Abstract:
A two-wheeled stroller is disclosed and claimed. The stroller is a tow-type stroller to enable a child to accompany an attendant who is engaged in walking or running activity over a variety of ground surfaces and grades at various walking and running velocities. The stroller includes a carnage assembly, a tow bar assembly, and a harness assembly. The carnage assembly includes a seat upon which the child being transported is seated and two wheels, with the center of gravity of the carriage assembly and child (if present) positioned below the wheel axis of rotation. The harness assembly is adjustably affixed to the attendant, and is connected to the carriage assembly by the tow bar assembly.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to strollers, and, more particularly, the present invention relates to an improved tow-type walking, running or jogging stroller. 
       BACKGROUND ART 
       [0002]    Jogging strollers (also referred to as running strollers, walking carriages, jogging carriages and running carriages) are a popular means by which adult attendants can take their babies, toddlers and small children along when the adult attendants are engaged in walking, jogging, or running exercises. The vast majority of commercially available jogging strollers are pushed by the attendant. Push-type strollers require that the attendant use one or both of his or her arms and hands to propel and control the stroller during operation. This requirement restricts arm swing that naturally occurs in humans during walking and running. Arm swing during running, at any speed, affects factors such as center of mass; forward propulsion; and various components of angular momentum. Therefore, restricted arm swing can affect critical factors that mediate the biomechanical efficiencies inherent in human locomotion. 
         [0003]    Steering mechanisms employed by push-type strollers may compromise the safety of the child and the attendant at higher travel velocities. Steering designs often employed by push-type strollers include front wheels that swivel or caster to allow the attendant to steer the stroller while maintaining wheel contact with the ground at all times. Similar to shopping cart wheels, the front caster(s) used for push-type strollers tend(s) to “shimmy” as the stroller is propelled at higher velocities and could create lateral instability localized at the front end of the stroller. This instability could result in loss of steering control at increased travel speeds and thus compromise the child&#39;s safety. When subjected to uneven travel surfaces or obstacles along the path, such as a pebble, the direction of the affected caster tends to deviate from the path of progression, potentially resulting in abrupt changes in stroller direction that may further compromise control of the stroller. Strollers designed for higher jogging speeds often employ three wheels with a non-caster front wheel. To steer this type of stroller, the front wheel must be lifted away from the ground. This maneuver requires that the runner press downwardly on the rear stroller handle, using the rear wheel axle as a fulcrum by which to lift the front wheel up and away from the ground sufficiently to turn the stroller laterally, either completely or incrementally, in the desired direction. The weight of the stroller and the occupant is borne over the rear axle and is solely dependent on the stability and strength of the attendant&#39;s arm(s) to maintain balance during this maneuver. Some manufacturers offer front wheel designs that may be placed in either the fixed or swivel position but recommend that users lock the wheel in the “forward” position when operating the stroller at higher jogging speeds for the safety reasons stated above. 
         [0004]    The vertical load component of known “hands-free” stroller designs result in decreased biomechanical running efficiencies due to the additional vertical load(s) placed on the attendant, and produce a jarring interaction between attendant and carriage (and child) generated by the attendant&#39;s movements, especially at higher running velocities. 
         [0005]    When walking, jogging, or running, a person typically exhibits some lateral motion that can be translated to the carriage (and therefore the child passenger) via the tow bar. Control of this motion is especially critical for two wheeled vehicles, given the possibility that the resulting side-to-side carriage motion, as it periodically changes direction of the carriage&#39;s inertia (from left to right and right to left), could achieve a resonant frequency that could result in loss of steering control or, at minimum, result in a jarring motion for both the attendant and the child. 
         [0006]    Furthermore, the attendant&#39;s walking/jogging/running motion may create anterior/posterior impulses between the attendant and the carriage during operation. In bipedal human locomotion, whether walking or running, the attendant&#39;s COG accelerates upon “push off” and decelerates upon “heel contact” of each step. This anterior/posterior acceleration/deceleration is translated to the carriage assembly and occupant via the tow bar—albeit asynchronously. Upon “push off,” the attendant&#39;s COG accelerates along the path of progression and the carriage experiences a corresponding acceleration. Upon heel contact, the attendant&#39;s COG decelerates. Due to the inertia of the carriage, however, the corresponding carriage deceleration will lag behind that of the attendant&#39;s deceleration, thus establishing a cycle by which the acceleration/deceleration of the carriage and attendant will be out of phase. This repetitive action generates a jarring impulse experienced at each end of the tow bar by both the attendant and the carriage at each of the attendant&#39;s steps. 
       DISCLOSURE OF INVENTION 
       [0007]    Disclosed herein is a tow-type two-wheeled jogging stroller that employs a dropped axle design, whereby the carriage frame, wheels, occupant seat and body engaging means are arranged such that the degrees of freedom of each component, relative to each other, are limited to a rotation in the saggital plane about a single axis of rotation, and the load bearing components of the carriage assembly are arranged such that the center of gravity of the carriage load is borne below the single axis of rotation. The body engaging means, comprising a tow bar assembly, a cross bar, an articulated assembly and a waist belt, is configured such that the attendant tows and steers the carriage assembly without the use of the attendant&#39;s arms or hands. 
         [0008]    In preferred embodiments, the tow bar assembly provides a resilient means by which the anterior/posterior and medial/lateral impulses generated between the carriage and the attendant during operation are mediated. Thus, as will be described in more detail below, the carriage assembly and tow assembly components of the stroller are arranged to minimize the vertical and horizontal loads borne by the attendant, to attenuate the impulses imparted on the carriage assembly, and to maximize the safety of the child occupant consequential to the mechanical interaction between the carriage assembly and attendant during walking or running. 
