Valve for an explosion protection apparatus

A valve (1) for an explosion protection apparatus comprises a pipe element having a pipe wall (11). Two slides (15, 15') can be pushed from the outside into the pipe element, through in each case one opening (111, 111') in the pipe wall (11). An expandable diaphragm (14) is arranged on the inside of the pipe wall (11) and forms an inner pipe which can be closed by means of the slide (15, 15') by mutually opposite diaphragm regions being pressed against one another. The expandable diaphragm which forms an inner pipe does not provide any accretion points for solid particles of product-loaded gas flow to collect on.

FIELD OF THE INVENTION 
The present invention relates to a valve for an explosion protection 
apparatus. 
BACKGROUND OF THE INVENTION 
Such valves are used, for example, in explosion protection apparatuses in 
industrial systems where there is an explosion risk, for automatically 
preventing the penetration of pressure waves and/or flames from a system 
part where there is an explosion risk into an adjacent system part. In the 
case of explosion protection apparatuses, it is of critical importance 
that, when necessary, the passageway between two system parts, in general 
a transport pipe, is closed, sealed, as quickly as possible. The closing 
process must be completed before pressure waves and/or flames arrive at 
the closing point. To this end, a closing element is moved at high speed 
to the passageway to be closed, and is braked quickly on reaching the 
closed position. 
EP-A-0 824 027 describes an explosion protection apparatus having a valve 
which has a pipe element with an opening in the wall, through which 
opening a slide can be pushed, from the outside, as a closing element into 
the pipe element which, in the closed position, closes the passageway. 
This valve is particularly suitable for transport pipes through which 
gases flow. If the gas flows are loaded with solid products, then there is 
a risk of solid particles collecting in the closing region which, on the 
one hand, can lead to the closure not being sealed and, on the other hand, 
contaminates the valve, which often means that costly cleaning is 
necessary when a product change takes place. 
OBJECTS OF THE INVENTION 
With regard to the disadvantages of the already known valves which have 
been described above, the invention is based on the following object. The 
aim is to provide a valve for an explosion protection apparatus of the 
type mentioned initially, which is even suitable for use with 
product-loaded gas flows, and which ensures sealed closure at any time. 
Preferred design variants result from the dependent patent claims. Patent 
claims 12 and 13 define an explosion protection apparatus having such a 
valve, as well as an application, as claimed in the invention, of said 
valve. 
SUMMARY OF THE INVENTION 
The essence of the invention is that, in a valve for an explosion 
protection apparatus, an expandable diaphragm is arranged on the inside of 
the wall of a pipe element and forms an inner pipe which can be closed by 
mutually opposite diaphragm regions being pressed against one another. At 
least one slide, which can be pushed into the pipe element from the 
outside through an opening in the pipe wall, is provided in order to press 
the diaphragm regions against one another. 
The expandable diaphragm, which forms an inner pipe, offers no accretion 
point for solid particles of a product-loaded gas flow to collect on. The 
valve is thus scarcely contaminated, and sealed closure is possible at any 
time. 
In the case of a preferred design variant, the valve comprises two mutually 
opposite, flat slides which can be moved toward one another. These two 
slides may have planar end surfaces whose shape is independent of the pipe 
wall interior and which, when they close, pinch the inner pipe between 
them. Since two slides are used, the distance which has to be traveled by 
each slide during the closing process can also be halved, by which means 
the closing time is reduced. 
In the case of another advantageous design variant, the valve comprises a 
flat slide whose end part is formed to be essentially complementary to the 
part of the pipe wall interior opposite it. This valve has the advantage 
that it requires only one slide drive, can be constructed relatively 
easily, and is cost-effective. 
A flange for attaching the pipe element to a pipe of an industrial system 
is preferably provided at least at one end of the pipe element of the 
valve as claimed in the invention, and the expandable diaphragm extends 
over a part of the flange exterior, where it acts as a seal between the 
valve flange and the pipe flange. The expandable diaphragm thus carries 
out not only a closing function but also a sealing function and is firmly 
clamped by the flange joint between the pipe and the pipe element. 
In the case of a preferred design variant, the expandable diaphragm is 
designed to be thicker in the two edge regions and in the diaphragm 
regions which can be pressed against one another than in the diaphragm 
regions located in between. The thinner diaphragm regions form weak 
bursting points which are not so severely loaded as long as no explosion 
occurs, while the thicker edge regions are designed for attaching the 
diaphragm to the pipe element, and the thicker diaphragm regions that can 
be pressed against one another are designed as attachment points for the 
slide or slides, and for sealed closure. 
