Source: http://www.google.com/patents/US7681689?ie=ISO-8859-1&dq=U.S.+Patent+
Timestamp: 2015-04-25 01:38:33
Document Index: 432397613

Matched Legal Cases: ['arts 16', 'arts 16', 'arts 16', 'arts 16', 'arts 12', 'arts 111', 'arts 111', 'arts 131', 'arts 131', 'arts 131', 'arts 111']

Patent US7681689 - Vibration damping device and bucket for construction machine - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inAdvanced Patent SearchPatentsA vibration damping device capable of maintaining high vibration damping effect, and a bucket for a construction machine. The vibration damping device has a laminated plate (20) having at least its inner region fixed in a noise-emitting base material (11), the inner region being a region (G) other then...http://www.google.com/patents/US7681689?utm_source=gb-gplus-sharePatent US7681689 - Vibration damping device and bucket for construction machineAdvanced Patent SearchPublication numberUS7681689 B2Publication typeGrantApplication numberUS 10/526,224PCT numberPCT/JP2003/011181Publication dateMar 23, 2010Filing dateSep 2, 2003Priority dateSep 2, 2002Fee statusPaidAlso published asCN1678842A, CN100400925C, DE10393242T5, US7743881, US8438759, US20050268500, US20080222928, US20100218403, WO2004023001A1Publication number10526224, 526224, PCT/2003/11181, PCT/JP/2003/011181, PCT/JP/2003/11181, PCT/JP/3/011181, PCT/JP/3/11181, PCT/JP2003/011181, PCT/JP2003/11181, PCT/JP2003011181, PCT/JP200311181, PCT/JP3/011181, PCT/JP3/11181, PCT/JP3011181, PCT/JP311181, US 7681689 B2, US 7681689B2, US-B2-7681689, US7681689 B2, US7681689B2InventorsKazuya Imamura, Kuniaki Nakada, Taizou NakagawaOriginal AssigneeKomatsu Ltd.Export CitationBiBTeX, EndNote, RefManPatent Citations (52), Classifications (13), Legal Events (2) External Links: USPTO, USPTO Assignment, EspacenetVibration damping device and bucket for construction machine
US 7681689 B2Abstract
1. A vibration damping device for damping vibrations of a machine, the vibration damping device comprising a laminated plate formed by laminating a specified number of inner plates and an outer plate that is disposed on an outside of the specified number of the inner plates, wherein intermittent welding is performed on peripheral edges of the inner plates along a circumferential direction of the inner plates when the laminated plate is coupled to a member of the machine that is an object of vibration damping and the specified number of inner plates are tightly sealed by the outer plate and the member of the machine,
wherein the laminated plate is formed by laminating the specified number of the inner plates, and the outer plate which is disposed on the outside of the specified number of inner plates and whose peripheral edge has a shape that partially differs from a shape defined by peripheral edges of the inner plates, the inner plates are caused to contact with the member of the machine that is the object of vibration damping, and the laminated plate is coupled to the member of the machine by performing continuous welding on the peripheral edge of the outer plate and performing the intermittent welding on the peripheral edges of the inner plates.
2. A vibration damping device for damping vibrations of a machine, the vibration damping device comprising a laminated plate formed by laminating a specified number of inner plates and an outer plate that is disposed on an outside of the specified number of the inner plates, wherein intermittent welding is performed on peripheral edges of the inner plates along a circumferential direction of the inner plates when the laminated plate is coupled to a member of the machine that is an object of vibration damping and the specified number of inner plates are tightly sealed by the outer plate and the member of the machine,
wherein the member of the machine has a contact member that is capable of contacting end portions of the laminated plate, the inner plates define a contact part that protrudes from a peripheral edge of the outer plate and contacts with the contact member, and continuous welding that covers the contact part of the inner plates is performed between the peripheral edge of the outer plate and the contact member.
