improvements in ՆԵ ՆՄԱՆ ԱՆՆԱ and Modes of Hanging Maximum and Minimum Thermometers.
Year: 1888

page_text: improvements in ՆԵ ՆՄԱՆ ԱՆՆԱ
and Modes of Hanging Maximum and Minimum Thermometers.
I CHARLES THOMAS MITCHELL of 3 New Court Lincolns Inn in the County of
Middlesex, Barrister at law do hereby declare the nature of this invention to be as
follows:-
The construction of minimum and other thermometers for use outside a window, or
elsewhere between the spectator and the light, having the tube mounted on an opaque
frame. in or against a slit or openings in the frame, notched perforated marked or
divided in such a way that the height of the thermometer can be readily seen against
the light.
Also contrivances, to be used in combination with the above or otherwise, for
hanging maximum or minimum thermometers, hung horizontally outside a window
and set by gravity, with one end suspended by means of a chain cord or rod passing
through the window bar or window frame by which the thermometer can be tilted and
set without opening the window.

page_text: and Modes of Hanging Maximum and Minimum Thermometers.
I CHARLES THOMAS MITCHELL of No. 3 New Court Lincolns Inn in the County of
Middlesex Esquire 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 :-
Thermometers having the tube mounted in wood iron or other non-transparent
material (with which alone my improvement in the construction of thermometers-is-
concerned) cannot be conveniently used when hung between the spectator and the
light from the fact that the scale, which must be turned towards the spectator, is
then turned from the light, and at the same time seen against it. Generally,
_ there is the further inconvenience that the side of the thermometer exposed to
the light is that which it is desired to expose to the air to take-the-temperature, but
even where this is not the case, or where, as in some instances, as for example in the
common French minimum thermometer mounted on a zinc frame, the frame is cut or
cast with a slit or opening to receive the tube, so that the tube is more or less
exposed to the air at the back as well as the front, the same difficulty exists as
to reading the scale.
My improvement in the construction or mounting of thermometers consists in
the construction of minimum and other thermometers, for use outside a window
or elsewhere between the spectator and the light, having the tube mounted on an
opaque frame in or against a slit or opening or series of openings in the frame
notched perforated or divided in such a way that the height of the thermometer
can be readily seen against the light.
The disadvantage of being unable conveniently to hang the thermometer against
the light is specially felt in the case of the ordinary minimum thermometer set
by gravity when used outside a window. It must in general be hung at the side
of the window, so as to expose the same face to the outside air and light and to
the spectator within. Often there is no room there to hang it horizontally (as it
must be hung), or if there is a sufficient space, the wall is usually faced with
some hard and brittle material into which it is difficult to fix a nail. With my
improvement, it can be hung (with or without the Letter hereinafter described)
from any horizontal bar of the window.
The ordinary thermometer can only be seen when close by, and in its usual position,
it can only be seen sideways. In my improved Thermometer, the fluid in the tube and
the notches or other indications on the scale show clearly against the light so that the
height can be roughly seen even from the middle of the room. Also since you look
at this Thermometer full face, you can obtain a more accurate reading.
The manner in which I prefer to carry out my improvement is shewn in the
sketch Nod. 1 in the drawings that accompany this specification. The tube is sunk in
a groove at the back of the frame and seen through à V shaped slit made through the

