Patent Grant
6848933
The present invention relates generally to industrial control systems, and more particularly to a system and methodology to facilitate distributed and efficient control of a modular conveyor system.
Control systems are often employed in association with conveyor systems for moving objects along guided tracks, including modular conveyor sections or “sticks”. Conveyor systems for moving objects between stations in a manufacturing environment or for accumulating and distributing products in a warehouse operation are well known in the art. Such conveyor systems provide upwardly exposed conveying surfaces, such as rollers, positioned between guiding side rails. The rollers can be powered by controllable motors to move objects placed on top of the rollers along a track defined by the rails.
Assembly of conveyor systems can be facilitated by employment of “conveyor sticks” which may include one or more short sections of rollers and guide rails, which are connected together to form a final conveyor system. The conveying surface of each conveyor stick may be broken up into one or more zones, respective zones associated with a sensor for detecting the presence of an object on the conveyor at the zone. A control circuit communicates with the zones and associated sensors via a number of cables to control the zones, in order to accomplish a number of standardized tasks.
Such conveyor systems may be adapted to perform one or more tasks or operations. One such task is that of “accumulation” in which a control circuit for a given zone operates its rollers when the sensor, in an adjacent “upstream” zone, indicates an object is at that zone and the sensor of an adjacent “downstream” zone indicates that no object is in that downstream zone. This logic causes the conveyor zones to move objects along to fill adjoining zones with objects. Generally, each upstream control circuit operates its rollers to move its objects downstream one zone. In order to perform these tasks, the control circuit for a particular conveyor stick may communicate in a limited fashion with the control circuits (or at least the sensors) of an associated, adjacent upstream and downstream conveyor stick. This may be accomplished via cabling between control cards or sensors of the conveyor sticks, typically within one of the side rails.
Several problems currently exist with conventional distributed zone control systems, however. One such problem relates to transmission line issues (e.g., reflections, noise) as a plurality of control stations can be concatenated for larger conveyor lines. Other problems relate to cable and associated installation expenses when adding additional stations to an existing line or in the initial design and installation of the conveyor line itself. This can be caused by the amount of different types of sensors, actuators and controllers that have to be interconnected to form a cohesive system. Still yet another problem involves speed and smoothness during conveyor operations. Due to communications limitations between zones, conveyor speed generally must be limited to avoid causing instabilities in the overall conveyor and associated control process.
Employing a centralized controller over all the zones can alleviate some of the control and stability issues described above. Industrial controllers are special purpose computers utilized for controlling industrial processes, manufacturing equipment, and other factory automation, such as conveyor systems. In accordance with a control program, the industrial controller measures one or more process variable or inputs reflecting the status of a controlled conveyor system, and changes outputs effecting control of the conveyor system. The inputs and outputs may be binary, (e.g., on or off), as well as analog inputs and outputs assuming a continuous range of values. The control program may be executed in a series of execution cycles with batch processing capabilities.
Measured inputs received from a conveyor system and the outputs transmitted to the conveyor system generally pass through one or more input/output (I/O) modules.
These I/O modules serve as an electrical interface between the controller and the conveyor system, and may be located proximate or remote from the controller. The inputs and outputs may be recorded in an I/O table in processor memory. Input values may be asynchronously read from the controlled conveyor system by one or more input modules and output values are written directly to the I/O table by the processor for subsequent communication to the conveyor system by specialized communications circuitry. An output module may interface directly with a conveyor system, by providing an output from an I/O table to an actuator such as a motor, valve, solenoid, and the like.
Various control modules of the industrial controller may be spatially distributed along a common communication link in several racks. Certain I/O modules may thus be located in close proximity to a portion of the control equipment, and away from the remainder of the controller. Data is communicated with these remote modules over a common communication link, or network, wherein modules on the network communicate via a standard communications protocol. Although centralized industrial controllers can be effective in controlling a conveyor line, these type solutions can add significant expense to a conveyor system. These expenses include the controller such as a Programmable Logic Controller (PLC), associated racks, I/O modules, communications modules, program software development, and extensive cabling to facilitate centralized control of a distributed conveyor system.
The following presents a simplified summary of the invention in order to provide, a basic understanding of some aspects of the invention. This summary is not an extensive overview of the invention. It is intended to neither identify key or critical elements of the invention nor delineate the scope of the invention. Its sole purpose is to present some concepts of the invention in a simplified form as a prelude to the more detailed description that is presented later.
