TECHNICAL FIELD

[001] The present application relates to corrugated pipe and in particular to corrugated pipe having a coupling configured to accommodate limited after installation movement of connected pipe sections.

BACKGROUND

[002] Double wall corrugated pipe is formed to include a male/female connection for connecting two pipe sections. Such corrugated pipe is extensively used in water drainage applications, however it also has application in other fields. Double wall corrugated pipe is well known and is manufactured using two streams of extruded plastic with one stream of plastic forming an outer corrugated surface and a second stream of plastic forming an inner smooth wall of the pipe. The outer corrugations are connected to the inner smooth wall of the pipe and significantly contribute to the structural properties of the pipe. It is also known to apply a further outer wall connected to the corrugated wall to form triple wall corrugated pipe.

[003] A male/female connection is used to join pipe sections with each pipe section having a female connector at one end of the pipe section and a male connector at an opposite end of the pipe section. Typically the pipe is manufactured in a continuous process and the pipe sections are cut inline as part of the manufacture process to produce the separate independent pipe sections. Male/female connection mold blocks are appropriately inserted to form these components. [004] Conventional double wall pipe has the male and female connectors molded as part of the pipe section to form a unitary structure. It is also known to attach injection molded connectors to corrugated pipe sections although this process is more involved and time consuming. The known male/female connectors are designed to have a full insertion of the male connector such that the male connector bottoms out against or is in abundance with a restricting inner surface of the female connector. The structure of the male and female connectors can be quite complex as the overall strength rating of the pipe is often determined by the strength of the pipe connection.

[005] The present invention utilizes a male/female connection capable of accommodating limited additional inward movement of the male component relative to the female component if required after installation of the pipe, and preferably or alternatively the male/female connection also accommodates limited partial withdrawal of the components after installation while maintaining a satisfactory connection. In a preferred embodiment, the connecting components have an initial centered position that is used to form the initial connection during pipe installation. With this arrangement the connected pipe sections after installation can accommodate limited inward movement between two connected pipe sections and/or limited partial separation of these components. The advantage of such a connection can be appreciated in installations that may be subject to future ground movement such as ground settling, pipe repair, pipe inspection or other natural events such as earthquakes. The pipe connection has a range of movement and a satisfactory connection is provided throughout the range. SUMMARY

[006] According to the invention, a male/female connection joins a first corrugated pipe section to a second corrugated pipe section with the first corrugated pipe section having a male connector of the male/female connection and the second corrugated pipe section having a female connector of the male/female connection. The male connector includes an elongate spigot and the female connector includes an elongate receiving socket engaging and overlapping with the elongate spigot to form a satisfactory pipe connection between the first and second pipe sections. The elongate spigot is movable relative to the elongate receiving socket through a range of movement, allowing the elongate spigot to move further into the elongate receiving socket increasing the overlap between the elongate spigot and the elongate receiving socket, or to move outwardly decreasing the overlap between the elongate spigot and the elongate receiving socket while maintaining the satisfactory pipe connection throughout the range of movement.

[007] In an aspect of the invention, the female connector includes a covering cuff that receives an end segment of the first pipe section. The end segment is of a circumference greater than the elongate spigot and is connected to the elongate spigot at an inward end of the elongate spigot. The covering cuff overlaps with the end segment and a projecting portion of the elongate spigot extends outwardly from the elongate receiving socket to protect a cavity defined between the end segment and an entrance to the elongate receiving socket that is bound in a radial direction by the covering cuff. The cavity accommodates movement of the elongate spigot further into the elongate receiving socket and movement of the end segment into the cavity. [008] In a further aspect of the invention, the elongate spigot is of a length equal to or greater than a length of the first pipe section that includes two corrugations.

[009] In a preferred aspect of the invention, the range of movement is at least 100mm and preferably the corrugated pipe sections are of a double wall type.

[0010] In a preferred aspect of the invention, the covering cuff is of a length to cover any projecting length of the elongate spigot and a portion of the end segment throughout the range of movement.

[0011] According to an aspect of the invention, the elongate spigot is of a single wall thickness defined by two layers of connected plastic. Preferably the covering cuff receives corrugations of the first pipe section and is of a length to receive at least 3 corrugations of the first pipe section.

[0012] According to a third aspect of the invention, the range of movement is greater than an average spacing between adjacent corrugations of the first pipe section.