page_text: frame with the wider opening in front and narrowing at the back to a width just
sufficient to shew the thread of fluid in the tube. The notches, which are transverse
to the line of the slit, are made as V shaped grooves on its upper and lower faces:
and I find it most convenient to make the notches at every tenth degree of the
Fahrenheit scale on the upper face, and at the freezing point (32°), and at 60°
and 90° on the lower face, and just deep enough to shew the whole thickness of the
glass of the tube.
I find it convenient in making the thermometer to cut the frame completely in
halves along the line of the slit. This enables the sides of the slit to be made
and marked with the scale and grooved as described with accuracy more easily
than is otherwise possible. The two parts are afterwards fixed together by an
ordinary screw at each end. The line of division between the two halves is shown
in figure 1 by the line a, b, c, d, e, f: and the heads of the screws are shown at
the points g & h.
•
I prefer to shew the intervals on the scale by notches in the way I have described,
but the intervals may be shewn instead by projections, or by interruptions or
divisions crossing the slit, or by substituting for the slit a series of openings or
perforations at convenient points or intervals of the scale; and the frame or setting
may be made of metal or any other material, but I prefer to make it of wood
as I have described.
Where this thermometer is used outside a sash window, it will generally be
be so
found most convenient to hang it from the bottom of the upper sash. It may
suspended by two fixed hooks, in which case, if the thermometer be a self registering
thermometer, it is necessary (as with the ordinary registering thermometer) to open
the window in order to set it. As a further and distinct improvement, I avoid this
necessity in the case of any registering thermometer set by gravity by suspending the
end of the thermometer that has to be lowered by what I call a "setter."
There are several forms in which I construct the setter, but I prefer to construct it
as shewn to some extent in figure 1, and more fully in figure 2, of a flat plate of
brass, a. b, about four or five inches long and half an inch wide, having at one end a
hole or opening, c, through which passes a light brass chain, and at the other end a
peg, d, for the attachment of a ring, e, at one end of the chain, or some equivalent
fastening. At the other end of the chain there is an S shaped hook, f, from which
the thermometer (shewn in figure 2 as a plain block, g) is to be suspended. This
setter is intended (when the thermometer is suspended in the position I have
described), to be screwed down inside the window to the bottom bar of the upper sash,
with its opening over a vertical hole to be made through the sash bar in place of the
fixed hook at that end of the thermometer which has to be lowered. After the plate
is fixed the chain is dropped through the hole in the sash, the S hook being detached-
for this purpose and hooked on again so as to be close up to the wood when the chain
is drawn up and fastened. The thermometer is of course set by undoing the
fastening de, and letting down the chain, so as to lower the end of the thermometer
suspended by the S hook.
In this and the other forins of setter hereinafter described, the size of the fixed hook
and that on the chain should be adjusted so that when the chain is drawn up and fixed,
the tube of the thermometer slopes slightly downwards towards the bulb. The length
of the chain should be such that when it is let down to its utmost extent the
thermometer slopes to such an angle that the indicator that is used (according to
the ordinary construction of a minimum thermometer set by gravity) to register the
minimum height may fall or slide by its weight to the surface of the fluid. Subject
to these requirements, the precise dimensions are unimportant. I find that a sufficient
slope is secured if the drop of the chain is about two thirds of the distance between
the rings or other points of suspension on the thermometer.
Four other forms in which I make the setter are shewn in figures 3, 4, 5 & 6
respoctively where they are represented as screwed down to a slip of wood which is
intended to represent the sash bar.
The setter shewn in figure 3 is made in the form of a long hinge, one arm being a

