COMMERCIAL VEHICLE WITH MOVABLE REAR EXTENSION

Description

[0001] The present invention relates to a commercial vehicle with a movable rear extension according to the preamble of claim 1.

[0002] Commercial vehicles are known from the state of the art that feature a rear extension to adapt the length of the commercial vehicle to a load. Examples of this include trailers designed as container chassis. With the Box Liner SDC 27 eLTU5-2 – a container chassis from the applicant – containers in the sizes 1 x 40', 1 x 45', 2 x 20', 1 x 20' centrally (up to 30 tons), and optionally 1 x 30' containers flush with the rear can be transported. A corresponding container chassis is disclosed in DE 10 2008 021 795 A1. To adapt the container chassis to different container sizes, it features a rear extension. Mechanical and pneumatic drives are known for extending and retracting the rear extension.

[0003] The mechanical drives are often designed as rack and pinion gears. The rack of the rack and pinion gear is fixedly connected to the rear extension, and the gear of the rack and pinion gear is mounted on a drive shaft mounted on the frame. The drive shaft extends in a direction transverse to the longitudinal center axis of the commercial vehicle frame and transverse to the extension direction in which the rear extension can be extended. A hand crank is attached to the end of the drive shaft facing away from the gear, with which the gear can be rotated in a desired direction. The rotating movement of the gear is transferred via the rack into a linear movement of the rear extension. Document US 4,580,805 A discloses a commercial vehicle with a rear extension mounted on the frame of the commercial vehicle, according to the preamble of the present claim 1.

[0004] Further commercial vehicles with rear extensions are disclosed in the publications DE 101 45 432 A1, EP 1 500 579 B1, and DE 10 2016 007 667 B3. Vehicle chassis with longitudinally adjustable frames are disclosed in the publications US 3 254 903 A, EP 0 825 097 A1, and DE 103 27 075 A1. The adjustment devices disclosed in these publications are sometimes hydraulically or pneumatically operated, which results in considerable construction complexity. In some cases, the adjustment technology is not described in detail; only the publication US 3 254 903 A discloses a rack and pinion drive, which, however, cannot be used to operate a rear extension.

[0005] The problem with rack and pinion drives is that loading or unloading operations, with the associated vertical impacts on the rear extension, which also affect the drive components, can lead to damage or complete failure of the rack and pinion drive. In such cases, the teeth of the gear and / or rack break or bend. Depending on the severity of the damage, the functionality of the rear extension is limited or completely blocked.

[0006] It is the object of the present invention to design the drive in such a way that the risk of damage during loading and unloading processes is reduced.

[0007] The problem is solved by the features of claim 1.

[0008] The adjustment device allows the gear to move back and forth between a first position, in which the teeth of the gear engage with the teeth of the rack, and a second position, in which the teeth of the gear do not engage with the teeth of the rack. When the gear is in the first position, it can rotate to move the rack and thus the rear extension in the desired direction. When the gear is in the second position, it can no longer be used to move the rear extension, but the teeth of the gear and / or the rack can no longer be damaged by impacts when loading or unloading the commercial vehicle, because the teeth of the rack and the gear no longer hit each other.Damage to the drive is avoided if the gear of the rack and pinion gear is only in the first position when the rear extension is to be moved, and is in the second position the rest of the time. Since loading and unloading of the commercial vehicle does not take place when the rear extension is being moved, damage to the rack and pinion gear is ruled out. The drivable shaft on which the gear is held can be driven by a mechanical or motor drive. The drivable shaft can extend in a direction transverse to the longitudinal center axis of the commercial vehicle frame and transverse to the extension direction in which the rear extension can be extended. A hand crank, for example, can be used as a mechanical drive, and a pneumatic, hydraulic or electric motor can be used as a motor drive.

[0009] The adjustment device can be operated via a rod or lever, or it can also be motorized. It can also be designed with a lock to prevent accidental automatic adjustment.

[0010] When we refer to a rack and pinion gear above, this should not be understood as a numerical limitation to a single rack and pinion gear. For example, a commercial vehicle may also have two rack and pinion gears, which are used to move the rear extension.

