CA1081628A - Multi-layer pipe with single corrugation in inner wall - Google Patents
Multi-layer pipe with single corrugation in inner wallInfo
- Publication number
- CA1081628A CA1081628A CA311,689A CA311689A CA1081628A CA 1081628 A CA1081628 A CA 1081628A CA 311689 A CA311689 A CA 311689A CA 1081628 A CA1081628 A CA 1081628A
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- CA
- Canada
- Prior art keywords
- corrugation
- pipe
- layer
- helical
- seam
- 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
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- Rigid Pipes And Flexible Pipes (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A multi-layer, spirally wound tube or pipe product with a substantially smooth inner wall having a single, helical corru-gation and a corrugated exterior wall. The pipe has an inner pipe layer consisting of an elongated sheet of flat material curled into adjacent, helical convolutions and an outer pipe layer consisting of an elongated sheet of corrugated material curled into adjacent, helical convolutions about the inner pipe layer. The inner and outer pipe layers share a common helical seam. A single, continuous helical corrugation is located in the inner pipe layer along the helical seam, thereby causing the seam to be located within the single corrugation.
A multi-layer, spirally wound tube or pipe product with a substantially smooth inner wall having a single, helical corru-gation and a corrugated exterior wall. The pipe has an inner pipe layer consisting of an elongated sheet of flat material curled into adjacent, helical convolutions and an outer pipe layer consisting of an elongated sheet of corrugated material curled into adjacent, helical convolutions about the inner pipe layer. The inner and outer pipe layers share a common helical seam. A single, continuous helical corrugation is located in the inner pipe layer along the helical seam, thereby causing the seam to be located within the single corrugation.
Description
~0~ i28 MULTI-LAYER PIPE WIT~I
SINGLE CORRUGATION IN INNER WALL
SUMMARY OF THE INVENTION
The Bac~round This invention relates to spirally wound pipe products, and more particularly to a helical pipe having two or more pipe wall thicknesses, the inner wall of the pipe being generally smooth ~\ and the outer wall of the pipe being corrugated.
- It is well known to form spiral pipe from an elongated sheet of metal or other ductile material. Such pipe products are illus-trated, for example, in United States Patent Nos. 1,179,577;
SINGLE CORRUGATION IN INNER WALL
SUMMARY OF THE INVENTION
The Bac~round This invention relates to spirally wound pipe products, and more particularly to a helical pipe having two or more pipe wall thicknesses, the inner wall of the pipe being generally smooth ~\ and the outer wall of the pipe being corrugated.
- It is well known to form spiral pipe from an elongated sheet of metal or other ductile material. Such pipe products are illus-trated, for example, in United States Patent Nos. 1,179,577;
2,337,374; 3,106,177 and 3,132,616. Multi-layer spiral pipe is illustrated in United States Patent No. 3,340,901.
In the conventional apparatus for producing a helical pipe product, an elongated sheet of metal is impressed with longitudinal corrugations and then spiralled into adjacent, helical convolutions which are joined either by welding or by formation of a continuous lock seam. One apparatus for forming a spirally wound pipe product is illustrated in the applicant's Canadian application entitled "Spiral Pipe Formincl Machine With Device For Aligning Spiralling Rolls", Serial No. 273,181, filed March 4, 1977.
Many pipe products of the prior art, although exhibiting suffi-cient load bearing capacity to be used as a drainage culvert for highways and the like, suffer the disadvantage of having a non-smooth inner wall. For example, helically corrugated pipe producedby the apparatus of the applicant's above-identified patent or Freeze U.S. Patent No. 2,136,943 has helical corrugations in the inner wall as well. The result of a non-smooth inner wall is in~i-bition to fiow of liquids through the pipe, forcing the pipe user to :
~`? ;.~
-1- ~
~081628 select a larger diameter pipe than would be needed were the wall of the pipe smooth.
The prior art has recognized that the strength of a corrugated pipe in combination with a smooth inner wall is a favourable material combination. For example, Lombardi U.S.
Patent No. 3,340,901 has disclosed a pipe product formed from at least two layers of metal including a corrugated pipe outer shell and a smooth pipe inner shell.
