DE102015103643B4 - drum brake - Google Patents

Abstract

Drum brake designed as an expanding wedge brake with two brake shoes (3A, 3B) pivotably mounted on a brake carrier (1) which can be expanded against a brake drum (2), in which the two brake shoes (3A, 3B) can be expanded away from one another by a respective piston (11, 12), wherein the pistons (11, 12) are guided in an expansion housing (10) and are supported at their ends facing away from one another against the respective brake shoe (3A, 3B) and at their ends facing one another against pressure transmission rollers (37A, 37B), between which an expanding wedge (30) is arranged which can be moved transversely to the direction of movement of the pistons, and wherein the pressure transmission rollers (37A, 37B) are arranged so as to be rotatable in a roller carrier (35), and that the roller carrier (35) is movable on the expanding wedge in the longitudinal direction of the expanding wedge (30) is arranged, and wherein both pressure transmission rollers (37A, 37B) are arranged in a common roller carrier (35), characterized in that the expanding wedge (30) is guided so as to be longitudinally movable via support rollers (41 - 44) which are rotatably mounted in the roller carrier (35), wherein the support rollers (41 - 44) are simultaneously supported against the expanding housing (10) and against a rail (40) formed on the expanding wedge (30) and extending in the longitudinal direction of the expanding wedge.

Description

The invention relates to a drum brake designed as an expanding wedge brake, as is usually used as a vehicle brake.

From the WO95/12769 A1 A drum brake is known in which two brake shoes are pivotally mounted on the brake carrier of the drum brake in a largely symmetrical design, each of which can be spread away from one another and against the brake drum by a piston. The pistons, which are arranged in alignment with one another in bores of an expansion housing, are supported at their outer ends against the respective brake shoe, whereas the inner ends of the pistons facing one another are designed as a rolling surface for a pressure transmission roller each. The pressure transmission rollers are arranged on either side of an expansion wedge that can be moved transversely to the direction of movement of the pistons. The expansion wedge, in turn, is located at the end of a pressure rod that is acted upon outside the brake housing by a suitable force element, e.g. a compressed air cylinder. When the force element is activated, the expansion wedge slides between the pressure transmission rollers so that they exert an outward pressure on the two pistons, and the brake shoes are brought into contact with the brake drum. Such a drum brake is therefore also called a wedge brake.

The WO95/12769 A1 The spreading device described works with very little friction, which is mainly due to the two pressure transfer rollers, which carry out a pure rolling movement to spread the brake shoes. To ensure a slip-free rolling movement of the pressure transfer rollers, the drum brake is designed according to the WO95/12769 A1 An additional guide roller is provided, which is supported on the one hand against a rolling surface on the brake carrier and on the other hand against a rolling surface on the expanding wedge, whereby this rolling surface extends exactly in the longitudinal direction of the expanding wedge. The additional guide roller helps to ensure the precise rolling of the two pressure transmission rollers, which is important for the functioning of the expanding wedge brake.

From the US 258793 A , GB1101701A , GB314607A , EP0181004A1 , DE 2631704 A1 , US 5443135 A and DE 1625699 A Various types of drum brakes are known. From the DE 3308356 A1 A drum brake designed as an expanding wedge brake with the features of the preamble of claim 1 is known.

The aim of the invention is to create a reliably functioning drum brake designed as an expanding wedge brake. For this purpose, a drum brake is proposed which has the features specified in patent claim 1.

The aim is to achieve a reproducible, precise rolling or rolling of the pressure transmission rollers of the spreading mechanism at all times in order to keep the frictional forces occurring during pressure transmission low and the efficiency of the drum brake high.

For this purpose, in one embodiment of the drum brake, the two brake shoes can be spread apart from one another by a piston each, the pistons being guided in a spreading housing and supported at their ends facing away from one another against the respective brake shoe and at their ends facing one another against pressure transmission rollers, between which a spreading wedge is arranged that can be moved transversely to the direction of movement of the pistons, the pressure transmission rollers being arranged in a roller carrier so that they can rotate, and the roller carrier being arranged on the spreading wedge so that it can move in the longitudinal direction of the spreading wedge.

