Abstrict A piston and cylinder unit for a gyratory crusher including a cylinder
having an upper piston carrying the crusher head and a lower piston
dividing the interior of the cylinder into a hydraulic chamber and
a gas chamber. The hydraulic chamber is selectively chargeable with
hydraulic fluid to adjust the crushing gap between the crusher head
and the bowl of the crusher, and the gas chamber is connected in
communication with a pressure relief chamber within the lower piston
to provide an accummulator within the unit accommodating the momentary
displacement of the crusher head by noncrushable materials moving
through the crushing gap during crushing operations.
Claims The embodiments of the invention in which an exclusive property
or privilege is claimed are defined as follows:
1. A supporting unit for a gyratory crusher including a crusher
bowl and a gyratable crusher head supported by the unit in normally
selectively spaced realtion to the bowl which accommodates momentary
displacement of the crusher head by noncrushable materials moving
through the crusher between the head and the bowl during crushing
operations, comprising:
a piston cylinder closed on one end;
first piston means for carrying the crusher head mounted within
the cylinder;
second piston means mounted within the cylinder between said first
piston means and the closed end of the cylinder to divide the interior
of the cylinder into two chambers, one of said chambers being prechargeable
with pressurized fluids to form a first fluid cushion within said
chamber, and the other of said chambers being selectively chargeable
with pressurized fluids to form a second fluid cushion operatively
associated with said first fluid cushion for positioning said first
piston means carrying the crusher head within the cylinder;
said second piston means enclosing a pressure relief chamber and
having valve means providing fluid communication between said one
chamber and the pressure relief chamber; and
said valve means accommodating one-way flow of fluids from said
one chamber into the pressure relief chamber attendant to displacement
of the crusher head by noncrushable materials and attenuated flow
of fluids from the pressure relief chamber into said one chamber
during movement of the crusher head back to its normal operating
position.
2. The supporting unit according to claim 1 and
said one of the chambers being disposed between said second piston
means and the closed end of the chamber; and
said other of the chambers being disposed between said first and
second piston means.
3. The supporting unit according to claim 1 and
the fluid in said one of the chambers and said pressure relief
chamber being a compressible gas; and
the fluid in said other of the chambers being hydraulic fluid.
4. The supporting unit according to claim 1 and
relief valve means connected in fluid communication with said other
of the chambers accommodating evacuation of fluids from said chamber
upon predetermined pressurization of the fluids within said chamber
attendant to displacement of the crusher head by noncrushable materials.
5. The supporting unit according to claim 1 and
stop means secured within the cylinder above said second piston
means to limit movement of said second piston means.
6. The supporting unit according to claim 5 and
said stop means comprising a cylindrical bushing having an interior
diameter sized to receive said first piston means in concentric
sliding relation.
7. The supporting unit according to claim 1 and
said first piston means being of a generally cup-shaped configuration
including a first piston head and a first cylindrical wall portion;
and
said second piston means including a second piston head and a second
outer cylindrical wall portion concentrically receiving said first
wall portion in sliding telescoping relation.
8. The supporting unit according to claim 7 and
said first piston means being adapted to support bearing means
carrying the crusher head;
a lubricant port in the cylinder opening into the interior of the
cylinder;
a groove in said first outer cylindrical wall portion aligned in
registry with said lubricant port during normal crushing operations;
and
a lubricant duct within said first piston head providing fluid
communication between said groove and the bearing means.
9. The supporting unit according to claim 7 and
said cylinder having a fluid port opening into the interior of
the cylinder; and
said second cylindrical wall portion have an exteriorly opening
annular slot about its periphery aligned in registry with said fluid
port in fluid communication with said other of the chambers.
10. The supporting unit according to claim 7 and
said second piston means including a housing containing said presure
relief chamber concentrically aligned within said first and second
cylindrical outer wall portions.
Description BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to gyratory crushers and in particular
to a piston and cylinder arrangement supporting the crusher head
accommodating momentary displacement of the head to allow noncrushable
materials to pass through the crusher.
2. Description of the Prior Art
The prior art includes a variety of gyratory crushers wherein the
crusher head is supported by a hydraulic system which includes means
for lowering the crusher head to allow tramp iron or other noncrushable
materials to pass through the crusher.