[0011] According to one embodiment of the invention, the adjusting device is designed as an adjusting means with which the drivable shaft connected to the frame, with the gearwheel connected thereto, is movable in an axial direction between the first and second positions. The gearwheel is preferably fixedly fastened to the drivable shaft. With the adjusting means, the drivable shaft can be displaced in the axial direction far enough that the gearwheel located on the drivable shaft is displaced from a position in which the gearwheel is not in engagement with the teeth of the rack into the first position, and / or the gearwheel is moved with the drivable shaft from the first position into a position in which the teeth of the gearwheel are laterally offset next to the teeth of the rack.The adjustment means can act in only one axial direction, or it can be designed so that the driveable shaft can be moved in opposite directions using the adjustment means. The adjustment means can, for example, be a handle connected to the driveable shaft and with which the driveable shaft can be pulled or pushed in an axial direction. The handle can, for example, also be a section of the driveable shaft that is offset by an angle, for example 90°, to the axial direction of the driveable shaft. However, the adjustment means can also be a motor drive with which the driveable shaft is moved back and forth in the axial direction between the first and second positions.

[0012] According to one embodiment of the invention, the driveable shaft is held so as to be movable in the axial direction and in the direction of rotation in at least two bearing blocks which are arranged at a distance from one another and firmly connected to the frame. A first seat ring is placed on the driveable shaft, and a first tension spring is arranged between one of the bearing blocks and the first seat ring. The first tension spring is supported at its first end on one of the bearing blocks and at its second end on the first seat ring. In a compressed state, the first tension spring presses the driveable shaft in a direction in which the gear is in the second position. The bearing blocks enable precise and secure guidance of the driveable shaft. The first tension spring builds up restoring forces when the driveable shaft with the first seat ring is pressed in one direction against the force of the first tension spring.The first tension spring is advantageously installed in such a way that it presses the gear in the tensioned state from the first position into the second position in which the gear is not in engagement with the rack. The driven shaft is then in a type of parking position. The first tension spring forms an adjustment means with the described mode of operation, with which the driven shaft can be moved at least in one axial direction. In a tensioned state, the first tension spring is a motor drive with which the driven shaft can be moved in an axial direction. Due to the proposed direction of force of the first tension spring, the driven shaft with the gear must be deliberately pressed against the force of the first tension spring from the parking position into the first position in which the gear is in engagement with the rack.The force of the first tension spring immediately moves the driven shaft with the gear back to the second position as the parking position and normal position as soon as the actuating force against the first tension spring decreases or disappears completely.

[0013] According to one embodiment of the invention, the first seat ring is fastened to the outside of the driveable shaft. The first seat ring can be designed so that it can be fastened in various positions on the outside of the driveable shaft. The first seat ring can be fastened to the driveable shaft using clamping screws. If the driveable shaft has a smooth outer contour, the first seat ring can be fixed in various positions on the driveable shaft. The driveable shaft can also have an external thread on its outer circumference, onto which the first seat ring is screwed. The position of the first seat ring can be continuously adjusted along the longitudinal axis of the driveable shaft over the length of the thread using the external thread. If the first seat ring is located on an external thread, it is easily accessible if the position of the first seat ring needs to be changed.If the first seat ring is rotated on the external thread, the position of the first seat ring on the driven shaft changes the preload of the first tension spring. The first tension spring can be adjusted to a desired value in this way.

[0014] According to one embodiment of the invention, a second seat ring is attached to the outside of the driven shaft, via which the driven shaft is supported on a first support surface supported on the frame side. The second seat ring can serve the driven shaft to hold the driven shaft in the second position in the axial direction and thus in the parking position, in that the second seat ring is supported on the first support surface supported on the frame side, which forms a stop against the force of the first tension spring. If the first support surface does not protrude into the space filled by the driven shaft or into the projection of the driven shaft in an axial direction and insofar as no stop is present, the driven shaft can also be moved in the axial direction past the first support surface.Depending on the position in which the second seat ring is fastened on the drivable shaft, this results in the second position in which the gear is held in the parked position. The spatial position of the gear in the second position can thus be determined via the second seat ring. In this embodiment of the invention, the drivable shaft can therefore be moved back and forth in an axial direction at least between the second position predetermined by the second seat ring and the first support surface and the first position in which the gear is in engagement with the rack. The position of the second seat ring on the drivable shaft can be designed to be adjustable. For example, the drivable shaft can have an external thread onto which the second seat ring is screwed; the position of the second seat ring can then be continuously adjustable via the length of the thread.The second seat ring can also be clamped onto the driven shaft with clamping screws. If the driven shaft has a smooth circumferential surface, the seat ring can then be mounted in various positions on the driven shaft. If the first and second seat rings are adjusted to positions where a residual tension is maintained in the first tension spring even when the gear is in the second position, the driven shaft is held in this position without rattling. This prevents the gear from accidentally moving to the first position, even when the commercial vehicle is moving.

