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Patent Searching and Data


Title:
PLASTIC PIPE JOINTS AND FORMATION THEREOF
Document Type and Number:
WIPO Patent Application WO/1999/013256
Kind Code:
A1
Abstract:
An improved system for production of a high-strength, preferably fluid-tight pipe joint, includes improved apparatus and method for welding tubular members (12, 14) together by inserting an electrical welding coil (16) therebetween so as to form a pipe joint; wherein at least one of the tubular members (12, 14) is formed of a cold recoverable material at least a portion of which has been either expanded or compressed prior to its connection with another tubular member, so as to enable utilization of mechanical memory effects stored therein.

Inventors:
KOTZER MOSHE (IL)
Application Number:
PCT/IL1998/000433
Publication Date:
March 18, 1999
Filing Date:
September 07, 1998
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
KOTZER MOSHE (IL)
International Classes:
B29C57/04; B29C65/00; B29C65/34; B29C65/66; B29C69/02; F16L47/02; B29C65/68; (IPC1-7): F16L13/02
Foreign References:
US4362684A1982-12-07
US5366253A1994-11-22
US5328210A1994-07-12
US3062940A1962-11-06
US5406871A1995-04-18
US4508368A1985-04-02
US3788928A1974-01-29
US4626308A1986-12-02
Attorney, Agent or Firm:
Ben-david, Yirmiyahu M. (Jeremy M. Ben-David & Co. Har Hotzvim Hi-Tech Park P.O. Box 91450 Jerusalem, IL)
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Claims:
CLAIMS
1. A pipe joint system which includes: first and second tubular members, each having end portions arranged for connection to each other, wherein said first member is formed of an elastically deformable material, thereby to enable said end portions of said first and second members to be fitted together in a mating arrangement, and a cylindrical welding member, which includes an electrical welding coil, and which is configured to be disposed between opposing contact portions of said end portions of said first and second tubular members when fitted together; wherein, after said fitting together of said end portions of said first and second tubular members, said end portion of said first tubular member seeks to return to its nondeformed shape, thereby applying a radial force to said welding member and to said end portion of said second tubular member, and wherein at least said contact portions of said end portions of said first and second tubular members are formed of polymers, and wherein, on application of an electrical current to said welding coil, said welding coil is operative to become heated to a temperature of a magnitude which is at least that required to provide a welded connection between said contact portions of said end portions of said first and second tubular members.
2. A system according to claim 1, wherein at least said contact portions of said end portions of said first and second tubular members are formed of polyethylene.
3. A system according to claim 1, wherein said first tubular member includes crosslinked polyethylene.
4. A system according to claim 1, wherein a first one of said contact portions is formed of noncrosslinked polyethylene, and a second one of said contact portions is formed of crosslinked polyethylene. A system according to claim 1, wherein said welding member includes said electrical ing coil coated with a welding material which is operative, on application of an ical current to said welding coil, to become heated to a temperature of a magnitude z is at least that required to weld said contact portions together. A system according to claim 1, wherein said welding member includes: said electrical welding coil, and a sleeve formed of a welding material, associated with said welding coil. A system according to claim 6, wherein said welding coil is embedded in said sleeve ed of a welding material. A system according to claim 7, wherein said sleeve has a generally helical form, and brmed on a predetermined surface thereof a helical channel, and said welding coil des electrical conductor apparatus which is wound along said channel. A system according to claim 8, wherein said channel has formed along its length an ; ate opening which has a width narrower than the diameter of said electrical conductor ratus. A system according to claim 9, wherein said channel has a predetermined depth for nmodating said electrical conductor apparatus, and wherein the width of said channel ases inwardly from said opening. A system according to claim 8, wherein said helical sleeve is formed from a portion flexible, generally planar profile member formed of a welding material, said profile ber having first and second generally parallel sides, said first side being generally planar said second side having a plurality of channels formed thereon, said profile member ; foldable into a cylinder, thereby to position said channels formed thereon so as to e a single helical channel, and wherein said electrical conductor apparatus includes an electrical wire which is wound along said channel, so that ends of the wire are located at opposite ends of said cylinder.
5. 12 A system according to claim 8, wherein said helical sleeve is formed from a portion of a flexible, generally planar profile member formed of a welding material, said profile member having first and second generally parallel sides, said first side being generally planar and said second side having a plurality of channels formed thereon, said profile member being foldable into a cylinder having first and second ends, thereby to position said channels formed thereon so as to define a pair of parallel helical channels extending between said first and second ends, and wherein said electrical conductor apparatus includes an electrical wire which is wound along said channels, so as to define exposed ends at a preselected end of said cylinder.
6. 13 A system according to claim 1, wherein said welding member is arranged for placement onto the exterior of said end portion of said second tubular member, said end portion of said first member initially has an internal diameter which is smaller than the external diameter of said welding member when said welding member is located on the exterior of said end portion of said second tubular member, and said end portion of said first member is formed of a material that is expandable in response to a radially outward force applied thereto, and seeks to contract to its nonexpanded shape after removal of the force therefrom.
7. 14 A system according to claim 1, wherein said welding member is arranged for placement into the interior of said end portion of said second tubular member, generally coaxially therewith, said end portion of said first member initially has an external diameter which is greater than the internal diameter of said welding member when said welding member is located in the interior of said end portion of said second tubular member, and said end portion of said first member is formed of a material that is contractible in response to a radially inward force applied thereto, and seeks to expand to its noncontracted shape after removal of the force therefrom.
8. 15 A system according to claim 1, wherein a predetermined one of said first and second tubular members includes a connector sleeve having end portions, and said system also includes a third tubular member, similar to a predetermined one of said first and second tubular members, wherein said connector sleeve has end portions configured for connecting end portions of the others of said tubular members.
9. 16 A device for expanding a free end portion of a tubular plastic member, which includes: an adjustable expansion head which defines an outwardfacing cylindrical contact region parallel to an axis; and an actuator mechanism for selectively applying a force relative to said axis so as to cause a desired lateral expansion of said contact region while retaining said contact region cylindrical, and parallel to said axis, wherein, when located in the free end portion of a tubular member, said contact region is operative to apply radially outward forces thereto, so as to cause expansion thereof.
10. 17 A device according to claim 16, wherein said device further includes a linked support arrangement for supporting said expansion head and said actuator mechanism, and said expansion head includes a plurality of segmental expansion elements, each mounted onto said linked support arrangement via hinged connections, and wherein each said expansion element defines an outwardfacing segmental contact surface.
11. 18 A device according to claim 17, wherein said linked support arrangement, said expansion elements and said actuator mechanism are configured so as to retain the segmental contact surfaces equidistant from and parallel to said axis.
12. 19 A device according to claim 18, wherein said linked support arrangement includes: a rigid base member arranged transverse to said axis and having formed thereon at least three hinge locations, arranged along an arc of greater than 180° and spaced equidistantly about said axis; and at least three parallel elongate connector members of equal length and having first and second ends, wherein each said first end is hingedly connected to one of said hinge locations, and each said second end is hingedly connected to one of said segmental expansion elements.
13. 20 A device according to claim 19, wherein said expansion head further defines an inwardfacing conical region oriented at a predetermined angle relative to said axis, such that each said expansion element defines an inwardfacing segmental inclined surface, also inclined at the predetermined angle to said axis, wherein each expansion element defines a rear portion and a front contact portion terminating in a front end, wherein each said second end of said connector members is connected to said expansion element at said rear portion thereof, wherein said actuator mechanism includes an actuator member mounted for selectable movement along said axis between said base member and said front ends of said expansion elements, wherein said actuator member has a generally conical shape formed symmetrically about said axis and tapering towards a front end thereof, adjacent to said expansion head, wherein said actuator member is operative, when forced axially away from said base member and towards said front ends of said expansion elements, to contact said inwardfacing inclined surfaces of said segmental expansion elements so as to force them radially apart, and wherein said expansion elements are prevented by said hinged connection thereof to said connector members from undergoing both linear translation and angular translation parallel to said axis.
14. 21 A device according to claim 20, and also including resilient compression apparatus for applying to said expansion elements a radially inward compressive force thereby to retain said expansion elements in a retracted orientation, in the absence of a radially outward force of greater magnitude.
15. 22 A device according to claim 19, wherein each said expansion element defines rear and front portions, and said second end of each said connector member is connected to said rear portion of one of said expansion elements, wherein said actuator mechanism includes an actuator member mounted for selectable movement along said axis between said expansion elements, and is connected to each said expansion element by means of an intervening pair of parallel intermediate connector members, such that said actuator member defines, together with each said expansion element and said intervening pair of connector members, a parallelogram arrangement, such that, regardless of the axial position of said actuator member with respect to said expansion elements, said segmental contact surfaces are always retained parallel to said axis, and wherein said actuator member is operative, when forced axially away from said base member and towards said front portions of said expansion elements, to rotate said intermediate connector members towards a generally perpendicular position relative to said axis, thereby to force said expansion elements radially apart.
16. 23 A device according to claim 20, wherein said actuator mechanism also includes a displacement power source for selectively displacing said actuator member along said axis.
17. 24 A device according to claim 16, and further including an adapter element for coaxial placement about said expansion head, thereby to increase the diameter of said contact region.
18. 25 For use with a plastic tubular member formed of a recoverable material and having a mechanically deformed free end portion for connection to the free end portion of another tubular member, a recovery delay device for preventing recovery of the free end portion until after a desired time has elapsed after deforming thereof, which includes: a support ring which defines a generally cylindrical contact surface for braced engagement with the deformed free end portion to prevent recovery thereof, and apparatus for permitting selectable release of said support ring, thereby facilitating its disengagement from the deformed free end portion.
19. 26 A recovery delay device according to claim 25, wherein said support ring is made from a material having a high modulus of elasticity.
20. 27 A recovery delay device according to claim 25, wherein the mechanically deformed free end portion is an expanded free end portion, and said support ring is configured for placement inside the free end portion, thereby to brace it against contraction.
21. 28 A recovery delay device according to claim 27, wherein said support ring is a split ring having a pair of edges which are arranged for touching engagement when said support ring is positioned inside the free end portion.
22. 29 A recovery delay device according to claim 28, wherein said apparatus for permitting selectable release of said support ring includes apparatus for permitting inward displacement of a selected one of said edges relative to the other of said edges, thereby to enable release of said support ring from the free end portion.
23. 30 A recovery delay device according to claim 27, wherein said support ring includes a compressible bidirectional gripping ring having at least one opening formed therein, and wherein said recovery delay device also includes at least one spacer for insertion into at least one of said openings, thereby to brace said gripping ring against the interior surface of the expanded free end portion.
