10001 ] The invention relates to pipes. The invention relates in particular to helically wound pipes and strips windable into helically wound pipes.

BACKGROUND

[0002] The applicant has developed various technologies to allow trenchless pipe rehabilitation. The applicant's International Patent Application No. PCT/AU87/00069 titled "Method and Means for Lining and Overwrapping Conduits" described a method and means of lining conduits, pipes or tunnels. The method described in that patent included helically winding a strip into a pipe and holding the pipe at a selected diameter during placement within the pipe to be rehabilitated. The method described further included the step of applying pulling force to the newly helically wound pipe to cause the inter engaged edges of the strips forming the pipe to slip with respect with each other so as to increase the diameter of the pipe progressively until it engages the walls of the conduit to be relined.

[0003 ] A further patent application by the applicant, PCT/AU88/0031 1 titled "Slip Control for Helically Wound Pipes" deals with the problem of positively unl ocking the pipe to allow for a controlled diameter change.

[0004] The technology described above can be described as expanding helically wound pipe technology. The expanding helically wound pipe technology requires the use of a strip having a pair of non-sliding lock complimentary connecting formations extending along opposite edge portions of a base. In order to make the aforesaid complimentary connecting formations non-sliding, a friction material is typically applied to a female connecting formation. Friction between the friction material and a male formation of the

complimentary connecting formations prevents slipping.

[0005] It is an object of the invention to improve on the above-mentioned prior art or to at least offer the public a useful choice.

SUMMARY

[0006 ] According to a first aspect of the invention, there is provided a strip windable into a hel ically wound pipe, the strip including:

a base having an inner face for forming an internal wall of the helically wound pipe; a pair of sliding lock complementary connecting formations extending along opposite edge portions of an outer face of the base, the sliding lock complementary connecting formations adapted to interlock when the strip is helically wound; and

a pair of non-sliding lock complementary connecting formations extending along opposite edge portions of the outer face of the base, the non-sliding lock complementary connecting formations adapted to gripably interlock when the strip is helically wound, the non-sliding connecting formations including a male formation and a female formation, the male formation including a head interlockably receivable in a cavity formed by the female formation, the cavity having a cavity wall, the female formation including a pair of parallel spaced apart and separate gripping portions, the gripping portions extending towards each other from opposite sides of the cavity wall, the gripping portions grippably engagable with the head of the mal e formation of the non-sliding connecting formations.

[0007 ] In one form, the cavity wall of the female formation is shaped to define a pair of parallel spaced apart landings separated by a slot, and the head of the mal e formation has a pair of parallel spaced apart barb surfaces, the landings and the barb surfaces mutually shaped to prevent disengagement of the head from the cavity.

[0008] In one form, the gripping portions are spaced from the landings thereby allowing intimate contact between the barb surfaces and the landings.

[0009] In one form, the male formation of the non-sliding lock complementary connecting formations is positioned outboard of the male formation of the sliding lock complementary connecting formations.

[0010 ] In one form, the gripping portions include the second material, the second material a higher coefficient of friction against the first material than the first material against the first material.

[001 1 ] In one form, the sliding lock complementary connecting formations include a lubricant, the lubricant facilitating sliding movement.

[0012 ] According to a second aspect of the invention, there is provided a method of producing a strip, the strip windable into a helically wound pipe, the method including the steps of:

(a) extruding a strip including:

a base having an inner face for forming an internal wall of the helically wound pipe;

a first pair of complementary connecting formations extending along opposite edge portions of an outer face of the base, the first pair of complementary connecting formations adapted to interlock when the strip is helically wound; and

a second pair of complementary connecting formations extending along opposite edge portions of an outer face of the base, the second pair of complementary connecting formations adapted to gripably interlock when the strip is helically wound, the second pair of connecting formations including a male formation and a female formation, the male formation including a head interlockably receivable in a cavity formed by the female formation, the cavity having a cavity wall; and

(b) applying a pair of parallel spaced apart and separate gripping portions to the cavity wall of the femal e formation of the second pair of connection formations, the gripping portions adapted to frictionally engage with the male formation of the second pair of connection formations so as to prevent relative sliding.

[0013 ] In one fonn, the applying step includes pumping an adhesive material through a nozzle, the nozzle positioned within the cavity, and directing the adhesive material onto the cavity wall to fonn the non-sliding female fonnation.

[0014 J In one form, the nozzle is positioned within the cavity such that an end of the nozzle contacts an apex of a "V" fonned by the cavity.

[0015] The present invention may be practised according to the claims without some or all of these specific details. For the purpose of clarity , technical material that is known in the fields related to the invention has not been described in detail so that the invention is not unnecessarily obscured.

BRIEF DESCRIPTION OF DRAWINGS

10016] Embodiments of the present invention will be discussed with reference to the accompanying drawings wherein:

[0017] Figure 1 shows a cross-sectional view of adjacent convolutions of a single strip, or a pair of strips, according to the invention in an interlocked condition;

[0018] Figure 2A is a similar view to Figure 1 but shows adjacent convolutions of a strip according to the invention before interlocking;

[0019] Figure 2B is a magnified view of a portion of Figure 2A.

