CN107938736B

CN107938736B - Working arm support of excavator and excavator

Info

Publication number: CN107938736B
Application number: CN201711167703.3A
Authority: CN
Inventors: 司建明; 王晓明; 苏运动
Original assignee: Taiyuan Heavy Industry Co Ltd
Current assignee: Taiyuan Heavy Industry Co Ltd
Priority date: 2017-11-21
Filing date: 2017-11-21
Publication date: 2020-11-27
Anticipated expiration: 2037-11-21
Also published as: CN107938736A

Abstract

The utility model relates to a machinery front shovel formula excavator technical field, machinery front shovel formula excavator is a professional equipment that is used for large-scale strip mine to exploit, concretely relates to work cantilever crane and excavator of excavator, work cantilever crane includes lower cantilever crane, bracing piece, upper arm frame and top pulley: the lower end of the lower arm support is hinged to the working platform, the upper end of the lower arm support is hinged to one end of the supporting rod, the other end of the supporting rod is hinged to the top of the A-shaped frame, the lower arm support, the supporting rod and the A-shaped frame are of a triangular supporting structure, the lower end of the upper arm support is hinged to the upper end of the lower arm support, the upper end of the upper arm support is provided with a top pulley, the upper end of the upper arm support is connected with the top of the A-shaped frame through a. The structure optimizes the stress structure of the working arm support, reduces the bending moment applied to the lower arm support in the pushing and pressing process of the bucket rod, and improves the working performance of the whole machine; the arm support with the supporting rod is additionally arranged, so that the possibility that the machine is damaged by jacking the working arm support when the bucket gnaws the root is avoided.

Description

Working arm support of excavator and excavator

Technical Field

The disclosure relates to the technical field of excavators, in particular to a working arm support of an excavator and the excavator.

Background

A related art mechanical front shovel excavator, also called a mining excavator, is a special equipment for strip mining, and the working mechanism of the excavator mainly includes an a-frame, a boom, a dipper, a bucket, a pushing device, a lifting device, a guy rope, a traction rope, and the like. The bucket finishes the excavation to the material under wire rope's lifting force and the thrust combined action that bulldozes the gear during operation, and the bucket that fills up the material is together turned round certain angle under slewer's effect together with the upper portion of whole machine, and when the bucket was located haulage vehicle's top, the bucket bottom was opened and is unloaded the material, then the upper portion of whole machine is turned back again, and the dipper is withdrawed, and the promotion wire rope transfers, prepares to carry out next endless operation.

In the operation process of the excavator, when the bucket excavates the material at the bottommost part of the front end of the material pile, the lifting force is small, the pushing mechanism pushes the bucket rod out in a full force mode, the boom is jacked up through the pushing counter force, the boom rotates around the foot, the guy rope is loosened (in actual work, the situation is called as 'gnawing the root of the foot'), and at the moment, if the boom is lowered through inertia, the guy rope is impacted greatly, so that the service lives of the guy rope and related parts are shortened. In addition, the whole crane boom has heavy weight, and the corresponding machine counterweight is also large, so that the weight of the whole crane boom is increased, the idle work of the machine is increased, and the performance of the machine is influenced.

The crane boom is an important component of a working mechanism of the mining excavator, and the structure, the working strength and the service life of related parts of the crane boom directly influence the production efficiency and the reliability of equipment. Therefore, it is necessary to research a boom and an excavator, so as to improve the performance and work efficiency of the excavator, and to improve the operation quality of the whole equipment.

It is to be noted that the information disclosed in the above background section is only for enhancement of understanding of the background of the present disclosure, and thus may include information that does not constitute prior art known to those of ordinary skill in the art.

Disclosure of Invention

An object of the present disclosure is to provide a working boom of an excavator and an excavator, thereby overcoming, at least to some extent, one or more problems due to limitations and disadvantages of the related art.