[0013] The present invention, in a preferred embodiment, is directed to first and second corrugated pipe sections connected by a male connector of the first pipe section received in a female connector of the second pipe section and each pipe section is of at least a double wall configuration having an inner wall defining a tubular passage through the pipe section reinforced by a connected outer corrugated wall attached to the inner wall. The male connector includes an elongate spigot portion forming a projecting extension of the inner wall of the first pipe section partially received in an outwardly stepped socket of the second pipe section. The outwardly stepped socket of the second pipe section includes an inner wall about the spigot portion with a majority of the spigot portion overlapping with the stepped socket. The stepped socket is reinforced by a connected corrugated outer wall and the female connection at a free end of the second pipe section includes a cuff portion overlapping with a corrugated section of the first pipe section that is immediately adjacent the spigot portion and is received in the cuff portion. The first stepped portion at an inner end thereof extends beyond the spigot portion and the spigot portion at an inner end extends into the cuff portion to accommodate further inward movement of the spigot portion and the corrugated section of the first pipe section if required. The spigot portion overlaps with the stepped socket sufficiently to allow partial separation of the spigot portion from the stepped socket if required while maintaining the male/female connection of the pipe sections. A corrugated pipe section according to a preferred embodiment of the present invention has a generally smooth inner tubular wall and an outer wall defining a first series of corrugations attached to and forming a reinforcing wall about the inner tubular wall. The corrugated pipe section has a female connector at one end of the corrugated pipe section and a male connector at an opposite end of the corrugated pipe section. The male connector is of a size for insertion in the female connector. The male connector includes an elongate spigot portion having an inner surface sized to correspond to an inner surface of the smooth inner tubular wall of the corrugated pipe section. The male connector includes at one end of the elongate spigot portion a second series of corrugations of a reduced exterior size relative to the first series of corrugation. The second series of corrugations transition to the first series of corrugations at a junction of the male connector and the long corrugated section. The female connector is at a junction between the long corrugated sections and the female connector includes a first stepped portion of a length corresponding to a length of the spigot portion and sized to receive the spigot portion. The first stepped portion merges with and is outwardly stepped relative to the inner tubular wall of the corrugated pipe section. The first stepped portion then merges with an outer cuff of a length and size capable of receiving the second series of corrugations.

[0015] In an aspect of the invention the outer cuff has an outer edge generally aligned with the outer edge of the corrugated pipe section.

[0016] In another aspect of the invention the first stepped portion has a centered position in an axial length of the connection corresponding to an installation initial position of the spigot portion within the female connector. This centered position allows for limited additional inward movement of the spigot portion into the first stepped portion or limited partial withdrawal of the spigot portion from the centered position while maintaining the integrity of the male/female connection between two connected sections of corrugated pipe.

[0017] According to an aspect of the invention a visual identification arrangement is associated with the male connector or the female connector and provides guidance when connected components are generally in the centered position.

[0018] In an aspect of the invention, the first stepped portion includes a recess seal cavity immediately adjacent to the second stepped portion with the recess seal cavity radially opening into the interior of corrugated pipe section.

[0019] According to an aspect of the invention, the recess seal cavity includes a separate wiper seal located therein. [0020] In a preferred aspect of the invention, the second series of corrugations of the male connector include at least one corrugation with a recessed exterior surface forming a wiper seal seat for a separate ring seal.

[0021] In an aspect of the invention an end of the spigot portion is spaced from an inner end of the first stepped portion at least 75mm when the spigot and the first stepped portion are in the centered position.

DESCRIPTION OF DRAWINGS

[0022] Preferred embodiments of the invention are shown in the drawings, wherein:

[0023] Figure 1 is a partial side view through one wall of two corrugated pipe sections that are joined by male/female connection components;

[0024] Figure 2 is a view similar to Figure 1 showing the position of two cuts used to separate the two pipe sections and to form the end of the female connection and the end of the male connection;

[0025] Figure 3 shows the cut pipe sections of Figure 2 with the male connection inserted into the female connection and with these components located in a centered position;

[0026] Figures 4, 5 and 6 are similar to Figures 1, 2 and 3 however the pipe sections include an outer wall forming a triple wall corrugated pipe and a triple wall cuff of the female connection;

[0027] Figures 7, 8 and 9 are similar to Figures 1, 2 and 3 however in these embodiments the cuff of the female connection is of a single wall thickness; [0028] Figure 10 is a partial sectional view of mold blocks and an extrusion die for forming of the male/female connection of the corrugated pipe;

[0029] Figure 1 1 is a view similar to Figure 10 where the mold blocks have advanced; and

[0030] Figure 12 shows the male/female connection in a centered assembled configuration where the cuff connection is slightly greater than the diameter of the corrugated pipe.

