Improvements relating to Switches, specially applicable to Switches for Electromotors and the like.
Year: 1899

page_text: Date of Application, 23rd Nov.,
1899
Complete Specification Left, 23rd Aug., 1900-Accepted, 6th Oct., 1900
PROVISIONAL SPECIFICATION.
Improvements relating to Switches, specially applicable to Switches
for Electromotors and the like.
We, ROBERT ALEXANDER SLOAN and JOHN EDWARD LLOYD BARNES, both of
34, Castle Street, Liverpool, in the County of Lancaster, Consulting Engineers,
do hereby declare the nature of this invention to be as follows:-
This invention relates chiefly to starting switches for electro-motors, and
more particularly to such switches as comprise a main switch and a resistance or
regulating switch mutually interlocked after the manner described in the Com-
plete Specification of an application for a patent made by us, dated the 16th of
January, 1899, and Numbered 1044.
Our objects in the present invention are to provide suitable automatic devices by
means of which the main switch is opened when the current rises above or falls
below predetermined limits, and to so construct the regulating switch as to pre-
vent its being rapidly moved from the starting position to the normal running
position.
It will be seen on reference to our prior specification referred to that, in virtue
of the mode of interlocking there described, the handle of the main switch
must be moved so as to be clear of the main switch bars before the regulating
switch can be moved from the starting position, and that this feature renders
this type of switch particularly suitable to those cases in which it is desired to
fit automatic circuit opening devices.
When the switch is designed for currents of, say, under 100 amperes, we con-
struct maximum and minimum automatic devices as follows:-
We provide, preferably for each switch bar, (if of the double-pole type), a
suitable spiral or other spring and plunger adapted to overcome the frictional
resistance between the switch bar and its contacts and to push the former clear
of the latter, and we usually fit the switch bars with lighter independent springs
which, when the bars are clear of the contacts, carry them to their full "off"
position; and we provide a retaining device, for the first mentioned springs,
under the control of two electro-magnets, and so arranged that when the switch
is closed the said springs are held in their compressed state so long as the current
is over the minimum but under the maximum.
We have found that the frictional resistance which has to be overcome in
releasing an ordinary detent is too great, and of too uncertain a value, especially
when fairly large forces have to be dealt with, to render it advisable to act
directly on a detent of this kind by means of electro-magnets, and we therefore
arrange the electro-magnets to act on a retaining device constructed as follows:-
We pivotally connect one end of a link A to the end of the spring or to a
plunger or other moving piece actuated thereby, and we connect the other end
of this link to the free end of a link B whose other end is anchored to a fixed
pivot, and we so adjust the lengths and centres of these links that when the
spring is compressed by closing the switch, the centres of the said links come so
nearly into line in the unstable position that the pivotal friction is enough to
hold the spring compressed, a light spring being fitted, if need be, to help to
bring the links into and retain them in this position.

page_text: The armatures of the magnets are so disposed in relation to the links that one
of them that of the minimum magnet-is moved against its magnet poles as
the switch is closed, in opposition to a spring which, when the current is below
the minimum, moves it away from the said poles and in so doing displaces the
links from their position of unstable equilibrium; the other armature-that of
the maximum magnet-also has the same effect on the links when the current
rises above the maximum and the armature is so drawn towards its poles; in
either case, a slight relative displacement of the links is sufficient to render
them inoperative in restraining the spring, which therefore pushes the switch
bar clear of its contacts.
Each switch bar may have an arrangement similar to that described, or the
spiral spring of one of them may be retained by an ordinary detent which is
released by the energy potential in the other compressed spring, so that the
electromagnetic release of the one switch bar has the effect of opening both, and
of course either the maximum device 'inay be dispensed with; or the one may be
fitted to the one switch bar and the other to the remaining bar.
It will be noticed that neither of the automatic devices interfere with the
opening of the switch by hand in the ordinary way.
When heavy currents have to be dealt with we modify the construction as
follows:-
The switch bars are each fitted with springs adapted to move them to the
"off" position against a moderate frictional resistance between them and their
contacts, but we provide means, preferably of a toggle-joint type, adapted to
increase the pressure between the bars and their contacts by movement of the
latter when the switch is closed, and we control the lever which operates this
toggle by a retaining device, under the control of two electro-magnets, as de-
scribed in connection with the form of switch just described. It will be noted
that the automatic devices described may be applied in the case of automatic
circuit breakers for general purposes, although specially useful in connection
with the arrangements mentioned.