It is advantageous that both pressure transfer rollers are arranged in a common roller carrier, as this ensures that both pressure transfer rollers work synchronously and unfavorable transverse forces on the expanding wedge are avoided.

According to the invention, the expansion wedge is guided in a longitudinally movable manner via support rollers that are pivotally mounted in the roller carrier, the support rollers being supported simultaneously against the expansion housing and against a rail formed on the expansion wedge and extending in the longitudinal direction of the expansion wedge. Preferably, at least one first support roller is supported against the rail from one side and at least one second support roller from the other side.

The support rollers can each be pivotally mounted in slots or grooves in the roller carrier, with the slots or grooves being open towards the rail and closed at the other end. This leads to an advantageous solution in terms of assembly, since the support rollers can be inserted in the longitudinal direction of the slots or grooves during assembly, but they cannot come out of the slots or grooves again during operation, since they are then secured by the rail formed on the expansion wedge.

The installation can be further simplified if the slots or grooves slope upwards towards the rail. In this design, the support rollers are held in the elongated holes or grooves by gravity or their own weight during the assembly process, before they are secured by the rail formed on the expanding wedge after assembly is completed.

In another embodiment of the drum brake, the expanding wedge has a first longitudinal section with a first wedge angle and at least one further longitudinal section with a further wedge angle that is different from the first wedge angle, with the narrower of the two longitudinal sections having the larger wedge angle. This embodiment makes it possible to increase the braking torque build-up of the expanding wedge brake with increasing actuation stroke. If a compressed air-operated diaphragm cylinder serves as the force element of the expanding wedge brake, the design of the expanding wedge with at least two longitudinal sections ensures that the force characteristic of the diaphragm cylinder, which drops with a larger stroke, is counteracted accordingly.

• - eine Druckscheibe mit einer daran ausgebildeten Druckfläche zur Anlage der jeweiligen Druckübertragungsrolle,
• - ein an der Druckscheibe in Spreizrichtung abgestütztes und um die Spreizachse verdrehbares äußeres Schraubelement,
• - und ein mit dem äußeren Schraubelement über ein Schraubgewinde verbundenes inneres Schraubelement, gegen das die jeweilige Bremsbacke abgestützt ist.

According to another embodiment as a wedge brake, components of each piston are:

• - a pressure disc with a pressure surface formed thereon for the application of the respective pressure transfer roller,
• - an outer screw element supported on the pressure disc in the expansion direction and rotatable about the expansion axis,
• - and an inner screw element connected to the outer screw element via a screw thread, against which the respective brake shoe is supported.

In another advantageous embodiment, measures are taken to reset the adjustment device. A reset takes place, for example, after replacing worn brake shoes with new ones. A design in which at least one of the two outer screw elements is provided with a toothing for the engagement of a pinion is advantageous. A reset device designed in this way is not only suitable for use in wedge brakes, but also for use in other drum brake types, and also for disc brakes.

Preferably, only one of the two pistons is provided with elements of an adjustment device integrated therein to compensate for brake shoe wear, wherein the adjustment device is designed to rotate the outer screw element about the expansion axis.

If the elements of the adjustment device are only implemented on one of the two pistons, an arrangement for the same or opposite rotational synchronization of the outer screw element of the piston having the elements of the adjustment device with the outer screw element of the other piston is particularly advantageous. This synchronization leads to a structural simplification, since the same adjustment of the other brake shoe can also be achieved with a single adjustment device. Preferably, a component of the arrangement for the same or opposite rotational synchronization is a transmission shaft, which simultaneously engages with gears formed on the two outer screw elements. The axis of rotation of the transmission shaft can be arranged either parallel to the expansion axis or at a right angle to the expansion axis.

For the adjustment device, a design is advantageous in which a component of the adjustment device is an adjusting bush which is mounted in the piston guide so as to be longitudinally and rotationally movable, wherein the adjusting bush can be moved longitudinally by the outer screw element and/or by the pressure disk and can be set in a superimposed rotation about the expansion axis.

