Abstract:
An air supply system for a large vehicle air brake system includes an air compressor for supplying compressed air. The compressed or pressurized air is routed to an air dryer which includes a desiccant bed through which the compressed air flows for drying. The air dryer is located between a wet tank and a dry tank for the air supply system and air moves from the dryer to the wet tank. From the wet tank the air passes through a conduit through the air dryer to the dry tank. The air dryer is mounted on tracks allowing it to withdrawn from between the air tanks for replacement or service.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to air brakes for motor vehicles and trailers, and more particularly relates to the air supply system for such brakes. 
     2. Description of the Problem 
     Mechanical braking systems for heavy trucks have been largely displaced by more reliable air and hydraulic brakes. Air brakes, requiring no hydraulic liquid, are clean and have fewer environmental concerns should a coupling fail than hydraulic units and have proven popular. An air brake system usually includes a compressor, two air storage tanks, various control valves and air lines. Pressure regulating systems control the compressor. Conduits and valves control application of air pressure to pneumatically driven components. The compressor draws air from the atmosphere and delivers it to one of the tanks which functions as a first stage tank often called the wet tank. From the wet tank the air passes to a second stage tank often called the dry tank from which the air is distributed. 
     Air brakes can be vulnerable to moisture and because the source of air for the compressed air system is the ambient atmosphere, which may hold much moisture, an air drying system is usually provided between the compressor and the wet tank. Obviously, this air drying system should be highly reliable. At the same time, the air drying system should not complicate assembly or maintenance of a vehicle and it should not be excessively expensive. 
     Contemporary practice favors desiccant based air drying systems. A desiccant based air dryer provides a molecular sieve through which air passes. The molecular sieve comprises a hydrophillic compound which pulls the moisture from the air. Over time the molecular sieve can break down from repeated cycles of wetting and drying, or from contamination from other impurities. Periodic replacement of the desiccant may be required. 
     Desiccants have been provided in replaceable, spin-on canisters similar to those used for replaceable oil or fuel filters. The hydrophillic material is located in an outer chamber so that inlet air from the compressor enters the outer chamber, passes through the hydrophillic material, and then passes to the outlet via an inner core. While spin-on canisters are readily replaceable, the amount of water they can remove is dependent upon the length of the flowpath through the desiccant. The space in the canisters is limited and they often cannot be readily lengthened to improve air drying. 
     The addition of canisters to the air brake system has also added to the complexity of an already complicated pneumatic plumbing system. U.S. Pat. No. 6,074,462 to Quinn is directed to the problem. Numerous air lines have been required to connect the pressure tanks to the brake and other components. Air lines are provided interconnecting the tanks. The tanks have often been located, spaced from one another, wherever room was available on the vehicle frame. The desiccant canister and compressor have also required air lines. Simplification of the entire system, consistent with providing effective and easily maintained air drying would be advantageous. 
     SUMMARY OF THE INVENTION 
     According to the invention there is provided a vehicle having an air supply system for a vehicle brake system. The air supply system is based on a compressor for supplying compressed air. The compressed or pressurized air is routed to an air dryer which includes a desiccant bed through which the compressed air flows. The desiccant bed is housed in an outer canister having opposite facing mating sides and a flow through pipe through the bed connecting the opposite facing mating sides. A first stage air tank, located along a first of the opposite facing mating sides, receives air from the air dryer through a port. A second stage air tank is located along the remaining one of the mating sides and communicates with the first stage air tank through the flow through pipe. The air dryer is mounted on tracks allowing it to withdrawn from between the air tanks for replacement or service. 
     Additional effects, features and advantages will be apparent in the written description that follows. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself however, as well as a preferred mode of use, further objects and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings, wherein: 
     FIG. 1 is a top plan view of a vehicle chassis with an installed air brake system. 
     FIG. 2 is a schematic diagram of an air charging system utilizing the present invention. 
     FIG. 3 is a perspective view of the air dryer and tanks assembly. 
     FIG. 4 is a cross sectional view of the air dryer and tanks assembly. 
     FIGS. 5A and 5B are perspective, disassembled views of components of the air dryer and tanks assembly. 
     FIG. 6 is a cross sectional view of a port to port connection between the air dryer module and a tank. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the figures and in particular to FIG. 1 there is illustrated a vehicle chassis  80  for a vehicle equipped with air actuated, pneumatic brakes  92 . Chassis  80  comprises a pair of parallel, longitudinally extending frame rails  10  and  12  which extend from the front end  82  of the vehicle to the rear end  84 . Frame rails  10  and  12  are connected to one another by a plurality of cross members  83 . Front steerable wheels  86  are carried on a front axle  88  while rear drive wheels  90  are carried on a rear axle  92 . 
     Vehicle chassis  80  is equipped with air brakes  70  associated with front steerable wheels  86  and rear drive wheels  90 . Air brakes  70  are pneumatically actuated by application of pressurized air through an air line  72 . Air is supplied to air line  72  from reservoir tanks  13  and  14  and a compressor  18  installed on the vehicle. 
