ALAN LI

The Swirly: Improving the Mop Wringer With Frictional Torsion

 

Our group was asked to design a solution that would solve the problem of repetitive strain injuries, or RSI, induced by the use of mop wringers, specifically for the use by housekeepers at the various University Health Network hospitals in the Downtown Toronto Area. The mop wringers that they use now require the user to exert force at a rather uncomfortable, bent body position when wringing the mop. This uncomfortable behaviour is further aggravated by the fact that users usually have to perform the wringing motion multiple times to get a sufficient amount of water out. As a result of these observations, our team chose to formulate a design revolved around satisfying three main objectives:

 

1. Improve body position

2. Reduce amount of force exerted

3. Reduce number of cycles required

 

- all the while maintaining the usability and maintainability of the wringer.

 

The resulting design solves these problems with three major components:

 

1. The Cone

 

The central mechanism of this cone is frictional torsion. The mop head, when placed in the cone, is twisted by the rotating cone and pulled further into the narrower part of the cone as it twists. The force to pull the mop deeper into the cone is the friction exerted by the rubber threads, lying on the inside wall of the cone. In the bottom portion of the cone, there is a tighter grip on the mop due to smaller space, which allows the mop to twist with less slippage. This wrings out water like you would wring out a towel.

 

2. The Handle

 

The handle is what rotates the gears as it is pushed down. The teeth along the edge of the handle align with the teeth of the gears and turn them. The user applies a vertical force instead of a torque like the conventional wringer. The user can use their upper arm strength and body weight to push down the handle instead of their shoulder muscles. This prevents the shoulder pain the Housekeepers described, as the forearm muscles are much stronger and less prone to Repetitive Strain Injury. The handle design also keeps the wrist straight during use, which prevents wrist pain. The conventional wringer also requires the user to bend over, which is a source for Repetitive Strain Injury. Our handle does not have the same rotational motion and only requires a small displacement, so it does not force the user to bend over when they push down the handle.

 

3. The Gears

 

The gear system translates the linear force applied by pushing down on the handle into the rotational force induced on the cone. It eill allow for the cone to turn multiple times with just one push of the handle. This would further enhance our third main objective of reducing the number of cycles required to wring out the mop.With all this, it can be seen that we kept our design to be strictly mechanical, without any circuits and automation involved. This ensures the cleanability and maintainability of the entire structure, something that is of primary importance as this wringer would be something to be used in a hospital environment.