Switch Apparatus for Electromotors, with Automatic Resistance Regulator.
Year: 1896

page_text: Date of Application, 17th Apr., 1896--Accepted, 23rd May, 1896
COMPLETE SPECIFICATION.
Switch Apparatus for Electromotors, with Automatic
Resistance Regulator.
We, SIEMENS BROTHERS & Co. LIMITED of 12 Queen Anne's Gate,
Westminster, in the County of London, Electrical Engineers, do hereby declare
the nature of this invention (which has been communicated to us from abroad by
Siemens & Halske, of Berlin in the German Empire, Electrical Engineers) and
in what manner the same is to be performed to be particularly described and
ascertained in and by the following statement:-
When it is desired, during the work of electromotors connected in series to
connect them quickly in parallel, or the converse, it is necessary either to open the
circuit or to temporarily short circuit one of the motors.
In either case considerable sparking occurs at the switch and commutator brushes
if the change is effected suddenly.
.
Such sparking can however be almost entirely avoided if, shortly before effecting
the change, a resistance is introduced into the circuit.
The present invention relates to a switch apparatus so arranged that at each
switching operation there is automatically introduced into the circuit, immediately
before the opening of the contacts, a resistance that will effectually prevent.
sparking, this being effected quite independently of the will of the driver.
For this purpose the axle of the switch is mechanically connected to the switch
device of a regulating resistance in such manner, that each movement of the switch
spindle sets free a force whereby the resistance regulator is so placed that.
resistance is introduced into the circuit.
The accompanying drawing shews one arrangement for carrying this invention.
into practice.
Figure 1 shews a sectional plan, Figure 2 a cross section at X X and Figure 3.
a cross section at Y Y. Within a casing A are arranged two parallel spindles B
and C, of which B is rotated by a crank handle D for actuating the switch
apparatus while the spindle C is rotated by a hand wheel E for actuating the
regulating resistance. The switch apparatus consists of a number of contact.
levers F which under the action of springs G press against fixed contacts H. The
axle B carries a number of cams J which on rotating the axle B are made to press
the contact levers sideways so as to open the contacts at H. The several cams are
shifted round through a certain angle relatively to each other in order that, with
a definite position of the crank handle, the necessary contacts are closed and
opened for effecting a desired order of connection of the circuits. If for example-
there are two motors, to be connected either in series or in parallel the following.
arrangement can be employed.
In the position (1) of the crank (Figure 2) all the contacts are open and.
consequently both motors are out of circuit; in the position (2) the motors are
connected to the circuit in series and run for forward motion; in the position (3)
they are connected in parallel and act as brakes; in position (5) the current is.
reversed so that the motors run backwards, being connected in series.
The axle C of the regulating resistance actuates in a similar way a number of
contact levers by means of corresponding cams (not shewn) which levers, on the
rotation of the hand wheel E to the right hand, are applied consecutively to a.
corresponding series of fixed contacts whereby the several sections of the regulating
resistance are consecutively short circuited.

page_text: By such rotation of the axis C a spiral spring is simultaneously wound up and
the axle is held in its several positions against the action of such spring by means
of a pawl K gearing with a ratchet wheel L fixed on the axis. The pawl is
controlled by a disc M having notches on its periphery and fixed on the axle B.
When the crank handle D is in one or other of the principal positions indicated by
1 to 5, the tail of the pawl K enters one of the notches of the disc M and thus
holds the ratchet wheel and axle C in a corresponding position.
If on the other hand the crank D is moved from one such position into another,
then before it has reached the second position, the periphery of the disc M presses
the tail of the pawl outwards and thereby disengages it from the ratchet wheel,
whereupon the strained spiral spring will cause the axle C to rotate suddenly to the
left, thus putting all the resistance into circuit.
It will be seen from the above arrangement that so long as during the working,
the switch crank handle is in one of the positions indicated by 1 to 5, that is to
say, so long as the motors are operating in a particular manner, it is possible to
increase the torque of the motors by cutting part of the regulating resistance out
of the circuit by hand. As soon however as the connections of the motors are
changed by rotation of the crank D, the resistance which has been previously
excluded will again be included in the circuit, and will thereby prevent sparking
at the switches and commutators.
The above described apparatus is equally applicable for regulating a single
electromotor, the field magnet winding of which is divided into sections that can
be connected either in series or in parallel.
Instead of employing a single regulating resistance, several such may be used,
the switch axles of which are connected with the switch axle B in the same way
as C is connected therewith, so that on rotating the crank-handle D the axles of
all the regulating resistance are suddenly rotated so as to put the entire resistance
into the circuit.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
A switch apparatus for electromotors consisting of the combination of a switch
actuated by a rotatable axis with one or more regulating resistances, also controlled
by a rotatable axis or axes the axis of the resistance being so arranged relatively
to the switch axis that at each movement of the latter the axis of the resistance
regulator is rotated by a force set free by such movement, so as automatically
to include resistance in the circuit before the switch breaks contact and thus
prevent sparking at the switch and commutator when changing two or more
electromotors from parallel to series connection or the converse, or when
changing the connections of separate winding-sections of a single motor,
substantially as described.
Dated this 17th day of April 1896.
ABEL & IMRAY,
Agents for the Applicants..