The Convenient Chair
Kevin Lema, Mariana Restrepo, Yvan Tanzi SHEMA, Erica Wong
With age, we must succumb to the idea of weakness. Our bones become brittle, our strength is depleted, and we also start to see it in our loved ones. It is one of the certainties of life and is a growing concern with the phenomena known as the Graying of America. The Graying of America refers to the increasing proportion of the older population. Since the Baby Boomers, the birth rate has declined through the 1970s and continued to decline until 2007. While 17% of the US population is estimated to be elderly people (65+ years), the percentage will keep growing as stated by the U.S. Census Bureau. To put it into perspective, the US Census (2018) has noted that the population of older people (age 65 and older) will be around 77 million, while the population of children (under age 18) will be around 76.5 million in 2034. The older population is gradually dominating the U.S. due to declining birthrates and medical advances continuously increasing the average lifespan.
However, this group is at great risk of falls because of poor vision, dizziness, and decreased strength of lower limbs resulting in aging (Lytras et al, 2022). Every year more than a million staircase falls are reported, these falls differ in how severe they are, from simple to fatal ones with 39000 deaths of the elderly population as of the year 2021 according to the U.S. Centers For Disease Control and Prevention (CDC, 2024). Addressing these issues requires government intervention, and with the Graying of America becoming a reality, there must be an emphasis on accommodating the growing older population and ensuring their needs are met.
The national conversation about the older population often projects age as a disability. However, age should not be a reason to limit their independence. The Convenient Chair is designed to help older people adapt to the challenges of daily tasks conveniently and comfortably.
The main purpose of the Convenient Chair is to help older adults who live in apartments run errands, especially those living in apartments that do not have elevators. According to the NYC Buildings Department, five or more story buildings should have elevators (Building Bulletin, 2017). This law itself will pose a difficulty to older people using buildings that are not required to have elevators and to solve this challenge a stair lift can be implemented. Although a stair lift already exists, certain situations, like carrying groceries up the stairs, may be challenging for older persons if an ordinary stair lift does not accommodate them. To solve this issue, our product will include an attachable medium compartment to store groceries and lift the person to their destination.
Besides that, we shall ensure comfortability with a boosted cushion attached to the seat. This cushion assists seniors in standing up as they exit the lift, supporting those who struggle to rise due to muscle loss. These features allow seniors to keep their freedom without relying on others to do basic tasks. We will be focusing on straight stairlifts as they are the most common type of stairs see figure 1 below for an example.
Figure 1 depicts the use of a standard straight stairlift.
Why Choose the Convenient Chair?
We designed the Convenient Chair to make apartment buildings more accessible to older persons while also being an affordable remedy that does not take long to install. Many may argue that elevators may be a better remedy but forget that “On average, the price of a home elevator starts at about $35,000 and ranges upward to $100,000+ “(LifeWay Mobility, 2025), whereas “The cost of a stair lift for a straight staircase typically ranges between $2,500-$8,000 (new or used)” (LifeWay, 2025), making our product more affordable to apartment owners with less than 5 story buildings as they are not obligated to have elevators there.
Installing the Convenient Chair is also more favorable since elevators may take up to a few weeks to a few months to install (Buckley Elevator, 2024), while straight stairlifts (model of our invention) only take a few hours to half a day to install (Senior Stairlifts, n.d.). This quick installation means you will have access to your home quicker (within the next day compared to an elevator installation) without having workers constantly bothering your peace. Besides that, elevators also pose an issue of needing room to build an elevator shaft and pit (Stannah, 2025).
These problems prevent older tenants in small apartment complexes from living independently and comfortably. This is where the Convenient Chair comes into play, making seniors’ lives more convenient.
Design of the Convenient Chair
The design of our Convenient Chair is quite simple and comprises the main parts: the rail, the seat, the carriage (part of the stairlift that moves up and down and carries the motor, batteries, and circuit board), and the grocery compartment attachment. All of these components use simple resources/mechanisms to produce efficient results. In this section, we will discuss how each component works to make it easy for you to use and operate.(Maybe a diagram of the four key parts should be added here and after this, the four key components will be broken down into parts as we explain how they function and their cost).
