Improvements in Electric Demand Meters.
Year: 1897

page_text: PROVISIONAL SPECIFICATION.
Improvements in Electric Demand Meters.
I, ARTHUR WRIGHT, of 26, Park Crescent, Brighton, in the County of Sussex,
Electrical Engineer, do hereby declare the nature of this invention to be as
follows:-
:―
My invention relates to improvements in what are now known as electric
demand meters, that is to say, instruments which record the maximum or
minimum demand which has been made upon the supply circuit during a given
period of time
As is well known the record given by such instruments is a record of the
maximum deflection in one direction or the other of the movable indicating part
of the instrument.
My invention consists of a simple means of recording such maximum
deflections and it consists essentially of the combination of a detaining device and
a detainable device. To these essential elements I sometimes find it convenient
to add what I may term a reinforcing device, that is to say, a device which will
insure a proper and sufficient action of the detaining device upon the detainable
device when required. I employ the devices herein before mentioned in combina-
tion with the elements of any convenient form of galvanometer or electric meter.
All forms of galvanometer or electric meter depend for their indications upon
the relative movement or change of relative position of a fixed and a movable
element or of two movable elements and in carrying my invention into
effect what I do is to cause the detaining device of my invention to engage with
the detainable device at the point of maximum deflection so as to prevent any back-
ward movement of the deflected or movable part of the instrument, whilst at the
same time permitting of any further deflection due to an increased demand upon
the supply circuit.
The detaining device in my invention may consist of any convenient form of
gripping device suited to the detainable device which may consist of any pro-
longed or extended part adapted to be gripped or held at different places through-
out its length. Thus if the detainable device be a rack or a ratchet wheel for
example, the detaining device may conveniently take the form of a click or pawl
and if this rack or ratchet wheel be attached to the movable part of the instrument
and the click or pawl to the fixed part of the instrument, so as to prevent any back-
ward movement of the said detainable part, a record of the maximum deflection
can easily be obtained. For example let us assume that an ordinary form of gal-
vanometer is employed in which the movable part consists of a pointer mounted
rigidly upon an angularly moving axis. If now a ratchet wheel be attached to
the said axis so as to move angularly with the pointer or needle and if a click or
pawl be attached to any convenient fixed part of the instrument in such manner
that when deflection in the normal direction takes place the click will ride over
the teeth of the ratchet wheel but will lock between two of the said teeth when
backward movement takes place, then it will be clear that the detaining and the
detainable devices will be locked together at the point of maximum deflection and

page_text: that backward movement will be prevented. Further deflection on increase of
demand will not however be prevented as the end of the click will upon such
further deflection simply ride over the teeth of the ratchet wheel. The parts
will always be locked therefore at the position of maximum deflection, that is to
say at the position of greatest deflection which has taken place during the period
of time for which the demand reading is required. To express this in another way
and with reference to the specific form of instrument mentioned, the needle whilst
free to be deflected in one direction cannot retrace its path but will remain at its
position of maximum deflection and thus indicate the maximum demand which
has been thrown upon the supply circuit during the given period of time.
It is obvious that the teeth of the ratchet wheel and the pawl may be very small
in size, for example the roughened edge or even the smooth edge of a disc might
be substituted for the teeth and a friction block might be substituted for
the click or pawl. But practically any extended body, such for example
as a wire or prism, might serve for the detainable device and any clutch
or gripping device might be substituted for the click or pawl, all that is necessary
for a detainable device being something gripable at a part proportional to the
deflection and all that is necessary for a detaining device being something capable
of gripping the something gripable.
I have hereinbefore referred to a reinforcing device. This may conveniently
consist for example of a weight which will be raised as deflection takes place or
a spring which will be moved as deflection takes place, and which raising of the
weight or movement of the spring will tend to bring the deflected part back
towards its original position and so secure a more positive grip between the detain-
able device and the detaining device. Anything which will tend to reinforce the
grip of the detaining upon the detainable device will answer the purpose.
In speaking of maximum deflection I do not of course limit myself to maximum
deflection in one direction. The said maximum deflection may be in either direc-
tion as for example as shown in certain forms of demand meters described in the
Specification accompanying my Letters Patent No. 3409 of the year 1896.
And
I may employ my invention in connection with instruments giving deflection in
both directions it being understood that in the case of such duplex instruments
the parts are set for a mean or normal demand.
I may when desired employ a dash pot or retarding device of any convenient
form for the purpose of obviating (or minimising the chance of) any record being
given of a mere kick or accidental or short-lived deflection or a prolongation of
deflection due to momentum or the like.
Improvements in Electric Demand Meters.
I, ARTHUR WRIGHT, of 26, Park Crescent, Brighton, in the County of Sussex, 4
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:―
My invention relates to improvements in what are now known as electric
demand meters, that is to say, instruments which record the maximum or

