EP4735285A1 - Single-axle tractor - Google Patents

Abstract

Disclosed is a single-axle tractor (1) comprising: a structural frame (2) comprising two lateral walls (21) structurally interconnected to each other and arranged spaced apart from each other on either side of a battery compartment (9), wherein the battery com- partment (9) is arranged on an inside between the two lateral walls (21) and comprises at least one battery module (91A, 91B, 91C) supported with respect to the structural frame (9); two wheel drive units (3) each comprising a wheel (4) attached to an axle and a motor for driving said wheel (4) around said axle; wherein the wheel drive units (3) are mounted on the outside of the lateral walls (21) respectively, such that central axes of the wheel drive units (3) meet.

Description

SINGLE-AXLE TRACTOR

FIELD OF THE DISCLOSURE

The present invention relates to a single-axle tractor, in particular to a battery powered single-axle tractor.

BACKGROUND OF THE DISCLOSURE

Single-axle tractors are a type of small tractor carried on a pair of wheels, typically used for horticultural, agricultural, industry, landscaping, farm and home work. They are arranged to push and/or pull auxiliary equipment. An operator usually walks behind the single-axle tractor, gripping a pair of handles to steer and/or otherwise control the singleaxle tractor. The operator may also, at times, for some tractors, stand on a small platform at the rear of the tractor.

Auxiliary equipment may be attached to the front and/or the rear of the tractor. Singleaxle tractors may have permanently attached auxiliary equipment, or may have one or more interfaces allowing for the attachment and removal of different auxiliary equipment. A considerable range of auxiliary equipment has been developed for use with single-axle tractors, including plows, hoes, cultivators, hay balers, hay rakes, rototillers, cutter bars, mowers, sweepers, snow blowers, snowploughs, harrows, mulchers, weed brushes, and so on. The interface provides for a mechanical connection to the auxiliary equipment, (i.e. for fixing of the auxiliary equipment to the tractor and optionally for supporting at least part of the weight of the auxiliary equipment). The interface typically also includes a driveline connector such that the tractor can drive the auxiliary equipment Single-axle tractors with combustion engines are well known and comprise a centrally arranged combustion engine and a transmission coupled to a lateral drive, the lateral drive shaft being connected to the wheel axles. A differential arranged on the drive shaft controls power to each wheel, allowing for the tractor to steer. Other tractor designs include an engine driven hydraulic pump connected to two hydraulic motors, each hydraulic motor connected to a wheel axle. A hydraulic system which distributes pressure between the left and right hydraulic motors is used to steer the tractor.

Single-axle tractors with electric engines have also been developed, in an effort to make horticultural work more sustainable and reduce emissions. Additionally, the benefits of electric engines include more favorable torque curves, lower noise, and reduced weight. A problem that needs to be addressed, however, is operational time, as the energy density of batteries is approximately a factor of 100 less than that of gasoline typically used in combustion engines. Therefore, for achieving a comparable operational time, i.e. time between recharging, requires the installation of large, and therefore heavy and costly battery modules.

The design of known single-axle tractors has not yet satisfactorily addressed the issue of providing sufficient battery storage, while at the same time maintaining a compact and balanced overall apparatus.

For example, EP3471988A1 discloses an electrically driven single-axle tractor with a drive axle connected to two wheels, a single electric motor coupled to the drive axle, and electrical energy sources arranged above the drive axle. A secondary electric motor is coupled to an equipment drive shaft for releasable coupling with a piece of equipment. A disadvantage of the single-axle tractor according to this disclosure is that the overall space provided for the battery remains a small proportion of the total volume occupied by the tractor. SUMMARY OF THE DISCLOSURE

It is an object of embodiments disclosed herein to provide a single-axle tractor. In particular, it is an object of the embodiments disclosed herein to provide a single-axle tractor which does not have at least some of the disadvantages of the prior art.

A single-axle tractor is disclosed comprising a structural frame. The structural frame comprises two lateral walls structurally interconnected to each other. The lateral walls are arranged spaced apart from each other on either side of a battery compartment. The battery compartment is arranged at least partially on an inside of the structural frame between the two lateral walls. The battery compartment comprises at least one battery module supported with respect to the structural frame. The single-axle tractor comprises two wheel drive units. Each wheel drive unit comprises a wheel attached to an axle and a motor for driving said wheel around said axle. The two wheel drive units are mounted on the outside of the two lateral walls respectively. The central axes of the wheel drive units, i.e. the virtual lines extending through the axle of both wheel drive units, meet. In other words, a first central axis of the first wheel drive unit intercepts a second central axis of the second wheel drive unit. Each wheel drive unit has an attached wheel.

In an embodiment, the two wheel drive units are mounted on the outside of the two lateral walls in that each wheel drive unit is arranged on the outside of the structural frame and attached to the respective lateral wall. The wheel drive unit, in particular the motor and the wheel, does not extend into the structural frame. Thereby, the available space inside the structural frame is not reduced by the motor and more space is available for the battery compartment.

Depending on the embodiment, the wheel drive unit may include connecting members for attaching the wheel drive unit to the lateral walls, which connecting members extend into and/or through the lateral walls. The connecting members may end or terminate immediately adjacent to the inside of the lateral wall, for example in that the connecting member has a head abutting against the inside of the lateral wall. For example, the connecting members may comprise bolts which extend through the lateral walls. As described below in more detail, there may be provided a counter support on the inside of the lateral walls, the parts to better distribute loads into the lateral walls.

