IMPROVEMENTS IN PREVENTING OR NEUTRALIZING EARTH OR FOREIGN CURRENTS IN ELECTRIC
Year: 1883

page_text: LETTERS PATENT to John William Fletcher of Stockport in the County
of Chester Telegraph Engineer for an Invention of "IMPROVEMENTS IN
PREVENTING OR NEUTRALIZING EARTH OR FOREIGN CURRENTS IN ELECTRIC
PROVISIONAL SPECIFICATION left by the said John William Fletcher at
the Office of the Commissioners of Patents on the 9th October 1883.
JOHN WILLIAM FLETCHER, of Stockport in the county of Chester, Telegraph
Engineer, IMPROVEMENTS IN PREVENTING OR NEUTRALIZING EARTH OR FOREIGN
CURRENTS IN ELECTRIC TELEGRAPH WIRES AND IN APPARATUS THEREFOR
The object is to counteract or neutralize earth or foreign currents and prevent
them from objectionably affecting the instruments or apparatus used with telegraph
wires. For this purpose I introduce insulators in new positions in certain kinds of
signalling appliances and provide novel means and connections for neutralizing any
unexpected or other earth or foreign current.
In the ordinary three wire railway block signalling apparatus where the working
of the block instrument is from one end only I introduce an insulator in the bridge
spring or its equivalent so as to disconnect the line when the apparatus is not being
used.
In electric telegraph circuits generally where in the normal state the sending
and receiving instruments must be connected and in which the insulators above
described cannot be used, I insert in the line and connect to the line wire, apparatus
for bringing into circuit sufficient current to balance or overcome the earth current.
The said apparatus is coupled to a sufficient number of cells and consists of a drum,
Blide, or equivalent device fitted with spring or other connectors and provided with
an adjusting or controlling handle or button which when moved in one direction
gives a positive or negative current by bringing one or more cells into action, and
the converse when moved in the opposite direction

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said John William Fletcher in the Patent Office on the 9th April
1884.
JOHN WILLIAM FLETCHER of Stockport in the County of Chester, Telegraph
Engineer, "IMPROVEMENTS IN PREVENTING OR NEUTRALIZING EARTH OR FOREIGN
CURRENTS IN ELECTRIC TELEGRAPH WIRES AND IN APPARATUS THEREFOR
"
The object is to counteract or neutralize earth or foreign currents and prevent
them from objectionally affecting the instruments or apparatus used with telegraph
wires. For this purpose I introduce insulators in new positions in certain kinds of
signalling appliances and provide novel means and connections for neutralizing any
unexpected or other earth or foreign current.
In the ordinary three wire railway block signalling apparatus where the working
of the block instrument is from one end only I introduce an insulator in the bridge
spring or its equivalent so as to disconnect the line when the apparatus is not being
used.
Fig 1 of the accompanying sheet of drawings illustrates a method of carrying
the above part of my invention into effect.
a is the transmitting instrument, 6 the receiving instrument, c line wire, & earth
plates e battery, f operating handle and contact maker, g g¹ contact or bridge
spring, insulator to keep the two parts g g¹ of the bridge spring separate so that
the line shall be incomplete when the instrument a is not being used and the
handle is in the position shown. With the above arrangement of parts earth
currents cannot pass when the instrument is not in use and false signals are thereby
prevented.
In electric telegraph circuits generally, where, in the normal state, the sending
and receiving instruments must be connected, and in which the insulators above
described cannot be used I insert in the line, and connect to the line wire, apparatus
for bringing into contact sufficient Battery current to balance or overcome the earth
current. The said apparatus is coupled to a sufficient number of cells and consists
of a drum slide or equivalent device fitted with spring or other connectors and
provided with an adjusting or controlling handle or button which when moved in
one direction gives a positive or negative current by bringing one or more cells into
action and the converse when moved in the opposite direction.
Fig 2 is a plan, fig 3 an elevation, and fig 4 a longitudinal section of apparatus
under my invention for use in electric telegraph circuits generally 1. 1 line wire
connected to the bearings 2. 2" which carry the end spindles 3. 3* of the drum 4.
The drum 4 is made of non conducting material and the interior carries electrical
conductors. 5. 5* separated by insulating material 6. The end spindles 3. 3° are in
metallic contact with the conductors 5. 5° respectively. Secured to the drum at
one end are contact pieces 7. 7* in metallic connection with the conductors 5. 5*
respectively and at the other end semi ring pieces 13 and 13° are also in contact
with the conductors 5. 5° respectively. 8. 8° 9.9° 10. 10° 11. 11° 12. 12° are contact
pieces in connection with the conductors 5. 5* respectively. 14 are insulating
pieces between the semi rings 13 and 13. 7b8byb 10° 11° 12° and 13° are springs
for making contact with the pieces 7. 7" 8. 8* 9. 9* 10 10 11. 11 and 12. 12 and
semi rings 13. 13. 15. 16. 17. 18. 19 and 20 are cells in which the zinc of 15 is
connected to the spring 7b and the copper of 20 to the spring 13. The zincs and
coppers of the intermediate cells are connected together and to the springs 8b 9b 10b
11 and 12b. 21 is a contact stud connected to the conductor 5* in such position
that when the spring 13b is on the insulating piece 14 the spring 22 attached to the
bearing 2 and line wire 1 is in contact with the said piece 21. 23 ratchet and click
mechanism to retain the drum in position, 24 gearing for giving motion to the
indicating dial 25.

