Brake drum, drum brake, and operating method

Abstract

The present invention relates to a brake drum (26), a drum brake (20), and an operating method (100) for a drum brake (20). The brake drum (26) has a brake surface (36) against which at least one brake shoe (22), which is rotatable relative to the brake drum (26), of the drum brake (20) presses radially during a braking process. Advantageously, a lubricant reservoir (40) is provided for delivering lubricant to the brake surface (36) during the braking process.

Description

[0001] Brake drum, drum brake and operating procedures

[0002] The present invention relates to a brake drum, a drum brake and an operating method for a drum brake.

[0003] Drum brakes have proven to be a reliable means of reducing or at least limiting rotational speeds. In a widely used design, two brake shoes fitted with brake linings act on the inside of a brake drum, although other configurations, such as those with external brake shoes or brake bands, are also possible. Compared to other brake types, such as coil spring brakes, drum brakes have the advantage of a relatively large braking surface, also known as the running surface. Furthermore, drum brakes can be constructed to be very robust, making brake failure extremely unlikely even under heavy loads. For these reasons, although the principle has been known for more than 150 years, drum brakes are used in many technical fields. For example, a drum brake for an autonomously operated vehicle is disclosed in DE 10 2020 213 917 A1.

[0004] Depending on the application, drum brakes can also present certain problems. For example, drum brakes are prone to generating braking noise. This noise can be disruptive when used in medical devices, such as lifting columns for positioning patient trays or X-ray equipment. Similarly, when using a drum brake in a lubricated environment, such as inside or near a gearbox, considerable effort is usually required to keep the drum brake's running surfaces free of lubricant.

[0005] Against this background, it is an object of the present invention to further improve a drum brake and its operating behavior, in particular to lower the barriers to the use of a drum brake in a medical environment. This object is achieved by a brake drum, a drum brake and an operating method for a drum brake according to the independent claims.

[0006] Preferred embodiments of the invention are the subject of the dependent claims and the following description.

[0007] According to a first aspect of the invention, the brake drum for a drum brake, particularly in a linear drive, has a braking surface against which, during a braking operation, at least one brake shoe of the drum brake, rotatable relative to the brake drum, presses radially. Advantageously, a lubricant reservoir, particularly a dedicated one, is provided for supplying lubricant to the braking surface during the braking operation.

[0008] One aspect of the invention is based on the approach of lubricating at least one running or braking surface of a drum brake, or providing at least one lubricated running or braking surface. It has surprisingly been found that the braking effect of a lubricated drum brake or a lubricated braking surface of a brake drum is sufficient for a large number of applications. For example, a load-driven rotation of a threaded spindle of a linear drive, such as those used for positioning patient trays or X-ray equipment, can be prevented or at least significantly slowed down with a lubricated drum brake or braking surface.

[0009] The lubrication of the drum brake is expediently achieved via the brake drum. For this purpose, the brake drum preferably has a lubricant reservoir that is filled or fillable with a lubricant. The lubricant reservoir is preferably integrated into the brake drum. The brake drum can, for example, be manufactured as a single piece with the lubricant reservoir; that is, the lubricant reservoir is integrated into the brake drum during its manufacture or formed together with the brake drum.

[0010] The lubricant reservoir provided in the brake drum prevents, in particular, the displacement of lubricant between the at least one brake shoe and the brake drum when the brake shoe makes contact with the brake drum. Specifically, the lubricant, for example grease, can escape from the lubricant reservoir during braking and spread across the braking surface of the brake drum and / or the at least one brake shoe. The lubricant can escape continuously from the lubricant reservoir during braking, thus ensuring constant lubrication of the drum brake. If necessary, the lubricant can also flow back into the lubricant reservoir when the brake is stationary, i.e., when the brake shoe(s) are not pressed against the braking surface of the brake drum.

[0011] Lubricating the drum brake, particularly the braking surface of the brake drum, reduces wear on the drum and / or brake shoe(s). This extends the service life of the drum brake. Lubrication also reduces operating noise during braking. This can be particularly desirable in noise-sensitive environments, such as medical facilities. Finally, a lubricated drum brake can also reduce or at least better predict operational risks. Especially when used in a lubricated environment, a decrease in drum brake performance, i.e., a reduction in braking effect, caused by lubricant ingress from the surrounding environment can be prevented or at least mitigated.In summary, specific challenges regarding wear and noise generation can be addressed through targeted lubrication of the drum brake, particularly the braking surface of the brake drum. The lubricated drum brake, and especially the lubricated braking surface of the brake drum, offers a robust solution that ensures reliable function even under potentially problematic conditions such as lubricant ingress.

