Diverter for sorter and method of diverting

A positive displacement sorter and method of diverting articles includes providing a plurality of interconnected parallel slats defining an endless web that travels in a longitudinal direction, an upper surface of which defines an article-conveying surface and a plurality of pusher shoes. Each of the shoes travels along at least one of the slats in order to laterally divert articles on the conveying surface. Each of the shoes has a diverting member extending below the conveying surface. A plurality of diverting rails below the conveying surface are each capable of engaging the diverting member to cause the associated shoe to travel laterally to divert an article. A plurality of diverters are provided for selectively diverting at least one of the diverting members from a non-diverting path extending longitudinally along the sorter to one of said diverting rails in a diverting state. At least one of the diverters has a gate having a diverting surface. The gate is selectively moveable between the diverting state and a non-diverting state. An actuator moves the gate between the non-diverting state and the diverting state. The actuator may include a rotary actuator having a generally horizontal axis of rotation. An electronic divert control may be provided to apply an activation control signal to the actuator to move the gate between one of the states and the other of the states. The control monitors movement of the gate and adjusts the activation control signal as a function of the movement of the gate.

BACKGROUND OF THE INVENTION

The present invention is directed to a conveyor system and, in particular, to a diverter for use with a positive displacement sorter made up of a travelling web, the upper surface of which defines a longitudinally travelling conveying surface. The web is defined by a series of interconnected laterally elongated slats and pusher shoes that travel along the slats. Diverting members extending below the conveying surface on each of the shoes are engaged by a particular diverting rail in order to laterally divert an article travelling on the conveying surface. The diverter selectively transfers one or more of the diverting members to an associated diverting, rail to initiate the divert.

SUMMARY OF THE INVENTION

A positive displacement sorter and method of diverting articles with a positive displacement sorter, according to an aspect of the invention, includes providing a plurality of interconnected parallel slats defining an endless web that travels in a longitudinal direction, an upper surface of which defines an article-conveying surface. A plurality of pusher shoes each travels along at least one of the slats in order to laterally divert articles on the conveying surface. Each of the shoes has a diverting member extending below the conveying surface. A plurality of diverting rails below the conveying surface are each capable of engaging the diverting member to cause the associated shoe to travel laterally to divert an article. A plurality of diverters each selectively diverts at least one of the diverting members from a non-diverting path extending longitudinally along the sorter to one of the diverting rails in a diverting state.

A diverter includes a gate having a diverting surface. The gate is selectively moveable between the diverting state and a non-diverting state. An actuator moves the gate between the non-diverting state and the diverting state. The actuator is a rotary actuator having a generally horizontal axis of rotation.

The rotary actuator may be a rotary solenoid or a brushless torque actuator. The gate may rotate between the diverting and non-diverting states about another horizontal axis that is generally concentric with the generally horizontal axis of rotation. A slip joint may be provided between the rotary actuator and the gate. The slip joint resists diverting motion being transferred from the gate to the rotary actuator.

A sensor may be provided that monitors operation of the diverter. The sensor senses the diverting state of the gate and/or the non-diverting state of the gate. An electronic divert control may be provided that applies an activation control signal to the actuator to operate the gate between one of the states and the other of the states. The control monitors the sensor and adjusts the activation control signal as a function of the movement of the gate. The control may adjust the activation control signal to provide critical damping of movement of the gate between states.

The gate may include a mechanical bias tending to return the gate to the one of the states. The control may provide a return control signal when the gate is moving to the one of the states. The return control signal at least partially counteracts the bias. The control may adjust the return control signal as a function of movement of the gate. The control may adjust the return control signal in order to provide critical damping of movement of the gate between the states.

The gate may include a flexible member defining the diverting surface. The flexible member absorbs impact from contact between the diverting member and the diverting surface. The diverting member may include a rotary bearing and a pin extending below said bearing with the gate positioning the diverting surface to engage the bearing in the diverting state. The diverting surface may be in the form of a curved surface. Alternatively, the gate may position the diverting surface to engage the pin when in the diverting state.

The generally horizontal axis of the actuator may be oriented at least partially in the longitudinal direction. The generally horizontal axis of the actuator may be oriented at least partially in the lateral direction, or some intermediate orientation between longitudinal and lateral.

A positive displacement sorter and method of diverting articles with a positive displacement sorter, according to another aspect of the invention, includes providing a plurality of interconnected parallel slats defining an endless web that travels in a longitudinal direction, an upper surface of which defines an article-conveying surface. A plurality of pusher shoes each travels along at least one of the slats in order to laterally divert articles on the conveying surface. Each of the shoes has a diverting member extending below the conveying surface. A plurality of diverting rails below the conveying surface are each capable of engaging the diverting member to cause the associated shoe to travel laterally to divert an article. A plurality of diverters each selectively diverts at least one of the diverting members from a non-diverting path extending longitudinally along the sorter to one of the diverting rails in a diverting state.

A diverter includes a gate having a diverting surface. The gate is selectively moveable between the diverting state and a non-diverting state. An actuator moves the gate between the non-diverting state and the diverting state. An electronic divert control applies an activation control signal to the actuator to move the gate between one of the states and the other of the states. The control monitors movement of the gate and adjusts the activation control signal as a function of the movement of the gate.

The control may adjust the activation control signal to provide critical damping of movement of the gate between the one of the states and the other of the states. The control may adjust the activation control signal in order to apply a minimal duration actuation current that is capable of causing the gate to change states. The activation control signal may include an actuation signal applied to the actuator and the control may discontinue the actuation signal before the gate reaches the other state and commences a gate hold signal approximately when the gate reaches the other state. The control may adjust either the actuation signal or the gate hold signal as function of a comparison of the time it takes the gate to change from the one of the states to the other of the states.

The control may compare the recent time that it takes the gate to move between the one of the states and the other of the states to a historic time that it takes the gate to move between the one of the states and the other of the states and indicate an error condition if the recent time is substantially different than the historic time.

The gate may include a mechanical bias tending to return the gate to the one of the states. The control may provide a return control signal when said gate is moving to the one of the states. The return control signal counteracts the bias. The control may adjust the return control signal as a function of movement of the gate. The control may adjust the de-actuation signal in order to provide critical damping of movement of the gate between the other of the states and the one of the states. The control may apply a minimal duration of a de-actuation current that is capable of causing the gate to substantially avoid mechanical shock when returning to the one of the states. The control may adjust the return control signal as a function of a comparison of the time it takes the gate to change from the other of the states to the one of the states.

