Jaw Crusher Working Principle

911metallurgist.com/blog/jaw-crusher-working-principle

LD February 23, 2016

Michaud

A sectional view of the single-toggle type of jaw crusher is shown

below. In one respect, the working principle and application of
this machine is similar to the Dodge crushers; the movable jaw has
its maximum movement at the top of the crushing chamber, and
minimum movement at the discharge point. The motion is,
however, a more complex one than the Dodge motion, being the
resultant of the circular motion of the eccentric-shaft at the top of
the swing jaw. combined with the rocking action of the inclined
toggle plate at the bottom of this jaw. The motion at the receiving
opening is elliptical; at the discharge opening it is a thin crescent, Crushers
whose chord is inclined upwardly toward the stationary jaw. Thus,
at all points in the crushing chamber, the motion has both, vertical and horizontal,
components.

Metso

It will be noted that the motion is a “rocking” one. When the swing jaw is rising, it is
opening, at the top, during the first half of the stroke, and closing during the second half,
whereas the bottom of the jaw is closing during the entire up-stroke. A reversal of this
motion occurs during the downstroke of the eccentric.

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 jaw crusher cross section

The horizontal component of motion (throw) at the discharge point of the single-toggle jaw
crusher is greater than the throw of the Dodge crusher at that point; in fact, it is about
three-fourths that of Blake machines of similar short-side receiving-opening dimensions.
The combination of favorable crushing angle, and non choking
jaw plates, used in this machine, promotes a much freer action
through the choke zone than that in the Dodge crusher.
Capacities compare very favourably with comparable sizes of the
Blake machine with non-choking plates, and permissible
discharge settings are finer. A table of ratings is given.

The single-toggle type jaw crusher has been developed

extensively. Because of its simplicity, light weight, moderate
cost, and good capacity, it has found quite a wide field of
application in portable crushing rigs. It also fits into the small,
single-stage mining operation much better than the slower
Dodge type. Some years since, this type was developed with very wide openings for
reduction crushing applications, but it was not able to seriously challenge the gyratory in
this field, especially when the high-speed modern versions of the latter type were
introduced.

https://www.youtube.com/watch?v=ncwe9e_FO8Y

Due to the pronounced vertical components of motion in the single-toggle machine, it is

obvious that a wiping action takes place during the closing strokes; either, the swing jaw
must slip on the material, or the material must slip along the stationary jaw. It is inevitable
that such action should result in accelerated wear of the jaw plates; consequently, the
single-toggle crusher is not an economical machine for reducing highly abrasive, or very
hard, tough rock. Moreover, the large motion at the receiving opening greatly accentuates
shocks incidental to handling the latter class of material, and the full impact of these
shocks must be absorbed by the bearings in the top of the swing jaw.

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The single-toggle machine, like the Dodge type, is capable of making a high ratio-of-
reduction, a faculty which enables it to perform a single-stage reduction of hand-loaded,
mine run ore to a suitable ball mill, or rod mill, feed.

Within the limits of its capacity, and size of receiving

openings, it is admirably suited for such operations.
Small gravel plant operations are also suited to this
type of crusher, although it should not be used where
the gravel deposit contains extremely hard boulders.
The crusher is easy to adjust, and, in common with
most machines of the jaw type, is a simple crusher to
maintain.

As rock particles are compressed between the inclined

faces of the mantle and concaves there is a tendency
for them to slip upward. Slippage occurs in all
Slippage Principle
crushers, even in ideal conditions. Only the particle’s
weight and the friction between it and the crusher
surfaces counteract this tendency. In particular, very hard rock tends to slip upward
rather than break. Choke feeding this kind of material can overload the motor, leaving no
option but to regulate the feed. Smaller particles, which weigh less, and harder particles,
which are more resistant to breakage, will tend to slip more. Anything that reduces
friction, such as spray water or feed moisture, will promote slippage.

Leading is a technique for measuring the gap between fixed

and moveable jaws. The procedure is performed while the
crusher is running empty. A lead plug is lowered on a
lanyard to the choke point, then removed and measured to
find out how much thickness remains after the crusher has
compressed it. This measures the closed side setting. The
open side setting is equal to this measurement plus the
throw of the mantle.
The minimum safe closed side setting depends on:

character of the material.

amount of fines in the feed.
liner shape Leading a jaw crusher
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 whether the crusher is operated as choke fed or
regulated fed

Crushing_Handbook and Crushing Plant Design and Layout Considerations

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JAW CRUSHERS FOR SALE

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 Overhead Pivot (Double Toggle) Similar
applications to Blake. Overhead pivot;
Blake (Double Toggle) Originally the standard reduces rubbing on crusher faces, reduces
jaw crusher used for primary and secondary choking, allows higher speeds and therefore
crushing of hard, tough abrasive rocks. Also for higher capacities. Energy efficiency higher
sticky feeds. Relatively coarse slabby product, because jaw and charge not lifted during
with minimum fines. cycle.

