Abstract:
The invention relates to a drive device for moving a movable furniture part, in particular a drawer, said drive device acting as a latching and unlatching spring-loaded ejection device for ejecting the furniture part from a closed position in the opening direction and as a spring-loaded refraction device for retracting the furniture part into the closed position. The same spring spring-loads the drive device both when the latter acts as an ejection device and when the drive device acts as a refraction device.

Description:
The invention concerns a drive device for moving a movable furniture part, in particular a drawer. The invention further concerns a drawer extension guide having such a drive device and an article of furniture having such a drive device. 
     So-called touch-latch mechanisms for movable furniture parts such as drawers, drop doors and so forth have already been known from the state of the art for some time. They involve automatic opening of the movable furniture part after pressure is applied to the movable furniture part in the closing direction by a user. Separate switches which perform such an opening movement are sometimes also provided. That extra pressure applied to the movable furniture part triggers the ejection device, whereupon the movable furniture part is ejected from the furniture carcass in the opening direction by a force storage means being released. In most cases corresponding ejection devices are disposed beneath the drawer bottom or behind the drawer. 
     Mechanisms which facilitate or improve closing of a movable furniture part have also been known from the state of the art for some time. In that respect there are various versions of retraction devices by which a movable furniture part is automatically pulled in over the last region of the closing movement (generally a few centimeters) so as to guarantee that the drawer or the movable furniture part is securely closed. 
     An example of a publication showing both an ejection device and also a retraction device is WO 2007/028177 A1 to the present applicant. Two Figures originating from that specification are shown in the present specification as  FIGS. 15 and 16 . They show on the one hand an ejection device  8  as a structural unit. Shown as a second separate structural unit between the drawer rail  30  and the carcass rail  31  is a retraction device  9  which performs the closing movement of the drawer rail  30  relative to the carcass rail  31  in the closing direction SR. In that case the retraction device  9  must have its own spring, its own housing and all further entrainment members and so forth integrated therein so that the retraction operation can be satisfactorily implemented. In addition that specification shows a damping device  13  for the retraction device  9 . 
     A disadvantage with that known construction is that two separate, independent and costly structural units have to be provided in the region of an extension guide in order thereby to be able to perform on the one hand ejection and on the other hand retraction. In addition, in the state of the art, it is often relatively complicated to provide for stressing of the springs without a user noticing that as a difficulty when producing the movement upon opening or closing. 
     The object of the invention is to provide a drive device which is improved over the state of the art. In particular the invention seeks to provide that the ejection device and the retraction device are combined as much as possible into one structural unit so that fewer components are required. 
     That object is attained in conjunction with the features of the classifying portion of an aspect of the invention, in that the drive device acts on the one hand as a lockable and unlockable spring-loaded ejection device for ejecting the furniture part from a closed position in the opening direction, and on the other hand as a spring-loaded retraction device for retracting the furniture part into the closed position, wherein the same spring spring-loads the drive device both in its function as an ejection device and also in its function as a retraction device. By virtue of such a design configuration the spring provides both for acting to produce the ejection movement of the ejection device and also acting to produce the retraction movement of the retraction device. In that respect the spring can be in the form of a compression or a tension spring. In that respect the term spring also embraces force storage means in the form of gas ressure springs. Basically the spring can also be in the form of a magnetic spring. 
     To implement a stressing process that is as simple as possible for the ejection device and the retraction device, it can preferably be provided that the spring can be stressed along a stressing travel upon opening or closing of the movable furniture part and has a relief travel, wherein the spring retracts the movable furniture part in a first part of the relief travel and ejects the movable furniture part in a second part of the relief travel. With that arrangement it is no longer necessary—as in the state of the art—to find a possible way of providing two matching stressing travels for the spring of the retraction device and for the separate spring of the ejection device. 
     In the present invention therefore the precise arrangement and configuration of the invention can be per se any desired arrangement and configuration as long as stressing of the spring necessitates only one stressing travel of which the stress relief energy can be used in regard to one part for retraction and in regard to the other part for ejection. 
     It is preferably provided however that the spring is in the form of a single spring. That affords substantial simplification and a reduction in the space required. As an alternative option however the possibility of the spring being in the form of a spring pack should not be excluded. That permits different adaptations so that a part of the spring pack deploys its stress relief action to a particularly great degree for example upon ejection while a further part of the spring pack which is preferably simultaneously loaded causes the stress relief energy to act in the closing direction of the movable furniture part relatively slowly and gently during the retraction movement. It is essential that the springs of the spring pack are stressed during a common stressing operation, in which respect however the beginning and the end of the stressing of the individual springs or the parts of the spring pack can differ. It can preferably be provided that the individual springs of the spring pack are connected in mutually parallel relationship. 
     To permit the spring that double function with so-to-speak oppositely directed retraction and ejection movements, it can preferably be provided that the spring in the closed position of the furniture part has a first medium spring stress, after ejection of the furniture part the spring has a second, substantially relieved spring stress at a given ejection spacing after leaving the closed position, upon closure of the furniture part at a given retraction spacing before reaching the closed position the spring reaches a third spring stress which is increased in relation to the first, and starting from the third spring stress with stress relief and automatic retraction of the furniture part the spring is relieved to the first spring stress. In that way an ejection travel (second relief travel) in which the furniture part can be ejected is available to the spring, from the medium spring stress. Upon retraction the spring is stressed to a spring stress which is above the medium spring stress (stressing travel), whereupon in the last closing portion the furniture part is automatically pulled in by the spring being relieved of stress from the highest spring stress to the medium spring stress (first relief travel). 
     It can particularly preferably be provided that the retraction spacing is less than the ejection spacing. That provides that retraction takes place during a relatively short travel distance while the ejection travel is relatively long so that ejection does not occur excessively abruptly. 
     It can further particularly preferably be provided that the stressing travel is longer than the second part of the relief travel. That is the case in particular when the stressing angle is relatively shallow, whereby the spring is stressed easily and almost unnoticed by the user. 
