CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a United States National Phase Application of International Application PCT/EP2013/065721 filed Jul. 25, 2013 and claims the benefit of priority under 35 U.S.C. §119 of German Patent Application DE 10 2012 015 288.4 filed Jul. 31, 2012, the entire contents of which are incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The invention to an unlocking unit for a vehicle seat with at least two locking devices, which unlocking unit transmits a movement, which is introduced via an actuating element, for unlocking purposes to the at least two locking devices, wherein each locking device is in each case assigned an unlocking element, wherein, when the locking device is locked, the assigned unlocking element is in the locking position and wherein, when the locking device is unlocked, the assigned unlocking element is in the unlocking position. The invention also relates to a vehicle seat with such an unlocking unit. 
     BACKGROUND OF THE INVENTION 
     DE 10 2010 052 273 A1 discloses an unlocking unit of the type in question and a vehicle seat of the type in question. The vehicle seat here comprises a pivotable backrest which is lockable to the seat structure of the vehicle seat by means of two locking devices. By unlocking said locking devices, the backrest is pivotable about a horizontal pivot axis. The two locking devices here are unlockable simultaneously. 
     DE 10 2006 015 922 B4 also discloses a vehicle seat of the type in question. The vehicle seat here is lockable to a seat rail by means of two locking devices. By unlocking said two locking devices, the vehicle seat is detachable from the seat rail and is removable from the vehicle. The two locking devices are unlockable simultaneously. 
     After the vehicle seat is reinserted into the vehicle, it is important to lock the two locking devices in order to hold the vehicle seat securely. Checking of the locking state of the locking devices is visually possible. That is to say, a user can look at each individual locking device and can see whether said locking device is locked or unlocked. 
     DE 102 30 637 A1 discloses a vehicle seat with a locking device for locking a backrest of the vehicle seat to a vehicle body. The locking device comprises an optical display element which indicates whether the locking device is locked or unlocked. 
     SUMMARY OF THE INVENTION 
     The invention is based on the problem of improving an unlocking unit of the type mentioned at the beginning, in particular of providing a display for the locking state of the two locking devices, which display indicates whether the two locking devices are locked. 
     An unlocking unit of the type in question for a vehicle seat for unlocking at least two locking devices, which unlocking unit transmits a movement, which is introduced via an actuating element, for unlocking purposes to the at least two locking devices, comprises two unlocking elements, wherein each locking device is in each case assigned an unlocking element, and wherein, when the locking device is locked, the assigned unlocking element is in the locking position, and wherein, when the locking device is unlocked, the assigned unlocking element is in the unlocking position. 
     According to the invention, a display element is provided which is in the display position when the at least two locking devices are unlocked, and which is in the non-display position when the at least two locking devices are locked, and each unlocking element located in the unlocking position prevents a movement of the display element into the non-display position, wherein the display element remains in the display position as long as at least one locking device is unlocked. 
     As a result, the display element remains in the display position as long as at least one unlocking element is in the unlocking position. Only when all of the locking devices are locked and all of the assigned unlocking elements are in the locking position does the display element move into the non-display position. 
     The display element here is preferably connected fixedly to the actuating element or is formed integrally therewith. As a result, a user can already see the locking state of the locking devices by way of the actuating element itself. 
     The actuating element here is preferably designed as a flexible belt strap and, as a result, is cost-effective and handleable in a simple manner. The display element here can be configured as a display region marked in color on the belt strap. 
     According to an advantageous development of the invention, a gearwheel mechanism is provided which transmits a movement, which is introduced via the actuating element, for unlocking purposes to the unlocking elements. The unlocking elements transmit the movement for unlocking purposes further to the locking devices. 
     The gearwheel mechanism advantageously comprises an unlocking lever with an unlocking toothing and a control gearwheel with a control toothing, wherein the unlocking lever is connected to the actuating element. The unlocking toothing meshes here with the control toothing. 
     According to an advantageous refinement of the invention, in the event of a movement, which is introduced via the actuating element, for unlocking purposes, the control gearwheel first passes through an idle travel and then carries along the unlocking elements. 
     For this purpose, a driver is preferably attached to the control gearwheel, said driver striking against a first counterstop of the first unlocking element and against a second counterstop of the second unlocking element. 
     The unlocking lever here has a stop element which, when the unlocking element is in the unlocking position, is in contact with the unlocking element. As a result, the display element, which is kinematically coupled to the unlocking lever, remains in the display position until all of the unlocking elements are in the locking position. 
