An automatic retraction apparatus and a pull-out guide The present invention relates to an automatic retraction apparatus for a pull-out rail-guided moving furniture part according to the preamble of claim 1, and to a pull-out guide for drawers, furniture pull-outs or the like according to the preamble of claim 13. Automatic retraction apparatuses and pull-out guides comprising the same are known in many embodiments. The automatic retraction apparatuses are used to reliably draw a pull-out rail-guided moving furniture part to the closed position. Especially in the case of furniture parts which are movably fastened to a furniture body by way of a so-called "fully extendable pull-out", the control of the sequence of the profiles of the pull-out, i.e. the mutual displacement of running rail, middle rail and guide rail, represents a problem in the manner that jamming of the pull-out occurs as a result of dislocations of the profiles with respect to one another by very heavy items placed in the movable furniture part. The prior known automatic retraction apparatuses and pull-out guides come with the further disadvantage that the actuating forces required for pretensioning such an automatic retraction apparatus need to be very high and the user of such a movable furniture part therefore needs to apply a large amount of force in order to draw furniture part from the furniture body. It is therefore the object of the present invention to improve the control of the sequence of the profiles of the pull-out and to improve the convenience in operating a furniture part equipped with an automatic retraction apparatus. This object is achieved by an automatic retraction apparatus with the features of claim 1 and by a pull-out guide with features of claim 13. Advantageous embodiments of the invention are the subject matter of sub-claims. In accordance with the invention, the automatic retraction apparatus comprises a tensioning mechanism with two drivers which are coupled to at least one energy store and synchronously block or activate the tensioning mechanism. 2664869_1 (GHMatter) P86983.AU The installation of such an automatic retraction apparatus in accordance with the invention enables a co-ordinated sequence of the profiles of the pull-out. A potential dislocation is effectively prevented by the synchronous blocking or activation of the energy store by the drivers. In accordance with a further embodiment of the invention, the energy store is arranged in form of springs which are respectively arrested on the first end on the base body and on the second end on a driver. As a result of this arrangement, the tension springs are arranged parallel with respect to each other, so that in the pull-out direction it is only necessary to apply a force corresponding to the spring constant of one of the tension springs when pretensioning the energy store, as a result of which the operating convenience is increased considerably. Preferably, the drivers are coupled with a damper arranged on the base body, by means of which a counterforce damping the closing movement and acting opposite of the direction of the closing forces is applied shortly before reaching the final closing position. The dampers ensure that the pull-out rails coupled with the automatic retraction apparatus are drawn at low speed into the closing position, so that there are no disturbing noises when the pull-out rails meet the limit stop. In accordance with a further embodiment of the invention, one respective damper is arranged on opposite areas of the base body, which damper is respectively coupled with at least one of the drivers. It is thus ensured that the damping function on the guide rail and on the running rail is individually adjustable. Preferably, the drivers are mutually coupled by means of a gearwheel control. This ensures reliable coupling of the movement of the pull-out guides coupled with the respective drivers. In accordance with an alternative embodiment of the invention, each of the drivers is coupled with a locking web which is displaceably held along the base body, with each of the drivers in its blocking position blocking the locking web of the respective other driver. It is thus prevented that the automatic retraction is already activated when only one of the drivers is activated by the movement of the pull-out rail coupled with the same before the other pull-out rail has reached the triggering point for activating the automatic retraction apparatus. 2664869_1 (GHMatters) P86983.AU A coordinated movement of the middle rail in the guide rail and the running rail in the middle rail is enabled by fastening the automatic retraction apparatus to the middle rail of a pull-out guide for drawers, pull-outs or the like. The invention will be explained below by reference to several embodiments shown in the enclosed drawings, wherein: Fig. I shows a perspective view of a first embodiment of an automatic retraction apparatus in accordance with the invention; Fig. 2 shows a perspective exploded view of the automatic retraction apparatus of Fig. 1; Fig. 3 shows a perspective view of a second embodiment of an automatic retraction apparatus in accordance with the invention; Fig. 4 shows a perspective exploded view of the automatic retraction apparatus of Fig. 3; Fig. 5 shows a perspective view of a further