Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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The principle of hydropneumatic dampers,
designed to absorb pressure and flow variations in a
hydraulic installation, essentially consists in pressure-
balancing a compressible gas with a hydraulic fluid
inside a close-volume capacity.-
It is known that to prevent the gas fromdissolving into the liquid and to allow a pre-compression
of the gas without any hydraulic pressure, it is neces-
sary to place between the gas and the liquid a supple
- 10 deformable dividing wall to restrain the gas.
Two main embodiments of ~uch a supple wall are
known, these are the ~bladder~ type and the ~'diaphragm"
type. In the bladder type, the damper is made up by
cylinder-shaped metallic reservoir ending in two
substantially spherical caps in which is introduced
a bladder which, in the free state, adopts the shape
~ of the reservoir. The upper cap comprises a connecting
means for the neck of the bladder permitting to inflate
it by way of a valve; the lower part comprises a
connection permitting the communication with the liquid
of the circuit a~ well as a grid or a valve ~y~tem
limiting the downwards course of the bladder whenever
its inflating pressure exceeds that of the circuit.
The di~advantage with this device, which can be
pre-inflated to a suitable pre~sure before being connect-
ed to the circuit, is that it iR unsuitable for thick
liquids which risk to obstruct the system connecting
it to the circuit and to damage the bladder. In addition,
in case of insufficient inflating or of a gas leak,
the bladder is pressed back towards the top where there
is no abutment system, so that it suffers e~cessive
deformation which can ruin the blad~er. Finally,
even in normal conditions of operation the deformations
necessary for the device to work, demand a ~upple
~k
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diaphragm with a good bending Ytrength, this implying
the use of ela~tomer-type materials, the chemical
behaviour of which is unsuitable for certain applications.
In the diaFhragm type, the reservoir is made
up by two symmetrical metallic shells and the dividing
diaphragm substantially adopts, in the free state~ the
inside shape of the shells; said diaphragm i~ tightly
qecured by its periphery in the shell-joining plane.
The upper shell contains the inflating device and the
lower shell contains the connection to the circuit and
a grid or equivalent valve device preventing the
extrusion of the diaphragm. This device presents one
advantage over the preceding one in that the diaphragm
suffers less mechanical fatigue and in that it is
better protected against damages in case of gas leaks
or of excessive pressure. It has nonetheless the same
disadvantage of the abutment system beccming obstructed
~ by a thick liquid.
It should also be noted that it i~ often advan-
tageous in order to obtain the best possible damping
results, to have a volume of gas which is clearly greater
than the volume corresponding to the maximum deflection
of the diaphragm~which latter is less than the inner
volume of the shells. It is then necessary to use the
known dampers associated with auxiliary gas capacities,
using a system of pipes and fittings, which increases
the risks of leaks, the overall size of the instal-
lation and the cost of the equipments.
It is the object of the present invention to
overcome these disadvantages by proposing an easy-to-
produce hydropneumatic damper, which uses a diaphragm-
type separation, and is equipped with mean~ permitting
to limit the possible deformations of the diaphragm
due to a gas leak or to excessive pressure, or due
to in~lating under a nil hydraulic pressure, these means
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permitting to as~ociate, in simple manrier, an auxiliary
capacity of gas which communicateq directly with the
air chamber of the damper, the volume of which
capacity i~ adjustable a~ required.
The invention proposes to this effect a hydro-
pneumatic damper constituted by an.enclosure divided
into two chambers, sealed one from the other by way of a
deformable diaphragm, one of said chambers being provided
with a conduit connecting it with a hydraulic instal-
lation, whereas.the other chamber is provided with
a conduit connecting it with an auxiliary capacity of
gas.
According to one characteristic of the invention,
the aforesaid dividing diaphragm is equipped in its cen-
ter with a built-in element consisting of two parts
symmetrical with respect to the diaphragm, of substantial-
ly truncated shape, whereas the two aforesaid conduits
issue into their reapective chamber through a widening-
out sub~tantially truncated portion, having the same
conicity a~ said two parts, said truncated portions
and parts being in axial alignment.
Preferably, each truncated part of said element
is axially extended by a centering projection.
According to one advantageou~ embodiment of
the invention, said diaphragm is provided in its center
with an orifice of which the annular edge is substantial-
ly flat, and comprises on each face a substantially
semi-annular bead wherea~ the two parts of said element
comprise two plane faces one opposite the other, each
one of which is provided with a semi-annular groove
to receive the said bead, and one of ~aid part~ forming
~crew to be joined to the other part through the orifice
of the diaphragm, said two parts gripping the said bead
between them.
