Lightweight waterproof brake drum

Abstract

This invention relates to the field of brake technology and discloses a lightweight, waterproof drum brake, comprising: a brake box housing, brake shoes, a camshaft, and a rocker arm assembly. The brake box housing has a central shaft hole in the middle, and symmetrically arranged mandrels and camshaft holes adapted to the camshaft on both sides of the central shaft hole. The brake shoes are disposed inside the brake box housing via the mandrels and the camshaft. One end of the rocker arm assembly is disposed inside the brake box housing via the camshaft, and the other end of the rocker arm assembly has a brake cable connection assembly. The other end of the brake cable connection assembly passes through the outer side of the brake box housing and connects to the brake cable. The rocker arm assembly consists of a rocker arm body and an adjustment mechanism disposed within the rocker arm body. The adjustment mechanism adjusts the braking stroke after brake shoe wear. This overcomes the problem of inconvenient brake stroke adjustment in existing built-in rocker arm drum brakes due to improper installation or brake shoe wear.

Description

Technical Field

[0001] This invention relates to the field of brake technology, specifically to a lightweight waterproof brake drum brake. Background Technology

[0002] Currently, the rocker arm and the rotating shaft that cooperate with the rocker arm in common drum brakes are usually located outside the brake. For example, CN108180235A discloses a vehicle-mounted balanced fixed drum brake. Because the rocker arm is located outside the brake cover assembly, rainwater, mud and other impurities can easily enter the brake when the vehicle is driving in rainy or snowy weather or on muddy roads, causing internal components to rust and wear, thereby reducing the service life of the brake. In addition, the rocker arm and the rotating shaft that cooperate with the rocker arm are located outside the brake, making them prone to contact with other objects, which can cause the rocker arm to jam or be damaged, making the brake unable to work properly or causing a safety accident. To address this, CN114294352A discloses a sealed and waterproof safety drum brake. By placing the rocker arm inside the brake box and connecting the cable through the brake box to the built-in rocker arm, the overall sealing performance is improved, preventing rainwater and mud from entering the brake box and avoiding damage to the internal components. As mentioned above, the built-in rocker arm waterproof drum brake has good safety, waterproof and sandproof functions, but if it is not assembled properly or the brake shoes are worn, the rocker arm or the brake cable connected to it needs to be adjusted to achieve the specified braking stroke. The adjustment of this drum brake is generally achieved by adjusting the installation angle between the rocker arm and the camshaft or the through-hole adjusting screw between the brake cable sleeve and the core wire. Both of these adjustment methods require more or less to adjust the winding and unwinding of the rocker arm or the brake core wire connected to the tail of the rocker arm. Since the rocker arm is built into the brake box, this adjustment operation requires the brake to be removed from the whole vehicle before it can be adjusted, which is very cumbersome and inconvenient. Furthermore, due to the previous national standard for electric vehicles restricting the use of plastic parts, the replacement of plastic parts with metal materials has increased the weight of the vehicle. This necessitates weight reduction for other vehicle components. In addition, the rising price of aluminum alloy materials has increased the cost of brakes. The market urgently needs a hub brake that can significantly reduce weight, maintain its original cost, is safe and waterproof, has convenient stroke adjustment, and has good overall performance. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides a lightweight, waterproof drum brake, which solves the problems mentioned in the background section. To achieve the above objectives, this application provides the following technical solution: a lightweight waterproof drum brake, comprising: a brake box housing, brake shoes, a camshaft, and a rocker arm assembly. The brake box housing has a central shaft hole in the middle, and a stator shaft and a camshaft hole adapted to the camshaft are symmetrically arranged on both sides of the central shaft hole. The brake shoes are disposed inside the brake box housing via the stator shaft and the camshaft. One end of the rocker arm assembly is disposed inside the brake box housing via the camshaft, and the other end of the rocker arm assembly is provided with a brake cable connection assembly. The other end of the brake cable connection assembly passes through the outer side of the brake box housing and is connected to the brake cable. The rocker arm assembly consists of a rocker arm body and an adjustment mechanism disposed within the rocker arm body. The adjustment mechanism adjusts the braking stroke after the brake shoes wear out.

