Tire for self-inflating tire system

A tire for a self-inflating tire system includes an annular air tube-receiving groove formed within a tire carcass wall at a prescribed radial location. The groove has an access opening, a primary internal groove chamber dimensioned and profiled for close receipt of an annular air-pump tube. A secondary expansion chamber of the groove communicates with the internal groove chamber for operationally receiving a flattened air-pump tube extended portion during tire operation. A passageway is located at a prescribed outlet location along the annular air tube-receiving groove, the passageway extending from the groove to an axially inward terminal end within the tire carcass wall separated from a tire inner liner by a removable wall partition of reduced sectional thickness.

FIELD OF THE INVENTION

The invention relates generally to self-inflating tires and, more specifically, to a tire constructed for a self-inflating tire system.

BACKGROUND OF THE INVENTION

Normal air diffusion reduces tire pressure over time. The natural state of tires is under inflated. Accordingly, drivers must repeatedly act to maintain tire pressures or they will see reduced fuel economy, tire life and reduced vehicle braking and handling performance. Tire Pressure Monitoring Systems have been proposed to warn drivers when tire pressure is significantly low. Such systems, however, remain dependant upon the driver taking remedial action when warned to re-inflate a tire to recommended pressure. It is a desirable, therefore, to incorporate a self-inflating feature within a tire that will self-inflate the tire in order to compensate for any reduction in tire pressure over time without the need for driver intervention.

SUMMARY OF THE INVENTION

In one aspect of the invention, a tire for a self-inflating tire system includes an annular air tube-receiving groove formed within a tire carcass wall at a prescribed radial location. The groove has an access opening, a primary internal groove chamber dimensioned and profiled for close receipt of an annular air-pump tube. A secondary expansion chamber of the groove communicates with the internal groove chamber for operationally receiving a flattened air-pump tube extended portion during tire operation. A passageway is located at a prescribed outlet location along the annular air tube-receiving groove, the passageway extending from the groove partially through the tire carcass wall toward the tire cavity. An axially inward terminal end of the passageway within the tire carcass wall at an outlet location along the groove is separated from the tire cavity a wall barrier of reduced sectional thickness. The pilot hole represented by the passageway is approximately 0.55 to 0.65 the thickness of the wall whereby placing the terminal end 0.35 to 0.45 of the nominal wall thickness to the inside of the tire. The wall barrier is formed penetrable material composition and thickness rendering the barrier removable from its position in a post-cure punching operation, whereby opening the passageway from the groove to the tire cavity.

Still in a further aspect of the invention, the groove has a U-shaped configuration and the passageway extends axially inward from the groove toward the tire cavity. The passageway is constructed to provide first and second axially extending air channels for receipt of an outlet device positioned within the groove.

DEFINITIONS

“Aspect ratio” of the tire means the ratio of its section height (SH) to its section width (SW) multiplied by 100 percent for expression as a percentage.

“Asymmetric tread” means a tread that has a tread pattern not symmetrical about the center plane or equatorial plane EP of the tire.

“Axial” and “axially” means lines or directions that are parallel to the axis of rotation of the tire.

“Chafer” is a narrow strip of material placed around the outside of a tire bead to protect the cord plies from wearing and cutting against the rim and distribute the flexing above the rim.

“Equatorial Centerplane (CP)” means the plane perpendicular to the tire's axis of rotation and passing through the center of the tread.

“Footprint” means the contact patch or area of contact of the tire tread with a flat surface at zero speed and under normal load and pressure.

“Groove” means an elongated void area in a tire wall that may extend circumferentially or laterally about the tire wall. The “groove width” is equal to its average width over its length. A grooves is sized to accommodate an air tube as described.

“Inboard side” means the side of the tire nearest the vehicle when the tire is mounted on a wheel and the wheel is mounted on the vehicle.

“Lateral” means an axial direction.

“Lateral edges” means a line tangent to the axially outermost tread contact patch or footprint as measured under normal load and tire inflation, the lines being parallel to the equatorial centerplane.

“Net contact area” means the total area of ground contacting tread elements between the lateral edges around the entire circumference of the tread divided by the gross area of the entire tread between the lateral edges.