     As upon unlocking of the movable furniture part or applying increased pressure thereto, the movable furniture part is further moved in the closing direction for a short time before the closed position, it can preferably be provided that the spring has a fourth spring stress which is slightly increased in relation to the third, upon unlocking of the ejection device. 
     To make the retraction movement gentler and softer there is preferably provided a damping device for damping the retraction movement of the retraction device. As the damping device acts in the opening direction of the furniture part the retraction force and the locking force should exceed the force of the damping device, that is acting in the opposite direction. The damping device guarantees that the retraction process does not take place excessively abruptly and loudly but gently and quietly. 
     To permit use of a single spring both for the ejection device and also for the retraction device in a structurally simple fashion it can preferably be provided that the drive device has a first base element and a second base element which are movable relative to each other in the opening direction and the closing direction respectively of the movable furniture part, a control element which is mounted movably, preferably pivotably, on the first base element, the spring which acts on the control element, and a locking element connected to the control element, wherein the control element is guided with the locking element in a preferably cardioid-shaped portion of a locking and unlocking path and a drive element for the second base element is arranged on the control element, wherein the second base element has a guide path for the drive element and said guide path has an ejection portion in which the second base element is movable relative to the first base element in the opening direction of the movable furniture part by the drive element, has a free-running portion in which the drive element is freely movable in the opening direction, has a stressing portion in which the drive element is movable in opposition to the spring force of the spring acting on the control element, and has a retraction portion in which the drive element moves the second base element relative to the first base element in the closing direction of the movable furniture part with partial stress relief of the spring, wherein the ejection portion of the guide path, with the control element, the locking element and the drive element and the spring forms the lockable and unlockable ejection device and the retraction portion of the guide path with the control element, the drive element and the same spring forms the retraction device. 
     In other words the spring acts on a control element which controls the ejection movement and the retraction movement of a movable furniture part in relation to the furniture carcass. In that respect the first and second base elements respectively represent the furniture carcass and the movable furniture part, wherein the first base element can be mounted to the movable furniture part and the second base element can be mounted to the furniture carcass and vice-versa. In addition it is important in that respect that provided in the region of the second base element is a guide path with which the control element cooperates by way of a drive element. The most important portions in such a guide path are the ejection portion, the stressing portion and the retraction portion. 
     In a particularly preferred embodiment of the invention it can be provided that the spring is relieved in the ejection portion from the medium spring stress to the second spring stress, the relieved spring stress remains substantially the same in the free-running portion, the spring is stressed from the relieved spring stress to the increased spring stress in the stressing portion, and the spring is relieved from the increased spring stress to the first spring stress in the retraction portion. This therefore clearly shows the logical connection between the individual spring stresses and the guide path portions. 
     In a preferred embodiment of the invention it can be provided that the control element is mounted pivotably to the first base element. Alternatively the control element could also be mounted linearly movably. To limit the movement of that control element it can preferably be provided that the control element has a limiting projection which limits the movement of the control element between two abutments which are preferably in the first base element. In that way the control element can be moved between two abutments with stressing and stress relief of the spring. 
     If the locking and unlocking mechanism of the ejection device is also to be completely integrated into the drive device, then the locking and unlocking path for the locking element, which path has a cardioid-shaped portion, should be provided in the first base portion. 
     In regard to stressing of the spring it can be provided on the one hand that the guide path in the stressing portion moves the drive element upon closure of the movable furniture part in opposite relationship to the spring force of the spring. On the other hand the drive element could already pass into a stressing portion for stressing the spring upon opening or ejection of the movable furniture part. 
     As the entire drive device should be relatively compact it is necessary for the first base element and the second base element also to be able to move freely without influencing each other. That is particularly desirable between the approximately half open position of the drawer and complete opening of the drawer. In order however in that respect to guarantee that the drive element does not pass into the wrong guide path when leaving the region with the guide portions and when passing again into the region with the guide portions, it can preferably be provided that the second base element has a preferably spring-loaded movement switch which allows the opening movement of the drive element from the free-running portion into a further completely free free-running portion and which guides the drive element from the further free-running portion into the stressing portion in the closing movement. For that purpose it is possible to provide for example an inclined deflection means or a movement switching spring. 
     To be able to connect the control element on the one hand to the guide path for retraction and ejection and on the other hand to the locking and unlocking path for the locking element and to be able to coordinate same a preferred embodiment provides that the locking element is mounted pivotably to the control element. 
     For an optimum stressing operation and retraction operation in respect of the spring it can preferably be provided that the ejection portion extends substantially transversely relative to the opening direction, the free-running portion extends substantially in the opening direction, the stressing portion has at least region-wise an angle between 5° and 70°, preferably between 15° and 50°, relative to the opening direction, and the retraction portion has at least region-wise an angle between 130° and 175°, preferably between 140° and 165°, relative to the opening direction. For that purpose it can further be provided that at least one of the portions of the guide path extends at least partially in a curve. The precise configuration of those stressing and relief paths can lead to a soft and gentle, fast and/or easily implementable manual movement of the movable furniture part, in which case—without the user noticing it—all spring stressing processes are implemented by the manual movement on the part of the user. Accordingly: the smaller or shallower the angle of the stressing portion, the correspondingly easier can the stressing operation be performed. 
     Particularly preferably the curved shape of the stressing portions can be such that the transition between the stressing portion and the retraction portion corresponds to the retraction spacing and there the spring reaches the highest spring stress. In that case the stressing portion and the retraction portion form so-to-speak a hill, at the highest point of which the spring is most heavily stressed and the spring is relieved of stress after passing beyond that point and in that case retracts the movable furniture part by pressing the drive element against the retraction portion. In other words that hill shape can be described by the stressing portion and the retraction portion being spaced from the free-running portion in transverse relationship to the opening direction, wherein the greatest spacing of both portions with respect to the free-running portion is at the given retraction spacing. 
