Abstract:
A towing arrangement on a vehicle includes a pair of glad hands for receiving pressurized air and a plurality of double check valves connecting the glad hands to valves associated with a braking system of the vehicle. Air from a first glad hand is supplied through a first of the double check valves to a spring brake modulating relay valve associated with spring brakes of the vehicle. Air from a second glad hand is supplied through a second of the double check valves to a first release valve associated with service brakes of a front axle of the vehicle and through a third of the double check valves to a second release valve associated with service brakes of a rear axle of the vehicle.

Description:
BACKGROUND 
     This invention relates to controlling the braking systems of a towed vehicle by a towing vehicle. 
     Towing of vehicles such as trucks is known. Typically, a vehicle having mechanical or other problems that prevents its operation is towed by a towing vehicle to a place for repair, etc. A malfunctioning vehicle such as a truck can be towed by having one axle hoisted by a towing truck and the towed vehicle is moved on its other axle. 
     Trucks are also towed by pulling them with all axles on the ground (road). Trucks are increasingly being equipped with a glad hand structure (such as front glad hands to couple the brake system with the towing vehicle) to facilitate towing of the truck in this manner. In addition to the physical connections made between the towing vehicle and towed vehicle for facilitating towing, the glad hand structure is utilized for controlling the brakes on the towed vehicle from the towing vehicle. 
     A truck has two types of brakes—service brakes and parking brakes. The service brakes can be separated into primary brakes and secondary brakes. The primary brakes are associated with the drive axle (i.e. the rear wheels). The secondary brakes are associated with the steer axle (i.e. the front wheels). Parking brakes may also be referred to as emergency brakes or as spring brakes. Parking brakes are also associated with the drive axle (i.e. the rear wheels). 
     In order to permit vehicle motion, pressurized air is used to compress the emergency brake springs (i.e. to release the emergency brake). In order to stop the vehicle using the emergency brake (i.e. to apply the emergency brake), the springs are released by releasing the pressurized air from the spring brake chambers. The air system is used to engage or disengage the brakes on a truck. Pressurized air (or, high pressure air) in the brake system is supplied by a compressor powered by the engine. 
     A general braking system  100  associated with trucks is illustrated in  FIG. 1A . Braking system  100  includes a wet (or supply) tank  105  which receives air that has been pressurized by a compressor. Air from the wet tank  105  is supplied to the primary air tank  110  and the secondary air tank  115 . In general, air from the primary tank  110  is used to operate and control the rear brakes (i.e. the drive axle)  150  while air from the secondary tank  115  is used to operate and control the front brakes (i.e. the steer axle)  170 . For illustrative purposes, only one rear axle  150  is shown; a truck may have more than one rear axle. The rear axle  150  includes both (rear or primary) service brake chambers  15  and spring brake chambers  25 . Air is supplied to each of these chambers via separate lines as illustrated. 
     The primary tank  110  and the secondary tank  115  supply air to a treadle valve that is actuated by the brake pedal. The treadle valve may include or consist of two pneumatically separate valves such as a top or primary portion TVR  140  and a bottom or secondary portion TVF  160 . The portion of the valve closest to the brake pedal, TVR  140 , receives air from the primary tank  110  and controls the rear axle brakes  150 . The remaining portion of the valve, TVF  160 , receives air from the secondary tank  115  and controls the brakes on the front axle  170 . 
     When the brake pedal is depressed, TVR  140  is triggered and a signal is communicated to rear axle relay valve, RV  145 , which applies air to the rear brakes  150  to slow or stop the vehicle. The air is supplied from the primary tank  110 . Simultaneously, the secondary portion of the treadle valve, TVF  160 , is triggered and air is delivered via the quick release valve, QRV  165 , to activate the front brakes  170 . 
     Air from the primary tank  110  is supplied via a T fitting  120  (a T fitting is herein after referred to as a T) to TVR  140  and to double check valve DCV  125 . Air from the secondary tank  115  is supplied to TVF  160  and double check valve DCV  125 . Air from DCV  125  is supplied via T  130  to parking control valve PCV  135  and to spring break relay valve SBRV  190 . Air from PCV  135  is also supplied to spring brake control valve SBCV  180 . As is known, a double check valve permits air from one of multiple sources to flow based on which source provides the higher pressure—the higher pressure air is permitted to flow. 
     The parking or emergency brake is controlled by PCV  135 . In order to facilitate vehicle motion, the parking brake is released by applying pressurized air from PCV  135  (via SBCV  180  and SBRV  190 ) to spring brake chambers on rear brakes  150 . This pressure releases the rear brakes. The vehicle can be stopped using the parking brake by shutting off pressurized air from PCV  135  to the spring brake chambers. This results in the parking brakes being applied. 
     Brakes on trucks typically fail due to loss of pressure in the primary circuit (associated with the primary tank). In such a situation, the parking or spring brakes have traditionally been controlled by the park control relay valve (such as PCV  135 ). More recently, federal regulations specified the use of a spring brake inversion valve to facilitate the control of parking or spring brakes via the treadle rather than having to use the instrument panel-mounted park control valve. 
