Abstract:
The apparatus is a highly maneuverable, curb mounting double baby stroller. To improve maneuverability, the rear wheels are placed closer than usual to the front wheels, decreasing the wheelbase and providing greater leverage between the rear wheels and the rear handle. To compensate for the instability caused by the reduced wheelbase, a trailing support is provided behind the rear wheels. The trailing support may be a simple bar extension or have small wheels. The trailing support can be unlatched to permit it to pivot for lifting the front wheels to mount a curb.

Description:
[0001]     This application is based upon provisional patent application Ser. No. 60/485,417 filed Jul. 8, 2003. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     The invention deals generally with push type child transport vehicles such as baby strollers and similar vehicles and more specifically with a stroller or other similar vehicle that is easier to maneuver on flat surfaces and to raise over obstacles such as street curbs.  
         [0003]     Baby strollers are well known and commonly used in our culture, but some of the problems in their use are not appreciated because they are not apparent to users of typical strollers. However, several of these problems are greatly exaggerated when a stroller is constructed and used to transport two children. Most such strollers are built so that the two children sit one in front of the other, and that significantly increases the length of the stroller. That extra length and the extra weight of a second child then raise problems that are not as severe with strollers used for a single child.  
         [0004]     One such problem is limited maneuverability. The added length and weight make it much more difficult just to turn the stroller, but an even greater problem occurs when raising such a stroller over a street curb or even a door sill. It is almost impossible for an average person to lift a stroller with two children up and onto such an obstruction.  
         [0005]     It would very beneficial to have a stroller that could be maneuvered easier than the typical double stroller and which could be moved over a curb or similar obstruction without lifting as much of the weight.  
       SUMMARY OF THE INVENTION  
       [0006]     The present invention alleviates the problem of maneuvering a double stroller by changing the basic geometry of the stroller, and once the benefits of the new geometry are appreciated it becomes apparent that the geometry will also improve the maneuverability of single child strollers, baby carriages, and other similarly constructed vehicles.  
         [0007]     The new geometry is essentially an increase in the ratio of the handle rearward extension to the wheelbase, however, since it is undesirable to increase the overall length of the stroller, in the preferred embodiment, this change of ratio is accomplished by reducing the wheelbase.  
         [0008]     The wheelbase of a typical double stroller, the distance between the front and rear axles, usually measures between 27 and 29 inches, while the handle rearward extension, the horizontal distance between the center of the handle grip and the rear axle, typically ranges from 9 to 11 inches. Typical strollers have a handle rearward extension which is ⅓ the length of the wheelbase.  
         [0009]     In the preferred embodiment of the stroller of the present invention the wheelbase is reduced to 22.13 inches while the handle rearward extension is increased to 17.31 inches. These changes increase the total of these two dimensions by only 0.58 inch, but produce a geometry in which the handle rearward extension is ¾ the length of the wheelbase, more than double the typical ratio. This larger ratio yields dramatic improvements in maneuverability and the ability to tilt the front of the stroller upward to overcome obstacles such as curbs.  
         [0010]     These benefits are attained because the new geometry places the rear wheels much closer to the center of gravity of the stroller and to the front wheels. This reduces the weight on the front wheels making it easier for swivels on the front wheels to turn, and also means that there is less weight to lift off the ground in the curb mounting action of tilting the front wheels upward.  
         [0011]     Perhaps the greatest benefit of the change in geometry is the increase in the lever arm upon which the handle operates. It is there where the larger ratio of the handle rearward extension to the wheelbase is most beneficial. The effect of any force that needs to be applied to the handle, whether horizontal to turn the stroller or vertical to lift the front wheels, is enhanced because the force is acting on an approximately 70 percent longer lever arm. For the stroller of the preferred embodiment with a typical full load of two children and 10 pounds of accessories, for both turning the stroller 90 degrees on its rear wheels and for pushing the handle down to raise the front wheels, the forces required are less than half those required for prior art strollers under similar conditions.  
         [0012]     There is, however, a drawback to the reduced wheelbase of the stroller. The very fact that it takes less force to raise the front wheels of the stroller means that it is easier to accidentally tip such a stroller over backwards. In the preferred embodiment this danger is addressed by using a trailing support, essentially a stabilizer bar, with or without wheels, that extends some distance to the rear of the stroller&#39;s rear wheels just above the ground. Such a stabilizer bar will prevent the stroller from tipping backwards, but will act against both accidental actions and, unfortunately, one of the original goals of the new design, the action of tipping the front wheels up to mount a curve.  
