Linear-motor conveyor system

A tray conveyor in which plastic trays with rows of embedded translators are driven by stators. Washing stations in cleaning zones are provided to automatically clean empty trays in the conveyor's return path.

BACKGROUND

The invention relates generally to power-driven conveyors and in particular to tray conveyors driven by linear motors.

Transport systems in which carriers driven by linear synchronous motors route individual carriers along various paths in a complex network of tracks are used to convey articles to selected destinations. An example of such a transport system is described in U.S. Pat. No. 8,967,051, “Transport System Powered by Short Block Linear Synchronous Motors and Switching Mechanism,” to Nathanael N. King et al. of Magnemotion, Inc., Devens, Mass., U.S.A., Mar. 3, 2015. These systems work well, but are not so easy to clean. The housings of the linear-motor stators present large, flat, closed upper surfaces that collect grease and other food particles in food-processing applications. Unless properly cleaned, the surfaces can become contaminated with bacteria. And hard-to-access undercut surfaces in the transport system can harbor those bacteria.

SUMMARY

One version of a conveyor system embodying features of the invention comprises a plurality of conveyor sections and a plurality of conveyor trays. Each conveyor section comprises a tray guide that extends in length from a rear end to a front end of the conveyor section and in width from a left side to a right side of the conveyor section. At least one linear stator extends in length through the tray guide between the rear end and the front end. The conveyor trays have at least one translator that forms a linear motor with the at least one linear stator to drive the conveyor trays along the tray guide in the conveying direction. The plurality of conveyor sections are arranged to form a carryway path along which the trays can carry articles and a return path along which empty trays return to the carryway path. The conveyor system comprises one or more cleaning zones along the return path for cleaning the trays.

Another version of a conveyor system embodying features of the invention comprises a plurality of conveyor sections and a plurality of trays. Each conveyor section has a tray guide that extends in length from a rear end to a front end of the conveyor section and in width from a left side to a right side of the conveyor section. Left-side and right-side linear stators extend in length through the tray guide between the rear end and the front end. The left-side linear stator is closer to the left side, and the right-side linear stator is closer to the right side. The conveyor trays have translators that form linear motors with the left-side and right-side linear stators to drive the conveyor trays along the tray guide in the conveying direction.

Yet another version of a conveyor system comprises a conveyor comprising a single conveyor segment or a series of conveyor segments and a plurality of conveyor trays. Each conveyor segment comprises a tray guide that extends in length from a rear end to a front end of the conveyor segment and in width from a left side to a right side of the conveyor segment. Left-side and right-side linear stators extend in length through the tray guide between the rear end and the front end. The left-side linear stator is closer to the left side, and the right-side linear stator is closer to the right side. The conveyor trays have a translator that forms a linear motor with the left-side and right-side linear stators to drive the conveyor trays along the tray guide in the conveying direction.

In another aspect a conveyor tray embodying features of the invention comprises: (a) an article-supporting surface having a front edge, a rear edge, a left edge, and a right edge; (b) a first linear translator disposed below the article-supporting surface and extending in length along a line intersecting the rear and front edges; (c) a second linear translator disposed below the article-supporting surface and extending in length parallel to the first linear translator between the first linear translator and the right edge; (d) a third linear translator disposed below the article-supporting surface and extending in length perpendicular to the first and second linear translators; and (e) a fourth linear translator disposed below the article-supporting surface and extending in length parallel to the third linear translator between the third linear translator and the rear edge inclusive.

Another version of a conveyor tray comprises: (a) a top surface having a front edge, a rear edge, a left edge, and a right edge defining four corners; (b) a left linear translator disposed below the top surface and extending in length along a line parallel to the left edge and intersecting the rear and front edges; (c) a right linear translator disposed below the top surface and extending in length parallel to the left linear translator between the left linear translator and the right edge; (d) a front linear translator disposed below the top surface and extending in length along a line perpendicular to the left and right linear translators and intersecting the left and right edges; and (e) a rear linear translator disposed below the top surface and extending in length parallel to the front linear translator between the front linear translator and the rear edge.

In another aspect an elevator embodying features of the invention comprises first and second vertical sections. Each vertical section includes a vertical left stator rail encapsulating a linear stator and a vertical right stator rail parallel to the left stator rail and encapsulating a linear stator. A first carriage rides on the first vertical conveyor section, and a second carriage rides on the second vertical conveyor section. Each of the carriages includes: (a) a left translator that extends in length along a left side of the carriage between a lower end and an upper end of the carriage and forms a linear motor with the linear motor encapsulated in the vertical left stator rail; (b) a right translator that extends in length along a right side of the carriage between the lower end and the upper end and forms a linear motor with the linear motor encapsulated in the vertical right stator rail; and (c) an upper rail that extends across the upper end from the left side to the right side and encapsulates an upper linear stator. The upper rails of the first and second carriages are at the same level. A first horizontal stator at the top of the first vertical conveyor section and a second horizontal stator at the top of the second vertical conveyor section form linear motors with the upper linear stators of the first and second carriages.

In another aspect a conveyor embodying features of the invention comprises a first elongated enclosure having open ends and a conveying surface that extends along a length of the first elongated enclosure. A left-side linear stator extends in length along the left side of the conveying surface, and a right-side linear stator extends in length along the right side of the conveying surface. A plurality of conveyor trays supported on the conveying surface, the conveyor trays have translators that form linear motors with the left-side and right-side stators to drive the conveyor trays through the first elongated enclosure.

Another version of a conveyor tray comprises a tray body having an article-supporting surface, a front edge, a rear edge, a left edge, and a right edge. A first linear translator is disposed below the article-supporting surface and extends in length along a line intersecting the rear and front edges. A second linear translator is disposed below the article-supporting surface and extends in length parallel to the first linear translator between the first linear translator and the right edge. A left skirt extending downward from the left edge, and a right skirt extends downward from the right edge. The first linear translator is disposed in the left skirt and the second linear translator is disposed in the right skirt.

A carriage for a tray conveyor embodying features of the invention comprises a tray guide extending in length from a rear end to a front end of the carriage and in width from a left side to a right side of the carriage. Left and right linear stators extend in length through the tray guide between the rear end and the front end. The left linear stator is closer to the left side, and the right linear stator is closer to the right side. A rear translator is disposed at the rear end of the carriage, and a front translator is disposed at the front end of the carriage.

A carriage assembly embodying features of the invention comprises a carriage and a motor rotating the carriage through a predetermined angle. The carriage includes a first linear stator that extends in length along one side of the carriage and a second linear stator that extends in length along the opposite side of the carriage.

A conveyor embodying features of the invention comprises a plurality of trays and a conveyor section that includes a linear-motor stator. Each tray includes a linear-motor translator that forms a linear motor with the linear-motor stator to convey the tray along the conveyor section and indicia indicating a family of which the tray is a member. A sensor sensing the indicia and sends a sensor signal to a controller. The conveyor section is assigned to convey trays that belong to a predetermined family. The controller determines the family of the tray from the sensor signal and stops the conveyance of the tray on the conveyor if the family of the tray does not match the predetermined family.

In another aspect a method embodying features of the invention for operating a conveyor comprises: (a) assigning each of a plurality of conveyor trays to one of a plurality of families by indicia indicating the assigned family; (b) assigning a predetermined family of conveyor trays to a conveyor; (c) identifying the assigned family of each conveyor tray on the conveyor; (d) identifying conveyor trays whose family does not match the predetermined family assigned to the conveyor; (e) removing the conveyor trays whose family does not match the predetermined family assigned to the conveyor from the conveyor; and (f) conveying the conveyor trays whose family matches the predetermined family along the conveyor through a process.

