Belt-crawler undercarriage for a vehicle

Abstract

The present invention relates to a belt-crawler undercarriage for all terrain vehicles with at least one shape changeable belt crawler unit arranged underneath the vehicle to be operated with the vehicle when needed or desired. The shape changeable belt-crawler undercarriage may be kept in a linear shape under the vehicle when not in use or in a resting position, but during operation the front and rear wheels of the belt crawler unit(s) are lowered by a radial movement of individual frame components forming a triangular shaped belt.

Description

[0001] BELT-CRAWLER UNDERCARRIAGE FOR A VEHICLE

[0002] Field of the invention

[0003] The invention relates to a belt-crawler undercarriage to be arranged under a vehicle with at least one shape changeable belt crawler unit. Furthermore, the invention relates to a drivetrain adapted to operate with shape changeable belt crawler units under a vehicle.

[0004] Background

[0005] Belt crawlers or track belts are known in the art and are used for various types of vehicles for traversing difficult terrain. Belt crawlers are particularly common in off-road vehicles, construction machinery, agricultural equipment, military vehicles, and specialized vehicles used in exploration or scientific research. Belt crawler units work by providing a continuous surface area for gripping the ground and allowing vehicles with track belts to move across various terrains. Such belt crawler units provide vehicles with enhanced traction, stability, and manoeuvrability in a wide range of terrains, which makes them well-suited for applications such as off-road vehicles, construction machinery, agricultural equipment, and military vehicles.

[0006] Traditionally belt crawler units comprise a series of interconnected links or segments that form a continuous loop or belt around a set of wheels or sprockets for continuous traction across a terrain. The belt is wrapped around the belt wheels or sprockets which creates a continuous surface making contact with the ground enabling constant traction on the terrain. Belt crawler units provide good weight distribution of a vehicle over a larger surface area compared to wheeled vehicles, which helps to reduce ground pressure and preventing the vehicle from sinking into soft soil or mud and minimizing soil compaction. Furthermore, belt crawler units provide flexibility and adaptability as they can conform to the shape of the terrain, allowing vehicles to traverse obstacles such as rocks, tree roots, and uneven surfaces more easily than wheeled vehicles.

[0007] US 5,287,938 discloses vehicle for on-and off-road use comprising a belt track unit mounted under the vehicle frame between front and rear wheels. The belt track unit has auxiliary frames with continuous tracks on carrier wheels where each auxiliary frame is independently vertically displaceable relative to the vehicle frame by means of corresponding lifting cylinders between a fully retracted position for travel on wheels only, and a fully extended position for tracks only travel.

[0008] US2017001671 discloses continuous track assembly having forward and rearward track engaging wheels with an intermediate track engaging wheel position between them and a continuous track extending over the wheels. A foldable frame is arranged to change the position of the wheels between a linear position and a triangular configuration in a synchronized movement of front and rear wheel arms and a retracting actuator. Summary of the Invention

[0009] The present invention provides a belt crawler unit, which may be used alone or as one of a plurality of belt crawler units in a belt-crawler undercarriage to be arranged underneath and operated with all-terrain vehicles when needed or desired. . The belt crawler unit of the present invention is adapted for multi-shape change during operation, where the tension on the crawler belt is maintained during change from one shape to another so that the crawler belt will not fall off the frame. The belt crawler unit is based on movable frame arms, at least one central wheel attached to the chassis or the undercarriage of the vehicle and a plurality of belt wheels arranged on the frame arms. In a simple embodiment front and rear wheels are connected to front and rear pivotal frame arms, which may be lowered to change the shape of the belt crawler unit from a linear shape to a triangular shape and thereby engage with the terrain underneath the vehicle. When the belt-crawler unit is not in use or in a resting position, the belt crawler unit has a linear shape under the vehicle. However, during operation the front and / or rear wheels of the crawler unit(s) are lowered by a radial movement of the front and rear pivotal frame arms changing the shape of the belt crawler unit. The belt crawler unit may also comprise further frame components, such as a longitudinal telescopic connection arm connecting the front and the rear wheel. These variation are shown and further outlined in figure 1.

[0010] The shape change of the belt crawler unit is facilitated by actuators affecting one or more frame arms, length adjusters in one or more of the frame arms, and pivotal connections to and / or between one or more of the frame arms, where the movement of each frame arm and their length adjustment is synchronized in order to always maintain tension on the crawler belt through a shape change. A shape change of the belt crawler unit requires at least one of the frame arms to comprise a length adjuster for altering the length of one or more frame portions. The radial movement of the front and rear pivotal frame arms is facilitated by pivotal actuators arranged with the front and rear pivotal frame arms. This is shown and further outlined in figure 2. The length adjusters in one or more frame arms may further comprise suspension elements to further aid the belt crawler unit to maintain circumferential tension on the crawler belt through the shape change and during operation.

[0011] The belt-crawler unit of the present invention differs from all other prior art arrangements in that it uses pivotal actuators and length adjusters to change the shape of the belt-crawler unit from linear to multiform geometries, such as a triangular shape, where only one of front or rear wheel(s) may be lowered to the ground or both of them.

[0012] In some embodiments the belt crawler unit comprise three wheels, i.e. a static central wheel attached to the chassis or the undercarriage of the vehicle, a front wheel and a rear wheel attached to the front and rear pivotal frame arms respectively, whereas other embodiments may comprise one or more static central wheel(s) a front wheel and a rear wheel attached to pivotal frame arms, and two or more belt wheels arranged either on a longitudinal telescopic connection arm between the front wheel and the rear wheel, or on separate frame arms pivotally connected to the front and rear pivotal frame arms respectively.

[0013] In some embodiments the central wheel is arranged with a drive axle for rotating or driving the belt of the belt crawler unit. The front and rear wheels, as well as the any additional belt wheels arranged on frame arms of the belt crawler unit(s) may be driven by additional drive shafts connected to the frame through mechanical transfer components such as internal drive shafts, angled drive components, chains and cogwheels. All the wheels of the belt crawler unit(s) may also be powered by electrical motors.

[0014] The present invention further provides a drivetrain and suspension system for vehicles such as four-wheel drive vehicles in combination with the belt-crawler undercarriage of the invention. Such drivetrain may comprise a front and rear wheel set units, left and right wheels on an axle with a differential, a vehicle drive shaft connected to the engine and gear system of the vehicle and a pivotal left and right connection arms for the front and rear wheel set units, attached to the vehicle chassis, to enable pivotal movement of the front and rear wheel set unit for co-ordinated operation of the vehicle drivetrain and the belt crawler unit.

[0015] In some embodiments the actuators and length adjusters of belt crawler unit(s) and the suspension systems for the drivetrain is independently controlled but may also be coordinated through a computer system.

[0016] The belt-crawler undercarriage can be mounted under any kind of vehicle, such as larger road and off-road vehicles including jeeps, lorries etc, tractors, heavy equipment vehicles / machines for construction, mining, agriculture, forestry and paving including bulldozers and shovel vehicles, etc, military vehicles such as panzer vehicles and tanks, snowmobiles and motorbikes.

