Diaphragm valve comprising a sleeve-shaped elastic diaphragm

A diaphragm valve comprises a housing (1) provided with a supply and a discharge opening, and adapted to be inserted in a conduit. A sleeve-shaped elastic diaphragm (4) is accomodated in the housing (1), and extends between the openings. The diaphragm (4) is adapted to be loaded from the outside by a pressure fluid. In its unloaded condition, the diaphragm (4) is at a radial distance from a core body (5) located centrally therein, and the valve is open. In its fully loaded condition, a middle section (11) of the diaphragm (4) is pressed against the core body (5), and the valve is closed. The wall of the resilient diaphragm has means (10) for increasing its stiffness. These means (10) only extend from an end of the diaphragm (4) to a place near its middle section (11), thus simplifying manufacture of the diaphragm (4) and improving its sealing.

The invention relates to a diaphragm valve comprising a housing provided 
with a supply and a discharge opening and adapted to be inserted in a 
conduit, a sleeve-shaped elastic diaphragm accomodated in said housing 
extending between said openings and adapted to be transversely loaded from 
the outside by a pressure fluid, the wall of said resilient diaphragm 
having means to increase the stiffness thereof, said valve having in 
addition a core body located centrally in the diaphragm and the latter 
defining together with said core body the passage through the valve, 
extending in its unloaded condition at a radial distance from the core 
body to keep said passage open, but being pressed in its fully loaded 
condition with a longitudinal middle section against the core body to keep 
said passage closed. 
A diaphragm valve of this type has been disclosed in the French patent 
specification 1.595.857. Used in this known valve is, for the purpose to 
increase the stiffness of the resilient diaphragm, an intermediate layer 
of intersecting, about the axis of the diaphragm helically wound wires, 
which extend from one end of the diaphragm to the other end thereof and 
are firmly secured, mostly by a vulcanization-process, to the elastic 
material of the diaphragm throughout their entire length. 
This construction of the diaphragm, which usually consists of vulcanized 
natural or synthetic rubber, has several disadvantages. For instance, the 
manufacture of the diaphragm asks for a building-up in different layers 
which requires several stages of vulcanization. Furthermore, there will be 
induced, due to the firm anchoring of the long wires in the elastic 
material of the diaphragm, when the diaphragm is bent towards the core 
body, between said material and said wires shear stresses which in the 
long run may lead to the appearance of cracks. Moreover, the web of wires 
appears to hamper the compression in circumferential direction of the 
elastic material in the longitudinal middle section so much that a 
reliable seal is only obtained, when the pressure fluid has a relatively 
high overpressure. 
The invention has the object to provide a diaphragm valve of the afore 
described kind, in which the disadvantages of the known valve are 
substantially overcome and in addition advantages as described below are 
gained. In accordance with the invention this is achieved in that the 
means to increase the stiffness of the diaphragm are fabric or canvass 
layers, bars of spring steel, resilient synthetic material or comparable 
material which extend only from an end of the diaphragm to a place near 
the longitudinal middle section of the diaphragm, with which the latter, 
when fully loaded by the pressure fluid, is pressed against the core body. 
In this case the longitudinal section of the diaphragm for closing the 
valve remains free from means for stiffening the diaphragm, therefore very 
flexible as well as easily compressible in circumferential direction, so 
that also at lower overpressures of the pressure fluid a reliable seal is 
guaranteed. The stiffness of the diaphragm increasing means which are not 
half so long as the usual means induce, even if they are firmly vulcanized 
to the elastic material of the diaphragm, considerably lower shear 
stresses in the diaphragm during bending thereof, so that the risk of 
cracking said material is also much smaller. To manufacture the diaphragm 
mostly a vulcanization process one only will do. An additional advantage 
of the shorter means to increase the stiffness of the diaphragm is that 
during the bending of the diaphragm towards the core body the longitudinal 
middle section of the diaphragm is at the same time circumferentially 
compressed and longitudinally stretched by the inward movement of said 
means, so that the tendency of said section to decrease its inner diameter 
is increased and, consequently, the sealing pressure between the diaphragm 
and the core body is also increased. 
In many cases it suffices to locate the layers of fabric or canvass or the 
bars only in the downstream portion of the diaphragm. Only in that portion 
of the diaphragm the danger is great that the diaphragm is unacceptably 
deformed by the great difference between the pressure of the pressure 
fluid acting on one side and that of the fluid in the cut off down stream 
portion of the valve passage acting on the other side of the diaphragm. 
It appears to be advantageous when the means increasing the stiffness of 
the resilient diaphragm are bars which extend each with their end portion 
remote from the said longitudinal middle section of the diaphragm in a 
boring or a groove of a supporting ring provided at the relevant end of 
the diaphragm and preventing said end portion to tilt at least in radial 
direction, when the diaphragm is loaded and thereby bent onto the core 
body. This avoids the risk that said end portions of the stiffness 
increasing means tilt and both stretches and compresses the elastic 
material of the diaphragm locally in a very unfavourable way. 
Furthermore, it is recommended to so construct the diaphragm valve that, 
when the stiffness increasing means are bars, the latter extend free to 
move in fitting cavities which are formed in the elastic material of the 
diaphragm. In that case there will hardly be induced shear stresses 
between said means and said bars, when the diaphragm is bent.

