Switching Apparatus Cam Lever Mechanism Reduces Torque
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Solution Overview
Problem
Current high and medium voltage electrical switching devices with common drive means for movable contacts face issues such as significant size, high torque requirements, and unwanted reaction forces due to the design of existing control mechanisms.
Innovation Solution
A control mechanism featuring a rotating control shaft with a disc cam and pairs of levers, where the geometric shape and arrangement of the levers and cam grooves provide a variable drive ratio, reducing torque and reaction forces, and allowing self-locking of contacts in their extreme positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a single rotating drive shaft is used to drive movable contacts in translation, then the device size is reduced and mechanical coordination is improved, but the torque requirement increases significantly and unwanted reaction forces are generated on the shaft
Solution Approach 1:
The patent introduces an intermediary mechanism consisting of a cam profile and lever system between the rotating drive shaft and the movable contacts. The cam profile converts rotational motion into controlled linear motion, while the lever system provides mechanical advantage to reduce the torque required on the drive shaft. This intermediary mechanism allows the drive shaft to operate at lower torque while still achieving the required contact movement.
Solution Approach 2:
The patent changes the motion parameters by using a cam profile with specific geometric characteristics that vary the transmission ratio during the switching cycle. The cam profile is designed to provide high mechanical advantage (low transmission ratio) when force is needed, and lower mechanical advantage when speed or stroke is needed, thereby optimizing the torque requirements throughout the operation cycle.
2Ease of operation
If a single rotating drive shaft is used to drive movable contacts, then operational coordination between switches is improved, but reaction forces are generated on the shaft when contacts are in closed position
Solution Approach 1:
The patent extracts the force transmission function from the rotating drive shaft by introducing a separate lever system. The levers are hinged to fixed points and connected to the movable contacts, allowing them to support and isolate reaction forces when contacts are closed. This separates the rotational driving function from the linear force support function, eliminating unwanted reaction forces on the drive shaft.
Solution Approach 2:
The lever system acts as an intermediary between the cam-driven motion and the movable contacts. When contacts are in the closed position, the levers support the reaction forces independently, preventing these forces from being transmitted back to the rotating drive shaft. This intermediary mechanism protects the drive shaft from unwanted loads while maintaining operational coordination.
3Length of moving object
If the disc cam is designed to accommodate the full stroke of movable contacts, then the drive ratio is sufficient, but the device size increases significantly
Solution Approach 1:
The patent employs a dynamic lever system where the effective lever arm length changes during operation. The levers are hinged at fixed points and connected to movable contacts, creating a dynamic mechanical advantage that varies with position. This allows a more compact cam design since the lever system compensates for reduced cam stroke through its own geometric transformation, reducing the overall device size while maintaining sufficient drive ratio.
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 solution results in a more compact design with reduced torque requirements, self-locking of contacts, and minimized reaction forces on the control shaft, enhancing the efficiency and reliability of the switching device.
Implementation Method 1
the busbar disconnector and the earthing switch are arranged in insulating enclosures each filled with a dielectric gas under a controlled atmosphere, such as SF6
Implementation Method 2
at least one disc cam integral with the control shaft and comprising two distinct internal grooves... the geometric shape, length and arrangement of the two pairs of levers as well as the profile of the cam(s) grooves allow for an additional drive ratio
Implementation Method 3
two pairs of levers hinged together, one of the levers of a given pair having one end hinged to a fixed point and the other end hinged to the other of the levers of the given pair itself hinged to one of the movable contacts
Data Source
Figure 1
Figure 2
Figure 3~5
AI summary
The mechanism has a common actuator unit (22) including levers (2210, 2220, 2211, 2221) hinged together. One of the levers is hinged to one of movable contacts (200, 210). Spigots (2230, 2231) are arranged between two ends (222, 224) of each lever. The spigots are engaged in one of cam grooves (221R0, 221R0) so as to constitute a follower, where geometry, length and disposition of the levers and profiles of the grooves provide an additional drive ratio between a disk cam (221) and the associated movable contact. An independent claim is also included for a medium and high voltage gas insulated switch including a casing in which movable contacts of two interrupters are arranged.