State of the Art: In the processing of various kinds of meat for food, machines have been developed for a variety of purposes. A primary concern in such processing has been to leave in the meat as little as possible of relatively hard, inedible components, such as pieces or particles of bone, heavy connective tissue, and skin, as in the processing of chunks cut from carcasses of various animals for grinding into hamburger meat or the like, or in the processing of skeletal remains of poultry, especially chicken or turkey, to recover the small amount of flesh remaining attached to the skeletal bones following removal of as much of the flesh as possible by cutting and stripping from the bone.

A type of grinding machine that is widely used throughout the world in the production of hamburger meat, comprises a perforate screening plate of flat and usually disc formation usually having a rotary knife operable at and over the entry face thereof into which the meat material is fed. A flow channel may extend across the entry face of such a screening plate for collecting bones and other relatively hard matter as

pushed across such entry face by the rotating knife, which not only scrapes the bone and other relatively hard matter from the entry face of the screening plate toward discharge therefor but also tends to push flesh through the screen openings, see Speco, Inc.'s Charles W. Hess U. S. Patent No. 4,004,742 of January 25, 1977.

Other machines widely used for processing skeletal remains of poultry, especially chicken, are known as"deboning"machines in accordance with Beehive Machinery, Inc.'s Archie R. McFarland U. S. Patent No. 3,739,994 of June 19,1973, as reissued on July 17,1984 as Re. 31,631, the Claudio dos Santos U. S. Patent No.

4,189,104 of February 19,1980, and the McFarland et al. U. S.

Patents No. 4,340,994 of July 27,1982, No. 4,480,980 of November 6,1984, and No. 4, 566, 640 of January 28,1986.

A later machine developed by Archie R. McFarland for Diamond Stainless Corporation of Salt Lake City, Utah, is disclosed in Patent No. 5,580,305 of December 3,1996 for "Segregating Meat from Bone, Heavy Tissue, and Skin". This machine operates primarily on chunks of cut meat that include sizeable pieces of bone and often heavy connective tissue and skin.

Although the early deboning machines provide for the build- up of a so-called filter mat"across the inner face of a tubular screen through which the feed material is advanced by a conveyor screw for filtering out small particles of bone from the flesh about to pass through the screen, the McFarland machine of Patent No. 5,580,305 is not concerned with such a filter mat. Rather it increases production of the relatively soft product while effectively dealing with relatively large pieces of bone usually contained by the chunks of cut meat.

There, a conveying cutter helical screw or auger is provided in close cutting relationship with the perforations of the usual cylindrically tubular screen in combination with a bone-cutting ring valve at the discharge end of such screen, which provides advantageous back pressure within the tubular screen as does the ring valve of a usual deboning machine.

An older McFarland U. S. patent assigned to Beehive Machinery, Inc. is No. 3,825,231 of July 23,1974 entitled"Twin Screw Continuous Processing machine". It discloses twin helical screws at the bottom of a hopper for mixing meat materials in the hopper and for discharging the mixed material into the entry face of a flat disc grinder screen with anything that does not pass through the screen falling back into one of the screws for transfer to the other screw for further mixing.

Summary of the Invention A principal object in the making of the present invention was to effectively discharge pieces of bone and other relatively hard components that accompany cut pieces of meat or other materials fed to a processing machine, substantially without the grinding or cutting of such relatively hard components as occurs in present grinder screen machines or as occurs in the other machines of the above-mentioned patent.

This is preferably accomplished by utilizing the first of the aforementioned types of processing machines, i. e., one having a flat plate grinder screen with a rotary knife active on the entry face of the screen, rather than a tubular screen with material conveying, helical screw or auger. The rotary knife is preferably one with multiple blades radiating from a central shaft for pushing pieces of relatively hard material against and across the flat entry face of the flat plate screen as confronted by the blades of the rotary knife. As in the aforementioned Speco, Inc.'s Hess Patent No. 4,004,742, such a screen may be provided with a bone-receiving and guiding flow channel, or one with a circumferentially-directed channel as presently used in generally similar machines, but, in accordance with the present invention, in combination with a special back- pressure-providing discharge device which effectively receives and removes the pieces of bone and of other relatively hard material if present substantially without cutting it.

