A fluid flow sensing device having at least a stem and a paddle portion which is pivotally disposed with the stem, and a magnetic opener which biases the paddle away from the stem to into an off position. Upon sufficient pressure impending on the paddle by flowing fluid to overcome the force of the magnetic opener, the paddle pivots towards the stem to an on position, which is sensed by a device such as a Hall effect sensor, reed switch, or optical sensor.

A gas flow indicator device (10) has an elongate housing (12) defining a chamber (20) enabling gas flow from an inlet (22) at a first end (16) to an outlet (24) at a second end (18). An indicator member (26) within the chamber (20) extends from adjacent the first end (16) over part of the length of the chamber (20) and is of annular form enabling gas to enter the chamber along a bore (28) through the indicator member (26). The indicator member (26) is spaced from an inner surface (30) of a peripheral sidewall (14) of the housing (12) to define an annular space (32) within the chamber (20). A concealment member (34) is movable from the first end (16) by a sufficient pressure generated by gas flow through the chamber (20), against a biasing member (36) acting to bias the concealment member (34) to the first end (16). An annular skirt (38) of the concealment member (34) is receivable into the annular space (32) so one end (40) of the skirt (38) provides a seal against an annular surface (42) at an end wall (44) at the first end (16), while a transverse wall (48) at the other end (46) of the concealment member (34) defines an opening (50) providing resistance to gas flow. The one end (40) of the skirt (38) can be held in sealing engagement at the annular surface (42) to conceal the indicator member (26) from view through an adjacent window (52) of the housing (12). Increasing gas flow rate to achieve the sufficient pressure overcomes the bias, enabling the concealment member (34) to move towards the second end (18), exposing the indicator member (26) to view through the window (52), and thereby providing a visual indication of gas flow.

A surgical instrument flow indicator comprises a body defining a flow passage comprising an inlet and an outlet, wherein the inlet is configured to be fluidically coupled to a fluid supply source and wherein the outlet is configured to be fluidically coupled to the surgical instrument. The flow indicator further comprises a flow indication mechanism in flow communication with the flow passage, the flow indication mechanism being configured to transition from a first state to a second state in response to a threshold force exerted on the flow indication mechanism, wherein in the second state, the flow indication mechanism has an arrangement indicating to an observer that the flow indication mechanism transitioned from the first state to the second state.