The structural frame is preferably load-bearing in that it supports the load of the singleaxle tractor. In particular, the structural frame transfers loads and/or forces from components of the single-axle tractor, in particular the battery compartment, to the wheel drive units. The components of the single-axle tractor, in particular the battery compartment and the wheel drive units, are connected, preferably directly interconnected, with the structural frame.

The structural frame is preferably implemented as a unibody structural frame in which the structural frame further at least partially defines a body of the single-axle tractor.

An advantage of the tractor as disclosed is that the battery modules are arranged as low as possible in the structural frame. This ensures a low center of gravity of the tractor which improves the stability of the tractor, for example on inclined terrain, as well as improving the handling. Another advantage of the tractor as disclosed is that the battery capacity, and therefore the run-time of the tractor, is greatly increased over prior art tractors, as the design of the structural frame provides for a large volume in which the battery compartment may at least partially be arranged. The battery compartment may extend, at least on a top side of the structural frame, beyond the walls, i.e. beyond the confines, of the structural frame.

The term “single-axle” is not to be interpreted as limited to a tractor which has a single continuous axle extending between two wheels. Rather, the term “single-axle” is to be understood as generic term referring to a tractor (a self-propelled work machine) which may be typically operated by hand, in particular by an operator or user walking behind the tractor. As such, the term “single-axle” refers to the presence of two wheels, each connected to an axle, however which axles are not contiguous.

In an embodiment, the lateral walls of the structural frame are interconnected to each other by a front wall. The front wall comprises a mechanical interface to attach an auxiliary equipment to the single-axle tractor. The mechanical interface may be implemented as a removable coupling. The mechanical interface may be pivotable such that the auxiliary equipment may rotate through a defined angular range. The structural frame may include, on the front wall, at least one support member which extends across the front wall, horizontally, vertically, or diagonally, and is connected to the mechanical interface. The single-axle tractor may further include an electrical interface configured to provide electrical power and/or data communication signals to the auxiliary equipment. The electrical interface is electrically connected to the one or more battery modules of the battery compartment. The term interconnected may refer to a structural arrangement in which the interconnected parts do not have any intermediate parts arranged between them, i.e. they are directly connected to each other.

In an embodiment, the two lateral walls are interconnected to each other by: a bottom wall, a rear wall, a top wall, and/or a spacer. The two lateral walls may be congruent with respect to each other, i.e. having the same shape and/or size. The two lateral walls may be arranged essentially parallel to each other. The lateral walls may comprise local reinforcements. The lateral walls, the bottom wall, the front wall, and/or the rear wall may be sealingly connected to each other, in particular such as to prevent water and/or dust ingress. The rear wall may be at least partially openable and/or removable.

In an embodiment, the structural frame, in particular the walls (e.g., the lateral walls, the front wall, the bottom wall, and/or the rear wall), is at least partially made from sheet metal panels. The sheet metal panels may be bent and/or folded in one or more places. For example, the sheet metal panels may be folded at one or more edges, such as to form an overlapping region of sheet metal when joining two panels together. The sheet metal panels may also have one or more bends in a section of the panel, e.g. forming corrugations or otherwise profiled or shaped metal sheets (e.g., square, sinusoidal, and/or zigzag), for improved structural stability. At least two walls, for example the two lateral walls and the spacer (such as the bottom wall), may be integrally formed from one single sheet metal panel, thereby forming a substantially U-shaped partial enclosure.

In an embodiment, the structural frame, in particular the walls (e.g., the lateral walls, the front wall, the bottom wall, and/or the rear wall), is made at least partially from one or more elongated members, such as beams, rods, struts, and/or profiles joined together. Thereby, the structural frame may include a truss-like structure, in particular comprising one or more planar trusses, such as a parallel chord truss.

In an embodiment, the structural frame is made of both sheet metal panels and one or more elongated members. The one or more elongated members may in particular serve to reinforce the structural frame, for example in places where particularly high loads are present, such as on the lateral wall(s) where the wheel drive unit is mounted and/or on the front wall where the mechanical interface is mounted.

In an embodiment, the battery compartment comprises a plurality of horizontally and/or vertically stacked battery modules. The dimensions of the battery compartment may be constrained at least in part by the bottom wall, the rear wall, the front wall, and/or the two lateral walls. The battery compartment may extend beyond an edge of at least one of the walls, in particular, the battery compartment may extend beyond a top edge of the lateral walls.

In an embodiment, the battery compartment comprises one or more battery module attachment members to support the at least one battery module with respect to the lateral walls. The battery compartment may also be attached to the front wall and/or back wall. The battery module attachment members may include one or more trays, and/or one or more rails (i.e. , a rack rail or telescopic rail). The battery module attachment members may include linear guiding means for insertion and/or removal of battery modules. These linear guiding means may be in the form of the aforementioned trays and/or rails. The battery module attachment means may be arranged on the lateral walls and/or on the bottom wall. The battery modules may be mounted in an auxiliary frame arranged in the battery compartment. The battery modules may be shifted, for example laterally, to balance the single-axle tractor, in particular to shift a center of mass of the single-axle tractor.

