Gyratory crushers are well known, and in one arrangement the concave liner is fixed and the centre of the conical head is caused to carry out orbital movement to vary the radial clearance between the head and the concave liner circumferentially of the crushing zone. In an alternative arrangement, the conical head is fixed, and the centre of the concave liner carries out orbital movement.

It is known to provide mechanical driving arrangements to apply the required gyratory movements, and these necessarily have to be robustly constructed, bearing in mind the shock loadings which arise inevitably during crushing operations.

The traditional"Symons"crusher is a design going back many years, having a mechanical driving arrangement, and this general style of traditional crusher has been made and supplied throughout the years. However, more recently, there have been proposals to use hydraulically operated actuators to exert required gyratory movements, but to date such proposals have been complicated and have not worked very well in practice.

The invention has therefore been developed primarily with a view to providing an improved hydraulic control system to operate hydraulically operated actuators in a simple and reliable manner.

According to the invention there is provided a gyratory crusher, having a frame, a conical head and a concave liner mounted on the frame in order to define a crushing zone between an external surface of the conical head and a facing internal surface of the concave liner, and a drive arrangement operative to provide a cycle of relative gyratory movement between the conical head and the concave liner in order to exert a progressive crushing action circumferentially of the crushing zone, in which the drive arrangement comprises: a set of hydraulically operated actuators a, b, c, d, e, f, g, etc spaced apart circumferentially with respect to the crushing zone; and a hydraulic control arrangement to provide an operational cycle of the set of actuators such that, during energisation of any individual actuator (a) one or more downstream actuators, other than adjacent actuator (b), undergo pressurisation so as to exert a combined crushing force between the concave liner and the conical head.

Accordingly, a gyratory crusher according to the invention has a hydraulic control arrangement which exerts a commutative type of control of the set of actuators, in which any individual actuator (a) undergoes pressurisation and, during pressurisation, by feedback control initiates pressurisation of one or more downstream actuators (c) etc, whereby the centre of the crushing element undergoing gyratory movement (the concave liner or the conical head) will undergo orbital movement during a cycle of operations.

Preferably, the concave liner is fixed, and the conical head is driven by the set of actuators so that the centre of the conical head carries out orbital movement with the circumferentially spaced set of actuators being pressurised and then depressurised in a controlled manner via the hydraulic control arrangement, to provide the required advancing movement of the crushing actions circumferentially of the crushing zone.

In one simple preferred embodiment of the invention, the set of actuators can be considered as consecutive arrays of three actuators, 1,2, 3, in which the cycle of operation of each array involves initial pressurisation of the first actuator 1, and which initiates pressurisation of the third actuator 3 during pressurisation of the first actuator 1.

Each actuator may therefore have a corresponding diverter valve which responds to pressurisation (and consequently position) of the actuator, and thereby controls the'operation of a related downstream actuator, i. e. the diverter valve associated with first actuator 1 controls the supply of pressurised fluid to the third actuator 3, and second actuator 2 has a diverter valve which controls the pressurisation of downstream actuator 4, and so on.

Therefore, in each array of first, second and third actuators 1, 2,3, each actuator may be connected mechanically to a spool type diverter valve, and the set point at which each valve switches flow from pressure to return may be arranged at a convenient distance between minimum and maximum stroke of the related actuator piston of the actuator.

In a preferred embodiment, the conical head or"cone"is supported at the crown by a spherical bearing, which allows free movement in all three axes, within the confines of the concave liner. The motion is transferred to the cone by a ring of pistons of plungers circumferentially spaced from each other, and facing outwards, and on an axis normal to the direction of the crushing force (i. e. tangential to the arc described in section by the rotation of the centre of the cone during its orbital movement, permitted by the spherical bearing).

Hydraulic pressure is applied to the pistons in a sequence controlled by a distributor valve, which creates a wave motion in the piston rods. The piston rods may be hardened with radiused ends and bear directly upon a hardened insert in the inner face of the cone. The motion of the pistons directly imparts a cyclic gyratory movement in the cone without generating any rotational movement.

The movement may be loosely compared to that of a radial piston motor, but having the pistons inclined and facing outwards. Where the pistons of a radial piston motor apply force to an eccentric cam form on a central shaft, in the preferred embodiment of the invention the travel of the pistons is limited and is controlled by the interaction of the inner face of the cone.

The advantages of the embodiment of the invention are far-reaching. Only flow and return pipes are required to pass through (the lower frame support members or) "spider", along with minor control lines and monitoring sensors. The spider can be designed to carry the applied

forces without any need for mounting or accommodating drives, equipment or a mainshaft.

Far less depth will be required below the cone and bearing lubrication systems and consequent dust/sealing systems to prevent lubricant contamination will be redundant. Indeed, the only bearing required in the system is an easily inter-changed spherical joint which is preferably formed of self-lubricating plastics.

