WO2007062490A1

WO2007062490A1 - Fluid flow control means for a reverse circulation down hole hammer

Info

Publication number: WO2007062490A1
Application number: PCT/AU2006/001844
Authority: WO
Inventors: Brian Thomas Sanfead
Original assignee: Sds Digger Tools Pty Ltd
Priority date: 2005-12-02
Filing date: 2006-12-01
Publication date: 2007-06-07

Abstract

A fluid flow control means for a reverse circulation down hole hammer is disclosed. The down hole hammer is of the type that includes a piston that reciprocates within a hammer barrel to repeatedly impact a drill bit by high pressure fluid control means. The fluid flow control means includes a flange portion located on an anvil end of the drill bit and a sleeve portion to slidably receive the flange portion, wherein the sleeve portion includes fluid flow means to allow flow of high pressure fluid past the flange portion.

Description

FLUID FLOW CONTROL MEANS FOR A REVERSE CIRCULATION

DOWN HOLE HAMMER

FIELD OF THE INVENTION The present invention relates to reverse circulation down hole hammers. In a particular form, the present invention relates to fluid flow control means for a reverse circulation down hole hammer.

BACKGROUND OF THE INVENTION Reverse circulation down hole hammers are effective to return chippings and debris from the bottom of the hole being drilled to the surface where they may be collected and analysed. By appropriate porting and venting means, compressed air that is used to drive the hammering motion of the piston is exhausted about the outer surface of the drill bit. This high pressure air is then guided by the combination of shrouding means located near the cutting face and the walls of the hole to collect material being cut from the rock face. This material is then carried by means of the high pressure air flow through a central bore located in the drill bit and further through a longitudinally extending central channel which extends upwardly through the entire drill string.

Clearly, the amount of air that is able to be directed towards the cutting face will be closely related to the efficiency of the reverse circulation down hole hammer's ability to collect samples from the bottom of the hole. Referring now to the right hand side of Figure 1 (as generally indicated by B), this depicts a part front sectional view of a reverse circulation down hole hammer assembly 200 as known in the prior art. Compressed air that is vented during the reciprocating action of the piston 250 at the strike face 213 of the drill bit 210 will travel down a number of circumferentially equally spaced splines 211 located around the drill bit 210, these. splines 211 extending longitudinally down an upper portion of the drill bit 210 in a direction towards the cutting face 10.

The drill bit 210 is retained in an outer sleeve 220 by an increased radius portion of the splines at the anvil or piston end of the bit that forms a flange section 212 having a number of circumferential channels or cut away portions which channel into the splines 211 described above. The outer faces of the flange section 212 engages and slides within the inner surface 241 of the sub bush 240 which is held in place between a first retaining ring 230 and a drill bit retaining ring 260 by virtue of the drive sub 270 which is inserted and screwed into the end of the outer sleeve 220. .

The drill bit 210 is able to move between a lower or inoperative position, where the flange section 212 abuts the drill bit retaining ring 260 and remains clear of piston 250, to an operative or upper position where the bottom end of the piston 250 strikes the strike face 213 of drill bit 210 . In this manner, when the drill string is withdrawn from the hole the drill bit 210 will slide downwards, clear of the piston 250 to be held within the outer sleeve 220 by virtue of the flange section 212 of the drill bit 210 abutting the drill bit retaining ring 260.

Although this air or fluid flow arrangement located about the bit retaining assembly is workable, there are a number of associated disadvantages with this approach which add to the cost of the drill bit and furthermore reduce its efficacy in directing air down past the cutting face of the bit. Having longitudinally extending splines that terminate in a channelled flange section at the anvil or piston end of the drill bit adds to the cost and complexity of machining the drill bit component. As this part of the drill bit must accommodate high percussive loads, the ability to shape this section to improve the air flow past this region is reduced, especially directly at the anvil end where the channelled flange section is located. In addition, the required structural integrity required in this region restricts the number and depth of channels and associated splines which normally would be incorporated to improve air flow about the drill bit.

It is an object of the present invention to provide fluid flow control means capable of providing enhanced fluid flow in a reverse circulation down hole hammer.

SUMMARY OF THE INVENTION

In a first aspect the present invention provides a fluid flow control means for a reverse circulation down hole hammer, the down hole hammer including a piston that reciprocates within a hammer barrel to repeatedly impact a drill bit by high pressure fluid control means, the fluid flow control means including: a flange portion located on an anvil end of the drill bit; and a sleeve portion to slidably receive the flange portion, wherein the sleeve portion includes fluid flow means to allow flow of high pressure fluid past the flange portion.

Preferably, the fluid flow means includes a plurality of elongate channels located along an inner surface of the sleeve portion.

Preferably, the elongate channels include inwardly extending walls forming slidable engagement means to slidably receive the flange portion. Preferably, the slidable engagement means include engagement surfaces located at the end of the inwardly extending walls.

