Abstract:
A lightweight collapsible four-wheeled scooter with a large platform, the scooter including a height-adjustable non-steering foldable handle assembly in front for gripping by a rider, an adjustable height removable push bar extending to the rear for use by a pusher, a pair of non-swivelable wheels extending to the rear, and a pair of swivelable wheels in the front to enable steering, the scooter being capable of supporting a single standing rider or multiple standing riders, the scooter platform being capable of accommodating an optional removable seat having an optional removable carry basket.

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates generally to scooters or carts for use in transporting people. More specifically, the present invention relates to a lightweight collapsible four-wheeled scooter with a large platform, the scooter including a height-adjustable non-steering foldable handle in the front for gripping by a rider, an adjustable height removable push bar extending to the rear, a pair of non-swivelable wheels in the rear, and a pair of swivelable wheels in the front to enable steering. 
   Scooters or carts for transporting people are known in the prior art. While numerous configurations have been designed for this purpose, each lacks the combination of features and functionality found in the platform scooter of the present invention. In general, earlier devices such as those discussed below may be referred to as wheeled vehicles, carts, or scooters. A common difference from the present invention is that some devices may accommodate only a single rider, a sitting rider, or a standing rider. Also, some devices are not steerable or can be steered only by the rider. Further, other devices are self-propelled by the rider and do not provide means for a separate person to push the device. Further still, some devices do not provide a handlebar or grip that is adjustable to the height or size of the rider. Additionally, some devices are not readily collapsible for transport or storage. 
   Scooters of the most basic single person, non-steerable, self-propelled type are represented by U.S. Des. Pat. No. D176,736 [Rumsey], which shows a basic four-wheeled cart with a fixed handgrip for a rider. One possible improvement, the addition of steerability, is representatively illustrated by U.S. Des. Pat. Nos. D146,365 [Kinslow] and D208,791 [Purdy], which both provide a means, by either a fixed-height handlebar or lever, of manipulating the direction of the front wheels. 
   Another possible improvement, the addition of collapsibility, is illustrated by U.S. Des. Pat. No. D328,316 [Rogers], a non-steerable scooter with a foldable fixed-height front handle also including a small basket, and by U.S. Pat. No. 5,820,146 [Van Ligten], which includes an adjustable-height handle and converts into a two-wheeled luggage cart. A variation on this theme is disclosed in U.S. Pat. No. 4,179,134 [Atkinson] that shows the addition of a fixed-height handle to the front of a skateboard to create a self-propelled, steerable, single person scooter also including a brake. A variation of a different type is shown in U.S. Pat. No. 5,547,205 [do Rosario Sousa de Cabedo], intended as a luggage cart but usable as a self-propelled scooter, which includes a basket and provides a retractable seat for use when the cart is not in motion. However, all of these devices are self-propelled by the rider and include no provision for a pusher. 
   A wheeled vehicle of the most basic pushable type is disclosed in U.S. Pat. No. 6,416,070 [Lin], essentially a modified wheel chair with a fixed handlebar for the single seated rider to grip. A rider steerable extension of this pushable design is disclosed in U.S. Patent Application No. US 2002/0105155 A1 [Hou], which includes a fixed steering wheel and adjustable push bar, and provides transportation for a single seated child. An altogether different configuration of a pushable device for use with a single standing child is disclosed in U.S. Pat. No. 5,380,023 [McBee] and includes multiple swivelable casters. A yet different device, a pullable and steerable four-wheeled cart for transportation of a single injured athlete in the seated position is disclosed in U.S. Pat. No. 4,986,563 [Grant]. Lastly, a four-wheeled cart for a single seated rider is disclosed in U.S. Pat. No. 6,302,421 [Lee], this cart having a fixed steering wheel and push bar, as well as pedals for the rider, is capable of being both propelled and steerable either by the rider or by the pusher. 
