Numerous different types of rock crushing machines are used in mining, quarrying and other similar activities to reduce the size of the rocks processed. The type of machinery employed will vary from application to application as will the initial and final sizes of the rocks processed.
One type of rock crushing machine developed is a Vertical Shaft Impact (VSI) crusher which is normally top fed by a supply system and associated conveyor belt. A good example of this type of crusher is discussed in U.S. Pat. No. 3,970,257.
Some types of VSI Crusher divide rock to be crushed into two streams of material. The first stream is supplied directly into a rotor, while the second stream is placed into a cascading flow past the side or sides of the rotor. Rock going into the rotor is spun and ejected tangently into the cascading stream of rock, to crush and break up both the cascaded and energised rock.
For different types of rocks it is preferable to vary the ratio of material supplied to the rotor to material placed into cascade past the rotor. Rock to be crushed can be processed more efficiently if the cascade ratio of material supplied to the rotor compared to material placed in the cascade is customised to suit the particular rock in question.
However, the amount of material normally supplied to the crusher can vary substantially over time, which makes it difficult to maintain a particular cascade ratio. A gate or valving mechanism associated with the rotor can be opened or closed to allow more material to enter the rotor when comparatively more material is supplied to the crusher. This will allow the cascade ratio of the crusher to be maintained as the additional material supplied to the rotor is balanced by further additional material placed into cascade. The opposite process can also be completed to reduce the size of the rotor gate when less material is supplied to the crusher to in turn maintain the correct cascade ratio for the particular material being crushed.
However, it is difficult to maintain a consistent cascade ratio for such VSI crushers using current technology. With existing technology a manual operator is required to monitor the amount of material being placed into cascade and going through the rotor and to make adjustments to the rotor gate (and potentially a feed-in rate mechanism for the crusher) to maintain the correct cascade ratio. However, this is an inefficient use of labour as well as a monotonous task for the operator. Furthermore, a degree of skill or experience is also required from the operator to correctly judge both the current cascade ratio of the crusher and also the correct settings of control systems for the crusher.
An improved control system for a rock crusher which addressed the above problems would be of advantage. A control system which could automate the monitoring of the cascade ratio of a rock crusher and which could automatically adjust the control systems of the crusher to maintain a constant cascade ratio would be of advantage.
All references, including any patents or patent applications cited in this specification are hereby incorporated by reference. No admission is made that any reference constitutes prior art. The discussion of the references states what their authors assert, and the applicants reserve the right to challenge the accuracy and pertinency of the cited documents. It will be clearly understood that, although a number of prior art publications are referred to herein, this reference does not constitute an admission that any of these documents form part of the common general knowledge in the art, in New Zealand or in any other country.
It is acknowledged that the term ‘comprise’ may, under varying jurisdictions, be attributed with either an exclusive or an inclusive meaning. For the purpose of this specification, and unless otherwise noted, the term ‘comprise’ shall have an inclusive meaning—i.e. that it will be taken to mean an inclusion of not only the listed components it directly references, but also other non-specified components or elements. This rationale will also be used when the term ‘comprised’ or ‘comprising’ is used in relation to one or more steps in a method or process.
It is an object of the present invention to address the foregoing problems or at least to provide the public with a useful choice.
Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only.