A positive displacement sorter and method of diverting articles with a positive displacement sorter, according to yet another aspect of the invention, includes providing a plurality of interconnected parallel slats defining an endless web that travels in a longitudinal direction, an upper surface of which defines an article-conveying surface. A plurality of pusher shoes each travels along at least one of the slats in order to laterally divert articles on the conveying surface. Each of the shoes has a diverting member extending below the conveying surface. A plurality of diverting rails below the conveying surface are each capable of engaging the diverting member to cause the associated shoe to travel laterally to divert an article. A plurality of diverters each selectively diverts at least one of the diverting members from a non-diverting path extending longitudinally along the sorter to one of the diverting rails in a diverting state.

A diverter includes a gate having a diverting surface. The gate is selectively moveable between the diverting state and a non-diverting state. An actuator moves the gate between the non-diverting state and the diverting state. An electronic divert control controls the actuator to move the gate between one of the states and the other of the states. The gate includes a mechanical bias tending to return the gate to the one of the states. The control provides a return control signal when said gate is moving to the one of the states. The de-actuation signal at least partially counteracts the bias.

The control may adjust the return control signal as a function of movement of the gate. The control may adjust the return control signal in order to provide critical damping of movement of the gate between the other of the states and the one of the states. The control may apply a minimal duration of a de-actuation current that is capable of causing the gate to substantially avoid mechanical shock when returning to the one of the states. The control may adjust the return control signal as a function of a comparison of the time it takes the gate to change from the other of the states to the one of the states.

A positive displacement sorter and method of diverting articles with a positive displacement sorter and diverter assembly, according to yet another aspect of the invention, includes providing a plurality of interconnected parallel slats defining an endless web that travels in a longitudinal direction, an upper surface of which defines an article-conveying surface. A plurality of pusher shoes each travels along at least one of the slats in order to laterally divert articles on the conveying surface. Each of the shoes has a diverting member extending below the conveying surface. A plurality of diverting rails below the conveying surface are each capable of engaging the diverting member to cause the associated shoe to travel laterally to divert an article.

A plurality of diverter assemblies are provided that are capable of selectively diverting at least one of the diverting members from a non-diverting path extending longitudinally along the sorter to one of the diverting rails. At least one of the diverter assemblies includes first and second redundant diverters. Each of the redundant diverters is capable of selectively diverting at least one of the diverting members from the non-diverting path to one of the diverting rails.

The first redundant diverter may be a magnetic diverter that utilizes magnetic force to at least partially divert at least one of the diverting members from the non-diverting path to one of the diverting rails. The second redundant diverter may be a mechanical diverter that utilizes mechanical force to at least partially divert at least one of said diverting members from the non-diverting path to one of the diverting rails.

An actuator assembly, according to another aspect of the invention, includes an actuator having a shaft and a coil. The shaft is selectively moveable between a first state and a second state. The coil moves the shaft between the first state and the second state. An electronic control applies an activation control signal to the coil to move the shaft between one of the states and the other of the states. The control monitors movement of the shaft and adjusts the activation control signal as a function of movement of the shaft to provide critical damping to the movement of the shaft.

An actuator assembly, according to another aspect of the invention, includes an actuator having a shaft and a coil. The shaft is selectively moveable between a first state and a second state. The coil moves the shaft between the first state and second state. An electronic control controls the coil to move the shaft between one of the states and the other of the states. The shaft includes a mechanical bias tending to return the shaft to one of the states. The control provides a return control signal when the shaft is moving to the one of the states. A return control signal at least partially counteracts the bias.

These and other objects, advantages and features of this invention will become apparent upon review of the following specification in conjunction with the drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings and the illustrative embodiments depicted therein, a positive displacement sorter30includes an endless web32travelling in a longitudinal direction, the upper surface of which defines an article-conveying surface34(FIG. 1). Web32is defined by a series of laterally elongated parallel slats36interconnected at their ends. A plurality of pusher shoes38travel along one or more of the slats in order to laterally divert an article A on conveying surface34, such as to a particular chute (not shown). Sorter30may be any type known in the art, such as of the type disclosed in commonly assigned U.S. Pat. Nos. 5,127,510; 6,814,216; 6,860,383; 6,866,136; 7,086,519; 7,117,988; 7,513,356; and 7,240,781, the disclosures of which are hereby incorporated herein by reference.

Each of shoes38includes a diverting member39extending below conveying surface34in order to laterally displace the pusher shoe, as will be described in more detail below (FIG. 2). Diverting member39may include a bearing52and a pin54extending coaxially below the bearing.

Sorter30further includes a diverting assembly41below conveying surface34for each divert destination (FIG. 3). Diverting assembly41includes a diverter module50made up of a plurality of diverters43and one or more diverting rails42which terminate at a terminal assembly45. Each diverter43is capable of selectively diverting one or more diverting members39from a non-diverting path40, to a diverting rail42extending from that diverter assembly in order to cause the associated pusher shoe38to travel laterally across conveying surface34to thereby laterally displace an article A travelling on the conveying surface. Non-diverting path40extends longitudinally along sorter30under conveying surface34to guide diverting member39of shoes until they are diverted. Each of diverting rails42is capable of engaging diverting member39, such as at bearing52or alternatively at pin54, to cause the associated shoe38to travel laterally to divert an article. Each diverting rail42may be combined with a nose51having a moveable member53that is capable of being deflected if struck head-on by a diverting member39of a pusher shoe in a manner that tends to increase the opening to the corresponding diverting rail42and thereby completes a partial divert as disclosed in more detail in commonly assigned U.S. Pat. Application Publication No. 2009/0139834 A1, the disclosure of which is hereby incorporated herein by reference (FIG. 7).

Terminal assembly45includes a series of generally boat-shaped buffers46having first surfaces47athat guide a diverting member39travelling along an associated diverting rail42to a diverted path48. Buffers46further include a second surface47bthat guide a diverting member39travelling along diverted path48. In the illustrated embodiment, buffers46have a symmetrical configuration that allows them to be usefully installed irrespective of orientation: Diverting rails42may be made of a structural plastic material, such as Nylon, over a vertical steel support plate to reduce noise and/or expense. The buffers46and other portions of diverting assembly41may also be made of structural plastic, such as UMHW.

