Protection device for a hydraulic cylinder, hydraulic cylinder assembly, grapple, and work machine

Abstract

The present utility model relates to a protection device for a hydraulic cylinder, a hydraulic cylinder assembly, a grapple, and a work machine. The protection device comprises a flange, a protection tube, and a locking plate detachably mounted on the flange. The flange is mounted around a cylinder rod of the hydraulic cylinder. The protection tube is installed around the flange and a cylinder barrel of the hydraulic cylinder, and an inner wall of the protection tube is provided with a circumferential groove and an axial groove. The locking plate has a protruding portion extending radially outward from an outer peripheral surface of the flange. The protection tube is rotatable relative to the flange between an unlocked position and a locked position. The protruding portion of the locking plate is configured to, in the unlocked position, be aligned axially with the axial groove and be capable of entering and exiting the circumferential groove via the axial groove, and, in the locked position, to be engaged within the circumferential groove. The protection device of the present utility model transmits possible axial impact force on the protection tube to the flange and the cylinder rod via the locking plate having a larger force-bearing area and a higher strength, thereby avoiding the risk in the prior art where the protection tube and bolts are damaged due to the axial impact force on the protection tube being directly borne by the bolts.

Description

[0001] Description

[0002] PROTECTION DEVICE FOR A HYDRAULIC CYLINDER, HYDRAULIC CYLINDER ASSEMBLY, GRAPPLE, AND WORK MACHINE

[0003] Technical Field

[0004] The present utility model relates to the technical field of work machine components, and more particularly, to a protection device for a hydraulic cylinder, a hydraulic cylinder assembly including the protection device, a grapple including the hydraulic cylinder assembly, and a work machine including the grapple.

[0005] Background

[0006] In a work machine, such as a crane, that is equipped with a grapple, a hydraulic cylinder provides power to the grapple formed by multiple jaws or jaw plates to drive it to open and close, thereby grasping and discharging materials.

[0007] In the prior art, to protect the hydraulic cylinder, a protection tube or protective sleeve is typically sleeved around the periphery of the hydraulic cylinder. The protection tube is fixed to a free end of the cylinder rod that is extended from the cylinder barrel, via two bolts opposing each other in the diameter direction, thereby enabling the protection tube to telescopically move along with the cylinder rod relative to the cylinder barrel while protecting the cylinder rod from external damage. The heads of the bolts are often exposed at the outside of the peripheral wall of the protection tube and are susceptible to impact forces from the materials to deform the bolts. Furthermore, the harsh working environment of the grapple may subject the protection tube to significant external impact forces, particularly in the axial direction, during the operation of the grapple. These impact forces are transmitted to the cylinder rod via the bolts, thereby generating substantial shear forces at the contact points between the bolts and the protection tube, leading to plastic deformation of both the protection tube and the bolts, or even resulting in complete fracture of the bolts.

[0008]

[0009] It is an object of the present utility model to solve at least one of the above problems and / or other defects existing in the prior art.

[0010] To achieve the above object, according to one aspect of the present utility model, a protection device for a hydraulic cylinder is provided. The hydraulic cylinder comprises a cylinder barrel and a cylinder rod capable of telescoping relative to the cylinder barrel. The protection device comprises a flange, a protection tube, and a locking plate detachably mounted on the flange. The flange is mounted around a free end portion of the cylinder rod that extends out from the cylinder barrel. The protection tube is installed around the flange and the cylinder barrel and comprises a fixed end portion fixable to the flange. An inner wall of the fixed end portion is provided with a circumferential groove extending circumferentially and an axial groove extending axially from an axial end face of the fixed end portion to the circumferential groove. The locking plate has a protruding portion extending radially outward from an outer peripheral surface of the flange. The protection tube is rotatable relative to the flange between an unlocked position and a locked position. The protruding portion of the locking plate is configured to, when the protection tube is in the unlocked position, be aligned axially with the axial groove and be capable of entering and exiting the circumferential groove via the axial groove, and when the protection tube is in the locked position, to be engaged within the circumferential groove.

