A device for non-contact detection of an external electric or magnetic field is presented. The device comprises an active unit cable of emitting an interrogation signal, and a passive unit to be positioned at a spot where the external field is to be detected. The passive unit comprises a substrate, which is capable of transporting therethrough a wave sensitive to the external field, and is formed with a delay line thereon. The delay line forms a wave channel for the wave""s propagation, and is capable of converting the interrogation signal into an output response signal. The wave channel is exposed contactlessly to action of the external field, which effects a change in a velocity of the wave propagation through the wave channel, the response output signal being thereby informative of the external field. The active unit is capable of receiving and processing the output response signal for determining and indicating the external field at the spot.

This invention relates to a device and method for the contactless detection of external electric and magnetic fields.
As is widely known, piezoelectric materials possess the special property of becoming electrically polarized under mechanical pressure. The converse effect is known as well. Such properties have given rise to the development of various piezoelectric sensors and detectors.
The mentioned converse approach enables piezoelectric elements to be utilized for sensing electric voltage applied thereto. In such sensors, the voltage applied to the element results in respective mechanical deformation of the element, which can be registered.
U.S. Pat. No. 4,340,872 describes a controllable piezoelectric crystal delay line. An input signal is transmitted through input lines to an input transducer and an output signal is received through output lines from an output transducer. The input signal is converted to a surface acoustic wave (SAW) propagating along the surface of the piezoelectric crystal. Control electrodes are applied to surfaces of the piezoelectric crystal and are connected to control lines. A control signal (an electric voltage) is applied to the control lines, and thus an electric field applied to the piezoelectric crystal alters its longitudinal dimension and, consequently, controls the propagation distance between the input transducer and the output transducer. By varying the propagation distance between the transducers, the control signal continuously varies the propagation delay of SAW. Thus, the time delay between the input and output signals is a function (i.e., a measure) of the control voltage applied to the driven lines. However, the device of US""872 provides for measuring an electrical field using contacts, i.e., without guarantying desired safety.
EP 810724 describes a tunable piezoelectric delay line comprising a SAW conducting piezoelectric substrate, two transducers and an additional electrode. This device is claimed to be used as a voltage sensor. The delay line is tuned by applying electric voltage to the additional electrode manufactured as a capacitive MOS structure (a semiconductor plate) which is superimposed on the piezoelectric substrate between the transducers of the delay line. The electroconductivity of the semiconductor plate electrode is controlled by the electric field effect. Since the SAW velocity depends on the electroconductivity of the adjacent electrode, the application of voltage to the MOS structure controls the delay time of the delay line. The structure described in EP 810724 is quite complex to prepare and, besides that, has low sensitivity to the applied electrical voltage. Another drawback of the device is its inapplicability to cases where non-contact detection of electric field or voltage is required, since in the device, the voltage of interest has to be applied to the semiconductor plate via electrical contacts.
Technique aimed at measuring external fields are also disclosed in the following publications: DE 19514342, WO 97/09624, and WO 93/13495.
According to the technique disclosed in DE 19514342, a current transformer assembly is used for determining voltage by measuring an electric current flowing in a high-voltage power line (electrical wire). However, for example, in the case of line disruption, this technique does not allow to determine the presence of a high voltage unambiguously.
According to WO 97/09624, a voltmeter utilizing an impedance voltage divider is used, being inserted between an electrical conductor whose electrical potential is to be measured relative to an electrical base potential, and this base potential. A surface-wave device is used as a part of the voltmeter, and has the function of measuring an electric voltage occurring across the voltage divider, namely, a voltage whose electric field has a valuable effect on the wave propagation in the surface-wave device. This technique, however, is not a contactless one.
WO 93/13495 discloses the use of a passive surface-wave sensor that can be wirelessly interrogated and used for measuring an external temperature field. The description of this technique focuses on the kinds of interrogation signals and a code used in an acoustic line, presenting no specific construction of a measuring device suitable to be used with this technique. The interrogation signals are frequency-modulated, and the acoustic line is chirped-coded and located in a particular place, where some external temperature field is to be fixed or measured.
Thus, practically, no solution has been found so far in the relevant prior art for the non-contact detection of electric fields or voltages, i.e., for safe measurement. This problem prevents performing a quick and safe test to determine whether a required voltage exists between electric wires in a power supply line, or in other hard-to-reach points.
Another modification of a delay line, such as a so-called resonator delay line is also known in the art. It comprises a transducer placed on a substrate and two systems of reflectors disposed bilaterally of the transducer.
U.S. Pat. No. 5,469,170 describes a system of passive SAW-identification tags to be placed on a plurality of articles, wherein the tags operate with the aid of a chirp transducer. The passive SAW-ID tag device is provided with a piezoelectric substrate having bus bars, spaced electrode taps between the bus bars and a built-in antenna, connected with an input SAW transducer matched to an input chirp signal generated by a nearby located chirp transmitter (an interrogating transmitter). The SAW-ID tags are intended for identifying articles and do not perform any additional function.
The main idea of the present invention consists of utilizing an effect, other than the converse piezoelectric effect. The converse piezoelectric effect is the linear effect consisting of the mechanical deformation of a piezoelectric element caused by an external electrical field to which the element is exposed. The effect utilized in the present invention is a non-linear effect and consists of a change in the velocity of propagation of a wave in a substrate capable of transporting the wave therethrough, wherein said change is caused by the application of an external electric or magnetic field. This physical effect, the so-called electroacoustic effect, is described, for example, in the following publications: xe2x80x9cPhysical properties of crystalsxe2x80x9d, J. F. Nye, Oxford, At the Clarendon Press, 1957; and R. B. Thompson and C. F. Quata, J. Appl. Phys. 42, 907 (1970).
Magneto-static and magneto-elastic waves can be created in magnetic materials (such as ferrites) when a micro-strip transducer mounted on a surface thereof is excited by an electromagnetic signal. Delay lines, functionally analogous to those known with respect to piezoelectric substrates, are described also for the magnetic materials. Moreover, the wave propagation characteristics, such as phase and group velocities and attenuation, depend on an external magnetic field to which the materials are exposed. The above properties are described, for example, in a monograph xe2x80x9cSpin waves and magnetic excitationsxe2x80x9d. Edited by A. Borovik-Romanov, S. K. Sinha. North Holland. Amsterdam-New-York-Tokyo, 1988.
The present invention is particularly useful for the non-contact detection of the existence of an external electric or magnetic field in the vicinity of a high-voltage electric line. It should be understood that if the external field to be detected is an electric field, a piezoelectric or electrostriction substrate is used and said wave is an acoustic wave. If the external field to be detected is a magnetic field, the substrate is made of a magnetic material and said wave is a magnetic wave. The term xe2x80x9cmagnetic wavexe2x80x9d used herein signifies a magneto-static or magneto-elastic wave in magnetic materials.
The inventors have found that when dealing with the detection of an external electric or magnetic field, the above-indicated non-linear effect of the change in the velocity of wave propagation is much stronger than the linear effect of mechanical deformation of a piezoelectric crystal. The sensitivity of the sensor device is thus significantly increased.
It is therefore an object of the invention to provide a method and a device suitable for non-contact and, optionally, also the remote detection of external magnetic and/or electric fields and voltages, utilizing the effect of the wave velocity change caused by the application of such external field.
Another object of the invention is to provide a sensor with high sensitivity for use in the above device, which is capable of measuring electric and magnetic fields over a wide range of intensities.
Still a further object of the invention is to provide a system for the remote contactless detection of external fields in hard-to-reach spots, for example around any selected electric wire or at any string insulator unit of an electric power line, at inaccessible contacts in switchboards, etc.
Besides the above, a method of utilizing the inventive system for tracing malfunctions in electric power lines forms yet an additional aspect of the present invention.
The term xe2x80x9cexternal fieldxe2x80x9d used herein below with reference to the inventive device and method should be understood as meaning at least one component from the following list: an alternating electric field, an alternating magnetic field, a static electric field and a static magnetic field.
According to one aspect of the invention, there is provided a sensor for use in a device for non-contact detection of an external field by positioning the sensor at a spot where the external field is to be detected, the sensor comprising a delay line, which is to be exposed contactlessly to action of the external field and comprises:
a transducer arrangement that is provided on a substrate made of a material capable of transporting therethrough a wave sensitive to said external field, and defines a wave channel for the wave propagation through the substrate, the transducer arrangement being capable of being actuated by an interrogation signal to generate said wave propagating through the wave channel and capable of converting the wave into an output response signal, said external field affecting a change in a velocity of the wave propagation, said output response signal being thereby informative of said external field.
According to another aspect of the present invention, there is provided a device for non-contact detection of an external field, comprising:
active and passive units, wherein the passive unit is to be positioned at a spot where the external field is to be detected, and the active unit is operable to emit an interrogation signal to be received at the passive unit, receive an output response signal coming from the passive unit, and process said output response signal for determining and indicating the external field, the passive unit comprising:
a substrate made of a material capable of transporting therethrough a wave sensitive to said external field, and
a delay line provided on said substrate to define a wave channel for the wave propagation through the substrate, the delay line comprising a transducer arrangement capable of being actuated by said interrogation signal to generate said wave propagating through the wave channel and capable of converting the wave into said output response signal, said wave channel being exposed contactlessly to action of the external field, which effects a change in a velocity of the wave propagation, said output response signal produced by the passive unit being thereby informative of said external field.
In accordance with the first basic embodiment of the device, it is intended for detecting external electric fields. Therefore, in the above definition, said external field to be detected is an electric field; said substrate is made of a piezoelectric material or electrostriction material (e.g., BaTiO3), and said wave is an acoustic wave (in our case a surface acoustic wavexe2x80x94SAW).
The second basic embodiment of the device is intended for detecting magnetic external fields, and the device comprises the substrate of a magnetic material (such as Yttrium Iron Garnet or other ferrite with low magnetic losses) capable of transporting a magnetic wave, if appropriately excited.
The transducer arrangement can be composed of a pair of transducers placed on a surface of said substrate and forming therebetween a wave channel. The pair of transducers is capable of launching said wave in the wave channel whenever the electromagnetic interrogation signal is received, and converting the wave into an electromagnetic response signal.
The delay line of the above-mentioned type can be formed in both basic embodiments of the device, i.e., on the piezoelectric or electrostriction substrate and on the ferrite substrate. The selection of transducers for these two embodiments are to be provided whilst considering the specific features of the respective substrates. For example, in the piezoelectric-based embodiment of the device, one transducer of the mentioned pair of the transducers in the passive unit serves to launch SAW in response to the interrogation signal. The acoustic channel, being contactlessly exposed to and directly controllable by the external electric field, changes the velocity of propagation of SAW therethrough with the intensity of said field. The output transducer of the pair derives a delayed signal in response to the launched SAW, and change in the response signal""s delay will be informative of the intensity of the external electric field. Analogous processes take place in the second basic embodiment, where a magnetic material is used for the propagation of magnetic waves.
In the piezoelectric basic embodiment, said delay line may be easily implemented by a so-called resonator delay line, which is characterized by relatively small dimensions at a relatively high total delay time. The resonator delay line can be formed by one transducer placed on a surface of the substrate between a pair of reflectors, which define the wave channel being an acoustic resonator. Each of the reflectors may constitute, for example, a system of parallel grooves, lugs, metal strips, etc. provided on the surface of the piezoelectric substrate. Such reflectors cause the SAW, whenever launched by the transducer in the acoustic resonator, to be successively reflected, thereby producing on the transducer a considerable resonance response signal at a certain resonance frequency value of the delay line. Since the wave channel is subjected to the direct action of the external field, any change in the external electric field will affect the velocity of propagation of the SAW between the reflectors (i.e., the time of propagation or phase shift). To achieve a resonance condition in the wave channel, the double time of run between both reflectors should be an integer number of time periods of the carrier frequency of a signal. Hence, the change of SAW velocity will cause a shift (change) of the resonance frequency from said certain value. The shift of the resonance frequency is thus informative of the intensity of the external electric field.
According to a preferred embodiment, said active unit may comprise a signal source capable of transmitting the interrogation signal, a receiver capable of receiving the response signal from said passive unit, and processing means capable of determining the external field by processing the response signal and the reference signal for further indicating the determined field.
For the embodiments where the delay line comprises two transducers, the processing means are to be adapted to process the phase shift between the response signal and the reference signal. In the embodiment with the resonator delay line, the processing means are to be adapted to detect and process the detected shift of the resonance frequency from said certain resonance frequency value.
Owing to the non-contact exposure of the passive unit of the device to the field to be detected, the present invention enables measurements to be carried out safely. It goes without saying that the safety of remote measurement as opposed to just non-contact one is higher.
According to the most preferred embodiment of the device, said active unit can be positioned remotely from the passive unit; both the active and passive units are provided with respective emitting-receiving antennas, and said signal source of the active unit constitutes a transmitter, thus enabling safe non-contact and remote detection of external fields.