3. A vibration damping device for damping vibrations of a machine, the vibration damping device comprising a laminated plate formed by laminating a specified number of inner plates and an outer plate that is disposed on an outside of the specified number of the inner plates, wherein intermittent welding is performed on peripheral edges of the inner plates along a circumferential direction of the inner plates when the laminated plate is coupled to a member of the machine that is an object of vibration damping and the specified number of inner plates are tightly sealed by the outer plate and the member of the machine,
wherein a plurality of protruding parts that match a peripheral edge shape of the outer plate are disposed on the peripheral edge of the inner plates, and the plurality of protruding parts of the inner plates are intermittently welded by performing continuous welding on the peripheral edge of the outer plate.
4. The vibration damping device according to claim 2, wherein a length of the contact part of the inner plates is 100 to 280 mm.
5. The vibration damping device according to claim 3, wherein the plurality of protruding parts of the inner plates are disposed at intervals of 100 to 280 mm.
6. The vibration damping device according to claim 2, wherein the contact part is demarcated by a cut-out part, and the cut-out part has a rectangular shape.
7. The vibration damping device according to claim 2, wherein the contact part is demarcated by a cut-out part, and the cut-out part has a wave shape.
8. The vibration damping device according to claim 6, wherein the cut-out part is embedded by welding and the inner plates are attached to the machine when the laminated plate is coupled to the members of the machine. Description
Accordingly, in response to the demand for the development of a low-cost vibration damping device which has a high durability and involves no burning during repair, the assignee of the present application has already developed a laminated plate and filed a patent application for this plate, which has been disclosed in Japanese Patent Application Laid-Open No. 2000-219168 (or U.S. Pat. No. 6,332,509), Japanese Patent Application Laid-Open No. 2002-48188 and the like. With respect to the abovementioned publications, an explanation will be made with reference to FIG. 2. A plurality of thin steel plates 21 (hereafter referred to as �thin plates 21�) are laminated on the side plate 11 of the bucket, thus forming laminated plate 20. It is indicated that relatively thick steel plate 30 (hereafter referred to as �protective plate 30�) that protect the thin plates 21 is further superimposed on top of the laminated plate 20, and that the periphery 20 a (see FIG. 1) is fastened by performing all round fillet welding or intermittent fillet welding, or by performing intermittent plug welding, bolt fastening or the like. Since the laminated plate 20 is constructed from an inexpensive material that has a high durability and is resistant to burning, i. e., steel, the problem points encountered in conventional viscoelastic materials can be solved.
The mechanism whereby the laminated plate 20 suppresses the vibration generated in the side plate 11 and thus reduces the noise emitted from the side plate 11 is described in the abovementioned publications; this mechanism will be described with reference to FIGS. 4A and 4B. Specifically, when the side plate 11 vibrates, this vibration is transmitted to the laminated plate 20, so that the thin plates 21, 21′ constituting the laminated plate 20 undergo deformation. In the laminated plate 20 in which numerous thin plates 21, 21′ are superimposed, the amount of deformation differs in each layer. Specifically, the respective curvature radii r1 and r2 differ in adjacent thin plates 21, 21′. Accordingly, in the thin plates 21, 21′ in which the original displacement was X (see FIG. 4A), the displacement respectively varies to X+ΔX2 and X+ΔX1 as a result of the microscopic displacement caused by the vibration, so that a relative displacement of ΔX2−ΔX1 is generated between the two thin plates 21 and 21′. This relative displacement of ΔX2−ΔX1 causes the generation of a frictional force (hereafter referred to as an �inter-layer frictional force�) between the thin plates 21 and 21′. The vibration energy generated in the side plate 11 is converted into thermal energy by this inter-layer frictional force. As a result, the vibration generated in the side plate 11 is suppressed so that the noise emitted from the side plate 11 is reduced.
Secondly, during actual work performed by construction machinery, excessively large external forces are commonly applied to the side plate 11 as a result of the bucket striking rocks and the like. Consequently, the laminated plate 20 in which the internal portions are not fastened and only the peripheries 20 a are fastened is easily caused to �float upward� by these excessive external forces. In other words, the laminated plate 20 separates from the side plate 11, and the thin plates 21 and 21′ separate from each other. As a result, the inter-layer frictional force that should be generated between the thin plates 21 and 21′ during the vibration of the side plate 11 is either not generated at all or generated only to a very slight extent, so that a vibration damping effect is either not obtained at all or obtained only to a very slight extent.
