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BACKGROUND OF THE INVENTION 
     The present invention concerns a retraction device for retracting a movably supported furniture part into the closed end position relative to a furniture carcass. The device includes an entrainment member which can be releasably coupled to the movable furniture part and which is supported movably along an at least portion-wise linear displacement path, and at least one spring device for applying force to the entrainment member. The spring device can be stressed by way of a spring holder separate from the entrainment member. 
     In addition, the invention concerns a drawer extension guide and an article of furniture having a retraction device of the kind to be described. 
     Retraction devices of that kind (known, for example, from EP 0 391 221 B1 to the present applicant) are used in particular with drawers or sliding doors which are freely displaceable over a large part of their extension region and engaged by the entrainment member of the retraction device only towards the end of the closing movement, and are pulled securely and reliably into the closed end position by spring force. The movable furniture part is thus pulled into the furniture carcass automatically without further application of force by the user and is held there with a predetermined closing force. That last portion of the closing movement can be damped by an additional damping device so that a gentle closing process can be achieved without annoying impact sounds. Upon opening of the movable furniture part, the user firstly has to apply a force against the spring resistance of the retraction device, by pulling, until after a predetermined distance the entrainment member is uncoupled from the movable furniture part and is moved into a prestressed parking position in which the spring remains in a stressed readiness position so that in the next closing process the movable furniture part can be pulled in again. For a user, uncoupling of the entrainment member in the opening movement for the drawer frequently makes itself noticeable with a jerky movement as, as a consequence of the sudden spring separation force, the drawer is now freely movable and is accelerated unduly towards the user by virtue of the previously exerted pulling force. 
     Retraction devices in accordance with the classifying portion of claim  1  are described for example in WO 2009/132626 A1 and in EP 1 470 769 A1. In those structures, there are an entrainment member and a spring holder separate therefrom, in which case however the force of the spring device abruptly ceases when the entrainment member is parked into the prestressed parking position. Thus, the drawer is accelerated in the opening direction. 
       FIG. 15   a  and  FIG. 15   b  diagrammatically show two different retraction devices  8  according to the state of the art.  FIG. 15   a  shows a linearly displaceable slider  16  on which an entrainment member  12  is supported tiltably about an axis of rotation  15 . The entrainment member  12  which is in the form of a tilting segment is supported displaceably along a linear displacement path  10  by way of two guide elements  13  and can be moved into a tilted position towards the end of the extension movement into a curved or angled portion  11  so that the coupling element  14  of the drawer  3   a  can be uncoupled. In  FIG. 15   a  the spring device is articulated on the linearly displaceable slider  16  while in  FIG. 15   b  the spring device  17  directly engages the tiltably mounted entrainment member  12 . 
       FIG. 17  shows a further embodiment of a retraction device  8  according to the state of the art, the spring device  17  directly engaging the tiltably mounted entrainment member  12 . 
     SUMMARY OF THE INVENTION 
     Therefore, the object of the invention is to propose a retraction device of the general kind set forth in the opening part of this specification, which particularly also in the opening process permits a harmonic movement of the movable furniture part. 
     According to the invention, that object is attained by the features described below. Further advantageous configurations of the invention are also described. Thus, it is therefore provided that the spring holder is movably supported at or on the entrainment member, and there is a coupling device for motional coupling between the entrainment member and the spring holder. Due to the coupling device, the articulation mounting point of the spring device on the spring holder falls back when the entrainment member is pulled out relative to the position of the moving entrainment member, and the movement of the articulation mounting point of the spring device on the spring holder is slower than the movement of the entrainment member. Due to the coupling device, the articulation mounting point of the spring device on the spring holder falls back when the entrainment member is pulled out relative to the position of the moving entrainment member before the entrainment member passes into a parking position in which it releases a coupling element connected to the movable furniture part. The spring holder is continuously but movably connected to the entrainment member. 
     In that way, the spring device is stressed less than corresponds to the displacement travel of the entrainment member so that before reaching the parking position the entrainment member can move gently and softly thereinto. In that respect, from the point of view of a user, on the one hand less force has to be applied to open the movable furniture part while on the other hand the transition upon uncoupling of the entrainment member occurs with less of a jerk. 
     In one embodiment, the travel distance made available for the spring holder is greater than the effective travel distance of the entrainment member. Thus, (in accordance with the physical formula work=force times distance) less manual force is also required for stressing the spring device. The provision of a longer stressing travel for the spring device means that the friction can also be reduced, so that less manual force is also necessary for opening the movable furniture part. 
