Wireless telephone service is provided by a distribution network including fixed stations and wireless digital telephones linked by radio to the fixed stations, a digital public switching telephone network to which each fixed station is connected, service control points connected to the public switching telephone network and each including a wireless telephone service subscription database and a call processing logic device generating a call ticket at the end of each telephone call, and a service management system processing each call ticket to generate a billing ticket and including a reference database storing the characteristics of each subscription and all the billing tickets. A user data access method for this service includes storing and keeping up to date in real time in a reference database file of the service management system, billing tickets classified by subscription and, when a user requests access to subscription data: designating a subscription of interest, setting up a link between a user terminal and a server of the service management system, authenticating the identity of the user, reading billing tickets of the subscription in the file under the control of the user terminal, according to the user's access rights, and processing the information from the read billing tickets.

1. Field of the invention
The invention concerns a wireless telephone service subscription data user access method, said data essentially comprising the subscription characteristics and the billing data. A wireless telephone service is provided by a network essentially comprising: fixed stations; wireless telephones linked by radio to the fixed stations; and an integrated services digital public switched telephone network. The invention is more particularly concerned with a wireless telephone service provided by an intelligent network to be described later.
2. Description of the Prior Art
It is feasible to rent wireless telephones to short-term users, for example when an automobile is rented at a train station or an airport. Such rentals can be of very short duration, for example 24 hours. This situation is comparable with the renting of a fixed telephone as part of renting an hotel room. In the case of an hotel, the PABX of the hotel includes individual meters controlled by signals supplied by the network so that the amount of telephone charges incurred by a customer is shown in real time. The hotel management can therefore bill this amount when the customer wishes to check out of the hotel. In the case of wireless telephones, calls pass through fixed stations in diverse locations and it is therefore not possible for the renter to use this method to determine the amount of telephone charges incurred by a customer.
One known method of collecting billing data for a wireless telephone service consists in storing in each fixed station call tickets produced by the fixed station in respect of calls passing through it; this method consists in reading this data once each day and transmitting it to a management center. Billing tickets are generated in this center from the call tickets. For a user requiring to know the amount of charges incurred on a subscription, the time delay before billing tickets are available is the sum of the following times:
the time for reading tickets in each fixed station from a management center; PA1 the time for processing all the billing tickets that the subscriber may have generated in all the fixed stations served by a management center, as billing must be comprehensive; PA1 the time for collating all billing tickets from other management centers, in cases where not all the fixed stations of a network are managed by the same management center, so that there is an additional transfer time and an additional processing time; and PA1 the time for the user to access the billing tickets via the sales office of the network operator. PA1 a distribution network comprising fixed stations and wireless digital telephones linked by radio to said fixed stations; PA1 a digital public switched telephone network to which each fixed station is connected; PA1 service control points connected to said public switched telephone network and each telephone service subscription database and a call processing logic device generating a call ticket at the end of each telephone call; PA1 a service management system processing each call ticket to generate a billing ticket and comprising a reference database storing the characteristics of each subscription and all said billing tickets; PA1 setting up a link between said user terminal and a server of said service management system; PA1 authenticating the identity of said user; PA1 reading billing tickets of said subscription in said file under the control of said user terminal, according to the user's access rights; and PA1 processing the information from the read billing tickets. PA1 indicating to said user which data is accessible for reading and which data is accessible for writing, according to the user's access rights; PA1 processing an access request from said user terminal to read or write accessible data; PA1 sending to said terminal a "modification executed" acknowledgement in the case of a write access request which is processed immediately; and PA1 sending to said terminal a processing acknowledgement in the case of a write access request that is processed off-line. PA1 transmitting from said terminal to said service management system a password specific to said user; PA1 reading in said database of said service management system at least one password associated with said subscription; and PA1 verifying that the password transmitted matches a password associated with said subscription. PA1 determining in a smart card connected to said terminal a first signature using a random number and a secret key specific to said user and transmitting said first signature to said service management system; and PA1 in said service management system:
Additionally, the subscription characteristics are not readily accessible to the subscriber. The subscriber who rents a wireless telephone to a customer cannot easily modify the subscription characteristics. For this reason, all valid subscriptions have the same characteristics. In other words, all subscribers have the same rights all the time, except for subscribers whose subscription has been blacklisted. It is not possible to customize the rights of each subscriber, for example to bar access to the international telephone network or to set a ceiling to prevent further use of the telephone when the amount of charges incurred has reached or exceeded the ceiling or to terminate use of the telephone at a predetermined date which is not the date at which the subscription expires.
One object of the invention is to propose a method that can be used in an intelligent network to enable a user to obtain very fast access to the data of a subscription using a standard terminal connected to the public switched telephone network and which makes provision for controlling such access to protect the data.

Wireless telephone service subscription data user access method


A repetitive striking type pneumatically operated nail gun for repeatedly striking, by a drive bit, a head of a nail for sinking the nail into a workpiece. The drive bit is connected to a piston reciprocally movably disposed in a cylinder. A return chamber is provided around the cylinder and in communication therewith. A head valve chamber is provided at a position above a head valve disposed above the cylinder. A drive air is provided for selectively applying compressed air to the head valve chamber or into the cylinder. A repetitive valve chamber is provided for providing selective communication with the return valve, the head valve chamber and a trigger valve. A cylinder guide is provided which prevents the cylinder from being moved in its axial direction in a case where the pressure within the return chamber becomes higher than that in the drive air chamber. A partition segment is provided to the cylinder guide for separating the return chamber from the drive air chamber. Further, an air passage is formed in the cylinder guide for fluidly connecting the repetitive valve chamber to the return chamber.