[0017] It is an object of the present invention to overcome and / or ameliorate the aforementioned drawbacks of the prior art and to provide an improved and / or alternative and / or additional belt-crawler undercarriage being arranged under a vehicle and configured to be operated with the vehicle. Moreover, it is a preferred object of the present invention to provide belt-crawler units configured for changing the shape of each belt crawler unit from a linear shape to any multi-form shape or geometry, such as a triangular shape during operation of a vehicle. It is also a preferred object of the present invention to provide a drivetrain for a vehicle adapted to operate with the belt-crawler undercarriage of the present invention.

[0018] The object(s) underlying the present invention is (are) particularly solved by the features defined in the independent claims. The dependent claims relate to preferred embodiments of the present invention. Further additional and / or alternative aspects are discussed below.

[0019] Thus, at least one of the preferred object of the present invention is solved by a beltcrawler unit configured for changing the shape of the belt crawler unit, where the belt crawler unit comprises: i) at least one central wheel, ii) a frame further comprising ii) a front pivotal frame arm having a proximal end connected to a first axial joint, and forward-extending distal end connected to a front wheel, iii) a rear pivotal frame arm with a proximal end connected to said first axial joint or a second axial joint, and rearward-extending distal end connected to a rear wheel, and iv) a crawler belt, where the belt crawler unit further comprises a front and a rear pivotal connected to each of the front and rear pivotal frame arms for actuating pivotal movement of the distal end of the front and / or rear pivotal frame arms about the first and / or second axial joint, and where the rear pivotal frame arm further comprises a length adjuster for adjusting the length of the rear pivotal frame arm to maintain tension on the crawler belt during a shape change of the belt crawler unit.

[0020] Another preferred object of the present invention is solved by a belt-crawler undercarriage system configured for changing the shape of one or more belt crawler units, the system comprising: i) providing at least one belt crawler unit, where the belt crawler unit further comprises: at least one central wheel, a frame further comprising a front pivotal frame arm having a proximal end connected to a first axial joint, and forward-extending distal end connected to a front wheel, a rear pivotal frame arm with a proximal end connected to said first axial joint or a second axial joint, and rearwardextending distal end connected to a rear wheel, and crawler belt, where the front pivotal frame arm and / or the rear pivotal frame arm further comprise a length adjuster for adjusting the length of the front and / or the rear pivotal frame arms. The belt crawler unit further comprises a front and a rear pivotal actuators connected to each of the front and rear pivotal frame arms and configured for actuating independent pivotal movement of the distal end of the front and / or rear pivotal frame arms about the first and / or second axial joint, where the adjustment of the length of the front and / or the rear pivotal frame arms by the length adjuster and the independent pivotal movement of the distal end of the front and / or rear pivotal frame arms actuated by the pivotal actuators is synchronized to maintain tension on the crawler belt during a shape change of the belt crawler unit. One of the objects of the present invention is solved by a belt-crawler undercarriage system configured for changing the shape of one or more belt crawler units, where the system comprises: i) providing at least one belt crawler unit of the present invention, and ii) arranging the at least one belt crawler unit under a vehicle, where the vehicle further comprises a front and rear wheel set units each comprising left and right wheels and a front and rear axle, where the at least one belt crawler unit is configured for changing the shape of one or more belt crawler units to adapt to the terrain said vehicle is crossing by actuating an independent pivotal movement of the distal end of the front and / or rear pivotal frame arms about the first and / or second (7) axial joint, and by adjustment of the length of the front and / or the rear pivotal frame arms by the length adjuster to maintain tension on the crawler belt during a shape change of the belt crawler unit.

[0021] Another object of the present invention is solved by a belt-crawler unit configured for changing the shape of the belt crawler unit, where the belt crawler unit comprises: i) at least one central wheel, ii) a frame further comprising ii) a front pivotal frame arm having a proximal end connected to a first axial joint, and forward -extendi ng distal end connected to a front wheel, iii) a rear pivotal frame arm with a proximal end connected to said first axial joint or a second axial joint, and rearward -extendi ng distal end connected to a rear wheel, and iv) a crawler belt, where the belt crawler unit further comprises a front and a rear pivotal connected to each of the front and rear pivotal frame arms for actuating pivotal movement of the distal end of the front and / or rear pivotal frame arms about the first and / or second axial joint, and where the front pivotal frame arm and / or the rear pivotal frame arm further comprise a length adjuster for adjusting the length of the front and / or the rear pivotal frame arms to maintain tension on the crawler belt during a shape change of the belt crawler unit.

[0022] In the present context the terms "frame arm", "frame portion", and "connecting arm" relate to components of a belt-crawler unit for connecting the wheels of the belt crawler unit together and connecting the belt crawler unit to the vehicle, where one or more of these components comprise telescopic properties to facilitate the shape change of each belt crawler unit between a linear shape and a triangular shape and at the same time maintaining tension on the crawler belt during the shape change of the crawler belt.

[0023] In the present context the term "actuator", relates to devices such as telescopic devices or torque devices, which activate, regulate or facilitate movement of components of the belt crawler unit of the present invention, such as frame arms.

[0024] In the present context the term "length adjuster", relates to devices such as telescopic devices or beams which are regulated to alter the length of components of the belt crawler unit of the present invention, such as frame arms. In an embodiment of the present invention the front pivotal frame arm further comprises a length adjuster for adjusting the length of the front pivotal frame arm to maintain tension on the crawler belt during a shape change of the belt crawler unit.

[0025] In an embodiment of the present invention the belt crawler unit is configured for a multishape change of the belt crawler unit.

[0026] In an embodiment of the present invention the belt crawler unit is configured for changing the shape of the belt crawler unit between a linear shape and (multi-shape) a triangular shape.

[0027] In an embodiment of the present invention the shape change of the belt crawler unit comprises i) pivotal movement of the front pivotal frame arm and / or the rear pivotal frame arm through the front and / or the rear pivotal actuator respectively, and ii) adjusting the length of the length adjuster of the front pivotal frame arm and / or the rear pivotal frame arm.

[0028] In an embodiment of the present invention the i) pivotal movement of the front pivotal frame arm and / or the rear pivotal frame arm, ii) actuation of the pivotal movement of the distal end of the front and / or rear pivotal frame arms by the front and / or the rear pivotal actuator, and iii) adjustment of the length of the length adjuster of the front pivotal frame arm and / or the rear pivotal frame arm, is synchronized to maintain tension on the crawler belt during a shape change of the belt crawler unit.

[0029] In an embodiment of the present invention the pivotal movement of the front pivotal frame arm and / or the rear pivotal frame arm is independent.

[0030] In an embodiment of the present invention the adjustment of the length of the front and / or the rear pivotal frame arms by the length adjuster maintains a set or a constant tension on the crawler belt during a shape change of the belt crawler unit.