However, prior art pipe of this nature generally suffers -~
the disadvantage of having a relatively weak juncture of adjacent convolutions of the pipe shell. Stressive forces inherent in a spirally wound pipe and experienced by a spirally wound pipe when buried beneath the earth tend to weaken the seam of the Lombardi pipe, requiring the pipe maker to employ greater thickness pipe material than otherwise would be necessary in order to obtain sufficient strength for the pipe seam.
~ .~
The Invention The above disadvantages of the prior art and others are overcome by the present invention which provides a multi-layer, spirally wound pipe having a smooth inner wall and corrugated outer wall which has a single corrugation in the inner wall of the pipe in which the helical seam of adjacent pipe convolutions is located.
Thus, according to the present invention, there is provided a multi-layer, spirally wound pipe with a substantially smooth interior wall having a single, helical corrugation in the inner wall and a corrugated exterior wall. The pipe comprises an inner pipe layer consisting of an elongated sheet of material curled into adjacent, helical convolutions, with the inner pipe layer convolutions being joined by a helical seam.
~ .
~ . . . . .
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A single, continuous helical corrugation is located in the inner pipe layer and has the same helix angle as the helical convolutions. The helical seam is located within the single corrugation on a neutral axis of the single corrugation. An outer pipe layer consisting of an elongated sheet of corrugated material is curled into adjacent, helical convolutions about the inner pipe layer, and the outer pipe layer convolutions are joined by a helical seam which is located on a neutral axis of a corrugation of the outer pipe layer. The helix angle of the helical convolutions of the outer pipe layer is substantially the same as the helix angle of the single corrugation, whereby the single corrugation lies within one of the corrugations of the outer pipe layer. ~ means joins the inner and outer pipe layers.
~ The invention also encompasses the novel method of forming a multi-layer, spirally wound pipe which has a single, helical corrugation located in the inner pipe wall, wherein the inner pipe wall is generally smooth between adjacent convolutions of the single corrugation. The process comprises longitudinally corrugating an elongated sheet of material, forming a multi-layer sheet by positioning a flat sheet in a contiguous layer upon the corrùgated sheet, with the edges of the sheets being generally coextensive, shaping a first portion of the single corrugation in one marginal edge of the multi-layer sheet, and shaping a second portion of the single corrugat-ion complementary to the first portion in the other marginal edge of the multi-layer sheet. The multi-layer sheet is spiralled into adjacent, helical convolutions having the first and second portions abutting to form the single corrugation, and the adjacent convolutions are joined along the corrugation
In the conventional apparatus for producing a helical pipe product, an elongated sheet of metal is impressed with longitudinal corrugations and then spiralled into adjacent, helical convolutions which are joined either by welding or by formation of a continuous lock seam. One apparatus for forming a spirally wound pipe product is illustrated in the applicant's Canadian application entitled "Spiral Pipe Formincl Machine With Device For Aligning Spiralling Rolls", Serial No. 273,181, filed March 4, 1977.
Many pipe products of the prior art, although exhibiting suffi-cient load bearing capacity to be used as a drainage culvert for highways and the like, suffer the disadvantage of having a non-smooth inner wall. For example, helically corrugated pipe producedby the apparatus of the applicant's above-identified patent or Freeze U.S. Patent No. 2,136,943 has helical corrugations in the inner wall as well. The result of a non-smooth inner wall is in~i-bition to fiow of liquids through the pipe, forcing the pipe user to :
~`? ;.~
-1- ~
~081628 select a larger diameter pipe than would be needed were the wall of the pipe smooth.
The prior art has recognized that the strength of a corrugated pipe in combination with a smooth inner wall is a favourable material combination. For example, Lombardi U.S.
Patent No. 3,340,901 has disclosed a pipe product formed from at least two layers of metal including a corrugated pipe outer shell and a smooth pipe inner shell.
However, prior art pipe of this nature generally suffers -~
the disadvantage of having a relatively weak juncture of adjacent convolutions of the pipe shell. Stressive forces inherent in a spirally wound pipe and experienced by a spirally wound pipe when buried beneath the earth tend to weaken the seam of the Lombardi pipe, requiring the pipe maker to employ greater thickness pipe material than otherwise would be necessary in order to obtain sufficient strength for the pipe seam.
~ .~
The Invention The above disadvantages of the prior art and others are overcome by the present invention which provides a multi-layer, spirally wound pipe having a smooth inner wall and corrugated outer wall which has a single corrugation in the inner wall of the pipe in which the helical seam of adjacent pipe convolutions is located.
