end as shown at 78 an air outlet 80 may have an enlarged ridged end portion 81 for connecting it to the vacuum line 33 it should be noted that the cylindrical housing 77 is open to provide an outlet to the ambient air as will now be explained the three way valve is formed by a box like hollow structure 83 having a disk shaped end 84 the hollow box 83 is provided with a cylindrical opening 85 into which fits a piston 86 slidably arranged in the cylindrical opening 85 and urged outwardly by a spring 87 the piston 86 normally blocks the air outlet 80 of the trigger asembly similarly the box 83 unblocks the air inlet 75 of the desoldering barrel 32 hence as clearly shown in fig8 the air inlet 75 is disposed below the air outlet 80 the box 83 in turn is spring biased by a spring 88 having one end bearing against the wall 78 while its other end bears against the disk 84 the spring 88 is a compression spring adapted to urge the box 83 to block the vacuum line 33 the box 83 is connected for example by two legs 90 to a hollow piston 91 having a central opening 92 connectable to the desoldering barrel 32 and the vacuum pipe 33 an o ring 93 seals the piston 91 slidably into.