  In this work, the role of the $\Delta ^{\ast }$ resonances in the process of
$pp\rightarrow nK^{+}\Sigma ^{+}$ are systematically investigated with the
effective Lagrangian approach and the isobar model. We find that a $P_{31}$
state, either $\Delta ^{\ast }(1750)$ or $\Delta ^{\ast }(1910)$, is favored by
the data while the $P_{33}$ state, namely $\Delta ^{\ast }(1920)$, has small
contribution. Besides, either sub-threshold $S_{31}$ $\Delta ^{\ast }(1620)$
resonance or strong $n\Sigma $ final state interaction or both have possible
contribution at near threshold region, depending on the measured cross
sections. We demonstrate the invariant mass distributions and the Dalitz Plots
in order to investigate whether it is possible to distinguish the controversial
$K\Sigma $ production mechanism in these observables.
