Patent Application
20090033051
1. Field of the Disclosure
The present disclosure is generally directed to strollers, and more particularly to a stroller wheel construction with an integrated or modular suspension system.
2. Description of Related Art
Strollers are known in the art to employ various types of wheel suspension mechanisms. Such strollers typically employ a suspension system that is integrated into the frame or as part of a wheel-to-frame swivel joint. These suspension systems make it difficult to add or subtract suspension elements to a particular stroller or line of strollers without performing major design modifications to the stroller frame and/or the swivel joint structure.
The vast majority of stroller suspension systems are of the swing arm variety. These types of systems utilize a coil spring and, very often, a telescoping tube arrangement that is coupled to a swing arm on a frame part or on a swivel joint. The suspension system imparts up and down pivotal movement of the swing arm or arms to which the wheel or wheels are attached. The wheel suspension is achieved by this motion being biased against the spring or other biasing element. In the stroller industry, the vast majority of strollers that employ a suspension system utilize one of many different permutations of this basic swing arm/spring design. There are very few stroller wheel suspension designs that employ suspension concepts other than a variation of the swing arm/spring system. These other systems are more elaborate and also require specific frame structure design characteristics in order to be mounted on the stroller.
The known swing arm and other suspension systems have a number of disadvantages. First, the suspension systems that are currently used must be integrated into the stroller frame or a swivel joint assembly positioned between the frame and the wheels. These structural requirements and components make it extremely difficult to add, remove, or modify a suspension system relative to a given stroller frame construction. Modification can require extensive changes to other parts of the stroller including the frame, swivel joint components, axles, struts, and the like. It is typically not feasible to add a suspension system to an existing stroller that was not designed to include any type of suspension. This is because of the magnitude of tooling changes required. Adding suspension geometry may adversely affect other aspects of an existing stroller, such as the frame or fold geometry in a collapsible stroller. This can force a designer to compromise between the suspension and other elements and features of the existing stroller.
Another disadvantage is that the range of travel of a conventional suspension system is limited by the length of the swing arm. Increasing suspension travel can require increasing the length of the swing arm. Increased swing arm length can adversely affect frame geometry, material usage, design and performance characteristics, and part cost. With regard to features of a stroller that are sensitive to part design and geometry, such as the front swivel assemblies often used on the strollers front wheels, optimal steering geometry is often at odds with optimal suspension geometry.
An additional disadvantage of a swing arm-type suspension system is that these have a fixed direction of suspension travel. Generally, the geometry of the suspension allows the wheel to travel upward and, in some instances, slightly rearward when an obstacle is encountered. The suspension travel is typically either linear in nature or limited to a fixed travel path, and also limited to a single travel direction. While this type of suspension system may be suitable for traveling over small obstacles, it may not provide sufficient cushion or damping during frontal impact with, or while running over, larger obstacles such as a curb or a step. In such instances, optimal suspension travel may be more rearward than upward, more forward than upward, or even entirely or directly rearward or forward. A swing arm system may offer little or no suspension function or benefit during use of a stroller in many instances.
Another disadvantage is that in front dual-wheel swivel assemblies or in solid rear stroller axle applications, a swing arm-type suspension system typically does not allow the wheels to move independently of one another. The suspension motion of both front wheels on a common front swivel joint application is typically locked together. The two front wheels may not experience the same obstacle or degree of impact at any one time, and yet the suspension system is typically configured in a manner that moves or deflects both front wheels identically. Similarly, in a solid rear stroller axle application, both rear wheels are typically not suspended at all. This can cause a relatively rough ride if the rear wheels contact obstacles, and particularly when such impact is different at each wheel at any given moment. If suspended, the rear solid axle results in both rear wheels being required to travel or deflect identically.
From an aesthetic stand point, it is often difficult for a consumer to see a stroller wheel suspension system. The system components are typically concealed behind or between the front strollers wheels and are sometimes covered with a decorative housing. Stroller manufacturers often resort to on-board “advertsing” techniques to inform consumers of the benefits of a particular suspension system. Some stroller manufactures employ a non-functional rubber boot over the suspension components in order to “advertise” the existence of the suspension system or to make it stand out and thus notify a consumer that the stroller has wheel suspension. These rubber boots add unnecessary expense and complexity to a stroller design while achieving no suspension or other functional benefit. Also, it can be difficult for a user to detect wheel suspension action in a stroller because of the relatively limited range of travel of a conventional swing arm-type suspension system.
