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  • 180 degree opening mechanism

    Discussion in 'The main mechanical design forum' started by _Maniac_, Mar 27, 2015.

    1. _Maniac_

      _Maniac_ Member

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      I have one let say simple question...

      which mechanism to use instead of hinges?

      Please check enclosed image...

      P.S.
      No collision allowed... sensitive wooden parts...

      Thank you :)...

      BR

      [​IMG]
       
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    3. Lochnagar

      Lochnagar Well-Known Member

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      Hi Maniac,

      It is not very clear from your post - what you are expecting/wanting to achieve. However, to try and move the debate on - see a picture of a mechanism with the hyperlink below that is regularly used to achieve at least 180 degree rotation on digger buckets. (Zoom in on image 2 in the hyperlink below).
      You say the parts are wooden - so I am going to take a guess you would not want a hydraulic actuator to move this mechanism - but you could use an electric motor to drive a small leadscrew (to replace the hydraulic actuator in the picture below) - and use proximity switches to trip the motor out - when you reach the extremities of the two positions, i.e. 0 degrees and 180 degrees.

      http://www.google.com/patents/US5592762



      Hope this helps.
       
      Last edited: Mar 29, 2015
    4. _Maniac_

      _Maniac_ Member

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      Well... no actuators (pulled/moved by hand)... I'm making some kind of extendable chair... please check enclosed images (solidworks)... those parts are some kind of frames, and I should fit mechanisam between (inside) those two parts... For testing purposes I put piano hinges and it works great, but that affects look and I'm trying to avoid it if possible...

      red marked two centers of rotation

      [​IMG]

      [​IMG]

      [​IMG]

      [​IMG]
       
      Last edited: Mar 29, 2015
    5. Lochnagar

      Lochnagar Well-Known Member

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      Hi Maniac,

      Thanks for the additional pictures - I can see what you are trying to do now. However, I would like to ask the obvious question - which is - how is your design going to be better than the one depicted below in the hyperlink - because the sun-lounger shown below is simplicity itself?
      Additionally, with the sun-lounger depicted below - you can adjust the height (angle) of the back rest very easily - which is an important "design feature" - which I can't see is possible in your design.
      I appreciate that everyone wants to come up with something new - but it is always worth asking yourself - is it really better than what than what has already been designed by your competitors.

      http://www.houzz.com/photos/2201898...-modern-patio-furniture-and-outdoor-furniture

      Hope this helps.

      P.S. It is a long time since I worked in Croatia - but I have fond memories of it:)
       
      Last edited: Mar 29, 2015
    6. _Maniac_

      _Maniac_ Member

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      Well I hope I'll have just memories one day about croatia :)...

      I can adjust angle for back rest and also one additional feature that isn't shown here :D...
       
    7. Lochnagar

      Lochnagar Well-Known Member

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      Hi Maniac,

      One important feature of any sun-lounger is its structural stability. I would like to see how you envisage changing the angle of the back rest - whilst maintaining good structural stability?
      What is the additional feature that you haven't shown?
      One type of hinge is a round bar of wood - with a metal bar running through it - see the picture below.

      http://www.swimming-pool-online.com/teak-garden-furniture/teak-sun-loungers-bahia.html

      Hope this helps.
       
    8. _Maniac_

      _Maniac_ Member

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      I have already tested prototype and it works great... but only thing that I wanted to change is those piano hinges that I used on prototype...

      there are three or maybe just two angles (not a big thing to change) to set for backrest, but main problem was unstability when you sit at the very end... this problem is solved with simple mechanism, but I'm not allowed to show it how...


      solution with the mechanism on the outside isn't solution, looks cheap :)... thank you anyway for idea...
       
    9. Lochnagar

      Lochnagar Well-Known Member

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      Hi Maniac,

      Ah - so you are not looking for a mechanism - but just a replacement for the piano hinge.

      Sometimes there is a need to synchronize the moving parts - and one way this can be done is with a geared hinge - see link below. You can perhaps see the idea - and make your own - to suit the structural loads.

      http://www.acelocksmith.com/continuous_door_hinge.html

      Hope this helps.
       
    10. _Maniac_

      _Maniac_ Member

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      I was looking at that profile few days ago and it could work, but it takes more space and bigger gap appears between those two wooden parts...

      Only thing that I found and that could work fine is - concealed hinges

      http://www.downwindmarine.com/images/P/105299.jpg

      only drawback is high price...


      P.S.
      I used similar gear mechanism for robotic gripper I built few years ago...
       
    11. K.I.S.S.

      K.I.S.S. Well-Known Member

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      Hi Maniac,
      From the images you've posted, it doesn't appear that a 90 degree rotation will be exceeded per individual hinge?
      Have you considered a continuous plastic strip embedded within the wooden frame? Something like Polyethylene perhaps?
      There's actually a refinement to this https://www.inventables.com/technologies/shape-retaining-plastic
      It might work for your application as the change of state within your product will be relatively low for the lifespan of the product. Of course, some calculation would need to be performed to get a balance between flexibility and ridgidity.

      K.I.S.S.
       

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