Preferably, in order to set the adjusting bushing into the superimposed rotation, it is provided with a helical structure which engages with a counter-structure arranged on the piston guide.

In another embodiment of the drum brake, a device for optical display and thus easy detection of brake shoe wear is provided. This device comprises a shaft which is rotatably mounted on the brake carrier at right angles to the spreading axis or the spreading direction, on which a driver arm is arranged on a first longitudinal section of the shaft, which is coupled in movement to one of the brake shoes, and on a second longitudinal section of the shaft, which is located outside the brake carrier, a pointer protruding radially from the shaft. In this embodiment, the wear that has occurred on the brake shoes can be very easily checked from the outside. For example, the brake shoe can be provided with a slot arranged essentially transversely to the spreading axis, into which a pin formed on the driver arm and extending parallel to the shaft engages.

In another embodiment of the drum brake, each brake shoe consists of a curved brake pad carrier and two brake shoe webs supporting it on its inside. To absorb the transmitted spreading force, a pressure piece is placed between the two brake pads. ck webs and detachably connected to both brake shoe webs. This design of the drum brake enables easy replacement of the pressure piece, which is itself subject to wear, which is why the pressure piece should preferably be replaceable together with the friction linings.

An advantageous fastening or connection is characterized by a bolt which leads through a hole in the pressure piece and through openings in the brake shoe webs that are aligned therewith. Preferably, projections are formed on the pressure piece, offset from the bolt, which protrude into recesses in the brake shoe webs in such a way that a positive connection is achieved between the projections and recesses in the circumferential direction of the bolt.

• 1 in perspektivischer Darstellung das eine Ende einer Fahrzeugachse mit einer als Spreizkeilbremse gestalteten und zwei Bremsbacken aufweisenden Trommelbremse, und zwar bei abgenommener Bremstrommel;
• 2a einen Schnitt durch den Spreizmechanismus der Fahrzeug-Trommelbremse;
• 2b einen anderen Schnitt durch den Spreizmechanismus der Fahrzeug-Trommelbremse;
• 2c einen weiteren Schnitt durch den Spreizmechanismus der Fahrzeug-Trommelbremse;
• 3a einen in dem Spreizmechanismus verwendeten Spreizkeil mit einem auf den Spreizkeil aufgesetzten Rollenträger;
• 3b Spreizkeil und Rollenträger getrennt voneinander;
• 4 einen Längsschnitt durch den Spreizkeil;
• 5a in einer Teilansicht der Trommelbremse den Bereich zwischen Spreizeinrichtung und Bremsbacke einschließlich einer Einrichtung zur Anzeige des Bremsbelagverschleißes, wobei kein Abdeckblech montiert ist;
• 5b die Teilansicht nach 5a bei montiertem Abdeckblech;
• 6a in perspektivischer Darstellung eine der beiden Bremsbacken der Trommelbremse;
• 6b die Bremsbacke nach 6a in einer Explosionsdarstellung;
• 7a eine andere Variante einer der beiden Bremsbacken der Trommelbremse;
• 7b die Bremsbacke nach 7a in einer Explosionsdarstellung;

Further details and advantages emerge from the following description of embodiments of a drum brake and with reference to the drawings. In them:

• 1 in perspective view, one end of a vehicle axle with a drum brake designed as an expanding wedge brake and having two brake shoes, with the brake drum removed;
• 2a a cross-section through the spreading mechanism of the vehicle drum brake;
• 2 B another cross-section through the spreading mechanism of the vehicle drum brake;
• 2c another section through the spreading mechanism of the vehicle drum brake;
• 3a an expanding wedge used in the expanding mechanism with a roller carrier mounted on the expanding wedge;
• 3b Expanding wedge and roller carrier separated from each other;
• 4 a longitudinal section through the expanding wedge;
• 5a in a partial view of the drum brake, the area between the spreading device and the brake shoe including a device for indicating brake pad wear, with no cover plate mounted;
• 5b the partial view after 5a with cover plate mounted;
• 6a in perspective view one of the two brake shoes of the drum brake;
• 6b the brake shoe after 6a in an exploded view;
• 7a another variant of one of the two brake shoes of the drum brake;
• 7b the brake shoe after 7a in an exploded view;

The drum brake described below in the preferred design of a wedge brake is preferably used as a compressed air-operated wheel brake in commercial vehicles and in particular in commercial vehicle trailers.

