EP4660380A1

EP4660380A1 - Cover device and construction machine

Info

Publication number: EP4660380A1
Application number: EP24842792.4A
Authority: EP
Inventors: Nobuhiro Wakabayashi
Original assignee: Hitachi Construction Machinery Co Ltd
Current assignee: Hitachi Construction Machinery Co Ltd
Priority date: 2023-07-20
Filing date: 2024-04-25
Publication date: 2025-12-10
Also published as: CN120752396A; JPWO2025017992A1; WO2025017992A1

Abstract

A cover device 40 includes: a cover 50 in contact with an outer surface 21a of a boom 21 (front work device 20) to close an access hole 30; and a bracket 60 located inside the boom 21, attached to the boom 21 via a screw seat 90, and detachably fastened to the cover, in which an attachment position between the bracket 60 and the boom 21 is at a position more distant than an outer peripheral edge 50a of the cover 50 with respect to the access hole 30, and an attachment position between the bracket 60 and the cover 50 is on a center 30b side with respect to an inner peripheral edge 30a of the access hole 30.

Description

Technical Field

The present invention relates to a cover device that closes an access hole formed in a front work device of a construction machine, and the construction machine.

Background Art

Conventionally, in a construction machine, a technique of attaching a cover to a structure is known. For example, Patent Document 1 discloses an under cover device of a construction machine in which an under cover is fastened to a lower surface of a frame of a lower traveling body by a plurality of fasteners, a spacer is arranged between the fastener and a bolt insertion hole portion while a vibration-damping rubber is provided between the frame and the under cover, thereby reducing vibration transmitted from the frame to the fasteners and the under cover.

Prior Art Document

Patent Document

Patent Document 1: Japanese Patent No. 5179419

Summary of the Invention

Problems to be solved by the Invention

Incidentally, a front work device of a construction machine is formed of a welded structure formed in a hollow box shape, an access hole for maintenance is formed so as to allow approach into an inside of the welded structure, and a closing cover may be attached to the access hole. In a case where the cover is fastened to the front work device with a fastener such as a bolt, vibration of the construction machine is transmitted to the fastener or the cover via the front work device. In particular, since the front work device operates for work such as excavation, the front work device receives large vibration and impact. As a result, cracks around an insertion hole of the front work device, deformation of the cover, breakage of the fastener, and the like may occur. Even if the spacer is arranged around the bolt insertion hole as in the under cover device described in Patent Document 1, there is a possibility of not sufficiently preventing damage based on the insertion hole in the front work device that greatly operates and is easily deformed during the work of the construction machine.
The present invention has been made in view of such problems, and an object of the present invention is to more appropriately protect a cover device that closes an access hole for maintenance formed in a front work device of a construction machine and the front work device.

Means for Solving the Problems

To achieve the above-described object, a cover device of the present invention is a cover device that closes an access hole for maintenance formed in a front work device of a construction machine, the front work device being formed in a hollow box shape, the cover device comprising: a cover in contact with an outer surface of the front work device to close the access hole; and a bracket attached to an inner surface of the front work device and to which the cover is detachably fastened, wherein the bracket is attached to the inner surface of the front work device at a position radially outside an inner peripheral edge of the access hole, and the cover is detachably fastened to the bracket at a position on a center side of the access hole with respect to the inner peripheral edge of the access hole.
To achieve the above-described object, a construction machine of the present invention is a construction machine comprising: a vehicle body; a hollow box-shaped front work device provided in the vehicle body; and an access hole for maintenance provided in the front work device, the construction machine further comprising: a cover device including a cover in contact with an outer surface of the front work device to close the access hole, and a bracket attached to an inner surface of the front work device and to which the cover is detachably fastened, wherein the bracket is attached to the inner surface of the front work device at a position radially outside an inner peripheral edge of the access hole, and the cover is detachably fastened to the bracket at a position on a center side of the access hole with respect to the inner peripheral edge of the access hole.