     Due to the coupling device, upon movement of the movable furniture part, the relative position between the entrainment member and the articulation mounting point of the spring device on the spring holder is variable. The coupling device can, for example, convert a linear movement of the entrainment member into a pivotal movement of the spring holder or vice-versa. In that case, the coupling device can include the slider and the spring holder, wherein the slider and the spring holder can have mutually interengaging tooth arrangements. In a possible embodiment, a tooth arrangement can be arranged on a rolling region of the spring holder while the slider has a straight tooth arrangement. 
     The coupling device can have, for example, a step-down mechanism or a step-down transmission, whereby the speed of the entrainment member can be stepped down to a lower speed of the spring holder at least over a region of the stressing travel. In that case, the spring device is stressed less for each travel unit covered by the entrainment member. In that way, the forces required for stressing the entrainment member can be reduced. For that purpose, the coupling device can include at least one rack-gear arrangement and/or a lever mechanism—in particular with lever arms of differing lengths. The coupling device can also have a gear transmission or a step-down arrangement with cables or belts. 
     In another embodiment of the invention, the coupling device cooperates with at least one control curve, and the spring holder of the spring device is guided along the control curve. The presence of a control curve on which the spring holder of the spring device can run means that the beginning, the configuration and the end of the spring force acting on the entrainment member can be freely selected in the most widely varying design configurations. 
     The control curve can be provided at least portion-wise separately from the displacement path of the entrainment member or can portion-wise overlap therewith—in particular, in the last retraction region of the entrainment member. 
     In another embodiment of the invention, the control curve of the spring holder—particularly in the region of the last stressing travel to the end of the stressing travel—has a curved shape so that sudden cessation of the spring force when the entrainment member is moved into the prestressed parking position can be alleviated. 
     The control curve of the spring holder can extend at least portion-wise in non-parallel relationship with the linear displacement path of the entrainment member, and the control curve of the spring holder at least portion-wise has a linear shape or has a substantially completely linear configuration. It is therefore possible for the linear displacement path of the entrainment member and the control curve of the spring holder to form two straight lines which extend transversely to each other. Alternatively or additionally, it is possible for the control curve of the spring holder to have a curved shape at least portion-wise, preferably over at least a third of the length, and preferably in the region of the last stressing travel, so that conclusion of the force of the spring device takes place less abruptly. 
     The entrainment member is mounted movably—as is known per se—between a parking position in which the spring is stressed and an end position in which the spring is at least partially relieved of stress. The parking position of the entrainment member can be secured in force-locking and/or positively locking relationship, and transfer of the entrainment member into the parking position can also take place over a guide portion which is curved or angled away from the linear displacement path of the entrainment member. It is also possible to bring about parking of the entrainment member by eccentric coupling of the spring device, whereby the entrainment member can be urged into the parking position by the acting spring force. A further option provides that the entrainment member has at least one guide element by way of which the entrainment member can be guided along the linear displacement path and is movable into the parking position—preferably over a guide portion which is curved or angled away from the linear displacement path. 
     In an embodiment of the invention, the entrainment member can also be arranged on a displaceable slider. In that case, the entrainment member can be rigidly connected to the slider and, in particular, can also be formed integrally with the slider. It is also possible for the entrainment member to be connected movably, preferably tiltably, to the slider. An integral configuration of the entrainment member on the slider in the form of a resilient catch portion which can be releasably coupled to the drawer or to an extendable rail of a drawer extension guide is also possible. 
     The spring holder is mounted movably at or on the entrainment member itself—preferably along a guide on the entrainment member. The spring holder can have a two-part or also multi-part configuration. The spring holder can be at least portion-wise linearly movably supported and/or can perform a pivotal movement at least portion-wise, which is possible without any problem, for example, by the provision of a suitable control curve. 
     To damp the retraction movement, there can be a damping device by which a movement of the entrainment member can be damped. In that respect, the damping device can be in the form of a fluid damper. In that respect, numerous variants are available to the person skilled in the art. For example, a—preferably hydraulic—piston-cylinder unit or also a rotational damper with at least two damping components which are rotatable relative to each other in the damping stroke movement and between which is arranged a fluid damping medium which retards the relatively movement of the two damping components can be used. 
