MENTS IN INDICATING THE PRESSURE OF STEAM AND OTHER FLUIDS, WHICH IMPROVE- •MENTS ARE ALSO APPLICABLE TO GOVERNORS AND OTHER REGULATING APPARATUS, to be as follows
Year: 1855

page_text: PROVISIONAL SPECIFICATION left by Andrew Barclay at the Office of
the Commissioners of Patents, with his Petition, on the 12th November
1855.
I, ANDREW BARCLAY, of Kilmarnock, in the County of Ayr, North Britain,
Engineer, do hereby declare the nature of the said Invention for "IMPROVE-
MENTS IN INDICATING THE PRESSURE OF STEAM AND OTHER FLUIDS, WHICH IMPROVE-
•MENTS ARE ALSO APPLICABLE TO GOVERNORS AND OTHER REGULATING APPARATUS,
to be as follows:-
"
This Invention relates, in the first place, to improved apparatus for indicating
the pressure of steam or other fluids, and is susceptible of being carried out
under various modifications. According to one plan, the apparatus consists of
a tube of caoutchouc, which is closed at one end, whilst the other end is in com-
munication with the boiler pipe or other container of the steam, the presence
of which is to be indicated. The tube is enveloped by a helical spring of
metal wire, for the purpose of preventing the lateral dilatation of the tube,
and for aiding its reaction or contraction. This tube may or may not be con-
tained in a larger tube, in which it works with perfect freedom; an index
pointer, fixed or connected to the tube in any convenient way, is made to
traverse over a scale as the variation in the internal pressure causes the elastic
tube to elongate or contract, the scale being suitably divided to indicate the
pressures corresponding to the different positions of the pointer. It is preferred
to fill the elastic tube and a portion of the communicating pipe with water, so
that the heat of the steam may not affect the caoutchouc, the pressure being

page_text: transmitted through the water; and water may also be placed in the tube
which envelopes the elastic tube, so as to keep the outside of the latter in a
moist state. By connecting the communicating pipe with a condenser, the
elastic tube becomes a vacuum indicator; but in this case the helical spring
must be placed inside the elastic tube, to prevent the external pressure from
squeezing it together, and to compel this pressure to act longitudinally.
According to another modification, a bag or receptacle made of caoutchouc
is fitted between two rigid metal cup-shaped discs, which are also connected
by metal springs. The pressure being allowed to exert itself inside this bag, it
separates the discs more or less, and an index pointer being connected to one
of them, points out the pressure on a scale.
According to another modification, the elastic tube with its external or
internal springs, as the case may be, is made to act as a governor for regu-
lating the speed of motive power engines, by arranging a pump worked by the
engine to pump into or exhaust from the tube any suitable fluid, the tube
being provided with a separate aperture, through which the fluid can escape or
enter at a certain rate only. If the rate of the engine varies, the fluid is
pumped into or exhausted from the tube at a different rate, and the tube is
correspondingly elongated or contracted; and being connected with the throttle
valve, or other regulating mechanism of the engine, adjusts it so as to bring
back the engine to its prescribed rate. The elastic tube or receptacle may
also be arranged to adjust a damper according as the steam pressure in the
boiler may vary. It will, however, be obvious that the apparatus described,
or a modification of it, is applicable in all cases where it is required to obtain
the movement of indicating, regulating, or adjusting mechanism by means of
steam or other fluid. Thus, for example, it may be advantageously adopted
in the construction of indicators for shewing the power of steam engines.