[0004] Further: One end of the rocker arm assembly is provided with a cam limiting hole adapted to the camshaft, and the other end is provided with a brake cable connection part adapted to connect with the brake cable connection assembly. One end of the camshaft passes through the camshaft hole and is sealed to the outside of the brake box housing through the connection assembly. The connection assembly includes: a camshaft bushing, a gasket, and a connecting bolt connecting one end of the camshaft, which are sleeved between the camshaft hole and the camshaft. One end of the camshaft bushing passes through the camshaft hole and abuts against the rocker arm assembly, and the flange face of the other end fits against the outer side of the brake box housing. One end of the camshaft is provided with a threaded connection hole adapted to be inserted into the central through hole of the camshaft bushing and connected to the outside of the brake box housing through the connecting bolt. The gasket is disposed between the outer side of the brake box housing and the flange face of the camshaft bushing.

[0005] Further: The outer side of the brake box housing is also provided with a frame limiting groove, and a brake cable insertion hole is provided on one side of the frame limiting groove. The inner side of the brake box housing, at the position corresponding to the brake cable insertion hole, is provided with a guide limiting groove for the brake cable connection assembly. The brake box housing is a one-piece magnesium alloy structure. A T-shaped pressure sleeve is also embedded between the camshaft bushing and the camshaft hole. The flange face of the T-shaped pressure sleeve abuts against one end face of the rocker arm assembly. The brake cable connection assembly includes: a brake cable connecting rod connecting the rocker arm body, a crossbar set at one end of the brake cable connecting rod and snapped to the rocker arm body, and a brake cable connector set at the other end of the brake cable connecting rod. The brake cable connector is set on the outside of the brake box housing through the brake cable connecting rod. A limiting buckle is also provided between the brake cable connector and the brake box housing. A reset elastic structure is also sleeved on the brake cable connecting rod on the inner side of the brake box housing.

[0006] Furthermore, an adjustment window is provided on the gate housing at the corresponding position of the rocker arm assembly on one side of the camshaft hole. A detachable waterproof cover is provided above the adjustment window and the camshaft hole. The adjustment mechanism on the rocker arm assembly adjusts the relative position of the rocker arm body and the camshaft through the adjustment window.

[0007] Further: The adjustment mechanism includes: a ratchet rotatably disposed within a connecting through hole at one end of the rocker arm body, an adjusting pawl adapted to the ratchet, and a telescopic component disposed at one end of the adjusting pawl; the adjusting pawl and the telescopic component are disposed within an open cavity structure of the rocker arm body, and the pawl portion at one end of the adjusting pawl is adapted to and adjustablely engaged with the ratchet; the first opening of the open cavity structure is disposed on one end face of the rocker arm body and is parallel to the axis of the connecting through hole, the open cavity structure is provided with a second opening perpendicular to the inner side of the connecting through hole and communicating with the connecting through hole, one end of the adjusting pawl abuts and engages with the ratchet through the second opening, and the other end is connected to the telescopic component and limits the rotation of the ratchet, and one side of the adjusting pawl is also provided with an outwardly protruding handle that moves back and forth along the first opening; the center of the ratchet is provided with a cam limiting hole adapted to the camshaft, and the cam limiting hole is configured as a polygonal structure or a toothed structure adapted to the camshaft.

[0008] Further: One end of the connecting through hole is provided with an annular retaining edge that abuts against one end face of the ratchet, and the other end is provided with an annular groove that is connected to the ratchet by a limiting spring.

[0009] Furthermore, one end of the ratchet is also provided with a limiting groove that is adapted to the limiting spring.

[0010] Furthermore, the telescopic assembly consists of a cone block disposed at the other end of the adjusting pawl, expansion blocks symmetrically adapted to both sides of the cone block, and a return spring disposed on the outer side of the two expansion blocks. The other side of the two return springs abuts against the inner wall of the opening cavity structure.

