Abstract:
An automotive or similar type vehicle seat comprising a seat back having an adjustable central portion which may be selectively adjustably positioned to minimize driver fatigue. The adjustable area is actuable upon rotation of an adjustment knob which controls rotation of a shaft which is connected via suitable linkages to a pivotal support mechanism for pivotably adjusting the central portion of the seat back.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates in general to vehicular seats which help the driver and/or passenger feel more comfort and less fatigue. In particular, this invention relates to automotive seats with a mobile seat back which is adjustable to the contours of the driver&#39;s body, and which thereby reduces fatigue of the driver and results in a more comfortable ride. 
     In general, automotive seats have been designed to minimize the fatigue of the driver during driving, i.e., the seat backs have been designed with optimum stress-strain relationship in mind. It has been reported that positioning a vehicle seat back in the position shown in FIG. 4 such that the maximum stress range (the stress of 60 g/cm 2  range in the figure) is located at the second and third lumbar vertebra gives a driver minimum fatigue and maximum comfort during driving. However, such seat back designs fit the body contour of an average driver, and depending upon body contours of individual drivers and the reclining angle of the particular seat, deviation from the optimum stress distribution takes place, thus increasing fatigue and discomfort of the driver. In addition, even if the driver sits in the optimum seating configuration, sitting in the same position for prolonged time causes constant stress on the same parts of the body, which often leads to fatigue and discomfort to the driver. 
     One generally satisfactory solution to the problem of overcoming the deficiencies of conventional vehicular seats is disclosed in U.S. patent application entitled Seat for Vehicle, Ser. No. 323,662, filed Nov. 20, 1981 and assigned to the assignee of the present invention. While the vehicular seat disclosed therein is quite successful in fulfilling its objectives, further comfort is constantly being strived for. 
     BRIEF SUMMARY OF THE INVENTION 
     The invention comprises an improved vehicle seat having a seat portion and a back portion and an adjustable lumbar support assembly for reducing back fatigue of the seat occupant. The overall construction and design of the vehicular seat of this invention is shown in FIG. 1. The seat back in the invention is made up of two parts, namely, one part supported by the main seat back frame and being relatively fixed, and the other part being mobile with its movement controlled by an adjustment knob. The separation of the mobile seat back from the main seat back frame is most pronounced at the lower part of the mobile cushion. Thus the discontinuity between mobile cushion and the seat back frame is least pronounced at the upper part of the cushion. The has been found to add greatly to the comfort of the seat. When the mobile seat back comes forward toward the back of the driver (FIG. 1), the maximum stress range of lumbar vertebra goes upward, and when the mobile seat back goes backward away from the back of the driver, the maximum stress range goes downward. Consequently, the deviation from the optimum stress ranges due to the difference in body contours of drivers can be corrected by adjusting the mobile seat back. 
     The lumbar support assembly comprises a support frame having upper and lower portions pivotally secured to the seat back portion for movement about a generally horizontal axis adjacent the upper portion of the support frame. Carried on the support frame is a cushion designed to engage the lumbar region of the seat occupant during use. A fulcrum disposed in fixed relation to the seat back portion pivotally secures a lever generally at the center thereof. The lever in turn is coupled to the lower portion of the support frame so that pivotal movement of the lever about the fulcrum causes the lower or bottom portion of the lumbar engaging cushion to move inwardly or outwardly with respect to the plane of the seat back. A manually actuable threaded shaft is interconnected with the lever by means of linkage for translating rotating movement of the shaft into translating movement of an axle, which in turn causes the lever to pivot about the fulcrum. 
     It is a general object of the invention to provide a new and improved vehicular seat which overcomes or reduces the deficiencies of conventional vehicular seats described above and which improves upon the vehicular seat disclosed in U.S. patent application Ser. No. 323,662. By incorporating an adjustable, mobile seat back in a vehicular seat, a driver can freely select the seat back position and adjust the seat back to his own body contours. 
     Another objective is to enable the driver to adjust or correct the body stress distribution to specific seating positions. When driving congested streets or driving minimum angle of reclining, the body stress becomes concentrated at upper part of vertebra, thus deviating from the optimum stress distribution. 
     Another object is to provide a driver during long distance driving with more comfort and less fatigue by enabling occasional adjusting and readjusting of the mobile seat back, which avoids the constant stress on the same part of the body. A driver suffering fatigue due to long hours of driving may take corrective measures via means for adjusting seating positions; for example, by moving the upper part of the mobile seat between back and forward, the driver during long hours of driving can adjust the body stress on his back, thus contributing to reduction of fatigue. 
     The objects described above can be achieved with the seat in the invention. The driver in this seat can choose seating position and adjust the mobile seat back in order to reduce fatigue during driving. 
