Abstract:
A device ( 10 ) having a cylinder housing ( 12 ) with a bore ( 12   a ) receives a piston sleeve ( 14 ) in which a tapered bore is formed in radially movable sections extending from the piston head. A rope gripping split sleeve ( 16 ) having a tapered outer circumference and formed of separable sections which are radially movable but maintained in axial alignment is received in the tapered bore of the piston sleeve. A rope is placed in the split sleeve which is inserted in the piston sleeve and in turn in the housing bore. A valve ( 18 ) disposed in the head ( 14   a ) of the piston sleeve allows piston movement inwardly but resists outward movement of the piston, allowing a metering fluid flow providing a timed release of the rope dependent on the force level applied. In a second embodiment device ( 100 ) includes a piston rod ( 122 ) attached to the piston sleeve which extends through a guide plug ( 116 ) into a compression chamber. Fluid is allowed to flow through a valve ( 128 ) in piston head ( 122   b ) when the piston is moved inwardly to set the device but fluid flow in the opposite direction is prevented by the valve. When sufficient outward force is applied to the rope, movement of the piston is enabled by a metering flow of fluid through a bore of a needle ( 130 ) extending through the piston plug ( 126 ). An interlocking member ( 14   k   , 122   m ) provides a minimum selected force for initial movement of the piston member from the set position.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     Benefit is claimed of Prov. Appl. No. 60/114,667, filed Jan. 4, 1998. 
    
    
     FIELD OF THE INVENTION 
     This invention relates generally to fishing gear such as nets and lobster traps and the like placed in bodies of water and more specifically to apparatus used for allowing whales which may become entangled in such fishing gear to break away before serious damage to the whales occurs. 
     BACKGROUND OF THE INVENTION 
     Entanglement of whales in fishing gear has become a world wide problem causing significant human-caused mortality to such whales through entanglement with passive fishing gear. The problem is especially severe with respect to certain species of whales, such as the Northern Right Whale, an endangered species with only some 300 believed to presently exist. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide apparatus which can be attached to fishing gear and which will allow an entangled whale to break free before serious injury to the whale can occur. 
     Briefly described, a whale release device made in accordance with a first embodiment of the invention comprises a cylinder having a bore with a closed end in which is slidably received a piston sleeve having a head formed with a circumferentially extending liquid seal and axially extending elongated sections which in turn define a bore formed with a taper. A rope gripping split sleeve member having radially movable but axially aligned sections and having a matching taper on its outer periphery is received in the tapered bore of the piston sleeve. A rope is inserted between the sections of the split sleeve which in turn is received in the bore of the piston sleeve. To set the device for operation, the piston sleeve along with the rope gripping split sleeve are pushed toward the closed end of the housing bore with the wall of the housing bore applying a radial bias on the piston sleeve which in turn is transferred to the rope gripping split sleeve. As the piston sleeve is pushed inwardly, fluid flows freely through a valve in the head of the piston sleeve. The piston sleeve is provided with tabs extending outwardly from its outer circumference and which are received in an increased diameter portion of the housing bore so that outbound movement of the piston sleeve is resisted. When the rope is pulled, the rope gripping split sleeve is compressed due to the tapers which increases the gripping force on the rope. When sufficient force is exerted on the rope, the piston sleeve moves outwardly creating a partial vacuum and enabled by a metered flow of fluid, i.e., sea water, through the valve until the outer part of the piston sleeve is outside the housing and the axially elongated sections are free to move radially outwardly thereby releasing the force on the split sleeve and in turn on the rope. In a second embodiment, a piston rod carrying a piston head extends inwardly from the piston sleeve and is received through a guide plug into a pressure chamber filled with fluid of a selected viscosity. Fluid is allowed to freely pass in one direction into one side of the chamber through a valve mounted in a piston plug in turn mounted on the piston head. Flow in the opposite direction is metered through a hollow needle providing a metered flow and consequent timed release. Preferably, an interlocking lip and notch are respectively formed in the end face of the piston head and one of the plugs to maintain the piston head in the closed position until a selected force is applied to the rope. 
