Patent Application
20080139030
This invention relates to electrical socket assemblies used in overfill prevention systems for liquid carrying tanker trucks. Tanker trucks, such as those used to carry petroleum products from storage depots to service stations, are typically loaded at the storage depot from a loading rack or island. Each tank, or compartment, on the truck is loaded from the bottom expelling air into a vent system located at the top of the compartment. Because the compartment are typically fabricated of metal and sealed, the fluid level in a tank cannot be visually checked to determine whether the tank is full. Therefore, it is relatively easy for the tank to be overfilled causing the liquid product to overflow into the vent system at the top of the tank, thereby potentially releasing the product into the environment with accompanying environmental damage. In order to prevent such overflows, electrical overflow prevention systems have been designed to detect an overflow condition and automatically stop the filling process.
A typical overflow prevention system uses a sensor located in each compartment. The sensor senses when the liquid level in the compartment is approaching an overfill condition and electrically communicates with the loading rack to stop the filling process. To electrically connect each sensor to the loading rack, the sensor is wired to an electrical socket assembly mounted on the truck. When the truck arrives at the loading rack, a plug connected to the end of a cable extending from an overfill monitor located at the loading rack is attached to the socket assembly on the truck to connect the sensors on the truck to an overfill prevention circuit at the loading rack.
The socket assembly mounted on each truck typically includes an electrically insulating cylindrical contact block, in turn, containing a plurality of electrically conductive pins which are wired to the sensors and ground. The contact block is surrounded by a socket ring. The socket ring and contact block are mounted to a face plate which is, in turn, secured to a housing in which the wires from the sensors terminate and are connected to the pins. The housing, face plate and socket assembly protects the sensor wires from weather conditions.
The plug assembly is cup-shaped with spring-loaded pins and fits over the socket ring. The outer surface of the socket ring has several “J-shaped” slots which receive studs extending from the inside of the plug. When the plug is pushed over the socket ring, the studs on the inside of the plug slide into the “J” shaped slots of the socket ring. The plug is then rotated so that the studs slide into the short leg of the “J-shaped” slots and the studs are held in position by the spring tension of the pins. In the rotated position, the pins in the plug line up with the pins in the contact block and establish electrical contact.
When they are new, the plug and socket assembly function well, however, the truck on which the socket is mounted may be loaded thousands of times and each time a loading is accomplished the plug and socket assembly must be connected and unconnected. Over time the “J” shaped slots on the outside of the socket ring experience wear when the plug is slid over them. Eventually, the wear becomes sufficient that the pins in the plug and the pins in the socket assembly do not maintain good electrical contact and no longer are able to function properly. Consequently, the socket ring with the worn “J” shaped slots must be replaced.
There are several problems associated with replaceable socket rings. First, the socket ring can be made of several materials, but is typically made of machined stainless steel and the cost of a new socket ring can be considerable. In addition, the socket ring is typically bolted to the face plate by bolts that pass through the face plate into threaded holes at the back of the socket ring. Thus, the socket ring can be separated from the face plate by removing the bolts. Typically, the bolts are also stainless steel. However, over time and due to the influences of water and dirt, the socket and bolts can corrode and fuse, making it extremely difficult to remove the bolts in order to replace the socket. In addition, the bolts are sometime cross-threaded during assembly, again making it difficult to remove them the next time that the socket ring must be replaced. In order to overcome this difficulty, lubricants have been applied to the bolts before inserting them into the socket ring, but the lubricant also makes the assembly prone to loosening over time.
Further, in some conventional socket assemblies the socket ring has a shoulder on its inner surface that engages another shoulder or lip on the contact block in order to prevent the contact block from being pushed through the socket ring when the plug is pressed over the socket ring. In these assemblies, in order to remove and replace a worn socket ring, the pins in the contact block must be detached from the wires so that the contact block and pins can be pulled out of, and free, the socket ring. Since there are typically several wires and pins, the possibility of an error when the wires and pins are reconnected is significant.