[0011] Further: The oral cavity structure has a cross-shaped inner cavity, the two expansion blocks and the reset spring are adapted to be set in the transverse cavity of the cross-shaped inner cavity, the adjusting pawl is set in the longitudinal cavity with one end communicating with the second opening, the top of the longitudinal cavity is opened with a first opening near the second opening, the cone is set as a frustum structure with a smaller outer side and a larger inner side, and the inner side of the expansion block is provided with an inclined surface adapted to the cone.

[0012] Furthermore, the telescopic assembly also includes a limiting block disposed between the two expansion blocks. The limiting block is movably sleeved on the connecting part between the cone block and the adjusting pawl body, and the two sides of the limiting block abut against the inner sides of the two expansion blocks respectively. An L-shaped anti-reverse groove is provided at the abutment point between the two expansion blocks and the limiting block.

[0013] Compared with the prior art, the present invention has the following advantages: This application integrates a rocker arm assembly inside the brake box housing and rotatably connected to the camshaft between the brake shoes. One end of the rocker arm assembly is connected to a brake cable connection assembly that runs through the outside of the brake box housing. The other end of the camshaft is sealed to the outside of the brake box housing via a connecting assembly. This allows the key braking components of the drum brake to be internally mounted, preventing rainwater and mud from entering, reducing component wear, and increasing the service life of the brake. Furthermore, the brake will not come into contact with other objects while the vehicle is in motion, ensuring the vehicle's safe and reliable operation. The rocker arm assembly with built-in ratchet and adjustable pawl facilitates adjustment of the travel after brake shoe wear and addresses misalignment between the rocker arm assembly and camshaft, ensuring stable braking performance and travel. This built-in adjustable travel rocker arm assembly, combined with the brake cable connection assembly, eliminates the need for adjustment of the rocker arm body and brake cable; travel adjustment can be completed simply by rotating the camshaft, which is convenient and quick, while also protecting the brake cable and extending its service life. The brake box housing is made of SMM magnesium alloy in one piece, which reduces the weight by one-third compared to aluminum alloy, effectively reducing the overall weight of the brake. In summary, this application is a hub brake that maintains the original product cost, is safe and waterproof, has convenient stroke adjustment, and has good overall performance. Attached Figure Description

[0014] Figure 1 This is a three-dimensional structural schematic diagram of the present invention; Figure 2 This is a three-dimensional structural diagram of the other side of the present invention; Figure 3 This is an exploded view of the gate housing and rocker arm assembly of the present invention; Figure 4 This is an exploded structural diagram of a component of the present invention; Figure 5 This is a schematic diagram of the connection component and rocker arm component of the present invention; Figure 6 This is an exploded view of the rocker arm assembly of the present invention; Figure 7 Exploded view of the rocker arm assembly of this invention; Figure 8 A three-dimensional cross-sectional view of the rocker arm body of the present invention; Figure 9 A cross-sectional view of the connection between the camshaft and the rocker arm body of the present invention.

[0015] Attached image labels: Brake box housing -1; Borehole -11; Camshaft hole -12; Frame limiting groove -13; Brake cable threading hole -14; Guide limiting groove -15; Adjustment window -16; Brake shoe -2; Brake cable connecting assembly -3; Brake cable connecting rod -31; Crossbar -32; Brake cable connector -33; Limiting buckle -34; Reset elastic structure -35; Waterproof cover -4; Stator shaft -5; Camshaft -6; Threaded connection hole -61; Limiting structure -62; Rocker arm assembly - 7; Rocker arm body - 71; Adjustment mechanism - 72; Adjustment pawl - 721; Pawl part - 7211; Protruding handle - 7212; Cone block - 7213; Connecting part - 7214; Ratchet - 722; Limiting groove - 7221; Telescopic assembly - 723; Expansion block - 7231; Return spring - 7232; Limiting block - 7233; Cam limiting hole - 73; Brake cable connecting part - 74; Opening cavity body structure - 75; First opening - 751; Second opening - 752; Connecting through hole - 76; Annular flange - 78; Limiting snap ring - 79; Connecting assembly - 8; Camshaft bushing - 81; Connecting bolt - 82; T-type pressure sleeve - 83; Gasket - 84. Detailed Implementation

