Patent Description:
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 <CIT>. 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.

<CIT> relates to a transport system for transporting sliced food products originating from a high-speed slicer and discloses the features of the preambles of claims <NUM> and <NUM>.

In a first aspect of the present invention there is provided a method according to claim <NUM> for operating a conveyor comprising:.

In a further aspect of the present invention there is provided a conveyor system according to claim <NUM>.

A conveyor segment for constructing a cleanable conveyor system embodying features of the invention is shown in <FIG>. The conveyor segment <NUM> comprises left and right side rails <NUM>, <NUM> extending in length in a conveying direction <NUM>. The two side rails are supported in a minimal conveyor frame comprising legs <NUM> and connecting structure in the form of cross beams <NUM> maintaining the two side rails <NUM>, <NUM> parallel to each other. The entire conveyor frame is made of a plastic material, but could be made of other materials. Top surfaces <NUM> of the side rails <NUM>, <NUM> and top surfaces <NUM> of the cross beams <NUM> are convexly curved, or rounded, to minimize the buildup of grease and contaminants.

As shown in <FIG>, a three-phase linear-motor stator <NUM> is embedded in the right side rail <NUM>. A similar stator is embedded in the left side rail. The stator <NUM> comprises 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 stator <NUM> produces a magnetic flux wave that travels along the side rail <NUM> in or opposite to the conveying direction <NUM> shown. The magnetic flux wave is directed horizontally outward from the outer wall <NUM> of the side rail <NUM> in this example. Also embedded in the side rail <NUM> are sensors <NUM> at spaced apart sensor positions along the side rail's length. Each sensor <NUM> is used to detect the presence of a tray on the side rails at the sensor position.

The stators <NUM> and the sensors <NUM> are powered and controlled by electronic and power circuits <NUM> embedded in the cross beams <NUM> over wires <NUM> embedded in the conveyor frame and the side rails <NUM>, <NUM> as shown in <FIG>. Power, control, and data wires <NUM> connecting the electronics module <NUM> to a source of power and a system controller are embedded in the legs <NUM> of 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 in <FIG>. The stator <NUM> comprises a linear series of three sets of coils 130A, 130B, 130C-one set for each of the three phases-alternately arranged along the length of the side rail. Each set of coils 130A, 130B, 130C is driven by an amplifier 132A, 132B, 132C. The phasing sequence and frequency of the stator <NUM> are controlled through a stator drive control <NUM>, which sends coil control signals 136A, 136B, 136C to the amplifiers 132A, 132B, 132C. The stator drive control <NUM> includes a computer in communication with a remote system computer <NUM>, which also communicates with the stator drive controls in other conveyor segments. The stator drive control <NUM> receives commands from and sends data to the system computer <NUM> wirelessly or over a hard-wired connection <NUM>. The sensors <NUM> send sensor signals <NUM> indicating the position of a conveyor tray over a sensor bus to the stator drive control <NUM>, which uses those signals to determine when to energize and de-energize the stator <NUM>. All those components, except for the remote system computer <NUM>, are encapsulated in the conveyor frame as in <FIG>. The magnetic flux wave produced by the stator in the rail causes a conveyor tray with an embedded permanent-magnet array <NUM> to advance along the rail in the conveying direction <NUM>.

<FIG> illustrates how two adjacent conveyor segments <NUM>, <NUM>' are maintained with their left and right side rails <NUM>, <NUM> aligned to form continuous rails. An alignment magnet <NUM> is embedded in the end of an appendage <NUM> at the bottom of each side rail <NUM>, <NUM>. A similar magnet <NUM> is embedded in a similar appendage <NUM> at the confronting end of the side rail of the adjacent conveyor segment <NUM>'. The magnets <NUM>, <NUM> are 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 segments <NUM>, <NUM>' is shown in <FIG> supporting a series of conveyor trays <NUM> on the tops <NUM> of the side rails <NUM>, <NUM>, which serve as a tray guide. The trays <NUM> are not connected to each other and are independently movable in or opposite to the conveying direction <NUM> by the stators embedded in the side rails <NUM>, <NUM>. The trays <NUM> can 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 in <FIG>, each tray <NUM> is shown as a rectangular tray body <NUM> with a rear edge <NUM>, a front edge <NUM>, a left edge <NUM>, and a right edge <NUM>. The tray <NUM> has an upper article-supporting surface <NUM> extending to the edges <NUM>, <NUM>, <NUM>, <NUM>. Skirts <NUM>, <NUM> extend downward from the left and right edges <NUM>, <NUM>. Embedded in each skirt <NUM>, <NUM> is an array of permanent magnets <NUM> extending in length along the skirt between the rear and front edges <NUM>, <NUM>. The magnet arrays are arranged with their magnetic fields directed generally parallel to the article-supporting surface <NUM> to maximize the magnetic coupling with the traveling magnetic wave produced by the stators in the side rails of the conveyor segments. The skirts <NUM>, <NUM> overlap the conveyor side rails and help keep the trays <NUM> laterally in place. At least the skirts <NUM>, <NUM> are made of a non-magnetic material, such as plastic. And the upper article-supporting surface <NUM> can 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 surface <NUM> could extend beyond the front, rear, left, and right edges of the main tray body.

Straight conveyor segments <NUM>, <NUM>' as in <FIG> can be joined to curved conveyor segments <NUM> as in <FIG> to form a banked racetrack conveyor section <NUM>. The side rails <NUM>, <NUM> of the curved segments <NUM> are curved out of coplanarity with the straight segments to form the banked racetrack section <NUM>. Articles <NUM> carried on the conveyor trays <NUM> are diverted off the trays <NUM> and over the lower side rail <NUM> upon entering the banked racetrack section <NUM>. In this way the racetrack serves as a tilt conveyor to allow conveyed products to drop from the trays in the banked section <NUM>. The banked racetrack section <NUM> also permits the construction an endless track without a lower returnway along its entire circuit. And the trays <NUM> are shown routed through a washing station including a cleaning zone containing an automatic washing enclosure <NUM> like that used in car washes along a return section <NUM> downstream of the banked section <NUM>. Washing the trays <NUM> in the automatic washing enclosure <NUM> in the return <NUM> reduces 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 arrays <NUM> with the magnets arranged in alternating polarities as shown in <FIG>. 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 in <FIG>, the trays could include magnetic strips <NUM> extending along their undersides in the joints <NUM> between the skirts <NUM> and the bottom of the article-supporting surface <NUM>. As the trays advance along a conveyor segment <NUM>, the magnetic fields of the magnetic strips <NUM> induce currents in electrically conductive strips <NUM> embedded in and extending the length of stator rails <NUM>. 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 in <FIG>. The carriage <NUM> comprises a left rail <NUM> and a right rail <NUM> connected and maintained in parallel by a pair of connecting members <NUM>. The tops of the left and right carriage rails <NUM>, <NUM> form a two-rail carriage tray guide for the trays. Like the rails in the conveyor segments, the left rail <NUM> encapsulates a left linear stator, and the right rail <NUM> encapsulates a right linear stator. A rear translator at a rear end <NUM> of the carriage <NUM> comprises a left rear translator in a left rear housing <NUM> suspended below and outward of the left rail <NUM> and a right rear housing <NUM> suspended below and outward of the right rail <NUM>. In a similar way a front translator at a front end <NUM> of the carriage <NUM> comprises left and right front translators in left and right front housings <NUM>, <NUM>. As shown in <FIG>, each translator includes one or two three-phase windings. In this example the right rear housing <NUM>, shown open to reveal the translators suspended from the right rail <NUM> at the rear end <NUM>, has a vertical translator <NUM> and a horizontal translator <NUM>. The vertical translator <NUM> has a horizontal magnetic axis <NUM>, and the horizontal translator <NUM> has a vertical magnetic axis <NUM>. The translators in the corner housings <NUM>, <NUM>, <NUM>, <NUM>, besides coacting with conveyor-frame stators to propel the carriage along a track, couple power to the stators in the left and right rails <NUM>, <NUM>. The rail stators, when energized, propel trays along and off the rails <NUM>, <NUM>. So the translators are electrically connected to the rail stators. The carriage could also encapsulate one or more weight sensors <NUM> in the rails <NUM>, <NUM> or in the corner translator housings <NUM>, <NUM>, <NUM>, <NUM> to weigh the trays and their contents.

