Constant current non-bridging section insulator

A section insulator including a plurality of discrete runners with associated diodes preventing current from passing from a first circuit to a second circuit and vice versa of a power line having separate circuits to prevent arcing as an electric vehicle's current collector passes along the section insulator between the first and second circuits while the vehicle maintains a constant flow of electric current as it passes along the section insulator.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a method and structure for insulating separate 
power circuits of overhead electrical contact lines used by light rail 
vehicles and the like and more particularly relates to a structure which 
prevents arcing between such power circuits as the vehicle's current 
collector passes along such lines. 
2. Description of the Prior Art 
Electrified light rail vehicles, trolleys, small railroad trains and the 
like use a pantograph contact, shoe contact or other type of current 
collector to supply the vehicle with power from a suspended overhead power 
line. Such overhead lines generally utilize a plurality of separate 
circuits along their length separated by insulators. The problem of arcing 
between the circuits in the prior art occurs when the pantograph or other 
current collector passes from one circuit to another along the overhead 
power line. Such arcing between the circuits creates significant heat and 
causes damage to the power lines and to the section insulators between the 
separate circuits which damage shortens the useful life of the power 
lines. This arcing problem is especially significant when the traveling 
pantograph or shoe does not bridge the gap between the two power circuits 
as it passes across the section insulator. Under normal conditions arcing 
occurs on the contact wire as the pantograph passes on to the insulator, 
and pitting will cause a decrease in the cross-sectional area of the wire 
over time which worn areas must be replaced with pieces of new contact 
wire on a periodic basis because if not frequently replaced, the contact 
wire will fail and break. 
Structures in the prior art have tried to minimize this arcing effect such 
as suggested in U.S. Pat. No. 4,320,820 to Elbert for a Section Insulator 
with Improved Arc Control which discloses a system of changing current 
paths to redirect magnetic fields to cause the arcs to move in a direction 
away from the section insulators. Others have approached the problem in a 
different way. S. H. Short's Multiple Arc Railway System patented in 1892 
in U.S. Pat. No. 473,361 sectionalizes a long piece of contact wire fed 
from one generator into many short sections where each is isolated by a 
separate fuse which allows sections to remain energized while other 
sections can be repaired. Problems with this type of structure include 
service disruption and the necessity of frequent fusible element 
replacement. Others have approached the problem using diode arrangements 
and quenching circuits controlled by SCR loops such as U.S. Pat. No. 
3,833,820 to Itoh issued Sept. 3, 1974 and West German Patent 2841434 to 
Siei. In Morq, USSR Patent 1303456 it is suggested to divide the overhead 
system into sections. Another USSR patent which Applicant believes is the 
most pertinent of the prior art to the instant invention is No. 1339040 to 
Lupo. The Lupo patent utilizes contact wire and supporting messenger wire 
overlaps at anchor locations. The anchor locations are composed of two 
separate catenaries (contact wire and supporting messenger wires) which 
are parallel with the messenger above the contact wire, and overlap a 
distance so that the pantograph travels along the contact wire of one 
catenary and then on both contact wires (the overlap) and then on to the 
other contact wire of the other catenary. The current collector does not 
travel on the messenger but only on the contact wire. A typical overlap 
can be from 3-30 meters in length depending on the type of line 
construction and voltage. Insulating links with neutral inserts are 
attached to the contact wire, and the pantograph passes from the first 
circuit's contact wire by the first insulating link, by the central 
insulating link, by the second insulating link, and then onto the second 
circuit contact wire. During this passage an arc is created when the 
pantograph passes from the first contact wire through the insulating 
links, and the created arc is deionized in time due to the passage of 
current through a diode chain. This structure is designed for use on 
alternating current electric railroads using a catenary support system and 
requires heavy overlapping-type construction where anchoring locations in 
such catenary system must have additional poles with support spans and 
bracket arms with significant extra hardware. The structure cannot be 
placed at other locations on the line unless a specific overlap anchoring 
system is first installed. This structure is also subjected to significant 
electrical wear from half-wave arcing since it diminishes, but does not 
eliminate, the arcing factor. There is always the possibility of a 
locomotive or vehicle stopping with its pantograph between contact wire 
and the insulating link which, if occurring, would cause a continuous 
electrical arc to be drawn due to the auxiliary loads of the vehicle 
(heat, light, and compressor) and such arc would continue to burn until 
the contact wire was broken. 