To this end, a method of contactless (and optionally, remote) detection of electric fields (or voltages) includes mounting the passive unit at a spot where the electric field is to be detected, and activating the active unit of said device to obtain indication of the electric field at said spot.
Another important aspect of the invention is to provide a highly sensitive sensor suitable for use as the passive unit of the above device, and enabling the measurement of external fields over a wide range of intensities. To this end, at least one of the following features can be used:
The interrogation signal can be a specifically phase-code (PC) signal, and one transducer in the pair of transducers is a phase-coded transducer capable of processing said phase-coded interrogation signal, while the other transducer converts a signal without changing its envelope. Any phase coded (e.g., bi-phase coded) transducer forms its maximal response signal in response to a PC coded signal exciting it only when all code intervals of the input signal are summarized and the phases of the code intervals are exactly the same that in the corresponding transducer""s code sections. Due to the dependence of the SAW velocity on the external field, the quality of the mentioned phase matching depends on the external electric field. Therefore, a change in the amplitude of the response signal is informative of an external field.
The passive unit may be designed so as to define two wave channels (defined by two delay lines), wherein one wave channel is exposed to the external field to be detected, and the other is screened from the external field. The first and second wave channels have different lengths to ensure the phase shift between two output signals produced by the two delay lines. In this case, the output signal is a vector sum of said two output signals. The provision of the screened channel increases the sensitivity of the sensor and reliability of device as a whole.
A field transformer can be used with the sensor to amplify or concentrate the field influencing the SAW propagation in given proportion to the external field. Such a field transformer aimed to amplify the field may be composed of two capacitors having different values of capacitance and different distances between the capacitor""s plates, such that the capacitor with the smaller capacity is that having a smaller distance between the electrodes. The capacitors are connected in parallel and are both mounted at said spot where the external field is to be detected. At a certain relation between the capacitances and the geometric sizes of the capacitors, the intensity of the inner electric field of the capacitor of the smaller capacity can be larger than the intensity of the external field a predetermined ratio. The substrate with said delay line is mounted as the dielectric in the capacitor of the smaller capacity (and larger inner field), and in such a way that the inner field of that capacitor influences the SAW velocity.
Alternatively, such a field transformer may be in the form of a metallic plate (electrode) having a part thereof extending predominantly along the external field lines and ending with a sharp edge in the nearest vicinity of the SAW path. Such an electrode has no connection with the source of the field (e.g., wire), but is placed in the external field to be detected, thereby serves as a concentrator of this field.
Thus, according to yet another aspect of the present invention, there is provided a sensor for mounting at a spot where an external field is to be detected, the sensor comprising:
a substrate made of a material capable of transporting therethrough a wave sensitive to said external field,
a first delay line provided on said substrate to form a first wave channel for said wave""s propagation contactlessly exposed to action of the external field, said first delay line comprising a first transducer arrangement capable of being actuated by a certain interrogation signal to generate said wave propagating through the first wave channel and capable of converting the wave into a first output signal; and
a second delay line provided on said substrate to form a second wave channel for said wave""s propagation, said second delay line comprising a second transducer arrangement capable of being actuated by a certain interrogation signal to generate the wave propagating through the second wave channel and capable of converting said wave into a second output signal; wherein said second wave channel is screened from the external field and has the length differing from that of the first wave channel to ensure a phase shift between the first output signal and the second output signal;
the first and the second delay lines of said sensor are connected in parallel to provide an output response signal formed by superposition of said first and second output signals and being thereby informative of the external field.
Preferably, the first (unscreened) wave channel can be designed to change its output signal""s amplitude as the external field changes. In one particular case, the amplitude of the output signal decreases with the growth of the external field.
As indicated above, the sensor can be formed in two basic modifications, i.e., with a piezoelectric or electrostriction substrate, and a ferrite substrate, being thereby sensitive to electric and magnetic external fields, respectively.
A number of embodiments of the piezoelectric modification of the sensor will be described below.
According to one embodiment of the sensor, it is intended for detection of external electric fields, and comprises said substrate of piezoelectric material, bearing:
said first transducer arrangement comprising a first pair of transducers placed on a surface of said substrate and forming therebetween said first wave channel constituting a first acoustic channel, said transducers being capable of launching a SAW into said first channel in response to an input electromagnetic signal and converting the SAW into a first output electromagnetic signal;
said second transducer arrangement comprising a second pair of transducers placed on a surface of said substrate and forming therebetween said second wave channel constituting a second acoustic channel, said second pair of transducers being capable of launching SAW into said second channel in response to said input electromagnetic signal and converting the SAW into a second output electromagnetic signal;
thereby, owing to the difference in lengths of said first unscreened and said second screened acoustic channels, the phase of the response signal formed by superposition of said first and said second output signals is indicative of the external electric field.
The difference in length between the two acoustic channels is preferably a fraction of the SAW wavelength in the screened channel.
The above-described sensor effectively detects the presence of external fields, owing to the fact that in one of the mentioned acoustic channels, the amplitude of the output signal depends on the external field, and in the other (screened) channel, does not if, for example, the amplitude of the output signal of the acoustic channel exposed to external electric field decreases as the electric field increases, the response signal (being a vector sum of the output signals of the screened channel and the unscreened channel): a) will never have its amplitude reduced to zero, and b) will be nearer to the phase of the xe2x80x9cunscreenedxe2x80x9d channel output signal as the field increases.
If narrow band transducers are used, their bandwidth are should be such as not to exceed their central frequency shift due to the electric field to be detected. If relatively wide band transducers are used, frequency of the interrogation signal can be selected within the range of the slope of the frequency response of the transducers.
Analogous embodiments can be constructed on the ferrite substrates, to obtain the sensor capable of detecting external magnetic fields.
In the embodiment of the sensor, preferably applicable to its piezoelectric modification, said first pair of the transducers is identical to said second pair of the transducers, wherein one transducer from each pair is a phase coded transducer capable of processing a phase coded signal, and the otherxe2x80x94converts a signal without changing its envelope. The use of the phase coded transducers enhances the dependence of the first (unscreened) channel""s output signal on the external field, and improves field sensitivity of the sensor. When the external electric field""s change causes a multi-phase coded transducer to produce a progressively smaller output signal, this fact, in turn, will make the total response signal of the sensor progressively closer to the output of the second (screened) acoustic channel. Hence, the response signal remains non-zero, which thus enhances the reliability of device.
It is clear that the sensor using a phase-coded signal should be based purely on an electroacoustic effect. Indeed, the distances between electrodes are small (of the order of SAW wavelength). So, their changes due to piezoelectric effect are small too (i.e., this change is proportional to the distance itself). Hence, distances between the electrodes remain independent on the external field. This means that the change in the signal induced by the increase in the external field takes place only due to the change in SAW velocity.
The interrogation signal is a high frequency electromagnetic signal, the frequency of which is determined by the required sensitivity of the passive unit to the external electric field under test. According to acoustic, geometric and technological considerations, the frequency of the interrogator device for so-called piezoelectric embodiments of the sensor and the device can be selected at about 1 GHz. For the so-called ferrite embodiments, the frequency can be higher, e.g., up to 10 GHz.
It is understood, that for all embodiments of the device and the sensor (except for that of resonator type or that with the phase-coded transducers), the interrogation signal is a high frequency pulse with the duration smaller than the delay time of the delay line(s).
In the case of one-channel passive unit of the device, sensitivity of the device can also be improved by increasing the delay time. In the case of the two-channel design, the interrogation signal is preferably a multi-phase-coded high frequency signal matched with codes of the transducers in the sensor at the external field equal to a certain reference value. Hence, the detection of a maximal output signal is indicative of that the external field is equal to its reference value. As previously mentioned, the multi-phase coded interrogation signal increases the sensitivity of the sensor and, additionally, permits to interrogation only one particularly matching sensor. It should be mentioned, that the sensor""s sensitivity can be increased by selecting correct parameters of the phase-coded interrogation signal, such as the length of the code interval, a number of phase gradations in the code, a number of bits in the code and, of course, the frequency of the signal.
Electric fields which are detectable by the above-described piezoelectric or electrostriction sensor and device, are preferably those that are substantially static with respect to the sensitive element, i.e., those with a period much greater than the delay time of the piezoelectric sensor.
The above-described device in its remote modification can be successfully used for detecting strong external fields, for example, for determining whether electric voltage is present between high voltage wires in an electric power line. The device can also be utilized for checking the integrity of string insulators in the electric power lines. Yet another application of the sensor is for determining voltages at hard-to-reach places in complex electrical appliances and installations such as switchboards, control panels, electric machines, etc.
According to yet another aspect of the present invention, there is provided a sensor for use in a device for non-contact detection of an external field in the vicinity of an electric wire, the sensor comprising:
a substrate carrying a delay line to define a wave channel for the wave propagation through the substrate, and
a field transformer operable to increase intensity of a field within a delay line, as compared to the intensity of the external field outside said delay line, in a known proportion, the increased field affecting a velocity of the wave propagating within the delay line, the delay line comprising:
a transducer arrangement capable of being actuated by an interrogation signal to generate said wave propagating through the wave channel and capable of converting the wave into an output response signal, said wave channel being exposed contactlessly to action of the external field, which effects a change in a velocity of the wave propagation, said output response signal produced by the passive unit being thereby informative of said external field.
Applications of the inventive device should not be limited to the mentioned ones.
To this end, and in accordance with a further aspect of the invention, there is provided a system for remotely detecting the presence of an external field at a plurality of check points to be examined; the system comprising the above-described device comprising one said active unit and a number of said passive units; said passive units of the device being mountable at the respective check points, while the active unit is capable of remotely communicating with said passive units by emitting said number of interrogation signals respectively associated with the number of the passive units, and recognizing the number of respective response signals.
In other words, the system for remotely detecting the presence of, say, an electric field or voltage at a plurality of check points (e.g. of an electric circuit), may comprise a number of passive units and one active unit, wherein each of said passive units and said active unit is provided with an emitting-receiving antenna, and wherein:
each of said passive units is mountable at one of said check points and being responsive to one particular interrogation signal whenever received from said active unit; all said passive units being responsive to different interrogation signals, respectively;
said active unit comprising a transmitter, a receiver and processing means; said transmitter being capable of emitting said different interrogation signals to be received by said respective passive units; said receiver is capable of receiving and recognizing response signals from said passive units, wherein said processing means is adapted to determine the external electric field at each of said check points by comparing a response signal received from the respective passive unit with a corresponding reference signal for further indicating the electric field detected at said check point.
The passive unit may be a piezoelectric or electrostriction sensor with one or two acoustic paths.
it is understood that for determining electric fields at a plurality of check points, such a system must be capable of discriminating between different check points, i.e. must possess a high selectivity. As has been explained, this task can be best resolved if each interrogation signal represents a phase coded signal matched with a code of a particular passive unit; in such a case, the passive unit serves as a matched filter. A variety of such interrogation signals can be achieved by phase coding. If the transducers of the passive units are designed according to the respective phase codes, each particular interrogation signal will be received by only one (matching) passive unit. Again, both the sensitivity and the selectivity of the system can be improved by judiciously selecting parameters of the phase coded signal (such as the length of the code interval, number of phase gradations in the code, the code rank, the carrier frequency of the signal).
In a particular example, the system for remotely detecting the presence of high voltage between the wires of an electric power line will comprise a required number of the passive units, each mountable on a particular wire of the electric power line; all said passive units being responsive to different interrogation signals, respectively, said active unit being designed in the form of a portable remote apparatus capable of selectively or simultaneously communicating with the respective passive units to allow detection and indication of the presence of high voltage regarding the particular wires bearing the respective passive units.
According to another application, the system having a number of sensors (passive units) and one active unit can be used for checking the integrity of suspension insulator strings of an electric power line. In this case, the passive units can be mounted on the bodies of respective insulator strings. If a particular insulator is its regular state, the respective passive unit will cause the system to detect the presence of a predetermined nominal voltage applied to the insulator""s ends. If the insulator is ruptured completely or partially, the detected voltage will differ from the nominal value.
Both the system for checking the voltages on the wires, and the system for checking the condition of suspension insulator strings in electric power lines can be fulfilled in situ by passing along the power line, where said passive units are preliminarily mounted, with the aid of any vehicle carrying the portable active unit and remotely providing the measurements of interest. Such a method is extremely useful and effective in emergency situations.

