Abstract:
A preventative stop valve system for a wheeled trailer carrying hydraulic equipment is disclosed comprising a stop valve fitted for insertion in-line into the hydraulic line servicing the trailer equipment; the stop valve comprising a reciprocating piston moveable between open and closed positions. The stop valve is connected to the pressurized air line extending to the air brakes of the trailer. Actuation of the stop valve is controlled pneumatically by the setting and release of the air brakes of the trailer by the operator, utilizing conventional controls for the air brakes. A manual override mechanism is further provided for opening the stop valve manually in the event that the hydraulic equipment carried by the trailer must be utilized when pressurized air line to the trailers is disconnected.

Description:
TECHNICAL FIELD 
     The invention relates in general to fluid stop valves and, more specifically, stop valves for hydraulic lift systems. 
     BACKGROUND ART 
     Hydraulic lift systems are common in many industrial applications. By way of example, many truck units employ one or more hydraulic cylinders for the purpose of elevating and lowering a truck bed. In such applications, a trailer is generally coupled to a tractor and includes a bed, or other hydraulic superstructure, that can be raised or lowered. It is common to carry loose material within the bed such as gravel or earth. The bed is pivotally coupled to the trailer frame at a rearward location. One hydraulic cylinder or, as is more typical, a system of telescopic hydraulic cylinders is mounted to a forward end of the trailer, below a forward end of the trailer bed. Hydraulic fluid is pumped from the tractor into the hydraulic cylinders to cause the cylinders to extend and raise the forward end of the trailer bed. Once raised, the trailer is readily emptied of its contents. Thereafter, the operator of the unit causes hydraulic pressure to be gradually withdrawn from the lift cylinders and the cylinders slowly retract, lowering the bed of the trailer. 
     The user activates the hydraulic lift system from the cab of the tractor or from an exterior location, depending upon the design of the lift. Hydraulic fluid is highly pressurized and directed to the lift cylinders by appropriate flexible conduits. The conduits or hoses, typically formed of rubber or composite materials, are routed from the pump unit, along the trailer chassis, and to the lift cylinder(s). The route followed by the flexible hydraulic hoses is typically non-linear and includes several bends or elbows. These bends or elbows, however, represent constrictions where breakage of the high pressure line can, and frequently does, occur. Moreover, breakage generally occurs when the line is in the high pressure mode; that is, when the bed is raised and the lift cylinders fully extended. 
     Breakage in the hydraulic line at or near the lift cylinders causes immediate expulsion of the pressurized hydraulic oil to the ground or upon the equipment. In addition to creating an environmental event requiring extensive clean up, the expulsion of the pressurized hydraulic fluid causes an immediate loss of pressure to the lift system. If the breakage occurs while the cylinders are extended and the bed elevated, the lift cylinders will retract immediately, rather than gradually, and the bed of the trailer will precipitously fall. The falling bed can destabilize and tip the tractor and trailer over, causing considerable damage to the trailer and/or tractor. More importantly, a freefalling bed can pose a risk of bodily injury to surrounding individuals or the operator of the unit. The operator, stationed at the controls for the hydraulic system, will generally observe a breakage in the hydraulic line to the lift cylinders. However, even if a breakage is detected, the operator is powerless to prevent the resultant sudden failure of the lift system and consequent rapid collapse of the elevated bed. 
     A preventative stop valve system, accordingly, is needed in the industry to prevent a precipitous loss of hydraulic fluid from a lift system in the event rupture of hydraulic lines occur. Such a stop valve would be useful if positioned in the hydraulic system so as to stop rapid expulsion of hydraulic fluid from the lift cylinders in the event the hydraulic lines rupture. The valve, however, to be effective, must operate quickly to stem the outflow of hydraulic oil. The valve should further be of reliable construction, be convenient to activate, and operate predictably when needed to effectively abate the loss of fluid. In addition, because of the large number of lift units already in use, a suitable preventative stop valve system should be capable of retrofit implementation into existing lift units with a minimum level of inconvenience and expense. Achievement of a suitable valve system would prevent a catastrophic collapse of the lift system and eliminate consequential damage to property and injury to personnel. 
     SUMMARY OF THE INVENTION 
     It is, therefore, an object of the invention to provide a preventative stop valve system for hydraulic lift units that prevents a precipitous loss of hydraulic fluid in the event rupture of hydraulic lines occurs. 