The present invention relates to a repetitive striking type nail gun, and more particularly, to a pneumatically operated nail gun for repeatedly striking, with a drive bit, fasteners such as nails and staples by repetitive reciprocation of a piston during pulling of a trigger.
Throughout the specification, expressions such as "upward," "downward," "above," "below," "upper" and "lower" are used in explanations of conventional art and the present invention to define the various parts when a nail gun is disposed in an orientation for driving a nail downward into a workpiece.
A conventional pneumatically operated repetitive striking type nail gun is disclosed in a Japanese Patent Application Kokai (OPI) No. Hei-2-172682. As shown in FIG. 7, the nail gun includes a main body 101, a handle 136 connected to the main body 101, an exhaust cover 102 provided to the upper portion of the main body 101, and a tail cover 112 provided to a lower portion of the main body 101. A drive air chamber 103 is defined in the main body 101 and the handle 136. The drive air chamber 103 is fluidly connected to a compressed air source (not shown), so that a compressed air is filled in the drive air chamber 103.
Within the main body 101, a cylinder 109 is provided, and a piston 110 is reciprocally and slidably disposed in the cylinder 109. A lower end of the cylinder 109 is in abutment with the lower portion of the main body 101. The piston 110 is integrally provided with a drive bit 111 extending in an axial direction of the cylinder 109.
A generally cylindrical return chamber 104 is defined between the main body 101 and the cylinder 109. At a lower peripheral portion of the cylinder 109, a plurality of return holes 124 are formed, so that the return chamber 104 and the cylinder 109 can be fluidly connected together. Further, at an axially intermediate portion of the cylinder 109, a plurality of communication holes 117 are formed. Radially outer ends of the communication holes 117 are covered by a flexible one-way valve 123, so that air in the cylinder 109 can be discharged toward the return chamber 104 through the communication holes 117, but air in the return chamber 104 cannot be flowed into the cylinder 109 through the communication holes 117.
At a position immediately above the communication holes 117, a first annular flange portion 109A is provided at an outer peripheral surface of the cylinder 109. Further, at the upper portion of the cylinder 109, a second annular flange portion 109B is provided.
A trigger 118 is pivotally movably supported to the main body 101, and a trigger valve 119 is retained in the main body 101. The trigger 118 is abuttable on the trigger valve 119 upon pivotal movement thereof for actuating the trigger valve 119. That is, if the trigger 118 is pulled upwardly, the trigger valve 119 is actuated so that compressed air in an upper head valve chamber 107 (described later) can be discharged to the atmosphere through the trigger valve 119.
In the tail cover 112, a fastener such as a nail can be supplied. Further, a push lever 120 is movably guided by the tail cover 112. The push lever 120 has a lower end in contact with a workpiece surface, and has an upper end engageable with the trigger 118. The upper end of the push lever 120 is normally biased downwardly by a spring 137 interposed between the main body 101 and the upper end of the push lever 120, so that the push lever 120 can provide a locking position of the trigger 118. On the other hand, if the entire tool is pressed downwardly, the workpiece surface pushes the lower end of the push lever 120 upwardly against the biasing force of the spring 137 for releasing the locking state of the trigger 118. The drive bit 111 is extendible into and is guided by the tail cover 112 upon downward movement of the piston 110 for striking the head of the nail supplied in the tail cover 112.
A head valve 105 is slidably disposed relative to the exhaust cover 102 and at a position between the exhaust cover 102 and the upper end of the cylinder 109. The head valve 105 is biased in the axial direction of the cylinder 109 downwardly by a head valve spring 126 interposed between the head valve 105 and the exhaust cover 102, so that the head valve 105 can be seated on the upper open end of the cylinder 109. Further, the upper head valve chamber 107 is defined between the exhaust cover 102 and the head valve 105. The head valve 105 is formed with an air passage 125 which provides fluid communication between the drive air chamber 103 and the upper head valve chamber 107. Further, an exhaust valve 121 is defined at the upper portion of the head valve 105 for discharging compressed air in the cylinder 109 and above the piston 110 when the head valve 105 is moved downwardly.
At a lower surface of the exhaust cover 102, a cylindrical recess is formed for defining a cylindrical repetitive valve chamber 108 in which a repetitive valve 106 is movably provided. An upper surface of the repetitive valve 106 serves a pressure receiving surface whose area is greater than that of the lower surface of the repetitive valve 106. The repetitive valve 106 divides the repetitive valve chamber 108 into a lower repetitive valve chamber 127 and an upper repetitive valve chamber 128.
Further, in the exhaust cover 102, an air passage 114 connecting the upper head valve chamber 107 with the lower repetitive valve chamber 127 is formed. A cross-sectional area of the air passage 125 formed in the head valve 105 is sufficiently smaller than that of the air passages 114 and another air passage 115 (described later). One open end of the air passage 114 faces the lower surface of the repetitive valve 106.
Between the exhaust cover 102 and the second flange 109B of the cylinder 109, a spacer or a cylinder guide 122 is fixedly positioned. More specifically, a packing 131 is provided between the exhaust cover 102 and the upper end of the main body 101. The cylinder guide 122 has an upper end 122A in abutment with the packing 131, a sleeve portion 122B extending along the inner peripheral surface of the main body 101, and a lower portion 122C in abutment with the second flange portion 109B of the cylinder 109. With this arrangement, an axially movement of the cylinder 109 can be prevented by the abutment between the lower portion 122C and the second flange 109B. More specifically, if the cylinder guide 122 is not provided, the cylinder 109 may be vibrated in its axial direction at every reciprocation. As a result, air inlet opening area between the upper open end of the cylinder 109 and the head valve 105 may be varied, so that the pressure applied to the cylinder 109 and above the piston 110 becomes changed at every striking operation. Accordingly, the nail cannot be desirably driven into the workpiece. To avoid this problem, the above described spacer or the cylinder guide 122 is provided to avoid axial movement of the cylinder 109.
Further, a radially inward annular projection 113 is provided integrally with the main body 101 at a position in contact with the first flange 109A. This annular projection 113 serves as a partition member for partitioning the return chamber 104 from the drive air chamber 103.
Further, the air passage 115 is provided for fluidly connecting the lower repetitive valve chamber 127 with the trigger valve 119. Thus, the air passages 114 and 115 provide a fluid communication between the upper head valve chamber 107 and the trigger valve 119 provided that the repetitive valve 106 maintains its upper position. Furthermore, an elongated air passage 116 is provided in the main body 101 for fluidly connecting the upper repetitive valve chamber 128 with the return chamber 104.
In operation, if the lowermost end of the push lever 120 is pressed against the workpiece, the uppermost end of the push lever 120 releases the lock of the trigger 118. With this state, if the trigger 118 is pulled upwardly, the upper head valve chamber 107 is brought into communication with the atmosphere through the air passage 114, the lower repetitive valve chamber 127, the air passage 115 and the trigger valve 119. Therefore, the compressed air in the upper head valve chamber 107 is discharged to the atmosphere out of the trigger valve 119.
Accordingly, the head valve 105 is moved upwardly, so that the upper open end of the cylinder 109 is opened. Consequently, driving air in the drive air chamber 103 is flowed into the cylinder 109 and rapidly urges the piston 110 downwardly. Because the drive bit 111 is provided integrally with the piston 110, the nail in the tail cover 112 is driven into the workpiece.
In this downward stroke of the piston 110, the air in the cylinder 109 and below the piston 110 is flowed into the return chamber 104 through the return hole 124, and is compressed in the return chamber 104. Further in the downward stroke, if the piston 110 moves past the communication hole 117, the compressed air in the cylinder 109 and above the piston 110 is also flowed into the return chamber 104 through the communication hole 117.
The compressed air flowed into the return chamber 104 will be flowed into the upper repetitive valve chamber 128 through the air passage 116. In this state, because atmospheric pressure is applied in the lower repetitive valve chamber 127 through the trigger valve 119 and the air passage 115, the repetitive valve 106 is urged downwardly so that the repetitive valve 106 is seated on the open end of the air passage 114. Thus, fluid communication between the air passages 114 and 115 is shut off. That is, the upper head valve chamber 107 is shut off from the atmosphere.
Because the upper head valve chamber 107 is communicated with the drive air chamber 103 through the air passage 125, application of the compressed air in the drive air chamber 103 into the upper head valve chamber 107 will increase pneumatic pressure in the upper head valve chamber 107 and in the air passage 114. Here, the lower surface of the repetitive valve 106 has a pressure receiving area smaller than that of the upper surface of the repetitive valve 106, and therefore, the repetitive valve 106 maintains its downward position for a given period, i.e., the communication between the air passages 114 and 115 is maintained in shut off state in spite of the pressure increase in the upper head valve chamber 107.
In accordance with the increase in pneumatic pressure in the upper head valve chamber 107, the head valve 105 is moved downwardly in cooperation with the biasing force of the head valve spring 126, and as a result, the head valve 105 is seated on the upper open end of the cylinder 109, whereby fluid communication between the drive air chamber 103 and the cylinder 109 is blocked. At the same time, compressed air in the cylinder 109 and above the piston 110 is discharged to the atmosphere through the discharge valve 121, because the discharge port is opened upon downward movement of the head valve 105. Accordingly, the piston 110 can be returned to its original top dead center position because of the application of the compressed pressure to the cylinder 109 and below the piston 110 from the return chamber 104 through the return hole 124.
The compressed air in the return chamber 104 is also discharged to the atmosphere through the minute gap between the drive bit 111 and the tail cover 112. Further, because of the expansion of the compressed air, the pneumatic pressure in the return chamber 104 is lowered, and therefore, the pressure applied to the upper repetitive valve chamber 128 through the air passage 116 is also lowered. Accordingly, the repetitive valve 106 is moved upwardly because of the pressure applied to the lower repetitive valve chamber 127 from the upper head valve chamber 107.
By the upward movement of the repetitive valve 106, the head valve chamber 107 is brought into communication with the atmosphere through the air passage 114, the lower repetitive valve chamber 127, the air passage 115 and the trigger valve 119. Thus, the compressed air in the upper head valve chamber 107 and in the air passage 114 can be discharged to the atmosphere out of the trigger valve 119.
Because the cross-sectional area of the air passage 125 is sufficiently smaller than that of the air passages 114 and 115, compressed air flowing amount into the upper head valve chamber 107 from the drive air chamber 103 through the air passage 125 is smaller than the air discharge amount from the upper head valve chamber 107 to the atmosphere through the air passages 114, 115 and the trigger valve 119. As a result, pressure in the upper head valve chamber 107 is rapidly lowered.
Thus, the head valve 105 is again moved upwardly to introduce the driving air in the drive air chamber 103 into the cylinder 109 to perform second striking or driving operation. The above described operation is consequentially and repeatedly performed so that the nail is subjected to repeated striking by the drive bit 111 as far as the trigger 118 is maintained in its pulling state.
With the conventional arrangement, the air passage 116 largely extends through the main body, and therefore, large machining area results. Further, since the radially inward annular projection 113 is provided integrally with the main body 101. Therefore, the radially inward annular projection 113 may become an undercut in die-casting or injection molding process. Therefore, the main body 101 would not be available as the die-casting molding product.
To avoid this problem, as shown in FIG. 8, a separate partitioning piece 213 can be hermetically provided at the hollow cylindrical space between a main body 201 and a cylinder 109. However, a fixing member such as a stop washer 240 is required for fixing the position of the separate partitioning piece 213.
Further, instead of the radially inward annular projection 113 provided to the main body 101, a corresponding partitioning segment can be integrally provided to the outer peripheral surface of the cylinder 109 at a position corresponding to the first annular flange 109A. However, in the latter case, the radially outward protruding length of the partitioning segment becomes large. Therefore, an original crude cylinder before machining must provide a large diameter, and machining labor is also increased, to degrade productivity.

Repetitive striking type pneumatically operated nail gun


Systems and methods include a system for controlling a downhole multi-circuit switch using a downhole actuator mechanism. A command is sent, by a surface controller coupled to downhole electrically-powered equipment in a wellbore of a well, to change electrical power flow in a multi-circuit switch to a specified position of multiple positions. A connection between the surface controller and the downhole electrically-powered equipment includes at least two separate input electrical connections for supplying electrical power to the downhole electrically-powered equipment. The command is received by a downhole actuator mechanism from the surface controller. The command indicates to switch from a first electrical connection of the at least two separate input electrical connections to a second electrical connection of the at least two separate input electrical connections. The multi-circuit switch is switched by the downhole actuator mechanism based on the command to change a power source of the downhole electrically-powered equipment, including isolating a first input electrical connection.

Drilling operations, for example in oil or gas wells, may use electrically-powered downhole equipment, such as electric submersible pumps (ESPs) that are powered through power cables from a power source on the surface. Shorts in a power cable can cause the electrically-powered downhole equipment to stop working. Conventional techniques may require rig intervention to service the electrically-powered downhole equipment that has failed due to a primary electric transmission system failure.


Provided is a method for manufacturing a semiconductor package. In the method, a wafer for a cap substrate is provided. The wafer for the cap substrate includes a plurality of vias and via electrodes on a lower surface. A wafer for a device substrate is provided. The wafer for the device substrate includes a circuit unit and a connection electrode on an upper surface. The wafer for the cap substrate and the wafer for the device substrate are primarily bonded by a medium of a primary adhesive. A trench is formed to expose the upper surface of the wafer for the device substrate to an outside along an outer edge of the primary adhesive. A secondary bonding operation is performed by a medium of a secondary adhesive to electrically connect the via electrode and the connection electrode. The wafer for the device substrate is diced along a virtual cut line.

