BACKGROUND OF THE INVENTION 
     There are many different kinds of food loaves in a wide variety of shapes and sizes. Meat loaves are made from various different meats, including ham, pork, beef, lamb, turkey, fish, and others. Meat loaves come in different shapes such as round, square, rectangular, oval, and others, and in different lengths up to six feet or longer. The cross-sectional sizes of the loaves can be dissimilar, the maximum transverse dimension may be as small as 1½ inches or as large as 10 inches. Loaves of cheese or other foods are also available in varying compositions, in a wide range of shapes, lengths, and transverse sizes. 
     Food loaves are typically sliced, the slices grouped in accordance with a particular weight requirement, and then packaged and sold. The number of slices in a group may vary, depending on the size and consistency of the food loaf and on the desires of the producer, the wholesaler, or the retailer. For some products, neatly aligned stacked slice groups are preferred. For others, slice groups can be shingled so that a purchaser can see a part of every slice. 
     Examples of known high-speed food loaf slicing machines are described in U.S. Pat. Nos. 5,974,925; 4,805,503 and 4,428,263. U.S. Pat. Nos. 5,649,463; 5,704,265; EP 0 713 753; or WO 99/08844, also disclose high-speed food loaf slicing machines. Slicing apparatus are also embodied in the FORMAX FX180 Slicer available from Formax, Inc. of Mokena, Ill., U.S.A. 
     As described in U.S. Pat. No. 5,974,925, a versatile high-speed slicing machine is capable of slicing two, three, or more loaves from a single cyclically driven knife blade, with accommodation for food loaves that vary in transverse dimension. The machine is also capable of varying the slice thickness for groups of slices cut simultaneously from different loaves. 
     The slicing machine includes a slicing station comprising a knife blade, a knife blade drive for moving the blade along an arcuate cutting path, and an inclined loaf support for supporting a food loaf for movement by gravity along a loaf path intersecting the cutting path. Two short loaf feed conveyors are arranged along the loaf path, the short conveyors being spaced from each other and engaging opposite sides of the food loaf immediately ahead of the cutting path. A variable speed conveyor drive circulates the two short conveyors at variable speeds to vary thickness of slices cut from the loaves. 
     An orifice plate is arranged adjacent to the cutting path. The orifice plate includes two orifices for gripping and guiding the two loaves individually into the cutting path during the slicing operation. The orifices of the orifice plate are adjustable in size by use of slide members moved by rods, the slide members each forming part of a rim of an orifice. Adjustment of orifice size to conform to varying loaf transverse dimensions is taken up from one side, by moving a respective rod from the outside. By reducing or enlarging the orifice using this arrangement, the location of the centerline of the orifice is moved. 
     U.S. Pat. No. 4,428,263 also discloses an adjustable orifice size in a slicing machine. The automatic adjustment of the orifice size is also taken up from one direction and as a result of orifice size adjustment; the location of the centerline of the orifice is moved. 
     The present inventors have recognized that it would be desirable to provide a slicing machine that would accommodate orifice size adjustment without changing the location of the centerline of the loaf being sliced. The present inventors have recognized that it would be desirable to provide a slicing machine that could accommodate loaves of varying lateral dimension while at the same time maintaining a constant centerline of the loaf being sliced such that slices cut from the loaf can be neatly stacked or shingled along a common centerline on a receiving surface. 
     SUMMARY OF THE INVENTION 
     The invention provides an adjustable orifice member for guiding one or more food loaves into the cutting path of a cyclically operating slicing blade. The invention includes the orifice member being automatically adjustable to grip food loaves of varying lateral dimension while also maintaining a constant orifice centerline. 
     The invention is particularly advantageous in that slices cut from a food loaf having a constant orifice centerline can be received on a receiving surface in a constant and precise centerline alignment. Straight stacks can be accumulated in a reliable manner on a stationary receiving surface and shingled stacks can be formed along a straight longitudinal line on a receiving conveyor. This provides for a more attractive arrangement of slices for packaging and sale. 
     The invention provides a slicing machine that is particularly adapted to slice two loaves simultaneously wherein the two loaves are gripped and guided by an orifice plate having dual, automatically adjusted orifices. 
     According to an exemplary embodiment, an orifice assembly includes one or more subassemblies that each include a slide housing mounted for sliding on a stationary frame, and a slide member mounted slidably on the slide housing. The slide housing and slide member together define an orifice. 
     A plunger is secured to the slide member and is acted upon by an actuator that exerts a continuous inward force on the slide member. A linkage is operatively connected to the plunger and to the slide housing. The linkage is configured to draw the slide housing in an outward direction by an amount equal to the inward movement of the slide member during orifice contraction. The linkage also ensures that during orifice expansion by force from the loaf against the slide housing and slide member, against the urging of the actuator, the slide housing and slide member move by an equal amount. By drawing the slide housing and the slide member together, or by allowing the slide housing and the slide member to move apart, by equal distances, the location of the orifice centerline remains constant. 
