Abstract:
Traps, and more particularly collapsible traps used to capture crabs or other live animals. More particularly still, collapsible live animal traps that utilize one or more support members that are stable when assembled, yet easily collapsible.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application claims priority from copending U.S. Provisional Patent Application Ser. No. 60/577,828, which was filed on Jun. 8, 2004 and entitled “Collapsible Crab Trap,” the completed disclosure of which is incorporated herein by reference for all purposes. 

   TECHNICAL FIELD 
   The present invention relates to traps, and more particularly to collapsible live animal traps used to capture crabs and other shellfish. More particularly still, the invention relates to live animal traps that utilize one or more support members that are stable when assembled, yet easily collapsible. 
   BACKGROUND 
   Crab pots and traps are used both commercially and recreationally to capture crabs and other shellfish. They typically function by luring the target through a “tunnel” and into the pot with some type of bait, and then preventing exit by some means such as a unidirectional gate, also known as a “trigger” mechanism. 
   One system for trapping crabs is provided by U.S. Pat. No. 2,716,304 to Taylor, which discloses a trap including upper and lower circumferential rings that are separated by a plurality of substantially vertical stays. The stays are fixedly attached to the lower ring, and removably attached to the upper ring using a u-shaped clip portion of each stay to engage a portion of the upper ring. Unfortunately, such u-shaped and similar clip-on stays may be accidentally detached in a variety of circumstances, leading to unwanted collapse of the trap. Furthermore, the clip portions of the stays may be relatively weak, possibly leading to partial collapse of the trap even when the stays do not become accidentally detached. 
   Another shortcoming of existing crab traps involves the collapsibility of the entry tunnel and unidirectional gate (or trigger) of the trap. In many existing traps, the tunnels and triggers are not configured to collapse smoothly along with other portions of the trap, resulting in possible interference between various parts of the trap and difficulty in collapsing the trap. Some existing traps attempt to coordinate collapse of the tunnel and/or trigger with collapse of the other portions of the trap. For example, the system provided by U.S. Pat. No. 2,760,297 to Buyken discloses a collapsible trap having a curved unidirectional gate, the curvature of which causes it to collapse along with the entry tunnel of the trap. However, the free ends of the gates in such systems are prone to interference by trapped crabs, possibly causing damage to the crabs, allowing crabs to escape, and/or causing unwanted collapse of the trap. 
   Yet another shortcoming in prior art crab traps relates to the structure of the side netting used in such traps. Typically, this netting includes interwoven horizontal and vertical strands that either are knotted together at their points of intersection, or that slide freely relative to each other in both the horizontal and vertical directions. In practice, each of these configurations can result in unwanted entanglements of the netting with other portions of the trap when the trap is collapsed and reassembled. 
   In view of the shortcomings in the prior art described above, a need exists for a collapsible crab trap having improved stability when assembled, yet which may be easily collapsed and reassembled in a coordinated manner. 

   
     BRIEF DESCRIPTION OF THE FIGURES 
       FIG. 1  is a perspective view showing an assembled crab trap with its netting and harvest door removed, according to aspects of the present disclosure. 
       FIG. 2  is a perspective view of the crab trap of  FIG. 1 , showing the trap of  FIG. 1  collapsed. 
       FIG. 3  is a partial side sectional view showing a collapsible support member attached to upper and lower perimeters of a crab trap, according to aspects of the present disclosure. 
       FIG. 4  is a partial front elevational view of the collapsible support member and perimeters of  FIG. 3 . 
       FIG. 5  is a partial perspective view of a collapsible tunnel and trigger mechanism attached to upper and lower perimeters of a crab trap, according to aspects of the present disclosure. 
       FIG. 6  is a perspective view of an assembled collapsible crab trap with its netting and harvest door attached, but with the top and bottom walls partially cut away for clarity, according to aspects of the present disclosure. 
       FIG. 7  is a perspective view of an assembled collapsible crab trap with an alternative form of netting and harvest door attached, but with the trigger mechanisms removed and the top and bottom walls partially cut away for clarity, according to aspects of the present disclosure. 
       FIG. 8  is a magnified view showing the structure of the side wall netting of the trap of  FIG. 7  in more detail. 
