WO2013155610A1

WO2013155610A1 - Segmented mould for cylindrical articles

Info

Publication number: WO2013155610A1
Application number: PCT/CA2013/000378
Authority: WO
Inventors: Gregory J.A. ANDRIGO; Rizalde G. ANGEL
Original assignee: Top-Co Inc.
Priority date: 2012-04-20
Filing date: 2013-04-18
Publication date: 2013-10-24

Abstract

A mould assembly for forming cylindrical articles includes a base; a core mandrel mountable on the base and having a cylindrical outer surface; multiple sidewall segments mountable on the base to form a generally cylindrical shell surrounding and radially spaced from the mandrel; and retainer means to hold the sidewall segments' upper ends in position. The sidewall segments may have profile recesses formed into their inner surface for forming ribs or other features projecting from the article to be formed. The side edges of the sidewall segments may be parallel to or angled relative to the mandrel. A liquid moulding material may be poured into the annular space between the mandrel and the assembled sidewall sections to form the desired cylindrical article. After the moulding material has cured, the retainer means may be removed to release the sidewall segments and permit extraction of the moulded article.

Description

SEGMENTED MOULD FOR CYLINDRICAL ARTICLES

FIELD OF THE DISCLOSURE

The present disclosure relates in general to moulds and moulding procedures for forming generally cylindrical articles, and in particular for forming such articles having radial protrusions, such as but not limited to solid-body casing centralizers having axially-oriented, obliquely-oriented, or helically-configured blades protruding outward from the main body of the centralizer.

BACKGROUND Centralizing devices ("centralizers") are commonly used in well-drilling operations to keep a drill string or casing string substantially centered within a wellbore as a well progresses further into the ground, in order to minimize wear on drill string components from abrasion against the drilled wellbore surfaces, and also to maintain an effective wellbore annulus around the pipe string to facilitate optimal flow of drilling fluid carrying drill bit cuttings up to the ground surface. Centralizers are particularly beneficial for drilling "directional" wells; i.e., wells that deviate from a vertical orientation. When a wellbore transitions from a vertical orientation to a horizontal or other non-vertical orientation, it will follow a curved profile through the transition section of the wellbore. A drill string or casing string passing through the transition section will naturally come into contact with the wellbore as it bends to get around the curve. This can cause considerable wear on the drill string or casing string components, especially when the wellbore passes through rock or other highly abrasive subsurface materials. As well, the flow of drilling fluid can be severely impeded through these transition regions due to the drill string bearing against the wellbore. In horizontal wellbores, similar problems can develop because the drill string or casing string will naturally fall against the bottom of the wellbore due to gravity.

These problems can be mitigated or prevented by fitting the drill string or casing string with external centralizers at intermittent locations along the length of the string. There are many different styles of centralizers, but they all are necessarily configured so as not to unduly impede the flow of drilling fluid through the wellbore annulus.

One known style of centralizer has a solid main body with a cylindrical bore to permit mounting onto drill pipe or casing, with axially-oriented or obliquely-oriented ribs or blades projecting outward from the cylindrical main body. The radius to the outer edges of the blades generally corresponds to the gauge of the wellbore, and drilling fluid is free to flow past the centralizer through the channels formed between adjacent blades. Such centralizers can advantageously be of unitary construction. They can be made from steel or other metal, but they can also be advantageously made from a hard plastic material to reduce weight and eliminate the risk of corrosion.

However, unitary solid-body plastic centralizers having external blades can be difficult to form using conventional moulding techniques. This is most particularly true for unitary solid-body centralizers having obliquely-oriented or helically-oriented blades, which pose the challenge of how to mould the centralizers with these integral features while being able to recover the completed centralizers from the moulds with relative ease and allowing the mould to be re-used. For the foregoing reasons, there is a need for improved methods and apparatus for forming unitary plastic centralizers or other generally cylindrical articles having external projections such as blades or ribs.

BRIEF SUMMARY The present disclosure teaches mould assemblies and moulding techniques that facilitate the production of unitary solid-body plastic centralizers with external blades, as well as other generally cylindrical articles.

