Combined Electro-magnetic Shaft Coupling and Brake Apparatus.
Year: 1890

page_text: Date of Application, 2nd May, 1890
Complete Specification Left, 28th Jan., 1891-Accepted, 28th Feb., 1891
PROVISIONAL SPECIFICATION.
[Communicated from abroad by the firm of SIEMENS AND HALSKE, of 94, Mark-
grafen Strasse, Berlin, in the Empire of Germany, Electrical Engineers.]
Combined Electro-magnetic Shaft Coupling and Brake Apparatus.
We, SIEMENS BROS. & Co., LIMITED, of No. 12, Queen Anne's Ginte,
Westminster, in the County of Middlesex, do hereby declare the nature of this
invention to be as follows:-
This invention relates to an electromagnetic apparatus for coupling together two
shafts or spindles, wherein the driving shaft has fixed upon it an electro-magnet
while the shaft to be driven carries an armature, so that on the electro-magnet
being excited by the closing of an electrical circuit, it attracts the armature and
carries it, and consequently also the other shaft round with it in the same way as an
ordinary frictional coupling. A second, fixed electro-maguet is so arranged as to
act upon the armature in the opposite direction, so that when the circuit of the
revolving electro-magnet is broken and that of the fixed one is closed, the latter
draws the armature away from the former and into contact with itself, and is
thereby made to act as a friction brake in stopping the rotation of the driven shaft.
The current is conveyed to the coils of the rotating magnet in any suitable manner
such as by two insulated discs on the shaft connected respectively to the ends of
the electro-magnet coil, and having two sliding contacts with which the leads from
a battery are connected. The armature may be formed as a toothed or frictional
wheel or band pulley for imparting motion.
The successive breaking of the circuit of the one electro magnet and closing of
that of the other may be effected by switches worked either by hand or by an
electric current. In the latter case the switches may be carried by a pivotted disc
with weighted arm or spring action which is held in position for making the one
set of contacts by a catch. This catch is held in gear by an electro magnet of
which the catch, or a tail piece thereon, forms the armature; the electric circuit of
this magnet has one or more switches or spring contacts, by moving which the
circuit is broken so as to render inactive the electro magnet, whereupon the
catch is drawn by a spring or weight out of gear with the switch disc, and
this is then turned by its weighted arm so as to reverse the position of the
coupling switches.
In order to prevent the proper action of the clutch and brake apparatus from
being affected by residuary magnetism in the electro-magnets, it is preferred, when
changing the connections, to pass a reversed current through the coils of the electro
magucts so as to neutralize such residuary magnetism and thereby prevent the
armature from sticking.
This may be effected by providing two sets of contacts to the coil of each
electro-magnet, so arranged that the switch in passing from the one extreme
position to the other makes at an intermediate point a second contact with the coil
which is being put out of action, but in the reverse manner, so as to pass a reversed
current through it.
Dated this 2nd day of May 1890.
ABEL & IMRAY,
Agents for the Applicants.

page_text: COMPLETE SPECIFICATION.
Combined Electro-magnetic Shaft Coupling and Brake Apparatus.
We, SIEMENS Bros. & Co., LIMITED, of No. 12, Queen Anne's Gate,
Westminster, in the County of Middlesex, do hereby declare the nature of this
invention, anil 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 an electro-magnetic safety coupling for transmitting
motion from or to shafting, which consists of the combination of an electro-magnetic
coupling and an electro-mugnetic brake in such manuer that on the coupling being
thrown out of action so as to prevent the further transmission of power from the
driving to the driven part, the latter shall at the same time have its motion
arrested by the action of the brake. By this means the great advantage is
obtained that on any driven machine getting out of order, or on the entangle-
ment of any person with such machine or with driving gear not only is the
continued driving of the machine or gear prevented but any continuance of the
motion thereof due to the momentum of its parts is checked, and consequently any
damage to the machine or to the entangled person will be obviated.
For the effectual operation of the said combined electro-magnetic coupling and
brake, there is also employed an automatically operated switch apparatus, which by
means of an electro magnet excited by a constant current is ordinarily locked in
such a position as to maintain the electro-magnetic coupling operative, while when
the circuit of the exciting current is broken, the switch is made first to connect up
the electric circuit with the electro-magnetic coupling in the reverse direction so as
to destroy any residuary magnetism thereof, and then to connect up the electric
circuit with the electro-magnetic brake.
We will proceed to describe the construction of the said combined electro-
magnetic coupling and brake as also of the switch apparatus, with reference to the
accompanying drawings in which
Figure 1 shows the said combination as applied to the coupling of two shafts
while
Figure 2 shews the same applied to the coupling of a loose pulley to its
shaft,
Figures 3 and 4 shew diagrams of the electrical connection of the said combined
apparatus with the controlling switch operated by hand.
Figure 5 shews a diagram of the automatically operated switch and its controlling
circuit, and
Figure 6 shows a practical construction of the switch.
In Figure 1, B is the driving shaft and 13 the driven one. On the former is
fixed the electro magnet E' of an annular trough shape, the ends of the coil e of
which are connected to the insulated rings as ou the shaft B, on the outer surfaces
of which hear brushes connected to two leads of a suitable electric circuit, in which
is included the before mentioned switch apparatus, E is a second similarly con-
structed electro magnet fixed to the bearing C of the second shaft B, the coil of
the electro magnet being also connected by leads to the said circuit.
Upon the end of the shaft 13, is fixed a soft iron dise A which acts as armaturo
to both the electro magnets E' and E. The shaft B being capable of slight end
motion, or the disc A being arranged to slide longitudinally thereon to a limited
extent, it will be seen that on coupling up the electro magnet E', with the circuit
by means of the switch, the magnet will attract the armature disc A and will thus
effect the coupling of the shaft B. If on the other hand it be desired to stop the
motion of the shalt B, this is effected by actuating the switch so as to disconnect E
from the circuit, and couple up the coils of E³ thereto, whereby the armature A will
be attracted by the fixed electro magnet E and the shaft 133 will thus be brought
to a standstill. In the arrangement shewn at Figure 2, the armature A is formed
na a pulley, loose upon the shaft B, and receiving motion therefrom ou being

