CN116508479A - Work machine - Google Patents

Abstract

The invention provides a working machine, which comprises a base, a supporting component and a height adjusting component. The support assembly includes a front axle and a rear axle for supporting the front and rear wheels for rotation about the front and rear wheel rotational axes, respectively, and the base is supported on the front and rear axles in a manner such that the mounting position is offset relative to the front and rear wheel rotational axes. The height adjustment assembly includes a longitudinally disposed link having a front end pivotally coupled to the front axle about a first axis offset relative to the front wheel rotational axis and a rear end pivotally coupled to the rear axle about a second axis offset relative to the rear wheel rotational axis; and an adjustment device having an eccentric rotatable about an eccentric axis, the link abutting a side of the eccentric, the link being longitudinally movable in response to rotation of the eccentric. According to the invention, the height of the base can be adjusted by rotating the eccentric about the eccentric axis to drive the link longitudinally back and forth. The adjusting component has the advantages of small number of parts, simple and compact structure and simple and convenient operation mode.

Description

Work machine

Technical Field

The present invention relates to a work machine, and more particularly, to a work machine having a height adjustment function.

Background

Work machines are typically configured to perform corresponding tasks by way of the functional components they have, such as a mower having a cutting device to perform a mowing task, a snowblower having a purging device to perform a snow blowing task, and so forth. These functional components are typically provided on a base of the work machine. Further, to accommodate different work scenarios, work machines also typically have a height adjustment function to adjust the height of the functional assembly relative to the work surface. Such a function is very advantageous for work machines such as lawnmowers, plows, etc. However, the operation mode of the height adjusting mechanism of the existing working machine is complicated and the structure is complex.

Accordingly, there is a need to provide a work machine having a height adjustment function to ameliorate the deficiencies of the height adjustment mechanisms of existing work machines.

Disclosure of Invention

The invention aims to provide a working machine with a height adjusting function, so as to solve the problems of complex structure, complex operation mode and the like of a height adjusting mechanism of the traditional working machine.

According to one aspect of the invention, the work machine comprises:

a base;

a support assembly supporting the base, comprising:

a front axle supporting a front wheel rotatable about a front wheel rotation axis, the base being supported on the front axle at a position offset relative to the front wheel rotation axis; and

a rear axle supporting a rear wheel rotatable about a rear wheel rotation axis parallel to the front wheel rotation axis, the base being supported on the rear axle at a position offset relative to the rear wheel rotation axis;

the work machine further includes:

a height adjustment assembly for adjusting the height of a base relative to the front wheel axis of rotation and/or the rear wheel axis of rotation, comprising:

a link disposed generally along a longitudinal direction of the work machine, a front end pivotally coupled to the front axle about a first axis offset relative to the front wheel rotational axis, and a rear end pivotally coupled to the rear axle about a second axis offset relative to the rear wheel rotational axis; and

an adjustment device having an eccentric rotatable about an eccentric axis, the connecting rod abutting a side of the eccentric, the connecting rod being movable in the longitudinal direction in response to rotation of the eccentric.

In some embodiments, the connecting rod is provided with a U-shaped groove, and the eccentric wheel is disposed in the U-shaped groove and abuts against the side wall of the U-shaped groove along the longitudinal direction.

In some embodiments, the U-shaped channel is configured to be integrally formed with the link, or the U-shaped channel is configured as a separate component from the link and fixedly coupled to the link.

In some embodiments, the height adjustment assembly further comprises a positioning member having an opening, the adjustment device further having a positioning engagement portion coaxial with the eccentric axis, the opening of the positioning member rotatably receiving the positioning engagement portion and restricting movement of the positioning engagement portion in a direction perpendicular to the eccentric axis, the positioning member preferably being fixed to the base.

In some embodiments, a plurality of positioning grooves are formed in the inner side surface of the opening at intervals along the circumferential direction around the eccentric axis, the adjusting device is provided with positioning lugs protruding from the outer side surface of the positioning matching part along the radial direction of the eccentric axis and capable of elastically stretching, when the adjusting device rotates to a preset angle, the positioning lugs are elastically clamped into the corresponding positioning grooves, and the positioning lugs can be moved out of the positioning grooves along with the rotation of the adjusting device.