         [0013]     The design therefore requires one more feature, a latch and a release for the stabilizer bar that permits the stabilizer bar itself to pivot up when unlatched and thus permit the stroller to tip backwards a limited distance and permit the front wheels to be lifted up. In the preferred embodiment the latch release is activated by either of two foot pedals, so that the person pushing the stroller needs only to step on one of the pedals while pushing down on the handle. Once the foot pedal is released and the stroller front wheels are lowered, the stabilizer bar automatically latches and the stroller regains full stability. The condition of the stabilizer bar does not affect the turning ability of the stroller.  
         [0014]     The present invention therefore provides a highly maneuverable and very stable stroller and requires only a simple additional action to permit it to mount a curb. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]      FIG. 1  is a schematic side view of a typical two child stroller of the prior art.  
         [0016]      FIG. 2  is a schematic side view of the stroller of the preferred embodiment.  
         [0017]      FIG. 3  is a perspective view of the trailing support, stabilizer bar, and rear axle of the stroller of the preferred embodiment of the invention.  
         [0018]      FIG. 4  is a perspective view of the latch bracket of the trailing support of the preferred embodiment of the invention.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0019]      FIG. 1  is a schematic side view of a typical two child stroller  10  of the prior art in which two children can be accommodated. Forward seat  12  is located approximately over front swiveling wheels  14  (only one of which is shown), and rear seat  16  is located slightly forward of rear wheels  18  (only one of which is shown). Handle  20  is conventionally located to the rear and slightly above the top of rear seat  16 . The wheelbase of stroller  10 , the distance between centers  22  of front wheels  14  and centers  24  of rear wheels  18 , is designated by dimension W. In typical prior art strollers this wheelbase usually measures between  27  and  29  inches. Handle rearward extension R, the horizontal distance between centers  24  of rear wheels  18  and the location of handle  20  typically ranges from 9 to 11 inches in prior art strollers.  
         [0020]     Such dimensions yield typical strollers having a handle rearward extension that is ⅓ the length of the wheelbase. However, it is of significance that handle rearward extension R furnishes a lever arm of only approximately 10 inches to maneuver or lift the front end of such prior art strollers. Since the total weight of a stroller with two children aboard along with the accessories needed for travel with children can easily reach 110 pounds, this makes such strollers very difficult to control. In fact, under such circumstances, the weight on the front wheels alone can be fifty pounds, and for tilting the front wheels upward to mount a curb by pushing the handle down, a downward force of over 100 pounds is required. This is simply too much to ask of many parents.  
         [0021]      FIG. 2  is a schematic side view of stroller  30  of the preferred embodiment depicting the differences of the present invention from the prior art stroller shown directly above in  FIG. 1 . The same identifying numbers are used for all parts in  FIG. 2  which are unchanged from  FIG. 1  and in the same location.  
         [0022]     The essential difference between preferred embodiment stroller  30  and the prior art is the relocation of rear wheels  32  of stroller  30  to a location closer to front wheels  14 . This not only reduces wheelbase W 2 , but also increases handle rearward extension R 2 . In the preferred embodiment wheelbase W 2  is reduced to 22.13 inches and handle rearward extension R 2  is increased to 17.31 inches. This relationship can be accomplished either, as in the preferred embodiment of the invention, by reducing the wheelbase while maintaining the handle in essentially the same location, or by increasing handle rearward extension R 2  and accepting a longer vehicle.  
         [0023]     This rearrangement has some very beneficial results. One is that rear wheels  32 , which are the pivot point for turning any stroller, are now located closer to the center of mass. This also reduces the weight on the front wheels permitting the swivels on the front wheels to turn much easier. The weight on the front wheels of preferred embodiment stroller  30  is 31.5 pounds compared to the prior art stroller front wheel weight of 50 pounds. This makes the stroller much easier to steer.  
         [0024]     The change in wheelbase and handle rearward extension dimensions also dramatically changes the relationship of handle rearward extension R 2  to wheelbase W 2 . Whereas in the typical prior stroller the handle rearward extension length is about ⅓ of the wheelbase, in the preferred embodiment handle rearward extension R 2  is greater than ¾ the length of the wheelbase. In fact, the desirable dimensions for wheelbase W 2  and handle rearward extension R 2  are best defined by the comparative lengths of the two dimensions. For the purpose of the present invention the handle rearward extension should be at least 0.5 times the length of the wheelbase of the vehicle upon which it is used.  
