Abstract:
A self-inflating tire assembly includes an air tube connected to a tire and defining an air passageway, the air tube being composed of a flexible material operative to allow an air tube segment opposite a tire footprint to flatten, closing the passageway, and resiliently unflatten into an original configuration. The air tube is sequentially flattened by the tire footprint in a direction opposite to a tire direction of rotation to pump air along the passageway to an inlet device for exhaust from the passageway or to an outlet device for direction into the tire cavity.

Description:
FIELD OF THE INVENTION 
     The invention relates generally to self-inflating tires and, more specifically, to a pump mechanism for such tires. 
     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. 
     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. 
     “Circumferential” means lines or directions extending along the perimeter of the surface of the annular tread perpendicular to the axial direction. 
     “Equatorial Centerplane (CP)” means the plane perpendicular to the tire&#39;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. 
     “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&#39;s footprint. 
     “Tread element” or “traction element” means a rib or a block element defined by having shape adjacent grooves. 
     “Tread Arc Width” means the arc length of the tread as measured between the lateral edges of the tread. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described by way of example and with reference to the accompanying drawings in which: 
         FIG. 1  is an side view of tire having a pump assembly mounted therein; 
         FIG. 2  is a cross-sectional view of the bead area of the tire of  FIG. 1 ; 
         FIG. 3  is a cross-sectional view of a first embodiment of a pump assembly; 
         FIGS. 4-6  illustrate assembly of the pump assembly; 
         FIG. 7  illustrates a side view of the tire during operation of the pump to the tire cavity when the tire rotates. 
         FIG. 8  is a cross-sectional view of a second embodiment of a pump assembly; 
         FIGS. 9-12  illustrate a third embodiment of a pump assembly. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIGS. 1 and 2 , a tire assembly  10  of the present invention includes a tire  12  and a pump assembly  14 . The tire mounts in a conventional fashion to a conventional tire wheel  16 . The tire is of conventional construction, having a ground engaging tread region  38 , and a pair of sidewalls  32  extending from the tread to the bead areas  34  mounted on the wheel  16 . The tire and wheel enclose a tire cavity  30  for holding pressurized air. 
     As shown in  FIGS. 1 and 2 , the pump assembly  14  includes a pump  41  that is assemblied with a passageway  43  located in the sidewall area of the tire, preferably near the bead region. Although the positioning of the pump  41  is specifically shown near the bead region  34  and the rim surface  26 , it is not limited to same, and may be located at any region of the tire such as anywhere in the sidewall or tread that undergoes compression. 
     A passageway  43  is formed in the tire, preferably in the sidewall of the tire and is preferably annular in shape. The pump  41  is made of a tube or a pre-molded tube shape in the tire formed of a resilient, flexible material such as plastic, silicone, elastomer or rubber compounds, and is capable of withstanding repeated deformation cycles when the tube is deformed into a flattened condition subject to external force and, upon removal of such force, returns to an original condition. The tube is of a diameter sufficient to operatively pass a volume of air sufficient for the purposes described herein and allow a positioning of the tube in an operable location within the tire assembly as will be described. Preferably, the tube has a circular cross-sectional shape, although other shapes such as elliptical or lens shape may be utilized. 
       FIG. 4  illustrates how the pump is constructed. The pump is formed from a tube  60  preferably including one or more optional pockets  62  for receiving miniature check valve  50 . The miniature check valve is preferably a duckbill check valve, although other type of miniature check valves such as umbrella valve or ball valve may be utilized. The check valves  50  are inserted into the tube  60 . If pockets  62  are utilized, the check valves are inserted into each pocket  62  as shown in  FIG. 5 . The check valves  50  are spaced apart from each other a desired distance L. L may range from about 12 mm to about 150 mm and which depends on tire size/load capacity and tire inflation limit. The check valves are aligned in the same direction. An optional cover strip of rubber  66  as shown in  FIG. 6  may be applied over the assembly of  FIG. 5 . 
       FIG. 3  illustrates the tube  60  arranged into a pump  41 . The pump  41  has an inlet end  41   a  and an outlet end  41   b , with the plurality of check valves  50  arranged in the tube and spaced apart a distance L. The inlet end  41   a  is in fluid communication with the atmospheric air. The tube outlet end is in fluid communication with the tire cavity  30 . As shown, the inlet end  41   a  and the outlet end  41   b  are spaced apart in the range of about 330-360 degrees. Other variations may be utilized, such as two 180 degree pumps as shown in  FIG. 8 , or other angular variations such as 270 degrees (not shown), etc. Pump outlet end  41   b  extends into the tire cavity so that it is in fluid communication with the tire cavity. The outlet end may further include an optional check valve  45  to prevent backflow of air from the cavity into the pump  41 . 
