Abstract:
An overfill probe is utilized in each compartment of a multi-compartment transport tanker and has a depending sensing tube for detecting liquid overfill conditions. An overfill detector is within the bottom end of the probe tube and is thus protected from damage. Internal damage to the probe and malfunction of the system also precluded by connecting the exposed cap of the probe to the detector by a longitudinally extensible, stretchable cable extending through the tube to the detector, or a circuit board may be retained within the depending tube. Additionally, a thermistor socket and an optic socket are provided which are part of the overfill protection system, each having contact connections that may be readily replaced when worn without removing or replacing the wiring within the socket assembly.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of a prior filed, provisional application Ser. No. 61/177,810, filed May 13, 2009, entitled OVERFILL DETECTION SYSTEM FOR TANK TRUCKS. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to improvements in the delivery systems for tank trucks that transport and deliver petroleum fuels to storage tanks which are typically underground, and may be located at filling stations or at other sites where vehicles are refueled and serviced. 
     BACKGROUND OF THE INVENTION 
     The loading and off-loading of petroleum products into the compartments of transport trucks, and from such compartments into storage tanks are common procedures well-known in the art. The separate compartments of a typical tank truck will often contain different fuels such as various grades of gasoline, diesel, fuel oils and kerosene. When loading these compartments with fuel, visual inspection is typically not possible and thus overfill sensors are installed in the respective tanks to provide signal feedback to shut down the delivery pumps when loading is complete. An example of such a delivery system is, for example, set forth in United States Patent Application Publication 2005/0139286 where a modular multi-port manifold and fuel delivery system is disclosed having a plurality of ports in fluid communication with corresponding compartments of the fuel delivery vehicle. 
     There are, however, limitations in such fuel delivery systems as they may be readily compromised and thus operate in less than an optimal manner. Since the tanks of transport trucks usually cannot be visually inspected while filling, overfill sensors are utilized to provide signal feedback to shut down the loading pumps when the appropriate level is reached. These typically comprise a probe that extends downwardly from the top of the tank compartment and, if properly operational, will sense the presence of the fuel when it rises to a sensor on the bottom end of the probe. However if the probe is non-functional for any reason, such as mishandling by operating personnel or component failure, or if the length of the probe tube that carries a sensor that detects the presence of the fuel is not properly matched to the compartment in which it is installed, the compartment may be either underloaded or overfilled. This can occur, for example, when a defective probe is replaced after a repair and a probe of improper length is installed. Also, improper signal wiring during installation of a system also adds to poor reliability, resulting in frustrated end users. 
     An overfill detection probe in common use comprises an optical detector and an electronic circuit board which communicates with the detector and also interfaces with other electronics of the system. However, the detector projects from the bottom end of the probe and is thus exposed to damage and malfunction if not carefully handled and installed. Also, the circuit board and associated wiring connections in the probe may be damaged due to mishandling and render the probe inoperable. Any such failure of an electrical element of the system may require the end user to recertify system integrity. 
     SUMMARY OF THE INVENTION 
     An overfill probe of the present invention is utilized in multi-compartment transport tankers and similar fuel loading applications. A probe having a depending sensing tube is provide for each compartment for detecting liquid overfill conditions. The overfill detector is within the probe tube and is thus protected from damage. Furthermore, in one aspect of the present invention the overfill probe has an exposed cap which, when removed, remains connected to the sensor by a longitudinally extensible, stretchable cable extending through the probe housing and the depending tube to the emitter and detector of the level sensor, thereby precluding internal damage to the probe and malfunction of the system if operating personnel improperly remove and withdraw the cap. A circuit board may be mounted in the cap and connected to the wiring of the electrical system. 
     In another aspect of the present invention, a circuit board may be retained within the depending tube. 
     In a further aspect of the present invention, a thermistor socket and an optic socket are provided which are part of the overfill protection system, each of which receives a plug secured to a cable extending from a control monitor at a loading island. Each socket has front contact pins and J-slots on the outside of the body of the socket that may be readily replaced when worn without removing or replacing the wiring within the socket assembly. 
     Other advantages of this invention will become apparent from the following description taken in connection with the accompanying drawings, wherein is set forth by way of illustration and example, embodiments of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of a tank truck showing four overfill probes of the present invention removed from their respective compartments for illustrative purposes, bottom retain sensors being also removed from their respective compartments for illustration, and an on-board monitor and associated sockets connected thereto. 
