Abstract:
A measurement device ( 10; 110; 210 ) and associated seating arrangement, in particular for measuring a weight acting on a vehicle seat, that includes: a force transmission element ( 12; 112; 212 ), which is connectable to a first unit, preferably a vehicle seat, and a measurement assembly ( 14; 50; 114; 214 ), which is rigidly connectable to a second unit ( 80 ), preferably a vehicle body part. The force transmission element ( 12; 112; 212 ) is pivotable about at least one axis around the measurement assembly ( 14; 50; 114; 214 ).

Description:
[0001]    The following disclosure is based on German Patent Application No. 101 63 308.4, filed on Dec. 21, 2001, which is incorporated into this application by reference.  
         FIELD OF AND BACKGROUND OF THE INVENTION  
         [0002]    The present invention relates to a measurement device, particularly for measuring a weight acting on a vehicle seat, and to an associated seating arrangement.  
           [0003]    Measurement devices are generally used for determining the weight acting on a vehicle seat. This is particularly of interest in the development of air bag systems. In this way, more precise triggering of the airbag may be achieved. Thus, for example, it may be differentiated whether a very heavy person or a child is located on the vehicle seat. Furthermore, it may be established whether the person sits centrally or off-center on the seat. The air bags are then correspondingly triggered if necessary.  
           [0004]    Such measurement devices are known, for example, from International Publication WO 01/18507 A1, as having a force transmission element and a measurement assembly. The force transmission element is attached to a vehicle seat and is rigidly connected to the measurement assembly. The measurement assembly is connected to a seat rail in the floor of the vehicle or another suitable vehicle body part. Such measurement devices from the related art have the disadvantage, however, that not only the vertical weight, which is to be measured, is conducted into the measurement device, but also forces that act in other directions and that therefore distort the measurement result.  
           [0005]    A measurement device is described in European Patent Application 0 670 480 A1, in which the pressure force to be measured is supplied to the measurement cell via a strut. In this case, the strut may perform a slight rotational and bending movement.  
           [0006]    European Patent Application 0 566 182 A1 discloses a device for attaching a weighing element changeably. The device includes a body having a convex support surface and a body having a support surface with an offset. The two bodies are movably coupled via their support surfaces.  
         OBJECTS OF THE INVENTION  
         [0007]    It is therefore an object of the present invention to provide a measurement device and a seating arrangement which allow precise and reliable measurement of the force conducted into the measurement device.  
         SUMMARY OF THE INVENTION  
         [0008]    This and other objects are achieved, according to one formulation of the present invention, by a measurement device, particularly for measuring a force acting on a vehicle seat, including: (a) a force transmission element, such as a rocker, which is connectable to a first unit, preferably a vehicle seat, and (b) a measurement assembly, such as a force absorber, which is preferably rigidly connected to a second unit, preferably a vehicle body part. The force transmission element is pivotable about at least one axis around the measurement assembly and is designed in such a way that at least one of tensile forces and pressure forces is transmitted from the first unit to the measurement assembly.  
           [0009]    Because the force transmission element is pivotable about at least one axis around the measurement assembly, only the perpendicular force acting on the measurement device is conducted into the measurement assembly. In particular, only the weight directed vertically downward, which acts on the measurement device, is absorbed by the measurement assembly. Forces which act transversely or diagonally to the measurement devices are not conducted into the measurement assembly due to the pivoting of the force transmission element around the measurement assembly. Therefore, an advantageous decoupling of the force acting on the measurement device and the torque acting on the measurement device may also be achieved. In this way, only the actual force acting on the measurement assembly may be measured, without this assembly being influenced through undesired torques. Furthermore, the measurement assembly is not stressed by torques, which leads to a longer service life of the measurement assembly.  
           [0010]    Preferably, a region is provided in the force transmission element into which the measurement assembly may be inserted. As a consequence, the force transmission element essentially encloses the measurement assembly around its circumference. Through the form-fitting arrangement, a force to be measured is transmitted from the force transmission element into the measurement assembly.  
           [0011]    The force transmission element preferably encloses the measurement assembly at least partially around its circumference.  
