squeezing the tube section 1 against the tube track 31 the circular motion of the rollers 21 is driven by a motor 4 in this case the tube pressing member 3 is releasably installed on the two arm 36 and 37 helical torsion spring 35 at the working or locked position p 2 and r 2 see fig2 for carrying out fluid transfer or at the retracted or open position p 1 and r 1 for loading or unloading the tube section 1 or replacing the tube pressing member 3 with the straight tube locking arm 36 of the torsion spring 35 inserted through its longitudinal through hole 38 the tube pressing member 3 rides along the straight tube locking arm 36 and can be removed or loaded in directions of 36 a when a disposable tube cassette is used as in u s pat no d264 134 in place of the tube pressing member the same retractable and arm sliding mechanism may be applied for quick change of the pumping tube fig2 shows the pump assembly of the present invention in the locked position with a tube section 1 and fluid flow 10 in place the arcuate side 30.