Abstract:
An air decelerator for an inspection and sorting system employing pneumatic ejectors, comprising an air plenum adapted to generally cause a stream of air to flow in a direction opposing acceptable articles moving in a trajectory, and thereby decelerate the velocity of the articles to reduce the impact of the articles when they come into contact with the receiving surface to minimize damage to the articles caused by the impact.

Description:
TECHNICAL FIELD 
     This invention relates to pneumatic sorting systems and in particular to air decelerator units for decelerating the velocity of articles after sorting by pneumatic ejectors, and thereby reduce damage, breakage, and bruising of the articles by cushioning their impact upon contact with a receiving surface. 
     BACKGROUND OF THE INVENTION 
     Pneumatic sorting systems are employed in a variety of applications, including automated optical inspection and sorting equipment. Such pneumatic sorting systems for automated optical inspection are described in U.S. Pat. No. 5,318,173 of Datari for a &#34;Hole Sorting System and Method&#34; that is assigned to the assignee of this application. 
     FIG. 1 shows a prior art automatic inspection and sorting system 10 that is capable of inspecting and sorting, for example, raw or processed fruits or vegetables, such as apples, pears, potato chips, wood chips, recycled plastics, and other similar articles. 
     In operation, conveyor belt 12 carries articles 14 in a direction 16 through an inspection area 18 of a video camera 20. Video camera 20 delivers to a video signal characteristic of articles 14. Video signal processor 22 is programmed to identify particular characteristics of articles 14 such as, for example, color, shape, size, or the presence of defects. Articles 14 that include defect 24 can now be separated from articles 14 that do not include a defect. 
     After articles 14 pass through inspection area 18, they are propelled along a trajectory 26 toward an acceptance conveyor belt 28 that turns acceptable articles to subsequent processing station (not shown). Whenever video signal processor 22 determines from the video signal that an article 14 includes a defect 24, an ejection activation signal is delivered to a suitable one of multiple air ejection modules 30. In response to the ejection activation signal, ejection module 30 generates a blast of air 32 that deflects defective article 24 from trajectory 26 in a trajectory 27 toward a reject chute 34. Typically, articles 24 are deflected into reject chute 34 where they are funneled toward a reject conveyor belt 36 for removal. Reject chute 34 is intended to reduce spillage of defective articles. 
     A problem with prior art system 10 is that as video detection and processing technology improves, belt speeds of a sorting system such as shown in FIG. 1 have increased substantially. The sophistication of such sorters has significantly improved the throughput capacity and thus the performance efficiency of these state-of-the-art sorting systems provide accurate sorting of a variety of products according to multiple parameters at very high speeds. 
     The resulting high velocity of these rapidly conveyed and pneumatically ejected articles is high, and the high speed impact of the fragile articles such as potato chips on chute, conveyor belt, and other receiving surfaces may compromise the integrity of the articles, and undermine their saleability. A damaged article may not fulfill the specifications and standards of purchasers. Some damage, such as bruising and tearing of fruits, vegetables and other edible articles, may accelerate spoilage, thereby decreasing the shelf life of such an item. Indeed, with the improved quality of food products and processing, shelf lives of food items have increased in recent years. To keep pace with such escalating food quality standards, the need to minimize damage to food products is commensurately increased. 
     Addressing such heightened quality requirements in view of breakage-provoking sorter velocity rates, prior art mechanisms attempt to alleviate damage to articles caused by impact with a receiving surface have been developed. Such attempts were based on increasing the distance between the ejected article and any acceptance chutes, belt, or containers. However, reliance on mere distance alone and the limited product slowdown imposed by the combined forces of gravity and friction have proved insufficient to soften the surface impact to an extent required to reduce damage of fragile articles to an acceptable level, particularly in state-of-the-art inspection and sorting systems. In addition, space constraints in many sorting and processing facilities have limited the available distance that can be placed between ejectors and acceptance chutes or belts. This has compounded the need for a system which can soften the impact of and thereby prevent or minimize damage to an article impinging on a proximal surface. Moreover, as such systems utilize higher velocity rates, mere distance may not provide the deceleration required to prevent damage to the sorted articles. Thus, unfortunately, no prior sorting system has provided a mechanism that, to an acceptable extent, minimizes damage caused to articles by impact with a receiving surface after they have been pneumatically sorted. 
     SUMMARY OF THE INVENTION 
     The present invention addresses such and other problems relating to damage pneumatically sorted articles on prior art inspection and sorting systems by employing an air decelerator system wherein an air plenum adapted to an inspection and sorting system projects a stream of air to flow in a direction opposing the sorted articles, thereby decelerating the articles to cushion their impact when they come into contact with a receiving area surface. This air decelerator system is adaptable to a variety of such systems for sorting unacceptable and acceptable articles according to predetermined characteristics, wherein the articles are conveyed past a video scanning camera that sends video data to a video signal processor for actuating selected combinations of multiple ejection modules. The ejection modules of such systems deflect unacceptable articles with an ejection gas toward a first trajectory directed to one or more rejection duties, belts or similar receiving area. Acceptable articles that are not deflected by an ejection gas are permitted to proceed in a second trajectory directed to a second area surface for receiving acceptable articles. A stream of air flowing from the air plenum is channeled in a direction opposing articles in the second trajectory to decelerate the velocity of the articles. Thus decelerating the articles in the second trajectory cushions their impact when the articles come into contact with the second area surface. 
