Environmentally sealed connector for use with a load cell block

An environmentally sealed electrical connector for use with a load cell block. The connector includes a jacketed cable that extends through a pliable connector block. The connector block is injection molded directly around the cable to insure an environmental seal between the cable and the connector block. The connector block includes a cylindrical protrusion that extends downwardly into a passageway in the load cell block. A double-sided adhesive gasket is located between the load cell block and the connector to help form an environmental seal between the connector and the load cell block and to help attach the connector to the load cell block. The connector is attached to the load cell block using four fasteners that extend through a stiff pressure plate, the connector, and are received by holes in the side of the load cell. As the fasteners are tightened, a force is placed on the pressure plate, which in turn compresses the connector block into the load cell block, establishing an environmental seal.

FIELD OF THE INVENTION 
The present invention relates to instrumented load cell blocks, and, more 
particularly to connectors for use with a load cell block. 
BACKGROUND OF THE INVENTION 
Load weighing systems for commercial vehicles, such as logging and other 
trucks, generally use a plurality of load cell assemblies to monitor the 
amount of weight loaded on the beds of the truck trailers. Each load cell 
assembly usually includes a machined load cell block that is supported 
between two load carrying members, such as log supports, and mounting 
members, such as a truck trailer frame. As an increasing load is placed on 
the trailer, the load cell blocks are subject to increasing deflections 
that are directly related to the load placed on the trailer. 
Strain gauges applied to various locations on the load cell blocks and 
protected from damage by cover plates are used to determine the 
deflections of the load cell blocks as a trailer is loaded. The deflection 
data obtained from the strain gauges is then used to calculate the weight 
of the load placed on the trailer. 
The strain gauges are connected to monitoring equipment that calculates and 
records the load placed on the trailer by wiring that is connected at one 
end to the strain gauges or other sensing elements, passes through an 
internal passageway in the load cell block, and is connected at the other 
end to an electrical connector mounted on the a side or end of the load 
cell block. The electrical connector on the side of end of the load cell 
block is in turn releasably connected to a mating electrical connector 
that includes a cable connected to the monitoring equipment. 
Prior electrical connectors mounted on the load cell blocks are prone to a 
number of problems. Because load cell blocks are mounted on the exterior 
of trailers, they are exposed to harsh environmental elements including 
extreme temperature and moisture variations. When used on logging truck 
trailers, the load cell blocks and electrical connectors are also subject 
to extreme physical punishment from frequent contact with logs, tree 
limbs, etc. 
In the past, it has been difficult, if not impossible, to maintain an 
environmental seal between the load cell block and the electrical 
connector mounted on the load cell block. Over time, moisture migrates 
through the seal between the load cell block and electrical connector and 
into the interior of the load cell block. Even small quantities of 
moisture in the interior of the load cell block can corrode or short out 
the strain gauges or electrical wiring within the load cell block. This 
moisture problem is magnified by movement and loosening of the electrical 
connector as the load cell block is placed under load or is vibrated 
during operation of the truck. 
In addition to corrosion caused by moisture, the electrical connection 
between the load cell block and the mating electrical cable is prone to 
physical damage caused by contact with exterior objects. Sometimes, 
sufficient force is placed on the electrical cable or electrical connector 
to damage the connector or, in some cases, pull or knock the electrical 
connector entirely off of the load cell block. Prior electrical connectors 
extend outward normal to the surface of the load cell a sufficient 
distance to present a relatively large target that can be easily damaged. 
In applications requiring a great deal of accuracy, the electrical 
connection between the load cell block and the cable is sometimes a source 
of errors in load measurements made using the load cell block. As with 
most releasable electrical connectors, sometimes a poor connection is 
established between the parts of the connector. Electrical connectors 
formed of multiple pans are also more prone to errors introduced by 
movement or vibration of the connector. 
Thus, there exists a need for an electrical connector that reduces or 
eliminates some of the disadvantages of the prior electrical connectors 
used on load cell blocks. Specifically, there exists a need for an 
electrical connector that will reduce load cell failures caused by 
moisture or physical damage to the electrical connectors. 
SUMMARY OF THE INVENTION 
In accordance with the invention, an environmentally sealed electrical 
connector for use with a load cell block is provided. In one embodiment, 
the environmentally sealed connector includes an electrical cable that 
extends through an integral connector block molded around the electrical 
cable. A surface of the connector block establishes an environmental seal 
between the connector block and the side of a load cell block. 
