Abstract:
A baby stroller for transporting a child is disclosed. This baby stroller has a folding mechanism to facilitate folding for easier stowing and transporting. The folding mechanism, a unique feature of the design is directed toward compactness, ease of use, reliability, and reduction in manufacturing costs.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority as a continuation application to U.S. patent application Ser. No. 14/528,615 filed on Oct. 30, 2014, which claims priority as a continuation application to U.S. patent application Ser. No. 13/645,981 filed on Oct. 5, 2012, which claims priority as a continuation application to U.S. patent application Ser. No. 12/611,363 filed Nov. 3, 2009, which claims priority as a continuation application to U.S. patent application Ser. No. 11/118,621 filed on Apr. 28, 2005 which claims priority to non-provisional patent application to U.S. Provisional Patent Application No. 60/567,325 filed on Apr. 30, 2004, which are all incorporated by reference in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to baby strollers, and more particularly, to all-terrain baby strollers that can be folded. 
     2. Description of the Related Art 
     Traditionally, baby strollers have been used to push an infant slowly on a relatively hard smooth floor or sidewalk. As a result, the strollers were made small and light. These strollers work well enough at slow speed, but are extremely unwieldy and even dangerous on rough surfaces or at high speeds. 
     All-terrain baby strollers have been designed to overcome these problems. These strollers typically employ much larger wheels, often large bicycle tires. The stroller frame members are constructed of metal tubular stock and durable plastic frame connectors or other durable material to connect the frame members together to handle the heavy duty use they may receive. The frame connectors are used also to rotate or pivot one frame member relative to another, and are used to removably connect other frame members together. 
     Some advanced designs on all-terrain strollers have allowed for a certain degree of folding of the all-terrain baby strollers into less than a desirable amount of compactness. In addition, conventional folding mechanisms include complications that increase cost and reduce reliability and ease of use. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention resides in a folding baby stroller and a folding mechanism usable with a foldable baby stroller. 
     The folding mechanism includes a folding assembly having a first and second rotatable members rotatably mounted to rotate relative to each other. The first rotatable member is positioned for rotation in a first rotation plane and the second rotatable member is positioned for rotation in a second rotation plane, the first and second rotation planes being spaced apart. The first rotatable member has a first gear and the second rotatable member has a second gear. The folding assembly further has a third gear and a fourth gear configured to rotate together as a unit. The third gear is positioned in driving engagement with the first gear and the fourth gear is positioned in driving engagement with the second gear so that the first rotatable member and the second rotatable member rotate relative to each other in geared coordination. The first rotatable member is configured for attachment to a first one of first, second and third frame members, the second rotatable member being configured for attachment to a different second one of the first, second and third frame members, and the third and fourth gears configured for support by another different third one of the first, second and third frame members. 
     The first gear of the folding mechanism may have a first pitch and second gear a second pitch different than the first pitch, and the third gear may have a third pitch compatible with the first pitch of the first gear and the fourth gear may have a fourth pitch compatible with the second pitch of the second gear. 
     In one embodiment of the folding mechanism, the first rotatable member has a first aperture and the first gear is formed in a first edge portion of the first rotatable member defining the first aperture, and the second rotatable member has a second aperture and the second gear is formed in a second edge portion of the second rotatable member defining the second aperture. The third gear is positioned in the first aperture and the fourth gear is positioned in the second aperture. The first and second edge portions may be radially displaced from each other. Further, the first and second rotatable members each may have a face portion with the face portions arranged in face-to-face juxtaposition. 
     The first and second rotatable members may be rotatably mounted on a pivot member for rotation about a common axis of rotation, and the third and fourth gears may be coaxially mounted to rotate about an axis parallel to and spaced apart from the common axis of the first and second rotatable members. 
     In one embodiment of the folding mechanism the third gear has a first number of gear teeth and fourth gear has a second number of gear teeth different than the first number, and the third gear has a pitch compatible with the pitch of the first gear and the fourth gear has a pitch compatible with the pitch of the second gear. 
     The folding assembly may be used as part of a foldable baby stroller frame or other device. The baby stroller typically has a front wheel support, a rear wheel support and a handle member. The folding assembly may include a pivot member, a first rotatable member with a first aperture having a first gear, and a second rotatable member with a second aperture having a second gear. The first and second rotatable members are rotatably coupled to the pivot member to rotate about common axis of rotation. A third gear is positioned in both the first and second apertures in driving engagement with the first gear and the second gear so that the first rotatable member and the second rotatable member rotate relative to each other in geared coordination. 
