Abstrict A rock crusher includes a bowl coupled to a frame and a head assembly
coupled to the frame defining a crushing gap between the head assembly
and the bowl. The rock crusher further includes a number of fixed
displacement hydraulic motors adapted to rotate the bowl with respect
to the frame and a hydraulic fluid source providing a flow rate
of hydraulic fluid to the hydraulic motors. A hydraulic control
valve is adapted to remove one of the hydraulic motors from operation,
directing the hydraulic fluid to the remaining hydraulic motors.
The flow rate of hydraulic fluid remains unchanged, thereby increasing
the hydraulic fluid flow rate provided to and the speed of the remaining
hydraulic motors.
Claims What is claimed is:
1. A method of adjusting a bowl with respect to a frame in a cone
crusher, comprising the steps of: providing a plurality of hydraulic
motors adapted to rotate the bowl with respect to the frame; providing
at least one hydraulic pump adapted to provide fluid to the hydraulic
motors; setting a first adjustment speed having a first torque by
operating more than one motor and the at least one hydraulic pump;
and setting a second adjustment speed having a second torque by
removing one of the operating motors from operation while maintaining
operation of the at least one hydraulic pump; wherein the second
adjustment speed is greater than the first adjustment speed and
the second torque is less than the first torque.
2. The method of claim 1 wherein the at least one hydraulic pump
is driven by an electric motor.
3. The method of claim 1 wherein the plurality of hydraulic motors
is two.
4. The method of claim 1 wherein the plurality of hydraulic motors
are fixed displacement hydraulic motors.
5. The method of claim 1 wherein the plurality of hydraulic motors
are variable displacement hydraulic motors.
6. The method of claim 1 further comprising the step of setting
a third adjustment speed by removing a second hydraulic motor from
operation.
7. A cone crusher, comprising: a frame; a bowl coupled to the frame;
a head assembly coupled to the frame defining a crushing gap between
the head assembly and the bowl; a plurality of fixed displacement
hydraulic motors adapted to rotate the bowl with respect to the
frame; a hydraulic fluid source providing a flow rate of hydraulic
fluid to the plurality of hydraulic motors; and a hydraulic control
valve adapted to remove one of the plurality of hydraulic motors
from operation wherein the hydraulic fluid is directed to the remaining
hydraulic motors, wherein the flow rate of hydraulic fluid remains
unchanged, thereby increasing the hydraulic fluid flow rate provided
to and speed of the remaining hydraulic motors.
8. The cone crusher of claim 7 wherein the hydraulic fluid source
is a hydraulic pump driven by an electric motor.
9. The cone crusher of claim 8 wherein the hydraulic fluid source
comprises a plurality of hydraulic pumps.
10. The cone crusher of claim 7 further comprising an adjustment
ring fixed to the frame and wherein the bowl is rotatably coupled
to the adjustment ring via threads.
11. The cone crusher of claim 7 wherein the plurality of fixed
displacement hydraulic motors is two fixed displacement motors.
12. The cone crusher of claim 7 wherein the fixed displacement
hydraulic motors are piston type motors.
13. The cone crusher of claim 12 further comprising an inlet port
and an outlet port for the hydraulic motor that is removed from
operation, wherein the inlet port and the outlet port are connected
when the motor is taken out of operation.
14. A method of increasing the torque available for adjusting a
crushing gap in a cone crusher having a bowl and a frame, comprising
the steps of: providing more than one fixed displacement hydraulic
motor adapted to rotate the bowl with respect to the frame, at least
one of the hydraulic motors not operating, the remaining hydraulic
motors being operating hydraulic motors; providing a hydraulic fluid
source to provide a flow rate of hydraulic fluid to the operating
hydraulic motors; and placing the not operating hydraulic motor
into operation by providing a portion of the flow rate of hydraulic
fluid to the not operating hydraulic motor, the flow rate of hydraulic
fluid from the hydraulic fluid source remaining unchanged, thereby
increasing the torque available for adjusting the crushing gap.
15. The method of claim 14 wherein the hydraulic fluid source
comprises a hydraulic pump driven by an electric motor.
16. The method of claim 14 wherein two fixed displacement motors
are provided.
17. The method of claim 16 wherein the two fixed displacement
motors are piston type motors.
18. The method of claim 16 wherein the two fixed displacement
motors are the same size, resulting in a doubling of the available
torque when the out of operation motor is placed into operation.
19. The method of claim 18 wherein the two fixed displacement
motors have a displacement of 2.44 cubic inches per revolution.
