P00/o1 Regulation 3.2 AUSTRALIA Patents Act 1990 COMPLETE SPECIFICATION Invention Title: ELECTRIC STUNNER The following statement is a full description of this invention, including the best method of performing it known to me: -2 Electric Stunner Field 5 The invention relates to electric stunners used to stun animals before slaughter. Background of Invention 10 Conventional manual stunners for small animals such as sheep, pigs, bobby calves, and goats consist of either a pistol grip with electrodes attached, or a long rod with a pair of electrodes at the end. In either case, the operator has to press the electrodes against the head or neck of the moving animal as it is trapped in a confined space, typically in a race or in a restrainer conveyor, and to hold the electrodes steady against the animal's skull whilst the electric 15 charge is applied. Such stunners have been used in abattoirs for many years, and give rise to operator fatigue, as the operator has to try and hold the electrodes steady against the animal's head or neck while the animal moves and tries to avoid contact. This interplay of the operator trying to 20 position the electrodes on the animal's head or neck, and the animal either shaking, or trying to escape often results in a poor electrical contact between the electrodes and the animal's head or neck, resulting in inefficient and inconsistent stuns, as insufficient current may be applied to the animal to stun it sufficiently to provide humane slaughter. 25 Object of the Invention It is an object of this invention to provide an improved electrical stunner, or one which will at least provide the public with a useful choice. 30 -3 Summary of Invention In a first aspect the invention provides an electric stunner having a stunner head on which a pair of moveable electrodes are positioned, and means for moving the pair of electrodes so 5 that they contact, and clamp onto a portion of the animal, and means for applying an electric current to the electrodes to stun the animal. Preferably the head has a pair of electrodes, with each electrode pivotally mounted, so that they may move from an open disengaged position, towards a closed engaged position in 10 which they clamp onto the animal. Preferably the spacing of the electrodes and the size of the stunner head is such that the electrodes are designed to clamp onto the head of an animal to be stunned. 15 Preferably the electrodes are actuated by one or more actuators. Preferably the actuators are pneumatic cylinders. Preferably the stunner head is attached or attachable to an insulated handle, of sufficient 20 length to enable the operator to stand back from the animal and to engage the animal's head so that the electrodes can be clamped onto the animal's head. In another aspect the invention provides a method of stunning animals in which an animal is held in a confined space and contacted by a pair of clamping electrodes which are moved 25 towards one another to clamp onto a portion of the animal, and applying a stun current through the clamping electrodes to stun the animal. Preferably the animal is held in a restrainer conveyor and the clamping electrodes are moved down from above into contact with the animal's head or neck. 30 -4 Preferably the control sequence is such that the operator having made contact with the animal's head can cause the electrodes to clamp onto the animal, and then the electrical stunning current can be applied to the electrodes for a sufficient period of time to provide a humane stun, and then the current can be switched off, and the electrodes disengaged. 5 Brief Description These and other aspects of the invention, which should be considered in all its novel aspects, will become apparent from the following description, which is given by way of example only 10 with reference to the accompanying drawings, in which: Drawings Figure 1 is a top plan view of a prototype electric stunner head, showing the electrodes 15 in two positions (engaged and disengaged). Figure 2 is a stun test showing the variation in current applied to an animal using a prior art electric stunner. Figure 3 is a stun test using the prototype electric stunner as shown in Figure 1 of this 20 application. Figure 4 is an explanatory side view of the conveyor and stunner position with the stunner approaching the animals head. Description of Drawings 25 Example 1: Sheep Stunner. A preferred electric stunner for sheep has a head 10, and a stem 11, the stem has a trigger grip (not shown) at right angles to the stem having a trigger which the operator can use to 30 initiate the clamping action and start the stun current.