24. 31 A recovery delay device according to 27, wherein said support ring has a first hinge location and a pair of second hinge locations spaced thereabout so as to define a pair of arc portions between said first hinge location and said second hinge locations, and said apparatus for permitting selectable release includes apparatus for applying a radially inward pulling force to said arc portions, thereby to cause said arc portions to pivot towards each other about said first hinge location, and, further, to pivot inwardly about said second hinge locations, away from the interior surface of the expanded free end portion of the tubular member, thereby to release it.
25. 32 A recovery delay device according to claim 25, wherein the mechanically deformed free end portion is a compressed free end portion, and said support ring is configured for placement about the free end portion, thereby to brace it against expansion.
26. 33 A recovery delay device according to claim 32, wherein said support ring is a split sleeve member, and said recovery delay device also includes selectably releasable apparatus for locking said split sleeve member about the compressed free end portion, thereby to brace it against expansion.
27. 34 A recovery delay device according to claim 33, wherein said split sleeve has a pair of opposing free edges and said apparatus for locking includes : alternating pairs of knuckles formed on said opposing free edges of said split sleeve member, said pairs of knuckles being operative to define a barrel when arranged in mating engagement together with each other, and a selectably removable locking pin for insertion into said barrel.
28. 35 A pipe joint system according to claim 1, and also including a device for expanding said end portion of said first tubular member which includes: an adjustable expansion head which defines an outwardfacing cylindrical contact region parallel to an axis; and an actuator mechanism for selectively applying a force relative to said axis so as to cause a desired lateral expansion of said contact region while retaining said contact region cylindrical, and parallel to said axis, wherein, when located in said end portion of said first tubular member, said contact region is operative to apply radially outward forces thereto, so as to cause expansion thereof.
29. 36 A pipe joint system according to claim 1, and also including a recovery delay device for preventing recovery of an elastically deformed said end portion of said first tubular member, until after a desired time has elapsed after deforming thereof, wherein said recovery delay device includes: a support ring which defines a generally cylindrical contact surface for braced engagement with said deformed end portion of said first tubular member, to prevent at least a partial recovery thereof, and apparatus for permitting selectable release of said support ring, thereby facilitating its disengagement from said deformed end portion.
30. 37 A pipe joint system according to claim 35, and also including a recovery delay device for preventing recovery of an elastically deformed said end portion of said first tubular member, until after a desired time has elapsed after deforming thereof, wherein said recovery delay device includes: a support ring which defines a generally cylindrical contact surface for braced engagement with said deformed end portion of said first tubular member, to prevent at least a partial recovery thereof, and apparatus for permitting selectable release of said support ring, thereby facilitating its disengagement from said deformed end portion.
31. 38 A method of connecting first and second tubular members each having end portions arranged for connection to each other additionally employing a cylindrical electric welding member configured to be disposed between opposing contact portions of the end portions of the first and second tubular members when fitted together, wherein at least the contact portions of the end portions of the first and second tubular members are formed of polymers, and wherein the method includes the following steps: a) elastically deforming the end portion of the first tubular member to a size such that it can be fitted together with the second tubular member in a mating arrangement; b) placing the electric welding member relative to the second tubular member, such that it becomes disposed between opposing contact portions of the end portions of the first and second tubular members when these are fitted together; c) fitting together the first and second tubular members in a mating arrangement; d) allowing the elastically deformed end portion of the first tubular member to partially return to its nondeformed size; and e) applying an electrical current to the welding member so as to cause heating thereof to a temperature of a magnitude which is at least that required to melt the contact portions of the end portions of the first and second tubular members, thereby providing a welded connection between the end portions of the first and second tubular members.
32. 39 A method according to claim 38, wherein, in said step d) the deformed end portion of the first tubular member applies a radial force to the electric welding member and to the end portion of the second tubular member.
33. 40 A method according to claim 38, wherein the end portion of the first tubular member initially has an internal diameter which is smaller than the external diameter of the welding member when the welding member is located on the exterior of the end portion of the second tubular member, and wherein said step a) includes applying to the end portion of the first tubular member a radially outward force so as to expand the end portion of the first tubular member such that its internal diameter exceeds the external diameter of the welding member; said step b) includes placing the welding member onto the exterior of the end portion of the second tubular member; said step c) includes inserting the end portion of the second tubular member and the welding member placed thereon, into the expanded end portion of the first tubular member; and said step d) includes removing the radial force from the end portion of the first tubular member, thereby allowing it to partially contract to its nonexpanded shape, thereby to apply a radially inward force to the welding member and to the end portion of the second tubular member.
34. 41 A method according to claim 38, wherein the end portion of the first tubular member initially has an external diameter which is greater than the internal diameter of the welding member when the welding member is located in the interior of the end portion of the second tubular member, and wherein said step a) includes applying to the end portion of the first tubular member a radially inward force so as to contract the end portion of the first tubular member such that its external diameter becomes smaller than the internal diameter of the welding member; said step b) includes placing the welding member into the end portion of the second tubular member, generally coaxially therewith; said step c) includes inserting the contracted end portion of the first tubular member into the welding member located in the end portion of the second tubular member; and said step d) includes removing the radial force from the end portion of the first tubular member, thereby allowing it to partially expand to its noncontracted shape, thereby to apply a radially outward force to the welding member and to the end portion of the second tubular member.
35. 42 A method of connecting end portions of a pair of tubular members by use of a connector sleeve formed of a polymer, and a cylindrical welding member which is configured to be disposed between opposing contact portions of end portions of the connector sleeve and the end portions of the pair of tubular members when fitted together, the method comprising the following steps: a) elastically deforming a single one of the group consisting of : (i) at least one elastically deformable end portion of the pair of tubular members, and (ii) at least one elastically deformable end portion of the connector sleeve, to a size such that they can be fitted together with nondeformed end portions in a mating arrangement; b) placing the electric welding member such that it becomes disposed between opposing contact portions of the end portions of the connector sleeve and of the end portions of the tubular members when these are fitted together; c) fitting together the connector sleeve and the tubular members in a mating arrangement; d) allowing the elastically deformed end portions to partially return to their nondeformed size; and e) applying an electrical current to the welding member so as to cause heating thereof to a temperature of a magnitude which is at least that required to melt the contact portions of the end portions of the connector sleeve and of the tubular members, thereby providing a welded connection between the end portions of the connector sleeve and of the tubular members.
36. 43 A method according to claim 42, wherein, in said step d) the deformed end portions apply a radial force to the electric welding member and to the end portions fitted together therewith.
37. 44 A method according to claim 43, wherein the deformed end portions initially have internal diameters smaller than the external diameter of the welding member when the welding member is disposed between opposing contact portions of the end portions of the connector sleeve and of the end portions of the tubular members when these are fitted together, and wherein said step a) includes applying a radially outward force so as to expand the elastically deformable end portions such that their respective internal diameters exceed the external diameter of the welding member; and said step d) includes removing the radial forces from the expanded end portions, thereby allowing them to partially contract to their nonexpanded shape, thereby to apply a radially inward force to the welding member and to the nonexpanded end portions.
38. 45 A method according to claim 43, wherein the deformed end portions initially have external diameters larger than the internal diameter of the welding member when the welding member is disposed between opposing contact portions of the end portions of the connector sleeve and of the end portions of the tubular members when these are fitted together, and wherein said step a) includes applying a radially inward force so as to contract the elastically deformable end portions such that their respective external diameters become smaller than the internal diameter of the welding member; and said step d) includes removing the radial forces from the contracted end portions, thereby allowing them to partially expand to their noncontracted shape, thereby to apply a radially outward force to the welding member and to the noncontracted end portions.
39. 46 A method of preparing a plastic tubular member formed of a cold recoverable material for connection to another tubular member, which includes: mechanically deforming a free end of the plastic tubular member so as to allow mating thereof with a free end of the other tubular member, thereby to set up recovery forces in the free end of the plastic tubular member, urging it to recover its original size; bracing the free end of the plastic tubular member against recovery; and permitting at least partial recovery of the free end of the plastic tubular member after a desired time period has elapsed after said step of deforming.
40. 47 A method according to claim 46, wherein said step of mechanically deforming is performed at environmental temperatures.
41. 48 A method according to claim 46, wherein said step of bracing includes applying recoveryresistant forces to the free end of the plastic tubular member opposite to the recovery forces, thereby to delay recovery of the free end of the plastic tubular member.
42. 49 A method according to claim 46, wherein said step of mechanically deforming includes expanding the free end of the plastic tubular member, and said step of bracing includes inserting a generally cylindrical recovery delay device inside the free end of the plastic tubular member, thereby to brace the free end of the plastic tubular member against contraction.
43. 50 A method according to claim 49, wherein the recovery delay device has at least one opening formed therein, and said step of bracing includes inserting a spacer into the at least one opening.
44. 51 A method according to claim 46, wherein said step of mechanically deforming includes compressing the free end of the plastic tubular member, and said step of bracing includes placing a generally cylindrical recovery delay device about the free end of the plastic tubular member, thereby to brace the free end of the plastic tubular member against expansion.
45. 52 A method according to claim 46, wherein the plastic tubular member is formed of polyethylene.
46. 53 A method according to claim 46, wherein the plastic tubular member is formed of crosslinkedpolyethylene.
47. 54 A method according to claim 38, wherein step a) of elastically deforming the end portion of the first tubular member includes mechanically deforming the end portion of the first tubular member, thereby to set up recovery forces therein urging the end portion to recover to its original size, and wherein said step a) also includes the steps of : bracing the end portion of the first tubular member against recovery; and removal of the bracing from the end portion of the first tubular member after a desired time period has elapsed after said step of deforming.
48. 55 A method according to claim 42, wherein said step a) of elastically deforming includes mechanically deforming a single one of the group consisting of : (i) at least one elastically deformable end portion of the pair of tubular members, and (ii) at least one elastically deformable end portion of the connector sleeve, to a size such that they can be fitted together with nondeformed end portions in a mating arrangement; and wherein said step a) includes the steps of : bracing the mechanically deformed end portions against recovery; and removal of the bracing from the deformed end portions after a desired time period has elapsed after said step of deforming.
Description:
PLASTIC PIPE JOINTS AND FORMATION THEREOF FIELD OF THE INVENTION The present invention relates to the joining of tubular members generally, and in particular, to the joining of tubular members of which at least one is plastic, and formed using memory effects.