   Accordingly, it is an object of the present invention to provide a four-wheeled scooter capable of carrying a single rider or multiple riders. It is also an object of the present invention to provide a four-wheeled scooter that can accommodate a rider in the standing or in the sitting position. It is a further object of the present invention to provide a four-wheeled scooter that may be either self-propelled or alternatively propelled by a person pushing or pulling the scooter from behind. 
   It is another object of the present invention to provide a four-wheeled scooter that may be steered by the pusher or possibly with the assistance of the rider. It is an additional object of the present invention to provide a four-wheeled scooter that includes an adjustable handlebar to accommodate riders of various heights and sizes. It is yet a further object of the present invention to provide a four-wheeled scooter that is collapsible for easy transport and storage. 
   Other objects will appear hereinafter. 
   SUMMARY OF THE INVENTION 
   The present invention overcomes the foregoing disadvantages inherent in the known types of scooters existing in the prior art. The present invention provides a four-wheeled platform scooter capable of transporting one or more riders in a standing position, or one or more riders in a seated position. The scooter of the present invention further includes a handlebar for gripping by the single rider or by the forwardmost of multiple riders, and additionally provides a push bar so that a person may push or pull the scooter from behind. The front wheels of the scooter swivel to enable steering by the pusher, or by the rider when there is no pusher. Additionally, the scooter is collapsible for transport by removing the rear push bar and folding the hingedly mounted handle portion downwardly and rearwardly onto the top of the platform. These objects, and others expressed or implied in this document, are accomplished by the present invention. 
   In the deployed state, the platform scooter is supported by four wheels, two fixed and two swivelable, and includes a base platform portion, a push bar portion, and handle portion. The non-swivelable pair of wheels is mounted directly to the rear end of the platform, and each of the two swivelable front wheels is incorporated into the handle portion of the scooter. The front-mounted forward-facing handle portion is interconnected rigidly to the platform by an insert and sleeve system, and is secured by a latching mechanism and quick release skewer similar to that used to retain bicycle wheels. The rear-mounted rearward-facing push bar portion is interconnected rigidly to the platform portion by an insert and sleeve system, and is secured by aligned pins snugly passing through both the insert and the sleeve. 
   The scooter should be utilized with the push bar mounted. To assist in steering, the rider can lean left or right, the shifting of the rider&#39;s weight causing the front casters to rotate slightly in the direction of leaning. The height of the handlebar is readily adjusted upward or downward by a clamping collar sleeve and telescoping insert system to accommodate various sizes and heights of riders. 
   With the push bar mounted, a pusher can propel the scooter forward or backward by simply grasping the push bar and walking in either direction. The pusher can steer the scooter by applying unequal pressure to one hand or the other, causing the front casters to rotate slightly in much the same way a shopping cart or a baby carriage may be steered. When a pusher is propelling the scooter, a rider may stand with both feet on the platform and one or both hands gripping the handlebar. An additional rider may stand behind the first rider with both feet on the platform and both hands on the waist or the shoulders of the first rider. Optionally, a seat may be mounted on the platform so that a rider may be seated with neither, one, or both hands gripping the handlebar while being propelled by a pusher. 
   For pushers of differing heights, the push bar is mounted so that the angle of the mounting may be varied so that the distal end of the push bar, the horizontal bar against which the pusher exerts his or her force, is adjusted up or down to accommodate the pusher. The proximal ends of the push bar handle are inserted into identical angle-adjustable sleeves and pinned in the selected position by a securing pin such that the height of the push bar handle is dependent upon the angle of insertion into the receiving sleeves. The push bar can be adjusted in height by removing the upper securing pin, altering the angle and reinserting the securing pin with the push bar at the newly selected position. 
