GB2269411A - A drill rod valve - Google Patents

Abstract

A drill rod 12, 14 has a non-return valve at its end nearest the shank adaptor 18 by which the rod (or other rods in the same drill string) will be connected to a drill. The valve allows fluid flow from the shank adaptor towards the bit 16 but prevents fluid flow in the opposite direction. The valve minimises loss of drilling fluid when connecting/disconnecting drill rods, especially when drilling above the horizontal. <IMAGE>

Description

A Drill Rod This invention relates to a drill rod for drilling holes in rock, where the rod is tubular and the central bore of the rod is used for flushing fluid from the head of a drill string to a bit on the outer end of the string.

In rock drilling, particularly rotary percussive rock drilling, a hole is drilled by means of a drill string which comprises a shank adaptor which interfaces at one end with the rock drill and at the other end with a drill rod and which has an entry hole for flushing fluid, a plurality of drill rods connected end to end with one rod connected to the shank adaptor, and a drill bit at the other end of the string. During drilling flushing fluid is fed into the shank adaptor and passes along the string through all the rods to reach the bit. The fluid then passes out through the bit and carries out the rock debris as drilling proceeds.

During the course of drilling it is from time to time necessary to interrupt the string, for example to insert an additional rod into the string. If the hole is being drilled above the horizontal, then the flushing fluid in the whole length of the string tends to run out as the string is interrupted, and before drilling can recommence the string must be refilled with flushing fluid. This is a messy and time consuming business.

According to the present invention, there is provided a tubular drill rod which has a non-return valve at one end which permits fluid flow through the rod in one direction but prevents fluid flow in the opposite direction.

The non-return valve is preferably arranged at the end of the rod which, in use, will be closest to the shank adaptor.

It is preferred for the valve to be as close as possible to the end of the rod, but for practical reasons it may be necessary for the valve to be spaced a certain distance in from the end of the rod.

In many applications, the rod will have a female thread at one end and a male thread at the other end. It is conventional for the female threaded ends to be closest to the shank adaptor and it is preferred to have the non-return valve at the female threaded end of the rod.

The non-return valve may be a ball valve which is lifted off a seat by flow of flushing fluid in a forward direction and which is pushed back onto its seat by flushing fluid flow in the opposite direction.

The invention will now be further described, by way of example, with reference to the accompanying drawings, in which: Figure 1 shows a drill string, partly broken away, incorporating drill rods in accordance with the invention; Figure 2 is an exploded view of one end of a drill rod in accordance with the invention; Figure 3 is an elevation, partly in section, of a non return valve for use in a rod in accordance with the invention; Figure 4 is an end view of the valve of Figure 3 taken in the direction of the arrow A; Figure 5 shows a rod end in accordance with the invention with an imposed flow in one direction; and Figure 6 is a view corresponding to Figure 5 but showing an imposed fluid flow in the opposite direction.

Figure 1 shows a drill string made up of a shank adaptor 10, a first drill rod 12, a second drill rod 14 and a drill bit 16. The drill rods 12 and 14 will be identical and will be of considerable length. It should be noted that only the extreme ends of each of the rods 12 and 14 are shown in Figure 1. The shank adaptor 10 is also shown at less than its full length.

The shank adaptor has a splined end 18 which will fit into a correspondingly splined socket of a drill motor. At its other end the shank adaptor 10 has a male threaded portion 20 which will engage with a female threaded portion 22 on the rod 12. Similarly a male thread 20a will engage with a female thread 22a on the rod 14 and a male end 20b on the rod 14 will engage with a female thread inside the bit 16.

When the components 10, 12, 14 and 16 are coupled together flushing fluid is introduced to the drill string through a hole 24 in the shank adaptor. This fluid passes along the drill string in the direction of the arrow 26 which is also the direction of drilling, through internal bores in each of the components, to the bit 16. The bit 16 has holes through its wall (not shown) through which the fluid flows out, and the fluid then flows back through the hole which has been drilled to flush out the drilling debris.

