Abstract:
A seat track assembly for an automotive seat positioner mechanism includes a threaded spindle fixed at one end to a lower track and a mating nut in a gear case on the spindle mounted to an upper track by a bracket attached thereto. The bracket is stabilized against crash forces by interfit portions on the bracket and side walls of the upper track. The spindle is directly attached to the lower track by fasteners passed through a flattened end of the spindle and a bottom wall of the lower track.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]    This invention claims the benefit of U.S. provisional Serial No. 60/443,674, filed Jan. 29, 2003. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates to seat track assemblies used in positioner mechanisms for automobile seats.  
         BACKGROUND OF THE INVENTION  
         [0003]    Automotive powered seat positioning mechanisms are known of the type using a threaded spindle engaged by a gear nut carried by an upper track, with the gear nut driven by a worm gearing in turn driven by a motor. Rotation of the gear nut causes the gear nut and an enclosing gear case to drive the upper track so as to be advanced in either direction along the spindle. Such mechanisms are described in U.S. Pat. No. 4,802,374 and WO 9951456.  
           [0004]    The gear nut and worm gear are typically carried in a gear casing mounted on a U-shaped bracket having its legs attached to the upper track to cause the movement of the gear nut to drive the upper track in either direction. The spindle is mounted spaced above the bottom wall of a lower track on a pair of brackets each located at an opposite end of the spindle, these brackets in turn attached to the lower track.  
           [0005]    The automobile seat is held in any adjusted position by the gear nut and spindle and these components are thus subjected to high loads in the event of a crash or other high stress event and the support for these components must therefore be designed to have adequate strength to resist the stresses imposed.  
           [0006]    It is desirable that the seat adjustment mechanism be fully functional after a crash.  
           [0007]    The bracket supporting the gear nut and gear casing tends to be distorted as the upper track supporting the seat and the occupant tends to move forward in a crash or other high stress event, and this is resisted by the gear nut-spindle engagement, applying of forces offset from the point of attachment to the upper track. The unattached lower ends of the legs of the bracket cannot effectively resist these forces. The bottom location of the leg connecting portion of the bracket prevents any fastener attachment to the side walls of the upper track after assembly since that portion is then completely inaccessible. Thus, heavy gauge steel must be employed to construct the bracket to resist the forces applied in this manner.  
           [0008]    The spindle itself must be well anchored to resist these stresses, which typically is done by a heavy gauge bracket mounted at each end of the spindle. These sturdy brackets must in turn be securely attached to the lower track.  
           [0009]    It is the object of the present invention to provide a track assembly in which the connection between the bracket and the upper track provides a balanced loading of the bracket which efficiently resists the forces imposed thereon in a crash or other high stress event.  
           [0010]    It is another object to simplify the attachment of the spindle to the lower track while still providing ample strength to withstand the crash induced stresses imposed thereon.  
         SUMMARY OF THE INVENTION  
         [0011]    The above object and others which will become apparent upon a reading of the following specification and claims are achieved by a track assembly including nested upper and lower channel shaped tracks. The upper track and gear case bracket also have portions which are configured to be interfit together when the upper track is placed over the bracket which creates a connection therebetween resisting relative displacement therebetween in the lengthwise direction of the track. The upper track has side walls and a top wall to which an upper end of the bracket is fixed after the upper track is installed onto the bracket. The interfit portions of the bracket may comprise a pair of protrusions projecting side ways in opposite directions from a respective side of bracket leg connecting portion located at the bottom of the bracket. These protrusions may comprise tabs or teeth which are received in a complementarily shaped notch in a bottom edge of each upper track sidewall, when the upper track is placed over the bracket during assembly.  
           [0012]    This design secures both the top and bottom portions of the bracket relative to the upper track so as to efficiently resist the tendency of the bracket to be deformed under the stresses developed in a crash event.  
           [0013]    The spindle itself is anchored at one end by being flattened at one end with an offset locating the flattened end against the lower track bottom wall so that the spindle is spaced above the bottom track bottom wall. The flattened end is directly attached to the lower track bottom wall with fasteners which can also attach the lower track to the floor pan or a separate mounting bracket.  
           [0014]    This creates a high strength anchoring of the spindle while eliminating the two supporting brackets typically employed to mount the spindle. This lowers the manufacturing costs and precludes any possibility of such support brackets breaking loose in a crash.  
       
    
    
     DESCRIPTION OF THE DRAWINGS  
       [0015]    [0015]FIG. 1 is a pictorial view of an automotive seat supported and positioned by a pair of parallel track assemblies according to the invention and a drive system therefore.  
         [0016]    [0016]FIG. 2 is a pictorial view of one of the track assemblies shown in FIG. 1.  
         [0017]    [0017]FIG. 3 is a view of a transverse section taken through the track assembly shown in FIG. 2.  
         [0018]    [0018]FIG. 4 is an inverted pictorial view of an installed gear casing bracket together with a fragmentary portion of the upper track to which it is mounted.  
         [0019]    [0019]FIG. 5 is an exploded pictorial reverse view of a fragmentary part of the track assembly shown in FIG. 2.  
         [0020]    [0020]FIG. 6 is a longitudinal section taken through the track assembly shown in FIG. 2.  
         [0021]    [0021]FIG. 7 is an exploded pictorial view of the gear casing and mounting bracket. 
     
