Pipe joints or couplings – Particular interface – Tapered
Patent
1982-09-17
1985-09-10
Callaghan, Thomas F.
Pipe joints or couplings
Particular interface
Tapered
175 57, 175320, F16L 5500
Patent
active
045402000
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a rock drill and more precisely to a drilling assembly for use in percussion rock drilling comprising a drill bit having a first conical surface and adapted for connection to a drill rod having a corresponding second conical surface.
In percussion rock drilling either integral drill steels or detachable drill bits are used. Such drill bits are, during drilling, connected to a drill rod by means of a threaded connection or conical frictional connection.
The disadvantage of the conical connections is primarily that, during certain circumstances, there is a risk that the drill bit is lost, and that the drill rod sometimes has a tendency to slip or spin in the drill bit. Loss of the drill bit may happen if a firm frictional connection is not yet created which means that the drill bit may be dislodged by appearing shock wave forces. Slip of the drill rod, or spinning thereof in a non-rotating drill bit may be caused if the drill bit enters a cavity in the rock, which means that the shock waves are not transmitted to the rock but instead do loosen the firm connection between drill bit and drill rod.
The object of the present invention is to provide a drilling assembly having a conical frictional connection which does not have the above disadvantage.
This and other objects of the invention have been attained by giving the invention the characterizing features stated in the appending claims. The invention is described in the following with reference to the accompanying drawings in which one embodiment is shown by way of example. It is to be understood that this embodiment is only illustrative of the invention and that various modifications may be made within the scope of the claims.
In the drawings,
FIG. 1 shows a drilling assembly according to the invention.
FIG. 2 shows on an enlarged scale the cooperating conical surfaces in the position when contact first arises during the connection of the drill bit and drill rod.
FIG. 3 shows the conical surfaces in FIG. 2 in their final connected position.
The drilling assembly according to the invention comprises a percussion drill bit 10, which is intended to be connected to a drill rod 11. The drill bit 10 is in conventional manner provided with a plurality of hard metal inserts 12. During drilling flushing medium is supplied to the bottom of the drill hole through a passage 13 in the drill rod and one or several branching passages 14 in the drill bit.
The drill bit 10 is provided with a conical surface 15 and the drill rod 11 has a corresponding conical surface 16. For purposes of obtaining a more reliable connection between the drill bit 10 and the drill rod 11 the conical surface 16 is provided with a helical thread 17.
In the preferred embodiment the thread 17 is made by means of a turning tool. The radius of curvature r of the profile of the thread, thus, coincides with the radius of the indexable insert of the turning tool. Preferably, the radius of curvature r is constant and has a value within the interval 0.5 mm to 2.0 mm, with preference for values somewhat smaller than 1.0 mm.
The conical surface 15 of the drill bit 10 is smooth, i.e. unthreaded, before the connection of the drill bit to the drill rod 11. During the connection, thus, contact first arises at the crests of the thread 17, see FIG. 2. During drilling, then, the thread 17 will impress a corresponding thread in the drill bit by means of the shock wave forces from the rock drilling machine. Thus, a miniature-thread connection is obtained which together with the tapered embodiment ensures a safe and reliable attachment of the drill bit to the drill rod. It has been found that in a drilling assembly according to a preferred embodiment of the present invention a substantially conversely congruent thread is impressed in the drill bit 10. In order to ensure such impression it has been found that the conical surface 16 shall be harder than the conical surface 15, preferably at least 10 Rockwell "C" units (H.sub.RC) harder. Such a difference in hardness also means that the d
REFERENCES:
patent: 91291 (1869-06-01), Wegmann
patent: 635636 (1899-10-01), Bailey
patent: 1776615 (1930-09-01), Boothman et al.
patent: 1974150 (1934-09-01), Creveling
patent: 2711913 (1955-06-01), Jungblut
patent: 2793884 (1957-05-01), Jungblut
patent: 2872226 (1959-02-01), Wright et al.
patent: 3175850 (1965-03-01), Steczynski
patent: 3224794 (1965-12-01), Crissy
patent: 3272539 (1966-09-01), Asbury, Sr.
patent: 3508773 (1970-04-01), Coberly et al.
patent: 3519090 (1970-07-01), Herring
patent: 4298221 (1981-11-01), McGugan
Callaghan Thomas F.
Santrade Ltd.
LandOfFree
Rock drill does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Rock drill, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Rock drill will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1424786