GB2131265A - Electrical stunning of animals - Google Patents

Abstract

A method of stunning consists in applying to animals a pulse of direct electric current whose duration amplitude causes reversible depolarization of nerve cell membranes. Electric current is supplied in the form of a single pulse with an active duration of 0.4 to 1,000 ms and an amplitude of 5 to 600 A. A device for implementing the method comprises a direct current source connected with electrodes (1, 6) fitted in the animals' path. The electric (6), connected with a controlled commutator switch, is movable in a vertical plane over the central part of the animals' path and is provided with guides (7) fixed at an angle to the animals' path. <IMAGE>

Description

SPECIFICATION A method of electrical stunning of animals and a device for implementing same The invention relates to meat industry and, more specifically, to a method of electrical stunning of animals and a device for implementing the same.

The present invention may be used to the best advantage for stunning of pigs and cattle prior to slaughter, and also in other industries requiring immobilization of animals, e.g. in agriculture and veterinary practice.

Raising labour productivity at initial cattle dressing lines and improving the quality of products is inseparably linked with perfection of equipment and processes, the problem of animal slaughter being one of the most important problems of the cattle dressing process.

The process of cattle slaughter includes two phases, i.e. stunning and bleeding. These operations are closely interdependent, thus affecting the quality of meat. The better the animal is bled, the longer meat and meat products remain fresh. The degree of bleeding depends on cardiac activity during slaughter. When cardio-vascular centres in the cerebrum are affected, cardiac activity ceases and reflex fu nctions of blood vessels are paralysed, due to which part of the blood is withheld in capillary blood vessels, finding its way into fatty and muscular tissues and into the internals. The sooner the animal is bled after stunning, the more completely the blood is drained and the better the quality of meat.It has been proved that the blood yield and the quality of meat are also dependent on the method of stunning the animal.The determining factor in correct and complete bleeding is retention of normal cardiac activity during animal stunning.

The effectiveness of stunning depends on the current voltage and intensity, the duration of action upon the anivoltage and intensity, the duration of action upon the animal, and also on the animal's species, age and fatigue. Excessive dose of current results in the animal's instantaneous death, whereas insufficient dose restores its motorfunctions before it is completely bled.

An object of the present invention is to improve the quality of meat.

Another object of the present invention is to raise the capacity of a device for animal stunning.

Yet another object of the present invention is to provide a means for automatic control of the process of animal stunning.

These and other objects are attained by providing a method of electrical stunning of animals by pulsating direct current, according to the invention, the duration and amplitude of the pulse applied to the animal by means of electrodes being of magnitudes causing reversible depolarization of the nerve cell membranes.

The proposed method of animal stunning allows hemorrhages both in the internals and in the fatty and muscular tissues to be considerably lessened, thereby improving the quality of meat.

The method rules out the animal's convulsions, prolongs the stunned state, precludes tactile algetic sensitivity, ventricular febrillation and vocalization, and also ensures the animal's muscular relaxation.

The invention allows the same amount of energy to be applied to different species of animals, which renders it universal.

It is practicable to supply electric current in the form of a single pulse with an active duration of 0.4 to 1,000 ms and an amplitude of 5 to 600 A (active duration is duration at a level of 0.5A).

When a pulse is fed to the animal, the latter features prolonged muscular relaxation with temporary loss of motor activity and sensitivity, which promotes effective bleeding of the animal and allows high-quality meat to be obtained. Use of pulsating current makes it possible to inhibit considerably the development of the process of postmortem stiffening, owing to which muscular tissues retain a high degree of swelling during the entire term of subsequent storage of meat. As a result, myofibrillar structures become readily accessible to the action of proteolytic enzymes of the meat.

The selected parameters of the electric current pulse help to avoid ventricularfebrillation, and also the formation of an explosion wave when the pulse is applied to the animal. Use of a shorter than 0.4 ms pulse fails to stun the animal, whereas a longer than a 1,000 ms pulse results in the animal's postmortem stiffening.

It is most expedient to use electric current with a pulse voltage amplitude of 0.5 to 20 kV.

In one embodiment of the invention electrodes are applied to the animal's head, behind the auricles, the pulse amplitude ranging from 10 to 600 A.

