ZA200810094B - Hydraulic rock drill hammer - Google Patents

Description

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HYDRAULIC ROCK DRILL HAMMER

FIELD OF THE INVENTION

This invention relates to a rock drill and more particularly to a hydraulically powered impact drill hammer.

BACKGROUND TO THE INVENTION

Drill hammers of this nature are well known. A piston is caused to reciprocate in a cylinder and act as a hammer to strike a drill bit. Specific application of these drill hammers is found in mining and construction operations where they are used to drill holes in rock.

For such drills to be lightweight is generally desirable. This is especially so where they have to be handled by operators. In turn it is required that, in order to be effective, the

B.200 . BB 0094 blows struck on the drill be delivered at a high rate. In this way the required energy to break the rock can be transferred in a short space of time.

One particular drill utilizes a lost motion poppet valve assembly to control its operational cycle. An elongate poppet has an annular valve at one end and a concentric shuttle valve relatively reciprocatable on its body. The shuttle valve controls and directs the flow of operating fluid to different surfaces in the drill assembly to give the fast reciprocation and striking of the hammer piston on the end of the drill bit.

These known drill assemblies do however have a tendency to “lock-up” when the supply fluid is cut off. With such an interrelated positioning of valve components re-application of the supply fluid cannot start the operational sequence and the drill remains inoperative. In an effort to overcome this difficulty a biasing compression spring assembly has been introduced into the drill. While of assistance in starting of the drill these springs are not always effective and the drill requires physical shaking for start up.

All of this is not too serious a draw-back when the drills are handheld or readily accessible. However where the drills are used on remote controlled rigs in underground mining operations, particularly in confined areas, automatic starting is essential.

Another problem with the drills of this kind is failure of the poppet valve control assembly : and, in particular, the poppet valve. This component is subjected to impact stresses as it is oscillated between its operational positions under action of the working fluid. It is also stopped against full velocity and differential pressures repeatedly during operation.

These problems also extend to down-the-hole drills which operate on a similar cycle.

OBJECT OF THE INVENTION

It is an object of one aspect of the present invention to provide a drill of the kind referred to where the problem with remote starting is mitigated. It is an object of another aspect of this invention to at least partially alleviate the abovementioned problem with poppet valve failure.

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SUMMARY OF THE INVENTION

In accordance with a first aspect of this invention there is provided a drill assembly comprising a casing having a front passage with a hollow piston hammer slidably engaged at each end and a rear passage housing a flow control valve assembly coaxial with the piston hammer, the valve assembly including an axially slidable hollow poppet valve with an annular shuttle valve slidably supported thereon, the poppet valve having a seat on the rear end of the piston hammer and a shuttle valve seat provided behind the front passage, the assembly connectable to a pressurized fluid supply to feed the front and rear passage via respective flow paths, with the flow path to the rear passage having a delay valve.

The invention further provides for the rear passage to have a pressure sensitive outlet valve resiliently biased to an open position; and a seal provided between the poppet valve and shuttle valve to allow a limited leak.

Further features of the invention provide for the outlet valve to include a hollow annular outlet valve member which slidably receives the rear portion of the poppet valve in sealing engagement therewith and is resiliently biased forwardly off a cooperating valve seat; and for the outlet valve seat to be provided by a socket supported behind the control valve assembly which slidably receives outlet valve member.

One embodiment of the first aspect of this invention provides for the flow path to the rear passage to extend from the front passage via a pressure sensitive delay valve resiliently biased to a closed position; for the delay valve to be an accumulator; and for the accumulator to include a diaphragm secured against a perforated support which extends across the front and rear passages. The delay valve may alternatively be a pressure sensitive time delay poppet valve in the flow path to the rear passage.

Another embodiment of the first aspect of this invention provides for the flow path to the rear passage to have a delay valve comprising a poppet in a cylinder resiliently biased to a position which allows a bleed passage past the poppet to the rear passage; and for the flow path to the rear passage to be via lateral vents in the wall of the delay valve cylinder.

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In accordance with a second aspect of this invention there is provided a drill assembly comprising a casing having a front passage with a hollow piston hammer slidably engaged at each end and a rear passage housing a flow control valve assembly coaxial with the piston hammer, the valve assembly including an axially slidable hollow poppet valve with an annular shuttle valve slidably supported thereon, the poppet valve having a seat on the rear end of the piston hammer and a shuttle valve seat provided behind the front passage, wherein the rear end of the piston hammer and the forward end of the shuttle valve are adapted contact each other around the forward portion of the poppet valve.