     The spring device can have a spring—in particular a coil spring—or can be formed by a spring pack comprising parallel springs which are all moved equally far when the entrainment member is pulled out. 
     The drawer extension guide according to the invention is characterized by a retraction device of the kind described. In that case, the drawer extension guide has a carcass rail to be fixed to a furniture carcass and at least one drawer rail which is movable relative thereto, and which towards the end of the closing movement is engaged by the entrainment member of the retraction device and can be pulled thereby into the completely closed position. 
     The article of furniture according to the invention is characterized by a drawer extension guide of the foregoing kind and/or by a movable furniture part which can be retracted into the closed end position relative to a furniture carcass by the retraction device according to the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further details and advantages of the present invention are described by means of the specific description hereinafter. In the drawings: 
         FIGS. 1   a ,  1   b  are perspective views of an article of furniture, wherein the retraction device is on the one hand part of a drawer extension guide and on the other hand is fixed as a separate component to a furniture carcass, 
         FIG. 2  is an exploded view of the retraction device, 
         FIG. 3  shows the retraction device in the assembled condition, the entrainment member being in engagement with a coupling element of the drawer, 
         FIGS. 4   a ,  4   b  are a side view of the retraction device in the completely retracted closed position of the entrainment member, and an enlarged detail view in relation thereto, 
         FIGS. 5   a ,  5   b  show a position of the entrainment member which is extended further in relation to  FIGS. 5   a  and  5   b  and an enlarged detail view thereof, 
         FIG. 6   a ,  6   b  show a further open position of the entrainment member and an enlarged detail view in respect thereof, wherein from that moment in time the movement of the spring holder is continued with a differing movement characteristic, 
         FIGS. 7   a ,  7   b  show an opening movement which is continued in relation to  FIGS. 6   a  and  6   b , wherein the entrainment member is near the parking position, and an enlarged detail view thereof, 
         FIGS. 8   a ,  8   b  show the retraction device with the entrainment member arrested in the parking position and a view in which the coupling element is completely uncoupled from the entrainment member, 
         FIGS. 9   a - 9   e  show an alternative embodiment of the retraction device, the spring holder being guided along a linear control curve, 
         FIG. 10  is an exploded view of a retraction device according to a further embodiment, 
         FIGS. 11   a ,  11   b  are a perspective view of the retraction device of  FIG. 10 , and an enlarged detail view thereof, 
         FIGS. 12-12   c  are various views of the retraction device of  FIGS. 10 ,  11   a  and  11   b,    
         FIGS. 13   a - 13   e  show time sequences of the stressing process for the spring device in an embodiment of the retraction device shown in  FIGS. 10 through 12 , 
         FIG. 14  shows a graph comparison of the configuration of the opening force in a retraction device according to the state of the art and a possible configuration of the opening force according to the invention plotted against the extension travel of the movable furniture part, 
         FIGS. 15   a ,  15   b  show two diagrammatically illustrated retraction devices according to the state of the art, 
         FIGS. 16   a - 16   c  are diagrammatic views of the extension process of a retraction device according to the invention as further developed from  FIGS. 15   a  and  15   b,    
         FIG. 17  shows a further diagrammatically illustrated embodiment of a retraction device according to the state of the art, 
         FIGS. 18   a - 18   c  are diagrammatic views of the extension process of a retraction device according to the invention as further developed from  FIG. 17 , and 
         FIG. 19  is a diagrammatic view of the position of the spring articulation mounting point which is falling back relative to the position of the moving entrainment member. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1   a  is a perspective view of an embodiment of an article of furniture  1 , wherein movable furniture parts  3  in the form of drawers  3   a  are supported displaceably relative to a furniture carcass  2  by way of drawer extension guides  4 . The drawer extension guide  4  in a known manner has a carcass rail  5  to be fixed to the furniture carcass  2 , and at least one drawer rail  7  displaceable relative to the carcass rail  5 . A displaceable central rail  6  is supported between the carcass rail  5  and the drawer rail  7  in order to permit full extension of the drawer  3   a  relative to the furniture carcass  2 . The drawer extension guide  4  has a retraction device  8  by which the central rail  6  or the drawer rail  7  (and therewith the drawer  3   a ) is engaged towards the end of the closing movement and can subsequently be pulled into the completely closed position. 
