CN112093737A - Crank arm and crank arm type aerial work platform - Google Patents

Abstract

The invention discloses a crank arm and a crank arm type aerial work platform, wherein the crank arm comprises an upper connecting body, the upper connecting body comprises a first concave base plate, a first folded plate and a shaft seat plate, a closed box-shaped structure is arranged on the first concave base plate, and a first hinge mechanism is arranged between the two closed box-shaped structures; the first folded plate is connected with the first concave base plate to form a first semi-closed box-shaped structure, and a second hinge mechanism is arranged between the two first semi-closed box-shaped structures; the shaft seat plate is fixed on the first concave base plate, and a third hinge mechanism is arranged between the shaft seat plate and the side wall of the first concave base plate; the crank arm type aerial work platform is provided with the crank arm. The closed box-shaped hinged stress structure can enhance the connection rigidity of the hinged part of the upper connecting body and the main arm; the simple support hinged stress structure formed among the shaft seat plate, the side wall of the first concave base plate and the third hinge mechanism can improve the connection rigidity of the hinged part of the upper connector and the upper folding arm.

Description

A kind of crank arm and crank arm type aerial work platform

technical field

The invention relates to the field of aerial work platforms, in particular to a crank arm and a crank arm type aerial work platform.

Background technique

As a device for transporting personnel, materials and tools to a designated location for operation, aerial work platforms are widely used because of their flexibility and efficiency. The crank arm of the current articulated boom aerial work platform generally includes a turntable, a lower folding arm, a lower link, a lower connecting body, an upper folding arm, an upper link, an upper connecting body, a main arm, a working platform, a lower folding arm and a lower link. The two ends of the connecting rod are hinged on the turntable and the lower connecting body respectively, the two ends of the upper folding arm and the upper connecting rod are hinged on the upper connecting body and the lower connecting body respectively, and the main arm is hinged on the upper connecting body. The upper and lower connectors are the main load-bearing components.

However, in the existing articulated boom aerial work platform, there exist the part of the sleeve where the upper connecting body is connected with the main arm, the part of the sleeve where the upper connecting body is connected with the upper folding arm, and the part of the sleeve where the lower connecting body is connected with the upper connecting rod. The problem of poor strength and rigidity, and these parts bear a large load force, so it is easy to deform, which affects the movement stability and operation safety of the crank arm.

SUMMARY OF THE INVENTION

The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention proposes a crank arm and a crank arm type aerial work platform, and the crank arm type aerial work platform using the crank arm can move the crank arm more accurately and stably during operation.

A crank arm according to an embodiment of the present invention includes: a main arm, a main arm oil cylinder, a leveling oil cylinder, an upper connecting body, an upper folding arm, an upper connecting rod, a lower connecting body, a lower folding arm, a lower connecting rod, and a folding arm The oil cylinder, wherein the upper connecting body comprises: a first concave base plate, two first folded plates, and a shaft seat plate. The upper end of the side wall of the first concave base plate is provided with two symmetrical closed box-shaped structures, and a first hinge mechanism for connecting the main arm is provided between the two closed box-shaped structures. The first folded plate is fixedly connected to the middle part of the inner side of the side wall of the first concave base plate, and the first concave base plate and the first folded plate are connected to form two symmetrical first semi-closed box structures and a second hinge mechanism for connecting the main arm oil cylinder and the upper link is arranged between the two first semi-closed box structures. The number of the axle seat plates is two and is fixedly connected to the lower end of the first concave base plate. The third hinge mechanism of the upper folding arm.

