Braking device for a mining machine

Abstract

The invention relates to a braking device for a mining machine comprising at least two brake elements mounted in pairs on a brake frame, which act simultaneously on at least one braking surface, and a brake release device arranged on each brake element, which generates a force opposing the braking force to release a brake lining of the brake element. To enable purely electrical operation of the braking device, the invention proposes that the brake release device be based on the principle of the magnetic attraction of opposite poles of two magnet pairs. To ensure proper operation, in particular a uniform attraction of the two magnet pairs, each brake element has a spring arrangement designed to maintain a matching air gap between the two magnets of each magnet pair, so that the magnetic forces are distributed evenly between the two magnet pairs.In that at least one of the two magnets of each magnet pair can be temporarily energized and the poles of the two magnets only attract each other when energized, the force opposing the braking force for releasing the brake pad can be generated and controlled electrically.

Description

[0001] The invention relates to a braking device for a mining machine comprising - at least one braking surface, - at least two braking elements mounted in pairs on a brake frame, which act simultaneously on the braking surface, - a brake release device arranged on each brake element, wherein each brake element generates a braking force acting axially in the direction of the braking surface on a brake pad and each brake release device generates a force opposite to the braking force for releasing the brake pad, wherein the brake release device has two magnet pairs, each with two magnets, and at least one of the two magnets of each magnet pair is a temporarily energizable electromagnet.

[0002] Braking devices for mining must in particular comply with the specific requirements of the TAS (Technical Requirements for Shaft and Inclined Conveyor Systems) and the BVOS (Mining Ordinance for Shaft and Inclined Conveyor Systems).

[0003] Braking systems in use for mining machinery that meet the above requirements are electro-hydraulic and electro-pneumatically operated braking systems.

[0004] In addition, electromagnetic braking devices are known, however not in connection with mining machines, but rather with elevator lifting machines, for example from DE 11 2013 006 987 T5 and JP 2004-189 418 A.

[0005] Finally, WO 2023 / 169933 A1 discloses a purely electrically operated braking device for a mining machine, comprising at least two braking elements mounted in pairs on a brake frame, which act simultaneously on at least one braking surface, and a brake release device arranged on each braking element, which generates a force opposing the braking force to release a brake pad of the braking element. To enable the braking device to be operated purely electrically, it is proposed that the brake release device be based on the principle of magnetic repulsion of matching poles of at least one pair of magnets. Since at least one of the two magnets can be temporarily energized and the poles of the two magnets repel each other only when energized, the force opposing the braking force to release the brake pad can be generated and controlled electrically.The braking device according to the invention does not require any pneumatic or hydraulic supply in addition to the electrical control which is required anyway.

[0006] Based on this prior art, the object of the invention is to provide a braking device for a mining machine of the type mentioned at the outset, which can be operated purely electrically, which enables a higher braking force with matching dimensions and which enables the braking systems on existing winches and hoisting machines to be retrofitted.

[0007] As is common with all braking systems for mining machinery, individual brake elements are mounted in pairs on a brake frame, particularly a brake stand, and act simultaneously and in opposite directions on a braking surface, particularly a brake disc. This design allows for easy adaptation of the brake elements to the brake disc diameter required for the respective winch or hoisting machine.

[0008] The object of the invention is achieved by a braking device having the features of claim 1. Advantageous embodiments emerge from the features of the subclaims.

[0009] The brake ventilation device of the braking device for a mining machine of the type mentioned at the beginning has two pairs of magnets (6, 7) each with two magnets, wherein - different poles of the two magnets of each magnet pair are facing each other, - two magnets of the two magnet pairs form a double magnet and different poles of the two magnets of the double magnet face each other and - at least one of the two magnets of each magnet pair is a temporarily energizable electromagnet, whereby in the energized state the poles of the two magnets of each magnet pair attract each other and thereby generate the force opposing the braking force for releasing the brake pad.

[0010] The brake release device according to the invention is based on the principle of magnetic attraction of the different poles of each magnet pair as well as the mutually facing poles of the two magnets of the double magnet.

[0011] A higher braking force is made possible because the attraction between unlike poles is stronger than the repulsion between like-pole magnets. According to the invention, a total of four magnets act in the same direction, with different poles facing each other between all the magnets. This makes the interacting magnets in the stack stronger overall and can generate a greater force to release the brake pad, counteracting the braking force, than is possible with magnetic repulsion for a stack of the same height. In addition, when force is generated based on magnetic repulsion, different poles of the two magnets of the double magnet face each other, consequently exerting no repulsive effect and thus not contributing to generating the force to release the brake pad, counteracting the braking force.

