Pipe connection assembly

A connector assembly is provided for connecting two pipes of dissimilar material. In particular, an assembly is provided for connecting a first end portion of a first pipe to a second end portion of a second pipe formed as a bell housing having a larger inside diameter than an outside diameter of the first end portion and which second end portion overlaps the first end portion. The connector assembly includes a mandrill for attachment to the first end portion, which is formed as a flange extending radially from an outside circumference of the first end portion to face at least a portion of an end face of the bell housing, and an axial tubular extension extending from the flange so as to, upon assembly, reach a point approximately equal to an axial end point of the first pipe, and reside within the second end portion creating an annular space therebetween. A sealing gasket, formed of an electrically insulating material, is formed as a base in the form of a tubular collar for residing fittingly around an outside circumference of the first end portion, and at least one annular fin projecting radially from an outside circumference of the base at an angle with respect thereto, said fin being rotatable inwardly about said angle towards the base and being biased outwardly about said angle, and said fin being substantially inflexible along its radial width.

BACKGROUND OF THE INVENTION 
The present invention relates to a device for connecting two pipes. In 
connecting two pipes of dissimilar material, for example steel to concrete 
(or clay or aluminum piping), a current may be formed at the point of 
contact, resulting in corrosion or degradation. Accordingly, the invention 
relates to a quick seal, self-locking dielectric arrangement, which is 
especially useful for connecting pipes of dissimilar material. 
SUMMARY OF THE INVENTION 
A connector assembly is provided for connecting a first end portion of a 
first pipe to a second end portion of a second pipe having a larger inside 
diameter than an outside diameter of the first end portion and which 
second end portion is in the form of a bell housing which overlaps the 
first end portion. The connector assembly comprises a mandrill attachable 
to the first end portion. The mandrill comprises a flange and an tubular 
extension, with the tubular extension being supportably connected to the 
first end portion, preferably by a radially extending ring. Preferably, an 
intermediate tubular ring is bonded to the tubular extension. A dielectric 
sealing gasket is then slipped over the intermediate ring. A further 
dielectric gasket is placed at an interface between the opposing faces of 
the flange and the bell housing of the second end portion and/or between 
opposing faces of the radially extending mandrill ring and and end face of 
the second end portion. Thus, all possible contact points between the two 
pipes are electrically insulated, so that where two pipes of dissimilar 
material are used, corrosion by way of a circuit can be avoided. 
The sealing gasket comprises a base in the form of a tubular collar for 
residing fittingly around an outside circumference of the axial extension 
of the mandrill, or if present, the intermediate ring. At least one, and 
preferably a plurality of annular fins project radially from an outside 
circumference of the base, coaxially with the base, and at an angle with 
respect to the circumference of the base. The fin is rotatable inwardly 
about said angle towards the base against an outward bias, while being 
substantially inflexible along its radial width. 
The fin projects at an acute angle .alpha. from the base, with a constant 
width A measured from the an inner circumference to an outer circumference 
of the fin along the body of the fin. A distance B measured radially 
perpendicular from the outer circumference of the base to the outer 
circumference of the fin decreases as a function of a decrease imparted to 
angle .alpha.. The angle .alpha. and distance B may be decreased upon 
radially inward pressure upon the fin, which occurs when the base, 
residing about a smaller diameter pipe end, is slid within the end of a 
larger diameter pipe end with the angle opening away from the second pipe 
end. The distance B of the uninstalled connector is chosen so as to be 
greater than the radial gap C between the outer circumference of the base 
and an inner circumference of the larger pipe end. Thus, the larger pipe 
acts to force the fin inward so as decrease angle .alpha. (and distance B) 
to correspond with the distance C, and to thereby grippingly retain the 
larger pipe end by way of the outer circumferential edge of the fin 
against axial movement in an opposite direction. The connector should be 
constructed of a suitable plastic or rubber which can allow for 
flexibility of the angled fin with respect to the base, while providing 
sufficient rigidity to the fin itself; furthermore, the connector, or at 
least the free edge of the fin, must be of a sufficiently frictional 
material to act as a gripping means, to provide frictional resistance 
against reverse axial movement along the inside circumferential surface of 
the larger pipe.

