Improvements in Thermostats and Apparatus Operated by Differences in the Thermal Expansion of Metals.
Year: 1889

page_text: Date of Application, 31st Aug., 1889-Accepted, 21st Dec., 1889
COMPLETE SPECIFICATION.
Improvements in Thermostats and Apparatus Operated by
Differences in the Thermal Expansion of Metals.
I, JOSEPH WACH of Hoechst am Main in the Kingdom of Prussia and German
Empire, 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 :-
This Invention relates to Thermostats and apparatus operated by the differences
in the amount of the thermal expansion of different or heterogeneous metals, when
exposed to changes of temperature.
I will proceed to describe my Improvements with reference to the accompanying
drawings in which the simplest form of the apparatus is shewn in Figs. I and 2.
The inner element E of the apparatus is shewn in Figs. 3 and 4. The device consists
of a straight rods having a high specific rate of expansion and two links G having
a low specific rate of expansion. These links have a T shape and their limbs s' form
an angle a with the rod s.
At every change of temperature this angle a will become smaller in consequence
of the increased expansion of the rod s, and consequently the points oo of the
sides ss and also the points o¹ o, of the sides s² of the links G (Fig. 3) will approach
proportionately. The diminution between the points o¹ o' becomes consequently so
much smaller than the diminution of the distance between oo as the sides ²² have
expanded in length between o¹ o' at the same time.
The sides of the links G are joined at their ends o¹ o' (as in Figures 1 and 2)
with two bent rods ³ ³ which form an angle a¹ to s² and this angle is proportionately
increased at every change of temperature by the joint action of the diminution of the
distance of o¹ and the simultaneous expansion of the long rods 3. The alteration of
this angle a' or the alteration of the distance between the rods 33 in their centres is
quite considerable at every change of temperature in the system in consequence of the
peculiar combination of the links with different powers of expansion.
In Figs. 7 and 8 the elements have been represented diagrammatically.
The advantages of the Improvements can be further utilised if the apparatus be
provided with two or more of the parts E as represented in Figs. 5 and 6. In this
construction, assuming that the other proportions are the same as represented in
Figs. 1 and 2 the contraction of the inner element formed by the combination of two
of the parts E will at every increase of temperature be twice as large as in the
arrangment shewn in Figs. 1 and 2 and therefore the difference in distance of the
rods s³ at their centres will be proportionately increased. A still greater difference
of distance between the rods ³ ³ at their centres will be obtained if the middle rod s
of the apparatus represented by Figs. 1 and 2 is replaced by one or more of the
parts E as shewn in Figs. 9 and 10. It will be obvious that in this construction the
inaterials of which the elements are constructed must be reversed. If for example,
in Fig. 3 the elements G G are of iron and the rod s of brass, then in the parts E E
which replace the rods, the elements G G must be formed of brass and the rods
which are enclosed thereby, of iron. These parts E E will attain a far greater
expansion for a given increase of temperature than the rod s Fig. 3, the contraction
of the points o o¹ will be considerably larger, and therefore also the distortion of
the two outer rods s³ $3.
In steam traps and steam pressure reducing valves for example differences of
temperature of 15°-50° Centigrade occur; to obtain the necessary expansions the
dimensions of the apparatus to be applied for these purposes may according to the
foregoing examples, be very small.
In the case of very small differences of temperature an efficient alteration of
condition in the apparatus can easily be obtained and it therefore becomes useful as a
regulator or governor of the temperature in heating and ventilation installations.

page_text: It is also possible in the before described apparatus to reverse the direction of the
effective expansion if the bodies having the greatest and smallest specific expansion
are exchanged.
The size of the apparatus in the reverse direction will be almost as large as
before described.
The use of the apparatus in the single form (Figs. 1 and 2) in a steam trap is
shewn in Fig. 11. The apparatus is joined on one side with the closing part S of
the lift valve V and on the other side with a spindle S¹, which serves for
adjusting the apparatus before the same is put in use. The steam enters at A an
leaves at A¹.
If the apparatus is filled with steam and heated, S closes. As soon however as the
apparatus is submerged in the collecting condensation water, it is cooled down and by
its contraction the valve is opened.
In the same way the application to steam pressure reducing valves can be explained
by reference to Fig. 11. The apparatus with the closing piece is so adjusted by the
spindle S¹ that at the temperature of the low steam pressure which is desired to be
obtained it only opens so far as to reduce the high pressure steam which enters at I
in the vessel to the desired lower pressure. The steam is then conducted by the
branch A or A and in consequence of the large sensibility of the thermal expansion
body it regulates the steam admission exactly according to requirements, so that an
increase of steam pressure is only possible within very small limits.
To use the apparatus as a regulator or governor of temperatures, the expansion
body is inserted in the spindle or guide rod of the shut off valve proper of a throttle
arrangement which is intended to regulate the supply of hot blast in heating arrange-
ments. In such a case of course the throttle arrangement is automatically acted upon
so that a self acting regulation of the heating or ventilation is ensured.
Having now particularly described and ascertained the nature of my said Inven-
tion and in what manner the same is to be performed, I declare that what
1 claim is
(1) A thermostat or thermal expansion apparatus constructed arranged and
operating substantially as and for the purposes hereinbefore described with reference
to the accompanying drawings.
(2) In a thermostat or thermal expansion apparatus; one or more cross shaped
elements E each consisting of a rod or strip and two members G G; constructed and
arranged substantially as and for the purpose herein before described with reference to
the accompanying drawings.
(3) In a thermostat or thermal expansion apparatus; the combination and arrange-
iment of one or more elements E with two bent rods or strips s s, substantially as
herein before described with reference to the accompanying drawings.
Dated this 29th day of August A.D. 1889.
WILLIAM E. HEYS,
Agent for the Applicant.