Year: 1898

page_text: Date of Application (in United Kingdom), 20th May, 1898
Complete Specification Left, 18th Feb., 1899-Accepted, 25th Mar., 1899
I, HARRY PHILLIPS DAVIS, of 327, Neville Street, Pittsburg, in the County of
Allegheny, State of Pennsylvania, United States of America, Electrical Engineer,
do hereby declare the nature of this invention to be as follows:-
-
My invention relates to mechanism for controlling the operation of electrically
propelled vehicles and particularly to electrically operated braking mechanism
for such vehicles.
The object of my invention is to provide means whereby apparatus of the
character specified may be controlled more readily and operated more effectively
than has been possible with apparatus which has heretofore been generally em-
ployed for this purpose.
I have found in practice that under certain conditions of operation, as, for
example, when the rails are wet or coated with mud, ice or snow, and current is
applied to brake magnets connected in series with a plurality of motors acting
as generators, one of the brake shoes is liable to stick and thus completely stop
the revolution of the corresponding truck wheels. If the controller is thrown
to the emergency braking position, this liability is particularly great. While
this condition will stop the supply of current from the armature geared to the
wheels that have ceased to revolve, the other armature will furnish current to
both brake magnets and thus serve to prevent any rotation of the sliding wheels.
It will be readily seen that under such conditions no control whatever can be
had over the sliding wheels either electrically or by means of a hand brake.
I propose to obviate this difficulty by placing a brake magnet in each armature
circuit; then, if one pair of wheels is prevented from revolving by reason of
excessive friction of the corresponding brake and lack of friction between the
wheels and the rails, the corresponding armature will not only cease to supply
current to its brake magnet, but the armature of the other motor will supply
current to said magnet which will be opposite in direction to the magnetizing current
normally supplied to it. The brake shoe will thus be demagnetized and
the wheels released. The released wheels will then begin to revolve and cause
the corresponding armature to supply magnetizing current to its brake magnet.
If the brake should again stick, this operation would be repeated and the car be
thus kept under perfect control.
I provide also an automatic demagnetizing switch which serves to throw the

page_text: brake magnets into circuit when the power current is shut off and to cut them
out of circuit when the power current is again supplied to the motors.
In the accompanying drawings Figure 1 is a diagram of an electrically pro-
pelled car equipment containing my invention. Figure 2 is a side elevation of
the demagnetizing switch forming a part of the equipment shown in Figure 1,
the enclosing casing or box of the switch being in section. Figure 3 is a plan
view of the demagnetizing switch and its box, the cover of the latter being
removed. Figure 4 is a diagram of the circuits corresponding to the various
positions of the controller drum.
+
Referring particularly to Figures 1, 2 and 3, the surface of the controller drum
is shown as developed into a plane, the working positions on the same being
indicated by the spaces between the broken lines. The spaces designated by
numerals 1 to 13 are the operative positions on the power side of the controller
drum, and the spaces designated by the letters A B C D E and F are the
operative positions on the brake side of such drum. The contacts G, C, C1, C2,
B, R2, R, R, R, R7 and T, which will be hereinafter designated as the main
stationary contacts, co-operate respectively with the contact strips on the drum
in horizontal alignment therewith. The contacts C and R also engage and co-
operate with the strips on the drum in horizontal alignment therewith and will
hereinafter be designated as auxiliary stationary contacts.
It will be readily seen that the relative positions of the main and auxiliary
contacts is such that when the former are in position 1 on the drum, the latter
will be in position 9, and that when the former are in position A, the latter will
be in position 5. If this relation be borne in mind, the circuits corresponding
to the various positions of the drum may be traced without difficulty.
A set of supplemental stationary contacts L and two sets of movable contacts P
and B are also employed for the purpose of securing the desired relation of
motors and co-operating apparatus. The contacts and B are preferably
mounted upon a drum which is either rigidly attached to the shaft of the main
drum or is geared thereto in any usual and well known manner, so that the con-
tacts L and P will be in engagement when the main drum is in position to
supply line current to the motors, and so that the contacts L and B will be in
engagement when the main drum is in any one of the braking positions. The
resistance R for the circuits is rendered variable by dividing it into five parts,
r, 1, 2, 3 and r¹, as is usual in equipments of this general character. A blow-
out magnet K may also be employed, if desired. The two motor field magnets
forming parts of the equipment are designated as F and Fa, and the correspond-
ing motor armatures as A and A2. M and M2 are the brake magnets which are
respectively in circuit with the armatures A¹ and A².
