Improvements in Adjustable Liquid Resistances for Starting and Regulating Electric Motors.
Year: 1897

page_text: This Print is in accordance with the Original Specification as it stands after
Amendment (under Section 11 of the Patents, &c. Act, 1883) as required
by the decision of the Chief Examiner of the 14th day of June 1898.
Date of Application, 20th Jan.,
1897
Complete Specification Left, 20th Sept., 1897-- Accepted, 13th Nov., 1897
PROVISIONAL SPECIFICATION.
Improvements in Adjustable Liquid Resistances for Starting and
Regulating Electric Motors.
I, JOHN HENRY HOLMES, of Portland Road, Newcastle on Tyne, in the County
of Northumberland, Electrical Engineer, do hereby declare the nature of this
invention to be as follows:-
The object of the improvements is to so construct and arrange the working parts
that the apparatus is rendered more compact and the materials are used to the
best advantage.
This invention is applicable to the type of liquid resistance in which the
electric circuit is completed through a metallic plate dipping into a conducting
liquid contained in a suitable containing vessel and in which the adjustment of
the resistance is affected by the greater or less immersion of the plate in the
liquid.
Resistances of this class have been constructed with the plate attached to a lever
turning on a centre situated at or near to one end of the vessel containing the
liquid and so arranged that when the lever is moved through approximately
90 degrees of arc the plate is carried from a position of almost complete immersion
to a position in which it is entirely withdrawn from the liquid.
Resistances of this class have also been constructed in which the plate is moved
in a vertical direction by guide bars or equivalent devices so as to withdraw or
immerse the plate as desired for the purpose of varying the resistance.
I do not make claim to apparatus of either of the types I have just described
but only to the type which is the object of this invention and which differs
radically from others as will be made clear by the following description.
Liquid resistances made according to this invention consist essentially of a
metallic plate supported on a horizontal spindle and capable of being dipped into
a conducting liquid by revolving the plate around the axis the situation of which
axis is a little distance above the surface of the liquid and approximately at the
middle of the length of the vessel containing the conducting liquid.
This axis as far as the plate is concerned is situated near one side of the plate
and at the middle of that side and at right angles to the surface of the plate.
The range of movement of the spindle which carries the plate is approximately
180 degrees of arc and the parts are so arranged that at one of the extreme limits
of the movement the plate will be entirely withdrawn from the liquid whilst at
the other end of the travel the plate will be almost entirely immersed in the
liquid.
I prefer to make the plate nearly semicircular in shape and having the centre

page_text: of the semicircular arc coincident with the axis around which the plate is
revolved.
This semicircular shape is very compact and makes it possible to work with the
minimum quantity of liquid and when the plate is immersed with a very short
distance between every part of the plate and the liquid containing-vessel
especially when the vessel is also semicircular in cross section at right angles to
the axis.
I find that liquid resistances constructed according to this invention are
especially adapted to use in connection with reversing electric motors in as much
as it is immaterial whether the rotation of the spindle carrying the plate be made
to the right hand or to the left as a movement of 180 degrees in either direction
will result in changing the condition of the plate from one of total withdrawal
to one of nearly total immersion in the liquid or vice versa.
It is often convenient to control a reversible electric motor by means of a lever
acting on the reversing and starting resistance switches and arranged so that a
movement of such a lever from a middle position will cause the armature of the
motor to revolve in one direction or the opposite according to whether the lever
be moved towards one side of its mid position or the other. The movement of
such levers is usually limited to about 90 degrees of arc and in such cases I prefer
to work the reversing switch through a direct connection with the lever whilst
the requisite angular movement of the plate spindle is obtained by gearing up.
I sometimes make use, upon the same spindle, of more than one plate dipping
into the same liquid-containing-vessel so as to expose a greater surface to the
liquid when immersed or the surface of the plates may be increased by ribs for a
similar object. The vessel containing the liquid may also be fitted with ribs or
partitions to decrease the resistance through the liquid when the plate is
immersed.
To make the movement of the plate round the axle smoother and almost
independent of the force of gravity balance weights may be fixed on the side of
the spindle opposite to the plate or plates but further along the spindle so that
the balance weights may revolve in a plane outside of the vessel containing the
resistance.
T
1011 1
T
1007
Improvements in Adjustable Liquid Resistances for Starting and
Regulating Electric Motors.
I, JOHN HENRY HOLMES, of Portland Road, Newcastle on Tyne, in the County
of Northumberland, 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:
According to this invention I use in combination (a) an adjustable liquid
resistance consisting of a metallic plate or plates mounted on a spindle lying
across the top of a vessel containing a conducting liquid, such spindle requiring
an angular movement of approximately 180° degrees of arc to carry the plate
from a position of total withdrawal from to one of almost total immersion in
the liquid, substantially as described and illustrated in the accompanying draw-
ings; (b) a reversing switch; (c) a lever operating the same, and (d) gearing
for producing a different angular velocity of the reversing switch and the spindle
upon which the plate (or plates) is mounted.