SUMMARY OF THE INVENTION 
It is an object of this invention to provide a structure to insulate 
separate power circuits from one another on overhead contact lines 
associated with electrified light rail vehicle systems which systems can 
include trolleys, streetcars, mine locomotives, trolley buses and the like 
to prevent arcing from occurring between power circuits as the vehicle's 
current collector passes along such lines. The current collectors pass 
freely through and by the structure of this invention with no interruption 
to the current flow of the vehicle while at the same time not bridging the 
two power circuits to which the structure of this invention is 
interconnected. 
The structure of this invention incorporates a main insulator to which the 
contact wire is terminated, a running/wearing surface which the current 
collector travels upon, a diode array held within an enclosure and a 
suspension system. The running/wearing surface consists of three main 
runners insulated from each other and insulated from the approach 
transition clamps. These runners are bolted together so as to form one 
long piece which is attached under the contact wire and main insulator. 
The current collector passes from the contact wire of one circuit to the 
entering transition clamp, along the main runners to the leaving 
transition clamp and then on to the contact wire of the other circuit 
smoothly. The running/wearing surface allows trolley poles with shoes and 
pantograph current collectors to pass through the structure in either 
direction. The power is transmitted to the three main runners insulated 
from each other and the power circuits through feeder tap jumpers attached 
to each main runner, the other end of which tap jumper being connected to 
diodes in a diode array as will be described further below. 
Providing constant current to the collector and non-bridging of the two 
circuits are the primary objects of this invention. The transition clamps 
are energized due to direct connection with their associated power 
circuits. The entering transition clamp can be bolted to the first circuit 
contact wires, and leaving transition clamp can be bolted to the second 
circuit contact wire. Between the clamps insulated from one another and 
the clamps are runners A, B and C which are energized by interconnection 
to the power circuits with jumper cables in series with a plurality of 
diodes. A first jumper cable interconnects the first circuit through first 
and second diodes to runner A through a second jumper which, in turn, is 
interconnected through a third and fourth diode along a third jumper to 
runner B. First, second, third and fourth diodes are biased to allow 
current only to pass one way from the first circuit to runners A and B and 
will not allow any current to flow to the first circuit from the second 
circuit. The third jumper also extends through a fifth and sixth diode to 
a fourth jumper attached to runner C which also interconnects through a 
seventh and eighth diode to a fifth jumper attached to the second circuit. 
Fifth, sixth, seventh and eighth diodes are biased oppositely to first, 
second, third and fourth diodes so that fifth, sixth, seventh and eighth 
diodes only allow current from the second circuit to reach runners C and 
B; and fifth, sixth, seventh and eighth diodes prevent any current from 
the first circuit to reach the second circuit. As the current collector 
travels from the first circuit onto runner A, power is transmitted both 
from the contact wire of the first circuit and from the first jumper cable 
connected to the transition clamp through first and second diodes to the 
second jumper connected to runner A. Current cannot flow from the second 
circuit to runner A because it is blocked by the third and fourth diodes, 
preventing its travel in that direction. Current also cannot flow from the 
first circuit to the second circuit because it is blocked by fifth and 
sixth diodes. When the current collector is completely on the main runner 
A and does not bridge transition clamp, all current flows to the current 
collector from the first circuit through the first and second diodes. The 
third and fourth diodes prevent the current from the second circuit 
flowing to runner A and further prevent the current from the second 
circuit flowing into the first circuit. As the current collector travels 
onto runner B while it is still on runner A, it receives power from the 
first circuit through the second jumper cable attached to runner A and the 
third jumper cable attached to runner B. The current flows from the first 
circuit; through the first, second, third and fourth diodes; to runner B; 
but the current from the first circuit cannot flow to the second circuit 
due to the blocking action of the fifth, sixth, seventh and eighth diodes. 
The current collector also receives from runner B current from the second 
circuit through the third jumper. The current from the second circuit 
flows through the fifth, sixth, seventh and eighth diodes, through the 
third jumper, to runner B, but current from the second circuit cannot flow 
to the first circuit due to the blocking action of the first, second, 
third and fourth diodes. When the current collector is completely on the 
central runner B, it receives power from both the first circuit and the 
second circuit at the same time, but there is no feedback of current from 
either circuit to the other because of the blocking nature of the diode 
arrangement. When the current collector travels on to runner C and is 
still partially on runner B, it receives power from the first circuit and 
also power from the second circuit. When the current collector is 
completely on runner C and does not bridge runner B, all current flowing 
to the current collector is flowing from the second circuit as explained 
in further detail below. 
