Method and device for boning a leg

Abstract: Method and device for boning a leg (4) or a part thereof of a slaughtered animal. Prior to the removal of the meat from the leg (4) or the part thereof, an incision is made through a tendon at the position of the condyle (42) of the tibia (43) in the ankle joint. During scraping of meat from the lower leg, the lower leg is retained by a lug (56) which engages in the canalis tendineus (53). Prior to or during the boning operation, the kneecap (12) of the leg (4) is pressed through an opening (72) of a stop element (68), following which the kneecap (12) projecting from the opening (72) is removed.

Description: The invention relates to a method and device for boning a leg or lower leg of a slaughtered animal. Such an animal is in particular a bird, such as a chicken, a turkey, a duck, an ostrich or the like, but it can also be other large or small livestock or game, such as a cow, a pig, a horse, a deer, a rabbit etc. When reference is made below to "upper" or "lower" in connection with a leg, "upper" will be understood as meaning: in the direction of the hip joint or at the hip joint side of the leg, and "lower" will be understood as meaning: in the direction of the (possibly imaginary) toes or at the (possibly imaginary) toes side of the leg. In connection with a device feature, "above" and "below" have their normal meaning. Legs of slaughtered animals can be boned in various ways before or after being cut away from the body of the animal. Of relevance in the context of this invention, on the one hand, are methods and devices for use where initially both the lower leg (the part of the leg below the knee joint, known as the drumstick in birds) and the upper leg (the part of the leg above the knee joint, that is the thigh) form part of the leg, which lower leg and upper leg are connected to each other in the knee joint. Of relevance in the context of this invention, on the other hand, are methods and devices by means of which operations are carried out on a lower leg which has already been separated from the corresponding upper leg. Relevant prior art in the context of the present invention is NL-A-9,301,238 disclosing the processing of poultry legs suspended from the tibia near the ankle joint, where a tendon incision is performed near the ankle joint. US-A-5,067,927 discloses the processing of thighs of poultry by making an incision at the condyle of a thigh bone at the hip joint thereof, above a point of suspension, in order to prepare for stripping the thigh meat from the thigh bone. A drawback of the known methods and devices is that the tendon incisions made above the ankle joint result in that the drumstick meat obtained in this way does not look very attractive. This is because the drumstick meat running down from the knee joint and above the ankle joint passes into various tendons which run towards the ankle joint and, once severed, fan out in such a way that in the trade this is known as the undesirable "flower" effect. The object of the invention is to eliminate the abovementioned problem, and to this end the invention firstly provides a method according to claim 1. The tendons which produce the flower effect in the prior art come together in the Achilles tendon of the leg. Cutting into the Achilles tendon therefore means that the tendons remain interconnected, and the flower effect does not occur. Greatly improved presentation of the leg meat obtained is achieved in this way. An advantageous further tendon incision near the condyle of the tibia is a tendon incision at the front of the leg or the part thereof. The defined separation produced by this leads to a more attractive appearance of the meat to be scraped off, and during the scraping the forces exerted upon the ankle joint by which the leg or the part thereof is normally suspended are not so great. At least the leg or a part thereof is preferably suspended by the ankle joint prior to the boning operation, and the leg or the part thereof is then clamped in the transverse direction thereof, in particular below the ankle joint, relative to the suspension, following which the tendon incision is made. This measure ensures that the intended incision point and incision depth can be predetermined, and the incision can therefore be carried out fully automatically by means of a device. Such a device for boning at least a leg or a part thereof of a slaughtered animal, in particular a bird, is defined in claim 5. In this way, the tendon incision can be made at such a point that the flower effect is avoided. In a preferred embodiment, the suspension means are in the form of a plate which is provided with one or more suspension openings in the form of notches running at right angles to the edge of the plate, which notches are designed to accommodate the shin bone of the leg or the part thereof above the ankle joint. Clamping means, which form part of the machine, for clamping the leg or lower leg in the transverse direction relative to the suspension means, comprise one or more stops which are at least partially movable relative to the plate. Cutting means, which form part of the machine, for making a tendon incision, operate above the plate. The device described above lends itself particularly well to a carousel design. In a preferred embodiment, the clamping means operate above the plate. This produces fixing by a part of the leg lying outside the fleshy area thereof, so that there is no risk of the meat being damaged and of its quality being reduced. In another preferred embodiment, a cutting element operates below the plate, in order to make a tendon incision at the front of the leg or the part thereof. The invention further provides an interacting lug and stop, which lug, which is movable to and fro preferably in a direction essentially at right angles to the lower leg, is adapted for engaging in the canalis tendineus of the lower leg, and which stop is adapted for supporting the lower leg at the opposite side. This means that, during the scraping of the meat from the