In an embodiment, the battery compartment is accessible via a rear opening in the structural frame, wherein the rear opening is provided by opening and/or removing a releas- ably attached rear wall. For example, the rear wall may be connected using one or more hinges. The rear wall may, additionally or alternatively, be entirely removable. The rear wall may be removable by hand and/or by using tools. Additionally or alternatively, the battery compartment may also be accessible via the bottom, top, or front of the structural frame, e.g. by opening and/or removing a releasably attached bottom wall, top wall or front wall of the structural frame, respectively.

In an embodiment, each wheel drive unit is mounted on the outside of the lateral walls by way of a counter support arranged on the inside of the lateral walls adjacent to the wheel drive unit. A plurality of connecting members (e.g. including, bolts, pins, or the like) extend through the lateral walls to fasten the wheel drive unit to the counter support. The counter support may be in the form of a metal support member which improves a load distribution of loads imparted on the structural frame, in particular on the lateral walls, through the wheel drive units. Depending on the embodiment, the wheel drive unit may be attached in one or more positions. Accordingly, the counter support may include a plurality of connection points, such that the wheel drive units can be mounted in a plurality of discrete locations. The plurality of connection points are, for example, arranged in a horizontal line. Thereby, the balance of the single-axle tractor may be shifted, in particular the relationship (i.e. a distance and/or direction) of a midpoint between the wheel drive units and a center of mass of the single-axle tractor may be altered. The counter support may also be configured such that, in addition to or alternatively to the discrete mounting locations, the wheel drive units can be continuously shifted along a continuum of mounting locations. For example, the counter support may include an elongated connection member, such as a rail, recess, or other guiding element. Thereby, the balance of the tractor can be adjusted depending on the particular type of auxiliary equipment attached. For example, auxiliary equipment which is relatively heavy may require the wheel drive units to be located further forward to ensure an even front to back distribution of weight of the tractor and the wheel drive unit. In another example, if the attached auxiliary equipment which has one or more wheels of its own, or other ground support members (e.g, skis or sleds), the wheel drive units may be located further back to ensure a greater overall stability of the tractor with the auxiliary equipment attached.

In an embodiment, the battery compartment is arranged at least partially between the wheel drive units. For example, the battery compartment is arranged such that a virtual line extending between the axes of the wheel drive units passes through the battery compartment, in particular though at least one battery module. In particular, the battery compartment may be designed such that a center of mass of the one or more battery modules lies, in the x-y plane (i.e. in the forward-back and lateral dimensions), above the wheel drive units, in particular within approximately a distance of one wheel diameter from the x-y plane, in particular such that a y-position (i.e. lateral position) of the center of mass in the x-y plane lies directly between the wheel drive units and the x-position (i.e. , the forward and back position) of the center of mass lies above the virtual line extending between the wheel drive units.

In an embodiment, the single-axle tractor further comprises a power electronics module attached to the structural frame and an electrical battery connection, the electrical battery connection configured to electrically connect the at least one battery module to the power electronics module. The power electronics module is preferably arranged at least partially above the battery compartment. The power electronics module may be arranged at least partially on the outside of at least one of the lateral walls and/or the front wall, such that it may occupy at least some space above the wheel drive units.

In an embodiment, the wheel drive units are implemented as electric motors and the single-axle tractor further comprises two electrical motor connections for electrically connecting the power electronics module with the two electric motors, respectively. Each electrical motor connection preferably runs adjacent to the battery compartment on the outside of each lateral wall.

It is also an object of the present disclosure to provide an operating arm for use with a tractor, in particular suitable for use with a single-axle tractor as described herein. In particular, the operating arm is pivotably arranged on a top side of the structural frame of the tractor described herein, and an operating unit is attached to the operating arm. The operating arm may be pivotably arranged on the top side of the structural frame by way of a bearing. The bearing is connected to the operating arm. The bearing may include a shaft attached to a disc pivotably arranged between two plates, wherein the plates are connected to the top wall of the structural frame. The operating arm includes a parallelogram linkage including a retention mechanism. The retention mechanism may include a spring and/or a damper. The retention mechanism may include a gas spring. The retention mechanism may include a punched bar allowing for discrete adjustment of the parallelogram linkage. The linkage can, additionally or alternatively, be continuously adjusted such that the parallelogram may be adjusted continuously between an extended position and a retracted position, in particular wherein the retention mechanism is configured such that the operating arm can be set at any desired position between the extended position and the retracted position. Preferably, the gas spring retention mechanism includes a biasing mechanism such that, when a latch is released, the linkage moves to the retracted position without requiring any external force.

BRIEF DESCRIPTION OF THE DRAWINGS

The herein described disclosure will be more fully understood from the detailed description given herein below and the accompanying drawings which should not be considered limiting to the invention described in the appended claims. The drawings in which:

Fig. 1 shows a perspective view of a schematic drawing of a single-axle tractor according to an embodiment of the disclosure;

Fig. 2 shows a second perspective view of a schematic drawing of the single-axle tractor;

Fig. 3 shows an exploded perspective view of a schematic drawing of the singleaxle tractor;

Fig. 4 shows a cutaway perspective view of a schematic drawing of a selection of components of the single-axle tractor, including in particular the structural frame and the wheel drive units;

Fig. 5 shows a perspective view of a schematic drawing of an operating arm of a single-axle tractor in a retracted position; and

Fig. 6 shows a perspective view of a schematic drawing of an operating arm of a single-axle tractor in an extended position. DESCRIPTION OF THE EMBODIMENTS

Reference will now be made in detail to certain embodiments, examples of which are illustrated in the accompanying drawings, in which some, but not all features are shown. Indeed, embodiments disclosed herein may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Whenever possible, like reference numbers will be used to refer to like components or parts. For the sake of improved clarity in the drawings, where multiple of the same features are shown, not all instances of the same features may be labeled with reference numbers to reduce clutter.