In accordance with other aspects of the invention, the connector block 
includes a protrusion extending from one surface of the connector block at 
least partially into a passageway in the load cell block. The connector 
block also includes a conical portion extending outwardly from one side. 
The electrical cable passes through the conical portion, into the 
connector block, bends through an angle of approximately ninety degrees, 
and exits a side of the connector block. 
According to still other aspects of the invention, the connector block is 
formed at least partially of a pliable, resilient material. A pressure 
plate, located on one side of the connector block remote from the load 
cell block, is used to place a force on the connector block to press the 
connector block into the side of the load cell block to establish an 
environmental seal. In other embodiments of the invention, the connector 
block includes a cylindrical protruding portion that screws into the 
passageway in the load cell block. O-ring type gaskets may also be used 
between the connector block and the load cell block to form a seal. 
Forming the connector block around the electrical cable as an integral part 
allows the present invention to form an environmental seal between the 
electrical cable and the connector block. The pliable, resilient connector 
block used in combination with the pressure plate allow the present 
invention to also form an environmental seal between the connector block 
and the side of the load cell block. The pliable, resilient nature of the 
connector block maintains the environmental seal even during vibration or 
slight movement of the connector relative to the load cell block.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
The present invention is an environmentally sealed electrical connector for 
load cell blocks. FIGS. 1-3 illustrate a first embodiment of an electrical 
connector formed in accordance with the invention. The embodiment includes 
a pigtail connector 10 attached to a beam-type load cell block 12. 
The deflection of the load cell block 12 is measured using electrical 
strain gauges (not shown) that are attached to the lower surface or other 
locations on the load cell block depending upon the application. The 
electrical strain gauges are in turn electrically connected to monitoring 
equipment (not shown) via an electrical cable 14 that forms part of the 
pigtail connector 10. The cable 14 includes a plurality of wires 18 that 
are connected at one end to the strain gauges. The cable leaves the load 
cell block 12 via a passageway 40. The cable 14 may extend to the 
monitoring equipment or be connected to another cable that runs to the 
monitoring equipment. The connections between the cable 14 and the strain 
gauges, and the locations of the strain gauges are not shown because they 
are not relevant to the disclosure of the present invention. Likewise, the 
connections between the cable 14 and the monitoring equipment are not 
shown because they are not relevant to the present invention. 
The pigtail connector 10 also includes a solid one-piece seal block 20. The 
seal block 20 includes a truncated conical section 22 that extends 
outwardly approximately normal to one side of an integral rectangular 
section 24 and lies approximately parallel to the side of the load cell 
block 12 on which the connector 10 is mounted. The base of the conical 
section 22 is located at the rectangular section and the conical section 
tapers outwardly to its distal end. The seal block 20 also includes an 
integral cylindrical protrusion 30 that extends outwardly, generally 
normal to the side of the rectangular section 24 that faces the load cell 
block 12. The circumference of the cylindrical protrusion 30 is sized to 
fit snugly in the outer end of the passageway 40, as described below. 
The electrical cable 14 extends longitudinally through the center of the 
conical section 22 into the rectangular section 24. The cable 14 then 
curves through angle of approximately ninety degrees and exits through the 
center of the cylindrical protrusion 30. The cable 14 includes a 
protective jacket 16 that surrounds the plurality of wires 18 that are 
connected to the strain gauges of the load cell. In the embodiment shown, 
the jacket 16 terminates at an end 26 external to the outer end of the 
cylindrical protrusion 30. 
The seal block 20, which includes the rectangular section 24, the conical 
section 22, and the cylindrical protrusion 30, is formed as a single piece 
by placing a suitably shaped mold around the cable 14 and injecting a 
suitable material into the mold in a single forming operation. The 
material used to form seal block 20 should be capable of withstanding the 
harsh environment experienced by the connector 10. In addition, the 
material used to form the seal block 20 should be sufficiently resilient 
and compliant to form a good seal between the seal block 20 and the load 
cell block 12 when the connector 10 is attached to the load cell block, as 
described below. The material used to form the seal block 20 must also be 
compatible with the material used to form the jacket 16 of the cable 14 to 
ensure that a proper bond and seal are formed between the seal block and 
the cable 14. 
In one actual embodiment of the invention, the jacket 16 of the cable 14 
and seal block 20 are formed of a polyurethane material. In alternate 
embodiments, other materials could be used. Further, the end 26 of the 
jacket 14 could terminate within the cylindrical protrusion 30, 
rectangular section 24, or conical section 22. Obviously, the jacket 16 
must extend a sufficient distance into the seal block 20 to ensure that a 
proper seal is created between the jacket and connector block. 