[0031] In an embodiment of the present invention the adjustment of the length of the front and / or the rear pivotal frame arms by the length adjuster maintains the tension on the crawler belt above a set value during a shape change of the belt crawler unit.

[0032] In an embodiment of the present invention the adjustment of the length of the front and / or the rear pivotal frame arms by the length adjuster maintains the tension on the crawler belt within a predetermined range during a shape change of the belt crawler unit.

[0033] In an embodiment of the present invention one or more belt-crawler units form a beltcrawler undercarriage for a vehicle.

[0034] In an embodiment of the present invention the one or more belt-crawler units forming a belt-crawler undercarriage for a vehicle is configured to be secured to a chassis of a vehicle. In an embodiment of the present invention the belt-crawler undercarriage further comprises a central frame portion.

[0035] In an embodiment of the present invention the central frame portion is positioned between proximal ends of the front pivotal frame arm and / or the rear pivotal frame arm.

[0036] In an embodiment of the present invention the central frame portion is attached to the chassis of the vehicle.

[0037] In an embodiment of the present invention the first axial joint and / or the second axial joint are pivot joints.

[0038] In an embodiment of the present invention the first axial joint and / or the second axial joint are configured to be fixed to the chassis of said vehicle.

[0039] In an embodiment of the present invention the first axial joint and / or the second axial joint are configured to be fixed to the central frame portion.

[0040] In an embodiment of the present invention the first axial joint and / or the second axial joint are

[0041] In an embodiment of the present invention the central frame portion further comprises a movable connection (axial joint) for facilitating the pivotal movement of the front pivotal frame arm and / or the rear pivotal frame arm.

[0042] In an embodiment of the present invention the axial joint of the central portion to the front and / or rear pivotal frame arms comprises a hinge-connection.

[0043] In an embodiment of the present invention the length adjuster of the front and / or rear pivotal frame arms further comprises a telescopic length adjuster, such as a telescopic beam.

[0044] In an embodiment of the present invention the length adjuster of the front and / or rear pivotal frame arms further comprises a suspension device.

[0045] In an embodiment of the present invention the front pivotal frame arm and / or the rear pivotal frame arm comprises a main portion and an extension portion.

[0046] In an embodiment of the present invention the front and / or rear pivotal frame arms comprise an A-frame main portion.

[0047] In an embodiment of the present invention the main portion of the front and / or rear pivotal frame arms comprises an A-frame main portion.

[0048] In an embodiment of the present invention the front and / or rear pivotal frame arms comprise a frame structure with three-point connection properties. In an embodiment of the present invention the front and / or rear pivotal frame arms comprise a longitudinal frame portion.

[0049] In an embodiment of the present invention the extension portion of the front and / or rear pivotal frame arms comprises a longitudinal frame portion.

[0050] In an embodiment of the present invention the front and / or rear pivotal frame arms comprise an A-frame main portion and a longitudinal frame portion.

[0051] In an embodiment of the present invention the longitudinal frame portions of the front and / or rear pivotal frame arms extend in a forward and rear direction of the belt-crawler unit.

[0052] In an embodiment of the present invention the longitudinal frame portions of the front and / or rear pivotal frame arms further comprise the length adjuster for adjusting the length of the front and / or rear pivotal frame arms.

[0053] In an embodiment of the present invention the longitudinal frame portions of the front and / or rear pivotal frame arms are rotationally, pivotally or movably arranged, connected or secured to the A-frame main portion of the front and / or rear pivotal frame arms.

[0054] In an embodiment of the present invention the extension portion of the front and / or rear pivotal frame arms is uniformly formed with the main portion of the front and / or rear pivotal frame arms.

[0055] In an embodiment of the present invention the front and / or rear pivotal frame arms comprise a torque arm.

[0056] In an embodiment of the present invention the frame further comprises a length adjustable connection arm.

[0057] In an embodiment of the present invention the frame further comprises a length adjustable connection arm connected to the distal ends of the front and rear pivotal frame arms.

[0058] In an embodiment of the present invention the length adjustable connection arm comprises a length adjuster for adjusting the length of the length adjustable connection arm to maintain tension on the crawler belt during a shape change of the belt crawler unit.

[0059] In an embodiment of the present invention the length adjuster of the length adjustable connection arm comprises a telescopic length adjuster.

[0060] In an embodiment of the present invention the length adjustable connection arm comprises a telescopic length adjuster, such as a telescopic beam. In an embodiment of the present invention the length adjustable connection arm further comprises a suspension device.

[0061] In an embodiment of the present invention the length adjustable connection arm further comprises a suspension properties.

[0062] In an embodiment of the present invention the length adjustable connection arm provides a connection to the distal ends of the front and / or rear pivotal frame arms.

[0063] In an embodiment of the present invention the length adjustable connection arm is pivotally connected to the distal ends of the front and / or rear pivotal frame arms through a front and rear axial joints.

[0064] In an embodiment of the present invention the length adjustable connection arm comprises one or more lateral telescopic and / or suspension devices for altering the distance between the front and rear wheel.

[0065] In an embodiment of the present invention the length adjustable connection arm provides a connection to the front and rear wheel respectively.

[0066] In an embodiment of the present invention the at least one central wheel is in a fixed position in relation to chassis of the vehicle.

[0067] In an embodiment of the present invention the at least one central wheel is statically arranged to the chassis.

[0068] In an embodiment of the present invention the at least one central wheel is in a fixed position between the first and second axial joints.

[0069] In an embodiment of the present invention the at least one central wheel is statically arranged between the proximal end of the centrally connected the front and / or rear pivotal frame arms.

[0070] In an embodiment of the present invention the at least one central wheel is a drive wheel for the belt-crawler unit.

[0071] In an embodiment of the present invention the at least one central wheel is arranged on a drive shaft.

[0072] In an embodiment of the present invention the front wheel is arranged at the distal end of the front pivotal frame arm.

[0073] In an embodiment of the present invention the front wheel is movable with respect to the chassis.

[0074] In an embodiment of the present invention the front wheel is adapted for a pivotal downward movement of the front pivotal frame arm. In an embodiment of the present invention the front wheel is adapted for a pivotal downward movement of the front pivotal frame arm through actuation of the front pivotal actuator.

[0075] In an embodiment of the present invention the rear wheel is arranged at the distal end of the rear pivotal frame arm.

[0076] In an embodiment of the present invention the rear wheel is movable with respect to the chassis.

[0077] In an embodiment of the present invention the rear wheel is adapted for a pivotal downward movement by the rear pivotal frame arm.

[0078] In an embodiment of the present invention the rear wheel is adapted for a pivotal downward movement by the rear pivotal frame arm through actuation of the pivotal actuator.

[0079] In an embodiment of the present invention the front pivotal frame arm and the length adjustable connection arm are connected by the front wheel through a front axial joint.

[0080] In an embodiment of the present invention the front axial joint is a parallel connection through the front pivotal frame arm and longitudinal telescopic connection arm.

