IMPROVEMENTS IN COMPENSATOR FRAMES FOR UNIMETALLIC THERMOMETERS, CLOCK PENDULUMS, DEAD STANDARDS, AND OTHER PURPOSES
Year: 1873

page_text: LETTERS PATENT to Thomas James Smith, of the Firm of Robertson,
Brooman, and Company, of 166, Fleet Street, in the Oity of
London, Patent Agents, for the Invention of “IMPROVEMENTS IN
COMPENSATOR FRAMES FOR UNIMETALLIC THERMOMETERS, CLOCK PENDULUMS,
DEAD STANDARDS, AND OTHER PURPOSES."-A communication from
abroad by the Societé Tremeschini et Cie, of Paris, 23, Boulevard
.de Strasbourg.
PROVISIONAL SPECIFICATION left by the said Thomas James Smith
at the Office of the Commissioners of Patents, with his Petition, on
the 11th August 1878,
I, THOMAS JAMES SMITH, of the Firm of Robertson, Brooman, and
5 Company, of 166, Fleet Street, in the City of London, Patent Agants,
do hereby declare the nature of the said Invention for "IMPROVEMENTS IN
COMPENSATOR FRAMES FOR 'UNIMETALLIC THERMOMETERS, CLOCK PENDULUMS, DEAD
STANDARDS, AND OTHER PURPOSES," to be as follows:-

page_text: to unimetallic thermometers, clock pendulums, and dead or gauge
standards, with the object of imparting greater accuracy to the
indications or working of the said instruments than was attainable by
the arrangements hitherto in use.
The construction of the said compensation frame is based on a 5
geometrical theorem, as will be explained hereafter, and presents two
points capable of keeping between them a distance apart, which is
theoretically invariable whatever may be the variations in temperature
of the ambient, and besides, offers the advantage of presenting an
unlimited number of points, the relative distances of which increase or 1
diminish in the inverse ratio of the lowering or the rising of the
ambient temperature.
<.
The above-mentioned theorem is as follows, see Figure 1: If two
parallel lines C, D, and F, G, be intersected by several straight lines
1
A¹, B¹, A, B, A², B2, A2, B³, and if the points of intersection C¹, C, C³, C³,
of C, D, be situated at a distance apart, smaller than that existing
between the corresponding intersection points f¹, ƒ,ƒ³, ƒ³, of F, G, and
this distance be regulated in a constant ratio, such for instance that
if the ratio of the distances of the points C³, C, C³, C³, be 10, c¹, c, forming
for instance a unit, and those of the points f¹, f,ƒ³, f³, be 18 (ff, 2
forming the unit) then the lines A, B, A¹, B¹, A³, B³, A³, B³, will
intersect each other at a point P common to all of them. If now a
line M, N, be drawn parallel to A, B, and the lines M³, P, M³, P³,
perpendicular to M, N, these lines M', P, and M³, P³, will be of equal
length, whereas the perpendiculars M³, P³, M*, P', will be propor- 2
tionately smaller than M¹, P, and M³, P³. In this 'theorem we have
consequently a line M³, P, of a constant length, and a series of lines
M³, P³, M³, P³, M', P, and so on, the length of which diminishes in
the same ratio, as they are situated nearer to P. If now C, D, and
E, G, represent two rods of exactly the same shape and size but of 3
different metals, viz., the rod C, D, of soft steel, and the rod E, G, of
brass; and if c, c¹, and f,ƒ³, respectively represent the coefficients of
longitudinal dilatation of the said rods, say, for instance, the dilation
for one or any other suitable number of degrees of temperature. Whilst
the points c³, c³, andƒ³, ƒ³, indicate the variations in length for certain 3
changes in temperature, then the point of intersection of the lines A³, ƒ³,
A³, ƒ³, &c., with the line A, B, will correspond with the point of inter-
section P of the lines A¹, f¹, and A, B.