I have found that discharging of relatively large pieces of bone and the like into the entry end of dual, elongate, material-conveying, helical screws, that have their spiral flights overlapped and intermeshed to form a longitudinally running series of bone-carrying compartments each being of

length capable of accepting unusually long pieces of bone and other relatively hard and normally unwanted material or even relatively small pieces of material, such as berry seeds accompanied by liquid, the size of the compartments being adjustable by substitution of different helical screws having the pitch of the helical threads suitably altered. Moreover, the carrying capacity of the dual helical screws can be altered by changing their rate of rotation. I have found that the longitudinally running, overlapped and intermeshing flights provide not only for very effective carrying of unusually long bones, etc., but, also, for back-pressurizing the material being screened as previously done by a bone-cutting ring valve at the discharge end of a tubular screw in accordance with the aforementioned McFarland U. S. Patent No. 5,580,305.

Thus, the overlapping, double helical screw, discharge device acts as a rotary valve and can be used in combination with either a flat screen or a tubular screen for separating components of a variety of composite materials.

The Drawings The best mode of each of different ways presently contemplated for carrying out the invention is illustrated in the accompanying drawings, in which: Fig. 1 represents a view in longitudinal side-elevation of a meat grinding machine of the invention, shown partially in axial vertical section revealing the overlapped and intermeshed, material-discharging, helical screws in combination with a flat disc grinder screen; Fig. 2, a view in horizontal section taken along the line 2-2 of Fig. 1; Fig. 3, an isometric view of the machine of Figs. 1 and 2 drawn to somewhat larger scale and having a longitudinal portion cut away to reveal the overlapping helical screws and other internal parts; Fig. 4, a pictorial exploded view showing the various parts of the machine of the preceding figures in series arrangement extending from the flat disc grinder screen through the material-discharging dual screws; and Fig. 5, a view corresponding to that of Fig. 1 but showing a different embodiment of the invention wherein the material- discharging screws are combined with a tubular screen having a cutting auger for moving the material along the interior cylin- drical face of the screen.

Detailed Description of the Illustrated Embodiments In the form of the invention illustrated in Figs. 1-4, a composite material, such as lumps of cut meat having relatively soft flesh together with pieces of bone and other relatively hard components such as connective tissue and skin, or such as fruit having relatively soft flesh together with pits, stems, seeds or other normally waste parts, is fed from a source of same through a tubular hopper 10, shown fragmentarily in Fig. 1, usually under pumping pressure or by a helical screw or auger driven in any suitable manner. Hopper 10 empties across the entry face of a vertically positioned, flat plate grinder screen 11 against which the blades 12a of a multibladed, rotary knife 12 extend radially, or otherwise angularly, from rigid mounting of such knife on a drive shaft assembly 13 in a casing 14 and driven in any suitable manner, as by a motor (not shown) operating through a standard gearbox 15. Drive shaft assembly 13, as illustrated in Figs. 1,2, and 3, comprises a rotatable shaft part 13a coupled to the output shaft of the gearbox 15, a second rotatable shaft part 13b, coupled by a square or other polygonally shaped end member 13c to rotatable part 13a and having an opposite, annular end portion into which fits, rotatably and movably longitudinally, a shaft part 13d. Into the open annular end of such shaft part 13d is screwed a shaft portion 12b of rotary knife 12, so that knife 12 is rotated by its connection with gearbox 15 but is also constantly pressed forwardly by a spring 16 housed within shaft part 13b to take up any slack due to knife blade wear.

