Improvements in Mechanism for Electric Traction Systems in which the Electric Current is Supplied to the Cars or Locomotives from Studs, Sections of Rails or the like Laid in the Road.
Year: 1897

page_text: Date of Application, 11th June, 1897
Complete Specification Left, 12th Apr., 1898-Accepted, 28th May, 1898
PROVISIONAL DIEVITICATIOA
Improvements in Mechanism for Electric Traction Systems in which
the Electric Current is Supplied to the Cars or Locomotives from
Studs, Sections of Rails or the like Laid in the Road.
We, SILVANUS PHILLIPS THOMPSON, of Morland, Chislett Road, West Hampstead,
and MILES WALKER, of 23, Southcote Road, London, N., Doctor of Science and
Electrical Engineer, respectively, do hereby declare the nature of this invention
to be as follows:--
Our invention relates to automatic switches and safeguards for use in those
systems of electric traction in which the electric current is supplied to the cars
or locomotives from studs or sections of rail laid in the road, each of such studs or
sections of, rail being in turn connected to a main conductor or feeder main by
means of an automatic switch when the car is above or near it and disconnected
from the main conductor or feeder after the car has passed on.
By means of our improvements, we are able to increase the distance between
the road contacts and at the same time to ensure absolute safety in working.
In the Specification of Patent No. 19455 of 1896 we described various automatic
switches, whose action depends on the closing or partial closing of a magnetic
circuit by masses of iron carried in the cars, and which are therefore free from the
risk of being kept closed by current leaking from the road contacts after the
car has gone past. One of our improvements consists in making the initial closing
or partial closing of the switch independent of the closing of the magnetic circuit
by masses of iron on the cars so that the moving parts of the switch may be set
in operation before the skate on the car comes in contact with the stud, and yet so
arranging the circuits that the holding up of the switch when once closed is
dependent upon the said closing of the magnetic circuit, so that the switch operates
sharply before it is called upon to deliver current to the car and yet cannot fail
to open after the car has passed.
One method of doing this is simply to have the moving iron armature of any of
the forms shown in the figures of the above named specification, not exactly at the
position of magnetic balance as there described but displaced some distance.
When current is passed through the coils the displaced armature moves sharply
towards the position of balance and in so doing partially. closes the switch or by
swinging past the point of magnetic balance completely closes the switch for a
short interval of time. When the iron on the car comes over the stud the switch
is completely closed and so held until the car has gone past.
Another method is to wind the "actuating" coil so that it closes the switch as
an ordinary electro-magnet would, independent of any magnetic balance; while
the "
retaining "coil can only hold the switch closed when a mass of iron is
over the switch box, the magnetic balance being effected in any of the ways
described in our said specification.
In order to enable the road contacts to be placed at greater distances apart
we sometimes use a short auxiliary skate parallel to the main skate but fixed at

page_text: the rear end of the latter or at some distance from its fore end. This auxiliary
skate by coming into contact with an auxiliary stud near a switch box closes an
electric circuit having the following path: from the rear end of the main_skate to
the auxiliary skate, from the auxiliary skate to the auxiliary stud, from the
auxiliary stud to the actuating coils of switch next ahead and thence to the car
motor either by means of the main stud next ahead and the fore part of the main
skate (insulated from the rear end), or by means of another auxiliary skate and
stud. In any of the methods described in this specification, where a connection is
carried from a live stud to another stud ahead of or behind the car, care is taken
that such uncoverd stud is wholly disconnected from the live stud when the switch
to which it belongs is open. The essential feature of this method of actuating the
switch next ahead is that such switch is not actuated until a point near the rear of
the car comes over the switch box that is already alive.
The switch is held closed by the retaining coil, connected between the switch
contacts and the main stud, which operates only when a mass of iron is over the
switch box.
In the case or, cases where we employ two auxiliary studs the actuating coil is
connected between these and is wholly disconnected from the main except when
the short auxiliary skates are passing the studs so that it is impossible for current
to leak from these studs after the car has passed.