   For transport or storage, the platform scooter may be converted to a collapsed state. The optional seat is removed from the platform. Further, the push bar is removed by extracting the securing pins and lifting the push bar upward and outward from the sleeves on the platform. Further still, the handle portion is folded to lay against the platform by first unclamping the quick release skewers and latching mechanism securing the handle portion to the platform, next lifting the handle portion upward and outward from the sleeves on the platform, then rotating the handle portion about the quick release skewers towards the top surface of the platform, and finally clamping the quick release skewers to hold the handle portion in place. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For the purpose of illustrating the invention, there is shown in the drawings forms which are presently preferred; it being understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. 
       FIG. 1  is a side elevation view of the platform scooter of the present invention. 
       FIG. 2  is a front elevation view of the platform scooter of the present invention. 
       FIG. 3  is a side view of the platform scooter of the present invention showing the means for allowing collapse and storage of the platform scooter. 
       FIG. 4  is a side view of the platform scooter of the present invention showing a seat and carry basket mounted to the platform. 
       FIG. 5  is an enlarged view of the rear portion of the platform showing one of the push bar receiving sleeves and bracket. 
       FIG. 6  is a sectional view taken along LINE  6 — 6  of  FIG. 5  showing the receiving sleeve and bracket and securing pins for modifying the height of the push bar. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The following detailed description is of the best presently contemplated mode of carrying out the invention. The description is not intended in a limiting sense, and is made solely for the purpose of illustrating the general principles of the invention. The various features and advantages of the present invention may be more readily understood with reference to the following detailed description taken in conjunction with the accompanying drawings. 
   Referring now to the drawings in detail, where like numerals refer to like parts or elements, there is shown in  FIG. 1  the platform scooter  10 . The scooter  10  comprises the base portion  12 , the handle portion  14 , and the push bar portion  16 . The scooter  10  further comprises a pair of non-swivelable rear wheels  28  and a pair of freely swivelable front wheels  60 . The scooter  10  may be deployed for use as shown in  FIG. 1 . Additionally, it may be collapsed for transporting, or for storage, by removing the push bar portion  16  from the base portion  12  and by folding the hingedly mounted handle portion  14  inwardly towards the top side of the base portion  12 , as illustrated in  FIG. 3 . As is shown in  FIG. 2 , the scooter  10  is symmetric about the longitudinal center axis, having identical, but reversed, left and right halves. 
   The details of the base portion  12  are best described with reference to  FIGS. 1 and 2 . The base portion  12  comprises the platform  20 , the two reinforcing members  22 , the two handle sleeves  32 , the two push bar sleeves  80 , the two rear wheel forks  24  holding the two rear wheels  28 , and the two rear fenders  30 . To achieve the desired purpose, the platform  20  of the base portion  12  must be of sufficient thickness and rigidity to support the weight of a rider. The intended rider or riders of the platform scooter  10  could be a large child, multiple small children, or a small handicapped adult, with total rider weight of not more than approximately  120  pounds. The two reinforcing members  22  run the length of the platform  20 , one on the right side and the other on the left side thereof, integral with the underside thereof, providing structural support and rigidity thereto. The side reinforcing members  22  further protect the underside of the platform  20  from damage due to any upwardly protruding obstacles that the scooter  10  may run over or against during use. 
   Two tubular handle sleeves  32  are rigidly attached to the front portion of the top side of the platform  20  to provide a means for securing the handle portion  14  to the base portion  12 . The handle sleeves  32  extend at a fixed angle upwardly and forwardly from the platform  20 , with one sleeve  32  positioned on the right side of the platform  20  and the other sleeve  32  positioned symmetrically on the left side of the platform  20 . The pair of handle sleeve tabs  34 , integral to each handle sleeve  32  and located at the upper open end thereof, are adapted to receive the quick release skewer  36 . When closed, the quick release skewer  36  squeezes the tabs  34  together against the outer surface of the handle insert  40  and provides clamping force to secure the handle insert  40  inside the handle sleeve  32 . When the quick release skewer  36  is opened, the clamping pressure is relieved and the handle insert  40  may be moved inwardly or outwardly or rotationally with respect to the handle sleeve  32  as will be described in more detail following. The quick release skewer  36 , well known in the art, is similar to those used to retain bicycle wheels and it is therefore deemed unnecessary to describe this element of the invention in further detail. 
