Patent Description:
Conventional conveying systems, such as those conveying articles on flat belts, modular belts or chains, and powered or gravity rollers, provide many harbors for pathogens and other contaminants. Motors, gearboxes, roller bearings, shafts, pulleys, and sprockets can all collect food particles and grease and require regular cleaning. In food applications all the conveyor parts have to comply with demanding food-use standards. Furthermore, conventional conveyors require significant electrical infrastructure for power and control. Cable routing and connections add additional harbors for contaminants.

<CIT> discloses a solid state commutated linear motor with an ironless multiphase armature which has a magnetic field array having periodic alternating polarity, an ironless multiphase armature, and a solid state commutating system for driving a moving element and positioning it with respect to a reference element.

<CIT> discloses a linear motor consisting of movable elements provided with a scale of a linear scale and a permanent magnet, a sensor for reading the scale, and stators provided with a coil generating a shifting magnetic field to the permanent magnet.

<CIT> discloses a sealed linear motor system including a sealed coil assembly having a plurality of coil windings within a base plate and comprising covers disposed about the base plate and coil windings to prevent moisture and/or chemical ingress into the base plate and the coil windings.

A conveyor according to the invention is described in the independent claim. Further aspects of the invention are described in the dependent claims.

A portion of one version of a conveyor embodying features of the invention is shown in <FIG>. The conveyor section <NUM> is constructed of a series of tray conveyor segments <NUM> connected end to end at bonded joints <NUM> for smooth transitions. As also shown in <FIG>, the tray conveyor segments <NUM> each comprise a pair of closely spaced rails <NUM>, <NUM> having convexly rounded tops <NUM>, <NUM> and bottoms joined by a rail base <NUM> from which a single leg <NUM> extends downward to mount to a floor. The two rails <NUM>, <NUM> are separated by a narrow slot <NUM>. A tray <NUM> has a platform <NUM> with a top article-supporting surface <NUM> and an opposite bottom surface <NUM> supported on the tops <NUM>, <NUM> of the rails <NUM>, <NUM>. A blade <NUM> extends downward from the bottom surface <NUM> of the tray <NUM> into the slot <NUM>. The tray <NUM> shown in this example with a centrally located blade <NUM> forms a T in a vertical cross section. A linear array of permanent magnets <NUM> in each rail <NUM>, <NUM> produces a magnetic field through the slot <NUM> and the tray blade <NUM>. The magnitude and direction of the static magnetic field vary periodically along the length of the slot <NUM>. Forcer coils (not shown in <FIG>) in the tray blade <NUM> produce a varying electromagnetic field that interacts with the magnetic field produced by the linear permanent-magnet arrays in the rail to create a force propelling the tray <NUM> along the conveyor in a conveying direction <NUM>.

As shown in <FIG>, the slot <NUM> above the leg <NUM> extends upward from a lower blind end <NUM> formed by the rail base <NUM> to a top opening <NUM> that widens at the tops <NUM>, <NUM> of the rails <NUM>, <NUM>. Elsewhere, the slot <NUM> is open at both top and bottom. As shown in <FIG>, the linear array of permanent magnets <NUM> is embedded in the rail <NUM> close to an inside wall <NUM> of the rail bounding the slot <NUM>. To increase the intensity of the magnetic field in the slot <NUM>, the permanent magnets <NUM> are shown arranged to form a Halbach array. The static magnetic field traversing the slot <NUM> varies spatially in amplitude and direction in the conveying direction <NUM>.

As shown in <FIG>, a series of forcer drive coils <NUM> is housed in the tray blade <NUM>. The coils <NUM> are arranged in an alternating three-phase pattern along the length of the blade <NUM>. A tray controller <NUM> housed in the tray <NUM> electronically commutates the currents through the three-phase coils <NUM> to produce an electromagnetic field that travels along the blade <NUM> and interacts with the static magnetic field in the slot. The controller <NUM> and auxiliary components are mounted on a circuit board <NUM>. The cores of the coils <NUM> are ironless to avoid attraction to the rail magnets and increased friction. The drive coils <NUM> thus form a brushless linear dc motor with the permanent-magnet arrays in the rails. The permanent magnet arrays form the motor's stator and the coacting tray coils <NUM> form the motor's forcer.

