Brake system for axle

Abstract

axle with an axle housing (1) having an axle housing flange (14) and with a brake unit which is arranged in the axle housing, wherein the axle has two shafts (2, 3) rotatable about a common axis of rotation (20), wherein the brake unit comprises: - an electromagnet unit (4) with at least one coil (5, 6) for generating a magnetic field; - at least one spring element (10, 11); - at least one brake rotor (12, 13) per shaft (2, 3), which is rotationally fixed to the corresponding shaft (2, 3), but is axially displaceable thereon; and - at least one magnetizable armature element (8, 9); where - the electromagnetic unit (4) is fixed in position in the axle housing (1); - the magnetizable armature element (8, 9) and the brake rotors (12, 13) are arranged between the electromagnet unit (4) and the axle housing flange (14); - the magnetizable armature element (8, 9) is arranged axially displaceable but non-rotatable in the axle housing (1) between the brake rotors (12, 13) and the electromagnet unit (4) along the axis of rotation (20); and - the spring element (10, 11) is arranged and supported in such a way that it pre-tensions the anchor element towards the brake rotors (12, 13) to provide a braking force, characterized in that, in order to generate a braking force, the current flow through one or both of the coils (5, 6) is reduced, thereby reducing the attractive force on the corresponding magnetizable armature element (8, 9) or on both magnetizable armature elements (8, 9), wherein, when the attractive force becomes sufficiently low, the corresponding magnetizable armature element (8, 9) is pressed by the corresponding spring element (10, 11) towards an axially displaceable force transmission element (7), which displaces accordingly towards a first of the brake rotors (12), which, due to its displaceability, is in turn displaced towards a displaceable friction element (16), which in turn is displaced towards a second of the brake rotors (13), whereby corresponding frictional forces occur between the axle housing flange (14), the second brake rotor (13), the friction element (16), the first brake rotor (12) and the force transmission element (7), which cause braking and, if necessary, complete locking of the rotatable shafts (2, 3). wherein the electromagnet unit (4) is firmly connected to the axle housing (1) and / or the axle housing flange (14), in particular by screwing.

Description

[0001] The present invention relates to an axle according to the preamble of claim 1. In particular, the invention relates to such an axle as a drive axle, the rotatable shafts of which are each connected to a drive motor, wherein the brake unit is arranged between the drive motors. In particular, the invention relates to a forklift truck with an axle according to the invention between two opposing wheels with wheel drive motors.

[0002] A generic axle is known from DE 10 2013 203 401 A1 and from DE 10 2012 015 389 A1.

[0003] Reference is also made to DE 10 2014 105 607 A1, DE 10 2007 028 688 A1 and DE 295 10 168 U1.

[0004] These known axles with brake units have several disadvantages with regard to the brake unit itself. For example, the various elements of the brake unit in these axles do not form a cohesive unit, resulting in a complex design and requiring significant assembly effort. Because the various elements do not form a single unit, they are only properly assembled during the installation process. This increases the likelihood of assembly errors and necessitates relatively tight manufacturing tolerances to compensate for inaccuracies in the alignment of the individual elements. Furthermore, the magnet unit used in these known brake units is axially displaceable. This is disadvantageous due to its considerable weight, particularly as it can lead to vibrations. Additionally, these known brake units only offer two settings: either maximum braking force or complete release of the rotating shafts.As a result, when the brake is switched on and there is still movement, in combination with possible vibrations, especially from the magnet unit, large forces repeatedly occur, which can lead to loosening, shifting or warping of elements, thus making the overall maintenance effort for known axles with brake units relatively high.

[0005] The present invention therefore aims to provide an axle with a brake unit and two rotatable shafts, in which the manufacture, assembly and maintenance are considerably simplified, in particular that maintenance is hardly or no longer required.

[0006] This problem is solved by an axis according to claim 1. Advantageous embodiments are the subject of the dependent claims.

