Abstract:
This invention provides a method of providing a barrier coating over the surfaces of a plurality of sinkers ( 10 ), each having a line passageway ( 21 ) therethrough, and to sinkers ( 10 ) having a barrier coating ( 25, 27 ) over the exposed surfaces thereof including the line passageway ( 21 ). According to the invention, sinker bodies ( 11 ) are pressed from metal iron powder and immersed to paint the line passageway ( 21 ). The external surface of the body ( 11 ) is then cleaned so that the sinker may be handled leaving the passage coating ( 26 ) intact. The body is conveyed through successive spray stations at which opposite sides are painted and rolled over between painting stations for this purpose. Different barrier coatings such as epoxy coatings may be applied to the line passageway and the exterior surface.

Description:
This invention relates to weights and sinkers and methods of manufacturing same. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention has particular application to sinkers for underwater use, such as those used for fishing lines and as weights for diving belts and the like. Such weights and sinkers will hereinafter be referred to collectively as sinkers. 
     Large quantities of lead are used to manufacture sinkers, especially for fishing lines and nets and the like and for diver&#39;s weight belts. Sinkers are mostly formed from lead which is toxic and are often manipulated by hand and thus they expose many persons, and especially young persons, to potential contamination from the lead from which they are formed. Furthermore, many sinkers, and particularly fishing line sinkers are lost during use and litter the beds of fish habitats. This constitutes a significant contamination of fish habitats which is difficult to remove or reduce. 
     The present invention aims to alleviate at least one of the above disadvantages and to provide sinkers and methods of manufacturing sinkers which will be efficient in use. 
     BRIEF SUMMARY OF THE INVENTION 
     With the foregoing in view, this invention in one aspect resides broadly in a sinker having a non-toxic metal body provided with a line passageway therethrough and a non-toxic barrier material coating all surfaces of the sinker body whereby the body material is isolated from interaction with the surrounding atmosphere or water. 
     The sinker bodies are preferably formed from steel and may be formed by being supplied as cylindrical steel billets fed randomly to a forge in which the billet is forged between heads having part-spherical cavities into a substantially spherical shape and finished with a passageway therethrough. Alternatively the sinker bodies may be cast from steel or iron or folded or formed from blanks about a mandrel or in such a manner that a line passageway remains through the formed body. 
     Preferably the body is formed from non-toxic metal powder which may be ferrous or non-ferrous metal powder. Advantageously, the body is formed from a non-toxic magnetic material so that lost sinkers, especially in an underwater environment in a localised fish habitat, may be readily recovered by scanning with a suitable magnet to recover the sinkers. 
     In the preferred form the body is formed from compressed iron powder and more preferably iron powder which contains a lubricant such as zinc stearate and which is sintered to at least some extent to increase its resistance to breakage due to impact. Suitably the iron powder is compressed at a pressure of about forty-five tons per square inch, providing a decrease in volume of the iron powder of about two and one-half times. 
     Suitably the compressed powder metal body is formed in a cylindrical passage in a die into and/or through which opposed punches move to compress a measured quantity of metal powder therebetween. 
     Preferably one punch supports a reciprocable pin about which the metal powder is compressed and the opposing punches are moveable through the die after the pressing process to remove the compressed body from the cylindrical passage. Thereafter the pin is withdrawn into its supporting punch to dislodge and discharge the compressed body therefrom 
     It is also preferred that the compressed powder metal body discharged from the compression means be sintered in an oven for increasing the strength of the body. The body may be sintered in known manner at high temperatures in the order of 1100° C. in an oven in the presence of an inert gas such as nitrogen which flows through the oven. 
     Preferably however where the metal powder is iron powder, the sintering process is performed as a low temperature process in which the temperature in the oven is maintained below that which will cause visible oxidisation of the body such that the presence of an inert gas is not required. This also enables a relatively low cost bell-type oven to be utilised. 
     Preferably the sintering process is performed in the range of 350° C. to 800° C. for about thirty minutes so that the sintered body is generally capable of withstanding a throw-down test onto a concrete floor. Bodies tested in this manner prior to the sintering process mostly fail and shatter. 
     It is further preferred that the barrier material is a non-metallic coating material which is inert in its intended environment. However the coating may be an electroplated coating. 