[0012] A lubricated drum brake can therefore be particularly advantageous as a brake in a linear drive, especially in a linear drive used in a medical environment. Here, the drum brake can be arranged as an operative connection between a gearbox and a rotatably mounted threaded spindle of a linear unit of the linear drive, in order to transmit motor torque supplied by the gearbox to the spindle on the one hand, and conversely, to prevent or at least reduce the transmission of a load-induced torque exerted by the spindle to the gearbox. The drum brake is necessarily located in a lubricated environment, since both the gearbox and the spindle, or a spindle nut operatively connected to the spindle, are lubricated.The use of the lubricated drum brake eliminates the need for further precautions to protect against the ingress of lubricant from the gearbox or linear unit into the drum brake.

[0013] Preferred embodiments of the invention and their further developments are described below. These embodiments can be combined with each other and with the aspects of the invention described below, unless expressly excluded.

[0014] In a preferred embodiment, the lubricant reservoir is at least partially open towards the braking surface. The lubricant can thus be distributed directly onto the braking surface, particularly when the braking surface is contacted by at least one brake shoe during the braking process, without the need to introduce the lubricant into the brake or between the brake drum and the brake shoe. In particular, lubrication can be self-regulating by means of a lubricant reservoir in the brake drum that is open towards the braking surface.

[0015] In a further preferred embodiment, the lubricant reservoir comprises at least one recess in the braking surface that is filled or fillable with lubricant. Such a recess can also be referred to as a lubricant pocket. Such a recess can be manufactured with minimal effort. For example, such a recess can be incorporated into the brake drum during its manufacture.

[0016] In a further preferred embodiment, the lubricant reservoir comprises at least one groove in the braking surface that is filled or fillable with lubricant. In particular, the recess or lubricant pocket can be designed as a groove. From such a groove, the lubricant can be reliably distributed onto the braking surface during the braking process by the relative rotation of the at least one brake shoe and the brake drum relative to each other.

[0017] In a further preferred embodiment, the at least one groove runs substantially in a circumferential direction of the brake drum. Here, "substantially in a circumferential direction" means a direction in which the orientation of the corresponding groove deviates only slightly, e.g., by no more than 10°, preferably no more than 5°, from the circumferential direction. Such a groove, running substantially in the circumferential direction of the brake drum, ensures that at least a surface section of the braking surface can be continuously contacted by the at least one brake shoe during the braking process. At the same time, this ensures continuous lubrication of the braking surface.

[0018] In an alternative embodiment, several grooves are provided in the braking surface, which run essentially in the axial direction of the brake drum. The multiple grooves are advantageously aligned parallel to each other.

[0019] A course that is essentially axial can be understood as a course in which the orientation of the corresponding groove is only slightly affected, i.e.,

[0020] The deviation from the axial direction is less than 10°, preferably less than 5°. The multiple grooves, running essentially in the axial direction, ensure that the lubricant is distributed over the entire length of the brake drum, i.e., the entire braking surface in the axial direction.

[0021] Alternatively, it is also conceivable that at least one groove runs in a helical pattern in the braking surface. This allows for a compromise between continuous lubrication and the distribution of lubricant over the entire length of the brake drum.

[0022] In a further preferred embodiment, the lubricant reservoir comprises several bores filled or fillable with lubricant. This allows for the creation of many relatively small lubricant reservoirs that can dispense lubricant evenly under operating load, i.e., during braking. With the aid of several such bores, lubricant can be dispensed particularly homogeneously across the braking surface. In a further preferred embodiment, the brake drum is porous. The lubricant reservoir advantageously comprises pores in the brake drum. These pores in the brake drum can be filled or fillable with lubricant. A porous brake drum significantly reduces the effort required to manufacture a lubricant reservoir. In particular, no dedicated manufacturing step is necessary to create a recess in the braking surface.For example, the brake drum can be made of a sintered material, particularly sintered steel. The lubricant contained in the pores can then be released during braking by operating heat and mechanical forces.