   Two tubular push bar sleeves  80  are rigidly attached to the rear portion of the top side of the platform  20  to provide a means for securing the push bar portion  16  to the base portion  12 . The push bar sleeves  80 , as shown in  FIGS. 1–4 , extend at a fixed angle upwardly and rearwardly from the platform  20 , with one sleeve  80  positioned on the right side of the platform  20  and the other sleeve  80  positioned symmetrically on the left side of the platform  20 . A pair of through holes  82  near the upper open end of each push bar sleeve  80  are adapted to receive the push bar securing pin  84 . When an end of the push bar  86  is inserted into one of the push bar sleeves  80 , the securing pin  84  fits snugly through the holes  82  in the push bar sleeve  80  and through similar aligned holes in the other push bar sleeve (not illustrated) near the end of the push bar  86  to prevent the push bar  86  from being pulled out from the push bar sleeve  80 . When the securing pins  84  are removed, the push bar  86  may be moved inwardly or outwardly with respect to the push bar sleeve  80  for purposes of assembly and disassembly, respectively, of the platform scooter  10 . 
   Two rear wheel forks  24  extend rearwardly from the back end of the base portion  12 , each fork  24  being rigidly secured to both the platform  20  and one of the reinforcing members  22  running along underneath the sides of the platform  20 . The structural members of the rear fork  24  possess sufficient strength and stiffness to support the weight of a rider or multiple riders. The rear fork  24  supports the rear wheel assembly  28 , comprising an axle, bearings, and a wheel, the axle being secured into the through holes  26  in the rear fork  24 . Since such wheel and axle assemblies are common, it is believed unnecessary to show the details of this assembly. The rear wheel assemblies  28  cannot swivel with respect to the platform  20  but are rigidly mounted so that the wheels roll on the ground as the scooter  10  moves in a generally longitudinal direction, forward and backward. 
   Two rear fenders  30 , positioned over the two rear wheels  28 , are attached to the rear edge of the platform  20  and are formed to follow the curvature of the rear wheels  28 . The rear fenders  30  prevent a rider from accidentally stepping on one of the rear wheels  28  and also prevent any road debris or water from being lifted or spun up by the rear wheels  28  towards the rider. Additionally, the fenders  30  add visual appeal to the overall appearance of the platform scooter  10 . 
   In the preferred embodiment of the body portion  12 , the platform  20  and the reinforcing members  22  are fabricated from one piece of sheet steel, with the edges of the platform  20  being rolled under and up to form the reinforcing members  22 . The steel handle sleeves  32  are fabricated from a section of heavy walled rectangular tube with rounded corners having one end cut at an angle of approximately 30 degrees from the perpendicular and the other end cut to form the two tabs  34 , each tab  34  having a through hole  38  for receiving the quick release skewer  36 . The angle cut end of each handle sleeve  32  is welded to the front portion of the top surface of the platform  20  so that the handle sleeve  32  extends upwardly and forwardly therefrom. The steel push bar sleeves  80  are fabricated from a section of heavy walled round tube or pipe having one end cut at an angle of approximately 30 degrees from the perpendicular and the other end cut perpendicular, further including two through holes  82  for receiving the securing pin  84 . The angle cut end of each push bar sleeve  80  is welded to the rear portion of the top surface of platform  20  so that the push bar sleeve  80  extends upwardly and rearwardly therefrom. The steel rear wheel forks  24  are fabricated from rectangular bar stock and include through holes  26  for receiving the axle of the rear wheel assembly  28 . Each rear wheel fork  24  is welded to both the platform  20  and the one of the reinforcing members  22  and extends rearwardly from the platform  20 . The steel rear fenders  30  are welded to the rear of the platform  20  between the legs of each rear wheel fork  24  to project rearwardly over the rear wheels  28 . 