[0081] In an embodiment of the present invention the parallel connection through the front pivotal frame arm and the length adjustable connection arm comprises an axle or a bearing.

[0082] In an embodiment of the present invention the rear pivotal frame arm and the length adjustable connection arm are connected by the rear wheel through a rear axial joint.

[0083] In an embodiment of the present invention the rear axial joint is a parallel connection through the rear pivotal frame arm and the length adjustable connection arm.

[0084] In an embodiment of the present invention the parallel connection through the rear pivotal frame arm and the length adjustable connection arm comprises an axle or a bearing.

[0085] In an embodiment of the present invention the rear wheel is connectable to the frame by the length adjuster in the rear pivotal frame arm.

[0086] In an embodiment of the present invention the rear wheel is connectable to the frame by the rear pivotal frame arm in the rear pivotal frame arm and a rear telescopic device in the length adjustable connection arm.

[0087] In an embodiment of the present invention the belt-crawler unit further comprising one or more belt wheels between the front wheel and the rear wheel. In an embodiment of the present invention the one or more additional belt wheels may be arranged on the length adjustable connection arm.

[0088] In an embodiment of the present invention the one or more additional belt wheels may be arranged on a connecting wheel arm connected to the length adjustable connection arm.

[0089] In an embodiment of the present invention the connecting wheel arm for the one or more (additional) belt wheels is pivotally connected to the length adjustable connection arm.

[0090] In an embodiment of the present invention the connecting wheel arm for the one or more additional belt wheels further comprises a suspension device.

[0091] In an embodiment of the present invention the one or more additional belt wheels may be arranged on a separate connecting wheel arm connected to the front and / or rear pivotal frame arms.

[0092] In an embodiment of the present invention the connecting wheel arm for the one or more additional belt wheels is pivotally connected to the front and / or rear pivotal frame arms.

[0093] In an embodiment of the present invention the one or more belt wheels may comprise a second front belt wheel behind the front wheel.

[0094] In an embodiment of the present invention the one or more belt wheels may comprise a second rear belt wheel in front of the rear wheel.

[0095] In an embodiment of the present invention the wheels of the belt crawler unit comprise a parallel wheel set arranged on a joint or axle.

[0096] In an embodiment of the present invention the non-static wheels of each belt crawler unit comprise a parallel wheel set arranged on a joint or the same axle.

[0097] In an embodiment of the present invention the joint axle is arranged in one or more portions of the frame.

[0098] In an embodiment of the present invention the one or more of the parallel wheel sets are connected to the frame by an axle joint axle going through one or more portions of the frame.

[0099] In an embodiment of the present invention the one or more of the central wheel(s), the front wheel, the rear wheel and the one or more additional belt wheels further comprise a cogged wheel for engaging with the crawler belt.

[0100] In an embodiment of the present invention the one or more of the central wheel(s), the front wheel, the rear wheel and the one or more additional belt wheels further comprise a cogged wheel arranged on the axle with the parallel wheel set for engaging with the crawler belt.

[0101] In an embodiment of the present invention the cogged wheel is arranged on the axle between the parallel wheel set.

[0102] In an embodiment of the present invention the at least one static central wheel comprises a cogged wheel for engaging with the crawler belt.

[0103] In an embodiment of the present invention the one or more of the central wheel(s) comprises two central wheels arranged on the first axial joint and the second axial joint respectively.

[0104] The belt-crawler unit according to claim, wherein the one or more of the central wheel(s) comprises one or more central wheels arranged between the two central wheels arranged on the first axial joint and the second axial joint.

[0105] In an embodiment of the present invention the front wheel, the rear wheel the one or more (additional) belt wheels between the front wheel and the rear wheel comprise parallel wheel sets are arranged on the frame by separate axles.

[0106] In an embodiment of the present invention the front wheel, the rear wheel, and the one or more additional belt wheels between the front wheel and the rear wheel may comprise parallel wheel sets arranged on the length adjustable connection arm.

[0107] In an embodiment of the present invention a belt-crawler undercarriage comprises two belt-crawler units.

[0108] In an embodiment of the present invention the two belt-crawler units are mirror images parallel arranged on the left and the right side of the vehicle.

[0109] In an embodiment of the present invention the belt-crawler undercarriage further comprises a drive unit for driving or rotating at least one of the wheels of each of the belt crawler units.

[0110] In an embodiment of the present invention the drive unit is adapted to rotate one or more of the wheels of each of the belt crawler units.

[0111] In an embodiment of the present invention the drive unit comprises a belt axle.

[0112] In an embodiment of the present invention where at least one belt crawler unit is arranged under a vehicle, the vehicle further comprises a front and rear wheel set units each comprising left and right wheels and a front and rear axle.

[0113] In an embodiment of the present invention where at least one belt crawler unit is arranged under a vehicle, the vehicle further comprises i) front and rear suspension devices for the left and right side of the vehicle, ii) front and rear axle connectors movably connected to the chassis of the vehicle and to the front and rear wheel axle respectively for pivotal movement of the distal end of the front and rear axle connectors, and iii) a vehicle drive shaft, said vehicle drive shaft comprising a central wheel shaft, a front drive shaft within the front axle connector, and a rear drive shaft within the rear axle connector.

[0114] In an embodiment of the present invention the front and rear suspension devices for the left and right side of the vehicle is synchronized to aid in the shape change of the beltcrawler undercarriage.

[0115] In an embodiment of the present invention the: i) pivotal movement of the front pivotal frame arm and / or the rear pivotal frame arm through the front and / or the rear pivotal actuator respectively, ii) adjustment of the length of the length adjuster of the front pivotal frame arm and / or the rear pivotal frame arm, and iii) movement of the front and rear suspension devices for the left and right side of the vehicle is independently controlled and / or synchronized.

[0116] In an embodiment of the present invention the vehicle drive shaft is connected to the belt axle of the belt-crawler undercarriage for mechanical transfer from the vehicle drive shaft to the one or more belt-crawler units of the belt-crawler undercarriage.

[0117] Description of various embodiments

[0118] The present invention will become more fully understood from the detailed description given hereinafter and the accompanying drawings which are given by way of illustration only, and thus, are not limitative of the present invention, and wherein:

[0119] FIG. 1 is a schematic drawing showing alternative embodiments of a shape changeable belt crawler units of the present invention.

[0120] FIG. 2 is a schematic drawing showing variations for length adjusters and actuators for the shape changeable belt crawler units of the invention.

[0121] FIG. 3 is a schematic drawing showing belt crawler units with different number of wheels and shapes.

[0122] FIG. 4 is a perspective side view of belt-crawler units having different shape or geometry based on pivotal movement of frame arms.

[0123] FIG. 5 is a schematic drawing showing top view of a belt crawler unit with five wheels.

[0124] FIG. 6 is a perspective top view of the belt crawler unit in Fig. 5. FIG. 7 is a perspective side view of belt-crawler undercarriage of the invention.

