Sack Truck News

A pneumatic in-line skating wheel having a tire body and central hub chemically bonded during a polyurethane casting process and further including an annularly encapsulated air bladder centrally spaced within the tire body to provide shock absorption. The bladder in one embodiment is in communication with a valve for inflation and deflation thereof such that the overall tire resiliency may be adjusted, enabling adjustable performance characteristics of the wheel. One embodiment of the valve incorporates a resilient core within a rigid barrel and stretchable to allow an inflation needle to stretch the core and drive a poppet off a seat at the interior end of the barrel.

A pneumatic in-line machine skate wheel comprising:

a relatively rigid urethane hub formed with an annular drop-center having axially spaced apart retainer flanges;

stand off ribs disposed in annular spaced relation about said drop center;

an annular bladder surrounding said drop center and stood off from said drop center by said ribs to form an air chamber; and

a relatively soft molded urethane tire body substantially surrounding said bladder and formed with laterally opposite sides bonded to said retainer flanges.

A pneumatic in-line machine skate wheel according to claim 1 wherein:

said bladder comprises a resilient annular bladder formed with a plurality of pre-pressurized individually sealed annular air chambers disposed substantially about a common axis.

A pneumatic in-line machine skate wheel according to claim 2 wherein:

said bladder is formed of a substantially triangular cross section.

A pneumatic in-line machine skate wheel according to claim 2 wherein:

said bladder is in the form of an extruded thermoplastic material.

A pneumatic in-line machine skate wheel according to claim 1 to be inflated by an inflation needle carried from a needle housing wherein:

said hub is formed with side flanges that angle radially and axially outwardly at a predetermined angle;

said bladder is configured with a triangular cross section to define said walls projecting radially and axially outwardly at said predetermined angle from an apex seated on said hub;

a valve bore angling axially inwardly and radially outwardly through one of said side flanges, through said tire body and through one of said side walls;

a valve including a rigid barrel received in said bore and terminating at its interior end within said bladder in an annular valve seat, and at its opposite end in a needle housing socket, a resilient core in said barrel and projecting interiorly therefrom past said seat to form a circular poppet normally seated on said seat, said resilient core further formed with an axial bore projecting inwardly from said socket to terminate in a stop, a cross bore leading from said axial bore to the periphery of said resilient core behind said poppet, said resilient core having sufficient resiliency to normally draw said poppet against said seat and to, upon insertion of said needle in said axial bore and engagement with said stop, lift said poppet off said seat to establish an air communication path from said cross bore to exhaust in the space between said poppet and said seat.

A pneumatic in-line machine skate wheel according to claim 5 wherein:

said bladder is formed with a substantially triangular cross section having a rounded interior corner spaced from said valve seat.
A pneumatic in-line machine skate wheel according to claim 5 wherein:

said hub, said tire and said bladder are formed of thermoplastic polyurethane.

A pneumatic in-line machine skate wheel according to claim 5 wherein:

said valve barrel is formed of a metal, and said resilient core is formed of thermoplastic.

An adjustably resilient pneumatic in-line machine skate wheel to be inflated by an inflation needle and comprising:

a relatively rigid urethane hub formed with an annular drop-center and axially spaced apart retainer flanges, one of said flanges including a throughbore;

a plurality of stand off ribs disposed in annular spaced relation about said drop center and formed with pairs of nub tabs spaced axially from a central plan in said drop center;

an annular air bladder surrounding said drop center and formed of a substantially triangular cross section and stood off from said drop center by said ribs and aligned axially between the tabs of the respective said pairs surrounding said drop center, said bladder formed with a bladder bore aligned axially with said throughbore;

a relatively soft molded urethane tire body formed with laterally opposite sides bonded to said retainer flanges and configured to surround said bladder, said tire body being further formed with a valve bore aligned axially with said bladder bore and said throughbore; and

a pneumatic valve sealably received in said throughbore bladder bore and valve bore and including a rigid valve barrel formed with a distal end and a proximal end, said distal end being formed with an annular seat, and a resilient core fixed medially in said barrel and free of said barrel on said distal end, said resilient core being formed at said distal end with an enlarged in cross section poppet normally seated in said seat, said resilient core being further formed with a blind axial bore open to its proximal end for receipt of said needle and closed at its distal end to define a stop and a cross bore leading from said axial bore to the lateral side of said resilient core, said resilient core having sufficient resiliency to, upon insertion of said needle through said axial bore, engage said stop and push said poppet to be spaced away from said seat for fluid communication between said needle and the space between said poppet and seat.
Description

Currently available in-line machine skate wheels generally comprise a hard plastic hub surrounded by a tough polyurethane tire body. Various flanging arrangements exist to help keep the tire from breaking away from the hub and exposing the skater to potential injury. The tire body is designed to a predetermined resiliency and reflects a specific band of performance parameters for proper operation under certain conditions. Such conditions include, speed, cornering and shock absorption characteristics. Skaters desiring different performance characteristics have in the past been forced to change machine skate wheels to achieve satisfactory results. The present invention enables a skater to vary the performance parameters of a skate merely by adjusting the pressure in an air chamber within the tire of a machine skate wheel. In addition, the present invention incorporates a novel bonding technique designed to positively hold a pneumatic wheel on its hub to thus protect the skater from potential injuries arising out of tire separation.