The present invention relates to a system and methodology to facilitate efficient and robust control of zone conveyer sections in a distributed conveyor assembly. A modular system having sensing input, power output, communications and control logic capabilities is provided in a single zone module that cooperates with other similarly adapted zone modules in a coordinated manner. This includes module packaging features (e.g., low-profile, compact housing), logic decisions, and communications protocols (e.g., serial, parallel, wireless) that facilitate rapid module installation and configuration along conveyor sections while mitigating cable and installation costs. Zone modules cooperate to control multiple conveyor sections having upstream and downstream ends, wherein control can be achieved via multi-zone logic decisions and associated communications. The conveyor sections support powered roller assemblies and associated object sensors that are respectively driven and sensed by the zone modules in accordance with multiple output and input configuration options.
The zone modules of the present invention can be adapted in a plurality of different configurations that support ease of installation and mitigate complexities associated with programming and coordinated control. For example, the zone modules can be installed along the line of a flat cable via clamping style connections such as from insulation piercing vampire pins or other type connection such as from an insulation displacement connection (IDC). Although convenient and robust installation can be achieved via cabling and associated clamping options, the present invention also provides zone control logic that is operative over multiple zones (e.g., considers other zones than just adjacent zones when making zone control decisions)—which supports not only cabled communications but wireless communications can be adapted as well (e.g., Blue tooth/wireless markup language protocol between zone modules and/or between zone module and associated I/O).
According to one aspect of the present invention, a zone module employable in a conveyor system is provided with components for receiving at least one end of a flat cable and a set of vampire pins for engaging with conductors of the cable. This can include power, interface and logic to link several adjacent zones with a minimal set of conductors while mitigating expense and complicated set-up of an addressed communications network. A packaging concept is applied whereby modules contain a sensor and actuator interface as well as logic connecting other similar modules in a conveyor control system by being “stabbed or staked” to a flat, N-conductor cable employing the vampire pins (N being an integer). Unlike other systems, this type connection is daisy-chained rather than bussed, wherein the cable is cut according to a location the module is to be attached—in such a manner as to bridge the aforementioned cut (e.g., directly connected for some conductors and indirectly connected through electronics for others). This type arrangement facilitates a process for configuring a first zone module and automatically configuring another zone module via communications with the first zone module. The process can further employ a serial broadcast message to convey first zone module configurations to other zone modules via module-to-module passage of the first zone module configurations. This can include a module configuration replication feature that enables a user or module to input operational settings at one module and have the settings automatically replicated from module-to-module, thus reducing time and cost to input settings at respective modules.
Yet another aspect of the invention relates to a sophisticated signaling system that provides suitable communication to implement conveyor logic. Conveyor logic includes a coordinated logic system for respective zones in a multi-zone conveyor turning on or off as conveyed product is available to be moved. Communications can be achieved via current and/or voltage pulses that facilitate substantially high electrical noise immunity. In addition, since respective zones signal directly (e.g., electrically) to upstream zones and downstream zones, electrical characteristics of the cable generally do not limit maximum signaling length or effect signal quality from transmission line effects or noise. With periodic addition of diode isolated power supplies, cable length is essentially unlimited.
The signaling and logic system can provide detection of and response to jam conditions (e.g., items jammed when leaving a conveyor zone as well as items jammed when entering a zone) on the conveyors and also to turn off zones that have little productive reason to be running such as initiating a sleep condition to conserve power or reduce audible noise. In contrast to conventional systems, a respective zone module can employ look-ahead or look-behind logic that can incorporate multiple upstream and/or downstream events from non-adjacent zone modules when determining whether to initiate a shut-down in response to detected jam or sleep conditions.
Another aspect provides access (e.g., a multi-use electrical connector that) for temporarily connecting modules together for test purposes in a factory without utilizing vampire connections to the flat cable, which is more permanent. This aspect is significant because conveyors are often factory assembled for test purposes and then disassembled for shipment. The same connector can also be employed as a programming port for inputting operational settings to lower cost versions of the zone module, which may not have other programming aspects (e.g., rotary switches, pushbuttons) of user interface.
According to other configuration aspects of the present invention, different types of zone modules can be connected to the N-conductor cable, including for example, an in-feed module which can be utilized at a very first zone, wherein product loads are introduced to the conveyor system. Other module types can be provided with and without local timing settings along centralized zones of the conveyor, including master module types at the end of the conveyor system. Master modules can issue broadcast settings of timers for substantially all centralized modules that employ similar settings and do not have a separate user interface. Centralized modules that have unique timing requirements can have an associated user interface to set timer values and typically ignore (but relay) broadcast timing settings.