In a second aspect the present invention accordingly provides a piston for use with a reverse circulation down hole hammer, wherein the piston in use reciprocates within a hammer barrel to repeatedly impact a drill bit by high pressure fluid control means, the down hole hammer further including fluid flow control means that includes: a flange portion located on an anvil end of the drill bit; and a sleeve portion to slidably receive the flange portion, wherein the sleeve portion includes fluid flow means to allow flow of high pressure fluid past the flange portion.

In a third aspect the present invention accordingly provides a hammer barrel for use with a reverse circulation down hole hammer, wherein the down hole hammer includes a piston that reciprocates within the hammer barrel to repeatedly impact a drill bit by high pressure fluid control means, the down hole hammer further including fluid flow control means that includes: a flange portion located on an anvil end of said drill bit; and a sleeve portion to slidably receive said flange portion, wherein the sleeve portion includes fluid flow means to allow flow of high pressure fluid past said flange portion.

A drill bit for use with a reverse circulation down hole hammer, wherein the down hole hammer includes a piston that reciprocates within a hammer barrel to repeatedly impact the drill bit by high pressure fluid control means, the down hole hammer further including fluid flow control means that includes: a flange portion located on an anvil end of the drill bit; and a sleeve portion to slidably receive the flange portion, wherein the sleeve portion includes fluid flow means to allow flow of high pressure fluid past the flange portion.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred embodiment of the present invention will be discussed with reference to the accompanying drawings wherein:

FIGURE 1 depicts side by side front sectional views of a reverse circulation down hole hammer showing on the right hand side fluid flow control means as known in the prior art (as generally indicated by B) and on the left hand side fluid flow control means according to a preferred embodiment of the present invention (as generally indicated by A);

FIGURE 2 is a part sectional front 3-dimensional view of the fluid flow control means as illustrated in part A of Figure 1; FIGURE 3 is a top perspective 3-dimensional view of the fluid flow control

.means illustrated in Figure 2; and

FIGURE 4 is a sectional perspective view of the sub^" bush and bit retaining ring components of the fluid flow control means illustrated in Figure 2.

In the following description, like reference characters designate like or corresponding parts throughout the several views of the drawings.

DESCRIPTION OF PREFERRED EMBODIMENT

Referring now to the left hand side of Figure 1 (as generally indicated by A) and Figures 2 to 4, there is shown a fluid flow control means 100 according to an illustrative embodiment of the present invention. Fluid flow control means 100 includes a cylindrical flange or flange portion 112 located on the hammer or anvil end 117 of drill bit 110 and a sub bush or sleeve portion 140 incorporating a plurality of longitudinally extending elongate channels 142 formed by inwardly extending parallel walls 141. The inner surfaces 144 of the inwardly extending walls 141 are squared off or alternatively machined in a variety of ways to result in circumferential flat faces or engagement surfaces that in combination form a sleeve that slidably receives the cylindrical flange 112, thereby allowing the drill bit to slide up and down within the outer sleeve 120 in this slidable engagement means.

These elongate channels 142 extend along the length of travel of flange 112 from the operative position (as best seen in Figure 1) where reciprocating piston 250 strikes the strike surface 113 of drill bit 110 to the inoperative or lower position (as best seen in Figures 2 and 3) at which point drill bit 110 is displaced from piston 250. In the inoperative position, drill bit 110 is retained by virtue of drill bit retaining ring 160, which includes an upper abutment surface 161 which extends inwardly to abut with cylindrical flange 112.

Whilst in this preferred embodiment, elongate channels 142 ₍are formed as part of sub bush 140, equally these channels could be formed directly on any inner surface of the outer sleeve 120 which interfaces directly with the drill bit flange 112 in cases where a sub bush 140 or similar component is not part of the down hole hammer assembly configuration. Equally, other air flow means which form part of the sub bush 140 or more generally a sleeve portion that slidably receives flange 112 such as air flow conduits or bores formed in the wall of the sleeve portion are contemplated to be within the scope of the invention.

Drill bit retaining ring 160 further incorporates a plurality of channels 162 (as best shown in Figure 4) of a larger size and dimension to that of elongate channels 142 although these may be varied as required. However, it will be understood by those skilled in the art that other bit retaining means may be used in combination with the air flow control assembly of the present invention. This could for example include inwardly extending opposed tab portions or projections fixed to the inner surface 121 of the outer sleeve 120.

Below flange 112, the middle portion 111 of drill bit 110 is formed as a cylindrical waisted section having an approximate length corresponding to the length of elongate channels 142. Below middle portion 111, the drill bit 110 incorporates a lower splined section 114 that includes a plurality of circumferential longitudinal channels 115 formed in the drill bit 110 which extend down the drill bit 110 and function in combination with shroud 180 to direct high pressure air, as generally indicated by the arrows, towards the cutting face 10. The top portion of lower splined section 114 includes tapered faces 116 which seats against bottom abutment surfaces 162 that form part of drill bit retaining ring 160.