“Non-directional tread” means a tread that has no preferred direction of forward travel and is not required to be positioned on a vehicle in a specific wheel position or positions to ensure that the tread pattern is aligned with the preferred direction of travel. Conversely, a directional tread pattern has a preferred direction of travel requiring specific wheel positioning.

“Outboard side” means the side of the tire farthest away from the vehicle when the tire is mounted on a wheel and the wheel is mounted on the vehicle.

“Peristaltic” means operating by means of wave-like contractions that propel contained matter, such as air, along tubular pathways.

“Radial” and “radially” means directions radially toward or away from the axis of rotation of the tire.

“Rib” means a circumferentially extending strip of rubber on the tread which is defined by at least one circumferential groove and either a second such groove or a lateral edge, the strip being laterally undivided by full-depth grooves.

“Sipe” means small slots molded into the tread elements of the tire that subdivide the tread surface and improve traction, sipes are generally narrow in width and close in the tires footprint as opposed to grooves that remain open in the tire's footprint.

“Tread element” or “traction element” means a rib or a block element defined by having a shape adjacent grooves.

“Tread Arc Width” means the arc length of the tread as measured between the lateral edges of the tread.

DETAILED DESCRIPTION OF THE INVENTION

Referring toFIGS. 1,2,3,6B,7A,8A, and8B, a tire assembly10includes a tire12, a peristaltic pump assembly14, and a tire rim16. The tire mounts in conventional fashion to a pair of rim mounting surfaces18adjacent outer rim flanges20. The rim flanges20have radially outward facing surface22. The tire12is of conventional construction, having a pair of sidewalls24extending from opposite bead areas26to a crown or tire read region28. The tire and rim enclose a tire cavity30. The tire carcass is reinforced by one or more ply layers32that wrap around a bead core34in the bead area26. The carcass plies32form a turnup36having a radially outward end above the bead core34.

Referring toFIGS. 1,7B,8A, and8B, an annular groove38is positioned within the tire carcass12in a high flex region in order to effect operation of a peristaltic pump assembly as will be explained. The positioning of groove38is preferably within a sidewall24in the bead region26at a radial location above the upper end of rim flange20, radially above the bead core34, and radially above the ply turnup ends36. Such a position provides the requisite flexing properties to actuate the peristaltic pump while avoiding contact between the pumping mechanism and the rim. Such a position also avoids the ply turnup ends.

The groove38is generally U-shaped an is profiled in section to include an access opening41opening to a sidewall outward side; a primary groove chamber39of generally circular cross-section sized and shaped to closely receive a peristaltic pump tube as will be explained; and an expansion chamber40surrounding the primary groove chamber. The expansion chamber40generally creates a space adjacent to the primary groove chamber39within which the peristaltic pump tube can expand as it is progressively flattened by flexing of a rolling tire. The expansion chamber40lies in part axially inward from the primary groove chamber39as shown byFIGS. 8A and 8B. The groove38circumscribes the tire carcass at a high flex location and is molded into the tire during tire construction, preferably.

At an outlet device-receiving location along the groove38, the groove is molded to have a cross-sectional profile to accommodate receipt of an outlet device as will be explained. At the outlet device-receiving location along the groove, the groove is molded to further include a tire cavity-directed passageway42extending axially inward from the expansion chamber40partially toward tire cavity30. The passageway42is configured to provide a pair of parallel spaced apart cylindrical passageway segments42A,42B (only42A shown inFIG. 8AandFIG. 8B). The passageway segments42A,42B, groove chambers39,40are molded within the tire sidewall at a desired outlet device-receiving location within the groove38during tire construction.

As molded, the passageway segments42A,42B represent pilot pathways and extend axially inward from the expansion chamber40partially to the tire cavity30of the tire carcass12. The passageway segments extend into sidewall a distance that separates terminal ends48of the segments axially from the tire cavity30by a barrier wall44having a reduced sectional thickness “D” relative to the carcass wall into which the groove38is molded. The thickness of barrier wall44is approximately forty percent of the thickness of the carcass wall with the passageway segments42A and42B extending approximately sixty percent through the carcass wall. The barrier wall44of the sidewall lies between the terminal ends48of the segments42A,42B and the inner liner46in the post-constructed tire carcass at a specific outlet device receiving location along the groove38. The barrier wall44is of like composition as the tire sidewall and, being of rubber composition, the reduced section barrier wall44is readily penetrable and removable from the tire carcass in a post-construction procedure. Once the barrier wall44is removed from the tire carcass, the passageway segments42A,42B represent through-passages open from the chamber40axially inward to the tire cavity30.

