prong of fork 39 abuts barrier 41 to form a seal therewith during the accumulation part of the cycle while the outer prong is recessed from the inner prong and abuts the radially textured inner surface of wall 50 accordingly a channel 71 defined by aperture 37 outer prong of fork 39 and wall 50 extends from conduit 42 and allows chemical to flow into accumulation chamber 80 along the direction of arrow b during an accumulation phase as illustrated in fig4 and 5 because the inner prong of fork 39 is sealed against the radially outer edge of barrier 41 fluid is unable to flow out of accumulation chamber during the accumulation phase as best illustrated in fig5 the radially inner surface of wall 50 is textured to provide a timing seal that permits a slow leak to allow chemical to flow into accumulation chamber 80 from conduit 42 the textured surface thus provides flow regulation as pressure increases due to a temperature rise in a room in which the can is stored the forks 39 will tend to deflect outward and thus more tightly against the textured surface this reduces the cross sectional area of passages through the textured surface thereby reducing flow to compensate for the increased room temperature the textured surface can be molded as part of the adjoining wall using the same material e g polypropylene polyethylene etc alternatively the surface could be adhered to the wall or the wall could even be smooth which would enable a greater flow rate into accumulation chamber 80 the textured surface could also be of an elastomeric material such as kraton that is co molded or two shot molded onto the wall in operation a consumer rotates the valve assembly.