In another aspect one version of a rail scrubber embodying features of the invention comprises front and rear wheels riding along left and right conveyor rails of a conveyor and left and right scrubbing wheels having brushes engaging the left and right conveyor rails. Nozzles positioned at the left and right conveyor rails to spray fluid from a fluid tank onto the left and right conveyor rails. A drive system drives the rail scrubber along the left and right conveyor rails.

Another version of a scrubber comprises front and rear wheels riding along a top surface of a conveyor, left and right scrubbing wheels having brushes engaging the top surface of the conveyor, nozzles positioned to spray fluid from a fluid tank onto the top surface of the conveyor, and a drive system driving the scrubber along the top surface of the conveyor.

Another version of a conveyor comprises a tray and a conveyor section supporting the tray. The tray includes a tray body having an upper surface and an opposite underside, a plurality of rollers in the tray body, and a linear translator at the underside extending in length along the length of the tray. The conveyor section includes a linear drive stator that extends in length along the conveyor section adjacent the linear translator and forms a linear motor with the translator to propel the tray along the conveyor. A tray-roller actuator coacts with the plurality of rollers to rotate the rollers as they pass by.

In another aspect a conveyor tray comprises a tray body having an upper surface and an opposite underside, a plurality of rollers that extend through the thickness of the tray body past the upper surface and the underside, and a linear translator at the underside that extends in length along the length of the tray.

DETAILED DESCRIPTION

A conveyor segment for constructing a cleanable conveyor system embodying features of the invention is shown inFIG. 1. The conveyor segment100comprises left and right side rails102,104extending in length in a conveying direction106. The two side rails are supported in a minimal conveyor frame comprising legs108and connecting structure in the form of cross beams110maintaining the two side rails102,104parallel to each other. The entire conveyor frame is made of a plastic material, but could be made of other materials. Top surfaces112of the side rails102,104and top surfaces114of the cross beams110are convexly curved, or rounded, to minimize the buildup of grease and contaminants.

As shown inFIG. 2, a three-phase linear-motor stator116is embedded in the right side rail104. A similar stator is embedded in the left side rail. The stator116comprises a series of poles separated by slots in a linear core. Three-phase windings in the slots complete the stator. The core can be ironless to avoid the frictional effects of remanent magnetism when not energized. When energized, the stator116produces a magnetic flux wave that travels along the side rail104in or opposite to the conveying direction106shown. The magnetic flux wave is directed horizontally outward from the outer wall118of the side rail104in this example. Also embedded in the side rail104are sensors120at spaced apart sensor positions along the side rail's length. Each sensor120is used to detect the presence of a tray on the side rails at the sensor position.

The stators116and the sensors120are powered and controlled by electronic and power circuits122embedded in the cross beams110over wires124embedded in the conveyor frame and the side rails102,104as shown inFIG. 3. Power, control, and data wires126connecting the electronics module122to a source of power and a system controller are embedded in the legs108of the conveyor frame. Because the wires, electronics, stators, and sensors are all encapsulated in the conveyor frame and side rails, the conveyor segment provides no flat surfaces or nooks and crannies that can collect and harbor contaminants. So the conveyor segment is easy to clean.

A block diagram of the electronics module and the stator drive is shown inFIG. 4. The stator116comprises a linear series of three sets of coils130A,130B,130C—one set for each of the three phases—alternately arranged along the length of the side rail. Each set of coils130A,130B,130C is driven by an amplifier132A,132B,132C. The phasing sequence and frequency of the stator116are controlled through a stator drive control134, which sends coil control signals136A,136B,136C to the amplifiers132A,132B,132C. The stator drive control134includes a computer in communication with a remote system computer140, which also communicates with the stator drive controls in other conveyor segments. The stator drive control134receives commands from and sends data to the system computer140wirelessly or over a hard-wired connection142. The sensors120send sensor signals146indicating the position of a conveyor tray over a sensor bus to the stator drive control134, which uses those signals to determine when to energize and de-energize the stator116. All those components, except for the remote system computer140, are encapsulated in the conveyor frame as inFIG. 3. The magnetic flux wave produced by the stator in the rail causes a conveyor tray with an embedded permanent-magnet array148to advance along the rail in the conveying direction106.

FIG. 5illustrates how two adjacent conveyor segments100,100′ are maintained with their left and right side rails102,104aligned to form continuous rails. An alignment magnet150is embedded in the end of an appendage152at the bottom of each side rail102,104. A similar magnet154is embedded in a similar appendage156at the confronting end of the side rail of the adjacent conveyor segment100′. The magnets150,154are arranged with their opposite poles facing each other so that they attract. The attraction of the magnets keeps the confronting rails in alignment. Instead of having magnets in both confronting side-rail ends, one end could have a piece of ferrous material that would be attracted by the magnet in the adjacent conveyor segment to maintain alignment.

A short conveyor section constructed of two conveyor segments100,100′ is shown inFIG. 6supporting a series of conveyor trays160on the tops112of the side rails102,104, which serve as a tray guide. The trays160are not connected to each other and are independently movable in or opposite to the conveying direction106by the stators embedded in the side rails102,104. The trays160can be simply lifted from the conveyor segment for cleaning, maintenance, or other removal needs. And the trays can be replaced on the conveyor segment just as easily. As shown inFIG. 7, each tray160is shown as a rectangular tray body161with a rear edge162, a front edge164, a left edge166, and a right edge168. The tray160has an upper article-supporting surface170extending to the edges162,164,166,168. Skirts172,174extend downward from the left and right edges166,168. Embedded in each skirt172,174is an array of permanent magnets176extending in length along the skirt between the rear and front edges162,164. The magnet arrays are arranged with their magnetic fields directed generally parallel to the article-supporting surface170to maximize the magnetic coupling with the traveling magnetic wave produced by the stators in the side rails of the conveyor segments. The skirts172,174overlap the conveyor side rails and help keep the trays160laterally in place. At least the skirts172,174are made of a non-magnetic material, such as plastic. And the upper article-supporting surface170can be continuous or foraminous, flat or curved, and smooth or textured with nubs, cones, diamonds, or other patterns. Furthermore, the conveyor tray could have left, right, front, and rear sides standing up from the left, right, front, and rear edges for use as, for example, a baking pan. The article-supporting surface170could extend beyond the front, rear, left, and right edges of the main tray body.

Straight conveyor segments100,100′ as inFIG. 6can be joined to curved conveyor segments900as inFIG. 58to form a banked racetrack conveyor section906. The side rails902,904of the curved segments900are curved out of coplanarity with the straight segments to form the banked racetrack section906. Articles908carried on the conveyor trays160are diverted off the trays160and over the lower side rail902upon entering the banked racetrack section906. In this way the racetrack serves as a tilt conveyor to allow conveyed products to drop from the trays in the banked section906. The banked racetrack section906also permits the construction an endless track without a lower returnway along its entire circuit. And the trays160are shown routed through a washing station including a cleaning zone containing an automatic washing enclosure909like that used in car washes along a return section907downstream of the banked section906. Washing the trays160in the automatic washing enclosure909in the return907reduces or eliminates the manual washing of the trays and, thus, increases productivity and ensures consistent tray hygiene.

For even better magnetic coupling, the permanent-magnet arrays can be arranged as Halbach arrays178with the magnets arranged in alternating polarities as shown inFIG. 8. Each magnet array, whether Halbach or not, forms the secondary of a magnetic circuit whose primary is the stator in a side rail. When the secondaries are permanent magnet arrays, they form a linear synchronous motor with the stators. The magnet array in the tray could be replaced with electrically conductive material in which the magnetic flux wave produced by the stator induces eddy currents. The eddy currents produce a secondary magnetic field that interacts with the stator's primary magnetic field, i.e., the traveling magnetic flux wave, to generate a propulsive force to move the tray along the rail. When electrically conductive material is used instead of magnets in the tray, the electrically conductive material forms a linear induction motor with the stator. As another alternative, the tray could have a platen including a linear array of pole faces with three-phase windings with a different pole pitch from that of the three-phase stator poles on a stator platen to form a linear reluctance motor. Whether linear synchronous, induction, or reluctance motors are formed, the secondaries in the trays are referred to in this description and in the claims as translators—analogous to rotors in a standard rotating motor. And, as shown inFIG. 54, the trays could include magnetic strips700extending along their undersides in the joints702between the skirts703and the bottom of the article-supporting surface704. As the trays advance along a conveyor segment706, the magnetic fields of the magnetic strips700induce currents in electrically conductive strips708embedded in and extending the length of stator rails710. The induced currents create induced magnetic fields that interact with the magnetic fields of the magnets to produce a levitation force acting upward and outward on the trays for low-friction, levitated travel.