As seen fromFIGS. 1,3,4A through4D,5A through5C,8A, and8B, the peristaltic pump assembly14includes an annular air tube50that encloses an annular passageway. The tube50is formed of a resilient, flexible material such as plastic or a rubber compound that is capable of withstanding repeated deformation cycles wherein the tube is deformed into a flattened condition subject to external force and, upon removal of such force, returns to an original condition generally circular in cross-section. The tube is of a diameter sufficient to operatively pass a volume of air sufficient for the purpose of self-inflating the tire12during tire operation. The tube50and the groove38are compatibly sized and configured such that the tube50inserts through the access opening41and closely resides within the primary groove chamber39. The tube50within the groove38are placed in a high flex region of the tire carcass12as described previously.

The peristaltic pump assembly14further includes an inlet device location54and an outlet device location52spaced apart approximately 180 degrees within the circumference of annular air tube50. Situated at the outlet location52is an outlet device72having an elongate body73in which L-shaped outlet tubes84,86extend and exit. The body73is preferably of molded plastic construction and provides retention flanges74,76at opposite upper sides, a retention groove78along opposite elongate sides beneath flanges74,76, and a cylindrical lower body portion80. A pair of barb ridges82are placed at each end of the body73adjacent to the body grooves. Outlet tubes84,86are preferably formed of plastic or stainless steel material and have axial through passageways extending end to end. The tubes84,86are housed within opposite ends of the outlet device body73. So situated, the L-shaped tubes84,86and the axial passageways therein extend from intake ends88,90to exhaust ends92,94. The tube ends88,90are diametrically dimensioned to couple to ends of the annular air tube50while ends92,94extend and direct air into the tire cavity30. Retention ribs95may be formed in some or all of the tube ends88,90,92, and94to assist in coupling the ends88,90with the annular air tube50and ends92,94with devices or apparatus such as a pressure regulating valve/device within the tire cavity30(not shown). The tubes84provide conduits for the passage of air from the annular tube50into the tire cavity30(directional arrow96) and air from the cavity back into and out of the tube50(directional arrow98) if necessary or desired.

As shown byFIGS. 1,3, and4A through4D, the inlet device54is connected to the tube50at an inlet location opposite to the outlet device72. The inlet device54has a cylindrical tube body56and an array of through perforations or openings58extending through the body56to allow ambient air into an axial passageway through the body56(FIGS. 4A through 4D). Surrounding the mid-portion of the tube body56is a filter sleeve60formed of porous cellular material of a density allowing air to pass through but blocking undesired particulates. The sleeve60is formed having a pair of outwardly extending lobe protrusions62,64; a pair of channels65adjacent to respective lobe protrusions; and a pair of barb detent ridges66on opposite sides of the sleeve that define with the lobe protrusions62,64the channels65. The sleeve positioned around the body56filters input air flow in direction61passing through the sleeve and through perforations58into the body56. The tube body56has opposite ends68,70that project outward free of the sleeve60. The ends68,70may be provided with externally formed detent barbs or ridges to facilitate attachment of the ends to free ends of the annular air tube50. The diameter of the tube body56is generally equivalent to that of the air tube50such that both may fit in-line within the annular groove38formed within the tire sidewall. Moreover, a bored sleeve body portion67surrounding the tube body is formed of a cellular or foam filtering material such that the portion67may be compressed to an extent necessary to force fit with the tube body56into the tire groove38. The detent barb ridges66engage the sides of the tire groove38upon insertion to mechanically affix the inlet device into the tire groove. Additional means of attachment such as adhesive may be employed to fix the inlet device54into the groove38if desired.FIG. 2illustrates the peristaltic tube assembly14, including inlet device54and outlet device52attached to the tube50, installed into the groove38of the tire carcass.

