Note: Descriptions are shown in the official language in which they were submitted.
2077280
The invention relates to a valve controlled in dependence on
differential pressure with a set-point reference setting facility,
having a valve housing, which comprises a valve seat and a closure
member provided with a valve rod, with a diaphragm housing, which is
mounted on the valve housing and is divided by a diaphragm acting on
the valve rod into two pressure chambers, and with a setting device,
which is mounted on the diaphragm housing and comprises a set-point
spring acting on the diaphragm and an adjusting means for the set-
point spring.
In the case of a known valve of this kind (EP-OS 354 427),
in which the diaphragm housing is arranged between the valve housing
and the setting device, use is made of a continuous valve rod, which
at one end carries the closure member, in the middle is connected to
the diaphragm, and at the other end is loaded by the set-point spring.
The set-point spring bears at one end against the diaphragm housing
and at the other against a spring plate, which is arranged to screw
onto the valve rod. After removal of a cover, the springs can also be
exchanged.
In the known construction, manipulation of the set-point
spring (adjusting and exchanging it) poses problems because the space
receiving the spring is connected to the system by way of the pressure
chamber remote from the valve and is therefore accessible only after
additional precautions have been taken in the system. Because the
valve rod is long and is mounted with one free end close to the
closure member in a guide means of the valve housing, there is a
danger that it will buckle under the influence of the axial forces
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and/or transverse forces that are caused, for example, by
unsymmetrical spring forces (skewed state). That would lead to
increased friction at all sealed points, to a corresponding hysteresis
of the valve movement, and to wear and tear at the sealing points.
For that reason, the valve rod is of very thick construction. It is
therefore heavy and expensive, in particular when it consists of
stainless steel or another expensive material in order to be
compatible with the medium to be controlled.
The invention is based on the problem of providing a valve
of the kind mentioned in the introduction that is controlled in
dependence on differential pressure and in which the set-point spring
can be adjusted or exchanged at any time.
Generally speaking, the present invention may be considered
as providing a valve controlled in dependence on differential pressure
with a set-point reference setting facility, comprising: a valve
housing having a valve seat and a closure member provided with a valve
rod; a diaphragm housing mounted on the valve housing and divided by
a diaphragm acting on the valve rod into two pressure chambers, from
which chambers a pin connected to the diaphragm projects in a sealed
manner; a setting device mounted on the diaphragm housing; the setting
device being removable as a unit from the diaphragm housing; a set-
point spring acting on the diaphragm and arranged between a supporting
plate and a spring plate; adjusting means for the set-point spring;
and a releasable coupling transferring the spring forces to the pin.
Because the pin is guided in a sealed manner out of the
diaphragm housing, no further sealing is required in the setting
device. The set-point spring is located in the atmosphere and can be
adjusted at any time. Because the setting device is removable as a
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unit, exchange of the springs can also be effected in a simple manner.
There is no continuous valve rod. On the contrary, the coupling
effects a separation between the spring plate loaded by the spring
force and the pin transferring the forces to the diaphragm and the
closure member. This coupling must be releasable, so that the setting
device can be removed as a unit. A releasable coupling has so much
play that skewed positions or lateral displacements caused by skewed
springs are compensated in that the pin passing through its seal is
not subjected to any detrimental transverse forces. If desired, this
can be further assisted by suitable design of the coupling, for
example as a flexible coupling. Because the pin is virtually free
from transverse forces, it, and the entire valve rod, can be
manufactured with a smaller cross-section and therefore at a lower
cost. The smaller the cross-section, the greater also is the
independence from the static pressure in the system.
Valves of this kind controlled in dependence on differential
pressure are used, for example, in hot water heating systems, in order
to guarantee a given pressure difference between the supply pressure
and the return pressure in the heating circuit. In this and in other
cases, the pressure chamber remote from the valve carries the higher
pressure and the pressure chamber closer to the valve carries the
lower pressure. For this application therefore, care has to be taken
that the coupling is designed to transfer tensile forces. The set-
point spring must be effective against the diaphragm loading.
In a preferred embodiment, the set-point spring is a helical
compression spring, the end of which close to the diaphragm is engaged
by the supporting plate and the end of which remote from the diaphragm
is engaged by the spring plate. Because it is not the spring plate
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that is adjustable relative to the valve rod but the supporting plate
that is adjustable relative to a stationary part of the setting
device, a stable construction is created.
The coupling is preferably arranged at the end of the
setting device close to the diaphragm. The lever arm acting on the
pin between the coupling and the seal is small, so that for this
reason too, any stress on the seal is negligible.