Method and device for non-contact detection of external electric or magnetic fields


The blood-simulating fishing lure is a fishing lure having a chain of lightweight spherical elements or ball chain threaded through or attached to an artificial lure body, such as a float or plug, to simulate a bleeding or wounded baitfish as it moves through the water. The spherical elements are preferably colored red and made from aluminum or other lightweight material. The chain is preferably attached to the lure so that a portion of the chain extends on both sides of the float or plug.

1. Field of the Invention
The present invention relates to fishing lures, and more particularly to a blood-simulating fishing lure that uses a float, plug, or other artificial lure body and a ball-chain to simulate a wounded and bleeding baitfish.
2. Description of the Related Art
The use of fishing lures or other artificial devices that simulate the movement or appearance of natural or live bait is well known. Because game fish, like northern pike or walleyes, feed on insects, minnows, frogs, worms, and even small birds or mammals, it has been common to fish with live baits. Bloodworms and minnows have seen the most use, with varying degrees of success. The use of live bait does have drawbacks. Some live bait is not available in all areas or at certain times of the year. Some live bait may be expensive to purchase, and of course all live bait dies with use. Additionally, the use of certain types of bait and baitfish, such as frogs or minnows, can be restricted in certain areas, and in some areas it is illegal to fish with live bait.
Because game fish are predatory in nature, a variety of artificial lures have been developed over the years. Most commonly, these lures are designed to emulate as closely as possible the natural prey of the game fish. Many of these lures were designed to be pulled through the water, or bounced up and down in the water, to simulate the movements of injured or wounded prey, as it is presumed that injured or wounded prey appears more vulnerable and thus more attractive to the predatory game fish. In addition, spinners, propellers and other objects have been attached to lures to attract the attention of a hungry fish. Other lures have been designed to incorporate scents and aromas of various types. Scents lose potency with use, however, and many artificial lures are not natural in appearance.
Thus, a blood-simulating fishing lure solving the aforementioned problems is desired.


This invention is generally directed to a note or bill acceptor having a bezel adapted to display detailed information about the status of the bill acceptor, and other information related to its operation. The bezel is positioned at the intake slot of the bill acceptor. The bezel employs multiple indicators to visually display information. For example, the enhanced bezel may include indicators to display error conditions such as xe2x80x9cnote box fullxe2x80x9d or xe2x80x9ctransport path jammedxe2x80x9d conditions, and other information useful for maintenance and diagnostic purposes. Additional visual indicators may display set up information, such as which denominations the bill validator of the machine is programmed to accept, display prompts or instructions to assist the player, such as a display of the denomination of the last bill accepted, or even simple decorative patterns. The bezel may provide additional status information, such as a jammed transport path or full note box, for use by attendants.