     The first gear may have a first pitch and second gear a second pitch different than the first pitch, and the third gear may include a first gear portion with the first pitch and a second gear portion with the second pitch. The first and second portions of the third gear are configured to rotate as a unit. The first gear portion of the third gear is positioned in the first aperture in driving engagement with the first gear and the second gear portion of the third gear is positioned in the second aperture in driving engagement with the second gear. 
     The pivot member is configured to be supportingly engaged by one of the front wheel support, rear wheel support and handle member; the first rotatable member is configured to be attached to a different one of the front wheel support, rear wheel support and handle member; and the second rotatable member is configured to be attached to another different one of the front wheel support, rear wheel support and handle member. 
     The first gear is formed in a first edge portion of the first rotation member defining the first aperture and the second gear is formed in a second edge portion of the second rotation member defining the second aperture. In the depicted implementation the first and second edge portions are radially displaced from each other. 
     The first and second apertures may be elongated with the elongated first and second apertures at least in part overlapping. The first gear may have a first pitch diameter, and the second gear a second pitch diameter, with the first pitch diameter and the second pitch diameter not being the same. The first gear may be positioned radially outward of the second gear. 
     The depicted implementation has the first pitch diameter of the first gear sized to rotate the one of the front wheel support, rear wheel support and handle member to which the first rotatable member is configured to be attached through a first angle of rotation from a folded position to an unfolded position of the foldable baby stroller frame, and the second pitch diameter for the second gear is sized to rotate the one of the front wheel support, rear wheel support and handle member to which the second rotatable member is configured to be attached through a second angle of rotation from a folded position to an unfolded position of the foldable baby stroller frame, with the first and second angles of rotation not being the same. 
     The first rotatable member has an arm configured to be attached to the one of the front wheel support, rear wheel support and handle member to which the first rotatable member is configured to be attached, and the second rotatable member has an arm configured to be attached to the one of the front wheel support, rear wheel support and handle member to which the second rotatable member is configured to be attached. 
     The folding assembly may include a movable member, and the first and second rotatable members may each further include a notch to receive the member therein when the first and second rotatable members are rotated about the pivot member to position the notches of the first and second rotatable members in alignment. 
     The folding assembly may also include a housing in which the pivot member is positioned. The housing is configured to be attached to the one of the front wheel supports, rear wheel supports and handle members to which the pivot member is configured to be supportingly engaged. 
     Other features and advantages of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  is an isometric view of an exemplary implementation of a baby stroller embodying the present invention shown in a fully unfolded state ready for usage. 
         FIG. 2  is an isometric view of the stroller frame of  FIG. 1  without a seat and a leg guard. 
         FIG. 3  is a front elevational view of the stroller frame of  FIG. 2 . 
         FIG. 4  is a side elevational view of the stroller frame of  FIG. 2 . 
         FIG. 5  is a side elevational view of the stroller frame of  FIG. 2  shown in the partially folded state. 
         FIG. 6  is a side elevational view of the stroller frame of  FIG. 2  shown in a fully folded state with both left and right front supports and left and right side handle supports being rotated about their respective side folding assemblies toward respective side rear wheel supports and with the front wheel removed. 
         FIG. 7  is an exploded isometric view of the right side folding assembly of the implementation shown in  FIG. 1 , the left side folding assembly being a mirror image thereof. 
         FIG. 8  is an enlarged, fragmentary, right side elevational view of the right side folding assembly of  FIG. 7  with its outer half housing removed and in the fully unfolded state. 
         FIG. 9  is a fragmentary, left side elevational view of the right side folding assembly of  FIG. 7  with its inner half housing removed and in the partially unfolded state. 
         FIG. 10  is an enlarged isometric view of a pinion gear and pin used in an alternative embodiment of the folding assembly shown in  FIG. 12  where the pinion gear has two gear portions. 
         FIG. 11  is an enlarged isometric view of a pinion gear and pin used in yet another alternative embodiment of the folding assembly shown in  FIG. 13  where the pinion gear is comprised of two gears affixed together for use. 
         FIG. 12  is an exploded isometric view, corresponding to  FIG. 7 , of the right side folding assembly of an alternative embodiment of the folding assembly, the left side folding assembly being a mirror image thereof. 
         FIG. 13  is an exploded isometric view, corresponding to  FIG. 7 , of the right side folding assembly of yet another alternative embodiment of the folding assembly, the left side folding assembly being a mirror image thereof. 
         FIG. 14  is an exploded isometric view, corresponding to  FIG. 7 , of a center folding assembly used in a double baby stroller shown if  FIG. 15  having two release levers. 
