WO2009038513A1

WO2009038513A1 - Coupling for pipes, suitable in particular for connecting plastic drill-casing

Info

Publication number: WO2009038513A1
Application number: PCT/SE2008/000499
Authority: WO
Inventors: Svante Larsson
Original assignee: Sl Innovation Ab
Priority date: 2007-09-19
Filing date: 2008-09-08
Publication date: 2009-03-26
Also published as: SE0702083L

Abstract

The invention is a pipe coupling suitable for connecting plastic drill-casings such as HDPE pipes. Drill casing connections should be thin-walled in addition to strong. Such a connection is known : a screw coupling, bell and spigot, fused into the plastic material of the pipe ends. The invention, however, achieves thin-walledness and strength by simpler means: Two flanges (1), a coupling sleeve (2), and several latches (3), all hard and stiff compared to the pipes, are included as components. The sleeve is tightly slid over the flanges that are anchored, one at each end, to the two pipes that are joined. Around its circumference the sleeve is furnished with several apertures (4) that overlap each pipe behind its flange. The latches are encased into the apertures, serving as projecting ridges of the sleeve wall, ridges that blocks the sleeve from being pulled off each pipe's flange.

Description

COUPLING FOR PIPES , SUITABLE IN PARTICULAR FOR CONNECTING PLASTIC DRILL-CASING

BACKGROUND OF THE INVENTION - TECHNICAL FIELD

The present invention is a coupling for pipes, suitable in particular for connecting plastic pipes or other pipes that are flexible in comparison with steel. It is a kind of sleeve coupling and a kind of flange coupling. The invention may also be categorized as a pipe connection having high tensile strength, that is to say, high strength for forces acting, lengthwise along the pipes, to pull apart two connected pipe sections .

The present invention may be used as a drill casing connection in the field of overburden drilling, a kind of drilling where the drill bit on its way through earth and gravel pulls along pipes—the drill casing—for lining the bore-hole wall. This technique is illustrated in fig 1. The pipes (R) are transported to the drilling location, usually in sections of 3 meter in length, and are end-to-end joined as the drilling progress. The drawing shows three pipes and one connection (S) between two of them. BACKGROUND OF THE INVENTION - TECHNICAL PROBLEM SOLVED BY THE INVENTION

There are several known pipe couplings that may be used in overburden drilling with plastic pipes. These couplings, however, either do not endure very deep overburden drillings or are needlessly complicated.

There are particularly two constraints to consider: First, drill casing connections must be thin walled; a connection should not exceed the drill casing wall thickness. Second, drill casing connections are subjected to very large external forces, and particularly large are the forces that tend to pull apart two connected pipe sections.

High-density polyethylene, shortened HDPE, is a suitable material for lining bore-hole walls. HDPE is quite flexible; steel, for example, being more than 100 times as stiff. HDPE is however not 100 times as weak as steel, because HDPE can be deformed much more than steel without any permanent rupture in the material. When performing overburden drilling, the forces on the pipes are as said very large, so large that appreciable elastic shape-changes of the HDPE pipes must be considered. Thus, a pipe connection must be made unbreakable even when the plastic material is appreciably bent or stretched or compressed. A known solution is to fuse a metal collar into the wall at the end of the plastic pipe. However the fabrication of that pipe connection is complicated; the invention solves the problem in a different and in a simpler way.

BACKGROUND OF THE INVENTION - PRIOR ART

The pipe coupling depicted in figure 4 of patent US 5542483, includes a bell and a spigot, both made of a metal material, heat fused into the ends of drill casings made of a plastic material. The bell has inner threads and the spigot has outer treads; two abutting pipe sections are connected by screwing them into each other.

Another coupling for plastic pipes, purposed for overburden drilling, is described in patent SE 503459. Saw-toothed grooves in the plastic material of pipe ends that have been wedged into each other, accounts for the coupling's tensile strength.

