GB2170088A - Apparatus for electrically stunning animals - Google Patents

Abstract

Apparatus for applying a pulse of direct electric current to the animals being stunned with the duration and amplitude of the pulse being chosen to cause reversible depolarization of nerve cell membranes, comprises a direct current source connected with electrodes (1,6) fitted in the animals' path. The electrode (6), connected with a controlled commutator switch (24), 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 Apparatus for electrically stunning animals The present invention relates to the meat industry, more specifically, to an apparatus for electrically stunning animals.

The present invention may be used 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 or the most important problems of the cattle dressing process.

The process of cattle slaughter includes two phases, 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 functions of blood vessels are paralysed, causing blood to be 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 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 motor functions before it is completely bled.

According to the present invention there is provided an apparatus for use in electrically stunning animals, particularly by a method in which pulses of direct electric current are applied to the animals by means of electrodes, and are of such duration and amplitude to cause reversible depolarization of the animal nerve cell membranes, the apparatus comprising electrodes located in a predetermined path of movement of the animal and connected to a direct current source including a stunning pulse generation circuit for supplying pulses of direct current to said electrodes, one electrode being movable in a vertical plane over the central portion of the path and having guides positioned within said predetermined animal's path to ensure contact of said electrode with the head of an animal moving along the path.

The apparatus embodying the invention 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 one of the electrodes is connected with a controlled commutator switch.

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 animal's path, making it possible to ensure automatic control of the process of animal stunning.

To automatically apply a stunning pulse to the animal, the apparatus is provided with a limit switch connected to the controlled commutator switch, and a hinged lever with arms having different masses, the arm with the greater mass interacting with the electrode, and the other arm with the limit switch.

Thus, it is possible to send a stunning pulse at the moment of tight contact (owing to the lever's 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 a preferred embodiment the device is provided with an arrangement for pressing the electrode to the animal's head at the moment the stunning pulse is fed, 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.

According to a further embodiment of the invention, 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 to stun the animal.

To prevent the 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 at a distance therefrom exceeding the length of the rods, and having holes for inserting and extracting the rods in the process of animal stunning.

The invention and its advantages may be more fully understood from the following detailed description in which reference is made to the accompanying drawings, wherein: Figure 1 is a front view of a device for animal stunning; Figure 2 is a side veiw 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 stunning pulse; Figure 5 illustrates section V-V in Figure 1; Figure 6 shows section VI-VI in Figure 5; 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 dis charge; Figure 9 is a schematic of a discharge device; Figure 10 is a circuit diagram of a discharge device.

The preferred apparatus of the invention is used to stun animals by a method in which direct current pulses are applied to the animal and have a duration and amplitude selected so as to ensure reversible depolarization of nerve cell membranes.

The current can be fed in the form of a single pulse with an active duration of 0.4 to 1,000 ms and an amplitude of from 5 to 600 A. The amplitude of the voltage pulse may vary from between 0.5 and 20 kV.

When a pulse is fed to the animal, the latter experiences prolonged muscular relaxation with the 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 duration 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 both ventricular fibrillation, and the formation of an explosion wave when the pulse is applied to the animal. Use of a shorter than 4.0 ms pulse fails to stun the animal, whereas a longer than a 1,000 ms pulse results in the animal's postmortem stiffening.

When the electrodes are applied to the animal's head behind the auricles the pulse amplitude varies from 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 used 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.

An apparatus for implementing the above method comprises an arrangement for conveying the animals, which is really a conveyor 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 conveyor 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 conveyor, simultaneously performing the function of a guide for the animals being stunned.

Arranged on the apron 2 in two bearings 3 is an axle 4 mounting a lever 5 of the apparatus with the lower arm thereof made from a current-carrying material and representing a positive electrode 6 free to move in a vertical plane over the central part of the animal's path. The electrode 6 has two guides 7 made in the form of plates of an insulating material, disposed at an angle to the animal's 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 extracted 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.

Apparatus 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 that the pressing effort is applied only before the stunning pulse is fed and is removed immediately after it has operated. The apparatus 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 apparatus 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 circuit. The limit switch 15 is connnected with the primary winding of the transformer 25, the control circuit of the thyratron 24 and the mains. The apparatus contains a switch 29 to connect the former with the mains. The control circuit of the thyratron 24 includes a resistor 30.

The apparatus 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 conveyor where they are fixed by the transporters and carried thereby in this position.

The animal being transported by the conveyor 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 positive 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 is then repeated. The apparatus 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 36 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 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 of the thyratron 24.

