Designing from the Inside: A Practitioner-Led Invention for Zero-Transfer Patient Weighing

Current methods for weighing immobile, bedridden patients require either physical transfer to a hoist-and-sling apparatus — a procedure demanding multiple staff, 15–30 minutes, and significant musculoskeletal load, or integrated bed scales that weigh the entire bed frame, mattress, and patient simultaneously and subtract tare weight, a method vulnerable to error from linens, IV poles, and mattress compression variability. No existing solution permits weighing an immobile patient without moving them from the surface they are lying on and without including mattress weight in the measurement. This preprint describes a novel hospital bed design; the Split-Mattress Weighing Bed (SMWB), in which the mattress divides longitudinally into two halves that retract horizontally, allowing a central rigid weighing platform to rise through the gap and support the patient in isolation from the mattress. Load cells measure only platform and patient weight. Mechanical decoupling is physical, not mathematical: no tare subtraction occurs. The patient undergoes zero transfer, experiences no perceptible movement, and the procedure completes in approximately 60 seconds. The paper documents the invention's clinical origin, engineering architecture, prior art gap, and the practitioner positionality that made the problem visible. A Gebrauchsmusteranmeldung (German Utility Model Application) was filed with the Deutsches Patent- und Markenamt (DPMA) in May 2026 under document ID SMWB-2026-001.