     There are essentially two possible design configurations for the present invention. The first design configuration provides that the first base element is associated with the movable furniture part and the second base element is associated with a furniture carcass on or in which the furniture part is movably mounted. In that embodiment it is preferably provided that the locking element is formed integrally with the drive element. Accordingly that preferably integral component is displaced on the one hand in the locking and unlocking path and on the other hand in the individual portions of the guide path for the drive element. In addition in that respect it can preferably be provided that the spring is in the form of a leg spring, wherein one leg acts on the first base element and one leg acts on the control element. 
     The second possible design configuration of the present invention provides that the first base element is associated with a furniture carcass and the second base element is associated with the movable furniture part. In this embodiment it can preferably be provided that the limiting projection forms the drive element. In that way the limiting projection is additionally used to apply the spring force of the control element by way of the drive element or the limiting projection to the ejection portion and thus to eject the furniture part. 
     Protection is claimed for a drawer extension guide for a movable furniture part in the form of a drawer, having a drive device according to the invention. In that respect it can preferably be provided that the second embodiment of the present drive device is arranged on or fixed to the drawer extension guide. In that arrangement the drawer extension guide can have a drawer rail and a carcass rail, wherein the first base element is arranged on the carcass rail and the second base element is arranged on the drawer rail. 
     Protection is further claimed for an article of furniture comprising a furniture carcass and a movable furniture part, wherein the furniture part can be retracted and ejected by a drive device according to the invention. 
     In the first embodiment of the drive device described herein it can be provided in that respect that the first base element is arranged on the movable furniture part, preferably at the underside of a drawer bottom, and the second base element is arranged on the furniture carcass, preferably on a carcass rail of a drawer extension guide, that is fixed to the furniture carcass. 
     If the drive device is in the form of the second embodiment then the first base element is arranged on the furniture carcass, preferably a carcass rail of a drawer extension guide, that is fixed to the furniture carcass, and the second base element is arranged on the movable furniture part, preferably on a drawer rail of the drawer extension guide, that is associated with the furniture part. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further details and advantages of the present invention are described more fully hereinafter by means of the specific description with reference to the embodiments by way of example shown in the drawings, wherein  FIGS. 1 a  through 13 a    show various views of the first embodiment of a drive device from below and  FIGS. 1 b  through 13 b    show in the same sequence views of the second embodiment of a drive device from above. In detail: 
         FIGS. 1 a   + 1   b  show a view of an article of furniture with a drive device mounted to the underside of a movable furniture part, 
         FIGS. 2 a   + 2   b  show an exploded view of a drawer extension guide and the drive device, 
         FIGS. 3 a   + 3   b  show the extension guide with drive device in the assembled condition, 
         FIG. 3 c    shows the second embodiment of the drive device from below, 
         FIGS. 4 a   + 4   b  show the drive device in the locked position, 
         FIGS. 5 a   + 5   b  show the drive device in the unlocked position, 
         FIG. 6 a   + 6   b  show the drive device upon ejection, 
         FIGS. 7 a   + 7   b  show the drive device after termination of the ejection process, 
         FIGS. 8 a   + 8   b  show the continuing opening movement after ejection, 
         FIGS. 9 a   + 9   b  show the drive element when leaving the free-running portion, 
         FIGS. 10 a   + 10   b  show the position of the base elements in completely free-running relationship with each other, 
         FIGS. 11  a+ 11   b  show the position of the drive device upon stressing of the spring, 
         FIGS. 12 + 12   b  show the position of the drive device with the completely stressed spring, 
         FIGS. 13 a   + 13   b  show the position of the drive device upon retraction of the movable furniture part, 
         FIG. 14  shows a force-travel diagram of the spring and the drawer with the corresponding positions along the guide path, 
         FIG. 15  shows an ejection device according to the state of the art upon termination of stressing of the ejection spring, 
         FIG. 16  shows an ejection device according to the state of the art, wherein a separate retraction device retracts the furniture part, 
         FIG. 17  shows a 3-D image of a third embodiment with a furniture drive for a furniture flap, 
         FIG. 18  shows an exploded view of  FIG. 17 , 
         FIGS. 19 through 26  show the succession of movements of the third embodiment in a side view, and 
         FIGS. 27 through 35  diagrammatically show the succession of movements of a fourth embodiment of a drive device with a spring for ejection and retraction. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1 a    shows a partly broken-away 3-D view of an article of furniture  32  from below. In this case this article of furniture  32  has a furniture carcass  26  and three movable furniture parts  11  in the form of drawers. Those movable furniture parts  11  are mounted movably in drawer extension guides  29  fixed to the furniture carcass  26 , and its drawer rails  30  and carcass rails  31 . In this case arranged at the underside U of the drawer bottom  33  is a drive device  10  which is both in the form of an ejection device  8  and also a retraction device  9  for the movable furniture part  11 . That drive device  10  comprises a first base element  14  arranged on the movable furniture part  11  and a second base element  15  arranged on the furniture carcass  26  or the carcass rail  31 . A control element  16  acts between those two elements  14  and  15 . That control element  16 —particularly appropriately in the case of wide drawers—can be connected by way of a synchronization bar  35  and a synchronization device  34  (see  FIG. 14 ) to a second drive device (not shown) at the other side of the movable furniture part  11  to provide for synchronization of the retraction movement and the ejection movement at both sides. 
       FIG. 2 a    shows a drawer side frame member  36  connected to the drawer extension guide  29  comprising the carcass rail  31 , the central rail  37  and the drawer rail  30 . To damp the closing movement of the drawer rail  30  relative to the carcass rail  31  a damping device  13  can be integrated in the drawer extension guide  29 . Shown in the lower region is the second base element  15  which forms an upwardly curved ejection abutment  38  forming the ejection portion A. That second base element  15  is mounted to the carcass rail  31 . Fixed on that second base element  15  is the retraction guide element  39  having the retraction portion D. A movement switch  25  is connected rotatably to that retraction guide element  39  by way of a pivot axis member  41  and is acted upon by a movement switch spring  40 . The curved stressing portion C is provided on the movement switch  25  itself. 