[0016] To enhance understanding of the present invention, the invention will be further described in detail below with reference to the accompanying drawings. This embodiment is only used to explain the invention and does not constitute a limitation on the scope of protection of the invention.

[0017] In the description of this invention, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the combination or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0018] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0019] Figure 1-5 The diagram shows a lightweight waterproof drum brake, comprising: a brake box housing-1; brake shoes-2; a camshaft-6; and a rocker arm assembly 7. The brake box housing 1 has a central shaft hole 11 in the middle, and a stator shaft 5 and a camshaft hole 12 adapted to the camshaft 6 are symmetrically arranged on both sides of the central shaft hole 11. The brake shoes 2 are set inside the brake box housing 1 through the stator shaft 5 and the camshaft 6. One end of the rocker arm assembly 7 is set inside the brake box housing 1 through the camshaft 6, and the other end of the rocker arm assembly 7 is provided with a brake cable connection assembly 3. The other end of the brake cable connection assembly 3 passes through the outer side of the brake box housing 1 and is connected to the brake cable. The rocker arm assembly 7 consists of a rocker arm body 71 and an adjustment mechanism 72 set inside the rocker arm body 71. The adjustment mechanism 72 adjusts the braking stroke of the brake shoes 2 after wear.

[0020] Specifically: such as Figure 5-9 As shown, one end of the rocker arm assembly 7 is provided with a cam limiting hole 73 adapted to the camshaft 6, such as... Figure 5 As shown, the limiting structure 62 provided with the cam limiting hole 73 and the camshaft 6 can be configured as a matching square structure; the other end of the rocker arm assembly 7 is provided with a brake cable connection part 74 that is adapted to connect with the brake cable connection assembly 3, and the brake cable connection part 74 can be configured as follows: Figure 5 The diagram shows two parallel, spaced-apart open hook structures; one end of the camshaft 6 passes through the camshaft hole 12 and is sealed to the outside of the gate housing 1 via the connecting assembly 8; wherein, one end of the rocker arm body 71 is provided with a connecting through hole 76, and the adjusting mechanism 72 includes: a ratchet 722 rotatably disposed in the connecting through hole 76, an adjusting pawl 721 adapted to the ratchet 722, and a telescopic assembly 723 disposed at one end of the adjusting pawl 721; the adjusting pawl 721 and the telescopic assembly 723 are disposed in the open cavity structure 75 of the rocker arm body 72, and the pawl portion 7211 at one end of the adjusting pawl 721 is adapted to and adjustablely engaged with the ratchet 722; the first of the open cavity structure 75 An opening 751 is provided on one end face of the rocker arm body 71 and is parallel to the axis of the connecting through hole 76. The opening body structure 75 is perpendicular to the inner side of the connecting through hole 76 and has a second opening 752 communicating with the connecting through hole 76. One end of the adjusting pawl 721 abuts and engages with the ratchet 722 through the second opening 752, and the other end is connected to the telescopic component 723 and limits the rotation of the ratchet 722. One side of the adjusting pawl 721 is also provided with a protruding handle 7212 that moves back and forth along the first opening 751. The center of the ratchet 722 is provided with a cam limiting hole 73 that is adapted to the camshaft 6. The cam limiting hole 73 is a polygonal structure or a toothed structure adapted to the camshaft. Specifically: such as Figure 6-9 As shown, the telescopic assembly 723 consists of a cone block 7213 disposed at the other end of the adjusting pawl 721, expansion blocks 7231 symmetrically adapted to both sides of the cone block 7213, and return springs 7232 disposed on the outer sides of the two expansion blocks 7231. The other side of the two return springs 7232 abuts against the inner wall of the opening cavity structure 75; as shown Figure 8 As shown: The open mouth body structure 75 has a "+" shaped inner cavity. Two expansion blocks 7231 and a return spring 7232 are adapted to be set in the transverse cavity of the "+" shaped inner cavity. The adjusting pawl 721 is set in the longitudinal cavity with one end communicating with the second opening 752. The top of the longitudinal cavity is close to the second opening 752 and has a first opening 751. The cone block 7213 is a truncated cone structure with a smaller outer diameter and a larger inner diameter. The inner side of the expansion block 7231 has an inclined surface adapted to the cone block 7213. The telescopic component 723 also plays a role in limiting and stopping the rotation of the ratchet 722. At the same time, it adjusts and positions the rotation angle of the camshaft 6, which is positioned at the center of the ratchet 722, relative to one end of the brake shoe 2, thereby adjusting the braking stroke of the rocker arm assembly after the brake shoe 2 wears.

