Railway switches and signals – Electric actuation – Switch signals
Reexamination Certificate
1998-09-08
2001-02-13
Le, Mark T. (Department: 3617)
Railway switches and signals
Electric actuation
Switch signals
C246S401000, C246S476000
Reexamination Certificate
active
06186448
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to an electric motor driven switch machine for switching railroad tracks so that trains may switch from one track to another. More particularly, the present invention relates to a captive point detection system of a switch machine, for detecting, with a single switch position target, whether a railroad track has been properly switched, in order that such detection may indicated by indication means positioned locally at the switch machine or at a remote location.
2. Description of the Related Art
As is known in the art, a common method for switching a train from one railroad track to another is to install an electric motor driven switch machine next to a switching point of the track. Since modern versions of these switch machines are usually operated from a remote location, it is essential that a remote operator be able to determine that the switch has, in fact, been thrown as requested. Moreover, because switch point closure is imperative to safe railroad train operation, Federal Railroad Administration (FRA) rules and regulations mandate not only that the position of the switch points be mechanically locked to prevent the points from opening during train traffic, but also that the locked position of the switch points be continuously monitored to detect any undesirable movement. A circuit controller that includes a point detection system as an integral part of either a mainline switch machine or a stand-alone unit is used to accomplish this type of switch point monitoring, detection and subsequent indication to the switch machine or remote location.
A related art point detection and indication system is described by U.S. Pat. No. 5,669,587, issued Sep. 23, 1997 in the name of Van Alstine et al, which is hereby incorporated by reference in its entirety. In the Van Alstine et al. reference, there is provided an electric motor driven switch machine for positioning a railroad track at a switching point having rail point detection and indication mechanism. In particular, the detection and indication mechanism has a latch out mechanism that identifies a latch out condition when the railroad tracks are not at, or near, their proper positions before or after switching the railroad tracks. The detection and indication mechanism includes a four bar linkage which comprises a point detector bar, two cam followers, and a link arm assembly. The cam followers, supported in part by the link arm assembly, are connected to two point detector switches, so that the switch machine is operating when either one of these switches is closed or the railroad tracks are being switched.
Referring now to
FIG. 1
herein, there is shown an overhead planar view of a typical related art point detection and indication system
100
housed within a portion of a switch machine
105
, wherein a cover (not shown) of the switch machine
105
has been omitted from the figure. As is commonly known, the switch machine
105
is located adjacent to a set of stock rails having a set of switching rails situated therebetween (not shown). The general structure and positioning of switch machines relative to railroad tracks is known in the art and therefore, is not described in detail.
In the related art, a hand throw lever
110
(partially shown in phantom) is connected to a gear box (not shown) and is utilized typically for manual operation of the switch machine
105
. Of the various components of the switch machine
105
, only the base
115
of the switch machine
105
and the elements relevant to the operation of the related art detection and indication system
100
are shown. The basic design of the related art detection and indication system
100
typically includes a point detector bar
120
and adjacent normal and reverse cam followers
125
,
130
, respectively, which are generally each physically connected to mechanical linkages
135
.
As is known in the art, the point detector bar
120
is a long cylindrical rod positioned perpendicular across the longitudinal axis of the switch machine
105
such that movement by the point detector bar
120
corresponds to movement by switching rails relative to the position of stock rail on either side (not shown). The point detector bar
120
typically passes through a wall
122
and a wall
124
of the switch machine
105
. In
FIG. 1
, the wall
122
faces toward the railroad track (not shown) on a track side
140
and the wall
124
faces away from the railroad track on a field side
145
. Typically, the point detector bar
120
is held in place with threaded adjustment bushings
150
,
155
, and a movable adjustment sleeve
160
that extends outwardly from the wall
122
and the wall
124
into the track side
140
and the field side
145
, respectively. The point detector bar
120
is capable of moving in two opposing directions: a normal direction
165
and a reverse direction
170
. When the point detector bar
120
is moving upward in
FIG. 1
toward the railroad tracks (not shown) on the track side
140
of the switch machine
105
, the bar is moving in the reverse direction
170
; when the point detector bar
120
is moving downward in
FIG. 1
toward the field side
145
of the switch machine
105
, the bar is moving in the normal direction
165
. Typically, a reverse cam
175
is defined at a fixed position on the point detector bar
120
and a normal cam
178
is defined by the movable adjustment sleeve
160
such that the detection and indication system
100
of the related art can identify movement by the switching rails by monitoring the position of the reverse cam
175
with the reverse cam follower
130
and the normal cam
178
with the normal cam follower
125
.
A common problem in the related art electro-mechanical type point detection and indication systems is slack or lost motion in the mechanism that results due to wear over time. Related art point detection and indication systems of an electro-mechanical type typically detect the position of the point detector bar and related locking device using mechanical linkages to operate mechanical contacts, micro-switches, rotary switches, or a similar device. Over time, the mechanical linkages wear, thereby creating slack or lost motion in the mechanism. With undesired slack or lost motion, if the point detector bar should move unintentionally, thereby indicating unsafe switch point movement, the mechanical linkages detecting the internal point detector bar must move a given distance to take up or absorb the lost motion before the mechanical contacts or similar devices are actuated. The result is decreased sensitivity in switch point monitoring, which ultimately may cause an undesirable safety hazard.
Another problem with related art point detection and indication systems is that their design commonly requires the point detector bar to protrude out both sides of the switch machine. The protrusion of the point detector bar typically causes interference with the manual hand throw lever on dual controlled mechanisms. Interference between the hand throw lever and the protrusion of the internal point detector bar creates a pinch point
180
for a manual operator's hands, which is a safety hazard.
Another problem with related art point detection and indication systems is the complex manner that is required for adjusting a two-piece point detector bar that is connected to the switch machine and the track. As shown in
FIG. 1
, the two-piece point detector bar comprising point detector bar
120
and movable adjustment sleeve
160
typically passes through and is held in place by the bearings
150
,
155
. The point detector bar
120
is located on the track side
140
of the switch machine
105
, and the movable adjustment sleeve
160
is located on the opposing track side
145
of the switch machine
105
. The point detector bar
120
must be adjusted first at the fixed independent field side
140
of the switch machine, and then the movable adjustment sleeve
160
must be adjusted, thereby to align the cam followers
125
Brushwood Daniel H.
Wydotis Leonard M.
Eckert Seamans Cherin & Mellott , LLC
Houser Kirk D.
Le Mark T.
Radack David V.
Union Switch & Signal Inc.
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