Thus, in order to obtain a high vibration damping effect, it is desirable that the internal portions of the laminated plate 20 not be fastened, so that the deformation of the thin plates 21 is not impeded. However, if the internal portions of the laminated plate 20 are not fastened, �floating� occurs as a result of thermal strain during the manufacture of the bucket and external forces during the use of the bucket, so that the problem of a loss of the vibration damping effect arises.
The present invention was devised in order to solve such problems encountered in the prior art; it is an object of the present invention to provide a vibration damping device in which a high vibration damping effect can be maintained by fastening appropriate parts in the interior part of the laminated plate so that there is no loss of the vibration damping effect due to thermal strain during manufacture or the occurrence of �floating� caused by external forces during use, and so that there is no interference with the independent deformation of the thin plates that make up the laminated plate. Furthermore, it is an object of the present invention to provide a bucket for a construction machine which is devised so that noise countermeasures can be taken with the minimum required effort, without performing noise experiments or the like on the bucket, and which makes it possible to reinforce the bottom plate of the bucket with the minimum required increase in weight. Moreover, it is an object of the present invention to provide a vibration damping device which is superior in terms of vibration damping performance, and which can prevent the generation of noise in the internal portions.
When the amplitude distribution of the vibration is taken in a case where the base material 11 is caused to vibrate in the vibration mode 1 at a specified frequency, the size of the amplitude varies according to the part even in the case of the same structure, as is shown in FIG. 5A. Specifically, there is a part (PH in FIG. 5A) where the amplitude is large, i. e., the part that forms a loop of the vibration mode 1, and a part (PL in FIG. 5A) where the amplitude is small, i. e., the part that forms a node of the vibration mode 1. In the part where the amplitude is large, the amount of deformation of the thin plates 21, 21′ that form the laminated plate 20 is also large, and the frictional force between layers is also large.
The part G that forms the node of the vibration mode 1 is inherently a part where the deformation of the thin plates 21, 21′ that make up the laminated plate 20 is either small or almost non-existent. Accordingly, even if fastening is performed in this part, the vibration damping effect that is lost is either extremely small or almost non-existent. Consequently, the deleterious effect on the vibration damping effect caused by the fastening of the laminated plate 20 can be suppressed to a minimum. Thus, in the first construction, since the construction is devised so that the optimal part G in the interior parts of the laminated plate 20 is fastened, there is no loss of the vibration damping effect due to thermal strain during manufacture or the occurrence of �floating� caused by external forces during use. Furthermore, the independent deformation of the thin plates 21 that make up the laminated plate 20 is not impeded, so that a high vibration damping effect can be maintained.
In this first bucket construction, the standard for the requirement of noise countermeasures in the bottom plate is clearly defined as �the ratio Wp/Hs of the width Wp of the bottom plate to the height Hs of the side plate being 1.47 or greater�, and the bottom plate is reinforced according to this standard. As a result, noise countermeasures can be taken with the minimum required effort only in the case of buckets that require noise countermeasures (among the various types of buckets), without performing noise experiments or the like.
The second aspect of a bucket for a construction machine is a bucket for a construction machine comprising a side plate, a bottom plate, at least a portion of which is connected to the side plate, and a laminated plate which is attached to the outside of the side plate, characterized in that in cases where a ratio Wp/Hs of a width Wp of the bottom plate to a height Hs of the side plate is 1.47 or greater, a part, which forms a loop of a vibration mode, of the potion where the side plate and bottom plate are connected is reinforced.
