Abstract:
The invention relates to a forwardly movable vehicle seat having an underframe including a longitudinal adjusting device, the longitudinal adjusting device including two pairs of rails, two catch devices and one actuation lever for actuating the catch devices. The vehicle seat further includes a seat pan that is carried by the underframe, and a seat back that is pivotal about a seat back axis and on which there is disposed a disengagement lever. In an actuated condition, the seat back is unlocked so as to be foldable, the actuation lever being actuated and the catch devices unlocked and the seat being allowed to be brought from an initial position to a forwardly moved position when the seat back is folded forward.

Description:
TECHNICAL FIELD OF THE INVENTION 
   The invention relates to a forwardly movable vehicle seat with an underframe comprising a longitudinal adjusting device, said longitudinal adjusting device comprising two pairs of rails, two catch devices united by a transverse bar and an actuation lever connected to said transverse bar for actuating said catch devices, with a seat pan that is carried by the underframe, with a seat back that is pivotal about a seat back hinge associated with a stop device and on which there is disposed a disengagement lever for unlocking the stop device when in the actuated position so that the seat back is foldable, a driver mechanism connecting the seat back to the transverse bar being provided and the catch devices being unlocked and the seat being allowed to be brought from an initial position to a forwardly moved position when the seat back is folded forward. 
   BACKGROUND OF THE INVENTION 
   Forwardly movable vehicle seats of this kind are mainly in use in vehicles having but one door on either side. They facilitate access to a back seat while boarding the vehicle through the only side door. When the vehicle seat is moved forward, access to the back seat located behind is facilitated. 
   Such type vehicle seats have to meet the requirement of being readily and safely forward movable in mechanical terms. This forward movement is initiated by actuating the disengagement lever which releases the normally locked seat back hinge. The then enabled forward tilt of the seat back causes the two catch devices to be released so that the seat may be moved forward within the pairs of rails of the longitudinal adjusting device. If the seat is moved back thereafter, the initial position has to be found again. This is achieved by means of the memory mechanism. Said memory mechanism ensures that the seat is only allowed to move back as far as the initial position. 
   A forwardly movable vehicle seat of the type mentioned herein above is known from EP 0 844 133 B1. Similar forwardly movable vehicle seats are also known from U.S. Pat. No. 5,893,610, DE 107 597 111 C1 and DE 197 571 110 C1. 
   The following problem may possibly arise with such type forwardly movable vehicle seats: the catch devices are unlocked both through the pivotal movement of the seat back and through actuation of the actuation lever. Accordingly, two different devices may act upon the catch devices. Problems may arise when, one device having already unlocked the catch devices, the second device is knowingly or unknowingly actuated as well. The objective of the invention is to avoid the disadvantages resulting therefrom. More specifically, the objective of the invention is to avoid damage due to maloperation, in particular to prevent damage to the driver mechanism as a result of maloperation of the actuation lever. 
   When the seat back is folded forward, the catch devices are unlocked. In order to allow maintaining the catch devices in the unlocked condition, the driver mechanism must remain active, that is, it must for example be under tension. The driver mechanism comprises for example a sheathed cable that may e.g., be configured to be a Bowden cable. If said sheathed cable is tense, such a condition being provided when the seat back is folded forward, and if the actuation lever is pushed at the same time, meaning, is pivoted in a direction counter to the direction in which, when actuated, it is in a normal limit stop position, said sheathed cable is overtensioned. The cable itself, its fastening means or other parts of the driver mechanism may be destroyed thereby. Usually, the actuation lever is located beneath the front edge of a seat, normally it slightly protrudes therefrom. It is connected to the transverse bar through quite long a lever arm. As a result, quite high a force may be exerted onto the transverse bar, and as a result thereof, onto the driver mechanism as well. 
   BRIEF SUMMARY OF THE INVENTION 
   This is where the invention comes in. It aims at eliminating the problems arising from improper use and occurring with the prior art vehicle seats and at developing said vehicle seats so that the driver mechanism is prevented from being damaged as a result of improper use. 
   This object is solved by the forwardly movable vehicle seat having the features of claim  1 . 
   Either the actuation lever and/or the driver mechanism, more specifically their connection to the transverse bar, are configured so that the overload spring yields when overloaded so that mechanical damage to discrete components is prevented from occurring. Overload occurs from maloperation; as far as mechanical maloperation is possible at all, the overload spring absorbs the forces that might otherwise damage the components. 
