This pump consists of two rotating gears; an Internal Gear with the teeth on the outside, and an External gear with the teeth on the inside. The External Gear is larger and has more teeth, but the teeth are the same size.
As the teeth separate, they pass over the intake hole . They “suck” in fluid, then the gears are separated by a Crescent Seal.
When the teeth start to come together again, they squeeze the fluid through the outlet hole.
Normally the inner gear is attached to a drive shaft and the outer gear is turned by the inner gear at the point of contact.
Advantages of the crescent pump include its simple design and low maintenance requirements. The crescent pump is common in many applications including automatic transmissions.
The Ctesibian pump is over two thousand years old. Firefighters used Ctesibians for centuries. It is a type of force pump.
It is operated by two, four or six men — sometimes more — standing on either end of the “walking beam” to which the piston rods are attached.
The cylinders are made of copper or brass, the pistons often of wood. There are two valves for each cylinder and the base of the pump sits in the water source.
An air chamber below the nozzle acts as a hydraulic accumulator to maintain an even flow of water out the nozzle.
The water source might be suppied by a bucket brigade of people. The purpose of the pump is to create a stream of water for putting out the fire.
Cylindrical Energy Module ™
CEM or Cylindrical Energy Module is a fascinating, simple new pump/compressor/engine invented by Eddie Paul, president of EP Industries in El Segundo, CA.
The CEM is a modification of the swash-plate pump. In the model shown, six cylinders in a rotating rotor assembly are moved back and forth via Piston Drive Pins which follow a stationary Sinusiodal Cam Track that encircles the rotor assembly.
With each revolution, each piston moves back and forth twice. The pistons are double-headed so there are 24 power strokes per revolution. There are no valves.
At each end of the pump, four stationary holes the diameter of the pistons function as intake and exhaust ports. Output volume is proportional to rotational speed, and pressure is proportional to the horsepower of the drive motor. Mr. Paul has not even begun to figure out all the things his new pump can do, but with only seven moving parts and a virtually clog-free operation, a multitude of worldwide uses are certain to appear. This new pump shows that even after thousands of years, there is still room for radical new ideas from inventive geniuses. Diaphragm Pump
Cars often use a Diaphragm Pump to move gasoline from the gas tank to the carburetor or fuel injection plugs.
The gasoline diaphragm pump in a car is operated by a cam geared directly to rotating parts of the engine. The cam pushes a pushrod.
The brown rod shown in this drawing is moved by the pushrod. It pushes the diaphragm in (a spring forces it back out.)
Fuel pumps like this one operate continuously but have a safety valve which returns fuel to the input side of the pump if pressure rises above a set level.
The pump usually has a fuel filter built into it. (The fuel system will have several other filters.)
Diaphragm pumps are very common and come in many sizes. Modern plastics are flexible and long lasting making this an ideal low-maintenance pump for many applications.