Apparatus and methods for controlling atmospheric gas composition within a container

Abstract

A method of controlling gas composition within a container containing respiring produce is described. The container includes at least one gas outlet and at least one gas inlet and the method includes the steps of: drawing gas from within the container through a selective membrane element under selected control conditions through the at least one gas outlet; introducing ambient air from outside die container into the container through the at least one gas inlet under selected control conditions to control the relative composition of gases inside the container. Apparatus for containing the goods and for controlling the atmosphere in the container according to the method are also described.

1 . A method of controlling gas composition within a container containing respiring produce, the container including at least one gas outlet and at least one gas inlet, the method including the steps of:
 drawing gas from within the container at predetermined time intervals to outside the container through a selective membrane element through the at least one gas outlet; and   introducing ambient air from outside the container into the container through the at least one gas inlet under selected control conditions to control the relative composition of gases inside the container.   
     
     
         2 . The method in accordance with  claim 1  wherein the predetermined time drawing intervals are such that there is a drawing step when a pump is actuated to draw gas through the membrane element from within the container at a selected range of flowrates and a holding step where the flowrate through the membrane is minimised. 
     
     
         3 . The method in accordance with  claim 2  wherein the drawing step and the holding step are alternated so that there is generally intermittent drawing of gas. 
     
     
         4 . The method in accordance with with  claim 1  wherein the control conditions are that the drawing step is of one duration and a holding step is of another duration and the two durations are of unequal size. 
     
     
         5 . The method in accordance with  claim 4  wherein the drawing step is shorter than the holding step to facilitate an equilibrium of gas components and pressures within the container. 
     
     
         6 . (canceled) 
     
     
         7 . The method in accordance with  claim 1  wherein the drawing step includes selectively drawing carbon dioxide through the membrane element, so that it is extracted from the container at a higher rate than other gases present within the container. 
     
     
         8 . (canceled) 
     
     
         9 . The method in accordance with  claim 1  wherein the method includes the step of monitoring levels of one or more gas components inside the container to provide one or more oxygen or carbon dioxide or nitrogen level readings and the introducing step is conducted by a controller in response to the one or more oxygen or carbon dioxide or nitrogen readings. 
     
     
         10 . (canceled) 
     
     
         11 . (canceled) 
     
     
         12 . The method in accordance with  claim 1  wherein the selected control conditions under which introducing ambient air is conducted are that a rate of introduction of ambient air from outside the container changes over a selected time. 
     
     
         13 . The method in accordance with  claim 1  wherein the selected control conditions under which introducing ambient air is conducted are that there is an introduction of ambient air from outside the container based on the difference between the monitored level of oxygen and a desired oxygen set point. 
     
     
         14 . A container suitable for storing respiring produce, the container including:
 opposed end and side walls, and opposed floor and roof;   at least one gas outlet and a selective membrane unit in fluid communication with the gas outlet so that in use gas within the container may be drawn therethrough, from the container to outside the container;   a pump in fluid communication with the membrane unit for drawing gas through the membrane unit;   at least one gas inlet for introducing atmospheric gas from outside the container and a valve for controlling gas flow through the gas inlet; and   one or more controllers set for intermittent operation of the pump and valve at predetermined timed intervals.   
     
     
         15 . The container in accordance with  claim 14  wherein the one or more controllers include a processor, a memory, an input/output device, such that the or each controller is responsive to a program to operate the operation of valves and pumps in response to various inputs. 
     
     
         16 . The container in accordance with  claim 14  wherein the or each controller also includes a timer for measuring time elapsed in storage for the respiring produce so as to operate a control algorithm which operates the pump in fluid communication with the membrane unit based on time elapsed. 
     
     
         17 . The container in accordance with  claim 14  wherein the or each controller is adapted to receive inputs from devices selected from the group consisting of: a timer; thermocouple; gas concentration monitor; operator input device. 
     
     
         18 . The container in accordance with  claim 14  wherein the memory and processor is adapted to be loaded with tables for calculating pump and valve run times for various payloads and produce types. 
     
     
         19 . The container in accordance with  claim 14  wherein the membrane element includes a selectivity which allows carbon dioxide gas to permeate through the membrane element at a higher rate than oxygen and nitrogen. 
     
     
         20 . (canceled) 
     
     
         21 . The container in accordance with  claim 14  wherein the container includes an oxygen, carbon dioxide or nitrogen sensor. 
     
     
         22 . (canceled) 
     
     
         23 . The container in accordance with  claim 14  wherein the container includes a second gas outlet for evacuating container gas therethrough. 
     
     
         24 . The container in accordance with  claim 23  wherein a valve is provided on the second outlet to control the evacuation of container atmospheric gas therethrough. 
     
     
         25 . The container in accordance with  claim 14  wherein the container includes a refrigeration unit. 
     
     
         26 . A computer that is arranged for operation in accordance with a method of controlling atmospheric gas composition within a container suitable for storing respiring produce, the container including at least one gas outlet and at least one gas inlet, the method including the steps of: drawing gas from within the container through a membrane element through the at least one gas outlet at predetermined timed intervals; and introducing atmospheric gases from outside the container into the container through the at least one gas inlet under selected control conditions to control the relative composition of gases inside the container. 
     
     
         27 . (canceled) 
     
     
         28 . (canceled) 
     
     
         29 . (canceled)