Patent US 5813484 describes a metal collar, more precisely categorized as a metal casing shoe, attached to a plastic drill casing. That casing shoe is, in particular, said to be simpler to attach than the casing shoe shown in figure 2 of the previously mentioned US 5542483. Also US 5964297 describes a metal casing shoe for plastic drill casings. None of these two devices are pipe couplings, but should nevertheless be considered because they teach how metal collars may be anchored to plastic pipes. 90 The pipe coupling of US 4035005, owes its tensile strength to a coupling sleeve's "tangs" 55, which are a kind of latches, and a plastic pipe's "stop shoulder" 38, which is a kind of flange against which the said latches locks. Patent US 6499771 describes similar components, "teeth" 62 and

95 "groove" 68, having the same purpose. These components deserves attention, even though the couplings as such, cannot be used as dill casing connections.

ioo DRAWINGS AND COMPONENTS

fig 1 Usage and Prior Art fig 2 First Embodiment fig 3 Addition to First Embodiment

105 fig 4 Second Embodiment fig 5 Flange to Pipe Anchoring fig 6 Summarizing Drawing

J Overburden no B Bedrock

R Pipe Section

S Connection

1 Flange

2 Coupling Sleeve us 3 Latch

4 sleeve Wall Aperture

5 Anchoring Means 120 5m Seat

5u Bulge

5s Pin and Hole

5f Hole and Plug Bonded to Pipe

5p Punched Sleeve and Pipe

125 6 Collar

7 Exterior of Pipe Body

8 Groove for Gasket

11 Edge of Flange

12 Flange Opening i3o 31 Edge of Plate

51 Abrupt Bulge

52 Waist

53 Softly-inclined Bulge 61 Part of Collar

135 62 Part of Collar g Gap

DESCRIPTION OF THE INVENTION - ADVANTAGES PROVIDED BY THE 140 INVENTION

The invention, as well as prior art, provides a high tensile strength, thin walled, coupling for pipes made of relatively- flexible materials such as HDPE.

145

In addition the invention, in contrast to prior art , provides simple fabrication compared to the previously 150 mentioned known pipe coupling (patent US 5542483) that, in common with the invention, is suitable for drill casings and includes a metal reinforcement of the plastic material at the pipe ends. The spigot 12A and the bell 12B are relatively complicated to fabricate, as we understand. This is

155 particularly so because of the threads, outer threads 14A on the spigot and inner threads 14B on the bell, and because of the holes through the spigot and bell walls. The necessity to fuse the spigot and bell walls (13A respective 13B) into the pipe walls, at the end of approximately 3 meter long pipes,

160 seems to aggravate the fabrication appreciably. In addition to simplified fabrication, the joining procedure is also simplified by the invention, since the pipes do not need to be screwed, but can be joined by pushing them into each other.

is5 The other mentioned pipe coupling usable as a drill casing connection, SE 503459, withstands five and a half tons of tensile force, according to a statement in the patent description, which is a good figure, but we think that the present invention is capable of actual drilling to greater

170 depths. Even if this has not been confirmed, the components and the construction of that coupling are, in any case, of other kinds than those of the invention.

175 DESCRIPTION OF THE INVENTION - EMBODIMENTS

First Embodiment ^• The drawing in fig 2 depicts a first i8o embodiment. The exploded view, fig 2a, shows the ends of two pipes (R). Between the pipes, there are some components: a flange (1) belonging to the upper pipe, a sleeve (2) , several plates (3), and a similar flange belonging to the lower pipe. For overburden drilling purposes the drill casing would

185 typically be manufactured of HDPE pipes having 8 mm wall thickness, and the flanges and the sleeve would typically be manufactured of steel pipes having 2 mm wall thickness. A flange and a part of the sleeve are shown enlarged in fig 2b. The plates are cut-out pieces that have been seated in

190 apertures (4) of the sleeve; each such cut-out piece—plate—is still partly connected to the sleeve, but has been bent, making it displaced somewhat from the aperture. The sleeve with its displaced pieces, is viewed straight from above in fig 2c. Each pipe end has a seat (5m) for the flange. The seat

195 consists of a waist (52) , an abrupt bulge (51) adjacent to the pipe end, and a cone-shaped bulge (53) neighboring the pipe body. A dividing gap (12) of the flange, facilitates attaching the flange around the waist. On a finished connection the sleeve has been slid over the flange, in which state, the

200 plates' edges (31) rest against the flange's edge (11). The bulge's coned shape gives precise but sufficient room for the plates; meanwhile the shape of the seat, including the coned shape, is a compromise between simple fabrication of the seat and strength of the pipe at the seat . The plates have capacity

205 to flex, into the apertures, flush with the sleeve wall, and this capacity is employed when sliding the sleeve over the flange. The plates are a form of latches—from the sleeve wall, 2io interior side, raised obstacles (ledges) acting as locks—which locks the sleeve to the flange (and thereby, to the pipe) .