     Advantageously, a control spring is arranged in each case between the control gearwheel and each unlocking element, which control spring loads the unlocking element relative to the control gearwheel toward the unlocking position. 
     The unlocking elements and the control gearwheel are advantageously mounted rotatably about a common control pivot axis, as a result of which the design of the unlocking unit is simplified. 
     The control gearwheel here is preferably arranged in the axial direction between the first unlocking element and the second unlocking element. 
     A simple design of the unlocking unit is also produced if the unlocking lever is mounted pivotably about an actuating pivot axis which runs parallel to the control pivot axis. 
     The unlocking unit preferably also has a return spring which loads the unlocking lever constantly in the direction of a rest position. 
     Each locking device is in each case connected by means of a Bowden cable to the assigned unlocking element. As a result, the unlocking unit is arrangeable so as to be removed from the locking devices. 
     The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings: 
         FIG. 1  is a perspective illustration of an unlocking unit; 
         FIG. 2  is a perspective illustration of the unlocking unit from  FIG. 1  with the baseplate removed; 
         FIG. 3  is a schematic illustration of the unlocking unit with locked locking devices in a starting position; 
         FIG. 4  is a schematic illustration of the unlocking unit during the unlocking of the locking devices; 
         FIG. 5  is a schematic illustration of the unlocking unit with unlocked locking devices in an activating position; 
         FIG. 6  is a schematic illustration of the unlocking unit after the unlocking of the locking devices and with the unlocking lever pivoting back; 
         FIG. 7  is a schematic illustration of the unlocking unit with unlocked locking devices in the display position; 
         FIG. 8  is a schematic illustration of the unlocking unit with an unlocked and a locked locking device; 
         FIG. 9  is a schematic illustration of the unlocking unit with locked locking devices after return to the starting position; 
         FIG. 10  is an exploded illustration of an unlocking unit; 
         FIG. 11  is a perspective illustration of a vehicle seat structure; and 
         FIG. 12  is a schematic illustration of a vehicle seat. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A vehicle seat  1  for a motor vehicle has a seat part  2  and a backrest  3 . The arrangement of the vehicle seat  1  within the vehicle and the customary direction of travel thereof define the direction information used in the following text. In this case, a direction which is oriented perpendicularly with respect to the ground is referred to below as the vertical direction and a direction perpendicular with respect to the vertical direction and perpendicular with respect to the direction of travel is referred to below as the transverse direction. 
     The backrest  3  is attached to the seat part  2  so as to be pivotable about an axis running in the transverse direction and comprises, inter alia, a backrest plate  4 . By means of an adjustment fitting, the backrest  3  is adjustable in a plurality of angular positions relative to the seat part  2 . A headrest  7  which is of height-adjustable and inclination-adjustable configuration in the present case is attached to one end of the backrest  3 , which end faces away from the seat part. 
     The vehicle seat  1  is displaceable in the direction of travel by means of two pairs of rails which run approximately in the direction of travel and which in each case have a lower rail  5  connected to the vehicle structure and an upper rail  6  guided in the lower rail  5 . The upper rails  6  are lockable to the lower rails  5  by means of a rail locking unit (not illustrated). The two pairs of rails here are arranged next to each other in the transverse direction and in a manner running in parallel. 
     The seat part  2  here is connected detachably to the upper rails  6 . For this purpose, the seat part  2  has a respective front foot  8  on both sides in the front region in the direction of travel, which foot, in the present case, enters the respective upper rail  6  and latches there. Furthermore, the seat part  2  has a respective rear foot  9  on both sides in the rear region in the direction of travel, which foot comprises a locking device  90 . A locking device of this type is disclosed, for example, in WO 2004 069 585 A1, the disclosure of which in this regard is expressly incorporated. 
     In the use position of the vehicle seat  1 , the locking devices  90  are locked to bolts attached to the respective upper rails  6 . In order to transfer the vehicle seat  1  into a package position, the two locking devices  90  of the rear feet  9  are opened simultaneously, as a result of which the rear feet  9  are detached from the upper rails  6 . A vehicle seat configured in such a manner is disclosed, for example, in DE 10 2006 015 922 B4, the disclosure of which in this regard is expressly incorporated. 
     The front feet  8  can also in each case have a locking device, as is also disclosed in DE 10 2006 015 922 B4. It is also conceivable that the vehicle seat  1  does not have any pairs of rails for the longitudinal adjustment, but rather that the front feet  8  and the rear feet  9  are connected directly to the vehicle structure. 
