CA1095551A - Pipe of oriented thermoplastics polymeric material - Google Patents
Pipe of oriented thermoplastics polymeric materialInfo
- Publication number
- CA1095551A CA1095551A CA287,557A CA287557A CA1095551A CA 1095551 A CA1095551 A CA 1095551A CA 287557 A CA287557 A CA 287557A CA 1095551 A CA1095551 A CA 1095551A
- Authority
- CA
- Canada
- Prior art keywords
- blank
- mould
- pipe
- wall thickness
- tube
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Abstract
ABSTRACT OF THE DISCLOSURE
A pipe of oriented thermoplastic polymeric material having an integral socket is manufactured by expanding a tubular blank having a portion of greater wall thickness which is positioned in a portion of a female mould defining the socket.
The tubular blank is heated by circulation of hot water to a temperature at which deformation will induce orientation of the polymer molecules, and is then expanded radially out-wards against the mould by application of internal pressure.
In this manner the wall thickness and rigidity of the socket are increased.
A pipe of oriented thermoplastic polymeric material having an integral socket is manufactured by expanding a tubular blank having a portion of greater wall thickness which is positioned in a portion of a female mould defining the socket.
The tubular blank is heated by circulation of hot water to a temperature at which deformation will induce orientation of the polymer molecules, and is then expanded radially out-wards against the mould by application of internal pressure.
In this manner the wall thickness and rigidity of the socket are increased.
Description
1~95S51 - The invention relates to a pipe of oriented thermoplastic polymeric material and also to a method of manufacturing such a pipe.
In our United Kingdom Patent No. 1 1~32 539 we have taught a method of, and apparatus for, forming a pipe from orientable thermoplastic poly-meric material by radially expanding a tubular blark into a mould at a tem-perature at which expansion of the pipe will causeorientationofthe polymer molecules. In this manner the finished pipe has an oriented structure cap-able of withstanding a greater hoop stress for a given wall thickness than - a pipe made of the same material which has not been oriented, and has an enlarged oriented socket for carrying a sealing ring. In this manner a pipe was produced with an integral socket having a specified bursting strength with a smaller wall thickness than was previously possible, thereby reduc-ing the volume of plastics used for a given pipe diameter and strength and ,:~
minimising the cost of the materials required. Such pipes are typically manufactured from PVC, chlorinated PVC, high or low density polyethylene, ;; polypropylene or ABS, although other suitable orientable polymers may be used. As the enlarged socket is of greater diameter than the remainder of ' the pipe, -the wall of the socket is thinner than the pipe wall and conse-' quently more flexible.
In practice we have found that, whilst -the reduced rigidity of ` the socket is not critical, large diameter pipes subjected to high pressures can incur leaks past the socket seal due to the increased flexibility of the thinner socket wall.
According to one aspect of the invention a method of forming a pipe of orientable thermoplastic polymeric material having an integral socket of enlarged internal diameter includes a tubular blank having a por-tion Of Breater wall thickness in a female mould with the por-tion of greater -; wall thickness positioned within a portion of the female mould defining the ; - 2 -'-' '`
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integral socket, heating tbe tubular blank to a temperature at which defor-mation will induceorientationofthe polymer molecules, applying internal pressure to the tubular blank to expand it radially outwards against the female mould whilst orienting the polymer molecules, the portion of greater wall thickness being expanded into the portion of thefemale mould defining the socket, cooling the moulded pipe to a rigid condition, and then remov-ing the applied internal pressure. The tubular blank is preferably beated by means of a fluid, such as water, at a suitable temperature. The internal pressure is preferably applied by compressed gas or liquid under pressure.
The method may also include forming the tubular blank with the portion of - greater wall thickness by supporting a tube of constant -thickness within a mould defining the portion of greater wall thickness, heating the tube to a moulding temperature, compressing the tube axially within the mould to form the portion of greater thickness, cooling the moulded blank and removing it from the mould.
; According to another aspect of -the invention a pipe of oriented thermoplastic polymeric material has an integral socket of wbich the cross-section of area is greater than the cross-sectional area taken through an-other portion of the pipe. Tbe thickness of the socket is preferably equal to, or greater than, the wall thickness of tbe pipe.