Advantageous Effects of the Invention

According to the present invention, it is possible to more appropriately protect a cover device that closes an access hole for maintenance formed in a front work device of a construction machine and the front work device.

Brief Description of the Drawings

FIG. 1 is a side view illustrating a hydraulic excavator according to an embodiment.
FIG. 2 is a perspective view illustrating a part of an outer surface of a boom.
FIG. 3 is an explanatory view illustrating a part of the outer surface of the boom in a state where an access hole is closed by a cover device.
FIG. 4 is an exploded perspective view illustrating the cover device.
FIG. 5 is a front view of the cover device as viewed from an inner surface side of the boom.
FIG. 6 is a perspective view of a state in which a part of the cover device is removed as viewed from the inner surface side of the boom.
FIG. 7 is a perspective view of a state in which a part of the cover device is further removed as viewed from the inner surface side of the boom.
FIG. 8 is a cross-sectional view taken along line A-A in Fig. 5.
FIG. 9 is an enlarged cross-sectional view illustrating a range surrounded by a two-dot chain line in Fig. 8.
FIG. 10 is a perspective view illustrating a member surrounded by a two-dot chain line in Fig. 4.
FIG. 11 is a cross-sectional view illustrating a vicinity of an attachment position between a second bracket and a cover in a case where a vibration-damping rubber is omitted.

Mode for Carrying out the Invention

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that, in the following description, a front-rear direction, a right-left direction, and an up-down direction of a construction machine are expressed mainly with respect to an operator who is on board the construction machine. Fig. 1 is a side view illustrating a hydraulic excavator according to the embodiment. a hydraulic excavator 1 is a construction machine used for, for example, excavation work of earth and sand at a construction site. As illustrated in Fig. 1, the hydraulic excavator 1 includes a vehicle body 10 and a front work device 20 which is a work device.
The vehicle body 10 includes a lower traveling body 11 and an upper rotating body 12. The lower traveling body 11 includes a crawler 11a driven by a hydraulic motor for traveling (not illustrated) as a drive device for causing the hydraulic excavator 1 to travel. The upper rotating body 12 is driven by a hydraulic motor for rotating (not illustrated) and is rotatably provided on the lower traveling body 11. A cab 13 on which an operator boards is provided in a front portion on a frame 12a of the upper rotating body 12. Further, a fuel tank 14, a machine room 15, a counterweight 16, and the like are provided behind the cab 13 of the upper rotating body 12. The machine room 15 is equipped with an engine (not illustrated), a hydraulic pump (not illustrated) that is driven by the engine and pressure-feeds hydraulic oil to be supplied to the hydraulic motor for traveling, the hydraulic motor for rotating, and each component of the front work device 20 to be described below, and the like.
The front work device 20 is an articulated work device, and is attached to a front portion on the frame 12a of the upper rotating body 12. The front work device 20 includes a boom 21, an arm 22, a bucket 23, and a plurality of hydraulic cylinders 24, 25, and 26. The boom 21 and the arm 22 of the front work device 20 are welded structures formed in a hollow box shape. The boom 21 is coupled to the upper rotating body 12 so as to be movable upward and downward. The arm 22 is coupled to the boom 21 so as to be movable upward and downward. The bucket 23 is a hydraulic work tool for performing excavation work and the like, and is coupled to the arm 22 so as to be movable upward and downward. In a case where the bucket 23 is replaced with a hydraulic breaker or a hydraulic crusher, the replaced device functions as the hydraulic work tool. The hydraulic cylinder 24 is coupled between the upper rotating body 12 and the boom 21, and adjusts an angle of the boom 21 by expanding and contracting by hydraulic pressure. The hydraulic cylinder 25 is coupled between the boom 21 and the arm 22, and adjusts an angle of the arm 22 by expanding and contracting by hydraulic pressure. The hydraulic cylinder 26 is coupled between the arm 22 and the bucket 23, and adjusts an angle of the bucket 23 by expanding and contracting by hydraulic pressure.
Fig. 2 is a perspective view illustrating a part of an outer surface of the boom 21. An access hole 30 is formed in an outer surface 21a of a side plate portion 211 (Fig. 1) in the right-left direction of the boom 21, as an opening for a worker to perform maintenance such as inspection or repair of the front work device 20. During normal operation of the hydraulic excavator 1, the access hole 30 is closed by a cover in order to prevent entry of foreign matter into the front work device 20.
Here, in a case where the cover is fastened to the front work device 20 using a fastener, vibration of the hydraulic excavator 1 is transmitted to the fastener or the cover via the front work device 20. In particular, since the front work device 20 operates for work such as excavation, the front work device receives large vibration and impact. As a result, cracks around an insertion hole for the fastener of the front work device 20, deformation of the cover, breakage of the fastener, and the like may occur. To suppress the occurrence of such damage, the hydraulic excavator 1 includes a cover device 40.

