Note: Descriptions are shown in the official language in which they were submitted.
CA 02255247 2003-07-17
RAILROAD CROSSING GATE MECHANISM COUNTERWEIGHT
RAISING DEVICE
THE FIELD OF THE INVENTION
The present invention relates to a railroad highway crossing gate mechanism
and
more specifically to a control system which includes both electrical and
mechanical elements for
both raising and holding the gate counterweights in the event that the gate
arm should be broken
and the counterweights should be in a down position. In the past, in a failure
mode as
described, the counterweights are usually raised by some form of mechanical
device which
requires very substantial effort on the part of maintenance personnel. In the
present invention, a
maintenance relay has been added to the gate control system with this relay
applying power
directly to the gate motor in the event of the described failure mode, with
the motor then
functioning to raise the counterweights. Once the counterweights have been
raised, there is
provision for a mechanical lock to hold them in this position while
maintenance personnel
perform the required functions. Further, there is an added safety feature in
that the
maintenance relay cannot be operated when the normal snubbing relay of the
gate control system
is powered. Thus, the maintenance relay can only be used under maintenance
conditions and
when no power is applied to the normal operating circuit of the gate arm
control system.
SUMMARY OF THE INVENTION
The present invention relates to a railroad highway crossing gate mechanism
CA 02255247 1998-12-03
and particularly to its control system and more specifically to a control
system which
includes a maintenance relay for use in raising the gate counterweights in the
event that such
are in a down position due to a broken gate arm.
Another purpose of the invention is a railroad crossing gate arm control
system
as described in which the maintenance relay has a normally open switch in
circuit between its
relay coil and the source of power, with further protection being provided by
a maintenance
safety relay in circuit with the normally open switch.
Another purpose of the invention is to provide a reliable and efficient
electrical
and mechanical mechanism for raising and holding the gate arm counterweights
of a railroad
crossing gate mechanism in the event they are in a failure mode and the
counterweights have
been lowered.
Other purposes will appear in the ensuing specification, drawings and claims.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention is illustrated diagrammatically in the following drawings
wherein:
Fig. 1 is a diagrammatic illustration of a typical railroad highway crossing
gate
mechanism;
Fig. 2 is an enlarged side view, in part section, of the gate motor and the
mechanical elements for raising and lowering the gate;
Fig. 3 is an enlarged section along plane 3-3 of Fig. 2;
Fig. 4 is a diagrammatic illustration of the locking mechanism for holding the
counterweights in a raised position; and
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CA 02255247 1998-12-03
Fig. 5 is a schematic of the control system for the crossing gate mechanism
shown and described herein.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Existing railroad highway crossing gate mechanisms use 4 pole/4 field coil or
2 pole/2 field coil series wound or permanent magnet motors and operate in a
generally
uniform manner using direct current. The present invention will be described
in connection
with a motor having four series wound field coils. The invention is equally
applicable to
other types of motors and to motors having a mixture of permanent magnet and
series wound
field coils.
4 In typical railroad crossing gate mechanisms, the weight of the arm on the
roadway side of the mechanism is offset by heavy counterweights on the
opposite or field
side. The balance is set at installation to favor the arm side as described by
torque
requirements in AAR Manual, Part 3.2.15. This insures that the gate will move
to a down
position whenever there is a power failure. Arm descent is controlled by a
motor power
5 down circuit to a 45 ° position at which time the gate is moved by
gravity to a full down
position, with the down speed during arm descent being controlled by means of
a motor
generated snub circuit. Failure modes may take many forms. The present
invention is
specifically directed to a failure mode resulting from an arm knockdown and
subsequent
rapid descent of the heavy counterweights. The counterweights may move only to
a 45 °
'.0 position in which further lowering of the counterweights is resisted by
the motor power down
circuit. If there is a loss of power, the counterweights may move to a full
down position.
The present invention provides an electrical circuit for raising the
counterweights, once they
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are in a down position and power is available to the gate control system. The
invention
further provides a mechanical stop bar to hold the counterweights in an up
position once they
have been so moved by the electrical control system.
