A method for checking the position of alignment marks after a chemical mechanical polishing (CMP) process and automatically compensating for alignment of a wafer stepper based on the position checking is described. A wafer is provided having an alignment mark thereon for the purpose of aligning a reticle in the wafer stepper. The wafer is polished by CMP. Thereafter, alignment mark positioning is checked for deviation from a normal vectorial position of the alignment mark whereby information about the deviation is fed back to the wafer stepper and wherein the wafer stepper automatically compensates for correctable alignment error based on the deviation information.

(1) Field of the Invention
The invention relates to the fabrication of integrated circuit devices, and more particularly, to a method of automatically compensating for alignment of a wafer stepper in the fabrication of integrated circuits.
(2) Description of the Prior Art
In the fabrication of integrated circuit devices, multiple layers of conductors and insulators are deposited and patterned to construct the integrated circuit. It is critical to align each subsequent layer with the previous layer with precision. As design rules scale to smaller dimensions, the overlay budget; i.e., the relative displacement between a patterned layer and the previously defined layer, is expected to be reduced. For example, the overlay budget for 0.25 xcexcm feature size is about 90 nm; for 0.18 xcexcm feature size, about 70 nm; and for 0.13 xcexcm feature size, the overlay budget is expected to be 50 nm. The shrinking overlay budget is one of the most difficult obstacles in lithography where level-to-level alignment is concerned, especially in complex structures of metal and contacts or vias.
The overlay tolerance can shrink even further by the use of zero enclosure or borderless design rules, which are gaining popularity among circuit designers due to significant savings in the device area. This means that an accurate mechanism of stepper alignment is needed.
The alignment accuracy of the patterning machine is of particular importance to deliver the overlay budget as stipulated. Today""s patterning machines rely very much upon the equipments"" capability, including the stage accuracy for wafer and reticle. Alignment is typically accomplished by using alignment marks. A wafer stepper tool uses the alignment marks on a wafer as a reference point for adjusting a reticle over the wafer. The reticle contains the pattern to be generated within the layer. The morphology of the alignment mark is important in determining the quality of alignment. The impact of process variations on the alignment mark implies that robust and extremely tightly controlled variables are required in the process of achieving a very small overlay budget. As far as mass production is concerned, where more than one machine is used for patterning, machine matching will also be required for acceptable overlay performance.
Removal of correctable overlay errors is often achieved through adjustments to stepper parameters. The magnitudes of these process corrections are determined typically by exposing test or pilot wafers 12 and measuring the overlay using the overlay machine,14, as elaborated in FIG. 1. Compensations for stepper alignment are determined 16 and then implemented. In this way, the amount of rework can be reduced significantly as the test wafer is used as a dummy to test the alignment before proceeding with the rest of the wafers 18.
The test wafer procedure normally is conducted in the research and development mode as well as in production when a new device is introduced. This procedure is followed through until the process is stable. However, in many cases, when there is a shift in process conditions, the stepper compensations will be shifted also. As such, misalignment is detected and the test wafer procedure has to be followed through once more.
In a foundry where many types of devices are manufactured, a very thorough data base has to be kept in order to maintain the stepper compensation scheme. This procedure and scheme can be very time consuming and expensive.
U.S. Pat. No. 5,503,962 Caldwell discloses an alignment mark and CMP process in which alignment marks are formed in oxide layers using the same process as for contact and via formation. U.S. Pat. Nos. 5,627,624 and 5,329,334 Yim et al disclose test reticles containing various types and sizes of alignment marks and an alignment mark optimization method. Co-pending U.S. Pat. No. 6,184,104 to J. B. Tan et al, filed on Sep. 10, 1998, teaches the generation of alignment marks only at the oxide layers for use with CMP processes.
A principal object of the present invention is to provide an effective and very manufacturable method of increasing the accuracy of patterning machines to pattern wafers with minimum overlay.
Another object of the invention is to provide a method of automatically checking the position of alignment marks in the manufacture of integrated circuits.
A further object of the invention is to provide a method of automatically checking the position of alignment marks so that the stepper can compensate for correctable alignment error.
