Abrasion-resistant hydraulic hammer with low noise level

There is provided an improved abrasion-resistant hydraulic hammer with a low noise level for preventing the leak-out of the noise made inside. The object is to provide an abrasion-resistant hydraulic hammer with a low noise level which can contribute to the establishment of a comfortable working environment and meet environmental standards against noise pollution by reducing leaked-out crashing sound. To achieve the object, a cylindrical plastic member containing oil is installed to a hole formed outward under a piston installed inside the hydraulic hammer, for guiding a tool in contact with the circumferential surface thereof.

BACKGROUND OF THE INVENTION 
The present invention relates to a hydraulic hammer for breaking a solid 
rock or concrete by operation using oil pressure, and more particularly, 
to an improved abrasion-resistant hydraulic hammer with a low noise level 
for preventing the noise made inside the hammer from being heard outside. 
The hydraulic hammer is a device in which the oil pressure generated by a 
hydraulic pump is transferred to an oil passage, a piston installed inside 
the hammer moves up and down according to control of the oil passage and 
the oil pressure, to hit a tool, and the tool cracks a solid rock or 
concrete with the reaction force from the hitting. In the hydraulic 
hammer, therefore, the loudest noise and biggest vibration are made 
between the piston and the tool. Along with the recent reinforcement of 
environmental standards, however, restraint of noise pollution has been 
tightened. Therefore, the need for a low noise level hydraulic hammer is 
increased. 
SUMMARY OF THE INVENTION 
The object of the present invention is to provide a solid 
abrasion-resistant hydraulic hammer with a low noise level which can 
contribute to the establishment of a comfortable work environment and meet 
environmental standards against noise pollution by decreasing the level of 
leak-out crashing sound. 
To achieve the above object, there is provided a hydraulic hammer with a 
low noise level, according to the present invention, comprising: 
a body; 
a piston installed inside the body for moving up and down; 
a hole formed outward under the piston in the body; 
a tool inserted into the hole for crashing into the piston when the piston 
descends; and 
a cylindrical plastic member containing oil provided to the hole for 
guiding the tool, in contact with the circumferential surface of the tool. 
According to the present invention, another cylindrical metal bush is 
further provided to the entrance of the hole and the cylindrical plastic 
member containing oil is installed between the contact surfaces of the 
bush and the tool. 
The abrasion-resistant hydraulic hammer with a low noise level as 
constituted above, according to the present invention, can contribute to 
the establishment of a comfortable working environment and can be used 
longer time by reducing crashing sound leaked out of the hammer.

