Design and Modelling

Our device meets the project requirements by using a four-bar slider crank mechanism. The mechanism unfolds the outer and inner petals with a downward force on one of the outer petals. To allow for an flat surface when unfolded, the inner petals fold and fit inside of the sides formed by the outer petals. These petals fold on two hinges located on the center of each inner petal. These hinges rotate about a steel shaft that acts one of the links of each four-bar mechanism. Four U-joints were added later that connect to the inner petals and cause them to fold on their hinges while the entire table folds upward. These U-joints emulate spherical joints and allow the inner petals to be approximately the same size as the outer petals when unfolded. These joints act create a 3D four-bar linkage, similar to the 2D linkages analyzed in this class.

The four-bar slider crank mechanism is comprised of machined steel shafts for links and pinned joints, 3D printed PLA connection pieces, and laser cut acrylic for the longest links and the petal. In addition to those parts, the entire table has 54 bushings, 6 aluminum rods, and 39 snap rings.

The slider piece was 3D printed with PLA and moves along a single shaft that acts as the stem of the tulip table. By 3D printing the sliding mechanism, we were able to cut down on material costs and create the complicated geometry shown in the CAD model. Additionally, 3D printing allowed us to easily create the complicated slider geometry and rapidly iterate between designs. The slider supports the mechanisms and connects the four-bar linkages to the stem of the table.

The device is powered by a downward force exerted on one outer petal or the 3D printed slider. At the request of 3 of Hearts Design, we have not included any necessary motors or electronics in our design. When the downward force is applied, the table and it’s inner petals unfold to create a flat, table-like surface.

The final prototype consists of six completed linkage mechanism with three pairs of interlocking petals.  The specific shape of the petals are not final because the goal of this project is to achieve the correct table opening motion, not to design the geometry of the table petals.