The expandable diaphragm preferably has annular beads on both sides of the 
slide or slides, which annular beads point toward the pipe wall and ensure 
that, even after possible bursting of the diaphragm, the diaphragm regions 
which are pressed against one another close the inner pipe. The annular 
beads prevent the diaphragm regions which are pressed against one another 
from sliding out between the two slides or between the slide and the pipe 
wall. 
The space between the pipe wall and the expandable diaphragm is 
advantageously sealed and is provided with a vacuum-pressure connection. 
The valve may be used even if gas flows at a reduced pressure through the 
pipe in which it is installed. To do this, an even lower vacuum pressure 
is just produced in the said space, so that the diaphragm is not sucked 
inward by the gas flowing through.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 
The illustrated explosion protection apparatus comprises a valve 1 having a 
pipe element with a pipe wall 11, to each of whose two ends a flange 12 or 
16, respectively, is fitted, in this case being welded. An expandable 
diaphragm 14, which forms an inner pipe, extends over the inside of the 
pipe wall 11 and over a part of the respective outside of the two flanges 
12, 16. The diaphragm regions which rest against the two flanges 12, 16 
are each provided with an annular bead 141 or 142, respectively, which are 
held by annular recesses in the flanges 12 and 16, respectively. In this 
way, the expandable diaphragm 14 is fitted quite firmly against the pipe 
element. 
The valve 1 can be attached to a pipe of an industrial system, for example, 
by means of the flanges 12, 16. In this case, the expandable diaphragm 14 
is clamped firmly between the valve flange and the pipe flange, and is at 
the same time used as a seal. 
Opposite regions of the expandable diaphragm 14 can be pressed away from 
the pipe wall interior and toward one another by means of two slides 15 
and 15'. In the position where they are pressed together, as is 
illustrated by a dashed line, the expandable diaphragm 14 closes the 
passageway through the pipe element, so that neither pressure waves nor 
flames can pass, to be precise in neither of the two directions A, B. The 
valve may also be closed and opened slowly, and may thus also be used as a 
shut-off device. 
The expandable diaphragm 14 is composed, for example, of rubber, in 
particular silicone rubber, which can be pinched without breaking. It is 
advantageous to use a rubber which is approved for use in contact with 
foodstuffs. The thickness of the expandable diaphragm 14 is between 2 and 
10 mm, preferably between 3 and 5 mm. The diaphragm may also have fabric 
reinforcement. 
The two slides 15, 15' are designed to be relatively flat and have a width 
which corresponds roughly to the internal diameter of the pipe element. 
Their mutually opposite end surfaces 151 and 151', respectively, are 
essentially planar with rounded edges, in order to avoid damaging the 
expandable diaphragm 14. The slides 15, 15' can be pushed into the pipe 
element through openings 111 and 111' in the form of slots, in the pipe 
wall 11. Slide guides 13 and 13' are fitted, in this case welded, to the 
pipe wall 11 in order to guide the slides 15, 15'. 
The slides 15, 15' are driven in a conventional manner, for which there are 
many different possibilities, in principle. EP-A-0 824 027 describes 
various slide movement mechanisms and triggering devices, which allow very 
short closing times without using a pyrotechnic detonator. 
In the present exemplary embodiment, the slides 15, 15' are fitted to 
piston rods 2, 2', to which pistons 3, 3' are attached. The pistons 3', 3' 
are mounted such that they can move in cylinders 4, 4', with annular seals 
31, 31' being arranged at the periphery of the pistons 3, 3' and ensuring 
a seal between the pistons 3, 3' and the cylinder inner wall. The interior 
of the cylinder 4, 4' is divided by the pistons 3, 3' respectively into a 
first chamber 41, 41' and a second chamber 42, 42'. 
The piston rods 2, 2' are prestressed toward the expandable diaphragm 14 by 
means of compressed springs 6, 6', which are mounted in spring housings 
61, 61'. The springs 6, 6' press sleeves 21, 21', which are arranged 
around the piston rods 2, 2', against annular heads 22, 22' which rest 
against annular plates 23, 23' that are connected firmly to the piston 
rods 2, 2', and thus produce a prestressing force. This prestressing force 
can be increased, if desired, by producing a pressure in the second 
chambers 42, 42' that is higher than that in the first chambers 41, 41'. 
This can be achieved using a compressed-gas supply, via gas channels 43, 
43', from compressed-gas reservoirs which are not illustrated, but are 
arranged around the cylinders 4, 4'. 
