WO2006118390A1

WO2006118390A1 - Low noise hydraulic breaker

Info

Publication number: WO2006118390A1
Application number: PCT/KR2006/001563
Authority: WO
Inventors: Hyung-Goo Kim
Original assignee: Hyung-Goo Kim
Priority date: 2005-04-29
Filing date: 2006-04-25
Publication date: 2006-11-09
Also published as: KR100630438B1

Abstract

The present invention relates to a low noise hydraulic breaker including: a cylinder (110) having a piston (111) movable in upward and downward directions at the inside thereof if gas is supplied from a valve (113) to a gas chamber (112) located at the upper portion thereof, while pressure pulsation is being removed at an accumulator (114); a breaking part (120) having a chisel (121) located at the lower portion of the cylinder (110) for breaking a given broken-to-be object; a striking part (130) having a striking chamber in which the piston (111) of the cylinder (110) strikes the chisel (121) of the breaking part (120) and fixedly supported by means of upper and lower bushes (132) and (134) with respect to the chisel (121) and by means of a key (133) coupling the upper and lower bushes (132) and (134); a noise-absorbing part (140) for absorbing the striking noise generated at the inside of the striking chamber (131) of the striking part (130); and an exhausted air absorbing part (150) for secondarily absorbing the exhausted air at a state where the noise is primarily removed at the noise-absorbing part (140).

Description

LOW NOISE HYDRAULIC BREAKER

Technical Field

[1] The present invention relates to a low noise hydraulic breaker, and more particularly, to a low noise hydraulic breaker that is provided with a noise-absorbing plate disposed in a striking chamber in which a piston strikes a chisel, at the inner surface of the striking chamber, for absorbing striking noise generated upon striking, with an air- circulating chamber disposed at the rear side of the noise-absorbing plate for circulating the compressed air that is passed through the noise-absorbing plate therein to transmit the circulated air through an exhaust port, with an exhausted air absorbing part connected to the exhaust port for passing the exhausted air therethrough to secondarily remove the striking noise, and with a striking portion noise-absorbing plate and a support portion noise-absorbing plate mounted along the outer peripheries of striking and supporting portions formed on the upper portion of the chisel for absorbing the striking noise generated when the piston applies a striking force to the chisel. Background Art

[2] Generally, a hydraulic breaker is mounted at construction equipment like an excavator, a loader or the like, wherein a piston is dynamically moved in upward and downward directions by hydraulic pressure of a cylinder to apply a striking force to a chisel so as to break a broken-to-be object, e.g., a concrete block, a rock or the like.

[3] Recently, restriction rules for suppressing the generation of noise become stricter in construction sites, and indications of noise values for construction equipment are desirably recommended and obligatory in 2006. Such the construction equipment includes about 20 products inclusive of an excavator, a dozer, a loader, and a breaker.

[4] Further, the area that is within a distance of 50m from dwelling houses, apartments, schools, hospitals, public libraries and the like is defined as a noise calming area, and so as to start construction causing high noise generation in the noise calming area, a constructer should build soundproof facilities before construction and has the obligation to report the addition of high noise generating construction equipment in accordance with the laws of ministry of environment.

[5] So as to meet the regulations for suppressing the generation of noise, thus, there are provided various improvements of the hydraulic breaker wherein low noise is desirably generated, and as such the low noise hydraulic breakers that satisfy the regulations for noise values are authenticated by the organizations related thereto, the development for the low noise hydraulic breakers is positively encouraged. [6] The noise generated during the operation of the hydraulic breaker is primarily caused when the piston moving in upward and downward directions at the inside of the hydraulic breaker applies a striking force to a chisel used as a striking tool that comes in contact with a broken-to-be object, which is like the principle where a hammer strikes a nail so as to break the broken-to-be object. Generally, a noise value that is admitted in the construction sites is in a range of 9OdB to 11OdB at a distance of about 7.5m from a breaker body according to a breaker size in a case of a general hydraulic breaker and is in a range of 8OdB to 95dB in a case of a low noise hydraulic breaker.

[7] The general hydraulic breaker includes: a nitrogen gas chamber disposed at the top portion of the inner side of a cylinder to which hydraulic pressure is provided, the nitrogen gas chamber containing nitrogen gas supplied from a valve, while pressure pulsation is being prevented in an accumulator; the cylinder disposed below the nitrogen gas chamber wherein a piston is slidably received in upward and downward directions by the gas supply; a breaking part having a chisel disposed below the piston for breaking a broken-to-be object like a concrete block by the upward and downward movements of the piston; and a striking chamber at which the piston of the cylinder applies the striking force to the chisel of the breaking part.

