GB2057615A

GB2057615A - A pipe fitting

Info

Publication number: GB2057615A
Application number: GB8015609A
Authority: GB
Original assignee: FISCHER CASTINGS Ltd
Current assignee: FISCHER CASTINGS Ltd
Priority date: 1978-02-01
Filing date: 1979-03-30
Publication date: 1981-04-01
Also published as: GB2057615B

Abstract

For joining a synthetic deformable pipe (1) such as a polyethylene pipe, to a pipe fitting of metallic material, the pipe fitting has an inner bore section with lands (4) and channels (5) and an annular flange (6), in which bore section the pipe (1) is inserted with a clearance fit. A metal insert is arranged within the pipe (1) in the inner bore section of the fitting with an enlarged end portion of the insert in contact with the flange (6). A mandrel (11) with a former (12) is inserted and the former (12) displaced to expand the insert and place the pipe (1) within the inner bore section under compression. The contour of the inner pipe section substantially reduces the tendency of the pipe (1) to migrate from areas under compression. <IMAGE>

Description

SPECIFICATION A pipe fitting This invention relates to a method of connecting a pipe formed of synthetic deformable material, such as polyethylene to a pipe fitting of metallic material, and a particular form of fitting therefor and a tool for use therein.

An industrial field in which the method finds application is the gas industry where one use of synthetic deformable pipe is for the connection of a domestic supply from a large diameter metal main pipe to a meter inlet of a domestic dwelling.

Stringent regulations are laid down governing the requirements for joins between the synthetic deformable pipe and gas pipe fitting applied to its ends.

In the prior art there are gas pipe fittings which are applied to the synthetic deformable pipe on site. One such pipe fitting compresses the synthetic deformable pipe against an inner core by an outer sleeve which is secured by threaded engageable collars.

As some synthetic deformable materials, such as polyethylenes and other long chain polymers have the property that when under strain their material migrates from high compressive regions to low compressive regions, there is a need to ensure that any such migration does not lessen the effectiveness of a connection between such a pipe and a fitting.

Another feature of the joint is that when a connection or joint is made between synthetic deformable pipe and a pipe fitting, especially one used in a domestic location, then that connection should be permanent and tamper-proof.

The expression herein "synthetic deformable pipe" is used herein to mean a pipe formed of "synthetic deformable material", and "synthetic deformable material" is used herein to include polyethylene and other polymers from which flexible gas piping is manufactured.

In order to obtain a joint which meets the above requirements it is necessary to provide a suitable method of joining deformable pipe to metal fittings.

According to a first aspect of the invention there is provided a method of joining synthetic deformable pipe to a pipe fitting of metallic material, comprising selecting a pipe fitting having an inner bore section to receive the outer diameter of the synthetic deformable pipe, this inner bore section having at least one portion with a diameter such as to be a clearance fit on the pipe and at least one other portion of greater bore diameter than the pipe diameter between said one portion and an annular flange of the fitting defining one end of the inner bore section, selecting a deformable metal insert of cylindrical section having an enlarged end portion of enlarged outer diameter with respect to a major portion of an outer diameter dimensioned relative to the inner diameter of the pipe, to be a close fit therein, the enlarged diameter being dimensioned relative to the annular flange so that as the insert is displaced co-axially within said fitting said enlarged end portion thereof abuts said annular flange, inserting the pipe into the inner bore section of the pipe fitting, inserting the insert into the inner bore section of the pipe fitting so as to extend co-axially within the pipe and such that the enlarged end portion thereof abuts the flange on the pipe fitting, selecting a mandrel with an insert ex#anding former, inserting a shaft of the mandrel within the assembly formed by the insert, pipe and pipe fitting, and displacing the mandrel former through the insert so as to expand the major portion of the insert to place the pipe under compression in the region of said at least one portion of said inner bore section, wherein the pipe within the inner bore section is contoured to substantially reduce the tendency of the synthetic deformable material to migrate from said at least one portion to said at least one other portion of the inner bore section.

