HPGR and Schonert... a personal reflection

First published as an obituary by Michael Battersby, Director of CEEC, in his Dragons Breath Blog. 24th October 2011.


Prof. Dr.-Ing. Klaus Schonert (1927 – 2011) – A Real Inventor

Klaus Schonert passed away on the 24th September 2011. I doubt if any individual has contributed more to the advancement of comminution, energy savings and minerals processing over the last 40 years and maybe we will struggle to find someone to compare over the next 40 years. His patent ”Method of Fine and Very Fine Comminution of Materials Having Brittle Behaviour” (US patent) is revolutionising the way we undertake size reduction and is now represented by the High Pressure Grinding Rolls (HPGR’s).

I had met personally with Klaus Schonert only about a dozen times but was always struck by the practicality of this Emeritus Professor. I first met Schonert briefly at the University of Clausthal at the end of the 1980’s whilst researching HPGR’s for Billiton. However my first real discussions with him were after I’d joined KHD, at the Sydney IMPC in 1993. To my astonishment and pleasure he spent many hours with me at the KHD exhibition stand where we discussed, amongst many things, how to get the HPGR’s (KHD’s Roller Press and Polysius’s POLYCOM) accepted into the minerals market. There had been an immediate and rapid uptake in the cement industry. The entry into the minerals market was more challenging, mainly due to the increased wear associated with wet metallic minerals.

Whilst in our profession of minerals processing we have been blessed with a number of highly acclaimed academics and researchers, who have contributed immensely to our understanding of fundamentals, few if any, have been able to produce something really practical and usable. Schonert was somebody who did this with the High Pressure Grinding Rolls.  From fundamental research into single particle breakage in the 1960’s through to inter-particle breakage in a particle bed in the 1970’s and his work with piston presses he noted, contrary to conventional wisdom, that much higher pressures increased the efficiency of breakage. Up to this time high pressures were avoided as they were thought to agglomerate the particles and thus have a negative effect on comminution and increase the energy requirements for size reduction.  For a full description of these developments see “The History of Grinding” by Alban Lynch and Chester Rowland (SME 2005) where Schonert himself describes these developments.

The fundamental research was impressive. However the genius was identifying a way the concept could be transferred to a practical industrial method. Schonert identified that briquetting and compacting presses had the basic pre-requisites but were used for particle agglomeration, not comminution. These machines had been around for many decades. They consisted of two counter rotating rolls, either smooth for compaction into flakes or with a surface profile design for the manufacture of briquettes.  Generally the pressure applied to form the agglomerates was with metal springs. Next, he realised that no one had connected this with size reduction and it was therefore patentable. What followed in the next 10 years was the most intense patent litigation seen in our industry between licensees of the Schonert patents and those companies who had compacting technology and saw it as “obvious” that it could be now used for size reduction.

Schonert originally non-exclusively licenced his patents to Polysius, a German based equipment supply company. It’s interesting that Polysius did not have any prior briquetting/compaction technology and had to develop things from scratch. Their design applied the high pressures required by pistons against the bearing housing of one set of rolls. Soon after in 1979 KHD, another German based equipment supply company, who did have briquetting/compaction technology initiated opposition proceedings to Schonert’s German patents.  After much wrangling Schonert, Polysius and KHD agreed that KHD could also have a non-exclusive licence if it dropped its patent opposition. Also that both Polysius and KHD had a right of veto of any new licences and that Schonert, Polysius and KHD would work in collusion in enforcing the Schonert patents, with Polysius and KHD jointly sharing the cost of such enforcement.

This agreement to defend the intellectual property led to the most intense and complex litigation ever seen in the mineral processing equipment supply industry and is still referred to and studied in general patent case law today.  There were a few international litigation actions but the principle one was between Polysius and the Fuller Company of the USA. In this case Fuller (later being taken over by FLSmidth in 1990) was charged with patent infringement. It counter sued with a defence of “patent invalidity, patent misuse and fraud of the patent office”.  In addition, Fuller also counter claimed and sought damages for “alleged anti-trust and other unfair competition violations” in the USA.

The Pennsylvania District Court handed down its judgement on 3 February 1989, which was subsequently upheld in the United States Court of Appeals, Federal Circuit on 12 October 1989. The courts found in favour of Schonert and Polysius, upheld the validity of the patent and dismissed all anti-trust claims made by Fuller. The judgement and opinion of the courts makes excellent reading for anyone who has an interest in the technology or IP protection. The full transcript can be viewed in this link.

The transcript is interesting as it records not only of the technicalities and legalities of the applied patent law but because it also details claims of industrial espionage and subdiffusion and also has many references to Taggart. Maybe it’s the good basis of a thriller film!

The court case also highlights the enormity of the reputation of Professor Klaus Schonert. From the judge;

“....no one except Schonert had the genius to combine the separate elements into the teaching of the ‘287 patent”.

“The most telling objective indicator.... is that the Fuller engineers, when they heard of that “German professor”, did not go to Taggart or any other prior art cited by Fuller in this case. Instead Fuller’s engineer went directly to that “German professor”.

The judge also made much of Schonert’s  Gaudin award from the SME.

“I am convinced that Schonert’s peers placed him on a high pedestal for the invention of the process“.

“Schonert is a scholar of high repute”.

“I find that Schonert is a scholar of the first order (and) that his testimony is highly credible”.

This is high praise not normally dished out by a high court judge in judgement!

I guess that Schonert was tied in by Polysius and KHD with the licence because you would expect it to be more beneficial to him to have more licensees. But I know he didn't do too badly out of his patents. In German law the IP/Patent rights reside with the inventor/academic, not with the university as his employer. During my time at KHD in the 1990’s I was tasked with checking the annual calculation of sales of the Roller Press and Schonert’s 3% licence fee. It was not an inconsiderable amount. Bear in mind that also Polysius were selling a similar amount of HPGR’s.  I understand though that Schonert gifted much to the university to fund departments and research.

Despite having such an involvement with HPGR’s  it was about 25 years after the event it suddenly dawned on me about my first encounter. In the early 80’s during my graduate training with Anglo American Corporation in South Africa I spent some months with De Beers. One of my boring tasks for a few weeks was to do sieve screen size analysis. I remember that the labels referred to something like piston press samples. I did not know at the time that De Beers were investigating Schonert’s work for the liberation of diamonds from kimberlite without breakage. Subsequently De Beers installed the first four HPGR’s in the minerals industry at Premier Diamond Mine. Small world!