According to an aspect of the present disclosure, a working boom of an excavator is provided, the excavator includes a working platform, an a-frame fixed on the working platform, an arm, and a bucket fixed at one end of the arm, the working boom includes a lower boom, a support rod, an upper boom, and a top pulley:

the lower end of the lower arm support is hinged to the working platform, and the upper end of the lower arm support is hinged to the supporting rod; one end of the supporting rod is connected to the lower arm support, and the other end of the supporting rod is hinged to the top of the A-shaped frame; the lower arm support, the support rod and the A-shaped frame are of a triangular support structure;

the lower end of the upper arm support is hinged to the upper end of the lower arm support, the top pulley is arranged at the upper end of the upper arm support, and the upper end of the upper arm support is connected with the top of the A-shaped frame through a guy rope; the bucket rod is arranged on the lower arm support.

In an exemplary embodiment of the disclosure, the lower arm support and the upper arm support are both inclined upward at the same angle as the working platform, and during excavation, an additional component force applied to the upper arm support is deflected below the axis of the upper arm support, and the additional component force and its own gravity form a balance with the pulling force of the guy rope, so that the working arm support is in a stable state.

In an exemplary embodiment of the present disclosure, the support rod includes left and right main bodies and a middle transverse link, and one end of each main body is hinged to the top of the a-frame, and the other end is hinged to the upper end of the lower arm support.

In an exemplary embodiment of the disclosure, a pushing mechanism is further disposed on the lower arm support, the pushing mechanism includes a pushing shaft and a pushing gear, the pushing shaft penetrates through a support body of the lower arm support, and the pushing gear is engaged with a rack on the bucket rod and used for pushing out and pulling back the bucket rod.

In an exemplary embodiment of the disclosure, the bucket rod is of a U-shaped structure, the left and right rod bodies of the bucket rod are inserted at two sides of the lower arm support, the bucket rod can swing around the center of the pushing shaft, and in a plane perpendicular to the pushing shaft, the meshing point is in a meshing movable area; the central line of the supporting rod passes through or is adjacent to the meshing active area

In an exemplary embodiment of the present disclosure, the upper arm rest includes a combination of one or both of a truss structure and a beam structure.

According to one aspect of the disclosure, an excavator is provided, which comprises a working arm support of the excavator.

In an exemplary embodiment of the disclosure, the excavator further includes a traction rope, one end of the traction rope is connected to a lifting device fixed on the working platform, the other end of the traction rope passes around the top pulley and is connected to the bucket, and the traction rope is driven by the lifting device to lift or lower the bucket.

According to the technical scheme, the working arm support of the excavator has the advantages and positive effects that:

the utility model provides a pair of work cantilever crane of excavator, wherein the excavator includes work platform, is fixed in A type frame, dipper on the work platform and is fixed in the scraper bowl of dipper one end, and the work cantilever crane includes cantilever crane, bracing piece, upper arm frame and top pulley down: the lower end of the lower arm support is hinged to the working platform, the upper end of the lower arm support is hinged to one end of the supporting rod, the other end of the supporting rod is hinged to the top of the A-shaped frame, the lower arm support, the supporting rod and the A-shaped frame are of a triangular supporting structure, the lower end of the upper arm support is hinged to the upper end of the lower arm support, a top pulley is arranged at the upper end of the upper arm support, the upper end of the upper arm support is connected with the top of the A-shaped frame through a guy rope, a bucket rod.

On one hand, the working arm support of the excavator provided by the disclosure has a stable stress structure, so that the impact on structural members such as a guy rope can be eliminated when the excavator gnaws the root (namely, the bucket excavates the bottommost material at the front end of a material pile), the crane arm is jacked up, and then the impact is quickly released downwards, and the service life of the structural members such as the guy rope is prolonged.

On the other hand, the upper arm support and the lower arm support are used for replacing the original crane arm, and a lower arm support supporting rod is additionally arranged near the hinge point of the lower arm support supporting rod, so that the lower arm support is only one part of the truss; when the excavator works normally, the pushing reaction force is mainly borne by the lower arm support rod, and because the distance from the meshing point of the pushing gear and the upper rack of the bucket rod to the hinge point of the support rod is very close (or coincident), the lower arm support mainly bears the positive tension and compression stress and bears a small bending moment; meanwhile, the upper arm support only bears the tensile and compressive stress in the positive direction but not bears the bending moment, the stress of the arm support is improved by the structure, compared with the original crane arm, the section modulus of the upper arm support and the section modulus of the lower arm support can be obviously reduced, and the weight of the arm support and the whole working arm support is further reduced; the weight of the corresponding counter weight is also reduced, so that the weight of the whole machine can be reduced, the rotary inertia is further reduced, the rotary time is shortened, the consumption of rotation and walking is reduced, and the working performance of the whole machine is greatly improved.