The invention further provides for the piston hammer to have a rearwardly extending annular shuttle contacting formation locatable around the forward end of the poppet; and : for the formation to be castellated or perforated.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of the invention will become apparent from the following : description, by way of example only, of three preferred embodiments shown in the accompanying drawings -

Figure 1: which is a longitudinal cross-section through one embodiment of a hydraulic drill in accordance with this invention;

Figure 2: which is a similar view of a down-the-hole hydraulic drill also in accordance with this invention; and

Figure 3: which is a similar view of a down-the-hole hydraulic drill according to yet a further version of the invention.

= 20087 19094

DETAILED DESCRIPTION OF THE INVENTION

Referring to Figure 1, a rock drill (101) comprises an outer casing (102) the major length of which provides a front flow passage (103) around piston hammer (104). A rear flow passage (105) is provided in the casing (102) behind the piston hammer (104).

Located in the rear flow passage (105) is a flow control valve assembly (106) comprising an elongate poppet valve (107) and annular shuttle valve (108) co-axial with the piston hammer (104). The poppet valve (107) is hollow and seals against the rear end (109) of the piston hammer (104).

The outside of the poppet valve (107) supports, in sliding engagement therewith, the shuttle valve (108). Seals (110) inside the shuttle valve (108) provide for sufficient sealing but allow a limited leak between these valves (107) and (108). The significance of this leak will be described below.

The rear portion of the piston hammer (104) is slidably supported in sealing engagement by sleeve (111) between the passages (103) and (105). The sleeve (111) is secured in a portion (112) of the casing (102) having a reduced diameter. Provided at the rear end of the sleeve (111) is an annular valve seat (113) against which the shuttle valve (108) seals.

The rear portion (114) of the poppet valve (107) has two oppositely facing shoulders (115) and (116). The shoulder (115) determines the rearward end of the stroke of the shuttle valve (108) on the poppet valve (107) and the shoulder (116) limits the poppet valve (106) movement against the forward end of an annular outlet valve member (117).

An accumulator (118) in the wall of the casing (102) extends from the front passage (103) across the portion (112) to the rear passage (105). The accumulator (118) includes a gas container (119) separated from the passages (103) and (105) by a flexible diaphragm (120).

Pressure fluid supply passage (121) is provided to the front passage (103) through the casing (102) and is also connected to the rear passage (105) through openings (122) in

C—— 720087 10094 a perforated diaphragm support (123) between the passages (103) and (105) and the diaphragm (120).

The accumulator (118) provides a pressure sensitive delay valve (118) with a flow path (124) connecting the two passages (103) and (105) extending between the support (123) and the diaphragm (120). The delay valve (118) is accordingly resiliently biased to its closed position and is shown in this condition in the drawing.

The front portion of the piston hammer (104) is slidably located in sealing engagement with a retaining ring (125) provided at the forward end of the casing (102). The piston hammer (104) has an axial bore (126) therethrough. This bore (126) and the hollow poppet valve (107) provide an exhaust passage for the driving fluid which will discharge through a hollow drill rod (not shown) in the bottom of the drill hole to flush drilled rock.

In an alternative embodiment, which uses oil hydraulic, there will be no such flushing and all the fluid will be exhausted through the hollow poppet valve (107) to the rear of the drill (101) where it is collected for reuse.

The piston hammer (104) is provided a rearwardly extending annular shuttle contacting formation (127). The formation (127) is larger in diameter than the forward enlarged : portion of the poppet (107). A series of inward steps provide the formation (127) with a castellated profile.

The rear flow passage (105) has a pressure sensitive outlet valve (128), the valve member (117) of which has already been referred to. The annular valve member (117) is located slidably in a socket (129) provided in a retaining ring (130). The valve member (117) slidably receives the rear portion of the poppet valve (107) in sealing engagement.