     An unlocking unit  10  which is fastened to the backrest plate  4  is provided for the simultaneous unlocking of the two locking devices  90  of the rear feet  9 . The unlocking unit  10  here is arranged on the front side of the backrest plate  4  in the direction of travel. 
     The unlocking unit  10  comprises a baseplate  70  which is arranged substantially parallel to the backrest plate  4  and which, together with the backrest plate  4 , forms a partial encapsulation of the remaining parts of the unlocking unit  10 . A plurality of webs  79  protrude at right angles from the baseplate  70 , wherein those ends of the webs  79  which face away from the baseplate  70  are inserted into corresponding openings in the backrest plate  4  such that the baseplate  70  is fastened to the backrest plate  4  in an interlocking manner. 
     The baseplate  70  furthermore has a first bearing opening  71  which serves for the mounting of a rotary control pin  41 , and a second bearing opening  72  which serves for the mounting of a rotary actuating pin  42 . In the present case, the rotary control pin  41  and the rotary actuating pin  42  have an approximately cylindrical shape and are connected to the baseplate  70 . Those ends of the rotary actuating pin  42  and of the rotary control pin  41  that face away from the baseplate  70  are mounted here in corresponding openings in the backrest plate  4 . 
     The cylinder axis of the rotary actuating pin  42 , which cylinder axis is referred to below as the actuating pivot axis  44 , protrudes at right angles from the baseplate  70  and from the backrest plate  4 . Similarly, the cylinder axis of the rotary control pin  41 , which cylinder axis is referred to below as the control pivot axis  43 , protrudes at right angles from the baseplate  70  and from the backrest plate  4 . The control pivot axis  43  and the actuating pivot axis  44  therefore run parallel to each other. 
     An unlocking lever  30  is mounted pivotably about the actuating pivot axis  44  of the rotary actuating pin  42 . For this purpose, the unlocking lever  30  in the present case has a continuous, circular lever opening  35  through which the rotary actuating pin  42  penetrates. A return spring  60  is hooked at a first end into a spring eye  32  of the unlocking lever  30 . The second end of the return spring  60 , which end faces away from the first end, is hooked into a fastening eye  74  on the baseplate  70 . In the present case, the return spring  60  is configured as a spiral tension spring and loads the unlocking lever  30  constantly in the direction of a rest position. 
     On a first arm, the unlocking lever  30  has a belt eye  31 , into which a belt strap  62  which serves as an actuating element is hooked. The belt strap  62  runs first of all from the belt eye  31  in the vertical direction to a belt leadthrough  73  on the baseplate  70 . The belt leadthrough  73  is an opening in the baseplate  70  in the region of a web  79 . At the belt leadthrough  73 , the belt strap  62  is deflected counter to the direction of travel and is guided to a belt opening  66  in the backrest plate  4 . The belt strap  62  is guided through the belt opening  66  and protrudes out of the backrest  3  counter to the direction of travel, i.e. toward the rear. At that end of the belt strap  62  which protrudes out of the backrest  3 , a display region  64  which serves as a display element is provided, which display region is designed in an optically conspicuous manner, in the present case colored red. 
     By pulling on that end of the belt strap  62  which protrudes out of the backrest  3 , the unlocking lever  30  is pivoted about the actuating pivot axis  44  in the direction of the actuating position thereof. A limiting element  78  provided on the baseplate  70  acts as a stop and limits the movement of the unlocking lever  30  after the actuating position is reached. 
     A control gearwheel  20  is mounted so as to be rotatable about the control pivot axis  43  of the rotary control pin  41 . For this purpose, in the present case, the control gearwheel  20  has a continuous, circular gearwheel opening  25  which is penetrated by the rotary control pin  41 . Approximately along half of its circumference, the control gearwheel  20  has a control toothing  23  which meshes with an unlocking toothing  33  of the unlocking lever  30 . The unlocking toothing  33  here is attached to a second arm of the unlocking lever  30 , which arm lies approximately diametrically opposite the first arm with the belt eye  31 . 
     A first unlocking element  11  is mounted on the rotary control pin  41  axially next to the control gearwheel  20  so as to be rotatable about the control pivot axis  43 . The first unlocking element  11  has, inter alia, a cylinder-segment-like region with a first lateral surface  55 , in which a first guide groove  15  is formed. A first Bowden cable  83  is inserted into the first guide groove  15 . The end of the first Bowden cable  83  has a first nipple  85  which is hooked into a first Bowden cable hook-in means  13  of the first unlocking element  11 . 