(Cover Device)

Fig. 3 is an explanatory view illustrating a part of the outer surface 21a of the boom 21 in a state where the access hole 30 is closed by the cover device 40. Fig. 4 is an exploded perspective view illustrating the cover device 40. Fig. 5 is a front view of the cover device 40 as viewed from an inner surface 21b side of the boom 21, Fig. 6 is a perspective view of a state in which a part of the cover device 40 is removed as viewed from the inner surface 21b side of the boom 21, and Fig. 7 is a perspective view of a state in which a part of the cover device 40 is further removed as viewed from the inner surface 21b side of the boom 21. Fig. 8 is a cross-sectional view taken along line A-A in Fig. 5, and Fig. 9 is an enlarged cross-sectional view illustrating a range surrounded by the two-dot chain line in Fig. 8. Fig. 10 is a perspective view illustrating a member surrounded by the two-dot chain line in Fig. 4. The cover device 40 includes a cover 50, two brackets 60, a vibration-damping rubber 101 (first vibration-damping rubber), a vibration-damping rubber 102 (second vibration-damping rubber), and a vibration-damping rubber 103 (third vibration-damping rubber).

(Cover)

As illustrated in Fig. 3, the cover 50 is a disk-shaped member that closes the access hole 30 from the outside of the front work device 20. The cover 50 is not limited to a disk-shaped member, and may be, for example, a quadrangular flat plate member. The cover 50 is formed to have a diameter larger than the diameter of the access hole 30, and is in contact with the outer surface 21a of the boom 21 via the vibration-damping rubber 102. The vibration-damping rubber 102 is formed in an annular shape, and is attached to the cover 50 as a groove formed along an inner peripheral surface thereof being fit into an outer peripheral edge of the cover 50 from radially outside. Note that the vibration-damping rubber 102 may be attached to the cover 50 with an adhesive.
A cover grip 53 that is gripped by the worker when the worker attaches or detaches the cover 50 is formed on a front surface 51 of the cover 50. A bolt insertion hole 501 (Fig. 4) for fastening the bracket 60 (a second bracket 80 to be described below) is formed in the cover 50. Two bolt insertion holes 501 are arranged at an interval outside the cover grip 53 at each side across a center of the cover 50. Furthermore, as illustrated in Fig. 5, a chain 130 attached to the inner surface 21b of the boom 21 is attached to a back surface 52 of the cover 50. As a result, it is possible to prevent the worker from accidentally dropping the cover 50 in a state where the cover 50 is removed. Note that, in Fig. 8, the chain 130 is not illustrated.

(Bracket)

As illustrated in Figs. 5 to 8, each bracket 60 is arranged inside the boom 21. Specifically, the two brackets 60 are arranged in the vicinity of the access hole 30 at an interval along a longitudinal direction of the boom 21 (the front-rear direction of the hydraulic excavator 1). Each bracket 60 includes a first bracket 70 and the second bracket 80.

