NZ512101A

NZ512101A - Self resetting pest control trap using pyrotechnics to provide a lethal blow to the pest's head

Info

Publication number: NZ512101A
Application number: NZ51210101A
Authority: NZ
Inventors: Peter Jeffrey Allen
Original assignee: Peter Dyer; Peter Jeffrey Allen
Priority date: 2001-06-01
Filing date: 2001-06-01
Publication date: 2004-06-25

Abstract

A resettable humane trap for killing animals, particularly but not exclusively for possums, wherein the trap includes means for storage and dispensing of dispensable explosives material into an internal chamber, means capable of sensing a head of an animal when within the trap. The trap includes means for generating at least one explosion within the internal chamber and a killing mechanism having a biased movable member coupled to a moveable wall of the internal chamber, the movable member is capable, on rapid movement driven by an explosion within the chamber of moving from a ready position and delivering a lethal blow to said animal head. The movable member being biased so as to be returned to a ready position, and the trap reset means including a plurality of apertures opening into the internal chamber, and an aperture to allow the killed animal to fall from the trap.

Description

<div class="application article clearfix" id="description"> 1 512101 Patents Form No. 5. Patents Act 1953 Complete after Provisional Specification. \ self resetting pest control trap I, Peter Jeffrey ALLEN, of RD 1 Whakapirau Road Maungaturoto, 0581 Northland New Zealand, a New Zealand citizen, do hereby declare this invention to be particularly described in the following statement: iteiim&a! Property QSm> of N.Z. 29 2002 eceived intellectual property office OF N.Z. 12 MAR 2004 received TITLE self resetting pest control trap FIELD This invention relates to a trap, and in particular to a humane self-resetting trap for agricultural or conservation pest control, where the pests are small mammals such as (but not limited to) possums, stoats and ferrets. BACKGROUND A particular stimulus to invention is the problem faced in New Zealand where the introduced Australian brushtailed possum, Trichosurus vulpecula has few natural predators and as a result it is estimated that some 70 million possums now exist here, where they (a) 10 consume native trees, often killing a specific tree, (b) eat grass intended for farm animals, (c) are known to eat native bird nestlings, and in particular (d) carry bovine tuberculosis which is a very important zoonosis and a threat to farm exports. A much greater scale of eradication programme than can be mounted is required in order to make a significant dent in their numbers. The species is surprisingly resistant to eradication considering that it is 15 almost endangered in its native land. Possum eradication is a matter of great economic importance. Methods under use or consideration include trapping, shooting, poisoning, introduction of disease vectors, and genetically engineered diseases, also sterilisation. Apart from poisoning by air drops of 1080 (sodium monofluoroacetate), trapping is one of the most widely used of 20 current methods yet almost all traps include the objection that they have to be visited and emptied after each kill. Many traps such as gin traps are notably inhumane. Many traps are not specific and are likely to catch native species such as kiwi, morepork, weka, and the like, some of which are endangered. Possums are not the only small mammal that presents a problem in the New Zealand bust. 25 Mustelids (stoats and ferrets) wild cats, rats, and wild dogs also are the target of extermination programmes from time to time. PRIOR ART A survey of the prior art shows little comparable art. US 4640043 is a mole trap; it is a single-use trap having an explosive action obtained by a process of pucturing a distended 30 bag, not by "pyrotechnics". US 4213265 is a pyrotechnical mole trap; it is able to be used twice before having to be dug up and reset. Similar traps are cited therein. In the class of self-resetting traps, including "multiple-catch traps" the "large bucket under a slippery pole" group (eg US 4748766, US 4876821, US 5996274) is well known. For complexity, see US 4669216. US 5918409 teaches a resettable electrocution trap for animals in a tunnel. It has an 35 elevator mechanism to lift out the electrocuted rat. US 4418493 is similar. In contrast the present invention is (a) explosive; using pyrotechnics, (b) multiple-use and self-resetting, and (c) self-clearing after each use. OBJECT It is an object of this invention to provide an improved trap suitable for trapping vermin, or 40 at least to provide the public with a useful choice. STATEMENT OF INVENTION In a first broad aspect this invention provides a humane and automatically resettable 14- pest control trap, wherein the trap is powered by chemical energy released in an explosion, and wherein a process of actuation of the trap may be repeated indefi 45 