Interchangeable Chair Design: 4-Bar Linkage Solution

[titus_polo]

Just want to ask a question..
do u have any idea, what linkage is possible for this one.
Well, just wanted to make a simple chair, wherein the position of the back rest cushion is interchangeable, without changing the position of the lower part and the linkage wouldn’t be seen. I was thinking of a 4-bar linkage, but I think it would overlap the connection..please luk at the attachment below.
Tnx in advance
View attachment seats.bmp

 

[Danger]

How about just a telescoping tube with a locking knob? If you cover it with accordion-pleat fabric, it won't show.

 

[titus_polo]

i can't picture using a telescoping tube,the backrest should be reversible,wherein the knee edge of position 1 would be the back edge at position 2...
it supposed to be a design for a subway train wherein the seats are positioned laterally,and when the train travel at the opposite way,i have to position the backrest facing the other direction.

 

[Danger]

Sorry; I misinterpreted your drawing. I thought that they were just different views of the same thing, and the back isn't the same height above the seat on the right side as it is on the left. I therefore thought that you just wanted it to raise and lower.
In regard to what you really want, I would look at just mounting the outer edges of the backrest on rails that span the depth of the seat. The back itself can be vertically symmetrical so it can flip over on a central axle after sliding to the other side. Being for a public conveyance, I assume that there must be structural requirements for safety which will have to be met.

 

[titus_polo]

yeah they were different views of the same thing,that linkage is what i have in mind..well..but i thnk that hard to do,the thing is,the back rest shouldn't be detachable..and the same backrest cushion would be the cushion of position 2... so i have to use the same backrest for both position,i can't just flip it over.. and another condition,the linkages should be hidden..but i can't thnk of a way to make a connection at the bottom of the bench.

 

[Danger]

Okay... let me fiddle with it a bit in Illustrator. There might be a problem, since I couldn't get ImageShack or Image Cave to put my last stuff up properly. That was quite a while back, though, so maybe it's straightened out.

 

[Danger]

Okay, I started fiddling... but I barely got started drawing the thing when I had another idea which would be an awful lot easier and cheaper to implement. Just use the exact same components for the back as for the seat and join them permanently at whatever lay-back angle you want. Run an axle through the junction (at the 'V'). Then you can simply unlock the pivot and rotate the whole assembly so that the back becomes the seat, and the seat becomes the back, facing the other way.

edit: I realize that in its simplest form, this will change the location of the seat relative to the cabin. If that's a problem, the whole thing can be mounted on a slider system to move it back where it belongs.

2nd edit: Nuts! ImageShack still won't take my drawing.

 

[titus_polo]

yep..i really can't thnk of the right linkages..

 

[Danger]

Well now... I'm not sure what I did differently this time, but I got the picture uploaded. This is what I was thinking of (just one view for now, with no details).

"[URL=http://img61.imageshack.us/my.php?image=seatks1.jpg[/URL]

 

[titus_polo]

yeah..but the objective is that backseat would be the same backseat for either position,anyway tnx a lot.
the only possible linkage i can't thnk of is a 4 bar linkage..but I am having a hard time connecting it,the linkages should be hidden at the bottom part of the chair

 

[titus_polo]

hmm..i saw something that looks like this, its somewhat called "walkover seats" for rail cars,but my problem is that the backrest isn't cushioned for 2 sides,only one side is supposed to be the backrest, have to maintain that side at the other direction.