Typically, as shown in U.S. Pat. No. 4060205 the main shaft
of the crusher head is supported by a hydraulic piston and cylinder
unit which is supplied with hydraulic fluid by a pump and accumulator
which can be actuated to maintain the desired crushing gap between
the crusher head and the bowl of the crusher. This type of arrangement
has generally been necessary in order to compensate for wear in
the surface of the crusher head during use. In the event a piece
of tramp iron is fed into the crusher, the crusher head is driven
down by the tramp iron which tends to jam in the crushing gap until
the gap is sufficiently enlarged to allow this material to pass
through the crusher. This downward movement of the crusher head
effectively forces the hydraulic fluid in the unit through a conduit
into the accumulator until the tramp iron passes through the gap.
Thereafter, once the tramp iron has passed through the gap, the
accumulator forces the fluid back through the conduit and into the
unit which returns the crusher head to its normal operating position.
While tramp iron relief arrangements such as the foregoing have
been for the most part satisfactory, the frictional losses inherent
in any system requiring the movement of hydraulic fluids through
a series of conduits necessarily retards or reduces the response
time of the system. This response time, or the time required to
lower the crusher head sufficiently to allow a piece of tramp iron
to pass through the crushing gap, is particularly important since
the longer a piece of tramp iron remains jammed in the crushing
gap, the greater the likelihood of damage to the crusher head and
its driving mechanism.
SUMMARY OF THE INVENTION
The present invention relates to a supporting unit adapted to support
the crusher head of a gyratory crusher in selectively spaced relation
to the crusher bowl while accommodating momentary displacement of
the crusher head to allow noncrushable materials to pass through
the crusher.
The supporting unit includes a cylinder mounted on the frame of
the crusher beneath the head shaft carrying the crusher head, and
a pair of pistons reciprocably mounted within the cylinder. The
uppermost of the pistons is adapted to support the head shaft, and
the other piston is mounted between the upper piston and closed
lower end of the cylinder to divide the interior of the cylinder
into a gas chamber and a hydraulic chamber. The gas chamber is precharged
with pressurized gases to form a fluid cushion within the chamber
and the hydraulic chamber is selectively charged with hydraulic
fluid to adjust the crushing gap between crusher head carried by
the upper piston and the crusher bowl mounted on the frame of the
crusher.
When a piece of tramp iron or other noncrushable material is fed
into the crusher, the crusher head is forced down by the tramp iron
until the gap is sufficiently enlarged to allow the material to
pass through the crusher. As a result, both of the pistons are driven
down in the cylinder to compress the gases in the gas chamber. As
the gases are compressed, they flow into a pressure relief chamber
in the lower piston through a one-way check valve in the piston
between the gas and relief chambers. Thereafter, once the material
has passed through the crushing gap, the gases flow back into the
gas chamber from the relief chamber through a return port which
throttles the flow to stabilize the system as the pistons and crusher
head are returned to their normal operating position by the compressed
gases.