The invention will now be described by way of example only with reference to the accompanying drawings in which:
Figure 1 is a cross-section of a mould con-taining one form of tub-ular blank;
Figure 2 illustrates a modification of Figure l;
Figure 3 is an enlarged scrap section of a socket at the end of a pipe produced in accordance with our United Kingdom Patent No. 1 432 539 and Figures 4 and 5 are scrap sections similar to .
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Figure 3 but illustrating sockets produced at the end of a pipe by the mould of Figure 1 or Figure 2.
With reference to Figure 1, a tubular blank 10 of an unplasticisea PVC having a vicat softening point of 82 C is located inside a split female mould having an upper half 11 and a lower half 12. The blank 10 is sealed into the mould by means of external seals 13 and 14 so than an annular cham-:. ber 15 is defined between the outer surface of the blank 10 and the inwardly facing surfaces of the two mould halves 11 and 12. The annular chamber 15 can be filled with hot water through an inlet pipe 16 and drained by an out-let pipe ]7. The inwardly facing surfaces of the two mould halves 11 and 12 , are generally cylindrical as shown but define at one end an annular recess 18 for forming a socket a-t the end of the pipe. The two mould halves 11 and 12 would be clarnped sealingly togeth.er in a convenient manner and are arranged and operated generally as taught in our United Kingdom Patent No.
.i 1 432 539.
However, it will be noted that the external seal 14 has a greater internal diameter than the external seal 13 and engages a portion 19 of the blank 10 which is generally of greater wall thickness. After the mould halves 11 and 12 have been clamped together so that the seals 13 and 14 en-20 gage the blank 10, hot water at a temperature of 92 C is passed through the inlet pipe 16 into the annular chamber 15 and is recirculated, through the outlet pipe 17 and an unshown water heater, back to the inlet pipe 16 for a sufficient -time to heat the blank 10 to a temperature between 82C and 92 C
at which its expansion will result in orientation ofthe polymer molecules.
Hot water may also be recirculated through the bore of the blank 10. Once ~ the blank 10 has achieved the required temperature, the water in the annular chamber 15 is completely drained away, and hot water is fed under pressure - into the bore of the blank 10 thereby expanding the thicker portion 19 .
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radially outwards in-to the anmllar recess 18, and expanding the portion of normal thickness into the cylindrical portion of the mould. In this manner the material of the tubular blank 10 is oriented with a corresponding in-crease in the hoop strength of -the finished pipe. The water pressure ap-plied to the bore of the blank 10 may conveniently be applied to either, or both, ends of the blank through appropriate internal or external seals.
After the blank 10 has been fully expanded into themould 11 and 12~ the re-sultant pipe is cooled in any convenient manner, for instance by cooling the mould halves 11 and 12 with cold water, or by passing cold water through the bore of the pipe at an appropriate pressure to retain the pipe shape, until its temperature has dropped below the point at which reversion could occur.
After the pipe has been cooled, the mould halves 11 and 12 are separated and the formed pipe removed. The formed pipe is then trimmed by removing the surplus material at each end.
~s shown in Figure 3, two finished pipes 20 and 21 are sealed to-.
; gether by a sealing ring 22 engaged within a recess 23 defined by an inte-gral socket 24 which is of greater diameter than the main cylindrical por-tions of the pipes 20 and 21. The integral socket 24 shown in Figure 3 has been formed in accordance with our United Kingdom Patent No. 1 432 539 from ':, a cylindrical blank of constant wall thickness and, as a result, it will be noted that the wall of the integral socket 24 is consequently thinner than ; the pipe wall. This is because the cross-sectional areas of the integral socket and the pipe wall are equal, and the socket 24 has a greater diameter ~.
than the pipe. Althoughorientationincreases the burst strength of the pipe roughly pro rata with -the stretch ratio, its effect on stiffness is relat-ively small. Thus, although -the socket 24 will probably have a higher hoop tensile strength than the cylindrical section of the pipe by virtue of its higher stretch ratio, its flexibility will be relatively greater and could ' . .