   The invention makes it possible to virtually keep to the largest possible extent the original construction of the vehicle seat. It only needs some few additional components. The overload spring has a space-saving configuration and may be disposed so as to occupy very little additional space. The overload spring may also readily be a low-cost spring, for example a torsion spring or a leaf spring. 
   Generally, the invention provides a load-limiting device using but a few, simple mechanical means, said load-limiting device permitting the vehicle seat to keep functioning even upon maloperation of the actuation lever. The maloperation problems occurring with prior art are considerable, they impair the use of the vehicle seat and require complicated repair work. 
   The overload spring of the invention causes the driver mechanisms and the actuation lever to separate from each other so that the actuation lever is prevented from acting directly onto the driver mechanism. Now, driver mechanisms and actuation lever are no longer united directly, but merely through an elastic means, namely the overload spring. 
   The transverse bar unites the two seat rails of the longitudinal adjusting device in a known manner. It synchronizes the actuation of the two catch devices. The actuation lever is disposed on said transverse bar so as to be preferably pivotal and carried by the overload spring. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other features and advantages of the invention will become more apparent upon reviewing the appended claims and the following non restrictive description of embodiments of the invention, given by way of example only with reference to the drawing. In said drawing: 
       FIG. 1  is a schematic side view of a forwardly movable vehicle seat, 
       FIG. 2  is a perspective illustration of the main parts of the invention, when viewed obliquely from the top rear side, these parts being a pair of rails with catch device, a transverse bar, an actuation lever and elements of a seat back, with seat back and actuation lever being in the normal position, 
       FIG. 3  is a perspective illustration, as seen from the top, of the parts according to  FIG. 2 , but in addition thereto with a second pair of rails and the associated parts, 
       FIG. 4  is a view like  FIG. 2  of the same unit, with said unit being now in the actuated position, 
       FIG. 5  is the view like  FIG. 4 , but now in the overtravel position, 
       FIG. 6  is an illustration like  FIG. 4 , but now in the improper use position and 
       FIG. 7  is an illustration like  FIG. 2 , with an overload spring having been added in the actuation lever. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  schematically illustrates a vehicle seat shown in a side view. It is shown in the initial position, which is for example the normal position of utilization, by a continuous line. The forwardly moved position is shown by a dashed line. 
   The vehicle seat has an underframe  20  that comprises a longitudinal adjusting device. Said adjusting device has a left and a right pair of rails, each comprising a floor rail  22  and a seat rail  24 . Said rails are slidable against each other in the longitudinal direction that is, from the left to the right and reverse in the image plane. Normally, the rails  22 ,  24  are locked, a catch device  26  being associated with each pair of rails. The two catch devices  26  of the seat sides are synchronized together by a transverse bar  28 , see  FIG. 2 , that unites the two seat rails  24  and is rotatable. Said transverse bar  28  is connected to an actuation lever  30  that causes it to pivot, this causing the catch devices  26  to move from the normal catch position to a release position. As best seen in  FIG. 3 , the actuation lever  30  is located on one seat side, the transverse bar  28  being located between a respective one of the catch devices  26  and a handle  31  of the actuation lever  30 . On the other seat side, a short actuation piece is provided only. 
   The seat further has a seat pan  32  that is carried by the underframe. The seat further has a seat back  34  that is pivotal about a seat back hinge  36 . Above the seat back hinge  36 , the seat back  34  also has a normal seat back adjusting device that is known per se and is only outlined here. A release lever  38  is disposed on the seat back. It is connected via a connecting means  39  to a stop device  40  that normally locks the seat back hinge  36 . Upon actuation of the release lever  38 , the stop device  40  is released and the seat back  34  may now be folded forward about the axis of the seat back hinge  36 . 
   The seat back  34  is connected to the transverse bar  28  or rather to the catch devices  26  via a driver mechanism. Said driver mechanism includes a sheathed cable  41  that is connected to the seat back  34  underneath the axis of the pivot hinge  36 . Said sheathed cable is tensioned when the seat back  34  is folded forward from the normal position, as shown in  FIG. 1 . This tensile force is used to unlock the catch devices  26 . A memory mechanism  42  is additionally provided; such a memory mechanism is known and will not be discussed herein. 