Each diverter43is a mechanical diverter that utilizes mechanical force to at least partially divert diverting members39in a diverting state from non-diverting path40to the associated one of diverting rails42(FIGS. 6-11). Each diverter43may be actuated by an electronic divert control56that is illustrated inFIG. 16and described in more detail below. Electronic divert control56receives a timing input318afrom a slat sensor61a.In the illustrated embodiment, slat sensor61ais a proximity sensor that monitors movement of slats36in order to actuate diverters at an appropriate time to engage a selected diverting member39without interfering with diverting members that are not selected for actuation by that diverter. However, other types of sensors are possible. Electronic divert control56may also receive a timing input318bfrom a pin sensor61b.In the illustrated embodiment, pin sensor61bis a proximity detector that senses bearing52of a pusher shoe38in order to allow divert control56to combine inputs318a,318bto more accurately determine the position of diverting member39.

A plurality of diverters43may be combined in a diverter module50. Such a diverter module may be used to mount the diverter assemblies and at least a portion of the diverting rails42associated with one divert location, such as a chute or takeaway conveyor, if the sorter is a parallel divert sorter. Each diverter43includes a gate72having a diverting surface74. Gate72is selectively moveable between a diverting orientation or diverting state, illustrated inFIGS. 6 and 8, and a non-diverting orientation or non-diverting state, illustrated inFIGS. 9 and 10. Diverting surface74is capable of selectively diverting one or more diverting members39from non-diverting path40to its associated diverting rail42when gate72is in the diverting state. The position of diverting surface72allows one or more diverting members39to continue to travel along non-diverting path40when gate72is in the non-diverting state. In the illustrated embodiment, gate is formed from a durable polymeric material, such as Delrin, or the like.

Diverter43further includes an actuator76that is capable of actuating gate72between its non-diverting state and its diverting state. Actuator76is a rotary actuator having a generally horizontal axis of rotation. Rotary actuator76may be in the form of a rotary solenoid of the type that is known in the art. Alternatively, rotary actuator76may be in the form of a brushless torque actuator78, illustrated inFIG. 37, having a connector66for connection with electronic divert control56. Gate72is rotatably mounted to a shaft98to rotate between the diverting and non-diverting orientations about another horizontal axis that is concentric with the generally horizontal axis of rotation of rotary actuator76.E A slip joint80may be provided between rotary actuator76and gate72in order to resist diverting motion being transferred from gate72to rotary actuator76. In the illustrated embodiment, slip joint80is defined by a slot90in gate72that is engaged by an extension92of a paddle-shaped member94mounted to generally horizontal shaft96of rotary actuator76. Extension92is free to move within slot90radially and/or axially with respect to both shafts96and98, thus preventing transfer of shock from diverting surface74to shaft96. The presence of a slip joint avoids difficulties associated with known mechanical diverters utilizing a rotary solenoid having a vertically oriented axis. In such known systems, shock and vibration induced in the diverter from contact by the diverting member can be transferred directly to the rotary solenoid, thereby reducing the useful life of the rotary solenoid.

Diverter43may include a sensor62for monitoring operation of the diverter. Sensor62senses rotation of paddle member94in order to determine when the gate has arrived at a particular state. In the illustrated embodiment, sensor62is made up of a proximity sensor84that senses one or more flags86a,86bpositioned at paddle member94, but may be positioned at other portions of the gate. As gate72rotates, flags86a,86bmove out of, and then into, sensing range of sensor84to indicate change of state of the gate.

Gate72may include a flexible member87that defines diverting surface74. Flexible member87absorbs impact from contact between a diverting member39and diverting surface74. In the illustrated embodiment, a portion of gate72is excavated to define a void at88behind diverting surface74. The presence of void88, the thickness of Member87and the material-defining gate72may be selected to impart a desired degree of flexibility to member87as would be within the capabilities of one of ordinary skill in the art.

Gate72is configured to position diverting surface74to engage the bearing52of the diverting member39when the gate is in its diverting orientation. This tends to reduce wear on diverting surface74because it is engaging a member that is free to rotate. Therefore, the movement of diverting member39with respect to diverting surface74during the divert is at least partially one of rotation not slipping. In order to enhance the interaction between diverting surface74and bearing52, member87may be configured to provide a curved surface for the diverting surface. However, it should be understood that other embodiments of the invention provide a gate that positions a diverting surface to engage pin54when in the diverting orientation, as will be described in detail below. In the illustrated embodiment, no special material is applied to diverting surface74to increase its hardness. Diverting surface74is defined by the polymeric material forming gate72.

In diverter43, the generally horizontal axis of rotary actuator76is generally longitudinally oriented to be aligned with the motion of web32. However, other horizontal orientations of the axis of rotation of the rotary actuator are possible. For example, in embodiments that will be described in more detail below, the horizontal orientation of the axis of rotation of the rotary actuator may be generally laterally orientated to be aligned perpendicular to the motion of web32or may be at an angle between lateral and longitudinal orientation.

In the illustrated embodiment, gate72is selectively moveable by an actuation system300from the non-diverting state to the diverting state under the motive force of actuator76and returns to the non-diverting state under the bias of a mechanical biasing device332, which may be a mechanical spring, or the like (FIGS. 16-19). Alternatively, the actuator may move the gate from the diverting state to the non-diverting state and return the gate to the diverting state with biasing device332. Actuation system300includes electronic divert control56that applies an actuation current at output308a,308bto coil302of actuator76according to an activation control signal219to move gate72between one of the states and the other of the states and to hold it in that state. Control56is made up of a driver circuit304and a programmed microprocessor306or other logic control circuit of the type that are well known in the art. Microprocessor306receives input318afrom slat sensor61a, which senses the leading and trailing edges of slats36and input318bfor pin sensor61b, which senses bearing52in order to provide timing signals for driver circuit304to move gate72at the proper time to intercept a desired diverting member39to be diverted and not interfere with any leading or trailing diverting member39that is not intended to be diverted by that gate. Microprocessor306also receives a gate motion input309from proximity sensor84in order to monitor movement of gate72and to adjust activation control signal219as a function of the movement of the gate, as will be described in more detail below. Activation control signal219is made up of an actuation signal320, a flux dissipation interval322, and a gate hold signal324.

