Patent Description:
In the mining industry, large bore shafts, either vertical, angle or horizontal, have been created with the use of percussion tools for many years.

Cluster drills traditionally use air percussion hammers and all of the drill cuttings are blown with air pressure and air volume (CFM) out of the shaft. However, cluster drills with air hammers are very long and require very large air volumes which make them unsuitable for use in tunnel boring machines (TBM). In this regard, the air exhausted from such TBMs would mean that the tunnel behind the TBM while operating would not be accessible.

Water hammer drills have also been in use for many years. However, the requirement for high volumes of water to operate these drills and the difficulties created by the exhausted water make them unsuitable for use as part of a TBM. One example can be found in the document <CIT> (<FIG>, <FIG>, <NUM>).

The present invention seeks to provide a liquid hammer drill that addresses the problems discussed above. At the very least the present invention seeks to provide an alternative to current solutions for drills suitable for use in TBMs.

According to a first aspect, the present invention provides a liquid hammer drill according to claim <NUM>.

Preferably, the liquid hammer drill is relatively short in terms of length. For the purposes of the present invention, the term "relatively short" is intended to differentiate the liquid hammer drill from existing hammer drills that tend to be longer. Preferably, the liquid hammer drill has a length of or about <NUM>, <NUM>, <NUM>, <NUM> or <NUM>. Even more preferably, the liquid hammer drill has a length of equal to or less than <NUM>, <NUM>, <NUM> or <NUM>.

Preferably, the liquid hammer drill has a width or diameter of about <NUM> to <NUM>, <NUM> to <NUM>, <NUM>-<NUM> or <NUM>-<NUM>.

Preferably, the ratio of the length of the liquid hammer drill to its width is less than <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or <NUM>. Preferably, the width referred to in the ratio is the largest width of the liquid hammer drill. For example, if the liquid hammer drill has a non-uniform width, the ration is based on the largest width thereof.

Preferably, the liquid is water, salt water, petroleum or liquefied gas.

Preferably, the housing is generally cylindrical.

Preferably, the housing has a circular cross section.

Preferably, the housing defines a tapered leading end.

Preferably, the housing comprises a leading end adapted to receive the drill bit.

Preferably, the housing is adapted to removably receive the drill bit.

Preferably, the housing defines a retention member for the drill bit. Even more preferably, the retention member is a collar member or chuck supported on the housing. Preferably, the retention member includes a first threaded portion adapted to engage with a second threaded portion of the drill bit. Preferably, the collar member is generally ring shaped.

Preferably, the housing defines a port for the liquid inlet circuit and/or the liquid outlet circuit. Even more preferably said port is located at the trailing end of the housing.

Preferably, the drill bit has a relatively low profile.

Preferably, the drill bit is mounted to the outside of the housing. Even more preferably, the drill bit comprises a collar member or shank that extends over an outside portion of the housing when the drill bit is fitted. Preferably, the collar member comprises a threaded portion. It will be understood that by mounting the drill bit on the outside of the housing, the piston member can, relative to prior art hammer drills, be located closer to the trailing end of the drill bit. This, in turn, allows the leading end of the piston member or strike face to be close to the drill face e.g. about <NUM> to <NUM> from the drill face.

Preferably, the drill bit has a relatively short bit reach. Even more preferably the drill bit has a reach of about <NUM>, <NUM>, <NUM>, <NUM> or <NUM>.

Preferably, the drill bit comprises a threaded portion for removably attaching the drill bit to the drill.

Preferably, the drill bit defines a strike face for the piston member at its trailing end.

The strike face comprises at least one water relief groove. In this regard, if any liquid does ingress to the trailing end of the drill bit then said water relief grooves ensure the piston member still strikes the drill bit in a substantially liquid free environment.

Preferably, the drill bit defines at least one locating member that co-operates with a compatible member to positively locate the drill bit and control its movement when in use. Preferably the locating member and the compatible member are a spline or groove.

