DE2360430A1 - SILENCER FOR PNEUMATIC IMPACT TOOLS - Google Patents

Description

The invention relates to sound attenuation devices and, more particularly, relates to a lowering sound attenuator the operating noise level for a pneumatic impact tool.

Against the use of pneumatic impact tools, e.g. pneumatic hammers to break up road surfaces and The like., have long been objections because of the high noise level collected with which such tools work. This operating noise is not only because of its strength, but also perceived as annoying because of its frequency range. In other words, the noises made when operating are undamped Pneumatic impact tools / tools are not just one low fundamental frequency, but they also contain numerous harmonics that are spread across the audible spectrum Distribute frequencies. Therefore, most people consider at least some or all of these frequencies to be felt annoying. Since the working fluid escaping from the outlets of such tools usually pulsates, they result also pulsations of the noises, which therefore result from this to-

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additional G-round to an even greater extent than disturbing eir.pxunaen will.

\ äs have been proposed various types of damping devices üie, should serve to dampen eräusche above-the pneumatic impact tools in .Betrieb incurred. Such devices are described, for example, in U.3.A. Patents 5 63? 299, 2 7o9 653, 3 224 527, 3 255 S44 and 3 365 022. However, these known shock absorption devices have various disadvantages, for example the complexity of the iLOnstriuztion, an excessive need for external equipment, insufficient adaptability to tools of various types and insufficient damping of the operating noise of the tool in question.

Furthermore zählreiche Schalldämpfungsvorric proposed hr obligations already that do make it possible to attenuate the Setrxebsgeräusch the indicated tool sufficient in which this jedocn only at the cost of reducing the erneblichen v7irkungsgrades the tool is possible. In addition, some of the known sound attenuation devices are not capable of withstanding the usual rough handling of such tools in use.

The invention is now based on the object ', a To create soundproofing device for pneumatic impact tools, in which the Iiachteiie mentioned up to now known Schalldämpfungsvorrxchtungen are avoided, which also makes it possible to substantially within the entire in Question coming frequency range and in particular in range of the high frequencies to dampen the noises caused by a pneumatic impact tool without affecting the efficiency of the tool decreased to a noticeable extent which is of compact and robust construction, a Achieved long service life, can be produced in an economical manner and easily and quickly with the associated unite pneumatic impact tool or can be separated from it.

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This task is for a silencer to reduce the operating noise of a pneumatic hammer mechanism. stuff with an elongated main body and in this trained skipping over which during operation d & s Tool's compressed air escapes, solved by the fact that an ifan "cel is present, which surrounds the main body of the tool in the area of the outlets and cooperates with the main body in such a way that that between it and the main body a first and a second expansion chamber are present, that the first Relaxation chamber compressed air supplied from the outlets is that the second expansion chamber is connected to the first expansion chamber that the compressed air from the first expansion chamber passes into the second relaxation chamber, that the jacket has at least one outlet) the establishes a connection between the second relaxation chamber and the atmosphere, and that after the installation of the Sound attenuation device on the main body of the tool the first and second expansion chambers are located on opposite sides of the main body.

Advantageous Y / pus formations result from the subclaims and the further description »

The silencer described in detail below is preferably composed of two main parts, which one could compare with the two halves of a fluffy shell. The two halves of the muffler preferably have a symmetrical shape and are intended to enclose part of the main body of the associated striking tool in the area of the outlet ducts. After the tool has been attached to the main body, the silencer forms a cantilever which, together with the exterior of the main body, delimits at least one relaxation chamber and preferably several relaxation chambers or are provided with guide organs which are connected to the outer surface of the body of the work, so that they delimit two of the ji'n ospaniiiungskammer. ¹ This relaxation 3-

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chambers are through a first Prosseleinrichtung with a Interconnected predetermined passage cross-section, the silencer also has a third expansion chamber on, which is formed by two elongated channels, each of which connects with one end to the second expansion chamber, while their opposite ends in Are connected to the outlet of the jacket, via which the relaxed compressed air escaping from the outlets of the tool is discharged to the outside. The third “expansion chamber, which acts as a throttle device, also has a predetermined one Passage cross-section. The two silencer halves consist of an elastomeric material that increases the durability of the silencer as well as the damping High frequency noise is improved.