nitely. Preferably the chemical energy is released in incremental portions from a store. In a related aspect this invention provides a humane trap for animals; in particular but not exclusively for possums, wherein the trap includes animal head sensing means capable of sensing a head of an animal when within the trap and animal 50 destruction means having a wait state, an active state, and a reset state; the wait state comprising availability of a chemical explosive material, presence of a form of energy, presence of a path capable of carrying the form of energy from the animal head sensing means to (a) means for releasing an aliquot of the explosive material, and (b) means for initiating an explosion in a chamber, and a mechanism in a 55 position ready to administer a lethal blow to the head; the active state comprising production of an explosion in a chamber within the mechanism thereby producing a 3 compressed gas capable of driving a moveable member at the animal head; the reset state comprising return of the moveable member to the ready position, dissipation of the burnt gas, and reflex withdrawal of the animal from the trap; so that the 60 humane trap is capable of operating more than twice without attention. Preferably the "form of energy" is electricity, the "path" is an electric circuit, and preferably the explosion is triggered by an electric current, caused to flow by closure of an electric contact or proximity switch located at a specific place in relation to the bait and the path of the knife. 65 Preferably a microswitch is used as a proximity switch to detect an animal's presence. In a first subsidiary aspect, the explosion is created within a mixture of an explosive gas and air, inside a chamber; one wall of which is formed by a piston connected to the moveable member. 70 Preferably the explosive gas is supplied as an aliquot from storage means through electrically controlled gas release means. Preferably the explosive gas comprises a gas selected from the range of methane, propane, butane, LPG, CNG, and acetylene. Preferably the explosion is initiated by an electric spark; the spark being generated as 75 a result of current flow within a circuit including a proximity sensing means. In a second subsidiary aspect, the pyrotechnic explosion is created by detonation of an explosive charge inside a chamber one wall of which is formed by a piston. Preferably the or each explosive charge comprises a manufactured item stored in a reservoir comprising a magazine and capable of being detonated by impact at a 80 mechanically sensitive end. In a third subsidiary aspect the lethal blow is applied by a blade, in the manner of a captive bolt, pushed by the force of the explosion against the rear of the head of the animal; the head being aligned by virtue of the position of the proximity sensing means in relation to an entry portal of the trap when the proximity sensing means is 85 activated. 4 Optionally the alignment of the head of the animal is assisted by means of position restricting means at each side of the head. In a fourth subsidiary aspect the body of the animal is removed downward from the trap by its own weight. 90 Preferably the trap is laid out in a vertical axis, wherein the bait station is at a lower end of a vertical structure and inside a cavity designed to restrict access to the target species, the retractable striking knife is fired downwards, and the whole trap is fixed above the ground so that animals killed fall away from the trap, sometimes aided by reflex convulsions arising from the damage to the nervous system. 95 PREFERRED EMBODIMENT The description of the invention to be provided herein is given purely by way of example and is not to be taken in any way as limiting the scope or extent of the invention. DRAWINGS 100 Fig 1: is a diagram showing a trap according to the invention, powered from a gas cartridge. Fig 2: is a diagram showing the trap of Fig 1 in side view. Fig 3: is a diagram showing a trap according to the invention, powered from a blank eg "Ramset" cartridge. 105 Fig 4: is a diagram showing the magazine of Fig 3 from above. EXAMPLE 1 - Gas driven resettable humane trap This version of the invention employs chemical energy released in an explosion of propane gas (or the like) and air, the propane being stored in a cylinder, released under solenoid control, and mixed with air just before detonation. Refer to Fig 1. The effect of the 110 explosion is to cause a retractable striking knife to be impelled downward and into the head of the animal which at the instant that the explosion is set off is located beneath the knife at 5 5 position X. The trap 100 is laid out in (usually) a vertical axis, wherein the bait station is at a lower end of a vertical structure and inside a cavity designed to restrict access to the target species, the retractable striking knife is fired downwards, and the whole trap is fixed above 115 the ground perhaps on a tree stump, so that