Method and apparatus for cutting open the stomach of a bird
BACKGROUND OF THE INVENTION 
     The invention relates to a method for cutting open the stomach of a bird, especially the stomach of a turkey and to an apparatus for carrying out said method, comprising a cutting means and positioning means for positioning the stomach relative to the cutting means. 
     While processing birds for obtaining products to be sold one of the steps comprises cutting open the stomach which previously has been eviscerated from the bird in a way know per se. After the stomach has been cut open its contents are removed and, using a so called stomach peeler, the stomach membrane is separated from the stomach. 
     In a known method and apparatus for cutting open the stomach of a bird the cutting means comprises a rotating knife. The stomach is guided along the rotating knife through the positioning means in such a way that a cut is made along the entire length of a stomach wall, after which the stomach as it were may be folded open to a planar position. In this open position the contents of the stomach can be removed and the stomach can be supplied to the stomach peeler. 
     Such a known method and apparatus, in which the cutting means comprises a rotating knife, have several disadvantages. The setting of the rotating knife should occur extremely precisely in order to avoid that the cut made by the rotating knife not only extends in one stomach wall but also in the opposite stomach wall. In this respect it is complicating that the stomachs of different birds have different dimensions. 
     Especially when cutting open the stomach of turkeys the application of a rotating knife offers another disadvantage. It is not uncommon that turkeys swallow pebbles or alike. These pebbles reach the stomach and the rotating knife cannot be prevented from hitting these pebbles. As a result the knife quickly gets blunt and has to be sharpened or has to be replaced by a new knife. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     It is an object of the invention to provide a method and apparatus in which the mentioned disadvantages are removed in a simple but nevertheless effective way. 
     Thus the method according to the invention is characterized in that at least one high-pressure liquid jet is used for cutting only one stomach wall and for internally pressurizing the stomach. 
     Surprisingly it appears that using such a liquid jet the stomach of the bird can be cut open in an extremly effective way. The highly pressurized liquid jet enters through the respective wall of the stomach and into the stomach cavity. There the pressure of the liquid jet has diminished so far that the opposite stomach wall is not damaged. However, the liquid jet creates a pressure rise in the stomach cavity which supports the cutting action of the liquid jet in such a way that starting from the already made cut the stomach as it were bursts open. Thus the high pressure liquid jet functions in two ways: at one hand for making a cut in the stomach wall and at the other hand for creating an internal pressure in the stomach cavity such as to further tear open the stomach wall as starting from that cut. This combined effect provides for a quick and effective cutting open of the stomach of the bird, even with relatively low pressures of the liquid jet. 
     It is known on itself that meat or meat products can be cut using a pressurized liquid jet. However this requires pressures in the amount of 3000 bar. If the liquid jet does not entirely get through the meat at such high pressures unaccessible damages of the products occur because the liquid swirls through the meat and pulverizes it. Further for creating these pressures complicated installations are required. The previously mentioned combination effect of cutting and internal pressure however leads to the possibility of a substantial reduction of the required pressure, for example to about 250 bar. 
     The application of a high pressure liquid jet for cutting open the stomach of a bird also offers a further advantage. Already at cutting open the stomach the contents of the stomach of the bird is flushed and the stomach is cleansed. Separate devices for cleansing the stomach after cutting it open, such as rotating brushes or alike, then can be left out. 
     The apparatus according to the invention is characterized in that the cutting means consists of at least one nozzle for ejecting a high-pressure liquid jet. 
     In accordance to a preferred embodiment of the apparatus according to the invention the nozzle is oriented such as to eject the liquid jet in upward direction, whereas the positioning means comprise a conveyor for conveying the stomach to be cut open overhead the nozzle. 
     If the stomach is cut open by the liquid jet leaving the nozzle the internal surface of the stomach uncovered then is directed downwards, such that the contents of the stomach can be flushed downwards by the liquid without contaminating the outer surface of the stomach. 
     Further it is advantageous if, according to another embodiment of the apparatus according to the invention, the nozzle is displaceable towards or away from the stomach to be processed. As a result the nozzle can be positioned at the ideal distance from the stomach for an optimised cutting operation. It also may be advantageous if the nozzle is spring-loaded towards the stomach to be processed. Thus the nozzle automatically adapts itself to the shape of a passing stomach. In this connection according to a constructively simple embodiment the nozzle is mounted at the outer end of an arm pivoting in a vertical plane, said outer end engaging the stomach through guiding means. The guiding means may comprise at least one follower roll. The follower roll follows the contour of the stomach to be processed, thus providing an automatic adaption of the position of the nozzle to the passing stomach. 
     The apparatus for cutting open the stomach of a bird according to the invention may be part of several apparatuses for processing slaughtered poultry known per se, such as a stomach peeler for peeling the stomach of a bird. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Hereinafter the invention will be elucidated with reference to the drawing, in which an embodiment of the apparatus according to the invention is illustrated. 
     FIG. 1 shows schematically and in a side elevational view an embodiment of the apparatus according to the invention, and 
     FIG. 2 shows on a larger scale a cross section according to II--II in repeat use of reference characters in the following specification and appended drawings is intended to represent the same or analogous features or elements of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The apparatus for cutting open the stomach of a bird illustrated in FIG. 1 comprises a conveyor shaped as a chain 1 with carriers 2. The chain 1 runs around chain wheels 3. Below the lower part of the chain 1 a number of guidings 4 extend, for example shaped as guiding rods. As appears from FIG. 1 the illustrated embodiment comprises two guidings 4. 
     The stomachs 5 to be cut open are supplied through a hopper 6. The stomachs 5 decend along the hopper and are gripped by the carriers 2 of chain 1 and are moved along the guidings 4, in the drawing from left to right. 
     Below the chain 1 an arm 8 pivoting around a pivot 7 is provided which carries a nozzle 9 at its free outer end. The arm 8 is upwardly loaded by a spring 10. 
     Apart from the nozzle 9 the arm 8 also carries a follower roll 11 near its free outer end. 
     The nozzle 9 is connected to a, not illustrated, source for providing pressurized liquid through a hose 12. The liquid may consist of water. 
     The operation of the apparatus is as follows: the stomachs 5 supplied through the hopper 6 are moved along the guidings 4 by the carriers 2 of the chain 1. When a stomach 5 passes the nozzle 9 the follower roll 11 engages the lower side of the stomach thus pivoting the arm 8 against the spring load of the spring 10 towards such a position that the nozzle 9 is at a favorable distance from the stomach 5 for carrying out its cutting action. When the stomach 5 passes overhead the nozzle 9 the highly pressurized liquid jet leaving the nozzle 9 cuts open the respective stomach wall, as a result of which the liquid jet also may enter the stomach cavity. Due to the cutting action of the liquid jet and the pressure created by the liquid jet entering the stomach cavity the respective stomach wall is cut open quickly and effectively. 
     Already while cutting open, and afterwards, the stomach contents are flushed from the stomach by the liquid jet. For the stomach faces downwardly with its cut open side the stomach contents cannot spoil the remainder of the stomach. 
     After passing the nozzle 9 the stomach 5 is folded open by the guidings 4, which are correspondingly shaped, and in some cases is supplied to an apparatus for a further operation (not illustrated). For example such an apparatus may comprise a stomach peeler. 
     The invention is not limited to the embodiment described before which may be varied widely within the scope of the invention. It will be apparent to those skilled in the art that various modification and variations can be made in the apparatus and method of the present invention without departing form the scope and spirit of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come with the scope of the appended claims and their equivalents.