A battery <NUM> consisting of one or more cells <NUM> powers the controller <NUM> and provides the commutated currents to the coils <NUM>. Because the permanent magnets are in the rails and the trays are battery-powered, no wiring is needed in the tray conveyor segments. The tray segments are completely passive. Optional charging coils <NUM> in one or both sides of the tray <NUM> are available to recharge the battery <NUM>. Alternatively, the charging coils <NUM> could be used to couple power to the tray <NUM> to power the controller <NUM> and the forcer coils <NUM>. In that alternative mode of operation, in which the primary power is inductively coupled to the tray <NUM> through the charging coils <NUM>, the battery <NUM> can be used as a secondary power source when external power is unavailable to the charging coils. So either the battery <NUM> or the charging coils <NUM> can serve as the in-tray power supply. When the primary external power source is active, the charging coils <NUM> can trickle-charge the battery <NUM>. Tuning capacitors <NUM> connected in parallel with the charging coils <NUM> are available to tune the charging-coil and capacitor circuit to the resonant frequency of the external charging waveform to increase the efficiency of the induced power transfer to the tray <NUM>. As a third alternative, the battery <NUM> could be non-rechargeable and serve as the exclusive power source. In that case the charging coils <NUM> and the tuning capacitors <NUM> would not be necessary. If the battery <NUM> is not rechargeable, it could be replaceable though an end cap (<NUM>, <FIG>), or the entire tray could be disposable.

When the charging coils <NUM> are used either to recharge the battery <NUM> or as part of the main power source, one or more active conveyor segments <NUM> as in <FIG> are used. Two closely spaced rails <NUM>, <NUM> define a narrow slot <NUM> to receive and guide the blade <NUM> of the tray <NUM>. The rails <NUM>, <NUM> each have lateral extensions <NUM>, <NUM> with flat tops <NUM>, <NUM> supporting the tray <NUM>. Primary conductor loops <NUM> powered by an ac power source (not shown) extend along the length of the active conveyor section <NUM> in each rail extension <NUM>, <NUM>. The primary conductor loops <NUM> are mounted in E cores <NUM>. The conductor loops are, for example, low-loss wire, such as Litz wire. Primary tuning capacitors (not shown) are distributed across the loop along the length of the rails <NUM>, <NUM> to provide highly efficient high-Q inductive power transfer to the secondary charging coils <NUM> in the tray <NUM>. The majority of the conveyor can be constructed of active segments <NUM> as in <FIG> or of a combination of active segments and passive segments <NUM> as in <FIG>. For example, a conveyor having a main carryway run along which articles are conveyed and a return run could have passive segments on the carryway and active inductive-power-transfer segments on the return to recharge the batteries. In another alternative the active tray segment has a primary conductive loop on only one side. In that case a tray could be made with a secondary charging coil and tuning capacitor on only one side.

Yet another tray-charging or -powering arrangement is shown in <FIG>. In this version the tray <NUM> has a single centrally located charging coil <NUM> connected in parallel with two tuning capacitors <NUM>. Although two tuning capacitors <NUM> are shown, a single tuning capacitor could be used instead. In this version a primary conductor loop is formed by a left conductor segment <NUM> in a left rail <NUM> connected to a right conductor segment <NUM> in a right rail <NUM>. The endless primary conductor loop is tuned to resonance with one or more tuning capacitors (not shown) and is powered by an ac source (not shown). This version can be used with rails without lateral rail extensions.

One version of an electrical block diagram schematic of a conveyor as in <FIG> or <FIG> is shown in <FIG>. The tray controller <NUM> in this example is powered by either an external ac power source <NUM> or the battery <NUM>. When the external source <NUM> is available, its power is inductively coupled to the tray from the primary conductive loop <NUM> to the secondary charging coil <NUM>. The tuning capacitors <NUM>, distributed along the length of the loop <NUM>, and the tray tuning capacitor <NUM> tune the primary and secondary circuits to resonate at the frequency of the ac source <NUM> to maximize power transfer. The secondary ac voltage is converted to dc by a rectifier or ac-to-dc converter <NUM> whose output is diode-ORed with the battery voltage <NUM> through a diode <NUM> to produce a dc supply voltage <NUM> that powers the tray. Normally, the externally sourced voltage will exceed the battery voltage <NUM> and power the tray controller <NUM> and other active devices in the tray. The battery <NUM> switches in to power the tray when the externally sourced voltage drops below the battery voltage <NUM>. When the external voltage exceeds the battery voltage <NUM>, it charges the battery <NUM> through a charging element <NUM>. The diode-ORed arrangement constitutes a rudimentary switch that switches between external and battery power for the tray. One example of an alternative switch useful for switching from external power to battery power includes an electromechanical or an electronic switch that connects the tray's dc supply voltage <NUM> to the battery voltage <NUM> from the externally sourced dc voltage when the external power is too low. A low-voltage detector sensing the incoming ac voltage or its rectified dc voltage sends a low-voltage signal to the switch to switch to battery power.

