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Shutter or door mechanism

  1. Jun 15, 2008 #1
    Hi all,

    i have faced a problem in the designing stage of a machine.

    I need to use a mechanism to close a door (very small metallic door of about 20 grams) for a period of time(this period can go up to 10 or more minutes) and then go back to its previous position in which another door is closed. I mean that the door is in position 1, closing a path all the time, and then for some time maybe once a week for a certain application it should go to position 2 and close another path for about 10 minutes or more.
    the door is square shaped metal which is rotated around one if its edges to go to position 1 or 2.

    two things are very important.
    1. The door should go to an exact position that it should be in order to effectively close the doors.(i am using a stopper at each end to make sure that the door doesnt go further.)

    2. when the door is in a position, some objects are passing the path and they hit the door. i dont want these objects to move the door and the other path(which is currently closed by the door) becomes open.

    what kind of motor or actuator do you suggest?
    if a dc motor, how can i make sure that it remains in its position all the time because i know that the electricity should not be maintained on the motor because it will overheat and short circuit.

    thank you all,

    sorry for the long question.
  2. jcsd
  3. Jun 15, 2008 #2


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    Generally you would use a solenoid and stops at each end.
    How important is no bounce?
    For a small experiment/prototype where you don't want to do a lot of engineerign I have used remote control model servo motors.
    These are little boxes with a motor+gearbox and an arm on top that moves throuigh 90 or 180 deg. They only power the motor when moviong and then because of the gearbox there is a lot of torque on the arm when the power is off .
    They are driven by a PWM signal but it's very easy to generate a full on/full off signal if you only want the ends of the travel.
  4. Jun 15, 2008 #3


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    Usually, if I want soemthing to travel from one position to another, and I don't need it to stop anywhere in between, and I want it to really hold it's position at the two extremes, I reach for a penumatic or hydraulic cylinder.

    How big are the "objects" that will be hitting this door, and how hard do you expect them to hit?

    And out of curiosity; will it be toggling back forth automatically (in response to some conditions), or will you be activating it manually?
  5. Jun 15, 2008 #4
    let me exactly tell you what the application is...

    the machine is a vending machine. inside the machine is a path from which the coins are dispensed into a tray or a box. the function of the door is to close the entrance path to the box while the coins are supposed to fall into change tray and it also should close the entrance of the path to change tray while the coins are supposed to fall into the box. box is used for coin collection and when the coins are dispensing into it, there are many coins falling fast into it. in this part i have seen with some dc motors that i used once for experiment, coins that hit the shutter or lets say splitter, can move it and then the entrance will not be perfectly closed anymore.

    Normal vector of these two path entrances are 120 degrees different so the splitter goes a round path to reach both ends. at each end i put a stopper (one edge of the path is protruding).

    i hope you get the picture now.
    the reason that i dont use a solenoid is that i havent found a rotating one (i didnt search very well) and more importantly that when the power is released from the solenoid it will be loose and can easily be moved.

    i was thinking of using a gear motor but i dont know when it hits the stopper what will happen. im just afraid of need for extensive maintenance.

    also stepper motor can be used but i dont have any experience in using it, there are many questions like what will happen when it is stopped by the stopper and not based on its own stepping. and also what will happen if you release the power input; will it maintain its position or it may move while being hit by coins.

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