11- Project Proposal

Introduction: 

A cup holder is a well known idea integrated into many useful products. However, there are not many products where you can choose whether or not the cup holder is accessible. Sometimes it may be useful to not have the cup holder to be there and instead there is just a flat surface. So we want to create a product (beginnings of a product) that uses a 4 to 6 bar mechanism that would allow the user to choose whether the product has a usable cup holder or not thus giving the user options.

With this idea we are wanting to create a product where there is a built-in mechanism where you can press a button or open a compartment and a cup holder will unfold from this compartment. Or, in reverse, if you want to have a place to rest your arm without the extra space for a cup holder you can fold the arm back in and have a normal arm rest. Imagine if you don't have room for a bedside table but want a place to store a drink. If you had a retractable cup holder attached to the wall, you could have a cup holder when you want or just a flat surface when you don’t. This device could also be directly integrated into a chair for the same purpose.

Description of the problem:

If effectively created, a mechanical folding cup holder might provide a number of advantages, making it a worthwhile and useful solution. When not in use, a mechanical folding cup holder offers a compact and space-saving design that improves user convenience and makes better use of the available space. The cup holder's versatility allows it to accommodate a wide range of user preferences and beverage containers due to its ability to adjust to different cup sizes and shapes. The folding design enhances the visual attractiveness of the product or system it is integrated into by giving it a sleek and attractive appearance when not in use. In the right capacity, we are able to enhance the ability of using cups as an automatic tool is right at the finger tips of the user. The design will safely hold cups without putting them under undue pressure by using the right amount of force and coordination. This reduces the possibility of damage and guarantees a longer lifespan for the cup holder and the cups it holds. When folded, the cup holder increases space utilization in confined spaces like cars or small living rooms, which helps create effective design solutions. It can also be used in any facet, sitting in chairs or on the couch. 

For the folding cup holder to properly transition between the open and closed states, a complex motion profile is required. This entails establishing exact trajectories for every part of the folding mechanism. In order to accommodate a variety of cup sizes and shapes, the motion profile must guarantee that the cup holder may vary dynamically in its folding behavior. The folding cup holder presents issues for finding the right force to accommodate cups of different materials and weights. The mechanism needs to be built with enough force to hold the cup firmly without breaking it as unintended outcomes must be avoided by taking into account elements including material flexibility, cup weight distribution, and potential external pressures acting on the cup holder (such as abrupt movements). It is crucial to achieve perfect synchronization between the various parts of the folding cup holder. This entails the coordinated motion of several components to guarantee a smooth and dependable folding procedure. Taking into consideration differences in cup location, orientation, and user interactions found in real-world scenarios increases the complexity of coordination. The system needs to adjust to these changes without losing its usefulness. Under a variety of circumstances, such as fluctuations in temperature, humidity, and mechanical wear, the folding cup holder must demonstrate long-term durability and dependability as it is crucial to design parts that can sustain numerous cycles of folding and unfolding without sacrificing functionality.

Description of a proposed mechanism that could solve this problem: 

The first mechanism considered is seen above. It was either a 3 or 4-bar mechanism that allowed for sliding and approximately 90 degrees of rotation of the particular link that would be the cupholder. In 2D space, it would have required a ground link with one to two rotating joints and one sliding joint. In 3D space, there would have been a ground link on either side, each the exact same but mirrors of each other. 

The base of the cup holder link would have most likely slid along a slot in the ground link. There would have been at least one rotating link that would ensure the cup holder link tracked through the correct path and did not interfere with the frame of the mechanism. 

After consideration, we decided a more challenging path forward would be to create the same motion but with only rotating links, no sliding links. This could be done by replacing the slot in the ground link with two links that fold/unfold along a similar path as the slot. At first, this looked like it should be a 5-bar mechanism like the one seen below. However, the two folding links do need to be connected somehow to ensure they unfold simultaneously. 

The angle between the dark and light gray links needs to be twice that of the angle between the dark gray link and horizontal to provide the motion required. These links can either be connected in this way using gears or pulleys. These options will be explored down the line. 

Proposed scope of work for final project: 

We aim to complete the design, analysis, fabrication, and assembly of the deployable/retractable cup holder. Additionally, we hope to implement an electronic drive input motor if time and budget permits, but this is a secondary objective because it will add additional constraints and complexity to the project. We will need to perform analysis of the maximum stresses in individual joints and links, both in driving the mechanism and holding up a certain amount of weight, acting as a cantilevered beam when fully deployed.

Our project should account for aesthetic appeal and user-friendly, ergonomic design. The joints should not have too much friction and resistance because then it would be difficult to deploy and retract the cupholder. There should not be edges between links that could easily pinch the skin of the user if it gets caught in between them while operating the mechanism. Lastly, we should minimize the space that the mechanism occupies while in its retracted position while still allowing it to be large enough to be useful as a cup holder and tray. These practical considerations will determine how feasible the mechanism will be to implement into a larger system such as a plane, car, or train.

Preliminary Design Ideas:

As seen in the sections above, we have a few ideas of how to solve the “stowing cup holder” problem. The first option was to use a sliding joint that would guide the back end of the cup holder through its path. The second option uses two unfolding links to not just guide but also push the cupholder through its path. The simple solidworks assembly and lego design show how linking the two folding bars with gears can be used to control their angle relative to each other. 

The gears in these two assemblies could also be replaced with a timing belt and pulley setup. This would potentially lower the part count and friction involved in the system while still producing similar results. 

This folding bar setup would also allow for more motion through the whole path. We believe that when the design is complete, the cup holder will be twice the width of the original arm rest. In other words, a 3” arm rest can contain a cup holder that reaches 6 inches at its furthest extent. 

Finally, below are some preliminary notes concerning the analysis portion of the project at the current time.