[0021] This application integrates a rocker arm assembly 7 inside the brake box housing 1, between the brake shoe 2 and the camshaft 6. One end of the rocker arm assembly 7 is connected to a brake cable connection assembly 3 that extends through the outside of the brake box housing 1. One end of the camshaft 6 is sealed to the outside of the brake box housing 1 via a connecting assembly 8. This internal integration of the key braking components of the drum brake protects against rain and mud, reduces component wear, and extends brake lifespan. Furthermore, it prevents contact with other objects during vehicle operation, ensuring safe and reliable driving. The rocker arm assembly with its built-in ratchet 722 and adjusting pawl 721 facilitates stroke adjustment after brake shoe wear and addresses misalignment between the rocker arm assembly and the camshaft, ensuring stable braking performance and stroke. This built-in adjustable stroke rocker arm assembly, combined with the brake cable connection assembly 3, eliminates the need for manual adjustment of the rocker arm body and brake cable; stroke adjustment is achieved simply by rotating the camshaft, making it convenient and quick while protecting the brake cable and extending its lifespan. The operating principle is as follows: the adjusting pawl 721 is moved backward by the protruding handle 7211 and is no longer engaged with the ratchet 722. Then, the top of the adjusting screw 82 on the connecting assembly 8 is rotated with a tool, which drives the camshaft 6 and the ratchet 722 to rotate together at an angle. The protruding handle 7211 of the adjusting pawl 721 is released, and the adjusting pawl 721 resumes engagement with the ratchet 722, so that the rocker arm body 71 and the brake cable connected to it remain stationary. By simply rotating the ratchet 722 relative to the engagement position of the adjusting pawl 721 built into the rocker arm body, the increased braking stroke due to brake shoe wear can be easily adjusted.

[0022] An alternative implementation: such as Figure 5 , 9 As shown, the connecting assembly 8 includes: a camshaft bushing 81, a gasket 84, and a connecting bolt 82 connecting one end of the camshaft 6, all fitted between the camshaft hole 12 and the camshaft 6. One end of the camshaft bushing 81 passes through the camshaft hole 12 and abuts against one end face of the ratchet 722 in the rocker arm assembly 7. The flange face of the other end fits against the outer surface of the brake housing 1. One end of the camshaft 6 has a threaded connection hole 61 that fits into the central through hole of the camshaft bushing 81 and is connected to the outside of the brake housing 1 by the connecting bolt 82. The gasket 84 is located between the outer surface of the brake housing 1 and the flange face of the camshaft bushing 81. The connecting bolt 82 has a cross groove or hex socket for easy adjustment. The camshaft bushing 81 and the gasket 84 are made of plastic or rubber and have a waterproof sealing function.