     In  FIG. 1   a , retraction devices  8  are pre-fitted to the furniture carcass  2  of the article of furniture  1 , in a condition of being released from the extension guides  4 . The extension guide  4  in the illustrated embodiment can be in the form of a so-called rolling pushing guide which itself does not have its own spring-assisted retraction device. The retraction device  8  can therefore also be fitted to the furniture carcass  2  in the form of a self-contained unit which is to be retro-fitted. 
       FIG. 2  shows an exploded view of a possible embodiment of a retraction device  8 . The retraction device  8  has a main body  9  which can be fixed either to the furniture carcass  2 , to the drawer extension guide  4 , or also to the drawer  3   a . The main body  9  has a linear displacement path  10  and a guide portion  11  which is angled or curved away therefrom for guiding an entrainment member  12 . The entrainment member  12  can have guide elements  13  which in the stressing process can firstly pass along the linear displacement path  10  and then into the curved or angled guide portion  11 , in which case the entrainment member  12  can be releasably arrested in a pre-stressed parking position. The entrainment member  12  can be releasably coupled to a coupling element  14  which is connected either to the drawer  3   a , to the central rail  8 , to the drawer rail  7  or to the carcass rail  5  of the extension guide  4 . The coupling element  14  is only shown by way of example, and can be in the form of a protruding projection which can be releasably coupled to the entrainment member  12 . In the illustrated embodiment, the entrainment member  12  is connected tiltably about a—preferably horizontal—axis of rotation  15  to a slider  16  which is supported linearly displaceably relative to the main body  9 . For applying force to the entrainment member  12 , the arrangement has a spring device  17  by which the entrainment member  12  can be pulled into the completely closed position, starting from a parking position thereof (and thus the drawer  3   a ). The spring holder  18  for stressing the spring device  17  or for pulling in the entrainment member  12  has a multi-part structure in the illustrated embodiment, and includes a spring connection  18   a  as well as a tilting portion  18   b  which are pivotably connected together by an articulation mounting part (shaft)  18   c . The articulation mounting part  18   c  of the spring device  17  is limitedly movably supported within a—for example slot-like—guide  19  of the slider  16 . The tilting portion  18   b  has guide portions  20  which are mounted movably along a control curve  21  of the main body  9 , that is separate from the linear displacement path  10 . In the illustrated embodiment, the control curve  21  has a linear portion and a curved portion, wherein the spring device  17  can be stressed towards the end of the stressing travel over the curved portion of the control curve  21 . It is also possible to see a coupling device having two cooperating tooth arrangements  22   a  and  22   b , whereby the relative position of the spring holder  18  is variable relative to the linearly displaceable slider  16 . In the illustrated Figure, the tilting portion  18   b  has a tooth arrangement  22   a  which can roll against a tooth arrangement  22   b  of the slider  16 . The tooth arrangement  22   b  of the slider  16  can be in the form of a straight or linear tooth arrangement. To damp the closing movement of the entrainment member  12  (and thus to damp the last closing movement of the drawer  3   a ) there can be a damping device  23  which in the illustrated embodiment is in the form of a piston-cylinder unit, in which a piston with a piston rod  25  is arranged displaceably within the cylinder  24 . The cylinder  24  is to be fixed to the slider  16  and the piston rod  25  is supported in the assembled condition against a counterpart abutment  26  of the main body  9 . In the spring-assisted retraction movement of the entrainment member  12 , the cylinder  24  is displaced relative to the stationary piston rod  25 , wherein that retraction movement can be damped by fluid damping and/or by frictional damping. 
       FIG. 3  shows a perspective view of the retraction device  8  in the assembled condition, a cover which covers the retraction device  8  not being shown for the sake of clarity of the drawing. The entrainment member  12  of the retraction device  8 , that is mounted tiltably about the axis of rotation  15 , is in the completely retracted position and, in that case, is in engagement with the coupling element  14  of the drawer  3   a . By pulling on the drawer  3   a , the entrainment member  12  is pulled by way of the guide elements  13  along the linear displacement path  10  in the extension direction (A) while the tilting portion  18   b  of the spring holder  18  is moved by way of the guide portions  20  along the separate control curve  21 , whereby the spring device  17  is stressed. It is possible to see the tilting portion  18   b  which has the tooth arrangement  22   a  and which is pivotably connected to the spring connection  18   a  by way of the articulation mounting part  18   c . The cylinder  24  of the damping device  23  is also moved with the linearly displaceable slider  16 , in the extension movement, wherein the piston rod  25  is constantly supported against the counterpart abutment  26  of the main body  9 . 
