Electric or hybrid work machine with lifting arm

Abstract

[An electric or hybrid work machine comprises a chassis having two parallel longitudinal members, a lifting arm extending parallel to the longitudinal axis, the lifting arm being articulated to the two longitudinal members between the two longitudinal members so as to be movable by pivoting about a pivot axis extending perpendicular to the longitudinal axis. A pair of front wheels mounted to a front end portion of the chassis and a pair of rear wheels mounted to a rear end portion of the chassis. Each wheel is driven in rotation by a drive device (21) independent of all the other wheels, is suspended from the chassis by a suspension device (31, 34, 40) independent of all the other wheels, and is steerable relative to the chassis by a steering device (48) independent of all the other wheels.]

Description

technical field

[0001] The invention relates to an electric or hybrid work machine comprising a lifting arm. Previous technique

[0002] Document WO2023001621A1 describes an electric or hybrid work machine comprising a mobile chassis that can be moved on the ground surface, the chassis having two parallel longitudinal members extending parallel to a front-rear axis of the machine, and a lifting arm, the lifting arm being mounted between the two longitudinal members so as to be mobile by pivoting relative to the two longitudinal members.

[0003] Such a work machine is equipped with two axles which have the advantage of taking on various functions, such as wheel fixing, wheel connection with the chassis, steering of the steering wheels, connection of the drive wheels with the electric transmission motor, speed reduction.

[0004] However, for work equipment intended for lifting, the power required for propelling the chassis and for operating the lifting arm is significant. Summary of the invention

[0005] Some aspects of the invention stem from the idea of ​​improving the efficiency of the traction function in order to offer a machine that is as energy-efficient as possible.

[0006] Some aspects of the invention are based on the idea of ​​extending the life of the machine by facilitating the replacement or maintenance of components with a limited lifespan.

[0007] According to a first object, the invention thus proposes an electric or hybrid work machine comprising: a chassis comprising two parallel longitudinal members extending parallel to a longitudinal axis of the work machine; a lifting arm extending parallel to the longitudinal axis, the lifting arm being articulated to the two longitudinal members between the two longitudinal members so as to be movable by pivoting relative to the two longitudinal members around a pivot axis extending perpendicularly to the longitudinal axis;a pair of front wheels mounted to a front end portion of the chassis and a pair of rear wheels mounted to a rear end portion of the chassis, wherein each of the wheels of at least one pair among the pair of front wheels and the pair of rear wheels is driven in rotation by a drive device independent of all other wheels, is suspended from the chassis by a suspension device independent of all other wheels, and is steerable relative to the chassis by a steering device independent of all other wheels.

[0008] According to one embodiment, each of the wheels among the front wheel pair and among the rear wheel pair is driven in rotation by a wheel motor independent of all the other wheels, is suspended from the chassis by a suspension device independent of all the other wheels, and is orientable relative to the chassis by an orientation device independent of all the other wheels.

[0009] This results in a work machine in which each of the front and / or rear wheels is independent with regard to traction, steering and suspension, which allows for great modularity and can offer varied functionalities for driving the work machine.

[0010] In particular, the independent orientability of each wheel makes it possible to offer, in addition to conventional 2 or 4 steering wheel modes of movement, advanced movement functionalities, such as straight crab movement, straight oblique movement, rotation on the spot around a vertical axis, etc.

[0011] The term "end portion" here refers not only to an end of the chassis but also to an area near the end. Thus, the chassis may include an overhanging portion in front of the front wheels and / or behind the rear wheels.

[0012] Depending on the embodiment, such a work machine may have one or more of the following characteristics.

[0013] According to one embodiment, the drive device for said wheel comprises an electric geared motor unit and a wheel carrier coupled directly to an output shaft of the electric geared motor unit, said wheel being mounted on the wheel carrier.

[0014] According to one embodiment, the orientation device of said wheel comprises a hub armature carrying the electric geared motor unit and a hub carrier on which the hub armature is pivotally mounted around a vertical orientation axis.

