A method and apparatus for performing error correction on data read from a multistate memory are disclosed. According to one embodiment of the present invention a cell in a memory device is read to generate a read voltage determined by a state of the cell and one of an ordered succession of encoded signals is selected based on the read voltage, where each encoded signal corresponds to a field of bits and adjacent encoded signals correspond to respective fields of bits that are different only in a single bit. The selected encoded signal is decoded to generate a field of uncorrected bits and a field of syndrome bits indicating any error in the uncorrected bits. The syndrome bits are decoded to generate correction bits to correct the error, and the uncorrected bits are combined with the correction bits to generate a field of corrected bits.

1. Field of the Invention
The present invention relates to methods and apparatus for performing error correction on data read from memory systems (preferably integrated flash memory circuits) which are "multistate" systems in the sense that each memory cell has more than two states (each state determining a different data value). More particularly, the invention is a method and apparatus for performing error correction on data read from a multistate memory system (preferably a flash memory circuit), in which the data read from each memory cell is encoded so that in response to detection of an error in the encoded data from one memory cell, the error is corrected by changing one bit of the encoded data.
2. Description of Related Art
Throughout the specification, including in the claims, the term "connected" is used (in the context of an electronic component being "connected" to another electronic component) in a broad sense to denote that the components are electrically or electromagnetically coupled with sufficient strength under the circumstances. It is not used in a narrow sense requiring that an electrically conducting element is physically connected between the two components.
Multistate memory systems are becoming increasingly commercially important. Such systems include one or more arrays of memory elements, with each memory element having more than two states (each state determining a different data value). The synonymous terms "cell" of a memory array and "element" of a memory array are used interchangeably herein. A flash EEPROM multistate memory system is described in U.S. Pat. No. 5,043,940, issued Aug. 27, 1991, and an electrically alterable non-volatile multistate memory system is described in U.S. Pat. No. 5,394,362 issued Feb. 28, 1995.
Throughout the specification, including in the claims, the term "bit" is used herein to denote the data stored in one memory element of a memory system (which can be either a multistate memory system or a two-state memory system). In the special case of a two-state memory system, each element stores a "binary" bit (whose value can be denoted by the binary representation "0" or "1"). In the special case of a four-state memory system, each element stores a bit having one of four possible values (which can be denoted by the binary representations "00", "01", "10", and "11").
It has been proposed to design nonvolatile memory chips (integrated circuits) as multistate memory systems, so each memory element ("cell") of such a system has more than two states. Since analog values can be stored on the floating gate of a typical nonvolatile memory cell (e.g., a flash memory cell), it is possible to define more than two states for each such cell and hence reduce the area per stored bit for each cell. It is predictable that improved technology will continue to reduce the practical size of memory cells and that in some designs, a cell will be implemented as an intersection of two poly elements.
A problem with multistate storage is that by putting more states on each cell, the effective voltage range for each state becomes smaller. E.g., for a 5 volt window of operation on a floating gate (this window being determined by the particular circuitry used to "read" the cell), one can define the midpoint to be the boundary (or threshold) between the two states. Thus, a voltage stored on the gate determines a first state (corresponding to a first binary bit) if it is detected to be in the upper 2.5 volts of the window, and a voltage stored on the gate determines a second state (corresponding to a second binary bit) if it is detected to be in the lower 2.5 volts of the window. However, if a "read" circuit having the same window is used to distinguish between four states of the floating gate, each state corresponds to only 1.25 volts of the window. So, the noise margin for each state (e.g., the maximum range of voltage change, from the center of the window portion for the state, before the state is no longer valid) is reduced by a factor of two when the floating gate is used as four-state cell rather than a two-state cell.
There is also a limit to the precision with which circuitry can store an analog value on the floating gate of a nonvolatile memory cell. With today's architectures and high densities, cells across a nonvolatile memory array do not all behave identically. For these reasons, conventional circuitry for performing a program or erase of the bits in a nonvolatile memory array is typically designed to perform the task in an algorithmic manner in which the circuitry asserts an appropriate voltage level to a cell, then interrogates the value of the cell, and if the cell has not yet developed a sufficient margin, the circuitry again asserts an appropriate voltage level thereto. Using such circuitry, incremental varying of the voltage on a floating gate of each cell is not difficult, so that multistate storage becomes feasible.
To reduce the cost of nonvolatile memory systems, defective memory arrays can be tolerated and error correction employed to regain the data integrity. If one allows memory arrays having a few bad elements to be used in a system, the price of the system can be substantially reduced since much greater manufacturing yield can be attained. In order to enable the reader to more readily appreciate the present invention, we next describe (with reference to FIGS. 1 and 2) a nonvolatile memory system having conventional design, which includes conventional error detection and correction circuitry, including ECC encoder 40, ECC decoder 41, error correction unit 42, and syndrome decoder 43 (of FIG. 1).
Nonvolatile memory chip 3 of FIG. 1 includes an array 16 of nonvolatile memory cells, each cell comprising a transistor having a floating gate capable of semipermanent charge storage. The current drawn by each cell depends on the amount of charge stored on the corresponding floating gate. Thus, the charge stored on each floating gate determines a data value that is stored "semipermanently" in the corresponding cell.
In one particularly useful implementation of memory chip 3, each cell of array 16 comprises a flash memory device (a transistor). The charge stored on the floating gate of each flash memory device (and thus the data value stored by each cell) is erasable by appropriately changing the voltage applied to the gate and source (in a well known manner).
As shown in FIG. 1 (a simplified block diagram of nonvolatile memory chip 3), chip 3 includes a host interface 10 (including an I/O buffer for input data received from an external device and output data to be asserted to an external device), an address buffer 30, row decoder circuit (X address decoder) 12, column multiplexer circuit (Y multiplexer) 14, memory array 16 (comprising columns of nonvolatile memory cells, such as column 16A), sense amplifier circuit 15, and control unit 29.
Address bits received at interface 10 from an external device are asserted to address buffer 30. In response to a set of address bits A0 through Ap received from an external device, address bits A0 through An are asserted from buffer 30 to X decoder 12, and address bits An+1 through Ap are asserted from buffer 30 to Y multiplexer 14.
Chip 3 executes a write operation by receiving data bits (to be written to memory array 16) from an external device at interface 10, buffering the data in interface 10, including ECC check bits with the data (in unit 40), and then writing the data (and ECC check bits) to the appropriate memory cells of array 16. Chip 3 can also be controlled to execute a read operation in which data that has been read from array 16 undergoes error detection and correction in units 41, 42, and 43, and the corrected data is then buffered in interface 10 and asserted to the external device.
Since the cells of array 16 are flash memory cells, data is typically written to cells which have been erased. Each cell is either allowed to remain in the erased state, or is programmed to a desired state (a single programmed state when array 16 is operated as a binary memory, and a selected one of at least two different programmed states when array 16 is operated as a multistate memory) by applying appropriate voltages to the source, drain, and control gate of the cell for an appropriate time period (using write driver circuitry within circuit 14). This causes electrons to tunnel or be injected from a channel region to a floating gate. The amount of charge residing on the floating gate determines the voltage required on the control gate in order to cause the cell to conduct current between the source and drain regions.
In typical implementations, the FIG. 1 system is designed so that when it executes a write or read operation, it processes multiple bits of data in parallel. When executing a write operation with such an implementation of the system, sets of X bits of input data (where X is an integer greater than one) are received in parallel at ECC encoder 40, and encoder 40 generates M check bits for each X-bit set of data (typically X=8, and M=4). It is irrelevant to operation of ECC encoder 40 whether each set of X binary data bits that encoder 40 receives is to be stored in a single cell of array 16 (as where array 16 is operated as a multistate memory) or in X different cells of array 16 (as where each cell of array 16 is operated as a binary memory device). Encoder 40 asserts each set of X+M data and check bits in parallel to circuit 14 which causes them (or a sequence of subsets of them) to be written in parallel to cells of array 16 determined by corresponding address bits supplied to circuits 12 and 14. When each cell of array 16 is operated as a multistate device having four states, the write driver circuitry within circuit 14 writes two bits (two data bits or two check bits) in each cell by placing the cell in one of three programmed states (or allowing the cell to remain in an erased state).