In some embodiments, the adjusting device is provided with a mounting groove opened at an outer side surface of the positioning engaging portion, a first biasing member configured to elastically bias the positioning protrusion outward is provided in the mounting groove, the mounting groove preferably extends in the radial direction, an end portion of the positioning protrusion, which is engaged into the mounting groove, is preferably spherical, hemispherical, or conical, and the first biasing member is preferably a spring.

In some embodiments, the positioning slot has an arc-shaped cross section perpendicular to the eccentric axis.

In some embodiments, the height adjustment assembly further comprises a plurality of visual positioning indicia, the adjustment device being provided with an indicator that aligns with a corresponding positioning indicia when the adjustment device is rotated to a predetermined angle.

In some embodiments, the top end of the adjusting device is provided with a straight rib, and the rib is formed as the indication mark.

In some embodiments, the adjusting device comprises a grip portion for gripping, the grip portion having a plate-like body, the ribs being provided on an upper surface of the body portion, a side of the body portion opposite the ribs being provided with a first plug-in part for securing the grip, the first plug-in part preferably being a protruding post or rib, the plate-like body preferably being a circular plate.

In some embodiments, the height adjustment assembly further comprises a locking member having a first mating structure, the adjustment device being provided with a second mating structure and being movable along the eccentric axis between a first position in which the first mating structure is in locking engagement with the second mating structure to prevent rotation of the adjustment device about the eccentric axis, and a second position in which the first mating structure is unlocked from the second mating structure to allow rotation of the adjustment device about the eccentric axis, the locking member preferably being fixed to the base, the first mating structure and the second mating structure preferably comprising tooth structures and groove structures that are engageable.

In some embodiments, the adjusting device comprises a locking portion, the second engagement structure comprises a plurality of protruding teeth arranged on the outer circumferential side of the locking portion, and the end face of the locking portion is provided with a second engagement portion for engagement with the first engagement portion of the grip, the second engagement portion preferably being a groove.

In some embodiments, the height adjustment assembly further comprises a second biasing member, preferably a spring, configured to bias the adjustment device toward the first position, the second biasing member preferably being located in a U-shaped groove longitudinally abutting the eccentric.

In some embodiments, the eccentric axis extends generally vertically or generally horizontally.

In some embodiments, the work machine is a garden tool, in particular a lawn mower.

The working machine according to the invention is provided with an eccentric having a cam surface extending substantially vertically. A connecting rod connecting the front shaft and the rear shaft abuts the cam surface. Thus, the connecting rod can longitudinally move back and forth under the drive of the eccentric wheel by only rotating the eccentric wheel around the eccentric axis, and the front shaft and the rear shaft rotate around the respective wheel axes while the connecting rod moves back and forth, so that the height of the base relative to the wheel axes is adjusted. Since the wheel axis remains substantially at a constant height relative to the working surface (approximately equal to the radius of the wheel), the height of the base relative to the working surface is adjusted. The adjusting mechanism has the advantages of small number of parts, simple and compact structure and simple and convenient operation mode.

In addition, the link moves up and down with respect to the cam surface while moving back and forth in the longitudinal direction. Since only two smooth surfaces abut longitudinally between the link and the cam surface without other mutual constraints, the link can move up and down unimpeded relative to the cam surface. This makes the operation of adjusting the height more simple, flexible and labor-saving.

Drawings

For a better understanding of the above and other objects, features, advantages and functions of the present invention, reference should be made to the preferred embodiments illustrated in the accompanying drawings. Like reference numerals refer to like parts throughout the drawings. It will be appreciated by persons skilled in the art that the drawings are intended to schematically illustrate preferred embodiments of the invention, and that the scope of the invention is not limited in any way by the drawings, and that the various components are not drawn to scale.