(First Bracket)

As illustrated 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 illustrated in Figs. 6 and 7, the main body portion 72 includes a flat plate-shaped substrate portion 721 and three rib portions 722 extending along edge portions and a central portion of the substrate portion 721. Two bolt insertion holes 702 (Fig. 4) are formed in the other end of the main body portion 72 opposite to the access hole 30. Two bolt insertion holes 703 (Fig. 4) for fastening the second bracket 80 are formed in the fastening surface portion 74. As illustrated in Fig. 8, the first bracket 70 is arranged such that the main body portion 72 extends along the inner surface 21b of the boom 21.
Here, as illustrated in Fig. 8, the boom 21 has a screw seat 90 attached to the inner surface 21b by welding at a position more distant than the outer peripheral edge 50a of the cover 50 with respect to the access hole 30. In the present embodiment, the screw seat 90 is an attachment portion of the bracket 60 in the boom 21 (front work device 20). Similarly to the brackets 60, two screw seats 90 are arranged at an interval along the longitudinal direction of the boom 21 (the front-rear direction of the hydraulic excavator 1). Then, 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 seat 90. As described above, an attachment position of the first bracket 70 and the boom 21 (the position of the screw seat 90) is located more distant than the outer peripheral edge 50a of the cover 50 with respect to the access hole 30. Further, the fastening surface portion 74 of the first bracket 70 is formed at a position slightly protruding from the inner peripheral edge 30a of the access hole 30.

(Second Bracket)

As illustrated in Figs. 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 illustrated in Fig. 10, the main body portion 82 includes a flat plate-shaped substrate portion 821 and two rib portions 822 extending along respective edges of the substrate portion 821. At the other end of the main body portion 82, two long hole-shaped bolt insertion holes 803 (Fig. 4) extending along a thickness direction of the boom 21 are formed.
As illustrated in Fig. 8, the second bracket 80 is arranged such that the main body portion 82 is in contact with the fastening surface portion 74 of the first bracket 70, and extends along the thickness direction of the boom 21 inside the access hole 30. Then, the first bracket 70 and the second bracket 80 are fastened by fastening bolts B3 as fasteners inserted in the bolt insertion holes 703 and 803 (Fig. 4) to nuts N3.
Further, as illustrated in Fig. 10, the second bracket 80 is provided with the vibration-damping rubber 101. The vibration-damping rubber 101 is attached to an L-shaped rubber attaching member 87 attached to each of the rib portions 822 of the main body portion 82 with an adhesive. As illustrated in Fig. 8, the vibration-damping rubber 101 is located on the first bracket 70 side with respect to the main body portion 82, and is located on the inner surface 21b side of the boom 21 with respect to the first bracket 70 in the state where the second bracket 80 is disposed. Then, the second bracket 80 is fastened to the first bracket 70 at a position where the vibration-damping rubber 101 is in contact with the inner surface 21b of the boom 21.
Here, as described above, the bolt insertion hole 803 of the main body portion 82 is formed in a long hole shape extending along the thickness direction of the boom 21. Accordingly, the position of the second bracket 80 in the thickness direction of the boom 21 can be adjusted by adjusting a fastening position of the bolt B3 in the bolt insertion hole 803. Further, the second bracket 80 is arranged such that the vibration-damping rubber 101 is in contact with the inner surface 21b of the boom 21, whereby 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, for example, in a case where a pipe-shaped member protruding from the inner surface 21b of the boom 21 is attached along a peripheral edge of the access hole 30, the second bracket 80 can be easily positioned.
Further, the second bracket 80 is configured such that the fastening surface portion 84 is substantially flush with the outer surface 21a of the boom 21 in the state of being fastened to the first bracket 70. As illustrated in Figs. 9 and 10, two bolt insertion holes 801 are formed at an interval in the fastening surface portion 84. A vibration-damping rubber 103 is stuck around each bolt insertion hole 801 with an adhesive, and a spacer 86 protruding from the vibration-damping rubber 103 is provided inside the vibration-damping rubber 103.
As illustrated in Fig. 9, a bolt B1 as a fastener is inserted into each of the bolt insertion holes 501 of the cover 50 and each of the bolt insertion holes 801 of the second bracket 80 via a washer W1, and the bolt B1 is fastened to a nut N1. Thereby, the cover 50 and the second bracket 80 are fastened, and in this state, the vibration-damping rubber 103 is in contact with the back surface 52 of the cover 50 and the spacer 86 is in contact with the washer W1. As a result, it is possible to secure an axial force of the fastening by the bolt B1 and the nut N1 while interposing the vibration-damping rubber 103 between the cover 50 and the second bracket 80. As illustrated in Fig. 8, the attachment position between the cover 50 and the second bracket 80 (the fastening position by the bolt B1 and the nut N1) is located on a center 30b side of the access hole 30 with respect to an inner peripheral edge 30a of the access hole 30. Further, the cover 50 is in contact with the outer surface 21a of the boom 21 via the vibration-damping rubber 102 in a state of being fastened to the second bracket 80.

