Spearhead assembly

Abstract

A spearhead assembly (10) comprises a base (12) having an outer surface (14), a slot (16), a spear point (18) and a guard (20). The slot (16) is formed in the base (12) and has an opening (22) that opens onto the outer surface (14). A proximal end of the spear point (18) is located in the slot (16) and pivotally coupled about a pivot axis (26) to the base (12). The spear point (18) can pivot about axis (26) between two positions that are angularly spaced by 180°. The guard (20) is coupled to the proximal end of the spear point (18) and configured to at least partially occupy the opening (22) when the spear point is in a location at or between the two spaced apart positions. The guard (20) acts to minimise the risk of an operator's hand or glove worn by the operator from being pinched or caught in the slot (16) between the spear point (13) and base (12) as the spear point (18) is pivoted between the two positions.

Description

FIELD OF THE INVENTION

The present invention relates to a spearhead assembly of the type used in mining and subsurface drilling to enable the coupling of down hole equipment to a wire line to facilitate the tripping of the equipment down a drill hole, drill string or casing.

BACKGROUND OF THE INVENTION

The present Applicant is the applicant in relation to International publication WO 2004/018831 in relation to a spearhead assembly. The spearhead assembly in the aforementioned International publication comprises a base provided with a slot at one end that opens onto an outer surface of the base. The outer surface is composed of three contiguous surface portions. A proximal end of the spear point is located in the slot and pivotally coupled to the base. An opposite distal end of the spear point extends or projects beyond the slot. The spearhead assembly further comprises a spear point positioning system that urges the spear point toward one of a plurality of angularly spaced positions. These positions are characterized by the spear point extending substantially perpendicular to adjacent edges of the slot. This spear point positioning system holds the spear point in one of the positions until application of a positive external force.

In the claims of this application and in the description of the invention, except where the context requires otherwise due to express language or necessary implication, the words “comprise” or variations such as “comprises” or “comprising” are used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.

It is to be understood that, if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms a part of the common general knowledge in the art, in Australia or any other country.

SUMMARY OF THE INVENTION

According to one aspect of the present invention there is provided a spearhead assembly comprising:

• • a base having an outer surface;
  • is a slot formed in the base and having an opening that opens onto the outer surface;
  • a spear point having a proximal end located in the slot and pivotally coupled about a pivot axis to the base to enable pivotal motion of the spear point between two angularly spaced positions; and,
  • a guard coupled to the proximal end of the spear point, the guard configured to at least partially occupy the opening when the spear point is in at least one location at or between the two positions, or a range of locations at or between the two positions.

The guard has a side portion of which lies across the opening when the guard is in the at least one or range of locations.

The portion of the side may lie substantially flush with the opening. However in an alternate embodiment the portion of the side may lie proud of the opening, for example to form a substantially continuous curve with the outer surface. Indeed the side may comprise different portions which lie substantially flush with the opening and proud of the opening respectively when the guard is in different locations between the two positions. That is the side of the guard may take different shapes and configurations. In its simplest form when the guard is in the general configuration of a disc the side would comprise a simple curved surface having a linear transverse section. However in an alternative embodiment the side or portion of the side may be of a complex configuration and have for example a stepped, wave or zigzag transverse section. One example of this is where the side comprises a plurality of radially and/or axially extending and spaced apart ribs or webs. In this embodiment the spacing between the ribs or webs forms one or more channels or grooves in the radially outermost surface.

It is further envisaged that the guard may comprise a central recess for seating the proximal end of the spear point. The spearhead assembly may further comprise an attachment mechanism for attaching the guard to the spear point. In one possible embodiment, the attachment mechanism comprises a snap coupling between the guard and the proximal end of the spear point. This can be facilitated by the provision of a hole or cavity in the guard and a knob or barb-like projection at the proximal end of the spear point that is pushed into or through the hole or cavity.

In one embodiment the base comprises two spaced apart walls between which the slot is defined and the opening is formed; and, two barriers, one of each extending into the opening on opposite sides of the slot between the spaced apart walls. In one embodiment, the barriers may be in the form of lips. Advantageously, one or more passages are formed in the barrier and/or between the barrier and the walls.