   As an alternative to the welded steel construction, the entire base portion  12  comprising the platform  20 , the reinforcing members  22 , the handlebar sleeves  32 , the push bar sleeves  80 , the rear wheel forks  24 , and the rear fenders  30  could be fabricated as one integral piece from a composite material such as carbon fiber, fiber glass, or a sufficiently strong and rigid plastic material. As another alternative, the reinforcing members  22 , the handlebar sleeves  32 , the push bar sleeves  80 , the rear wheel forks  24 , and the rear fenders  30  may be fabricated as separate parts, from the same or different materials, and each bolted individually to the platform  20  to form the base portion  12 . 
   The push bar portion  16  comprises an upper push bar section  86 , a lower push bar section  88 , a push bar handle  90 , and a push bar cross member  92 . The upper push bar  86  is fabricated from a piece of steel tube or pipe bent into a U-shape to create the push bar handle  90  in between two equal length push bar legs  86 . The cross member  92  is rigidly attached to both of the push bar legs  86  near their respective midpoints to impart structural rigidity to the push bar portion  16 . The length of the push bar handle  90  equals the distance between the two push bar sleeves  80  that extend upwardly and rearwardly from the top surface of the platform  20 . The outer diameter of the upper push bar legs  86  is slightly less than the inner diameter of the lower push bar  88  so that the upper push bar legs  86  can slide inwardly and outwardly into and out of the lower push bar legs  88 , creating a telescoping motion for adjusting the height of the push bar  16 . A spring lock  96  formed into the lower end of the upper push bar legs  86  on the outward facing surface cooperates with a series of apertures  98  on the lower push bar legs  88  to lock the upper and lower push bar legs  86 ,  88  in a selected position to achieve the desired height of the push bar  16 . The lower push bar legs  88  have an outer diameter that is slightly less than the inner diameter of the sleeves  80 . The end of each lower push bar leg  88  is capable of being inserted into one of the push bar sleeves  80 , which aligns with the through hole  82  in the push bar sleeve  80 , for receiving the securing pin  84 . When the push bar portion  16  is mounted to the base portion  12  in this manner, the push bar handle  90  may be pushed and pulled by a person to propel the scooter  10  in the forward and reverse directions, respectively. In the preferred embodiment, the steel cross member  92  is welded to the steel upper push bar  86 . 
   The handle portion  14  comprises two front casters  52  with swivelable front wheels  60 , a pair of handle inserts  40  each rigidly connected to the corresponding front caster  52  and adapted to be received by one of the handle sleeves  32  on the platform  20 , a handle cross member  62  rigidly interconnecting between the two front casters  52 , and an adjustable handlebar assembly  64  rigidly mounted to the cross member  62  and extending upwardly therefrom. 
   Each front caster  52  is a double bearing design well known in the art and therefore it is believed unnecessary to describe in detail every component of the casters  52 . Comprising the caster  52  are components including the bearing sleeve  54 , the bearing shaft  56 , the front wheel fork  58 , and the front wheel assembly  60 . The bearing sleeve  54  provides the outer races for the two internal bearings located near the ends thereof, as well as the mounting surfaces for attachment of the caster  52  to the handle insert  40  and the handle cross member  62 . The bearing shaft  56  is held concentrically within the bearing sleeve  54  and provides the inner races for the two internal bearings so that the bearing shaft  56  can rotate freely within the bearing sleeve  54 . In the preferred embodiment, the bearings are tapered roller bearings to provide both axial support and rotational freedom. Attached rigidly to the lower end of the bearing shaft  56  is the front wheel fork  58 , comprising two structural members with sufficient strength and stiffness to support the weight of a rider, the front wheel fork  58  rotating together with the bearing shaft  56 . 