In Fig. 1 the gate arm is indicated at 10 and the counterweights are indicated
S at 12. The gate will move about a point of rotation 14 and will be driven by
a gate control
mechanism and electrical motor with its associated circuit all located within
the housing 16.
The gate structure will rest upon the cor~entional concrete pedestal 18.
As shown in Fig. 2, the point of rotation for the gate indicated at 14 in Fig.
1
is a shaft 22. The motor pinion which will rotate the shaft 22 is indicated at
24. The motor
0 and gear housing is indicated at 26 and it will drive the pinion which will
in turn cause
rotation of the shaft 22 in the appropriate direction to raise or lower the
gate.
Focusing on Fig. 3, the motor and gear frame is indicated at 28 with the
pinion 24 extending out from the frame. There is a mounting plate 30 attached
by bolts 32
to the frame 28 which bolts may be the motor mounting bolts. The cabinet door
for the
housing 16 is shown at 34 and it will be pivoted to the cabinet frame 16 as at
36. A stop bar
is indicated at 38 and Fig. 3 illustrates the unused position of the stop bar.
At one end the
stop bar has a slot 40 which will be engaged with a pivot lug 42. Centrally
located in the
stop bar is a key slot 44 which will be used to hold the bar on one of the
motor mounting
bolts 32.
-0 Fig. 4 illustrates the use of the stop bar 38. Note that the cabinet door
34 is
open whereas in Fig. 3 it was closed. In this instance, the control system to
be described
has raised the counterweights and it is necessary to hold the pinion 24 in
this position to
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CA 02255247 1998-12-03
maintain the counterweights in a raised condition. The stop bar has been moved
from its
Fig. 3 position and the end 46 of the stop bar 40 has been inserted between
two of the gear
teeth of the pinion 24 with the result that the stop bar will prevent rotation
of the pinion in a
direction to lower the counterweights. Thus the stop bar 38 holds the
counterweights in a
S raised position once they have been so moved by the motor through the use of
the control
circuit to be described.
In Fig. S, a terminal board is indicated at 50 and has terminals designated as
1
through 12 with terminals 4, 5, 6, 7 and 10 being pertinent to the present
invention and with
terminals 6, 7 and 10 having contacts, the operation of which will be
described. Terminal 8
is for the flashing light on the gate and terminal 9 is for the gate bell
system. Battery power
is provided to operate the gate and the battery negative terminal is indicated
at 54 and battery
positive terminals are indicated at 56 and 58, with the latter terminal being
designated as the
up terminal. This represents an external control which is closed to apply
battery voltage
when the gate is raised and opened when the gate is lowered. Power down
contacts are
indicated at 60, a pickup circuit is indicated at 62 and an up position hold
circuit is indicated
at 64, both of which are conventional in crossing gate mechanisms.
The motor and snub relay is indicated generally at 66 and includes a relay
coil
68 connected to battery negative through terminal 5 and connected to a battery
positive
terminal through the contacts of terminal 7 on board 50 which as shown in Fig.
5 are open.
?0 The contacts for the motor and snub relay, which are shown in the down or
non-powered
position, consists of four independent contacts, all of which are connected in
parallel. Each
contact has an arm 70, input terminal 72 and 74 and an output terminal 76.
There is a
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snubbing resistor 78 and a power down resistor 80, with the snubbing resistor
being
connected to terminal 10 and to the parallel connected input terminal 74 of
relay 66. The
power down resistor 80 is connected on one side to the G terminal of the two
down coils 82
of motor 52, the two up coils being indicated at 84 and the armature being
designated at 86.
The three terminals for the motor are indicated at G for coil 82, N for the
armature 86 and
H for coil 84.