A first brake shoe 3A and a second brake shoe 3B are movably mounted on a brake carrier 1 mounted on a vehicle axle 1A. For this purpose, one end of the brake shoes 3A, 3B are pivotally mounted on bearing pins 4 that are firmly attached to the brake carrier 1, while the other ends of the brake shoes 3A, 3B can be spread apart from one another by means of a spreading mechanism, so that the brake shoes 3A, 3B press against the cylindrical braking surface 6 ( 5a) the brake drum 2 and thus absorb the braking torque. Each brake shoe usually consists of a curved carrier and the friction lining attached to the outside.

According to the 2a - 2c The spreading device of the drum brake here consists, among other things, of a spreading housing 10 rigidly attached to the brake carrier, two pistons 11, 12 arranged therein so as to be movable along the spreading axis S, and a spreading wedge 30 which is movable transversely to the spreading axis S. The spreading wedge 30 is located at the end of a push rod 29, against which a force element arranged outside the brake carrier 1 works. The force element is preferably a compressed air-operated brake cylinder 5 ( 1 ), the cylinder housing of which is screwed to the brake carrier 1 or to the expansion housing, and the actuating rod of which works axially against the push rod 29.

To introduce the braking force, the expanding wedge 30 moves into the gap between the two pistons 11, 12, whereby the pistons 11, 12 are moved away from each other on the expanding axis S, and the brake shoes 3A, 3B are pushed outwards against the brake drum 2 ( 5a) reach.

The two pistons 11, 12 are each guided in cylindrically designed piston guides 11A, 12A of the expansion housing 10. Components of each piston 11, 12 are a pressure disk 14 with a pressure surface 13 formed thereon, against which the expansion wedge 30 works, an outer screw element 17A, 17B supported on the pressure disk 14 in the expansion direction and rotatable about the expansion axis S, and an inner screw element 18 connected to the outer screw element 17A, 17B via a screw thread 20, against which the respective brake shoe 3A, 3B is supported.

The inner screw element 18 is designed towards the respective brake shoe as a radially expanded pressure piece 19, which is provided with a slot 21. The respective brake shoe 3A, 3B is supported on the bottom of this slot 21, whereby the inner screw element 18 is secured against rotation about the expansion axis S. The outer screw element 17A or 17B, which is connected to the inner screw element 18 via the screw thread 20, can rotate about the expansion axis S.

The thrust washer 14, in turn, is seated non-rotatably in the respective piston guide 11A, 12A, and is supported axially against the outer screw element 17A or 17B via a low-friction bearing washer.

The pressure disks 14 are not supported directly against the expanding wedge 30, but indirectly via pressure transfer rollers 37A and 37B arranged between them. The pressure transfer rollers 37A, 37B are cylindrical. On the one hand, they roll on wedge-shaped expanding surfaces 31, 32 of the expanding wedge 30 ( 3b) , and on the other hand on pressure surfaces 13 of the pressure disks 14, which are preferably arranged inclined to the spreading axis S, whereby the spreading device operates with the lowest possible friction.

According to 4 , which shows a longitudinal section through the expanding wedge 30, the expanding wedge has two different wedge angles. On a first longitudinal section L1, the expanding wedge has a wedge angle W1, and on a second, narrower longitudinal section L2, a wedge angle W2, with the narrower longitudinal section L2 having the larger wedge angle W2. This design counteracts the force characteristic of the brake cylinder, which drops with a larger stroke.

According to 3a and 3b the two pressure transfer rollers 37A, 37B are arranged in a common roller carrier 35, which is arranged to be longitudinally movable relative to the expansion wedge 30. For this purpose, the roller carrier 35 is guided to be longitudinally movable relative to the expansion wedge 30 via support rollers 41 - 44. The pressure transfer rollers 37A, 37B are seated in longitudinal roller guides 38 of the roller carrier and are thus guided on the roller carrier 35 in the expansion direction S.