[0023] According to a second aspect of the invention, the drum brake, particularly for a linear drive, comprises i) a brake drum, particularly according to the first aspect of the invention, and ii) at least one brake shoe rotatable relative to the brake drum. During braking, the at least one brake shoe presses radially against a braking surface of the brake drum. The braking surface or the brake shoe comprises a brake lining. In at least one predetermined operating state of the drum brake, e.g., during braking, when the at least one brake shoe presses against the braking surface of the brake drum, a lubricant provided for lubricating the drum brake is distributed between the brake lining and the brake shoe on the one hand, or between the brake lining and the braking surface on the other. Preferably, the braking surface and / or the brake lining on the one hand, or the brake lining and the at least one brake shoe on the other, is thus covered by a film of lubricant.This extends the service life of the drum brake, particularly the brake drum and / or brake shoe(s), and reduces noise emissions during braking. Because the drum brake is designed from the outset for use with lubricated running surfaces, i.e., a lubricated braking surface and / or lubricated brake shoes, the ingress of lubricant from the drum brake's surroundings, such as a gearbox or linear unit, does not pose an operational risk.

[0024] A third aspect of the invention relates to the operating method for a drum brake, in particular for a drum brake according to the second aspect of the invention, comprising a brake drum and at least one brake shoe rotatable relative to the brake drum, which presses radially against the brake drum during a braking operation, wherein the brake drum or the brake shoe comprises a brake lining. In this method, the brake shoe and / or the brake drum is lubricated with a lubricant so that, during the braking operation, the lubricant is distributed between i) the brake lining and the brake shoe or ii) the brake lining and the brake drum. In particular, the lubricant can escape from a lubricant reservoir in the brake drum during the braking operation.When the drum brake is applied, causing at least one brake shoe to rotate relative to the brake drum and be pressed against the drum's braking surface, the lubricant can be displaced from the reservoir and distributed across the braking surface by the rotating brake shoe. For example, the operating heat—that is, the heat generated by the brake shoe(s) contacting the drum during braking—and the mechanical forces acting on the drum can displace the lubricant from the reservoir. This not only increases the service life of the drum brake and prevents or at least reduces noise during braking, but also improves operational safety.Because of the targeted lubrication of the drum brake, the drum brake becomes insensitive to lubricant penetrating the drum brake from the environment.

[0025] In a preferred embodiment, the lubricant distributed between the brake lining and the at least one brake shoe, or between the brake lining and the brake drum, flows at least partially back into the lubricant reservoir of the brake drum when the at least one brake shoe no longer presses against the brake drum after a braking operation. This allows the lubrication to be self-regulating. In particular, it ensures that sufficient lubricant is always present in the lubricant reservoir and that the drum brake operates effectively and quietly even with repeated use.

[0026] The invention will now be explained in more detail with reference to the figures. Where expedient, elements with equivalent effects are designated with the same reference numerals. The invention is not limited to the embodiments shown in the figures – not even with regard to functional features. The preceding description, as well as the subsequent description of the figures, contains numerous features, some of which are summarized in the dependent claims. However, those skilled in the art will also be able to consider these features, as well as all other features disclosed above and in the subsequent description of the figures, individually and combine them into meaningful further combinations.In particular, all of the aforementioned features can be combined individually and in any suitable combination with the brake drum according to the first aspect of the invention, the drum brake according to the second aspect of the invention and the operating method according to the third aspect of the invention.

[0027] They show, at least partially schematically:

[0028] Fig. 1 shows an example of a linear drive with a drum brake;

[0029] Fig. 2 shows the drum brake of the linear drive from Figure 1;

[0030] Fig. 3 shows the brake drum of the drum brake from Figure 2;

[0031] Fig. 4 shows another example of a brake drum with a lubricant reservoir; and

[0032] Fig. 5 shows another example of a brake drum with a lubricant reservoir.

[0033] Figure 1 shows an example of a linear drive 1 with a drum brake 20 for coupling a gearbox 8, to which a motor 10 is connected on the drive side, to a threaded spindle 4 of a linear unit 2. The drum brake 20 is advantageously configured such that a torque generated by the motor 10 and transmitted by the gearbox 8 is transferred to the threaded spindle 4, which is rotatably mounted in a housing 14 by means of bearings 12, without triggering the drum brake 20, i.e., without any braking effect being exerted by the drum brake 20. The threaded spindle 4 is operatively connected to a spindle nut 6 of the linear unit 2, for example via a plurality of balls circulating inside the spindle nut 6, so that the rotary motion transmitted from the motor 10 via the gearbox 8 and the drum brake 20 to the threaded spindle 4 is converted into an axial movement of the spindle nut 6 along the threaded spindle 4.A thrust tube 16 is mounted on the spindle nut 6, which can transmit the axial movement of the spindle nut 6 to a load, for example a machine part, mounted on an end mounting section 16a of the thrust tube 16.