The following description and the annexed drawings set forth in detail certain illustrative aspects of the invention. These aspects are indicative, however, of but a few of the various ways in which the principles of the invention may be employed and the present invention is intended to include all such aspects and their equivalents. Other advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the drawings.
The present invention relates to conveyor control system(s) and/or method(s), which may be operatively coupled with other such systems in order to implement a control strategy for a modular conveyor system. A module and/or series of modules are provided that clamp to a cable (e.g., flat four-conductor cable, and/or bridge to other media than cable), the modules having associated logic and inter-module communications for control. This includes relatively inexpensive power distribution, interconnection (such as for example to photoelectric sensors and actuators such as air valves or motor controllers) and motion logic for industrial conveyor systems.
Referring initially to
Respective zone modules 120-126 include associated I/O interface components 130-136, logic portions 140-146, and user interface portions 150-156 that interface with object sensors 160-166 and actuator outputs 170-176, respectively, to control associated conveyor sections.
A segmented cable trunk line 180 provides power and facilitates control and communications between the zone modules 120-126, wherein attachments to the cable can be provided via vampire couplings illustrated at 190-196. Although the system 100 may be described in terms of flat cables and vampire couplings, it is to be appreciated that other interface media may be employed. For example, the trunk 180 could be provided as a round cable, wherein the couplings 190-196 are achieved via mini/micro connections. Other type couplings can include Insulation Displacement Connections (IDC) to the cable 180. Rather than a cable media 180, wireless communications can be provided between the zone modules 120-126 and/or between a respective zone module and an associated I/O point. For example, wireless protocols such as Bluetooth protocol (or other wireless protocol such as WML) can be utilized to coordinate communications between the zone models 120-126 and/or to a respective I/O node.
The zone modules 120-126 provide relatively low cost, feature rich aspects, which offers users substantial flexibility when engineering and assembling an accumulation conveyor system. This includes input connections at 160-166 for a photoelectric sensor, output connections at 170-176 to a solenoid or DC motor, for example, flat wire cable connections at 190-196 for DC power/communications, including provisions for multiple types of other zone modules (described below) in an upstream zone, a downstream zone, or both. Variations on basic module types also provide screw terminals for connection of a zone release switch, a slug release switch, a zone infeed switch, a zone state output and a separate connector which mirrors the flat wire 180 connections, for test mode.
The logic portions 130-136 can support various internal logic functions such as: single-zone control, multi-zone control employing non-contiguous module events, slug release mode, wherein a slug operation is defined as an operation that causes several zone modules to cooperate at the farthest portion of the downstream end to discharge a predetermined number of objects from the conveyor system. Other logic functions include sleep functions with settable timers, jam detect functions with settable timers, ON/OFF Delays for conveyor drive, output inversion functions, slug release one shot timers with hold features, zone release one-shot timers with reset features and other counter logic. These aspects will be described in more detail below.
The zone modules 120-126 can be housed in a molded plastic enclosure, for example, having vampire pins that pierce the flat cable 180. This can include I/O headers (e.g., photo-eye and actuator) and a test header to mimic or mirror the flat cable 180 connections. In addition, PCB header connectors and screw terminals can be provided for a zone release input, a slug release input and the master full output signal, if desired. The user interface 150-156 can include various combinations of switches, pushbuttons, lights or LEDs, connectors and/or other components to facilitate programming, configuration, and/or control of the system 100.
The present invention provides many advantages over conventional systems. This includes employment of flat cable media with vampire style pins (or other type such as IDC), thus cable wiring or tubing between zones to drive actuators is mitigated. Other features include support of pneumatic valves or power rollers and support of a factory or testing harness/connection without making permanent connections to the zone modules 120-126 or cable 180. Other logic capabilities include module configuration replication features, low power consumption for enabling a large number of nodes on a single class II bus, a multi-zone sleep/jam mode algorithm wherein non-adjacent zone events are considered, a current loop interface for high noise immunity, high density, and inter-zone connectivity on a single wire, and providing flexibility to support additional logic extensions or control options.