   The front fork  58  supports the front wheel assembly  60 , comprising an axle, bearings, and a wheel, the axle being secured into the through holes  59  in the front fork  58 . Since such wheel and axle assemblies are common, and since the front wheel assembly  60  is identical to the rear wheel assembly  28 , it is believed unnecessary to show the details of this assembly. The handle cross member  62  is rigidly connected to the bearing sleeve  54  of each caster  52  so that the front wheels  60  extend downwardly therefrom when the handle portion  14  is assembled to the deployed scooter  10 . 
   The adjustable handlebar assembly  64 , which provides a gripping point and support for a rider but is not used to steer the scooter  10 , enables the scooter  10  to accommodate riders of various sizes and heights. The handlebar assembly  64  comprises the handlebar  72 , the upper handle stem  70 , the handle extender tube  68 , and the lower handle stem  66 . The round tubular upper handle stem  70  is rigidly connected to the midpoint of the round tubular handlebar  72 , extending outwardly therefrom to form a symmetric T-shape. When assembled to the deployed scooter  10 , the handlebar  72  is mounted in a horizontal position and includes hand grips  74  at either end, and the upper handle stem  70  extends vertically downward. The round tubular lower handle stem  66  is rigidly connected to the midpoint of the handle cross member  62 , extending upwardly therefrom to form a symmetric T-shape. The lower handle stem  66  extends away from the cross member  62  in the opposite direction from the casters  52 . The lower handle stem  66  and the upper handle stem  70  are fabricated from the same diameter tube. 
   The handle extender tube  68  telescopically interconnects between the lower handle stem  66  and the upper handle stem  70 . The inner diameter of the handle extender tube  68  is slightly larger than the outer diameter of both the lower handle stem  66  and the upper handle stem  70 , and therefore the lower stem  66  and the upper stem  70  can slide readily into and out of the extender tube  68 . The position of the lower stem  66  within the extender tube  68  is secured by tightening the lower stem collar  76 , which squeezes the inner surface of the lower end of the extender tube  68  against the outer surface of the lower stem  66 . The position of the upper stem  70  within the extender tube  68  is secured by tightening the upper stem collar  78 , which squeezes the inner surface of the upper end of the extender tube  68  against the outer surface of the upper stem  70 . Therefore, the height of the handlebar assembly  64  is infinitely adjustable, with the maximum height being nearly the sum of the lengths of the lower stem  66 , the extender tube  68 , and the upper tube  70 , and the minimum height being shorter than the maximum height by approximately the length of the extender tube  68 . See the phantom extended height handlebar  72 A in  FIG. 2 . It is noted that other equivalent means of achieving longitudinal adjustment may be used, such as pins or threaded connections. 
   To provide a collapsible means for attachment of the handle portion  14  to the base portion  12 , the handle insert  40  is rigidly attached to the rear portion of each front caster  52 , extending rearwardly and downwardly therefrom. The handle insert  40  is fabricated from tubular material of the same cross sectional geometry as the handle sleeve  32  but having outer dimensions slightly smaller than the inner dimensions thereof, enabling the handle insert  40  to slide smoothly but snugly into the handle sleeve  32 . 
   The handle insert  40  includes a longitudinal through slot  42  (best seen in  FIG. 3 ) adapted for receiving the quick release skewer  36  and a through hole  44  adapted for receiving the latching mechanism  46 . The slot  42  enables the handle insert  40  to have a limited range of movement with respect to the handle sleeve  32 , when the quick release skewer  36  is inserted, so that the handle portion  14  may be rotated about the base portion  12  and collapsed for storage or deployed for use. When stowed for storage, the handle portion  14  is secured in position by clamping down the quick release lever  36 . When deployed for use, the clamping force of the quick release lever  36  is insufficient to support the weight of a rider and therefore the handle portion  14  is additionally locked into place by the latching mechanism  46 . 