In one embodiment of the method, the assembly of said pipe, insert, pipe fitting and mandrel is accomplished by placing said insert on the mandrel and one end portion over the insert with said expanding former positioned on the mandrel shaft, inserting the mandrel through the inner bore section of the pipe fitting to a position in which said enlarged end portion of the insert abuts said annular flange, said annular flange being located internally of said inner bore section, and wherein the insert is expanded by displacing the mandrel former through the insert so as to expand the major portion of the insert to a diameter substantially that of the enlarged diameter of the insert.

Advantageously, the mandrel comprises a securing member adapted to be located in fixed relation to the pipe fitting and having a journal for the mandrel shaft whereby the shaft may be rotated relative to the securing member to effect displacement of the mandrel former along the shaft, said insert being expanded by rotating the mandrel shaft in the sense which causes said mandrel former to advance through the insert.

In a second embodiment of the method, said annular flange is located at one outer end of the inner bore section and has an inclined external face which the enlarged diameter portion of the insert may abut, the assembly of said pipe, insert, pipe fitting and mandrel being accomplished by inserting an end portion of said pipe through the end of said inner bore section of the pipe fitting remote from said flange and displacing said pipe end portion to abut the flange internally of the inner bore section, inserting the insert major portion into said one outer end of the inner bore section and displacing the insert until said enlarged portion thereof abuts the inclined external face of the flange, inserting the shaft of the mandrel through said one outer end of the inner bore section and the assembled insert and pipe, and securing the mandrel relative to the pipe fitting, wherein the insert is expanded by displacing the mandrel former along the shaft in a direction through the flange and along the major portion of the insert to expand the insert to place the pipe under compression. Advantageously the mandrel comprises a securing member adapted to be located in fixed relation to the pipe fitting and a journal for the mandrel shaft whereby the shaft may be rotated relative to the securing member to effect displacement of the mandrel former along the shaft, wherein the step of expanding the insert is accomplished by rotating the mandrel shaft in the sense which causes the mandrel former to advance into and along the inner bore section of the pipe fitting.It is a preferred feature that the pipe fitting is provided with an internally threaded collar for subsequent connection to a fitting and said securing member on the mandrel has an external thread adapted for connection with said internally threaded collar, the mandrel being located in fixed relation relative to the pipe fitting by threadedly engaging the collar and securing member and rotating one of these until the securing member abuts the expanded portion of the insert in contact with the inclined external face of the flange on the pipe fitting.

According to a second aspect of the invention there is provided a mandrel for use in a method of joining synthetic deformable pipe to a pipe fitting of metallic material by expanding an insert to place the pipe under compression in the region of at least one portion of an inner bore section of the pipe fitting, comprising a mandrel shaft having a threaded portion carrying an internally threaded mandrel former, a securing member journalled to receive said mandrel shaft for rotation of said shaft relative to the securing member without axial displacement of the mandrel shaft, said shaft carrying means for rotating the shaft to effect displacement of said mandrel former relative to said mandrel shaft to enable said mandrel former, in use, to expand an insert of ductile metal within a synthetic deformable pipe located within an inner bore section of the pipe fitting.It is a preferred feature that said securing member comprises a body portion providing said journal for the shaft and a collar portion externally threaded to threadedly engage an internally threaded collar on the pipe fitting, whereby the securing member may be fixedly located relative to the pipe fitting by threadedly engaging the securing member with the collar of the pipe. Preferably the means for rotating the shaft comprises a threaded member threadedly engaging the shaft on a further threaded portion of the shaft said further threaded portion being spaced from the first mentioned threaded portion by a section of the shaft adapted to be journalled in the securing member.

According to a third aspect of the invention there is provided a pipe fitting for use in the method hereinbefore defined, comprising an inner bore section to receive a synthetic deformable pipe having a suitably related outer diameter, this inner bore section having at least one portion with a bore diameter such as to be a clearance fit on the pipe and at least one other portion of greater bore than the pipe diameter, said other portion being located between said one portion and an annular flange of the fitting defining one end of the inner bore section, wherein the inner bore section of the pipe fitting is contoured to substantially reduce the tendency of deformable material of a synthetic deformable pipe to migrate under compression from said at least one portion to said at least one other portion when said pipe is held therein under compression after the expansion therein of an insert of deformable metal. It is a preferred feature of one embodiment that said flange is located internally of the pipe fitting and separates the inner bore section from a passage from which a mandrel former may be drawn through the flange to expand a said insert.