When executing a read operation with the implementation of the FIG. 1 system described in the previous paragraph, the system reads Z-bit sets of cells in parallel (Z is an integer, typically equal to four or eight). In reading such a set of cells, sense amplifier circuit 15 outputs ZN binary bits indicative of the data stored in the Z cells (where each cell has one of 2.sup.N states). S-bit subsets of each set of ZN binary bits are asserted in parallel from circuit 15 to ECC decoder 41 (where S can be equal to or less than ZN. Decoder 41 generates T syndrome bits from each ZN-bit set that it receives (typically T=M) and asserts the syndrome bits in parallel to syndrome decoder 43. Decoder 41 also asserts a set of P binary bits of uncorrected data to correction unit 42. The uncorrected data bits may be identical to the P input data bits written to the cells being read, or they may differ (by one or more erroneous bits) from the P input data bits. Syndrome decoder 43 decodes the syndrome bits to generate a set of P correction bits in response to each set of syndrome bits that is indicative of one or more correctable errors, and decoder 43 asserts such set of correction bits in parallel to correction unit 42. Unit 42 processes each set of correction bits with the corresponding set of uncorrected bits to generate a set of P corrected bits, and asserts the corrected bits to interface 10 (to enable them to be asserted to an external device). Each set of corrected bits output from unit 42 bits comprises original data bits (data bits in the bit stream received by unit 41 which were determined not to be erroneous) and replacement data bits (bits which replace those data bits in the bit stream received by unit 41 which were determined to be erroneous).
Typically, decoder 43 includes circuitry for asserting a failure signal in response to a set of syndrome bits indicative of non-correctable errors in the corresponding set of uncorrected data. Such failure signal is fed back to control unit 29 (to cause unit 29 to assert appropriate status and control signals in response thereto) and/or asserted to interface 10 (for transmission to an external device).
Each of the cells of memory array circuit 16 is indexed by a row index (an "X" index determined by decoder circuit 12) and a column index (a "Y" index output determined by multiplexer circuit 14). FIG. 2 is a simplified schematic diagram of two columns of cells of memory array 16 (with one column, e.g., the column on the right, corresponding to column 16A of FIG. 1). The column on the left side of FIG. 2 comprises "n" memory cells, each cell implemented by one of floating-gate N-channel transistors N1, N3, . . . , Nn. The drain of each of transistors N1-Nn is connected to bitline 13, and the gate of each is connected to a different wordline (a different one of wordline 0 through wordline n). The column on the right side of FIG. 2 also comprises "n" memory cells, each cell implemented by one of floating-gate N-channel transistors N2, N4, . . . , Nm. The drain of each of transistors N2-Nm is connected to bitline 23, and the gate of each is connected to a different wordline (a different one of wordline 0 through wordline n). The source of each of transistors N1, N3, . . . , Nn, and N2, N4, . . . , Nm is held at a source potential (which is usually ground potential for the chip during a program or read operation).
Each of transistors N1, N3, . . . , Nn, and N2, N4, . . . , Nm has a floating gate capable of semipermanent charge storage. The current drawn by each cell (i.e., by each of transistors N1, N3, . . . , Nn, and N2, N4, . . . , Nm) depends on the amount of charge stored on the corresponding floating gate. Thus, the charge stored on each floating gate determines a data value that is stored semipermanently in the corresponding cell. In cases in which each of transistors N1, N3, . . . , Nn, N2, N4, . . . , and Nm is a flash memory device (as indicated in FIG. 2 by the symbol employed to denote each of transistors N1, N3, . . . , Nn, N2, N4, . . . , and Nm), the charge stored on the floating gate of each is erasable (and thus the data value stored by each cell is erasable) by appropriately changing the voltage applied to the gate and source (in a well known manner).
In response to each set of address bits A.sub.n+1 -A.sub.p, circuit 14 (of FIG. 1) determines a column address which selects one (or a set of two or more) of the columns of cells of array 16 (connecting the bitline of the selected column to Node 1 of FIG. 1), and in response to address bits A.sub.0 -A.sub.n, circuit 12 (of FIG. 1) determines a row address which selects one cell in each selected column. Consider an example in which the column address selects the column on the right side of FIG. 2 (the column including bitline 23) and the row address selects the cell connected along wordline 0 (the cell comprising transistor N2). To read the data value stored in the selected cell, a signal (a current signal) indicative of such value is provided from the cell's drain (the drain of transistor N2, in the example), through bitline 23 and circuit 14, to Node 1 of FIG. 1. To write a data value to the selected cell, appropriate voltages are provided to the cell's source, gate, and drain.
More specifically, chip 3 of FIG. 1 executes a read operation as follows. In response to a read command (supplied from control unit 29, or from an external device through interface 10), a current signal indicative of data values stored in the cells of array 16 (a "data signal") determined by the current row and column addresses is supplied from the drain of each selected cell through the bitline of each selected cell and then through circuit 14 to sense amplifier 15. This data signal is processed in amplifier 15 (in a manner to be described below), the output of amplifier 15 undergoes error detection and correction in circuits 41, 42, and 43, and the corrected data output from unit 42 is asserted to interface 10.
The following description of the manner in which sense amplifier 15 and units 41, 42, and 43 process the data signal from each selected cell of array 16 applies to an operating mode of chip 3 in which chip 3 operates as a two-state memory system (so that each cell of array 16 determines a binary bit). A predetermined voltage is applied to the control gates of each selected cell of array 16 and the cells are read (i.e., the predetermined voltage is applied to all or selected ones of the wordlines of array 16 and the cells connected to such wordlines are read) using sense amplifier 15. If a selected cell is in an erased state, the cell conducts a first current and the data signal indicative of this current is converted to a first voltage in sense amplifier 15. If the selected cell is in the other state (the programmed state), it conducts a second current and the data signal indicative of this current is converted to a second voltage in sense amplifier 15 (the "second current" flowing through a programmed cell is negligibly small when the cell is read by a typical, conventional read operation). Sense amplifier 15 determines the state of each selected cell (i.e., whether it is programmed or erased corresponding to a binary value of 0 or 1, respectively) by comparing the voltage indicative of the cell state to a reference voltage. The outcome of each such comparison (an output which is either high or low, corresponding to a binary value of one or zero) is sent from sense amplifier 15 to ECC decoder 41. In response, decoder 41 and circuits 42 and 43 operate in the manner described above to assert a set of error-corrected data bits to interface 10 (unless decoder circuit 43 determines that the bits output from sense amplifier 15 contain uncorrectable errors, in which case decoder circuit 43 asserts the above-described "failure signal").
Circuits 40, 41, 42, and 43 implement any conventional error detection and correction operation (many such operations are well known).
U.S. Pat. No. 5,233,610, issued on Aug. 3, 1993, describes a non-volatile memory system which includes an array of memory cells and conventional circuitry for generating ECC check bits, writing the ECC check bits to an array with corresponding data bits of interest, and performing error detection and correction on data read from the array. The disclosure of U.S. Pat. No. 5,233,610 is incorporated herein by reference.
In conventional two-state memory systems, it is known to employ an ECC encoder (e.g., unit 40) and error detection and correction circuitry (e.g., units 41-43) to detect errors in single binary bits (each binary bit indicative of the state of one memory cell) and to correct each detected error by changing each erroneous binary bit. It had not been known until the present invention how efficiently to implement error correction in a multistate memory system.
Memory chip 3 of FIG. 1 can also execute an erase operation in which all or selected ones of the cells of memory array 16 are erased in response to a sequence of one or more commands (e.g., an "Erase Setup" command followed by an "Erase Confirm" command), by discharging a quantity of charge stored on the floating gate of each cell. Typically, all cells of array 16 or large blocks of such cells are erased at the same or substantially the same time during an erase operation. Each erase operation comprises a sequence of steps, including verification steps for verifying that the cells have desired threshold voltages at each of one or more stages of the erase operation.
More specifically, if cells of memory array 16 of FIG. 1 are to be erased, an "Erase Setup" command and then an "Erase Confirm" command are sent from an external device to interface 10. The commands are transferred from interface 10 to control unit 29. Control unit 29, which typically includes command execution logic and a state machine, processes the command to generate instruction data, and supplies the instruction data to circuit 14 and sense amplifier 15 (and to other components of memory chip 3 of FIG. 1) to cause chip 3 to execute a sequence of steps required for erasing the specified cells of array 16. These steps typically include verification steps for verifying that one or more of the cells have desired threshold voltages at each of one or more stages of the erase operation.
A conventional memory erase operation, of the type implemented by a memory system identical in relevant respects to chip 3 of FIG. 1, is described in greater detail in U.S. Pat. No. 5,557,576, filed Jul. 28, 1995 (and assigned to the assignee of the present application), the disclosure of which is incorporated herein in full by reference.
Although conventional error detection and correction of the type implemented by ECC encoder 40 and error detection and correction circuitry 41-43 of FIG. 1 is desirable in two-state memory systems (for the reason noted above) it is even more desirable to implement error detection and correction in multistate memory systems due to the reduced noise margin per state in the latter systems (as noted above). However, to do so requires using some of the cells of the array to store ECC check bits, which reduces the array's effective capacity for storing data bits of interest. The present invention is based on the inventor's recognition that:
1. the effective capacity of a memory array (operated as an array of multistate cells) can be maximized by minimizing the number of ECC check bits that must be stored with any given number of data bits to enable performance of error detection and correction on the data after it has been stored in the array; and PA1 2. if a specially chosen encoding method is employed to generate encoded data fields (each field typically consisting of two or more binary bits) which represent data (and ECC check bits) read from each of a set of multistate memory cells, error detection and correction can be performed on the data (after it has been read from the cells) in a manner requiring storage of a minimal number of ECC check bits with the data of interest.
Until the present invention, it had not been known to design or operate a multistate memory system to implement error detection and correction efficiently, in a manner minimizing the number of ECC check bits that must be stored with the data of interest to enable performance of the error detection and correction.