[0007] The axle according to the invention comprises an axle housing with an axle housing flange and has two shafts rotatable about a common axis of rotation. The axle according to the invention is characterized in that, unlike in the prior art, the electromagnetic unit is fixed in position within the axle housing, i.e., it does not move relative to the axle housing when the brake is engaged / disengaged, as is the case in the prior art. This fixed position, while simultaneously achieving a sufficient braking function, is achieved by arranging at least one magnetizable armature element and the brake rotors of the two shafts between the electromagnetic unit and the axle housing flange, wherein the magnetizable armature element is arranged between the brake rotors and the electromagnetic unit so as to be axially displaceable but non-rotatable along the axis of rotation within the axle housing.This allows the spring element to be arranged and supported in such a way that it pre-tensions the magnetizable armature element towards the brake rotors to provide a braking force.

[0008] As long as the electromagnetic unit exerts a sufficiently strong force on the magnetizable armature element, the brake rotors are not engaged and the rotating shafts can spin freely. As soon as the electromagnetic unit exerts no force, or a sufficiently small force, on the magnetizable armature element, it is pressed towards the brake rotors by the spring element. Consequently, due to the reduced distance between the magnetizable armature element and the axle housing flange, the brake rotors can no longer spin freely, and the rotation of the wheels is restricted due to the fixed connection of the brake rotors to the corresponding shafts.

[0009] The braking effect is ensured by arranging the elements of the brake unit, in particular the brake rotors, the magnetizable armature element, and the axle housing flange, in such a way that when the magnetizable armature element is displaced by the power supply being switched off, the brake rotors experience a force or clamping effect. In some embodiments, the magnetizable armature element can directly contact a brake rotor during braking, thereby braking and displacing it (which then also exerts a force on other brake rotors), or further friction and / or force transmission elements, described later, can be interposed.

[0010] The axle housing is not necessarily a single piece, but can be composed of several different housings, for example, a housing that surrounds the brake unit and adjacent engine housings or wheel housings. In particular, the axle housing flange can also be a corresponding surface, for example, a side surface of an engine housing.

[0011] A particular advantage here is that the electromagnetic unit can be positioned fixed relative to the axle housing, which significantly reduces and even essentially eliminates vibrations. Furthermore, key components of the brake unit—namely the electromagnetic unit, the magnetizable armature element, and the spring element—are arranged along only one of the rotating shafts, allowing them to be designed as a single unit, which considerably simplifies both assembly and manufacturing.

[0012] In particular, unlike known axles, whose essential braking elements must be arranged along both rotatable shafts, no transverse forces occur within the system exerting the braking force, which can occur in the prior art if the two rotatable shafts are no longer exactly coaxial to each other due to certain force effects or aging.

[0013] The axle according to the invention is particularly preferably a drive axle, especially a drive axle of a forklift truck, since appropriate braking systems are required for drive axles of forklift trucks. At the same time, they should be particularly low-maintenance. This is preferably in accordance with the usual embodiment, namely that the axle according to the invention is a drive axle, wherein each of the rotatable shafts is connected to a drive motor, in particular a wheel drive motor of a forklift truck, with the braking unit arranged between the drive motors.

[0014] Preferably, in the axis according to the invention, the coil of the electromagnet unit is arranged and designed such that, when a magnetic field is generated by energizing the coil, its magnetizable armature element experiences a force towards the coil that is preferably greater than the restoring force of the spring element, particularly at maximum current. In principle, such a force acting on the armature element is technically simplest and most robust when achieved solely by a magnetic field generated by a current-carrying coil. This can be realized by appropriately dimensioning the spring element, the coil, and the current / voltage source of the coil such that, when the coil is energized, the spring force of the spring element is overcome and the magnetizable armature element is attracted accordingly towards the electromagnet unit.

[0015] In a preferred embodiment, the braking force acting on the brake rotors is adjustable in multiple stages. This means, in particular, that the force exerted on the brake rotors can vary depending on the setting. This offers the advantage of avoiding or reducing strong forces when braking the rotating shafts, thereby reducing wear and thus maintenance. A further advantage lies in the smooth deceleration of the vehicle. The stages can be controlled individually or sequentially, so that the deceleration rate is either at a constant low level or increases gradually. This prevents load loss when the vehicle comes to a stop. Depending on the application, different deceleration rates can be provided (slow deceleration; progressive braking; shortest possible braking distance).