In another embodiment of the invention the negative electrode is applied to the head, and the positive to the middle of the animal's back, the pulse amplitude being from 5 to 300 A and active duration varying within 0.4 to 600 ms.

In accordance with yet another embodiment of the invention the negative electrode is applied to the animal's head and the positive, to the legs, the pulse amplitude being 10 to 500 A and active duration, 2 to 160 ms.

The electrodes may be applied to the animal's forelegs and hindlegs, in which case the pulse amplitude ranges within 5 to 410 A and active duration varies from 10 to 1,000 ms.

A device for implementing the method, comprising a direct current source connected with electrodes fitted in the animals' path, according to the invention, is provided with a stunning pulse generation circuit including series-connected accumulator connected to the direct current source, a choke, a controlled commutator switch and the electrodes applied to the animal to ensure closing of the stunning pulse generation circuit.

The proposed device allows the implementation of the proposed method in the most rational manner.

The device makes it possible to smooth out the leading edge of the generated pulse, thereby precluding the appearance of an explosion wave.

In one embodiment of the invention an electrode connected wtih a controlled commutator switch is movable in a vertical plane over the central part of the animals' path and is provided with guides fixed along the animals' path to ensure contact of the electrode with the head of each animal.

Such an arrangement of the electrode and guides allows the stunning pulse to be reliably applied to the central part of the animal's head. The guides may be installed at an angle to the animals' path, which, in turn, makes it possible to ensure automatic control of the process of animal stunning.

To automatically feed a stunning pulse to the animal, the device is provided with a limit switch connected with the controlled commutator switch, and a hingedly installed lever with the arms thereof having different masses, the arm with the greater mass interacting with said electrode and the other arm, with the limit switch.

Such design of the device makes it possible to send a stunning pulse at the moment of tight contact (owing to the lever own weight) between the animal's head and the electrode, thereby allowing effective use of the supplied pulse and fully automatic control of the process of animal stunning and, hence, an increase in the capacity of the device.

In the preferred embodiment the device is provided with an arrangement for pressing the electrode to the animal's head at the momentthe stunning pulse is fed, made in the form of a rocking lever with one end thereof interacting with the first of said levers and the other end carrying a load.

Such a construction enhances the effectiveness of the stunning pulse application.

According to one embodiment ofthe device, the portion of the electrode contacting the animal is provided with pointed rods through which the stunning pulse is applied to the animal's head.

The presence of rods inserted into and extracted from the animal's head allows the stunning pulse to be applied in close proximity of the cerebrum, which reduces considerably the amount of energy required to stun the animal.

To preventthe animal's hide from being pierced with the pointed rods, the portion of the electrode carrying the latter is provided with a spring-loaded limiter made in the form of said portion, located therefrom at a distance exceeding the length of the rods, and having holes for inserting and extracting the rods in the proces of animal stunning.

Other objects and advantages of the present invention will become apparent from the following detailed description of embodiments thereof taken in conjunction with the accompanying drawings, wherein: Figure lisa front view of a device for animal stunning; Figure 2 is a side view of a device for animal stunning; Figure 3 is a top view of a device for animal stunning; Figure 4 represents a mechanical diagram of an arrangement for automatic supply of a stunning pulse; Figure 5 illustrates section V-V in Figure 1; Figure 6shows section VI-VI in FigureS; Figure 7 is a schematic circuit diagram of a device for animal stunning; Figure 8 is a graph showing variation of current and voltage in the area of the stunning pulse discharge.

Figure 9 is a schematic of a discharge device; Figure 10 is a circuit diagram of a discharge device.

The method consists in acting upon the animal by direct current pulses with the duration and amplitude thereof selected so as to ensure reversible depolarization of nerve cell membranes. The current is fed in the form of a single pulse with an active duration of 0.4 to 1,000 ms and an amplitude of 5 to 600 A.

In one embodiment of the invention the amplitude of the voltage pulse is equal to 0.5-20 kV.

When applying electrodes to the animal's head behind the auricles the pulse amplitude equals 10-600 A. In the event of the negative electrode being applied to the animal's head and the positive electrode to the middle of its back the pulse amplitude is 5-300 A with an active duration of 0.4 to 600 ms.