           [0012]    The force transmission element and the measurement assembly preferably essentially form a ball joint, e.g. a ball and socket joint, the measurement assembly preferably having a region which it uses as a ball pivot, e.g. a complete ball, and the force transmission element preferably having a region which it uses as a ball socket.  
           [0013]    By providing the measurement assembly and the force transition element as a ball joint arrangement, pivoting of the force transmission element in all tangential directions around the measurement assembly is possible. Therefore, it may be ensured even more reliably that undesired forces are not conducted into the measurement assembly.  
           [0014]    The force transmission element preferably has, in at least some regions, essentially the shape of a hollow spherical zone, e.g. spherical cup and/or a hollow half sphere whose cap is cut off, and has an attachment element positioned on an equator region of the spherical zone region, which attaches the force transmission element to the first unit. Furthermore, the measurement assembly essentially has a spherical zone region, e.g. a spherical cup region, which has a radius that permits it to fit together with the inside of the spherical zone region of the force transmission element. The force acting on the measurement device is therefore conducted into the measurement assembly essentially via the equator region of the force transmission element. The region into which the force is transmitted essentially encloses the measurement assembly around its circumference. In this way, both tensile and pressure forces may be transmitted.  
           [0015]    An attachment element is preferably implemented essentially around the circumference along the equator region of the spherical zone region of the force transmission element. The attachment element is advantageously configured integrally with the spherical zone region of the force transmission element. In a preferred embodiment, the attachment element essentially has the shape of a circular ring. However, it is also possible to implement the attachment element in a rod shape. Therefore, the measurement device may be attached to the first unit in a suitable way.  
           [0016]    In a preferred embodiment, the measurement device also includes a union or positioning device, which is designed in such a way that it fixes the force transmission element in the radial direction in relation to the measurement assembly and allows at least limited rotation of the force transmission element in the tangential direction in relation to the measurement assembly. Furthermore, a projection is preferably provided on the pole of the spherical zone region, in order to receive the positioning device.  
           [0017]    By providing the positioning device, the force transmission element is easily and reliably kept in its radial position in relation to the measurement assembly.  
           [0018]    In a preferred embodiment, the internal shape of the positioning device is essentially a spherical shape in at least some regions, preferably having a flattened pole, and is designed to correspond essentially to the external shape of the ball joint. Therefore, the force transmission element is secured in position even better.  
           [0019]    The projection of the spherical zone region of the measurement assembly is advantageously provided with a thread, preferably an external thread.  
           [0020]    The positioning device advantageously also has a thread, preferably an internal thread, which fits together with the thread of the measurement assembly, and which fixes the positioning device, preferably non-rotatably, on at least one part of the measurement assembly. The positioning device is therefore screwed onto the projection of the measurement assembly and the force transmission element is kept securely in its position. The positioning device is also preferably elastically implemented in such a way that a pre-tension, originating from a part of the positioning device, acts on the ball joint.  
           [0021]    In another preferred embodiment, the positioning device is fixed on the measurement assembly, so that it is rotatable in relation thereto, using a fixing device, preferably a nut. The positioning device is also preferably provided with a bearing region, from which a pre-tension acting on the ball joint originates. A pre-tension element and/or a pre-tension body, preferably a spring washer, is also preferably provided between the nut and the positioning device. The force of the pre-tension element advantageously acts in the direction of the axis, e.g. the axis of symmetry, of the positioning device. The pressure of the force transmission element on the measurement assembly may therefore be regulated in a simple way.  
           [0022]    The attachment element preferably has at least one recess, and the positioning device preferably has at least one section projecting in a tangential direction, which is designed to engage in the recess of the attachment element and to allow rotation of the force transmission element in relation to the measurement assembly.  
           [0023]    In another preferred embodiment, the force transmission element is rotatable and/or pivotable about two axes around the measurement assembly.  
           [0024]    The force transmission element is preferably rotatable around a first axis that lies in the plane of the force transmission element, and around a second axis that essentially corresponds to the longitudinal axis of the measurement assembly.  
           [0025]    In yet another preferred embodiment, a preferably circular hole is provided in the force transmission element, in which a rotating element and/or circular ring is rotatably mounted around the first axis. A circular opening is provided in the rotating element, in which the cylindrical measurement assembly is rotatable around the second axis.  