<FIG> is a block diagram of the circuit embedded in the carriage frame. The carriage-rail stator drive system including the three-phase stator coils <NUM>, the coil-drive amplifiers <NUM>, the carriage drive control <NUM>, and the position sensors <NUM> is schematically the same as for the conveyor segments described with respect to <FIG>. The stator drive-system components are distributed between the rails and the translator housings within the carriage frame. The output <NUM> of the three-phase horizontal and vertical translator windings <NUM> provides electrical power to the drive control <NUM>, amplifiers <NUM>, and rail stators <NUM> to drive the conveyor-tray translators <NUM> and to the position sensors <NUM> and the weight sensors <NUM>. The translator windings <NUM> receive power inductively from a conveyor-frame stator <NUM>. 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 control <NUM> and the system computer. The position sensors <NUM> and the weight sensors <NUM> send sensor signals to the carriage drive control <NUM>. A power and communication system <NUM> includes: (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 control <NUM>; (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 windings <NUM>. The stator drive control <NUM> processes the decoded incoming messages received from the power and communication system <NUM> and sends data messages to the power and communication system for transmission over the power system. The carriage translator <NUM> forms a switched-reluctance linear motor with the conveyor-frame stator <NUM> to move the carriage. When the carriage is stopped, the power from the conveyor-frame stator <NUM> is used to drive conveyor trays along the carriage rails.

<FIG> describe one example of a conveyor system using a carriage. The conveyor has four conveyor sections: a first lower section <NUM>; a second lower section <NUM> in line with the first lower section <NUM>; a third lower section <NUM> parallel to and laterally offset from the first conveyor section <NUM>; and a fourth upper section <NUM> horizontally and vertically offset from the first conveyor section <NUM>. The four conveyor sections <NUM>, <NUM>, <NUM>, <NUM> are separated from each other across gaps forming a main space <NUM>. A gantry is disposed in the space <NUM>. The gantry has two parallel horizontal guide tracks <NUM>, <NUM> and three pairs of parallel vertical guide tracks <NUM>, <NUM>, <NUM>. To simplify the drawing the gantry frame supporting the guide tracks is not shown. The translator housings <NUM>, <NUM>, <NUM>, <NUM> ride in the guide tracks <NUM>, <NUM>, <NUM>, <NUM>, <NUM>. Upper lips <NUM> along 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 carriage <NUM> with a conveyor tray <NUM> atop it is shown in <FIG> in a position in which the tray <NUM> can be passed along the carriage rail from the first lower conveyor section <NUM> to the inline second lower conveyor section <NUM>. 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 sections <NUM>, <NUM>. If the tray <NUM> is selected for another destination, the carriage <NUM> is propelled along the horizontal guide tracks <NUM>, <NUM> to a position in which the rails are aligned with the third lower conveyor section <NUM> as shown in <FIG>. The stators in the carriage may then be energized to propel the tray <NUM> off and onto the third conveyor section as shown in <FIG>. If the scheduled destination is the upper conveyor section <NUM>, the carriage <NUM> is raised by the stators in the vertical guide tracks <NUM>, <NUM> to the level of the upper conveyor section, as shown in <FIG>. The carriage's stator rails are then energized to propel the tray <NUM> off the carriage <NUM> and onto the upper conveyor section <NUM>.

A more complex conveyor system is shown in <FIG> in which two rows of gantries <NUM>, <NUM> are used to move a carriage <NUM> with trays <NUM> horizontally and vertically along guide tracks from an infeed conveyor section <NUM> onto or off parallel conveyor sections <NUM> arranged 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 carriage <NUM> in its home position shown in <FIG> from the infeed conveyor section <NUM> onto a discharge conveyor section <NUM>. When trays in the accumulator section <NUM> are scheduled for processing, they are moved to a position at the gantries <NUM> and onto a carriage <NUM>, 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 section <NUM>. Although only a single carriage <NUM> is shown in the gantries <NUM>, <NUM> in <FIG>, more than one carriage can be used.

<FIG> depict the operation of a merge conveyor constructed of three infeed conveyor sections <NUM>, <NUM>, <NUM> with dual stator rails <NUM>, <NUM> as in the conveyor section of <FIG>. The three infeed sections <NUM>, <NUM>, <NUM> are shown side by side in parallel. A first pair <NUM> of horizontal guide tracks extends perpendicular to the conveying direction <NUM> at the common ends of the left and center infeed conveyor sections <NUM>, <NUM>. The first pair <NUM> of guide tracks bridges those two conveyors and forms a first diverter section. A first carriage <NUM> (<FIG>) rides on the first pair <NUM> of tracks to move trays <NUM> horizontally to a discharge conveyor section <NUM> in line with the center infeed conveyor <NUM> across a space. The right infeed conveyor section <NUM> extends past the ends of the other two infeed sections <NUM>, <NUM> to an end <NUM> laterally across from the front end of the first carriage <NUM>. A second pair <NUM> of guide tracks parallel to the first pair <NUM> bridges the space between the right infeed conveyor section <NUM> and the discharge conveyor section <NUM>. The second pair <NUM> of guide tracks form a second diverter section to drive a second carriage <NUM>. The sequence of operations required to merge Tray <NUM>, Tray <NUM>, and Tray <NUM> onto the discharge conveyor section <NUM> is as follows:.

In this one-level version no vertical elevation is required, and the translators <NUM> in a connecting member <NUM> joining the rails of the carriages <NUM>, <NUM> require only horizontal translators. The same configuration of conveyor sections can be used as a <NUM>-to-<NUM> switch by reversing the conveying direction <NUM>. In that case, the discharge conveyor section <NUM> would operate as an infeed conveyor section, and the three infeed conveyor sections <NUM>, <NUM>, <NUM> would be discharge conveyors, with the guide tracks <NUM>, <NUM> and carriages <NUM>, <NUM> as the switches.

