Improvements in Trolleys for Electrically Propelled Cars.
Year: 1897

page_text: Date of Application, 21st June, 1897-Accepted; 16th Oct., 1897
COMPLETE SPECIFICATION.
Improvements in Trolleys for Electrically Propelled Cars.
I, EGMONT HOEGERSTAEDT of Halensee near Berlin, in the Kingdom of Prussia,
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:-
In the electric traction of cars the motors of which are fed from a central
station interruptions and stoppages are frequently caused by loss of current, which
loss is of less importance in the working wire which in many current supply
systems is exposed to the influence of the weather, than that arising from those
portions of the current conducting parts of the trolley which are not completely
insulated and in multiple contact systems also arising from the exposed portions
of the multiple contact conductor.
The object of this invention is to prevent the loss of current from taking place
in the two latter cases, and this object is attained by means of a trolley in which
the current conducting parts, even those by which the current is collected are
during this time completely insulated on the outside by means of electrically
non-conducting materials. In practice however this insulation can only be carried
out by at the same time insulating on the outside the current supply wire at
and adjacent to those points which at any time are in contact with the trolley:
Hence it follows that in the multiple contact systems the exposed portions of
the conductors from which the current is taken, may if they are not of large
dimensions, be completely insulated together with the trolley by the material
insulating this latter. Such multiple contact working presents, as distinguished
from all others, the advantage that all the current conducting parts from the
generating dynamo to the motor clamps, are completely insulated so that all
loss of current and the evil arising therefrom is avoided.
In the accompanying drawing is shewn a construction of trolley designed
for a multiple contact system in which the multiple contact conductors terminate
in contact plates located in the car track. In this case the supply of current is
obtained through magnets.
Fig. 1 is a part sectional side view of the trolley and Fig. 2 a part sectional
end view of the same the section being on line A-B of Fig. 1.
The trolley comprises two discs c, cl, placed loose and held at a certain distance
apart upon an axle which is formed of two hollow axles a, b, placed one within
the other. A tyre d made of an elastic electrically non conducting material,
india rubber for instance, bulged outwards connects the two discs and shuts off
water tight the space between them. In the vertex of the tyre and passing water
tight through the same are fixed at equal distances apart contact pieces e whichr
either do not project or only slightly project beyond the outside surface of the
tyre whilst they project considerably out from the inner surface of the same
and have there a suitably shaped end.
A circuit closing arrangement is provided in the space between the two
discs c, c. It consists substantially of a bar composed of three parts, the middle
one of which is formed of a material which is a conductor of electricity and
the outer parts g, g', of a material which is not a conductor of electricity. This

page_text: bar lies parallel to the track and is held; at a certain height above the contact
pieces e, suspended by means of a spring i from a frame & which is firmly attached
to the axle part b. Said frame is made of insulating material and has formed
in it guide ways for the three part bar f, g, g', so that this latter can only move
vertically. The middle part f is in direct conducting connection with the motor
through the metal parts 7 and the insulated wire m.
The construction of the circuit closer is not limited to that described but may
be of any other suitable construction.
The trolley is in connection with a magnet which partly for the purpose of
insuring the most favourable form for its magnetic field and partly to protect it
from weather influences is suitably arranged inside the trolley.
The magnet
may be a natural magnet, an electro magnet or both at the same time. The
two latter may be energised either by an accumulator or by the working current
in main or shunt, connection. The use of a natural magnet as electro magnet
has the great advantage of being capable of actuating the circuit closing arrange-
ment of the multiple contact conductor even when from any cause the action of
the electro magnet as such is stopped. The arrangement shewn in the drawing
of a round magnet with the discs c, c¹, serving to support it, is preferred because
it occupies but little room and admits of the most favourable distribution of the
lines of force.
The operation of the trolley thus constructed is as follows:-
The axle a, b, is fixed immovably to a frame directly connected with the wheel
axles of the car and at such a height above the contact plates h. that with the
compression or flattening of the rubber tyre d, the three part bar f, g, g', comes
upon the contact pieces e underneath it and causes all of them to come into close
contact with itself and with the track. The tyre is thereby pressed so flat and
close against the track that the contact pieces e and contact plates h within the
surface of contact between track and tyre are completely insulated on the out-
side. If one of the contact pieces e while in contact with the bar part f comes
upon a contact plate h and if this latter is in electric connection through: the
electro magnet with the working conductor the current is taken off, the car set
in motion and at the same time the trolley rotated. The contact pieces coming.
on to the track must pass between this and the bar f, g, galong which they
slide. The parts g, g¹, serve solely to bring the insulated contact pieces e into
the proper working position before they come into contact with the part for.
to maintain them in the proper working position until they have completely left
said part which latter serves to bring all the contact pieces e sliding along it
into electric communication with the motor.
In order that the part of may come, along its whole length simultaneously,
into electric communication with the working conductor, the magnetic. field of
the electro magnet through which the current is supplied to the multiple contact.
conductor, must be at least so large that, in the moment in which each .contact
plate h, which must already beforehand have had a contact piece e brought against
it, comes into electric communication with the bar part f, it also comes into
electric communication with the working conductor, and so that the com- 4
munication with this latter only ceases at the moment the contact piece and
contact plate leave the conducting bar part f. Of course the magnetic field
may be even larger so that contact pieces and contact plates would already. be.
in conducting connection with the working conductor before they come into.
contact with the bar part f and close the circuit and so that this conducting
connection with the working conductor is maintained for a time after said parts
have left the bar part f and thereby broken the circuit.
By such a formation of the magnetic field the trolley, in addition to collecting
current, at the same time fulfils a second very important purpose, namely that
of preventing the sparking in the multiple contact conductor, which is so much.
feared. The precedure is however very simple and as follows:- The circum-
stance that through the electro magnet a conducting connection is established.