       FIG. 9  is a perspective view showing an alternate embodiment of an assembled crab trap with its netting and harvest door removed, according to aspects of the present disclosure. 
       FIG. 10  is a perspective view showing another alternate embodiment of a live animal trap with its top and bottom walls removed for clarity, according to aspects of the present disclosure. 
   

   DETAILED DESCRIPTION 
     FIG. 1  shows a collapsible crab trap  10  in a partially assembled state, according to an embodiment of the present invention. Trap  10  includes an upper perimeter  12 , a lower perimeter  14 , and a plurality of collapsible legs  16  disposed around the periphery of the trap. For clarity, trap  10  is shown with its trigger mechanisms and top, bottom, and side walls removed, but in general these walls will be in place when the trap is fully assembled and ready for practical operation, so as to prevent escape of captured crabs or other creatures. 
   In the depicted embodiment, each perimeter—and thus the trap as a whole—has a circular cross section. More generally, however, traps according to the present disclosure may be configured to have various shapes, such as elliptical, rectangular, or square shapes, among others. The structural portions of the trap depicted in  FIG. 1  may be constructed from any suitable material, including metals such as aluminum, steel, or various metal alloys; and plastic materials including polyvinylchloride (PVC) and other sturdy composite materials. 
   Each collapsible leg  16  of trap embodiment  10  includes an elongate support member  18 , a head portion  20 , a hollow engagement portion  22 , and a hinge mechanism  24 . A lower, or proximal portion  26  of each leg attaches to a base portion  28 , which is connected to lower perimeter  14  in a secure fashion, such as by welding or by integral formation with the lower perimeter. An upper, or distal portion  30  of each elongate support member is configured to pass through a sleeve  32  that is securely connected to upper perimeter  12 , for instance by welding or by integral formation with the upper perimeter. 
   Each sleeve  32  is sized to allow passage of elongate support member  18  of the collapsible leg, but to prevent passage of head portion  20  of the leg. When the trap is in its assembled position, engagement portion  22  of each leg is configured to slide along the corresponding support member and may be engaged with distal portion  30  of the corresponding support member, in a manner that will be described in more detail below. However, engagement portion  22  is sized to prevent its passage through sleeve  32 , so that when the engagement portion is engaged with the distal portion of the support member, it holds sleeve  32  in proximity to head portion  20  of the corresponding leg. The legs thus may be collectively configured to hold the upper perimeter of the trap at a substantially fixed distance from the lower perimeter of the trap. 
   In addition to sliding engagement portion  22 , the invention also contemplates other methods of engaging the elongate support member of the leg with the sleeve attached to the upper perimeter. For example, the sleeve may have a solid top surface (not shown) configured to rotate into and out of position, and the distal portion of the support member may engage with the sleeve simply by passing into the sleeve and being held in position by the top surface of the sleeve. To collapse the trap, the solid top surface of the sleeve may be rotated out of position, allowing the support member to pass through the sleeve. 
   Alternatively, the trap may include a clamp mechanism such as a set screw or a quick-release lever configured to clamp the sleeve around the leg to hold the trap in a securely assembled position. To collapse the trap, the clamp mechanism is loosened, allowing the support member of the leg to pass through the sleeve. In general, any engagement mechanism is suitable which securely engages the support member with the sleeve so as to hold the upper perimeter of the trap at a substantially fixed distance from the lower perimeter. 
   Trap  10  also includes a pair of collapsible tunnels  34 . Each tunnel  34  includes a top member  36 , a bottom member  38 , a pair of side members  40 , and a plurality of attachment members  42  for attaching the tunnel to the upper and lower perimeters. Attachment members  42  may be rotationally connected to the upper and lower perimeters, for example, by rivets  44 , or by any other suitable mechanism such as hinges, pins, or the like. As depicted in  FIG. 1 , the attachment members each may be rotationally connected to a support block  46 , rather than directly to the upper and lower perimeters. The support blocks may be fixedly attached to the upper and lower perimeters by welding, gluing, or any other suitable means. Each side member  40  further may include a hinge mechanism  48  that allows the side member to bend or fold into two substantially parallel segments when the trap is collapsed, in a manner that will be described in greater detail below. 