animals killed fall away from the trap and stray ground foragers which could otherwise blunder into the trap (such as kiwi, weka, etc) do not accidentally die. Means to fix the trap to a support are not shown here. In Fig 1, 100 is the outer wall of a cylinder, within which a piston 115 is from time to time driven down by an explosion in the space 128 above, the explosion being of an air-gas 120 mixture. The gas is typically propane or the like supplied from a cylinder or canister 120 having a valve 121 connected to a solenoid valve 109 through a regulator 110, so that a set amount, portion, or aliquot of gas is rapidly delivered through the nozzle 107 into the space 128 when the solenoid 109 is activated through wires and a circuit-closing momentary action type switch 124 connected to a battery 119. At the same time an ignition coil 108 the 125 primary winding of which is also connected through the switch generates a pulse of high-voltage electricity led to the spark plug 106; the resulting spark igniting the gas-air mixture inside the chamber 128. Optionally the "make" of the switch opens the gas-admitting solenoid, and the "break" generates an ignition spark very soon after. It will be appreciated the the gas is not liberated during the "wait state" of the trap. 130 The circuit-closing switch 124 is preferably a type of microswitch having an extended operating arm 125 located at a specific place in relation to the bait and the path of the knife. Restoration of air within the chamber 128 is provided for by the apertures 102 (preferably about 7 are provided) in the cap 101 of the invention, and by the similar apertures 116 through the body of the piston and by a set of apertures 118 in the side of the cylinder. Sets 135 of apertures 102 and 116 are closed during use by a corresponding wide rubber washer (103 and 113 respectively) which has a slight curl or else is lifted so that the apertures are uncovered unless an explosion is under way. This acts as a simple form of valve. Note that the piston clearance shown here is exaggerated. At the end of a piston rod 117 there is a striking blade 123 (see also Fig 2) and as shown in Fig 2 a restoring spring is provided so 140 that the mechanism can be returned to a "ready" position after each use. (The restoring spring could also be a compression spring placed around the piston rod 117). In use this trap is preferably located above the ground; for example it may be tied to or otherwise supported by a tree or stump. This Example serves to illustrate the re-usable facility of the humane trap although I have 145 not yet implemented gas control measures capable of compensating for cold weather condi6 tions under which the explosion sometimes failed to occur. Causes of this may include damp spark plug 106, reduced gas pressure in the gas canister 120, solenoid sticking, and the like. Therefore, a second Example has been devised in which prepared explosive charges (such as 150 "Ramset" (R) charges) are used, as part of a drive for better reliability. EXAMPLE 2 - Cartridge driven resettable humane trap In this Example a similar layout of the trap is provided, although the energy source comprises a magazine disc 218 having a series of holes passing between one surface and the other, each of which holes is capable of accepting a blank cartridge. This disk comprises the 155 magazine. Figs 3 and 4 show this version in a diagrammatic form. Many details are not shown here, such as safety catches, but will nevertheless be evident to one skilled in the relevant arts. A frame, a bait reservoir, and means to support the trap in place are not shown. If an animal to be destroyed is attracted by bait (not shown) to put its head at position X, it 160 will close the momentary-action switch at the end of sensing arm 125 and current from the batteiy 119 will briefly pass through and actuate the solenoids 213 and 213B. (Wiring not shown here). Solenoid 213, on activation causes a trip pin 210 to retract so allowing a roller/support 207 holding the rigid arm 205 to move down (collapse), whereupon the arm 205 ceases to support the firing pin 203; the firing pin tip 203A moves down, encouraged by 165 spring 204 and hits the cartridge currently in place in the magazine 218, and the cartridge is detonated. Each cartridge comprises one portion of energy. Detonation creates a substantial gas pressure within the firing chamber 222. The pressure causes the piston 224 to be driven rapidly downwards and (as for example 1) the animal in the trap is killed by a blow from striking knife 123. 170 The process of resetting the trap is more complex than for example 1, but not unlike mechanisms known in the relevant arts. Magazine: See Fig 4. Activation of solenoid 213B causes the pawl 234 to be pulled in against internal spring (not shown) pressure, then released again so that engagement of the pawl with each of the 30 teeth 233 causes the magazine to turn by one increment, 175 presenting another unused cartridge below the firing pin. This magazine has 30 cartridge holders. In another embodiment, a ratchet mechanism which is activated by contact with the back of the striking knife when the knife is restored to its original position causes the magazine to turn to the next cartridge. This is not shown, but such a mechanism is well- 7 known to those skilled. 