Appliance for Automatically Regulating the Frictional Pressure on the Rails of the Driving Wheels of Electrically Propelled Vehicles.
Year: 1899

page_text: Date of Application, 31st Jan., 1899-Accepted, 4th Mar., 1899.
COMPLETE SPECIFICATION.
Appliance for Automatically Regulating the Frictional Pressure on
the Rails of the Driving Wheels of Electrically Propelled Vehicles.
We, SIEMENS BROTHERS & Co. LIMITED, of 12, Queen Anne's Gate, West-
minster, in the County of London, Electrical Engineers, do hereby declare the
nature of this invention (as communicated to us from abroad by Siemens &
Halske Aktien Gesellschaft, of No. 94, Markgrafen Strasse, Berlin, S.W., in the
Empire of Germany, Electrical Engineers,) and in what manner the same is to
be performed, to be particularly described and ascertained in and by the following
statement:-
With railway vehicles, and in particular locomotives, that run on smooth rails
where the frictional adhesion produced by weight does not alone suffice for the
required tractional force, auxiliary driving wheels are sometimes employed that
are pressed against the rails by springs or other mechanical devices for affording
the necessary adhesion for the maximum tractional force required to be exerted
by the driving wheels. This arrangement has the disadvantage that even when
only a small tractional force is exerted the maximum pressure of the auxiliary
wheels continues to be applied, resulting in an unnecessary expenditure of power
for overcoming the frictional contact and producing an excessive wear of the
rails.
The present invention has for its object to obviate this disadvantage; we will
describe the same with reference to the accompanying drawing which shews a
diagrammatic view of the auxiliary driving wheels of the locomotive with devices
in connection therewith for automatically regulating their pressure.
PP are wheels gripping the rail between them and driven by the motor
engine, ee is an electromagnet which is carried by the shaft of the wheel P and
eel is an armature carried by the shaft of wheel P¹.
The electromagnet is provided with an exciting winding h which is included
in the main circuit of the electromotor m, so that the armature e¹ is attracted
with greater or less force and consequently the wheels PP¹ are pressed with
greater or less power against the rail according as a stronger or weaker current
is supplied to the motor for exerting the necessary tractional force at the peri-
phery of the wheels.
By suitably proportioning the electromagnet and the lines of force thereof,
the pressure exerted by the driving wheels PP¹ can be made to vary approxi-
mately in proportion to the variations of the tractional force exerted.
When the motor engine is worked by means of rotary phase currents the
exciting winding of the magnet can be included in the circuit of the stator as
well as in that of the rotor.
In order to insure a sufficient pressure of the driving wheels with a small load
on the engine, such as when running empty, it is advisable to provide the electro-
magnet with a small auxiliary winding n connected in shunt with the motor
circuit in order to obtain a sufficient adhesion of the wheels with a weak current,
as the strength of electromagnets decreases very rapidly with weak currents.

page_text: If the running wheels of the engine are driven as well as the pressing wheels
the adhesion of the former will generally suffice for producing the requisite trac-
tional force with a small amount of current.
In this case the shunt winding n might still be advantageously employed for
regulating the pressure of the wheels PP independently of the strength of cur-
rent working the motors. Such regulation can however also be effected by the
main winding itself either by short circuiting more or less thereof or by the
employment of a regulating resistance in a shunt of the main winding or by
varying the magnetic resistance in any known manner.
Having now particularly described and ascertained the nature of this invention
and in what manner the same is to be performed, we declare that what we claim
is:-
:-
1. In electrically propelled railway vehicles an appliance for automatically
pressing the driving wheels against the rail consisting in an electromagnet in-
cluded in the circuit of the motor, and so arranged that the force with which it
presses the wheels against the rails is made to vary more or less in proportion
with the variations in the strength of current operating on the electro-motor
substantially as and for the purpose described.
2. Providing the electromagnet referred to in the first claim with an auxiliary
winding included in a shunt of the motor circuit substantially as and for the
purposes described.
1000
ABEL & IMRAY,
Agents for the Applicants.