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 Dodge Bottom pivot gives closer sized
product than Blake,but Dodge is difficult to
build in large sizes, and is prone to choking.
Generally restricted to laboratory used.

Overhead Eccentric (Single Toggle)

Originally restricted to sampler sizes by
structural limitations. Now in same size of
Blake which it ha s tended to supersede,
because overhead eccentric encourages feed
and discharge, allowing higher speeds and
capacity, but with higher wear and more
attrition breakage and slightly lower energy
efficiency. In addition as compared to an
equivalent double toggle, they are cheaper and
take up less floor space.

JAW CRUSHERS
Since the jaw crusher was pioneered by Eli Whitney Blake in the the 2nd quarter of the
1800s, many have twisted the Patent and come up with other types of jaw crushers in
hopes of crushing rocks and stones more effectively. Those ‘other’ types of jaw crusher
inventors having given birth to 3 groups:

1. Double Toggle of the Blake Type

2. Dodge Type
3. Universal
4. Single Toggle AKA Overhead Eccentric (also of the Blake jaw crusher family)

For their lighter constructions, single-toggle jaw crushers are

almost half the weight of double toggle machines.

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Heavy duty crushing applications of hard-to-break, high Work Index rocks do prefer
double-toggle jaw crushers as they are heavier in fabrication. A double-toggle jaw
crusher outweighs the single-toggle by a factor of 2X and well as cost more in capital for
the same duty. To perform its trade-off evaluation, the engineering and design firm will
analyse technical factors such as:

The Abrasion Index (Ai)

Capital cost
Expected life of mine
The Work Index of the ore (CWi)
F80 feed size
Rock’s compressive strength
Required reduction ratio

A jaw crusher size is obtained by looking at its

feed opening (gape) and length.

As an example a monster 7959 of 79″ x 59″ (2m x 1.5m) will

have its fixed jaws 79″ apart where the feed enters on a 59″
wide set of liner plates.

The factors list below will enhance crusher capacity

and performance:

1. Proper selection of the jaws.

2. Proper feed gradation.
3. Controlled feed rate.
4. Sufficient feeder capacity and width.
5. Adequate crusher discharge area.
6. Discharge conveyor sized to convey maximum crusher capacity.

Double-Toggle Jaw Crushers

The Double-toggle has its moveable jaw driven via an eccentric shaft
that moves the rear and front toggles down and up on each shaft
revolutions resulting in the jaws closing at the downstroke and conversely
open at the upstroke. A spring loaded tension rod keeps the toggle in its
seats.
Although the image below is of a single-toggle, it illustrates the shims
used to make minor setting changes are made to the crusher by adding
or removing them in the small space between the the crusher’s main
frame and the rea toggle block.

For major crusher closed-side setting adjustment, the length of the front
toggle is changed.

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The jaw crusher discharge opening is the distance from the valley between corrugations on
one jaw to the top of the mating corrugation on the other jaw. The crusher discharge
opening governs the size of finished material produced by the crusher.

Measuring Discharge Opening:

1. Measure distance at bottom of jaws at the

point of the crushing cycle when bottom of
jaws are closest together.
2. Turn flywheel so that counter weights are
parallel with movable jaw.
3. Using a piece of lumber as a “feeler gage”
check the distance between the valley of the
corrugations on one jaw to the crown of the
corrugations on the other.

Adjusting the discharge side opening:

1. Loosen nuts (4) before making adjustment.

2. Loosen tension if crusher is to be adjusted
for finer crushing.

Crusher must be adjusted when empty and stopped. Never close crusher discharge opening
to less than minimum opening. Closing crusher opening to less than recommended will
reduce capacity of crusher and cause premature failure of shaft and bearing assembly.

To compensate for wear on toggle plate, toggle seat, pitman toggle seat and jaws additional
shims must be inserted to maintain the same crusher opening. The setting adjustment
system is designed to compensate for jaw plate wear and to change the CSS (closed side
setting) of the jaw crusher. The setting adjustment system is built into the back frame
end.

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 ON NEW GENERATION CRUSHERS: A toggle plate is fitted between an
upper toggle seat and a lower toggle seat. Behind the toggle seat holder,
two hydraulic cylinders can push the setting wedges inwards to decrease
the discharge setting. The moving jaw is pushed closer to the stationary
jaw and when the gap between the two jaws decreases only smaller
fragments of processed material are allowed to pass through. If the
hydraulic cylinders move outwards, the gap increases and larger
fragments of processed material can pass through. The setting
adjustment system is kept in place by a retraction arrangement with a
hydraulic cylinder.

