Centrifugal Contact Apparatus for Effecting the Connection of the Armature Windings of Rotary Phase Electromotors on the attain- ment of a certain speed.
Year: 1896

page_text: Date of Application, 30th Sept., 1896
Complete Specification Left, 25th June, 1897-Accepted, 14th Aug.,
1897
[Communicated from abroad by SIEMENS & HALSKE, of Berlin, in the German Empire,
Electrical Engineers.]
Centrifugal Contact Apparatus for Effecting the Connection of the
Armature Windings of Rotary Phase Electromotors on the attain-
ment of a certain speed.
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 to be as follows:-
This invention relates to the means for controlling the induced currents in short
circuited windings of the armatures of rotary phase electromotors described in the
Specification to Patent No. 21141 of 1894.
According to the specification of that patent, the points A¹ A2 and A3 of Fig. 3 of
the drawings have to be put in conducting connection as soon as the motor has
attained a certain speed.
According to the present invention this connection is effected automatically by the
following means.
Instead of connecting the starting points A1 A2 A3 of the armature windings as
described with reference to Fig. 3 of the said specification, the points A¹ and A2 are
each connected to a separate contact plate and the point A3 is connected to two other
contact plates, arranged opposite those of A1 and A2, and a centrifugal governor is
made to close the contacts by moveable contact pieces, as soon as the motor has
attained the required speed. The centrifugal governor employed for this purpose is
of the following construction.
Within a cylindrical casing receiving rotary motion from the are ature shaft are
arranged four contact plates, each constituting one of the before mentioned contact
plates connected to the points A1 A2 A3 ; two of these, say those connected to the
point A³, are each connected by a flexible conductor to a contact piece fixed on a
block pivotted to the bottom of the casing, these blocks being made of such a form
that they tend to fly outwards by centrifugal action on the rotation of the casing, so
as eventually to bring the contact pieces carried thereby into contact with the two
contact plates connected to A1 and A2, and thus establish the above described
connection of A1 A2 and A³.
The said two centrifugal blocks are held against the centrifugal action by means of
helical springs, one end of which is fixed to the block, while the other is adjustably
attached to the casing. The strength of these springs is so proportioned that they
will prevent the blocks from swinging outwards to such an extent as to make contact
with the said contact plates of A and A so long as the speed of rotation of the
armature, and consequently of the governor casing, does not correspond to the speed
at which the points A1 A2 A3 require to be connected, but when this speed is attained,
the resulting increase of the centrifugal moment of the blocks being greater than the
increase of tensional moment of the springs, the two contact pieces will suddenly fly
into contact with the contact plates of A¹ and A2, thus establishing the said connection
of the arinature windings.

page_text: As it is necessary that both contacts shall be made simultaneously, this is
ensured by providing, loose on the central boss of the casing, a disc having two radial
slots into which project pins fixed on the two pivotted blocks, so that, should the one
block be moved outward by centrifugal force to a slightly greater extent than the
other one, it will, in turning the said disc, cause the other slot thereof to effect a
corresponding outward motion of the other block.
On the other hand, owing to the slotted connection of the disc to the pins of the
two blocks, the disc will not interfere with the necessary independent action of the
blocks when making contact.
Dated this 30th day of September 1806
ABEL & IMRAY,
Agents for the Applicants.
Centrifugal Contact Apparatus for Effecting the Connection of the
Armature Windings of Rotary Phase Electromotors on the
attainment of a certain speed.
We, SIEMENS BROTHERS & Co., LIMITED, of 12 Queen Anne's Gate, Westminster, in
the County of London, 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:-
This invention relates to the means for controlling the induced currents in short
circuited windings of the armatures of rotary phase electromotors described in the
Specification to Patent No. 21141 of 1894.
According to the specification of that patent, the points A¹ A2 and A3 of Figure 3
of the drawings have to be put in conducting connection as soon as the motor has
attained a certain speed.
According to the present invention this connection is effected automatically by the
following means.
Instead of connecting the starting points A1 A2 A3 of the armature windings as
described with reference to Figure 3 of the said specification, the points A¹ and A²
are each connected to a separated contact plate and the point A³ is connected to two
other contact plates, arranged opposite those of A1 and A2, and a centrifugal governor
is made to close the contacts by moveable contact pieces, as soon as the motor has
attained the required speed.
Figure 1 of the accompanying drawings shews a diagram of the connections for this
purpose; C, C, are the contact plates to which the points A' and A2 are connected, and
DD are the contact plates to which A³ is connected.
Figure 2 shews a plan of the centrifugal governor employed for the above purpose
with the cover removed, Figure 3 is a cross section on line X Y Figure 2, and Figures
4 and 5 shew enlarged details of contacts D.
The operative parts are enclosed in a cylindrical casing T, which is fixed on the
shaft of the motor so as to rotate therewith. CC and DD are the contact plates
above referred to. The necessary four supply leads to these pass from the armnature
of the motor through the back of the casing T, two of them being led to the contact
plates C C and the other two to the connecting blocks K K. As the two sets of these
parts are identical with each other, they are indicated by the same letters of reference
and in the following description only those belonging to one pair of contacts will
be referred to.
From K the flexible conductor B passes to the contact plate D which is secured to
and insulated from the centrifugal body M. pivotted at Z to the casing. As this body