In order to control driver circuit304, microprocessor306supplies a shut-down mode signal310, a master enable signal312and a direction signal314to circuit304. Shut-down mode signal310affects the manner in which driver circuit304discontinues actuation signal320and dissipates the magnetic flux built up in coil302during flux dissipation period322, as will be explained in more detail below. Master enable signal312instructs driver circuit304to start and stop actuation signal320and gate hold signal324. Direction signal314causes outputs308a,308bto drive current in one direction through coil302to produce actuation signal320to move actuator76and gate hold signal324to hold the actuator; or in the opposite direction through coil302to produce a demagnetization pulse326to rapidly dissipate the magnetic flux in coil302. Driver circuit304supplies a confirm signal316to microprocessor306to confirm that current is being supplied to coil302. This confirm signal316is used by microprocessor306to assist in monitoring motion of gate72so that microprocessor306will be able to distinguish whether flag86aor flag86bis being sensed by proximity sensor84.

The manner in which actuation system300operates may be seen by reference toFIGS. 17a-17d.FIG. 17aillustrates movement of gate72during an activation sweep (from time mark1to time mark2) when actuator76is moving gate72from one state to the other state against the bias of biasing device332. During a hold position (from time mark2to time mark3), actuator76is holding gate72in the other state against the bias of biasing device332. In a return sweep period (from time mark3to time mark5) the bias of biasing device332is returning gate72to the one, or home, position from the other position.FIG. 17b, which is aligned with the time marks ofFIG. 17a, illustrates current being supplied to coil302by driver circuit304. In order to begin movement of gate72to the other position, driver circuit304applies an activation control signal319that begins with an actuation signal320that is applied to coil302. This causes gate72to begin moving. Before gate72reaches the other position, actuation signal320is discontinued and the flux in coil302is dissipated during a flux dissipation interval322. About the time that the gate reaches the other state (at time mark2), a gate hold signal324is applied to the temporarily motionless gate in order to hold the gate in the other state for the duration of the hold position (from time mark2to time mark3) against the bias of biasing device332.

As will be described in more detail below, the relative times of actuation signal flux dissipation interval322and gate hold signal324that collectively make up activation control signal319may be adjusted in a feedback loop in order to provide critical damping to movement of gate72during its activation sweep. In particular, this critical damping is to cause the bias of biasing device332to stop gate72approximately as the gate reaches the other state. When microprocessor306has determined from slat sensor input318aand pin sensor input318bthat it is time to return gate72to the original position, a return control signal325is carried out. Return control signal325may optionally provide a demagnetization pulse326(at time mark3) in order to rapidly dissipate the magnetic flux in coil302so that gate72can immediately begin the return sweep. Demagnetization pulse326is optional and may not be required if coil302is not large. Following demagnetization pulse326(if any), coil302enters a no action period328(from the end of the demagnetization pulse to time mark4) during which no current is applied to the coil. During no action period328, the bias of biasing device332moves gate72toward its home state. Before the gate reaches the home state, the driver circuit applies a de-actuation signal330(between timing mark4and timing mark5) that operates against biasing device332in order to arrest the movement of gate72approximately as it reaches the home position. The timing of return control signal325may be controlled in a feedback loop in order to provide critical damping of the movement of gate72during the return sweep.

Thus, it may be seen that divert control56may adjust activation control signal319and/or return control signal325in order to provide critical damping of movement of gate72between the one of the states and the other of the states. Divert control56may adjust activation control signal319in order to apply a minimal duration of the actuation current that is capable of causing the gate to change states. Divert control module56may discontinue actuation signal320during flux dissipation interval322before the gate reaches the other state. Critical damping of movement of gate72may be achieved by divert control module56adjusting activation control signal319as function of a comparison of velocity of gate72which is determined from the time it takes gate72to change from one, or home, state to the other or activated state during the present or prior activation cycles. This may be accomplished by adjusting the activation control signal319. In the illustrated embodiment, this is accomplished by having a constant duration actuation signal320and adjusting the start time of gate hold signal324. However, the duration of actuation signal320could, alternatively, be varied.

By providing critical damping to actuation of the diverter gate, the actuation system is capable of minimizing the amount of time it takes to move from one state to the other state. This is because it is not necessary to wait for the gate to settle down from the mechanical bounce that would otherwise be experienced when the gate reaches the mechanical limit of travel. As is understood by one skilled in the art, the ability to reduce the time it takes diverter43to reliability change from a home position to an actuated position allows web32to move at a faster speed for a given slat pitch. Moreover, the critical damping of movement of gate72may eliminate the need for a mechanical buffer at the end of travel of the gate at the actuated state. Also, the avoidance of mechanical shock against the mechanical stop at the actuated state from the critical damping may extend the useful life of the diverter and its actuator.

Moreover, divert control module56may retain a running average of the time it takes for gate72to move from one state to the other state. (Time can be converted to gate velocity and, therefore, will be used herein interchangeably with velocity.) Control module56may compare a more recent time that it takes the gate to move between states to the historic time that it takes the gate to move between states to indicate an error condition on an error indication output334if the recent time is substantially different than the historic time. This lengthening of time may be a result of accumulation of debris in the diverter, which operates in a relatively harsh environment. Such lengthening of time usually is first noticed during the return sweep (from time mark3to time mark5) when movement of the gate is guided by mechanical biasing device332. The error indication output334may be supplied, for example, to an upper level control (not shown) to call for maintenance of sorter30.

As previously observed, divert control module56is capable of providing a return control signal325when gate72is moving from the actuated state to the home state in a return sweep. Return control signal325includes a de-actuation signal330that counteracts the bias provided by mechanical biasing device332. Divert control56may adjust each occurrence of return control signal325as a function of the movement of the gate72. In particular, divert control56may adjust return control signal325in order to provide critical damping of the movement of the gate between the other, or actuated, of the states and the one, or home, of the states. This may be accomplished by divert control56applying a minimal level of de-actuation signal330that is capable of causing gate72to avoid mechanical shock when returning to the home state. Divert control56may adjust return control signal325as function of a comparison of the time it takes gate72to change from the actuated to home states to the same time during this or previous cycles of diverter43.