Another version of a diverter section <NUM> is shown in <FIG>. A carriage <NUM> has rear and front skirts <NUM>, <NUM> depending from a carriage body <NUM>. The skirts <NUM>, <NUM> have built-in translators, such as permanent-magnet arrays as in the conveyor trays. The diverter section <NUM> has stator rails <NUM>, <NUM> like those in the conveyor segments of <FIG>. The carriage <NUM> moves along the tracks defined by the rails <NUM>, <NUM> in a translation direction <NUM>. Cross pieces <NUM> joining the diverter's stator rails <NUM>, <NUM> house coils that energize the stators in carriage rails <NUM>, <NUM> extending upward from left and right sides of the carriage body <NUM>. When the carriage rails <NUM>, <NUM> are aligned with rails <NUM>, <NUM> of discharge or infeed conveyor sections, the carriage-rail stators are energized to induct trays <NUM> like the tray of <FIG> onto or to propel them off the carriage.

<FIG> shows a dual-rail elevator <NUM> using two carriages <NUM>, <NUM> to form an elevator platform for a conveyor tray <NUM>. The carriages <NUM>, <NUM> are similar to the carriage <NUM> shown in <FIG>. The elevator <NUM> comprises two upgoing vertical conveyor sections <NUM>, <NUM> each with left and right stator rails <NUM>, <NUM>. At the top of each upgoing conveyor section <NUM>, <NUM> is a shuttle conveyor segment <NUM> with stator rails <NUM> aligned with the left and right stator rails <NUM>, <NUM> in a first position. Each shuttle <NUM> translates laterally outward as indicated by arrows <NUM> with one of the carriages <NUM>, <NUM> from an associated upgoing conveyor section <NUM>, <NUM> to one of two downgoing conveyor sections <NUM>, <NUM> with left and right stator rails <NUM>, <NUM>. When the shuttles are in a second position with their rails <NUM> aligned with the downgoing rails <NUM>, <NUM>, the carriages <NUM>, <NUM> are advanced onto the downgoing rails <NUM>, <NUM> for their trips back to the bottom of the elevator <NUM>. Then the upper shuttles <NUM> return inward to their first positions. Identical lower shuttles <NUM> are disposed at the bottom of the elevator <NUM> to carry the carriages <NUM>, <NUM> from the outer downgoing rails <NUM>, <NUM> to the inner upgoing rails <NUM>, <NUM>. In this up-down elevator <NUM>, multiple pairs of carriages can run simultaneously. (The operation of the shuttles <NUM>, <NUM> is also described in reference to elevator carriages shown in <FIG>, which operate identically in moving vertically instead of horizontally. ) The upgoing conveyor sections <NUM>, <NUM> are arranged in parallel, facing each other in a conveyor frame <NUM>. The carriages <NUM>, <NUM> have left and right skirts <NUM>, <NUM> with translators, such as an array of permanent magnets, that form linear motors with the linear stators in the vertical stator rails <NUM>, <NUM>. The linear motors drive the carriages <NUM>, <NUM> up the upgoing elevator rails <NUM>, <NUM>. Each carriage <NUM>, <NUM> has an upper stator rail <NUM> at its upper end. The stator in the carriages' upper rails <NUM> form linear motors with translators in the tray's skirts <NUM> to induct the tray <NUM> onto or propel it off the elevator <NUM>. The two carriages <NUM>, <NUM> are driven up and down parallel to each other with their upper rails even to form a level platform for the tray <NUM>. At the bottom of the elevator <NUM>, the upper carriage rails <NUM> are aligned with rails <NUM> of a lower conveyor section <NUM>. Coils in horizontal cross pieces <NUM> in the lower shuttles <NUM> energize the stators in the carriage's upper rails <NUM>. The energized carriage stators induct trays <NUM> onto or propel them off the carriage platform. Coils are also disposed in upper cross pieces <NUM> in the upper shuttles <NUM> at the top of the elevator <NUM> to similarly feed trays <NUM> to or receive trays from an upper conveyor section <NUM>. In case power to the elevator <NUM> is interrupted, each carriage <NUM>, <NUM> has a brake (not shown, but described later) that engages to prevent the carriage from falling.

A multi-tray sorter is shown in <FIG>. A pair of side-by-side infeed conveyor sections <NUM>, <NUM> transport a group of four conveyor trays <NUM> in a conveying direction <NUM>. The infeed conveyor sections <NUM>, <NUM> are spaced apart from four discharge conveyor sections <NUM>, <NUM>, <NUM>, <NUM> across a space <NUM>. Two horizontal guide tracks <NUM> are positioned in the space <NUM> perpendicular to the conveying direction <NUM>. The guide tracks <NUM> support and drive a pair of carriages <NUM>, <NUM> along the tracks. The carriages <NUM>, <NUM> receive the trays <NUM> from the infeed conveyor sections <NUM>, <NUM> and move them laterally to their destination infeed conveyor section as shown in <FIG>. The carriage rails are then energized to propel the trays <NUM> onto the destination outfeed conveyor section. Two carriages <NUM>, <NUM> are used-one for each infeed conveyor section <NUM>, <NUM>. 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 trays <NUM> remain together as a group on the infeed conveyor sections, clamping magnets are positioned on the trays as shown in <FIG>. Each conveyor tray <NUM> has a rear clamping magnet <NUM> and a front clamping magnet <NUM>. 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 Tray <NUM> in <FIG> attracts the front clamping magnet of Tray <NUM> to keep the trays together on the left infeed conveyor section <NUM>. Either the front clamping magnet <NUM> or the rear clamping magnet <NUM> could be replaced by a ferrous material that would be attracted by the clamping magnet of the leading or trailing tray. As shown in <FIG>, the magnets are polarized to exert a high magnetic clamp force along a polar axis in a direction <NUM> perpendicular to the front and rear edges <NUM>, <NUM> of the trays <NUM> and 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 carriages <NUM>, <NUM> (<FIG>) for sorting as in <FIG>. To keep laterally adjacent conveyor trays in each group together, such as Tray <NUM> and Tray <NUM> or Tray <NUM> and Tray <NUM> in <FIG>, the conveyor trays <NUM> have one or more left and right clamping magnets <NUM> at the left and right edges <NUM>, <NUM> of the conveyor trays. The left and right clamping magnets <NUM> are polarized to exert a high shear force along a polar axis in a direction <NUM> parallel to the left and right edges <NUM>, <NUM> and 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 in <FIG> is shown in <FIG>. The elevator <NUM>, shown in a raised position, comprises a carriage <NUM> having left and right stator rails <NUM>, <NUM> maintained in parallel by cross members <NUM>. Vertical translators <NUM> depend from the left and right rails <NUM>, <NUM> at rear and front ends <NUM>, <NUM>. The translators are electrically connected to stators embedded in the elevator rails <NUM>, <NUM>. The elevator carriage <NUM> is supported on a frame <NUM> that has vertical guide tracks <NUM> backed by an embedded vertical linear stator at each corner. The stators backing the vertical guide tracks <NUM> form linear motors with the translators <NUM> that raise and lower the elevator carriage <NUM>. The elevator frame <NUM> also has a pair of parallel stator rails <NUM>, <NUM> that are perpendicular to the elevator carriage rails <NUM>, <NUM>. When the carriage <NUM> is in its lower position, the carriage rails <NUM>, <NUM> sit at a level lower than the level of the frame rails <NUM>, <NUM> to provide clearance for the conveyor trays as they enter the elevator <NUM>.