The invention is explained in more detail below with reference to schematic drawings of an exemplary embodiment explained-. It shows:

Pig. 1 is a perspective view of a pneumatic percussion tool in the form of a percussion hammer, which with is equipped with a silencer j

! ig. Figure 2 is a somewhat enlarged section along line 2-2 in Pig. 1;

Pig. Figure 3 is a section along line 3-3 in Pig, drawn to an even larger scale. 1;

Pig. 4 shows a partial section along the line 4-4 in Pig. 2; Pig. 5 shows a partial section along the line 5-5 in Pig. 4;

Pig. 6 is a section along broken line 6-6 in Pig. 4; and

Pig. 7 is an exploded perspective view of the Pig muffler. 1 to 6, from which the

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The arrangement of the parts of the muffler in relation to a pneumatic tool can be seen

In Pig. 1 is a muffler, generally designated 10, in connection with a pneumatic tool, e.g. a pneumatic hammer designated as a whole with B, shown »In the present Pail the pneumatic hammer B an elongated tool body 11, which at his upper end is provided with handles 12 and a lever 13 for regulating the operation of the tool «According to Fig» 1 is in the A drill bit 14 made of steel is inserted at the lower end 16 of the tool body 11, as described in the TJ.S.A. patent application 260 of June 7, 1972 is described ". The drill bit 14 is locked in the tool body 11 by a locking device 17 held.

The working medium - in the present case compressed air is supplied to the tool B via a connection 18 at the upper end, and an automatic valve (not shown here) in the upper end of the main body 11 is used to * control the supply of compressed air to a piston or hammer 22? according to Pig. 4 is guided up and down in a bore 23 of the main body 11 and is used _{to exert s} impacts on the upper end of a plunger 24, which is guided up and down in a stepped bore 25 in the Iferkzeugkörper 11 and the impacts on the upper The end of the drill bit 14 transfers. The used compressed air is discharged from the tool body 11 at the end of each working stroke of the piston 22 via an outlet device in the form of several outlet channels 26. The pneumatic tool B works without interruption as long as the throttle lever 13 is held in its lower position and the tool is continuously supplied with compressed air the connection 18 is fed ο

According to Pig. 7, the muffler 10 is made up of two Parts or halves 10a and 10b together, preferably to each other are symmetrical and. made of an elastomer material,

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e.g. polyurethane. The reasons for using this material and the advantages resulting from it will be discussed in more detail below.

The muffler halves 10a and 10b have a general semi-cylindrical side wall 32a and 32b and upper and lower end walls 33a and 33b and 34a and 34b, respectively. The top and lower end walls are provided with recesses 36a, 37a and 36b, 37b, respectively, which are shaped so that they meet the Adjust outer surfaces of the tool body 11 exactly when the muffler 10 is attached to the tool. In the present Case, the recesses 36a and 36b of the upper end walls 33a and 33b have a generally semicircular shape, while the recesses 37a and 37b of the lower end walls 34a and 34b are generally V-shaped.

In order to ensure that the walls of the recesses 36a, 36b, 37a and 37b cooperate with a sealing effect with the outer surfaces of the tool body 11 as soon as the silencer 10 is attached, according to FIG. 1 and 7 two tensioning straps 42 and 43 are present, which work together with axially extending lugs 44a or 44b and 45a or 45b on the upper and lower end walls of the jacket halves 10a and 10b by enclosing and pulling them together Tensioning straps 42 and 43 come to rest firmly against the walls of the recesses on the parts of the tool body 11 adjacent to them.

To create a pressure-tight connection between the touching edge surfaces of the silencer halves 10a and 10b, the two halves have outwardly projecting flanges 47a and 47b, each with several Openings 48a and 48b, respectively, are provided for receiving a plurality of fasteners such as screws 52. Since the Flanges 47a and 47b as well as the other parts of the silencer halves 10a and 10b, preferably made of an elastomer material are made, they contain reinforcing inserts

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2360Λ30

made of metal. In Mg. 4 are two reinforcement inserts 53b and 54Ta that are inserted into the flange. 47b of the muffler half 10b are embedded, indicated with dashed lines. Two similar reinforcing inserts are embedded in the plan 47a of the muffler half 10a. In the embodiment shown, the reinforcement inserts 3b and 54b have threaded holes. Receiving the screws 52, while the reinforcing inserts are provided in the flange 47a with smooth bores for receiving the screws protruding through this flange. When the screws 52 are tightened, the flanges 47a and 47b are therefore brought into abutment against one another in order to effect a pressure-tight seal.

As mentioned, the silencer 10 has at least one and preferably several expansion chambers, which serve to absorb the compressed air pulsing at high speed from the outlets 26 of the tool and to reduce the level of the noise generated by this outflow when the tool is in operation will. TJm to delimit these chambers in the silencer 10, the halves 10a and 10b are stranded according to FIGS. 4 to 7 with inner partition walls 56a and 56b, by which the interior of each silencer half is divided into two chambers. The partition walls 56a and 56b are preferably related to the material of the relevant silencer half, and each partition wall includes two ribs 57 and 5.8 which extend in the longitudinal direction and are separated by a transverse distance. These ribs have such a radial width that their free inner edges come to rest against the outer surface of the tool body 11 and cooperate with it with a sealing effect when the two silencer halves are united with the tool body. When this has been done in the manner shown in FIG. 6, the partitions 56a and 56b delimit a first expansion chamber 61 and a second expansion chamber 62, each of which has a generally semi-cylindrical shape and is arranged on opposite sides of the tool body.