[0011] According to an embodiment of the present utility model, the flange is provided with a mounting slot recessed radially inward from its outer peripheral surface. The locking plate comprises a mounting portion engaged within the mounting slot and is detachably mounted to the flange via a first fastener passing axially through the flange and the mounting portion.

[0012] According to an embodiment of the present utility model, the locking plate is detachably fixed to the flange by two parallel said first fasteners.

[0013] According to an embodiment of the present utility model, two locking plates arranged opposite each other in a diameter direction are mounted on the flange. The fixed end portion of the protection tube is provided with twosaid axial grooves corresponding respectively to the protruding portions of the two locking plates. The circumferential groove is a closed loop groove extending circumferentially to receive the protruding portions of the two locking plates.

[0014] According to an embodiment of the present utility model, a first fixing hole extending radially is provided on the outer peripheral surface of the flange. A second fixing hole is provided on the fixed end portion of the protection tube. When the protection tube is in the locked position, the first fixing hole and the second fixing hole are aligned with each other and receive a second fastener to lock the protection tube relative to the flange.

[0015] According to an embodiment of the present utility model, the second fastener is a hex socket head bolt, and its head is at least partially embedded in the second fixing hole of the protection tube.

[0016] According to an embodiment of the present utility model, the flange is further provided on its outer peripheral surface with a through recess extending axially through the thickness of the flange and circumferentially offset from the locking plate. The through recess and the inner wall of the protection tube together define a flow passage in communication with a space between the protection tube and the cylinder barrel.

[0017] According to another aspect of the present utility model, a hydraulic cylinder assembly is provided. The hydraulic cylinder assembly comprises a hydraulic cylinder and the protection device according to any one of the above.

[0018] According to yet another aspect of the present utility model, a grapple is provided. The grapple comprises a plurality of jaws and the hydraulic cylinder assembly as described above driving each of the jaws to pivot.

[0019] According to a further aspect of the present utility model, a work machine is provided. The work machine comprises the grapple as described above.

[0020] In the protection device of the present utility model, a circumferential groove is provided on the inner wall of the fixed end portion of the protection tube, and a locking plate is fixed on the flange of the cylinder rod.By having the protruding portion of the locking plate engaged within the circumferential groove, the protection tube and the flange can be fixed relative to each other in the axial direction. Thereby, possible axial impact force on the protection tube during grapple operation can be transmitted to the flange and the cylinder rod via the locking plate. Having a larger force-bearing area and a higher strength than bolts, the locking plate can avoid the risk in the prior art where the protection tube and bolts are damaged due to the axial impact force on the protection tube being directly borne by the bolts.

[0021]

[0022] The features and advantages of the present utility model will be clearly understood through the following detailed description provided with reference to the accompanying drawings. It should be understood that the following drawings are merely schematic and not necessarily drawn to scale, and therefore should not be construed as limiting the present utility model, wherein:

[0023] FIG. 1 shows a perspective view of a protection device installed on a hydraulic cylinder, according to an embodiment of the present utility model.

[0024] FIG. 2 shows an exploded view of the protection device and the hydraulic cylinder shown in FIG. 1.

[0025] FIG. 3 shows a perspective view of a flange in the protection device shown in FIG. 1.

[0026] FIG. 4 shows an end view of the protection device assembled with the cylinder rod of the hydraulic cylinder shown in FIG. 1.

[0027] FIG. 5 shows a cross-sectional view taken along line A-A of the protection tube in the protection device shown in FIG. 4 when in an unlocked position.

