Abstract:
A backrest structure for strollers has a linkage bar to connect the frame and the backrest to enable the backrest of the stroller to be folded or anchored synchronously with the collapsing or extending of the frame. The backrest structure includes a backrest adjusting means to provide the aforesaid linkage movement and also offer multiple stage adjustment of the backrest angle.

Description:
FIELD OF THE INVENTION  
         [0001]    The invention relates to a backrest structure for strollers that is movable synchronously with the stroller frame and adjustable angularly in multiple stages.  
         BACKGROUND OF THE INVENTION  
         [0002]    Strollers (infant carriers) are generally designed with a collapsible function to facilitate carrying and storage. Many folding features have been developed over the years to enhance operation effectiveness. For instance, U.S. Pat. No. 5,454,584 discloses a collapsible stroller that has a frame movable between a collapsed position and an operating position. It has a back movable between a first position (sitting position) and a second position (recumbent position). A latch means is provided between the frame and the back that includes a boss in a rear leg tube and a slot on a latch. The boss may be positioned within the slot to keep the back at the first position. The latch means, back and frame are so designed that when the back is at the first position, the frame may be moved from the operating position to the collapsed position, and when the boss is separated from the slot, the latch means automatically releases the back to allow the back to move (drop) automatically to the second position. Hence users do not need to release the back separately to fold the stroller. Although the cited patent claims it enables the back to move (drop) automatically when the stroller is folding, the boss cannot always overcome the friction between the slot and the boss and separate smoothly from the slot. As a result, the back does not always move automatically as desired. Thus users have to release the back separately to fold the stroller. There is a need to design an improved backrest mechanism to fold the back effectively and safely.  
         SUMMARY OF THE INVENTION  
         [0003]    The primary object of the invention is to provide a backrest structure that has a linkage bar between the frame and the backrest so that the backrest may be folded or extended synchronously with the collapsing or extension of the frame. The backrest structure maintains the stability of the backrest while the stroller is moving to improve the safety of the infant.  
           [0004]    Another object of the invention is to provide a backrest adjusting means to enable the backrest to interact with the linkage bar and provide multiple stages of adjustment for the angle of the backrest to enhance comfort for the infant.  
           [0005]    According to the invention, the stroller includes a frame movable between a sitting position and a collapsed position and a loading rack having an anchor section, which has a portion for seating the passenger. The backrest structure of the invention includes a backrest adjusting means that is pivotally mounted on the anchor section, a movable backrest that is pivotally engaged with the backrest adjusting means and is movable between a first position and a second position when the frame is at the sitting position—with the passenger sitting generally upright when the backrest is at the first position and lying rearwards when the backrest is at the second position—and a linkage bar with a first end pivotally engaged with the frame and a second end pivotally engaged with the backrest adjusting means. When the frame is at the sitting position, the linkage bar supports the backrest adjusting means and the backrest at the first position. When the frame is moved from the sitting position to the collapsed position, the frame moves the linkage bar and pushes the backrest adjusting means to make the backrest turn synchronously with the frame and fold at the second position to enable the stroller be folded smoothly. In addition, when the frame is at the sitting position, the backrest adjusting means may be adjusted in multiple stages to alter the angle of the backrest to suit the passenger&#39;s requirements.  
           [0006]    The foregoing, as well as additional objects, features and advantages of the invention will be more readily apparent from the following detailed description, which proceeds with reference to the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]    [0007]FIG. 1 is a schematic view of the stroller of the invention at the sitting position.  
         [0008]    [0008]FIG. 2 is an exploded view of the backrest adjusting means of the backrest structure of the invention.  
         [0009]    [0009]FIG. 3 is a schematic view of the backrest structure of the invention at the lying position according to FIG. 1.  
         [0010]    [0010]FIG. 4 is a schematic view of the stroller of the invention at the collapsed position.  
         [0011]    [0011]FIG. 5 is a perspective view of the invention according to FIG. 1, with the backrest at the first position.  
         [0012]    [0012]FIG. 6 is a fragmentary perspective and enlarged view of the invention according to FIG. 4, with the backrest at the second position. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0013]    Refer to FIG. 1 for a stroller  1  at a sitting position. The stroller  1  has a frame  10  that includes a push tube (first rack)  11 , a front leg tube (second rack)  12 , a rear leg tube (third rack)  13 , a latch means  14  and a seat tube (loading rack)  20 . The seat tube includes an anchor section  20   a  that has a portion for seating a passenger.  
         [0014]    The push tube  11  has a first end connecting to a handle  11   a  and a second end pivotally engaging with the latch means  14 . The front leg tube  12  has a first end fastening to the latch means  14  and a second end engaging with a plurality of front wheels  12   a.  The front leg tube  12  further has a pivotal point  12   b  between the first end and the second end to pivotally engage with the anchor section of the seat tube. The rear leg tube  13  has a first end pivotally engaging with the latch means  14  and a second end engaging with a plurality of rear wheels  13   a.  The rear leg tube  13  further has a pivotal point  13   b  between the first end and the second end to pivotally engage with the anchor section of the seat tube. The latch means  14  may latch or separate the push tube  11  and the front leg tube  12 . The structure of the latch means  14  is known in the art and forms no part of the invention. Any conventional latch mechanism that provides latching or separating functions may be adopted, such as the one disclosed in U.S. Pat. No. 5,454,584.  