[0020] Figure 3 is an isometric detailed view of a portion of a strip shown in Figure 2;

[0021 ] Figure 4 is an isometric view of a further portion of the strip of Figure 2;

[0022] Figure 5A is an detailed cross-sectional view of a portion of a background art strip of the type shown in Figures 1 to 4; [0023] Figure 5B is an detail cross-sectional view of a portion of the strip according to the invention as is shown in Figure 1 to 4;

[0024] Figure 6 is an detailed cross-sectional view of a portion of the strip shown in Figure 2;

[0025 ] Figure 7 is a detailed cross-sectional view of a portion of the pair of strips shown in Figure 1 showing interlocking;

[0026] Figure 8A is an isometric cross-sectional view similar to that of Figure 3, but shows a cavity within the formation before addition of a friction material into the formation shown in Figure 3 ;

[0027] Figure 8B is an isometric cross-sectional view of a nozzle injecting a friction material into the formation shown in Figure 3;

[0028] Figure 9 is a similar view to Figure 8, but shown in a cross-sectional view;

[0029] Figure 10A is an isometric view of a strip as shown in Figure 2 being injected with a friction material using the nozzle shown in Figures 8 and 9 in accordance with a method of the invention.

[0030] Figure 10B is an isometric cross-sectional view of the nozzle of Figure lOA injecting a friction material into the formation shown in Figure 3, where the nozzle end engages an apex 35 of a "V" formed by the cavity;

[0031 ] Figure 1 1 shows a schematic cross-sectional view of an underground conduit being relined using a strip or strips according to the invention.

DESCRIPTION OF EMBODIMENTS

[0032] Figures 1 , 2A and 2B show a strip 10 windable into a helically wound pipe, such as the pipe 9 shown in Figure 1 1. The strip 10 includes a base 12 having an inner face 13 for forming an internal wall of the helically wound pipe. The strip 10 may also have one or more strengthening ribs 14. The strip 10 also includes a pair of sliding lock complementary connecting formations 19extending along opposite edge portions of an outer face 15 of the base 12, the sliding lock complementary connecting formations 19adapted to interlock when the strip is helically wound, as can be seen in Figure 1. The strip 10 further includes a pair of non-sliding lock complementary connecting formations 17extending along opposite edge portions of the outer face 15 of the base. The non-sliding lock complementary connecting formations 17are adapted to gripably interlock when the strip 10 is helically wound. [0033] The non-sliding complementary connecting formations 17include a male formation 20 and a female formation 30. The male formation 20 includes a head 25 that is most clearly shown in Figures 4 and 6. The head 25 is receivable in a cavity 32 formed by the female formation 30. The cavity 32 has a cavity wall 33, as is shown in Figure 5B.

10034] The female formation 30 of the non-sliding connecting formations 17includes a pair of parallel spaced apart and separate gripping portions 72, 76, most clearly shown in Figure 3. The gripping portions 72, 76 extend towards each other from opposite sides of the cavity wall 33. In use, the gripping portions 72, 76 engage with the head 25 of the male formation 20 of the non-sliding connecting formations 17. This is shown most clearly in Figure 7. The friction between the surfaces 73,77 of the gripping portions 72, 76 and the head 25 of the male formation 20 prevents relative sliding movement between adjacent convolutions of the wound strip 10.

[0035 ] In Figures 1 , 2A and 2B, it can be seen that the male formation 20 of the non-sliding lock complementary connecting formations 17is positioned outboard of the male formation 40 of the sliding lock complementary connecting formations 19.

[0036] Referring to Figure 5B, it can be seen that the cavity wall 33 of the female formation 30 is shaped to define a pair of parallel spaced apart landings 35,36, separated by a slot 38.

[0037] Referring to Figure 6, the head 25 of the male formation 20 has a pair of parallel spaced apart barb surfaces 23,24. The landings 35,36 and the barb surfaces 23,24 are mutually shaped to prevent

disengagement of the head 25 from the cavity 32.

[0038] Again referring to Figure 5B, it can be seen that the gripping portions 72,76 are spaced from the landings 35,36 thereby allowing intimate contact between the barb surfaces 23,24 and the landings 35,36, as is illustrated in Figure 7. By eliminating material that forms the gripping portion 72,76 from the landings, a stronger and more reliable male to female engagement is provided. The contrast is clear when the cross- sectional view of Figure 5A, showing background art, is compared to the cross-sectional view of Figure 5B. It can be seen that in Figure 5A the adhesive which forms a gripping portion, extends over the landings.

[0039] The strip 10 is formed from at least a first and a second material. For instance, the first material may be uPVC (unplasticized polyvinyl chloride). The second material may be a hot melt material adhesive material comprising polyamide, synthetic hydrocarbon resins and other ingredients (such as HMS 44/4 supplied by H.B. Fuller Company). The second material will generally have a high co-efficient of friction against the first material (eg. uPVC) as compared to a co-efficient of material between the first material against more of the first material (eg. as compared to uPVC on uPVC). Alternative suitable materials may be used.