       FIG. 4   a  shows a side view of the retraction device  8 , wherein the entrainment member  12  is coupled to the coupling element  14  of the drawer  3   a  and is in the completely retracted closure position.  FIG. 4   b  shows a view on an enlarged scale of the region circled in  FIG. 4   a . If now the drawer  3   a  is pulled out of the completely closed position, the entrainment member  12  is also moved in the extension (opening) direction A against the force of the spring device  17 . The entrainment member  12  can be moved along the linear displacement path  10  by the guide element  13  shown in  FIG. 2 , while the tilting portion  18   b  of the spring holder  18  can be guided by the guide portion  20  along the preferably curved control curve  21 . 
       FIG. 5   a  shows a slightly open position of the entrainment member  12 , which has been pulled out further in relation to  FIGS. 4   a  and  4   b .  FIG. 5   b  shows an enlarged detail view of the region circled in  FIG. 5   a . At the beginning of that extension movement in the extension direction (A), the tooth arrangement  22   a  of the tilting portion  18   b  does not roll against the tooth arrangement  22   b  of the slider  16 , whereby therefore the travel distance covered by the slider  16  substantially corresponds to the travel distance covered by the spring holder  18 . Initially, therefore, this involves identical motional relationships between the slider  16  and the spring holder  18 . In this process, the cylinder  24  of the damping device  23  is also moved so that the piston rod  25  is pulled out of the cylinder  24 . The piston rod  25  can be supported against the counterpart abutment  26  of the main body  9 , for example, by the force of a return spring supported in the cylinder  24 . It will be appreciated that the piston rod  25  can also be fixedly connected to the counterpart abutment  26 . 
       FIG. 6   a  shows a further open position of the entrainment member  12 , which is extended further as compared to  FIGS. 5   a  and  5   b , wherein the function of the coupling device—which in the illustrated embodiment includes the slider  16  with its tooth arrangement  22   b  and the tilting portion  18   b  with its tooth arrangement  22   a —is explained. As from a predetermined relative position of the tilting portion  18   b  with respect to the slider  16 , the tooth arrangement  22   a  of the tilting portion  18   b , arranged on the rolling region, can roll against the straight tooth arrangement  22   b  of the slider  16 , whereby the tilting portion  18   b  is pivotable relative to the slider  16 , namely about the coupling element  20  which is supported in the control curve  21  and which in this case forms an axis of rotation (along with articulation mounting part  12   c ). If now the drawer  3   a  is further pulled, that movement is continued with different motional relationships to the spring connection  18   a , whereby therefore the spring device  17  is less stressed per unit of travel covered by the entrainment member  12 . In that way, the forces required for stressing the spring device  17  can be reduced.  FIG. 6   b  shows an enlarged view of the region circled in  FIG. 6   a.    
       FIG. 7   a  shows the position of the entrainment member  12  which has now reached the end of the linear displacement path  10  in the stressing operation. In the illustrated embodiment, the entrainment member  12 , at its tip, has a guide element  13  ( FIG. 3 ) whereby, in a continued opening movement, the entrainment member  12  can be tilted about the axis of rotation  15  relative to the slider  16 . In that arrangement, the guide element  13  of the entrainment member  12  can pass into the curved or angled guide portion  11 , whereby the entrainment member  12  and the spring device  17  which is now stressed can be arrested in that parking position. It should obviously be noted that the person skilled in the art can also find further embodiments by way of example for tilting movement of the entrainment member  12  without being inventively active in that respect.  FIG. 7   b  shows an enlarged view of the region circled in  FIG. 7   a.    
       FIG. 8   a  now shows the entrainment member  12  which has been tilted into the parking position and arrested, wherein the coupling element  14  is released by a tilting movement of the entrainment member  12 , and so the drawer  3   a  is freely displaceable over the remaining extension travel path. The coupling element  14  which is completely uncoupled from the entrainment member  12  is shown in  FIG. 8   b . The entrainment member  12  now remains in that parking position until the drawer  3   a  is pushed in again and thus the coupling element  14  again approaches the entrainment member  12 . Towards the end of the closing movement, the coupling element  14  can pass into the notch of the entrainment member  12 , whereby the latter tilts out of the arrested parking position again and is pulled into the completely closed position along the linear displacement path  10  by the force of the previously loaded spring device  17 . That retraction movement can be damped by a damping device  23 . In the illustrated embodiment, the cylinder  24  supported on the slider  16  is pushed in relative to the stationary piston rod  25 , in which case a braking effect can be generated in particular by a fluid in the cylinder  24 . The stressing process upon opening the drawer  3   a  can then begin afresh again, as is shown in  FIGS. 4   a  through  8   b.    
