Information about physical places is gathered to develop quality scores for targeting advertisements to users of mobile devices sharing geographic location events with service providers. A scoring model incorporates selected attributes about places (e.g., created by a service provider vs. user-generated, category, keywords, census data providing population density by location, property values by area, popularity, special events, government vs. private area, whether place is associated with a brand, chain, or is independent) that have been gathered from multiple sources, verified, and normalized. Advertisements are targeted to users running mobile applications based on a location event shared with the service provider using the quality score for the place indicated in the location event in addition to other attributes of the place. In one embodiment, the system uses a machine learning algorithm to analyze conversion rates of targeted advertising to provide feedback to the scoring model.

This invention relates generally to software and computer systems, and more specifically, to an advertising system.
Traditionally, advertisers have used geographic location in targeting advertisements in a one-size-fits-all mentality, assuming that users in regions, states, cities, and/or neighborhoods respond to similar types of advertising. For example, users that live in the same zip code as a supermarket may receive advertisements about the supermarket, even if some of those users only shop online for their groceries for organic foods. In this way, the geographic location of those users has been wasted on a supermarket advertisement that is not relevant.
Location-based mobile applications have recently gained popularity among mobile device users. These applications enable users to share their physical locations in real time, providing insight into the daily routines, habits, and favorite places of users of these applications. Although basic demographic information is captured about users of these mobile applications, few advertisers have taken advantage of the location information gathered from these "check-ins," or location events that include a geographic location in real time.
The proliferation of location-based applications has led to duplicate entries for businesses, inaccurate check-ins, and a lack of mechanisms to handle the uncertainty of user-generated places, such as "Casa de Joe." Further, advertisers have been struggling to understand how to utilize this new-found location information. Service providers enabling these check-in events only provide the category of location, such as an entertainment venue, restaurant, or park, basic identification information about the place, such as its address and name, and the number of times users have checked into the place. This limited information does not enable advertisers to target users by location. With millions of people sharing their various physical locations at brick and mortar businesses, parks, landmarks, and even public transit vehicles, advertisers have a goldmine of information about users and the locations they visit, yet mechanisms to effectively target users of mobile applications based on their geographic location have not been devised. Tools and methods are needed to aggregate and normalize these locations and evaluate their potential for being paired with an advertisement.


A method for bonding together two substrates that includes applying to a first substrate an adhesive composition that includes (a) a trifunctional olefinic first monomer, (b) an olefinic second monomer that is copolymerizable with the first monomer and (c) a free radical initiator and then contacting a second substrate to the composition-applied first substrate so that the first and second substrate adhesively bond together. There is also provided a method for providing a coating on a substrate that includes applying to the substrate a composition that includes (a) a trifunctional olefinic first monomer, (b) an olefinic second monomer that is copolymerizable with the first monomer and (c) a free radical initiator and then allowing the composition to cure. Preferably, the adhesive or coating composition includes (a) a free radical polymerizable monomer component that includes a trifunctional olefinic first monomer and an olefinic second monomer that is copolymerizable with the first monomer and (b) a redox initiator system, wherein the adhesive composition is a liquid at room temperature and is curable at room temperature.