A valve seat (131) is provided by an inwardly extending flange at the rear of the ring (130). This cooperates with a shoulder (132) on the valve member (117). A disc spring (133) biases the member (117) forwardly off its seat (131) to an open position. The shoulder (132) locates off the seat (131) when the pressure in the rear passage is sufficiently low to be overcome by the resilience of the spring (133). In this condition, vents (134) adjacent the rear of the member (117) are placed in communication with the rear flow passage (105). The member (117) will move into and be retained in its closed

— ¥ 2008710094 position under the effect of operational pressure in the rear flow passage (105). It is in this condition that the valve (128) is shown.

On the drawing are indicated certain diameters of surfaces subject to working pressures.

These are numbered D; through Ds. These diameters provide surfaces subjected to the pressure fluid supply which result in forces as follows:-

D; <D,; D; > D4; D3 > Dy; Ds > Ds; Ds > Dg; and Dg > Ds.

Those familiar with the type of drifter drill described understand that these forces acting on the lightweight poppet valve (107), shuttle valve (108) and piston hammer (104) result in high frequency reciprocation of the piston hammer (104). Such a drill will in practice have a working stroke designed to generate desired energy, velocity and frequency in conjunction with the dimension parameters of the assembly.

When supply pressure is applied to the passage (103) the piston hammer (104) is moved rearwardly. Once pressure builds up in the front passage (103), the working fluid displaces the diaphragm (120) opening a flow path (124) to the rear passage (105) via openings (122). The fluid pressure in the rear passage (105) then acts on the rear end of piston (104) onto which the poppet valve (107) is seated. The first impact stroke of the piston (104) is delivered and the drill (101) operates in the known manner.

The drill (101) uses lost motion of the poppet valve (107) to control the operational cycle.

The shuttle valve (108) controls and directs the flow of operating fluid to different surfaces in the assembly to give the fast reciprocation and striking of the piston (104) on the end of a drill bit.

During operation of the drill (101), when the piston (104) returns towards the valve assembly (106), the shuttle valve (108) will be forward on its seat (113) and the poppet valve (107) will be against the front of the shuttle valve (108) as shown in the drawing.

The rear end (109) of the piston hammer (104) and the forward end of the shuttle valve (108) are adapted to contact each other around the forward portion of the poppet valve (107). Accordingly, the piston (104) will first strike the shuttle valve (108) with its formation (127). At the point of this contact, a space of about 0.3mm to 0.5mm is

-~_ ®72008/ 14094 provided between the front of the poppet valve (107) and its seat at the rear end (109) of the piston hammer (104). The piston (104) moves the shuttle valve (108) off the valve seat (113) and then engages the poppet valve (107).

A significant impact on the poppet valve (107) which would otherwise result from the piston hammer (104) striking the shuttle valve (108) through the poppet valve (107), in the normal fashion, is thus avoided. The stepped profile of the castellated formation (127) allows flow of working fluid past the piston (104) and shuttle valve (108) where they contact each other. Alternative formations (127) which may include suitable perforations may also be used to avoid trapping fluid and will be within the design competence of a suitably skilled person.

When the supply fluid is cut off from the front passage (103) the piston (104) will come to standstill once the energy accumulated in the diaphragm (120) has dissipated through exhaust of the working fluid via bore (126) of the piston (104).

In this state, the pressure in the rear passage (105) is normally sufficiently reduced to enable the pressure sensitive outlet valve (128) to open under resilience of spring (133) and vent the remaining pressure in the passage (105).

Where the piston (104) comes to a stop in a rearward position coupled with the poppet valve (107) and the shuttle valve (108) is on the valve seat (113), the pressure contained in the rear passage (105) may prevent desired operation of the flow sensitive outlet valve (128). Such a “lock-up” would also ordinarily prevent automatic starting of the drill (101). However, as mentioned above, the seals (110) of the shuttle valve (108) are provided with leakage grooves to allow limited leaking. This reduces the pressure in the rear passage (105) sufficiently to allow operation of the outlet valve (128) to vent the pressure as required for automatic start up as described.

Another advantage of providing valves (107) and (108) with limited leak seals (110) between them is that they are less inclined to overheat and this provides for longer life.