DETAILED DESCRIPTION

[0031] A continuous length of corrugated pipe 2 is schematically shown in Figure 1 as manufactured and before cutting into corrugated pipe sections. The corrugated pipe 2 includes two long corrugated pipe sections 4 joined by the formed female connector 14 and male connector 18. The female connector 14 is separated from the male connector 18 by a cut-out portion 17 that is removed and recycled as part of the manufacturing process. The male connector 18 and the female connector are shown in the male/female connection 11.

[0032] The corrugated pipe sections 4 preferably each include a smooth inner wall 6 and an outer corrugated wall 8 formed by a first series of corrugations 10. The first series of corrugations 10 at an inner edge merge and connect with the smooth inner wall 6. The female connector 14 is provided at the first end 12 of the first pipe section. The male connector 18 is provided at the second end 14 of the following pipe section. Preferably each pipe section 4 includes a female connector at one end and a male connector at an opposite end of a unitary construction.

[0033] The female connector 14 and the male connector 18 have been configured to accommodate a limited range of movement of the male connector within the female connector after the pipe has been installed. Preferably the male and female connectors, as will be described with respect to Figure 3, have a centered position which is easily recognized during initial installation of the corrugated pipe sections. It is desirable with respect to the flow characteristics of the connected pipe sections for many applications that the connected pipe provide a generally smooth interior surface for the fluid to flow through the pipe connection. Previously the male/female connection has a male connector fully received in a female connector to define an installed position where the end of the male connector is in abutment with an inner surface of the female connector such that further inward movement of the male connector is not possible. In addition in the prior art structures partial withdrawal of the male connector may present a significant gap causing fluid flow disturbance and/or seal problems and in most cases loss of the designed structural integrity of the connection.

[0034] To overcome these disadvantages, the present invention uses a male connector having an extended spigot 20 that is received within an oversized in length first stepped portion 34 of the female connector. As shown in the initial install position, the male/female components are installed in the centered position of Figure 3. The spigot portion 20 is spaced from and not in abutment with an inner end face of the female connector. A gap 50 is provided between the end 25 of the elongate spigot 20 and inner end 35 of the first stepped portion 34. The first stepped portion 34 and the elongate spigot 20 are each of a length to provide a substantial overlap in all positions within a designed range of movement. The elongate spigot is able to move in the length of the first stepped portion 34 while maintaining sufficient overlap to maintain the structural integrity of the male/female connection.

[0035] It can be seen in Figure 3 that gap 50 allows for limited inward movement of the elongate spigot 20 along the first stepped portion 34 before any abutment of the components occurs (one end of the range of movement). The spigot portion is separated from the inner end 35 of the first stepped portion a desired distance for example 75 to 125 mm when the elongate spigot is in the centered position as shown in Figure 3. Similarly the overlap of the first step portion and the elongate spigot 20 is preferably of a length to accommodate partial withdrawal of the spigot portion a similar distance while still maintaining an effective overlap of the spigot portion with the first stepped portion. It is apparent from the above description that this range of movement could be in one direction only or in a non-equal distribution.

[0036] These components can be designed to accommodate a specified movement and the limits of 75 mm to 125 mm are provided as guidance with respect to a common design requirement but the present invention is not limited to this preferred range.

[0037] In the embodiment shown in Figure 3, seal 60 is provided in a recess 62 of the first stepped portion. This ring type seal can be used to provide partial sealing between the first stepped portion and the spigot portion, and it can also be used to provide an indication with respect to whether the spigot portion has been centered in the appropriate initial installation position relative to the first stepped portion 34. For illustration purposes two further seals 63 are shown however seals 63 are an alternative to seal 62. Seals 63 are in recesses 65 of the first two corrugations however one or more seals could be in the gaps between corrugations received in the cuff 19 of the female connector 14.