In a first aspect, the present disclosure teaches a mould assembly for forming a generally cylindrical article, wherein the mould assembly comprises: · a plurality of sidewall segments, each sidewall segment having an upper end, a lower end, opposite side edges, an outer surface, and a generally cylindrical inner surface having a first radius; • a core mandrel having a longitudinal axis, an upper end, a lower end, and a generally cylindrical outer surface having a second radius, with the second radius being less than the first radius;

• a mould base adapted to retainingly receive the lower end of the core mandrel, and further adapted to retainingly receive the lower ends of the sidewall segments such that each side edge of each sidewall segment abuts a side edge of an adjacent sidewall segment, and such that the sidewall segments when thus assembled on the mould base will define a generally cylindrical shell enclosing the core to form an annular space between the inner surfaces of the sidewall segments and the outer surface of the core mandrel; and

• retainer means for retaining the upper ends of the sidewall segments in position relative to each other after assembly of the sidewall segments on the mould base.

Optionally, at least one of the sidewall segments may have a profile recess formed into its inner surface, such as (by way of non-limiting example) to form a rib or blade when the mould assembly is being used to make a plastic centralizer. The profile recess may be configured such that the resultant rib or blade on the centralizer will be substantially parallel to the axis of the centralizer. Alternatively, the profile recess could be configured such that the rib or blade will be at an oblique angle to the centralizer axis.

In certain embodiments, the side edges of the sidewall segments will be parallel to the core mandrel axis when the sidewall segments are positioned on the mould base in conjunction with the core mandrel. In other embodiments, the side edges of the sidewall segments may be at an oblique angle or helically oriented relative to the core mandrel axis.

Optionally, the mould base may define a mandrel recess for retainingly receiving the lower end of the core mandrel, and/or the mould base may define a sidewall segment recess for retainingly receiving the lower ends of the sidewall segments. The sidewall segment recess may comprise an annular recess. Optionally, locator pins may be used to position the sidewall segments on the mould base, with corresponding locator pin holes being provided on the mould base and in the lower ends of the sidewall segments. In one embodiment, the retainer means may be provided in the form of a circular retainer ring removably engageable with the upper ends of the sidewall segments. However, this is by way of non-limiting example only; the upper segment retainer means may be provided in any functionally effective form, and embodiments in accordance with the present disclosure are not limited or restricted to the use of retainer means of any particular type or form.

In a second aspect, the present disclosure teaches a method for manufacturing a generally cylindrical article, comprising the following steps:

• providing a mould assembly in accordance with the first aspect of the disclosure as described above;

• assembling the core mandrel and the sidewall segments on the mould base as described above;

• engaging the retainer means with the upper ends of the sidewall segments;

• introducing a liquid plastic material into the annular space between the core mandrel and the sidewall segments;

• allowing the plastic material to set;

• disengaging the retainer means from the sidewall segments;

• disengaging the sidewall segments from the mould base; and

• withdrawing the core mandrel from the cylindrical plastic article, before or after disengaging the sidewall segments from the mould base.

BRIEF SUMMARY OF THE DRAWINGS

Embodiments in accordance with the present disclosure will now be described with reference to the accompanying Figures, in which numerical references denote like parts, and in which:

FIG. 1 is an exploded view of a first embodiment of a mould assembly in accordance with the present disclosure. FIG. 2 is an isometric view of the mould assembly in FIG. 1 , shown fully assembled.

FIG. 2A is an isometric view of a second embodiment of a mould assembly in accordance with the present disclosure, shown fully assembled.

FIG. 3 is a vertical cross-section through the mould assembly in FIG. 2.

FIG. 4 is a top view of the mould assembly in FIG. 2.

FIG. 5 is a horizontal cross-section through the mould assembly in FIG. 2.

FIG. 6 is an isometric view of a typical sidewall segment of the mould assembly in FIG. 1.

FIG. 7 is an isometric view of a unitary solid-body plastic centralizer formed using a mould assembly as in any of the illustrated embodiments.