Objects, features, and advantages of the present invention will become apparent upon reading the following description in conjunction with the drawing figures, in which:
The stroller wheel examples disclosed herein solve or improve upon one or more of the above-noted and other problems and disadvantages with known stroller suspension mechanisms and systems. In one example, the disclosed stroller wheel eliminates the need for a swing arm-type suspension system that is common on many strollers. In another example, the disclosed stroller wheels have a resilient structure integrated into the wheel that creates the suspension function. The disclosed stroller wheels can be mounted on strollers that have not been configured to accept a stroller wheel suspension system without having to modify the existing stroller configuration and construction. No part on an existing stroller frame or on the disclosed wheel structures need be assembled, disassembled, modified, or otherwise altered in order to add wheel suspension characteristics to a stroller. The disclosed wheels need only be swapped for existing stroller wheels to add wheel suspension. In a further example, the disclosed stroller wheels are less susceptible to contaminants affecting their overall performance. In yet another example, the disclosed stroller wheels can be designed to achieve any number of various aesthetic configurations. The disclosed wheels can be configured to mask or hide the existence or presence of the suspension system. The disclosed wheels can also be designed to enhance the overall appearance of the stroller without affecting suspension performance and/or to make readily apparent the existence of the modular stroller suspension incorporated into the wheel design.
Turning now to the drawings,
The wheel 20 is shown in side view in
In the disclosed example, the hub 30 has a perimeter circumferential surface 40 that faces radially outward. The hub 30 also has a pair of end faces 42 that define the opposed ends of the hub slug shape. The hub 30 defines the wheel axis W extending axially between the end faces 42 and is centered relative to the surface 40. As noted above, the wheel 20 is configured to rotate about the wheel axis W and the hub is configured to mount relative to an axle for rotation about the axis W. The structure of the hub 30 can also vary from the slug shape as shown. The hub can include radial ribs and recesses in the end faces 42 in one example. The surface 40 need not be a smooth surface in another example. The hub 30 can vary within the spirit and scope of the present invention.
The rim 32 is formed as a continuous annular ring that is centered about the wheel axis W. In the disclosed example, the rim 32 surrounds the hub 30 and is positioned directly radially outward relative to the hub surface 40, lying generally coplanar with the hub. In an optional example, the rim and hub can lie in offset planes relative to one another along the rotation axis W. In such an example, the rim and hub can rotate about the same axis W but lie out of plane with one another. In this example, the rim 32 has an inner circumferential surface 50 that faces radially inward toward the hub perimeter surface 40. The rim 32 also has an outer circumferential surface (not shown) to which the tire 36 is mounted. The rim 32 also has opposed outward facing side surfaces 52. The structure of the rim 32 can also vary from that shown. The rim need not be a circular ring or need not be continuous. Instead, the rim could have separate sections supporting a tire in one example. The sides 52 can vary from the smooth surfaces in another example. The rim 32 can vary within the spirit and scope of the present invention.
In the disclosed example, the hub 30 and rim 32 can be formed of virtually any suitable material. However, it is preferable that the rim and hub each be substantially rigid, strong, and durable to perform their intended functions. The hub 30 mounts the wheel 20 to the stroller and should be sturdy to endure loads encountered during normal stroller usage. The hub 30 should also be substantially rigid so as to provide a fixed attachment of the wheel 20 to the stroller frame parts 22 and to minimize play at the axle to stroller frame part connection. Similarly, the rim 32 in this example should also be sturdy and strong to retain a round and smooth rolling shape and to withstand applied loads and impacts during normal stroller usage. The materials for the hub 30 and rim 32 can include, but are certainly not limited to, steel, aluminum, other metal alloys, plastic, thermoplastic, composites, wood, carbon fiber, and the like. The material and/or the shape and structure of the rim and hub components can be selected and designed so that the rim and hub are substantially rigid so that the wheels roll true and round during normal use.