FIGS. 5A through 5D are distribution diagrams showing the size of the amplitude when the side plate in the first embodiment is caused to vibrate in respective vibration modes (PL (in the figures) indicating �a node�, PH indicating �a loop�, and PM indicating �an intermediate area� (which is not the node but which has a small amplitude)), with FIG. 5A showing the vibration mode 1, FIG. 5B showing the vibration mode 2, FIG. 5C showing the vibration mode 3, and FIG. 5D showing the vibration mode 4;
A case in which the vibration occurring in the side plates of the bucket of a construction machine is suppressed, so that the noise emitted from these side plates is reduced, will be described as a first embodiment. FIG. 1 shows the side plate 11 of the bucket 10 that is the object of vibration damping in the first embodiment, and FIG. 2 shows a sectional view of the side plate 11. As is shown in FIG. 2, a plurality of thin steel plates 21 are laminated on the side plate 11 of the bucket 10, thus forming laminated plate 20. Furthermore, relatively thick steel protective plate 30 that protect the thin plates 21 are further superimposed on the laminated plate 20, and the entire peripheries 20 a are fastened to the side plate 11 by fillet welding as indicated by the hatching shown in FIG. 1. The protective plate 30 is installed in order to prevent the thin plates 21 from becoming worn by earth and sand or the like. Furthermore, working in which protective plate 30 is not installed on the laminated plate 20 is also possible. Furthermore, in regard to the method that is used to fasten the peripheries (peripheral edges) of the laminated plate 20 to the side plate 11, besides a method in which fastening is accomplished by all round fillet welding as described above, fastening can also be accomplished by an arbitrary fastening method such as intermittent fillet welding, intermittent plug welding, bolt fastening or the like. For example, these fastening methods are described in Japanese Patent Application Laid-Open No. 2000-219168, U.S. Pat. No. 6,332,509 and Japanese Patent Application Laid-Open No. 2002-48188.
FIG. 3 shows the amount of deformation of the laminated plate 20 corresponding to the loops and nodes of the vibration mode 1 in a case where the base material 11 is caused to vibrate in this vibration mode 1 at a specified frequency. FIG. 5A shows the distribution of the size of the amplitude of the vibration in a case where the base material 11 is caused to vibrate in the abovementioned vibration mode 1; here, the respective parts are indicated by different patterns corresponding to the size of the amplitude. In FIG. 5A, the parts indicated by PH are the parts of loops where the amplitude is large, and the parts indicated by PL are the parts where the amplitude is 0, i. e., the parts of nodes. Thus, even in the case of the same structure, the size of the amplitude differs according to the part; there are both parts where the amplitude is large, i. e., parts that are loops of the vibration mode 1, and parts where the amplitude is small, i. e., parts that are nodes of the vibration mode 1.
The part G forming a node of the vibration mode 1 is inherently a part where the amount of deformation of the thin plates 21, 21′ forming the laminated plate 20 is small or almost non-existent. Accordingly, even if this part is fastened, the vibration damping effect that is lost is extremely small or almost non-existent. Consequently, the deleterious effect on the vibration damping effect caused by the fastening of the laminated plate 20 can be suppressed to a minimum. Thus, in the first embodiment, since the construction is devised so that the optimal part G in the interior part of the laminated plate 20 is fastened, there is no loss of the vibration damping effect due to thermal strain during manufacture or �floating� caused by external forces during use. Furthermore, the independent deformation of the thin plates 21 that make up the laminated plate 20 is not impeded, so that a high vibration damping effect can be maintained. Moreover, in the first embodiment, a part other than the loop for a single vibration mode with a single frequency is fastened; however, a part other than a loop for respective vibration modes at a plurality of frequencies may also be fastened.
Thus, in the second embodiment, the standard for the requirement of noise countermeasures with respect to the bottom plate 12 is clearly set as the �ratio Wp/Hs of the width Wp of the bottom plate to the height Hs of the side plate being 1.47 or greater�, and the bottom plate 12 is reinforced according to this standard. As a result, noise countermeasures can be taken with the minimum required effort for the minimum required buckets (among various types of buckets), without performing noise experiments or the like. Accordingly, the cost of the design and manufacture of buckets can be greatly reduced. Furthermore, the question of whether or not the bottom plate 12 should be reinforced can be decided from the dimensions of respective parts in the design stage when buckets are newly designed, so that confirmation by noise experiments or the like is unnecessary. Accordingly, the process from design to manufacture can be shortened.