     Other objects, features, and advantages of the present invention will become apparent from the subsequent description and the appended claims, taken in conjunction with the accompanying drawing, in which: 
    
    
     DETAILED DESCRIPTION OF THE DRAWING 
     FIG. 1 is an elevated perspective view of a seat with the mobile seat back of the present invention; 
     FIG. 2 is a partially broken away view of the seat of the present invention; 
     FIG. 3 is a longitudinal cross-sectional view of the seat back taken along the line of body contour of a driver; and 
     FIG. 4 is a schematic and graphic body stress distribution-fatigue analysis. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     From the drawings, it will be seen that the automotive seat of the invention has a seat back consisting of two primary parts, namely, the upper part 1 and the lower mobile cushion part 2. Bolsters 3 are fixed to he upper stationary part 1. In order to move the mobile part of the seat back, a knob or switch 4 is installed, as shown in FIG. 4. 
     FIG. 4 shows the body stress distribution which results in minimum fatigue. Body stress distribution is dependent upon the contours of individual driver&#39;s body, and therefore, in order to achieve the body stress ranges (the areas of 40 g/cm 2  or more in FIG. 4) should be separated from whole seat back and should be made to move independently and continuously so that the driver can achieve the optimum body stress distribution with symmetry in respect to the back seat. 
     The seat back of the invention is constructed as shown in FIGS. 2 and 3. Tubular frame 5 supports the whole seat back and bolster frames 6a and 6b with elastomeric foam, such as polyurethane foam, and constitutes the upper stationary seat back part. The lower mobile cushion 2 of the seat back is constructed in such a way that the driver can achieve the optimum stress distribution by adjusting the angle of the lower, mobile part of the seat back. The lower mobile cushion 2 is attached to or carried by a generally rectangular support frame 7 which is pivotaly secured along the upper end thereof by means of angle brackets 8 disposed on bolster frames 6a and 6b, support brackets 9 and hinge pins 10. Angle brackets 8 include a long hole 11 arranged to permit upward and downward sliding motion of pin 10 and bracket 9 generally in a plane parallel to the tubular frame 5. The invention further comprises a fulcrum or pin 21 carried or disposed in fixed relation to the seat back portion by means of elongated brackets 22 disposed on bolster frames 6a and 6b. Pivotally secured about each fulcrum pin 21 is a crescent-shaped lever 19. The mid section of each lever 19 is pivotal about the respective fulcrum pin 21, while the lower end thereof is secured for pivotal movement with respect to the bottom of frame 7, as with pins 23. The upper end of each lever 19 includes an elongated slot 20. A linkage axle 11 is received in slots 20 for sliding and rotating movement therein. Axle 11 is further carried for sliding movement in a second pair of elongated slots 18 formed in bracket members 22. It will be seen that when axle 11 moves upwardly, the seat back frame 7 rotates about the generally horizontal axis passing through pins 10 due to forces exerted through lever 19 about fulcrum pin 21, whereby the lower part of the mobile cushion 2 moves laterally inwardly towards tubular frame 5. On the other hand, when the axle 11 moves downwardly, the seat back frame 7 rotates about the axis through pin 10, whereby the lower part of the mobile cushion moves laterally outwardly away from tubular frame 5. Thus it will be seen that the mobile cushion is adjustable so that the lower portion thereof is movable between retracted position Xa and extended Xb. At the same time it will be seen that the upper portion of mobile seat cushion 2, as at Y, remains relatively stationary with respect to the tubular frame 5. It has been found that this makes for a more comfortable seat by providing for very little, if any, discontinuity or lateral movement of the lumbar support cushion at its upper end Y. It will be understood that some would find any significant discontinuity between the upper seat portion 1 and the upper portion of mobile cushion 2 to be quite uncomfortable. It will further be appreciated that the elongated slots 18 and 20 and long hole 16 permit a certain amount of sliding movement of the entire lumbar support assembly generally in a plane parallel to the tubular frame 5. Such movement permits the lumbar support cushion to move in the trajectory shown in FIG. 3, within the confines of the space defined by the upper seat portion 1. 
     In order to move the axle 11 up and down, an adjusting shaft or axle 12 is introduced at the back of the mobile seat back frame 7. Both ends of the adjusting axle 12 are supported by holes in the respective side walls of supporting brackets 17 which are secured to bolster frames 6a and 6b. The adjusting axle 12 has reverse threads at its opposite ends, and includes thread holders 13a and 13b which have threads with the same pitch as the threads on the axle 12. Rods 14a and 14b connect the thread holders 13a and 13b and the axle 11. An adjusting knob 4 is attached at the end of the adjusting axle 12. By rotating the adjusting knob 4, the thread holders 13a and 13b move horizontally and this movement causes the up-down movement of the axle 11 through the joint rods 14a and 14b. Thus, the driver can move the mobile seat back by rotating the adjusting knob 4. 
     As shown in FIGS. 2 and 3, the mechanism for moving the mobile seat back is effectively contained in narrow space within the seat; yet this mechanism exhibits strong enough force to move the mobile seat back overcoming the stress caused by the driver&#39;s back. Other types of mechanisms for adjusting the mobile seat back in the invention such as gears, cams, crankshaft or electronic motors can also be conceivable within the scope of the invention. Towards this end FIG. 2 illustrates the use of optiional drive motor 24 coupled through gears 25 to axle 12. 
     While it will be apparent that the preferred embodiments of the invention disclosed are well calculated to fulfill the objects above stated, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope or fair meaning of the invention.