[0012] Since at least one of the two magnets in each magnet pair is a temporarily energizable electromagnet, and the poles of the two magnets in each magnet pair only attract each other when energized, the force opposing the braking force for releasing the brake pad can be generated and controlled electrically. The braking device according to the invention requires no pneumatic or hydraulic supply in addition to the electrical control system already required.

[0013] To ensure proper operation, in particular even attraction of the two pairs of magnets, each braking element has a spring arrangement designed to maintain a consistent air gap between the two magnets of each pair of magnets so that the magnetic forces are evenly distributed between the two pairs of magnets.

[0014] In principle, it is sufficient for each magnet pair to have a temporarily energizable electromagnet and a permanent magnet. If permanent magnets are provided, they preferably form the double magnet. In an advantageous embodiment of the invention, all magnets are designed as electromagnets.

[0015] The electromagnets can be powered by direct or alternating voltage.

[0016] All electromagnets are preferably designed as so-called magnetic coils, i.e., without moving armatures or other actuating means. The magnetic coil comprises a coil body and a coil in which a magnetic field is formed as a result of an electric current. The coil body is preferably made of a metallic material.

[0017] A structurally advantageous design of a braking element of the braking device is characterized by the following features: - The magnets are arranged in a first housing of the braking element, which is fixed to the frame. The first housing, which is fixed to the frame, is particularly shaped like a circular cylinder, whose longitudinal axis coincides with the direction of the braking force. - A spring assembly generates the braking force acting axially in the direction of the braking surface on the brake pad. The spring assembly preferably comprises at least one compression spring. - The spring assembly is arranged in a second, frame-mounted housing of the brake element, separate from the first housing. The interior of the second frame-mounted housing is preferably circularly cylindrical and open at the outer end. The longitudinal axis of the circularly cylindrical interior coincides with the direction of the braking force. - The spring assembly acts on a brake pad carrier, which is axially movable relative to the second housing, fixed to the frame, in the direction of the braking surface and in the opposite direction. The brake pad carrier is arranged on the outer open end face of the second housing, fixed to the frame; it essentially consists of a support plate for the brake pad and a circumferential, circular-cylindrical edge, which extends from the side of the support plate opposite the brake pad and is guided in a sliding manner along the circular-cylindrical inner wall of the second housing, fixed to the frame. - The first housing, which is fixed to the frame, and the second housing, which is fixed to the frame, have a common housing wall formed as a flange with a passage. The flange is expediently attached to the lower front opening of the circular-cylindrical first housing. The attachment can be materially and / or positively connected. - A pull rod extends axially from the brake pad carrier through the passage at least as far as the magnet forming an upper end of the first housing fixed to the frame, said magnet being firmly connected to the first housing fixed to the frame. The fastening can be materially and / or positively connected. The pull rod can have a constant or stepped, preferably cylindrical, cross-section. The pull rod can be provided with an external thread in certain sections. - The magnet arranged in the first housing fixed to the frame adjacent to the flange is movable in the axial direction, ie in the direction of the braking surface and in the opposite direction, the force for releasing the brake pad being transmitted via the pull rod, which is firmly connected on the one hand to the brake pad carrier and on the other hand to the movable magnet. - The double magnet is arranged so that it can be displaced axially along the pull rod. For this purpose, the double magnet preferably has a central passage whose dimensions allow the double magnet to move smoothly along the pull rod.

[0018] As is usual with braking systems for mining machinery, the braking force acting axially towards the braking surface is generated by a spring assembly. The release device temporarily reduces or completely eliminates the braking force, releasing the brake disc. To do this, the electromagnets of each magnet pair are energized, causing the opposite poles of the two magnets in each magnet pair to attract each other. This reduction in the distance between the two magnets in each magnet pair causes a force to be introduced into the pull rod via the axially movable double magnet and the movable magnet arranged adjacent to the housing wall. This force counteracts the braking force acting axially towards the braking surface. Since the pull rod is connected to the brake pad carrier, the energization reduces or completely eliminates the braking force on the brake pad.

[0019] In order to adjust the maximum braking force, each braking element is designed in an advantageous embodiment of the invention so that - the pull rod extends axially movable through the magnet forming the upper end of the first housing fixed to the frame, - the pull rod has an external thread at least on a section projecting beyond the upper end, onto which an adjusting nut is screwed, designed to adjust the preload in the spring assembly via the pull rod when the magnets are not energized.