The construction of the female threaded end 22 of the rod 12 is shown in more detail in Figure 2, and it is to be understood that the rod 14 will be identical, as will be all the other drill rods to be connected into the same drill string.

The female thread 22 of the rod is conventional and runs from the end of the rod up to an annular groove 28. Inboard of the groove 28 is a further counterbore 30 which ends in the shoulder 32 and includes an annular groove 34. Beyond the shoulder 32 the rod has a tubular bore 36 which extends right through the rod.

A valve generally designated 38 is fitted in the counterbore 30. The valve comprises a valve housing 40, a ball 42, a ball-retaining pin 44 and a housing retaining ring 46. To assemble these components the ball 42 is placed in the housing 40, the pin 44 is fitted behind the ball through diametrically opposite apertures 48, 50. The housing is fitted in to the counterbore 30 with the pin 34 being retained by the walls of the counterbore, and the ring 46 is fitted into the annular groove 34 to retain the housing in place. The assembly is then as shown in Figure 5.

It will be noted that the housing 40 has a valve seat 52 at its left hand end. The diameter of the seat 52 is less than that of the ball 42 so that the ball cannot pass out of the housing but forms a seal when it rests against the seat 52.

In use, when drilling is taking place flushing fluid passes through the rod 12 in the direction indicated by the arrow 26 (see Figure 5). The fluid flow lifts the ball 42 away from the valve seat 52 so that the fluid can flow through the valve as indicated by the arrows 54 in Figure 5. The ball is retained in the housing 40 by the pin 44.

However when drilling stops and when the fluid pressure on the left hand end of the rod becomes less than that on the right hand end, then the ball 42 moves back to sit on the seat 52 and to prevent reverse flow of fluid through the rod. A volume of flushing fluid will then be trapped in the rod between the ball 42 and the extreme right hand end (20a in Figure 1) of the rod. Because this happens all the way up the string, the whole string will remain full of fluid ;nd other rods can be added to or removed from the string without the flushing fluid draining from the string.

It will be noticed from Figures 5 and 6 that the length of the counterbore 30 is somewhat longer than the length of the housing 40 so that the housing can be pushed far enough into the bore to allow the ring 46 to be clipped into the groove 34. The left hand end of the housing 40 has a shoulder which covers the ring 46 and prevents it falling out when the housing slides back into the counterbore 30, as shown in Figures 5 and 6.

Since drill rods of the type described are normally stored in an upright position in a purpose built carousel on a drill rig, the only time it is necessary to fill each individual rod with flushing fluid is the very first time it is introduced into service. Thereafter the flushing fluid remains in the rod until the rod is discarded or purposely emptied.

References in this specification to "right" and "left" are used for convenience of reference to the accompanying drawings and should not be taken as limiting in any way the possible orientations of the components described.

Claims (8)

Claims

1. A tubular drill rod which has a non-return valve at one end which permits fluid flow through the rod in one direction but prevents fluid flow in the opposite direction.

2. A drill rod as claimed in Claim 1, wherein the nonreturn valve is arranged at the end of the rod which, in use, will be closest to a shank adaptor which is used to connect a rod end to a drill.

3. A drill rod as claimed in Claim 1 or Claim 2, wherein the rod will has a female thread at one end and a male thread at the other end, the female threaded end is, in use, closest to the shank adaptor and the non-return valve is at the female threaded end of the rod.

4. A drill rod as claimed in any preceding claim, wherein the non-return valve is a ball valve which is lifted off a seat by flow of flushing fluid in a forward direction and which is pushed back onto its seat by flushing fluid flow in the opposite direction.

5. A drill rod as claimed in any preceding claim, wherein the ball valve comprises a housing which can be fitted in a bore in the rod and a ball which is held captive in the housing.

6. A drill rod substantially as herein described with reference to the accompanying drawings.

7. A drill string incorporating at least one rod as claimed in any preceding claim.

8. A drill string substantially as herein described with reference to Figure 1 of the accompanying drawings.