A series of magnetic field sensors <NUM>, such as Hall-effect sensors positioned periodically along the length of the tray blade <NUM> (<FIG>), determine the position of the tray coils <NUM> relative to the magnetic-field positive and negative peaks. The sensor signals <NUM> are sent to the controller <NUM>, which includes a commutator <NUM>. The commutator <NUM> is a software routine that runs in program memory of the controller <NUM>, e.g., a microcomputer or microcontroller. The commutator <NUM> generates three output signals <NUM>, which are properly phased as determined by the sensor signals <NUM>, to control the current through the three-phase forcer coils <NUM>. The three output signals <NUM> are amplified by amplifiers <NUM> that supply the commutated current waveforms to the forcer coils <NUM> to drive the tray.

The tray controller <NUM> in each tray communicates with a conveyor controller <NUM> external to the trays. A transmitter-receiver <NUM> on the tray circuit board <NUM> is linked wirelessly over antennas <NUM>, <NUM> to an external transmitter-receiver <NUM> connected to the system controller <NUM>. The system controller <NUM> sends command and data requests to the tray controllers <NUM> over the wireless link and receives data from the tray controllers. The tray antenna <NUM> is shown in <FIG> as a dipole embedded in the tray platform <NUM> along one end of the tray <NUM> as one example.

A tray carriage <NUM> used to transfer trays from one conveyor segment to another is shown in <FIG>. The carriage <NUM> is the same as the trays described previously, but with a pair of passive transfer rails <NUM>, <NUM> mounted on the top surface <NUM>. Like the tray rails <NUM>, <NUM> in <FIG>, the transfer rails <NUM>, <NUM> have permanent-magnet arrays disposed along their lengths. The narrow slot <NUM> between the transfer rails <NUM>, <NUM>, extends in length perpendicular to the plane of the carriage blade <NUM>.

<FIG> illustrate how the carriage <NUM> transfers trays from one conveyor segment <NUM> to another <NUM>'. A tray <NUM> advancing along a first conveyor segment <NUM> at an end of a first conveyor run is received on the transfer rails <NUM>, <NUM> of the carriage <NUM>. The carriage <NUM> is supported on a carriage conveyor segment <NUM> extending perpendicular to the planes of the slots <NUM> in the first and second conveyor segments <NUM>, <NUM>'. The carriage conveyor segment <NUM> is below the level of the tray conveyor segments <NUM>, <NUM>' so that the transfer rails <NUM>, <NUM> are at the same level as the tray conveyor rails <NUM>, <NUM>. In that way the transfer rails <NUM>, <NUM> and the transfer slot <NUM> can be aligned with the tray coils <NUM>, <NUM> and the tray slot <NUM> on the first tray conveyor segment <NUM> to smoothly receive the tray <NUM> as in <FIG>. Once the tray <NUM> resides completely on the carriage <NUM>, it stops itself. The carriage <NUM> energizes its drive coils and propels itself and the tray <NUM> laterally in a transverse direction <NUM> as in <FIG> along the carriage conveyor segment <NUM>. The carriage conveyor segment <NUM> has permanent-magnet carriage rails <NUM>, <NUM> and a carriage slot <NUM> like the tray conveyor segments. The carriage segment <NUM> has a shorter leg <NUM> than the tray conveyor segment to position the top surface <NUM> of the carriage segment <NUM> skewed perpendicular to and below the tops of <NUM>, <NUM> of the conveyor segments <NUM>, <NUM>'. When the carriage <NUM> reaches a position with its transfer rails <NUM>, <NUM> aligned with the tray rails <NUM>, <NUM> of the second tray conveyor segment <NUM>' as in <FIG>, the carriage <NUM> stops, and the tray <NUM> energizes itself to advance off the transfer rails <NUM>, <NUM> and onto the aligned conveyor segment rails <NUM>, <NUM> on the second conveyor segment <NUM>'. With an identical carriage conveyor segment at the opposite end of the two tray conveyor sections, an endless tray conveyor is formed. The carriage <NUM> then translates back to the first conveyor segment <NUM> to receive the next tray.