   The latching mechanism  46  is rotatably mounted into through holes  44  near the slot  42  in the handle insert  40 , the through holes  44  being positioned between the caster  52  and the slot  42 . The latching mechanism  46  includes a latching hook  50  (not illustrated) which is located internal to the tubular handle insert  40 , extending downwardly towards the slot  42 . The latching mechanism  46  further includes a latch lever  48  which, when actuated, swivels the latching hook  50  inside the tubular handle insert  40 . 
   When the handle portion  14  is rotated into its deployed position about the base portion  12  and the handle insert  40  is inserted fully into the handle sleeve  32  as limited by the slot  42  and the quick release skewer  36 , the quick release skewer  36  is clamped and the latch lever  48  is actuated thereby rotating the latching hook  50  to engage the quick release skewer  36 . The positive latching action of the latching hook  50  with the quick release skewer  36  enables the scooter  10  to support the weight of a rider, preventing the tendency of the handle insert  40  to slide outwardly from the handle sleeve  32  which could occur if the handle insert  40  were to be held in place only by the clamping force of the quick release skewer  36 . 
   In order to rotate the handle portion  14  into its stowed position, the latch lever  48  is deactuated, disengaging the latching hook  50  from the quick release skewer  36 , the quick release skewer  36  is unclamped, the handle insert  40  slides outwardly fully from the handle sleeve  32  as limited by the slot  42  and the quick release skewer  36 , and the handle portion  14  is free to rotate about the quick release skewer  36  inwardly towards the top of the platform  20  of the base portion  12 . 
   In the preferred embodiment of the handle portion  14 , the steel handle inserts  40  are fabricated from a section of heavy walled rectangular tube with rounded corners having one end cut at an angle of approximately 60 degrees from the perpendicular and the other end cut perpendicular. The angle cut end of each handle insert  40  is welded to the rear of the steel bearing sleeve  54  of the corresponding caster  52  so that the handle insert  40  extends downwardly and rearwardly therefrom. The handle cross member  62  is fabricated from steel angle with both ends cut square, and is welded at each end to the steel bearing sleeve  54  of one of the casters  52  with the flat faces of the angle oriented to face forward and upward. The round tubular steel lower handle stem  66  is welded to the midpoint of the top face of the handle cross member  62  to extend upwardly therefrom. The round tubular steel upper handle stem  70  is welded to the midpoint of the round tubular steel handlebar  72  to extend downwardly therefrom. The round tubular handle extender tube  68  and the clamping collars  76 ,  78  may be fabricated from steel or from a sufficiently rigid composite material, as desired. 
   When assembled and deployed for use, the scooter  10  may carry a rider or multiple riders, and is propelled in the forward or reverse direction by a pusher. The sole rider, or the front rider of multiple riders, may adjust the handlebar assembly  64  to the appropriate height by loosening the upper stem collar  78  and the lower stem collar  76 , sliding the upper handle stem  70  and the lower handle stem  66  inward or outward with respect to the handle extender tube  68  as required, and then tightening the upper collar  78  and the lower collar  76  to secure the handlebar assembly  64  as a rigid structure with the handlebar  72  at the desired height. The pusher, while gripping the push bar handle  90 , drives the scooter  10  forward or backward, and may steer the scooter  10  by exerting lateral pressure on the push bar handle  90  causing the swivelable front wheels  60  to turn toward the desired direction of travel, in much the same way as a shopping cart or baby carriage is steered. 
   With reference to  FIG. 4 , a modified embodiment of the scooter  10  includes a seat assembly  100 , comprising a seat  102  and optionally a basket  104 . The seat assembly  100  is attached to the top surface of the platform  20  by bolting or equivalent removable means, and is positioned to allow the seated rider to reach the handlebar  72 . The seat assembly  100  expands the range of potential riders of the scooter  10  to include handicapped persons who are unable to stand or small children who are too old or too large for a stroller but may be too tired to stand or walk. The basket  104  optionally incorporated into the rear of the seat  102  enables the scooter  10  to be used for shopping or to carry items during a walk in the park or around the neighborhood. 