1. Field of the Invention
The present invention relates to a method for manufacturing a semiconductor package, and more particularly, to a method for manufacturing a semiconductor package solidly bonding a cap substrate and a device substrate having different thermal expansion coefficients through two times of bonding.
2. Description of the Related Art
A semiconductor package forms a circuit unit on a device substrate and covers a cap substrate having an external electrode and a through electrode electrically connected with the circuit unit to protect the circuit unit.
The semiconductor package is used for a surface acoustic wave (SAW) filter having an interdigital transducer (IDT) electrode which is sensitive to the influence of an external environment and thus requires blocking from the external environment, or an image sensor having an image forming region. These parts are manufactured at a wafer level for miniaturization.
Examples of a related art regarding a method of manufacturing the semiconductor package include U.S. Pat. No. 5,448,014 and Japanese Laid Open Patent No. 2004-366879.
However, since the method for manufacturing the semiconductor package passes through a process of bonding at high temperature, bonding is twisted or crack is generated in the case where the device substrate and the cap substrate have different thermal expansion coefficients. Accordingly, there is a limitation of having to manufacture the device substrate and the cap substrate using only the same material or materials having similar thermal expansion properties. Accordingly, even a material of the cap substrate merely covering the device substrate to protect or seal a circuit unit such as an IDT electrode provided inside the cap substrate should be manufactured using the same material as that of an expensive device substrate. Therefore, there has been a limit in cost reduction and a process required for dealing with the expensive substrate is complicated.

Method for manufacturing semiconductor package


Firing mechanism for firearms, including a hammer which is actuated by a spring and rotates about a pivot, defining a cocked position and a percussion position; the spring acts directly on the hammer on a surface point which defines a lever arm with the pivot of the hammer, so that the lever arm is variable as the hammer moves between the cocked and percussion positions.

The firing mechanism of a firearm is generally constituted by a hammer which rotates about a pivot and is actuated by a spring.
One end of the hammer is provided with a hammer dog which is adapted to engage an associated trigger dog of the trigger, so that a rotation of the trigger leads to the disengagement of the hammer, which, being actuated by the spring, acts on the percussion pin.
In the firing action there are two critical moments in the action of the spring on the hamme: the first critical moment is the percussion step, during which the spring should preferably act with the maximum possible force on the hammer; the second critical moment is the hammer cocking step, which naturally must encounter the least possible resistance, especially in the case of automatic or semiautomatic firearms.
In known firing mechanisms, the spring is generally in the maximum compression position in the cocking step, whereas in the percussion step it is in its maximum extension position; in this manner it is apparent that the spring exerts excessive resistance during the cocking step, while not all the possible force is exerted on the hammer during the percussion step.
A few attempts to solve this problem have been made, at the cost of an excessively complex construction, however. It would be in fact easy to design a mechanism, with the desired characteristics, comprising several levers; such mechanism, however, would be too expensive and unreliable, as well as heavy and cumbersome.
A simpler design has been proposed in U.S. Pat. No. 4,693,027 which discloses a flat gun spring, for handguns. The spring has a progressively decreasing depth that permits more energy to be stored in the spring during the early stages of the hammer rotation and less energy in the later stages of the hammer rotation. This design substantially aims at eliminating "stack up" immediately prior to hammer release.


An electronic apparatus, for inputting a DC power through an adapter, includes a loading circuit and a DC power input apparatus. The loading circuit, including a first power input terminal and a second power input terminal, is used for receiving the first DC power. The DC power input apparatus, for inputting the first DC power to the loading circuit, includes a fuse and rectifier. The fuse includes a first terminal coupled to a first voltage terminal of the adapter, and a second terminal coupled to the first voltage input terminal of the loading circuit. The rectifier, coupled to the fuse, includes a first polarity terminal coupled to the second terminal of the fuse, and a second polarity terminal coupled to a second voltage terminal of the adapter and the second power input terminal of the loading circuit. The second polarity terminal has a polarity inverse to the second voltage terminal.

1. Field of the Invention
The invention relates in general to an electronic apparatus and protection apparatus thereof, and more particularly to an electronic apparatus, which uses a fuse to prevent a reverse current from inputting to a loading circuit therein via an adapter, and DC power input apparatus thereof.
2. Description of the Related Art
FIG. 1 is a block diagram of a conventional notebook computer structure. Referring to FIG. 1, the notebook computer 100 includes a loading circuit 110, a DC power input circuit 120, and a battery power device 130. The DC power input circuit 120 has a first switch 122, while the battery power device 130 has a second switch 132 and a battery 134. By switching the first switch 122 and the second switch 132, the notebook computer 100 can selectively use the DC power input circuit 120 to input a DC power DC1 to the loading circuit 110 via an adapter 140, or use the battery 134 to input a DC power DC2 to the loading circuit 110.
Owing that the first switch 122 and the second switch 132 usually have parasitic diodes 123 and 133 respectively, when a reverse voltage is inputted to the notebook computer 100 due to inverse-polarity connection of the adapter 140 or interior device damage, the induced reverse current Ir will still damage the loading circuit 110 or the battery 134 via the parasitic diode 123 or 133 even though the first switch 122 or the second switch 132 is turned off.
In order to prevent the reverse voltage from damaging the loading circuit 110 or the battery 134, a rectifier 124, such as a set of diodes 126 connected in parallel, is usually configured in the adapter 120 as a protection circuit. Through rectification effect of the rectifier 124, the above-mentioned reverse current Ir cannot flow by the diodes 126, thereby achieving the purpose of protecting the loading circuit 110 or the battery 134.
However, along with the increase of power used by the notebook computer 100, the bias current If inputted from the adapter 140 is getting larger and larger. Therefore, in order to effectively protect the loading circuit 110 or the battery 134, the above-mentioned rectifier 124 must have features of large bias current, low power consumption, and small reverse leakage current, which increases number of the diodes 126, thus magnify the space occupied by the rectifier 124, and largely increases the cost for manufacturing the notebook computer 100.

Electronic apparatus and DC power input apparatus thereof


The invention relates in general to digital encoding and decoding of information. More particularly, the invention relates to efficient implementation of digital analysis and synthesis filter banks used in encoding and decoding. The invention permits the length of a digital transform used to implement critically-sampled analysis and synthesis filter banks to be adaptively selected.