[0038] The centered position can be indicated by alignment of certain surfaces and/or a physical neutral bias can be provided at the centered position. Various known approaches can be used to indicate a desired relative position of components. The preferred or recommended installation is based on a flow direction and this flow direction would be from right to left in Figure 3.

[0039] With respect to identifying a centered position it can be appreciated that the free end 41 of the second stepped portion 40 can be used in combination with one of the second series of corrugations 22 of the male connection 18 to identify the desired position. One of these corrugations can include a mark used to align the end 41 with that particular corrugation to indicate that the spigot portion has been appropriately centered.

[0040] The second series of corrugations can also include recessed portions 65 in the exterior surface to receive a ring seal member such as 63.

[0041] With the male/female connection in the centered position of Figure 3, the two connected corrugated sections are joined in an end to end manner by the male connector of one pipe section inserted in the female connector of the other pipe section generally in the desired centered position. This connection allows for limited inward movement of the elongate spigot in a compressive type displacement or partial withdrawal of the elongate spigot while still maintaining the integrity of the male/female connection. The amount of movement accommodated is a design feature of the male/female connection and may vary with particular applications. One effective range is at least 75 mm in either direction from the centered position. The actual distance accommodated is a function of the overlap and length of the spigot portion and the first stepped portion. Given that the spigot portion 20 is preferably of a double wall thickness, and the cuff in the area of the first stepped portion 34 includes both an inner wall and a corrugated outer wall, the strength of the male/female connection is quite high throughout the range. Similarly, the strength of the male/female connection between the second stepped portion and the second series of corrugations 22 of the male connector also provides a high strength connection similar to the overall strength of the corrugated pipe.

[0042] Figures 1 through 3 show a double layer cuff 19 of a double wall thickness and can include its own small corrugations 45.

[0043] Figures 4, 5 and 6 are similar to Figures 1 through 3 and shown an alternate embodiment where the corrugated pipe, rather than being double wall corrugated pipe, is triple wall corrugated pipe. The cuff 19 again includes the first stepped region and the second stepped region however additional strength is provided in that a third outer wall 78 has been applied to the corrugations. In addition to the cut-out area 17, a second cut-out of the third wall, namely the outer wall, is provided to expose the male connector 18. The structure of Figures 4 through 6 provides additional strength while still allowing for the after installation movement of the male/female connection if required.

[0044] Figures 7, 8, and 9 show a further embodiment where the cuff 19 defined by second stepped region of the female connector 14 is of a single wall thickness as the inner wall is removed in area 21 as shown in Figure 8. Again, this structure provides for limited after installation movement of the pipe sections inwardly or outwardly from each other.

[0045] The corrugated pipe sections of Figures 19 through 9 are shown with a male/female connection where the outer surface of the female connector is at the same radial position as the outer wall of the corrugated pipe. This is desirable as the pipe can be installed in a trench having a consistent depth. It is possible to use a bell mouth and spigot type connection where the female connector is somewhat larger than the outer diameter of the pipe (see Figures 10 to 12). The advantages of the coupling connection being tolerant of limited inward or outward movement is also effective with the bell mouth connector and in some applications this type of connector may be preferred. Additional size may also allow for additional design strength of the connection if required.

[0046] The sectional view of Figure 10 shows the extruder 100 having die outlets 102 and 104 used to extrude envelopes of plastic 106 and 108 used to form an outer corrugated wall and an inner smooth wall 151 of the double wall corrugated pipe. The series of mold blocks 120 define the outer corrugated wall 153 of the double wall corrugated pipe. The second envelope of plastic 108 forms the inner wall of the double wall corrugated pipe and is in engagement on the interior surface with the sizing die 122 that may also be a cooling die.

[0047] During the forming of the long corrugated pipe sections, the mold blocks passing the die outlets 106 and 108 will be of the type shown as 130 and 132 where the outer corrugations of the corrugated pipe are consistent and a smooth inner tubular wall of the double wall corrugated pipe is formed. Mold blocks 123, 124, 126 and 128 essentially define the configuration of the male/female connection.

[0048] Mold block 132 in the embodiment of Figure 10 forms corrugations of the pipe section immediately adjacent a formed elongate spigot 170 of the male connector. Mold blocks 123 and 132 form the male portion of the pipe connection and the two envelopes of plastic 106 and 108 merge to form the elongate spigot of the male connection. The corrugations of mold block 132 are immediately adjacent and connected to the elongate spigot being formed in mold block 123.