In the drawing a cylindric housing is indicated by 1 which has flanges 2 
and 3 for the connection of the valve to conduits for the transport of a 
fluid, e.g. water or air, or an other fluid. In the housing a body of 
elastic material, e.g. natural or synthetic rubber or an other elastic 
synthetic material, is accomodated and fastened in the housing by 
clamping. Said body consists of a diaphragm 4 which is cylindric when it 
is in its unloaded condition, a core body 5 located centrally in the 
diaphragm and longitudinal ribs 6 which interconnect the diaphragm and the 
core body locally and divide, when the diaphragm is in its unloaded 
condition, the then open passage through the valve into separate 
longitudinal passages 7, which during loading of the diaphragm are each 
closed by an individual portion of the diaphragm. The pressure fluid for 
loading the diaphragm is supplied through the connecting nipple 8 into the 
cavity 9 located between the housing 1 and the diaphragm 4. A diaphragm 
valve having a plurality of separate passages has been described in the 
Dutch patent specification 99179. The valve constructed in accordance with 
the invention differs from this known valve by the features which will be 
elucidated hereinafter. 
For the purpose of increasing the stiffness of the diaphragm 4 in order to 
prevent the deformation of the loaded diaphragm 4, even at considerably 
higher pressures than the usual ones of about 3 ato of the pressure fluid 
and that of the fluid controlled by the valve, from deviating from the arc 
illustrated in the drawings, longitudinal bars 10 of spring steel, 
resilient synthetic material or comparable material are, according to the 
invention, embedded in a concentric layer of the diaphragm. However, these 
bars extend only from an end of the diaphragm to a place near the 
longitudinal middle section 11 of the diaphragm 4 which in the closed 
condition of the valve is pressed against the core body 5 and keeps the 
valve closed. This has the advantage that the longitudinal middle section 
of the diaphragm remains supple and for the adjustment of its inner 
surface to the outer surface of the core body not only is compressed in 
circumferential direction but also longitudinally stretched by the bending 
of the bars towards the core body, when it is forced inwards by the 
pressure of the pressure fluid. Due thereto a better seal is guaranteed 
and the controllability of the diaphragm appears to be more reliable. 
Moreover, the diaphragm may be controlled by pressure fluid of lower 
pressure than usual. 
The longitudinal bars 10 are each inserted with their end portion near the 
end of the diaphragm in a circular groove of a supporting ring 12 having a 
cross sectional area in the shape of a lying U and being embedded in an 
end of the body 4,5,6 of elastic material. This ring prevents the said end 
portions of the bars from radially tilting in the elastic material of said 
body 4,5,6, whereby said material is both locally compressed and 
stretched, when the diaphragm 4 is bent towards the core body 5, which 
appears in the long run to be detrimental for the portion of the body 
4,5,6 near the flanges thereof. 
Although the bars 10 extend only between the ends of the diaphragm 4 and 
the middle section 11 thereof they appear to prevent the diaphragm from 
undesired deformation even under extreme conditions and the then induced 
maximum pressure differences acting on the flexible diaphragm. That is why 
in several cases it suffices to use said bars only in the down stream part 
of the diaphragm, in which said maximum pressure differences occur, when 
the valve is in its closed condition. 
It will be obvious that the supporting rings 12 may have a circular row of 
borings instead of the circular groove, in which the end portions of the 
bars 10 are inserted. 
The cavities for the supporting rings 12 at the ends of the body 4,5,6 are 
sealed by sealing rings 13, which may be held down by the flange 
connections of the valve. 
The relatively short bars 10 can be easily inserted in fitting cavities of 
the diaphragm which are previously formed therein. In that case said bars 
are not secured to the elastic material of the diaphragm by vulcanization 
or other process but remain free to move in said cavities when the 
diaphragm is bent. The risk of cracking the elastic material of the 
diaphragm by shear stresses is then very small. The cavities for the 
longidudinal bars 10 and the supporting rings 12 may be formed in the 
elastic material of the body 4,5,6 by means of inserts of the required 
shape and size placed in the mould to form said body and which do not 
adhere to the elastic material, so that said inserts can be removed from 
said body after the latter has been completed and, if required, vulcanized 
to make place for said bars and supporting rings.