In addition to the electrical cable 14 and the seal block 20, the connector 
10 includes a double-sided gasket 32, a pressure plate 34 and four 
fasteners in the form of cap screws 36. The double-sided gasket 32 is 
sized to match the side of the seal block juxtaposed against the load cell 
block in the manner described below and the pressure plate is sized to 
match the opposite or outer side of the seal block 20. The double-sided 
gasket includes a hole (not shown) through which the cylindrical 
protrusion 30 passes. 
As best illustrated in FIG. 3, the pressure plate 34 is rectangular in 
shape and is sized to correspond to the size and shape of the rectangular 
section 24 of the connector 10. The pressure plate 34 includes four 
elongated holes 52 sized to receive the screws 36. The elongated holes 52 
also allow limited sidewise movement of the pressure plate 34 relative to 
the screws 36, thus ensuring a proper fit and relieving undue stress 
between the screws and pressure plate as the screws are tightened in the 
manner described below. 
As best seen in FIG. 1, the connector 10 is attached to the side of the 
load cell block 12 by first feeding the wires 18 through the hole in the 
double-sided gasket 32 and then into the passageway 40, where the wires 
are connected to the strain gauges (not shown). The end of the passageway 
40 opposite the end that receives the connector 10 is sealed with a plug 
46 having a cylindrical protrusion 48 that extends into the passageway. In 
alternate embodiments, the passageway 40 may not extend all the way 
through the load cell block, eliminating the need for the plug 46. 
The double-sided adhesive gasket 32 is sized to fit around the 
circumference of the cylindrical protrusion 30 such that the gasket 
against the outer surface of the rectangular section 24 that surrounds the 
protrusion. The double-sided gasket 32 and connector 10 are placed against 
the side of the load cell block 12 such that the cylindrical protrusion 30 
extends into the passageway 40. The contact between the side of the 
cylindrical protrusion 30 and wall of the passageway 40 forms a first 
seal. A second seal is formed between the surface of the rectangular 
section 24 and the side of the load cell 12 by the double-sided gasket 32. 
It is preferred that the gasket 32 include adhesive on both sides to help 
insure a proper seal and to structurally bond the connector 10 to the side 
of load cell block 12. In other embodiments a gasket without adhesive 
could be used or the gasket could be eliminated altogether. 
The connector 10 is attached to the side of the load cell block 12 by the 
four screws 36. One screw extends through one of the holes 52 located in 
the corners of the pressure plate 34 and then through corresponding holes 
located through the corners of the seal block 20. The screws are received 
in corresponding holes 50 in the load cell block. As described next, the 
pressure plate 34, which is formed of a rigid material, creates a sealing 
pressure. 
As the screws 36 are tightened, they force the pressure plate 34 into the 
rectangular section 24, thus forcing the connector 10 against the side of 
the load cell block 12. To ensure that a relatively evenly distributed 
force is applied to the connector 10, as noted above, the pressure plate 
34 should be formed of a suitably rigid material, for example, a metal 
such as steel. The rigid pressure plate 34 also prevents the screws 36 
form being pulled through the compliant seal block 20 during tightening. 
As the fasteners 36 are tightened further, the pressure plate 34 compresses 
the rectangular section 24, causing the sides of the rectangular section 
24 to bow slightly outwardly. The pressure places a sufficient force on 
the rectangular section 24 to form a seal between the rectangular section 
24, the gasket 32, and the facing side of the load cell block 12. 
The structure of the connector 10 insures that a water-tight seal is 
created and maintained between the connector 10, the cable 14 and the load 
cell block 12, thus keeping moisture out of the passageway 40. Because the 
compliant rectangular section 24 is maintained in a compressed state by 
the pressure plate 34 and the screws 36, a seal is maintained even during 
vibrations or slight movements of the load cell block 12 relative to the 
connector 10. The dual attachment of the connector 10 to the side of the 
load cell block 12 using the double-sided adhesive gasket 32 and the 
screws 36 also helps to ensure that the connector 10 remains attached and 
sealed to the load cell block 12. 
Forming the cable 14 directly into the seal block 20 such that the cable 
extends into the seal block 20 on one side and exits from an adjacent side 
produces a connector with a low profile. The low profile connector 10 
helps reduce damage to the connector caused by contact with external 
forces, such as tree branches, etc., during operation of a truck on which 
the load cell block is used. 
