excavator

Abstract

The present invention relates to engineering machinery. The present invention constructs an excavator, whose working device includes a boom, a dipper arm, a dipper arm cylinder, a variable amplitude active cylinder, a variable amplitude slave cylinder, and a variable amplitude rocker arm; the front and rear ends of the variable amplitude slave cylinder are correspondingly connected to the first end of the variable amplitude rocker arm and the boom; the front and rear ends of the dipper arm cylinder are connected to the dipper arm and the second end of the variable amplitude rocker arm; the variable amplitude rocker arm is rotatably mounted on the boom via a rocker arm pin; the variable amplitude active cylinder is mounted on the rear portion of the boom, with both ends connected to the boom and a slewing platform, and when the boom is lifted beyond a preset position, the extension stroke of the piston rod of the variable amplitude active cylinder is the shortest; the large chamber and small chamber of the variable amplitude active cylinder are correspondingly connected to the large chamber and small chamber of the variable amplitude slave cylinder. The present invention can drive the variable amplitude rocker arm to rotate by the variable amplitude cylinder, thereby changing the position of the rear end of the dipper arm cylinder, increasing the distance between the attachment and the main machine when the dipper arm swings back and the amplitude of the dipper arm swing back during transportation, thereby facilitating transportation.

Description

Technical Field

[0001] The present invention relates to an engineering machine, and more particularly to an excavator. Background Art

[0002] The working device of the excavator includes a boom connected to the rotating platform at the rear end, a bucket arm installed at the front end of the boom, and accessories installed at the end of the bucket arm. A boom cylinder is connected between the boom and the rotating platform. The boom cylinder telescopes and supports the boom to swing up and down around the rear end of the boom. A bucket arm cylinder is connected between the bucket arm and the boom. The bucket arm telescopes and pushes the bucket arm to swing back and forth around its upper end.

[0003] In existing excavator working devices, the boom cylinder is directly connected to the boom, with a fixed hinge point. When the boom cylinder is retracted to its shortest position, the angle between the boom and boom is at its lowest. For conventional excavators, the design allows the boom to be raised to its highest point and swung back to its limit without collisions between the attachments and the main machine, such as the slewing platform and the cab. However, for ultra-long-arm excavators, since both the boom and boom are longer than those of conventional excavators, conventional designs can create a safety hazard when the boom is raised to its highest point and the boom is retracted to its limit, with the attachments potentially colliding with the slewing platform or cab. Summary of the Invention

[0004] The technical problem to be solved by the present invention is that the excavator's accessories with an extra-long boom may collide with the main machine, and an excavator is provided.

[0005] The technical solution for achieving the object of the present invention is as follows: an excavator comprising a slewing platform and a working device; the working device comprises a boom whose rear end is hinged to the slewing platform, a dipper arm mounted at the front end of the boom, and a dipper arm cylinder; and further comprises a luffing active cylinder, a luffing slave cylinder, and a luffing rocker arm;

[0006] The front end of the luffing slave cylinder is connected to the first end of the luffing rocker arm, and the rear end is connected to the boom;

[0007] The front end of the bucket cylinder is connected to the bucket, and the rear end is connected to the second end of the luffing rocker arm;

[0008] The luffing rocker arm is rotatably mounted on the movable arm via a rocker arm pin;

[0009] The luffing active oil cylinder is installed at the rear of the boom, one end of which is connected to the boom and the other end is connected to the slewing platform. When the boom is raised, the extension stroke of the piston rod of the luffing active oil cylinder is reduced;

[0010] The large chamber and the small chamber of the luffing active oil cylinder are correspondingly communicated with the large chamber and the small chamber of the luffing slave oil cylinder.

[0011] When the boom is lifted, the extension stroke of the piston rod of the boom-shifting active cylinder is reduced. The extension stroke of the piston rod of the boom-shifting active cylinder may change in association with the lifting height of the boom within the entire lifting stroke range of the boom, or the extension stroke of the piston rod may change in association with the lifting height of the boom within a certain middle range of the entire lifting stroke range of the boom, while the extension stroke of the piston rod does not change in association with the lifting height of the boom or changes only slightly outside the range.

