U-shaped sealing device on a pipe

A sealing device on a pipe includes an elastic sealing ring of generally U-shaped cross-section, which is clamped on the pipe by a clamping strap. The U-flanges of the sealing ring are so loaded by the pressure exerted by the clamping strap on the U-web of the sealing ring as to occupy a substantially radial position.

FIELD OF THE INVENTION 
The present invention relates to a sealing device on a pipe, and more 
specifically to a device according to the preamble of appended claim 1, 
which is based on the prior art disclosed in U.S. Pat. No. 4,050,703. 
The invention also relates to a sealing ring included in the sealing 
device, according to the preambles of appended claims 2 and 5, which is 
based on a variant of the solution disclosed in the above-mentioned U.S. 
patent. 
DESCRIPTION OF THE PRIOR ART 
The problem of achieving a seal between two pipes inserted in each other 
has long been addressed by those skilled in the art. During the last 
decades, a number of different solutions have been suggested to solve the 
specific problem of providing a seal between two ventilation ducts 
inserted in each other with close fit. In most cases, the preferred option 
is to fix an elastic sealing ring, generally of rubber, outside as well as 
inside the end portion of the first pipe where the other pipe is to be 
connected. Thus, the sealing ring is applied on the inner tube, and 
generally has one or two radially projecting flanges which are bent by the 
outer tube when this is passed on to the inner tube. 
U.S. Pat. No. 4,050,703, hereby incorporated by reference, discloses a 
double-lip seal of U-shaped cross-section, which is anchored in a 
circumferential groove in a pipe. The seal has a web which is applied 
against the outer side of the pipe, and two sealing lips projecting from 
the web and extending radially outwards from the pipe. The web applied to 
the outer side of the pipe is fastened by a clamping strap being placed on 
the web of the seal and tightened so as to urge the U-web against the 
outer side of the pipe, whereupon the clamping strap is anchored by spot 
welding. The sealing lips projecting radially from the pipe are bent 
sideways when the pipe is inserted in an outer pipe with close fit. The 
sealing effect is achieved by a portion of the respective sealing lip 
tightly engaging the inner side of the outer pipe, while the web is 
pressed against the outer side of the inner pipe. 
In terms of sealing, this solution is quite excellent, but when 
automatically fastening the sealing strip, problems are caused by the 
tendency of the clamping strap, when being applied., to be laid over 
either of the sealing lips. Since the distance between the substantially 
parallel, radially-projecting sealing lips corresponds to the width of the 
clamping strap, the application of the strap on the seal web requires 
great accuracy to avoid that any of the sealing lips interferes with the 
strap. Moreover, sectional elements that are extruded and spliced by 
curing tend to slant, i.e. the sealing lips tend to be slightly angled, 
this making it still more difficult to apply the clamping strap correctly. 
An alterantive embodiment of a double-lip seal, which also represents the 
background art, is shown in FIGS. 1-2 of the drawings, where FIG. 1 is a 
section showing the sealing ring secured to a pipe, while FIG. 2 is a 
section showing the pipe provided with the sealing ring inserted in an 
outer pipe. 
This prior-art sealing ring has, like the above-mentioned double.-lip seal, 
a generally U-shaped cross-section including a U-web 1 and two sealing 
lips 2 and 3 projecting from the web 1. The sealing ring is secured on the 
outside of a pipe 4 by means of a clamping strap 5. 
As opposed to the double-lip seal shown in U.S. Pat. No. 4,050,703, the 
sealing lips 2 and 3 shown in FIG. 1 are however divergent, this 
facilitating the application of a clamping strap on the web of the seal. 
On the other hand, this solution suffers from other drawbacks. The major 
one is that the sealing lips, when being inserted in an outer pipe, are 
bent to a different extent owing to their divergence. 