         FIG. 15  is an isometric view of an exemplary implementation of a double baby stroller embodying the present invention shown in a fully unfolded state ready for usage but without a seat and a leg guard. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As shown in the drawings for purposes of illustration, the present invention is embodied in an all-terrain baby stroller  10 , as shown in  FIG. 1 , having a foldable, tubular metal frame  12  and a transversely extending rear axle assembly  14  with a transverse, non-rotating tubular rear axle  15 . Left and right side rear wheels  16  are rotatably mounted to the ends of the rear axle assembly  14 . The forward end of the frame  12  has a single front wheel  18  rotatably mounted thereto. 
     The frame  12  has no base frame members extending rearwardly from the front wheel  18  to the rear axle assembly  14  as do most conventional all-terrain strollers. Instead, the frame  12  includes left and right side, downwardly and forwardly sloping front wheels frame members or supports  20 , which each extend downward from a corresponding one of left and right side folding assemblies  22  in a converging configuration to the front wheel  18 . A forward free-end  20   a  of each of the left and right side front wheel supports  20  has a plastic front wheel connector  20   b  fixedly attached thereto and a corresponding one of the left and right ends of an axle  18   a  of the front wheel  18  removably attached thereto to mount the front wheel to the stroller frame  12 . 
     The front wheel supports  20  are interconnected by a foot rest  23  that spans between them toward but rearward of their forward free-ends  20   a  and that is fixedly attached to each at a position rearward of the axle  18   a  of the front wheel and extending partially over the front wheel  18 . As a result of the interconnection provided by the foot rest  23 , and also the front wheel  18  when attached to the left and right side front wheel connectors, the left and right side front wheel supports  20  form a stationary unit with respect to the left and right side folding assemblies  22  upon folding and unfolding of the stroller  10 , as will be described in greater detail below. 
     The frame  12  also includes left and right side, upwardly and rearwardly sloping handle frame members or supports  24 , which each extend upward from the corresponding one of the left and right side folding assemblies  22  in a generally parallel configuration to a handle  26  extending between the left and right side handle supports. The handle  26  is covered by a foam grip. The handle supports  24  are interconnected by the handle  26  that spans between them at their rearwardmost and uppermost extension and that is fixedly attached to each. 
     As a result of the interconnection provided by the handle  26 , the left and right side handle supports  24  move as a unit with respect to the left and right side folding assemblies  22  upon folding and unfolding of the stroller  10 , as will be described in greater detail below. It is noted that in lieu of the interconnecting handle  26 , the handle supports  24  may each be provided with a handle portion at the upper end thereof such as used with umbrella style strollers. 
     In the illustrated embodiment of the invention the left and right side handle supports  24  and the handle  26  are formed as an integral unit by bending a single length of aluminum tube. The left and right side handle supports  24  are movable relative to the left and right side front wheel supports  20  for folding of the stroller  10  and do not together form an integrated rigid upper frame. 
     The frame  12  also includes left and right side, downwardly and rearwardly sloping rear wheel frame members or supports  30 , which each extend downward from the corresponding one of the left and right side folding assemblies  22  in a generally parallel configuration to the rear axle assembly  14 . A rearward free-end  30   a  of each of the left and right side rear wheel supports  30  is fixedly attached to the tubular rear axle  15  toward a corresponding one of the left and right ends of the tubular rear axle  15 . The rear wheel supports  30  are interconnected by the rear axle assembly  14  that spans between them at the rearward free-ends  30   a  thereof. A cross-frame member  31  with a U-shape extends between the left and right side rear wheel supports  30 . As a result of the interconnection provided by the rear axle assembly  14  and the cross-frame member  31 , the left and right side rear wheel supports  30  move as a unit with respect to the left and right folding assemblies  22  for folding and unfolding of the stroller  10 , as will be described in greater detail below. The left and right side rear wheel supports  30  are also movable relative to the left and right side front wheel supports  20  and the left and right side handle supports  24  for folding of the stroller  10 . Further, the left and right side rear wheel supports  30  and the rear axle assembly  14  connected thereto do not form a part of a base frame extending between the rear and front wheels  16  and  18 . Much of the structural strength of the stroller  10  and the interconnection of the front wheel supports  20 , the handle supports  24 , and the rear wheel supports  30  are provided by the centrally positioned left and right side folding assemblies  22 , and not by a base frame. 
     In the illustrated embodiment of the stroller  10 , the left and right side front wheel supports  20 , the left and right side handle supports  24 , and the left and right side rear wheel supports  30  are made from aluminum tube. Suitable alternative materials may be used. 