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As mentioned, the expansion chambers 61 and 62 are connected in series in terms of flow. To this end is a first throttle device for connecting the chambers 61 and 62 available. This throttle device is gate-based formed by two gaps 63 and 64 recognizable in FIGS. 4 and 5, which are formed by the lower end edges 66 of the ribs 56a and 56b and the adjacent end face 67 of a flange 68 on the main body 11 of the tool are delimited.

With this construction, the pulsating compressed air flow escaping via the outlets 26 of the tool B arrives first into the expansion chamber 61, into which it enters at an angle that is determined by the inclination angle shown in FIG the outlets are determined. After entering the chamber 61, the compressed air relaxes and nierbei the sound of the compressed air flow is muffled. Some attenuation is also created by an interference between the Pressure waves are brought about in the stream as the pressure waves from the different walls of the chamber 61 alternate be thrown back in one direction and the other.

After the compressed air discharged from the outlets 26 has completely relaxed in the chamber 61, the air continues to flow through the first throttle device or the column 63 and 64 at the lower ends of the partition walls 56a and 56b to then enter the second expansion chamber 62. the Dimensions of the column 63 and 64 and the other geometric relationships of the muffler 10 are chosen so that the passage cross section of the first throttle device approximately between 1.4 times and 1.5 times the total cross section the outlet channels 26 in the main body 11 of the tool lies.

After the initial relaxation in the chamber 61, the flow of compressed air emitted from the outlets 26 changes as it passes through of the column 63 and 64 its direction to then- in the

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lower end of the second "expansion chamber 62. This change in direction of the exhaust air flow contributes to the damping of the noise generated by the air flow, -The relaxation of the exhaust air flow in the second expansion chamber leads to a further reduction in the level of the noise.

When reaching the upper end of the second expansion chamber 62, the exhaust air flow changes its direction again, to enter the upper end of a third expansion chamber, which according to Mg. 3 to 6 through two elongated channels 72a and 72b is formed, which by two longitudinal extensions 73a and 73b on the inner surfaces of the side walls 32a and 32b the muffler halves 10a and 10b run. According to FIG. 4 and FIG. 6 hang the lugs 73a and 73b with the material of FIG Halves 10a and 10b together, and have channels 72a and 72b generally oval cross-sectional shape. The lugs 73a and 73b extend longitudinally through the second expansion chamber 62 from the lower end walls 34a and 34b of the halves 10a and -10b in the direction of the upper end walls 33a and 33b, but end just before the upper end walls according to FIGS. 4, 5 and 7, so that the channels 72a and 72b in of the second expansion chamber 62 and separated from it except for its upper ends 74a and 74b, which a second throttle device form which a connection between the second and the third expansion chamber of the Silencer manufactures »

The length of the channels 72a and 72b preferably corresponds to about 70 $ of the length of the expansion chamber 62 ₉ and the total passage cross-section of the two channels is preferably in the range of about Aerei quarters to seven-eighths of the passage cross section of the first Drosseleinrichtungο

After the exhaust air flow has entered the upper ends 74a and 74b of the channels 72a and 72b, the air flows through them

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Channels in the axial direction further down, to then to the Atmosphere via outlet openings 76a and 76b (Pig. 3) into the lower end walls 34a and 34b to be delivered. The last part of the "relaxation of the exhaust air" takes place at the outlet openings 76a and 76b.

The relationship described between the passage cross-sections of the first throttle device and the outlet channels 26 in the body 11 of the tool and between the passage cross sections the second throttle device and the first throttle device leads to an attenuation of the high-frequency Noises which are generated by the compressed air escaping via the outlets 26, such as that which is present in the exhaust air Water vapor forms frost and / or freezes after condensation. In addition, the presence of the described Relationships between the passage cross-sections do not lead to a noticeable increase in the caused by the muffler Back pressure, so that the efficiency of the pneumatic motor of the Yferkzeugs is not reduced

As mentioned, the muffler 10 is preferably made of an elastomer material, e.g. Polyurethane. The usage Such a material not only contributes to an increase in the sound-absorbing effect of the muffler, but also leads to a dampening of the noises generated by the piston 22 pushing the plunger 24 and 22 the ram exerts impacts on the upper end of the chisel 14 inserted into the tool body 11. Since the work The material of the silencer is a resilient durable plastic, eventually there is a risk of damage or destruction of the muffler as a result of rough. treatment and under the effect of impact or the like. Essentially switched off.