Method and apparatus for performing error correction on data read from a multistate memory


A writing implement in which a joint connecting an ink supply section and a ballpoint pen tip together is configured from three members. The three members configuring the joint are a substantially cylindrical center member, a substantially cylindrical surrounding member formed at the outer periphery of the center member, and an interposing member that is molded by a soft member molded so as to cover the outer periphery of the center member and the surrounding member. An annular gap section is provided between the center member and the surrounding member. The leading end of the ink supply section is fitted into the gap section. The joint is formed by two color molding. The center member and the surrounding member are molded by primary molding, and the interposing member is integrally molded onto the center member and the surrounding member by secondary molding.

Hitherto, in technology related to writing implements that enable tilting of the writing tip and improve the writing sensation, writing implements such as those described in Patent Document 1 are known in which an elastic body is interposed between a shaft body and a tip member, such that the writing tip is tilted by flexing of the elastic body according to the force during writing.


A fireplace, comprising an inner jacket and an outer jacket defining an air circulation path therebetween, is provided with a smoke chamber convection wall and a baffle convection wall oriented so as to efficiently transfer heat from the fire box to the air circulation path. A damper plate and a back draft blocking wall are positioned in the fireplace so as to effectively block back drafts in both the open and closed damper positions. The fireplace also includes exterior controls whereby the damper plate and an outside air vent can be controlled in a safe manner. A clean out shaft and a draft control are also provided to facilitate safe operation of the fireplace.