     The left and right outward ends of the tubular rear axle  15  are open and internally threaded to receive a threaded stub axle  32  forming a part of the corresponding one of the left and right rear wheels  16 . A lock nut (not shown) when tightened against the face of the stub axle  32  locks the stub axle against loosening during usage of the stroller  10 . Alternative constructions may be used to fixedly or removably attach the rear wheels  16  to the tubular rear axle  15 , and any suitable alternative manner of mounting the rear wheels  16  to the real wheel supports  30  may be used. 
     The frame  12  of the stroller  10  is shown in  FIG. 1  in the fully unfolded state with a fabric seat  33   a , and a fabric leg support and guard  33   b . The seat  33   a  is suspended from the left and right side handle supports  24 , and the leg guard  33   b  spans between and is supported by the left and right side front wheel supports  20 . For purposes of illustration, the frame  12  is shown in  FIG. 2  without the seat  33   a  and the leg guard  33   b.    
     For the depicted implementation, user operation of the left and right side folding assemblies  22  will now be described. The left and right side folding assemblies  22  have the same construction, with one being the mirror image of the other, and the description below, while in the singular, is applicable to both. Each of the left and right rear wheel supports  30  supports an inwardly extending lever  34 , which has a predominantly vertical orientation, as shown in  FIG. 3 , when the frame  12  of the stroller  10  is locked in the fully unfolded position. To begin the procedure to fold the frame  12 , each of the levers  34  is pulled upward and inward as depicted by arrows R 1  to thereby put the left and right side folding assemblies  22  in an unlocked state as further explained below. A strap (not shown) may be connected by its ends to the levers  34  to facilitate movement of both levers at the same time. 
     With each of the left and right folding assemblies  22  in an unlocked state, the left and right handle supports  24 , along with the handle  26 , and the left and right front wheel support  20 , along with the front wheel  18 , can be rotated about the left and right folding assemblies, respectively, toward the left and right rear wheel supports  30 , respectively, as depicted by arrows R 2  shown in  FIG. 4 . As shown, when the stroller  10  is folded, the folding assemblies  22  allow a greater rotation angle for the handle supports  24  (greater than 90°) than for the front wheel supports  20  (less than 90°). As explained further below, the front wheel supports  20  move in geared coordination with movement of the handle supports  24 . As the frame  12  is being folded, the front wheel supports  20  are rotated clockwise about the folding assemblies  22  as viewed in  FIG. 4 , while the handle supports  24  are also rotated counterclockwise about the folding assemblies as viewed in  FIG. 4 . The frame  12  is shown in a partially folded state in  FIG. 5 . In a fully folded state, both the front wheel supports  20  and the handle supports  24  have been rotated in geared coordination with each other about the folding assemblies  22  to be positioned in close proximity to the rear wheel supports  30  as shown in  FIG. 6 . To do so the front wheel  18  is removed. 
     The right side folding assembly  22  is shown in exploded view in  FIG. 7  and includes a laterally outward positioned forward rotatable member  35 ′ and a laterally inward rearward rotatable member  35 ″, each with a flat face facing toward the other. The forward rotatable member  35 ′ has a plate or disk  36 ′ with a central plate portion having a central aperture  37 ′. The forward rotatable member  35 ′ also includes a notch  38 ′, a radially outward internal gear  39 ′ in an elongated aperture  41 ′, and an arm  40 ′. The rearward rotatable member  35 ″ has a plate or disk  36 ″ with a central plate portion having a central aperture  37 ″. The rearward rotatable member  35 ″ also includes a notch  38 ″, a radially inward internal gear  39 ″ in an elongated aperture  41 ″, and an arm  40 ″. For each of the rotatable members  35 ′ and  35 ″, the disks  36 ′ and  36 ″ and the arms  40 ′ and  40 ″ are depicted as being formed as part of a single flat plate piece; however, in other implementations the disks and arms are individual pieces that are fixedly attached together. 
     The rotatable members  35 ′ and  35 ″, along with a corresponding one of the rear wheel supports  30 , are contained between inner and outer slotted halves of a housing  42  that allow the arms  40 ′ and  40 ″ to protrude outside of the housing. The inside wall of each half of the housing  42  has a recess  42   a  sized and shaped such that when the two halves of the housing are positioned together, the recesses form a cavity to receive an upper free-end portion  30   b  of the corresponding rear wheel support  30  therein and an upper free-end portion of the cross-frame member  31 . A bolt (not shown) extends through an aperture  42   f  in each half of the housing  42  and through an aperture  30   c  in the upper free-end portion  30   b  of the rear wheel support  30  and an aperture of the upper free-end portion of the cross-frame member  31  to securely clamp the rear wheel support and the cross-frame member between the inner and outer halves of the housing. 
