JPH07301078A - Connection unit structure of rod and bit of rock drill - Google Patents

Abstract

PURPOSE:To enhance the durability by preventing a loosening of threaded part of a connection part between a rod and a bit and the penetration of fine power of a rock or water into the threaded part of the connection part. CONSTITUTION:Parallel portions 1P and 2P, which are opposed each other, are formed on a rod 1 of a rock drilling machine, which is connected to each other by means of screws 1S and 2S and partially on a connected area of a bit 2. An elastic body having an interference in the radial direction are mounted between the parallel portions 1P and 2P. Even when a rotary reaction which the bit 2 undergoes drops to a specified value and below during rock drilling work, the elastic body produces a friction reaction between the rod 1 and the bit 2, which hinders the rotary motion, thereby preventing the screws 1S and 2S of the connected area between the rod 1 and the bit 2 from being loosened by an impact force. Even when a clearance is produced between the end faces of the rod, and the bit if interruption between fluid supply holes 4 and 5 and the screws 1S and 2S is effected, thereby preventing the penetration of fine particles of rocks or water into the screws.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure for fastening a rod and a bit of a rock drill for preventing loosening of screws.

[0002]

2. Description of the Related Art A bit is attached to the tip of a rod of a rock drill, and the rotational force and the impact force given to the rod by the rock drill are transmitted to the bit to drill a rock.
As shown in FIG. 5, generally, a rod 1 and a bit 2 of a rock drill are fastened to each other by screws 1S and 2S, and the rotational force is transmitted from the rod 1 to the bit 2 through the screws 1S and 2S, and the impact is given. The force is transmitted from the rod 1 to the bit 2 via the abutting end faces 1E, 2E.

Normally, the bit 2 receives a rotational reaction force from the rock to be drilled, so that the screws 1S and 2S at the fastening portion between the rod 1 and the bit 2 are tightened firmly.

[0004]

However, the physical properties of the rock to be drilled are not uniform, and the rotational reaction force received by the bit 2 often changes during the drilling operation. Bit 2
When the rotational reaction force received by is reduced to a predetermined value or less, the striking force loosens the screws 1S and 2S at the fastening portion between the rod 1 and the bit 2. When the loosened state of the screws 1S, 2S is continuously generated, as shown in FIG. 6, an axial gap C is generated between the rod 1 and the bit 2, so that the screw 1S of the rod 1 and the bit 2 of the fastening portion, 2S repeatedly collide with each other, and wear of the screws 1S and 2S, which are collision surfaces, progresses at an early stage.

When an axial gap C is formed between the rod 1 and the bit 2, the end faces of the rod 1 and the bit 2 which should originally be in contact with each other from the fluid supply holes 4 and 5 for supplying the flushing fluid. There is a problem that fine rock powder and water enter between the screws 1S and 2S of the fastening portion through the gap C generated between 1E and 2E, further promoting wear of the screws 1S and 2S.

The present invention is intended to solve such a problem in the fastening portion between the rod and the bit of the rock drilling machine, and to loosen the screw in the fastening portion between the rod and the bit, and the fastening portion for fine rock powder or water. It is an object of the present invention to provide a structure for fastening a rod and a bit of a rock drill that prevents penetration between the screws and improves durability.

[0007]

According to the present invention, parallel portions facing each other are formed in a part of a fastening portion of a rod and a bit of a rock drill that are fastened to each other by a screw, and the fastening portions are radially tightened between the parallel portions. The above problem is solved by mounting an elastic body having a margin.

[0008]

Since an elastic body is attached to a part of the fastening portion between the rod and the bit of the rock drill, even if the rotational reaction force received by the bit drops below a predetermined value during drilling work, A frictional resistance that prevents rotation acts between them, and loosening of the screw at the fastening portion between the rod and the bit due to the striking force is prevented.

Further, since the mounted elastic body has a tightening margin, even if a gap is created between the end surface of the rod and the bit, the fluid supply hole is disconnected from the screw, and fine rock powder or Water is prevented from entering between the screws.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory view of a connecting structure of a rod and a bit of a rock drill, which is an embodiment of the present invention, FIG. 2 is an explanatory view showing a state before the connecting of the rod and the bit, and FIG. 3 is a rod. It is explanatory drawing which shows the state which produced the clearance gap between a bit. The drill 1's rod 1 and bit 2 are equipped with screws 1S, 2S which are fastened together. Fluid supply holes 4 and 5 are formed in the centers of the rod 1 and the bit 2. Parallel portions 1P and 2P facing each other are formed at the front end portions of the fastening portions of the rod 1 and the bit 2, and the elastic body 3 is mounted between the parallel portions 1P and 2P. As an assembling procedure, first, the elastic body 3 is attached to the parallel portion 2P of the bit 2, and then the rod 1 and the bit 2 are screwed.

Here, the inner diameter D ₁ of the parallel portion 2P of the bit 2
Is slightly larger than the root diameter of the screw 2S of the bit 2, and the outer diameter D ₄ of the parallel portion 1P of the rod 1 is slightly smaller than the root diameter of the screw 1S of the rod 1. The outer diameter D ₂ of the elastic body 3 is larger than the inner diameter D ₁ of the parallel portion 2P of the bit 2, and the inner diameter D ₃ of the elastic body 3 is smaller than the outer diameter D ₄ of the rod 1. Therefore, the thickness t of the elastic body 3 is determined by the distance (D ₁ −
Since it is larger than D ₄ ) / 2, it has a tightening margin in the radial direction and an appropriate rotation resistance can be obtained at the time of tightening.