     A further object of the invention is to provide a preventative stop valve system that operates quickly to stem the outflow of hydraulic oil in the event that a rupture of hydraulic lines occurs. 
     Another object of the invention is to provide a preventative stop valve system that is capable of retrofit implementation into existing lift units with a minimum level of inconvenience and expense. 
     Still further, it is an object of the invention is to provide a preventative stop valve system that is of reliable construction, convenient to activate, and operates predictably when needed to effectively abate the loss of fluid. 
     Yet another object of the invention is to provide a preventative stop valve system that self-tests responsive to normal operation of a tractor-trailer unit. 
     An additional object of the invention is to provide a stop valve system for a trailer lift unit having an override mechanism for allowing use of the lift unit when the trailer is decoupled from a tractor. 
     An ancillary object of the invention is to provide a preventative stop valve system for a trailer lift unit compatible with existing user-operated controls for the trailer. 
     A further object of the invention is to provide a method of retrofitting existing trailers with a preventative stop valve system that operates quickly to stem the outflow of hydraulic oil in the event that a rupture of hydraulic lines occurs. 
     These and other objects, which will be apparent to one skilled in the art, are achieved by a preferred embodiment described below. The preventative stop valve system comprises a stop valve interposed in the hydraulic line of a trailer lift unit. The valve includes an elongate housing having an internal chamber and intake and outlet fluid portals extending through sidewalls of the housing and establishing with the internal chamber a fluid flow path. A piston member is reciprocally moveable within the chamber between an open and closed position. In the closed position, the piston obstructs the fluid flow path while, in the open position, the piston permits fluid to flow through the housing chamber. A spring member biases the piston in the closed position. The housing further includes an air intake portal in one end connected to the air brakes of the trailer. High pressure at the intake portal, a consequence of setting the trailer air brakes, is necessary to override the spring member and open the valve. Release of the air pressure to the brakes, typically from the cab of the tractor, drops the air pressure at the valve air intake portal and causes the valve to close. The switch used to release the brakes can thus be activated by the user to close the valve and stop the release of hydraulic oil in the event that a rupture in the hydraulic lines is detected. An override arm is further provided to allow activation of the stop valve with the trailer decoupled from its associate tractor. The override arm accordingly allows the valve to be opened and the lift unit raised when the brake system of the trailer is decoupled from the tractor. 
     For the benefit of existing tractor-trailer units, a method of retrofitting existing units with a preventative stop valve system is provided. The method comprises the steps of: a.) connecting a stop valve housing in the hydraulic line, the housing including an air intake portal at one end; an elongate piston seated within a central chamber of the housing and reciprocally moveable within the chamber responsive to a drop in air pressure at the air intake portal between an open position and a closed position, the piston obstructing the flow of fluid through the housing in the closed position and allowing the flow of fluid through the housing in the open position; b.) connecting the air intake portal of the valve housing to the trailer brake air line; and c.) selectively releasing the brakes of the tractor-trailer to cause a drop in air pressure at the air intake portal of the stop valve and consequently move the piston into the closed position. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevation view of a tractor-trailer unit shown with the bed raised in an elevated position and the subject preventative stop valve system installed. 
     FIG. 2 is a left front perspective view of the subject preventative stop valve. 
     FIG. 2B is an exploded perspective view of the preventative stop valve. 
     FIG. 3 is longitudinal section view through the preventative stop valve showing the piston in the open position. 
     FIG. 4 is a longitudinal section view through the preventative stop valve taken along the line  4 — 4  of FIG.  2 A and showing the piston in the closed position. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring initially to FIG. 1, the subject preventative stop valve system is intended for incorporation into a typical tractor-trailer rig as depicted at  10 . While of specific utility for such an application, the stop valve system has applications for other types of units that employ hydraulically operated cylinders. In the context of tractor-trailer units, the subject stop valve system may be incorporated by the manufacturer as original equipment or the stop valve system may be retrofitted into existing tractor-trailers as will be explained below. 