The spearhead assembly may further comprise a fluid channel extending through the base and in communication with the slot to allow a fluid flow through the spearhead assembly.

The spearhead assembly may further comprise a spear point positioning system that urges the spear point toward, or holds the spear point in, one of a plurality of angularly spaced positions. The spear point positioning system may comprise a plate through which the spear point extends, the plate being retained on the spear point at a location where the plate contacts the outer surface of the base.

In one embodiment, the spear point positioning system further comprise a biasing mechanism that urges the spear point into one of the plurality of set positions and holds the spear point in one of the plurality of set positions. Moreover, the biasing mechanism acts to bias the plate against the outer surface of the base.

In one embodiment of the invention, the opening of the slot comprises a plurality of contiguous lengths where mutually adjacent lengths lie in respective non-parallel planes, and wherein the plurality of set positions are positions where the spear point extends perpendicular to the plane of the length of the opening from which the spear point extends.

In an alternate embodiment, the guard itself may be configured to act as a type of spear point positioning system. In this embodiment, the side of the guard comprises at least two oppositely disposed straight length the straight lengths being arranged to extend parallel to the spear point and wherein a transverse distance between the straight lengths is slightly smaller than an inner diameter of the drill pipe or other conduit through which the spear point assembly travels. It will be appreciated that by dimensioning the straight lengths in this way, when the spear point assembly is initially entering a drill pipe or other conduit, and the spear point is pivoted more than say a few degrees away from the longitudinal axis of the assembly, contact of one of the straight edges with the opening of the drill pipe or conduit will cause pivoting of the guard and spear point so as to lie substantially parallel to the longitudinal axis. Further, once inside the drill pipe, pivoting of the guard or spear point marginally away from the longitudinal axis will result in contact of one of the straight edges with the inner diameter of the pipe or conduit thereby limiting any further pivotal movement away from the longitudinal axis. This will accordingly maintain the spear point within a narrow arc from the longitudinal axis thereby substantially ensuring coupling with an overshot.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings in which:

FIG. 1 is a representation of an embodiment of the spearhead assembly in accordance with the present invention;

FIG. 2 is an enlarged view of the portion of the spearhead assembly with the spear point inclined from a longitudinal axis of the spearhead assembly;

FIG. 3 is an enlarged view of the spearhead assembly with the spear point extending perpendicular to the longitudinal axis of the spearhead assembly;

FIG. 4 is an isometric view from the front of a guard incorporated in the spearhead assembly;

FIG. 5 is an isometric view from the top of the guard shown in FIG. 4;

FIG. 6 is an isometric view from a lower edge of the guard;

FIG. 7 is an isometric view of the base incorporated in the spearhead assembly; and,

FIG. 8 is a view of section AA of the base depicted in FIG. 7.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

Referring to the accompanying drawings an embodiment of the spearhead assembly 10 in accordance with the present invention comprises a base 12 having an outer surface 14, a slot 16 (see in particular FIG. 7), a spear point 18 (shown in FIGS. 1-3) and a guard 20 (shown in FIGS. 1-6). The slot 16 is formed in the base 12 and has an opening 22 that opens onto the outer surface 14. The spear point 18 has a proximal end located in the slot 16 and pivotally coupled about a pivot axis 26 to the base 12 to enable pivotal motion of the spear point 18. The spear point 18 can pivot about the axis 26 between two angularly spaced positions. These two positions are spaced by approximately 180° and with reference to FIG. 1 correspond to the spear point 18 being pivoted about axis 26 in an anti-clockwise direction to extend substantially perpendicular to a longitudinal axis 28 and pointing into the page, and a second position where the spear point 18 is pivoted in a clockwise direction about axis 26 to lie perpendicular to the longitudinal axis 28 and pointing out of the page.