Figure 1 shows a perspective view of a schematic drawing of a single-axle tractor 1 according to an embodiment of the disclosure.

A structural frame 2 is shown comprising two lateral walls 21 (only one of which is visible in Fig. 1) and a front wall 22. The lateral wall 21 shown is arranged vertically, i.e. in the x-z plane. The lateral wall 21 extends in the forward x-direction and preferably has a length of 40 cm to 80 cm. The lateral wall extends in the vertical z-direction and preferably has a height of 30 cm to 70 cm. The top edge of the lateral wall 21 is obscured. The lateral wall 21 is made of sheet metal, preferably having a thickness of 0.5 mm to 10 mm. The lateral wall 21 has a rectangular shape with a truncated bottom rear corner.

The single-axle tractor 1 preferably has a total width, including the wheels, of approximately 100 - 140 cm, more preferably 120 cm. The lateral wall 21 has attached to it a wheel drive unit 3. The wheel drive unit 3A shown in most detail extends from the lateral wall 21 in the positive y-direction. A second wheel drive unit 3B is only partially visible in Fig. 1. The wheel drive unit 3 itself does not extend through the lateral wall 21 , in particular not through to an inside face of the lateral wall 21. The wheel drive unit 3A is merely attached to the lateral wall 21. In such a way, the wheel drive unit 3A does not reduce the volume inside the structural frame 2 available for housing the battery compartment (not shown).

The wheel drive unit 3 is configured to have a wheel 4 attached to it. One wheel 4 depicted in Fig. 1 has been shifted in the positive y-direction for illustrative purposes to show the wheel drive unit 3. The wheel 4 is driven by the wheel drive unit 3, in particular in that a motive force is applied, by the wheel drive unit 3, to the wheel 4, such that the wheel 4 may be rotated in the forward direction or the backward direction with a particular rotational speed and/or torque such as to drive the tractor 1.

Both wheel drive units 3 are arranged coaxially, i.e. such that a virtual line extending through the axle of both wheel drive units 3 coincide. However, other arrangements are also possible, in particular in that the wheel drive units 3 form an angle with respect to each other, e.g. such that the wheel drive units 3 are tilted upwards slightly and/or tilted towards each other slightly, which may improve handling or stability in some situations.

The wheel 4 may include a central hub and a rim. Depending on the embodiment, a tire (e.g., a pneumatic tire) may be mounted on the rim to provide traction on the ground. Alternatively, the rim itself may implement traction means, such as the spikes 41 shown on the wheel 4 as depicted. The wheel 4 may be swapped and/or replaced as needed according to work requirements.

In an embodiment, the wheel 4 may have a track, in particular a continuous band or belt of trades or track plates attached to it, for providing better traction and support on terrain.

The wheel drive unit 3 includes a motor (not shown). The motor is, either directly or indirectly, attached to a wheel 4, and is configured to provide motive force for driving the wheel 4. For example, the motor is attached to the wheel 4 using an axle. Each motor and wheel 4 has its own axle, i.e. both wheels 4 do not share an axle. In particular, the axle of each wheel 4 does not extend into or through the lateral wall 21.

The motor is preferably implemented as an electric motor, for example a radial-flux electric motor or an axial-flux electric motor. The motor may be implemented as a hydraulic motor, i.e. a mechanical actuator configured to convert hydraulic pressure and flow into torque and rotation. The hydraulic pressure may be generated by a hydraulic pump arranged in the tractor 1 , the hydraulic pump connected to the hydraulic motor by way of hydraulic connections. The hydraulic pump is preferably configured as an electric hydraulic pump, i.e. a hydraulic pump which is driven by an electric motor.

The motor may be implemented as an inner rotation motor, in which the rotor is rotatably arranged inside a cylindrical stator. The rotor may, in this case, correspond to a wheel axle of the wheel 4. The motor may alternatively be implemented as an outer rotation motor, in which the rotor is arranged on the outside of a fixed stator and rotates around it.

The motor may be implemented as a hub motor.

The wheel drive unit 3 may include a transmission. In an example where the wheel drive unit 3 includes an electric motor, the transmission may be omitted, or may include gearing. Other gearing is also possible, in particular a gearing system implementing a plurality of different gears. The gearing system may be implemented as a planetary gearing system arranged between the motor and the wheel 4.

The wheel drive unit 3 includes a housing 31 to protect the interior of the wheel drive unit 3, in particular the motor, from the environment. The housing 31 is substantially cylindrical in shape and extends from the lateral wall 21 , in the y-direction, towards the wheel 4. The wheel drive unit 3 is fixed to the tractor 1 , in particular the lateral wall 21 , by way of connection members 32 which mechanically attach the wheel drive unit 3 to the lateral wall 21 . The connection members 32 are preferably arranged on a flange 33 of the wheel drive unit 3, the flange 33 extending radially from the wheel drive unit 3 where it is connected to the lateral wall 21. In an example where the connection members 31 are implemented bolts, a bolt circle may be formed on the flange 33.