The invention relates to adhesives and coatings that include a free radical polymerizable component wherein the free radical polymerizable component includes a trifunctional olefinic monomer.
Reactive acrylic adhesives that cure by free radical polymerization of (meth)acrylic esters (i.e., acrylates) are known, but suffer from certain drawbacks. Commercially important acrylic adhesives tend to have an offensive odor, particularly those that are made from methyl methacrylate. Methyl methacrylate-based acrylic adhesives also have low flash points (approximately 59xc2x0 F.). Low flash points are particularly an issue during storage and transportation of the adhesives. If the flash point is 141xc2x0 F. or lower, the U.S. Department of Transportation classifies the product as xe2x80x9cFlammablexe2x80x9d and requires marking and special storage and transportation conditions.
Another problem with reactive, two-part, acrylic adhesives utilizing a benzoyl peroxide/tertiary amine free radical initiator system is that the volume mix ratio of one part with the other part is not 1:1xe2x80x94it is typically 4:1 or 10:1. Obviously, this requires more careful measurement calculation during application of the adhesive and causes packaging problems. The mix ratio problem results largely from the instability of mixtures of free radical initiators such as benzoyl peroxide with (meth)acrylic monomers at room temperature. The free radical initiators generate a sufficient amount of free radical to gel the monomers over a short time period.
Styrenic monomers such as styrene and vinyl toluene have been suggested as alternatives to (meth)acrylic adhesives (see, e.g., U.S. Pat. No. 2,981,650), but these have at least two drawbacks. The film formed from styrenic monomers is too brittle and the cure rate of styrenic monomers is too slow to be useful as a structural adhesive.
A two part reactive adhesive with reduced odor and flammability that could be mixed at a 1:1 volume ratio without comprising shelf life stability or adhesive performance would be very desirable.
The composition of the invention is a reactive adhesive or coating that includes two parts or sides that are mixed together at the time of use. The reaction of the two parts acts to cure the adhesive or coating. It has been discovered that a certain copolymerization system provides a reactive adhesive or coating composition that has very useful characteristics.
In particular, a trifunctional olefinic first monomer and an olefinic second monomer copolymerize when mixed together with a free radical initiator system. If the initiator and monomer mixture is applied to a substrate, the copolymerization process acts to form a highly crosslinked composition that is strongly adhesively bonded to the substrate.
Thus, according to a first embodiment of the invention there is provided a method for bonding together two substrates that includes applying to a first substrate an adhesive composition that includes (a) a trifunctional olefinic first monomer, (b) an olefinic second monomer that is copolymerizable with the first monomer and (c) a free radical initiator and then contacting a second substrate to the composition-applied first substrate so that the first and second substrate adhesively bond together.
According to a second embodiment of the invention there is provided a method for providing a coating on a substrate that includes applying to the substrate a composition that includes (a) a trifunctional olefinic first monomer, (b) an olefinic second monomer that is copolymerizable with the first monomer and (c) a free radical initiator and then allowing the composition to cure.
According to a further embodiment of the invention there is provided a bonded assembly that includes a first substrate, a second substrate and an adhesive composition between the first and second substrates wherein the adhesive composition is the cured product of a reaction mixture comprising (a) a trifunctional olefinic first monomer, (b) an olefinic second monomer that is copolymerizable with the first monomer and (c) a free radical initiator.
According to another embodiment of the invention there is provided an adhesive composition comprising (a) a free radical polymerizable monomer component that includes a trifunctional olefinic first monomer and an olefinic second monomer that is copolymerizable with the first monomer and (b) a redox initiator system, wherein the adhesive composition is a liquid at room temperature and is curable at room temperature.
One advantage of trifunctional olefinic monomers is that they do not homopolymerize in the presence of a free radical initiator. Thus, in a two-part reactive composition the trifunctional olefinic monomer can be included in the same part as the free radical initiator. This more easily allows for the formulation of 1:1 equal mix ratio between the two parts since the trifunctional olefinic monomer can be used as a reactive diluent for the initiator-containing part thus allowing adjustability of the volume and mole ratio relative to the other part. Additional advantages of the reactive adhesive system according to the invention is lower odor and lower flammability, particularly a flash point of 141xc2x0 F. or higher. A further advantage is that certain trifunctional olefinic monomer/copolymerizable olefinic monomer systems exhibit low viscosity allowing for compounding with inexpensive fillers. In addition, the reactivity of the trifunctional olefinic monomers with stryenic monomers allows for commercially practical use of styrenic monomers in adhesives.
Unless otherwise indicated, description of components in chemical nomenclature refers to the components at the time of addition to any combination specified in the description, but does not necessarily preclude chemical interactions among the components of a mixture once mixed.
As used herein, the following terms have certain meanings.
xe2x80x9cFlash pointxe2x80x9d is the temperature at which a substance evolves sufficient flammable vapor to give a visible flash on the introduction of a spark or a small flame.
xe2x80x9cRoom temperaturexe2x80x9d means ambient workplace (manufacturing or assembly plant, laboratory, etc.) temperature range, typically 10-40xc2x0 C., more typically 20-30xc2x0 C.
The trifunctional olefinic monomers are monomers that include olefinic or ethylenic unsaturation and at least three functional groups that are each bonded directly to the unsaturated carbon atoms. As used in the context of xe2x80x9ctrifunctionalxe2x80x9d, xe2x80x9cfunctional groupxe2x80x9d includes alkyl as well as the various functional groups conventionally referred to in the organic chemical art. The trifunctional olefinic monomers are electrophilic.
Useful trifunctional olefinic monomers typically have a generic structure represented by formula A
wherein each X is the same or different and is an electron withdrawing group such as xe2x80x94SO2R1, xe2x80x94CN, SO2Ar, xe2x80x94(Cxe2x95x90O)R2, or halogen (wherein R1 is alkyl, alkoxy, alkyl ether, amino, alkylamino, alkylimino, or alkylamimidoyl; Ar is an aryl or substituted aryl group; R2 is R1, xe2x80x94OR1, xe2x80x94N(H)R1, or xe2x80x94NH2); Y is xe2x80x94R1, xe2x80x94Ar or an electron withdrawing group as identified for X; and Z is a moiety selected from the first or second row elements of the Periodic Chart in the form of either a single element (such as xe2x80x94H or xe2x80x94F) or linearly bonded multiple elements (such as xe2x80x94CN). The two X groups or the X and Y groups also could form a fused ring system such as a lactone, anhydride or imide. Both unsaturated carbon atoms of the trifunctional olefinic monomer are sterically hindered by the functional groups. Preferably, X is xe2x80x94CN or xe2x80x94COOR1; Y is xe2x80x94CN, xe2x80x94COOR1 or xe2x80x94Ar; Z is hydrogen; and R1 is a primary or secondary linear or branched alkyl having 1 to 18 carbon atoms. xe2x80x9cPrimaryxe2x80x9d alkyl means that the carbon atom of R1 bonded to xe2x80x94OOCxe2x80x94 is also bonded to only one non-hydrogen atom (thus, it is bonded to two hydrogen atoms). xe2x80x9cSecondaryxe2x80x9d alkyl means that the carbon atom of R1 bonded to xe2x80x94OOCxe2x80x94 is also bonded to two non-hydrogen atoms (thus, it is bonded to only one hydrogen atom).
Illustrative trifunctional olefinic monomers include arylidenecyanoacetates such as benzylidenecyanoacetate (i.e., ester of benzylidenecyanoacetic acid); arylidenecyanoacetamides; alkylidenecyanoacetates such as ethylidenecyanoacetate; arylideneacetoacetates such as benzylidineacetoacetate; substituted fumarate esters such as di(cyano)fumarate ester, cyanofumarate esters and bromofumarate esters; di(cyano)acrylates such as ethyl 2,3-di(cyano)acrylate or methyl 1,1-di(cyano)-2-carboxyethene; tricarboalkoxyethenes; tri(cyano)ethylenes; carboxyalkylmaleic anhydrides; esters of di(cyano)fumaric acid; esters of tri(cyano)acrylic acid; esters of xcex2-halocyanoacrylic acids; esters of 2-halo-2-cyanoacrylic acid; xcex1-carboalkoxy-N-phenyl maleimide; and xcex1-(phenylsulfonyl)maleic anhydride.
Benzylidenecyanoacetates having a generic structure represented below by formula B are particularly preferred.
wherein R3 is a linear or branched alkyl, alkoxy, alkyl ether, amino, alkylamino, alkylamino, or alkylamimidoyl. Preferably, R3 is an alkyl or alkyl ether, particularly one having 1 to 18 carbon atoms. Methyl, ethyl, n-butyl, n-hexyl, 2-ethylhexyl, n-propyl, isopropyl, allyl, iso-octyl, 2-methoxyethyl, 2-ethoxyethyl, 2-methoxy-2-propyl and 2-ethoxy-2-propyl are particularly preferred for R3. Benzylidenecyanoacetates are identified herein according to the R3 group. Thus, if R3 is methyl then the benzylidenecyanoacetate is referred to as xe2x80x9cmethyl benzylidenecyanoacetatexe2x80x9d.
Especially useful in the present invention are benzylidenecyanoacetates wherein R3 is a secondary alkyl or secondary alkyl ether. In other words, the carbon atom of R3 bonded to xe2x80x94OOCxe2x80x94 is also bonded to two non-hydrogen atoms (meaning that it is bonded to only one hydrogen atom) as represented by formula C shown below.
wherein each of R4 and R5 is the same or different and is selected from alkyl, alkoxy or alkyl ether. Preferably, R4 and R5 are different and each have 1 to 10 carbon atoms and more preferably are methyl, ethyl, propyl, methoxy, hexyl, ethoxy, butyl, pentyl and branched alkyl groups.
Certain secondary benzylidenecyanoacetates such as xc2x11-methoxy-2-propyl benzylidenecyanoacetate and xc2x12-octyl benzylidenecyanoacetate are particularly preferred because it has been found that they exist as liquids at room temperature.
Trifunctional olefinic monomers that are liquid at room temperature are preferred. Solid or waxy benzylidenecyanoacetates, however, can be used by dissolving or dispersing them in a reactive diluent, the copolymerizable second olefinic monomer or a solvent.
Arylidenecyanoacetates, alkylidenecyanoacetates and arylideneacetoacetates can be made via catalyzed Knoevenagel condensation of aldehydes with cyanoacetates or acetoacetates as described in Gilath et al, J. Appl. Poly Sci., 14, 1491 (1970). This condensation reaction typically is performed in a conventional solvent such as hexane, cyclohexane, heptane, octane, benzene, toluene, xylene, ethanol and propanol. The catalyst usually is a base capable of removing a proton from the cyanoacetate. Examples include piperidine, a mixture of piperidine with acetic acid, pyridine, diethyl amine, propyl amine, potassium hydroxide, triethyl amine and butyl lithium. The reaction temperature typically is controlled by the boiling point of the solvent. Water is evolved in this reaction, and it may or may not be removed by distillation. The exotherm, if any, can be controlled by the slow addition of one of the reactants.
Second monomers particularly useful for copolymerization with the trifunctional olefinic monomers are those that include olefinic or ethylenic unsaturation. Such monomers tend to be electron-donating. Copolymerizable olefinic monomers are represented by the generic structure shown below as formula D:
wherein A is aryl, substituted aryl, alkyl, alkenyl, alkoxy, alkenyloxy, alkadienyl or acetoxy and each R6 is the same or different and is selected from hydrogen or alkyl. Preferably, A is aryl or substituted aryl and R6 is hydrogen.