We operate the arm of the regulating switch by epicyclic gear, the train of
wheels comprising two concentric wheels of equal diameter, one fixed, and the
other attached to the switch arm concentrically with its centre of motion; these
wheels whose respective numbers of teeth differ by, say, one, both gear with an
epicyclic pinion which is carried bodily round by an arm on which it is carried
and which, as it rotates also about its own axis freely, gives a slow movement of
rotation to the wheel fixed to the switch arm.
In those cases where, even with the last mentioned construction, it is within
the power of the attendant to move the switch arm too quickly, we modify the
arrangement as follows:
-
We pivot a double pawl at the end of the switch arm whose opposite ends
engage alternatively with teeth, formed on a sector over which the arm moves,
so as to lock the arm against movement excepting when the pawl is oscillated,
when the arm can be moved over one tooth for each double oscillation.
A loose handle is centred on the arm and it is arranged to so engage with the
pawl that it has to be rotated-relatively to the arm-through a considerable
engle in order to oscillate the pawl. It is therefore necessary, in order to move
the arm, to rotate the hand alternately in opposite directions to oscillate the pawl,
and as the angle of rotation may be arranged to be almost as great as four right
angles, it will be seen that with this arrangement it is impossible to move the
switch bar too quickly.
The pawl may be arranged to lock the arm in both directions, or by backing
off the teeth, the arm may be left always free to be quickly moved backwards.
Dated this 22nd day of November 1899
SLOAN & LLOYD BARNES,
Chartered Patent Agents,
34, Castle Street, Liverpool,

page_text: Improvements relating to Switches, specially applicable to Switches
for Electromotors and the like.
We, ROBERT ALEXANDER SLOAN and JOHN EDWARD LLOYD BARNES, both of
34, Castle Street, Liverpool, in the County of Lancaster, Consulting Engineers,
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 chiefly to starting switches for electro-motors, and more.
particularly to such switches as comprise a main switch and a resistance or
regulating switch mutually interlocked after the manner described in the Com-
plete Specification to our British Letters l'atent dated the 16th of January, 1899,
and Numbered 1044.
Our objects in the present invention are, to provide suitable automatic devices
by means of which the main switch is opened when the current rises above or
falls below predetermined limits, and to so construct the regulating switch as
to prevent its being rapidly moved from the starting position to the normal
running position.
It will be seen on reference to our prior specification referred to that, in virtue
of the mode of interlocking there described, the handle of the main switch must
be moved so as to be clear of the main switch bars before the regulating switch
can be moved from the starting position, and that this feature renders this type
of switch particularly suitable to those cases in which it is desired to fit auto-
matic circuit opening devices.
We have illustrated our invention in the accompanying drawings, in which
Fig. I is a front elevation and Fig. II is a plan, the magnets being removed
in the latter view for the sake of clearness; Fig. III is a side elevation and
Fig. IV is a fragmentary section on the line A, A, of Fig. I. Figs. V, VI, and VII
are fragmentary views showing details of the magnets for effecting the auto-
matic opening of the main switch, Fig. V being a plan as seen from above,
Fig. VI a plan as seen from below, and Fig. VII a sectional elevation on the
line B, B, of Figs. IV and V. Figs. VIII and IX are detail views of the device
for ensuring that the resistances cannot be cut out too quickly, Fig. VIII being
an elevation with the hand knob. removed, and Fig. IX a sectional plan on the
line C, C, of Fig. VIII. Figs. X, XI and XII show a modification of the switch
suitable for heavy currents. the views being respectively front elevation, side
elevation, and plan; Fig. XIII is a fragmentary view showing the positions of
the toggle joints when the switch is open.
Referring in the first instance to Figs. I to IX, we provide a double-pole main
switch comprising switch bars a which are adapted, when the switch is closed, to
connect the contacts b and c, and which are operated by levers & connected by
an insulating har e to a handle f; the handle f, the bar e, and the levers d thus
form a loose or disconnected handle by means of which the switch may be
opened and closed. The poles of this switch are preferably mounted on separate
slates as shown, the negative on, say the right hand or narrow slate and the
positive on the left hand slate.