   Said driver mechanism further includes a driver lever  44 . It is disposed so as to rotatable about the transverse bar  28 . One end of the sheathed cable  40  is attached thereon. Said driver lever has an abutment region  46  located on top of the actuation lever  30 . As a result thereof, the pivot path of the driver lever is limited in one direction of rotation. 
   Finally, the driver mechanism has an overload spring  48 . In the first embodiment in accordance with the  FIGS. 2 through 6 , it is configured to be a torsion spring. It has two angled end regions. Two bearing pillows  50 , which form a receptacle for the overload spring  48 , are fastened to the transverse bar  28 . A first end region of the abutment spring  46 , which in  FIG. 2  is located remote from the driver lever  44 , abuts the transverse bar  28 . The other end region elastically fits against the driver lever  44  and brings it to fit against the actuation lever  30 . 
   The  FIGS. 2 and 3  illustrate the normal initial position with the longitudinal guide being locked by the catch devices  26 . In  FIG. 3 , the seat back  34  is folded forward so that the driver mechanism is now under tension; more specifically, the sheathed cable  41  has been tensioned so as to draw the driver lever  44  backward and slightly nearer to it. The driver lever  44  still abuts the overload spring  48  which is still in the same position. It is sufficiently strong to cause the transverse bar  28  to rotate via the overload spring  48 . As a result, the actuation lever  28  is also caused to pivot, its rear actuation arm, which is placed on an actuation tongue of the catch device  26  so as to be free toward the top, being caused to move downward so that the associated catch device  26  is unlocked. The catch device on the other seat side, which is not shown in  FIG. 3 , undergoes the same procedure. 
   The same position of the actuation lever  30  as in  FIG. 4  is also achieved if the actuation lever  30  is itself actively actuated. In this case however, the seat back  34  is not pivoted. In this case, the driver mechanism is slack. 
   It can be seen from  FIG. 4  that the overload spring  48  has sufficient force to allow transfer of the pivot movement of the driver lever  44  onto the transverse bar  28  and unlocking of the two catch devices  26  without the overload spring  48  markedly deflecting. 
     FIG. 5  shows what is termed an overtravel condition. This means that the seat back is pushed even further downward than shown in  FIG. 1 . The driver mechanism is loaded as a result of this larger pivot angle of the seat back  34 . Now, the driver lever  44  may pivot against the action of the overload spring  48 , said overload spring  48  yields so that breakage or destruction is prevented. From  FIG. 5  it can be seen that the overload spring  48  yields when a larger force, more specifically a force at least three times, preferably a force at least five times the force needed to unlock the two catch devices  26 , is applied on the driver lever  44 . 
   Conditions similar to those in  FIG. 5  also result from improper use such as shown in  FIG. 6 . In this case, the actuation lever  30  is improperly pushed downward, which causes the transverse bar  28  to pivot accordingly. The catch devices  26  are unlocked; it appears clearly that the corresponding lever arm of the actuation lever  30  is located far above the actuation tongue of the catch device  26  from which it is completely free. 
   Improper actuation of the actuation lever  30  however resulted in the driver lever  44  not being pivoted like the transverse bar  28 ; instead, it lags behind said transverse bar  28 . This could happen because the overload spring  48  has yielded. Thus, damage of part of the driver mechanism could be avoided. 
   A second embodiment is shown in  FIG. 7 . In this FIG. the arrangement with the overload spring  48  in the form of a torsion spring according to the embodiments shown in the  FIGS. 2 through 6  is shown again; the actuation lever  30  however has been modified with a short region being now realized by an overload spring  48  in the form of a leaf spring. Said overload spring  48  is also dimensioned such that normal actuation of the catch devices  26  is possible, an actuation force causing the lever to go beyond this normal actuation position, which may cause damage to the driver mechanism, being impaired, though. When such a force is applied, the leaf spring  48  constituting the overload spring flexes instead. 
   It cannot be seen from the FIGS. that the actuation lever  30  only has a certain range of motion due to the space available for mounting said lever in an automotive vehicle. The respective overload spring  48  only has to be configured for this range of motion. 
   In the embodiment according to  FIG. 7 , the overload spring  48  in the form of a torsion spring may be obviated. Then, the driver lever  44  can be rigidly connected to the transverse bar  28 . Improper use of the actuation lever  30  will not cause the driver mechanism to be destroyed as the overload spring  48  configured to be a leaf spring will flex soon enough to prevent destruction thereof.