     Shown in the upper region of  FIG. 2 a    is the first base element  14  mounted to the underside U of the drawer bottom  33 . Provided at the underside of that first base element  14  is a pivotal path  43  having end abutments  23  and  24  between which the control element  16  is pivotable by way of a limiting projection  22  (not shown here). Arranged between the first base element  14  and the control element  16  is a leg spring  12  having the legs  27  and  28 , the spring  12  acting on the base element  14  and the control element  16 . Mounted pivotably on the control element  16  is an integral component which has on the one hand the drive element  20  and on the other hand the locking element  17 , wherein that locking element  17  is displaceable in the locking and unlocking path  19  in the first base element  14 . The drive element  20  in turn engages through the control element  16  and bears against the corresponding portions A, C and D of the second base element  15 . 
       FIG. 3 a    shows a part of a movable furniture part  11 , wherein the drawer bottom  33  is mounted to the drawer rail  30 . In addition the base elements  14  and  15  which are fixed to the carcass rail  31  and the drawer bottom  33  respectively are shown in the mounted position, the control element  16  being mounted along the pivot axis S on the first base element  14 . The drive element  20  bears against the ejection abutment  38  (ejection portion A). 
       FIG. 4 a    shows a drawer bottom  33  from below, wherein the drawer front SF is diagrammatically shown in the form of a broken line in the upper region. In this view in  FIG. 4 a    the locking element  17  is locked in the closed position SS in the cardioid-shaped portion  18  of the locking and unlocking path  19 . The spring  12  is in the condition of first medium spring stress  1 . The drive element  20  is between the retraction guide element  39  and the ejection abutment  38 . 
     In  FIG. 5 a   , by applying pressure to the drawer front SF in the closing direction SR, the drawer bottom  33  with the drawer rail  30  is also moved rearwardly in the closing direction SR relative to the carcass rail  31  whereby the locking projection  17  moves out of the cardioid-shaped portion  18  of the locking and unlocking path  19 . That provides for unlocking of the drive device  10 . The spring  12  is moved into the condition of slightly increased spring stress  2  by the application of additional pressure in the closing direction SR. 
       FIG. 6 a    shows what happens after unlocking of the locking element  17 : because the locking element  17  is no longer locked in the cardioid-shaped portion  18  of the locking and unlocking path  19  the spring  12  can deliver its spring force F to the control element  16  by way of the leg  28  whereby the control element  16  is pivoted relative to the first base element  14 . In that case the drive element  20  arranged on the control element  16  presses against the ejection portion A of the guide path  21 , formed by the ejection abutment  38  of the second base element  15 . As a result the first base element  14  and therewith the entire drawer  11  moves in the opening direction OR relative to the second base element  15  and thus also relative to the carcass rail  31  and the furniture carcass  26 . Thus the drive device  10  forms the ejection device  8 , the spring  12  applying the ejection spring force F. 
     In  FIG. 7 a    the ejection process is terminated and the spring  12  has been relieved of stress to the second, relieved spring stress  3 , wherein the relative movement of the control element  16  with respect to the first base element  14  is ended by the limiting projection  22  butting against the abutment  24 . It is also clear from  FIG. 7 a    that the drive element  20  has thus reached the end of the ejection portion A and is no longer limited in the opening direction OR by the retraction guide element  39 . The ejection spacing y was covered by the drawer  11  from unlocking until the end of the ejection portion A was reached. 
     In  FIG. 8 a    the drive element  20  is in the free-running portion B, the movable furniture part  11  being pulled out in the opening direction OR. In that case the spring  12  is in the condition of relieved spring stress  4 . 
     If as shown in  FIG. 9 a    the movable furniture part  11  is moved further in the opening direction OR then the drive element  20  presses the movement switch  25  against the force of the switch spring  40  and pivots or turns the movement switch  25  on the pivot axis member  41  in relation to the retraction guide element  39  and thus the second base element  15 . 
     If as shown in  FIG. 10 a    the drawer  11  is moved further in the opening direction OR and passes outside the free-running portion B then the switch spring  40  pulls the movement switch  25  back into the starting position again. The movable furniture part  11  is now in the complete free-running portion E in which the movable furniture part  11  can be moved as desired in the opening direction OR and the closing direction SR. The spring  12  is still in a condition of relieved spring stress  5 . It will be seen in the region of the second base element  15  that the movement switch  25  and its stressing portion C involve an average angle a relative to the closing direction SR and the retraction guide element  39  and its retraction portion D involve an angle β relative to the closing direction SR. Those angles α and β can be such that it is possible to implement an optimum gentle drawer movement complying with the user&#39;s wishes. The shallower the angle α is, the correspondingly longer is the stressing portion C whereby the stressing process can take place more gently and with an easier movement. When transposed to the force-travel diagram in  FIG. 14  that is also given by the long and relatively shallow stressing travel SW. 
     In  FIG. 11 a    the movable furniture part  11  is again moved in the closing direction SR, wherein the drive element  20  moves along the stressing portion C on the left-hand side of the movement switch  25  by virtue of the movement switch  25  being moved back again. Due to the movement of the drive element  20  along the stressing portion C which is inclined with respect to the closing direction SR the control element  16  is pressed with respect to the base element  14  against the leg  28  of the spring  12  whereby the spring  12  is stressed against the spring force F and the increasing spring stress  6  is attained. In that movement of the control element  16  the locking element  17  also moves along the locking and unlocking path  19  in the direction of the cardioid-shaped portion  18 . The limiting projection  22  is also moved from the abutment  24  in the direction of the abutment  23  again. The high point in the stressing process is reached at the point of the stressing portion C, at which the spacing z relative to the free-running portion B is at the greatest. 
     That point is reached in  FIG. 12 a   , in which case the spring  12  is stressed by the complete pivotal movement of the control element  16  as far as the abutment  23  in the first base element  14 , to reach the third condition of increased spring stress  7 . That point of the drive element  20  involves the transition from the stressing portion C into the retraction portion D. 