[0016] A preferred embodiment, particularly with regard to multi-stage adjustability of the braking force, is that the braking unit comprises several spring elements and several magnetizable armature elements, each magnetizable armature element being biased towards the brake rotors by at least one of the spring elements. By appropriately different dimensions and designs of the magnetizable armature elements and the spring elements, it can be achieved that the different armature elements exert different braking forces and only exert these braking forces at different values ​​of the attractive force from the electromagnet unit. This allows for multi-stage adjustability of the braking force acting on the brake rotors, in particular by energizing the coils of the electromagnet unit with currents appropriate to the different spring elements.

[0017] In one embodiment, the various magnetizable armature elements preferably do not overlap in the radial direction. This means that the magnetizable armature elements extend along the direction orthogonal to the axis of rotation of the rotating shafts in different sections. In other words, this means that when projected onto a plane along the axis of rotation, the magnetizable armature elements have no overlapping area. This is advantageous because each magnetizable armature element can then exert its corresponding force without affecting the other magnetizable armature elements.

[0018] In other embodiments, some or all of the magnetizable armature elements can be designed to overlap. This means that when the current is switched off, some of the magnetizable armature elements are not only moved by their associated spring element(s), but also move other magnetizable armature elements towards the brake rotors.

[0019] A further development is that the electromagnet unit comprises several coils, and each of the armature elements, pre-tensioned by one of the spring elements, is arranged so close to a coil that when a magnetic field is generated by energizing that coil, the armature element experiences a force towards the coil. This force is preferably greater than the restoring force of the corresponding spring element. This allows specific magnetizable armature elements to be precisely controlled, by energizing or de-energizing the corresponding coils, to exert a braking force or not.

[0020] This is particularly advantageously achieved when the multiple coils and the multiple magnetizable armature elements are arranged in such a way that only the corresponding magnetizable armature element experiences a force when its corresponding coil(s) are energized, while the other armature elements pre-tensioned with one of the spring elements are arranged in such a way that they experience no force when this coil is energized, or only a force smaller than a spring force of the spring element pre-tensioning them.

[0021] This allows for a multitude of possible settings by appropriately selecting spring elements of varying strengths and armature elements of different shapes. For example, if four different magnetizable armature elements with four different spring strengths are used, in addition to the two settings of no braking force and maximum braking force, there are up to 62 different braking force settings. Depending on the requirements for adjustable braking force, a correspondingly adapted number of magnetizable armature elements, spring elements, and coils can be provided in different versions of the axle according to the invention.

[0022] According to the invention, the electromagnetic unit is fixed in position relative to the axle housing by being rigidly connected to it, in particular by being screwed to it. A rigid connection or screwing of the electromagnetic unit to the axle housing also includes connections made via intermediate elements. For example, the electromagnetic unit can be arranged in its own housing and rigidly connected to it, with this housing then being screwed to the axle housing. Conversely, the axle housing may also include an inner housing or further fastening elements to which the electromagnetic unit is connected or screwed. All these possible connections or screwings via intermediate elements are referred to within the scope of the invention as connections or screwing.To understand how the electromagnet unit is screwed to the axle housing.

[0023] In one embodiment, the spring elements and the electromagnet unit, which may also include its coils, are attached to a common frame that is firmly connected or screwed to the axle housing. This allows for particularly simple manufacturing and assembly, as the corresponding elements can be suitablely connected to each other directly during manufacturing, and during assembly, only the frame needs to be connected to the axle housing. Optionally, some or all of the magnetizable armature elements can also be connected to the frame. Likewise, other elements of the electromagnet unit, such as corresponding iron elements, can be connected to the frame.

[0024] Preferably, the brake unit further comprises magnetizable or non-magnetizable axially movable but non-rotatable friction elements arranged between the magnetizable armature element and one of the brake rotors, and / or one of the brake rotors and another of the brake rotors, and / or one of the brake rotors and the axle housing flange. This is advantageous for braking force and durability, as the corresponding friction elements can be designed for optimal friction, and magnetizability is not strictly necessary. In particular, it also allows for the adjustment of a suitable clearance between the elements by providing a suitable number and positioning of brake rotors and friction elements between the magnetizable armature element(s) and the axle housing flange, so that, when the current is switched off, the spring elements press the magnetizable armature elements against the friction elements.Brake rotors press against other friction elements or brake rotors, so that the entire arrangement of brake rotors and friction elements is sufficiently clamped between the magnetizable armature element(s) and the axle housing flange, resulting in sufficient braking force.