The negative electrode may be applied to the animal's head and the positive electrode to its legs, the pulse amplitude in this case being 10-500 A and active duration, 2-160 ms.

With the electrodes applied to the animal's forelegs and hindlegs, the pulse amplitude ranges within 5 to 410 A and active duration varies from 10 to 1,000 ms.

A device for implementing the proposed method comprises an arrangement for conveying the aninmals, which is really a conveyer made in the form of a pair of apron transporters disposed at an angle to each other, with the aprons thereof representing a negative electrode 1 (Figures 1, 2, 3). Fitted at a certain height over the conveyer is an apron 2 carrying a device for automatic feed of the stunning pulse.

The apron 2 prevents the animals from falling out of the conveyer simultaneously performing the function of a guideforthe animals being stunned.

Arranged on the apron 2 in two bearings 3 is an axle 4 mounting a lever 5 of the device with the lower arm thereof made from a current-carrying material and reresenting a positive electrode 6 free to move in a vertical plane over the central part of the animals' path. The electrode 6 has two guides 7 made in the form of plates of an insulating material, disposed at an angle to the animals' path, and a central part 8. The central part 8 of the electrode 6 is provided with pointed rods 9 (Figures 4, 5, 6) and a spring-loaded limiter 10 having the shape of the central part 8 of the electrode 6. The limiter 10 has holes for the rods 9 to be inserted thereinto, as the moving animal contacts the electrode 6 and extrated therefrom as the animal moves on. The limiter 10 is loaded by springs 11, and is offset from the central part 8 of the electrode 6 by a distance exceeding the length of the rods 9. The stunning pulse is fed to the central part 8 of the electrode 6 through a flexible cable 13 (Figures 1,3) secured on an insulator 12.

A device for automatic feed of the stunning pulse contains a post 14 (Figures 1,2) carrying a limit switch 15 and a lever 17 hingedly installed on an axle 16. The arms of the lever 17 have different masses, the arm with the greater mass interacting with the upper arm of the lever 5. The device is also provided with an arrangement for pressing the electrode 6 to the animal's head, made in such a manner tht the pressing effort is applied only before the stunning pulse is fed and is removed immediately after it has operated. The device includes a rocking lever 18 secured on an axle 19. A load 20 is movably installed on one arm of the lever 18. A stop 21 limits the movement of the lever 18 and the load 20.

To supply direct electric current to the animal, the device is provided with a stunning pulse generating circuit including a reservoir capacitor 22 (Figure 7) connected to a direct current source, a choke 23, a controlled thyratronic commutator switch 24, and the electrodes 1 and 6, all elements being connected in series.

The direct current source contains an autotransformer 25, a high-voltage transformer 26 and a rectifier 27. A transformer 28 is provided in the thyratron filament ciruit. The limit switch 15 is connected with the primary winding of the transformer 25, the control circuit of the thyratron 24 and the mains. The device contains a switch 29 to connect the former with the mains. The control circuit of the thyratron 24 includes a resistor 30.

The device operates as follows.

Prior to operation, the switch 29 is turned on to supply power to the device, and the filament circuit of the thyratron 24 is energized.

The switch 15 feeds voltage to the primary winding of the transformer 25 and thence to the transformer 26, wherefrom power is supplied through the rectifier 27 to the capacitor 22 to be accumulated therein.

The animals are herded to the conveyer where they are fixed by the transporters and carried thereby in this position.

The animal being transported by the conveyer deflects the electrode 6 (Figure 4) with its head, the electrode turning around the axle 4. As this takes place, the limiter 10 of the electrode 6 is positioned on the frontal part of the animal's head. As the electrode 6 turns, the upper arm of the lever 5 deflects the lever 17 around the axle 16; the lever 17, in turn, deflects the lever 18 around the axle 19, one arm of the lever 18 carrying the load 20, whose position on the lever 18 controls the effort with which the pointed rods 9 passing through the holes in the limiter 10 are pressed to the animal's head.

Simultaneously, the lever 17 actuates the limit switch 15.