From the foregoing, it can be seen that the invention contemplates
a tramp iron relief arrangement which substantially enhances the
response time of the system which is also easy to adjust and maintain
in the field. It is to be understood that various changes can be
made in the arrangement, form and construction of the apparatus
disclosed herein without departing from the spirit and scope of
the invention.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is an elevational view, partially in section, of a gyratory
crusher including the piston and cylinder unit embodying the invention;
FIG. 2 is an enlarged cross-sectional view of the piston and cylinder
unit shown in FIG. 1;
FIG. 3 is a cross-sectional view taken substantially along line
III--III in FIG. 2;
FIG. 4 is a cross-sectional view taken substantially along line
IV--IV in FIG. 2;
FIG. 5 is a view similar to FIG. 2 showing the crushing gap adjustment
feature of the unit; and
FIG. 6 is a view similar to FIG. 5 showing the general position
of the pistons while tramp iron is moving through the crushing gap.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIG. 1 the gyratory crusher 1 embodying the invention
includes a lower frame 2 provided with a vertical hub 3 an upper
frame 4 supporting a crusher bowl or liner 5 a spider-like frame
6 mounted on the upper frame 4 and a centrally located gyratable
head shaft 7 carrying a crusher head or cone 8 in spaced relation
to the interior of the bowl to provide an annular crushing zone
or gap 9 between the bowl and the crusher cone. The head shaft 7
which is carried on an axial thrust bearing 10 supported by a piston
and cylinder unit 11 mounted on the lower frame 2 beneath the shaft,
is rotatably journaled within an eccentric sleeve bearing carried
within the vertical hub 3 to direct the gyratory movement of the
shaft. As shown in FIG. 1 the sleeve bearing includes an eccentric
sleeve 12 having an outer cylindrical surface 13 journaled within
the hub 3 and an eccentrically disposed internal bore 14 which receives
the shaft 7 along an axis inclined to the external surface of the
sleeve. The eccentric sleeve is carried by a supporting bearing
15 on the lower frame 2 and includes a ring gear 16 secured about
its periphery which is driven by a driving pinion 17 mounted on
a horizontally extending drive shaft 18 journaled within the lower
frame 2. The drive shaft 18 is connected with a suitable rotary
drive (not shown) which in turn rotates the sleeve 12 through the
ring gear 16 and pinion 17 to effect gyratory movement of the head
shaft about the bushing 19 mounted in the spider-like frame 6 as
is well known in the art.
The piston and cylinder unit 11 includes an outer cylindrical casing
20 having an open upper end and a closed lower end which is enclosed
by a removable cover plate 21 secured to the casing by bolts 22
or the like. As shown in the drawings, a pair of cylindrical pistons
23 and 24 are reciprocably mounted within the cylindrical casing
20 to form a gas chamber 25 and a hydraulic chamber 26 it being
noted that piston rings or seals 27 and 28 are secured in associated
annular grooves about the respective peripheries of the pistons
to seal each of the chambers 25 and 26 within the casing. The gas
chamber 25 is connected with a conventional gas storage cylinder
29 through a valved inlet 30 in the cover plate 21 secured to the
lower end of the casing. This arrangement accommodates precharging
of the gas chamber 25 with air, or preferably nitrogen, to form
a fluid cushion urging the lower piston 24 against a fixed cylindrical
bushing 31 secured in the casing above the piston 24. The upper
piston 23 which is sized to reciprocate within the bushing 31 and
the outer cylindrical wall 32 of the lower piston 24 cooperates
with the lower piston 24 to contain the hydraulic chamber 26. Hydraulic
fluid is supplied to the hydraulic chamber 26 from a hydraulic reservoir
33 by a reversible pump 34 connected via conduit 35 having a pressure
relief valve 36 to a port 37 in the wall of the casing. The port
37 opens into an external annular groove 38 about the circumference
of the outer cylindrical wall 32 which in turn opens into an internal
annular groove 39 about the inner face of the wall 32 through a
plurality of ports 40 spaced about the circumference of the wall,
and the internal groove 39 communicates with the hydraulic chamber
26 through a series of ports 41 spaced about the circumference of
the cylindrical wall 42 of the upper piston 23. Thus, by using the
reversible pump 34 to vary the quantity of hydraulic fluid in the
hydraulic chamber 26 an operator can adjust the axial spacing between
the upper piston 23 carrying the head shaft 7 and the normally stationary
lower piston 24 to maintain the desired crushing gap between the
crusher head and the crusher bowl, and, in the event a particularly
large piece of tramp iron becomes jammed in the crushing gap causing
the lower piston 24 to bottom-out in the cylinder, the pressure
relief valve 36 accommodates evacuation of hydraulic fluid from
the hydraulic chamber 26 to allow the upper piston and thus the
crusher head to drop to prevent damage to the crusher head and driving
mechanism. Additionally, it should be noted that the upper piston
23 includes a duct 43 for directing lubricant to the thrust bearing
10 from a lubricant port 44 including an interiorly opening annular
groove in the wall of the bushing 31 through an exterior groove
45 in the periphery of the upper piston.
