Automated method and apparatus for separating poultry legs into thighs and drumsticks
A method of separating a poultry leg into its constituent thigh and drumstick includes bending the leg at the knee to impart stress to the tissue surrounding the knee knuckle and urge the end of the drumstick bone away from the end of the thigh bone. Further stress is imparted and the bones are further urged apart by pushing the top of the drumstick in a direction opposite the knee. The tissue above the knee is then pushed up and the tissue below the knee is pushed down to maximize tension in the tissue and move the ends of the bones apart as far as possible without tearing the tissue. The tissue at the knee is then progressively sliced by a rotary cutter. The initial slice relieves tension in the tissue causing it to pull apart and move the ends of the bones further apart. The slice is then completed between the now spaced apart ends of the bones to separate the thigh from the drumstick without producing bone shards and splinters that can contaminate the meat of the thigh and the drumstick. An apparatus for performing the method is disclosed.
1. An automated method for separating a poultry leg having an ankle, a knee, a thigh bone, a drumstick bone, and a knee knuckle into a thigh and a drumstick, the method comprising the steps of:
(a) suspending the poultry leg by the ankle with the poultry leg extending downwardly;
(b) conveying the suspended poultry leg in a processing direction;
(c) securing and positioning the suspended poultry leg as the poultry leg is conveyed in the processing direction;
(d) bending the poultry leg at the knee to create tension in tissue and ligaments surrounding the knee joint and to urge the thigh bone and the drumstick bone apart at the knee joint;
(e) initiating a cut through tissue at the knee joint to begin to relieve the tension in the tissue thereby allowing the thigh bone and the drumstick bone to separate further at the knee joint;
(f) continuing the cut between the ends of the thigh bone and the drumstick bone to separate the thigh from the drumstick without cutting the thigh bone or the drumstick bone;
(g) collecting the thigh; and
(h) collecting the drumstick.
2. The method of claim 1 further comprising the step following step (d) of creating additional tension in tissue and ligaments surrounding the knee joint prior to step (e).
3. The method of step 2 wherein creating additional tension comprises engaging the leg above the knee joint with at least one tensioning plate as the leg is conveyed in the processing direction.
4. The method of claim 3 wherein the tensioning plate has an upsloping forward edge that progressively urges the drumstick away from the thigh as the leg is conveyed in the processing direction.
5. The method of claim 4 further comprising engaging the leg above the knee with a second tensioning plate higher than the first tensioning plate after the leg is engaged by the first tensioning plate.
6. The method of claim 1 wherein step (c) comprises progressively capturing the leg between a thigh positioner and a drumstick positioner.
7. The method of claim 6 wherein the thigh positioner and the drumstick positioner are components of an intermediate positioning assembly moving synchronously with the leg in the processing direction.
8. The method of claim 7 wherein the thigh positioner and the drumstick positioner are movable components of the intermediate positioning assembly and wherein step (c) comprises moving the thigh positioner and the drumstick positioner progressively toward one another with the leg positioned between them.
9. The method of claim 1 wherein step (d) comprises engaging the leg with a guide rail.
10. The method of claim 9 wherein engaging the leg with a guide rail comprises engaging the leg with the guide rail between the ankle and the knee as the leg is conveyed in the processing direction.
11. The method of claim 1 wherein step (e) comprises engaging the tissue with a rotating blade as the leg is conveyed in the processing direction.
12. The method of claim 11 wherein the rotating blade is sized so that the initial cut made by the blade is in the tissue surrounding the knee.
13. The method of claim 1 wherein step (f) comprises conveying the leg past a rotating blade.
14. The method of claim 1 wherein step (g) comprises allowing the separated thigh to fall to a collection location and step (h) comprises continuing to convey the drumstick to a separate location.
15. An apparatus for separating a poultry leg having an ankle, a knee, a thigh bone, a drumstick bone, and a knee knuckle into a thigh and a drumstick, the apparatus comprising:
a shackle from which the poultry leg can be suspended by its ankle with the leg extending downwardly;
the shackle being attached to a conveyor configured to move the shackle and a poultry leg suspended therefrom in a processing direction;
a positioning assembly vertically aligned below the shackle;
a drive system configured to move the positioning assembly in the processing direction synchronously with the shackle above;
the positioning assembly comprising a thigh positioner and a drumstick positioner selectively movable toward each other to capture and position a poultry leg suspended from the shackle above as the poultry leg and the positioning assembly are conveyed together in the processing direction;
the thigh positioner and the drumstick positioner being configured to bend the poultry leg at the knee as the poultry leg is captured to create initial tension in tissue and ligaments surrounding the knee joint and to urge the thigh bone and the drumstick bone apart at the knee joint;
a knife located along the processing path and positioned to be engaged by the tensioned tissue and ligaments surround the knee joint as the poultry leg and positioning assembly move together in the processing direction to begin to cut through the tensioned tissue and ligaments and allow the thigh bone and the drumstick bone to separate further as a result of tension relief;
continued movement of the poultry leg in the processing direction past the blade severing the poultry leg into a thigh and a drumstick without cutting the thigh bone and drumstick bone.
16. The apparatus of claim 15 further comprising an upper guide rail located along the processing path and being shaped and positioned to engage the captured drumstick to tension further the tissue around the knee knuckle and further urge the bones of the thigh and drumstick apart at the knee.
17. The apparatus of claim 15 further comprising a primary tensioning plate located along the processing path upstream of the knife, the primary tensioning plate being positioned and configured to engage the poultry leg just above the knee joint to exert upward force on the poultry leg at the knee to impart even greater tension to the tissue surrounding the knee knuckle.
18. The apparatus of claim 17 further comprising a secondary tensioning plate located downstream of the primary tensioning plate and being positioned and configured to engage the poultry leg above the knee joint to exert additional upward force on the poultry leg at the knee and impart maximum tension to the tissue surrounding the knee knuckle before the poultry leg encounters the knife.
19. The apparatus of claim 15 wherein the knife is a rotary knife.
20. The apparatus of claim 15 wherein the thigh positioner comprises a thimble in which the thigh is captured and positioned as the positioning assemblies capture the poultry leg.