DESCRIPTION FIGS. 1 , 2, 3, 4, and 5 illustrate a mould assembly 100 for forming a unitary centralizer having a number of oblique or helical blades. Mould assembly 100 comprises a plurality of generally arcuate sidewall segments 10, a representative example of which is illustrated in FIG. 6. Each sidewall segment has a generally cylindrical inner surface 12 and an outer surface 16 (which typically but not necessarily will be generally cylindrical as shown). Typically (but not necessarily always), sidewall segments 10 will be equal in number to the number of blades required for the centralizer, with a desired blade profile 14 being machined or otherwise formed into the inner surface 12 of each sidewall segment 10.

Mould assembly 100 includes a base 20 adapted to receive and releasably retain the lower end 30L of an elongate core mandrel 30 having a generally cylindrical outer surface 32, such as by means of a circular recess 22 as illustrated. In the illustrated embodiments, core mandrel 30 is hollow, which is desirable to minimize weight and to facilitate handling but is not essential; in alternative embodiments, core mandrel 30 could be a solid piece. Base 20 is further adapted to receive and releasably retain the lower ends 10L of sidewall segments 10, such as by means of an annular recess 24 as illustrated. An annular groove 19 may optionally be formed into the outer surfaces 16 of sidewall segments 10 at their lower ends 10L as shown, to facilitate engagement and retention within annular recess 24 in base 20. Optionally, the assembly of sidewall segments 10 onto base 20, or within recess 24 in base 20, can be aided by the use of one or more locator pins 25 disposable into corresponding pin holes 21 and 11 in base 20 and lower ends 10L of sidewall segments 10 respectively, as shown in FIGS. 1 and 3. When thus disposed and retained on or within base 20, sidewall segments 10 combine to form a cylindrical mould shell surrounding core mandrel 30.

In the illustrated embodiments, the upper ends 10U of sidewall segments 10 are adapted to receive suitable retainer means for maintaining upper ends 10U of sidewall segments 10 in a tight circular configuration. In a preferred embodiment, the retainer means is provided in the form of a circular retainer ring 40 that fits into an annular groove 18 formed into the outer surfaces 16 of sidewall segments 10 at their upper ends 10U. However, this is by way of non-limiting example only; the upper ends 10U of sidewall segments 10 may be retained in desired position using any functionally effective means or method without departing from the scope of the present disclosure.

FIG. 2A illustrates a variant mould assembly 200 which is largely similar to mould assembly 100 except that whereas sidewall segments 10 of mould assembly 100 embodiment have vertical side edges, mould assembly 200 has sidewall segments 210 having side edges 213 that are angled in fully-assembled mould assembly 200. Sidewall segments 210 are otherwise generally similar to sidewall segments 10 of mould assembly 100. Typically (though not necessarily), the angle of side edges 213 of sidewall segments 210 will generally correspond to the desired blade angle of the centralizer to be made using mould assembly 200. As discussed in greater detail later in this disclosure, the use of sidewall segments 210 with angled side edges 213 facilitates the manufacture of centralizers having more steeply inclined blades than may be conveniently possible with a mould assembly having the same number of vertical-edged sidewall segments 10, while being able to form each entire blade profile 14 within the dimensional limits of a single sidewall segment.

FIG. 7 illustrates a plastic centralizer 80 fabricated using a mould assembly 100 or 200. Centralizer 80 has a generally cylindrical main body 82 with a central bore 84, and a plurality of obliquely-oriented ribs or blades 86 projecting outward from main body 82.

In typical (but not necessarily all) embodiments, core mandrel 30 extends above the upper ends 10U of sidewall segments 10. The upper end 30U of core mandrel 30 may be adapted to receive a mandrel cap member 35, but this is not essential.