Introduction
There is considerable interest among those in the field of signal processing to develop efficient means to transmit or store information. Improving coding efficiency includes (1) reducing informational requirements, that is, reducing the amount of information required to adequately represent a signal during transmission or storage, and (2) reducing processing requirements, that is, reducing the amount of processing required to implement the encoding and decoding processes.
In high-quality audio coding applications, informational requirements can sometimes be reduced without loss of perceptible audio quality by exploiting various psychoacoustic effects. Signal recording, transmitting, or reproducing techniques which divide the useful signal bandwidth into narrow bands with bandwidths approximating the human ear's critical bands can exploit psychoacoustic masking effects. Such techniques divide the signal bandwidth with an analysis filter bank, process the signal passed by each filter band, and reconstruct a replica of the original signal with a synthesis filter bank.
Two common coding techniques are subband coding and transform coding. Subband coders and transform coders can reduce the informational requirements in particular frequency bands where the noise caused by the resulting coding inaccuracy is psychoacoustically masked. Subband coders may be implemented by a bank of digital bandpass filters defining subbands of varying bandwidth. Transform coders may be implemented by any of several time-domain to frequency-domain transforms. One or more adjacent transform coefficients are grouped together to define "subbands" having effective bandwidths which are sums of individual transform coefficient bandwidths.
The mathematical basis for digital subband filter banks and digital block transforms is essentially the same. See Tribolet and Crochiere, "Frequency Domain Coding of Speech," IEEE Trans. Acoust., Speech, and Signal Proc., ASSP-27, October, 1979, pp. 512-30. Therefore, throughout the following discussion, the term "subband coder" shall refer to both a true subband coder and a transform coder. The term "subband" shall refer to portions of the useful signal bandwidth whether implemented by a true subband coder or a transform coder. The terms "transform" and "transforming" shall include digital filters and digital filtering, respectively.
In most digital coding applications, processing requirements can be reduced by increasing the efficiency of subband filtering. Improved processing efficiency permits implementation of encoders and decoders which are less expensive to build, or which impose lower signal propagation delays through an encoder/decoder system.
In many subband coder systems, the analysis and synthesis filter banks are implemented by discrete time-domain to frequency-domain transforms such as the Discrete Fourier Transform (DFT), the Discrete Cosine Transform (DCT), and the Discrete Sine Transform (DST). The number of time-domain signal samples, referred to herein as the time-domain signal sample block length, processed by such transforms is sometimes called the transform length, and the amount of processing required to perform these transforms is generally proportional to the square of the time-domain signal sample block length.
The number of frequency-domain transform coefficients generated by a transform is also sometimes called the transform length. It is common for the number of frequency-domain transform coefficients generated by the transform to be equal to the time-domain signal sample block length, but this equality is not necessary. For example, one transform referred to herein as the E-TDAC transform is sometimes described in the art as a transform of length 1/2N that transforms signal sample blocks with a length of N samples. It is possible, however, to also describe the transform as one of length N which generates only 1/2N unique frequency-domain transform coefficients. Thus, in this discussion the time-domain signal sample block length and the discrete transform length are generally assumed to be synonyms.
Various techniques have been utilized to reduce the amount of time required to perform a transform, or to reduce the processing power required to perform a transform in given amount of time, or both. One technique is taught in Narashima and Peterson, "On the Computation of the Discrete Cosine Transform," IEEE Trans. on Communications, COM-26, June, 1978, pp. 934-36. Briefly, this technique evaluates an N-point DCT by rearranging or "shuffling" the samples representing the input signal, performing an N-point DFT on the shuffled samples, and multiplying the result with a complex function. It is approximately twice as efficient as other techniques using a 2N-point FFT, however, Narashima and Peterson only teach how to improve the efficiency of filter banks implemented by one particular DCT.
Another technique which yields approximately a two-fold increase in processing efficiency concurrently performs two real-valued discrete transforms of length N with a single complex-valued FFT of length N. A subband coder utilizing this technique to concurrently perform a modified DCT with a modified DST is described in International Patent Application PCT/US 90/00501, Publication No. WO 90/09022 (published Aug. 9, 1990). The significance of these modified DCT and modified DST is discussed in Princen and Bradley, "Analysis/Synthesis Filter Barik Design Based on Time Domain Aliasing Cancellation," IEEE Trans. on Acoust., Speech, Signal Proc., ASSP-34, 1986, pp. 1153-1161. The authors describe a specific application of these transforms as the time-domain equivalent of an evenly-stacked critically-sampled single-sideband analysis-synthesis system. They are referred to collectively herein as the Evenly-stacked Time-Domain Aliasing Cancellation (E-TDAC) transform.
Another technique to reduce processing requirements is taught by Malvar, "Lapped Transforms for Efficient Transform/Subband Coding," IEEE Trans. Acoust., Speech, Signal Proc., ASSP-38, June, 1980, pp. 969-78. This technique implements an N-point modified DCT by performing a 1/2N-point DST after combining pairs of the samples representing the input signal, or "folding" the N input signal samples into a smaller set of 1/2N points. It is approximately twice as efficient as performing the modified DCT in a straight-forward manner, however, Malvar only teaches how to fold input samples for a filter bank implemented by one specific modified DCT whose input samples have been weighted by a specific sine-tapered analysis window.
The specific modified DCT implemented by Malvar is discussed in greater detail by Princen, Johnson, and Bradley, "Subband/Transform Coding Using Filter Bank Designs Based on Time Domain Aliasing Cancellation," ICASSP 1987 Conf Proc., May 1987, pp. 2161-64. The authors describe this transform as the time-domain equivalent of an oddly-stacked critically sampled single-sideband analysis-synthesis system. It is referred to herein as the Oddly-stacked Time-Domain Aliasing Cancellation (O-TDAC) transform.
It is desirable to implement encoders and decoders with the ability to use different time-domain signal sample block lengths in order to optimize coder performance. It is well known in the art that longer time-domain signal sample block lengths improve the selectivity or frequency-resolving power of subband coders, and better filter selectivity generally improves the ability of a subband coder to exploit psychoacoustic masking effects. See International Patent Application PCT/US 90/00507, Publication No. WO 90/09064 (published Aug. 9, 1990) which discusses the importance of time-domain signal sample block length and subband filter selectivity.
But longer time-domain signal sample block lengths degrade the time-resolution of a subband filter bank. Inadequate time-resolution can produce audible distortion artifacts when quantizing errors of signal events, such as transients, producing pretransient and post-transient ringing which exceed the ear's temporal psychoacoustic masking interval. See for example, Edler, "Coding of Audio Signals with Overlapping Block Transform and Adaptive Window Functions," Frequenz, vol. 43, no. 9, 1989, pp. 252-56. Hence, it is desirable that techniques which improve subband filter bank processing efficiency should also permit adaptive selection of the time-domain signal sample block length.

Low computational-complexity digital filter bank for encoder, decoder, and encoder/decoder

Dolby Laboratories Licensing Corporation


An aircraft transparency in a glass piece, wherein the glass piece includes a chemically tempered first major surface and a chemically tempered opposite second major surface, a first case depth begins at the first major surface, a second case depth begins at the second major surface, and a tensile stress zone is within the glass piece between the end points of the first and the second case depths. The glass between the end points of the first and second case depth has a glass composition including:

1. Field of the Invention
This invention relates to an aircraft transparency having chemically tempered lithia-alumina-silica containing glass and to a method of making the chemically tempered glass.
2. Technology and Utility Discussion
Chemical strengthening (or "chemical tempering") of glass involves an exchange of ions near the surface of the glass, e.g. a glass article with ions from an external source, typically a molten inorganic salt bath, to generate a zone near the surface of the glass which is in a state of compression relative to the interior portions of the glass. There are two types of ion exchange strengthening which differ substantially in theory and operation. The first type of ion exchange treatment is carried out above the strain point of the glass and has as its objective the alteration of the glass composition at the surface to lower the thermal coefficient of expansion in the surface layer. As the glass is cooled, a compressive stress develops at the surface of the glass due to the expansion differential. The first type of ion exchange strengthening is discussed in U.S. Pat. No. 2,779,136. The second type of ion exchange strengthening is characterized by treatment below the strain point of the glass. In the second type, the surface compression is generated by substituting large ions from an external source (e.g., a molten salt bath) for smaller ions in the glass. Typically, the substitution is sodium or potassium ions for lithium ions in a lithia-alumina-silica glass, e.g. of the type discussed in U.S. Pat. Nos. 3,218,220; 3,752,729; 3,900,329; 4,156,755 and 5,928,793, or potassium ions for sodium ions in a soda-alumina-silica glass, e.g. of the type discussed in U.S. Pat. Nos. 3,485,702; 3,752,729; 4,055,703, and 4,015,045.
Of the two types of ion exchange strengthening, the second (below the strain point) type is preferred for large-scale commercial use because maintaining the glass below its strain point avoids undesirable distortion defects in the glass. Of the two types of glass compositions, the lithia-alumina-silica glass compositions are preferred over the soda-alumina-silica glass compositions, and the preferred ion exchange is the sodium ion for the lithium ion. The lithia-alumina-silica glass compositions and the exchange of the sodium ion for the lithium ion are preferred because a deeper depth of ion exchange ("case depth") in a shorter period of time at lower temperatures can be obtained.
An appreciation of the selection of the lithia-alumina-silica glass compositions and the exchange of the sodium ion for the lithium ion is had when a comparison of the ionic crystal radius of the sodium, lithium and potassium ions is made. The sodium atom has an ionic crystal radius of about 95 picometers ("pm"), the lithium atom has an ionic crystal radius of 60 pm and the potassium ion has an ionic crystal radius of about 133 pm. The lithium ion having a smaller ionic crystal radius than the sodium ion requires less energy to displace from the glass than the sodium ion, and the sodium ion having a smaller ionic crystal radius than the potassium ion requires less energy than the potassium ion to displace the lithium ion from the glass.
As mentioned above, lithia-alumina-silica glasses are available, e.g. disclosed in U.S. Pat. Nos. 3,218,220; 3,752,729; 3,900,329; 4,156,755 and 5,928,793. As can be appreciated by those skilled in the art, it would be advantageous to provide additional lithia-alumina-silica glass compositions for ion exchange strengthening, and in particular lithia-alumina-silica glass compositions that can attain a higher strength than the presently available lithia-alumina-silica glass compositions.

This patent is subject to a terminal disclaimer.

Aircraft transparency having chemically tempered lithia-alumina-silica containing glass and method of making the chemically tempered glass

Abstract: IngredientPercent by weightSiO260 to 75;Al2O318 to 28; andLi2O3 to 9, andthe glass has at least one of the following properties (a) a log 10 viscosity temperature of at least 1413° F. and (b) a liquidus temperature of at least 2436° F.


Medical devices, medical device components, and methods of making the same. For example, one embodiment provides a method of making a reinforcing member adapted and configured for use in a medical device. The method includes providing one or more structural elements adapted and configured for creating the reinforcing member, the one or more structural elements including a surface having a portion with an initial surface area, and treating at least the portion of the surface of the one or more structural elements to provide a final surface area that is greater than the initial surface area. The one or more structural elements are used in creating the reinforcing member. The reinforcing member can then be incorporated into the structure of the medical device.

It is generally known to provide reinforcing members for use in medical devices, such as intravascular guidewires, catheters, and the like. The prior art offers a number of different structures and mechanisms for incorporating reinforcing structures into medical devices. Each of these different structures and mechanisms has certain advantages and disadvantages. There is an ongoing need to provide alternative structures and mechanisms to help incorporate reinforcing structures in medical devices.

Surface modified reinforcing member for medical device and method for making same


A fastener for insertion into pierced openings of a tissue wound has a body formed of a generally bioabsorbable polymer defining an initial capture area. The body includes a pair of arms, each with an inwardly projecting cleat operably joined at an elbow portion defining an internal elbow angle. The arms are operably joined to a backspan at a shoulder portion defining an internal shoulder angle. A durable tissue retention zone is defined between the cleat and the arm. The elbow portion and the internal elbow angle define an insertion width greater than a width of the pierced openings resulting in the pierced openings stretching over the cleat and being elastically retained within the durable tissue retention zone. The fastener captures wound tissue in the initial capture area and then dynamically reforms in response to lateral stresses without a fracture failure of the fastener until a minimum degradation period.