The two wheel drive units 3 are not directly structurally connected with each other. Thereby, the loads exerted on the wheel drive units 3 are not directly coupled to each other. As a consequence, the loads on the wheel drive units 3 act on the lateral walls 21 . The connection members 32 do not extend between the lateral walls 21. This maximizes an interior space and volume available for the battery compartment (not shown).

For additional structural support of the wheel drive units 3, a counter support (not shown) may be arranged on an interior wall of the lateral wall 21 , the counter support arranged adjacent to the wheel drive unit 3, i.e. facing the wheel drive unit 3 on the other side of the lateral wall 21 . The connection members 32 are attached to the counter support such that the wheel drive unit 3 and the counter support sandwich the lateral wall 21. Thereby, the counter support acts in the same way a washer does in that it distributes the load on the lateral walls 21 over a larger area. The counter support may comprise a steel plate. The steel plate is arranged adjacent to the lateral wall 21 and includes bores for receiving the connection members 32. The steel plate may be milled to reduce weight, for example, such that unnecessary or superfluous parts of the steel plate are removed. In particular, the steel plate may have a shape or outline complementary to the arrangement of the connection members 32. In particular, the steel plate may comprise at least one area or section which forms an at least partially crescent and/or semi-circular shape with a radius of curvature similar to a radius of curvature of the wheel drive unit 3, in particular a flange of the wheel drive unit 3. The counter support may be configured to provide multiple mounting positions of the wheel drive unit 3, in particular multiple mounting positions in the x-direction. Thereby, the wheel drive units 3 can be arranged further forward or further rearward depending on work requirements. The counter support may be configured to provide a discrete number of mounting positions, or a continuous range of mounting positions, for example by including an extended member or feature such as a rail or guide along which the wheel drive unit 3 may be arrange in one of a plurality of mounting positions.

The front wall 22 is arranged between the two front edges of the lateral walls 21. The front wall 22 is arranged vertically in the y-z plane. The front wall 22 is rectangular in shape and preferably extends in height (i.e. in the z-direction) along the entire front edges of the lateral walls 21. The front wall 22 thereby may have a height of between 30 cm and 70 cm. The front wall 22 may extend above a height of the lateral walls 21 , or may not reach them entirely. The front wall 22 is made of sheet metal, preferably having a thickness of 0.5 mm to 8 mm. The front wall 22 may be integrally formed with the lateral walls 21. The front wall 22 may alternatively be formed separately and attached to the lateral walls 21.

The front wall 22 has a mechanical interface 5. The mechanical interface 5 may be integrally formed on the front wall 22 or may be attached to the front wall 22. The mechanical interface 5 is configured for mounting or otherwise attaching auxiliary equipment (not shown) to the tractor 5. The auxiliary equipment may include, for example, a plow, hoe, cultivator, hay baler, hay rake, rototiller, cutter bar, mower, sweeper, snow blower, snowplough, harrow, mulcher, weed brush.

The mechanical interface 5 may be configured to provide a permanent and non-detach- able mechanical connection with the auxiliary equipment. The mechanical interface 5 may alternatively be configured to provide a removable, i.e. detachable, interface or mechanical coupling between the tractor 1 and the auxiliary equipment. For example, the mechanical interface 5 includes a central coupling member 51 onto, into, and/or against which the auxiliary equipment may be attached. The mechanical interface 5 may comprise engagement means, or external engagement means may be used, for securing the connection may be provided.

The mechanical interface 5 may be attached to the front wall 22 in such a manner than the mechanical interface 5, or a member with which the mechanical interface is structurally interconnected, does not extend substantially into an interior of the structural frame 2. Thereby, an interior space of the structural frame 2 is not substantially reduced by the mechanical interface 5 or member which directly supports it.

For example, the mechanical interface 5 has a flange 52 with a bolt circle for attaching the mechanical interface 5 to the front wall 22. The front wall 22 may have arranged, on an inner surface, a counter support (not shown), similar to the counter support used for attaching the wheel drive unit 3 described above, for providing additional structural stability and load distribution of the mechanical interface 5, in particular the auxiliary equipment attached.

The mechanical interface 5 may be configured such that the auxiliary equipment may turn, in particular about the x-direction (which may also be defined as a roll axis), by a defined angular range. Thereby, the auxiliary equipment may turn, pivot, or roll to account for surface variations in the terrain, the auxiliary equipment thereby following or tracking contours in the terrain more closely. To this end, the mechanical interface 5 may include a bearing arranged for rotation about the x-axis. The bearing is preferably includes a shaft onto which the auxiliary equipment is coupled. The shaft, which may correspond with the central coupling member 51 , is attached to a disc (not shown) rotatably arranged between a front plate and a back plate. The front and back plates may form the flange 52 at least partially. The front and back plates may include one or more interior surfaces, in particular in contact areas with the disc, which enables for a defined rotational friction, including a defined static friction and/or a defined sliding friction, of the disc between the plates.

The tractor 1 further includes an electrical interface 6 for providing power and/or data signals to the auxiliary equipment. The electrical interface 6 is connected to a power electronics module (not shown). The electrical interface may be implemented using one or more power sockets and/or other electrical connectors. The electrical interface 6 is arranged on a front-facing portion of the tractor 1 , thereby allowing for short cable runs between the auxiliary equipment and the tractor 1.