As is shown in FIG. 10, the size of the amplitude differs according to the part even if the structure is the same, so that there are parts where the amplitude is large, i. e., parts that form loops of the vibration mode, and parts where the amplitude is small, i. e., parts that form nodes of the vibration mode. It is conceivable that the parts that form loops of the vibration mode in the corner parts 16 might be the main sources of noise emitted from the bottom plate 12. Accordingly, the part K that forms the loop of the vibration mode in the corner parts 16 are found from the amplitude distribution shown in FIG. 10, and connecting members 15 are attached in the part K. In Example 2, the system is devised so that reinforcement is effected by attaching connecting members 15 only in the part K that forms the loop of the vibration mode in the corner parts 16 where the side plate 11 and bottom plate 12 are connected; accordingly, reinforcement of the bottom plate 12 is accomplished by the minimum necessary reinforcement, so that the deleterious effect on the performance of the construction machine can be kept to a minimum.
Connecting members 15 are attached in a configuration in which the ratio Wp′/Hs of the substantial width Wp′ of the bottom plate 12 to the height Hs of the side plate 11 is smaller than 1.47. As is shown in FIGS. 8A and 8B, connecting members 15 are respectively attached to both corner parts 16 of the bottom plate 12, and the length of a line segment that connects the connection parts 12 a of the connecting members 15 is designated as the �substantial bottom plate width Wp′�. Here, as is shown in FIG. 9, it is assumed that the value of the ratio Wp/Hs prior to the attachment of the connecting members 15 is J2, and that this is in the region Q where the noise contribution T2 of the bottom plate 12 is the dominant factor. Connecting members 15 are attached in the region Q so that the reduction of the noise emitted from the bottom plate 12 is most efficient in reducing the noise of the bucket 10.
In the abovementioned Examples 1 through 5, a case in which buckets 10 in which the ratio Wp/Hs is 1.47 or greater are reinforced is envisioned. However, working in which reinforcing members such as connecting members 15 or the like are attached in parts where the side plate 11 and bottom plate 12 are connected on the inside of the bucket 10, i. e., on the opposite side from the surfaces to which the laminated plate 20 is attached, is also possible. In this case, the reinforcing members may be disposed over the entire region of the inside connection parts of the side plate 11 and bottom plate 12, or may be disposed in only some of the inside connection parts.
Here, the results of a test confirming the relationship between the noise reducing effect and the welding pitch of the inner plates 111 will be described. Basically, the noise reducing effect of a vibration damping device using laminated plate increases as the number of points constraining the laminated plate is reduced, i. e., as the length of the welded parts becomes shorter. As will also be understood from the previous description of the operation, the reason for this is that relative displacement between the layers is facilitated, so that a larger frictional force is generated. Accordingly, it would appear that a larger welding pitch of the inner plates 111 is desirable. However, if the welding pitch is excessively large, the conflicting problem of the generation of a knocking sound due to knocking between the inner plates caused by local vibration of the peripheral edges of the inner plates arises.
Accordingly, it is desirable to set the welding pitch of the inner plates 111 in the third embodiment, i. e., the length L1 of the contact parts 111 b in the circumferential direction, at a value between 100 mm and 280 mm. The length L1 of the contact parts 111 b in the circumferential direction is defined as shown in FIG. 18.
Next, a fourth embodiment will be described with reference to FIGS. 20 through 23B. The fourth embodiment is an embodiment in which laminated plate is applied to the hopper of a mobile crusher. In this mobile crusher 120, as is shown in FIG. 20, a motive force device 123 is mounted on the rear part of a base 122 equipped with a track type propulsion device 121, a crusher is mounted on the central part of the base 122. Matter constituting the object of crushing which is placed into a hopper 125 disposed on the front part of the base 122 (e. g., rocks, concrete debris, wood, construction waste or the like) is crushed to a specified size by the crusher 124, and is fed out to the rear by a feed-out device which extends to the rear from the lower part of the base 122.
According to the measurement data shown in FIG. 17, it is desirable to set the spacing between the protruding parts 131 a of the inner plates 131 in the fourth embodiment, i. e., the length L2 of the cut-out parts 131 b in the circumferential direction, in the range of 100 mm to 280 mm. The length L2 of the cut-out parts 131 b in the circumferential direction is defined as shown in FIG. 24.
Furthermore, the present invention is not limited to the third and fourth embodiments; alterations and modifications may be performed within the scope of the present invention. For instance, an example in which the inner plates 111 were constrained by intermittent welding in five places on the side of the wear plate 108 (i. e., the cut-out parts 111 a) was described; however, such constraints may be appropriately selected in accordance with the required strength and the frequency band of the noise for which a reduction is desired.