DEFINITIONS Unless specifically mentioned otherwise, the term"cold recoverable"is used in the following specification and claims to mean a plastic body which, under certain conditions, has the property or tendency of recovering its original shape at environmental temperatures after undergoing deformation, also at environmental temperatures.

The term"tubular member"is employed throughout the present specification and claims to include all pipes, tubes, conduits, as well as the tubular free ends of various fittings with which a connection or joint with another tubular member may be sought.

BACKGROUND OF THE INVENTION There exist various types of pipe joints and connectors therefor, especially for pipes used in supplying fluids, such as main water pipes, oil lines, or domestic water pipes. These generally include a number of lengths of pipe which are connected together, and which may also have various fittings, such as at T-junctions and at valve connections. All of these connections should be fluid-tight, and as simple and inexpensive as possible. A particular problem in providing suitable joints, however, is that the pipe ends are often smooth, and that the joint itself must therefore be provided by applying pressure between a connector element and the pipe end, and by sealing therebetween.

There is also known in the art, a method which employs the use of electric socket welding devices, in which there is provided a sleeve having a current-carrying electrical heating coil embedded in an inner wall thereof. The sleeve is open ended, and ends of plastic pipes that it is sought to join are inserted into the sleeve. Application of a voltage across the coil causes it to become heated, thereby to cause the inner sleeve layer and an outer surface of the pipes, to melt, thereby welding them together.

A disadvantage of joints produced by the electric socket welding methods of prior art, is the inability to ensure an absence of gaps in the weld at joints so produced. This is due to the relatively large difference in diameter size between the sockets and at least one of the pipes being connected, which renders conventional welding techniques problematic, particularly with respect to non-melting material, such as cross-linked polyethylene.

There are further known in the art, techniques which employ memory properties of plastic in order to form joints. These include the use of"mechanical"and"thermal"memory phenomena, as they apply to polymer-based materials, in forming pipe joints. In brief, the main difference between mechanical memory and thermal memory is that, whereas mechanical memory provides for cold deformation of a pipe end and subsequent recovery of the pipe end after removal of a deformation force, thermal memory provides for application of heat to the pipe end and deformation of the softened, heated pipe end, freezing of the pipe end, and reapplication of heat, which causes a recovery of the pipe end to its original shape.

By way of example of joints formed using mechanical memory effects, German patent publication no. 4025840 describes the joining of polyolefin pipes to a connecting piece, employing this phenomenon. Pipes are joined in a process in which one end of a polyolefin pipe is expanded and fitted over a connecting piece. The pipe end, whose internal diameter is smaller than the outer diameter of the connector, is reversibly expanded at room temperature by means of a spreader mandrel to an internal diameter greater than the outer diameter of the connector; the spreader is removed and the pipe and connector are fitted together, after which the connector is attached firmly to the pipe by reversing the expansion.

Medium density and cross-linked polyolefins in particular are cold formed and they tend to revert to their original shape. The expanded pipe thereafter shrinks back again.

Reference is now made to US Patent No. 4,927,184 to Bourjot et al, entitled"Pipes Based on Polyolefin Resin for Manufacturing Pipelines and Couplings for Assembling Them", as an example of joints produced using thermal memory effects. In addition to describing the use of multi-layer hot welding devices for joining multi-layer polyolefin pipes, wherein both the device and the pipes each have a layer of thermoplastic resin and a layer of cross-linked polyolefin resin, this patent also describes the use of heat to soften the end of a first pipe end, after which it can be easily expanded and placed over a second pipe end. As the heated pipe end cools, it attempts to return to its previous size.

In considering the merits of prior art devices which employ mechanical or thermal memory phenomena, a number of disadvantages arise, including the following: In the case of devices employing mechanical memory effects, the mechanical memory of a pipe will cause it to seek to shrink back to its original shape, only if the elastic limit of the pipe has not been exceeded. This effect is observed mostly with cross-linked polyethylene.

The above phenomenon of shrinking occurs at environmental temperatures typically in a range from-20 to 50°C. The gradual shrinkage of the material occurs over a period of several minutes up to approximately one hour, depending on the dimensions of the pipes, the materials used, and the environmental conditions.