[0025] Although this can be achieved without friction elements through appropriate dimensioning, as described, the transmission of braking force through appropriately designed friction elements is advantageous.

[0026] The use of a friction element in the embodiment with several magnetizable armature elements is particularly advantageous in that the friction element is arranged as a force transmission element between one of the brake rotors and the magnetizable armature element pre-tensioned by one of the spring elements, such that each of the magnetizable armature elements pre-tensioned by one of the spring elements is biased by the at least one spring element to bear against the force transmission element. This allows even small-area magnetizable armature elements to be used, because they do not directly exert a braking or frictional force on a brake rotor, but rather, by interposing the force transmission element, their braking or frictional force can be transferred to a differently and, in particular, larger area, and this area only comes into contact with the brake rotor later.This allows, in particular, a more uniform force effect on the brake rotors in the embodiment with multi-stage adjustable braking force.

[0027] In embodiments with overlapping magnetizable armature elements, the force transmission element is omitted, and instead, one or more magnetizable armature elements are designed to engage with and brake the brake rotors themselves. They thus function as force transmission elements for the magnetizable armature elements with which they overlap. This design requires less space along the axis of rotation and fewer components, but reduces the number of adjustable braking forces, since the overlap means that the corresponding magnetizable armature elements can no longer exert braking force independently of one another.

[0028] It should be noted that in a preferred embodiment, when the brake is released, i.e., when the coils are energized and the corresponding release is achieved by pulling away the magnetizable armature elements or the magnetizable armature element from the brake rotors, the brake rotors and any friction elements are not further affected and instead, as a result of the rotation of the shafts, they shift axially so slightly due to the mutually acting forces that they can rotate freely.

[0029] In other embodiments, the brake rotors and, if applicable, the friction elements can also be pre-tensioned to a zero position by at least one elastic element and / or a spring element, in which the brake rotors do not contact other brake rotors or, if applicable, friction elements, thus releasing them. This embodiment is advantageous if the initial force acting between brake rotors or friction elements immediately after the brake is released is to be avoided.

[0030] It should be noted that the terms "elastic element" and "spring element" are to be understood as all known bodies that change their shape under the influence of a force and thereby exert a force that causes them to return to their original shape when the force is removed. All bodies with these properties can be used as elastic elements or spring elements within the scope of the present invention. Springs are preferably used as spring elements, in particular helical springs, spiral springs, volute springs, disc springs, elastomer springs, but also gas springs or air springs.

[0031] In general, axle housings and axle housing flanges can be either multi-part or single-piece. The axle housing flange can also be attached to a motor housing or formed integrally with it. Similarly, axle housings and one or both motor housings can be formed integrally, in which case the axle housing flange can be formed by the motor housing or be a separate, single-piece or attached element.

[0032] In a further embodiment, which can be combined with all other embodiments, the brake unit comprises a manually operated device, preferably a lever, the actuation of which presses the magnetizable armature element(s) against the spring element(s) towards the electromagnet unit. Alternatively, the actuation of the manually operated device or lever can press the power transmission element against the magnetizable armature element(s). This allows the brake to be released mechanically, and in particular by a user, without requiring the coils to be energized, i.e., without the need to supply electrical energy. This is particularly advantageous for moving a forklift truck when the motor or electrical systems are switched off or have failed.

[0033] Preferably, the manually operated device or lever is provided with an operating handle arranged outside the axle housing, which is operatively connected to eccentric discs via which forces can be transmitted from the operating handle to the magnetizable armature element or the power transmission element. This ensures particularly easy operation from the outside.

[0034] Preferably, the electromagnetic unit has at least one recess in which the at least one spring element is at least partially received. In particular, the electromagnetic unit can have a corresponding recess for each spring element. This is advantageous because it simultaneously ensures the lateral stabilization of the spring elements.

[0035] It is generally preferred that the magnetizable armature element rests against the electromagnet unit when the spring element is compressed, as this minimizes the force to be generated by the electromagnet unit. In particular, in the embodiment with recesses in the electromagnet unit, the dimensions of the spring elements and the recesses can be designed such that the spring element is completely enclosed in the recess when compressed.

