Tubing and fittings with cast-in-place liners

Tubing and fittings with cast-in-place liners. Relatively thin and lightweight liners can be made of relatively expensive or inconvenient materials to provide chemical resistance or other special requirements. The liner can be cast in place in a jacket made of less expensive material to provide the necessary strength. To couple a pair of these tubings, the jacket of one is cut back to expose an end portion of the liner. The exposed end portion is flared outwardly against a sleeve to form a tapered seal surface. The liner of the other tubing has a nose that projects beyond the end of its jacket with a tapered seal surface that bears against the other tapered surface. A compression device such as a nut or a clamp holds the tubings together.

FIELD OF THE INVENTION 
This invention relates to tubing and fittings which have cast-in-place 
liners, and to joinders for them. 
BACKGROUND OF THE INVENTION 
In order to provide for special requirements such as corrosion resistance, 
it is common practice to make entire valve and tubing structures from a 
material which has the necessary properties. This is tolerable if the 
material is not too expensive, or if the nature of the installation is 
such that it can absorb the expense. Often, however, a relatively 
expensive material, or one which is difficult to employ, must be used. For 
such installations, it would be good practice, if possible to utilize less 
expensive material for strength and structure, and the more expensive 
material only as a liner and seal. 
Pipe linings are, of course, well known in the art. Slush coatings, and 
wiped-on coatings are known for both the inside and outside walls of 
pipes. Also, plated coatings are known. A problem with many of the prior 
art expedients is that they often have faults and leaks, and in some 
installations this can lead to expensive and dangerous situations. 
It is an object of this invention to provide tubings and fittings which 
have cast-in-place liners that are unlikely to have faults or leaks, that 
are cast into jackets of relatively inexpensive materials such as organic 
plastic materials. 
Another object of this invention is to provide coupling assemblies for such 
tubings and fittings, that are expedient to prepare and install. 
BRIEF DESCRIPTION OF THE INVENTION 
This invention utilizes two tubular conduits. Either or both of them may 
merely be a pipe, or may be a fitting such as a union or branch fitting. 
One tubular conduit has a central tubular liner and an outer organic 
plastic jacket surrounding the liner and having an outer wall. An end of 
the outer jacket is cut back to expose a length of the liner. A sleeve 
member is placed around the outer wall and bears against the shoulder on 
the jacket. It provides a forming surface against which the exposed length 
of liner is pressed, thereby forming a seal surface. 
A second tubular conduit also has a central liner and an organic plastic 
jacket. This liner extends beyond an end of the jacket where it forms a 
tapered nose with a seal surface that is complementary to the first named 
seal surface. 
Compressive means such as a nut or a clamp holds the tubular conduit 
together. 
According to a preferred but optional feature of the invention, the liners 
are made of organic plastic material such as polytetrafluoroethylene sold 
commercially under the trademark Teflon.

DETAILED DESCRIPTION OF THE INVENTION 
In FIG. 1 there is shown a first tubular conduit 10 which has a tubular 
liner 11 and an outer jacket 12 which is preferably made of organic 
plastic material. The material of the tubular liner 11 is selected for 
some special property such as chemical resistance. A convenient example is 
Teflon. The outer material may be less sensitive to those conditions and 
considerably less expensive, for example polyvinyl chloride or polyvinyl 
acetate pipe. The two should be temperature-compatible, so that casting 
one around the other does not change the shape or properties of the other. 
Conduit 10 has an outer wall 13. At the right hand end shown in FIGS. 4 and 
5, the outer jacket has been cut back to expose a length 14 of the tubular 
liner, thereby to form at the end of the outer wall an abutment shoulder 
15. 
As best shown in FIG. 6 a sleeve member 20 is fitted over the end of the 
conduit 10 which is cut back. The sleeve includes a tubular portion 21 
which engages and is preferably fixed to the outer wall of the jacket. 
While a friction fit is adequate and meets the definition of "fixed" in 
many installations it will be preferable either to adhesively bond it or 
to sonically bond it to the outer jacket. The sleeve includes an internal 
step 22 which bears against abutment shoulder 15. The sleeve member 
further carries a tapered forming surface 23 which enlarges in diameter as 
it extends away fromthe abutment shoulder. The sleeve also carries a nut 
retaining flange 24 on its external periphery. 
A forming tool (not shown) such as a heated element is applied to the 
exposed length, and this reforms it to the shape shown in FIG. 7 so as to 
make a tapered seal surface 25. If the initial forming does not make a 
smooth or accurate surface, it can be modified by a cutting tool. 
A second tubular conduit 30 is shown as part of a larger fitting which in 
this case is a union having two other tubular exits, two tubular ports and 
passages 31, 32 which are fluidly interconnected with tubular conduit 30. 
This fitting, and of course, the second tubular conduit, includes a liner 
33 which at the tubular conduit 30 portion is tubular. It is cast-in-place 
in an outer jacket 34, which is preferably made of orgnic material. The 
materials usually will be the same as those utilized in the first tubular 
conduit. The outer jacket includes an abutment surface 35 and an external 
thread 36 surrounding the tubular conduit. 
The central liner further includes a flange 37 which bears against abutment 
surface 35, and beyond the end of the outer jacket a nose 38 with a seal 
surface 39 whose shape is complementary to the seal surface on the first 
tubular member. 
Compression means 40, in this example a nut, has an internal shoulder 41 to 
engage shoulder 24 on the sleeve, and an internal thread 42 to engage 
thread 36 on the second tubular conduit. 
The assembly of the foregoing is shown in FIG. 7. It will be appreciated 
that the exposed length 14 will have been formed against the tapered 
forming surface 23 so as to form its tapered seal surface 25 as shown in 
FIG. 7. Then the two tubular conduits are brought together and the nut is 
threaded on to the thread so as to clamp the two tubular members together, 
the nut being one embodiment of compression means. 
Another embodiment of compression means is shown in FIG. 8, wherein a 
Harmon-type metal clamp 45 is applied to tapered shoulders 46, 47 on 
respective first and second tubular conduits 48, 49, all other features 
being identical. The Harmon clamp includes a circular band 50 and a screw 
51 to tighten the band thereby to draw the tubular conduits together and 
hold the clamp together. 
FIG. 3 shows a useful modification of the end of the second tubular conduit 
30. It is modified by providing a recess 55 to receive flange 37 of the 
liner. It may further be modified by providing an O-ring recess 56 and an 
O-ring 57 for making a more reliable seal. 
A tubing with a cast-in-place liner may be formed by any suitable process. 
For example, the liner may be formed as a tube, and then passed through a 
crosshead extruder to apply the outer jacket. 
A fitting, or in general any structure which includes an end such as on the 
second tubular conduit must be cast-in-place in a mold. The complex shape 
of the liner itself can readily be molded, and then this structure can be 
placed in a cavity so as to receive the outer jacket in a conventional 
molding process. 
It will be understood that the fitting as shown may have more or fewer 
ports and passages and may also be utilized as a connector between two 
lengths of tubing such as the first tubular conduit. 
This invention enables the use of relatively inexpensive materials for the 
main strength of the conduitry and lesser quantities of more expensive or 
more troublesome materials for the inside liner. Because of the processes 
used, flaws and pores in the construction are unlikely to occur, and parts 
are readily manufactured and the combination is easily assembled. 
This invention is not to be limited by the embodiments shown in the 
drawings and described in the description which are given by way of 
example and not of limitation, but only in accordance with the scope of 
the appended claims.