Please select the most similar patent number from A, B, C and D. Which number is?
A chair capable of being used as a bed, comprising a seat (1), a back (2) rotatably connected to one end of the seat (1), a headrest part (3) rotatably connected to the top of the back (2), and an angle adjustment device mounted on the back (2). The angle adjustment device comprises a connecting rod holder (4) movably engaged with the back (2), a locking mechanism (5) engaged with the back (2) and capable of moving back and forth along a height direction of the back (2), and a first connecting rod (6) supported between the locking mechanism (5) and the seat (1). The headrest part (3) is provided with an engagement part (7) that protrudes to one side of the top of the connecting rod holder (4) and drives the headrest part (3) to rotate towards the seat (1) under the pushing caused by the movement of the connecting rod holder (4). The back (2) can reciprocate between a first position and a second position relative to the seat (1). When the back (2) is at the first position, the back (2) is inclined relative to or perpendicular to the seat (1), and the headrest part (3) is parallel to the back (2); when the back (2) is at the second position, the back (2) is parallel to the seat (1), the locking mechanism (5) gets close to the headrest part (3), and the headrest part (3) is inclined relative to or perpendicular to the back (2). The chair can implement quick bed/chair switching, and is simple to operate.
A: Disclosed is an office lounge chair, comprising chair legs (21), and a chair seat (1) and a chair back (22) which are arranged above the chair legs (21), wherein the chair seat (1) is provided with a footrest adjustment mechanism, with the front end of the footrest adjustment mechanism being provided with a foot pad body (2); the footrest adjustment mechanism comprises at least two telescopic rods (4) fixed in the chair seat (1), with the front ends of the telescopic rods (4) extending into the foot pad body (2) and being fixedly connected to the foot pad body (2), and the telescopic rods (4) extending or retracting and driving the foot pad body (2) to be unfolded or folded; and the front end of the chair seat (1) is further provided with an accommodation space, and when the foot pad body (2) is in a folded state, the foot pad body (2) is collapsed in the accommodation space. The footrest adjustment mechanism of the foot pad body (2) has a simple structure, and is convenient to assemble. In addition, the chair back (22) is provided with a back rest (23), thereby greatly improving the human body comfort.
B: A multi-function safety seat for a driver seat of a vehicle, having a seat surface (1), a seat back (2), and a headrest (3). The seat back (2) is movably provided behind the seat surface (1), and the headrest (3) is provided above the seat back (2). A steering device is provided on the rear side of the seat back (2), and the steering device comprises a height regulator (4) and an angle regulator (5). The angle regulator (5) is provided with two swing arms (5-2, 5-3) which can rotate relative to each other around the axis. The tail end of one swing arm (5-2) is directly and fixedly connected to the rear side of the seat surface (1). The tail end of the other swing arm (5-3) is fixedly connected to the tail end of the height regulator (4). The height regulator (4) is fixedly connected to the bottom end of the seat back (2) and can regulate the movement of the seat back (2) in the up-down direction with respect to the seat surface (1). The height regulator (4) is a screw drive device which is provided with a screw sleeve (4-1), a screw (4-2), and a stepping motor (4-3). The screw sleeve (4-1) is a sleeve with internal threads, the mating screw (4-2) is provided on the screw sleeve (4-1), and the tail end of the screw (4-2) is dynamically connected to the stepping motor (4-3).
C: An adjustable seat headrest mounted on a backrest comprises supports (1). The support (1) is provided with a headrest plate (2) at an upper end thereof and a fixing plate (7) at a right end thereof. A soft bag (4) is provided at the exterior of the headrest plate (2). A lower end of the fixing plate (7) is connected, by means of a toothed rod (6), to a lower end of the headrest plate (2). A movable sleeve (8) is sleeved onto the support (1). The movable sleeve (8) is connected to a U-shaped support (10) by means of a movable support (9). There are two of each of the support (1), the movable sleeve (8) and the movable support (9), respectively. A horizontal adjustment motor (5) is disposed at a lower end of one of the movable sleeves (8). An output terminal of the horizontal adjustment motor (5) is provided with a gear (17) engaging the toothed rod (6). The U-shaped support (10) is provided with a headrest control center (3) thereon, and has one end provided with a gear support (11) connected to a stationary gear (18) and the other end hinged with a hinged angle-adjustable support (14). The interior of the gear support (11) is provided with an angle-adjusting screw (12) engaging the stationary gear (18). The angle-adjusting screw (12) is connected to an angle-adjusting motor (13). An arc-shaped rest-plate (15) is disposed at an upper portion of the hinged angle-adjustable support (14). There are two arc-shaped rest-plates (15). The two arc-shaped rest-plates (15) are mutually connected by connecting an arc angle adjusting motor (16) fixed to one of the arc-shaped rest-plates (15) to an arc angle adjusting screw (19) fixed to the other arc-shaped rest-plate (15). The invention solves a problem in the prior art in which a seat headrest cannot be adjusted forward and backward automatically, and is comfortable and convenient.
D: The present invention relates to a passenger seat, an assembled chair-bed dual-purpose seating unit, and a multi-purpose seating unit. A chair-bed dual-purpose seat comprises a support (3), a seat (2), a back support (1), and a back support frame. The seat (2) is provided on and supported by the support (3); the back support (1) is provided on the support (3) via the back support frame; the lower portion of the back support frame is hinged to the support base (3); the back support (1) is hinged to the upper portion of the back support frame; the back support (1) is able to rotate relative to the back support frame and able to revolve relative to the support (3) along with the back support frame; a angle-adjusting device is provided between the back support frame and the support (3); a back support locking and unlocking device is provided between the back support (1) and the back support frame. The back support frame comprises at lease one main connecting rod (4), the lower portion of the main connecting rod (4) is hinged to the support (3); the upper portion of the main connecting rod (4) is hinged to the back support (1). By assembling a chair-bed dual purpose seat with another same seat, the assembled chair-bed dual-purpose seating unit enables improved comfort and utilization rate.
Answer: D