When the controller drums are in any one of the braking positions, a local
circuit is established which contains two parallel branches each of which con-
tains a motor and a corresponding brake magnet. An equalizing wire connects
the branches between the field magnets and the armatures, and the connections
between corresponding ends of the branches also have equalizing functions.
In order to demagnetize the brake magnets when no braking effect is desired,
I provide an automatic switch enclosed in a box M, the construction of which
is as follows. m is an electro magnet one terminal of the coil of which leads to
the trolley or otherwise connects with the source of current employed for actuat-
ing the motors, the other terminal of the coil being connected with the conductor
leading to the blow-out magnet K and thence to the contact T.
Pivotally mounted longitudinally in the box M is a bar H which has fastened
to its under side a transversely extending bar or plate H¹. One end of the
bar H¹ is provided with an armature a, which is directly over the magnet m.
and the other end of said bar is connected to the bottom of the box M by means of
a coiled springs, which serves to hold the armature a out of contact with the
poles of the magnet m when the latter is not energized. The bar H is provided
at one end with a contact plate or strip i which extends transversely in both

page_text: directions, and at its opposite end with a similar plate or strip ¹. The end of
the box M corresponding to the strip is provided with terminals t, t, t, the
terminal t being permanently connected to the contact strip i, and the terminal 1ª, t*
projecting inside the box in such position as to be engaged by the corresponding
ends of the strip i. The other end of the box is provided with similar ter-
minals, 3 and 5, which are correspondingly related to the strip 2¹.
The relation of the circuits and the operation of the apparatus is as follows,
reference being had to Figure 4 of the drawings in connection with the preceding
figures.
Assuming that the controller drum is rotated to bring the main stationary
contacts into position 1, and the contacts P into engagement with the contacts L,
the magnet m of the demagnetizing switch will attract its armature a and thus
rock the bar H to separate the strips i and i¹ from the terminals and to and
bring them into engagement with the terminals and 3. The circuits of the
brake magnets M and M2 will thus be broken and the conductors d and d¹ in-
serted in lieu thereof. In this position the two motors will be in series with all
of the resistance R in circuit. In position 2 sections r and r of the resistance
are short-circuited, the other portions of the resistance and the motors remaining
in series. In position 3 resistance sections r, 1 and 2 are short-circuited, leaving
the remaining resistance sections and the two motors in series. In position 4 all of
the sections of the resistance except r are short-circuited and that section and the
two motors are in series. In position 5, all of the resistance is cut out or short-
circuited, leaving the two motors in series without resistance. In position 6,
the resistance section is reinserted. In position 7 resistance sections 2,3
and are inserted and motor A2, F2 is cut out. Position 8 is the same as
position 7. In position 9 resistance sections and r¹ are cut out, the two motors
being connected in parallel with the remaining portion of the resistance in circuit.
Position 10 is the same as position 9. Position 11 differs only in the short-
circuiting of the additional section of the resistance. In position 12 all of the
resistance except the portion is short-circuited and in position 13 the motors
are in parallel with all of the resistance cut out or short-circuited, this being the
final running position on the power side.
In order to stop the car, the controller drum is reversed until the main
stationary contacts are in position A, and the contacts B₁ are in engagement
with contacts L. As soon as stationary contact T leaves position in the
reverse movement of the drum, the magnet m of the demagnetizing switch will
be de-energized and the spring s will throw the strips i, into contact with ter-
minals tand, so that when position A is reached, the brake magnets M¹ and M²
will be respectively in circuit with motors A¹, F1 and A2, F2.
When the stationary contacts are in position A all of the resistance R is in
the local circuit which includes the motors and brake magnets, as will be readily
seen by referring to Fig. 4. The momentum of the car acquired from the motors
or by reason of a down grade, or both, will now serve to drive the motors as
generators, and each will energize its brake magnet to a degree determined by
the speed of rotation of the armature and the amount of resistance in circuit. A
further braking effect is produced by moving the controller drum to bring the
main contacts to position B, thus short-circuiting the resistance section r. In
position C resistance sections r, 1 and 2 are short-circuited and in position E all
of the resistance except the portion 4 is short-circuited. In position F none of
the resistance is in circuit, this being the maximum or emergency braking
position.
It will be readily seen that each armature normally supplies current to its
own brake magnet only and that if the conditions are such as to stop the rota-
tion of either armature, the other armature will send a demagnetizing current
through the brake magnet corresponding to the non-rotating armature and thus
effect the release of the corresponding truck wheels, as has already been
pointed out.

page_text: I desire it to be understood that my invention is in no wise limited as regards
structural details or the relative location of the apparatus employed.