         FIG. 2  is an enlarged illustration of the on-board monitor panel. 
         FIG. 3  is an enlarged view of the sockets that connect to the on-board monitor. 
         FIG. 4  is a plan view of an overfill probe of the present invention. 
         FIG. 5  is an elevational view of the probe of  FIG. 4 . 
         FIG. 6  is an elevational view of the probe of  FIG. 4  as seen from the right side of the illustration of  FIG. 5 . 
         FIG. 7  is an enlarged, vertical cross-sectional view of the probe of  FIG. 5  showing the internal components thereof. 
         FIG. 8  is a detail view of a retainer clip that secures the depending tube within the probe housing at a desired vertical position. 
         FIG. 9  is a perspective view of the probe of  FIGS. 4 ,  5  and  6 . 
         FIG. 10  is a fragmentary, exploded view of the depending probe tube showing the internal components of a level sensor. 
         FIG. 11  is an exploded view of the probe assembly showing the circuit board (in the probe cap) and illustrating the expandability of the connecting cable that permits the probe cap to be removed from the housing without damage to components in the probe tube. 
         FIG. 12  is a fragmentary, exploded view showing the sensor components housed within the lower end portion of the probe tube, and shows an alternative embodiment in which the circuit board is in the probe tube. 
         FIG. 13  is an enlarged cross-sectional view of the bottom end of the probe tube. 
         FIG. 14  is a cross-sectional view taken along line  14 - 14  in  FIG. 13 , looking in the direction of the arrows. 
         FIG. 15  is a detail, bottom view similar to  FIG. 14  illustrating the emitter and the detector within the glass head, and showing the signal path when the fuel level is below the bottom end of the probe (dry condition). 
         FIG. 16  is a view identical to  FIG. 15  but showing the light path in the wet condition where the level of the fuel is at the glass head. 
         FIG. 17  is a perspective view of a thermistor socket. 
         FIG. 18  is an exploded view of the thermistor socket of  FIG. 17 . 
         FIG. 19  is vertical cross-sectional view of the socket of  FIG. 17  showing internal components including two of the contact pins. 
     
    
    
     DETAILED DESCRIPTION 
     Referring initially to  FIG. 1 , a typical tank truck  20  for delivery of petroleum fuels has a compartmental tank  22  carried by the frame  24  of a trailer and, in the illustrated embodiment, is divided into multiple, separate compartments and thus may transport different types of fuel such as, for example, diesel fuel and gasoline of three different grades.  FIG. 1  shows a typical four-compartment tank truck for reference. Each of the compartments is provided with an overfill probe  26 , each of which, for illustrative purposes, is shown above the compartment with which it is associated. An electrical cable  28  connects the probes  26  to an on-board monitor  30  ( FIGS. 1 and 2 ) which is located on the side of the tank  22  seen in  FIG. 1 . Cable  28  terminates at a connector  28 ′ at the monitor  30  ( FIG. 2 ). 
     The overfill probe  26  of each compartment provides a signal input to the monitor when the compartment is “empty,” i.e., the fuel level is below the probe. An output signal, referred to as a “permit signal,” is generated at a loading station (not shown) and the compartment may then be loaded to a maximum level sensed by the probe. As is conventional, the monitor terminates the permit signal when the level of fuel in the compartment reaches the overfill probe  26  and the signal from the overfill probe ceases. A system may or may not employ an on-board monitor, and operate only with probes and sockets and a responsive fuel delivery control. 
     Also, as is conventional, each of the compartments of tank  22  may have a bottom retain sensor  32  which is part of the monitoring system and which initiates a signal in the control system when the fuel level in the associated tank reaches a predetermined minimum level. 
       FIGS. 1 and 3  illustrate a thermistor socket  34  and an optic socket  36  associated with the overfill protection system. Sockets  34  and  36  are subject to wear due to the many fuel loadings inherent in the operation of a tank truck. Socket  34  is shown in detail in  FIGS. 17-19 . 
