, not illustrated, of a chair and/or lounger and/or chaise longue or for instance of the mattress of a bed.  
         [0041]     The inventive support system  2  is equipped with a first embodiment of a furniture drive mechanism  18  according to the invention, which, in the case of this embodiment, serves to adjust the torso support section  12  and the head support section  14  relative to the center support section  6 . In this embodiment example the furniture drive mechanism  18  is accommodated in a hollow lateral rail or beam  19  of the center support section  6 .  
         [0042]      FIG. 2  is a sectional view along the line II-II in  FIG. 1   
         [0043]      FIG. 3  shows the inventive furniture drive mechanism  18  per  FIG. 2  on an enlarged scale. The furniture drive mechanism  18  encompasses an electric motor  20  that is mounted on a wall of the lateral rail  19  and, via a gear transmission  22 , connects to and rotationally drives a fixed, screw-type drivable spindle  24  of a spindle drive mechanism. A spindle nut  26  positioned on the spindle is rotationally locked while capable of moving back and forth in the direction of a double-headed arrow  28 . As a function of the direction of rotation of the drive shaft of the electric motor  20 , and thus of the direction of rotation of the spindle  24 , the spindle nut  26  moves along a linear axis of travel  30  in  FIG. 3 , to the left or to the right.  
         [0044]     The support system  2  in this embodiment features an inventive adjustment assembly  32  which in the case of this embodiment encompasses a pivot shaft  36  that can rotate around a swivel axis  34 , that is mounted on the frame  4  of the support system  2  and is rigidly connected to a pivot lever  38 . The pivot lever  38  connects to the torso support section  12  and to the head support section  14  in such fashion that a rotation of the pivot shaft  36  around the swivel axis  34  causes the torso support section  12  and the head support section  14  to change position. The adjustment assembly  32  according to this invention includes a swivel unit that is rigidly connected to the pivot shaft  36  and in the case of this embodiment is in the form of a gear-wheel segment  40  that meshes with a flexible traction element in the form of a chain  42  one end of which is attached to the gear-wheel segment  40  while its other end is attached to the spindle nut  26 . In this embodiment the chain  42  serves as the drive unit of the furniture drive mechanism  18  that is movable along the linear axis of travel  30 .  
         [0045]     According to the invention, provisions are incorporated that keep the drive unit in the embodiment per  FIG. 1 , i.e. the chain  42 , engaged in the swivel unit, here the gear-wheel segment  40 , at an substantially fixed point P along the linear axis of travel  30  throughout the adjustment movement. In the embodiment per  FIG. 1 , these provisions consist in a design whereby the gear-wheel segment  40  is in the form of a cam serving as the guide element for the chain  42 . In this embodiment the gear-wheel segment  40  substantially has a limited circular-arc i.e. quarter-circle profile. During the adjustment movement the gear-wheel segment  40  pivots around the swivel axis  34 , which changes the wrap angle of the chain  42  around the gear-wheel segment  40 . But the chain  42  remains constantly engaged in the gear-wheel or gear segment  40  at an substantially fixed point P along the linear axis of travel  30 , which in turn leaves the effective length of the lever arm, symbolized in  FIG. 3  by a dashed line  44 , through which the chain  42  engages in the pivot shaft  36 , substantially unchanged during the adjustment movement.  
         [0046]     The functional operating mode of the inventive furniture drive mechanism  18  is as follows:  
         [0047]     To move the torso support section  12  and the head support section  14  from an adjustment-movement starting position, not shown, in which the torso support section  12  and the head support section  14  jointly with the center support section  6  form one horizontal support plane, into an adjusted position as illustrated in  FIG. 2 , the electric motor  20  drives the spindle  24  via the gear transmission  22  in such fashion that the spindle nut  26  per  FIG. 3  travels to the right. During that process the chain  42  meshes with the teeth of the gear-wheel segment  40  so that, as the spindle nut  26  per  FIG. 3  is set in motion, the gear-wheel segment is tilted clockwise to the right around the swivel axis  34  as viewed in  FIG. 3 . Because of the rigid connection between the pivot lever  38  and the pivot shaft  36 , the pivot lever in  FIG. 3  as well is shifted in a clockwise direction, consequently tilting the torso support section  12  and the head support section  14  per  FIG. 1  in a clockwise direction.  
         [0048]     During the adjustment movement the chain  42  at point P is continuously engaged in the gear-wheel segment  40 , as a result of which the effective length of the lever arm  44 , through which the chain  42  engages in the pivot shaft  36 , will not change during the adjustment movement. In turn, since the effective length of the lever arm  44  does not change during the adjustment movement, a constant driving torque of the electric motor  20  will keep the adjustment force that the furniture drive mechanism  18  can bring to bear on the torso support section  12  and the head support section  14  during the adjustment movement substantially unchanged. In other words, the furniture drive mechanism  18  according to this invention is capable of applying substantially constant forces on the torso support section  12  and the head support section  14  throughout the adjustment movement.  
         [0049]      FIG. 4  depicts another embodiment of a furniture drive mechanism  18  according to this invention, which differs from the embodiment per  FIG. 3  in that the drive unit employs a flexible belt  46  instead of a chain. In this embodiment, the swivel element that is rigidly connected to the pivot lever  38  and constitutes a cam-like guide element for the belt  46 , is in the form of a belt pulley  48  that works along the principle of a rope reel. One end of the belt  46  is attached to the pulley  48  while its other end is attached to the spindle nut  26 . During the adjustment movement in this embodiment, the belt  46  engages the pulley  48  at an substantially fixed point P along the linear axis of travel  30 , so that the effective length of the lever arm  44  through which the belt  46  engages in the pivot shaft  36  remains substantially unchanged during the adjustment movement.  
         [0050]      FIG. 5  shows that the pulley  48  of  FIG. 4 , viewed from the left, is composed of two mutually connected disks  44  whose ends facing away from the swivel axis  34  are bent outward so as to form a groove  54  that accepts the belt  46 . Retaining the belt  46  in the groove  54  prevents the belt  46  from slipping off the pulley  48  during the adjustment movement.  
         [0051]      FIG. 6  illustrates a third embodiment of a furniture drive mechanism  18  according to the invention, which differs from the embodiment per  FIG. 3  in that the drive unit is provided with a toothed rack  56  in place of a chain  42 , which rack is integrated into the end of the spindle nut  26  facing the gear-wheel segment  40 . For example, the toothed rack  56  and the spindle nut  26  may include of a single integrated molding of a synthetic material. The teeth of the toothed rack  56  are so shaped as to substantially match and mesh with the teeth of the gear or gear-wheel segment. During the adjustment movement in this embodiment the toothed rack  56  remains engaged in the gear-wheel segment  40  at an substantially fixed point P of the linear axis of travel throughout the adjustment movement, so that the length of the lever arm through which the toothed rack  56  engages in the pivot shaft  36  will remain substantially unchanged.  
         [0052]     The furniture drive mechanism  18  according to this invention is uncomplicated, it can be produced at low cost, and it is of a rugged design.  
         [0053]     While this invention has been described as having a preferred design, it is understood that it is capable of further modifications, and uses and/or adaptations of the invention and following in general the principle of the invention and including such departures from the present disclosure as come within the known or customary practice in the art to which the invention pertains, and as may be applied to the central features hereinbefore set forth, and fall within the scope of the invention or limits of the claims appended hereto.