[0020] In one embodiment of the invention, a spring arrangement arranged partially outside the first frame-fixed housing comprises the following: - A carrier attached to the double magnet, having a first support surface and a second support surface opposite the first support surface. The support surfaces are preferably designed as flat surfaces arranged parallel to one another. - An opening, for example in the form of a longitudinal slot in the first housing fixed to the frame, through which the driver extends outward. The dimensions and arrangement of the longitudinal slot are determined such that the driver does not impair the axial movement of the double magnet along the pull rod. The support surfaces of the driver are located outside the first housing fixed to the frame. - Two compression springs acting in the axial direction, each of the two compression springs being supported on the one hand on the outside of the first housing fixed to the frame and on the other hand on the opposite support surfaces of the driver. For external support on the first housing fixed to the frame, brackets can be attached to its outer surface. To prevent buckling of the cylindrical compression springs, a guide rod can be arranged in the axial direction between the brackets, with the compression springs surrounding the guide rod. The driver has a passage for the guide rod between the support surfaces and is movable in both directions along the stationary guide rod together with the coupled double magnet, so that either one or the other compression spring is compressed.

[0021] In another embodiment of the invention, the spring arrangement can also be completely housed in the first frame-mounted housing by inserting aligned blind holes into the mutually facing surfaces of the magnet bodies of the two magnets of each magnet pair, with each pair of aligned blind holes accommodating a compression spring. The length of the compression spring(s) is determined such that a consistent air gap is maintained between the two magnets of each magnet pair when the at least one temporarily energizable electromagnet of each magnet pair is not energized.

[0022] In a further embodiment of the braking element with the features of claim 6, a spring element can be arranged inside and outside the first housing fixed to the frame. In this case, the spring arrangement comprises a driver attached to the double magnet with only one support surface used to support only one compression spring arranged outside the housing. Arranged within the first housing fixed to the frame is a sleeve that acts axially in the opposite direction of force to the one compression spring. This sleeve surrounds the pull rod and is supported on the adjusting nut on the one hand and on the double magnet on the other.The passage already present in the upper magnet closing the housing is larger in cross-section than the passage in the double magnet arranged below it in order to accommodate not only the pull rod but also the pull rod with the sleeve surrounding it in an axially movable manner.

[0023] The invention is explained in more detail below with reference to the drawings. Fig. 1 a schematic side view of a braking device according to the invention, Fig. 2 a representation of a braking element of the braking device according to Fig. 1, where Fig. 2a the overlying and Fig. 2b shows the released brake element, Fig. 3 a representation of a second embodiment of a braking element, wherein Fig. 3a the overlying and Fig. 3b shows the released brake element.

[0024] Fig. 1 shows a braking device (1) according to the invention, which has at least one braking surface (2) in the form of a brake disc, and two braking elements (3) fastened in pairs to a brake frame (not shown), which act simultaneously on the brake disc.

[0025] A release device (4) is arranged on each brake element (3), which generates a force opposing the braking force acting in the axial direction of the braking surface (2) to release a brake pad (5). Both the direction of the braking force and the opposite direction of the release force run parallel to a longitudinal axis (12) of the brake element (3).

[0026] The ventilation device (4) of each brake element (3) has two pairs of magnets (6, 7) each with two magnets (6.1, 6.2) or (7.1, 7.2), as can be seen from Fig. 2 a), Fig. 2b). In the illustrated embodiment, each magnet (6.1, 6.2, 7.1, 7.2) is designed as a magnetic coil. Each magnet (6.1, 6.2, 7.1, 7.2) has two opposing poles, one pole (9), the north pole, and one pole (8), the south pole. Different poles (8, 9) of the first magnet pair (6.1, 6.2) and different poles (8, 9) of the second magnet pair (7.1, 7.2) face each other.

[0027] The magnets (6.2, 7.1) of the two magnet pairs (6, 7) form a double magnet, with the opposite poles (8, 9) of the two magnets (6.2, 7.1) of the double magnet facing each other. The magnets (6.2, 7.1) combined in the double magnet form a single structural unit.

[0028] As is particularly evident from Fig. 2a), Fig. 2b), the magnets (6.1, 6.2, 7.1, 7.2) of both magnet pairs (6, 7) are arranged in a first housing (10) of the braking element (3) which is fixed to the frame.