20. The method of claim 14 further comprising the step of opening
a hydraulic control valve to provide hydraulic fluid to the out
of operation hydraulic motor.
Description FIELD OF THE INVENTION
The present invention relates generally to rock crushing equipment.
More particularly, the present invention relates to a rock crusher
capable of adjusting the crushing gap at more than one speed.
BACKGROUND OF THE INVENTION
A rock crushing system generally breaks apart rock, stone or other
material in a crushing gap between two elements. For example, a
conical rock crusher is comprised of a head assembly including a
crushing head which gyrates about a vertical axis within a stationary
bowl attached to a main frame of the rock crusher. The crushing
head is assembled with an eccentric mechanism that rotates to impart
the gyrational motion of the crushing head which crushes rock, stone
or other material in a crushing gap between the crushing head and
the bowl. The eccentric mechanism can be driven by a variety of
power drives such as an attached bevel gear, driven by a pinion
and counter shaft assembly, and a number of mechanical power sources,
such as electrical motors or combustion engines.
The exterior of the conical crushing head is covered with a protective
or wear resistant mantle that engages the material which is being
crushed, such as rock, stone, ore, minerals or other substances.
The bowl which is mechanically fixed to the main frame is fitted
with a bowl liner. The bowl liner and the bowl are stationary and
spaced apart from the crushing head. The liner provides an opposing
surface from the mantle for crushing the material. The material
is crushed in the crushing gap between the mantle and the liner.
The gyrational motion of the crushing head with respect to the
bowl crushes rock, stone, or other material within the crushing
gap. Generally, the rock, stone or other material is fed into a
top of the crushing gap and is crushed as it travels through the
crushing gap and exits at a bottom of the crushing gap. The size
of the crushing gap determines the maximum size of crushed material
which exits the crushing gap.
Generally, the bowl is movably attached to the adjustment ring
which is connected to the main frame. The size of the crushing gap
can be adjusted by vertically moving the bowl with respect to the
crushing head. As the bowl vertically moves with respect to the
adjustment ring and main frame, the bowl and bowl liner move vertically
with respect to the mantle. A conventional crusher, such as, an
HP700.TM. conical rock crusher manufactured by Metso Minerals of
Milwaukee, Wis. includes a bowl threaded to an adjustment ring which
is fixed to the main frame by tramp release cylinders. The bowl
and connecting adjustment cap is coupled to a gear which surrounds
the adjustment cap.
A conventional adjustment mechanism comprised of a hydraulic motor
rotates the bowl with respect to the adjustment ring via the gear.
The hydraulic motor rotates the bowl with respect to the main frame
so that the bowl is vertically raised or lowered, thereby adjusting
the gap size.
In another conventional crusher, an MP1000.TM. conical rock crusher
manufactured by Metso Minerals of Milwaukee, Wis. includes an adjustment
mechanism having four hydraulic motors. The four hydraulic motors
are necessary to move the large bowl associated with the MP1000.TM.
crusher. The four motors rotate the bowl with respect to the main
frame to adjust the gap size.
Generally, the bowl must be moved with respect to the head in at
least two different situations. First, the bowl is rotated with
respect to the head to remove it from the rock crusher for repair
and maintenance. Removing the bowl from the annular ring attached
to the main frame requires a significant amount of time (e.g., over
one hour) as the bowl is threadably disengaged from the annular
ring. Alternatively, the bowl can be moved to various gap size heights
to allow access and inspection of components of the rock crusher.
Maintenance may include operations in which the mantle, crushing
head, bowl liner, or bowl are repaired or replaced. Alternatively,
other equipment in the crusher can be repaired and replaced or lubricated
during maintenance operations. Generally, the bowl is removed when
the rock crusher is not operational.
Second, the bowl is moved with respect to the head to adjust the
gap size. The gap size is adjusted to alter the size of crushed
material exiting the rock crusher. For example, to create crushed
material which is smaller, the gap size is decreased. In contrast,
to create crushed material which is larger, the gap size is increased.
Generally, adjustments of the gap size to create smaller or larger
size crushed material require relatively fine positioning of the
bowl with respect to the crushing head (e.g., a slow rotation of
the bowl with respect to the main frame is necessary).
The gap size can be adjusted while the rock crusher is operating
(adjustment under load) or while the rock crusher is non-operational
(no load). Adjustments under load require larger amounts of torque
than the amount of torque required to adjust the bowl or remove
the bowl under no load. Accordingly, conventional gap adjustment
mechanisms have required a high torque, slow speed motor.