On two opposite sides of the expansion wedge 30 there are rails 40 which are supported by the support rollers 41 - 44 against the roller supports 35, which are made in one piece and preferably from formed sheet steel. The rails 40 are preferably made in one piece with the expansion wedge 30. On the other hand, the support rollers 41 - 44 are also supported on running surfaces of the expansion housing 10, so that the expansion wedge 30 is guided in the expansion housing 10 without any significant lateral play.

Of the support rollers 41 - 44 arranged in pairs, one support roller 41, 42 is supported against the rail 40 from one side and the other support roller 43, 44 from the other side.

In an alternative not shown in the drawing, each support roller 41 - 44 is pivotally mounted in a slot or groove of the roller carrier 35. The slots or grooves are each open towards the rail 40. At their other end they are closed by a semicircular bearing shell. The fact that the slots or grooves are open on one side leads to an advantageous solution in terms of assembly, since the support rollers 41 - 44 can be inserted in the longitudinal direction of the slots or grooves when assembling the expanding wedge brake, but they cannot emerge from these slots or grooves again after assembly has been completed, since they are prevented from doing so by the rail 40 formed on the expanding wedge 30.

It is advantageous if the elongated holes or grooves run at an angle towards the rail 40. This design means that the support rollers 41 - 44 are held in the elongated holes or grooves by gravity or by their own weight as long as the roller carrier 35 is not yet placed on the expanding wedge 30 or the push rod 29, before their securing by the rail 40 is ensured after assembly is completed.

The support rollers 41 - 44 have the task of limiting the movement of the expansion wedge 30 in the expansion direction S by resting on and rolling against the running surfaces of the expansion housing 10. In this way, an asymmetry of the braking force transmitted by the two brake shoes is avoided.

The roller carrier 35 consists of a metal sheet which, as a result of punching and bending processes, is formed as a cage which receives and rotatably supports the individual rollers 37A, 37B, 41, 42, 43, 44.

The wedge brake described here has an integrated adjustment device 50. To adequately compensate for the wear on the friction linings that occurs over time, it is sufficient if only one of the two pistons 11, 12 is provided with structurally integrated elements of the adjustment device 50. In the embodiments, this is the one shown in the 2a - 2c right-hand piston 12.

The adjustment device 50 is designed to rotate the outer screw element 17A of the piston 12 about the expansion axis S and thus to successively unscrew the inner screw element 18 via the screw thread 20 in accordance with the increasing lining wear.

In addition to the outer screw element 17A, the adjusting device 50 includes an adjusting bush 51, a star disk 53, a one-way clutch 55 and an overload clutch 59. All of these parts are combined in the piston 12 and are located within the cylindrical piston guide 12A.

In the piston 12, the right outer screw element 17A is made up of a radially expanded collar 27 and a slimmer section 28 screwed to the inner screw element 18, which has a cylindrical outer surface. The adjusting bushing 51 is supported axially against the collar 27, i.e. in the direction of the expansion axis S. The adjusting bushing 51 is mounted in the piston guide 12A so that it can move longitudinally and rotationally. The adjusting bushing 51 is provided on its outer circumference with a helical groove into which a pin or pin 58 arranged in a fixed position on the expansion housing 10 engages. In this way, a longitudinal movement of the adjusting bushing 51 is always superimposed by a rotational movement about the axis S.

The star disk 53 is connected to the adjusting bushing 51 in the axial direction. The star disk 53 is spring-loaded from the other side and is connected to the adjusting bushing 51 via a type of claw coupling. The claw coupling works in the circumferential direction with a fixed play, i.e. turning the adjusting bushing 51 does not immediately and directly lead to an equal rotation of the star disk 53, but only after the preset play has been passed through.

