Seat adjuster for vehicle seat

A seat adjuster for use in automotive seat employing a pair of slide rails for fore-and-aft adjustment of the seat with a locking mechanism, wherein, at one of the two slide rails disposed adjacent to a center of the automobile, there are arranged first and second shafts, such that the second shaft, which is provided with an operation handle, is disposed lower than the second one which is connected with the locking mechanism, with a link mechanism interposed between the two shafts for their mutual simultaneous rotations. Hence, the operation handle is positioned lower close to the automobile floor and disposed adjacent to the inner or center side of the automobile, so that occupant's foot or clothes is not contacted with the handle.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a seat adjuster by which the seat is 
adjusted its fore-and-aft position. 
2. Description of Prior Art 
In general, a seat adjuster for fore-and-aft adjustment of seat consists 
basically of a pair of movable rail and fixed rail, both of which are 
fitted together in a slidable manner, and a lock mechanism provided over 
the two rails for permitting locking unlocking of the movable rail against 
the fixed rail at a desired point along the longitudinal direction 
thereof. The movable rail carries a seat and fixed rail is fixed on a 
floor of the vehicle. 
A concrete example of this seat adjuster is shown in FIGS. 1 and 2, which 
depict a conventional, vertically arranged type of seat adjuster. 
According thereto, there is provided a vertical-type slide rail (2) 
comprising a fixed rail (4) of a generally C-shaped configuration in 
section, which is fixed upon a floor of a vehicle (not shown) and a 
movable rail (3) fitted slidably via balls (5) within the fixed rail (4), 
whereupon the width-wise planes of both fixed and movable rails (4)(3) 
stand vertically in relation to a horizontal plane of the floor, as 
opposed to an ordinary flat-type slide rail. 
To that movable rail (3), a seat cushion frame (1) is fixed, on which a 
seat cushion (c) is mounted. At the inner side of the frame (1), a shaft 
(8) is supported by a bearing member (7) in a rotatable way, the shaft (8) 
extending along the longitudinal direction of the frame (1). A lock pawl 
(6) is fixed to the shaft (8), with its forward end passing through the 
hole (1a) perforated in the frame (1). 
As best seen from FIG. 2, the forward end of lock pawl (6) passes through a 
through-hole (3a) formed in the movable rail (3) and through one of plural 
lock slots (9) formed in the fixed rail (4), whereupon the slide rail (2) 
is in a locked state. The plural lock slots (9) are formed in an 
equidistant way from one another along the longitudinal direction of the 
fixed rail (4). 
A spring (10) is provided on the shaft (8) to biasingly cause the shaft (8) 
to be rotated normally in a direction to cause the lock pawl (6) to be 
engaged in one of the plural lock slots (9). 
Figures only shows the right-side seat adjuster, but though not shown, 
there is provided a left-side seat adjuster, hence constituting a pair of 
right and left seat adjusters in a way sandwiching the seat cushion (c) 
for bilateral locking/unlocking purpose to the seat against the 
fore-and-aft sliding of the movable rail (4). 
At the forward end of the shaft (8), a link piece (11) is fixed, with its 
lower end directed downwardly. 
A second link piece (12) is fixed on a left-side shaft (8') such that the 
piece (12) is disposed opposite to the first one (11) and directed 
upwardly. 
A pull wire (13) is extended between the first and second link pieces 
(11)(12), with both ends of the wire (13) being each connected to the 
respective free ends of the first and second link pieces (11) (12). 
The left-side shaft (8') is provided at its forward end with an operation 
handle (14) and disposed at the door side of the seat. 
Designation (15) denotes a cushion frame for receiving the seat cushion 
(C), which is disposed between the two shafts (8)(8'). 
Operating the handle (14) results in causing synchronized, simultaneous 
rotation of the two link pieces (11)(12) about the respective axises of 
the two opposite shafts (8)(8') by virtue of the pull wire (13). Of 
course, the shafts (8)(8') are rotated overcoming the biasing force of the 
spring (10). Then, the lock pawl (6) is rotated in a direction to be 
disengaged from the lock slot (9), allowing fore-and-aft sliding 
adjustment of the seat. After having adjusted a position of the seat, 
release of the handle (14) allows the lock pawl (6) to be returned into 
engagement with another one of the lock slot (9) under the biasing force 
of the spring (10). 
In that way, the movable rail (3) is unlocked and locked at desired point 
relative to the fixed rail (4), and thus the seat is adjusted in its 
fore-and-aft position. 
