Cover device and construction machine

Abstract

A cover device 40 includes: a cover 50 that comes into contact with an outer surface 21a of a boom 21 (front implement 20) to close an access hole 30; and a bracket 60 that is positioned inside the boom 21, is attached to the boom 21 via a screw seat 90, and is detachably fastened to the cover. The attachment position of the bracket 60 and the boom 21 is located farther than an outer peripheral edge 50a of the cover 50 with respect to the access hole 30, and the attachment position of the bracket 60 and the cover 50 is located closer to a center 30b than to an inner peripheral edge 30a of the access hole 30.

Description

Covering equipment and construction machinery

[0001] The present invention relates to a cover device that closes an access hole formed in a front working implement of a construction machine, and to the construction machine.

[0002] Conventionally, techniques for attaching covers to structures in construction machinery have been known. For example, Patent Document 1 describes an undercover device for construction machinery in which an undercover is fastened to the underside of a frame of a lower traveling body with a plurality of fasteners, vibration-isolating rubber is provided between the frame and the undercover, and spacers are disposed between the fasteners and bolt insertion holes, thereby reducing vibration transmitted from the frame to the fasteners and the undercover.

[0003] Patent No. 5179419

[0004] The front working implement of a construction machine is a welded structure formed in a hollow box shape. A maintenance access hole is formed to allow access to the interior of the implement, and a cover is sometimes attached to the access hole. When the cover is fastened to the front working implement with fasteners such as bolts, vibrations from the construction machine are transmitted to the fasteners and the cover via the front working implement. In particular, the front working implement is subjected to large vibrations and shocks as it moves during work such as excavation. As a result, cracks may occur around the insertion holes of the front working implement, deformation of the cover may occur, and damage to the fasteners may occur. Even if spacers are placed around the bolt insertion holes as in the undercover device described in Patent Document 1, damage originating from the insertion holes may not be sufficiently prevented in the front working implement, which moves widely and is prone to deformation during work.

[0005] The present invention was made in consideration of these problems, and its purpose is to provide a cover device that covers a maintenance access hole formed in the front working implement of a construction machine and to more appropriately protect the front working implement.

[0006] In order to achieve the above object, the cover device of the present invention is a cover device that covers a maintenance access hole formed in a front working machine of a construction machine that is formed in the shape of a hollow box, and includes a cover that abuts against the outer surface of the front working machine to cover the access hole, and a bracket that is attached to the inner surface of the front working machine and to which the cover is removably fastened, wherein the bracket is attached to the inner surface of the front working machine at a position radially outer than the inner peripheral edge of the access hole, and the cover is removably fastened to the bracket at a position closer to the center of the access hole than the inner peripheral edge of the access hole.

[0007] In order to achieve the above object, the construction machine of the present invention is a construction machine comprising a vehicle body, a hollow box-shaped front working machine provided on the vehicle body, and a maintenance access hole provided on the front working machine, and further comprising a cover device including a cover that abuts against the outer surface of the front working machine to close the access hole, and a bracket that is attached to the inner surface of the front working machine and to which the cover is removably fastened, wherein the bracket is attached to the inner surface of the front working machine at a position radially outer than the inner circumferential edge of the access hole, and the cover is removably fastened to the bracket at a position closer to the center of the access hole than the inner circumferential edge of the access hole.

[0008] According to the present invention, it is possible to more appropriately protect the cover device that covers the maintenance access hole formed in the front working implement of a construction machine, and the front working implement.

