and drilling chip removal, the non-hole gasket can also be placed, that is, the strong
jet air can be canceled, so that the compressed air can be used to drive the DTH
hammer to work, and the consumption of compressed air can be saved.
When another compressed air enters the ring groove of the inner and outer
cylinders, it enters the front chamber (the space surrounded by the piston 5, bushing
7 and inner cylinder 4) of the DTH hammer through the radial hole of the inner
cylinder and acts on the piston. Because the piston has an annular area difference,
the piston goes up and starts to return. When the middle ring of the piston runs to
the lower end of the inner cylinder, the intake passage of the front chamber is
closed, and the front chamber is in a closed state. The piston stroke in this section is
the intake stroke of the front chamber (Lfi). Thereafter, the compressed air in the
front chamber works by expanding itself, pushing the piston upward until the lower
end of the piston moves to the radial hole in the middle of the bushing, and the
expanding work stroke ends, which is the working stroke of the front chamber
expansion (Lfe). Since then, the piston continues to move upward due to inertia,
and its lower end surface passes through the radial hole in the middle of the
bushing. The gas in the front chamber is discharged through the axial hole in the
upper end surface of the bushing, the radial hole in the middle, the central hole in
the drill bit, and the exhaust hole. The piston runs upward until the upper dead
point, which is the exhaust stroke of the front chamber (Lfo).
Corresponding to the intake, expansion, and exhaust of the front chamber, the
rear chamber (the space enclosed by valve seat, inner cylinder and piston) undergoes
three-valve distribution processes. The piston moves upward from the lower dead
point until the upper end of the piston contacts the lower end of the valve seat. In this
process, the gas in the rear chamber is discharged through the piston center hole, the
drill center hole and the exhaust hole, which is the exhaust stroke of the rear chamber
(Lbo). After the exhaust stroke is terminated, the piston continues to move upward
until the lower end of the piston’s upper ring contacts the lower edge of the inner
cylinder ring groove. This stroke is the compression stroke of the rear chamber
(Lbc). The piston continues to ascend, the lower ring surface of the upper end surface
exceeds the lower edge of the inner cylinder ring groove, and compressed air enters
the rear chamber through the annular clearance of the inner cylinder ring groove,
which gradually increases the gas pressure in the rear chamber and decelerates the
piston until it finally forces the piston to stop moving, i.e., the piston moves to the
upper dead point. This stage is the rear chamber intake stroke (Lbi).
After the piston returns to the upper dead point, the piston reverses into the
stroke stage because the high-pressure air continuously enters the rear chamber and
acts on the upper end face of the piston to push the piston downward. The same
motion as the piston return stroke, in the stroke motion the front chamber undergoes
exhaust stroke (Lfo), compression stroke (Lfc) and intake stroke (Lfi) in turn, while
the rear chamber experiences intake stroke (Lbi), expansion stroke (Lbe) and
exhaust stroke (Lbo).
The piston return stroke completes one cycle at a time, realizing one impact.
According to the working principle, when DTH hammer works, the valve distribution process is completed by the reciprocating motion of the piston itself.
11.2 Principle and Classification of Pneumatic DTH Hammer
201
jet air can be canceled, so that the compressed air can be used to drive the DTH
hammer to work, and the consumption of compressed air can be saved.
When another compressed air enters the ring groove of the inner and outer
cylinders, it enters the front chamber (the space surrounded by the piston 5, bushing
7 and inner cylinder 4) of the DTH hammer through the radial hole of the inner
cylinder and acts on the piston. Because the piston has an annular area difference,
the piston goes up and starts to return. When the middle ring of the piston runs to
the lower end of the inner cylinder, the intake passage of the front chamber is
closed, and the front chamber is in a closed state. The piston stroke in this section is
the intake stroke of the front chamber (Lfi). Thereafter, the compressed air in the
front chamber works by expanding itself, pushing the piston upward until the lower
end of the piston moves to the radial hole in the middle of the bushing, and the
expanding work stroke ends, which is the working stroke of the front chamber
expansion (Lfe). Since then, the piston continues to move upward due to inertia,
and its lower end surface passes through the radial hole in the middle of the
bushing. The gas in the front chamber is discharged through the axial hole in the
upper end surface of the bushing, the radial hole in the middle, the central hole in
the drill bit, and the exhaust hole. The piston runs upward until the upper dead
point, which is the exhaust stroke of the front chamber (Lfo).
Corresponding to the intake, expansion, and exhaust of the front chamber, the
rear chamber (the space enclosed by valve seat, inner cylinder and piston) undergoes
three-valve distribution processes. The piston moves upward from the lower dead
point until the upper end of the piston contacts the lower end of the valve seat. In this
process, the gas in the rear chamber is discharged through the piston center hole, the
drill center hole and the exhaust hole, which is the exhaust stroke of the rear chamber
(Lbo). After the exhaust stroke is terminated, the piston continues to move upward
until the lower end of the piston’s upper ring contacts the lower edge of the inner
cylinder ring groove. This stroke is the compression stroke of the rear chamber
(Lbc). The piston continues to ascend, the lower ring surface of the upper end surface
exceeds the lower edge of the inner cylinder ring groove, and compressed air enters
the rear chamber through the annular clearance of the inner cylinder ring groove,
which gradually increases the gas pressure in the rear chamber and decelerates the
piston until it finally forces the piston to stop moving, i.e., the piston moves to the
upper dead point. This stage is the rear chamber intake stroke (Lbi).
After the piston returns to the upper dead point, the piston reverses into the
stroke stage because the high-pressure air continuously enters the rear chamber and
acts on the upper end face of the piston to push the piston downward. The same
motion as the piston return stroke, in the stroke motion the front chamber undergoes
exhaust stroke (Lfo), compression stroke (Lfc) and intake stroke (Lfi) in turn, while
the rear chamber experiences intake stroke (Lbi), expansion stroke (Lbe) and
exhaust stroke (Lbo).
The piston return stroke completes one cycle at a time, realizing one impact.
According to the working principle, when DTH hammer works, the valve distribution process is completed by the reciprocating motion of the piston itself.
11.2 Principle and Classification of Pneumatic DTH Hammer
201