     Structurally, the air plenum is defined by a housing having outer surfaces enclosing a generally hollow interior, a lower surface of which is oriented in a proximate position above and substantially parallel to the second trajectory. The housing has an open inlet through which a stream of air enters the interior of the housing and an open outlet configured to channel the stream of air flowing out of the housing in a direction along the lower surface of the housing such that the stream of air opposes articles in the second trajectory. 
     In one embodiment of the present invention, the housing of the air plenum is defined by opposing walls that are radially joined to form a generally arcuate lower outer surface and a generally rounded lower end. The transverse axis of the lower outer surface of a wall faces downwardly toward the second trajectory and preferably extends at least across the width of the second area surface. The lower outer surface of a preferred embodiment is curved inwardly to form a shallow concave surface beneath which the stream of air flows. 
     The present invention further includes a generally circumferential inlet duct integrally connected with the open outlet such that the stream of air entering the duct flows in a generally downward direction. 
     The open outlet may be a slot extending across the width of the lower end of the housing which is defined by an upper portion stepped up from a lower portion such that the slot faces substantially downward toward the portion of the second trajectory directly below the slot. 
     The present invention may further include a baffle plate containing perforations to more evenly disperse air directed toward the open outlet mounted along a transverse axis within the housing. 
     The stream of air inducted in the open inlet of the air plenum is preferably generated by a blower. The velocity of the stream of air generated may be further controlled by a damper. An exemplary air velocity rate at the outlet slot suitable for sorting potato chips may range between about 2,800 feet/minute and about 4,900 feet/minute. Static pressure in the plenum may be between about 0.50 inch and about 1.5 inch water column (w.c.). To maximize the proportion of articles entrained in the stream of air beneath the lower outer surface of the housing in a direction opposing the articles in the second trajectory, the air plenum is preferably mounted at a slightly declining slope in a position slightly above the trajectory. An angle of between about 25 degrees and about 35 degrees could suitably orient the air plenum from the horizontal plane. 
     The present invention further includes a method of decelerating the velocity of articles by providing and orienting an air plenum, and adjusting an associated blower and/or damper, as detailed herein, and blowing a stream of air into the open inlet of the housing such that at least a portion of the stream of air is blown in a direction that flows along the lower surface of the housing and thereby opposes the articles in the second trajectory to decelerate the velocity of the articles and thus reduce the impact of the articles when the articles come into contact with the second area surface. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a simplified isometric schematic diagram of a prior art inspection and sorting system employing pneumatic ejectors, reject chute and conveyor belt. 
     FIG. 2 is a simplified schematic side view of a pneumatic sorting system employing an air decelerator unit according to the present invention shown partly in cross-section to reveal the baffle plate in the air plenum. 
     FIG. 3 is an isometric perspective view of a preferred embodiment of the present invention. 
     FIG. 4 is a cross-section view of the preferred embodiment taken along lines IV--IV as shown in FIG. 3. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 2 schematically illustrates a pneumatic sorting system employing a preferred embodiment of the air decelerator unit 40 is to cushion the impact of articles 14 in trajectory 26 after articles 14 including defects 24 are deflected by ejection modules 30 in a trajectory 27 toward reject chute 34, as detailed below. 
     Air decelerator unit 40 includes a housing 42 defining an air plenum 44. Housing 42 is generally rectangular with four opposing sidewalls the lower horizontal edges of which are radially joined to form an arcuate lower outer surface 43 and a rounded lower end wall that form a continuous interface. In the upper portion of housing 42 is seated an open inlet duct 46, and in the rounded lower end wall is an open outlet slot 48. Flowing in a direction depicted by the arrows shown in FIG. 3, a stream of air blown by blower 49 enters into air plenum 44 through open inlet duct 46, and then flows through baffle 50 that disperses the stream of air so it is more evenly distributed as it flows toward and through open outlet slot 48. 
     Air plenum 44 is oriented along a parallel plane lying in a proximate position above trajectory 26 so that air expelled through open outlet slot 48 flows along the lower outer surface 43 of housing 42 in a direction that opposes the flow of articles 14 moving along trajectory 26, as depicted by the relevant arrows. The opposing flow of the stream of air beneath lower outer surface 43 of housing 42 decelerates the velocity of articles 14 in trajectory 26. This slowdown cushions the impact when articles 14 come into contact with conveyor 54 immediately following their deceleration and thereby abates damage to articles 14. 