     The central apertures  37 ′ and  37 ″ of the disks  36 ′ and  36 ″, respectively, are sized to receive a bushing  43  therethrough having a length longer than the cumulative thickness of the two disks. The rotatable members  35 ′ and  35 ″ are rotatably mounted on the bushing for rotation within the housing  42  in parallel rotation planes about an axis of rotation transverse to the plane of the disks  36 ′ and  36 ″. The end portions of the bushing extending beyond the central apertures  37 ′ and  37 ″ each have a circumferential groove  43   a  to receive a C-clip  43   b  to retain the bushing  43  in place. The bushing  43  also extends through a washer  43   d  positioned between the disks  36 ′ and  36 ″ of the rotatable members  35 ′ and  35 ″ to serve as a spacer and bearing surface for rotational movement of the rotatable members about the bushing  43 . Each of the disks  36 ′ and  36 ″ has a flat face in face-to-face juxtaposition with the flat face of the other disk with the washer  43   d  positioned therebetween. 
     The end portions of the bushing  43  extending beyond the C-clip  43   b  are each positioned in and retained by a retaining cup  42   b  formed by the inside wall of a correspondingly positioned one of the inner and outer halves of the housing  42 . Each of the inner and outer halves of the housing  42  has an aperture  42   c  in communication with the corresponding retaining cups  42   b . The bushing  43  has a longitudinally extending central aperture  43   c  aligned with apertures  43   b  of inner and outer halves of the housing  42 , and sized to receive a bolt  45  therethrough that extends fully through the inner and outer halves of the housing. A nut  45   a  is threaded onto a threaded end portion of the bolt  45  to clamp the inner and outer halves of the housing  42  of the folding assembly  22  securely together with the disks  36 ′ and  36 ″ freely rotatable on the bushing  43  and being spaced apart by the washer  43   d , and with the arm  40 ′ extending forwardly through a forward portion of a slot  42   e  in the housing and the arm  40 ″ extending rearwardly through a rearward portion of the housing slot. The arms  40 ′ and  40 ″ are flat elongated plates. 
     As noted above, the disks  36 ′ and  36 ″ of the rotatable members  35 ′ and  35 ″ have their flat faces in face-to-face juxtaposition. This provides laterally adjacent parallel plates with elongated apertures  41 ′ and  41 ″, each having the gear teeth of a corresponding one of the radially outward and inward gears  39 ′ and  39 ″ formed along an edge portion of the corresponding one of the elongated apertures  41 ′ and  41 ″. The gear teeth of the radially outward gear  39 ′ of the disk  36 ′ are formed along the radially outward edge of the elongated aperture  41 ′, and the gear teeth of the radially inward gear  39 ″ of the disk  36 ″ are formed along the radially inward edge of the elongated aperture  41 ″. The planar disks  36 ′ and  36 ″ are arranged in spaced apart parallel planes, and the radially outward and inward gears  39 ′ and  39 ″ are similarly arranged in spaced apart parallel planes and not in a common plane or in direct engagement with each other. The elongated apertures  41 ′ and  41 ″ are positioned on the disks  36 ′ and  36 ″ so as to be at least in part overlapping during the rotation of the rotatable members  35 ′ and  35 ″ between the folded and unfolded states of the stroller  10 . 
     A pinion gear  44  is positioned within the elongated apertures  41 ′ and  41 ″ in simultaneous geared engagement with both the radially outward gear  39 ′ of the forward rotatable member  35 ′ and the radially inward gear  39 ″ of the rearward rotatable member  35 ″. The pinion gear  44  is positioned to extend through and beyond each of the elongated apertures  41 ′ and  41 ″ of the disks  36 ′ and  36 ″ at a position where the elongated apertures overlap during folding and unfolding of the stroller  10 , and span fully between the radially outward and inward gears  39 ′ and  39 ″ of the disks  36 ′ and  36 ″ in simultaneous geared engagement with both of the gears. The pinion gear  44  transmits the driving rotational force between the front wheel supports  20  and the handle supports  24  which causes one to rotate in response to rotation of the other. 