The present invention relates to an enhanced bezel intended for use with a currency or bill acceptor which is to be incorporated into an electronic gaming machine, vending machine, point of sale devices and similar host machines.
Bill acceptors are now in widespread use in host machines such as gaming machines, vending machines and point of sale devices. Bill acceptors receive paper currency or notes and, using a validator having both hardware and software components, the received currency or note is scanned with a variety of sensors. The sensor information is analyzed to determine authenticity and denomination of the currency or note. If the note is determined to be authentic, e.g. a United States $1, $5, $10, $20, $50 or $100 bill or other legal tender, the note is transported to a cash box within the bill acceptor for storage. Further, based upon the denomination of the accepted currency or note, a signal is sent from the validator to the host machine""s controller or processor to cause the host machine to credit or accumulate a corresponding amount within the machine""s credit meter representing the cash value available for purchasing products or wagering. Bill acceptors of this type are known and are discussed for example in U.S. Pat. No. 5,863,039 issued Jan. 26, 1999 to Suzuki.
The use of bill acceptors has given rise to a problem associated with users who believe that they have inserted a bill having a higher value than what the machine provides as credits. For example, the user may believe that he or she has inserted a twenty dollar bill while the machine only provides ten dollars in credit. This problem generally requires the attention of an attendant who may be required to open the machine to show the user the last bill inserted to resolve the dispute. Alternatively, the attendant may have to place the machine into a xe2x80x9cdiagnostic modexe2x80x9d to allow extraction of the information on the correct denomination of the last inserted bill. These types of activities are both labor intensive and inefficient as the machine is taken out of operation until the issue is resolved.
A bill acceptor generally has a rectangular slot where the note or currency is to be inserted. The location of the rectangular slot may be readily identified by a bezel which, in the context of gaming machines, vending machines or the like, is a structure projecting from the front portion of the bill acceptor below the intake slot. The use of bezels in the gaming machine industry has been limited to providing passive functions. For example, it is known to have bezels with several light emitting devices (LEDs) arranged to flash in a runway sequence to attract the patron""s attention and identify where the note is to be inserted. It is also known that bezels with different color LEDs, i.e. green and red, are available to provide an indication of whether the bill acceptor is operational. The status information available from these bezels is, however, very limited, i.e. whether the bill acceptor of the machine is enabled or disabled, and it does not provide any other functional utility.
The present invention is generally directed to a note or bill acceptor, and-more particularly, to an enhanced bezel positioned at or near the intake slot of the bill acceptor. The enhanced bezel is adapted to display detailed information about the status of the bill acceptor, and other information related to its operation.
The enhanced bezel of the present invention employs multiple indicators to visually display information. For example, the enhanced bezel may include indicators to display error conditions such as xe2x80x9cnote box fullxe2x80x9d or xe2x80x9ctransport path jammedxe2x80x9d conditions, and other information useful for maintenance and diagnostic purposes. Additional visual indicators may display set up information, such as which denominations the bill validator of the machine is programmed to accept, display prompts or instructions to assist the player, such as a display of the denomination of the last bill accepted, or even simple decorative patterns.
More specifically, the enhanced bezel may include a display area to provide a visual display of information about the bills, vouchers, script and/or currency (hereinafter, collectively xe2x80x9cnotesxe2x80x9d) accepted by the bill acceptor. For example, the display may have a visual depiction or back-lighted display to show if the received bill has a $1, $5, $10, $20, $50 or $100 denomination. The display is connected to the bill acceptor""s processor which receives information from the note validator which senses the authenticity, denomination, amount and type of the note passing through the bill acceptor and which issues a signal corresponding to the note type to the bill acceptor processor and the host machine""s processor for accumulation of credits. The same information can be used to control the display on the enhanced bezel.
Further, the bill acceptor will include a note box provided to receive deposited notes and a transport assembly for transporting notes accepted through the note validator to the note box. The bill acceptor processor controls the transport assembly to direct notes received through the note validator to the note box and detects any interference with the operation of the bill acceptor. The bill acceptor""s processor also keeps track of the number of bills sent to the note box for retention. Thus, by connecting the processor to the enhanced bezel, additional status information, such as a jammed transport path or full note box may be visually displayed by the enhanced bezel.
The enhanced bezel display system of the present invention thus provides an easy method of interacting with the user of the machine to provide a verification of the denomination of received notes. The enhanced bezel display system of the present invention also enables the attendant of the machine to quickly retrieve information regarding various operations, including the status of the bill acceptor, without having to interrupt the use of the machine.


An improved method of making expandable stent for implantation in a body lumen, such as an artery, from a single length of tubing. The stent consists of a plurality of radially expandable cut cylindrical elements generally aligned on a common axis and interconnected by one or more interconnective elements, the elements having a rectangular cross-section from cut-to-cut. The individual radially expandable cylindrical elements are disposed in an undulating pattern. The stent is manufactured by direct laser cutting from a single metal tube using a finely focused laser beam passing through a coaxial gas jet structure to impinge on the working surface of the tube as the linear and rotary velocity of the tube is precisely controlled.

This invention relates generally to improvements in the manufacture of expandable metal stents and, more particularly, to new and improved methods and apparatus for direct laser cutting of metal stents and providing stents of enhanced structural quality.
Stents are expandable endoprosthesis devices which are adapted to be implanted into a patient's body lumen, such as a blood vessel, to maintain the patency of the vessel. These devices are typically used in the treatment of atherosclerotic stenosis in blood vessels and the like.
In the medical arts, stents are generally tubular-shaped devices which function to hold open a segment of a blood vessel or other anatomical lumen. They are particularly suitable for use to support and hold back a dissected arterial lining which can occlude the fluid passageway.
Various means have been provided to deliver and implant stents. One method frequently described for delivering a stent to a desired intraluminal location includes mounting the expandable stent on an expandable member, such as a balloon, provided on the distal end of an intravascular catheter, advancing the catheter to the desired location within the patient's body lumen, inflating the balloon on the catheter to expand the stent into a permanent expanded condition and then deflating the balloon and removing the catheter.
One example of a particularly useful expandable stent is a stent which is relatively flexible along its longitudinal axis to facilitate delivery through tortuous body lumens, but which is stiff and stable enough radially in an expanded condition to maintain the patency of a body lumen such as an artery when implanted within the lumen. Such a desirable stent typically includes a plurality of radially expandable cylindrical elements which are relatively independent in their ability to expand and to flex relative to one another. The individual radially expandable cylindrical elements of the stent are precisely dimensioned so as to be longitudinally shorter than their own diameters. Interconnecting elements or struts extending between adjacent cylindrical elements provide increased stability and a preferable position to prevent warping of the stent when it is expanded. The resulting stent structure is a series of radially expandable cylindrical elements which are spaced longitudinally close enough so that small dissections in the wall of a body lumen may be pressed back into position against the lumenal wall, but not so close as to compromise the longitudinal flexibilities of the stent. The individual cylindrical elements may rotate slightly relative to adjacent cylindrical elements without significant deformation, cumulatively giving a stent which is flexible along its length and about its longitudinal axis, but is still very stiff in the radial direction in order to resist collapse.
The aforedescribed stents generally have a precisely layed out circumferential undulating pattern, e.g. serpentine. The transverse cross-section of the undulating component of the cylindrical element is relatively small and preferably has an apect ratio of about two to one to about 0.5 to one. A one to one apect ratio has been found particularly suitable. The open reticulated structure of the stent allows for the perfusion of blood over a large portion of the arterial wall which can improve the healing and repair of a damaged arterial lining.
The radial expansion of the expandable cylinder deforms the undulating pattern similar to changes in a waveform which result from decreasing the waveform's amplitude and the frequency. Preferably, the undulating patterns of the individual cylindrical structures are in phase with each other in order to prevent the contraction of the stent along its length when it is expanded. The cylindrical structures of the stent are plastically deformed when expanded so that the stent will remain in the expanded condition and, therefore, they must be sufficiently rigid when expanded to prevent their collapse in use. During expansion of the stent, portions of the undulating pattern will tip outwardly resulting in projecting members on the outer surface of the expanded stent. These projecting members tip radially outwardly from the outer surface of the stent and embed in the vessel wall and help secure the expanded stent so that it does not move once it is implanted.
The elongated elements which interconnect adjacent cylindrical elements should have a precisely defined transverse cross-section similar to the transverse dimensions of the undulating components of the expandable cylindrical elements. The interconnecting elements may be formed as a unitary structure with the expandable cylindrical elements from the same intermediate product, such as a tubular element, or they may be formed independently and connected by suitable means, such as by welding or by mechanically securing the ends of the interconnecting elements to the ends of the expandable cylindrical elements. Preferably, all of the interconnecting elements of a stent are joined at either the peaks or the valleys of the undulating structure of the cylindrical elements which form the stent. In this manner, there is no shortening of the stent upon expansion.
The number and location of elements interconnecting adjacent cylindrical elements can be varied in order to develop the desired longitudinal flexibility in the stent structure both in the unexpanded, as well as the expanded condition. These properties are important to minimize alteration of the natural physiology of the body lumen into which the stent is implanted and to maintain the compliance of the body lumen which is internally supported by the stent. Generally, the greater the longitudinal flexibility of the stent, the easier and the more safely it can be delivered to the implantation site.
It will be apparent from the foregoing that conventional stents are very high precision, relatively fragile devices and, ideally, the most desirable metal stents incorporate a fine precision structure cut from a very small diameter, thin-walled cylindrical tube. In this regard, it is extremely important to make precisely dimensioned, smooth, narrow cuts in the stainless tubes in extremely fine geometries without damaging the narrow struts that make up the stent structure. While the various cutting processes, including chemical etching, heretofore utilized by the prior art to form such expandable metal stents, have been adequate, improvements have been sought to provide stents of enhanced structural quality in terms of resolution, reliability and yield.
Accordingly, those concerned with the development, manufacture and use of metal stents have long recognized the need for improved manufacturing processes for such stents. The present invention fulfills these needs.