Expectations;

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Claims (18)

A-. H PROBLEMS \ : 1. ) Silencer for reducing the operating noise level of a pneumatic impact tool with an elongated tool body and outlet channels formed therein, from which compressed air escapes during operation of the tool, characterized in that a jacket (10) is present which surrounds the tool body (11 ) encloses in the area of the outlet channels (26) and, together with the tool body, delimits a first expansion chamber (61) and a second expansion chamber (62), that the first expansion chamber receives the air escaping from the outlet channels, that the second expansion chamber of the first expansion chamber , tension chamber is downstream fluid-technically, that the jacket has at least one outlet opening (76a, 76b) connecting the second expansion chamber to the atmosphere, and that the first and the second relaxation chamber are attached to the tool body on opposite sides of the tool body after the sound absorber has been attached are. 2. Silencer according to claim 1, characterized in that each of the expansion chambers (61, 62) has a generally semi-cylindrical shape and extends generally in the circumferential direction of the tool body (11). 3. Silencer according to Claim 1 or 2, characterized Ken η records that the first expansion chamber (61) is connected to the second expansion chamber (62) by a first throttle device (63 »64). 409 8 23/0403 44 023 4. Silencer according to claim 3 »characterized» that the first throttle device (63, 64) is arranged essentially at one of the axial ends (34a, 34b) of the jacket (10). 5. Silencer according to claim 3 or 4 »characterized in that the jacket (10) has a general cylindrical side wall section (32a, 32b), which after attaching the jacket to the tool body (11) is separated by a distance from the outer surface of the tool body that the inner surface of the side wall portion has two partition walls (56a, 56b), and that these partition walls have radially inwardly directed edges which with the v / tool body with sealing effect work together to to delimit the expansion chambers (61, 62). 6. Silencer according to claim 5, characterized in that the jacket (10) by an axial Distance separated end wall sections (33a, 33b and 34a, 34b) has that the partition walls (56a, 56b) in the axial direction extend from one end wall section in the direction of the other end wall section, and that at least one of the partition walls has an end (66) which is opposite the inner surface of the other end wall section in the axial direction is offset inwardly to define a gap (63, 64) which forms part of the first throttle device. 7. Silencer according to claim 6, characterized in that the ends (66) of both partition walls (56a, 56b) are offset inward in the axial direction in relation to the other end wall section (34a, 34b) by two gaps (63, 64) to delimit which is the first throttle restriction form. 8. Silencer according to one of claims 3 to 7, characterized in that the effective passage cross section the first throttle device (63, 64) about the 409823/0403 44 023 1.4 times "to about 1.5 times the passage cross-section corresponds to the outlet channels (26). 9. Sound absorber ex · according to one of the claims 3 "to 8, thereby characterized in that the effective passage cross-section of the second throttle device (62) about three quarters "to seven eighths of the effective passage cross-section corresponds to the first throttle device (63, 64). 10. Silencer according to one of claims 1 to 9 »thereby characterized in that in the jacket (10) one Third expansion chamber (72a, 72b.) Is formed that one end (74a, 74b) of the third expansion chamber with the second expansion chamber (62) is connected, and that the other end of the third expansion chamber in communication with an air outlet opening (76a, 76b) of the jacket. 11. Silencer according to claim 10, characterized in that the third expansion chamber (72a, 72b) at least one elongated, in connection with the second expansion chamber (62) belongs to a standing channel. 12. Silencer according to claim 11, characterized in that the elongated channel (72a, 72b) in the jacket (10) extends in the axial direction. 13. Silencer according to claim 11 or 12, characterized in that the Ij & nge of the elongated channel (72a, 72b) is approximately equal to 70% of the length of the second expansion chamber (62) » 14 »Silencer according to one of claims 11 to 13» characterized in that the elongated channel (72a ₉ 72b) is formed in a projection (73a _s 73b) on the inner surface of the cylindrical side wall (32a _s "32b). 409823/040 3 44 023 15. Silencer according to one of claims 11 to 14, characterized characterized in that the jacket (10). has two elongated channels (72a, 72b). 16. Silencer according to one of claims 1 to 15, characterized characterized in that the jacket (10) consists of at least two separable parts (10a, 10b) so that the muffler is easily attached to the Attach body (11) of tool (B) or can be separated from it. 17 · Silencer according to claim 16, characterized in that the parts (10a, TOb) of the casing (10) are shaped substantially symmetrically. 18. A muffler according to claim 16 or 17, characterized in that there is Jc that the jacket (10) consists of an elastomer material which is suitable at least high frequency To muffle noises. 19. Silencer according to Claim 18, characterized in that the elastomer material is polyurethane heard. Blank page