embodiment of an automatic retraction apparatus in accordance with the invention; Fig. 6 shows a perspective exploded view of the automatic retraction apparatus of Fig. 5; Fig. 7 shows a perspective view of a further embodiment of an automatic retraction apparatus in accordance with the invention; Fig. 8 shows a perspective exploded view of the automatic retraction apparatus of Fig. 7; Figs. 9 and 10 show different perspective views of an embodiment of a pull-out guide in accordance with the invention; Fig. 11 shows a top view of the pull-out guide of Figs. 9 and 10; Fig. 12 shows a rear view of the pull-out guide of Figs. 9 and 10; Fig. 13 shows a front view of the pull-out guide of Figs. 9 and 10; 26M4869_1 (GHMatters) P86983 AU Fig. 14 shows a further perspective view of the pull-out guide of Figs. 9 and 10; Figs. 15 and 16 show perspective views of the pull-out guides of Figs. 9 and 10 in different positions; Figs. 17 to 20 show further perspective views of the pull-out guide of Figs. 9 and 10. Figs. I to 8 show different embodiments of an automatic retraction apparatus 100, 200, 300, 400 for a pull-out rail-guided moving furniture part, especially for drawers, pull-outs or the like. All these automatic retraction apparatuses 100, 200, 300, 400 comprise a base body 101, 201, 301, 401, and an energy store arranged on the base body 101, 201, 301, 401 which is tensioned during the opening of the movable furniture part and stored energy of which can be utilized during the closing process as a retraction aid to the final closing position, and a tensioning mechanism for pretensioning the energy store which is coupled with the movable furniture part up to a predetermined opened position and is automatically decoupled upon exceeding the mentioned specific opened position and blocks the tensioned energy store in this position. In accordance with the invention, the tensioning mechanism comprises two drivers 109, 113, 207, 208, 305, 306, 405, 406 which are coupled with the energy store and synchronously block the tensioning mechanism. In the embodiment as shown in Figs. 1 and 2, the automatic retraction apparatus 100 substantially consists of three components, which are a base body 101 which is arranged on an upper side and a bottom side with latching hooks 117, 118, and two identical housings 104, 105 which can each be latched together with the latching hooks 117, 118, with one respective driver 109, 113 being mounted in the housings 104, 105. These housings 104, 105 are arranged to be open on one of their lateral surfaces. The driver 109, 113 held in the housing protrudes from this open side of the respective housing 104, 105. The drivers 109, 113 are arranged on their side protruding from the housing 104, 105 in such a way that they can be coupled with an activator 7, 8, as is shown in Fig. 15 by way of example, so that they are displaced in the housing 104, 105 when a movable furniture part is moved out of its closed position. The base body 101 is fastened to the middle rail 4. The activator 7 is arranged on the running rail 3 and the activator 8 is arranged in the guide rail 5. 2664869_1 (GHMatters) P86983 AU Two tension springs are locked as an energy store on the drivers 109, 113 (not shown in Figs. I and 2), the other ends of which are fastened to the base body 101 in the receivers 121. As a result, both tension springs are tensioned simultaneously when a movable furniture part is moved out of its closed position. For the purpose of locking these tensioned positions, the drivers 109, 113 are guided in L-shaped link guides 112, 116 in the housings 104, 105 via guide pins 110, 111, 114, 115 provided on the drivers. The protruding guide pin 114 engages in an opening 122 of a rack 107 and the protruding guide pin 111 engages in an opening 123 of a rack 106. As soon as the guide pins 110, 115 of the drivers 109, 113 which are closer to the short L-section of the link guides 112, 116 are slid into the short L-section of the link guides 112, 116, the drivers 109, 113 are tilted into the housing 104, 105 in such a way that the activators 7, 8 which are coupled with the drivers 109, 113 are decoupled by the drivers 109, 113, so that the running rail 3 which is connected with the activated 7 is displaceable in the decoupled state in the direction of its maximum opening position, while the energy store is fixed in a completely tensioned way. At the same time, the middle rail 4 is moved together with the running rail 3 relative to the guide rail 5 coupled with the activator 8. The energy store associated with the activator 8 is thus also completely tensioned and fixed. When the running rail 3 is moved back to its closed position again, the coupling between the activator 7 and the driver 113 and the coupling between the activated 8 and the driver 109 is reproduced again, so that now the stored energy of the energy store can be utilized as a retraction aid of the movable furniture part to its final closed position. Only when both activators 7, 8 are in engagement again with the drivers 109, 113 will the system trigger and the automatic retraction apparatus 100 will become effective and will thus cause the closing of the pull-out guide 1. Running errors in form of an offset of the cage are thus effectively prevented or remedied. In one embodiment, the drivers are