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lead to displacement of the seaLing ring 22 and a consequent failure of the joint under pressure. However, by using the thicker wall portion 19 as de-scribed with reference to Figure 1, -the wall thickness of the integral socket 24 can be increased as shown in Figures 4 and 5 in which the sarne reference numerals have been used to iden-tify equivaLent components. In Figure 4 it will be noted tha-t the wall thickness of the socket 24 is equal to the wall thickness of the pipe, and in Figure 5 it will be noted that the wall thickness of the socket 24 is greater than -the wall thickness of -the pipe. In fact, the wall thickness of the finished socket 24 can be closely controlled by appropriately selecting the wall thickness of the thicker por-tion 19 of the tubular blank 10. The axial length and position of the thicker portion 19 can be altered from that shown in Figure 1 to strengthen any specific portion of the finished pipe which it is desired to strengthen.
It will be noted from Figure 1 that the thicker portion 19 has been formed by locally increasing the outer diameter of the tubular blank 10. Figure 2 is generally similar to Figure 1 and the same reference num-erals have been used to identify equivalent components. However, it will be noted that the seals 13 and 14 have the same external diameter as the outer diameter of the tubular blank 10 is constant, and the thicker portion 19 is provided by locally decreasing the internal diameter. Whi:Lst the blank 10 shown in Figure 2 could be rnanufactured as taught in United Kingdom Patent No. 997 551, it couLd alternatively be manufactured by heating a tubular blank of constant wall thickness in a mould which defines the internal and external diameters of the thickened end portion 19, and by compressing the tubular blank 10 axially within that mouLd to define the thickened end por-tion 19 and by cooling and removing the blank from that mould. ~he tubuLar blank 10 illustrated in Figure 1 could conveniently be made in the same manner.
.
~(;1 9SS51 United Kingdom Patent No. 997 552 teaches how a tubular blank with a thickened end portion can be formed into a non-oriented tube by expanding a core within the thickened portion to define an enlarged coupling socket.
Although it has consequently been known for some time that a streng-thened coupling socket can be formed at the end of a tube by expanding a tubular blank having a portion of greater wall thickness, it has not previously been proposed to use such a blank in the production of a pipe of oriented thermo-.~ plastic polymeric material manufactured, for instance, as taught in our United Kingdom Patent No. 1 432 539. The reason why we have not considered this possibility previously is that it was felt that the application of in-ternal pressure to a tubular blank of non-constant wall thickness would cause the thinner portion of the tube to expand in preference to the thicker por-tion and that the operation would either be comp~etely uncontrollable or it would not be possible to obtain a product which reflected thedimensional differences present in the blank. To the contrary, we have found that the process in our United Kingdom Paten-t No. 1 432 539 will expand, in a satis-factory controllable fashion, a tubular blank having a portion of greater ! wall thickness, and that the result is an orien-ted pipe having an integral socket of greater rigidity than has hitherto been possible.
The mould used to produce the blank 10 of Figure ] does not have to be split in the rnanner illustrated in the drawing. An alternative mould may be in the form of a tube with an end cap, giving a split at the socket - groove.
.
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In our United Kingdom Patent No. 1 1~32 539 we have taught a method of, and apparatus for, forming a pipe from orientable thermoplastic poly-meric material by radially expanding a tubular blark into a mould at a tem-perature at which expansion of the pipe will causeorientationofthe polymer molecules. In this manner the finished pipe has an oriented structure cap-able of withstanding a greater hoop stress for a given wall thickness than - a pipe made of the same material which has not been oriented, and has an enlarged oriented socket for carrying a sealing ring. In this manner a pipe was produced with an integral socket having a specified bursting strength with a smaller wall thickness than was previously possible, thereby reduc-ing the volume of plastics used for a given pipe diameter and strength and ,:~
minimising the cost of the materials required. Such pipes are typically manufactured from PVC, chlorinated PVC, high or low density polyethylene, ;; polypropylene or ABS, although other suitable orientable polymers may be used. As the enlarged socket is of greater diameter than the remainder of ' the pipe, -the wall of the socket is thinner than the pipe wall and conse-' quently more flexible.
In practice we have found that, whilst -the reduced rigidity of ` the socket is not critical, large diameter pipes subjected to high pressures can incur leaks past the socket seal due to the increased flexibility of the thinner socket wall.
