This document outlines the service and repair procedures for the brake system on various Hyster internal combustion engine trucks. It covers both dry and wet brake systems, providing comprehensive instructions for maintenance, disassembly, assembly, and adjustment.
Function Description
The brake system is a critical safety component designed to slow down or stop the lift truck. It comprises several interconnected parts that work in unison to achieve controlled deceleration. The manual distinguishes between two primary types of brake systems: dry brake systems and wet brake systems.
- Dry Brake System: This system typically includes a master cylinder, brake shoes, wheel cylinders, and a parking brake system. When the brake pedal is pressed, hydraulic pressure from the master cylinder actuates the wheel cylinders, which in turn force the brake shoes against the inside of the brake drums, creating friction and slowing the wheel. The parking brake system operates independently, usually via cables, to hold the truck stationary.
- Wet Brake System: Found on specific lift truck models, the wet brake system integrates the brake discs within the planetary carrier housing of the drive axle. This design often means the brake components operate in an oil bath, which helps dissipate heat and can contribute to longer component life and smoother operation. Similar to the dry system, it also includes a master cylinder and a parking brake system. The manual refers to a separate document for detailed removal and installation procedures of the wet disc brakes, indicating their specialized nature.
Usage Features
The manual emphasizes proper operation and adjustment to ensure the brake system functions effectively and safely.
- Brake Pedal Operation: The primary method of engaging the service brakes is through the inching/brake pedal. Proper adjustment of this pedal is crucial for responsive braking.
- Parking Brake Operation: The parking brake is engaged via a hand lever and an adjustment knob. It is designed to hold the lift truck stationary, particularly when parked on an incline. The manual details procedures for loosening and tightening the parking brake cables to ensure correct engagement and release.
- Inching Overlap Adjustment: For certain models equipped with wet brake systems, an "inching overlap adjustment" feature is available. This allows for fine-tuning the interaction between the inching function (which controls low-speed movement) and the braking system. The adjustment is performed using scroll buttons on a display switch cluster, offering a ten-point range to customize the overlap, with a default setting of 5. This feature likely enhances maneuverability and control in specific operating conditions.
- Automatic Adjusters: The manual mentions automatic adjusters for brake shoes. These mechanisms are designed to maintain the correct clearance between the brake shoes and the drum as the linings wear. However, it cautions that if the initial clearance is too large or too small, the automatic adjusters may not function correctly, potentially leading to improper braking or wear.
Maintenance Features
The manual provides extensive guidelines and procedures for maintaining the brake system, with a strong emphasis on safety and the use of approved parts.
- Safety Precautions: A dedicated section highlights critical safety warnings, including the dangers of asbestos-containing brake linings (though modern linings are typically asbestos-free, the caution remains relevant for older systems or general best practice). It strictly prohibits creating dust during brake maintenance, recommending vacuum equipment or specific cleaning procedures to wet down dust. It also warns against using oil solvents on brake linings and emphasizes the importance of wearing safety glasses and disconnecting the battery before maintenance.
- Regular Inspection: Technicians are instructed to regularly inspect various brake components for wear and damage. This includes checking the wheel cylinder bore for scratches, return springs for wear, back plates for grooves, brake shoes for cracks or damage, and brake drums for deep grooves or excessive internal diameter. The manual provides specific wear limits for brake drums, beyond which replacement is necessary.
- Cleaning Procedures: Detailed instructions are given for cleaning brake parts, stressing the use of approved solvents and methods to prevent the release of hazardous dust. Contaminated cleaning materials must be disposed of safely.
- Disassembly and Assembly: The manual provides step-by-step procedures for removing and disassembling various brake components, such as axle shafts, wheel assemblies, brake shoes, and wheel cylinders. It emphasizes noting the arrangement of parts during disassembly to aid in correct reassembly.
- Component Replacement: It mandates the replacement of brake shoes on both wheels if any shoe is damaged to ensure equal brake performance across the axle. Only HYSTER APPROVED parts should be used for repairs to maintain the system's integrity and performance.
- Lubrication: Specific instructions are provided for lubricating components like the back plate with lithium grease and adjuster cables, ensuring smooth operation and preventing premature wear. Wheel bearings also require cleaning and lubrication with wheel bearing grease.
- Torque Specifications: Precise torque values are given for fastening various components, including axle shaft capscrews, wheel cylinder capscrews, and wheel nuts. These specifications are critical for ensuring components are securely fastened and function as intended.
- Bleeding the Brake System: The manual refers to a "Brake System Air Removal" procedure, which is essential after any work that introduces air into the hydraulic brake lines. This ensures a firm brake pedal and effective braking.
- Adjustments: Detailed adjustment procedures are outlined for brake shoe clearance, wheel bearings, and the parking brake system. These adjustments are vital for optimal brake performance and to prevent issues like uneven braking or premature wear. The manual specifically warns about the different thread directions for adjuster wheels on left and right brakes.
- Return Spring Installation: The correct installation of return springs is highlighted, with specific instructions and diagrams to ensure they are properly positioned and tensioned, which is crucial for the brake shoes to retract correctly. The manual even specifies the order of installing different colored springs (white then black) for certain models.
In summary, this manual serves as an indispensable guide for trained and experienced technicians to perform safe and effective maintenance and repair of Hyster lift truck brake systems, covering both dry and wet brake configurations and emphasizing safety, proper procedures, and the use of approved components.
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