While the illustrated embodiment has an accumulator (118) as the pressure sensitive delay valve (118) to control flow through the flow path (124) from the front (103) to the an = 2043s 1009¢ 10. i rear (105) passage, it will be appreciated that alternative valves may be used for this purpose. For example, the flow path may be provided with a poppet valve spring biased to closed position. Pressure from the front passage (103) will overcome the bias, opening the valve as required for operation. Such a poppet valve may conveniently be provided on the end of a piston slidably located in and extending from a cylinder through the casing (102) wall which is in communication with the atmosphere. The spring will be provided on the piston between the poppet and the wall around the cylinder.

The amount of force by which the delay valve (118) is to be resiliently biased into its closed position and by which the outlet valve (128) is to be resiliently biased into its open position will be within the design competence of a suitably skilled person.

Referring now to Figure 2, a down-the-hole drill hammer (201) in accordance with this invention is also shown.

The arrangement of the outer casing (202), front flow passage (203), piston hammer (204), sleeve (210) and rear flow passage (205) are substantially the same as for the drill (101) in Figure 1. So too are the flow control valve assembly (206) with its elongate poppet valve (207) and annular shuttle valve (208), the latter of which also cooperates with annular seat (213) provided by sleeve (210) about the rear end (209) of the piston hammer (204).

Pressure fluid supply is through an inlet (221) at the rear end of the casing (202). A : check valve (251) controls flow through the inlet (221). Ports in the wall of the casing provide a first flow path (241) that leads from the inlet (221) to the front passage (203).

Flow through a second flow path (242) to the rear passage (205) is controlled by a delay valve (252). The delay valve (252) comprises a poppet (253) slidable in an axial cylinder (254). The cylinder (254) is provided in the rear end of an elongate support (255) located longitudinally in the rear passage (205). A spring (256) in the cylinder (254) biases the poppet (253) outwardly and into a position where it locates over lateral vents (257). The vents (257) connect the cylinder (254) to the rear passage (205) providing the second flow path (242).

A clearance of about 0.1mm provides a bleed passage between the poppet (253) and cylinder (254). The delay valve (252) provides a time delay in the pressurization of the rear passage (205).

Like the first drill (101), the rear flow passage (205) is provided with a pressure sensitive outlet valve (228). An annular valve member (217) is located slidably in a socket (229) in the forward end of the elongate support (255). The member (217) is hollow and slidably receives the rear portion (214) of the poppet valve (207) in sealing engagement. The valve member (217) is biased outwardly from the cylinder (229) by disc spring (233). A valve seat (231) is provided at the mouth of the socket (229). This cooperates with a rearward annular shoulder (232) on the valve member (217). The shoulder (232) locates off its seat (231) when the pressure in the rear passage is sufficiently low to be overcome by the resilience of the spring (233). A clearance of about 0.25mm to 0.5mm is provided between the wall of the socket (229) and body of the valve member (217).

This provides a bleed passage between these components (229) and (217) to vents (234) and to the exhaust passage through the hollow poppet (207) and bore (226) of the piston hammer (204). The valve member (217) will move into the closed position during operation of the drill (201).

As described with reference to drill (101) in Figure 1, start-up relies on the pressurization of the front passage (203) first. This is achieved through free flow of pressurized fluid through the first flow path (241). The resulting hydraulic bias moves the piston hammer (204) and with it the valve assembly (206) rearwardly.

Initially, the pressurized fluid can only bleed past the delay valve (252) and into the rear passage (205) via the second flow path (242). However, the outlet valve (228) is in an open position when the drill (201) is started. Fluid from the rear passage (205) escapes between the wall of the socket (229) and body of the valve member (217) to exhaust through the piston bore (226) via vents (234). The respective clearances around the outlet valve member (217) and the delay valve poppet (253) are selected to provide flow to exhaust sufficient to prevent pressurization of the rear passage (205) at this stage.

The delay provided by the delay valve (252) allows pressure in the front passage (103) to bring the components to a start up condition. The outlet valve (228) is closed and the first impact stroke of the piston hammer (204) delivered. With the working pressure established in the rear passage (205) the poppet (252) is unbalanced and the bias of spring (256) is overcome. During operation of the drill (201), the delay valve (252) remains open.

The operation cycle is substantially the same as that of the drill in Figure 1, with the exception that the working fluid in the front passage (103) does not pass through a flow path (124) to the rear passage (105) and then exhaust through the piston bore (226).

