a venturi tube , or venturi , usable in a deheading system embodying features of the invention is shown in fig2 . the venturi 16 is a restricted portion of a conduit 18 enclosing a fluid channel 19 conveying a shrimp - laden fluid along a fluid path 20 . the conduit has an open entrance end 22 and an opposite open exit end 23 downstream of the entrance end . an input portion 24 of the conduit extends downstream from the entrance end 22 and defines the fluid channel with a cross - sectional area a 1 . a transition portion 26 of the conduit extends downstream from the input portion 24 to the venturi 16 . the transition portion 26 defines a length of the fluid channel with a converging cross - sectional area formed by two pairs of converging parabolic walls : large walls 25 and small walls 27 . the venturi 16 has a cross - sectional area a 2 that is less than that of the input portion 24 . in the example of fig2 , the shape of the cross - sectional area a 2 of the venturi is rectangular , but may be other shapes , e . g ., elliptical or oval , having a minor axis 28 shorter than its major axis 29 . the venturi 16 extends downstream to an open end 30 . in fig2 , the venturi &# 39 ; s end 30 opens into a downstream transition portion 32 of the conduit defining a length of the fluid channel 19 diverging outward from the cross - sectional area a 2 of the venturi to a larger cross - sectional area of an output portion 34 of the conduit . in this example , the output portion 34 has the same cross - sectional area a 1 as the input portion 24 . thus , the conduit 18 in fig2 is reversible . but the downstream transitional portion 32 may be eliminated and replaced with a flat plate having an opening forming an end wall of the output portion 34 at the open end 30 of the venturi 16 . as shown in fig3 a - 3c , the transition portion of the conduit 18 may be gradual ( fig3 a with a 30 ° taper of the long parabolic walls 25 relative to the direction of the fluid path 20 and a long length ), sharp ( fig3 c with a 60 ° taper of the long parabolic walls 25 and a short length ), or intermediate ( fig3 b with a 45 ° taper of the long parabolic walls 25 and an intermediate length ). the sharp transition portion 26 of fig3 causes a more abrupt acceleration of the fluid through the channel than the longer tapers of fig3 a and 3b and is more useful for sturdier shrimp . as indicated by the convergence of streamlines 36 in the transition portion 26 of the conduit , the flow accelerates to a higher speed in the venturi 16 . the converging flow tends to orient the shrimp along the streamlines by minimizing the surface area broadside to the flow . the hydrodynamic forces caused by the rapid acceleration of the flow at the venturi and by the non - uniformity of the flow just upstream of the venturi is sufficient to detach heads from the shrimp . the major axis 29 of the venturi cross - sectional area a 2 is long enough to admit a major portion of , if not all , the length of a shrimp into the venturi without severe collisions with the interior walls of the conduit that could break the shrimp between segments . for this reason , the venturi of fig2 is especially useful for deheading fragile cold - water shrimp . one version of a complete deheading system 40 is shown in fig4 a and 4b . shrimp are conveyed out of a feed tank 42 by a conveyor belt 44 and dropped into a fluid - filled trough 46 . a food pump 48 draws shrimp - laden fluid from the trough 46 and pumps it into a conduit system 50 , which has two venturis 52 , 53 at spaced apart locations along its length . shrimp are deheaded in the venturis and conveyed by the fluid through the conduit system to a feed plenum 54 . the shrimp bodies and detached heads drop from the plenum onto a screen slide 56 . the fluid drains through the screen and into a tank 58 in fluid communication with the trough 46 . a perforated plate 60 between the tank and the trough prevents shrimp in the trough from entering the tank 58 . the food pump 48 is driven by a pump motor 62 . together , the pump and the motor form flow control means that controls the flow rate and the fluid speed through the conduit system . the deheading system shown in fig5 has five venturis 64 connected in series in a conduit system 66 . a food pump 68 induces a flow through the conduit system 66 . such a multiple - venturi system can be effective for deheading sturdy shrimp . the deheading system of fig6 adds fluid - pressure sensor 69 at sensor locations in the conduit system 66 , for example , at locations just upstream of the final four venturis 64 to measure the hydrodynamic force of the flow . the outputs 70 of the pressure sensors control valves 72 connected between a boost pump 74 and fluid lines 76 injecting fluid into the conduit system at injection locations 78 near the sensor locations , for example , to replace any leaked fluid and to maintain the fluid pressure along the length of the fluid channel . although the invention has been described in detail with respect to a few versions , other versions are possible . for example , if large - diameter conduit , such as ten - inch — diameter pipes instead of 4 - inch — diameter pipes , the cross - sectional area of the venturis could be circular or square because the diameter of the circular opening or the lengths of the sides of the square opening would be large enough to allow shrimp through without damaging collisions with the walls of the conduit . as another example , a complete system using only a single venturi may be sufficient to detach heads from the shrimp in some situations . so , as these suggestions suggest , the claims are not meant to be limited to the details of the exemplary embodiments .
apparatus and methods for deheading shrimp using the venturi effect . a shrimp - laden fluid is pumped through a conduit system and lined with one or more venturi tubes . the acceleration of the fluid through the venturis detaches the heads from the shrimp . the cross - sectional areas of the venturis each have a major axis and a shorter minor axis . the major axis is long enough to receive the majority of or all the length of a shrimp and minimize hard collisions with the entrance to the venturi that could damage the shrimp .