page_text: from the working conductor to the contact piece, before a current can pass
through the same, excludes the possibility of sparking in the multiple contact
conductor which sparking however is removed to a place where a moment later the
circuit between contact piece e and bar part f is closed. On the other hand the
circuit between the latter and the same contact piece is broken with consequent
sparking before electric communication between this contact piece and the
working conductor is stopped, and then sparking can no longer take place.
Sparking occasioned by inductive action is of course removed in the same way
to another place where sparking is of no importance and also not so energetic
owing to the peculiar construction of the circuit closing device.
Obviously the magnetic field should not be so large as to bring contact plates
into conducting connection with the working conductor, or such connection exist
before said plates are insulated by the rubber tyre, or after their insulation by
the tyre has ceased, otherwise the current might be diverted, but as already
stated, loss of current is in any case prevented.
For the purpose of a continuous and regular collection of current it is necessary
that the dimensions of the contact pieces e and contact plates h and their distance
apart from one another should be such that at least one contact piece is always
so far in contact with a contact plate as will serve for conducting the required
strength of current. If it be desired to increase this distance two or more
trolleys may be applied one behind the other.
Obviously the trolley may also be employed to deliver current as well as to
collect it, or two similar devices may be provided in the same wheel, the one for
taking off and the other for delivering current.
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. In a trolley for electrically propelled cars, the combination with the current
conducting parts of electrically non conducting materials insulating said current
conducting parts including those portions of the same by which the collection
of the current is immediately effected, for the purpose specified, substantially as
described and shewn.
2. In a trolley for electrically propelled cars, the combination with an elastic
and electrically non conducting body of one or more contact pieces embedded
in said body and, for the purpose of conducting the current, in conducting con-
nection with the car motor by means of a switch, said body being thereby pressed
against that part of the track in which the contact plates are located so that
all the contact plates and contact pieces lying within the flattened surface of
said body are completely insulated on the outside, for the purpose specified,
substantially as described and shewn.
3. In a trolley for electrically propelled cars, the combination with two coupled
discs of a convex shaped rubber tyre enclosing the space between the two discs
water tight, of contact pieces fixed at certain intervals water tight in the vertex
of said tyre, and entering into conducting connection with the motor by means
of a switch, the axle of said tyre being so carried that the latter is always rolled
over the track under pressure, for the purpose specified, substantially as described
and shewn.
4. In a trolley for electrically propelled cars, the combination with two coupled
discs of a convex shaped rubber tyre enclosing the space between said discs
water tight, of contact pieces fixed at certain intervals water tight in the vertex
of said tyre, of a switch or circuit closer in said space consisting of a three part
bar, the middle part of which is of electrically conducting material and the
outer parts of electrically non conducting material, the bar being held suspended
by a spring from a frame of insulating material which is attached to the wheel
or tyre axle, said middle part of the bar however always being in electric con-
nection with the motor and the wheel or tyre axle being so carried that the

page_text: wheel is always rolled over the track under pressure, for the purpose specified
substantially as described and shewn.
5. The combination with a trolley for electrically propelled cars, of a circuit
closing device consisting of a three part bar suspended by mean of a spring
from, and vertically guided in, a frame of insulating material which is attached
to the axle of the trolley wheel or tyre, said bar being located parallel to the
track and at such a height above the same that the contact pieces in between
come into intimate contact therewith, and the middle part of said bar being in
direct electrical connection with the binding clamps of the motor, said middle
part being formed of a conducting material and the outer parts of said bar of
non conducting material, for the purpose of avoiding sparking in the multiple
contact conductor, substantially as described and shewn.
Dated this 21st day of June 1897.
THOMAS R. SHILLITO,
89 Chancery Lane, London, W.C., Agent for the Applicant.