[8] The general hydraulic breaker as constructed above conducts the upward and downward movements of the piston by the supply of nitrogen gas, while preventing the pressure pulsation at the accumulator, so as to apply a striking force of the piston to the chisel, such that the broken-to-be object like a concrete block, a rock or the like is broken. By high pressure nitrogen gas, however, noise is seriously generated during the striking operation, which becomes a big trouble in the construction sites.

[9] So as to greatly reduce the noise generated from the hydraulic breaker, thus, there is disclosed in Korean Utility Model Application No.20- 1998-0025964 wherein a low noise hydraulic breaker is introduced, which is shown in FlG.1.

[10] As shown, the conventional low noise hydraulic breaker having a bracket 2 having an opened bottom portion, a body disposed at the inside of the bracket 2, a piston disposed at the inside of the body in such a manner as to be slidable in upward and downward directions, a chisel adapted to be inserted into the opened bottom portion of the bracket and having the striking force applied by the downward movement of the piston, and a lower bush 7 adapted to be inserted between the lower portion of the body and the outer periphery of the chisel, the hydraulic breaker including: a round buffering member 20 fitting along the outer periphery of the chisel 4 in such a manner as to seal a space between the chisel 4 and the bracket 2, while being in close contact along the bottom surface of the lower bush 7; and a round wiper 22 disposed below the buffering member 20 in such a manner as to be fit along the outer periphery of the chisel 4, the round wiper 22 having a lip 22a adapted to be in close contact with the outer periphery of the chisel 4.

[11] According to the conventional low noise hydraulic breaker as constructed above, the buffering member and the wiper are located below the lower bush supporting the chisel, thereby reducing the noise generated by the application of a striking force of the piston to the chisel. However, this structure prevents the noise generated by the stroke of the piston from being diffused, but it does not reduce the noise basically.

[12] According to the conventional low noise hydraulic breaker, moreover, the buffering member that is disposed below the lower bush serves to absorb the noise generated in the striking chamber where the piston strikes the chisel as it conducts the reciprocal movements, and in this case, the buffering member suppresses the generation of noise, while having a given distance from the noise source generated, thereby providing a relatively low noise absorbing efficiency.

[13] According to the conventional low noise hydraulic breaker, further, the striking noise generated by the stroke of the piston against the chisel as the piston conducts the reciprocal movements is diffused through air to the outside, thereby failing to prevent the diffusion of noise through the air. Disclosure of Invention Technical Solution

[14] Accordingly, the present invention has been made to solve the above-mentioned problems occurring in the prior art, and it is an object of the present invention to provide a low noise hydraulic breaker that is provided with a noise-absorbing plate having given thickness and density that is located along the wall surface of a striking chamber of a striking part where a piston disposed at the upper portion of a cylinder in such a manner as to be reciprocated therein strikes a chisel of a breaking part, an air- circulating chamber that is located along the rear surface of the noise-absorbing plate for circulating the air passed through the noise-absorbing plate, and an exhaust port that is located at one side of the air-circulating chamber for exhausting the circulating air, whereby the noise generated from the striking operation is directly absorbed, thereby increasing a noise-removing efficiency.

[15] It is another object of the present invention to provide a low noise hydraulic breaker wherein the noise generated by striking a chisel of a breaking part by the upward and downward movements of a piston is primarily absorbed by means of a noise-absorbing part located along the wall surface of a striking chamber of a striking part, and if the primarily absorbed air is exhausted to an exhaust port through an air-circulating chamber, it is secondarily absorbed by means of an exhausted air absorbing part connected to the exhaust port, thereby making a noise-removing efficiency more optimized. [16] It is still another object of the present invention to provide a low noise hydraulic breaker wherein the compressed air containing the noise generated when a piston strikes a chisel is primarily absorbed by means of a noise-absorbing plate of a noise- absorbing part located at a striking chamber, and if the compressed air is transmitted to an air-circulating chamber located at the rear side of the noise-absorbing plate, it is absorbed by means of an absorbing blower connected to an exhaust port of the air- circulating chamber in such a manner as to be forcedly exhausted to an exhausted air absorbing part for rapidly removing the noise generated by the striking of the piston, thereby increasing a noise-removing efficiency.

