Drum brake

Abstract

A drum brake (1) for a utility vehicle has a brake drum (2) which is rotatably mounted about an axis of rotation (AR), at least two brake shoes (3) which are mounted in a receiving space of the brake drum (2), an anchor plate (7) with a brake application device (4) rotationally fixedly arranged thereon with a wedge ring (41) that can be shifted on a cylinder sleeve (71) of the anchor plate (7) parallel to the axis of rotation (AR) of the brake drum (2), with which the brake shoes (3) can be pressed onto a casing inner surface of the brake drum (2) in a radial direction relative to the axis of rotation (AR) of the brake drum (2), a brake cylinder arrangement (6) rotationally fixedly arranged on the anchor plate (7) in the receiving space of the brake drum (2) for actuating the wedge ring (41), with a brake cylinder housing (61) secured on the anchor plate (7), in which a service brake unit and a parking brake unit are arranged, wherein the parking brake unit has a parking brake piston (63) that can be moved in a parking brake pressure chamber (67) and a spring element (66) which, when the parking brake pressure chamber (67) is filled with compressed air, is held in a release position by the parking brake piston (63) against a spring force of the spring element (66) and, when the parking brake pressure chamber (67) is vented, the parking brake piston (63) is pressed from a non-braking position into a braking position, wherein at least one emergency release device (5) is arranged on the anchor plate (7), with which the spring element (66) can be held in the release position even when the parking brake pressure chamber (67) is vented.

Description

[0001] 2024PF00270

[0002] drum brake

[0003] The invention relates to a drum brake according to the preamble of claim 1.

[0004] Drum brakes generally feature a cylindrical rotor with friction surfaces arranged on the inside of the rotor, also known as the brake drum. Braking force is generated by brake shoes that are pressed against the inner friction surface of the brake drum.

[0005] Current technology typically uses drum brakes for commercial vehicles, in which the applied actuating force is usually amplified by means of an S-cam to generate the necessary braking torques.

[0006] In the drum brakes of the type considered here, for example known from DE 10 2021 115 785 B3, whose force transmission is designed such that a force introduced axially to the axis of rotation is amplified by its deflection so that the reaction force acts radially on the friction surface of the brake drum, the brake shoes are pressed against by means of a wedge that is displaceable in the direction of the axis of rotation.

[0007] The force required for this is generated by a brake cylinder built into the drum brake with a service brake unit and a parking brake unit (also called a parking brake unit) by venting a service brake piston of the service brake unit with compressed air and thereby displacing the wedge parallel to the axis of rotation of the drum brake.

[0008] It is advantageous to arrange the actuating force acting on the wedge of the operating mechanism and also of the parking brake unit axially in series with the movable wedge.

[0009] Since this type of drum brake requires the parking brake to be released in emergency situations where the vehicle's own compressed air supply is unavailable, for example, during towing of a disabled vehicle, a mechanical emergency release device is needed. This device allows the legally mandated mechanically operated parking brake to be bypassed. It is important that the state set on the vehicle by the emergency release function (parking brake released or parking brake engaged) is visually identifiable.

[0010] The object of the present invention is to further develop a drum brake of the generic type in such a way that an emergency solution of the parking brake is ensured in a simple manner.

[0011] The problem is solved by a drum brake having the features of claim 1.

[0012] The drum brake according to the invention for a commercial vehicle has a brake drum rotatably mounted about an axis of rotation and at least two brake shoes mounted in a receiving space of the brake drum.

[0013] A clamping device is arranged in a rotationally fixed manner on an armature housing of the drum brake according to the invention.

[0014] The clamping device has a wedge ring that can be moved on a cylindrical sleeve of the armature housing parallel to the axis of rotation of the brake drum, with which the brake shoes can be pressed against an inner surface of the brake drum radially to the axis of rotation of the brake drum.

[0015] The drum brake further comprises a brake cylinder assembly arranged in the receiving space of the brake drum on the armature housing in a rotationally fixed manner for actuating the wedge ring, with a brake cylinder housing attached to the armature housing in which a service brake unit and a parking brake unit are arranged.

[0016] The parking brake unit has a parking brake piston movable in a parking brake pressure chamber and a spring element which, when the parking brake pressure chamber is filled with compressed air, is held in a release position by the parking brake piston against a spring force of the spring element and, when the parking brake pressure chamber is vented, pushes the parking brake piston from a non-braking position into a braking position.