According to one aspect of the invention a method of forming a pipe of orientable thermoplastic polymeric material having an integral socket of enlarged internal diameter includes a tubular blank having a por-tion Of Breater wall thickness in a female mould with the por-tion of greater -; wall thickness positioned within a portion of the female mould defining the ; - 2 -'-' '`
:
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` l`~)9~S~
integral socket, heating tbe tubular blank to a temperature at which defor-mation will induceorientationofthe polymer molecules, applying internal pressure to the tubular blank to expand it radially outwards against the female mould whilst orienting the polymer molecules, the portion of greater wall thickness being expanded into the portion of thefemale mould defining the socket, cooling the moulded pipe to a rigid condition, and then remov-ing the applied internal pressure. The tubular blank is preferably beated by means of a fluid, such as water, at a suitable temperature. The internal pressure is preferably applied by compressed gas or liquid under pressure.
The method may also include forming the tubular blank with the portion of - greater wall thickness by supporting a tube of constant -thickness within a mould defining the portion of greater wall thickness, heating the tube to a moulding temperature, compressing the tube axially within the mould to form the portion of greater thickness, cooling the moulded blank and removing it from the mould.
; According to another aspect of -the invention a pipe of oriented thermoplastic polymeric material has an integral socket of wbich the cross-section of area is greater than the cross-sectional area taken through an-other portion of the pipe. Tbe thickness of the socket is preferably equal to, or greater than, the wall thickness of tbe pipe.
The invention will now be described by way of example only with reference to the accompanying drawings in which:
Figure 1 is a cross-section of a mould con-taining one form of tub-ular blank;
Figure 2 illustrates a modification of Figure l;
Figure 3 is an enlarged scrap section of a socket at the end of a pipe produced in accordance with our United Kingdom Patent No. 1 432 539 and Figures 4 and 5 are scrap sections similar to .
.-; - : . . :
., . , : :...... : :
~9sss ~
Figure 3 but illustrating sockets produced at the end of a pipe by the mould of Figure 1 or Figure 2.
With reference to Figure 1, a tubular blank 10 of an unplasticisea PVC having a vicat softening point of 82 C is located inside a split female mould having an upper half 11 and a lower half 12. The blank 10 is sealed into the mould by means of external seals 13 and 14 so than an annular cham-:. ber 15 is defined between the outer surface of the blank 10 and the inwardly facing surfaces of the two mould halves 11 and 12. The annular chamber 15 can be filled with hot water through an inlet pipe 16 and drained by an out-let pipe ]7. The inwardly facing surfaces of the two mould halves 11 and 12 , are generally cylindrical as shown but define at one end an annular recess 18 for forming a socket a-t the end of the pipe. The two mould halves 11 and 12 would be clarnped sealingly togeth.er in a convenient manner and are arranged and operated generally as taught in our United Kingdom Patent No.
.i 1 432 539.
However, it will be noted that the external seal 14 has a greater internal diameter than the external seal 13 and engages a portion 19 of the blank 10 which is generally of greater wall thickness. After the mould halves 11 and 12 have been clamped together so that the seals 13 and 14 en-20 gage the blank 10, hot water at a temperature of 92 C is passed through the inlet pipe 16 into the annular chamber 15 and is recirculated, through the outlet pipe 17 and an unshown water heater, back to the inlet pipe 16 for a sufficient -time to heat the blank 10 to a temperature between 82C and 92 C
at which its expansion will result in orientation ofthe polymer molecules.
Hot water may also be recirculated through the bore of the blank 10. Once ~ the blank 10 has achieved the required temperature, the water in the annular chamber 15 is completely drained away, and hot water is fed under pressure - into the bore of the blank 10 thereby expanding the thicker portion 19 .
:
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radially outwards in-to the anmllar recess 18, and expanding the portion of normal thickness into the cylindrical portion of the mould. In this manner the material of the tubular blank 10 is oriented with a corresponding in-crease in the hoop strength of -the finished pipe. The water pressure ap-plied to the bore of the blank 10 may conveniently be applied to either, or both, ends of the blank through appropriate internal or external seals.
After the blank 10 has been fully expanded into themould 11 and 12~ the re-sultant pipe is cooled in any convenient manner, for instance by cooling the mould halves 11 and 12 with cold water, or by passing cold water through the bore of the pipe at an appropriate pressure to retain the pipe shape, until its temperature has dropped below the point at which reversion could occur.
After the pipe has been cooled, the mould halves 11 and 12 are separated and the formed pipe removed. The formed pipe is then trimmed by removing the surplus material at each end.
~s shown in Figure 3, two finished pipes 20 and 21 are sealed to-.