When using a sleeve of steel with a wall thickness of 2 mm and a diameter of 170 mm, we optimized the plates' height to 215 approximately 12 times the wall thickness, the plates' width to approximately 1/6 of the diameter, and the distance between the plates to approximately 1/5 of the diameter.

The measures and the materials given in the embodying 220 example, are not claimed to be features of the invention; the measures must be adapted to particular applications and to the materials used for the pipe, the sleeve, the latches, and the flange.

225 Additions to the first embodiment are illustrated in fig 3. The left drawing, fig 3a, shows the end of a pipe with assembled flange,- the right drawing, fig 3b, shows the cross sections of the pipe and of the flange detached from the pipe. The seat's cone-shaped bulge verges to a collar (6) . On a

230 finished connection the sleeve has been slided, closely fitted, onto the flange and onto the collar. The collar gives support for the sleeve; as a result, the coupling is strengthened. The sleeve is countersunk with respect to the pipe, to place the sleeve's exterior curved surface flush with

235 the pipe's exterior curved surface (7), which gives the connection the same wall thickness and the same diameter as the pipe. At the pipe end there is a groove (8) in which a 240 gasket can be seated for sealing the connection.

Second Embodiment- A second embodiment is shown in fig 4. It is the anchoring of the flange and the form of the collar, that differ from those of the first embodiment; other

24s components or forms could be the same. The flange (1) is seated in the waist (52) , supported against the abrupt bulge (51) adjoining the pipe end. The collar (6) is a short tube, a kind of hoop, fastened to the waist, beside the flange. On a finished connection the sleeve is closely fitted with the

250 flange and with the collar. The collar almost completely occupies the space between the sleeve and the pipe, which not already is occupied by the flange and the latches and the bulge, thereby strengthening the connection. The toothed end (62) of the collar, in addition to its void-filling function,

255 also prevents the flange from being displaced from its position when the sleeve is slided over the flange, the same function that is achieved by the cone-shaped bulge of the first embodiment . Note—as the drawing connotes—that the flange and the collar may be united as one component: a hoop with

260 holes for the latches.

The groove (8) in fig 3, 4 is intended for a gasket. A gasket seals, for example against intruding water and fine soil during overburden drilling, but in addition to this 2S5 obvious benefit, a gasket has another advantage: It effectively centers the sleeve on the pipe. This is important since a play of only fractions of a millimeter, in the case 270 when the flange is 2 mm thick, can greatly change the properties of the connection. One could of course consider making the fit between the sleeve and the pipe exact, but a small gap is usually needed because the pipe is of another material than that of the sleeve and the flange,- and a

275 different temperature dependence could therefore also be expected. For example the diameters of a pipe in HDPE and of a flange-sleeve arrangement in steel, changes unequally fast with the temperature. This is not to claim that HDPE for the pipe, and that steel for the flange and the sleeve, must be

2B0 used. The problem may however persist even if other materials are used and even if other means of anchoring the flange to the pipe are used.

Flange Anchoring Means- The flange is allowed to be 285 rotatable, but not allowed to be pulled off the pipe end—just as the case is for pipe flanges in general. The flange, which must be of a harder material than the pipe, should equalize the large stresses that the hard latches cause in the flange, to smaller stresses that the flange causes in the soft pipe. 290 An anchoring means between the flange and the pipe, having those properties, can be obtained by letting the pipe have a waist in accordance with the presented embodiments. The waist should however be viewed as a mere example of an anchoring means, and not as a feature of the invention. Some other 295 embodying examples are illustrated in fig 5. The first example, fig 5a, shows the flange countersunk and placed against the bulge (5u) by the pipe end. In the second example, 300 fig 5b, the flange is anchored to the pipe by letting the flange have many holes in which some material has been bonded, for example by being fused, to the pipe wall. The next example, fig 5c, shows anchoring by means of pins that are attached through holes of the flange and of the pipe wall. In

BOS the last example, fig 5d, the anchoring means consists of hook-shaped teeth in the flange wall, penetrating the pipe wall. The waist, the bulge, and the other arrangements (5m, 5u, 5f , 5s, 5p) are examples of the anchoring means (5) , indicated in fig 6, that the invention includes.