       FIGS. 9   a - 9   e  show an alternative embodiment with a linearly extending control curve  21  in time sequences of the stressing process.  FIG. 9   a  shows a side view of the retraction device  8 , wherein the retraction device  8  can also have all components of the preceding Figures, with the same references denoting the same parts. The difference in relation to the preceding Figures is therefore that the control curve  21  for guiding the spring holder  18  (spring connection  18   a  and tilting portion  18   b  which are pivotably connected together by way of the articulation mounting point  18   c  which is in the form of an axis pin) extends—preferably exclusively—linearly. The tilting portion  18   b  has at least one guide portion  20  by which the tilting portion  18   b  is guided along the control curve  21 .  FIG. 9   a  shows the retraction device  8  in the closed position. A pulling movement is applied to the entrainment member  12  by manually pulling on the drawer  3   a  ( FIG. 1   a ) by way of the coupling element  14 . In that case, the tooth arrangement  22   a  of the tilting portion  18   b  runs against the tooth arrangement  22   b  of the slider  16  ( FIG. 9   b ). When a further pulling movement is applied to the drawer  3   a , the guide portion  20  passes to the end of the control curve  21  ( FIG. 9   c ), wherein the guide portion  20  as from that position forms a pivot axis for the tilting portion  18   b . It will be seen from  FIG. 9   d  that the entrainment member  12  can pass into the curved or angled portion  11  by way of the guide element  13  arranged on the entrainment member (for example  FIG. 3 ), in which case the entrainment member  12  is tiltable relative to the slider  16  by way of a pivot axis  15  and in that case releases the coupling element  14  connected to the drawer  3  so that the drawer  3   a  is freely displaceable over the remaining extension travel. In  FIGS. 9   d  and  9   e  therefore the entrainment member  12  is arrested in a pre-stressed parking position—preferably by way of the guide element  13  shown in  FIG. 3 . In the next closing movement of the drawer  3   a  the coupling element  14  moves closer to the entrainment member  12 , and guides it out of the pre-stressed parking position whereby the coupling element  14  (and therewith the drawer  3   a ) can be pulled into the closed end position by the previously stressed spring device  17 , wherein that retraction movement can be damped by the damping device  23  shown in  FIG. 9   a . The spring holder  18  can be guided over a longer stressing travel by way of the control curve  21  whereby less manual force is also required for stressing the spring device  17 . 
       FIG. 10  shows an exploded view of a retraction device  8  of a further embodiment. Provided on or in the main body  9  is a control curve  21  which has two guide portions  21   a  and  21   b  for guiding the tilting portion  18   b  and/or for locking the entrainment member  12 . In addition, arranged on the main body  9  are the linear displacement path  10  and the curved or angled portion  11  adjoining same, for guiding the entrainment member  12 . The entrainment member  12  can be guided by way of a guide element  13  along the displacement path  10  and along the angled or curved portion  11 . The spring device  17  can be stationarily fixed on the one hand to a mounting point  17   a  of the main body  9  while on the other hand the spring device  17  is coupled to the spring connection  18   a . The spring connection  18   a  is connected movably by way of the articulation mounting point  18   c  to a tilting portion  18   b . The tilting portion  18   b  has an arcuate tooth arrangement  22   a  which in the mounted position is in engagement with a corresponding tooth arrangement  22   b  of the slider  16 . Arranged on the tilting portion  18   b  is a first guide part  20   a  which can pass into the guide portion  21   a  of the control curve  21 —but not into the guide portion  21   b  of the control curve  21 . In addition, the tilting portion  18   b  has a second guide part  20   b  which can pass into the guide portion  21   b  but not into the guide portion  21   a  of the control curve  21 . That kind of guidance is made possible by pin-shaped guide parts  20   a  and  20   b  which can be of a differing diameter and/or a differing length. In addition, the guide portions  21   a  and  21   b  of the control curve  21  can also be of a different passage width and/or a different passage depth. The entrainment member  12  is connected to the slider  16  pivotably—preferably by way of a horizontal axis of rotation  15 . Supported on the slider  16  is a damping device  23  having a piston-cylinder unit  24 ,  25  by which the retraction movement of the entrainment member  12  (and therewith the drawer  3   a ) can be damped. 
