| US3924690A | 1975-12-09 |
| 1. | A method for regulating the penetration of a drilling equip ment, where a tool (1) in the drill head comprises two or mor individually drilling bits, which can be backed in their holdin devices characterized in that when, because of load, one o more drilling bits are in backed position in the tool body (1) penetration of tool or the whole drill unit or the pushin force used for forward driving is restricted. |
| 2. | A method according to claim 1 characterized in that th pushing force or the penetration is so restricted, that for th whole drill unit or the tool (1) a pushing force is formed equa to the pushing force of the permitted load of one bit at th most. |
| 3. | A method according to claims 1 and 2 characterized in tha the restriction of the pushing force or the penetration i switched off when a bit or all the bits have returned to thei extreme position. |
| 4. | A method according the patent claims 1 3 characterized i that overload of any single bit causes backing of bit an restriction of the drill unit or the tool (1). |
| 5. | An equipment for drilling soil or rock, in which there ar in the tool body (1) of the drill head in the drill unit two o more individually drilling bits, which are, because of bein loaded, capable of backing individually, characterized in tha the bits are comprised of devices or medium driven couplings fo detecting backing of bits and for transmitting this informatio to the regulating apparatus of the bit unit. |
| 6. | An equipment according to patent claim 5 characterized i that the force pushing the whole bit unit or the tool body (1 is adjustable, at the most, to the same level as the loa permitted for one bit. |
| 7. | An equipment accordining to patent claims 5 or 6 characteriz¬ ed in that the backing of the bits and coupling of the bits to the regulaton system is carried out mechanically or by means of a medium. |
| 8. | An equipment according to patnt claims 57 characterized in that the springy holding device of the bits is a cylinder (7) driven by a medium. |
| 9. | An equiment according to any of the above patent claims 58 characterized in that the bits are individually springy inwards and the sustaining force of their extreme postition adjustable. |
The invention relates to an equipment drilling soil or rock and a method for regulating its penetration, where the penetration is restricted if one or several drill bits are overloaded.
Among previously known drilling equipment there is a.o. one in the Finnish application No. 891706, where drilling is carried out either by means of a hammering or a rotating tool. In the applicaton is is described how a hammer furnished with a drill bit and with or without a bit-rotating tool can be backed in its cylinders if the drilling unit is driven too much forward.
The pressure schocks caused by the tool upon drilling are a disadvantage of the above solution, because they disturb the control of backing of the whole tool unit. Generally, it is possible to control the backing only when the drill head is driven on the wall which is being drilled and it can detected by the backing that the tool and the whole drill head have reached the target.
The solution of this invention enables elimination of possibili- lities for the single bits to get damaged and dependable control of the backing of the drill bits. The invention is characterized by the features described in the patent claims.
It can be considered the major advantage of the invention that even in a multi-bit tool the single bits can be conrolled individually , their overload detected and, accordingly, the feed motion st pe or feeding f rce restricted in order to prevent the bits from getting amaged. Wi h such a tool it is possible to drill in soft soil very fast and on facing rock, no matter at which angle, even at the reach of one bit only, the bit is not damaged by its backing capacity. A single bit in a conventional multi-bit tool would not remain undefected in such a situation since it would then have to take the whole feeding force alone.
In the following the invention is described in detail with reference to the enclosed drawings where Fig. 1 is a multi-bit drilling tool Fig. 2 is a cross—section of a shock—absorbing cylinder of a bit Fig. 3 is a diagram of a hydraulic system Fig. 4 is a diagram of an alternative hydraulic system
Figure one shows a rotatable tool 1 at the head of which there are several drill bits of different types. As a matter of principle, all the bits are cutting discs 4 which, on cutting soil or rock, get into slow rotation around their shaft while tool 1 is rotated and fed forward. The drill bit rods 5 are at the same time rods of pistons 6 of hydraulic cylinders 7, at the heads of which supporting parts 2,3 for the cutting discs 4 are fixed.
Figure 2 shows a hydraulic system by means of which the backing of a bit is functioning. From the former cylinder hydraulic pressure enters into cylinder 7 through back-valve 18. The drill bit and the piston are then in a slightly backed position.
1. If feeding is stopped because of overload in this drill bit, the piston is affected by pressure, e.g. adjusted to 100 bar, over valve 18, pushing the piston to its extreme position. From the other side of piston oil escapes through valve 15, the opening pressure of which is for istance 120 bar. Due to the considerably smaller cross-section area of the piston, pressure can rise even more thus capable of opening valve 15 and oil can flow to lower pressure. Through the oil outlet pipe 12 no oil leaks out, wich is a sign that the piston is in backed position at least in one of the cylinders.
When the piston reaches its extreme position the spindles 13 and 14 open respective valves, whereat oil starts to flow trough the
piston along channel 17 and further along channel 12 to the next cylinder. The piston remains in its extreme position if there is no overload though same pressure of ab . 100 bar prevails on both sides of the piston. In the piston a force, remains active which is caused by the cross-section ratio and considered proper load for the drill bit. If there would be a similar backed situation in other series-connected cylinders, the pressure of ab . 100 bar along channel 12 to the next cylinder would cause travel of the corresponding piston to its extreme position and only then a forward flow of oil along channel 12 again.
2. If there is an overload situation in figure 12, where piston 6 is still backing, valve 19 is open letting oil through the piston. Proper opening pressure would be 180 bar for instance. Then also valve 11 must let some oil forward and its opening pressure could be 140 bar. Backing stops as soon as the forward feeding of tool is switched off.
A situation where a cylinder has got into baking position can be detected from the total or almost total interruption of oil flow from channel 12 if the last cylinder is backing.
Figure 3 shows a hydraulic diagram of a series connection of cylinders 24. The feeding pressure upper limit is kept at least in 100 bar with regulation valve 22. The valve lets oil into tank 21 when the pressure limit is clearly exceeded. Valve 23 regulates and sustains pressure in cylinders. The valve opening pressure can be 100 bar. If valve 23 allows more oil through than the pump deplacement, all drill bits are then in their extreme position. A smaller flow of oil indicates that one or more drill bits are backed .
Figure 5 shows cylinders 25 connected in parallel. A pressure of ab . 100 bar is conducted along line 29 to the rear of each
cylinder. Through sensor valves 28 connected to each cylinder, the same oil is circulated back to the pump. With the pistons in their extreme position, said valves 28 are opened by levers 27, and the oil circulates. Stopping of oil circulation indicates that a bit or the bits are backed. Oil returns over the back valve 33 to the regulation valve 34, which sustains a pressure of ab. 100 bar. Regulation valve 31 lets oil direct to the return line if a cylinder is backed and has closed respective valve 28. The opening pressure of valve 31 can be for instance 140 bar. Valve 32 is adjustable, and with this valve it is possible to regulate certain counter pressure on the other side of the pistons in situations where pistons are driven outward by pressure.
By means of the systems overload of even one single bit can be detected as interruption of back-flow oil. Then the feeding of tool may be switched-off or the feeding force reduced so much that even a single bit can take it without damage if only one of the bits hits on hard surface such as rock. After this driving is continued with a small pushing force till the bit has managed the rock and got off the backed position or till the oncoming rock has broaden out in front of several bits. Then the backed single bit is not anymore loaded by a very great pushing force and has the possibility to reach its extreme position. Hereafter it can be tested whether a greater pushing force could be used. The invention is not limited only to the described embodiments but it can be modified within the limits of the inventional idea introduced in the patent claims. The flexibility of drill bits can be provided even mechanically in using for instance springs or combinations of mechanical and medium operated devices.