It is a preferred feature of another embodiment that said flange is located at an outer end of the inner bore section and has an inclined external face. In this embodiment it is a preferred feature to provide a collar rotatably mounted about one end of the inner bore section and internally threaded to receive a securing member of a mandrel.

It is a preferred feature of the pipe fitting that said at least one portion is a series of lands and said at least another portion is a series of channels between said lands, one of said channels adjoining said annular flange.

An embodiment of the method, pipe fitting and a mandrel according to the present invention will now be described by way of example only, with reference to the accompanying drawings in which: Fig. 1 shows a longitudinal section taken through the axis of a ductile metal insert; Fig. 2 shows a longitudinal section taken through the axis of an inner bore section of a pipe fitting: Fig. 3 shows a longitudinal section taken through the axis of both the insert and pipe fitting of Figs. 1 and 2 with the insert and a pipe arranged on a mandrel; Fig. 4 shows the insert, pipe and pipe fitting of Fig. 3 after the mandrel has been drawn through the insert; and Fig. 5 shows a detachable part of a fitting, partly in longitudinal section together with an insert, pipe and mandrel of a modified type to be drawn out of the fitting.

Reference is made to Figs. 3 and 4 which schematically illustrate the preferred method of joining synthetic deformable pipe 1 to a pipe fitting 2 of metallic material. The pipe fitting 2 (shown per se in Fig. 2) has an inner bore section 3 which receives the outer diameter of the synthetic deformable pipe 1. This inner bore section 3 has a series of first portions or lands 4 with a diameter such as to be a clearance fit and preferably a close fit on the pipe 1 and a series of second portions or channels 5 of greater diameter than the pipe diameter. One of said channels is located adjacent to an internal annular flange 6 of the pipe fitting 2 which defines one end of the inner bore section 3. A ductile metal insert 7 (shown per se in Fig. 1 ) is formed with right cylindrical section. One of its end portions 8 has an enlarged outer diameter with respect to a major portion 9 of an outer diameter equal to the inner diameter of the pipe. The enlarged diameter end portion 8 is dimensioned relative to the diameter of a passage 10 bounded by the annular flange 6 in the fitting so that as the said one end portion 8 of the insert 7 is displaced co-axially within said fitting 2 it abuts said annular flange 6.

A mandrel 11 with an insert expanding portion or former 12 is employed to align the pipe 1 and insert 7 coaxially with passage 10. The insert 7 is placed on the mandrel 1 1 and the pipe is slid longitudinally over the insert 7 with said expanding portion 12 entering the end 13 (Fig. 1) of the insert 7 remote from the enlarged diameter portion 8. In order that the components then attain the attitude of Fig. 3 the mandrel 11 is inserted through the inner bore section 3 of the pipe fitting 2 to a position in which said one end portion 8 of the insert 7 with the pipe end portion 1 thereon abuts the annular flange 6.The mandrel 1 1 is connected to suitable means (not shown) for drawing the mandrel 11 through the annular flange 6 and the displacement of the mandrel 11 through the annular flange 6 causes expanding portion 1 3 of the mandrel 1 1 to expand the major portion 9 of the insert 7 to a diameter substantially that of the enlarged diameter portion 8 of the insert 7 in order to #place portions 14 of the pipe 1 under compression in the region of the lands 4. It should be noted that whereas Figure 4 shows portions 14 of pipe 1 wholly filling the channels 5 in practice these channels 5 are only partially filled.

The inner bore section 3 of the pipe fitting is contoured to eliminate deterioration of the joint now formed, by the tendency of the polyethylene material of pipe 1 to migrate from the region of lands 4 to the region of the channels 5.

Now that the insert 7 is deformed, the pipe 1 is nonreleasably attached to the pipe fitting 2.

Variations are possible in the arrangement of lands 4 and channels 5 within the overall requirement to eliminate deterioration of the join due to migration of the material of the pipe 1.

Likewise, the configuration of the remainder of the pipe fitting 2 beyond the flange 6 forms no limitation on the configuration of the pipe fitting 2 which is employed, save that provision for drawing the mandrel is necessary.