Certain conventional rock crushers, such as, the MP1000.TM. rock
crusher have utilized two hydraulic pumps to drive the four hydraulic
motors. The two hydraulic pumps allow the power unit to drive the
four motors at two different speeds. One pump is used for the gap
adjustments (e.g., slow speed), both pumps are used for installation
and removal of the bowl assembly (e.g., high speeds). However, the
use of two hydraulic pumps adds to the cost and size of the power
unit.
Thus, there is a need for a low cost, an efficient variable speed
gap adjustment mechanism. Further still, there is a need for a variable
speed adjustment mechanism which does not require two hydraulic
pumps.
SUMMARY OF THE INVENTION
The present invention relates to a method of adjusting a bowl with
respect to a frame in a cone crusher, the method including the steps
of providing a plurality of hydraulic motors adapted to rotate the
bowl with respect to the frame and providing at least one hydraulic
pump adapted to provide fluid to the hydraulic motors. Further steps
include setting a first adjustment speed having a first torque by
operating more than one motor and the at least one hydraulic pump
and setting a second adjustment speed having a second torque by
removing one of the operating motors from operation while maintaining
operation of the hydraulic pump. The second adjustment speed is
greater than the first adjustment speed and the second torque is
less than the first torque.
The invention further relates to a cone crusher having a frame,
a bowl coupled to the frame, a head assembly coupled to the frame
defining a crushing gap between the head assembly and the bowl,
and a plurality of fixed displacement hydraulic motors adapted to
rotate the bowl with respect to the frame. The cone crusher further
includes a hydraulic fluid source providing a flow rate of hydraulic
fluid to the plurality of hydraulic motors, and a hydraulic control
valve adapted to remove one of the plurality of hydraulic motors
from operation, wherein the hydraulic fluid is directed to the remaining
hydraulic motors and wherein the flow rate of hydraulic fluid remains
unchanged, thereby increasing the hydraulic fluid flow rate provided
to and speed of the remaining hydraulic motors.
Further still, the invention relates to a method of increasing
the torque available for adjusting the crushing gap in a cone crusher
having a bowl and a frame. The method includes the steps of providing
more than one fixed displacement hydraulic motors adapted to rotate
the bowl with respect to the frame, at least one of the hydraulic
motors not operating, the remaining hydraulic motors being operating
hydraulic motors. Further steps include providing a hydraulic fluid
source to provide a flow rate of hydraulic fluid to the operating
hydraulic motors and placing the not operating hydraulic motor into
operation by providing a portion of the flow rate of hydraulic fluid
to the not operating hydraulic motor, the flow rate of hydraulic
fluid from the hydraulic fluid source remaining unchanged, thereby
increasing the torque available for adjusting the crushing gap.
The invention is capable of other embodiments and of being practiced
or being carried out in various ways. Alternative exemplary embodiments
relate to other features and combinations of features as may be
generally recited in the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
Exemplary embodiments will hereinafter be described with reference
to the accompanying drawings, wherein like numerals denote like
elements and:
FIG. 1 is a general block diagram of a rock crushing system in
accordance with an exemplary embodiment;
FIG. 2 is a perspective view, in partial cutaway, of the rock crushing
system illustrated in FIG. 1;
FIG. 3 is a detailed hydraulic schematic diagram of the rock crushing
system illustrated in FIG. 1; and
FIG. 4 is a detailed hydraulic schematic diagram of a rock crushing
system of an additional exemplary embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to FIG. 1 a conical rock crusher or rock crushing system
10 includes a gap adjustment mechanism 2 a selector 4 a hydraulic
fluid source 6 and a rock crusher 8. Gap adjustment mechanism 2
includes a hydraulic motor unit 9. Hydraulic motor unit 9 can include
one or more hydraulic motors. Preferably, hydraulic motor unit 9
includes at least one variable displacement hydraulic motor.
Hydraulic fluid source 6 can be any fluid source for providing
fluid under pressure. Hydraulic fluid source 6 can be a conventional
hydraulic power unit composed of a cabinet with a self contained
oil tank, an electric motor, a hydraulic pump, an accumulator, valves,
gauges, and other necessary electrical and hydraulic components.
Selector 4 is a valve that selects the toned displacement of the
motors and therefore ultimately determines torque and speed at which
gap adjustment mechanism 2 adjusts the crushing gap associated with
rock crusher 8.
