Portable Door Assist Device

Problem Definition

• Heavy swing doors and self-latching handles require simultaneous press/twist and push/pull—often a two-handed, high-force task at awkward angles while piloting a chair and carrying gear.
• “Accessible” often means technically compliant, not functionally usable: tight clearances, heavy closers, scarce or broken powered openers, harsh thresholds.
• Needed: a portable, door-agnostic tool that supplies force, control, and safety—without modifying buildings or relying on bystanders.

Design Principles

• Independence first: user controls timing, opening distance, and closing.
• Portability: carry-sized kit; deploy in ≤ 30 seconds; stows in a small pouch.
• Universality: right/left swing; push/pull; lever or knob.
• Non-destructive: suction/adhesive and clips only; no screws into property.
• Phased safety: never cross a moving door; brake before pass-through; easy “panic release.”
• No chair tipping: B never attaches to the chair; loads route into fixed surfaces.

Quick Summary (what it is / how it works)

• A — Anchor + Lock Handler: sticks near the handle; clamps/holds the latch or knob in the “open” position.
• R — Redirect (hinge-side): small clip with a low-friction ring used only for push-away doors.
• B — Winch/Hub: compact battery micro-winch with soft start/stop, brake, and reverse; mounts to a stable wall/doorframe—never to the chair.
• Pull mode (door swings toward you): line runs A → B.
• Push mode (door swings away from you): line runs A → R → B (triangle).
• Brakes engaged before you pass through.
• Retriever cord for phased retrieval (B reels to A, then A detaches) so nothing whips/snaps.
• Red rip-cord on A for instant release if anything feels wrong.

Status: concept fully specified and ready for bench testing. All build/test results will be published openly as they occur.

System Components (v1 prototype)

A — Anchor + Lock Handler

• Anchor: heavy-duty suction pad or re-usable adhesive pad with D-ring; bright rip-cord tab.
  • Lever latch: clamp presses lever down and holds.
  • Round knob: clamp wraps knob, rotates, and ratchets at angle to hold the latch retracted.
• Controls: optional A-brake button (line hold) and red rip-cord for instant detach and auto-release of the clamp.

R — Redirect (hinge-side)

• Clip body with low-friction ring (alpine/ceramic guide).
• Soft silicone bite to grip frame; one-pull quick-release tab.

B — Winch/Hub + Retriever

• Micro-winch: 30–50 lbf rated pull (prototype range) with soft start/stop, momentary brake/hold, reverse, and a simple button.
• Mount: large suction/adhesive pad onto wall/frame only (never chair).
• Line: flat webbing or paracord; high-visibility; no metal cables.
• Retriever: thin cord/leash tied to A; reverse reels A to B after use.
• Dock magnet: coin magnets on A and B so A “parks” on B when reeled in.

Modes & Workflows (operator cards)

Card A — Pull (door swings toward you)

1. Stick A near the handle; engage Lock Handler (press lever / twist knob as needed).
2. Stick B to a stable wall/frame ahead of you.
3. Clip line A → B (no R).
4. Press B to pull; the door swings toward you.
5. Hit Brake (A or B). Door freezes.
6. Roll through.
7. Retrieve: pull retriever → B slides to A, then A detaches (rip-cord if needed).
8. Dock A onto B; stow.

Card B — Push (door swings away from you)

1. Stick A near the handle; engage Lock Handler.
2. Clip R to the hinge-side frame.
3. Stick B to wall/frame near R.
4. Route A → R → B.
5. Press B; pull via R pushes the door open away.
6. Hit Brakes (A and/or B).
7. Roll through.
8. Retrieve: retriever → B returns toward R → R + B move toward A → A detaches last; dock A to B; pop R; stow.

Rule: You only pass through when brakes are engaged and the door is steady.

Safety Requirements (functional)

• Braking: positive hold at any position; no creep while passing.
• Soft start/stop: no jerks; acceleration ramp ≤ 0.5 s to target speed.
• Instant release: red rip-cord on A detaches in < 0.3 s; R quick-release detaches in < 0.3 s.
• No pinch path: lines and hardware stay outside wheel path and hand zones.
• Visibility & tactility: high-contrast straps and tabs; tactile bumps on controls.
• No chair anchoring: B must never mount to the chair.
• Environment: materials rated for −10 °C to 45 °C and typical humidity.
• Hygiene: smooth, wipeable surfaces; alcohol-wipe compatible.

Performance Targets (initial)

Targets to test—verify during the bench phase. These are not promises.

