JUSTIFING OF PARAMETERS OF PNEUMOPERCUSSION MACHINE FOR FORMATION MAIN CRACKS FROM HOLE OF NATURAL STONE

In the work, issues of development of percussive machine for directed destruction of stone rocks are considered. The percussive machine impacts to rock destructive tool implemented into the hole, after that rock wedging and growth of main crack along blast-hole line occur. For that purpose, pneumatic machine of percussion action and gravitational type is chosen. Scheme of the machine is justified based on dynamic simulation of its key assembly units, numerical analysis of constructive and energetic parameters is carried out. Working cycle of the device has been estimated by energy value, percussion frequency, compressed air discharge. It is established that working cycle of gravitational pneumo-percussion machine with elastic valve provides economy of compressed air discharge and high energy of the strike. Results of numerical simulation are proved by experimental data of Institute of Mining.

Synthesis of Dynamical Structure of the Hydraulic Breaker With a Vibration-Free Handle

An approach to the synthesis of a dynamical structure of the hand-held percussion machine with a vibration-free handle is presented. This is based on the consideration of the optimal dynamic conversion of energy in hand-held percussion machines founded as a solution of the equivalent problem of the optimal control [1]. For an accomplishment of the optimal regime a proper dynamic structure of the percussion machine as a multi-body vibro-impact system with one body (casing/handle) being free of vibration is found and investigated. Computer simulations and initial experiments validated the new approach. The main feature of the proposed design realising the synthesised structure is the use of a mechanism with zero differential stiffness. A hydro-pneumatic unit with zero stiffness was developed and tested. Theoretical recommendations have been applied to a commercial hydraulic breaker. A proper modification of the design and effective use of existing hydraulic power source provided a significant improvement in performance.

Hand-Held Percussion Machine As an Optimal Converter

The problem of interaction of hand-held percussion machine with operator and load is presented and optimized as a problem of dynamical conversion of the operator effort into sequence of impulses produced with the help of machine drive. Some recommendations on the estimation of the main characteristics of the machine design are presented.