Method and apparatus for direct laser cutting of metal stents


The present invention relates to tires and vehicular tracks having minimal-marking rubber treads and particularly to skid steering, fixed axle, tire/wheel or track assemblies where said tire or vehicular track has a minimal-marking tread. In particular, such rubber tread has a surface intended to be ground-contacting which is also intended to be minimal-marking and having suitable physical properties for a tire tread.

The present invention relates to tires and vehicular tracks having minimal-marking rubber treads and particularly to skid steering, fixed axle, tire/wheel or track assemblies where said tire or vehicular track has a minimal-marking tread. In particular, such rubber tread has a surface intended to be ground-contacting which is also intended to be minimal-marking and having suitable physical properties for a tire tread.
Tires and vehicular tracks are typically provided with rubber treads which contain carbon black reinforcement and also contain rubber staining amine-based antidegradants and sometimes rubber staining aromatic rubber processing oils.
However, sometimes tires and vehicular tracks are provided for vehicles which are intended to be driven over surfaces other than black-colored asphalt pavement, such as for example concrete, for which it is desired that their treads do not leave colored marks, especially black marks, on the surface when the vehicle itself is driven over the surface.
Particular tire treads marking problems are considered herein to be often evident for vehicles which control their direction of travel by what is known as xe2x80x9cskid-steeringxe2x80x9d. For such skid-steering phenomenon, the vehicular front wheel, or track, is mounted on a fixed axle which is not allowed to pivot to enable the vehicle to change its direction of travel. In such case, the vehicle is turned by causing one wheel, or track as the case may be, to turn faster, or slower, than its opposite wheel, or track, on the other side of the vehicle. Thus the tread xe2x80x9cslidesxe2x80x9d over the surface with a typical abrading away of a portion of the tread on the surface over which the tread skids.
Accordingly, the treads of such vehicular tires or tracks, as the case may be, which xe2x80x9cskid-steerxe2x80x9d have a relatively high rate of tread wear and incidence of marking of the surface over which the tread skids, even if the vehicle is a relatively slow moving vehicle.
For example, medium to small vehicles which rely upon skid steering to control their direction of travel may be used to haul rocks and dirt, as well as individuals over various paved road surfaces which may be of rough or smooth non-black colored surfaces (e.g. concrete) where it is desired that the treads to not excessively mark the surfaces with cosmetically unacceptable marks. Such paved surfaces may be, for example, a factory floor or a garage for parking the vehicle as well as a driveway associated with such garage.
Accordingly, it is desired to provide a tire and vehicular track with rubber treads that do not easily leave marks on a non-black substrate, or ground yet still has acceptable physical properties for a tread.
Vehicular tracks, as contemplated herein, are conventionally endless rubber tracks, usually positioned over at least two fixed axle vehicular wheels, normally a drive wheel for engaging an inner surface of the rubber track and driving the track and at least one vehicular driven wheel to aid in guiding the contorted path of the rubber track as it moves around the vehicular wheels to propel the associated vehicle over the ground.
The outer surface of the rubber track, namely its tread, is intended to be ground contacting and typically contains a plurality of raised rubber lugs designed to contact, or engage, the ground.
While it may be readily thought of to provide such a tread without, or with only a minimal amount of carbon black, and with an alternate reinforcing filler such as, for example, amorphous silica, there are other factors to take into consideration for the rubber composition to be resistant to marking of a non-black substrate and to also have appropriate physical properties.
For example, such treads preferably have a balance between good traction and resistance to wear.
It is recognized that it is well known to use various materials, and amounts of various individual materials, for tire treads such as, for example, carbon black reinforcement, amorphous silica (e.g. precipitated silica) reinforcement, rubber processing oil and antidegradants (particularly antioxidants), as well as individual elastomers, for example, cis 1,4-polyisoprene natural and synthetic rubber, cis 1,4-polybutadiene rubber and styrenelbutadiene copolymer rubber.
Indeed for tire and vehicular track treads intended to be non-marking for non-black substrates, it is considered herein that particular considerations should be made. For such purpose, this invention is primarily based upon the use of known materials used in what is considered herein to be novel, material-specific combinations for a tire tread.
In the description of this invention, the terms xe2x80x9crubberxe2x80x9d and xe2x80x9celastomerxe2x80x9d if used herein, may be used interchangeably, unless otherwise prescribed. The terms xe2x80x9crubber compositionxe2x80x9d, xe2x80x9ccompounded rubberxe2x80x9d and xe2x80x9crubber compoundxe2x80x9d, if used herein, are used interchangeably to refer to xe2x80x9crubber which has been blended or mixed with various ingredients and materialsxe2x80x9d and such terms are well known to those having skill in the rubber mixing or rubber compounding art.
In the description of this invention, the term xe2x80x9cphrxe2x80x9d refers to parts of a respective material per 100 parts by weight of rubber, or elastomer. The terms xe2x80x9crubberxe2x80x9d and xe2x80x9celastomerxe2x80x9d may be used interchangeably unless otherwise indicate. The terms xe2x80x9ccurexe2x80x9d and xe2x80x9cvulcanizexe2x80x9d may be used interchangeably unless otherwise indicated.
In accordance with this invention, a minimal-marking tread intended to be ground-contacting for a tire or vehicular track wherein said tread is of a rubber composition which comprises, based upon 100 parts by weight rubber (phr),
(A) 100 parts by weight of at least one conjugated diene-based elastomer,
(B) about 35 to about 100, alternately about 40 to about 90, phr of particulate filler comprised of aggregate of synthetic amorphous silica and from about zero to about 7, alternately from one to about 5, and preferably zero, phr of carbon black,
(C) about 2 to about 5 phr of a phenolic-based antidegradant to the exclusion of an amine-based antidegradant,
(D) about five to about 15 of a paraffinic rubber processing oil which contains less than about 14 weight percent aromatic compound(s) to the exclusion of rubber processing oil containing greater than 15 weight percent of aromatic compounds and
(E) at least one coupling agent having a moiety reactive with hydroxyl groups contained on the surface of the said amorphous silica (e.g. silanol groups) and another moiety interactive with at least one of said diene-based elastomers.
Therefore, for the purposes of this invention, the tire, or track, tread rubber compositions do not necessarily have to be devoid of carbon black, and therefore may be of a black color, however, they are to contain only a minimal amount of carbon black, if any amount of carbon black at all. Accordingly, for many applications, it may be desired that the tread rubber compositions do not contain carbon black and are therefore reinforced with silica as described above. With such treads required to contain a relatively quantitative amount of silica and a minimal, if any, amount of carbon black, it is considered herein that it remains to be a challenge to provide such tread rubber compositions which have suitable physical properties for a tire or track tread.
In one aspect of the invention, said tread rubber is desired to be prepared by a sequential mixing process in at least one internal rubber mixer, which comprises, based upon parts by weight per 100 parts by weight rubber (phr)
(A) mixing in at least two sequential preparatory blending steps in at least one internal rubber mixer to a temperature in a range of about 100xc2x0 C. to about 180xc2x0 C. a blend of ingredients comprised of, based on 100 parts by weight rubber (phr)
(1) 100 parts by weight of at least one conjugated diene-based elastomer,
(2) about 35 to about 100, alternately about 40 to about 90, phr of particulate filler comprised of aggregates of synthetic amorphous silica having hydroxyl groups on its surface and from about zero to about 7, alternately from one to about 5, and preferably zero, phr of carbon black,
(3) about 5 to about 15 of a paraffinic rubber processing oil which contains less than about 14 weight percent aromatic compound(s) to the exclusion of rubber processing oil contain greater than 15 weight percent of aromatic compounds and
(4) a bis-(3-triethoxysilylpropyl) polysulfide having from 2 to 6, with an average of from 2 to 2.6, connecting sulfur atoms in its polydisulfidic bridge, and
(B) mixing the product of said at least two preparatory mixing steps with a conjugated diene-based rubber vulcanizing amount of sulfur and vulcanization accelerator and from about 5 to about 15 phr of bis-(3-triethoxysilylpropyl) polysulfide having from 2 to 6, with an average of from 2 to 2.6, or from 3.5 to 4, connecting sulfur atoms in its polysulfidic bridge, to a temperature in a range of about 110xc2x0 C. to about 120xc2x0 C.; wherein a total (sum) of from about 1 to about 5 phr of at least one phenolic antidegradant to the exclusion of an amine-based antidegradant is mixed with said elastomer(s) in at least one of said mixing steps; and
wherein said rubber composition is removed from said internal rubber mixer at the conclusion of each mixing stage and cooled to a temperature below 40xc2x0 C. followed by shaping and sulfur vulcanizing said tread rubber composition.
In further accordance with this invention, a skid steering, fixed axle, assembly as a tire/wheel assembly or a drive wheel/vehicular track assembly is provided where said tire and said vehicular track has the said minimal-marking tread.
Thus such tread rubber composition for said tread is provided as a sulfur vulcanized tire tread rubber composition where the tread is sulfur vulcanized as a part of the respective vehicular tire or vehicular track.
In practice, the drive wheel/vehicular track assembly is comprised of a rubber track positioned over at least two fixed axle vehicular wheels, namely a drive wheel for engaging an inner surface of the rubber track and driving the track and at least one vehicular driven wheel to aid in guiding the contorted path of the rubber track as it moves around the vehicular wheels, including the associated drive wheel, to propel the associated vehicle over the ground.
The outer surface of the rubber track, namely its tread, is intended to be ground contacting and typically contains a plurality of raised rubber lugs designed to contact, or engage, the ground.
