GB2188270A

GB2188270A - Hammer drill for percussion drilling

Info

Publication number: GB2188270A
Application number: GB08705877A
Authority: GB
Inventors: Peter Stephan
Original assignee: Bergwerksverband GmbH
Current assignee: Bergwerksverband GmbH
Priority date: 1986-03-25
Filing date: 1987-03-12
Publication date: 1987-09-30
Also published as: DE3610014C1; GB8705877D0; GB2188270B

Abstract

A hammer drill for percussion drilling is provided with an impact piston 2 driven with compressed air or electrohydraulically and transmitting the impact energy to the insert end 11 connected to the drill rod 12 and with a conversion means 14 provided with a gear mechanism. In particular to reduce the dead length of the hammer drill the piston (2) is disposed in a direction deviating from the drill hole axis (3) and for deflecting the impact energy from the piston (2) into the working direction of the drill rod (12) an arcuately extending fluid cushion (4) is provided (Figure). The cushion 4 is closed by limiting or hydraulic pistons 5, 6. Impact is transmitted via piston 6, cushion 4, and piston 5 to the rod 12. After return of piston 2 the cushion 4 and pistons 5, 6 are reset by means of a spring element 10. The element 10 is rubber or a spring. The cushion 4 may be fluid oil or Freon. A water cooled path 8 dissipates heat. Flushing water is supplied via a guide 9 to a supply in the rod 12. <IMAGE>

Description

SPECIFICATION Hammer drill for percussion drilling The invention relates to a hammer drill for percussion drilling comprising an impact piston driven with compressed air or electrohydraulically and transmitting the impact energy to the insert end connected to the drill rod and a conversion means provided with a gear mechanism.

On introduction of rock bolts or anchors into the rock surrounding the tunnel or underground road or heading problems are encountered due to the restricted space conditions in the road or heading in conjunction with the large dead length ofthe percussion drills. The large dead length of percussion drills restricts the possible useful dril rod length. To overcome these difficulties eitherthe time-consuming lengthening or shortening ofthe drill rod system must be put up with or alternatively the placing of long anchors or bolts, appropriate from the point of view of rock mechanics, must be dispensed with entirely. These problems greatly restrictthewidespread use of otherwise very effective rock bolting, in particular in great depths and/or in pit rooms of small cross-section.

To improve the efficiency and performance of hammer drills for percussion drilling in effective mannertheindividual impactenergycan be increased in two ways. Firstly, the impact piston can be lengthened and secondly the acceleration path of the impact piston can be lengthened. Both modifications lead however two an increase in the overall length ofthe hammer drill and assuming unchanged geometrical conditions within the tunnel or heading this change meansthata reduction ofthe useful length of the drill rod system must be accepted.

In comparison, the invention is based on the problem of avoiding the aforementioned disadvantages by providing a hammerdrillfor percussion drilling in which the dead length, important for example in the setting of bolts or anchors, is reduced to such an extent that even an increase in the drilling power by increasing the length ofthe impact piston or the acceleration path does not have any appreciable influence on the disadvantageous dead length in the direction ofthe drill hole axis.

This problem is solved according to the invention in that the impact piston is disposed in a direction deviating from the drill hole axis and for deflecting the impact energy out of the working direction ofthe impact piston into the working direction of the drill rod an arcuately extending fluid cushion is provided.

The dead length of a hammer drill hitherto to be measured in the direction ofthe drill hole axis and impairing the entire drilling operation is deflected by the arcuately extending fluid pad or cushion so that the substantially longer portion of the housing when setting forexample rock bots is aligned inthe longitudinal axis ofthe heading. Such a construction ofthehammerdrill housing with the corresponding means permits with only a slight increase in the dead length in the direction ofthe drill hole axis any desired increase in the single impact energy by increasing the length ofthe impact piston or increasing the length of the acceleration path ofthe impact piston.

