Chairs and seats – Movable back – Tiltable
Reexamination Certificate
1999-06-10
2001-12-11
Barfield, Anthony D. (Department: 3624)
Chairs and seats
Movable back
Tiltable
C297S369000
Reexamination Certificate
active
06328382
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a reclining seat having a seat cushion and a seat back pivotally mounted on the seat cushion and, in particular but not exclusively, to a locking structure for the reclining seat to lock the seat back relative to the seat cushion.
2. Description of the Related Art
Japanese Laid-Open Patent Publication (unexamined) No. 8-214978 discloses a reclining structure for use in a reclining seat. This reclining structure includes a lower arm mounted on a rear end of a seat cushion, an upper arm mounted on a lower end of a seat back, an internally-toothed gear formed on the upper arm, a pair of protruding portions formed on the lower arm and placed inside the internally toothed gear, two guide grooves defined between the pair of protruding portions, and a pair of pawls received in the two guide grooves, respectively, so as to be movable in opposite directions.
The pair of pawls are placed symmetrically with respect to an operation shaft connected to an operation lever. Upon operation of the operation lever, the pair of pawls are moved between a locked position where the pawls engage with the internally-toothed gear and an unlocked position where the pawls disengage from the internally-toothed gear. When the pawls are held at the locked position, rotation of the seat back about the operation shaft is prevented, thereby maintaining the posture of the seat back relative to the seat cushion. In contrast, when the pawls are held at the unlocked position, the angle of inclination of the seat back relative to the seat cushion can be changed by rotating the seat back about the operation shaft.
Recently, the locking structure tends to be made compact, followed by miniaturization of its component parts. However, if the size of the pawls is reduced, the area of contact between the pawls and the pair of protruding portions is reduced. As a result, the pawls cannot be positively supported by the protruding portions and readily chatter within the guide grooves, thus making it impossible to stably maintain the posture of the seat back and lowering the comfort of sitting on the seat.
Furthermore, it is likely that a “biased action” will occur in which only one of the pawls is held in mesh with the internally-toothed gear due to manufacturing errors, making it difficult to set the seat back at a desired angle of inclination.
SUMMARY OF THE INVENTION
The present invention has been developed to overcome the above-described disadvantages.
It is accordingly an objective of the present invention to provide a locking structure for a reclining seat capable of locking the seat back relative to the seat cushion without looseness and preventing the “biased action” of the pair of pawls.
Another objective of the present invention is to provide the locking structure of the above-described type which can be readily manufactured at a low cost.
In accomplishing the above and other objectives, a locking structure according to the present invention includes a first bracket fixed to the seat cushion and a second bracket fixed to the seat back. First and second projections are formed on one of the first and second brackets, and each of them has first and second flat surfaces opposite to each other. The first and second flat surfaces of the first projection confront the second and first flat surfaces of the second projection, respectively, and extend parallel thereto. The other of the first and second brackets has a recess defined therein and an internally-toothed gear formed around such recess. The first and second projections are received in the recess so that the second bracket can be rotated relative to the first bracket. The locking structure also includes first and second lock gears each having a pawl engageable with the internally-toothed gear. The first lock gear is slidably interposed between the first flat surface of the first projection and the second flat surface of the second projection, while the second lock gear is slidably interposed between the second flat surface of the first projection and the first flat surface of the second projection. A cam is provided to move the first and second lock gears selectively away from and towards each other; and a cam shaft is connected to the cam for rotation together therewith and is loosely inserted into a center hole defined in the first bracket and into a center hole defined in the second bracket.
According to the above-described locking structure, rotation of the seat back relative to the seat cushion is normally prevented by the engagement of the pair of pawls with the internally-toothed gear, thereby maintaining the angle of inclination of the seat back. When the cam is rotated in a predetermined direction, the pair of lock gears are moved towards each other while being guided along the first and second projections, respectively, thereby releasing the engagement of the pawls with the internally-toothed gear. As a result, the second bracket is allowed to rotate about the cam shaft, making it possible to rotate the seat back relative to the seat cushion.
Thereafter, when the seat back has been set at a desired angle of inclination and when the cam is rotated in a direction opposite to the predetermined direction referred to above, the pair of lock gears are moved away from each other and the pawls are brought into engagement with the internally-toothed gear, thereby preventing rotation of the second bracket about the cam shaft and maintaining this posture of the seat back relative to the seat cushion.
Furthermore, because the cam shaft is loosely inserted into the center holes of the first and second brackets, even if the longitudinal axis of the cam shaft is not properly aligned therewith, the cam can be smoothly rotated by the cam shaft, making it possible to positively operate the pair of lock gears and prevent the “biased action” which has been hitherto caused due to dimensional errors and in which only one of the lock gears is held in engagement with the internally-toothed gear.
Advantageously, each of the first and second lock gears has first and second flat surfaces extending in a direction of movement thereof. In this case, when the cam is rotated, the first flat surface of the first lock gear is held in sliding contact with the second flat surface of the second lock gear, while the second flat surface of the first lock gear is similarly held in sliding contact with the first flat surface of the second lock gear.
With this arrangement, not only are the pair of lock gears held in sliding contact with each other along the flat surfaces thereof extending in the direction of movement thereof, but also both of them are guided by the two guide members under the condition in which the former are interposed between the latter, thereby reducing looseness of the lock gears.
Conveniently, third and fourth projections are formed on the first and second projections, respectively, and slidably received in a guide groove formed radially inwardly of the internally-toothed gear.
With this arrangement, because the internally-toothed gear is positioned radially outwardly of the guide groove, it becomes possible to reduce the locking pitch (the central angle of two neighboring teeth of the internally-toothed gear) at which rotation of the second bracket relative to the first bracket is locked, resulting in accurate positioning of the seat back.
REFERENCES:
patent: 5749626 (1998-05-01), Yoshida
patent: 5762400 (1998-06-01), Okazaki et al.
patent: 5816656 (1998-10-01), Hoshihara et al.
patent: 5873630 (1999-02-01), Yoshida et al.
patent: 0 232 192 (1987-08-01), None
patent: 0 773 133 (1997-05-01), None
patent: 0 858 927 (1998-08-01), None
patent: 8-214978 (1996-08-01), None
Barfield Anthony D.
Delta Kogyo Co. Ltd.
Wenderoth , Lind & Ponack, L.L.P.
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