The operation of the right-angle elevator is shown in <FIG>. A conveyor tray <NUM> is shown advancing along an infeed conveyor section <NUM> in <FIG> toward a right-angle elevator section <NUM>. The rails of the infeed conveyor section <NUM> are aligned with the elevator frame rails <NUM>, <NUM> so that the tray <NUM> can be transferred onto the lowered elevator carriage <NUM>. Once the tray <NUM> is on the lowered elevator carriage, the elevator <NUM> lifts the carriage <NUM> and tray <NUM> to the upper position shown in <FIG>. Besides having left and right skirts <NUM>, <NUM> with translators, the tray <NUM> has rear and front skirts <NUM>, <NUM> with translators. When the tray <NUM> is lifted by the elevator <NUM> off the frame rails <NUM>, <NUM>, it is supported by the carriage rails <NUM>, <NUM>. The skirts <NUM>, <NUM>, <NUM>, <NUM> do not extend all the way to the corners of the trays <NUM>. Slits <NUM> are formed in the skirts <NUM>, <NUM>, <NUM>, <NUM> at each of the four corners of the trays <NUM>. The slits <NUM> provide passages for the elevator rails so that the trays <NUM> can be transferred onto the elevator <NUM> and off at a right angle onto a discharge conveyor section <NUM>.

<FIG> shows a rectangular spiral conveyor constructed of conveyor segments as in <FIG> and right-angle elevators as in <FIG> at the corners. The spiral conveyor <NUM> is constructed of conveyor sections <NUM> arranged to form one tier of a four-sided stepped spiral of consecutive conveyor sections vertically offset from each other. An elevator section <NUM> at each corner of the spiral conveyor raises or lowers trays <NUM> from one vertical level to the next. Multiple tiers can be formed with additional conveyor sections <NUM> and right-angle elevators <NUM> at the corners.

<FIG> depict an elevator having an upgoing path and a horizontally offset downgoing path for an elevator carriage. An infeed conveyor section <NUM> feeds trays <NUM> to an upgoing elevator <NUM> providing a vertical guide track <NUM> for elevator carriages <NUM>. A carriage <NUM> at the bottom of the upgoing guide path defined by the vertical tracks <NUM> with its stator rails aligned with the stator rails of the infeed conveyor section <NUM> receives a tray <NUM>. Stators in the vertical guide tracks <NUM> energize vertical translators of two-axis translators <NUM> at the corners of the carriage <NUM> to raise the carriage and the tray <NUM> sitting atop it, as shown in <FIG>. Once the carriage <NUM> reaches the top of the upgoing guide path, horizontal stators along upper horizontal guide tracks <NUM> energize horizontal translators of the two-axis translators <NUM> to move the carriage <NUM> from atop the upgoing elevator <NUM> to atop a downgoing elevator <NUM>. 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 carriages <NUM>. A lower horizontal guide path <NUM> guides the trays back into the home position at the bottom of the upgoing elevator <NUM> in position to receive another incoming tray <NUM>. Thus, the elevator allows a number of carriages <NUM> to 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 carriage <NUM> is at the top of the downgoing elevator <NUM>, as in <FIG>, the carriage's rail stator is energized to propel the tray <NUM> off onto a discharge conveyor section <NUM>. The discharge conveyor <NUM> can be contained within a pipe <NUM> suspended 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 trays <NUM> from external sources.

Details of the two-axis translators <NUM> are shown in <FIG>. Outward-facing pole faces <NUM> of a core <NUM> are arranged in an array. Three-phase horizontal and vertical windings <NUM>, <NUM> on the core <NUM> allow the translator <NUM> to move vertically or horizontally in a direction <NUM> parallel to the carriage rails. The carriages <NUM> have safety brakes <NUM> suspended from the translator housings. As shown in <FIG>, the safety brake <NUM> includes a solenoid <NUM> with a plunger <NUM> connected to an outward-facing permanent magnet <NUM> through an outwardly-biasing coil spring <NUM>. As shown in <FIG>, the solenoid <NUM> is electrically in series with the translator windings. As long as the carriage <NUM> is powered, the solenoid <NUM> is actuated as shown in <FIG> to draw the plunger <NUM> and the magnet <NUM> inward away from the elevator guide track so that the carriage <NUM> can move along the elevator guide tracks. When electric power to the carriage <NUM> is lost, the solenoid <NUM> is de-actuated, and the compressed spring <NUM> releases to push the plunger <NUM> and the magnet <NUM> outward to a braking position at the outside <NUM> of the translator housing as in <FIG>. The magnet <NUM> in the braking position is close enough to the metal of the guide tracks for magnetic attraction to hold the unpowered carriage <NUM> in place and prevent it from plummeting to the bottom of the elevator.

The conveyor tray <NUM> in <FIG> can be used as a cover for a conveyor tray <NUM> as shown in <FIG>. The tray <NUM> is generally the same as the cover tray <NUM>, except that it has a rear wall <NUM> and a front wall <NUM> upstanding from the rear edge <NUM> and the front edge <NUM> of the article-conveying surface <NUM>. As shown in <FIG>, the underside of the cover tray <NUM> is supported atop the two walls <NUM>, <NUM> of the covered tray <NUM>. The rear and front walls <NUM>, <NUM> can be shaped as shown to fill the gap at the rear and front ends of the cover between the skirts <NUM>, <NUM> to completely enclose the volume between the two trays <NUM>, <NUM>.

A conveyor for covering and uncovering a tray <NUM> with a cover tray <NUM> is shown in <FIG>. In <FIG>, a cover tray <NUM> is transported along an upper conveyor section <NUM> in a first conveying direction <NUM> toward an open end <NUM>. A walled tray <NUM> to be covered advances in the same direction <NUM> on a lower conveyor section <NUM> directly below the upper conveyor section <NUM>. An elevator section (frame and guide tracks not shown) including a carriage <NUM> bridges a space <NUM> between the lower conveyor section <NUM> and an aligned second lower conveyor section <NUM> when the carriage is in a lower position as in <FIG>. The elevator raises the carriage <NUM> with the tray <NUM> into an upper position to receive the cover tray <NUM>, as shown in <FIG>. Once the cover tray <NUM> is in place covering the lower walled tray <NUM>, the elevator carriage <NUM> is lowered and the stator rails in the carriage and the second lower conveyor <NUM> are energized to propel the covered tray downstream as in <FIG>.