The releasable coupling is especially advantageously a
snap-fit coupling. The coupling is automatically brought into its
effective position as the setting device is placed on the diaphragm
housing or on brief depression of the spring plate.
It is recommended for the snap-fit coupling to be formed by
a head on the pin and by a holder comprising at least two resilient
arms engaging behind the head. By opening out the arms, the snap-fit
coupling can also be released again.
In a preferred embodiment, provision is made for the spring
plate to have a tubular extension running towards the diaphragm; at
its free end, the extension carries the holder and to form the
resilient arms is provided with slots. Because of the extension, the
slots are comparatively long. Small forces are therefore sufficient
to open out the arms.
It is especially favourable if the head has sloping faces at
its end remote from the diaphragm and/or if the holder has sloping
faces on its side close to the diaphragm in order to facilitate the
snap-fit action. The sloping faces facilitate automatic snapping-on.
The spring plate is preferably connected by way of a conical wall
tapering towards the diaphragm with the tubular extension, and the
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slots extend right into the conical wall. If a tool is pressed onto
the conical wall, the arms open out.
Moreover, it is favourable for the pin to pass through a
sealing housing secured to the diaphragm housing and provided on its
periphery with profilings, and for an annular base of the setting
means to be arranged to be pushed onto the sealing housing and be
secured to it by means of at least one screw engaging behind the
profilings. In this manner the setting device can be secured
releasably yet securely to the diaphragm housing.
In further development of the invention, provision is made
for the supporting plate to be held so that it cannot rotate and to
have an external thread which engages with an internal thread of a
rotary knob concentrically surrounding the set-point spring, and for
the rotary knob to be held so that it is able to rotate yet is axially
fixed on a base of the setting device. This is an especially simple
construction for adjusting the set-point spring.
An index ring, which engages by means of at least one radial
pointer through an axial slot in the rotary knob, is preferably
located rotatably on the supporting plate. A scale can be mounted at
this axial slot. An indication of the desired value that has been set
can be obtained in a simple manner.
The invention is explained in detail hereinafter with
reference to a preferred embodiment illustrated in the drawing. The
single Figure shows a longitudinal section through a valve according
to the invention.
The valve illustrated consists of three parts fastened to
one another, namely, a valve unit 1, a fit-on diaphragm unit 2 and a
setting device 3.
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The valve unit 1 comprises a valve housing 4 with a valve
seat 5. The latter co-operates with a closure member 6 which is
connected to a valve rod 7. The closure member is arranged to be
~crewed onto a threaded portion 8 of the valve rod 7 and clamps the
base of a cup 9 drawn from sheet metal fixedly to a step in the valve
rod 7. An insert lo in the housing 4 forming a passage-way has a
guide section 11 for the valve rod 7 and a seal 12 for the cup 9.
This creates a compensation chamber 13 which is connected by way of a
system of ducts 14 in the closure member 6 and in the valve rod 7 to
the inlet chamber 15 of the valve housing 4. Static pressure
compensation at the closure member is obtained in this way.
The fit-on diaphragm unit 2 has a diaphragm housing 16 with
a lower shell 17 and an upper shell 18 connected to the lower shell by
crimping. A fixing ring 19, which can be fastened to the valve
housing 4 by means of a union nut 20, is secured to the lower shell 17
by crimping. A sealing housing 21 acting as a packing gland is
secured to the upper shell 18 by crimping and has a profiling 22 in
the form of a circumferential annular groove with conical side walls.
A diaphragm 23 is clamped peripherally between the shells 17 and 18
and is covered on both sides by supporting plates 24 and 25. An
insert 26 has a circumferential wall 27 which passes through a central
opening in the supporting plates 24, 25 and is fixed there by
crimping. At its upper end the valve rod 7 carries a contact face 28
formed by a plate, which is pressed with the aid of a valve spring 29
against the insert 26.
The diaphragm 23 divides the diaphragm housing 16 into a
pressure chamber 30 close to the valve and a pressure chamber 31
remote from the valve. The pressure chamber 30 is connected by way of
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a bore 32 to the compensation chamber 13, and thus to the inletchamber 15 of the valve housing 4. The pressure chamber 31 has a
connection 33 for a pulse line, by which a system pressure to be
monitored, which is generally higher than the pressure in the pressure
chamber 30, can be supplied. In the pressure chamber 30 there is a
diaphragm spring 34 which urges the diaphragm 23 upwards, and in the
pressure chamber 31 there is a diaphragm spring 35 which urges the
diaphragm 23 downwards. A guided pin 36 is connected at its lower end
by way of an articulation 37 to the insert 26. The pin projects
lo through the sealing housing 21 to the outside. The articulation 37
comprises a hemispherical head 38, which is connected to the pin 36 by
a neck 39, and an articulation socket 40, which engages behind the
articulation head 38. The articulation socket is formed by a
transverse bore 41, the axis of which is at right angles to the plane
of the drawing and adjoining the upper side of which is a slot 42
running in the same direction for the passage of the neck 39. On
assembly, the articulation head 38 is pushed from the side into the
transverse bore 41 and is held in the middle of the bore by a
pushed-on cap 43 so that it is able to perform a limited swivel
movement in all directions.