           [0026]    In this way, because the measurement assembly is positioned in the circular hole of the force transmission element via the rotating element, i.e., the force transmission element essentially encloses the measurement assembly around its circumference, tensile and pressure forces are transmitted to the measurement assembly.  
           [0027]    Furthermore, it is possible for the force transmission element and the measurement assembly to be implemented as a universal joint having mechanical axes.  
           [0028]    A friction-reducing layer, preferably made of Teflon, is advantageously provided between the force transmission element and the measurement assembly in at least some regions. In this way, the friction during rotation and/or pivoting of the force transmission element around the measurement assembly can be reduced. A friction-reducing layer, preferably made of Teflon, is also preferably provided between the force transmission element and the positioning device in at least some regions. The friction-reducing layer is advantageously implemented as a coating or molded part.  
           [0029]    The measurement assembly preferably has a polygonal, preferably rectangular, region that connects the measurement assembly to the second unit, so they are essentially locked. The measurement assembly also preferably has a threaded region that fixes the measurement assembly to the second unit. Therefore, the measurement device may be easily and securely attached to the second unit.  
           [0030]    The measurement assembly advantageously includes a strain gauge.  
           [0031]    In a further preferred embodiment, the measurement assembly includes a force conduction element, a force delivery element, and an expansion body that is provided between the force conduction element and the force delivery element. The expansion body is enclosed by at least one of the force conduction element or the force delivery element in a plane parallel to the effect of the weight. At least one strain gauge, which absorbs a shear force parallel to the weight, is positioned on the expansion body.  
           [0032]    The present invention is additionally directed to a seating arrangement, which includes a measurement device e.g. according to a preferred embodiment of the present invention. The seating arrangement may particularly be a vehicle seat, an aircraft seat, a desk chair, or a wheelchair. Furthermore, the measurement device according to the present invention may also be used in a hospital bed. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0033]    Further objects, features, and advantages of the present invention will become apparent from a more detailed description of preferred embodiments of the present invention with reference to the attached drawing, in which:  
         [0034]    [0034]FIG. 1 shows a sectional view of a measurement device according to a first embodiment of the present invention;  
         [0035]    [0035]FIG. 2 shows a partial sectional view of a measurement device according to the first embodiment of the present invention;  
         [0036]    [0036]FIG. 3 shows a sectional view of a measurement device according to a second embodiment of the present invention;  
         [0037]    [0037]FIG. 4 shows a top view of a force transmission element of a measurement device according to the second embodiment of the present invention; and  
         [0038]    [0038]FIG. 5 shows a partial sectional view of a measurement device according to the second embodiment of the present invention;  
         [0039]    [0039]FIG. 6 shows a perspective view of a measurement device according to the second embodiment of the present invention;  
         [0040]    [0040]FIG. 7 shows a perspective exploded view of a measurement device according to the second embodiment of the present invention;  
         [0041]    [0041]FIG. 8 shows a partial sectional view of a measurement device according to a third embodiment of the present invention;  
         [0042]    [0042]FIG. 9 shows a perspective view of a measurement device according to the third embodiment of the present invention;  
         [0043]    [0043]FIG. 10 shows a perspective exploded view of a measurement device according to the third embodiment of the present invention;  
         [0044]    [0044]FIG. 11 shows a perspective view of a measurement device according to a fourth embodiment of the present invention;  
         [0045]    [0045]FIG. 12 shows a perspective view of a force transmission element of the measurement device from FIG. 11;  
         [0046]    [0046]FIG. 13 shows a perspective view, partially in section, of a measurement assembly according to a preferred embodiment of the present invention; and  
         [0047]    [0047]FIG. 14 shows a perspective view, partially in section, of a measurement assembly according to a further preferred embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0048]    [0048]FIG. 1 shows a sectional view of a measurement device  10  according to a first preferred embodiment of the present invention. Since essentially all parts of the measurement device according to the present invention are rotationally symmetric, only one half of the sectional view is shown.  