Yet another object is to provide a method of automatically checking the position of alignment marks after a chemical mechanical polishing (CMP) process and providing feedback if a deviation occurs.
A still further object of the invention is to provide a method of checking the position of alignment marks after a chemical mechanical polishing (CMP) process and automatically compensating for alignment of a wafer stepper based on the position checking in the fabrication of integrated circuits.
In accordance with the objects of this invention a method for checking the position of alignment marks after a chemical mechanical polishing (CMP) process and automatically compensating for alignment of a wafer stepper based on the position checking is achieved. A wafer is provided having an alignment mark thereon for the purpose of aligning a reticle in the wafer stepper. The wafer is polished by CMP. Thereafter, alignment mark positioning is checked for deviation from a normal vectorial position of the alignment mark whereby information about the deviation is fed back to the wafer stepper and wherein the wafer stepper automatically compensates for correctable alignment error based on the deviation information.

Accurate wafer patterning method for mass production

Chartered Semiconductor Manufacturing Ltd.


An improved silane/silica sol copolymer hardcoating composition for protecting optical plastic substrates from scratching is able to be manufactured at lower costs and to provide much-improved ease of use in transportation, storage, dipbath stability, and blush resistance in ordinary cleanroom atmospheres. The silane/silica sol copolymer is formed as a direct reaction product of an acidic silica sol and an monomethyl trialkoxy silane, preferably substantially monomethyltriethoxysilane, in ratios of 30:70 to 70:30, most preferably about 40:60. A tail solvent aids blush resistance and adhesion to unprimed polycarbonate. Optionally, colloidal silica sol dissolved in water-miscible solvent may be reacted in a second stage with acidic aqueous colloidal silica sol earlier silanized with monomethyl trialkoxy silane.

Clark (U.S. Pat. No. 3,986,997, issued Oct. 19, 1976; and U.S. Pat. No. 4,027,073, issued May 31, 1977) is the basis for the first commercially useful silane/silica sol copolymer hardcoats for optical plastics, and Clark is still serving as the basis for the commercially successful line of nontintable clear hardcoats for optical plastics offered by SDC Coatings of Anaheim, Calif. (SDC is a joint-venture company of Swedlow and Dow Corning; the latter is the assignee of the Clark patents). SDC's commercial dipcoating formulation Silvue 101 is believed to be a higher % solids version of a Clark formulation (suited for dip coating); all Clark coatings are acidic pH.
Next came the GE Silicone entries into this field, as embodied in Frye (U.S. Pat. No. 4,299,746, issued Nov. 10, 1981; U.S. Pat. No. 4,324,839, issued Apr. 13, 1982; U.S. Pat. No. 4,413,088, issued Nov. 1, 1983) and Vaughn (U.S. Pat. No. 4,309,319, issued Jan. 5, 1982; U.S. Pat. No. 4,324,712, issued Apr. 13, 1982; U.S. Pat. No. 4,414,349, issued Nov. 8, 1983). All the abovementioned GE Silicone patents employ an alkaline pH aqueous colloidal silica dispersion, and their resulting coatings are alkaline pH, in contrast to Clark's. GE's commercial dipcoating formulation SHC-1200 is a commercially useful reference point.
Both the Clark/SDC and the Frye/Vaughn/GE coatings form heat-cured clear coating films of excellent scratch resistance (commonly tested with steel wool pads under load with a rubbing action, to simulate cleaning-type damage) and thereby offer essentially equivalent protection to the clear plastic substrates, when applied and cured at equal thicknesses. Both are sold at very high prices (on 100% solids basis, typically $80-110 per pound or more). Because of a greater propensity for autopolymerization inherent in the alkaline aqueous dipcoating solutions of the Frye/Vaughn/GE formulas, wherein polysiloxane bond formation via condensation reaction is favored over maximizing silanol stability (particularly as storage temperature or bath temperature is increased towards room temperatures), use of the acidic aqueous silica/silica sol copolymer Clark/SDC compositions is believed to be preferred, and therefore is the chemical basis for the present invention.