     Accordingly  FIG. 13 a    shows how the spring  12  is relieved of stress again by the sliding movement of the drive element  20  along the retraction portion D and thereby pulls the movable furniture part into the furniture in the closing direction SR. Accordingly the drive device  10  also operates as a retraction device  9  insofar as the same spring  12  acts in a retracting mode on the movable furniture part  11  by way of the control element  16 , the drive element  20  and the retraction portion D, and the movable furniture part  11  reaches the closed position SS after covering the retraction spacing x. 
       FIG. 14  shows a force-travel diagram, wherein the spring force F of the spring  12  is plotted on the Y-axis and the travel s of the movable furniture part in the opening direction OR or the closing direction SR is plotted on the X-axis. The broken line shows an idealized configuration and can naturally involve fluctuations and curves, in an actual embodiment. From the first medium spring stress  1  in the closed position SS of the movable furniture part the movable furniture part  11  is further moved in the closing direction SR by the application of an increased pressure thereto, in which case the spring force is additionally stressed to the slightly increased spring stress  2 . After that unlocking action which is effected by the application of the increased pressure the spring  12  is relieved from the slightly increased spring stress  2 , with ejection of the furniture part  11  in the opening direction OR along the second relief travel EW 2  as far as the second relieved spring stress  3 , the ejection spacing y having been covered in that case. During the further opening movement of the drawer  11  the spring force F of the spring  12  remains at the spring stress  4  and  5 . When the movable furniture part  11  is closed a part of the drive device  10  passes into the stressing portion C (stressing travel SW of the spring  12 ), thereby reaching the increasing spring stress  6  which reaches its high point at point  7  of the spring stress. From that spring stress  7  retraction of the movable furniture part  11  by the retraction spacing x is implemented by way of the retraction portion C and by relief of the stress of the spring force F along the relief travel EW 1  from the highest spring stress  7  to the medium spring stress  1 . It will also be seen from  FIG. 14  that the ejection spacing y is greater than the retraction spacing x. The lower region of  FIG. 14  shows the positions of the drive element  20  along the guide path  21 , which substantially coincide with the spring stress points  1  through  7 . 
     That overall force-travel diagram in  FIG. 14  forms a hysteresis system. In other words after the cause of stressing ceases to apply (cause: closing movement of the movable furniture part) the energy stored in the stressing operation is delivered in two steps (retraction movement and ejection movement), thereby giving continuity of the action of the stressing process after cessation of the stress-inducing closing movement. Thus the stressing travel SW between the spring stresses  5  and  7  is longer than the ejection travel EW 2  between the spring stresses  2  and  3 . 
       FIG. 1 b    shows a view of an article of furniture  32  from below, wherein arranged at the underside U of the drawer bottom  33  in the front region is a second embodiment of a drive device  10  according to the invention, the drive device  10  forming both the retraction device  9  and also the ejection device  8 . In this respect identical references denote the same elements as in the first embodiment shown in  FIGS. 1 a  through 13 a   . Accordingly in  FIG. 1 b    the first base element  14  (with the pivotable control element  16 ) is mounted to the carcass  26  or the carcass rail  31  while the second base element  15  is mounted to the drawer rail  30 . 
       FIG. 2 b    shows an exploded view of a drawer extension guide  29 , with a damping device  13  being operative between the carcass rail  31  and the drawer rail  30 . It will be appreciated that in the first embodiment also such a damping device  13  can be used in a similar or the same fashion. Unlike the first embodiment the second base element  15  is fixed to the drawer rail  30  and has a vertically spring-loaded movement switch  25  in the form of a tongue spring. The first base element  14  is mounted to the carcass rail  31  and at its underside has a control element  16  which is mounted pivotably at the pivot axis S and which is limitedly pivotably mounted between the abutments  23  and  24  by way of the limiting projection  22 . The limiting projection  22  at the same time forms the drive element  20  for the second base element  15 , while provided at the underside thereof (see  FIG. 3 c   ) is the guide path  21  (not yet shown) into which the limiting projection  22 /drive element  20  engages. The control element  16  is acted upon by the coil spring  12  and in the front region has a pivotably mounted locking element  17  which engages into a locking and unlocking path  19  at the underside of the first base element  14  (see  FIG. 3 c   ). 
       FIG. 3 b    shows the drawer extension guide  29  with the drive device  10  mounted thereto in the assembled condition. 
     Corresponding thereto  FIG. 3 c    shows a view from below of the drive device  10 , showing the inclined deflection portion  42  of the movement switch  25  which deflects the drive element  20  in the direction of the stressing portion C. As an alternative configuration of the present invention,  FIG. 3 c   , in broken line, shows a second spring  12   a  for forming a spring pack which could additionally act on the control element  16 . Depending on its respective configuration and arrangement, the spring pack could deploy its effect for example primarily upon retraction or ejection and could thus improve the process which is being respectively assisted and could thus make it easier in terms of motion. 
     In comparison with the first embodiment of the present drive device  10   FIGS. 4 b  through 13 b    show the drawer front, illustrated in broken line, in the lower region of the respective Figure. In addition  FIGS. 4 b  through 13 b   —in contrast to  FIGS. 4 a  through 13 a   —show a view from above onto the drive device  10 . 
     In  FIG. 4 b    the locking element  17  is in the closed position SS in the cardioid-shaped portion  18  of the locking and unlocking path  19 . The spring  12  is in the first condition of medium spring stress  1 . 
     The locking element  17  is unlocked by applying an increased pressure to the drawer  11  in the closing direction SR and the spring  12  is in the condition of slightly increased spring stress  2  (see  FIG. 5 b   ). 
     In  FIG. 6 b    the drawer rail  30  is ejected by the guide path  21  in the second base element  15  and its ejection portion A by way of the drive element  20 , wherein the drive element  20  is moved in the pivotal path  43  of the limiting projection  22  in the direction of the abutment  24  by relief of the spring  12  in the direction of the spring force F. Thus the spring  12  serves as a force-generating device for the drive device  10  which functions as the ejection device  8 . 