(Attaching/Detaching Work of Cover)

In the cover device 40 configured as described above, in a case where the worker enters the inside of the boom 21 from the access hole 30, first, as illustrated in Fig. 6, the fastening between the cover 50 and the second bracket 80 is released, and the cover 50 is positioned at a position separated from the outer surface 21a of the boom 21. Further, as illustrated in Fig. 7, the second bracket 80 is removed from the first bracket 70. As a result, the worker can easily enter the inside of the boom 21 from the access hole 30 while keeping the opening range of the access hole 30 from being narrowed by the bracket 60. Note that, in a case where the cover 50 is attached to the cover device 40 again, the second bracket 80 is simply fastened to the first bracket 70 and the cover 50 is simply fastened to the second bracket 80 in a reverse procedure to the above procedure.
As described above, the cover device 40 according to the embodiment closes the access hole 30 for maintenance formed in the hollow box-shaped front work device 20 included in the hydraulic excavator 1 (construction machine). The cover device 40 includes the cover 50 that is in contact with the outer surface 21a of the boom 21 (front work device 20) to close the access hole 30, and the bracket 60 that is located inside the boom 21, is attached to the inner surface 21b of the boom 21 via the screw seat 90 (welding portion), and is detachably fastened with the cover 50.
With the configuration, the bracket 60 can be attached to the boom 21 via the screw seat 90 as an attachment portion (welding portion) 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, it is not necessary to form a bolt insertion hole or a fastening hole for fastening the cover device 40 to the boom 21, and it is possible to prevent occurrence of cracks based on these holes.
Further, in the present embodiment, the attachment portion (screw seat 90) of the bracket 60 in the boom 21 is provided at the position more distant than the outer peripheral edge 50a of the cover 50 with respect to the access hole 30. That is, the bracket 60 is attached to the inner surface 21b of the boom 21 (front work device 20) at the position radially outside the access hole 30 with respect to the inner peripheral edge 30a of the access hole 30. Therefore, it is possible to provide the screw seat 90 at the position far from the periphery of the access hole 30 where relatively high stress is likely to occur, and it is possible to improve durability in the vicinity of the attachment position of the bracket 60 to the boom 21.
Further, the attachment position of the bracket 60 and the cover 50 (the fastening position by the bolt B1 and the nut N1) is located on the center 30b side of the access hole 30 with respect to an inner peripheral edge 30a of the access hole 30. That is, the cover 50 is detachably fastened to the bracket 60 at the position on the center side of the access hole 30 with respect to the inner peripheral edge 30a of the access hole 30. Therefore, as illustrated in Fig. 8, it is possible to fasten the cover 50 and the bracket 60 without causing the bracket 60 (second bracket 80) to largely protrude from the access hole 30. Thereby, it is possible to suppress an increase in size of the bracket 60, to suppress swinging of the bracket 60 due to vibration from the front work device 20, and to improve durability of the bolt B1 that fastens the cover 50 and the bracket 60 or the bracket 60 itself. As described above, according to the configuration of the embodiment, it is possible to more appropriately protect the cover device 40 that closes the access hole 30 for maintenance formed in the front work device 20 of the hydraulic excavator 1 and the front work device 20.
Further, the vibration-damping rubber 101 (first vibration-damping rubber) is arranged between the inner surface 21b of the boom 21 and the bracket 60. With the configuration, it is possible to reduce the vibration transmitted from the boom 21 to the bracket 60 by the vibration-damping rubber 101, and it is possible to more appropriately protect the cover 50, the bracket 60, and the bolts B1 to B3.
Further, the vibration-damping rubber 102 (second vibration-damping rubber) is arranged between the outer surface 21a of the boom 21 and the cover 50. With the configuration, it is possible to reduce the vibration transmitted from the boom 21 to the cover 50 by the vibration-damping rubber 102, and it is possible to more appropriately protect the cover 50. Further, it is possible to prevent a gap from being formed between boom 21 and cover 50 to suppress intrusion of water or dust into the access hole 30.