The one-way clutch 55 is arranged coaxially between the adjusting bush 51 and the cylindrical section of the screw element 17A. This operates as a freewheel in one direction of rotation and locks in the other direction of rotation. The one-way clutch 55 is supported axially against the radially inner area of the star disk 53. However, this support is not direct, but rather indirect with the interposition of an overload clutch 59 composed of a large number of balls. The overload clutch 59 transfers low torques from the star disk 53 to the one-way clutch 55 without slipping. At higher torques, however, slippage occurs at the overload clutch, i.e. relative rotation.

With the adjustment device 50 according to the 2a - 2c the adjusting bushing 51 is axially supported against the outer screw element 17A. Alternatively, it is possible for the adjusting bushing 51 to be axially supported against the thrust washer 14.

Since the adjustment device 50 is only arranged in one piston 12, synchronization is required in order to achieve an equal adjustment of the other piston 11. The rotation synchronization is carried out by a transmission shaft 65 ( 2 B) , which simultaneously engages with the teeth 60 formed on the outside of the two screw elements 17A, 17B. In the embodiment described here, the axis of rotation D of the transmission shaft 65 is parallel to the spreading axis S. Alternatively, it is also possible to arrange the axis of rotation of the transmission shaft at right angles to the spreading axis S.

The transmission shaft 65 also serves to carry out the reset. Measures have been taken to reset the adjustment device 50. This reset takes place after replacing worn brake shoes 3A, 3B with new brake shoes.

For the purpose of resetting, one of the two screw elements 17A or 17B is prepared for the engagement of a pinion 70 ( 2c ). The pinion 70 is designed such that it can engage with the teeth 60 of the screw element 17A.

To reset the drum brake, the pinion 70 is moved axially against a spring force until the pinion 70 engages with the teeth 60 of the screw element 17A and is then rotated.

According to 5a , 5b the drum brake has a device 80 for indicating brake pad wear. The device 80 comprises a shaft 81 which is rotatably mounted on the brake carrier 1 at right angles to the spreading direction S and on which a driver arm 86 is arranged on a first longitudinal section of the shaft, which is coupled in motion to the brake shoe 3A or 3B, and on a second longitudinal section of the shaft lying outside the brake carrier 1, a pointer 83 protruding radially from the shaft 81 is arranged. The pointer 83 is assigned a scale 85 on the outside of a cover plate 88 which covers the brake on the inside and is attached to the brake carrier 1. The pointer 83 is therefore already located outside this cover plate 88. Since the pointer 83 is therefore also located outside the drum brake, the wear that has occurred on the brake shoe can be very easily checked from the outside.

To drive the shaft and the pointer 83, the brake shoe is provided with a slot 84 arranged approximately transversely to the spreading axis S, into which a pin formed on the driver arm 86 and extending parallel to the shaft 81 engages.

In the 6a , 6b It is shown how each of the two brake shoes 3A, 3B of the drum brake is composed of a curved brake pad carrier 101, which carries the friction lining on the outside, and of two brake shoe webs 102 supporting the brake pad carrier 101 on its inside. To absorb the spreading force transmitted by the respective piston 11 or 12, an exchangeable pressure piece 105 is arranged between the two brake shoe webs 102 and is detachably connected to both brake shoe webs 102. The pressure piece 105 can be provided with a molded web 120. The web 120 then engages in the slot 21 on the pressure piece 19 ( 2a) so that the inner screw element 18 cannot twist when the brake shoe 3A or 3B is mounted. The pressure piece 105 therefore secures the screw element 18 against twisting.

For this detachable connection, a bolt 110 is provided which leads through a cylindrical bore 112 in the pressure piece 105 and through aligned, round openings 113 in the brake shoe webs 102.

For a simple but precise attachment of the pressure piece 105 to the brake shoe, projections 116 are formed on the pressure piece 105, offset from the bolt 110. The projections 116 protrude into recesses 117 on or in the brake shoe webs 102 in such a way that a positive engagement of the projections 116 in the recesses 117 is achieved in the circumferential direction of the bolt 110. In this way, no relative movements of the pressure piece 105 in relation to the two brake shoe webs 102 are possible, but the pressure piece 105 can still be replaced quickly and easily by removing just the individual bolt 110. The pressure piece 105 is subject to wear because the pressure piece 19 of the inner screw element 18 rests against it under friction. For this reason, the pressure piece 105 should preferably be replaced together with the friction lining.