[0015] To drive a wheel, the machine can use an electric geared motor unit, in other words, an electromechanical drive. The electric geared motor unit includes a reduction gear train. The electric geared motor unit can be dedicated to propulsion.

[0016] According to one embodiment, the hub carrier comprises a connecting piece coupled to the chassis by the suspension device of said wheel and two pivot bearings spaced in the vertical direction and projecting outwards from the connecting piece in a transverse direction of the chassis, the hub armature being pivotally mounted between the two pivot bearings.

[0017] According to one embodiment, the connecting piece has a curved profile with a concavity facing towards the hub frame.

[0018] According to one embodiment, the hub frame comprises a main support extending in the vertical direction, the main support being traversed by the electric geared motor unit in the transverse direction of the chassis, and two mounting lugs spaced in the vertical direction and projecting from the main support inwards in the transverse direction of the chassis, the mounting lugs of the hub frame being pivotally mounted on the two pivot bearings.

[0019] Thanks to these features, it is possible to space the main support belonging to the hub frame and the connecting piece belonging to the hub carrier in the transverse direction of the chassis, thus creating space to house all or part of the electric motor-gear unit. This results in a relatively compact arrangement.

[0020] According to one embodiment, the wheel orientation device further comprises a steering arm integral with at least one mounting lug of the hub frame and a steering actuator coupled to the steering arm to modify an orientation of the hub frame around the vertical orientation axis.

[0021] According to one embodiment, the suspension device for said wheel comprises a lower arm extending in the transverse direction of the chassis and having an inner end articulated to the chassis and an outer end articulated to a lower portion of the connecting piece, the suspension device comprising a suspension cylinder extending in a vertical or oblique direction and having a lower end connected to the lower arm and an upper end connected to the chassis.

[0022] According to one embodiment, the suspension device for said wheel further comprises an upper arm extending in the transverse direction of the chassis and having an inner end articulated to the chassis and an outer end articulated to an upper portion of the connecting piece, the upper arm having an opening through which the suspension cylinder passes.

[0023] In one embodiment, the chassis further comprises two transverse plates extending parallel to each other between the two side members at the front or rear end portion of the chassis, namely at the front end portion for mounting the front wheels or at the rear end portion for mounting the rear wheels. In one embodiment, the inner end of the lower arm, and optionally the inner end of the upper arm, is housed between the two transverse plates and pivotally mounted about a longitudinal pivot axis carried or formed by the two transverse plates.

[0024] According to one embodiment, the inner ends of the lower arms of the suspension devices of the two wheels of said at least one pair are mounted pivotally about a first common longitudinal pivot axis carried or formed by the two transverse plates.

[0025] According to one embodiment, the inner ends of the upper arms of the suspension devices of the two wheels of said at least one pair are mounted pivotally about a second common longitudinal pivot axis carried or formed by the two transverse plates.

[0026] According to one embodiment, the first and / or second common longitudinal pivot axis is disposed in a median position between the two longerons.

[0027] According to one embodiment, the chassis further comprises two intermediate plates arranged between the two transverse plates, the two intermediate plates extending parallel to the transverse plates between the two longitudinal members, the upper end of the suspension cylinder being housed between the two intermediate plates and mounted pivotally around a third longitudinal pivot axis carried or formed by the two intermediate plates.

[0028] In one embodiment, the first and / or second common longitudinal pivot axis passes through both intermediate plates. In this case, the two intermediate plates reinforce the mounting of the suspension arm axes.

[0029] According to one embodiment, the steering actuator is linked to the chassis by a mounting bracket attached to a so-called intermediate plate.

[0030] According to one embodiment, the chassis further comprises a horizontal base plate extending transversely between the two longitudinal members to form the bottom of a housing intended to accommodate the lifting arm in a low position, and in which the transverse plates extend vertically lower than the horizontal base plate.