Illustrative olefinic monomers include styrenic monomers; vinyl ethers; vinyl esters such as vinyl acetate; n-vinylcarbazole; diene monomers such as 2,3-dichloro-1,3-butadiene, 1,3-cyclohexadiene, myrcene and 2-chloro-1,3-butadiene. xe2x80x9cStyrenic monomerxe2x80x9d means styrene per se and styrenes substituted with additional functional groups. Illustrative styrenic monomers include styrene, 2-vinyl toluene, 3-vinyl toluene, 4-vinyl toluene, p-acetoxy styrene, chloromethyl styrene, ethyl styrene, divinyl benzene, 2-fluorostyrene, 3-fluorostyrene, 4-fluorostyrene, 2-chlorostyrene, 3-chlorostyrene, 4-chlorostyrene, 2-bromostyrene, 3-bromostyrene, 4-bromostyrene, 2,3,4,5,6-pentafluorostyrene, 4-vinyl benzoic acid, esters of 4-vinyl benzoic acid, 9-vinylanthracene, 4-methoxystyrene, 4-ethoxystyrene, 4-vinylbiphenyl, 2,4-dimethylstyrene, 4-vinylaniline, 4-cyanostyrene and glycidyl vinylbenzyl ether. Styrene, 2-vinyl toluene, 3-vinyl toluene and 4-vinyl toluene are preferred. Vinyl toluene is preferred (particularly 3-vinyl toluene, 4-vinyl toluene and mixtures thereof) because it has a higher flash point and less odor compared to styrene. As mentioned above, an important advantage of the invention is that the favorable copolymerization rate of the trifunctional olefinic monomers with styrenic monomers now allows for their use in adhesives.
The trifunctional olefinic monomer and the second olefinic monomer can be present in any amount effective to react together. Generally, the mole ratio of the trifunctional olefinic monomer to the second olefinic monomer may be 0.05 to 1.2, preferably 0.2 to 1.0.
The composition of the invention can include an optional third monomer that is copolymerizable with the second olefinic monomer and the trifunctional olefinic compound. The optional third monomer typically is also an olefinically or ethylenically unsaturated monomer but it has less than three functional groups bonded directly to an unsaturated carbon atom. Illustrative third monomer classes include maleate esters (ROOC)CHxe2x95x90CH(COOR) and corresponding half-esters; fumarate esters (i.e., trans-isomer of maleate ester) and corresponding half-esters; and (meth)acrylic acids and their esters. The optional third co-monomer can be present in amount of 0 to 80, preferably 1 to 30 weight percent, based on the total weight of the part of the adhesive composition that does not include an oxidizing agent. The optional third monomer could provide greater control of polymer flexibility, wetting, hydrophobicity and surface characteristics and might reduce the cost of the system.
The trifunctional olefinic monomer and second olefinic monomer react together resulting in a reaction product that includes an idealized polymer having a backbone structure represented by formula E below.
wherein X and Y are the same as in formula A and ED is the residual moiety from the second copolymerizable monomer. For example, if styrene is the second copolymerizable monomer, ED is a phenyl group.
The polymer of formula E can be a substantially equimolar 1:1 alternating copolymer, but preferably an excess of the second copolymerizable monomer is reacted with the trifunctional olefinic monomer to provide a copolymer with an alternating structure that is distributed over a certain range such as a composition that includes a mixture of polymer chains forming a gradient of structures from 1:1 alternating copolymer to the homopolymer of styrene.
Of course, when the trifunctional olefinic monomer and the copolymerizable olefinic monomer are included in a multi-component adhesive or coating composition with other reactive components the resulting reaction product is much more complex. The resulting reaction product (i.e., the cured adhesive or coating) will include a certain molecular distribution of polymers having the idealized copolymer backbone structure of formula E, and branched and crosslinked polymers that will include the backbone structure of formula E and moieties and chains from the other reactive components. For example, as described below, reactive toughening agents or polymers are often formulated into the composition. These toughening agents and polymers also react with the trifunctional olefinic monomers, the copolymerizable monomers, and the resulting copolymer to form a highly branched and crosslinked structure.
The copolymerization of the trifunctional olefinic monomer and the second olefinic monomer typically occurs via a free radical mechanism at room temperature. The free radical mechanism can be any system capable of generating a free radical such as a thermal systems, redox systems and photoinitiation systems. Examples of thermal free radical initiators include azobisisobutyronitrile, 2,2xe2x80x2-azobis-(2,4-dimethyl valeronitrile), 2,2xe2x80x2-azobis (methyl isobutyrate), benzoyl peroxide, acetyl peroxide, cumyl peroxide, t-butyl peroxide, t-butyl hydroperoxide, cumyl hydroperoxide, and t-butyl perbenzoate. Examples of photoinitiation systems include benzophenone, acetophenone, benzoin, benzoin ethers, benzil and benzil ketals. The preferred free radical initiator is a redox system as explained below in more detail.
As described above, the polymerizable combination finds particular usefulness in an adhesive composition wherein curing of the adhesive composition occurs via the above-described free radical systems. The adhesive composition can be a one part composition that is cured by thermal free radical initiation or photoinitiation or it can be a two part adhesive composition that is cured by the mixture of a redox free radical initiator system.
The compositions of the invention preferably are substantially 100% reactive. In other words, all components of the adhesive react during curing and thus there is no volatilization of organic compounds. Preferably or alternatively, the adhesive is substantially free of volatile organic compounds as solvents (less than one weight percent, based on the total amount of the adhesive composition. Such adhesive compositions are also known as 100% solids. As explained below, reactive diluents are used rather than volatile solvents.
Compositions that include the trifunctional olefinic monomer and the copolymerizable olefinic monomer can include a diluent that is reactive with the other components of the adhesive, particularly the trifunctional olefinic monomer and the copolymerizable olefinic monomer. Reaction of the reactive diluent also contributes to the curing of the adhesive, provides adhesive strength and aids in wetting. The diluent can be a monomer selected from those listed above for the second olefinic monomer and thus can serve a dual function. Particularly useful reactive diluents are the styrenic monomers.
The compositions can also include at least one polymeric material, preferably an elastomer, which can act as a toughening agent. The polymeric material may or may not include an ethylenically unsaturated structure that is capable of reacting with at least one of the ethylenically unsaturated monomers described above. The polymeric material can be, for example, polychloroprene as described in U.S. Pat. No. 2,981,650; a polymer-in-monomer syrup as described in U.S. Pat. Nos. 3,725,504 and 4,223,115; butadiene-based elastomers and urethane-modified butadiene-based elastomers as described in U.S. Pat. Nos. 4,223,115; 4,452,944; 4,769,419 and 5,641,834; chlorosulfonated polyethylene rubbers and/or a mixture of sulfonyl chloride with chlorinated polyethylene as described in U.S. Pat. Nos. 3,890,407, 5,206,288 and 4,536,546; and olefinic urethane reaction products of an isocyanate-functional prepolymer and a hydroxy-functional monomer as described in U.S. Pat. Nos. 4,223,115, 4,452,944, 4,467,071, and 4,769,419.
Polymer-in-monomer syrups are well known in the art. The monomer can be any of the ethylenically unsaturated monomers described above. The monomer of the polymer-in-monomer syrup can itself serve as the polymerizable component of the composition or a pre-formed polymer-in-monomer syrup can be mixed with an ethylenically unsaturated monomer. Exemplary polymer-in-monomer syrups are described in U.S. Pat. Nos. 3,725,504 and 4,223,115.
Representative liquid olefinic-terminated elastomers include homopolymers of butadiene; copolymers of butadiene and at least one monomer copolymerizable therewith, for example, styrene, acrylonitrile, methacrylonitrile; as well as modified elastomeric polymeric materials, such as butadiene homopolymers and copolymers as noted above modified by copolymerization therewith of trace amounts or up to about 5 percent by weight of the elastomeric material of at least one functional monomer (such as acrylic acid, methacrylic acid, maleic anhydride, fumaric acid, styrene and methyl methacrylate). The secondary hydroxyl group of liquid butadiene-based elastomers can be reacted with an isocyanate to form a liquid urethane-modified butadiene elastomer as described in U.S. Pat. Nos. 4,769,419 and 5,641,834.
Other useful elastomers include a homopolymer or copolymer of epichlorohydrin and ethylene oxide and copolymers of ethylene and acrylate esters, such as methyl acrylate and ethyl acrylate, wherein the copolymer contains at least 30 weight percent acrylate ester that are available from E. I. duPont under the tradename VAMAC.
The chlorosulfonated polyethylene and sulfonyl chloride/chlorinated polyethylene mixture embodiments can have a chlorine content of 25 to 67 weight percent and 3 to 160 mmols sulfonyl chloride moiety per 100 grams of polymer. Further, the polyethylene from which the chlorosulfonated polyethylene is made preferably has a melt index of 4 to 500.
An illustrative adhesive system is a room temperature-curable structural adhesive that includes
(a) 5-60, preferably 10-50, weight percent of the trifunctional olefinic monomer;
(b) 10-90, preferably 30-60, weight percent of the second olefinic monomer;
(c) 0-50, preferably 10-40, weight percent of at least one elastomeric toughening agent;
(d) 0-20 weight percent of a phosphorus-containing compound having one or more olefinic groups and no less than one Pxe2x80x94OH group; and
(e) a room temperature-active initiator system that includes at least one reducing agent and at least one oxidizing agent that are co-reactive at room temperature to generate free radicals that are capable of initiating and propagating the cure of said adhesive composition,
wherein the weight percents are based on the total weight of components (a)-(d).
The free radical-polymerizable adhesive compositions of the invention are normally provided as two-part or package systems, with the parts being mixed or contacted at the time of use to provide a free radical curing adhesive. As described above, an advantage of the invention is that the trifunctional olefinic compound can be included in the part with an oxidizing agent. However, the trifunctional olefinic compound does not have to be included in the part with the oxidizing agent. In more detail, these two-part systems can include
(I) a first part or side comprising
(a) 10-90, preferably 30-60, weight percent of the second olefinic monomer;
(b) 0-50, preferably 10-40, weight percent of at least one elastomeric toughening agent;
(c) 0-20, preferably 1-3, weight percent of a phosphorus-containing compound having one or more olefinic groups and no less than one Pxe2x80x94OH group; and
(d) 0.5-10, preferably 1-3, weight percent of at least one reducing agent which is interactive with a peroxide oxidizing agent to produce free radicals which are capable of initiating and propagating free radical polymerization reactions; and
(II) a second part or side comprising
(a) 1-99, preferably 10-90, weight percent, of the trifunctional olefinic monomer; and
(b) a bonding activator containing a peroxide oxidizing agent of a room temperature-active redox couple initiator system, the peroxide oxidizing agent being reactive at room temperature with reducing agent (d) when the first and second parts are mixed to produce free radicals which are capable of initiating and propagating free radical polymerization, the amount of the peroxide oxidizing agent being sufficient to interact with reducing agent (d), wherein the weight percents of the first part are based on the total weight of components (a)-(c) and the weight percent of the second part is based on the total weight of the second part.
Phosphorus-containing compounds that enhance metal adhesion as well as slow cure rate can be any derivative of phosphinic acid, phosphonic acid or phosphoric acid having at least one Pxe2x80x94OH group and at least one organic moiety characterized by the presence of an olefinic group, which is preferably terminally located. A listing of such phosphorus compounds is found in U.S. Pat. No. 4,223,115. A preferred phosphorus-containing compound has a structure that may be represented by the formula
wherein R20 is selected from the group consisting of hydrogen, an alkyl group having from one to 8, preferably one to 4, carbon atoms, and CH2xe2x95x90CHxe2x80x94; R21 is selected from the group consisting of hydrogen, an alkyl group having from one to 8, preferably one to 4 carbon atoms; A is selected from the group consisting of xe2x80x94R22Oxe2x80x94 and (R23O)n, wherein R22 is an aliphatic or cycloaliphatic alkylene group containing from one to 9, preferably 2 to 6, carbon atoms; R23 is an alkylene group having from one to 7, preferably 2 to 4, carbon atoms; n is an integer from 2 to 10, and m is one or 2, preferably one.