FIG. 1 is a perspective view of a work machine according to a preferred embodiment of the present invention;

FIG. 2 is a side view of the height adjustment assembly and support assembly of the work machine shown in FIG. 1;

FIG. 3 is a perspective view of the height adjustment assembly and support assembly of the work machine shown in FIG. 1, with the front and rear wheels omitted;

FIG. 4 is a perspective view of an adjustment device of the height adjustment assembly of the work machine shown in FIG. 1;

FIG. 5 is an exploded perspective view of the adjustment device shown in FIG. 4;

FIG. 6 is a perspective view of a locking member of the height adjustment assembly of the work machine shown in FIG. 1;

FIG. 7 is a schematic illustration of a positioning tab and a positioning slot of the height adjustment assembly of the work machine of FIG. 1 engaged; and

fig. 8A to 8C are schematic views illustrating a relative positional relationship between an eccentric and a U-shaped groove during a height adjustment of a height adjustment assembly of the working machine shown in fig. 1.

Reference numerals illustrate:

1. mower

10. Base seat

20. Support assembly

21. Front axle

22. Rear axle

23. Front wheel

24. Rear wheel

30. Height adjusting assembly

31. Connecting rod

32. Adjusting device

321. Eccentric wheel

322. Cam surface

323. Second matching structure

324. Positioning matching part

325. Mounting groove

326. Positioning lug

327. First biasing member

33 U-shaped groove

331 Side wall of U-shaped groove

34. Second biasing member

35. Cam part

351. First concave part

36. Locking part

361. A first protrusion

362. Second concave part

37. Holding part

371. Convex rib

372. Second protrusion

38. Positioning piece

381. Positioning groove

39. Locking piece

391. First matching structure

392. Positioning mark

AX1 front wheel rotation axis

AX2 rear wheel rotation axis

AX3 first axis

AX4 second axis

AX5 eccentric axis

LD longitudinal direction

Detailed Description

Specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings. What has been described herein is merely a preferred embodiment according to the present invention, and other ways of implementing the invention will occur to those skilled in the art on the basis of the preferred embodiment, and are intended to fall within the scope of the invention as well.

The present invention provides a work machine, in particular a garden tool, which can be moved between different positions by means of a moving device, such as a wheel, under external traction and/or driving force provided by its own prime mover. One example of a work machine is a lawn mower arranged to be movable over a surface on which a lawn or grass grows and operated to perform a function of mowing. This action is commonly referred to as "trimming the lawn," and is typically undertaken by gardeners or landscaping workers to maintain the lawn surface. In addition, other examples of the working machine may also be a snow blower, a plow, a wheel cleaner, or the like. A preferred embodiment according to the present invention will be described in detail below with reference to the accompanying drawings by taking a mower as an example.

As shown in fig. 1 to 3, the mower 1 includes a base 10, a support assembly 20, and a height adjustment assembly 30. The base 10 may be supported by metal and/or rigid plastic or the like, which may serve as a mounting base for mating components, such as a prime mover (not shown) for providing a driving force, a working assembly (not shown), a control circuit board (not shown), a sensor (not shown), and the like. In the mower 1, one example of a working assembly may be a cutting device, which may be provided at the underside of the base 10, driven by the above-described prime mover to cut, clean weeds on a lawn.

The base 10 is supported on a work surface such as a lawn or the like by a support assembly 20. The support assembly 20 includes a front axle 21 and a rear axle 22, both ends of the front axle 21 are provided with a pair of front wheels 23 rotatable about a front wheel rotation axis AX1, and both ends of the rear axle 22 are provided with a pair of rear wheels 24 rotatable about a rear wheel rotation axis AX 2. Thus, the base 10 may also be moved between different work sites by the support assembly 20. The pedestal 10 is mounted on the front axle 21 and the rear axle 22 with its mounting position on the front axle 21 offset with respect to the front wheel rotation axis AX1, and with its mounting position on the rear axle 22 offset with respect to the rear wheel rotation axis AX 2. Such an arrangement allows the base 10 to be adjusted in height relative to a work surface by a height adjustment assembly 30, described below.

