Mechanism Development

It was clear for my first maquette that the mechanism would need to be simple but effective in delivering the cards. I drew out another concept for the mechanism using Rhino and laser cut it onto styrene sheet. Although not the best material for laser cutting, styrene sheeting is much cheaper than acrylic and after a few test cuts I was able to cut fairly accurate parts for testing. To aid the quality of the cut it is recommended that the sheet be covered in masking tape (above).

The first laser cut maquette came together very well (above) and provided a good insight into the problems that need to be overcome. The level of the top card in relation to the PEZ body is crucial in ensuring one card is dispensed at a time (below).

The issue of how to provide the pressure from below the cards has been in my head for the last few weeks. My initial idea was to use the same principle as the standard dispensers which use a spring within the body. Having looked at several types of spring and not really finding anything I thought would do the job (wrong sizes, too strong ect) I came up with a temporary solution. Using the spiral binding from a sketchbook I was able to adjust the pressure by slotting the rings of the binding into the slot at the bottom of the mechanism body (below).

Whilst this method worked in theory, it was nowhere near as concentrated as I needed it to be. The upward force onto the carrier has to cover the whole surface area and the small coils of the binder were far from sufficient for the job. Will suggested trying to come up with a counterweight system of some kind that would rely on gravity as opposed to a physical source of pressure. I thought about this for a while and modified the maquette to accommodate tracks for the carriage to follow on the side using rods inserted through holes in its sides (see below).

This method means that the carriage is much more controlled as it travels up and down the mechanism body (see below left). By using the pivot rod for the dispensing device at the top of the body as an additional pivot point for thread (see below right) I was able to attach thread without great changes to the design.

When in place the gaps at each side of the carrier are perfectly suited to the job of hoisting it up and down as required. By taking the thread from the pivot point at the top and down through a hole back in to the body at the bottom, a weight can then be attached to give an upward pressure sufficient and widespread enough to keep the carrier at the top of its travel (below left). Pushing down on the carrier hoists the weight upward creating stored energy as the weight pulls down on the carrier (below right). This means cards loaded onto the carrier are forced upward as dispensed and will automatically be reloaded until the carrier reaches the top of its travel.

It was necessary to add extra supporting brackets at the side of the mechanism to hold it level when placed in the body (visible above and below). These are not present on the standard dispensers as the flexible front section holds the mechanism in place. My version does not feature this flexible section as I decided it would be too perishable for the size of the mechanism and the pressures on it.

The dispensing 'arm' idea (below) that uses one movement rather than transferring energy as previously attempted has potential to work well. I am still unsure about the actual contact between the arm and the card in terms of material. I hope to try out several different techniques in the coming days. One change I made right away was to move the pivot rod further forward to give the arm more travel and thus contact with the card. In the central position the arm only just pushed the card out of the body. By moving it forward the card it pushed much further out (see below).