         [0025]     This increase in the length of handle rearward extension R 2  relative to the length of wheelbase W 2  provides a very beneficial benefit of the invention, because it increases the lever arm with which the handle operates and reduces the lever arm upon which the weight of the front wheels act. Thus, the effect of any force that needs to be applied to the handle, whether horizontal to turn the stroller or vertical to lift the front wheels, is enhanced because, in the preferred embodiment, the force on the handle is acting on an approximately 70 percent longer lever arm while the weight on the front wheels is acting with a 78 percent shorter lever arm. For the stroller of the preferred embodiment with a typical full load of two children and  10  pounds of accessories, for both turning the stroller  90  degrees on its rear wheels and for pushing the handle down to raise the front wheels, the forces required are less than half those required for prior art strollers under similar conditions.  
         [0026]     The table below shows the dramatic changes in test results between a typical prior art stroller and stroller  30  of the preferred embodiment.  
                                                             Preferred           Prior Art   Embodiment                                Wheelbase (inches)   28.25   22.13       Handle rearward extension (inches)   10.61   17.31       Rearward Ext./Wheelbase Ratio   0.376   0.782       Front wheel weight (pounds)   50   31.5       Handle force for 90° turn (pounds)   20.81   9.60       Handle force for curb mount (pounds)   105   41 (released)       Handle force for rear tipping (pounds)   105   125 (latched)                  
 
         [0027]     Unfortunately, however, the reduced forces on the handle also suggest a safety problem. Since it takes less force to raise the front wheels  14  of stroller  30 , it is also easier to accidentally tip such a stroller over backwards. In the preferred embodiment this danger is addressed by using trailing support  36  described in greater detail in regard to  FIG. 3 . Trailing support  36  is essentially stabilizer bars  38 , with or without trailing wheels  40 . Trailing support  36  extends some distance to the rear of rear wheels  32  of stroller  30  and is located just far enough above the support surface to put trailing wheels  40  in contact with the support surface. If trailing support  36  is used without wheels it is located just high enough to prevent contact with the support surface. Trailing support  36  prevents the stroller from tipping backwards, but will, of course, act against both accidental actions and, also one of the original goals of the new design, the facilitated action of tipping the front wheels up to mount a curve. Trailing support  36  therefore includes a latch and release mechanism described in detail in regard to  FIG. 3 .  
         [0028]      FIG. 3  is a perspective view of trailing support  36  that includes stabilizer bars  38  and rear axle  34  of stroller  30  of the preferred embodiment of the invention. Trailing support  36  is shown with one rear wheel  32  removed from rear axle  34  to better view the structure of trailing support  36 , however, the structure near both wheels  32  is the same except for the changes required because of the location of the two wheels on opposite ends of axle  34 .  
         [0029]     For the preferred embodiment stroller  30 , the particular construction and components of trailing support  36  have been at least partly determined by its attachment to prior art stroller  10 . Thus, trailing support  36  is constructed to be attachable to the rear legs by means of curved leg extensions  44 .  
         [0030]     Mounting brackets  46 , constructed with outside parts  48  and inside parts  50 , attach trailing support  36  to rear legs  42 , and include cylindrical holes  52  to aid in stabilizing trailing support  36  relative to rear legs  42 . Rear axle  34  penetrates and is attached to both outside parts  48  and inside parts  50  of mounting brackets  46 . Spacing rod  54 , which is attached to inside parts  50  along with screws  56 , which penetrate leg extensions  44  and attach to mounting brackets  46 , aid in making trailing support  36  into a rigid structure.  
         [0031]     The basic function of trailing support  36  is performed by stabilizer bars  38  which, even by themselves, prevent stroller  30  from tipping over backwards. However, the function of stabilizer bars  38  is facilitated by adding trailing wheels  40 , and the structure is strengthened by the addition of trailing bar  58 .  
         [0032]     As previously described, the function of trailing support  36  is to prevent stroller  30  from tipping over backwards, but this also prevents stroller  30  from being intentionally tipped backwards for mounting curbs. An apparatus for latching and releasing trailing support  36  is therefore required.  