We also mount on this latter slate a regulating switch comprising an arm,
moving over a series of contacts h, and means (to be hereinafter described) for
preventing the arm g being moved too rapidly as it is pushed over to cut out the
resistances inserted between the successive contacts h. The main switch and the
regulating switch are also interlocked by means of a segmental locking piece i

page_text: ou one of the levers d, (the positive one in the arrangement illustrated), and a
quadrantal locking piece on the switch arm g: From an inspection of the draw-
ings, Figs. I, II and III, it will be seen that the interlocking of these two
locking pieces renders it impossible either (1) to close the main switch when the
regulating arm is in any position other than the one in which it is shown in
Fig. I, which is the starting position; or (2) to move the arm from this
position till the handle f has been drawn back (after the switch is closed) clear
of the switch bars, (as indicated in dotted lines in Fig. III.) thus leaving the
latter quite free to open.
We also provide a maximum device M and minimum device N; the former
causes the main switch to open when there is an overload, and the latter causes
it to open when there is an underload or when the supply is cut-off.
It will be convenient before describing the devices M and N, to revert to the
main switch and describe the details of its construction. The contact pieces e
are of ordinary construction, but the others, b, as will be seen more particularly
from Fig. IV, are hollow, and are provided with plungers k, normally pressed
outwardly by the springs 1. The latter springs when compressed and free to act
are of-sufficient strength to overcome the frictional resistance between the switch
bars a and their contacts, so that unless the springs are held in their compressed
state it is impossible to leave the switch closed; the bars may each be provided
with a smaller spring m adapted to carry the switch bar over to its full "off"
position after the spring 7 has reached its outward limit, as indicated in dotted
lines in Fig. IV. The mode of holding the spring in its compressed position is
as follows: We attach to the plunger (see Figs. II and IV, negative con-
tact ) a pin n which is articulated to the fixed pivot o by means of the two
links P and which, (as will be seen clearly in Fig. II), form a toggle joint, the
arrangement being such that when the plunger is pushed in and the spring com-
pressed, in the act of closing the switch, the three pivots of the toggle joint are
brought into line or approximately so; if however a very slight force be applied
to turn the link g clock-wise, the pivotal friction being very small, such slight
force will turn it past the dead centre, when, of course, the spring again be-
An exactly
comes operative and pushes the switch bars clear of the contacts.
similar arrangement may be adopted in the case of each of the contacts b, but we
have shown, in connection with the positive contact b, an arrangement which we
find works well in practice; the plunger in this case is held in its retracted
of the toggle
position by an ordinary detent r which is articulated to the link
by a rods, the connection being such that the link q can move from its "dead
centre" position for some distance before it begins to operate the detent r. The
object of the latter provision is to make use of the energy stored up in the
spring of the contact b to operate the detent r, and this is, of course, done in
the arrangement illustrated, inasmuch as the link 9, as soon as it is just clear of
the dead centre position, is deflected by the full force of the spring / acting
with an increasing leverage. We have found that with any form of ordinary
detent, the force required to disengage is so considerable and variable that the
action is very uncertain when only comparatively small forces are available, and
we attach considerable importance to what we term the pivotal form of detent
described, which forms such a delicate trigger that the force necessary to operate
it may be very small; moreover we find the resistance to be overcome by such
operating force is exceedingly constant.
"
Returning now to the maximum and minimum devices M and N:-The maxi-
mum device comprises a magnet t having suitable pole pieces and an armature u
which form a fairly complete magnetic circuit. The mode of carrying the
armature is shown in Figs. V. VI and VII; the magnet and its pole pieces are
attached to non-magnetic cheeks and in the upper one of which, v, there is a
slot shaped as shown in Fig. VII, and the armature is undercut, as indicated in
this latter figure, and is carried by a knife edge formed in the cheek and is
thus very freely suspended, and its lower end is guided in a slot formed in the

page_text: دو
lower cheek w. The armature u has a screwed rod a on which a counterbalance y
fits as a nut; this counterbalance keeps the armature u in its "off" position,
away from the lower pole face, as shown in the drawings, and the force to be
overcome in order to move it from this position may be varied by varying the
position of the counterbalance y on the screw x. When however the current
circulating round the coils of the maximum magnet t reaches a predetermined
limit and pulls the armature over, the lower end of the latter engages with the
dead centre
abutment on the link q, (see Fig. II), and moves it from its
position, with the result already described.
