Seat back inertia latch system
REFERENCE TO PRIOR APPLICATION 
     This application is a continuation in part of our co-pending U.S. application Ser. No. 06/090,343 filed on Nov. 1, 1979 for U.S. Pat. No. 4,295,682 for Seat Back Adjuster. 
    
    
     BACKGROUND OF THE INVENTION 
     Seat back inertia latch systems such as disclosed in our prior U.S. pat. applications Ser. No. 945,303 filed Sept. 25, 1978 now U.S. Pat. No. 4,223,946, Ser. No. 06/047,362 filed June 11, 1979 now and U.S. Pat. Ser. No. 06/090,343 filed Nov. 1, 1979 employ inertia elements having backward extensions positioning the inertia element in an engagement oriented relationship with the latch element when the seat back is in normal position which overcomes the gravity biasing of such inertia element toward a release position. Disengagement of each such extension with a stationary element of the seat is progressively effected by initial seat back tilting in a forward direction to permit gravity release of the inertia element from its latching orientation. Such backward extension of the inertia element per se together with the cooperating stationary back stop project to some extent into the available space fo the rear passenger. Such extension and back stop also involve some weight and material costs which potentially can be saved if eliminated. In addition tolerance requirements inherently involve some clearance between the inertia and latching element, together with some inertia element movement upon sudden deceleration, in order to reach full latch engagement orientation which to some extent inhibits latching efficiency. 
     SUMMARY OF THE PRESENT INVENTION 
     In order to reduce encroachment into the space for rear passengers by the inertia latch system, reduce weight and cost, and normally bias the inertia latch into full latch engaging orientation, the present invention eliminates the backward extension of the inertia element and cooperating stationary back stop and provides a supplemental element for biasing the inertia element into full latch engagement orientation when the seat is fully back which supplemental element is released upon initial forward tilting of the seat back. Such element may be located forwardly of the inertia element pivot and constructed with less weight and at reduced costs relative to the prior constructions. 
     In our prior co-pending U.S. application Ser. No. 06/090,343 one embodiment of the present invention was shown and described in and with reference to FIG. 11, corresponding to FIG. 1 of the present disclosure. Additional embodiments are also disclosed herein. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a fragmentary side elevation of a preferred embodiment of a seat hinge provided with an inertia latch system of the present invention shown with the seat back in normal position; 
     FIG. 1a is a similar view showing the relationship of the inertia latch system components upon initial forward tilting of the seat; 
     FIG. 2 is a view similar to FIG. 1 showing a modified embodiment of the present inertia latch system; 
     FIG. 2a is a view similar to FIG. 1a of the modified embodiment; 
     FIG. 3 is a view similar to FIG. 1 showing a second modified embodiment; 
     FIG. 4 is a view similar to FIG. 1 showing a third modified embodiment. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     With reference to FIGS. 1 and 1a the hinge fitting comprises a first hinge member 10 connectable to the seat of an automotive vehicle by suitable fasteners, not shown, and a second main hinge member 11 connectable to the back rest of the vehicle seat by suitable fasteners, not shown. Pivotal connection 12 is provided between the first and second hinge members. Optionally the seat hinge may be provided with an intermediate adjustment member 13 for changing the angle of the seat back to a reclining or other position by adjustment mechanism known in the art in which case stop 14 on such intermediate member will establish the limited backward travel of hinge member 11 for the operative position of the seat back through registration with engaging surface 15 of hinge member 11. Inertia latch element 16 pivotally connected at 17 to hinge member 11 is provided with latch nose 18 for engaging abutment 19 on an integral extension of adjustment member 13 in order to arrest forward travel of the seat back under a condition of sudden deceleration of the vehicle whereupon inertia operating on center of gravity 20 maintains the inertia latch in its operative orientation as shown in FIG. 1 for effective latch engagement. 
     Such orientation is established and normally maintained, when the seat back is moved to its operative position, by leaf spring 21 pivotally mounted at 22 to hinge member 11 having extension 23 engaging shoulder 24 of adjustment member 13 deflecting extension 23 from its free position 23a thereby biasing spring extension 25 against forward surface 26 of the inertia element to induce counterclockwise pivoting of such element to its operative orientation and overcoming the gravity force operating at the center of gravity 20 urging the inertia element to pivot in a clockwise direction. With reference to FIG. 1a, upon initial forward tilting of the seat back when the vehicle is stationary relaxation of spring tension in extension 23 permits gravity to actuate the inertia element 16 to the release position shown. 
     With reference to FIGS. 2 and 2a a similar result is accomplished with plastic bellcrank element 27 pivotally mounted on hinge member 11a having leg extension 28 for engaging shoulder 24a and leg extension 29 for engaging forward surface 26a of inertia element 16a when the seat back is moved to the rest position shown in FIG. 2. Tension spring 30 anchored to hinge member 11a at 31 moves bellcrank 27 in a counterclockwise releasing direction upon initial forward seat back tilting when the vehicle is stationary as shown in FIG. 2a. 
     With reference to FIG. 3 showing the adaptation of the present link to a pendulum type suspended inertia element 32 pivoted at 33 to lower seat bracket 34, leaf spring 35, similar to spring 21 of FIGS. 1, 1a, is pivotally mounted at 36 to lower seat bracket 34 and is provided with extension 37 for engaging the forward outside surface of latch projection 38 of inertia element 32 and with extension 39 for engaging the outside forward surface of latch abutment 40 projecting from upper seat back hinge member 41 pivotally connected at 42 to lower seat back member 34. Here again upon initial forward tilting of the seat back center of gravity at 43 of pendulum inertia element 32 produces counterclockwise movement of the inertia element to a release position permitted by movement of abutment 40 permitting clockwise pivoting of leaf spring 35. 
     Manual override lever 44, also pivoted at 42, has arm 45 with projection 46 extending through slot 47 and bracket cover 48 which permits manual release of inertia latch element 32 in the event of malfunction. 
     With reference to FIG. 4 plastic bellcrank 50, similar to bellcrank 27 of FIGS. 2 and 2a, pivotally connected at 51 to the lower seat hinge assembly serves the function of leaf spring 35 in FIG. 3 being retracted by tension spring 52 to an inertia latch release position upon initial forward tilting of the seat back. 
     In each of the embodiments of FIGS. 3 and 4 the rest position of the seat back is established by engagement of limit stop pin 53 anchored to the lower seat hinge assembly with one end of arcuate slot 54, centered on the hinge pivot 42, provided in seat back hinge member 41. 
     From the foregoing description of several embodiments it will be understood that other return linkage provisions may be made for either pendulum or above pivot center inertia elements which are within the scope of the invention as defined in the appended claims.