[0031] Thanks to these features it is possible to position the pivot axis(es) of the suspension arms lower than the horizontal base plate and thus create space in the chassis under the base plate, for example to house electric batteries.

[0032] Alternatively, to drive a wheel, the machine can use one or more hydraulic motors instead of the electric geared motor unit, in other words, an electro-hydraulic drive. The hydraulic transmission chain may include a hydraulic pump driven by an electric pump motor and at least one hydraulic wheel motor driven by a hydraulic flow generated by the hydraulic pump. The hydraulic transmission chain may be a hydrostatic transmission chain, i.e., a closed-loop system. The hydraulic pump and the electric motor may be dedicated to propulsion. Alternatively, the hydraulic pump and the electric pump motor may be shared with other hydraulic functions of the machine, such as a hydraulic actuation function for the lifting arm or other functions.

[0033] For actuation of the lifting arm, the machine may include one or more electric actuators, such as an electric actuator, and / or one or more hydraulic actuators powered by one or more pumps driven by one or more electric motors, such as an electro-hydraulic actuator, such as a hydraulic cylinder. Several actuators of different types, such as at least one electric actuator and at least one hydraulic actuator, or of the same type, such as several hydraulic actuators, may be provided to actuate different movements or degrees of freedom of the lifting arm. For example, the different movements may be selected from the group consisting of: an up-down movement, an extension-retraction movement, and a tilting movement of a tool holder.

[0034] According to one embodiment, the work machine further comprises a hydraulic pump coupled to an electric pump motor and at least one hydraulic actuator powered by the hydraulic pump to actuate at least one movement of the lifting arm.

[0035] In the case of electro-hydraulic actuation of one or more movements of the lifting arm and electro-hydraulic drive of one or more pairs of wheels, independent hydraulic pumps may be used, or a single hydraulic pump may be used. The independent hydraulic pumps may be driven by several individual electric motors.

[0036] In all cases, battery elements can be electrically connected to a single electric motor or to several electric motors to provide power to said electric motor(s) for chassis propulsion and for actuation of the lifting arm.

[0037] According to one embodiment, the work machine further comprises a cab for a work machine operator, the cab being located projecting from one side of the work machine chassis.

[0038] The weight of the cab can be balanced in various ways. For example, the cab's weight can be balanced by components located in a protruding compartment on a second lateral side of the work machine's chassis, opposite the cab. These components might include batteries, an electric drive motor, an electric actuation motor, a hydraulic pump, a hydraulic fluid reservoir, and / or other elements. Brief description of the figures

[0039] The invention will be better understood, and other objects, details, features and advantages thereof will become more apparent from the following description of several particular embodiments of the invention, given solely by way of illustration and not limitation, with reference to the accompanying drawings. [ Fig. 1 ] There figure 1 is a perspective view of a work machine. Fig. 2 ] There figure 2 is a perspective view of a chassis and ground connection system of the work machine of the figure 1 . [ Fig. 3 ] There figure 3 is an enlarged view of detail III of the figure 2 . [ Fig. 4 ] There figure 4 is a cross-sectional view of the chassis along line IV-IV of the figure 2 . Description of the implementation methods

[0040] There figure 1This is a perspective overview of a work machine 1, shown here as a telescopic handler. As depicted in this figure, the work machine 1 comprises a chassis 2 and a lifting arm 3. Line A represents a longitudinal axis of the work machine 1.

[0041] The chassis 2 is mobile and movable on the ground surface (not shown), by means of two front wheels 7, one on the left and the other on the right, and two rear wheels 8, one on the left and the other on the right.

[0042] Chassis 2 has two longitudinal members 10, which are more clearly visible in particular on the figure 2The longitudinal members 10 are generally flat metal pieces, parallel to each other and generally perpendicular to the width of the work machine. The longest dimension of the longitudinal members 10 extends parallel to the longitudinal axis of the work machine 1. The chassis 2 is typically a welded assembly that can be made of steel sheets.

