How a Coleman® Lantern and Stove Works_ Old Town Coleman

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How a Lantern Works

It is not magic nor is it difficult to understand. Pressurized lamps, lanterns,stoves, irons and burners all use simple mechanics and basic principles foroperation.

This "theory" chapter will discuss a Coleman lantern. The principals are thesame for just about every pressurized gasoline or kerosene lamp or lantern,regardless of manufacturer. Many of these functions also apply to stoves,however, a stove creates flame rather than light so we will also cover the basicsof how a stove works at the end of the discussion.

Part One: Building and maintaining pressure.The driving force behind anypressurized appliance is pressure. Pressure is created and maintained within thefount, or tank, of an appliance.

Fig 1

Figure 1 shows the fount of a single-mantle lantern. Imagine this as any lanternor lamp sitting on any table, ready to be lit.

The pump and the check valve are used to create pressure. The fuel fillercap gasket is important for maintaining the pressure.

I'd like you to notice the pump, air stem and check valve first. The pump is fullyclockwise, or "closed," and this means that the threaded air stem is all the waydown and fully seated in the check valve. When we are to use a lantern the firstthing we do is give the plunger a counter-clockwise twist, grab it and startpumping away. Simple enough but let's look at what happens.

Fig 2

In Figure 2 we've taken the first step and turned the pump plunger counter-clockwise.

The graphic is over-exaggerated for clarity but you see what occurred. Thetwisting motion of the pump actually turns the air stem and unseats it from thecheck valve. There is now sufficient space at the bottom of the air stem for air to

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pass.

Fig 3

In Figure 3 we're pulling the pump plunger back to pump the lantern.

This pulling motion creates a small vacuum inside of the plunger cylinder, belowthe pump cup. The check valve at the very bottom has a small ball bearing in itthat is being pulled up into the closed position with this motion. This helps createthe vacuum because no air can be drawn out of the fount. In order to fill thevacuum, air is pulled down the pump cylinder and around the outside diameterof the pump cup.

Fig 4

Figure 4 illustrates what happens when you press the pump plunger down topump the lantern.

During the down-stroke the pump cup forces that air in the pump cylinder intothe fount. As the pump cup moves downward, the increasing pressure in thecylinder forces the check valve (down) to unseat it, and air passes freely throughthe valve. After the check valve, air travels up through an inlet tube and into thefount.

Wondering why the air inlet tube the end of the pump cylinder travels "up" tonear the top of the fount? This is a clever safety feature. Should the check valvefail while the appliance is under pressure, air (rather than fuel) will be releasedback up into the pump cylinder. With a burning mantle or flame, it would bemuch better to have air coming out of the pump than fuel!

Fig 5

After (let's say) 30 pumps, Figure 5 shows what the lantern looks like now that ithas been pressurized and is ready to operate.

First note that the constantly (30 times in this case) increasing amount of air hasput pressure on the fuel and this pressure has caused it to flow upward into thetube in the center. The fuel has risen to the level allowed, that being to the(closed) main valve above the fount. Also note the ball in the check valve. Due


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to the extreme pressure inside the fount the ball is locked into the "up" position,thus keeping air (and pressure) from leaving the fount via the pump cylinder.

When you're finished pumping up the lantern the last step is the opposite of thefirst: turn the pump plunger fully clockwise to "CLOSE." This will re-seat the airstem in the check valve and acts as additional protection against an unwantedrelease of air.

Before we leave Figure 5 we should discuss one part inside the fount that will beimportant later in the lesson. The fuel and air tube is fitted to the bottom of thevalve and extends down into the fount. Older appliances have nothing more thana small hollow tube called the "pick-up tube." The fuel and air tube has a hole atthe very bottom for fuel and passages near the top for air. The rod is used tometer the amount of fuel versus air and the spring acts as a counter to thedownward force applied by the valve stem.

When the valve is off the conical tip of the valve stem is forcing the rod down.When we turn the valve stem counter-clockwise, the conical end will pull backout of the valve body and relax the downward pressure on the rod. As the valveopens, more fuel and less air will be delivered to the system. This means that avery lean mixture is applied when you first crack the stem open and anincreasingly rich mixture as the valve is opened.. This allows the lantern to use alean mixture during initial lighting and then a standard mixture during normaloperation.

Part Two: From gas to gas. That doesn't make a lot of sense but it is exactlywhat a lantern, lamp, stove or burner does.

Fig 6

Refer to Figure 6 and note that the pressurized fuel is resting below the closedlantern valve, which means that the valve stem is fully clockwise. Also noticethat, although exaggerated for illustration purposes, the tip cleaner stem is inthe "up" position causing the tip cleaner to be exposed above the generator .Red indicates an air and fuel mixture, not pure fuel.