    
     DETAILED DESCRIPTION  
       [0022]    In the following detailed description, certain specific terminology will be employed for the sake of clarity and a particular embodiment described in accordance with the requirements of 35 USC 112, but it is to be understood that the same is not intended to be limiting and should not be so construed inasmuch as the invention is capable of taking many forms and variations within the scope of the appended claims.  
         [0023]    Referring to the drawings, FIG. 1 illustrates the mounting of an automotive seat  10  on a pair of parallel track assemblies  12  secured to the vehicle floor pan  14  and to the seat bottom  16  in conventional fashion. A separate mounting bracket (not shown) may also be used rather than a direct attachment to the floor pan. A rotary drive system  18  is employed to simultaneously drive an upper track  20  of each track assembly  12  to move the seat forward or backwards in the well known manner on a lower track  24  comprised of an upward facing channel within which the upper track  20  is nested.  
         [0024]    This general arrangement is described in U.S. Pat. No. 4,802,374 and WO 9951456.  
         [0025]    In this arrangement, each of the upper tracks  20  are driven by rotation of an associated threaded horizontal spindle  22  mounted to the lower track  24  of each track assembly  12  extending in a lengthwise direction, and a gear nut  26  is threaded onto the spindle  22  (FIG. 3). The gear nut  26  is rotatable within a gear casing  28  (FIG. 7) and has a lengthwise driving engagement with the upper track  20  by being captured between the straddling legs  44  of a U-shaped bracket  30  attached to the upper track  20 . The gear case  28  may be made of two die cast parts assembled together using integral alignment posts as indicated on one part received in mating holes in the other part as per a common manufacturing practice.  
         [0026]    A worm gear  34  is also rotatably held in the gear casing  28  rotated by the drive system  18  by a cable or shaft (not shown) mating with a square drive socket in the ends of the worm gear. The cable or shaft can pass through an opening  36  (FIG. 7) in the side of the gear casing  28  from the side of each upper track  20 . An aligned hole  37  is also provided in each side wall  54  of the upper track  20  for this same purpose.  
         [0027]    Each bracket  30  has a pair of mounting flanges  32  each located at the top of a respective leg  44 , and each having a hole  40  receiving a screw  38  passing through an aligned hole  39  in the upper wall  41  of the upper track  20  to be secured thereto.  
         [0028]    The parallel legs  44  each extend down from a respective flange  32  (best seen in FIG. 7) and are connected together at their lower ends with a connecting portion  46 . The legs  44  have aligned holes  48  to accommodate passage of the spindle  22 .  
         [0029]    The bracket  30  has a pair of protrusions  50  which may be comprised of tab or tooth features each projecting laterally out in an opposite direction towards a respective upper track side wall  54  from a respective side edge of the connecting portion  46  of the bracket  30  (FIGS. 3 and 6).  
         [0030]    As noted above, the upper track  20  comprises a downwardly facing elongated channel section nested within the lower track  24  which comprises an upwardly facing elongated channel section as best seen in FIG. 3.  
         [0031]    The upper track  20  is slidably mounted on the lower track  24  by a bearing arrangement as described in detail in U.S. Pat. No. 6,557,809 B2, assigned to the assignee of the present application.  
         [0032]    This arrangement includes a reversely formed lip  52  extending up from a rolled bottom edge  74  of each side wall  54  of the upper track  20  (FIG. 3). An angled portion  56  of the lip  52  faces an angled portion  58  of each side wall  60  of the lower track  20  to create a roughly square bearing space into which are disposed “load transmission elements”, here shown as balls  62 . An interference is created so that at least one of the tracks is resiliently deflected by the balls  62 , as described in detail in U.S. Pat. No. 6,557,809 B2.  
         [0033]    The rolled bottom edge  74  of each of the upper track side walls  54  are formed with recesses here shown as notches  64 , which are shaped to mate with the protrusions  50  received therein. The notches  64  extend horizontally into the rolled edges  74  at the lower end of each side wall  54 . Thus, as the upper track  20  is lowered onto the lower track  24  and over the bracket  30 , the tabs  50  move into the notches  64 . This effectively creates an interconnection resisting lengthwise movement of bracket portion  46  relative the upper track  20  without the need for installing any fasteners nor any access to the now enclosed bracket  30 .  
         [0034]    This interconnection with the bottom edge of the upper track  20  at the lower end of the bracket  30  complements the connection of the upper end of the bracket  30  provided by the later installed fasteners  38  to create a box structure greatly strengthening the ability of the bracket  30  to withstand distorting forces imposed by the nut gear  26  and gear casing  28  in as much as the legs  44  of the bracket  30  are restrained from bending, and the load is shared with the screws  38 . The bracket  30  can thus be made lighter and is less likely to fail. This connection is achieved without any additional parts or assembly labor.  
         [0035]    The spindle  22  is mounted to the lower track  24  by flattening one end  66  of the spindle  22  (made from alloy steel bar stock).  
         [0036]    The flattened end  66  is pierced with mounting holes  68  to receive screws  70  passing through holes  72  in the bottom wall of the lower track  24  (as well as a section of the vehicle floor pan  14  or separate mounting bracket) to secure the one end of the spindle  22  thereto.  
         [0037]    The spindle  22  is formed with an offsetting transition  76  which positions the spindle  22  spaced above the bottom wall of the lower track  24 , as best seen in FIG. 4.  
         [0038]    This mounting completely eliminates the spindle brackets used in prior designs which reduces the cost of the track assembly and avoids any possibility of failure by separation of separate brackets in the event of a crash or other high stress event.  
         [0039]    The track assembly is assembled by attaching the spindle to the lower track  24  using screws  70 , which at the same time may be attached to the floor pan  14  (or to a separate mount). The bracket  30 , gear nut  26 , and gear casing  28  are preassembled to the spindle  22 . The upper track  20  is placed into the lower track  24  with the holes  39  in the top wall  41  aligned with holes  40  in the bracket flanges  32 . The fasteners  38  are then used to fix the bracket flanges  22  to the top wall  41 .  
         [0040]    The protrusions  50  and recesses  64  are automatically mated when the upper track  20  is installed on the lower track  24  with the holes  39  and  40  aligned.