180 Firing mechanism: The firing pin 203 is restored to its original height by a bleed back of some of the expanded gas from the firing chamber 222 into a cylinder 211 surrounding the firing pin. At this time the trip pin mechanism 210, 212 and the rigid arm 205 are returned to a "wait state". The recoil mechanism (including pipe 214) is used to reset the magazine each time after the first use of a new magazine (when it is manually reset by pulling the 185 handle 201). Excess gas pressure is dissipated to the exterior through holes 225. Preferably a silencer or muffler arrangement is provided by the surrounding second cylinder 232, provided with a set of exhaust holes 227. These assist in keeping grit out of the piston area, as does the circumferential seal 226. Knife and piston: A spring 221 pulls upward and thereby restores the original position of the 190 striking knife 123, which is sturdily connected to an extension 224A of piston 224, sliding inside piston sleeve 228 and preferably with a seal 226 to keep grit from entering the piston area. I prefer that the process be provided with effective safety devices, such as one to prevent rapid firing of subsequent cartridges, and one to lock the system if the trip becomes 195 jammed, and a generally secure safety catch analogous to that on a rifle. One safety solenoid is shown as 213A, activation of which prevents the "trigger" release action within 210-215. Specific safety device disposition may depend on details of construction. For example, the electric means shown in Fig 4 to advance the magazine may be provided with a time delay 235 so that solenoid 213B is not activated for a period (such as 60 seconds) so that the 200 magazine will not actually advance for one minute. (It is unlikely that possums will queue up to enter the trap). VARIATIONS The general principle of using a reservoir of stored energy, released in fractional bursts each of lethal amount, is also included. For example, it might be possible to use stored electrical 205 energy either to drive a knife into the skull, to cause electrocution, or even to administer an injection of a lethal substance although operator safety must be considered. It might be possible to use an explosive charge to fire a captive bolt rather than a striking knife, or to fire a free bullet. (We generally prefer that free bullets not be used, for safety reasons). Non-electric triggering may be useful, especially where electrical reliability is a problem. 210 (Both examples used electric triggering but any mousetrap shows alternative methods which may be developed). 8 Head position means and access restriction means (cowling and entry shape) may be used, optionally in conjunction with selected kinds of bait, so that the trap is attractive to, and capable of killing, only a desired type of animal. The "braincase" of a possum occupies a 215 relatively small part of the head along the central front-back axis, and an off-centre blow may not be lethal. Therefore, head positioning means such as brackets made of metal or wood, having the effect of restricting side-to-side movement, may be placed on each side of the knife so that alignment is improved and so that the blade strikes the animal on the centre back area of the head causing instant humane death. 220 It might be possible to expel the animal using some of the energy released by combustion. COMMERCIAL BENEFITS or ADVANTAGES A principal benefit of the trap is that it is humane in that a severe impact to the animal's brainstem is delivered instantaneously, causing an immediate state of unconsciousness and death. 225 The trap resets itself, so that each trap is capable of trapping more than one animal after being left in place by a trapper. 30 "shots" is an adequate number though the invention could be modified to provide more, or less. The cost of the consumables (explosive material and battery) is less than the cost of revisiting the trap. The skin of the animal is not damaged (an economic advantage). In any case 230 a promising use of possum fur is in composite garments with wool where pelt integrity is not important. Surprisingly, nearby possums do not learn to associate the noise of the trap with danger. Finally, it will be understood that the scope of this invention as described and/or illustrated herein is not limited to the specified embodiments described and shown herein. Those of 235 skill will appreciate that various modifications, additions, known equivalents, and substitutions are possible without departing from the scope and spirit of the invention as set forth in the following claims. 9 </div>