The structural frame 2 includes a top wall 23 arranged horizontally in the x-y plane. The top wall 23 is connected to the lateral walls 21 and may be connected to the front wall 22. The top wall 23 preferably extends between the lateral walls 21. The top wall 22 comprises two beams extending, in the y-direction, between the lateral walls 21. The structural frame 2 further comprises a rear wall 24 (not shown) and a bottom wall 25 (not shown). Similarly to the other walls 21 , 22, 23, the rear wall 24 and/or the bottom wall 25 provide structural stability to the tractor 1 .

The structural frame 2 is designed such that the walls 21-25 provide, at least from some directions, an enclosure for the battery compartment which protects the battery compartment from water, moisture, and/or dust ingress. In particular, at least some of the walls 21-25 may be joined together to form tight seals with each other.

The structural frame 2 may include, along with the walls 21-25 described herein, one or more structural members, such as beams or profiles, which extend along the walls 21- 25 to provide additional structural support. The structural frame 2 may further include one or more additional structural members 26 which extend between two walls 21-25, for example spacers 26 arranged horizontally in the y-direction between the lateral walls 21 , thereby providing additional bracing to the structural frame 2. These spacers 26, however, merely provide additional support to the structure of the tractor 1 , which structure is primarily supported by the walls 21-25 of the structural frame 2. These additional structural members 26 are further configured such that they do not substantially reduce the interior volume of the structural frame 2 and thereby do not significantly reduce the space available for battery modules.

The tractor 1 comprises an operating arm 7 and an operating unit 71 which are described in more detail with reference to Figs. 5 and 6 below. The operating arm 7 is preferably rotatably attached to the tractor 1 , in particular to the top wall 23, such that the operating arm can be swung horizontally around the z-direction by a defined angular range. The operating arm 7 may be attached to the top wall 23 by a rotatable interface 72. The rotatable interface 72 may be designed similarly to the mechanical interface 5 described herein, in particular in that it may implement a rotatable disc slidably arranged between two plates, the plates preferably forming a flange for attaching the rotatable interface 72 to the top wall 23. Thereby, the rotatable interface 71 does not occupy and substantial interior space of the structural frame 2, thereby increasing an available volume for the battery compartment.

The tractor 1 further comprises a power electronics module comprising a power distribution unit (PDU) 81 and an inverter 82. The tractor 1 further comprises a control module 83, which may be part of the power electronics module or arranged/implemented separately. The control module 83 may include a vehicle control unit (VCU). The power electronics module may further comprise a back-up battery, for example for powering the control module 83.

The power electronics module is preferably arranged in a bay 84 which is arranged at least partially on an outside of the lateral walls 21 , in particular in an area above the wheel drive units 3. The bay 84 may extend over the front wall 22 and may also extend at least partially above the top wall 23. The bay 84 includes a housing and/or cover to shield the power electronics module from the environment. The bay 84 at least partially defines a housing for the power electronics module.

The power electronics module is configured to distribute and/or regulate the electrical energy from and/or to the battery modules, in particular for powering the tractor and/or recharging the battery. The power electronics module in particular may be configured to regulate a current and/or a voltage supplied to components of the tractor 1 , for example the wheel drive units 3.

The power electronics module 81 is connected to the battery modules 91A-91C of the battery compartment 9 by way of an electrical battery connection, and is further connected to an electric motor, in particular to each electric motor of each wheel drive unit 3. The power electronics module is further connected to the control module 82. The power electronics module is primarily configured to regulate power delivery to the wheel drive units 3 according to control signals received from the control module 83. The power electronics module may further be configured to provide power to the auxiliary equipment via the electrical interface 6.

The PDU 81 is connected to the battery modules 91A-91C. The PDU 81 is in turn connected to at least one inverter 82. The at least one inverter 82 is then connected to the wheel drive unit 3. Preferably, the tractor 1 comprises two inverters 82, each inverter 82 connected to a wheel drive unit 3. In particular, each particular inverter 82 is arranged on the lateral wall 21 in an area above the particular wheel drive unit 3.

The PUD 81 may further be connected to the electrical interface 6 for powering, if necessary, the auxiliary equipment. The power electronics module may further be configured to receive mains power for recharging the battery modules of the tractor 1. The tractor 1 may include a charging port for recharging the battery modules.

The control module 83 is configured to receive operator commands from the operating unit 71 , to generate control signals according to the received operator commands, and to provide, to the power electronics module, the generated control signals. The control module 83 may be connected to the PDU 81 and/or the inverter(s) 82.

The power electronics module, in particular each inverter 82, is connected to each wheel drive unit 3 by way of an electrical motor connection 85 arranged on an outside of the lateral wall 21. By arranging the inverters 82 above the respective wheel drive units 3 to which they are connected, the length of the electrical motor connection 85 is reduced.

Figure 2 shows the tractor 1 from a different perspective view, in particular from a bottom perspective view, thereby showing some features not visible in Figure 1. In particular, the bottom wall 25 and the rear wall 24 are shown. The bottom wall 25 extends between the lateral walls 21 , and further also between the front wall 23 and the rear wall 24.