         [0049]    The measurement device  10  according to the present invention includes a force transmission element  12 , a measurement assembly/force absorber  14  and a swivel device/positioning device/union nut  16 . The force transmission element  12  and the measurement assembly  14  together form a ball joint/ball and socket joint.  
         [0050]    In the following, the individual parts of the measurement device according to the first embodiment of the present invention are described with reference to FIGS. 1 and 2.  
         [0051]    The force transmission element  12  has a spherical zone region/spherical cup region  18 , i.e., a region which essentially corresponds to a half sphere having a cut-off cap. An attachment element  22  extends in the radial direction in at least some regions from an equator region  20  of the spherical zone region  18  of the force transmission element  12 . The attachment element  22  is preferably implemented in one piece with spherical zone region  18 . Attachment element  22  may have the shape of a circular ring which extends around the circumference of the equator region  20  of the spherical zone region  18 . Furthermore, the attachment element  22  may instead extend in the radial direction from the spherical zone region  18  in only some regions. It is even conceivable that attachment element  22  is implemented as one or more mounting ribs. The measurement device  10  may be attached to a vehicle seat, for example, by the attachment element  22 .  
         [0052]    The measurement assembly  14  also includes a spherical zone region/spherical cup region  24 , whose external radius is designed in such a way that it is somewhat smaller than the internal radius of the spherical zone region  18  of the force transmission element  12 , so that the force transmission element  12  may rotate around the measurement assembly  14 . The measurement assembly  14  has a projection  26  on one end (left side in FIG. 1), which preferably essentially projects from the pole of the spherical zone region  24 . An external thread  28  is provided on the projection  26 . Using this thread  28 , a positioning device  16  (described later) is fixed on the measurement assembly. A square  30  and a thread  32  are provided on the other end of the measurement assembly  14  (right side in FIG. 1). During installation of the measurement device  10  into a vehicle, for example, the square  30  is engaged with a corresponding recess in a vehicle body part  80 , e.g., a seat rail on a vehicle body, and fixed and locked using an attachment nut  34 , which is screwed onto the thread  32 . The measurement assembly may be implemented using a molded part  44 , which essentially encloses the spherical zone region  24  and the projection  26 , and a sensor device  46 , which is preferably implemented as one piece with the square  30  and the thread  32 . The molded part  44  is preferably welded to the sensor device  46  at the position indicated with reference number  48 . However, it is also conceivable to connect the molded part  44  and the sensor device  46  to one another in another suitable way or to implement them in one piece.  
         [0053]    The region that is at least partially enclosed by the spherical zone region  18  is a region into which the measurement assembly  14  may be inserted.  
         [0054]    The measurement assembly  14 , which preferably is or includes the sensor device  46 , advantageously includes one or more strain gauges. However, any other suitable type of sensor, for example piezoelements, may also be used.  
         [0055]    The positioning device  16  is implemented in such a manner as to secure the force transmission element  12  against movement in radial directions. For this purpose, the positioning device  16  has a spherical zone region/spherical cup region  36 , whose internal radius essentially corresponds to the external radius of the spherical zone region  18  of the force transmission element  12 , but is designed to allow rotation and/or pivoting of the force transmission element  12  around the measurement assembly  14 . Furthermore, the positioning device  16  has an internal thread  38 , which fits with the external thread  28  of the measurement assembly  14 , so that the positioning device  16  may be screwed onto the projection  26  of the measurement assembly  14 .  
         [0056]    The force to be measured is advantageously conducted into the measurement assembly  14  essentially or at least approximately perpendicularly to the longitudinal extension of the measurement assembly  14 . Herein, the longitudinal extension of the measurement assembly  14  refers to the extension of the measurement assembly  14  in the horizontal in FIGS. 1 and 2. The force transmission element  12  is also positioned essentially perpendicular to the longitudinal extension of the measurement assembly  14  and encloses the measurement assembly  14  essentially around its circumference (FIG. 2). Therefore, in particular, both a force acting from top to bottom in FIG. 2, i.e., a pressure force, and a force acting from bottom to top in FIG. 2, i.e., a tensile force, may be transmitted by the force transmission element  12  to the measurement assembly  14 .  