The radius of outer surface 32 of core mandrel 30 is less than the radius of the inner surfaces 12 of the sidewall segments 10, such that the difference between these two radii at a given point along the length of core mandrel 30 defines the local radial thickness TR of the generally cylindrical main body 82 of a centralizer 80 formed using mould assembly 100 (or 200). Accordingly, an annular space or circumferential gap 50 is formed between outer surface 32 of core mandrel 30 and the inner surfaces 12 of the assembled sidewall segments 10 (or 210). A liquid plastic material may be poured into the assembled mould through gap 50, preferably aided by the use of a suitable pouring funnel 60, which can be positioned and secured (temporarily or permanently) to retainer ring 40 using one or more locator pins 64 disposable into corresponding pin holes 41 and 61 in retainer ring 40 and funnel 60 respectively (or using any other suitable means). Any or all of the various components of mould assembly 100 (or 200) may be fabricated from aluminum or an aluminum alloy, primarily to obtain such materials' benefits of strength, light weight, and machinability. However, the components of mould assembly 100 (or 200) may be fabricated from any other functionally suitable material without departing from the scope of the present disclosure. The use of mould assembly 100 may readily understood with reference to the various views of the assembled mould in FIGS. 2 and 3. A selected two-component thermosetting polymer mixture (or other selected pourable material) is poured into the mould's circumferential gap (annular space) 50, preferably aided by the use of funnel 60. After the polymer material cures and hardens, the mould is opened up by removing retainer ring 40 from the top of sidewall segments 10, which can then be individually removed from base 20 to expose a formed centralizer 80 as illustrated in FIG. 7. Core mandrel 30 can be withdrawn from centralizer 80 either before or after the removal of sidewall segments 10.

After removal of centralizer 80, mould assembly 100 can be easily and quickly reassembled using simple tools (if any), and ready for use to make another centralizer.

In the embodiment shown in FIG. 7, centralizer 80 has a total of five equally- spaced blades 86, each of which is formed within a single sidewall segment 10 of mould assembly 100. For the illustrated configuration of mould assembly 100 (i.e., with the side edges 13 of the assembled sidewall segments 10 being substantially parallel to the longitudinal axis A of core mandrel 30, and therefore parallel to the axis of centralizer 80, and with each blade profile recess 14 being formed within a single sidewall segment 10), the maximum angle of blades 86 relative to the centralizer axis (which angle can also be referred to as the "fleet angle") will be determined by the desired number of blades, the diameter of the centralizer, and the length of the centralizer and/or the length of the blades.

However, the alternative mould assembly 200 illustrated in FIG. 2A allows the maximum fleet angle to be increased, for a given combination of the above-noted variable factors, by virtue of sidewall segments 210 having angled side edges 213 such that more steeply angled blades 86 can be formed fully within each sidewall segment 210.

In other unillustrated alternative embodiments, sidewall segments 10 having vertical side edges 13 could be formed such that the blade profile recess 14 required to form a given blade 86 will span across adjacent sidewall segments 10. However, the assembly and use of mould assemblies in accordance with these alternative embodiments will be substantially the same as for the illustrated mould assemblies 100 and 200. It will be readily appreciated by those skilled in the art that various modifications to embodiments in accordance with the present disclosure may be devised without departing from the scope and teaching of the present teachings, including modifications which may use equivalent structures or materials hereafter conceived or developed. It is to be especially understood that the scope of the claims appended hereto should not be limited by any particular embodiments described and illustrated herein, but should be given the broadest interpretation consistent with the description as a whole. It is also to be understood that the substitution of a variant of a claimed element or feature, without any substantial resultant change in functionality, will not constitute a departure from the scope of the disclosure.

In this patent document, any form of the word "comprise" is intended to be understood in its non-limiting sense to mean that any item following such word is included, but items not specifically mentioned are not excluded. A reference to an element by the indefinite article "a" does not exclude the possibility that more than one such element is present, unless the context clearly requires that there be one and only one such element. Any use of any form of the terms "connect", "engage", "couple", "attach", "mount", or any other term describing an interaction between elements is not meant to limit the interaction to direct interaction between the elements in question, but may also extend to indirect interaction between the elements such as through secondary or intermediary structure. Relational terms such as "parallel", "perpendicular", and "concentric" are not intended to denote or require absolute mathematical or geometrical precision. Accordingly, such terms are to be understood as denoting or requiring substantial precision only (e.g., "substantially parallel") unless the context clearly requires otherwise. Wherever used in this document, the terms "typical" and "typically" are to be interpreted in the sense of representative of common usage or practice, and are not to be interpreted as implying essentiality or invariability.