[0043] The lifting arm 3 also extends in the longitudinal direction of the work machine 1. The lifting arm 3 is positioned between the two side members 10 and has a proximal end articulated to the two side members 10 at two bearings 11 so as to be movable by pivoting relative to the two side members 10 around a pivot axis P. The pivot axis P is parallel to the width direction of the work machine 1. Suitable means for making the lifting arm 3 movable by pivoting are well known as such and are not described in detail here.

[0044] The lifting arm 3 can be made in various ways, including as several telescopic sections as shown, or alternatively as a fixed-length arm. A distal end of the lifting arm 3 opposite the pivot axis P can carry a working tool or, as shown in the figure 1 , a modular tool holder 5 capable of receiving various types of work tools, according to known technology. By work tool, we mean, for example, a pair of forks, a bucket, a winch, a clamp, etc.

[0045] We can also see on the figure 1that the work machine 1 includes a cab 4 in which a driver of the work machine 1 can sit, and a box 6 which can receive various equipment used for the operation of the work machine 1. The cab 4 and the box 6 are located here on either side of the longitudinal members 10, that is to say that the cab 4 is located on a first lateral side of the work machine 1, and that the box 6 is located on a second lateral side of the work machine, the first lateral side and the second lateral side being on either side of the two longitudinal members 10.

[0046] The cabin 4 can be mounted by means of a support arm 12 which projects laterally from a longitudinal member 10, as seen on the Fig. 2 .

[0047] A battery bank, not shown, is connected to the electric motors of the work machine 1, which will be described in detail later. The battery bank may be of various types, for example, lead-acid or lithium-ion. The work machine 1 may include a power distribution circuit, not shown, including, for example, variable speed drives, which is configured to supply power to the electrical components of the work machine 1. Such power distribution circuits are known as such and are not described in detail here.

[0048] The battery pack and / or the power distribution circuit can, for example, be housed in box 6.

[0049] The ground connection system of the work machine 1 is generally visible on the Fig. 2 . There Fig. 2shows the wheel carriers 20 intended to receive the four wheels 7 and 8. The connecting device that links the wheel carrier 20 to the chassis 2 can be made identically for all four wheels and will now be described with reference to figures 3 And 4 .

[0050] The wheel carrier 20 is mounted on the output shaft of a geared motor unit 21, which comprises an electric motor and a reduction gear train housed in a common casing 30. Such a geared motor unit is commercially available. On the figures 1 to 4The axles of wheels 7 and 8 and wheel carriers 20 are consistently shown oriented in the transverse direction of the chassis, perpendicular to the longitudinal axis A. This configuration corresponds to straight-line movement. It goes without saying that the wheel steerability allows this orientation to be modified, as will be described below. However, for the sake of brevity, the ground contact structure will be described below in this straight-line configuration, assuming the vehicle is resting on a horizontal surface.

[0051] The housing of the geared motor unit 21 is rigidly mounted on a hub frame which provides the connection between the geared motor unit 21 and a hub carrier 24. The hub frame consists of a main support plate 22, the outline of which is visible on the Fig. 3presents a general circular shape, and two mounting tabs 23 which protrude from the main support plate 22 transversely towards the chassis 2.

[0052] The main support plate 22 has a central opening (not shown) through which the geared motor group 21 passes. Thus, a first portion of the geared motor group 21 is located on the inside of the main support plate 22 in the transverse direction, and a second portion of the geared motor group 21, smaller than the first portion, is located on the outside of the main support plate 22.

[0053] The two mounting lugs 23 are housed between two flanges 25 of the hub carrier 24, forming pivot bearings to allow the geared motor assembly 21 (and therefore the corresponding wheel) to pivot around a vertical axis S. To control this pivoting, and thus the orientation of the corresponding wheel, there is a steering actuator, here in the form of a steering cylinder 48 having an outer end coupled to a steering arm 46 integral with the upper mounting lug 23, and an inner end 49 coupled to the chassis 2 by means of a mounting lug 47 ( Fig. 4 ).

