Pipe connection of fibre reinforced plastic pipe parts

A pipe connection of a first and a second fibre reinforced plastic pipe by accommodating a free end portion of each pipe in a centering plastic pipe part, an adhesive layer being present between the inner side of the centering pipe part and the outer side of the free end portions. A reinforcing layer extends over the centering pipe part and over parts of the first and second pipe part adjoining the free ends of the centering pipe part, preferably the centering pipe part has a smaller wall thickness than the wall thickness of the first and second pipe parts. The free end portions have a smaller wall thickness than the wall thickness of the centering pipe part. The centering pipe part may be formed as a bend, or part of a saddle or branch saddle and consists of a reinforced thermosetting plastic material. The bend may be formed from a plurality of standard bend parts of relatively small length, e.g. 5.degree. or 10.degree., each having an end widening and a bend part end portion of a consecutive bend part penetrating into said widened end, an adhesive layer engaging said penetrating bend part end portion and the opposite inner wall of the widening. The fibre reinforced plastic pipes, the centering pipe part and the reinforcing layer all consist of thermosetting resin.

BACKGROUND OF THE INVENTION 
This invention relates to a pipe connection interconnecting a first fibre 
reinforced plastic pipe part and a second fibre reinforced plastic pipe 
part, comprising an adhesive connection between the two pipe parts and a 
reinforcing layer, extending over the adhesive connection, and over the 
pipe part portions adjoining the adhesive connection and cooperating with 
same. 
A pipe connection of this type, consisting of a first fibre reinforced 
plastic pipe part interconnected with a second fibre reinforced plastic 
pipe part consisting of a thermosetting resin, e.g. epoxy resin and 
comprising an adhesive connection is known in the art. 
To obtain such a connection a first and second fibre reinforced plastic 
pipe part are sawn off in a straight manner or if curves are to be made 
preferably mitre sawn, whereupon the front end portions so obtained are 
placed opposite each other and the slit between said front end portions is 
subsequently filled with a filler glue or resin whether reinforced by 
means of a fibrous web or not. To obtain the desired strength of the 
obtained connection a laminate layer of a fibre reinforced thermosetting 
resin is wrapped around the outer side of the end portion of the first 
fibre reinforced plastic pipe part and around the opposite end portion of 
the second fibre reinforced plastic pipe part. 
However, several disadvantages may arise with regard to such a connection 
and the production thereof: 
(a) firstly it is very difficult to accurately saw off the end portions of 
the two pipe parts, especially in case mitre sawn pipe end portions are 
desired; 
(b) the fibre reinforced filler glue or resin for filling the slit between 
the two plastic pipe parts to be interconnected, does not always adhere 
satisfactorily, so that leakages might take place in a pipe conduit, 
(c) between the free end portions of the fibre reinforced plastic pipe 
parts and the laminate layer wrapped around them delamination may easily 
occur, 
(d) especially in the event of greater pipe diameters it is extremely 
difficult to accurately place the front end portions of the first and 
second fibre reinforced plastic pipe parts to be interconnected, opposite 
each other, thus enhancing the risk of future leakages occurring. 
SUMMARY OF THE INVENTION 
The present invention aims to provide a pipe connection of the kind as 
described above by means of which said disadvantages are overcome, while, 
more particularly, it is ensured that a reliable seal of the connection 
will be obtained. 
This object is attained according to the invention in that a free end 
portion of the first fibre reinforced plastic pipe part and a free end 
portion of the second fibre reinforced plastic pipe part are accommodated 
in a centering pipe portion, the adhesive connection at least extending 
between the free end portions of the first and the second plastic pipe 
part and the centering pipe portion. 
The use of such a centering pipe portion will result in an optimum adhesive 
connection between the first fibre reinforced plastic pipe part and the 
second fibre reinforced plastic pipe part, ensuring a very reliable seal. 
In addition the first and second fibre reinforced plastic pipe part to be 
interconnected can easily be centered in the correct manner, so that the 
strength of the adhesive connection is improved in this manner too. 
Moreover mitre sawing plastic pipe parts to obtain a curve has thereby 
become redundant. 