However, in this vertically assembled type of seat adjuster, in case of the 
seat shown being disposed at the left-side half in the automobile in 
relation to the center thereof; namely, at the door side of the 
automobile, the operation handle (14) projects at a high level under the 
seat, adjacent to the door of the automobile. This poses a problem that an 
occupant, when entering into or getting out of the car, will stumble over 
the seat, with his or her foot or a lower part of clothes being hit or 
caught by the highly projected operation handle (14). Moreover, 
particularly if the seat is an assistant seat next to the driver's one, 
the door-side disposition of the handle (14) prevents access thereto from 
a driver on the driver's seat and the driver can not reach the handle (14) 
to adjust the fore-and-aft adjustment of the assistant seat. Yet further, 
as understandable from FIG. 2, during operation of the handle (14), the 
left-side link piece (11) is hindered its upward movement due to contact 
with the seat cushion frame (15). 
SUMMARY OF THE INVENTION 
In view of the above drawbacks, it is a purpose of the present invention to 
provide an improved seat adjuster for vehicle seat which permits an 
operation handle to be disposed adjacent to a center of a vehicle and 
lower under the seat to avoid contact of the handle with occupant's foot 
and clothes. 
To attain such purpose, the present invention, using the foregoing 
prior-art seat adjuster, comprises a first shaft and second shaft provided 
at the centerside slide rail (corresponding to the slide rail (1)), with 
such an arrangement that the first shaft (corresponding to that (8)) is 
disposed higher than the second shaft and connected with a locking 
mechanism (corresponding to that (6)), and that the second shaft is 
provided with a handle, wherein such second shaft is operatively connected 
with the first one via a link mechanism, and wherein a pull wire is at its 
one end connected to the second shaft for interlocking purpose in the dual 
slide rail and locking mechanism as described in the foregoing prior art 
description. 
Accordingly, the operation handle is disposed lower close to the floor of 
vehicle and adjacent to the center of vehicle, which makes the handle free 
from contact with foot or clothes of an occupant who enters or gets out of 
the vehicle at the door side. 
Further, in case of the seat being an assistant seat next to a driver's 
seat, a driver can easily reach the handle. 
In one aspect of the invention, the link mechanism is a vertically movable, 
parallel type of links, which prevents itself against contact with a seat 
cushion frame located adjacent the slide rail.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT OF THE INVENTION 
First of all, the present invention is based on the above-stated prior art, 
utilizing most of the elements and mechanisms therein, and thus all like 
designations to be used in the herein description correspond to all like 
ones given in the prior art description above. Description is omitted for 
the common elements between the present invention and prior art, for the 
sake of simplicity. 
Referring to FIGS. 3 and 4, there is shown a seat adjuster according to the 
present invention, which is applied to the vertical type of slide rail (2) 
with the locking mechanism (7, 6, 1a, 3a, 9). 
As is apparent, at the forward free end of the shaft (8) provided at the 
left-side support bracket (1), there is arranged a link mechanism (20). To 
that link mechanism (20), the operation handle (14) is connected, 
whereupon in contrast to the prior art, the operation handle (14) is 
disposed at the left side of the seat; namely adjacent to the center of an 
automobile (not shown). 
Specifically, in addition to the first bearing member (7) to which the 
shaft (8) is rotatably secured, another second bearing member (17) forming 
one of the link mechanisms (20) is fixed to the inner wall of the support 
bracket (1), such that the second bearing member (17) is disposed at the 
forward portion of the support bracket (1). 
The second bearing member (17) includes a pair of spaced-apart bearing 
sections: Namely, a first 
bearing section (17a) in which the forward end of the shaft (8) is secured 
rotatably, and a second bearing section (17b) in which the rearward end of 
drive shaft (18) is secured rotatably. 
The first and second bearing sections (17a)(17b) are disposed in a 
vertically offset relation with each other, such that the first one (17a) 
is at the same level with that of the shaft (8), higher than the second 
one (17b), whereas the second one (17b) is located lower adjacent to the 
lower edge of the support bracket (1), than the first one (17a). Hence, 
the drive shaft (18), which is supportively secured in the second bearing 
section (17b), is situated adjacent and along the lower edge of the 
bracket (1), whereupon the operation handle (14) fixed to the forward end 
of the drive shaft (18) is disposed close to a floor of automobile (not 
shown). 
Within the space between the first and second bearing members (17a)(17b), 
the rearward end of the drive shaft (18) and forward end of the shaft (8) 
project inwardly of the space in a manner opposing each other, and also in 
that space, the link mechanism (20) is disposed, by means of which, the 
drive shaft (18) is operatively connected to the shaft (8). 