For users purchasing these liquid coatings, in addition to paying high prices for the coating material, there is the special handling required of refrigerated shipping and storage, and most particularly when dipcoating tanks are of large capacity, the necessity to keep the contents chilled to minimize rate of auto polymerization. "For maximum solution stability, Silvue abrasion-resistant coatings should be refrigerated at -18 to +4 C. degrees (0 to 40 F. degrees)" from SDC Product Information Sheet #130-0, 03/93).
Another indirect cost to the user is the need to apply these water-based silane/silica sol copolymers in dip, flow or spray coating operations and coating solvent-drydown areas at very low humidity, typically a maximum of 35-40% R.H. Reference is made to GE Silicones product literature titled "SHC 1200 Optical Grade Abrasion-Resistant silicone Hard Coat & SHP Primer" #CDS 4532 (5/90), stating . . . "relative humidity controlled to 35% or less", and the previously-referenced Silvue literature, stating . . . "relative humidity of less than 40% is recommended. Variations from these conditions may result in blushing of the coating or a poor film formation". Thus, for optically and cosmetically satisfactory hardcoatings of spectacle lenses and other optical polycarbonate products, not only are the usual clean room conditions, with HEPA-filtered, laminar airflow desirable, but the mandated maximum relative humidities are below the range which can be readily attained by ordinary HVAC interior air conditioning systems during year-round use. Supplemental dehumidification is needed, calling for expensive regenerative-desiccant-bed air-handling equipment which can easily exceed $100,000 capital, just to handle the volume of clean air recirculating within a fully-enclosed automated cleaning and dipcoating line for spectacle lenses.
"Blush" can be defined as a hazy or foggy appearance within the otherwise-transparent cured film of the coating. By Applicants' personal knowledge, early versions of low-solids, high-water-content Clark coatings when applied, dried, and cured in ordinary, ambient conditions had very poor "blush" resistance; 30 grains of moisture or less was then specified as necessary in the coating drydown area's air. Subsequently, the added step of azeotropic stripping of those 20% nominal solids was found to remove both excess alcohol and part of the excess water, so that the resulting stripped 35%-solids Clark solutions had greater "blush" resistance & humidity tolerance. However, this stripping operation adds substantially to manufacturing costs.
Since the time of the Clark and Frye/Vaughn inventions, solvent-based colloidal silica sols have become commercially available. Potentially, they represent an alternative way of reducing these silane/silica sol copolymer hardcoats' sensitivity to ambient levels of humidity and increased "blush" resistance. Excess water in the liquid coating composition is defined as that which exceeds 100% stoichemetric amounts needed for hydrolysis of the alkoxy groups on the silane (3 moles of water per 1 mole of trialkoxy silane), in order to form the siloxane bond between the silane and the silica sol. Use of a solvent-based silica sol may actually require adding water to meet stoichemetric requirements for proper formation of the copolymer. However, the economic impact of replacing the aqueous silica sols with solvent-based silica sols is extremely negative, by at least a five-fold to ten-fold price factor. For example, Clark's preferred aqueous silica, Nalcoag 1034A (from Nalco Chemical; Naperville, Ill.), costs about $3 per pound on 100% solids basis, in drum quantities. By comparison, an alcohol-based sol of equivalent particle size from Nissan Chemical (New York City) costs over $75 per pound on equivalent 100% solids basis. A more recent one commercialized by Nalco costs about $17 per pound on 100% solids basis, so for lowest costs, solvent-based silicas need to be minimized or eliminated in the coating formulation.
Notwithstanding this cost factor, solvent-based silicas have been copolymerized with various organofunctional (most commonly, epoxide attached by propyl to silicon) trialkoxy silanes to make tintable dipcoatings for protecting plastic ophthalmic prescription spectacle lenses. Such coated lenses can be readily dip-dyed for desirable colorations. In these formulations, the organofunctional group attached to the silane is chosen for dye receptivity. Such coatings can be crosslinked by heat (examples in which Applicant Lewis was co-inventor are U.S. Pat. No. 5,013,608 and 5,102,695) or by ultraviolet radiation (examples in which Applicant Lewis was co-inventor are U.S. Pat. No. 5,221,560 and 5,296,295). These specialized tintable Rx lens coatings are used in lower volumes high priced lenses, so they can tolerate higher-priced silicas and silanes than the general-purpose Clark hardcoatings.