[0036] Preferably, to provide a braking or clamping force or clamping effect, the distance between the magnetizable armature element and the axle housing flange, as well as the force and length of the springs, are designed such that a clamping effect occurs when the attractive force from the magnet unit is removed. Abstractly speaking, the distance between a force-free position and the axle housing flange is preferably equal to or less than the width of all elements arranged between the axle housing flange and the magnetizable armature element. The force-free position of the magnetizable armature element is understood to be the position it would assume if the coil were not energized and no obstacles would stop the movement caused by the spring element. At the same time, the magnet unit is preferably...the corresponding coil is designed so that it can exert sufficient force on the magnetizable armature element to pull it back against the spring.

[0037] As a further aspect of the invention, a forklift truck with an axle according to the invention is proposed.

[0038] An embodiment of the invention is described below with reference to the Fig. Figure 1 explains, showing a partial longitudinal section through the central area of ​​an axle designed as a two-motor drive axle according to the invention.

[0039] The axle shown comprises the axle housing 1, with drive motors arranged to the left and right of the section shown, each connected to the rotatable shafts 2 and 3. In this embodiment, one of the motor housings 14 serves as the axle housing flange 14. Opposite the motor housing 14 is the electromagnetic unit 4, which can be rigidly connected to the axle housing 1 by screws or, as in the illustrated embodiment, to the axle housing flange 14 by screws (without reference numeral; the cavity below the electromagnetic unit 4 serves to receive screws or bolts that engage in an opening in the axle housing flange 14, not shown). In either case, a rigid connection to the axle housing 1 is achieved.

[0040] The electromagnet unit 4 comprises coils 5 and 6 as well as recesses for spring elements 10 and 11. In the illustrated embodiment, the electromagnet unit 4, and thus also the coils 5 and 6, extend not only in the shown sectional plane but also in a ring-like fashion around the rotatable shaft 2. Adjacent to the electromagnet unit 4 are the magnetizable armature elements 8 and 9, which also extend in a ring-like fashion around the shaft 2. The armature elements 8 and 9 are axially displaceable along the shaft 2 and do not rotate with it.

[0041] The force transmission element 7 is also connected to the magnetizable armature elements in a ring-like manner. The force transmission element 7 is axially movable and does not rotate with the shaft 2. It is designed such that both the magnetizable armature element 8 and the magnetizable armature element 9 bear against, or can bear against, the force transmission element 7. It should also be noted that the magnetizable armature elements 8 and 9 do not radially overlap, meaning that the magnetizable armature element 8 can move in the direction of the force transmission element 7 without affecting the other magnetizable armature element 9, and vice versa.

[0042] The first of the brake rotors 12 follows the power transmission element 7. It is rotationally fixed to the single rotatable shaft 2 but axially displaceable along it. This is followed by the friction element 16, which is essentially identical in design to the power transmission element 7. In the illustrated embodiment, both are designed to be non-magnetizable; however, one or both could also be designed to be magnetizable.

[0043] The friction element 16 is followed by the brake rotor 13, which is connected to the other shaft 3 in a rotationally fixed but axially displaceable manner. The motor housing 14 follows the brake rotor 13.

[0044] The position of the brake unit shown is the release position, i.e., coils 5, 6 are energized, which attracts the magnetizable armature elements 8, 9 so strongly that the spring elements 10, 11 are compressed. This gives the power transmission element 7, the friction element 16, and the two brake rotors 12, 13 sufficient play so that, when the rotatable shafts 2, 3 rotate, the brake rotors 12, 13 sufficiently disengage from the motor housing 14, the friction element 16, and the power transmission element 7, allowing the rotatable shafts 2, 3 to rotate freely.

[0045] If a braking force is to be applied, the current flow through one or both of the coils 5, 6 is reduced. This reduces the attractive force on the corresponding magnetizable armature element 8, 9 or on both magnetizable armature elements 8, 9. If this force is sufficiently low, i.e., especially if no current at all flows through the coils 5, 6, the corresponding magnetizable armature element 8, 9 is pressed by the corresponding spring element 10, 11 towards the force transmission element 7. Since this element is axially displaceable, it moves accordingly towards the brake rotor 12, which, due to its displaceability, is in turn moved towards the friction element 16. The friction element 16, due to its displaceability, is then moved towards the brake rotor 13, which, due to the fixed installation of the motor housing 14, cannot move any further.This results in corresponding frictional forces between motor housing 14, brake rotor 13, friction element 16, brake rotor 12 and power transmission element 7, which cause braking and, if necessary, complete blockage of the rotatable shafts 2, 3.

