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  • Mechanical timer/lever

    Discussion in 'The main mechanical design forum' started by Yitzy, Oct 17, 2012.

    1. Yitzy

      Yitzy New Member

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      Hi, I am trying to design a mechanical timer that initially opens and then, when the time runs out, shuts a lever (90 degrees). The open and shut process can not be too gradual; it can take max. one or two minutes out of a total 60.
      My initial idea was to put a gear on the main axle with only a few teeth so that that it will turn another gear attached to the lever during the first and last 2 minutes. (Appropriate sizing of the gears would enable, e.g. 12 degrees on the first gear to turn 90 on the second.)

      However, the lever is pretty stiff and I'm not sure that the axle of a standard mechanical (60min) timer would cope.

      What is the best way to increase torque in such a situation?

      Does anyone have a better idea how I could open and shut a 90 degree lever with a mechanical timer?

      (the lever is on a ball valve)

      Thanks
       
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    3. Dana

      Dana Well-Known Member

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      How about a cam wheel on the motor and a roller on the lever?
       
    4. Yitzy

      Yitzy New Member

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      I realised I can't use the timer as any force exerted by it on the lever would just slow it down; not the best result for a timekeeping device. This means I need another source of force; i thought maybe a tall push button that the user pushes down that causes the lever to turn and contracts a spring. The push button catches when it is fully down keeping the spring tensed (and the lever open) and then the when the timer finishes, it releases the catch causing the button to pop up and the spring to shut the lever.
      (I'll extend the lever to increase distance and move it using a belt.)

      I'm having a little trouble actualising this even in theory:(

      I'll enclose an image if that helps. The space for the whole device is max 4.5 cm which is why I (may) need to put the timer face perpendicular to the timer mechanism.[​IMG]
       
    5. mvalenti

      mvalenti Well-Known Member

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      not sure what you are trying to achieve. Is it closing and opening a valve at different times? Google solenoid actuated valves as well as 555 timing circuits.
       
    6. Dana

      Dana Well-Known Member

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      What is driving the main axle? A motor, spring, etc.?
       
    7. Yitzy

      Yitzy New Member

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      I apologise for not being clear. I have a lever that opens and closes a (gas) ball valve. I want to be able to clip a mechanical timer on it (and the wall/pipe) so that when i set the timer it opens the valve and when it finishes, it closes it. It must be mechanical as opposed to electrical.

      Specifically to your points; i don't want to have to replace the valve, i just want to clip an external timer onto it. The main axle is driven by the standard clockwork of a 60 min mechanical timer. I realise now that I would be unable to tap into this as it would effect the actual timing of the timer (make it finish sooner or later). That is why I thought perhaps of a button that opens the lever and then you set the timer which eventually releases the button letting the lever spring shut.

      Thanks
       
    8. pri

      pri New Member

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      Sorry for asking, Why designing timer ? Instead usign avaliable TIMER on the MARKET ?
       
    9. I am not understanding what you wanna know!!!
       
    10. Dana

      Dana Well-Known Member

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      I think I see.

      Mount a lever on the valve, with a roller on the end of the lever. A spring closes the valve. The roller rolls on a cam disk that's mounted on the timer. The roller rolls on the circular portion of the cam disk when it's timing, holding the valve open against the spring. At the end of the time, the cam is cut away so the spring can pull the lever to the closed position.

      The transition from the open to the closed portion of the cam can be straight so it drops closed instantly, or curved/angled, so it closes gradually. In the first case, you'd have to manually open the valve and then rotate (wind) the timer under the roller. In the latter case, if the angle isn't too steep it might be able to drive the roller up to open the valve without holding it open manually.
       
    11. Nice Dana.
       

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