Where's the reward?
This was a follow on to the Dog Treat Feeder Mk1.
To provide a way to dispense one of two types of treat to an assistance dog whilst under training when the user was in her electric wheelchair.
The device should be contained within the profile of the wheelchair and yet dispense the treat outside of the wheel.
The only place I could find on the wheelchair was a slim slot under the arm rest, so a slim solution was required. I could not slim down the conveyor mechanism as used in the Mk1 device, so experimented with an archimedes screw.
To fit 30 treats (the initial requirement), the archimedes screw would need to be 600mm long and then the motor assembly would need to be beyond that, making it too long for two reasons 1). Even our new Creality CR10S5 (500x500x500mm bed) 3D printer would struggle, even with when printed on the diagonal and 2) there was not enough space on the wheelchair.
We settled on a 550mm screw housed within a cassette that itself was housed in a casing. The cassette could be taken out of the casing through a slot on one end and be filled with treats. The cassette would then be slid into the housing where a dog clutch (originally no pun intended) would couple the screw to the motor/gearbox/cam assembly. The motor was a standard Pololu geared motor. The cam and cluch were 3D printed. On depressing the clicker, the motor will rotate and will continue rotating until the button is released and the cam switch detects that the screw has completed a cycle (or more if the button is kept depressed)
With the larger Creality CR10S5 printer it was possible to print each item in one piece instead of gluing several parts together as was needed for the Mk1 that was printed on a Prusa i3Mk3 3D printer. However several of the parts were designed to be glued together e.g. the outer casing and motor assembly.
An aluminium clamp was machined to fit the accessory rail on the side of the wheelchair to hold the complete unit in place.
A separate battery holder box was 3D printed and is located at the rear of the wheelchair.
A clear flexible pipe was used coupled to the exit chute (white in the photo) so that the treat could be dispensed outside of the wheels. It is hoped that the flexible tube will be resilient to any knocks that it might suffer, in the worst case scenario it will get detached from the exit chute and can be pushed back on again.
The same clicker mechanism used in the MK1 was used.
Find the mechanism!
The client can now feed reward treats to the dog and the dog associates her with the click and the reward.
With it’s slim design and positioning, it should not suffer any collision damage.