DETAILED DESCRIPTION OF THE INVENTION 
FIG. 1 is a cross-sectional view of a main portion of a conventional 
hydraulic hammer. As shown, a piston 1 is installed inside a hydraulic 
hammer 10, and an oil passage 2 and various valves 9 are provided so that 
piston 1 may move up and down. 
A tool 3 is installed under piston 1 and moves up and down by the guidance 
of an upper bush 5 and a lower bush 6 provided to the body 4 of the 
hydraulic hammer. A groove 11 is formed into the circumferential surface 
of tool 3 to a predetermined length. Since a tool pin 12 penetrates body 4 
of the hydraulic hammer through groove 11, the up-and-down stroke of tool 
3 depends on the length of groove 11. Tool 3 and lower bush 6 are made of 
metals and an annular rubber seal 7 is attached to lower bush 6. 
In the hitting stroke of the hydraulic hammer as constituted above, the oil 
filling an accumulator 8 and the high-pressure oil from a pump 20 are 
provided to the upper and lower parts of piston 1, and thus piston 1 
descends rapidly and hit tool 3. In this course, very big crashing sound 
and strong vibration are generated between tool 3 and piston 1 and with 
the reaction force from the crash, tool 3 crushes a rock. 
Since tool 3 and lower bush 6 are made of metals, the contact surfaces of 
tool 3 and lower bush 6 are abraded due to the frictional force 
therebetween in the course of crushing a rock 31 by tool 3. In addition, 
the heat generated on the contact surfaces degrades rubber seal 7, to 
lower the sealing effects. Further, when dust and/or grains of sand 
blow(s) in between tool 3 and lower bush 6 in crushing rock 31 by tool 3, 
the abrasion of the contact surfaces is accelerated, thereby leaking out 
the inside crashing sound. 
The leaked-out crashing sound deteriorates working environments and gives 
rise to restraint of operations according to noise pollution regulation 
which has been tightened along with the reinforcement of environmental 
standards. Therefore, the leak-out of noise remains a critical concern to 
be solved. 
FIG. 2 is a cross-sectional view of a main portion of an abrasion-resistant 
hydraulic hammer with a low noise level according to the present 
invention. As shown, a piston 1 is installed inside a hydraulic hammer 10, 
and a passage 2 and various valves 9 are provided for moving piston 1 up 
and down. 
A tool 3 is inserted into a hole formed in a body 4 under piston 1, is 
brought into contact with an upper bush 5 and a lower bush 6 which are 
attached to the upper and lower parts of the hole, respectively, and moves 
up and down by the guidance thereof. A groove 11 is formed into the 
circumferential surface of tool 3 to a predetermined length. Since a tool 
pin penetrates body 4 through groove 11, the up-and-down stroke of tool 3 
depends on the length of groove 11. 
Upper bush 5 is made of a polyamide-series plastic containing oil with high 
abrasion resistance and a good sealing property. Therefore, the noise made 
when piston 1 hits tool 3 is firstly prevented by upper bush 5, thereby 
enabling the safe up-and-down motions of tool 3. 
Tool 3 and lower bush 6 are made of metals. A cylindrical rubber seal 7 and 
a cylindrical soundproofing member 30 fabricated of a polyamide-series 
plastic containing oil are attached to lower bush 6. Tool 3 moves up and 
down in contact with soundproofing member 30 and seal 7, thereby secondly 
preventing the noise made in the course of hitting tool 3 by piston 1. 
In the hitting stroke of hydraulic hammer 10, the oil filling an 
accumulator 8 and the high-pressure oil from a pump 20 are provided to the 
upper and lower parts of piston 1, and thus piston 1 descends rapidly and 
hit tool 3. In this course, very big crashing sound and strong vibration 
are generated between tool 3 and piston 1 and with the reaction force from 
the crash, tool 3 crushes a rock 31. Unless the airtight state between 
tool 3 and upper bush 5 and/or soundproofing member 30 is maintained, the 
noise will leak out. 
Even though tool 3 and lower bush 6 are made of metals, tool 3 makes 
up-and-down motions in contact with plastic soundproofing member 30 
containing oil, not in a direct contact with lower bush 6. 
Due to a small frictional coefficient of the plastic used for soundproofing 
member 30, the frictional heat and the abrasion between the contact 
surfaces can be prevented, and the plastic containing oil obviates the 
necessity for periodically providing oil. 
Further, despite the possible blow-in of dust and/or grains of sand between 
tool 3 and lower bush 6 in the course of crushing a rock, they stick into 
plastic soundproofing member 30. Thus, a severe abrasion of the contact 
surface of tool 3 can be prevented. That is, the noise from the crash of 
piston 1 and tool 3 in hydraulic hammer 10 can be sealed not to be heard 
outside. 
Further again, unlike a conventional hydraulic hammer where the piston is 
damaged along with the damage to the tool, piston 1, according to the 
present invention, remains intact in spite of the damage of tool 3 since 
polyamide plastic upper bush 5 serves as a buffer against impact 
transferred from tool 3. 
As described above, since the abrasion-resistant hydraulic hammer with a 
low noise level according to the present invention makes possible a long 
sealing of noise, the deterioration of working environments can be 
prevented and the life of the hammer can be extended.