Improvements in Steam Pressure Gauges.
Year: 1891

page_text: ate of Application, 13th Jan., 1891-Accepted, 14th Nov., 1891
COMPLETE SPECIFICATION.
Improvements in Steam Pressure Gauges.
I, MURDOCK MCNEIL, of 28 Beach Street, Boston, in the County of Suffolk,
and State of Massachusetts, United States of America, Inventor, do hereby
declare the nature of my invention for IMPROVEMENTS IN STEAM PRESSURE
GAUGE, 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 pressure gauges in which the spring which actuates the
index or pointer is a bent metal tube usually of a flattened or elliptical shape in
cross section. The connection between the gauge and boiler is made by a pipe in
which the steam is condensed, the water of condensation filling the said spring and
receiving the steam pressure so that the curvature of the spring varies with the
steam pressure, the movement given the free end of the spring by the variation
of its curvature being imparted through suitable mechanism to the indicator or
pointer, as shown in the Bourdon Patent of the United States No. 9,163.
The invention has for its object to provide improved means for securing to the
spring and casing an auxiliary spring which shall supplement the curved spring
and prevent the loss of elasticity of the latter from effecting the operativeness of
the apparatus, and to this end the invention consists in the improvements which I
will now proceed to describe and claim.
Of the accompanying drawings forming a part of this Specification,
Fig. 1, represents a front view of a steam gauge embodying my improvements
(the dial plate being removed).
.
Fig. 2, represents a section on line 2, 2, Fig. 1.
The same letters of reference indicate the same parts in all the figures.
In the drawings: A represents the bent metal tube which is rigidly attached to
the casing A' and the other end to rod B, which is connected at C to a lever D,
which is fulcrumed at 1, .and has a toothed segment E at its other end. The
latter gears into a pinion F (Fig. 2) on the spindle G of the index or pointer H.
The construction above described in common and of itself forms no part of my
invention. When the water is forced up by the steam pressure into the tube A the
tendency of said tube is to straighten and thus impart motion to the segmental
lever and through the latter to the index or pointer. When the gauge is in good
order the index should always go back to zero when the pressure is removed. It
has been found, however, that the spring tube A has a tendency to lose its elasticity
by use, so that the gauge is often rendered unreliable.
My invention is intended to remedy the above mentioned defect, and it is carried
into practice as follows: a represents a spring preferably helical in form, suitably
secured at its outer and inner ends to lugs or nuts 6. The nut at the outer end
of said spring is adapted to receive a screw c and the nut b' at the inner end of the
spring receives a screw d having its lower end provided with a slot e to receive an
ear f formed on a clamp g surrounding the tube A and secured thereon by a screw h,
the arrangement being such that a jointed connection is formed between the tube
and spring by a pin i passing through the ear f and screw c as will be clearly
understood by reference to Fig. 2.
j represents a bushing which is suitably fitted into the casing A. and through
which passes the screw c, the latter being provided with a left hand screw thread
and adjustably secured by jam-nuts k k.
It is obvious that by means of the screw c the pressure of the spring a on the
spring tube A may be adjusted to any desired extent. It will be seen that the
force of the spring a is always exerted to keep the tube in its normal position or
that which it occupies when the pointer H is at zero, and that whenever the steam

page_text: pressure operates to vary the curvature of the tube A. it must also operate against
the spring a, said spring receiving all the pressure and being compressed to an
extent corresponding to the displacement of the tube A, so that its force is
exerted to compel the tube A to return to the proper point when the pressure
decreases.
My improvement can be easily applied to any gauge of this class and is not limited
to steam pressure gauges.
Another important function of the spring a is to prevent the vibration of the
pointer H by the jar of the machinery with which it is connected. The spring a
may be of other than spiral form if preferred, although I prefer the spiral form as
the most convenient.
I am aware that an auxiliary spring has been before employed in connection with
a Bourdon spring, hence I do not claim broadly the combination of an auxiliary
spring with a Bourdon spring.
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 I
claim is :-
1. In a pressure gauge, the combination of the casing, the spring tube A. therein,
the spring a interposed between the casing and the tube, a holder or support for
the outer end of said spring attached to the casing, a clamp attached to the tube,
a nut or collar engaged with the inner end of the spring, and a hinge or joint
connecting the collar with the clamp, as set forth.
2. In a pressure gauge, the combination of the casing, the tube A therein, the
spring a, interposed between the casing and the tube, the adjusting screw c engaged
with the casing and supporting a nut which is engaged with the outer end of the
spring a, the clamp g attached to the tube, the nut or collar b¹ engaged with the
inner end of the spring, and the hinge or joint connecting said collar b¹ with
the clamp g, as set forth.
Dated this 13th day of January 1891.
F. W. BAKKEK,
Applicant's Agent.