Supine Fall Arrest Harness with Sternal Lanyard
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Solution Overview
Problem
Conventional fall arrest harnesses can cause suspension trauma due to venous pooling when a person is suspended for an extended period, particularly because leg straps concentrate pressure at the inside thigh and groin areas, leading to potential death within twenty minutes of immobile suspension.
Innovation Solution
A fall arrest harness design that suspends the wearer in a supine position with the weight supported by a seat and back portion, eliminating the load on leg straps and using energy-absorbing extension straps to automatically reposition the lanyard connection from a dorsal to a sternal position during a fall, thereby reducing venous restriction and allowing the wearer to pull themselves up using an ascender device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the lanyard connection member is positioned in a dorsal position on the wearer's back, then the wearer is suspended in a vertical feet-down position which minimizes interference with work operations, but the leg straps concentrate pressure at the inside thigh and groin area causing venous pooling and suspension trauma
Solution Approach 1:
The lanyard connection member is inverted from the conventional dorsal position to a sternal position on the front of the wearer's body. This inversion changes the suspension geometry so that the wearer hangs in a supine position with the seat portion supporting the body weight, eliminating pressure on the legs while keeping the connection point accessible for work operations
Solution Approach 2:
The position parameter of the lanyard connection member is changed from dorsal to sternal, and the suspension posture parameter is changed from vertical feet-down to supine horizontal. This parameter change transforms the pressure distribution from concentrated on legs to distributed across the seat and back portion
2Device complexity
If the leg straps are used to support the wearer's weight during suspension, then the harness structure is simplified, but the venous system in the legs is restricted leading to orthostatic shock and death within twenty minutes
Solution Approach 1:
The weight support function is segmented from the leg straps and assigned to the seat portion and back portion. The leg straps are relieved of load-bearing responsibility and only serve to position the harness on the wearer's body, while the rear section structure assumes the primary weight support function
Solution Approach 2:
The seat portion acts as an intermediary between the lanyard connection member and the wearer's body. It transfers the suspension load from the lanyard to the wearer's stronger body regions (seat and back) while protecting the vulnerable leg veins from pressure
3Stability of the object's composition
If the lanyard connection member is positioned in an inaccessible location, then the harness provides stable suspension, but rescue operations are delayed allowing suspension trauma to become fatal
Solution Approach 1:
The sternal position of the lanyard connection member serves multiple functions: it provides stable suspension by anchoring to the strong sternal region, keeps the connection point accessible for both work operations and rescue activities, and maintains proper suspension geometry. This single position achieves what previously required compromise between conflicting requirements
Data Source
AI summary
A fall arrest harness comprises a pair of shoulder straps, a pair of leg straps and a rear section extending therebetween, a lanyard connection member being connected to a sternal or chest region of the shoulder straps, the rear section defining a seat portion, adapted to lie across the sub-pelvic region or seat of the wearer, and a back portion, adapted to overlie at least a portion of the back of the wearer, the shoulder straps extending between side regions of the seat portion, preferably adjacent a lower edge thereof, and an upper region of the back portion, whereby the wearer, when suspended in the harness by the lanyard connection member, lies in a supine position with the weight of the wearer supported by the seat portion and back portion of the rear section and the shoulder straps with no load being borne by the leg straps.