[0029] To ensure proper operation, particularly uniform attraction of the two magnet pairs (6, 7), each brake element (3) has a spring arrangement (22) designed to maintain a consistent air gap (23) between the two magnets (6.1, 6.2, 7.1, 7.2) of each magnet pair (6, 7). This ensures that the magnetic forces are distributed evenly between the two magnet pairs (6, 7).

[0030] Adjoining the first frame-mounted housing (10) is a second frame-mounted housing (13), in which a spring assembly (14) is arranged, which generates the braking force acting axially in the direction (21) of the braking surface on the brake pad (5). The spring assembly (14) acts on a brake pad carrier (17), which is movable axially relative to the second frame-mounted housing (13) in the direction (21) of the braking surface (2) and in the opposite direction. Fig. 2a), Fig. 2b) it can be seen that the movement of the brake pad carrier (17) in the second housing (13) is guided by the circumferential edge (17.1) extending in the axial direction.

[0031] The first frame-mounted housing (10) and the second frame-mounted housing (13) are separated by a flange (15) with a passage (19). The flange (15) is attached to the inner surface of the first housing (10) and simultaneously forms the abutment for the spring assembly (14) in the second frame-mounted housing (13).

[0032] A stepped pull rod (18) extends in the axial direction from the brake pad carrier (17) through the passage (19) in the flange (15) and the passages in the magnets (6.1, 6.2, 7.1, 7.2) aligned with the passage (19).

[0033] The magnet (7.2), arranged in the first housing (10) fixed to the frame, adjacent to the flange (15), is arranged to be movable in the axial direction within the housing (10), wherein the magnet (7.2) rests against the flange (15) when de-energized. The force for releasing the brake pad (5) is transmitted via the pull rod (18), which is firmly connected to the brake pad carrier (17) on the one hand and to the movable magnet (7.2) on the other. The fixed connection is in particular a materially bonded or force-fit connection between the pull rod (18) and the passage in the movable magnet (7.2).

[0034] The double magnet (6.2, 7.1) is arranged axially displaceably along the pull rod (18) and within the first frame-mounted housing (10). The passage in the double magnet (6.2, 7.1) and the pull rod (18) form a sliding guide for the double magnet (6.2, 7.1).

[0035] The magnet (6.1) forming the upper end of the first housing (10) fixed to the frame is attached to the first housing (10). The pull rod (18) extends axially movably through the stationary upper magnet (6.1). The upper magnet (6.1) can be attached to the inner wall of the first housing (10) using a positive and / or non-positive fit. The attachment must at least prevent any movement of the upper magnet (6.1) relative to the first housing (10) in the direction (21) of the braking surface (2).

[0036] The pull rod (18) has an external thread on a section projecting beyond the upper end, onto which an adjusting nut (20) is screwed in order to change the preload in the spring assembly (14) via the pull rod (18) when the ventilation device (4) is not active, i.e. when the magnets are not energized. The adjusting nut (20) is therefore only effective when the brake is applied. By adjusting the preload, the maximum braking force that the brake pad (5) exerts on the braking surface (2) can be set. By increasing the preload, the brake pad carrier (17) with the brake pad (5) is moved slightly further into the second housing (13) fixed to the frame, thereby reducing the maximum braking force.

[0037] The examples according to Fig. 2 and Fig. 3 differ only in the spring arrangement (22), which is described in detail below. Furthermore, the details of the braking element according to Fig. 3a), Fig. 3b) fully to the statements on the braking element according to Fig. 2a) 2b). Components with the same function are provided with the same reference numerals.

[0038] The spring arrangement (22) of the brake element (3) according to Fig. 2 comprises a driver (22.1) attached to the double magnet (6.2, 7.1) with a first support surface (22.2) and a second support surface (22.3) opposite the first support surface (22.2). The preferably flat support surfaces (22.2, 22.3) are arranged at a parallel distance from one another on opposite sides of the driver (22.1).

[0039] An opening, in particular a longitudinal slot, is provided in the first housing (10) fixed to the frame, through which the driver (22.1) with the support surfaces (22.1, 22.2) extends outwards, the dimensions and arrangement of the longitudinal slot being determined such that the driver (22.1) does not impair the displaceability of the double magnet (6.2, 7.1) in the direction of the longitudinal axis (12) of the braking element along the pull rod (18).

[0040] Furthermore, the spring arrangement (22) comprises two compression springs (22.4, 22.5) acting in the axial direction. Each of the two compression springs is supported on one side by one of two brackets (22.6, 22.7) arranged on the outer surface of the first housing (10) fixed to the frame, and on the other side by one of the two opposite support surfaces (22.2, 22.3) of the driver.