Preferably, the cutting face has a substantially circular cross section. Alternatively, the cutting face may have a substantially polygonal cross section such as a square shaped cross section. Preferably, the cutting face has a relatively low profile or thickness.

Preferably, the cutting face comprises a plurality of buttons. Preferably, the buttons are ovoid shaped.

Preferably, the cutting face defines at least one groove to assist with clearing chips away from the cutting face during use.

Preferably, the drill bit comprises at least one aperture therethrough to allow for the passage of fluid. Preferably, said aperture comprises a vent for air and or liquid that enters the area immediately adjacent to the strike face or trailing end of the drill bit.

Preferably, the piston member comprises a main body portion at its trailing end and its leading end tapers in relative to the main body portion.

Preferably, the intermediate portion defines a shoulder.

Preferably, the main body portion defines a cavity therein for receiving the liquid, during use to move the piston member to its second position.

Preferably, the piston member has a generally circular cross section.

Preferably the piston member, in use, has a travel distance or stroke of about <NUM>, <NUM>, <NUM> or <NUM>.

Preferably, the liquid circuit does not exhaust liquid via the drill bit.

Preferably, the liquid circuit comprises a return portion that delivers the liquid transferred outside the housing via the liquid outlet back into the liquid circuit. In this regard, liquid used in the liquid hammer drill can be circulated and reused.

Preferably, the liquid circuit further comprises a flow controller operable to move between a first and a second position to create pressure differentials that move the piston between its first and second positions. In this regard, the flow controller works in the usual fashion of a conventional water powered down the hole (DTH) hammer. Preferably, the pressure differentials are between the trailing end of the piston member and the liquid outlet.

Preferably, the sealing member is located towards the leading end of the piston member. Preferably, the sealing member is located between the leading end of the piston member and an adjacent section of the housing.

The sealing member is adapted to prevent any liquid from contacting the trailing end of the drill bit such that when the piston member strikes the trailing end of the drill bit it does so in a liquid free environment. However, it will be appreciated that if a small amount of liquid passes the sealing member the liquid hammer drill will still operate as intended. In this regard, for the purposes of the present invention the term "liquid free environment" means an environment that is free or substantially free of liquid.

Preferably, the sealing member comprises an O-ring or similar device.

Preferably, the sealing member comprises a plurality of O-rings or similar devices.

According to a second aspect, the present invention provides a cutter head assembly for a tunnel boring machine, the cutter head assembly comprising: (a) a cutter head including a cutting face; and (b) a plurality of liquid hammer drills as described herein configured to locate within the cutter head.

According to a third aspect, the present invention provides a tunnel boring machine comprising a cutter head and a plurality of liquid hammer drills as described herein configured to locate within the cutter head.

Preferably, the tunnel boring machine comprises a cutter head assembly according to a second aspect of the present invention.

In order to facilitate a better understanding of the present invention, preferred embodiments are described herein with reference to the accompanying drawings, in which:.

The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown.

A liquid hammer drill according to one embodiment of the first aspect of the present invention is depicted in <FIG> and generally indicated by the numeral <NUM>.

The drill <NUM> includes a housing <NUM> and a drill bit <NUM> at the leading end of the housing <NUM>. The drill bit <NUM> includes a leading end defining a cutting portion <NUM> that includes a plurality of ovoid shaped toughened buttons <NUM>. Whilst not shown in <FIG>, the cutting portion <NUM> includes an aperture that allows for any ingress fluid (air or liquid) to be expelled.

The drill bit <NUM> has a relatively low profile and is removably attached to the housing <NUM> with a bit retention means in the form of collar <NUM> that allows for the drill bit <NUM> to be threaded on to the housing <NUM>. The trailing end <NUM> of the drill bit <NUM> defines a strike face that is described further hereunder.