   Trap  10  also may include a door portion  50 , which typically is configured to be rotatable into and out of a plane defined by the upper perimeter. In  FIG. 1 , the door portion takes the form of a semicircular section of tubing that is attached to upper perimeter  12  with a pair of rotatable pins  52 . At each attachment point, a support bracket  54  may be securely attached to the upper perimeter, e.g. by welding or soldering, and may provide further stability to the door portion. The door portion in this embodiment also includes an attached stop  56 , which prevents the door portion from rotating into the interior of the assembled trap. The operation of the door portion will be described in greater detail below. 
   Trap  10  is shown in its collapsed state in  FIG. 2 , again with its top, bottom and side walls removed for clarity. As  FIG. 2  depicts, when the trap is collapsed, engagement portion  22 , which may be internally threaded, is disengaged from threads  33  of distal portion  30  of the corresponding elongate support member, allowing the engagement portion to move along the support member until it is positioned below hinge mechanism  24  (i.e., between the lower perimeter and the hinge mechanism). This allows sleeve  32  to move away from head portion  20  of the leg, which causes the upper perimeter of the trap to move towards the lower perimeter. When sleeve  32  is positioned below hinge mechanism  24 , the upper and lower perimeters of the trap will be relatively close together, defining a common plane. At this point, the legs may be folded over—typically in either a radial direction (as indicated in  FIG. 2 ) or a tangential direction (not shown)—so that the distal portions of the support members lie substantially in the plane defined by the upper and lower perimeters. 
   As  FIG. 2  shows, tunnels  34  also collapse as the upper and lower perimeters are brought together. The rotational attachment of attachment members  42  to the upper and lower perimeters allows those members to rotate as the trap is collapsed, while hinge mechanisms  48  allows each side member  40  to bend or fold into two substantially parallel segments. Thus, as  FIG. 2  indicates, the attachment members, side members, and top and bottom members of the tunnels all may be positioned substantially in the plane defined by the upper and lower perimeters when the trap is collapsed. This allows convenient transportation and storage of the trap when it is not in use. 
     FIGS. 3 and 4  are close-up views of one of collapsible legs  16  while trap  10  is partially assembled, showing in more detail how the legs operate to securely hold the upper and lower perimeters of the trap at a substantially fixed distance from each other.  FIG. 3  shows a tangential cross section of a portion of the trap, and  FIG. 4  shows a radial view of the same portion of the trap. As indicated at  33 , distal portion  30  of support member  18  of the leg may be externally threaded. In this case, engagement portion  22  of the leg may be internally threaded in a complementary manner, to rotationally engage the distal portion of the support member. 
   Engagement portion  22  is sized to prevent its passage through sleeve  32  of the trap. Thus, when engagement portion  22  is rotated into greater engagement with threaded distal portion  30 , it contacts sleeve  32 , and causes the sleeve to move towards head portion  20  of the leg. Since, as indicated at  58 , sleeve  32  is secured to upper perimeter  12  by welding, soldering, gluing, or the like, this also causes upper perimeter  12  to move away from lower perimeter  14  of the trap. After sufficient rotation of the engagement portion, sleeve  32  may be pressed against head portion  20  so that no further movement of the sleeve is possible, and the upper perimeter will be securely held at a substantially fixed distance from the lower perimeter. When this step has been accomplished for each leg, the trap will be in an assembled state. 
   To collapse the trap, engagement portion  22  of each leg is rotated in the direction opposite the direction used to tighten it, thus loosening the engagement portion until it disengages from threads  33  of the leg. This allows the engagement portion to slide down the leg until it is below hinge mechanism  24 . When the engagement portion of each leg is disengaged in this manner, the upper perimeter of the trap will be free to move towards the lower perimeter. When the upper and lower perimeters are brought sufficiently close together so that sleeves  32  and engagement portions  22  are disposed between hinge mechanisms  24  and the lower perimeter, the legs may be collapsed into the common plane of the perimeters as indicated in  FIG. 2  and as described above. 
     FIG. 5  shows a close-up view of one of collapsible tunnels  34 , including a gate  60 , also known as a trigger mechanism, attached to top member  36  of the tunnel. Gate  60  typically is unidirectional, i.e. it can be opened in an inward direction (towards the center of the trap), but not in an outward direction. This allows crabs and other desired animals to pass into the trap from the outside, but prevents them from escaping through the gate once trapped. As  FIG. 5  indicates, gate  60  may include a plurality of longitudinal members  62 , spaced laterally apart by a distance less than the typical dimension of an animal whose escape it is desired to prevent. Longitudinal members  62  may be joined by a cross member  64  to which they are securely attached, for example, by welding, soldering, or any other suitable attachment method. 