It will be appreciated that two front wheels 23 and two rear wheels 24 are shown here, one at each end of the respective mounting axle, however in other embodiments the number of front and/or rear wheels and the mounting locations on the respective corresponding mounting axle are not limited thereto.

Referring to fig. 2 and 3 in combination, the height adjustment assembly 30 includes a link 31 disposed generally along a longitudinal direction LD of the mower 1 (which is transverse to the front wheel rotation axis AX1 and the rear wheel rotation axis AX 2), coupled at a front end to the front axle 21 about the first axis AX3, and coupled at a rear end to the rear axle 22 about the second axis AX 4. The first axis AX3, the second axis AX4, the front wheel rotation axis AX1, and the rear wheel rotation axis AX2 are substantially parallel. However, the first axis AX3 is offset with respect to the front wheel rotation axis AX1, and the second axis AX4 is offset with respect to the rear wheel rotation axis AX2, so that the front shaft 21, the rear shaft 22, and the link 31 are formed as a link mechanism.

Further, the height adjustment assembly 30 further comprises an adjustment device 32 rotatable about a substantially vertically extending axis AX5 and comprising an eccentric 321 of substantially cylindrical configuration. The own axis of the eccentric 321 is offset with respect to the axis AX5, so that the outer side surface of the eccentric 321 forms a cam surface 322. Wherein the axis AX5 may also be referred to as an eccentric axis. The link 31 has a structure of abutting against a cam surface 322 of the eccentric 321 in the longitudinal direction LD. When the adjusting device 32 rotates about the eccentric axis AX5, the position of the cam surface 322 abutting the link 31 reciprocates in the longitudinal direction LD, thereby bringing the link 31 to move together in the longitudinal direction LD. In the link mechanism, however, the movement of the link 31 in the longitudinal direction LD causes the mounting positions of the base 10 on the front axle 21 and the rear axle 22 to move up and down with respect to the front wheel rotation axis AX1 and the rear wheel rotation axis AX2, and therefore, the height of the base 10 with respect to the working surface is adjusted. In some embodiments, the axis AX5 may also be arranged to extend substantially horizontally or to extend obliquely at an angle to the horizontal.

Preferably, as shown in fig. 2 and 8A-8C, the connecting rod 31 is provided with a U-shaped groove 33. The eccentric 321 of the adjustment device 32 is arranged in the U-shaped groove 33 and abuts against a side wall 331 of the U-shaped groove 33. Fig. 8A-8C, among others, clearly illustrate the change in position of the U-shaped groove 33 along the longitudinal direction LD relative to the eccentric axis AX5 during rotation of the eccentric 321 about the eccentric axis AX 5. In the illustrated embodiment, the U-shaped slot 33 is made separately from the link 31 and is secured to the link 31 by fasteners such as screws. However, in other embodiments, the U-shaped groove 33 may also be configured to be integrally formed with the link 31.

It is understood that the entire weight of the base 10 acts on the front axle 21 and the rear axle 22, so that the mounting positions of the base 10 on the front axle 21 and the rear axle 22 have a tendency to rotate to the lowest point about the front wheel rotation axis AX1 and the rear wheel rotation axis AX2, respectively. In order to enable the base 10 to be stably at a desired height, as shown in fig. 1 and 6, the height adjustment assembly 30 is preferably provided with a locking piece 39 having a first fitting structure 391. Accordingly, the adjustment device 32 is provided with a second engagement structure 323, and the adjustment device 32 is movable along the eccentric axis AX5 between the first position and the second position. In the first position, the second engagement structure 323 can be lockingly engaged with the first engagement structure 391 to inhibit rotation of the adjustment device 32 about the eccentric axis AX5, thereby enabling the base 10 to be secured at a desired height. While in the second position, the second engagement structure 323 can release the lock with the first engagement structure 391 to allow the adjustment device 32 to rotate about the eccentric axis AX5, so that the height of the base 10 can be adjusted by rotating the adjustment device 32.