page_text: The action of the apparatus is as follows in its normal position. The spring 22
is in contact with the stud 21 and there is electrical connection between the line
wire 1. 1 through the conductor 5ª and spindle 3* and bearing 2. As long as the
line is in equilibrium or no current passing the position of the apparatus remains
unchanged, but should an earth or other irregular current pass through or affect
the wire the drum 4 is turned to the right or left by the knob 26 until the number
of cells required to neutralize the action of the current are duly thrown into
circuit. Say a positive current of the strength of three cells is required, then the
drum is turned until the piece 10 is in contact with the spring 10b and the spring 13b
with the semi ring 13*. A current then flows along the line wire 1 through the
bearing. 2. end spindle, 3. conductor, 5. contact piece, 10. spring 10%. cells 18. 19. 20.
spring 13 semi ring 13" core 5ª end spindle 3* and bearing 2* to the line 1: should
a negative current of the same strength be required the drum is turned in the
opposite direction until the spring 10b rests on the contact piece 10" and the
spring 13 on the semi ring 13.
Fig 5 is a front elevation, fig 6 a plan and fig 7 a side elevation of a modification
of my improved apparatus also for use in telegraph circuits generally. In this
modification a disc 4 is used instead of a drum. 1. 1° line wire connected to the
bearings 2.2 3. 3° end spindles attached to the semi disc conductors 5. 5 and 7.7*
respectively, the conductors 5 and 7* are formed with contact pieces as shown.
7 8 9 10 11 12 13b springs attached to a battery in the manner setforth in
respect of figs 2. 3. 4. 21 contact studs on 7. 22 spring attached to the bearing 2.
23 ratchet mechanism. 24 dial.
The action of the apparatus is as follows. In the normal position when the line
is balanced or undisturbed there is electrical connection from the line wire 1 through
one of the studs 21 and conductors 7* and 7 spindle 3ª and bearing 2* to the line 1*.
If the disc is moved in one or other direction a piece on one or other of the
conductors 5.7* comes in contact with one on other of the springs 7b 8b 9b 10° 11° 12°,
and one or other of the pieces 5* 7 comes in contact with the spring 13b. One or
more cells of the battery is or are consequently thrown into circuit either in one
direction or the other as required.
It will be obvious that instead of a disc or drum a slide might be used but not
so advantageously.
Having now described and illustrated the said invention in such manner that
others will be enabled to carry my improvements into effect I claim:-
First. In telegraph circuits worked from one end only, introducing an insulator
substantially in the manner and for the purpose setforth.
Second. In telegraph circuits generally apparatus constructed substantially in
the manner and for the purpose setforth
Third. The combination in telegraph circuits generally of a drum disc slide or
equivalent, contact makers and a battery connected and arranged to operate
substantially as herein setforth.
In Witness Whereof I the said John William Fletcher have hereunto set my
hand and seal this Fourth day of April in the year of Our Lord, one thousand
eight hundred and eighty four,
TTRACTED
(OTT)
ADOLAT TA ON
Witness
E. EDMEAD.
L & NW Rly Co
Manchester.