[0028] FIG. 6 shows a cross-sectional view taken along line A-A of the protection tube in the protection device shown in FIG. 4 when in a locked position.List of reference numerals:

[0029] 1. Hydraulic cylinder; 11. Cylinder barrel; 111. Protrusion; 12. Cylinder rod; 2. Flange; 21. Mounting slot; 22. First side wall; 221. First opening; 23. Second side wall; 231. Second opening; 24. First fixing hole; 25. Through recess; 3. Protection tube; 31. Fixed end portion; 311. Circumferential groove; 312. Axial groove; 313. Second fixing hole; 32. Main body portion; 4. Locking plate; 41. Protruding portion; 42. Mounting portion; 5. First fastener; 6. Second fastener; 7. Flow passage; 8. Support ring.

[0030] Detailed

[0031]

[0032] Embodiments of the present utility model will be described below with reference to the accompanying drawings. In the following description, numerous specific details are set forth in order to make those skilled in the art fully understand and implement the present utility model. However, it will be apparent to those skilled in the art that the present utility model may be implemented without some of these specific details. Furthermore, it will be appreciated that the present utility model is not limited to the specific embodiments described herein. Rather, any combination of features and elements described below can be used to implement the present utility model, regardless of whether they relate to different embodiments. Therefore, the following aspects, features, embodiments and advantages are for illustration only, and should not be regarded as elements or limitations of the claims, unless explicitly stated in the claims.

[0033] Terms such as "first" and "second" are used herein to describe the elements of the present application, but they are only used to distinguish individual elements, rather than to limit the nature, order or number of the elements. The terms "comprising", "including" and “having” are used to indicate an open-ended inclusion, and mean that there may be other elements / components besides the listed elements / components.

[0034] Work machines such as cranes or loaders can be equipped with work tools such as two-jaw grapples or multi -jaw grapples. Such a grapplecomprises a plurality of jaws arranged at equal intervals circumferentially. Each of the jaws can be driven by a corresponding hydraulic cylinder to pivot, causing the entire grapple to perform opening and closing actions to grasp or discharge materials. To address the harsh working environment of the grapple, the hydraulic cylinder can be equipped with a protection device to particularly protect the cylinder rod of the hydraulic cylinder, which needs to telescopically move relative to the cylinder barrel.

[0035] FIGS. 1 and 2 show a protection device according to an embodiment of the present utility model and the corresponding hydraulic cylinder. As shown in FIGS. 1 and 2, the hydraulic cylinder 1 may comprise a cylinder barrel 11 and a cylinder rod 12. The cylinder barrel 11 is tubular in shape with one end open and the other end closed, and a hydraulic chamber (not shown) is defined within the cylinder barrel. A fixed end portion of the cylinder rod 12 is disposed within the hydraulic chamber and is connected to a piston (not shown). The piston divides the hydraulic chamber into a rod chamber and a rodless chamber. Two oil pipes (not shown) are provided outside the cylinder barrel 11. One oil pipe communicates with the rod chamber, and the other oil pipe communicates with the rodless chamber. A free end portion of the cylinder rod 12 extends out of the cylinder barrel 11 from the open end of the cylinder barrel 11. The closed end of the cylinder barrel 11 is provided with a connecting portion having a through hole. The free end portion of the cylinder rod 12 is also provided with a connecting portion having a through hole. These two connecting portions are respectively hinged to a grapple mounting structure on the work machine and to one of the jaws of the grapple, so that the cylinder rod 12 is driven to extend or retract by hydraulic oil entering the rod chamber or the rodless chamber, thereby driving the jaw to pivot. The protection device for the hydraulic cylinder 1 according to this embodiment may comprise a flange 2, a protection tube 3, and a locking plate 4.

[0036] FIG. 3 shows a perspective view of the flange 2 according to this embodiment. As shown in FIG. 3, the flange 2 is centrally provided with a through hole for the cylinder rod 12 to pass through, and is thus fixedly mountedaround the free end portion of the cylinder rod 12. In order to mount the locking plate 4, the flange 2 may be provided, for example, with a mounting slot 21 recessed radially inward from an axially middle portion of its outer peripheral surface. Thereby, a first side wall 22 and a second side wall 23 are formed on two axial sides of the mounting slot 21, respectively. The first side wall 22 is provided with a first opening 221, and the second side wall 23 is provided with a second opening 231 corresponding to the first opening 221.