page_text: If now, as shown in Figure 2, R represents a rod of soft steel, and S
an exactly similar rod of brass, both rods securely fixed by one of their
ends to a cross bar T, and connected, both at the opposite end, in a
movable manner to another cross bar U, say, for instance, by slots and
pivots, or other suitable means; supposing further, P, p, to represent
the position of the centre line of the bar U at the normal temperature,
say, for instance, at 10 degrees of the ambient atmosphere, then at
various increases in temperature the line P, p, will assume various angular
positions P, F, P, P, and so on, all meeting at P, which point P will con-
sequently remain at a fixed distance from other fixed points X, Y, and if
consequently one end of a thin strip or wire, of silver or other suitable
metal, be fixed to the point P, and the other end of this strip or wire
be caused to act on a lever arm or other mechanical arrangement for
amplifying to a suitable extent the variations in length of the strip or
wire and indicating these variations in a proper index, then the entire
will form a thermometer, the indications of which will be fully
independent of any variation in length of the rods R and S.
If the latter arrangement represents the general features of a clock
pendulum, and the bob of this latter be applied to the point P, it will
be evident that in that case the invariability, in as far as required in
practice of the distance between the points of suspension and of
oscillation will thus be obtained; in practice also a set screw or other
appropriate means may be made use of for suitably altering the position
of the bob, so as to compensate for the variations both of the pendulum
and of the movement, viz., that whenever an increase in temperature
should produce a dilatation of the parts of the movement, and thus
make the clock go faster, my arrangement of the pendulum will cause
its centre to rise towards the point of suspension and thus operate the
required compensation, whereas if, by the effect of a diminution in
temperature a contraction of the parts of the movement occurs a
compensating displacement of the centre of gravity of the pendulum
will take place in the contrary direction.
If at the point P of the cross bar V be fixed a shoulder, and another
one at a point P² of the cross bar T exactly opposite the point P,
then these two shoulders will remain at a fixed distance for any
ordinary changes of temperature of the ambient atmosphere, and the
arrangement will consequently constitute a perfect gauge standard,
-

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Thomas James Smith in the Great Seal Patent
Office on the 11th February 1874.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, THOMAS
JAMES SMITH, of the Firm of Robertson, Brooman, and Company,
of 166, Fleet Street, in the City of London, Patent Agents, send
greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Eleventh day of August, in the year of
our Lord One thousand eight hundred and seventy-three, in the thirty-
seventh year of Her reign, did, for Herself, Her heirs and successors, give
and grant unto me, the said Thomas James Smith, Her special licence
that I, the said Thomas James Smith, my executors, administrators,
and-assigns, or such others as I, the said Thomas James Smith, my
executors, administrators, and assigns, should at any time agree with
and no others, from time to time and at all times thereafter during the
term therein expressed, should and lawfully might make, use, exerciso
and vend, within the United Kingdom of Great Britain and Ireland,
the Channel Islands, and Isle of Man, an Invention for "IMPROVEMENTS
IN COMPENSATOR FRAMES FOR UNIMETALLIC THERMOMETERS, CLOCK PENDULUMS,
DEAD STANDARDS, AND OTHER PURPOSES," communicated to me from abroad
by the Societé Tremeschini ot Cie, of Paris, 23, Boulevard de
Strasbourg, upon the condition (amongst others) that I, the said
Thomas James Smith, my executors or administrators, by an instru-
ment in writing under my, or their, or one of their hands and seals, 1
should particularly describe and ascertain the nature of the said In-
vention, and in what manner the same was to be performed, and cause
I the same to be filed in the Great Seal Patent Office within six calendar
months next and immediately after the date of the said Letters Patent.
NOW KNOW YE, that I, the said Thomas James Smith, do hereby
declare the nature of the said Invention, and in what manner the same
is to be performed, to be particularly described and ascertained in and
by the following statement thereof, reference being had to the Drawings
hereunto annexed, that is to say :-
The Invention as communiented to me solator

page_text: dead or gauge standards, with the object of imparting greater accuracy
to the indications or working of those instruments than was attainable
by the arrangements hitherto used.
The construction of this compensation frame is based upon a
geometrical theorem, as will be explained hereafter, and presents two
points capable of keeping between them a distance apart which is
theoretically invariable whatever may be the variations in temperature.
of the surrounding atmosphere, and offers in addition the advantage of
presenting an unlimited number of points, the relative distances of
which increase or diminish in the inverse ratio of the lowering or the
rising of the ambient temperature.
The above mentioned theorem is as follows:-If two parallel lines C, D,
and F, G, be intersected by several straight lines A', B¹, A, B, A², B³,
A³, B³, and if the points of intersection c, c, c³, c³, of C, D, be situated
at a distance apart smaller than that existing between the corresponding
intersection points ƒª¹‚ƒ, ƒ³,ƒ³, of F, G, and this distance be regulated in
a constant ratio, such for instance as if the ratio of the distances of the
points c¹, c, c³, c³, be 10, c³, c, forming for instance a unit, and those of
the points ff.ƒ³,ƒ³, be 18, ƒ^, f, forming the unit, then the lines A,
B, A, B, A, B, A³, B³, will intersect each other at a point P common
to all of them. If now a line M, N, be drawn parallel to A, B, and
the lines M², P, M², P³, perpendicular to M, N, these lines M², P,
and M³, P³, will be of equal length, whereas the perpendiculars M³, P³,
M*, P', will be proportionally smaller than M³, P, and M², P* Mess".
Tremeschini and Co. say, "In this theorem we have consequently a
** line M², P, of a constant length; and a series of lines M², P³, Mª, P³,
" and so on, the length of which diminishes in the same ratio as they.
66 are situated nearer to P. If now C, D, and F, G, represent two rods
"of exactly the same shape and size but of different metals, viz., the
"*rod O, D, of soft steel and the rod F, G, of brass, and if c, c', and f,f',
"respectively represent the coefficients of longitudinal dilatation for one
" or any other-suitable number of degrees of temperature, there the
" point of intersection of the lines A³,ƒ³, A³, fs, etc., with the line A, B,
" will correspond with the point of intersection P of the lines A, ƒ¹,
and A. B.