A tray washer <NUM> is shown covering a portion of the return run <NUM> in an endless conveyor configuration <NUM> in <FIG>. A carriage conveyor segment <NUM> is shown at one end of the endless conveyor <NUM> for transferring trays <NUM> from a carryway run <NUM> to the return run <NUM>. The tray washer <NUM> includes spray nozzles and brushes to clean, rinse, sanitize, and dry the trays <NUM>.

As shown in <FIG>, the carriage conveyor segment <NUM> can be used to transfer trays <NUM> between many conveyor sections 136A, 136B, 136C, 136D. The four tray conveyor sections are arranged parallel to each other with two on each side of a gap <NUM> across which the carriage <NUM> translates perpendicular to the tray conveyor sections 136A-D.

The conveyor configuration of <FIG> has two tray conveyor segments 140A, 140B in line across a gap <NUM>. A third tray conveyor segment 140C extends obliquely away from the gap <NUM>. The obliquely oriented conveyor segment 140C constitutes a divert path for trays <NUM> away from a straight-through path on the in-line conveyor segment 140B. A diverter carriage segment <NUM> includes a diverter carriage <NUM> that resides in the gap <NUM>. Diverter rails <NUM>, <NUM> with embedded permanent-magnet arrays are selectively aligned with either the rails of the in-line tray conveyor segments 140A, 140B or with the oblique tray conveyor segment 140C. The diverter carriage <NUM> includes a post <NUM> extending downward from the rails <NUM>, <NUM> to a diverter carriage platform <NUM>, which is supported on a cylindrical diverter base <NUM>. The base <NUM> houses a ring of permanent magnets that creates a magnetic field directed radially from the base's periphery. The diverter carriage platform <NUM> has side skirts <NUM> that extend downward around the periphery of the diverter base <NUM>. Diverter carriage drive coils (not shown) in the skirts driven by a diverter controller (not shown) in the diverter carriage <NUM> produce an electromagnetic field that interacts with the permanent-magnet magnetic field of the base <NUM> to rotate the diverter carriage <NUM> between an in-line tray pass-through position as in <FIG> and an oblique tray divert position as in <FIG>. The diverter carriage segment <NUM> can be used to merge products from the tray segments 140B, 140C onto the tray segment 140A when the trays <NUM> advance opposite to the direction of the arrows in <FIG>.

Claim 1:
A conveyor comprising:
a rail (<NUM>, <NUM>) having an array of permanent magnets (<NUM>) embedded in and extending along the length of the rail (<NUM>, <NUM>) to form a permanent-magnet stator creating a magnetic field;
a tray (<NUM>) supported on the rail (<NUM>, <NUM>) and having a top article-supporting surface (<NUM>) and having a series of commutated drive coils (<NUM>) as a forcer coacting with the permanent-magnet stator to form a brushless linear dc motor to propel the tray (<NUM>) along the rail (<NUM>, <NUM>);
a tray conveyor segment (<NUM>) extending from a first end to a second end in a conveying direction (<NUM>) and including:
a pair of the rails (<NUM>, <NUM>) closely spaced and separated by a slot (<NUM>) and having tops (<NUM>, <NUM>), each of the rails (<NUM>, <NUM>) including such an array of permanent magnets (<NUM>) creating a magnetic field across the slot (<NUM>);
wherein the tray (<NUM>) includes:
a platform (<NUM>) forming the top article-supporting surface (<NUM>) and a bottom surface (<NUM>) supported on the tops (<NUM>, <NUM>) of the rails (<NUM>, <NUM>);
a blade (<NUM>) extending downward from the bottom surface (<NUM>) and in the conveying direction (<NUM>) to ride in the slot (<NUM>) and housing the series of commutated drive coils (<NUM>);
a tray controller (<NUM>) driving the drive coils (<NUM>) to produce a traveling electromagnetic wave that interacts with the magnetic field to propel the tray (<NUM>) in the conveying direction (<NUM>);
wherein the slot (<NUM>) widens at the tops (<NUM>, <NUM>) of the rails (<NUM>, <NUM>) and the tops (<NUM>, <NUM>) of the rails (<NUM>, <NUM>) are convexly curved.