[17] It is yet another object of the present invention to provide a low noise hydraulic breaker wherein the compressed air containing the noise generated when a piston strikes a chisel is primarily absorbed by means of a noise-absorbing plate of a noise- absorbing part located at a striking chamber, and if the compressed air is transmitted to an air-circulating chamber located at the rear side of the noise-absorbing plate, it is absorbed by means of a plurality of noise-absorbing partitions located at the inside of an exhausted air absorbing part connected to an exhaust port of the air-circulating chamber such that the noise is reduced through the plurality of noise-absorbing partitions, thereby improving a noise-removing performance.

[18] It is yet another object of the present invention to provide a low noise hydraulic breaker that is provided with a striking portion noise-absorbing plate located at an upper portion of a chisel where a piston reciprocating at the inside of a cylinder strikes the chisel to break a broken-to-be object, and a support portion noise-absorbing plate located at a portion supporting the chisel moving in upward and downward directions, whereby the noise generated at the portion to be struck of the chisel and at the supporting portion of the reciprocating movement of the chisel is removed by means of the striking portion noise-absorbing plate and the support portion noise-absorbing part, thereby improving a noise-removing efficiency. Brief Description of the Drawings

[19] Further objects and advantages of the invention can be more fully understood from the following detailed description taken in conjunction with the accompanying drawings in which:

[20] FTG.1 is a sectional view showing a conventional hydraulic breaker;

[21] F1G.2 is a partly cut perspective view showing a low noise hydraulic breaker according to the present invention;

[22] FlG.3 is a sectional view showing the low noise hydraulic breaker according to the present invention;

[23] F1G.4 is a sectional view showing an absorbing blower mounted at an exhausted air absorbing part in the low noise hydraulic breaker according to the present invention; and

[24] F1G.5 is a sectional view showing a plurality of noise-absorbing partitions mounted at the exhausted air absorbing part in the low noise hydraulic breaker according to the present invention. Best Mode for Carrying Out the Invention

[25] To accomplish the above objects, according to the present invention, there is provided a low noise hydraulic breaker wherein if gas is supplied from a valve to a gas chamber located at the upper portion thereof, while pressure pulsation is being removed at an accumulator, a piston that is located at the inside of a cylinder moves in upward and downward directions in such a manner as to strike a chisel of a breaking part supported by upper and lower bushes coupled by means of a key at a striking chamber of a striking part located at the lower portion thereof, thereby breaking a broken-to-be object, the low noise hydraulic breaker including: the breaking part having a striking portion noise-absorbing plate located along the outer periphery of a portion to be stuck by the piston at the upper portion of the chisel, for absorbing the noise generated upon striking, and having a support portion noise-absorbing plate located along the outer periphery of a coupled side of the portion to be struck of the chisel with the upper bush, for absorbing the noise generated upon striking; a noise- absorbing part having a noise-absorbing plate located along the inner side of the striking chamber of the striking part, having an air-circulating chamber defined by forming a given depth of groove at the inside of the noise-absorbing plate for circulating the air passed through the noise-absorbing plate, and having an exhaust port located at one side of the air-circulating chamber for exhausting the circulated air; and an exhausted air absorbing part having a noise-absorbing plate located at the inside of a housing connected at one side thereof with the exhaust port of the noise-absorbing part by means of an exhausted air connecting pipe in such a manner as to fluidically intercommunicate with the exhaust port and having a plurality of exhaust through holes located at the other side of the housing for exhausting the exhausted air at a state where the noise is removed.

[26] Also, the striking portion noise-absorbing plate and the support portion noise- absorbing plate of the breaking part, the noise-absorbing plate of the noise-absorbing part, and the noise-absorbing plate of the exhausted air absorbing part have a thickness in a range of 80mm to 90mm and a density in a range of 80Kg/m to 90kg/m .

[27] The exhausted air absorbing part is connected through the exhausted air connecting pipe with the exhaust port of the air-circulating chamber, and has an absorbing blower located at one side of the exhausted air connecting pipe for forcedly exhausting the air in the air-circulating chamber.

[28] The exhausted air absorbing part is connected through the exhausted air connecting pipe with the exhaust port of the noise-absorbing part, and has a plurality of noise- absorbing partitions located at the inside of the housing in such a manner as to have passages crossing one another therein for secondarily removing the noise generated upon striking. Mode for the Invention

[29] An explanation on a low noise hydraulic breaker according to the present invention will be given below with reference to the attached drawings.

