  The single-pion production reactions $pp\to d\pi^+$, $pp\to np\pi^+$ and
$pp\to pp\pi^0$ were measured at a beam momentum of 0.95 GeV/c ($T_p \approx$
400 MeV) using the short version of the COSY-TOF spectrometer. The central
calorimeter provided particle identification, energy determination and neutron
detection in addition to time-of-flight and angle measurements from other
detector parts. Thus all pion production channels were recorded with 1-4
overconstraints. Main emphasis is put on the presentation and discussion of the
$np\pi^+$ channel, since the results on the other channels have already been
published previously. The total and differential cross sections obtained are
compared to theoretical calculations. In contrast to the $pp\pi^0$ channel we
find in the $np\pi^+$ channel a strong influence of the $\Delta$ excitation
already at this energy close to threshold. In particular we find a $(3
cos^2\Theta + 1)$ dependence in the pion angular distribution, typical for a
pure s-channel $\Delta$ excitation and identical to that observed in the
$d\pi^+$ channel. Since the latter is understood by a s-channel resonance in
the $^1D_2$ $pn$ partial wave, we discuss an analogous scenario for the
$pn\pi^+$ channel.