page_text: plate a b, and the other arm, k 7, having the extremity of the chain attached to it
atk in such a way that, when the hinge is closed, the point of attachment, h, comes
over the opening c, & the chain falls through. The chain is drawn up by opening
the hinge, the length of the rings being such that, when the hinge is fully opened,
and the moving arm lies back on the sash, as shewn in the figure, the chain is stretched
to its full extent, and the thermometer is drawn up with the S hook close to the
sash bar.
In this and the following figures the slip of wood to which the setters are fixed is
made thinner than an ordinary sash bar, and the hook hangs below, but in actual
fixing the hook is always to be linked on close up to the sash.
In making the hinge I prefer not to joint the second arm to the actual extremity of
the plate which forms the first, as, if it be so constructed, the tension of the chain has
a tendency to pull the second arm over and to close the hinge. I prefer to make a
flange or projection m as shown in the figure standing up vertically from the side
of the fixed plate (supposed horizontal), and I hinge the second arm to this by a
horizontal pin at 1, about a quarter of an inch from the angle between the plate and
flange, and I make the second arm of the hinge as a stout strip of metal placed in a
vertical plane against the flange, and hinged to it so that it moves against the flange
in a vertical plane, the end being shaped so as to form a convenient handle by which
to take hold of the arm and turn it over. The advantage of thus placing the axis of
the hinge above the plane of the first plate is that when the hinge is open the chain
-(which then rests on the plate) passes below the axis of the hinge, and tends to keep
open and not to close it.
it
The setter shewn in figure 4 has a rod, n, o, with a short length of chain attached,
the rod taking the place of so much of the chain as is drawn through the hole when
the chain is drawn up as in the first form of setter described. The peg and ring or
other fastening used in the first form of setter is dispensed with, and the chain when
drawn up is prevented from slipping back-by-the weight of the rod as it rests
horizontally or nearly so on the bar of the sash, or on the fork which I make at the
end a of the plate to receive it as shewn in the figure.
In the form of the setter shewn in figure 5, the chain is attached to a bolt or slide
which draws tho chain up as it moves to the left. I find it convenient to make this
setter by turning over one edge of a strip or plate of brass, a b, so as to form a
tube, 9, along that side of the plate, giving the whole the section of the letter Por
the Greek letter P but leaving a space about equal to the thickness of the plate where
the edge turned over meets it. Calling this the guide, I make the slide in a similar
way with a section such that it will slide with its tube inside the tube of the guide,
and with its plate resting on the guide plate. i turn up one end of the plate of the
slide to form an attachment for the chain and a projection by which it is held and
moved along the guide as shown in the figure. I find that if the slide be accurately
fitted the friction between it and the guide is sufficient to hold it in its place against
the tension of the chain, and I prefer this mode of construction, but a catch of any
kind may be used if preferred. There is one disadvantage in this form of setter, that
the chain is more liable to catch at the edge of the hole, c, the chain being drawn, while
tense, round a sharp angle.
The form of setter shewn in figure 6 is made with a wheel to wind up the chain. I
prefer to make the wheel with a deep groove round the circumference in which the
chain is contained and to fix it in a vertical plane between two cheeks rising from
the plate a b, so that the chain coming vertically through the sash bar passes on to the
circular groove at a tangent. The wheel may be held when the chain is coiled up by
any sort of catch or spring, but I find that friction is sufficient to hold it, and can be
conveniently applied either by a flat spring, s, attached to and projecting upwards
beyond one of the cheeks, and bent so as to press against the side of the wheel near
its circumference, or by making one or each of the cheeks as a broad flat spring
attached to the plate so as to clip the wheel between the cheeks near its circumference,
the axis or pin on which the wheel turns being in this case more conveniently fixed
to the wheel and turning in holes in the cheeks. I make the wheel of such a

page_text: circumference that a single coil round the groove is enough to wind the chain up, the
extremity of the chain being fixed at any point of the circumference, and I let
the wheel stand (as shown in the figure) clear above the cheeks, so that it can be
readily turned by the hand.
In constructing the setter in any of the forms described I do not confine myself to
the use of any particular metal or other material, and a cord may be used or anything
else of a similar character instead of a chain. Where a chain is used it should be one
that will run smoothly through the bole, and I find an ordinary clock chain suitable
for this purpose.
In describing the setter and the mode of fixing it, I have described it as used with
a thermometer hung from the lower bar of the upper sash of a sash window; but for
other than sash windows, or where it cannot be conveniently hung below the sash, it
may be necessary or convenient to hang it against the side of a window bar or other
attachment. In such case the setter may be used with a small pulley or block fixed
against the bar or other attachment, the chain passing over the pulley and horizontally
or otherwise through a hole to the setter, which may be fixed in any convenient
position inside the room.
The setter may be used in combination, not only with the improved thermometer
herein before described, but with any other self registering thermometer set by gravity
to be hung against, the light.
my
Having now particularly described and ascertained the nature of said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. The construction of minimum and other thermometers, for use outside a window
or elsewhere between the spectator and the light, having the tube mounted on an
opaque frame in or against a slit or opening or series of openings in the frame
notched, perforated, or divided, in such a way that the height of the fluid in reference
to the scale can be readily seen against the light by the aid of notches, projections,
interruptions, perforations, openings or divisions at convenient points or intervals of
the scale, as and for the purposes described.
3. The construction or use of a setter, as and for the purposes described, in
combination with any self registering thermometer to be hung between the spectator
and the light.
Dated this 27th day of December 1888.
CHAS. T. MITCHELL.