page_text: Fig. 1 is a side elevation, and Fig. 2 a cross section, of an adjustable liquid
resistance such as above referred to combined with a reversing switch of a well
known type, so as together to constitute a starting stopping and reversing switch
and adjustable resistance controlled by one lever and adapted for use in connec-
tion with electric motors.
A metallic plate 1 is mounted on a spindle 2 carried in one long bearing 3,
the position of the parts being such that the plate may be dipped into a conduct-
ing liquid contained in the metallic box 4 by rotation of the spindle 1 in either
direction. The plate is counterbalanced by the weight 6.
The bearing 3 is electrically insulated from box 4 by reason of the bearing
being bolted to a stout slate 8, which in turn is attached to the box 4 by bolts 9 at
its four corners. The slate 8 also serves as a support, as well as an insulation, for
the contacts of the reversing switch, and also carries the pivot 10 upon which the
lever 11 is rotated.
The contacts of the switch are constructed so that connection may be made to
them by means of springy copper brushes 12 pressing upon the two surfaces of
the contacts. The two upper brushes 12 in Fig. 1 are metallically connected,
but insulated from the lever 11 by which they are moved, and the two lower
brushes 12 are similarly disposed. The contacts of the switch are of such a length
that when the lever is in a vertical, or middle position, as shewn on the drawings
Figs. 1 & 2, the springy brushes 12 do not touch the contacts, but a slight
angular movement of the lever 11 in either direction makes connection between
the brushes and the contacts, and causes the current to flow through the armature
of the motor in one direction, or the reverse, as is easily understood by persons
conversant with apparatus of this kind. I prefer to make the upper contact of
the switch in three parts 13, 14 and 15 as shewn, 13 and 14 being connected to the
bearing 3, and the middle piece 15 being connected to the box 4. The object of
this construction is to short circuit the liquid resistance when the lever is hard
over in either direction.
The lever 11 is intended to have a maximum angular movement of 45 degrees
of arc in either direction, and to enable this movement to effect the immersion
in, and withdrawal from, the liquid of the plate, the spindle 2 carrying the latter
is geared to the lever as shewn by a toothed pinion 16 keyed on to the spindle 2
and meshing with an internal toothed segment 17 forming part of the lever 11.
The proportions of the gearing are such that the plate 1 receives an angular
movement of 180 or a slightly greater number of degrees of arc for a movement
through 45 degrees of the lever 11. It will be observed that a gradual movement
of the lever 11 to either side of the middle or vertical position first of all inserts
the armature in the circuit, and then completes the connection by dipping à
corner of the plate 1 into the liquid; a further movement reduces the resistance
in a gradual manner by reason of a greater immersion of the plate 1 in the liquid
and at the last short-circuits the liquid resistance at contact 15 as explained
above.
It will be obvious that reversing switches of different pattern might be used,
and that the gearing shewn in drawings Figs. 1 & 2 might be modified, and for
example an external toothed segment 17 might be found more convenient in
certain cases.
I sometimes make use, upon the same spindle, of more than one plate dipping
into the same liquid-containing vessel, so as when immersed to expose a greater
surface to the liquid, or the plate 1 and box 4 may be fitted with ribs or gills,
so as to expose a large surface to the liquid, and thus reduce the resistance when
the plate is immersed.
I do not claim broadly, for starting and regulating electric motors, the use
of liquid resistances of the type in which the electric circuit is completed through
a metallic plate or plates dipping into a conducting liquid, contained in a suitable
vessel, and in which the the adjustment of the resistance is effected by the greater
or less immersion of the plate or plates in the liquid.

page_text: I am aware that resistances of this class have been constructed, having the
plate or plates attached to a lever turning on a centre situated at or near the one
end of the vessel containing the liquid, and so arranged that when the lever is
moved through approximately 90 deg. of arc, the plate is carried from a position
of almost complete immersion to a position in which it is entirely withdrawn
from the liquid; also that resistances of this class, have been constructed in
which the plate is moved in a vertical direction by guide bars or equivalent
devices, so as to withdraw or immerse the plate as desired for the purpose of
varying the resistance; -also that a reversing switch has been combined with
the liquid resistance-comprising a liquid-containing vessel or vessels, and a
plate able to move about a horizontal axis into and out of the liquid, the arrange-
ment being such as to break or make the current at the surface of the liquid
while the commutator brushes are in contact with the conducting surfaces of
the commutator; also that in apparatus comprising an electric current revers-
ing switch or commutator, and a liquid resistance so arranged as to cause the
break or make of the current to take place at the surface of the liquid while the
commutator brushes are in contact with the conducting surfaces of the commu-
tator, it has been proposed to connect by gearing a controlling lever with a recti-
lineally moving plate or plunger in such manner as to give a long range of
action to it, as compared with the commutator, and its controlling lever. I am
further aware that in connection with non reversing switches resistances have
been proposed constructed with plates attached to an axle lying across a vessel
containing a conducting liquid so arranged that if the axle were moved through
approximately 180 degrees of arc, the plates would be carried from a position of
almost complete immersion to a position in which they would be entirely with-
drawn from the liquid
I do not make claim to apparatus of either of the kinds just described, but
only to the type which is the subject of my invention as set forth in the claiming
clauses hereinafter contained.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what
I claim is:
First. For starting and regulating electric motors, the combination of (a) an
adjustable liquid resistance consisting of a metallic plate or plates mounted on
a spindle lying across the top of a vessel containing a conducting liquid, such
spindle requiring an angular movement of approximately 180 degrees of arc to
carry the plate from a position of total withdrawal from to one of almost total
immersion in the liquid, substantially as described and illustrated in the accom-
panying drawings, (b) a reversing switch (c) a lever operating the same, and (d)
gearing for producing a different angular velocity of the reversing switch, and
the spindle upon which the plate (or plates) is mounted.
Secondly. The starting, stopping and reversing switch and adjustable resistance
as a whole substantially as described with reference to Figs. 1 & 2 of the
accompanying drawings."
Dated this Eighteenth day of September 1897.