Seat
The seat of the Convenient chair is designed with simplicity and comfort in mind. The chair’s structure is made of durable plastic and layered with vinyl fabric for added comfort while sitting. For safety, a seat belt is attached to prevent falls during use. On the sides of the chair, the armrests feature a controller with three buttons to help you control your stairlift experience. At the top, there will be two side-by-side buttons, one with an upward arrow and the other with a downward arrow indicating the direction of movement along the stairlift rail. To operate, you must press and hold the button toward the direction you are going until you reach your destination. Below those two buttons, there is another button “P” for “STAND.” This button activates the booster seat, which uses a metal mechanism to gently lift the seat, assisting users in standing up vertically with ease. In addition, the armrests will be foldable and modeled after the Bruno stair lift, to accommodate the attachment of a grocery compartment to the side of the seat. See figure 2 and 3 below for controller design and cart compartment design.
Figure 2 shows directional controllers (UP/DOWN), “P” button
Figure 3 cart compartment and magnetic attachments.
Carriage
The carriage will use a rack and pinion mechanism, commonly found in most typical stairlifts. This system converts rotational motion into linear motion, allowing the chair to move along the railing. It consists of a circular gear, the pinion, that engages with the linear gear, the rack. This interaction enables the chair to ascend and descend smoothly along the railing with the help of the gear teeth.
The rack and pinion system’s simplicity and compact design make it suitable for tight spaces, such as the stairways in apartment complexes. With minimal moving parts, it requires less maintenance and offers greater durability. This would be well suited for landlords as it is inexpensive to install and maintain compared to the cost of elevators. The system is typically made of stainless steel or steel for strength, while a plastic cover protects it from visibility and external damage.
Rail
The rail will be a double tube design to provide a comfortable, smooth ride. We will also make the tubes and support beams out of aluminum since it is a common material used by other stairlifts. For easy installation, we will make the rail attach to the stair treads, and it will have small holes located at the support beams to indicate where you should place your screws for safe attachment. We will also attach a metal clamp across the rail as a safety measure to prevent the rail from failing forward due to the excessive weight force (idea from video of stairlift installation in our group chat).
Our rail will also have a charging strip embedded within because rails, specifically straight rails, are typically “fitted with a charging strip that provides a constant charge, powering the stairlift’s battery, regardless of where you decide to park the chair” (Stannah, n.d.). We will use this design because it will make your ride convenient and as peaceful as possible, especially considering that you don’t have to worry about where you park the chair for it to work or charge up. Also, a limit switch will be attached to the bottom of the rail near the edges to alert your stairlift that it should slow down and come to a complete stop. Besides that, we are installing top-notch sensors that will detect any obstacle in the path and bring the lift to a quick stop. These are all added as safety measures to prevent you from crashing onto the ledge too hard and getting potential injuries.
Grocery Compartment Attachment
A distinct feature of our stairlift is the grocery storage compartment. Using a magnetic attachment often viewed in dentistry procedures, mostly in magnetic dentures, we decided to implement it as one of our most important accessibility features. This simple-to-use magnetic attachment allows you to carry up to 50 pounds of groceries up the stairs. The compartment, a rectangular prism with an open top, is made from stainless steel for its high durability and low maintenance. The compartment does not have a lid to ensure that children or pets who might crawl inside can safely exit without becoming trapped. The size of the compartment will be designed to take up minimal space to preserve the overall functionality of the stairs.
The compartment features keeper magnets on its sides, making it easy to attach to the carriage. To prevent damage to the carriage, silicone foam rubber padding is added at the points where the magnets connect. Attaching the compartment will seem as simple and intuitive as closing a refrigerator door. See figures 4 and 5 below for measurements of the cart compartment and railing specifications.
Figure 4. The assumed measurements for the grocery compartment.
Figure 5 shows carriage and railing attachments for the chair’s mobility.
Operational Explanations
The Convenient Chair is an ingenious device designed to ensure safe and smooth transportation along a staircase, combining the coordination of several key components. The journey starts after the user has kept their belongings in the compartment, comfortably sat in the chair, and fastened their seatbelt, then the user activates the lift through controls on the chair’s armrest, signaling the motor to kick into action. This motor is powered by a rechargeable battery that drives the chair along a sturdy rail system (Stannah, 2024).
Our Convenient Chair employs a rack-and-pinion mechanism: imagine a motorized gear (pinion) engaging with a toothed track (rack) on the rail to transform rotational motion into smooth linear motion, propelling the chair up or down the stairs with ease. In some models, a cable-driven system performs a similar function, ensuring a smooth ride (Muscoplat, R. 2024).