When the switch 15 operates, the power accumulation circuit (not shown in Figures) in the capacitor 22 is cut out, and the thyratron 24 fires as postive voltage appears across its grid. The electromagnetic process developing in the device owing to the energy accumulated in the electric field of the capacitor 22 causes electric current to flow through the circuit as a result of which the required voltage drop giving rise to reversible depolarization of nerve cell membranes is produced in the animal's discharge area.

For effective stunning, use is made of a current pulse determined by the parameters of the circuit (animal's resistance, inductance, ohmic resistance of the choke 23 and capacitance of the capacitor 22), the current in the discharge area first increasing and then decreasing (see Figure 8). The greater the current amplitude, the shorter its active duration measured at a level of half its amplitude. After the lever 5 moves out of mesh with the lever 17 the effort on the electrode 6 and on the animal is discontinued, the switch 15 assumes the initial position, and power starts accumulating on the capacitor 22.

Simultaneously, the rods 9 are extracted from the animal's head by the action of the springs 11. After the animal loses contact with the electrode 6, the latter returns to the initial position, its upper arm deflecting the lever 17 which returns to the initial position due to the difference in masses of its arms.

The operating cycle of the device is then repeated.

The device can be provided with a discharge device 31 (Figure 9) comprising contacts 32 and 33 set so that the gap therebetween can be adjusted and a mechanism to adjust said gap. This mechanism comprises a stationary member 34 carrying the contact 33, while the other contact 32 is arranged on one of the ends of a lever 35 whose other end is hinged to a stationary member 36. The lever 35 is secured to a pusher 37 intended to change the position of contacts 32 and 33 when the lever 35 changes its position. The free end of the pusher 37 is connected to a spring 38 which in turn is connected to an armature 39 of the electromagnet. Both members 34 and 36 are electrically insulated from each other and secured on a base 40, a limit switch 41 being arranged under the central portion thereof.

A gap setter 42 is mounted on the pusher 37 to regulate the gap between the contacts 32 and 33.

This gap setter 42 can be a flange arranged on the threaded portion of the pusher 37.

The circuit of the discharge device 31 is equipped with a magnetic starter comprising a coil 43 (Figure 10) and make contacts 44 and 45, and a current relay having a coil 46 and break contacts 47.

The contacts 32 and 33 are connected in series with a rectifier 48 via the coil 46 of the current relay.

The rectifier 48 and the capacitor 22 are connected in series with the secondary winding of the transformer 25. The primary winding of the transformer 25 is connected via the limit switch 15, the limiting resistance 49 and make contacts 44 of the magnetic starter to a power source 50.

The coil 43 of the magnetic starter is connected in series with the break contacts 47 of the current relay and to "stop" button 51 and "start" button 52. This circuit is also connected to the power source 50.

Make contacts 53 of the limit switch 41 are connected in parallel to the button 52.

A coil 54 of the electromagnet is connected via the make contacts 45 of the magnetic starter to the power source 50.

The capacitor 22 is connected in series with the choke 23, electrodes 1 and 6 applied to the animal and the cathode anode of the thyratron 24 intended to produce the stunning pulse in the circuit.

The control circuit of the thyratron 24 has an additional resistance 30 connected to the limit switch 15 and the grid ofthethyratron 24.

The discharge device operates as follows.

When the button 52 is depressed, the voltage is applied to the coil 43 of the magnetic starter and via the make contacts 44 of said magnetic starterto the primary winding of the transformer 25 through the resistance 49 and the switch 55, and via the contact 45 to the coil 54 of the electromagnet. In this case the armature 39 of the electromagnet acts through the spring 38 and pusher 37 on the lever 35 which open the contacts 32 and 33. A gap is established between the contacts 32 and 33. A gap is established between the contacts 32 and 33, which depends on the position of the gap setter 42 on the pusher 7. The gap setter 42 acts on the limit switch 41 and blocks the button 52 by the make contact 53 of the switch 41.

When the voltage is removed, the lever 35 goes down by its mass and the mass of the pusher 37, gap setter 42, spring 38 and the armature 39 of the electromagnet connected thereto, and closes the contacts 32 and 33. Here, the capacitor 22 discharges through the coil 46 to the secondary winding of the transformer 25 and the circuit assumes its initial state.