[0015] According to one embodiment of the invention, the drive shaft is designed as a hollow shaft and a locking rod is passed through the hollow shaft, which locks the rear extension in its retracted position and releases it in its extended position. By designing the drive shaft as a hollow shaft, it is possible to pass a locking rod through the hollow space of the hollow shaft, with which the rear extension can be locked. This spatially combines the locking and unlocking of the rear extension as well as the drive for adjusting the position of the rear extension, thereby simplifying operation. The locking rod is held and guided by the hollow shaft. The hollow shaft can be designed as a simple tube.By extending the locking rod in the unlocked position, the lack of locking of the rear extension is immediately noticeable to a driver when looking at the commercial vehicle, and it is therefore unlikely that the commercial vehicle will be accidentally operated with an unlocked rear extension. Locking is achieved using a positive fit, for example by pushing the locking rod through suitable holes in the rear extension. The rear extension can then no longer be moved in a direction transverse to the axial direction of the locking rod. Once the locking rod has been pulled out of the holes, the rear extension can be moved in this direction again. Several holes can be arranged in the rear extension in the extension direction to enable the rear extension to be locked in different positions.

[0016] According to one embodiment of the invention, a slotted guide is mounted in a rotationally fixed manner on the end face of the driveable shaft facing away from the gearwheel, said slotted guide having a number of recesses, wherein at least a first of the recesses has a circumferential shape which allows a projection projecting beyond the circumferential surface of the locking rod to pass through during an axial movement of the locking rod, and at least a second of the recesses has a formation in which the projection is held in a positionally fixed, form-fitting manner in the slotted guide when it rests against the formation, and a thrust force and / or rotational force acting on the locking rod can be transmitted via the formation to the driveable shaft via the projection held in the formation.With the configuration described above, the locking rod can be used to engage the gear with the teeth of the rack and to drive the gear mounted on the drive shaft in rotation, thereby extending or retracting the rear extension. The recess in the second recess has a base against which the projection rests, at least in part, so that the projection cannot penetrate through the second recess in the slotted guide in the region of the recess, as is the case with the first recess.

[0017] The first recess allows the locking rod to be pushed through the guide rail into the locking position despite the projection. With a suitable angular position of the locking rod around its extension axis, the projection passes through the first recess in the guide rail without collision during an insertion movement of the locking rod. However, the locking rod can also be pulled out of the locking position through the first recess and out of the drive shaft with the projection until the projection is outside the drive shaft and can rotate freely with the locking rod.The projection can then be brought into a position by rotating the locking rod through an angle of rotation about its axis of extension, in which it dips into the formation in the second recess upon an axial movement of the locking rod in the opposite direction towards the gear wheel and is held there in a form-fitting manner by a mutually compatible formation of the projection and the formation in the second recess.

[0018] If the pushing movement of the locking rod is continued in the direction of the gear, the driven shaft with the gear on it is moved in an axial direction from the parked position into the first position, in which the teeth of the gear are in engagement with the teeth of the rack. At the same time, the first tension spring is compressed. If the pressure acting on the driven shaft is maintained, a rotational force acting on the locking rod is transferred via the projection and the formation in the second recess to the driven shaft, which in turn transfers the rotational force and the resulting rotary movement to the gear and the gear to the rack. The rack converts the rotating movement of the gear into a linear movement of the rear extension.In this way, with a crank movement of the locking rod, the rear extension can be moved back and forth in a linear movement depending on the direction of rotation of the locking rod.