In the 7a , 7b is a variant of the 6a , 6b is shown. Again, each of the two brake shoes 3A, 3B of the drum brake is composed of a curved brake pad carrier 101, which carries the friction lining on the outside, and of two brake shoe webs 102 supporting the brake pad carrier 101 on its inside. To absorb the spreading force transmitted by the respective piston 11 or 12, the replaceable pressure piece 105, which is round here with a circumferential web 120, is arranged between the two brake shoe webs 102 and is detachably connected to both brake shoe webs 102.

For the detachable connection, the bolt 110 is provided, which leads through a cylindrical bore 112 in the round pressure piece 105 and through aligned openings 113 in the brake shoe webs 102.

List of reference symbols

1

Brake carrier

1A

Vehicle axle

2

Brake drum

3A

Brake shoe

3B

Brake shoe

4

Bearing journal

5

Brake cylinder

6

Braking surface

10

Expansion housing

11

Pistons

11A

Piston guide

12

Pistons

12A

Piston guide

13

Printing area

14

Pressure disc

17A

outer screw element

17B

outer screw element

18

inner screw element

19

Pressure piece

20

Screw thread

21

slot

27

Federation

28

slim section

29

Push rod

30

Expanding wedge

31

Spreading area

32

Spreading area

35

Roller carrier

37A

Pressure transfer roller

37B

Pressure transfer roller

38

Roller longitudinal guide

40

rail

41

Support roller

42

Support roller

43

Support roller

44

Support roller

50

Adjustment device

51

Adjusting bush

53

Star disc

55

One-way clutch

58

Pen

59

Overload clutch

60

Gearing

65

Transmission shaft

70

pinion

80

Device for displaying brake pad wear

81

Wave

83

pointer

84

slot

85

scale

86

Driving arm

88

Cover plate

101

Brake pad carrier

102

Brake shoe web

105

Pressure piece

110

bolt

112

drilling

113

opening

116

head Start

117

Recess

120

web

D

Rotation axis

L1

Longitudinal section

L2

Longitudinal section

S

Spreading axis, spreading direction

W1

Wedge angle

W2

Wedge angle

Claims (19)

