DESC:FIELD OF THE INVENTION
The present invention relates to a modified casing connector for casing pipes. More particularly, the present invention relates to a modified casing connector for casing pipes comprising of at least two members i.e. a circular box connector and a circular pin connector with a locking system and wherein the thickness of wall of the box connector is increased by increasing the outer diameter of the box connector to prevent damaging at the time of assembling and handling during transportation of the connector.

BACKGROUND OF THE INVENTION
Casings strings or pipes or tubular members, are used in a number of applications, and are important in the oil and gas industry. In offshore and land operations for drilling and oil production, pipes, casing or strings need to undergo within the ground to get supply of liquid or gas. For such operations pipes, or casings needs to be connected end to end in series like a structure using connectors such as threaded, or snap lock like connectors.
Threaded connectors between pipe members are typically made by providing one end of one pipe member with a pin connector having external threads, and providing the end of another pipe member with a box connecter which receives the pin member. The pin and box members may come as integral parts of their respective pipe members, or may be added thereto by welding.
Typical connectors available include the threaded type, breach block connectors, snap lock connectors, and multi thread connectors. Some connectors use heat, fluid pressure, or mechanical force to obtain a fit. In some cases, complex tools or other machinery are required to complete such connections. Various added constructions are known, including tapered threads and straight threads. Said connections don’t provide secure locking as in said operations there are different types of forces acting on the said pipe, casing or string joints such as vibration from fluid flow and machine operations, force exerted by fluid itself is high on the joints that could cause problems while operation so there is need to overcome these issues.
US 8056940 describes a pipe connector comprising a tubular pin member having a frustoconical outer surface and a tubular box member having a frustoconical inner surface corresponding to the outer surface of the pin member and which overlies the frustoconical surface of the pin member when the members are fully engaged. The members are provided with inter-engageable annular projections and grooves on the said peripheral surfaces for axially locking the members together when they are fully engaged together. However, the product achieved using the cited document uses very different technology and is quite complicated for inter- engaging.
US4770448A describes a pipe joint coupling for deep well pipe strings has a female thread with a slightly longer pitch than the standard API thread of the pipe end. The difference in pitch is predetermined so as to equal the elastic elongation of the pipe end threads due to loading of the made up joints when suspended in a well. The coupling, in addition to having a slightly longer thread pitch may also have a different taper or tapers than that of the standard pipe end. The main drawback of the present invention is that it is likely to get loose and the connection may open due to back rotation.
Therefore, the present invention overcomes the drawbacks of the cited art and provides a modified connector comprising of at least two members; wherein, one member is a circular box connector and other member is a circular pin connector with a locking system and has increased outer diameter of box connector to prevent damaging at the time of assembling and handling during transportation of the connector and is reliable and relatively inexpensive.

OBJECT OF THE INVENTION
The main object of the present invention is to provide a modified casing connector comprising of at least two members; wherein, one member is a circular box connector and other member is a circular pin connector to prevent damage at the time of assembling and transportation of the connector.
Another object of the present invention is to provide a modified casing connector comprising of a circular box connector wherein the thickness of wall of box connector is increased by increasing the outer diameter to increase the strength of the connector to prevent damage at the time of assembling, handling and during transportation of the connector.
Yet another object of the present invention is to provide a modified casing connector of at least two members; wherein, one member is a circular box connector and other member is a circular pin connector with a locking system to prevent backing-off of the connector joint during drilling operations, and also with reduced thickness at specified places in the box connector to help ensure easy operations during locking of the casing pipe joints.