additionally coupled with one respective damper 102, 103 which is arranged on the base body and by means of which a counterforce damping the closing movement and acting opposite of the direction of the closing forces is applied shortly before reaching the final closing position. The base body 101 is fixed to the middle rail 4. The housing 104 is fixed via the latching hooks 117 to the base body 101, and the housing 105 is fixed to the base body 101 via the latching hooks 118. The rack 106 is guided in a sliding manner in the slot 120 in the base body 101, which rack is associated with the driver 109 and is connected via the protruding guide pin I I I of the opening 123 in the rack 106. The rack 107 is guided in a sliding manner in the slot 119 in the base body 101, which rack is associated with the driver 113 and is connected via the protruding 2664869_1 (GHMattm) P88983.AU guide pin 114 of the opening 122 in the rack 107. The gearwheel 108 is fixed centrally to the base body 101 in such a way that it runs in the racks 106, 107, thus synchronizing the system. The racks 106, 107 are permanently in engagement with the gearwheel 108. The two racks 106 and 107 consist of a fastening plate which can be fastened to the respective housing 104, 105, and of one toothed web which stands perpendicularly to the fastening plate, with the toothed webs of the racks 106, 107 being opposite of one another, so that the gearwheel 108 can simultaneously engage in both racks 106, 107. It is thus ensured that a displacement of the driver 109 is always accompanied by a displacement of the driver 113. In the embodiment of the automatic retraction apparatus 200 as shown in Figs. 3 and 4, both drivers 207, 208 are connected with the same damper 202. The base body 201 comprises one respective plateau at its respective ends in this embodiment, on the edge of which the drivers 207, 208 are guided. The damper 202 is arranged between these two plateaus. The damper 202 is substantially arranged as a cylinder (as also the dampers of the other embodiments), with a web 210 of fixed length being arranged from its floor-side face side and a web 209 displaceable in the damper 202 on the head side, with the webs 209, 210 being coupled with respective face sides of the drivers 207, 208 facing the damper via ball-and-socket joints. For this purpose, socket-like recesses are provided on the face sides of the drivers 207, 208 facing the damper 202, in which the spherical ends of the damper webs 209, 210 are embedded. Each of the drivers 207, 208 is pivotably coupled via joints 230, 231 with a locking web 205, 206 displaceably held along the base body 201, with each of the drivers 207, 28 blocking in its blocking position this locking web 205, 206 of the respective other driver 207, 208. Guide webs 219 are provided on the base body 201 for the displaceable fixing of the locking webs 205, 206, which guide webs are preferably arranged in an L-shaped manner and stand offset to one another in pairs, so that the locking webs 205, 206 are displaceably arranged in the base body in the longitudinal direction of the locking webs or the base body. The locking webs 205, 206 have such a length which is dimensioned in such a way that the locking webs 205, 206 respectively protrude in the non-tensioned position beyond the face edges of the base body 201 on which the respective other driver is displaceably arranged, and are displaced in the displacement of the drivers 207, 208 to their blocking position to a position in which the end of the locking web 205, 206 which previously protrudes on the opposite end of the base body 201 is in alignment with the face edge of the base body 201. The side of the driver 207, 208 facing the locking web which is coupled with the respective other driver is arranged for this purpose with protrusions 211, 214 2664869_1 (GHMatters) P86983.AU which prevents a movement of the locking web coupled with the other driver beyond the edge of the base body 201 on its face sides 227, 228 as long as only one of the drivers 207, 208 was moved away from its blocking position. The guidance of the drivers 207, 208 on the base body 201 is additionally supported by one bent groove 213, 216 on the plateaus of the base body 201, in which a respective guide pin 215 on the drivers 207, 208 will engage. As is shown especially in Fig. 4, the tension springs 203, 204 are fastened with one respective end 221, 222 to latching recesses 224, 226 which are provided for this purpose on the base body 201 and are coupled at the respective other end 220, 223 with the respective drivers 207, 208 in the latching recesses 217. Figs. 5 and 6 show a further embodiment. The base body 301 of the apparatus in accordance with the invention is also arranged on the middle rail 4. The synchronization of the engagement of the activators 7, 8 which is necessary for the simultaneous triggering of the automatic retraction apparatus 301 and the actuation of the drivers 305, 306 occurs in this case by way of a gearwheel rotatably arranged on the middle rail 4, which gearwheel is in engagement over the entire pull out length on both sides with racks which are respectively fixed to the guide rail 5 and the running rail 3 (not shown). In this embodiment, the tension springs 303, 304 are arranged in a length which corresponds to the path