     The barrier material is preferably a coating applied to the body in liquid form or spray form but it may be applied in powder form and bonded thereto. The barrier material is suitably a polymer coating which when cured exhibits properties of chemical resistance and toughness. It may be a polyurethane resin coating or water reducible one or two pack polyurethane coating or a combination thereof. 
     The barrier material may be applied in a process such as that described in our co-pending International patent application No. PCT/AU96/00775 or it may be applied as described below. 
     Preferably the coating material is suitable for application directly to the body but if desired it may be applied to a primed body primed with a compatible primer. A preferred barrier coating is an epoxy resin coating applied to the sinker body. The epoxy resin coating may be a water reducible coating or a conventional two-part epoxy resin coating. 
     Preferably the coating for the line passage is less resistant to degradation in an underwater environment than the coating on the outer surface of the body such that in time the passage coating will degrade and expose the metal body to the degrading effects of an underwater environment, especially a saltwater environment. 
     For this purpose the line passage is preferably coated with a water reducible paint such as a water reducible epoxy resin and the outer surface of the body is coated with a conventional two-part epoxy resin This provides a tougher outer surface to withstand abrasion and impact from which the line passage is shielded. Thus a long shelf life may be achieved together with a reduced underwater life. 
     In a further aspect it is preferred that the sinker adapted for use with fishing line be coated with a coloured or a selection of barrier material colours which is selected for either camouflaging the presence of a sinker In an underwater fish habitat or for providing a fish attractant. As a fish attractant, the barrier material may include metal flakes or like particles of a distinctly different colour to the base coating which sparkle or reflect light. The base coating may also be a multi coloured coating. 
     In yet a further aspect this invention resides broadly in a method of providing a barrier coating over the surfaces of a plurality of sinkers each having a line passageway therethrough, the method including: 
     submerging the sinker in a bath of coating liquid able to flow into and coat the line passageway; 
     withdrawing the sinker to a cleaning station at which the coating liquid is substantially removed from the external surface of the sinker; 
     arranging the sinkers in spaced apart relationship on a conveyor; 
     painting the portions of the sinker exposed above the conveyor with a barrier coating and causing the coating to harden; 
     rolling the sinkers along on said conveyor to a position at which the sinkers are supported on the conveyor on their painted side; 
     painting the newly exposed portions of the sinker with a barrier coating and causing the coating to harden. 
     Preferably the painting operations are performed automatically at separate spray paint stations and the sinkers are transported to the spray paint stations on the conveyor. It is also preferred that the sinkers be fed randomly from the cleaning station to location means at which the location means provides separate locating positions in space apart relationship for receiving individual sinkers and being disposed above the conveyor, and the location means is operable to deposit the located sinkers onto the conveyor in aligned closely spaced rows of sinkers. 
     Preferably the painting operations are performed automatically at separate spray paint stations and the sinkers are transported to the spray paint stations on said conveyor. 
     It is further preferred that the conveyor assembly is a belt type conveyor having a consumable layer of sticky faced material, such as automotive fire rated masking tape, which receives sinkers in the pattern formed by the primary location means and positively holds the sinkers In that pattern. When supported on this layer the freshly part painted sinkers may be passed through a heating zone for quick hardening of the paint. 
     Suitably the pattern has the sinkers arranged in staggered rows whereby a minimum space of about 2 mm may be maintained between adjacent sinkers. This allows the upper surface of the sinkers to be spray painted without concern for the sinkers moving and contacting one another. 
     It is further preferred that in the rolling process all but the leading or trailing row of sinkers are rolled along the sticky faced material onto the unpainted sticky space previously occupied by another adjacent sinker whereby they are again positively located in spaced apart relationship for 
     further treatment painting. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In order that this invention may be more readily understood and put into practical effect, reference will now be made to the accompanying drawings which illustrate a typical embodiment of the invention adapted for coating fishing line sinkers and wherein: 
     FIG. 1 provides a series of diagrammatic cross-sectional views showing the punch and dies operations, where in FIG. 1A illustrates the filling of the metal power; FIG. 1B illustrates closure of the punch; FIG. 1C illustrates compression of the metal powder; and FIG. 1D illustrates removal of the formed sinker from the die. 