Dated this 20th day of May 1898.
W. P. THOMPSON & Co.,
322, High Holborn, London, W.C., Patent Agents for the Applicant.
improvement in Electric Brakes.
I, HARRY PHILLIPS DAVIS, of 327, Neville Street, Pittsburg, in the County of
Allegheny, State of Pennsylvania, United States of America, Electrical Engineer,
do hereby declare the nature of this invention and in what manner the same is
to be performed to be particularly described and ascertained in and by the
following statement:―
My invention relates to mechanism for controlling the operation of electrically
propelled vehicles and particularly to electrically operated braking mechanism
for such vehicles.
The object of my invention is to provide means whereby apparatus of the
character specified may be controlled more readily and operated more effectively
than has been possible with apparatus which has heretofore been generally em-
ployed for this purpose.
I have found in practice that under certain conditions of operation, as, for
example, when the rails are wet or coated with mud, ice or snow, and current is
applied to brake-magnets connected in series with plurality of motors acting
as generators one of the brake shoes is liable to stick and thus completely stop
the revolution of the corresponding truck wheels. If the controller is thrown
to the emergency braking position, this liability is particularly great. While
this condition will stop the supply of current from the armature geared to the
wheels that have ceased to revolve, the other armature will furnish current to
both brake-magnets and thus serve to prevent any rotation of the sliding wheels.
It will be readily seen that under such conditions no control whatever can be
had over the sliding wheels either electrically or by means of a hand brake.
I propose to obviate this difficulty by placing a brake-magnet in each armature
circuit; then, if one pair of wheels is prevented from revolving by reason of
excessive friction of the corresponding brake and lack of friction between the
wheels and the rails, the corresponding armature will not only cease to supply
current to its brake-magnet, but the armature of the other motor will supply
current to said magnet which will be opposite in direction to the magnetising
current normally supplied to it. The brake-shoe will thus be demagnetised and
the wheels released. The released wheels will then begin to revolve and cause
the corresponding armature to supply magnetising current to its brake-magnet.
If the brake should again stick, this operation would be repeated and the car be
thus kept under perfect control.
I provide also an automatic demagnetising switch which serves to 'throw the
brake magnets into circuit when the power current is shut off and to cut them
out of circuit when the power current is again supplied to the motors.
In the accompanying drawings Figure 1 is a diagram of an electrically pro-
pelled car equipment containing my invention. Figure 2 is a side elevation of
the demagnetising switch forming a part of the equipment shewn in Figure 1,
the enclosing casing or box of the switch being in section. Figure 3 is a plan
view of the demagnetising switch and its box, the cover of the latter being

page_text: removed. Figure 4 is a diagram of the circuits corresponding to the various
positions of the controller drum.
Referring particularly to Figures 1, 2 and 3, the surface of the controller drum
is shewn as developed into a plane, the working positions on the same being
indicated by the spaces between the broken lines. The spaces designated by
numerals 1 to 13 are the operative positions on the power side of the controller
drum, and the spaces designated by the letters A B C D E and F are the
operative positions on the brake side of such drum. The contacts G, C, C¹, C³,
B, R², R, R³, R6, R7 and T, which will be hereinafter designated as the main
stationary contacts, co-operate respectively with the contact strips on the drum
in horizontal alignment therewith. The contacts C and R³ also engage and co-
operate with the strips on the drum in horizontal alignment therewith and will
hereinafter be designated as auxiliary stationary contacts.
It will be seen that from the position marked A to the position 1 there is a
blank space equal to about three times the width of one of the positions. The
main contacts T, R7, etc., are opposite the middle of this blank space when the
supplementary contacts C³ are in position 7. If the drum be rotated so that T,
etc., come to position 1, R³ will come to position 9, if, on the other hand, the drum
be rotated in the opposite direction so that T comes to position A, R³ will come to
position 5. If the drum is operated so that T comes to position 11, R³ will come
to position A, and when T comes to position 12, R will be opposite the first blank
space, beyond position A, that is to say, towards the extreme right of the draw-
ing. When T comes to position 13, R3 will be opposite the second blank space
beyond A, that is at the extreme left of the figure. With controllers as ordinarily
constructed the drum cannot be moved further in this direction, and in order to
bring the main contacts T, etc., opposite the braking positions, it must be turned
back again and from what has been said above it is clear that when T is at C,
R3 will be at 3, when T is at E, R³ will be at 1, when T is at F, R³ will be in the
first blank space after 1. If this relation be borne in mind, the circuits corre-
sponding to the various positions of the drum may be traced without difficulty.
