Venting Device

Abstract

A vent device comprising at least one control member pivotably supported in an opening in a frame, for movement, in response to differential gas pressure between opposite sides of the opening, between a closed position in which the control member(s) substantially blocks the opening and an open position in which the control member(s) leaves the opening substantially unobstructed for flow of gas therethrough, wherein the or at least one of the control members has associated therewith a restraining mechanism, operable to apply a force to the control member to influence movement thereof between its open and closed positions.

1 . A vent device comprising at least one control member pivotably supported in an opening in a frame, for movement, in response to differential gas pressure between opposite sides of the opening, between a closed position in which the at least one control member substantially blocks the opening and an open position in which the at least one control member leaves the opening substantially unobstructed for flow of gas therethrough, wherein at least one control member has associated therewith a restraining mechanism, operable to apply a force to the control member to influence movement thereof between its open and closed positions. 
     
     
         2 . A vent device according to  claim 1 , wherein the at least one control member is able to pivot in opposite directions from its closed position to respective open positions, in accordance with the direction of the differential gas pressure between opposite sides of the opening. 
     
     
         3 . A vent device according to  claim 1  wherein the restraining mechanism provides a check to hold the control member in its closed position, until a predetermined pressure differential between opposite sides of the opening is reached. 
     
     
         4 . A vent device according to  claim 1  wherein the restraining mechanism comprises a cam and cam follower arrangement, the cam and cam follower undergoing relative movement as the control member moves between its open and closed positions. 
     
     
         5 . A vent device according to  claim 4  wherein the cam follower is provided on the control member and the cam is provided on the frame relative to which the control member is pivotably moveable. 
     
     
         6 . A vent device according to  claim 5  wherein the cam is provided on the control member and the cam follower is provided on the frame relative to which the control member is pivotably moveable. 
     
     
         7 . A vent device according to  claim 4  wherein the cam follower is resiliently biased into engagement with a cam surface of the cam member. 
     
     
         8 . A vent device according to  claim 7  wherein the force with which the cam follower is biased into engagement with the cam surface is adjustable. 
     
     
         9 . A vent device according to  claim 7  wherein the form of the cam surface provides a generally uniform resistance to movement of the control member as the control member moves from its closed position to its open position(s). 
     
     
         10 . A vent device according to  claim 7  wherein the form of the cam surface of the cam member is such that resistance to movement of the control member from its closed position to its open position(s) varies in the course of such movement. 
     
     
         11 . A vent device according to  claim 2 , wherein the restraining mechanism provides for different characteristics in respect of movement of the control member in its opposite directions from its closed position to its open positions. 
     
     
         12 . A vent device according to  claim 2  wherein the restraining mechanism provides the same characteristics in respect of movement of the control member from its closed position to its respective open positions. 
     
     
         13 . A vent device according to  claim 4  wherein the cam has a recess, with which the cam follower engages to provide a check to hold the control member in its closed position, until a predetermined pressure differential between opposite sides of the opening is reached. 
     
     
         14 . A vent device according to  claim 1  wherein the control member is of double-wall construction, comprising two wall members secured together with a space therebetween. 
     
     
         15 . A vent device according to  claim 14  wherein the wall members are identical to one another. 
     
     
         16 . A vent device according to  claim 14  wherein a part of the restraining mechanism is accommodated between the wall members of the control member. 
     
     
         17 . A vent device according to  claim 1  wherein the centre of gravity of the control member is positioned substantially on or adjacent the pivot axis of the control member. 
     
     
         18 . A vent device according to  claim 17 , wherein an edge of the control member is weighted so as to cause the centre of gravity to be so positioned. 
     
     
         19 . A vent device according to  claim 1  comprising a mechanism for bringing the control member(s) to a closed position and/or retaining it/them in that position. 
     
     
         20 . A vent device according to  claim 19  wherein the mechanism is temperature-responsive. 
     
     
         21 . (canceled)