[0009] 5 is an enlarged cross-sectional view showing the area surrounded by the two-dot chain line in FIG. 8; and FIG. 6 is a cross-sectional view showing the area surrounded by the two-dot chain line in FIG. 4. The present invention will be described in detail below with reference to the accompanying drawings, in which: FIG. 5 is a side view of a hydraulic excavator according to an embodiment; FIG. 6 is a perspective view showing a part of the outer surface of a boom; and FIG. 7 is an explanatory view showing a part of the outer surface of a boom with an access hole blocked by a cover device. The present invention will be described in detail with reference to the accompanying drawings, in which: FIG. 5 is a cross-sectional view showing the area surrounded by the two-dot chain line in FIG. 8; and FIG. 7 is a perspective view showing the area surrounded by the two-dot chain line in FIG. 4; and

[0010] An embodiment of the present invention will be described below with reference to the drawings. In the following description, the front-rear, left-right, and up-down directions of the construction machine will be described with reference to an operator riding on the construction machine. FIG. 1 is a side view showing a hydraulic excavator according to an embodiment. The hydraulic excavator 1 is a construction machine used, for example, for excavating earth and sand at a construction site. As shown in FIG. 1, the hydraulic excavator 1 includes a vehicle body 10 and a front working implement 20, which is a working device.

[0011] The vehicle body 10 includes a lower traveling structure 11 and an upper rotating structure 12. The lower traveling structure 11 includes crawlers 11a driven by a traveling hydraulic motor (not shown) as a drive device for traveling the hydraulic excavator 1. The upper rotating structure 12 is driven by a swing hydraulic motor (not shown) and is rotatably mounted on the lower traveling structure 11. A cab 13 for an operator is provided at the front of the frame 12a of the upper rotating structure 12. A fuel tank 14, a machinery room 15, a counterweight 16, and the like are provided behind the cab 13 of the upper rotating structure 12. The machinery room 15 houses an engine (not shown), a hydraulic pump (not shown) that is driven by the engine and pressurizes hydraulic oil to be supplied to the traveling hydraulic motor, the swing hydraulic motor, and each component of the front work implement 20 (described later).

[0012] The front work implement 20 is an articulated work device and is attached to the front of the frame 12a of the upper rotating body 12. The front work implement 20 includes a boom 21, an arm 22, a bucket 23, and multiple hydraulic cylinders 24, 25, and 26. The boom 21 and arm 22 of the front work implement 20 are welded structures formed into a hollow box shape. The boom 21 is connected to the upper rotating body 12 so as to be able to move up and down. The arm 22 is connected to the boom 21 so as to be able to move up and down. The bucket 23 is a hydraulic work tool used for excavation work and the like, and is connected to the arm 22 so as to be able to move up and down. If the bucket 23 is replaced with a hydraulic breaker or hydraulic crusher, the replaced equipment functions as the hydraulic work tool. The hydraulic cylinder 24 is connected between the upper rotating body 12 and the boom 21 and adjusts the angle of the boom 21 by hydraulically extending and retracting. The hydraulic cylinder 25 is connected between the boom 21 and the arm 22, and adjusts the angle of the arm 22 by extending and retracting hydraulically. The hydraulic cylinder 26 is connected between the arm 22 and the bucket 23, and adjusts the angle of the bucket 23 by extending and retracting hydraulically.

[0013] Figure 2 is a perspective view showing a portion of the outer surface of the boom 21. An access hole 30 is formed in the outer surface 21a of the side plate portion 211 (Figure 1) in the left-right direction of the boom 21 as an opening that allows an operator to perform maintenance such as inspection and repair of the front working implement 20. During normal operation of the hydraulic excavator 1, this access hole 30 is closed with a cover to prevent foreign matter from entering the interior of the front working implement 20.

[0014] When fastening the cover to the front working implement 20 using fasteners, vibrations from the hydraulic excavator 1 are transmitted to the fasteners and the cover via the front working implement 20. In particular, the front working implement 20 is subjected to large vibrations and shocks as it operates for work such as excavation. As a result, cracks may occur around the fastener insertion holes in the front working implement 20, the cover may be deformed, the fasteners may be broken, and so on. To prevent such damage from occurring, the hydraulic excavator 1 is provided with a cover device 40.