Claims

<div class="application article clearfix printTableText" id="claims"> 51210 1 i claim ^ 8 ^ 8

1. A resettable humane trap for killing animals; particularly but not exclusively for 240 possums, wherein the trap includes means for storage and dispensing of a dispensable explosive material into an internal chamber, means capable of sensing a head of an animal when within the trap, and animal destruction means; the trap including means for generating at least one explosion within the internal chamber and a killing mechanism having a biased moveable member coupled to a 245 moveable wall of the internal chamber; the moveable member being capable, on rapid movement driven by an explosion within the chamber of moving from a ready position and delivering a lethal blow to said animal head; the moveable member being biased so as to be returned to a ready position, and trap reset means including a plurality of apertures opening into the internal chamber, and 250 an aperture for allowing the killed animal to fall from the trap.

2. A resettable humane trap for killing animals as claimed in claim 1, wherein the trap has a ready state, an active state, and a reset state; the active state being initiated by said animal head sensing means and comprising a first response comprising the release into the internal chamber of a portion of the explosive 255 material, and a second response comprising detonation of the explosive material released into the chamber, so that the animal is thereby killed by the lethal blow as the moveable member moves from the ready position; the ready state being initiated by biased return of the moveable member to the ready position, dissipation of the burnt explosive material, and passive withdrawal of the animal from 260 the trap so that the resettable humane trap returns to the ready state and is capable of operating more than twice without attention.

3. A resettable humane trap as claimed in claim 2, wherein the explosion is created inside the internal chamber using a mixture of an explosive gas and air; one wall of said chamber including a moveable piston connected to the moveable member. 265

4. A resettable humane trap as claimed in claim 3, wherein the portion of explosive gas is supplied from storage means through electrically controlled gas release means as the first response, and the explosion is initiated by an electric spark as 10 10 INTELf£CTUAL PROPERTY OFFICE OF M7 1 0 MAR 2003 received 512 1 275 280 285 the second response; the spark being generated as a result of current flow within a circuit including the animal head sensing means.

5. A resettable humane trap as claimed in claim 2, wherein the explosion is created by detonation of one of a set of mechanically detonatable explosive charges presented in sequence by means of a magazine.

6. A resettable humane trap as claimed in claim 2 or in claim 5, wherein the lethal blow is applied by a blade, in the manner of a captive bolt, pushed by the force of the explosion against the rear centre of the head of the animal; the head being aligned at the time by virtue of the position of the animal head sensing means in relation to an entry portal of the trap when the animal head sensing means is activated.

7. A resettable humane trap as claimed in claim 6, wherein the alignment of the head of the animal is assisted by means of position restricting means at each side of the head.

8. A resettable humane trap as claimed in claim 2, wherein the body of the animal is removed downward from the trap by its own weight.

9. A resettable humane trap as claimed in claim 8, wherein passive falling-out of the body of the animal is assisted by reflex convulsions resulting from the lethal blow.

10. A resettable humane trap as described in the accompanying text with reference to any one of the accompanying drawings. Ensor and Associates for Peter Jeffrey Allen. li </div>