[0023] An alternative implementation: such as Figure 3-5As shown, the outer side of the brake box housing 1 is also provided with a frame limiting groove 13, and a brake cable insertion hole 14 is provided on one side of the frame limiting groove 13. The inner side of the brake box housing 1, at the position corresponding to the brake cable insertion hole 14, is provided with a guide limiting groove 15 adapted to the brake cable connection assembly 3. The brake box housing 1 is a one-piece magnesium alloy structure. A T-shaped pressure sleeve 83 is also embedded between the camshaft bushing 81 and the camshaft hole 12. The flange surface of the T-shaped pressure sleeve 83 abuts against one end face of the rocker arm assembly 7. The brake box housing 1 is made of one-piece magnesium alloy, which reduces the weight by one-third compared to aluminum alloy. Specifically, SMM magnesium alloy AM60B can be used, which can effectively reduce the overall weight of the brake. At the same time, the T-shaped pressure sleeve 83 is made of insulating material, which can effectively isolate the direct contact between the brake box housing and the camshaft. The T-shaped pressure sleeve 83 is preferably made of plastic. Similarly, in this embodiment, the mandrel 5 on the brake box housing 1 is made of rust-proof material or rust-proof treatment or insulating material. The brake cable insertion hole 14 and the camshaft hole 12 are provided with corresponding insulating sleeves.

[0024] An alternative implementation: such as Figure 3 , 5 As shown, the brake cable connection assembly 3 includes: a brake cable connecting rod 31 connecting to the rocker arm body, a crossbar 32 that is snapped to the rocker arm body 71 at one end of the brake cable connecting rod 31, and a brake cable connector 33 at the other end of the brake cable connecting rod 31. The brake cable connector 33 is located on the outside of the brake box housing 1 through the brake cable connecting rod 31. A limiting buckle 34 is also provided between the brake cable connector 33 and the brake box housing 1. A reset elastic structure 35 is also sleeved on the brake cable connecting rod 31 on the inside of the brake box housing 1. The reset elastic structure 35 is a reset spring, and an adjustable threaded T-shaped sleeve is provided at the end of the reset spring near the limiting buckle 34, which abuts against the inside of the brake cable insertion hole 14. The brake cable end connected to the brake lever is directly snapped to the brake cable connector 33, making the connection convenient and reliable. The limiting buckle 34 is a fixed stroke assembly limiting structure during brake assembly and can be removed during vehicle assembly.

[0025] An alternative implementation: such as Figure 3-5 As shown, an adjustment window 16 is also provided on the brake housing 1 on one side of the camshaft hole 12, corresponding to the position of the rocker arm assembly 7. A removable waterproof cover 4 is provided above the adjustment window 16 and the camshaft hole 12. The adjustment mechanism 72 provided on the rocker arm assembly 7 adjusts the relative position of the rocker arm body 71 and the camshaft 6 through the adjustment window 16. The adjustment window 16 makes the adjustment more intuitive and convenient. The waterproof cover 4 provided above the adjustment window 16 and the camshaft hole 12 provides a fully enclosed external design, ensuring reliable braking performance and better waterproof performance.

[0026] An alternative implementation: such as Figure 6-9As shown, in order to improve the reliability of the ratchet 722 connection, one end of the connecting through hole 76 is provided with an annular retaining edge 78 that abuts against one end face of the ratchet 722, and the other end is provided with an annular groove 77 that is connected to the ratchet 722 by a limiting snap ring 79.

[0027] An alternative implementation: such as Figure 6-9 As shown, the reliability of the connection limit between the ratchet 722 and the connecting through hole 76 and the adjustment engagement accuracy between the ratchet 722 and the adjusting pawl 721 are further improved. A limiting groove 7221 that is adapted to the limiting snap ring 79 is also provided on one side of the ratchet 722.