[0015] (Cover Device) FIG. 3 is an explanatory diagram showing a portion of the outer surface 21a of the boom 21 with the access hole 30 blocked by the cover device 40. FIG. 4 is an exploded perspective view showing the cover device 40. FIG. 5 is a front view of the cover device 40 as viewed from the inner surface 21b of the boom 21. FIG. 6 is a perspective view of the cover device 40 with a portion removed as viewed from the inner surface 21b of the boom 21. FIG. 7 is a perspective view of the cover device 40 with a further portion removed as viewed from the inner surface 21b of the boom 21. FIG. 8 is a cross-sectional view taken along line A-A in FIG. 5. FIG. 9 is an enlarged cross-sectional view showing the area surrounded by the two-dot chain line in FIG. 8. FIG. 10 is a perspective view showing the members surrounded by the two-dot chain line in FIG. 4. The cover device 40 includes a cover 50, two brackets 60, a vibration-isolating rubber 101 (first vibration-isolating rubber), a vibration-isolating rubber 102 (second vibration-isolating rubber), and a vibration-isolating rubber 103 (third vibration-isolating rubber).

[0016] (Cover) As shown in FIG. 3 , the cover 50 is a disc-shaped member that closes the access hole 30 from the outside of the front attachment 20. The cover 50 is not limited to a disc-shaped member and may be, for example, a rectangular flat plate member. The cover 50 is formed with a diameter larger than the diameter of the access hole 30 and abuts against the outer surface 21 a of the boom 21 via vibration-damping rubber 102. The vibration-damping rubber 102 is formed in an annular shape and is attached to the cover 50 by fitting a groove formed along its inner circumferential surface into the outer circumferential edge of the cover 50 from the radially outer side. The vibration-damping rubber 102 may also be attached to the cover 50 with an adhesive.

[0017] The cover 50 has a front surface 51 formed with a cover grip 53 that an operator grips when attaching or removing the cover 50. The cover 50 also has bolt holes 501 ( FIG. 4 ) for fastening a bracket 60 (a second bracket 80, described later). The bolt holes 501 are spaced apart, two at a time, on the outer side of the cover grip 53, with two bolt holes 501 spaced apart from each other across the center of the cover 50. Furthermore, as shown in FIG. 5 , a chain 130 is attached to the inner surface 21 b of the boom 21 and attached to the back surface 52 of the cover 50. This prevents an operator from accidentally dropping the cover 50 after removing it. The chain 130 is not shown in FIG. 8 .

[0018] (Bracket) As shown in Figures 5 to 8 , each bracket 60 is disposed inside the boom 21. Specifically, two brackets 60 are disposed near the access hole 30 and spaced apart along the longitudinal direction of the boom 21 (the front-to-rear direction of the hydraulic excavator 1). Each bracket 60 includes a first bracket 70 and a second bracket 80.

[0019] (First Bracket) As shown in FIGS. 4 to 8 , the first bracket 70 includes a main body portion 72 and a fastening surface portion 74 provided to close one end of the main body portion 72. As shown in FIGS. 6 and 7 , the main body portion 72 has a flat base portion 721 and three rib portions 722 extending along each edge and the center of the base portion 721. Two bolt insertion holes 702 ( FIG. 4 ) are formed in the other end of the main body portion 72 opposite the access hole 30. Furthermore, two bolt insertion holes 703 ( FIG. 4 ) are formed in the fastening surface portion 74 for fastening the second bracket 80. As shown in FIG. 8 , the first bracket 70 is disposed so that the main body portion 72 extends along the inner surface 21 b of the boom 21.