         [0009]    In general, embodiments of the invention include a carriage assembly, a tow bar, and a harness. The carriage assembly includes a seat for accommodating a passenger and two wheels having an axis of rotation. The tow bar assembly has first and second ends, the first end coupled to the carriage assembly, and the second end being coupled to the harness, which may be adjustably configured to be connected to the attendant. The components are coupled together such that when the carriage assembly is in use, the COG is located below the axis of rotation of the wheels. Moreover, the seat preferably is positioned such that when a child is seated therein, a combined center of gravity of the child and the carriage assembly is located below the axis of rotation while the stroller is in use. To facilitate positioning the center of gravity below the axis of rotation, the carriage assembly may be provided with two axles, a first axle associated with a first of the two wheels and a second axle associated with a second of the two wheels, the first and second axles being separate and substantially collinear. 
         [0010]    The carriage assembly may include a carriage frame. Preferably, the carriage frame is rotatably coupled to the wheels and adjustably coupled to the seat. More preferably, the carriage frame, wheels, and seat are rotatably coupled together about a single axis of rotation. The carriage frame may define a plurality of connection points configured to be coupled to the seat, the connection points providing a plurality of locations to which the seat can be coupled to the carriage frame. Thus, the seat may be repositioned as desired. 
         [0011]    The carriage assembly may also include an elongate cross bar. Preferably, the cross bar is fixedly coupled to the carriage assembly along the wheel axis of rotation at first and second ends thereof, and rotatably coupled to the tow bar at an intermediate location thereof. The carriage assembly may further include one or more stops to limit the rotation of the cross bar relative to the frame. 
         [0012]    The tow bar preferably is configured to attenuate acceleration of the harness relative to the carriage assembly. To this end, the tow bar may include a first member coupled to the carriage assembly, a second member coupled to the harness, and a damping element coupled to the first and second members. The first and second members are coupled together so as to allow relative movement therebetween, and the damping element is configured to provide resistance to such movement. These elements may be positioned in a variety of ways. For example, the first and second members may be substantially parallel with the damping element being substantially parallel to the first and second members when the tow bar assembly is in a neutral, compressed or extended position. As another example, the first and second members may be substantially parallel with the damping element being substantially perpendicular to the first and second members. 
         [0013]    The combination and assembly of the components disclosed below provide a number of benefits over previous tow-type stroller designs, including without limitation: (1) minimized overall vertical load bearing by the attendant while walking or running; (2) reduced vertical movement as experienced by the carriage assembly occupant; (3) attenuated anterior/posterior impulses experienced by the attendant and carriage assembly occupant; (4) minimized lateral carriage assembly movement imparted by attendant&#39;s side-to-side motion during walking or running; and (5) improved occupant safety by means of a seat provided with safety roll bars, which is situated such that the center of gravity is below the wheel axis. The disclosed arrangement of components also provides improved biomechanical efficiency over conventional push-type strollers by permitting natural arm swing during walking/running, as well as improved steering stability at higher jogging/running speeds. 
         [0014]    The major carriage assembly components are configured to permit the seat to be quickly engaged/disengaged from the carriage frame, the distance of the seat&#39;s center of gravity to be adjusted relative to the wheel axis, and the tow bar assembly to be quickly engaged/disengaged from the carriage assembly and from the body engaging means located at the rear of attendant&#39;s lower back. Furthermore, the wheel assembly may be quickly engaged/disengaged from the carriage frame or may be rotated along an axis perpendicular to wheel hub axis to and about the carriage assembly to substantially reduce the size and volume of the carriage assembly to facilitate easier storage when it is not in use. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0015]    The present invention is described with reference to the accompanying drawings, which illustrate exemplary embodiments and in which like reference characters reference like elements. It is intended that the embodiments and figures disclosed herein are to be considered illustrative rather than restrictive. 
           [0016]      FIG. 1  shows a tow-type stroller in a use position, in accordance with one embodiment of the present invention, while the stroller is being propelled and controlled by an attendant. 
           [0017]      FIG. 2  shows a front view of the carriage assembly of the tow-type stroller of  FIG. 1 . 
           [0018]      FIG. 3  shows an exploded view of the connection of the carriage assembly and cross-bar components of the tow-type stroller of  FIG. 1 . 
           [0019]      FIG. 4A  shows a single seat assembly of the tow-type stroller of  FIG. 1 . 
           [0020]      FIG. 4B  shows an alternative means of connecting the single seat assembly shown in  FIG. 4A  to the axle sleeve of the tow-type stroller shown in  FIG. 1 . 
           [0021]      FIG. 5  shows a side view of another embodiment of the carriage assembly component of the tow-type stroller of  FIG. 1 . 
           [0022]      FIG. 6A  shows an exploded view of the carriage assembly of  FIG. 5 . 
           [0023]      FIG. 6B  shows the detail of a latch mechanism associated with the carriage assembly shown in  FIG. 6A . 
           [0024]      FIG. 7  shows an example of a tow bar assembly of the tow-type stroller of  FIG. 1 . 
           [0025]      FIGS. 8   a  and  8   b  show graphs illustrating the states of transition between compression and extension in the tow bar assembly of the tow-type stroller of  FIG. 1 . 
           [0026]      FIG. 9  shows an alternate tow bar assembly of the tow-type stroller of  FIG. 1 . 
           [0027]      FIG. 10  shows a schematic illustrating the tow bar assembly function when elastic members connected to the tow bar components are arranged to permit an extended neutral zone in the tow bar assembly. 
           [0028]      FIGS. 10   a ,  10   b  and  10   c  show various states of the tow bar assembly of  FIG. 9 . 
