The structure of down-the-hole hammer

The down-the-hole hammer is an important component of a pneumatic water well drilling rig. It is mainly used to provide axial reciprocating rock-breaking impact force to the drill bit in order to cool the drill bit and entrain cuttings. The structure of the down-the-hole hammer is shown in the figure below. It is mainly composed of a piston. , rear joint, outer sleeve, check valve, air regulating plug, cylinder, valve seat, guide sleeve, butterfly spring, snap ring, spring, retaining ring, rubber ring, front joint, etc.

piston

The piston of the down-the-hole hammer is the main moving part of the hammer, even a quasi-uniform moving part. The piston of the down-the-hole hammer can be divided into three types according to the structure: same-diameter piston, different-diameter piston, and series piston. From the perspective of the role of the piston in the gas distribution device and the load it bears during work, the piston should have high dimensional accuracy and surface smoothness, so that it has a good gas-tight effect and is suitable for reciprocating motion at high speeds (its speed Up to 10m/s); it has a reasonable geometric shape, which not only ensures sufficient strength, but also efficiently transmits impact energy.

Valve

There are various types of valves available for valve-type hammers. From the perspective of the coupling between the gas distribution valve and the piston movement, the valve should be light and sensitive in action; from the perspective of gas distribution diversion, the valve should have good air tightness and small local resistance loss; from the perspective of use and maintenance, The valve should have a high lifespan.

Valve discs are generally made of low alloy steel. In recent years, products made of nylon and aluminum alloys at home and abroad have shown the advantages of light weight, impact resistance and long service life.

Cylinder

The cylinder is not only the guide device for the piston movement, but also the frame of the entire hammer. From the perspective of gas distribution, the cylinder is also used to transport the working medium. For this reason, the actual structure can be divided into single-cylinder structure and double-cylinder structure. ‘

The so-called single-cylinder structure means that there are only cylinder parts, and its outer diameter is the outline size and inner diameter of the hammer (that is, the diameter of the hammer piston); the double-cylinder structure is also called the inner and outer two-cylinder structure. The comparison of these two structures is as follows:

(1) The single-cylinder station structure is simple, while the double-cylinder structure is complex.

(2) The piston contained in the single-cylinder structure has a large radial size, so the effective power is relatively large.

(3) A single cylinder will be scrapped as long as one side of its inner diameter and outer diameter is worn beyond the limit, while a double cylinder will need to replace the damaged parts; the connection methods between the double cylinders include welding connection and threaded connection, and the latter is suitable for replacement. .

As far as the cylinder structure is concerned, the upper and lower joints of a single cylinder structure are used. It is also the development trend of modern down-the-hole hammers to use threads to connect with the cylinder body.

Drill bit connection and hanging device

The main functions of the connection and hanging device of the drill bit: accommodate the tail of the drill bit, control the telescopic position of the drill bit, transfer torque when the drilling machine rotates and impact drilling, and drive the drill bit to rotate; when the tail of the drill bit is impacted by the piston, it can move axially within a certain range Move; when the down-the-hole hammer is lifted away from the bottom of the hole and suspended, hang the tail of the drill bit to prevent the drill bit from slipping out of the hammer.

There are many forms of connection between the down-the-hole hammer and the drill bit. According to the way of transmitting rotational torque, the tail of the drill bit has splines, circles, triangles, hexagons, etc.; according to the form of the tail of the hanging drill bit, there are snap rings, round pins, flat pins, etc. Pins, balls, self-locking splines, etc.

Other parts

Most hammers are equipped with a waterproof check valve. Its function is to isolate the hammer from the drilling tool airway when the air supply is stopped, so that part of the gas remains inside the hammer to prevent rock powder and water from influxing into the impact. device.

When the hammer works, it is generally accompanied by vibration, which will reduce the efficiency of the drilling tool and cause early damage and scrapping of parts. Some hammers are equipped with shock absorbers. Commonly used vibration reduction devices include vibration reduction rubber rings, etc., which have good vibration reduction effects.