Patent Abstract:
A cargo carrier suspension for installation on a cargo carrier having a seat and wheels, skis or rollers on which the seat rides, the cargo carrier suspension comprising: a leaf spring connectable on a cargo carrier between the seat and the wheels, skis or rollers, and a clamping device for engagement on the leaf spring and adjustable to select the degree of flexibility of the leaf spring.

Full Description:
FIELD OF THE INVENTION 
     The invention relates to a cargo carrier suspension and, in particular, to a cargo carrier suspension having an adjustment for suspension resistance. 
     BACKGROUND OF THE INVENTION 
     Suspensions are provided on cargo carriers such as bicycle trailers or strollers. The suspension provides a smoother ride for the occupant or load. Sometimes, the suspension includes a means for resistance adjustment. 
     SUMMARY OF THE INVENTION 
     A cargo carrier suspension has been invented. The suspension acts between the cargo support area, for example the seat, and the transport means on which the carrier rides such as, for example, wheels, rollers, skis etc. 
     In accordance with a broad aspect of the present invention, there is provided a cargo carrier suspension for installation on a cargo carrier having a cargo support and a transport means on which the cargo support rides, the cargo carrier suspension comprising: a leaf spring connectable on a cargo carrier between the seat and the transport means; and a clamping device for engagement on the leaf spring and adjustable to select the degree of flexibility of the leaf spring. 
     In accordance with another broad aspect, there is provided a cargo carrier comprising: a cargo support; a transport means on which the cargo support is supported to ride; a suspension for damping vibration between the transport means and the cargo support, the suspension including a leaf spring connected to act between the cargo support and the transport means and a clamping device for engagement on the leaf spring and adjustable to select the degree of flexibility of the leaf spring. 
     The suspension acts between the cargo support and the transport means to damp vibration from the transport means to the cargo support. The cargo support can be, for example, a floor or a seat. The cargo support can be rigid or flexible, as formed of fabric. However, if the cargo support is flexible it includes a rigid member, such as a support frame, onto which the suspension is connectable. As an example, the cargo support can be rigid and the suspension connectable directly thereto, the cargo support can include a support frame to which the suspension is connectable or the cargo—support can be mounted in a frame for the cargo carrier and the suspension is connectable between the cargo carrier frame and the transport means. The transport means can be any apparatus on which the seat can ride. As an example, transport means can include wheels, skis and rollers. 
     The suspension is connectable to the cargo carrier in any way such as, for example, by forming integral therewith, by welding or fusing or by fasteners such as clamps, bolts, screws, straps or rivets. 
     The leaf spring can be formed of spring steel or other materials having resilient, spring properties such as, for example, polymers or metals. The leaf spring can include one leaf or a plurality of leaves forming a spring pack. 
     The clamping device is selected to be engageable on, and adjustable to select the degree of flexibility of, the leaf spring. In one embodiment, the clamping device acts to select the degree of flexibility of the leaf spring by controlling its free flexing length. In another embodiment, the clamping device acts to select the degree of flexibility of the leaf spring by controlling the stiffness of the spring, for example, as determined by the number of leaves acting in the spring pack or the frictional engagement of the plurality of springs in the spring pack. The clamp can be engageable on the leaf spring in various ways such as, for example, by bolting thereon, by engagement of a pin in a detent or by spring biasing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A further, detailed, description of the invention, briefly described above, will follow by reference to the following drawings of specific embodiments of the invention. These drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. In the drawings: 
     FIG. 1 is side elevation of a cargo carrier according to the present invention with a suspension; 
     FIG. 2 a  is side elevation of a cargo carrier according to the present invention with a suspension; 
     FIG. 2 b  is a perspective view of a suspension according to the present invention; 
     FIGS. 3 a ,  3   b  and  3   c  are side elevations of the suspension of generally as shown in FIG. 2 in progressively flexed conditions; 
     FIG. 4 is a perspective view of another suspension according to the present invention; 
     FIG. 5 is a perspective view of another suspension according to the present invention; and 
     FIG. 6 is a perspective view of another suspension according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIG. 1 there is shown a cargo carrier  10  in the form of a bicycle trailer for carrying a child. Cargo carrier  10  includes a frame  12 , a seat  14  supported on the frame and wheels  16  acting as transport means to support and permit transport of the carrier. While there are two wheels  16  on the cargo carrier, in the drawing one is disposed behind the other. The Illustrated cargo carrier Is specifically is a trailer for towing behind a bicycle, and therefore includes a tow arm  17 . It is to be understood that while a bicycle trailer has been shown, a cargo carrier according to the present invention can also be other forms of trailers, a stroller or a sled such as for example, a three or four wheeled stroller, a cargo trailer having a cargo support floor rather than a seat, a trailer having any number of wheels or a trailer for human towing such as a rickshaw. 