In other conventional socket assemblies, the socket ring does not have a shoulder which prevents the contact block from being pushed through the ring. Instead, a shoulder on the face plate prevents the contact block from being pushed through the socket ring. However, with a socket assembly of this type, the bolts holding the socket ring to the face plate must still be removed before the socket ring can be removed and replaced. Thus, the aforementioned problems with the bolts are still present in this design.
Still another problem occurs because water and other liquids enter the housing through the contact block and corrode the wires and electronic apparatus within the housing. In particular, the contact pins are typically press-fitted into the contact block. Although the pins fit very tightly into the contact block, nevertheless leakage of water and other liquids typically occurs at this point.
A still further problem occurs in electrical socket assemblies that include truck identification modules. A truck identification module contains an interface, an electronics package including a memory that generates a code which uniquely identifies a particular tanker truck and a battery to power the electronics package. The code generated by the module can be passed through the electrical socket assembly to the loading station so that the truck can be identified to the loading station for billing purposes. Typically, the entire module is sealed in order to prevent tampering with the truck identification code. However, because the module contains all of the identification apparatus, when the battery runs out, the entire module must be replaced, resulting in a significant expense.
In accordance with the principles of the invention, an improved electrical socket assembly is provided which solves the aforementioned problems. In one embodiment, the socket ring and contact block of an electrical socket assembly are affixed to the faceplate by two snap rings. An outer snap ring fits into a groove cut into the outer end of the contact block. This snap ring bears against a shoulder on the inner surface of the socket ring and prevents the contact block from being pushed through the socket ring. A roll pin fits into a hole formed at the interface of the contact block and the socket ring and prevents the contact block from rotating relative to the socket ring. The contact block then extends through socket ring and further through the face plate where it is secured by an inner snap ring that bears against the inner surface of the face plate. The roll pin also extends through a cutout in the faceplate and prevents relative rotation between the contact block and the faceplate. The socket ring and the contact block are thus affixed to the face plate without using any bolts.
In another embodiment, each contact pin is sealed by an elastomeric O-ring to the contact block at the outer end of the pin. The pins are inserted into the contact block and secured by setscrews. Thus, the entire contact block, including all of the contact pins is weather-tight, obviating any corrosion problems.
In a still further embodiment, an air brake control is comprised of a commercially-available air poppet valve and a valve extension. The commercially-available valve reduces the cost of the air brake control while the valve extension increases the travel distance of the commercially-available valve so that the valve is reliably activated when a plug is attached to the socket assembly, but the valve actuator pin does not interfere when the plug is attached.
In yet another embodiment, the socket assembly incorporates a two-part truck identification module. The electronics portion of the module is located in a secure pocket that is molded into a portion of the socket assembly housing and permanently affixed in the pocket by potting compound or epoxy thereby preventing the module from being tampered with. However, the battery which powers the module in located outside of the secure pocket and connected to the electronics by wires. The battery can therefore be easily replaced without replacing the entire unit.
The housing 10 made be fabricated from any suitable material, such as cast aluminum or other cast metal. In a similar manner, the faceplate 15 may also be made of cast metal. An elastomeric gasket 160 forms a liquid-tight seal between the face plate 15 and the housing 10.
The socket ring 20 may also be made of a cast metal, such as aluminum or stainless steel. Typically, the “J” shaped slots 22 and 24 are machined into the outer surface of the ring in order to maintain accurate tolerances. In one embodiment, the socket ring is made of a zinc material, such as ZA-3, and plated with chrome in order to provide a hard ring surface. It has been found that this chrome-plated zinc ring has a surface hardness equivalent to stainless steel, but can be fabricated at a fraction of the cost necessary to fabricate a stainless steel ring.
