Improvements in Pressure Gauges.
Year: 1895

page_text: Date of Application, 16th Apr., 1895
Complete Specification Left, 10th Jan., 18'6-Accepted, 15th Feb., 1896
Improvements in Pressure Gauges.
We, Philipp HERMANN ROSENKRANZ, Engineer, of 22, Sedanstrasse, ERNST
AUGUST DREYER, Manufacturer, of 22 Ferdinand Strasse, and ADOLF DROOP,
Manufacturer, of 2 and 3 Warmbüchsen Kamp, all of Hanover, in the German
Empire, do hereby declare the nature of this invention to be as follows:-
This invention relates to improvements in pressure gauges of the type known as
the Bourdon pressure gauge.
This form of pressure gauge has the disadvantage that the tube loses its
elasticity with time and the gauge therefore indicates incorrect pressures.
We have found by observation that the tubes of such gauges always open out
to the same extent under pressure even when they have become weakened, but
weakened tubes are unable to fully resume their original position.
The cause of this disadvantage is that the thin tubes, generally made of brass,
German silver or such like substances, become weakened with frequent use from
the effects of heat, damp and pressure.
The object of our invention is to remedy this disadvantage and we do this by
employing a special spring composed of durable, or tough and elastic material to
assist the tube of the pressure gauge. The most suitable material for the purpose
is steel the elasticity of which remains unaltered.
This auxiliary spring may be in the form of a ring arranged concentrically with
the tube and one end of which is connected to the free end of the tube, the other
end of the same being connected to the case of the pressure gauge.
Or the auxiliary spring may be in the form of a flat spring which is attached to
the case of the pressure gauge at one end, the other free end pressing against the
tube. If desired, several such springs could be employed preferably arranged
around the circumference of the tube.
In lieu of the flat springs, spiral springs could be used, arranged radially between
the case of the gauge and the tube.
We sometimes employ a spiral spring arranged tangentially to the tube, one end
of the spring being connected to the free end of the tube and the other to the
case of the gauge. This spring can serve independently as the auxiliary spring
for the tube, or it can be used in combination with other springs of the kind
hereinbefore described.
These auxiliary springs have the object of assisting the tube to return from the.
position it has assumed under pressure to its original position, and by the use of
such auxiliary springs it is possible to employ tubes of very thin metal which are
consequently very sensitive without fear that the accuracy of the gauges will suffer
from external influences.
Our improved pressure gauge has also the advantage that it can be constructed
to indicate much higher pressures than it has been possible hitherto to indicate with
such gauges.
Dated this 16th der of Anril 1905
G. F. REDFERN & Co.,
4, South Street, Finsbury, London, Agents for the Applicants.

page_text: We, PHILIPP HERMANN ROSENKRANZ, Engineer, of 22, Sedanstrasse, ERNST
AUGUST DREYER, Manufacturer, of 224, Ferdinand Strasse, and ADOLF DROOP,
Manufacturer, of 2 and 3, Warmbüchsen Kamp, all of Hanover, in the German
Empire, 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 improvements in pressure gauges of the type known as
the Bourdon pressure gauge.
In pressure gauges of this kind it has long been noticed that the tube loses its
elasticity with time and that the gauge therefore indicates incorrect pressures.
We have found by observation that the tubes of such gauges always open out to
the same extent under pressure even when they have become weakened, but the
weakened tubes are unable to fully resume their original position thereby giving
rise to incorrect results. The cause of this is that the thin tubes, generally made
of brass, German silver or such like substances, become weakened with frequent
use from the effects of heat, damp and pressure.
Attempts have been made to strengthen the tubes by spiral springs applied
radially or tangentially. Pressure gauges, however, constructed in this manner do
not answer to the conditions required of them as the spiral springs act differently
from the curved tube, that is to say, the tube and spring do not tend to move in
precisely the same direction so that the employment of such spiral springs sets up
strains in the tube which it is not designed to resist.
According to our invention we remedy the above mentioned disadvantage by
employing to assist or strengthen the tube of the pressure gauge a spring of durable
or tough and elastic material the said spring being arranged concentrically to the
tube. The most suitable material for the spring is steel the elasticity of which
remains unaltered.
To enable our invention to be fully understood we will describe it by reference
to the accompanying drawing in which a front elevation of a pressure gauge
constructed according to our invention is shewn.
The auxiliary spring D is arranged concentrically to the tube R and is connected
by one end y to the free end of the said tube R and by its other end to the case
of the pressure gauge. If desired, several such springs D can be employed in
which case they are preferably made in the form of flat steel springs arranged
concentrically to one another and attached by means of a single screw to the end
of the tube and by another screw to the case of the gauge. In the arrangement
shewn in the drawing the auxiliary spring is placed inside the tube but it can
also be placed outside the same so as to enclose it instead of being itself enclosed
by the tube.
In every case the auxiliary springs D have the object of assisting the tube R to
return from the position it has assumed under pressure to its original position
without subjecting it to lateral or tangential strains which have an unfavorable
action on the tube. By the use of such concentrically arranged auxiliary springs
it is possible to employ tubes of very thin metal and consequently very sensitive
without the fear that the accuracy of the gauges will suffer from external
influences.
Our improved pressure gauge has also the advantage that it can be constructed
to indicate much higher pressures than it has been hitherto possible to indicate with
this type of gauge.

page_text: 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:-
A Bourdon pressure gauge having an auxiliary spring arranged concentrically
with the tube of the gauge, the said spring being connected with the tube in such
a manner that it assists the latter to return to its original position after use without
straining the same, substantially as described.
Dated the 10th day of January 1896.
G. F. REDFERN & Co.,
4, South Street, Finsbury, London, Agents for the Applicants.