         [0057]    The force transmission element  12 , the measurement assembly  14 , and the positioning device  16  are arranged essentially in a form-fitting way in relation to one another. Therefore, the tensile and pressure forces acting on the measurement device  10  are conducted essentially without losses into the measurement assembly  14 .  
         [0058]    The positioning device  16  and the force transmission element  12  form a fixing device and/or coupling device for the measurement assembly  14  and/or an aid for the positioning measurement assembly  14 .  
         [0059]    Friction-reducing layers  40 ,  42  are provided between spherical zone region  24  of the measurement assembly  14  and spherical zone region  18  of the force transmission element  12  and between semicircular region  18  and spherical zone region  36  of positioning device  16 . These friction-reducing layers are preferably made of Teflon and may be implemented as molded parts or as a coating.  
         [0060]    A measurement device  110  according to a second embodiment of the present invention is shown in FIGS.  3  to  7 .  
         [0061]    The measurement device  110  according to the second embodiment of the present invention includes elements which are similar or identical to elements of the measurement device  10  according to the first embodiment of the present invention. Such similar or identical elements are indicated with the same reference numbers as in the first embodiment, and a more detailed description thereof will be dispensed with here.  
         [0062]    Measurement device  110  includes a force transmission element  112 , a measurement assembly  14 , and a union/positioning device  116 .  
         [0063]    The force transmission element  112  according to the second embodiment of the present invention includes, like the force transmission element  12  according to the first embodiment of the present invention, a spherical zone region  118 , an equator region  120 , and an attachment element  122 . Recesses  150  are provided in the attachment element  122  according to the invention for receiving regions of the positioning device  116 , which are described in greater detail hereinafter. Four recesses  150  are advantageously provided. However, it is also possible to provide another number of recesses  150 . The recesses  150  are preferably configured concentrically to the spherical zone region  136 . The measurement assembly  14  of the measurement device  110  is implemented similarly to the measurement assembly  14  of the measurement device  10 , so that a more detailed description thereof will be dispensed with at this point. However, the projection  26  may be implemented to be longer in the second embodiment than in the first embodiment.  
         [0064]    The positioning device/union/positioning part  116  according to the second embodiment of the present invention also has a spherical zone region  136 , whose internal radius is designed to correspond essentially to the external radius of spherical zone region  118  of the force transmission element  112  and to allow rotation and/or pivoting of the force transmission element  112  around the measurement assembly  14 . Furthermore, spherical zone region  136  has projecting regions/spherical zone fingers  152 , which engage with recesses  150  in the assembled state of the measurement device  110 . The external radius of spherical zone region  136  of the positioning device  116  is designed to be smaller than the external radius of the recesses  150 . The same number of projecting regions  152  are provided as there are recesses  150 . In the embodiment shown in FIGS.  3  to  7 , the recesses  150  are provided as holes in the force transmission element  112 , so that the projecting regions  152  can extend through the recesses  150  of the force transmission element  112 . By providing the projecting regions  152 , the friction reducing region between the force transmission element  112  and the positioning device  116  may be enlarged. The positioning device  116  according to the second embodiment of the present invention also has a bore  154 . The bore  154  is of a size such that it may receive the projection  26  of the measurement assembly  14 , but simultaneously only allows slight play between the projection  26  and the positioning device  116 . The positioning device  116  is preferably rotatable around the measurement assembly  14 . The positioning device  116  is secured using a nut  156 , which is screwed onto the thread  28  of the measurement assembly  14 . A pretension device  158  can be provided between the nut  156  and the positioning device  116 . The pre-tension device  158  is preferably configured as a spring washer. Therefore, the pressure of the positioning device  116  on the force transmission element  112  may be suitably regulated and/or adjusted.  
         [0065]    As in the first embodiment, friction reducing layers  40 ,  42 , preferably made of Teflon and implemented either as a separate molded part or a coating, may be provided between spherical zone region  24  and spherical zone region  118  and between spherical zone region  118  and spherical zone region  136 .  