Rather, in the case of this drill (201), the working fluid in the front passage (203) oscillates during operation. The piston hammer (204) is also provided with a rearwardly extending annular shuttle contacting formation (227) with a castellated profile to extend the life of the poppet valve (207).

Turning now to Figure 3, a further version of a down-the-hole drill hammer (301) is shown. In this figure, the hammer (301) is shown in an initial position with only the front portion of the hammer (301) shown, the rear part being substantially similar to that shown in Figure 2. In addition, the majority of the components of hammer (301) are the same as those of hammer (201); they have thus been numbered similarly and their operation will thus also not be repeated here.

The main feature of the hammer (301) is the presence of a spring ring (302) adjacent the vents (234). The spring ring (302) provides a gap of approximately 1.5 mm for allowing water to flow from chamber (205), through holes (234) to the outlet so as to drain the chamber (205) during the start cycle, and then closes to remain closed when the passage (205) is pressurized.

The invention thus provides a hydraulic drill that will be more reliable to start-up and having improved life of the poppet valve. Two significant problems with drills of this type are at least partially alleviated.

Further variations to the described embodiments which make use of a delayed pressurization of the rear passage and venting of the rear passage as described for successful start-up will be appreciated. Variations to the form of the piston hammer . and/or the shuttle valve which allow contact of these components around the forward portion of the poppet valve will also be appreciated.

These variations will be within the design competence of one suitably skilled in the art and such a person will understand that these variations still fall within the scope of this invention.

Claims (13)

-14- {VAAN Ce CLAIMS ST

1. A drill assembly comprising a casing having a front passage with a hollow piston hammer slidably engaged at each end and a rear passage housing a flow control valve assembly coaxial with the piston hammer, the valve assembly including an axially slidable hollow poppet valve with an annular shuttle valve slidably supported thereon, the poppet valve having a seat on the rear end of the piston hammer and a shuttle valve seat provided behind the front passage, the assembly connectable to a pressurized fluid supply to feed the front and rear passage via respective flow paths, with the flow path to the rear passage having a delay valve.

2. The drill assembly of claim 1, wherein the rear passage comprises a pressure sensitive outlet valve resiliently biased to an open position; and a seal provided between the poppet valve and shuttle valve to allow a limited leak.

3. The drill assembly of claim 2, wherein the outlet valve includes a hollow annular outlet valve member which slidably receives the rear portion of the poppet valve in sealing engagement therewith and is resiliently biased forwardly off a cooperating valve seat.

4, The drill assembly of claim 3, wherein the outlet valve seat comprises a socket supported behind the control valve assembly which slidably receives outlet valve member. :

5. The drill assembly of any one of the preceding claims, wherein the flow path to the rear passage extends from the front passage via a pressure sensitive delay valve resiliently biased to a closed position.

6. The drill assembly of claim 5, wherein the delay valve comprises an accumulator.

7. The drill assembly of claim 6, wherein the accumulator includes a diaphragm secured against a perforated support which extends across the front and rear passages.

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8. The drill assembly of claim 5, wherein the delay valve comprises a pressure sensitive time delay poppet valve in the flow path to the rear passage.

9. The drill assembly of any one of the preceding claims, wherein the flow path to the rear passage comprises a delay valve comprising a poppet in a cylinder resiliently biased to a position which allows a bleed passage past the poppet to the rear passage.

10. The drill assembly of claim 9, wherein the flow path to the rear passage is via lateral vents in the wall of the delay valve cylinder. :

11. A drill assembly comprising a casing having a front passage with a hollow piston hammer slidably engaged at each end and a rear passage housing a flow control valve assembly coaxial with the piston hammer, the valve assembly including an axially slidable hollow poppet valve with an annular shuttle valve slidably supported thereon, the poppet valve having a seat on the rear end of the piston hammer and a shuttle valve seat provided behind the front passage, wherein the rear end of the piston hammer and the forward end of the shuttle valve are adapted contact each other around the forward portion of the poppet valve.

12. The drill assembly of claim 11, wherein the piston hammer comprises a rearwardly extending annular shuttle contacting formation locatable around the forward end of the poppet, the formation being castellated or perforated.

13. A drill assembly substantially as herein described and illustrated. DATED THIS 27" DAY OF NOVEMBER 2008 OWMAN GILFILLAN INC. (JOHN & KERNICK) FOR THE APPLICANT