     Additional objects and features of the invention will be set forth in part in the description which follows and in part will be obvious from the description. The objects and advantages of the invention may be realized and attained by means of the instrumentality&#39;s and combinations particularly pointed out in the appended claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate preferred embodiments of the invention and, together with the description, serve to explain the objects, advantages and principles of the invention. In the drawings: 
     FIG. 1 is a cross sectional view of a whale release device made in accordance with the invention shown in a fully set condition; 
     FIG. 2 is an exploded cross sectional view of a split sleeve used in the FIG. 1 device along with one end of a rope or line used to attach the device to a buoy or the like; 
     FIG. 2 a  is an end view of one of the sections of the FIG. 2 split sleeve; 
     FIG. 3 is a view similar to FIG. 2 but shown with the split sleeve clamping the line; 
     FIG. 4 is a cross sectional view of a piston and valve apparatus used in the FIG. 1 device; 
     FIG. 5 is a cross sectional view taken on lines  5 — 5  of FIG. 4; 
     FIG. 6 is a view similar to FIG. 4 but shown with the FIG. 3 structure received in a cavity or bore formed in the piston; 
     FIG. 7 is a partial cross sectional view of a cylinder housing used in the FIG. 1 device; 
     FIG. 8 is a left side view of a valve bladder used in the FIG. 1 device; 
     FIG. 9 is a cross sectional view taken on line  9 — 9  of FIG. 8; 
     FIG. 10 is a cross sectional view of a valve member used in the FIG. 1 device; 
     FIGS. 11-13 are views similar to FIG. 1 showing the whale release device in different operational modes; 
     FIGS. 14 and 15 are horizontal cross sectional views of second and first punch members used for resetting the FIG. 1 device; 
     FIG. 16 is a front view of the FIG. 15 punch member; and 
     FIG. 17 is a left end view of the FIG. 16 punch member. 
     FIG. 18 is a view similar to FIG. 12 of a whale release device made in accordance with a second embodiment of the invention shown in the open or released position; 
     FIG. 19 is a view of the FIG. 18 device shown with the rope gripping split sleeve member butting against the outboard end of the piston sleeve in the maximum compression rope gripping position; 
     FIG. 20 is a view of the FIG. 18 device shown in the reset or closed position; 
     FIG. 21 is a blown-apart view, partly in cross section, showing components of the piston assembly of the second embodiment; 
     FIG. 22 is an enlarged portion of the piston head shown in FIGS. 18-20; 
     FIG. 22 a  is a still further enlarged portion of FIG. 22; 
     FIG. 23 is an enlarged broken away portion of FIGS.  19 , 20  showing an interlocking mechanism; and 
     FIG. 23 a  is a further enlarged portion of FIG.  23 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Whale release  10  made in accordance with the invention is shown in FIG.  1  and comprises a generally cylindrical cylinder housing  12  formed with a bore  12   a  in which is received a piston sleeve  14  having a cylindrical head portion  14   a  and a plurality of generally axially extending sections  14   b . Axially extending sections  14   b  in turn form a cavity or bore  14   c  in which is received a split sleeve  16  which is formed with a rope or line receiving inner surface  16   a . These parts are preferably formed of inert, high strength, tough, slippery plastic material such as Delran. It is preferred that the material used have a specific gravity greater than sea water so that the device will sink when placed in the ocean. 
     As best seen in FIG. 2, rope gripping split sleeve  16  comprises mating sections  16   b ,  16   c , each having a head portion  16   d  and axially extending fingers  16   e  and  16   f  respectively. As shown, each section  16   b ,  16   c  is formed with two fingers (see FIG. 2 a ) however, three or more fingers could be provided if desired. Sections  16   b  and  16   c  are formed with interfitting tongue and groove portions, tongues  16   g  and grooves  16   h  on section  16   b  and tongues  16   i  and grooves  16   j  on section  16   c , to permit independent radial movement of the sections while maintaining the sections axially aligned with one another. The inside surface  16   a  of the sections taken together is generally cylindrical and formed with a plurality of ribs  16   k  spaced a selected distance apart, such as approximately one half inch, preferably formed with a relatively sharp, rope engaging edge. Ribs  16   k  are formed so that surface  161  of each rib closest to the head portion  16   d  extends in a generally radial direction to improve the rope gripping ability. The free distal ends of fingers  16   e ,  16   f  are formed with an enlarged periphery  16   m , and with an abrupt transition surface  16   p . The axially extending outer surface  16   n  of fingers  16   e ,  16   f , as well as the axially extending outer surface  16   o  of distal end portions  16   m , are formed with a slight taper, for example approximately 2 degrees, with the radius of the surface decreasing as one goes in the direction from the head  16   d  toward the distal free end of the fingers. 