[0020] As shown in FIG. 8 , the boom 21 has a screw seat 90 attached by welding to its inner surface 21b at a position farther away from the access hole 30 than the outer peripheral edge 50a of the cover 50. In this embodiment, the screw seat 90 is an attachment portion for the bracket 60 on the boom 21 (front work implement 20). Like the bracket 60, two screw seats 90 are arranged at intervals along the longitudinal direction of the boom 21 (the fore-aft direction of the hydraulic excavator 1). The first bracket 70 is attached to the boom 21 by fastening bolts B2, which serve as fasteners, inserted through the two bolt insertion holes 702 to the screw seats 90. In this manner, the attachment position of the first bracket 70 and the boom 21 (the position of the screw seat 90) is located farther away from the access hole 30 than the outer peripheral edge 50a of the cover 50. The fastening surface portion 74 of the first bracket 70 is configured to be positioned slightly protruding from the inner peripheral edge 30a of the access hole 30.

[0021] 6, 8, and 10, the second bracket 80 includes a main body portion 82 and a fastening surface portion 84 provided to close one end of the main body portion 82. As shown in Fig. 10, the main body portion 82 has a flat plate-shaped base plate portion 821 and two rib portions 822 extending along each edge of the base plate portion 821. Two elongated bolt insertion holes 803 (Fig. 4) extending along the thickness direction of the boom 21 are formed at the other end of the main body portion 82.

[0022] 8, the second bracket 80 is disposed so that the main body 82 abuts against the fastening surface 74 of the first bracket 70, and extends along the thickness direction of the boom 21 inside the access hole 30. The first bracket 70 and the second bracket 80 are fastened together by fastening bolts B3, which are inserted into the bolt insertion holes 703, 803 (FIG. 4), with nuts N3.

[0023] 10, the second bracket 80 is provided with anti-vibration rubber 101. The anti-vibration rubber 101 is attached with an adhesive to L-shaped rubber attaching members 87 that are attached to the rib portions 822 of the main body portion 82, one by one. As shown in FIG. 8, in the arrangement state of the second bracket 80, the anti-vibration rubber 101 is positioned closer to the first bracket 70 than the main body portion 82, and is positioned closer to the inner surface 21b of the boom 21 than the first bracket 70. The second bracket 80 is fastened to the first bracket 70 at a position where the anti-vibration rubber 101 abuts against the inner surface 21b of the boom 21.

[0024] As described above, the bolt insertion hole 803 of the main body 82 is formed as an elongated hole extending along the thickness direction of the boom 21. As a result, by adjusting the fastening position of the bolt B3 in the bolt insertion hole 803, the position of the second bracket 80 in the thickness direction of the boom 21 can be adjusted. Furthermore, by disposing the second bracket 80 so that the vibration-damping rubber 101 abuts against the inner surface 21b of the boom 21, the second bracket 80 is positioned in the thickness direction of the boom 21. Therefore, even if the thickness of the boom 21 changes for some reason, such as when a pipe-shaped member that protrudes from the inner surface 21b of the boom 21 is attached along the periphery of the access hole 30, the second bracket 80 can be easily positioned.

[0025] Additionally, the second bracket 80 is configured so that the fastening surface 84 is generally flush with the outer surface 21a of the boom 21 when fastened to the first bracket 70. Two bolt insertion holes 801 are formed spaced apart in this fastening surface 84, as shown in Figures 9 and 10 . Anti-vibration rubber 103 is affixed with an adhesive around each bolt insertion hole 801, and furthermore, a spacer 86 is provided inside the anti-vibration rubber 103, protruding further than the anti-vibration rubber 103.

[0026] As shown in FIG. 9 , bolts B1 serving as fasteners are inserted through the bolt insertion holes 501 of the cover 50 and the bolt insertion holes 801 of the second bracket 80 via washers W1, and the bolts B1 are fastened to nuts N1. This fastens the cover 50 and the second bracket 80 together, with the vibration-isolating rubber 103 abutting against the back surface 52 of the cover 50 and the spacer 86 abutting against the washer W1. As a result, the axial force of the fastening by the bolts B1 and nuts N1 can be secured with the vibration-isolating rubber 103 interposed between the cover 50 and the second bracket 80. As shown in FIG. 8 , the attachment position of the cover 50 and the second bracket 80 (the fastening position by the bolts B1 and nuts N1) is located closer to the center 30b of the access hole 30 than the inner periphery 30a of the access hole 30. Furthermore, when fastened to the second bracket 80, the cover 50 abuts against the outer surface 21a of the boom 21 via the vibration-isolating rubber 102.