           [0029]      FIGS. 11   a  and  11   b  illustrate an example of an alternative crossbow arrangement of a tow bar assembly having a cantilever type spring for creating a neutral compression/extension zone. 
           [0030]      FIG. 12  shows a crossbar component of the tow-type stroller of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0031]      FIG. 1  illustrates a tow-type stroller being propelled and controlled by an attendant while the attendant is jogging. It should be understood, however, that embodiments of the present invention may also be beneficially used while the attendant is merely walking. Certain embodiments may also be configured to attach to a bicycle or other vehicle, so as to permit the attendant to bring a baby, small child or toddler along for the ride. As shown in  FIG. 1 , the stroller includes two wheels  1 , each with a wheel hub  2 , a carriage frame  3 , a seat assembly  4  to accommodate a child occupant, a cross bar  5 , a tow bar assembly  6 , an articulating assembly  7 , and a waist belt  8 . 
         [0032]      FIG. 2  depicts a carriage frame  3  provided with two supporting wheels  1  spaced apart along the wheel axis  9  in a direction laterally of the direction of movement of the carriage frame  3  where each of two wheel axle  10  means is secured directly to the carriage frame  3 . Both wheel axle means  10  are coaxial to the wheel axis  9  and together bear the carriage assembly load such that all of the load supporting base of the carriage frame  3  is suspended from the axle means below the wheel axis (dropped axle) and the load base portion is positioned below a horizontal plane including the wheel axis at all times during normal use of the carriage assembly, including when the carriage is at rest and in transporting position. The purpose of this configuration is to position the load center of gravity (COG)  12  below the wheel axis  9 . 
         [0033]      FIG. 3  shows an exploded view of the connection of the carriage frame  3  and cross-bar  5  components of the tow-type stroller of  FIG. 1 . For the sake of simplicity, only one of the connections is shown in exploded view in  FIG. 3 . As shown in  FIGS. 2 and 3 , the axle means  10  is comprised of an axle sleeve  13  permanently affixed to the carriage frame  3 . Each axle sleeve  13  is secured to a lateral portion of the carriage frame  3  and is located along the carriage frame  3  such that the bottom most portion of the carriage frame  3  does not contact the travel surface (ground) during operation. 
         [0034]    Each axle sleeve  13  accepts a wheel spindle  15 , which is rotatably connected to the wheel hub  2 . One or both ends of the spindle  15  may be threaded to accept a locknut  16 . The locknut  16  provides a means to prevent lateral travel of the wheel spindle  15  when the locknut abuts the wheel hub  2 . Alternatively, one end of the spindle  15  could be formed into a head to similarly prevent lateral travel of the wheel spindle  15  when the locknut abuts the wheel hub  2 . Perpendicular to the axis of the spindle, a groove  17  may be machined along the length of the spindle  15 . There are a variety of ways by which the spindle  15  may be secured within the axle sleeve  13 . In this illustration, a toggle clamp  18  is shown as a possible means to detachably connect said spindle  15  within the axle sleeve  13 . The toggle clamp  18  is connected to the carriage frame  3  such that when the toggle clamp plunger  19  is extended, it passes through a hole  20  drilled in the anterior portion of the carriage frame  3  and a hole  21  drilled perpendicular to the axis of the axle sleeve  13 . The wheel spindle  15  is accepted into the axle sleeve  13  such that the wheel spindle groove  17  lines up with the two holes  20  and  21 . When the toggle clamp plunger  19  is extended, it passes through said holes  20  and  21  and is pressed and seated within the wheel spindle groove  17  when the wheel spindle  15  is located within the axle sleeve  13 . 
         [0035]    The lengths of the axle sleeves  13  that protrude through the interior portions of the carriage frame  3  provide a means to connect a detachable crossbar  5 . When connected, the crossbar  5  rotates freely about the wheel axis  9 . 
         [0036]    Referring again to  FIG. 1 , one end of the tow bar assembly  6  is connected to the crossbar  5 . The other end of the tow bar assembly  6  is connected to the attendant for the purpose of towing the carriage assembly. There are numerous means by which to detachably connect the tow bar assembly to the cross bar. As an example, a hole  22  may be drilled through the center portion of the crossbar  5  (the bottom of the “U”) to accept one end of the tow bar assembly  6  such that the axis of the tow bar assembly  6  is perpendicular to the wheel axis  9  whenever it is connected to the crossbar  5 . In this example, a toggle clamp assembly  23  is used to detachably connect the tow bar assembly  6  to the crossbar  5  in a manner similar to the method by which the toggle clamp  18  is utilized to detachably connect said spindle  15  within the axle sleeve  13 . 
         [0037]    Beneficially, the carriage frame  3 , cross bar  5 , axle sleeves  13  and wheel hub  2  components are configured relative to each other such that all relative motion between said components is limited to single degree of rotational movement in the saggital plane about a single wheel axis  9 . 
         [0038]    Excessive forward rotation of the carriage frame  3  about the wheel axis  9  could result in the front most portion of the carriage assembly striking the travel surface. Similarly, excessive rearward rotation could cause the back portion of the carriage assembly to contact the travel surface. Excessive rotation as described above may be controlled via a rotation limiter. There are numerous means by which to govern excessive rotation. One possible means to govern the rotation of the carriage assembly about the wheel axis is shown and includes an upward limiting arm  24  and a downward limiting arm  25 . The upward limiting arm  24  is rotatably connected to a post  26 . The axis of said post is oriented in the direction of travel and is connected to the carriage frame  3 . The position of the upward limiting arm  24  may be maintained onto the post  26  via a retaining clip and is oriented such that that the upward limiting arm  24  contacts the superior aspect of the crossbar  5  and resists the forward rotation of the carriage frame  3  at a rate and magnitude of force determined by the properties of a governing device such as a torsional spring  27  as shown in the illustrated embodiment. Similarly, a downward limiting arm  25  provides a means to resist the backward rotation of the carriage frame  3 . 