310

Drilling experiments of ours, using pipes of HDPE, have shown that a steel hoop, acting as a flange, of such a simple design as in fig 2b, measuring 15 mm and 2 mm in width and in thickness, gives a durable coupling. While the steel hoop's 3i5 absence, caused the latches (of the form shown in fig 2b) to penetrate the waist adjoining, or scrape along the outside of, the sharp bulge (of the form shown in fig 3) .

When carrying out overburden drilling with steel pipes, 320 which is the common procedure, the pipes cannot be rotated in relation to each other. However the drillings we have done, have shown that the first embodiment's connection, characterized by the sleeve being rotatable around each pipe, is durable and maybe even more so than if the connection had 325 been rigid. 330 DESCRIPTION OF THE INVENTION - GENERAL DESCRIPTION

The invention is a coupling for pipes of relatively soft and flexible materials such as plastic, has capacity for great tensile strength and thin walls, and is especially suitable as 335 a drill casing connection for overburden drilling with HDPE pipes as drill casings.

A cut-out piece of the present coupling and a piece of one pipe (R) , are illustrated in fig 6. The coupling includes a

340 flange (1) for each pipe, a coupling sleeve (2) , and a number of latches (3) between the flanges and the sleeve. These three components must be harder and stiffer than the pipes. The flanges are fastened to the pipes. The sleeve is slid onto, tightly fitted to, the exterior of the flanges; only a small

345 gap (g) is allowed between the interior of the sleeve wall and the exterior of each flange wall. The sleeve wall has several apertures (4) that are about evenly distributed around the sleeve circumference. The sleeve apertures are placed so far from the rims of the sleeve, that they at least partly cover

35o each pipe behind its flange, that is to say, the apertures are, at least partly, further away from the pipe ends than the flanges are. The latches are fastened to the sleeve, encased in the apertures, acting as struts between the sleeve and the flanges, in order to stop the sleeve and the flanges from

355 being pulled apart. In the drawing, a piece of the sleeve is cut away near a sleeve aperture, in order to more clearly show how a latch is blocked by, and supports against, a flange. The 360 latches are exercising pressure against the flange, a pressure that, via anchoring means (5) of the flange, appear as compressive or other mechanical stresses in the pipe.

The anchoring means is the means by which a flange and a

3S5 pipe are united, a means that has many possible forms as evidenced by the embodying examples. The anchoring means shall be so constituted that the, in the pipe arosed, stresses are more evenly distributed, and of a smaller magnitude, than the compressive stresses that the latches give rise to in the

37Q flanges. To this end we determine that a flange's fastening surface—the surface of the stress absorbing bond between the flange and the pipe, when the anchoring means is a chemical or an adhesive bond, or the supporting surface between the flange and the pipe, when the anchoring means is a coupling—effected

375 by external forces acting on the connection, must be larger than the latches' total supporting surface against the flange. The anchoring means is also, evidently, but here mentioned for sake of clarity, sufficiently strong to prevent the flange from being pulled off the pipe when the connection is

380 subjected to, in other respects, tractable external forces.

A more restricted form of the anchoring means—a restriction by which simple anchoring of the flange is achieved—is a seat (5m) for the flange, consisting of a sharp bulge (51) toward 385 the pipe end, a waist (52), and a slow-ramped bulge (53) toward the pipe body. A flange may have the shape of a steel hoop adapted, in circumference and width, to precisely fit 390 around the waist and support against the bulges. The abrupt bulge is, optimally, approximately as high as the steel hoop is thick. The slow-ramped bulge may be a shallow but abrupt bulge, or a bulge whose height slowly increases along the pipe. Its shape should, if possible, precisely give space for

395 the latches but not more, because voids between the latches and the pipe, will weaken the connection. The steel hoop that constitute the flange, is allowed to be open (12) , making it easy to attach the hoop on the waist, a feature that is allowed because the coupling sleeve, which tightly encloses

400 the flange, prevents the flange from expanding (as it otherwise would) by the the latches' pressure.

