GB2276217A - A connector with a dowel device for connecting rotary drill casings - Google Patents

Abstract

A rotary-drill casing connector has interconnecting male 1 and female 2 sleeves incorporating lugs 5 and sockets 6 around the periphery for the purpose of transmitting rotary motion and providing segmental abutment faces for supporting axial compressive loads. The two sleeves 1, 2 are held together by means of a flexible multi-stranded steel wire rope dowel (10, Figure 1) which is inserted manually from the outside via an aperture 11 into a circular annular cavity, half of which 7 is formed on the inside face of the female sleeve 2 and half 8 formed on the outer face of the male sleeve 1. The connection is sealed against leakage or ingress of fluids by the provision of a pliable sealing 'O' ring contained in a groove 8 formed in the sleeve 1 such that the seal is compressed when the parts are connected together. <IMAGE>

Description

A DOWEL DEVICE FOR CONNECTING ROTARY DRILL CASINGS This invention relates to a method particularly for securing earth rotary drill casing sections at an intersection joint and to apparatus for use in that method.

In construction and ground exploration industries an existing way of forming drilled and cased holes in the ground is to rotate and push downwardly a cylindrical steel casing carrying a cutting edge at its lower end and helicoidal flights on the external surface of the casing. Soil is transported upwardly from the drilled hole by the external helical flights during rotation. Another way of forming cased holes is to drive downwardly, by impact without rotation, a casing which carries no external members. The present invention relates only to the rotary method of drilling.

When a length of casing has penetrated in a downward direction sufficiently, an additional length of casing is connected. In the rotary method of drilling holes, short lengths of drill casing may conveniently be used in order to avoid the need for excessively tall structures used for guiding the casing prior to installation. One to three metres is typical of the length of section used for rotary drilling. To achieve greater depths, a multiplicity of casing section joints is required. It is desirable that the means for fixing the casings together and for separating them on completion of drilling shall be as quick, efficient and simple as possible.

According to one common practice there is provided at the ends of the rotary casings to be joined, mutually engaging male and female threads of well known form. Another form of connection is by interlocking male and female spigots, the spigots being engaged when a joint between the casings is made. A series of circumferential interlocking lugs and spaces on the peripheries of the male and female spigots engage with each other to provide means for transmitting rotary motion from one casing to the adjoining casing. Existing means for preventing axial separation of such connections of casings is by inserting screws radially through the joined spigots, or, where casings are driven by impacting into the ground without rotation; by inserting, by way of an external entrance aperture, a rigid or semi-rigid dowel member into an annular cavity formed in the contiguous cylindrical surfaces of the engaged spigots.

Existing connectors embody dowel members comprising relatively stiff or semi-rigid round steel rods or wire, or bars of generally rectangular form, all of which require special provision to enable such rods or bars to be inserted into the annular cavity. Typically, the centre line of existing entrance apertures must essentially be tangential to the centre line of the circumferential annular cavity in order for a preformed curved dowel member to be inserted with the minimum of contra-flexure. It is a further disadvantage of existing methods that the stiff dowel member must be impacted into and out of the annular cavity provided. In existing methods an essentially tangential entrance aperture creates a lengthy circumferentially discontinuous portion of the external cylindrical spigot thus causing undesirable weakness in the strength of the female cylindrical part. Other forms of entrance aperture embody a relatively large cut away portion of the outer spigot in order to permit easy access for insertion of the rigid dowel member into the annular cavity. Such entrance apertures require the use of obturators which in turn require fixing screws for security of the method.

A further disadvantage of existing methods is that a stiff semi-circular pre-formed dowel member must be positioned upon the external surface of the casing prior to being rotated about the casing in order to enter the entrance aperture and progress into the annular cavity; A casing which carries fully helicoidal flight members upon it's outer surface precludes the possibility to rotate the stiff dowel about the casing.

The drilled hole formed in the ground may be used for the purpose of forming a pile where the casing is filled with concrete and the casings extracted by rotating and pulling upwardly. Another use for the hole is for the installation of a perforated tube to be used as a well point in suitable aquifers. A further use for the hole is for the extraction of natural gases arising from waste material deposited in landfill sites.

During extraction from the ground, lengths of casing are disconnected and removed.