[30] F1G.2 is a partly cut perspective view showing a low noise hydraulic breaker according to the present invention, FlG.3 is a sectional view showing the low noise hydraulic breaker according to the present invention, F1G.4 is a sectional view showing an absorbing blower mounted at an exhausted air absorbing part in the low noise hydraulic breaker according to the present invention, and F1G.5 is a sectional view showing a plurality of noise-absorbing partitions mounted at the exhausted air absorbing part in the low noise hydraulic breaker according to the present invention.

[31] As shown in F1GS.2 to 5, a low noise hydraulic breaker according to the present invention includes: a cylinder 110 having a piston 111 movable in upward and downward directions at the inside thereof if gas is supplied from a valve 113 to a gas chamber 112 located at the upper portion thereof, while pressure pulsation is being removed at an accumulator 114; a breaking part 120 having a chisel 121 located at the lower portion of the cylinder 110 for breaking a given broken-to-be object; a striking part 130 having a striking chamber in which the piston 111 of the cylinder 110 strikes the chisel 121 of the breaking part 120 and fixedly supported by means of upper and lower bushes 132 and 134 with respect to the chisel 121 and by means of a key 133 coupling the upper and lower bushes 132 and 134; a noise-absorbing part 140 for absorbing the striking noise generated at the inside of the striking chamber 131 of the striking part 130; and an exhausted air absorbing part 150 for secondarily absorbing the exhausted air at a state where the noise is primarily removed at the noise-absorbing part 140.

[32] The breaking part 120 has a striking portion noise-absorbing plate 122 located along the outer periphery of a portion to be stuck of the chisel 121, at the upper portion of the chisel, for absorbing the noise generated upon striking, and has a support portion noise-absorbing plate 123 located along the outer periphery of a coupled side of the portion to be struck of the chisel 121 with the upper bush 132 of the striking part 130, for absorbing the noise generated upon striking, thereby making the generation of noise substantially reduced upon striking. [33] The noise-absorbing part 140 has a noise-absorbing plate 141 located along the inner side of the striking chamber 131 of the striking part 130, an air-circulating chamber 142 defined by forming a given depth of groove at the inside of the noise- absorbing plate 141 for circulating the air passed through the noise-absorbing plate 141, and an exhaust port 143 located at one side of the air-circulating chamber 142 for exhausting the circulated air.

[34] The exhausted air absorbing part 150 has a noise-absorbing plate 153 located at the inside of a housing 151 connected at one side thereof with the exhaust port 143 of the noise-absorbing part 140 by means of an exhausted air connecting pipe 152 in such a manner as to fluidically intercommunicate with the exhaust port 143, and has a plurality of exhaust through holes 154 located at the other side of the housing for exhausting the exhausted air at a state where the noise is removed.

[35] In this case, the striking portion noise-absorbing plate 122 and the support portion noise-absorbing plate 123 of the breaking part 120, the noise-absorbing plate 141 of the noise-absorbing part 140, and the noise-absorbing plate 153 of the exhausted air absorbing part 150 have a thickness in a range of 80mm to 90mm and a density in a range of 80Kg/m to 90kg/m , which makes the noise-absorbing efficiency most desirably obtained.

[36] Also, the exhausted air absorbing part 150 is connected through the exhausted air connecting pipe 152 with the exhaust port 143 of the air-circulating chamber 142, and has an absorbing blower 155 located at one side of the exhausted air connecting pipe 152 for forcedly exhausting the air in the air-circulating chamber 142.

[37] Further, the exhausted air absorbing part 150 is connected through the exhausted air connecting pipe 152 with the exhaust port 143 of the noise-absorbing part 140, and has a plurality of noise-absorbing partitions 156 located at the inside of the housing in such a manner as to have passages crossing one another therein for secondarily removing the noise generated upon striking.

[38] Now, an explanation on the operation of the low noise hydraulic breaker according to the present invention will be given below.

[39] First, at a state where a hydraulic breaker 100 is mounted at the construction equipment like an excavator, a loader or the like, if the chisel 121 of the breaking part 120 is placed at a broken-to-be object, the valve 113 is operated to supply and exhaust gas to and from the gas chamber 112, while the pressure pulsation is prevented at the accumulator 114, such that as the piston 111 is repeatedly moved in upward and downward directions, it strikes the upper portion of the chisel 121 located below the piston 111, thereby making the broken-to-be object.