Tn addition, one of said parts is provided with
951
a radial shoulder member on which abuts the other part,
and which is at a di~tance from its plane face
substant-ially equal to the thickness of the flat edge
of the diaphragm.
Moreover, the said diaphragm is made of rubber
and coated on its face directed towards the hydraulic
chamber with a layer of plastic material, and it
comprises an external annular edge whicll is substantially
flat and provided with semi-annular beads fastening
it to the enclosure.
The central part of the membrane which extends
between the two aforesaid flat edges, take on, in the
free state, a substantially annular shape.
Finally, the damper according to the invention
will be advantageously constituted by two half-shells,
between which are gripped the external beads of the
diaphragm, the conduit of communication with the auxiliary
capacity being constituted by an orifice traversing
one of the half-shells, and the said capacity being
constituted by a sleeve surrounding the said orifice
and cooperating tightly by one of its ends with a base
member and by its other end, with the ~aid half-shell,
the said ba4e member and the other half-~hell comprising
means for fastening together the stacked up assembly.
The invention will be more readily understood
on reading the following description with reference to
the accompanying drawings, in which :
- Figure 1 is a diagrammatical cross-section
of the apparatus according to the invention;
- Figure 2 illustrates a cross-section of a
preferred embodiment of the center of the diaphragm
in the damper according to the invention.
Referring first to Figure 1, this shows an
enclosure 1 made up by two half-shells la and lb
defining an internal volume. A dividing diaphragm 2
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divides this internal volume into two chambers A and B,
chamber A being the hydraulic chamber and ~hamber B being
the air chamber of the damper. The lower shell la
is provided at it~ lower part with a threaded orifice 3a
by which it is connected with a hydraulic installation
(not shown). The conduit 3a issues into chamber A via
a widening out portion forming a conical bearing 4a
which connects up with the inner wall of the half-shell
la. Said half-shell comprises, in one piece therewith,
an external flange 5 provided with holes to allow
the passage of assembling bars 7. The half-shell la is
also pro~ided on its face resting against the half-shell
lb, with a semi-annular groove 8a.
The inside shape of the upper half-shell lb
is symmetrical to the inside shape of the half-
shell la. Said upper half-shell lb is also provided with
an orifice 3b issuing into chamber B through a bearing
~ part 4b, said orifice forming the end of a conduit
connecting the chamber B with an au~iliary capacity
of gas to be described in more detail hereinafter. And
its face resting on the half-shell la also comprises
a semi-annular groove 8b.
The half-shell lb is topped by a sleeve 9,
a tight connection between these two elements being
ensured by an 0-ring 10. Said qleeve is closed at its
other end by a base member 11 which is also provided with
an 0-ring 12. Said base member, which is edged with a
flange 13, is held in position against the sleeve 9,
which acts as a tie -piece, resting on the half-shell 30 lb and applying it against the half-shell la by means
of assembly bars 7.
The internal volume 14 of the sleeve constitutes
the auxiliary capacity of gas, which communicates with
- the chamber B via the orifice 3b and is adapted to be
inflated through a valve 15. A conduit 16 can be used
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1~769Sl
to inse~ in a pre~sure gauge.
The dividing diaphragm 2 is, in the illu~trated
example, a composite diaphragm, constituted by a layer
2b ~the thickest) on the side of chamber B, in
synthetic or natural rubber, and by a layer 2a (the
thinnest) on the side of chamber A, in plaqtic material
such as for example tetrafltloroethylene, The thickne~
proportion of the two constituents is around 4/5, 1/5.
Said diaphragm comprises a substantially flat
peripheral annular portion 17. Each face of thi~ periph-
eral portion comprises a bead 17a, 17b constituted by
half a torus, the radius of which is about equal to the
thickness of the diaphragm. It will be noted on the
figure that one at least of~ the mutual bearing faces
i5 f the half-shells la lb comprises a kind of spot-
facing over a depth substantially equal to the thic~ess
of the diaphragm. And the grooves 8a and 8b have
dimensions such that when two shells are applied one
against the other, the crushing of the beads 17a,
17b does not exceed 20% of the thickness of the
diaphragm in that point. Said diaphragm is thus
in~erted between the half-shells la, lb solely at the
level of the beads 17a, 17b which cooperate with the
grooves 8a, 8b in the same way as 0-rings, to ensure
tightness between chambers A and B. As a result, the
life of the diaphragm which is spared excessive strains
at the level of its anchoring, is lengthened.
Towards the center, the said diaphragm compriseg
a part 18 which is substantially annular shaped when
in the free state. The radius of said annular part
is such that the total length of the meridian section
of the diaphragm is equal to the total length of the
inner meridian section of one of the half-shells la,
lb. It will also be noted that the shape (like
spherical caps for example) of the inner walls of the
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enclosure 1 is such that the deflection of the diaphragm
does not exceed 10 to 15% of its ~erviceable diameter.