By providing critical damping through the use of a return control signal, the system is capable of further minimization of the amount of time it takes to move between states. This is because it is not necessary to wait for the gate to settle down at the home state from the mechanical bounce that would otherwise be experienced when the gate reaches the home state under operation of biasing device332. As is understood by one skilled in the art, the ability to reduce the time it takes diverter43to reliability change from an actuated state to the home state allows web32to move at an even faster speed for a given slat pitch. Moreover, the critical damping of movement of gate72may eliminate the need for a mechanical buffer at the end of travel of the gate at the home state. Also, the avoidance of mechanical shock against the mechanical stop at the home state from the critical damping returning to the home state may extend the useful life of the diverter and its actuator.

In the illustrated embodiment, driver circuit304is a controlled current circuit. For reference, the voltage that would be measured across coil302is shown as a voltage signal336seen inFIG. 17c. However, it should be understood that driver circuit304could, alternatively, operate as a controlled voltage circuit, as would be understood by the skilled artisan. In the illustrated embodiment, driver circuit304utilized an H-bridge configuration to produce current in coil302through actuation/de-actuation lines308a,308b(FIG. 19). Control circuit304includes an H-bridge340made up of separate arms, one made up of series transistors Q7and Q15and the other of series transistors Q3and Q11, with the arms connected in parallel between a DC voltage source342and ground344. The node between transistors Q7and Q15supplies one line308ato coil302. The node between transistors Q3and Q11supplies the other line308bto coil302. A set of precision resistors R142, R148and R153connected in parallel with each other is used to sense the current flowing through coil302on a current sense line346. In the illustrated embodiment, voltage source342is operated at 340 VDC. However, a greater or lesser voltage may be used.

A pair of half-bridge driver circuits U22and U23each drive one half of bridge340. In particular, driver circuit U22operates transistors Q7and Q15in order to turn the transistors on and off in proper sequence so that only one transistor is on at a time. In a similar fashion, driver circuit U23operates transistors Q3and Q11. A pulse-width modulation (PWM) circuit U48coordinates the operation of half-bridge driver circuits U22and U23to produce a controlled current in coil302by producing PWM to the coil. PWM circuit U48senses the voltage on current sense line346and regulates half-bridge driver circuits U22and U23to produce controlled current in coil302. In order to produce actuation signal320, gate hold signal324and de-actuation signal330, transistors Q7and Q11are turned on and off and transistors Q3and Q15remain off or open.

Master enable signal312from microprocessor306causes half-bridge driver circuits U22and U23to activate bridge340. Shut down mode signal310from microprocessor306, in conjunction with master enable signal312, instructs driver circuits U22and U23what mode to use to dissipate flux in coil302, such as when actuation signal320is discontinued during flux dissipation period322. For example, in a mode known as “plugging” mode, either both top transistors Q7and Q3or both bottom transistors Q15and Q11are turned on together in order to dissipate the flux in coil302resulting in a deceleration of the divert gate's motion. Alternatively, in a mode known as “regenerative” mode, all transistors Q3, Q7, Q11and Q15are opened in order to more rapidly dissipate flux in coil302back through voltage source342. In the plugging mode, the slower flux dissipation is used in the illustrated embodiment during flux dissipation interval322in order to provide the ability to provide more control of the relationship between the actuation signal320and flux dissipation interval322. However, the regenerative mode could alternatively be used. In order to produce a demagnetization pulse326, transistors Q3and Q15are turned on in order to produce a reverse current in coil302and transistors Q7and Q11remain off or open.

Confirmation signal316responds to voltage at current sense node346in order to inform microprocessor306that current is flowing through coil302. This allows microprocessor306to validate the proper electrical operation of the combination of the H-bridge driver circuit304and the divert gate's actuator coil302.

A divert control program400runs on microprocessor306. In the illustrative embodiment, program400is an interrupt driven routine that is carried out repetitively according to an interrupt signal generated, for example, every 250 ms (FIGS. 18a-18q). When an interrupt occurs (402), the program polls all of its inputs (404) and evaluates the current state of the inputs (406) for use in the program's subsequent evaluation in a gate control state machine (410a,410b. . .410n). After performing additional housekeeping tasks (408), program400then accesses the gate control state machines (410a,410b. . .410n). One state machine is provided and managed per interrupt interval for ea diverter43.

State machine410aaccesses different portions of program400depending upon whether diverter43is in a home position (412), undergoing an activation sweep to the divert position (414,414a. . .414d), at the divert position (416), or undergoing a return sweep to the home position (418,418a. . .418g).

When in home state412and at the home non-divert position (420), the program determines if the state of proximity sensor element84monitors flags86aand86bto confirm that the divert gate is within the range of home position (422). If so, it is determined if an activation sweep trigger event is activated (424). If not, the program retains state420for re-evaluation on subsequent interrupts until the activation sweep trigger event occurs (428). The present iteration of this state machine (410a) is ended, allowing the processor to progress through the state machine associated with the other gates (410b. . .410n). If it is determined at424that a state activation sweep trigger event has occurred, a sweep activation is initiated by sourcing current to actuator76(426) and the state machine is advanced for the management of the activation sweep on the next interrupt driven iteration of this gate's state machine. The current iteration of this state machine is ended.

If it is determined at422that proximity sensor84does not confirm that the gate is at a home position, it is determined if the divert station is in the automatic divert mode (430). If so, it is concluded that a fatal error event has been detected during an automated mode which results in an error indication in line334and a lockout of future automated activation of this gate until examined by a maintenance technician (432). This prevents the “begin activation sweep trigger event” from activating while in the automatic mode. If it is determined at430that the divert station is not in an automated divert mode, it is concluded that the station is in a maintenance mode and the gate will be allowed to be activated in subsequent iterations (434). The current iteration of state machine (410a) is ended. For all process blocks within the flowchart that contains an end iteration statement, this is the means by which the program suspends the state of the present divert gate state machine, progress through the state machines associated to the other gates until all have been processed, and then finally exits the interrupt routine to await for the next 250 microsecond interrupt event to occur.

