Unlocked-state retention device and seat assembly having the same

1. A seat assembly comprising:

a base frame;

a seat body removably mounted on said base frame;

a locking unit that releasably interlocks said base frame and said seat body when said seat body is mounted on said base frame, said locking unit being operable

to lock said seat body relative to said base frame so that said seat body is placed in a locked state, where said seat body is irremovable from said base frame, or

to unlock said seat body relative to said base frame so that said seat body is placed in an unlocked state, where said seat body is removable from said base frame; and

an unlocked-state retention device that separates said seat body from said base frame and thereby prevents said seat body from moving to the locked state when said seat body is in the unlocked state,

wherein:

said locking unit has

a socket formed in an upper surface of said base frame,

a column body that projects downwardly from a bottom surface of said seat body and extends into said socket when said seat body is disposed on said upper surface of said base frame, and

tongue that is mounted slidably in said base frame and operable to move between a projecting position where a distal portion of said ton ue projects into said socket, and a retracted position where said distal portion of said tongue is retracted from said socket, and

said column body has a locking groove that is engaged with said tongue to place said seat body in the locked state when said distal portion of said tongue is at the projecting position,

wherein said unlocked-state retention device includes a pusher that is disposed movably in said seat body and includes a push member to retractably project from said bottom surface of said seat body and to push said upper surface of said base frame when said seat body is in the unlocked state,

wherein said pusher further includes a first resilient member disposed between said push member and said seat body to urge said push member when said seat body is in the unlocked state, said push member being retracted into said seat body when said seat body is in the locked state, and

wherein:

said push member is disposed in proximity to said column body;

said column body further has a column bottom surface that is opposite to said bottom surface of said seat body, and a column side surface that extends from said column bottom surface to said bottom surface of said seat body and that is formed with said locking groove;

said column body further has a restricting groove that is indented from said column side surface; and

said push member extends partially into said restricting groove such that said push member is restricted from projecting from said bottom surface of said seat body beyond a limited distance.

2. The seat assembly as claimed in claim 1 , wherein said locking groove is indented from said column side surface and is in spatial communication with said restricting groove.

3. The seat assembly as claimed in claim 1 , wherein said distal portion of said tongue is wedge-shaped.

4. The seat assembly as claimed in claim 3 , wherein said locking unit further includes a second resilient member that is disposed between said tongue and said base frame for biasing said tongue toward the projecting position.

5. The seat assembly as claimed in claim 4 , wherein said second resilient member is configured as a spring.

6. The seat assembly as claimed in claim 5 , further comprising an operating member that is mounted slidably in said base frame for operating said tongue between the projecting position and the retracted position.

7. The seat assembly as claimed in claim 1 , wherein said unlocked-state retention device includes two of said pushers that are disposed respectively at left and right sides of said seat body.

8. The seat assembly as claimed in claim 7 , wherein said base frame includes a main frame, a base body mounted on said main frame to support said seat body, and a cover plate mounted under said base body.

9. A seat assembly, comprising:

a base frame;

a seat body removably mounted on said base frame;

a locking unit that releasably interlocks said base frame and said seat body and operable

to lock said seat body relative to said base frame so that said seat body is placed in a locked state, where said seat body is irremovable from said base frame, or

to unlock said seat body relative to said base frame so that said seat body is placed in an unlocked state, where said seat body is removable from said base frame,

an unlocked-state retention device that separates said seat body from said base frame, and thereby prevents said seat body from moving to the locked state when said seat body is in the unlocked state;

an operating member mounted slidably in said base frame for operating said tongue between the projecting position and the retracted position

wherein:

said locking unit has

a socket that is formed in an upper surface of said base frame,

a column body that projects downwardly from a bottom surface of said seat body and that extends into said socket when said seat body is disposed on said upper surface of said base frame, and

a tongue that is mounted slidably in said base frame and operable to move between a projecting position where a distal portion of said tongue projects into said socket and a retracted position where said distal portion of said tongue is retracted from said socket, and

said column body has a locking groove that is engaged with said tongue to place said seat body in the locked state when said distal portion of said tongue is at the projecting position,

wherein said distal portion of said tongue is wedge-shaped,

wherein said locking unit further includes a second resilient member disposed between said tongue and said base frame for biasing said tongue toward the projecting position,

wherein said second resilient member is configured as a spring, and

wherein said operating member and said tongue slide respectively in two perpendicular directions, said operating member being formed with an elongate pin hole that extends in a direction inclined with respect to the two perpendicular directions, said locking unit further including a sliding pin that is connected co-movably to said tongue and that connects pivotally said tongue to said operating member, said sliding pin extending slidably through said elongate pin hole.