It is to be appreciated that the prepared tread rubber composition is appropriately extruded through a suitable extruder die to form a shaped tread stock strip, the tread strip built onto a tire or vehicular track carcass and the resulting assembly is sulfur-vulcanized in a suitable mold usually at a temperature in a range of about 130xc2x0 C. to about 160xc2x0 C. for this invention.
A significant aspect of the tread rubber composition for this invention is the use of aggregates of synthetic silica reinforcement in the absence of amine based antidegradants and processing oils with only a minimal amount, if any, of aromaticity and to a substantial exclusion of carbon black reinforcement.
This is considered herein to be important where it is desired to provide a tread for a tire or vehicular track which is minimal-marking, in any, on the ground over which it travels and, also, has good physical properties for use as a tread.
For the purposes of this invention, a minimal-marking tread is a tread that leaves a minimal, in any, visible residue, preferably no visible residue, on a hard substrate surface that can easily be physically brushed away, and does not stain such hard substrate surface, particularly for relatively slow moving skid steering tires, as compared to such treads which contain relatively high levels of carbon black (e.g. 50 to 75 phr of carbon black) and particularly in an amount equivalent to the amount of silica contained in the treads of this invention.
Thus, it is required that the tread rubber composition for this invention contains only minimal amount, if any, particulate carbon black bound to the rubber composition itself which, as the rubber might be abraded away on a hard surface over which the tread travels, little or no carbon black is contained in any residue deposited on such hard surface. Further, the tread rubber composition for this invention is required to be exclusive of rubber processing oils which contain appreciable amounts of aromaticity and exclusive of amine based antidegradants which may otherwise contribute to creating a coloration on various hard substrates over which the tread may travel.
A significant aspect of the method of preparation of the tire tread rubber composition is the split silica coupler addition in which one coupler is added in a preparatory, non-productive, mixing stage and another coupler is added in the subsequent productive mixing stage. This procedural aspect of the invention is considered herein to be important to cause effective binding of the silica in the elastomer host.
The forming of the tread is contemplated to be by conventional means such as, for example, by extrusion of rubber composition to provide a shaped, unvulcanized tread. Such forming of a tread is well known to those having skill in such art.
It is understood that the tire, or vehicular track, as the case may be, as a manufactured article, is prepared by shaping and sulfur curing the assembly of its components at an elevated temperature (e.g. 140xc2x0 C. to 180xc2x0 C.) and elevated pressure in a suitable mold. Such practice is well known to those having skill in such art.
The diene-based elastomers for the rubber composition of the tread of the tire and vehicular track of this invention, are, for example, homopolymers and copolymers of at least one conjugated diene such as, for example, isoprene and/or 1,3-butadiene and copolymers of at least one conjugated diene, such as for example, isoprene and/or 1,3-butadiene, and a vinyl aromatic compound such as styrene or alphamethyl styrene, preferably styrene. It is required that such elastomers contain non-staining antidegradants and therefore are exclusive of amine-based antidegradants.
Representative of such diene-based elastomers are, for example, elastomers comprised of cis 1,4-polyisoprene (natural and synthetic), cis 1,4-polybutadiene, high vinyl polybutadiene having a vinyl 1,2-content in a range of about 35 to about 90 percent, isoprene/butadiene copolymer elastomers, styrene/butadiene copolymer elastomers (organic solvent solution polymerization formed or prepared and aqueous emulsion polymerization formed or prepared) and styrene/isoprene/butadiene terpolymer elastomers.
Synthetic amorphous silicas are usually aggregates of precipitated silicas for use in this invention although they may be fumed silicas or even co-fumed silica and carbon black. Precipitated silicas are, for example, those obtained by the acidification of a soluble silicate, e.g., sodium silicate, including blends of a sodium silicate and aluminate. Such precipitated silicas are well known to those having skill in such art.
Such amorphous, particularly precipitated, silicas might be characterized, for example, by having a BET surface area, as measured using nitrogen gas, preferably in the range of about 40 to about 600, and more usually in a range of about 50 to about 300 square meters per gram. The BET method of measuring surface area is described in the Journal of the American Chemical Society, Volume 60, Page 304 (1930).
The silica may also be typically characterized by having a dibutylphthalate (DBP) absorption value in a range of about 100 to about 400, and more usually about 150 to about 300.
The silica is conventionally used in conjunction with a silica coupler as hereinbefore discussed to couple the silica to at least one of said diene-based elastomers and, thus, enhance the elastomer reinforcing effect of the silica.
It is readily understood by those having skill in the art that the rubber composition would be compounded by methods generally known in the rubber compounding art, such as mixing the various sulfur-vulcanizable constituent rubbers with various commonly used additive materials, as herein before discussed, as known to those skilled in the art, depending on the intended use of the sulfur vulcanizable and sulfur vulcanized material (rubbers), the various additives, unless otherwise indicated, are selected and commonly used in conventional amounts.
Representative of phenolic antidegradants for use in this invention are, for example, antioxidants such as polymeric hindered phenols from The Goodyear Tire and Rubber Company and Exxon Mobil, including phenolic antidegradants disclosed in The Vanderbilt Rubber Handbook (1978), Pages 344 through 346.
Representative non-aromatic rubber processing oils for use in this invention, namely such oils which contain less than 14 percent weight aromatic compounds, if at all, are, for example, Flexon 641 from Exxon Mobile.
Typical amounts of fatty acids, if used which can include stearic acid, comprise about 0.5 to about 3 phr. Typical amounts of zinc oxide comprise about 1 to about 5 phr. Typical amounts of waxes comprise about 1 to about 5 phr. Often microcrystalline waxes are used. Typical amounts of peptizers comprise about 0.1 to about 1 phr. Typical peptizers may be, for example, pentachlorothiophenol and dibenzamidodiphenyl disulfide.
The vulcanization is conducted in the presence of a sulfur vulcanizing agent. Examples of suitable sulfur vulcanizing agents include elemental sulfur (free sulfur) or sulfur donating vulcanizing agents, for example, a polymeric polysulfide. Preferably, the sulfur vulcanizing agent is elemental sulfur. As known to those skilled in the art, sulfur vulcanizing agents are used in an amount ranging from about 0.5 to about 4 phr, or even, in some circumstances, up to about 8 phr, with a range of from about 1.5 to about 2.5, sometimes from about 2 to about 2.5, being preferred.
The mixing of the rubber composition can preferably be accomplished by the aforesaid sequential mixing process. For example, the ingredients may be mixed in at least three stages, namely, at least two non-productive (preparatory) stages followed by a productive (final) mix stage. The final curatives are typically mixed in the final stage which is conventionally called the xe2x80x9cproductivexe2x80x9d or xe2x80x9cfinalxe2x80x9d mix stage in which the mixing typically occurs at a temperature, or ultimate temperature, lower than the mix temperature(s) of the preceding non-productive mix stage(s). The terms xe2x80x9cnon-productivexe2x80x9d and xe2x80x9cproductivexe2x80x9d mix stages are well known to those having skill in the rubber mixing art.
In one aspect of the invention, it is desired to provide a sulfur vulcanized (cured) silica reinforced diene-based rubber compositions which can have the following combination of threshold physical properties for use in treads of this invention which might be referred to herein as xe2x80x9cTarget Propertiesxe2x80x9d. Such properties are represented in the following Table A:
These Target Properties are considered significant because they relate to desired physical properties, particularly for predicting suitable tire tread performance for the tires desired for this invention.
In particular, a 300 percent modulus (ASTM Test D412, ring tensile method) of greater than 6 MPa (a range of 6 to 13 MPa) is important because it is considered herein to relate to better (less) abrasion and better handling characteristics. A Rebound value (ASTM D1054) at 100xc2x0 C. of at least 50 percent (a range of 50 to 68 percent) is important because it is considered herein to relate to better (reduced) tire heat build-up and rolling resistance characteristics.
A Shore A hardness value (ASTM D2240) at 100xc2x0 C. of at least 52 (a range of 52 to 70) is important because it is considered herein to relate to better tire handling and greater abrasion resistance (less wear) characteristics. A DIN abrasion loss (ASTM D5963, using 10 Newtons force) of a maximum of 85 cm3 volume loss is important because it is considered herein to relate to a better (reduced) treadwear characteristic.
The molded groove tear resistance (average molded groove tear strength) value (ASTM D624) of at least 15 Newtons is considered herein to be important as relating to damage resistance where a higher value is indicative of greater resistance to damage.
In practice the median molded groove tear strength of vulcanized rubber is measured according to ASTMD624 in which a rectangularly shaped cured rubber samples is obtained having a groove along its longitudinally central axis which basically divides the sample into two halves, namely one half on each side of the center of the groove. The test sample dimension is 2.54 cm wide, 12.7 cm long and 0.64 cm thick. The molded groove has an arc configuration of 14 degrees with a depth of 0.086 cm and a top groove width of 0.084 cm. The test is conducted by measuring the force, in Newtons, to initiate and propagate a tear along the groove in which the halves of the sample, at one end of the sample, are pulled apart at 180xc2x0 C. angle at a crosshead speed of about 51 cm per minute at about 23xc2x0 C.
In practice, while it is considered herein that the above-referenced rubber composition target properties are individually significant for relating to specifically desired tire characteristics, it is a desirable feature of this invention that all of the above target properties are obtained for a rubber composition by the practice of this invention.
The invention may be better understood by reference to the following examples in which the parts and percentages are by weight unless otherwise indicated.