The contact block assembly 25 is shown in more detail in the perspective view of
In accordance with the principles of the invention, the contact block body 27 is configured to mount the socket ring 20 on the faceplate 15 without the use of screws or bolts. In particular, the contact block body 27 has an outer groove 65 and an inner groove 85 cut into the outer surface of the body 27. The outer groove 65 accommodates an O-ring seal 75 and a snap ring 70 whereas the inner groove accommodates a snap ring 165 (shown in
Next, the contact block body 27 is slid into socket ring 20 until snap ring 70 seats against shoulder 92 formed in the inner diameter of socket ring 20. The snap ring 70 prevents the contact block assembly 25 from sliding through the socket ring 20. Roll pin 105 slides into a semi-circular groove in the inner diameter of socket ring 20 and prevents relative rotation between the contact block body 27 and the socket ring 20.
An elastomeric O-ring 95 is then slid over the inner end 90 of contact block body 27 so that it seats against a shoulder formed on the inner surface of socket ring 20. The inner end 90 of contact block body 27 is slid through hole 100 cut into faceplate 15 so that the O-ring seats against the outer surface 16 of faceplate 15 and shoulder 80 of contact block body 27 seats against the outer surface 16 of faceplate 15. Roll pin 105 slides through a cutout 102 in faceplate 15 and prevents relative rotation between the contact block assembly 25, socket ring 20 and faceplate 15.
Finally, snap ring 165 is expanded, slid over the inner end 90 of contact block body 27 and seated in groove 85. Snap ring 165 bears against the inner surface 170 of faceplate 15 as shown in
The snap ring 165 allows the socket ring 20 to be easily removed and replaced without disconnecting wires from the contact block assembly 25. In particular, in order to replace the socket ring 20, the faceplate 15 is separated from the housing 10 by removing the hold down bolts 205 and 210 (
After contact pin 180 has been inserted into the contact block body 27, the tang of a contact ferrule is inserted into a hole bored in the inner end of the contact pin. For example, referring to
It is desirable to use a commercially-available air valve for the air brake control 300 because commercially-available valves are considerably less expensive than custom-made valves. An example of such a commercially-available valve is a Clippard Minimatic model MAV-3R poppet air valve manufactured by Clippard Instrument Laboratory, Inc., Cincinnati, Ohio. Such a valve is opened when its actuator pin is pressed toward the valve body. However, in such commercially-available valves, the travel distance of the actuator pin from a position where the valve is closed to a position where the valve is open is small. Thus, it is difficult to position the valve 300 relative to the faceplate 15 in order to insure that the air brake control is actuated when an electrical plug is attached and to prevent the actuator pin from interfering with the attachment of the electrical plug to the electrical socket assembly if the actuator reaches the end of its travel distance before the plug is fully seated.
Housing 304 has its own threaded nipple 305 which can be screwed into faceplate 15 and secured by means of lock washer 314 and lock nut 312 in order to fasten the air brake control 300 to the faceplate 15. Nipple 305 of housing 304 is hollow and receives an extension pin 306 which slides within nipple 305. Pin 306 is sealed to nipple 305 via an elastomeric O-ring 326 that fits into a groove in pin 305.
Pin 306 also has a head 307. When slid outward as far as possible, head 307 bears against the inside surface of housing 304. When the air brake control is not actuated, a spring 322 maintains the pin 306 slid outward.
In accordance with one aspect of the invention housing 304 is dimensioned so that, in the non-actuated position, spring 322 maintains a small gap 324 of predetermined width between pin head 307 and valve actuator pin 320. For example, this predetermined width might be 1/16 inch. The presence of this gap effectively increases the actuator travel distance because, when an electrical plug is attached to the electrical socket assembly, pin 306 must first travel the width of gap 324 before contacting the actuator pin 322 of valve 302 and then travel the normal actuator travel distance of the valve 302 before the valve opens. Illustratively, in the case of the model MAV-3R poppet air valve mentioned above, the 1/16 inch gap increases the overall travel distance from ⅛ inch to 3/16 inch. The increased travel distance insures that the valve 302 will be actuated when the electrical plug is installed, but the actuator pin will not interfere with the electrical plug during its installation.
While the invention has been shown and described with reference to a number of embodiments thereof, it will be recognized by those skilled in the art that various changes in form and detail may be made herein without departing from the spirit and scope of the invention as defined by the appended claims.
