said first mentioned guiding means including means for slidably confining the front portions of the respective push buttons against movement away from {HEAD ~ said port member} to assist in maintaining {TAIL ~ compression} of said valve members and thereby maintaining sealing pressure between said valve members and said port member 
to assist in maintaining
said first mentioned guiding means including means for slidably confining the front portions of the respective push buttons against movement away from { HEAD ~ said port member } to assist in maintaining { TAIL ~ compression } of said valve members and thereby maintaining sealing pressure between said valve members and said port member
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH