Abstract:
Apparatus and methods for deheading and peeling shrimp hydraulically using the Venturi Effect. A shrimp-laden fluid is pumped through a conduit system including one or more venturi tubes. The acceleration of the fluid through the venturis detaches the heads and loosens or detaches the shells from the shrimp. The venturis may be used in conjunction with a roller peeler to increase peeling quality. An inspection station receives shrimp from the roller peeler and directs incompletely peeled shrimp back to the peeler or one or more of the venturis.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Patent Application No. 61/862,552, filed Aug. 6, 2013, and incorporated entirely by reference into this specification. 
    
    
     BACKGROUND 
     The invention relates generally to shellfish processing and more particularly to apparatus and methods for removing the heads and shells from shrimp. 
     Originally introduced because of the high labor costs of peeling small shrimp by hand, shrimp-peeling machines are now widely used in the shrimp-processing industry. Roller-type peeling machines, in particular, dominate the bulk shrimp-peeling industry. U.S. Pat. No. 2,778,055, Jan. 22, 1957, and U.S. Pat. No. 2,537,355, Jan. 9, 1951, describe the basic structure and principles of operation of roller-type shrimp peelers, which detach heads and shells from shrimp. But the fluids and slime squeezed from the heads of the shrimp coat the peeling rollers, which degrades their grip on the shrimp and peeling quality. 
     Deheading shrimp by hydrodynamic force is known from U.S. Pat. No. 5,195,921, Mar. 23, 1993. In that patent, a shrimp-laden fluid is pumped through conduit that abruptly narrows. The abrupt decrease in the cross-section of the conduit causes the flow to accelerate through the narrow cross section according to the Venturi Effect. Hydrodynamic forces caused by the change in cross-section tend to detach heads from shrimp. Because of the high-speed water flow and rollerless operation, the removal of heads is not degraded by shrimp fluids. As shown in  FIGS. 1A and 1B , cold-water shrimp  10 , for example, have a long, thin sixth segment  12  that is easy to damage. The joint  14  between the third and fourth segments is also susceptible to damage. The abrupt change in the cross-section of the conduit can cause shrimp to break at these and other weak spots. 
     Thus, there is a need for a shrimp-processing system that can dehead and shell shrimp without damaging shrimp meats. 
     SUMMARY 
     A system embodying features of the invention for processing shrimp comprises a hydraulic head detacher including one or more venturis that accelerate a flow of fluid carrying shrimp to subject the shrimp to turbulence detaching heads from the bodies of the shrimp. A peeler detaches shells, appendages, and residual heads from the headless shrimp bodies received from the hydraulic head detacher. An inspection station receives the shrimp bodies from the peeler and redirects those with residual shell or appendages back to the peeler. 
     In another aspect of the invention, a method for processing shrimp comprises: (a) detaching heads from the bodies of the shrimp by flowing a fluid carrying the shrimp bodies through one or more venturis; (b) peeling the headless shrimp bodies to remove the shells from the shrimp meat; and (c) inspecting the headless shrimp bodies for residual shell and appendages and repeating step (b) on headless shrimp bodies having residual shell or appendages. 
     In yet another aspect of the invention, a system for processing shrimp comprises a hydraulic head detacher and a hydraulic shell detacher. The head detacher includes one or more venturis that accelerate a flow of fluid carrying shrimp. The venturis subject the shrimp to turbulence that detaches heads from the bodies of the shrimp. A hydraulic shell detacher includes one or more venturis that accelerate a flow of water carrying headless shrimp to subject the shrimp to turbulence that detaches shell from the bodies of the shrimp received from the hydraulic head detacher. 
     In another aspect of the invention, a system for processing shrimp comprises a hydraulic shell detacher and an inspection station. The shell detacher includes one or more venturis that accelerate a flow of water carrying shrimp to subject the shrimp to turbulence that detaches shell from the bodies of the shrimp. The inspection station receives the shrimp bodies from the hydraulic shell detacher and redirects those shrimp bodies with residual shell or appendages back to the hydraulic shell detacher. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These aspects and features of the invention are described in more detail in the following description, appended claims, and accompanying drawings, in which: 
         FIGS. 1A and 1B  are side and top views of a shrimp; 
         FIG. 2  is an isometric view of a venturi tube for a deheading apparatus embodying features of the invention; 
         FIGS. 3A-3C  are side views of a venturi tube as in  FIG. 2  with a tapered transition region with taper angles of 30°, 45°, and 60°; 
         FIGS. 4A and 4B  are front and rear isometric views of a deheading system including venturi tubes as in  FIG. 2 ; 
         FIG. 5  is a schematic diagram of a multi-venturi deheading system using venturis as in  FIG. 2 ; 
         FIG. 6  is a schematic diagram of a multi-venturi deheading system as in  FIG. 5  including an additional boost pump; 
         FIG. 7  is a block diagram of one version of a shrimp-processing system embodying features of the invention including a venturi head detacher and a roller peeler; 
         FIG. 8  is a block diagram of a second version of a shrimp-processing system embodying features of the invention including venturi head and shell detachers; and 
         FIG. 9  is a block diagram of a third version of a shrimp-processing system having features of  FIGS. 7 and 8  and a reprocessing path selector. 
     
    
    
     DETAILED DESCRIPTION 
     A venturi tube, or venturi, usable in a shrimp-processing system embodying features of the invention is shown in  FIG. 2 . 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  FIG. 2 , 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  FIG. 2 , 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  FIG. 2  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  FIGS. 3A-3C , the transition portion of the conduit  18  may be gradual ( FIG. 3A  with a 30° taper of the long parabolic walls  25  relative to the direction of the fluid path  20  and a long length), sharp ( FIG. 3C  with a 60° taper of the long parabolic walls  25  and a short length), or intermediate ( FIG. 3B  with a 45° taper of the long parabolic walls  25  and an intermediate length). The sharp transition portion  26  of  FIG. 3  causes a more abrupt acceleration of the fluid through the channel than the longer tapers of  FIGS. 3A 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 downstream 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, gradually tapered venturis are especially useful for deheading fragile cold-water shrimp. Sharper tapered venturis are useful not only for deheading shrimp, but also for peeling, or shelling, shrimp. 
     One version of a deheading system  40  is shown in  FIGS. 4A 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 can also be used to loosen or detach shells and appendages from the shrimp. 
     The deheading and shelling system shown in  FIG. 5  has five venturis  64  cascaded 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 and shelling shrimp. The deheading and shelling system of  FIG. 6  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. 
     One version of a shrimp-processing system embodying features of the invention is shown in  FIG. 7 . An infeed system  80  feeds raw head-on, shell-on shrimp to a hydraulic head detacher  82 . The infeed system includes, for example, the feed tank  46  into which shrimp are conveyed, the food pump  48 , and the conduit  50  of  FIGS. 4A and 4B  through which the food pump pumps a shrimp-laden fluid, such as water, in a continuous flow. The hydraulic head detacher  82  comprises a single venturi ( 52 ,  FIG. 4A ) or a cascade of venturis. As shown in  FIG. 2 , the venturi detaches the loosely connected heads  11  from the shrimp bodies  13 . 
     The detached heads flow to a collector  84  that collects the headless shrimp bodies and the detached heads conveyed through connecting conduit from the head detacher  82 . One example of a collector includes the feed plenum  54  and the screen slide  56  of  FIGS. 4A and 4B . A conveyor  124  transports the detached heads and shrimp bodies to a roller peeler  88 . An optional water recirculator  86 , which includes filters or other water treatment components such as the screen  56 , the tank  58 , the perforated plate  60 , and the feed pump  48  of  FIGS. 4A and 4B  and inlet valves to admit fresh water to replenish lost fluid, recirculates the filtered spent fluid back into the flow at the front end of the head detacher  82 . The roller peeler  88 , which may be a Laitram® Model A peeler manufactured and sold by Laitram Machinery, Inc., removes the shells from the headless shrimp bodies and discards the shells along with the detached heads. The head detachment may be performed at the same location as the peeling or at different geographical locations. For example, the heads may be detached geographically close to where the shrimp are caught so that the headless shrimp can be shipped to a peeling operation for less cost because of the lower weight of headless shrimp and with less chance of spoilage because of the removal of head organs and fluids. 
     The peeled shrimp are conveyed to a shell separator  90 , which includes one or more cleaners or roller separators interconnected by conveyors or flumes. The shell separator separates loosened and detached shell and appendages from the peeled shrimp meats, which are conveyed to an inspection station  92 . The inspection station  92  may include a machine-vision accept-reject sorter or be a manned inspection station in which shrimp with residual shell or appendages are sorted from the accepted peeled shrimp meats. Rejected shrimp are conveyed back to the roller peeler  88  for re-processing. 
     Another version of a shrimp-processing system is shown in  FIG. 8 , in which the roller peeler  88  of  FIG. 7  is replaced by a hydraulic shell-removal system. The shrimp are deheaded as in  FIG. 7 . The headless shrimp bodies exiting the headless shell-on collector  84  are conveyed to a head separator  94 , which can be an air separator or a manual inspection station. The headless shrimp bodies are culled from the detached heads and transported to a second infeed system  96 . 
     Like the first infeed system  80 , the second infeed system  96  can include a feed tank, in which the headless shrimp with loosened shell and appendages are accumulated, a food pump for entraining the shrimp in a fluid flow through a conduit leading to another hydraulic detacher  98  that is used to detach shell and appendages from the headless shrimp bodies. The hydraulic shell detacher  40  is similar to the hydraulic head detacher  82 . The number of venturis, their velocity gradients, and their flow rates can all be tailored to detach shell and appendages without damaging the peeled shrimp meat. 
     The peeled shrimp are collected in a peeled shrimp collector  100 . Like the headless, shell-on collector  84  downstream of the hydraulic head detacher  82 , the peeled shrimp collector  100  can include a water removal screen, a collection tank, and an outfeed conveyor  44 . A water recirculator (not shown) may be used with the shell detacher and separator. The peeled shrimp collector drains the water from the shrimp meat and the detached shell and appendages. The shrimp meat and the detached shell and appendages are transported to the shell separator  90 , which separates the shrimp meat from the detached shell and appendages. The headless, shelled shrimp bodies are then sent to the inspection station  92 . Rejected shrimp with residual shell or appendages are returned to the headless shrimp infeed  96  for another pass through the hydraulic shell detacher  98 . 
       FIG. 9  shows a shrimp-processing system with a roller peeler  88  followed by a hydraulic shell detacher  98 . Headless, peeled shrimp exiting the roller peeler  88  are conveyed to an after-peeler infeed  97  like the first infeed  80  and the second infeed  96  in the processing system of  FIG. 8 . The headless, peeled shrimp are then subjected to further hydraulic shell detachment and separation in the shell detacher  98 , the peeled shrimp collector  100 , and the shell separator  90 . The processed shrimp meats are conveyed to the inspection station  92 . The rejected shrimp with residual material are optionally returned to the system for reprocessing. A reprocessing path selector  102  directs the rejected shrimp back into the roller peeler  88  or to the infeed  97  to the hydraulic shell detacher  98  depending on the amount of residual material on each processed shrimp.