The crank arm according to the above embodiment of the present invention has at least the following beneficial effects: the first hinge mechanism is arranged on the closed box-shaped hinge force receiving structure, which improves the support mode of the shaft, reduces the bending moment at the shaft support by half, and also reduces the The rigidity of the connection between the upper connecting body and the main arm is maximized, the bending deformation of the hinge pin is reduced, the adverse effect of the bending deformation of the hinge pin on the upper connecting body is reduced, and the welding seam at the hinge is reduced. A simply supported hinge receiving structure is formed between the axle seat plate, the side wall of the first concave base plate, and the third hinge mechanism, and the simply supported hinge receiving structure can connect the hinge generated between the upper connecting body and the upper folding arm. The force is shared between the first concave base plate and the axle seat plate, which reduces the bending moment of the shaft by half, and keeps the maximum bending moment away from the groove plate and the axle seat plate. The strength and rigidity ensure the accurate transmission of the motion relationship between the upper connecting body and the upper folding arm, and at the same time reduce the weld stress at the hinge and reduce the risk of cracking.

According to some embodiments of the present invention, a connecting plate is provided between the two first semi-closed box structures.

According to some embodiments of the present invention, each of the closed box structures includes a second folded plate and a shroud, and the shroud is welded to the second folded plate and the sidewalls of the first concave base plate, respectively. As a whole, the side walls of the enclosure plate and the first concave base plate are respectively provided with coaxial first hinge holes, and the first hinge mechanism includes two first shaft sleeves and a first shaft positioning sleeve, The first shaft sleeve is welded in the first hinge hole, the first shaft positioning sleeve is welded on the outer side of one of the side walls of the first concave base plate, the first shaft sleeve, the first shaft The axes of the positioning sleeve and the first hinge hole are coincident.

According to some embodiments of the present invention, the second hinge mechanism includes two second shaft sleeves and a second shaft positioning sleeve, and the side walls of the first concave base plate and the first folded plate are respectively provided with the same The second hinge hole of the shaft, the second shaft sleeve is arranged in the first semi-closed box-shaped structure and welded on the side wall of the first concave base plate, and the second shaft positioning sleeve is welded on the On the outer side of one of the side walls of the first concave base plate, the axes of the second shaft sleeve, the second shaft positioning sleeve and the second hinge hole coincide.

According to some embodiments of the present invention, the third hinge mechanism includes: a third bushing welded on the axle seat plate, a collar welded on the inner side of the side wall of the first concave base plate, and a The third shaft positioning sleeve on the outer side of the side wall of the first concave base plate, the side wall of the first concave base plate and the shaft seat plate are respectively provided with coaxial third hinge holes, the The axes of the three shaft sleeves, the collar and the third shaft positioning sleeve coincide with the axes of the third hinge hole.

According to some embodiments of the present invention, a coaxial fourth hinge hole is provided on one end of each of the shaft seat plates away from the third shaft sleeve and one of the side walls of the first concave base plate, and the A fourth shaft sleeve is provided on the side of the shaft seat plate facing the fourth hinge hole, and the leveling oil cylinder is connected to the upper connecting body through a pin shaft passing through the fourth hinge hole and the fourth shaft sleeve .

According to some embodiments of the present invention, the lower connecting body includes: a second concave base plate, a U-shaped plate, two first side plates, and a vertical plate. The bottom of the second concave base plate is provided with a notch, the notch is symmetrical about the left and right middle planes of the lower connecting body, and two symmetrical second semi-closed box shapes are arranged on both sides of the notch Each of the second semi-closed box-shaped structures is provided with a fourth hinge mechanism for connecting the upper link. The U-shaped plate is arranged between the side walls of the second concave base plate and is located below the notch, and the outer periphery of the U-shaped plate is welded with the second concave base plate as a whole. The first side plate is arranged on the inner side of the side wall of the second concave base plate, and the second concave base plate, the U-shaped plate and the first side plate are connected to form two symmetrical third semi-closed In the box-shaped structure, a fifth hinge mechanism for connecting the upper folding arm, the lower folding arm and the lower link is arranged between the two third semi-closed box-shaped structures. The number of the vertical plates is two and fixedly connected to the U-shaped plate. The two vertical plates are parallel to each other and are provided with a sixth hinge mechanism for connecting the folding arm oil cylinder.