[0125] FIG. 8 is a perspective view of belt-crawler undercarriage on a vehicle seen from below.

[0126] FIG. 9 is a schematic drawing showing top view of belt-crawler undercarriage with a drivetrain and suspension system for a vehicle.

[0127] FIG. 10 is a schematic drawing showing a side view of a shape changeable belt crawler unit in mounted on a vehicle.

[0128] Figure 1 shows different embodiments of a shape changeable belt crawler unit having three wheels, i.e. a central wheel 2 a front wheel 5 and a rear wheel 8. The front 5 and rear 8 wheels attached to a front pivotal frame arm 3 and rear pivotal arm 6 of the belt crawler unit's frame. For each embodiment the upper drawing shows the belt crawler unit in a resting / parked position having a linear shape, and the lower drawing shows the belt crawler unit in a triangular shape for assisting the vehicle over difficult terrain or up steep hills. The triangular shape is obtained by lowering the front wheel 5 and the rear wheel 8 of the crawler unit by a radial movement of the front 3 and rear 6 pivotal frame arms maintaining circumferential tension on the crawler belt 9 of the belt crawler unit. The functionality of the shape change is obtained by use of length adjustable arms in one or more of the frame portions of the belt crawler unit.

[0129] In Fig. 1A the belt crawler unit is shown with only front 3 and rear 6 pivotal frame arms and a length adjuster 12 in the rear pivotal arm 6. In Fig. IB the belt crawler unit is also shown with only front 3 and rear 6 pivotal frame arms, but also with a length adjuster 12 in both the front pivotal arm 3 and the rear pivotal arm 6. The crawler unit in Fig. 1C and Fig. ID have additional length adjustable connection arm 18 connecting the front wheel 5 and the rear wheel 8. In Fig. 1C the ability of shape changes of the belt crawler unit and the ability of maintaining circumferential tension on the crawler belt 9 are provided by the length adjuster 12 in the rear pivotal arm 6 and length adjuster 19 in the rear portion of the length adjustable connection arm 18. In Fig. ID the length adjustable connection arm 18 is shown with length adjuster 19 in both the front and the rear portion of the length adjustable connection arm 18, but this embodiment could also have only one length adjuster 19 in the rear portion of the length adjustable connection arm 18. Furthermore, both the front pivotal arm 3 and the rear pivotal arm 6 comprise a length adjuster 12 to facilitate shape changes of the belt crawler unit and the ability of maintaining circumferential tension on the crawler belt 9.

[0130] Figure 2 shows the function of various actuators and length adjustment elements for facilitating the shape change of a belt crawler unit according to the present invention. The drawing shows an embodiment similar to the belt crawler unit in Fig. 1A and Fig. 1C. In this drawing two embodiments are shown, where on the left (I) the frame comprises a front pivotal arm 3 and a rear pivotal frame arm 6 with a length adjuster 12 in the rear pivotal arm 6, and on the right (II) the frame further comprises an additional length adjustable connection arm 18 connecting the front wheel 5 and the rear wheel 8 having a telescopic length adjuster 19 in the rear portion of the length adjustable connection arm 18. The drawing also shows a front pivotal actuator 10 is connected to the front pivotal arm 3 and a rear pivotal actuator 11 is connected to the rear pivotal arm 6 for controlling the pivotal movement of the front 3 and rear 6 pivotal frame arms for both embodiments I and II. When the front 10 and rear 11 pivotal actuators are extended the distal end of the front and rear frame arms are diagonally lowered in a pivotal movement for changing the shape of each belt crawler unit from a linear shape to a triangular shape. The function of the lateral length adjustable connection arm 18 and the length adjuster 12 of the rear pivotal frame arm 6 is further explained in relation to embodiment II of this drawing. In Fig. 2A the telescopic length adjuster 19 at the rear end of the length adjustable connection arm 18 is extended when the belt crawler unit is in a linear position but the length adjuster 12 of the rear pivotal frame arm 6 (shown with a dotted line) is retracted, and the front and rear pivotal actuators 10,11 are fully retracted. Fig. 2B shows the belt crawler unit starting to change into a triangular shape, where the telescopic length adjuster 19 of the length adjustable connection arm 18 is retracting but the length adjuster 12 of the rear pivotal frame arm 6 is extending, and the front and rear pivotal actuators 10,11 are extending. In Fig. 2C the belt crawler has completed the change into a triangular shape. The telescopic length adjuster 19 of the length adjustable connection arm 18 is fully retracted but the length adjuster 12 of the rear pivotal frame arm 6 is fully extended, and the front and rear pivotal actuators 10,11 are fully extended. The function of all actuators and length adjusters for the chape change of the belt crawler unit from linear to triangular occurs through synchronised action of the actuators and length adjusters. This synchronised action facilitates a decrease in the distance between the front wheel 5 and the rear wheel 8 through the length adjustable connection arm 18, and a change in the height between the central wheel 2 on one hand and the front wheel 5 and the rear wheel 8 respectively through a radial movement of the front 3 and rear 6 pivotal frame arms, thereby maintaining circumferential tension on the crawler belt 9 of the belt crawler unit 2 through the shape change. For embodiment I, the same applies, except for the additional feature of the length adjustable connection arm 18.

[0131] Figure 3 shows three different embodiments of a belt crawler unit, where the shape of the belt crawler unit has been changed from a linear shape. In Fig. 3A the belt crawler unit has three wheels, i.e. a central wheel 2 a front wheel 5 and a rear wheel 8. In Fig. 3B the belt crawler unit has five wheels, i.e. a central wheel 2 a front wheel 5, a rear wheel 8 and two belt wheels, a second front belt wheel 24 and a second rear belt wheel 25, between the front and the rear wheel. In Fig. 3C the belt crawler unit has five wheels, i.e. two central wheels 2, 2a a front wheel 5 and a rear wheel 8 and two belt wheels, a second front belt wheel 24 and a second rear belt wheel 25, between the front and the rear wheel. Further embodiments are also shown in Fig. 4

[0132] Figure 4 shows a perspective side view of a belt crawler unit with a plurality of wheels adapting different shapes. In Fig 4A, the front pivotal frame arm has been lowered to make the front wheel 5 engage with the terrain under the vehicle. The drawing shows four static central wheels, where the front pivotal frame arm pivots about an axial joint aligned with central wheel 2a, the rear pivotal frame arm 6 extends from central wheel 2b, and central wheels 2c and 2d are drive wheels for the crawler belt 9. The drawing further shows additional belt wheels 24 and 25, where belt wheel 24 is arranged on connection arm 23, but is not lowered to engage with the terrain under the vehicle and belt wheel 25 is in a resting position together with rear pivotal frame arm 6 and rear wheel 8. Figure 4B is similar to Fig. 4A, apart from that the additional 24 being arranged on connection arm 23 has been lowered to engage with the terrain under the vehicle by pivotal movement of connection arm 23 from front pivotal frame arm 3. In Fig. 4C, both front 3 and rear 6 pivotal frame arms have been lowered to allow the front wheel 5 and the rear wheel 8 to engage with the terrain under the vehicle. In this embodiment, centrals wheels 2a, 2b, 2, and 2d have the same function and position as described for Fig. 4A. Furthermore, additional front belt wheel 24 and additional rear belt wheel 25 arranged on a connection arm 23 have been lowered to engage with the terrain under the vehicle by pivotal movement of connection arm 23 from front pivotal frame arm 3 and rear pivotal frame arm 6 respectively. Although this drawing shows the front pivotal frame arm being lowered, the rear pivotal frame could also be lowered with the front pivotal frame arm aligned with the chassis.