[0046] To release the brake, the coils 5, 6 are energized again, so that the magnetizable armature elements 8, 9 are pulled to the right again with respect to the figure, and thus sufficient play is provided for the power transmission element 7, friction element 16 and brake rotors 12, 13 so that these elements can move again into positions in which the brake rotors 12, 13 can rotate freely when the drive motors are started and the shafts 2, 3 begin to rotate.

[0047] In the illustrated embodiment, the braking force can be adjusted in three different stages, depending on whether one coil 5, the other coil 6, or both coils are energized. If only one of the coils 5, 6 is energized, only a smaller force acts on the force transmission element 7, namely only the force of one of the spring elements 10, 11. This still causes the force transmission element 7 to be displaced and results in a braking effect, but this braking effect is less than when both coils 5, 6 are energized, because the strength of a frictional force depends on the nominal force that triggers it.

[0048] If the spring elements 10 and 11 have different strengths, for example, if spring element 10 exerts a force 1 and spring element 11 exerts a force 2, the nominal force generating the braking force can be set to force 1, force 2, or force 1 plus force 2. This allows the braking force to be set to three levels.

[0049] It should be noted that in Fig. 1. Cables or conduits running upwards from coils 5 and 6 are shown without reference symbols. These serve to connect to a current or voltage source and can also be routed in other ways.