     The invention overcomes the difficulties of prior orifice adjusting arrangements wherein the lateral dimension of the orifice is adjusted from one side only wherein the adjustment effectively changes the location of the centerline of the orifice. 
     Numerous other advantages and features of the present invention will be become readily apparent from the following detailed description of the invention and the embodiments thereof, from the claims and from the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a high-speed slicing machine incorporating the present invention; 
     FIG. 2 is a fragmentary, diagrammatic sectional view of the junction between the loaf feed mechanism and the slicing station of the slicing machine of FIG. 1; 
     FIG. 3 is a rear view of an adjustable orifice assembly of the present invention; 
     FIG. 4 is a fragmentary, diagrammatic sectional view taken generally along line  4 — 4  of FIG. 3; 
     FIG. 5 is a sectional view taken generally along line  5 — 5  of FIG. 3; 
     FIG. 6 is a right side view of the assembly shown in FIG. 3; 
     FIG. 7 is an elevational view of a slide housing of the assembly shown in FIG. 3; 
     FIG. 8 is a right side view of the slide housing shown in FIG. 7; 
     FIG. 9 is an elevational view of slide member of the assembly shown in FIGS. 3; 
     FIG. 10 is a right side view of the slide member shown in FIG. 9; 
     FIG. 11 is an elevational view of a subassembly of the slide housing and slide member of FIGS. 7 and 9; 
     FIG. 12 is an elevational view of a link of the assembly of FIG. 3; 
     FIG. 13 is a rights side view of the link shown in FIG. 12; 
     FIG. 14 is an elevational view of a frame of the assembly of FIG. 3; 
     FIG. 15 is a right side view of the frame of FIG. 14; 
     FIG. 16 is an elevational view of a guide plate of the assembly of FIG. 3; 
     FIG. 17 is a fragmentary, diagrammatic sectional view taken generally along line  17 — 17  of FIG.  2 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     While this invention is susceptible of embodiment in many different forms, there are shown in the drawings, and will be described herein in detail, specific embodiments thereof with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the specific embodiments illustrated. 
     The present invention is an improvement in slicing machines of the type described in U.S. Pat. Nos. 5,974,925; 4,805,503 and 4,428,263, all herein incorporated by reference. Particularly, the invention provides an improvement in the orifice member that grips and guides food loaves into the slicing path of a slicing blade. 
     FIG. 1 illustrates a food loaf slicing machine  50  which includes a continuous loaf feed mechanism constructed in accordance with a preferred embodiment of the present invention. The slicing machine  50  comprises a base  51  which is mounted upon four fixed pedestals or feet  52  and has a housing or enclosure  53  surmounted by a top  58 . The slicing machine  50  includes an output conveyor drive  61  utilized to drive an output conveyor/classifier system  64 . The slicing machine  50  further includes a computer display/touchscreen  69  in a cabinet  67  that is pivotally mounted on, and supported by, a support that projects outwardly from a member  74  that is a part of a housing of slicing station  66 . 
     The upper right-hand portion of slicing machine  50  comprises a continuous automated loaf feed mechanism  1075 . Automated loaf loading into mechanism  1075 , may be provided on either or both sides of machine  50 . 
     In operation, slicing machine  50  produces a series of stacks  92  of food loaf slices that are transported outwardly of the machine by conveyor/classifier system  64 . The machine  50 , when slicing two food loaves, also produces a series of stacks  93  of food loaf slices that also move outwardly of the machine on conveyor system  64 . The stacks  92  and  93  are each shown as a straight stack of slices from a food loaf having a round cross-section. Alternatively, the groups of slices can be overlapping, shingled groups of slices instead of having the illustrated straight stack configuration. 
     FIG. 2 provides a sectional view of the portion of continuous food loaf feed mechanism  1075  immediately ahead of slicing station  66  and its continuously rotating knife blade  149 . The blade  149  may be of a circular configuration, driven in both a rotating motion and an orbiting motion, as in the slicing stations described in greater detail in prior patents and publications U.S. Pat. Nos. 5,649,463; 5,704,265; EP 0 713 753; or WO 99/08844, herein incorporated by reference. Alternatively, the blade  149  may be of an arcuate configuration, with rotating motion only, as described in at least one of the aforementioned patents and publications. Blade  149  cuts slices from the front end of a food loaf  1001  that is advanced through an orifice assembly  1011  as described below. 
     FIG. 2 has been tilted through an angle approximately 45 degrees so that it can be more readily described on the drawing sheet; horizontal is indicated by line  1161 . 
     The movement of loaf  1001 , during slicing, is in the direction of arrow P toward slicing station  66 . The rate at which loaf  1001  moves into slicing station  66  is controlled by a pair of short conveyors  1163  and  1165 , which have a common drive and operate at the same speed. 