A carriage for carrying a tray in a horizontal or a vertical direction or for propelling a tray along its rails is shown inFIG. 9. The carriage180comprises a left rail182and a right rail184connected and maintained in parallel by a pair of connecting members186. The tops of the left and right carriage rails182,184form a two-rail carriage tray guide for the trays. Like the rails in the conveyor segments, the left rail182encapsulates a left linear stator, and the right rail184encapsulates a right linear stator. A rear translator at a rear end188of the carriage180comprises a left rear translator in a left rear housing190suspended below and outward of the left rail182and a right rear housing192suspended below and outward of the right rail184. In a similar way a front translator at a front end189of the carriage180comprises left and right front translators in left and right front housings194,196. As shown inFIG. 10, each translator includes one or two three-phase windings. In this example the right rear housing192, shown open to reveal the translators suspended from the right rail184at the rear end188, has a vertical translator200and a horizontal translator202. The vertical translator200has a horizontal magnetic axis204, and the horizontal translator202has a vertical magnetic axis206. The translators in the corner housings190,192,194,196, besides coacting with conveyor-frame stators to propel the carriage along a track, couple power to the stators in the left and right rails182,184. The rail stators, when energized, propel trays along and off the rails182,184. So the translators are electrically connected to the rail stators. The carriage could also encapsulate one or more weight sensors207in the rails182,184or in the corner translator housings190,192,194,196to weigh the trays and their contents.

FIG. 11is a block diagram of the circuit embedded in the carriage frame. The carriage-rail stator drive system including the three-phase stator coils130, the coil-drive amplifiers132, the carriage drive control134, and the position sensors120is schematically the same as for the conveyor segments described with respect toFIG. 4. The stator drive-system components are distributed between the rails and the translator housings within the carriage frame. The output199of the three-phase horizontal and vertical translator windings201provides electrical power to the drive control134, amplifiers132, and rail stators130to drive the conveyor-tray translators148and to the position sensors120and the weight sensors207. The translator windings201receive power inductively from a conveyor-frame stator203. Power-line communication, in which data on a high-frequency carrier is superposed on the ac power, is used to communicate data and control signals between the carriage drive control134and the system computer. The position sensors120and the weight sensors207send sensor signals to the carriage drive control134. A power and communication system205includes: (a) a filter section to separate the communication signals from the ac power; (b) a rectifier to convert the ac power into dc; (c) a voltage regulator regulating the dc voltage to power the carriage drive control134; (d) a decoder to decode received communication signals; and (e) a modulator and line driver to transmit outgoing data messages including tray position and weight data over the translator windings199. The stator drive control134processes the decoded incoming messages received from the power and communication system205and sends data messages to the power and communication system for transmission over the power system. The carriage translator201forms a switched-reluctance linear motor with the conveyor-frame stator203to move the carriage. When the carriage is stopped, the power from the conveyor-frame stator203is used to drive conveyor trays along the carriage rails.

FIGS. 12A-12Ddescribe one example of a conveyor system using a carriage. The conveyor has four conveyor sections: a first lower section210; a second lower section212in line with the first lower section210; a third lower section214parallel to and laterally offset from the first conveyor section210; and a fourth upper section216horizontally and vertically offset from the first conveyor section210. The four conveyor sections210,212,214,216are separated from each other across gaps forming a main space218. A gantry is disposed in the space218. The gantry has two parallel horizontal guide tracks222,224and three pairs of parallel vertical guide tracks226,228,230. To simplify the drawing the gantry frame supporting the guide tracks is not shown. The translator housings190,192,194,196ride in the guide tracks222,224,226,228,230. Upper lips231along the sides of the guide tracks retain the translator housings in the tracks. Each of the guide tracks includes a linear stator (not shown) extending along the length of the guide track selectively propagating a magnetic flux wave along the track to propel the carriages' translators. A carriage180with a conveyor tray160atop it is shown inFIG. 12Ain a position in which the tray160can be passed along the carriage rail from the first lower conveyor section210to the inline second lower conveyor section212. The left and right rails of the carriage in that position are effectively continuous with the left and right side rails of the first and second conveyor sections210,212. If the tray160is selected for another destination, the carriage180is propelled along the horizontal guide tracks222,224to a position in which the rails are aligned with the third lower conveyor section214as shown inFIGS. 12B and 12C. The stators in the carriage may then be energized to propel the tray160off and onto the third conveyor section as shown inFIG. 12C. If the scheduled destination is the upper conveyor section216, the carriage180is raised by the stators in the vertical guide tracks226,228to the level of the upper conveyor section, as shown inFIG. 12D. The carriage's stator rails are then energized to propel the tray160off the carriage180and onto the upper conveyor section216.

A more complex conveyor system is shown inFIG. 13in which two rows of gantries220,221are used to move a carriage180with trays160horizontally and vertically along guide tracks from an infeed conveyor section230onto or off parallel conveyor sections232arranged in multiple horizontally offset rows of vertically stacked conveyor sections to accumulate trays with articles for later processing. Trays carrying articles scheduled for processing are passed directly across the carriage180in its home position shown inFIG. 13from the infeed conveyor section230onto a discharge conveyor section234. When trays in the accumulator section232are scheduled for processing, they are moved to a position at the gantries221and onto a carriage180, which is then moved along the guide tracks to the home position so the tray can be propelled off the carriage and onto the discharge conveyor section234. Although only a single carriage180is shown in the gantries220,221inFIG. 13, more than one carriage can be used.

FIGS. 14A-14Cdepict the operation of a merge conveyor constructed of three infeed conveyor sections236,238,240with dual stator rails242,244as in the conveyor section ofFIG. 1. The three infeed sections236,238,240are shown side by side in parallel. A first pair246of horizontal guide tracks extends perpendicular to the conveying direction106at the common ends of the left and center infeed conveyor sections236,238. The first pair246of guide tracks bridges those two conveyors and forms a first diverter section. A first carriage248(FIG. 14C) rides on the first pair246of tracks to move trays160horizontally to a discharge conveyor section250in line with the center infeed conveyor238across a space. The right infeed conveyor section240extends past the ends of the other two infeed sections236,238to an end252laterally across from the front end of the first carriage248. A second pair247of guide tracks parallel to the first pair246bridges the space between the right infeed conveyor section240and the discharge conveyor section250. The second pair247of guide tracks form a second diverter section to drive a second carriage254. The sequence of operations required to merge Tray1, Tray2, and Tray3onto the discharge conveyor section250is as follows:1. transport Tray1on the right infeed conveyor section240onto the second carriage254as inFIG. 14A;2. transport Tray2on the left infeed conveyor section236onto the first carriage248as inFIG. 14A;3. move the second carriage254and Tray1laterally along the second set247of guide tracks until the carriage is aligned with the discharge conveyor section250;4. move the first carriage248and Tray2laterally along the first set246of guide tracks until the carriage is in line with the discharge conveyor section250;5. with the two carriages248,254both in line with the center infeed conveyor section238and the discharge conveyor section250, energize all those rails to propel Tray1, Tray2, and Tray3onto the discharge conveyor section as inFIG. 14B;6. return the carriages248,254to their positions in line with the left and right infeed conveyors236,240as required to collect the next set of trays to be merged onto the discharge conveyor section250as inFIG. 14C.
In this one-level version no vertical elevation is required, and the translators256in a connecting member258joining the rails of the carriages248,254require only horizontal translators. The same configuration of conveyor sections can be used as a 1-to-3 switch by reversing the conveying direction106. In that case, the discharge conveyor section250would operate as an infeed conveyor section, and the three infeed conveyor sections236,238,240would be discharge conveyors, with the guide tracks246,247and carriages248,254as the switches.