The present invention relates to commercial and residential fireplaces. More particularly, it relates to a metal prefabricated fireplace.
Wood burning fireplaces are commonly used as primary or supplemental heating sources. The wood burning process creates noxious smoke which must be evacuated through a fireplace chimney located proximate the burning wood. A large amount of heat generated by the fire escapes through the chimney. The burning wood also creates a safety hazard for those operating the fireplace, building a fire, and/or extinguishing a fire.
Accordingly, there is a need for a fireplace which efficiently transfers heat from the fire box to the room in which the fireplace is disposed. Further, there is a need for a fireplace which ensures the safety of those operating the fireplace, building a fire, and/or extinguishing a fire.


A sheet media handling system is provided for use in supporting a sheet which has been expelled from an ink-jet printer's output port while ink on a preceding sheet is allowed time to dry. The system employs a guide mechanism with an elongate channel which receives a predetermined side edge of an expelled sheet. The channel is provided with an elongate first channel segment which extends in substantially parallel fashion with a generally horizontal media outflow axis, and an elongate second channel segment which turns upwardly and inwardly from the first channel segment, thereby establishing a sheet-stiffening bow in the expelled sheet.

In a conventional ink-jet printer, sheet media are directed through a print cycle which includes picking up a sheet from an input tray, feeding it through the printer's printing zone, and then expelling it through an output port. Once expelled, the sheet falls to an output tray, consecutive sheets piling one on top of the other to form an output stack. Because ink-jet printers print using wet ink, and because sheets often are stacked immediately after printing, ink-jet printers have in the past experienced difficulty with blotting and/or smearing of ink upon contact between consecutively printed sheets. This has been particularly apparent where the ink drying time exceeds the time between printing of consecutive sheets. Although a variety of solutions have been proposed to deal with this problem, none have provided adequate ink drying time without some cost to the printer's efficiency, versatility or size.
Some manufacturers have, for example, attempted to eliminate ink smearing and blotting problems by decreasing the ink's drying time. One solution has been to employ quick-drying ink, or specially coated paper. These products, however, have not always been available, and have often produced poor quality print. Another solution has been to provide some sort of drying lamp or heater adjacent the printed media, but this adds to the complexity of the printer, and consequently adds to the printer's price.
Other manufacturers have attempted to delay the deposit of printed sheets in the output tray so as to provide the previously-printed sheet with adequate drying time. The most basic of such solutions have involved simply slowing printer throughput by creating an artificial time delay between the printing of consecutive sheets. Although this solution does increase the time available for ink to dry, it has proven unacceptable in view of the ever-increasing desire to improve printer efficiency and speed.
Another solution proposed by printer manufacturers has been to employ a passive drop scheme wherein a sheet emerging from the printer's output port is guided along rails which suspend the sheet above the output tray. At the completion of printing, the sheet simply drops of its own weight into the output tray, the previously-printed sheet having had an opportunity to dry during printing of the present sheet. However, passive drop schemes are not always reliable due to a phenomenon known as cockling. As a result of such cockling, sheets do not always drop into the output tray after printing, but instead are pushed forward and out of the printer by the following sheet. This cockling effect becomes more pronounced with environmental extremes and large amounts of ink on the sheet.
Yet another common solution has involved the use of an active drop mechanism wherein a printed sheet is guided along a pair of movable wings which temporarily support the sheet above the printer's output tray. Once printing is completed, the wings retract, often pivotally, allowing the sheet to fall to an output tray below. The previously-printed sheet thus is provided with time to dry during printing of the present sheet. Although generally effective, active wing arrangements generally are not suitable for a wide range of media widths, and can significantly increase the printer's chassis size. Active drop mechanisms also may present problems related to sheet sail, a phenomenon which can result in sheets gliding out of the printer upon retraction of the wings.


A method of inspecting a heat exchanger including a plurality of tubes having ends fixed in a tubesheet includes the steps of: establishing a baseline for each tube of its location in the tubesheet and its unique eddy current pattern resulting, at least in part, from fixing the tube end in the tubesheet; inserting an eddy current probe into a first identified tube; obtaining eddy current data for the first identified tube in the region of the tubesheet; comparing the eddy current data obtained for the first identified tube with the baseline eddy current data for the tube, in order to verify the correctness of the tube identification; and accepting the obtained eddy current data if the correctness of the tube identification has been verified by the comparison. A computer program product for automatically carrying out the steps of the foregoing method is also disclosed.

1. Field of the Invention
The present invention relates generally to a method of inspecting a heat exchanger and, more particularly, to a method of using unique, tube-specific tubesheet eddy current signal characteristics to verify the identity of individual steam generator tubes having ends disposed in a tubesheet. The invention also relates to a computer program product for performing a method of inspecting steam generator tubes.
2. Background Information
Heat exchangers, such as, for example, steam generators used in pressurized water nuclear powered electric generating systems, generally include thousands of U-shaped heat exchanger tubes disposed within a generally cylindrical pressure vessel. The ends of the heat exchanger tubes are secured within a transverse plate called a tubesheet, which separates the steam generator into a primary side and a secondary side. Heated primary fluid from the nuclear reactor is passed through the tubes to effectuate a heat transfer with the secondary working fluid which, in turn, drives the turbo-machinery used to generate electricity. The primary fluid can be radioactive. Accordingly, to prevent leakage of the reactor coolant into the secondary side of the generator, which would contaminate the steam, the heat transfer tubes must be periodically inspected for flaws and degradation such as cracks, pits, dents and tube wall thinning. If a degraded tube is discovered, it is typically plugged at both ends. In view of the thousands of tubes in the steam generator, plugging of a few tubes does not appreciably affect the efficiency of the heat transfer.
Eddy current testing is a well known, commonly used method of nondestructive testing of steam generator tubes. Generally, in performing an eddy current test on steam generator tubes, a sensor or probe is advanced through the tube as signals are generated and recorded for later analysis. See, e.g., U.S. Pat. No. 3,302,105 (illustrating and describing the eddy current signatures of various types of tube defects); see also U.S. Pat. Nos. 3,693,075; 4,194,149; 4,207,520; and 4,631,688. U.S. Pat. No. 4,763,274, which was filed on Jun. 24, 1986 and issued to the assignee hereof, discloses eddy current inspection processes for nuclear steam generator tubes and computer analysis of the eddy current data for automatically detecting flaws in the heat transfer tubes of a steam generator.
The Electrical Power Research Institute (EPRI) is developing new criteria for data quality acceptance in eddy current steam generator inspection. One such requirement is to verify and ensure that the eddy current sensor or inspection probe is delivered to the correct tube for inspection thereof. Conducting efficient tube inspection and/or repair while minimizing the impact of such inspection on the steam generator operations (i.e., minimizing the downtime required for such inspection), requires quick and accurate tube identification and the ability to record information with respect to each tube for future reference and comparison.
Historically, heat exchanger tube inspection involved the use of technicians who would conduct tests using a variety of inspection devices (i.e., an eddy current probe) and then record the results for future reference. In view of the thousands of tubes in a typical generator, this was an extremely time consuming, arduous and tedious procedure, the results of which were highly susceptible to human error. Ensuring the accurate identity of an individual tube or relocating to a tube was also very difficult. Accuracy was dependent on the analyst correctly counting tubes to locate the desired tube. Moreover, it was a dangerous process, potentially exposing the technicians to an unacceptable dose of radiation.
A relatively recent improvement upon such manual inspections involves the use of computer controlled robotic arms with specialized end-effectors capable of conducting the inspection or repair. Generally, the robotic arm is secured beneath the tubesheet with the end-effector mounted at the end of the arm. The end-effector typically comprises an assembly mounted on the end of the robotic arm and including, for example, a television camera, one or more illumination sources, inspection tools, such as an eddy current sensor or probe, and tooling to plug effected tubes. A computer, under the control of an operator, is used to control the robotic arm. The operator can move the end-effector across the tubesheet using, for example, a joystick or by specifying a target tube destination using x, y cartesian coordinates. U.S. Pat. Nos. 5,751,610, 5,838,882 and 5,878,151, disclose several representative prior art robotic arm end-effectors for use in inspecting steam generator tubes. However, while such robotic systems have improved the inspection process, they are relatively deficient at pin-pointing or relocating to a specific tube, in order to, for example, check on the status of the tubes degradation or the integrity of a prior tube repair.
Accordingly, there have been several attempts to improve the accuracy and efficiency with which industrial steam generator tubes are identified. Known prior art methods of tube identification involve, for example, physical modification of the tube ends to create a computer readable marking system or use of a computerized tube position visualization and verification system.
U.S. Pat. No. 5,321,887, for example, discloses a process of marking each tube with a binary bar code formed from circular impressions and the absence of such impressions. The bar code is embossed on the exterior of the tubes during manufacture or alternatively on the interior of the tubes after they have been fixed in the tubesheet. A cartography is then produced in the factory or after installing the steam generator in the nuclear power station, using the bar codes to associate position information, in Cartesian coordinates, with the location of each tube in the tubesheet. When it is subsequently desired to locate a given tube, a computer is used to access the cartography and to provide automated control of the robotic arm to the desired tube. However, such a method requires physical modification of the tubes and is timely and costly to implement, particularly when modifying an existing steam generator to implement the technology.
U.S. Pat. No. 6,282,461, which was filed on Jul. 9, 1999 and issued to the assignee hereof, discloses an independent tube position verification system including a television camera mounted on the robotic arm end-effector, in order to visually track changes in position as the robotic arm changes position with respect to the tubesheet. The camera outputs successive image frames in order to track the physical displacement of a recognizable reference artifact, such as a plugged tube, as the end-effector moves across the tubesheet. The physical displacement information is then converted into velocity and direction information and compared against position information maintained by the robotic arm encoder. Mismatched readings indicate a loss of tracking integrity requiring re-calibration of the system.
Such image capturing and analysis systems are susceptible to several disadvantages. Factors such as illumination and associated shadows, robot arm bending, absence of an adequate reference artifact from which to calculate displacement and camera image distortion caused by, for example, the speed at which the end-effector is traveling and the end-effector's location relative to the tubesheet, can negatively impact the accuracy of the system. Calibration of robotic inspection systems can be problematic. The accuracy of the robotic arm and end-effector movement depends on the robot system design, calibration, the robot's onboard encoder or analyzer and communication of the robot with the computer control system. For example, it is not uncommon for the robotic arm to be subject to bending forces, particularly when it is fully extended with respect to its mounting location. Such bending can result in the robotic arm being located at a distance and location different from that calculated by the robot's onboard tube locating encoder or analyzer. It is, therefore, possible for the wrong tube to be inspected and/or repaired, thereby resulting in the potential of plugging or repairing a perfectly good tube or leaving a degraded tube un-inspected or un-repaired and returning it to service in its degraded condition. Additionally, known prior art methods of tube identification, whether from the robot or from the tube position verification system, do not update the data collection system to include the current status of the tube for updated future reference.
There is a need, therefore, for a method of quickly and accurately identifying and verifying the identity of the tubes of a steam generator for inspection and/or service thereof, that overcomes the aforementioned disadvantages.
Accordingly, there is room for improvement in heat exchanger inspection and in heat exchanger tube identification and verification.