Claims

[1] Axle with an axle housing (1) having an axle housing flange (14) and with a brake unit which is arranged in the axle housing, wherein the axle has two shafts (2, 3) rotatable about a common axis of rotation (20), wherein the brake unit comprises: - an electromagnet unit (4) with at least one coil (5, 6) for generating a magnetic field; - at least one spring element (10, 11); - at least one brake rotor (12, 13) per shaft (2, 3), which is rotationally fixed to the corresponding shaft (2, 3), but is axially displaceable thereon; and - at least one magnetizable armature element (8, 9); where - the electromagnetic unit (4) is fixed in position in the axle housing (1); - the magnetizable armature element (8, 9) and the brake rotors (12, 13) are arranged between the electromagnet unit (4) and the axle housing flange (14); - the magnetizable armature element (8, 9) is arranged axially displaceable but non-rotatable in the axle housing (1) between the brake rotors (12, 13) and the electromagnet unit (4) along the axis of rotation (20); and - the spring element (10, 11) is arranged and supported in such a way that it pre-tensions the anchor element towards the brake rotors (12, 13) to provide a braking force, characterized by , that to generate a braking force, the current flow through one or both of the coils (5, 6) is reduced, thereby reducing the attractive force on the corresponding magnetizable armature element (8, 9) or on both magnetizable armature elements (8, 9), wherein, when the attractive force becomes sufficiently low, the corresponding magnetizable armature element (8, 9) is pressed by the corresponding spring element (10, 11) towards an axially displaceable force transmission element (7), which displaces accordingly towards a first of the brake rotors (12), which, due to its displaceability, is in turn displaced towards a displaceable friction element (16), which in turn is displaced towards a second of the brake rotors (13), whereby corresponding frictional forces occur between the axle housing flange (14), the second brake rotor (13), the friction element (16), the first brake rotor (12) and the force transmission element (7), which cause braking and, if necessary, complete locking of the rotatable shafts (2, 3). wherein the electromagnet unit (4) is firmly connected to the axle housing (1) and / or the axle housing flange (14), in particular by screwing. [2] Axle according to claim 1, characterized by that the axle is a drive axle, wherein preferably each of the rotatable shafts is connected to a drive motor, in particular a wheel drive motor, wherein the brake unit is arranged between the drive motors. [3] Axle according to one of the preceding claims, characterized by , that the coil (5, 6) of the electromagnet unit (4) is arranged and designed such that when a magnetic field is generated by energizing the coil (5, 6), the magnetizable armature element (8, 9) experiences a force towards the coil (5, 6) which is preferably greater than the restoring force of the spring element (10, 11). [4] Axle according to one of the preceding claims, characterized by , that the braking force acting on the brake rotors (12, 13) is adjustable in multiple stages. [5] Axle according to one of the preceding claims, characterized by, that the brake unit comprises several spring elements (10, 11) and several magnetizable armature elements (8, 9), the latter preferably not overlapping in the radial direction, each magnetizable armature element (8, 9) being biased by at least one of the spring elements (10, 11) towards the brake rotors (12, 13). [6] Axle according to claim 5, characterized by, that the electromagnet unit (4) comprises several coils (5, 6) and each of the armature elements (8, 9) biased by one of the spring elements (10, 11) is arranged so adjacent to a coil (5, 6) that when a magnetic field is generated by energizing this coil (5, 6) this armature element (8, 9) experiences a force towards the coil (5, 6) which is preferably greater than the restoring force of the at least one spring element (10, 11) that biases this armature element (8, 9) towards the brake rotors (12, 13), wherein preferably the other armature elements (8, 9) biased by one of the spring elements (10, 11) are arranged such that they experience no force when this coil (5, 6) is energized or only a force less than a spring force of the spring element (10, 11) biasing them. [7] Axle according to one of the preceding claims, characterized by, that the coils (5, 6), the electromagnet unit (4) and the spring elements (10, 11) are attached to a common frame which is rigidly connected to the axle housing (1) and / or the axle housing flange (14). [8] Axle according to one of the preceding claims, characterized by , that the brake unit further comprises magnetizable or non-magnetizable axially movable but non-rotatable friction elements (7, 16) arranged between the magnetizable armature element (8, 9) and one of the brake rotors (12) and / or one of the brake rotors (12) and another of the brake rotors (13) and / or one of the brake rotors (13) and the axle housing flange (14). [9] Axle according to claim 8 in its reference to one of claims 5 or 6, characterized by, that one of the friction elements (7, 16) is arranged as a force transmission element (7) between one of the brake rotors (12) and the magnetizable armature elements (8, 9) pre-tensioned with one of the spring elements (10, 11) such that each of the magnetizable armature elements (8, 9) pre-tensioned with one of the spring elements (10, 11) is pre-tensioned by the at least one spring element (10, 11) to abut against the force transmission element (7). [10] Axle according to claim 8 or 9, characterized by , that the friction elements (7, 16) and / or the brake rotors (12, 13) are pre-tensioned to a zero position by elastic elements and / or spring elements, in which the brake rotors (12, 13) are not contacted by the friction elements (7, 16) and / or other brake rotors (12, 13), thus releasing them. [11] Axle according to any one of the preceding claims, characterized by, that the brake unit comprises several spring elements (10, 11) and several magnetizable armature elements (8, 9), the latter overlapping at least partially in the radial direction, each magnetizable armature element (8, 9) being biased by at least one of the spring elements (10, 11) towards the brake rotors (12, 13), preferably one magnetizable armature element (8, 9) being designed to bear against one of the brake rotors (12, 13) and exert a braking force. [12] Axle according to any one of the preceding claims, characterized by , that the axle housing (1) and the axle housing flange (14) are formed in one piece or in multiple parts and / or that the axle housing (1) is formed in one piece with a motor housing (14) and / or that the axle housing flange (14) is formed by a region of a motor housing (14). [13] Axle according to one of the preceding claims, characterized by, that the brake unit comprises a manually actuated device, the actuation of which pushes the magnetizable armature element (8, 9) against the spring element (10, 11) towards the electromagnet unit (4) and / or the actuation of which pushes the force transmission element (7) against the magnetizable armature element (8, 9). [14] Axle according to claim 13, characterized by , that the manually operated device comprises an actuating handle arranged outside an axle housing (1), which is in operative connection with eccentric discs, via which force can be transmitted from the actuating handle to the magnetizable armature element (8, 9). [15] Axle according to one of the preceding claims, characterized by , that the magnetizable armature element (8, 9) is in contact with the electromagnet unit (4) in a compressed state of the spring element (10, 11). [16] Industrial truck comprising an axle according to any of the preceding claims.

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