When we open the valve, that is to turn the valve stem counter-clockwise, theconical end will pull back out of the valve body. As previously discussed this willrelax the downward pressure on the fuel and air tube rod. The other result of thisaction is allowing pressurized fuel to pass from the fuel and air tube, through thevalve body and up into the generator. The amount of fuel mixture allowed topass is proportional to how much the valve is opened.


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Fig 7

Now a real tip cleaner stem in the "up" position probably would not stop fuel asthe picture shows. Also, the generator in the picture appears hollow except fortip cleaner stem. It has small coil springs or formed paper tubes or acombination of them inside. The reason for these is for heat transfer and toprovide resistance to the fuel flowing through the generator. They are essentialto rapid fuel vaporization.

Please notice what is above the generator: air. As important as fuel is good airflow. The graphic used is just one way to mix fuel from, and air above, thegenerator. Your lantern probably has a more common "air intake tube" that has acrook in it and the tip of the generator enters this bend. Whether from the sideair tubes as shown or a "crooked" air tube on other models, the point here is thatan unrestricted supply of air is directly above the tip of the generator.

We have pressurized fuel at the top of the generator and we have a good supplyof air above the generator. Let's turn the tip cleaner stem down and do somemixing.

Fig 8

The orifice of the gas tip at the end of the generator is very small, usually 0.005"to 0.012". Because there is a great deal of pressure inside the hot generator andthat small orifice is offering a great deal of resistance, the generator will "shoot"fuel up into the lantern, much like placing your finger over the end of a gardenhose. An "uncapped" generator will shoot a stream of gas a few feet in the air.

Now that we have a stream or spray of fuel coming out of the top of thegenerator it is a good time to stop and discuss fuel vapor. "Fuel," which is for allpractical purposes gasoline, will vaporize at room temperature. It has a -45degrees Fahrenheit flashpoint so as long as it is above that temperature it willproduce vapor. Our cold lantern will spray vapor, sure, but mostly what comesout initially is a mist of raw gasoline.


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This fuel/vapor enters an area we can generically call a mixing chamber. Ondouble mantle lanterns the top piece of the burner assembly is called the mixingchamber. On single mantle lanterns like the 200A, the fuel enters into a venturi.It makes no difference what we call it, the fuel is sprayed up and mixes with air.The shape of the mixing chamber will direct this mixture around and down intothe burner tube, burner cap and screen.

Wondering why kerosene lamps and lanterns need to be pre-heated? Kerosenehas a flash point of 100 degrees Fahrenheit which means it needs to reach thattemperature before it will produce vapor. Also, kerosene vapor is 30%-50%higher in density than gasoline vapor. Kerosene needs more air (or less fuel)than does gasoline so kerosene generators have a smaller orifice. Anotherinteresting item is that kerosene lanterns have basic fuel pickup tubes ratherthan fuel and air tubes.

Part Three: Producing Light.Finally we come to the end where the fuel vaporis ignited inside the mantle to produce light.

Fig 9

The mixture of fuel and air directed down the burner tube comes out the burnercap and to the mantle. When ignited, the flame is restricted to the inside of themantle during normal operation. This flame will cause the mantle to incandescewhich is why the mantle is much brighter than just a flame.

So what exactly is a mantle and why does it do what it does? Since I am not achemist or metallurgist, I can only provide the information I found after muchresearch...and the information that made sense to me.

Mantles are a fabric material saturated with metallic salts. Most modern mantlesare saturated with Yttrium and Cerium Nitrate. By pre-burning the mantle, thefabric burns away to leave a ceramic shell of Yttrium and Cerium dioxides and isveryfragile.

Yttrium has a very high melting point and incandesces when heat is applied to it.The light the lantern generates is not from the flame contained inside the mantle,rather, it is the result of the Yttrium and Cerium being heated by that flame.

Old mantles, and some of the currently-made off brand ones, are saturated withThorium rather than Yttrium. I point this out because Thorium is radioactive. Allcurrent Coleman mantles are made with Yttrium. Always pre-burn mantlesoutside with good ventilation and avoid breathing the fumes.

Please understand that these are the basics of how a pressure lantern works. Ithas been simplified, obviously, for the layman writer and the layman reader.They are relatively simple devices and keeping this simple is a good thing.

Part Four: Stoves in a Nutshell.Just about everything you just read onlanterns also applies to stoves, up to the point where fuel is shot out the end ofthe generator. You can even imagine tilting all the graphics above by 90 degreesand that lantern being a stove tank.

In a stove, the pressurized fuel is applied to the manifold rather than the burnercap. It travels through the manifold and to the burner(s) where the bunsen


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effect occurs to produce flame.

The Bunsen effect is really nothing more than using the correct amounts of gasand air to produce a very high temperature flame with little luminescence. Theair-gas mixture enters the burner where it is spread evenly to a pattern of smalloutlets. By igniting the fuel from these outlets we get a pattern, usually a smallcircle, of intense flame.

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How a Coleman® Lantern and Stove Works_ Old Town Coleman