Posts Tagged ‘compressed air’

The Depositor’s Pneumatically Actuated Pump

Monday, July 2nd, 2018

    Last time we learned how pneumatic actuators impart linear motion to machines.   Now, let’s see how the pneumatic actuator is connected to the depositor’s pump.   The connection imparts linear motion to the pump so it draws in jelly filling from the supply hopper and sends it streaming out of the nozzle onto a passing pastry.

    On the depositor, the pneumatic actuator’s piston rod is connected to the pump’s piston.   As such, the pistons in the actuator and pump move together. When compressed air is admitted to the right side of the pneumatic actuator, the pistons in actuator and pump move to the left.   As the pump’s piston moves to the left, a vacuum is formed in the pump.   This vacuum sucks the jelly out of the hopper, through the diverter valve, and into the pump as shown below.

 The Depositor’s Pneumatic Actuator Empties the Pump

The Depositor’s Pneumatically Actuated Pump

   

    Once the pump is full of jelly, compressed air is admitted to the left side of the actuator piston.   The pistons in actuator and pump move to the right as the compressed air expands and presses against the piston in the actuator.   As the pump’s piston moves to the right, pressure builds up on the jelly in the pump.   The pressure empties the jelly from the pump.   The jelly is forced from the pump, back through the diverter valve, and it streams out of the nozzle as shown below.

 The Depositor’s Pneumatic Actuator Empties the Pump

The Depositor’s Pneumatic Actuator Empties the Pump

   

    For the pumping process to take place, the diverter valve must be rotated to first allow jelly to flow from the hopper.   The diverter valve must be rotated again to allow jelly to flow through the nozzle.   Next time, we’ll see how a pneumatic actuator is attached to a mechanical linkage that rotates the diverter valve.

Copyright 2018 – Philip J. O’Keefe, PE

Engineering Expert Witness Blog

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The Depositor’s Pneumatic Actuator

Thursday, June 21st, 2018

    Last time we learned that a fruit jelly depositor in a food manufacturing plant is an example of a positive displacement pump at work.  Today we’ll see how pieces of equipment on the depositor, known as a pneumatic actuators, work.   Pneumatic actuators do not come in contact with the jelly flowing through the depositor.   In other words, no jelly flows through the actuators.   The jelly only flows through the transfer valve and positive displacement pump as we saw last time.  The pump and valve can’t move by themselves.   So, they need some device to set them in motion.   That’s where the pneumatic actuators come into play.   They impart movement to the pump and transfer valve to get the jelly flowing from the hopper and down through the nozzle and onto the pastry.

    A pneumatic actuator is a device that operates using compressed air.   Compressed air, from an external air compressor, enters into a tube in the actuator known as a cylinder.   Inside the cylinder is a piston that can move along the length of the tube.   Attached to the piston is a piston rod which extends to the outside of the cylinder.

    When compressed air is introduced into the cylinder on the left side of the piston, it forces the piston and piston rod to move towards the right side of the cylinder.   But, air must be vented out to atmosphere from the right side of the piston for this movement to occur.   If no venting took place, trapped air to the right of the piston will get squeezed between the piston and the right end of the cylinder.   When the air gets squeezed, it becomes pressurized.  The pressure will impede the movement of the piston.

    Likewise, when compressed air is introduced into the cylinder on the right side of the piston, it forces the piston and piston rod to move towards the left side of the cylinder.

 The Depositor’s Pneumatic Actuator

The Depositor’s Pneumatic Actuator 

 

    So, depending on which end compressed air is admitted to the pneumatic actuator’s cylinder, the piston rod will move to the left or the right.   In engineering terms, the actuator imparts linear motion to machines.   In other words, the piston rod moves back and forth in a straight line.

    Next time, we’ll see how the pneumatic actuator is connected to the depositor’s pump to impart the linear motion that draws jelly from the supply hopper and sends it streaming out of the nozzle onto a passing pastry.

Copyright 2018 – Philip J. O’Keefe, PE

Engineering Expert Witness Blog

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