     FIG. 2 is a diagrammatic elevational view of a preferred form of painting apparatus; 
     FIG. 3 is a diagrammatic plan view of the painting apparatus; 
     FIG. 4 is a perspective view which illustrates the sinker locating apparatus; 
     FIG. 5 illustrates the roll-over process for the part painted sinkers and 
     FIG. 6 is a cross-sectional view of a round sinker made in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION 
     The sinkers  10  of this embodiment each have a body  11  formed from fine iron powder which is compressed under high pressure, in the order of 45 tons per square inch, in a cylindrical passage  12  provided in a die  13  into and/or through which upper and lower cupped punches  14  and  15  move to compress a measured guantity of iron powder therebetween. 
     While the upper bolster of the punch supports a plurality of punch members  14  and the die has a corresponding number of passages  12  and lower punches  15 , for illustrative purposes reference will be made to the operational sequence of one punch and die set. 
     The upper punch  14  supports a reciprocable pin  16  having a lower extension  19  about which the metal powder is compressed. The lower punch  15  also supports a moveable pin  18  which is biased by spring means, not shown, into a blanking position across the upper end of the passage  17  within which the lower pin is constrained for movement. 
     The cupped lower punch  15  commences a cycle by closing the passage  12  for receipt of the measured quantity of metal powder within the passage  12 . As illustrated in FIG. 1A, the upper punch  14  is clear of the die for this filling operation and the lower pin  18  blanks off the upper end of the passage  17 . 
     After filling, the upper punch  14  with the pin  16  extended therefrom is engage within the passage  12  and moves therethrough to locate the lower end of the pin  16  in the corresponding passage  17  extending from the floor of the lower punch  15 . As this passage  17  is normally closed by the upper end of a closure pin  18 , the upper pin  16  must displaces the lower pin  18  for receipt in the upper end of the passage  17 . 
     Thereafter continued movement of the punches  14 ,  15  towards one another, as illustrated in FIG. 1C, compresses the metal powder to approximately two fifths its uncompressed volume to form the substantially spherical sinker  10  about the pin  16 . This pressing operation forms a very dense polished skin which mirrors the polished moulding surfaces of the punches  14 ,  15 . 
     Punches with other than semi-spherical recesses therein may be utilised to form bean shaped or conical ended sinkers if desired. 
     After the sinker body  11  has been formed, the lower punch  15  is pushed upwardly through the die  13  to force the sinker body from the passage  12 . The sinker body  11  is then carried on the pin  16  until the pin is retracted through the punch  14  to discharge the body  11  which is collected for sintering. This is Illustrated in FIG.  1 D. 
     The sintering process is carried out as a batch process in a bell oven at about 350° C. Heating continues for about thirty minutes before the sintered bodies are discharged directly into the atmosphere for relatively quick cooling. At this elevated temperature noticeable oxidising of the bodies does not occur, however the strength of the green bodies from the pressing process is greatly enhanced. Typically the sintered bodies will withstand a throw down test onto a concrete floor whereas the green bodies will not 
     The bodies  11  are then ready for coating to form a sinker  10  in accordance with the present invention as illustrated in FIG.  6  and having a body  11 , a line passage  21  therethrough which is painted with a water reducible epoxy paint  26  and an exterior surface  27  painted with a two part epoxy resin. 
     Referring to FIGS. 2 to  5  it will be seen that the illustrated coating process is utilised to coat round sinker bodies  11  formed with a line passageway  21  therethrough to enable the sinkers to be threaded onto a fishing line. The coating process is performed in two stages as the sinkers pass continuously along a belt conveyor assembly  22  covered in sticky paper. 
     The coating apparatus  30  includes a dipping station  31  at which a water reducible epoxy paint is caused to coat the line passage  21 , a paint stripping station  32  at which the paint is stripped from the external surface of the sinker bodies  11  leaving the line passage coating intact, a sorting and location station  33  to which the sinkers are randomly fed from the dipping station into the open upper end of the hopper  29  and sorted into staggered rows of sinker bodies  11  in a recessed roller  34 , a transfer station  35  at which the aligned rows of sinker bodies  11  are fed on a conveyor  36 , a first spray painting station  37  through which the sinker bodies  11  are fed to coat their exposed upper side, a first curing station  38  at which the part-painted bodies  11  are heated to about 120° C. for a few minutes, a air cooling station  39 , a rolling station  40  at which the sinkers are rolled, as at  58  along the conveyor to expose their unpainted side, a second spray painting station  41  followed by a further curing station  42 , cooling station  43  and a stripping station  44  at which the painted sinkers  10  are stripped from the conveyor  36 . 