Claims

WHAT IS CLAIMED IS:

1. A mould assembly comprising:

(a) a plurality of sidewall segments, each sidewall segment having an upper end, a lower end, opposite side edges, an outer surface, and a generally cylindrical inner surface having a first radius;

(b) a core mandrel having a longitudinal axis, an upper end, a lower end, and a generally cylindrical outer surface having a second radius, with said second radius being less than said first radius;

(c) a mould base adapted to retainingly receive the lower end of the core

mandrel, and further adapted to retainingly receive the lower ends of the sidewall segments such that each side edge of each sidewall segment abuts a side edge of an adjacent sidewall segment, and such that the sidewall segments when thus assembled on the mould base will define a generally cylindrical shell enclosing the core mandrel to form an annular space between the inner surfaces of the sidewall segments and the outer surface of the core mandrel; and

(d) retainer means, for retaining the upper ends of the sidewall segments in position relative to each other after assembly of the sidewall segments on the mould base.

2. A mould assembly as in Claim 1 wherein one of the sidewall segments has a profile recess formed into its inner surface.

3. A mould assembly as in Claim 2 wherein the profile recess corresponds to an elongate rib.

4. A mould assembly as in Claim 3 wherein the profile recess will be oriented at an angle oblique to the core mandrel axis when the associated sidewall segment is positioned on the mould base in conjunction with the core mandrel.

5. A mould assembly as in any one of Claims 1-4 wherein the side edges of the sidewall segments will be parallel to the core mandrel axis when the sidewall segments are positioned on the mould base in conjunction with the core mandrel.

6. A mould assembly as in any one of Claims 1-4 wherein the side edges of the sidewall segments will be at an angle oblique to the core mandrel axis when the sidewall segments are positioned on the mould base in conjunction with the core mandrel.

7. A mould assembly as in any one of Claims 1-6 wherein the core mandrel is hollow.

8. A mould assembly as in Claim 7, further comprising a core mandrel cap mountable to the upper end of the core mandrel.

9. A mould assembly as in any one of Claims 1-8 wherein the mould base defines a mandrel recess configured to receive and retain the lower end of the core mandrel.

10. A mould assembly as in any one of Claims 1-9 wherein the mould base defines a sidewall segment recess configured to receive and retain the lower ends of the sidewall segments.

1 1. A mould assembly as in Claim 10 wherein the sidewall segment recess comprises an annular recess.

12. A mould assembly as in any one of Claims 1-1 1 wherein the mould base and the lower ends of at least one of the sidewall segments are adapted to receive locator pins.

13. A mould assembly as in any one of Claims 1-12 wherein the retainer means comprises a circular retainer ring removably engageable with the upper ends of the sidewall segments.

14. A mould assembly as in Claim 13 wherein the upper end of each sidewall segment is formed with an annular groove for receiving the retainer ring.

15. A mould assembly as in any one of Claims 1-14, further comprising a funnel for pouring a liquid moulding material into the annular space between the core mandrel and the sidewall segments, after assembly of the core mandrel and the sidewall segments on the mould base.

16. A mould assembly as in Claim 13 or Claim 14, further comprising a funnel for pouring a liquid moulding material into the annular space between the core mandrel and the sidewall segments, after assembly of the core mandrel and the sidewall segments on the mould base, wherein said funnel is securable to the retainer ring.

17. A mould assembly as in Claim 16 wherein the funnel is removably securable to the retainer ring by means of locator pins engageable with the funnel and the retainer ring.

18. A method for manufacturing a generally cylindrical article, said method comprising the steps of:

(a) providing a mould assembly as defined in any one of Claims 1-17;

(b) assembling the core mandrel and the sidewall segments on the mould base as described in paragraph (c) in Claim 1 ;

(c) engaging the retainer means with the upper ends of the sidewall segments;

(d) introducing a liquid plastic moulding material into the annular space

between the core mandrel and the assembled sidewall segments;

(e) allowing the moulding material to set, thereby forming the desired

cylindrical plastic article;

(f) disengaging the retainer means from the sidewall segments;

(g) disengaging the sidewall segments from the mould base; and

(h) withdrawing the core mandrel from the cylindrical plastic article, before or after disengaging the sidewall segments from the mould base.

19. A method as in Claim 18 wherein the plastic moulding material comprises a two- component thermosetting polymer.