As shown in fig. 6, in some embodiments, the locking member 39 is configured as a housing structure that may be fixedly coupled to the base 10. In which the adjusting means 32 are movably accommodated. The second fitting structure 323 and the first fitting structure 391 are configured in shapes that can be fitted and locked to each other, such as teeth and grooves that can be engaged with each other, and the like. In some embodiments, the second mating structure 323 and the first mating structure 391 each include a plurality of teeth and grooves that are capable of interengagement.

Preferably, as shown in FIG. 2, the height adjustment assembly 30 further includes a biasing member 34 configured to bias the adjustment device 32 toward the first position such that it remains in locking engagement with the locking member 39. In some embodiments, the biasing member 34 may be a coil spring. For example, as shown in fig. 2, a spring is disposed below the adjustment device 32 and applies an upward resilient biasing force thereto. When the operator performs the operation of adjusting the height, a pressing force down along the eccentric axis AX5 may be first applied to the adjusting device 32 to move the adjusting device 32 to the second position against the elastic biasing force of the spring so as to be disengaged from the locking piece 39. The operator is then free to rotate the adjustment device 32 and exert a downward pressing force throughout the process. When the base 10 is adjusted to a desired height, the operator no longer applies a pressing force, and the adjusting device 32 moves again to the first position under the elastic biasing force of the spring and engages and locks with the locking piece 39, so that the base 10 is fixed at the desired height after adjustment. The biasing member 34 may preferably be disposed in the U-shaped slot 33.

Referring to fig. 2, 4 and 7 in combination, in some embodiments, the height adjustment assembly 30 further includes a positioning member 38 for positioning the adjustment device 32, which may be fixedly coupled to, for example, the base 10. The positioning piece 38 is provided with a substantially circular opening, and the adjusting device 32 is provided with a cylindrical positioning engaging portion 324 coaxial with the eccentric axis AX 5. The positioning engaging portion 324 is accommodated in the opening of the positioning member 38 and forms a small gap with the inner side surface of the opening so that the adjusting device 32 can freely rotate. Thereby, the positioning piece 38 positions the adjusting device 32 in a direction substantially perpendicular to the eccentric axis AX 5.

Preferably, the eccentric 321 is disposed below the positioning engaging portion 324. Preferably, a skirt protruding radially outward along the eccentric axis AX5 is further provided above the positioning engagement portion, and abuts against the upper surface of the positioning piece 38 when the positioning engagement portion 324 is accommodated in the opening of the positioning piece 38. It will be appreciated that when the skirt is provided, the positioning member 38 may be provided movable along the eccentric axis AX5 together with the adjustment device 32, and only along the eccentric axis AX5, to ensure its positioning function. In addition, in the illustrated embodiment, the opening of the positioning member 38 is a circular shape closed along the circumferential direction about the eccentric axis AX5, however, in other embodiments, the opening may be a circular shape or an arc shape with a circumferential notch.

For the height of the base 10, it is desirable to provide several different height steps within its variation range. Accordingly, it is desirable to be able to alert the operator when the adjustment device 32 is adjusted to the corresponding gear. Preferably, as shown in fig. 7, the inner side surface of the opening of the positioning piece 38 is provided with a plurality of positioning grooves 381 arranged at intervals along the circumferential direction around the eccentric axis AX 5. Accordingly, the outer side surface of the positioning engaging portion 324 of the adjusting device 32 is provided with a positioning protrusion 326, and the positioning protrusion 326 is telescopically provided along the radial direction of the eccentric axis AX5 and protrudes outward from the outer side surface of the positioning engaging portion 324.