     The dipping station  31  includes a barrel  45  having its lower portion containing a water reducible epoxy bath  46 . The barrel  45  is provided with an internal collector fin  49  fixed thereto and is rotated about its axis by a belt drive assembly  48  such that sinkers may rest in the bottom of the barrel  45  submerged in the bath  46  awaiting engagement by the collector fin  49 . 
     The fin  49  extend inwardly and in the direction of rotation of the barrel  45  so that, during its rotation sinkers will be retained behind the collector fin  49  and carried to an upper position from which they will spill onto a guide  50  for delivery to the paint stripping station  32 . At this station uncured paint on the outer surfaces of the dipped sinkers will be stripped by engagement with the constantly wet abutting rollers  51 ,  52  which contra-rotate and between which the sinker bodies  11  are conveyed. 
     The cleaned sinkers fall from the rollers  51 ,  52  into a collection bin  20 . In this operation, any membrane which may have formed across the line passageway  21  will rupture upon impact at the collection bin  20 . 
     As illustrated in FIG. 4, sorting and location station  33  is disposed at the lower end of a guide chute  55  which accepts the feed from the dipping station  31  via the collection bin  20 . At the bottom of the chute  55  there is provided a roller  34  having a perforated surface formed by staggered rows of recesses therein, each capable of holding a single body  11  and transferring the held bodies to a lower position, adjacent the leading end of the conveyor  36 , from which the sinker bodies fall uniformly thereto. 
     For sinkers of elongate form the recesses in the roller  34  have their longitudinal axis disposed parallel to the roller axis so that the sinkers may be rolled in unison along the conveyor  36 . 
     A consumable roll of automotive fire-rated masking tape  60  is supported beneath the conveyor  36  and is fed, sticky side up onto the conveyor belt to cover and move with the conveyor  36 . Sinker bodies falling thereon will not roll from their impacted position so that the order of the bodies  11  in the roll will be maintained. 
     For this purpose the surface speed of the roller  34  is substantially the same as the conveyor  36 . The apertures  56  are arranged in staggered rows  57  with a minimum spacing of about 2 mm between apertures  56 . 
     The staggered rows of bodies are carried through a first spray paint enclosure of conventional form with filters and extraction pumps. The masking tape  60  shields the conveyor belt and ensures the sinker bodies remain in formation during painting of the upper surface of their bodies. 
     After cooling during passage past the curing station  38 , at which the temperature is maintained at about 120° C., and the cooling station  39 , the part-painted bodies  11  are engaged with a relatively short overhead belt  24  driven independently by a motor and drive assembly  25  and which travels slightly faster than the conveyor  36  so as to cause the bodies to roll along the masking paper to be supported on their painted side and suitably in the sticky space vacated by another sinker. The speed of the belt  24  may be controlled to roll the sinkers one half turn or any number of turns onto their painted side to align with unpainted patches of paper for adherence thereto as required. 
     In this manner the fixed relative position of the bodies  11  on the covering tape  60  is maintained for passage through the second automatic spray paint booth  41  where the unpainted side of the sinkers are painted, suitably with a different colour to the opposite side. After passing through the further curing station  42  and cooling station  43 , the sinkers strike a bar which strips them from the tape  60  and delivers them to storage bins. 
     A sprinkling station, not illustrated, may be disposed between the second painting booth  41  and the curing station  42  for sprinkling glitter onto the uncured painted surface of the sinker. This will enhance the appeal of the sinkers, as it provided the potential to attract fish. The drives for the various components are computer controlled and are selectively variable to enable different settings to be readily configured for different production runs. 
     The coated steel or like material sinkers of this invention may be manipulated by adults and children without concern about possible contamination and resultant health effects. Furthermore such sinkers will not runt and will be suitable for long term storage and re-use in a fisherman&#39;s tackle box even in an adverse salt water environment. 
     In addition, sinkers lost in a fish habitat and coated with an inert material, such as the epoxy resin coating as described above, will not provide a toxic input to the fish habitat. However in the event that the coating be ruptured or degraded over a period of submersion, the steel body will relatively quickly degrade without contaminating the habitat to the same extent as would conventional lead sinkers. In addition recovery of concentrations of discarded iron sinkers can be effected using magnetic recovery techniques. 
     It will of course be realised that while the above has been given by way of illustrative example of this invention, all such and other modifications and variations thereto as would be apparent to persons skilled in the art are deemed to fall within the broad scope and ambit of this invention as is defined in the appended claims.