Triggering devices 5, 5' are fitted in fixed positions in the second 
chambers 42, 42' and, as long as current is supplied to annular 
electromagnets 51, 51' these annular electromagnets 51, 51' 
electromagnetically attract the annular plates 23, 23', which are firmly 
connected to the piston rods 2, 2', and hold them in the illustrated 
position. The current is supplied by electrical cables (which are not 
shown here) and is controlled by an explosion-identification sensor of a 
known type, in particular a pressure or infrared sensor, which is arranged 
in an adjacent system part where there is an explosion risk, or is 
connected to such a system part. 
If the current supply is interrupted, the electromagnets 51, 51' lose their 
attraction force, and the slides 15, 15' are moved to the closed position 
via the piston rods 2, 2', by the springs 6, 6' and, possibly, by the 
increased pressure in the second chambers 42, 42' in comparison with that 
in the first chambers 41, 41', in which closed position the expandable 
diaphragm 14 completely closes the passageway through the pipe element. If 
an increased pressure in the second chambers 42, 42' is used, the 
compressed-gas reservoirs which are connected to them ensure that the 
increased pressure is maintained throughout the entire movement of the 
piston rods 2, 2' and pistons 3, 3'. 
In order to move the slides 15, 15' and piston rods 2, 2' etc. back to 
their original position after the valve 1 has been closed, and to 
prestress them again, an increased pressure in comparison with that in the 
second chambers 42, 42' is produced in the first chambers 41, 41' by 
supplying compressed gas via gas channels 44, 44', which increased 
pressure is sufficient to compress the springs 6, 6'. 
In order to withstand the pressures that occur, various housing parts 7 and 
70, as well as 7' and 70', of the explosion protection apparatus are held 
together by means of tie bars 8, 8'. 
Various annular seals are denoted by 9 and 9'. 
FIG. 2 
The illustrated second exemplary embodiment of an expandable diaphragm 214 
comprises two edge regions 217 and 218, diaphragm regions 221 which can be 
pressed against one another, and two intermediate diaphragm regions 219 
and 220. At one of their ends, the edge regions 217 and 218 have a part 
which extends outward with an annular bead 241 or 242, respectively, for 
attachment to the pipe element. Annular beads 222 and 223 are arranged on 
the diaphragm regions 221 which can be pressed against one another, which 
annular beads 222 and 223 point outward and, when the valve is closed, 
prevent the diaphragm regions 221 which are pressed against one another 
from sliding out between two slides or between a slide and the pipe wall. 
The diaphragm is thinner in the regions 219 and 220 than in the edge 
regions 217, 218 and in the diaphragm regions 221 which can be pressed 
against one another, so that the regions 219, 220 form weak bursting 
points. 
FIG. 3 
The illustrated valve 201 comprises a pipe element having a pipe wall 211, 
to each of whose two ends a flange 212 or 216, respectively, is fitted, in 
this case welded. The expandable diaphragm 214, which has been explained 
in conjunction with FIG. 2, forms an inner pipe and extends on the inside 
of the pipe wall 211 and over a part of the respective outside of the two 
flanges 212, 216. The annular beads 241 and 242, respectively, of the 
diaphragm 214 are held by annular recesses in the flanges 212 and 216, 
respectively. In this way, the expandable diaphragm 214 is fitted quite 
firmly to the pipe element. 
In this exemplary embodiment as well, the valve 201 can be attached by 
means of the flanges 212, 216, for example, to a pipe of an industrial 
system. In this case, the expandable diaphragm 214 is clamped firmly 
between the valve flange and the pipe flange, and is at the same time used 
as a seal. 
Opposite regions 221 of the expandable diaphragm 214 can be pressed against 
one another by means of two slides 215 and 215', respectively. Slide 
guides 213 and 213' are fitted, in this case welded, to the pipe wall 211 
in order to guide the slides 215, 215'. 
The space 210 between the pipe wall 211 and the expandable diaphragm 214 is 
sealed and is provided with a vacuum-pressure connection 209, via which a 
vacuum pressure can be produced in the space 210, so that gas at reduced 
pressure can also flow through the valve 201 without the diaphragm being 
sucked inward by the gas flowing through. 
Other design variations of the valve and explosion protection apparatus 
described above are feasible. It should expressly be mentioned here that 
the valve as claimed in the invention can also be used in explosion 
protection apparatuses having triggering devices which comprise a 
pyrotechnic detonator.