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Engineering Projects

Published on Feb 28, 2016


A large concern for the elderly is forgetting to engage the parking mechanism on the rollator before using it as a seat or for support. Interviews and research indicate that the elderly are prone to falling because of the dependence on memory to activate the rollator’s parking mechanism and also the inability of the current rollator to effectively park when the braking mechanism is engaged.

The design project focuses on creating a rollator that will brake by default and thus will eliminate the need for users to rely on memory to activate the parking mechanism. The first iteration of the design is based on the concept of a pin-lock braking system that is activated by the top frame of the rollator. The second and final iteration of the design replaces the pin-lock with a chainlock. Based on another round of customer feedback, the next generation of the rollator will replace the chain-lock with a ratchet gear lock.

Parking Mechanism

The parking mechanism consists of a gear fixed to the axle of the wheel and an interlocking chain mounted on a track along the leg of the wheel. A steel wire connects the chain to the top frame. During the default parking state, the steel wire is slack and the interlocking chain fits with the teeth of the gear preventing motion due to the rigidity of the frame housing the chain.

When the steel wire becomes taut, the chain frame slides up along the track compressing a spring and unlocking the chain from the gear which allows motion of the wheel. When the steel wire becomes slack again, the compressed spring pushes the chain back onto the teeth of the gear thus parking the rollator.

In this default state, any force on the handle bars such as for support applies a clockwise torque around the pin counteracted by a horizontal stopper bar at the front of the walker as seen in Figure 4. To release the parking mechanism for motion, the user must consciously pull the top frame of the walker towards them effectively sliding the pin to the left side of the slot; pushing down on the handle bars then creates a counter-clockwise torque which pivots the frame about the pin. This in turn pulls up on the steel cable and raises the parking mechanism off of the back wheels allowing motion.

Rollator’s Parking Brake System

Top Frame

The top frame redesign of the rollator represents three main functionalities – default parking, differentiation between movement and support, and self-parking during non-use. Through these three functionalities, the needs of the user surrounding being intuitive, immobile during parking, and requiring less strength are addressed.

The slot and pin mechanism allows for the three functionalities. In the default state where the pin is at the right side of the slot and the frame is parallel to the ground, the steel wire connected to the parking brake is slack thus exhibiting default parking.

Self-parking when the rollator is not in use is the final major functionality of the top frame redesign. Continuing from when the top frame is pivoted counter-clockwise, if the user releases the force from the handles, a deflector lever with a stretched compression spring forces the frame to slide back along the slot to the right side and pivot clockwise until it hits the stopper thus returning it to the default parked position. Meanwhile, as the frame pivots, the steel cable becomes slack and activates the parking mechanism.

Project Done By Stephen Siu, Maria Wong, Aditya Shah, Heng Li, Alan Soong, Ray Cao