page_text: minimum demand which has been made upon the supply circuit during a given
period of time.
As is well known the record given by such instruments is a record of the
maximum deflection in one direction or the other of the movable indicating part
of the instrument.
My present invention consists of a simple means of recording such maximum
deflection and it consists essentially of the combination of a detaining device and
a detainable device. To these essential elements I sometimes find it convenient
to add what I may term a reinforcing device, that is to say, a device which will
ensure a proper and sufficient action of the detaining device upon the detainable
device when required. I employ the devices hereinbefore mentioned in combina-
tion with the elements of any convenient form of galvanometer or electric meter.
All forms of galvanometer or electric meter depend for their indications upon
the relative movement or change of relative position of a fixed and a movable
element or of two movable elements and in carrying my prevent invention into
effect what I do is to cause the detaining device of my invention to engage with
the detainable device at the point of maximum deflection so as to prevent any back-
ward movement of the deflected or movable part of the instrument, whilst at the
same time permitting of any further deflection due to an increased demand upon
the supply circuit.
The detaining device in my invention may consist of any convenient form of
gripping device suited to the detainable device which latter may consist of any pro-
longed or extended part adapted to be gripped or held at different places through-
out its length. Thus if the detainable device be a rack or a ratchet wheel for
example, the detaining device may conveniently take the form of a click or pawl
and if this rack or ratchet wheel be attached to the movable part of the instrument
and the click or pawl to the fixed part of the instrument, so as to prevent any back-
ward movement of the said detainable part, a record of the maximum deflection
can easily be obtained.
For example let us assume that an ordinary form of galvanometer is employed
in which the movable part consists of a pointer mounted rigidly upon an
angularly moving axis as is diagrammatically represented in the accompanying
drawings in which..
Figure I is an end elevation, and
Figure II a side elevation with part in section.
In these Figures, 1 is the pointer and 2 the angularly moving axis on which
it is mounted. If now a ratchet wheel 3 be attached to the said axis 2 so as to
move angularly with the pointer or needle 1 and if a click or pawl 4 be attached
to any convenient fixed part, as 5, of the instrument in such manner that when
deflection in the normal direction as shown by the arrow takes place the click will
ride over the teeth of the ratchet wheel but will lock between two of the said teeth.
when backward movement takes place, then it will be clear that the detaining and
the detainable devices will be locked together at the point of maximum deflection
and that backward movement will be prevented. Further deflection on increase
of demand will not however be prevented as the end of the click will upon such
further deflection simply ride over the teeth of the ratchet wheel. The parts will
always be locked therefore at the point of maximum deflection, that is to say at
the position of greatest deflection which has taken place during the period of time
for which the demand reading is required. To express this in another way and with
reference to the specific form of instrument mentioned, the needle whilst free to
be deflected in the direction shown by the arrow cannot retrace its path but will
remain at its position of maximum deflection and thus indicate the maximum
demand which has been thrown upon the supply circuit during the given period
of time.
It is obvious that the teeth of the ratchet wheel and the pawl may be very small
in size, for example the roughened edge or even the smooth edge of a disc
might be substituted for the teeth and a friction block might be substituted

page_text: for the click or pawl. But practically any extended body, such for example
as a wire or prism, might serve for the detainable device and any clutch
or gripping device might be substituted for the click or pawl, all that is necessary
for a detainable device being something gripable at a part proportional to the
deflection and all that is necessary for a detaining device being something capable
of gripping the something gripable.
I have hereinbefore referred to a reinforcing device. This may conveniently
consist for example of a weight which will be raised as deflection takes place or
a spring which will be moved as deflection takes place, and which raising of the
weight or movement of the spring will tend to bring the deflected part back
towards its original position and so secure a more positive grip between the detain-
able device and the detaining device. Anything which will tend to reinforce the
grip of the detaining upon the detainable device will answer the purpose. In the
case illustrated in the figures I have represented the reinforcing device as consisting
of a travelling weight 6 which for purposes of adjustment can be caused to travel
in one direction or the other on the rod mounted on the spindle 2.
In speaking of maximum deflection I do not of course limit myself to maximum
deflection in one direction. The said maximum deflection may be in either direc-
tion as for example as shown in certain forms of demand meters described in the
Specification accompanying my Letters Patent No. 3409 of the year 1896. And
I may employ my invention in connection with instruments giving deflection in
both directions it being understood that in the case of such duplex. instruments
the parts are set for a mean or normal demand.
I may when desired employ a dash pot or retarding device of any convenient
form for the purpose of obviating (or minimising the chance of) any record being
given of a mere kick or accidental or short-lived deflection or a prolongation of
deflection due to momentum or the like.
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:-
1. In an electric demand meter the combination of a detaining device and a
detainable device substantially as set forth.
2. In an electric demand meter the combination of a detaining device, a detain-
able device and a reinforcing device substantially as set forth.
3. In an electric demand meter, the combination of a detaining device consisting
of a click or pawl and a detainable device consisting of a ratchet wheel substantially
as set forth with reference to Figures I and II.
4. In an electric demand meter the combination of the specific parts mentioned
in Claim 3 with a reinforcing device substantially as set forth.
D
21 1
1909