As shown in the drawings for purposes of illustration, a first embodiment of the present invention is a pneumatic in-line skating wheel 2 with an adjustably resilient tire 4 annularly encasing an integrally bonded hub 6. Encapsulated within the tire is an annular air bladder 8 centrally spaced. A valve 10 positioned within the tire allows access to the air bladder for inflation or deflation thereof. The wheel assembly is fabricated using injection molding techniques with the hub and tire formed from materials known to form strong chemical bonds when sufficiently heated. During the molding and curing processes, an exothermic reaction within the air bladder is conveniently employed to distend the bladder causing it to firmly embrace the drop center of the hub. Hardness differentials between the valve and the tire provide for hermetic sealing of the assembly without the need for additional seals or gaskets.

The hub is constructed of hard polyurethane, typically have a durometer index of 65D and includes a central axle bore 21 configured at its opposite ends with countersunk cylindrical bearing assembly cavities 24 and 26 configured to receive the outer races of respective bearing assemblies for riding on the skate axle. The hub is formed with axially spaced apart, radially projecting flanges 12 and 14 which radiate outwardly from a drop center 20 angling outwardly along radially and axially outwardly tapered surfaces 46 and 48 to then turn axially outwardly to form radially outwardly facing flat bead seats 32 and 34. Conveniently, the axial exterior surfaces of the flanges 12 and 14 are configured with annular indentations configured concentric with the axle and axially indented 36 and 38.

The drop center is formed with a peripheral configuration of somewhat of a sawtooth shape to define angularly shaped stand off ribs 52 radiating outwardly to respective stand off apexes 54.

Formed on the respective apexes are axially spaced apart positioning hubs 56 (FIG. 2) which serve in practice to center the bladder during the molding process as will be described hereinafter.

The stand off teeth 52 are conveniently formed with axially projecting bores 42 disposed equidistant thereabout and countersunk on their opposite ends 44 for receipt of axially projecting screws (not shown).

It will be appreciated that the hub is integrally formed of a single piece of hard polyurethane having high strength properties. The material used to form the hub is carefully chosen to produce the highest degree of bonding strength during the fabrication process with the tire body. A preferred embodiment of the present invention uses thermoplastic polyurethane (TPU) as the material of choice. It will be appreciated that careful selection of the proper polyurethane materials to form the hub and the tire will create a permanent high temperature bond during the fabrication process without the need for any extraneous bonding means such as epoxies or glues. Such a bond created between the two components virtually results in a single integrally formed unit.

Referring to FIGS. 3 and 4, the bladder 8 is constructed of approximately 60 A durometer thermoplastic polyurethane to give it a soft, toroidal, self-distended shape to embrace the tips 54 of the hub ribs 52 annularly within the arrayed locator nipples 56 projecting therefrom. Sitting annularly within the drop-center 20, the bladder exterior is completely exposed except for the points of contact with the hub teeth. Due to the triangular shape of the teeth, only the tip of each tooth contacts the bladder, thus keeping the unexposed portions of the bladder to a minimum. It will be appreciated that this degree of exposure will provide, except for the respective contact points, a relatively complete encapsulation of the bladder within the tire body and simultaneously provide bonding with the polyurethane material of such bladder as well as to the surface area between the tire body and the hub to form a structurally integral system. It will further be appreciated that a predetermined volume of air is trapped within the bladder to cooperate with the wall thereof to provide sufficient ambient pressure to keep the bladder self distended and to expand upon heating during the wheel fabrication process such that the bladder maintains a constant position around the hub. As will be understood by those skilled in the art, the bladder itself may be constructed of a material such that the wall thereof will provide sufficient structural integrity to be self distending.

Referring to FIGS. 1 and 3, the tire body 4 is toroidally formed from a resilient thermoset polyurethane material, such as an MDI based polyurethane, to be chemically similar to the hub 6 material. Due to the fabrication process described hereinafter involved in the molding the tire body, the inner diameter of the tire body at the drop center 20 and the radial walls at the flange surfaces 46 and 48 bond positively to the hub to completely encapsulate the bladder between the tire and hub to form an air retaining capsule independent of the subsequent integrity of the bladder itself.

Formed to project axially and radially outwardly in the tire body 4 is a valve bore 66 having an outwardly opening frusto conically shaped passage 68. The passage extends from the tire body exterior 60 to the upper surface of the encapsulated bladder 70. Received within the passage is an elastomeric, open ended tubular valve 72 constructed of a more resilient urethane than the tire body and formed with a narrow compressible neck 74 to be compressed radially inwardly by the more rigid tire body. The cross section of the valve is oversized with respect to the passage so that the softer material will be compressed by the polyurethane tire body. One end 76 of the valve penetrates into the bladder 8, which is accessed during the fabrication process. The other end 78 slightly protrudes from the tire body exterior for ease of access. Midway through the passage lies a slightly enlarged cavity 80 which opens up into the neck. The cavity serves to define the neck opening that undergoes compression within the tire body. It will be appreciated by those skilled in the art that the hardness differential between the tire body and the valve will normally compressible close the valve at the neck, resulting in an airtight seal internally and externally. The bladder may be forcibly accessed using an appropriately hollowed needle for inflation or deflation of the bladder. Additionally, due to the hermetic construction of the tire body around the bladder, the air tight capacity of the wheel is not necessarily dependent on the bladder. Thus, various embodiments may integrate the bladder in the tire body.

It will be appreciated that one embodiment of the machine skate wheel of the present invention exhibits adjustable performance parameters. By varying the amount of air within the bladder, speed, traction, and shock absorption characteristics of the machine skate wheel may be substantially altered. Inflation or deflation of the bladder correspondingly makes the tire body less resilient or more resilient. A stiffer, less resilient tire body translates into a faster, slicker, and bumpier ride. A softer, more resilient tire body translates into a slower, grippier and relatively shock resistant ride. Further, skaters of different sizes and weights may purchase the same wheels and adjust them respectively to achieve the same skating experience.