Safety shut-off for gas lines

The invention takes as its basis the problem of creating a safety sealing device for gas pipes by which the bearing of the valve body should be frictionless, require no maintenance and which causes only minimal flow resistance. Further the safety sealing device should not require outward sealing connections. It should be easy to install and able to be fitted into existing gas piping or fittings without having to change them. The problem is solved in that with safety sealing devices with a valve body (6) which can be pressed against a valve seat (1), whereby the valve body (6) is supported so that it is movable in the axial direction of the valve seat (1) is against the force of a locking spring (8), the valve body is conducted only through a spring and is otherwise freely movable without additional support points. The invention concerns a safety sealing device for closing gas conduits in cases of damage, e.g. pipe bursts or hose ruptures, in order to prevent an uncontrolled leakage of gas and thereby a dangerous situation.

BACKGROUND AND SUMMARY OF THE INVENTION 
The invention concerns a safety sealing device for gas conduits with a 
valve body and a valve seat according to the introductory part of the 
first patent claim. 
These type of safety sealing devices serve, in cases of damage such as pipe 
bursts or hose ruptures, to seal the gas conduit in order to prevent an 
uncontrolled leakage of gas and thereby a dangerous situation. 
Safety sealing devices for gas conduits have already been known, which are 
arranged between the supply pipe and a using device and which should 
ensure that, for example with pipe bursts or hose ruptures, sealing of the 
supply pipe is achieved. 
Thus a safety sealing device is described in WO 92/01184, which seals a 
piping system should it be damaged without however effecting a premature 
closure of the supply line should a using device need the amount of gas 
corresponding to its output over a longer period of time. With this safety 
sealing device, a valve is supported against the force of a spring such 
that it can slide in the axial direction of a tubular shaped housing of a 
slidable plate valve. To achieve this, discs with axial support positions 
for the plate valve are placed in the housing, the discs having 
penetrations for gas flow around their circumferences. The housing has 
threads at both facing ends for connection to the piping or other 
fittings. 
With this solution it is disadvantageous that the movement of the valve 
head is conducted through supports. Because the available standing 
pressure forces, which then in cases of damage act on the valve head for 
the closure movement, is only a few millibars, the spring's force, which 
determines the flow rate at which the safety sealing device should 
operate, is extraordinary small. Thus support friction can substantially 
change this flow rate and hence the results are not reliably reproducible. 
This disadvantage is especially serious when it is considered that the 
valve is not activated under normal operation and therefore no movement of 
the valve shaft ensues within the bearing, which is exposed to 
contamination due to the gas flow. The use of such safety sealing devices 
is, amongst other things, intended however with gas pipes that are laid 
underground which means that they also have to retain their safety 
capabilities without maintenance over a longer period of time e.g. several 
decades. 
It is a further disadvantage that with the installation of the valve in a 
gas pipe two new outward sealing points are made and that when combining 
the safety device with another fitting, e.g. a hose cock, its 
constructional length is increased. When extending existing systems, it is 
necessary to shorten the existing gas supply line correspondingly. 
The penetrated discs which serve to bear the plate valve further create an 
additional pressure loss. Seen as a whole, this thereby results in a 
rather complex device due to the connection threads and the components. 
The invention takes as its basis the problem of creating a safety sealing 
device for gas pipes by which the bearing of the valve body should be 
substantially frictionless, require no maintenance and which causes only 
minimal flow resistance. Further the safety sealing device should not 
require outward sealing connections. It should be easy to install and able 
to be fitted into existing gas piping or fittings without having to make 
modifications thereto. 
According to the invention, the problem is solved in that the valve body is 
conducted only through a spring and is otherwise freely movable without 
additional support points. Thus the disadvantages associated with such 
support points and associated frictional forces discussed above are 
voided. 
Advantageous refinements of the invention are taken from the further patent 
claims given later. Because the safety sealing device has one or more 
sealing rings at its circumference, which simultaneously serve for 
attachment and internal sealing, whereby they are pushed into a gas pipe 
or the inlets or outlets of a gas fitting, whereby the diameter of the 
sealing rings is larger than the inner diameter of the gas pipe or the 
inlets or outlets of a gas fitting, it is possible to incorporate the 
present invention in such supply systems without additional outward 
sealing connections while at the same time the present invention is 
capable of easy installation. Preferably thereby, the sealing rings are 
made in one piece with the tubular shaped valve seat of the ring flanges 
connected to the safety sealing device. 