Another version of a diverter section818is shown inFIG. 56. A carriage820has rear and front skirts822,824depending from a carriage body826. The skirts822,824have built-in translators, such as permanent-magnet arrays as in the conveyor trays. The diverter section818has stator rails828,830like those in the conveyor segments ofFIG. 1. The carriage820moves along the tracks defined by the rails828,830in a translation direction832. Cross pieces834joining the diverter's stator rails828,830house coils that energize the stators in carriage rails836,838extending upward from left and right sides of the carriage body826. When the carriage rails836,838are aligned with rails840,842of discharge or infeed conveyor sections, the carriage-rail stators are energized to induct trays844like the tray ofFIG. 7onto or to propel them off the carriage.

FIG. 57shows a dual-rail elevator850using two carriages852,854to form an elevator platform for a conveyor tray856. The carriages852,854are similar to the carriage720shown inFIG. 56. The elevator850comprises two upgoing vertical conveyor sections858,860each with left and right stator rails862,864. At the top of each upgoing conveyor section858,860is a shuttle conveyor segment863with stator rails865aligned with the left and right stator rails862,864in a first position. Each shuttle863translates laterally outward as indicated by arrows857with one of the carriages852,854from an associated upgoing conveyor section858,860to one of two downgoing conveyor sections869,871with left and right stator rails873,875. When the shuttles are in a second position with their rails865aligned with the downgoing rails873,875, the carriages852,854are advanced onto the downgoing rails873,875for their trips back to the bottom of the elevator850. Then the upper shuttles863return inward to their first positions. Identical lower shuttles877are disposed at the bottom of the elevator850to carry the carriages852,854from the outer downgoing rails873,875to the inner upgoing rails862,864. In this up-down elevator850, multiple pairs of carriages can run simultaneously. (The operation of the shuttles863,877is also described in reference to elevator carriages shown inFIGS. 22A-22D, which operate identically in moving vertically instead of horizontally.) The upgoing conveyor sections858,860are arranged in parallel, facing each other in a conveyor frame866. The carriages852,854have left and right skirts868,870with translators, such as an array of permanent magnets, that form linear motors with the linear stators in the vertical stator rails862,864. The linear motors drive the carriages852,854up the upgoing elevator rails862,864. Each carriage852,854has an upper stator rail872at its upper end. The stator in the carriages' upper rails872form linear motors with translators in the tray's skirts874to induct the tray856onto or propel it off the elevator850. The two carriages852,854are driven up and down parallel to each other with their upper rails even to form a level platform for the tray856. At the bottom of the elevator850, the upper carriage rails872are aligned with rails876of a lower conveyor section878. Coils in horizontal cross pieces880in the lower shuttles877energize the stators in the carriage's upper rails872. The energized carriage stators induct trays856onto or propel them off the carriage platform. Coils are also disposed in upper cross pieces882in the upper shuttles863at the top of the elevator850to similarly feed trays856to or receive trays from an upper conveyor section884. In case power to the elevator850is interrupted, each carriage852,854has a brake (not shown, but described later) that engages to prevent the carriage from falling.

A multi-tray sorter is shown inFIGS. 15A-15C. A pair of side-by-side infeed conveyor sections260,262transport a group of four conveyor trays264in a conveying direction106. The infeed conveyor sections260,262are spaced apart from four discharge conveyor sections266,267,268,269across a space270. Two horizontal guide tracks272are positioned in the space270perpendicular to the conveying direction106. The guide tracks272support and drive a pair of carriages274,276along the tracks. The carriages274,276receive the trays264from the infeed conveyor sections260,262and move them laterally to their destination infeed conveyor section as shown inFIGS. 15B and 15C. The carriage rails are then energized to propel the trays264onto the destination outfeed conveyor section. Two carriages274,276are used—one for each infeed conveyor section260,262. Running a multi-tray sorter in reverse changes the conveyor's operation to that of a combiner joining individual groups of trays into a larger multi-tray.

To ensure that the trays264remain together as a group on the infeed conveyor sections, clamping magnets are positioned on the trays as shown inFIG. 16. Each conveyor tray264has a rear clamping magnet280and a front clamping magnet282. The front and rear clamping magnets attract the rear and front clamping magnets of leading and trailing trays on the same infeed conveyor section. For example, the rear clamping magnet of Tray1inFIG. 15Aattracts the front clamping magnet of Tray2to keep the trays together on the left infeed conveyor section260. Either the front clamping magnet282or the rear clamping magnet280could be replaced by a ferrous material that would be attracted by the clamping magnet of the leading or trailing tray. As shown inFIG. 16, the magnets are polarized to exert a high magnetic clamp force along a polar axis in a direction284perpendicular to the front and rear edges286,287of the trays264and a lower magnetic shear force in a direction parallel to the front and rear edges. That polarization holds consecutive trays together on each infeed conveyor, but allows them to be separated easily by the carriages274,276(FIG. 15) for sorting as inFIGS. 15B and 15C. To keep laterally adjacent conveyor trays in each group together, such as Tray1and Tray3or Tray2and Tray4inFIG. 15A, the conveyor trays264have one or more left and right clamping magnets288at the left and right edges290,292of the conveyor trays. The left and right clamping magnets288are polarized to exert a high shear force along a polar axis in a direction294parallel to the left and right edges290,292and a lower clamp force perpendicular to the left and right edges. In this way the laterally adjacent trays are held together side by side in the infeed conveyor and easily separated laterally by the carriages for sorting. Like the front and rear clamping magnets, one or the other of the left and right clamping magnets can be replaced by a ferrous material to be attracted to the clamping magnet.

A right-angle elevator section usable with conveyor segments as inFIG. 1is shown inFIG. 17. The elevator300, shown in a raised position, comprises a carriage301having left and right stator rails302,304maintained in parallel by cross members306. Vertical translators308depend from the left and right rails302,304at rear and front ends310,312. The translators are electrically connected to stators embedded in the elevator rails302,304. The elevator carriage301is supported on a frame314that has vertical guide tracks316backed by an embedded vertical linear stator at each corner. The stators backing the vertical guide tracks316form linear motors with the translators308that raise and lower the elevator carriage301. The elevator frame314also has a pair of parallel stator rails316,318that are perpendicular to the elevator carriage rails302,304. When the carriage301is in its lower position, the carriage rails302,304sit at a level lower than the level of the frame rails316,318to provide clearance for the conveyor trays as they enter the elevator300.

The operation of the right-angle elevator is shown inFIGS. 18A and 18B. A conveyor tray320is shown advancing along an infeed conveyor section322inFIG. 18Atoward a right-angle elevator section300. The rails of the infeed conveyor section322are aligned with the elevator frame rails316,318so that the tray320can be transferred onto the lowered elevator carriage301. Once the tray320is on the lowered elevator carriage, the elevator300lifts the carriage301and tray320to the upper position shown inFIG. 18B. Besides having left and right skirts324,326with translators, the tray320has rear and front skirts328,330with translators. When the tray320is lifted by the elevator300off the frame rails316,318, it is supported by the carriage rails302,304. The skirts324,326,328,330do not extend all the way to the corners of the trays320. Slits332are formed in the skirts324,326,328,330at each of the four corners of the trays320. The slits332provide passages for the elevator rails so that the trays320can be transferred onto the elevator300and off at a right angle onto a discharge conveyor section334.