A set of supplemental stationary contacts L and two sets of movable contacts P
and B are also employed for the purpose of securing the desired relation of
motors and co-operating apparatus. The contacts P and B are preferably
mounted upon a drum which is either rigidly attached to the shaft of the main
drum or is geared thereto in any usual and well known manner, so that the con-
tacts L and P will be in engagement when the main drum is in position to
supply line current to the motors, and so that the contacts L and B will be in
engagement when the main drum is in any one of the braking positions. The
resistance R for the circuits is rendered variable by dividing it into five parts,
1, 71, 72, 73 and rt, as is usual in equipments of this general character. A blow-
out magnet K may also be employed, if desired. The two motor field magnets
forming parts of the equipment are designated as F1 and F2, and the correspond-
ing motor armature as A1 and A2. M and M² are the brake magnets which are
respectively in circuit with the armatures A¹ and A².
When the controller drums are in any one of the braking positions, a local
circuit is established which contains two parallel branches each of which con-
tains a motor and a corresponding brake-magnet. An equalising wire connects
the branches between the field magnets and the armatures, and the connections
between corresponding ends of the branches also have equalising functions.
In order to demagnetise the brake-magnets when no braking effect is desired,
I provide an automatic switch enclosed in a box M, the construction of which
is as follows: m is an electro-magnet, one terminal of the coil of which leads to
the trolley or otherwise connects with the source of current employed for actuat-
ing the motors, the other terminal of the coil being connected with the conductor
leading to the blow-out magnet K and thence to the contact T.
Pivotally mounted longitudinally in the box M is a bar H which has fastened
to its under side a transversely extending bar or plate H¹. One end of the

page_text: bar His provided with an armature a, which is directly over the magnet m,
and the other end of said bar is connected to the bottom of the box M by means of
a coiled springs, which serves to hold the armature a out of contact with the
poles of the magnet m when the latter is not energised. The bar H is provided
at one end with a contact plate or strip i which extends transversely in both
directions, and at its opposite end with a similar plate or strip . The end of
the box H corresponding to the strip is provided with terminals t, t, t, the
terminal being permanently connected to the contact strip i, and the terminal, t
projecting inside the box in such position as to be engaged by the corresponding
ends of the strip i. The other end of the box is provided with similar ter-
.minals, and, which are correspondingly related to the strip ..
The relation of the circuits and the operation of the apparatus is as follows,
reference being had to Figure 4 of the drawings in connection with the preceding
figures.
Assuming that the controller drum is rotated to bring the main stationary
contacts into position 1, and the contacts P into engagement with the contacts L,
the circuit will be as follows:
From the trolley or other device for introducing the current through the magnet
coil m to the contact T and from the strip on the controller in connection with T
to the strip opposite the terminal R2 thence through the resistances r, 1, 2, 3,
to the terminal R' from the terminal R to the topmost contact L through
the top bar of the bars P thence to the fifth bar P to the
fifth contact L through the field-magnet coil Fl of the first motor
to the third contact Ľ to the third bar P from thence to the fourth
bar P to the fourth contact L through the armature A of the first
motor, the terminal t through the bar i, the terminal t, the brake-magnet M¹ to
the terminal C, the terminal C³ the strip on the controller drum opposite to the
terminal C3 to the terminal C¹ to the seventh contact L, the field-magnet F of
the second motor, the second contact L, the second bar P, the sixth bar P, the
sixth contact L, the armature A2 of the second motor, the terminal t¹, the bar i¹,
terminal 5, brake-magnet M³ and terminal G which is connected to the other
main. The magnet m of the demagnetising switch being energised will attract
its armature a and thus rock the bar H to separate the strips from the ter-
minals and to and bring them into engagement with the terminals 12, 13. The
circuits of the brake-magnets M, M2 will therefore be broken at once and the
conductors d, d inserted in lieu thereof. In this position, therefore, the two
motors will be in series with all of the resistance R in circuit as shewn in the
first diagram of Figure 4. In position 2 sections and r of the resistance are
short-circuited, the other portions of the resistance and the motors remaining in
series. In position 3 resistance sections r, r¹ and 2 are short-circuited, leaving
the remaining resistance sections and the two motors in series. In position 4 all
of the sections of the resistance except are short-circuited and that section and
the two motors are in series. In position 5 all of the resistance is cut out or
short-circuited, leaving the two motors in series without resistance. In position 6
the resistance section is reinserted. In position 7 resistance sections r², guit
and are inserted and motor A2, F2 is cut out. Position 8 is the same as posi-
tion 7. In position 9 resistance sections ? and r¹ are cut out, the two motors being
connected in parallel with the remaining portion of the resistance in circuit.