It appears from FIG. 2 that the inner sealing lip 2, when the pipe 4 is 
inserted in an outer pipe 6, has a significantly smaller surface engaging 
the inner side of the outer pipe 6 than the outer sealing lip 3, the two 
sealing lips thus producing an uneven sealing effect. Thus, if the sealing 
lip 3, producing the better sealing effect, is damaged, the overall 
sealing capacity is reduced by at least half, this considerably increasing 
the risk of leakage. 
Moreover, the outer sealing lip 3 is subjected to increased bending stress 
in the transition area between the lip and the web 1, which accelerates 
the ageing of the sealing ring material and adversely affects the 
resilience of the sealing ring. It will thus be appreciated that the 
increase in bending stress increases the risk of damage to the sealing 
lip, this increasing the risk of leakage. 
The known sealing rings described above also show poor dimensional 
stability, i.e. they are flabby, which is a problem when taking sealing 
rings from a store where the rings are mechanically separated. Also, it is 
difficult to correctly position the rings prior to automatic application 
thereof. 
There is thus a need for an improved sealing ring which obviates the 
above-mentioned drawbacks. 
SUMMARY OF THE INVENTION 
One object of the present invention therefore is to overcome the 
above-mentioned drawbacks by providing a sealing device for a pipe that 
produces an even sealing effect while facilitating the application of a 
clamping strap to the web of the seal. 
Another object of the invention is to provide a sealing ring which produces 
an even sealing effect and facilitates the application of a clamping strap 
on the web of the sealing ring. 
Yet another object of the invention is to provide a sealing ring having 
improved dimensional stability to facilitate separation and positioning of 
the ring. 
A still further object of the invention is to provide a pipe or duct having 
a seal which, with unimpaired sealing effect, is easier to mount than 
heretofore possible. 
These and other objects, which will appear from the following description, 
have now been achieved by means of a sealing device which is of the type 
described in the introductory part of the description and which 
additionally has the inventive features recited in the characterising 
clause of appended claim 1. 
The objects of the invention are also achieved by means of a sealing ring 
which is of the type discussed in the introductory part of the description 
and which additionally has the inventive features recited in the 
characterising clauses of appended claims 2 and 5. 
The objects of the invention are further achieved by means of a pipe 
according to appended claim 8. 
Other features of the invention appear from the dependent claims reciting 
preferred embodiments thereof. 
The invention confers several advantages. By the design of the sealing ring 
according to the invention, the sealing lips will not interfere with the 
clamping strap when this is being applied on the seal web, and both 
sealing lips will produce the same sealing effect. 
The design of the web also provides a sealing ring having improved 
dimensional stability, which facilitates separation and positioning of the 
sealing rings. This is a major advantage in automatic application of the 
sealing ring on the outside of a pipe.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIGS. 3-4 show a sealing device according to one embodiment of the 
invention. A pipe 10, which is intended to be partially inserted in 
another pipe to form e.g. a ventilation duct, has in conventional manner a 
circumferential groove 11 having a smaller diameter than the rest of the 
pipe 10. A sealing ring, generally designated 12, is placed on the pipe 10 
and intended to be secured to it, so as to form a seal in the joint 
between the two pipes inserted in each other. The sealing ring 12, 
preferably consisting of rubber, has a base portion or web 13 which, when 
fastened, engages in its entirety the bottom of the circumferential groove 
11, and two sealing lips 14, 15 projecting from the web 13 and, in FIG. 3, 
diverging away from the pipe 10. 
The sealing ring 12 has substantially U-shaped cross-section. The web 13 
located between the sealing lips 14, 15 is curved and retracted towards 
the space defined between the sealing lips 14, 15 so as to be situated, 
before being fastened on the pipe 10, at a distance from the bottom of the 
circumferential groove 11 with its central portion remotest from the pipe. 
FIG. 4 shows the sealing ring 12 after being fastened. 0n the web 13 of the 
sealing ring 12 is applied a clamping strap 16 which, when being 
tightened, presses the web 13 bulging from the pipe 10 completely flat 
against the bottom of the groove 11. As a result of the web 13 being 
forcibly pressed against the bottom of the groove 11, the sealing lips 14, 
15 will be moved closer to each other thanks to the design of the web 13. 