Since the shrinking back of an expanded pipe using mechanical memory typically occurs relatively quickly, there will often be a need for the expansion to be performed on site where a pipe is sought to be joined with another pipe or pipe fitting. For reasons well appreciated by persons skilled in the art, it is however most desirable to provide a product which is formed to its maximum extent on the production floor, and which requires a minimum amount of skill and effort in the field.

Similarly, where the phenomenon of thermal memory is employed, thermal recovery requires the use of a heat source on-site. A further disadvantage of using thermal memory techniques, is that irreversible damage may be caused to the pipe.

For the various reasons cited above, none of the above-described prior art methods facilitate high quality, relatively simple, connection and sealing of pipes, as proposed in the present invention.

SUMMARY OF THE INVENTION The present invention seeks to provide a novel pipe connection system and method of joining tubular members generally, which utilize a simple welding technique and are thus relatively simple, inexpensive, and highly reliable, thereby overcoming disadvantages of known art.

The present invention also seeks to provide a relatively inexpensive and convenient-to-use tool for the purpose of expanding the free ends of tubular members to which it is sought to attach other tubular members or fittings, on site.

Further, the present invention seeks to provide a method of preparing a plastic tubular member for connection to another tubular member by use of mechanical memory effects, wherein cold deformation of the free end of an elastic tubular member is not required to be performed on site, and the recovery stage is delayed until a desired time, this time preferably being such time as the tubular members to be joined are ready for assembly.

There is thus provided, in accordance with an embodiment of the invention, a pipe joint system which includes: first and second tubular members, each having end portions arranged for connection to each other, wherein the first member is formed of an elastically deformable material, thereby to enable the end portions of the first and second members to be fitted together in a mating arrangement, and a cylindrical welding member, which includes an electrical welding coil, and which is configured to be disposed between opposing contact portions of the end portions of the first and second tubular members when fitted together; wherein, after the fitting together of the end portions of the first and second tubular members, the end portion of the first tubular member seeks to return to its non-deformed shape, thereby applying a radial force to the welding member and to the end portion of the second tubular member, and wherein at least the contact portions of the end portions of the first and second tubular members are formed of polymers, and wherein, on application of an electrical current to the welding coil, the welding coil is operative to become heated to a temperature of a magnitude which is at least that required to provide a welded connection of said end portions of said first and second tubular members.

Additionally, in accordance with an embodiment of the invention, there is provided a device for expanding a free end portion of a tubular, plastic member, which includes an adjustable expansion head which defines an outward-facing cylindrical contact region parallel to an axis; and an actuator mechanism for selectively applying a force relative to the axis so as to cause a desired lateral expansion of the contact region while retaining the contact region cylindrical, and parallel to the axis, wherein, when located in the free end portion of a tubular member, the contact region is operative to apply radially outward forces thereto, so as to cause expansion thereof.

Further, in accordance with an embodiment of the invention, there is also provided a recovery delay device for preventing recovery of an elastically deformed end portion of a tubular member, until after a desired time has elapsed after deforming thereof, wherein the recovery delay device includes: a support ring which defines a generally cylindrical contact surface for braced engagement with the deformed end portion of the tubular member, to prevent at least a partial recovery thereof, and apparatus for permitting selectable release of the support ring, thereby facilitating its disengagement from the deformed end portion.

In accordance with another embodiment of the invention, there is provided a method of connecting first and second tubular members each having end portions arranged for connection to each other additionally employing a cylindrical electric welding member configured to be disposed between opposing contact portions of the end portions of the first and second tubular members when fitted together, wherein at least the contact portions of the end portions of the first and second tubular members are formed of polymers, and wherein the method includes the following steps: a) elastically deforming the end portion of the first tubular member to a size such that it can be fitted together with the second tubular member in a mating arrangement; b) placing the electric welding member relative to the second tubular member, such that it becomes disposed between opposing contact portions of the end portions of the first and second tubular members when these are fitted together; c) fitting together the first and second tubular members in a mating arrangement; d) allowing the elastically deformed end portion of the first tubular member to partially return to its non-deformed size; and e) applying an electrical current to the welding member so as to cause heating thereof to a temperature of a magnitude which is at least that required to melt the contact portions of the end portions of the first and second tubular members, thereby providing a welded connection between the end portions of the first and second tubular members.

It will be appreciated that, in step d) above, the deformed end portion of the first tubular member applies a radial force to the electric welding member and to the end portion of the second tubular member.

In accordance with a further embodiment of the invention, there is provided a method of connecting end portions of a pair of tubular members by use of a connector sleeve formed of a polymer, and a cylindrical welding member which is configured to be disposed between opposing contact portions of end portions of the connector sleeve and the end portions of the pair of tubular members when fitted together. This method includes the following steps: a) elastically deforming either (i) one or more of the elastically deformable end portions of the pair of tubular members, or (ii) one or more of the elastically deformable end portions of the connector sleeve, to a size such that they can be fitted together with non-deformed end portions in a mating arrangement; b) placing the electric welding member such that it becomes disposed between opposing contact portions of the end portions of the connector sleeve and of the end portions of the tubular members when these are fitted together; c) fitting together the connector sleeve and the tubular members in a mating arrangement; d) allowing the elastically deformed end portions to partially return to their non-deformed size; and e) applying an electrical current to the welding member so as to cause heating thereof to a temperature of a magnitude which is at least that required to melt the contact portions of the end portions of the connector sleeve and of the tubular members, thereby providing a welded connection between the end portions of the connector sleeve and of the tubular members.

In accordance with yet a further embodiment of the invention, there is provided a method of preparing a plastic tubular member formed of a cold recoverable material for connection to another tubular member, which includes: mechanically deforming a free end of the plastic tubular member so as to allow mating thereof with a free end of the other tubular member, thereby to set up recovery forces in the free end of the plastic tubular member, urging it to recover its original size; bracing the free end of the plastic tubular member against recovery; and permitting at least partial recovery of the free end of the plastic tubular member after a desired time period has elapsed after the step of deforming.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be more clearly understood and appreciated from the following detailed description, taken in conjunction with the drawings, in which: Figs. 1,2, and 3 are pictorial illustrations showing first, second, and third stages in the forming of a pipe joint by electric welding, in accordance with a method of the present invention; Fig. 4 is a schematic cross-sectional view of a simple pipe joint being formed between two pipe members, after initial assembly thereof ; Fig. 5 is a schematic cross-sectional view of a pipe joint being formed, at the same stage as that depicted in Fig. 4, but employing an additional sleeve member, Fig. 6 is a schematic cross-sectional view of a Tjoint being formed in accordance with the joints seen in Fig. 5; Fig. 7 is a detailed, schematic cross-sectional view of formation of the joint of Figs.

1-3, showing insertion of the end of an inner pipe into the end of an outer pipe, after initial assembly thereof ; Fig. 8 shows the joint of Figs. 1-3, after welding together thereof ; Fig. 9 is a detailed, schematic cross-sectional view of a joint formed in accordance with another embodiment of the present invention, in which there is employed a welding member formed of a welding coil embedded in a weldable plastic sleeve; Fig. 10 is a pictorial representation of a plastic profile from which a cylindrical welding coil sleeve may be formed, in accordance with a further embodiment of the invention; Fig. 11 is a schematic, cross-sectional side view of a joint employing a single wound cylindrical welding sleeve formed from the profile of Fig. 10; Fig. 12 is a schematic, cross-sectional side view of a joint employing a double wound cylindrical welding sleeve formed from the profile of Fig. 10; Fig. 13 is a schematic cross-sectional view of a simple pipe joint being formed between two pipe members, after initial assembly thereof, in accordance with yet one more embodiment of the present invention; Fig. 14 is a schematic side-sectional view of expander apparatus, useful in a method of the invention, in a retracted position; Fig. 15 is a schematic side-sectional view of the expander apparatus of Fig. 14 in an expanded position; Fig. 16 is a front elevational view of the apparatus of Figs. 14 and 15, taken in the direction of arrow 3 in Fig. 15; Fig. 17 is a schematic side-sectional view of expander apparatus, formed in accordance with another embodiment of the invention, in a retracted position; Fig. 18 is a schematic side-sectional view of the expander apparatus of Fig. 17 in a fully expanded position; Fig. 19 is a cross-sectional view of the device of Figs. 17 and 18, taken along line 6-6 in Fig. 18; Figs. 20 and 21 are views similar to those of Figs. 18 and 19, respectively, but showing use of an adapter ring; Fig. 22 is a graph showing force applied versus the displacement angle of the expansion head of the apparatus of Figs. 17-21; Fig. 23A is a plan view of the deformed free end of a plastic tubular member prepared by use of a recovery delay method in accordance with an alternative embodiment of the invention; Figs. 23B and 23C are cross-sectional views of the free end of Fig. 23A, taken along line B-B therein, using recovery delay apparatus constructed and operative in accordance with an embodiment of the invention, seen in a recovery delay position, and after extraction, respectively; Fig. 24 is a cross-sectional view similar to Fig. 23B, but illustrating recovery delay apparatus constructed and operative in accordance with another embodiment of the invention ; Figs. 25A, 25B and 25C are perspective views of the device seen in Fig. 24, in accordance with various embodiments of the invention; Figs. 26A and 26B are cross-sectional views similar to Fig. 23B, but illustrating recovery delay apparatus constructed and operative in accordance with a further embodiment of the invention, in expanded and collapsed positions, respectively; Fig. 27A is a plan view of the deformed free end of a plastic tubular member prepared by use of a recovery delay method in accordance with an alternative embodiment of the invention; and Fig. 27B is a cross-sectional view of the free end seen in Fig. 27A, taken along line B-B therein.

