Electric Switch with Offset Contacts for Hysteresis Elimination
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Solution Overview
Problem
Snap-action electric switches used in automated process control installations for detecting electromagnetic brake states and wear exhibit hysteresis, leading to unreliable detection of small air gap variations and requiring additional switches for monitoring.
Innovation Solution
An electric switch with a hollow cylindrical casing and an axially movable actuator, featuring a contact block with offset conductive areas and electrical contacts, eliminating hysteresis and allowing simultaneous monitoring of air gap opening and brake wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If snap-action switches are used for detecting electromagnetic brake states, then the switch structure is simple and easy to manufacture, but hysteresis phenomenon occurs leading to unreliable detection of small air gap variations
Solution Approach 1:
The switch is divided into two independent detection circuits: a first circuit for detecting air gap closure and a second circuit for detecting air gap opening. Each circuit has its own contact pair (first and second electrical contacts) that can be independently adjusted, eliminating the hysteresis problem of single-circuit snap-action switches while maintaining manufacturing simplicity.
Solution Approach 2:
The invention changes the adjustment parameter from spring differential movement to independent contact position adjustment. The first and second electrical contacts can be independently positioned along the axial direction, allowing precise setting of threshold values for circuit switching without hysteresis, thereby improving measurement precision while keeping the structure simple.
2Reliability
If snap-action switches are used for monitoring brake wear, then additional switches are required, but this increases device complexity and production cost
Solution Approach 1:
The single switch device performs multiple functions: it detects both air gap closure and opening states, and simultaneously monitors brake wear through the second electrical contact. This multi-functionality eliminates the need for additional switches, reducing device complexity while maintaining reliable monitoring capabilities.
Solution Approach 2:
The invention merges air gap detection and brake wear monitoring into a single integrated switch device. The first and second electrical contacts work together within one housing, combining multiple monitoring functions that would traditionally require separate switches, thereby reducing overall system complexity.
3Ease of operation
If snap-action switches are used with spring differential movement, then the switch operation is simple, but hysteresis causes different switching points for compression and release phases
Solution Approach 1:
Instead of using spring compression and release to drive contact movement (which causes hysteresis), the invention inverts the approach by using direct axial movement of the common contact block to simultaneously control both contact pairs. The switching points are determined by fixed threshold positions of the electrical contacts rather than spring differential movement, ensuring consistency between compression and release phases.
Data Source
AI summary
The present invention relates to an electric switch including a hollow cylindrical casing delimiting a cavity, and an actuator that can slide inside the cavity along an axial direction defined by the casing, and including at least one upper part positioned at least partially outside the casing and at least one lower part positioned inside the cavity. The electric switch also includes a contact block movable under the action of the actuator along the axial direction between two specific positions, namely upstream and downstream contact positions, with the contact block having at least two conductive areas, namely upstream and downstream conductive areas respectively positioned at the two ends of an oblong opening formed inside the contact block, and with the ends positioned in an offset manner along the axial direction. The electric switch further includes a pair of electrical contacts, namely upstream and downstream electrical contacts respectively projecting into the oblong opening. The upstream or downstream conductive area, respectively, and the upstream or downstream electrical contact, respectively, are electrically connected in the upstream or downstream contact position, respectively, of the contact block, thus closing a first electrical circuit or a second electrical circuit, respectively.