SUMMARY OF THE INVENTION
In an embodiment, the present invention provides a modified casing connector comprising of at least two members; wherein, one member is a circular box connector and other member is a circular pin connector to prevent damage at the time of assembling, handling and transportation of the connector.
In another embodiment, the present invention provides a modified casing connector comprising of at least two members, wherein one member is a circular box connector and the other member is a circular pin connector. The circular box connector has internal threads at inner surface and the circular pin connector has external threads at outer surface and these threads are on tapered surfaces in both of the connectors. Said members of the modified casing connector are coupled together by rotating one member to another with the help of said threads.
In yet another embodiment, the present invention provides a circular pin connector of the modified casing connector with external threads at its outer surface for engaging with the box connector having matching internal threads. The circular pin connector is hollow from inside to allow flow of a fluid or liquid and has four slots for safeguarding against anti-locking of the connector by back rotation.
In yet another embodiment, the present invention provides a circular box connector of the modified casing connector wherein the thickness of wall of box connector is increased by increasing the outer diameter to prevent damage at the time of assembling, handling and transportation of the casing pipes. On the outer surface of the box connector, at four places the material is removed up to a specified thickness so that the material from the box connector is locked into the four slots at and near the shoulder of the pin connector.
In still another embodiment, the present invention provides a modified casing connector with a locking arrangement against back rotation of said members over the circumference of the connector, provided by four slots on outer surface at and near the free end of the pin connector. These slots are provided over the circumference of the members at specified locations to achieve desired locking against back rotation.

BRIEF DESCRIPTION OF THE DRAWING
A complete understanding of the system and method of the present invention may be obtained by reference to the following drawing:
Figure 1 describes casing connector with a circular box connector and a circular pin connector.
Figure 2 describes the box connector with slots and increased outer diameter having threads on inner surface for engaging with the pin connector having matched external threads.
Figure 3 describes the box and pin connectors with casing pipes welded, showing groove on the pin connector for ‘O’ring installation, ‘shoulder’ on the pin connector for achieving full make- up when the pin connector is threaded to the box connector, and ‘free end’ of both pin and box connector.