         [0015]    The backrest structure for the stroller of the invention includes a movable backrest  20   b,  a backrest adjusting means  40  and a linkage bar  30 .  
         [0016]    Referring to FIGS. 1 and 2, the backrest adjusting means  40  includes a rotary member  41 , an anchor member  42  and a spring  60 . The rotary member  41  has one end forming a stepwise surface  41 ′ and has a first pivotal point  41  a to pivotally engage with the backrest  20   b,  a second pivotal point  41   b  to pivotally engage with the anchor section  20   a,  and a third pivotal point  41   c.    
         [0017]    The anchor member  42  is coupled with the backrest  20   b  and has one end forming a stepwise surface  42 ′ mating and engaging with the stepwise surface  41 ′ of the rotary member  41 . The spring  60  is located inside the backrest  20   b  to provide force to allow the anchor member  42  to engage with the rotary member  41 . When the stroller  1  is at the sitting position (as shown in FIG. 1), the stepwise surface  42 ′ of the anchor member  42  engages with the stepwise surface  41 ′ of the rotary member  41 , and the backrest  20   b  is erected upwards at the first position (as shown in FIG. 1) to provide back support for the sitting infant or child. When the anchor member  42  is separated from the rotary member  41 , the backrest  20   b  may be turned about the first pivotal point  41   a  to the lying position (as shown in FIG. 3).  
         [0018]    When the stepwise surfaces  41 ′ and  42 ′ have only one step, the backrest has only the first position and the lying position for two-stage adjustment. When the stepwise surfaces  41 ′ and  42 ′ have more than one step, the backrest may have adjusting inclination of three stages or more.  
         [0019]    The linkage bar  30  has one end  30   a  pivotally engaging with the pivotal point  13   c  of the rear leg tube  13  and a second end  30   b  pivotally engaging with the third pivotal point  41   c  of the rotary member  41 . When the stroller is at the sitting position and the backrest  20   b  is at the first position and erecting upwards, the linkage bar  30  supports the rotary member  41  and the backrest  20   b.    
         [0020]    When the stroller is moved from the sitting position to the collapsed position for folding (as shown in FIG. 4), the rear leg tube  13  turns about the pivotal point  14   a  of the latch means  14 , drives the linkage bar  30  and pushes the backrest adjusting means  40  to turn about the second pivotal point  41   b.  Thus the backrest  20   b  is turned synchronously with the rear leg tube  13  to the second position for folding (as shown in FIG. 6).  
         [0021]    The following is a summary of the movement principle and function of the backrest structure of the invention. When the stroller  1  is moved from the sitting position (as shown in FIG. 1) to the collapsed position (shown in FIGS. 4 and 6), first, the user releases the latched condition of the latch means  14  to separate the push tube  11  from the front leg tube  12 . Next, the user moves the handle  11   a  of the push tube  11  to turn clockwise about the pivotal point  14   b  of the latch means according to FIG. 1, the push tube  11  is moved close to the front leg tube  12  and drives the rear leg tube  13  at the same time, and the rear leg tube  13  turns about the pivotal point  14   a  of the latch means and moves to the front leg tube  12 . Meanwhile, the rear leg tube  13  drives the anchor section  20   a  of the seat tube to turn about the pivotal point  12   b  and moves to the front leg tube  12 . The rear leg tube  13  drives the linkage bar  30  at the same time. The linkage bar  30  exerts force on the third pivotal point  41   c  of the backrest adjusting means  40  through one end  30   b  to make the backrest adjusting means  40  turn clockwise about the second pivotal point  41   b.  Thereby the backrest  20 , which is folded onto the backrest adjusting means  40 , is turned synchronously towards the seat tube  20   a  until it reaches the second position (as shown in FIG. 6).  
         [0022]    In contrast, when the stroller  1  is moved from the collapsed position (FIG. 4) to the sitting position (FIG. 1), the backrest adjusting means  40  is driven by the linkage bar  30  and turns the backrest  20   b  synchronously to the sitting position of the stroller  1  for anchoring (FIG. 1).  
         [0023]    In addition, when the stroller  1  is at the sitting position, and is moved to separate the complementary surfaces  41 ′ and  42 ′ of the rotary member  41  and the anchor member  42 , the backrest  20   b  may be turned about the first pivotal point  41   a  to the lying position, which is almost on the same plane as a portion of the anchor section  20   a,  so that the infant may be laid thereon. It is to be understood that in such a condition, when folding the stroller, the linkage bar  30  also drives the rear leg tube  13  and the backrest adjusting means  40  to move synchronously. During the folding process the anchor member  42  of the backrest adjusting means  40  automatically latches onto the rotary member  41 , as shown in FIG. 6.  
         [0024]    The novel design of the backrest structure of the invention enables the backrest of the stroller to turn synchronously with the collapsing or extending of the frame for folding or anchoring. In addition, the linkage bar can support the backrest adjusting means  40 , and therefore can maintain the stability of the backrest  20   b  latched on the backrest adjusting means  40  to enhance the safety of the infant while the stroller is moving.  
         [0025]    While the preferred embodiment of the invention has been set forth for the purpose of disclosure, modifications of the disclosed embodiment of the invention as well as other embodiments thereof may occur to those skilled in the art. Accordingly, the appended claims are intended to cover all embodiments which do not depart from the spirit and scope of the invention.