Figure 3 shows an exploded perspective view of a schematic drawing of the single-axle tractor 1 , in which particular parts and components have been cut away to show the battery compartment 9. The battery compartment 9 is arranged at least partially inside the structural frame 2. In particular, the dimensions of the battery compartment 9 are at least partially constrained by the walls 21-25 of the structural frame 2. In particular, the battery compartment may be defined by at least some of the walls 21-25 of the structural frame. Part of the battery compartment 9 is arranged between the wheel drive units 3. Thereby, a low center of gravity of the tractor 1 is provided. Both wheel drive units 3 are arranged coaxially, i.e. such that a virtual line, i.e. both central axes CA, extending through the axle of both wheel drive units 3 coincide. The battery compartment 9 houses a plurality of battery modules 91A-91C which are shown as a horizontal stack of three battery modules 91A-91C. Each battery module 91A-91C has a roughly rectangular shape in the x-y plane. The battery modules 91A- 91 C include battery module attachment members 92 for mounting the battery modules 91A-91C inside the battery compartment 9, in particular for attaching the battery modules 91A-91C to walls 21-25 of the structural frame 2, specifically the lateral walls 21 , the rear front wall 21 , and/or the rear wall 24. The battery module attachment members 92, which as shown are fixed to the battery modules 91A-91C, are implemented as a band horizontally embracing the battery modules 91A-91C. The battery module attachment members 92 include attachment points for removably attaching the battery modules 91A-91C to the battery compartment 9.

The battery compartment 9 includes horizontal rails (not shown) which support the battery modules 91A-91C via battery module attachment members 92. The battery modules 91A-91C may be mounted in the battery compartment 9 by way of damping members. The damping members may be part of the battery modules 91 A-91 C or part of the battery compartment 9. The damping members are configured to attenuate vibrations and/or shocks.

The battery modules 91 A-91 C are replaceable. In particular, the battery modules 91 A- 91 C may be inserted into and/or removed from the structural frame 2 by removing the rear wall 24.

The structural frame 2 further includes horizontal structural members 26, in particular spacers 26, which extend between the lateral walls 21. The spacers 26 are configured such that they are arranged between the battery modules 91 A, 91 B.

Figure 4 shows a cutaway perspective view of a schematic drawing of a selection of components of the single-axle tractor 1 , including in particular the structural frame 2 and the wheel drive units 1 . The structural frame 2 has been cut away such that the battery compartment 9 is visible. Only one of the battery modules 91 A is shown inside the battery compartment 9. The remaining two battery modules 91 B, 91 C are shown removed.

The battery compartment 9 comprises rails 93 onto which the battery modules 91A-91C are mounted and by which they are supported. The rails 94 include one or more pins 95 which are arranged correspondingly to bores 96 in the battery module attachment members 92 to arrest a movement of the battery modules 91A-91C in the horizontal plane when mounted.

Structural members 26 are shown including horizontal structural members 26 extending between the lateral walls 21. In particular, the horizontal structural members 26 extend between the counter supports 27 by which the wheel drive units 3 are more securely attached to the lateral walls 21. Further structural members 26 are shown on the inside of the front wall 22, forming an ‘H’ shaped truss, for additional structural support.

Figures 5 and 6 show an operating arm 7, for use with a tractor, in particular a singleaxle tractor 1 as described herein. The operating arm 7 may however be used for other tractors.

The operating arm 7 is shown in two states.

In a first retracted state, as shown in Fig. 5, the operating arm 7 is partially folded together such that it does not occupy as much space horizontally. This allows for the operating arm 7 to take up less area and can be practical when parking the tractor to which it is attached, when stowing the tractor away, when maneuvering the tractor in tight spaces, and/or when operating the tractor not in a walk-behind mode where an operator walks behind the tractor, but when operating the tractor in a stand-on mode, where the operator stands on a small platform arranged on the rear of the tractor. In a second extended state, as shown in Fig. 6, the operating arm 7 is shown in an extended state, such that the operating arm 7 is at its full extent horizontally (i.e. in the x-y plane). The extended state is typically used when operating the tractor, as it allows for the operator to walk behind or to the side of the tractor.

The operating arm 7 may be moved continuously between the retracted state and the extended state.

The operating arm 7 comprises a parallelogram linkage 73 arranged between the rotatable interface 72 and an operating unit 71. In particular, the parallelogram linkage 73 may be configured for parallel motion. The operating unit 71 may also be used with a generic operating arm.

The parallelogram linkage 73 includes an upper member 731 connected to the operating unit 71 , a lower member 732 connected to the rotatable interface 72, and two linking members 733. The two linking members 733 are pivotably connected to the lower member 732 and the upper member 733. In particular, the lower member 732 includes so- called fixed pivots and the upper member includes so-called moving pivots.

The parallelogram linkage 73 preferably includes a retention mechanism 74 configured such that the operating arm 7 may be moved in a continuous fashion between the extended position and the retracted position. In particular the retention mechanism 74 is configured such that the operating arm 7 may be placed in both the extended position and the retracted position as well as any intermediate position. The retention mechanism 74 may include a spring and/or damper connected to the parallelogram linkage 73. The retention mechanism 74 may comprise a gas spring. The retention mechanism 74 is preferably arranged between the two linking members 733. The operating unit 71 includes operating means for locking and/or releasing the parallelogram linkage 73 such that it may be moved from the extended position to the retracted position, vice versa, and further to any intermediate position. It may be moved by the operator. In particular, the parallelogram linkage 73 may be designed to be moved using a defined minimal force. Preferably, the defined minimal force is able to be exerted one- handed by the operator. The parallelogram linkage 73 may be locked in any position. The operating means are preferably configured such that, when a particular button or other input means of on the operating unit 71 is activated, the parallelogram linkage moves, under its own power, into the retracted position, for example using energy stored in the retention mechanism 74.

