Improvement in Alarm Pressure Gauges.
Year: 1898

page_text: Improvement in Alarm Pressure Gauges.
FREDERICK HUNT LESTER, of Ormside Street, Old Kent Road, in the County
of London, Varnish and Paint Manufacturer, lo hereby declare the nature of
this invention to be as follows:
-
The
My invention relates to a method of indicating increase or decrease of pressure
particularly in gas mains and automatically signalling the same by means of an
alarum. The method employed is by a series of elastic metallic chambers into
which the gas is admitted and which are thereby expanded the movement of
these elastic metallic chambers is conveyed by levers multiplying the action and
finally making contact with the poles of a battery ringing an alarm bell.
instrument is furnished with a dial or scale corresponding with the inches of
pressure and exhaust indicated by the ordinary water pressure gauge. And by
setting the index hand to any given pressure or exhaust on the dial the alarm is
The ringing
given the instant the pressure in the main reaches that point.
continues so long as the pressure is maintained and ceases only when reduced to
some lower point. The instrument can be constructed to show pressure only,
or exhaust only, or both.
1
BOUT
1
1000
SPENCER CHAPMAN & Co.,
3, King's Bench. Walk, Temple, E.C.
Improvement in Alarm Pressure Gauges.
I, FREDERICK HUNT LESTER, of Ormside Street, Old Kent Road, in the County
of London, Varnish and Paint Manufacturer, do hereby declare the nature of
this invention and in what manner the same is to be performed; to be particu-
larly described and ascertained in and by the following statement:-
My invention relates to a method of indicating increase or decrease of pressure
particularly in gas mains (although I do not limit the application of my invention
to them), and automatically signalling such increase or decrease of pressure by
means of an electric bell or other alarm which rings when the pressure either
rises above or falls below certain predetermined values.
In order that my invention may be better understood I have annexed hereto
a sheet of drawings in which one form of my invention is illustrated.
Fig. 1
is a plan, the dial and hands and the gearing attached thereto having been
removed. Fig. 2 is an elevation partly in sections shewing the connection
between the hands and the rest of the mechanism.

page_text: In my invention I provide a contact arm A of light construction pivotted to
the frame of the instrument and provided at one end with two contact studs BB'
of platinum or other suitable metal situated one above and one below the lever
which I shall call the upper and lower contact studs respectively. The contact
arm is connected either directly or by a system of levers or other multiplying
gear with the pressure measuring device employed so that an increase of pressure
tends to raise the pivotted contact arm and a decrease of pressure tends to lower
it. Any pressure measuring apparatus can be used to give this motion to the
contact arm such as a series of elastic metallic chambers or a Bourdon tube,
and the movement produced by the changes of pressure within this apparatus
may be transmitted to the contact arm through any multiplying mechanism.
In the drawings the elastic chamber is lettered C.
Above and below the contact studs at the end of the contact arm are two
contact plates DD¹ of platinum or other suitable metal so arranged that each
of them is electrically insulated from the frame of the instrument and adapted
to be moved towards or away from each other as is hereinafter described. The
contact arm is in electrical connection with the frame of the instrument and a
terminal F which may be placed anywhere on the frame and the contact plates
are connected to terminals E E¹.
The contact plates and their terminals must be properly insulated from the
frame of the instrument.
When the contact arm A owing to an increase of pressure moves upwards
till its upper stud B contacts the upper plate 1) an electric circuit is completed
through the arm A the insulated upper plate D the terminal E a battery and
a bell and the terminal F and the bell thereupon ringing denotes that the upper
limit of pressure which has been predetermined as hereinafter described has
been reached. When the contact arm A owing to a decrease of pressure moves
downwards till its lower stud B₁ contacts the lower plate D₁ an electric circuit
is completed through the contact arm A the insulated lower plate D¹ the
terminal E a battery and the same bell as before or another bell and the
terminal F and the bell ringing denotes that the lower limit of pressure which
has been predetermined as hereinafter described has been reached.
The position of the contact plates is regulated by the position of two index-
hands HH either both arranged on one dial K as in the drawings or each
having a separate dial. The dial K (or dials) is provided with a scale of
pressures and the index hands may be set so as to point to any pressure on the
dial. The index hands HH transmit their motion to the contact plates DDi
which are preferably mounted on insulated flat springs LL by means of
screws S S¹ so that a rotary motion of an index hand produces an up and down
movement in the corresponding contact plate, and this may be very simply
accomplished by the ends of the screws bearing on the flat springs which carry
the contact plates.
Either the ends of the screws must consist of insulating material or they must
bear on insulated studs carried by the springs.
The mechanism connecting the index hands and the contact plates is so
adjusted that when the contact arm is in a position produced by a certain pressure
the setting of either index hand to that pressure on the dial will just cause the
corresponding contact plates to make contact with the corresponding stud on
the contact arm.
In the drawings the connection between the index hands and the contact plates
operates as follows. The rotation of the index hand H causes the spur wheel M
to rotate. The spur wheel M engages with a similar spur wheel N mounted
on a bracket P attached to the frame of the instrument. The spur wheel N
engages with the screw S by means of a cotter. The screw S bears on the
spring L and thus a rotation of the hand H causes the raising or lowering of
the contact plate, D. Similarly with the hand H¹ the gear M¹ N¹ and the

page_text: screw S¹, so that a rotation of the hand H' causes the raising or lowering of the
contact plate D¹.
If the hands are both on one dial no provision need be made for one hand
passing the other for the hand which points to the lower of the two pressures
must not be allowed to pass the one that points to the higher pressure and in
any positions of the two hands the predetermined limit of variation of pressure
which can occur without giving an alarm is the pressure indicated by one hand
to that indicated by the other. For example if the lower hand be set at 10lbs
to the inch and the upper hand to 15lbs. to the inch the bell will ring when the
pressure rises to 15lbs. and also when it falls as low as 10lbs. to the inch.
If the hands are on separate dials then one dial indicates the upper limit of
pressure and the other the lower limit of pressure at which the alarm is to be
given.
If the object is merely to ring a bell when the pressure attains a certain value
and it is immaterial to what value the pressure may fall the lower index hand
may be dispensed with and also if it is merely desired to give an alarm when
the pressure falls to a certain value the upper index hand and the mechanism
connected with it may be dispensed with.
The apparatus above described is clearly applicable to pressures below as well
as those above the ordinary atmospheric pressure.
In the above description
reference has been made throughout to an electric bell but any sort of electrically
operated alarm may equally well be used.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what
I claim is:—
1. In an alarm pressure guage the employment of a hand or of two hands on
one dial or on separate dials marked with a scale of pressure to determine the
position of a contact plate or contact plates placed in the path of a contact arm
which is operated by the pressure measuring apparatus substantially as described.
2. The improved alarm pressure guage substantially as described.
בד
211 .
1000