[0041] The spring arrangement (22) of the brake element (3) according to Fig. 3a), Fig. 3b) has a driver (22.1) attached to the double magnet (6.2, 7.1) with only one effective first support surface (22.2). An opening, in particular a longitudinal slot, through which the driver (22.1) extends outward, is provided in the first housing (10) fixed to the frame.

[0042] However, only one compression spring (22.4) acts on the driver (21), which is supported on the one hand by the bracket (22.6) fixed to the housing and on the other hand by the support surface (22.2) of the driver (22.1). The direction of force of the compression spring (22.4) corresponds to the direction of force for releasing the brake pad (5). In the opposite direction of force to the compression spring, i.e. in the direction of the braking force, a sleeve (24) surrounds the pull rod (18), whereby the sleeve (24) is supported on the one hand by the adjusting nut (20) and on the other hand by the double magnet (6.2, 7.1). The passage in the upper magnet (6.1) is larger in cross-section than the passage in the double magnet (6.2, 7.1) arranged below it in order to accommodate not only the pull rod (18), but also the pull rod (18) with the sleeve (24) surrounding it in an axially movable manner.

[0043] The operation of the brake according to the invention is explained below using Fig. 2a), Fig. 2b) explains in more detail: Fig. Figure 2a) shows the braking device (1) with non-energized magnets (6.1, 6.2, 7.1, 7.2) of the brake release device (4). The spring assembly (14) is retracted, and the brake pad carrier (17) with the attached brake pad (5) rests on the brake surface (2) or brake disc (not shown). If all magnets (6.1, 6.2, 7.1, 7.2) of the two magnet pairs (6, 7) are energized, the magnets (6.1, 6.2) of the magnet pair (6) and the magnets (7.1, 7.2) of the magnet pair (7) attract each other, so that the air gap (23) between the different poles (8) or (9) is reduced or closed, as shown in Fig. 2b) is shown.

[0044] When the air gap (23) is completely closed, the piston on the flange moves Fig. 2a) adjacent lower magnet (7.2) by the path “X” upwards into the Fig. 2b). Since the magnet (7.2) is connected to the brake pad carrier (17) via the pull rod (18), the brake pad (5) attached to the brake pad carrier (17) is simultaneously lifted from the braking surface (2), thereby completely releasing the brake.

[0045] To reduce the braking force in a controlled manner, it is advantageous to set an air gap of the same size between the two magnet pairs (6, 7) while releasing the brake. For this purpose, the size of the air gap between the two magnet pairs (6, 7) can be continuously monitored using sensors not shown in the figures. A control system for the current supply to the electromagnets changes the magnetic forces acting between the poles (8, 9) of the two magnet pairs (6, 7), taking the sensor signals into account, so that the air gap between the two magnet pairs is consistent.

[0046] If the current supply to the magnets (6.1, 6.2, 7.1, 7.2) of the two magnet pairs (6, 7) is interrupted, the released brake returns to its resting position after Fig. 2a) under the action of the spring assembly (14) so ​​that the maximum braking force acts on the braking surface (2). List of reference symbols 1 braking device 2 braking surface 3 brake element 4 Ventilation device 5 brake pad 6 pairs of magnets 6.1 Magnet 6.2 Magnet 7 pairs of magnets 7.1 Magnet 7.2 Magnet 8 Pole (S = South Pole) 9 Pole (N = North Pole) 10. First housing 11 Flange 12 Longitudinal axis brake element 13 Second housing 14 spring package 15 Flange 16 threaded rod 17 brake pad carrier 17.1 Surrounding edge 18 Drawbar 19 passage 20 Adjusting nut 21 Direction to braking surface 22 Spring arrangement 22.1 Driver 22.2 First support surface 22.3 Second support surface 22.4 Compression spring 22.5 Compression spring 22.6 Console 22.7 Console 23 Air gap 24 sleeve