         [0033]     The first part of the latching and release action is accomplished by extending stabilizer bars  38  forward to rear wheel axle  34  and using rear wheel axle  34  as a pivot point for stabilizer bars  38 . Clearly, this permits stabilizer bars  38  to pivot upward as handle  20  of stroller  30  is pushed down so that front wheels  14  are raised. Other pivot points could, of course, be used, but rear wheel axle is advantageously located to furnish a relatively long turning radius for stabilizer bars  38 . In the preferred embodiment latching brackets  62  and release foot pedals  64  then provide the ability to lock stabilizer bars  38  in their lowered position, as shown in  FIG. 3 , and to release them to permit curb mounting.  
         [0034]     The operation of latching assembly  60  of the preferred embodiment is best understood with reference to  FIG. 3  and it is shown with greater clarity in  FIG. 4 . Latching brackets  62  are two “L” shaped structures that resemble golf putters, and include near-vertical sections  63 . Latching brackets  62  are located at the inside surfaces of stabilizer bars  38 . Spacing bar  65  is attached between latching brackets  62  to establish the distance between them and to assure that they move in unison. Holes  66  located near the corner of the angle of each latching bracket  62  are penetrated by bolts  68  that act as pivot points for latching brackets  62 , and bolts  68  are also attached to the stabilizer bar  38  adjacent to each latching bracket  62 . Thus, when either of the release foot pedals  64  located on the ends of latching brackets  62  (see  FIGS. 2 and 3 ) is pushed down in the direction indicated by arrows A, the other ends of both latching bracket sections  63  move toward the rear of stroller  30  as indicated by directional arrows B.  
         [0035]     Each latching bracket  62  includes a slot  70  extending along the length of section  63  and a transverse slot  72  at the upper end of slot  70 . Transverse slot  72  includes a sloped depression  74  at its rearmost end. As seen in  FIG. 3 , bolts  76  fit through slots  70  and  72  and are attached to mounting brackets  46 .  
         [0036]     Thus, when sections  63  are positioned to place bolts  76  within slot  70 , slot  70  and trailing supports  36  are released and can move upward, but when sections  63  are positioned so that bolts  76  are within sloped depressions  74 , no upward movement of slots  70  is possible and trailing support  36  is latched in its lowest position. The difference between latching and release of trailing support  36  is therefore dependent upon the position of bolts  76  within transverse slot  72  and whether section  63  is moved in direction B toward the rear of stroller  30  for release or in the direction opposite of direction B toward the front of stroller  30  for latching.  
         [0037]     The rearward motion of sections  63  of latching brackets  62  is controlled by release pedals  64 . When an operator pushes down on either release pedal  64 , both latching brackets  62  pivot (clockwise in the view of  FIG. 3 ) and sections  63  move toward the rear of the stroller permitting slots  70  to move upward past bolts  76 . The rear of the stroller can then be pushed down to raise the front wheels.  
         [0038]     Then, when the operator stops pushing on release pedal  64 , spring  78 , which is stretched between rear axle  34  and spacing bar  65 , pulls spacing bar  65  and both latching brackets counterclockwise. Therefore, when the stroller is located on a flat surface and the weight of trailing support  36  lowers trailing wheels  40 , slot  70  moves down along bolt  76 , and when the top of slot  70  reaches bolt  76  the counterclockwise force of spring  78  on latching bracket  62  moves sloped depression  74  of transverse slot  72  into position around bolt  76  and latches trailing support  36  in its lowest position. Stroller  30  can then be safely used without the danger of tipping backward.  
         [0039]     The invention therefore provides a stroller that can mount a curb and be maneuvered more easily than prior art strollers and is actually more difficult to accidentally tip rearward than prior art strollers (as noted in the table on page  8 ).  
         [0040]     It is to be understood that the form of this invention as shown is merely a preferred embodiment. Various changes may be made in the function and arrangement of parts; equivalent means may be substituted for those illustrated and described; and certain features may be used independently from others without departing from the spirit and scope of the invention as defined in the following claims.  
         [0041]     For example, the apparatus of the invention can be used on push type child transport vehicles other than strollers, and can apply to vehicles for only one child and vehicles with only a single front wheel. Moreover, other latch and release mechanisms can be devised, other specific dimensions for wheelbases and for handle rearward extensions are useable, and other configurations of trailing supports could be used, including using one or more wheels or using no wheels at all.