Patent Application
20080129099
1. Technical Field
The present invention relates to seats of power wheelchairs, and more particularly, to a seat reclining mechanism for a power wheelchair.
2. Description of Related Art
Power wheelchairs, such as electric wheelchairs or motorized wheelchairs are mobility assistive devices commonly provided to disabled people or bed-bound patients for allowing them to move self-reliantly. Thus, good adaptability and maneuverability are obviously important in wheelchairs. For meeting such need, some wheelchairs may be equipped with reclining chairs for providing the users with comfortable and convenient usage.
As everyone knows, a chair is basically composed of a seat portion and a back portion, which is settled roughly perpendicular to the seat portion. A pair of arm rests and footrests may be also attached for the user's comfort. Further, the seat is preferable to possess position angle variability for providing convenience to the user for his movement between the wheelchair and a bed under or without others' assistance. Thus, it is desirable that a seat of a wheelchair can be reclined into a flat shape. To form such flat shape, the back portion has to perform a pivot motion with about a 90-degree pivot angle and the arm rests as well as footrests have to move toward an altitude approximately close to the seat.
Since the center-of-gravity position of a human body can consequently shift from hips toward the lumbar and back regions during reclining, person sitting on a reclining chair designed without consideration of gravity adjustment may fall down therefrom during operation of the reclining mechanism. Thus, a need exists for a seat reclining mechanism, which is capable of reclining the back portion and shifting the seat portion thereof in harmony with the center-of-gravity position of the wheelchair it attached to synchronously.
The present invention has been accomplished under the circumstances in view and provides a seat reclining mechanism comprising an actuator and a plurality of linkages mechanistically connected mutually.
It is one object of the present invention to provide a seat reclining mechanism for a power wheelchair which can be adjusted from an initial seat position to a reclined flat position to provide a horizontal carrying surface for facilitating a user's riding or alighting from the wheelchair.
It is another object of the present invention to provide a seat reclining mechanism for a power wheelchair, which keeps the center-of-gravity positions of both the wheelchair user and the wheelchair coincided through the reclining motions thereof, so that a safe and steady change of posture of the wheelchair user can be ensured.
It is still another object of the present invention to provide a seat reclining mechanism for a power wheelchair which accomplishes a smooth seat-reclining movement by implementing a single actuator and an ingenious linkage system with small costs and mechanical loading.
The invention as well as a preferred mode of use, further objectives and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings, wherein:
According to a concept of the present invention, the disclosed seat reclining mechanism can be applied to a mobility assistive device, such as a power wheelchair 100. As shown in
The orientation related to the seat reclining mechanism is firstly defined for further description. In following description, alleged front is referred to an end thereof corresponding to the actuating direction of the actuator 10, while the opposite end is defined as the rear.
The details of the seat reclining mechanism according to the present invention are to be elaborated in the following description. First, four junction points 92 on the stationary bracket 90 and four junction points 222 on the bottom of the seat frame 20 are arranged correspondingly and between each pair of the corresponding junction points 92, 222, a first bracket link 242 is provided to hold the seat frame 20 above the stationary bracket 90.
The back frame 40 is pivotably arranged at the rear end of the seat frame 20 and has a pair of junction points 422 positioned respectively at the lower ends of both sides thereof. To link up the stationary bracket 90 with each junction point 422 of the back frame 40, a second bracket link 442 is provided therebetween.
A connecting portion 226 is extended form the central bottom of the seat frame 20 and drivably connected to the actuator 10.
Through foresaid structure, when the seat reclining mechanism is at its initial seat position, as shown in
When the actuator 10 is started, the connecting portion 226 at the bottom of the seat frame 20 is pushed forward and renders the four first bracket links 242 oscillating forward synchronously. Such oscillations in turn cause the seat frame 20 to move forward smoothly and stably and stop at a predetermined advanced position. At this point, each first bracket link 242 is reclined with respect to the relevant junction point 92 on the stationary bracket 90.
As the seat frame 20 is pushed forward, the back frame 40 that is mounted at the rear end thereof is pulled forward proceedingly. Since the back frame 40 is further fastened to the stationary bracket 90 by the second bracket links 442, it is restrained from moving forward vertically and pulled to recline gradually along moving forward. Eventually, the back frame 40 is brought into a level position, as shown in
The disclosed seat reclining mechanism still comprises a pair of leg support linkages 60, as shown in
According to foregoing structure, when the seat reclining mechanism is at its initial seat position, the third bracket links 646 are approximately perpendicular to the stationary bracket 90, and the intermediate links 644 are also positioned approximately perpendicular to the stationary bracket 90 so that the footrest bars 648 as well as the footrests 622 are consequently oriented toward the ground.
When the actuator 10 is started, the seat frame 20 is pushed forward as previously discussed and in turn presses the bent link arm 642 forward to give an impetus to the intermediate link 644. At this point, the advancement of the intermediate link 644 lifts up the third bracket link 646 which is further fastened to the stationary bracket 90 and cause the intermediate link 644 to pivot on the bent link arm 642 and stop at an approximate level position. Thereby, the third bracket links 646, the intermediate link 644, leg rest 624 as well as the footrest 622 are relatively spread in a horizontal direction, as shown in
Also, referring to
Through said structure, when the disclosed seat reclining mechanism is at its initial seat position, the armrests 80 can be propped up by the L-shaped crutch 802 and maintained at a position horizontal to the seat frame 20, as shown in
Furthermore, a seat cushion 26 may be fixed to the seat frame 20 while a back cushion 48 is slidably attached to the back frame 40. As can be seen in
For achieving above shifting motion of the back cushion 48, according to the present embodiment, the back cushion 48 having a height smaller than that of the back frame 40 includes two sets of clamping pieces 482 for holding a pair of vertical bars 426 provided on the back frame 40, a reversed U-shaped frame 464 having a height similar to that of the back cushion 48 which is fixedly attached to the clamping pieces 482 beyond the vertical bars 426 and a pair of elongated guide slots 262 are provided at the lower back side of the back cushion 48 to receive a pair of extensible rods 468 each having a sleeve part fixed to the inner side of each back frame link 844 and thus the back cushion 48 with the sliding device is accomplished. In addition, the reversed U-shaped frame 464 may comprise a headrest holder 466 whereon a headrest 49 can be mounted in an adjustable way.
By the disclosed structure, when the seat reclining mechanism of the present invention is at the initial seat position, as the extensible rod 468 is now retracted, the back cushion 48 can be positioned at the upper portion of the back frame 40. When the actuator 10 is started, as the back frame 40 and back frame links 844 are pulled to move as previously described, the extensible rod 468 is therefore inclined and elongated to push the back cushion 48 to shift forward along the reclining back frame 40. Thus, when the seat reclining mechanism finally comes to the reclined flat position, the distance between the seat cushion 26 and the back cushion 48 as well as the headrest 49 are closer than the distance therebetween at the initial seat position so as to respond to the changes of the positions of a user's head and back when he has a posture change from setting to laying.
According to the presently discussed embodiment, a power wheelchair equipped with the disclosed seat reclining mechanism can be seen at the initial seat position in
Whereas, when the actuator 10 is operated reversely, the seat reclining mechanism has all the components driven to move reversely according to foresaid motions and returns to the initial seat position from the reclined position as shown in
Although a particular embodiment of the invention has been described in detail for purposes of illustration, it will be understood by one of ordinary skill in the art that numerous variations will be possible to the disclosed embodiments without going outside the scope of the invention as disclosed in the claims.