     The first Bowden cable  83  runs from the first unlocking element  11  in the vertical direction to a first deflecting bow  81  which is fastened to the baseplate  70  at a first recess  75 . The first Bowden cable  83  runs further through the first deflecting bow  81 , is deflected there approximately at right angles and runs further as far as one of the two locking devices  90 . 
     A second unlocking element  12  is likewise mounted on the rotary control pin  41  axially next to the control gearwheel  20  so as to be pivotable about the control pivot axis  43 . The second unlocking element  12  has, inter alia, a cylinder-segment-like region with a second lateral surface  56 , in which a second guide groove  16  is formed. A second Bowden cable  84  is inserted into the second guide groove  16 . The end of the second Bowden cable  84  has a second nipple  86  which is hooked into a second Bowden cable hook-in means  14  of the second unlocking element  12 . 
     The second Bowden cable  84  runs from the second unlocking element  12  in the vertical direction to a second deflecting bow  82  which is fastened to the baseplate  70  at a second recess  76 . The second Bowden cable  84  runs further through the second deflecting bow  82 , is deflected there approximately at a right angle and runs further as far as the other of the two locking devices  90 . 
     When the unlocking unit  10  is in the starting position, the unlocking lever  30  is in the rest position, the control gearwheel  20  is in the locking position, the unlocking elements  11 ,  12  are in the locking position, and the two locking devices  90  are locked. If the unlocking unit  10  is in the activating position, the unlocking lever  30  is in the actuating position, the control gearwheel  20  is in the unlocking position, the unlocking elements  11 ,  12  are in the unlocking position, and the two locking devices  90  are unlocked. 
     A first control spring  51  which loads the first unlocking element  11  relative to the control gearwheel  20  toward the unlocking position is arranged between the control gearwheel  20  and the first unlocking element  11 . Similarly, a second control spring  52  which loads the second unlocking element  12  relative to the control gearwheel  20  toward the unlocking position is arranged between the control gearwheel  20  and the second unlocking element  12 . In the present case, the control springs  51 ,  52  are designed as torsion leg springs and are inserted into corresponding openings in the unlocking elements  11 ,  12  and the control gearwheel  20 . In the axial direction with respect to the control pivot axis  43 , the control gearwheel  20  here is arranged between the first unlocking element  11  and the second unlocking element  12 . The control springs  51 ,  52  are in each case located between the control gearwheel  20  and the associated unlocking element  11 ,  12 . 
     In the starting position of the unlocking unit  10 , which starting position is illustrated in  FIG. 3 , one end of the belt strap  62  protrudes out of the backrest  3  toward the rear. The display region  64  here is located substantially within the backrest  3  and is not visible on the outside. The display region  64  is in the non-display position. This signals to a user that the two locking devices  90  are locked. 
     By pulling on that end of the belt strap  62  which protrudes out of the backrest  3 , the unlocking lever  30  is pivoted in the direction of the actuating position counter to the force of the return spring  60 . The control gearwheel  20  is rotated here in the direction of the unlocking position. After the control gearwheel  20  has passed through an idle travel, a driver  24  which is attached to the control gearwheel  20  strikes against a first counterstop  17  of the first unlocking element  11  and against a second counterstop  18  of the second unlocking element  12 , as illustrated in  FIG. 4 . 
     In the present case, the driver  24  is attached in a region of the control gearwheel  20 , which region lies diametrically opposite the control toothing  23 , and protrudes in the axial direction on both sides from said control gearwheel  20 . The counterstops  17 ,  18  of the unlocking elements  11 ,  12  are substantially designed as smooth surfaces which run in the radial and axial direction. 
     By further pulling on the end of the belt strap  62 , the control gearwheel  20  carries along the unlocking elements  11 ,  12 , as a result of which said unlocking elements are rotated in the direction of the unlocking position. Pulling takes place here on the Bowden cables  83 ,  84 , as a result of which the unlocking devices  90  are unlocked. This movement ends when the unlocking lever  30  strikes against the limiting element  78  and the unlocking unit  10  is in the activating position, as illustrated in  FIG. 5 . The display region  64  of the belt strap  62  protrudes here out of the backrest  3  and is visible on the outside. The display region  64  is in the display position. This signals to a user that at least one of the two locking devices  90  is unlocked. 