     The pinion gear  44  is rotatably mounted on a pin  44   a  that has each of its end portions extending beyond the pinion gear  44  positioned in the aperture of a flat bushing  44   b  and rotatably retained by the flat bushing. Each of the flat bushings  44   b  is positioned in and retained by a retaining cup  44   c  formed by the inside wall of a correspondingly positioned one of the inner and outer halves of the housing  42 . As such, the pinion gear  44  is supported by the housing  42 , which is rigidly attached to the corresponding one of the rear wheel supports  30  for movement therewith, of course, being rotatable about the axis of the pin  44   a . With such arrangement, the pinion gear  44  is rotatable about an axis of rotation transverse to the plane of the disks  36 ′ and  36 ″, and parallel to and spaced apart from the axis of rotation of the disks  36 ′ and  36 ″. 
     The pinion gear  44  engages both the radially outward gear  39 ′ of the forward rotatable member  35 ′ and the radially inward gear  39 ″ of the rearward rotatable member  35 ″. Consequently, through the pinion gear  44 , the radially outward gear  39 ′ and the radially inward gear  39 ″ are mutually drivingly engaged with each other so that if either is rotated, the rotational force is transmitted through the pinion gear to the other to cause the other to also rotate about the bushing  43 . As such, if the front wheel supports  20  or the handle supports  24  are rotated relative to the rear wheel supports  30 , the other of the front wheel supports and the handle supports is driven to rotate as well. 
     The radially outward and inward gears  39 ′ and  39 ″ have the same pitch since the pinion gear  44  engages both, but each has a larger pitch diameter than the pinion gear. However, the radially inward gear  39 ″ have a smaller radius of curvature or pitch diameter than the radially outward gear  39 ′, thus the resulting′ rotational movement of the rearward rotatable member  35 ″ will be greater than the rotational movement of the forward rotatable member  35 ′. In other words, for any amount the pinion gear  44  is rotated, the rearward rotatable member  35 ″ and hence the handle support  24  attached thereto will rotate more than the forward rotatable member  35 ″ and hence the front wheel support  20  attached thereto. This is useful since as noted above, and as shown in  FIG. 4 , to fold the front wheel supports  20  and the handle supports  24  tightly about the rear wheel supports  30  requires a greater rotation angle for the handle supports (in one embodiment about) 108° than for the front wheel supports (in that same embodiment about 72°). In another embodiment the rotation angle for the handle supports and the front wheel supports is the same (in the second embodiment about 90° for each). 
     The pitch diameter for each of the radially outward gear  39 ′ of the forward rotatable member  35 ′ and the radially inward gear  39 ″ of the rearward rotatable member  35 ″, and the pitch diameter of the pinion gear  44 , are selected to produce the desired ratio of rotational movement for the forward and rearward rotatable members  35 ′ and  35 ″ to fold the stroller  10  into a compact form with the handle supports  24  and the front wheel supports  20  nested tightly against the rear wheel supports  30 . However, while the ability to select different pitch diameters for the radially outward and inward gears  39 ′ and  39 ″ is helpful, even a greater degree of design flexibility may be desirable. 
     In another embodiment of the folding assembly  22  shown in  FIGS. 10 and 12 , a pinion gear  44 ′ is shown having first and second pinion gear portions  44   x  and  44   y , with the first pinion gear portion having a first pitch, a first pitch diameter and a first number of gear teeth, and the second pinion gear portion having a different second pitch, a second pitch diameter and a different second number of gear teeth. The first and second pinion gear portions  44   x  and  44   y  are made as a single part and rotate together as a unit in coaxial arrangement on the pin  44   a , but are essentially two pinion gears, each with its own gear parameters. The first pinion gear portion  44   x  is positioned to engage the radially outward gear  39 ′ and has a pitch corresponding thereto and five gear teeth, and the second pinion gear portion  44   y  is positioned to engage the radially inward gear  39 ″ and has a pitch corresponding thereto and four gear teeth. The first and second pinion gear portions  44   x  and  44   y  may have the same or different pitch diameters. In such manner, the radially outward and inward gears  39 ′ and  39 ″ and the first and second pinion gear portions  44   x  and  44   y  that engage them, respectively, may be designed with gear parameters to produce a wider range of differing amounts of rotational movement of the forward and rearward rotatable members  35 ′ and  35 ″ when folding and unfolding the stroller  10 . In effect, there is more design freedom and flexibility permitted since the radially outward gear  39 ′ and the first pinion gear portion  44   x  pair can be designed with first gear parameters to produce a first rotational movement of the forward rotatable member  35 ′, and the radially inward gear  39 ″ and the second pinion gear portion  44   y  pair can be designed with different second gear parameters to produce a different second rotational movement of the rearward rotatable member  35 ″, with independence in the first and second gear parameters selected. 
