Improvements in Electric Measuring Instruments.
Year: 1897

page_text: Date of Application, 15th Apr., 1897
Complete Specification Left, 11th Dec., 1897-Accepted, 15th Jan., 1898
PROVISIONAL SPECIFICATION.
Improvements in Electric Measuring Instruments.
We, EVERSHED & VIGNOLES LTD., of Woodfield Works, Harrow Road,
London, W., Electrical Engineers, and SYDNEY EVERSHED, of the same address,
Electrical Engineer, do hereby declare the nature of this invention to be as
follows:-
This Invention relates to Ammeters, Voltmeters Wattmeters and the like, and
its object is to make such instruments aperiodic or "dead-beat." It is well
known that certain types of instruments can be made aperiodic either by causing
a light vane attached to the moving parts to move in a viscid fluid, or by causing
a conducting electric circuit forming part of the working mechanism (or attached
for the purpose to the moving parts) to move in a strong magnetic field. These
two methods are however not readily applicable to the types of measuring instru-
ments more commonly employed on switchboards. Such instruments usually have
some form of working mechanism in which a horizontal axle carries an index
ranging over a dial in a vertical plane, and the inertia of the moving parts being
usually large compared with the forces acting upon them, no adequate means for
rendering the movements of the working mechanism and index aperiodic have
hitherto been known.
According to our Invention any electric measuring instrument in which an axle
capable of rotation through an angle less than 360 degrees is employed, and more
particularly such instruments as are commonly used on switchboards, is made
aperiodic by attaching a light vane of aluminium or other suitable material, pre-
ferably rectangular in shape, to the working axle and causing the vane to move
with very little clearance within a box, preferably cylindrical in shape, fixed
with its axis coincident with that of the working axle. The box is closed at each
end by a flat plate having a small hole at the centre through which the axle passes
with as little clearance as possible. Flat partitions are fixed to and within the
box so as to force the air within it when set in motion by the vane to pass
from one side of the vane to the other through the very small clearances left
between the edges of the vane and the internal surfaces of the box.
The positions of the partitions inside the box depend on the angular range of
the working mechanism one partition being fixed just beyond the zero position
of the vane, and another just beyond the position taken up by the vane when the
instrument is at its maximum reading. When the vane extends on both sides
of the axle four partitions are in general required, a pair for each end of the vane,
but when the angular range of the instrument is a little less than 180 degrees
two partitions will suffice.
An instrument to which our Invention has been applied will be absolutely

page_text: aperiodic provided suitable proportions depending on the inertia of the moving
parts are given to the box and vane.
Date : 101
A
100~
Improvements in Electric Measuring Instruments.
We, EVERSHED & VIGNOLES., LIMITED, of Woodfield Works, Harrow Road,
London, W., and SYDNEY EVERSHED, of the same address, 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:―
This Invention relates to Ammeters, Voltmeters Wattmeters and the like, and
its object is to make such instruments aperiodic or ❝ dead-beat." It is well
known that certain types of instruments can be made aperiodic either by causing
a ligne vane attached to the moving parts to move in a viscid fluid, or by causing
a conducting electric circuit forming part of the working mechanism (or attached
for the purpose to the moving parts) to move in a strong magnetic field. These
two methods are however not readily applicable to the types of measuring instru-
ments more commonly employed on switchboards. Such instruments usually have
some form of working mechanism in which a horizontal axle carries an index
ranging over a dial in a vertical plane, and the inertia of the moving parts being
usually large compared with the forces acting upon them, no adequate means for
rendering the movements of the working mechanism and index aperiodic have
hitherto been known.
According to our Invention any electric measuring instrument in which an axle
capable of rotation through an angle less than 360 degrees is employed, and more
particularly such instruments as are commonly used on switchboards, is made
aperiodic by attaching a light vane of aluminium or other suitable material, pre-
ferably rectangular in shape, to the working axle and causing the vane to move
with very little clearance within a box, preferably cylindrical in shape, and fixed
with its axis coincident with that of the working axle. The box is closed at each
end by a flat plate having a small hole at the centre through which the axle passes
with as little clearance as possible. Flat partitions are fixed to and within the
box so as to force the air within the box and when set in motion by the vane to pass
from one side of it to the other through the very small clearances left
between the edges of the vane and the internal surface of the box.
The positions of the partitions inside the box depend on the angular range of
the working mechanism one partition being fixed just beyond the zero position
of the vane, and another just beyond the position taken up by the vane when the
instrument is at its maximum reading. When the vane extends on both sides
of the axle four partitions are in general required, a pair for each end of the vane,
but when the angular range of the instrument is a little less than 180 degrees
two partitions will suffice.
An instrument to which our Invention has been applied will be absolutely
aperiodic provided suitable proportions depending on the inertia of the moving
parts are given to the box and vane. It is desirable that the working mechanism
of the measuring instrument should be designed to have as small a moment of

