Abstract:
A system for allowing vehicles equipped with pneumatic tires to continue operating after a tire failure which would normally cause deflation of the tire employs one or more airbags stored in deflated configuration either about the exterior surface of the rim supporting the pneumatic tire or externally of the tire. The system further includes a container for compressed gases. A sensor connected to the inflated tire to detect sudden deflation releases the compressed gases so as to inflate the airbag to either support the tire or provide an exterior running surface adjacent to the deflated tire.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority of U.S. Provisional Patent Application 61/377,127 filed Aug. 26, 2010, the contents of which are incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates to pneumatic tires and more particularly to a system employing auxiliary airbags associated with the tires and a source of pressured gases which may be released to expand the airbags in the event of an accidental deflation of the tires. 
       BACKGROUND OF THE INVENTION 
       [0003]    A failure of a pneumatic tire can expose the occupants of the affected vehicle to excessive risks of having to stop in high speed traffic or other high risk environments to evaluate the damage, to change the wheel and tire assembly, or to move slowly in an aggressive flow of traffic to a place of relative safety. 
         [0004]    The problem of pneumatic tire failure is particularly aggravated in military vehicles which may be operating in dangerous areas and in commercial and off-the-road vehicles where the cost of lost time required to recover from tire damage may be very significant. 
       SUMMARY OF THE INVENTION 
       [0005]    Accordingly, the present invention is directed toward a security system for pneumatic tires of vehicles which will allow the vehicles to continue operation, for at least limited periods of time, after damage to one of the vehicle&#39;s pneumatic tires which would normally disable the vehicle. 
         [0006]    The systems of the present invention involve collapsible, substantially gas impervious bags which may be stored in collapsed form either within the interior volume of a tire to be protected, or externally thereto, and which may be inflated upon the detection of a pressure change in the associated pneumatic tire which would impair its continued use. These systems may employ a tank for storing compressed gas which can be used to inflate the collapsed bags in the event of the detection the failure of the pneumatic tire. Alternatively, a gas generating reactor of a type similar to those employed with the inflators for automatic airbags, including pyrotechnic gas generators, may be employed. The gas sources or generators may be associated with each tire of the vehicle, or alternatively, a single source of compressed gas or a gas generator may service several tires or all the tires of the vehicle. 
         [0007]    In the form of the invention in which the collapsed bags are stored within each tire volume, they are preferably retained within the wheel rim so as to not hinder the normal operation of the tire, but when a traumatic decrease in pressure in the associated tire is detected, they can then be inflated to occupy sufficient volume within the disabled tire to allow the vehicle to continue normal operation, at least for a limited period of time. Depending on such factors as the tire size and the nature of the vehicle, one or more bags may be associated with each tire. When more than one bag is utilized they are preferably arranged at equal angles about the perimeter of the rim so that when expanded the volume within the tire is equally filled with the bags. 
         [0008]    In an alternative embodiment in which the airbags are stored externally of each tire they are similarly arrayed at equal circumferential intervals so that when expanded they effectively create an auxiliary tire which is supported adjacent to it on the same axle as the damaged tire to allow continued use of the vehicle. 
         [0009]    In still another embodiment of the invention, the tires may be protected by one or more airbags supported within the rim volume as well as a number of external airbags. Airbags stored within the tire volume could re-inflate the tire which would then share the vehicle load with the exterior airbags which are simultaneously inflated. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    Other objectives, advantages, and applications of the present invention will be made apparent by the following detailed description of the preferred embodiment of the invention. The description makes reference to the accompanying drawings in which: 
           [0011]      FIG. 1  is a cross section through a conventional pneumatic tire supported on a two piece wheel rim which also contains collapsed gas bags and a compressed gas inflation source for the collapsed bags; 
           [0012]      FIG. 2  is a plan view of the device of  FIG. 1 ; 
           [0013]      FIG. 3  is a sectional view through an alternative embodiment of the present invention supported on a one piece wheel rim; 
           [0014]      FIG. 4  is a plan view of the device of  FIG. 1 ; 
           [0015]      FIG. 5  is a cross sectional view of an embodiment of the invention like that in  FIG. 3  with the gas bags inflated and a portion of the tire blown away; 
           [0016]      FIG. 6  is a schematic illustration of an embodiment of the invention with  16  gas bags disposed at equal circumferential intervals about the interior volume of a tire; 
           [0017]      FIG. 7  is a sectional view through an embodiment of the invention employing a gas bag externally of the tire volume; 
           [0018]      FIG. 8  is a view of the device of  FIG. 7  with the external airbags inflated so as to create an auxiliary tire to support the vehicle in the event of failure of the basic pneumatic tire; 
           [0019]      FIG. 9  is a front view of a cover adapted to surround an emergency system like that shown in  FIGS. 1 and 3 , adapted to be disposed on the radial interior side of the gas bags which are collapsed within the rim; and 
           [0020]      FIG. 10  is a side view of the cover of  FIG. 9 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0021]    Referring to  FIGS. 1 and 2 , a first embodiment of the invention in which the collapsible air (or “gas”) bags are stored within the volume of the pneumatic tire  10  being protected, is illustrated. The tire  10  is shown in its inflated, undamaged position. The tire is affixed to a two piece wheel rim system  12  with the two sections of the rim being secured to one another by a nut and bolt  14 . A bead support and air assembly ring  16 , which may extend fully around the perimeter of the wheel, is supported on the interior side of the rim. The ring  16  is generally U-shaped in cross section and supports two collapsed airbag sections  18   a  and  18   b  within the “U”. A source of gas  20  is retained against the interior surface of the rim. 
