Abstract:
The present invention relates generally to skateboard and caster devices. More particularly, in a manner the invention concerns both dual wheel and single wheel axle supports of trucks and casters having a suspension mechanism for absorbing shock. The suspension mechanism is uniquely designed to progressively increase suspension resistance as forces acting on the mechanism increase by elastically deforming an independent arm in a manner to contact another arm or structure thereby transforming the independent arm into a dependent arm that results in a progressive resistance to a load until the forces are terminally engaged into a resilient abutment. A novel alignment mechanism functions to maintain the skateboard steering function.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    Not Applicable 
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not Applicable 
       INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC 
       [0003]    Not Applicable 
       BACKGROUND OF THE INVENTION 
       [0004]    1. Field of the Invention 
         [0005]    The present invention relates generally to skateboards and skate devices such as quad wheel roller skates, multi-wheel scooters, and to casters and caster devices such as scooters, caster boards, wheelchairs and utility carts. More particularly, the invention concerns both dual wheel and single wheel axle support mechanisms and casters with novel suspension mechanisms designed to absorb shock. Also disclosed is an embodiment for an extendable tilt axis alignment device for a truck hanger enabling full tilt steering functions when a truck hanger is mounted on a biased suspension mechanism. 
         [0006]    2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98 
         [0007]    Skateboards of various designs having a pair of trucks in opposing orientation disposed under a rider surface are well known in the art. The prior art trucks are typically fitted with a pair of wheels with steering being accomplished by the rider tilting the rider surface, thus pivoting the hangers on a tilt axis between 30° and 55°, rotating axles and wheels in opposite directions thus causing the board to turn. Two types of kingpin configurations for skateboard trucks are predominate in prior art. The first is the conventional kingpin truck consisting of a hanger that tilts on a kingpin which acts as the fulcrum for the hanger. The kingpin is mounted approximately perpendicular to the tilt axis through a central aperture of the hanger with the kingpin being fixedly attached to a mounting base. The hanger has a central alignment leg projecting in a transverse direction from the axle that maintains the tilt axis and is received by a pivot cup that is an articulation point in the mounting base. The hanger tilts along the axis and resistively compresses resilient tilt-crush bushings that bring the hanger back to a neutral position. The second is the torsion kingpin truck that consists of a hanger that tilts on a kingpin that is located longitudinally on the tilt axis so that the hanger can tilt on the kingpin to permit steering the truck. Various torsion mechanisms have also been disclosed that provide resistance to tilting and function to assist in bringing the hanger back to a neutral position. 
         [0008]    Prior art designs of non-biased casters often include a U-shaped wheel fork with a transversely mounted axle having a single wheel disposed on the axle and located between the arms of the wheel fork. Another form of prior art caster is the split wheel caster which has a central body portion with a transversely mounted axle passing through the central body and projecting on both sides to receive two wheels. Though the split wheel caster has two wheels, it effectively performs in the same manner as a single wheel caster. 
         [0009]    Prior art designs of non-biased axle support mechanisms for the skateboard and caster provide adequate performance over smooth surfaces, but can become extremely hazardous when a wheel of the device encounters an obstacle such as a small rock or minor curb transition. Because the prior art devices have no effective means to absorb the shock of the impact with a rock or curb transition, the rider can either be ejected from the device or dangerously lose control of the device. 
         [0010]    For over a century, many types of biased suspension mechanisms have been suggested to absorb shock and provide the user with a more compliant and safer passage over irregular terrain. However, none of these prior art devices have been able to provide the novel attributes of the present invention regarding shock absorption, stability, functionality and weight. 
         [0011]    By way of example, a biased skateboard truck with a conventional \ kingpin configuration is disclosed in U.S. Pat. No. 4,155,565 issued to de Caussin et al. The de Caussin device includes a truck that is mounted onto a separate biased plate-shaped member which comprises a duplication of the base structure and the biasing means and results in additional weight and undesirable added axle height thereby limiting functionality. 