     FIG. 3 is an isometric illustration of a preferred embodiment of the present invention. As shown, housing 42 has a generally rectangular upper portion and an arcuate lower outer surface 43. The lower outer surface 43 of housing 42 curves inwardly to form a shallow concave surface. The outer surface of a rounded rear wall extending from open outlet slot 48 to lower outer surface 43 at the downstream end of air plenum 44 entrains the stream of air against the adjacent curve in the lower outer surface 43 of housing 42, generating a laminar flow of the stream of air in a direction that opposes articles 14 in trajectory 26. Thus cushioned by this airflow, articles 14 are slowed to a low velocity in a short time, and settle onto conveyor 54, i.e., the second surface area. 
     Air flowing along lower outer surface 43 escapes upwardly past a substantially linear front wall 45 that is oriented at an angle of about 90 degrees from the horizontal plane. Front wall 45 extends upwardly beyond the upper surface of housing 42 into a planar wall for directing the stream of air in an upward direction. In the illustrated embodiment, the gap between the perpendicular wall of housing 42 and the closest component of the inspection and sorting system ejection module 30, is about 15 inches  38.1 cm!. In alternative orientations of air decelerator, this gap width may vary substantially. 
     In the illustrated embodiment, the lower outer surface 43 of housing 42 extends about two inches beyond each side of conveyor 54. A lower surface width that at least coextends with the entire belt width enhances dispersion of the stream of air through all paths through which articles 14 may move. Belt widths may measure between 24 inches  60.96 cm! and 72 inches  182.88 cm!, or more or less. However, an outer surface that does not extend to the width of a receiving belt or chute could be employed to effect deceleration of at least some of articles 14 in trajectory 26. 
     The housing shown in FIG. 3 has a width of about 52 inches  132.08 cm!, a length of about 4 inches  10.16 cm!, and a depth of about 12 inches  30.48 cm!. Air plenum 44 is installed on mounting brackets attached by bolts to frame members (not shown) of automatic inspection and sorting system 10, in a manner well known by persons of ordinary skill in the art. The embodiment shown is installed so the lower outer surface 43 is tilted at a slight downward angle of between about 25 degrees and about 35 degrees from the horizontal plane. The angle of housing 42 and airflow velocity blown from blower 43 may be adjusted to provide desired product placement on the second area surface. Damper 51 may further be adjusted to generate a suitable static pressure. Satisfactory adjustments project an airflow velocity causing articles 14 in trajectory 26 to occasionally &#34;graze&#34; the bottom surface 43 of housing 42. 
     Open outlet slot 48 is formed by a gap between two formed pieces of sheet metal measuring about 0.25 inches  10.64 cm! in width extending across the entire width of housing 42. According to this embodiment, open outlet slot 48 is defined by a stepped up upper lip forming a &#34;slit&#34; which projects over a lower lip to direct the stream of air moving through the open outlet slot 48 downwardly toward the portion of trajectory 26 below it. The air from open outlet slot 48 is directed tangent to the curve of lower end. Low pressure generated along the inward curve of outer lower surface 43 by the moving air causes the stream of air to bend and thereby essentially remain tangent to this curve bringing it in opposition to trajectory 26. In alternative embodiments, the particular configuration of open outlet slot 48 can vary. For example, it could consist of a single rounded or angular aperture, or of successive rounded or angular perforations, of varying shapes and dimensions. 
     Blower 49 and damper 51 are installed on the inspection and sorting system 10, and adjusted to blow air at suitable pressure and velocity rate into open inlet duct 46. Adjustments of blower 49 and damper 51 to generate suitable velocity rates will vary with component dimensions, and the volume and density of the articles sorted. As shown in the drawings, damper 51 may be adjusted to produce an airflow providing a velocity at the slot of between about 2,800 feet/minute and about 4,900 feet/minute and a static pressure within the plenum of between about 0.50 inch and about 1.50 inch w.c. In alternative applications, appropriate adjustments can be made for desired deceleration and cushioning of other fragile articles, such as cereals, chips processed from other fruits and vegetables, and similar crunchy but fragile snack foods. 
     The dimensions, configuration, and mounting of air plenum 44 may be adjusted to provide appropriate airflow for decelerating various articles in accordance with their size, density and configuration. In addition to suitable dimensions and spatial arrangements of air plenum 44 and its components, appropriate adjustment of blower 49 and damper 51 is requisite to providing an acceptable air velocity. 
     As shown, FIG. 4 is a cross-section taken along the plane in which baffle 50 is mounted. Baffle 50 has circular perforations 52 through which a stream of air is blown to more evenly disperse air moving through open outlet slot 48. In the illustrated embodiment, perforations 52 are circular, measuring about 0.25 inches  0.64 cm! in diameter, and cover the entire baffle 50. Baffle 50 shown is mounted on the wall of housing 42 in an orientation that is parallel to the edge of open outlet slot 48. Alternative embodiments of the present invention may include baffles with perforations of varying sizes and shapes, and may not include a baffle at all. 
     It will be obvious to those having skill in the art that many changes may be made to the details of the above-described embodiment of this invention without departing from the underlying principles thereof. The scope of the present invention should, therefore, be determined only by the following claims.