[0017] The armature housing is equipped with at least one emergency release device that keeps the spring element in the released position even when the parking brake pressure chamber is vented. Such a drum brake is particularly advantageous because no special tools are required for emergency release. Furthermore, the emergency release device is captive and directly attached to the armature housing of the drum brake.

[0018] Advantageous embodiments of the invention are the subject of the dependent claims.

[0019] According to an advantageous embodiment, the emergency release device is adjustable parallel to the axis of rotation of the brake drum. This allows force to be applied directly to the spring element.

[0020] According to a further advantageous embodiment, the emergency release device has a stop that can be pressed against the spring element or a support plate arranged between the spring element and the parking brake piston.

[0021] This results in an extremely simple design for the emergency release device.

[0022] According to an advantageous embodiment, the emergency release device has a rod guided through the anchor housing, the adjusting end of which, furthest from the stop, protrudes from an end face of the anchor housing.

[0023] This allows for easy activation of the emergency release device if needed.

[0024] According to an advantageous further development, the projection of the adjusting element removed from the stop on the end face of the anchor housing differs from the projection when the emergency release device is deactivated when the emergency release device is activated.

[0025] This also ensures a simple visual check to determine whether the emergency release device is activated or not.

[0026] According to a further advantageous embodiment, the longitudinal position of at least the rod of the emergency release device is adjustable via a threaded guide in the anchor housing. Such a threaded guide allows for easy adjustment of the emergency release device while simultaneously ensuring sufficient stability of its position to counteract the spring force of the spring element.

[0027] According to another advantageous embodiment, the emergency release device is rotationally secured in both of its end positions.

[0028] This prevents the emergency release device from being unintentionally activated or deactivated.

[0029] In a preferred embodiment, the stop of the emergency release device is designed as a pressure piece molded onto the end of the rod.

[0030] According to an alternative design variant, the stop of the emergency release device is designed as a pressure profile with a lever arm projecting radially towards the spring element. This allows the emergency release device to exert force on the spring element close to the spring element.

[0031] According to an advantageous further development, the pressure profile itself is arranged to be rotationally free relative to the rod of the emergency release device and rotationally fixed relative to the anchor housing.

[0032] According to another advantageous embodiment, the drum brake has several such emergency release devices.

[0033] This reduces or avoids the risk of the emergency release devices and / or the components interacting with them becoming jammed.

[0034] Preferred embodiments are explained in more detail below with reference to the accompanying drawings. They show:

[0035] Fig. 1 shows a schematic isometric view of an embodiment of a drum brake according to the invention.

[0036] Fig. 2 is a schematic isometric view of the drum brake according to Figure 1 with the brake drum hidden.

[0037] Fig. 3 shows a schematic sectional view of the drum brake shown in Fig. 2, illustrating the emergency release device guided through the armature housing of the drum brake with a stop designed as a pressure piece in the case of a ventilated parking brake piston chamber.

[0038] Fig. 4 shows a close-up of the area around the parking brake unit of the drum brake shown in Figure 3 with the parking brake piston chamber vented and the emergency release device not activated.

[0039] Fig. 5 shows another schematic sectional view of the drum brake shown in Fig. 2 with a ventilated parking brake piston chamber and activated emergency release device.

[0040] Fig. 6 shows a sectional view of the drum brake corresponding to Figure 3, illustrating the emergency release device guided through the armature housing of the drum brake with a stop designed as a pressure profile in the case of a ventilated parking brake piston chamber.

[0041] Fig. 7 shows a schematic isometric view of the stop designed as a pressure profile,

[0042] Fig. 8 shows a sectional view of the pressure profile shown in Fig. 7.

[0043] Fig. 9 shows a schematic isometric single view of an emergency release device with adapter piece for attaching the pressure profile and

[0044] Fig. 10 is a schematic isometric single view of an emergency release device with a stop molded onto the rod and designed as a pressure piece.

[0045] In the following figure descriptions, terms such as top, bottom, left, right, front, rear, etc., refer exclusively to the exemplary representation and position of the drum brake, brake drum, brake cylinder assembly and its components, emergency release device, and the like, as chosen in the respective figures. These terms are not to be understood as restrictive; that is, these references may change due to different working positions, mirror-symmetrical design, or similar factors.

[0046] In Figure 1, reference numeral 1 designates an embodiment of a drum brake according to the invention, particularly for use on a commercial vehicle. The drum brake 1 has a brake drum 2 rotatably mounted about an axis of rotation AR, which is connected via an armature housing 7 to a hub of a wheel axle (not shown).