When the voltage of the capacitor 22 goes over the value assigned by the setter 42, the air gap is jumped over. The circuit is formed comprising the contacts 32 and 33, the coil 46 of the current relay, the secondary winding of the transformer 25 and the capacitor 22. The coil 43 of the magnetic starter is disengaged. The primary winding of the transformer 25 is deenergized and the capacitor 22 discharges.

The button 51 is to be pushed to automatically remove the charge from the capacitor 22.

When switch 15 operates, the energy accumulating circuit of the capacitor 22 is disengaged and the voltage is then applied across the grid of the thyratron 24 via the resistance 30. The thyratron 24 is cut in and an electromagnetic process is started in the discharge circuit due to the energy accumulated initially in the electrical field of the capacitor 22.

Electric current passes through the animal and stuns it.

Claims (17)

1. A method of electrical stunning of animals by a pulse of direct electric current applied by means of electrodes; the duration and amplitude of the pulse applied to the animal are of magnitudes causing reversible depolarization of nerve cell membranes.

2. A method as claimed in claim 1, wherein electric current is supplied in the form of a single pulse with an active duration of 0.4 to 1,000 ms and an amplitude of 5 to 600 A.

3. A method as claimed in claim 2, wherein use is made of electric current with a pulse voltage ampli tudeofO.5to20kV.

4. A method as claimed in claim 2, wherein electrodes are applied to the animal's head behind the auricles, the pulse amplitude ranging from 10 to 600 A.

5. A method as claimed in claim 2, wherein the negative electrode is applied to the head, and the positive electrode to the middle of the animal's back, the pulse amplitude being 5 to 300 A and an active duration varying within 0.4 to 600 ms.

6. A method as claimed in claim 2, wherein the negative electrode is applied to the animal's head, and the positive, to the legs, the pulse amplitude being 10 to 500 A and active duration, 2 to 160 ms.

7. A method as claimed in claim 1, wherein the electrodes are applied to the animal's forelegs and hindlegs, the pulse amplitude ranging within 5 to 410 A and active duration varying from 10 to 1,000 ms.

8. A device for implementing the method as claimed in claim 1, comprising a direct current source connected with electrodes fitted in the animals' path, wherein provision is made of a stunning pulse generation circuit and an electrode connected with said circuit is movable in a vertical plane over the central part of the animals' path and provided with guides fixed along the animals' path to ensure contact of the electrode with the head of each animal.

9. A device as claimed in claim 8, wherein the guides are installed at an angle to the animals' path.

10. A device as claimed in claim 8, wherein it is provided with a limit switch fitted in the stunning pulse generation circuit and a hingedly installed lever with the arms there of having different masses, the arm with the greater mass interacting with the electrode and the other arm, with the limit switch.

11. A device as claimed in claim 10, wherein it is provided with an arrangement for pressing the electrode to the animal's head at the moment the stunning pulse is fed, made in the form of a rocking lever with one end thereof interacting with the first of said levers and the other end carrying a load.

12. A device as claimed in claims 8, 10, 11 wherein the portion of the electrode contacting the animal is provided with pointed rods through which the stunning pulse is applied to the animal's head.

13. A device as claimed in claim 12, wherein the portion of the electrode carrying the pointed rods is provided with a spring-loaded limiter made in the form of said portion, located therefrom art a distance exceeding the lengths of the rods, and having holes for inserting and extracting the rods in the process of animal stunning.

14. A device as claimed in claim 8, wherein the stunning pulse generation circuit includes an accumulator connected to the direct current source, a choke, a controlled commutator switch and the electrodes applied to the animal to ensure closing of the stunning pulse generation circuit, all elements being connected in series.

15. A device as claimed in claim 14, wherein the stunning pulse generation circuit comprises a discharge device having contacts positioned in the power source circuit so that the gap between them can be regulated and a mechanism to adjust said gap composed of a lever whose one end carries one of said contacts and is connected to a pusher to change the relative position of the contacts when the lever moves, the free end of the pusher being connected to an electromagnetic drive to provide the reciprocal motion of the pusher.

16. A method as claimed in any of the preceding claims, substantially as disclosed in the description and shown in the accompanying drawings.

17. A device as claimed in any of the preceding claims, substantially as disclosed in the description and shown in the accompanying drawings.