According to some embodiments of the present invention, each of the second semi-closed box-shaped structures includes a reinforcing plate, a special-shaped plate, and a sealing plate disposed on the second concave base plate and parallel to its sidewall, and each of the first The four-joint mechanism includes a fifth shaft sleeve and a fourth shaft positioning sleeve. The second concave base plate is also provided with a second side plate parallel to its side wall, the second side plate is close to the edge of the slot and its lower end is welded on the U-shaped plate, the second side plate is The concave base plate, the reinforcing plate and the second side plate are provided with coaxial fifth hinge holes. The special-shaped plate is welded between the side wall of the second concave base plate and the reinforcing plate, and the outer periphery of the sealing plate is connected to the reinforcing plate, the special-shaped plate and the second concave plate. The base plate is welded as a whole. The fifth bushing is welded between the side wall of the second concave base plate and the reinforcing plate and penetrates through the reinforcing plate. The fifth bushing is located outside the special-shaped plate and is welded to each other. The fourth shaft locating sleeve is welded on the outer side of the side wall of the second concave base plate, and the axes of the fifth shaft sleeve, the fourth shaft locating sleeve and the fifth hinge hole coincide.

According to some embodiments of the present invention, the special-shaped plate is partially lap welded on the first side plate.

Based on the same inventive concept, the present invention also proposes a crank arm type aerial work platform, including a turntable, a working platform and the crank arm in the above embodiment, the crank arm is arranged on the turntable, and the working platform is arranged on the main arm of the crank arm .

Additional aspects and advantages of the present invention will be set forth, in part, from the following description, and in part will be apparent from the following description, or may be learned by practice of the invention.

Description of drawings

The above and/or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of embodiments taken in conjunction with the accompanying drawings, wherein:

1 is a schematic structural diagram of an upper connector according to an embodiment of the present invention;

2 is a schematic structural diagram of a lower connector according to an embodiment of the present invention;

FIG. 3 is a schematic structural diagram of a crank arm according to an embodiment of the present invention.

Description of drawings:

Main arm 100, main arm oil cylinder 200, leveling oil cylinder 300, upper folding arm 500, upper connecting rod 600, lower folding arm 800, lower connecting rod 900, folding arm oil cylinder 1000, turntable 1100;

The upper connecting body 400, the first concave base plate 410, the closed box-shaped structure 411, the first hinge mechanism 420, the second folding plate 421, the surrounding plate 422, the first shaft sleeve 423, the first shaft positioning sleeve 424, the first hinge The hole 425, the first folding plate 430, the first semi-closed box structure 440, the second hinge mechanism 450, the second shaft sleeve 441, the second shaft positioning sleeve 442, the second hinge hole 443, the third hinge mechanism 470, the first hinge Three shaft sleeves 461, a collar 462, a third shaft positioning sleeve 463, a third hinge hole 464, and a connecting plate 480;

The axle seat plate 460, the fourth hinge hole 451, the fourth axle sleeve 452;

The lower connecting body 700, the second concave base plate 710, the slot 711, the second semi-closed box structure 712, the fourth hinge mechanism 720, the reinforcing plate 721, the special-shaped plate 722, the sealing plate 723, the fifth bushing 724, the first Four-axis positioning sleeve 725, second side plate 726, fifth hinge hole 727, process hole 728, U-shaped plate 730, first side plate 740, third semi-closed box structure 741, fifth hinge mechanism 750, vertical plate 760 , the sixth hinge mechanism 770 .

Detailed ways

Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals refer to the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary, only used to explain the present invention, and should not be construed as a limitation of the present invention.

In the description of the present invention, it should be understood that the azimuth description, such as the azimuth or position relationship indicated by up, down, front, rear, left, right, etc., is based on the azimuth or position relationship shown in the drawings, only In order to facilitate the description of the present invention and simplify the description, it is not indicated or implied that the indicated device or element must have a particular orientation, be constructed and operated in a particular orientation, and therefore should not be construed as limiting the present invention.