[0037] As shown in FIGS. 4 to 6, the locking plate 4 may comprise a protruding portion 41 and a mounting portion 42. The mounting portion 42 is engaged within the mounting slot 21 of the flange 2. Thereby, the first side wall 22 and the second side wall 23 located on the two axial sides of the mounting slot 21 can restrict the axial position of the mounting portion 42 and thus of the locking plate 4, so that the locking plate 4 can be securely fixed relative to the flange 2 bidirectionally in the axial direction and can transmit impact forces experienced by the protection tube bidirectionally in the axial direction. The mounting portion 42 is provided with a mounting hole. A first fastener 5, such as a bolt, passes sequentially through the first opening 221 on the flange 2, the mounting hole on the mounting portion 42, and the second opening 231 on the flange 2 along the axial direction of the flange 2 and the protection tube 3, thereby detachably mounting the locking plate 4 to the flange 2. In other embodiments, the mounting slot 21 may also be a slot that is recessed radially inward from the outer peripheral surface of the flange 2 but is delimited by only a first side wall 22 or a second side wall 23 on one of the axial sides and is open on the other axial side. In this case, the first fastener 5 is needed to fix the locking plate 4 relative to the flange 2 in the axial direction. In the illustrated embodiment, the locking plate 4 is detachably mounted on the flange 2 by two parallel first fasteners 5. Such two first fasteners 5 can keep the locking plate 4 fixed in the plane defined by the locking plate 4 (in various directions including circumferential and radial directions). Certainly, it is also feasible that only one fastener 5 is used and the mounting portion 42 of the locking plate 4 form-fits with the corresponding mounting slot 21, thereby keeping the locking plate 4fixed in its plane. The protruding portion 41 of the locking plate 4 extends radially outward from the outer peripheral surface of the flange 2 and is used for fixing the protection tube 3 relative to the flange 2 when the protection tube 3 is installed onto the flange 2 (described in detail below).

[0038] Referring to FIG. 2, the protection tube 3 is disposed around the cylinder barrel 11 and the flange 2 and may comprise a fixed end portion 31 and a main body portion 32. The fixed end portion 31 of the protection tube 3 can fix the protection tube 3 to the flange 2, while the main body portion 32 of the protection tube 3 covers the cylinder rod body of the cylinder rod 12 and at least a portion of the outer periphery of the cylinder barrel 11, enabling the protection tube 3 to slide axially outside the cylinder barrel 11 as the cylinder rod 12 extends and retracts. To facilitate the axial sliding of the protection tube 3, two protrusions 111 spaced apart from each other are provided on the outer peripheral wall of the cylinder barrel 11 near its open end, forming a limiting portion between the two protrusions 111. A support ring 8 can be snap-fitted into this limiting portion. When the protection tube 3 is installed in place, the outer peripheral wall of the support ring 8 abuts against the inner wall of the protection tube 3, thereby providing support for the main body portion 32 of the protection tube 3 and reducing friction between the inner wall of the protection tube 3 and the entire outer wall of the cylinder barrel when the protection tube 3 slides axially.

[0039] The inner wall of the fixed end portion 31 of the protection tube 3 is provided with a circumferential groove 311 and an axial groove 312. In the illustrated embodiment, the circumferential groove 311 may extend around the entire circumference of the protection tube 3 to form an integral closed loop groove; in other embodiments, the circumferential groove 311 may also extend only along a part of the circumference of the protection tube 3 to form an arcshaped groove. The axial groove 312 extends from the axial end face of the fixed end portion 31 to the circumferential groove 311 along the axial direction of the protection tube 3. The respective widths in the circumferential direction, of the axial groove 312 and of the protruding portion 41 of the locking plate 4 are setsuch that the axial groove 312 can receive the protruding portion 41, enabling the protruding portion 41 to enter and exit the circumferential groove 311 via the axial groove 312. The protruding portion of the locking plate 4 can extend into the axial groove 312 and the circumferential groove 311 during the process of installing and locking the protection tube 3 onto the flange 2.