     The cargo carrier has further installed thereon a suspension  18  for damping vibration, which would tend to be transferred from wheels  16  to seat  14 . In particular, suspension  18  is connected between a wheel axle (cannot be seen) and frame  12 . The cargo carrier preferably has no rigid connection between wheels  16  and seat  14  such that the suspension is free to act. 
     The suspension includes a leaf spring  20  connected by bracket  22  adjacent its first end to a lower section  12   a  of the frame. The leaf spring can be connected by other means such as by direct engagement by fasteners, welding, fusing or strapping, to the frame. However, care should be taken to ensure that the connection will accommodate the stress, which can be significant, without unacceptably low durability. The leaf spring is connected, again in any desired way, at its second end to the wheel axle. Again, while various connection arrangements are possible, care should be taken to address the material stress at this connection. 
     Leaf spring  20  is formed of any desired material having spring properties, but capable of supporting the frame. As an example, the leaf spring can be formed of spring steel, or polymeric materials. The leaf spring can include one or more spring leaves. 
     In the most usual arrangement, there is a leaf spring connected adjacent each wheel or at least each rear wheel of the cargo carrier. However, other arrangements can be used, such as one leaf spring centrally located between the wheels or a plurality of leaf springs spaced apart between the wheels and along the wheel axle or one or more leaf springs mounted up closer to the seat. 
     The wheel axle can be a common axle or cross member extending between the two wheels. Alternately, the leaf springs can be connected to an independent stub axle for each wheel. In such an embodiment, care should be taken to avoid twisting and fatigue of the leaf springs. 
     To provide some rigidity to the frame and to prevent a feeling of unstability, in one embodiment a stabilizer bar (cannot be seen in FIG. 1) is mounted to the lower frame  12   a . The stabilizer bar can be a member fastened to the lower frame or formed integral therewith. Of course, if the frame could be formed very rigid, this stabilizer bar could be omitted. 
     The suspension further includes a clamping device  24  that is engaged on leaf spring  20  and is adjustable to control the degree of flexibility in the spring and thereby the stiffness of the suspension. In one embodiment shown in FIGS. 1,  2  and  3 , the leaf spring is formed as a spring pack containing a plurality of spring leaves and the clamping device is adjustable to control the degree to which the plurality of spring leaves are connected to act together in the spring pack. In another embodiment shown in FIG. 4, the clamping device is adjustable to control the free flexing length of the spring. In yet another embodiment, the spring is formed as a spring pack containing a plurality of spring leaves and the clamping device is adjustable to control the degree of frictional engagement between the spring leaves, thereby adjusting the flexibility of the leaf spring. 
     It is useful to select the stiffness of a suspension to adjust the ride and/or to maintain a selected suspension flexibility, when the weight of the load is changed (i.e. to prevent the trailer from bottoming out when a heavier load is carried). In general, a stiffer suspension is desired when transporting a heavier load. 
     Referring to FIGS. 2 and 3, leaf spring  20  is formed as a spring pack containing a plurality of spring leaves  26   a ,  26   b . While two leaves are shown, other numbers can be used as desired. As will be appreciated, each of the spring leaves will have a characteristic spring force or degree of flexibility. However, when connected to act together, the spring pack provides a degree of flexibility, which is greater than that of either of the spring leaves alone. 