In the description of the present invention, unless otherwise clearly defined, terms such as setting, installation, and connection should be understood in a broad sense, and those skilled in the art can reasonably determine the specific meanings of the above terms in the present invention in combination with the specific content of the technical solution.

Referring to FIGS. 1 to 3 , a crank arm according to an embodiment of the present invention includes a main arm 100 , a main arm oil cylinder 200 , a leveling oil cylinder 300 , an upper connecting body 400 , an upper folding arm 500 , an upper connecting rod 600 , and a lower connection Body 700 , lower folding arm 800 , lower connecting rod 900 , and folding arm oil cylinder 1000 . The upper connecting body 400 has a symmetrical left and right structure, and includes: a first concave base plate 410 , two first folding plates 430 , and a shaft seat plate 460 .

Two symmetrical closed box structures 411 are disposed on the upper ends of the left and right side walls of the first concave base plate 410 , and a first hinge mechanism 420 for connecting the main arm 100 is disposed between the two closed box structures 411 .

The first folding plate 430 is a three-sided bending plate. The tops of the two side plates of the bending plate are welded on the inner side of the side wall of the first concave base plate 410 and are close to the middle of the side wall, and the sides of the bending plate are welded vertically. On the bottom surface of the first concave base plate 410 , a first semi-closed box-shaped structure 440 with one end open is formed, and a first semi-closed box-shaped structure 440 for connecting the main arm oil cylinder 200 and the upper link 600 is provided between the two first semi-closed box-shaped structures 440 The second hinge mechanism 450.

The number of the axle seat plates 460 is two, the two axle seat plates 460 are welded on the bottom surface of the first concave base plate 410 and arranged in parallel to each other, the two axle seat plates 460 are close to the lower end of the first concave base plate 410, the axle seat The plate 460 is also parallel to the side wall of the first concave base plate 410. A third hinge mechanism 470 is provided between the axle seat plate 460 and the side wall of the first concave base plate 410, and an upper folding arm is hinged on the third hinge mechanism 470. 500.

In some embodiments of the present invention, a connecting plate 480 for enhancing the structural strength of the upper connecting body 400 is disposed between the two first semi-closed box structures 440 , and the connecting plate 480 is a symmetrical octagonal flat plate, including one upper and one lower The side and the left and right sides are three sides respectively. The two upper sides of the left and right sides are welded to the surface of the first folding plate 430 , and the left and right sides are welded to the side wall of the first concave base plate 410 .

In some embodiments of the present invention, each closed box-shaped structure 411 includes a second folding plate 421 and a surrounding plate 422 , and the first hinge mechanism 420 includes two first shaft sleeves 423 and a first shaft positioning sleeve 424 . The second folded plate 421 is a two-sided folded plate, the enclosing plate 422 is a U-shaped plate with an oblique angle at the top, and the two sides of the enclosing plate 422 are respectively connected to the side of the second folded plate 421 and the side of the first concave base plate 410 . The walls are welded into a box-shaped structure, the side walls of the enclosure plate 422 and the first concave base plate 410 are respectively provided with coaxial first hinge holes 425, the first bushings 423 are welded in the first hinge holes 425, A shaft positioning sleeve 424 is welded on the outer side of the right side wall of the first concave base plate 410 , and the axes of the first shaft sleeve 423 , the first shaft positioning 424 and the first hinge hole 425 are coincident.

In some embodiments of the present invention, the second hinge mechanism 450 includes two second shaft sleeves 441 and a second shaft positioning sleeve 442. The sidewall of the first concave base plate 410 and the first folding plate 430 are respectively provided with the same The second hinge hole 443 of the shaft, the second sleeve 441 is disposed between the side wall of the first concave base plate 410 and the first folded plate 430, and the second sleeve 441 is welded to the side wall of the first concave base plate 410 On the upper side, the second shaft positioning sleeve 442 is welded on the outer side of the right side wall of the first concave base plate 410. In this embodiment, the axes of the four second hinge holes 443 are connected to the second shaft sleeve 441 and the second shaft positioning sleeve. The axes of 442 coincide.