         [0012]    Another prior art truck construction with a conventional kingpin configuration and suspension mechanism is disclosed in U.S. Publication No. 2008/0252026A to Kang. In the Kang device, a biased plate-shaped member supports a hanger that is a non-extendable link between opposing inwardly facing independent arms. With this construction, when a force is applied to the truck, the arms bind and negate each other&#39;s movement and shock-absorbing potential. 
         [0013]    U.S. Pat. No. 4,152,001 issued to Christianson, discloses an axle hanger that is mounted on a plate-shaped member. The Christianson device has the ability to conform to the terrain, but lacks a steering alignment mechanism to enable the hanger to maintain the steering tilt axis. Accordingly, the hanger is susceptible to axial forces that could cause loss of the integrity of the steering geometry and stability. 
         [0014]    U.S. Pat. No. 7,219,907 to Chang concerns a torsion kingpin truck configuration that has a suspension mechanism but has limitations due to the independent movement of the axles as the bottom of the central body can scrape the ground if the suspension is compressed, thus requiring large wheels to avoid this undesirable condition. 
         [0015]    U.S. Pat. No. 1,745,992 issued to Herold discloses a caster that compresses an elastomeric damper in a nutcracker fashion. The Herold device exhibits a very limited compression stroke and suffers unavoidable deterioration of the elastic damper due to repeated impact. 
         [0016]    The prior art U.S. Pat. No. 2,738,542 issued to Clark discloses a rather commonly adopted suspension mechanism for a caster and includes a saddle-shaped mounting bracket, a U-shaped wheel fork, a hinge pin and two helical coil springs. However, the Clark device is unduly complex in that it incorporates many separate components in addition to the biasing means to support the mechanism, adding additional cost and weight to the caster assembly. 
         [0017]    U.S. Pat. No. 5,394,589 issued to Braeger et al. discloses a somewhat simpler shock-absorbing caster, but uses multiple structural components not required in the novel apparatus of the present invention. 
       BRIEF SUMMARY OF THE INVENTION 
       [0018]    The present invention relates generally to skateboard and caster devices. More particularly, the present invention concerns both dual wheel and single wheel axle supports of trucks and casters and discloses a unique suspension mechanism for absorbing shock. The novel suspension mechanism of the present invention progressively increases suspension resistance as forces acting on the mechanism increase by elastically deforming an independent arm to contact another arm or structure thereby transforming the independent arm into a dependent arm that results in a progressive resistance to a load until the forces terminally engage a resilient abutment. The present invention also concerns an embodiment for an extendable tilt axis alignment device for a truck hanger that enables full tilt steering functions when a truck hanger is mounted on a novel suspension mechanism. 
         [0019]    With the foregoing in mind, it is an object of the present invention to provide a shock-absorbing suspension mechanism for use on skateboards and caster devices that markedly improves stability, riding enjoyment, and user safety by reducing undesirable shock and vibration. 
         [0020]    Another object of the invention is to provide a shock-absorbing suspension mechanism of the aforementioned character that maintains control of the device even when used on rough and uneven surfaces. 
         [0021]    Another object of the invention is to provide a shock-absorbing suspension mechanism of the character described that includes a suspension arm that is free to articulate and absorb shock and one that uniquely functions to progressively increase suspension resistance as forces acting on the mechanism increase. 
         [0022]    Another object of the invention is to provide a shock absorbing mechanism of the character described in the preceding paragraph that includes an independent arm that is adapted to contact another arm or structure thereby transforming the independent arm into a dependent arm that results in a progressive resistance to the load until the forces terminally engage a resilient abutment. 
         [0023]    Another object of the invention is to provide a shock-absorbing suspension mechanism of the class described in which a shock absorber is connected to the suspension mechanism to further dampen shock and vibration. 
         [0024]    Another object of the invention is to provide a shock-absorbing suspension mechanism for axle support constructions of the type used on skateboards and cart devices in which the kingpin, kingpin mount or caster fastener projects through a first independent arm and is slidably engaged into a secondary independent arm thus providing additional axial stability. 