     In  FIG. 7 b    the spring  12  reaches the condition of relieved spring stress  3  and the drive element  20  reaches the free-running portion B of the guide path  21 . 
     In that region the movable furniture part  11  or the second base element  15  can be freely moved in the opening direction OR while the spring  12  is further disposed in the relieved spring stress  4  ( FIG. 8 ). If in that case the drive element  20  slides along the movement switch  25  then the movement switch  25  is urged vertically upwardly against the spring force F so that the drive element passes from the position in  FIG. 9 b    into the further free-running portion E in  FIG. 10 b   . The preferred angles α and β for the stressing portion C and the retraction portion D are shown in  FIG. 10   b.    
     Upon the movement of the furniture part  11  in the closing direction (see  FIG. 11 b   ) the drive element  20  is deflected by the inclined deflection portion  42  into the stressing portion C whereby the control element  16  pivots against the action of the spring force F of the spring  12  (increasing spring stress  6 ). 
     In  FIG. 12 b    the drive element  20  reaches the high point or the transition between the stressing portion C and the retraction portion D, in which case the drive element  20 /limiting projection  22  at the same time reaches the abutment  23  of the pivotal path  43  and the spring  12  reaches the third, highest spring stress  7 . At that time the projection  44  on the drawer rail  30  also butts against the damping device  13 . The guide path  21  “kinks” at the transition between the portion C through between about 40° and 80°, preferably between 50° and 70°. 
     As soon as the highest point of the stressing portion C has been passed the drive element  20  passes into the region of influence of the retraction portion D, in which the spring  12  contracts, with pivotal movement of the control element  16 , and in that case moves the second base element  15  in the closing direction SR relative to the first base element  14 , in which case that movement can be damped by the damping device  13 . Thus in this second embodiment and therein as shown in  FIG. 13 b    the spring  12  also acts as a retraction force for the drive device  10  which takes over the function of a retraction device  9 . 
       FIGS. 15 and 16  showing the state of the art of separately provided ejection devices  8  and retraction devices  9  as disclosed in WO 2007/028177 A1 have already been appropriately discussed in the introductory part of the present description. 
       FIG. 17  onward shows a third embodiment of a drive device  10  according to the invention, which is part of a furniture drive  51  for a furniture flap (not shown). In this case the drive device  10  and a connecting device  54  are integrated into a per se known control arm arrangement (as can be seen for example from WO 2011/020130 A1 or DE 20 2005 021 541 U1) for the furniture flap and that is in turn fixed to a mounting plate  62 . 
       FIG. 18  shows an exploded view of  FIG. 17 , wherein all essential components are denoted by a reference numeral. Some subsidiary components such as for example connecting bolts or the like do not have any reference. Explanation of the operating principle however is possible even without directly specifying those components by means of references. The control arm  52  is shown in the closed position in both of  FIGS. 17 and 18 . 
       FIGS. 19 through 26  show the furniture drive  51  without furniture carcass and furniture flap (movable furniture part). This furniture drive  51  is fixed to a side wall of a furniture carcass  26  by way of the mounting plate  62  and moves a furniture flap by way of a control arm arrangement and a control arm  52 . Preferably that furniture flap is pivotable about a horizontal pivot axis. 
     In  FIG. 19  the control arm  52  (and thus also the furniture flap which is not shown) are in the closed position SS. In that case the trigger element  53  bears against the control arm  52  or against the furniture flap itself. That trigger element  53  is connected, in this case integrally, to the transmission mechanism  55  by way of the pivot axis  70  which is stationary relative to the mounting plate  62 . The spring  71  (tension spring) acts on the transmission mechanism  55  in such a way that the latter always seeks to move about the pivot axis  70  in the clockwise direction. At its end the transmission mechanism  55  is connected to an unlocking element  17   h  by way of a connecting pin  17   i . That unlocking element  17   h  is pivotable about the ejection pivot axis  54   e . The part  17   g  of an articulated lever is also pivotable about the ejection pivot axis  54   e . At the other end that part  17   g  is connected to the locking lever  17   a  by way of the articulated lever pin  17   j . Together  17   j ,  17   g  and  17   a  form the articulated lever. Coiled around the articulated lever pin  17   j  is a locking spring  17   d  which seeks to urge the articulated lever pin  17   j  upwardly with respect to the ejection pivot axis  54   e  and the holding nose pin  17   k . In the  FIG. 19  view the articulated lever pin  17   j  is slightly above a notional line between the ejection pivot axis  54   e  and the holding nose pin  17   k . Further movement of the articulated lever pin  17   j  upwardly is prevented by the holding nose  17   b  of the locking lever  17   a  bearing against the locking projection  17   e . That locking projection  17   e  is arranged on the stressing cam  54   d . The stressing cam  54   d  is in turn connected on the one hand to the locking lever  17   a  by way of the holding nose pin  17   k  and on the other hand to the contact lever  54   a  by way of the stressing cam pivot axis  54   f . That lever  54   a  in turn is mounted pivotably about the ejection pivot axis  54   e . In addition the lever  54   a  is connected to the connecting lever  54   b  by way of the ejection pin  54   g . The lever  54   b  in turn is connected to the element  56  of the lever mechanism  57  by way of the connecting pin  54   c  whereby the movements of the element  56  and the lever  54   a  constantly correspond. 