         [0022]    The gas source may be of the type that has been used to inflate automotive airbags for the security of passengers. These include containers of compressed nitrogen or argon, often with pyrotechnic operated release valves. Other gas sources include azide containing pyrotechnic gas generators. 
         [0023]    Alternative propellants may incorporate, for example, a combination of nitroguanidine, phase-stabilized ammonium nitrate (NH 4 NO 3 ) or other nonmetallic oxidizer, and a nitrogen-rich fuel different than azide (e.g. tetrazoles, triazoles, and their salts). The burn rate modifiers in the mixture may be an alkaline metal nitrate (NO 3 —) or nitrite (NO 2 —), dicyanamide or its salts, sodium borohydride (NaBH 4 ), etc. The coolants and slag farmers may be e.g. clay, silica, alumina, glass, etc. Other alternatives are e.g. nitrocellulose based propellants (which have high gas yield but bad storage stability, and their oxygen balance requires secondary oxidation of the reaction products to avoid buildup of carbon monoxide), or high-oxygen nitrogen-free organic compounds with inorganic oxidizers (e.g., di or tricarboxylic acids with chlorates (ClO 3 —) or perchlorates (HClO 4 )). 
         [0024]    A tire pressure sensor  22  is supported on the airbag assembly ring  16  within the inflated volume of the tire  10 . The sensor  22  may be of any conventional pressure sensitive type such as the diagram supported by a spring and preferably includes a small battery (not shown). When the sensor  22  detects a sudden decrease in the tire pressure below the usual value, an electrical signal is sent on line  24  to an output valve  25  connected to the airbag inflation device  20  which then releases its pressurized gas into the bags  18   a  and  18   b  causing them to inflate in the manner generally indicated in  FIG. 5 . 
         [0025]      FIG. 2  is a view looking downwardly from within the tire volume to the bags  18   a  and  18   b . It illustrates that the device in  FIG. 1  is associated with a particular segment of the wheel rim  12 . A plurality of similar segments may be arrayed at spaced intervals on an entire perimeter of the rim or a relatively few bags could be placed at equal intervals along the rim. 
         [0026]    In an alternative embodiment of the invention a single tire pressure sensor  22  might service a number airbags spaced along the rim. Additionally, a single container of compressed gas  20  might be supported on the vehicle with output connections to a plurality of airbags spaced about the rim. 
         [0027]      FIGS. 3 and 4  are very similar to  FIGS. 1 and 2  and illustrate a one piece rim  26 . 
         [0028]    When the airbags  18   a  and  18   b  are inflated, they combine to fill the normal volume occupied by an inflated tire, as illustrated in  FIG. 5 . In  FIG. 5  a section of the tire  10  is illustrated as broken away between the ends  28  and  30 , but the vehicle may be continued to be driven at least for a relatively short period of time, on the inflated airbag  18 . 
         [0029]      FIG. 6  is a schematic diagram of a tire equipped with an airbag system formed in accordance with the present invention taken through a plan transverse to the wheel axis. The volume between the wheel rim  40  and the original tire tread  42  is populated by  16  airbag segments  44 , arranged at equal circumferential intervals about the tire rim  40 . As has been noted the segments  44  may not be immediately adjacent to one another but could be spaced about the wheel. The number of airbags utilized will be depend upon the size of the tire, the nature of the vehicle, the area in which it is being used, and similar factors. 
         [0030]    An alternative embodiment to the invention is illustrated in  FIG. 7  wherein one or more airbags  50  are supported in container  52  affixed to a wheel rim  54 , but outside of the volume of the pneumatic tire  56 . In  FIG. 7  the container  52  is secured to the wheel rim  54  by the same bolt  58  which secures the rim to the wheel hub  60 . 
         [0031]      FIG. 8  illustrates the airbag  50  in inflated form which occurs when the tire  56  is damaged so the air pressure on its interior suddenly decreases which is sensed by a sensor (not shown) and sends the signal to the compressed gas container  62  or gas generator valve to release its compressed gas or initiate the gas generating reaction and feeds the gas into the airbag  50 . The bag then assumes a shape similar to the undamaged pneumatic tire to provide an emergency tire that may be used for a limited period of time. 
         [0032]    The compacted airbags such as  18  may be protected by an airbag cover  64  illustrated in  FIG. 9  and  FIG. 1 , which extends over the radial interior surfaces of all the airbags associated with the wheel.  FIG. 10  and  FIG. 1  show the wheel cover in plan view transverse to the wheel axis and  FIG. 9   b  shows the side view of the cover extending parallel to the wheel axis. The cover  64  normally lies in a closed hoop configuration with its two ends  72  and  74  overlapping one another. When the associated airbags are inflated, the ends  72  and  74  slip away from one another, allowing the hoop to open so that the airbags may escape into the interior of the tire volume.