   Gate  60  may be attached to top member  36  of the tunnel with curved segments  65  of the longitudinal members  62 , which may be partially or completely wrapped around the top member as indicated. This allows the gate to rotate inward, permitting ingress of desired animals. However, one or more of the longitudinal members may be greater in length than the length of side members  40  of the tunnel so as to overlap bottom member  38 , preventing the gate from rotating outward past the plane defined by the top, bottom, and side members of the tunnel, and thus preventing egress of trapped animals. 
   Gate  60  also may include one or more laterally extending members  66 . The laterally extending members may extend sufficiently far so that they contact one of side members  40  when the gate is in a closed position. Thus, when the trap is collapsed and side members  40  fold at hinge mechanisms  48 , each side member will urge the corresponding laterally extending member inward, causing the entire gate to rotate. Thus, as the tunnel is collapsed into the common plane defined by the upper and lower perimeters, the gate also will be automatically moved substantially into that same plane by the force of the side members on the laterally extending members. This further facilitates smooth collapse of the trap. 
     FIG. 5  also shows a wirekeeper mechanism  67  attached to one of side members  40 , and which may be used in some embodiments to help prevent some of the wire strands of the trap from becoming entangled. Although for clarity, only one wirekeeper is shown, in general a similar mechanism may be attached to each side member. As indicated, the wirekeeper mechanism may be bolted or otherwise attached to side member  40 , and may be configured to accept multiple strands of wire or netting, which then may be attached to the wirekeeper by crimping, soldering, or any other suitable method. 
   The multiple strands attached to the wirekeeper mechanism may provide a portion of the side netting of tunnel  34 , and may be attached to the upper and lower perimeters of the trap, or to other strands of side wall netting, among others. When the trap is collapsed, the hinged rotation of side member  40  causes wirekeeper  67  to be drawn inward towards the center of the trap, providing tension to the attached strands, and helping to prevent them from becoming entangled as the trap is collapsed and reassembled. 
     FIG. 6  shows trap  10  in a fully assembled state, including a screened top wall  68 , a screened bottom wall  70 , and a collapsible screened side wall  72 . For clarity, the top and bottom walls are shown partially cut away, so that part of the side wall and the netting around one of the tunnels of the trap may be seen unobstructed. The top and bottom walls generally may be formed from a plurality of crossed strands  74 , which may be constructed, for example, from metal wire, nylon, plastic, or any other suitable material. In general, the screened walls of the trap are constructed to create apertures that allow passage of animals having less than a particular size, while preventing passage (and thus escape) of animals having greater than a particular size. Strands  74  forming bottom wall  70  may be attached securely to bottom perimeter  14  at a plurality of locations spaced around the perimeter. The strands may be attached to the perimeter, for example, by soldering, by wrapping the strands around the perimeter, or by threading the strands through apertures in the perimeter, which may be hollow to accommodate this method of attachment. 
   In some embodiments, the perimeters of the trap may be hollow, and some or all of strands  74  may be attached to one of the perimeters by entering the perimeter through an aperture, and then being secured by screws or bolts screwed into the perimeter so as to frictionally secure the strands against the interior of the perimeter. For example, a strand may enter one of the perimeters through an aperture in the perimeter that faces radially inward, and then a screw or bolt may be screwed into another aperture in the perimeter that faces in an orthogonal direction, until the screw or bolt pushes the free end of the strand against the opposite side of the interior of the perimeter and securely holds it there. This method of attachment allows individual strands to be replaced or repaired without removing all of the strands of the associated top or bottom wall of the trap. 
   Similarly, the strands forming top wall  68  are securely attached to upper perimeter  12  at a plurality of locations. However, the strands of the top wall are attached to the semicircular tubing of door  50  around approximately one half of the upper periphery, to form a portion of the top wall that may be opened by pulling upward on door  50 , allowing access to the interior of the trap. Top wall  68  also includes one or more circular apertures  76 , which are sized to allow prey of less than particularly chosen dimensions to escape the trap. For example, apertures  76  may be approximately between 2 inches and 4 inches in diameter. Apertures  76  each may be formed by a rigid metal ring  78 , to which strands  74  may be attached using loops  80  formed from the strand material and wrapped around the metal rings. 