When an opening in tissue is created either through an intentional incision or an accidental wound or laceration, biological healing of the opening commences through the proximity of the opposed living tissue surfaces. If the opening is very large or if its location subjects the wound to continual movement, a physician will seek to forcibly hold the sides of the opening together so as to promote the healing process.
In the case of skin tissue, for example, healing occurs best when the opposing dermal layers of the skin tissue are held in tight, primary proximity with each other. Human skin tissue is comprised of three distinct layers of tissue. The epidermal layer, also known as the epidermis, is the outermost layer and includes non-living tissue cells. The dermal layer, or dermis, is the middle layer directly below the epidermal layer and comprises the living tissue of the skin that is the strongest of the three layers. The subcutaneous, or hypodermis layer, is the bottom layer of skin tissue and includes less connective tissue, making this the weakest layer of skin tissue.
The most prevalent method for forcibly closing a tissue opening is through the use of a suture or "stitches." As early as the second century, the Greeks were using sutures to physically close skin openings. In its simplest form, a suture is simply a length of material that is attached to a tissue-piercing device, such as a needle, and looped through the opposing sides of a tissue opening. The suture is then pulled tight and the loop closes, causing the opposing sides of the tissue opening to come into close physical contact. The suture loop is held tight by the tying of a knot, or knots, or some other locking mechanism. The first sutures were made of animal gut. Eventually other natural suture materials including leather, horsehair, flax, cotton and silk came into use. As the sciences of medical and materials technology have advanced over the course of the past century, new bioabsorbable materials have been developed to further improve upon the basic suturing concept.
While traditional suturing remains a popular method of effectuating closure of skin openings, the use of fasteners, for example staples and staplers, as a skin closure technique has become increasingly popular, especially in surgical settings where the opening is created through a purposeful incision. In these settings, the incision tends to make a clean, straight cut with the opposing sides of the incision having consistent and non-jagged surfaces. Typically, stapling of a skin opening, for example, is accomplished by manually approximating the opposing sides of the skin opening and then positioning the stapler so that a staple will span the opening. The stapler is then manipulated such that the staple is driven into the skin with one leg being driven into each side of the skin opening and the cross-member of the staple traversing the skin opening. Generally, the staple is made of a deformable material such as surgical stainless steel and the legs of the staple are driven into an anvil causing the staple to deform so as to retain the skin tissue in a compressed manner within the staple. This process can be repeated along the length of the opening such that the entire incision is held closed during the healing process.
The earliest medical staple designs were manufactured of metal and designed to deform around the captured tissue. Examples of these staples include U.S. Pat. Nos. 2,684,070, 3,273,562 and 4,485,816. Although effective, metal staples suffer from the drawback of requiring post-operative removal. As the science of medical polymers developed, staple designs incorporating bioabsorbable materials became available. The use of these bioabsorbable materials eliminated the need for post-operative removal of the staples. Examples of these staples include U.S. Pat. Nos. 3,757,629, 4,317,451, 4,741,337, 4,839,130 and 4,950,258. Due to the nature of bioabsorbable polymers; however, bioabsorbable staples could not be inserted with the same deformation approach used by metal staples. In fact, bioabsorbable staples were purposefully designed to avoid any deformation requirement, as deformation was seen as a potential failure mechanism. An example of such a design is illustrated by the inwardly biased skin fastener of U.S. Pat. No. 5,089,009. Thus, as the physical and chemical properties of bioabsorbable surgical staples evolved, the development of designs and insertion methods associated with bioabsorbable staples have focused on avoiding deformation of the bioabsorbable fastener.
One potential use for bioabsorbable fasteners is in the subcuticular application of such fasteners for use in closing skin wounds as shown, for example in a series of patents to Green et al. in U.S. Pat. Nos. 5,292,326, 5,389,102, 5,423,856, 5,489,287 and 5,573,541. These patents disclose the use of a bioabsorbable, rod-like fastener inserted in a subcuticular manner to assist the healing process. Another bioabsorbable fastener design contemplated for subcuticular wound closure is U.S. Pat. No. 5,618,311 to Gryskiewicz, in which a more traditional staple design is promoted.
If they could effectively retain tissue, the bioabsorbable staples of these designs would have many advantages over conventional metal staples, such as no visible scarring and no need for subsequent removal by a physician. Unfortunately, none of the designs for bioabsorbable staples to date has been incorporated into a medically or commercially efficacious fastener. It would be desirable to provide a bioabsorbable fastener for use in wound closure that could achieve the advantages of a bioabsorbable material and still provide for an efficacious wound closure.

Dynamic bioabsorbable fastener for use in wound closure


A refrigerator includes a housing defining a freezer storage compartment, an evaporator operatively coupled to the freezer storage compartment and configured to cool the freezer storage compartment, and an evaporator fan positioned to move air across the evaporator. The refrigerator also includes an ice maker positioned within the freezer storage compartment, a dispenser in flow communication with the ice maker and configured to dispense ice, and a control system configured to receive a signal from said dispenser indicating dispensing of a first amount of ice from the dispenser, the control system configured to activate the evaporator fan in response to the signal, the evaporator fan operating continuously for a time period upon activation.

This invention relates generally to refrigerators and, more particularly, to ice making assemblies for refrigerators.
Some known domestic refrigerators include an ice making assembly in a freezer storage compartment of the refrigerator. The ice making assembly generally includes a water reservoir into which water is supplied. The water is then frozen to form ice pieces or cubes. The ice pieces are then moved to a storage bin where they are held until a user accesses ice from the refrigerator through an ice dispenser typically mounted through the door of the refrigerator.
When a user obtains ice through the ice dispenser in the door of the refrigerator, a button is usually pressed which controls the delivery of the ice from the storage bin to the user. In certain instances, the ice storage bin may not hold a sufficient amount of ice to meet the demands of the user. Accordingly, the user has to wait for the ice making assembly to make more ice. The time required to make ice is dependent upon many factors including the temperature of water supplied to the ice making reservoir and the principles of convection.
Some consumers are interested in refrigerators having a highly efficient ice making assembly. In response to consumer demands, conventional attempts to resolve such ice producing problems have included adding an additional fan to increase convection of cool air within the ice making assembly and/or adding additional hardware, which undesirably increase the cost of manufacturing the refrigerator.

Apparatus and method for increasing ice production rate


A underwater communication device communicates data with another underwater communication device having another first coil and another second coil in water. The underwater communication device includes a first coil configured to transmit the data to and from the other first coil via a magnetic field, a second coil configured to transmit the data to and from the other second coil via a magnetic field, a supply unit configured to supply the data to the first coil and the second coil, a first capacitor connected to the first coil and forming a first resonance circuit that resonates with the first coil at a first resonance frequency, and a second capacitor connected to the second coil and forming a second resonance circuit that resonates with the second coil at a second resonance frequency that is different from the first resonance frequency.

Conventionally, ultrasonic communication (acoustic communication) is used for underwater communication (for example, in the sea). This is because a sound wave is effective in securing a transmission distance in water. For example, there has been known an underwater communication system in which the acoustic communication is performed between a water-surface station and an underwater station to reduce an influence of multiple reflections in water (see Patent Literature 1).

Underwater communication device and underwater communication system

PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO., LTD.


A mechanism for constructing Steiner trees using simultaneous blockage avoidance, delay optimization, and design density management are provided. An initial tiled timing-driven Steiner tree is obtained for an integrated circuit design. The Steiner tree is broken into 2-paths for which plates are generated designated the permissible area in which a Steiner point may migrate. Each 2-path is optimized by calculating a cost for each tile in the plate as a function of an environmental cost, a tile delay cost, and a trade-off value. A minimum cost tile is then selected as the point to which the Steiner point in the 2-path, if any, is to migrate. Once each 2-path is processed in this manner, routing is performed so as to minimize the cost at the source. This process may be iteratively repeated with new trade-off values until all of the nets have zero or positive slew.

1. Technical Field
The present invention is directed to an improved method and apparatus for performing buffer insertion into an integrated circuit design. More specifically, the present invention is directed to a routing and buffer insertion technique that simultaneously performs blockage avoidance, delay optimization, and design density management.
2. Description of Related Art
It is now widely accepted that interconnect performance is becoming increasingly dominant over transistor and logic performance in the deep submicron regime. Buffer insertion is now a fundamental technology used in modern integrated circuit design methodologies. As gate delays decrease with increasing chip dimensions, however, the number of buffers required quickly rises. It is expected that close to 800,000 buffers will be required for 50 nanometer technologies. Thus, it is critical to automate the entire interconnect optimization process to efficiently achieve timing closure.
In addition to timing issues, managing the density of an integrated circuit design is becoming more problematic. The performance of a design highly depends on how packed the logic is geographically in the physical integrated circuit. If the logic is completely spread out, the design is routable but the performance suffers significantly. On the other hand, if the logic is packed, the design is not routable but would yield the best timing characteristics. A packed design is unsuitable for later design changes, such as the insertion of additional logic, such as a synthesized clock tree, since there is no room for the new logic.
Physical synthesis is now prominent in the automated design of blocks for use in high performance processors and Application Specific Integrated Circuits (ASICs). Physical synthesis is the process of concurrently optimizing placement, timing, power consumption, crosstalk effects, and the like, in an integrated circuit design. Physical synthesis helps to eliminate iterations between synthesis and place-and-route. Physical synthesis has the ability to repower gates, insert buffers, clone gates, and the like. Hence, the area of logic in the design remains fluid.
During physical synthesis, buffer insertion is called for to either optimize nets for delay or to fix nets due to electrical violations. One mechanism for performing buffer insertion on a fixed Steiner integrated circuit topology is the van Ginneken algorithm. Van Ginneken's dynamic programming algorithm, described in "Buffer Placement in Distributed RC-tree Networks for Minimal Elmore Delay," Int'l Symposium on Circuits and Systems, 1990, pp. 865–868, which is hereby incorporated by reference, has become a classic in the field. Given a fixed Steiner tree topology, the van Ginneken algorithm finds the optimal buffer placement on the topology under an Elmore delay model for a single buffer type and simple gate delay model. The primary idea of van Ginneken is to choose a set of buffer candidate locations that lie on the Steiner topology at some uniformly fixed distance apart. Buffer insertion then proceeds for that particular set of candidates from sink to source.
One problem with the van Ginneken approach to buffer insertion is that buffers are inserted at uniformly placed points along a net. That is, there is no consideration for the density of the logic in the vicinity of the candidate point. Thus, buffers may be inserted into regions that are very densely packed with logic or into regions that are sparsely populated with logic, depending on the particular uniform spacing of the candidate points.
In addition, the major weakness of the van Ginneken approach is that it requires a fixed Steiner tree topology that has to be provided in advance. This makes the final buffer solution quality dependent on the input Steiner tree. Even though a particular van Ginneken solution may be optimal for a given topology, the van Ginneken algorithm will yield poor solutions when fed a poor topology. That is, the van Ginneken approach does not take into consideration the physical layout of the environment.
Recent trends toward hierarchical or semi-hierarchical chip design and system-on-chip design force certain regions of a chip to be occupied by large building blocks so that buffer insertion is not permitted in these regions. These constraints on buffer locations can severely hamper solution quality, and these effects need to be considered when optimizing an integrated circuit design.
Finally, the van Ginneken algorithm does not differentiate between critical and non-critical nets. To the contrary, the van Ginneken algorithm treats all nets as having the same criticality and provides a uniform distribution of buffer insertion locations regardless of the actual criticality of the nets. However, in some cases, critical nets should be considered differently from non-critical nets when performing routing and buffer insertion in order to make sure that the delay in the nets is optimized.
Thus, it would be beneficial to have a method and apparatus for generating Steiner trees for routing of nets in an integrated circuit design and performing buffer insertion that takes into account blockage avoidance, delay optimization and design density management.