Tire with minimal-marking tread and skid steering, fixed axle, tire/wheel or vehicular track assembly where said tire or track has a minimal-marking tread


Method and apparatus for efficiently performing nearest neighbor queries on a database of records wherein each record has a large number of attributes by automatically extracting a multidimensional index from the data. The method is based on first obtaining a statistical model of the content of the data in the form of a probability density function. This density is then used to decide how data should be reorganized on disk for efficient nearest neighbor queries. At query time, the model decides the order in which data should be scanned. It also provides the means for evaluating the probability of correctness of the answer found so far in the partial scan of data determined by the model. In this invention a clustering process is performed on the database to produce multiple data clusters. Each cluster is characterized by a cluster model. The set of clusters represent a probability density function in the form of a mixture model. A new database of records is built having an augmented record format that contains the original record attributes and an additional record attribute containing a cluster number for each record based on the clustering step. The cluster model uses a probability density function for each cluster so that the process of augmenting the attributes of each record is accomplished by evaluating each record's probability with respect to each cluster. Once the augmented records are used to build a database the augmented attribute is used as an index into the database so that nearest neighbor query analysis can be very efficiently conducted using an indexed look up process. As the database is queried, the probability density function is used to determine the order clusters or database pages are scanned. The probability density function is also used to determine when scanning can stop because the nearest neighbor has been found with high probability.

An important class of problems in the areas of database decision support and analysis are similarity join problems, also known as nearest-neighbor queries. The basic problem is: given a record (possibly from the database), find the set of records that are "most similar" to it. The term record here is used in general to represent a set of values, however the data can be in any form including image files, or multimedia files, or binary fields in a traditional database management system. Applications are many and include; marketing, catalog navigation (e.g. look-up products in a catalog similar to another product), advertising (especially on-line), fraud detection, customer support, problem diagnosis (e.g. for product support), and management of knowledge bases. Other applications are in data cleaning applications, especially with the growth of the data warehousing market.
It has been asserted in the database literature that the only way to answer nearest neighbor queries for large databases with high dimensionality (many fields) is to scan the database, applying the distance measure between the query object and every record in the data. The primary reason for this assertion is that traditional database indexing schemes all fail when the data records have more than 10 or 20 fields (i.e. when the dimensionality of the data is high). Consider databases having hundreds of fields. This invention provides a method that will work with both low dimensional and high dimensional data. While scanning the database is acceptable for small databases, it is too inefficient to be practical or useful for very large databases. The alternative is to develop an index, and hope to index only a small part of the data (only a few columns but not all). Without variation, most (probably all) schemes published in the literature fail to generalize to high-dimensionality (methods break down at about 20 dimensions for the most advanced of these approaches, at 5 or 6 for traditional ones).
This problem is of importance to many applications (listed above) and generally is a useful tool for exploring a large database or answering "query-by-example" type queries (e.g., the graphic image closest to a given image). Hence it can be used as a means for extending the database and providing it with a more flexible interface that does not require exact queries (as today's SQL requires). It can also be used to index image data or other multi-media data such as video, audio, and so forth.
Most practical algorithms work by scanning a database and searching for the matches to a query. This approach is no longer practical when the database grows very large, or when the server is real-time and cannot afford a long wait (e.g. a web server). The solution is to create a multi-dimensional index. The index determines which entries in the database are most likely to be the "nearest" entries to the query. The job then is to search only the set of candidate matches after an index scan is conducted. Note that the query can be just a record from the database and the answer is determining other records similar to it. Another example is an image query where the answer is images "similar" to this query by some user defined distance metric.
As an example, consider a database that contains the ages, incomes, years of experience, number of children, etc. on a set of people. If it was known ahead of time that queries will be issued primarily on age, then age can be used as a clustered-index (i.e. sort the data by age and store it in the database in that order). When a query requesting the entry whose age value is nearest some value, say 36 years, then one only need visit the relevant parts of the database. However, indexing rapidly becomes difficult to perform if one adds more dimensions to be indexed simultaneously. In fact, as the number of indexes grows, the size of the index structure dominates the size of the database.
This problem has been addressed in prior work on index structures (including TV-trees, SS-Tree, SR-Trees, X-Trees, KD-trees, KD-epsilon-Trees, R-trees, R+-trees, R*-trees, VA-File) and methods for traversal of these structures for nearest neighbor queries. Any indexing method has to answer three questions: 1. how is the index constructed? 2. how is the index used to select data to scan? and 3. how is the index used to confirm that the correct nearest neighbor has been found?
Prior art approaches had serious trouble scaling up to higher dimensions. Almost always a linear scan of the database becomes preferable between 20 and 30 dimensions. For traditional indexing scheme this happens at 5 dimensions or even lower. Statistical analysis of k-d tree and R-tree type indexes confirms this difficulty; see Berchtol S., Bohm C., Keim, D., Kriegel, H.-P.: "Optimized Processing of Nearest Neighbor Queries in High-Dimensional Space", submitted for publication, 1998 and Berchtold S., Bohm C., Keim D. and Kriegel H. P.: "A Cost Model for Nearest Neighbor Search in High Dimensional Space", ACM PODS Symposium on Principles of Database Systems, Tucson, Ariz., 1997. Indexes work by partitioning data into data pages that are usually represented as hyperectangles or spheres. Every data page that intersects the query ball (area that must be searched to find and confirm the nearest neighbor point) must be scanned. In high-dimensions for hyperrectangles and spheres, the query ball tends to intersect all the data pages. This is known as the "curse of dimensionality". In fact, in a recent paper, by Beyer K., Goldstein J., Ramakrishnan R., Shaft U, "When is Nearest Neighbor Meaningful?" submitted for Publication, 1998, the question is raised of whether it makes sense at all to think about nearest neighbor in high-dimensional spaces.
Most analyses in the past have assumed that the data is distributed uniformly. The theory in this case does support the view that the problem has no good solution. However, most real-world databases exhibit some structure and regularity. In fact, a field whose values are uniformly distributed is usually rare, and typically non-informative. Hence it is unlikely that one would ask for nearest neighbor along values of a uniformly distributed field. In this invention the statistical structure in the database is exploited in order to optimize data access.

Density-based indexing method for efficient execution of high dimensional nearest-neighbor queries on large databases


A novel photoresist stripping process is disclosed. Specifically, it has been found that if a printed wiring board panel having photoresist on its surface is used as a cathode during electrolysis in an alkaline solution, the result is a rapid and complete photoresist removal with minimal sheeting of removed photoresist and no evidence of chemical attack upon metallic traces on the printed wiring board.