The discharge apparatus 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 starter to the primary winding of the transformer 25 through the resistance 49 and the switch 15, and via the contact 45 to the coil 54 of the eiectromagnet. In case the armature 39 of the electromagnet acts through this 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, 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.

The method of stunning animals described herein is also described and claimed in our patent application no. 8234788 (Publication No. 2131265) from which the present application has been divided out.

Claims (8)

1. An apparatus for use in electrically stunning animals, particularly by a method in which pulses of direct electric current are applied to the animals by means of electrodes, and are of such duration and amplitude to cause reversible depolarization of the animal nerve cell membranes, the apparatus comprising electrodes located in a predetermined path of movement of the animal and connected to a direct current source including a stunning pulse generation circuit for supplying pulses of direct current to said electrodes, one electrode being movable in a vertical plane over the central portion of the path and having guides positioned within said predetermined animal's path to ensure contact of said electrode with the head of an animal moving along the path.

2. Apparatus according to claim 1, wherein the guides are inclined at an angle to the predetermined path of the animal.

3. Apparatus according to claim 1 or 2, comprising a hinged lever having arms of different masses, the arm with the greater mass interacting with said one electrode and the other arm interacting with a limit switch included in the stunning pulse generation circuit.

4. Apparatus according to claim 3, wherein a rocking lever is provided for pressing said one electrode to the animal's head at the moment the stunning pulse is fed, one end of the rocking lever interacting with said hinged lever and the other end carrying a load.

5. Apparatus according to any one of the preceding claims, wherein said one electrode is provided with pointed rods for applying the stunning pulse to the animal's head.

6. Apparatus according to claim 5, wherein a portion of said one electrode carrying said pointed rods is provided with a spring-loaded limiter having the same shape as said rod carrying portion and spaced therefrom at a distance exceeding the length of the rods, the limiter having holes for movement of the rods into and out of contact with the head of the animal.

7. Apparatus according to any one of the preceding claims, wherein the stunning pulse generation circuit comprises an accumulator connected to the direct current source, a choke, and a commutator switch all connected in series.

8. Apparatus according to claim 7, wherein the stunning pulse generation circuit comprises a discharge device having contacts connected to a power source circuit and so arranged that the gap between the contacts can be adjusted, and a mechanism for adjusting said gap comprising a lever one end of which carries one of said contacts, the lever being connected to a pusher for changing the relative position of the contacts in response to movement of the lever, and a free end of the pusher being connected to an electromagnetic drive to provide reciprocal motion of the pusher.

8. Apparatus according to claim 7, wherein the stunning pulse generation circuit comprises a discharge device having contacts connected to a power source circuit and so arranged that the gap between the contacts can be adjusted, and a mechanism for adjusting said gap comprising a lever one end of which carries one of said contacts, the lever being connected to a pusher for changing the relative position of the contacts in response to movement of the lever, and a free end of the pusher being connected to an electromagnetic drive to provide reciprocal motion of the pusher.

9. Apparatus for electrically stunning animals substantially as herein described with reference to the accompanying drawings.

Amendments to the claims have been filed, and have the following effect: Claims 1-8 above have been deleted. New claims have been filed as follows:

1. An apparatus for use in electrically stunning animals, the apparatus comprising conveyor means for transporting the animals, the conveyor means defining a first electrode, a second electrode positioned above the conveyor means, and a direct current source connected to said second electrode and including a stunning pulse generation circuit for supplying pulses of direct current to said electrodes, said second electrode being movable in a vertical plane over a central portion of the conveyor means and having guides positioned to ensure contact of said second electrode with the head of an animal being conveyed.

2. Apparatus according to claim 1, wherein the guides are inclined at an angle to the conveyor means.

3. Apparatus according to claim 1 or 2, comprising a hinged lever having arms of different masses, the arm with the greater mass interacting with the second electrode and the other arm interacting with a limit switch of the stunning pulse generation circuit.

4. Apparatus according to claim 3, wherein a rocking lever is provided for pressing the second electrode to the animal's head at the moment the stunning pulse is fed, one end of the rocking lever interacting with said hinged lever and the other end carrying a load.

5. Apparatus according to any one of the preceding claims, wherein the second electrode is provided with pointed rods for applying the stunning pulse to the animal's head.

6. Apparatus according to claim 5, wherein a portion of the second electrode carrying said pointed rods is provided with a spring-loaded limiter having the same shape as said rod carrying portion and spaced therefrom at a distance exceeding the length of the rods, the limiter having holes for movement of the rods into and out of contact with the head of the animal.

7. Apparatus according to any one of the preceding claims, wherein the stunning pulse generation circuit comprises an accumulator connected to the direct current source, a choke, and a commutator switch all connected in series.