     As will be appreciated from  FIG. 7  and  FIG. 3 , as the tire rotates in a direction of rotation  88 , a footprint  103  is formed against the ground surface  98 . A compressive force  104  is directed into the tire from the footprint  103  and acts to flatten a segment  111  of the pump  41 . Flattening of the segment  111  of the pump  41  forces air from the flattened segment  111 , in the direction shown by arrow  84 , through the check valve  50  and into an adjacent segment  110 ′. The check valves  50  prevents the reverse flow of air (counterclockwise) in each tube segment. 
     As the tire continues to rotate in direction  88 , the pump tube  41  is sequentially flattened or squeezed segment by segment  111 ,  111 ′,  111 ″ etc. The sequential flattening of the pump tube  41  segment by segment causes the column of air located between the flattened segments to be pumped in the direction  84  to the outlet of the pump and then into the tire cavity. The progression of squeezed or flattened tube segments can be seen to move in a clockwise direction, counter to the tire rotation in direction  88 . As segment  111  moves away from the footprint  103 , the compression forces within the tire from the footprint region are eliminated and the segment  111  is free to resiliently reconfigure into an unflattened state as segment  111  refills with air from the inlet end. The above-described cycle is then repeated for each tire revolution, each rotation resulting in pumped air going into the tire cavity. Even if the tire rotation direction  88  is the same as direction  84 , pump  41  will generate similar pump action in the direction  84  (bi-directional pumping accomplished by check valve controlling the flow direction) with slightly lower pumping efficiency. 
       FIG. 8  illustrates a second embodiment of first and second pump assembly  100 ,  110 , respectively. The first and second pump assemblies are configured into two 180 degree pumps  100 ,  110 . Each pump  100 , 110  includes a tube  60  having a plurality of check valves  50  mounted therein. Pump  100  has the plurality of check valves oriented to allow fluid flow in the clockwise direction, opposite the tire rotation. The check valves prevent fluid flow in the direction of tire rotation. Pump  110  has its inlet end  110   a  oriented adjacent to the inlet end  100   a  of pump  100 . The inlet ends  100   a ,  110   a  are each in fluid communication with the atmospheric air. Pump  110  has its check valves  50  oriented to allow fluid to flow in the counterclockwise direction  122 , same as the tire rotation direction. Preferably, a check valve  50  is located at a distance L/2 from each inlet end  100   a , 110   a  and at a distance L/2 from each outlet end  100   b ,  110   b  of the tube. The check valves  50  prevent backflow from the tire cavity into the tubes  100 , 110 . The tube outlet ends  100   b , 110   b  are preferably co-located and are each in fluid communication with the tire cavity  30 . 
     The second embodiment of the first and second pump assembly  100 , 110  works similar in operation to the pump  41  described above. As the tire rotates in the counterclockwise direction, the air in pump  100  is squeezed in the clockwise direction from the tire squeezing the tube under the footprint. Air is forced from one segment  120  through the check valve  50  and then into an adjacent segment. As the tire continues to rotate, air is channeled through the check valves  50  and segments  20  until the air reaches the outlet of the tube. The air is forced into the tire cavity to fill the tire. As the tire rotates into contact with the second pump  110 , pumping will continue to occur with slightly lower pumping efficiency as described in section [0028]. This form of assembly provides same pumping efficiency regardless of the tire rotation/mounting direction. 
     A third embodiment of a pump assembly  300  is shown in  FIGS. 9-12 . The pump assembly  300  is comprised of a plurality of tube sections  310 . Interposed between the tube sections are a plurality of bases  320 . Each base  320  is solid in cross-section except for at least two holes  322 , 324 , preferably three holes  322 , 324 , 326 . A stem  342  of a check valve  340  is inserted in hole  324 . The check valve  340  having a circular portion  344  which is positioned to cover the holes  322 ,  326 . The tube segments are joined together with the bases  320  housing the check valves, so that the check valves are all aligned in the same direction as shown in  FIG. 11 . An optional cover strip may be applied over the tube, base and check valve assembly as shown in  FIG. 12 . 
     Variations in the present invention are possible in light of the description of it provided herein. While certain representative embodiments and details have been shown for the purpose of illustrating the subject invention, it will be apparent to those skilled in this art that various changes and modifications can be made therein without departing from the scope of the subject invention. It is, therefore, to be understood that changes can be made in the particular embodiments described which will be within the full intended scope of the invention as defined by the following appended claims.