DETAILED DESCRIPTION OF THE INVENTION
Many aspects of the invention can be better understood with references made to the drawings below. The components in the drawings are not necessarily drawn to scale. Instead, emphasis is placed upon clearly illustrating the components of the present invention. Moreover, like reference numerals designate corresponding parts through the several views in the drawings. Before explaining at least one embodiment of the invention, it is to be understood that the embodiments of the invention are not limited in their application to the details of construction and to the arrangement of the components set forth in the following description or illustrated in the drawings. The embodiments of the invention are capable of being practiced and carried out in various ways. In addition, the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting.
The present invention provides a modified casing connector comprising of a circular box connector and a circular pin connector with wall thickness of the box connector increased by increasing outer diameter of the box connector to prevent damage at the time of assembling and handling of casing pipes with connectors during transportation of the same.
In a most preferred embodiment, referring to Figure 1, the present invention provides a modified casing connector (1) comprising of at least two members; wherein, one member is a circular box connector (2); and the other member is a circular pin connector (3). The circular box connector (2) has internal threads (4) at inner surface and this inner surface is tapered with respect to the axis of the connector and is also called frustoconical surface, and further the circular pin connector (3) has external threads (5) at outer surface and this outer surface is tapered surface with respect to axis of the connector and is also called frustoconical surface; with tapered surface of the box connector matching with the tapered surface of the pin connector; and the members are coupled together by rotating one member to another with the help of said threads. In the box connector (2) of the modified casing connector (1) the thickness of wall of the box connector is increased by increasing the outer diameter of box connector. The modified casing connector (1) has locking arrangement against back rotation of said members over the circumference of the connector (1) and is provided by four slots provided at the surface and near the shoulder of the pin connector (3). These slots (6) are provided over the circumference of the members at specified locations to achieve desired locking against back rotation. The pin connector (3) is hollow to allow flow of a fluid or liquid and has four slots for safeguarding against anti-locking of the connector (1) by back rotation. Modified buttress thread with flank angle of 25º has been used for thread profile of the threads on both the pin connector (3) and the box connector (2).
The material of the pin connector (3) and the box connector (2) is changed from X60 to higher grade material like X70 (material grade as per API 5L) so the strength of the material is increased significantly. Thus, the values of tension yield, bending yield, burst pressure and collapse pressure have been increased so that these values are more than that for casing pipes. Therefore, failure of connectors is not likely to happen. If any failure happens in the casing pipe, it may happen in the pipe, not in the connector (1).
The thickness of the wall of the box connector (2) has been increased and material at the place of said slot places (6) has been removed in such a manner that the force required for deforming the box connector (2) at position of slots (6) is easily obtained by a readily available tool and is sufficient for locking of the box connector (2) over the circumference of the pin connector (3) against back rotation. Thus, the locking of the connector members (2, 3) is done easily. Thread profile of the threads on both the pin and box connector are modified buttress threads with a flank angle of 25º. Said improvements in members of the casing connector (1) are carried out for all different connectors for different casing sizes 18.625” to 36”, typical casing sizes being 18.625 X 0.435, 20.0 X 0.625,20 X 0.438, 26 X 1, 30 X 1, 30 X 1.5 and 36 X 1.5, all dimensions in inches, the first number being the casing OD (outer diameter) and the second number being the wall thickness, thus 18.625 X 0.435 means casing with nominal outer diameter 18.625” and wall thickness 0.435”.
In another preferred embodiment referring to Figure 2, the present invention provides a circular box connector (2) of the modified casing connector (1) wherein the thickness of the wall of the box connector is increased by increasing the outer diameter of the box connector (2) to prevent damage at the time of assembling, handling and transportation of the connector (1). On the outer surface of the box connector (2), at four places the material is removed up to a specified thickness so that the material from the box connector (2) is locked into the slots at and near the shoulder of the pin connector (3). Both the box connector (2) and the pin connector has modified buttress thread with flank angle of 25º used for profile of the threads.
In yet another preferred embodiment, the present invention provides a circular pin connector (3) of the modified casing connector (1) with external threads (5) at its outer surface on a surface that is tapered with the axis of the connector, for engaging with the box connector (2) having matched internal threads (4) and also at a tapered surface with the axis of the connector matching with the tapered surface of the pin connector. The circular pin connector (3) is hollow from inside to allow flow of fluid and has four slots for safeguarding against anti-locking of the connector by back rotation.
In still another embodiment, as shown in Figure 3, the present invention provides casing pipes (7) with modified box and pin connectors (2, 3) which are self-aligned so that when the casing joints are made using these casing pipes (7), all the connected pipes remain aligned. On one side of the casing pipe (7), there is a box connector (3) joined via casing weld (8) and on the other side of the casing pipe (7), there is a pin connector (3) joint via another casing weld (8). The box connector (2) and pin connectors (3) are welded with casing pipes (7). On the pin connector (3) there is groove (9) for ‘O’ ring installation, and shoulder (10) for achieving full make- up when the pin connector (3) is threaded to the box connector (2). The free-end (11) of both pin and box connector face outwards for box and pin connectors welded to same casing pipe (7). The casing joints (8) are made using low torque make-up with rig tongs. These casing pipes (7) with modified casing connectors (1) require less than one turn to make-up when the casing joints are made using these casing pipes. This is done by using multi-start threads in the connectors (1). In case, 4 start threads are provided in the connectors (1), and casing pipes (7) with these connectors (1) require less than half a turn to make casing joints. In case, 2 start threads are provided in the connectors (1), and casing pipes (7) with these connectors (1) require less than one turn to make casing joints.
The modified connectors welded to casing pipes provide visual indication when the make- up of the casing joints is completed. When pin connector is fully tightened into box connector, free end of box connector is in the same line as shoulder (10) of pin connector as clearly visible in Figure 1 also.
In still another embodiment, the present invention provides casing pipes with modified connectors which are suitable for piling and so the casing pipes with these connectors are subjected to hammering operation with the help of drive sub and this is helpful when initially lowering these pipes with these connectors welded to it are lowered one over the other. These casing pipes with connectors and such casing pipes are reversible and reusable.
The present invention provides casing pipes with connectors welded where the threads in the connectors are preloaded for fatigue.
Here, the connectors are made with material of higher grade and so the connectors are stronger than the casing pipes. Due to this fact, the connector does not fail even if casing pipes fails, and if failure occurs it will be failure in the casing pipe and the casing connector does not fail. The connectors provide high pressure sealing and are capable of bearing high pressure gas or liquid in the well and its connections remain leak proof against this. In a case, the connectors when welded with the casing pipes, are from inside flush with the internal surface of the casing pipe.
EXAMPLE 1
20” CONNECTOR
In case of a 20” connector, two of the four slots are provided each at 30º angle with respect to thread starting point as vertical line and other two of the four slots are diametrically opposite to the first two slots. These slots are at four places at 30ºangle with respect to thread starting point (as vertical line) to achieve desired anti-locking over the circumference of the connector members. Further in the connectors, modified buttress thread has been used. Buttress thread provides high load carrying capacity and is easily made by applying low torque required during rotation of casing pipe for making the casing joints. Further, the buttress thread is on tapered axis. And still further a groove is provided on the pin connector for an ‘O’ ring and ‘O’ ring helps to stop leakages. The modified buttress thread angle with stab flank angle of 25º provides the optimum results for both the load bearing capacity and the ease to fully engage the threads for this case of drilling casing strings.