; gether by a sealing ring 22 engaged within a recess 23 defined by an inte-gral socket 24 which is of greater diameter than the main cylindrical por-tions of the pipes 20 and 21. The integral socket 24 shown in Figure 3 has been formed in accordance with our United Kingdom Patent No. 1 432 539 from ':, a cylindrical blank of constant wall thickness and, as a result, it will be noted that the wall of the integral socket 24 is consequently thinner than ; the pipe wall. This is because the cross-sectional areas of the integral socket and the pipe wall are equal, and the socket 24 has a greater diameter ~.
than the pipe. Althoughorientationincreases the burst strength of the pipe roughly pro rata with -the stretch ratio, its effect on stiffness is relat-ively small. Thus, although -the socket 24 will probably have a higher hoop tensile strength than the cylindrical section of the pipe by virtue of its higher stretch ratio, its flexibility will be relatively greater and could ' . .
: , . . ~:
.:
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~ ' 1~3g~5~
lead to displacement of the seaLing ring 22 and a consequent failure of the joint under pressure. However, by using the thicker wall portion 19 as de-scribed with reference to Figure 1, -the wall thickness of the integral socket 24 can be increased as shown in Figures 4 and 5 in which the sarne reference numerals have been used to iden-tify equivaLent components. In Figure 4 it will be noted tha-t the wall thickness of the socket 24 is equal to the wall thickness of the pipe, and in Figure 5 it will be noted that the wall thickness of the socket 24 is greater than -the wall thickness of -the pipe. In fact, the wall thickness of the finished socket 24 can be closely controlled by appropriately selecting the wall thickness of the thicker por-tion 19 of the tubular blank 10. The axial length and position of the thicker portion 19 can be altered from that shown in Figure 1 to strengthen any specific portion of the finished pipe which it is desired to strengthen.
It will be noted from Figure 1 that the thicker portion 19 has been formed by locally increasing the outer diameter of the tubular blank 10. Figure 2 is generally similar to Figure 1 and the same reference num-erals have been used to identify equivalent components. However, it will be noted that the seals 13 and 14 have the same external diameter as the outer diameter of the tubular blank 10 is constant, and the thicker portion 19 is provided by locally decreasing the internal diameter. Whi:Lst the blank 10 shown in Figure 2 could be rnanufactured as taught in United Kingdom Patent No. 997 551, it couLd alternatively be manufactured by heating a tubular blank of constant wall thickness in a mould which defines the internal and external diameters of the thickened end portion 19, and by compressing the tubular blank 10 axially within that mouLd to define the thickened end por-tion 19 and by cooling and removing the blank from that mould. ~he tubuLar blank 10 illustrated in Figure 1 could conveniently be made in the same manner.
.
~(;1 9SS51 United Kingdom Patent No. 997 552 teaches how a tubular blank with a thickened end portion can be formed into a non-oriented tube by expanding a core within the thickened portion to define an enlarged coupling socket.
Although it has consequently been known for some time that a streng-thened coupling socket can be formed at the end of a tube by expanding a tubular blank having a portion of greater wall thickness, it has not previously been proposed to use such a blank in the production of a pipe of oriented thermo-.~ plastic polymeric material manufactured, for instance, as taught in our United Kingdom Patent No. 1 432 539. The reason why we have not considered this possibility previously is that it was felt that the application of in-ternal pressure to a tubular blank of non-constant wall thickness would cause the thinner portion of the tube to expand in preference to the thicker por-tion and that the operation would either be comp~etely uncontrollable or it would not be possible to obtain a product which reflected thedimensional differences present in the blank. To the contrary, we have found that the process in our United Kingdom Paten-t No. 1 432 539 will expand, in a satis-factory controllable fashion, a tubular blank having a portion of greater ! wall thickness, and that the result is an orien-ted pipe having an integral socket of greater rigidity than has hitherto been possible.
The mould used to produce the blank 10 of Figure ] does not have to be split in the rnanner illustrated in the drawing. An alternative mould may be in the form of a tube with an end cap, giving a split at the socket - groove.
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., .
