Sprinkler head with improved spray uniformity

In a fire protection sprinkler head of the type including a base having a throat of predetermined cross-section through which a stream of fire retardant fluid can flow and a frame comprising two or more frame arms and a central boss for supporting a spray distributing deflector, said frame arms extending outwardly from said base and joining in an arch-form to support said boss at a position spaced from and disposed in the path of fluid discharged from said throat, said boss being adapted to deflect fluid outwardly therefrom, towards said spray distributing deflector, the improvement wherein said frame arms conform to the following parameters:

• (i) the portion of each frame arm in the region adjacent said boss is shaped and positioned to intercept about one half of the radial dimension of the stream profile, said profile comprising a projection, parallel to the axis of flow, of the exit cross-section of said throat, said exit cross-section being substantially circular;
• (ii) the leading edge of each frame arm in said fluid intercept region is substantially straight and forms an angle, relative to the axis of flow, of about 20 degrees;
• and
• (iii) the cross-section of each frame arm is of generally streamline shape with narrow leading and trailing portions, the length of the cross-section of each frame arm in the fluid intercept region, measured perpendicular to the leading edge of the frame arm, being about three times the maximum thickness of the frame arm,
• whereby fluid intercepted by each frame arm can be guided to flow into the region immediately downstream of the trailing edge of said frame arm to provide a substantially uniform sprinkler distribution pattern essentially free of frame shadow effects.