Thus, according to the present invention, there is provided a multi-layer, spirally wound pipe with a substantially smooth interior wall having a single, helical corrugation in the inner wall and a corrugated exterior wall. The pipe comprises an inner pipe layer consisting of an elongated sheet of material curled into adjacent, helical convolutions, with the inner pipe layer convolutions being joined by a helical seam.
~ .
~ . . . . .
1C~81~:iZ~
A single, continuous helical corrugation is located in the inner pipe layer and has the same helix angle as the helical convolutions. The helical seam is located within the single corrugation on a neutral axis of the single corrugation. An outer pipe layer consisting of an elongated sheet of corrugated material is curled into adjacent, helical convolutions about the inner pipe layer, and the outer pipe layer convolutions are joined by a helical seam which is located on a neutral axis of a corrugation of the outer pipe layer. The helix angle of the helical convolutions of the outer pipe layer is substantially the same as the helix angle of the single corrugation, whereby the single corrugation lies within one of the corrugations of the outer pipe layer. ~ means joins the inner and outer pipe layers.
~ The invention also encompasses the novel method of forming a multi-layer, spirally wound pipe which has a single, helical corrugation located in the inner pipe wall, wherein the inner pipe wall is generally smooth between adjacent convolutions of the single corrugation. The process comprises longitudinally corrugating an elongated sheet of material, forming a multi-layer sheet by positioning a flat sheet in a contiguous layer upon the corrùgated sheet, with the edges of the sheets being generally coextensive, shaping a first portion of the single corrugation in one marginal edge of the multi-layer sheet, and shaping a second portion of the single corrugat-ion complementary to the first portion in the other marginal edge of the multi-layer sheet. The multi-layer sheet is spiralled into adjacent, helical convolutions having the first and second portions abutting to form the single corrugation, and the adjacent convolutions are joined along the corrugation
- 3 -16~8 portions to form the multi-layer pipe and complete the single corrugation. The joining of the adjacent convolutions includes the step of forming the juncture of the corrugation portions on a neutral axis of the single corrugation.
Preferably, and in order to obtain a sufficiently strong helical seam, the helical seams of the inner and outer pipe convo-lution are formed as a common double lock seam located within the single corrugation in the inner pipe layer convolutions. The lock seam is normally located on a neutral axis of the single corrugation in order to reduce to a minimum the stressive forces which tend to cause the pipe to unravel or weaken along the lock seam.
With the lock seam located in the single helical con-volution, i~ is located beneath the "sight-line" of the inner surface of the pipe, out of the path of liquids which may flow through the pipe. Additionally, the lock seam fills a portion of the inner corrugation, thereby reducing the turbulent flow which would otherwise be expected from an inner corrugation in the pipe.
The distance between adjacent convolutions of the inner corrugation vary depending on the width of the elongated sheets used to manufacture the pipe. The wall of the pipe between such corrugation convolutions is normally smooth, so that the inner ~.
108~ 8 pipe wall presents a generally smooth surface to liquids and reduces turbulent flow characteristics to the least possible minimum.
BRIEF DESCRIPTION OF THE DRAWING
The invention will be described in greater detail with reference to the drawing, in which:
Figure 1 is a schematic representation of a portion of a pipe product according to the invention, and Figure 2 is a broken section taken along lines 2-2 of Figure 1.
DETAILED DESCRIPTION OF THE INVENTION
.
Turning now to the drawing, a tube or pipe according to the invention is generally designated 10. The pipe illustrated is composed of a pair of elongated sheets of ductile material, such as galvanized steel, which are formed into adjacent, helical convolutions. As illustrated, the inner wall of the pipe is formed from a generally flat sheet 12, while the outer wall of the pipe is composed of a corrugated sheet 14. Adjacent convolutions of the sheets 12 and 14 are joined in a common double lock seam 16.
In a first embodiment of the invention,as shown in greater detail in Figure 2, the inner wall of the pipe 10 is generally smooth along the surface of the sheet 12, excepting a single helical corrugation 18 formed in the pipe at the juncture of adjacent helical convolutions. The lock seam 16 is formed on a neutral axis of the single corrugation 18, that portion of the corrugation between a hill 20 and a valley 22. If desired, and although not illustrated, the lock seam 16 can as easily be located between the valley 22 and a second hill 24 of the cor-rugation 18, so long as the lock seam 16 is located on theneutral axis.