page_text: “their ends to a cross bar T and connected each at their opposite ends,
"and in a moveable manner to another cross bar U, say for instance by
"slots and pivots or other suitable means. Supposing further P, p, to
"represent the position of the bar V at the normal temperature, say for
" instance at 10 degrees of the ambient atmosphere, then at various
" increases in temperature the line P, p, will assume various angular
" positions P, F, P, P, and so on, all meeting at P, which point P
"will consequently remain at a fixed distance from other fixed
points X, Y, and if consequently one end of a thin strip or wire, of
"-silver or other suitable metal, be fixed to the point P, and the other
"end of this strip or wire be caused to act at P¹ on a lever arm or other
"mechanical arrangement for amplifying to a suitable extent the
"variations in length of the strip or wire, and indicating these variations
on a proper index, then the entire apparatus will form a thermometer,
"the indications of which will be quite independent of any variations
"-in length of the rods R and S.
"
$6
.
"
66
66
.
"If the arrangement at Figure 2 represents the general features of
a clock pendulum, and the bob of this pendulum be applied to the
point P, it will be evident that in this case the invariability as far as
required in practice of the distance between the points of suspension
" and of oscillation will be obtained; in practice also a set screw or
" other appropriate means may be made use of for suitably altering the
* position of the bob so as to compensate for the variations both of the
* pendulum and of the movement, viz., that whenever an increase in
* temperature would tend to produce a dilatation of the parts of the
"movement, and thus make the clock go faster, our arrangement of
"the pendulum will cause its centre to rise towards the point of sus-
"pension, and thus operate the required compensation; whereas if by
"the effect of a diminution in temperature a contraction of the parts of
"the movement would occur a compensating displacement of the centro
of gravity of the pendulum will take place in the contrary direction...
•
"If at the point P of the cross bar V be fixed a, shoulder, and another
one at a point P¹ of the cross bar T exactly opposite the point P, then
" these two shoulders will remain at a fixed distance for any ordinary
"changes of temperature of the ambient atmosphere, and the arrange-
"ment will consequently constitute a perfect gauge standard.
"In Figure 3 we have represented a thermometer provided with our

page_text: "compensating device. The apparatus is fixed on a central support a
* adapted to the bottom of the casing 6, this support is crossed by the
" steel rod o which is respectively fixed and hinged at its two ends into
"two brass pieces disposed transversely d, f. At one of the ends the
"two brass pieces d, f, are connected by a brass rod g which is parallel
"with C, and the other end of the piece d bears a brass strip h, which
" by means of a pin i is geared into a notch formed underneath the
"branches of a forked lever j; this latter oscillates by means of a
"knife & underneath the piece f (see the plan Figure 4), and it is.
" hinged at its opposite end with the oscillating lever which carries
"the toothed sector m acting on the pinion of the needle n. The rod o
" serves to maintain the lever l'against its seat of articulation, and to
"transmit the movement of the lever ; to the sector. The spring p
"maintains the sector m against the pinion of the needle n in con-
." junction with the rod o, and the spring q causes the lever ; to remain
"supported upon its articulation underneath the piece f. The principle
" of action of this apparatus of compensation is the same as before
." detailed, and it is therefore unnecessary to describe it again.
66
"In some places we may replace the toothed sector m by an
" apparatus provided with a 'vernier' for operations which require great
" precision, then we employ the arrangement represented in the
"Figure 5, in which the rod / is divided into two and provided with a
spring, the two branches of which carry divided sectors which move
" in relation one from the other in order to constitute the vernier.
"The rod o is equally divided into two in order to be fixed at each
"branch Z. The two rods o are reunited by a lower cross þar upon
"which the lever jacts. A microscope is also fitted to the instrument
" in order to fix the observation in a single point. We may adapt this
"apparatus of compensation to gauge standards, clock pendulums, and
« to all apparatus in general."

page_text: And, Thirdly. The modified arrangement with the employment of the'
vernier, as described and shown with reference to Figure 5 of the accom.
panying Drawings.
In witness whereof, I, the said Thomas James Smith, have here-.
unto set my hand and seal, this Eleventh day of February, One
thousand eight hundred and seventy-four.
m T
TMTY