The lower tray <NUM> is uncovered as shown in <FIG>. The covered and covering trays <NUM>, <NUM> are conveyed on the second lower conveyor section <NUM> in a conveying direction <NUM> toward the elevator carriage <NUM> in its lower position, as shown in <FIG>. The ends <NUM>, <NUM> of the stator rails in the upper conveyor section <NUM> serve as stops that prevent the cover tray <NUM> from advancing farther with the lower walled tray <NUM> as it proceeds onto the first lower conveyor section <NUM>, as shown in <FIG>. Once the walled conveyor tray <NUM> is clear of the elevator carriage <NUM>, the elevator raises the carriage to the upper position, energizes the carriage's stator rails, and propels the cover tray <NUM> onto the upper conveyor section <NUM> as shown in <FIG>.

<FIG> depict a diverter section usable in conveyors constructed of conveyor segments as in <FIG>. The diverter section <NUM> comprises a circular track <NUM>-a ring, for example-that houses a curved stator <NUM> subtending an angle α around the circular track. An identical curved stator (not shown) is diametrically opposite the curved stator <NUM> in the circular track <NUM>. The circular track <NUM> is supported in a diverter frame <NUM>. Two orthogonal pairs of side rails <NUM>, <NUM> are supported on translators <NUM> that ride on a raceway ledge <NUM> of the circular track <NUM>. One pair of the side rails <NUM> is optional. The side rails <NUM>, <NUM> may be manually lifted from the ledge <NUM> for repair, replacement, or cleaning.

<FIG> show a diverting conveyor using the diverter section <NUM> of <FIG>. The diverter section <NUM> resides in a gap <NUM> (<FIG>) between an infeed conveyor section <NUM>, an inline discharge conveyor section <NUM>, and a side-off conveyor section <NUM>. The infeed conveyor section <NUM> conveys trays <NUM> toward the diverter section <NUM> in a conveying direction <NUM>. The curved stators in the circular track <NUM> inductively energize stators in the inline rails <NUM> in the diverter <NUM> to send a leading tray 160A straight across the diverter onto the inline discharge conveyor section <NUM>, as shown in <FIG>. When a tray 160B meant to be diverted onto the side-off discharge conveyor section <NUM> reaches the diverter <NUM>, the curved stators are energized to rotate translators over a divert angle δ until the inline diverter rails <NUM> are aligned with the rails <NUM> of the side-off conveyor section <NUM>, as shown in <FIG>. The curved stators in the circular track <NUM> then energize the stators in the diverter rails <NUM> to propel the tray 160B onto the side-off conveyor section <NUM>, as shown in <FIG>. The angle α (<FIG>) subtended by the stationary curved diverter stator is greater than or equal to the divert angle δ of the conveyor. As shown in <FIG> and <FIG>, the rails of the discharge conveyor sections <NUM>, <NUM> dip down to provide notches <NUM>, <NUM> at their intersection to accommodate the passing tray skirts.

A conveyor with a curved lower return is shown in <FIG>. The conveyor comprises a flat upper main carryway section <NUM> with a curved lower returnway section <NUM> directly below. The upper carryway <NUM> is constructed of one or more conveyor segments as in <FIG>. The lower return is constructed of similar segments, but with curved rails. And portions of the lower returnway conveyor section include two end portions <NUM>, <NUM> that are coplanar with the ends of the carryway section <NUM> to resemble a gondola. The rails of the carryway section <NUM> and the end portions <NUM>, <NUM> are aligned across narrow gaps <NUM>, <NUM>. The gaps <NUM>, <NUM> are narrow enough for trays <NUM> on the carryway section <NUM> to pass over with little slowdown and wide enough for trays to move onto the returnway section <NUM> without contacting the carryway section.

<FIG> show a skirtless tray <NUM> having two orthogonal pairs of translators <NUM>, <NUM> at the underside <NUM> of the tray. The upper side <NUM> of the tray <NUM> provides a flat article-supporting surface. The translators <NUM>, <NUM> comprise permanent-magnet arrays whose magnetic fields are directed downward perpendicular to the tray's article-supporting surface <NUM> and underside <NUM>. Corner magnets <NUM>, such as Halbach arrays, are optionally disposed in the corners of the tray <NUM> for magnetic levitation as described subsequently. The trays may also include side, front, and rear clamping magnets <NUM> at the tray sides so that the trays can be used to form a larger multi-tray <NUM> as in <FIG>. The clamping magnets are like those in the trays <NUM> shown in <FIG>. The skirtless trays <NUM> with underside translators are designed to run on flat-top rails <NUM> with stators that form linear motors with the translators <NUM>, <NUM>. The rails <NUM> with embedded stators serve as a tray guide for the trays <NUM>. In <FIG> two conveyor sections <NUM>, <NUM> are arranged side by side to allow for the formation of the multi-tray <NUM>. Connecting structure <NUM> maintains the left and right rails in parallel.

Another version of a conveyor segment embodying features of the invention is shown in <FIG>. The conveyor segment <NUM> has two parallel stators <NUM>, <NUM> that extend in length from one end of the segment to the other. The stators <NUM>, <NUM> are ironless and spaced apart a distance substantially the same as the distance between opposite translators <NUM> on the trays <NUM> (<FIG>). The stators <NUM>, <NUM> each produce a magnetic flux wave that travels along the length of the stator in a conveying direction <NUM>.

Electrically conductive magnetic-levitation (maglev) plates <NUM>, <NUM> extend along the length of the conveyor segment <NUM> laterally outward of the stators <NUM>, <NUM>. While a conveyor tray <NUM> as in <FIG> is propelled in the conveying direction <NUM> by the stators <NUM>, <NUM>, the tray's corner magnets <NUM> (<FIG>) induce electric currents in the maglev plates <NUM>, <NUM> that generate reactive magnetic fields opposing the corner magnets' fields with enough force to levitate the trays for a low-friction ride. Position sensors <NUM> are positioned along the length of the conveyor segment <NUM> to detect the presence of trays at their positions and send a sensor signal indicating that detection to an electronic drive-control circuit <NUM>. Electric power and communication wiring to the drive control <NUM> can be routed to external circuits or computers through legs <NUM> of a conveyor frame <NUM>. The stators <NUM>, <NUM>, the position sensors <NUM>, the electronic drive-control circuits <NUM>, and the wiring are all encapsulated in a tray-guide housing <NUM> having a flat top surface <NUM> and forming a tray guide along which trays are propelled. Just inside the housing <NUM> at each end along both sides are alignment magnets <NUM> or ferrous elements attracted by the magnets to align adjacent sections as in <FIG>. In the conveyor segments of <FIG> and <FIG>, 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 of <FIG>. Like the trays in <FIG>, the trays <NUM> are easy to remove and replace without interference from interlocking or other conveyor structure.

<FIG> shows another version of a conveyor segment in which the maglev plates <NUM>, <NUM> of <FIG> are replaced by air ducts <NUM>, <NUM>. Pressurized air from an air source (not shown) is injected into the ducts <NUM>, <NUM> and expelled through openings <NUM> in the tops of the ducts to levitate conveyor trays on an air cushion. In this case corner magnets <NUM> as in <FIG> are not required on the trays <NUM>.