In grinding chunks of, for example, cut meat containing or otherwise associated with pieces of bone and usually with pieces of heavy connective tissue and skin, such composite material is

passed from hopper 10 onto the entry face of meat grinder screen 11 into the path of the rotating blades 12a of knife 12, where they are pushed against and across such entry face of the screen and dropped into the central recess 12c of the rotary knife 12 and into the entry end of rotary valve discharge structure provided by dual, intermeshing, helical screws 17 and 18 that are rotatably mounted within a casing 14-1 extending from casing 14. The flesh passes through the perforations of screen 11 and, as here shown, into an annular, open discharge chamber 19, from where it is discharged into a receiving vessel (not shown) as a valuable ground meat product of the operation.

As here shown and preferably, each blade 12a of the rotary knife 12 is mounted so as to collectively define the recessed or dish nature of the knife, usually angularly with respect to the substantially radial sweep of the carrying arms 12d of the knife so the sharp cutting edge of the blade moves in fiber-cutting relationship with the entry openings of the screen.

Since the chunk material to be subjected to separation of the soft flesh thereof from the relatively hard components thereof is introduced into the recess 12c of the knife in advance of the entry face of the screen, usually under pumping pressure, the flesh readily passes through the screen, while the large pieces of bone and other relatively hard material are pushed along the entry face of the screen substantially without being cut prior to passing into the entry ends of conveying screws 17 and 18, whose helical flights 17a and 18a are overlapped to provide longitudinally running and bone-receiving compartments 20, Figs. 1 and 2, the helical pitch of such screws 17 and 18 being great enough to accommodate the anticipated maximum length of pieces of bones and other hard materials that

are associated with the chunks of meat in the composite material to be ground.

It is advantageous, but not always necessary, that the spiral flights 17a and 18a of the helical, material-carrying screws 17 and 18 be reduced in width along the discharge end portions of such screws so as to not overlap and to therefore provide an elongate opening 21 between the preferably still helical portions of the screws for facilitating release and dropping of the carried bone and other hard materials into offtake chute 22, Fig. 1.

The helical, material-carrying screws 17 and 18 are rotated in opposite directions toward or away from each other depending upon the arrangement of their overlapped flights by preferably a speed-adjustable motor 23 and appropriate gear box 24 with respective screw-coupling out-put shafts 24a and 24b, Fig. 2.

As previously indicated, the screen may be tubular, as shown at 25, Fig. 5, preferably converging toward its discharge end 25a so as to be somewhat conical, whereby an auger screw 26 with a helical, cutting flight 26a is continually pressed against the inner cylindrical entry face thereof by a spring (not shown) to take up any slack that might otherwise occur through wear, as in the McFarland et al. Beehive Machinery, Inc. Is U. S. Patent No. 4,566,640 and the McFarland Diamond Stainless, Inc.'s U. S. Patent No. 5,580,305.

The relatively soft flesh component of the composite material being processed passes through the perforations of screen 25, while the relatively hard components are carried by helical flight 26a of auger screw 26 through annular passage 27 into the entry end portions of the dual, helical, conveying screws 28 and 29, whose flights 28a and 29a overlap up to non-

overlapped, discharge end portions 28c and 29c of such helical screws 28 and 29 which overlie the entrance to a discharge conduit (not shown) that may correspond to the offtake conduit 22 in the embodiment of Figs. 1-4.

It should be realized that here, as in the first embodiment of the machine of this invention, the dual conveying helical screws produce back pressure on the composite material awaiting to be screened.

It should be realized that the material conveying and mixing machine of my aforementioned patent, No. 3,825,231, is not only structurally different from the present machine in that the helical screws do not overlap to provide longitudinally running, material-carrying compartments between them, which receive their contents from the blade scraped entry face of the screen and carry them to remote discharge at the opposite ends of such compartment-forming screws, but that the individual placement and operation of the structure effect different results from that of the present machine.

Whereas this invention is here illustrated and described with reference to embodiments thereof presently contemplated as the best modes of carrying out such invention in actual practice, it is to be understood that various changes may be made in adapting the invention to different embodiments without departing from the broader inventive concepts disclosed herein and comprehended by the claims that follow.