the brushes to expand when the channels 24 are expanded it will aid in the removal of the debris from the bristles 22 referring to fig3 it may be seen that as the unit is pulled upward as shown by the u2018 u u2019 arrow that the brushes 20 would be compressed by the friction on the inside pipe surface so that the brushes 20 would be pushed upward by the washer 18 because of the upward movement of the bolts 14 therefore it may be seen that by moving the rod 12 by the supporting cable 28 unit for a few feet upward and then permitting it to lower a few feet downward would scrub the inside surfaces of the pipe also as it alternates between upward movement and downward movement there would be a repeated dispersing of debris from the bristles the bristles 22 and their attachment in channel 24 is shown in fig6 and 7 the attachment is formed with bristles made from crimped red polypropylene stock measuring 0 8 mm thick u00d7 1 05 mm wide the bristles 22 are looped around wire 25 the wire with the bristles are clamped into the channel 24 the channel 24 and the wire 25 are resilient since they.