     Loaf feed mechanism  1075  can include another pair of short conveyors, a lower short conveyor, and an upper short conveyor, substantially identical to the conveyors  1163 ,  1165 , and arranged in parallel to the conveyors  1163 ,  1165  on the near side of the slicing machine, for feeding a second loaf  1002  into the slicing station simultaneously with the first loaf  1001 . 
     In this specification the term “short”, as applied to the conveyors that feed loaves into the slicing station  66  of the machine, refers to the length of the conveyors in the loaf feed direction, arrow P. The conveyor length is not critical; a typical length for conveyors  1163  and  1165 , FIG. 2, is about twelve inches (30 cm). The upper surface of the lower short conveyor  1163  is parallel to the direction of loaf feed, arrow P. The lower conveyor  1163  engages the bottom surface of loaf  1001  and is aligned with the bottom of orifice  1102  in orifice assembly  1011 . The location of conveyor  1163  can be adjusted vertically in a direction normal to arrow P, to accommodate food loaves of different sizes. 
     The positions of the upper conveyor  1165  is also made adjustable toward and away from food loaves so that feed mechanism  1075  can accommodate a variety of different sizes and shapes of food loaves. 
     FIG. 3 illustrates the assembled orifice assembly  1011 , particularly when used to slice two loaves  1001 ,  1002 . FIGS. 4-16 illustrate the details of components of orifice assembly  1011  used in slicing machine  50 . 
     FIG. 3 illustrates the food loaf (upstream) side of assembly  1011 . Assembly  1011  includes far and near side orifice-defining subassemblies  1101 ,  1105  respectively, having a far side orifice  1102  and a near side orifice  1103  respectively into which loaves  1001  and  1002  enter as shown in FIG.  17 . 
     Far side orifice-defining subassembly  1101 , is illustrative of both subassemblies  1101  and  1105 , the subassembly  1105  being configured in mirror image fashion across a vertical center plane. Therefore, the subassembly  1105  need not be described in detail. 
     The size and shape of the orifice  1102  depends on the size and shape of the loaves (loaf  1001 ) being sliced. For loaves of different sizes or shapes, a different, conforming orifice member (not illustrated) should be used is 
     Typically, for a round food loaf, such as illustrated loaf  1001 , the diametrical size of orifices  1102  may range from 2 in. (five cm) to about 5½ inches (14 cm). Other size ranges may be employed, depending on the needs of the user of slicing machine  50 . Similar size ranges may be established for food loaves of square, rectangular, or other cross-sectional configuration. 
     The orifice assembly  1011  includes a rectangular frame  1012  having a relatively large rectangular central opening  1013  and upper and lower recessed ledges  1008 ,  1009  adjacent to perpendicular wall surfaces  1008   a ,  1009   a . The far side orifice subassembly  1101  is mounted in opening  1013  by appropriate means such as a plurality of screws or other fasteners  1014 . Fasteners  1014  mount two guide plates  1016  and  1017  on the frame  1012 . 
     Guide plates  1016  and  1017  engage the upper and lower edges, respectively, of a slide housing  1022  and a slide member  1023 , slidingly engaged to the slide housing  1022 . The fasteners  1014  penetrate elongated holes  1018  through the slide housing  1022  and engage into threaded bores  1020  in the recessed ledges  1008 ,  1009  of the frame  1012 . The slide housing  1022  is guided for sliding on the ledges  1008 ,  1009  by the perpendicular wall surfaces  1008   a ,  1009   a  of the frame  1012  and by the fasteners  1014  within the elongated holes  1018 . For this reason, each of the fasteners  1014  can include a bearing sleeve  1019  (FIG. 5) within the elongated holes  1018  to ensure reduced-friction and a precise sliding within the holes  1018 . The slide member  1023  is captured by the guide plates  1017  on the slide housing  1022 , but permitted to slide laterally with respect to the slide housing  1022 . 
     The slide housing  1022  and the slide member  1023  include rim regions  1022   a ,  1023   a  that together define the orifice  1102 . The slide housing  1022  and the slide member  1023  can be composed of machinable plastic so that the face of the orifice can be sliced away by the cutting blade (blade  149 ) with continued use and will always present a smooth, planar surface at the entrance to the slicing stations. 
     A plunger  1024  operatively connected to the slide housing  1022  and to the slide member  1023  is used to adjust the slide housing and member in the direction of arrow Y to modify the size of orifice  1102 . Similarly, a plunger  1025  affixed to the assembly  1105  is moved to vary the size of orifice  1103 . 
     The plunger  1024  is in the form of a headed stud, having a head  1040 , a shaft  1042 , and a threaded end  1044 . The shaft slidingly penetrates a bore  1048  through the frame  1012  and is threadedly engaged into a threaded bore  1052  of the slide member  1023 . 