A relief valve 44 is provided in the insert 26 and comprises
a valve ball 45 which is pressed by a spring 46 against the free end
of an axial bore 47 connected to the transverse bore 41.
The setting device 3 comprises an annular base 48, which is
arranged to be pushed onto the sealing housing 21 and is to be
fastened to the diaphragm housing 16 by means of screws 49 that engage
with conical points in the annular groove 22. A set-point spring 50
in the form of a helical compression spring extends coaxially with the
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pin 36 between a supporting plate 51 close to the diaphragm and a
spring plate 52 remote from the diaphragm. The supporting plate 51 is
prevented from rotating by a guide member 53 and has an external
thread 54 which engages with a corresponding internal thread on the
circumferential wall 55 of a rotary knob 56. At its lower end, the
rotary knob 56 has resilient tongues 57 which engage by means of
projections 58 beneath a step of the base 48. The rotary knob 56 is
therefore capable of rotation, but is axially fixed. Mounted on the
supporting plate 51 is an index ring 59 which has radial pointers 60
lo that project through two axial slots 61 in the knob 56 and cooperate
with markings on the outside of the knob.
The spring plate 52 is joined by way of a conical wall 62 to
a tubular extension 63 which extends as far as the vicinity of the
fit-on diaphragm unit 2 and there forms with the pin 36 a coupling 64,
in particular a snap-fit coupling. For that purpose, the pin 36 has
a head 65 which is provided at its top end with a sloping face 66.
This co-operates with a holder 67, which likewise has sloping faces
68, engaging behind it. The holder is constructed on resilient arms
69 which are created by axially parallel slots 70 in the tubular
extension 63. The slots 70 extend into the conical wall 62 so that,
by introducing a tool through an end opening 71 in the rotary knob 56,
the spring arms 69 can be spread apart at the transition from the
extension 63 to the conical wall 62, and the coupling 64 can thereby
be released.
Assuming that the illustrated valve is intended to keep the
pressure drop constant in a system, for instance in a hot water
heating system, then the valve is arranged at the exit of the system,
that is to say, in the return line, and the connection 33 is connected
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to the supply line. The lower pressure chamber 30 then carries the
return pressure and the upper pressure chamber 31 carries the supply
pressure. This produces a force acting in the closing direction.
counteracting this is the force of the set-point spring 50 which is
effective to apply a tensile force in the region of the articulation
37 and the coupling 64. In the usual manner, a state of equilibrium
is established, in which the pressure drop in the system has the
desired value.
The set-point spring can be adjusted at any time by rotating
the rotary knob 56. If it is desired to use a different spring
assembly, the setting device 3 can simply be exchanged as a unit.
Using a tool which has a smaller angle of taper than the conical wall
62, the spring arms 69 are opened out so that the coupling 64 is
released. On renewed assembly, the coupling 64 snaps on automatically
by virtue of the sloping faces 66 and 68. Should the force of the
set-point spring 50 be too great, it is sufficient to press the spring
plate 52 downwards somewhat; that can be effected without difficulty
through the opening 71.
The play and the articulation mobility of the coupling 64
prevents transverse forces, which may occur on account of asymmetry of
the set-point spring 50 on the spring plate 52, from being transferred
to the pin 36 to an intrusive degree. The same applies in respect of
the articulation 37 too, if the diaphragm 23 should be positioned
askew. The pin 36 can therefore be guided with low friction, and so
that it is easily movable, right through the sealing housing 21.
Transverse forces cannot be transmitted from the diaphragm to the
valve rod 7 either, because the valve rod 7 is separated from the
insert 26, and only compressive forces can be transmitted. As a
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consequence, there is no need to fear undesirable friction at the seal
12, Which would obstruct the mobility of the valve and cause
undesirable wear and tear.
In heating systems, it may happen that by shutting off all
loads the return pressure will drop in the pressure chamber 30 on
account of cooling of the water and the contraction associated
therewith, while the supply pressure in the pressure chamber 31
corresponds to the normal system pressure, for example 5 bar. So that
thick and sluggish diaphragms do not have to be used, the relief valve
44 is provided, which opens under the said circumstances and effects
a partial pressure equalization between the two pressure chambers 30
and 31.
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