When the gate control state machine410achanges to the activation sweep sub-state414, the program retains this sub-state (436) for a fixed period of time, such as 10 ms in the illustrated embodiment. While this state is active (the duration of the predetermined period), current is sourced to the gate's actuator coil to actively drive the gate towards the divert position (actuation signal320ofFIG. 17b). It is also expected that, during this early stage of the activation sweep, the associated gate sensor element84will continue to indicate that the gate is in the range of the home position (438). If not, an error flag is set and that divert gate is disabled from future activation (440). However, the current activation will be completed. The unexpected change in status that was reported within this early stage of activation is an indication that the gate position sensor is defective or misaligned and thus cannot be trusted. An internal flag is set such that when the predetermined activation pulse time is completed (444,446), control of the activation sweep will transition to the fixed error recovery timing method (450). Otherwise, at the end of the activation pulse, the control transitions to use the dynamic gate position feedback method (448).

For each interaction of this sub-state (414), the program entered at point436and both the gate position status reported (438) by sensor element84and the internal timer (442) are evaluated once per iteration until it is determined at442that the timer has expired resulting in the flag being set at444, and the internal error flag (446) being set during the time since the start of the activation sweep. If the flag is set (450), the state machine is advanced to use the fixed timing error recovery method (sub-state414d). If not, the state machine is advanced to use the dynamic gate position feedback method (sub-state414a). In either case, in this embodiment, both transitions result in control of the gate actuator coil (302) to be placed in the plugging mode which will begin the flux dissipation interval322. This has the effect of decelerating the gate's movement towards the divert position.

When the sub-state414cis active (within the dynamically controlled method sequence of gate activation control), the program will begin processing the gate state machine at point484on each iteration of410a. It begins by testing if the delay timer has expired (486). If so, the delay after the R.E. event is complete (490) and the H-bridge drive circuit304to the divert gate's actuator coil302is re-enabled to source the hold current324(if not already done so in process block480ofFIG. 18e). The state machine then declares the “Activation Sweep Complete” and transitions to the “Divert Position” state for the next iteration (transition to major state416for the associated divert gate). If not, then the present sub-state machine is held (414c) for re-evaluation on the next interrupt driven iteration (488).

If an error flag was set during the activation sweep sequence (sub-states414,414a, or414b) the program would have transitioned to the appropriate staging within the error recovery sub-state414d, after setting the appropriate internal error flags and control of the divert gate's drive circuit, in order to cleanly recover from the associated error event. When the error recovery sub-state is active on each interrupt driven evaluation interval, the program enters at point492and then the time since start of activation sweep is checked and performs the appropriate action in accordance with the scheduled timing events (494) for the control of the drive circuit until completion of the activation sweep is declared and the state machine is finally advanced to the Divert Position State (416).

Upon completion of the activation sweep state414, gate control state machine410aenters the “Divert Position” state416. While this state is active, it is expected that the gate will hold the divert position because the hold current324should maintain the gate in the divert position against the return spring332action; until such time that a “begin gate return sweep trigger” event has occurred. To that end, the program enters at point495on each iteration of410awhen the416state is active. It then determines (496) if the “begin gate return sweep trigger” event has occurred. If not, it is then determined if the divert gate position feedback sensor84indicates the gate is at the divert position (497). If it is, the program retains the Divert Position state (416) for re-evaluation on subsequent iterations until an occurrence of a return activation event occurs (498). If it is determined at497that the gate position feedback sensor is not reporting the divert position, then unexpected divert gate movement has occurred.

The severity of the error reporting is dependent on whether the divert station is in Automatic Divert mode or not (500). If the divert station is set to a maintenance mode (504), then the error reporting is local and the “begin gate return sweep request” will be initiated by the service personal's manual mode override control (this means in which maintenances mode was activated by service personal). If it is determined at500that the divert station is in the automated divert mode, it is then determined that a fatal event has occurred (502). An error flag is set, a “begin gate return sweep request” is issued, and automatic activation of the gate is locked out until reset by an operator or the host system. In either case, if the divert mode is determined at500, the divert position state is retained until the “begin gate return sweep request” is synchronized with slat position timing for the “begin gate return trigger event” to be activated and subsequently evaluated of the gate's state machine410a. The state machine then advances to the return sweep state418.

If it is determined at496that the “begin gate return sweep trigger” event is active, then it is determined if the gate position feedback sensor84is indicating that the gate is at the divert position (506). If not, it is concluded that an unexpected timing event has occurred and that the program cannot deem the output of sensor84to be reliable (508). An error flag is set and future activation is disabled until reset.

If it is determined at506that the gate position feedback sensor is indicating the gate is in the divert position, the dynamic gate position feedback technique is initiated during the return sweep state by setting an internal flag (512). In either case (508,512), the process block510will be executed and the return sweep state418is initiated by the activation of a demagnetization pulse (326). The skilled artisan will recognize that a demagnetization pulse is not strictly required and that the regenerative mode could be used in its place for the initial portion, such as the first 8 ms, of the return sweep sequence. The advantage of a demagnetization pulse is that it more efficiently depletes residual magnetism within the coils core over that of the regenerative mode. This advantage becomes more significant in shortening the return sweep action as the inductance value and/or size of the core of a chosen core (302) becomes larger. However, the demagnetization pulse326is optional and may not be necessary for small core and low inductance values of coil302.

The transition from divert position state (416) in this embodiment will always begin the return sweep by initiating the demagnetization pulse thus the transition is to sub-state418where the control of the demagnetization pulse is managed using fixed timing (time pre-determined to maximize the performance of the chosen coil302).

When the sub-state demagnetization (418) is active, the program will begin processing at point512. On each iteration of410a, it will then begin (514) the evaluation of the divert gate's feedback sensor element84to verify that the gate remains in the range of the divert position (flag86abeing seen by sensor element84) for the first 10 ms of the time since the start of the return sweep. If not, it will flag the fixed error recovery timing method that is used on the transition out of this sub-state. After the evaluation of the feedback sensor, the evaluation of the “time since start of return sweep” is made to sequence the driver circuit through its required stages, at the appropriate time intervals, in order to generate the desired demagnetization pulse (516). The demagnetization sub-state is held for re-evaluation on subsequent intervals until the 10 ms event becomes active; at which point, the internal error flag that would have been set if unexpected gate movement was seen is used to select between one of two sub-state transitions. If gate movement was seen, then it is concluded that the sensor element84cannot be trusted and fixed return sweep error recovery timing must be used (transition to sub-state418gwith the “Await Time Since Start of Return Sweep A Delay of 20 ms” flagging activated). Otherwise, use the dynamic gate position feedback method by transitioning to await the falling edge (F.E.) event from the sensor84.