~Q81~iZ8 The purpose of the single corrugation 18 is to assur~
that the lock seam 16 is located on a neutral axis. When the pipe 10 is buried in use, stressive forces act along a line running between the hill 20 and ~alley 22, tending to compress or extend the lock seam 16 at its strongest point, across the folded-over portions of the lock seam. Were the single corrugation 18 omitted and the lock seam 16 formed along the inner surface of the flat sheet 12, stressive forces would tend to bow the seam 16, helping cause failure of the pipe 10 along the seam.
As further illustrated in Figure 2, all portions of the sheet 12 between adjacent convolutions of the corrugation 18 are generally flat, and rest upon hills 26 of the corrugated sheet 14. Therefore, the inner surface of the pipe 10, with the exception of the single corrugation 18, is smooth.
The lock seam 16 is formed as illustrated with a heel 28 and a heel 30 located adjacent opposite ends of the seam 16 to strengthen the seam. Also, as illustrated, the material of the seam 16, aLthough below the "sight-line" of the inner surface of the pipe 10, occupies and fills a portion of the corrugation 18. Therefore, the seam 16 aids in reducing tur-bulent flow characteristics caused by pro~ision of the single corrugation 18 in an otherwise smooth inner wall of the pipe 10.
One method for construction of the pipe 10 is described in the applicant's co-pending Canadian Patent Application No.
311,688, entitled "Method and Apparatus for Making Multi-Layer Spiral Pipe", filed September 20, 1978. The pipe 10 may be made by first impressing corrugations in a flat sheet of material to form the corrugated sheet 14, lying the flat sheet 12 upon the corrugated sheet 14, and then forming portions of the single corrugation 18 in opposite marginal edges of the multi-layer sheet. At the same time, portions of the seam 16 may be formed 1(~816~
in the sheet along the portions of the corrugation 18.
After the layered sheets are suitably prepared, the sheets are curled into adjacent, helical convolutions and lock seam portions interengaged and formation of the double lock seam 16 completed. The pipe is then cut to desired lengths by a suitable severance mechanism. Preferably, and as illus-trated in the applicant's United States Patent No. 3,815,455, severance of succeeding pipe sections is accomplished by a flying saw.
Changes may be made to the foregoing multi-layer pipe without departing from the spirit thereof. For example, the lock seam 16 may be omitted and a welded seam formed in its place along a neutral axis of the corrugation 18. The scope of the invention is defined by the following claims.
: ' :
~ *~ 7 -~81f~Z8 SUPPLEMENTARY DISCLOSURE
A further description of the details of the invention will be observed with reference to the additionaI drawing, wherein:
Figure 3 is a broken section of a modification of the pipe shown in Figure 2.
Figure 3 illustrates a second embodiment of the invention modified somewhat from that shown in Figure 2 and being parti-cularly useful for pipe having deep corrugations in the outer wall, such as that having corrugations on the order of one inch deep, which consequentially have a large neutral axis.
As shown in Figure 3, the inner wall of the pipe 10 is composed of curled convolutions of a sheet 12 which is generally smooth with the exception of a single helical corrugation 32 formed in the inner wall at the juncture of adjacent helical convolutions. In this embodiment of the invention, the single hèlical corrugation 32 is not fully coextensive with the external corrugation 34 of the corrugated sheet 14 forming the outer wall of the pipe in which the corrugation 32 is located.
As shown, a common double lock seam 16' joins adjacent convolutions of the sheets 12 and 14. In this embodiment, due to the depth of the external corrugation 34, and due to the relatively shallow depth of the single corrugation 32, the lock seam 16', while formed on a neutral axis of both the single corrugation 32 and the external corrugation 34, is adjacent a common hill 38 shared by the corrugations 32 and 34. Hence, the neutral axis of the corrugation 32 in which the seam 16' is located is coextensive with a portion of the neutral axis of the corrugation 34 of the outer layer which shares the seam 16'. The remaining portions of the corrugation 32 are located within but not coextensive with the corrugation 34. The result is a single corrugation 32 in the inner wall of the pipe 10 having approximately the same depth as the single corrugation 18 shown in Figure 2, but the outer wall of the J~
. - pipe having a deeper corrugation profile for added strength and rigidity.
