110 is about 5½ inches for the infeed portion 114, and then begins a constant taper from the junction between the infeed portion 114 and the compression portion 116, through the compression portion 116 and through the deboning portion 118. In this embodiment, the diameter of the root 110 is about 7¼ inches at the distal end of the deboning portion 118, that is, the end that is distal from the infeed portion 114.

In addition, the lead angle of the screw flights 122, 124, 126 decreases from the infeed portion 114 through the compression portion 116 to the deboning portion 118. Thus, the infeed lead angle θ_INon the infeed screw flights 122 in FIG. 7A is greater than the compression lead angle θ_COMon the compression screw flights 124 in FIG. 7B, which in turn is greater than the deboning lead angle θ_DEBon the deboning screw flights 126 in FIG. 7C.

Now referring to FIGS. 7A to 7C in particular, it can be seen that in the illustrative embodiment, concavely curved fillets extend between the root 110 and the screw flights 122, 124, 126. These include infeed fillets 134 on the infeed portion 114, compression fillets 136 on the compression portion 116, and deboning fillets 138 on the deboning portion 118. The concavely curved fillets 134, 136, 138 extend along at least ten percent of the flight depth of the screw flights 122, 124, 126, preferably along at least fifteen percent of the flight depth of the screw flights 122, 124, 126, and still more preferably along at least twenty percent of the flight depth of the screw flights 122, 124, 126. Moreover, the outer diameter of the thread 112 is substantially constant along the length of the compression screw 102. In one preferred embodiment, the outer diameter of the thread 112 is between about 9 inches and about 12 inches. Because the outer diameter of the thread 112 is substantially constant, as the diameter of the root 110 increases from the infeed portion 114 where it smallest, along the compression portion 116 toward and through the deboning portion 118 where it is largest, the flight depth (measured from the root 110) increases and the proportion of the flight depth of the screw flights 122, 124, 126 along which the fillets 134, 136, 138 extend also increases. Thus, the deboning fillets 138 extend along a larger proportion of the deboning screw flights 126 than the compression fillets 136 extend along the compression screw flights 124, and in turn the compression fillets 136 extend along a larger proportion of the compression screw flights 124 than the infeed fillets 134 extend along the infeed screw flights 122.

Referring now again to FIG. 8 (and also to FIGS. 1 to 4), the screw assembly housing 104 is carried by a support 140, which also carries a motor housing 142 in which is disposed a motor 144 for driving the compression screw 102. As such, the compression screw 102 is connectable to a drive member 146 of the motor 144 for driving rotary movement of the compression screw 102 within the barrel 106.

Continuing to refer to FIG. 8 and now also to FIGS. 6 and 9, the barrel 106 comprises an infeed section 150, a compression section 152, a deboning section 154 and a bone residue outlet section 156, with an annular bone residue outlet 158 formed at a terminus 160 of the bone residue outlet section 156. The terminus 160 of the bone residue outlet section 156 also defines the terminus of the barrel 106. In the illustrated embodiment, the infeed section 150, the compression section 152, the deboning section 154 and the bone residue outlet section 156 are each formed by individual barrel pieces having outwardly projecting annular flanges that are bolted together; other assembly techniques are also contemplated. In other embodiments, two or more sections of the barrel, or the entire barrel, may be of monolithic construction. The infeed section 150 is disposed adjacent the motor housing 142, the compression section 152 is disposed between the infeed section 150 and the deboning section 154, and the deboning section 154 is disposed between the compression section 152 and the bone residue outlet section 156. The bone residue outlet section 156 extends from the deboning section 154 opposite the compression section 152. Each adjacent section of the barrel 106 is in fluid communication with each adjacent section. Thus, the infeed section 150 communicates with the compression section 152, which communicates with the deboning section 154, which communicates with the bone residue outlet section 156; hence the bone residue outlet 158 is in fluid communication with the deboning section 154.

Referring now to FIG. 9A, the deboning section 154 comprises a plurality of deboning screens 162 formed by a plurality of meat apertures 164 (see FIG. 9) through the deboning section 154 of the barrel 106. The meat apertures 164 are configured to permit passage of deboned meat therethrough, while inhibiting the passage of larger pieces of bone. The term “deboned meat”, as used herein, does not require that the meat be entirely devoid of bone matter. Rather, as used herein the term “deboned meat” means meat having bone particles measuring up to 25 mm in size, measured along the longest/largest dimension of a given piece of bone.

In the embodiment shown, the meat apertures 164 in the deboning section 154 each include a sizing bore 166 extending outwardly from the interior surface 168 of the deboning section 154 and a counterbore 170 extending inwardly from the outer surface 172 of the deboning section 154, coaxially with each sizing bore 166. In a preferred embodiment, the sizing bores 166 are at least 0.120 inches in length, but otherwise kept as short as practicable to reduce the pressure required to force deboned meat through the sizing bores 166. Without being limited by theory, it is believed that the counterbores 170 improve meat texture and reduce temperature increases in the deboning section 154. The dimensions of the sizing bores 166 and the counterbores 170 will vary depending on the type of animal and the type of bone. For example, and without limitation, for pork or beef, the sizing bores 166 may be between about 2 mm in diameter to about 15 mm in diameter, with the counterbores 170 being about 1 mm to about 4 mm wider than the sizing bores 166. By way of non-limiting example, an 8 mm sizing bore 166 may have a 10 mm counterbore 170. In one preferred embodiment, the meat apertures 164 are radial with respect to the barrel 106, that is, normal to the axis of rotation R; in other embodiments the meat apertures 164 may have a pitch relative to the barrel 106 such that the meat apertures 164 are non-normal to the axis of rotation R.