Method of inspecting a heat exchanger and computer program product for facilitating same


The present invention relates to a process for permanently coating the inner surface of columns, capillaries and microchannel systems with hydroxylic polymers, such as polyvinyl alcohol, and to the thus prepared columns, capillaries and microchannel systems and their use.

The present invention relates to a process for permanently coating the inner surface of columns, capillaries and microchannel systems with hydroxylic polymers. Such interior coating is effected by treating the surface to be coated with a solution of a cross-linking reagent and a solution of the polymer, which results in an immobilization of the polymer on the capillary surface. The process described is particularly suitable for the coating of fused silica (FS) capillaries and systems having microfluidic structures for capillary electrophoresis with a highly hydrophilic polymer, such as polyvinyl alcohol. The invention further relates to the thus prepared columns and capillaries, and their use in capillary electrophoresis and related techniques.
Methods of capillary electrophoresis (CE) can be used to obtain separations of mixtures of various compounds by differential migration of the analytes in an electric field. The separations are usually performed in capillaries of fused silica filled with a, mostly aqueous, electrolyte. The inner surfaces of such capillaries have the following properties in their application in capillary electrophoresis:
Due to the acidic silanol groups of the fused silica material, there is an electroosmotic flow (EOF) towards the cathode which depends on the pH value of the electrolyte. However, in uncoated fused silica capillaries, the absolute value of the EOF can highly vary, which significantly deteriorates the precision and reproducibility of analyses in capillary electrophoresis.
The fused silica surfaces exhibit a highly adsorptive behavior towards many compounds. In particular, basic compounds and large biopolymers, such as proteins, are strongly adsorbed from aqueous solutions. This deteriorates the quality and resolution of a capillary-electrophoretic separation of such compounds considerably or even makes it impossible.
The properties of such capillaries can be changed in a well-aimed manner by providing the capillary surface with a suitable coating. Coated fused silica capillaries are employed in capillary electrophoresis for the following reasons:
For a manipulation of the electroosmotic flow: By coating the surface, both the absolute value and the direction of the EOF can be changed. A CE separation can be optimized thereby with respect to resolution and analysis time. The constancy of the EOF is mostly higher in coated capillaries as compared to untreated fused silica capillaries, which results in improved reproducibility of CE analyses.
To suppress the interactions between analytes and the wall, coatings are employed which exhibit a low adsorptivity towards the compounds to be examined. Higher separation efficiencies of adsorptive compounds, such as proteins, and thus a better resolution is thereby achieved in capillary-electrophoretic separations.
A suitable inner coating of capillaries for CE should have the following properties: i) a constant EOF over a broad pH range; ii) long-term stability towards a wide variety of electrolytes; iii) the adsorptivity of the coating should be as low as possible towards a wide variety of analytes.
Fused silica capillaries can be very easily coated with cationic polymers, such as Polybrene(copyright) or polyvinylamine [M. Chiari, L. Ceriotti, G. Crini, and M. Morcellet; J. Chromatogr. A 836(1999) 81], because these are strongly adsorbed to the contrarily charged fused silica surfaces. Due to the reversed, anodic EOF, these capillaries are particularly suitable for the accelerated analysis of highly mobile anions.
The use of hydrophilic non-ionic capillary interior coatings, such as polyacrylamide or polyethylene glycol coatings, has proven particularly useful in capillary electrophoresis, because such coatings both significantly reduce the EOF and suppress the adsorption of basic compounds and especially proteins to the capillary wall. Different methods have been developed for chemically binding hydrophilic molecules to a fused silica capillary surface, mostly after previous silanization (S. Hjerten; J. Chromatogr. 347 (1985) 191; G. M. Bruin, J. P. Chang, R. H. Kuhlmann, K. Zegers, J. C. Kraak and H. Poppe; J. Chromatogr. 471 (1989) 429; K. A. Cobb, V. Dolnik and M. Novotny; Anal. Chem. 62 (1990) 2478; A. Malik, Z. Zhao and M. L. Lee; J. Microcol. September 5 (1993) 119).
Among all the capillary coatings described in the literature, those based on polyvinyl alcohol (PVA), which has to be considered the most hydrophilic polymer, have proven to exhibit a particularly good performance. In capillaries coated with PVA, extraordinarily high separation efficiencies could be achieved, especially for proteins. In addition, the electroosmotic flow is suppressed over a broad pH range and very stable (M. Gilges, H. Kleemixcex2 and G. Schomburg; Anal. Chem. 66 (1994) 2038).
The preparation of capillaries coated with polyvinyl alcohol is relatively difficult to perform with conventional methods. This is due to the particular properties of polyvinyl alcohol: i) Polyvinyl alcohol is soluble only in water, and therefore classical chemical reactions in organic solvents for fixing the polymer to the capillary surface, such as by silanization, are not possible. ii) Due to their high hydrophilicity, aqueous solutions of polyvinyl alcohol will wet the fused silica capillaries but poorly; therefore, it is difficult to produce homogeneous films of polyvinyl alcohol on the capillary surfaces by adsorption alone. To date, the following methods have been described for producing PVA-coated capillaries:
1) Gilges and Schomburg (M. Gilges, H. Kleemixcex2 and G. Schomburg; Anal. Chem. 66 (1994) 2038; DE 42 30 403 A1) have applied a PVA film to a capillary wall by adsorption of polyvinyl alcohol from an aqueous solution to the fused silica surface. Thus, a capillary filled with the PVA solution was emptied very slowly in a nitrogen flow using overpressure. Only by carefully and very slowly emptying the capillary, a homogeneous polymer film could be produced on the surface despite the poor wetting of the surface by the polymer solution. In the original publication (Anal. Chem. 66 (1994) 2038), a flow-restricting capillary was coupled to the capillary to be coated for a controlled emptying.
The immobilization of the polymer film, which is water-soluble at first, was then effected by heating in a gas flow. Polyvinyl alcohol is thereby converted to a pseudocrystalline state and thus insoluble in water.
With this method, stable polyvinyl alcohol coatings could be applied to the capillaries without expensive multistep chemical reactions. However, since the polymer film is applied in this method from a polymer solution which wets the fused silica wall but very poorly, this part of the process is rather error-prone.
2) Shieh (U.S. Pat. No. 5,605,613) was able to prepare PVA-coated capillaries in a multistep process. Thus, a hydrophobic intermediate layer was first bound to the fused silica surface through Sixe2x80x94Oxe2x80x94Si linkages. Polybutadienyltriethoxysilane was mentioned as a preferred reagent. Thereafter, the monomer vinyl acetate is bound to this layer through its vinyl functionality by free-radical polymerization. Subsequently, the polyvinyl acetate covalently bonded to the intermediate layer is hydrolyzed and thus converted to polyvinyl alcohol.
The procedure described by Shieh is based on a lengthy multistep reaction. The first step is based on a silanol derivatization and is therefore highly dependent on the concentration of silanol groups on the fused silica surface and thus on the respective capillary preparation process and/or the chosen preliminary treatment of the capillary.
3) The method described by Karger (U.S. Pat. No. 5,840,388) is very similar to that described by Shieh. An intermediate layer which will react with the monomer vinyl acetate is also first applied through Sixe2x80x94Oxe2x80x94Si linkages by a silanization reaction in organic solvents, preferably using vinyltrimethoxysilane. Then, as in Shieh, covalently bonded polyvinyl acetate is generated in a free-radical copolymerization reaction of the intermediate layer with vinyl acetate. Then, following hydrolysis, polyvinyl alcohol covalently bonded to the silica surface is obtained by analogy with Shieh.
It has been the object of the invention to provide a quick and reliable process for coating capillaries with hydroxylic polymers, preferably polyvinyl alcohol, and their use in electromigrative separation methods.
This object of permanently coating a capillary with a polymer, preferably polyvinyl alcohol, is achieved by chemically cross-linking the dissolved polymer during the coating process and thus immobilizing it on the capillary wall. Thus, a dissolved bi- or multifunctional reagent, preferably a dialdehyde, such as glutaraldehyde, is transferred into the capillary. Thereafter, a plug of the polymer solution, preferably a polyhydroxy compound, such as polyvinyl alcohol, is forced through the capillary, for example, using a pressurized gas, such as nitrogen or other gases usual in a laboratory, e.g., helium, argon, hydrogen, or by means of a mercury plug. The reaction occurring between the polymer solution and the cross-linking reagent enables a good wetting of the capillary wall with the polymer solution and at the same time immobilizes the produced polymer layer on the capillary wall. The thus generated very stable polymer coatings can be employed immediately after drying by additional flushing with gas, and exhibit the following properties in capillary electrophoresis: suppressed EOF both in acidic and alkaline pH ranges, very high separation efficiencies for adsorptive analytes, such as basic proteins, long-term stability upon use of aqueous and non-aqueous electrolytes, stability towards highly acidic and alkaline rinsing solutions, such as diluted HCl or NaOH solutions.
This process enables PVA-coated capillaries of high quality to be prepared very quickly and with a high reliability. The coating process takes a few minutes, and the drying of the capillaries is effected in a nitrogen flow over several hours. The drying time can be significantly reduced by increasing the temperature so that the capillaries can be available in less than an hour.
Capillaries coated with PVA and glutaraldehyde as a cross-linking reagent in accordance with the present process can be prepared with substantially higher reliability as compared to the analogous process with no cross-linking reagent (with exclusively thermal immobilization). FIG. 1 shows the separation efficiencies achievable in CE separations of basic proteins for different capillaries prepared successively. If glutaraldehyde is used as the cross-linking reagent, very high separation efficiencies (N greater than 400,000) for the strongly basic protein cytochrome c can be achieved in over 80% of the capillaries prepared.
However, if the coating is effected without the cross-linking reagent, separation efficiencies N of greater than 400,000 are obtained in only 20% of the capillaries prepared. In 30% of the capillaries thus prepared (Nos. 1, 5, 12, 15), no signal can be obtained for the strongly adsorptive protein, because it was irreversibly adsorbed as with uncoated capillaries.
In addition to classical capillaries, surfaces of systems having microfluidic structures, such as microchannels of a capillary electrophoresis chip (CE chip), can also be coated with the present process. Thus, it becomes possible to suppress the electroosmotic flow in CE chips and to prevent the adsorption of analytes such as proteins. By selectively coating individual microchannels of a more complex system while others remain uncoated, electroosmotically induced liquid flows in networks of microchannels can be manipulated in a well-aimed way. Thus, for CE chips with crossed microchannels, it is possible to coat only the main channel relevant to the separation and thus to enable the analysis of adsorptive proteins while the injection channel remains uncoated and enables electroosmotic injection in the direction towards the cathode.
The present process for the preparation of polymer-coated capillaries is characterized by the following properties:
Since the process is based on chemical cross-linking of the polymer and chemical binding of the polymer to the capillary wall is not required, it can be applied to a wide variety of capillary materials, such as glass, fused silica, various plastics, such as Teflon, pEEK, polyacrylates, and it is also applicable to channels having different structures, such as classical round capillaries, (rect)angular channels/capillaries and microchannels in microfluidic systems (such as CE chips).
The process is easy to perform.
The process is very quick.
The capillaries obtained can be repeatedly prepared in a very high quality (few rejections).
The coated capillaries prepared by this process have the following properties:
They can be repeatedly employed for separations.
They allow for CE separations of highly adsortive compounds such as proteins in acidic, neutral and alkaline electrolytes.
The electroosmotic flow is highly reduced over a broad pH range, at least from pH 2 to pH 10, and is highly constant.
The chemically immobilized PVA coatings have proven stable under the conditions of CE.
The capillaries are especially suitable for the following applications: CE separations of basic and acidic compounds, capillary gel electrophoresis, isoelectric focusing, CE separations with very low ionic strengths of the electrolyte, and CE separations with organic solvents as electrolytes, such as for the coupling of capillary electrophoresis with mass spectrometry.
The capillaries and microfluidic systems prepared according to the invention can be employed, inter alia, for the dosage of samples to be analyzed, e.g., in mass spectrometry, and for microsynthetic methods in chemistry.

