Improvements in and relating to Pressure Gauges.
Year: 1898

page_text: [Communicated from abroad by the Firm of SCHAFFER AND BUDENBERG, of
Buckan bei Magdeburg, Saxony, Engineers.]
Improvements in and relating to Pressure Gauges.
I, WILLIAM EDWIN HEYS, of 70, Market Street, Manchester, in the County of
Lancaster, Chartered Patent Agent, do hereby declare the nature of this invention
to be as follows:
-
In pressure gauges of the Bourdon type constructed with tubes made from
bronze and other suitable copper alloys for high pressures, considerable trouble
and inconvenience are experienced in connection with the means at present em-
ployed for connecting the tubes with the bodies of the gauges, which are avoided
by the present improvements. According to the existing usual practice, the
Bourdon tube is drawn or flattened to an oval cross section and its appropriate end
is fitted and soldered into a corresponding oval hole in the body and end piece,
the soldering being relied upon to make the joint and to hold the tube in position
against the pressure in the tube. The objection to this method is that it is not
reliable since the solder may become melted if exposed to considerable heat.
As an additional precaution when the gauges are to be used with the higher
pressures now common, the ends of the tubes are screwed as well as soldered into
the body and end piece, the flattened end of the tube being bulged up to the
original circular section and an ordinary screw thread cut thereon. This has
the further objection that the cutting of the screw thread necessarily weakens it.
The object of the present invention is to make such a joint in which no reliance
is placed upon solder either to effect the joint against internal pressure or for
holding the tube in position. For this purpose the screw thread is formed upon
the end of the tube by pressure exerted either through suitable dies or by rolling
and, instead of making the ordinary angular thread, a rounded form of thread
is produced. By this means no metal is removed and the end of the tube is not
weakened. The tube is further held more securely by belling its end and making
with it a metallic joint. This may be accomplished by undercutting the hole
in which the tube end fits and by a plug screwed into the body or end piece from
the side opposite to that at which the tube is entered. Or, the lower part of
the hole in the body or end piece may be formed with an annular recess formed
between the undercut bottom of the hole and a core having the form of the
frustrum of a conc. When the tube is screwed in, the core bells or expands
its lower end into the undercut annular recess and it is then impossible to
displace the tube or break the joint by pressure, since the material of the tube

page_text: will yield before the joint. The core may be separately formed and be intro-
duced into the hole before the tube or it may be used from the back as part of
the hereinbefore described plug.
T
ค
1 1
W. E. HEYS & SON,
Agents for the Applicant.
Mausto
1, WILLIAM EDWIN HEYS, of 70, Market Street, Manchester, in the County of
Lancaster, Chartered Patent Agent, 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:-
In pressure gauges of the Bourdon type, constructed with tubes made from
bronze and other suitable copper alloys, for high pressures, there are experienced,
in relation to the means at present employed for connecting the tubes with the
bodies of the gauges, considerable trouble and inconvenience which are avoided
by the adoption of the present improvements. According to the existing usual
practice, the Bourdon tube is drawn or flattened to an elliptical cross section,
and its appropriate end is fitted and soldered into a correspondingly shaped hole
in the body and end piece, the soldering being relied on to make the joint and
to hold the tube in position against the pressure in the tube. The objection to
this method is that it is not reliable, since the solder may become melted if
exposed to considerable heat. As an additional precaution, when the gauges have
to be used with the high pressures now common, the ends of the tubes are
screwed as well as soldered into the body and end piece, the flattened end of
the tube being bulged up for this purpose to the original circular cross section
and an ordinary screw thread cut thereon. This method has the further objection
that the cutting of the screw thread necessarily weakens the tube and the joint
made with it.
The object of the present invention is to make a joint between the Bourdon tube
and the body and end piece without relying upon the use of solder or its equi-
valents. For this purpose, a screw thread is formed upon the bulged up end of
the flattened tube, by pressure, exerted through the agency of suitable dies or
by rolling, and, instead of making the ordinary screw thread, by producing a
rounded form of thread. By this means, no metal is removed, and the end
of the tube is not weakened." The tube is further held more securely by belling
its end and making with it a metallic joint. This may be accomplished by under-
cutting the hole in which the end of the tube fits and by means of a plug which
may be screwed into the body or end piece from the side opposite to that at which
the tube is entered. Or, the lower part of the hole in the body or end piece
may be formed with an annular recess produced between the undercut bottom of
the hole, and a core piece having the form of the frustrum of a cone. When
the tube is screwed in, the core bells or expands its lower end into the undercut
annular recess and it is then impossible to displace the tube or break the joint
by pressure, since the material of the tube will yield before the joint. The core
may be separately formed and be introduced into the hole before the tube, or it
may be introduced from the back as part of the hereinbefore described plug.
The accompanying drawings illustrate in what manner these improvements
may be carried into practice, and will be hereinafter referred to.
Each of the Figures 1, 2, and 3, represent a cross section of the joint in a

page_text: different modification. The end of the bourdon tube is in each case indicated by
the reference letter T, and the end piece in which it is secured, by the letter A.
In the arrangement of the joint shewn by Figure 1, the tube, which is elliptical
in cross section at E, and circular in a similar section at C, has produced in the
part C, by pressure, the screw thread indicated, so that no part of the metal of the
tube is cut away. The hole in which it is fitted is correspondingly screw threaded
and ends at the bottom by an undercut portion which may be wholly or partly
formed by the female screw thread itself. At the bottom of the hole there is a
coned piece D, which may either be turned out of the body of the end piece,
or be a separate part as indicated by the dotted lines, in which case it may be
introduced into the hole before the insertion of the tube. The interior of the
tube may be stiffened by the introduction therein of a short screwed plug P,
having a passage through it for the communication of the fluid pressure to the
tube.
In the modification illustrated by Figure 2, instead of screwing the metal of
the tube itself, it is provided with a screwed collar F, and the end of the tube
is seized between the undercut collar and the cone.
In the modification represented by Figure 3, only a very slight screw thread is
produced on the tube, just sufficient to prevent the tube being driven forward
by the closing up of the coned plug D, which is screwed in from the back.
If the tube be firmly held relatively to the end piece, while the coned part D
is introduced, the screwing of the tube may be wholly omitted, and a complete
metallic joint will be made by the compression of the belled end of the tube
between the coned part and the undercut part of the hole.
It will be obvious that other modifications may be made in the construction of
the joint which it is not necessary to describe.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, as communicated to
me by my foreign correspondents, I declare that what I claim is:-
1. The herein before described manufacture or production of joints in pressure
gauges, which consists in compressing the end of the Bourdon tube against the wall
of the hole in which it is inserted, by means of a coned part, substantially as
herein before described with reference to the accompanying drawings.
2. Joints in Bourdon pressure gauges produced as and by the means herein-
before described with reference to the accompanying drawings.
Datad this 201
35
1000