Further, the vibration-damping rubber 103 (third vibration-damping rubber) is arranged between the bracket 60 and the cover 50. With the configuration, it is possible to reduce the vibration transmitted from the boom 21 to the cover 50 via the bracket 60 by the vibration-damping rubber 103, and it is possible to more appropriately protect the cover 50 and the bolt B1. Further, it is possible to prevent a gap from being formed between the bracket 60 and the cover 50 to suppress intrusion of water and dust into the access hole 30 through the bolt insertion hole 501 formed in the cover 50.
Further, the bracket 60 includes the first bracket 70 attached to the boom 21 via the screw seat 90 (welding portion) and the second bracket 80 detachably attached to the first bracket 70 and located in the access hole 30. Further, the second bracket 80 is detachably fastened to the cover 50. With the configuration, by removing the second bracket 80 from the first bracket 70, it is possible to secure the opening range of the access hole 30, and to allow the operator to easily enter the boom 21.
Further, the bolt insertion hole 801, which is the fastening position of the second bracket 80 to the first bracket 70, is formed in the long hole shape extending in the thickness direction of the boom 21. With the configuration, it is possible to adjust the position of the second bracket 80 in the thickness direction of the boom 21 in accordance with a change in the thickness of the boom 21. Further, the vibration-damping rubber 101 is arranged between the boom 21 and the second bracket 80. With the configuration, the second bracket 80 is arranged so as to bring the vibration-damping rubber 101 into contact with the inner surface 21b of the boom 21, and thus it is possible to easily position the second bracket 80 in the thickness direction of the boom 21.
Further, the two brackets 60 and the two screw seats 90 as attachment portions of the brackets 60 to the boom 21 are arranged at intervals along the longitudinal direction of the boom 21. With the configuration, it is easier to secure the space for attaching the bracket 60 and the screw seat 90 to the inner surface 21b of the boom 21 than a case where the bracket 60 and the screw seat 90 are arranged at an interval in a short direction of the boom 21. As a result, it is possible to sufficiently secure the size of the access hole 30. Furthermore, by arranging the two brackets 60 as described above, it is possible to stably support the cover 50 without being cantilevered, and furthermore to more appropriately suppress the occurrence of twisting of the cover 50.
The description of the embodiment is completed as above, but aspects of the present invention are not limited to this embodiment. For example, in the present embodiment, the vibration-damping rubber 103 is provided between the second bracket 80 and the cover 50, but the vibration-damping rubber 103 may be omitted. Fig. 11 is a cross-sectional view illustrating a vicinity of the attachment position between the second bracket 80 and the cover 50 in the case where the vibration-damping rubber 103 is omitted. In this case, as illustrated in the drawing, the vibration-damping rubber 103 and the spacer 86 may be omitted, and the fastening surface portion 84 of the second bracket 80 may be brought into contact with the cover 50.
Further, in the present embodiment, the vibration-damping rubber 101 is attached to the second bracket 80, but the vibration-damping rubber 101 may be attached to the first bracket 70 to be in contact with the inner surface 21b of the boom 21.
Further, in the present embodiment, the bracket 60 and the screw seat 90 are arranged at an interval in the longitudinal direction of the boom 21, but the arrangement positions of the bracket 60 and the screw seat 90 are not limited thereto. The bracket 60 and the screw seat 90 are preferably provided in a range where stress is as small as possible in consideration of magnitude of the stress generated in the inner surface 21b of the boom 21. Further, the case where the screw seat 90 is integrally attached to the boom 21 by welding a member formed separately from the boom 21 to the boom 21 has been described, but the configuration of the screw seat 90 is not limited thereto. For example, in a case where strength of the boom 21 is secured, such as in a case where the relevant portion of the boom 21 is formed sufficiently thick, the screw seat 90 may be formed by directly performing screw processing in the boom 21. Even in this case, it is possible to suppress the occurrence of cracks around the insertion hole as compared with the case where the insertion hole for bolt insertion is formed at least in the boom 21.
Further, the second bracket 80 may be undetachably fixed to the first bracket 70 or the first bracket 70 and the second bracket 80 may be an integral member as long as the opening range for allowing the worker to enter the access hole 30 can be secured.
Further, in the present 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 an upper plate portion 212 or a 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.