A maintenance power relay is indicated generally at 90 and has a coil 92
connected through a normally open switch 94 to a maintenance safety relay 96
having a coil
98 and normally closed contacts 100. The coil 98 of the maintenance safety
relay 96 is
connected directly to battery negative at terminal S of board 50 and will be
connected to
battery positive through terminal 7 of board 50. The maintenance safety relay
is connected
in parallel with the coil 68 of the snubbing relay 66. The maintenance relay
90 has a
plurality of parallel contacts, with the input terminals being indicated at
102, the contact
arms being indicated at 104 and the output terminals being indicated at 106
and 108.
Assuming the gate is in a down position, the contacts of terminal 7 on board
50 will be closed and the contacts of terminal 6 will be open. In this
condition, the coil 68
of relay 66 will be connected to battery negative through terminal 5 and to
battery positive
through the closed contacts of terminal 7, to up control battery positive at
58. Thus, relay
66 will be up and each of the input terminals 72 will be connected to an
output terminal 76.
?0 With the relay in that position, battery positive at 56 will be connected
through relay 66 to
the H terminal of coils 84 of motor 52, with the return to battery negative
being through the
N terminal of armature 86 to terminal 5 of board 50. The motor will operate in
the up
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CA 02255247 1998-12-03
direction to raise the gate from essentially a zero degree position to
approximately 89 degrees
or to an almost vertical position. At this point, the contacts of terminal 7
will open and the
hold circuit 64 will maintain the gate in its full raised or vertical
position. Hold circuit 64 is
connected directly across terminals 5 and 7 so that battery power will be
applied to the hold
clear device to maintain the gate in the up position. Note that when coil 68
is powered as
described, coil 98 of maintenance safety relay 96 is also powered, providing
an open circuit
in the circuit path to coil 92 of maintenance power relay 90. Thus even if
switch 94 is
closed, the maintenance power relay will not be activated.
When the gate is to be lowered, the power down contacts 60 will be closed
i0 and hold clear device 64 opens. The contacts of terminal 6 on board 50 will
be closed and
the circuit through the contacts of terminal 7 on board 50 will be open. Relay
66 will have
dropped to the down position. Battery positive is applied from terminal 6 to
power down
resistor 80 to coils 82 of motor 52, with the return to battery negative being
through the N
terminal of armature 86 to terminal 5 of board S0. The gate will be lowered to
an
.5 approximately 45 ° position with the last 45 degrees of movement
being essentially by gravity
with some snubbing being provided by variable resistor 78.
In the event of a failure mode in which the gate's arm is broken and the
counterweights have moved down to a 45 ° position and battery power is
still available at the
crossing gate, and assuming that no power is being applied to the snubbing
relay which
'_0 would mean no power is applied to the maintenance safety relay 96, the
closure of switch 94
by maintenance personnel will cause the contacts of relay 90 to move to the up
position
which will complete a circuit from battery positive at terminal 4 of board 50,
through the
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CA 02255247 1998-12-03
contacts of relay 90, to the G terminal or down coils 82 of motor 52, through
armature 86
and back to battery negative at terminal 5 of board S0. The armature will thus
be driven to
move the counterweights in an up direction. Once the counterweights have
reached an up
position which would be consistent with the arm being in a down position if
the arm were on
the gate, maintenance personnel will then take the stop bar 38 and move it to
the position
shown in Fig. 4, locking the pinion against further movement which holds the
counterweight
in an up position. Maintenance personnel may now make the necessary repairs to
the gate
arm. The counterweights will have been moved up by power, will be held in an
up position
by the mechanical locking bar and the gate mechanism can be fully repaired.
0 The maintenance relay provides an efficient and reliable means for
maintenance personnel to raise the very heavy counterweights when the gate is
in the failure
mode described. The locking bar holds the counterweights in the raised
position. However,
the maintenance relay cannot be operated if power is applied to the snubbing
relay as it
would be in the event the gate is being moved in an up direction. Thus the
maintenance
safety relay provides, as its designation indicates, safety to insure that the
raising of the
counterweights by the maintenance relay will not be activated or operated or
used when the
snubbing relay is otherwise powered and the gate arm would be moving.
Whereas the preferred form of the invention has been shown and described
herein, it should be realized that there may be many modifications,
substitutions and
alterations thereto.
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