     An end of line  2  is placed between sections  16   b ,  16   c  of rope gripping split sleeve  16  and the sections are fitted together as seen in FIG. 3, the assembled split sleeve  16  and line  2  is then placed within axially extending sections  14   b  of piston sleeve  14  as shown in FIG.  6 . Piston sleeve  14 , as best seen in FIG. 4, comprises a cylindrical head portion  14   a  having a plurality of circumferential O-ring grooves  14   c . Axially extending sections  14   b , when in an at rest position preferably are somewhat spread apart, for example, several degrees (not shown). The axially extending sections are formed with a generally cylindrical outer surface having a first enlarged diameter portion  14   d  intermediate to the fixed end of the sections and the center thereof and formed with a tapered transition surface  14   e  at one end and an abrupt transition surface  14   f  at its opposite end. A second enlarged diameter portion  14   g  is formed adjacent to the free distal end of sections  14   b  and has an abrupt transition surface  14   h  at the inboard end thereof. The end face  14   i  is preferably formed with an inclined surface  14   j  to be discussed below. A plurality of circumferentially spaced, radially extending tabs  14   k  project outwardly from a selected axial location intermediate to enlarged diameter portions  14   d ,  14   g . A generally cylindrical bore  141  is formed in sections  14   b , taken together, the bore formed with a surface  14   m  having a taper the same as, but opposite to, that of tapered surface  16   n  of split sleeve  16 . Bore  141  is also provided with a recessed surface  14   n  having the same taper as that of surface  16   o , but opposite to, and with transition surface  14   o  being relatively abrupt. An abrupt transition surface  14   t  extends from the opposite end of recessed surface  14   n  to a line receiving bore  14   u . Head  14   a  is formed with a valve receiving recess  14   p  on the side of the head adjacent to sections  14   b  and a bladder receiving recess  14   q  on the outer end face  14   s  of head  14   a , the recesses connected by a reduced diameter bore  14   r.    
     Valve member  18 , seated in recess  14   p  along with O-ring  20  and extending through bore  14   r  and bladder  22  received in recess  14   q  of piston sleeve  14  are shown in FIG.  1 . With particular reference to FIGS. 8-10, valve member  18  is generally cylindrical having a plate portion  18   h  and hub  18   e  and a centrally disposed, axially extending orifice  18   a  of a suitable, small diameter, such as 0.006 inch. A recess  18   b  is formed in the end face  18   k  of the valve member and is provided with a smooth radiused surface  18   c  surrounding the orifice to enhance flow of water therethrough. Orifice  18   a  communicates with enlarged diameter bore  18   d  which extends through hub portion  18   e . Rear wall  18   f  of plate portion  18   h  is received against the bottom wall of recess  14   p  with an O-ring  20  therebetween as seen in FIG.  1 . Hub portion  18   e  is formed with a bladder receiving circumferential groove  18   g . Bladder  22  is formed of suitable, chemically inert, spring material and has an outer, cylindrical rim  22   a  with a truncated conical wall  22   b  having a centrally disposed bore  22   c . Wall  22   b  extends inwardly from the rim and in a direction toward end face  14   s  of piston  14 . A plurality of apertures  22   d  are formed through wall  22   b  with slots  22   e  formed between at least some of the apertures and bore  22   c  to form, in effect, a plurality of spring blades as well as to provide a water passage, as will be explained below. The lip of wall  22   b  defining bore  22   c  is snapped into bladder receiving groove  18   g  using an appropriate tool. This places a bias on valve element  18  which tends to move the valve element away from its seat, for a purpose to be discussed below. 
     Cylinder housing  12 , shown best in FIG. 7, comprises a tubular cylindrical body having an open end  12   a  and an opposed closed end  12   b  and formed with a bore  12   c  having an enlarged diameter portion  12   d  over a first axial length with a tapered transition wall  12   e  which interacts with tapered wall portion  14   e  of piston sleeve  14  to limit inward axial travel of the piston into bore  12   c . A second axial length portion has a still larger diameter portion  12   f  which is adapted to receive enlarged diameter  14   d  of piston sleeve  14  upon movement of the piston to that axial position which allows sections  14   b  of the piston to spread apart to a normal spread apart position. A third axial length has a surface portion  12   g  having a slightly smaller diameter than portion  12   f  and is formed with an abrupt transition surface  12   h  therebetween. A circumferential groove  12   i  is formed slightly inboard of open end  12   a  which is adapted to receive tabs  14   k  which extend radially outwardly from piston sleeve  14  a distance which causes an interference fit with surface portion  12   g  even when sections  14   b  are compressed together. With reference to FIG. 1, piston  14 , rope gripping split sleeve  16  and line  2  are received in bore  12   c  with one, two or three O-rings, as desired, (not shown) received in grooves  14   c , as discussed above, ready for use. 