The outer diameter of the valve body without the elastic sealing element is 
smaller than inner diameter of the valve seat associated with it, whilst 
the outer diameter of the valve body with the sealing element is larger 
than this inner diameter. Also a circular shoulder is formed in the inner 
diameter of the valve seat at a tubular end-piece in the flow direction 
thereof. The length of the tubular end piece is so dimensioned that a 
blocking element, with a sealing element in place, does not leave this 
tubular shaped end-piece in the closure direction of the safety sealing 
device, whereas with a missing sealing element, the valve body can be 
pressed so far into the valve seat that the blocking element protrudes out 
of the end-piece. Thus, the installation can be carried out very easily, 
in which the valve body together with the locking spring, the sealing 
element not being fitted, is placed so far into the valve seat, that the 
blocking element can readily be connected to a lug belonging to the valve 
boy in the flow direction. In conclusion, the installation of the sealing 
element is carried out. 
It is an advantage that the lug is provided with a thread on which that for 
example, a wire clip as blocking element is easily attached and is 
adjustable in the axial direction of the lug for adjustment purposes. 
Of course it also possible that the valve body is screwed on to the lug 
thread in the flow direction whilst the blocking element, resting on the 
shoulder of the valve seat, is rigidly attached to the lug thread. 
It is shown that it is especially satisfactory if the valve body is 
suspended plate, which is spring biased so as to rest in the open position 
on a circlip elastically deformable in the radial direction. The circlip 
is itself latched into a notch, which is preferably formed in one piece 
with the valve seat. Thereby the circlip can be formed for example by, an 
expanding spring or a split annular ring which preferably has three 
radially inwardly extending flanges distributed evenly around the 
circumference whereby the flow cross-section is reduced immaterially. Due 
to the extremely low weight, this model has the advantage that the 
occurring mass reaction, depending on the installation location which for 
example has influence on the deflection and balance of forces and 
therefore also on the closure process, is lower. 
That thereby to enable adjustment without changing the flow cross-section, 
it is a proven advantage if the support shoulder of the spring end facing 
the valve body is adjustable in the axial direction in that it is 
connected, for example, to the valve seat by a thread. Due to this 
adjustable support shoulder, a possibility for adjusting the safety 
sealing device has been found which suffices without changing the flow 
cross-section. 
In order to achieve a very high sealing efficiency also without additional 
elastic sealing elements, the valve body and the valve seat should 
constructed such that either the valve body is spherical in the area of 
the sealing surface or the opposite valve seat is shaped as a concave 
sphere in the area of the sealing surface. 
For safety sealing devices which are found only in gas pipe lines which are 
very difficult to access, e.g. in underground gas pipes, it is a proven 
advantage if the valve body has a leakage bore because it can re-open 
after repair of the damage which lead to the closure of the safety sealing 
device. 
Especially for use in connection with a commercial gas stopcock, it is an 
advantage if the safety sealing device is inserted in the gas inlet of the 
gas stopcock, whereby the plate of the safety sealing device has a 
lug-shaped extension on its side facing the spring in the axial direction, 
which protrudes from the same when the safety sealing device is closed 
whereas it is within the same when the safety sealing device is open. It 
is of course also possible that the valve seat made in one piece with the 
gas inlet of the gas stopcock. Thereby the safety sealing device is 
located so far inside the gas inlet that the lug-shaped extension 
protrudes into the swivel area of the closure member of the gas stopcock. 
With this solution the safety sealing device can close completely sealed. 
A leakage flow bore for automatic re-opening of the gas stopcock is not 
necessary. With the closing of the gas stopcock, which is normally the 
case in damage repair, e.g replacing a hose, the lug-shaped extension is 
pushed in the axial direction whereby the safety sealing device is 
re-opened so that the gas can flow again after damage repair and on 
opening the gas stopcock. 
For polyethylene gas pipes, connections are made in many cases with so 
called electro-welded sleeves. For the special use of the safety sealing 
device in connection with electro-welded sleeves, the safety sealing 
device is constructed such that the outer diameter of the tubular shaped 
valve seat is the same as the outer diameter of the gas pipe, whereby a 
sealing ring, if it is to be used, is dimensioned self-evidently such that 
its diameter is larger than the outer diameter of the gas pipe. It is 
obvious that the valve seat can be connected with the electro-welded 
sleeve in one piece. 