In some embodiments of the present invention, the third hinge mechanism 470 includes: a third bushing 461 welded on the axle seat plate 460 , a collar 462 welded on the inner side of the side wall of the first concave base plate 410 , and a The third shaft positioning sleeve 463 on the outer side of the side wall of the first concave base plate 410, the side wall of the first concave base plate 410 and the shaft seat plate 460 are respectively provided with coaxial third hinge holes 464, and the third shaft sleeve The axes of 461 , the collar 462 and the third shaft positioning sleeve 463 coincide with the axis of the third hinge hole 464 .

In some embodiments of the present invention, a coaxial fourth hinge hole 451 is provided on the end of the shaft seat plate 460 away from the third shaft sleeve 461 and the left side wall of the first concave base plate 410 , and the shaft seat plate 460 faces the fourth hinge hole 451 . A fourth shaft sleeve 452 is welded at the position of the fourth hinge hole 451 , and the leveling cylinder 300 is connected to the upper connecting body 400 through a hinge shaft passing through the fourth hinge hole 451 and the fourth shaft sleeve 452 . Such a structural design can realize dual use of the axle seat plate 460 .

In some embodiments of the present invention, the left and right structures of the lower connecting body 700 are symmetrical, and include: a second concave base plate 710 , a U-shaped plate 730 , two first side plates 740 , and a vertical plate 760 . The bottom of the second concave base plate 710 is provided with a notch 711. The notch 711 is symmetrical with respect to the left and right middle planes of the lower connecting body 700. Two symmetrical second semi-closed box structures 712 are arranged on both sides of the notch 711. Each of the second semi-closed box structures 712 is provided with a fourth hinge mechanism 720 for connecting the upper link 600 . The U-shaped plate 730 is disposed between the side walls of the second concave base plate 710 and located below the notch 711 , and the outer periphery of the U-shaped plate 730 is welded to the second concave base plate 710 as a whole. The first side plate 740 is arranged on the inner side of the side wall of the second concave base plate 710, and the second concave base plate 710, the U-shaped plate 730 and the first side plate 740 are connected to form two symmetrical third semi-closed box structures 741, A fifth hinge mechanism 750 for connecting the upper folding arm 500 , the lower folding arm 800 and the lower link 900 is disposed between the two third semi-closed box structures 741 . Two vertical plates 760 are provided and welded on the U-shaped plate 730 . The two vertical plates 760 are parallel to each other and are provided with a sixth hinge mechanism 770 for connecting the folding arm oil cylinder 1000 .

In some embodiments of the present invention, each second semi-closed box-shaped structure 712 includes a reinforcing plate 721, a special-shaped plate 722, and a sealing plate 723 disposed on the second concave base plate 710 and parallel to the sidewall thereof, and each first The four-joint mechanism 720 includes a fifth shaft sleeve 724 and a fourth shaft positioning sleeve 725 . The second concave base plate 710 is also provided with a second side plate 726 parallel to its side wall. The second side plate 726 is close to the edge of the notch 711 and its lower end is welded on the U-shaped plate 730. The second concave base plate 710, The reinforcing plate 721 and the second side plate 726 are provided with coaxial fifth hinge holes 727 . The special-shaped plate 722 is welded between the side wall of the second concave base plate 710 and the reinforcing plate 721 . The outer periphery of the sealing plate 723 is welded with the reinforcing plate 721 , the special-shaped plate 722 and the second concave base plate 710 to form a box-shaped structure. The fifth bushing 724 is welded between the side wall of the second concave base plate 710 and the reinforcing plate 721 and is located outside the box-shaped structure. The shaped plates 722 are welded to each other. The fourth shaft positioning sleeve 725 is welded on the outer sides of the left and right side walls of the second concave base plate 710 , and the axes of the fifth shaft sleeve 724 , the fourth shaft positioning sleeve 725 and the fifth hinge hole 727 are coincident. The second concave base plate 710 , the special-shaped plate 722 and the sealing plate 723 are welded to form a semi-closed box-shaped hinge bearing structure, which can greatly improve the supporting strength and rigidity of the fifth bushing 724 .