[0027] (Attaching and Removing the Cover) When an operator enters the interior of the boom 21 through the access hole 30 in the cover apparatus 40 configured as described above, first, as shown in FIG. 6 , the operator releases the fastening between the cover 50 and the second bracket 80 and positions the cover 50 away from the outer surface 21 a of the boom 21. Then, as shown in FIG. 7 , the operator removes the second bracket 80 from the first bracket 70. This prevents the bracket 60 from narrowing the opening area of ​​the access hole 30, allowing the operator to easily enter the interior of the boom 21 through the access hole 30. Note that when reattaching the cover 50 to the cover apparatus 40, the operator simply fastens the second bracket 80 to the first bracket 70 and then fastens the cover 50 to the second bracket 80 in the reverse order of the above.

[0028] As described above, the cover device 40 of this embodiment closes the maintenance access hole 30 formed in the hollow box-shaped front working implement 20 provided on the hydraulic excavator 1 (construction machine). The cover device 40 includes a cover 50 that abuts against the outer surface 21a of the boom 21 (front working implement 20) to close the access hole 30, and a bracket 60 that is located inside the boom 21 and attached to the inner surface 21b of the boom 21 via a screw seat 90 (welded portion) and to which the cover 50 is detachably fastened.

[0029] With this configuration, the bracket 60 is attached to the boom 21 via the screw seat 90 as an attachment part (welded part) welded to the boom 21, and the cover device 40 can be detachably attached to the boom 21 by the bracket 60. As a result, there is no need to form insertion holes or fastening holes for bolts to fasten the cover device 40 to the boom 21, and it is possible to prevent cracks from occurring at these points.

[0030] Furthermore, in this embodiment, the mounting portion (screw seat 90) of the bracket 60 on the boom 21 is located at a position farther away from the access hole 30 than the outer peripheral edge 50a of the cover 50. In other words, the bracket 60 is mounted to the inner surface 21b of the boom 21 (front attachment 20) at a position radially outward of the access hole 30 than the inner peripheral edge 30a of the access hole 30. Therefore, the screw seat 90 can be located at a position far away from the periphery of the access hole 30, where relatively high stress is likely to occur, and durability in the vicinity of the mounting position of the bracket 60 to the boom 21 can be improved.

[0031] Furthermore, the attachment position of the bracket 60 and the cover 50 (the fastening position by the bolt B1 and nut N1) is closer to the center 30b of the access hole 30 than the inner peripheral edge 30a of the access hole 30. That is, the cover 50 is detachably fastened to the bracket 60 at a position closer to the center of the access hole 30 than the inner peripheral edge 30a of the access hole 30. Therefore, as shown in FIG. 8 , the cover 50 and the bracket 60 (second bracket 80) can be fastened together without significantly protruding from the access hole 30. This prevents the bracket 60 from becoming too large and suppresses swinging of the bracket 60 due to vibrations from the front working implement 20, thereby improving the durability of the bolt B1 fastening the cover 50 and the bracket 60 itself. As described above, the configuration of the embodiment allows for more appropriate protection of the cover device 40 that covers the maintenance access hole 30 formed in the front working implement 20 of the hydraulic excavator 1 and the front working implement 20.

[0032] Additionally, a vibration-isolating rubber 101 (first vibration-isolating rubber) is disposed between the inner surface 21b of the boom 21 and the bracket 60. With this configuration, the vibration-isolating rubber 101 reduces vibrations transmitted from the boom 21 to the bracket 60, thereby more appropriately protecting the cover 50, the bracket 60, and the bolts B1 to B3.