page_text: attracted by the electro magnet E³, which motion it imparts to machinery by a belt,
while on rendering E' inactive, and the fixed electromagnet E' active, the pulley is
attracted by the latter and is brought to a standstill. As before stated, on sluunting
the electric current from the one clectromagnet to the other by means of the switch
it is preferred on breaking the circuit to send a current in the contrary direction
through the same electro magnet before coupling up the other one, in order to
neutralize any residuary magnetism and thus facilitate the attraction of the armature
by the other clectromagnet.
Figs. 3 and 4 shew diagrams of switch apparatus for this purpose which are
worked by hand. In the arrangement at Fig. 3 the double pole switch D, which is
connected to the exciting circuit F, when in the position shewn completes the circuit
with the contacts a' a² of electromagnet E'; on breaking this connection the switch
first passes over contacts ³, thereby sending a current through E and is then
brought momentarily upon the contacts a³ and a', thus reversing the current
through E¹, and it is then brought on to the contacts of the electromagnet Eª
so as to send a current through it in the direction for attracting the armature. In
like manner on breaking the circuit of E, the switch after passing over contacts aª a³
is brought momentarily on the contacts so as to reverse the current therein.
In Fig. 4 the contacts are arranged somewhat differently for the same mode of
action, as will be readily understood.
It is preferred to work the switch automatically by a constant current, as this
arrangement would give the great advantage that the switch circuit can be so
arranged with a number of make and break contacts that the switch could be
operated at various points at a distance, instead of a person being required to go to
the switch to operate it, whereby valuable time might be lost. Figure 5 shews a
diagram of such an arrangement, and Figure 6 shews a suitable construction of the
switch. The switch D Figure 5 has its moving contacts on a rotatable disc d,
having a weighted arm d' which is ordinarily held in the horizontal position shewn
by a spring pawl H, a tail H¹ of which constitutes the armature of an electro-
magnet the windings of which are connected to a circuit J through which a
current flows continuously so that the magnet I in attracting the tail H¹ keeps the
pawl H engaged with the disc d and thereby causes the switch to pass the current
from the circuit F through the electro magnetic coupling E' Figures 1 to 4.
Upon the circuit J are arranged any number of make and break contacts j
situated at convenient places so that by operating any one or other of these by hand
the switch circuit is broken, whereupon the spring K will draw the pawl H out of
gear with disc d and the weighted arm d' will now turn the switch into the dotted
position, in which it breaks the circuit of the coupling E' and closes that of the
brake E. The weighted arm d' is afterwards raised by hand again so as to
bring the switch back to its original position.
In the construction of the switch shewn at Figure 6, the disc d has a projecting
pin d which engages with the catch H; otherwise the construction is substantially
the same as above described.
It will be evident that the arrangement shewn at Figure 2 may be variously
modified, thus instead of B' being the driving part and A the driven, A might be
the driving part, and in being attracted alternately by the electromagnets E' and E'
it would ordinarily drive the shaft B' and should occasion arise, owing to entangle-
ment with its belt, would have its own motion arrested by the break E². Also,
in place of A being a belt pulley, it might be a toothed wheel.
We are aware that it has before been proposed to employ electromagnetic clutch
apparatus and we do not claim such apparatus otherwise than in combination with
an electromagnetic brake as described.
Having now particularly described and ascertained the nature of our said inven-
tion, and in what manner the same is to be performed, we declare that what we
claim is :-
1. A combined electromagnet coupling and brake for shafting, consisting of two

page_text: electromagnets, one of which is on the driving or the driven part while the other
is fixed, and an armature carried by the driven or the driving part, and which can
be brought in contact with either electromagnet, the first named celectromagnet
being rendered operative by an electric circuit so as to attract the armature when
the two moving parts require to be compled, while the second or brake electro-
magnet is rendered operative so as to attract the armature and arrest, its motion
when the two moving parts require to be uncoupled substantially as described.
2. In combination with the electromagnetic coupling and brake, operating as set
forth in the preceding claim, a switch for connecting and disconnecting the two
electro magnets to and from an electric circuit, such switch being provided with
contacts so arranged, that after being moved so as to break the circuit of the one or
the other electro magnet, the switch causes a reversed current to be passed
momentarily through its coils so as to destroy any residuary magnetism therein,
substantially as described.
3. An electro magnetic switch apparatus for controlling the combined electro
magnetic coupling and brake referred to in the first claim wherein the moveable
part of the switch is held in position for operating the electro magnetic clutch by a
catel controlled by an electro magnet continuously excited by an electric circuit
so that on breaking such circuit at any point the catch is made to release the switch
which is then moved by a weight or spring so as to disconnect the coupling and
render the brake operative substantially as described.
Dated this 28th day of January 1801
ABEL & IMRAY,
Agents for the Applicants.