DETAILED DESCRIPTION OF THE INVENTION 
FIG. 1 shows an end portion of a steel pipe 2 with a mandrill 4 welded 
thereto, situated as a male portion within the female end portion 6, 
formed as a bell housing, of a concrete pipe 8. There is a certain 
clearance in the shape of an annular space 16 between the outside diameter 
12 of the mandrill 4 and the inside diameter 14 of the connecting portion 
6 of the concrete pipe. Although a steel and concrete pipe are shown and 
discussed herein, the invention is applicable to dissimilar pipes of any 
material, and of course may be used with similar pipes as well. 
The mandrill 4, preferably formed of metal, is formed to provide a flange 
4a extending radially from the outer circumference of the pipe end portion 
2, so as to face a substantial portion of the opposing face 9 of the bell 
housing 6. An axial tubular extension 4b sets out from the flange, so as 
to reside substantially within the length of the bell housing 6, and to 
leave an annular clearance space 16 between the outer circumference of the 
axial extension and the inner circumference of the bell housing. To 
provide additional support for the axial extension 4b, a radial extension 
4c is preferably provided between axial extension and the outer 
circumference of the pipe 2. Thus, the mandrill 4 is comprised of the 
three parts 4a, 4b and 4c. The mandrill is fitted to the pipe 2 so that a 
constant flow line is maintained between the two pipes upon connection 
thereof, thus avoiding build-up of flow materials at the connection point. 
It is crucial that no electrical conductance be permitted between the two 
dissimilar pipes. Therefore, the opposing outer faces of the mandrill and 
the inner faces of the bell housing must not touch, and preferably will 
have an insulating means therebetween. In order to insure non-conductivity 
between the two pipes, a gasket 30a is preferably provided interposed 
between the faces of the flange 4a and the end face 9 of the bell housing. 
Alternately, or in addition, thereto, a similar gasket 30b may be provided 
between the opposing faces of the radial support extension 4c and the end 
face 7 of the main portion of the concrete pipe. 
A sealing gasket 10 of non-conductive material, preferably rubber, formed 
as a tubular base, is fit about the axial extension 4b, to sealingly and 
lockingly connect the two pipes. An intermediate ring 18, also of 
non-conductive material, may be optionally bound circumferentially about 
the axial extension, so that the sealing gasket may be slipped over the 
intermediate ring upon assembly. 
An enlarged detail of the sealing gasket in cross-section is shown in FIG. 
3. A tubular base 20 is provided with at least one, and preferably a 
plurality of flexible fins 22 extending radially outward therefrom, 
forming a plurality of essentially parallel, angled rings extending from 
the base, preferably in coaxial orientation with the base. The fins 22 are 
formed on the base at an acute angle .alpha., so that when the connector 
is properly installed, the angle .alpha. opens away from the connecting 
end face 7 of the concrete pipe. 
The fins are also characterized by a fixed length A along the fin 22 from 
base to tip. A variable distance B is measured from the outside surface of 
the base along a perpendicular line to the tip of the fin. Because the fin 
forms an acute angle .alpha. with respect to the base, the distance B is 
shorter than the length A, which length A is effectively the hypotenuse 
with respect to the "side" B. 
The connector assembly, and particularly the fins, is sized to allow entry 
of the steel pipe fitted with the assembly into the bell housing of 
concrete pipe to provide a seal. However, because of the unique structure 
of the fins, the connector is self-locking. Since the connection point, or 
more accurately connection circumference, between the base of the fins and 
the base (i.e. outside circumference) of the sealing gasket is slightly 
flexible, the fins may be rotated inwardly about the connection point so 
as to decrease the angle .alpha., as the steel pipe with connection 
assembly fittingly enters the connecting area of the concrete pipe bell 
housing. However, once installed, the steel pipe and connector can not be 
withdrawn. The preferably rubber fins, which are biased rotatably outward, 
grip the inside of the concrete connecting portion. More importantly, 
however, angle .alpha. of the fins has resultingly been compressed to fit 
within the annular space at an angle .alpha. reduced from the uninstalled 
state, so that the distance B essentially coincides with the width C of 
the annular space. Any attempt to pull the steel pipe/connection assembly 
in the direction of withdrawal will require a decrease in the distance B, 
i.e. the effective diameter of the pipe/connection assembly must be 
decreased. However, because the length A is fixed, any movement in the 
withdrawal direction will provide a force trying to increase the angle 
.alpha., and hence an increase in the distance B, caused by the gripping 
resistance of the fins against the inside of the concrete pipe. Since the 
distance B can not be increased once installed, this action results in the 
self-locking of the sealing gasket within the concrete pipe. 
Those skilled in the art will appreciate that the fins must be constructed 
to provide sufficient rigidity and support, while also being able to 
provide sufficient resistance against withdrawal. Therefore, the thickness 
to length ratio of the fins will be an important consideration, and will 
be dependent on size of the gap between the pipes to be connected, as well 
as the properties of the particular connector material used. This ratio 
can be, for example, a maximum of 0.375 inches for a thickness of 0.190 
inches, which would be useful for a concrete pipe of 24 inch inside 
diameter. If the fins were too long with respect to the thickness, there 
would be insufficient rigidity, and the fins could be forced to flex to 
allow withdrawal of the steel pipe. 
The invention may also be practiced with respect to alternate types of 
mating pipe ends. FIG. 4 shows an example of a concrete pipe 108 having a 
sloped outwardly oriented fitting end 114, in contrast to the inwardly 
oriented bell housing of the previous embodiment. In similar fashion, a 
mandrill 104 is assembled on the outer circumference of steel pipe 102, 
comprising a flange 104b and an axial extension 104b for surrounding the 
fitting end 114 with an annular space left therebetween. An optional 104c 
can also be provided to support the mandrill. A dielectric gasket 130 may 
also be provided. As above, the connection assembly is preferably 
constucted to provide unimpeded flow from one pipe to the next. The 
intermediate ring 112 and sealing gasket 118 operate as above. The 
principles set forth herein may be applied to any variations of pairs of 
pipe ends.