The inlet filter sleeve67is preferably constructed of a material such as a porous membrane that passes air and blocks fluids from entering into the tube body56and there from the pump tube50. A suitable material, without limiting the invention, is polytetraflouroethylene (PTFE). The filter sleeve67is thus self-cleaning and capable of high volume air flow into the tube body56. The sleeve67further provides mechanical protection to the body56and is positioned in-line with the tubes56and50. The inlet device54may be assembled as a single assembly with fittings at the inlet ends68,70for attachment to the tube50. Minimization of components and a higher reliability results.

As shown inFIGS. 8A and 8B, andFIGS. 5A through 5C, the outlet device52connects to the air tube50opposite to the inlet device54. Ends88,90of the outlet device52and ends68,70of the inlet device54couple to ends of the air tube50to form the assembly14ofFIGS. 1 and 3. The inlet device ends and outlet device ends have generally the same diametric dimensions as the tube50to facilitate the coupling. The assembly14is thereafter assembled to a tire12in a post-cure operation. The tire12is formed as described above having molded groove38, including chambers39,40and partial passageways42A,42B at an outlet device location along the annular groove38. The assembly14is aligned with the groove38of the tire12, with the outlet device52opposite the outlet device location of the groove38. Thereafter, the tube50, inlet device54, and outlet device52are press inserted into the groove38. The inlet device cellular sleeve60is compressed to facilitate press insertion. In the fully inserted position, the tube50resides in the primary groove chamber39of the groove38, and the inlet and outlet devices reside at respective inlet and outlet device locations along the groove38. The profiled configuration of the inlet device54captures edges defining the groove38within the channel65as barb ridges66and the lobe projections62,64capture the groove edges therebetween. The configuration of the outlet device52, as shown inFIGS. 8A,8B, similarly captures edges defining the groove38between ridges82and the retention flanges74,76.

It will be noted that attachment of the assembly14to the tire12occurs after the molded barrier wall44is removed from the tire in a post-manufacture and cure boring procedure. Once the barrier wall44is removed, the legs84,86of the device52can project through the primary groove chamber39, the adjacent expansion chamber40, and through the dual parallel passageways42A,42B to reach the tire cavity30. Once fully inserted, the passageway from the tube50communicates through the passageways of the outlet tubes84,86with the tire cavity30. The ends90,92of the tubes84,86may be coupled to a pressure regulator mechanism (not shown) within the tire cavity that opens to allow air flow into the cavity (direction96) when the cavity pressure falls below a preset level or out of the cavity (direction98) should the pressure exceed a recommended level.

As will be appreciated fromFIG. 2, the inlet device54and the outlet device52are positioned within the circular air tube50generally 180 degrees apart. The tire rotates in an operational mode, causing a footprint to be formed against a tire-contacting ground surface. A compressive force as shown inFIG. 7Ais directed into the tire from the footprint and acts to flatten the air tube50segment by segment as the tire rotates. Extended portions100of the air tube50caused by the segment by segment flattening of the tube are accommodated by the groove expansion chamber40as shown inFIG. 7A.FIG. 7Ashows an expansion portions100of the tube moving into the expansion chamber40of the groove50. Flattening of the tube50segment by segment draws ambient air into the air tube50through the inlet device54, filtered by sleeve60, and forces air along tube passageway toward and into the outlet device52. From the outlet device, air is forced through the outlet tubes84,86through the tire sidewall and into the tire cavity30. A peristaltic pump of the subject type is disclosed and described in co-pending U.S. patent application Ser. No. 12/643,176 filed on Dec. 21, 2009, incorporated herein by reference.

The post-cure assembly of the pump assembly14to the tire12are after the groove38(including primary chamber38), tube expansion chamber40, and partial passages42A,42B are molded in. The advantages attended the procedure is that such assembly requires that minimal or no ply cords be cut. Moreover, the integrity of the tube50and devices52,54may better be ensured. A uniform tube50shape, location and passage integrity is thus achieved and no change or diminishment of plant capacity utilized in tire construction results. The expansion chamber40is molded in with the groove38. The passage segments42A and42B are at the same radial location as the pump tube50in the tire12. The passage segments42A,42B are opened to the tire cavity30by removal of the barrier wall44of the tire sidewall through drilling or punching by use of an awl or other apparatus. The passageways42A,42B are molded in as deep as possible as pilot pathways so as not to puncture a press shaping bladder during the tire build. It is preferred that the barrier wall44be dimensioned having a sectional thickness within a range of 35 to 45 percent the thickness of the carcass wall.