Explanation of Reference Signs

1 Hydraulic excavator
10 Vehicle body
20 Front work device
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 (welding portion or attachment portion)
101 Vibration-damping rubber (first vibration-damping rubber)
102 Vibration-damping rubber (second vibration-damping rubber)
103 Vibration-damping rubber (third vibration-damping rubber)
501, 702, 703, 801, 803 Bolt insertion hole
B1, B2, B3 Bolt
N1, N3 Nut
W1 Washer

Claims

A cover device that closes an access hole for maintenance formed in a front work device of a construction machine, the front work device being formed in a hollow box shape, the cover device comprising:
a cover in contact with an outer surface of the front work device to close the access hole; and

a bracket attached to an inner surface of the front work device and to which the cover is detachably fastened, wherein

the bracket is attached to the inner surface of the front work device at a position radially outside an inner peripheral edge of the access hole, and

the cover is detachably fastened to the bracket at a position on a center side of the access hole with respect to the inner peripheral edge of the access hole.
The cover device according to claim 1, wherein a first vibration-damping rubber is arranged between the inner surface of the front work device and the bracket.
The cover device according to claim 1, wherein a second vibration-damping rubber is arranged between an outer surface of the front work device and the cover.
The cover device according to claim 1, wherein a third vibration-damping rubber is arranged between the bracket and the cover.
The cover device according to any one of claims 1 to 4, wherein
the bracket includes a first bracket attached to the inner surface of the front work device via a welding portion, and a second bracket detachably attached to the first bracket and located in the access hole, and

the cover is detachably fastened to the second bracket.
The cover device according to claim 5, wherein a bolt insertion hole serving as a fastening position of the second bracket with the first bracket is formed in a long hole shape extending in a thickness direction of the front work device.
The cover device according to claim 6, wherein a first vibration-damping rubber is arranged between the front work device and the second bracket.
The cover device according to claim 1, wherein the two brackets and two attachment portions of the brackets to the front work device are arranged at intervals along a longitudinal direction of the front work device.
A construction machine comprising: a vehicle body; a hollow box-shaped front work device provided in the vehicle body; and an access hole for maintenance provided in the front work device,
the construction machine further comprising:
a cover device including

a cover in contact with an outer surface of the front work device to close the access hole, and

a bracket attached to an inner surface of the front work device and to which the cover is detachably fastened, wherein

the bracket is attached to the inner surface of the front work device at a position radially outside an inner peripheral edge of the access hole, and

the cover is detachably fastened to the bracket at a position on a center side of the access hole with respect to the inner peripheral edge of the access hole.