In the same manner as shown in Figure 2, the material of the lock seam 16' is below the "sight line" of the inner surface of the pipe 10. Since the seam occupies and fills a portion of the single corrugation 32, the seam aids in reducing turbulent flow characteristics caused by the provision of the single corrugation 32 in an otherwise smooth inner wall of the pipe 10.
It should be recognized that although the neutral axis of the corrugation 32, opposite the neutral axis in which the seam 16' is located, is shown to be of the same general pitch as that in which the seam is located, the pitch of the opposite neutral axis can be substantially steepened, and even vertical or greater, so long as the common seam 16' ~ remains located on a neutral axis of both the corrugations 32 and 34. Thus, the pitch of the right-hand portion of the corrugation 32 (as shown in Figure 3) may be changed from that shown without altering pipe strength, but with the possible benefit of reduced turbulent flow through the pipe 10.
By providing a relatively shallow single corrugation 32 in the inner wall of the pipe 10 with the outer wall of the pipe having substantially deeper external corrugations, turbulent flow characteristics caused by the provision of the single corrugation 32 are reduced to a minimum, yet the strength of the pipe is not at all compromised from that shown in Figure 2, since the lock seam 16' is located on a neutral axis, and therefore stressive forces act along the common neutral axis shared by the corrugations 32 and 34, tending to compress or extend the lock seam 16' at its strongest point, along the folded-over portions of the seam.
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Preferably, and in order to obtain a sufficiently strong helical seam, the helical seams of the inner and outer pipe convo-lution are formed as a common double lock seam located within the single corrugation in the inner pipe layer convolutions. The lock seam is normally located on a neutral axis of the single corrugation in order to reduce to a minimum the stressive forces which tend to cause the pipe to unravel or weaken along the lock seam.
With the lock seam located in the single helical con-volution, i~ is located beneath the "sight-line" of the inner surface of the pipe, out of the path of liquids which may flow through the pipe. Additionally, the lock seam fills a portion of the inner corrugation, thereby reducing the turbulent flow which would otherwise be expected from an inner corrugation in the pipe.
The distance between adjacent convolutions of the inner corrugation vary depending on the width of the elongated sheets used to manufacture the pipe. The wall of the pipe between such corrugation convolutions is normally smooth, so that the inner ~.
108~ 8 pipe wall presents a generally smooth surface to liquids and reduces turbulent flow characteristics to the least possible minimum.
BRIEF DESCRIPTION OF THE DRAWING
The invention will be described in greater detail with reference to the drawing, in which:
Figure 1 is a schematic representation of a portion of a pipe product according to the invention, and Figure 2 is a broken section taken along lines 2-2 of Figure 1.
DETAILED DESCRIPTION OF THE INVENTION
.
Turning now to the drawing, a tube or pipe according to the invention is generally designated 10. The pipe illustrated is composed of a pair of elongated sheets of ductile material, such as galvanized steel, which are formed into adjacent, helical convolutions. As illustrated, the inner wall of the pipe is formed from a generally flat sheet 12, while the outer wall of the pipe is composed of a corrugated sheet 14. Adjacent convolutions of the sheets 12 and 14 are joined in a common double lock seam 16.
In a first embodiment of the invention,as shown in greater detail in Figure 2, the inner wall of the pipe 10 is generally smooth along the surface of the sheet 12, excepting a single helical corrugation 18 formed in the pipe at the juncture of adjacent helical convolutions. The lock seam 16 is formed on a neutral axis of the single corrugation 18, that portion of the corrugation between a hill 20 and a valley 22. If desired, and although not illustrated, the lock seam 16 can as easily be located between the valley 22 and a second hill 24 of the cor-rugation 18, so long as the lock seam 16 is located on theneutral axis.
~Q81~iZ8 The purpose of the single corrugation 18 is to assur~
that the lock seam 16 is located on a neutral axis. When the pipe 10 is buried in use, stressive forces act along a line running between the hill 20 and ~alley 22, tending to compress or extend the lock seam 16 at its strongest point, across the folded-over portions of the lock seam. Were the single corrugation 18 omitted and the lock seam 16 formed along the inner surface of the flat sheet 12, stressive forces would tend to bow the seam 16, helping cause failure of the pipe 10 along the seam.