The operating unit 71 comprises two handles 711. The handles 711 each include a safety switch 712 implemented as a lever. The operator typically activates both safety switches 712 during use. Thereby, the operating unit 71 and/or the tractor may determine that the operator is present. The operating unit 71 and/or the tractor 1 with which it is connected is configured to enter a safety mode, which may involve the power being shut down (i.e. turning off the tractor) and/or stopping the tractor and/or auxiliary equipment, if neither of the safety switches 712 are activated. In particular, only one of the safety switches 712 needs to be activated to enter a normal operating mode of the tractor. This allows the operator to operate the tractor, at times, with only one hand actually holding the safety switch 712. The handles 711 may additionally include input means such as a joystick 713. The joystick 713 is preferably configured such that it may be operated using a thumb. The operating unit 71 is configured such that the joystick input may be mapped to one or more different types of control signal which the operating unit 71 may generate.

For example, one or both of the joysticks 713 may be configured to control the steering of the tractor, for example by toggling the joystick 713 to the side. One or both of the joysticks 713 may be configured to control a forwards and/or a backwards movement of the tractor, for example by toggling the joystick 713 forwards and/or backwards, respectively.

The operating unit 71 further comprises a dashboard 733. The dashboard 733 may include one or more display elements 734 configured to provide information to the opera- tor. The display elements 734 may include lights, such as LEDs, as well as one or more displays. The display elements 734 may thereby inform the operator about the current and/or projected state of the tractor 1 , for example a current battery level, a current operating time, a predicted operating time left before recharging of the battery is required, etc. The above-described embodiments of the disclosure are exemplary and the person skilled in the art knows that at least some of the components and/or steps described in the embodiments above may be rearranged, omitted, or introduced into other embodiments without deviating from the scope of the present disclosure.

Claims

1. A single-axle tractor (1) comprising: a structural frame (2) comprising two lateral walls (21) structurally interconnected to each other and arranged spaced apart from each other on either side of a battery compartment (9), wherein the battery compartment (9) is arranged on an inside between the two lateral walls (21) and comprises at least one battery module (91 A, 91 B, 91 C) supported with respect to the structural frame (9); two wheel drive units (3) each comprising a wheel (4) attached to an axle and a motor for driving said wheel (4) around said axle; wherein the wheel drive units (3) are mounted on the outside of the lateral walls (21) respectively, such that central axes of the wheel drive units (3) meet.

2. The single-axle tractor (1) according to any of the preceding claims, wherein the lateral walls (21) of the structural frame (2) are interconnected to each other by a front wall (22), said front wall (22) comprising a mechanical interface (5) to attach an auxiliary equipment to the single-axle tractor (1).

3. The single-axle tractor (1) according to any of the preceding claims, wherein the two lateral walls (21) are interconnected to each other by one or more of the following: a bottom wall (25), a rear wall (24), a top wall (23), or a spacer (26).

4. The single-axle tractor (1) according to any of the preceding claims, wherein the battery compartment (9) comprises a plurality of horizontally and/or vertically stacked battery modules (91 A, 91 B, 91 C).

5. The single-axle tractor (1) according to any of the preceding claims, wherein the battery compartment (9) and/or the battery modules (91 A, 91 B, 91 C) comprise one or more battery module attachment members (92, 95) to support the at least one battery module (91A, 91 B, 91C) with respect to the lateral walls (21).

6. The single-axle tractor (1) according to any of the preceding claims, wherein the battery compartment (9) is accessible via a rear opening in the structural frame (2), wherein the rear opening is provided by opening and/or removing a releasably attached rear wall (25).

7. The single-axle tractor (1) according to any of the preceding claims, wherein each wheel drive unit (3) is mounted on the outside of the lateral walls (21) by way of a counter support (27) arranged on the inside of the lateral walls (21) adjacent to the wheel drive unit (3), wherein a plurality of connecting members extend through the lateral walls to fasten the wheel drive unit (3) to the counter support (27).

8. The single-axle tractor (1) according to any of the preceding claims, wherein the battery compartment (9) is arranged at least partially between the wheel drive units (3).

9. The single-axle tractor (1) according to any of the preceding claims, further comprising a power electronics module attached to the structural frame (2) and an electrical battery connection, the electrical battery connection configured to electrically connect at least one battery module (91 A, 91 B, 91 C) to the power electronics module.

10. The single-axle tractor (1) according to any of the preceding claims, wherein the motors are electric motors and the single-axle tractor (1) further comprises two electrical motor connections (85) for electrically connecting the power electronics module with the two electric motors, respectively.

11. The single-axle tractor (1) according to any of the preceding claims, further comprising an operating arm (7) pivotably arranged on a top wall (23) of the structural frame (2), and an operating unit (71) attached to the operating arm (7).

12. The single-axle tractor (1) according to claim 11, wherein the operating arm (7) includes a parallelogram linkage (73) configured such that the operating arm (7) may be moved from an extended position to a retracted position, wherein the operating arm (7) includes a retention mechanism (74) configured such that the op- erating arm (7) can be set at any desired position between the extended position and the retracted position.