[0034] While the drum brake 20 allows torque from the motor 10 to be transmitted to the threaded spindle 4, it is preferably designed to prevent or at least limit torque transmission in the opposite direction, i.e., from the threaded spindle 4 to the gearbox 8 and thus ultimately also to the motor 10. For this purpose, the drum brake 20 is expediently designed or configured such that a torque exerted by the threaded spindle 4, which can be caused, for example, by a tensile or compressive load on the thrust tube 16 and thus by the spindle nut 6 running along the threaded spindle 4, triggers the drum brake 20, i.e., causes the drum brake 20 to exert a braking effect. This will be explained in more detail below with reference to Figure 2.

[0035] Figure 2 shows the drum brake 20 of the linear drive 1 from Figure 1. The drum brake 20 comprises two brake shoes 22, which are connected to each other via two spring elements 24, and a brake drum 26. The two brake shoes 22 are arranged radially inside the brake drum 26 and are rotatable relative to the brake drum 26 about an axis of rotation R. Brake linings 28 are arranged on the brake shoes 22, which, during a braking operation, press radially against a braking surface of the brake drum 26 (not visible in Figure 2) and thus prevent or at least impede rotation of the brake shoes 22 relative to the brake drum 26. In an alternative embodiment, not shown, the brake drum 26 could also be provided with the brake linings 28 (or a single brake lining).

[0036] The two brake shoes 22 are designed in a bridge-like fashion, forming a central receiving space 30 between them for an actuating element 4a. The actuating element 4a is arranged at the end of the threaded spindle 4. The actuating element 4a and the resulting receiving space 30 are dimensioned such that the actuating element 4a has some play within the receiving space 30 when the drum brake 20 is unloaded, i.e., when there is no torque transmission between the gearbox 8 and the threaded spindle 4. The actuating element 4a is designed such that when the threaded spindle 4, and thus the actuating element 4a, is rotated relative to the brake shoes 22, the brake shoes 22 are pressed radially against the brake drum 26. The actuating element 4a can therefore cause the two brake shoes 22 to spread apart within the brake drum 26.

[0037] At the same time, the brake shoes 22 have radially outward engagements 32 with respect to the axis of rotation R or the receiving space 30 for claws 34, which are connected to an output shaft of the transmission 8 indicated in Figure 1. When the claws 34 rotate relative to the brake shoes 22, they press the two brake shoes 22 together, i.e., away from the braking surface of the brake drum 26. The drum brake 20 can thus be released by a motor torque (transmitted by the transmission). Advantageously, pressing the brake shoes 22 together also creates a positive locking connection between the brake shoes 22 and the actuating element 4a of the threaded spindle 4, so that a torque exerted by the claws 34 can be transmitted to the threaded spindle 4.

[0038] The drum brake 20 is advantageously lubricated. This means that, at least during one operating state of the drum brake 20, namely during the braking process, a film of lubricant is present between the brake shoes 22 or their brake linings 28 and the brake drum 26. The use of a lubricated drum brake 20 in the linear drive 1 of Figure 1 is advantageous because it not only reduces running or braking noise and increases the service life of the brake drum 26 and / or the brake shoes 22 or their brake linings 28, but also makes the drum brake 20 insensitive to the ingress of lubricant from the adjacent gearbox 8 or the adjacent bearings 12 or the linear unit 2. Thus, there is no longer a risk that the braking effect of the drum brake 20 will unexpectedly decrease due to unwanted lubricant ingress. In this respect, the operational reliability of the linear drive 1 can be increased.

[0039] Figure 3 shows the brake drum 26 of the drum brake 20 from Figure 2. The brake drum 26 is designed like a sleeve so that the brake shoes 22, as shown in Figure 2, can be received by the brake drum 26. In Figure 3, the inner braking surface 36 of the brake drum 26 is visible, against which the brake shoes 22 are pressed radially during a braking process.

[0040] The brake drum 26 has a lubricant reservoir 40, in particular for dispensing lubricant during a braking process. In the present example, the lubricant reservoir 40 comprises several recesses in the braking surface 36, which are designed as axially extending grooves 42a.

[0041] Figure 3 also illustrates an operating method 100 for the drum brake 20 from Figure 2. According to this operating method 100, the brake drum 26 and / or the brake shoes 22 (not shown in Figure 3) or their brake linings 28 are lubricated with the lubricant. For this purpose, the axially extending grooves 42a are open towards the braking surface 36, allowing lubricant located in the grooves 42a to escape. It has been shown that lubricant located in the grooves 42a can be forced out during braking, thus making it available for lubrication. In particular, the operating heat generated by pressing the brake shoes 22 against the brake drum 26 and the forces acting upon them can cause the lubricant to escape from the grooves 42a. Consequently, lubrication advantageously occurs automatically, especially during braking.