       FIG. 11   a  shows a perspective view of the retraction device  8  shown in  FIG. 10 . In  FIG. 11   b , in contrast, the region circled in  FIG. 11   a  is shown as an enlarged view. In the illustrated Figure, the retraction device  8  is in the completely retracted closed position. If now a pulling force is applied to the drawer  3   a  in the closed position, the entrainment member  12  can be moved along the linear displacement path  10 . At the beginning of that extension movement, the tooth arrangement  22   a  of the tilting portion  18  can still remain in its relative position with respect to the tooth arrangement  22   b  of the slider. 
       FIG. 12   a  shows a perspective view of the rear side of the retraction device  8 . It is possible to see the two guide parts  20   a  and  20   b  of the tilting portion  18   b  which—as can be clearly seen from the enlarged detail view in  FIG. 12   b —can be of a different diameter and a different length. It is possible to see in  FIG. 12   c  a part of the main body  9  having the control curve  21  and the two guide portions  21   a  and  21   b  branching therefrom. The guide portions  21   a  and  21   b  have different passage widths and they are provided to receive the respective guide parts  20   a  and  20   b . That construction can provide that the guide part  20   a  can only pass into the guide portion  21   a  upon stressing of the spring device  17 , while in contrast the guide part  20   b  can only pass into the guide portion  21   b  of the control curve  21 . 
       FIGS. 13   a - 13   e  show time sequences of the stressing process for the spring device  17 . In  FIG. 13   a  the drawer  3   a  is in the completely closed position. By pulling on the drawer  3   a  the coupling element  14  is also moved whereby the entrainment member  12  is also pulled in the extension (open) direction (A) along the linear displacement path  10  and the spring device  17  is stressed. The two guide parts  20   a  and  20   b  of the tilting portion  18   b  are disposed within the linear portion of the control curve  21 , while the tooth arrangement  22   a  of the tilting portion  18   b  is connected to the tooth arrangement  22   b  of the slider  16 . If now the drawer  3   a  is further pulled, then the guide part  20   a  passes into the guide portion  21   a  ( FIG. 13   b ) whereupon the tilting portion  18   b  is pivoted and the guide part  20   a  butts against the end of the guide portion  21   a . The guide part  20   b  which is of the larger diameter can now pass into the wider guide portion  21   b  of the control curve  21  ( FIG. 13   c ), wherein the tooth arrangement  22   a  of the tilting portion  18   b  and the tooth arrangement  22   b  of the slider  16  can move relative to each other whereby the tilting portion  18  is pivoted in the counter-clockwise direction ( FIG. 13   d ). In  FIG. 13   e  the entrainment member  12  has moved into the curved or angled portion  11 , wherein the entrainment member  12  was pivoted relative to the slider  16  so that the coupling element  14  of the drawer  3   a  is released and the drawer  3   a  is freely displaceable over the remaining extension travel. Just before the tilting movement of the entrainment member  12 , therefore, the force is transmitted to the tilting portion  18   a , wherein the entrainment member  12  per se is no longer substantially subjected to any more pulling force as the entrainment member  12  can be arrested in the readiness position by way of the tilting portion  18   b  and by way of the guide parts  20   a ,  20   b  which are disposed in the guide portions  21   a  and  21   b.    
       FIG. 14  diagrammatically shows a graphic comparison of the opening force variation X1 in the case of a retraction device according to the state of the art and an opening force variation X2 by way of example according to the invention plotted in relation to the extension travel S of the drawer  3   a . In the case of the opening force variation X1 in the state of the art, the drawer  3   a  which is in the closed position is pulled, in which case the force required to open the drawer  3   a  firstly rises linearly until parking of the entrainment member  12  causes an abrupt drop in the force F. That drop in force F makes itself apparent to a user by an (unwanted) acceleration of the drawer  3   a  in the opening direction. In the case of the opening force variation X2 according to the invention, the force required to open the drawer  3   a  initially also rises but that force then continuously drops, whereby it is possible to bring about a harmonic motion characteristic for the opening process. It will also be clear from the opening force variation X2 that the force required to open the drawer  3   a  is reduced in relation to the opening force variation X1. 