[0012] In the excavator of the present invention, a luffing cam is fixed on the slewing platform, and the luffing cam is a disc cam; the cylinder barrel of the luffing active oil cylinder is fixedly mounted on the boom, and the piston rod is provided with a roller that cooperates with the curved groove of the luffing cam; or the cylinder barrel and piston rod of the luffing active oil cylinder are respectively hinged to the boom and the slewing platform through a pin shaft.

[0013] In the excavator of the present invention, the curved groove of the luffing cam is composed of three sequentially connected sections: a first curved groove, a second curved groove, and a third curved groove. The cam profiles of the first and third curved grooves are arcs centered on the boom rear end pin, and the radius of the cam profile of the third curved groove is greater than the radius of the cam profile of the first curved groove. During the process of lifting the boom from its lowest point to its highest point, when the boom is lifted by an angle less than a first angle, the roller rolls on the first curved groove; when the boom is lifted by an angle greater than the first angle but less than a second angle, the roller rolls on the second curved groove; and when the boom is lifted by an angle greater than the second angle, the roller rolls on the third curved groove. While the roller rolls on the first and third curved grooves, the piston extension position of the luffing active cylinder remains unchanged. As the roller rolls from the first curved groove through the second curved groove to the third curved groove, the piston rod extension position of the luffing active cylinder gradually decreases.

[0014] In the excavator of the present invention, there are two said boom active cylinders, which are correspondingly installed on both sides of the boom and the large chambers and small chambers of the two said boom active cylinders are correspondingly connected; two pairs of said boom cams are arranged on both sides of the boom on the rotary platform and are connected to the piston rods of the said boom active cylinders.

[0015] In the excavator of the present invention, the upper end of the bucket arm is connected to the front end of the boom via a pin; the first end, the second end and the rocker arm pin are arranged in a triangle.

[0016] In the excavator of the present invention, the first end and the second end of the luffing rocker arm are located on the same side of the straight line where the rocker arm pin and the rear end hinge point of the luffing slave cylinder are located, and are also located on the same side of the straight line where the rocker arm pin and the front end hinge point of the boom slave cylinder are located. Furthermore, the first end and the second end of the luffing rocker arm are located on the upper side of the straight line where the rocker arm pin and the rear end hinge point of the luffing slave cylinder are located, and are also located on the upper side of the straight line where the rocker arm pin and the front end hinge point of the boom cylinder are located.

[0017] In the excavator of the present invention, the boom cylinder, the luffing slave cylinder and the luffing rocker arm are all arranged in pairs; the two luffing rocker arms are respectively arranged on both sides of the movable arm and connected to the two ends of the rocker arm pin shaft; each luffing rocker arm is connected to one boom cylinder and one luffing slave cylinder; the large chambers of the two luffing slave cylinders are connected to each other.

[0018] The excavator of the present invention further comprises a connecting rod, and both ends of the connecting rod are fixedly connected to the two luffing rocker arms respectively.

[0019] In the excavator of the present invention, the rocker arm pin is rotationally connected to the boom, the variable-length rocker arm and the rocker arm pin are fixedly connected, and / or the distance from the rocker arm pin to the first end on the variable-length rocker arm is greater than the distance from the rocker arm pin to the second end.

[0020] In the excavator of the present invention, each of the luffing rocker arms is a double-plate structure, and corresponding ends of the boom cylinder and the luffing slave cylinder are located between the two plates of the luffing rocker arm.

[0021] In the excavator of the present invention, the luffing rocker arm includes a left rocker arm and a right rocker arm respectively arranged on the left and right sides of the boom; the boom cylinder is arranged on the upper side of the boom, and its front end is connected to the rear end of the boom, and the rear end is connected to the upper ends of the left and right rocker arms; the luffing slave cylinder is arranged on the lower side of the boom, and its front end is connected to the lower ends of the left and right rocker arms, and the rear end is connected to the boom.

[0022] In this invention, when the boom is raised to its highest position, the luffing master cylinder retracts under the action of the luffing cam. The oil in its large chamber flows into the large chamber of the luffing slave cylinder, and the oil in the small chamber of the luffing slave cylinder enters the small chamber of the luffing master cylinder. The piston rod of the luffing slave cylinder retracts and pulls the luffing rocker arm. The rotation of the luffing rocker arm changes the position of the rear end of the boom cylinder, thereby adjusting the angle between the boom and the boom when the boom is raised to its highest point, preventing collisions between the attachment and the excavator body. When the boom is lowered, the cam pulls the piston rod of the luffing master cylinder, causing it to extend. The luffing slave cylinder then retracts, reducing the angle between the boom and the boom, thereby increasing the swing amplitude of the boom and facilitating transportation.