     In situ, whale release device  10  is attached to fishing gear such as lobster traps (not shown) via coupling  12   k  with line  2  extending up to a suitable buoy (not shown) or the like. In the FIG. 1 position, face  14   s  of the piston is closely adjacent to closed end  12   b  of cylinder bore  12   a  with its inward movement limited by the interaction of tapered wall portions  14   e  of piston  14  and  12   e  of cylinder housing  12 . Line  2  is tightly grasped by split sleeve  16  with a radially inward force applied to split sleeve  16  through axially extending sections  14   b  of piston  14  which are constrained by bore portions  12   d  and  12   g  and with tabs  14   k  received in bore portion  12   f  without any interference. The assembly will remain in the FIG. 1 position indefinitely with a pull force of up to approximately 300 pounds exerted on line  2  caused by ocean currents, wind, tides, waves, drag encountered in returning gear to the ocean, and the like. 
     In the event that a pull force is exerted on line  2  in excess of the above noted level, for example 1000 pounds, a timed release is initiated. As seen in FIG. 11, split sleeve  16  moves within the bore formed by axially extending sections  14   b  with the taper  16   n ,  16   o  of the split sleeve moving against the opposite taper  14   m ,  14   n , respectively, thereby squeezing line  2  to a greater extent, with ribs  16   k  biting further into the line, until a maximum squeezing action is obtained when distal end portions  16   m  butt up against transition surface  14   t  of the piston. As shown, the total travel of split sleeve  16  is approximately 1.25 inches, however the specific length is a matter of choice. Up to this point piston  14  has not moved relative to cylinder housing  12 . 
     With reference to FIG. 12, as the pull force continues, the force is transferred directly to transition surface  14   t  of piston sleeve  14  through distal end portions  16   m  and the piston starts to move outwardly with tabs  14   k  forming an interference fit with diameter portion  12   g  and being forced to move through that portion. The amount of interference is chosen so that there is only a slight flexing of tabs  14   k  and with eight tabs, as shown, the particular number being a matter of choice, a significant amount of force is required to continue such movement. It has been found that an interference of approximately 0.004 inch is suitable. Outward movement of piston sleeve  14  is also resisted by vacuum created between face  14   s  of the piston and the closed end of bore  12   b . Movement of the piston is enabled by sea water which is sucked through orifice  18   a  which, as stated above, has a size which is chosen so that its opening is sufficiently small that a selected time delay is obtained for the piston to travel to the FIG. 13 position where enlarged diameter portion  14   d  of piston sleeve  14  is received in enlarged diameter bore portion  12   f  of cylinder housing  12  and enlarged portion  14   g  is disposed outside of the cylinder bore thereby allowing sections  14   b  to spread apart and split sleeve portions  16   b ,  16   c  to relax and release line  2  with no knots or plastic components attached to the line. Tabs  14   k  are received in groove  12   i  which serves to prevent further outward movement of piston  14  now that the pull force has been removed. The specific time delay for the release is dependent upon the level of the sustained pull force exerted on line  2  but typically a 1200 to 1500 pound load will result in a time delay of 20 to 30 minutes. The length of the delay can be adjusted by the number of O-rings used in grooves  14   c  of piston  14 , the size of orifice  18   a  in valve element  18  as well as the friction of the side walls. 
