(2) Net opening/closing mechanism

　The VMPS is equipped with multiple nets, which are opened in sequence to collect samples from different depth layers for each net. This section describes the net opening and closing mechanism of the VMPS.

　The VMPS net consists of four plankton nets with square mesh openings, connected to each other by one edge of the mesh opening (Figure 6-a). are closed (Figure 6-b). A metal bar, the net opening/closing bar (hereafter referred to as the "opening/closing bar"), is inserted in the joint between the nets. Sliding the opening/closing bar closes the opening of net 1 and simultaneously opens the opening of the next net (net 2: green) (Figure 6-c).

Figure 6 Shape of the net and state of opening and closing of the net opening

a) Shape of the net

b) Net 1 open state

c) Net 1 closed (Net 2 open)

　Next, the mechanism by which the open/close bar is driven is explained based on Figure 7. Both ends of the open/close bar are fixed to a plate spring. When the open/close bar is fixed to the trigger, the plate spring is extended (Fig. 7-a). When the trigger is actuated, the open/close bar slides due to the contracting force of the plate spring (Fig. 7-b).

　　　　　　Fig. 7 Positions of the net opening/closing bar and expansion/contraction state of the plate spring

　　　　　　　　　　　　　　a) Before trigger activation b) After trigger activation

　Finally, the trigger mechanism for opening and closing the net is shown in Figure 8. A fixing wire is connected to the center of the opening/closing bar. The metal ball at the end of the fixing wire is hooked into a notch in the latch to secure the opening/closing bar (Figure 8-a). (Figure 8-a). The latch is secured by engaging the trigger hook (Figure 8-b). When the submersible station receives the open/close signal from the onboard station, the trigger motor is activated and the cam rotates. When the trigger hook is released by the movement of the cam, the latch jumps up and the securing wire is released (Figure 8-c), resulting in the opening and closing of the net.

Fig. 8 Mechanism of net opening/closing trigger

a) Fixed state of the net opening/closing bar

b) Trigger set state

c) Movement when trigger is released