[0040] The protection tube 3 is rotatable relative to the flange 2 between an unlocked position and a locked position. FIG. 5 shows that the protection tube 3 is in the unlocked position relative to the flange 2 in FIG. 4. FIG. 6 shows that the protection tube 3 is in the locked position relative to the flange 2 in FIG. 4. When the protection tube 3 is in the unlocked position, the protruding portion 41 of the locking plate 4 is aligned axially with the axial groove 312, allowing the protruding portion 41 to enter and exit the circumferential groove 311 along the axial groove 312. When the protection tube 3 is rotated relative to the flange 2 from the unlocked position to the locked position, the protruding portion 41 is no longer aligned axially with the axial groove 312 but is instead engaged within the circumferential groove 311. At this time, the locking plate 4 and thus the flange 2 are fixed relative to the protection tube 3 in the axial direction.

[0041] In the illustrated embodiment, the flange 2 has two mounting slots 21 arranged opposite each other in its diameter direction. Each mounting slot 21 receives one locking plate 4. Correspondingly, the fixed end portion 31 of the protection tube 3 is provided with two axial grooves 312 arranged opposite each other in its diameter direction, allowing the two corresponding locking plates 4 to enter and exit the circumferential groove 311 respectively and enabling the protection tube 3 to be fixed axially relative to the flange 2. Such two oppositely arranged locking plates 4 can achieve balanced and stable fixing of the protection tube 3 relative to the flange 2, and can transmit greater impact forces. It should be noted that the number and arrangement of the locking plates 4 (and the corresponding axial grooves 312) are not particularly limited. Besides the two arranged opposite each other in the diameter direction as shown, there could be one, or three or more arranged at equal or unequal intervals circumferentially, aslong as the impact force borne on the protection tube 3 can be sufficiently transmitted.

[0042] As shown in FIGS. 2 and 3, the flange 2 may further be provided with a first fixing hole 24 at a position circumferentially offset from the mounting slot 21. The fixed end portion 31 of the protection tube 3 is provided with a second fixing hole 313 corresponding to the first fixing hole 24 on the flange 2. When the protection tube 3 is in the locked position, the first fixing hole 24 and the second fixing hole 313 are aligned with each other and can receive a second fastener 6 passing them through, thereby locking the protection tube 3 relative to the flange 2 in the circumferential direction.

[0043] In the present embodiment, the second fastener 6 may be a hex socket head bolt, and its head may be at least partially embedded in the second fixing hole 313 of the protection tube 3, thereby reducing the chance of being hit by external materials. Additionally, the first fastener 5 may also be a hex socket head bolt whose head is at least partially embedded in the first opening 221 of the flange 2. Thus, the first fastener 5 and the second fastener 6 can be conveniently installed using a hex key tool.

[0044] As shown in FIG. 3, the flange 2 may further be provided with a through recess 25 at a position circumferentially offset from the mounting slot 21 (or the locking plate 4) and the first fixing hole 24. The through recess 25 extends in the axial direction of the flange 2 (i.e., the axial direction of the hydraulic cylinder) through the thickness of the flange 2. Thus, when the protection tube 3 is installed around the outer periphery of the flange 2, the through recess 25 can define a flow passage 7 as shown in FIG. 4 together with the inner wall of the protection tube 3. The space between the protection tube 3 and the cylinder barrel 11 can be communicated with the outside via the flow passage 7, facilitating venting and drainage of that space. The through recess 25 is provided on the outer periphery of the flange 2, which is easy to machine and relatively concealed in position. Therefore, while facilitating venting and drainage, the through recess 25 also makes external foreign objects hard to enter the above-mentioned space.The present utility model also provides a hydraulic cylinder assembly comprising the aforementioned protection device. The hydraulic cylinder assembly comprises the aforementioned hydraulic cylinder 1 and protection device.