[0023] Compared with the prior art, the present invention can push the boom active cylinder to extend and retract during the boom raising and lowering process through the cam, and correspondingly make the boom active cylinder retract and extend, thereby changing the position of the rear end of the boom cylinder, and increasing the distance between the attachment and the main machine to avoid collision when the boom swings back to the extreme position; and when the excavator is transported, the amplitude of the boom swing is increased to facilitate transportation. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a structural schematic diagram of the excavator of the present invention.

[0025] Figure 2 It is a schematic diagram of the connection structure of the excavator bucket cylinder of the present invention.

[0026] Figure 3 It is a schematic diagram of the exploded connection structure of the excavator bucket cylinder of the present invention.

[0027] Figure 4 It is a schematic diagram of the exploded structure of the connection between the luffing active oil cylinder and the luffing cam of the excavator according to the present invention.

[0028] Figure 5 This is a second connection diagram of the luffing slave cylinder and the luffing rocker arm of the excavator according to the present invention.

[0029] Parts names and serial numbers in the figure:

[0030] Main machine 10, boom 11, arm 12, attachment 13, luffing rocker arm 14, arm cylinder 15, luffing slave cylinder 16, front end pin 17 of arm cylinder, rocker arm pin 18, rear end pin 19 of luffing slave cylinder, rear end pin 20 of arm, boom cylinder 21, luffing active cylinder 22, roller 221, cylinder fixing bolt 222, luffing cam 23, curved groove 231, first curved groove 2311, second curved groove 2312, third curved groove 2313, cam fixing bolt 232, rear end pin 233 of boom, slewing platform 24, oil pipe 25, front end pin 26 of boom. DETAILED DESCRIPTION

[0031] The specific implementation scheme is described below with reference to the accompanying drawings.

[0032] The excavator in the present invention includes a slewing platform and a working device; the working device includes a boom 11 whose rear end is hinged to the slewing platform 24, a dipper arm 12 installed at the front end of the boom 11, and a dipper arm cylinder 15. It also includes a boom active cylinder 22, a boom slave cylinder 16, and a boom rocker arm 14; the front end of the boom slave cylinder 16 is connected to the first end of the boom rocker arm 14, and the rear end is connected to the boom 11. The front end of the boom cylinder 15 is connected to the boom 12, and the rear end is connected to the second end of the luffing rocker arm 14; the luffing rocker arm 14 is rotatably mounted on the boom 11 through the rocker arm pin 18; the luffing active cylinder 22 is installed at the rear of the boom 11, one end of which is connected to the boom 11, and the other end is connected to the rotary platform 24. When the boom 11 is lifted beyond a predetermined angle, the piston rod of the luffing active cylinder 22 has the shortest extension stroke; the large chamber and small chamber of the luffing active cylinder 22 are correspondingly connected to the large chamber and small chamber of the luffing slave cylinder 16. When the boom 11 is raised or lowered, it drives the luffing active cylinder 22 to retract and extend. The retraction and extension of the luffing active cylinder 22 corresponds to the extension and shortening of the luffing slave cylinder 16. The change in the length of the luffing slave cylinder 16 changes the position of the rear end of the arm cylinder 15 through the luffing rocker arm 14, thereby changing the minimum angle between the arm 12 and the boom 11. When the boom is lifted beyond a predetermined angle, the angle between the arm and the boom is large enough to avoid collision between the attachment 13 and the excavator main body 10. When the boom 11 is lowered to the lowest point, the angle between the arm 12 and the boom 11 is small enough to ensure that the height of the excavator in the transport state meets the transportation requirements.

[0033] Specifically, if Figure 1 As shown, the excavator includes a main machine 10 and a working device. The working device includes a boom 11, an arm 12 mounted at the front end of the boom 11, an arm cylinder 15, a luffing slave cylinder 16, and a luffing rocker arm 14. The upper end of the arm 12 is connected to the front end of the boom 11 via a pin, and the luffing rocker arm 14 is rotatably mounted to the boom 11 via a rocker arm pin 18. The front end of the luffing slave cylinder 16 is connected to the first end of the luffing rocker arm 14, and the rear end is connected to the boom 11. The front end of the arm cylinder 15 is connected to the arm 12, and the rear end is connected to the second end of the luffing rocker arm 14. When the arm cylinder is extended or retracted, it pushes the arm to swing back and forth around a pin 20 at the rear end of the arm.