The lateral alignment of abutting conveyor segments <NUM>, <NUM>' is shown in <FIG>. In this example one conveyor segment <NUM> has a pair of alignment magnets <NUM> at one side and a pair of ferrous elements <NUM> at the other side. The facing end of the adjacent conveyor section <NUM>' has a pair of magnets <NUM> at one side and a pair of ferrous elements <NUM> at the other. The magnets <NUM> attract the ferrous elements <NUM>. The lateral dimensions of the magnets <NUM> and ferrous elements <NUM> match for accurate lateral alignment of the abutting segments <NUM>, <NUM>'. Of course, all the ferrous elements <NUM> may be replaced with magnets of opposite polarity to the confronting magnets of the abutting conveyor segment. But by arranging the magnets <NUM> and ferrous elements <NUM> as described, all the segments can be made the same, and the polarity of the magnets will not matter.

As shown in the conveyor section <NUM> of <FIG>, a cover <NUM> provides a smooth joint between the housings <NUM> of abutting conveyor segments <NUM>. As <FIG> also shows, the conveyor trays <NUM> may be advanced individually or together in a train.

<FIG> show a conveyor arrangement for a <NUM>-to-N switch. A single infeed conveyor section <NUM> feeds conveyor trays <NUM> onto an x-y conveyor segment <NUM> extending in length perpendicular to the infeed conveyor section <NUM>. The x-y conveyor segment <NUM> has two pairs of stators <NUM>, <NUM> perpendicular to each other. The first pair of stators <NUM> drives the trays <NUM> in the main conveying direction <NUM>. The second pair of stators <NUM> drives the trays <NUM> transverse to the main conveying direction to one of N (three are shown) discharge conveyor sections <NUM>. The first stators <NUM> form linear motors with the left and right translators in the trays, and the second stators <NUM> form linear motors with the front and rear translators. Conductive plates <NUM> flanking the pairs of stators levitate the trays <NUM> as they advance along the x-y conveyor segment <NUM>.

A merge conveyor is shown in <FIG> in which N (three are shown) infeed conveyor sections 544A-544C propel conveyor trays <NUM> in a main conveying direction <NUM> to an x-y conveyor section <NUM>. The x-y conveyor section <NUM> inducts the trays <NUM> from the infeed sections 544A-544C and translates them to a single discharge conveyor section <NUM>. The topology of the merge conveyor is the same as that of the switch conveyor of <FIG> with the main conveying direction reversed.

A multi-level conveyor <NUM> for a conveyor tray <NUM> as in <FIG> is shown in <FIG>. The layout of the conveyor as shown is the same as that for the three-dimensional tray sorter shown in <FIG>. And the operation is similar. Conveyor stators along horizontal and vertical guide tracks <NUM>, <NUM> propel a tray-supporting carriage <NUM> laterally and vertically. The carriage <NUM>, shown in more detail in <FIG>, has two-axis translators <NUM> in translator housings <NUM> at each corner. The housings are shaped to ride in the guide tracks <NUM>, <NUM>. The carriages <NUM> also include a pair of stators <NUM> embedded in the carriage body forming a carriage tray guide with the housing. The stators reside below a continuous top tray-guide surface <NUM> to induct trays <NUM> into the carriage and to propel them off. Like the carriage of <FIG>, the carriage <NUM> can include weight sensors <NUM> at the corners (only one shown in <FIG>). The weight sensors <NUM> communicate and, along with the stators <NUM>, are powered through the translators <NUM>, which receive power inductively from the conveyor stators along the guide tracks <NUM>, <NUM>. Electrically conductive strips <NUM>, like those <NUM>, <NUM> in the levitating conveyor segment <NUM> of <FIG>, extend along the carriage <NUM> beside the stators <NUM> and are used in levitating the trays <NUM>.

Another version of a conveyor tray is shown in <FIG>. The tray <NUM>, instead of supporting articles on a flat top surface, supports articles atop rollers <NUM> that extend through the thickness of the body of the tray. Drive stators (not shown) under left and right stationary conveyor side walls <NUM>, <NUM> coact with translators (not shown) along the left and right side edges <NUM>, <NUM> of the tray <NUM> to propel it in a main conveying direction <NUM>. Front and rear walls <NUM>, <NUM> on the tray <NUM> prevent articles from falling off the front and rear edges of the tray during starts, stops, and other accelerations. The rollers <NUM> reside in cavities <NUM> that open onto the upper surface <NUM> and the underside of the tray body and are freely rotatable on axles defining axes of rotation <NUM> oblique to the main conveying direction <NUM>. Elongated actuating rollers <NUM>, supported in the conveyor frame adjacent an opening <NUM> in the right conveyor side wall <NUM>, rotate freely on axles defining axes <NUM> parallel to the main conveying direction <NUM>. The actuating rollers <NUM> are arranged in line with the columns of tray rollers <NUM>. As the tray <NUM> passes over the actuating rollers <NUM>, the bottoms of the tray rollers <NUM> rotate on their oblique axes <NUM> and push articles atop the rollers off the side of the tray <NUM> and through the opening <NUM> in a right-side divert direction <NUM>. Roller balls without axles and rotatable in all directions could alternatively be used in the trays and actuated by the same actuating rollers.

<FIG> shows the same conveyor with trays <NUM> having rollers <NUM> arranged at the same oblique angle as in <FIG>. A set of actuating rollers <NUM>' is supported in the conveyor frame adjacent to an opening <NUM> in the left side wall <NUM>. A tray <NUM> traveling in the main conveying direction <NUM> is stopped after passing the actuating rollers <NUM>'. The stator field is reversed to drive the tray <NUM> in the reverse direction <NUM> back over the actuating rollers <NUM>'. The tray rollers <NUM> engaging the actuating rollers <NUM>' in the reverse direction <NUM> opposite to the main direction rotate in the opposite direction to push conveyed articles through the opening <NUM> in the left side wall <NUM> in a left-side divert direction <NUM>.

The conveyor tray <NUM> in <FIG> has stacked roller sets <NUM> (<FIG>) arranged in columns. The bottom roller <NUM> of each set protrudes beyond the underside of the tray <NUM>. The top roller <NUM> protrudes beyond the upper surface <NUM> of the tray <NUM>. The top roller <NUM> rests on the bottom roller <NUM>-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 in <FIG> is shown without side supports and axles for the top roller <NUM> for clarity. ) Both the top and bottom rollers <NUM>, <NUM> are arranged to rotate on parallel axles defining axes <NUM>, <NUM> oblique to the conveying direction <NUM>. As the conveyor tray <NUM> is propelled over the actuating rollers <NUM>, the bottom rollers <NUM> rotate forward on their axes <NUM>, which rotates the article-supporting top rollers <NUM> rearward. Because the component of rearward rotation of the top tray rollers <NUM> equals the forward motion of the trays <NUM> along the conveyor, articles are diverted off the trays in a divert direction <NUM> perpendicular to the main conveying direction <NUM>.