[0040 ] The sliding lock complimentary connecting formations 19will generally include a lubricant, the lubricant facilitating sliding movement.

[0041 ] The strip 10 described by the drawings and description above provides a number of advantages over early known strips, including strips as shown in Figure 5A. For instance the slippage resistance provided by the non-sliding lock is significantly higher than that of the earlier known strip which features a single gripping portion 60, which lines the majority of the cavity 32. The current invention enables higher torque holding which enables more reliable pipe winding during pipe rehabilitation. This is achieved while requiring less hot melt adhesive or other friction material used to create the gripping portions 72, 76 than that used to create the gripping portion 60 of the early known strips. The holding torque is important because if the strip slips during winding then pipe re-lining cannot be completed and the partially wound pipe may need to be scrapped.

[0042 ] It has also been found that the male fonnation 20 is more readily and reliably forced into the cavity 32 formed by the female formation 30 with the arrangement of the invention shown in Figure 5B as opposed to Figure 5A, where the gripping portion 60 fills the void where the head 25 of the male fonnation 20 resides when interlocked, sometimes not allowing the male formation 20 to adequately interlock in the female formation 30.

[0043 ] Figure 8B is an isometric cross-sectional view of a nozzle 1 10 injecting a friction material into the formation shown in Figure 8A to form the gripping portions 72,76. Figure 9 shows the same in a cross- sectional view. The nozzle 1 10 features an internal passage 1 12 connected to two opposing nozzle holes 1 13, 1 14, whereby the friction material is injected at a desired rate through the internal passage 1 12 and out each opposing nozzle hole 1 13, 1 14 and applied along opposite sides of the cavity wall 33.

[0044] Referring now to Figures 8, 9 and 10, a method of forming the strip 10 of the invention using the nozzle shown in Figures 8B and 9 will be described.

[0045 ] A method of producing a strip 10 described above, the strip windable into a helically wound pipe, includes the steps of:

(a) extruding a strip 10; and

(b) applying a pair of parallel spaced apart and separate gripping portions72, 76 to a cavity wall 33 of a female fonnation 30 of the extruded strip 10, the gripping portions 72,76 extending towards each other from opposite sides of the cavity wall 33. This is illustrated in Figures 1 OA and 10B using the nozzle 110, which is located on the strip production line and is connected to a supply of hot melt friction material 100. After the strip 10 is extruded, it passes the nozzle 1 10 which sits within the female formation 30 injects the friction material 100 through the nozzle holes 1 13, 1 14 onto opposing cavity walls 33 at a desired rate, forming the gripping portions 72,76 as shown in Figures 8 and 9.

[ 0046] The step of extruding a strip 10 referred to above includes extruding:

a first pair of complementary connecting formations 19 extending along opposite edge portions of an outer face of the base 12 (such as is shown in Figure 1 ), the first pair of complementary connecting formations 19 adapted to interlock when the strip 10 is helically wound; and

a second pair of complementary connecting formations 17 extending along opposite edge portions of an outer face of the base 12 (such as is shown in Figure 1 ), the second pair of complementary connecting formations 17 adapted to gripably interlock when the strip 10 is helically wound, the second pair of connecting formations including a male formation 20 and a female formation 30, the male formation 20 including a head 25 interlockably receivable in a cavity 32 formed by the female formation 30, the cavity 32 having a cavity wall 33;

[0047] The applying step described above includes pumping an adhesive material through the nozzle 1 10 shown in Figures 10A and 10B, the nozzle 1 10 positioned within the cavity 32, and directing the adhesive material onto the cavity wall to form the non-sliding female portion.

[0048] The nozzle has an nozzle end 1 15 as can be seen in Figures 8B and 9. In these figures there is some clearance between the nozzle end 1 15 and an apex 35 of a "V" formed by the cavity. The method of producing the strip 10 may include the step of positioning the nozzle end 1 15 within the cavity such that an end of the nozzle 1 15 contacts an apex 35 of a "V" formed by the cavity as is shown in Figure lOB. This contact assists in the production of strip 10 with consistent properties. It assists in accurate placement of the adhesive material on to the cavity wall to form the non-sliding female portion. This, in turn, assists with the achieving a consistent non-sliding lock.

[0049] The finished strip created by the process described above with reference to Figure 10A can be spooled ready for delivery to a pipe rehabilitation site. The spooled strip 10 can then be fed from a spool such as the spool 7 illustrated figuratively in Figure 1 1 to a winding machine 500 so as to be helically windable to form a pipe 9.

[0050] Referring to Figure 1 1, a helically wound pipe 9, would from the strip described above, is shown. The helically wound pipe 9 is typically used to re-line an underground conduit or host pipe 5. A winding machine 500 having a drive tray 560 is lowered down through a manhole or access hole 3. The strip 10 of the invention is then fed from a spool 7 on the surface. The method of re-lining a conduit using the strip of the invention as described above is generally as has been described in the applicant's earlier patent applications referred to in the background section of this specification.