page_text: is unsymmetrical relatively to the radius of the motor shaft passing through Z, on
the rotation of the motor shaft the resulting centrifugal action will produce a turning
moment in M round Z. A coiled spring Facts in opposition to this moment; it is
connected at the one end by a bar P to a pin S on the body M, while the other end is
connected by the screwed adjustable rod H to the casing. The bar P passing through
the spring serves to maintain this in a straight line when the centrifugal force
tends to bend it transversely outwards.
The pull of the spring is so adjusted that its moment holds the moment of
the centrifugal body M in equilibrium until the speed is attained at which the
contacts are required to be closed. On this speed being attained the body M
will consequently move outward, from its original position.
As the elasticity of the spring is so proportioned, by giving it a sufficient number
of convolutions, that the moment of the spring power increases more slowly than
the centrifugal force of the mass M which increases proportionally to the increase
of the radius, the body M, after once leaving the original position, will move outward
with increasing acceleration so as to effect the contact between C and D with
suddenness and with a surplus of energy.
The two contacts are required to close simultaneously; this could however not be
always insured if the two contact devices were quite independent of each other, even
with great accuracy of adjustment of the two springs, on account of possible unequal
variations in the friction of the parts &c. On the other hand the pairs of contacts
must arrive independently of each other at their end position, in order to insure a
reliable contact in both. In order to fulfil both conditions, there is provided loose on
the central boss of the casing a dise W having radial slots R R with which are engaged
with a certain amount of play, pins & fixed to the bodies M.
If now the one body starts from its original position sooner than the other one, is
will, after moving to the extent of the play of 8 in the slots, transmit its motion to the
other body M, and as it will then have already attained an excess of energy, any
difference between the tension of the two springs will thereby be prevented from
detrimentally affecting the simultaneous closing of the two contacts, while on the
other hand the play of the pins & in the slots R will render the contact positions of
the plates independent of each other.
The contact plates D are shewn in Figure 3 as single pieces; they are however
preferably made of two pieces as shewn more clearly in the enlarged elevation and
plan at Figures 4 and 5, namely the main contact D 1 which is fixed to and insulated
from the centrifugal body M, and the auxiliary contact d which can turn on the pin t
of D 1 and is pressed forward by the spring f acting on its end face as shewn.
The object of this construction is to avoid sparking on closing the contacts, which
sparking would otherwise be produced in consequence of the recoil.
The auxiliary contact d moves in advance of D1 in consequence of the contrifugal
action and that of the spring f, and consequently it makes contact with plate C
before D 1 but it does not recoil therefrom, because its small mass is subject to the
opposing influence of the spring f, and because it still has an advancing motion with
the main contact. It constitutes therefore during the short time of the recoil after
the impinging of the main contact, a conducting connection between this and the
plate Cand thus prevents the sparking that would otherwise occur.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed we declare that what we
claim is
1. A centrifugal contact apparatus for automatically actuating the circuit closing
device described in the Specification to Patent No. 21141 of 1894, consisting of the
herein described construction of centrifugal bodies M carrying contacts D and acting
in combination with springs F in such manner that on the speed determined for
closing the contacts being attained the moment of the springs F operating on the
pivots 7, of the bodies M increases more slowly than the centrifugal force of the said

page_text: bodies, so that these move suddenly-outwards into the contact position, substantially
as described.
2. The combination with the bodies M referred to in the preceding claim, of the
disc W connected thereto with a certain amount of play, for the purpose of causing
the centrifugal motion of the one body to be transmitted to the other one, while
nevertheless the contacts are effected independently of each other, substantially
as described.
3. Constructing the contact plates D connected to the bodies M referred to in the
preceding claims, of a main contact piece D₁ and an auxiliary contact piece d
pivotted thereto which piece is caused by spring action and centrifugal force to move
in advance of the main contact piece D¹ and thereby to prevent sparking that would
otherwise occur on the recoil of the latter in making contact, substantially as
described.
1005
ABEL & IMRAY,
Agents for the Applicants.