Method and apparatus for generating steiner trees using simultaneous blockage avoidance, delay optimization and design density management

International Business Machines Corporation


A device for transporting persons between spaced landings using pairs of drive rollers, preferably gears, having a flexible belt loop therebetween made to abut the handrail to move the handrail. Springs and idler gear can be used to maintain the abutting relationship. The drive rollers are carried by shafts mounted on bearings bolted to the fixed supporting structure.

This invention relates to a novel escalator or moving sidewalk hand rail drive mechanism.
Various escalator and moving walks structures have been described in the prior art.
Taylor, U.S. Pat. No. 3,653,484 relates to a handrail driving assembly for belt type moving passenger conveyors in which a plurality of traction providing rollers are disposed along the length of the conveyor to operate independently of each other, each deriving its motive power from the motion of the belt.
Clark, U.S. Pat. No. 3,414,109 describes the return run of a moving handrail engages a plurality of successive traction rollers, each provided with a pressure roller. A cantilever mounting of rollers provides accessibility. A coil spring mechanism is used to keep the handrail in contact with the traction rollers.
Taher et al., U.S. Pat. No. 3,779,360 pertains to a transportation device having an endless handrail driven about a closed loop by drive means which include traction and pressure rollers. The pressure rollers are biased against the handrail, opposite the traction rollers, by biasing means which includes at least one main leaf spring member. A leaf spring member is stressed from a predetermined unstressed curved configuration to a flat configuration when the handrail is disposed between the traction and pressure rollers.
Meyer et al., U.S. Pat. No. 5,307,920 discloses an escalator handrail drive system which includes a powered drive belt engaging the underneath surface of the handrail along the return path of travel of the latter. A series of pressure rollers engage the outer surface of the handrail to press the latter against the drive belt. The pressure rollers are all biased against the handrail by a single tensioning spring. The drive belt is pretensioned by an adjustable pretension spring assembly which can apply a fixed pretensioning force to the drive belt which will not substantially change irrespective of whether the handrail is being driven in the "up" direction or in the "down" direction on the escalator.
Ahls et al., U.S. Pat. No. 5,117,960 discusses an escalator or moving walkway handrail driven by a pair of linear belts which engage opposite sides of the handrail along the return path of travel thereof. The belt that engages the underside of the handrail is a powered drive belt, and the belt that engages the upper-side of the handrail is a pressure or reaction belt. Both belts are held against the handrail by a set of biased pressure rollers which urge the reaction belt against the handrail. The belts serve to convert line contact with the pressure rollers into area contact with the handrail thereby spreading out the driving forces acting upon the handrail. Ahls et al., 5,341,909 describes a direct drive wheel to handrail contact drive assembly utilizes a pair of drive rollers which contact the handrail directly. The drive rollers are powered by a single drive shaft. A pair of pressure rollers oppose the drive rollers so as to press the handrail against the drive rollers. The pressure rollers are spring biased against the handrail. The drive assembly is used to drive the handrail of an escalator or moving walkway.
Nurnberg et al., U.S. Pat. No. 5,125,494 relates to a drive pulley system provided for a handrail drive mechanism of a passenger conveyor. The system includes a pulley, with a handrail drive belt wrapped about the pulley for rotation therewith. A pair of disc-like members are disposed on opposite sides of the pulley to sandwich the pulley therebetween. The disc-like members have diameters greater than that of the pulley and are rotatable relative to the pulley, or the disc-like members may be fixed to the pulley and be fabricated of low friction material. The handrail is wrapped about the outer peripheries of the disc-like members, spacing the handrail from the drive belt, and thereby allowing differential linear movement between the handrail drive belt and the handrail due to the relative rotation between the disc-like members and the pulley, or due to slippage between the handrail and the low friction disc-like members. The system also includes an idler pulley disposed in an area between the pulley and a second pulley and about which both the handrail drive belt and the handrail drive are wrapped to impart drive to the handrail by the drive belt. The idler pulley substantially spans the area between the other two pulleys to provide a large included angle of engagement between the idler pulley, the handrail and the handrail drive belt.
Bruehl et al., U.S. Pat. No. 4,895,240 pertains to the handrail of an escalator of other passenger conveyor is driven by traction rollers which engage the handrail and also directly engage links which are connected to and drive the steps or tread of the conveyor. The handrail is biased into engagement with the traction rollers, and moves at substantially precisely the same speed as the steps or tread due to the direct connection between the step or tread drive and the handrail drive.
Hermann et al., U.S. Pat. No. 4,875,568 refers to an escalator handrail is driven by a pair or angularly offset rollers. The angular offset of the rollers causes a wedging effect at a roller nip whereby the driving force imparted by the rollers to the handrail is increased. Hermann et al discloses a spring tensioning arrangement.
German Patent Document No. 4301512A1 relates to a three-state planetary reduction gearbox for driving a coaxial handrail pulley for an escalator in which a bearing housing is bolted in the handrail drive.
The problem with prior are devices is that the handrails tend to slip with respect to the foot pieces or passenger load run which requires the passenger to release his or her grip from the handrail from time-to-time to avoid being dragged forward or backward of the place on which they are standing. The relative displacement of the handrail vis-a-vis the foot pieces can result in accidents including falls which has lead to increasing liability insurance costs. The slippage of the handrail is due to slippage in the handrail drive mechanism. The present invention presents a solution to this problem by providing a mechanism to maintain synchronous movement between the handrail and the foot pieces.


A process for the fluid catalytic cracking of mixed hydrocarbon feeds from different sources is described, such as feeds A and B of different crackability, the process being especially directed to obtaining light fractions such as LPG and comprising injecting feed A in the base of the riser reactive section and feed B, of lower crackability, at a height between 10% and 80% of the riser, with feed B comprising between 5% and 50% of the total processed feed. The process requires that the feeds present differences in the contaminant content, improved dispersion of feeds A and B and feed B injection temperature same or higher than that of feed A.