DETAILED DESCRIPTION OF THE INVENTION The present invention seeks to provide an improved system for production of a high-strength, preferably fluid-tight pipe joint. As seen from the description below, the system of the present invention includes improved apparatus and method for welding tubular members together so as to form a pipe joint; wherein at least one of the tubular members is formed of a cold recoverable material at least a portion of which is either expanded or compressed prior to its connection with another tubular member, so as to enable utilization of the mechanical memory effects stored therein.

The system of the invention further includes improved apparatus and method for deformation of a free end of a tubular member formed of a cold recoverable material, as well as improved apparatus and method for optionally delaying the recovery stage of a deformed tubular member until a desired time, thereby enabling prior off site preparation of components of a pipe joint.

More specifically, the apparatus employed in the preparation of a pipe joint formed in accordance with the system of the present invention, includes: (i) apparatus for welding two tubular members, as described hereinbelow in conjunction with Figs. 1-13; (ii) apparatus for expansion of a tubular member, as described hereinbelow in conjunction with Figs. 14-21; and (iii) apparatus for optionally delaying the recovery of an expanded or compressed tubular member, as described hereinbelow in conjunction with Figs. 22A-26B.

Referring now specifically to Figs. 1,2, and 3, there are shown pictorial illustrations depicting first, second, and third stages in the formation of a simple pipe joint, referenced generally as 10, in accordance with one embodiment of the present invention. Pipe joint 10 is formed by electrically welding together first and second tubular members, respectively referenced 12 and 14, thereby to provide therebetween a high-strength, preferably fluid-tight joint.

Referring now initially to Fig. 1, first and second tubular members 12 and 14, have end portions, respectively referenced 22 and 24, which are arranged for connection to each other. First tubular member 12 may be the end of a length of piping which it is sought to join to second tubular member 14. It may alternatively be a connector sleeve 52, as shown and described below in conjunction with Figs. 5 and 6. Similarly, second tubular member 14 may be any free end of any sort of weldable plastic pipe, tube, or connector, to which it is sought to join first tubular member 12.

In accordance with the present invention, first member 12 is formed of a polymer which, on the one hand, is not only flexible, but also has mechanical memory properties.

Accordingly, while first member 12 may be formed of any suitable polymer, including polyethylene, it is most preferably formed of cross-linked polyethylene (PEX). The first member may alternatively be formed so as to have plural layers, of which at least one is cross-linked polyethylene, and at least one is weldable and typically formed inwardly of the PEX layer.

Second member 14 is preferably formed of a polymer, such as polyethylene.

There is also provided a welding member 15 which, in its simplest form, seen in Fig.

1, is an electric heating element in the form of a coil which is configured for placement over an outward-facing surface of end portion 24 of second tubular member 14, as shown in Fig.

1. Coil 15 may either be fully exposed, or may alternatively be coated, with an insulating, and optionally, weldable material, such as polyethylene.

In accordance with the present embodiment, first member 12 has an end portion 22 which has an inner diameter Do which is initially smaller than the outer diameter D2 of electric heating coil 15, and which, upon application of a radially outward stretching force is elastically stretchable to a size D1 which is larger than the outer diameter D2 of electric heating coil 15 when placed over second tubular member 14 and which, upon removal of the stretching force, seeks to shrink to its original size.

Referring now to Fig. 2, there is shown pipe joint 10 with second tubular member 14, having electric heating coil 15 (Fig. 1) located thereon, inserted into the stretched end portion 22 of first tubular member 12. As shown in the drawing, electric heating coil 15 is further configured so that when second tubular member 14 is inserted into first tubular member 12, the ends 16 of the coil 15 remain exposed. This allows coil 15 to be connected to an electrical circuit so that an electrical current may be passed therethrough, thereby heating it and tubular members 12 and 14 and initiating the electric welding process.

Referring now to Fig. 3, there is shown pipe joint 10 after first tubular member 12 has shrunk around second tubular member 14, thereby applying an inward radial force thereto, and after electrical current has been passed through electric heating coil 15, thereby forming a high-strength, preferably fluid-tight joint by electric welding.

Referring now to Fig. 4, there is seen a pipe joint, referenced generally 40, formed in accordance with the above-described embodiment of the invention. Pipe joint 40 is formed between first and second tubular members, respectively referenced 42 and 44, which it is sought to connect.

Referring now to Fig. 5, there is seen a pipe connection, referenced generally 50, in which a connector sleeve 52 is used, in accordance with the present invention, to connect two tubular members, referenced 54'and 54", in end to end fashion. In this embodiment, each end 56 of connector sleeve 52 is joined to an end portion 58'or 58"of an associated tubular member 54'or 54", respectively, so as to define a joint thereat, referenced generally 50'. It will be appreciated that joint 50'is formed in substantially the same manner as joint 40, seen in Fig. 4, that connector sleeve 52 has similar properties and generally corresponds to first tubular member 42, and that tubular members 54'and 54"have similar properties and generally correspond to second tubular member 44.

Referring now to Fig. 6, there is seen a T-connection, referenced generally 60, in which a plurality of sleeve members 52 are used to connect a plurality of tubular members, referenced 64', 64", and 64"'to a T-member 66. In this embodiment, each end 56 of connector sleeve 52 is joined to an end portion 68', 68", or 68"'of an associated tubular member 64', 64", and 64"', respectively, so as to define a joint thereat, referenced generally 60'. It will be appreciated that joints 60'are formed in substantially the same manner as joint 40, seen in Fig. 4, and that tubular members 64', 64", and 64"'have similar properties and generally correspond to second tubular member 44.

In general, it is seen that the joint 40 of Fig. 4 represents a general case which can be applied to many different connection arrangements, including variously configured arrangements not specifically described herein, and that the connections shown and described in conjunction with Figs. 5 and 6, are merely representative of this fact.

Referring now to Figs. 7 and 8 there are shown, respectively, detailed, schematic, cross-sectional views of formation of joint 10, shown and described above in conjunction with Figs. 1-3. Fig. 7 shows insertion of end portion 24 of second tubular member 14 into end portion 22 of first tubular member 12, prior to connection of the tubular members to each other, while Fig. 8 shows the welded connection after its formation. It is seen that, in order to provide the described connection, electric heating coil 15 has been placed onto end portion 24 of second tubular member 14, prior to the two tubular members 12 and 14 being fitted together. The welding is performed at the interface between the two pipe portions being joined, defined by contact portions thereof, the contact portion of the end of first tubular member 12 being referenced 23, and the contact portion of the end of second tubular member 14 being referenced 25.

As will be understood from the following description, tubular members which may be joined in accordance with the present invention may be formed either from a single or multiple layers, and may be made of different materials. Regardless of materials from which other portions of the tubular members may be formed, the respective contact portions 23 and 25 must be made from weldable materials.

Thus, in one embodiment of the invention, end portion 22 of first tubular member 12, and thus contact portion 23 thereof, is formed of a single layer of cross-linked polyethylene (PEX), and the end portion 24 of second tubular member 14, and thus also contact portion 25 thereof, is formed of a single layer, either of non-cross-linked polyethylene or of PEX.