[0045] The present utility model further provides a grapple and a work machine. The grapple comprises a plurality of jaws and the aforementioned hydraulic cylinder assembly. The hydraulic cylinder of the hydraulic cylinder assembly is capable of driving each of the jaws to pivot for grasping or discharging materials.

[0046] Industrial

[0047]

[0048] As described above, the protection device according to the present utility model is applicable to various work machines equipped with a grapple as work tool, with an aim to protect the hydraulic cylinders that drive the grapple to open and close. However, it should be understood that the protection device according to the present utility model can also be applied to hydraulic cylinders in other scenarios where protection of the cylinder rod is required.

[0049] The installation and disassembly of the protection device relative to the hydraulic cylinder 1 is described in detail below by taking the embodiment shown in FIGS. 1 to 6 as an example. The flange 2 is pre-installed and fixed in place on the cylinder rod 12 to form an integral unit with the cylinder rod 12.

[0050] During the installation of the protection device, first, the protection tube 3 is sleeved onto the cylinder rod 12 from its free end portion, making the flange 2 exposed from the fixed end portion 31 of the protection tube 3. Then, the mounting portions 42 of the two locking plates 4 are respectively inserted into the two mounting slots 21 of the flange 2, and the two locking plates 4 are fixed to the flange 2 by means of a plurality of first fasteners 5. Next, the protection tube 3 is rotated so that the two axial grooves 312 of its fixed end portion 31 are respectively aligned with the protruding portions 41 of the two locking plates 4; at this time, the protection tube 3 is in the unlocked position. Then, the protection tube 3 is pulled towards the flange 2, enabling eachprotruding portion 41 to slide through the corresponding axial groove 312 and reach the circumferential groove 311 on the inner wall of the fixed end portion 31. Subsequently, the protection tube 3 is rotated again, causing the protruding portions 41 to engage into the circumferential groove 311 and rotate along the circumferential groove 311 until they are no longer aligned with the axial grooves 312, thus preventing them from exiting the circumferential groove 311 via the axial grooves 312. At this point, the protection tube 3 enters the locked position, and the protruding portions 41 are axially limited within the circumferential groove 311, i.e., axial fixation of the locking plates 4 and thus the flange 2 relative to the protection tube 3 is achieved. Finally, the protection tube 3 is further rotated until the second fixing hole 313 on the protection tube 3 is aligned with the first fixing hole 24 on the flange 2. Then, the second fastener 6 is passed radially through the second fixing hole 313 and the first fixing hole 24 in sequence, thereby locking the protection tube 3 relative to the flange 2 in the circumferential direction.

[0051] The disassembly process of the protection device is the reverse of the installation steps described above: First, the second fastener 6 is removed. Then, the protection tube 3 is rotated so that the axial grooves 312 at the fixed end portion of the protection tube 3 are aligned with the protruding portions 41 of the corresponding locking plates 4. Next, the protection tube 3 is pushed or pulled towards the closed end of the cylinder barrel 11, enabling the protruding portions 41 to disengage from the protection tube 3 along the axial grooves 312, thereby exposing the locking plates 4 from the protection tube 3. Then, each of the first fasteners 5 is removed, and the mounting portions 42 of the locking plates 4 are pulled out of the mounting slots 21, i.e., the locking plates 4 are removed.

[0052] Finally, the protection tube 3 is pushed or pulled to slide it past the flange 2 and completely remove it from the free end portion of the cylinder rod 12.

[0053] In the protection device of the present utility model, a circumferential groove is provided on the inner wall of the fixed end portion of the protection tube, and a locking plate is fixed on the flange of the cylinder rod. By having the protruding portion of the locking plate engaged within thecircumferential groove, the protection tube and the flange can be fixed axially relative to each other. Thereby, possible axial impact forces on the protection tube during grapple operation can be transmitted to the flange and the cylinder rod via the locking plate. Having a larger force-bearing area and a higher strength than bolts, the locking plate can avoid the risk in the prior art where the protection tube and bolts are damaged due to the axial impact force on the protection tube being directly borne by the bolts.