     As noted above, with the first embodiment described only the pitch diameters of the radially outward and inward gears  39 ′ and  39 ″ differed, but in the embodiment of  FIGS. 10 and 12 , the radially outward gear  39 ′ and the first pinion gear portion  44   x  pair and the radially inward gear  39 ″ and the second pinion gear portion  44   y  pair can be designed essentially independent of the other to produce a desired result, such as a desired ratio of rotational movement of the radially outward gear  39 ′ and the radially inward gear  39 ″, and hence the desired ratio of rotational movement of the forward and rearward rotatable members  35 ′ and  35 ″ when folding and unfolding the stroller  10 . For example, this permits design of the folding assemblies  22  with more control over the amount of movement of both the handle supports  24  and the front wheel supports  20  relative to the rear wheel supports  30  resulting during folding of the stroller  10  and hence allows folding into a compact form where the handle supports and the front wheel supports can be moved to nest tightly against the rear wheel supports. 
     In yet another embodiment of the folding assembly  22  shown in  FIGS. 11 and 13 , a pinion gear  44 ″ is shown having first and second pinion gears  44   xx  and  44   yy  made as separate parts but fixedly attached together for rotation together as a unit on the pin  44   a , such as by welding, an insertion pin or some other manner. Alternatively, the first and second pinion gears  44   xx  and  44   yy  may be keyed to the pin  44   a  so long as the pin is free to rotate. The first pinion gear  44   xx  has a first pitch, a first pitch diameter and a first number of gear teeth (shown as five in this embodiment), and the second pinion gear  44   yy  has a different second pitch, a second pitch diameter and a different second number of gear teeth (shown as four in this embodiment). The first pinion gear  44   xx  is positioned to engage the radially outward gear  39 ′, and the second pinion gear  44   yy  is positioned to engage the radially inward gear  39 ″. As above, the radially outward gear  39 ′ and the first pinion gear  44   xx  pair and the radially inward gear  39 ″ and the second pinion gear  44   yy  pair can be designed with gear parameters essentially independent of the other to providing greater flexibility in designing the folding assemblies  22  to produce a desired ratio of rotational movement of the radially outward gear  39 ′ and the radially inward gear  39 ″, and hence the desired ratio of rotational movement of the forward and rearward rotatable members  35 ′ and  35 ″ when folding and unfolding the stroller  10 . 
     The length of the radially outward gear  39 ′ of the forward rotatable member  35 ′ and the radially inward gear  39 ″ of the rearward rotatable member  35 ″, and also the length of the elongated apertures  41 ′ and  41 ″ within which the pinion gear  44  is positioned, impact the amount of rotation possible for the forward and rearward rotatable members  35 ′ and  35 ″. The range of movement is limited by stops  51 ′ and  51 ″ attached to the perimeter portion of the forward and rearward rotatable members  35 ′ and  35 ″, respectively. Each of the stops  51 ′ and  51 ″ extends laterally toward the adjacent rotatable member and radially outward of the perimeter of the adjacent rotatable member. The stops  51 ′ and  51 ″ are attached to the rotatable members  35 ′ and  35 ″ at positions along the perimeter of the rotatable member to which attached such that when the rotatable members are rotated to place the folding assemblies  22  in the fully unfolded state, as shown in  FIG. 8 , the stops  51 ′ and  51 ″ are in engagement and prevent further rotational movement of the rotatable members in that rotational direction. In the depicted implementation, the stops  51 ′ and  51 ″ are positioned to allow a rotation angle for the handle supports  24  of about 108° and for the front wheel supports  20  of about 70°. 
     It should be understood that while in the depicted implementation the front wheel supports  20  and the handle supports  24  are attached to the rotatable members  35 ′ and  35 ″ of the left and right side folding assemblies  22  (and the rear wheel supports  30  fixedly attached to the housing  42 ), other implementations may have the rear wheel supports  30  and the handle supports  24  attached to the rotatable members  35 ′ and  35 ″ of the folding assemblies  22  (and the front wheel supports  20  fixedly attached to the housing  42 ) such that they rotate to fold about the front wheel supports. Similarly, the rear wheel supports  30  and the front wheel supports  20  may be attached to the rotatable members  35 ′ and  35 ″ of the folding assemblies  22  (and the handle supports  24  fixedly attached to the housing  42 ) such that they rotate to fold about the handle supports. 