         [0025]    Another object of the invention is to provide an extendable tilt axis alignment mechanism for use on a skateboard truck that permits the axle hanger to maintain a tilt axis throughout the suspension compression cycle and one which uses articulation points and extendable portions to counteract any axial forces encountered, thereby providing predictable and stable tilt steering from the truck in virtually all riding conditions. 
         [0026]    Another object of the invention is to provide a shock-absorbing suspension mechanism and complementary extendable steering alignment device for use on a skateboard that maintains comparable attributes of axle height, weight and cost to prior art non-biased trucks. 
         [0027]    Another object of the invention is to provide a shock-absorbing suspension caster that is extremely simple in construction, is cost-effective to build, and comprises only three primary assembly components, namely a biasing member, an axle and a wheel. 
     
    
     
       BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS 
         [0028]      FIG. 1A  is a generally perspective view of one form of skateboard truck of the invention mounted on a structural member. 
           [0029]      FIG. 1  is a cross-sectional view of the skateboard truck illustrated in  FIG. 1A . 
           [0030]      FIG. 2  is a cross-sectional view similar to  FIG. 1 , but showing the skateboard truck in a compressed state. 
           [0031]      FIG. 3  is a generally perspective view of one form of the suspension member of the skateboard truck shown in  FIGS. 1 and 1A . 
           [0032]      FIG. 4  is a generally perspective view of the kingpin truck hanger assembly of the skateboard truck shown in  FIG. 1 . 
           [0033]      FIG. 5  is a generally perspective view of the extendable tilt axis alignment mechanism of the skateboard truck shown in  FIG. 1 . 
           [0034]      FIG. 6  is a generally perspective view of the suspension mechanism of the skateboard truck shown in  FIG. 1 . 
           [0035]      FIG. 7  is a cross-sectional view of an alternate embodiment of the skateboard truck of the invention. 
           [0036]      FIG. 8  is a cross-sectional view similar to  FIG. 7 , but showing the skateboard truck in a compressed state. 
           [0037]      FIG. 9  is a generally perspective view of the kingpin truck hanger assembly of the skateboard truck shown in  FIG. 7 . 
           [0038]      FIG. 10  is a generally perspective view of the extendable tilt axis alignment mechanism of the skateboard truck shown in  FIG. 7 . 
           [0039]      FIG. 11  is a generally perspective view of the suspension mechanism of the skateboard truck shown in  FIG. 7 . 
           [0040]      FIG. 12  is a cross-sectional view of still another embodiment of the skateboard truck of the invention. 
           [0041]      FIG. 13  is a cross-sectional view similar to  FIG. 12 , but showing the skateboard truck in a compressed state. 
           [0042]      FIG. 14  is a generally perspective view of the kingpin truck hanger assembly of the skateboard truck shown in  FIG. 12 . 
           [0043]      FIG. 15  is a generally perspective view of the extendable tilt axis alignment mechanism of the skateboard truck shown in  FIG. 12 . 
           [0044]      FIG. 16  is a generally perspective view of the suspension mechanism of the skateboard truck shown in  FIG. 12 . 
           [0045]      FIG. 17  is a cross-sectional view of yet another embodiment of the skateboard truck of the invention. 
           [0046]      FIG. 18  is a cross-sectional view similar to  FIG. 17 , but showing the skateboard truck in a compressed state. 
           [0047]      FIG. 19  is a generally perspective view of the kingpin truck hanger assembly of the skateboard truck shown in  FIG. 17 . 
           [0048]      FIG. 20  is a generally perspective view of the extendable tilt axis alignment mechanism of the skateboard truck shown in  FIG. 17 . 
           [0049]      FIG. 21  is a generally perspective view of the suspension mechanism of the skateboard truck shown in  FIG. 17 . 
           [0050]      FIG. 22  is a generally perspective view showing variations of rib profiles formed transverse to the longitudinal axis of the independent arm of the suspension mechanism shown in  FIG. 21 . 
           [0051]      FIG. 23  is a cross-sectional view of still another embodiment of the present invention. 
           [0052]      FIG. 24  is a generally perspective view of the single wheel caster of the embodiment of the invention shown in  FIG. 23 . 