On the other hand, on the occasion that a long-arm mining excavator is needed, only the upper arm frame part can be lengthened, and the lower arm frame and related parts are kept unchanged, so that convenience is provided for the same machine type to be used on different occasions; in addition, the original integral crane boom is changed into an upper boom frame and a lower boom frame which are two sections, so that the manufacturing and the maintenance are convenient, and the cost is further reduced.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present disclosure and together with the description, serve to explain the principles of the disclosure. It is to be understood that the drawings in the following description are merely exemplary of the disclosure, and that other drawings may be derived from those drawings by one of ordinary skill in the art without the exercise of inventive faculty.

FIG. 1 shows a side view schematic of a related art mining excavator work boom;

fig. 2 shows a schematic side view of a mining excavator comprising a working boom in an exemplary embodiment of the disclosure;

FIG. 3 is a schematic cross-sectional view taken along A-A of FIG. 2;

FIG. 4 is a schematic view of the support rod in the exemplary embodiment of the present disclosure in the direction B of FIG. 2;

fig. 5 shows a side view schematic of another mining excavator including a work boom in an exemplary embodiment of the present disclosure.

Detailed Description

Example embodiments will now be described more fully with reference to the accompanying drawings. Example embodiments may, however, be embodied in many different forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of example embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to give a thorough understanding of embodiments of the disclosure. One skilled in the relevant art will recognize, however, that the subject matter of the present disclosure can be practiced without one or more of the specific details, or with other methods, components, devices, steps, and the like. In other instances, well-known technical solutions have not been shown or described in detail to avoid obscuring aspects of the present disclosure.

The terms "a," "an," "the," and "said" are used in this specification to denote the presence of one or more elements/components/parts/etc.; the terms "comprising" and "having" are intended to be inclusive and mean that there may be additional elements/components/etc. other than the listed elements/components/etc.; the terms "first" and "second", etc. are used merely as labels, and are not limiting on the number of their objects.

Fig. 1 shows a schematic side view of a related art mining excavator work boom.

One embodiment of a large mining excavator in the related art is shown in fig. 1, and the structure mainly includes: crawler, undercarriage, mid-swing, upper platform 101, a-frame 102, boom 103, top sheave 104, stick 105, bucket 106, pusher 107, hoist, swing, and electrical control system, among others. Wherein the a-frame 102, the boom 103, the top sheave 104, the stick 105, the bucket 106, and the pushing device 107 constitute the main working mechanism; during operation, the bucket 106 finishes digging materials under the combined action of the lifting force of the steel wire rope 108 and the thrust of the push gear, the bucket 106 filled with the materials and the upper part of the whole machine rotate for a certain angle under the action of the rotating device, and when the bucket 106 moves to the upper part of the transport vehicle, the bottom of the bucket 106 is opened to unload the materials; the upper part of the machine is then rotated back into the working position, the boom 105 is retracted and the hoist rope 108 is lowered in preparation for the next cycle of work.

The excavator in the related art is characterized in that: the crane boom 103 is an integral welding part, the root part of the crane boom 103 is hinged at the front end of the upper platform 101, the top end of the crane boom 103 is provided with a top pulley 104, and the pushing device is arranged at the middle part of the crane boom 103. With present understanding and appreciation, the embodiment, as it is limited by the construction and control principles, is believed to suffer from at least the following significant drawbacks:

on the one hand, when the excavator gnaws the root, the lifting force is small, the pushing mechanism pushes the bucket rod out in a full force mode, the boom can be jacked up through the pushing counter force, the boom rotates around the heel, the guy rope is loosened, and if the boom is placed down through inertia, the guy rope is impacted greatly, so that the service lives of the guy rope and related parts are shortened. The root gnawing bottom means that the excavator bucket excavates the materials at the bottommost part in front of the material pile, the pushing mechanism is pushed out fully at the moment, the lifting force for lifting the steel wire rope is small, and the phenomenon that the boom is jacked up by the bucket rod easily occurs.