Position 10 is the same as position 9. Position 11 differs only in the short-cir
cuiting of the additional section 2 of the resistance. In position 12 all of the
resistance except the portion is short circuited and in position 13 the motors are.
in parallel with all of the resistance cut out or short-circuited, this being the
final running position on the power side.
In order to stop the car, the controller drum is reversed until the main
stationary contacts are in position A, and the contacts B¹ are in engagement
with contacts I. As soon as stationary contact T leaves position 1 in the
reverse movement of the drum, the magnet m of the demagnetising switch will
be de-energised and the spring s will throw the strips, into contact with ter-

page_text: minals 't and t³, so that when position A is reached, the brake-magnets M¹ and M³
will be respectively in circuit with motors A', F¹ and A³, F. The circuit will
be as follows: Beginning at the terminal R which is at the end of the
resistance the circuit is through the whole of the resistance R to the terminal R²,
the strip of the controller drum opposite said terminal, the strip of the controller
drum opposite the terminal B, to the terminal G; from thence the circuit divides
one branch going direct through the brake-magnet M², terminal to, bar 2, ter-
minal through the armature A2 of the second motor to the sixth terminal of
the series L; said sixth terminal is connected through the last four of the
strips to the junction of the armature A' and the field-magnet F and also to
the end of the field-magnet F2; through the field-magnet F2, the circuit travels
to the second terminal L, thence through the first two of the strips B¹ to the first
terminal of the series L and direct to the terminal 17 again. From the ter-
minal G the circuit will also pass through the strips of the controller drum oppo-
site the terminals G and respectively, through the brake-magnet M¹, the
terminal, the bar i, the terminal t, the armature A¹ of first motor, the fourth
terminal of the series L through the lower four of the strips B¹ to the end of the
field-magnet F¹, and to the end of the armature A2 and to the end of the field-
magnet F2; after passing through the field-magnet F the circuit will pass to
the other end of the field magnet F2 to the first of the series of terminals L and
direct to the terminal R7. It will therefore be seen that the circuit is the same
as shewn in the position A of Figure 4. The field-magnet, armature and brake-
magnet are joined in parallel with the field-magnet, armature and brake-magnet
of the second motor also the common terminal of the field-magnet and armature
of the first motor are joined to the common terminal of the field-magnet and
armature of the second motor. These two groups of apparatus connected in
parallel are further joined in multiple with the whole of the resistance R.
The momentum of the car acquired from the motors or by reason of a down
grade, or both, will now serve to drive the motors as generators, and each will
energise its brake-magnet to a degree determined by the speed of rotation of the
armature and the amount of resistance in circuit. A further braking effect is
produced by moving the controller drum to bring the main contacts to position B,
thus short-circuiting the resistance section r. In position C resistance sections r
and rare short-circuited, in position D resistance sections r, r¹ and 2 are short-
circuited and in position E all of the resistance except the portion is short-
circuited. In position F- none of the resistance is in circuit, this being the
maximum or emergency braking position.
It will be readily seen that each armature normally supplies current to its
own brake magnet only and that if the conditions are such as to stop the rota-
tion of either armature, the other armature will send a demagnetising current
through the brake magnet corresponding to the non-rotating armature and thus
effect the release of the corresponding truck wheels, as has already been
pointed out.
I desire it to be understood that my invention is in no wise limited as regards
structural details or the relative location of the apparatus employed.
Having now particularly described and ascertained the nature of my said in-
vention and in what manner the same is to be performed I declare that what I
claim is
1. For an electrically propelled vehicle, a braking apparatus in which the
brakes are applied to the wheels by the agency of electro-magnets supplied with
current from the motors when they are cut off from the current supply main
and through the momentum of the vehicle act as generators, and further charac-
terised by the arrangement that each brake-magnet is connected in series with
one of the motors the said motors and brake-magnets being connected in parallel
whereby one motor cannot supply current in the proper direction to any other
than its corresponding brake-magnet.

page_text: 2. In a braking apparatus of the kind described, an electro-magnetically
actuated switch which cuts out the brake-magnets thereby releasing the brakes
when and as long as the motors are connected to the current supply main, being
controlled by a spring so as to cut in the brake-magnets as soon as the power
current is cut off from the motors.
3. The improved electric-braking apparatus constructed and operating sub-
stantially as described.
Dated the 18th day of February 1899.
W. P. THOMPSON & Co.,
Of London, Liverpool, Manchester, and Birmingham.