A preferred embodiment of gyratory crusher according to the invention will now be described in detail, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a schematic vertical sectional view of a gyratory crusher according to the invention, having a crushing"cone"arranged to carry out gyratory movement within a fixed concave liner (not shown); Figure la is a view, similar to Figure 1, but to an enlarged scale, and also showing the fixed concave liner; Figures 2a and 2b are schematic plan view illustrations of a set of hydraulically operated actuators to provide required wave motion type of gyratory movement applied to the cone; and Figure 3 is a detailed view of part of a hydraulic control arrangement to operate the set of actuators shown in Figures 2a and 2b.

Referring first to Figures 1 and la of the drawings, this is a vertical sectional illustration of a gyratory crusher according to the invention, designated generally by reference 10, having a crusher frame 14 in which a conical head or"cone"13 is mounted, and in such a way as to be capable of carrying out gyratory movement within a concave liner 18 fixed to the frame 14.

The cone 13 and the concave liner 18 define a crushing zone 19 between the outer surface of the cone 13 and the facing inner surface of the concave liner, and during a cycle of operation, the centre of the cone carrying out orbital movement so that a progressive crushing action moves circumferentially of the crushing zone.

A wear-resistant mantle 12 is usually attached to cone 13, and the cone 13 and mantle 12 are linked to the crusher frame 14 via a spherical joint 11 which allows movement in all three planes, limited only by the confines of the frame 14.

Gyratory movement is applied to the cone assembly by means of a set of circumferentially spaced actuators, which in the illustrated arrangement comprises a ring of pistons 17.

While the illustrated embodiment has a fixed concave liner, and a gyratory"cone", it should be understood that the hydraulic actuators and hydraulic control system to be described below with reference to the drawings, may be applied, with suitable modification, to a gyratory crusher in which the cone or conical head is fixed, and the concave liner carries out gyratory movement.

Referring now to Figures 2a and 2b, this shows a set of actuators a, b, c, d, e, f, g etc, spaced apart circumferentially, and corresponding to the actuators 17 of Figure 1. The set of circumferentially spaced actuators can be considered to be repeating sequences of three actuators, and description below will be given, in relation to actuators a, b, c by way of illustration. With pressure applied to the pistons of actuators a, b, c in a static situation, the system will be in equilibrium. The piston of actuator b will be fully extended, while the pistons of actuators a and c will be limited in their stroke by the structure of the cone.

In order to cause rotation of the centre of the cone, i. e. required orbital movement, the piston of actuator a will be depressurised and piston of actuator d will be pressurised and the orbital movement will take place until the equilibrium is reached once more.

Effectively, there is therefore provided a commutative type of system, and as the"cone offset" rotates, the approaching piston must be pressurised and the trailing piston de-pressurised.

Referring now to Figure 3, a hydraulic control system to control the operation of the actuators will now be described, as an example only of a practical system for commutating the pressure and creating an operational sequence.

In Figure 3, there is shown an instantaneous sequence of three actuator pistons 1,2, 3, each connected mechanically via connection 4 to a spool type of diverter valve 6. The set point at which each valve 6 switches flow from pressure to return is arranged at a convenient distance between minimum and maximum stroke of the related piston 1, 2,3.

Consider piston 1 extending under pressure and reaching the set point of its diverter valve 6: pressurised hydraulic oil is now diverted by valve 6 to piston 3, causing it to begin extending.

Since the movement of piston 3 is constrained by the physical limit of the cone, the thrust of piston 3 will be added to the force exerted on the cone 13 by all of the"active"pistons.

When first piston 1 has passed is maximum extension, its hydraulic supply will be diverted back to drain 8, and it will be pushed back into its cylinder. Even although piston 1 is no longer pressured, it will still maintain supply of hydraulic pressurisation to third piston 3 until the diverter valve 6 associated with piston 1 has passed its predetermined"set point".

References 1 to 3 and 7 shown in Figure 3 correspond generally with references 15 and 17 in Figure 1.

Figure 3 is intended to be an illustration only, for the purposes of ease of understanding, and shows only three interacting pistons and diverter valves. In practice, any individual piston p will actually control the valve gear actuating a downstream piston p+n several positions spaced circumferentially from it. The condition that is to be achieved via the arrangement of Figure 2a is such that, when piston of actuator a is de-pressurised, piston of actuator b will be at full extent and the pistons of actuators c through to g are all pressurised and opening. As the piston of actuator b moves past full extension, it is then de-pressurised, to reduce cross-flow within the valve gear to minimise losses and flow velocities.

The precise settings applied to the diverter valves and also the switching of the pistons of the actuators between pressurisation and depressurisation, will be determined by calculation, and empirically using numerical data collected from site testing.

Figure la shows the wear resistant liner 12 secured to cone 13, and the opposite part against which rock is crushed is the concave liner 18. This fits into the upper part of the frame of the crusher, usually referred to as the"bowl".

The threaded engagement between the bowl and the frame is one frequently used method of adjustment of the"setting"or opening distance between the mantle 12 and the concave liner

18, which determines the size of crushed products. However, other hydraulically actuated methods of adjustments are possible.

The inter-action between the actuator and each diverter valve in the hydraulic control system of the invention, may be effected by mechanical, hydraulic, electronic or other means of transmission.