     Spring leaves  26   a ,  26   b  are connected together at end  20   a  by bracket  22 . This bracket also serves to connect leaf spring  20  to frame  12   b  of a cargo carrier. The bracket includes an opening  28  for accepting frame  12   b  therethrough and an opening  30  for leaves  26   a ,  26   b . The bracket, spring leaves and frame include alignable apertures through which bolts  32  are inserted and secured by nuts  34 . Through this connection any force in leaves  26   a ,  26   b  at end  20   a  will be transmitted to frame  12   b  through the bracket. 
     Leaf spring  20  is connected at its opposite end  20   b  to a bracket  36 . Bracket  36  includes an opening  38  in which a wheel axle  40  and a hollow axle  42  are secured. The bracket can be formed in any way to secure the axle and to serve other purposes such as, for example, in the illustrated embodiment, the bracket includes an extension  41  for retaining a parking brake. 
     While the bracket can be secured to the leaf spring in various ways such as by forming one integral with the other, fusing, welding, riveting, fastening etc, in the illustrated embodiment, bracket  36  is secured to leaf spring  20  via a flange  44  having apertures which can be aligned with apertures on the leaf spring  20  to accept bolts  46  and nuts  48 . 
     While leaf spring  20  includes a spring pack of leaves  26   a ,  26   b , it is to be noted that only one of the leaves  26   a , is directly connected to bracket  36  and thereby to the wheels. The other spring leaf  26   b  is only connected indirectly to the wheel through engagement by a clamping device  24  to spring leaf  26   a.    
     Clamping device  24  is engaged to leaf spring  20  and, in particular, secures spring leaf  26   b  to spring leaf  26   a  so that they can flex together. Clamping device  24  controls the degree to which the spring leaves are connected to act together in the spring pack in response to the application of force. 
     In the illustrated embodiment, clamping device  24  includes an opening  50  sized to accommodate the spring leaves in a such a way that the clamping device surrounds the spring leaves, but that the clamping device can be moved along the leaves if not engaged in a position. Clamping device  24  further includes a knob  52  with a threaded stem that is threadedly engaged in a threaded aperture (cannot be seen) through device  24 . The aperture is formed such that the stem can be threaded into opening  50  to engage against spring leaf  26   a  to hold the clamping device in a selected position on leaf spring  20  and to clamp leaves  26   a ,  26   b  together. To adjust the position of the clamping device along the leaf spring, the stem can be withdrawn from engagement with leaf  26   a  and the device can be slid along to another position. While one clamping device has been shown and described, it is to be understood that any device that operates to clamp the leaf springs together can be used. For example, a U-shaped clamp can be used in a similar fashion as device  24 , a bolt, or other removable fastener such as a clip or wire, can be inserted through a selected one of a plurality of aligned pairs of apertures formed through the spring leaves and a spring-biased pin could be used in place of the stem. 
     A stabilizer bar  55  is secured between lower frame member  12   b  and the lower frame member on the other side of the trailer. 
     FIGS. 3 a  to  3   c  are provided to facilitate understanding of the invention. FIG. 3 a  shows the suspension at a generally neutral position wherein insufficient force is applied to the cargo carrier wheel, and thereby to bracket  36 , to cause flexing of leaf spring  20  out of its neutral position. However, in FIG. 3 b  some force is applied upwardly to the bracket to cause leaf spring to flex and in FIG. 3 c  a force greater than the force in FIG. 3 b  is applied to the bracket. The force could be, for example, that applied to the wheel by pulling or pushing the cargo carrier over a bump or curb. 
     Clamping device  24  is engaged at a selected position along leaf spring  20  and clamps leaves  26   a ,  26   b  together at this position. Thus, on one side of clamping device  24 , indicated as A, leaves  26   a ,  26   b  act together in response to applied force and exhibit a first degree of flexibility, while on the other side, B, spring leaf  26   a  acts alone in response to applied force and exhibits a second degree of flexibility which is greater than that of portion A. This is illustrated in the drawings. When no force is applied to leaf spring  20 , as in FIG. 3 a , the leaves  26   a ,  26   b  remain in their neutral position. In the illustration, the leaf spring is maintained in a flexed position, termed preloading, to provide the spring with a selected stiffness, which is greater than the stiffness that it would have without the preload effect. Because of preloading, the spring leaves lie close together in the neutral position. While preloading is useful with some springs to accommodate a change in cargo weight (i.e. putting a child in the seat) without activating the suspension, it is to be noted that it is not necessary to preload the spring pack. 