If the return sweep sub-state418ais activated, the program will begin processing the gate state machine at point518on each iteration of the divert gates state machine (410a). It will then be determined if the falling edge (F.E.) event of sensor element84has occurred (520). If so, the F.E. event has occurred within the expected timing window (522) and the dynamic timing sequence can continue by transitioning for the next iteration to await on the rising edge (R.E.) event (transition to sub-state418b). If it is determined at520that the F.E. event did not occur, then it is determined (524) whether the time since the beginning of the returning sweep has exceeded the expected F.E. window (20 ms for the illustrated embodiment). If not, the program retains the present sub-state for re-evaluation on subsequent iterations (526). If it is determined at524that the time since the start of the return sweep has exceeded the expected F.E. window, the appropriate error flags are set and the state machine transitions (528) to the fixed return sweep error recovery timing sub-state (418g).

If the return sweep sub-state418bis activated, the program will begin processing the gate state machine at point530on each iteration of divert gates state machine (410a). It is then determined if the R.E. event of sensor element84has occurred (532). If so, the R.E. event has occurred within the expected timing window (534) and the dynamic timing sequence can continue by calculating the velocity associated to the gates movement; which is inversely proportional to (R.E.-F.E) event timing relative to the start of the return sweep. It is then determined if the gate velocity is fast enough to require a de-actuation signal330to provide deceleration (536). If it is determined at536that additional deceleration is required, a delay of 1.5 ms is initiated and the width of the counter pulse is calculated inversely proportionally to the prior calculated gate return velocity (540). The state machine is then transitioned to manage the remaining control sequence (transition to sub-state418cto await the expiration of the 1.5 ms delay). If it is determined at536that the gate was moving slowly enough that a de-actuation signal is not required, then preparations are made to transition the H-bridge driving circuit from the plugging mode into the regenerative mode (538). This is done by transitioning to the sub-state418efor the next iteration of410a. If it is determined at532that the R.E. event did not occur, then it is determined at542whether or not the time since the beginning of the returning sweep has exceeded the expected R.E. window (30 ms for the illustrated embodiment). If not, the program retains the present sub-state for re-evaluation on subsequent iterations of410a(544). If it is determined at542that the time since the start of the return sweep has exceeded the expected R.E. window, it is declared that the gate return movement is outside acceptable limits and a fatal error has occurred (546). The appropriate error flags are set and the state machine transitions to the fixed return sweep error recovery timing sub-state with no de-actuation signal to be applied (transition to sub-state418g).

If the return sweep sub-state418cis activated, the program will begin processing the gate state machine at point550on each iteration of divert gates state machine (410a). It will decrement the associated delay after R.E. event countdown by the interrupt interval time (552) and determine if the delay time has then expired (554). If not, the present sub-state is held for re-evaluation on subsequent intervals of410auntil the timer expires (556). If the determination of554is that the delay timer has expired then the H-bridge drive circuit340is energized to generate the counter pulse330and transition to the sub-state to await the expiration of the timer controlling the width of the counter pulse (558) (transition to sub-state418d).

If the return sweep sub-state418dis activated, the program will begin processing the gate state machine at point560on each iteration of divert gates state machine (410a). It will decrement the associated Counter Pulse Width Countdown Timer by the interrupt interval time (562) and determine if the pulse width time has then expired (564). If not, the present sub-state is held for re-evaluation on subsequent intervals of410auntil the timer expires (566). If it is determined at564that the pulse width timer has expired, then the H-bridge drive circuit340is placed in plugging mode to lightly resist the springs return action and complete the critically dampening effect of gate motion (568). A short delay is initiated to provide the gate to physically complete return to the “HOME” position. The state machine transitions to sub-state418fto wait on the expiration of this short delay (3 ms in the illustrated embodiment).

If it was determined at438that no de-actuation signal was required, the sub-state418eis activated to perform the housekeeping task of setting the H-bridge driver circuit304into shutdown mode. This is a single iteration sub-state and, as such, will result in a 250 microsecond delay (570) prior to performing the control housekeeping of the H-bridge and initiating a delay, such as 3 ms, to provide adequate physical time for the gate to reach the “HOME” position (572). The delay countdown is initiated by block572concluding by transitioning to sub-state418fto wait on the expiration of the delay.

If the return sweep sub-state418fis activated, the program will begin processing the gate state machine at point580on each iteration of divert gates state machine (410a). It will then decrement the associated delay countdown timer by the interrupt interval time (582) and determine if the delay time has then expired (584). If not, the present sub-state is held for re-evaluation on subsequent intervals of410auntil the timer expires (586). If it is determined at584that the delay has expired, then the H-bridge drive circuit340is placed in shutdown mode, internal housekeeping is preformed, and the return sweep is declared complete (588). The state machine transitions to the “Home” position state of412.

If an error was detected during the return sweep's sub-states (418,418a. . .418c), then the state machine would have transitioned to the error recovery sub-state418g.When this sub-state is activated, the program will begin processing the gate state machine at point590on each iteration of divert gates state machine (410a). It will then perform the associated fixed timing event to control of the H-bride drive circuit to complete the return sweep (592). Once the “time since start of return sweep” is evaluated to be 32 ms, the return sweep is declared complete and the associated housekeeping is preformed, and the state machine transitions to the “HOME” non-divert state of412with the error signal334being active.

Thus, it is seen that program400achieves stability through critical damping of the motion of gate72during actuation by an activation control signal. The activation control signal includes a flux dissipation period322that allows biasing spring332to apply a braking force to the gate after a predetermined time of applying actuation signal320. The program then monitors digital feedback of gate position sensor84. The time delay within expected timing windows between the first falling edge (F.E.) and rising edge (R.E.) of the signal produced by proximity sensor84sensing flags86a,86bis used to determine a relative rotational velocity of the gate activation sweep to determine dynamically when to apply gate hold signal324to give critical damping to the mechanical activation response. For the case of the return sweep, since it is achieved by the action of biasing device332, return control signal325includes applying de-actuation signal330to decelerate the action of the gate. Again, the time measurement of the falling edge and rising edge of the signal produced by gate sensor84that occur within an expecting timing window are used to determine the relative velocity of the gate during the return sweep. This timing measurement is used to determine a time offset and duration of de-actuation signal330to provide critical damping to mechanical control of the gate. In addition, during the start of the return sweep phase, an optional demagnetization pulse326may be used to quickly remove any residual magnetic flux within the inducted core of the actuator. This translates into improved response at the start of the gate return sweep.

