A client was a lady in a powered wheelchair and training her new assistance dog.
She needed a method to deliver reward treats to the dog but unable to do so.
She was pressing a ‘clicker’ with her right hand and and an assistant was giving the treat on the left hand side of the wheelchair. The dog was seeing that the assistant was giving the treat and rewarding it, not the owner, who was in the wheelchair, this needed to be remedied.
There were three grades of treats ‘good’, ‘better’ and ‘excellent’ which was in the form of liver paste (this option was dropped).
The treats were different shapes and some were soft and could stick to one another.
Any treat issued had to fall clear of the wheelchair otherwise the dog might get injured by the wheelchair wheels.
Anything protruding outside of the wheelchair profile had to be retractable to enable he wheelchair to pass through doorways.
Several methods were discussed and some tried, – gravity tubes, catapult, gum ball machine mechanisms etc – but they all failed. The answer was to use a pre-loaded cassette of the treats. It was estimated that no more than 30 treats would be needed on any one outing and that they would fit in a 20mm cube (some requiring being cut in half to fit).
A vertical conveyor belt with 20mm compartments was constructed from 3D printed parts. This was housed in a case with a front opening door which also included a 3v electric motor, gearbox and cam switch. A momentary contact would cause the conveyor to be rotated and one treat dropped at a time. A retaining plate and mount was created which the cassette clipped into and made electrical contact. A second cassette was mad that would mount on top of the first cassettes and the electrical contacts made through the first cassette on into the retaining plate.
The only place this could be fitted on the wheelchair was in front of the armrest; but then the treat would drop right in front of the wheel – considered to be a bad idea!
A mechanism was created that had a crank handle just to the front of the armrest which would enable the bottom of the cassette mechanism to be swung out past the wheel. A sliding plate on the retaining plate extended the length of the dispensing ramp so that the treats fell outside of the wheel.
Two commercial dog training ‘clicker’ devices were bought and dismembered. A new case to enclose both clicker mechanism and electrical contacts was 3d printed.
Although it functioned very well, the positioning on the wheelchair left it vulnerable to accidental collision when in the extended position and it soon ended in a broken state – so a Mk2 was needed (see separate entry)
Within 30 seconds of seeing (and smelling it), the dog knew where the treats were and associated a click from it’s owner and the delivery of a treat. This had two benefits, the owner had independence from her assistant and the dog knew that it was her given the reward.