Fluid catalytic cracking (FCC) is carried out by contacting hydrocarbons in a tubular reaction section or riser with a catalyst made up of a fine particulate material. The most common feedstocks to be submitted to a FCC process are usually those refinery streams from vacuum tower side cuts named heavy vacuum gasoils (HVGO) or heavier than the latter, from the bottom of atmospheric towers, named atmospheric residua (ATR), or still, admixtures of these streams.
These streams, having densities typically in the range of from 8° to 28° API, in order to deeply alter their composition and convert them to lighter, more valuable hydrocarbon streams, should be submitted to a chemical process such as the catalytic cracking process.
During the cracking reaction, substantial amounts of coke, as a reaction by-product, are deposited on the catalyst. Coke is a high molecular stock made up of hydrocarbons that contain of from 4 wt % to 9 wt % hydrogen in their composition.
The coke-recovered catalyst normally designed as "spent catalyst" is directed to the regenerator. In the regeneration zone, in a regenerator vessel kept at high temperature, coke deposited on the surface and in the catalyst pores is burned. Coke withdrawal by combustion leads to the catalyst activity recovery and releases heat in a sufficient amount to provide for the thermal requirement of the catalytic cracking reactions.
The fluidization of the catalyst particles by gaseous streams allows the catalyst transport between the reaction zone and the regeneration zone and vice-versa. The catalyst, besides doing its essential task of promoting the chemical reaction catalysis, is also the heat transport medium from the regenerator to the reaction zone.
The technique is abundant in descriptions of hydrocarbon cracking processes in a stream of fluidized catalyst, with catalyst transport between the reaction zone and the regeneration zone, and burning of coke in the regenerator.
In spite of the rather long existence of FCC processes, there is a continuous search for new techniques for improving the process, increasing the yield in more valuable products, such as gasoline and LPG. Broadly, it may be stated that the main objective of FCC processes is the maximization of said more valuable products.
The maximization of these products is basically obtained in two ways. One is the increase of the so-called "conversion", corresponding to the reduction in the production of heavy products such as clarified oil and light cycle oil. Another way is the reduction in the coke and fuel oil yields, that is, through the lower "selectivity" to these products.
The lower production of these two latter products, increasing the process selectivity to the target products, has as further beneficial results the need of smaller air blowers and wet gas compressors, those being big-sized, energy-consuming machines generally limiting of the UFCC capacity. Besides, it is economically interesting to promote the rise of more valuable products such as gasoline and LPG.
One important aspect to consider is the interest or need to increase LPG production according to the refiner's needs.
The experts know that an important feature of the FCC process is the initial contact of the catalyst and feed, this having a paramount influence on the conversion and selectivity of the process to generate valuable products. In a FCC process, the pre-heated hydrocarbon feed is injected near the bottom of a conversion zone or riser, where it contacts the flux of regenerated catalyst. It is from the regenerated catalyst that the feed receives heat in sufficient amount to vaporize and provide for the thermal demand of the endothermic reactions that predominate in the process.
After the riser, a long vertical tube having dimensions in an industrial unit of ca. 0.5 m to 2.0 m diameter by 25 m to 40 m height, where the chemical reactions occur, the spent catalyst, having coke deposited on its surface and pores, is separated from the reaction products. The spent catalyst is then directed to the regenerator to burn the coke in order to have its activity restored and generate the heat that, being transferred from the catalyst to the riser, will be used by the process.
The conditions existing in the feed injection location of the riser are determining as related to the products formed in the reaction. In this region the initial mixture of the feed and regenerated catalyst occurs, heating the feed until the boiling point of its constituents is attained with the vaporization of most of such constituents. The total residence time of the hydrocarbons in the riser is around 2 seconds.
In order to process the catalytic cracking reactions, it is required that the feed vaporization in the region of admixture with the catalyst occurs quickly so that the vaporized hydrocarbon molecules may contact the catalyst particles—the size of which is around 60 microns—permeating through the catalyst micropores and reacting in the acidic sites. Failure in achieving this quick vaporization results in the thermal cracking of the feed liquid fractions.
It is well known that thermal cracking favors the build up of by-products such as coke and fuel gas, mainly during the cracking of residual feeds. Coke poisons the acidic sites and may even block catalyst pores. Therefore, thermal cracking in the riser bottom undesirably competes with the catalytic cracking, object of the process.
The optimization of the feed conversion usually requires the maximum coke removal from the catalyst in the regenerator. Coke combustion may be obtained in a partial or total combustion regimen.
In the partial combustion regimen, the gases produced by coke combustion are mainly made up of CO2, CO and H2O and the coke content in the regenerated catalyst is of the order of 0.1 wt % to 0.3 wt %. In the total combustion regimen, to be carried out in the presence of larger oxygen excess, practically all the CO produced in the reaction is converted to CO2.
The oxidation reaction of CO to CO2 is highly exothermic, making total combustion to occur with a large heat release, resulting in high regeneration temperatures. However, total combustion leads to a catalyst having less than 0.1 wt % and preferably, less than 0.05 wt % coke, this being a favorable feature relative to the partial combustion, besides avoiding the need of a costly boiler for further CO combustion.
The coke increase on the spent catalyst causes an increase of the coke burned in the regenerator by mass unit of the circulated catalyst. In conventional FCC units heat is removed from the regenerator in the combustion gas and mainly in the hot regenerated catalyst stream. An increase in the coke content on the spent catalyst increases the temperature of the regenerated catalyst as well as the temperature difference between the regenerator and the reactor.
Therefore a decrease in the regenerated catalyst flow rate to the reactor, normally designated as catalyst circulation rate, is required in order to attend to the reactor thermal demand and keep the same reaction temperature. However, the lower catalyst circulation rate required by the larger temperature difference between the regenerator and the reactor leads to a lower catalyst/oil ratio, this in turn reducing conversion.
Thus, catalyst circulation from the regenerator to the reactor is ascertained by the riser thermal demand as well as by the regenerator temperature, which is a function of coke production. Since the catalyst circulation itself affects coke produced in the riser, it is concluded that the catalytic cracking process works under a thermal balance regimen. In view of the preceding, operation at high regeneration temperatures is to be avoided.
Generally, on using modern FCC catalysts, regenerator temperatures and therefore regenerated catalyst temperatures are kept below 760° C., preferably below 732° C., since activity loss would be severe above this figure. A desirable operation range is of from 685° C. to 710° C. The lower limit is dictated mainly by the need to secure suitable coke combustion.
On processing increasingly heavy feeds, there is a tendency to increase coke production and the operation under total combustion requires the use of catalyst coolers to keep the regenerator temperature within acceptable limits. Generally, catalyst coolers remove heat from a regenerator catalyst stream, and return to said vessel a substantially cooled catalyst stream.
As for the fluid-dynamic features of the riser, where the catalytic cracking reactions of the invention occur, it is well known that catalyst solid particles are entrained in the reaction medium during contact with the feed and other vaporized materials.
This kind of reactor is normally of tubular shape where, in order to reduce by-products, operation should be carried out according to a hydrodynamic flow regimen, so that the superficial gas velocity is high enough to cause that catalyst flux is in the same direction as that of the feed and of other gases present therein. That is, the liquid and vaporized feed entrains the catalyst particles throughout the entire path in the tubular reactor.
These flow regimens are known by the experts as fast fluidized bed, riser regimen or more generally as transport regimen, those regimens being the preferred ones when one deals with reaction systems that require continuous flow reactors.
Generally, for a certain cross section area of a tubular reactor, which is a function of the reactor diameter, the catalyst concentration, in a fluidized bed reactor, is reduced as a result of increased superficial gas velocity. The higher the superficial gas velocity, the higher will be the reactor lengths required to allow that a certain amount of feed may contact the required amount of catalyst. Those higher superficial gas velocities require a higher L/D (Length/Diameter) ratio or aspect ratio of the reactor, which is the ratio between the reactor length and its diameter.
In the patent literature several publications suggest the multiple injection of the same feed in FCC units.
U.S. Pat. No. 3,246,960 teaches an FCC apparatus built so that the injection of the same feed in different locations of the riser is carried out so as to promote a more uniform mixture between feed and catalyst, with the consequent increase in gasoline octane rating.
International publication WO 0100750A1 teaches the re-cracking of naphtha to increase LPG yield, simultaneously with the split-feed injection of the same feed. The split-feed is injected in at least two different locations above the reactor lower position. The process aims at maximizing diesel oil production.
U.S. Pat. No. 4,869,807 teaches a process for converting a non-segregated hydrocarbon feed in a FCC reactor in the presence of a zeolitic catalyst for producing gasoline. The same feed is divided in portions and injected into a plurality of locations along the length of the FCC reactor, with of from 60 to 75% by volume being injected in the lowest injection position. The distance between this location and the immediately superior location comprises at least 20% of the total reactor length. Multiple injection would allow increased gasoline octane rating.
U.S. Pat. No. 5,616,237 teaches the same technique of multiple injection of the same feed in different locations to secure selectivity improvements. This approach reduces the contact time of the feed, with the consequent bottom conversion. It is also suggested to promote a recycle of the non converted friction to several injection locations along the riser length.
U.S. Pat. No. 6,416,656 discloses a process for catalytically cracking hydrocarbon stocks in a riser or fluidized bed reactor to increase simultaneously the yields of diesel and liquefied gas. The process includes the steps of: first, charging a gasoline stock and a catalytic cracking catalyst into a lower zone of the reactor to permit contact between the catalyst and the gasoline stock and to produce a liquefied gas-rich oil-gas mixture containing reacted catalyst. The resulting liquefied gas-rich oil-gas mixture (still containing reacted catalyst) is then introduced into a reaction zone above the lower zone of the reactor. Simultaneously, at least one conventional catalytic cracking hydrocarbon feed is also fed independently into at least two sites situated at different heights above the lower zone of the reactor. The resulting mixture is then separated in a conventional fashion.
Another approach from the patent literature involves injecting an auxiliary stream such as water or petroleum fractions in a location downstream of the injection of the feed to be cracked in order to promote an increase in the mixing temperature in the area of the feed injection. This is done aiming at increasing the vaporized percent of residual feeds, without altering the riser outlet temperature.