   Side wall  72  is collapsible, and generally also may be formed from a plurality of crossed strands  82 . Strands  82  of the side wall are typically constructed of a flexible material such as stainless steel wire, nylon, plastic, or the like, to facilitate collapse of the side wall. Strands  82  may be knotted together at their intersection points, to form a plurality of apertures which are smaller than the size of the desired prey, to prevent escape of the prey through the side wall. Strands  82  may be attached to the upper and lower perimeters of the trap by any secure method of attachment, such as by using screws or bolts to secure the strands within the perimeters as described above, or by wrapping the strands around the perimeters and knotting them. In the vicinity of the tunnels, the strands of the side wall may extend between the connecting members  42  of the tunnel rather than between the perimeters, to allow prey to pass into the trap through the tunnels. 
     FIG. 7  shows trap  10  with an alternate side wall  84 , which is formed from a plurality of crossed strands  86 ,  88 . As in  FIG. 6 , the top and bottom walls are shown partially cut away in  FIG. 7 , so that part of the side wall and the netting around one of the tunnels of the trap may be seen unobstructed. Like strands  82  of side wall  72 , the strands of side wall  84  are formed from a flexible material such as metal wire or plastic. However, unlike strands  82 , strands  86  and  88  are not knotted together. Instead, strands  86 , which extend substantially vertically between upper and lower perimeters  12  and  14 , form a plurality of loops  90 , through which substantially horizontal strands  88  pass. This configuration provides strands  86  a degree of freedom with respect to strands  88 ; i.e., strands  86  may slide along strands  88 , although the amount of such sliding may be limited by tension in the strands  86 , due to their fixed connections with the upper and lower perimeters. On the other hand, strands  88  are in substantially fixed relation to each other, because loops  90  are not free to move along the strands  86 . 
   To provide a degree of freedom between the strands in a similar but alternate manner (not shown), strands  88  may form loops through which the strands  86  pass. Furthermore, to provide rotational freedom between the vertical and horizontal strands at the intersection points of the strands without providing a sliding degree of freedom, both vertical strands  86  and horizontal strands  88  may form a plurality of intersecting loops, with each loop formed in the manner shown in  FIG. 8 . This configuration of intersecting loops may provide the same aperture stability as traditional, knotted netting, while allowing each segment of the netting to rotate freely, which may lead to fewer entanglements than using knots at the intersection points. In some embodiments, the vertical and horizontal strands may intersect with a sliding degree of freedom in some regions of the trap, rotational freedom in other regions of the trap, and in standard knotted fashion in still other regions, or using any desired combination of these intersection methods. 
     FIG. 8  shows in greater detail how a loop  90  may be constructed from one of strands  86  (or horizontal strands  88 ) of the side wall. To form the loop, the strand may be passed through a hollow sleeve  92 , doubled back, and then passed through the sleeve a second time. The sleeve may be constructed from any suitable material, such as metal or plastic, and its diameter may be chosen in relation to the diameter of strands  86  such that the sleeve is held substantially fixed in place along the strand by friction. As described previously, this fixes the locations of loops  90 , so that strands  86  have a degree of freedom to slide along strands  88 , but the spacing of strands  88  is constrained by the fixed locations of the loops. This configuration may allow the strands of the side wall to reposition themselves as the trap is collapsed, leading to relatively fewer entanglements of the side wall, and thus to more convenient operation of the trap. 
     FIG. 9  shows an alternate embodiment  100  of a trap, in accordance with aspects of this disclosure. Trap  100  includes an upper perimeter  102 , a lower perimeter  104 , and a single central collapsible leg  106  disposed along the central axis of the trap. For clarity, trap  100  is shown with its top, bottom, and side walls removed, but in general these walls will be in place when the trap is fully assembled and ready for practical operation, so as to prevent escape of captured creatures. 