In some embodiments of the present invention, the second side plate 726 is provided with a process hole 728 to facilitate welding of the reinforcing plate 721 .

In some embodiments of the present invention, the special-shaped plate 722 is partially lap welded on the first side plate 740. Such a design is conducive to the reasonable transmission of structural stress streamlines, thereby greatly reducing the structural stress level, reducing weld stress and cracking risk.

The present invention also provides a crank type aerial work platform, including a turntable 1100, a working platform (not shown), and the crank arm in the above embodiment. The lower folding arm 800 and the lower link 900 in the crank arm are hinged on the turntable 1100, the working platform is set on the main arm 100 of the crank arm.

In the description of this specification, reference to the terms "one embodiment," "some embodiments," "exemplary embodiment," "example," "specific example," or "some examples," or the like, is meant to incorporate the embodiments. A particular feature, structure, material or characteristic described or exemplified is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

Although embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, The scope of the invention is defined by the claims and their equivalents.

Claims (10)

1. A crank arm, comprising a main arm (100), a main arm oil cylinder (200), a leveling oil cylinder (300), an upper connecting body (400), an upper folding arm (500), an upper connecting rod (600), a lower A connecting body (700), a lower folding arm (800), a lower connecting rod (900), and a folding arm oil cylinder (1000), characterized in that the upper connecting body (400) comprises: The upper end of the side wall of the first concave base plate (410) is provided with two symmetrical closed box-shaped structures (411), and a connection between the two closed box-shaped structures (411) for connecting the main arms (411) is provided. 100) of the first hinge mechanism (420); Two first folded plates (430), the first folded plates (430) are fixedly connected to the middle part of the inner side of the side wall of the first concave base plate (410), the first concave base plate (410) and The first folded plates (430) are connected to form two symmetrical first semi-closed box-shaped structures (440), and a space between the two first semi-closed box-shaped structures (440) for connecting the main arms is provided a second hinge mechanism (450) of the oil cylinder (200) and the upper link (600); Two axle seat plates (460) fixedly connected to the lower end of the first concave base plate (410), each of the axle base plates (450) and the side wall of the first concave base plate (410) A third hinge mechanism (470) for connecting the upper folding arms (500) is arranged therebetween. 2. The crank arm according to claim 1, characterized in that a connecting plate (480) is provided between the two first semi-closed box structures (440). 3. The crank arm according to claim 1 or 2, wherein each of the closed box structures (411) comprises a second folded plate (421) and a shroud (422), the shroud (411) 422) are respectively welded to the second folded plate (421) and the side walls of the first concave base plate (410) into one body, and the surrounding plate (422) and the first concave base plate (410) Coaxial first hinge holes (425) are respectively provided on the side walls, and the first hinge mechanism (420) includes two first shaft sleeves (423) and a first shaft positioning sleeve (424). The shaft sleeve (423) is welded in the first hinge hole (425), the first shaft positioning sleeve (424) is welded on the outer side of one of the side walls of the first concave base plate (410), the The axes of the first shaft sleeve (423), the first shaft positioning sleeve (424) and the first hinge hole (425) are coincident. 4. The crank arm according to claim 1 or 2, characterized in that, the second hinge mechanism (450) comprises two second shaft sleeves (441), a second shaft positioning sleeve (442), the first The side wall of a concave base plate (410) and the first folded plate (430) are respectively provided with coaxial second hinge holes (443), and the second shaft sleeve (441) is arranged on the first hinged hole (443). The semi-closed box structure (440) is welded on the side wall of the first concave base plate (410), and the second shaft positioning sleeve (441) is welded on the first concave base plate (410). On the outside of one of the side walls, the axes of the second shaft sleeve (441), the second shaft positioning sleeve (442) and the second hinge hole (443) are coincident. 