:-
Another method of operating the switches is the following:-
At each side of the main stud is an auxiliary stud here distinguished as the
right and left stud, respectively. Three skates (extending the full length of the
car if desired) are employed, one resting on each stud. The connections are made
so that the current passes direct from the switch contacts to the middle skate,
thence to the right skate, thence to the right stud, thence through the operating
coil of the, switch and so to the left skate and car motor (or vice versa).
In some cases it is convenient to use three parallel skates and connect the
switch coils between two studs which are only connected to the main cable when
the skates are over the studs, as above described; the main stud, which is joined
by the switch direct to the main cable or feeder, is either set in a separate road box to
these two, or else the lid of the box is so constructed that the metal of the cover
surrounds the main stud and intercepts any leakage current which may pass from
it, thus rendering it impossible for any leakage current to pass through the switch
coils. This main stud may in some cases, be connected to one of the auxiliary ones
by a single wide skate in place of two narrower ones.
With the above arrangement we may use any suitable form of switch, as for
example, any of those described in Specification of Patent No. 19455 of 1896;
or if preferred any of those referred to above and described in Specification of Patent
No. 19455 of 1896.
The switches may further, if required, be interconnected as described in
Specification of Patent No. 19456 of 1896, so that each switch is closed and its
main stud made alive before the skates reach it. Further the coils of these
switches may be arranged either so that the main current passes through them in
series with the car motors, or they may be arranged as shunts to the same.
In some cases we arrange that the switches shall have no permanent inter-
connections among themselves, but shall be temporarily interconnected by suitable
arrangements of skates on the car, in such a way that each switch is closed and its
main stud made alive, before it is necessary to pick up current from it. One
method that, we employ for this purpose is to have two studs, and two parallel skates
divided as hereafter described; the current passes direct from the main cable
through the switch contacts to the auxiliary stud, and the switch coils are
permanently connected between this stud and the main stud.
If the switches are wound for series working, we divide the auxiliary skate into
two parts, insulated from one another; these parts may be either equal or unequal;
the main skate is divided into two parts insulated from one another, the front part
being a little longer than the distance between two road boxes and the back part

page_text: being comparatively short; the front of the auxiliary skate is electrically con-
nected to the back portion of the main skate. The two skates are placed side by
side and their total length is approximately the same, or one may be longer than
the other. The current passes from the main cable or feeder main through the
switch contacts to the auxiliary stud, thence through the switch coils to the
main stud and to the front part of the main skate and from there to the motors.
When this portion of the main skate leaves the stud its front end has already
reached the next stud; its switch however has not yet closed; the current now
passes to the back portion of the main skate, thence to the front portion of the
auxiliary skate, and so to the auxiliary stud of the box in front, through the
switch coils of this box to the main stud of same and so to the front portion of
the main skate and to the motors as before, and this current closes the switch of
this box.
By dividing the main skate into three parts instead of two and putting a suitable
arrangement on the car for altering the electrical connections between the skates,
we work the cars in either direction with the same switches and the same skates.
In this case it is convenient to make the auxiliary skate in two parts that are
approximately equal; and to make the main skate in three parts, the two end ones
being equal and the middle one of such a length that together with one end one
it is a little longer than the distance between two successive road boxes. In which-
ever direction it is required to work,, we connect the back part of the main skate to
the front part of the auxiliary skate, and the front part of the main skate to the
middle part of the main skate. The circuits are then exactly as above. If the
switches are wound for shunt working we use two parallel skates which are longer
than the distance between two successive road contacts. From one of these the
current is taken direct from the main cable and the first stud to the motors and 30
to earth. The switch coils are as before connected between the two studs; and
the shunt current passes through them to the second stud and the second skate,
and so to earth.
In some cases we use one stud only and one skate and connect the switch coils
permanently between this stud and earth, using with this system of connection
one of the forms of switch described in Specification of Patent No. 19455 of 1896.
We use divided skates and shunt wound switches in some cases; the main skate
consisting of a back part longer than the distance between two contact studs or
boxes and a shorter front part; and the auxiliary skate having a long front portion
which is connected to earth and a shorter back portion which is electrically
connected to the front part of the main skate.
Throughout this specification we have spoken of short studs for the road contacts
and skates on the car; but it is obvious that any of the above systems may be
used with long road contacts or rails, and suitable brushes or shoes on the car.
