A pick force calculation method suggested for tool lacing of mechanical excavators employing drag tools

Abstract

This paper deals with tool lacing design of partial-face cutting machines employed for mechanical excavations of rocks, coal and stones. A rational comparison between relief cutting and groove deepening was made by simulating actual cutting actions of picks under the same conditions at different spacing to depth ratios, respectively, through full-scale laboratory linear cutting experiments with radial and point attack tools. It was found that the top portion of a groove with approximately polygonal-shaped cross section has no significant effect on the magnitude of tool forces. The effective cutting was understood to take place mainly in the lower portion of this cross section, termed ‘effective area’, which is encompassed by a triangle with an apex angle twice the breakout angle of unrelieved groove. This finding has led to the introduction of a pick force calculation method for computer assessment of tool lacing for rock, coal and stone cutting machines. The ‘effective area’ of cross sections which were calculated by this method, was found to be in good correlation with corresponding measured tool forces. The method is simple and free from assumptions which have to be specified for various pick cutting position. It was also verified by the results of some experimental data of previous investigations.

Keywords:

• Cutting head design
• roadheaders
• drum shearers
• natural stones
• mechanical excavation

Acknowledgements

The author wishes to thank Dr R. J. Fowell (formerly at the University of Newcastle Upon Tyne, now at the University of Leeds) for his invaluable helps and guidance, and Turkish Coal Enterprises (TKI) for financial support. The views expressed here are the author’s own and not necessarily those of TKI.