Reference is now made to Fig, 5 for the description of modification to the above embodiment of the method, pipe fitting and mandrel. With the above embodiment as described with reference to Figs. 3 and 4 the mandrel former 12 is drawn through the pipe fitting from the end 13 of the insert 7 of smaller diameter towards and through the end portion 8 of larger diameter. By modifying the tool as shown in Fig. 5, the mandrel former 12 may be driven through the pipe fitting 4 in a direction from the end portion 8 to the other end portion 13 of the insert 7. This modification to the method of connecting the pipe of synthetic deformable material to a pipe fitting of metallic material has particular relevance to the connection of pipe to Tfittings but is applicable to the method when used to make the connections previously described.

In the embodiment described with reference to Fig. 5 like parts will be designated with the same reference numeral as the corresponding parts in Figs. 3 and 4. A pipe fitting 2 with lands 4, channels 5 and an internal annular flange 6 is to be connected to the pipe 1 and to a T-fitting not shown. For threaded connection to a T-fitting, the fitting 2 carries collar 15 which is internally threaded at 16. Collar 15 is mounted to be freely rotatable about one end of the inner bore section of fitting 2 and axially displaceable relative thereto when the fitting 2 is not secured. Mandrel 11 carries former 12 on a first threaded portion thereof and each is threaded such that rotation of the shaft effects displacement of the former.In this embodiment, the mandrel shaft also comprises a securing member 17 carrying a rotary bearing 18 for the mandrel shaft 1 1 such that the shaft 1 1 is freely rotatable without axial displacement with respect to the securing member 17 and the fitting 2. Securing member 17 is fixed relative to the collar 15 by threaded engagement with the collar 15 for which purpose it has externally threaded collar portion 19, and by abutment with fitting 2. Mandrel shaft 11 also carries displacement nut 20 for displacing the shaft 1 1 and former 12 relative to the pipe 1.

insert 7 and fitting 2. Displacement nut 20, which provides means for rotating the shaft, threadedly engages a further threaded portion 24 of shaft 1 1 which is spaced from the first threaded portion 23 of shaft 1 1 carrying former 12, by portion 25 of the shaft adapted to be journalled in the bearing 18 of the securing member 17.

As shown schematically in Fig. 5, the former 12 is driven through the insert 7 to accomplish the connection between pipe 1 of synthetic material and fitting 2 whereby channels 5 receive displaced portions of the pipe material and the pipe material 14 in the region of lands 4 is under compression.

Initially prior to expansion, the insert 7 is inserted in pipe which is already placed in fitting 2. The expanded diameter portion 8 abuts an inclined external face of flange 6 to limit any further axial movement of the insert 7, whilst the end of pipe 1 within the fitting abuts the internal face of flange 6. Securing member 17 with former 12 within it, is then threadedly connected to collar 15 and rotated until its leading end abuts the insert portion 8 in contact with the fitting 2: it will be noted that the collar portion of securing member 17 defines an internal cavity 21 which initially houses the former 12 and which has an inclined leading face 22 for abutment with the enlarged outer portion of insert 8.At this stage the portion of pipe 1 within the fitting 2 has a clearance or close fit with the lands 4, and the diameter of the major portion 9 of insert 7 allows a close fit within the pipe 1. Now by rotating the displacing nut 20 in the appropriate sense, and thus the mandrel shaft 1 ,the former 12 is driven through the insert 7 and pipe 1 in the direction of arrow A thereby accomplishing a connection between pipe 1 1 and fitting 2 by expansion of the insert portion 9 and compression of the surrounding portion of pipe 1 into channels 5. Thereafter, former 12 may be retracted by reversing the direction of displacing member 20. Then securing member 17 is released from collar 16. Collar 16 may then be threaded onto a T-fitting.

With reference to the above, reference is made to the mandrel portion or former 12. This is shaped as illustrated such that the final inner dimension of insert 7 is that of passage 10. As one mandrel 11 is to be used on site for many fitting operations, it will have a former 12 made of hardened and wear resistant material. When the insert 7 is expanded, it is expanded by yielding and consequently it does not return to its former state.