[0047] As shown in Figure 2, several brake shoes 3, each with a friction lining 31, are arranged in a receiving space within the brake drum 2. The brake shoes 3 are arranged with their friction linings 31 facing an inner surface of the brake drum 2.

[0048] A clamping device 4 with a wedge ring 41 which is displaceable on a cylindrical sleeve 71 of the anchor housing 7 parallel to the axis of rotation AR of the brake drum 2, is arranged on the anchor housing 7, with which the brake shoes 3 can be pressed against the inner surface of the brake drum 2, which is designed as a friction surface, radially to the axis of rotation AR of the brake drum 2 (direction r shown in Figure 1).

[0049] To transmit the movement of the wedge ring 41 to the brake shoes 3, a pressure wedge is arranged on one side of a (not shown) friction lining carrier facing away from the friction lining 31, as part of each brake shoe 3. The pressure wedge is connected to the friction lining carrier via a pressure piston.

[0050] The basic operating principle of the wedge ring 41 for moving the brake shoes is described in detail, for example, in WO 2022 / 263324 A1.

[0051] The wedge ring 41 can be moved from a non-braking position to a braking position via a service brake piston 62 of a brake cylinder arrangement 6 parallel to the axis of rotation AR of the brake drum 2.

[0052] Between the wedge ring 41 and the pressure wedge of the brake shoes 3, a slide 42 with several rolling elements 43 is arranged to reduce friction between the pressure surface of the wedge ring 41 and the pressure wedge of the brake shoes 3.

[0053] The brake cylinder assembly 6, as part of the clamping device 4, serves to carry out the radial pressing movement of the brake shoes 3 against the inner surface of the brake drum 2. As shown in Figures 3 to 6, the brake cylinder assembly 6 has a housing 61 that is fixedly attached to the armature housing 7 in the receiving space of the brake drum 2.

[0054] Relative to this housing 61, the service brake piston 62 is arranged to be displaceable parallel to the axis of rotation AR of the brake drum 2.

[0055] Furthermore, the brake cylinder arrangement 6 has a parking brake piston 63 which is displaceable relative to the housing 61 parallel to the axis of rotation AR of the brake drum 2 and which can be acted upon by the spring force of a spring element 66 preferably designed as a disc spring via a support plate 65.

[0056] The brake cylinder assembly 6 also has several plungers 64 which serve to transmit a movement of the parking brake piston 63 to the service brake piston 62.

[0057] Furthermore, compressed air inlets are provided, which lead firstly into a service brake pressure chamber 68 between the housing 61 and the service brake piston 62 and secondly into a parking brake pressure chamber 67 between the housing 61 and the parking brake piston 63.

[0058] The movement of the service brake piston 62 is always important for the actuation of the brake shoes 3; this movement is effected by supplying compressed air to the service brake pressure chamber 68 in the case of an intended reduction in the speed of the commercial vehicle, a so-called service braking process.

[0059] In the event of an intended locking of the brake, which serves to prevent the commercial vehicle from unintentionally rolling away in a parked situation, compressed air present in the parking brake pressure chamber 67 during ferry operation is released from the parking brake pressure chamber 67, which results in a displacement of the parking brake piston 63 in the direction of the service brake piston 62, as is shown by way of example in Figure 4.

[0060] The displacement is caused by the force exerted by the spring element 66 on a rear side of the parking brake piston 63 facing away from the service brake piston 62.

[0061] As further shown in Figures 3 to 6, the service brake piston 62 of the brake cylinder arrangement 6 is sealed on both sides against the housing 61 by seals 69 in order to seal the service brake pressure chamber 68 airtight.

[0062] Furthermore, the parking brake piston 63 is also sealed relative to the housing 61 by seals 69 in order to also seal the parking brake pressure chamber 67 airtight.

[0063] In order to release the parking brake in the event of a failure of the vehicle's own compressed air supply, at least one emergency release device 5 is arranged on the anchor housing 7, with which the spring element 66 can be held in the release position even when the parking brake pressure chamber 67 is vented.

[0064] The arrangement of the at least one emergency release device 5 on the anchor housing 7 can be implemented on an inner or outer surface of the anchor housing 7 or, as shown for example in Figure 3, in a bore provided for this purpose in the anchor housing 7.

[0065] The released position of the spring element 66, as shown in Figures 3, 5 and 6, is the tensioned position of the spring element 66.

[0066] In order to achieve this tensioned position of the spring element 66 despite the lack of compressed air in the parking brake pressure chamber 67, the emergency release device 5 is designed to be adjustable parallel to the axis of rotation AR of the brake drum 2 in the embodiment variants shown in Figures 3 to 6.