When the adjustment device 32 is rotated by a predetermined angle, the base 10 is in the desired height gear. The positioning grooves 381 are positioned such that one (or a pair) thereof corresponds to the predetermined angle. When the positioning boss 326 is rotated and moved to a position corresponding to the one positioning groove 381 with the adjusting device 32, it is changed from a state of abutting against the inner side surface of the opening of the positioning piece 38 to a state of being caught in the corresponding positioning groove 381. A biasing member 327 may be provided to apply an outward biasing force to the positioning tab 326. The biasing force causes the detent tab 326 to snap into the detent 381 with a corresponding tactile feel. So that the operator can clearly understand that the height of the base 10 has been adjusted to one of the plurality of height steps.

It will be appreciated that the detent 381 has a sufficient depth along the eccentric axis AX5 such that in embodiments where the detent 38 is fixedly disposed in all directions, the detent tab 326 is able to move with the adjustment device 32 within the detent 381 as the adjustment device 32 moves between the first and second positions.

For distinction, the biasing element 327 acting on the positioning tab 326 may be referred to as a first biasing element and the biasing element 33 acting on the adjustment device 32 may be referred to as a second biasing element. With continued reference to fig. 7, one example of the biasing member 327 may preferably be a coil spring. The adjusting device 32 may be provided with a mounting groove 325 opened at an outer side surface of the positioning engaging portion 324, and the coil spring is provided in the mounting groove 325 in a state compressed by the positioning protrusion 326. The positioning tab 326 is preferably configured as a spherical structure having a dimension less than the width of the mounting slot 325 so as to be able to at least partially retract into the mounting slot 325 when pressed by the inner side of the positioning member 38. Also, in a section perpendicular to the eccentric axis AX5, the positioning groove 381 has an arc shape. The spherical configuration and arcuate shape may conveniently guide the positioning tab 326 out of the positioning slot 381 as the adjustment device 32 is rotated.

In some embodiments, the positioning protrusion 326 may be provided in a hemispherical shape, a rounded tapered shape, or the like, or the positioning protrusion 326 may be provided in a columnar structure as a whole and the end thereof that is caught in the mounting groove 325 may be provided in a spherical shape, a hemispherical shape, a rounded tapered shape, or the like.

In some embodiments, the positioning tabs 326 may comprise a set of opposing radial directions along the eccentric axis AX5, so that the adjustment device 32 is force balanced, facilitating operation. However, in other embodiments, only one positioning tab 326 may be provided.

In addition, to indicate the current height of the base 10, the height adjustment assembly 30 is preferably also provided with visual positioning indicia 392. The positioning marks 392 may be provided in plurality, respectively, and correspond to the plurality of positioning grooves 381. In some embodiments, as shown in fig. 6, the locating indicia 392 may be a number or symbol indicating each height gear, which is preferably located on the outer surface of the locking member 39, but may be located adjacent to the adjustment device 32 in other locations for convenient viewing by the operator.

Corresponding to the positioning mark 392, the adjustment device 32 is provided with an indication mark. When the positioning tab 326 snaps into the positioning slot 381, the index mark is uniquely aligned with the positioning mark 392 corresponding to the positioning slot 381, so that the operator can know what height the current base 10 is at. Preferably, in some embodiments, the indicator is configured as an in-line rib 371 provided at the upper end of the adjustment device 32. The ribs 371, in addition to indicating the height of the base 10, may be held by an operator to facilitate manipulation of the adjustment device 32. Of course, in other embodiments, the indicator may also be other identifiers (e.g., arrows, triangular patterns, etc.), which may be a protruding structure, a recessed score, etc.

Referring to fig. 5, in some embodiments, the adjustment device 32 is constructed as a split structure including a cam portion 35, a locking portion 36, and a grip portion 37. Wherein the eccentric 321 and the positioning engaging portion 324 are formed as the cam portion 35. A tooth structure and a groove structure forming the second fitting structure 323 are provided on the outer peripheral side of the locking portion 36, and a convex rib 371 for gripping and indication is provided on the upper end of the grip portion 37.