A plurality of the spokes 34 are provided on the disclosed wheel 20. Each of the spokes 34 is coupled to the hub at an inner end 60 and is coupled to the rim 32 at an outer end 62. In this particular example, the spokes 34 are equally spaced apart from one another circumferentially around the wheel 20. Each spoke 34 is also curved in a circumferential direction such that the attachment point of the inner end 60 to the hub 30 is circumferentially or angularly offset relative to the attachment point of the outer end 62 to the rim 32. As shown in
The spokes 34 can be formed from a material that is either different from or the same as the rim and hub material, as desired. The spokes 34 can alternatively be formed as an integral part of the rim and/or hub if desired. The shape, thickness, width, length, and/or material selection for the spokes 34 can be altered separately or in combination with one another to create the desired flex, deformation, and/or resiliency in the spokes. In any instance, the spokes 34 are intended to be formed as a resilient and flexible or non-rigid structure in comparison to the hub and rim. Each spoke should be formed having a desired unloaded natural or static shape and a desired in-use shape when installed on the wheel 20. The in-use or installed shape may or may not be the same as the static or natural shape. The spokes 34 should be capable of bending, stretching, compressing, twisting, and/or otherwise deforming upon application of a load in the assembled wheel 20. Each spoke 34 should also be resilient so as to return to a “home” or at-rest shape upon release of the applied load on the assembled wheel 20.
In this disclosed example, the spokes 34 are formed from a spring steel strip material and have a generally thin, flat, and wide blade-like body shape. The spokes 34 are identical to one another in this example as to their size and shape in order that the spokes 34 each produce the same consistent spring characteristics. This will result in consistent suspension effect or performance regardless of the wheel rotational position. In this example, a portion of the inner ends 60 of the spokes are embedded in the surface 40 of the hub 30 and into the hub material as shown in
In another example, the end portion of the inner ends 60 can be formed having one or more holes (not shown) through the spoke material. Alternatively or in addition, each end 60 can include an enlarged or thickened edge 66 to further assist in preventing the spokes from pulling out of the hub material. During an insert molding process, the hub material will flow through the holes and create a mechanical interlock between the inner end 60 of the spoke 34 and the hub 30 material. In another example, the hub 30 can be formed having a plurality of slots into the surface 40. The spokes 34 can be formed having one or more of the one-way barbs or tangs 64 as shown. The spokes 34 can be forcibly installed in the slots after formation of the hub 30. The barbs or tangs 64 can inhibit the spokes from being withdrawn from the slots after the spokes 34 are installed.
The outer ends 62 of the spokes can have end portions that are attached or connected to the rim 32 in the same or a different process used to attach the spokes 34 to the hub 30. The spokes 34 can be insert molded to both the hub 30 and rim 32 during a simultaneous process to fabricate both rim and hub. Alternatively, the spokes 34 can be placed in a first mold and attached to the rim 32 during a two step process. Either the rim 32 or the hub 30 can first be fabricated with the spokes attached, and then that assembly can be inserted into a second mold to form the other of the rim and hub connected to the spokes.
In yet another example, the rim, hub, or both can be formed in two or more parts that are assembled width-wise to capture the spokes between parts. In such an example, slots can be pre-formed in both sides of the rim, hub, or both. The edges of the appropriate end or ends of the spokes can be inserted laterally into the slots in one of the halves and then the other half can be slipped over the exposed edges of the spokes. Fasteners 68, as represented in
In the disclosed example, the spokes 34 are configured to retain the hub 30 centered on the rotation axis W, which can be termed a home or at rest position. Upon application of a load or impact to the tire 36, such as the tread surface 37, the spokes 34 can resiliently deflect as shown in
Depending upon the flex, curvature, and resiliency characteristics of the spokes 34, as well as the weight of the stroller 24 and any stroller occupant(s), the hub 30 may always operate with the wheel rotation axis W offset slightly downward relative to the wheel or rim center axis C as the wheel 20 rolls during use. As the wheel 20 rolls, the spokes 34 may flex and bend accordingly to maintain a consistent relationship between rim and hub, but which in effect may be a fluid, dynamic relative positioning between hub and rim. The relative movement of the hub 30 and rim 32 create the suspension function. The flex, curvature, and resiliency of the spokes can be selected and designed to determine the degree of damping, bounce, and the like of the system. Material selection, and thus the material properties, and the spoke dimensional characteristics can be altered to achieve different suspension functional parameters.
In addition, the shape and bend in the spokes 34, if any, and the wheel rolling direction may alter, either slightly or more significantly, the suspension functional parameters of the wheel 20. In the disclosed example, the spokes 34 are curved in a circumferential direction around the wheel 20. Thus, in one direction indicated by the arrow A in
Although certain stroller wheels and suspension arrangements have been described herein in accordance with the teachings of the present disclosure, the scope of coverage of this patent is not limited thereto. On the contrary, this patent covers all embodiments of the teachings of the disclosure that fairly fall within the scope of permissible equivalents.