Rock crusher 8 can be any type of rock crusher which utilizes a
crushing gap. Preferably, crusher 8 has a crushing gap which is
set via a rotational interface, such as, a bowl threadably engaged
to a main frame. Rock crusher 8 can be HP.TM. series rock crusher,
such as, the HP700 rock crusher, an MP series rock crusher, a WF
Series rock crusher, or a Symons.TM. cone crusher manufactured by
Metso Minerals of Milwaukee, Wis. Alternatively, rock crusher 8
can be any number of rock crushers manufactured by a variety of
sources. Rock crusher 8 is not described in a limiting fashion with
respect to the claims of the present application.
Gap adjustment mechanism 2 advantageously can adjust the crushing
gap according to at least two speeds. Preferably, mechanism 2 has
a higher speed, lower torque mode of operation for removing the
bowl associated with rock crusher 8 and a higher torque, lower speed
mode for adjusting the gap size associated with rock crusher 8 under
load or for making finer adjustments to the crushing gap. The higher
speed, lower torque mode is generally utilized in maintenance operations
(no load conditions) and the lower speed, higher torque mode is
generally utilized under load conditions.
Selector 4 can effectuate the selection of the appropriate speed
for adjusting the gap associated with crusher 8 by adjusting the
displacement setting associated with hydraulic motor unit 9. A higher
displacement setting is utilized for a higher torque, lower speed
mode and a lower displacement setting is used for a lower torque,
higher speed mode. Additional displacement settings can provide
additional torque speed modes.
Referring to FIG. 2 rock crusher 8 is embodied as a HP 700 rock
crusher. Rock crusher 8 includes a structure or main frame 12 having
a base 14. Crusher 8 can be any size rock crusher or any size of
crusher head, such as a short head or a standard head. Base 14 rests
upon a platform-like foundation which can include concrete piers
(not shown), a foundation block, a platform, or other supporting
members.
Central hub 16 of main frame 12 includes an upwardly diverging
vertical bore or tapered bore 28. Bore 28 is adapted to receive
a main shaft 30. Shaft 30 is preferably held stationary in bore
28 with respect to central hub 16 of frame 12.
Shaft 30 supports an eccentric mechanism 48 which is coupled to
a head assembly 44. Eccentric mechanism 48 rotates about shaft 30
thereby causing head assembly 44 to gyrate within rock crushing
system 10. The gyration of head assembly 44 within a bowl 46 which
is fixed to adjustment ring 55 connected to main frame 12 allows
rock, stone, ore, minerals, or other materials to be crushed between
a mantle 50 and a bowl liner 51. Materials are crushed in a crushing
gap 54. Bowl liner 51 is held against bowl 46 and mantle 50 is
attached to head assembly 44. Head assembly 44 forces mantle 50
towards bowl liner 51 to effect the rock crushing operation.
Bowl 46 is threadably engaged to an adjustment ring 55 fixed to
main frame 12. Bowl 46 is coupled to a gear 58 which is in communication
with a gear 60 associated with hydraulic motor unit 9. System 10
preferably includes a second hydraulic motor unit 9 located 1/3
the arc distance along gear 58. A third hydraulic motor unit or
a idler assembly can be utilized at 2/3 the arc distance along gear
58 to balance the loading along gear 58. Alternatively, system 10
can include any number of motor units 9. In another alternative
embodiment, a single motor unit 9 can drive multiple gears 60.
The adjustment of the size of gap 54 is accomplished by rotating
gear 60 via motor unit 9. Rotation of gear 60 rotates gear 58 which
in turn rotates bowl 46 with respect to adjustment ring 55. In this
embodiment, a counter-clockwise rotation of bowl 46 increases the
size of gap 54 and a clockwise rotation of bowl 46 decreases the
size of gap 54. Alternatively, ring 55 and bowl 46 may be configured
such that a counter clockwise rotation of bowl 46 decreases the
size of gap 54 and accordingly a clockwise rotation of bowl 46 increases
the size of gap 54. Further, other interferences, threadable or
otherwise adjustable, can be utilized to position bowl 46 with respect
to assembly 44.
System 10 can advantageously rotate bowl 46 at more than one speed
by utilizing a variable displacement hydraulic motor in unit 9.
Selector 4 allows the speed to be chosen by adjusting the displacement
setting for the variable displacement hydraulic motor. Preferably,
unit 9 motors 122 and 124 (FIG. 3) can be set to a higher speed
setting or a lower speed setting. Accordingly, motor unit 9 effectuates
rotation of gear 60 and hence, the adjustment of gap 54 at two different
speeds.