           [0053]      FIG. 25  is a generally perspective view of a dual wheel caster usable with the suspension mechanism of the embodiment of the invention shown in  FIG. 23 . 
           [0054]      FIG. 26  is a generally perspective view of the suspension mechanism of the embodiment of the invention shown in  FIG. 23 . 
           [0055]      FIG. 27  is a cross-sectional view of yet another embodiment of the invention. 
           [0056]      FIG. 28  is a cross-sectional view similar to  FIG. 27 , but showing the mechanism in a compressed state. 
           [0057]      FIG. 29  is a generally perspective view of the embodiment of the invention shown in  FIG. 27 . 
           [0058]      FIG. 30  is a generally perspective view of yet another embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0059]    Referring to the drawings and particularly to  FIGS. 1 through 6 , one form of the truck of the invention is there shown and generally designated by the numeral  40 . As will become clear from the description that follows, the truck of the invention is usable with a skateboard, scooter, or like vehicle of the character having a structural member  42 , such as a deck upon which the truck can be mounted. An important feature of the invention is the suspension mechanism  44  that is connected to the structural member in the manner shown in  FIG. 1A . Suspension mechanism  44  here comprises a base  48 , a first flex member  50  connected to base  48  and extending angularly outwardly therefrom and a second flex member  52  connected to the base and extending outwardly therefrom in a direction toward the first flex member (see  FIG. 3 ). As best seen in  FIG. 3 , first flex member  50  of said suspension mechanism extends from base  48  at an angle of between about 25° and about 65°. As illustrated in  FIGS. 1 and 2 , first flex member  50  is constructed and arranged to flex between a first position shown in  FIG. 1  and a second position shown in  FIG. 2  wherein it resides proximate second flex member  52 . As best seen in  FIGS. 3 and 6 , first flex member  50  is provided with a transversely extending, concave rib  53  that tends to enhance the flexing capability of member  50 . It is to be understood that the transversely extending rib can be formed in various configurations. For example,  FIG. 22  illustrates several alternate variations of rib profiles that can be formed in first flex member  50 , which variations are identified in  FIG. 22  as  53   a ,  53   b  and  53   c  respectively. 
         [0060]    Suspension member  46  is preferably constructed from a single piece of material selected from the group consisting of metal, plastic, fiberglass, KEVLAR® and carbon fiber. 
         [0061]    Connected to first flex member  50  is a hanger assembly  54 , the character of which is shown in  FIG. 4  of the drawings. Hanger assembly  54  has a tilt axis “TA”, a hanger body  54   a  and a pivot leg  55  affixed to hanger body  54   a  and disposed substantially parallel to the pivot axis. Hanger assembly  54  also comprises a kingpin assembly  56 , an axle  58  connected to the kingpin assembly, and first and second wheels  60  and  62  that are rotatably mounted on axle  58 . Kingpin assembly  56  includes a kingpin  64  and an alignment guide  66 . Extending outwardly from kingpin  64  is an alignment sleeve  68  that houses a rotatably mounted spherical bearing  70  that has a central bore  70   a.    
         [0062]    Operably associated with hanger assembly  54  is the important alignment means of the invention which functions to maintain the orientation of the tilt axis of the hanger assembly as the first flex member  50  flexes between its first and second position. The construction and operation of the alignment means will presently be described. 
         [0063]    Also connected to base  48  of the suspension member  44  is a bumper assembly  72  that includes a bumper stop  74  which, in a manner presently to be described, is engagable by the kingpin  64  of the kingpin assembly  56 . 
         [0064]    In the present form of the invention, the important alignment means comprises an alignment assembly  76  that includes a body portion  77  that is connected to the structural member  42  and to the suspension mechanism  44  in the manner illustrated in  FIG. 1A . Alignment assembly  76  also includes a hinge pin assembly  78  that is rotatably connected to body portion  77  and includes a transversely extending pin portion  79  and a connector member  80  that is connected to pin portion  79  and extends outwardly therefrom. As seen in  FIGS. 1 and 2 , the connector member  80  is receivable within the central bore  70   a  of spherical bearing  70  for reciprocal movement therewithin between the first position shown in  FIG. 1 , through a distance  39  into the second position shown in  FIG. 2 . 