         [0066]    In the third embodiment of the present invention shown in FIGS.  8  to  10 , the recesses  150  of the second embodiment are configured as depressions  160 . Only one depression  160  is advantageously provided, extending in the shape of a ring which is essentially concentric to spherical zone region  136 . The projecting region  152  is then also preferably implemented in a ring shape.  
         [0067]    In a further preferred embodiment, the positioning device  16 ,  116  may also be designed to fix the force transmission element  12 ,  112  in the axial direction, i.e., in the longitudinal direction of the measurement assembly  14 ,  114 , in order to allow at least limited rotation of the force transmission element  12 ,  112  around the axis of symmetry/longitudinal axis of the measurement assembly  14 ,  114  and to allow it to pivot out of the plane that runs perpendicular to the axis of symmetry of measurement assembly  14 ,  114 .  
         [0068]    The force transmission element  12 ,  112  is preferably implemented in the form of a plate, one end of which is connectable to the vehicle seat (not shown). The other end of the force transmission element  12 ,  112  is preferably configured to be semicircular in cross-section, or at least rounded, whereby the radius of the circle preferably corresponds to half the width of force transmission element  12 ,  112 . Each spherical zone region  18 ,  118  is implemented in the semicircular section of the force transmission element  12 ,  112 .  
         [0069]    In the following, the operation of the measurement devices according to the first to third embodiments of the present invention is described in detail. Since the modes of operation of the measurement devices according to the first to third embodiments are essentially identical, the measurement device according to the first embodiment is referred to in the following, by way of example.  
         [0070]    The completely assembled measurement device  10  is attached, by means of the attachment element  22 , to a first unit, which is, for instance, a vehicle seat, and, by means of the square  30  and the thread  32 , to a second unit, such as a vehicle body, so that it is secured against twisting.  
         [0071]    Firstly, the case will be described in which a force is applied perpendicularly onto the vehicle seat and therefore perpendicularly onto measurement device  10 . In this case, the entire force conducted into the measurement device  10  is conducted from the force transmission element  12  into the measurement assembly  14 .  
         [0072]    Now, the case will be described in which a force is applied diagonally onto the vehicle seat and therefore diagonally onto the measurement device  10 . The force applied may be divided into one component that acts perpendicularly on the measurement device  10 , i.e., in the radial direction, and one component that acts parallel to the measurement device  10 , i.e., in the tangential direction. The use of a ball joint mount between the force transmission element  12  and the measurement assembly  14  ensures that only the force acting perpendicularly on the measurement device  10  is conducted from the force transmission element  12  into the measurement assembly  14 . The force acting in the tangential direction is not transmitted, since the force transmission element  12  can move in the tangential direction around the measurement assembly  14 . Only the actual force, i.e., the force acting perpendicularly on the vehicle seat, is conducted into the measurement assembly  14 . In particular, it is thereby ensured that only the actual weight acting on the vehicle seat is conducted into measurement assembly  14 . Interfering, diagonally acting forces are therefore not taken into consideration in the measurement, and a more precise measurement result is achieved. Furthermore, undesired loading of the measurement assembly  14  is prevented.  
         [0073]    Tensile forces are also transmitted to the measurement assembly  14  in a manner analogous to that described above. In this case as well, only the perpendicular components of the force acting on the measurement device  10  are conducted into the measurement assembly  14  and therefore measured.  
         [0074]    [0074]FIG. 11 shows a perspective view of a measurement device  210  and FIG. 12 shows a perspective view of a force transmission element  212  according to a fourth embodiment of the present invention.  
         [0075]    The force transmission element  212  is implemented in the form of a plate, one end of which is connectable to the vehicle seat (not shown). The other end  216  of the force transmission element  212  is preferably rounded and/or semicircular, the radius of the circle corresponding to half the width of the force transmission element  212 . A hole  218  is provided in the rounded end  216 , in which a rotatably mounted rotating element/circular ring  220  is provided.  
         [0076]    The circular ring is preferably rotatable around an axis A-A, which extends essentially perpendicular to the longitudinal extension of the force transmission element  212 . A slip ring  240  is provided in an opening  222  of the circular ring  220 , into which a preferably cylindrical measurement assembly  214 , which includes a sensor device  246 , is inserted. The slip ring  240  may be provided as a coating or as an insertable molded part. The measurement assembly  214  is rotatable around its longitudinal axis in the opening  222  of the circular ring  220  with the aid of the slip ring  240 . Furthermore, it is possible for the external shape of the circular ring  220  to have a shape other than a circle and for the opening  222  to have a shape corresponding thereto.  