     When force is applied to the wheel and thereby to the bracket, as shown in FIG. 3 b , spring  20  will flex to absorb the force. On side A, the leaves  26   a ,  26   b  being clamped together at both ends will flex together. However, on side B, leaf  26   a  which is secured between device  24  and bracket  36  will separate from leaf  26   b  and flex to an amount greater than that of side A. In FIG. 3 c , the applied force is greater and so the effect is greater. 
     The overall flexibility of leaf spring  20  is determined by the proportion of the spring that is acting as a leaf pack relative to the portion of the spring that is acting as a single spring. The flexibility of leaf spring  20  can, therefore, be adjusted by securing the clamping device at various positions along the spring. In particular, moving clamping device  24  closer to end  20   a , thereby reducing the length of side A, causes spring  20  to have increased flexibility, such as would be useful for carrying lighter loads, and moving the clamping device in the opposite direction, toward the bracket  36  and the free end of spring leaf  26   b , decreases the spring flexibility. 
     Markings  58  can be placed along a visible surface of the leaf spring as shown or on frame  12   b  to guide a user on an appropriate placement of the clamping device  24  for a specified load. Leaf springs  26   a ,  26   b  can be treated or surface coated to enhance appearance or wear characteristics. In the illustrated embodiment, a rubber sheet  59  is secured to leaf spring  26   a  to protect the surface of the spring and to enhance the grip between device  24  and the spring. 
     In the illustrated embodiment, frame  12   b  extends out under leaf spring  20 . Although this is not necessary, as shown in FIG. 1, the frame in the embodiment of FIGS. 2 and 3 permits connection of some upper frame members (not shown) of the cargo carrier though aperture  60 . In addition, frame  12   b , underlying leaf spring  20 , limits the range of movement of the spring. In particular, the spring is free to flex upwardly, away from the frame, but is limited in its downward flex by abutment against the frame. Bumpers  62   a ,  62   b , such as rubber or polymeric pads, can be secured between the leaf spring and the frame to reduce the noise caused by the spring hitting against the frame. In addition, bumpers, such as bumper  62   a , can be sized to urge the spring into a preload (preflexed) condition. 
     Referring to FIG. 4, another suspension is shown including a leaf spring  120  and a clamping device  124 . The clamping device  124  permits the flexibility of the leaf spring to be adjusted, depending on the clamped position of the clamping device along the leaf spring. 
     Leaf spring  120  includes one, as shown, or more spring leaves connected at one end by a bracket  122  to a frame  12   b  of a cargo carrier. At its other end, spring  120  is connected to a bracket  36  for accepting a wheel axle (not shown) of a cargo carrier. If the leaf spring includes more than one spring leaf, all of the leaves are secured together to respond to application of force. 
     Leaf spring  120  extends adjacent to frame  12   b . Clamping device  124  includes an opening  170  sized to fit closely around both leaf spring  120  and frame  12   b  to clamp them together. This clamping causes end  120   a  to be fixed against flexing in response to application of force, while free end  120   b , between bracket  36  and clamping device  124 , is free to flex in response to any force applied. As will be appreciated, the length of end  120   b  determines the stiffness of the suspension. In particular, as clamping device  124  is moved in direction B to shorten end  120   b , the stiffness of the suspension will increase and the flexibility of the leaf spring will decrease. 
     To permit the clamping device to be locked in a selected position, a spring-biased pin  172  is mounted to releasably engage in detents  174  on the leaf spring. Pin  172  is manipulated by grasping knob  176 . 
     In another embodiment shown in FIG. 5 the clamping device  124   a  is secured to frame  12   c  by a knob/fastener  180 . The fastener can be, for example, a bolt, a spring loaded pin or a push button. In yet another embodiment shown in FIG. 6, the clamping device  124   b  is secured to frame  12   d  by a lock pin  182  that is inserted through alignable apertures in the clamp and the frame. 
     It will be apparent that many other changes may be made to the illustrative embodiments, while falling within the scope of the invention and it is intended that all such changes be covered by the claims appended hereto.

Technology Classification (CPC): 1