leg and the operations connected therewith, the forces on the lower leg directed away from the ankle joint can be absorbed much better than in the case of fixing or suspension at the position of the ankle joint part, and the risk of said joint part breaking off is consequently considerably reduced. Moreover, the use of the lug increases the stability of the fixing of the bone concerned, so that the tendons are positioned more accurately and can consequently be cut with greater accuracy. The invention is explained below with reference to the drawing, in which: Fig. 1 shows a side view of a leg of a bird suspended from a carrier, in order to illustrate a number of preparatory operations for the boning thereof; Fig. 2 shows the view according to Fig. 1 in a subsequent phase of the boning operation; and Figs. 3 - 6 illustrate subsequent phases of the boning operation. The same reference numbers relate to the same elements in the various figures. Fig. 1 shows a carrier 2 with an aperture in which a leg 4 of a bird is suspended by its ankle joint 6. Although in the description which follows operations are explained with reference to a bird leg, it will be clear that similar operations can also be carried out on legs of other animals, such as those mentioned in the preamble of the description. The carrier 2 can be formed by a plate or an essentially plate-shaped element, along the edge of which one or more apertures are made for the accommodation of the shin bone of one or more respective legs, but the carrier can also be formed by, for example, a hook which is moved along continuously or intermittently in a conveyor line. In the leg, the lower leg bone or drumstick bone 8, the upper leg bone or thigh bone 10 and the kneecap 12 are shown diagrammatically. Two preparatory cutting operations are being carried out on the leg 4 in Fig. 1, in which a left hand 14 of a person is holding the leg 4 by its underside, while the right hand makes the incisions from positions 16a, 16b by means of a knife 18. A first incision is made from the position of the right hand indicated by 16a, in the direction of arrow 20 along dashed-and-dotted line 22 up to the region of the hip joint of the thigh bone 10. A second incision is made from the position of the right hand indicated by 16b, in the direction of arrow 24 along dashed-and-dotted line 26 through the knee joint up to the kneecap 12 thereof. Fig. 2 illustrates how the thigh bone 10 is then removed from the upper leg following the cut along the dashed-and-dotted line 26, by moving the knife 18 with the right hand 16c in the direction of arrow 28 along a path indicated by dashed-and-dotted line 30. The operations described above with reference to Figs. 1 and 2 are not essential for the present invention, and could be omitted, if desired, if use is made of a suitable method or device for removal of the meat from both the lower leg and the upper leg, in which case the knee joint remains intact, as described in, for example, publication NL-A-9301238. Besides, a manual operation is shown in Figs. 1 and 2 purely for reasons of clarity. Some or all of these operations can also be carried out mechanically, as described in publications US-A-5,176,562 and EP-A-0,594,934. It will also be clear that, instead of a whole leg, it is also possible to start from a part of the leg, such as the drumstick, for the operations to be described below. In the phase of the boning of the leg 4 illustrated in Fig. 3, the ankle joint 6 is clamped in the transverse direction above the carrier 2 by means of stops 34 and 36 which are movable relative to the carrier 2 in the directions of the arrows 32a and 32b. The cutting side of a knife 38 is then inserted into the ankle joint 6 in the direction of arrow 40, in order to make an incision through the Achilles tendon at the back of the leg 4 at the position of the condyle 42 of the tibia 43, for the purpose of preventing the flower effect. Any incision made near the condyle at the front of the leg or the part thereof is made at the point indicated by 37. Fig. 4 illustrates how the meat is scraped from the bone 8 of the lower leg after the Achilles tendon incision shown in Fig. 3 has been made. For this purpose, a pair of scraper plates 44 and 46, each of which is provided with an aperture 44b and 46b at a front edge 44a and 46a respectively, are partially overlapped, so that a scraping opening is produced, as is usual in the art for scraping meat from the leg of a bird. The scraper plates 44 and 46 can be moved both towards and away from each other by means of arms 48 and 50 respectively fixed thereto, the movements of which arms are produced by, for example, curved path control. The scraper plates 44 and 46 in the mutual position shown in Fig. 4 are moved in the direction of arrows 52 from a position directly below the carrier 2 to an end position which is shown in Fig. 5. As soon as the scraper plates 44 and 46 shown in Fig. 4 have left their initial position directly below the carrier 2 and have passed the canalis tendineus 53 of the lower leg bone, a lug 56 is placed from one side in the direction of arrow 54 in the canalis tendineus 53, and stop 56a is placed against the bone in the opposite direction, in a manner not shown in any further detail, for stabilization of the bone, and for absorbing the scraping forces exerted on the bone 8 by the scraper plates 44 and 46, in order to prevent the bone 8 from breaking off near the ankle joint 6. When the scraper plates 44 and 46 have reached their end position shown in Fig. 5, said plates and the lug 56 are withdrawn from the leg. Fig. 6 illustrates how the lower leg bone 8 is fixed by means of one or more, in this case two, stops 58 and 60 which are fitted on arms 62 and 64 respectively, for moving the stops 58 and 60 relative to the bone 8. It is also possible not to make the transverse cut shown in Fig. 1, and not to remove the thigh bone until after the meat has been scraped from the whole leg. Here again, the situation shown in Fig. 6 will then ultimately be reached.

