Windrower Park Brake Valve Layout for Failure Maneuverability
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Solution Overview
Problem
Existing spring applied hydraulic release brakes in self-propelled windrowers face challenges in maneuverability during hydraulic failures, as the emergency brake is automatically applied, complicating vehicle repair and operation.
Innovation Solution
A redundant hydraulic control system is implemented using an electrically operated hydraulic fluid supply valve and check valve, ensuring the parking brakes remain released during electrical failures, with manual and automatic modes for control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If spring applied hydraulic release brakes are used, then the parking brake can be released by hydraulic pressure, but the brake is automatically applied upon loss of hydraulic pressure, reducing maneuverability during hydraulic failures
Solution Approach 1:
The patent inverts the default fail-safe behavior by using a check valve that defaults to the open position (allowing brake release) upon loss of electrical power, rather than closing to apply the brake. This inversion allows the brake to remain released during electrical failures while still providing automatic application during hydraulic failures through the supply valve's fail-closed design.
Solution Approach 2:
The check valve acts as an intermediary device between the hydraulic supply valve and the parking brake. It mediates the conflicting requirements by allowing hydraulic fluid to pass through to release the brake under normal conditions, while preventing fluid from returning to the supply line, thus maintaining brake release status during electrical failures.
2Device complexity
If hydraulic pressure is required to release the parking brake, then the brake system is simple, but the vehicle cannot be maneuvered for repair after hydraulic pressure loss
Solution Approach 1:
The check valve is pre-configured to maintain hydraulic pressure in the brake release line by preventing fluid return. This preliminary action ensures that if electrical power is lost, the brake remains in the released position, providing the preliminary condition needed for vehicle maneuverability during failures.
Solution Approach 2:
The redundant valve system provides a cushioning effect against total brake failure. By having the check valve prevent hydraulic fluid from returning to the supply line, the system cushions against pressure loss scenarios, maintaining brake release status even when the supply valve fails closed due to electrical power loss.
3Reliability
If the check valve prevents hydraulic fluid flow back to the supply valve, then brake pressure is maintained, but the system requires additional valves increasing complexity
Solution Approach 1:
The check valve is a passive, self-regulating device that automatically prevents hydraulic fluid from flowing back to the supply valve based on pressure differential. It requires no external control signals or additional complexity beyond its inherent check valve mechanism, serving itself to maintain brake pressure through its one-way flow characteristic.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Ensures operational redundancy and maneuverability of the windrower even during hydraulic or electrical failures, allowing safe and controlled vehicle movement for repairs.
Implementation Method 1
a resilient member biased by a spring in the checking position. The resilient member is flexible enough to allow the check valve to shift to the open position when exposed to higher pressure hydraulic fluid
Implementation Method 2
A parking brake is configured to apply a braking force to at least one of the ground engaging units, the parking brake being configured to be released by application of the higher pressure hydraulic fluid to the parking brake
Data Source
AI summary
A hydraulic system of a windrower includes a hydraulic pressure source of a higher pressure hydraulic fluid and a hydraulic pressure return for receiving lower pressure hydraulic fluid. A parking brake is configured to be released by application of the higher pressure hydraulic fluid. A hydraulic fluid supply line is communicated with the parking brake. An electrically operated hydraulic fluid supply valve communicates the supply line with the hydraulic pressure source or with the hydraulic pressure return. An electrically operated selectable check valve is disposed in the supply line between the supply valve and the parking brake, the check valve being shiftable between a checking position permitting hydraulic fluid flow from the supply valve to the parking brake and preventing hydraulic fluid flow from the parking brake to the supply valve, and an open position communicating the supply valve with the parking brake.