Due to the enlargement of the outer diameter of the valve seat or the 
single piece construction, it is also possible to enlarge the inner 
diameter of the safety sealing device through which pressure loss caused 
by the safety sealing device can be minimized. 
In order to keep the constructional increase in length small, which is 
necessary in order to guarantee the double-ended welding length used for 
connection with the gas pipe, it is an advantage if the safety sealing 
device has a collar at its outflow end whereby the outer diameter of the 
collar is smaller than the inner diameter of the gas pipe.

The safety sealing device for gas pipes, according to the invention, shown 
in FIG. 1 consists of a tubular shaped valve seat (1), which has at its 
outer diameter, which is otherwise smaller than the inner diameter gas 
pipe (26) (not shown in FIG. 1, but shown in different figures) with which 
the safety sealing device is to be used, a ring flange (2) whose diameter 
is on the other hand larger than the inner diameter of gas pipe (26). In 
order to guarantee an easy insertion of the safety sealing device, 
according to the invention, the ring flange (2) is advantageously provided 
with an insertion bevel (3). Further it is a proven advantage if the ring 
flange (2) is provided with a circular groove (4) on both sides in order 
to achieve a better elasticity by means of the enlarged height of the ring 
flange (2). Ring flange (2) is intended to form a friction fit sealing 
relationship with the inside diameter of the gas pipe to which it is 
fitted and may be slightly deformed during installation. 
At its rear face, against the flow direction shown by an arrow, a sealing 
surface (5) is located in the form of a concave ball. A valve body (6), 
movable in the axial direction, is arranged within the valve seat (1) and 
has a ring shaped notch for the accommodation of a circular ring (7) 
serving as a sealing element. Thereby the valve body (6) and circular ring 
(7) dimensions are determined such that the outer diameter of valve body 
(6) without circular ring (7) is smaller than the inner diameter of its 
associated valve seat (1) whilst the outer diameter of the valve body (6) 
with mounted circular ring (7) is larger than this inner diameter. 
On the flow direction side of valve body (6), one of the valve bodies (6) 
is held supported in the open position by spring (8) preferably formed as 
a compression spring, which is supported at its other end by circular 
shoulder (9) which is integrally formed with and connects to valve body 
(6) within its associated inner circumference of valve seat (1). 
For guiding spring (8), the valve body (6) has a circular collar (10) on 
which a lug (11) is connected in the flow direction. Lug (11) has a 
through-hole (12) at its end which serves to accommodate a blocking 
element (13), in this case a rod (FIG. 1). There is the relationship 
between the length of lug (11) and the length of the tubular shaped 
end-piece (14) connected on shoulder (9), that the blocking element (13) 
with mounted circular ring (7) does not leave this tubular shaped 
end-piece (14) in the closed position of safety sealing device (FIG. 2) 
whereas without circular ring (7), the valve body (6) can be pressed so 
far into the valve seat (1) that the blocking element (13) protrudes out 
of the end piece (14) (FIG. 3). 
A somewhat different version is shown in FIG. 4. Hereby lug (11) is 
provided with a thread at its downstream end and a wire clip (15), which 
is formed such that it can be screwed on to lug (11) (FIG. 5) and serves 
as blocking element (13). 
In FIG. 6 a further version is shown. This solution differs from the 
previous version in that the valve body (6) and the lug (11) consist of 
two separate components whereby the valve body (6) has an axial threaded 
bore (16) with which it is screwed on to the threaded lug (11) located in 
the flow direction upon which the supported blocking element (13) is 
rigidly attached to shoulder (9) of valve seat (1). In order to guarantee 
the necessary sealing and prevent twisting, an appropriate material, e.g. 
in this case a commercial PTFE (polytetraflorethylene) tape (17) is 
located between lug (11) and the bore (16). In this version, an elastic 
sealing element is dispensed with. To achieve the desired sealing 
efficiency, valve body (6) is spherically shaped whilst the sealing 
surface (5) is executed as a bevel. To accommodate spring (8) and at the 
same time to reduce mass, valve body (6) has additionally a recess (27). 
In a further safety sealing device, according to the invention shown in 
FIG. 7, the ring flange (2) found at the end of valve seat (1) is made 
significantly stronger than in the form of construction described above, 
whereby it also has an insertion bevel (3). This type of valve seat (1) is 
especially suitable for the installation in gas pipes consisting of 
polyethylene as they are shown allusively under (26) in FIG. 7. The safety 
sealing device is hereby installed in which the gas pipe (26), e.g. 
consisting of polyethylene pipe, is heated. The yielding component is in 
this case not the ring flange (2) but the gas pipe (26). 