         [0039]      FIG. 4A  illustrates a single seat assembly  4  for a child occupant. The seat assembly may be detachably connected to the load supporting portions of the carriage frame  3  either along the interior bottom portions of the carriage frame  3  or the lateral interior portions of the carriage frame  3 . In another embodiment, a bracket  28  connected to the exterior and lateral portion of the seat assembly  4  provides a means to adjustably connect the seat assembly to the axle sleeve  13  such that the seat assembly rotates about the wheel axis  9 . In this example, the bracket provides a plurality of holes  29  each of which can accept the protruding end of the axle sleeve  13  for the purpose of adjusting the relative position of the COG  12  from the wheel axis  9 . (See  FIG. 2 ). 
         [0040]    Alternatively, and as illustrated in  FIG. 4B , the function of adjusting the COG position relative to the wheel axis may be accomplished by connecting a bracket  30  to the exterior and lateral portion of the seat assembly  4  as shown. A sliding connector comprised of a sliding member  31  that can be positioned and secured along the length of the bracket  30  and a locking pin  32 , which is connected to the sliding member  31 . A coupling mechanism  33  is secured to the end portion of the axle sleeve  13  and oriented so that the portion of the coupling mechanism  33  that accepts the locking pin  32  faces the locking pin. In this example, the locking pin  32  is secured within the coupling mechanism  33  by a latching mechanism  34  when said latching mechanism  34  is in the locked position. The locking pin  32  is released from the coupling mechanism  33  when the latching mechanism  34  is in the open position. 
         [0041]    Due to the single axis arrangement, it is desirable to minimize the saggital plane rotation of the seat assembly  4  to thus reduce excessive forward or backward tipping of the carriage assembly during operation. Maximum rotational stability of the assembly may be achieved by localizing the COG directly below the axis line  9 . As the body mass distribution of differently sized occupants (children) may result in a varying COG location of the seated occupant, it is desirable to provide a means for adjusting the COG such that it is directly beneath the axis line. 
         [0042]    In the example, the seat assembly  4 , is comprised of a rigid bottom and a back support and provides a foot rest  35  specially modified in connection with the seat assembly  4  to provide for relative adjustment to accommodate a range of occupant lower limb lengths. The foot rest assembly is comprised of two supporting members  36  each with one end rotatably connected to an exterior portion of the seat assembly  4  and the other end constructed to accept the ends of the foot rest  35 , said footrest  35  being generally oriented horizontally with respect to the ground. During operation, the structure of the footrest  35  prevents a seated child&#39;s feet from contacting the travel surface. A flexible or a rigid barrier  37  connected between the lengths of the supporting members  36  prevents the seated child&#39;s lower limbs from contacting the travel surface. 
         [0043]    The leading portion of the footrest  35  has a slight upward angle with respect to ground in the sagittal plane such that the bottom portion of said footrest  35  provides a rigid skid to engage the edge portion of a step, curb, or abutment (curb) to facilitate movement of the carriage assembly thereacross. As the front- and bottommost portion of the skid engages the curb, the carriage frame  3  and seat assembly  4  rotate about the wheel axis  9  permitting unobstructed forward travel of the stroller until the wheels  1  engage the edge portion of the curb. As the stroller is propelled forward, the wheels  1  surmount the curb and thus lift the entire carriage assembly over the curb without further contact between the curb and other portions of the stroller. 
         [0044]    A headrest  38  is attached to the back support portion of the seat assembly such that the vertical position of the headrest may be adjusted relative to the seat back to accommodate a variety of seated occupant body heights. 
         [0045]    Attached to the seat assembly  4  is a restraining apparatus wherein one or more flexible, strap-like members  39  can be engaged with the body of the child prevent, restrain, or limit movement of the child relative to the seat assembly  4  should the stroller sharply decelerate, collide with another object, or be involved in any sudden, unexpected movement or termination of movement. 
         [0046]    Attached to the seat assembly  4  is/are one or more bar arrangements  40  extending over and around the occupant compartment, such bars or bar arrangement  40  designed to protect the occupant should the vehicle overturn. 
         [0047]    Attached to the seat assembly  4  and/or the bar arrangements  40  is a flexible film, cloth, mesh, or solid material barrier  41  that prevents the child from accidentally placing any part of the child&#39;s body near moving parts of the carriage assembly. 
         [0048]      FIG. 5  illustrates an alternative embodiment of the carriage assembly and is heretofore referred to as the cage frame assembly  42 . The cage frame assembly  42  is comprised of a bar arrangement to protect the occupant and includes a structural means to connect the supporting wheels  1  and the seat assembly  4 . In this example, the wheels  1  are rotatably connected to the cage frame assembly  42  via a horizontal bar member  43 . The illustration shows how the crossbar  5  is connected directly to the wheel axle and the tow bar assembly  6  is connected to the crossbar. 
         [0049]      FIG. 6A  shows the cage frame assembly  42  is comprised of one or more light-weight tubes fashioned to provide a rigid support for two wheels  1  spaced apart along the wheel axis  9  in a direction laterally of the direction of movement of the cage frame assembly  42  such that the COG  12  is maintained below the wheel axis  9  (See  FIG. 2 ) at all times during normal use, including when the carriage assembly is at rest and in the transporting position as previously described. 