[0049] In contrast to the male/female connection shown in Figures 1 through 9, the cuff portion of the female connector produced by the apparatus of Figure 10 is slightly larger than the maximum diameter of the corrugations of the pipe sections defined by mold block 132. In this way, the normal size corrugations of the pipe section are of a size to be received in the cuff portion of the female connector as shown in Figure 12. This configuration has the advantage that a cut section of corrugated pipe without an elongate spigot can be inserted in the cuff portion or connect with the cuff portion. This connection is not as effective but may be advantageous in certain circumstances. In the embodiment of Figures 10 through 12 it can be seen that the cuff portion is of slightly greater diameter than the corrugations of the pipe sections.

[0050] It is possible to have a number of corrugations associated with the elongate spigot of slightly reduced diameter and the cuff can then be of the same diameter as the corrugated pipe. Such a connection as shown in Figures 1 through 9 is referred to as an in-line connection. Such an inline connector of the cuff is not able to receive the larger corrugations located between the male connector and female connector of a pipe section.

[0051] Returning to Figure 10, it can be seen that the mold block 128 in combination with a portion of mold block 126, has inwardly projecting land portions 150 and 152 that are offset from the sizing die 122. This arrangement allows the stepped recess 160 of the female connector to be formed between the inner wall and the sizing die. As shown in Figure 12, area 160 is of a size to accommodate and engage the male elongate spigot 170 shown in the male/female connection 140 of Figure 12.

[0052] Mold blocks 126 and 124 are configured to form the cuff 180 which in this embodiment is of a double layer thickness, namely the envelope of plastic 106 has been applied to the mold blocks as well as the envelope 108 has been applied to layer 106 to form the double thickness. Part of the pipe formed between mold blocks 124 and 123 will be cut and removed as illustrated at 192 in Figure 11. In this way the female connector will be at the end of one pipe section and the male elongate spigot will be at the end of the trailing pipe section.

[0053] With the male/female connection 140 of Figure 12, it can be seen that the elongate spigot 170 has been inserted into the female connector 194 which is defined by the cuff 196 and the stepped receiving socket 198. The leading corrugations 200, 202 and 204 that are immediately adjacent the elongate spigot 170 are received within the cuff 196 and a seal 206 is in engagement with a valley between corrugations 200 and 202 and the seal also engages an inside surface of the cuff 196. With this arrangement, there is a cavity 210 in front of corrugation 200 and this cavity is limited by wall 212 of the female connector 194. This cavity 210 allows for further movement of pipe section 225 into the female connector 194 of pipe section 227. Similarly, there is a gap immediately in front of the lead edge of the elongate spigot 170 defining a space 160 that accommodates further movement of the spigot into the female connector.

[0054] The cuff 196 not only provides a seal with the corrugations of pipe section 225, it also serves to protect the cavity 210 and in this way debris or contamination will not build or accumulate in this cavity. With the connection as shown in Figure 12 pipe section 225 may move further into the female connector a certain distance before striking the transitional wall 212. In addition, due to the substantial length of the elongate spigot 170, pipe section 225 can be partially withdrawn from the female connector while still maintaining the spigot in the receiving cavity 160 with a number of corrugations of pipe section 225 still in engagement with the cuff 196. Preferably there is a range of movement from the centered position of the male connector and the female connector that accommodates a range of movement. The range of movement is a design variable that affects the parameters of the male and female connectors. Ranges of movement in the order of 90 mm to 150 mm are often satisfactory. In some applications a range of movement of 100 mm or a range of movement only in one direction is appropriate.

[0055] With the present invention the male and female connectors are configured to accommodate a desired range of movement while maintaining a satisfactory connection throughout the range.

[0056] In the end positions of this range of movement the elongate spigot still overlaps with the receiving cavity of the female connector and a number of corrugations associated with the male connector are still in engagement with the cuff or overlap with the cuff. Thus the cuff serves to protect the corrugations beneath it and avoids contamination in the male/female connection.

[0057] Although various preferred embodiments of the present invention have been described herein in detail, it will be appreciated by those skilled in the art, that variations may be made thereto without departing from the appended claims.