     The tractor-trailer units of the type depicted in FIG. 1 generally comprise a tractor  12  that hitches to and transports a trailer  14 . The trailer may be equipped with various hydraulic apparatus for performing specific functions. In FIG. 1, a bed  16  is pivotally mounted at a rearward end to the trailer  14  by pivot connection  17 . An assembly of telescoping hydraulic cylinders  18  are mounted to a forward end of trailer  14 . The cylinder assembly  18  comprises three stages; namely, an uppermost, smaller diametered, cylinder  20 , a middle, intermediate diametered, cylinder  22 , and a lower or bottom, larger diametered cylinder  24 . While three stages are shown in the embodiment of FIG. 1, the invention need not be so restricted. More or fewer cylinders may be used in sundry applications. The cylinders  20 ,  22 ,  24  telescope together and expand as shown in FIG. 1 in commonly used tractor-trailer units. The upper end of cylinder  20  is coupled to the bed  16  and the lower cylinder  24  is connected to the trailer  14  by conventional means. 
     Pressurized hydraulic fluid is routed to the lower cylinder  24  by hydraulic line  26 . Conduit  26  is typically formed of rubber or composite material and extends from an oil pump (not shown) carried by the tractor  12 . The conduit is routed to cylinder  24  and the path invariably includes several bends or elbows as will be observed in FIG.  1 . The oil carried by the conduit  26  is highly pressurized, typically to four thousand pounds per square inch. It is common in the industry to couple the conduit  26  to the cylinder  24  by means of a swivel fitting  31  that is attached to an input conduit  30 . The input conduit communicates with the cylinder  26 . 
     The user activates the hydraulic system from a control typically located in the cab of the tractor. Once the control is actuated by the user, the hydraulic pump forces hydraulic fluid into the conduit  26 . The pressurized fluid exits the hose  26 , travels through the swivel fitting  31 , and enters into the cylinder  24  via input conduit  30  where it applies the mechanical force required to extend the cylinder assembly  18 . As the cylinders telescope outward, the bed  16  is tilted backward and the contents may be discharged from a rearward end. Once the bed  16  is emptied, the user cuts the hydraulic pump off and the fluid slowly exits the cylinder system  18 , causing the cylinders  20 ,  22 , and  24  to telescope in and the bed  16  to fall gradually back upon the trailer  14 . 
     FIG. 1 illustrates that trailers in common use in the industry include wheels  27  and a pneumatic braking system (not shown). The pressurized air necessary to set the pneumatic brakes for wheels  27  is supplied by an air conduit or hose  28 . The brake air line  28  extends from a compressor that is typically carried by tractor  12 . The user activates the air brakes by a switch or control located in the cab of the tractor  12 , and causes the compressor to force pressurized air at approximately one hundred twenty-five p.s.i. to the air brakes of trailer  14  via conduit  28 . The conduit  28  is generally routed along the length of the chassis of the trailer  14  to the brake units. The air brakes to the trailer  14  are normally set and released many times during the course of a day&#39;s work by the operator of the tractor-trailer  10 . Each time the brakes are set and released the air pressure in the air line  28  goes from a high to low state. 
     As mentioned previously, the conduit or hose  26  supplying pressurized hydraulic fluid to the cylinders system  18  typically includes several bends or elbows. At high pressure, i.e. when the cylinder system  18  is fully extended and the bed  16  is fully raised, the hose  26  is prone to breakage. The breaks commonly occur at the bends or elbows in the line. When the line breaks, the hydraulic fluid in the cylinder system  18  drains very quickly, causing a precipitous retraction of the cylinders  20 ,  22 , and  22  and a rapid fall of the bed  16 . The oil is discharged upon the ground and/or the tractor-trailer and can cause environmental damage. In addition, the time and effort to gather the discharged oil is considerable and creates a significant expense. More significantly, the rapid descent of the bed  16  creates a dangerous situation for the tractor-trailer unit and the operator. The collapse of bed  16  can act to tip the tractor-trailer over or cause significant damage. Such an uncontrolled descent can also cause bodily injury to the operator. 
     Shown assembled to the tractor-trailer  10  in FIG. 1 is a preventative stop valve  32 . The valve  32  is interposed in the hydraulic line  26  where the line enters the input conduit  30  by way of swivel fitting  31 . The unit  32  may be manufactured and installed as original equipment in the tractor-trailer  10  or be installed into existing tractor-trailers as a retrofit. The purpose of the stop valve  32  is to prevent oil from draining from the cylinder assembly  18  in the event that the hydraulic  26  ruptures. For this reason, it is desirable to locate the valve unit  32  adjacent to the cylinder  24 . However, the unit  32 , while preferably located at the input conduit  30  to cylinder  24 , may be located at other locations along the hydraulic line  26  if so desired. 