We also have throughout used the word "earth" to signify the return conductor
of whatever form it may be.
1
•
A T
1000
Improvements in Mechanism for Electric Traction Systems in which
the Electric Current is Supplied to the Cars or Locomotives from
Studs, Sections of Rails or the like Laid in the Road.
We, SILVANUS PHILLIPS THOMPSON, of Morland, Chislett Road, West Hampstead,
and MILES WALKER, of 23, Southcote Road, London, N., Doctor of Science and

page_text: Electrical Engineer, respectively, 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:-
Our invention relates to automatic switches and safeguards for use in those
systems of electric traction in which the electric current is supplied to the cars
or locomotives from studs or sections of rail laid in the road, each of such studs or
sections of rail being in turn connected to a main conductor or feeder main by
means of an automatic switch when the car is above or near it and disconnected
from the main conductor or feeder after the car has passed on.
In the Specification of Patent No. 19455 of 1896 we described various automatic
switches, whose action depends on the closing or partial closing of a magnetic
circuit by masses of iron carried in the cars, and which are therefore free from the
risk of being kept closed by current leaking from the road contacts after the
car has gone past. One of our improvements consists in making the initial closing
or partial closing of the switch independent of the closing of the magnetic circuit
by masses of iron on the cars so that the moving parts of the switch may be set
in, operation before the skate on the car comes in contact with the stud, and yet so
arranging the circuits that the holding up of the switch when once closed is
dependent upon the said closing of the magnetic circuit, so that the switch operates
sharply before it is called upon to deliver current to the car and yet cannot fail
to open after the car has passed.
One method of doing this is simply to have the moving iron armature of any
of the forms shewn in the figures of the above named specification, not exactly at
the position of magnetic balance as there described but displaced some distance
When current is passed through the coils the displaced armature moves sharply
towards the position of balance and in so doing partially closes the switch. When
the iron on the car comes over the stud the switch is completely closed and so held
until the car has gone past.
Figure 1 shews the arrangement of the magnetic parts of a switch working
on this principle. P is the plunger connected to the operating mechanism
sufficiently described in one of our former specifications. Q is a loose piece of
iron resting on the top of the operating coil M (which is connected up to the
mains in any of the ways described in our specifications) and g is a guiding peg of
brass which keeps Q in position. When current is passed round the coil M an
attraction occurs between Q and P and P is pulled smartly up to Q, thus setting the
operating parts, of the switch in motion without the aid of the iron skate K. The
motion of P to Q is however not sufficient to close the main switch. Where the
iron skate K comes over the stud S the plunger P together with the piece Q are
moved bodily up towards the skate and in so doing completely operate the switch
in the manner described in our former specification. We do not confine ourselves
to the particular mode here described. We may have Q of any convenient shape
suitable for the other operating iron parts described in our former specification.
The main object we have in view is to make the initial movement of the operating
parts controlled by a strong magnetic force, and the final movement controlled
by the presence of a mass of iron over the switch. Another method is to wind the
actuating coil described in our former specification so that it closes the switch
as an ordinary electromagnet would independently of any magnetic balance as
there described, while the retaining coil can only hold the switch closed when a
mass of iron is over the switch box. The magnetic balance may be effected in
any of the ways described in our said specification.
One advantage of this partial movement of the operating parts without the
presence of the iron over the top is that such partial movement can be made to
remove an earth connection from the stud before the skate comes up. Thus the
studs may be normally earthed when the car has passed them.
A method of connecting the operating coils with the mains and switch contacts
is shown in Figure 2. There are three skates in line with each other K1 K2 K³ and

page_text: alongside of them two other skates K and K5 in line, with each other. When
the car is running in the direction indicated by the arrow, K¹ is connected to K³
and K2 to K+ as shewn.
The main studs are marked S, the auxiliary studs Z. In the position of the
skates shewn in the figure current is passing from the feeder main F, F through
the main contacts C' and C2 of switch No. 1 to S. Thence it passes to K² and K+
and then descending by the auxiliary stud Z of switch No. 2 passes through the
magnet coil M of switch No. 2 operating that switch, and on to S, thence to K³
and K, and so the motors of the car as described in our former specifications.
