Improvements in Bourdon Pressure Tubes.
Year: 1887

page_text: Date of Application, 12th May, 1887
Specification Accepted, 2nd Aug., 1887
Improvements in Bourdon Pressure Tubes.
I, RICHARD GRADENWITZ of Bendlerstrasse, Berlin in the German Empire,
Engineer, do hereby declare the nature of said invention for "IMPROVEMENTS IN
BOURDON PRESSURE TUBES" and in what manner the same is to be performed, to
be particularly described and ascertained in and by the following statement :-
The purpose of this invention is to render practicable the construction of so called
"Schinz" or "Bourdon" tubular springs with a relatively larger bending movement-
consequent upon the pressure of liquids or gases acting inwardly or outwardly thereon-
and in the manner that the one half of the spring or one portion thereof is increased
whilst the other half is diminished relatively in rigidity.
The "Schinz" or "Bourdon" tubes hitherto employed for measuring pressure are
elliptic or oval in cross section. Under pressure such cross sectional form undergoes
alteration according as the pressure acts inwardly or outwardly into a more circular
or flattened cross section. By this alteration of cross section the tubular spring is
bent to a more open or closed position. The movement thereby occasioned which is
proportional to the pressure acting upon the tubular spring is transferred either direct
or through toothed mechanism to a pointer that by its movement indicates the pressure
present inside or outside the said spring. Such tubular springs are made by rolling
rectangular strips of sheet metal together, then brazing, drawing, and bending them.
The tubular springs of this invention are shewn in the accompanying drawing.
Their construction is based on the principle that one side or part of the spring is in a
neutral plane and remains always unchanged in superficial shape when the spring is
under pressure so that only the side or part which is opposite the neutral side, changes
its shape.
Fig. 1 shews a tubular spring with an undulating side A opposite a neutral flat
side B, the undulations being at right angles to the longitudinal axis. When subjected
to internal pressure it tends to change the undulating side to a flat shape so as to
increase its length; consequently it opens outwardly in proportion to the pressure
acting upon it. When subjected to outside pressure the reverse action takes place,
the spring bending inwardly.
Fig. 2 shows a tubular spring with undulations parallel to the longitudinal axis.
The action is similar to that of Fig. 1.

page_text: Figs. 3, 4, 5, 6, 7, 8 shew different forms of cross section, of which the tubular
springs may be made.
The movements brought by varying pressures are transferred either direct or
through a pinion and toothed segment to a pointer over a dial.
Both kinds may be constructed with the two sides alike in superficial shape or
without undulations as in Fig. 5 the side serving as the neutral side B¹ being made
stronger than the opposite side A¹ or this difference of strength may obtain in all
cases as shewn also in Fig. 6.
If the tubular spring is formed of an undulating form on the outside, and flat on the
inside, then. according as the pressure acts upon the inside or outside it will bend
inwardly or outwardly.
The method of construction also differs from that of the tubular springs hitherto
made in that they are worked and drawn from the solid.
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 "Schinz or "Bourdon" tubular springs the increase of the bending move-
ment of one side or part lengthwise by increasing the superficial area of the said side
or part substantially as shewn and described with reference to Figs. 1 and 2 of the
drawing.
2. In "Schinz" or "Bourdon" tubular springs the increase of the bending
movement of one side or part lengthwise by giving to the same a diminished or less
strength as compared with the opposite side or part substantially as described and
shewn.
3. The production of tubular springs of the kind referred to without brazed or
soldered seams by drawing from the solid substantially as described.
CAPITAINE & VON HERTLING,
89, Chancery Lane, London, W.C.,
Agents for the Applicant.