Another Way Wheelchairs Go Up Stairs!

I think I've cracked it!

… In my previous Idea:, I loosely described the principles upon which a mechanism could be designed whereby a wheelchair occupant could “row” the chair up the stairs using handles attached to the mechanism.

But having thought about it a lot, the complexity of the system I proposed (A kind of “inch-worm”, movement of three separate stages) may be infeasible, and due to this complexity, open the door to the increased likely-hood of failure.

So I have since come across a different underlying mechanism, of much greater simplicity of operation, but still utilising the “rowing” technique to enact it.

This time, instead of a mechanism requiring the movement of the chair sections themselves to advance it up the stairs... I am borrowing a principle familiar to anyone who has used, and knows how a workshop vice functions:

The gripping surface travelling along a set of teeth toward it's fixed counterpart by means of a screw being wound by a handle.

Very much as Archimedes water-screw works... except, as his is a screw in a fixed position, and turned in order to move the fluid mass of water, I propose an inversion of this process, whereby the (for want of a more appropriate term) medium is fixed (the stairs), but the screw is the object moving (and whatever is attached to it: a wheelchair) by the process of rotation.

Just like the vice in the workshop, with the screw travelling along the teeth towards the fixed end, here the screw, mounted under the wheelchair, travels upwards along the stairs, which at as the teeth, to the top of the staircase... or flight of stairs.

While I haven't yet worked out the exact details of this mechanism, I believe the principle Is sound, In that a screw can be positioned from underneath the wheelchair when stairs are encountered, and then, using ratcheted rowing handles (so it doesn't just wind back down the stairs), turned in such a way as to wind the chair up the stairs.

The screw, being fixed in relation to the chair, and the chair, being stabilised, and confirmed in it's direction of travel by having three points of contact with the stairs: the screw, and the two wheels on either side which ride over the stair edges (compensation needs to be made for the difference between stair edges, and the angle where the riser meets the stair top, as the distance between these two points changes, so either the wheels would have to move in and out to make up this difference, in relation to the screw, or the screw would have to move up and down in relation to the wheels).

And finally, the leading edge of the screw itself, where it is on contact with the stairs, has small wheels placed at regular intervals all around this “thread edge” which rotate counter to the direction of rotation of the screw (actually moving roughly in an angular direction from the depth of the step where the riser meets the stair top toward the stair edge), so the screw itself winds up the stairs travelling counter to the small wheels on the edge which rotate the other way in such a manner as to be perpetually going “downstairs”.

So there you have it.

This time I have supplied a very bad drawing in order to illustrate the principles described above.


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