Such an approach is taught in U.S. Pat. No. 4,818,372 that relates to a FCC apparatus with temperature control including an upflow or downflow reactor, a device to introduce the hydrocarbon feed under pressure and in contact with a regenerated cracking catalyst. The FCC apparatus comprises further at least a device for injecting an auxiliary fluid downstream of the reactor zone where feed meets the catalyst, whereby it is desired to attain a higher temperature in the mixing zone of feed and catalyst. This document does not contemplate feed segregation, rather, it makes use of an inert, external fluid the main effect of which is the cooling of the injection region of said fluid, with temperature control and increase in catalyst circulation rate. In this respect please see Example 1, column 7, lines 55 to 60 of said patent, where it is defined that the feed is the same feed, injected once in the riser base while the other injection is effected with a cooling fluid as water or either a product of the cracking itself. The proposed process is directed to the cracking of a residual feed, the main feature of which is to contain at least 10% of a fraction having boiling point higher than 500° C. The desired goal when increasing the mixture temperature is to secure the vaporization of heavier fractions, while at the same time promoting a thermal shock on said fractions, aiming initially at converting the bigger molecules into lighter compounds, able to vaporize and catalytically cracking in a further step.
This is attained by injecting an auxiliary fluid above the feed injection location, from which the cracking reactions occur under milder conditions, at constant reaction temperature and independently of the desired mixing temperature.
The goal of the present invention is different and directed to the situation where feeds of different crackability are processed at the same time in one single riser. Under these conditions, it is suggested to inject the feed of lower crackability, the coke selectivity of which as well as the contaminant concentration is higher, in a riser downstream injection location. This aims at increasing the severity of the reactions of the feed of better quality injected in the beginning of the reactive section of the riser aiming mainly at higher LPG yields. This is obtained by a localized increase in the regenerated catalyst circulation as well as of the temperature of the riser section comprised between the two injections. Further, regenerated catalyst that contacts the better quality feed in the beginning of the riser reactive section is less deactivated by virtue of the local absence of contaminants as well as the higher coke production caused by the lower crackability feed.
The injection location of the feed of lower crackability in the riser is chosen so as to maximize LPG production, and is a function of the properties of the different feeds to be processed, as well as of the riser outlet reaction temperature.
A further distinguishing point between the present invention and U.S. Pat. No. 4,818,372 is that in this latter the total catalyst circulation is substantially increased. This may be observed from Example 1, in the Table of column 8, which sets forth an increase in the catalyst circulation rate from 4.6 to 6.7 by injecting a certain flow rate of water in the middle location of the riser. As a consequence, more coke will be formed, overloading the air blower of the regeneration section that normally is already very tight in terms of accepting any coke increase.
In the present invention, the resulting rise in catalyst circulation rate is only local, being limited to the section comprised between the lower and upper injections, but there is no significant increase in total catalyst circulation rate. Actually, as the lower crackability feed and normally having higher coke selectivity, is processed in the riser under milder temperature and contact time conditions, it is to be expected coke production to be slightly reduced.
Further, in the downstream injection location, the catalyst is recovered by a considerable content of deposited coke, this making it less selective to further coke formation. This way no overburden is expected on the air blower of the regeneration section, instead, a relief is to be expected.
A further disadvantage of the teachings of said U.S. Pat. No. 4,818,372 is the overburden of the riser, reactor cyclones, transfer line, main fractionator as well as of the top condensers of the fractioning section at the moment of the injection of make up water in the riser. This leads to adapt the dimensioning of most of the equipment to the requirement of the claimed process.
Besides, injecting water in the riser means a poor energetic balance of the FCC process, since all the energy that water removes from the converter is lost when the same water condenses on the top of the main fractionator coolers. It should also be mentioned the further disadvantage of additional acidic water generation in the refinery.
As taught in U.S. Pat. No. 4,818,372, the segregated injection of an external stream in a downstream riser location is carried out aiming at controlling the riser temperature profile. This makes possible to keep the upstream section of the riser at a relatively higher temperature without altering the riser top temperature or TRX (reaction temperature). Such control may also be carried out through a heavy naphtha recycle, as taught in U.S. Pat. No. 5,087,349.
Aiming at the same goal, U.S. Pat. No. 5,389,232 teaches a heavy naphtha recycle in downstream riser locations.
Aiming at minimizing naphtha overcracking reactions, U.S. Pat. No. 4,764,268 suggests the injection of a LCO stream in the top of the riser.
A similar alternative, taught in U.S. Pat. No. 5,954,942 aims at increasing conversion, through a quench or quick cooling with the aid of a steam auxiliary stream in the riser upper region.
International publication WO 93/22400 mentions the possibility of injecting along the riser a cracking product such as LCO aiming at cooling the riser and consequently promoting an increase in the catalyst circulation rate so as to make possible improved performance of ZSM-5 additives.
Contrary to U.S. Pat. Nos. 4,818,372, 4,764,268, 5,389,232, 5,954,942 and International publication WO 93/22400, in the present invention the feed injected in the one or more downstream riser locations is not an auxiliary external stream but rather one of the streams that normally make up the feed of the FCC unit. Since the segregated feed is injected at a temperature equal or higher than the feed temperature, the improved yields should not be considered as caused by an increase in the total catalyst circulation rate.
As regards the injection of the segregated feed in different locations of the riser, some publications suggest to differentiate feeds as a function of the nitrogen content only.
Thus, U.S. Pat. No. 4,985,133, aiming at reducing NOx release into the regenerator, teaches an alternative for the injection of the higher total nitrogen feed in the riser base, the less contaminated feed being injected in a higher nozzle.
U.S. Pat. No. 4,218,306 teaches a FCC process for producing gasoline and distillate by combining cracking of a distillation gasoil injected in the base of a cracking zone of a riser for admixture with a regenerated catalyst to form a catalyst suspension at high temperature. A second hydrocarbon fraction having more difficult cracking features is charged at a location 3.05 m to 9.14 m (10 to 30 feet) downstream the first injection. The riser outlet temperature is limited to the range between 482° C.-593° C. (900° F. to 1100° F.), preferably 510° C.-530° C. (950° F. to 985° F.).
Said U.S. Pat. No. 4,218,306 is directed to improved gasoline yields, as set forth in the main claim. In a patentably distinguishing way, the present invention is a much more flexible process, directed to either LPG only or to the sum LPG+gasoline, according to the injection location of the feeds in the riser as well as the desired riser outlet temperature. Besides, contrary to the teachings of said US patent, according to the invention, the injection of the lower crackability feed is not limited to the riser section placed 10 to 30 feet (corresponding to 6% to 30% of the reactive section of a typical industrial riser) downstream of the riser base injection of the better crackability feed.
In the present invention the injection location of the lower crackability feed is set forth aiming at obtaining the maximum possible LPG yield. Such location is a function of the properties of the feeds of different sources to be processed, of the percent of the lower crackability feed processed based on the total feed flow rate as well as of the riser outlet reaction temperature. Said injection location may be positioned at any location downstream the injection of the lower feed, but preferably of from 10% to 80% of the riser reactive section. As a general rule, the ideal location for injecting the lower crackability feed is that, which provides for the operation conditions favoring the maximization of LPG production in the section between the two feed injections. Further, said location should conform to the minimum residence time required by the lower crackability feed to undergo the desired conversion to lighter products, including LPG.
It should be noted that in column 4, line 3 of U.S. Pat. No. 4,218,306, it is stressed that the downstream injection should be submitted to very slight or no heating at all, this featuring a feed cooling or quenching, such cooling being completely absent from the inventive process. Therefore, the concept of the said US patent, as applied to the main objective of the present invention, that is, maximum LPG production would not lead to the desired results.
U.S. Pat. No. 6,123,832 teaches a FCC process for the conversion of hydrocarbon mixtures based on a non-linear phenomenon consisting in the fact that the lower yield in valuable products is not linearly reduced, neither the coke yield increases linearly, with the increase in heavy component in the FCC feed.
This means that the marginal deleterious effect caused by feed contaminants on the FCC catalyst is weaker with the increase in heavy components. Alpha and beta different quality feeds are to be injected in different nozzles. Alternatively, different nozzles may be used. Still alternatively, the riser is divided in two zones for separate cracking in one portion of the riser. Thus, the benefit of using at least one high CCR feed stems from the fact that the lower CCR feed increases conversion to a much higher degree than the conversion loss due to the higher CCR content feed.
The conditions for differentiating alpha- and beta-feeds are: a) the CCR figures differ from at least 2 points in wt %; or b) they differ in hydrogen content by at least 0.2 wt %; or c) they differ in API gravity by at least two points; or d) they differ in nitrogen content by at least 50 ppm; or e) they differ in the C/H ratio by at least 0.3; or f) they differ in average boiling point by at least 93.3° C. (200° F.). The technique taught in said US patent is not clear as regards which feed is to be injected in which nozzle or riser position, or in which riser. One claim is directed to the methodology for calculating possible feed mixtures that could lead to desirable results in terms of valuable products. Injection is non-linear (claim 2, column 9).
Another alternative is the injection of an external stream such as an alcohol, ether or a gasoil of better quality than the feed injected in the riser base, as taught in U.S. Pat. No. 5,271,826. This approach does not contemplate feed segregation according to the concept of the invention.
Another approach for feed segregation, as taught in U.S. Pat. No. 4,422,925 and U.S. Pat. No. 3,617,497 is based on the difference between feeds exclusively focused on molecular weight, while suggesting multiple injections in the riser. The lower molecular weight feed is injected in the riser base aiming at maximizing gasoline yields. However, as will be seen hereinafter in the present specification, a single parameter for differentiating feeds is not sufficient for obtaining the desired results in terms of yields and products.
On the other hand, it is well known that the density is closely associated to the extent of feed contamination, as reported on page 132 of the article by M. A. Torem et al., in "Development of a new coefficient to predict FCC feedstock cracking", ACS 206th National Meeting—Advances in Fluid Catalytic Cracking—1993, Chicago, USA.
The considerations set forth above indicate that, in spite of the extended literature and patent publications, there is no description nor suggestion, In isolated or combined way, of a FCC process free of overall sensible cooling effect and without significant alteration of the total catalyst circulation rate, having improved conversion to light products such as LPG and gasoline, this being obtained from a mixed A and B hydrocarbon feed where feed B is produced by a thermal process or by physical separation, is more selective to coke formation relative to the feed to be injected in the base of the riser reactive section, is more refractory to cracking and is more heavily contaminated, where the conditions for injecting the segregated feed involve suitable distances between the injection locations in the riser and optimized dispersion of both feeds A and B aiming at maximizing LPG production, such process being described and claimed in the present application.

Process for the fluid catalytic cracking of mixed feedstocks of hydrocarbons from different sources