The drill <NUM> further comprises a piston member in the form of piston <NUM>, located inside the housing <NUM>. The piston <NUM> has a generally circular cross-sectional shape and has a trailing end <NUM> that defines a cavity <NUM>, a leading end <NUM> and an intermediate portion therebetween that defines a shoulder <NUM>. The leading end <NUM> is tapered or narrower relative to the trailing end <NUM>. The piston <NUM> is capable of movement between a first position and a second position at which the leading end <NUM> impacts the trailing end <NUM> of the drill bit <NUM> and is operable by a liquid circuit that delivers liquid to the piston member via inlet <NUM> and transfers the liquid outside the housing via outlet <NUM>. Conventionally, liquid is exhausted to the cutting face of the drill bit <NUM> but the present invention allows for the exhaust of the liquid to be captured via the outlet <NUM>. Thus, the liquid is contained and exits the housing via outlet <NUM> so it can be delivered back to the drill via inlet <NUM>. This represents an essentially closed liquid circuit.

Between the inlet <NUM> and outlet <NUM> is a flow controller in the form of a valve <NUM>. Liquid, such as water, is delivered to the drill via inlet <NUM> and differential pressure between the inlet <NUM> and outlet <NUM> causes the valve <NUM> to move between first and second positions that in turn creates a pressure differential that causes the piston <NUM> to oscillate between its first and second positions and repeatedly strike the trailing end <NUM> of the drill bit <NUM>: the frequency of the oscillation being a product of the differential pressure. This oscillating movement corresponds to that widely used in water hammer drills and is familiar to those skilled in the art.

When the piston <NUM> strikes the trailing end <NUM> of the drill bit <NUM>, it does so in a substantial liquid free environment. The substantial liquid free environment is a result of the action of the sealing member in the form of the O-ring seals <NUM> that isolate the trailing end <NUM> of the drill bit <NUM> from the water. Although some water may pass the O-ring seals <NUM> any such ingress does not overly compromise the operation of the drill <NUM>.

An alternate embodiment of the drill bit that forms part of the drill according to the first aspect of the present invention is depicted in <FIG> and generally indicated by the numeral <NUM>.

The drill bit <NUM> also has a relatively low profile and a relatively short bit reach of about <NUM> and is adapted to be threaded onto the housing via a threaded engagement on collar <NUM>. The drill bit <NUM> has a generally square shaped cross section but incorporates an irregular shaped outside edge created by a plurality of cut-outs <NUM> that form a scalloped edge. The cutting face of the drill bit <NUM> includes a plurality of buttons <NUM> of toughened material and a pair of grooves 160a, 160b that run diagonally across the cutting face and assist with the removal of material away from the cutting face during use. At the centre of the cutting face is an aperture <NUM> that allows for any fluid (air or liquid) to be expelled from inside the housing of the drill.

The trailing end of the drill bit <NUM>, best shown in <FIG>, includes a pair of water relief grooves 172a, 172b to manage any liquid ingress to the trailing end of the drill bit <NUM>. A locating member in the form of a series of splines <NUM> located around the periphery of the inside of the collar <NUM> assist with the location and engagement of the drill bit <NUM>.

Advantages, in use, of the present invention including one or more of the performance features in the table below where #<NUM>, #<NUM> and #<NUM> represent <NUM> different embodiments of a drill according to a first aspect of the present invention:.

Throughout this specification, unless the context requires otherwise, the word "comprise" or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

Claim 1:
A liquid hammer drill configured for insertion into a cutter head of a tunnel boring machine comprising:
(a) a housing;
(b) a drill bit disposed at a leading end of the housing the drill bit including a trailing end and a leading end, the leading end defining a cutting portion;
(c) a piston member located inside the housing and having a trailing end and a leading end, the piston member configured to move between a first position and a second position, such that in the second position the leading end of the piston impacts the trailing end of the drill bit;
(d) a closed liquid circuit for delivering a liquid to the piston member within the housing to cause the piston member to oscillate between the first and second positions; wherein the trailing end of the drill bit defines a strike face for the piston member and the strike face comprises at least one liquid relief groove; and
(e) a sealing member for isolating the trailing end of the drill bit from the closed liquid circuit, such that the piston member impacts the trailing end of the drill bit in a substantial liquid free environment.