III. Objectives of the Present Invention
It is one objective of the present invention to make an acidic silane/silica sol copolymer hardcoating with the lowest possible manufacturing costs, by employing mostly or all low-cost aqueous silica sols with minimal or no solvent-based sols, and furthers by using the copolymer "reaction Products" without any subsequent step of azeotropic stripping of excess solvent and water.
It is another objective of the present invention to make said acidic silane/silica sol copolymer compositions which heat-cure to transparent films of equal or better hardness and steel-wool scratch resistance as the competitive SDC and GE coatings.
It is another objective of the present invention to make said silane/silica sol copolymer compositions with improved resistance to autopolymerization/gellation and thereby eliminate any need for refrigerated transportation, and improves stability in dipbath operating conditions and/or in inventory storage.
It is another objective of the present invention to eliminate any need to use desiccant air-drying equipment where the liquid coating is applied and devolatilized, and be able to successfully dry down these coating films without "blush" using relative-humidity-control conditions (typically 40-55 % R.H.) achievable with normal HVAC air-conditioning.
It is another objective of the present invention to make a silane/silica sol copolymer in a "self-priming" formulation which successfully adheres to polycarbonate substrates without priming or any special pre-treatment other than standard washing to remove surface impurities.
IV. Summary of Invention.
The present invention is an improved acidic silane/silica sol copolymer hardcoating composition for protecting optical plastic substrates. In a preferred embodiment, the acidic silane/silica sol copolymer is formed as a direct reaction product of an acidic aqueous silica sol and an monomethyl trialkoxy silane other than methyl trimethoxy silane, in dry weight ratios of 30:70 to 70:30, most preferably about 40:60. Preferably, no distillation off nor vacuum stripping of excess solvent and/or excess water is required, just control of temperature and time. The formulation also contains a "tail solvent". Herein, a "tail solvent" defined as "the last to leave" during devolatilization of the wet coating film. Therefore, in an aqueous coating with one or more alcohols (as byproduct of silane hydrolysis, if not added as part of the formulation), a tail solvent has lower volatility than water and the lowest evaporation rate and/or highest boiling point of all the solvents present. Preferrably, it may have a B.P.>100.degree. C.
Surprisingly, it has been found that the "monomethyl trialkoxy" silane of choice in the cited Clark & Frye/Vaughn patents, methyltrimethoxysilane (Z6070, in Dow Corning product nomenclature) contributes greatly to the problems previously listed. Both of the SDC and GE commercial hardcoatings mentioned previously also can be logically deduced to substantially employ this silane as the monomethyl trialkoxy silane constituent (as seen by their % solvent breakdown in their respective MSDS data sheets, which show very high % methanol). The only exception to this is an example found in Frye U.S. Pat. No. 4,324,839 wherein tiny amounts of monomethyl triacetoxy silane is used with predominantly methyltrimethoxysilane in order to buffer the alkaline sol pH in Examples 1-3 (thus using the tiny amounts of monomethyl triacetoxy silane as latent source of acetic acid).
Applicants have found that higher-alcohol substituents for the alkoxy group are preferred over methoxy, for reasons mentioned herein, and specifically, ethoxy is preferred over methoxy. All silane/silica sol copolymer prior art is silent on any such advantages, nor even consideration of ethoxy-based silanes in any examples. Therefore, the central element of the present invention is that Applicants employ mostly monomethyltriethoxysilane (using ethanol--or higher alcohols--as the alkoxy group) in Applicants' choice for monomethyl trialkoxy silane, with minor (<50%) or, preferably, no methyltrimethoxysilane in the formulation.