Referring again to FIGS. 6, 8 and 9, the inlet 108 communicates with the infeed section 150 of the barrel 106 and is adapted to feed meat-laden bones into the infeed section 150. In the illustrated embodiment the inlet 108 is fed by a chute 174 but this is merely one example; in other embodiments the inlet may be fed by a conveyor belt, a pump, or any other suitable feed mechanism.

As noted above, the compression screw 102 is rotatably disposed within the barrel 106. More particularly, as shown in FIGS. 6 and 8 the infeed portion 114 of the compression screw 102 is disposed in the infeed section 150 of the barrel 106 in registration with the inlet 108, the compression portion 116 of the compression screw 102 is disposed in the compression section 152 of the barrel 106, and the deboning portion 118 of the compression screw 102 is disposed in the deboning section 154 of the barrel 106 in registration with the deboning screens 162. The deboning portion 118 of the compression screw 102 extends beyond the deboning section 154 of the barrel 106 into the bone residue outlet section 156 of the barrel 106.

At the terminus 160 of the bone residue outlet section 156, the inner surface 176 of the barrel 106 is infundibular. A correspondingly infundibular pressure cap 178 is received in the inwardly infundibular terminus of the bone residue outlet section 156, and the distal tip 120 of the compression screw 102 is received within an axial bore 180 of the pressure cap 178 (see FIG. 8 in particular). The bone residue outlet 158 is formed by an annular gap 182 between the pressure cap 178 and the inner surface 176 of the barrel at the terminus 160 of the bone residue outlet section 156. The pressure cap 178 is movable axially relative to the barrel 106 and the compression screw 102 to vary a volume of the annular gap 182, and a pressure cap actuator 184 is coupled to the pressure cap 178 to effect axial movement of the pressure cap 178 toward and away from the barrel 106 and the compression screw 102. The pressure cap actuator 184 may be, for example, a solenoid or a piston-cylinder assembly. Of note, the pressure cap 178 is non-rotatable relative to the barrel 106, and in particular the terminus 160 thereof.

As shown in FIGS. 6 and 8, the thread 112 of the compression screw 102 engages the inner surface of the barrel 106 along substantially the entire length thereof. As used herein, the term “engages”, although not necessarily requiring actual physical contact, denotes an extremely close, flush fit between two components. For example, a spacing between about 0.005 inches and about 0.100 inches would fall within the meaning of “engages”. Thus, the thread 112 on the infeed portion 114 of the compression screw 102 engages the inner surface of the infeed section 150 of the barrel 106, the thread 112 on the compression portion 116 of the compression screw 102 engages the inner surface of the compression section 152 of the barrel 106, and the thread 112 on the deboning portion 118 of the compression screw 102 engages the inner surface of the deboning section 154 of the barrel 106 as well as the inner surface of the bone residue outlet section 156 of the barrel 106. In a preferred embodiment where the outer diameter of the thread 112 is between about 9 inches and about 12 inches, the inner diameter of the barrel 106 would be the same, plus the clearance value, which would add between about 0.010 inches and about 0.200 inches (double the radial clearance of between about 0.005 inches and about 0.100 inches).

Importantly, and in fact critically, the barrel 106 and the compression screw 102 are configured to cooperate with one another to encourage axial movement of the meat-laden bones along the compression screw 102 and the barrel 106 and, at least within the deboning section 154 of the barrel 106, to inhibit the meat-laden bones from co-rotating within the barrel 106 along with the compression screw 102. Thus, while the compression screw 102 rotates within the barrel 106, the meat-laden bones generally proceed axially along the barrel 106 but without substantial rotation within the barrel 106; the threads 112 of the compression screw 102 generally rotate past the meat-laden bones. Without being limited by theory, it is believed that when the meat-laden bones in a conventional compression screw separator rotate within the barrel along with the compression screw, this causes bone pieces to grind on the inside of the barrel and break at the junction of the thread and the inner surface of the barrel. This increases the number of bone fragments that end up in the resulting meat, increasing the calcium levels and thereby reducing the quality of the meat.

One method for inhibiting the meat-laden bones from co-rotating within the barrel 106 along with the compression screw 102 involves the use of guide channels.

Turning now to FIGS. 9, 9A and 10, in the illustrated embodiment a plurality of circumferentially-spaced, longitudinally extending guide channels 186 are formed in the interior surface 188 of the barrel 106 and extend substantially parallel to an axis of rotation R of the compression screw 102 within the barrel 106. Thus, the guide channels 186 are substantially linear and non-helical.

The guide channels 186 extend at least through the deboning section 154 of the barrel 106, preferably from the compression section 152 into and through the deboning section 154, more preferably from the infeed section 150 into and through the compression section 152 and into and through the deboning section 154, and still more preferably from the infeed section 150 into and through the compression section 152, into and through the deboning section 154 and into the bone residue outlet section 156 as shown in the illustrated embodiment.

The interior surface 188 of the barrel 106 is inwardly crenellated from the infeed section 150 into and through the compression section 152, into and through the deboning section 154 and into the bone residue outlet section 156. This crenellation forms alternating inwardly projecting merlons 190 and crenels 192 between the merlons 190, with the crenels 192 being outwardly recessed relative to the merlons 190. The guide channels 186 are formed by the crenels 192. The meat apertures 164 are formed in the merlons 190, and in the illustrated embodiment no meat apertures are formed in the crenels 192 so that the guide channels are free of meat apertures. Thus, each of the merlons 190 functions as a deboning screen 162. In other embodiments, meat apertures may be formed in the crenels as well.