When the drill bit 110 is in the operative position, high pressure air that is vented from the reciprocating piston system will flow through elongate channels of fluid flow means 142 and past cylindrical flange 112. Referring once again to Figure 1 - section B, this is in direct contrast with the prior art means for controlling air flow, as air flows directly through the flange section 212 as it incorporates channels in the flange section, which flow directly into splines 211, located on the shaft of the drill bit. As described previously, this arrangement restricts the air flow past the flange section 212 as the number, depth and width of the channels are restricted given the structural and rigidity requirements of this region that are required due to the impact forces of piston 250.

Once the air has moved past flange 112 it then continues to flow past cylindrical waisted mid portion 111 at which point it enters the lower splined section 114 of drill bit 110 via air channels 162 formed in drill bit retaining ring 160 (as described above). As the drill string is being withdrawn from the hole, drill bit 110 will move downwards to the inoperative position at which point flange 112 will abut the upper abutment surface 161 of drill bit retaining ring 160 thereby retaining drill bit 110 and at all times allowing air to continue to be vented past flange 112.

A brief consideration of the above described embodiment will indicate that the invention provides an extremely simple, economical fluid flow control assembly which is effective to significantly improve air flows past the top flange section of the drill bit when compared to prior art methods.

Although a preferred embodiment of the present invention has been described in the foregoing detailed description, it will be understood that the invention is not limited to the embodiment disclosed, but is capable of numerous rearrangements, modifications and substitutions without departing from the scope of the invention as set forth and defined by the following claims.

Claims

THE CLAIMS:

1. A fluid flow control means for a reverse circulation down hole hammer, the down hole hammer including a piston that reciprocates within a hammer barrel to repeatedly impact a drill bit by high pressure fluid control means, the fluid flow control means including: a flange portion located on an anvil end of the drill bit; and a sleeve portion to slidably receive the flange portion, wherein the sleeve portion includes fluid flow means to allow flow of high pressure fluid past the flange portion.

2. The fluid flow control means of claim 1, wherein the fluid flow means includes a plurality of elongate channels located along an inner surface of the sleeve portion.

3. The fluid flow control means of claim 2, wherein the elongate channels include inwardly extending walls forming slidable engagement means to slidably receive the flange portion.

4. The fluid flow control means of claim 3, wherein the slidable engagement means include engagement surfaces located at the end of the inwardly extending walls.

5. A piston for use with a reverse circulation down hole hammer, wherein the piston in use reciprocates within a hammer barrel to repeatedly impact a drill bit by high pressure fluid control means, the down hole hammer further including fluid flow control means that includes: a flange portion located on an anvil end of the drill bit; and a sleeve portion to slidably receive the flange portion, wherein the sleeve portion includes fluid flow means to allow flow of high pressure fluid past the flange portion.

6. The piston of claim 5, wherein the fluid flow means includes a plurality of elongate channels located along an inner surface of the sleeve portion.

7. The piston of claim 6, wherein the elongate channels include inwardly extending walls forming slidable engagement means to slidably receive the flange portion.

8. The piston of claim 7, wherein the slidable engagement means include engagement surfaces located at the end of the inwardly extending walls.

9. A hammer barrel for use with a reverse circulation down hole hammer, wherein the down hole hammer includes a piston that reciprocates within the hammer barrel to repeatedly impact a drill bit by high pressure fluid control means, the down hole hammer further including fluid flow control means that includes: a flange portion located on an anvil end of said drill bit; and a sleeve portion to slidably receive said flange portion, wherein the sleeve portion includes fluid flow means to allow flow of high pressure fluid past said flange portion.

10. The hammer barrel of claim 9, wherein the fluid flow means includes a plurality of elongate channels located along an inner surface of the sleeve portion.

11. The hammer barrel of claim 10, wherein the elongate channels include inwardly extending walls forming slidable engagement means to slidably receive the flange portion.

12. The hammer barrel of claim 11, wherein the slidable engagement means include engagement surfaces located at the end of the inwardly extending walls.

13. A drill bit for use with a reverse circulation down hole hammer, wherein the down hole hammer includes a piston that reciprocates within a hammer barrel to repeatedly impact the drill bit by high pressure fluid control means, the down hole hammer further including fluid flow control means that includes: a flange portion located on an anvil end of the drill bit; and a sleeve portion to slidably receive the flange portion, wherein the sleeve portion includes fluid flow means to allow flow of high pressure fluid past the flange portion.

14. The drill bit of claim 13, wherein the fluid flow means includes a plurality of elongate channels located along an inner surface of the sleeve portion.

15. The drill bit of claim 14, wherein the elongate channels include inwardly extending walls forming slidable engagement means to slidably receive the flange portion.

16. The drill bit of claim 15, wherein the slidable engagement means include engagement surfaces located at the end of the inwardly extending walls.