Thus, once fastened, the sealing lips will extend radially outwards from 
the outer side of the pipe 10 substantially parallel to each other. 
It should be pointed out that the sealing ring 12 according to this first 
embodiment need not necessarily be disposed in a groove but may instead be 
mounted anywhere on the pipe 10. 
An alternative embodiment of the sealing ring according to the invention is 
shown in FIGS. 5-6. A sealing ring, generally designated 20, has, like the 
embodiment described above, a substantially U-shaped cross-section 
including a web 21 and two sealing lips 22, 23. As in the embodiment 
described above, the web 21 is intended to be applied to the outer side of 
a pipe 24 in a circumferential groove 26. In FIG. 5, the sealing lips 22, 
23 are divergent outwards from the web 21 away from the pipe 24. 
Projections in the form of flanges 27, 28 are provided in the respective 
transition areas between the web 21 and the sealing lips 22, 23. The 
flanges 27, 28 project from the transition areas towards the opposite 
walls of the groove 26 and engage these walls, such that the web 21 of the 
sealing ring 20, prior to fastening, is spaced in its entirety from the 
bottom of the groove 26. 
When the sealing ring 20 has been secured to the pipe 24, as shown in FIG. 
6, a clamping strap 25 forcibly urges the web 21 down against the outside 
of the pipe 24 in the circumferential groove 26, so that the web 21 is 
clamped against the groove 26 and the flanges 27, 28 are deformed in such 
a manner as to snugly follow the opposite walls of the circumferential 
groove 26. This is achieved by tightening the clamping strap 25 round the 
pipe 24 and fixing it, e.g. by spot welding. When pressing the web 21 
against the outer side of the pipe 24, the sealing lips 22, 23 are caused 
to extend substantially radially outwards away from the pipe and occupy a 
position substantially parallel to each other, whereby to produce a 
uniform sealing effect. According to this variant, highly efficient 
sealing against the walls of the groove 26 is achieved. Before applying 
the clamping strap 25, the flanges 27, 28 are located substantially in the 
centre plane of the U-web 21, and are substantially parallel to the 
longitudinal axis of the pipe 24. 
As will have been appreciated, the embodiments of the invention described 
above yield substantial advantages. Major advantages are that a sealing 
device according to the invention produces a uniform sealing effect by the 
sealing lips, and that correct placement of the clamping strap between the 
sealing lips is facilitated. 
Moreover, the sealing ring according to the invention exhibits improved 
dimensional stability as compared with conventional sealing rings thanks 
to its special cross-sectional shape, which is also an advantage when 
separating and positioning the sealing rings. 
To conclude, it should be pointed out that the inventive concept is by no 
means restricted to the embodiments described in the foregoing, but 
several modifications are conceivable within the scope of the inventive 
idea appearing from the appended claims. In particular, it should be noted 
that the sealing ring may have many different cross-sectional shapes 
within the scope of the invention. One example hereof (FIG. 7) is that the 
projections which consist of flanges in the alternative embodiment 
described above can be replaced by outwardly directed beads 29 or 
thickened portions which are also provided in the transition areas between 
the web and the sealing lips. 
In a variant (FIG. 8) of the first embodiment, the web of the sealing ring 
is undulate, that is, has two curved portions 30 and a central pointed 
portion 31 to be applied against the pipe. 
Of course, the cross-sectional shape of the sealing ring is dependent on 
manufacturing considerations, and on the pressure to which the sealing 
ring is subjected in use. The essential point is that the force applied to 
the U-web tends to move the free ends of the U-flanges towards each other. 
In addition, the seal may have more than two lips, in which case clamping 
straps are suitably tightened round all the base portions between the lips 
for reliable anchorage of the seal.