When the means for connecting the spigots to enable extraction by pulling upwardly is by means of radial dowels, or screws, or by means of split collars embodying interlocking cicumferential grooves, or by means of tangential dowels there is projection externally to the spigots within the space formed by the external flight members. The projections interfere with and obstruct the transportation of soil upwardly along the flights. In current practice, to minimise such interference, a minimum number of radial dowels is used. With a minimum of such dowels the shearing and bearing stresses in the dowels during the upward lifting process is high, resulting in loosening or loss of the dowels and separation of the casings. When looseness or separation of the casings occurs, water may ingress and destroy the end purpose of forming the hole. The lower casings may be lost in the ground.

It is a purpose of the present invention to provide a new and improved method for joining rotary drilling casings at the intersecting joint and to provide a new form of apparatus for use in that method.

According to the present invention there is provided a method of securing rotary drill casings at an intersection casing joint, comprising at least one circumferential annular groove on the inner cylindrical surface of the female spigot aligning with another circumferential annular groove on the outer cylindrical surface of the male spigot when the spigots are engaged together.

Comprising also of at least one entrance aperture extending from the circumferential groove in the internal cylindrical surface of the female spigot to the outer surface of said spigot, in a direction which is essentially non-tangential to said circumferential annular groove. At the coincidence of the centre line of the annular cavity with the centre line of the entrance aperture said centre line of the entrance aperture makes an angle with the radius of the drill casing of not less than one hundred degrees. The length of the entrance aperture so formed through the thickness of the female cylindrical spigot is considerably shorter than that of a tangential aperture, the reduced loss of metal due to the smaller aperture so formed improves the strength of the outer spigot of the coupling. The relatively sharp changes of direction in proceeding along the centre lines of entrance aperture to annular cavity prohibit the use of existing pre-formed rigid or semi-rigid dowel member forms.

Inserting into said entrance aperture a flexible steel dowel member passing additionally into said circumferential annular cavity, said flexible steel dowel member passing further into engagement in said cavity in both male and female spigots.

Preferably also, said flexible steel dowel member is located wholly within the complete circumference of the said annular cavity such that relative axial force in the direction to separate the spigots imposes shear loading into the axial length and diameter of the flexible steel dowel member. The flexible steel dowel member is embodied by a multi-stranded steel wire rope form which has individual wire strands laid in such manner, well known as 'Lang's Lay', that all wire strands lie with their axes crossing the circular plane of shear between the contiguous inner and outer spigots of the coupling. Each of the steel wire strands embodied in the multi strand rope dowel member therefore presents maximum shear resistance to the force of separation between the casing coupling parts.

An embodiment of the present invention will now be described by way of an example with reference to the following drawings, in which; Fig.l is a part oblique elevation of rotary drill casings showing male spigot 1, female spigot 2, flexible steel dowel member 10, entrance aperture 11. and external helicoidal flight members 12.

Fig.2 is a diagramatic section through a male spigot 1.

Fig.3 is a top plan view of male spigot of Figure 2 Fig.4 is a diagramatic part section through a female spigot 2.

Fig.5 is an underside view of the female spigot of Figure 4 showing entrance aperture 11.

Fig.6 is a part diagramatic section through the joined male and female spigots 1 and 2 showing entrance aperture 11 connecting the internal groove 7 of the female spigot 2 to the external surface of said spigot.

Referring to Fig.l showing an embodiment of the invention being male spigot 1 and female spigot 2 preassembled and fixed by welding to drill casings inserted into sockets 3 and 4 of figures 2 and 4. The drill casings conveniently being preassembled with helicoidal flight members fixed by welding to the outer surfaces. The helical flight members on each casing also arranged to form a continuous helical path passing externally over the spigots 1 and 2. The male 1 and female 2 spigots embody interlocking lugs 5 (fig.2) and spaces 6 (fig.4) which engage with each other to transmit rotary motion from one casing to the adjoining casing. A flexible dowel member 10 (fig.l) conveniently being a multi-stranded steel wire rope may be tapered at one end to facilitate easy insertion.

The spigots are assembled into full engagement so that the internal groove 7 of spigot 2 (fig.4) is in axial alignment with external groove 8 of spigot 1 (fig.2).

A flexible steel dowel member 10 (fig.l) is inserted into aperture 11 (figs.1, 4, 5 and 6) and is conveniently pushed manually into full engagement in the annular cavity formed by the two grooves 7 and 8 (fig.6). Conveniently, most of the length of the flexible steel dowel member fully engages cicumferentially in the grooves 7 and 8, leaving a short exposed end of the flexible dowel member protruding externally to be accessible for being gripped by well known means so that the flexible dowel member may be extracted completely by manual force in order to enable separation of the male and female spigots.