Phosphorous-containing compounds having vinyl unsaturation are preferred over such compounds having allylic unsaturation, with monoesters of phosphinic, phosphonic and phosphoric acids having one unit of vinyl or allylic, especially vinyl, unsaturation presently being preferred. Representative phosphorus-containing compounds include, without limitation, 2-hydroxyethyl methacrylate phosphate; bis-(2-methacryloyloxyethyl)phosphate; 2-acryloyloxyethyl phosphate; bis-(2-acryloyloxyethyl)phosphate; methyl-(2-methacryloyloxyethyl)phosphate; ethyl methacryloyloxyethyl phosphate; methyl acryloyloxyethyl phosphate; ethyl acryloyloxyethyl phosphate; compounds of the above formula wherein R8 is hydrogen or methyl and R9 is propyl, isobutyl, ethylhexyl, halopropyl, haloisobutyl or haloethylhexyl; vinyl phosphonic acid; cyclohexene-3-phosphonic acid; alpha-hydroxybutene-2 phosphonic acid; 1-hydroxy-1-phenylmethane-1,1-diphosphonic acid; 1-hydroxy-1-methyl-1-diphosphonic acid: 1-amino-1 phenyl-1,1-diphosphonic acid; 3-amino-1-hydroxypropane-1,1-diphosphonic acid; amino-tris(methylenephosphonic acid); gamma-amino-propylphosphonic acid; gamma-glycidoxypropylphosphonic acid; phosphoric acid-mono-2-aminoethyl ester; allyl phosphonic acid; allyl phosphinic acid; xcex2-methacryloyloxyethyl phosphinic acid; diallylphosphinic acid; xcex2-methacryloyloxyethyl) phosphinic acid and allyl methacryloyloxyethyl phosphinic acid.
The compositions of the invention can also contain at least one unsaturated polyester resin. Such resin esters are derived from polycarboxylic acids and polyhydric alcohols, preferably dicarboxylic acids and dihydric alcohols, with at least one of the acid and alcohol components being unsaturated. Preferably, the unsaturated polyester resin component will contain a relatively large number of double bonds and be derived from short chain aliphatic polyhydric polyols, such as ethylene glycol and 1,3-propylene glycol, and short chain unsaturated polybasic acids, such as fumaric acid and maleic acid. Such resins can contain quantities of longer chain polyols such as 1,6-hexanediol, as well as higher polybasic acids, such as adipic acid and phthalic acid.
Still further, the compositions of the invention can optionally contain at least one polyvinyl alkyl ether. Polyvinyl alkyl ethers are well known in the art. Such ethers will preferably contain 1-8, more preferably 1-4, carbon atoms in the alkyl moiety of the ether.
The compositions of the invention can also include a pre-formed polymeric component (in addition to the polymeric materials listed above) having an intrinsic viscosity of 0.1 to 1.3 that are obtained by the polymerization of at least one (meth)acrylic, styrene, substituted (meth)acrylic and non-acrylic olefinic monomers. Exemplary additional pre-formed polymeric materials include poly(methyl methacrylate/n-butylacrylate/ethyl acrylate) (90/5/5); poly (n-butyl methacrylate/isobutyl methacrylate) (50/50); poly (n-butyl methacrylate) and poly (ethyl methacrylate).
The preferred composition can optionally include an epoxy component that can be any monomeric or polymeric compound or mixture of compounds having an average of greater than one 1,2-epoxy groups per molecule. The polymeric epoxide materials can have a number-average molecular weight of 300 to 10,000. Useful epoxy compounds are well-known and include the polyglycidyl ethers of polyhydric alcohols such as ethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,5-pentanediol, 1,2,6-hexanetriol, glycerol and 2,2-bis(4-hydroxy-cyclohexyl)propane; the polyglycidyl esters of aliphatic or aromatic polycarboxylic acids such as oxalic acid, succinic acid, glutaric acid, terephthalic acid, 2,6-naphthalene dicarboxylic acid and dimerized linolenic acid; the polyglycidyl ethers of polyphenols such as bisphenol A, 1,1-bis(4-hydroxyphenyl)ethane, 1,1-bis(hydroxyphenyl)isobutane, 2,2-bis(4-hydroxy-t-butylphenyl)propane, 1,5-dihydroxynaphthalene and novolak resins; and cycloaliphatic polyglycidyl compounds.
Another optional component is up to 1 percent by weight of a waxy substance selected from the group consisting of paraffin wax, beeswax, ceresin wax and spermaceti wax.
The environmental resistance of an adhesive system made from the composition of the invention can be improved by the optional addition of a mixture of a metal molybdate such as zinc molybdate, calcium molybdate, barium molybdate and/or strontium molybdate and an inert filler such as zinc phosphate, calcium phosphate, magnesium phosphate and/or calcium carbonate. Such mixtures are more fully described in U.S. Pat. No. 4,017,315.
The compositions can also optionally include polybasic lead salts of phosphorus acid and saturated and unsaturated organic dicarboxylic acids and acid anhydrides, particularly dibasic lead phthalate, monohydrous tribasic lead maleate, tetrabasic lead fumarate, dibasic lead phosphite and mixtures thereof; and zinc oxide. These compounds can be effective in improving environmental resistance.
The room temperature-reactive initiator systems that may be employed are well-known redox couple systems. Basically, such systems comprise at least one oxidizing agent and at least one reducing agent that are co-reactive at room temperature to generate free radicals effective to initiate addition polymerization reactions and cure the adhesive.
The oxidizing agent (also known as free radical generator) should be a peroxide. Representative peroxides include, without limitation, organic peroxides, such as benzoyl peroxide, dicumyl peroxide and other diacyl peroxides, hydroperoxides such as cumene hydroperoxide and tertiary butyl hydroperoxide, peresters such as xcex2-butylperoxybenzoate and tertiary butyl peroxide acetate, and ketone hydroperoxides such as methyl ethyl ketone hydroperoxide.
Representative reducing agents (also known as accelerators) include, without limitation, sulfinic acids; alpha-aminosulfones such as bis(tolysulfonmethyl)-benzyl amine; tertiary amines such as diisopropyl-p-toluidine, dimethyl aniline, dialkyl-p-halogenated aniline and dimethyl-p-toluidine; and aminealdehyde condensation products, for example, the condensation products of aliphatic aldehydes such as butyraldehyde with primary amines such as aniline or butylamine. The use of known promoters (such as an organic salt of a transition metal, such as cobalt, nickel, manganese or iron naphthenate, copper octoate, copper acetylacetonate, iron hexoate or iron propionate) with the redox couple initiator systems can be advantageous. Preferably, the amount of reducing agent is in the range from about 0.05 to about 10, preferably about 0.1 to about 6, percent by weight of the first part.
The second part of the composition can include a bonding activator that includes the peroxide oxidizing agent for the redox catalyst system. The bonding activator can include (1) from about 0.5 to about 50 percent by weight, based on total weight of bonding activator, of at least one peroxide oxidizing agent which can function as an oxidant of a redox couple initiator system; and (2) from about 30 to about 99.5 percent by weight, based on total weight of bonding activator, of a carrier vehicle. In addition, the bonding activator also can contain either the epoxy component or the phosphorus-containing compound.
The carrier vehicles that are suitable for use in the bonding activators can be a simple inert solvent or diluent such as methylene chloride, or butyl benzyl phthalate, including mixtures of such solvents or diluents. The carrier vehicle should contain no more than 5% by weight of any moiety that is reactive with the oxidizing agent at room temperature. The carrier vehicle can be a more complex mixture including at least one film-forming binder in addition to inert solvent or diluent. In this case, the film-forming binder is preferably substantially inert with respect to the oxidant that is present in the accelerator composition. Among the polymeric film-forming binder materials that can be employed in the carrier vehicle are, without limitation, polyalkylacrylates and methacrylates and copolymers thereof, polystyrene and copolymers thereof, vinyl polymers and copolymers, polyesters, polyketones, polysulfones, phenolic resins, polyvinyl butyrals and polycarbonates. The carrier vehicle can contain, in addition to solvent or solvent and film-forming binder, additives such as external plasticizers, flexibilizers, suspenders and stabilizers, providing that any such additives do not unacceptably adversely affect the stability of the activator composition.
Another optional component is a tertiary amine represented by the structure
wherein Z is methylene; Y is selected from the group consisting of hydrogen, hydroxy, amino, halogen, alkyl having 1 to 8, preferably 1 to 4, carbon atoms, and alkoxy having 1 to 8, preferably 1 to 4, carbon atoms; a is 0 or 1; and b is 1 or 2.
This tertiary amine is advantageous in accelerating the cure of such compositions containing the unsaturated organophosphorus compounds. Especially preferred tertiary amines are N,N-dimethyl aniline and N,N-dimethylaminomethylphenol.
The components of the composition are mixed together by means well known in the art. The catalyst, of course, is not activated until curing of the composition is desired.
The adhesive systems preferably are provided as multipack adhesive systems where one package contains a portion of the polymerizable component and the reducing agent and a second package contains the other portion of the polymerizable component and the bonding activator, with the two packages being mixed at the time of use.
It is necessary that the epoxy compound when incorporated into the adhesives be kept separate from compounds having acidic moieties, such as the phosphorus-containing compound and methacrylic acid to inhibit premature reaction between these components. Thus, in such cases, prior to using the compositions, one package will contain the phosphorus-containing compound and the other package will contain the epoxy component. Preferably, the epoxy component will be incorporated into the bonding activator that contains the oxidizing agent of the redox couple initiator system, with the phosphorus-containing compound being incorporated into the package containing the polymerizable component. While other multipack systems are available, e.g., the bonding activator can contain the reducing agent of the redox couple catalyst system and the epoxy resin with the oxidizing agent and polymerization inhibitors being incorporated into the package containing the polymerizable adhesive mass, they are less preferable with respect to shelf stability. After mixing the individual packages, one or both surfaces to be joined are coated with the mixed adhesive system and the surfaces are placed in contact with each other.
Generally, the composition systems include the first and second parts in conventional amounts, for example, in a volume ratio of about 24:1 to about 1:1, preferably about 10:1 to about 1:1, most preferably 1:1, first part: second part.
As mentioned above, compositions that include the trifunctional olefinic monomer preferably have a flash point less than 141xc2x0 F. In the case of benzylidenecyanoacetates, the flash point preferably is 130 to 150xc2x0 F.
The adhesive systems may be used to bond together any types of substrate surfaces. The adhesive is particularly useful for bonding metal surfaces, such as steel, aluminum and copper, to a variety of substrates, including metal, plastics, and other polymers, reinforced plastics, fibers, glass, ceramics, wood and the like. It is a feature of the present invention that the herein-described adhesive compositions can be employed to bond metal substrates such as steel, aluminum and copper with little, if any, pretreatment of the metal surface prior to application of the adhesive. Thus, bonding can be effected even to oily metal surfaces which are otherwise clean without an extensive pretreatment as is usually required with the vast majority of currently available primers and adhesives. Additionally, the adhesive systems of this invention provide effective bonding at room temperature, thus heat is not required either for applying the adhesive systems to the substrates or for curing. The copolymer system of the invention is especially useful in the formulation of a structural adhesive used in the bonding of lightweight metal and plastic materials in the fabrication, repair and reconstruction of transportation vehicle bodies and component parts. The copolymerization system of the invention also is useful in formulating coatings and primers for metals and plastics.
The invention is described in more detail by way of the following non-limiting examples.