         [0077]    The force to be measured is advantageously conducted into the measurement assembly  214  essentially or at least approximately perpendicularly to the longitudinal extension of the preferably cylindrical measurement assembly  214 . The force transmission element  212  is, at least in the rest position, also positioned essentially perpendicular to the longitudinal extension of the measurement assembly  214  and encloses the measurement assembly  214  essentially around its circumference (FIG. 11). Therefore, both a force acting from top to bottom in FIG. 11, i.e., a pressure force, and a force acting from bottom to top in FIG. 11, i.e., a tensile force, can be transmitted by the force transmission element  212  onto the measurement assembly  214 .  
         [0078]    Therefore, the force transmission element  212  and the measurement assembly  214  are embodied essentially as a universal joint, or the measurement assembly is mounted in a way similar to a universal joint.  
         [0079]    If a force to be measured acts diagonally on the force transmission element  212 , this element is slanted in relation to the circular ring  220  and the measurement assembly  214  along the axis A-A (FIG. 12). Therefore, the components of the force to be measured which act parallel to the longitudinal extension of the measurement assembly  214  are not conducted into the measurement assembly  214  and only the force components which act perpendicular thereto are transmitted. Furthermore, using the rotatable mounting between the circular ring  220  and the measurement assembly  214 , a force component which acts in the tangential direction in relation to the preferably cylindrical measurement assembly  214  may be prevented from being transmitted into the measurement assembly  214 .  
         [0080]    In this embodiment, the circular ring  220  and the force transmission element form a fixing device and/or coupling device for the measurement assembly  214  and/or an aid for positioning the measurement assembly  214 .  
         [0081]    The hole  218  and/or the opening implemented by circular ring  220  form a region into which the measurement assembly  214  may be inserted in this case.  
         [0082]    Similarly to the first three embodiments, the measurement assembly  214  is connected to a component such as a vehicle body part.  
         [0083]    In the following, a preferred embodiment of a measurement assembly  14  in the form of a force absorber  50 , whose use has been shown to be particularly advantageous in connection with the measurement device  10 ,  110  according to the first to third embodiments of the present invention, is described in detail with reference to FIG. 13.  
         [0084]    The force absorber  50  has a force conduction element  52 , which is configured as a housing shaped like a spherical zone. Furthermore, the force absorber  50  has an expansion body  56  positioned centrally in the force conduction element  52 , which is welded on one end  62  to the force conduction element  52 . On the end opposite to end  62 , the expansion body  56  is connected to a force delivery element  54 , which is implemented as a screw bolt and which is, in turn, rigidly connected to the vehicle body part  80 . The force delivery element  54  may, if desired, be made in one piece with the expansion body  56 . The cylindrical expansion body  56  has a surface  64 , which runs parallel to the direction of action of the weight, and onto which strain gauges  58  are either glued or applied using thin film technology. The strain gauges  58  are respectively positioned opposite to one another at an angle of  450  to the longitudinal axis of the expansion body  56 .  
         [0085]    A similar surface, provided with two strain gauges  58 , may be attached to the side of the expansion body  56  lying opposite the first, in relation to the longitudinal axis of expansion body  56 . The total of four strain gauges  58  in this embodiment can be connected into a Wheatstone bridge circuit, in order to thus elevate the quality of the measurement signal.  
         [0086]    A thin gap  60  is provided between a thickened portion of the expansion body  56  and the force conduction element  52  on the end of the expansion body  56  lying opposite to the end  62 .  
         [0087]    Through the loading of the vehicle seat (not shown), a weight force is conducted into the force transmission element  12 , which is relayed via the force transmission element  12  to the force conduction element  52 . Via the rigid connection to the expansion body  56 , this force is conducted at end  62  of the force conduction element  52  into the expansion body  56  in such a way that the expansion body  56  is displaced, relative to its end that is rigidly connected to the vehicle body part  80  via the force delivery element  54 , in the direction of action of the weight and parallel thereto. A pronounced shear therefore arises in expansion body  56 , which is detected via the strain gauges  58 .  