     If the user then releases the belt strap  62 , the unlocking lever  30  is pivoted in the direction of the rest position by the force of the return spring  60 . As a result, the control gearwheel  20  is also rotated in the direction of the locking position, and the driver  24  moves away from the counterstops  17 ,  18  of the unlocking elements  11 ,  12 . The unlocking elements  11 ,  12  remain in the unlocking position because of the loading by the control springs  51 ,  52 . This state is illustrated in  FIG. 6 . 
     The movement of the unlocking lever  30  ends when a stop element  34  of the unlocking lever  30  strikes against the first lateral surface  55  and/or against the second lateral surface  56 . In the present case, the stop element  34  is of cylindrical configuration and is attached to a third arm of the unlocking lever  30 , which arm is arranged close to the second arm with the unlocking toothing  33 , and protrudes in the axial direction on both sides from the third arm. 
     This state is illustrated in  FIG. 7 . The unlocking lever  30  is now in the hold-open position, and the unlocking unit  10  is in the display position. Although, in comparison to the activating position, the belt strap  62  is pulled partially into the backrest  3 , the display region  64  of the belt strap  62  still protrudes out of the backrest  3  and is visible on the outside. The display region  64  is therefore still in the display position. This signals to a user that at least one of the two locking devices  90  is unlocked. 
     The rear feet  9  of the vehicle seat  1  can then be removed from the upper rails  6 , and the vehicle seat  1  can be folded forward or removed from the vehicle. When the rear feet  9  are placed again onto the upper rails  6 , the vehicle seat  1  can tilt. In this case, only one of the two locking devices  90  locks to the assigned pin in the upper rail  6 , whereas the other of the two locking devices  90  does not lock, or locks only with a time delay, to the assigned pin in the upper rail  6 . 
     Such a state, in which the locking device  90  connected to the first unlocking element  11  is unlocked and the locking device  90  connected to the second unlocking element  12  is locked, is illustrated in  FIG. 8 . During the locking, the locking device  90  which is connected to the second unlocking element  12  pulls on the second Bowden cable  84 , as a result of which the second unlocking element  12  is rotated into the locking position. However, the first unlocking element  11  remains in the unlocking position. 
     The stop element  34  of the unlocking lever  30  loses contact here with the second lateral surface  56 , but still bears against the first lateral surface  55 . The unlocking lever  30  therefore remains in the hold-open position, and the display region  64  of the belt strap  62  still protrudes out of the backrest  3 . The display region  64  is therefore still in the display position and signals to a user that at least one of the two locking devices  90  is unlocked. 
     If the locking device  90  which is connected to the first unlocking element  11  then also locks, said locking device pulls on the first Bowden cable  83 , as a result of which the first unlocking element  11  is also rotated into the locking position. This state is illustrated in  FIG. 9 . In this case, the stop element  34  of the unlocking lever  30  also loses contact with the first lateral surface  55 , and the unlocking lever  30  is rotated back into the rest position by the force of the return spring  60 . The control gearwheel  20  is also rotated here back into the locking position. 
     The unlocking unit  10  is therefore in the starting position again. The belt strap  62  is pulled by the unlocking lever  30  into the backrest  3  to such an extent that the display region  64  of the belt strap  62  is substantially located within the backrest  3  and is not visible on the outside. The display region  64  is therefore in the non-display position again. This signals to a user that the two locking devices  90  are locked. 
     The unlocking unit  10  can also interact with more than two locking devices  90 . In this case, for each locking device  90 , a dedicated unlocking element is arranged on the rotary control pin  41 . 
     The features disclosed in the above description, the claims and the drawings can be of importance both individually and in combination for implementing the invention in the various refinements thereof. 
     While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.
An unlocking unit ( 10), for a vehicle seat ( 1), transmits a movement introduced via an actuation element ( 62) to at least two locking devices ( 90) for unlocking purposes. Each locking device ( 90) is paired with an unlocking element ( 11, 12) and the unlocking element ( 11, 12) is in the locked position when the respective locking device ( 90) is locked and in the unlocked position when the respective locking device ( 90) is unlocked. A display element ( 64) is in the display position when the locking devices ( 90) are unlocked and is in the non-display position when the locking devices ( 90) are locked. Each unlocking element ( 11, 12) which can be found in the unlocked position prevents the display element ( 64) from moving into the non-display position, and the display element ( 64) remains in the display position as long as at least one locking device ( 90) is unlocked.