[0034] In this embodiment, the extension and retraction of the luffing slave cylinder 16 drives the luffing rocker arm 14 to pivot about the rocker arm pin 18. The second end of the luffing rocker arm 14 also drives the rear end of the arm cylinder 15 forward and backward, effectively adjusting the mounting position of the arm cylinder 15 on the boom. During operation, rotating the second end of the luffing rocker arm 14 forward increases the minimum angle between the arm 12 and the boom 11, preventing the attachment 13 at the end of the arm 12 from colliding with the excavator body 10. During transport, rotating the second end of the luffing rocker arm 14 backward decreases the minimum angle between the arm 12 and the boom 11, bringing them closer together and ensuring a lower transport height.

[0035] Alternatively, as Figure 3 As shown, the arm cylinder 15, the luffing slave cylinder 16, and the luffing rocker arm 14 can also be arranged in pairs. The two luffing rocker arms 14 are arranged on either side of the boom 11 and connected to the ends of the rocker arm pin 18; the first and second ends of each luffing rocker arm 14 are connected to a luffing slave cylinder and an arm cylinder respectively.

[0036] Optionally, the luffing rocker arms 14 on both sides of the boom 11 may be fixedly connected by a connecting rod (not shown in the figure), with both ends of the connecting rod fixedly connected to the luffing rocker arms 14. The connecting rod connects the two luffing rocker arms 14, making the luffing rocker arms 14 on both sides rigid and having greater strength, while also ensuring the synchronization of the rotation of the luffing rocker arms 14 on both sides.

[0037] Optionally, the first end, the second end, and the rocker arm pin 18 of the luffing rocker arm 14 may be arranged in a triangle.

[0038] like Figure 2 Figure 3 As shown, the luffing rocker arm 14 is rotatably mounted at point A via the rocker arm pin 18. The first end of the luffing rocker arm 14 is hinged to the front end of the luffing slave cylinder 16 at point C. The second end of the luffing rocker arm 14 is hinged to the front end of the arm cylinder 15 at point B. The rear end of the luffing slave cylinder 16 is mounted to point E of the boom 11 via the rear end pin 19 of the luffing slave cylinder. The front end of the arm cylinder 15 is hinged to point D of the arm 12 via the front end pin 17 of the arm cylinder. Points A, B, and C are arranged in a triangle.

[0039] The first and second ends of the luffing rocker arm 14 are located on the same side of the line containing the rocker arm pin 18 and the rear end hinge point of the luffing slave cylinder (point E). They are also located on the same side of the line containing the rocker arm pin 18 and the front end hinge point of the boom cylinder (point D). That is, points B and C are located on the same side of line AE, and also on the same side of line AD. Preferably, points B and C are located above lines AE and AD. When the luffing slave cylinder 16 is retracted to its shortest position or extended to its longest position, points B and C are located on the same side of line AE, enabling the luffing slave cylinder to limit the position. The simultaneous location of points B and C above lines AE and AD allows for more clear space under the boom.

[0040] Optionally, the rocker arm pin 18 and the boom 11 may be connected in a rotational manner, while the luffing rocker arm 14 and the rocker arm pin 18 may be fixedly connected. The luffing rocker arm 14 is mounted via the rocker arm pin 18, which is rotatably mounted relative to the boom. In other embodiments, the rocker arm pin 18 and the boom 11 may be fixedly connected, while the luffing rocker arm 14 and the rocker arm pin 18 may be connected in a rotational manner.

[0041] like Figure 2 As shown, the distance from the rocker arm pin 18 to the first end of the luffing rocker arm 14 may be greater than the distance from the rocker arm pin 18 to the second end, that is, the length of AB is less than the length of AC.

[0042] like Figure 3 As shown, each luffing rocker arm 14 can be a double-plate structure. Each luffing rocker arm 14 is composed of two parallel plates. The corresponding ends of the arm cylinder 15 and the luffing slave cylinder 16 are located between the two plates of the luffing rocker arm 14 and are rotatably connected to the luffing rocker arm 14 via a pin. The double-plate structure of the luffing rocker arm ensures sufficient strength while reducing the material required for the luffing waist plate.