FIG. 19shows a rectangular spiral conveyor constructed of conveyor segments as inFIG. 1and right-angle elevators as inFIG. 17at the corners. The spiral conveyor340is constructed of conveyor sections342arranged to form one tier of a four-sided stepped spiral of consecutive conveyor sections vertically offset from each other. An elevator section300at each corner of the spiral conveyor raises or lowers trays320from one vertical level to the next. Multiple tiers can be formed with additional conveyor sections342and right-angle elevators300at the corners.

FIGS. 20A-20Cdepict an elevator having an upgoing path and a horizontally offset downgoing path for an elevator carriage. An infeed conveyor section350feeds trays160to an upgoing elevator352providing a vertical guide track354for elevator carriages356. A carriage356at the bottom of the upgoing guide path defined by the vertical tracks354with its stator rails aligned with the stator rails of the infeed conveyor section350receives a tray160. Stators in the vertical guide tracks354energize vertical translators of two-axis translators358at the corners of the carriage356to raise the carriage and the tray160sitting atop it, as shown inFIG. 20B. Once the carriage356reaches the top of the upgoing guide path, horizontal stators along upper horizontal guide tracks360energize horizontal translators of the two-axis translators358to move the carriage356from atop the upgoing elevator352to atop a downgoing elevator362. The downgoing elevator has a vertical guide track defining a downgoing guide path adjacent to the upgoing guide path. The downgoing guide path serves as a return path for emptied carriages356. A lower horizontal guide path364guides the trays back into the home position at the bottom of the upgoing elevator352in position to receive another incoming tray160. Thus, the elevator allows a number of carriages356to circulate around the closed loop formed by the upgoing and downgoing guide paths and the upper and lower horizontal guide paths. When the tray-carrying carriage356is at the top of the downgoing elevator362, as inFIG. 20C, the carriage's rail stator is energized to propel the tray160off onto a discharge conveyor section366. The discharge conveyor366can be contained within a pipe368suspended from above to prevent anything from falling from the trays onto the floor or onto persons or conveyors below and to prevent contamination of products on the conveyor trays160from external sources.

Details of the two-axis translators358are shown inFIG. 31. Outward-facing pole faces480of a core482are arranged in an array. Three-phase horizontal and vertical windings484,485on the core482allow the translator358to move vertically or horizontally in a direction486parallel to the carriage rails. The carriages356have safety brakes488suspended from the translator housings. As shown inFIGS. 32A and 32B, the safety brake488includes a solenoid490with a plunger492connected to an outward-facing permanent magnet494through an outwardly-biasing coil spring496. As shown inFIG. 11, the solenoid490is electrically in series with the translator windings. As long as the carriage356is powered, the solenoid490is actuated as shown inFIG. 32Ato draw the plunger492and the magnet494inward away from the elevator guide track so that the carriage356can move along the elevator guide tracks. When electric power to the carriage356is lost, the solenoid490is de-actuated, and the compressed spring496releases to push the plunger492and the magnet494outward to a braking position at the outside498of the translator housing as inFIG. 32B. The magnet494in the braking position is close enough to the metal of the guide tracks for magnetic attraction to hold the unpowered carriage356in place and prevent it from plummeting to the bottom of the elevator.

The conveyor tray160inFIG. 21Acan be used as a cover for a conveyor tray370as shown inFIG. 21B. The tray370is generally the same as the cover tray160, except that it has a rear wall372and a front wall374upstanding from the rear edge376and the front edge378of the article-conveying surface380. As shown inFIG. 21C, the underside of the cover tray160is supported atop the two walls372,374of the covered tray370. The rear and front walls372,374can be shaped as shown to fill the gap at the rear and front ends of the cover between the skirts172,174to completely enclose the volume between the two trays370,160.

A conveyor for covering and uncovering a tray370with a cover tray160is shown inFIGS. 22A-22D. InFIG. 22A, a cover tray160is transported along an upper conveyor section380in a first conveying direction382toward an open end384. A walled tray370to be covered advances in the same direction382on a lower conveyor section386directly below the upper conveyor section380. An elevator section (frame and guide tracks not shown) including a carriage388bridges a space390between the lower conveyor section386and an aligned second lower conveyor section392when the carriage is in a lower position as inFIG. 22B. The elevator raises the carriage388with the tray160into an upper position to receive the cover tray160, as shown inFIG. 22C. Once the cover tray160is in place covering the lower walled tray370, the elevator carriage388is lowered and the stator rails in the carriage and the second lower conveyor392are energized to propel the covered tray downstream as inFIG. 22D.

The lower tray370is uncovered as shown inFIGS. 23A-23C. The covered and covering trays370,160are conveyed on the second lower conveyor section392in a conveying direction394toward the elevator carriage388in its lower position, as shown inFIG. 23A. The ends396,397of the stator rails in the upper conveyor section380serve as stops that prevent the cover tray160from advancing farther with the lower walled tray370as it proceeds onto the first lower conveyor section386, as shown inFIG. 23B. Once the walled conveyor tray370is clear of the elevator carriage388, the elevator raises the carriage to the upper position, energizes the carriage's stator rails, and propels the cover tray160onto the upper conveyor section380as shown inFIG. 23C.

FIGS. 24 and 25depict a diverter section usable in conveyors constructed of conveyor segments as inFIG. 1. The diverter section400comprises a circular track402—a ring, for example—that houses a curved stator404subtending an angle α around the circular track. An identical curved stator (not shown) is diametrically opposite the curved stator404in the circular track402. The circular track402is supported in a diverter frame406. Two orthogonal pairs of side rails408,410are supported on translators412that ride on a raceway ledge414of the circular track402. One pair of the side rails410is optional. The side rails408,410may be manually lifted from the ledge414for repair, replacement, or cleaning.

FIGS. 26A-26Dshow a diverting conveyor using the diverter section400ofFIGS. 24 and 25. The diverter section400resides in a gap401(FIG. 26C) between an infeed conveyor section416, an inline discharge conveyor section418, and a side-off conveyor section420. The infeed conveyor section416conveys trays160toward the diverter section400in a conveying direction106. The curved stators in the circular track402inductively energize stators in the inline rails408in the diverter400to send a leading tray160A straight across the diverter onto the inline discharge conveyor section418, as shown inFIG. 26B. When a tray160B meant to be diverted onto the side-off discharge conveyor section420reaches the diverter400, the curved stators are energized to rotate translators over a divert angle δ until the inline diverter rails408are aligned with the rails422of the side-off conveyor section420, as shown inFIG. 26C. The curved stators in the circular track402then energize the stators in the diverter rails408to propel the tray160B onto the side-off conveyor section420, as shown inFIG. 26D. The angle α (FIG. 25) subtended by the stationary curved diverter stator is greater than or equal to the divert angle δ of the conveyor. As shown inFIGS. 26A and 27, the rails of the discharge conveyor sections418,420dip down to provide notches424,426at their intersection to accommodate the passing tray skirts.

A conveyor with a curved lower return is shown inFIG. 28. The conveyor comprises a flat upper main carryway section430with a curved lower returnway section432directly below. The upper carryway430is constructed of one or more conveyor segments as inFIG. 1. The lower return is constructed of similar segments, but with curved rails. And portions of the lower returnway conveyor section include two end portions434,436that are coplanar with the ends of the carryway section430to resemble a gondola. The rails of the carryway section430and the end portions434,436are aligned across narrow gaps438,440. The gaps438,440are narrow enough for trays160on the carryway section430to pass over with little slowdown and wide enough for trays to move onto the returnway section432without contacting the carryway section.