V. Detailed Description of Invention.
The silica sol constituents are dispersions of colloidal silica of average particle size <100 millimicrons in diameter, preferrably acidified and predominantly aqueous (although some blends with solvent-based sols have special benefits which may offset their higher costs), and more preferably, an average particle size of 10-30 millimicrons. In one preferred embodiment, the chosen acidified silica sol is Nalcoag 1042 (from Nalco Chemical; Naperville, Ill.), having nominal 34% SiO.sub.2 solids and about 15-millimicron average particle size. Nyacol 2034DI, made by the PQ Corporation, Valley Forger Pa., is a functional equivalent to Nalcoag 1042. See Example 1 & others. In another preferred embodiment, a solvent-based sol (Nalco 1057, 30% solids in glycol ether (2-propoxyethanol)) is chosen along with the acidified aqueous silica sol Nalcoag 1042, so the resultant coating is a copolymer of both. See Example 2 & others.
In the preferred 30:70 to 70:30 dry weight ratios (calculated as SiO.sub.2 : CH3SiO3/2) of the present invention for silica sol:monomethyl trialkoxy silane, there may be a stoichemetric excess of water already present. Mixing monomethyltriethoxysilane and silica sol constituents in the presence of acetic acid (or formic acid, or similar weak organic acid) at the desired pH range causes hydrolysis of the alkoxy groups on the silane and start of condensation-reaction copolymerization between the silica sol and silane constituents, which is optionally promoted by warming the reaction mixture to a moderately elevated temperature. Copolymerization rate (sometimes called "silanization") is a function of the specific acid, concentrations of reactants, time, temperature and pH. Generally, a pH from 4.5 to 5.5 appears to be optimum for storage stability of the liquid coating. Less acid during hydrolysis can speed up the aging or "bodying" of the coating (with more acid added later) but can increase undesirable branching of the siloxane oligomers formed. Only small amounts of strong organic mineral acids can be tolerated by the coatings (extremely low pH is to be avoided)--the buffered weak organic acids are strongly preferred, in the previously mentioned preferred pH range. These weak organic acids, such as acetic acid, are buffered by the added catalyst and can be further buffered by volatile amines, whether or not they act as cure catalysts.
Coatings of the present invention are thermosetting, crosslinking after evaporation of the solvent and water by well-known siloxane condensation reactions, so in theory any of those siloxane condensation catalysts commonly known to those skilled in the art could be used in the cure reaction. However, some work better at the lower temperatures which are tolerated by the optical plastic substrates (typically 80-130 C.), and others lack miscibility, or upset the pH range needed for coating solution stability. So, like the Clark acidic aqueous silica sol:monomethyl trialkoxy silane copolymers, cure reactions can employ buffered latent catalysts; alkali metal salts of carboxylic acids, amines or quaternary amines (amine carboxylates), and ammonium carboxylates. For example, sodium acetate acts as an in situ latent buffered catalyst, such that, after all solvent and water is removed and heating occurs, the catalyst breaks down to give the high-pH conditions known to promote siloxane condensation. Applicants also have prior experience with metal complexes such as aluminum acetylacetonate, but find the quaternary amines (amine carboxylates) are preferred as most active. Typical concentrations are 1.0% or less, measured "solids on solids" ("s/s"), based on the total dry weight in the formulation.
In addition to the methyltriethoxysilane used as a major component of the coatings of the present invention, smaller amounts of other organofunctional silanes such as methacryloxypropyl trimethoxysilane, glycidoxypropyl trimethoxysilane, chloropropyI trimethoxysilane, glycidoxypropyl methyldiethoxysilane, etc., may be added. Typically, such silanes would be added to increase adhesion to a substrate or to a subsequently applied overcoating (especially via vacuum deposition) or to further increase flexibility of the coating. In order to maximize cured coating film hardness and scratch resistance, the resulting silane mix should still be mostly monomethyl silane. Tint-uptake enhancing additives (see previously-cited U.S. Pat. Nos. 5,013,608 and 5,102,695), UV absorbing, or antifog-promoting additives are also contemplated.
When the desired degree of copolymerization (sometimes called "bodying") has been reached, cooling and/or dilution of the reaction mixture with cold solvent helps stop the copolymerization. Diacetone alcohol or (blends of) lower-aliphatic alcohols are preferred. Up to about half of the aqueous silica may be replaced with an alcohol-based silica, if desired, to further improve the coating stability.