[0054] The hub carrier 24 comprises two flanges 25 spaced vertically apart and a connecting plate 26 that extends generally vertically and supports the two flanges 25 at its upper and lower ends. The two flanges 25 project transversely from the connecting plate 26 opposite the chassis 2. The first portion of the geared motor assembly 21 is thus positioned in a space between the connecting plate 26 and the main support plate 22. Furthermore, the connecting plate 26 has a curvature whose concavity faces this space to increase its size. This arrangement allows for a relatively large first portion of the geared motor assembly 21 to be housed, thereby limiting the transverse dimensions of the ground connection system.

[0055] Having described the drive and steering mechanisms of a wheel, we will now describe its suspension system. This consists mainly of an upper suspension arm 31, a lower suspension arm 34, and a suspension cylinder 40.

[0056] The upper and lower ends of the connecting plate 26 each carry a bearing allowing the outer end 27 of the upper suspension arm 31 and the outer end 35 of the lower suspension arm 34 respectively to be assembled to it, with a degree of freedom in pivoting around two horizontal and longitudinal axes.

[0057] Similarly, the inner end 33 of the upper suspension arm 31 and the inner end 36 of the lower suspension arm 34 are assembled to the chassis 2 with a degree of freedom in pivoting around two horizontal and longitudinal axes.

[0058] Each of the upper suspension arms 31 and lower suspension arms 34 has a general H-shape. In the lower suspension arm 34, the crossbar of the H supports the lower end of the suspension cylinder 40, which is assembled to it with one degree of freedom in pivoting about a horizontal and longitudinal axis 41. The suspension cylinder 40 extends obliquely from its lower end to an upper end 45, which is assembled to the frame 2 with one degree of freedom in pivoting about a horizontal and longitudinal axis 39 ( Fig. 4 ). At the level of the upper suspension arm 31, the suspension cylinder 40 passes through an opening 32 between the two arms of the H.

[0059] As seen on the figures 3 And 4The upper suspension arms 31 of two transversely opposed wheels are linked to the chassis by means of a common pivot axis 37 and the lower suspension arms 34 of two transversely opposed wheels are linked to the chassis by means of a common pivot axis 38. The common pivot axes 37 and 38 are spaced in the vertical direction and located in a median position with respect to the chassis 2, namely midway between the two longitudinal members 10.

[0060] Back on the Figure 2 In the front end portion of the chassis 2, the mounting of the suspension arm pivot points involves two parallel transverse plates 13 and 14, extending perpendicularly to the longitudinal axis A and joining the two side members 10. The transverse plate 13 forms the front end of the chassis 2, while the transverse plate 14 is spaced rearward from it. The same arrangement, partially shown in the Fig. 4 , can be used in the rear end portion of the chassis 2. Between the two transverse plates 13 and 14 are two intermediate plates 16, also parallel, which also extend perpendicularly to the longitudinal axis A and join the two longitudinal members 10.

[0061] The common pivot points 37 and 38 of the suspension arms can extend longitudinally from the cross plate 13 to the cross plate 14, passing through the two intermediate plates 16, thus providing a particularly robust assembly. The upper suspension arms 31 and lower suspension arms 34 are arranged so that the two arms of the H are positioned respectively on either side of the two intermediate plates 16, namely between the cross plate 13 or 14 and one of the intermediate plates 16.

[0062] As for the suspension cylinders 40, their upper ends 45 are housed between the intermediate plates 16 and their pivot axes 39 extend longitudinally between the two intermediate plates 16, which provides a robust mounting.

[0063] In operation, the upper suspension arms 31 and lower suspension arms 34 of a wheel can oscillate parallel to each other, forming a parallelogram articulated with the connecting plate 26 and the intermediate plates 16. Their oscillation is damped by the suspension cylinder 40.