Alternatively, first tubular member 12 may be formed of two or more layers, at least one of which, preferably an outer layer, referenced 76, is formed of PEX, and the innermost layer 78, is formed preferably of non-cross-linked polyethylene. In such an embodiment, after expansion of and subsequent removal of the expansion force from end portion 22 of first tubular member 12, contraction of the PEX layer 76, as it seeks to regain its original shape, causes the end portion 22 to shrink around second tubular member 14, thereby applying an inward radial force thereto. When the interface between the two contact portions 23 and 25 is heated by electrical current passing through electric heating coil 15, the contact portion 23-constituted here by inner polymer layer 78 of first tubular member 12-is heated so that it welds together with contact portion 25 of second tubular member 14, thereby forming a high-strength, preferably fluid-tight, joint 10 by electric welding.

Referring now again to Figs. 1-3, in accordance with the present invention, the following is a summary of the steps required to form joint 10: a) placing electric heating coil 15 onto the end portion 24 of the second tubular member 14; b) stretching the end portion 22 of the first tubular member 12 to a size larger than the outer diameter of the electric heating coil 15 when placed over the second tubular member 14; c) inserting the end portion 24 of the second tubular member 14, having the electric heating coil 15 located thereon, into the stretched end portion 22 of the first tubular member 12 ; d) allowing stretched end portion 22 of the first tubular member 12 to shrink and to apply an inward radial force to the electric heating coil 15 and to the end portion 24 of the second tubular member 14; e) applying electrical current to electric heating coil 15 via ends 16 thereof, thereby heating the outward-facing surface of the end portion 24 of the second tubular member 14 and the inward-facing surface of the end portion 22 of the first tubular member 12 to melting temperature, thereby causing the end portions 22 and 24 of the first and second tubular members 12 and 14 to become welded together.

Referring now to Fig. 9, there is seen a pipe joint, referenced generally 10', which is generally similar to any of those shown and described above in conjunction with Figs. 1-4,7 and 8. All components of pipe joint 10'with counterpart components in Figs. 1-4,7 and 8, are identified in Fig. 9 by corresponding reference numerals.

In accordance with the present embodiment, welding member 115 is formed of electrical heating coil 15 embedded in a welding sleeve 116, formed of a weldable material, such as, non-cross-linked polyethylene. It will be appreciated that this is useful particularly in cases wherein both the first and second tubular members 12 and 14 are formed of PEX, the melted non-cross-linked polyethylene layer formed between the contact portions thereof, effecting a weld therebetween, as per the present invention.

Referring now to Fig. 10, there is seen a flexible, generally planar profile member, referenced generally 200, formed of a welding material, such as polyethylene, from which cylindrical welding sleeves, seen at 216 in Fig. 11 and at 316 in Fig. 12, are formed. The profile member 200 has first and second generally parallel sides, referenced 202 and 204, respectively. First side 202 is generally planar, and second side 204 has formed thereon a plurality of channels 206. The profile member 200 is flexible, as mentioned, and may be cut from a larger portion (not shown) so as to be foldable into a cylinder such that channels 206 are positioned along a seam 208 (Fig. 11), thereby to define a single helical channel 210, extending from a first end 221 of sleeve 216 to a second end 223 thereof. This arrangement is seen in Fig. 11, in which a single electrical wire 215 is wound along the length of the channel 210, so as to form a coil. In this embodiment, it is seen that the coil has a pair of ends 217 which protrude from opposite ends of the channel 210, for connection to an electrical power source. Accordingly, welding sleeve 216 is particularly useful in conjunction with connector sleeve 252, whose use is similar to that of connector sleeve 52, shown and described above in conjunction with Fig. 5, and which are thus not described again herein.

Referring now specifically to Fig. 12, profile member 200 may be cut so as to be foldable into a cylinder such that channels 206 are positioned along a seam 308 (Fig. 12), thereby to define two parallel helical channels 310a and 310b, extending from a first end 321 of sleeve 316 to a second end 323 thereof. It is seen in the drawing that an electrical wire 315 is wound along the length of channels 310, thereby to form a coil whose ends 317 protrude from second end 323 of sleeve 316, for connection to an electrical power source.

A bend in the wire, referenced 319, is seen at first end 321 of welding sleeve 316.

Referring now to Fig. 13, there is seen a pipe joint, referenced generally 410, formed in accordance with an alternative embodiment of the invention. Pipe joint 410 is formed between first and second tubular members, respectively referenced 412 and 414, which it is sought to connect, thereby to provide a high strength, preferably fluid-tight joint.

First and second tubular members 412 and 414 are generally similar to first and second tubular members 12 and 14, shown and described above in conjunction with Figs.

1-3,7,8,9, and 12, except as described herein, and are thus not specifically described again herein, in detail. Similarly, an electric welding member 415 is employed in the present embodiment, also as shown and described above. While welding member 415 is exemplified herein as an electric welding coil, it will be appreciated that it is interchangeable with any of the various welding members shown and described hereinabove, and should thus be taken merely to be representative thereof.

It is seen that the sole difference between the presently illustrated joint 410 and joint 10 of any of Figs. 1-3,7,8,9, and 12, is that, whereas, in order to form any of the above joints, first tubular member 12 is expanded, and thereafter placed over electric heating coil 15 and second tubular member 14, this is not the case in the present embodiment.

In the present embodiment, first tubular member 412 initially has an external diameter that is larger than the inner diameter of the coil 415 when coil 415 is located coaxially within end portion 424 of second tubular member 414. It is thus seen that, in order to form the illustrated joint 410, first tubular member 412 is contracted so as to reduce its outer diameter to less than the internal diameter of coil 415, whereafter the two end portions 422 and 424 can be fitted together such that coil 415 is disposed between respective contact portions 423 and 425 thereof. More specifically, coil 415 may either be placed over first end portion 422, after which the pipes are fitted together; or coil 415 may be inserted coaxially inside second end portion 424, following which the pipes are fitted together.

The joint being formed is then left so as to allow the first end portion 422 to expand, thereby applying a radially outward force to the electric heating coil 415 and to second tubular member 414. The remainder of the process, wherein an electric current is passed through coil 415 thereby heating it so as to cause welding and joining together of the respective contact portions 423 and 425, is substantially as described above in conjunction with any of Figs. 1-3,7,8,9, and 12, and is thus not described again herein.

It will be appreciated that joint 410 is by way of example only, and that the various joint configurations shown and described above in conjunction with Figs. 4,5, and 6, as well as other pipe joint configurations, may be formed in accordance with the present embodiment of the invention.

Turning now to Figs. 14,15 and 16, there is seen therein, apparatus referenced 500, constructed in accordance with one embodiment of the present invention and operative to expand a free end portion 522 of a tubular member 512, such as is depicted in dashed lines in Figs. 14 and 15. Tubular member 512 is formed generally similar to first tubular member 12, shown and described above in conjunction with Figs. 1-3,7-9, and 12, in that it is made of any suitable resilient material, such as plastic, having mechanical memory characteristics.

Figs. 14 and 15 respectively illustrate tubular member 512 prior to and following expansion.

Apparatus 500 typically includes an adjustable expansion head 516, a power source 518 mounted onto a base member 520, and an actuator member or head 521, which is connected to power source 518 via a power transfer portion 524.

Expansion head 516 defines an outward-facing generally cylindrical contact region 526 which is formed parallel to an axis 528. In more detail, it is seen that expansion head 516, as seen particularly in Fig. 16, is formed of a plurality of segmental expansion elements 516', each mounted onto a linked support 530 via a hinged connection 532. Each expansion element 516'defines an outward-facing segmental contact surface 526', which, together with the contact surfaces 526'of the other expansion elements 516', constitutes the contact region 526. Each expansion element 516'further defines an inward-facing segmental inclined surface 534, inclined at a predetermined angle a to the axis 528.

Actuator member 521 is seen to be generally conical, such that it defines a conical contact surface 536 (Figs. 15 and 16) which tapers, also at angle a, towards front ends 537 of expansion elements 516', when in the retracted orientation seen in Fig. 14.

Power source 518 may be a suitable pneumatic or hydraulic power source, or a mechanical system, such as a worm gear system, or the like.

Linked support 530 is constituted by base member 520 and a plurality of elongate connector members 538, which are mutually parallel and are of substantially equal length.