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Claims (17)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of forming a pipe of orientable thermoplastic polymeric material having an integral socket of enlarged internal diameter, including placing a tubular blank having a portion of greater wall thickness in a female mould of which a portion defines the integral socket, positioning the portion of greater wall thicknesses within said socket portion of the mould, heating the blank to a temperature at which deformation will induce orientation of the polymer molecules, applying internal pressure to the blank to expand it radially outwards against the mould whilst orienting the polymer molecules, the portion of greater wall thickness being expanded into the socket portion of the mould, cooling the moulded pipe to a rigid condition, then removing the applied internal pressure.
2. A method, as in claim 1, including heating the blank by means of a fluid at a suitable temperature.
3. A method, as in claim 2, including circulating the fluid between the blank and the mould and draining the fluid away before the blank is deformed against the mould.
4. A method, as in claim 2, including circulating the fluid through the bore of the blank,
5. A method, as in claim 3, including circulating the fluid through the bore of the blank,
6. A method, as in claim 4, including increasing the pressure of the fluid within the bore of the blank to cause the radially outward expansion.
7. A method, as in claim 5, including increasing the pressure of the fluid within the bore of the blank to cause the radially outward expansion.
8. A method, as in any of claims 1 to 3, including applying the internal pressure by compressed gas or liquid under pressure.
9. A method, as in claim 4 or 5, including applying the internal pressure by compressed gas or liquid under pressure.
10. A method, as in any of claims 1 to 3, including forming the blank with the portion of greater wall thickness by supporting a tube of constant thickness within a mould defining the portion of greater wall thickness, heating the tube to a moulding temperature, compressing the tube axially within the mould to form the portion of greater thickness, cooling the moulded blank, and removing the cooled moulded blank from the mould.
11. A method, as in any of claims 4 to 6, including forming the blank with the portion of greater wall thickness by supporting a tube of constant thickness within a mould defining the portion of greater wall thickness, heating the tube to a moulding temperature, compressing the tube axially within the mould to form the portion of greater thickness, cooling the moulded blank, and removing the cooled moulded blank from the mould.
12. A method, as in claim 7, including forming the blank with the portion of greater wall thickness by supporting a tube of constant thickness within a mould defining the portion of greater wall thickness, heating the tube to a moulding temperature, compressing the tube axially within the mould to form the portion of greater thickness, cooling the moulded blank, and removing the cooled moulded blank from the mould.
13. A method, as in any of claims 1 to 3, including a) forming the tubular blank with the portion of greater wall thickness by supporting a tube of constant thickness within a mould defining the portion of greater wall thickness, heating the tube to a moulding temperature, compressing the tube axially within the mould to form the portion of greater thickness, cooling the moulded blank, and removing the so formed cooled moulded tubular blank from the mould, and b) including forming the pipe of orientable thermoplastic polymeric material having an integral socket of enlarged internal diameter by applying the internal pressure to said so formed tubular blank by compressed gas or liquid under pressure.
14. A method, as in claim 4 or 5, including a) forming the tubular blank with the portion of greater wall thickness by supporting a tube of constant thickness within a mould defining the portion of greater wall thickness, heating the tube to a moulding temperature, compressing the tube axially within the mould to form the portion of greater thickness, cooling the moulded blank, and removing the so formed cooled moulded tubular blank from the mould, and b) including forming the pipe of orientable thermoplastic polymeric material having an integral socket of enlarged internal diameter by applying the internal pressure to said so formed tubular blank by compressed gas or liquid under pressure.
15. A pipe of oriented thermoplastic polymeric material having an integral socket of which the cross-sectional area is greater than the cross-sectional area taken through another portion of the pipe.
16. A pipe, as in claim 15, in which the thickness of the socket is equal to the wall thickness of the pipe.
17. A pipe, as in claim 15, in which the thickness of the socket is greater than the wall thickness of the pipe.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA287,557A CA1095551A (en) | 1977-09-27 | 1977-09-27 | Pipe of oriented thermoplastics polymeric material |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA287,557A CA1095551A (en) | 1977-09-27 | 1977-09-27 | Pipe of oriented thermoplastics polymeric material |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1095551A true CA1095551A (en) | 1981-02-10 |
Family
ID=4109636
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA287,557A Expired CA1095551A (en) | 1977-09-27 | 1977-09-27 | Pipe of oriented thermoplastics polymeric material |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1095551A (en) |
-
1977
- 1977-09-27 CA CA287,557A patent/CA1095551A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |