101 start from a top end of the enclosure 102 and extend to about half of the height of the enclosure 102 there is a rim 103 in the enclosure 102 near where the threads 101 end the lower flow regulating structure 106 consists of a disk 113 and a ring housing 110 fig1 b shows a plan view of the upper flow regulating structure 104 in an example embodiment the upper flow regulating structure 104 has a circular protrusion 104 a in the centre there are two holes 104 b aligned on a centre line on the surface of the protrusion 104 a in the example embodiment the two holes 104 b extend from the surface of the protrusion 104 a to the other side of the upper flow regulating structure 104 there are threads not shown around the outer circumference of the upper flow regulating structure 104 fig1 c shows a top view of the disk 113 of the lower flow regulating structure 106 fig1 a in an example embodiment the disk 113 is made of thermosetting plastics there are numerous small channels 113 a around the circumference of the disk 113 a series of small protrusions 113 b is arranged in a circular manner in front of the various channels 113 a referring back to fig1 a the disk 113 is disposed in the ring housing 110 there is a rim 105 on the inner side of the ring housing 110 for receiving the top part 107 of the disk 113 the lower flow regulating structure 106 is then received in the mesh socket 108 in.