     The specific configuration of the stop valve  32  is shown in FIGS. 2A,  2 B,  3 , and  4 . With reference to such views, the valve  32  is seen to comprise a rectangular, elongate housing  34  preferably formed of high strength metal such as steel. The housing  34  includes a central axially disposed, generally cylindrical chamber  36  defined by sidewalls  37 . Extending through one end of the housing  24  is a cylindrical bore  38  and extending through an opposite end of the housing  24  is a threaded assembly bore  40 . Bores  38 ,  40  communicate with the central chamber  36 . The chamber  36  extends between opposite ends  42 ,  44 . 
     An elongate, generally cylindrical piston  46  is provided mounted within the chamber  36 . Piston  46  is machined preferably from a high strength metal such as steel and includes a forward nose portion  48  of relatively smaller diametric dimension; a mid-portion  50  diametrically dimensioned nominally smaller than the chamber  36 ; a rearward neck portion  52  of relatively smaller diametric dimension; and an end portion  54  having a diameter substantially equivalent to the mid-portion  50 . An annular O-ring channel  56  is formed within and circumscribes the piston nose portion  48 . Two additional spaced-apart O-ring channels  58 ,  60  are formed within and circumscribe the end portion  54 . The channels  56 ,  58 ,  60  are dimensioned to closely receive and seat O-rings  64 ,  66 ,  68 , respectively. The O-rings  64 ,  66 ,  68  are commercially available and are composed of elastomeric rubber or composite plastic material. More or fewer O-rings may be used is desired. 
     A helical compression spring  70  mounts to the nose portion  48  of piston  46 . The spring  70  is commercially available and is preferably formed of high strength steel or other material having acceptable spring properties. The spring  70  is received over the nose portion and abuts against the piston mid-portion  50 . The stop valve assembly further includes an end cap  72  of generally cylindrical form, preferably composed of a hard material such as steel. The end cap, or plug  72  is externally threaded as indicated at  74 . The cap  72  includes an axial hexagonal socket  76  extending therein from a rearward end and a counter bore  78  extending from the socket  76  through the cap  72 . The cap  72  has an outer diameter dimensioned to enable cap  72  to screw into the bore  40  of housing  34 . 
     As seen in FIG. 1, the housing  34  is intended to be positioned in-line with the hydraulic line  26 , preferably proximate to the cylinder  24 . A feeder air line  80  extends from the rearward end of the housing  34  downward to tap into the main brake air line  28 . A conventional tap fitting (not shown) terminates the lower end of feeder line  80  and connects line  80  into a conveniently accessible portion of line  28 . The upper end of feeder line  80  includes an annular hex nut  82  and annular end fitting  84 . Illustrated best by FIGS. 2B,  3  and  4 , the fitting  84  is sized for press fit into the forward bore  78  of cap  72 . The hex nut  82  of the line  80  resides within the socket  76  of the cap  72 . So connected, the feeder line  80  represents an air conduit from the brake line  28  to the internal chamber  36  of housing  34 . 
     An override bolt  86  is configured having a rearward end head  88 ; a threaded shank  90 ; a terminal forward end  92 ; and a lock nut  94 . The bolt  86  is preferably fabricated from a suitably high strength material such as steel. Bolt  86  is usually disattached from the housing  34  and is only used when needed, as will be explained below. When disattached, the bolt  86  is stored at a location conveniently accessible to the user of the tractor-trailer. The bore  38  through housing  34  is closed by a plug (not shown) of cylindrical configuration when the bolt  86  is disattached. The shank  90  of bolt  86  is dimensioned to closely protrude through bore  38  of housing  34  and thread into the bore  62  of piston  46  a distance of approximately three-eighths of an inch. The nut  94  is positioned thereby external of and against the housing  34  as shown in FIG. 3, accessible to the operator. The nut  94  may be adjusted by selective clockwise or counterclockwise rotation by an appropriately sized wrench. 