On the other hand, the whole crane boom has heavy weight, and the corresponding machine counterweight is also large, so that the weight of the whole crane boom is increased, the idle work of the machine is increased, and the performance of the machine is influenced.

Fig. 2 shows a schematic side view of a mining excavator comprising a working boom in an exemplary embodiment of the disclosure; FIG. 3 is a schematic cross-sectional view taken along A-A of FIG. 2; fig. 4 is a schematic view of a support rod in an exemplary embodiment of the disclosure in a direction B in fig. 2.

The embodiment of the present example first provides a working boom of an excavator, as shown in fig. 2 to 4, a specific structural example thereof is as follows:

the working arm support of the excavator provided by the disclosure is applied to the excavator, wherein the excavator comprises an A-shaped frame 204 and an arm 210 which are fixed on the working platform 208, and a bucket 211 fixed at one end of the arm, and the working arm support comprises a lower arm support 201, a support rod 203, an upper arm support 202 and a top pulley 205: the existing integrated crane boom is divided into an upper boom frame 202 and a lower boom frame 201, and a support rod 203 is arranged between the upper part of the lower boom frame 201 and the top of an A-shaped frame 204, so that the lower boom frame 201, the support rod 203 and the A-shaped frame 204 are in a triangular support structure; a top pulley 205 is arranged at the top end of the upper arm support 202 and is connected with the upper end of the A-shaped frame 204 through a guy rope 206, and the upper arm support 202 and the top pulley 205 on the upper arm support realize the support and reversing of the lifting rope 212; in addition, the arm 210 is disposed on the lower arm support 201.

On one hand, the crane boom and the working boom frame formed by the crane boom have stable stress structures, so that the impact on structural members such as guy ropes and the like can be eliminated when the excavator gnaws the root (namely the bucket excavates the bottommost material at the front end of a material pile), and the service life of the structural members such as the guy ropes and the like can be prolonged.

On the other hand, the upper arm support and the lower arm support are used for replacing the original crane arm, and a lower arm support supporting rod is additionally arranged near the hinge point of the lower arm support supporting rod, so that the lower arm support is only one part of the truss; when the excavator works normally, the pushing counter force is mainly borne by the lower arm support stay bar, and because the distance from the center of the pushing shaft to the hinge point of the support bar is very close (even coincident), the bending moment borne by the lower arm support is smaller, the lower arm support mainly bears the forward tension and compression stress, and similarly, the upper arm support only bears the forward tension and compression stress but not the bending moment, the structure improves the stress of the arm support, compared with the original boom, the section modulus of the upper arm support and the lower arm support can be reduced, and the weight of the arm support and the whole working arm support is further reduced; the weight of the corresponding counter weight is also reduced, so that the weight of the whole machine can be reduced, the rotary inertia is further reduced, the rotary time is shortened, the consumption of rotation and walking is reduced, and the working performance of the whole machine is greatly improved.

On the other hand, on the occasion that a long-arm mining excavator is needed, only the upper arm frame part can be lengthened, and the lower arm frame and related parts are kept unchanged, so that convenience is provided for the same machine type to be used on different occasions; in addition, an original integral crane boom is changed into an upper boom frame and a lower boom frame which are two sections, so that the welding, processing, transportation and maintenance are facilitated, and the cost is further reduced.

Next, a working boom of an excavator in the present exemplary embodiment will be further explained.

In the exemplary embodiment, as shown in FIG. 2, an excavator may include a work platform 208 and an A-frame 204 secured to the work platform 208, a stick 210 and a bucket 211 secured to an end of the stick 210; the lower end of the lower arm support 201 can be hinged with the front end of the working platform 208, and can also be hinged with the lower end of an A-shaped frame 204 close to the front end of the working platform 208; in order to form a stable supporting structure for the lower arm frame 201, a supporting rod 203 is further required to be arranged between the lower arm frame 201 and the a-shaped frame 204, two ends of the supporting rod 203 can be respectively hinged with the upper end of the lower arm frame 201 and the top end of the a-shaped frame 204, and the three form a stable triangular supporting structure.

In this exemplary embodiment, both the lower arm frame 201 and the upper arm frame 202 may be inclined upward at the same angle as the working platform 208, that is, the lower arm frame 201 is hinged to the upper arm frame 202, and the central axes of the two may be on the same straight line, during the excavation operation, the additional component force applied to the upper arm frame 202 is biased to be below the upper arm frame axis, and the additional component force and its own gravity form a balance with the pulling force of the guy rope, so that the working arm frame is in a stable state.