The monitoring of the rising edge and falling edge of gate position sensor84may also be used to determine overall operation performance of the movement of the gate. This information may be used to detect any degradation in performance and statistically determine if preventative maintenance is required prior to an actual failure of the diverter. At a higher level of system control, this information may be used to determine a maximum speed that sorting may be carried out by sorter30or to allow the associated sortation destination lane to be disabled until repairs are made.

In the illustrated embodiment, actuator76is a slightly modified version of a commercially available brushless torque actuator that is marketed by Sala-Burgess, Inc. under Model DTA-5 Series. However, other forms of rotary solenoids may be used.

Also, certain aspects of the disclosed embodiments may be used with other forms of actuators. For example, although illustrated for use with a rotary actuator that rotates a gate in order to change states, actuation system300and divert control program400may be used with other forms of actuators, such as linear actuators that move in a line between states. Certain aspects may also be used with other forms of actuation, such as pneumatic actuation, hydraulic actuation, and the like. Also, the actuator may be used for other control operations than moving a diverter gate through a sweep motion and may be used in other applications besides sorters. Although sensor84monitors portions of the gate to determine movement of the gate, it should be understood that various encoders can be positioned on the gate shaft, the actuator shaft, or the like.

Diverter43may be used in a diverter assembly44as a redundant diverter48in combination with another diverter46, such as an electromagnetic diverter (FIGS. 20 and 21). Each redundant diverter46,48is capable of selectively diverting one or more diverting members39from non-diverting path40to the associated diverting rail42.

In the illustrated embodiments, first redundant diverter46is a magnetic diverter that utilizes magnetic force to at least partially divert the diverting members39in a diverting state from non-diverting path40to the associated diverting rail42. An example of such a magnetic diverter that utilizes only magnetic force is disclosed in U.S. Pat. No. 5,409,095, the disclosure of which is hereby incorporated herein by reference. An example of such a magnetic diverter that initiates the divert magnetically, but completes the divert mechanically, is disclosed in commonly assigned U.S. Pat. No. 6,615,972, the disclosure of which is hereby incorporated herein by reference.

An advantage of the combination of redundant diverters for diverter assembly44is that, if the divert is carried out magnetically by the first redundant diverter46, the divert may be quieter because there is minimal impact between diverting member39and diverter46. However, second redundant diverter48is available to divert the diverting member, if for any reason the divert is not carried out by the first redundant diverter46. This may be particularly useful in circumstances where increased friction between pusher shoes38and slats36may make diverting of the pusher shoes difficult to initiate. In the illustrated embodiment, both first and second redundant diverters46,48are actuated for each divert, as will be described in more detail below. However, the skilled artisan will appreciate that the second redundant diverter may be actuated only under circumstances where the first redundant diverter fails to carry out a desired divert.

Electronic divert control56may have a first driver circuit304that selectively actuates first redundant diverter48and a second driver circuit304that selectively actuates second redundant divert48. In one embodiment, both first and second driver circuits are operated together to ensure that if diverter46does not carry out the divert, diverter48will. In another embodiment, the first driver circuit304may operate as a master control and the second driver circuit304may operate as a slave control that responds to operation of the first driver circuit. In this embodiment, the first driver circuit would respond to a signal from slat sensor61aand/or pin sensor61bin order to initiate the divert and a divert sensor (not shown) to indicate that a divert occurred. In this embodiment, the second driver circuit responsive to the first driver circuit carries out the divert if the first driver circuit indicates that a divert did not occur. In this manner, second redundant diverter48is actuated only if first redundant diverter48fails. Thus, in either embodiment, diverter assembly44is capable of exceptionally reliable operation.

In an alternative embodiment, a positive displacement sorter130includes a diverter module150made up of a plurality of divert assemblies144having a first redundant diverter146and a second redundant diverter148(FIGS. 22-29). Second redundant diverter148may be in the form of a mechanical diverter170with a rotary actuator176having a generally horizontal axis generally laterally oriented (FIGS. 22-29). In particular, rotary actuator176has a laterally oriented shaft196that is generally perpendicular to the motion of the web (not shown) of sorter130. It should be understood that although illustrated as a redundant diverter, mechanical diverter170may be used as a standalone diverter in the manner previously described.

Mechanical diverter170includes a gate72that is rotatable between a non-diverting orientation, illustrated inFIGS. 26 and 28, and a diverting orientation, illustrated inFIGS. 27 and 29. Gate172defines a diverting surface174that diverts diverting members39when in the diverting orientation. Diverter170may further include a slip joint180in the form of an elongated slot and paddle in the slot that allows relative movement of gate172with respect to the shaft of rotary actuator176. Gate172is configured to position diverting surface174to engage bearing52of diverting member39when in the diverting orientation. Thus, in a similar manner to mechanical diverter70, diverter170is capable of diverting a rotatable body thereby reducing wear on diverting surface174.

In another alternative embodiment of positive displacement sorter230includes a diverter module250made up of a plurality of diverter assemblies244, each having a first redundant diverter246and a second redundant diverter248(FIGS. 30-36). Second redundant diverter248may be in the form of a mechanical diverter270with a gate272and a rotary actuator276having a generally horizontal axis that is at an angle to the longitudinal direction and to the lateral direction of the sorter. In particular, rotary actuator276has a shaft296that is at an angle to the motion of the web (not shown) of sorter230. It should be understood that although illustrated as a redundant diverter, mechanical diverter270may be used as a standalone diverter.

Mechanical diverter270includes a gate272that is rotatable between a non-diverting orientation illustrated inFIGS. 30 and 32and a diverting orientation illustrated inFIGS. 31 and 33. Gate272defines a diverting surface274that diverts diverting members39when in the diverting orientation. Diverter270may further include a slip joint280similar in configuration to slip joint80. Gate272is configured to position diverting surface274to engage pin54of diverting member39when in the diverting orientation.

As may be seen inFIG. 37, brushless torque actuator78includes a rotor100that is rotated by electrical energy applied to a winding102and includes an internal biasing device332(not shown inFIG. 37).