Claims

[1] Braking device (1) for a mining machine, comprising - at least one braking surface (2), - at least two brake elements (3) attached in pairs to a brake frame, which act simultaneously on the braking surface (2), - a ventilation device (4) arranged on each brake element (3), wherein each brake element (3) generates a braking force acting axially in the direction (21) of the braking surface (2) on a brake pad (5) and each ventilation device (4) generates a force opposite to the braking force for ventilating the brake pad (5), wherein - the ventilation device (4) has two pairs of magnets (6, 7) each with two magnets (6.1, 6.2, 7.1, 7.2), wherein - different poles (8,9) of the two magnets (6.1,6.2,7.1,7.2) of each magnet pair (6,7) face each other, - two magnets (6.2,7.1) of the two magnet pairs (6,7) form a double magnet and different poles (8,9) of the two magnets (6.2,7.1) of the double magnet face each other, - at least one of the two magnets (6.1, 6.2, 7.1, 7.2) of each magnet pair (6, 7) is a temporarily energizable electromagnet, wherein, in the energized state, the poles (8, 9) of the two magnets (6.1, 6.2, 7.1, 7.2) of each magnet pair attract each other and thereby generate the force opposing the braking force for releasing the brake pad (5), - a spring arrangement (22) arranged on the braking device, designed to maintain a matching air gap between the two magnets (6.1,6.2,7.1,7.2) of each magnet pair. [2] Braking device according to claim 1, characterized by that the double magnet is a permanent magnet. [3] Braking device according to claim 1, characterized by that all magnets (6.1,6.2,7.1,7.2) are electromagnets. [4] Braking device according to one of claims 1 to 3, characterized by that all electromagnets are designed as magnetic coils. [5] Braking device according to one of claims 1 to 4, characterized by , that - the magnets (6.1, 6.2, 7.1, 7.2) are arranged in a first frame-fixed housing (10) of the braking element (3), - a spring assembly (14) generates a braking force acting axially in the direction (21) of the braking surface (2) on the brake pad (5), - the spring assembly (14) is arranged in a second housing (13) of the braking element (3) which is fixed to the frame, - the spring assembly (14) acts on a brake pad carrier (17) which is movable axially in the direction (21) of the braking surface (2) and in the opposite direction relative to the second housing (13) fixed to the frame, - the first frame-fixed housing (10) and the second frame-fixed housing (13) have a common housing wall designed as a flange (15) with a passage (19), - a pull rod (18) extends from the brake pad carrier (17) through the passage (19) at least as far as the magnet (6.1) forming an upper end of the first housing (10) fixed to the frame, said magnet (6.1) forming the upper end being fixedly connected to the first housing (10) fixed to the frame, - the magnet (7.2) arranged in the first frame-fixed housing (10) adjacent to the flange (15) is movable in the direction (21) of the braking surface (2) and in the opposite direction, wherein the force for releasing the brake pad (5) is transmitted via the pull rod (18) which is firmly connected on the one hand to the brake pad carrier (17) and on the other hand to the movable magnet (7.2) and - the double magnet is arranged to be axially displaceable in the direction (21) of the braking surface (2) and in the opposite direction along the pull rod (18). [6] Braking device according to claim 5, characterized by , that - the pull rod (18) extends axially movably through the magnet (6.1) forming the upper end of the first frame-fixed housing (10), - the pull rod (18) has an external thread at least on a section projecting beyond the upper end, onto which an adjusting nut (20) is screwed, designed to adjust the preload in the spring assembly (14) via the pull rod (18). [7] Braking device according to claim 5 or 6, characterized by that the spring arrangement (22) comprises: - a driver (22.1) attached to the double magnet with a first support surface (22.2) and a second support surface (22.3) opposite the first support surface (22.2), - an opening in the first frame-fixed housing (10), through which the driver (22.1) with the support surfaces (22.2, 22.3) extend outwards, wherein the dimensions and the arrangement of the opening in the first frame-fixed housing (10) are determined such that the driver (22.1) does not impair the displaceability of the double magnet along the pull rod (18), - two compression springs (22.4, 22.5) acting in the direction of the longitudinal axis (12) of the braking element (3), each of the two compression springs being supported on the one hand on the outside of the first housing (10) fixed to the frame and on the other hand on one of the two opposite support surfaces (22.2, 22.3) of the driver (22.1). [8] Braking device according to claim 6, characterized by that the spring arrangement (22) comprises: - a driver (22.1) attached to the double magnet with a first support surface (22.2), - an opening in the first frame-fixed housing (10), through which the driver (22.1) with the first support surface (22.2) extends outwards, wherein the dimensions and the arrangement of the opening in the first frame-fixed housing (10) are determined such that the driver (22.1) does not impair the displaceability of the double magnet along the pull rod (18), - a compression spring (22.4) acting in the axial direction, the compression spring (22.4) being supported on the one hand on the outside of the first housing (10) fixed to the frame and on the other hand on the first support surface (22.2) of the driver (22.1), - a sleeve (24) surrounding the pull rod (18) and supported on the one hand on the adjusting nut (20) and on the other hand on the double magnet.

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