         [0050]    As an example of utilization of the cage frame assembly  42  as a means of supporting the wheels  1 , the illustration shows that the threaded end of the wheel spindle  15  protrudes through the exterior portion of the wheel hub and through the end portion of the crossbar  5  (only half of the crossbar is shown to simplify the drawing) and connected to a locknut  16 . The other end of the spindle  15  supports part A  65 A of a latch mechanism so that the cage frame may be quickly engaged/disengaged from the crossbar and wheel assembly.  FIG. 6B  shows the detail of the latch mechanism. As shown in  FIG. 6B , part B  65 B of the latch mechanism is comprised of a structural member  72  fashioned such that it provides support for: a striker  67 ; a means to slide along the horizontal bar member  43  (in this illustration by way of holes  71  on the lateral portions of the structural member  72 ); a type of plunger  66  such that when the striker is engaged in the receiving notch  74  of part A  65 A of the latch mechanism, both arms  73  of the structural member  72  engage around the lateral portion  69  of part A  65 A of the latch mechanism to prevent lateral movement of part B  65 B relative to part A  65 A of the latching mechanism. Part A  65 A of the latching mechanism is comprised of a structural member  69  which is fashioned such that it provides a means to connect to the wheel spindle through the hole  75  shown. Part B  65 B of the latch mechanism is connected to the horizontal bar member  43  via the holes  71  such that part B  65 B of the latch mechanism can slide back and forth along the length of the horizontal bar member  43  in the direction of travel. Furthermore, the position of part B  65 B of the latch mechanism along the length of the horizontal bar member  43  may be fixed via a plunger  66  that secures part B  65 B to the horizontal bar member  43  via a plurality of holes  44  along the top of the horizontal bar member  43 . The purpose of this sliding and locking function of part B along the horizontal bar member  43  is to provide a means to adjust the distance of the COG relative to the wheel axis  9 . Ideally, the attendant can perform this adjustment with minimal effort. However, the position of the final adjustment must remain secured without the possibility of a change in the adjustment position during operation of the stroller. The materials used for the members of this assembly must provide a rigid structure for maintaining a fixed relative position between the wheels  1 . 
         [0051]    This alternative cage frame assembly  42  provides a means of incorporating a footrest  46  comprised of a rigid structure with two ends each bent at a certain angle to generally form a “U” shape along a certain plane. The ends of said foot rest are further bent away from the plane at a certain angle (theta) that the front end of the footrest  46  structure forms and upwardly angled rigid skid to engage the edge portion of a step, curb, or abutment that may be encountered during operation similar in function to the footrest  35  previously described. 
         [0052]    The height, relative to the ground, of each of sliding means  47  attached to the lower front portion of the carriage frame  42  may be raised or lowered. Each sliding means  47  can accept one end of a rigid tube member  48  of a certain length. Each of two rigid tube members  48  is oriented generally in the direction of travel and at a certain angle relative to the ground. The ends of the footrest member  46  can accept an end of the rigid tube member  48  such that the distance between the footrest  46  and the cage frame  42  may be adjusted and secured into place by the user and to provide a means to adjust for different limb lengths of a child occupant. 
         [0053]      FIG. 7  shows an example of a resilient tow bar assembly  6  which is comprised primarily of two elongated tubes: the first tube  49  and the second tube  50  are arranged to slide longitudinally with respect to each other either coaxially (telescopically) or collocated as shown in the illustration and parallel to the direction of travel. In this example, the means by which both tubes  49  and  50  are connected to each other permits a free, sliding movement between the tubes with the first tube  49  detachably connected to the cross bar  5  and the second tube  50  is detachably connected to the articulating assembly  7 . The length of the portion of the second tube  49  that is accepted into the drilled hole  22  in the crossbar  5  is limited by the location of a limiting collar  51  along the length of the first tube  49 . 
         [0054]    In the example shown, brackets  52 A and  52 B span across both of the tubes  49  and  50  such that one portion of each bracket is directly affixed to the first tube  49  and the other portion of each bracket is fixed to a linear bearing  53 A and  53 B. Each linear bearing is coaxially connected to the second tube  50 . When the first tube  49  is connected to the cross bar  5 , the resulting assembly arrangement constrains movement of the second tube  50  to slide only back and forth in the direction of travel towards and away from the cross bar  5 . A simplified resilient means by which to mediate the anterior/posterior impulses generated between the carriage and the attendant during operation is illustrated by coupling the pair of tubes with a pair of elastic members  54 A and  54 B. The elastic members are arranged such that they restrict the relative linear motion between both of the tubes  49  and  50 . A simplified example of a connecting means by which to couple the elastic members to the tow bar assembly  6  is shown. In this example a connecting means  55 A is attached to one end of the second tube  50 . One end of elastic member  54 A is attached to connecting means  55 A. The other end of the elastic member  54 A is attached to connecting means  55 B. Connecting means  55 B is connected to bracket  52 A. When the first tube  49  is connected to the cross bar  5 , the resilient assembly described above resists the overall compression of the tow bar assembly  6  and moderates the rate of displacement of the second tube  50  towards the cross bar  5  and thus, the carriage assembly. Similarly, the overall extension of the tow bar assembly  6  is moderated via a resilient assembly where a connecting means  55 C is connected to bracket  52 B. One end of the elastic member  54 B is attached to connecting means  55 C. The other end of elastic member  54 B is attached to connecting means  55 D. Connecting means  55 D is connected to the other end of the second tube  50 . 