When a solvent-based silica is used in conjunction with an aqueous silica, it is important that the aqueous silica be at least partially silanized before adding the solvent-based silica (and additional silane), or else compatibility problems and/or precipitates can result. Likewise, silanization should be far along toward completion before the latent catalyst ingredient is added, whichever type of silica is used, or else precipitates and gel formation will be excessive. It is preferred to react the solvent-based silica with silane in the presence of the (silanized) aqueous silica, so that the latter is the source of water for hydrolysis of the silane reacted with the solvent-based silica.
In a specially preferred embodiment, diacetone alcohol is selected as the "tail solvent". It is present at a level of 3-20% of the total coating formulation in its "ready-to-use" state. Diacetone alcohol was found to be preferred over ordinary aliphatic alcohols such as butanol, 1-methoxy-2-propanol, or Cellosolve (alkoxy ethanol) alcohols or their esters, or commonly available ketones, for its desirable balance of hydrogen bonding, polarity, and miscibility with the siloxane copolymer backbone. It also seems to contribute to primerless adhesion on polycarbonate substrates and to minimizing blush problems during drydown.
The coating compositions of the present invention can be applied by any conventional process, including dip, flow, spin, and spray, although for high-volume automated coating of both sides of the optical plastic substrates at minimum costs, dipping is usually preferred.
A unique and surprising feature of the coating solutions of the present invention is that they can be prepared at ambient temperature in a simple process using extremely simple hardware. In the place of expensive custom-engineered reactors, wiped-film evaporators and/or distillation systems for stripping under reflux which are used with some prior art technologies known to Applicants, we have found that a balance, transfer pump, tubing, filter, and a manual or mechanical means of solution agitation are all that are required in simplest elements. A drum heater to accelerate the initial aging or "bodying" of the coating solution is optional. Thus, the capital costs for equipment can be reduced to 1/10th or less. Chillers, as would be required for making--or using--methyltrimethoxysilane-based coatings, are also unnecessary.
"Bodying" of the coating solution, i.e., heating to elevated temperature or aging at room temperature to increase viscosity, presumably by fostering oligomerization and molecular weight of the resulting silane/sol copolymer thermoset resin, is commonly carried out to improve flow-out of the coating. The use of leveling or wetting agents improves flow-out and smoothness of the coating, especially when non-aqueous silicas are used. Such surfactants are preferably Fluorad FC-430 (a non-ionic fluorinated alkyl ester made by 3M Co., St. Paul, Minn.), used at a typical concentration of 0.01-0.1PHR (parts hundred resin), but alternatively a silicone-glycol copolymer such as DC 190 made by Dow Corning Corp., Midland, Mich.) or BYK-300 (made by Byk-Chemie USA; Wallingford, Conn.) could be used. Use of such surfactants is preferred because of the good surface smoothness obtained, even on imperfectly cleaned substrates, and because reducing the need for a bodying step can improve the subsequent shelf life of the coating.
The storage and dip-bath stability of the coating compositions of the present invention depends, as expected from the prior art cited, on a variety of factors including pH, co-solvents or tail solvents added, loss of solvent and/or water due to evaporation, and ambient temperature. Nevertheless, under normal use and storage, the coating compositions of the present invention will be essentially stable (i.e., useful) for at least several weeks at room temperature, and may be useably stable for months. Stability--or the lack thereof--is determined by significant increases in haze or plugging of filters due to the rate of gelation or onset of catastrophic gelation; or the loss of desired properties in the cured coating such as adhesiveness to the coated substrate, scratch resistance, or clarity. On polycarbonate, the coatings may require longer cure at a given temperature (typically 121-130 C.) to achieve 100% adhesion as the coating ages. This increasingly reluctant adhesion with increased aging of the liquid coating continues until even an overnight cure (nominal 16 hours) is insufficient (unless freshly-prepared coating is blended in). In contrast, with fresh coating, 100% adhesion is achieved typically in 2-6 hours at 121-130 C., as measured by the well-known cross-hatched tape adhesion test (ref:ASTM-D-3359, modified by substitution of 3M #600 tape instead of #710 for use in this test, due to its greater adhesiveness, thus providing a relatively more "severe" test).
