Constant Force Rail Clamp with Variable Slope Cam
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Solution Overview
Problem
Existing spring actuated, hydraulically released braking mechanisms for cranes and material handling equipment face issues with varying spring force, leading to inconsistent clamping or braking force due to changes in rail width and brake pad wear, which affects the reliability and safety of the operation.
Innovation Solution
A novel rail clamp with a variably sloped cam surface profile that adjusts the mechanism ratio to counteract spring force variations, maintaining a constant clamping force by changing the slope of the cam surfaces as the spring extends and compresses, ensuring consistent braking performance across different rail widths and brake pad wear conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a spring actuated mechanism is used to apply braking force, then the braking system is simple and reliable, but the spring force varies as the spring extends and contracts, leading to inconsistent clamping force
Solution Approach 1:
The cam surface profile is designed with varying slope angles that change as the cam rotates. This parameter variation in the cam surface geometry compensates for the spring force changes, maintaining constant clamping force on the rail throughout the spring's extension and contraction cycle.
Solution Approach 2:
The cam mechanism acts as an intermediary between the spring and the brake levers. It transforms the varying spring force into a constant clamping force through its specially profiled surface, mediating the force transmission to eliminate inconsistencies.
2Force
If the mechanism ratio of clamp levers and toggle mechanism is increased to compensate for spring force decrease, then clamping force can be maintained, but the mechanism becomes more complex
Solution Approach 1:
The complex toggle mechanism is extracted and replaced with a simpler cam mechanism. The cam's profiled surface inherently provides the necessary mechanical advantage variation without requiring additional levers, pivots, or linkage components, thus reducing overall mechanism complexity.
3Force
If a wedge mechanism is used to pivot clamp levers, then braking force can be applied, but the braking force decreases as the spring extends and force decreases
Solution Approach 1:
The cam surface profile is designed with varying slope angles that change as the cam rotates. This parameter variation in the cam surface geometry compensates for the spring force changes, maintaining constant clamping force on the rail throughout the spring's extension and contraction cycle.
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
The solution maintains a substantially constant braking or clamping force, enhancing operational predictability and safety by compensating for spring force changes and wear-related losses, thereby improving the reliability of the braking mechanism.
Implementation Method 1
A spring biases the cam in a first direction
Implementation Method 2
Each of the variably sloped cam surfaces has a profile of varying slope so as to counteract variations in a spring force of the spring as the cam is displaced
Implementation Method 3
Each of the variably sloped cam surfaces has a profile of varying slope so as to counteract variations in a spring force of the spring as the cam is displaced, thereby maintaining a constant braking or clamping force
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A rail clamp comprises a frame and a pair of levers. Each of the levers has a brake pad at a first end thereof, a cam follower at second end thereof, and is mounted to the frame by a pivot disposed between said first and second ends. A cam is disposed between the levers and a spring biases the cam in a first direction. A clamp release actuator is operable to displace the cam in a second direction. The second direction is opposite to the first direction. A pair of variably sloped cam surfaces are disposed on opposite sides of the cam. Each of the variably sloped cam surfaces is in contact with the cam follower of a corresponding one of the levers, and each of the variably sloped cam surfaces has a slope which varies to counteract variations in a spring force of the spring as the cam is displaced, thereby maintaining a constant clamping force.