         [0055]    Preferably, both elastic members  54 A and  54 B are attached to the respective pair of connecting means such that the elastic members are placed in a particular amount of tension when there is no axial load on the tow bar assembly. Preferably, the connecting means  55 A, and  55 D may be repositioned along the second tube  50  to increase or decrease the tension placed on each of the elastic members  54 A and  54 B. Alternatively, the overall resistance to extension and compression of the tow bar assembly  6  can be modified via selection of elastic members possessing either an increased or a decreased modulus of elasticity. 
         [0056]    The resilient tow bar assembly  6  serves two primary functions: 1) to connect the carriage assembly and attendant so that the attendant may propel and control the carriage assembly velocity and direction, and 2) to attenuate the forward and backward impulses along the tow bar assembly  6  resulting from the accelerations and decelerations associated with walking or running as the attendant propels the carriage assembly. The resilient tow bar assembly  6  includes two rigid, elongated members which may be arranged either concentrically or in parallel and are connected to each other by means of either bushings or bearings such that the free movement between the two members is restricted to a linear motion along the axis of said members if arranged concentrically or along parallel axes if arranged in parallel. One end of the first elongated member is connected to the cross bar and the other end of said member is connected to the second elongated member. One end of the second elongated member is connected to the first elongated member and the other end of the second elongated member is connected to the attendant via an articulated assembly and a belt assembly. 
         [0057]    The overall length of the tow bar assembly  6  varies with the position of the two elongated members  49  and  50  relative to each other. When connected to the attendant and to the carriage assembly, the overall length of the tow bar assembly extends or compresses in proportion to the distance between the carriage assembly and the attendant as the attendant either accelerates away from the carriage assembly when propelling it in the forward direction (extension) or when the attendant decelerates and the carriage continues to travel in the direction of the attendant due to the carriage&#39;s momentum (compression). Thus, the state of the tow bar assembly may be defined as being in extension or compression depending on the instantaneous overall length of the tow bar assembly. A third state, the length of the tow bar assembly at which the transition between extension and compression occurs may be defined as “neutral.” 
         [0058]    The forward and backward impulses transmitted through the tow bar assembly  6  and experienced by the attendant and the carriage assembly as the attendant propels the stroller may be attenuated by controlling the rates at which the tow bar assembly  6  extends and compresses. This may be achieved by connecting one or more elastic or damping members to the components of the tow bar assembly  6  in an arrangement that permits said elastic or damping members to moderate the extension or compression motions of the tow bar assembly  6  and thus, the rate at which the tow bar assembly  6  extends or compresses. 
         [0059]    The forward end of the tow bar assembly  6  is detachably connected to an articulating assembly  7 . In this example, a toggle clamp assembly  56  is shown as a possible means to quickly connect and disconnect one end of the second tube  50  to a connector tube  57 . The articulating assembly  7  provides four degrees of freedom of movement at the point of connection between the tow bar assembly  6  and the attendant (vertical translation and rotation in the saggital plane, lateral translation and rotation in the transverse plane) relative to the carriage assembly during operation. The articulating assembly  7  comprises a belt  58  of material sufficient in strength to support the towing loads during operation having at least two holes  59  to accept standoffs  60 ; a single, horizontally oriented tube  61  parallel to the ground supported by said standoffs  60 ; a slider tube  62  fitting over said horizontally oriented tube  61  with an inner diameter greater than the outer diameter of the horizontally oriented tube  61  to permit said slider tube  62  to travel laterally and to follow the path of the horizontally oriented tube  61 ; a swivel pin  63  connected to the slider tube such that the axis of rotation created by the swivel pin is normal to the ground; and a connector tube  57  of which one end is connected to said slider tube  62  by means of the swivel pin  63  and the other end connects telescopically within the second tow bar assembly tube  50  providing a means to selectively vary the running distance between the attendant and the carriage assembly. The function of the swivel pin  63  serves to facilitate turning of the carriage assembly by the attendant during operation by permitting rotation of the attendant&#39;s body in the transverse plane when changing the direction of travel. 
         [0060]      FIG. 7  shows that the articulating assembly  7  is secured to the rear portion of a waist belt  58  which is, in turn, used to connect to the attendant&#39;s waist or hips. A harness or vest may also be used in place of the waist belt provided that said harness or belt adequately distribute the anterior/posterior forces involved in propelling the carriage assembly across the attendant&#39;s torso. The belt or vest may be comprised of any variety of materials but preferably of those materials that provide the strength necessary to withstand said anterior/posterior forces involved in operation while permitting ventilation means to transfer heat away from the interior of the belt nearest the attendant&#39;s body to the incident environment. Further, the belt should provide for facile circumferential adjustment around the attendant&#39;s waist or hips to minimize movement between the articulating assembly  7  and the attendant&#39;s torso. 
         [0061]    The tightness of the waist belt  58  around the attendant&#39;s waist provides sufficient friction around the attendant&#39;s waist to support the vertical and horizontal loads generated, in all three planes, during operation of the loaded carriage assembly. 
         [0062]    As previously described, one of the functions of the resilient tow bar assembly is to attenuate the forward and backward impulses along the tow bar assembly resulting from the accelerations and decelerations associated with walking or running as the attendant propels the carriage assembly. Attenuation of said impulses may be accomplished by various means. The exemplary tow bar assembly shown in  FIG. 7  utilizes elastic members  54 A and  54 B that are connected to the components of the tow bar assembly in an arrangement such that one or more of the elastic members are maintained in a state of tension irrespective of the amount of tow bar extension or compression. The graph in  FIG. 8   a  illustrates the relationship between the resistive forces exerted by said elastic members as a function of the tow bar compression/extension. In the graph, the horizontal axis represents the measure of the tow bar assembly extension (increasing to the right) and compression (increasing to the left), the point of origin where the axes intersect represents the transition point between tow bar assembly extension/compression (neutral position), and the vertical axis represents the amount of resistance to the compression or extension movement exerted by the elastic members on to the tow bar assembly. It is important to note that in this arrangement, there exists a single transition point between extension and compression states. 
