The idea behind this project was is to design a mechanism for a trash container that is able to deposit trash from a tray atop of the container into an opening at the back of the container, without the trash falling off the tray. The tray must begin and end in the positions indicated in the diagram to the left, and any pivots used must not extend beyond the bounds of the container itself. Additionally, the tray must not collide with the container in any manner.

For this design, I created a 4-bar mechanism that moves the tray between the two positions shown without allowing trash in the container to fall out.

To generate the initial design parameters, specifically the location of the pivots and length of links, I created a SolidWorks sketch containing the main features of the movement. Namely, the container itself, the initial position, and the final position. I then chose two (centered and colinear) points on the tray to act as the tray pivot locations.

The next step was to generate the solution space for the container pivot locations by finding the perpendicular bisector between each pair of points on the tray. A container pivot must be equidistant from the corresponding tray pivot start and end location, and so all possible solutions must lie along a perpendicular bisector.

Since there were currently only 2 points defining the circular path each tray pivot would take, a third point is needed for each to fully define the path. So, an intermediate tray position can be chosen in a desirable position, which would then in turn generate the path. Since both container pivots had to fall on a line cutting 45 degrees to the top left corner of the container, I recognized that the intermediate tray points had to also fall on this line, to allow for the tray to smoothly "flip".

Once an intermediate position has been chosen, the pivot positions can be determined. this is done by drawing a 3-point arc using each start, intermediate, and final tray pivot position, and designating the center as the pivot point. Finally, lines joining the container pivots to their respective tray pivots are drawn, and their lengths locked.

Once the pivot positions and link lengths were determined, the full range of motion was tested. The motion smoothly went between the two positions, and the positions of the pivots were slightly refined such that the action was a little shorter. Additionally, sides and a back added to the tray such that it functioned more like a "scoop" with the intention of minimizing the risk that trash falls off the tray along the motion.