Which Hinges?

[auldain]

I have a trap door giving access to my basement and need regular access so need it to be hinged. Trouble is that while the door is flush with the surrounding floor (25mm tongue and groove) there will soon be fitted a new carpet raising the overall floor level on the trap door and the rest of the floor by another 20mm. The 4 sides of the trap door and the surrounding floor aperture are edged with 20mm wide oak (to the same level as the carpet height to allow the carpet fitter to have a finished edge to work to). So my dilemma is what hinges are available, which are not visible when door is closed, but allow the trap door to open without it binding at its hinged side. Piano hinges would of course do the job but the knuckle would be visible when closed, so I'm hoping there is a specialised hinge someone knows of that can be fitted onto the vertical surface of the joists which make up the trap door opening and the underside of the the trap door, so that when opening throws the door far enough away to prevent the binding. And if these hinges can be easily fitted from below with the trap door in its closed position all the better. Any one know of such hardware?

 

[foxhole]

http://www.kbbproducts.com/165-degree-hinges-standard-pair-1065-p.asp
These would work but may require 3 or 4 depending on weight of door and a chain would help reduce strain when fully open as they won't open beyond the 165 degrees.