Drum brake designed as an expanding wedge brake with two brake shoes (3A, 3B) pivotably mounted on a brake carrier (1) which can be expanded against a brake drum (2), in which the two brake shoes (3A, 3B) can be expanded away from one another by a respective piston (11, 12), wherein the pistons (11, 12) are guided in an expansion housing (10) and are supported at their ends facing away from one another against the respective brake shoe (3A, 3B) and at their ends facing one another against pressure transmission rollers (37A, 37B), between which an expanding wedge (30) is arranged which can be moved transversely to the direction of movement of the pistons, and wherein the pressure transmission rollers (37A, 37B) are arranged so as to be rotatable in a roller carrier (35), and that the roller carrier (35) is movable on the expanding wedge in the longitudinal direction of the expanding wedge (30) is arranged, and wherein both pressure transmission rollers (37A, 37B) are arranged in a common roller carrier (35), characterized in that the expanding wedge (30) is guided so as to be longitudinally movable via support rollers (41 - 44) which are rotatably mounted in the roller carrier (35), wherein the support rollers (41 - 44) are simultaneously supported against the expanding housing (10) and against a rail (40) formed on the expanding wedge (30) and extending in the longitudinal direction of the expanding wedge. Brake after Claim 1 , characterized in that at least one first support roller (41, 42) is supported against the rail (40) from one side and at least one second support roller (43, 44) from the other side. Brake after Claim 2 , characterized in that the support rollers (41 - 44) are each rotatably mounted in elongated holes or grooves of the roller carrier (35), that the elongated holes or grooves are open towards the rail (40) and closed at their other end, and that the elongated holes or grooves run obliquely rising towards the rail (40). Brake after one of the Claims 1 until 3 , characterized in that the expanding wedge (30) has a first longitudinal section with a first wedge angle (W1), and at least one further longitudinal section with a second wedge angle (W2) different from the first wedge angle, wherein the narrower of the two longitudinal sections has the larger wedge angle (W2). Brake after one of the Claims 1 until 4 , characterized in that the pistons (11, 12) are guided in piston guides (11A, 12A) of the expansion housing (10), and that components of the pistons (11, 12) are each: - a pressure disk (14) with a pressure surface (13) formed thereon for the respective pressure transmission roller (37A or 37B), - an outer screw element (17B or 17A) supported on the pressure disk (14) in the expansion direction and rotatable about the expansion axis (S), and - an inner screw element (18) connected to the outer screw element (17B, 17A) via a screw thread (20), against which the respective brake shoe (3A, 3B) is supported. Brake after Claim 5 , characterized in that one of the outer screw elements (17A) is provided with a toothing (60) for the engagement of a pinion (70) for the return. Brake after Claim 5 or 6 , characterized in that only one of the two pistons (11, 12) is provided with structurally integrated elements of an adjusting device (50) for compensating the brake shoe wear, wherein the adjusting device (10) is designed to rotate the outer screw element (17A, 17B) about the spreading axis (S). Brake after Claim 7 , characterized by an arrangement for the same or opposite rotational synchronization of the outer screw element (17A) of the piston (12) having the elements of the adjusting device (10) with the outer screw element (17B) of the other piston (11). Brake after Claim 8 , characterized in that part of the arrangement is a transmission shaft (65) which simultaneously engages with gears (60) formed on the two outer screw elements (17A, 17B). Brake after Claim 9 , characterized in that the axis of rotation of the transmission shaft (65) is arranged parallel to the spreading axis (S). Brake after Claim 10 , characterized in that the axis of rotation of the transmission shaft is arranged at right angles to the spreading axis (S). Brake after one of the Claims 7 until 11 , characterized in that components of the adjusting device (50) are an overload clutch and a one-way clutch. Brake after one of the Claims 7 until 12 , characterized in that a component of the adjusting device (50) is an adjusting bush (51) which is mounted in the piston guide (12A) so as to be longitudinally and rotationally movable, can be carried along in the longitudinal direction by the outer screw element (17A) and/or by the pressure disk (14), and can be set in a superimposed rotation about the spreading axis (S). Brake after Claim 13 , characterized in that the adjusting bush (51) for setting in the superimposed rotation is provided with a helical structure which is in engagement with a counter structure (58) arranged on the piston guide (12A). Brake according to one of the preceding claims, characterized by a device (80) for optically displaying the brake shoe wear, wherein the device (80) comprises a shaft (81) which is rotatably mounted on the brake carrier (1) at right angles to the spreading axis (S) or to the spreading direction, on which shaft a driver arm (86) which is coupled in movement to one of the brake shoes (3A, 3B) is arranged on a first longitudinal shaft section, and a pointer (83) which projects radially from the shaft (81) is arranged on a second longitudinal shaft section located outside the brake carrier (1). Brake after Claim 15 , characterized in that the brake shoe (3A, 3B) is provided with a slot (84) arranged substantially transversely to the spreading axis (S) or to the spreading direction, into which a pin formed on the driver arm (86) and extending parallel to the shaft (81) engages. Brake according to one of the preceding claims, characterized in that each brake shoe (3A, 3B) has a curved brake pad carrier (101) and two brake shoe webs (102) supporting the latter on its inner side, and in that a pressure piece (105) is arranged between the two brake shoe webs (102) and is detachably connected to both brake shoe webs (102) to absorb the spreading force. Brake after Claim 17 , characterized by a bolt (110) which leads through a bore (112) in the pressure piece (105) and through openings (113) aligned therewith in the brake shoe webs (102). Brake after Claim 18 , characterized in that projections (116) are formed on the pressure piece (105) offset from the bolt (110), which protrude into recesses (117) in the brake shoe webs (102) in such a way that there is a positive connection between the projections (116) and recesses (117) in the bolt circumferential direction.

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