   Collapsible leg  106  includes an elongate support member  108 , a head portion  110 , a hollow engagement portion  112 , and a hinge mechanism  114 . A lower, or proximal portion  116  of the leg attaches to a base portion  118 , which is connected to lower perimeter  106  with a plurality of lower radial struts  120 . Struts  120  are securely attached to base portion  118  and to lower perimeter  104  by, for example, soldering, welding, or by integral formation with the lower perimeter. An upper, or distal portion  122  of elongate support member  108  is configured to pass through a sleeve  124  that is securely connected to upper perimeter  102  with a plurality of upper radial struts  126 . Struts  126  are securely attached to sleeve  124  and to upper perimeter  102  by, for example, soldering, welding, or by integral formation with the upper perimeter. 
   Collapsible leg  106  may be used to selectively assemble and collapse trap  100 , in a manner substantially similar to the manner in which collapsible legs  16  (depicted in  FIGS. 1-4  and described above) may be used to assemble and collapse trap  10 . More specifically, sleeve  124  is sized to allow passage of elongate support member  108  of the collapsible leg, but to prevent passage of head portion  110  of the leg. When the trap is in its assembled position, engagement portion  112  of the leg is configured to slide along the support member, and may be securely engaged with the support member by threading the engagement portion onto the distal portion of the support member. To facilitate this engagement, the interior of hollow engagement portion  112  may be threaded, and the exterior of distal portion  122  of the support member may be threaded in a complementary manner. 
   Engagement portion  112  is sized to prevent its passage through sleeve  124 , so that when the engagement portion is engaged with the distal portion of the support member, it holds each sleeve  124  in fixed proximity to head portion  110  of the leg. Since lower and upper radial struts  120 ,  126  respectively rigidly connect the proximal and distal portions of the leg to the lower and upper perimeters, this also holds the upper perimeter of the trap at a substantially fixed distance from the lower perimeter, providing stable assembly of the trap. To collapse the trap, engagement portion  112  is unscrewed, so that both the engagement portion and hollow sleeve  124  may slide down the leg, past hinge  114  and towards base  118 . When both engagement portion  112  and sleeve  124  are positioned between hinge  114  and base  118 , upper perimeter  102  and lower perimeter  104  will be in relatively close proximity, and the leg may be folded over and into the common plane defined by the two perimeters. 
   Trap  100  also includes a plurality of tunnels  128  to allow entry into the trap by prey, but to prevent their egress. Tunnels  128  are connected to the upper and lower perimeters of the trap by a plurality of members  130 , and may be rotatably connected in a manner similar to the connection of tunnels  34  to the upper and lower perimeters of trap  10  (see, e.g.,  FIGS. 1 and 2 ). Tunnels  128  also may include top, bottom and hinged side members  132 ,  134 ,  136 , also similar in construction to the members of tunnels  34  of trap embodiment  10 . When fully assembled, each tunnel  128  of trap  100  also may include a unidirectional gate similar to gates  60  of trap  10 , and which are configured to collapse into the common plane of the perimeters when the trap is collapsed. Trap  100  also will include a screened top wall defined by its upper perimeter, a screened bottom wall defined by its lower perimeter, and a screened side wall. These features (not shown) may be substantially similar to the screened walls depicted in trap embodiment  10  shown in  FIGS. 7-8 , and may include walls with crossed strands having zero, one, or two sliding degrees of freedom and/or rotational freedom with respect to each other, as described above. 
     FIG. 10  shows another alternate embodiment  200  of a trap, in accordance with aspects of this disclosure. Trap  200  includes an upper perimeter  202 , a lower perimeter  204 , a middle perimeter  206 , and a plurality of collapsible legs  208  disposed around the periphery of the trap. As indicated, in this embodiment, legs  208  may be disposed interior to perimeters  202 ,  204 , and  206 . For clarity, trap  200  is shown with its top and bottom walls removed, but in general these walls will be in place when the trap is fully assembled. 
   Each collapsible leg  208  of trap embodiment  200  includes an elongate support member  210 , a head portion  212 , a hollow engagement portion  214 , and a hinge mechanism  216 . A lower, or proximal portion  218  of each leg attaches to a base portion  220 , which is connected to lower perimeter  204  in a secure fashion, such as by welding or by integral formation with the lower perimeter. An upper, or distal portion  222  of each elongate support member is configured to pass through a sleeve  224  that is securely connected to upper perimeter  202 , for instance by welding or by integral formation with the upper perimeter. 
