other by a spring a leaf spring 35 is flexed and a length of a strain gauge 36 changes as a result a resistance changes the strain gauge 36 constitutes one side r 1 of a bridge of the detection circuit shown in fig7 in fig7 an output of the bridge circuit 40 due to the change of the strain gauge resistance r 1 is supplied to an amplifier 41 the output of the amplifier 41 immediately before the record medium is fed is applied to a negative terminal of an amplifier 42 by a sampling signal from the cpu and the output of the amplifier 41 after the record medium has been fed is supplied to a positive terminal of the amplifier 42 a difference therebetween is produced at the output of the amplifier 42 and it is supplied to the cpu through an a d converter 43 the output of the a d converter 43 has 4 bits or 16 states the minimum value is used to indicate non feed of the record medium and the maximum value is used to indicate double feed of the record media accordingly 14 states are actually used to indicate the thickness although any other number of states may be used fig8 illustrates the ink discharge status and the ink discharge timing in accordance with the present invention fig8 a shows ink discharging paths when a spacing between the record medium and the print head is.