[0064] As seen on the Fig. 4 , the fixing bracket 47 can be fixed to the intermediate plate 16 located further forward.

[0065] As seen on the Fig. 2The center of the chassis 2 has a horizontal plate 15 which joins the two side members 10 and forms a bottom wall for a housing intended to accommodate the lifting arm 3 in a lowered, folded position. Relative to the horizontal plate 15, the front end portion 17 of the side members 10 extends lower in the vertical direction. This allows the transverse plates 13 and 14 and the intermediate plates 16, which are attached, notably welded, to the front end portion 17 of the side members 10, to also extend lower than the horizontal plate 15 in the vertical direction. The same applies to the rear end portion 19 of the longitudinal members 10. This arrangement makes it possible to free up a central space 18 in the lower part of the chassis, namely under the horizontal plate 15 between the rear end portion 19 and the front end portion 17 of the longitudinal members 10, while preserving a satisfactory ground clearance for off-road use.This central space 18 can accommodate various components, for example electric batteries.

[0066] In one embodiment, only one of the two pairs of wheels conforms to the ground contact system just described. The other pair of wheels can be mounted differently.

[0067] In the examples described above, the front wheels 7 and / or the rear wheels 8 are driven by electric propulsion motors. However, other configurations are possible, including a hydraulic drive chain. Thus, in all the preceding examples, one or both of the electric motors can be replaced by a hydraulic motor performing the same function as the electric motor.

[0068] In one embodiment, a thermal engine may be provided in addition to the electric motors, in particular to generate electricity by means of an on-board generator and / or to provide additional drive torque to an electric pump motor.

[0069] Although the invention has been described in connection with several particular embodiments, it is clearly evident that it is by no means limited to them and that it includes all technical equivalents of the means described as well as their combinations if these fall within the scope of the invention.

[0070] The use of the verb "comporter", "comprendre" or "include" and its conjugated forms does not exclude the presence of other elements or steps than those stated in a claim.

[0071] In claims, any reference sign in parentheses shall not be interpreted as a limitation of the claim.

Claims

1. Electric or hybrid work machine (1) comprising: a chassis (2) having two parallel longitudinal members (10) extending parallel to each other and extending parallel to a longitudinal axis (A) of the work machine (1); a lifting arm (3) extending parallel to the longitudinal axis, the lifting arm (3) being articulated to the two longitudinal members (10) between the two longitudinal members so as to be movable by pivoting relative to the two longitudinal members (10) around a pivot axis (P) extending perpendicularly to the longitudinal axis;a pair of front wheels (7) mounted to a front end portion (17) of the chassis side members (10) and a pair of rear wheels (8) mounted to a rear end portion (19) of the chassis side members (10), wherein each of the wheels of at least one pair among the pair of front wheels (7) and the pair of rear wheels (8) is driven in rotation by a drive device (21) independent of all other wheels, is suspended from the chassis by a suspension device (31, 34, 40) independent of all other wheels, and is steerable relative to the chassis by a steering device (48) independent of all other wheels.; 2. Work machine (1) according to claim 1, in which each of the wheels among the front pair of wheels (7) and among the rear pair of wheels (8) is driven in rotation by a wheel motor independent of all the other wheels, is suspended from the chassis by a suspension device independent of all the other wheels, and is steerable relative to the chassis by a steering device independent of all the other wheels.

3. Work machine (1) according to any one of claims 1 to 2, wherein the drive device of said wheel comprises an electric geared motor unit (21) and a wheel carrier (20) directly coupled to an output shaft of the electric geared motor unit, said wheel being mounted on the wheel carrier.

4. Work machine (1) according to claim 3, in which the orientation device of said wheel comprises a hub armature (22, 23) carrying the electric geared motor unit (21) and a hub carrier (24) on which the hub armature (22, 23) is pivotally mounted about a vertical orientation axis (S).

