Abstrict A hydraulic control system for a gyratory crusher has a hydraulically
supported main shaft. An inlet line to the cylinder is provided
with a pressure relief valve. When the pressure in the cylinder,
e.g. because of a disturbance, exceeds the opening pressure of the
relief valve, fluid flows from the cylinder through the pressure
relief valve to the lubricating circuit of the crusher and further
to the return line. The safety system of the crusher is simple,
reliable, and quick.
Claims We claim:
1. A hydraulic control system for a gyratory crusher in which a
main shaft of the crusher is supported hydraulically by a piston
movable in a cylinder and the crusher is lubricated by a lubricating
circuit, the system comprising:
a tank for hydraulic fluid,
a pump unit and inlet lines which lead hydraulic fluid from the
tank into the cylinder and into the lubricating circuit,
a return line which leads hydraulic fluid from the cylinder and
from the lubricating circuit into the tank, and
a pressure relief valve connected to the inlet line and having
associated therewith an opening pressure at which the relief valve
opens, and a by-pass line connected between the relief valve and
lubricating circuit, such that when the pressure in the cylinder
exceeds the opening pressure of the relief valve, fluid flows from
the cylinder through the relief valve to the lubricating circuit
and further to the return line.
2. A system in accordance with claim 1 wherein the by-pass line
is integrated the crusher.
3. A system in accordance with claim 2 further comprising
a transducer which monitors a height position of the main shaft
in the crusher, and
a control unit connected to the transducer and to the pump unit
such that when the pressure in the cylinder is below the opening
pressure of the relief valve, the control unit operates the pump
unit to automatically position the main shaft at a predetermined
position.
4. A system in accordance with claim 2 wherein the by-pass line
is placed in the frame of the crusher.
5. A system in accordance with claim 4 further comprising
a transducer which monitors a height position of the main shaft
in the crusher, and
a control unit connected to the transducer and to the pump unit
such that when the pressure in the cylinder is below the opening
pressure of the relief valve, the control unit operates the pump
unit to automatically position the main shaft at a predetermined
position.
6. A system in accordance with claim 1 further comprising
a transducer which monitors a height position of the main shaft
in the crusher, and
a control unit connected to the transducer and to the pump unit
such that when the pressure in the cylinder is below the opening
pressure of the relief valve, the control unit operates the pump
unit to automatically position the main shaft at a predetermined
position.
7. A system in accordance with claim 1 wherein the pressure relief
valve is integrated into the crusher.
Description FIELD OF THE INVENTION
The present invention relates to a hydraulic control system of
gyratory crushers. The invention relates especially to a safety
system for overload situations in such crushers where the main shaft
is hydraulically supported by a piston.
BACKGROUND OF THE INVENTION
The main shaft of a gyratory crusher is usually hydraulically supported
by a piston such that the vertical position of the main shaft can
be adjusted. The hydraulic circuit in such crushers is usually also
provided with a safety system for overload situations. When a noncrushable
particle enters the crusher, the system allows the piston and thereby
the main shaft to move downwards and thus let the particle go through
the crusher. Thereafter the main shaft must rise to the original
position to continue the crushing process. In such known systems
there is a pressure relief valve and a pressure accumulator. Pressure
accumulators are however quite expensive and they require a relatively
large space. They also have to be checked relatively often.
SUMMARY OF THE INVENTION
Now a hydraulic control system for gyratory crushes has been invented.
Preferable embodiments of the invention are described in the other
claims.
In the invention it is essential that in an overload situation
the pressure relief valve allows the fluid to flow from the cylinder
to the lubricating circuit of the crusher, and thus makes the main
shaft to move downwards. When, after the disturbance, an automatic
control system reacts to this movement and pumps fluid back to the
crusher, and thus lifts the main shaft to the pre-determined position.
No pressure accumulator and no corresponding hoses are needed.
According to a preferable embodiment, the pressure relief valve
is integrated to or into the crusher.
BRIEF DESCRIPTION OF THE EXAMING FIGURES
In the drawings of the description,
FIG. 1 shows the hydraulic scheme of a system in accordance with
the invention,
FIG. 2 shows a partial sectional view of a crusher that can be
used in the system of FIG. 1
FIG. 3 shows a partial sectional view of another crusher.
DETAILED DESCRIPTION OF THE INVENTION
Crusher 1 comprises a frame and therein a main shaft supported
through a suitable bearing by a piston movable in a hydraulic cylinder.
The main shaft can be kept at a desired position by adjusting the
amount of hydraulic fluid in the cylinder. Pressurized fluid is
led from pump unit 2 through inlet line 3 into the cylinder to support
the piston and thereby the main shaft. The fluid is normally led
out from the cylinder through the line 3 and adjusting means of
the pump unit into tank 4. The pump unit then takes fluid from the
tank.
The inlet line 3 is provided with a pressure relief valve 5 integrated
to or preferably into the crusher. In case of an overload situation
in the crusher, for instance because of an uncrushable particle,
overpressure in the cylinder opens the relief valve, and fluid flows
from the inlet line through a by-pass line 61and outlet 7 to return
line 8.
The crusher is also provided with a setting transducer 9 which
detects the change of the main shaft position. When an overload
situation is over, the shaft is automatically raised to the original
position. The process is controlled by means of control unit 10
connected to the pump unit and to the transducer.
Because there is no pressure accumulator, the system is simpler,
more compact and easier to assemble than the known systems. Further,
when the relief valve is joined without hoses to the crusher, the
system response times are very short. This is an important advantage
especially in cold climates, where the resistance in hoses is even
more significant. In an overload situation there is also no counterpressure
to the oil, which further increases the efficiency and reliability
of the system. Also the service demand is reduced.
The setting transducer 9 may comprise of a toothed rack attached
to the piston and of a corresponding gear wheel connected to a angle
detector.
As normally, hydraulic fluid is used here also as a lubricating
oil. Fluid is taken from the tank 4 by a lubrication pump unit 11
and led into the crusher lubricating circuit through a lubrication
inlet line 12. From the lubricating oil circuit the fluid is returned
through the outlet 7 to the return line 8.
The pump unit 2 tank 4 and lubrication pump unit 11 are provided
with normal auxiliary equipment necessary for reliable operation
of such systems.
FIG. 2 shows in more detail how the relief valve 5 is mounted into
the frame of the crusher. The by-pass line 6 has been made into
the frame so as to lead from the valve 5 into the lubrication circuit.
In a normal situation the stem of the valve closes the by-pass line.
In an overload situation the stem moves backwards and allows fluid
to flow into the by-pass line.
Alternatively, an external by-pass line can be used.
FIG. 2 also shows a cuplike piston 13 surrounding the main shaft
14. In this way the height of the crusher is lower than in conventional
crushers with a piston-cylinder pair totally below the main shaft.
The present invention can of course be applied also to conventional
crushers.
FIG. 3 shows an embodiment in which relief valve 5' has been placed
in a conventional piston 14'. In an overload situation fluid flows
from the cylinder through the relief valve into the lubrication
circuit.
|