No arcing or burning can take place in this invention because the 
insulators between the runners A, B, C and the transition clamps are 
shorter than the length of the conducting strips of the pantograph current 
collectors or trolley pole shoe current collectors. No arcing occurs 
because the pantograph collector conducting strips or trolley pole shoe 
overlap the insulators so that the voltage is equalized. With equal 
potential, the current going to the collector will not be interrupted at 
any time. 
The design of this invention is especially useful for low voltage direct 
current service in the 3,000 volt or less range with either pantograph or 
trolley pole/shoe current type collector devices and can be used with 
light rail vehicles, trolley buses, mine locomotives, or electric railroad 
direct current locomotives. 
The structure of this invention further provides for an easily replaceable 
wear surface that can be replaced without disturbing the tension in the 
contact wires and can be suspended with a soft-style parallelogram 
suspension support system.

DESCRIPTION OF THE PREFERRED EMBODIMENT(S) 
FIG. 1 illustrates first circuit 10 separated from a second circuit 12 by 
the structure of this invention. The collector pantograph or shoe travels 
along first circuit 10 and then travels along entering transition clamp 14 
while still receiving current from the first circuit. A series of runners 
are disposed having insulators therebetween. Runner A 16 is insulated from 
the transition clamp 14 by insulator 22. Runner B 18 is insulated from 
runner A 16 by insulator 24 and runner C 20 is insulated from runner B 18 
by insulator 26. Runner C 20 extends to the leaving transition clamp 30 
which clamp is insulated from runner C 20 by insulator 28. Leaving 
transition clamp 30 extends to second circuit 12. Transition clamps 14 and 
30 are energized due to their direct connection to their associated power 
circuit. The entering transition clamp 14 is bolted or otherwise attached 
to the contact wire of first circuit 10, and the leaving transition clamp 
is likewise bolted or attached to the contact wire of second circuit 12. 
Runners A, B and C are energized by connections to a series of power 
circuits through jumper cables as will be described below. As the current 
collector travels from first circuit 10 over the entering transition clamp 
14, it passes onto runner A 16 and the power is transmitted from first 
circuit 10 to the current collector's contact. First jumper cable 32 
attached to first circuit 10 passes the current through first and second 
diodes 41 and 42, respectively, and through second jumper cable 34 to 
runner A 16. No current can flow from second circuit 12 to main runner A 
because it is blocked by third and fourth diodes 43 and 44, respectively. 
Current cannot flow from first circuit 10 into second circuit 12 because 
it is also blocked by fifth and sixth diodes 45 and 46, respectively. When 
the current collector is completely on runner A 16 and does not bridge the 
entering transition clamp 14 or receive current from runner B 18, then all 
current flows to the current collector from first circuit 10 through first 
and second diodes 41 and 42, respectively. As the current collector 
travels onto runner B 18 and still has a portion on runner A 16, the 
collector receives power from first circuit 10 from second jumper cable 34 
through first and second diodes 41 and 42, respectively, and through third 
jumper cable 36 which receives current from first circuit 10 through the 
first, second, third and fourth diodes and from second circuit 12 through 
the fifth, sixth, seventh and eighth diodes 45, 46, 47 and 48, 
respectively. Due to the blocking nature of the third and fourth diodes 
indicated by 43 and 44, respectively, the current from second circuit 12 
cannot pass into first circuit 10 nor can the current from first circuit 
10 pass to second circuit 12 because of the blocking nature of fifth and 
sixth diodes 45 and 46 preventing any current going in that direction. 
When the current collector is completely on runner B 18, it receives power 
from both the first and second circuits as described above. When the 
current collector passes on to runner C 20 and is still on runner B, it 
receives power from first circuit 10 through third jumper 36 with current 
passing through first, second, third and fourth diodes, 41, 42, 43 and 44, 
respectively, but current from the first circuit 10 cannot flow into 
second circuit 12 due to the blocking action of seventh and eighth diodes 
47 and 48. The current collector also receives power from second circuit 
12 through third jumper 36 attached to runner B 18 through fifth and sixth 
diodes 46 and 45, respectively, and power is directed to runner C 20 over 
fourth jumper 38 and through the eighth and seventh diodes 48 and 47, 
respectively. Current from second circuit 12 cannot flow into first 
circuit 10 due to the blocking action of fourth and third diodes 44 and 
43, respectively. When the current collector is completely on runner C 20 
and does not bridge at all on runner B 18 or leaving transition clamp 30, 
all of the current flowing to the current collector is from second circuit 
12 through fourth jumper 38 extending to runner C 20 through the eighth 
and seventh diodes 48 and 47. The fifth and sixth diodes 45 and 46 prevent 
current from first circuit 10 from flowing to runner C 20 and the fourth 
and third diodes 44 and 43 prevent current from second circuit 12 from 
flowing to first circuit 10. As the current collector travels from runner 
C 20 onto leaving transition clamp 30, power is transmitted from the 
contact wire of second circuit 12 and from the fourth jumper cable 38 
connected to runner C 20. Current in fourth jumper 38 flows from second 
circuit 12 through fifth jumper 40 and through eighth and seventh diodes 
48 and 47. When the current collector travels off main runner C onto the 
leaving transition clamp 30 and directly onto second circuit 12, it will 
receive all of its power from the trolley contact wires of second circuit 
12. The arcing and burning of the prior art does not take place because 
the insulators 22, 24, 26 and 28 between the transition clamps and runners 
A, B and C are shorter than the length of the conducting strips of the 
pantograph current collectors or trolley pole/shoe current collectors. 