The guard 20 is coupled to the proximal end of the spear point 18 and configured to at least partially occupy the opening 22 when the spear point is in a location at or between the aforementioned two spaced apart positions. Consequently, the guard acts to minimise the risk of an operator's hand or glove worn by the operator from being pinched or caught in the slot 16 between the spear point 18 and the base 12 as the spear point 18 is pivoted between the two positions. Thus embodiments of the spear head assembly 10 and in particular guard 20 assist in reducing the likelihood of injury or accident during raising and lowering of a device to which the assembly 10 is attached, as well as during the coupling and decoupling of the spear point assembly with an overshot.

With particular reference to FIGS. 7 and 8, the base 12 comprises a pair of spaced apart walls 30 and 32 between which the slot 16 is defined, and the opening 22 is formed. The walls 30 and 32 project from one end of a spigot or a tube 34. The walls 30 and 32 each have a generally semi-cylindrical outer surface which constitutes a major portion of the outer surface 14 of the base 12; and respective inner planar walls 31 and 33. An axial channel 36 is formed in the tube 34 that communicates with the slot 16. A concavely curved wall 38 is provided in the base 12 between the walls 30 and 32, and onto which the channel 36 opens. Holes 40 and 42 are formed in the walls 30 and 32 respectively co-axial with the pivot axis 26. These holes receive a pivot pin 44 that also extends through the proximal end of the spear point 18 and the guard 20, coupling the spear point 18 to the base 12.

The opening 22 of the slot 16 can be considered as comprising a plurality of contiguous lengths which are shown most conveniently in FIG. 8 as lengths 46, 48, 50, 52 and 54. These lengths correspond with edges formed between the outer peripheral surfaces of the walls 30 and 32 and their corresponding inner planar surfaces 31 and 33. In general, the lengths 46-54 trace a path in the shape of an inverted U. It will be further observed that a plane containing the length 46 is inclined (ie not parallel) to a plane containing a length 48, which in turn is not parallel to a plane containing a length 50, which in turn is not parallel to a plane containing a length 52, which lies in a plane not parallel to a plane containing a length 54.

Barriers, in the form of upstanding lips 56 and 58 project into the opening 22 between the walls 30 and 32. More particularly, the lip 56 projects into the length 46 of the opening, while the lip 58 projects into the length 54 of the opening. The lips 56 and 58 have respective surfaces interior of the slot 16 that follow the curvature of the concave wall 38. In this embodiment, the lips 56 and 58 extend upwardly only a relatively short distance and terminate at a level short of the holes 40 and 42. The lips 56 and 58 act to limit the pivotal motion of the spear point 18 as well as further assist in the prevention of pinching of an operators hand or glove. Passages 60 are formed between opposite lateral edges of each of the lips 56 and 58 and the adjacent walls 30 and 32.

Referring to FIGS. 4-6, the guard 20 comprises a body 62 having opposite planar surfaces 64 and 66 that face the inner planar walls 31 and 33 respectively, and a generally arcuate radially outer surface, or side 68 between the surfaces 64 and 66. A central recess or seat 70 is formed in the body 62 for receiving the proximal end of the spear point 18. A hole 72 is formed through the body 62 at the bottom of the recess 70. The radial outer surface or side 68 can be considered as comprising three parallel radially extending ribs or webs 74 and an axially extending rib 76. The webs 74 and 76 lie in the vicinity of the opening 22 irrespective of the pivotal position of the spear point 18. However depending on the particular pivotal location of the spear point 18 the webs 74, 76 may lie inside or outside of the actual opening 22. Their actual position relative to the opening is not per se critical to the working of the invention. The function performed by the webs 74, 76 and moreover the guard 20 as a whole is to substantially occupy the opening 22 to prevent pinching of an operators hand or glove.

Channels or grooves 78 are formed between the webs 74, 76, which provide flow paths that communicate with the passage 60 and channel 36 so that drilling fluids or naturally occurring fluids within a drill hole are able to flow through the spearhead assembly 10.

By forming a small barb like projection or knob at the proximal end of the spear point 18 and having an outer diameter largely greater than the diameter of the hole 72, an attachment mechanism is effectively formed to enable the easy coupling of the guard 20 to the spear point 18.