     The spring  12  (compression spring) is fixedly connected at one end to the mounting plate  62  by way of the mounting elements  10   m . At the other end the spring  12  is connected to a guide projection  10   n  which in turn is guided in a guide path  10   k  in the mounting plate  62 . In addition the spring  12  is connected by way of the guide projection  10   n  to the ejection lever  10   a  which in turn is pivotable about the fixed pivot axis  10   g  connected to the mounting plate  62 . At the right-hand lower end the ejection lever  10   a  has a pressure roller  10   b  which is in contact in the slightly inwardly displaced region between the contact lever  54   a  and the stressing cam  54   d . In that closed position SS the force of the spring  12  presses against the stressing cam  54   b  by way of the pressure roller  10   b . Since as a further consequence force is applied to the locking lever  17   a  by way of the holding nose pin  17   k  the articulated lever pin  17   j  is urged upwardly in the closed position SS to such an extent as is allowed by abutment of the holding nose  17   b  against the locking projection  17   e.    
     If now—as shown in  FIG. 20 —pressure is applied in the closing direction SR to the furniture flap or the control arm  52  the trigger element  53  is also urged in the closing direction SR and the transmission mechanism  55  is pivoted about the pivot axis  70  against the force of the spring  71 , whereby in turn as a further consequence the unlocking element  17   h  is moved about the ejection pivot axis  54  in the counter-clockwise direction by way of the connecting pin  17   i . As a result the unlocking element  17   h  comes into abutment with the rear part  17   g  of the articulated lever and thereby moves the articulated lever pin  17   j  below the notional line between the ejection pivot axis  54   e  and the holding nose pin  17   k . That also takes place against the force of the locking spring  17   d . As soon as the articulated lever pin  17   j  passes below the notional line the spring force of the opening spring  12  no longer acts lockingly on the locking lever  17   a  and the holding nose  17   b  by way of the pressure roller  10   b  and the stressing cam  54   d , but bends the articulated lever in against the force of the spring  17   d . The parts identified by references  17   a ,  17   b ,  17   d ,  17   e ,  17   g ,  17   h ,  17   i ,  17   j  and  17   k  jointly form a locking device  17  corresponding to the locking element  17  of the first two embodiments. 
     Due to the unlocking action the articulated lever passes into the completely inwardly displaced position shown in  FIG. 21  in which the articulated lever pin  17   j  is clearly below the notional line between the ejection pivot axis  54   e  and the holding nose pin  17   k . Simultaneously with the inward movement of the articulated lever the stressing cam  54   d  is also pivoted in the clockwise direction about the stressing cam pivot axis  54   f  so that the left-hand edges (cam surfaces) of the stressing cam  54   d  and of the ejection lever  54   a  come to bear precisely one above the other and cover each other from the illustration point of view. Simultaneously with the inward pivotal movement of the stressing cam  54   d  the pressure roller  10   b  also begins to roll along with stress relief of the spring  12  whereby the ejection lever  54   a  is rotated in the counter-clockwise direction about the ejection pivot axis  54   e.    
     As a result the open position OS is reached as shown in  FIG. 22 , in which the control arm  52  is shown with the opening angle γ. That opening movement is effected by the connecting lever  54   b  being moved with the pivotal movement of the lever  54   a  and triggering pivotal movement of the element  56  of the lever mechanism  57 . Due to that pivotal movement of the element  56 , as a further consequence the lever  65  of the lever mechanism  57  is moved towards the right and the control arm  52  together with the furniture flap opens. In the  FIG. 22  view the main spring  59  is already somewhat relieved of stress in comparison with the view in  FIG. 21 . The ejection movement involves moving beyond the dead point in the main mechanism (control arm arrangement with main spring  59 ). The damping device  13  no longer bears against the lever  72  of the lever mechanism  57 . By virtue of the return spring  71  the transmission mechanism  55  has pivoted about the pivot axis  70  again whereby the trigger element  53  like also the unlocking element  17   h  was moved into the starting position again (as in  FIG. 19 ). In  FIG. 22  the parts denoted by references  10   a ,  10   b ,  10   g ,  10   k ,  10   m ,  10   n  and  12  form the drive device  10  which can function as an ejection device  8  and also as a retraction device  9 . 
     After the spring  12  has been completely relieved of stress (as in  FIG. 22 ) the furniture flap is further moved by hand in the opening direction OR. As in that further movement no spring force F now acts by the spring  12  on the stressing cam  54   d  by way of the ejection lever  10   a  and its pressure roller  10   b  the locking spring  17   d  can relieved of stress and urges the articulated lever into the position shown in  FIG. 23 . In that case the articulated lever pin  17   j  is again above the notional line between the ejection pivot axis  54   e  and the holding nose pin  17   k  and the holding nose  17   b  bears against the locking projection  17   e.    
     If now the furniture flap is further moved in the opening direction OR (see  FIG. 24 ) the stressing cam  54   d  comes out of engagement with the pressure roller  10   b  and the completely open position is reached. 
     In  FIG. 25  the movable furniture part  11  (furniture flap) is moved in the closing direction SR, stressing of the spring  12  beginning in the opening angle region Δ. Stressing begins by the stressing cam  54   d  which is locked by the locking lever  17   a  and the holding nose  17   b  coming to bear against the pressure roller  10   b  by way of the stressing portion C and by the spring  12  being pushed in by way of the ejection lever  10   a  and thus stressed. 
     That stressing continues until the pressure roller  10   b  has reached the highest point on the stressing cam  54   d  and passes into the retraction portion E. Upon reaching that retraction portion E the spring  12  can be slightly relieved of stress (movement from  FIG. 26  to  FIG. 19 ) and thus actively pulls the movable furniture flap in, in the last closing portion. In other words, by virtue of moving beyond the high point of the stressing cam  54   d , the connecting lever  54   b  is actively rotated in the clockwise direction about the ejection pivot axis  54   e  so that a retraction effect is applied to the control arm  52 . It will be noted however that this relief of stress takes place only until the pressure roller  10   b  passes into the depression between the stressing cam  54   d  and the connecting lever  54   b . The closed position SS shown in  FIG. 19  is reached again in that way. In the retraction movement the damping device  13  can also permit slight damping of the retraction movement triggered by the spring  12 . 
     A synchronization bar can be fixed in the region of the ejection pivot axis  54   e  to transmit the rotary movement to a preferably mirror-symmetrical lever mechanism on another side of the furniture carcass  26 . 