[40] In this case, the striking portion noise-absorbing plate 122 is located at the upper portion to be stuck of the chisel 121 by the sliding movement of the piston 111, and the support portion noise-absorbing plate 123 is located at the upper bush 132 supporting the upward and downward movements of the chisel 121 upon striking, thereby absorbing the noise generated from the chisel 121 upon striking.

[41] Also, the noise generated during the upward and downward strokes of the piston

111 against the chisel 121 is primarily passed and absorbed through the noise- absorbing plate 141 of the noise-absorbing part 140 located at the inside of the striking chamber 131, and the noise-absorbed air is circulated to the air-circulating chamber 142 defined in a given space at the rear surface of the noise-absorbing plate 141. Next, the circulated air is emitted through the exhaust port 143.

[42] The air where the noise is primarily removed is transmitted through the exhausted air connecting pipe 152 of the exhausted air absorbing part 150 to the noise-absorbing plate 153 located at the inside of the housing 151 and is then exhausted to the plurality of exhaust through holes 154, such that the noise is secondarily absorbed to make the volume of noise greatly reduced.

[43] At this time, the absorbing blower 155 is located at the rear side of the exhausted air connecting pipe 152 for rapidly absorbing the air in the air-circulating chamber 142 to supply the absorbed air to the exhausted air absorbing part 150, thereby improving the noise-absorbing performance.

[44] Further, the exhausted air absorbing part 150 may have the plurality of noise- absorbing partitions 156 located at the inside of the housing 151 in such a manner as to have passages crossing one another therein for secondarily removing the noise generated upon striking.

[45] In this case, the striking portion noise-absorbing plate 122 and the support portion noise-absorbing plate 123 of the breaking part 120, the noise-absorbing plate 141 of th e noise-absorbing part 140, and the noise-absorbing plate 153 of the exhausted air absorbing part 150 have a thickness in a range of 80mm to 90mm and a density in a range of 80Kg/m³ to 90kg/m³, which makes the noise-absorbing efficiency most desirably obtained.

[46] When the low noise hydraulic breaker of this invention and the conventional low noise hydraulic breaker were under the same operation conditions as each other, the noise values generated therebetween were measured several times by Korean National Seoul Industrial University, such that it was found that when the noise value of the conventional low noise hydraulic breaker was in a range of 9OdB to 95dB, the noise value of the low noise hydraulic breaker of this invention was in a range of 7OdB to 75dB. That is, the noise value of the low noise hydraulic breaker of this invention is lower by about 2OdB than that of the conventional low noise hydraulic breaker, and therefore, it is appropriated that the present invention has a more excellent noise- absorbing efficiency than the conventional low noise hydraulic breaker. Industrial Applicability

[47] As described above, there is provided a low noise hydraulic breaker according to the present invention that includes a noise-absorbing plate having given thickness and density that is located along the wall surface of a striking chamber of a striking part where a piston disposed at the upper portion of a cylinder in such a manner as to be reciprocated therein strikes a chisel of a breaking part, an air-circulating chamber that is located along the rear surface of the noise-absorbing plate for circulating the air passed through the noise-absorbing plate, and an exhaust port that is located at one side of the air-circulating chamber for exhausting the circulating air, whereby the noise generated from the striking operation is directly absorbed, thereby increasing a noise-removing efficiency.

[48] According to the low noise hydraulic breaker of this invention, the noise generated by striking a chisel of a breaking part by the upward and downward movements of a piston is primarily absorbed by means of a noise-absorbing part located along the wall surface of a striking chamber of a striking part, and if the primarily absorbed air is exhausted to an exhaust port through an air-circulating chamber, it is secondarily absorbed by means of an exhausted air absorbing part connected to the exhaust port, thereby making a noise-removing efficiency more optimized.

[49] According to the low noise hydraulic breaker of this invention, the compressed air containing the noise generated when a piston strikes a chisel is primarily absorbed by means of a noise-absorbing plate of a noise-absorbing part located at a striking chamber, and if the compressed air is transmitted to an air-circulating chamber located at the rear side of the noise-absorbing plate, it is absorbed by means of an absorbing blower connected to an exhaust port of the air-circulating chamber in such a manner as to be forcedly exhausted to an exhausted air absorbing part for rapidly removing the noise generated by the striking of the piston, thereby increasing a noise-removing efficiency.