5. Work machine (1) according to claim 4, in which the hub carrier comprises a connecting piece (26) coupled to the chassis by the suspension device (31, 34, 40) of said wheel and two pivot bearings (25) spaced in the vertical direction and projecting outwards from the connecting piece (26) in a transverse direction of the chassis, the hub armature (22, 23) being pivotally mounted between the two pivot bearings (25).

6. Work machine (1) according to claim 5, in which the connecting piece (26) has a curved profile having a concavity turned towards the hub armature (22, 23).

7. Work machine (1) according to claim 5 or 6, wherein the hub frame comprises a main support (22) extending in the vertical direction, the main support (22) being traversed by the electric geared motor unit (21) in the transverse direction of the chassis, and two mounting lugs (23) spaced in the vertical direction and projecting from the main support (22) inwards in the transverse direction of the chassis, the mounting lugs (23) of the hub frame being pivotally mounted on the two pivot bearings (25).

8. Work machine (1) according to claim 7, wherein the steering device of said wheel further comprises a steering arm (46) integral with at least one mounting lug (23) of the hub frame and a steering actuator (48) coupled to the steering arm (46) to modify an orientation of the hub frame around the vertical steering axis (S).

9. Work machine (1) according to any one of claims 5 to 8, wherein the suspension device of said wheel comprises a lower arm (34) extending in the transverse direction of the chassis and having an inner end (36) articulated to the chassis and an outer end (35) articulated to a lower portion of the connecting piece (26), the suspension device comprising a suspension cylinder (40) extending in a vertical or oblique direction and having a lower end (41) connected to the lower arm (34) and an upper end (45) connected to the chassis.

10. Work machine (1) according to claim 9, wherein the suspension device of said wheel further comprises an upper arm (31) extending in the transverse direction of the chassis and having an inner end (33) articulated to the chassis and an outer end articulated to an upper portion of the connecting piece (26), the upper arm (31) having an opening (32) through which the suspension cylinder (40) passes.

11. Work machine (1) according to claim 9 or 10, wherein the chassis further comprises two transverse plates (13, 14) extending parallel to each other between the two longitudinal members (10) at the front or rear end portion of the chassis, and wherein the inner end (36) of the lower arm is housed between the two transverse plates (13, 14) and pivotally mounted about a longitudinal pivot axis (38) carried or formed by the two transverse plates (13, 14).

12. Work machine (1) according to claim 11, in which the inner ends (36) of the lower arms of the suspension devices of the two wheels of said at least one pair are mounted pivotally about a first common longitudinal pivot axis (38) carried or formed by the two transverse plates (13, 14).

13. Work machine (1) according to claim 11 or 12 taken in combination with claim 10, wherein the inner ends (33) of the upper arms (31) of the suspension devices of the two wheels of said at least one pair are mounted pivotally about a second common longitudinal pivot axis (37) carried or formed by the two transverse plates (13, 14).

14. Work machine (1) according to claim 12 or 13, wherein the first and / or second common longitudinal pivot axis (37, 38) is disposed in a median position between the two longitudinal members (10).

15. Work machine (1) according to any one of claims 11 to 14, wherein the chassis further comprises two intermediate plates (16) disposed between the two transverse plates (13, 14), the two intermediate plates (16) extending parallel to the transverse plates between the two longitudinal members, the upper end (45) of the suspension cylinder being housed between the two intermediate plates (16) and pivotally mounted about a third longitudinal pivot axis (39) carried or formed by the two intermediate plates (16).

16. Work machine (1) according to claim 15 taken in combination with claim 8, in which the steering actuator (48) is linked to the chassis by a fixing lug (47) fixed to said intermediate plate (16).

17. Work machine (1) according to any one of claims 11 to 16, wherein the chassis further comprises a horizontal base plate (15) extending transversely between the two longitudinal members (10) to form the bottom of a housing intended to accommodate the lifting arm (3) in a low position, and wherein the transverse plates (13, 14) extend vertically lower than the horizontal base plate (15).

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