     A fourth embodiment of the present invention is shown in  FIGS. 27 through 35 . These purely diagrammatically show the sequence of movements in a drive device  10  upon closure, retraction and ejection of a movable furniture part  11 . In all the Figures, of the movable furniture part  11 , only the entrainment member  44  associated with that movable furniture part  11  is shown. 
       FIG. 27  shows that entrainment member  44  upon closure of the movable furniture part at the moment at which it butts against the locking element  17 . The locking element  17  is mounted movably to the furniture carcass  26 . Disposed on the locking element  17  is a control element  16  which moves in a locking and unlocking path  19 . The locking and unlocking path  19  has a cardioid-shaped portion  18 . The locking and unlocking path  19  is stationary relative to the furniture carcass  26 . The locking element  17  is connected at one end to the spring  12  (tension spring). That spring in turn is connected by way of a damping device  13  (rotational damper with rack and gear), wherein that rotational damper is connected at one end to a locking slider  46 . The locking slider  46  is held in a holding path  47  or displaceable therein in accordance with its respective position, by way of the locking projections  45  and  48 . The holding path  47  is stationary relative to the furniture carcass  26 . 
     If now the movable furniture part  11  and therewith the entrainment member  44  is moved from the position in  FIG. 27  into the position in  FIG. 28  in the closing direction SR the spring  12  is stressed or loaded. 
     Upon further movement in the closing direction ( FIG. 29 ) the control element  16  is deflected by the locking and unlocking path  19  and the control element  16  moves into the locked position ( FIG. 30 ) in the cardioid-shaped portion  18  of the locking and unlocking path  19 . While the control element  16  passes into the locking position the entrainment member  44  comes out of engagement with the locking element  17  and passes between the catch elements  49  of the locking slider  46 . As the movable furniture part  11  and thus the entrainment member  44  are further moved in the closing direction SR the locking slider  46  (in particular its first locking projection  45 ) is moved out of the locking position in the holding path  47  (see  FIG. 29 ) into an unlocked position (see  FIG. 30 ). By virtue of that unlocking the right-hand end of the spring  12  is no longer locked by the locking slider  46  and the spring  12  can contract whereby the spring  12  moves/retracts the entrainment member  44  and thus the movable furniture part from the position shown in  FIG. 30  into the closed position SS in  FIG. 31 . Thus in that region the drive device  10  functions as a retraction device  9  and the spring  12  has a retracting action during its first part of the relief travel EW 1 . The retraction movement of the spring  12  is damped by the damping device  13 . 
     That retraction movement is effected until the locking slider  46  and its second locking projection  48  has reached the locking position in  FIG. 31 . In that position the entrainment member  44  is still caught between the catch elements  49  but at the same time bears against the left-hand limiting abutment  50  of the locking element  17 . 
     If now as shown in  FIG. 32  pressure is further applied to the movable furniture part in the closing direction SR when in the closed position SS triggering of the drive device  10  takes place. By virtue of movement of the entrainment member  44  because of the application of increased pressure applied to the movable furniture part towards the left the limiting abutment  50  and therewith the locking element  17  are moved towards the left. As a result on the one hand the control element  16  moves out of the cardioid-shaped portion  18  into its free-running region of the locking and unlocking path  19 . On the other hand the locking slider  46  also moves into a position in which the entrainment member  44  is released—in this case by pivotal movement as a consequence of a suitable design configuration of the holding path  47 —. 
     By virtue of relief of the spring  12  the locking element  17  and by way of its limiting abutment  50  the entrainment member  44  and thus the movable furniture part  11  are actively ejected and reach the position shown in  FIG. 33 . In that region therefore the drive device  10  serves as an ejection device  8  whereby the spring force F serves for ejection of the movable furniture part  11  in the second part of the relief travel EW 2 . 
     After the entrainment member  44  has reached the position shown in  FIG. 33  the spring  12  is completely relieved of stress and the movable furniture part  11  can be further moved in the opening direction OR by hand. 
     As soon as the entrainment member  44 , in that movement, reaches the right-hand limiting abutment  50   a  of the locking element  17  (see  FIG. 34 ) the damping device  13  is stressed and the locking slider  46  reaches the locked position shown in  FIG. 35 . The configuration of the holding path  47  and the locking slider  46  is only diagrammatically shown in the views, but can be provided by a man skilled in the art in the field of furniture drives with suitable pivotal paths or locking portions. From the right-hand limiting abutment  50   a  the entrainment member  44  can pass onto the right-hand side of the locking element  17  by downwardly pressing the locking element  17  (similarly to  FIG. 29 ) by virtue of an inclined deflection portion or by suitable force applications, whereby the starting position shown in  FIG. 27  is reached again. 
     In principle it should be stated in relation to this fourth embodiment that the drive device  10  could also be associated with the movable furniture part  11  and in contrast the entrainment member  44  could be associated with the furniture carcass  26 . The damping device  13  does not have to be in the form of a rotational damper but for example can also be in the form of a fluid damper. The damping device  13  however can also be omitted whereby the spring force F of the spring  12  acts undampedly on the movable furniture part  11 . 
     Thus all embodiments of the present invention present a drive device  10  which is substantially improved and simplified over the state of the art and which is both in the form of an ejection device  8  and also a retraction device  9 , wherein the same spring  12  functions as a respective force storage means for retraction and ejection. It will be appreciated that the possibility should not be ruled out that two springs  12 ,  12   a  which are parallel or which also act in different directions on the drive element  20  are provided in the drive device  10 . What is essential is that this at least one spring  12  serves for retraction during a part of its relief travel EW 1  and serves for ejection during a further part of the spring relief travel EW 2 . The possibility should also not be ruled out that—depending on the respective configuration—the spring relief travel EW 1  from the highest spring stress  7  to the medium spring stress  1  serves for ejection while further stress relief EW 2  from the medium spring stress  1  to the relieved spring stress  3  serves for retraction.