The cam portion 35 and the lock portion 36 and the grip portion 37 are coupled and fixed by protruding portions and recessed portions. Specifically, as shown in fig. 5, the top end of the cam portion 35 is provided with a first concave portion 351 having a rectangular cross section, and the bottom end of the locking portion 36 is provided with a first protruding portion 361 having a shape complementary to the first concave portion 351 so that rotational torque can be transmitted therebetween. The first protrusion 361 is inserted into the first recess 351 so that the cam portion 35 can rotate together with the locking portion 36. The tip of the lock portion 36 is provided with two spaced second recesses 362, and the bottom of the grip portion 37 is provided with two spaced second protrusions 372 (only one of which is shown in the figure). The second protrusion 372 corresponds to and is complementary to the second recess 362 so that rotational torque can be transmitted therebetween. The second protrusion 372 is inserted into the second recess 362 so that the grip portion 37 is coupled with the locking portion 36 and the locking portion 36 can rotate together with the grip portion 37.

It will be appreciated that in other embodiments, the adjustment device 32 may be a two-part, four-part or other more-part structure, and that the various parts comprising the adjustment device 32 may be coupled by other means, such as a threaded coupling, snap-fit coupling, etc. Alternatively, the individual functional parts of the adjusting device 32 can also be formed in a separate structure, so that the adjusting device 32 is constructed as a one-piece structure.

The foregoing description of various embodiments of the invention has been presented for the purpose of illustration to one of ordinary skill in the relevant art. It is not intended that the invention be limited to the exact embodiment disclosed or as illustrated. As above, many alternatives and variations of the present invention will be apparent to those of ordinary skill in the art. Thus, while some alternative embodiments have been specifically described, those of ordinary skill in the art will understand or relatively easily develop other embodiments. The present invention is intended to embrace all alternatives, modifications and variations of the present invention described herein and other embodiments that fall within the spirit and scope of the invention described above.

Claims (15)

1. A work machine, the work machine comprising:

a base (10);

-a support assembly (20), the support assembly (20) being for supporting the base (10), comprising:

a front axle (21), wherein the front axle (21) supports a front wheel (23) rotatable about a front wheel rotation axis (AX 1), and the base (10) is supported on the front axle (21) at a position offset relative to the front wheel rotation axis (AX 1); and

a rear axle (22), the rear axle (22) supporting a rear wheel (24) rotatable about a rear wheel rotation axis (AX 2) parallel to the front wheel rotation axis (AX 1), the base (10) being supported on the rear axle (22) at a position offset relative to the rear wheel rotation axis (AX 2);

the work machine further includes:

-a height adjustment assembly (30), the height adjustment assembly (30) for adjusting the height of the base (10) relative to the front wheel rotation axis (AX 1) and/or the rear wheel rotation axis (AX 2), comprising:

-a link (31), the link (31) being arranged substantially along a Longitudinal Direction (LD) of the working machine, a front end being pivotably coupled to the front axle (21) about a first axis (AX 3) offset with respect to the front wheel rotation axis (AX 1), a rear end being pivotably coupled to the rear axle (22) about a second axis (AX 4) offset with respect to the rear wheel rotation axis (AX 2); and

-an adjustment device (32), the adjustment device (32) having an eccentric (321) rotatable about an eccentric axis (AX 5), the connecting rod (31) being in abutment with a side of the eccentric (321) movable in the Longitudinal Direction (LD) in response to rotation of the eccentric (321).

2. Work machine according to claim 1, characterized in that the connecting rod (31) is provided with a U-shaped groove (33), the eccentric (321) being arranged in the U-shaped groove (33) and abutting against a side wall (331) of the U-shaped groove (33) in the Longitudinal Direction (LD).

3. The working machine according to claim 2, characterized in that the U-shaped groove (33) is configured as an integral formation with the connecting rod (31) or the U-shaped groove (33) is configured as a separate part from the connecting rod (31) and fixedly coupled to the connecting rod (31).