It is found particularly advantageous within the scope ofthe invention for the fluid cushion to be enclosed on both sides by limiting pistons with correspondingly high-performance sealing elements. The bordering or limiting pistons permit a transfer ofthe single impact energyfrom the closure piston disposed on the hammer side via the fluid column to the closure piston disposed on the drill rod side, said impact energy being further transmitted onto the insertion end of the drill rod.

After return of the impact piston the fluid cushion is reset along with the sealing or closure pistons with the aid of a spring element. The system-inherent heat development due to fluid friction is dissipated via a cooling system in the guide piece of the hammer drill housing. It is possible to use the cooling watersupplied via asuitablesupplylineto the water cooling subsequently as flushing water in the central flushing water guide or supply in the drill rod.

The technical advance of the invention resides substantially in that the hammer drill is better adapted to the constricted space conditions and that the temporary lengthening orshortening ofthedrill ins system can in many cases be dispensed with and in this manner anchoring desirable from the rock mechanics point of view with correspondingly long bolts can be carried out in simple manner.

An example of embodiment of the invention is illustrated as a schematic section through a hammer drill in the drawing and will be explained in detail hereinafter.

In the example of embodiment of a hammer drill for percussion drilling shown schematically in section in the drawing the hammer drill housing extending with a troublesome dead length in the direction ofthe drill hole axis 3 is shown in dashed line and designated byl'.Asfurtherapparentfrom the example of embodiment illustrated in the drawing the impact piston 2 operates within the angled hammer drill housing 1 in a direction deviating from the drill hole axis 3. In the same axis as the impact piston 2 in front ofthe latter there is the acceleration path 15. The deflection of the impact pulse is via a fluid cushion 4which is disposed in an arcuate guidepiece. As fluid oil can for example be used or any other medium allowed in underground mining,forexamplealso Freon.The fluid cushion 4 is closed on both sides by limiting or hydraulic pistons 5,6 which are provided with high-performance sealing elements. When the impact piston 2 strikes the limiting piston 6 ofthe fluid cushion 4 disposed on the hammer side the pulses are deflected to the limiting piston 5 which is disposed on the drill rod side and which transmits theimpactviatheinsertend 11 tothedrill rod 12.

After return of the impact piston 2 the fluid cushion 4 with the limiting pistons 5,6 are reset with the aid of a spring element 10 which is disposed for example at the end of the insert end 11. The spring element 10 is preferably made of an elastically resilient material, for example rubber or a spring. To dissipate the heat inherently formed by the system, as apparent from the example of embodiment in the drawing, at least in the region of the guide piece 7 ofthe hammerdrill housing 1 the fluid cushion 4 is provided with an annularly surrounding cooling path 8. Via the water supply 16 cooling water is introduced into the cooling section 8 and it is convenientthereafterto supply the cooling water as flushing water via the flushing water guide 9 to the central flushing water supply in the drill rod 12. An expansion of the fluid cushion due to heat is compensated by adequate clearance at the limiting piston 5 disposed on the drill rod side. To enable the conversion means with the drive 13 to be accommodated conveniently in the hammer drill housing 1 the necessary gear mechanism 14 is constructed as bevel spur gearing.

Claims

1. Hammerdrillforpercussiondrilling comprising an impact piston driven with compressed air or electrohydraulically and transmitting the impactenergy to the insert end connected to the drill rod and a conversion means provided with a gear mechanism, characterized in thatthe impact piston (2) is disposed in a direction deviating from the drill hole axis (3) and for deflecting the impact energy out of the working direction of the impact piston (2) into the working direction of the drill rod (12) an arcuatelyextending fluid cushion (4) is provided.

2. Hammer drill according to claim 1, characterized in thatthe fluid cushion (4) is enclosed on both sides by limiting pistons (5, 6).

3. Hammer drill according to claim 1, characterized in that at least in the guide piece (7) receiving the arcuate fluid cushion (4) an at least partiaily annularlyformed cooling section (8) is provided.

4. Hammerdrill accordingtoclaim3, characterized in that a water cooling is provided which can be connected in front of the central flushing water guide (9).

5. Hammer drill according to claim 1, characterized in that for resetting the fluid cushion (4) a spring element (10) of spring steel or rubber is provided.