     A braking system utilizing a spring inversion valve (which may also be referred to as an inversion valve or a spring brake modulating relay valve) is illustrated in  FIG. 1B . If a pressure loss occurs in the primary tank, the spring brake modulating relay valve, SBMRV  185 , allows the spring brakes to be applied by the treadle valve  140 ,  160  rather than having to use the park brake control valve, PCV  135 . 
     When the air brake system is functioning properly, SBMRV  185  monitors delivery pressure from the treadle valve TVR  140  and TVF  160  (via Ts  240  and  260  for example). When the parking control valve, PCV  135 , is pushed in to release the spring (or parking) brakes, the modulating relay valve SBMRV  185  opens a path from the secondary tank  115  to the spring brake chambers to keep the spring brakes released to permit vehicle motion. 
     Air from the primary tank  110  is supplied to the treadle TVR  140  and to PCV  135  via T  230 . Air is also supplied to the relay valve for the rear brakes, RV  145 , by the primary tank  110  and by TVR  140 . Air from the secondary tank  115  is supplied to the treadle TVF  160  and to PCV  135  via T  250 . Air from the secondary tank  115  is also supplied to the modulating relay valve SBMRV  185  via a check valve  195 . Air from TVF  160  is also supplied to the front brakes  170  via T  240  and quick release valve, QRV  165 . 
     A loss of primary pressure at the spring brake modulating relay valve, SBMRV  185 , results in an unbalanced condition inside the valve since secondary control pressure from treadle valve TVF  160  is present without control pressure from the relay valve RV  145 . A service brake application (via the treadle) allows pressure from the secondary tank to enter SBMRV  185  in proportion to the amount of force applied to the treadle valve. The modulating relay valve SBMRV  185  then allows a proportionate amount of spring brake hold-off pressure to exhaust from the spring brake chambers. 
     Towing via glad hands is not compatible for trucks utilizing the spring brake modulating relay valve such as SBMRV  185 . Previous front towing glad hand systems utilized only the primary circuit (i.e. the primary tank). In order for the spring brake modulating relay valve to function properly, air from the secondary circuit/tank is also (i.e. in addition to air from the primary tank) required. A need exists, therefore, to provide a braking system for towing a vehicle having glad hands and a spring brake modulating relay valve. 
     SUMMARY 
     In one embodiment, a towing arrangement on a vehicle is disclosed. The towing arrangement comprises: at least two glad hands for receiving pressurized air and a plurality of double check valves connecting the glad hands to valves associated with a braking system of the vehicle, wherein air from a first one of the glad hands is supplied through a first one of the double check valves to a spring brake modulating relay valve associated with spring brakes of the vehicle, and air from a second one of the glad hands is supplied through a second one of the double check valves to a first release valve associated with service brakes of a front axle of the vehicle and through a third one of the double check valves to a second release valve associated with service brakes of a rear axle of the vehicle. 
     In another embodiment, a method for controlling a motion of a truck is disclosed. The method comprises: establishing a connection from a towing truck to a plurality of glad hands of the truck, providing air to a first double check valve via a first one of the glad hands, releasing spring brakes of the truck with the air supplied to the first double check valve, detecting application of service brakes on a towing truck, providing air to a second double check valve and a third double check valve via a second one of the glad hands and engaging service brakes of the truck with the air supplied to the second and third double check valves. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The several features, objects, and advantages of Applicants&#39; invention will be understood by reading this description in conjunction with the drawings, in which: 
         FIG. 1A  illustrates a general air brake system for a truck without a spring brake modulating relay valve; 
         FIG. 1B  illustrates an air brake system utilizing a spring brake modulating relay valve; 
         FIG. 2  illustrates a truck with front glad hands; 
         FIG. 3  illustrates an air brake system according to an exemplary embodiments of the invention; and 
         FIG. 4  illustrates a method according to an exemplary embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     The following description of the implementations consistent with the present invention refers to the accompanying drawings. The same reference numbers in different drawings identify the same or similar elements. The following detailed description does not limit the invention. Instead, the scope of the invention is defined by the appended claims. 
     As illustrated in  FIG. 2 , a truck  200  can be equipped with glad hands  210  and  220 . Brakes on a towed truck may be controlled by the towing truck via controls associated with glad hands  210  and  220 . 
     In exemplary embodiments, as illustrated in  FIG. 3 , emergency brake glad hand  220  connects to wet tank  105  via T  320  and check valve CV  325  to provide air to primary tank  110  and secondary tank  115 . Emergency glad hand  220  also connects (via T  320 ) to spring brake modulating relay valve SBMRV  185  via a double check valve, DCV  1   370 . 
     Service glad hand  210  supplies air to quick release valve QRV  165  (via T  315 ) through double check valve DCV 2   380  (and T  350 ). Service glad hand  210  also supplies air to relay valve RV  145  (via T  315 ) through double check valve DCV 3   390  via T  315 . 
     Primary tank  110  supplies air to relay valve RV  145  and to both TVR  140  and PCV  135  via T  330 . Secondary tank  115  supplies air to SBMRV  185  via check valve CV  195 . Secondary tank  115  also supplies air to both TVF  160  and PCV  135  via T  340 . 