Single-toggle Jaw Crushers

The single-toggle crusher is also known as an overhead eccentric for its

eccentric shaft is up above compared to the Dodge which has its shaft
below/under. Here, the eccentric is integrated in the “swing” jaw plate that’s
moving up/down as the fly wheel rotated by the motor. A single-toggle
pivots at the base of the swing plate which is causing the jaw’s arc-like
motion. The rock pinching resulting from its flowing/passing between a fixed By
and a swing moveable plate causes the ore to crush as it is “between a rock design,
and a hard place”. tramp
Here also the toggle is keep in place by a compression spring. Large CSS metal will
adjustments are made to the jaw crusher by modifying the length of the shear
toggle. Again, shims allow for minor gap adjustments as they are inserted and
between the mainframe and the toggle block. break the
toggle to
protect
the
machine.

Sizing Jaw Crushers

is done considering the maximum rock-lump or large stone expected to be crushed and
also includes the TPH tonnage rate needing to be crushed. In sizing, we not that jaw
crushers will only have around 75% availability and extra sizing should permit this
downtime.

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Here is a Guide-for-Sizing-Jaw-Crushers thanks to https://www.sagmilling.com

Rock breaker at crusher station

As a rule, the maximum stone-lump dimension need not exceed 80% of the jaw crusher’s
gape. For entense, a 59″ x 79″ machine should not see rocks larger than 80 x 59/100 = 47″
or 1.2 meter across. Miners being miners, it is a certainty during day-to-day operation, the
crusher will see oversized “ore” but is should be fine and pass thru if no bridging takes
place.

In large open-pit mines the excavator too often dictated the max feed size of rocks going to
the crusher.

The primary rock breaker that is most commonly used in small plants is a jaw crusher of
the Blake type, a typical section of which is shown in Fig. 4.

It will be seen that the pitman (226) is suspended from an eccentric on the flywheel shaft
and consequently moves up and down as the latter revolves, forcing the toggle plates
outwards at each revolution. The seating (234) of the rear toggle plate (239) is fixed to the
crusher frame ; the bottom of the swing jaw (214) is therefore pushed forward each time
the pitman rises, a tension rod (245) fitted with a spring (247) being used to bring it back
as the pitman falls. Thus at each revolution of the flywheel the movable jaw crushes any
lump of ore once against the stationary jaw (212) allowing it to fall as it swings back on the
return half-stroke, until eventually the pieces have been broken small enough to drop out.
It follows that the size to which the ore is crushed.

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The jaw crusher is not so efficient a machine as the gyratory crusher described in the next
paragraph, the chief reason for this being that its crushing action is confined to the forward
stroke of the jaw only, whereas the gyratory crusher does useful work during the whole of
its revolution. In addition, the jaw crusher cannot be choke-fed, as can the other machine,
with the result that it is difficult to keep it working at its full capacity— that is, at maximum
efficiency.

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Tables 5 and 6 give particulars of different sizes of jaw crushers. The capacity figures are
based on ore weighing 100 lb. per cubic foot ; for a heavier ore the figures should be
increased in direct proportion to its weight in pounds per cubic foot.

TABLE 5. ALLIS-CHALMERS SUPERIOR JAW CRUSHERS.

Product sizes correspond approximately to the discharge opening measured from the tip of
a corrugation on one jaw plate to the bottom of the corrugation on the other when the jaws
are open.

Capacities are based on material weighing 100 lb. per cubic foot.

Google Patents and Wills’ Mineral Processing Technology as well as www.metso.com

and www.miningandconstruction.sandvik.com

The JAW crusher and the GYRATORY crusher have similarities that put them into the
same class of crusher. They both have the same crushing speed, 100 to 200 R.P.M. They
both break the ore by compression force. And lastly, they both are able to crush the same
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size of ore.

In spite of their similarities, each crusher

design has its own limitations and
advantages that differ from the other one.
A Gyratory crusher can be fed from two
sides and is able to handle ore that tends to
slab. Its design allows a higher speed
motor with a higher reduction ratio
between the motor and the crushing
surface. This means a dollar saving in
energy costs.
A Jaw crusher on the other hand requires
an Ely wheel to store energy. The box
frame construction of this type of crusher
also allows it to handle tougher ore. This
design restricts the feeding of the crusher
to one side only.

Another prime consideration is the space

that each takes up. The Jaw crusher tends to end up
working underground because of its smaller size and its
single feed point.

The Jaw crusher gets its name from the type of crushing
surface used. This surface is literally two jaws. One of
which is a STATIONARY OR FIXED JAW. The other is
called a SWING JAW.

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The ore enters from the top and the swing jaw squeezes it against the stationary jaw until it
breaks. The broken ore then falls through the crusher to be taken away by a conveyor that
is under the crusher. Although the jaws do the work, the real heart of this crusher is the
TOGGLE PLATES, the PITMAN, and the PLY WHEEL.