Base member 520 may be of any suitable shape, and is located at the rear of the apparatus 500, and transversely to axis 528. Connector members 538 extend between front hinge locations 532 and rear hinge locations 542, whereat they are connected to base member 520. At least three hinge locations 532 and 542 are provided, arranged along an arc of greater than 180°, and spaced preferably equally about axis 528. In the present example, seen in Fig. 16, four pairs of hinge locations 532 and 542 are provided, spaced apart at 90° intervals.

As seen in Figs. 14,15 and 16, there are preferably also provided one or more resilient compression members 544, such as a rubber belt, or the like, for applying to the expansion elements 516'a radially inward compressive force. This serves to retain the expansion elements 516'in a retracted orientation, in the absence of a radially outward force of greater magnitude.

In general, operation of power source 518 causes a linear translation of actuator head 521 along axis 528, thereby to cause a lateral expansion of expansion head 516, as described below. It is a particular feature of the invention that operation of power source 518 causes a desired lateral widening of the contact region 526 defined by expansion head 516, while maintaining the generally cylindrical form thereof, and thus also the parallel orientation thereof with respect to axis 528. It will thus be appreciated that, when the expansion head 516 is located within free end portion 522 of tubular member 512, the contact region 526 is operative to apply forces thereto, in radially outward directions only, so as to cause an evenly distributed radial expansion of the free end portion 522.

It is also a particular feature of the present invention that hinge locations 532 and 542 define respective pivot axes 533 and 543, and that both the mounting of expansion elements 516'at pivot axes 533 and the mounting of connector members 538 at pivot axes 543 are with a single degree of rotational freedom only. Hinge locations 532 are formed such that pivot axes 533 are arranged in a common plane 535 (Figs. 14 and 15), perpendicular to axis 528, and so as to be spaced equidistantly from axis 528. Similarly, hinge locations 542 are formed such that pivot axes 543 are also arranged in a common plane 545 (Figs. 14 and 15), parallel to plane 535, and so as to be spaced equidistantly from axis 528. This geometric arrangement, in conjunction with the above-described geometry of expansion elements 516'and of actuator head 521, limits the movement of expansion elements 516'to a substantially radial motion only, as actuator head 521 advances along axis 528, substantially preventing movement of these elements 516'in any other direction.

Accordingly, in order to expand free end portion 522 of tubular member 512, expansion head 516, in its retracted position shown in Fig. 14, is inserted into end portion 522. Power source 518 is then operated so as to move actuator head 521 along axis 528, in the direction indicated by arrow 546 (Fig. 15), such that conical contact surface 536 thereof slides along the inward-facing inclined surfaces 534 of expansion elements 516', thereby forcing them radially apart, as indicated by arrows 548. In the present example, the diameter of contact region 526 is shown to be just slightly smaller than the interior diameter of free end portion 522 of tubular member 512, such that contact surfaces 526'contact the interior of free end portion 522 even after a small amount of expansion of actuator head 516. This is by way of example only, however, and, within predetermined ranges, apparatus 500 of a predetermined size may be used for expansion of different sizes of tubular members, up to a predetermined maximum size.

As actuator head 521 is displaced successively further along axis 528, expansion elements 516'continue to be displaced further apart, until-in the present example-contact surfaces 526'engage the inward-facing surface of tubular member 512 so as to expand free end portion 522, to a desired size.

Subsequently, after a desired expansion of free end portion 522 has been achieved, actuator head 521 is withdrawn along axis 528, such that the compressive force applied to expansion elements 516'by compression member 544, causes them to contract together, so as to permit removal of the expansion head 516, and of the apparatus 500, from tubular member 512. A desired fitting, pipe, or other tubular member that is sought to fit together with member 512, may then be inserted into the expanded free end portion 522.

Referring now to Figs. 17-19, there is shown therein, expansion apparatus, referenced 600, constructed in accordance with an alternative embodiment of the invention, and operative for expanding a free end 622 of a tubular plastic member 612. Some portions of apparatus 600 are similar, at least in function, if not in form, to those shown and described above in conjunction with apparatus 500, and are therefore not specifically described again hereinbelow. These similar portions are denoted in Figs 17-19, for ease of understanding, by reference numerals which are similar to their counterpart portions in the embodiment of Figs. 14-16, but which commence with a"6"prefix in place of a"5"prefix.

In the present embodiment, each expansion element 616'defines front and rear portions, respectively referenced 660 and 662, each element 616'being connected to a connector member 638 at hinge location 632 via rear portion 662.

Actuator member 621 is mounted for selectable movement along the axis 628 between the expansion elements 616'. Actuator member 621 is connected to each expansion element 616'by means of two intervening sets of parallel intermediate connector members 738, so as to form, together with each expansion element 616'and the two intervening pairs of connector members 738, a parallelogram arrangement. Each'set'of connector members 738 is typically either a single member or, as in the present example, it may be a pair of members.

It is a particular feature of the present invention that hinge locations 632 and 642 define respective pivot axes 633 and 643, and that both the mounting of expansion elements 616'at pivot axes 633 and the mounting of connector members 638 at pivot axes 643 are with a single degree of rotational freedom only. Hinge locations 632 are formed such that pivot axes 633 are arranged in a common plane 635 (Figs. 17 and 18), perpendicular to axis 628, and so as to be spaced equidistantly from axis 628. Similarly, hinge locations 642 are formed such that pivot axes 643 are also arranged in a common plane 645 (Figs. 17 and 18), parallel to plane 635, and so as to be spaced equidistantly from axis 628. This geometric arrangement, in conjunction with the above-described parallelogram arrangement, limits the movement of expansion elements 616'to a substantially radial motion only, as actuator head 621 advances along axis 628, substantially preventing movement of these elements 616'in any other direction.

In operation, a generally forward axial movement of the actuator member 621, as indicated by arrow 646 (Fig. 18), away from the base member 620, causes a pivoting of the intermediate connector members 738-as shown by arrows 647 (Fig. 18)-towards the generally perpendicular position relative to the axis 628 seen in Fig. 18. This forces the expansion elements 616'radially apart, as indicated by arrows 648, thereby also causing expansion of the tubular member free end portion 622, generally as described above conjunction with Figs. 14-16.

Referring now briefly to Figs. 20 and 21, there is shown therein, apparatus 600 which has located thereon an expandable adapter ring, referenced 650. Adapter ring 650 may be any suitable elastic structure, and may be formed of a suitable elastomer, or any other expandable structure. Different sizes of adapter ring 650 may be used so as to effectively increase the diameter of the contact region 626 (Fig. 17 and 18), thereby enabling expansion apparatus 600 of a given size, to be used with a range of sizes of tubular members 612. As a further option, several such rings may be used concentrically, so as to successively increase the effective maximum diameter of expansion.

Referring now briefly to Fig. 22, there is shown a graph of maximum radial force that can be exerted by the expansion head 616, versus the angular displacement between the actuator member 621 and the expansion head 116. This angular displacement is depicted in Fig. 17 by the letter ß, and can vary between 0 and 90°. As clearly seen in the graph of Fig.

22, the force exerted increases considerably towards the end of a forward'stroke'of actuator member 621. This phenomenon can be used to great advantage for expansion of pipe end portions, particularly those formed of especially stiff material, and particularly, when employing the apparatus of the invention to expand a pipe end having a diameter which is just smaller than the diameter of the expansion head 616 at its point of maximum expansion. In such a case, after expansion has been achieved by opening the expansion head 616 to its maximum extent, successive adapter rings 650 can be placed concentrically on expansion head 616, each time effectively increasing its diameter, and thus enabling a step-by-step expansion of the free end portion 622 of tubular member 612.

Further advantages afforded by use of adapter ring 650 include the fact that its use serves to spread the expansion force applied by expansion head 616, over substantially the entire tubular member engaged thereby, thereby ensuring generally uniform expansion of the tubular member, and also serving to protect the interior surface thereof.

It will be appreciated that, while adapter ring 650 has been shown and described in conjunction with apparatus 600, it may also be used in conjunction with apparatus 500, shown and described above in conjunction with Figs. 14-16.

Referring now to Figs. 23A-27B generally, there is seen illustrated recovery delay apparatus, constructed for use in the system and method of the present invention, and operative for optionally delaying the cold recovery of a portion of tubular member which has undergone mechanical deformation by means of cold expansion or cold compression.