   Collapsible legs  208  may be used to selectively assemble and collapse trap  200 , in a manner substantially similar to the manner in which collapsible legs  16  (depicted in  FIGS. 1-4  and described above) may be used to assemble and collapse trap  10 . More specifically, each sleeve  224  is sized to allow passage of elongate support member  210  of its associated collapsible leg, but to prevent passage of head portion  212  of the leg. When the trap is in its assembled position, engagement portion  214  of each leg is configured to slide along its associated support member, and may be securely engaged with the support member by threading the engagement portion onto the distal portion of the support member. To facilitate this engagement, the interior of hollow engagement portions  214  may be threaded, and the exterior of distal portions  222  of the support members may be threaded in a complementary manner. 
   Engagement portions  214  are sized to prevent their passage through sleeves  224 , so that when each engagement portion is engaged with the distal portion of its associated support member, it holds each sleeve  224  in fixed proximity to head portion  212  of the leg. Since sleeves  224  and base portions  220  are respectively rigidly connected to the lower and upper perimeters, this also holds the upper perimeter of the trap at a substantially fixed distance from the lower perimeter, providing stable assembly of the trap. To collapse the trap, engagement portions  214  are unscrewed, so that both the engagement portions and hollow sleeves  224  may slide down their respective legs, past hinges  216  and towards base portions  220 . When engagement portion  214  and sleeve  224  of each leg are positioned between hinge  216  and base  220 , upper perimeter  202 , lower perimeter  204 , and middle perimeter  206  will be in relatively close proximity, and the legs may be folded over and into a common plane defined by the three perimeters. 
   As  FIG. 10  depicts, middle perimeter  206  may be configured to slide freely along the exterior of legs  208 . However, the middle perimeter has substantially the same diameter as upper and lower perimeters  202 ,  204 , and is therefore bounded above and below by the upper and lower perimeters. In other words, although the middle perimeter is not directly attached to the legs of the trap, it is confined to the region between the upper and lower perimeters. 
   A screened side wall  226  is attached to lower perimeter  204  and middle perimeter  206 , such that the side wall is raised and lowered in conjunction with the upward and downward movement of the middle perimeter. Thus, when the middle perimeter is in a lowered position (in relatively close proximity to the lower perimeter), the side wall also will be in a lowered position, allowing prey to enter the trap. However, when the middle perimeter is in a raised position (in relatively close proximity to the upper perimeter), the side wall also will be in a raised position, and prey will neither be able to enter or to leave the trap. Side wall  226  may include crossed strands having zero, one, or two sliding degrees of freedom with respect to each other, as described previously with respect to the other embodiments of the trap. 
   Middle perimeter  206 , and thus side wall  226 , may be raised and lowered by respectively applying and relaxing tension to a tension mechanism such as a cord or rope  228 , which as depicted may have multiple strands attached to various points on middle perimeter  206 . Rope  228  also may be used to conveniently lower trap  200  into the water and subsequently to retrieve it. After the trap has been lowered into the water and is resting on a solid underwater surface, tension in rope  228  may be relaxed, lowering middle perimeter  206  and side wall  226  and allowing prey to enter the trap. To retrieve the trap, the user pulls up on the rope, raising the middle perimeter and the side wall and trapping the prey while the trap is pulled up and out of the water. 
   Trap  200  also will include a screened top wall defined by its upper perimeter, and a screened bottom wall defined by its lower perimeter. These walls (not shown) may be substantially similar to the screened walls depicted in trap embodiment  10  shown in  FIGS. 7-8  and described above. 
   While the invention has been disclosed in its preferred form, the specific embodiments thereof as disclosed and illustrated herein are not to be considered in a limiting sense as numerous variations are possible. Applicant regards the subject matter of the invention to include all novel and non-obvious combinations and subcombinations of the various elements, features, functions and/or properties disclosed herein. No single feature, function, element or property of the disclosed embodiments is essential. The following claims define certain combinations and subcombinations which are regarded as novel and non-obvious. Other combinations and subcombinations of features, functions, elements and/or properties may be claimed through amendment of the present claims or through presentation of new claims in this or a related application. Such claims, whether they are broader, narrower or equal in scope to the original claims, are also regarded as included within the subject matter of applicant&#39;s invention.