In the abovementioned third and fourth embodiments, a description was presented using a construction example in which the thickness of the laminated plate 110, 130, i. e., the total laminated height of the inner plates and outer plates, was set at substantially the same height as the height of the wear plates 108, 138. However, it is desirable to set the total laminated height at a height that is equal to or less than the height of the wear plates 108, 138; in such a case, wear or damage of the welded parts of the laminated plate can be more securely prevented by the wear plates. The bucket 101 of a hydraulic excavator (including respective constituent members such as the side plate 3 or the like) and the hopper 125 of a mobile crusher (including respective constituent members such as the inclined wall surfaces 128 or the like) were cited as examples of machine members to which the laminated plate was bonded. However, the laminated plate can be applied to arbitrary machine members for which a reduction in noise is desired, and it goes without saying that such laminated plate can also be applied to buckets of wheel loaders or hoppers of fixed crushing equipment. As was described above, invasion by rain water can be prevented by continuously welding the outer plate of the laminated plate so that the occurrence of rusting between plates can be prevented, and the degree of constraint of the inner plates of the laminated plate can be kept low by intermittently welding these inner plates; accordingly, superior vibration damping characteristics can be obtained so that a vibration damping device that has a conspicuous noise reducing effect can be obtained.
An example in which the first embodiment and second embodiment are combined is also possible. Specifically, as is shown in FIG. 34, the bucket 200 is devised in the same manner as in the first embodiment so that laminated plate 220 is attached to the side plate 211 by all round fillet welding 230, and the interior parts of the laminated plate 220 and the side plate 211 are welded by plug welding 250 in parts corresponding to the part D shown in FIG. 1 (optimization of plug welding). Furthermore, in the bucket 200, bridge form connecting members 215 that connect the side plate 211 and bottom plate 212 are attached in specified part K (see FIG. 10) among the corner parts where the side plate 211 and bottom plate 212 are connected (in the same manner as in the second embodiment). The relationship between the width Wp of the bottom plate 212 and the height Hs of the side plate 211 in this embodiment is in the region Q shown in FIG. 9 (i. e., the ratio Wp/Hs is 1.47 or greater). Moreover, in FIG. 34, reinforcing members 214 are fastened to the corner parts where the side plate 211 and bottom plate 212 are connected; however, the use of reinforcing members 214 may be omitted.
The noise energy reduction rate obtained using such a combination example will be described with reference to FIG. 35. Here, the noise energy reduction rate Ed is determined by experimentally measuring the noise energy generated before and after the attachment of laminated plate 220 and/or connecting members 215, and calculating this noise energy reduction rate as Ed=[(noise energy E1 generated prior to attachment−noise energy E2 generated after attachment)/E1]�100(%). The side plate contribution and the bottom plate contribution indicate the rates in the reduction of the noise respectively emitted from the side plate and bottom plate. �OVERALL� in FIG. 35 indicates the value obtained by totaling the respective reduction rates of the side plate and bottom plate after multiplying these rates by the contribution rates. In the bucket 200 of the present example prior to the attachment of laminated plate 220 or the like, the side plate contribution rate is 39%, and the bottom plate contribution rate is 61%; accordingly, this is a case where the contribution of the noise emitted from the bottom plate 212 is larger.
Item 1: all round fillet welding 230 of the laminated plate 220, and plug welding (not shown in the figures) in the parts of �loops� of the vibration mode.
Item 3: manufacture (no plug welding) so that �floating� is not generated in the laminated plate 220, with the fact that the manufacturing cost is extremely high when all round fillet welding 230 of the laminated plate 220 to the side plate 211 being ignored.