page_text: inertia as possible and for this reason we prefer to make the index of our aperiodic
instruments of aluminium in the form of strips or tubes.
In order that our Invention may be clearly understood we will describe it with
reference to the accompanying drawings Figs. 1, 2, 3, 4, 5 & 6, in which like letters
refer to like parts.
In Figs. 1 & 2 we show respectively an axial section and front elevation of an
ammeter or voltmeter to which our present Invention has been applied. We show
an instrument with a horizontal axle and a gravity control but our Invention is
equally applicable to axles in any position and controlled by other forces than
gravity. The working mechanism M of the ammeter is attached to an axle A
pivotted in centres JJ which are attached to a frame F. Attached to the frame
and preferably forming part of it is a cylindrical box B herein called the ", vane-
box within which a light vane V fixed on the axle is able to rotate with very
small clearance. The front of the vane-box is closed by two semi-circular discs D D
The index I and controlling weight W are fixed to the axle in front of the discs D D
in such a position that the index may range over a suitable dial S. In order to
prevent the free motion of the air within the vane-box we fix radial partitions P P
in such positions as will allow the vane and index to move over an angle a little
greater than that covered by the scale of the instrument.
To facilitate the construction of a vane-box and vane with small clearances we
prefer to attach the vane to a small tube T which is fixed concentrically to the
axle, and the partitions P P are fixed so that they very nearly touch this tube
leaving only a small passage for the air.
The working coil C of the instrument is fixed at the back of the vane-box. In
Fig. 2 the frame F and discs D D are omitted in order to show the vane-box and
vane more clearly.
The ammeter shown in the drawings as an illustration of our Invention is that
patented under No. 20723/1893. Our Invention is however readily applicable to
other types of measuring instruments it being only necessary to modify the frame F
in order to adapt it to any of the working mechanisms commonly used in
Ammeters, Voltmeters, Wattmeters, and similar electrical Measuring Instruments.
In Fig. we have shown four partitions in the vane-box which limit the
angular movement of the vane and index to an angle of about 90 degrees. When
an angular range approaching 180 degrees is required we prefer to use only two
partitions as shown in Fig. 3 and when an angular range approaching 360 degrees
is required, we use only one partition and a vane extending only on one side of
the axle as shown in Fig. 4.
For small angular ranges we may use the modified form of vane-box and vane
illustrated in Fig. 5 where four partitions are shown equally spaced and two
vanes fixed at right angles are shown attached to the axle.
In Fig. 6 we show another modification in which there is a cylindrical exten-
sion E at each end of the vane and concentric with the axle and the vane-box.
This extension is adapted to move within a narrow circular channel R forming
part of the vane-box. The object of this modification is to provide a greater
resistance to motion than is afforded by the vanes shown in the previous figures.
In an instrument such as that shown in Figs. 1 & 2 we find that with a light
aluminium index 4" or 5" in length, a vane-box about 2" in diameter and 3/4"
deep suffices to make the instrument aperiodic provided the clearances between
the vane and box do not exceed 1/32" but these proportions although suitable for
the particular instrument described may be modified in order to adapt our Inven-
tion to other forms of instrument.
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:-
-
In an electrical measuring instrument a vane or vanes fixed on the pivotted
axle of the working mechanism and adapted to move with small clearances within

page_text: a box containing one or more partitions; for the purpose set forth and substantially
as described, reference being had to the accompanying drawings.
Dated this 9th day of December 1897.
EVERSHED & VIGNOLES LIMITED.
HORACE M. GREGORY,
W. E. AYRTON,
Directors