In an advantageous embodiment at least one side of the centering pipe 
portion is provided with an internal abutment surface, so that an optimum 
centering action is guaranteed, especially when the abutment surface is an 
annular abutment collar. 
Very advantageously the wall thickness of the free end portions of the 
first and second fibre reinforced plastic pipe parts is smaller than that 
of the portions adjoining them so that in the finished connection the 
outer diameter of the centering pipe portion may correspond to the outer 
diameter of the first and second fibre reinforced plastic pipe part, a 
laminate connection of a homogeneous thickness resulting therefrom, when 
applying a laminate layer. Said features all contribute to obtaining a 
very reliable seal between the two plastic pipe parts. 
According to a preferred embodiment the centering pipe portion is a 
thinwalled socket pipe portion. 
The centering pipe portion may also advantageously be a bend, the 
reinforcing layer then extending over the end portions of the first and 
second plastic pipe part and over the aforementioned bend. 
In case the centering pipe portion is provided with an abutment collar, the 
inner diameter of the said collar substantially corresponds to the inner 
diameter of the first and second plastic pipe part.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1a illustrates a connection, known per se, of a first fibre reinforced 
plastic pipe part 1 with a second fibre reinforced plastic pipe part 2, 
the front end portions 1', 2' of the two fibre reinforced plastic pipe 
parts being placed opposite each other so that a slit is otained, filled 
with a filler glue or resin whether or not reinforced by a fibrous web. 
The pipes 1 and 2 consist of polyester or epoxy resin reinforced by glass 
filaments. 
To obtain the required connecting strength a reinforcing layer 3 in the 
form of a laminate layer, is wrapped around the outer side of the first 
fibre reinforced plastic pipe part 1 and the outer side of the second 
fibre reinforced plastic pipe part 2. 
Said known connection is disadvantageous in that its seal is inappropriate 
because of the difficulties arising when trying to correctly place 
opposite each other the front ends of the fibre reinforced plastic pipe 
parts 1 and 2; in addition an optimum adherence of the filler glue or 
resin to the pipe parts cannot be obtained. 
FIG. 1b illustrates a connection according to the invention, comprising a 
first fibre reinforced plastic pipe part 1 of polyester resin and a second 
fibre reinforced plastic pipe part 2 of polyester resin, provided with 
pipe end portions 1a, 2a respectively, the wall thickness of same being 
smaller than the wall thickness of the parts adjoining them, said end 
portions being accommodated in a centering pipe portion 7 in the form of a 
thinwalled socket comprising an annular abutment collar. 
A good connection and seal are ensured by means of an annular glue layer 6 
between the end portion 1a and the centering pipe portion 7. In the same 
manner an annular glue layer 5 connects the end portion 2a with the other 
side of the centering pipe portion 7. A laminate layer 3 is wrapped around 
the outer side of the centering pipe portion 7 and the adjoining portions 
of the two plastic pipe parts 1 and 2. 
In this manner an optimum tight connection is obtained between the 
centering pipe portion 7 and the plastic pipe parts 1 and 2. The inner 
diameter of the inner wall 9a of the collar 9 of the centering pipe 
portion 7 substantially corresponds to the inner diameter of the first and 
second fibre reinforced plastic pipe part 1, 2. 
FIG. 2 illustrates a bend connection 10 between a first fibre reinforced 
plastic pipe part 1 and a second fibre reinforced plastic pipe part 2. 
Both fibre reinforced plastic pipe parts 1, 2 are provided with end 
portions having a reduced wall thickness and being accommodated in the 
centering pipe portion 7, in this case having the form of a bend. The 
connection between the centering pipe portion 7 having the form of a bend 
and the end portions 1a, 2a resp. of the fibre reinforced plastic pipe 
parts 1, 2 is obtained in a manner corresponding to the one illustrated in 
FIG. 1b, to wit by means of annular glue layers 6, 5 resp. 
A laminate layer 3 is wrapped around the centering pipe portion 7 in the 
form of a bend, said laminate layer extending upon the outer side of the 
first fibre reinforced plastic pipe part 1 and upon the outer side of the 
second fibre reinforced plastic pipe part 2. 