     Referring to FIGS. 1,  2 A,  2 B,  3 , and  4 , the housing  34  is intended for position in-line with the hydraulic conduit  26  to cylinder  24 . A terminal portion  96  of hose  26  is normally attached to the input block  30  of cylinder  24  by means of swivel fitting  31  in tractor-trailer units. The end portion  96  includes a connector comprising a swivel fitting  98 ; a threaded end fitting  100 ; and a coupling nut  102 . The end  100  threads into a socket (not shown) to swivel fitting  31  and secures end portion  96  to the input conduit  30  to cylinder  24 . 
     The subject preventative stop valve  32  may be retrofitted to existing trailers by disattaching the end  100  of end portion  96  from the swivel fitting  31  and interposing housing  34  between end portion  96  and the fitting  31 . End  100  of conduit end portion  96  screws into a threaded bore  104  in an underside of the housing  34 . The conduit end portion  96  is tightened into the bore  104  by coupling nut  102 . So connected, the conduit  26  via end portion  96  is in communication with the central chamber  36  of the housing  34 . At the opposite side of the housing  34 , a threaded outlet bore  106  is provided from the chamber  36  through the sidewall of housing  34 . A fitting  108  is provided that screws into the bore  106 . Fitting  108  includes external threads  110  and a coupling nut  112  for tightening the fitting  108  into the bore  106 . It will be appreciated that the outward end  114  of the fitting  108  is thus configured to couple with the swivel fitting  31  of the conduit  30  just as the fitting  98  of the conduit  96  prior to placing the stop valve in the hydraulic line. A fluid path is established through the housing  34  and extends from the input end  96  of conduit  26  through housing bore  104 , thence through chamber  36  of housing  34 , exiting out the housing bore  106 . The path continues on via input conduit  30  into the lower cylinder  24 . 
     FIGS. 2B,  3 , and  4  illustrate the position of the piston  46  within housing bore  36  relative to the connections of housing to hydraulic line  96  and pneumatic line  80 . The piston reciprocates between an “open” position illustrated by FIG. 3 and a closed position illustrated by FIG.  4 . In the open condition shown by FIG. 3, the air pressure at the rearward end of the chamber is high, forcing piston  46  to the right until piston neck portion aligns with bores  104 ,  106  of housing  34 . The fluid path from conduit end portion  96  through the housing is thus uninhibited and oil may pass through the housing  34  around neck portion  52  of the piston  46  and into cylinder  24  via conduit  30 . The stop valve  32  in the open position thus allows the cylinder system  18  to function in raising and lowering bed  16 . In the open condition, spring  70  is compressed against the forward end of the housing  34  as shown in FIG.  3 . 
     Should the air pressure at the rearward end of housing  34  drop, or go “low”, the compression spring  70  will release and drive piston  46  left into the “closed” position depicted in FIG.  4 . In the closed position, piston portion  50  is interposed between bores  104 ,  106 , obstructing the hydraulic fluid path through housing  34 . In the closed position, the stop valve  32  thus blocks oil from passing into or out of the cylinder  24 . The O-rings  64 ,  66 ,  68  are mounted to and move with the piston  46  along housing chamber  36  and establish a tight seal against the sidewalls  37 . 
     It will be appreciated that the stop valve air input line  80  is connected to the brake line  28  that extends along the trailer  14  and controls operation of the trailer brakes. The pressure at stop valve chamber  36  is high when the brakes of the trailer are set. That is, when the operator sets the trailer brakes from control switches in the cab, the operator is automatically pressurizing chamber  36  of housing  34  to a “high” condition which drives the piston  46  to the right, opening the valve. Releasing the brakes of the trailer  14  via line  28  causes the pressure at stop valve chamber  36  to go “low” releasing piston  46  to move to the left under the influence of spring  70 , closing the valve. In the closed condition, no oil will enter or leave the cylinder system  18 . 
     In operation, the subject stop valve provides a convenient, reliable spill preventative mechanism in the event that the hydraulic line  26  ruptures. The operator of the lift typically utilizes the hydraulic line controls from the cab of the tractor  12 . The pneumatic controls for line  28  which set and release brakes of the trailer  14  are in the same general location within the cab. An operator, in order to activate the lift assembly  18  must set the brakes to trailer  14 , whereby causing the stop valve  32  to open and allow hydraulic oil to flow into cylinder  24 . Should a rupture in line  26  occur, it will be immediately detected by the operator who, upon discovering the rupture, can release the brakes to trailer  14  by cutting the air pressure to the brakes via line  28 . Releasing the brakes causes stop valve  32  to immediately close, blocking the oil in the cylinder assembly  18  from escaping and spilling to the ground through the ruptured area of line  26 . 
