center at a point 36 the tip 12 is provided with a plurality of cylindrical spray openings 38 each having its cylindrical axis disposed on an extension of a radius of the spherical surface 34 that is the cylindrical axes of the openings 38 intersect the center point 36 thus the openings 38 are located so their upper portions intersect the second frusto conical surface 30 and define points 40 which are most remote from the spherical surface 34 points 40 are located in a common plane which in the configuration illustrated in fig2 is transverse to the longitudinal axis of the barrel 24 disposed within the barrel 24 for reciprocation in the direction of an arrow 42 by conventional means not shown is a valve 44 provided with a frusto conical tip 46 terminating in a flat surface 48 the surface of frusto conical tip 46 is less steep than frusto conical surface 28 more particularly angle a the angle of intersection of frusto conical surface 28 with plane 29 is greater than angle b the angle of intersection of fursto conical tip surface 46 with its major base 50 the difference between angle a and angle b in the embodiment shown is 1 u00b0 however it is preferably no greater than about 1 u00b0 30.