Knob Assembly with Stop Cam for Rotary Switch Inadvertent Actuation
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Solution Overview
Problem
Existing rotary switch designs in communications devices, such as satellite transceivers, often inadvertently turn off or reset due to accidental movement, leading to delayed communication resumption and increased device size from complex pull-to-turn or push-to-turn mechanisms, which are susceptible to dirt and grit.
Innovation Solution
A pull-to-turn rotary switch assembly with a stop cam and knob collar design that requires a user to exert force to rotate the switch, preventing inadvertent switching to non-preferred positions by using an upper and lower stop member system, reducing interior space requirements and susceptibility to dirt.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pull-to-turn or push-to-turn functionality is included within the body of the rotary switch, then inadvertent switching is prevented, but the switch body becomes larger, increasing the overall size of the satellite transceiver
Solution Approach 1:
The pull-to-turn functionality is extracted from the rotary switch body and implemented externally using a separate knob assembly with a stem that applies force to the switch body. This separation allows the rotary switch to remain compact while still providing inadvertent switching prevention through the external force requirement.
2Ease of operation
If groove systems are used for pull-to-turn or push-to-turn functionality, then rotation control is achieved, but the system becomes susceptible to dirt, sand, or grit, resulting in seizing or poor operation
Solution Approach 1:
The groove system is replaced with a stem-based mechanical interface. The knob assembly uses a smooth stem that pushes against the rotary switch body without requiring grooves or interlocking features, eliminating the susceptibility to dirt and grit while maintaining rotation control through the push-to-turn mechanism.
3Reliability
If additional complexity is added to the rotary switch body for pull-to-turn functionality, then inadvertent switching is prevented, but the device complexity increases
Solution Approach 1:
The complex pull-to-turn mechanism is extracted from the rotary switch body and implemented as a separate, simpler knob assembly. This reduces the complexity within the rotary switch itself while maintaining the reliability benefit of preventing inadvertent switching through the external force requirement.
Data Source
AI summary
A switch assembly (1) includes a rotary electrical switch body (13) having a plurality of switch positions, a switch stem (12) extending along a first axis (32) and having a first and second ends, the first end engaging the rotary switch (14) for alternating the rotary switch body between the plurality of switch positions responsive to rotation of the switch stem about the first axis, and a knob assembly (10). The knob assembly includes a knob core contacting the second end of the switch stem, a knob collar (22) contacting the knob core and adapted for rotating the knob core and the switch stem about the first axis, where the knob collar includes a first upper stop member (46), and a stop cam (20) having a fixed position relative to the switch stem and disposed between the knob core and the rotary switch, where the stop cam includes a lower stop member (31) having a feature for engaging the first upper stop member when the first upper stop member and the lower stop member are disposed along a common path. In the switch assembly, the first upper stop member travels in a circumferential path normal to the first axis responsive to the knob collar rotating the knob core and the switch stem, where the knob collar is displaceable along the first axis between first and second axial positions, where the lower stop member is in the circumferential path when the knob collar is in the first axial position, and where the lower stop member is removed from the circumferential path when the knob collar is in the second axial position.