       FIGS. 4-16  show the overfill sensor probe  26  in detail. Referring to  FIGS. 4-9 , a cylindrical probe housing  40  is provided with a depending, externally threaded ring  42  which, when the probe  26  is installed, is received by the mating threads of an opening (not shown) in the top of a corresponding tank compartment  22  of the tank truck  20 . A cylindrical probe tube  44 , preferably aluminum, is coaxial with the housing  40  and extends downwardly therefrom as shown, for example, in  FIGS. 5-7 . A cap  46  is secured to the top of housing  40  and is securely held thereon by four outwardly extending dogs  48 , each of which is received in a corresponding J-shaped slot  50  in the cap  46 . As may be appreciated from viewing  FIGS. 7 and 11 , the top, circular rim  56  of the housing  40  is received in a circular recess in cap  46  having a gasket  58  therein which assures a tight fit as the gasket is compressed when the dogs  48  are seated in the slots  50  as seen in  FIGS. 5 and 6 . As is also apparent in  FIG. 7 , the upper, circular rim  56  thus compresses the gasket  58  when the cap  46  is secured thereby providing a seal between the probe cap  46  and the housing  40 . A tamper screw  54  assures that any effort to remove the cap  46  by unauthorized personnel will be evident. 
     As seen in  FIG. 7  and the exploded view of  FIG. 11 , a circuit board  60  is mounted within the cap  46  and provides the necessary electrical components to provide communication between the probe  26  and the on-board monitor  30  to indicate, for example, the status of the associated tank compartment as either filled or underloaded. In this regard, it should be appreciated that the communication system from the tank compartments to the cab  21  is bus-based and thus each of the compartments of the tank  22  may individually communicate with the system either by wire or wireless. A Deutsch connector cable  62  extends from the circuit board  60  of each overfill probe  26  through cap  46  thereof for connection to the common cable  28 . When probe circuit board  60  is configured as wired or wireless communication, it may communicate to other probes, on-board monitor, sockets or other tractor cab electronics. These communications may contain status, prior recorded events, history or other value information. In the event of a malfunction, an LED  63  ( FIG. 4 ) beneath the cap  46  is energized and is immediately visible when the cap is removed. 
     Referring to  FIGS. 7 and 11 , a curly cord provides an insulated electrical cable  64  having its upper end attached to the probe cap  46 ; specifically, to a connector  66  on the inside of the cap  46 . The lower, opposite end of the cable  64  is anchored to a disk or plate  68  adjacent the lower end  70  of the probe tube  44 . Accordingly, any unauthorized tampering with the overfill probe or attempt to remove the cap  60  will not damage the internal components in either the tube  44  or the cap  46 , as the cable  64  will simply yield and stretch axially. The probe of the present invention is, therefore, protected against damage to its internal components by the action of unauthorized personnel during the loading process. 
     The overfill probe  26  has two opposed, circular openings  72  adjacent the lower, open end  70  of the probe tube  44  and thus loaded fuel enters the bottom end of the probe  26  and effects a termination of the loading of fuel into the associated compartment of the tank  22 . More particularly, as shown in  FIGS. 10 ,  13  and  14 , the exposed lower end  70  contains a level sensor comprising a circuit board  68  and gasket  69 , and a snap ring  74  therebelow between which a glass head  76  is mounted. As may be appreciated from a comparison of  FIGS. 10 ,  13  and  14 , the glass head  76  has a generally circular upper portion complemental to the circular interior configuration of the probe tube  44 , and a semi-circular, downwardly projecting portion  77 . An elongated emitter element  78  and an elongated detector element  80  are disposed in an arcuate slot  82  ( FIGS. 14-16 ) in the downwardly projecting portion  77  of the glass head  76 . The elements  78  and  80  depend from and are connected to the circuit board  68  which is secured to the lower end of the curly cable  64 . Both the emitter and detector elements  78  and  80  extend downwardly into the arcuate slot  82  as may be appreciated from  FIGS. 15 and 16 . If the bottom end of the probe is above the level of fuel in the tank, the signal from the emitter  80  will be deflected at the flat vertical surface  83  of the glass head  76  and will be received by the detector element  80  as illustrated in  FIG. 15 , thereby evidencing a dry condition in which the level of the fuel in the tank is below the sensor. However, if the level of the fuel has reached the emitter and detector elements  78  and  80 , a wet condition is indicated as shown in  FIG. 16  as the signal from the emitter is no longer reflected to the detector  80  as illustrated by the arrows. Accordingly, the circuit board  68  responds to the wet condition with a signal via the curly cable  64  to the circuit board  60  in the cap  46  for transmission via cable  62  to the cable  28  whereby the system responds by terminating the permit signal and fueling of the tank ceases. 
