US 20020043842 A1
The invention provides a back rest for a seat back which will not exert too much burden on the thoracic vertebrae and the lumbar vertebrae, resulting in the likelihood of accumulation of fatigue or pain in the lower back after a long hour driving being reduced being reduced. The back rest has a front side having a slight concave extending from the intermediate portion to the upper portion thereof and a convex extending from said intermediate portion to the lower portion, thus forming a configuration following an S line of the human spinal column while having a reverse side provided with reinforcement ribs together with a plurality of slits generally formed in said back rest.
1. A back rest for a seat back, said back rest having a front side and a reverse side, which back rest comprises a slight concave extending from substantially an intermediate portion of said front side to an upper portion thereof; a slight convex extending from said intermediate portion to a lower portion of said front side to form in combination a configuration following an S line of the human spinal column; and ribs provided for reinforcement at said reverse side, said back rest being generally formed with a plurality of apertures.
2. A back rest as set forth in
3. A back rest as set forth in any one of claims 1 and 2, wherein said apertures are a plurality of slits.
 The present invention relates to a back rest for the seat back of an automobile seat, an office chair seat, or a household chair seat which is set on the surface of such seat back.
 In general, the seat back of the seat such as that of an automobile seat is so soft that an excessive burden is exerted on the lower part of the back of the driver or passenger (hereinafter referred to as “driver”) or his spinal column, resulting in the fatigue or the pain in the lower part of the back.
 The present invention is made to solve such problems conventionally observed as mentioned above and its object is to provide a back rest for the seat back which is free from the likelihood of the accumulated fatigue or the lower back pain being caused after long hours of driving.
 In order to realize the above mentioned object of the invention, there is provided a back rest for the seat back, said back rest having a front side and a reverse side, said back rest comprising a slight concave extending from substantially an intermediate portion of said front side to an upper portion thereof; a slight convex extending from said intermediate portion to a lower portion of said front side to form in combination a configuration following an S line of the human spinal column; and ribs provided for reinforcement at said reverse side, said back rest being generally formed with a plurality of apertures.
FIG. 1 is a perspective view of one embodiment of the present invention in which said back rest is set on an automobile seat;
FIG. 2A is a front view of the embodiment of FIG. 1; FIG. 2B is a rear view thereof; FIG. 2C is a side elevation of FIG. 2B; FIG. 2D is a sectional side elevation taking along the line A-A of FIG. 2B; and FIG. 2E is a sectional view of FIG. 2B taken along the line B-B thereof;
FIG. 3A is a view showing the function of the above embodiment and FIG. 3B is an enlarged view of the a portion thereof; and
FIGS. 4A through 4C are an explanatory view of the back rest of the invention.
 Hereinafter, an embodiment of the present invention will be explained with reference to the drawings.
 Referring to FIG. 1, an automobile seat 1 comprises a seat cushion 1 a, a seat back 1 b and a head rest 1 c. On the surface of said seat back 1 b, a back rest 2 is set by means of suspender cords 3 which are tied together backwardly of the top of the seat back 1 b. Although the means for suspending the back rest 2 is not limited to said suspender cords 3 so long as it is capable of suspending the back rest 2 while vertically adjusting its position in accordance with the driver's sitting height, any materials like braids as soft and flexible as possible are preferred. Said back rest 2 has a front side 21 and a reverse side 22. At the lower part of the seat back 1 b, there are provided lower part fixing braids 4 to prevent the suspended back rest 2 from deflecting sideways such that said back seat is centrally positioned. In the case of the automobile seat 1, it is sufficient to provide said lower part fixing braids 4 on the external or door side of the seat but it is also acceptable to provide such lower part fixing braids on the internal side thereof and, if not necessary, such provision may be omitted.