As seen in FIG. 2, running/wearing surfaces 50 of runners A, B and C can 
easily be replaced when worn out without disturbing the tension in the 
contact wires by simply unbolting the wearing surface from the contact 
wires and removing it after first disconnecting the jumper cables. The new 
wearing surface can then be attached to the contact wires with the jumper 
wires then being reconnected. The suspension system can be attached only 
to the contact wires and does not have to be disturbed or dismantled 
during wear surface replacement procedures. Use of the structure of this 
invention which separates the electrical power circuits on the contact 
wires while providing insulation allows the current collectors to pass 
from one contact wire circuit to the adjoining circuit without losing 
power and without bridging the two power circuits. Electrical arcing that 
is associated with non-bridging section insulators is thereby avoided 
which arcing is eliminated due to the insulated conducting runners 
connected in series through the diode array as described above which 
arrangement prevents the current from one circuit passing to the other. 
A further advantage in the design of this invention is that even though 
there is a minimal voltage drop across the diodes in the range of a few 
volts, the large potential differences required for destructive arcing 
does not occur. Destructive arcing is arcing which removes significant 
amounts of material in the section insulator running surfaces. The diode 
arrangement between the first and second circuits further equalizes the 
voltage potential to prevent arcing from any difference of potential 
between the two circuits. Tests have shown the voltage drop across the PN 
junction of the diodes chosen for this device is insignificant to create a 
potential difference which would create destructive arcing. A typical 
3,000 volt diode drawing upwards of 1,000 amperes of current produces a 
voltage drop of only approximately 0.5-0.l volt. 
This structure of this invention, as discussed above, can be used with 
direct current overhead contact wire systems with voltages of 3,000 volts 
or less for electric railroads, light rail systems, trolley bus lines and 
underground mining operations. In underground mining operations, the 
structure of this invention is particularly useful because the absence of 
electrical arcing would help eliminate any explosions of gas which might 
be caused by such arcing. The structure of this invention can be installed 
on any type of contact wire system, either catenary or single contact 
wire. A suspension trapeze, as seen in FIG. 2, with the attached 
parallelogram wires can be utilized for soft suspension. The structure of 
this invention can also be used in catenary or direct hard suspension 
systems in locations where contact wire support bars or tube-running 
surface construction is needed at junctions or turnouts. The structure of 
this invention can be pre-bent or field-bent for use in curved 
construction. The diode enclosure can be supported at the trapeze on a 
catenary messenger or at a cross-span pole; or if utilized in a mine or 
subway, on the wall or ceiling. The structure of this invention can be 
placed anywhere in a length of contact wire even if it is under constant 
tension, and it does not require an overlap to be installed. The structure 
of this invention further is subjected to much less electrical wear 
because no arcing will take place and even though it is subject to 
mechanical wear from the current collectors, the replacement of the 
separate wear surfaces, not being under tension, is easier. Also, since 
the runners can be of large cross-sectional area with a high profile, 
extreme wear can be tolerated before replacement is needed and should the 
structure wear down to a point where it breaks and fails, only the wearing 
surface will be affected and the contact wires will remain intact. 
In some embodiments an existing cut-in section insulator can be used to 
provide insulation in the contact wires and the wear surface conducting 
pieces can be attached under this insulator with the diode array enclosure 
placed on the existing section insulator support span. This arrangement 
would allow for the use of the structure at a section break using a 
non-bridging but arc-creating insulator or bridging insulator which would 
then become a constant-current non-bridging section insulator without the 
necessity of adding spanning supports. 
Although the present invention has been described with reference to 
particular embodiments, it will be apparent to those skilled in the art 
that variations and modifications can be substituted therefor without 
departing from the principles and spirit of the invention.