Cable Gland Compression Limiter for Stable Sealing Pressure
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Solution Overview
Problem
Conventional cable glands experience over-compression of the bushing, leading to damage of the cable jacket and increased water ingress due to high contact pressure, which is exacerbated by aging and temperature changes.
Innovation Solution
A cable gland with a compression limiting assembly featuring a compression limiter and a stacked wave spring that limits the compression of the bushing, redirecting further tightening forces away from the bushing to maintain a constant contact pressure and prevent over-compression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If the gland nut is tightened to secure the cable connection, then the contact pressure between the bushing and cable increases, but the bushing may be over-compressed causing damage to the cable jacket
Solution Approach 1:
The compression limiter acts as an intermediary component between the gland nut and the bushing. It absorbs the excess compression force when the bushing reaches its optimal compression state, preventing further compression that would damage the cable jacket. The compression limiter includes a compression surface that engages with the bushing to limit axial compression while allowing radial expansion.
Solution Approach 2:
The compression limiter is pre-configured with a yield mechanism that activates before the bushing can be over-compressed. When the bushing compresses the cable jacket to the desired level, the compression limiter yields or deforms, creating a mechanical stop that prevents additional compression forces from being transmitted to the bushing and cable assembly.
2Reliability
If high contact pressure is applied to prevent water ingress, then sealing performance improves, but the bushing material may set permanently reducing contact pressure over time
Solution Approach 1:
The compression limiter serves as a mediator that decouples the tightening force from the bushing compression. It allows the gland nut to be tightened to high torque values without transmitting all that force to the bushing. The compression limiter absorbs the excess force, maintaining stable contact pressure on the bushing while still achieving the required sealing performance through controlled compression.
Solution Approach 2:
The compression limiter changes its mechanical properties under load, transitioning from a rigid state during installation to a yielded state during operation. This parameter change allows it to initially transmit compression force to achieve sealing, then maintain a constant limiting compression force that prevents permanent setting of the bushing material while preserving sealing integrity.
3Force
If the bushing is compressed to achieve proper cable grip, then cable securing improves, but further tightening redirects forces that could damage the cable
Solution Approach 1:
The compression limiter acts as a protective intermediary that absorbs redirecting forces from further tightening. When the gland nut is tightened beyond the point where optimal cable grip is achieved, the compression limiter yields and prevents these excess forces from being transmitted to the cable, thereby protecting the cable from mechanical damage while maintaining secure grip through the initial compression phase.
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
The solution prevents over-compression of the bushing, maintains a secure cable connection, reduces wear and tear, and allows the use of elastomeric materials like silicone over a broader temperature range, enhancing performance and compliance with certification standards.
Implementation Method 1
A stacked wave spring is disposed in the gland nut. Upon coupling of the gland nut to the body, the stacked wave spring is configured limit compression of the bushing.
Implementation Method 2
A spring is disposed between the compression limiter and the bushing
Data Source
AI summary
A cable gland includes a gland nut defining a longitudinal axis. The gland nut includes an interior wall defining a gland nut opening. A bushing is disposed within the gland nut. The bushing defines a bushing opening configured to receive a cable therein. A compression limiting assembly includes a compression limiter moveably disposed at least partially within the gland nut. A spring is disposed between the compression limiter and the bushing. A body defines a body opening configured to receive at least a portion of the cable therein. The body is configured to couple to the gland nut. Upon coupling of the gland nut to the body, the gland nut moves along the longitudinal axis compressing the bushing between the gland nut and the compression limiting assembly and around the cable.