4. A working machine as claimed in any one of claims 1 to 3, characterized in that the height adjustment assembly (30) further comprises a positioning element (38) having an opening, the adjustment device (32) further having a positioning engagement portion (324) coaxial with the eccentric axis (AX 5), the opening of the positioning element (38) rotatably receiving the positioning engagement portion (324) and limiting the movement of the positioning engagement portion (324) in a direction perpendicular to the eccentric axis (AX 5), the positioning element (38) preferably being fixed on the base (10).

5. Work machine according to claim 4, characterized in that the inner side of the opening is provided with a plurality of positioning grooves (381) at intervals along the circumferential direction around the eccentric axis (AX 5), the adjusting means (32) is provided with positioning lugs (326) protruding from the outer side of the positioning mating part (324) along the radial direction of the eccentric axis (AX 5) and elastically stretchable, when the adjusting means (32) is rotated to a predetermined angle, the positioning lugs (326) are elastically caught in the corresponding positioning grooves (381), and the positioning lugs (326) can be removed from the positioning grooves (381) with the rotation of the adjusting means (32).

6. Work machine according to claim 5, characterized in that the adjustment means (32) are provided with a mounting groove (325) open at the outer side of the positioning engagement portion (324), a first biasing member (327) being provided in the mounting groove (325) configured to resiliently bias the positioning lug (326) outwards, the mounting groove (325) preferably extending in the radial direction, at least the end of the positioning lug (326) that snaps into the mounting groove (325) preferably being spherical, hemispherical or rounded conical, the first biasing member (327) preferably being a spring.

7. Work machine according to claim 5 or 6, characterized in that the cross section of the positioning groove (381) perpendicular to the eccentric axis (AX 5) is arc-shaped.

8. The working machine according to any one of claims 1 to 7, wherein the height adjustment assembly (30) further comprises a plurality of visual positioning marks (392), the adjustment device (32) being provided with an indication mark which is aligned with the corresponding positioning mark (392) when the adjustment device (32) is rotated to a predetermined angle.

9. A working machine according to claim 8, characterized in that the top end of the adjustment device (32) is provided with a straight rib (371), which rib (371) is formed as the indicator mark.

10. Work machine according to claim 9, characterized in that the adjustment means (32) comprise a grip portion (37) for gripping, the grip portion (37) having a plate-like body, the ribs (371) being provided on the upper surface of the body portion, the side of the body portion opposite to the ribs (371) being provided with first sockets for securing the grip (37), the first sockets preferably being protruding posts or ribs, the plate-like body preferably being a circular plate.

11. Work machine according to any one of claims 1 to 10, wherein the height adjustment assembly (30) further comprises a locking member (39) having a first engagement structure (391), the adjustment means (32) being provided with a second engagement structure (323) and being movable along the eccentric axis (AX 5) between a first position, in which the first engagement structure (391) is in locking engagement with the second engagement structure (323) to prevent rotation of the adjustment means (32) about the eccentric axis (AX 5), and a second position, in which the first engagement structure (391) is unlocked from the second engagement structure (323) to allow rotation of the adjustment means (32) about the eccentric axis (AX 5), the locking member (39) preferably being fixed on the base (10), the first engagement structure (391) and the second engagement structure (323) preferably comprising tooth structures and groove structures that are engageable.

12. Work machine according to claim 11, characterized in that the adjustment means (32) comprise a locking portion (36), the second engagement structure (323) comprising a plurality of teeth arranged on the outer circumferential side of the locking portion (36), the end face of the locking portion (36) being provided with a second engagement portion for engagement with a first engagement portion of a grip piece (37), the second engagement portion preferably being a groove.

13. Work machine according to claim 11 or 12, wherein the height adjustment assembly (30) further comprises a second biasing member (34) configured to bias the adjustment device (32) towards the first position, the second biasing member (34) preferably being a spring, the second biasing member (34) preferably being located in a U-shaped groove (33) abutting the eccentric (321).

14. Work machine according to any one of claims 1 to 13, characterized in that the eccentric axis (AX 5) extends substantially vertically or substantially horizontally.

15. Work machine according to any of claims 1 to 14, characterized in that the work machine is a garden tool, in particular a lawn mower.