Spring-Applied Parking Brake Manual Release Collet
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Solution Overview
Problem
Existing spring-applied parking brakes for transit vehicles cannot be manually reactivated once pneumatic pressure is unavailable, limiting their functionality in scenarios where air pressure is not accessible.
Innovation Solution
A spring-applied parking brake system with a pneumatic cylinder, gearbox, and a collet mechanism that allows manual release and reapplication, utilizing a pushrod with helical threads and a radially expandable collet with flexible tines to enable axial motion and secure engagement with the piston, enabling manual operation independent of pneumatic pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pneumatic pressure is used to release the parking brake, then the brake can be released reliably when connected to a lead vehicle, but the brake cannot be manually reactivated when pneumatic pressure is unavailable
Solution Approach 1:
The parking brake system is designed to perform multiple functions: it can be released both by pneumatic pressure (when connected to a lead vehicle) and by manual cranking (when pneumatic pressure is unavailable). The manual crank mechanism engages with the pushrod through a gear box and threaded collet, allowing the operator to manually override the spring application and reset the brake without requiring pneumatic pressure.
Solution Approach 2:
The threaded collet acts as an intermediary mechanism between the manual crank and the pushrod. When the manual crank is rotated, the collet threads engage with the pushrod threads, converting rotational motion into axial motion to move the pushrod and release the brake. This intermediary allows manual operation to effectively control the brake without directly moving the pushrod.
2Ease of operation
If a manual release mechanism is provided to disconnect the piston from the pushrod, then the vehicle can move when pneumatic pressure is unavailable, but the brake cannot be reactivated until pneumatic pressure is available
Solution Approach 1:
The connection between the collet and pushrod is made dynamic rather than static. The collet is designed to be disengageable from the pushrod threads through manual cranking, allowing the operator to disconnect and reconnect the linkage as needed. This dynamic connection enables both manual release and potential manual reactivation scenarios.
Solution Approach 2:
The manual release mechanism segments the brake system into controllable portions: the collet can be independently engaged or disengaged from the pushrod through the gear box crank mechanism. This segmentation allows the operator to manually control the connection state, providing flexibility in both releasing and potentially reactivating the brake without requiring pneumatic pressure.
3Ease of manufacture
If the collet connection is used for slack adjustment in service brake mode, then service brake adjustment is achieved, but the brake cannot be manually reactivated after release
Solution Approach 1:
The threaded collet serves multiple functions: it provides slack adjustment for the service brake by allowing axial movement of the pushrod relative to the piston, and it enables manual brake release and potential reactivation by engaging with the manual crank mechanism through the gear box. This multi-functional design eliminates the need for separate adjustment and manual reactivation mechanisms.
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
Enables manual release and reapplication of the parking brake, ensuring operational reliability even without pneumatic pressure, by using a gearbox and collet mechanism that allows for secure engagement and disengagement of the pushrod, ensuring effective braking control.
Implementation Method 1
a parking brake spring extending between the piston and rear wall for biasing the piston to the front wall
Implementation Method 2
The collet has flexible radially expandable tines... the collet then grips the pushrod to carry it along with the piston
Implementation Method 3
a pneumatic pressure inlet for applying pressure to move the piston against the spring to the rear wall
Data Source
AI summary
A spring-applied parking brake with manual release and reapply. A gear box fixed relative to the rear wall of a cylinder has a manual crank. A pushrod extending through the cylinder and gear box is connected to provide braking force. A threaded collet surrounding helical threads on the pushrod has flexible radially expandable tines. When the gear box is manually cranked, the pushrod is rotated and due to interaction of the threads on the inside of the collet and on the pushrod, the pushrod is moved axially releasing or reapplying the brake.