[0028] An alternative implementation: such as Figure 6-9 As shown, the telescopic assembly 723 also includes a limiting block 7233 disposed between the two expansion blocks 7231. The limiting block 7233 is movably sleeved on the connecting part 7214 between the cone block 7213 and the adjusting pawl body. The two sides of the limiting block 7233 abut against the inner sides of the two expansion blocks 7231 respectively, keeping the adjusting pawl 721 engaged with the ratchet 722 when no external force is applied. An L-shaped anti-reverse groove is provided at the abutment point between the two expansion blocks 7231 and the limiting block 7233 to prevent the adjusting pawl 721 from retracting. This arrangement can enhance the impact resistance of the adjusting mechanism and ensure that it does not slip. Preferably, the limiting block 7233 can move backward over the L-shaped anti-reverse groove when it passes through the groove under the action of the adjusting handle.

[0029] The embodiments disclosed herein are preferred embodiments, but are not limited thereto. Those skilled in the art can readily grasp the spirit of the present invention based on the above embodiments and make different extensions and variations, but as long as they do not depart from the spirit of the present invention, they are all within the protection scope of the present invention.

Claims

1. A lightweight waterproof drum brake, comprising: The brake box housing (1), brake shoe (2), camshaft (6) and rocker arm assembly (7) are provided. The brake box housing (1) is provided with a central shaft hole (11) in the middle. The central shaft hole (11) is symmetrically provided with a core shaft (5) and a camshaft hole (12) adapted to the camshaft (6) on both sides. The brake shoe (2) is provided inside the brake box housing (1) through the core shaft (5) and the camshaft (6). The rocker arm assembly (7) is provided inside the brake box housing (1) at one end through the camshaft (6). The other end of the rocker arm assembly (7) is provided with a brake cable connection assembly (3). The other end of the brake cable connection assembly (3) passes through the outer side of the brake box housing (1) and is connected to the brake cable. The rocker arm assembly (7) is composed of a rocker arm body (71) and an adjustment mechanism (72) provided in the rocker arm body (71). The adjustment mechanism (72) adjusts the braking stroke after the brake shoe (2) is worn.

2. The lightweight waterproof drum brake according to claim 1, characterized in that: The rocker arm assembly (7) has a cam limiting hole (73) adapted to the camshaft (6) at one end and a brake cable connection part (74) adapted to the brake cable connection assembly (3) at the other end. One end of the camshaft (6) passes through the camshaft hole (12) and is sealed to the outside of the brake box housing (1) by the connecting assembly (8). The connecting assembly (8) includes: a camshaft bushing (81) sleeved between the camshaft hole (12) and the camshaft (6), a gasket (84), and a connection to one end of the camshaft (6). Connecting bolt (82); one end of the camshaft bushing (81) passes through the camshaft hole (12) and abuts against the rocker arm assembly (7), and the flange face of the other end fits against the outer side of the gate housing (1). One end of the camshaft (6) is provided with a threaded connection hole (61) adapted to be installed in the central through hole of the camshaft bushing (81) and connected to the outside of the gate housing (1) by connecting bolt (82). The gasket (84) is set between the outer side of the gate housing (1) and the flange face of the camshaft bushing (81).

3. The lightweight waterproof drum brake according to claim 2, characterized in that: The outer side of the brake box housing (1) is also provided with a frame limiting groove (13), and a brake cable insertion hole (14) is provided on one side of the frame limiting groove (13). The inner side of the brake box housing (1) and the corresponding position of the brake cable insertion hole (14) are provided with a guide limiting groove (15) adapted to the brake cable connection assembly (3). The brake box housing (1) is a one-piece magnesium alloy structure. A T-shaped pressure sleeve (83) is also embedded between the camshaft bushing (81) and the camshaft hole (12). The flange face of the T-shaped pressure sleeve (83) abuts against one end face of the rocker arm assembly (7). The brake cable connection assembly The component (3) includes: a brake line connecting rod (31) connecting the rocker arm body, a crossbar (32) set at one end of the brake line connecting rod (31) and snapped to the rocker arm body (71), and a brake line connector (33) set at the other end of the brake line connecting rod (31). The brake line connector (33) is set on the outside of the gate box housing (1) through the brake line connecting rod (31). A limiting buckle (34) is also provided between the brake line connector (33) and the gate box housing (1). A reset elastic structure (35) is also sleeved on the brake line connecting rod (31) on the inside of the gate box housing (1).