Reactive adhesives and coatings with trifunctional olefinic monomers


A cryogenic freezing system having a cooling tunnel with an inlet end, an outlet end and a floor therebetween, a tank for a liquid cryogenic material and with an inlet end, an outlet end, and a floor therebetween, a first conveyor for moving crumb material along the tunnel floor for depositing crumb material into the tank, and a second conveyor for moving crumb material along the tank. The tank floor includes a ramp, with the second conveyor positioned to move the crumb material along the floor of the tank upward along the ramp out of the liquid cryogenic material prior to reaching the tank outlet end. The conveyors are endless belts of open material, with openings of a size to pass the crumb material so that the crumb material will fall through the conveyor onto the floors. Scraper blades are carried on the belts projecting outward from the conveyors to move along and in contact with the floors.

The disposal of used tires for cars and trucks is a very large environmental problem for the U.S.A. and it is even more pronounced for some other densely populated countries all over the world. In the U.S. and Canada alone about 275,000,000 used tires are disposed of annually, usually in an open space. This is added to the estimated 2 to 3 billion tires already stockpiled in the U.S. The impact on the environment is enormous and represents health and fire hazards.
The used tires are composed of about 60% rubber, 40% steel and a small amount of plastic fiber. All these materials are reusable and recycling of used tires represents a very substantial new resource. The steel can be melted down, and the plastic fibers can be used several ways.
The use of rubber, the largest component of used tires, has received the most attention and it is fast expanding.
Rubber crumbs added to asphalt produce better and longer lasting roads. Other products such as floor tiles, rubber mats, tennis balls, trash cans, etc., are also made from crumb rubber. At this time there are several hundred developed applications for used rubber and the list is growing.
The development of rubber recycling technology started about two decades ago. However, the economical and environment-friendly recycling methods have been developed just recently. They can be classified as ambient grinding and cryogenic grinding methods. The final product of both methods is very similar, crumb rubber, by some called granules, ranging in size from 0.5 to 5 mm or ASTM classification 4-30 mesh. The larger sizes, 4 to 15 mesh, represent the most of production volume.
Some used rubber applications require much smaller sizes, 60-120 mesh, and the current price of this product is about $0.45/lb compared to about $0.15/lb for larger size crumb. Such price differences inspired development of methods to reprocess the crumbs to smaller size by secondary cryogenic freezing and grinding. The crumbs must be cooled to below -100.degree. F. to become hard and brittle, so that hammer-mill type equipment can be used to reduce the crumbs to a desired size.
Several methods, such as injecting liquid nitrogen in the mill, have been tried but the cost becomes prohibitive and it is not economically feasible. Several pounds of nitrogen are needed to freeze a pound of crumbs.

Cryogenic freezing system for rubber crumbs and other materials


A brightness control system enhances a displayed image. The system selectively alters the brightness of a portion of the image to improve the clarity, noticeability, and intelligibility of information provided on the display. When used with a vehicle navigation system, the brightness adjustment system may emphasize vehicle or destination location display, driving directions, route planning information, or other information provided to the driver.

1. Technical Field
The invention relates to a brightness controller for adjusting the brightness of an image on a display. In particular, the invention relates to a brightness control system for modifying the brightness of specific portions of an image.
2. Related Art
Both analog displays such as Cathode Ray Tubes (CRTs) and digital displays such as Liquid Crystal Displays (LCDs) create images from individual closely spaced points. Each point in the image is referred to as a picture element or pixel. The image data in the video data stream sent to the display conveys information which controls the brightness of each pixel.
In the past, dynamic changes to image brightness often required time consuming and computationally expensive brightness recalculations. This was particularly true when the recalculation of image data was done on a pixel-by-pixel basis. With the introduction and widespread use of high resolution displays, processing demands for dynamic brightness changes were often quite significant.
Displays are common components of vehicle navigation systems, entertainment systems, and game systems. A navigation system, for example, provides core functionality including the display of map location and route information to the driver. In addition to these core functions, the navigation system often provides extensive additional functionality for the driver. Thus, the processing demands on the navigation system (and other systems) are already significant, even without the added burden of dynamic image brightness control.
Therefore, a need exists for an improved brightness control system.


Methods are disclosed for transferring a pattern from a mask to a sensitive substrate. The mask is illuminated substantially orthogonally with a charged particle beam propagating along an optical axis. An image of the charged particle beam that has passed through the mask is projection-exposed onto the substrate. At multiple locations displaced from each other in the optical-axis direction, a size measurement is obtained on a transverse profile of the beam as incident on at least one of the mask and substrate. From the size measurements, a respective parallelism of the beam incident to the mask and/or substrate is determined. From these determinations, the parallelism of the beam relative to the mask and/or substrate is adjusted as required.

Relevant conventional apparatus and methods are exemplified by certain electron-beam projection-exposure apparatus. Projection-exposure using an electron beam is highly accurate but current methods are flawed by low throughput, and various approaches have been investigated in attempts to solve such problems. For example, various "batch"-type projection-exposure systems, termed "cell-projection," "character projection," or "block exposure" systems, have been developed. With such systems, a circuit pattern comprising a large number of repeating units of a particular arrangement of features is defined on a mask. Such a circuit pattern is typical of, for example, memory chips. The entire mask is not exposed in one exposure (or "shot") but rather one unit at a time in a repeating manner onto the substrate. As projected onto the substrate, each unit measures, e.g., about 10 .mu.m by 10 .mu.m square. However, such systems exhibit difficulty in projecting non-repeated areas of the circuit pattern.
Current efforts in the microlithography industry have been directed to the development of electron-beam projection-exposure apparatus that perform "demagnifying" projection-exposure (i.e., exposure in which the projected image of the mask is demagnified relative to the mask) of the mask pattern at much higher throughput than the batch-type systems summarized above. Various approaches have been investigated in which the mask defines the entire circuit pattern for a chip. In one approach, the electron beam is irradiated only on a certain portion of the overall mask pattern at any one instant, and an image of the irradiated portion is demagnified and "transferred" to (i.e., projection-exposed onto) the substrate using a projection lens. If one were to attempt to transfer, using such an apparatus, the entire mask pattern to the substrate in one shot, the entire mask pattern would not be transferred with sufficient accuracy. In addition, preparation of a mask for use in such an apparatus is very difficult.
Therefore, systems that are the subject of the most recent active research are not those in which the entire die pattern (or even multiple die patterns) is exposed in one shot. Rather, the most current approaches are directed to systems in which the projection optical system has a large optical field and the mask pattern is divided into multiple "subfields" that are projection-exposed one subfield at a time onto the substrate. Such systems are termed "divided" projection-exposure systems. With a divided projection-exposure system, exposure of each mask subfield is performed while correcting projection aberrations, such as image focus or field distortion, etc. Thus, projection-exposure can be performed with better image resolution and accuracy across an optically wider field than with systems that projection-expose an entire die in one shot.
In most conventional batch-type and divided projection-exposure systems, the projection-optical system projects a demagnified image of the irradiated portion of the mask onto the substrate. At the mask surface, if all locations of the transverse area of the beam used to illuminate the mask are not incident exactly orthogonally (i.e., telecentrically) at the mask surface, the trajectory of the beam between the mask and the substrate will not be ideal and more aberrations will be manifest.
In addition, at the substrate surface, if all locations of the transverse area of the beam used to project the image onto the substrate surface are not incident exactly orthogonally (i.e., telecentrically) on the substrate surface, problems will arise such as variations in image size as projected and/or image rotation at each transferred subfield, especially if the substrate surface exhibits any variation in elevation relative to the focusing plane of the projection-optical system. Such problems can seriously undermine, for example, the accuracy with which transferred subfields are "stitched" together on the substrate surface.
With semiconductor devices that require highly accurate fabrication, such as 1-Gbit and 4-Gbit DRAMs, the accuracy with which transferred subfields must be positioned and stitched together on the substrate surface is extremely high: about 10 to 30 nm. Therefore, it is becoming increasingly crucial, in such systems, to increase the accuracy with which all portions of the transverse area of the beam are incident orthogonally to the mask and substrate, and to be able to measure such orthogonality with high accuracy.
Conventionally, incidence orthogonality of the center of a beam flux is measured as described in Sturans et al., "Optimization of Variable Axis Immersion Lens For Resolution and Normal Landing," J. Vac. Sci. Technol. B8(6):1682-1685 (Nov./Dec., 1990). According to the method disclosed in that paper, a variable-shaped beam is projected onto the substrate. The size of the imaged pattern is controlled by shaping deflectors. Incidence orthogonality of the beam is measured only at the center of the beam flux. Unfortunately, in divided projection-transfer systems, such corrections cannot be realized.

Charged-particle-beam exposure methods with beam parallelism detection and correction


Fast fourier transforms are performed in digital signal processing using number theoretic transforms. Incoming pulse descriptor words are mapped into a matrix. The first convolution does forward and inverse number transforms on the rows. The second convolution does forward and inverse number transforms on the columns.

In many signal processing areas, and particularly in the area of airborne radar, it is desirable to perform fast fourier transforms (FFTs). FFTs are necessary to convert radar signal pulses received in the time domain to the frequency domain and back again. Many types of signal processing, including pulse compression decoding, can be done in the frequency domain more quickly.
In airborne radar systems, the signal processing equipment should be carried on board the airplane. However, space and power are strictly limited on board an aircraft. Accordingly, it is important to minimize the size and power consumption of the signal processing equipment. Since FFT engines constitute a substantial part of a radar system's signal processing equipment, it is important to simplify the mathematical operations required to perform FFTs as much as possible. This not only reduces the total amount of equipment required, but the cost of a digital radar system can also be reduced by using the same hardware for different operations and by using identical hardware for different systems.
Speed is also very important in airborne radar. A modern airplane and its targets fly quickly and collect vast amounts of radar information. In order for the aircraft crew to benefit from the information, it must be processed quickly enough for the crew to respond and quickly enough to make room for new information. The simpler the mathematical operations necessary to process the incoming information, the faster the processing can be performed.
Existing FFT engines, based most commonly on the Cooley-Tukey method, require a significant amount of hardware. Since FFTs must normally be performed several times in digital signal processing, this hardware constitutes a substantial part of the entire radar system. A meaningful reduction in the amount of hardware required and in the time it takes for the hardware to operate is of great benefit in the field.


In a consumable electrode gas shielded arc welding system, alternating current power is applied across the electrode and the base metal. The period during which the electrode is kept negative is varied to correspond to the electrode feeding rate. In addition, the levels of the output power during the negative and positive periods are individually set.