Referring now to
Type II zone modules 230 are typically a basic zone module having a small number of dipswitches (e.g., four) for basic mode and function configuration. This type can also process timers that have been initialized within it by a broadcast message from the master module 250. Typically, no other information or settings are achieved by broadcast messages that are employed when predominant or standard system timing values apply. The type I zone module 240 has the capabilities of the type II zone module 230 and in addition can have a pushbutton and rotary selector switches for configuring timers locally. It can be employed in curved and/or other conveyor sections that require unique or configurable timing other than utilized in the larger majority of zones in the conveyor. In addition, type I zone modules 240 generally do not respond to broadcast messages.
The type III zone module 220 is similar to the type II zone module 230 except that in addition, it can have an additional terminal block connector employed for connection to an external product fill switch, in-feed zone full output, and associated logic. It is configured to require no upstream communication or logic, process switch input for fill rather than release, and to disable broadcast mode. The master module 250 is similar to the type I zone module 240 except that in addition, it has the capability to generate broadcast messages to configure type II modules for timer settings, and it has additional terminal block connectors for connection to an external slug release switch, zone release switch and/or a master zone full output signal.
Referring to
Referring to
Referring now to
The modes illustrated at 550 or other modes described below facilitate coordination between zones. In general, a zone accepts direct state input from previous (upstream) zone, if any, from the following (downstream) zone, from the zone following the following zone, and so forth if so programmed, if any, and employs these states to drive its own actuator. A zone resolves its own logic and decides when to drive and when not to drive (e.g., except in slug release mode). This mitigates the need to connect zones with actuator wires or tubes. Thus, zone logic is generally set in the zone itself. A zone can also be configured for its own time delay and its own enabling or disabling of slug respond mode.
The Sleep mode at 554 is generally not initiated in a dormant zone but rather enabled by a previous (upstream) zone, subject to its own photo sensor state. A sleeping zone has an associated actuator set to off and otherwise is active, including communications. Slugged zones 530 are in a single contiguous group starting with the discharge (master) zone, wherein the configuration of slugged zone groups is optional. As will be described in more detail below, transport and accumulation logic can be based on direct states(e.g., photo states) as well as implied states (e.g., existence of a box between photo sensors implied by leaving one zone and not yet arriving at the next zone). On delay or Off delay modes at 544 and 548 can be set to zero for most zones or are set to similar values in most zones. Typically, most inner or centralized zones receive timer settings serially but some (e.g., type I) have them set locally at the module. In addition, modules can be configured according to a communications majority vote size that is based on a size required for a previous message.
Referring to
According to the logic described above at 600, several operating functions and modes are possible. This includes, for example, driving indicators 660 such an orange or other color indicator that illuminates when the actuator 664 is active and is otherwise dark except for: error conditions (e.g., SCP, lost communications, no photo margin in which case it can flash at a 0.5 Hz. or other rate (true for all modules); signifying the acceptance of timer values in which case the LED 664 can flash twice (or other number); and during a configuration replication process in which case the LED illuminates until either replication times out or a successful broadcast occurs in which case it can flash twice or other number (master module only).
The switches 648 enable selecting operating modes (all module types) including single zone logic, dual/multi zone logic, and slug mode. Other switch selections include, when set to ON or 1, for example, turns on output current when the zone logic is true or, alternately, when set to OFF or 0, turns off output current when the zone logic is true. This can include setting slug, on, off, jam and sleep timers/counter modes (e.g., master module and type I and III zone modules).
The rotary selector switch at 640 can set timer or counter values while a second rotary selector switch at 640 can set one of ten preset timer values, followed by pressing the enter pushbutton at 644 and releasing after which the indicator 660 flashes twice or other number to verify acceptance of the timer or counter value. Unused timers are generally set to zero. The time associated with switch positions can be factory set in memory 614 during final test and may range between 0 and 255 (or other range) multiplied by a time base that can be factory set as 50 mS or 100 mS, for example.
When a replication configuration dipswitch is cycled from OFF to ON (e.g., switch 648), replication of settings is generally enabled for 15 seconds or other predetermined time. During this time, when the enter pushbutton 644 is held, a unique message is broadcast to all zones, and interpreted by type II zone modules described above. For example, the message can consist of a 1800 uS sync start pulse (or other time) that identifies it as a configuration message, followed by a one byte preamble (or more or less than one byte), a 450 uS sync pause (or other time), 7 data bytes (or more or less bytes) (with standard 200 uS bit intervals (or other time) and parity protection) containing codes for respective timer settings with 450 uS sync between bytes (or other time), followed by an end of message byte and a checksum of the entire message.