4. The lightweight waterproof drum brake according to claim 1, characterized in that: An adjustment window (16) is also provided on the gate housing (1) on one side of the camshaft hole (12) and at the corresponding position of the rocker arm assembly (7). A detachable waterproof cover (4) is provided above the adjustment window (16) and the camshaft hole (12). The adjustment mechanism (72) provided on the rocker arm assembly (7) adjusts the relative position of the rocker arm body (71) and the camshaft (6) through the adjustment window (16).

5. The lightweight waterproof drum brake according to any one of claims 1-4, characterized in that: The adjustment mechanism (72) includes: a ratchet (722) rotatably disposed in a connecting through hole (76) at one end of the rocker arm body (71), an adjusting pawl (721) adapted to the ratchet (722), and a telescopic component (723) disposed at one end of the adjusting pawl (721); the adjusting pawl (721) and the telescopic component (723) are disposed in an open cavity structure (75) of the rocker arm body (72), and the pawl portion (7211) at one end of the adjusting pawl (721) is adapted to and adjustablely engaged with the ratchet (722); the first opening (751) of the open cavity structure (75) is disposed on one end face of the rocker arm body (71) and parallel to the axis of the connecting through hole (76). The opening structure (75) is provided with a second opening (752) that communicates with the connecting through hole (76) on the inner side of the opening structure (75). One end of the adjusting pawl (721) abuts and engages with the ratchet (722) through the second opening (752), and the other end is connected to the telescopic component (723) and limits the rotation of the ratchet (722). One side of the adjusting pawl (721) is also provided with an outwardly protruding handle (7212) that moves back and forth along the first opening (751). The center of the ratchet (722) is provided with a cam limiting hole (73) that is matched with the camshaft (6). The cam limiting hole (73) is provided with a polygonal structure or a toothed structure that matches the camshaft.

6. The lightweight waterproof drum brake according to claim 5, characterized in that: One end of the connecting through hole (76) is provided with an annular flange (78) that abuts against one end face of the ratchet (722), and the other end is provided with an annular groove (77) that is snapped together with the ratchet (722) through a limiting snap ring (79).

7. The lightweight waterproof drum brake according to claim 6, characterized in that: The ratchet (722) is also provided with a limiting groove (7221) on one side that is adapted to the limiting snap ring (79).

8. The lightweight waterproof drum brake according to claim 5, characterized in that: The telescopic assembly (723) consists of a cone block (7213) disposed at the other end of the adjusting pawl (721), expansion blocks (7231) symmetrically adapted to both sides of the cone block (7213), and return springs (7232) disposed on the outer sides of the two expansion blocks (7231). The other side of the two return springs (7232) abuts against the inner wall of the open mouth body structure (75).

9. The lightweight waterproof drum brake according to claim 8, characterized in that: The oral cavity structure (75) has a cross-shaped inner cavity. The two expansion blocks (7231) and the return spring (7232) are adapted to be arranged in the transverse cavity of the cross-shaped inner cavity. The adjusting pawl (721) is arranged in the longitudinal cavity that is connected to the second opening (752) at one end. The top of the longitudinal cavity is close to the second opening (752) and a first opening (751) is opened. The cone block (7213) is a frustum structure with a smaller outer diameter and a larger inner diameter. The inner side of the expansion block (7231) is provided with an inclined surface adapted to the cone block (7213).

10. The lightweight waterproof drum brake according to claim 9, characterized in that: The telescopic assembly (723) also includes a limiting block (7233) disposed between the two expansion blocks (7231). The limiting block (7233) is movably sleeved on the connecting part (7214) between the cone block (7213) and the adjusting pawl body. The two sides of the limiting block (7233) abut against the inner sides of the two expansion blocks (7231) respectively. An L-shaped anti-reverse groove is provided at the abutment point between the two expansion blocks (7231) and the limiting block (7233).

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