1. Field of the Invention
The invention relates to arc welding, in particular to a consumable-electrode AC gas shield arc welding method and an apparatus therefor.
2. Description of the Related Art
Prior art teaches welding in which DC current is passed through from an electrode (hereinafter referred to as wire) of positive polarity to a base metal of negative polarity in such a way that the average welding current may be controlled by varying the period of the base current while keeping its peak current, peak current period, and base current fixed, as disclosed in Japanese Patent Laid-Open Publication No. Sho. 56-165564. It is then possible to transfer the droplets formed at the tip of the wire towards the molten pool during the peak current period, thereby permitting welding which is less subject to spattering.
In order to obtain improved arc stability for small average welding current, Japanese Patent Laid-Open Publication No. Sho. 59-50672 discloses welding where a first electric pulse transfers the droplet from the wire and a second pulse prevents arc vanishing that follows the burning of the wire on the tip caused by the first pulse.
In a so-called reverse polarity welding where wire is given positive polarity and the base metal negative polarity, a substantially straight arc is established between the wire tip and a point of the surface (cathode spot) of the base metal just beneath the wire tip in the case of great welding current, while the cathode spot, and hence the arc itself, widely rambles on the surface of the base metal in the case of small welding current, so that the arc might vanish if it extends too long.
For these reasons the average welding current cannot be made smaller than a certain threshold in the said first prior art, nor said arc vanishing could not be prevented sufficiently in the said second prior art.
Japanese Patent Laid-Open Publication No. Sho. 57-130770 discloses a method for transferring the droplet to the molten pool in synchronism with the peak of the welding current which is passed through from a positive electrode (wire) to a negative base metal and is periodically varied between a maximum (peak current) and a minimum (base current).
For further understanding it would be appropriate to describe here a general relationship between the polarity of wire and the behaviors of arc. When the wire is given positive polarity, fairly immobile positive end of the arc is formed on the lower end of the droplet formed on the wire tip. As the result the arc is well bundled.
On the other hand if the wire is given negative polarity a diverging arc is formed from the droplet since mobile negative ends of the arc are then formed over the entire droplet surface. Therefore, when the polarity of the wire is changed from plus to minus, the arc pressure decreases as shown in FIG. 14 from curve a to curve b, so that the melting of the melting of the base metal is suppressed. However, if the wire is held minus only, much too large droplet is formed, since the amount of wire melt is governed by the polarity of the wire as depicted in FIG. 15, and hence the arc becomes unstable.
It should be noted that the use of AC current, permitting alternating polarities of plus and minus for the wire, may provide a stable arc configuration while suppressing melting of the base metal.
In a so-called reverse polarity welding where the wire is held positive and the base metal negative, the arc exhibits a greater pressure compared with positive polarity welding where the wire is held negative and the base metal positive, and consequently causes deeper penetration in the base metal and possible melting down of the metal if it is a thin metal plate. This is the case for metals like aluminum having low melting points.
In MIG braze welding using copper wire, excessive melting of the base metal must be avoided with great care since it causes the infiltration of copper into the base metal and results in weld cracks.
Suppression of the melting of the base metal is also desirable to reduce the dilution rate in the case of build-up welding of different metals.
In Japanese Patent Laid-Open Publication No. Hei. 1-186279 proposes a consumable electrode gas shield AC arc welding method and means therefor in which AC frequency is chosen appropriately chosen for a given wire feeding rate, along with a period and a level of reverse polarity current suitable for the shield gas and the material properties and diameter of the wire used, and levels of the normal and reverse polarity currents are controlled based on the arc voltage detected to keep the arc length constant.
The prior art welding mentioned above, however, has drawbacks described below. The prior art welding assumes AC rectangular waves, which are not in actuality perfectly rectangular as shown by a dotted waveform in FIG. 21 but rather trapezoidal as shown by a solid waveform. This is due to the fact that in actual welding processes the inductances and resistances of a power supply cable, usually 10 to 20 m long, affect the waveforms. In FIG. 21 the coordinate and abscissa represent current and time, respectively. The figure shows that the arc polarity is straight when the welding wire is negative (EN), while the polarity is reverse when the welding wire is positive (EP). I.sub.EP is the level or height of the rectangular current wave in the reverse polarity; T.sub.EP, its duration, while I.sub.EN is the height of the wave in the straight polarity; T.sub.EN, its duration, where I.sub.EP >I.sub.EN is assumed.
It is not possible with such trapezoidal waves to maintain AC current if the period T.sub.EN is shortened and the AC frequency is increased so as to meet the requirement of increasing wire feeding rate, since the time interval required for polarity change is not secured then, resulting in DC current as shown in FIG. 22. Furthermore, the period T.sub.EN will lose its constancy as the current changes from AC to DC, since the slopes of the trapezoidal wave are affected by the length and the arrangement of the welding cable used.
Furthermore, under a welding control method in which arc length is to be held constant as in prior art mentioned above, the current waveform changes as shown in FIGS. 23 and 24. Namely, if the arc length becomes shorter the electric current is increased to melt more wire so as to restore arc length and if the arc length becomes too long the current is decreased to melt less wire so as to restore the arc length, so that the amplitude of the current varies with the arc length. Consequently, AC Periods are eventually mingled with DC periods as shown in FIG. 25 as the period T.sub.EN of the wave having straight polarity is shortened.
Since AC and DC configurations are utterly different, coexistence of AC and DC arcs will result in fluctuations in penetration and melting of the wire, causing weld flaws such as overlaps and lack of fusion. Further, sudden change in arc configuration would upset welders and greatly reduce welding operability.
In non-consumable electrode AC gas shield arc welding as disclosed in Japanese Patent Laid-Open Publication No. Hei. 1-100672, a polarity EP (in which the electrode is negative) is maintained until an arc is initiated, but the current is switched from DC to AC immediately after the arc is initiated. This publication does not deal with welding whose arc is initiated by contacting the electrode on the base metal, since a high-frequency AC current is used in the non-consumable electrode AC welding method.
In a commercial consumable electrode DC gas shield arc welding apparatus an output power for arc initiation is set greater than that of normal operating output level.
Although such a consumable electrode DC welding as mentioned above deals with arc initiation with the consumable electrode in contact with the base metal, it is restricted to DC welding and no polarity switching is employed.
It should be noted that, because the penetration is smaller in EN polarity than in EP polarity, the switching of wire polarity from EP to EN immediately after the initiation of arc is likely to cause weld flaws and/or overlaps in the initiating arc region. Further, since the current is once reduced to zero and raised in opposite polarity, such polarity switching may destroy the initiating arc once and restart an arc, making an inherently unstable initiating arc more unstable.

Consumable-electrode AC gas shield arc welding method and apparatus therefor


The invention relates to a controlled acoustic wave guide configured as an elongated hollow chamber (1) which via an opening (2) in its first face end (3) is connected to a sound-conducting channel (4). The longitudinal resonances of the hollow chamber (1) can be adjusted to a sound spectrum to be dampened. To this end diaphragm vibrations are detected by means of a microphone (10) which is positioned directly in front of the diaphragm (8) of at least one loud-speaker (9) at the second face-end (6) of the hollow chamber (1). The microphone signal is then inverted using an amplifier (11) and fed back to the loud-speaker (9) after amplification in accordance with a sensor (12) signal characterizing the sound spectrum in the channel (4).

The present invention relates to a controlled acoustic waveguide for sound absorption in the manner of an elongate hollow chamber which communicates with a sound—transmitting duct via an opening on its first end surface. The longitudinal resonances may be tuned to a sound spectrum to be attenuated, by detecting the membrane vibrations with a microphone located directly in front of the membrane of at least one loudspeaker on the second end surface of the hollow chamber and by inverting the microphone signal with an amplifier and by feedback of the inverted microphone signal to the loudspeaker in an amplified form in dependence on a signal from a sensor, which is characteristic of the sound in the duct.
Sound absorbers are known for attenuating low-frequency noise in ducts, wherein the longitudinal resonances of elongate hollow chambers, so-called acoustic waveguides, are utilized, e.g. in accordance with the DE 19612572 or Lamancusa, J. S.: "An actively tuned passive muffler system for engine silencing". Proceedings Noise-Con 87, 1987, pp. 313–318. These waveguides are coupled to the sound-transmitting duct via an opening in the end surface thereof and either project orthogonally from the duct or conform thereto while extending in parallel therewith. For the first longitudinal resonance in particular, at which the length of the chamber corresponds to one quarter of the wavelength of the first resonance frequency, high attenuation levels are achieved over a narrow band. This limitation of the frequency range is, however, problematic when either a wide-band absorption is required or when the noise spectrum changes which was taken as a basis when the waveguide was dimensioned, The necessary adaptation of the chamber length is implemented, at least in stages, according to Lamancusa, by the provision of very long chambers with compartments from the very beginning, which may provision of very long chambers with compartments from the very beginning that be opened or closed whenever this is necessary. Another possibility of avoiding the inexpedient narrow-band restriction consists in the simultaneous application of different chamber lengths according to the German Document 196 12 572.
Another group of sound attenuators or absorbers for low frequencies comprises resonant cavities, i.e. both acoustic waveguides according to Okamoto, Y.; Boden, H.; Abom, M.: "Active noise control in ducts via side-branch resonators" in: Journ. of the Acoust. Soc. of America 96 (1994), No. 9, pp. 1533–1538, and equally Helmholtz resonators according to DE 4226885 or the U.S. Pat. No. 5,233,137, which are connected to a sound-transmitting duct or space via an opening and which have properties suitable for variation by electro-acoustical or active components, respectively. These systems share the joint approach that at least one microphone is present in the duct or space. The sound pressure signal so detected is initially filtered, amplified and subjected to further analysis steps and then serves as control variable for at least one loudspeaker in the waveguide or cavity. As a result, the loudspeaker emits a signal which, again upon modification by the resonator, is superimposed with opposite phase onto the sound at the site of the microphone in the duct or cavity, so effecting attenuation of the sound. With these actively influenced resonators, it is possible, on the one hand, to generate and hence also attenuate high sound pressures at low frequencies while, on the other hand, at least the loudspeaker is protected from potential, e.g. thermal, loads in the duct. The disadvantages of these methods include the fixed dimensioning of the resonators independently of possible variations of the sound spectrum in the duct, which is initially taken as a basis, and the lack of protection of the microphone.
According to DE 4027511, a passive sub-system is used instead of the resonant cavities so far mentioned, which consists preferably of passive absorber layers and protecting cover layers. In this case, too, the function of the electro-acoustical components mounted on the rear side relates to the modification of the passive absorber, aiming at the generation of a theoretically optimum acoustic impedance on the front side of the absorber, which impedance promise the highest propagation attenuation possible in the connected sound-transmitting duct. This method requires that a signal-shaping circuit proposed in DE 4027511 firstly compensates the intrinsic characteristics of all the electro-acoustic components (microphone, loudspeaker, box, etc.) and secondly imprints on the system the desired terminating impedance. The characteristics of the components have been thoroughly studied and described. In accordance with the results the conversion of this method into practice inevitably requires the implementation of complex transmission functions of the signal-shaping circuit, which cannot be realised in practical application except in approximation.
Reactive sound absorbers are operative without any additional passive layers or resonance systems according to WO 97/43754, wherein the membrane of a loudspeaker is a direct component of the wall in a sound-transmitting duct and wherein the membrane vibrations controlled or amplified with a feed-back circuit take a direct influence on the sound field in the duct. The adaptation to a sound spectrum to be attenuated, which is also necessary in this case, is based on the dimensioning of the resonance system consisting of the membrane mass and the pneumatic cushion in the form of the rear volume, which exists there-behind.