Finally, as shown more clearly in Figure 2,
the said part 18 i~ extended by a flat annular ring 19
which is also provided with bead~ 19a, 19b identical to
beads 17a, 17b, said ring surrounding a central
orifice 20.
A metal part 21 is ~ecured by its centre to the
diaphragm 2, It is composed of two symmetrical parts
21a, 21b, one of which carries a screw 22 and the other
is shaped into a nut 23. The nut and screw cooperation
is achieved through orifice 20. The part 21b presents
a radial bearing face 24 which cooperates with a radial
shoulder 25 of the part 21a. A kind of spotfacing
f radial face 26 is provided in the part 21a so that
the distance between the said face 26 and said
shoulder is equal to the thickness of the diaphragm.
S~mi-annular grooves 27a and 27b are provided in ~aid
face4 24 and 26 and cooperate with the beads 19a and
19b in the aame way as grooves 8a and 8b cooperate
with the beads 17a, 17b when the two parts 21a, 21b
are screwed one into the other.
Each of said parts comprise~ a truncated external
surface 28a, 28b, the angle at the top of which is
about 120, extended by an external surface 29a, 29b which
is also truncated, the angle at the top of which is
about 90, and which surrounds a projection provided
for centering the part 210 Thus, the bearing faces 4a
and 4b having the same conicity as the surfaces 28a,
28b, when the diaphragm is applied against the inner
walls of the enclosure 1, the said surfaces rest
against the said parts. In this case, tle diaphragm
rests entirely again~t the wall, working solely in
flexion, without any risk of elongation or extrusion
whatever the differential pr~ssure which urge~ it out-
i:~7695:1
wardly of the enclosure.
Finally, another faet to be noted is the
presence of slots 30a, 30b at the tops of part 21
provided for assembling and dismantling purposes.
The way in which this deviee works is well known
and can be ~ummed up as a sueeessionofpartial filling
and emptying of the upper part of the capacity with
deformation of the diaphragm : as a result, variations
in the pressure of the gas oecur whieh are dependent
on the ratio between the corresponding maximum and
minimum volumes~
Without going into detail, it will be simply
recalled that in normal operation, the cubic capacity
to be absorbed should be le~s than the deflection
i5 of the diaphragm between its abutmentq and that the
average position of saiddiaphragm depends on the
pre-inflatins pres~ure nlld on tl-e total volume,
including that of the auxiliary capaeity. Generally,
the greater the volume of gaA, the better the abqorbing
eapacity; on the other hand, the aeceptable variations
of the meAn pressure are that more reduced. Therefore,
it is poqsible in every ease of eirc~it and of operation~
to find a compromise between these different faetors.
Calculations and experience have shown that, in most
ca~es, the bladder type or diaphragm type dampers
in their conventionally-known form do not permit to find
this compromise without considerably larger dimensions,
leading to higher costs and more room-Apace. An auxili-
ary eapaeity eovering the total deflection of the
diaphragm, represents on the eontrary a satiA~`actory
eompromise for many applieations.
The volume of the auxiliary capacity 14 accord-
ing to the invention can easily be altered. Indeed,
the sleeve 9 can be replaeed by a longer or shorter
sleeve. As a variant, a capacitycan be provided which is
1176951
integral with the half-shell lb, this being obtained
by welding the sleeve 9 to the base ~ember 11 and to
the ~aid ~hell. Another possibility, is to design the
damper according to the invention with two half-4hells
identical to that la, with their fIange 5, the air
capacity being then connected by screwing in the same
way a~ the hydraulic circuit.
The ~pecial shape of the abutment, integral
with the diapbragm, which completely clears a wide
orifice in the working position and completely ~eals
it off at end-of-ctroke, permits to use the apparatus
with thick liquid~ without the risks of blockage and of
internal depo~its found with the known device~. Pre-
inflating in the open or on a non-pressurized circuit
is al~o pos~ible. The insulation, achieved on the ~ide
of the air chamber by the valve`21 on the bearing face 4b,
protect~ the diaphragm again~t any gas leaks or excesRive
pressures from the hydraulic circuit which would damage
a bladdcr-type damper. It enable~ to utilize the whole
deflection #troke, leaving a re~idual volume which will
help the damping, which i~ impo~sible with the
conventionally known bladder or diaphragm damper~, and
thi~ without any ri~k.for the diaphragm in all cases
of operation, even outside the normally prescribed
limit~. .
... .