[0067] The embodiments of the emergency release device 5 shown in Figures 3 to 10 each have a rod 51 guided through the anchor housing 7, the adjusting end 52 of which, furthest from the stop, protrudes from an end face 72 of the anchor housing 7, as shown, for example, in Figure 3, Figure 5 and Figure 6.

[0068] As further shown in Figure 2, more than one emergency release device 5 is preferably used on the drum brake 1 to prevent the spring element 66 or the support plate 65 from tilting when the parking brake is released.

[0069] The embodiment shown in Figure 2 for the drum brake 1 has, by way of example, three such emergency release devices 5, which, to activate the emergency release, are preferably moved alternately and successively incrementally in the direction of the spring element 66 and in the direction of the support plate 65, respectively. The three emergency release devices 5 are preferably arranged at approximately equal angular intervals along the armature housing 7.

[0070] As a comparison of Figures 3 and 5 shows, an oil protrusion of the adjusting element 52, removed from the stop, from the end face 72 of the anchor housing 7 is clearly different from an oil protrusion when the emergency release device 5 is activated.

[0071] In the embodiment shown in Figures 3 and 5, the excess oil is greater when the emergency release device 5 is deactivated (shown in Figure 3) than when the emergency release device 5 is activated (shown in Figure 5).

[0072] It is also conceivable, for example in the case of a transmission of force to the spring element 66 via a lever mechanism, that the oil protrusion of the adjusting element 52 from the end face 72 of the anchor housing 7 is smaller when the emergency release device 5 is deactivated than when the emergency release device 5 is activated.

[0073] Furthermore, preferably a cover plate 8 with openings 81 for the passage of the emergency release devices 5 is placed on an end face 72 of the anchor housing 7, from which the adjusting end 52 of the emergency release device 5 or the adjusting ends 52 of the emergency release devices 5 protrude, as shown in Figure 2.

[0074] The longitudinal position of the rod 51 of the emergency release device 5 is preferably adjustable via a threaded guide 73 in the anchor housing 7.

[0075] For this purpose, the rod 51 of the emergency release device 5 preferably has a thickened area 53 near its adjusting end 52 via a step, which is at least partially provided with an external thread that can be screwed into the threaded guide 73 in the anchor housing 7.

[0076] When the emergency release device 5 is activated, the stop preferably presses against a support plate 65 arranged between the spring element 66 and the parking brake piston 63. In turn, when the support plate 65 moves parallel to the axis of rotation AR of the brake drum 2, it presses the spring element 66 against its spring force into its release position. In one embodiment shown in Figures 3 to 5 and 10, the stop is designed as a pressure piece 54 integrally formed at the end of the rod 51.

[0077] Alternatively, it is also conceivable to design the stop of the emergency release device 5 as a pressure profile 9, as shown in Figures 7 and 8, with a lever arm 91 projecting radially in the direction of the spring element 66.

[0078] The pressure profile 9 is preferably arranged to be rotationally free relative to the rod 51 of the emergency release device 5 and rotationally fixed relative to the anchor housing 7.

[0079] As further shown in Figures 7 to 9, an adapter piece 55 is formed on the end remote from the adjusting end 52 of the emergency release device 5 to fix the pressure profile 9, which can be fixed into a receptacle 93 provided for this purpose in an adapter receiving piece 92 of the pressure profile 9.

[0080] The lever arm 91 of the pressure profile 9 makes it possible to place the point of force application for emergency solutions closer to the interface of the spring element 66 to the parking brake piston 63, which allows for a more compact design as well as a weight reduction of the support plate 65.

[0081] Even with spring elements 66 that are preferably designed as disc springs and have a smaller outer diameter, such a variant offers the possibility of placing the point of force application directly onto the spring element 66.

[0082] To prevent unintentional activation or deactivation of the emergency release device 5, the emergency release device 5 is preferably held in its two end positions in a rotationally secured manner on the armature housing 7 of the drum brake 1.