With reference to FIG. 3 the operation of gap adjustment mechanism
2 for conical crushing system 10 is described in more detail with
respect to the hydraulic components. Hydraulic fluid source 6 includes
a pump 102 driven by an electric motor 104. Pump 102 provides high
pressure hydraulic fluid through high pressure in-line filter 106.
Pump 102 draws hydraulic fluid through a magnetic suction separator
108 which can be a donut shaped ceramic magnet.
Gap adjustment mechanism 2 includes an overspeed protection apparatus
114 a gauge 112 a main relief valve 116 and an open loop valve
118. Open loop valve 118 is a neutral solenoid valve which removes
pressure from mechanism 2 when power is lost. Mechanism 2 also includes
directional control valves 122 and 124 for controlling the direction
of rotation of high variable speed hydraulic motors 132 and 134.
Valves 122 and 124 are preferably controlled by a solenoid and provide
hydraulic fluid in a first direction to motors 132 and 134 when
in a first position and provide hydraulic fluid in a second direction
when in a second position. Motors 132 and 134 rotate in a direction
corresponding to the direction of hydraulic fluid flowing through
motors 132 and 134.
System 2 also includes a cross bleed orifice 136 and release shuttle
138. Shuttle 138 disengages brakes 142 and 144 on motors 132 and
134 when fluid is provided to motors 132 and 134. Cross bleed orifice
132 allows for error in the flow when variable displacement motor
132 is set to zero displacement as described below.
Motors 132 and 134 are variable displacement parallel feed motors.
Alternatively, motors 132 and 134 can be piston motors or other
hydraulic motors capable of variable displacement and zero stroke.
Motor 132 can be set to a zero displacement setting or a 2.8 cubic
inches per revolution displacement setting. Motor 134 can be set
to a displacement setting of 2.3 cubic inches per revolution and
a displacement setting of 2.8 cubic inches per revolution.
The settings for motors 132 and 134 is controlled by a logic selector
valve 130. Preferably, logic selector valve 130 is a solenoid valve
which allows a user to select a high or low speed for mechanism
2. Valve 130 is preferably electrically coupled to a user interface
(selector 4 FIG. 1) which allows the user to select a first displacement
setting where motor 132 has a displacement of zero cubic inches
per revolution and motor 134 has a displacement setting of 2.3 cubic
inches per revolution or a second displacement setting where motor
132 has a displacement setting of 2.8 cubic inches per revolution
and motor 134 has a displacement setting of 2.8 cubic inches per
revolution.
When fluid is provided to motors 132 and 134 brakes 142 and 144
are disengaged via shuttle 138 and can rotate. When fluid is provided
to one or both of motors 132 and 134 shafts 148 and 150 associated
with gear 60 (FIG. 2) are rotated in the direction controlled by
valves 122 and 124.
In operation, gap adjustment mechanism 2 is set to a higher speed,
lower torque setting by setting motor 132 to the zero displacement
setting and setting motor 134 to the 2.3 cubic inch per revolution
setting. In this mode, mechanism 2 rotates at a lower torque, and
higher speed. Motor 134 provides the force for rotating shaft 150
while motor 132 follows the action of motor 134 because it is at
the zero cubic inches per revolution displacement setting. This
higher speed mode can be utilized to remove bowl 46 from adjustment
ring 55 for maintenance operations. Preferably, the settings provided
can allow the bowl to be removed in fifteen minutes or less for
a HP700 rock crusher.
A user can make finer adjustments under load or under no load conditions
via logic selector 130. Logic selector 130 can set motor 132 to
a displacement setting of 2.8 cubic inches per revolution and motor
134 to a displacement setting of 2.8 cubic inches per revolution.
At these settings, motors 132 and 134 provide a higher torque, lower
speed mode of operation. This mode can be utilized to provide finer
adjustments to the position of the bowl with respect to the frame.
In this way, mechanism 2 advantageously can turn bowl 46 at a slower
speed for adjusting under load and a faster speed for bowl installation
and removal. Preferably, motors 132 and 134 utilize a triple reduction
gear reducer.
Mechanism 2 can utilize a single motor with two displacement settings.
However, system 2 shown in FIG. 3 advantageously uses two motors
so greater torque is available and a smaller sized hydraulic fluid
source 6 can be utilized.
Referring to FIG. 4 in another exemplary embodiment, a pair of
hydraulic drive assemblies 200 202 are driven by hydraulic fluid
provided by a hydraulic power unit 204. The hydraulic power unit
204 may include a hydraulic pump 206 and an electric motor 208 as
described in earlier embodiments.