     An accessory support platform  20  hangs from side rails  10  and  12  between the front axle  88  and rear axle  92 . Accessory support platform  20  provides support to two compressed air tanks  13  and  14  and an air dryer unit  16  positioned between the air tanks. Accessory support platform  20  comprises three support rails  22 ,  24  and  26 , which are mounted below the frame rails  10  and  12 , parallel to one another and perpendicular to the frame rails. Support rails  22 ,  24  and  26  are substantially longer than the spacing between frame rails  10  and  12 , with the result that the support rails extend out from the frame rails toward the sides of the vehicle and can be used to provide a substantial area of support between the frame rails and toward the outside edges of the vehicle. An air line  73  is connected from compressor  18  to air dryer  16 . Air line  72  is connected to one of the two air tanks, commonly referred to as a dry tank  14 . Air tanks  13  and  14  are permanently mounted to chassis  80 . Air dryer module  16  may be withdrawn from between the air tanks  13  and  14  for replacement or service. 
     FIG. 2 shows an air charging system  31  with an air dryer module  16  according to the present invention. Air charging system  31  is based on an air compressor  18  which draws air from the ambient atmosphere. Compressed air is discharged from the pump to an air line  73  which conveys the air to an air dryer module  16  (denoted in phantom) disposed between a wet tank  13  and a dry tank  14 . Air passes from air line  73  into air dryer module  16  by a one way check valve  24 , passes through a desiccant bed  25  until escaping from the module into wet tank  13  by an outlet  29 . Air passes from wet tank  13  to dry tank  14  by a conduit  27  through the air dryer module which aligns with openings into the two tanks when module  16  is positioned between the tanks. An air line  75  applies air pressure from wet tank  13  to a control port inlet  76  on air compressor  18  so that when the air pressure in tank  13  is above a minimum, the load is removed from compressor  18 . Dry tank  14  has an outlet to the primary brake service circuit provided by air line  72 . A hand actuated water drain may be provided on the exterior of wet tank  13 . Air passes through substantially the full length of air dryer  16  which is advantageous for drying. 
     Exterior sides of air dryer module  16  are shaped to conform to the exterior shapes of the tanks and adapted to form an air tight seal against the adjacent air tanks  13  and  14 . Air dryer module  16  itself may be temporarily withdrawn from between tanks  13  and  14  for servicing or convenient replacement of the desiccant bed  25 . 
     Referring to FIG. 3 a concave side  37  of dryer module  16  adjacent the cylindrical exterior of dry tank  14 . The seal between tank  14  and module  16  is formed in part by a engagement track  35  provided on the exterior of tank  14 . 
     In FIGS. 4 and 5 tanks  13  and  14  are viewed in cross section with air dryer module  16 . Air dryer module  16  has outwardly facing elongated concave sides  37  and  39 , which are contoured to fit around the cylindrical dry and wet tanks  14  and  13 , respectively. Mounted to the outsides of tanks  13  and  14 , facing air dryer module  16 , are tracks  35  and  45 , respectively. Tracks  35  and  45  are elongated in a direction parallel to the central axes of tanks  13  and  14 , and centered with respect to the concave faces  37  and  39  of the air dryer module to cooperate with complementary tracks  41  and  43 , which are positioned facing outwardly within the concave faces. Each set of tracks comprises two rails, each of which cooperates with its opposite number from a complementary track to retain the tracks in a tight fit against one another. This can be implemented in a number of ways, for example, by two C channels which engage one another around one leg thereof, by making one rail somewhat larger than the other allowing it to be fitted around the smaller channel, or by making the rails of one track spaced rubber flanges, each of which is similar to the anchor for a windshield washer blade and making the rails of the second track channels for receiving the flanges. 
     FIGS. 5A-5B illustrate that tracks  35 ,  41 ,  43  and  45  extend the length of the tanks  13  and  14  and air dryer module  16 . Between the rails of the tracks  41  and  45  are ports, including ports  50  and  52  into air dryer module  16  and ports  51  and  53  in wet tank  13 . Port  51  aligns with port  50 , which is an outlet from the air dryer module and port  53  of wet tank  14  aligns with port  53 , which is an entry to conduit  27  which passes through air dryer module. Dry tank  14  and its track  35  have a port  53 A corresponding to port  53  of the wet tank  13  to align with conduit  27 . There are no direct connections between the interior of air dryer module  16  and dry tank  14 . 
     The tracks for retaining the air dryer module can be constructed in a number of ways, with FIG. 6 illustrates just one of many possible complementary track arrangements. In FIG. 6 track  141  comprises two rails  142 A and B, which have a flattened T cross sectional shape. Rails  142 A and B nest in rails  146 A and B, respectively, of track  145 . Rails  146 A and B are blocks with T-shaped slots for receiving the complementary rails. Port  153  extends upwardly between rails  146 A and  146 B to be impressed and seal against port  152  to provide a substantially air tight conduit. Rails and ports are made of a resilient material such as rubber. 
     The invention provides an air dryer module for an air driven brake system on a vehicle which simplifies both construction and maintenance of the brake system. 
     While the invention is shown in only one of its forms, it is not thus limited but is susceptible to various changes and modifications without departing from the spirit and scope of the invention.