The exposed end of the flexible dowel member may conveniently be fitted with a known form of ferrule to facilitate gripping or attachment for the purpose of extraction. In another embodiment of the invention there may be at least one circumferential groove with two entrance apertures such that the flexible member may enter by one aperture 11 and leave by another. In that embodiment the flexible dowel member 10 may be totally contained within the annular cavity spigots 1 and 2 with no outside projection. In a further embodiment the apertures 11 may be sealed by plugs of well known form.

In that embodiment a flexible removal tool similar to member 10 would be employed to push the enclosed member 10 via one aperture 11 into an exposed position at the other aperture where it can be gripped for removal. A groove 9 in spigot 1 (fig.2) is embodied to accomodate a rubber or plastic '0' ring seal of well known form.

The '0' ring seal is compressed into groove 9 by inner surface of spigot 2 (fig.4) effectively sealing the interior of the rotary drill casing from the outside.

Advantages of the present invention include a reduction in the time required to join and disconnect drill casings, a simple manual facility for securing the casings together, a method of locking drill casings together more securely and efficiently.

A further advantage is that there is a more secure leaksealing of the spatial connection between the inside and the outside of the joined drill casings through which leakage might occur. A further advantage is that there is a reduction of the obstruction to the flow path of excavated soil along the external helical flight space.

It will be understood that the annular flexible dowel member which has been described in the context of joining drill casings finds utility also in securing together other structural forms where members to be joined together are overlapped cylindrical forms which may be formed with annular grooves into which the flexible member can be fitted.

Claims (8)

1 A connecting device for securing together rotary drill casing members comprising a male and a female co-axially interengaging pair of cylindrical sleeves each weldable to cylindrical steel casings. The inner and outer contiguous cylindrical surfaces of the male and female sleeves each provided with an annular groove which is situated in common axial alignment with a groove in the contiguous surface of the other interconnected sleeve of the connection, in combination the grooves of the male and female sleeves forming a cylindrical annular cavity which has circular centre line of diameter common with the cylindrical contiguous surfaces of the male and female sleeves. The female cylindrical sleeve embodies an orifice of circular section. The centre line of said orifice being coincident with the centre line of said cylindrical annular cavity and extending essentially in a non tangential direction to the external surface of the female sleeve. The centre line of said orifice essentially making an angle greater than one hundred degrees with the inside radius of the female cylindrical sleeve. The extremity of the cylindrical female sleeve immediately adjacent to the connected male sleeve embodying an equally spaced number of rectangular slots which inter-engage with matching rectangular projections embodied on the external surface of the male cylindrical sleeve whereby contiguous longitudinal surfaces of said slots and said projections provide means to transmit rotary motion from one connected sleeve to another. Each said projection having a segmental surface extending in a circular plane perpendicular to and surrounding the axis of the male sleeve, said segmental surfaces making abutment with matching segmental surfaces at the bottom of said rectangular slots embodied in the female sleeve when the male and female sleeves are inter-engaged; such segmental abutments serving to support compressive axial loads applied to the lengths of connected drill casings.

A flexible multi-stranded steel wire rope dowel member manually insertable loosely into said annular cavity via said circular entrance orifice provided. Said inserted dowel member providing shear resistance against tensile forces applied to adjacent sections of rotary drill casing.

2 A connecting device as claimed in claim 1, wherein the external female sleeve of the connection is provided with an essentially non-tangential screw-threaded orifice which connects the annular cavity to the exterior.

3 A connecting device as claimed in claim 1 and claim 2, wherein there is a plurality of annular cavities.

4 A connecting device as claimed in claim 1 wherein the flexible dowel member comprises a multi-stranded steel wire rope form which has individual wire strands laid in the form well known as 'Lang's Lay'.

5 A connecting device as claimed in claims 1, 2 and 3 wherein the non-tangential orifice connects the annular cavity by a clockwise and outwardly direction to the exterior, and another non-tangential orifice connects the annular cavity by an anticlockwise direction to the exterior.

6 A connecting device as claimed in claim 4 wherein a flexible dowel member may be provided at one end with a ferrule fixture to be used for gripping by an extraction tool.

7 A connecting device as claimed in claim 1 wherein a pliable annular seal means is provided between male and female sleeves for sealing against fluid transfer into or out of the casing connection.

8 A rotary drill casing connecting device substantially as described herein with reference to Figures 1 to 5 of the accompanying drawings.