Use of analog computer to investigate valveless pneumopercussive mechanism with single driven chamber

Abstract

VALVELESSAt the institute of Mining of the Siberian Branch of the Academy of Sciences of the USSR we have developed new percussive pneumatic machines of type PUM-3 [1] for sinking metal rods of low longitudinal stiffness into the ground (e.g., grounding electrodes, roof bolts, injectors, etc.). The machines are compact hand-held types driven by a light mobile compressor with low output. In designing such machines we are faced with the problem of obtaining maximum impact power of the pneumopercussive mechanism with limited compressed air consumption and machine mass. This problem can be fairly simply solved by modeling on an analog computer [2, 3].The theoretical model of the pneumopercussive mechanism is shown in Fig. 1. It consists of a valveless unit with stepped striker, one driven chamber, and a through axial channel for locating the machine on the rod being sunk. In Fig. 1 x is the axial displacement; M, striker mass; t, time; l, length (stroke); h, width of the channel; V, initial volume; P, absolute pressure; T, absolutetemperature; S, area; 1, easing; 2, striker; 3, nut; 4, tube. The alphabetic subscripts denote whether the parameter pertains to the atmosphere (a), compressed air lines (m), chamber (c), or antechamber (p).