FIGS. 29A and 29Bshow a skirtless tray450having two orthogonal pairs of translators452,454at the underside456of the tray. The upper side458of the tray450provides a flat article-supporting surface. The translators452,454comprise permanent-magnet arrays whose magnetic fields are directed downward perpendicular to the tray's article-supporting surface458and underside456. Corner magnets459, such as Halbach arrays, are optionally disposed in the corners of the tray450for magnetic levitation as described subsequently. The trays may also include side, front, and rear clamping magnets460at the tray sides so that the trays can be used to form a larger multi-tray462as inFIG. 30. The clamping magnets are like those in the trays264shown inFIG. 16. The skirtless trays450with underside translators are designed to run on flat-top rails466with stators that form linear motors with the translators452,454. The rails466with embedded stators serve as a tray guide for the trays450. InFIG. 30two conveyor sections468,470are arranged side by side to allow for the formation of the multi-tray462. Connecting structure472maintains the left and right rails in parallel.

Another version of a conveyor segment embodying features of the invention is shown inFIGS. 33 and 34. The conveyor segment500has two parallel stators502,504that extend in length from one end of the segment to the other. The stators502,504are ironless and spaced apart a distance substantially the same as the distance between opposite translators452on the trays450(FIG. 29B). The stators502,504each produce a magnetic flux wave that travels along the length of the stator in a conveying direction506.

Electrically conductive magnetic-levitation (maglev) plates508,510extend along the length of the conveyor segment500laterally outward of the stators502,504. While a conveyor tray450as inFIG. 29Bis propelled in the conveying direction506by the stators502,504, the tray's corner magnets459(FIG. 29B) induce electric currents in the maglev plates508,510that generate reactive magnetic fields opposing the corner magnets' fields with enough force to levitate the trays for a low-friction ride. Position sensors511are positioned along the length of the conveyor segment500to detect the presence of trays at their positions and send a sensor signal indicating that detection to an electronic drive-control circuit512. Electric power and communication wiring to the drive control512can be routed to external circuits or computers through legs516of a conveyor frame514. The stators502,504, the position sensors511, the electronic drive-control circuits512, and the wiring are all encapsulated in a tray-guide housing518having a flat top surface520and forming a tray guide along which trays are propelled. Just inside the housing518at each end along both sides are alignment magnets522or ferrous elements attracted by the magnets to align adjacent sections as inFIG. 5. In the conveyor segments ofFIGS. 30 and 34, the tray guides support the trays along the tops of the tray guides by magnetic levitation rather than directly by contact as do the tray guides in the conveyor segments ofFIG. 1. Like the trays inFIG. 6, the trays450are easy to remove and replace without interference from interlocking or other conveyor structure.

FIG. 35shows another version of a conveyor segment in which the maglev plates508,510ofFIG. 33are replaced by air ducts524,526. Pressurized air from an air source (not shown) is injected into the ducts524,526and expelled through openings527in the tops of the ducts to levitate conveyor trays on an air cushion. In this case corner magnets459as inFIG. 29Bare not required on the trays450.

The lateral alignment of abutting conveyor segments500,500′ is shown inFIG. 36. In this example one conveyor segment500has a pair of alignment magnets522at one side and a pair of ferrous elements523at the other side. The facing end of the adjacent conveyor section500′ has a pair of magnets522at one side and a pair of ferrous elements523at the other. The magnets522attract the ferrous elements523. The lateral dimensions of the magnets522and ferrous elements523match for accurate lateral alignment of the abutting segments500,500′. Of course, all the ferrous elements523may be replaced with magnets of opposite polarity to the confronting magnets of the abutting conveyor segment. But by arranging the magnets522and ferrous elements523as described, all the segments can be made the same, and the polarity of the magnets will not matter.

As shown in the conveyor section524ofFIG. 37, a cover526provides a smooth joint between the housings518of abutting conveyor segments500. AsFIG. 37also shows, the conveyor trays450may be advanced individually or together in a train.

FIGS. 38 and 39show a conveyor arrangement for a 1-to-N switch. A single infeed conveyor section530feeds conveyor trays450onto an x-y conveyor segment532extending in length perpendicular to the infeed conveyor section530. The x-y conveyor segment532has two pairs of stators534,536perpendicular to each other. The first pair of stators534drives the trays450in the main conveying direction538. The second pair of stators536drives the trays450transverse to the main conveying direction to one of N (three are shown) discharge conveyor sections540. The first stators534form linear motors with the left and right translators in the trays, and the second stators536form linear motors with the front and rear translators. Conductive plates542flanking the pairs of stators levitate the trays450as they advance along the x-y conveyor segment532.

A merge conveyor is shown inFIG. 40in which N (three are shown) infeed conveyor sections544A-544C propel conveyor trays450in a main conveying direction546to an x-y conveyor section548. The x-y conveyor section548inducts the trays450from the infeed sections544A-544C and translates them to a single discharge conveyor section550. The topology of the merge conveyor is the same as that of the switch conveyor ofFIGS. 38 and 39with the main conveying direction reversed.

A multi-level conveyor552for a conveyor tray450as inFIGS. 29A and 29Bis shown inFIG. 42. The layout of the conveyor as shown is the same as that for the three-dimensional tray sorter shown inFIGS. 12A-12D. And the operation is similar. Conveyor stators along horizontal and vertical guide tracks554,556propel a tray-supporting carriage558laterally and vertically. The carriage558, shown in more detail inFIG. 41, has two-axis translators560in translator housings562at each corner. The housings are shaped to ride in the guide tracks554,556. The carriages558also include a pair of stators564embedded in the carriage body forming a carriage tray guide with the housing. The stators reside below a continuous top tray-guide surface561to induct trays450into the carriage and to propel them off. Like the carriage ofFIG. 10, the carriage558can include weight sensors563at the corners (only one shown inFIG. 41). The weight sensors563communicate and, along with the stators564, are powered through the translators560, which receive power inductively from the conveyor stators along the guide tracks554,556. Electrically conductive strips565, like those508,510in the levitating conveyor segment500ofFIG. 33, extend along the carriage558beside the stators564and are used in levitating the trays450.

Another version of a conveyor tray is shown inFIGS. 43 and 44. The tray570, instead of supporting articles on a flat top surface, supports articles atop rollers572that extend through the thickness of the body of the tray. Drive stators (not shown) under left and right stationary conveyor side walls574,575coact with translators (not shown) along the left and right side edges576,577of the tray570to propel it in a main conveying direction578. Front and rear walls580,581on the tray570prevent articles from falling off the front and rear edges of the tray during starts, stops, and other accelerations. The rollers572reside in cavities573that open onto the upper surface571and the underside of the tray body and are freely rotatable on axles defining axes of rotation582oblique to the main conveying direction578. Elongated actuating rollers584, supported in the conveyor frame adjacent an opening586in the right conveyor side wall585, rotate freely on axles defining axes588parallel to the main conveying direction578. The actuating rollers584are arranged in line with the columns of tray rollers572. As the tray570passes over the actuating rollers584, the bottoms of the tray rollers572rotate on their oblique axes582and push articles atop the rollers off the side of the tray570and through the opening586in a right-side divert direction590. Roller balls without axles and rotatable in all directions could alternatively be used in the trays and actuated by the same actuating rollers.

FIG. 44shows the same conveyor with trays570having rollers572arranged at the same oblique angle as inFIG. 43. A set of actuating rollers584′ is supported in the conveyor frame adjacent to an opening592in the left side wall574. A tray570traveling in the main conveying direction578is stopped after passing the actuating rollers584′. The stator field is reversed to drive the tray570in the reverse direction594back over the actuating rollers584′. The tray rollers572engaging the actuating rollers584′ in the reverse direction594opposite to the main direction rotate in the opposite direction to push conveyed articles through the opening592in the left side wall574in a left-side divert direction596.

