Tractor-trailer electronic transmission path

An electrical signal transmission path is provided along the air brake hose line to provide a dedicated connecting path between communication units on a tractor and trailer. A conductive line extends along the length of the air brake hose and is connected at one end to the communication unit on a tractor via a conductive linkage. The opposite end of the line is connected to a trailer communication unit via a conductive connection from the trailer end of a two part releasable air hose coupling which is isolated from the trailer and electrically connected to the trailer end of the conductive line.

BACKGROUND OF THE INVENTION 
The present invention relates to a tractor-trailer data transmission path 
or link forming part of a mobile communication system to allow data 
transmission back and forth between a tractor and attached trailer for 
subsequent transmission to a remote monitoring center. 
Mobile communication systems are used by commercial trucking companies to 
locate, identify and ascertain status of their vehicles, as well as to 
allow the vehicle operator to send and receive information. One major 
problem facing large trucking companies is keeping track of the location 
of all trailers throughout the country. When trailers are unhooked from a 
tractor, they are liable to be left at a location and potentially 
forgotten. This results in unnecessary down time and substantial economic 
impact on the company. 
In addition to keeping track of the location of all trailers at all times, 
it is also desirable to be able to ascertain the condition of trailer 
equipment, environmental conditions in a trailer, as well as the condition 
of the payload. This may be achieved by placing various sensors in the 
trailer. The sensors are typically connected to a suitable memory unit in 
the trailer in which trailer identification and cargo information is 
stored, and the sensor outputs as well as the trailer identification must 
be transmitted to the tractor over a suitable transmission medium. Trailer 
information is therefore transmitted to the tractor for transmission to a 
central facility where the information is monitored. Up to now, various 
transmission mediums have been contemplated including RF transceivers, 
infrared transceivers, dedicated wiring, and a sharing of existing wiring. 
RF and infrared transmission schemes can be costly and susceptible to 
interference. Dedicated wiring are not desired since additional connectors 
or a complete rewiring of existing trailers would be required. The 
preferred technique has been directed towards transmitting the information 
from trailer to tractor via existing tractor-trailer electrical wiring 
which provides power for the trailer lights as well as for equipment in 
the trailer. However, when the information signal is modulated onto a 
carrier and impressed upon the electrical power line, it is sometimes not 
easy to pick out the signal. 
One tractor-trailer communication system of this type is described in 
application Ser. No. 07/620,133, filed Nov. 30, 1990, of Moallemi et al., 
which is a Continuation of application Ser. No. 07/339,686, filed Apr. 18, 
1989, now U.S. Pat. No. 5,142,278 issued Aug. 25, 1992, the disclosure of 
which is incorporated by reference. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a new and improved 
tractor-trailer data transmission path to allow information to be 
transmitted more readily between a tractor and one or more attached 
trailers. 
According to the present invention, a tractor-trailer data transmission 
path is provided which comprises a conductive line extending along the 
length of a tractor-trailer air brake hose, a connector at the trailer end 
of the line for electrically connecting the line to an information storage 
and transmission unit on or in the trailer, and a connector at the tractor 
end of the line for electrically connecting the line to receiver unit in 
the tractor. 
Some existing hoses have embedded wire braiding for added strength, and may 
be used in a tractor/trailer air brake system. In this case, the existing 
wire braiding may be used as the connecting line, with suitable electrical 
connections to the braiding at the opposite ends of the line. 
Alternatively, where the brake hoses are coiled rubber hoses, a wire braid 
may be run along the length of a hose to provide the conductive line. 
Furthermore, in unbraided hoses an insulated wire strand or strands may be 
run the length of the hose. 
This arrangement allows one or more electrical lines to be dedicated to 
tractor-trailer data communications, allowing signals to be transmitted 
more easily and reliably.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 illustrates one type of mobile communication system in which the 
data transmission link of this invention may be used. As illustrated in 
FIG. 1, a mobile communications terminal (not shown) is mounted in a 
vehicle such as a truck 10 having a tractor 12 and at least one trailer 
14. Clearly the truck 10 may have more than one trailer connected in 
series. The mobile communication terminal in the truck 10 is connected to 
a suitable transmitter or antenna 16 for transmitting information to a 
central hub facility or terminal 18 in any suitable manner, for example 
via satellite 20. Information received from various trucks is transmitted 
in any conventional manner from the hub facility 18 to a customer facility 
22 via network management center 24 which controls the priority, access, 
accounting and transfer characteristics of the message data. Messages can 
be transmitted to and from the truck 10 using such a system. Typically, 
the messages transmitted from the truck include information such as 
vehicle location, vehicle status, trailer identification and trailer 
status, as well as other information and requests for information which 
may be entered manually by the truck driver. A mobile communication system 
of this type is described in U.S. Pat. No. 5,142,278 referred to above in 
which the tractor-trailer existing power line was contemplated as the 
transmission medium. An example of such a communication system is that of 
the OmniTRACS system employing OmniTRACS mobile communications terminals, 
both of Qualcomm Incorporated of San Diego, Calif. 