[0133] Figure 5 is a top view of a belt crawler unit 1 having five wheels. The belt crawler unit 1 has a frame having a central frame portion 15 which may be attached to the body or chassis of a vehicle. The central frame portion 15 may also be integrated or be formed into the chassis of a vehicle. The central frame portion 15 comprises a first axial joint 4 for attachment to a front pivotal frame arm 3 and a second axial joint 7 for attachment to a rear pivotal frame arm 6, which in this embodiment is a hinge-connection for allowing radial movement of the front 3 and rear 6 pivotal frame arms. The front and rear frame comprise an A-frame main shaped portion 16 having three connections points to provide strength for the belt crawler unit. The proximal ends of the front 3 and rear 6 pivotal frame arms are centrally arranged in the belt crawler unit with the distal ends of the front 3 and rear 6 pivotal frame arms extending in the backward and forward direction of the vehicle. The front 3 and rear 6 pivotal frame arms further comprise a longitudinal frame portion / extension portion 17 at their distal ends extending in the forward (front) and backwards (rear) direction of the belt-crawler undercarriage. In this embodiment the longitudinal frame portions 17 are formed as a part of the front 3 and rear 6 pivotal frame arms respectively through an outwardly extension of the A-frame shaped front 3 and rear 6 pivotal frame arms to extend within the crawler belt for wheel support. The belt crawler unit 1 in Fig. 5 has one central wheel 2, which is the drive wheel for the belt crawler unit by being arranged on a drive shaft 22 extending through the central frame portion 15 and is thereby in a fixed position in relation to chassis. The front wheel 5 is arranged on the distal end of the longitudinal frame portion 17 of the front pivotal frame arm 3 on an axle or bearing 20. In the same manner the rear wheel 8 is arranged on the distal end of the longitudinal frame portion 16 of the rear pivotal frame arm 6 on an axle or bearing 20.

[0134] In the embodiment shown in Fig. 5, the frame 3 further comprises a length adjustable connection arm 18 connecting the distal end of the front pivotal frame arm 3 at the front end of the length adjustable connection arm 18 through the axle 20 for the front wheel 5, and further connecting the distal end of the rear pivotal frame arm 6 at the rear end of the length adjustable connection arm 18 through an axle 20 for the rear wheel 8. The belt crawler unit has two additional belt wheels between the front wheel and the rear wheel arranged on the longitudinal shaft portion, i.e. a second front belt wheel 24 positioned behind the front wheel and a second rear belt wheel 25 positioned in front of the rear wheel. The central wheel 2, front wheel 5, the rear wheel 8, as well as the second front belt wheel 24 and the second rear belt wheel 25 are shown as parallel wheel sets 26. The parallel central wheel set 9 is arranged on the drive shaft 22, whereas the front wheel is jointly arranged on the front pivotal frame arm 3 and the length adjustable connection arm 18 through an axle 20 and the rear wheel is jointly arranged on the rear pivotal frame arm 6 and the length adjustable connection arm 18 through an axle 20. On the other hand the second front belt wheel 24 and the second rear belt wheel 25 are arranged on the length adjustable connection arm 18 being by separate axles 27.

[0135] The shape-change of the belt crawler unit 1 is facilitated by a number of length adjusters and actuators. A front pivotal actuator 10 is connected to front pivotal frame arm 3 for altering the height between the central wheel 2 and the front wheel 5 through radial movement of the front pivotal arm 3 for forming a triangular shaped belt. In the same manner a rear pivotal actuator 11 is connected to rear pivotal frame arm 6 for altering the height between the central wheel 2 and the rear wheel 8 through radial movement of the rear pivotal frame arm 6. In this manner the front wheel 5 is adapted for a downward movement when front pivotal frame arm 3 is lowered by a front pivotal actuator 10 and the rear wheel 8 is adapted for a downward movement when rear pivotal frame arm 6 is lowered by rear pivotal actuator 11 respectively, thereby lowering the front wheel 5 and the rear wheel 8 of the crawler unit by a radial movement of the front 3 and rear 6 pivotal frame arms maintaining circumferential tension on the crawler belt of the belt crawler unit. In addition to the pivotal actuators 10,11 the length adjustable connection arm 18 is shown with a lateral telescopic length adjuster 19 at the rear end of the length adjustable connection arm 18 for altering the distance between the front wheel 5 and the rear wheel 8. Furthermore, the rear pivotal frame arm 6 comprises a telescopic length adjuster 12 arranged in the longitudinal frame portion 16 of the rear pivotal frame arm 6. The rear wheel 8 is thereby connected to the frame by a parallel connection of a rear axle joint 21 through the telescopic length adjuster 12 of the rear pivotal frame arm 6 and through the telescopic length adjuster 19 of the length adjustable connection arm respectively. The central wheel set 2 is further arranged with a cogged wheel 28 on the drive axle 22 for engaging with the crawler belt (not shown).

[0136] Figure 6 shows a perspective top view of a belt crawler unit 1 with five wheels as disclosed in Fig. 5. The drawing shows the right belt crawler unit la and the edge of the left belt crawler unit lb. The distal ends of the front 3 and rear 6 pivotal frame arms, and thereby the front 5 and the rear 8 wheel, have been lowered to form a triangular shape of the belt 9 whereas the central wheel 2 is centrally positioned on an axle extending between the right 2a and left 2b belt crawler unit through a connection unit 29a which may be arranged with a drive connection 29b for the drivetrain of a vehicle. The drawing also shows the front pivotal actuator 10 in operational connection with the front pivotal arm 3 the rear pivotal actuator 11 having lowered the rear pivotal frame arm 6 for altering shape of the belt crawler units from linear to triangular. Also, the telescopic length adjuster 19, at the rear end of the length adjustable connection arm 18, is shown almost fully retracted after decreasing the distance between the front wheel 5 and the rear wheel 8, and the telescopic length adjuster 12 of the rear pivotal frame arm 6 is shown is extending after radial movement of the rear pivotal frame arm 6.