     By preventing the oil from escaping system  18 , environmental damage to the ground or equipment is prevented. Moreover, keeping the oil in the system  18  maintains the bed  16  in an elevated, safe position. Bed  16  is thus prevented from a precipitous fall to the trailer  14  that might otherwise cause damage to the tractor-trailer or injury to the operator or nearby personnel. The controls for lines  26 ,  28  are standard equipment in tractor-trailer units, located typically in the cab of the tractor. The subject preventative stop valve accordingly is controlled by available controls with which the operator is familiar. As such, the stop valve is convenient and easy to install and utilize in existing tractor-trailer units as a retrofit improvement. 
     It will be further be appreciating that the subject preventative stop valve is self-testing and, accordingly, operates dependably whenever it is needed. Each time the brakes to trailer  14  are set and released, the valve  32  cycles through an open-close cycle and its state of readiness is tested. Should the valve fail to open or close, the operator will immediately detect the failure and effect repairs, rather than waiting until a rupture occurs in the hydraulic line. Daily cycling the trailer brakes, and with them the stop valve  32 , assures the operator that the valve will function as intended should it become necessary. It should further be noted that releasing the brakes of trailer  14  by line  28  during a hydraulic line rupture does not place the trailer  14  in a free-rolling condition. Auxiliary, secondary, brakes of trailer  14  are present and will remain locked after the brakes to line  28  are released. The secondary brakes thus serve to maintain the trailer stationary should the stop valve be closed during an emergency by the release of brakes serviced by line  28 . 
     From time to time it may become necessary to elevate the bed  16  when the trailer  14  is unattached to the tractor  12 . By way of example, the trailer  14  may be in the process of being serviced. It may further be necessary to elevate the bed  16  during the execution of such repairs. An auxiliary hydraulic pump, connected to line  26 , is typically utilized to elevate the bed  16 . However, the valve  32  must be opened in order to allow the cylinders  18  to extend and, without the air compressor carried by tractor  12 , the valve  32  cannot be opened by air pressure through line  28 . In order to avoid this situation, a manual means of opening the valve  32  is provided by the actuating bolt  86 . Bolt  86 , as explained previously, is stored apart from the stop valve  32  during normal operation and a plug takes its place in housing bore  38 . Should it become necessary to manually open the valve, the operator can remove the plug and insert the bolt  86  through the housing bore  38 . End  92  screws into the piston bore  62  approximately three-eighths of an inch. 
     The nut  94  may be tightened to draw the piston from its closed position shown in FIG. 4 into its open position shown in FIG.  3 . The fluid path through the housing  34  may thereby be opened manually in order to permit the bed to be elevated. When it is no longer necessary to lock the valve in its open condition, the operator may loosen the nut  94  and allow the piston to return to its closed position of FIG.  4 . The bolt may thereafter be unscrewed from the piston, removed from housing  34 , and returned to storage until needed again. 
     From the foregoing, it will be seen that the subject invention achieves its stated objectives and other objectives that will be recognized by those skilled in the art. The subject preventative stop valve is of reliable construction, convenient to activate, and operates predictably when needed to effectively abate the loss of fluid from the hydraulic line in the event of a rupture. The valve is controlled pneumatically by the airline to the air brakes of the trailer and its operative status is tested each time the trailer brakes are set and released. Moreover, the operation of the valve is by means of brake controls that are familiar to, and within convenient access of, the operator. 
     In addition, the stop valve retrofits to existing trailer units with minimal inconvenience and can be installed simply and quickly. The method for installing the valve simply involves: disconnecting the oil line into the cylinder system  18 ; interposing the stop valve in-line with the oil line, preferably at the connection to the cylinder system  18 ; connecting the pneumatic control port of the stop valve to the brake air line to the brakes of the trailer; and utilizing the original controls for the trailer brakes to open and close the stop valve. Finally, manual override means is provided for situations where the valve must be in the open state but the pneumatic control line to the stop valve is disconnected. 
     While the above describes a preferred embodiment of the invention, the invention is not intended to be so limited. Other oil spill preventative valve configuration that function differently but which utilize the air line to trailer brakes as a control mechanism are intended to be within the scope and spirit of the invention.