Controlled acoustic waveguide for soundproofing

Fraunhofer-Gesellschaft zur Foerderung der angewandten Forschung e.V.


An optical zoom lens module includes, in this order from the object side to the image side thereof, a first lens group of positive refraction power, a second lens group of negative refraction power, a third lens group of positive refraction power, and a fourth lens group of positive refraction power. The optical zoom lens module satisfies the formula: 12<TTL/FW<16, and 6<F1/F<8, where TTL is the total length of the optical zoom lens module, FW is the smallest effective focal length of the optical zoom lens module, F1 is the effective focal length of the first lens group, and F is the effective focal length of the optical zoom lens module.

1. Technical Field
The present disclosure relates to optical technology and, particularly, relates to an optical zoom lens module with short overall length and an image capturing device using the same.
2. Description of Related Art
In recent years, resolution of image sensing chips has increased, while size of the image sensing chips has decreased. Therefore, it has become desirable to develop an optical zoom lens module with a short overall length and with an optical performance that matches image sensing chips with enhanced resolution.

Optical zoom lens module and image capturing device using same


A wrench includes a handle, a head formed at an end of the handle for engagement with a nut and a magnet embedded in the head. In an aspect, the head includes an intermediate portion and two jaws extending from the intermediate portion. The magnet is embedded in the intermediate portion or one of the jaws. Alternatively, a magnet is embedded in each of the jaws. In another aspect, the head is a ring for engagement with the nut. The magnet is embedded in the ring or includes a first tip embedded in the ring and an exposed second tip. Thus, the second tip of the magnet performs as a stop for the nut. In another aspect, the wrench is a quick-release wrench. The intermediate portion includes two surfaces for contact with two adjacent facets of the nut. The magnet is embedded in one of the surfaces of the intermediate portion. Another magnet may be embedded in the remaining one of the surfaces of the intermediate portion. In another aspect, the wrench is an adjustable wrench including a handle, a fixed jaw projecting from the handle and a movable jaw mounted thereon. The movable jaw can be moved toward and away from the fixed jaw by operation of a worm and rack mechanism. The magnet is embedded in the fixed jaw or movable jaw. In another aspect, the head includes facets for contact with facets of the nut. The magnet is embedded in one of the facets of the head.

1. Field of Invention
The present invention is related to a wrench with a magnet.
2. Related Prior Art
A typical conventional wrench includes a handle, a first pair of jaws extending from a first end of the handle and a second pair of jaws extending from a second end of the handle. Each pair of jaws can be engaged with a nut or bolt. Thus, a user can drive the nut or bolt by pivoting the handle. In using the wrench to drive the nut, a user has to be careful about the nut or bolt in order not to lose the nut or bolt The user often has to operate the wrench with one hand and hold the nut with the other hand. This could be difficult for the user particularly when operating the wrench in a narrow space such as a nacelle.
Taiwanese Patent Publication No. 359212 teaches a wrench. The wrench includes a handle, a first pair of jaws extending from an end of the handle and a second pair of jaws extending from the other end of the handle A groove is defined in each pair of jaws, extending from the tip of a jaw to the tip of the other jaw. A U-shaped magnet is received in the groove defined in each pair of jaws. During an operation of such a wrench on a nut or bolt, the U-shaped magnet avoids the nut or bolt leaving the wrench. However, the U-shaped magnet must be precisely made and finished so that it does not hinder engagement of each pair of jaws with the nut or bolt. Generally, only two short sections of the U-shaped magnet contact the nut or bolt. Hence, use of the U-shaped magnet entails a waste of material.
Taiwanese Patent Publication No. 435307 teaches a magnetic device for various hand tools. However, during an operation of such a hand tool on a nut or bolt, the magnetic device cannot avoid the nut or bolt leaving the hand tool due to the position of the magnetic device on the hand tool.
The present invention is therefore intended to obviate or at least alleviate the problems encountered in the prior art.


A circuit for generating a reference voltage of bandgap type. The circuit includes a current mirror assembly of cascode type including, from a high supply rail, at least two parallel branches of P-channel MOS transistors. The circuit also includes a bipolar assembly in series with one of the branches of the mirror assembly down to a low supply rail, formed of two parallel branches each including, in series, a diode-connected bipolar transistor and, respectively, one resistor and two resistors. The circuit also includes a differential amplifier for balancing the currents in the two branches of the bipolar assembly, the reference voltage being provided by the terminal of interconnection of the mirror assembly with the bipolar assembly.

Field of the Invention
The present invention relates to the field of reference voltage generators and, more specifically, to the forming of a bandgap voltage generator. Such a generator is used to generate a reference voltage which is steady in temperature and in supply voltage. The present invention also aims at providing such a reference voltage generator which is not sensitive to possible technological mismatches of the transistors forming it.
Another object of the present invention is to share such a reference voltage generator for the provision of a reference voltage of an analog-to-digital converter and of a voltage depending on the internal temperature of an integrated circuit in which the generator is formed, to form an integrated digital sensor of the internal temperature of a circuit.

Bandgap voltage generator with a bipolar assembly and a mirror assembly


Steering mechanism for trailer wheels is provided with a slide having a tongue selectively engaged with and retracted from the fifth wheel of a tractor. When the tongue is engaged with the fifth wheel, any pivoting of the fifth wheel about the kingpin connection between the tractor and trailer, as when the tractor is steered from a straight ahead position relative to the trailer, causes the tongue to swing a link pivoted on the slide mechanism under the trailer. This swinging of the link drives a flexible cable to control a valve of a power steering system for the trailer rear wheels. The components are mounted under the floor of the trailer and a cable driven winch with a crank or power drive at the side of the trailer advances and retracts the slide to move the tongue into and out of engagement with the tractor fifth wheel. Magnets are mounted in the tongue and a torsion spring is provided in the winch mechanism to maintain tight contact between the tongue and fifth wheel. An adjustable lost motion linkage may control the power steering valve for preventing sudden swing-out of the extended end portion of the trailer. The mechanism greatly reduces the turning radius for the vehicle, prevents turnover in the event of sudden acceleration, swerving and sudden turns, and improves the tracking of the trailer.

1. Field of the Invention
This invention relates to the art of steering trailer wheels under the control of the fifth wheel of a tractor in a conventional tractor semitrailer assembly and particularly deals with trailer mounted steering mechanisms coupled to and uncoupled from the standard fifth wheel of a tractor by a trailer mounted control.
2. Description of the Prior Art
Heretofore known systems for steering tractor wheels of tractor semitrailer vehicles have required special tractor mounted controls and mechanisms that were not easily uncoupled from the trailer so that it was not practical to provide trailer wheel power steering in tractor-trailer vehicles which were frequently uncoupled.
It would therefore be an improvement in this art to provide trailer mounted rear wheel power steering controlled by the standard tractor mounted fifth wheel coupled to the standard semitrailer kingpin.
It would be a further improvement in this art to provide a power steering system for the rear wheels of semi trailers which has a trailer mounted slide advancing and retracting a tongue into and out of coupling engagement with the fifth wheel of the tractor to control the system.
It would be a still further improvement in this art to provide a flexible control cable connection between a fifth wheel actuated trailer link and a control valve of a hydraulic trailer wheel power steering mechanism and it would be an additional improvement to provide a lost motion connection between the cable and valve to program the rear wheel steering for minimizing initial sudden swing-out of the extended end portion of the trailer.
Another feature of the invention is the provision of operation lights and alarms on the trailer to show when the power steering system is in an operating mode and to warn against abnormal steering conditions as in making extremely sharp turns for docking and when driving on rough roads.


A computer-implemented method, includes, in a pageable operating system environment that does not keep all kernel pages in memory, identifying one or more stack frame pages. The method includes storing the one or more stack frame pages in a logical dump volume, wherein the logical dump volume is accessed upon a system reboot. A corresponding computer system and computer program product are also disclosed.

The present invention relates generally to the field of data recovery and more particularly to stack detail recovery.
In computing, data recovery is a process of salvaging inaccessible data from corrupted or damaged secondary storage, removable media or files, when the data they store cannot be accessed in a normal way. Data recovery scenarios often involve an operating system failure, malfunction of a storage device, accidental damage, or accidental deletion. Data recovery may also be necessary if a drive-level failure occurs, such as a compromised file system or drive partition.

International Business Machines Corporation


A phase lock circuit comprising a phase frequency comparator having a first input for a reference signal and a second input for a feedback signal, as well as outputs for furnishing an up-signal or a down-signal to a control charge pump circuit, which control charge pump circuit is connected with the outputs of the phase frequency comparator and has an output which is connected via a loop filter with a voltage-controlled oscillator provided with tuning means, the output of the oscillator being connected via a frequency divider with the second input of the phase frequency comparator, while for furnishing a tuning voltage for the tuning means a voltage charge pump circuit is provided, which is combined with the control charge pump circuit to form a combined charge pump circuit connected with the output of the phase frequency comparator.