     The frame  1012  includes two pairs of lugs  1055  (FIG.  6 ), each pair forming a yoke or trunnion  1056 ,  1058  respectively. The yokes are arranged spaced equidistantly from the plunger  1024 . One link of a pair of links  1060 ,  1062  is pivotally fastened to each yoke  1056 ,  1058 . Rods  1064 ,  1066  in the form of headed studs are equidistantly spaced from the plunger  1024 , outside of the yokes  1056 ,  1058 . Each rod  1064 ,  1066  includes a head  1072 , a shaft  1074  and a threaded end  1076 . The rods  1064 ,  1066  slidingly penetrate the frame  1012  and are each threadedly engaged to a threaded bore  1078  in the slide housing  1022 . 
     Each link  1060 ,  1062  includes fork ends  1060   a ,  1062   a  respectively on opposite ends of each link. The fork ends  1060   a ,  1062   a  underlie the head  1040  of the plunger and an adjacent head  1072  of a respective rod  1064 ,  1066 . 
     In operation, to constrict the orifice  1102 , inward movement of the plunger  1024  driven by an actuator (FIG. 17) drives the slide member  1023  to the left as shown in the FIG.  3 . Simultaneously, the links  1060 ,  1062  pivot causing the rods to be driven to the right as viewed in FIG. 3, which pulls the slide housing  1022  to the right towards the slide member  1023 . The slide housing  1022  is moved to the right by an amount equal to the movement of the slide member  1023  to the left. Hence, the location of the centerline of the orifice  1102  remains constant. 
     Force from a loaf, larger than the orifice  1102 , entering the orifice, will expand the orifice by drawing the rods  1064 ,  1066  to the left, which causes the links  1060 ,  1062  to pivot and push the plunger  1024  against force from the actuator (FIG.  17 ), to the right an equal amount. The orifice centerline remains constant. 
     A resilient loaf guide  1031  for loaf  1001  is mounted on the frame  1012  by appropriate means such as screws or like fasteners  1033  via spacers  1033   a . A like resilient loaf guide  1032  engages the side of loaf  1002  and is mounted on the frame  1012  by screws or like fasteners  1034  via spacers  1034   a . Frame  1012  has a plurality of projections  1036  to locate assembly  1011  quickly and accurately in openings provided around the entrance to the slicing station of machine  50 . 
     FIGS. 7 and 8 illustrate the slide housing  1022 . The slide housing  1022  includes recessed ledges  1202 , 1204 , sized and space to receive the slide member  1023  on the ledges to be guided thereon for sliding movement by perpendicular wall surfaces  1206 , 1208  adjacent to the ledges  1202 , 1204 . 
     FIGS. 9 and 10 illustrate the slide member  1023 . The slide member includes flanges  1212 ,  1214  for being guided by the wall surfaces  1206 , 1208  and for sliding on the ledges  1202 ,  1204  of the slide housing. The slide member also includes recesses  1220 ,  1222  provided for clearance between the slide member and the fasteners  1033 . 
     FIG. 16 illustrates the guide plates  1016 ,  1017 . The guide plates are flat plates having plain holes  1228  positioned to register with the holes  1020  in the frame  1012 . 
     FIG. 17 illustrates the plungers  1024 ,  1025  being pressed by actuators in the form of pneumatic cylinders  1234 ,  1235  respectively. Each cylinder  1234 ,  1235  includes a chamber  1236  subjected to air pressure. A piston  1238  urges a rod  1240  which presses the respective plunger  1024 ,  1025 . The rods  1240  act to constrict or alternately to resist expansion of the respective orifices. 
     From the foregoing, it will be observed that numerous variations and modifications may be effected without departing from the spirit and scope of the invention. It is to be understood that no limitation with respect to the specific apparatus illustrated herein is intended or should be inferred. It is, of course, intended to cover by the appended claims all such modifications as fall within the scope of the claims.
An improved orifice plate assembly for a loaf slicing machine, the orifice plate assembly located adjacent to a moving slicing blade includes a frame defining an opening and a first orifice-defining member and a second orifice-defining member slidably mounted together slidably on the frame. The first orifice-defining member and the second orifice-defining member, together define an orifice. An adjustment mechanism is operatively connected to the frame and to each of the first and second orifice-defining members, the adjustment mechanism when adjusted changes the orifice dimension between the first and second orifice-defining members without substantially changing a centerline location of the orifice. The adjustment mechanism includes a stud fixed to the first orifice-defining member, and two links pivotally mounted to the frame and engaged to two rods fixed to the second orifice-defining member. The stud is engaged to one end of the links and the rods are engaged to a respective other end of the links such that a movement of the stud inwardly pivots the links to draw the second orifice-defining member toward the first orifice-defining member.