         [0088]    Forces acting orthogonally to the weight are not conducted into the force absorber  50  due to the ball socket mounting. In this manner, it is possible for essentially only the actual weight to be measured.  
         [0089]    The gap  60  provides an effective overload protection for the force absorber  50 . If the end  62  of the expansion body  56  is loaded in such a way that the movement of the rigid force conduction element  52  relative to loaded expansion body  56  is such that the end of the force conduction element  52  opposite to its end  62  comes into contact with the expansion body  56 , further shear loading of the expansion body  56  is precluded, since the force from the force conduction element  52  is conducted directly into the force delivery element  54  via the covered end of the expansion body  56 .  
         [0090]    For the force absorber  50  to function effectively, it is unimportant whether, as described above, the force conduction element  52  forms the housing of the expansion body  56  and the force delivery element  54  forms the bolt connected to the vehicle body part  80 , or whether the force is conducted via the pin and is delivered via the housing onto the vehicle body part  80 .  
         [0091]    Preferably, a region of the expansion body  56  is provided with a first recess (not shown), which leads to higher deformability of the measurement element and therefore to higher sensitivity of the strain gauges  58  positioned on the surface  64 .  
         [0092]    Furthermore, the force absorber  50  may be provided with an expansion body  56  that has a flat surface (not shown), projecting over the other contours, for attaching the strain gauges  58 . Since the surface projects over the other external contours of the expansion body  56 , the strain gauges  58  can thereby be attached simply onto the surface using thin film technology.  
         [0093]    The recess is preferably implemented as an oblong hole, which results in a further increase in sensitivity. At the same time, the remaining material cross-section is reduced without too strong of an adverse effect on the stability in lateral directions.  
         [0094]    Furthermore, a second recess (not shown) may be provided, whose axis runs essentially perpendicular to the axis of the first recess in the longitudinal direction of the expansion body  56  and which penetrates the first recess inside the expansion body  56 . The positioning of the second recess allows simple laying of electric lines for connecting the strain gauges  58 .  
         [0095]    Furthermore, the gap  60  may be covered by a membrane (not shown), in order to prevent the penetration of dirt particles into the force absorber  50 . Particularly effective protection of the force absorber  50  is ensured by implementing the membrane as a metal membrane. In this case, the metal membrane is welded between the force conduction element  52  and the force delivery element  54 .  
         [0096]    Instead of being a threaded bolt, the force delivery element  54  may instead have an internal thread.  
         [0097]    A particularly preferred embodiment of the measurement assembly  214 , whose use has been shown to be particularly advantageous in connection with the measurement device  210  according to the fourth embodiment of the present invention, is shown in FIG. 14. The basic construction of the sensor device is essentially the same as that of the force absorber  50 , so that a more detailed description will be dispensed with here. Rather, only those elements which are different from the force absorber  50  will be described.  
         [0098]    In the measurement assembly  214  illustrated in FIG. 14, a force conduction element  252  is configured to be cylindrical in shape. The diameter of the cylinder is selected to be somewhat smaller than the diameter of the opening  222  (FIG. 12), so that the measurement assembly  214  may rotate in the opening  222 . However, the diameter of the cylinder must be sufficiently large to allow force to be transmitted from the force transmission element  212  onto the measurement assembly  214 .  
         [0099]    The measurement devices  10 ,  110  according to the present invention are preferably used in a vehicle seat, an aircraft seat, a desk chair, or a wheelchair. Furthermore, the measurement devices  10 ,  110  according to the present invention can also be used in a hospital bed or any other apparatus in which the weight acting on the apparatus is to be detected.  
         [0100]    The above description of the preferred embodiments has been given by way of example. From the disclosure given, those skilled in the art will not only understand the present invention and its attendant advantages, but will also find apparent various changes and modifications to the structures and operations disclosed. It is sought, therefore, to cover all such changes and modifications as fall within the spirit and scope of the invention, as defined by the appended claims, and equivalents thereof.