The link mechanism (20) comprises a pair of upper and lower link members 
(20a)(20b), which are projected generally on a horizontal line in parallel 
with each other, and an intermediate link member (20c) which is interposed 
between the upper and lower link members (20a)(20b), thus forming a 
parallel link. 
The upper link member (20a) is at its base part fixed to the forward end of 
shaft (8) and at its outwardly projected free end connected pivotally to 
the upper end of the intermediate link member (20c). The lower link member 
(20b) is at its base part fixed to the rearward end of drive shaft (18) 
and at its free end connected pivotally to the lower end of the 
intermediate link member (20c). 
The drive shaft (18) is provided with a link piece (12), to which one end 
of the pull wire (13) is connected. 
Designation (11') denotes a link piece which is fixed to the forward end of 
another shaft (28) at other right-side bracket (not shown), which has been 
described in the previous prior art description. 
The pull wire (13) is at its another end connected to such link piece 
(11'), 
In this context, it is noted that, similar to the shaft (8') of the prior 
art, the shaft (28) extends along the right-side bracket opposite to the 
one (1) and is secured thereto rotatably, with its rearward portion being 
provided with a lock mechanism and spring similar to the ones (1a, 7, 6, 
10) at the left-side bracket (1). Thus, operational movement of the drive 
shaft (18) is transmitted to the shaft (18) through the wire (13) and link 
pieces (11, 12). 
The length of both upper and lower link members (20a)(20b) should be set to 
a degree that the intermediate link member (20c) is moved without contact 
with the seat cushion frame (15). 
With the above-described structure, when the operation handle (14) is 
rotated counterclockwise about the axis of the drive shaft (18) for 
unlocking purpose, as viewed from FIGS. 3 and 4, the lower link member 
(20b) is simultaneously rotated in the same direction, which causes upward 
movement of the intermediate link member (20c) to produce synchronized 
counterclockwise rotation between the upper and lower link members 
(20a)(20b). As such, those upper and lower link members (20a)(20b) are 
rotated in that direction, representing a crank motion on the whole to 
transmit the rotation to the shaft (8), whereby the shaft (8) is caused to 
be rotated counterclockwise, overcoming the biasing force of the spring 
(10), and the lock pawl (6) is rotated towards the inside of the bracket 
(1), thereby being disengaged from the lock slot (9) formed in the fixed 
rail (4). Then, the movable rail (3) is released from the locked state 
with the fixed rail (4), Likewise, at the same time, the other shaft (28) 
is caused to be rotated counterclockwise to effect the same unlocking 
actions, though not shown in the figures. 
Now, the seat is permitted to be adjusted forwardly and backwardly, with 
such unlocking state of the slide rail (2). 
After adjusting the fore-and-aft position of the seat, merely releasing the 
handle (14) allows the biasing force of the spring (10) to rotate 
clockwise the shaft (8), link members (20a, 20c) and drive shaft (18), to 
thereby return the lock pawl (6) to engagement into another selected one 
of the lock slots (9). 
Accordingly, by being constructed as above, the seat adjuster according to 
the present invention is endowed with the following advantageous effects: 
(i) The operation handle (14) is located at the side of the seat adjacent 
to the center of the automobile, as opposed to the prior-art handle (14) 
being located at the door side of the same. Thus, the handle (14) is 
completely free from contact with the occupant's foot or clothes. 
Particularly, in case of the seat being an assistant seat next to a 
driver's seat, a driver can easily reach and operate the handle (14) for 
adjustment of the assistant seat. 
(ii) The operation handle (14) is located at a lower level close to the 
floor of the automobile, by virtue of the lower disposition of the drive 
shaft (18) and vertically offset arrangement of the two bearing sections 
(17a)(17b) with link mechanism (20). This greatly reduces the possibility 
of the occupant's foot or lower part of his or her clothes being caught by 
the handle (14). 
(iii) In contrast to the link piece (11) of the prior art, the vertically 
movable, parallel-type link mechanism (20) is positively prevented against 
contact with the adjacent seat cushion frame (15). 
While having described the invention thus far, it should be understood that 
the embodiments are not necessarily restrictive thereto, but any other 
modifications, replacements and additions may structurally be possible 
without departing from the scope and spirit of the appended claims. For 
example, the pull wire (13) may be arranged lower with modification of the 
link pieces (11)(18), and further may be other rod member, instead of 
wire. The bracket (1), slide rail (2), lock pawl (6) and lock slots (9) 
may be formed in other proper structures.