FIG. 3 illustrates a bend 11 obtained by applying a connection according to 
the invention. In a thinwalled centering pipe portion 7 in the form of a 
socket having an abutment collar 9 is accommodated the end portion 12a of 
a pipe part 12, said end portion 12a having a reduced wall thickness, a 
glue layer extending between said end portion and the inner side of the 
centering pipe portion 7. 
On the other hand there is accommodated in and adhered by means of an 
adhesive to the socket-shaped centering pipe portion 7, the end portion 
18a of a fibre reinforced bend 18, said end portion also having a reduced 
wall thickness. 
The other side of the bend 18, also being provided with an end portion 18b 
with a reduced wall thickness, is accommodated in a second socket-shaped 
centering pipe portion 7 comprising an abutment collar 9. 
On the other hand there is accommodated in this second socket-shaped 
centering pipe portion 7 the end portion 13a of a pipe part 13, said end 
portion having a reduced wall thickness. In this case too there are 
provided glue layers 5 and 6 between the outer side of end portion 13a of 
pipe part 13, the thinned end portion 18b of the bend 18 respectively and 
the inner side of the socket-shaped centering pipe portion 7. 
In FIG. 3 the pipe part 12 is a spigot end portion and the pipe part 13 a 
socket end portion. 
A reinforcing laminate layer 3 is wrapped around the bend and also extends 
to beyond the outer side of the socket end 13 and the outer side of the 
spigot end 12. 
Due to the above features finally the bend 11 is obtained. 
FIG. 4 illustrates an additional modified embodiment of the connection 
according to the present invention. 
The centering pipe portion has the form of a thinwalled branch saddle 
portion. 
The wall of the first fibre reinforced plastic pipe part 15 is provided 
with a portion 15a having a reduced wall thickness, the recess formed at 
the outer side of pipe part portion 15a and provided on producing said 
pipe part portion, serving for accommodating the branch saddle portion 20. 
FIG. 4a illustrates the connection formed at the location of the thinned 
portion 15a; it should be noted that it is in certain cases preferable to 
provide the inner side of the branch saddle portion 20 with a shoulder 16, 
so as to obtain a reliable well-sealed connection. 
Obviously it is also possible to obtain a proper connection as illustrated 
in FIG. 4b, showing a recess with its transitional surface 19 and formed 
by the portion 15a, serving to accommodate the edge of the branch saddle 
portion 20. 
In addition a second fibre reinforced plastic pipe part 2 is accommodated 
in the saddle-shaped centering pipe portion 20, an adhesive layer then 
extending between the end portion of the second fibre reinforced plastic 
pipe part 2 and the inner side of the centering pipe portion 20. 
FIG. 5 shows a pipe connection according to the invention interconnecting a 
first and a second fibre reinforced plastic pipe 21, 22 respectively. 
The bend 28 has been formed by interconnecting a plurality of standard bent 
parts 28a-28e of e.g. 5.degree. or 10.degree.. Each standard bent part is 
a thinwalled fibre reinforced plastic bend part provided with an end 
widening 29 so that two consecutive bend parts 28a-28e are connected by 
means of a spigot-socket connection 30 and an adhesive layer 25 between 
the outer side of widening 29 and the opposite wall of penetrating bend 
part end portion 31. 
A thinned free end portion 22a of the second fibre reinforced plastic pipe 
22 is accommodated in widening 29 of a standard bent part 18e. 
A thinned free end portion 21a of a first fibre reinforced plastic pipe 
part 21 is accommodated in one end of socket 27 of fibre reinforced 
plastic material and a free end portion 28a' of a bent part 28a is 
accommodated in the other end of the socket, an adhesive layer 25 connects 
the socket 27 with portion 28' and free end portion 21a. 
A reinforcing layer 23 has been wound around bend 28 and adjoining portions 
of plastic pipes 21 and 22. 
Starting from equal standard bent parts 28a-28e of e.g. 10.degree. any 
desired bend can be formed. This simplifies the production of bends as no 
separate moulds are required for forming bends of different lengths and 
moreover simple moulds are sufficient for manufacturing said standard bent 
parts. At last these standard bent parts can be produced at low costs as 
they can be manufactured by an automatic winding process in contrast to 
the long integral bends as presently used.