Further, during normal operation of the excavator, the supporting rod 203 needs to bear a pushing reaction force from a hinge point of the lower arm support 201 and the upper arm support 202, and the pushing reaction force is relatively large, so as to achieve stable support, the structure provided with the supporting rod 203 may be a truss structure or a beam structure, as shown in fig. 4, the structure may include left and right main bodies and a plurality of transverse links in the middle, wherein one end of each main body may be hinged to the top of the a-frame 204, and the other end is hinged to the upper end of the lower arm support, in other embodiments, the supporting rod may also be a structure capable of bearing other pushing reaction forces, and the disclosure is not limited specifically herein.

In this example embodiment, a pushing mechanism 207 may be further provided on the lower arm support, the pushing mechanism 207 may include a pushing shaft and a pushing gear, the pushing shaft may pass through the frame body of the lower arm support 201, and the pushing gear may engage with a rack on the arm 203, and the pushing gear rotates to push out or pull back the arm 210.

Further, the arm 210 may be rotatably fixed between two ends of the lower arm support 201 through a connection device, the arm 210 may include a left rod and a right rod, the left rod and the right rod may be symmetrically inserted into two sides of the lower arm support 201, and the arm 210 may swing around the center of the pushing shaft.

The engagement point may be located within an engagement active region in a plane perpendicular to the push shaft, and the center line of the support rod 203 may be passed through or as close as possible to the engagement active region in order to minimize the bending moment generated on the lower arm frame in the reciprocating push-out and pull-back motions of the arm.

For example, in the present exemplary embodiment, as shown in fig. 2, the center line of the support rod 203 is adjacent to the meshing active region without passing through the push gear-rack meshing point for structural consideration. In other example embodiments, such as the other mining shovel in fig. 5 that includes a working boom in the example embodiment of the present disclosure, the hinge point of the support bar 303 passes through the push-rack-and-pinion engagement point (point M).

In the present exemplary embodiment, in order to lift the bucket 211, an upper arm support 202 and a top pulley 205 may be further provided on the basis of the above-mentioned triangular support structure. The lower end of the upper arm support 202 can be hinged to the upper end of the lower arm support 201, and the upper end of the upper arm support 202 can be connected with the top end of the A-shaped frame 204 through the guy rope 206, so that a stable triangular supporting structure is formed. Further, a top pulley 205 capable of rotating around a shaft can be arranged at the upper end of the upper arm support 202, and the top pulley 205 can be used for supporting and steering a traction rope connected to a working platform of the excavator.

In the exemplary embodiment, as shown in fig. 3, since the upper arm frame 202 does not bear bending moment during operation, but only bears tensile and compressive stress in the forward direction, compared with the original boom, the structure of the upper arm frame 202 can be reduced, and the upper arm frame may be a truss structure or a beam structure, or may be another structure capable of bearing tensile and compressive stress, and the disclosure is not limited specifically herein.

In the embodiment, an original integral boom is changed into the upper boom 202, the lower boom 201 and the supporting rod 203, when the excavator works normally, pushing reaction force is mainly borne by the supporting rod of the lower boom, and the lower boom mainly bears positive tension and compression stress; the bending moment formed by the pushing reaction force on the lower arm frame is small and even can be ignored; the ground jib only bears the forward tension and compression stress but not the bending moment, so the structure improves the stress of the jib and can reduce the section modulus of the upper and lower jibs compared with the original jib; the strength of the corresponding A-shaped frame can be enhanced, and as the integral stress is improved, the sum of the added weight of the supporting rod 203 and the added weight of the A-shaped frame due to the enhancement is smaller than the reduced weight of the upper arm support 202 and the lower arm support 201, so that the weight of the arm support and the whole working arm support is further reduced; the weight of the corresponding counter weight is also reduced, so that the weight of the whole machine can be reduced, the rotary inertia is further reduced, the rotary time is shortened, the consumption of rotation and walking is reduced, and the working performance of the whole machine is greatly improved.