[0042] By rotating the brake shoes 22 relative to the brake drum 26, the lubricant is distributed between the brake shoes 22 or their brake linings 28 and the brake drum 26. This is indicated by the black arrows.

[0043] When the brake shoes 22 no longer press against the brake drum 26 after the braking process, the lubricant distributed between the brake shoes 22 and the brake drum 26 can at least partially flow back into the several grooves 42a. The lubrication supply to the drum brake 20 via the lubricant reservoir 40 in the brake drum 26 is thus advantageously self-regulating.

[0044] Figure 4 shows another example of a brake drum 26 with a lubricant reservoir 40. In this example, the lubricant reservoir 40 comprises several recesses formed as bores 44 in a braking surface 36 of the brake drum 26. For the sake of clarity, only some of the bores 44 are labelled.

[0045] Figure 5 shows another example of a brake drum 26 with a lubricant reservoir 40. In this example, the lubricant reservoir 40 comprises several recesses formed as grooves 42b extending in a circumferential direction of the brake drum 26. Again, for the sake of clarity, not all of the circumferential grooves 42b are labeled with a reference numeral.

[0046] List of reference signs

[0047] Linear actuator

[0048] Linear unit

[0049] Threaded spindle and actuating element

[0050] Spindle nut

[0051] Gearbox 0 Motor 2 Bearing 4 Housing 6 Thrust tube 6a Mounting section 0 Drum brake 2 Brake shoe 4 Spring element 6 Brake drum 8 Brake lining 0 Receptacle 2 Engagement 4 Claw 6 Braking surface 0 Lubricant reservoir 2a Groove 2b Groove

[0052] 44 bore

[0053] 100 operating procedures

[0054] R axis of rotation

Claims

Patent claims 1. Brake drum (26) for a drum brake (20), with a braking surface (36) against which at least one brake shoe (22) of the drum brake (20) is radially pressed during a braking operation, and with a lubricant reservoir (40) for supplying lubricant to the braking surface (36) during the braking operation.

2. Brake drum (26) according to claim 1, wherein the lubricant reservoir (40) comprises at least one recess (42a; 42b; 44) in the braking surface (36) that can be filled with lubricant.

3. Brake drum (26) according to one of claims 1 or 2, wherein the lubricant reservoir (40) comprises at least one groove (42a; 42b) in the braking surface (36) that can be filled with lubricant.

4. Brake drum (26) according to claim 3, wherein the at least one groove (42b) extends substantially in a circumferential direction of the brake drum (26).

5. Brake drum (26) according to claim 3, wherein several grooves (42a) are provided in the braking surface (36) which extend substantially in an axial direction of the brake drum (26).

6. Brake drum (26) according to one of claims 1 to 3, wherein the lubricant reservoir (40) comprises several bores (44) that can be filled with lubricant.

7. Brake drum (26) according to one of the preceding claims, wherein the brake drum (26) is porous and the lubricant reservoir (40) comprises pores in the brake drum (26).

8. Drum brake (20), in particular for a linear drive (1), comprising a brake drum (26) and at least one brake shoe (22) rotatable relative to the brake drum (26), which presses radially against the brake drum (26) during a braking operation, wherein the brake drum (26) or the brake shoe (22) comprises a brake lining (28) and a lubricant provided for lubricating the drum brake (20) is distributed in at least one operating state of the drum brake (20) between the brake lining (28) and the brake shoe (22) or the brake lining (28) and the brake drum (26).

9. Operating method (100) for a drum brake (20), comprising a brake drum (26) and at least one brake shoe (22) rotatable relative to the brake drum, which presses radially against the brake drum (26) during a braking operation, wherein the brake drum (26) or the brake shoe (22) comprises a brake lining (28) and the brake shoe (22) and / or the brake drum (26) is lubricated with a lubricant, so that during the braking operation the lubricant is distributed between the brake lining (28) and the brake shoe (22) or the brake lining (28) and the brake drum (26).

10. Operating method (100) according to claim 9, wherein the lubricant distributed between the brake lining (28) and the brake shoe (22) or the brake lining (28) and the brake drum (26) flows back at least partially into a lubricant reservoir (40) of the brake drum (26) when the at least one brake shoe (22) no longer presses against the brake drum (26) after a braking operation.

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