[0083] The differently dimensioned projection di. of the adjusting element 52 of the emergency release device 5 from the stop, when the emergency release is activated or deactivated, allows for a simple visual check to determine whether the emergency release device 5 is activated or whether the vehicle is in a ready-to-drive state with the emergency release device 5 deactivated. Reference numeral list

[0084] 1 drum brake

[0085] 2 brake drums

[0086] 3 brake shoes

[0087] 31 Friction lining

[0088] 4 Clamping device

[0089] 41 Wedge ring

[0090] 42 sleds

[0091] 43 rolling elements

[0092] 5 Emergency release device

[0093] 51 bars

[0094] 52 adjustable

[0095] 53 thickened piece

[0096] 54 Print profile

[0097] 55 Adapter piece

[0098] 6 brake cylinder arrangement

[0099] 61 Brake cylinder housing

[0100] 62 service brake pistons

[0101] 63 Parking brake pistons

[0102] 64 pestles

[0103] 65 backing plates

[0104] 66 Spring element

[0105] 67 Parking brake pressure chamber

[0106] 68 Service brake pressure chamber

[0107] 69 Seal

[0108] 7 Anchor housing

[0109] 71 Cylinder sleeve

[0110] 72 Front surface

[0111] 73 Thread guide

[0112] 8 Cover element 81 Opening

[0113] 9 Print profile

[0114] 91 Lever arm 92 Adapter mounting piece

[0115] 93 recording

[0116] AR Rotation Axis

[0117] U Circumferential direction of the brake drum r Direction z Direction di. Protrusion

Claims

Claims 1. Drum brake (1 ) for a commercial vehicle, comprising - a brake drum (2) rotatably mounted about an axis of rotation (AR), - at least two brake shoes (3) mounted in a receiving space of the brake drum (2), - an anchor housing (7) with a clamping device (4) arranged thereon in a rotationally fixed manner and with a wedge ring (41) which is displaceable on a cylindrical sleeve (71) of the anchor housing (7) parallel to the axis of rotation (AR) of the brake drum (2), with which the brake shoes (3) can be pressed against an inner surface of the brake drum (2) radially to the axis of rotation (AR) of the brake drum (2), - a brake cylinder assembly (6) arranged in the receiving space of the brake drum (2) on the anchor housing (7) in a rotationally fixed manner for actuating the wedge ring (41), with a brake cylinder housing (61) attached to the anchor housing (7) in which a service brake unit and a parking brake unit are arranged, - wherein the parking brake unit comprises a parking brake piston (63) movable in a parking brake pressure chamber (67) and a spring element (66) which, when the parking brake pressure chamber (67) is filled with compressed air, is held in a release position by the parking brake piston (63) against a spring force of the spring element (66) and, when the parking brake pressure chamber (67) is vented, pushes the parking brake piston (63) from a non-braking position to a braking position, characterized in that - at least one emergency release device (5) is arranged on the anchor housing (7) with which the spring element (66) can be held in the release position even when the parking brake pressure chamber (67) is vented.

2. Drum brake (1 ) according to claim 1 , characterized in that the emergency release device (5) is designed to be adjustable parallel to the axis of rotation (AR) of the brake drum (2).

3. Drum brake (1 ) according to claim 1 or 2, characterized in that the emergency release device (5) has a stop which can be pressed against the spring element (66) or a support plate (65) arranged between the spring element (66) and the parking brake piston (63).

4. Drum brake (1 ) according to claim 3, characterized in that the emergency release device (5) has a rod (51) guided through the armature housing (7), the adjusting end (52) of which, furthest from the stop, protrudes from an end face (72) of the armature housing (7).

5. Drum brake (1 ) according to claim 4, characterized in that a projection (di.) of the adjusting element (52) located away from the stop from the end face (72) of the armature housing (7) when the emergency release device (5) is deactivated differs from a projection (di.) when the emergency release device (5) is activated.

6. Drum brake (1 ) according to one of the preceding claims, characterized in that the longitudinal position of at least the rod (51) of the emergency release device (5) is adjustable via a threaded guide (73) in the armature housing (7).

7. Drum brake (1 ) according to one of the preceding claims, characterized in that the emergency release device (5) is rotationally secured in its two end positions.

8. Drum brake (1 ) according to one of the preceding claims, characterized in that the stop of the emergency release device (5) is designed as a pressure piece (54) formed on the end of the rod (51 ).

9. Drum brake (1 ) according to one of claims 1 to 7, characterized in that the stop of the emergency release device (5) is designed as a pressure profile (9) with a lever arm (91) projecting radially in the direction of the spring element (66).

10. Drum brake (1 ) according to claim 9, characterized in that the pressure profile (9) is arranged rotationally free to the rod (51 ) of the emergency release device (5) and rotationally fixed to the anchor housing (7).

11. Drum brake (1) according to one of the preceding claims, characterized in that several emergency release devices (5) are arranged on the armature housing (7).

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