The illustrated embodiment of the spearhead assembly 10 includes a spear point positioning system 80 of a type described in International publication No. WO 2004/018831, the contents of which is incorporated herein by way of reference. Nevertheless, by way of brief explanation, the spear point positioning system 80 operates to urge the spear point 18 toward, and/or hold the spear point 18 in, one of a plurality of angularly spaced positions. These positions are characterised by the spear point 18 extending perpendicular to particular lengths 46-54 of the opening 22 from which it extends. For example, with reference to FIG. 1, the spear point position system operates to hold the spear point 18 in a position where it extends perpendicular to the length 50 of the opening 22. In FIG. 2, the positioning system 80 holds the spear point 18 at a position perpendicular to a plane containing the length 48 of the opening 22, and in FIG. 3 the positioning system holds the spear point 18 to extend perpendicular to a plan containing the length 46 of the opening 22. The positioning system 80 comprises a plate in the form of a washer 82 retained on the spear point 18, and a helical spring 84 also retained on the spear point 18 and acting to bias the washer 82 against the outer surface 14 and more particularly, the lengths 46-54 of the opening 22.

The positioning system 80 operates to provide a snap action when the spear point 18 is pivoted between the lengths 46-54 of the opening 22. More particularly, the system 80 acts to bias or snap the spear point 18 to lie perpendicular to the angularly closest length. For example, consider the spear point 18 being moved from a position shown in FIG. 1 where it extends perpendicular to the length 50, to the position shown in FIG. 2 where it extends perpendicular to the length 48. As the spear point 18 is being pivoted about the axis 26, the system 80 will urge the spear point toward the perpendicular of length 50 until it passes beyond the midway point to the perpendicular to the length 48. Thus if one were to release the force applied to the spear point 18 at that time, the system 18 would act to snap the spear point 18 back to the position shown in FIG. 1. However once the spear point 18 is rotated past the midway point, the system 80 acts to snap the spear point to a position perpendicular to the length 48.

Now that embodiments of the present invention have been described in detail it will be apparent to those skilled in the relevant arts that numerous modifications and various may be made without departing from the basic inventive concepts. For example, the base 12 is described and illustrated as including an axial passage 36. However in embodiments where the spear point is used in dry holes, the passage 36 is not required. Also in these circumstances, the channels 78 in the outer radial surface of the guard 20 are not necessary. Further, the configuration of the guard 20 is almost limitless. For example with reference to the guard 20 as illustrated, it may be modified by the inclusion of further axial ribs parallel to the axial rib 76 so that the outer surface 68 takes a mesh like appearance. Indeed in an alternate embodiment, a steel mesh or grid may be placed in the channels or grooves 78. Further, the entire guard 20 may be in the form of a wire mesh structure that is coupled to the proximal end of the spear point 18. In an alternate embodiment to that depicted in the drawings, the spear point 18 and the guard 20 could be moulded or otherwise constructed as a single piece.

It will be noted in particular from FIGS. 4 and 6 that the outer most ribs or webs 74 comprise respective straight edges or sides 79. In a further variation, it is possible to laterally extend the straight edges or sides 79 so that when the spear point 18 is in alignment with the longitudinal axis 28, the sides 79 lie marginally inside an inner diameter of the drill pipe through which a device attached to the spear point assembly 10 is tripped, (ie the transverse distance between the lengths 79 on opposite sides of the guard 20 is slightly smaller than the inner diameter of the pipe). This has the effect of self centering the spear point 18 when the assembly 10 enters and travels through the drill pipe. This obviates the need for the positioning system 80 particularly insofaras it operates to maintain the spear point 18 in general alignment with the axis 28, and longitudinal axis of the drill pipe. In this regard, it will be appreciated that by dimensioning the length 79 as described above, the spear point 18 will be maintained within a narrow arc from the axis 28 when inside a drill pipe due to contact of the lengths 79 with the inner diameter of the drill pipe upon pivoting of the guard 20 and the spear point 18 more than only several degrees away from alignment with the axis 28.