EXAMPLE 2
30” CONNECTOR
In another example of 30” connector, the two of these four slots are provided each at 45º angle with respect to thread starting point as vertical line and other two slots diametrically opposite to the first two slots. On the outer surface of the box connector with increased wall thickness, at four places, at and near the free end of the connector and on the wall surface, the material is removed up to a specified thickness so that the material from the box can be locked into the four slots provided on the outer surface of the pin at and near the shoulder of the pin. These slots are at four places at 45º angle with respect to thread starting point (as vertical line) to achieve desired anti-locking over the circumference of the connector members. Further in the connectors, modified buttress thread has been used. Buttress thread provides high load carrying capacity by applying low torque required during rotation of casing pipe. Further, it is on a surface tapered with respect to axis of the connector, and a groove for an ‘O’ ring is provided on the pin connector, the ‘O’ ring helps to stop leakages. The modified buttress thread angle with stab flank angle of 25º provides the optimum results for both the load bearing capacity and the ease to fully engage the threads for this case of drilling casing strings.
Hence, the present invention overcomes the issues during assembling, handling and transportation of connector i.e. the wall of the box member of the connector often gets damage when it gets hit/bent. Therefore, by increasing the thickness of the wall of the box connector, the above mentioned issues are resolved and locking is achieved over the circumference of the connector against back rotation of the connector members. Further, the design and material of the connector has been changed to a higher grade to increase the strength of material to ensure no failure during operation. This ensures even if a failure does occur, the failure occurs in the casing pipe and not in the connector.
The foregoing description of embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. The embodiments were chosen and described in order to explain the principals of the invention and its practical application to enable one skilled in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated.
,CLAIMS:CLAIMS

We claim:
1. A modified casing connector (1) comprising:

a box connector (2) with internal threads (4) at inner surface;

a pin connector (3) with external threads (5) at outer surface;

wherein,
said box connector (2) has an increased outer diameter for an increased wall thickness to prevent damage while handling and assembling;

said casing connector (1) has a locking arrangement including at least four slots (6) having a predefined angle with respect to thread starting point provided at the circumference of said modified casing connector (1) at predetermined locations to prevent back rotation;

said box connector (2) and pin connector (3) has a modified buttress thread profile with a multi-start thread and a desired flank angle; and

said box connector (2) and pin connector (3) are made of a material of grade X70.

2. The modified casing connector (1) as claimed in claim 1, wherein the increased wall thickness varies according to size of the casing.

3. The modified casing connector (1) as claimed in claim 1 and 2, wherein the increased wall thickness varies from 0.435-1.5 inches for size of casing varying from 18.625-36 inches.

4. The modified casing connector (1) as claimed in claim 1, wherein the desired flank angle is preferably 25º.

5. The modified casing connector (1) as claimed in claim 1, wherein said slots (6) are made by removing material of a specified thickness on outer surface of the box connector (2) to get locked in slots at and near shoulder of pin connector (3).

6. The modified casing connector (1) as claimed in claim 1, wherein said multi start thread includes but is not limited to a 2 start thread or a 4 start thread.

7. The modified casing connector (1) as claimed in claim 1, wherein said predefined angle of slots (6) with respect to thread starting point lies in the range of 30-45º.

8. The modified casing connector (1) as claimed in claim 1, wherein said box connector (2) has a frustoconical inner surface and said pin connector (3) has a frustoconical outer surface.