-5 The end of the stem has an eyelet so that the stunner can be attached to a cable and a counterbalance (to assist in taking the load of the stunner during use). The head 10 has a pair of jaws 12 and 13, with a moveable electrode positioned at the end of 5 each jaw. These moveable electrodes 20 and 21 are pivotally mounted on pivot 25 to an insulated block 29, and each electrode has a lever 26 positioned at substantially right angles to the extension of the electrode. These levers are pivotally connected at 31 to actuators 22, 23; such that each electrode 20, 21 has its lever 26 attached to a respective actuator 22 or 23. These actuators are pneumatic cylinders, and can be controlled by the operator. 10 Each of the electrodes 20, 21 is curved inwardly to assist in contacting and clamping against the animal's head. Figure 4 shows that the bulk of the assembly of the stunner head is protected by cover plates 15 50. On one side of the stunner head a pistol grip 51 extends at substantially right angles and has a trigger 52 to operate the rams and stun current. This drawing also shows the flexible power cables 55 and the counterbalanced wire support 56. The electrodes 20, 21 have an associated water supply 33 so that water is applied at the tips 20 of each electrode to improve the electrical contact with the animal. The pair of jaws 12, 13 tapers outwardly, so that their outer most extremities are spaced apart slightly wider than the maximum width of a sheep's head, with the curved electrodes 20, 21 extending beyond the extremities of the jaws 12, 13, normally held in the disengaged 25 position (the outermost position "A" shown in Figure 1), but when actuated, the pneumatic cylinders will retract, causing the levers to be pulled rearwardly, and the electrodes to pivot inwardly the innermost position "B". Figure 1 shows the two operative positions the outermost "A" being the disengaged position, 30 and the innermost position "B" being the engaged position. The animal is held in a restrainer (V-belt) conveyor (see Figure 4) which is stopped underneath the location of the stunner. The operator can then locate the stunner head on the -6 animal. The preferred location is to place the electrodes from above the animal's head so that the tips of the electrodes contact the soft tissue below the animal's ears. Figure 4 shows an animal in the restrainer conveyor and the position of the stunner 5 suspended from a cable at the stunning poison (typically near the end of this reach of the restrainer conveyor). The conveyor is stopped under the stunner typically for a period of 2 to 4 seconds and the operator lowers the stunner head until it is close to the animal's head. He depresses the trigger to operate the pneumatic rams so that the pair of electrodes then grips the animal's head to ensure good contact. The optional water sprays may also be activated to 10 ensure the point of contact is wet to assist in providing good electrical contact. Once the electrodes engage the animal the stun current can be applied (as discussed below). At the completion of the stun, the electrodes are released, the stunned animal slumps into the conveyor, and the conveyor starts up to eject the stunned animal from the end of the conveyor. Typically the animal will be expelled onto a ramp and dropped onto a killing 15 station depending upon the type of slaughter required. Preferably the electric stunner is controlled in such a way that once the electrodes have engaged the animal's head either by the operator placing it into contact with the animal and then pulling the trigger to actuate the pneumatic cylinders to clamp the pair of electrodes 20 against the animal's head, or in other embodiments where the stunner is set up so as to sense the position of the animal and automatically clamp against the animal's head, in either event once clamping has taken place then the stun current can be applied. In the case of sheep, the stun current is applied at 550v AC and can be set in increments from 25 0.7A to 2.OA. We prefer to apply the stun current at 2A for 2 seconds (as will be apparent from figure 3). The operator can watch a meter to ensure that the efficacy of the stun can be monitored. The duration of the stun current is timed and the operator will either see a visible signal on the 30 meter to show completion of the stun (that the current has been switched off) or he may hear an auditory cue (a loud click) when the stun current is turned off (or more likely he will experience both signals. When he is sure that the stun has finished he can release the trigger -7 to release the clamps. At that point the restrainer conveyor can start up (start up may be synchronised with the release of the clamping electrodes). As a safety feature, the stun current cannot be applied until such time as the cylinders have 5 been operated to cause the electrodes to clamp against the animal's head. The stun current can then be applied either by the operator, or more preferably can be applied automatically for the desired duration, immediately after the electrodes clamp onto the animal's head. 10 It may be possible to sense the effectiveness of the clamping process, by sensing the resistance of the preferably springy electrodes as they are pulled tightly against the animal's head. 15 Figure 3 shows the application of a substantially uniform current for duration of 2 seconds, to provide an effective and humane stun. Figure 2 on the other hand shows a much more problematic stun, where the operator manually pushes the electrodes (without clamping) against the animal's head, and tries to 20 maintain a fairly uniform contact during the application of the stun current. In this trace, the stun current has been applied for about 1.4 seconds, and after 0.2 seconds the operator lost contact with the animal's head, managed to find contact again, and hold it there from 0.3 to 1.4 seconds. But even during this contact, the current varied significantly, and it is by no means clear that the stun was of sufficient intensity and duration to provide an effective and 25 humane stun. In any event, the trace of Figure 2 is symptomatic of the variability of the stun achieved with prior art equipment. 30 -8 Advantages of the Preferred Embodiment The trace of Figure 3 shows the improved quality of the stun, as the moveable electrodes serve to both clamp the animal's head, enabling a much more effective electrical contact 5 during the application of stunning current, and making it easier for the operator to apply the stunner, and ensure the stunner is held in place during the application of the stunning current. Tests on the prototype of this new electrical stunner have shown that the stun current is more uniform than with prior art stunners, and operator fatigue can be reduced. 10 We have tested it on both sheep and bobby calves. We believe it will also be useful for stunning pigs, goats and other small animals. Variations 15 Although not shown the stem of the stunner can be attached to a handle so that the operator can place the head of the stunner against the animal's head. Alternatively the stunner can be suspended on a cable above a restrainer conveyor so that as an animal travels along the restrainer conveyor it will come into contact with the suspended stunner, and the stunner can 20 then be activated pneumatically to clamp against the animal's head. The electrodes may be provided with a water spray to ensure that the electrodes themselves are wet, and the portion of the animal's head into which they come into contact is also wetted with water to ensure a good electrical contact. 25 Although the prototype has been described with reference to a pair of pneumatic cylinders, other means of moving the electrodes into the clamping position may be used. Finally various other alterations and modifications may be made to the foregoing without 30 departing from the scope of this invention as set forth in the claims.