The valve body consists of a freely suspended plate (18) on spring (8) 
which in the open position rests against an elastic radially deformable 
circlip. In this form of construction, the circlip consists of, as can 
easily be recognized in FIG. 8, an expanding spring (20) which is latched 
into a circular inner notch (19) of the valve seat (1). 
Instead of the expanding spring (20), other shaped circlips can also be 
used. For example in FIG. 9, the circlip is formed by a split circular 
ring (24) which has preferably three radially inwardly extending flanges 
(25) arranged regularly around the circumference. Thereby it is to be 
observed that the surface area of the circlip which may reduce the flow 
cross-section is to be kept as low as possible. 
A circular ring (7) located on plate (18) serves to achieve the desired 
sealing efficiency, whilst the sealing surface (5) of valve seat (1) is on 
the other hand constructed in the form of a concave ball. 
Because gas piping of polyethylene tubing is generally underground and that 
the safety sealing device can only be reached with difficulty, the plate 
(18) has a leakage bore (23), which leads to a definitive and self-evident 
permissible leakage flow, whereby after repair of damage which caused the 
safety sealing device to close, the device re-opens itself. 
In FIG. 10, the safety sealing device already described in FIG. 7 is 
changed to the effect that the circlip shoulder (21), constructed as a 
separate component, is connected to valve seat (1) via a thread (22) and 
is thereby adjustable in the axial direction. This axial adjustment 
enables the spring force biasing the valve 18 into an open position to be 
varied thereby enabling control of the flow rate at which the valve is 
moved into a closed position. Thus an adjustment is made possible which 
dispenses with the need to change the flow cross-section. 
The use of the safety sealing device, according to the invention, in 
connection with a commercial gas stopcock (29) is shown in FIGS. 11 and 
12. Whilst in FIG. 11, the safety sealing device is inserted in the gas 
inlet of the gas stop cock, in FIG. 12 the valve seat (1) is constructed 
in one-piece with the gas inlet of the gas stopcock (29). In both 
constructions, plate (8) of the safety sealing device has a lug-shaped 
extension (28) on its side facing spring (8) in the axial direction, which 
protrudes from the safety sealing device when it is closed (FIG. 11), 
whereas in the open position of the safety sealing device the lug (28) is 
within it. Thereby the safety sealing device is arranged so far in the gas 
inlet that the lug-formed extension (28) protrudes into swivel range of 
the closure member (32) of the gas stopcock (29) when the safety sealing 
device is closed. With the closing of the gas stopcock (29), which usually 
takes place when damage occurs, the lug-shaped extension (28), whose end 
is correspondingly shaped, is pushed in the axial direction (FIG. 12), 
whereby the safety sealing device completely re-opens again due to the 
effects of spring (8), so that after damage repair gas flow can take place 
again when the gas stopcock (29) is opened. 
With gas pipes (26) consisting of polyethylene tubing, connections are made 
in many cases by means of so-called electro-welded sleeves (30). A safety 
sealing device advantageous for this case is shown in FIGS. 13 and 14. 
Whilst in FIG. 13, the safety sealing device is inserted in the 
electro-welded sleeve (30), in FIG. 14 the valve seat (1) is constructed 
in one-piece with the same. In order to realize the circlip (33) simply 
for the plate (8), the circular ring (24) which serves as a circlip shown 
in FIG. 9 has teeth (34), which press into the electro-welded sleeve, in 
addition to the flanges (25) distributed around the outer circumference. 
As can be seen from both figures, the inner diameter of the safety sealing 
device can be enlarged, as they are located outside the gas pipe (26), 
whereby pressure reduction due to the safety sealing device can be 
minimized. 
In order to keep the constructional increase in length, to accommodate the 
safety sealing device small while still guaranteeing sufficient welding 
length used for connection with the gas pipe (26), it is an advantage if 
the safety sealing device has a reduced diameter collar (31) at its 
outflow end, whose flow cross-section is otherwise larger than the flow 
cross-section in the plate area, whereby the outer diameter of the collar 
(31) is smaller than the inner diameter of the gas pipe (26). 
It is obvious that the individual constructions described in this 
specification lay no claim on completeness. For example it is possible 
that the individual components given in the above construction can be 
interchanged without leaving the claimed area of protection.