     To prevent the unintended folding of the stroller  10  when the folding assemblies  22  are in a fully unfolded state, as shown in  FIG. 8 , each folding assembly has a releasable locking mechanism with a slidably mounted head  50  having a locking lug  52 . A spring  54  applies a bias force to the head  50  to maintain the locking lug  52  in contact with a smooth, rounded perimeter portion of each of the disks  36 ′ and  36 ″ of the folding assembly as the rotatable members are rotated close to the stroller fully unfolded state. The notches  38 ′ and  38 ″ of the disks  36 ′ and  36 ″ are positioned along a reinforced perimeter portion of the disks in a location where when the stroller  10  reaches the fully unfolded state, the notches are in alignment and the spring  54  will drive the head  50  forward to position the locking lug  52  in both notches, and hence prevent rotation of the disks toward the folded state. The portion of the disks  36 ′ and  36 ″ around the notches  38 ′ and  38 ″ has increased thickness for added strength. 
     The head  50  is slidably mounted in the housing  42  at a position above the recess  42   a  receiving the upper free-end portion  30   b  of the rear wheel support  30 . The upper end of the spring  54  engages the head  50  and the lower end engages a spring support  56  positioned inside the upper free-end portion  30   b  of the rear wheel support  30 . The lever  34  for the folding assembly  22  is pivotally mounted to the rear wheel support  30  and has a nose portion extending through an aperture in the head  50  and in engagement with a pin within the head so that when the lever  34  is pulled upward and inward as depicted by the arrows R 1  in  FIG. 3 , the head  50  is moved downward, away from the disks  36 ′ and  36 ″, thereby causing the locking lug  52  to be retracted from the notches  38 ′ and  38 ″ and permitting the disks  36 ′ and  36 ″ to rotate toward the fully folded state shown in  FIG. 6  in a generally clam shell movement to position the handle supports  24  and the front wheel supports  20  nested tightly against the rear wheel supports  30 . The folding assembly  22  is shown in  FIG. 9  between the unfolded and folded states with the locking lug  52  of the head  50  retracted from the notch  38 ′ and  38 ″. 
     While the spring  54  supplies enough force to the head  50  to keep the locking lug  52  in the notches  38 ′ and  38 ″ to lock the stroller  10  in the fully unfolded state, the force is not so great as to require undue force to be applied to the lever  34  by the user to retract locking lug from the notches when the folding assembly is to be folded. 
     Each of the left and right side folding assemblies  22  has the corresponding left or right front wheel support  20  bolted onto the arm  40 ′ of the forward rotatable member  35 ′ and the corresponding left or right handle support  24  bolted onto the arm  40 ″ of the rearward rotatable member  35 ″. 
     It should be understood that while the rotatable members  35 ′ and  35 ″ were depicted as including the disks  36 ′ and  36 ″, in other implementations the rotatable members  35 ′ and  35 ″ may have other shapes. 
     Another embodiment of an all-terrain baby stroller  10 ′ is shown in  FIG. 15 . This embodiment has the basic same design as the stroller  10 , but is designed to carry two children is side by side arrangement. The frame  12  of the stroller  10 ′, in addition to having the left and right side frame supports  24 , has a center frame support  24 ′ which extends upward from a center folding assembly  22 ′ (shown in  FIG. 14 ) of the same construction as the previously described folding assemblies  22 , except the center folding assembly  22 ′ has left and right side outwardly extending levers  34 . Either of the levers for the center folding assembly  22 ′ may be pulled upward and outward to place the center folding assembly  22 ′ in an unlocked state. Much as with the folding assembly  22  described above, each lever  34  for the center folding assembly  22 ′ is pivotally mounted to a rear wheel support  30 ′ and has a nose portion extending through an aperture in the head  50  of the center folding assembly  22 ′, although from opposite sides thereof. Movement of either lever  34  when pulled upward and outward causes the head  50  of the center folding assembly  22 ′ to moved downward, away from the disks  36 ′ and  36 ″ of the center folding assembly  22 ′, thereby causing the locking lug  52  to be retracted from the notches  38 ′ and  38 ″ and permitting the disks  36 ′ and  36 ″ to rotate toward the fully folded state. A strap (not shown) may be connected by its ends to the lever  34  of the left side folding assembly  22  and to the left side lever  34  of the center folding assembly  22 ′, and another strap (not shown) may be connected by its ends to the lever  34  of the right side folding assembly  22  and to the right side lever  34  of the center folding assembly  22 ′ to facilitate movement of both levers to which the strap is connected at the same time. 
     From the foregoing it will be appreciated that, although specific embodiments of the invention have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit and scope of the invention. Accordingly, the invention is not limited except as by the appended claims.