All such variations and modifications together with others that would be obvious to a person of ordinary skill in the art are deemed to be within the scope of the present invention the nature of which is to be determined from the above description.

Claims

1. A spearhead assembly comprising: a base having an outer surface;a slot formed in the base and having an opening that opens onto the outer surface;a spear point having a proximal end located in the slot and pivotally coupled about a pivot axis to the base to enable pivotal motion of the spear point between two angularly spaced positions; and,a guard coupled to the proximal end of the spear point, the guard configured to at least partially occupy the opening when the spear point is in at least one location at or between the two positions, or a range of locations at or between the two positions.

2. The spearhead assembly according to claim 1 wherein the guard has a side portion of which lies across the opening when the guard is in the one or range of locations.

3. The spearhead assembly according to claim 2 wherein the portion of the side lies substantially flush with the opening.

4. The spearhead assembly according to claim 2 wherein the portion of the side lies proud of the opening.

5. The spearhead assembly according to claim 1 wherein the guard comprises different side portions which lie substantially flush with the opening and proud of the opening respectively when the guard is in different locations between the two positions.

6. The spearhead assembly according to claim 1 wherein the guard is in the general configuration of a disc.

7. The spearhead assembly according to claim 2 wherein the side comprises a plurality of radially and/or axially extending and spaced apart ribs or webs.

8. The spearhead assembly according to claim 1 wherein the guard comprises a central recess for seating the proximal end of the spear point.

9. The spearhead assembly according to claim 1 further comprising an attachment mechanism for attaching the guard to the spear point.

10. The spearhead assembly according to claim 9 wherein the attachment mechanism comprises a snap coupling between the guard and the proximal end of the spear point.

11. The spearhead assembly according to claim 9 wherein the attachment mechanism comprises a hole or cavity in the guard and a knob or barb-like projection at the proximal end of the spear point that is pushed into or through the hole or cavity.

12. The spearhead assembly according to claim 1 wherein the base comprises two spaced apart walls between which the slot is defined and the opening is formed; and, two barriers, one of each extending into the opening on opposite sides of the slot between the spaced apart walls.

13. The spearhead assembly according to claim 12 wherein the barriers are in the form of lips.

14. The spearhead assembly according to claim 12 wherein one or more passages are formed in the barrier and/or between the barrier and the walls.

15. The spearhead assembly according to claim 1 further comprising a fluid channel extending through the base and in communication with the slot to allow a fluid flow through the spearhead assembly.

16. The spearhead assembly according to claim 1 further comprising a spear point positioning system that urges the spear point toward, or holds the spear point in, one of a plurality of angularly spaced set positions.

17. The spearhead assembly according to claim 16 wherein the positioning system comprises a plate through which the spear point extends, the plate being retained on the spear point at a location where the plate contacts the outer surface of the base.

18. The spearhead assembly according to claim 16 wherein the positioning system comprises a biasing mechanism that urges the spear point into one of the plurality of set positions and holds the spear point in one of the plurality of set positions.

19. The spearhead assembly according to claim 18 wherein the biasing mechanism acts to bias the plate against the outer surface of the base.

20. The spearhead assembly according to claim 16 wherein the opening of the slot comprises a plurality of contiguous lengths where mutually adjacent lengths lie in respective non-parallel planes, and wherein the plurality of set positions are positions where the spear point extends perpendicular to the plane of the length of the opening from which the spear point extends.

21. The spearhead assembly according to claim 16 wherein the guard is configured to act as a type of spear point positioning system.

22. The spearhead assembly according to claim 21 wherein the side of the guard comprises at least two oppositely disposed straight length the straight lengths being arranged to extend parallel to the spear point and wherein a transverse distance between the straight lengths is slightly smaller than an inner diameter of the drill pipe or other conduit through which the spear point assembly travels.

23. A guard for a spearhead assembly having a base, a slot that opens onto an outer surface of the base, and a spear point with a proximal end pivotally coupled to the base inside the slot, the guard comprising a body adapted for coupling to the proximal end of the spear point and configured to at least partially occupy the opening.