Coatings with cross-linked hydrophilic polymers


The invention provides a method for both disposing of an environmentally undesirable material comprising petroleum coke and the sulfur and heavy metals contained therein and of providing fuel for a process of making molten iron or steel preproducts and reduction gas in a melter gasifier having an upper fuel charging end, a reduction gas discharging end, a lower molten metal and slag collection end, and means providing an entry for charging ferrous material into the melter gasifier; introducing petroleum coke into the melter gasifier at the upper fuel charging end; blowing oxygen-containing gas into the petroleum coke to form at least a first fluidized bed of coke particles from the petroleum coke; introducing ferrous material into the melter gasifier through the entry means, reacting petroleum coke, oxygen and particulate ferrous material to combust the major portion of the petroleum coke to produce reduction gas and molten iron or steel preproducts containing heavy metals freed from combustion of the petroleum coke and a slag containing sulfur freed from combustion of the petroleum coke.

The invention relates to a method of both disposing of an environmentally undesirable material, namely petroleum coke and the sulfur and heavy metals contained therein, and of providing fuel for a process of making molten iron or steel preproducts and reduction gas in a melter gasifier.
Petroleum coke is a product of refinery operations and is produced in the United States utilizing three types of coke processing technology. Specifically these technologies as known to one skilled in the art are delayed, fluid and flexi. By far most petroleum coke in the United States is produced using delayed technology. In 1990, according to the U.S. Department of Energy, 55 refineries in the United States which had coking facilities and a refinery capacity of 8 million barrels per day produced slightly over 76,000 short tons per day of petroleum coke. The residual petroleum coke produced amounted to about 6% by weight of each barrel of crude oil processed by the refineries.
Petroleum coke is generally the bottom end of refinery operations after most of the light ends and oils have been recovered from the original crude. The make up of petroleum coke will vary depending on a number of factors including the crude being processed and the process being utilized. Generally on a dry basis petroleum coke will be composed largely (approximately 90%) of fixed carbon and typically include sulfur (0.05% to 6%) and nitrogen (2% to 4%). Various metals typically including vanadium, iron and nickel are found in petroleum coke. Usually, a typical petroleum coke contains about 10% volatile matter. Petroleum coke contains up to 10 to 15% moisture before drying.
Petroleum coke is produced either as blocky sponge coke or needle coke from delayed cokers or in a shot size form from fluid bed cokers. Sponge coke from delayed cokers is by far the most important coke produced in the United States. Calcined sponge coke is used primarily in the manufacture of graphite electrodes, anodes and shaped products. Approximately one-third of the sponge coke production is used in these products.
Until recent years the remainder of the petroleum coke in the U.S. was used as fuel for power plants and cement kilns. However due to the high sulfur content, the need for blending with coal to maintain ignition and flame stability and environmental problems, petroleum coke has become less suitable as a boiler fuel. The high sulfur content of petroleum coke also poses problems for cement kilns. Excess sulfur will cause finished concrete to expand and crack and also influences setting time. The high vanadium content also poses problems. Thus there is a substantial amount of excess petroleum coke which must be disposed. The high sulfur content and the relatively high amounts of metals such as vanadium and nickel make such disposal a real environmental problem which the present invention is directed to solving.
U.S. Pat. No. 4,849,015 to Fassbinder et al. discloses a method for two-stage melt reduction of iron ore, in which iron ore is prereduced substantially to wustite and at the same time melted down in a melting cyclone, and then liquid hot metal is produced in an iron bath reactor connected to the outlet of the melting cyclone and receiving the melted wustite by adding carbonaceous fuels and oxidizing gas to the melt. The resulting reaction gas from the melt is afterburned, and the dust-laden, partly burned reaction gases from the iron bath reactor are accelerated and further afterburned by adding a hot blast with a temperature of 800.degree. C. to 1500.degree. C., and at least a portion of such accelerated, after burned reaction gases are introduced into the melting cyclone to reduce and melt fresh iron ore.
Carbonaceous fuels, such as coke, carbonized lignite, petroleum coke, etc., but preferably coal of varying quality, are fed to the melt in the iron bath reactor. Slag-forming additives, such as lime, fluorspar, etc., are also fed to the iron melt to set the desired slag composition. Although it is irrelevant for the present invention whether these substances are introduced into the melt on the bath surface or from below the bath surface, it is preferable to add them through underbath feed nozzles.
U.S. Pat. No. 4,806,158 to Hirsch et al. discloses a process for the production of reduced iron oxide-containing materials. Iron oxide and solid carbonaceous reducing agent are charged into a first expanded fluidized bed, which is supplied with an oxygen-containing fluidizing gas. The gas residence time selected is controlled in the reactor containing the first fluidized bed so that the reduction potential will result in a reduction of the iron oxide material not in excess of the FeO stage. A gas-solids suspension discharged from the first fluidized bed is supplied to a second expanded fluidized bed, which is supplied with a strongly reducing fluidizing gas. Strongly reducing gas and a major portion of the resulting devolatilized carbonaceous material are discharged from the upper portion of the second fluidized bed. Reduced material having a metallization of 50 to 80% and the remaining devolatilized carbonaceous material are discharged from the lower portion of the second fluidized bed. Suitable carbonaceous materials include all coals, from anthracite to lignite, carbonaceous minerals and waste products, such as oil shale, petroleum coke or washery refuse, provided that they are solid at room temperature. The oxygen-containing gas preferably consists of oxygen or of oxygen-enriched air.
U.S. Pat. No. 4,897,179 to Mori et al. provides a method of producing reduced iron and light oil from iron ore and heavy oil which comprises a thermal cracking step of subjecting heavy oil to thermal cracking while retaining iron ore particles in a fluidized state to produce light oil and simultaneously to deposit coke as by-product on the surface of the iron ore particles; a gasification step of putting the coke-deposited ore in contact with an oxidizing gas including steam and oxygen in a fluidized state to react the coke with the gas thereby to produce a reducing gas containing hydrogen and carbon monoxide and of heating the coke-deposited ore upward of a reduction temperature of iron ore by partial oxidization of the coke; and a reduction step of reducing the coke-deposited iron ore in a fluidized state by the reducing gas to produce reduced iron. When the gasification step is performed by an oxidizing gas containing a majority of steam and up to 15 vol. %, based on the steam, of oxygen at 800.degree. -1000.degree. C. under a pressure of 0-10 kg/cm.sup.2 G, a reducing gas containing high-concentration hydrogen gas is obtained.
Slags of high sulfur capacity have been utilized in applications associated with ferrous metallurgy. Kleimeyer et al. in U.S. Pat. No. 4,600,434 describe the use of high sulfur capacity slag and magnesium metal to desulfurize molten iron while it is contained in a torpedo car. Quigley, U.S. Pat. No. 4,853,034, describes using a vanadium-bearing, high-magnesia synthetic calcium aluminate slag for absorbing sulfur during ladle refining of steel. Knauss et al., U.S. Pat. No. 4,695,318, describe using a synthetic slag similar to that of U.S. Pat. No. 4,853,034, and the refractory brick of the ladle itself, to desulfurize molten iron contained in said ladle.
In recent years methods utilizing a melter gasifier have been developed to produce molten iron or steel preproducts and reduction gas. Most of these processes utilize a coal fluidized-bed. A high temperature is produced in the melter gasifier utilizing coal and blown in oxygen to produce a fluidized bed and iron sponge particles are added from above to react in the bed to produce the molten iron.
Thus in European Patent B1-0010627, a coal fluidized-bed with a high-temperature zone in the lower region is produced in a melter gasifier, to which iron sponge particles are added from above. On account of the impact pressure and buoyancy forces in the coal fluidized-bed, iron sponge particles having sizes greater than 3 mm are considerably braked and substantially elevated in temperature by the heat exchange with the fluidized bed. They impinge on the slag layer forming immediately below the high-temperature zone at a reduced speed and are melted on or in the same. The maximum melting performance of the melter gasifier, and thus the amount and temperature of the molten iron produced, not only depends on the geometric dimensions of the melter gasifier, but also are determined to a large extent by the quality of the coal used and by the portion of larger particles in the iron sponge added. When using low-grade coal, the heat supply to the slag bath, and thus the melting performance for the iron sponge particles, decline accordingly. In particular, with a large portion of iron sponge particles having grain sizes of about 3 mm, which cannot be heated to the same extent as smaller particles by the coal fluidized-bed when braked in their fall and which, therefore, necessitate a higher melting performance in the region of the slag layer, the reduced melting performance has adverse effects in case low-grade coal is used.
A melter gasifier is an advantageous method for producing molten iron or steel preproducts and reduction gas are described in U.S. Pat. No. 4,588,437. Thus there is disclosed a method and a melter gasifier for producing molten iron or steel preproducts and reduction gas. A first fluidized-bed zone is formed by coke particles, with a heavy motion of the particles, above a first blow-in plane by the addition of coal and by blowing in oxygen-containing gas. Iron sponge particles and/or pre-reduced iron ore particles with a substantial portion of particle sizes of more than 3 mm are added to the first fluidized-bed zone from above. A melter gasifier for carrying out the method is formed by a refractorily lined vessel having openings for the addition of coal and ferrous material, openings for the emergence of the reduction gases produced, and openings for tapping the metal melt and the slag. Pipes or nozzles for injection of gases including oxygen enter into the melter gasifier above the slag level at at least two different heights.
Another process utilizing a melter gasifier is described in U.S. Pat. No. 4,725,308. Thus there is disclosed a process for the production of molten iron or of steel preproducts from particulate ferrous material as well as for the production of reduction gas in the melter gasifier. A fluidized-bed zone is formed by coke particles upon the addition of coal and by blowing in oxygen-containing gas by nozzle pipes penetrating the wall of the melter gasifier. The ferrous material to be reduced is introduced into the fluidized bed. In order to be able to produce molten iron and liquid steel preproducts in a direct reduction process with a lower sulfur content of the coal used, the ferrous material to be reduced is supplied closely above the blow-in gas nozzle plane producing the fluidized bed. An arrangement for carrying out the process includes a melter gasifier in which charging pipes penetrating its wall are provided in the region of the fluidized-bed zone closely above the plane formed by the nozzle pipes. The ferrous material to be melted as well as the dusts separated from the reduction gas and, if desired, fluxes containing calcium oxide, magnesium oxide, calcium carbonate and/or magnesium carbonate are introduced therethrough.
There is also a process known as the COREX.RTM. process (COREX.RTM. is a trademark of Deutsche Voest-Alpine Industrieanlagenbau GMBH and Voest-Alpine Industrieanlagenbau). This process is described in Skilling's Mining Review, Jan. 14, 1989 on pages 20-27. In the COREX.RTM. process the metallurgical work is carried out in two process reactors: the reduction furnace and the melter gasifier. Using non-coking coals and iron bearing materials such as lump ore, pellets or sinter, hot metal is produced with blast furnace quality. Passing through a pressure lock system, coal enters the dome of the melter gasifier where destructive distillation of the coal takes place at temperatures in the range of 1,100.degree.-1,150.degree. C. Oxygen blown into the melter gasifier produces a coke bed from the introduced coal and results in a reduction gas consisting of 95% CO +H.sub.2 and approximately 2% CO.sub.2. This gas exits the melter gasifier and is dedusted and cooled to the desired reduction temperature between 800 and 850.degree. C. The gas is then used to reduce lump ores, pellets or sinter in the reduction furnace to sponge iron having an average degree of metalization above 90% The sponge iron is extracted from the reduction furnace using a specially designed screw conveyor and drops into the melter gasifier where it melts to the hot metal. As in the blast furnace, limestone adjusts the basicity of the slag to ensure sulfur removal from the hot metal. Depending on the iron ores used, SiO.sub.2 may also be charged into the system to adjust the chemical composition and viscosity of the slag. Tapping procedure and temperature as well as the hot metal composition are otherwise exactly the same as in a blast furnace. The top gas of the reduction furnace has a net calorific value of about 7,000 KJ/Nm.sup.3 and can be used for a wide variety of purposes.
The fuels used in these processes are typically described as a wide variety of coals and are not limited to a small range of coking coal. The above-noted article from Skilling's Mining Review notes that petroleum coke suits the requirements of the COREX.RTM. process. Brown coal and steam coal which are relatively poor quality coal having a relatively high ash content i.e. plus 15%, have been identified as suitable for use in these processes. Coke made from coal has also been identified as a fuel for many of the processes utilizing melter gasifiers.

Method of providing fuel for an iron making process


An arciform photosensor assembly for use in an optical apparatus for detecting the radial intensity distribution of light scattered, for instance, from particles suspended in a fluid medium. The assembly includes three groups of arciform photosensor to be used for adjusting the optical axis of the optical apparatus in which this arciform photosensor assembly is used as a light detector.

The present invention relates to an arciform photosensor assembly for use in an optical apparatus for measuring the intensity distribution of light scattered forward by particles suspended in a fluid medium.
For instance, among various means for detecting the size distribution of particles, there is known a method based on a theory about the small-angle light scattering by particles suspended in a fluid medium. Conformably to the method an optical system as shown schematically in FIG. 4 is employed in combination with a photosensor assembly as shown in FIG. 5. According to FIG. 4, the optical system consists baiscally of a light source 1 such as a laser, a lens assembly 2 for providing a light beam F having a desired thickness, a transparent flow cell 3 in which a suspension suspending sample particles is made to flow, a Fourier-transform lens 4 and a photodetector 5a made up of an assembly of concentric semicircular photosensors S.sub.i (i=1, 2, . . . , N) as shown in FIG. 5. In the optical system of FIG. 4, the light beam F incident into the flow cell 3 is scattered or diffracted by the sample particles, and then focused circularly on the detector 5 by the Fourier-transform lens 4, thus forming a circular image whose intensity varies in the radial direction. The radial-directional intensity distribution is detected by the above N concentric semicircular photosensors S.sub.i, and then mathematically analized by a mirocomputer (not shown) in accordance with the Mie scattering theory and/or the Fraunhoher diffraction theory to finally give the size distribution of the sample particles.
In such an optical system, that substantially constitutes an apparatus for detecting the intensity distribution of light scattered forward by particles suspended in a fluid medium, it is essentially important to adjust the direction of the light beam B so as to be directed precisely to the common center of the concentric semicircular photosensors S.sub.i. It also is important to adjust the light beam B so as to have a desired thickness. The direction and thickness of the beam B have conventionally been adjusted through directly watching the beam with the eye or by using a special jig. However, the visual method of adjustment is harmful to the eye, while the use of a jig is often troublesome and inconvenient.


This invention relates to personal computers, and more particularly to the provision of shielding for attenuating the emission of electromagnetic radiation and the like from an enclosure for such computers. A personal computer in accordance with this invention has a chassis for mounting a planar board and having a base, a front panel, and a rear panel. The front panel defines at least one bay for receiving a data storage device. In order to attenuate the emission of electromagnetic radiation through the windows formed for the bays in the front panel of the chassis, this invention contemplates that at least one manually removable shield member will be mounted in any bay.