         [0063]    The relationship between tow bar compression/extension and resistive force may be modified from the example above through an alternate configuration wherein the elastic members may be connected to the components of the tow bar assembly in an arrangement such that the state of transition between compression/extension is expanded and bounded by a certain interval along the horizontal axis as shown in  FIG. 8   b . This represents a different function than the previous example where the transition between compression and extension states were limited to a single point along the horizontal axis as shown in the graph in  FIG. 8   a . Expanding the length of the neutral state creates a “neutral zone” along the horizontal axis. The graph in  FIG. 8   b  shows a neutral zone defined by an interval length along the horizontal axis in which the resistance to the extension or compression of the tow bar assembly is reduced or negligible. This configuration serves to reduce or to uncouple anterior and posterior forces between carriage and attendant whenever the tow bar assembly length is within the neutral zone, thus reducing or eliminating impulses that occur when the tow bar assembly transitions between states of compression and extension. There are several arrangements by which elastic members may be connected to the tow bar assembly components to accomplish the function of creating a “neutral zone” as described above. 
         [0064]      FIG. 9  illustrates an example of such an arrangement where a first elongated member  80  of the tow bar assembly with one end connected to the cross bar  5  and the other end detachably connected to a second elongated member  81  of the tow bar assembly by means of a linear bearing assembly  82 . Said bearing assembly is permanently connected to one end of the second elongated member  81 . Said second elongated member  81  is connected to the attendant via articulated assembly  7  and belt  58 . The first elongated member  80  is permitted to slide axially within the linear bearing assembly  82  such that no lateral movement between the first and second elongated members is permitted. Furthermore, along a certain portion of body of the first elongated member  80  which corresponds approximately to the neutral position as previously defined, is a connecting means for connecting to one end of an elastic member such as a spring, latex tubing, resistance band, bungee cord, etc. shown as connection A which may be comprised of an eye hook traversing the body of the first elongated member  80  such that the elongated member is permitted to freely slide within the linear bearing assembly  82 . 
         [0065]    A cross bracket  83  is permanently connected to the linear bearing assembly  82  such that the elongated portions of the cross bracket extend away from the linear bearing assembly in a direction which is perpendicular to the general axis of the tow bar assembly. The purpose of the cross bracket is to provide a rigid structure upon which to support connection points for the elastic members  84  and  85  as shown in the illustration. In this example, the cross bracket  83  is comprised of a rigid, elongated member of a certain length that is fixedly connected to the linear bearing  82 , said linear bearing  82  is connected to the second elongated member  81  of the tow bar assembly. The cross bracket  83  is oriented such that the elongated portion of the bracket is perpendicular to the axis of the tow bar assembly and the ends of the bracket are equidistant from the axis of the tow bar assembly. 
         [0066]    A means for connecting elastic members  84  and  85  to the tow bar assembly components are located at each end of the elongated portion of the cross bracket shown as connection B and C, respectively. The means for connecting to the elastic members  84  and  85  to the cross bracket  83  may include, but are not limited to, an eye hook as previously described. 
         [0067]    The schematics in  FIG. 10  illustrate the tow bar assembly function when the elastic members connected to the tow bar assembly components are arranged to permit an extended “neutral zone” whereby said elastic components provide little or no resistance to the extension and compression motion of the tow bar assembly.  FIG. 10   a  shows that each elastic member  84  and  85  increasingly resists the extension of the tow bar assembly as the first elongated member  80  is translated from the neutral zone towards the direction of increased extension relative to the position of the second elongated member  81 . Similarly, but in the opposite sense, the compression of the tow bar assembly is resisted by the same elastic members  84  and  85  as the first elongated member  80  proceeds from the neutral zone towards the direction of increased compression (relative to second elongated member  81 ) as shown in  FIG. 10   b .  FIG. 10   c  shows the state of the tow bar assembly is neutral when connection point A on the first elongated member  80  is in line with connection points B and C on the cross bracket  83 . This position is defined as the neutral point. When the tow bar assembly length is at the neutral point, the elastic members exert no resistance to the movement between the components of the tow bar assembly. This is because each elastic member can provide resistance only in the direction axial to the elastic member. This holds true even when the elastic members are connected to their respective connection points under tension. While the position of connection A is within the “neutral zone”, the elastic members impart minimal resistance because the magnitude of the axial resistive force component as compared to magnitude of the perpendicular resistive force component is relatively small. However, as connection point A travels beyond the “neutral zone” in either direction, the elastic members exert an increasingly significant resistance to the extension and compression movements of the tow bar assembly. This is because the magnitude of the axial resistive force component becomes increasingly comparable to the magnitude of the perpendicular resistive force component. 
         [0068]    An alternate design by which to create a “neutral zone” for the tow bar assembly utilizes, in place of axial elastic members, a resistive component such as a leaf spring to control the rate of extension and compression of the tow bar assembly. Unlike the axial resistance provided by the elastic members described above, a leaf spring provides resistance in a direction which is perpendicular to the elongated axis of said leaf spring. 
         [0069]      FIG. 11   a  illustrates an example of an alternative arrangement for creating a “neutral zone” as described above; a cantilever type spring connected to the tow bar assembly components in an arrangement to provide resistance to the extension and compression movements of the tow bar assembly. Unlike the elastic members previously described which provide axial resistance, the cantilever type spring provides resistance to lateral deflection of said cantilever spring. A crossbow is an example of a cantilever spring. 