     Air from TVF  160  is supplied to DCV 2   380 . DCV 2  permits air from either TVF  160  or T  315  to flow to T  350  depending on the pressure of air from each of these sources (i.e. T  315  or TVF  160 )—air from the higher pressure source is permitted. Air from DCV 2   380  is supplied to both QRV  165  (for engaging the front brakes  170 ) and to SBMRV  185 . 
     Air from TVR  140  is supplied to DCV 3   390 . DCV 3  permits air from either TVR  140  or T  315  to flow to RV  145  depending on the pressure of air from each of these sources—air from the higher pressure source is permitted. 
     Air from PCV  135  is supplied to DCV 1   370 . DCV 1   370  permits air from either PCV  135  or emergency glad hand  220  (via T  320 ) to flow to SBMRV  185  based on the source having the higher pressure. 
     The arrangement as illustrated in  FIG. 3  provides the air needed to operate both front brakes  170  and rear brakes  150  of a towed truck. Such an arrangement speeds up the braking of the towed vehicle without affecting the breaking of the towing vehicle. 
     Glad hands S  210  and E  220  may be mounted to the front portion of a truck which can be towed. The connection between T  320  and wet tank  105  is via a one way check valve CV  325  permitting air flow into the wet tank  105  (and does not permit reverse flow from wet tank  105 ). The air flow from wet tank  105  to each of primary tank  110  and secondary tank  115  is also via a one way check valve permitting air flow toward the primary and secondary tanks. 
     A method (or process  400 ) of towing or controlling the motion of a truck in accordance with exemplary embodiments may be described with reference to  FIG. 4 . A glad hand connection, using glad hands  210  and  220 , may be made between the towed truck and a towing truck at  410 . The towing truck has two buttons for “charging” up (or supplying pressurized air to release) the spring brakes. One of these buttons is designated for the towing truck and the other button is designated for the truck being towed. The button designated for the towed truck may be actuated at  420 . Pressurized air (from the compressor of the towing truck) may be supplied through emergency glad hand  220  to supply tank  105  and to DCV 1   370  at  430 . 
     Air from DCV 1   370  may be supplied to SBMRV  185  to release the spring brakes at  440 . Air from the supply tank  105  may charge the primary and secondary tanks  110  and  115 . Air may be supplied by the primary tank  110  to treadle TVR  140 , PCV  135  and RV  145 . Air may be supplied by the secondary tank  115  to SBMRV  185 , treadle TVF  160  and PCV  135 . 
     The spring brakes of the towed truck are now released to permit vehicle motion and towing by the towing truck (the button designated for towing truck is also actuated to release the spring brakes of the towing truck). As the truck is being towed, if the operator of the towing truck applies the (service) brakes (on the towing truck), pressurized air may be supplied to the service glad hand  210 . 
     Referring to  FIG. 4 , the operator may apply (service) brakes on the towing truck at  450  (via the treadle of the towing truck). Air may be supplied through service glad hand  210  to DCV 2   380  and DCV 3   390  (via T  315 ) at  460 . Air from DCV 2   380  may be supplied to engage or apply front service brakes F  170  and air from DCV 3   390  may be supplied to engage or apply rear service brakes R  150  at  470 . 
     The operator may release the service brakes on the towing truck at  480 . Pressure to the front brakes  170  and rear brakes  150  may be released at  490  to permit vehicle movement. 
     When the truck is being towed, no operator interaction may be present in the towed truck. As such, there is no operator interaction with the treadle TVR  140  and TVF  160  or with PCV  135 . Therefore, no pressure is provided from PCV  135  to DCV 1   370 , TVF  160  to DCV 2   380  or from TVR  140  to DCV 3   390 . However, once towing is complete and the glad hands are disconnected, no air flows to DCV 1 , DCV 2  and DCV 3  from the glad hands and the air system of the truck returns to a normal operation mode by receiving air from PCV  135 , TVR  140  and TVF  160  to engage or release each of the spring brakes, the rear service brakes R  150  and front service brakes  170 . 
     The term air or pressure as used herein may refer to pressurized or compressed air that is needed to apply service brakes or to release the spring brakes. Furthermore, in some embodiments, application and release of spring brakes on the towing truck may be detected prior to providing pressurized air to the towed truck. 
     It will be appreciated that the procedures (arrangement) described above may be carried out repetitively as necessary to control a vehicle. To facilitate understanding, many aspects of the invention are described in terms of sequences of actions. It will be recognized that the various actions could be performed by a combination of specialized circuits and mechanical elements. 
     Thus, the invention may be embodied in many different forms, not all of which are described above, and all such forms are contemplated to be within the scope of the invention. It is emphasized that the terms “comprises” and “comprising”, when used in this application, specify the presence of stated features, steps, or components and do not preclude the presence or addition of one or more other features, steps, components, or groups thereof. 
     The particular embodiments described above are merely illustrative and should not be considered restrictive in any way. The scope of the invention is determined by the following claims, and all variations and equivalents that fall within the range of the claims are intended to be embraced therein.