This invention relates to personal computers, and more particularly to the provision of shielding for attenuating the emission of electromagnetic radiation and the like from an enclosure for such computers.
Personal computer systems in general and IBM personal computers in particular have attained widespread use for providing computer power to many segments of today's modern society. Personal computer systems can usually be defined as a desk top, floor standing, or portable microcomputer that consists of a system unit having a single system processor and associated volatile and non-volatile memory, a display monitor, a keyboard, one or more diskette drives, a fixed disk storage, and an optional printer. One of the distinguishing characteristics of these systems is the use of a motherboard or system planar to electrically connect these components together. These systems are designed primarily to give independent computing power to a single user and are inexpensively priced for purchase by individuals or small businesses. Examples of such personal computer systems are IBM's PERSONAL COMPUTER AT and IBM's PERSONAL SYSTEM/2 Models 25, 30, 50, 60, 70 and 80.
These systems can be classified into two general families. The first family, usually referred to as Family I Models, use a bus architecture exemplified by the IBM PERSONAL COMPUTER AT and other "IBM compatible" machines. The second family, referred to as Family II Models, use IBM's MICRO CHANNEL bus architecture exemplified by IBM's PERSONAL SYSTEM/2 Models 50 through 80. The Family I models typically have used the popular INTEL 8088 or 8086 microprocessor as the system processor. These processors have the ability to address one megabyte of memory. The Family II models typically use the high speed INTEL 80286, 80386, and 80486 microprocessors which can operate in a real mode to emulate the slower speed INTEL 8086 microprocessor or a protected mode which extends the addressing range from 1 megabyte to 4 Gigabytes for some models. In essence, the real mode feature of the 80286, 80386, and 80486 processors provide hardware compatibility with software written for the 8086 and 8088 microprocessors.
It is well known that the components of a personal computer housed within an enclosure and supported from the chassis or connected with the planar board are capable of emitting electromagnetic radiation at various frequencies and that standards have been established for limiting the emission of such energy to various limits depending on the environment of use of the computer. Further, it is known that higher speed processors and circuits associated with such processors, such as those specifically mentioned above, typically emit radiation of differing frequencies and amounts than the earlier designed, slower processors. Heretofore, shielding has been accomplished in various ways, including providing metal enclosures and/or coating or lining the enclosures and covers provided. In achieving shielding in these ways, and attenuating radiation, it has been noted that openings provided in such enclosures and covers can present particularly difficult problems in shielding.
It has also become desirable to provide for the possibility that a personal computer may be provided with direct access storage devices such as magnetic disk, optical disk, tape backup, and other drives. In making provision for such additions, the chassis and enclosure for a personal computer may be provided with areas, known as "bays", designed to receive and accommodate additional devices. While such bays provide flexibility in arranging the components of a personal computer, they also present additional openings to be dealt with in arranging shielding.
As the development of personal computer technology has advanced, personal computers have been enabled to incorporate 10 increasingly higher data handling speeds in processors, data storage devices, and memory. Such higher speeds bring with them greater emission of electromagnetic radiation, increasing the demands placed on enclosures for the attenuation of such emissions. Other terms used to refer to such requirements have been electromagnetic compatibility and the suppression of electromagnetic interference. In efforts to bring emissions within the required standards while attaining the sought for high speeds, designs have moved toward a completely grounded enclosure with minimal gaps and openings.

Personal computer enclosure with shielding


A blade arrangement is provided for a gas turbine, in which blade leaves, having a leading edge and a trailing edge and also a pressure side and a suction side, are assembled sealingly with platforms configured as separate components. A peripheral sealing arrangement is provided between the blade leaves and the associated platforms, which seals off an interspace between the blade leaves and platforms against hot gas flowing around the blade leaves. A directed site-dependent supply of cooling air for purging the sealing arrangement is provided on a side of the sealing arrangement which faces away from the hot gas. A method of operating the above blade arrangement is also provided. The method includes supplying cooling air for purging the sealing arrangement at a pressure which decreases from the leading edge of the blade leaves to the trailing edge.

It has long been known from the prior art to execute moving blades and/or guide vanes of a gas turbine in a built-up or otherwise constructed blade arrangement in which the blade leaves and the upper and/or lower platforms of the blades are formed as separate components which are then assembled in the blade arrangement and sealingly connected.
A guide vane arrangement is shown in U.S. Pat. No. 5,332,360, which is incorporated by reference, shows two guide vanes, which are assembled together with an outer and an inner shroud portion and are soldered to one another along peripheral grooves. Sealing between the blades and shrouds or platforms in this case achieved by means of the soldering itself. A comparable configuration is reproduced in FIG. 1: In the blade arrangement 10 of FIG. 1, two blade leaves 11 are inserted in corresponding openings of two mutually opposite platforms or shroud segments 12 and 13. Each of the blade leaves has a leading edge 14 and a trailing edge 15. The hot gas flowing through the blade leaves 11 between the two platforms 12 and 13 flow in this case from the leading edge 14 to the trailing edge 15. A comparable arrangement is also shown in U.S. Pat. No. 5,797,725, which is incorporated by reference.
Furthermore, U.S. Pat. No. 7,052,234, which is incorporated by reference, shows, in blade arrangements, to combine ceramic blade leaves with metallic platforms or shrouds and to seal off the interspaces between the blade leaves and platforms by means of special seals. However, directed leakages of cooling air may also be used, as shown in U.S. Pat. No. 7,329,087, which is incorporated by reference, in order to prevent hot gas from penetrating into the interspaces between the ceramic blade leaves and the metallic platforms.
U.S. Patent Application Publication No. 2010/124502, which is incorporated by reference, shows to produce the blade leaf and blade platform as separate components and to assemble them, so as to decouple the two parts mechanically. In this case, too, specific seals have to be provided between the components in order avoid the penetration of hot gas.
In most cases, it is necessary, in addition to installing a simple linear sealing arrangement around the blade leaf, to purge this sealing arrangement also from the rear side with cooling air which is under a corresponding pressure higher than the pressure of the hot gas, but identical along the entire sealing arrangement. This means, in particular, that the pressure of the purging air is the same on the pressure side of the blade leaf as on the suction side, where, in fact, less pressure is required on account of the lower pressure in hot gas. This leads to a higher and needless consumption of cooling air in those regions of the blade leaf or of the sealing arrangement where a lower pressure would be sufficient. This then also applies to the leading edge and the trailing edge of the blade leaf where different pressure conditions prevail in the hot gas.

Blade arrangement for a gas turbine and method for operating such a blade arrangement


An arrangement for curing concrete products, which contains a curing chamber having several curing cells arranged in at least one column, in which curing cells are located on a vertical stack. The curing cells are formed to curing cell groups, in which one curing cell group contains at least one curing cell, advantageously 2-4 curing cells, and wherein the curing cell group is insulated in respect of other curing cell groups of the curing chamber. A method for curing concrete products in a curing chamber, which includes several curing cells arranged in at least one column, in which the curing cells are located on a vertical stack. In the method the moisture level of curing cells is controlled such that in the curing cells the temperature is desired.

1. Field
The present disclosure relates to casting of prefabricated concrete products in a casting production process. More precisely the present disclosure relates to an arrangement for curing concrete products and to a method for curing concrete products.
2. Description of Related Art
In casting production processes, the casting is performed in different stages at work stations, and different types of lines are used, for example circulating lines such as forced circulation lines and center conveyance lines. In forced circulation lines, mold tables and molds built on them are transferred by a roll trestle in a successive order from one work station, in which a process stage is performed, to a next work station, in which the next process stage is performed, and thus the process stage taking the longest time defines the speed of the forced circulation line. In circulating lines, mold tables, on which casting molds are built, are mounted on tracks and circulate through the work stations for the stages of the production process.
The casting lines thus comprise a plurality work stations between which the casting mold table is transferred for the different stages of the production process. The stages of the production process can comprise, for example, cleaning of the mold table, furnishing the mold table with fixed and detachable mold sidewalls to form the casting mold and setting of other required equipment, such as reinforcements etc., on the mold, casting of the concrete mass to the mold, together with required vibrating actions during the casting, leveling the upper surface of the product to be cast, curing the fresh cast product, demolding, in which the cast product is removed from the mold, generally together with tilting of the mold and removing the mold sidewalls from the mold table.
Depending on the type of the production process line, the line may comprise one or more work stations for one type of process stage.
The curing stage generally takes place at a curing chamber where temperature during the curing can be monitored and adjusted such that the surface of the concrete product to be cured remains moist in order to avoid cracks. taking into account that as temperature in the curing chamber increases, the moisture level decreases.
In the curing stage, the molds with cast products are generally located in columns of several molds on top of each other so that the area required by curing the products can be minimized. Further, the curing area is advantageously enclosed so that the heat released for the concrete during the curing process can be used for speeding up the curing process.
Typically, the curing chambers are continuously operating, such that at one end of the curing chamber fresh cast products to be cured are brought in, and at the other end, the cured cast products are taken out and transferred to the next process stage. Typically, the fresh cast product is brought to a free location of a column of the curing chamber, from which the cured cast product has been taken out so that in the curing chamber there are cast products of different curing stages, i.e. at different temperatures, at the same time. This is problematic in view of the known heating systems of the curing chambers as the relative moisture level is not optimal for cast products of different temperatures, and balance between temperature and moisture level is disturbed. A cold cast product that has just entered the curing chamber creates a high condensate level on its surface, but a warm cast product that has already been in the curing chamber for a longer time needs a higher relative moisture level for proper curing. In practice, the cold cast products define the relative moisture level of the curing chamber by condensing moisture from air.

Arrangement and method for curing concrete products


A throttle valve for throttling the combustion air flow for an internal combustion engine is disclosed, having a body with a throat, a butterfly in the throat to throttle flow, and a shaft connected to the butterfly to operate it. The shaft has an arm that abuts a throttle stop to maintain the butterfly in an almost-closed (or idle) position. The arm has an opening that permits access to the head of the throttle stop to adjust the throttle stop when the throttle valve is in the almost-closed position. The opening is located so that a tool such as a hex wrench can pass through the opening and engage a socket in the head of the throttle stop, pemitting it to be rotated and adjusted. The throttle shaft and arm are preferably integrally molded of plastic, and the throttle stop head is preferably larger than the threaded shaft of the throttle stop.