of one of the drivers 306, 305 plus the entire damper 302. The latching recesses 312, in which one respective end 310, 313 of the tension springs 303, 304 is latched, are disposed in this embodiment on the face ends of the base body 301. In the embodiment of the automatic retraction apparatus as shown in Figs. 7 and 8, the entire automatic retraction mechanism, which on its part is arranged on the middle rail 4, is arranged in a base body 401 which is partly arranged as a housing which encloses the damper 403 and two tension springs 410, 411 and racks 407, 408 and a gearwheel 409 arranged between these racks 407, 408 on three sides, with the open side being closable by a plate 402. For this purpose, two pins 422, 420 are arranged in the plate 402, which pins engage in openings on an area of the base body 401 which extends parallel to the plate 402. The plate 402 further comprises a cylindrical pin 421 which protrudes perpendicularly from the plate into the interior of the housing part of the base body 401. The gearwheel 409 is rotatably arranged on this cylindrical pin 421. The gearwheel 409 is in permanent engagement with two racks 407, 408 which are arranged with their gearing opposite of one another. The rack 407 which is the upper one in the drawing is 264869_1 (GHMattem) P86983.AU arranged between the pivotable driver 406 and the tension spring 410. The other end of the tension spring 410 is fastened to the base body 401. The bottom rack 408 is coupled to the pivotable driver 405. It is thus ensured in a simpler manner that the tensioning apparatus is always tensioned evenly and when a blocking position is lifted only one of the drivers 405 will continue to block the retraction aid by the blocking position of the other driver 406, and will only act when both drivers 405, 406 have left their blocking position. Figs. 9 to 20 show different views of one embodiment of a pull-out guide in accordance with the invention. The variant shown in the drawings is especially suitable for drawers or pull-outs. The pull-out guide designated with reference numeral I substantially consists of a guide rail 5 which can be fixed to a furniture body and in which a middle rail 4 will engage, on which a running rail 3 is arranged which can be connected with a drawer for example. The automatic retraction apparatus is fastened to the middle rail 4. Both the guide rail 5 and the running rail 3 are each equipped with an activator 7, 8, which are respectively coupled with one of the drivers 305, 306, as is shown in closer detail in Fig. 15. During the relative displacement of the running rail 3 relative to the middle rail 4 and the middle rail 4 relative to the guide rail 5, the drivers 305, 306 are simultaneously moved by the activators 7, 8 and the energy store of the automatic retraction apparatus 6 is thereby tensioned. If a specific pull-out path is exceeded by the running rail 3 and the middle rail 4 and the guide rail 5, the drivers 305, 306 are tilted away from the engagement region of the activators 7, 8 by respective guides of the drivers and are locked in this position. The running rail 3 and the middle rail 4 can now be pulled to their full pull-out position and the automatic retraction apparatus 6 remains in a position in which the energy store of the automatic retraction apparatus remains completely tensioned. The angle brackets 2, as shown in Fig. 12, are used for fixing the pull-out guide 1 to a furniture body (not shown here). If the running rail 3 and the middle rail 4 are slid back in the closing direction, the activators 7, 8 again reach a region of the drivers 305, 306 in a specific displacement position, unlock them and thus release the energy store. The running rail 3 and the middle rail 4 are automatically retracted to the closing position by the respective force, this being by interaction between the drivers 305, 306 and the activators 7, 8. 2684869_1 (GHMaters) P86983 AU List of reference numerals I Pull-out guide 2 Angle bracket 3 Running rail 4 Middle rail 5 Guide rail 6 Automatic retraction apparatus 7 Activator 8 Activator 100 Automatic retraction apparatus 101 Base body 102 Damper 103 Damper 104 Housing 105 Housing 106 Rack 107 Rack 108 Gearwheel 109 Driver 110 Guide pin Ill Protruding guide pins 112 Link guide 113 Driver 114 Protruding guide pins 115 Guide pin 116 Link guide 117 Latching hook 118 Latching hook 119 Slot 120 Slot 121 Receiver 122 Opening 2664869_1 (GHMatlers) P86983.AU 123 Opening 200 Automatic retraction apparatus 201 Base body 202 Damper 203 Tension spring 204 Tension spring 205 Locking web 206 Locking web 207 Driver 208 Driver 209 Web 210 Web 211 Protrusion 214 Protrusion 216 Groove 217 Latching recess 219 Guide web 220 End 221 End 222 End 223 End 224 Latching recess 225 Guide pin 226 Latching recess 227 Face side 228 Face side 230 Joint 231 Joint 300 Automatic retraction apparatus 301 Base body 302 Damper 303 Tension spring 304 Tension spring 2664869_1 (GHMatters) P86983.AU 305 Driver 306 Driver 310 End 312 Latching recess 313 End 314 End 318 Guide track 319 Guide track 400 Automatic retraction apparatus 401 Base body 402 Plate 403 Damper 405 Driver 406 Driver 407 Rack 408 Rack 409 Gearwheel 410 Tension spring 411 Tension spring 418 Guide track 419 Guide track 420 Pin 421 Cylindrical pin 422 Pin 2664869 1 (GHMatters) P86983 AU