At the time of drilling work, the rotational force is applied to the screws 1S, 2
The striking force is transmitted from the rod 1 to the bit 2 via S, and the striking force is transmitted from the rod 1 to the bit 2 via the abutting end faces 1E, 2E.
Be transmitted to. Normally, the bit 2 receives a rotational reaction force from the rock to be drilled, so that the screws 1S and 2S at the fastening portion of the rod 1 and the bit 2 are tightened tightly. When the force falls below a predetermined value, the striking force is applied to the screw 1 at the joint between the rod 1 and the bit 2.
It acts to cause looseness in S and 2S. At this time,
The rotation resistance of the elastic body 3 acts to prevent loosening.

This rotation resistance is explained as follows from the relational expression between torque and tightening force. The relationship between the torque and the tightening force of a general screw fastening portion according to JISB1083 is expressed by the equation (1). T _f = T _S + T _w = KF _f d (1) Here, K = (P / π + μ _S d ₂ secα ′ + μ _w D _w ) / 2d ... (2) T _S = F _f (P / π + μ _S d ₂ secα ') / 2 ... (3) T _w = F _f μ _w D _w / 2 ... (4) When the contacting seat is annular, _Dw = 2 (D _O ³ −D _i ³ ) / 3 (D _O ² −D _i ² ) ... (5) D _w : Equivalent diameter of friction torque on seat surface D _i : Inner diameter of seat surface in contact D _O : Outside of seat surface in contact Diameter F _f : Initial tightening force or tightening force K: Torque coefficient P: Thread pitch T _f : Tightening torque T _S : Thread torque T _w : Seat surface torque d: Nominal thread diameter d ₂ : Effective thread diameter α : Thread flank angle α ': In the cross section perpendicular to the thread peak Flank angle (tanα '= tanαcosβ) β: lead angle of the screw mu _S: threaded surface friction coefficient mu _w: seating surface friction coefficient equation (1), equation (3), the following equation from equation (4) is derived. T _f = F _f (P / π + μ _S d ₂ secα ′ + μ _w D _w ) / 2 (6) On the other hand, in the present invention, the relationship between the torque and the tightening force is expressed by the following equation. T = F (P / π + μ _S d ₂ secα '+ μ _w D _w ) / 2 + D ₄ μ _p F _p / 2 ... (7) where: T: tightening torque F: tightening force D ₄ : outer diameter of parallel part of rod μ _p : friction coefficient of parallel part of rod F _p : tightening of parallel part of rod In Equations (6) and (7), P / π is + when tightened and − when loosened.

As is clear from the above equations (6) and (7), in the conventional fastening portion structure using only screws, if the fastening force F _f (rotational reaction force received by the bit 2) is lost, it is easy to cause mutual interference. While rotation occurs, the fastening structure of the present invention,
Even if the tightening force F is lost, the tightening torque T is always D ₄ μ
It is never smaller than _p F _p / 2. Therefore, since a torque resisting mutual rotation of D ₄ μ _p F _p / 2 or more exists between the rod 1 and the bit 2, the rotational reaction force received by the bit 2 becomes less than a predetermined value during drilling work. Even if lowered, the screws 1S, 2 of the fastening portion between the rod 1 and the bit 2 due to the striking force
The loosening of S is prevented.

Further, since the mounted elastic body 3 has a tight margin, even if a gap C is created between the rod 1 and the end faces 1E, 2E of the bit 2, the fluid supply holes 4, 5 and the screws 1S, 2S.
Since it is cut off from between, the intrusion of fine rock powder or water between screws is prevented, so there is no risk of early wear, and the durability of the joint between rod 1 and bit 2 The property is improved.

FIG. 4 shows the configuration of another embodiment of the present invention. In this embodiment, parallel portions 1P and 2P facing each other are formed at the rear ends of the fastening portions of the rod 1 and the bit 2, and the elastic body 3 is mounted between the parallel portions 1P and 2P. As an assembling procedure, first, the elastic body 3 is attached to the parallel portion 1P of the rod 1, and then the rod 1 and the bit 2 are screwed. The other structure is similar to that of the embodiment shown in FIG.

In this embodiment, it is possible to effectively prevent fine rock powder or water from entering between the screws 1S and 2S from the rear end side of the bit 2. If the embodiment of FIG. 1 and the embodiment of FIG. 4 are combined and the elastic body 3 is mounted before and after the screws 1S, 2S, the dustproof and waterproof effect can be further enhanced.

[0018]

As described above, according to the structure of the connecting portion between the rod and the bit of the rock drilling machine of the present invention, the screw at the connecting portion between the rod and the bit is loosened, and the fine rock powder or water is fastened. Durability can be improved by preventing penetration between the threads of the part.

[Brief description of drawings]

FIG. 1 is an explanatory view of a structure for fastening a rod and a bit of a rock drilling machine according to an embodiment of the present invention.

FIG. 2 is an explanatory view showing a state before fastening of the rod and the bit in the embodiment of FIG.

FIG. 3 is an explanatory diagram showing a state in which a gap is created between a rod and a bit.

FIG. 4 is an explanatory view of a structure for fastening a rod and a bit of a rock drilling machine which is another embodiment.

FIG. 5 is an explanatory view of a structure of a fastening portion between a rod and a bit of a conventional rock drill.

FIG. 6 is an explanatory diagram showing a state in which a gap is created between the rod and the bit in FIG.

[Explanation of Codes] 1 rod 1E end face 1P parallel part 1S screw 2 bit 2E end face 2P parallel part 2S screw 3 elastic body 4 fluid supply hole 5 fluid supply hole

Claims (1)

[Claims] 1. A parallel portion facing each other is formed in a part of a fastening portion of a rod and a bit of a rock drill that are fastened to each other by a screw, and an elastic body having a tightening margin in a radial direction is mounted between the parallel portions. The structure of the joint between the rod and bit of the rock drill.