As illustrated in Fig. 3, the insert 7 is a push fit within pipe 1, which, in turn, is a push fit within the inner bore section 3 prior to drawing. After the drawing operation the pipe has been deformed and is now firmly and permanently clamped between the insert 7 and fitting 2. Such a join of the preferred method has the advantages that (a) the join is capable of transmitting forces beyond those which normally cause damage to the pipe itself having regard to the tensile strength of the material of the pipe; and (b) the join creates a seal which is capable of remaining effective at fluid pressures within the pipe and join which otherwise are sufficient to burst the pipe itself.

In a modification of the mandrel of Fig. 5, the securing member 17 has an externally threaded portion 1 7a for threadedly engaging the collar 15, which is formed separately from a body portion 1 7b of the securing memberjournalled to receive the mandrel shaft 11. This enables the threaded portion of the securing member to then be threadedly engaged with the collar 15 and thereafter the remainder of the mandrel positioned such that the body portion of the securing member 17 abuts the separate threaded portion thereof.

The fitting 2 of Fig. 5 may be used to connect the flexible pipe 1 to a variety of couplings. Tfittings have already been mentioned. Other fittings to which Fittings 2 may be connected include "Swivel-T-fittings", Transition fittings (fittings between two sections of pipe 1). Another form of coupling is one in which a fitting 2 of Fig. 4 has an external threaded portion which threadedly receives a collar, the collar itself threadedly engaging the internal thread of collar 1 5 of the fitting of Fig. 5.

Claims

1. A pipe fitting for connecting to a synthetic deformable pipe comprising an inner bore section to receive a synthetic deformable pipe having a suitably related outer diameter this inner bore section having at least one portion with a bore diameter such as to be a clearance fit on the pipe and at least one other portion of greater bore than the pipe diameter characterised in that said other portion is located between said one portion and an annular flange of the fitting defining one end of the inner bore section, said flange acting to prevent axial bore section, said flange acting to prevent axial movement of the pipe during deformation thereof by a mandrel, the inner bore section of the pipe fitting is contoured to substantially reduce the tendency of deformable material of a synthetic deformable pipe to migrate under compression from said at least one portion to said at least one other portion when said pipe is held therein under compression after the expansion therein of an insert of deformable metal by a mandrel.

2. A pipe fitting as claimed in Claim 12, wherein said flange is located internally of the pipe fitting and separates the inner bore section from a passage from which a mandrel former may be drawn through the flange to expand a said insert.

3. A pipe fitting as claimed in Claim 12, wherein said flange is located at an outer end of the inner bore section and has an inclined external face.

4. A pipe fitting as claimed in any one of Claims 12 to 15 a collar rotatably mounted about one end of the inner bore section and internally threaded to receive a securing member of a mandrel.

5. A pipe fitting as claimed in any one of Claims 12 to 15 wherein said at least one portion is a series of lands and said at least one other portion is a series of channels between said lands, one of said channels adjoining said annular flange.

6. A pipe fitting arranged, constructed and adapted to operate substantially as hereinbefore described with reference to Figs. 2 to 4 or Fig. 5 of the accompanying drawings.

7. In combination a pipe fitting as claimed in any one of Claims 1 to 6 and a mandrel for use in joining a synthetic deformable pipe to the pipe fitting by expanding an insert to place the pipe under compression in the region of at least one portion of an inner bore section of the pipe fitting, comprising a mandrel shaft having a threaded portion carrying an internally threaded mandrel former, a securing memberjournalled to receive said mandrel shaft for rotation of said shaft relative to the securing member without axial displacement of the mandrel shaft, said shaft carrying means for rotating the shaft to effect displacement of said mandrel former relative to mandrel shaft to enable said mandrel former, in use, to expand an insert of ductile metal within a synthetic deformable pipe located within inner bore section of the pipe fitting.

8. The combination as claimed in Claim 7, wherein said securing member comprises a body portion providing said journal for the shaft and a collar portion externally threaded to threadedly engage an internally threaded collar on the pipe fitting, whereby the securing member may be fixedly located relative to the pipe fitting by threadedly engaging the securing member with the collar of the pipe.

9. The combination as claimed in either Claim 7 or Claim 8, wherein the means for rotating the shaft comprises a threaded member threadedly engaging the shaft on a further threaded portion of the shaft said further threaded portion being spaced from the first mentioned threaded portion by a section of the shaft adapted to be journalled in the securing member.