The present invention relates to a cathodic photoresist stripping process. More particularly, the present invention relates to a method for stripping photoresist from a printed wiring board panel by connecting the printed wiring board to a DC power supply and using it as a cathode during electrolysis of an alkaline solution.
Printed wiring boards (PWBs) are used throughout the electronics industry. These boards serve to mount and secure electronic components while providing electrical connection among them. Refinements to PWB manufacture can result in higher quality, more reliable PWBs as well as PWBs having smaller and/or more densely packed conductive traces. As a result, smaller PWBs resulting in smaller electronic devices can be manufactured.
The majority of PWBs are manufactured using a semi-additive technique. In order to define a conductive pattern on the surface of the PWB, an organic polymer resist layer in the form of either a dry film or liquid is applied to a copper-clad insulating panel. If the resist is of a xe2x80x9cnegative working photo-defined typexe2x80x9d, the panel is exposed to a pattern defining artwork and the unexposed portion of the resist is developed off. In a xe2x80x9cpositive working systemxe2x80x9d, the exposed areas are rendered soluble in a developing solution. As an alternative, the resist image may be defined using a screen printing process, or less commonly, using electron beam or laser ablation.
After the resist image has been defined, the PWB surface is exposed to plating or etching steps, depending upon the board type and the manufacturing technique. Subsequently, it is typically necessary to remove the photopolymer resist layer to allow further processing of the PWB. Removal of the photopolymer resist layer is accomplished in a resist stripping process.
Strongly alkaline, i.e., caustic, solutions are known to remove photoresists. However, caustic-based strippers are usually not widely used in commercial applications due to their slow stripping speed, poor solution life, xe2x80x9csheetingxe2x80x9d effect, inability to process fine line circuitry, and propensity to attack tin and tin/lead alloys. Each of these is discussed below.
Slow stripping speeds when using caustic solutions to remove photoresist following the formation of patterns on PWBs are undesirable in that the time needed to remove a typical dry film photoresist using a caustic-only solution is often two to three times longer than that needed to remove such photoresist using commercially-available organic amine based strippers. Furthermore, whereas commercial organic amine based strippers typically can strip between about 800-1,200 mil square feet of photoresist per gallon of the stripping solution, common caustic-based strippers can only strip between about 200-250 mil square feet of photoresist per gallon.
The mechanism of stripping using caustics is different from that using organic amine based strippers. Rather than break photoresists up into small particles, as organic amine based strippers do, caustics tend to swell most resists and strip them in large sheets. This is often referred to as a xe2x80x9csheetingxe2x80x9d effect. Unfortunately, such stripped large sheets can redeposit onto the copper surface creating problems in subsequent etching steps. Additionally, these stripped resist sheets can clog filters and nozzles in spray machines, thereby rendering the equipment inoperable. As a result of the xe2x80x9csheetingxe2x80x9d effect, it is impossible to cleanly strip swelled resist between electroplated copper and tin or tin/lead overplated fine-line traces. Unstripped resist particles entrapped between the fine traces cause severe defects (xe2x80x9cshort circuitxe2x80x9d) in subsequent etching steps. Additionally, tin and lead, which are commonly used as etch resist on outer layers of the PWB, are amphoteric metals that dissolve in caustic solutions. Caustic based strippers attack tin or tin/lead etch resist, creating serious problems. Finally, as tin accumulates in stripping solution, it can re-deposit on copper surfaces creating so-called xe2x80x9ctin bleedingxe2x80x9d defect, which also results in xe2x80x9cshort circuitxe2x80x9d defects.
A typical proprietary resist stripping composition consists of a mixture of aliphatic or cyclic organic amines, organic quaternary ammonium hydroxides and organic solvents. In some instances, inorganic alkali metal hydroxides are also used as secondary alkalinity carriers. U.S. Pat. No. 5,545,353 describes a photoresist stripper composition containing an organic polar solvent, an alkanolamine and a thiocarboxylic acid as a corrosion inhibitor. U.S. Pat. No. 5,556,482 teaches a method of stripping photoresist with a composition comprising organic polar solvents, basic amines and an inhibitor. U.S. Pat. No. 4,904,571 discloses a method for removing photoresist in a solution which comprises alcohols, ethers, ketones, chlorinated chlorocarbons, aromatic hydrocarbons, alkali metal hydroxides, carbonates, phosphates, pyrophosphates, borohydrides and organic amine borane compounds.
The present invention is based upon the discovery that, if a PWB panel with imaged and developed photoresist on its surface is connected to a DC power supply and used as a negative electrode (cathode) during the electrolysis of an alkaline solution, a rapid and complete photoresist removal will occur with minimal xe2x80x9csheetingxe2x80x9d effect, and no evidence of chemical attack on the copper and tin forming the conductive traces of the PWB.
The process of electrolysis is widely used in PWB manufacture as well as in the metal finishing industries for electroplating and electrodeposition of various metals. Electrodeposited copper is used in PWB manufacturing processes to interconnect two or more layers of copper foil by electroplating it into vias. Electroplated tin or tin-lead alloys are used as etch resist. Electrodeposited nickel and gold are used as final finishes to preserve solderability of the PWB. Furthermore, a wide variety of metals are used in the metal finishing industry for corrosion protection, decorative purposes, or for imparting various functional properties to the underlying substrate. For example, plastic substrates are commonly electroplated to render their surfaces electrically conductive. In each of the examples above, electrolysis is utilized to electrodeposit various metals onto the substrate surface.
Alkaline solutions conduct electricity and, therefore, can be electrolyzed. In such solutions, in the absence of metal complexes that can be cathodically reduced to metallic state, no metal deposition takes place, since alkali or alkaline earth metals thermodynamically cannot be electrodeposited out of aqueous solutions, whereas organic alkalis do not contain any metal ions. As noted above, it has surprisingly been found that if a PWB panel with photoresist on its surface is connected to a DC power supply and used as a negative electrode (cathode) during an electrolysis process of an alkaline solution, a rapid and complete photoresist removal occurs with reduced xe2x80x9csheetingxe2x80x9d effect and minimal evidence of chemical attack on copper or tin.
During the process of electrolysis, two electrodes are connected to an electric power supply and immersed into an electrolyte solution. If the electrolyte is an alkali metal hydroxide solution, the following reactions will take place in the bulk of the solution and at the electrodes:
Solution:
MeOHxe2x86x92Me++OHxe2x88x92
H2Oxe2x86x92H++OHxe2x88x92
(where Me is any alkali or alkaline earth metal)
Cathode:
2H++2exe2x88x92xe2x86x92H2
Anode:
40Hxe2x88x92xe2x88x924exe2x88x92xe2x86x92O2+2H2O
Subsequently, during the electrolysis process, oxygen gas will evolve at the anode, (i.e., the positive electrode), and hydrogen gas will be generated at the cathode, (i.e., the negative electrode). Similar reactions will take place if a solution of an organic alkali or an alkaline salt (which forms an alkali in the solution due to hydrolysis) is electrolyzed.
A PWB panel with photoresist on its surface can be immersed in such an alkaline solution and connected as a negative electrode (cathode) to a power supply. A dimensionally stable anode (DSA) or any conventional insoluble anode can serve as a positive electrode (anode). Once a PWB panel is immersed into the alkaline stripping solution, the solution will start to soften and swell the photoresist polymer. At the same time, hydrogen gas will begin to evolve on the exposed metal areas. Depending on the voltage applied and the conductivity of the solution, the evolution of hydrogen gas can be quite vigorous. The bubbles of the hydrogen gas evolving on the copper surface, including copper and the photoresist interface, will lift the edges of the swollen photoresist film, tear it into smaller pieces, and remove it from the copper surface. Furthermore, since H+ions are being consumed at the cathode for the hydrogen gas evolution, the pH of the solution adjacent to the cathode will become more alkaline, thus increasing photoresist dissolution and the stripping rate. As a result, the resist stripping on the cathode will occur in a much faster and more efficient manner than in an alkaline solution without the application of electric current.
This process offers several significant and novel features when compared to conventional or caustic-based resist stripping processes. In particular, as compared to caustic-based strippers, the stripping process of the present invention provides improved stripping speed and solution life. Additionally, the stripping process of the present invention minimizes the xe2x80x9csheetingxe2x80x9d effect, allows the processing of fine line circuitry and eliminates attack on tin and tin-lead traces.
The use of the cathodic photoresist stripping process described above has been found to remove typical photoresists faster than is commonly expected for the removal of photoresist using conventional organic amine-based or caustic-based resist strippers. As a result, the processing time of the PWB can be shortened. Additionally, because of the faster stripping time, the photoresist particles are quickly removed from the solution by filtration, thereby preventing them from dissolving in the solution and neutralizing it. As a result, solution neutralization is minimized, and a longer solution life results.
As noted above, the electrolysis procedure of the present invention results in the evolution of hydrogen, which can be, at times, quite vigorous. The hydrogen evolution tends to tear the photoresist into smaller pieces, thus, preventing the formation of photoresist sheets and effectively minimizing the xe2x80x9csheetingxe2x80x9d effect and problems associated with it. The evolution of hydrogen also provides a scrubbing action which acts to efficiently clean out small photoresist particle residues which can remain between overplated fine lines, and which to date, have been difficult to remove using conventional resist strippers. Additionally, continuous hydrogen evolution keeps the stripped particles away from the panel, effectively preventing their redeposition on the panel. Finally, the reducing action of the electric current at the cathode acts to protect the metallic surface from oxidation, i.e., caustic attack, thereby preventing damage to tin and tin-lead surfaces.
Additional benefits can be achieved by the inventive resist stripping process if the anodes of the apparatus are separated from the chamber on which stripping takes place by an anion-selective membrane. During the stripping process, carboxylic acid groups within the photoresist polymer react with cations in the solution to form carboxylate salts. Electric current drives negatively charged anions toward the positively charged anode. Anions migrate freely through the anion-selective membrane into the anode chamber. At the anode, oxygen evolution occurs resulting from decomposition of hydroxyl ions. As the concentration of the hydroxyl ions in the anolyte solution is depleted the pH of the solution decreases. At about neutral pH, the dissolved portion of the photoresist polymer starts to precipitate out of the anolyte. Thus, the stripping solution is continuously regenerated as the photoresist is removed from the main stripping chamber, precipitated in the anode chamber, and filtered out. At the same time, the pH of the main stripping chamber does not drop due to removal of the anions as it does in conventional resist stripping processes. On the contrary, the pH of the solution increases due to hydrogen gas evolution, which continuously removes H+ions from the solution. Therefore, there is no need for continuous addition of fresh resist stripping solution to maintain the pH. The resulting system is more economical, efficient and environmentally sound.
Alkali or alkaline earth metal hydroxides or their respective salts are the preferred alkalinity carriers in the solution for cathodic photoresist stripping. Additionally, other alkaline inorganic or organic salts as well as organic alkalis can be used as secondary conductivity and alkalinity enhancers. Horizontal conveyorized equipment such as described in U.S. Pat. No. 5,292,424, which is commonly used in PWB manufacturing steps such as, for example, electroplating steps, can be utilized for cathodic photoresist stripping to reduce handling and cycle time. As a result, increased productivity and a reduced defect rate is achieved.
Optionally, ultrasonic agitation can also be provided in order to create cavitation at the photoresist/solution interface, thereby enhancing the stripping rate.