Impact hammer

Abstract: An improved abrasion-resistant hydraulic hammer (10) has a low noise level, by preventing the leak-out of internal noise. Such a hammer can contribute to the establishment of a comfortable working environment and meet environmental standards against noise pollution. A cylindrical plastics member (5,30) containing oil is installed in a passage formed in a body (4) under a piston (1) installed within the hydraulic hammer (10), for guiding a circumferential surface of a tool (3).

Description: The present invention relates to solid-rock-breaking power hammers and is concerned particularly, although not exclusively, with hydraulic hammers for breaking solid rock or concrete by operation under hydraulic oil pressure. A typical hydraulic hammer is a device in which oil pressure generated by a hydraulic pump is transferred to an oil passage, a piston inside the hammer moves up and down according to control of the oil passage and the oil pressure, to impact upon a tool, and the tool cracks eg solid rock or concrete with the reaction force from the impact. In a hydraulic hammer, the loudest noise and biggest vibration are typically 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. Figure 1 of the accompanying diagrammatic drawings is a cross-sectional view of a main portion of a conventional hydraulic hammer. As shown, a piston 1 is arranged within a bore inside a hydraulic hammer 10, and an oil passage 2 and various valves 9 are provided so that the piston 1 may move up and down. A tool 3 is disposed under the piston 1 and moves up and down, guided by an upper bush 5 and a lower bush 6 provided in a body 4 of the hydraulic hammer. A groove 11 is formed to a predetermined length in a circumferential surface of the tool 3. A tool pin 12 penetrates body 4 of the hydraulic hammer 10 to interengage the groove 11, to limit the up-and-down stroke of the tool 3 in dependence upon the length of the groove 11. The tool 3 and lower bush 6 are of metal and an annular rubber seal 7 is attached to lower bush 6. In the impact stroke of the hydraulic hammer 10, the oil filling an accumulator 8 and high-pressure oil from a pump 20 are provided to the upper and lower parts of piston 1, and thus piston 1 descends rapidly to hit tool 3. In the course of this, a very loud crashing sound and strong vibration are generated between tool 3 and piston 1 and with the reaction force from the impact, tool 3 crushes a rock 31. Since tool 3 and lower bush 6 are of metal, their mutual contact surfaces tend to abrade due to the frictional force therebetween in the course of crushing rock 31 by tool 3. In addition, heat generated on the contact surfaces tends to degrade rubber seal 7, to lower its sealing effect. Further, when dust and/or grains of sand blow in between tool 3 and lower bush 6 in crushing rock 31 by tool 3, abrasion of the contact surfaces is accelerated, thereby allowing the internal crashing sounds to leak out. The leaked-out crashing sounds deteriorate working environments and can give rise to restraint of operations according to noise pollution regulations, which have been generally tightened along with the reinforcement of environmental standards. Therefore, the leak-out of noise remains a critical problem to be solved. EP-0505726-A describes a manual, fluid-operated (therefore hydraulic or pneumatic) impact tool which includes a polyurethane annular member in the passage of the tool body, in contact with a circumferential surface of the tool. The annular member serves as a sound-damping device. On either side of the polyurethane annular member, the tool passes through bushes and at the point at which the tool emerges from the passage defined by the bushes and the annular member (through the lower bush) is lined with a polyurethane disc, which cooperates with a flange on the tool to absorb the shock of the tool returning to its retracted position. The tool passes through a further bore in the base of a housing. WO94/05464 describes a rock-breaking hammer in which the tool passes through a housing, a shock-absorber, a retainer and a closure bush. It also describes a somewhat different rock-breaking hammer in accordance with the preamble of claim 1, in which the tool passes through an upper metallic plain bearing, an upper shock-absorber, a retainer, a lower shock absorber and a lower plain metallic bearing in a housing. The housing 5 and closure bush 4 or the plain bearings 18 constrain the lateral movement of the tool. Preferred embodiments of the present invention aim to provide a solid abrasion-resistant hydraulic hammer with 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 leaking-out crashing sounds. According to one aspect of the present invention, there is provided A solid-rock-breaking hammer comprising: a body formed with a bore; a piston arranged within the bore for reciprocating movement up and down within the body; power means for driving the piston; a passage formed in the body under the piston; a rock-breaking tool arranged within the passage for reciprocating sliding movement up and down under impact from the piston and projecting from an open end of the passage; and at least one cylindrical plastics member provided in the passage, in contact with a circumferential surface of the tool; characterised in that the plastics member is provided at or adjacent the open end of the passage, and in that lateral movement of the tool within the passage at or adjacent its open end is constrained by the cylindrical plastics member. Preferably, the plastics member is of a plastics material containing oil. Preferably, the plastics member is of a polyamide-series containing oil. Preferably, at least two such cylindrical plastics members are provided in the passage, in contact with the circumferential surface of the tool. Preferably, at least one such plastics member is provided at or adjacent an open end of the passage. Preferably, at least one such plastics member is provided at or adjacent an end of the tool which is remote from an open end of the passage. Preferably, at least one such plastics member is provided within a metal bush. Preferably, at least one such metal bush is provided at an open end of the passage, and carries an elastomeric sealing member which engages the tool. Preferably, the power means is pneumatic and/or hydraulic. Preferably, the body comprises at least two separable parts. Preferably, movement of the tool is limited by interengaging means on the tool and body. For a better understanding of the invention, and to show how embodiments of the same may be carried into effect, reference will now be made, by way of example, to Figure 2 of the accompanying diagrammatic drawings, which is a cross-sectional view of a main portion of one example of an abrasion-resistant hydraulic hammer with low-noise level, according to one embodiment of the present invention. In the figures, like reference numerals denote like or corresponding parts. As shown in Figure 2, a piston 1 is arranged within a bore formed inside a body 4 of a hydraulic hammer 10, and an oil passage 2 and various valves 9 are provided for moving the piston 1 up and down. A tool 3 is inserted into a passage formed in the body 4 under piston 1, and has a circumferential surface which bears against an upper bush 5 and a lower bush 6 which are attached to the upper and lower parts of the passage, respectively. The tool 3 moves up and down under impact from the piston 1, and is guided by the bushes 5 and 6. A groove 11 is formed in the circumferential surface of tool 3 to a predetermined length. Since a tool pin 12 penetrates body 4 and into the groove 11, the up-and-down stroke of tool 3 is limited, and depends on the length of groove 11. Upper bush 5 is made of a polyamide-series plastics containing oil, with high abrasion resistance and good sealing properties. Therefore, the noise made when piston 1 hits tool 3 is firstly restrained by upper bush 5, thereby enabling safe up-and-down movement of tool 3. Tool 3 and lower bush 6 are of metal. However, a cylindrical rubber seal 7 and a cylindrical soundproofing member 30 fabricated of a polyamide-series plastics containing oil are attached to lower bush 6. Tool 3 moves up and down in contact with soundproofing member 30 and seal 7, thereby further preventing the leak-out of noise made by the impact of the piston 1 upon the tool 3. In the impact stroke of hydraulic hammer 10, the oil filling accumulator 8 and high-pressure oil from a pump 20 are provided to the upper and lower parts of piston 1, and thus piston 1 descends rapidly to hit tool 3. In the course of this, a very loud crashing sound and strong vibrations 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 of metal, tool 3 moves up-and-down in contact with plastics soundproofing member 30 containing oil, not in direct contact with lower bush 6. Due to a small frictional coefficient of the plastics used for soundproofing member 30, frictional heat and abrasion between the contact surfaces with the tool 3 are limited, and the plastics material containing oil obviates the necessity for periodically providing oil. Further, even if dust particles and/or grains of sand blow in between tool 3 and lower bush 6 in the course of crushing a rock, they tend to stick into plastic soundproofing member 30. Thus, severe abrasion of the contact surface of tool 3 can be avoided. Thus, the noise from the crash of piston 1 and tool 3 in the hydraulic hammer 10 can be sealed in, rather than to be heard outside. Further, unlike a conventional hydraulic hammer where the piston is damaged along with damage to the tool, piston 1 in the Figure 2 embodiment tends to remain intact in spite of damage to the tool 3, since the polyamide plastics upper bush 5 serves as a buffer against impact transferred from the tool 3. As described above, the abrasion-resistant hydraulic hammer 10 of Figure 2 provides a low noise level and makes possible a long-term sealing against noise. Therefore, the deterioration of working environments can be prevented and the working life of the hammer 10 can be extended. As shown in Figure 2, the body 4 is preferably of at least two-part construction. In this specification, terms of absolute orientation are used conveniently to denote the usual orientation of items in normal use and/or as shown in the accompanying drawings. However, such items could be disposed in other orientations, and in the context of this specification, terms of absolute orientation, such as "top", "bottom", "left", "right", "vertical", "horizontal", "up" , "down", etc. are to be construed accordingly, to include such alternative orientations.