[0043] like Figure 1 Figure 4 As shown, the rear end of the boom 11 is rotatably connected to the rotary platform 24 via a pin shaft, and the telescopic movement of the boom cylinder 21 drives the boom 11 to rise and fall around the hinge pin shaft and swing back and forth.

[0044] The cylinder barrel of the active luffing cylinder 22 is fixed to the boom 11 via cylinder barrel fixing bolts 222, and a roller 221 is mounted on the end of the piston rod. The luffing cam 23 is fixed to the slewing platform 24 via cam fixing bolts 232. The luffing cam 23 has a curved groove 231, and the roller 221 at the end of the piston rod is located in the groove 231. When the boom 11 is raised or lowered, the roller 221 moves in the groove 231 and pushes the piston rod of the active luffing cylinder 22 to extend or retract.

[0045] The large chamber and small chamber of the luffing active cylinder 22 are connected to the large chamber and small chamber of the luffing slave cylinder 16 correspondingly, that is, the large chamber of the luffing active cylinder 22 is connected to the large chamber of the luffing slave cylinder 16 through the pipeline 25, and the small chamber of the luffing active cylinder 22 is connected to the small chamber of the luffing slave cylinder 16 through the pipeline 25. When the luffing active cylinder 22 extends, the luffing slave cylinder 16 retracts, and when the luffing active cylinder 22 retracts, the luffing slave cylinder 16 extends.

[0046] Optionally, there may be two luffing active cylinders 22, each mounted on either side of the boom 11, with the large chambers and small chambers of the two luffing active cylinders 22 communicating with each other. Two pairs of luffing cams 23 are mounted on the slewing platform 24 to correspond to the two luffing active cylinders 22. The two pairs of luffing cams 23 are arranged on either side of the boom 22, with each pair of luffing cams 23 connected to one luffing active cylinder 22.

[0047] In this embodiment, when the boom 11 is raised or lowered, the luffing active cylinder 22 swings along with the boom 11, causing the roller 221 at the end of the piston rod to slide in the curved groove 231 of the luffing cam 23. As the roller 221 slides in the curved groove 231, it pushes the piston rod of the luffing active cylinder 22 to extend or retract.

[0048] In this embodiment, when the boom is raised, the piston rod extension stroke of the boom active cylinder is reduced, and the corresponding relationship between the boom lifting height and the boom active cylinder length can be determined by designing the curve of the curved groove 231. Figure 4 As shown, the curved groove 231 of the variable amplitude cam 23 consists of three sequentially connected sections: a first curved groove 2311, a second curved groove 2312, and a third curved groove 2313. The cam profiles of the first curved groove 2311 and the third curved groove 2313 are arcs centered on the boom rear end pin 233, and the cam profile radius of the third curved groove 2313 is greater than that of the first curved groove 2311. During the lifting process of the boom 11 from its lowest point to its highest point, when the lifting angle of the boom 11 is less than a first angle value, the roller 221 rolls on the first curved groove 2311; when the lifting angle of the boom 11 is greater than the first angle value but less than a second angle value, the roller 221 rolls on the second curved groove 2312; and when the lifting angle of the boom 11 is greater than the second angle value, the roller 221 rolls on the third curved groove 2313. When the roller 221 rolls on the first curved groove 2311 and the third curved groove 2313, the extension displacement of the piston rod of the boom active cylinder 22 does not change. When the roller 221 rolls from the first curved groove 2311 to the second curved groove 2312 to the third curved groove 2313, the extension displacement of the piston rod of the boom active cylinder 22 gradually decreases.

[0049] When the boom 11 is lifted and rotated backward by an angle exceeding the second angle value, the roller rolls in the third curved groove 2313, and the extension length of the piston rod of the boom control cylinder 22 does not change with the boom lift height, or changes very little. At this time, the piston rod has the shortest or smallest extension displacement. Correspondingly, when the boom 11 is lifted and rotated backward by an angle less than the first angle value, the roller rolls in the first curved groove 2311, and the extension length of the piston rod of the boom control cylinder 22 does not change with the boom lift height, or changes very little. At this time, the piston rod has the longest or longest extension displacement. When the boom 11 is lifted and rotated backward by an angle swinging between the first and second angle values, the boom control cam pushes the piston rod of the boom control cylinder 22 to extend or shorten.