The conveyor tray600inFIG. 45has stacked roller sets602(FIG. 45A) arranged in columns. The bottom roller604of each set protrudes beyond the underside of the tray600. The top roller606protrudes beyond the upper surface608of the tray600. The top roller606rests on the bottom roller604—at least when supporting an article—so that rotation of the bottom roller in one direction causes the top roller to rotate in the opposite direction. (The roller set inFIG. 45Ais shown without side supports and axles for the top roller606for clarity.) Both the top and bottom rollers604,606are arranged to rotate on parallel axles defining axes610,611oblique to the conveying direction578. As the conveyor tray600is propelled over the actuating rollers584, the bottom rollers604rotate forward on their axes610, which rotates the article-supporting top rollers606rearward. Because the component of rearward rotation of the top tray rollers606equals the forward motion of the trays600along the conveyor, articles are diverted off the trays in a divert direction612perpendicular to the main conveying direction578.

The conveyor tray614shown inFIGS. 46 and 46Ahas tray rollers616that rotate on axles defining axes of rotation618parallel to the main conveying direction578. An array of caster-like actuating rollers620, supported in the conveyor frame, provides tray-roller actuation in this version. The freely rotatable actuating rollers620can be swiveled about a vertical axis613by a rack-and-pinion system to change their axes of rotation622. With the actuating rollers620angled oblique to the main conveying direction578as shown, the tray rollers616rotate to push articles across the tray614toward an opening624in the right side wall626. Although the tray rollers616push the articles off the tray at900relative to the tray without contacting the front and rear tray walls617,619, they exit through the opening624in an oblique direction628because of the motion of the tray in the conveying direction578. When the actuating rollers620are swiveled so their axes622are at the same oblique angle on the other side of the main conveying direction, the actuated tray rollers616rotate toward the left side wall627and through an opening625in a divert direction629. Thus, the conveyor is useful for diverting articles off the trays in either direction by changing the orientation of the actuating rollers620.

The passive actuating rollers584ofFIGS. 43-45could be replaced by a tray-roller actuator in the form of a flat bearing surface on which the tray rollers572,604ride. The flat bearing surface can be stationary, or it can be a moving surface, such as the outer surface of a belt. Or tray-roller rotation can be achieved magnetically or electromagnetically. As one example, the tray-roller actuator supported in the conveyor frame could be permanent magnets, electromagnets, or stators producing magnetic or electromagnetic fields interacting with ferrous, magnetic, or electrically conductive rotors in the tray rollers572,604,616ofFIGS. 43-46.FIG. 55shows a conveyor segment100as inFIG. 1with a linear-motor stator712housed in a smooth housing between the side rails102,104. A conveyor tray714has an array of rollers716with rotors made of permanent magnets or electrically conductive material that form linear motors with the stator712, which can selectively actuate the rollers716into rotation.

A rail scrubber630is shown inFIGS. 47 and 48riding the rails632,633on a conveyor segment634. The scrubber630is shown in this example with three fluid tanks: a soap tank636, a water tank637, and a sanitizer tank638. Each tank is in the shape of an inverted U with a space between the legs of the inverted U. A drive system including a drive motor and battery (not shown) are housed in a housing640received in the space. The motor, powered by the battery, drives front or rear drive wheels642,643or both to drive the scrubber630along the rails632,633. The wheels642,643are mounted on axles644that extend through the housing640. The axles644are coupled to the drive motor. The wheels642,643each have a central groove646that receives the rail632,633and prevents derailment. The scrubber630also includes at least one set of scrubbing wheels648, two sets in this example, to scrub both rails632,633. Like the drive wheels642, the scrubbing wheels648are mounted on axles650that extend through the central housing640. The scrubbing wheels648are also driven by the drive motor, but perhaps geared differently to rotate at a higher speed than the drive wheels642. Or the scrubber wheels648can be driven by separate motors. The scrubbing wheels648include two wheel halves separated by a gap. Scrub-brush pads on confronting faces of the two wheel halves scrub the rail received in the gap. Soap, water, and sanitizer dispensers652,653,654include fittings655connected into the tanks636,637,638, upper and lower spray nozzles656,657, and tubing658connecting the fittings to the lower nozzles. The dispensers652,653,654are on each side of the tanks636,637,638with the nozzles directing a spray at the tops and bottoms of the rails632,633. The housing640also houses a scrubber computer that controls the speeds of the drive and scrubbing wheels and other electronic and power-supply circuits.

The rail scrubber630receives power inductively from the stator windings in the rails632,633through secondary coil windings housed in scrubber appendages662,663that ride along the rails. A single coil may suffice. The ac power transferred by transformer action to the coils is converted to dc power to power the electronics and charge the battery or drive the motors. Alternatively, the drive wheels642or the scrubber wheels648or both could include magnetic or electrically conductive rotors that are driven by the rail stators. In such a case a drive motor would not be necessary. Or the secondary coil could be replaced by a translator that responds to a rail-stator-generated magnetic flux wave traveling along the rail by pushing the scrubber along the rails. In that case the drive rollers642could be idle wheels not coupled to a drive motor.

The tops and sides of the scrubber630ofFIG. 47are covered by a smooth stainless steel cover660as shown inFIG. 48. Scrapers664extend outward from a front face666of the cover660. The scrapers664have an inverted-U cross section, a tapered top surface668, and tapered sides670to remove bulk debris from the tray drive rails632,633, which are received in the inverted U. The scrapers664taper inward away from the front face666of the cover660.

A similar scrubber910for cleaning the top surface520of the tray-guide housing518of a conveyor segment500as inFIGS. 33 and 34is shown inFIG. 59without a cover. This scrubber differs from the scrubber ofFIG. 47in that its wheels912don't ride on rails. Rather, they ride along the top surface520of the tray-guide housing518. Another difference is that the scrubber wheels914are rotated 90° from the scrubber wheels648ofFIG. 47. Brushes916on the bottoms of the scrubber wheels914scrub the top surface520of the tray guide. Water, soap, and sanitizer are sprayed onto the top surface520through spray nozzles918. The scrubber is powered by an internal battery or by a linear motor formed by the stator in the conveyor segment and permanent-magnet or electrically conductive rotors forming a translator for the scrubber910.

In some applications, it's important that trays used to transport certain products not be used to transport other products. This is especially true where cross-contamination is unacceptable. One way to avoid cross-contamination by preventing trays for one product from being used for another product is shown inFIG. 49. Four separate conveyor lines671,672,673,674are shown. Each conveyor line is dedicated to an individual product type or family, and the trays681,682,683,684bear identification as acceptable carriers for an individual product type or family. So each tray is an assigned member of one of a number of families that can be determined from the identification. The identification may be anything that can be detected by a sensor676positioned at a sensing position alongside the conveyor or embedded within the conveyor stator rails678. Examples of identifiable indicia675include tray shape, tray color, tray markings, bar codes, other product codes that can be read by optical sensors or determined by visioning systems, RFID tags readable by RFID readers, and magnet arrangements on the trays that are readable by magnetic sensors. When the sensor676detects a tray from a family not assigned to the sensor's conveyor, a local or system controller679receiving the sensor signal stops the conveyor and sounds an alarm or displays a warning so that an operator can remove the offending tray.

Other sensors that detect process parameters, such as temperature, may also be used to detect valid process temperature ranges and dwell times. For example, in a tray-washing process, the tray sensor would be used to validate proper wash, rinse, and dry cycles. The process sensors could be in or on the trays themselves or positioned along the conveyor lines where the trays undergo the process.

Each of the conveyor lines671-674shown in this example comprises a main conveyor section686defining a carryway conveying path on which the trays681,682,683,684carry products and a return conveyor section688defining a return conveying path on which the trays are empty. The infeed end of the main conveyor section686is linked to the discharge end of the return section688by an infeed diverter section690. The discharge end of the main conveyor section686is linked to the infeed end of the return section688by a discharge diverter section692. The diverter sections690,692may be the same as those shown inFIGS. 14A-14C.

