A Mystery Solved: How a Pneumatic CutOff Tool Works

1
A Mystery Solved How a Pneumatic Cut-Off Tool
Works

• Robin Maslowski
• 9/22/03
• High Impact

2
How?
Tool handle

• User cranks the tool handle
• Draws in air from the intake valve at the bottom
  of the tool

Intake valve
Picture from US patent D472441
3

• The air enters the main section of the tool and
  sets the rotor spinning
• As the rotor begins to spin, the sliding vanes
  push out to the edge of the rotors cylindrical
  casing
• This seals off four chambers of changing volume
• The chambers begin small with high pressure, but
  as the rotor rotates eccentrically within the
  casing, the chambers volume increases
• The results are four chambers of varying pressure
  and a spinning rotor which in turn powers the
  cutting wheel

Sliding vanes/fins
casing
Air flow into main section of the motor
4
Finally

• The results are four chambers of varying pressure
  and a spinning rotor which in turn powers the
  cutting wheel

5
The Past vs. the Present

• Patent AI000211
• Rotary Pump by L. Burnell
• Dec. 14, 1858
• First patent in US Classification 418

6
Improvements
PN4032269 by R. Sheth, June 28, 1977
PN60995 by W. Butterfield, Jan. 8, 1867
7
How fast does this tool operate?

• About 80,000 RPMs
• Assumption tool will be operating at the sonic
  level
• Using a critical mass flow rate of .0608 kg/s
• Dividing the total mass entering the high
  pressure side by the critical mass to find the
  time of one revolution

8
How much torque is it producing?

• Around 120 N of force
• Assumption temperature of the system remains
  constant
• Using the ideal gas law (PVnRT)
• Using the fact that Workthe integral of Pressure
  with respect to the Volume
• Using the fact that WorkForceDistance

9
How much air, and at what pressure does this tool
use?

• 4.42 e -5 kg of air
• 6.3 e 7 atm
• Using ideal gas law and previous calculation of
  air entering the cylinder