GB2197816A

GB2197816A - Drill rod

Info

Publication number: GB2197816A
Application number: GB08724175A
Authority: GB
Inventors: Nils Sture Hedman
Original assignee: Sandvik AB
Current assignee: Sandvik AB
Priority date: 1986-10-15
Filing date: 1987-10-15
Publication date: 1988-06-02
Also published as: BR8705519A; SE8604371L; FI874531A0; GB8724175D0; DE3734347A1; SE8604371D0; JPS63147083A

Description

1 Drill. rod The present invention refers to a drill rod for percussive

drilling, said rod comprising.an external thread at one.end _of the rod. The invention also refers to a sleeve to be mounted on the drill rod.

The coupling of drill rods for percussive drilling to a drill string is exclusively carried out by thread connections. The development of rock drilling machines for percussive drilling has lead to a tremendously increased impact rate for such machines. This has in its turn brought about a tendency tor the thread connection to unscrew, i.e. it is not tightened to a desireable degree to avoid is so-called pitting.

1 7 S 2 1 tor 1116 The- aim of the present invention is to present a drill rod of the type mentioned above, said drill rod being able to constitute a part of a thread connection that can work in a less tightened condition than thread coinecz:iJons of conventional type.

The aim of the invention is realized by a drill rod that has been given the characteristics of the appended claims.

Below an embodiment of the invention will be described, reference being made to the accompanying drawings, where Fig 1 shows a longitudinal section of a rod end according to the invention; Fig 2 shows a view along II-II in Fig 1; and Fig 3 shows a detail of an alternative embodiment.

The rod end 10 disclosed in Figs 1-3 comprises an external thread 11 and an internal hole 12 for supplying flushing medium.

A sleeve 13 is provided on the external thread 11, said sleeve on one hand being provided with an internal thread 14, that is in engagement with theexternal thread 11 of the rod end 10, and on the other hand with an external thread 15.

The rod end 10 including the sleeve 13 connected to an extension sleeve 16 that has an internal thread 17 that in operation is engaged with the external thread 15 of the sleeve 13.

The extension sleeve 16 can either be a so-called separate extension sleeve for connection of two externally threaded rod ends or an internally threaded sleeve that is integral with a drill rod.

The sleeve 13 is made out of a material that is softer than the material that the thread of the rod end 10 is made of, the latter material in practice being steel. The thread 13 is therefore suitably made out of a bearing material, preferably bronze.

Immediately adjacent to its termination, the rod end 10 is provided with an external, cylindrical surface 18 that does not constitute a portion of the external thread 11 itself. The sleeve 13 is provided correspondingly with an internal cylindrical surface 19 having an internal d-Lameter that mates with the external diameter of the surface 18.

This design of the rod end 10 and the sleeve 13 having mating cylindrical surfaces 18 and 19 respectively means that when the sleeve 13 is screwed upon the rod end these cylindrical sur.faces will cooperate with each other causing the sleeve - further axial displacement to the left to be locked against in Fig 1.

However, in order to guarantee also that the sleeve 13 remains on the rod end when the connection with the sleeve 16 is loosened, locking of the sleeve 13 against displacement to the right in Fig 1 is necessary. In Fig 2 is shown, as an example, how such locking is 1 -1 1 3 carried out by providing three Upsettings 21 paced around the circumference of the sleeve 13.

The material thickness of the sleeve 13 is constant in the embodiment according to Fig 1 and is in the range of 2-5 For a standard type thread having a diameter of 38 mm a material thickness of 4 mm, seems suitable for the sleeve 13.

In the alternative embodiment of Fig 3 the sleeve 13 has a material thickness that varies step-by-step. It is ensured that the thickened portions of the sleeve are located between the shoulders 22 and 23 of a thread connection that receive the load.

is The advantage of the alternative embodiment according to Fig 3 is that the sleeve 13 has the greatest material thickness in the portions being subjected to the highest wear.

As already mentioned in the beginning of the description a maintained tightness of the thread connec--ion is a problem for drilling machines having a high frequency. The sleeve according to the invention has in that respect an avourable influence to such "moderately" extraordinary 4. tightened thread connections by having a kind of lubricating effect. This means that the creation of so-called pitting is avoided even if the thread connection only is tightened to a moderate degree.

The invention is of course not restricted to the embodiments described above. Thus the locking of the sleeve 13 can be carried out in a different way, e.g. by brazing or adhesion.

The present invention preferably refers to threads having shoulders that are inclined 250-400 relative to the central axip of the drill rod and the pitch angle is in the interval of 6,50-90.

4 Although the described embodiments refer to trapezoidal threads the invention is in no way restricted to such threads but also other types of threads, e.g. rope threads, fall within the scope of the invention.

Also in other respects the invention can be freely varied within the scope of the appended claims.

is

Claims

1. Drill rod for percussive drilling comprising an external thread at one end of the rod, c h a r a c t r i z e d in that a sleeve, of a material that is softer than the material of the external thread, is mounted upon the external thread, said sleeve having an external thread.

2. Drill rod according to claim 1, wherein the sleeve is detachably connected to the rod end.

3. Drill rod according to claim 2, wherein the sleeve is locked against axial displacement in at least one direction by locking means.

4. Drill rod according to claim 3, wherein the locking means comprises a number of upsettings spaced around the circumference of the sleeve.

5. Drill rod according to any one of the preceding claims, wherein said external thread is made of steel and the sleeve is made of bronze.

6. Drill rod according to any one of the preceding claims, wherein said one end of the rod and the sleeve each comprise a cylindrical surface, said surfaces contacting each other.

7. Sleeve adapted to be connected to a thread of a drill rod for percussive drilling, and comprising both an internal thread and an external thread, the sleeve being made is softer than the material that a mating thread of the drill is made of.

1

8. Sleeve according to claim 7 and made of bronze.

9. Sleeve according to claim 7 or 8 and having a material thickness that varies in the longitudinal direction of the rod.

6

10. Sleeve according to claim 9 and having its greatest material thickness in the portions that. in the mounted position of the sleeve on the drill rod contact the load transferring shoulders of the thread connection between the sleeve and the rod.

11. A drill rod for percussive drilling, constructed and arranged for use and operation substantially as described herein with reference to the accompanying drawings.

12. A sleeve for threaded connection with a drill rod percussion drilling, constructed and arranged for use and operation substantially as described herein with reference to the accompanying drawings.