It should be noted that the partial passageways42A and42B may be molded in or drilled. The process for manufacturing the tire and peristaltic pump assembly is as follows.

The green tire carcass12is built by conventional means having the tire cavity30defined by the tire inner liner46, first and second sidewalls24extending respectively from first and second tire bead regions26to the tire tread region28;

The air tube-receiving groove38is molded into the green tire carcass within the green tire carcass wall at a prescribed radial location such as in bead region wall27. The groove38is molded in an annular configuration in a single form including the access opening41, primary internal groove chamber39and the secondary expansion groove chamber40adjacent to and communicating with the internal groove chamber39. The expansion groove chamber40operationally receives a flattened air-pump tube extended portion.

The groove38provides the partial pilot passageway(s)42A,42B located at a prescribed groove outlet location along the air tube-receiving groove38. The partial passageway(s)42A,42B extend from the groove chamber40partially through the tire carcass wall27toward the tire cavity and has an axially inward terminal end(s)92,94separated from the tire inner liner by a removable tire carcass barrier44of reduced sectional thickness relative to the tire carcass wall27.

The green tire carcass is cured to form a cured tire carcass; and the tire carcass barrier44is removed in a post-cure operation to create a through-bore from the groove38to the tire cavity30at the outlet device-receiving location of the groove38. Separately, the pump assembly14is assembled to include the air tube50; the inlet device54positioned along the air tube and having an inlet opening(s)58for admitting air into the air tube50; and the outlet device52positioned along the air tube opposite the inlet device54.

The wall barrier44is removed by drilling or punching. The outlet passage tubes84,86are plugged at ends92,94to prevent entry of contaminants. A sealant is introduced within the groove38. The pump assembly14is inserted into the tube-receiving groove38with the outlet device52registered within the groove at the prescribed outlet-receiving location of the groove. The outlet passage tubes84,86extend from the outlet device through the through-bore created by removal of barrier44and to the tire cavity30.

The sealant within the groove38is allowed to cure. Should a secondary sealant or covering layer be desired, the tire and assembly14may be mounted over a rim and the tire inflated. A secondary covering may then be applied over the pump assembly14and allowed to cure. The tire is then deflated and removed from the rim.

The plugs may then be removed from the outlet passage tubes84,86and a pressure regulating check valve assembly attached to the ends92,94of the outlet device. The check valve assembly (not shown) operates to regulate air flow into and out of the cavity30based on a preset desired cavity inflation pressure. Such a regulator is of a type available from regulator suppliers such as Emerson/ASCO Pneumatics located in Novi, Mich.; EATON Corporation located in Southfield Mich.; and Parker Corporation located in Otsego, Mich.

It will be further appreciated that the pump assembly14is constructed in an in-line configuration of components50,52, and54. Such a configuration enhances the efficiency of air intake through the inlet device54into tube50, along the tube50and into the outlet device52. Structural obstruction to the flow of air is avoided and the overall in-line annular assembly as shown inFIG. 3, lacking any interfering protrusions and structural obstructions, is relatively easy to insert into groove38. Moreover, the housings of the inlet device54and outlet device52in the form of filtering sleeve60and body73include retention ridges to engage and retain the devices52,54within groove38at desired respective inlet and outlet device-receiving locations. It will further be noted that the sleeve60fulfills the multifaceted functionality of serving as an inlet air filter, a covering to the inlet openings58that protect the openings from external originating contaminants, and a retention mechanism for holding the inlet device54within the groove38. Likewise, the outlet device52positioned along the air tube50is in-line, the outlet device providing tubular outlet body73and an axial passageway in-line with the air tube. The body73houses the L-shaped tubes84,86, and acts to retain the outlet device52within groove38. The passageways42A,42B are closed in an as molded configuration but become open to the tire cavity with the removal of barrier44. Accordingly, the passageways remain clear of contaminants until opened by the removal of barrier44to receive the tubes84,86in a post-cure assembly procedure.