[0050] When the boom 11 is lifted and rotated backward to an angle exceeding the second angle value, the luffing cam 23 pushes the piston rod of the luffing active cylinder 22 to retract to the shortest, and the oil in the large chamber of the luffing active cylinder 22 flows to the large chamber of the luffing slave cylinder 16. The piston rod of the luffing slave cylinder 16 extends and pushes the luffing rocker arm 14 to rotate. The luffing rocker arm 14 pushes the rear end of the arm cylinder 15 to move forward, increasing the angle between the arm 12 and the boom 11. At this time, even if the arm cylinder 15 retracts to the limit, the attachment 13 at the end of the arm 12 is at a sufficient safety distance from the excavator main body 10 to avoid collision with the excavator main body.

[0051] When the excavator is in the transport state, it is usually necessary to lower the boom 11. At this time, the boom 11 is lowered and rotated forward by an angle exceeding the second predetermined position. The piston rod of the boom active cylinder 22 has the longest extension displacement, and the oil in the large chamber of the boom slave cylinder 16 enters the boom active cylinder 22. The boom slave cylinder 16 retracts, and the boom rocker arm 14 drives the rear end of the arm cylinder 15 to move backward, reducing the minimum angle between the arm 12 and the boom 11, so that the height of the boom 11 can be lowered during transportation to meet the transportation requirements.

[0052] In the above embodiment, the cylinder barrel of the boom activation cylinder 22 is fixedly connected to the boom 11 and is connected to the slewing platform 24 through the boom cam 23. In other embodiments, the boom activation cylinder 22 can also be connected and installed in other forms. For example, the two ends of the boom activation cylinder 22 are respectively hingedly connected to the boom 11 and the slewing platform 24 through a pin shaft. The hinge points at the two ends of the boom activation cylinder 22 and the intersection points of the boom 11 and the slewing platform 24 form a triangle. When the boom 11 is lifted, the boom activation cylinder 22 is pressed back. When the boom 11 is lowered, the boom activation cylinder 22 is stretched.

[0053] In the above embodiment, the arrangement of the arm cylinder 15 and the luffing rocker arm 14 may also be in other forms, such as Figure 5 As shown, the rear portion of the arm 12 is hinged to the front end of the boom 11 via a pin shaft 26 at the front end of the boom, and the rear end of the arm 12 is hinged to the front end of the arm cylinder 15 via a pin shaft.

[0054] The luffing arm 14 includes a left rocker arm 141 and a right rocker arm 142, respectively positioned on the left and right sides of the boom 11. These arms are pivotally connected to the boom 11 via a rocker arm pin 18. The boom cylinder 15 is positioned above the boom 11, its front end hinged to the rear end of the boom 12 via a pin 17 at the front end of the boom cylinder. The rear end of the boom cylinder 15 is also connected to the upper ends of the left and right rocker arms 141, 142 via a pin. The luffing slave cylinder 16 is positioned below the boom 11, its front end hinged to the lower ends of the left and right rocker arms 141, 142 via a pin, and its rear end hinged to the boom 11 via a pin. In this structural arrangement, when the boom cylinder 15 extends, the boom 12 swings backward toward the excavator body 10. When the boom cylinder 15 retracts, the boom 12 swings away from the excavator body 10. When the boom 11 swings backward and is lifted, the luffing active cylinder 22 retracts and the luffing slave cylinder 16 extends. The luffing slave cylinder 16 pushes the lower end of the luffing rocker arm 14 forward and the upper end of the luffing rocker arm 14 moves backward. While the arm cylinder 15 keeps its length unchanged, the lower part of the arm 12 (accessories) moves forward relative to the boom 11, increasing the distance between the lower part of the arm 11 and the excavator mainframe 10, thereby preventing the arm 12 (accessories) from colliding with the excavator mainframe 10. When the boom 11 tilts forward and descends, the luffing active cylinder 22 extends and the luffing slave cylinder 16 retracts. The luffing slave cylinder 16 pushes the lower end of the luffing rocker arm 14 backward and the upper end of the luffing rocker arm 14 moves forward. When the arm cylinder 15 keeps its length unchanged, the lower part of the arm 12 (attachments) moves backward relative to the boom 11, reducing the angle between the arm 12 and the boom 11. When the excavator is in the transport state, the height of the boom can be reduced to meet the height limit requirement during excavator transportation.