In other embodiments, the upper arm frame 202 with different lengths can be replaced under the condition that a long-arm mining excavator is needed, and the lower arm frame and related parts are kept unchanged, so that convenience is provided for the same machine type to be used in different occasions.

The working arm frame in the embodiment of the invention changes the original integral crane arm into the upper arm frame and the lower arm frame which are two sections, thereby being convenient for manufacturing and maintaining and further reducing the cost.

According to a second aspect of the disclosure, an excavator is provided, which at least comprises the above-mentioned working boom.

The excavator in this example embodiment may further include a pull rope 212, one end of the pull rope 212 may be connected to a lifting device fixed to the work platform, the other end of the pull rope 212 may be connected to the bucket 211 by passing over the top pulley 205, and the pull rope 212 may be driven by the lifting device to lift or lower the bucket. Further, the hoisting device may be a winch, or may be another device that can hoist or lower the haulage rope, and the disclosure is not limited specifically herein.

The beneficial effects of the excavator in this exemplary embodiment are described in detail in the above-mentioned working arm support, and are not described again.

The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments, and the features discussed in connection with the embodiments are interchangeable, if possible. In the above description, numerous specific details are provided to give a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention may be practiced without one or more of the specific details, or with other methods, components, materials, and so forth. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention.

Other embodiments of the disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure disclosed herein. This application is intended to cover any variations, uses, or adaptations of the disclosure following, in general, the principles of the disclosure and including such departures from the present disclosure as come within known or customary practice within the art to which the disclosure pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the disclosure being indicated by the following claims.

It will be understood that the present disclosure is not limited to the precise arrangements described above and shown in the drawings and that various modifications and changes may be made without departing from the scope thereof. The scope of the present disclosure is to be limited only by the terms of the appended claims.

Claims

1. The utility model provides a work cantilever crane of excavator, the excavator includes work platform, is fixed in A type frame, dipper on the work platform and be fixed in the scraper bowl of dipper one end, its characterized in that, work cantilever crane includes lower cantilever crane, bracing piece, upper arm frame and top pulley:

the lower end of the lower arm support is hinged to the working platform, and the upper end of the lower arm support is hinged to the supporting rod; one end of the supporting rod is connected to the lower arm support, and the other end of the supporting rod is hinged to the top of the A-shaped frame; the lower arm support, the support rod and the A-shaped frame are of a triangular support structure; the lower arm support is also provided with a pushing mechanism, the pushing mechanism comprises a pushing shaft and a pushing gear, the pushing shaft penetrates through the frame body of the lower arm support, and the pushing gear is meshed with the rack on the bucket rod and used for pushing out and pulling back the bucket rod;

the lower end of the upper arm support is hinged to the upper end of the lower arm support, the top pulley is arranged at the upper end of the upper arm support, and the upper end of the upper arm support is connected with the top of the A-shaped frame through a guy rope; the bucket rod is arranged on the lower arm support;

the bucket rod is of a U-shaped structure, the left rod body and the right rod body of the bucket rod are inserted into two sides of the lower arm support, the bucket rod can swing around the center of the pushing shaft, and in a plane perpendicular to the pushing shaft, the meshing point is located in a meshing movable area; the center line of the supporting rod passes through or is adjacent to the meshing active area.

2. The working boom of the excavator according to claim 1, wherein the lower boom and the upper boom are both inclined upward at the same angle as the working platform, and an additional component force applied to the upper boom is deflected below the axis of the upper boom during the excavating operation, and the additional component force and the self gravity thereof are balanced with the pulling force of the guy rope, so that the working boom is in a stable state.

3. The excavator working boom of claim 1, wherein the support rod comprises left and right main bodies and a middle transverse connecting rod, one end of each main body is hinged to the top of the A-shaped frame, and the other end of each main body is hinged to the upper end of the lower boom.

4. The excavator boom of any one of claims 1 to 3, wherein the upper arm support comprises one or a combination of a truss structure and a beam structure.

5. An excavator, characterized in that, the excavator is provided with a working arm support of the excavator as claimed in any one of claims 1 to 4.

6. The excavator of claim 5 further comprising a pull rope having one end connected to a hoist secured to the work platform and the other end passing around the top sheave and connected to the bucket, the pull rope being driven by the hoist to raise or lower the bucket.