A surprising result obtained with the coatings of the present invention is the lack of crazing, cracking and/or adhesion loss when extra-thick coatings are applied and cured. While not wishing to be bound to a particular theory, we believe that, consistent with their lower tendency to gel in solution, the molecular structure of these compositions of the present invention cure, cross-link, and/or set up more slowly, after the wet coating has been applied onto plastic substrates, in a way that retains critical flexibility as the coating dries down and cures, reducing the residual stress within the coating film. By contrast, applicants believe that methyltrimethoxysilane-based coatings "set up" too quickly due to higher inherent reactivity, probably while there is still residual solvent in the coating. Thus, although from a theoretical viewpoint the final cured coating made from methyltrimethoxysilane ("MTMS") or methyltriethoxysilane ("MTES") would be expected to be the same, we find our cured coatings are in fact demonstrably different from prior art based on methyltrimethoxysilane, regarding lack of crazing, cracking and/or adhesion loss when extra-thick coatings are applied and cured.
A further advantage of coatings of the present invention over coatings of the prior art is the potentially higher flash point and lower vapor toxicity resulting from the effective replacement of methanol. The MSDS sheet for GE's SHC-1200 shows 17% methanol, which has 200 ppm TLV, and 19 C (67 F.) flash point. In contrast, Applicants Example 1 has 0% methanol, with ethanol instead having 1000 ppm TLV, and 25 C. (78 F.) flash point. A flash point of 23 C. (73 F.) or higher is required for expedited shipment by air freight.
In coatings of the present invention with "excess water", improved adhesion (or rate of development of adhesion at a given cure temperature) can be obtained by dipping twice to achieve the desired coating thickness (instead of dipping once at a faster withdrawal rate), by "pre-curing" to a "B stage" tack-free state (e.g., at 60.degree. C. for 10 minutes--sometimes used for pre-inspection for coating flaws before final cure), and/or by ramping up to final cure temperature or stepping up, e.g., 93 C for 10 minutes, 110 C. for 10 minutes, 121 C. for 5 minutes, then cure at 130 C.; instead of placing lenses in a preheated 130 C. oven directly. We believe that each of these 3 optional steps helps to selectively volatilize the water in (and released during initial cure of) the coating, while the tail solvent remains (sufficiently) to reduce initial dry-down or curing stresses and to promote bonding to the substrate.
Preparation of specific formulations of the present invention are now given in the examples below:

Low cost, blush-resistant silane/silica sol copolymer hardcoat for optical clear plastics


The present invention provides for a method or methods of targeted genetic recombination or mutagenesis in a host cell or organism, and compositions useful for carrying out the method. The targeting method of the present invention exploits endogenous cellular mechanisms for homologous recombination and repair of double stranded breaks in genetic material. The present invention provides numerous improvements over previous mutagenesis methods, such advantages include that the method is generally applicable to a wide variety of organisms, the method is targeted so that the disadvantages associated with random insertion of DNA into host genetic material are eliminated, and certain embodiments require relatively little manipulation of the host genetic material for success. Additionally, it provides a method that produces organisms with specific gene modifications in a short period of time.

Gene targeting—the process of gene replacement by homologous recombination or mutation—is a very useful, but typically inefficient technique for introducing desired changes in the genetic material of a host cell. Only when powerful selection for the targeted product can be applied is recovery of the desired alteration possible. A general method for improving the efficiency of gene targeting would be valuable in many circumstances, as would extension of this tool to a broader range of organisms.
It has been demonstrated in model experiments that introduction of a double-strand break (DSB) in host DNA greatly enhances the frequency of localized recombination. However, those tests required insertion of a recognition site for a specific endonuclease before cleavage could be induced. Similarly, in Drosophila the DSBs produced by P-element excision are recombinagenic, but require the P-element to preexist at the target site.