The latches can be further constrained to constitute cut-out pieces obtained by making fine slits, to produce said

405 apertures, in the sleeve wall. Recommendably, slits are made along three of the edges in a rectangle: two edges along, and one edge across, the lengthwise direction of the sleeve. The edge that has no slit, that is the fourth edge, is the one farthest away from the flanges. The cut out, rectangle shaped,

4io pieces must be inwardly bent somewhat (at the said fourth edge of the rectangle) to function as latches that locks the sleeve to the flanges. Although the pieces are inwardly bent, the sleeve can be slid in place, because the pieces are pressed out, to give room for the flange, when the sleeve is slid over

415 the flange, and springs back when the sleeve is in place. The three incised edges of the rectangle has the shape of the letter "TJ" written with three straight lines. Other U-shapes 420 are also possible. The latches shall however not be limited to these kind of, in a U-shape, from a sleeve, cut-out pieces. A constructor may decide to use other forms of known latches, within the scope of the present description and drawings. For example the latches could be stand-alone elements which, by

425 known means, are coupled or bonded to the sleeve.

The pipe coupling includes advantageously also a collar (6) around each pipe. On a finished coupling the collar is inserted in, and is tightly fitted with, the sleeve, though

430 with sufficient space for the latches and for the flange. The collar's essential function is to fill the whole or part of the space between the sleeve and the pipe, which not already is filled by the flange and the latches and the anchoring means. Observe in this context, that the flange and the collar

435 not necessarily must be separate units, but they can in general, and for example as proposed by the second embodiment, be joined as one unit.

Claims

1. Coupling for pipes, suitable in particular for connecting plastic drill-casings, including two flanges (1) , anchored one to each pipe section to be connected, a coupling sleeve (2), and several latches (3) , characterized in that, the flanges, the sleeve, and the latches are stiffer and harder than the pipes,- and that the sleeve has a number of apertures (4) through the sleeve wall, about evenly distributed around the sleeve circumference; and that the sleeve is tightly fitted to, and slid over, the two flanges, and has been adjusted, lengthwise along the pipes, to make the apertures wholly or partly cover the pipes behind the flanges; and that the latches are encased in the apertures, are fastened to the sleeve, and are protruding from—are ledges of—the sleeve wall interior, ledges that stop and support against the flanges and thereby prevent the sleeve and the flanged pipes from being pulled apart; and that the anchoring means (5) for joining the flange to its pipe, has a, by external forces caused stresses, stress absorbing surface that is larger than the supporting surface between the latches and the flange, in order to lower and level the latches' compressive stresses.

2. Coupling for pipes, suitable in particular for connecting plastic drill-casings, according to claim 1, characterized in that, the coupling sleeve and the latches are connected, forming a single component, as were this the result of making fine slits, in U-shaped patterns, through the wall on a sleeve yet without apertures, and thereafter bend the U-shaped pieces inwards somewhat at the remaining edges—the edge between the legs of the U of each piece—of the sleeve wall.

3. Coupling for pipes, suitable in particular for connecting plastic drill-casings, according to any of the previous claims, characterized in that, the anchoring means for each pipe, is a seat (5m) including an abrupt bulge (51) toward the pipe end, a waist (52) , and a softly-inclined bulge (53) toward the pipe body; and that the flange for each pipe, is an open (12) hoop, which is seated in the waist, encased between the two bulges.

4. Coupling for pipes, suitable in particular for connecting plastic drill-casings, according to any of the previous claims, characterized in that, a collar (6) , around each pipe, is included; and that the collars wholly or partly occupies the space between the pipes and the sleeve, which not already is occupied by the flanges and the latches and the anchoring means.

5. Coupling for pipes, suitable in particular for connecting plastic drill-casings, according to any of the previous claims, characterized in that, a gasket is seated between the sleeve and each pipe or its flange, in order to seal, or, to center the sleeve on the pipes and thereby increase the coupling's allowance for differences in temperature expansion between the pipes and the sleeve.