In the case of the minimum device N, the action, of course, requires to be such
that it operates the link when the current is less than a predetermined limit.
The construction of the magnet, pole-pieces, armature, and cheeks of the mini-
mum device is similar to that described in connection with the maximum device,
except that the minimum magnet 1 tends to draw the armature 2 away from
engagement with the pivot 3 of the toggle, and that a spring 4 is now provided
which normally tends to push the armature into engagement with the pivot 3
of the toggle, or, of course, with any convenient part of the link q. It will be
seen, therefore, that unless the current flowing round the minimum magnet
coils is sufficient to overcome the spring 4, the switch cannot be left closed; in
this way the two devices described, by their action on the link q, cause the
switch to open when the value of the current falls below or rises above assigned
limits.
It may be pointed out here that a considerable incidental advantage of the
pivotal detent results from the fact that as the switch is closed and the toggle
straightened, the armature of the minimum magnet is pushed, automatically,
almost into contact with the pole face, thus materially reducing the reluctance
of the magnetic circuit and therefore necessitating a much smaller magnetising
current than would have been necessary had there been a considerable air gap.
We will now describe the means for preventing the arm g, of the regulating
switch, from being too rapidly moved over its contacts. We provide a circular
toothed arc 5 (see Figs. I, II, VIII and IX) over which the end of the arm g
moves, and in a cavity in the underside of this arm we pivot a double engage-
ment pawl 6; this pawl is pivoted on, but is free to move about the spindle 7
which serves also to pivotally connect the knob 8 to the arm g, and it will be
seen from the shape of the pawl, that when it is partly rotated to cause the one
end to clear an engaging tooth of the arc 5, it has to be moved into such position
as ensures the engagement of the opposite end of the pawl with the same or the
next tooth; thus to move the arm in the direction indicated by the arrow,
becomes necessary to vibrate the pawl 6 after the manner of an escapement,
giving a step by step movement. If the pawl were directly connected to the
knob 8 it would be simply necessary to vibrate the knob through a comparatively
small angle, whilst maintaining the directional pressure, to ensure a fairly rapid
movement of the arm g; we find, however, that if, instead of making a direct
connection between these 'two, we carry a pin 9, secured to the pawl, through á
slot 10 in the arm g (see Fig. VIII), and provide the knob with an annular
groove 11 into which the pin 9 projects, we can, by making the annular slot
extend through nearly 360° and rendering it necessary to rotate the knob through
nearly 360° each time the pawl is to be vibrated, make it impossible to move
the arm rapidly, in the direction of the arrow, from one extreme position to the
other. It will be seen also that by altering the number of the teeth in the arc
or by altering the length of the groove 11 in the knob, the time taken to move
the arm from the one extreme position to the other may be varied within wide
limits.
it
Reverting again to the main switch, it will be seen that the spring must be
sufficiently strong to overcome the frictional resistance of the contacts, and
although in switches of moderate size it is quite practicable to use such springs,
especially where there is one spring for each switch bar, we find in very large

page_text: switches that it is desirable to modify the arrangement, as shown in Figs. X
to XIII, to which reference will now be made.
Instead of placing a spring in each contact, to act through a plunger, we use
a coiled spring 12 which tends to turn the switch bar 13 about its spindle 14
so as to withdraw it from the contacts 15, 16, and the spring is made strong
enough to overcome the normal frictional resistance. In order to keep the
switch closed, the friction is increased by increasing the normal pressure between
the surfaces. This is accomplished by making one of the extreme side pieces
of each contact rigid, and making the other side, (or where the contact is
multiple as shown in the drawing, the other portions) flexible, and so connecting
the extreme flexible portions, by means of pivots 17 and 18 and links 20, and 21,
pivoted together at 19, that the links form a toggle which when it is straightened,
so that the pivots are in line, increases the normal pressure between the con-
tacts. The main toggle is held in its straightened position by a pivoted de-
tent 22, 23, similar in its action to the one already described; this pivoted detent
is controlled by a maximum device M and a minimum device N similar to those
already described, except that in this arrangement the maximum device acts on
the tail of the link 22. The short link 21 of the main toggle consists of two
screws, one left handed and one right-handed, united by a nut, by means of
which the length of this link may be adjusted to take up wear. The short
link 23 of the pivoted detent is prolonged to form a handle which forms a very
convenient device for closing the main toggle; the action in this respect will
be clearly understood from Fig. XIII.