[0033] Furthermore, vibration-isolating rubber 102 (second vibration-isolating rubber) is disposed between the outer surface 21a of the boom 21 and the cover 50. With this configuration, the vibration-isolating rubber 102 reduces vibrations transmitted from the boom 21 to the cover 50, thereby more appropriately protecting the cover 50. Furthermore, by preventing a gap from being formed between the boom 21 and the cover 50, the intrusion of water and dust into the access hole 30 can be suppressed.

[0034] Furthermore, a vibration-isolating rubber 103 (third vibration-isolating rubber) is disposed between the bracket 60 and the cover 50. With this configuration, the vibration-isolating rubber 103 reduces vibrations transmitted from the boom 21 to the cover 50 via the bracket 60, thereby more appropriately protecting the cover 50 and the bolt B1. Furthermore, by preventing a gap from being formed between the bracket 60 and the cover 50, it is possible to prevent water and dust from entering the access hole 30 through the bolt insertion hole 501 formed in the cover 50.

[0035] Bracket 60 is made up of a first bracket 70 attached to boom 21 via screw seat 90 (welded portion), and a second bracket 80 detachably attached to first bracket 70 and positioned within access hole 30. Second bracket 80 is detachably fastened to cover 50. With this configuration, by removing second bracket 80 from first bracket 70, the opening range of access hole 30 is secured, allowing an operator to easily enter boom 21.

[0036] Furthermore, bolt insertion holes 801, which are the fastening positions of second bracket 80 and first bracket 70, are formed as elongated holes extending in the thickness direction of boom 21. This configuration makes it possible to adjust the position of second bracket 80 in the thickness direction of boom 21 in accordance with changes in the thickness of boom 21. Furthermore, vibration-damping rubber 101 is disposed between boom 21 and second bracket 80. With this configuration, second bracket 80 is disposed so that vibration-damping rubber 101 abuts against inner surface 21b of boom 21, making it easy to position second bracket 80 in the thickness direction of boom 21.

[0037] Furthermore, two brackets 60 and two screw seats 90, which serve as attachment portions for the brackets 60 to the boom 21, are arranged at a distance from each other along the longitudinal direction of the boom 21. This configuration makes it easier to ensure space for attaching the brackets 60 and the screw seats 90 to the inner surface 21b of the boom 21, compared to when the brackets 60 and the screw seats 90 are arranged at a distance from each other in the lateral direction of the boom 21. As a result, the size of the access hole 30 can be ensured to be sufficient. Furthermore, by arranging two brackets 60 as described above, the cover 50 can be stably supported without being cantilevered, and further, twisting of the cover 50 can be more appropriately suppressed.

[0038] Although the description of the embodiment has been completed, aspects of the present invention are not limited to this embodiment. For example, in this embodiment, the vibration-isolating rubber 103 is provided between the second bracket 80 and the cover 50, but the vibration-isolating rubber 103 may be omitted. Figure 11 is a cross-sectional view showing the second bracket 80, the cover 50, and the vicinity of the attachment position when the vibration-isolating rubber 103 is omitted. In this case, as shown in the figure, the vibration-isolating rubber 103 and the spacer 86 can be omitted, and the fastening surface 84 of the second bracket 80 can be abutted against the cover 50.

[0039] In addition, in this embodiment, the vibration-damping rubber 101 is attached to the second bracket 80, but the vibration-damping rubber 101 may also be attached to the first bracket 70 and abut against the inner surface 21b of the boom 21.

[0040] Furthermore, in the present embodiment, the bracket 60 and the screw seat 90 are disposed at intervals in the longitudinal direction of the boom 21, but the positions of the bracket 60 and the screw seat 90 are not limited to this. Taking into account the magnitude of stress generated on the inner surface 21b of the boom 21, the bracket 60 and the screw seat 90 are preferably disposed in a range where stress is as small as possible. Furthermore, although the screw seat 90 has been described as being integrally attached to the boom 21 by being formed separately from the boom 21 and welded to the boom 21, the configuration of the screw seat 90 is not limited to this. For example, if the strength of the boom 21 is ensured, for example, by forming the relevant portion of the boom 21 sufficiently thick, the screw seat 90 may be formed by threading directly on the boom 21. Even in this case, the occurrence of cracks around the insertion hole can be suppressed, at least compared to when an insertion hole for inserting a bolt is formed in the boom 21.