[0137] Figure 7 is a perspective side view of belt-crawler undercarriage with the right belt crawler unit la in a triangular shape and the left belt crawler unit lb in a linear shape. The drawing shows the position of the front and rear pivotal actuators 10,11 at the distal ends of the front and rear pivotal frame arms 3,6. The belt crawler units are shown with a crawler belt 9 arranged around five wheels, where the front wheel 5, the rear wheel 8 as well as the second front belt wheel 24 and the second rear belt wheel 25 arranged on the length adjustable connection arm 18. The length adjustable connection arm 18 has a recess in the middle of the frame portion to allow room for the drive axle (not shown) of the central wheel 2 when the belt crawler unit is in linear position.

[0138] Figure 8 is a perspective view of a position of a belt-crawler undercarriage between the front wheels 30 and rear wheels 31 of a vehicle seen from below. The drawing shows the belt crawler unit as in Fig. 7 with the right belt crawler unit la in a triangular shape and the left belt crawler unit lb in a linear shape for demonstration purposes. Figure 9 is a schematic top view drawing of a drivetrain and suspension system for a vehicle with a belt-crawler undercarriage. The drawing shows the right belt crawler unit la and the left belt crawler unit lb in relation to the undercarriage drivetrain of a four- wheel vehicle. The drivetrain has a front wheel set unit comprising the vehicle front wheels 30, front axle 32, and a front differential 42, as well as a rear wheel set unit comprising the vehicle rear wheels 31, rear axle 33, and a rear differential 43. The vehicle drive shaft is divided into a central wheel shaft 39, a front drive shaft 40 and a rear drive shaft 41, where the central vehicle drive 39 shaft is connected to the belt axle 22 of the right la and left lb belt crawler units for mechanical transfer from the vehicle drive shaft to the belt-crawler undercarriage. The drivetrain further comprises a front axle connector 34 housing the front drive shaft 40, and a rear axle connector 35 housing the rear drive shaft 41, where the front and rear axle connectors are movably connected 36 to the chassis of the vehicle and to the front and rear wheel axle respectively for pivotal movement of the distal end of the front and rear axle connectors. The drivetrain shown in Fig. 9 further comprises a left and right front wheel suspension unit 37 as well as a left and right rear wheel suspension unit 38 for raising or lowering the front and rear wheels 30,31 of the vehicle in relation to the position of the belt-crawler undercarriage and the terrain the vehicle is passing. Each suspension element of the drivetrain and suspension system for the vehicle as well as each of the actuators and length adjusters of the belt-crawler undercarriage may be independently controlled and synchronized by a computing device when changing the shape of each belt crawler unit between a linear shape and a triangular shape.

[0139] Figure 10 shows a side view of a shape changeable belt crawler unit in mounted on a vehicle. In Fig 10A the belt crawler unit 2 is in a linear shape with the telescopic length adjuster 19 of the length adjustable connection arm 18 fully extended and the front and rear pivotal actuators 10,11 are retracted. The front wheel suspension unit 37 and the rear wheel suspension unit 38 are also shown in relation to the front and rear wheel 30,31 of the vehicle. The drawing shows the front and rear axle connectors 34,35 from the front and rear wheel set units extending from the front and rear axles 32,33 towards the middle of the chassis 29. In Fig. 10B the belt crawler has a triangular shape, where the telescopic length adjuster 19 of the length adjustable connection arm 18 is retracting, but the front and rear pivotal actuators 10,11 as well as the length adjuster 12 of the rear pivotal frame arm 6 are extending. The front and rear pivotal frame arms 3,6 are lowered by the pivotal downward movement facilitated by the front and rear pivotal actuators 10,11 placing the front wheel 5 and the rear wheel 8 parallel to the ground. Furthermore, the sloping of the front and rear axles 32,33 is increased as compared to when the belt crawler unit 2 is in a linear shape. As used herein, including in the claims, singular forms of terms are to be construed as also including the plural form and vice versa, unless the context indicates otherwise. Thus, it should be noted that as used herein, the singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise.

[0140] Throughout the description and claims, the terms "comprise", "including", "having", and "contain" and their variations should be understood as meaning "including but not limited to", and are not intended to exclude other components.

[0141] The present invention also covers the exact terms, features, values and ranges etc. in case these terms, features, values and ranges etc. are used in conjunction with terms such as about, around, generally, substantially, essentially, at least etc. (i.e., "about 3" shall also cover exactly 3 or "substantially constant" shall also cover exactly constant).

[0142] The term "at least one" should be understood as meaning "one or more", and therefore includes both embodiments that include one or multiple components. Furthermore, dependent claims that refer to independent claims that describe features with "at least one" have the same meaning, both when the feature is referred to as "the" and "the at least one".

[0143] It will be appreciated that variations to the foregoing embodiments of the invention can be made while still falling within the scope of the invention. Features disclosed in the specification, unless stated otherwise, can be replaced by alternative features serving the same, equivalent or similar purpose. Thus, unless stated otherwise, each feature disclosed represents one example of a generic series of equivalent or similar features.

[0144] Use of exemplary language, such as "for instance", "such as", "for example" and the like, is merely intended to better illustrate the invention and does not indicate a limitation on the scope of the invention unless so claimed. Any steps described in the specification may be performed in any order or simultaneously, unless the context clearly indicates otherwise.

[0145] All of the features and / or steps disclosed in the specification can be combined in any combination, except for combinations where at least some of the features and / or steps are mutually exclusive. In particular, preferred features of the invention are applicable to all aspects of the invention and may be used in any combination.

Claims

Claims1. A belt-crawler unit (1) configured for changing the shape of the belt crawler unit, said belt crawler unit comprising:- at least one central wheel (2), a frame, said frame further comprising: a front pivotal frame arm (3) having a proximal end connected to a first axial joint (4), and forward-extending distal end connected to a front wheel (5), a rear pivotal frame arm (6) with a proximal end connected to said first axial joint (4) or a second axial joint (7), and rearward-extending distal end connected to a rear wheel (8), and- a crawler belt (9) characterised in that the belt crawler unit further comprises a front and a rear pivotal actuator (10,11) connected to each of the front and rear pivotal frame arms (3,6) for actuating pivotal movement of the distal end of the front and / or rear pivotal frame arms (3,6) about the first (4) and / or second (7) axial joint, and in that the front pivotal frame arm (3) and / or the rear pivotal frame arm (6) further comprise a length adjuster (12) for adjusting the length of the front and / or the rear pivotal frame arms (3,6) to maintain tension on the crawler belt (9) during a shape change of the belt crawler unit.

2. The belt-crawler unit (1) according to claim 1, wherein the belt-crawler undercarriage further comprises a central frame portion (15), and wherein the central frame portion (15) is positioned between proximal ends of the front pivotal frame arm (3) and / or the rear pivotal frame arm (6).

3. The belt-crawler unit (1) according to claim 1, wherein the length adjuster (12) of the front and / or rear pivotal frame arms (3,6) further comprises a telescopic length adjuster.

4. The belt-crawler unit (1) according to claim 1, wherein the length adjuster (12) of the front and / or rear pivotal frame arms (3,6) further comprises a suspension element.