The conveyor tray <NUM> shown in <FIG> has tray rollers <NUM> that rotate on axles defining axes of rotation <NUM> parallel to the main conveying direction <NUM>. An array of caster-like actuating rollers <NUM>, supported in the conveyor frame, provides tray-roller actuation in this version. The freely rotatable actuating rollers <NUM> can be swiveled about a vertical axis <NUM> by a rack-and-pinion system to change their axes of rotation <NUM>. With the actuating rollers <NUM> angled oblique to the main conveying direction <NUM> as shown, the tray rollers <NUM> rotate to push articles across the tray <NUM> toward an opening <NUM> in the right side wall <NUM>. Although the tray rollers <NUM> push the articles off the tray at <NUM>° relative to the tray without contacting the front and rear tray walls <NUM>, <NUM>, they exit through the opening <NUM> in an oblique direction <NUM> because of the motion of the tray in the conveying direction <NUM>. When the actuating rollers <NUM> are swiveled so their axes <NUM> are at the same oblique angle on the other side of the main conveying direction, the actuated tray rollers <NUM> rotate toward the left side wall <NUM> and through an opening <NUM> in a divert direction <NUM>. Thus, the conveyor is useful for diverting articles off the trays in either direction by changing the orientation of the actuating rollers <NUM>.

The passive actuating rollers <NUM> of <FIG> could be replaced by a tray-roller actuator in the form of a flat bearing surface on which the tray rollers <NUM>, <NUM> ride. 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 rollers <NUM>, <NUM>, <NUM> of <FIG>. <FIG> shows a conveyor segment <NUM> as in <FIG> with a linear-motor stator <NUM> housed in a smooth housing between the side rails <NUM>, <NUM>. A conveyor tray <NUM> has an array of rollers <NUM> with rotors made of permanent magnets or electrically conductive material that form linear motors with the stator <NUM>, which can selectively actuate the rollers <NUM> into rotation.

A rail scrubber <NUM> is shown in <FIG> riding the rails <NUM>, <NUM> on a conveyor segment <NUM>. The scrubber <NUM> is shown in this example with three fluid tanks: a soap tank <NUM>, a water tank <NUM>, and a sanitizer tank <NUM>. 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 housing <NUM> received in the space. The motor, powered by the battery, drives front or rear drive wheels <NUM>, <NUM> or both to drive the scrubber <NUM> along the rails <NUM>, <NUM>. The wheels <NUM>, <NUM> are mounted on axles <NUM> that extend through the housing <NUM>. The axles <NUM> are coupled to the drive motor. The wheels <NUM>, <NUM> each have a central groove <NUM> that receives the rail <NUM>, <NUM> and prevents derailment. The scrubber <NUM> also includes at least one set of scrubbing wheels <NUM>, two sets in this example, to scrub both rails <NUM>, <NUM>. Like the drive wheels <NUM>, the scrubbing wheels <NUM> are mounted on axles <NUM> that extend through the central housing <NUM>. The scrubbing wheels <NUM> are also driven by the drive motor, but perhaps geared differently to rotate at a higher speed than the drive wheels <NUM>. Or the scrubber wheels <NUM> can be driven by separate motors. The scrubbing wheels <NUM> include 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 dispensers <NUM>, <NUM>, <NUM> include fittings <NUM> connected into the tanks <NUM>, <NUM>, <NUM>, upper and lower spray nozzles <NUM>, <NUM>, and tubing <NUM> connecting the fittings to the lower nozzles. The dispensers <NUM>, <NUM>, <NUM> are on each side of the tanks <NUM>, <NUM>, <NUM> with the nozzles directing a spray at the tops and bottoms of the rails <NUM>, <NUM>. The housing <NUM> also houses a scrubber computer that controls the speeds of the drive and scrubbing wheels and other electronic and power-supply circuits.

The rail scrubber <NUM> receives power inductively from the stator windings in the rails <NUM>, <NUM> through secondary coil windings housed in scrubber appendages <NUM>, <NUM> that 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 wheels <NUM> or the scrubber wheels <NUM> or 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 rollers <NUM> could be idle wheels not coupled to a drive motor.

The tops and sides of the scrubber <NUM> of <FIG> are covered by a smooth stainless steel cover <NUM> as shown in <FIG>. Scrapers <NUM> extend outward from a front face <NUM> of the cover <NUM>. The scrapers <NUM> have an inverted-U cross section, a tapered top surface <NUM>, and tapered sides <NUM> to remove bulk debris from the tray drive rails <NUM>, <NUM>, which are received in the inverted U. The scrapers <NUM> taper inward away from the front face <NUM> of the cover <NUM>.

A similar scrubber <NUM> for cleaning the top surface <NUM> of the tray-guide housing <NUM> of a conveyor segment <NUM> as in <FIG> is shown in <FIG> without a cover. This scrubber differs from the scrubber of <FIG> in that its wheels <NUM> don't ride on rails. Rather, they ride along the top surface <NUM> of the tray-guide housing <NUM>. Another difference is that the scrubber wheels <NUM> are rotated <NUM>° from the scrubber wheels <NUM> of <FIG>. Brushes <NUM> on the bottoms of the scrubber wheels <NUM> scrub the top surface <NUM> of the tray guide. Water, soap, and sanitizer are sprayed onto the top surface <NUM> through spray nozzles <NUM>. 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 scrubber <NUM>.

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 in <FIG>. Four separate conveyor lines <NUM>, <NUM>, <NUM>, <NUM> are shown. Each conveyor line is dedicated to an individual product type or family, and the trays <NUM>, <NUM>, <NUM>, <NUM> bear 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 sensor <NUM> positioned at a sensing position alongside the conveyor or embedded within the conveyor stator rails <NUM>. Examples of identifiable indicia <NUM> include 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 sensor <NUM> detects a tray from a family not assigned to the sensor's conveyor, a local or system controller <NUM> receiving 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 lines <NUM>-<NUM> shown in this example comprises a main conveyor section <NUM> defining a carryway conveying path on which the trays <NUM>, <NUM>, <NUM>, <NUM> carry products and a return conveyor section <NUM> defining a return conveying path on which the trays are empty. The infeed end of the main conveyor section <NUM> is linked to the discharge end of the return section <NUM> by an infeed diverter section <NUM>. The discharge end of the main conveyor section <NUM> is linked to the infeed end of the return section <NUM> by a discharge diverter section <NUM>. The diverter sections <NUM>, <NUM> may be the same as those shown in <FIG>.