FIG. 2 shows the structure of said back rest 2, which is basically formed integrally with hard synthetic resin. As best seen from FIG. 2E, said back rest 2 is gently curved to envelope the driver's back from right to left. When viewed vertically as shown in FIG. 2D, the front side 21 of the back rest 2 has a slight concave 2 a extending from substantially an intermediate portion of said front side 21 to an upper portion thereof, where said front side is slightly dented in relation to the driver. On the other hand, the front side 21 of said back rest 2 has a convex 2 b extending from said intermediate portion to a lower portion, where said front face slightly swells in relation to the driver. Said concave 2 a and said convex 2 b forms in combination a configuration following an S line of the human spinal column.
 As seen from FIG. 2B, the periphery of the back rest 2 is provided with a reinforcement to form a stepped portion 2 c. The reverse side 22 of said back rest 2 is provided with reinforcement ribs 2 d arranged in crisscross fashion.
 The back rest 2 of hard synthetic resin is generally formed with apertures 2 e to lessen the hardness thereof such that said back rest 2 becomes agreeable to the driver 's body. In addition thereto, said apertures help make the frictional resistance of the back rest 2 against the driver's body and the seat back 1 b, which driver's body and the seat back press the back rest 2 from both sides thereof such that the driver's weight is easily transmitted by way of the back rest 2 to the seat back 1 b, resulting in the seat back 1 b supporting as much of his weight as possible. Said apertures 2 e also help the driver's perspiration while having a massaging effect. It is preferable that said apertures 2 e are slits as shown in the embodiment but do not have to be limited to such configurations and as long as said functions as mentioned in the foregoing are maintained, any form may be chosen.
 As especially shown in FIG. 3B, the driver's clothes W will eat into the apertures 2 e in the back rest 2 to assure that the lower hems 2 f of the respective aperture support the driver's weight. Thus, the surfaces of the back rest 2 having such plurality of apertures 2 e and the driver's back produce a great frictional resistance and, as a result of it, the weights of the driver's head and his upper part of the body is supported at said concave 2 a (extending to point X from point Y) such that the burden of the weight to be supported by thoracic vertebrae S and lumbar vertebrae K is reduced. In addition, the supporting function at said convex 2 b (extending from point Y to point Z) helps make said thoracic vertebrae S to form a natural S curve to reduce the burden on the lumbar vertebrae such that a long hour driving will not cause too much fatigue.
FIGS. 4A through 4C explain the method of adjusting the position and the condition of the back rest 2 being used. In FIG. 4A, it is shown that pads P are held at the upper and lower portions of the back rest 2 in case the seat back 1 b is too soft. If the seat back 1 b is too hard, on the other hand, such pads P are moved downward to be held at a lowered portion while the head rest 1 c is positioned closer to the driver's head. However, said pads P are preferably removed if the head rest is closer to the driver's head or if the deeper seat cushion 1 a are required. Further, if the driver is in need of a strong press on his back or if the seat cushion 1 a is too deep for the driver's height, folded towels T may be held therebetween in addition to the pads P.
 The back rest of the present invention is not only set on the surface of the seat back but also may be wrapped in a cloth cover. In the latter case, pads of urethane or the like may also be stuffed within the cover. It is also acceptable to contain the back rest within the seat back.
 Since the back rest of the invention is characterized in that the front side thereof has a slight concave extending from the intermediate portion to the upper potion and a convex extending from said intermediate portion to the lower portion such that an S line of the human spinal column is followed by the configuration formed by said concave and said convex in combination. Further, the rear side of the back rest is provided with reinforcement ribs while the back rest is substantially generally formed with apertures such that a frictional resistance between the driver and the back rest is increased, resulting in reducing the likelihood of the weight of the driver's head and the upper portion of his body being concentrated on the thoracic vertebrae and the lumbar vertebrae such that a long hour driving or the like will not cause any accumulation of fatigue or the pain in the back. Further, thanks to apertures in the back rest, there is either no likelihood of the perspiration being prevented.
 Further, since the back rest slightly curves from right to left to enclose a human back, it is possible to support the body for a long time.