[0019] If the pressure on the locking rod is reduced against the force of the first tension spring, the restoring forces built up in the first tension spring during the plunging movement push the drivable shaft back towards the second position, so that the gears of the gear and the teeth of the rack are disengaged again. With continued backward movement of the locking rod, the projection can be pulled out of the formation in the second recess, whereby the locking rod can then rotate freely again without rotating the drivable shaft. If the locking rod is rotated about its longitudinal axis so that the projection is precisely aligned with the first recess, the locking rod can be pushed back into the drivable shaft into its locking position.

[0020] Depending on the embodiment of the invention, a plurality of projections can be formed on the locking bar, for example, two projections, and a plurality of first and second recesses can also be formed in the slotted guide, for example, two first recesses and two second recesses that are aligned to form a plurality of projections. By having a plurality of projections distributed over the circumference of the locking bar, the forces acting on the projection, the slotted guide, and the driven shaft during an insertion movement and a rotational movement are distributed more evenly over the circumference of the driven shaft, thereby improving handling and the operating feel.

[0021] According to one embodiment of the invention, a driver is mounted on the outer circumference of the locking rod, which, when the locking rod is extended, strikes against a driver plate mounted on the locking rod and movable thereon in the axial direction, wherein a second tension spring is mounted on the locking rod on the side of the driver plate facing away from the driver, which, when the locking rod is extended, is supported at a first end on the driver plate and at a second end on a second support surface supported on the frame side, the length of the second tension spring, the position of the second support surface relative to the guide and the position of the driver on the locking rod are selected such that the second tension spring is pressed in by the driver when the projection is extended axially from the driveable shaft so far that the projection is located outside the driveable shaft,and the restoring force developed by the second tension spring in this position of the driver is greater than the restoring force of the first tension spring in the second position of the gear. The purpose of this design is to develop such a large restoring force in the second tension spring during an extension movement of the locking rod, which is required before the projection can be placed on the driven shaft in order to move the driven shaft into the first position and move the rear extension, that the second tension spring presses the locking rod and, along with the locking rod, the projection into the recess, holds it there, and moves the driven shaft against the restoring force of the first tension spring on the locking rod into a position in which the gear is in the first position. Thus, if an operator releases the locking rod after extending and pressing in the second tension spring,This snaps back, driven by the second tension spring, pressing the projection into the recess and then the driven shaft against the restoring force of the first tension spring into a position where the gear is in the first position. Once this position is reached, the locking rod and thus the gear can be rotated to move the rear extension. Separate actuation of any switches, adjusting devices, or the like is not required.

[0022] If the locking rod is to be moved back into the retracted position, in particular the locking position, the locking rod is first retracted against the force of the second tension spring, whereby the drivable shaft, together with the gear, initially moves automatically back into the second position, driven by the first tension spring. If the locking rod is retracted further against the force of the second tension spring, the projection can be pulled out of the recess in the second recess and the locking rod can be rotated about its axis until the projection is in front of the first recess and the locking rod can thus be pushed into its locking position into the drivable shaft with the projection.

[0023] With the proposed design, both the drive of the rack and pinion gear and the locking and unlocking of the rear extension can be accomplished solely with the locking rod. A simple extension and retraction movement, along with a rotation of the locking rod, is sufficient. The spring-actuated engagement and disengagement of the gear prevents the gear from remaining engaged with the rack even when the rear extension has already been locked in one position.

[0024] It is pointed out that the features of claim 1 can in principle be combined with the features of the individual subclaims, either individually or in any combination of several subclaims, provided that there are no technically compelling obstacles to this.

[0025] Further modifications and embodiments of the invention can be found in the following description, the drawings, and the claims. The invention will be described below using an exemplary embodiment. They show: Fig. 1: a view from the rear of a commercial vehicle with a rear extension, Fig. 2: an enlarged view from the top of the rear of the vehicle, Fig. 3: the Fig. 2 shown view of the rear area of ​​the vehicle from a different perspective, Fig. 4: the adjusting device with the adjusting means in a detail view, Fig. 5: the locking rod in an extended position, Fig. 5a: an enlarged view from diagonally above of the gate, Fig. 6: the view from Fig. 5 with a locking bar rotated by 90°, Fig. 6a: the projections in an alignment with the formations, Fig. 7: the section from Figur 5 with projection inserted into the formation, Fig. 7a: an enlarged view of the link, Fig. 8: the gear in the first position, which is in engagement with the rack, and Fig. 9: the adjusting device in the second position before pulling out the locking rod.