For the sake of clearness, the handle 24 of the switch is shown as being fixed
directly to the switch arm, but, of course, when the main switch is interlocked
with a regulating switch the handle is loosely connected like the handle f and
is interlocked like the latter.
It may be well here to draw attention to the following features of our inven-
tion:-
It is possible, notwithstanding the interlocking devices and the releasing
devices, to always open the switch by hand; the regulating switch cannot be
moved to the position in which the resistance is cut out until the switch bars are
left quite free for the operation of the releasing devices; and the switch cannot
be held closed against a dead short circuit on the motor, inasmuch as it can only
be held closed when all the resistance is in circuit, moreover, the minimum
armature is, as already described, automatically brought into engagement with
the magnet pole as the switch is closed.
The electrical connections can of course be varied; for instance the minimum
magnet may be wound with a shunt coil, or it may be put in series with the
shunt coil of a shunt motor.
It will also be noticed that the slow movement device for the regulating
switch is operative in one direction only, so that the resistance may be put in
quickly; and that part of our invention may be applied to those forms of motor
switches in which the arm is held in the running position, (that is where the
resistance is all cut out), by an electro-magnet which is de-energised when the
current falls below or rises above the limits in which case a spring pulls the
arm back to the starting position, the pawl tripping over the teeth and offering
no resistance.
Having now particularly described and ascertained the nature of our said
invention, and in what manner the same is to be performed, we declare that what
we claim is :-
1. In combination: A switch bar, a handle by which the bar is operated,
insulated contacts adapted to be electrically connected by the bar, a spring which
is compressed when the contacts are so connected and which tends to force the
bar out of the contacts, a detent for holding the said spring compressed but
which leaves the switch bar free to be opened by the handle, and means for

page_text: releasing the said detent when the current carried by the switch falls below
or rises above a predetermined limit; substantially as described and illustrated.
2. In combination: --A main switch bar, contacts therefor, a spring which is
compressed when the switch bar is in its contacts and which tends to force
the said bar out of its contacts; a detent for holding the said spring compressed
but which leaves the switch bar free to be operated by hand, means for releasing
the said detent when the current falls below or rises above predetermined limits,
a loose handle, adapted to open and close the switch bar and provided with a
locking piece; a regulating switch provided with a locking piece which, when
the regulating switch is in any position other than the starting position, locks
the main switch handle in its off position, and which, when the latter is in con-
tact with the closed switch bar, is locked in the starting position; substantially
as described and illustrated.
3. In combination:-The switch bar, the contacts, the spring tending to force
the bar out of its contacts, the pivoted links whose opposite ends are connected
respectively to a fixed pin and to a pin holding the spring, and which are adapted,
when closed so that their centres are in line, to hold the said spring compressed,
and the means for releasing the said spring by pushing the links out of line;
substantially as described and illustrated.
4. In a double-pole switch, in combination: -The switch bars, the contacts
the springs and the two detents, one of the latter consisting of pivoted links,
and the other of a detent connected to the said links by a rod which, when the
links are opening under the influence of the spring which they control, transmits
the force of the said spring to the detent to release it; substantially as described
and illustrated.
5. In a regulating switch, in combination, the switch arm, the toothed arc,
the double acting pawl, and the pivoted handle adapted to move the pawl in
opposite directions when the extremities of an annular slot therein engage with
a pin attached to the pawl; substantially as described and illustrated.
6. In a regulating switch, in combination; the switch arm, the toothed arc,
the double acting pawl and a handle adapted to oscillate the said pawl and to
move the switch arm; substantially as described and illustrated.
7. In a main switch, in combination; the switch bar, the contacts, one portion
of each of which is rigid and one portion flexible, the toggle adapted to press the
flexible parts towards the rigid parts, a detent to hold the said toggle, and means
for releasing the detent when the current through the switch falls below or
rises above a predetermined limit; substantially as described and illustrated.
8. The improved motor starting switch, substantially as described and illus-
trated in Figs. I to IX.
9. The improved motor starting switch, substantially as described and illus-
trated in Figs. X to XIII.
Dated this 22nd day of August 1900.
SLOAN & LLOYD BARNES,
Chartered Patent Agents,
34, Castle Street, Liverpool.