• Door opening force at handle: ~5–20 lbf for many doors; heavier closers and higher friction can exceed that.
• Winch pull rating: ≥ 40 lbf continuous recommended (headroom above typical).
• Adhesion: suction/adhesive pads resist ≥ 2× expected line load (e.g., ≥ 80 lbf).
• Line safety factor: rated ≥ 250 lbf (e.g., paracord 550 or kevlar webbing).
• Cycle time to open 60°: ≤ 3 s typical; adjustable.
• Setup time: goal ≤ 30 s (place A/R/B and clip line).
• Battery: ≥ 30 open/close cycles per charge in lab conditions.

Test Plan (bench → doorway → field)

Bench (safe rig first)

• Build a door simulator: scrap door + closer + frame on sawhorses.
• Measure opening force at handle vs. angle with a luggage scale; log the curve.
• Verify winch can move door through full arc with soft-start and brake.
• Test A/B adhesion on clean glass/painted wood/metal; record any slip.
• Abuse tests: sudden stops, mid-pull brake, emergency rip-cord—confirm controlled behavior.

Real doors (controlled)

• Test on known doors with varying closers/hinges (both pull and push).
• Try lever and knob handles (use Lock Handler).
• Evaluate set-up ergonomics from seated position: reach zones and tab sizes.

Field (observational)

• Quiet hours in public buildings (with permission).
• Collect timings (setup/open/pass/retrieve).
• Note failure modes (dirty surfaces, textured doors, wet conditions).

Known Risks & Mitigations

• Suction slip on textured/dirty paint → carry alcohol wipes; use reusable adhesive plates (Command-style) with pull-tabs; add a mechanical frame-lip hook accessory.
• Door closer too strong → winch stalls or line stretches; mitigate with 2:1 redirect (compound pulley at R) or up-spec the winch.
• Door slams if brake fails → carry a small rubber wedge; always brake before pass-through.
• Latch re-engages mid-pull → Lock Handler must fully hold; add a visual flag when fully engaged.
• Trip/pinch hazard → keep line shoulder-height where possible; bright color; minimal slack; never route across the floor in front of wheels.

Alternatives / Fallbacks (for tricky doors)

• Mechanical frame hook: clamp that grabs a frame lip when surfaces are dusty or porous.
• Adhesive micro-plates: leave removable low-profile plates at frequent locations (home/clinic) to guarantee strong mounts.
• Compound pulley kit: add a second ring at R for 2:1 advantage on heavy doors.
• Manual mode: if batteries die, Lock Handler + retriever + wedge still reduce strain and allow safer bystander assistance.

Human Factors & Ergonomics

• Large tabs that are easy to grasp with low hand strength.
• One-button logic: B = drive; A/R = brake; buttons distinguishable by touch.
• Contrast color coding: A (yellow), R (blue), B (orange), retriever (red).
• Mount heights within the seated reach zone (consider joystick side and range).

Minimal Bill of Materials (prototype)

• 2 × heavy-duty suction/adhesive anchors with D-rings (≥ 30 lbf)
• 1 × micro-winch (30–50 lbf continuous, soft start/stop, brake, reverse)
• 1 × low-friction ring (alpine ring) + small hinge-side clip body
• 1 × paracord 550 or 1/4″ flat webbing (≥ 250 lbf)
• 1 × thin retriever cord + small reel at B
• 4–6 × quick-release micro-carabiners or G-hooks
• 2 × coin magnets (dock)
• 1 × spring-loaded Lock Handler clamp (hinge + jaws + ratchet)
• Alcohol wipes; bright heat-shrink/fabric tabs; optional rubber wedge

Build Order (lean)

1. Mock A: suction pad + simple clamp to press a lever; add strap for knob twist.
2. Mock B: off-the-shelf micro-winch fixed to a sacrificial wall board.
3. Mock R: 3D-print or aluminum clip with alpine ring; add silicone bite and pull tab.
4. String the line: test A → B first; then A → R → B.
5. Add brake (if winch lacks it, use an in-line cam cleat as a temporary brake).
6. Add retriever + magnet dock + red rip-cord.
7. Iterate Lock Handler until it reliably holds both levers and knobs.

What Success Looks Like (acceptance criteria)

• Deploy Pull or Push in ≤ 30 s without help.
• Open a typical office/store door to ≥ 70° and hold steady while passing.
• No uncontrolled movement while the user is in the doorway.
• Retrieve and stow A/R/B in ≤ 20 s on the far side.
• No chair tipping, no chest “kickback,” no dropped hardware.

Where This Works and Where It Doesn’t

• Why it works: converts the need for simultaneous hand force into a controlled mechanical pull with redirection. The triangle path (A → R → B) lets a pull create a push.
• Where it may fail: poor adhesion (dirty/porous surfaces), extreme door closers, or geometry that blocks anchor placement. Fallbacks (adhesive plates, frame hook, 2:1 pulley) are included above.