[0026] In Fig. 1 Shown is an oblique rear view of a commercial vehicle 2 with a frame 4, in the rear of which is a rear extension 6, which can be adjusted back and forth in the longitudinal direction 8 of the commercial vehicle 2 between a retracted position and an extended position. The mobility of the rear extension 6 is indicated by a double arrow extending in the longitudinal direction 8.

[0027] The Fig. 2 shows an enlarged view obliquely from above of the rear area of ​​the vehicle 2. In this view, the adjusting device 10 can be seen, with which the drivable shaft 14, to which the gear 26 is connected in a rotationally fixed manner, can be moved back and forth in the direction of the double arrow via adjusting means 12 between a first position in which the teeth of the gear 26 are in engagement with teeth of the rack 28, and a second position in which the teeth of the gear 26 are not in engagement with the teeth of the rack 28. The drivable shaft 14 is rotatably mounted on two bearing blocks 16 and can move in the axial direction. An external thread (not shown in detail in the drawing) can be located on the outer circumference of the drivable shaft 14. A first seat ring 18 and a second seat ring 20 are attached to the drivable shaft 14 in a respective position.In the exemplary embodiment, the seat rings 18, 20 are fastened to the drivable shaft 14 via clamping screws.

[0028] The driven shaft 14 is designed as a hollow shaft into which the locking rod 24 is inserted. While the end of the locking rod 24 facing the outside of the commercial vehicle 2 has a crank 25, the end in Fig. 2 invisible end of the locking rod 24 into the center box 4a of the frame 4 in order to lock the rear extension 6 held therein in the locking position of the locking rod 24. The side wall of the center box 4a has a Fig. 2 opening (not shown in detail in the drawing) through which the locking rod 24 is guided. At least when the driven shaft 14 and the gear 26 mounted thereon in a rotationally fixed manner are in the first position, these also extend into the interior of the center box 4a so that the teeth of the gear 26 can mesh with the teeth of the rack 28 arranged in the center box 4a. Fig. 2 The locking rod 24 is shown in its retracted locking position. The locking rod 24 can be extended axially outward from the retracted locking position. In the extended position of the locking rod 24, the crank 25 can be turned manually, causing the locking rod 24 to rotate along with it.

[0029] In the Fig. 2 The first tension spring 32 is visible, which is mounted on the driven shaft 14. The second tension spring 34 is mounted on the locking rod 24. While the first tension spring 32 is supported at a first end on the bearing block 16 and at a second end on the first seat ring 18, the second tension spring 34 is supported at its first end on the drive plate 48 and at its second end on the second support surface 50.

[0030] In the Fig. 2 The backdrop 36 can also be seen, the function of which is explained in more detail below.

[0031] The Fig. 3 shows the Fig. 2 shown view of the rear area of ​​vehicle 2 from a different perspective. In The changed perspective shows the second bearing block 16 and the second support surface 50. The axial mobility of the driven shaft 14 and the locking rod 24 is indicated by double arrows.

[0032] To explain the functional sequence, Fig. 4 The adjusting device 10 with the adjusting means 12 is shown in a cutaway view. In the exemplary embodiment, the adjusting means 12 are, in particular, the tension springs 32, 34. The locking rod 24 is in its retracted locking position in this view. In the retracted position, the locking rod 24 extends transversely to the center box 4a. A box profile 6a is inserted into the center box 4a, with which the rear extension 6 is held in the center box 4a. The locking rod 24 penetrates the center box 4a and the box profile 6a through corresponding openings, whereby the rear extension 6 is positively locked in its position.

[0033] In the Fig. 4 In the sectional view shown, the gear 26 and the rack 28 can be seen as parts of the rack and pinion gear 30. The second seat ring 20, which is supported on the first support surface 22, is also visible. The first tension spring 32 presses the drivable shaft 14 away from the rack 28 via the first seat ring 18 in a direction indicated by an arrow, so that the gear 26 is in the second position and is held there by the first tension spring 32.