[50] According to the low noise hydraulic breaker of this invention, the compressed air containing the noise generated when a piston strikes a chisel is primarily absorbed by means of a noise-absorbing plate of a noise-absorbing part located at a striking chamber, and if the compressed air is transmitted to an air-circulating chamber located at the rear side of the noise-absorbing plate, it is absorbed by means of a plurality of noise-absorbing partitions located at the inside of an exhausted air absorbing part connected to an exhaust port of the air-circulating chamber such that the noise is reduced through the plurality of noise-absorbing partitions, thereby improving a noise- removing performance.

[51] The low noise hydraulic breaker of this invention is provided with a striking portion noise-absorbing plate located at an upper portion of a chisel where a piston reciprocating at the inside of a cylinder strikes the chisel to break a broken-to-be object, and a support portion noise-absorbing plate located at a portion supporting the chisel moving in upward and downward directions, whereby the noise generated at the portion to be struck of the chisel and at the supporting portion of the reciprocating movement of the chisel is removed by means of the striking portion noise-absorbing plate and the support portion noise-absorbing part, thereby improving a noise- removing efficiency.

[52] While the present invention has been described with reference to the particular illustrative embodiments, it is not to be restricted by the embodiments but only by the appended claims. It is to be appreciated that those skilled in the art can change or modify the embodiments without departing from the scope and spirit of the present invention.

Claims

[1] A low noise hydraulic breaker (100) wherein gas is supplied from a valve (113) to a gas chamber (112) located at the upper portion thereof, while pressure pulsation is being removed at an accumulator (114), and a piston (111) that is located at the inside of a cylinder (110) moves in upward and downward directions in such a manner as to strike a chisel (121) of a breaking part (120) supported by upper and lower bushes (132 and 134) coupled by means of a key (133) at a striking chamber (131) of a striking part (130) located at the lower portion thereof, thereby breaking a broken-to-be object, the low noise hydraulic breaker comprising: the breaking part (120) having a striking portion noise-absorbing plate (122) located along the outer periphery of a portion to be stuck of the chisel(121) at the upper portion of the chisel (121), for absorbing the noise generated upon striking, and having a support portion noise-absorbing plate (123) located along the outer periphery of a coupled side of the portion to be struck of the chisel (121) with the upper bush (132), for absorbing the noise generated upon striking; a noise-absorbing part (140) having a noise-absorbing plate (141) located along the inner side of the striking chamber (131) of the striking part (130), having an air-circulating chamber (142) defined by forming a given depth of groove at the inside of the noise-absorbing plate (141) for circulating the air passed through the noise-absorbing plate (141), and having an exhaust port (143) located at one side of the air-circulating chamber (142) for exhausting the circulated air; and an exhausted air absorbing part (150) having a noise-absorbing plate (153) located at the inside of a housing (151) connected at one side thereof with the exhaust port (143) of the noise-absorbing part (140) by means of an exhausted air connecting pipe (152) in such a manner as to fluidically intercommunicate with the exhaust port (143) and having a plurality of exhaust through holes (154) located at the other side of the housing (151) for exhausting the exhausted air at a state where the noise is removed.

[2] A low noise hydraulic breaker according to claim 1, wherein the striking portion noise-absorbing plate (122) and the support portion noise-absorbing plate (123) of the breaking part (120), the noise-absorbing plate (141) of the noise-absorbing part (140), and the noise-absorbing plate (153) of the exhausted air absorbing part (150) have a thickness in a range of 80mm to 90mm and a density in a range of 80Kg/m³to 90kg/m³.

[3] A low noise hydraulic breaker according to claim 1, wherein the exhausted air absorbing part (150) is connected through the exhausted air connecting pipe (152) with the exhaust port (143) of the air-circulating chamber (142), and has an absorbing blower (155) located at one side of the exhausted air connecting pipe (152) for forcedly exhausting the air in the air-circulating chamber (142). [4] A low noise hydraulic breaker according to claim 1, wherein the exhausted air absorbing part (150) is connected through the exhausted air connecting pipe (152) with the exhaust port (143) of the noise-absorbing part (140), and has a plurality of noise-absorbing partitions (156) located at the inside of the housing in such a manner as to have passages crossing one another therein for secondarily removing the noise generated upon striking.