Project Overview

Problem:
People bring sludge into buildings on the bottom of their boots, especially in the winter. The building then has to be cleaned up once the mess is spread out over hundreds of square feet. This creates a costly slipping hazard, and requires institutions like Dartmouth to hire extra janitorial staff during the winter months to help solve this problem.

Entryway of Dartmouth's Baker Library in February

Solution:
After interviewing various key stakeholders at Dartmouth, I identified unobtrusiveness as a key specification for a solution, as people entering buildings are often in a hurry and don’t have a stake in how dirty the floor gets. I designed a device to be embedded within the entryway floor (instead of the existing felt-covered grates) that simultaneously blows on the soles of shoes to dislodge debris, and vacuums it into a reservoir to keep the floor clean. My solution, The Vacuum Box, cleans off the bottom of visitors’ shoes as they enter a building, preventing sludge from accumulating indoors.

Pressure-activated vacuum box to clear sludge off shoes

Design Process

Preliminary Conceptual Design

I started with a conceptual design to demonstrate how the vacuum and fans could work synergistically to remove debris. This design had the following components:

1. Diffuse fan: A diffuse fan to dry boots

2. Floor-based vertical blowers: Blowers to dislodge sludge

3. Vacuum ports: Vacuum ports to suck off debris

4. High-pressure lateral blowers: High-pressure blowers to remove sludge from the side of the boot

Optimizing Vacuum Port Design

I realized that the vacuum ports in my conceptual model were too large and lacked a tight seal around the boot, so I started to experiment with other vacuum port shapes. Testing revealed that large grooves atop narrow pipes allowed for a good seal while still allowing surrounding sludge to be sucked through.

Spring Vacuum Port Idea

Testing an array of the grooved vacuum ports alerted me that the ports needed to be spring loaded to account for different heights of boot surfaces. I sketched up some designs, before creating the next iteration of the device for testing.

"Works Like" Model of Spring Vacuum Ports

I created prototypes based on my drawings of the spring vacuum ports, using two nested tubes, a spring, and a hose clamp to anchor the spring. The prototype confirmed the feasibility of the spring loaded vacuum box’s ability to contour to the bottom of boots and ensure a good seal.

Proof of Concept

Before going any further, I needed to be sure that with a good seal, a vacuum could succeed in sucking off the sludge from the bottom of a shoe or boot. I 3D printed a shop vacuum attachment to test this simplified scenario. The results confirmed the proof of concept, and successfully removed a ½ inch of sludge from the bottom of the shoe within seconds of contact.

Final Design and Prototype

Now that I knew that the concept was valid, and that I could contour the vacuum ports to shoes using springs, I moved forward and built a SolidWorks model and an aluminum prototype.

If implemented fully in an entryway, the system would turn on when the door was opened, and would remain on for one minute after the door was closed. This design would reduce wasted energy by allowing the system to remain off when not needed.

While both the vacuum system (1) and the blower system (2) turn on when the door opens, the vacuum localizes to where the ports are depressed to enhance suction performance.

Functional Prototype

The prototype functioned as expected. I designed it to only activate when depressed by a shoe, in order to minimize noise and reduce energy consumption.

Pressure Activated Vacuum Blower Box