       FIG. 12  illustrates an alternative embodiment of the overfill probe in which the circuit board  60  is not mounted within the cap  46  as illustrated in  FIG. 7 . More particularly, the probe tube  44   a  receives a tubular circuit board  60   a  which is retained inside the tube  44   a  and connected by wiring (not shown) to the cap  46  at a suitable connector within the cap, such as the connector  66  shown in the embodiment of  FIG. 7 . Accordingly, the curly cord comprising cable  64  in the embodiment of  FIG. 7  is not utilized in the modified form of the overfill probe tube assembly shown in  FIG. 12 . Otherwise, the functionality of the cylindrical probe tube  44   a  is the same as in the embodiment shown in  FIG. 10 . 
     The overfill probe  26  of the present invention also facilitates the establishment of the maximum fuel level in the tank as this is controlled by the extent to which the probe tube  44  extends downwardly into the tank. In  FIG. 7 , the tube  44  is fully inserted into housing  40  through a central opening in the bottom  83  and thus is at maximum height. However, it is held in the position illustrated by a spring clip  84  seen in  FIG. 7  and shown in detail in  FIG. 8 , which is secured to bottom  83  by a fastener  85 . By squeezing a pair of legs  86  of the clip  84 , the spring tension is momentarily released sufficiently to permit the operator to shift the tube axially from, in the illustrated embodiment, a position of maximum height to a lower level where the emitter and detector elements  78  and  80  are at a lower elevation within the tank and, therefore, define a lower level at which the permit signal will be terminated. 
     Thermistor and Optic Sockets 
     The thermistor socket  34  and the optic socket  36  are of essentially the same construction, the difference between the two sockets being the number of contact screws presented. As shown in  FIG. 3 , the thermistor socket  34  presents a total of ten screw heads, whereas the optic socket  36  presents six screw heads. The thermistor socket  34  is shown in detail in  FIGS. 17-19 , it being understood that the internal construction of the optic socket  36  is the same except for the lesser number of contact screws. This design allows for combinations of screw heads other than the primary six or ten. 
     Referring to  FIGS. 17-19 , the thermistor socket  34  has a housing  90  of essentially square configuration and presents a top surface  92  having a greater front to rear length than the bottom surface  94  of the housing, and thus the socket  34  is tilted downwardly at an angle of approximately thirty degrees from vertical. This minimizes the entry of moisture into the socket as it is typically mounted on the tank  22  and thus exposed to the elements. The socket  34  presents a circular, recessed face  96  where the heads of the contact screws  98  are exposed. Each screw  98  is relatively short and is received in a corresponding standoff  100  secured to a mounting plate  102  ( FIG. 19 ) to which a printed circuit board  104  is mounted and held by internal screws  106 . 
       FIG. 18  is an exploded view showing the contact screws  98  and corresponding standoffs  100 . The contact screws  98  are subject to heavy abuse requiring that repairs be made in the field. This is facilitated in the present invention as the contact screws  98  are separate from the standoffs  100  into which they are threaded. Each of the contact screws has a pair of spaced recesses  108  in the head thereof for receiving a screwdriver tip (not shown) presenting two male prongs that are inserted into the openings  108  so that a worn or otherwise defective screw  98  may be quickly replaced. Accordingly, in the present invention repairs are made in the field by simply replacing a worn screw  98  without the need to also replace the associated standoff  100  or other components. 
     The socket  34  is also provided with four J-slot locks  110  spaced around the socket for receiving a plug (not shown) on the end of a cable that extends from a loading island in the conventional manner. 
     It should be appreciated that in the sockets of the present invention, electronic circuit board  104  allows communication to occur between sockets, on-board monitors and other probes. During operation, status LED  112  ( FIGS. 17 and 19 ) shows the user different varieties of conditions (status) including, but not limited to, probe status, probe diagnostics, and pass/fail conditions when connected to the loading rack. The circuit board  104  also contains internal ground verification circuitry which not only precludes the need for a separate ground bolt, but can also report the quality of the ground verification connection to the vehicle and the rest of the system. 
     It is to be understood that while certain forms of this invention have been illustrated and described, the invention is not limited thereto except insofar as such limitations are included in the following claims.