5. The belt-crawler unit (1) according to claim 1, wherein the front pivotal frame arm (3) and / or the rear pivotal frame arm (6) comprises a main portion (16) and an extension portion (17).

6. The belt-crawler unit (1) according to claim 5, wherein the main portion (16) of the front and / or rear pivotal frame arms (3,6) comprises an A-frame main portion, wherein the extension portion (17) of the front and / or rear pivotal frame arms (3,6)comprises a longitudinal frame portion extending in a forward and rear direction of the belt-crawler unit (1) respectively.

7. The belt-crawler unit (1) according to claim 1, wherein the frame further comprises a length adjustable connection arm (18) connected to the distal ends of the front and rear pivotal frame arms (3,6).

8. The belt-crawler unit (1) according to claim 1, wherein the length adjustable connection arm (18) comprises a length adjuster (19) for adjusting the length of the length adjustable connection arm (18) to maintain tension on the crawler belt (9) during a shape change of the belt crawler unit.

9. The belt-crawler unit (1) according to claim 1, wherein the length adjuster (19) of the length adjustable connection arm (18) comprises a telescopic length adjuster.

10. The belt-crawler unit (1) according to claim 1, wherein the length adjustable connection arm (18) further comprises a suspension device (19).

11. The belt-crawler unit (1) according to claim 1, wherein the at least one central wheel (2) is statically arranged to a chassis (14) of a vehicle.

12. The belt-crawler unit (1) according to claim 1, further comprising one or more belt wheels between the front wheel (5) and the rear wheel (8).

13. The belt-crawler unit (1) according to claim 12, wherein the one or more additional belt wheels may be arranged on the length adjustable connection arm (18).

14. The belt-crawler unit (1) according to claim 1, wherein the one or more additional belt wheels are be arranged on a separate connecting wheel arm (23) connected to the front and / or rear pivotal frame arms (3,6).

15. The belt-crawler unit (1) according to claim 1, wherein the wheels of the belt crawler unit comprise a parallel wheel set (26) arranged on a joint or axle (20,21,27).

16. The belt-crawler unit (1) according to claim 1, wherein one or more two belt-crawler units (1) form a belt-crawler undercarriage (13) for a vehicle.

17. The belt-crawler unit (1) according to claim 16, wherein the belt-crawler undercarriage (13) comprises two belt-crawler units (1).

18. The belt-crawler unit (1) according to claim 17, wherein the two belt-crawler units (1) are mirror images parallel arranged on the left and the right side of the vehicle.

19. The belt-crawler unit (1) according to claim 16, further comprising a drive unit for driving or rotating at least one of the wheels of each of the belt crawler units.

20. A belt-crawler undercarriage system configured for changing the shape of one or more belt crawler units, the system comprising : providing at least one belt crawler unit (1), said belt crawler unit further comprising:- at least one central wheel (2), a frame, said frame further comprising: a front pivotal frame arm (3) having a proximal end connected to a first axial joint (4), and forward-extending distal end connected to a front wheel (5), a rear pivotal frame arm (6) with a proximal end connected to said first axial joint (4) or a second axial joint (7), and rearward-extending distal end connected to a rear wheel (8),- a crawler belt (9) wherein the front pivotal frame arm (3) and / or the rear pivotal frame arm (6) further comprise a length adjuster (12) for adjusting the length of the front and / or the rear pivotal frame arms (3,6), and characterised in that the belt crawler unit further comprises a front and a rear pivotal actuators (10,11) connected to each of the front and rear pivotal frame arms (3,6) and configured for actuating independent pivotal movement of the distal end of the front and / or rear pivotal frame arms (3,6) about the first (4) and / or second (7) axial joint, and in that the adjustment of the length of the front and / or the rear pivotal frame arms (3,6) by the length adjuster (12) and the independent pivotal movement of the distal end of the front and / or rear pivotal frame arms (3,6) actuated by the pivotal actuators (10,11) is synchronized to maintain tension on the crawler belt (9) during a shape change of the belt crawler unit.

21. The belt-crawler undercarriage system according to claim 20, wherein the at least one belt crawler unit is configured for a multi-shape change of the belt crawler unit.

22. The belt-crawler undercarriage system according to claim 20, wherein the at least one belt crawler unit is configured for changing the shape of the belt crawler unit between a linear shape and a multi-shape formation, such as a triangular shape.

23. The belt-crawler undercarriage system according to claim 20, wherein the shape change of the belt crawler unit comprises: pivotal movement of the front pivotal frame arm (3) and / or the rear pivotal frame arm (6) through the front and / or the rear pivotal actuator (10,11) respectively, andadjusting the length of the length adjuster (12) of the front pivotal frame arm (3) and / or the rear pivotal frame arm (6).

24. The belt-crawler undercarriage system according to claim 20, wherein:- the pivotal movement of the front pivotal frame arm (3) and / or the rear pivotal frame arm (6),- the actuation of the pivotal movement of the distal end of the front and / or rear pivotal frame arms (3,6) by the front and / or the rear pivotal actuator (10,11), and- the adjustment of the length of the length adjuster (12) of the front pivotal frame arm (3) and / or the rear pivotal frame arm (6), is synchronized to maintain tension on the crawler belt during a shape change of the belt crawler unit.

25. The belt-crawler undercarriage system according to claim 20, wherein the adjustment of the length of the front and / or the rear pivotal frame arms (3,6) by the length adjuster (12) either: i) maintains a set or a constant tension on the crawler belt (9) during a shape change of the belt crawler unit, ii) maintains the tension on the crawler belt (9) above a set value during a shape change of the belt crawler unit, or iii) maintains the tension on the crawler belt (9) within a predetermined range during a shape change of the belt crawler unit.

26. The belt-crawler undercarriage system according to claim 20, further comprising arranging the at least one belt crawler unit (1) under a vehicle, said vehicle further comprising a front and rear wheel set units each comprising left and right wheels 30,31 and a front and rear axle 32,33.

27. The belt-crawler undercarriage system according to claim 20, further comprising a front and rear suspension devices 37,38 for the left and right side of the vehicle, a front and rear axle connectors 34,35 movably connected 36 to the chassis of the vehicle and to the front and rear wheel axle respectively for pivotal movement of the distal end of the front and rear axle connectors, and a front and rear suspension devices 37,38 for the left and right side of the vehicle, a vehicle drive shaft, said vehicle drive shaft comprising a central wheel shaft 39, a front drive shaft 40 within the front axle connector 34, and a rear drive shaft 41 within the rear axle connector 35.

28. The belt-crawler undercarriage system according to claim 27 , wherein- the pivotal movement of the front pivotal frame arm (3) and / or the rear pivotal frame arm (6) through the front and / or the rear pivotal actuator (10,11) respectively, - the adjustment of the length of the length adjuster (12) of the front pivotal frame arm (3) and / or the rear pivotal frame arm (6), and movement of the front and rear suspension devices for the left and right side of the vehicle is independently controlled and / or synchronized.

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