Claims: A solid-rock-breaking power hammer (10) comprising: a body (4) formed with a bore; a piston (1) arranged within the bore for reciprocating movement up and down within the body (4); power means for driving the piston (1); a passage formed in the body under the piston (1); a rock-breaking tool (3) arranged within the passage for reciprocating sliding movement up and down under impact from the piston (1) and projecting from an open end of the passage; and at least one cylindrical plastics member (30) provided in the passage, in contact with a circumferential surface of the tool (3); characterised in that the plastics member is provided at or adjacent the open end of the passage, and in that lateral movement of the tool within the passage at or adjacent its open end is constrained by the cylindrical plastics member. A power hammer according to claim 1, wherein the plastics member (30) is of a plastics material containing oil. A power hammer according to claim 2, wherein the plastics member (30) is of a polyamide-series containing oil. A power hammer according to claim 1, 2 or 3, wherein at least two such cylindrical plastics members (5, 30) are provided in the passage, in contact with the circumferential surface of the tool (3). A power hammer according to any of the preceding claims, wherein at least one such plastics member (5) is provided at or adjacent an end of the tool (3) which is remote from an open end of the passage. A power hammer according to any of the preceding claims, wherein at least one such plastics member (30) is provided within a metal bush (6). A power hammer according to claim 6, wherein at least one such metal bush (6) is provided at an open end of the passage, and carries an elastomeric sealing member (7) which engages the tool (3). A power hammer according to any of the preceding claims, wherein the power means is pneumatic and/or hydraulic. A power hammer according to any of the preceding claims, wherein the body (4) comprises at least two separable parts. A power hammer according to any of the preceding claims, wherein movement of the tool (3) is limited by interengaging means (11, 12) on the tool (3) and body (4).

Inventors: LEE GUN-JIK, LEE, GUN-JIK
Applicants: HYUP SUNG HEAVY IND CO LTD, HYUP SUNG HEAVY INDUSTRIES CO. LTD.
Application year: 1996
Main classification: B25D1
IPC codes: B25D17, B25D9