Abstract:
A very reliable device, which can be implemented at a low cost, has a switch mechanism arranged on a fastening device which is installed on a vehicle seat and can engage with a plug element on a child seat; The switch mechanism has a stationary part attached to the fastening, device and a movable part, which is moved by the plug element into the stationary part on mutual engagement of the plug element with the fastenings device, thereby activating a switch so that occupancy of the vehicle seat by a child seat is signaled.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a device for detecting a child seat attached to a vehicle seat. 
     BACKGROUND INFORMATION 
     Studies by (NHTSA) the National Highway Traffic Safety Administration in the United States, for example, have shown that deployment of an airbag when a child is restrained in a child seat attached to an automotive seat can cause serious injuries. Deployment of one or more airbags belonging to a vehicle seat with a child seat attached to it should therefore be suppressed in any case. Thus, a controller provided in the vehicle to control deployment of the airbags must receive a signal to indicate when a child seat is on a passenger seat so that the airbags assigned to this seat will not be deployed in the event of an accident. There are conventional devices that detect a child seat on a vehicle seat and signal this condition to the controller. 
     For example, German Patent No. 44 09 971 ; German Utility Model No. 296 19 668 U1 and U.S. Pat. No. 5,605,348 describe child seat detection devices that operate according to the transponder principle, where an identification carrier, which in the simplest case is an electromagnetic tuned circuit, is provided on the child seat, and a transmission element emitting an electromagnetic alternating field is provided in the vehicle seat. A receiver element in the vehicle seat records the change in field caused by the interaction between the identification carrier on the child seat and the electromagnetic field emitted by the transmitting element. However, such a child seat detection based on the transponder principle is extremely complicated and expensive. 
     German Patent Application No. 44 26 677 describes a device for attaching a child seat to a vehicle seat. This device has a belt lock housing that is attached to the vehicle so that a plug element on the child seat can be locked into it. The belt lock housing contains a switch mechanism that has a movable part, which is inserted on engagement of the plug element in the belt lock housing, thereby closing a contact that sends a signal to an airbag controller indicating that deployment of the airbag must be suppressed because of the child seat. 
     An object of the present invention is to provide a device for detection of a child seat attached to a vehicle seat that can be implemented at the lowest possible expense and yet detects with a very high reliability a child seat attached to a vehicle seat. 
     The object described above is achieved due to the fact that fastening means, which are installed on a vehicle seat and can be engaged with a plug element on the child seat, is provided with a switch mechanism. The switch mechanism has a stationary part attached to the fastening means and has a movable part, which is moved by the plug element into the stationary part on mutual engagement of the plug element with the fastening means, thereby activating a switch which signals that the passenger seat is occupied by a child seat. 
     The switch, for example, is a reed switch. In addition, there is a magnet that alters the position of the reed switch on displacement of the movable part into the stationary part. 
     Such a switch mechanism can be installed very easily and detects reliably whether a child seat has been attached to a vehicle seat. In addition, this switch mechanism is designed to be very space saving. 
     The switch is arranged, for example, in the stationary part of the switch mechanism, and the magnet is arranged, for example, in the movable part. The magnet is directly above the reed switch and closes/opens it when the movable part is in its starting position where it has not be affected by the plug element. The magnet is located a distance away from the switch and opens/closes it when the movable part has been displaced by the plug element. 
     The movable part may be, for example, a slide that is pushed by the plug element into the stationary part on mutual engagement of the plug element with the fastening means. A compression spring used in the stationary part keeps the slide in its starting position when the plug element has not been engaged. 
     The movable part may also be a lever that is pivotably mounted in the stationary part and flipped by the plug element into the stationary part on mutual engagement of the plug element with the fastening means. A tension spring inserted into the stationary part holds the lever in its starting position when the plug element has not been engaged. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 a  shows a fastening clamp for a child seat. 
     FIG. 1 b  shows a first switch mechanism secured on a fastening clamp that has a slide in a starting position. 
     FIG. 2 shows the first switch mechanism with a slide inserted. 
     FIG. 3 shows a longitudinal cross section A—A through the first switch mechanism before engaging a plug element. 
     FIG. 4 shows a longitudinal cross section A—A through the first switch mechanism with the plug element engaged. 
     FIG. 5 shows a cross section E—E through the first switch mechanism perpendicular to cross section A—A. 
     FIG. 6 shows a cross section C—C through the first switch mechanism. 
     FIG. 7 shows a cross section D—D through the first switch mechanism. 
     FIG. 8 shows a three dimensional diagram of a second switch mechanism. 
     FIG. 9 shows the second switch mechanism in an assembled form. 
     FIG. 10 shows a longitudinal cross section F—F through the second switch mechanism before engaging a plug element. 
     FIG. 11 shows a longitudinal section F—F through the second switch mechanism with a plug element engaged. 
     FIG. 12 shows a longitudinal section G—G through the second switch mechanism. 
     FIG. 13 shows a tension spring. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 a ,  1   b  and  2  show perspective diagrams of a device for detecting a child seat attached to a motor vehicle seat. 
     FIG. 1 a  shows a fastening means  1  in the form of a clamp (hereinafter referred to as a fastening clamp), which is installed on a vehicle seat, usually the passenger seat. A plug element provided on a child seat can be engaged with this fastening clamp  1  to attach the child seat to the vehicle seat. To be able to determine whether fastening clamp  1  has been engaged with the plug element of a child seat, there is a switch mechanism (shown in perspective view in FIG. 1 b ) composed of a stationary part  2  attached to fastening clamp  1  and a movable part  3 . In this first embodiment of the switch mechanism, movable part  3  is composed of a slide that is pushed into the stationary part when the plug element on the child seat engages with fastening clamp  1 . The perspective diagram in FIG. 2 shows a switch mechanism where slide  3  has been pushed into stationary part  2 . 