[0041] Furthermore, as long as an opening range that allows an operator to enter the access hole 30 can be secured, the second bracket 80 may be fixed to the first bracket 70 in an undetachable manner, or the first bracket 70 and the second bracket 80 may be an integral member.

[0042] In this embodiment, the cover device 40 is applied to the access hole 30 formed in the side plate portion 211 of the boom 21. However, the access hole 30 may be formed in a portion such as the upper plate portion 212 or the lower plate portion 213 (FIG. 1) of the boom 21, or may be formed in the arm 22, and the cover device 40 may be applied to the access hole 30 formed in these positions.

[0043] REFERENCE SIGNS LIST 1 Hydraulic excavator 10 Vehicle body 20 Front work implement 21 Boom 21a Outer surface 21b Inner surface 30 Access hole 30a Inner peripheral edge 30b Center 40 Cover device 50 Cover 50a Outer peripheral edge 60 Bracket 70 First bracket 80 Second bracket 86 Spacer 90 Screw seat (welded portion, mounting portion) 101 Vibration isolating rubber (first vibration isolating rubber) 102 Vibration isolating rubber (second vibration isolating rubber) 103 Vibration isolating rubber (third vibration isolating rubber) 501, 702, 703, 801, 803 Bolt insertion hole B1, B2, B3 Bolt N1, N3 Nut W1 Washer

Claims

1. A cover device for covering a maintenance access hole formed in a front working machine of a construction machine formed in a hollow box shape, comprising: a cover that abuts against the outer surface of the front working machine to cover the access hole; and a bracket that is attached to the inner surface of the front working machine and to which the cover is removably fastened, wherein the bracket is attached to the inner surface of the front working machine at a position radially outward of the inner periphery of the access hole, and the cover is removably fastened to the bracket at a position closer to the center of the access hole than the inner periphery of the access hole.

2. The cover device according to claim 1, further comprising a first vibration isolating rubber disposed between the inner surface of the front working machine and the bracket.

3. The cover device according to claim 1, further comprising a second vibration isolating rubber disposed between the outer surface of the front working machine and the cover.

4. The cover device according to claim 1, further comprising a third vibration isolating rubber disposed between said bracket and said cover.

5. A cover device as described in any one of claims 1 to 4, characterized in that the bracket comprises a first bracket attached to the inner surface of the front working machine via a welded portion and a second bracket detachably attached to the first bracket and positioned within the access hole, and the cover is detachably fastened to the second bracket.

6. A cover device as described in claim 5, characterized in that the bolt insertion hole, which is the fastening position of the second bracket to the first bracket, is formed as an elongated hole extending in the thickness direction of the front working machine.

7. The cover device according to claim 6, further comprising a first vibration isolating rubber disposed between the front working mechanism and the second bracket.

8. A cover device as described in claim 1, characterized in that the bracket and the mounting portion for mounting the bracket to the front work machine are arranged in pairs at an interval along the longitudinal direction of the front work machine.

9. A construction machine comprising a vehicle body, a hollow box-shaped front working machine provided on the vehicle body, and an access hole for maintenance provided on the front working machine, further comprising a cover device including a cover that abuts against the outer surface of the front working machine to close the access hole, and a bracket that is attached to the inner surface of the front working machine and to which the cover is removably fastened, wherein the bracket is attached to the inner surface of the front working machine at a position radially outer than the inner circumferential edge of the access hole, and the cover is removably fastened to the bracket at a position closer to the center of the access hole than the inner circumferential edge of the access hole.