I have been developing a new type of tertiary or quaternary cone crusher for many years. It is different because it has a virtual vertical crushing stroke, rather than the traditional gyrations.
Primary crushers, particularly jaw crushers, reduce piano-sized lumps to a size that will enter the secondary crusher. The secondary crusher then reduces stone to a size which is acceptable to the tertiary crusher. Attention to product quality, gradation and shape is most important in the tertiary and quaternary stages.
I say a vertical stroke but this is not quite correct. The real crushing stroke is measured between the crushing head parallel zone, being the difference which occurs when the mantle is fully up, and completely down. A machine with a vertical movement of 90mm will have a crushing stroke, subject to the angle of the crushing head, of approximately 30mm.
The first machine trialled – the Auscone 500 – used a double toggle mechanism to create crushing force. It had a 500mm diameter head. The tests revealed some interesting crushing qualities, notably:
? The product shape was generally cubed, and better than that from cone crushers.
? The grade was less fine (-5mm dust), and more aggregate was produced (14+10, -10+7, and -7+5mm).
A 1000mm diameter head machine was built, and with the generous co-operation of Pioneer Construction Materials, testing was carried out at the Bass Point Quarry, south of Wollongong. The anticipated product grading is outlined in Table 1.
The larger machine could not operate at the correct revolutions per minute, as the reciprocating shaft did not, under gravity, return after each crushing stroke with even timing. Further, I nominated that the crusher must have a minimum vertical stroke of 80mm to achieve the planned throughput, but using the toggle mechanism, this was not mechanically possible. The crusher was installed with a vertical stroke of 40mm, and a crushing stroke of 13mm.
It was decided to modify the Auscone 500 crusher by removing the toggle mechanism and positioning the eccentric shaft below, and connecting it to the crushing head to provide a positive return after each crushing stroke.
This worked well and with the longer vertical stroke of 40mm, output increased markedly.
A patent was gained, and international patenting is under way, for a further design improvement.
We now wish to have the Auscone 1000 modified in the same manner. Coined the Auscone 1000 Mk1, it will have a vertical stroke of 90mm. Figure 1 shows the general arrangement of the modified crusher.
A change to aggregate quality/shape specifications was made some years ago, meaning that to produce adequate product shape, some producers had to install a vertical shaft impact crusher. This high operational cost quality fix was taken up by many operators in Australia and abroad. The cost was huge when consideration is given to the waste material (dust) created, the cost of wear parts, and the excess power usage cost.
This has motivated the development of the more dollar-efficient Auscone Mk1 crusher.
Some of the mechanical benefits of the design are:
? Less heat created by the relatively short stroke, versus the rotating speed of a conventional eccentric bearing which requires an oil cooling and filtering system.
? Better work hardening of the manganese steel mantle and concave, due to the impact action of the crushing head.
The operational benefits of the Auscone Mk1 crusher include:
? Constrained feed impact crushing.
? Less power is used to overcome the impact strength of the feed material.
? Balanced design, minimal foundations required.
? Less -5mm undersize material (dust).
? Excellent product shape.
? A greater yield of -14+10, -10+7, -7+5mm aggregates.
? A lower operating cost than current alternatives.
The Auscone Mk1 is a very different model of cone crusher from the original, which dates back over a hundred years. The design has the potential to deliver a quality of product and low cost of production that will set a new standard in crushing technology.
By Roger Kay
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