The description of the operation of the fourth conveyor line <NUM> exemplifies how each of the other conveyor lines <NUM>-<NUM> operates. The trays <NUM> of the family assigned to the predetermined process to be carried out along the main conveyor section <NUM> are fed onto the main conveyor section from the return conveyor section <NUM> by the infeed diverter <NUM>. Only those trays <NUM> passing the sensor <NUM> that are identified by the controller <NUM> as dedicated to the fourth conveyor line <NUM> are passed onto the main conveyor section <NUM>. After the trays <NUM> complete their processing on the main conveyor section <NUM> and their products are removed, they may be diverted by the discharge diverter <NUM> back to the return conveyor section <NUM> or diverted elsewhere for cleaning. Cleaned trays can be returned to the return conveyor section <NUM>. Or the cleaning process can be carried out automatically along the return conveyor section <NUM> in one or more enclosed automatic washing stations <NUM>. In all the tray-conveyor versions described in this application, fully automatic washing-station enclosures <NUM> can 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 sections <NUM>, <NUM>, <NUM>, <NUM> be cleaned upon completion of a process or upon the detection of an unacceptable conveyor tray, all the trays <NUM> are removed and sequestered for cleaning, for example, and a scrubber <NUM> is placed on the conveyor line <NUM> as shown in <FIG>. The scrubber <NUM> runs along all the conveyor sections <NUM>, <NUM>, <NUM>, <NUM> to remove residue from the rails <NUM>. After the scrubber <NUM> has cleaned the rails <NUM>, it is removed from the conveyor line <NUM>. The sequestered trays <NUM> can then be put back on the conveyor line <NUM>, typically on the return conveyor section <NUM>. Cleaning of the rails can also be required whenever an inappropriate tray is detected.

Alternatively, the conveyor line <NUM> can 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 controller <NUM>, 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 in <FIG>, the four conveyor lines <NUM>-<NUM> could be dedicated to four different products or processes <NUM>-<NUM> with corresponding designated conveyor trays <NUM>-<NUM>. The local or system controller, upon identifying a tray with the sensor <NUM>, 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 wall <NUM>, 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 in <FIG>. The pipe conveyor <NUM> comprises two elongated enclosures, or pipes <NUM>, <NUM> parallel 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 floor <NUM> of the pipes <NUM>, <NUM> at left and right sides <NUM>, <NUM> of the floor to propel the conveyor trays <NUM> like those in <FIG>. The pipes <NUM>, <NUM> may be suspended from above by attachments <NUM>, such as cables or rods. The two pipes <NUM>, <NUM> are open at a discharge end of the infeed pipe <NUM> and the re-entry end of the return pipe <NUM>. A carriage assembly comprises a tiltable carriage <NUM> and a guide track <NUM> in the form of a partial cylinder along which the carriage translates. The carriage <NUM> has a pair of left and right stator rails <NUM> joined through a rotor-translator <NUM> by a pair of depending arms <NUM> affixed to the rotor-translator. A θ-z stator <NUM> is positioned along the inner side of the cylindrical guide track <NUM>. The θ-z stator <NUM> produces a magnetic flux wave that travels circumferentially (in θ) along the guide track <NUM> to tilt the tray <NUM> about a tilt axis as shown in <FIG> a predetermined angle θ relative to horizontal (as in <FIG>) to discharge articles <NUM>. Magnets or ferrous materials in the carriage rails <NUM> and in the trays <NUM> attract each other enough to prevent the trays from sliding off the carriage when it tilts. The stator <NUM> also propagates a magnetic flux wave axially (in z) along the guide track <NUM> to translate the carriage <NUM> from a first position in line with the infeed pipe <NUM> to a second position in line with the return pipe <NUM>. In that way trays <NUM> can be returned. So the carriage <NUM> translates along its tilt axis.

An over-and-under pipe conveyor is shown in <FIG>. In this version a return pipe <NUM> is below an incoming pipe <NUM>. A carriage assembly has a circulating carriage <NUM> with two pairs of parallel stator rails <NUM>, <NUM> joined by arms <NUM>. Shaft segments <NUM> parallel to the rails <NUM>, <NUM> join the arms <NUM> to a rotor <NUM>. An outer stator <NUM> rotates the rotor <NUM> and the stator rails <NUM>, <NUM> a predetermined angle of <NUM>° to alternately position the stator rails in line with the upper and the lower pipes <NUM>, <NUM>. When the carriage <NUM> tilts, as in <FIG>, articles <NUM> drop from the tray <NUM>. When the carriage <NUM> completes its <NUM>° rotation, both sets of carriage stator rails <NUM>, <NUM> are aligned with the upper and lower pipes <NUM>, <NUM> because the two pairs of rails are rotationally separated by <NUM>°. The stator rails are energized to induct trays <NUM> onto the upper rails <NUM> for the upper pipe <NUM> and to return trays onto the lower rails <NUM> for the upside-down return trip. The ceiling <NUM> of the pipe <NUM> forms the conveying surface in the upside-down return. A scraper <NUM> attached to the open end of the lower return pipe <NUM> is positioned to scrape debris sticking to the article-supporting surface <NUM> of the upside-down tray <NUM> as it's propelled along the carriage <NUM>. The upside-down trays <NUM> are prevented from falling off the carriage <NUM> by magnets and ferrous elements as with the other conveyors just described.

An endless conveyor <NUM> having an upper carryway and a lower returnway is shown in <FIG>. The upper carryway <NUM> has a pair of stator rails <NUM>, <NUM>, like those in <FIG>, propelling trays <NUM>, like those in <FIG>. The lower returnway <NUM> has a pair of upside-down stator rails <NUM>, <NUM>. Both the carryway <NUM> and the returnway are supported in the same frame <NUM> in this example. Rotating carriages <NUM> in carriage assemblies at both ends of the conveyor transfer trays <NUM> between the carryway <NUM> and the returnway <NUM> to form an endless conveying path. Each carriage <NUM> has four pairs of parallel stator rails <NUM>. The four right-side rails define a right-side square <NUM> and the four left-side rails define a left-side square <NUM>. The squares <NUM>, <NUM> are joined by a shaft <NUM> to a motor <NUM>. The motor rotates the carriage <NUM> in predetermined <NUM>° increments so that it stops with one of the four pairs of rails <NUM> aligned with the carryway <NUM> and the opposite pair of rails aligned with the returnway <NUM>. The stator rails <NUM> aligned with the carryway <NUM> and the returnway are activated to discharge a tray <NUM> onto the carryway and to induct a tray from the returnway. Attracted magnetic and ferrous material in the carriage and returnway rails <NUM>, <NUM>, <NUM> and in the trays <NUM> prevent the upside-down or tilted trays from falling. A carriage like the carriage <NUM> in <FIG> can be used with the conveyor of <FIG>, and vice versa.

Claim 1:
A method for operating a conveyor comprising:
assigning each of a plurality of conveyor trays (<NUM>, <NUM>, <NUM>, <NUM>) to one of a plurality of families by indicia (<NUM>) indicating the assigned family;
assigning a predetermined family of conveyor trays (<NUM>, <NUM>, <NUM>, <NUM>) to a conveyor;
identifying the assigned family of each conveyor tray (<NUM>, <NUM>, <NUM>, <NUM>) on the conveyor;
characterized in the method comprising:
identifying conveyor trays (<NUM>, <NUM>, <NUM>, <NUM>) whose family does not match the predetermined family assigned to the conveyor;
removing the conveyor trays (<NUM>, <NUM>, <NUM>, <NUM>) whose family does not match the predetermined family assigned to the conveyor from the conveyor;
conveying the conveyor trays (<NUM>, <NUM>, <NUM>, <NUM>) whose family matches the predetermined family along the conveyor through a process.