Upon receiving a sync start pulse, any node that calculates a checksum error will drive the slug release line low at 650 through an open collector for 200 uS to indicate a message receive error. The master module can continue to retry until no receive message error signal is given or after a predetermined number of attempts (e.g., one hundred attempts), after which it will signal success with a brief flash of the indicator 660 three times, or failure by a long flash of the indicator three times (or other number). If a replication dipswitch is returned to the off position, replication will terminate. Other conditions can also terminate replication such as if the enter pushbutton 644 is released before successful transmission of parameters.
One pin on the programming connector 670 is employed to emit timer settings from the master module and to receive the same settings in either type I, or II or III modules. Type 1 or III or III modules will generally listen for this type signaling in normal operation. The signaling is emitted from the master module during a replication sequence. This causes configurations to be transmitted to the entire system of modules over the flat cable and also from the programming connector 670. This permits modules to be individually configured at anytime. Alternatively, configurations can be passed from module to module via serial communications.
It is to be appreciated that more than two zones can be considered in determining whether a zone can go into sleep mode. For example, an upstream zone D and E (not shown) could be employed to base sleep enable on the conditions of zone C in
At 1320 of
Before describing more detailed logic below,
The following tables and discussion describes various possible logic conditions for one or more of the previously described modes and/or features that relate to one or more of the state variables depicted in FIG. 17. The following tables illustrate:
Single Zone Logic For type I And II Modules:
Dual Zone Logic For Type I And II Modules:
Note: Drive if downstream zone clear or if zone after that is clear
Exiting from sleep under any circumstances results in an awakened zone setting own drive to 1 for 5 S before returning to transport logic.
Case A occurs when the jammed box is moved to the next downstream photo and case B occurs when a jammed box or object is removed.
The utilization of a sleep enable line to stop a downstream drive when a jam occurs at an upstream photo is a logic technique to minimize communications. The use of a sleep signal during jam generally implies that sleep mode and jam mode be exclusive. Thus, one mode may not be entered unless the other mode has terminated.
Logic:
Slug is set by dipswitch and is optional for a single contiguous group of zones including the master zone. Master module external slug line (screw terminals) transition from open to closed contacts (V plus to zero) and starts a non-retriggerable one shot slug timer in the master. The master asserts the slug control output (in the flat cable) and each type I, or II or III zone controller with slug enabled will turn on own drive, wait 50 mS then pass the slug signal on to the next zone.
When the slug timer is timed out AND the master module external slug line is open, the master will remove the slug control output from the flat cable and each type I, II or III module, if slug is enabled by dipswitch, will sequentially clear implied state variables TTO and TFM, then turn off its drive, wait 50 mS and then remove the slug signal to the next zone. Modules with slug disabled by dipswitch will ignore the slug signal on the flat cable and will not pass it upstream.
Zone Release:
Zone release only affects the type IV (master)—all other zones continue to process transport logic. The on delay for zone release is active for both counting and one shot timing. The external zone release (screw terminal) contact transition from open to closed (V plus to zero) starts an ON delay which in turn triggers the non-retriggerable one shot zone release timer and actuates drive. If, during timing, the zone release switch transitions open to closed a second time, the zone release one-shot timer is terminated as if it had timed out. After the one shot times out, the drive turns off, unless the contacts are still held closed, in which case the drive remains running until the contacts open. If the one shot is set to zero, this logic will respond as if the one-shot had been set to a nonzero value and timed out. In other words, if the one shot is set to zero, the drive will actuate when the contact closes and remain running until the contacts are released. If a non-zero zone release counter value is selected, counting is enabled. If a non-zero one-shot timer value is then set, the module resets the counter value to zero. If a non-zero zone release one-shot timer value is selected, timing is enabled. If a non-zero counter value is then set, the module resets the one-shot timer value to zero. Both are disabled by selecting a zero for both.
Counting:
Type IV (master) drive is actuated and preset count is decremented by 1 on each 0 to 1 (blocked to unblocked) transition of own photo. Type IV (master) reverts to standard transport and accumulation logic when count reaches zero. Count remains active through sleep cycles and power down cycles. Count is reset to zero when zone release switch transitions open to closed a second time.