The description of the operation of the fourth conveyor line674exemplifies how each of the other conveyor lines671-673operates. The trays684of the family assigned to the predetermined process to be carried out along the main conveyor section686are fed onto the main conveyor section from the return conveyor section688by the infeed diverter690. Only those trays684passing the sensor676that are identified by the controller679as dedicated to the fourth conveyor line674are passed onto the main conveyor section686. After the trays684complete their processing on the main conveyor section686and their products are removed, they may be diverted by the discharge diverter692back to the return conveyor section688or diverted elsewhere for cleaning. Cleaned trays can be returned to the return conveyor section688. Or the cleaning process can be carried out automatically along the return conveyor section688in one or more enclosed automatic washing stations689. In all the tray-conveyor versions described in this application, fully automatic washing-station enclosures689can be installed on the return sections in one or more cleaning zones to clean the empty trays as a substitute for manual tray removal and cleaning. Or the washing stations in the cleaning zones can be completely manual or semi-automatic and require some complementary human activity. Washing stations in the return sections of the multiple-stator conveyor systems described could also be used in single-stator tray conveyors.

If it's necessary or required that the conveyor sections686,688,690,692be cleaned upon completion of a process or upon the detection of an unacceptable conveyor tray, all the trays674are removed and sequestered for cleaning, for example, and a scrubber630is placed on the conveyor line674as shown inFIG. 50. The scrubber630runs along all the conveyor sections686,688,690,692to remove residue from the rails694. After the scrubber630has cleaned the rails694, it is removed from the conveyor line674. The sequestered trays684can then be put back on the conveyor line674, typically on the return conveyor section688. Cleaning of the rails can also be required whenever an inappropriate tray is detected.

Alternatively, the conveyor line674can be used for a different process or for the same process on different products. If contamination from the products or by-products of the previous process run is unacceptable, a different family of identifiable trays specific to the process being run is used. For example, to avoid contamination with allergens such as those associated with peanuts, a peanut-processing run could be followed by a subsequent process run on a different food product. The local or system controller679, based on the sensor signals, passes process- or product-specific trays of a predetermined family and locks out trays of other families dedicated to other processes or products. In a similar way as shown inFIG. 49, the four conveyor lines671-674could be dedicated to four different products or processes 1-4 with corresponding designated conveyor trays681-684. The local or system controller, upon identifying a tray with the sensor676, would lock out disallowed trays. In that way contamination is avoided. For sensitive processes, such as in the chemical, biomedical, pharmaceutical, food, and electronics industries, different processes have to be separated by a barrier, such as a wall696, into different zones. The method just described applies as well to those circumstances.

Another way to prevent cross-contamination is to make the trays so that only trays of a certain family are geometrically or drivably compatible with a conveyor. For example, conveyors for a certain process could have a rail gauge that fits only trays of a certain family. Or the stators could be positioned in the conveyor sections so that they align only with the translators in the trays of a certain family.

An overhead pipe conveyor with a same-level return is shown inFIGS. 51A and 51B. The pipe conveyor720comprises two elongated enclosures, or pipes722,724parallel to each other at the same level and open at opposite ends. Stators (not shown) extend along a conveying surface, in this case, the inner bottom floor725of the pipes722,724at left and right sides726,728of the floor to propel the conveyor trays730like those inFIG. 7. The pipes722,724may be suspended from above by attachments732, such as cables or rods. The two pipes722,724are open at a discharge end of the infeed pipe722and the re-entry end of the return pipe724. A carriage assembly comprises a tiltable carriage734and a guide track736in the form of a partial cylinder along which the carriage translates. The carriage734has a pair of left and right stator rails738joined through a rotor-translator740by a pair of depending arms742affixed to the rotor-translator. A θ-z stator744is positioned along the inner side of the cylindrical guide track736. The θ-z stator744produces a magnetic flux wave that travels circumferentially (in θ) along the guide track736to tilt the tray730about a tilt axis as shown inFIG. 51Ba predetermined angle θ relative to horizontal (as inFIG. 51A) to discharge articles746. Magnets or ferrous materials in the carriage rails738and in the trays730attract each other enough to prevent the trays from sliding off the carriage when it tilts. The stator744also propagates a magnetic flux wave axially (in z) along the guide track736to translate the carriage734from a first position in line with the infeed pipe722to a second position in line with the return pipe724. In that way trays730can be returned. So the carriage734translates along its tilt axis.

An over-and-under pipe conveyor is shown inFIGS. 52A-52C. In this version a return pipe750is below an incoming pipe752. A carriage assembly has a circulating carriage754with two pairs of parallel stator rails756,758joined by arms760. Shaft segments762parallel to the rails756,758join the arms760to a rotor764. An outer stator766rotates the rotor764and the stator rails756,758a predetermined angle of 180° to alternately position the stator rails in line with the upper and the lower pipes752,754. When the carriage754tilts, as inFIG. 52B, articles746drop from the tray730. When the carriage754completes its 180° rotation, both sets of carriage stator rails756,758are aligned with the upper and lower pipes752,754because the two pairs of rails are rotationally separated by 180°. The stator rails are energized to induct trays730onto the upper rails756for the upper pipe752and to return trays onto the lower rails758for the upside-down return trip. The ceiling759of the pipe754forms the conveying surface in the upside-down return. A scraper760attached to the open end of the lower return pipe760is positioned to scrape debris sticking to the article-supporting surface762of the upside-down tray730as it's propelled along the carriage754. The upside-down trays730are prevented from falling off the carriage754by magnets and ferrous elements as with the other conveyors just described.

An endless conveyor769having an upper carryway and a lower returnway is shown inFIG. 53. The upper carryway770has a pair of stator rails772,774, like those inFIG. 1, propelling trays730, like those inFIG. 7. The lower returnway776has a pair of upside-down stator rails778,780. Both the carryway772and the returnway are supported in the same frame782in this example. Rotating carriages784in carriage assemblies at both ends of the conveyor transfer trays730between the carryway770and the returnway776to form an endless conveying path. Each carriage784has four pairs of parallel stator rails786. The four right-side rails define a right-side square788and the four left-side rails define a left-side square790. The squares788,790are joined by a shaft792to a motor794. The motor rotates the carriage784in predetermined 90° increments so that it stops with one of the four pairs of rails786aligned with the carryway770and the opposite pair of rails aligned with the returnway776. The stator rails786aligned with the carryway770and the returnway are activated to discharge a tray730onto the carryway and to induct a tray from the returnway. Attracted magnetic and ferrous material in the carriage and returnway rails786,778,780and in the trays730prevent the upside-down or tilted trays from falling. A carriage like the carriage754inFIGS. 52A-52Ccan be used with the conveyor ofFIG. 53, and vice versa.

An endless conveyor920for conveyor segments500as inFIG. 33and skirtless trays450as inFIG. 29Ais shown inFIG. 60. Conveyor stators along four vertical guide tracks922form an elevator924at opposite ends of the conveyor902. Each elevator raises and lowers a carriage926to transfer a tray450between an upper tray carryway928and a lower tray returnway929. The carriage's embedded stators induct a tray450from the carryway or the returnway onto the carriage926. The carriage stators are then de-energized while the elevator924raises or lowers the carriage and the supported tray. Once the carriage926is aligned with the carryway928or the returnway929, the carriage stators are re-energized with the opposite phasing to propel the tray450off and onto the carryway or returnway. The elevator924then lowers or raises the carriage926in position to receive the next tray450. The carriage926is similar to the carriage558ofFIG. 41, but using only single-axis vertical translators in translator housings930at each corner. The translator housings930ride in the guide tracks922. Both the carryway928and the returnway929are constructed of one or more of the conveyor segments500providing levitating tray guides for the conveyor trays450.