Such apparatus may be useful in cases where advance off-site preparation of a free end of a cold recoverable tubular member by deformation thereof is expedient, so that the tubular member in its deformed state may be stored with the aid of recovery delay apparatus until such time as it is needed in the field.

It is noted that the exemplary recovery delay apparatus, shown and described hereinbelow in conjunction with Figs. 23A-27B, are all generally sleeve-shaped or ring-like.

It will be appreciated however, that this is for example only, and that recovery delay apparatus intended to fall within the scope of the present system of the invention, may also be constituted by members of other suitable configurations which are either hollow or solid in form.

Referring now to Figs. 23A-23C, there is seen the prepared free end 1022 of a plastic tubular member 1012 which, in the present example, is seen to have been expanded.

It is seen that recovery of the free end 1022 is prevented by the location of a recovery delay device, constituted in the present embodiment by a support ring 1045. Support ring 1045 is formed of a material which is strong, and which preferably also has a relatively high modulus of elasticity. Suitable materials include steel and aluminum, and a suitable plastic such as U-PVC.

Support ring 1045 has a slit 1004 (Fig. 23A) which extends across the entire width thereof, formed by free edges 1006a and 1006b. In use, support ring 1045 is inserted into the prepared free end 1022 after expansion thereof, so as to brace the free end against contraction. More precisely, it will be understood that ring 1045 is used to apply recovery-resistant forces to the free end of the tubular member, which are opposite and at least equal to the recovery forces in the deformed end, thereby to delay recovery thereof until a desired time, i. e. until connection of the plastic tubular member to another tubular member or pipe fitting.

An opening 1008 (also seen in hidden detail in Fig. 23A) is formed along slit 1004, so as to enable extraction of ring 1045 by insertion into opening 1008 of any suitably shaped tool, such as a screwdriver 1010, and a lateral pivoting of the tool while located in the opening 1008, so as to pry loose one of free edges 1006a or 1006b. This pivoting, indicated by arrow 1011 (Fig. 23B), causes one of the free edges to be retracted inwardly of the other edge, as seen in Fig. 23C. Subsequently, ring 1045 may be easily removed from the free end 1022. In the absence of the support ring 1045, the mechanical memory of the free end 1022 causes it to recover its original shape, as desired.

Referring now to Fig. 24, there is seen a prepared free end 2022 of a plastic tubular member, in which is located a recovery delay device 2002 constructed and operative in accordance with another embodiment of the apparatus of the invention. The delay device 2002 is formed of a support ring 2045, which may be formed of a material similar to those of ring 1045 (Figs. 23A-23C), and which has a longitudinal opening 2059, into which a spacer 2006 has been inserted. In use, support ring 2045 is inserted into the free end 2022 after expansion thereof, and spacer 2006 is placed in opening 2059, thereby to brace the support ring 2045, and thus also the free end 2022 against contraction. Subsequent removal from opening 2059 of the spacer 2006, which may optionally be attached to the ring 2045, causes a partial inward contraction or collapse of the ring, following which it may be easily removed from the free end 2022, allowing recovery thereof.

Spacer 2006 may be formed as a simple peg, and it may also have a hole 2008 formed therein in order to facilitate attachment thereto of a suitable gripping tool, or insertion thereinto of a piece of wire or string, so as to enable spacer 2006 to be pulled easily, possibly without requiring use of any tool.

Referring now to Fig. 25A, support ring 2045 of Fig. 24 may be constituted by a bi-directional gripping member 2145, which is configured to be disposed between end portions of two plastic tubular members to be connected generally as described above. It will be appreciated that, in the present examples, ring 2145 is dual-purpose, functioning both as a recovery delay device, substantially as described above, and, also as a bi-directional gripping member, thus also being an integral part of the connection. Support ring 2145 may be formed of metal, hard plastics, or of any other suitable materials.

It is thus seen that support ring 2145 is a split ring, having an opening 2159, and further has outward-facing and inward-facing surfaces, respectively referenced 2146 and 2148. Circumferential ridges 2152 are formed on surfaces 2146 and 2148, and serve to grip surfaces of a tubular member with which they are brought into contact. Provision of the opening or split 2159 permits compression of the support ring 2145 when located between a pair of assembled tubular member ends, but only after a spacer (not shown) such as spacer 2006 (Fig. 24) has been removed therefrom.

Referring now briefly to Fig. 25B, there is seen a dual-purpose ring 2245, similar to ring 2145, shown and described above in conjunction with Fig. 25A, but having a plurality of longitudinal openings 2259. Provision of the splits 2259 permits compression of the support ring 2245 when located between a pair of assembled tubular member ends, but only after one or more spacers (not shown) such as spacer 2006 (Fig. 24) have been removed from one or more of the openings 2259.

Referring now briefly to Fig. 25C, there is seen a support ring 2345 which, while serving a generally similar purpose to that of ring 2245 (Fig. 25B), has barbs 2352 in place of ridges 2152. The barbs 2352 extend from both surfaces 2346 and 2348, and are operative to"bite"into adjoining surfaces.

Referring now to Figs. 26A and 26B, there is seen a prepared free end 4022 of a plastic tubular member, in which is located a recovery delay device 4002 constructed and operative in accordance with yet another embodiment of the apparatus of the invention. The delay device 4002 may be formed of a material similar to those of ring 1045 (Figs.

23A-23C), and is formed as a ring 4045 with an integral, inwardly collapsible portion, indicated generally at 4010. The collapsible portion is typically defined by the provision of preferably one outward-facing groove 4011, surrounded by a pair of inward-facing grooves 4014. Grooves 4011 and 4014 function as integral hinges, and thereby define a pair of selectably rotatable arc portions 4013. A grip element 4016 extends inwardly from collapsible portion 4010 opposite the outward-facing groove 4011.

It will be appreciated that, while the provision of integral hinges is most convenient, grooves 4011 and 4014 may, alternatively, be replaced by non-integral hinges.

In use, delay device 4002 is inserted into the free end 4022 after expansion thereof, such that the free end is prevented from contracting. Removal of delay device 4002, prior to assembly of free end 4022 with the end of another tubular member, is facilitated by pulling inwardly on grip element 4016, as shown by arrow 4018. This causes arc portions 4013 to rotate inwardly about grooves 4011 and 4014, as illustrated by arrows 4020, thereby effectively constituting an inward collapse of collapsible portion 4010, enabling removal of delay device 4002 from the free end 4022.

Referring now to Figs. 27A and 27B, there is seen a prepared free end 5022 of a plastic tubular member 5012 which, in the present example, is seen to have been compressed. It is seen that recovery of the free end 5022 is prevented by the location of a recovery delay device 5002, constituted in the present embodiment by a support ring 5045.

Support ring 5045 may be formed of any material described above in conjunction with Figs.

23A-23C.

Support ring 5045 is a split, sleeve-shaped member which defines an opening 5059 between a pair of opposing free edges 5031 and 5033, which respectively have formed thereon, alternating pluralities of knuckles referenced 5032 and 5034. When the knuckle pluralities 5032 and 5034 are brought into mating engagement with each other, they together define a barrel 5036 through which a locking pin 5038 may be inserted, thereby to become locked together. A gripping ring 5040 may be attached to locking pin 5038 for ease of its withdrawal from barrel 5036.

In use, a fully assembled delay device 5002-with the knuckle pluralities 5032 and 5034 locked together via locking pin 5038-is placed around the free end 5022 after compression thereof, such that the free end is prevented from expanding to its original size.

Extraction of locking pin 5038 from barrel 5036, prior to insertion of free end 5022 into the end of another tubular member for assembly therewith, permits removal of delay device 5002 from free end 5022, so as to allow a desired recovery of the free end 5022.

Referring now briefly to Figs. 23A-27B, it is a feature of the present invention that, preferably, the various forms of recovery delay apparatus shown and described hereinabove, are typically not damaged during use, and may thus be reused several times.

In accordance with a further aspect of the system of the invention, however, the method of the invention may be performed in conjunction with a simple support ring formed of a brittle material, such as a brittle plastic or ceramic, which, while not being reusable, has the advantage of being cheap to manufacture and easy to remove from a braced pipe end, merely by breaking.

It will be appreciated by persons skilled in the art that the scope of the present invention is not limited to what has been particularly shown and described hereinabove, merely by way of example. The scope of the present invention is limited, rather, solely by the claims, which follow:




 
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