[0034] In Fig. 5 the locking rod 24 is extended. In the extended position of the locking rod 24, the projections 42 can be seen, which, when pushed in, Fig. 5 shown position on the link 36 or can be inserted into a recess 40. In addition, the drivers 46 are visible, which have struck the driver plate 48 during the extension movement of the locking rod 24 and, during a continued extension movement, have pressed the driver plate 48 against the second tension spring 34, so that the latter is in the position shown in Fig. 5 shown compressed state.

[0035] The Fig. 5a shows an enlarged view obliquely from above of the gate 36, as it appears when the locking rod 24 is in the position shown in Fig. 5 shown position. In this view, two first recesses 38 and a second recess 40 are visible. The locking rod 24 is in a rotational position in which it can be pushed axially into the driven shaft 14 without the projections 42 colliding with the edges of the first recesses 38. When the locking rod 24 is moved out of the position shown in the Fig. 5a shown position is rotated about its axis of rotation by an angle of 90°, the projections 42 are as shown in the Fig. 6, 6a shown in alignment with the second recess 40. When the locking rod 24 is pushed back from this position toward the drivable shaft 14, the projections 42 engage the recess 44 in the second recess 40. The projections 42 are then held in a form-fitting manner in a respective recess 44 in the axial and radial directions. Upon further pressure exerted on the link 36 via the projections 42 and the recess 44, the drivable shaft 14 is moved toward the rack 28, and a rotational movement generated at the crank 25 is also transmitted as a rotary movement to the drivable shaft 14.

[0036] The pressure acting on the locking rod 24 can be generated in particular via the second tension spring 34. Since the second tension spring 34 has been compressed by the drivers 46 and the driver plate 48 during the extension movement of the locking rod 24, restoring forces have built up in the second tension spring 34, which when the locking rod 24 is released by an operator from the Fig. 5 In the position shown, the drive plate 48, the drive elements 46, the projections 42, and the protrusions 44 press against the link 36, which in turn move the driven shaft 14 with the gear 26 mounted thereon into the first position. If the restoring forces in the second tension spring 34 are greater than the spring forces in the first tension spring 32, the second tension spring 34 also presses the gear 26 into the first position against the force of the first tension spring 32.

[0037] In the Fig. 6 the locking rod 24 is shown in a rotational position after it has been moved from the Fig. 5 shown position has been rotated by 90°. As is the Fig. 6a shows, the projections 42 are now directly in front of the formations 44.

[0038] The Fig. 7, 7a show the excerpt from Figur 5 with a locking rod 24 rotated by 90° with a projection 42 inserted into the formation 44, after the locking rod 24 has been released by an operator and the second tension spring 34 has pressed the locking rod 14 with the projection 42 into the formation 44.

[0039] The Fig. 8 shows the gear 26 with the driven shaft 14 in the first position, which is now in engagement with the rack 28. In In this first position, the gear 26 can be rotated with the crank 25 and the locking rod 24 to retract or extend the rear extension 6. When a desired position for the rear extension 6 is reached, the locking rod 24 is pulled outwards again, as shown in Fig. 9 is indicated. As a result, the gear 26 with the driven shaft 14 moves back into the second position, in which the teeth of the gear 26 are again disengaged from the teeth of the rack 28. When the pressure from the second tension spring 34 on the first tension spring 32 is removed due to the extension movement of the locking rod 24, the first tension spring 32 can move the gear 26 back into the second position. When the projection 42 is pulled out of the recess 44 during the extension movement of the locking rod 24, the locking rod 24 can be rotated again by 90° in order to then push the locking rod 24 with the projection 42 through the first recess 38 into the cavity of the driven shaft 14 and to push it through until the locking rod 24 is again in its Fig. 4 shown inserted locking position.