     In retrieving from the ocean, traps and other gear attached to whale release device  10 , a partial release may occur, particularly if the line becomes ensnared by obstacles on the sea bed, such as rock formations. In order to reset release device  10 , piston  14  is pushed inwardly to force water that has accumulated in bore  12   c  between the piston and the closed end of the bore. Valve member  18  is urged away from its seat by the spring action of bladder  22  allowing water to freely pass through openings  22   d ,  22   e  of the bladder and past valve member  18  which has an outer diameter less than that of recess  14   p . A reset mechanism for this purpose is shown in FIGS. 14-17 which comprises first and second punch members  24 , 26 , respectively. First punch member  24  shown in FIG. 15 has an elongated tubular member  24   a  and is formed with a line receiving slot  24   c  extending the length of tubular member  24   a and into head  24   b . Second punch member  26  has a first bore  26   a  adapted to slidingly receive elongated tubular member  24   a  therethrough and which opens to a second, larger bore  26   b  which is adapted to receive head portion  24   b . A slot  26   c  extends through the side wall of punch member  26  in communication with bore  26   a  along its entire length and in communication with bore  26   b  along a portion of its length. Second punch member  26  is provided with a circular flange  26   d  on its end face  26   e , the flange having an inclined camming surface  26   f . The axial length of head  24   b  is longer than the axial length of bore  26   b  for a purpose to be described. In use, elongated tubular portion  24   a  is inserted into bore  26   a  with the slots  24   c ,  26   c  aligned and the reset mechanism is positioned against whale release device  10  with line  2  received through the slots. The distal end of elongated tubular portion  24   a  is placed in contact with distal end portions  16   m  and head  24   b  is then struck with a mallet or the like to move split sleeve and line  2  all the way back into the cavity of piston  14 . Camming surfaces  26   f  then come into engagement with inclined surfaces  14   i  of sections  14   b  and moves the sections radially inward toward each other allowing transition surface to pass into diameter portion  12   g  of bore  12   c . Further hitting of head  24   b  will transfer force to transition surface  14   o  via distal end portions  16   m  of split sleeve  16  moving the piston back to the FIG. 1 position. The punches then can be easily removed due to slots  24   c ,  26   c.    
     Whale release devices  10  have been made in accordance with the invention just over 9 inches in length so that they are compact, easy to handle and require minimal storage space. 
     In the embodiment of FIGS. 1-13 operation of the whale release device is based on creating a partial vacuum. With reference to FIGS. 18-23 a , a second embodiment is based on creating compression. Cylindrical, tubular housing  112  is formed with a bore  112   a  formed with spaced apart threaded portions  112   b ,  112   c  which respectively receive a threaded cylinder end plug  114  to form a closed end of bore  112   a  and a threaded annular guide plug  116  creating a chamber  112   d  between the two plugs. Axially extending recesses  114   a ,  116   a  are formed in respective end faces of the plugs to facilitate installation. Suitable Teflon tape or the like is placed between the threads to form an effective fluid seal. 
     Piston sleeve  120 , best seen in FIG. 21, comprises a head or body portion  120   a  having an outer diameter selected to be slidingly received in bore portion  112   e  of housing  112 , slightly larger than bore  112   a . Piston sleeve  120  is formed with axially extending sections  120   b , corresponding to sections  14   b  of piston sleeve  14  of the first embodiment described above. Axially extending decreased outer diameter portions  120   c ,  120   d  are formed in the outer circumferential surface of piston sleeve  120  with a tapered transition surface  120   e ,  120   f , respectively on the outboard end of the decreased diameter portions, i.e., on the right side as viewed in FIG.  21 . Inclined surfaces  14   j  are formed on the end face, as in the first embodiment, for resetting as described above. Head portion  120   a  is formed with a threaded, coaxially extending bore  120   g.    
     Piston rod  122  has a threaded end  122   a  at one end received in threaded bore  120   g  of head portion  120   a  and a piston head  122   b  at its opposite end. As best seen in FIG. 22, piston head  122   b  is formed with circumferential grooves  122   c  in which are received high pressure flexible seal members, such as Parker U-shaped seals  124  with an optional back-up ring  124   a . U-shaped seals  124  are formed with legs  124   b  which spread apart when exposed to high pressure on the side facing the opening between the legs. A threaded bore forming a recess  122   d  is formed in the inbound end face of piston head  122   b  with first and second fluid channels  122   e  extending from the outer peripheral portion of the inner end of the recess to the outboard end surface  122   f . A fluid loading channel  122   h  extends centrally from recess  122   d  through piston rod  122  to an axially extending threaded bore  122   k , to be discussed below. 