5. The crank arm according to claim 1 or 2, wherein the third hinge mechanism (470) comprises: a third shaft sleeve (461) welded on the shaft seat plate (460), a welding a collar (462) on the inner side of the side wall of the first concave base plate (410) and a third shaft positioning sleeve (463) welded on the outer side of the side wall of the first concave base plate (410), The side wall of the first concave base plate (410) and the shaft seat plate (460) are respectively provided with coaxial third hinge holes (464), the third shaft sleeve (461), the shaft ring ( 462), the axis of the third shaft positioning sleeve (463) coincides with the axis of the third hinge hole (464). 6. The crank arm according to claim 5, characterized in that, one end of each of the axle seat plates (460) away from the third axle sleeve (461) and the end of the first concave base plate (410) One of the side walls is provided with a coaxial fourth hinge hole (451), and the side of the shaft seat plate (460) facing the fourth hinge hole (451) is provided with a fourth shaft sleeve (452). The leveling oil cylinder (300) is connected to the upper connecting body (400) through a pin shaft which is passed through the fourth hinge hole (451) and the fourth shaft sleeve (452). 7. The crank arm according to claim 1, wherein the lower connecting body (700) comprises: The second concave base plate (710) is provided with a notch (711) at the bottom, and the notch (711) is symmetrical with respect to the left and right middle planes of the lower connecting body (700). Two symmetrical second semi-closed box structures (712) are provided on both sides, and each of the second semi-closed box structures (712) is provided with a fourth hinge for connecting the upper link (600). Institution (720); A U-shaped plate (730) is arranged between the side walls of the second concave base plate (710) and is located below the notch (711), and the outer peripheral circumference of the U-shaped plate (730) is welding with the second concave base plate (710) as a whole; Two first side plates (740), which are arranged inside the side walls of the second concave base plate (710), the second concave base plate (710), the U-shaped plate (730) and the The first side plates (740) are connected to form two symmetrical third semi-closed box-shaped structures (741), and a connection between the two third semi-closed box-shaped structures (741) is provided for connecting the upper folding arms (741). 500), the lower folding arm (800) and the fifth hinge mechanism (750) of the lower link (900); There are two vertical plates (760) in number and are fixedly connected to the U-shaped plate (730). 1000) of the sixth hinge mechanism (770). 8. The crank arm according to claim 7, wherein each of the second semi-closed box-shaped structures (712) comprises a parallel to the sidewalls disposed on the second concave base plate (710) a reinforcing plate (721), a special-shaped plate (722), and a sealing plate (723), each of the fourth hinge mechanisms (720) includes a fifth shaft sleeve (724) and a fourth shaft positioning sleeve (725); The second concave base plate (710) is further provided with a second side plate (726) parallel to its side wall, the second side plate (726) is close to the edge of the slot (711) and its lower end is welded On the U-shaped plate (730), the second concave base plate (710), the reinforcing plate (721) and the second side plate (726) are provided with coaxial fifth hinge holes ( 727); The special-shaped plate (722) is welded between the side wall of the second concave base plate (710) and the reinforcing plate (721), and the outer periphery of the sealing plate (723) is connected to the reinforcing plate (721), the special-shaped plate (722) and the second concave base plate (710) are welded into one body; The fifth bushing (724) is welded between the side wall of the second concave base plate (710) and the reinforcing plate (721) and penetrates through the reinforcing plate (721). (724) are located on the outside of the special-shaped plate (722) and are welded to each other; A fourth shaft positioning sleeve (725) is welded on the outer side of the side wall of the second concave base plate (710), the fifth shaft sleeve (724), the fourth shaft positioning sleeve (725) and the fifth hinge hole (727) ) coincide with the axes. 9 . The crank arm according to claim 8 , wherein the special-shaped plate ( 722 ) is partially lap welded on the first side plate ( 740 ). 10 . 10. A crank-arm type aerial work platform, comprising a turntable (1100) and a work platform, characterized in that it further comprises the crank arm according to any one of claims 1 to 9 connected to the turntable and the work platform, respectively.

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