The lower piston 24 includes a closed housing 46 affixed to the
piston head 47 which provides a pressure relief chamber 48 contained
within the lower piston. The pressure relief chamber 48 communicates
with the gas chamber 25 through the piston head 47 by means of a
check valve 49 which accommodates one-way flow of gases from the
gas chamber 25 into the pressure relief chamber 48 and through
an open gas return port 50 which is sized to throttle or attenuate
a return flow of gases into the gas chamber 25 to prevent the development
of "water hammers" within the system as will be described.
As shown in FIG. 2 the check valve 49 is preferably of a conventional
ball and spring design which is adapted to open only when the pressure
in the gas chamber 25 exceeds the pressure in the pressure relief
chamber 48.
DESCRIPTION OF OPERATION
Referring to FIGS. 1 and 2 during normal crushing operations,
the upper and lower pistons 23 and 24 are supported in the positions
shown by the precharged gases in the gas chamber 25 and the hydraulic
fluid in the hydraulic chamber 26. As can be seen from the drawing,
the upper piston 23 is shown in its lowermost position relative
to the lower piston 24. This position generally corresponds to the
position of the upper piston after a new, unworn mantel has been
installed on the crusher head. Since the rock passing through the
crusher wears down the mantel after extended use, without some means
of adjusting the position of the crusher head relative to the crusher
bowl, the crushing gap will continue to grow until it is necessary
to replace the mantel in order to continue crushing operations.
As shown in FIG. 5 the present arrangement deals with this problem
by providing a system wherein hydraulic fluid can be periodically
pumped into the hydraulic chamber 26 to lift the upper piston 23
relative to the normally stationary lower piston 24 until the desired
spacing between the crusher head and the bowl is obtained. Conversely,
if it is desired to enlarge the crushing gap to produce a larger
aggregate size, this process is reversed.
When a piece of tramp iron jams in the crushing gap, the crusher
head is forced down by the jammed tramp iron. This forces upper
piston 23 carrying the head shaft 7 downwardly in the casing 20
as generally shown in FIG. 6 until the tramp iron has passed through
the crushing gap. Since the hydraulic fluid in the hydraulic chamber
26 maintains a relatively constant spacing between the upper and
lower pistons, both pistons are driven downward in concert. Thus,
as the lower piston moves down in the casing to compress the precharged
gas in the gas and pressure relief chambers 25 and 48 these chambers
function as an accumulator within the casing which essentially minimizes
the time required to lower the crusher cone enough to allow the
tramp iron to pass through the crushing gap as well as the time
necessary to lift the cone back into its normal operating position.
Typically, as the lower piston 24 is driven down in the casing 20
the gas pressure in both the gas and pressure relief chambers 25
and 48 increases to about 900-1000 psi from a normal operating pressure
of 400-500 psi. Since the one-way check valve 49 provides negligible
resistance to the gases as they flow into the pressure relief chamber
to equalize the pressures in those chambers, the present arrangement
has essentially eliminated any increase in the system's response
time due to frictional losses such as those encountered in the hydraulic
pressure relief systems discussed above in regard to the prior art.
After the tramp iron has passed through the crushing gap, the compressed
gases in the gas chamber 25 act on the lower piston 24 to begin
moving the pistons upwardly within the chamber and to return the
crusher head to its normal operating position. The resulting pressure
drop in the gas chamber 25 induces a return flow of gases from the
pressure relief chamber 48 into the gas chamber 25 through the return
port 50 until the crusher head has returned to its normal operating
position. In that position the pressures in the gas and relief chambers
are substantially the same. It should be particularly noted that
the throttling or flow attenuating feature of the return port 50
enhances the stability of the system both during the compression
or tramp iron relief stroke as well as during the return stroke.
Specifically, when the gyrating crusher head encounters a piece
of tramp iron in the crusher bowl, it tends to create pulsing pressure
surges or "water hammers" within the gas chamber 25. This
phenomenum is described in detail in the assignee's U.S. Pat. No.
4060205 which is discussed above in regard to the prior art. In
the present arrangement, this problem is effectively eliminated
by throttling the backflow of gases through the return port 50 during
the relief or compression stroke, and by attenuating the gas flow
through the return port as the crusher head returns to its normal
operating position. |