As further illustrated in Figure 2, all portions of the sheet 12 between adjacent convolutions of the corrugation 18 are generally flat, and rest upon hills 26 of the corrugated sheet 14. Therefore, the inner surface of the pipe 10, with the exception of the single corrugation 18, is smooth.
The lock seam 16 is formed as illustrated with a heel 28 and a heel 30 located adjacent opposite ends of the seam 16 to strengthen the seam. Also, as illustrated, the material of the seam 16, aLthough below the "sight-line" of the inner surface of the pipe 10, occupies and fills a portion of the corrugation 18. Therefore, the seam 16 aids in reducing tur-bulent flow characteristics caused by pro~ision of the single corrugation 18 in an otherwise smooth inner wall of the pipe 10.
One method for construction of the pipe 10 is described in the applicant's co-pending Canadian Patent Application No.
311,688, entitled "Method and Apparatus for Making Multi-Layer Spiral Pipe", filed September 20, 1978. The pipe 10 may be made by first impressing corrugations in a flat sheet of material to form the corrugated sheet 14, lying the flat sheet 12 upon the corrugated sheet 14, and then forming portions of the single corrugation 18 in opposite marginal edges of the multi-layer sheet. At the same time, portions of the seam 16 may be formed 1(~816~
in the sheet along the portions of the corrugation 18.
After the layered sheets are suitably prepared, the sheets are curled into adjacent, helical convolutions and lock seam portions interengaged and formation of the double lock seam 16 completed. The pipe is then cut to desired lengths by a suitable severance mechanism. Preferably, and as illus-trated in the applicant's United States Patent No. 3,815,455, severance of succeeding pipe sections is accomplished by a flying saw.
Changes may be made to the foregoing multi-layer pipe without departing from the spirit thereof. For example, the lock seam 16 may be omitted and a welded seam formed in its place along a neutral axis of the corrugation 18. The scope of the invention is defined by the following claims.
: ' :
~ *~ 7 -~81f~Z8 SUPPLEMENTARY DISCLOSURE
A further description of the details of the invention will be observed with reference to the additionaI drawing, wherein:
Figure 3 is a broken section of a modification of the pipe shown in Figure 2.
Figure 3 illustrates a second embodiment of the invention modified somewhat from that shown in Figure 2 and being parti-cularly useful for pipe having deep corrugations in the outer wall, such as that having corrugations on the order of one inch deep, which consequentially have a large neutral axis.
As shown in Figure 3, the inner wall of the pipe 10 is composed of curled convolutions of a sheet 12 which is generally smooth with the exception of a single helical corrugation 32 formed in the inner wall at the juncture of adjacent helical convolutions. In this embodiment of the invention, the single hèlical corrugation 32 is not fully coextensive with the external corrugation 34 of the corrugated sheet 14 forming the outer wall of the pipe in which the corrugation 32 is located.
As shown, a common double lock seam 16' joins adjacent convolutions of the sheets 12 and 14. In this embodiment, due to the depth of the external corrugation 34, and due to the relatively shallow depth of the single corrugation 32, the lock seam 16', while formed on a neutral axis of both the single corrugation 32 and the external corrugation 34, is adjacent a common hill 38 shared by the corrugations 32 and 34. Hence, the neutral axis of the corrugation 32 in which the seam 16' is located is coextensive with a portion of the neutral axis of the corrugation 34 of the outer layer which shares the seam 16'. The remaining portions of the corrugation 32 are located within but not coextensive with the corrugation 34. The result is a single corrugation 32 in the inner wall of the pipe 10 having approximately the same depth as the single corrugation 18 shown in Figure 2, but the outer wall of the J~
. - pipe having a deeper corrugation profile for added strength and rigidity.
In the same manner as shown in Figure 2, the material of the lock seam 16' is below the "sight line" of the inner surface of the pipe 10. Since the seam occupies and fills a portion of the single corrugation 32, the seam aids in reducing turbulent flow characteristics caused by the provision of the single corrugation 32 in an otherwise smooth inner wall of the pipe 10.
It should be recognized that although the neutral axis of the corrugation 32, opposite the neutral axis in which the seam 16' is located, is shown to be of the same general pitch as that in which the seam is located, the pitch of the opposite neutral axis can be substantially steepened, and even vertical or greater, so long as the common seam 16' ~ remains located on a neutral axis of both the corrugations 32 and 34. Thus, the pitch of the right-hand portion of the corrugation 32 (as shown in Figure 3) may be changed from that shown without altering pipe strength, but with the possible benefit of reduced turbulent flow through the pipe 10.