In order for the terminal in tractor 12 to collect information on trailer 
identification and status for transmission to a central facility, a 
transmission path must be provided between the tractor and the trailer to 
allow electronic communication. FIG. 2 illustrates a trailer-tractor 
communication link or transmission path according to an exemplary 
embodiment of the present invention which does not require any additional 
electrical cables to be provided from the tractor to the trailer but which 
provides a dedicated path for communications between the tractor and 
trailer. 
The tractor-trailer communication system basically comprises a transmitter 
unit 25 mounted on or in the trailer. Unit 25 will include a memory in 
which trailer identifying information is stored, and is designed to 
generate a carrier signal that is modified by a trailer identifying signal 
as well as any other information such as trailer or payload status 
information, which is obtained from various sensors linked to unit 25. 
Every trailer in a fleet will have a transmitter unit designed to transmit 
its own specific identifying signal. 
The tractor includes a receiver unit 26 for receiving information from the 
transmitter unit when the tractor is hooked up to a trailer. The receiver 
unit receives power from the vehicle electrical system/battery 27, and is 
linked to a mobile communication terminal 28 in the tractor. The receiver 
receives each identification signal modulated carrier signal transmitted 
from the trailer transmitter unit and demodulates the signal to provide an 
information or identification signal to the mobile communication center 
28. The identification signal is then transmitted to the central or hub 
facility. 
In using the transmitter such as described in U.S. Pat. No. 5,142,278, a 
power bus or electrical transmission path must be provided from the 
transmitter unit in the trailer to the tractor receiver unit in order to 
allow signal communications between these units. In the aforementioned 
patent the power bus is used such that power is provided from the 
system/battery to transmitter 25 for powering the unit. Up to now, 
tractor-trailer communication has been via the existing power cable 
linkage between the tractor and trailer for powering brake lights and 
other electrical equipment in the trailer. This invention provides a 
dedicated line for carrying the modulated carrier signal from the trailer 
to the tractor. 
In an alternate embodiment the transmission path between the tractor and 
trailer need not be a power bus. Therefore, electrical system/battery 27 
would not be connected to the transmission medium as illustrated in FIG. 
2. In either embodiment a common ground is shared between the tractor and 
trailer such that only one wire is needed to complete the transmission 
path. 
In one example of this alternate embodiment, transmitter 25 is configured 
as a transceiver, receiving power from the power bus, and transmitting and 
receiving its signals over the transmission medium. Similarly receiver 26 
is also configured as a transceiver for transmitting and receiving over 
the transmission medium. In this example, transceiver 26 generates a 
generic interrogation signal to which transceiver responds with an 
identification signal. Later transceiver 26 interrogates transceiver 25 
using a signal based upon the I.D. of transceiver 25. In the case of 
multiple trailer transceivers 25 a search protocol is used by transceiver 
26 upon receiving responses from multiple trailer transceivers 25. Again 
the trailer transceivers 25 respond to the transceiver specific signals 
transmitted by transceiver 26. 
In a tractor-trailer combination, air brake lines or hoses 29 are 
releasably connected between the tractor 12 and the trailer 14 to supply 
air to the trailer. Typically, each line 29 has a coupling or fitting 30 
at the tractor end which is screwed into an inlet or fitting 31 at the 
back of the tractor. A similar fitting 32 at the opposite end is screwed 
onto one part of a releasable coupling device 33 which is known as a "glad 
hand" at the trailer end for releasably securing the hose to an inlet 34 
at the front end of the trailer. Inlet 34 is linked via suitable means to 
the trailer brake system. One or more, typically two, such air brake hoses 
or lines are provided between the tractor and trailer, and similar hoses 
are provided between the first trailer and any subsequent trailer linked 
to the tractor where the tractor is pulling more than one trailer. When an 
operator hitches the tractor to a trailer, they connect the air brake hose 
to the trailer air brake inlet in a conventional manner. 
Some existing air brake hoses are of the wire braided type in which a 
metallic sheath 36 is embedded in a rubber or plastic hose 29 for added 
strength and durability. Although a metallic sheath is preferred since 
currently existing hoses are manufactured in this arrangement, it should 
be understood that in the alternative a wire strand embedded in the hose 
or an insulated wire strand mounted alongside the hose may be used. An air 
brake hose of this type is illustrated in FIG. 4. In the illustrated 
embodiment of this invention, the embedded metallic sheath 36 of a 
tractor-trailer air brake hose 29 is used as part of the electrical 
communications path between the transmitter unit 25 in a trailer and the 
receiver unit 26 in a tractor, as best illustrated in FIG. 2. 
As illustrated schematically in FIG. 2, a suitable electrical line 40 is 
connected between the receiver unit in the tractor and the metallic sheath 
36 at the tractor end of the air hose. Similarly, an electrical connecting 
line 42 is provided between the trailer end of the sheath 36 and the 
transmitter unit 25 in the trailer. The data transmission path is 
illustrated in more detail in FIGS. 3-6. As illustrated in FIG. 3, the 
coupling or fitting 30 at the tractor end of the hose is of metal such as 
brass and is suitably secured on the end of the hose. Fitting 30 has a 
projecting threaded end 44 for threaded engagement in tractor inlet 48. 
The metal fitting 30 will be electrically connected to the metallic sheath 
36 at the end of the hose in a similar manner to insulated electrical 
cables, by peeling back a short portion of the insulating cladding of the 
hose before securing the exposed end to fitting 30. Electrical wiring 40 
is connected to the fitting 30 at one end via a suitable clamping device 
46, as illustrated in FIG. 3, and extends through the rear wall of the 
tractor for connection to the receiver unit as generally illustrated in 
FIG. 2. Fitting 30 is electrically isolated from the tractor brake outlet 
fitting 31 via insulating plastic coupling 48 or any other suitable 
insulating means such as an insulating bushing. 
The metallic fitting 32 at the trailer end is mounted on the hose end and 
electrically connected to the trailer end of the metallic sheath in a 
similar manner to fitting 30. Fitting 32 has a projecting threaded end 50 
which is inserted into a correspondingly threaded inlet 52 of one part 54 
of the so-called "glad hand" connector 33 as is conventionally used to 
releasably connect air brake hoses to trailers. The other part 56 of the 
connector 33 is permanently mounted on mounting plate 58 at the front end 
of trailer 14 with an insulating layer disposed between part 56 and plate 
58. The two parts 54, 56 have through bores for passage of air through the 
parts and are designed to be connected and disconnected by rotating part 
54. This type of glad hand connection is well known in the field and will 
therefore not be described in any more detail. When the two parts 54, 56 
are coupled together, a path for air from the air hose is provided through 
connector 33 and mounting plate 58 to the trailer air brake system. 
Since the fitting 32 is in electrical contact with the trailer end of 
metallic sheath 36 (FIG. 4), and the glad hand is of metal, the trailer 
secured part 56 of the glad hand is electrically connected to sheath 36. 
Thus, the connecting lead to transmitter/transceiver unit 25 (FIG. 2) can 
be taken from the part 56 of the glad hand, and two exemplary alternative 
ways of doing this are illustrated in the drawings. In the alternative 
illustrated in FIGS. 3-6, the transmitter unit is configured as a 
transceiver and comprises a small memory and trailer id generating chip 60 
which is mounted via mounting bracket 62 on the trailer mounting plate 58. 
Since mounting plate 58 is grounded, bracket 62 also acts as a ground lead 
for the chip 60. 
Since the glad hand connector 33 is metal, it must be isolated from the 
trailer mounting plate 58 to allow the electrical path to be taken from 
part 56. One way of doing this is illustrated in FIGS. 3, 5 and 6. As best 
illustrated in FIG. 6, connector part 56 is secured to mounting plate 58 
via screws 68 which extend through the mounting plate and part 56 and have 
lock nuts 70 mounted at their free ends. In order to isolate the part 56 
from the screws and the mounting plate 58, an isolating pad 72 of suitable 
insulating material is inserted between the mounting plate 58 and the 
connector part 56, and the screws 68 project through aligned openings in 
the plate 58, pad 72 and connector part 56. Insulating bushings 74 are 
mounted on the projecting ends of the screws between the nuts 70 and 
connector part 56. Projecting cylindrical bosses 76 project from pad 72 
into enlarged openings in connector part 56 surrounding the screws so as 
to isolate the shank of each screw from the connector part. With this 
arrangement connector part 56 is completely isolated from the mounting 
plate 58, and fitting 32 is similarly isolated to prevent any signal 
losses to ground. 
A signal path from the connector part 56 to the chip or transmitter unit 60 
is provided via a conductive connecting plate or bracket 78 which is 
sandwiched between connector part 56 and pad 72 as illustrated in FIG. 6 
and which has an upwardly projecting tab 80 which is connected to the live 
lead of chip 60, which may be a Touch Memory.RTM. chip as manufactured by 
Dallas Semiconductors. Since chip 60 is exposed it may also be accessed by 
an operator with a touch interrogation device. 
In this embodiment, the transmitter unit is a simple trailer identification 
unit which transmits trailer identifying information along the 
transmission path of hose 29 to the receiver unit on receipt of a request 
signal from the receiver unit 26 (FIG. 2) which is configured as a 
transceiver. However, in alternative embodiments, as illustrated 
schematically in FIG. 2, the transmitter unit 25, or multiple transmitter 
units, may be suitably mounted within the trailer adjacent the air brake 
hose mounting plate 68. The internally mounted transmitter unit may be 
secured to the isolated glad hand part 56 via a suitable electrical lead 
secured to the part 56 in any suitable manner, for example a lead may be 
connected to tab 80 of connecting bracket 78, and extend from tab 80 into 
the trailer for connection to unit 25. 
Instead of mounting chip 60 externally on mounting bracket 62, a chip or 
transmitter unit 60' may be embedded within pad 72, as illustrated in FIG. 
6. In this case, the drip 60' is protected from the surrounding 
environment. Alternatively, an embedded chip 60' may be provided in 
addition to chip 60 for performing additional functions. Suitable 
connections will be provided from conductive plate 78 to chip 60', or 
plate 78 may be omitted and chip 60' may be connected directly to glad 
hand connector part 56. 
Additional connecting wires (not illustrated) may connect transmitter unit 
25 to sensors inside or outside the trailer for providing cargo status and 
other desired information via metal sheath 36 to the tractor receiver 
unit. The electrical connection to sensors and other electrical units in 
the trailer may use the trailer air brake hoses as part of the electrical 
path, in a similar manner to air brake hose 29 between the tractor and 
trailer. In any trailer, an air brake line will extend from the air brake 
inlet at the front end of the trailer to the trailer brake system. If this 
line has an embedded metallic sheath, it may be suitably connected to the 
transmitter unit with wiring, for example, and then may be connected to 
electrical units or sensors in the truck at any desired point in its 
length simply by tapping electrical leads into the hose at appropriate 
points. The brake end of the metallic sheath will be isolated in any 
suitable manner from any metal parts of the brake units. 
With this arrangement, a dedicated transmission path is provided between a 
transmitter unit on or in a trailer and a receiver unit in a tractor using 
existing brake hose lines without requiring any additional electrical 
cables between the tractor and trailer. This allows more reliable signal 
transmission and signal identification. This arrangement also does not 
require any change in the way drivers connect trailers. No change is 
required in the existing seven-way, electrical connector between 
tractor-trailer or existing glad hands. 
In the embodiment described above, the transmission path is provided along 
an air brake hose of the embedded wire sheath type. This type of air brake 
connection typically includes a pair of air brake hoses and a spring 
extending from the tractor for retracting the brake hose lines when 
released from the trailer. Thus, the electrical path could alternatively 
be provided along the metallic retraction spring in a similar manner, and 
an additional transmission path may be provided along the second air brake 
hose, since there are typically two such hoses connected between the 
tractor and coupled trailer. In tractors having coiled rubber air brake 
hoses without embedded metal sheaths, a conductive line could be simply 
mounted along the outside of the hose in any suitable manner, such as a 
metallic sheath or wire with an outer insulating layer, with the hose 
providing the support for the transmission path. 
Although a preferred embodiment of the invention has been described above 
by way of example only, it will be understood by those skilled in the 
field that modifications may be made to the disclosed embodiment without 
departing from the scope of the invention, which is defined by the 
appended claims.