Internal combustion engines are often provided with a throttle valve within their combustion air induction systems to control combustion airflow rate. The throttle valve is typically in the form of a butterfly valve, having a disk secured to a throttle shaft which is journaled to the generally cylindrical internal wall surface of a throat of a throttle body. The diameter of the disk is only slightly smaller than is the inside diameter of the throat, whereby the throttle plate may block all but a small portion of the air from passing through the throat in an idle condition. Typically, a return spring is used to bias the throttle shaft and butterfly closed with respect to the throat, shutting off almost all the airflow past through the throttle valve.
Provisions are made for adjusting the throttle valve to compensate for variations between particular engines, differences in their operating environments, gradual changes in characteristics due to wear, etc.
Adjusting the almost-closed position of the throttle valve is generally performed by rotating an adjusting screw that abuts the throttle arm. The throttle arm is affixed to the throttle shaft, and is disposed to approach a fixed surface of the engine when closed. The adjusting screw is typically screwed into either the arm or the fixed surface, and abuts the other. By rotating the adjusting screw, the almost-closed position of the throttle valve can be precisely regulated.
While a long thread engagement is not needed in such a low-force application, engagement of at least several threads is desirable to avert cross-threading and stripping of threads. This has necessitated the arm being constructed of metal having a thickness sufficient to accommodate the several threads when the adjusting screw is threaded into the arm.
Alternatively, it is known to threadedly engage an idle adjusting screw with a threaded aperture in a fixed surface disposed such that the end of the screw abuts the arm (U.S. Pat. No. 3,269,713, Beck, 1966; U.S. Pat. No. 4,161,928, Teague et al., 1979; U.S. Pat. No. 4,200,596, Iiyama et al., 1980; U.S. Pat. No. 4,502,436, Bonfiglioli et al., 1985; and U.S. Pat. No. 4,940,031, Mann, 1990). All such idle adjusting screws have a feature to enable rotation (e.g., a head having a screwdriver slot) located at the free end; i.e. the end not abutting the arm. In some configurations, and particularly in engine installations wherein there are many surfaces and pieces of auxiliary equipment near the engine, it is difficult to access such an adjusting screw.
It would be advantageous to provide for an engine throttle idle adjusting screw which is threadedly engaged with a fixed surface, abuts an arm of a throttle shaft for limiting rotation of the throttle shaft and thereby of a throttle plate, and is rotatably adjustable from the abutting end.


A method is specified for producing a rotary tool (2) having a base body (4), which extends in a longitudinal direction (L) and in which at least one flute (6) is ground in by grinding in a first partial flute (12A) with a first helix angle (W1) in a first grinding step and by subsequently grinding in a second partial flute (12B) with a second helix angle (W2) in a second grinding step, the second helix angle differing from the first helix angle (W1) so that a flute (6) that expands in the longitudinal direction (L) is formed, wherein the two partial flutes (12A, 12B) are ground in using the same grinding wheel (11). In this way, a particularly quick production is realized. Furthermore, a corresponding rotary tool (2) is specified.

The invention relates to a method for producing a rotary tool, which comprises a base body, which extends in a longitudinal direction and in which at least one flute is ground in by grinding in a first partial flute with a first helix angle in a first grinding step and by subsequently grinding in a second partial flute with a second helix angle that is different form the first helix angle in a second grinding step, so that a flute that expands in the longitudinal direction is formed. The invention furthermore relates to a rotary tool.
An appropriate rotary tool is described in U.S. Pat. No. 750,537, for example. The rotary tool shown there has two flutes, which substantially coincide and are connected to one another and thereby form a flute with an increasing width. For this purpose, the first flute is introduced first and then, along an edge of this flute, a second flute with a lesser flute depth is formed.

Method for producing a rotary tool and rotary tool


A fault indicator for indicating the occurrence of a fault in an electrical conductor has a plurality of trip settings, such as in the range of 50 A to 1200 A, that is automatically calibrated. The fault indicator includes a housing, a battery, an illuminated display, such as LEDs, a current sensor for sensing the load current in the conductor and a microcontroller that receives a current signal from the current sensor to determine the load current. In the calibration mode, a known load current is passed through the conductor, the microcontroller selects the trip level that is related to the load current, determines the load current from the current signal, and sequentially calibrates each of the plurality of trip levels for the respective known load currents. The calibration information is stored in memory. The illuminated display provides a distinctive pattern to indicate that each trip setting has been calibrated.

The present invention relates generally to current sensing devices for electrical systems, and more particularly to timed reset fault indicators for alternating current power systems with multiple trip settings that are configured.
Various types of self-powered fault indicators have been constructed for detecting electrical faults in power distribution systems, including clamp-on type fault indicators, which clamp directly over cables in the systems and derive their operating power from inductive and/or capacitive coupling to the monitored conductor; and test point type fault indicators, which are mounted over test points on cables or associated connectors of the systems and derive their operating power from capacitive coupling to the monitored conductor.
Such fault indicators may be either of the manually resetting type, wherein it is necessary that the indicators be physically reset, or of the self-resetting type, wherein the indicators are reset upon restoration of line current. Examples of such fault indicators are found in products manufactured by E. O. Schweitzer Manufacturing Company of Mundelein, Ill., and in U.S. Pat. Nos. 3,676,740, 3,906,477, 4,063,171, 4,234,847, 4,375,617, 4,438,403, 4,956,873, 4,458,198, 4,495,489, 4,974,329, 5,677,678, 6,016,105, 6,133,723 and 6,133,724.
Detection of fault currents in a monitored conductor by a fault indicator is typically accomplished by magnetic switch means, such as a magnetic reed switch, in close proximity to the conductor being monitored. Upon occurrence of an abnormally high fault-associated magnetic field around the conductor, the magnetic switch actuates a trip circuit that produces current flow in a trip winding to position an indicator flag visible from the exterior of the indicator to a trip or fault indicating position. Upon restoration of current in the conductor, a reset circuit is actuated to produce current flow in a reset winding to reposition the target indicator to a reset or non-fault indicating position, or the fault indicator may be manually reset. Some prior art fault indicators also utilize light emitting diodes (LEDs) to display a fault condition.
Such prior art fault indicators have a single trip setting. This means that a plurality of different fault indicators need to be manufactured, inventoried and sold to meet customers' requirements for fault indicators with 25 ampere (A), 50 A, 10 A, 200 A, 400 A, 600 A, 800 A, 1000 A, 1200 A and 2500 A trip settings to monitor conductors that carry correspondingly different load currents.
There is therefore a need for a fault indicator with multiple trip settings that can determine the present load current level in a monitored conductor and select one of the trip settings that is appropriate for present load current conditions on the monitored conductor.
A need also exists for methods or techniques to configure the multiple trip settings of such a fault indicator.
Because of the compact construction and limited power available in self-powered fault indicators, it is preferable that the desired functions of the fault indicator be accomplished with minimal structure and with internal circuitry that has minimal current drain on a high capacity battery. The fault indicator must also provide highly reliable and extended operation over a number of years.
Accordingly, it is a general object of the present invention to provide a new and improved fault indicator that automatically selects one of a plurality of configured trip settings that is related to the load current in the monitored conductor.
Another object of the present invention is to provide a fault indicator that is capable of operating over a broad range of load currents, such as from about 5 A to about 1200 A.
Yet another object of the present invention is to provide a means of configuring each of the multiple trip settings of such a fault indicator.
Another object of the present invention is to provide a fault indicator that is microprocessor controlled, with the selection of the multiple configured trip settings under microcontroller control.
A further object of the present invention is to provide a fault indicator with a microcontroller that assists in the configuration of the multiple trip settings.

Auto-calibration of multiple trip settings in a fault indicator


An ash catcher for a barbecue kettle comprises an open top tapered body shaped to fit within a trapezohedral space defined by upwardly-converging legs between the bottom of the kettle and a shelf connected to the lower ends of the legs. It has a profile enabling it to be withdrawn sidewise between adjacent legs. The embodiment illustrated comprises a triangular base wall and three trapezoidal side walls converging upwardly from the edges of the base wall. Ash-deflecting panels are hingedly connected to the respective side walls and are pivotally movable between upper, outwardly-extended, ash-deflecting, working positions, and lower, retracted positions folded along the side walls. Removable hooks are connected between adjacent ash-deflecting panels to hold them in their ash-deflecting, working positions.

The present invention relates generally to ash-producing portable outdoor barbecue grills of the kettle type, and particularly to an improved ash catcher therefor.
Heretofore, conventional outdoor barbecue kettle grills with a fire bowl in a hemispheroidal shape have employed a shallow metal tray located beneath the bowl to collect ashes and coals that may drop through ash discharge and vent holes located in the bottom of the bowl. This tray is supported by three cutouts at the edge of the tray equidistant from one another and hook around the support legs of the grill.
Problems in collecting ashes with these conventional trays include:
1. There is no protection from winds blowing hot ashes or coals out of the tray with the possibility of damaging lawns, decks, and users' clothing and bare skin.
2. The shallow tray described requires that for it to be emptied it must be raised, twisted to unhook it from the legs, and then lowered to a point wide enough to allow it to be removed from between the legs. The capacity of the tray is limited, so this procedure must be repeated to empty the grill. Because of this inconvenience in emptying the ashes, draft is impaired much of the time by ashes covering the vents.
3. In addition to being a cumbersome chore, this procedure is messy and even dangerous if the ashes and coals have not completely cooled down.
There is a need for an ash catcher which positively prevents the scattering of hot ashes and coals by wind and careless use; which has a large storage capacity; and which is easy, simple, and clean to use.