Electromagnetic Drum Brake Actuation via Cam Positioning
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Solution Overview
Problem
Internal shoe brakes with electromagnetic actuating devices face inefficiencies due to poor force utilization, limited structural size, and high costs, as the actuating force is applied offset from the brake shoe support bolts, restricting the diameter ratio and requiring expensive transmission elements.
Innovation Solution
The actuating cams of the electromagnet are positioned near the brake shoe supporting blocks, allowing direct force transmission to the brake shoes, enabling a larger diameter electromagnet for increased force generation without additional transmission elements, and utilizing a self-reinforcing duplex brake design with fixed pivot points for predictable braking behavior.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the actuating force is applied offset from the brake shoe support bolts (90° offset), then the brake structure can be simplified, but the force utilization efficiency deteriorates
Solution Approach 1:
The patent positions the actuating cams at the ends of the brake shoes rather than at the center, creating an asymmetric force application point. This asymmetric positioning allows the actuating force to be applied directly at the pivot point, eliminating the need for complex transmission elements while maximizing force utilization efficiency.
2Force
If the electromagnet diameter is increased to generate larger actuating forces, then the actuating force increases, but the ratio of hub diameter to brake shoe outside diameter decreases
Solution Approach 1:
The patent positions the electromagnet radially outside the brake shoes rather than inside, utilizing the axial dimension for force transmission. This dimensional repositioning allows larger diameter electromagnets to be used without reducing the radial installation space, as the electromagnet occupies axial space rather than radial space.
Solution Approach 2:
The actuating cams serve as intermediaries that transmit the electromagnetic force to the brake shoes. By placing the electromagnet outside and using cams as force transmission elements, the system achieves large actuating forces while maintaining a large hub-to-brake-shoe diameter ratio.
3Force
If transmission elements are added to increase actuating force, then the force transmission efficiency improves, but the device complexity and manufacturing cost increase
Solution Approach 1:
The patent extracts and eliminates complex transmission elements by directly positioning the actuating cams at the brake shoe ends. This simplification removes unnecessary intermediate components while maintaining high force transmission efficiency through direct electromagnetic actuation at the pivot points.
4Volume of moving object
If the electromagnet is mounted on its outer peripheral surface with cam discs inside rollers, then the brake structure is compact, but the magnetic body size is restricted
Solution Approach 1:
Instead of mounting the electromagnet inside the brake structure with cam discs constrained by rollers, the patent inverts the arrangement by positioning the electromagnet radially outside the brake shoes. This inversion allows the magnetic body to have a larger diameter without constraining the overall brake structure size.
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
This configuration achieves high actuating force efficiency with minimal power loss, reduces manufacturing costs, and provides a large installation space ratio, ensuring consistent braking performance without the need for adjustment devices due to the direct and proportional magnetic force application.
Implementation Method 1
an annular electromagnet is used which, during a braking process, i.e. when the electromagnet is energized, attracts an armature disk
Implementation Method 2
the electromagnet is rotated a small distance by the brake drum... in Frictional contact reached
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The shoe brake has a brake drum which is rotatably connected to anchor plate. The brake drum and anchor plate are frictionally engaged to electromagnet (3), so that rotation is possible. The brake shoes (2) are pulled together by shoe return springs. The electromagnet is provided with actuating cams which are arranged in vicinity of support brackets (7,8) for brake shoes and extended into the spaces between opposing end surfaces of brake shoe webs.