   The scooter  10  is readily disassembled and collapsed for storage or transport. The optional seat assembly  100 , if installed, is first detached from the platform  20 . The push bar securing pins  84  are removed and the push bar portion  16  is pulled upward and outward from the base portion  12 , sliding the lower push bar legs  88  out from the push bar sleeves  80 . The quick release skewers  36  are unclamped and the latching mechanism  46  is deactuated, allowing the handle portion  14  to slide freely upward and outward from the base portion  12 . The handle portion  14  is pulled upward and outward until the quick release skewers  36  mounted in the handle sleeves  32  contact the ends of the slots  42  in the handle inserts  40 , and the handle portion  14  is then rotated about the quick release skewers  36  until the handlebar  72  rests on the top surface of the platform  20 . The quick release skewers  36  are clamped to secure the handle portion  14  in the stowed position with respect to the base portion  12 . Reassembly of the scooter  10  is the reverse of disassembly. 
   In another alternate embodiment, the push bar  16  is also made to be adjustable by varying the angle at which it attaches to the scooter  10 . Referring to  FIG. 5 , the push bar  16  is inserted into a modified push bar sleeve or bracket  180  by inserting the lower push bar legs  88  into the modified push bar sleeve  180  and securing the push bar  16  within the sleeve  180  by inserting the push bar securing pin  184  through the cooperating apertures in both the sleeve  180  and the lower push bar legs  88 . The push bar height is then adjustable by moving the push bar  16  into one of several positions provided in the modified push bar sleeve  180 . The several positions, three positions being shown in  FIG. 5 , are arrayed along the upper edge portion of the modified push bar sleeve  180  and are comprised of a series of apertures  186  and a second push bar securing pin  188  and a series of cooperating cylindrical openings  190  arrayed along the interior of the modified push bar sleeve  180 . 
   Each of the cylindrical openings  190  is sized to approximate the outer dimension of the lower push bar legs  88  and are positioned to allow the second push bar securing pin  188  to be placed through the modified sleeve apertures  186  and cooperating apertures (not shown) in the lower push bar legs  88 . In this manner, the push bar  16  can be adjusted for vertical height by angularly rotating its lower end about the securing pin  184  and retaining the push bar in the selected position by inserting the second push bar securing pin  188  through the cooperating apertures in the selected position. To assist in this procedure, the cylindrical openings  190  are able to retain the push bar  16  in the selected position until the second securing pin  188  has been inserted as shown in  FIG. 6 . 
   The modified push bar sleeves or bracket  180  may be made from the same materials as described above, or from an extruded plastic have minimal elastic characteristics providing for the slight expansion of the walls of the sleeves  180  as the lower push bar legs  88  are repositioned from one cylindrical opening to another. This would be accomplished without the removal of the push bar  16  from the modified sleeve  180  and with the push bar securing pin  184  remaining in place. Alternatively, if the modified sleeve is made from the metal material described above, the push bar  16  is removed from one position in the modified sleeve  180  by removing the securing pin  184 , repositioned into another cylindrical opening  190 , and both the securing pin  184  and the second securing pin  188  placed through the modified sleeve  180  and the lower push bar legs  88  to secure the push bar  16  in its new position. When removing the push bar  16  from the scooter  10 , the securing pin  184  and the second securing pin  188  are removed from the modified sleeve  180  and the push bar  16  withdrawn from the cylindrical opening  190  in the modified push bar sleeves  180  so that the scooter  10  can be stowed as described above. 
   The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof and, accordingly, the described embodiments are to be considered in all respects as being illustrative and not restrictive, with the scope of the invention being indicated by the appended claims, rather than the foregoing detailed description, as indicating the scope of the invention as well as all modifications which may fall within a range of equivalency which are also intended to be embraced therein.