By providing a relatively shallow single corrugation 32 in the inner wall of the pipe 10 with the outer wall of the pipe having substantially deeper external corrugations, turbulent flow characteristics caused by the provision of the single corrugation 32 are reduced to a minimum, yet the strength of the pipe is not at all compromised from that shown in Figure 2, since the lock seam 16' is located on a neutral axis, and therefore stressive forces act along the common neutral axis shared by the corrugations 32 and 34, tending to compress or extend the lock seam 16' at its strongest point, along the folded-over portions of the seam.
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Claims (10)
1. A multi-layer, spirally wound pipe with a sub-stantially smooth interior wall having a single, helical corrugation in the inner wall and a corrugated exterior wall, comprising a. an inner pipe layer consisting of an elongated sheet of material curled into adjacent, helical con-volutions, said inner pipe layer convolutions being joined by a helical seam, b. a single, continuous helical corrugation located in said inner pipe layer having the same helix angle as said helical convolutions, said helical seam being located within said single corrugation on a neutral axis of said single corrugation, c. an outer pipe layer consisting of an elongated sheet of corrugated material curled into adjacent, helical convolutions about said inner pipe layer, said outer pipe layer convolutions being joined by a helical seam, said seam being located on a neutral axis of a corrugation of said outer pipe layer, d. the helix angle of the helical convolutions of said outer pipe layer being substantially the same as the helix angle of said single corrugation, whereby said single corrugation lies within one of the corrugations of said outer pipe layer, and e. means joining said inner and outer pipe layers.
2. A pipe according to Claim 1 in which the pitch and depth of said single corrugation are essentially the same as the pitch and depth of the corrugations of said outer pipe layer, thereby forming a concurrent unitary corrugation of said single corrugation and said one corrugation.
3. A pipe according to Claim 1 in which the helical seam of said inner pipe layer convolutions is a lock seam.
4. A pipe according to Claim 1 in which said inner and outer pipe layer convolutions are joined by a common helical seam.
5. A pipe according to Claim 4 in which said common helical seam is a double lock seam.
6. A pipe according to Claim 4 in which said common helical seam comprises said joining means.
7. A pipe according to Claim 1 in which said neutral axis of said single corrugation is coextensive with at least à portion of a neutral axis of one of the corrugations of said outer pipe layer.
8. A pipe according to Claim 7 in which said inner and outer layers are joined at said coextensive neutral axes.
9. A multi-layer, spirally wound pipe having a single, helical corrugation located in the inner pipe wall, said inner pipe wall being generally smooth between adjacent convolutions of said single corrugation, formed by the process of a. longitudinally corrugating an elongated sheet of material, b. forming a multi-layer sheet by positioning a flat sheet in a contiguous layer upon the corrugated sheet, with the edges of said sheets being generally coextensive, c. shaping a first portion of the single corrugation in one marginal edge of the multi-layer sheet, d. shaping a second portion of the single corrugation complementary to said first portion in the other marginal edge of said multi-layer sheet, e. spiralling the multi-layer sheet into adjacent, helical convolutions having said first and second portions abutting to form said single corrugation, and f. joining the adjacent convolutions along said corrugation portions to form the multi-layer pipe and complete said single corrugation, said joining of said adjacent convolutions including the step of forming the juncture of said corrugation portions on a neutral axis of said single corrugation.
10. A pipe according to Claim 9 in which the step of forming the juncture of the adjacent colvulutions includes the step of forming a double lock seam on a neutral axis of said single corrugation.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US86714078A | 1978-01-05 | 1978-01-05 | |
| US867,140 | 1978-01-05 | ||
| US06/025,201 US4220181A (en) | 1979-03-29 | 1979-03-29 | Multi-layer pipe with single corrugation in inner wall |
| US25,201 | 1979-03-29 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1081628A true CA1081628A (en) | 1980-07-15 |
Family
ID=26699429
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA311,689A Expired CA1081628A (en) | 1978-01-05 | 1978-09-20 | Multi-layer pipe with single corrugation in inner wall |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1081628A (en) |
-
1978
- 1978-09-20 CA CA311,689A patent/CA1081628A/en not_active Expired
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