         [0065]    When the trucks of the invention are connected to the skateboard deck  42  in the manner illustrated in  FIG. 1A , the skateboard can be operated in a conventional manner with steering being accomplished by the rider tilting the rider surface from side to side, thus pivoting the hangers on the tilt axis “TA” between 30° and 55° thus causing the skateboard to turn. As illustrated in  FIGS. 1 and 2 , as forces are exerted by the rider on the novel suspension mechanism  44  of the invention, the first flex member  50  will flex from the first position shown in  FIG. 1  toward the second position shown in  FIG. 2  and toward the second flex member  52 . 
         [0066]    As the first flex member  50  flexes toward the second position, the kingpin assembly  56 , which is connected to the first flex member by appropriate fasteners  84  in the manner shown in  FIGS. 1 and 2 , also moves downwardly. More particularly, as shown in  FIG. 2 , the lower end portion  64   a  of kingpin  64 , along with the lower end portion of the alignment guide  66 , moves into an aperture  86  formed in the second flex member  52  of the suspension mechanism and in a direction toward the bumper stop  74  of the bumper assembly  72 . 
         [0067]    It is to be noted that the suspension mechanism is uniquely designed to progressively increase suspension resistance as forces acting on the mechanism increase by elastically deforming the first flex member in a manner to contact the second flex member, thereby transforming the first flex member into a dependent arm that results in a progressive resistance to a load until the forces are terminally engaged into the bumper stop  74 . 
         [0068]    As the kingpin assembly  56  moves downwardly, the end portion  80   a  of the connector member  80  of the alignment assembly of the alignment means of the invention, moves reciprocally inwardly of the central bore  70   a  of spherical bearing  70  that is housed within alignment sleeve  68  of the kingpin assembly  56 . Spherical bearing  70  is maintained in position within the alignment sleeve by a retainer clip  71  ( FIG. 5 ). 
         [0069]    Referring now to  FIGS. 7 through 11  of the drawings, an alternate form of the truck of the invention is there shown and generally designated by the numeral  90 . This embodiment of the invention is similar in many respects to the embodiment shown in  FIGS. 1 through 6  of the drawings and like numerals are used in  FIGS. 7 through 11  to identify like components. 
         [0070]    The primary difference between this latest embodiment of the invention and the earlier described embodiment resides in a differently configured hanger assembly and a differently configured alignment means. As in the earlier described embodiment, an important feature of this latest form of the invention resides in the suspension mechanism  44  that is substantially identical in construction and operation to that previously described. 
         [0071]    Connected to the first flex member  50  is a hanger assembly  94  of the invention that is of somewhat different construction. However, as in the earlier described embodiment of the invention, hanger assembly  94  has a tilt axis “TA” and comprises a kingpin assembly  56 , an axle  58  connected to the kingpin assembly, and first and second wheels  60  and  62  that are rotatably mounted on axle  58 . Kingpin assembly  56  also includes a kingpin  64  and an alignment guide  66  that are substantially identical in construction and operation to those previously described. Extending outwardly from kingpin  64  is an alignment sleeve  68  that houses a differently constructed bearing  96 . More particularly, bearing  96  here comprises a rolling element bearing that has an outer race  98  and a plurality of circumferentially spaced ball bearings  98   a  that cooperate to define a central opening  99 . Bearing  96  is maintained in position within the alignment sleeve by a retainer clip  96   a  ( FIG. 10 ). 
         [0072]    Operably associated with hanger assembly  94  is the important alignment means of this latest form of the invention which functions to maintain the orientation of the tilt axis of the hanger assembly as the first flex member  50  flexes between its first and second position. The construction and operation of this alternate form of the alignment means of the invention will presently be described. 
         [0073]    Also connected to base  48  of the suspension member  44  is a bumper assembly  72  that is substantially identical in construction and operation to that previously described and includes a bumper stop  74  which is engagable by the kingpin  64  of the kingpin assembly  56 . 
         [0074]    In the present form of the invention, the important alignment means comprises an alignment assembly  100  that includes a body portion  102  that is connected to the structural member  42  and to the suspension mechanism  44  in the manner illustrated in  FIGS. 7 and 8 . Alignment assembly  100  here uniquely comprises a curved connector member  104  that is receivable within the central bore  99  of bearing  96  for reciprocal movement therewithin between the first position shown in  FIG. 7 , and through a distance  105  into the second position shown in  FIG. 8 . With this novel construction, as the first flex member  50  flexes between its first and second position, connector member  104  functions to positively maintain the orientation of the tilt axis of the hanger assembly. 
         [0075]    Turning next to  FIGS. 12 through 16  of the drawings, still another form of the truck of the invention is there shown and generally designated by the numeral  110 . This embodiment of the invention is also similar in many respects to the embodiment shown in  FIGS. 1 through 6  of the drawings and like numerals are used in  FIGS. 12 through 16  to identify like components. 
         [0076]    The primary difference between this latest embodiment of the invention and the earlier described embodiments once again resides in the differently configured hanger assembly and the differently configured alignment means. 
         [0077]    As in the earlier described embodiments, an important feature of this latest form of the invention resides in the suspension mechanism  44  that is substantially identical in construction and operation to that previously described. 
         [0078]    Connected to the first flex member  50  is a hanger assembly  114  of the invention that is of somewhat different construction. However, as in the earlier described embodiment of the invention, hanger assembly  114  has a tilt axis “TA” and comprises a kingpin assembly  116 , an axle  118  connected to the kingpin assembly, and first and second wheels  60  and  62  that are rotatably mounted on axle  118 . Kingpin assembly  116  also includes a kingpin  64  and an alignment guide  66  that are substantially identical in construction and operation to those previously described. Extending outwardly from kingpin  64  is a hinge pin assembly  120  that is rotatably carried by the yoke portion  122  of the differently configured kingpin assembly  116 . As best seen in  FIG. 14 , yoke portion  122  here comprises a pair of spaced apart legs  124 , each of which is provided with a bore  126 . Bores  126  rotatably receive the end portions of the transversely extending pin portion  128  of the hinge pin assembly  120 . Extending outwardly from pin portion  128  is a connector member  130 . 
         [0079]    In this latest form of the invention, the differently configured alignment means comprises an alignment assembly  132  that includes a body portion  134  that is connected to the structural member  42  and to the suspension mechanism  44  in the manner illustrated in  FIGS. 12 and 13 . As before, alignment assembly  132  functions to maintain the orientation of the tilt axis of the hanger assembly as the first flex member  50  flexes between its first and second position. Alignment assembly  132  also includes a housing  136  that houses a spherical bearing  138  that has a central bore  138   a . Bearing  138  is maintained in position within housing  136  by a retainer clip  140  ( FIG. 12 ). As depicted in  FIGS. 12 ,  13  and  15 , the connector member  130  of the hinge pin assembly  120  is receivable within the central bore  138   a  of spherical bearing  138  for reciprocal movement therewithin between the first position shown in  FIG. 12  and through the distance  139  into the second position shown in  FIG. 13 . With this novel construction, as the first flex member  50  flexes between its first and second position, connector member  130  functions to positively maintain the orientation of the tilt axis of the hanger assembly. 
         [0080]    Also connected to base  48  of the suspension member  44  is a bumper assembly  72  that is substantially identical in construction and operation to that previously described and includes a bumper stop  74  which is engagable by the kingpin  64  of the kingpin assembly  116 . 
         [0081]    Turning next to  FIGS. 17 through 21  of the drawings, yet another form of the truck of the invention is there shown and generally designated by the numeral  150 . This embodiment of the invention is similar in some respects to the embodiment shown in  FIGS. 12 through 16  of the drawings and like numerals are used in  FIGS. 17 through 21  to identify like components. 
         [0082]    As in the earlier described embodiments, an important feature of this latest form of the invention resides in the suspension mechanism  44  that is substantially identical in construction and operation to that previously described. 
         [0083]    Connected to the first flex member  50  is a hanger assembly  154  of the invention that is of somewhat different construction. However, as in the earlier described embodiment of the invention, hanger assembly  154  has a tilt axis “TA” and comprises a kingpin assembly  156 , an axle  158  connected to the kingpin assembly, and first and second wheels  60  and  62  that are rotatably mounted on axle  158 . Kingpin assembly  156  here includes a threaded stub connector  160  and an alignment guide  162  that, along with suitable locking nuts  163 , function to interconnect the kingpin assembly with the first flex member  50  in the manner illustrated in  FIGS. 17 and 18 . Also forming a part of the kingpin assembly is an elongated connector  164  that extending outwardly from axle  158 . 
         [0084]    In this latest form of the invention, the differently configured alignment means comprises an alignment assembly  166  that includes a body portion  168  that is connected to the structural member  42  and to the suspension mechanism  44  in the manner illustrated in  FIGS. 17 and 18 . As before, alignment assembly  166  functions to maintain the orientation of the tilt axis of the hanger assembly as the first flex member  50  flexes between its first and second position. Alignment assembly  166  also includes a housing  170  that houses a spherical bearing  172  that has a central bore  172   a . Bearing  172  is maintained in position within housing  170  by a retainer clip  174  ( FIG. 17 ). As depicted in  FIGS. 17 ,  18  and  20 , the end portion  164   a  of elongated connector  164  is receivable within the central bore  172   a  of spherical bearing  172 . The end portion  164   b  of elongated connector  164  is also receivable within the central bore  176   a  of a second spherical bearing  176  that is mounted within a housing  177  that forms a part of kingpin assembly  156  ( FIG. 20 ). End portion  164   b  is movable within second spherical bearing  176  between the first position shown in  FIG. 17  and through the distance  173  into the second position shown in  FIG. 18 . With this novel construction, as the first flex member  50  flexes between its first and second position, connector member  164  functions to positively maintain the orientation of the tilt axis of the hanger assembly. 
         [0085]    Also connected to base  48  of the suspension member  44  is a bumper assembly  72  that is substantially identical in construction and operation to that previously described and includes a bumper stop  74  which is engagable by the end of the threaded stub connector  160  (see  FIG. 18 ). 
         [0086]    Referring next to  FIGS. 23 through 26  of the drawings, an alternate embodiment of the invention is there shown. This embodiment concerns a novel caster assembly  180  for use on carts, caster boards, wheelchairs and the like having a structural member  182  ( FIG. 23 ). Caster assembly  180  here comprises a suspension mechanism  184  that is connected to the structural fender member  182 . This novel suspension mechanism here comprises a suspension member having a base  188 , a first flex member  190  connected to base  188  and extending angularly outwardly therefrom, and a second flex member  192  connected to base  188 . Second flex member  192  comprises a pair of transversely spaced arms  193  that extend toward first flex member  190  in the manner depicted in  FIG. 26 . 
         [0087]    Connected to suspension mechanism  184  and disposed between the transversely spaced arms  193  of second flex member  192  is a shock absorber assembly  194 . Shock absorber assembly  194  here comprises a hollow housing  198  having an inner chamber  200  and a shock absorber plate  202  that reciprocates within chamber  200 . Connected to shock absorber plate  202  is an elongate connector rod  204  that has a generally spherically shaped end portion  204   a.    
         [0088]    Connected to shock absorber assembly  194  by means of a connector assembly  205  is a caster wheel assembly  206  that here comprises a yoke-like wheel support  208 , a connector pin  209  that is carried by the yoke-like wheel support, an axle  210  connected to the wheel support and a wheel  212  that is rotatably mounted on axle  210 . Connector assembly  205 , which is connected to first flex member  190  by suitable connectors in the manner shown in  FIG. 23 , includes a connector housing  214  having an upper portion  214   a  and a lower portion  214   b . Lower portion  214   b  is provided with a socket  216  that rotatably receives the generally spherically shaped end portion  204   a  of connector rod  204 . Upper portion  214   a  is provided with a central bore  218  that receives the cylindrical shank portion  209   a  of connector pin  209  so as to enable the caster wheel assembly  206  to be interconnected with the suspension mechanism  184  in the manner shown in  FIG. 23 . End portion  204   a  and connector housing lower portion  214   b  terminate into bumper assembly  219  to stop movement. 