The hydraulic drive assemblies 200 202 may be coupled to the bowl
in a similar fashion to the embodiments described above. The hydraulic
drive assemblies 200 202 may include fixed displacement hydraulic
motors 210 212. In a preferred embodiment, the fixed displacement
hydraulic motors 210 212 are piston type motors having a displacement
setting of 2.44 cubic inches per revolution. In other embodiments,
the hydraulic motors may be internal gear, spur gear or vane type
motors.
Further referring to FIG. 4 hydraulic control valves 214 216
are utilized to control the direction of motors 210 212 and control
whether the motors 210 212 are operating via the provision of pressurized
hydraulic fluid.
When both fixed displacement hydraulic motors 210 212 are in service
or operating, that is, they are provided with hydraulic fluid from
the hydraulic power unit 204 a maximum amount of torque is provided
for adjusting the bowl during operation. Generally, the maximum
amount of torque is desired when the crushing gap is being adjusted
during crusher operation. During operation, rocks are present, thus
increasing the friction between the bowl and head assembly, requiring
greater torque.
During maintenance of the crusher, it may be desired to increase
the speed of bowl rotation to more quickly remove the bowl from
the adjustment ring. In order to increase the speed of bowl adjustment,
one fixed displacement hydraulic motor 210 may be taken out of operation
by de-energizing hydraulic control valve 214. The term "taken
out of operation" does not necessarily mean that the motor
is removed from the crusher, or even disengaged from the bowl, rather,
terminating the supply of hydraulic fluid will remove the motor
from operation. When motor 210 is removed from operation, the hydraulic
fluid provided by hydraulic power unit 204 is diverted to fixed
displacement hydraulic motor 212 thus increasing the flow rate
to and therefore speed of hydraulic motor 212.
In a preferred embodiment where hydraulic motors 210 212 are of
the same size, removing motor 210 from operation will double the
speed of motor 212 if the flow rate of hydraulic fluid provided
by the hydraulic power unit 204 remains constant, which is the case
in a preferred embodiment. Note that while the two fixed displacement
motors 210 212 are the same size in a preferred embodiment, the
motors may be of different sizes depending on the crusher configuration.
Note that removing hydraulic motor 210 from operation to double
the speed of bowl adjustment with hydraulic motor 212 results in
decreasing the available adjustment torque. The available torque
is decreased by half in the case where motors 210 212 are of the
same size. The decrease in torque is acceptable in the case of bowl
adjustment and removal during maintenance operations as the required
torque to rotate the bowl during such operations when materials
are not in the crushing gap is substantially less. Accordingly,
sacrificing torque to increase the speed of bowl adjustment is both
acceptable and desirable.
In an exemplary embodiment, a hydraulic idling valve 218 is provided
to connect the hydraulic motor ports 220 222 of the hydraulic motor
210 that is taken out of operation. Utilizing the hydraulic idling
valve 218 permits motor 210 to remain engaged with the adjustment
gear even when out of service without creating a resisting torque,
as fluid may flow in a loop as the bowl is rotated.
The use of fixed displacement hydraulic motors 210 212 as shown
in FIG. 4 may provide certain advantages over the use of variable
displacement hydraulic motors as depicted in FIG. 3. The primary
advantage of fixed displacement hydraulic motors is that such motors
are somewhat less expensive than variable displacement motors and
can be lighter weight and therefore more easily supported on the
crusher. The fixed displacement motors are also more durable and
tend to be more stable in operation.
Although two fixed displacement motors 210 212 are depicted in
FIG. 4 other exemplary embodiments may have a greater number of
motors, such as four motors. In such embodiments, it may be necessary
to provide an additional pump and motor combination to the hydraulic
power unit. In embodiments having more than two fixed displacement
motors, taking one or more of the motors out of service while maintaining
the same hydraulic fluid flow rate from the hydraulic power unit
will increase the speed of bowl adjustment while sacrificing torque.
Conversely, increased torque may be provided by adding formerly
non-operating motors to operation without changing the flow from
the hydraulic power unit, thus increasing torque while decreasing
the speed of bowl adjustment.
It is understood that the above description is of preferred exemplary
embodiment of the present invention. The present invention is not
limited to the specific form shown. For example, although a dual
motor system is shown, a single variable displacement motor or more
than two fixed displacement motors can be utilized. Also, the specific
displacement settings given are merely examples. These and other
modifications may be made in the design and arrangement of the elements
discussed here without departing from the scope of the invention
as expressed in the appended claims. |