Rotary moulding

Abstract

A valve in a mould as to provide a potential airflow pathway either way, the valving being characterised in that it has at least a substantially closed condition from which it can be opened by a pressure differential in one direction that is below that which will cause it to open or fail to allow an airflow in the other direction.

1 . A method of rotary moulding whereby there is a provision for an airflow (whether of air and/or other gases) into the mould when the pressure differential from without and within the mould favours such an inflow and where there can be an outflow only when there is a pressure differential where the pressure within the mould is above a specified limit (“threshold pressure”) with respect to the pressure without the mould.  
   
   
       2 . A method of  claim 1  wherein a valve accomplishes both functions.  
   
   
       3 . A method of  claim 1  where the separate functions are accomplished by different apparatus of and/or associated with the mould.  
   
   
       4 . A method of  claim 1  wherein a one way valve is provided in the mould to accomplish both functions and is adapted to fail (as a one way valve) when the pressure is above a relatively low specified threshold pressure which is less than that which would create potential mould damage.  
   
   
       5 . A method of  claim 1  wherein the threshold pressure is below a 5 bar differential.  
   
   
       6 . A method of  claim 5  wherein the threshold pressure is below a 2 bar differential.  
   
   
       7 . A method of  claim 4  wherein the one way valve is to be disrupted by a threshold differential pressure within the range of from 0 to 1 bar above the atmospheric pressure outside of the mould.  
   
   
       8 . In or for a rotation would, a venting feature which has the ability to allow a gas ingress to the mould at a pressure differential below that required to allow gas egress from the mould. The invention also consists in the use of such feature.  
   
   
       9 . Apparatus of  claim 8  wherein such pressure differential that acts as a gas egress threshold, when considered from the opposite condition (i.e. favouring ingress rather than egress), can be exceeded during gas ingress [i.e. there can be a gas (e.g. air) inflow over a wide pressure differential].  
   
   
       10 . A moulded valve component or moulded valve, said component and/or valve being adapted for insertion and retention in a mould so as to provide a potential airflow pathway either way, the valving being characterised in that it has at least a substantially closed condition from which it can be opened by a pressure differential in one direction that is below that which will cause it to open or fail to allow an airflow in the other direction.  
   
   
       11 . Apparatus of  claim 10  wherein it is a moulded item in the form of a plug defining a closed passageway, the passageway being adapted to be splayed open or otherwise opened at its closed end by airflow in one direction and to fail, by deformation and/or parting, in an outward flow direction to allow the over-pressure outflow the other way.