[0054] For those skilled in the art, various modifications and variations of the embodiments disclosed herein may be made without departing from the scope or spirit of the present utility model. Other embodiments of the present utility model will be apparent to those skilled in the art according to the practice of the present utility model disclosed herein. The Specification and examples disclosed herein shall be considered illustrative only, with the true scope of the present utility model being determined by the appended claims and their equivalents.

Claims

Claims1. A protection device for a hydraulic cylinder, said hydraulic cylinder (1) comprising a cylinder barrel (11) and a cylinder rod (12) capable of telescoping relative to the cylinder barrel, characterized in that said protection device comprises:a flange (2) mounted around a free end portion of the cylinder rod (12) that extends out from the cylinder barrel (11);a protection tube (3) installed around the flange (2) and the cylinder barrel and comprising a fixed end portion (31) fixable to the flange, an inner wall of the fixed end portion is provided with a circumferential groove (311) extending circumferentially and an axial groove (312) extending axially from an axial end face of the fixed end portion to the circumferential groove; and a locking plate (4) detachably mounted on the flange (2), said locking plate having a protruding portion (41) extending radially outward from an outer peripheral surface of the flange,wherein the protection tube (3) is rotatable relative to the flange (2) between an unlocked position and a locked position, and the protruding portion (41) of the locking plate (4) is configured to, when the protection tube (3) is in the unlocked position, be aligned axially with the axial groove (312) and be capable of entering and exiting the circumferential groove (311) via the axial groove, and when the protection tube (3) is in the locked position, to be engaged within the circumferential groove.

2. The protection device according to claim 1, characterized in that the flange (2) is provided with a mounting slot (21) recessed radially inward from its outer peripheral surface; the locking plate (4) comprises a mounting portion (42) engaged within the mounting slot and is detachably mounted to the flange (2) via a first fastener (5) passing axially through the flange and the mounting portion.

3. The protection device according to claim 2, characterized in that the locking plate (4) is detachably fixed to the flange (2) by two parallel said first fasteners (5).

4. The protection device according to any one of claims 1 to 3, characterized in that two locking plates (4) arranged opposite each other in a diameter direction are mounted on the flange (2), the fixed end portion of the protection tube (3) is provided with two said axial grooves (312) corresponding respectively to the protruding portions (41) of the two locking plates, and the circumferential groove (311) is a closed loop groove extending circumferentially to receive the protruding portions of the two locking plates.

5. The protection device according to claim 4, characterized in that a first fixing hole (24) extending radially is provided on the outer peripheral surface of the flange (2), a second fixing hole (313) is provided on the fixed end portion of the protection tube (3), and when the protection tube is in the locked position, the first fixing hole (24) and the second fixing hole (313) are aligned with each other and receive a second fastener (6) to lock the protection tube (3) relative to the flange (2).

6. The protection device according to claim 5, characterized in that the second fastener (6) is a hex socket head bolt, and its head is at least partially embedded in the second fixing hole (313) of the protection tube (3).

7. The protection device according to any one of claims 1 to 3, characterized in that the flange (2) is further provided on its outer peripheral surface with a through recess (25) extending axially through the thickness of the flange and circumferentially offset from the locking plate (4); said through recess and the inner wall of the protection tube (3) together define a flow passage (7) in communication with a space between the protection tube and the cylinder barrel (H).

8. A hydraulic cylinder assembly, characterized by comprising a hydraulic cylinder (1) and the protection device according to any one of claims 1 to 7.

9. A grapple, characterized by comprising a plurality of jaws and the hydraulic cylinder assembly according to claim 8 driving each of the jaws to pivot.

10. A work machine, characterized by comprising the grapple according to claim 9.

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