     A threaded piston plug  126 , received in threaded bore  122   d , has a coaxially extending stepped bore having larger diameter portion  126   a  extending from recess  126   c  on the inboard end side of piston head  122   b , coupled to smaller diameter portion  126   b  extending from end face  126   d  of plug  126 . An umbrella valve member  128  having a stem  128   a  formed with an enlarged bulb portion  128   b  intermediate its ends, extends from a flexible flap  128   f . Stem  128   a  is pulled through bores  126   a ,  126   b , stretching the stem and allowing bulb portion  128   b  to pass through and snap in place beyond the smaller diameter bore  126   b . A plurality of bores  126   e  extending from recess  126   c  to end face  126   d  are formed through plug  126  closely adjacent to the stepped bore. Flap  128   f  will allow flow through the valve when the piston is moved toward the closed end but will prevent fluid flow when the piston moves in the opposite direction. A small diameter bore  126   f  is formed through plug  126  from end face  126   g  to end face  126   d  near its outer periphery at a location out of alignment with flap  128   f  of the umbrella valve element. An open ended tubular needle  130  (FIG.  21 ), formed of suitable material such as stainless steel, is placed in bore  126   f  and sealed therein with suitable epoxy material. Needle  130  is formed with an internal diameter bore and length selected to provide a selected rate of fluid flow for fluid having a given viscosity. The internal diameter can typically range from approximately 0.003 inch to approximately 0.010 inch. When using a fluid such as corn oil, an internal diameter bore of 0.003 inch has been found to be suitable. 
     Piston rod  122  is received through the bore of annular guide plug  116  which is provided with U-shaped seals  132 , similar to seals  124 , disposed so that the legs face chamber  112   d , which are biased against the piston rod. Chamber  112   d  is filled with fluid having a selected viscosity, such as corn oil referenced above, and then bolt  136 , with washer  134 , is used to close channel  122   h  and fixedly attach piston rod  122  to piston sleeve head  120   a.    
     As in the first embodiment, the end of a rope is received in rope gripping split sleeve  16  disposed in bore  141  of piston sleeve  120  in the released or open position, FIG. 18, and set to the closed position, FIG.  20 . Pulling on rope  2  then causes the split sleeve  16  to move against the tapered surfaces to further compress and firmly grasp the rope with the ridges of ribs  16   k  biting into the rope. 
     When a further force, caused by a whale caught in the fishing gear attached to the release device, pulling the fishing gear up to the surface by a fisherman, or the like, is applied to the rope, the rope gripping split sleeve travels against the taper until it butts against surface  14   t  of piston sleeve  120  (FIG. 19) and pulls the piston sleeve and piston head  122   b  outwardly creating pressure on the fluid in chamber  112   d  forcing flap  128   f  of the umbrella valve against end face  126   d  closing the valve and forcing fluid through metering needle  130  to allow movement with the rope finally being released when the outer portion  120   h  passes beyond the end of housing  112  as shown in FIG. 18, thereby resulting in a timed release dependent upon the particular force level transferred. 
     In the case where a fisherman hauls the fishing gear onto the deck of a boat, the piston mechanism has generally moved to some extent from the closed position and is reset using the reset mechanism shown in FIGS. 14-17, discussed above in which the rope gripping split sleeve  16 , piston sleeve  120  and piston  122   b  are moved to the closed FIG. 20 position. 
     With reference to FIGS. 23,  23   a , it is preferred to provide a means to prevent movement of the piston assembly until a selected pulling force on the rope has been exceeded, similar to the function of tabs  14   k  in the first embodiment. Such means prevents winds, currents and the like from causing gradual movement of the piston over time. Piston head  122   b  is preferably formed with longitudinally extending flange  122   m  having a radially, inwardly extending lip  122   n  at the free end thereof. Flange  122   m  is receivable in an annular recess  116   a  formed with a cut-away notch portion  116   b  which interfits with lip  122   n . The interfitting lip and notch will lock piston head  122   b  in the closed position until a selected force, e.g., 200 lbs, is applied to the rope. It will be appreciated that flange  122   m  and lip  122   n  could be formed as spaced fingers, if desired. 
     This embodiment provides higher pressure—up to 2,000 psi—to more easily provide any required holding force. The closed fluid system is particularly advantageous in that it is free of possible contaminants which might occur when using sea water as in the first embodiment, e.g., sand, salt, etc. Release time is based on the viscosity of the fluid used as well as the internal diameter of the bore of needle  130 . When a fisherman pulls up his gear from the water he has a given amount of time, based on the particular level of force used, to get it on deck before the device releases. This time can be easily varied by using a needle with a different internal diameter bore and length as well as using fluid having different viscosity. 
     Although the invention has been described with regard to specific preferred embodiments thereof, variations and modifications will become apparent to those skilled in the art. It is therefore, the intention that the appended claims be interpreted as broadly as possible in view of the prior art to include all such variations and modifications.