This invention relates to a phase lock circuit comprising a phase frequency comparator having a first input for a reference signal and a second input for a feedback signal, as well as outputs for furnishing an up-signal or a down-signal to a control charge pump circuit, which control charge pump circuit is connected with the outputs of the phase frequency comparator and has an output which is connected via a loop filter with a voltage-controlled oscillator provided with tuning means, the output of the oscillator being connected via a frequency divider with the second input of the phase frequency comparator.
Such a phase lock circuit is known from practice. A similar circuit is also described in EP-A-0 945 986.
A high-quality voltage-controlled oscillator with a low phase noise is tuned with the aid of a varactor. A problem occurring in the known phase lock circuits and in particular with integrated phase lock circuits is that in many applications the supply voltage is too low to realize the tuning voltage range needed for the varactor. In applications for, for instance, pagers, cordless phones, cellular phones, etc., often a 1.5 V battery is used, while for a varactor a tuning voltage range of, for instance, 0.5-3 V may be required.
Heretofore, this problem was solved by the use of a so-called step-up converter, which can generate a supply voltage which is higher than the battery voltage. A drawback of this solution, however, is that it requires a coil of high self-induction, which cannot be formed on a chip. This results in an increase of the number of required components and the manufacturing costs of the circuit, as well as of the space occupied and the chance of parasitic effects as a result of the necessary connections between the circuit section on the chip and the off-chip coil.
Instead of a step-up converter, a charge pump circuit could be used to generate a voltage higher than the battery voltage. An example of such a charge pump is described in IEEE JSSC Vol. 33 No. 4, April 1998. A problem inherent to that solution is that such a charge pump circuit must have a lower output impedance than the, already low, output impedance of the low-pass filter, which loads the output of the phase frequency comparator.
A need therefore exists for a phase lock circuit which on the one hand furnishes a sufficiently great tuning voltage range for the voltage-controlled oscillator but on the other hand does not require any components which cannot be made on a chip in integrated form, and whereby, moreover, problems with regard to internal impedance adjustment are avoided.
The object of the invention is to provide for the need outlined. To that end, according to the invention, a phase lock circuit of the above type is characterized in that for furnishing a tuning voltage for the tuning means a voltage charge pump circuit is provided, which is combined with the control charge pump circuit to form a single charge pump circuit connected with the output of the phase frequency comparator.
In the following, the invention will be further described with reference to the appended drawing.


A radio communication apparatus in a radio packet communication system constituted by a plurality of radio stations and having a plurality of radio channels is provided. To allow radio stations belonging to different radio links to directly communicate with each other, when a packet as data is to be transmitted, a channel control section (101) inquires of a channel registration section (102) about a radio channel used for reception by a radio station corresponding to the destination address in input transmission data, and a radio channel used for packet transmission is selected. The packet is then transmitted from a transmission/reception section (103) via the selected radio channel. When a packet is to be received, the radio channel in the transmission/reception section (103) is switched to the self-station radio channel stored in a self-station channel storage section (104).

A radio LAN system is one of radio packet communication systems that have recently been standardized as systems for implementing high-speed data transmission by radio. In this radio LAN system, a plurality of radio stations form one radio link and share one channel by CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance). In the radio LAN system, if adjacent radio links use the same channel, the throughput decreases due to cochannel interference. Conventionally, in the radio LAN system, as a technique of preventing interference from radio waves forming different radio links, the technique disclosed in Ishi et al., "Proposal of Packet DCA for Radio LAN" (Proceedings of 1996 IEICE Society Conference B-652) (reference 1) is available.
The technique disclosed in this reference 1 is characterized as follows. To prevent interference between one radio station belonging to a given radio link and the other radio station belonging to another radio link in a single radio communication system, each radio station transmits/receives a control packet upon forming a new radio link. When a given radio station receives a control packet from another radio station, the radio station determines that the corresponding channel is used by the other radio station in the same radio communication system, and selects a channel for which a control packet from another radio station is not received, thereby preventing interference with other radio stations in the same radio communication system.
In the radio LAN system, in communication between radio stations belonging to different radio links, when the two radio links are connected to a single wire network via base stations and the like, the radio station on the transmitting side transmits a packet to a base station connected to the radio link to which the self-station belongs, and the base station transfers the packet to a base station connected to the radio link to which the radio station on the receiving side belongs via the wire network. The base station connected to the radio link to which the radio station on the receiving side belongs transmits the packet to the radio station on the receiving side, thereby implementing communication.
In the conventional systems, no consideration is given to communication between radio links using different channels. For this reason, in a radio packet communication system like the radio LAN system described above, communication cannot be efficiently performed.
According to the channel selection method described in reference 1 and the like, different channels are used for adjacent radio links. When two radio stations belonging to the respective radio channels are to communicate with each other, they cannot directly communicate with each other, because they use different channels, regardless of whether they are located at a distance from each other within which direction communication is allowed.
In addition, as described above, although communication can be performed via a wire network in some cases, when, for example, two radio stations belong to radio links to which no base stations are connected or base stations, if any, are connected to different wire networks, the two radio stations cannot communicate with each other. In some cases, therefore, in a radio packet communication system like the radio LAN system described above, even radio stations that are otherwise capable of direction communication cannot communicate with other by using the conventional radio communication apparatus.
In communication via a wire network, as described above, since communication between radio stations and base stations is performed via two radio links, the radio channel usage is twice that for direct communication. Therefore, when radio stations belonging to different radio links communicate with each other, the number of used channels doubles as compared with the case of direct communication.

Radio communication device for radio packet communication system


A flex circuit card with an elastomeric cable connector assembly is provided for transmitting high speed signals between two or more printed circuit boards in a high performance computer system. The flex circuit card connects a cable assembly to a printed circuit board. A conductor trace in the flex circuit card extends into an elastomeric end and terminates with a ball shaped contact which is angled to wipe against mating pads on the printed circuit card for making electrical contact. The cable assembly uses multiple wires attached to a plurality of elastomeric connectors. At least one elastomeric connector is attached to each end of the cable assembly and each elastomeric connector has a plurality of contacts which are used to mate with a plurality of pads on the surface of the printed circuit board. The elastomeric connector described in the present invention provides a high density, cable-to-board interconnection that is perpendicular to the surface of the printed circuit board.

In the computer industry, cable assemblies are used for many purposes including power distribution, low speed signal communication, and high speed signal communication. In a high performance computer system, specialized cable assemblies are used to transmit the high speed signals from processor to processor, processor to memory, and processor to I/O devices. These specialized high speed cable assemblies are mechanically and electrically connected to the printed circuit boards that support each of these key functions.
The time of flight or propagation delay for the high speed signals between these functions is critical to the overall performance of the computer system. The total propagation delay for these high speed signals is determined by the length of the circuit traces and wires used to transmit the signals from one point to another and the dielectric properties of the materials surrounding these circuit traces and wires. As computer systems increase in performance, the propagation delay for the high speed signals can be decreased by reducing the total path length for the signals to travel as well as improving the dielectric properties for the printed circuit boards and cable assemblies. An improvement in the propagation delay can be achieved by decreasing the board space required to connect to the high speed cable assemblies which in turn reduces the overall size of the board and the internal wiring along with the total space required for the system. The net result of the size reduction (or increase in packaging density) is a reduction in the signal propagation delay and an opportunity to increase the system performance.
The packaging density of a cable-to-board connector system is measured by the total number of signal and ground contacts divided by the total area used to attach and connect the cable assembly to the printed circuit board. This area is determined by the size of the cable mounting hardware and the distance or pitch between the rows and columns of contacts in the connector system. Decreasing the pitch between contacts is a common approach used to increase the packaging density of a cable connector system. As the pitch of the contacts is decreased, the size of the contacts is also decreased and smaller contacts are more prone to physical damage and quality defects.
Smaller spring contacts are more susceptible to stress relaxation of the spring material that can cause reliability problems in a connector system. Besides the material and quality limitations of using smaller contacts, there are many other limiting factors for increasing the packaging density of a cable connector including the physical size of the discrete high speed wires along with the wireability requirements of the printed circuit board. Another technique that is used for increased packaging density requires a connector system design that allows the individual cable assemblies to be stacked side by side and mounted perpendicular to the printed board surface.
Almost all cable assemblies use a separate connector mechanism to join the cable wires to a printed circuit board. The few exceptions use a flexible polyimide or mylar circuit instead of wire cables and the integral contacts are part of the wiring on the flex circuit. The separate connector mechanism can be mounted to the printed circuit board using a variety of fabrication and assembly techniques including using pins soldered into plated through holes, pins with compliant sections pressed into plated through holes, and surface mounted leads attached to pads on the surface of the printed circuit board. These techniques may require separate processing steps to attach the connectors to the printed circuit board. Separate connector components and processing steps will increase the cost of the total assembly.
These fabrication and assembly techniques are additional limiting factors for the packaging density of a cable connector system. Typical plated thru holes are drilled into the printed circuit board on a fixed rectangular 0.100.times.0.100 inch grid or an interstitial or staggered 0.050.times.0.050 inch grid. These packaging density limitations are determined by the diameter of the hole along with the width and spacing of the internal board wiring. Although surface mounted cable connectors eliminate the need for the plated thru holes in the printed circuit board, the packaging density is limited by the surface mounted lead configuration and the area required for the solder pads on the surface of the printed circuit board.
In order to provide a reliable electrical connection between the cable assembly and the printed circuit board, it is necessary to provide a sliding or wiping action between the contact surfaces in the cable connector. This wiping action allows the contacts to push aside debris and penetrate any oxides or films between the two contact surfaces. Typical two piece cable connectors use a pin (male) and spring loaded socket (female) contact geometry. As the pin is inserted into the socket, the mating contact surfaces wipe against each other. Another design consideration for a reliable electrical connection between a cable assembly and the printed circuit board is the number of independent contact interfaces for each signal or power connection. Two or more independent contact interfaces provide redundancy.
In addition, we would note that there are publications and patents of which we are aware which are listed below with a brief discussion of each of the publications and patents.

Flex circuit card elastomeric cable connector assembly

International Business Machines Corporation