         [0070]    As shown in  FIG. 11   a , this arrangement includes a cantilever spring  87  connected to the tow bar assembly to provide increasing resistance to the extension and compression movement of the tow bar assembly as the state of the tow bar assembly moves increasingly away from the “neutral zone”. The figure shows a first elongated member  80  of the tow bar assembly with one end connected to the cross bar  5  and the other end detachably connected to a second elongated member  81  of the tow bar assembly by means of a linear bearing assembly  82 . Said bearing assembly is rigidly connected to one end of the second elongated member  81 . The other end of the second elongated member is connected to the attendant via articulated assembly  7  and belt  58 . The first elongated member  80  is permitted to slide axially within the linear bearing assembly  82  such that no lateral movement between the first and second elongated members is permitted. Furthermore, along a certain portion of body of the first elongated member which corresponds approximately to the neutral position, as previously described, a means is provided for connecting to the first elongated member  80  a flexible material with high tensile strength, such as a wire. Said means, connection A, may be comprised of an eye hook, wire rope sling, or other wire rope assembly for the purpose of connecting to the first elongated member  80  either the ends of two separate wire lengths or the midpoint of a single length of wire. Alternatively, connection A may be comprised of a pin oriented perpendicular to the ground to provide a means of connecting to the first elongated member  80  a pair of rigid elongated members such as two metal rods so that the motion of each of the rods is limited to rotation in the transverse plane about connection A. For purposes of this discussion, either the wire or the pair of metal rods, previously described, which are attached to connection A are referred as the Cantilever Spring Hitch  86 . In either of the configurations, connection A must be of sufficient strength to withstand the forces involved in propelling the carriage and occupant under a variety of loading situations and must be connected to the first elongated member  80  such that the first elongated member  80  may freely slide in either direction within the linear bearing  82 . 
         [0071]      FIG. 11   a  shows the middle portion of a cantilever spring  87  rigidly connected to the linear bearing  82  such that the elongated portions of the cantilever spring  87  extend away from the linear bearing assembly  82  in a direction which is perpendicular to the general axis of the tow bar assembly.  FIG. 11   b  shows the ends of the cantilever spring  87  when deflected in either the compression or extension direction along the transverse plane. At each end of the cantilever spring  87  connections B and C provide a means for connecting to the Cantilever Spring Hitch  86 . Connections B and C are comprised of an eye hook, turnbuckle, or other such means that when said means are connected to the Cantilever Spring Hitch  86  act to deflect the ends of the cantilever spring  87  in the direction of travel of connection A as connection A travels increasingly towards either the elongation or compression state. In this arrangement, a cantilever spring type is connected to the components of the tow bar assembly to provide a “neutral zone” in which said cantilever spring offers negligible resistance to the extension and compression of the tow bar assembly while connection A is within said zone, however, said cantilever spring exerts increasing resistance to the tow bar assembly extension or compression as connection A travels further towards either of said states. 
         [0072]      FIG. 12  shows the crossbar  5  described in  FIG. 3  is comprised of a “U” shaped member with each arm connected to the interior aspect  11  of each hub. As an example of an alternative arrangement of the carriage components described above, an axle sleeve is shown in this illustration that would accept the spindle  15  as a means of rotatably connecting to the axle sleeve  66  the wheel hubs  2 . Said axle sleeve is comprised of a two tubes perpendicular to each other where the axle tube  66   a  is perpendicular to the direction of travel and the connecting tube  66   b  is parallel to the direction of travel. In this example, the threaded portion of the spindle  15  is accepted by the axle tube  66   a  and secured on each side of the axle tube  66   a  by two nuts  70 . The hub  2  accepts the non threaded portion of the spindle and is rotatably secured to the axle tube such that the exterior aspect  14  of the hub is adjacent to the axle tube  66   b . Each end of the crossbar  65  shown in this illustration accepts the connecting tube  66   b , as the diameter of the crossbar tube  65  is greater than that of the connecting tube  66   b.    
         [0073]    A slot or groove is machined into the side of the connecting tube  66   b  to accept a sliding pin  68  which is secured to the side of the crossbar  65  as shown. The slot is comprised of three sections. Section  67   a  allows the sliding pin to travel axially along connecting tube  66   b . Section  67   b  allows the sliding pin to travel transversely to connecting tube  66   b . When the connecting tube  66   b  is accepted by the end of the crossbar  65 , the sliding pin travels along the slot or groove just described to permit the wheel axle to be inserted, rotated, and locked into position. A collar clamp  69  may be used to clinch the outer tube of the crossbar  65  to the connecting tube  66   b  and thus securing the axle sleeve, spindle and wheel hub to the crossbar such that the arms of the crossbar are connected to the exterior portion  14  of the wheel hubs. 
         [0074]    The purpose of this design alteration would be to substitute the structural support function of the carriage frame member  3  shown in  FIG. 3  with the crossbar  5  shown in  FIG. 8 , providing that the cross bar member material is of sufficient strength and stiffness, thus eliminating the need for the carriage frame  3 . The crossbar, by connecting its arms to the exterior aspects of the hubs  14 , would serve to protect the wheels from coming in contact with obstacles that may be encountered during operation of the carriage. 
         [0075]    While the preferred embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not of limitation. It will be apparent to persons skilled in the relevant art that various changes in form and detail can be made therein without departing from the spirit and scope of the invention. Thus the present invention should not be limited by the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents. Furthermore, while certain advantages of the invention have been described herein, it is to be understood that not necessarily all such advantages may be achieved in accordance with any particular embodiment of the invention. Thus, for example, those skilled in the art will recognize that the invention may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other advantages as may be taught or suggested herein.