Cable-Actuated Safety Switch Hollow Shaft Locking Mechanism
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Solution Overview
Problem
Existing safety switches with rope-actuated quick shutdowns have complex locking mechanisms that consume space and compromise functional reliability, necessitating a simpler and more space-efficient design.
Innovation Solution
Integration of an axial blocking mechanism using a spring-loaded unlocking shaft within a hollow shaft, allowing for a compact design where the locking mechanism is partially accommodated by the shift drum, with a hexagonal shaft providing rotational stability and a compression spring or gas pressure spring for energy storage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a complex locking mechanism is used to maintain safety signals, then reliability is improved, but device complexity increases and space consumption increases
Solution Approach 1:
The patent combines the locking mechanism with the shift drum by integrating the unlocking shaft within the hollow shaft of the shift drum. The locking member is seated on the hollow shaft and works in conjunction with the shift drum's rotation, merging what would traditionally be separate assemblies into a unified structure that maintains safety signals while reducing overall complexity
Solution Approach 2:
The unlocking shaft is nested within the hollow shaft of the shift drum, creating a compact arrangement where the locking mechanism components are housed within the existing structural envelope. This nesting approach allows the locking mechanism to be accommodated without increasing external dimensions, thereby maintaining reliability while reducing device complexity and space consumption
2Reliability
If a complex locking mechanism is used to prevent unintentional resets, then reliability is improved, but space consumption increases
Solution Approach 1:
The locking mechanism is merged with the shift drum structure, where the unlocking shaft and locking member are integrated into the hollow shaft of the shift drum. This combination allows the safety signal maintenance function to be achieved within the existing housing volume without requiring additional space for separate locking assemblies
Solution Approach 2:
The unlocking shaft is positioned within the hollow shaft of the shift drum, and the locking member is seated on the hollow shaft. This nested arrangement ensures that all components required for preventing unintentional resets are contained within the existing structural envelope, thereby maintaining reliability while avoiding increased space consumption
3Stability of the object's composition
If a rigid coupling between shift drum and unlocking shaft is used, then rotational stability is improved, but sensitivity to cable tension increases causing false emergency shutdowns
Solution Approach 1:
The patent employs a spring-loaded unlocking shaft that can dynamically adjust its position in response to cable tension variations. The spring allows the unlocking shaft to move axially, absorbing slight tensile forces without transmitting them as rotational motion to the shift drum, thereby maintaining rotational stability while preventing false emergency shutdowns
Solution Approach 2:
The compression spring is pre-loaded to cushion against slight tensile forces on the cable before these forces can cause the unlocking shaft to rotate and trigger an emergency shutdown. This beforehand cushioning allows the system to tolerate normal cable tension variations while remaining sensitive to genuine emergency conditions
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 design maintains safety signals without unintentional resets, is space-saving, and ensures reliable operation by buffering slight tensile forces without triggering emergency shutdowns, while allowing manual reset through an unlocking button.
Implementation Method 1
The hollow shaft, which is preferably stationarily mounted in the switch housing, accommodates an energy store for driving the unlocking shaft. The unlocking shaft is thereby enabled to move the locking member guided by it in relation to a counter bearing. A compression spring, in particular also a gas pressure spring, is preferably provided as the energy store.
Implementation Method 2
A compression spring, in particular also a gas pressure spring, is preferably provided as the energy store. The compression spring can prestress the unlocking shaft in relation to the hollow shaft in a prestressed position
Implementation Method 3
The counter bearing has latching surfaces which prevent the locking member from rotating back, preferably by a mechanical stop.
Data Source
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AI summary
Safety switch with cable-operated rapid shutdown, comprising switching contacts (17) arranged in a housing (1), a switching drum (2) acting on the switching contacts, and an actuating device (3) acting on the switching drum (2), to which a cable pull (4) is connected, wherein the switching drum (2) is at least partially designed as a hollow shaft (5) in which a spring-loaded release shaft (6) coupled to the hollow shaft (5) in the direction of rotation is arranged to be axially displaceable, the release shaft (6) carries a release handle (7) at an actuating-side end, and a locking element (8) positioned rotationally fixed on the hollow shaft (5) and axially displaceable relative to the hollow shaft (5) is positively coupled to the release shaft (6), and the locking element (8) in an engagement position with a housing-fixed counter bearing (9) determines a spring-loaded axial stroke (X) of the release shaft (6).The rotation of the hollow shaft (5) required for axial detenting of the switching drum (2) after a rapid shutdown moves the locking element (8) into an out-of-engage position.