The rail, securely mounted on the stairs, provides the chair’s necessary structural support and stability. Safety is our top priority, with various mechanisms in place to protect the user. Sensors detect obstacles on the stairs, automatically stopping the lift to prevent accidents. Mechanical brakes ensure the chair doesn’t move uncontrollably or slide, while a speed governor maintains a consistent and smooth pace (Acorn Stairlifts, 2024).
At the end of the ride, the chair automatically halts at the top or bottom of the staircase, with the brakes securely engaging to hold it in place. To make it even more user-friendly and safe, the chair includes a swivel mechanism, allowing it to rotate for easy and secure entry and exit. The footrest, armrests, and seat are often foldable, saving space when the lift isn’t in use (Acorn Stairlifts, 2024).
Moreover, power management is seamlessly integrated into the system. Rechargeable batteries dock at a charging station on different floors, ensuring that the lift remains operational during power outages. Together, these components work harmoniously to provide a reliable, safe, and comfortable transportation solution for individuals with mobility challenges (Stannah, 2024).
Lastly, order buttons will be assigned to every floor to summon the Convenient chair on the very floor. These buttons will be near the Convenient chair path, on the wall. There will be a system that connects the button and the chair, by pressing the button the order will be made.
Materials and Cost
Having the Stannah chair model and Bruno stairlift as a reference, we have decided to utilize durable and cost-effective materials. The prices and materials listed were retrieved from AIP Publishing and Alibaba Electrical Manufacturing:
– High Density Polyethylene (HDPE) commonly used plastic ($5.69 per pound.)
– Neodymium magnets N52 grade (price per pound $0.24.)
– Motor rack and pinion for moving mechanism ($560 without proper installation.)
– Main control logic board ($230 uses data to slow and stop accurately.)
– Tracking integrated system ($200 Stair traction.)
– Aluminum 6061-T6 (price per pound $1.30.)
– Stainless steel 304 (price per pound $0.34.)
– Silicone rubber for padding protection (price per pound $3.00.)
Electrical Components
The control interface and motor circuit work together as an integrated system to ensure safe, controlled movement of the stair lift. We decided to follow the standard model of the Stannah and Bruno chairs for the motor control circuit. In this case, a DC motor (is a motor that takes energy from a direct current and turns it into mechanical energy.) A motor controller/driver board with an H-bridge circuit for direction control (an electronic circuit that switches the polarity of a voltage applied to a load.) H-bridge Polarity- electronic circuits.
When the user activates the directional control, the microcontroller sends signals to the motor control circuit, which uses an H-bridge configuration to determine the motor’s rotation direction. The motor’s speed is precisely regulated through Pulse Width Modulation (PWM), where the controller rapidly switches the power on and off at varying intervals to achieve smooth acceleration and consistent speed. We can also add thermal protection for overheating and potential liquid hazards and a brake control circuit (an electrical circuit that activates and controls the brakes on a trailer). For our control interface, we can find a Microcontroller/processor handling input from armrest controls, safety sensor monitoring, speed regulation, diagnostic functions, signal conditioning circuits, status LED drivers, and a key switch interface.
Conclusion
The Convenient Chair is a shining example of how engineering creativity and a heartfelt commitment to solving real-world problems can come together to make a difference. As the U.S. population ages, with more people living longer, the need for accessible living solutions becomes increasingly urgent. This chair isn’t just about accessibility; it’s about preserving the dignity, independence, and safety of older adults living in apartments.
Crafted with cost-effective materials and efficient mechanisms, the Convenient Chair offers a practical alternative to elevators, especially for buildings that aren’t legally required to have them. Its thoughtful features, like an attachable grocery compartment, booster seat, and intuitive controls, address everyday mobility challenges with ease. The chair also boasts advanced safety measures, including sensors, braking systems, and ergonomic designs, ensuring user well-being at every step.
But it’s more than just a chair; it’s a symbol of inclusive design. It recognizes the physical limitations that come with aging while empowering individuals to maintain their autonomy. This innovation shows that addressing demographic trends, such as the rising elderly population, requires practical, scalable, and compassionate solutions.
The journey toward equitable and accessible living conditions for all demands such innovations. With its emphasis on affordability, ease of installation, and user-centric design, the Convenient Chair is set to make a significant impact, enhancing the quality of life for countless older adults and paving the way for a more accessible future.
References
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