[0040] The invention is not limited to the embodiment described above, but rather to the claims. Those skilled in the art will have no difficulty modifying the embodiment in any way they deem appropriate to adapt it to a specific application, but always within the scope of the present claims. List of reference symbols

[0041] 2Commercial vehicle 4Frame 4aCenter box 6Rear extension 6aBox profile 8Longitudinal direction 10Adjustment device 12Adjustment means 14Driven shaft 16Bearing block 18First seat ring 20Second seat ring 22First support surface 24Locking rod 25Crank 26Gear 28Rack 30Rack gear 32First tension spring 34Second tension spring 36Link 38First recess 40Second recess 42Protrusion 44Shape 46Driver 48Driver plate 50Second support surface

Claims

1. Commercial vehicle (2) with a rear extension (6) held on the frame (4) of the commercial vehicle (2), which is movable between different positions in the longitudinal direction (8) of the commercial vehicle (2) by means of a rack-and-pinion gear (30), wherein a rack (28) of the rack-and-pinion gear (30) is firmly connected with the rear extension (6) and a gearwheel (26) of the rack-and-pinion gear (30) is held on a drivable shaft (14) connected with the frame (4), and a locking device, when actuated, the rear extension (6) is held locked in at least one position relative to the frame (4), characterized in that the gearwheel (26) is connected with an adjusting device (10) by means of which the gearwheel (26) can be moved back and forth between a first position, in which the teeth of the gearwheel (26) are in engagement with teeth of the rack (28), and a second position, in which the teeth of the gearwheel (26) are not in engagement with the teeth of the rack (28).

2. Commercial vehicle (2) according to claim 1, characterized in that the adjusting device (10) is designed as an adjusting means (12) with which the drivable shaft (14) connected with the frame (4) with the gearwheel (26) connected thereto can be moved in an axial direction between the first and second positions.

3. Commercial vehicle (2) according to claim 2, characterized in that the drivable shaft (14) is held movably in the axial direction and in the direction of rotation in at least two bearing blocks (16) which are arranged at a distance from one another and are firmly connected with the frame (4), a first seat ring (18) is placed on the drivable shaft (14), and a first tension spring (32) is arranged between one of the bearing blocks (16) and the first seat ring (18), which spring is supported at its first end on the bearing block (16) and at its second end on the first seat ring (18), the first tension spring (32), in a deflected state, pressing the drivable shaft (14) in a direction in which the gearwheel (26) is located in the second position.

4. Commercial vehicle chassis according to claim 3, characterized in that the first seat ring (18) is fastened on the outside of the drivable shaft (14).

5. Commercial vehicle (2) according to claim 4, characterized in that a second seat ring (20) is fastened to the outside of the drivable shaft (14), via which the drivable shaft (14) is supported on a first support surface (22) supported on the frame side.

6. Commercial vehicle (2) according to one of the preceding claims, characterized in that the drivable shaft (14) is designed as a hollow shaft and a locking rod (24) is passed through the hollow shaft, which locking rod locks the rear extension (6) in its pushed-in position and releases the rear extension (6) in its extended position.

7. Commercial vehicle (2) according to claim 6, characterized in that a guide (36), which has a number of recesses (38, 40), is mounted in a rotationally fixed manner on the end face of the drivable shaft (14) facing away from the gearwheel (26), wherein at least a first of the recesses (38, 40) has a circumferential shape which allows a projection (42), which projects beyond the circumferential surface of the locking rod (24) to pass through during an axial movement of the locking rod (24), and at least a second one of the recesses (38, 40) has a shaping (44) in which the projection (42) is held in a positively locking position in the guide (36) when bearing against the shaping (44), and a thrust force and / or rotational force acting on the locking rod (24) can be transmitted via the shaping (44) to the drivable shaft (14) via the projection (42) held in the shaping (44).

8. Commercial vehicle (2) according to claim 7, characterized in that a driver (46) is mounted on the outer circumference of the locking rod (24), which, during an extension movement of the locking rod (24), strikes against a driver plate (48) mounted on the locking rod (24) and movable thereon in the axial direction, wherein a second tension spring (34) is placed on the locking rod (24) on the side of the driver plate (48) facing away from the driver (46), which, in an extended position of the locking rod (24), is supported at a first end on the driver plate (48) and at a second end on a second support surface supported on the frame side, the length of the second tension spring (34), the position of the second support surface (50) relative to the guide (36) and the position of the driver (46) on the locking rod (24) are selected such that the second tension spring (34) is pressed in by the driver (46), when the projection (42) is pulled out of the drivable shaft (14) in the axial direction to such an extent that the projection (42) is located outside the drivable shaft (14), and the restoring force which the second tension spring (34) has built up in this position of the driver (46) is greater than the restoring force of the first tension spring (32) which the latter has in the second position of the gearwheel (26).