Additional Master Logic:
Dual zone logic:
In dual zone logic, the type IV (master) drives when TTO=1. In the type IV (master) module, the on delay typically operates only with transport logic. The state of the nonexistent “zone” downstream of the type IV master is dummied in as 0 (blocked) so that the zone upstream of the type IV master has correct input for the dual zone logic. The zone full output follows its own photoeye (when own eye is blocked, zone full output actively sinks).
Additional Type III Zone Specific Logic:
Single Zone Logic
Dual zone logic for type III is similar to type I and II logic. The type III module is typically the first module (most upstream) in the system. It has an external product fill switch that operates as follows:
When fill switch is closed, input voltage goes to a near zero value and this transition causes own drive to actuate until either the switch is released and closed a second time or when own eye goes to 0 (blocked). When own eye is blocked, the switch is ignored and logic decides if the actuator should drive. The zone full output follows own photo-eye (when own eye is blocked, zone full output actively sinks).
Referring now to
A switch diagram 1900 in
A switch diagram 2000 in
A switch diagram 2100 in
Referring to
Referring now to
It is noted that respective cut-outs depicted can be provided with a knock-out covering, such that if a feature is not employed for a respective zone module type, then the knock-out covering can remain intact, thus substantially covering non-utilized openings. A cut flat cable trunk line is illustrated at 2414 and 2418 that can be mated to vampire pins (illustrated below) via clamping components 2422 and 2426. As illustrated, screws 2430 can be employed through the clamping components 2422 and 2426 to secure the flat cable to the housing 2410 and associated vampire pins described below. It is further noted that more or less screws 2430 can be employed, wherein the screws can mate to nuts (shown below) molded into the housing 2410 or alternatively, taper into the housing via tapered/self-tapping threads.
The housing 2410 can include several receptacle and/or user interface locations. For example, an actuator port 2434 (e.g., female connector or receptacle) can be provided supporting multiple actuator types, the port including voltage inputs (e.g., 24 VDC) and current/voltage output's to drive the actuator (e.g., TTL, NPN, PNP, FET). An external port 2440 or receptacle can be employed to support zone release and stop signals, slug input/output signals, and zone state output signals. A commissioning port 2444 facilitates external zone module programming such as from an operator terminal or configuration device, and supports test mode connections (in parallel to vampire connections), wherein zone modules may be factory tested via the commissioning port without employing the flat cable 2414 and 2418, if desired. A sensor port 2450 or receptacle supports two and three-wire (or more) sensor types and includes voltage power inputs and current or voltage sensing inputs (e.g., 45 ma current input). At various locations on/through the housing 2410, user interface components can be provided that can be positioned in substantially any suitable location on or through the housing. This can include one or more pushbuttons illustrated at 2460, one or more light or LED ports at 2464, and one or more switches (e.g., rotary, dipswitch) at 2470 and 2480, respectively. As noted above, knock-out coverings can also be provided to cover unused interface or port options in the housing 2410—depending on the zone module type configured or selected.
Thus, as depicted in
What has been described above are preferred aspects of the present invention. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the present invention, but one of ordinary skill in the art will recognize that many further combinations and permutations of the present invention are possible. Accordingly, the present invention is intended to embrace all such alterations, modifications and variations that fall within the spirit and scope of the appended claims.
This application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/356,485, which was filed Nov. 13, 2001, entitled SENSING SYSTEM AND METHOD, which is incorporated by reference herein.
| Number | Name | Date | Kind |
|---|---|---|---|
| 3835444 | Plana et al. | Sep 1974 | A |
| 4284316 | Debaigt | Aug 1981 | A |
| 4444447 | Markwardt | Apr 1984 | A |
| 5037308 | Bryce et al. | Aug 1991 | A |
| 5044964 | Minerd et al. | Sep 1991 | A |
| 5064380 | Dale et al. | Nov 1991 | A |
| 5415556 | Schroll | May 1995 | A |
| 5509812 | Comerci et al. | Apr 1996 | A |
| 5620331 | Los et al. | Apr 1997 | A |
| 5660559 | Yamamoto et al. | Aug 1997 | A |
| 5675890 | Yamamoto et al. | Oct 1997 | A |
| 5722852 | Miek | Mar 1998 | A |
| 5967818 | Carron et al. | Oct 1999 | A |
| 6179644 | Adams et al. | Jan 2001 | B1 |
| 6328592 | Burke et al. | Dec 2001 | B1 |
| 6487091 | Malkowski et al. | Nov 2002 | B2 |
| Number | Date | Country | |
|---|---|---|---|
| 60356485 | Nov 2001 | US |