Claims: Method for boning a leg (4) or a part thereof of a slaughtered animal, in particular a bird, comprising the steps of: suspending at least the leg or the part thereof by the ankle joint (6) from suspension means (2) comprising a suspension opening which has smaller dimensions than the condyle (42) of the tibia (43); making at least one tendon incision near the ankle joint (6); and removing the meat from the leg or the part thereof, characterized in that the tendon incision is made through a tendon at the position of the condyle (42) of the tibia (43) above the suspension opening of the suspension means (2). Method according to claim 1, characterized in that at least the leg (4) or a part thereof is suspended by the ankle joint (6) prior to the boning operation, and the leg (4) or the part thereof is then clamped in the transverse direction thereof, in particular below the ankle joint (6), relative to the suspension, following which the tendon incision is made. Method according to claim 1 or 2, characterized in that the tendon incision is made in the Achilles tendon. Method according to any of claims 1 - 3, characterized in that a further tendon incision is made at the front of the leg or the part thereof. Device for boning at least a leg (4) or a part thereof of a slaughtered animal, in particular a bird, the device comprising: suspension means (2) for carrying at least the leg or the part thereof by a joint (6), the suspension means (2) comprising a suspension opening which has smaller dimensions than the condyle (42) of the joint (6); cutting means (38) for making a tendon incision above the suspension opening of the suspension means (2); and means for removing the meat from the leg or the part thereof, characterized in that the suspension means (2) are adapted for carrying the tibia (43) by the ankle joint (6), provision being made for fixing means for fixing the leg or the part thereof in a position below the knee joint in a direction transverse to a longitudinal axis extending between the ends of the tibia (43), relative to the suspension means (2). Device according to claim 5, characterized in that the fixing means are clamping means (34, 36) for clamping the leg (4) or the part thereof in the transverse direction relative to the suspension means (2). Device according to claim 6, characterized in that the suspension means (2) are in the form of a plate which is provided with one or more suspension openings in the form of notches running at right angles to the edge of the plate, which notches are designed to accommodate the shin bone of the leg (4) or the part thereof above the ankle joint (6); in that the clamping means comprise one or more stops (34, 36) which are at least partially movable relative to the plate (2); and in that the cutting means (40) operate above the plate. Device according to claim 7, characterized in that the clamping means (34, 36) operate above the plate (2). Device according to claim 7 or 8, characterized in that a cutting element operates below the plate, in order to make a further tendon incision at the front of the leg (4) or the part thereof. Device according to claim 5, characterized in that the fixing means comprise an interacting lug (56) and stop (56a), which lug (56) is adapted for engaging in the canalis tendineus (53) of the lower leg, and which stop (56a) is adapted for supporting the lower leg at the opposite side. Device according to claim 10, characterized in that the lug (56) is movable to and fro in a direction essentially at right angles to the lower leg.

Inventors: JANSSEN PETRUS CHRISTIANUS HEN, VAN DEN NIEUWELAAR ADRIANUS JO, JANSSEN, PETRUS CHRISTIANUS HENDRIKUS, VAN DEN NIEUWELAAR, ADRIANUS JOSEPHES
Applicants: STORK PMT, STORK PMT B.V.
Application year: 1996
Main classification: A22C17
IPC codes: A22C21, A22C17