Rack and Pinion design

The rack and pinion design is based around a rack mounted directly onto the bottom of a guide rail and a pinion gear that is connected the drive apparatus. The mated relationship between the rack and pinion is secured using several rollers to allow smooth movement along the guide rail and prevent any non linear motion.

FIG 1

Image taken from (http://www.google.com/patents/EP2452909B1?cl=en

As you can see from figure 1 this design uses a multitude of rollers, including a roller hidden by this image on the Y- Plane of the rack, to steady the drive apparatus and prevent any lateral movement. This design means that these followers bear a significant load , something that clearly can be achieved but will have to factor into our design process.

Another useful feature of this design is its ability to negotiate corners. The runner assemblies are mounted in such a way that they allow for a circular rotation , i.e the curve in the track,  whilst maintaining their resistance to the subjective loads. The two pinion gears are also mounted in a similar fashion  which allows for the curve of the track whilst maintaining their driven rotational motion. These features present some vital methods of overcoming some of the issues faced by our group from this project. However some of these assemblies seem very complex and may present some issues later in our design stage

FIG 3 (a stannah stair taken from https://www.google.co.uk/patents/US8087495?dq=stairlift&hl=en&sa=X&ei=6GqAVOXBIIzU7Aad8IGIAQ&ved=0CFoQ6wEwCDgK )           

The Reason for looking at this second design by stannah is to note the groove system mounted on the front of the rail to provide the stop/ start function upon reaching the top or bottom of the stairs . when the needle marked 67 on the diagram reaches the terminal marked 70, a mechanical signal is sent through the needle to the shaft marked 30, this shaft in turn turns a gear in which it is connected which will stop the stair lift instantly. This system will give us an interesting insight into a method of stopping our potential design.