FIELD OF INVENTION
The invention generally relates to electro-magnetic relays. More particularly, the
invention relates to an electro-magnetic current relay with improved electrical
reset and latch means adapted to Diesel Electric Locomotives for detection of
ground fault.
BACKGROUND OF THE INVENTION
In diesel electric locomotives, electro-magnetic relay for sensing of leakage
current is used, which has elaborate mechanical latching and reset mechanism.
The existing current relays used for sensing of leakage current is fitted with
mechanical latching and reset mechanism. The mechanical mechanism suffers
from mal-functioning in reset and latch operation.
The existing reset and latch system is mechanical. When the relay is energized,
the armature moves which operates the connected lever which gets mechanically
latched. Thus, when the relay is de-energized, contacts remains in ON states.
Reset is achieved by a mechanical knob attached to the relay, which is pushed
manually to release the lever from the latch mechanism. The existing latch
systems are therefore unreliable and cumbersome. Further resetting is
performed by a mechanical means. Accordingly, the existing systems are prone
to failure and lack reliability. The systems are complex and need regular
maintenance.

OBJECTS OF THE INVENTION
It is therefore an object of the present invention to propose an electro-magnetic
current relay with improved electrical reset and latch means, which eliminates
the disadvantages of the prior art.
Another object of the present invention is to propose an electro-magnetic current
relay with improved electrical reset and latch means, which enables remote reset
of the current relay.
Yet another object of the present invention is to propose an electro-magnetic
current relay with improved electrical reset and latch means in which the relay
can be mounted any where in the panel independent of location of the reset
means.
A still another object of the present invention is to propose an electro-magnetic
current relay with improved electrical reset and latch means, which is simple and
achieves reliable latch of the relay.
A further object of the present invention is to propose an electro-magnetic
current relay with improved electrical reset and latch means, which provides a
simple mounting arrangement of the relay in place of a cumbersome front
mounting arrangement.

SUMMARY OF THE INVENTION
Accordingly, there is provided an electro-magnetic current relay with improved
reset and latch means adaptable in Diesel Engine locomotives for detecting of
current leakage, the improvement by comprising a pole piece having a groove
mounted on the basic current relay the operating coil of the relay is mounted
over the pole piece; a spring loaded armature supporting a plurality of moving
contacts operable during reset and latch operation; a reset and latching means
comprising a reset coil a spring, a latch a latch support and a latch lever the
reset coil having at least one groove internally configured, the armature on
activation by a flow of current exceeding a preset value via the operation coil,
causes a downward movement of the latch lever thereby pushing the reset coil
into the groove for lockable engagement, the reset coil when energized by an
external circuit, the reset coil is pushed back resulting in release of the latch
lever from the engagement state thereby resetting the relay.
The inventive electro-magnetic current relay with improved electrical reset and
latch means, is used for detection of leakage current in

Diesel Electric Locomotives. However no change has been incorporated in the
basic relay. A groove is provided in the spring-loaded plate. The lever attached to
the armature of the relay gets latched in to it on energizing the relay. The steel
plate works as an armature for the reset coil fitted next to it. When the coil is
energized, it pulls back the steel plate so that the armature of the main relay is
released from the latch. The rest coil can be energized remotely.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 - Shows a front view of a current relay according to the prior art.
Figure 2 - Shows a plan view of the current relay of prior art.
Figure 3 - Shows the electro-magnetic current relay with improved reset and
latch means according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION
The detail description of the invention is explained below:
a. The prior art relay
Existing current relay (R) is shown in Figures 1 and 2. The relay (R) is
built on a relay base (1). A pole piece (5) is mounted on the relay base (1)
and an operating coil (2) along with a core (3) and a fixed finger block (6)
are mounted over it. An armature (4) is spring-loaded and supports a

plurality of moving contacts. The armature (4) and the moving contacts
operate during latch and rest operations.
A reset means (8, 9, 10, 11) is built over a reset support (7). When a
leakage current flows through the operating coil (2) and the value of the
current exceeds a preset value, the reset means operates. An indicator
(13) provided on the relay base (1) points to a red dot (14). The reset
means consisting of a reset rod (8), a spring (9), a guide plate (10). And a
roller and roller carrier (11) together keep the relay in latched condition
and does not allow the relay (R) to come back to reset position.
For resetting the relay (R), a reset knob (12) is pressed which activates
the roller carrier (11) through the reset rod (8), which releases the
armature (4) from the latch (11) and the relay (R) comes to its original
position.
b. Improved configuration of the current relay according to the
invention
The basic current relay designed has been retained as per the prior art,
and only the latch and reset means has been improved. The current relay
with electrical reset and latch means of the present invention is shown in
Figure 3. Following modifications have been incorporated in the existing
relay to achieve improved effect.
i. The relay base (1) including its cover has been eliminated.

ii. The reset means consisting of the reset rod (8), the spring (9),
the guide plate (10), the roller and roller carrier (11), the reset
knob (12), and indicator (13) have been eliminated.
iii. A new pole piece (15) has been provided to mount the reset
means.
iv. An electrical reset and latching means consisting of a reset coil
(16), a spring (17), a latch (18), a latch support (19) and a
latch lever (20) have been reconfigured and added in the
assembly.
c. Operating method of the invention
The current relay (RI) will operate on flow of the current in its coil (2)
exceeding specified value as in the existing relay (R). The armature (4) of
the relay (RI) will move up resulting in downward movement of the latch
lever (20), which will push the reset core (16) and will engaged in a
groove (G) provided in it. Since the reset core (16) is spring loaded, the
latch lever (20) will not be released until the core (16) is pushed back.
Thus, the relay (RI) will get latched in operated position. To reset the
relay (RI), the reset coil (16) is energized with an external circuit, which
attracts the reset core (16) and thereby the core (16) is pushed back
resulting is release of the latch lever (20). Thus, the relay is reset and
comes back to its normal position. In the proposed system, the relay (RI)
can be reset from any remote location by pressing a push button
connected in the energizing circuit of the reset coil (16).
WE CLAIM
1. An electro-magnetic current relay with improyed reset and latch means
adaptable in Diesel Engine locomotives for detecting of current leakage,
- a pole piece (15) having a groove (a) mounted on the basic current relay
(RI), the operating coil (2) of the relay (RI) is mounted over the pole piece
(15);
- a spring loaded armature (4) supporting a plurality of moving contacts
operable during reset and latch operation;
- a reset and latching means comprising a reset coil (16), a spring (2), a
latch (18), a latch support (9), and a latch lever (20),
characterized in that:
- the armature (4) on activation by a flow of current when exceeding a
preset value via the operation coil (2), causes a downward movement of
the latch lever (20) thereby pushing the reset coil (16) into the groove (a)
for lockable engagement, and wherein the reset coil (16) when energized
by an external circuit, the reset coil (16) is pushed back resulting in
release of the latch lever (20) from the engagement state thereby
resetting the relay (RI), and wherein the relay is resettable from a remote
location.
2. An electro-magnetic circuit relay with improved reset and latch means
adaptable to Diesel Engine locomotives for detecting current leakage as
substantially described herein with reference to the accompanying
drawings.