     To illustrate the functioning of the switch mechanism in greater detail, several longitudinal sections and cross sections are shown in FIGS. 3 through 7. FIG. 3 shows a longitudinal cross section A—A through the first switch mechanism illustrated in FIG. 1 b  with a slide  3  in its starting position, which it assumes when plug element  4  of the child seat is not engaged with fastening clamp  1 . Stationary part  2  of the switch mechanism has a receptacle space for a reed switch  6  designed, for example as a tube  5 . Terminals  7  of reed switch  6  lead out of stationary part  2  to a controller (not shown), which controls the deployment of airbags in the vehicle. Slide  3  slides along tube  5 . A permanent magnet  8  is embedded in the wall above tube  5 . Magnet  8  is directly above reed switch  6  in the starting position of slide  3 , i.e., when plug element  4  is not engaged with fastening clamp  1 , as shown in FIG.  3 . Depending on how the reed switch is designed, it is opened or closed by the field of magnet  8 . In the embodiment illustrated here, reed switch  6  is closed. 
     FIG. 4 shows a longitudinal cross section B—B through the switch mechanism illustrated in FIG. 2 in a state where slide  3  has been pushed into stationary part  2  by plug element  4 , which is engaged with fastening clamp  1 . In this position of slide  3 , magnet  8  is a distance away from reed switch  6 , so that reed switch  6  opens or closes according to its design. In the embodiment illustrated in FIG. 4, the moving away of the magnet leads to opening of reed switch  6 . Engagement of plug element  4  on the child seat with fastening clamp  1  on the vehicle seat thus leads to a change in the switch position which is registered by the controller for airbag deployment as the presence of a child seat on the vehicle seat. 
     A molded part  9  is screwed onto the bottom side of slide  3 , partially enclosing the fastening clamp and functioning as a sliding aid for slide  3 . 
     FIG. 5 shows another longitudinal cross section E—E perpendicular to longitudinal cross section A—A through the switch mechanism. This view shows that a compression spring  11  sits in stationary part  2  on a journal  10 , projecting into a recess  12  in slide  3  and ensuring that slide  3  will be held in its starting position if a plug element  4  is not pressing slide  3  against compression spring  11  into stationary part  2 . 
     A cross section C—C through stationary part  2  shown in FIG. 6 illustrates again the arrangement of compression spring  11  on journal  10  and magnet  8  which almost completely surrounds tube  5  in which reed switch  6  is located. The cross-sectional diagram in FIG. 6 also illustrates the screw connection of fastening clamp  1  to stationary part  2  with the aid of a screw  13  which is tightened into a threaded hole  14  in stationary part  2 . 
     A cross section D—D through slide  3  illustrated in FIG. 7 shows that molded part  9  is connected to slide  3  with the aid of a screw  15  which is tightened into a threaded hole  16  in slide  3 . 
     FIGS. 8 through 13 illustrate a second embodiment of a switch mechanism. 
     FIG. 8 shows a perspective view of the switch mechanism composed of a stationary part  17  and a movable part  18 . The two parts  17  and  18  are shown separately in FIG. 8 to illustrate that movable part  18  is composed essentially of a lever  19 , which is mounted so it can pivot about an axis  20  on a cover  21  that can be screwed onto stationary part  17 . 
     FIG. 9 shows a view of the switch mechanism, where movable part  18  is screwed onto stationary part  17 . A slot  22  is provided on the side of housing  17  opposite cover  21  so that fastening clamp  1  of the vehicle seat can be inserted into stationary part  17 . Screw holes  23  and  24  running perpendicular to slot  22  indicate that fastening clamp  1  is screwed into slot  22 . 
     The front side of stationary part  17  facing outward from the plane of projection is open so that plug element  4  of the child seat can be inserted through it and engaged with fastening clamp  1 . This procedure is illustrated in FIGS. 10 and 11 by longitudinal cross section F—F through parts  17  and  18 . 
     FIG. 10 shows that a chamber  25  is provided in the bottom of stationary part  17  to accommodate a reed switch  26 . Lever  19  can be pivoted about an axis  20  on cover  21  on the side of stationary part  17  opposite chamber  25 . Lever  19  has a magnet  27  on the end opposite pivot axis  20 . FIG. 10 shows the starting position of lever  19 , where plug element  4  is not inserted into stationary part  17  to engage with fastening clamp  1 . In this starting position of lever  19 , its magnet  27  is directly above reed switch  26 . Depending on the design of the reed switch, the magnetic field of magnet  27  causes the switch to either open or close. 
     When plug element  4  is pushed into stationary part  17  as illustrated in FIG. 11, lever  19  is pivoted upward, causing magnet  27  to move away from reed switch  26 . This produces a change in the switch status of the reed switch from closed to open or vice versa, which is a signal for the controller to suppress deployment of the airbags provided for that vehicle seat. 
     FIG. 12 shows a longitudinal cross section G—G at the height of cover  21  through the switch mechanism. This shows that a tension spring  28  such as that illustrated in FIG. 13 has been inserted into stationary part  17 . This tension spring  28  causes pivotable lever  19  to be retained in its starting position, i.e., the end of the lever is pressed against the bottom above chamber  25  of the stationary part (see FIG.  10 ).