Claims

1. An excavator comprising a slewing platform and a working device; the working device comprises a boom whose rear end is hinged to the slewing platform, a dipper arm mounted at the front end of the boom, and a dipper arm cylinder, characterized in that: It also includes a luffing active cylinder, a luffing slave cylinder, and a luffing rocker arm; The front end of the luffing slave cylinder is connected to the first end of the luffing rocker arm, and the rear end is connected to the boom; The front end of the bucket cylinder is connected to the bucket, and the rear end is connected to the second end of the luffing rocker arm; The luffing rocker arm is rotatably mounted on the movable arm via a rocker arm pin; The luffing active oil cylinder is installed at the rear of the boom, one end of which is connected to the boom and the other end is connected to the slewing platform. When the boom is raised, the extension stroke of the piston rod of the luffing active oil cylinder is reduced; The large chamber and the small chamber of the luffing active oil cylinder are correspondingly communicated with the large chamber and the small chamber of the luffing slave oil cylinder.

2. The excavator according to claim 1, characterized in that A luffing cam is fixed to the rotary platform, and the luffing cam is a disc cam; the cylinder barrel of the luffing active oil cylinder is fixedly mounted on the boom, and the piston rod is provided with a roller that cooperates with the curved groove of the luffing cam; or the cylinder barrel and piston rod of the luffing active oil cylinder are respectively hinged to the boom and the rotary platform through a pin shaft.

3. The excavator according to claim 2, characterized in that The curved groove of the variable amplitude cam is composed of three sections: a first curved groove, a second curved groove, and a third curved groove connected in sequence. The cam contour lines of the first curved groove and the third curved groove are arc lines with the pin shaft at the rear end of the boom as the center, and the radius of the cam contour line of the third curved groove is greater than the radius of the cam contour line of the first curved groove.

4. The excavator according to claim 2 or 3, characterized in that: There are two active cylinders for varying the length of the boom, which are correspondingly installed on both sides of the boom and whose large chambers and small chambers are correspondingly connected; two pairs of the said variable length cams are arranged on both sides of the boom on the rotary platform and are connected to the piston rods of the said active cylinders for varying the length of the boom.

5. The excavator according to any one of claims 1 to 3, characterized in that: The upper end of the bucket arm is connected to the front end of the boom through a pin shaft; the first end, the second end and the rocker arm pin shaft of the variable amplitude rocker arm are arranged in a triangle.

6. The excavator according to claim 5, characterized in that The first end and the second end of the variable amplitude rocker arm are located on the same side of the straight line where the rocker arm pin shaft and the rear end hinge point of the variable amplitude slave cylinder are located, and are also located on the same side of the straight line where the rocker arm pin shaft and the front end hinge point of the boom slave cylinder are located.

7. The excavator according to claim 6, characterized in that The first end and the second end of the variable amplitude rocker arm are located above the straight line where the rocker arm pin shaft and the rear end hinge point of the variable amplitude slave cylinder are located, and are also located above the straight line where the rocker arm pin shaft and the front end hinge point of the boom cylinder are located.

8. The excavator according to claim 4, characterized in that The arm cylinder, luffing slave cylinder and luffing rocker arm are all arranged in pairs; The two luffing rocker arms are respectively arranged on both sides of the boom and connected to the two ends of the rocker arm pin; each luffing rocker arm is connected to one boom cylinder and one luffing slave cylinder; The large chambers of the two luffing slave cylinders are communicated with each other.

9. The excavator according to claim 8, characterized in that The rocker arm pin is rotationally connected to the boom, the variable amplitude rocker arm and the rocker arm pin are fixedly connected, and / or the distance from the rocker arm pin to the first end of the variable amplitude rocker arm is greater than the distance from the rocker arm pin to the second end.

10. The excavator according to any one of claims 1 to 3, characterized in that: The luffing rocker arm comprises a left rocker arm and a right rocker arm respectively arranged on the left and right sides of the boom; The arm cylinder is arranged on the upper side of the boom, with its front end connected to the rear end of the arm, and the rear end connected to the upper ends of the left rocker arm and the right rocker arm; The amplitude-changing slave cylinder is arranged on the lower side of the boom, with its front end connected to the lower ends of the left rocker arm and the right rocker arm, and its rear end connected to the boom.

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