       FIGS. 16   a - 16   c  diagrammatically show time sequences of the extension process of a retraction device  8  which represents a development of the retraction devices  8  which are already known, as shown in  FIGS. 15 and 15   b . It is possible to see the linearly displaceable slider  16  on which the entrainment member  12  is mounted about an axis of rotation  15 . Mounted on the slider  16  is the articulation mounting part  18   c  of the spring device  17  which in  FIG. 16   a  is near the entrainment member  12 . In an extension movement of the drawer  3   a  the articulation mounting part  18   c  of the spring device  17  drops back relative to the displacement path  10  of the entrainment member  12  as is shown in  FIG. 16   b .  FIG. 16   c  shows the tilted position of the entrainment member  12  which has already released the coupling element  14  of the drawer  3   a . It will be seen that the stressing travel of the spring device  17 , by virtue of the illustrated position of the articulation mounting part  18   c , is less than the displacement path  10  of the entrainment member  12  so that the entrainment member  12  can be transferred into the tilted parking position, under a reduced tensile loading. 
       FIGS. 18   a - 18   c  show time sequences of the extension process by reference to a development of this configuration according to the state of the art shown in  FIG. 17 . In  FIG. 18   a  the spring device  17  is coupled to the entrainment member  12  by way of a spring holder  18 . When now the drawer  3   a  is pulled the articulation mounting part  18   c  drops back relative to the entrainment member  12  ( FIG. 18   b ).  FIG. 18   c  shows the tilted position of the entrainment member  12 , wherein the coupling element  14  has already been released. In that case the articulation mounting part  18   c  of the spring device  17  was moved relative to the entrainment member  12  at a reduced speed in order in that way to reduce the maximum stress on the entrainment member  12  and thus permit the entrainment member  12  to move into the parking position more gently. 
       FIG. 19  shows a diagrammatic view of the spring articulation mounting part  18   c  as it falls back, relative to the position of the moving entrainment member  12 . Starting from the closed position in which the spring device  17  is substantially relieved of stress the spring articulation mounting point  18   c , when the entrainment member  12  is pulled out, is moved along the first displacement travel S1 substantially at the same speed as the entrainment member  12 . Along a second displacement travel S2 adjoining the first displacement travel S1 the articulation mounting point  18   c  of the spring device  17  drops back further and further relative to the position of the moving entrainment member  12 , as will be clear from the ever increasing travel spacings ΔX1, ΔX2, ΔX3, ΔX4 between the entrainment member  12  and the spring articulation mounting point  18   c.    
     The present invention is not limited to the illustrated embodiments but embraces or extends to all variants and technical equivalents which can fall within the scope of the accompanying claims. The positional references adopted in the description such as for example “up”, “down”, “lateral” and so forth are also related to the usual position of installation of the components used and to the illustrated Figure and are to be appropriately transferred to the new position upon a change in position. The control curve  21  can be formed by any device which only permits a substantially line-shaped movement. The control curve  21  can be straight or curved or can also be portion-wise straight and/or portion-wise curved. It should also be noted that an electric motor can also be provided to drive the entrainment member  12 . In addition, the described retraction device  8  can be used not only for drawers  3   a  or drawer extension guides  4 , but generally for movable furniture parts  3  like sliding doors, pivotable doors, flaps or the like. When using the retraction device  8  with drawer extension guides  4 , it can be provided that the retraction device  8  is arranged on the carcass rail  5  and the coupling element  14  is arranged on the central rail  6 , the drawer rail  7  or on the drawer  3   a . In a mechanical reversal, it will be appreciated that it is also possible for the retraction device  8  to be mounted to the central rail  6 , to the drawer rail  7  or to the drawer  3   a  while the coupling element  14  is arranged on the carcass rail  5  or another component fixed with respect to the furniture carcass.

Summary:
A retracting device retracts a movably supported furniture part to the closed end position relative to a furniture body. The device includes a carrier, which can be detachably coupled to the movable furniture part and which is movably supported along a movement path that is linear at least in some sections, and at least one spring device for applying force to the carrier. The spring device can be tensioned by a spring retainer that is separate from the carrier, and the spring retainer is movably supported against or on the carrier. A coupling device is provided in order to couple motion between the carrier and the spring retainer. By the coupling device, the articulated attachment point of the spring device on the spring retainer falls back relative to the position of the moving carrier when the carrier is pulled out, so that the motion of the articulated attachment point of the spring device on the spring retainer is slower than the motion of the carrier.