Improvements in Automatic Electric Cut-outs.
Year: 1895

page_text: Date of Application, 3rd July, 1895-Accepted, 10th Aug.. 1895
COMPLETE SPECIFICATION.
Improvements in Automatic Electric Cut-outs.
We, CHARLES MARK DORMAN,, and REGINALD. ARTHUR. SMITH, both of
Ordsal Electrical Works, Salford, in the County of Lancaster, Electrical
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:-
Our invention relates to that class of electric cut-out in which dippers of metal or
other conductor are withdrawn from mercury.containers by causing the dippers to
revolve in a circular path round an axis by means of a variation in the strength of
an electric current or currents.
The object of our invention is to prevent variation in the position of the point
of unstable equilibrium of the revolving parts of the cut-out through variations in
the level of the surface of the mercury and also to prevent arcing on the surface of
the mercury.
Referring to the drawings Figs. 1 and 2 shew the side and front elevation of
one form of our improved cut-out and Figs. 3 and 4 show the side and front
elevation of another form of our improved cut-out.
In all the figures A. A. are the dippers B. B. are the mercury containers C is
the main axis or pivot round which the dippers revolve D is a solenoid or electro
magnet E is a core or armature. W is a weight.
It will be seen that in the cut-out illustrated the centre of gravity of the
revolving parts pivotted at C is slightly to the left of a vertical line through C.
Figs. 1 and 3, and consequently the cut-out remains at rest in the "on" position
with the dippers in the mercury containers, when however the electric current in
the coil D reaches the strength for which the cut-out is adjusted the core or
armature E is attracted and by means of a lever or link turns the revolving parts
pivotted at C until the centre of gravity of the revolving parts is to the right. of
the vertical line through C. Figs. 1 and 3, the revolving mass then falls over
bringing the dippers clear of the mercury containers. It will be seen that in the
cut-out shewn in Figs. 3 and 4 the position of the axis C is such that after the
dippers A. A. have revolved a few degrees round C they come in contact with
the inside of the mercury containers.
In order to prevent the motion of the revolving mass being arrested by this the
dippers are not rigidly attached to the rest of the revolving mass but are suspended
so that they can revolve freely round the axis F consequently when the switch is
in the "on" position the dippers hang vertically in the mercury containers but as
the switch falls into the "off" position the dippers are lifted by and sweep over
the edge of the mercury containers the final break taking place between the
dippers and the edge of the containers and not on the surface of the mercury.
It will be noticed that in our improved cut-outs the axis C is always placed in
a vertical plane which intersects the centre of buoyancy of the immersed parts of
the dippers when the switch is in the "on" position. The effect of this arrange-
ment is that any little variation in the level of the mercury in the containers does
not as is the case with cut-outs of this type of ordinary construction, where the
axis is differently placed, make any alteration in the balancing of the revolving
barts.
The cut-outs shewn are all of the maximum type in which an increase of the
electric current withdraws the dippers from the mercury containers and thus opens

page_text: the circuit, but it is obvious that our improvements are also applicable to cut-outs
of the minimum type in which the dippers are held in the mercury containers by
means of a solenoid or electro magnet against the action of gravity or a spring and
which open circuit when the current falls below the point for which the cut-out is
adjusted.
It is obvious that the current passing through the coils of the solenoid or electro-
magnet may be either the same current as is controlled by the cut-out or a shunt
therefrom or an entirely separate current.
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. In automatic electric cut-outs in which dippers of metal or other conductors
are withdrawn from mercury containers by causing the dippers to revolve in a
circular path round an axis by means of a variation in the strength of an electric
current or currents the improved method of arranging the axis round which the
dippers revolve in a vertical plane which intersects or approximately intersects the
centre of buoyancy of the immersed parts of the dippers when the switch is in
the "on" position for the purpose of preventing variation in the position of the
point of unstable equilibrium of the revolving parts of the cut-out through variations
in the level of the surface of the mercury.
2. The method of allowing the dippers to trail over the edge of the mercury
containers as shewn in Figs. 3 and 4 and described in the Specification in such a
manner that the final break takes place between the dippers and the edge of the
containers and not on the surface of the mercury.
Dated this 2nd day of July 1895.
CHARLES MARK DORMAN.
REGINALD ARTHUR SMITH.