Tool driving or impacting – Automatic control of power operated means – Tool advance causing or controlling means
Reexamination Certificate
2001-02-09
2001-11-20
Smith, Scott A. (Department: 3721)
Tool driving or impacting
Automatic control of power operated means
Tool advance causing or controlling means
C173S009000, C173S135000, C173S210000, C173S212000
Reexamination Certificate
active
06318478
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a damper pressure control apparatus for a hydraulic rock drill for crushing a rock or the like by striking a tool, such as a rod, chisel or the like.
2. Description of the Related Art
As shown in
FIG. 8
, in which is illustrated one of typical conventional hydraulic rock drills, a shank rod
102
is mounted at the front end of a hydraulic rock drill body
101
. A hole boring bit
106
is mounted on the front end of a rod
104
via a sleeve
105
. When a striking piston
107
of a striking mechanism
103
of the hydraulic rock drill strikes the shank rod
102
, a striking energy is transmitted to the bit
106
from the shank rod
102
via the rod
104
. Then, the bit
106
strikes a rock R to crush.
At this time, a reaction energy Er from the rock R is transmitted to the hydraulic rock drill body
101
from the bit
106
via the rod
104
and the shank rod
102
. By the reaction energy Er, the hydraulic rock drill body
101
is driven backward once. Then, the hydraulic rock drill body
101
is propelled by a thrust of a feeding device (not shown) for a crushing length in one strike from a position before striking. Then, at the advanced position, next strike is performed by the striking mechanism
103
. By repeating these steps, hole boring operation is performed.
Then, as a damping mechanism of the rock drill, namely a mechanism for damping the reaction energy Er, there have been developed a mechanism employing a two stage damping piston having a function for hydraulically damping the reaction energy Er and a function for improving striking transmission efficiency (dual damper type), and a mechanism employing a single damping piston which is not mechanically fixed the position thereof (floating type).
In
FIG. 9
the hydraulic rock drill employing the two stage damping piston is provided with a chuck driver
109
applying rotation for the shank rod
102
via a chuck
108
. For the chuck driver
109
, a chuck driver bushing
110
is fitted as a transmission member contacting with a large diameter rear end
102
a
of the shank rod
102
. Then, on the backside of the chuck driver bushing
110
, a front damping piston
111
and a rear damping piston
112
are arranged as a damping mechanism.
The rear damping piston
112
is a cylindrical piston having a fluid passage
113
communicating outside and inside thereof. The rear damping piston
112
is slidably mounted between a central step portion
101
c
and a rear step portion
101
b
provided in the hydraulic rock drill body
101
. The rear damping piston
112
is applied a frontward thrust by a hydraulic pressure in a fluid chamber
114
for the rear damping piston. On the other hand, the front damping piston
111
is a cylindrical piston having a small external diameter at the rear portion. The small diameter portion of the front damping piston
111
is inserted within the rear damping piston
112
in longitudinally slidable fashion. By a large diameter portion, the front damping piston
111
is restricted a longitudinal motion range between a front side step portion
101
a
of the hydraulic rock drill body
101
and a front end face
112
a
of the rear damping piston
112
. Between an outer periphery of the small diameter portion of the front damping piston
111
and an inner periphery of the rear damping piston
112
, a fluid chamber
115
for the front damping piston is defined for applying a frontward thrust to the front damping piston
111
.
The fluid chamber
115
for the front damping piston and the fluid chamber
114
for the rear damping piston are communicated through a fluid passage
113
. The fluid chamber
114
of the rear damping piston is communicated with a hydraulic pressure source
116
. A hydraulic pressure from the hydraulic pressure source
116
is fixed at a given pressure by a relief valve or pressure reduction valve (not shown). To the front damping piston
111
, a given thrust F
111
derived as a product of a pressure receiving area and a hydraulic pressure in the fluid chamber
115
of the front damping piston, acts. Similarly, to the rear damping piston
112
, a given thrust F
112
derived as a product of a pressure receiving area and a hydraulic pressure in the fluid chamber
114
for the rear damping piston, acts.
On the other hand, to the hydraulic rock drill body
101
, a frontward thrust F
101
is constantly applied. This thrust is transmitted to the front damping piston
111
and the rear damping piston
112
as reaction force from the rock R via the bit
106
, the rod
104
, the shank rod
102
and the chuck driver bushing
110
.
Here, the thrust F
111
acting on the front damping piston
111
and the thrust F
112
acting on the rear damping piston
112
are set relative to the thrust F
101
acting on the hydraulic rock drill body
101
to establish a relationship F
111
<F
101
<F
112
. Therefore, before striking, the front damping piston
111
and the rear damping piston
112
contact with each other to stop at striking reference position (position shown in
FIG. 9
) where the front end face
112
a
of the rear damping piston
112
contacts with the central step portion
101
c
of the hydraulic rock drill body
101
.
At the striking reference position, when the striking piston
107
of the striking mechanism
103
strikes the shank rod
102
, the striking energy is transmitted from the shank rod
102
to the bit
106
via the rod
104
. Then, the bit
106
strikes the rock R as crushing object. At this time, the reaction energy Er from the rock R is transmitted to the front damping piston
111
and the rear damping piston
112
from the bit
106
via the rod
104
, the shank rod
102
and the chuck driver bushing
110
. Then, the rear damping piston
112
is retracted until contacting the rear end face with a rear step portion
101
b
together with the front damping piston
111
with damping by the thrust F
112
. Thus, the reaction energy Er is transmitted to the hydraulic rock drill body
101
. Accordingly, the rear damping piston
112
performs damping function of the reaction energy Er, namely impact force absorbing function. Also, the thrust acting on the rear damping piston
112
serves as damping force.
By the reaction energy Er transmitted to the hydraulic rock drill body
101
, the main body
101
is driven backward once. Subsequently, the rear damping piston
112
is driven forward to stop at the striking reference position where the front end face
112
a
thereof abuts onto the central step portion
101
c
of the hydraulic rock drill body
101
by pushing back the front damping piston
111
, the chuck driver bushing
110
and the shank rod
102
since the thrust F
112
applied by the fluid pressure in the fluid chamber
114
for the rear damping piston is greater than the thrust F
101
applied to the hydraulic rock drill body
101
. At this condition, the next striking is awaited.
In the condition where contact between the bit
106
and the rock R is incomplete, the thrust F
101
of the hydraulic rock drill body
101
is not sufficiently transmitted to the rock R. Therefore, a reaction force much smaller than the thrust F
101
is transmitted to the rod
104
, the sleeve
105
, the shank rod
102
, the chuck driver bushing
110
and the front damping piston
111
from the bit
106
. Accordingly, the front damping piston
111
is moved away from the rear damping piston
112
by the thrust F
111
to urge the bit
106
toward the rock R via the chuck driver bushing
110
and the shank rod
102
to advance the bit
106
before advancement of the hydraulic rock drill body
101
to prevent blank striking. Accordingly, the front damping piston
111
performs action for tightly contacting the tool, such as bit
106
or the like onto the rock R, namely, floating action. Then, the thrust F
111
on the front damping piston
111
serves as floating force.
Subsequently, the hydraulic rock drill body
101
is advanced by the thrust F
101
. After contacting the bit
106
onto the rock R, since the thrust F
101
Furukawa Co., Ltd.
Smith Scott A.
Young & Basile P.C.
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