Forced Feed Jaw Crushers

These jaw crushers are ideal for small properties and they are of the high capacity forced
feed design. On this first Forced Feed Jaw Crusher, the main frame and bumper are cast of
special alloy iron and the initial cost is low. The frame is ribbed both vertically and
horizontally to give maximum strength with minimum weight. The bumper is ruggedly
constructed to withstand tremendous shock loads. Steel bumper can be furnished if
desired. The side bearings are bronze; the bumper bearings are of the antifriction type. This
bearing arrangement adds both strength and ease of movement. The jaw plates and cheek
plates are reversible and are of the best grade manganese steel. The jaw opening is
controlled by the position of an adjustable wedge block. The crusher is usually driven by a
V-to-V belt drive, but it can be arranged for either V-to-flat or fiat belt drive. The 8″x10″
size utilizes a split frame and may be packed for muleback transportation. Cast steel frames
can be furnished to obtain maximum durability.

This second type of forced feed rock crusher is similar in design to the Type H listed above
except for having a frame and bumper made of cast steel. This steel construction makes the
unit lighter per unit of size, and adds considerable strength. The bearings are all of special
design; they are bronze and will stand continuous service without any danger of failure.
The jaw and cheek plates are manganese steel; and are completely reversible, thus adding
to their wearing life. The jaw opening is controlled by the position of an adjustable wedge
block. The crushers are usually driven by V-to-V but can be arranged for V-to-flat and belt
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drive. The 5″x6″ size and the 8″x10″ size can be
made with sectionalized frame for muleback
transportation. This crusher is ideal for
strenuous conditions. Consider a multi jaw
crusher.

Type H—Cast Steel Frame. Anti-

friction Bumper Bearings, Bronze Side
Bearings.

Bronze Hearing Cast Steel Frame and

Bumper, Bronze Side and Eccentric
Bearings

Bulldog Jaw Crusher

Some jaw crushers are on-floor, some aboveground and others underground. This in many
countries, and crushing many kinds of ore. The Traylor Bulldog Jaw crusher has
enjoyed world wide esteem as a hard working, profit producing, full-proof and trouble free
breaker since the day of its introduction, nearly twenty years ago. To be modern and get
the most out of your crushing dollars, you’ll need the Building breaker. We’d value the
privilege of telling you why-by letter, through our bulletins or in person. Write us now –
today -for a Blake crusher with curved jaw plates that crush finer and step up production.

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Traylor Jaw Crusher
When a machine has such a reputation for excellence that buyers have confidence in its
ability to justify its purchase, IT MUST BE GOOD! Take the Type G Traylor Jaw
Crusher, for instance. The engineers and operators of many great mining companies
know from satisfying experience that this machine delivers a full measure of service and
yields extra profits. So they specify it in full confidence and the purchase is made without
the usual reluctance to lay out good money for a new machine.

The success of the Type G Traylor Jaw Crusher is due to several characteristics. It is (1)
STRONG almost to superfluity, being built of steel throughout; it is (2) FOOL-PROOF,
being provided with our patented Safety Device which prevents breakage due to tramp iron
or other causes of jamming; it is (3) ECONOMICAL to operate and maintain, being fitted
with our well-known patented Bulldog Pitman and Toggle System, which saves power and
wear by minimizing friction—power that is employed to deliver increased production; it is
(4) CONVENIENT to transport and erect in crowded or not easily accessible locations,
because it is sectionalized to meet highly restrictive conditions.

Jaw Crusher Foolproof

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Whenever mining man need a crusher that is
thoroughly reliable and big producer (which is of
all time) they almost invariably think first of a
Traylor Type “G” Jaw Crusher. By experience they
know that this machine has built into it the four
essentials to satisfaction and profit- strength,
foolproofness, economy and convenience.
Maximum STRENGTH lies in the liberal design
and the steel of which crusher’s parts are made-
cast steel frame, Swing Jaw, Pitman Cap and
Toggles, steel Shafts and Pitman rods and
manganese steel Jaw Plates and Cheek Plates.
FOOLPROOFNESS is provided by our patented
and time-tested safety Device which prevents
breakage due to packing or tramp iron.
ECONOMY is assured by our well known Bulldog Pitman and Toggle System, that saves
power and wear by minimizing friction, power that is used to deliver greater production.
CONVENIENCE in transportation and erection in crowded or not easily-accessible
locations, is planned for in advance by sectionalisation to meet any restrictive conditions.

Many of the world’s “greatest” mining companies have standardized upon the Traylor Type
“G” Jaw Crusher. Most of them have reordered, some of them several times. What this
crusher is doing for them in the way of earning extra dollars through increased production
and lowered costs, it will do for you! Investigate it closely. The more closely you do, the
better you”ll like it.

jaw-crushers
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