         [0089]    Referring to  FIG. 25 , an alternate form of caster wheel assembly is there shown and generally designated by the numeral  220 . This alternate form of caster wheel assembly can be connected to the suspension mechanism  184  in the manner previously described using connector assembly  205 . Caster wheel assembly  220  here comprises a wheel support  225 , a swivel  226 , a connector pin  229  that is carried by the wheel support, an axle  230  connected to the wheel support and a pair of wheels  222  that are rotatably mounted on axle  230 . 
         [0090]    Referring to  FIGS. 27 through 29  of the drawings, still another embodiment of the invention is there shown. This embodiment concerns a novel caster assembly  230  for use on carts, caster boards, wheelchairs and the like having a structural member such as swivel  232  ( FIG. 23 ). Caster assembly  230  here comprises a suspension mechanism  234  that is connected to the structural member  232 . This novel suspension mechanism here comprises a base  238 , a first flex member  240  connected to base  238  and extending angularly outwardly therefrom, and a second flex member  242  connected to base  238 . Second flex member  242  comprises a pair of transversely spaced arms  243  that extend toward first flex member  190  in the manner depicted in  FIG. 27 . Second flex member  242  is provided with a transversely extending, concave rib  242   a  that functions in the manner previously described to enhance the flexing of second flex member  242 . 
         [0091]    Connected to second flex member  242  by appropriate fasteners  245  in the manner illustrated in the drawings, is a caster wheel assembly  246  that here comprises an axle  248  and a wheel  250  that is rotatably mounted on axle  248 . 
         [0092]    It is to be noted that the suspension mechanism is uniquely designed to progressively increase suspension resistance as forces acting on the mechanism increase by elastically deforming the second flex member  242  in a manner to contact the first flex member  240 , thereby transforming the first flex member into a dependent arm that results in a progressive resistance to a load until the forces are terminally engaged by the end portion  240   a  of the first flex member  240 , engaging the base  238  (see  FIG. 28 ) and second arm  242 , terminally engaging stop  240   b  disposed on first flex member  240 . 
         [0093]    Referring finally to  FIG. 30  of the drawings, yet another embodiment of the invention is there shown. This embodiment is somewhat similar to that shown in  FIGS. 27 through 29  and also concerns a novel caster assembly  252  for use on carts, caster boards, wheelchairs and the like having a structural member such as, for example a swivel  232  of the character shown in  FIG. 23 . Caster assembly  252  here comprises a suspension mechanism  254  that is connected to the structural member. This novel suspension mechanism here comprises a base  258 , a first flex member  260  connected to base  258  and extending angularly outwardly therefrom, and a second flex member  262  connected to base  258 . Second flex member  262  comprises an outwardly extending arm  263  that extends toward first flex member  260  in the manner depicted in  FIG. 30 . Second flex member  262  is provided with a transversely extending, concave rib  262   a  that functions in the manner previously described to enhance the flexing of second flex member  262 . 
         [0094]    Connected to second flex member  262  by appropriate fasteners “F” in the manner illustrated in the drawings, is a caster wheel assembly  266  that here comprises an axle  268  and a pair of transversely spaced apart wheels  270  that is rotatably mounted on axle  268 . 
         [0095]    It is to be noted that, as before, the suspension mechanism is uniquely designed to progressively increase suspension resistance as forces acting on the mechanism increase by elastically deforming the second flex member  262  in a manner to contact the first flex member  260 , thereby transforming the first flex member into a dependent arm that results in a progressive resistance to a load until the forces are terminally engaged by the end portion  260   a  of the first flex member  260 . 
         [0096]    Having now described the invention in detail in accordance with the requirements of the patent statutes, those skilled in this art will have no difficulty in making changes and modifications in the individual parts or their relative assembly in order to meet specific requirements or conditions. Such changes and modifications may be made without departing from the scope and spirit of the invention, as set forth in the following claims.