In other embodiments of the invention, the seal block 20 could be formed in 
other shapes or from other materials without departing from the scope of 
the invention. For example, the conical section 22 could protrude from the 
surface of the seal block 20 remote from the load cell block. As a result, 
the conical section would extend approximately normal to the side of the 
load cell block 12. In still other embodiments, the conical connector 22 
could be eliminated altogether and the cable 14 could extend directly into 
the side or upper surface of rectangular section 24 of the seal block 20. 
In yet other embodiments, some electronics for the load cell block could 
be molded into the seal block 20. 
Additional embodiments of the invention are illustrated in FIGS. 4-7. 
Features of the additional embodiments similar to features of the first 
embodiment discussed above are identified with the same reference numerals 
as those used in the discussion of the first embodiment. Features of the 
additional embodiments not discussed below function in a manner similar to 
the first embodiment and may be understood by reference to the discussion 
of the first embodiment. 
In the embodiment illustrated in FIG. 4, the flat double-sided adhesive 
gasket 32 is replaced with an O-ring type gasket 60 that is located at the 
interface between the side of the load cell block 12 and the rectangular 
section 24 of the seal block 20. The O-ring type gasket 60 could be 
integrally formed as part of the rectangular block 20 or it could be a 
discrete part mounted in a groove in the rectangular section. The O-ring 
gasket could extend into a corresponding groove located in the juxtaposed 
surface of the load cell 12, or could be compressed into the flat surface 
of the load cell block 12 by the seal block 20. 
The embodiment illustrated in FIG. 5 is similar to the first embodiment of 
the invention, but includes an added O-ring type gasket 64 located between 
the cylindrical protrusion 30 and the wall of the passageway 40. Similar 
to the O-ring gasket 60 of the embodiment of FIG. 4, the O-ring gasket 64 
could be formed as an integral part of the cylindrical protrusion 30 or 
could be a discrete piece. The gasket 64 could extend into a corresponding 
groove formed in the wall of the passageway 40 or could be sandwiched 
between the wall of the passageway and the surface of the cylindrical 
protrusion 30. 
In the embodiment illustrated in FIG. 6, the plurality of screws 36 used in 
the first embodiment are replaced by a single threaded screw 66 that 
extends through the pressure plate 34, the rectangular section 24 of the 
seal block 20 into a threaded hole in an inner pressure plate 68. The 
inner pressure plate 68 is positioned against the end of the cylindrical 
protrusion 30. Tightening the fastener 66 causes the pressure plate 34 and 
the inner pressure plate 68 to move toward each other, compressing the 
cylindrical protrusion 30 and rectangular section 24. As the rectangular 
section 24 and the cylindrical protrusion 30 compress, the circumferential 
surface of the cylindrical protrusion 30 bulges outwardly against the wall 
of the passageway 40. The bulging creates sufficient frictional force 
between the connector 10 and the load cell block 12 to hold the connector 
in the load cell block. The connector 10 may also be sealed to the load 
cell block 12 by a double-sided adhesive gasket 32. 
Yet another embodiment of the invention is illustrated in FIG. 7. In this 
embodiment, the plurality of fasteners 36, and the pressure plate 34 
included in the first embodiment are eliminated. The connector 10 is 
attached to the load cell block 12 through the use of a double-sided 
adhesive gasket 32, as described above in respect to the first embodiment 
of the invention. In addition, the cylindrical protrusion 30 includes 
threading 70 that engages corresponding threading in the wall of the 
passageway 40. In this embodiment, the connector 10 is screwed into the 
passageway 40. As the connector 10 is screwed into the passageway 40, the 
tensile force placed on the cylindrical protrusion 30, pulls the connector 
10 into contact with the side of the load cell block 12, establishing a 
seal. As the connector 10 is threaded into the cavity 40, a compressive 
force is also placed on the outer surface of the threads 70, establishing 
a secondary seal between the threading of cylindrical protrusion 30 and 
the threading of the passageway 40. 
As an additive environmental seal, any of the embodiments of the invention 
discussed could use a sealing material, such as a silicone or other rubber 
or plastic material to fill the passageway 40 prior to attaching the 
connector to the load cell block 12. The inclusion of a sealing material 
further helps prevent moisture from entering the passageway 40 and 
corroding the wires 18. 
While the preferred embodiment of the invention has been illustrated and 
described, it will be appreciated that various changes can be made therein 
without departing from the spirit and scope of the invention.