Note: Descriptions are shown in the official language in which they were submitted.
20772g 1
The invention relates to a valve controlled in dependence on
differential pressure 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 desired value spring.
In the case of a known valve of this kind (EP-OS 354 427), use
10is made of a continuous valve rod, which joins together the closure
member, the diaphragm, and a spring plate loaded by the set-point
spring, and with a free end is mounted close to the closure member
in a guide of the valve housing. Transverse forces, which are
transferred in the region of the setting device and/or in the
region of the diaphragm to the valve rod, for example, because of
unsymmetrical spring forces (skewed state), lead to undesirable
friction stress in the sealed feed-through of the valve housing and
thus to hysteresis in the valve movement and to excessive wear and
tear.
20The invention is based on the problem of providing a valve of
the kind mentioned in the introduction, the valve rod of which is
readily accessible and is movable such that wear and tear is low.
Generally speaking, the problems of the prior art are overcome
by the present invention which provides a valve controlled in
dependence on differential pressure 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 into
two pressure chambers by a diaphragm acting on the valve rod; a
setting device mounted on the diaphragm housing including a
30set-point spring acting on the diaphragm and an adjusting means for
the set-point spring; and an insert fastened in the centre of the
diaphragm against which an end contact face of the valve rod lies
207728 1
under the bias of a valve spring; the insert being connected by way
of an articulation to a pin which projects into the setting device
and is there loaded by the set-point spring.
In that construction, the diaphragm is in contact by way of a
first coupling point, which is located between the insert and the
contact face, with the valve rod and by way of a second coupling
point, which is formed by the articulation, in contact with the pin
leading to the setting device. If the diaphragm arrangement is set
at an angle owing to structural asymmetries or unequal spring
forces, then the insert is able to pivot about the articulation and
move transversely with respect to the contact face of the valve
rod. No transverse forces are therefore transferred to the valve
rod. As a consequence, the valve rod moves easily with very low
hysteresis and negligible wear and tear.
It is advantageous for the pin to project out of the diaphragm
housing in a sealed manner, and for the setting device to be
removable as a unit from the diaphragm housing. The fact that the
pin is sealed enables the set-point spring to be located in the
atmosphere; it can therefore be adjusted at any time or be replaced
by exchanging the setting device. Because of the articulation, the
seal for the pin is at the most very slightly stressed by
transverse forces stemming from the diaphragm, and therefore does
not hinder the easy actuation.
An especially simple construction is obtained if the insert is
fastened to two supporting plates covering the diaphragm on both
sides. This arrangement can be effected such that the insert has
a circumferential wall which passes through a central
- 3 _ 2077281
opening in the supporting plates and is fixed there by
crimping. Joining the insert to the supporting plates
ensures that even a comparatively small insert is
securely joined to the diaphragm.
It is an advantage for the articulation to be
formed by an articulation head, which is fastened to
the pin by way of a neck, and by an articulation socket
in the insert engaging behind the articulation head.
That arrangement takes into account the fact that in
ordinary constructions of a valve controlled by
differential pressure, in which the higher pressure is
found in the pressure chamber remote from the valve,
the desired value springs act on the diaphragm with
tensile forces, and the articulation must therefore
transfer tensile forces.
According to a preferred construction, the
articulation head has a surface that is at least
partially spherical and the articulation socket is
formed by a transverse bore adjoining which is a slot
for receiving the neck. That facilitates the assembly
of insert and pin.
In that case, a cap that is lockable in the axial
direction and which engages over the insert in the
region of the transverse bore can be provided on the
pin. A light-weight plastics cap is adequate, because
the forces to be absorbed are not large.
In a further development, it is advisable to house
a relief valve in the insert, which joins the pressure
chamber charged with a higher pressure with the
pressure chamber charged with a lower pressure when a
given pressure difference is exceeded. A relief valve
between the two pressure chambers is known ~E se. In
the present case it is provided in the insert in a
space-saving manner and so that it is easy to
manufacture.
2077281
-- 4 --
In particular, connected to its transverse bore
the insert may have an axial bore against the free end
of which a valve ball is held by a spring.
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.
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 screwed 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 10 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
2077281
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 a bore 32 to the compensation chamber 13, and thus to the inlet
chamber 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 through the sealing housing 21 to the
outside. The articulation 37 comprises a hemi-spherical 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
2077281
fastened to the diaphragm housing 16 with the help of screws 49
that engage with cone points in the annular groove 22. A set-point
spring 50 in the form of a helical compression spring extends
coaxially with the 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 projects with radial pointers 60 through two axial slots 61
in the knob 56 and cooperates with a marking 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 towards 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
~3
.~
207 728 1
is connected 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 desired
value spring 50 which is effective as 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.
- 8 - 2077281
The play and the articulation mobility of the
coupling 64 prevents transverse forces, which may occur
on account of asymmetry of the desired value 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
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 equalisation between the two pressure chambers
30 and 31.