The noise energy reduction rates in the buckets with the abovementioned respective items will be described in comparative terms. Item 3 is the ideal attachment state of the laminated plate 220; however, this involves an extremely high manufacturing cost, and there are also problems in terms of the occurrence of floating caused by collisions during the use of the bucket, so that this item is not suitable for practical use. On the other hand, in the case of item 2 which uses the first embodiment, it is seen that a reduction rate that is substantially close to that of the ideal attachment state can be achieved. Moreover, in the case of item 1 which differs from Embodiment 1, in addition to the fact that the reduction rate is low, no effect on the bottom plate 212 is obtained, either. It appears that this is due to the fact that the vibrational energy cannot be sufficiently dissipated because of the insufficiency of the attenuating effect. Item 4 is an example that was worked in order to investigate the effect of the connecting members 215 alone; in this case, the reduction rate of the side plate contribution was 7%. It is inferred that this is due to the fact that the vibration amplitude of the peripheral edge parts of the side plate 211 is reduced by the connecting members 215, which also serve to reinforce the bottom plate 212. Thus, the reason that noise is reduced by the reinforcement of the bottom plate 212 is that the rigidity Y of the bucket 200 is increased, and the reason that noise is reduced by the laminated plate 220 is that the damping ratio ζ of the bucket 200 is increased. It is known that the vibrational energy Ev within a fixed period of time is proportional to �1/{2Yζ�(1−ζ2)1/2}�, and if an improvement in rigidity and an improvement in damping characteristics are simultaneously achieved, an effect that is greater than that obtained by simple addition is achieved.
Item 5 is a case in which the first embodiment (item 2) and second embodiment (item 4) are both used together (i. e., the example of FIG. 34). In cases where the second item and fourth item are used independently, the reduction rates are merely added to produce item 6. Accordingly, in item 5, an effect that is greater than additive is obtained as a result of a synergistic effect. Furthermore, in cases where plug welding is performed in the loops (item 1), the laminated plate has no effect on the bottom plate; accordingly, even if connecting members are attached, the effect is reduced (item 7).
Item 8: as in the third embodiment, the inner plates 311 of the laminated plate 320 are intermittently welded, and the outer plate 312 is welded by all round fillet welding; here, during welding, the fact that the manufacturing cost is extremely high is ignored, and manufacture is performed (without plug welding) so that �floating� does not occur in the laminated plate 320.
Item 9: as in the third embodiment, the inner plates 311 of the laminated plate 320 are intermittently welded, and the outer plate 312 is welded by all round fillet welding; furthermore, plug welding (not shown in the figures) is performed in the parts of the �loops� of the vibration mode.
The noise energy reduction rates in buckets with the abovementioned items 8 through 12 will be described in a comparative description. Item 8 is similar to item 3; although the reduction rate is high, the degree of practicality is low because of problems of manufacturing cost and floating. In the case of item 9, plug welding is performed in the loops, so that the reduction rate is greatly reduced. In the case of item 10, in which plug welding 250 is performed in the part D as in Embodiment 1 (in contrast to item 9), the positions of plug welding are optimized, so that there is no lowering of the reduction rate, and a practical structure is obtained. In the case of item 11 (i. e., the present embodiment shown in FIG. 36), compared to item 10, connecting members 215 are further attached as in the second embodiment, so that an extremely large reduction rate is obtained. In the case of item 11, as is clear from a comparison with item 12, an effect that is greater than a simple additive effect is obtained as a result of a synergistic effect.
Specifically, the laminated plate shown in FIG. 37C consists of a specified number of inner plates 912 that are laminated on the machine 901 that is the object of vibration damping, and an outer plate 911 which is further laminated on the outside of this specified number of inner plates 912, and which has the same area and same shape as the inner plates 912. As a result, the specified number of inner plates 912 are clamped by the machine 901 that is the object of vibration damping and the outer plate 911. Furthermore, a connecting member 918 is disposed on the entire periphery of the outer plate 911. The laminated plate 910 is positioned by causing the specified number of inner plates 912 and the outer plate 911 to contact the inner-wall of the connecting member 918. Furthermore, the outer plate 911 and connecting member 918 are connected by all round welding (the area of all round welding is indicated by 920), and the connecting member 918 and the machine 901 that is the object of vibration damping are further connected by all round welding (the area of this all round welding is indicated by 919). As a result, the machine 901 that is the object of vibration damping and the outer plate 911 are connected via the connecting member 918 so that the specified number of inner plates 912 are tightly sealed.
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