When it is required to run the car in the opposite direction, instead of the
connections shewn K³ is connected to K and K to K¹.
Another method employing two studs is shown in Figure 4.
We use a short auxiliary skate K10 parallel to the main skate but fixed at the
rear end of the latter or at some distance from its fore end. This auxiliary skate
by coming in contact with an auxiliary stud Z³ near a switch box closes an electric
circuit having the following path: from the rear end K of the main skate to the
auxiliary skate, K10, from the auxiliary skate to the auxiliary stud, Z3, from the
auxiliary stud to the actuating coils M of switch next ahead and thence to the car
motor by means of the main stud next ahead and the fore part K8 of the main
skate (insulated from the rear end). In any of the methods described in this
specification where a connection is carried from a live stud to another stud ahead
of or behind the car, care is taken that such uncovered stud is wholly disconnected
from the live stud when the switch to which it belongs is open. The essential
feature of this method of actuating the switch next ahead is that such switch is not
actuated until a point near the rear of the car comes over the switch box that is
already alive.
Another method of operating the switches, is shewn in Figure 3.
Here the essential feature is that there is no magnetizing coil between the main
stud S and the, feeder. The current is collected from S by the skate K6 and instead
of going direct to the car motor is passed on to an auxiliary stud Z' from this it
passes through the magnetizing coil of the switch then to a second auxiliary stud Z²
from which it is collected by the skate K7. On the arrival at the switch box next ahead
current passes down from Ko to Z of that switch box to operate the switch. It
is advisable to make skate K in two parts and adjust one part to make contact
with S and the other to make contact with Z. This is equivalent to three parallel
skates as described in our Provisional Specification. This main stud may in some
cases be connected to one of the auxiliary ones by a single wide skate in place of
two narrower ones.
With the above arrangement we may, use any suitable form of switch, as for
example, any of those described in Specification of Patent No. 19455* of 1896;
or if preferred any of those referred to above and described in Specification of Patent
No. 19455 of 1896.
The switches may further, if required, be interconnected as described in
Specification of Patent No. 19456 of 1896, so that each switch is closed and its
main stud made alive before the skates reach it. Further the coils of these
switches may be arranged either so that the main current passes through them in
series with the car motors, or they may be arranged as, shunts to the same.
Throughout this specification we have spoken of short studs for the road contacts
and skates on the car; but it is obvious that any of the above systems may be
used with long road contacts or rails, and suitable brushes or shoes on the car.
We also throughout have used the word "earth" to signify the return conductor
of whatever form it may be.
Having now particularly described and ascertained the nature of our said
invention and in what manner the same is to be performed we declare that what
we claim is:-
1. In a system of electric traction, an automatic switch the moving parts of

page_text: which begin to operate when a current is passed through its electro-magnet, the
complete operation of the switch and closure of the circuit occurring when but not
until a mass of iron carried by the car is brought near the switch.
2. An automatic switch having a magnetized operating part which when in
contact with a loose piece of iron has of itself no tendency to move being
magnetically balanced however strongly it is magnetized but which when dis-
placed from the said loose piece moves sharply towards the position of balance as
soon as a current is passed round its magnetizing coils.
3. For an automatic switch an electromagnet constructed and operating
substantially as described with reference to Figure 1 of the accompanying drawings.
4. In a system of electric traction, the method of operating the automatic
switches substantially as described with reference to Figures 2. and 4 of the
accompanying drawings.
5. In a system of electric traction in which the automatic switches are operated
by a current on its way from the main to the car motor, the combination of the
following elements:-
(a) A stud connected through the switch-contacts to the main, without the
inclusion of an operating coil,
(b) A skate carried by cars adapted to make contact with said stud and convey-
ing current to a secondary stud connected through the operating coil to a third
stud, and,
(c) A second skate carried by the car connecting said stud to the car motor.
6. In a system of electric traction the method of operating the automatic switches
substantially as described with reference to Figure 3 of the accompanying
drawings.
WM. P. THOMPSON & Co.,
Of London, Liverpool, Manchester and, Birmingham,
Patent Agents for the Applicant.