ADC JAW CRUSHER INFORMATION
Introduction to Jaw Crushers
This section of the Aggregate Designs Corporation web
site is intended to inform the reader about different aspects of jaw crushers.
There isn't a tremendous variation in jaw crushers, the primary differences is
in their size. Some units have hydraulic
relief systems that can allow non-crushable material to go through the jaw
crusher without snapping the toggle plate. These aren't terribly popular
though, as pit operators seem to prefer simplicity over the rare chance of
breaking a toggle plate.
Part 1 — Components of a Jaw Crusher
Jaw Crusher Pitman
The pitman is the main moving part in a jaw crusher.
It forms the moving side of the jaw, while the stationary or fixed jaw forms the
other. It achieves its movement through the eccentric machining of the
flywheel shaft. Total back and forth movement of the top of the pitman is
only about 1 1/2". This gives tremendous force to each stroke.
As an interesting
aside the term "pitman" means "connecting rod", but in a jaw crusher it really
doesn't perform this function, that is it doesn't connect two things.
Other mechanisms called pitmans such as linkages in car/truck steering systems
actually do connect things. Thus it appears this is just the name that was
applied to this part.
Manganese Dies in the Jaw Crusher
The jaw crusher pitman is covered on the inward facing
side with dies made of manganese, an extremely hard metal. These dies
often have scalloped faces. The dies are usually symmetrical top to bottom
and can be flipped over that way. This is handy as most wear occurs at the
bottom (closed side) of the jaw and flipping them over provides another equal
period of use before they must be replaced.
Jaw Crusher: Fixed Jaw Face
The fixed jaw face is opposite the pitman face and is
statically mounted. It is also covered with a manganese jaw die. It
is shown in the illustrations.
Eccentric Jaw Crusher Input Shaft
The pitman is put in motion by the oscillation of an
eccentric lobe on a shaft that goes through the pitman's entire length.
This movement might total only 1 1/2" but produces substantial force to crush
material. This force is also put on the shaft itself so they are
constructed with large dimensions and of hardened steel.
Jaw Crusher Input Sheave/Flywheel
Rotational energy is fed into the jaw crusher eccentric
shaft by means
of a sheave pulley which usually has multiple V-belt grooves. In addition
to turning the pitman eccentric shaft it usually has substantial mass to help
maintain rotational inertia as the jaw crushes material.
Protecting the Jaw Crusher: the Toggle Plate
The bottom of the pitman is supported by a reflex-curved piece of metal
called the toggle plate. It serves the purpose of allowing the bottom of
the pitman to move up and down with the motion of the eccentric shaft as well as
serve as a safety mechanism for the entire jaw. Should a piece of
non-crushable material such as a steel loader tooth (sometimes called "tramp
iron") enter the jaw and be larger than the closed side setting it can't be
crushed nor pass through the jaw. In this case, the toggle plate will
crush and prevent further damage.
Retaining the Toggle Plate: the Tension Rod
Without the tension rod & spring the bottom of the
pitman would just flop around as it isn't connected to the toggle plate, rather
just resting against it in the toggle seat. The tension rod system tensions
the pitman to the toggle plate as shown in the illustrations.
Jaw Crusher Sides: Cheek Plates
The sides of the jaw crusher are logically called cheeks
and they are also covered with high-strength manganese steel plates for
Jaw Crusher Eccentric Shaft Bearings
There are typically four bearings on the eccentric
shaft: two on each side of the jaw frame supporting the shaft and two at each
end of the pitman. These bearings are typically roller in style and
usually have labyrinth seals and some are lubricated with an oil bath
Jaw Crusher Adjustment: Closed Side Opening Shims
Depending on the disposition of the material being
crushed by the jaw different maximum-sized pieces of material may be required.
This is achieved by adjusting the opening at the bottom of the jaw, commonly
referred to as the "closed side setting". Shims (sometimes
implemented and a more adjustable or hydraulic fashion) allow for this
Part 2 — Important Considerations for Jaw Crushers
Jaw Crusher Opening Size
Jaw crushers are referred to by two sets of numbers, the
first being the opening size of the jaw; the second being the width. So, a
"1036" jaw would accept a 10" boulder at the top and be 3' wide. If the
pit where the jaw is being used has river rock which does not exceed 10" in size
then this size crusher would be acceptable. Larger crushers are better
choices when the average size is larger, such as where rock is blasted using
explosives. The width of the jaw directly impacts its throughput rate.
Jaw Crusher Nip Angle
The nip angle describes the angle the stationary jaw
plate and the pitman make with each other. The exact value of this angle
isn't quoted or even determinable due to curvature in the jaws themselves but
what is important is how wide vs. narrow it is. Wide nip angles can tend
to expel material as the jaw closes as a large ball might squirt out from under
a car tire. If the nip angle is narrow, not much vertical upward force is
generated and more consistent crushing takes place.
Part 3 — Jaw Crusher Terminology
Jaw Crusher Terms
"aggregate" Any combination of
crushed rock, gravel, sand or granular material suitable for the manufacture of
hot mix asphalt, batch mix concrete or any other construction purpose
Part 4 — Jaw Crusher Illustrations
||Cutaway view of a Jaw crusher. Click on the
picture to open a seperate window with a larger view
||Cutaway view of two of the eccentric shaft bearings.
This shows how the lobe portion of the shaft is enclosed in the pitman.
Click on the picture to open a seperate window with a larger view
||Animated view of a jaw crusher operating. A
grizzly feeder would normally divert material smaller than the
closed-side opening around the jaw
* Trademarks and photos are
property of their respective companies