Although previously demonstrated methods of genetic transformation had been highly successful, transformation without targeted recombination has also been accompanied by problems associated with random insertion of the introduced DNA. Random integration can lead to the inactivation of essential genes, or to the aberrant expression of the introduced gene. Additional problems associated with genetic transformation include mosaicism due to multiple integrations, and technical difficulties associated with generation of replication defective recombinant viral vectors.
Targeted genetic recombination or mutation of a cell or organism is now possible because complete genomic sequences have been determined for a number of organisms, and more sequences are being obtained each day. Not only would the ability to direct a mutation to a specific genetic locus greatly aid those studying the function of particular genes, targeted genetic recombination would also have therapeutic and agricultural applications. Methods of targeted genetic recombination are needed that are more general, efficient, and/or reproducible than currently available techniques.

This patent is subject to a terminal disclaimer.

Targeted chromosomal mutagenesis using zinc finger nucleases


The main rotor of a helicopter is driven by an epicyclic gearbox comprising a rotor sun gear coaxial and co-rotational with the rotor, a stationary sun gear coaxial with the rotor sun gear, at least one planet having an axis parallel to and rotating about the sun gear axis, and making contact with both sun gears. The planet comprises first and second planetary coaxial gears mechanically constrained to rotate together. The first planetary gear is in meshing engagement with the stationary sun gear and the second planetary gear is in meshing engagement with the rotor sun gear. The first planetary gear is also in meshing engagement with the internal teeth of a first ring gear and the second planetary gear is also in meshing engagement with the internal teeth of a second ring gear. The first and second ring gears are separately driven, and torque is combined by the planets.

This invention relates generally to a epicyclic gear arrangement for transmitting and combining torque from a plurality of sources or parallel power paths, and more particularly to a helicopter gearbox having redundant gearing.
In helicopters, power is commonly supplied by a pair of turbine engines running at 20,000 rpm or more. This power must be combined and delivered to a rotor at a speed that is reduced from the turbine speed by a factor of 50 to 150. It is desirable to split the drive train so that power is delivered within the transmission elements by two or more routes. In this way gear tooth loading is reduced, and operating safety is improved by the redundant gearing should one gear set fail during flight. Split torque gearing is known; for example, such arrangement of gears is disclosed in U.S. Pats. Nos. 5,135,442 and 5,802,918, the teachings of which are entirely incorporated herein by reference.
In the present invention, the main rotor of a helicopter is driven by an epicyclic gearbox comprising a rotor sun gear coaxial and co-rotational with the rotor, a stationary sun gear coaxial with the rotor sun gear, at least one planet having an axis parallel to and rotating about the sun gear axis, and making contact with both sun gears. The planet comprises first and second planetary coaxial gears mechanically constrained to rotate together. The first planetary gear is in meshing engagement with the stationary sun gear and the second planetary gear is in meshing engagement with the rotor sun gear. The first planetary gear is also in meshing engagement with the internal teeth of a first ring gear and the second planetary gear is also in meshing engagement with the internal teeth of a second ring gear. The first and second ring gears each have a second set of gear teeth (bull teeth) on the top, bottom or sides thereof for meshing engagement with one or more drive pinions. These bull teeth and may be external, face, or even internal. In a first embodiment, a first drive pinion drives the first ring gear and a second drive pinion drives the second ring gear in the same direction. Power derives from individual shaft connection with a pair of engines. In a second embodiment of the invention, input shaft power is further split prior to delivery to the epicyclic gearbox by a plurality of drive pinions.
The first planetary gear has a first planetary pitch diameter, and the second planetary gear has a second planetary pitch diameter, wherein the first planetary pitch diameter is different from the second planetary pitch diameter.
The present invention provides a plurality of power paths into the epicyclic gearing thereby reducing tooth loading and increasing the operational safety factor of the aircraft by adding drive redundancy.
It is therefore an object of the present invention to provide a epicyclic gearbox having parallel power input paths combined by at least one planetary gear.
It is another object of at least one embodiment of the invention to provide a gearbox having a plurality of power paths for driving the main rotor of a helicopter.


In a transmission during a shifting process while torque is transferred from a power-outputting clutch, which is initially in the adhered state, to a power-receiving clutch, which is initially open, the power-receiving clutch increases torque capacity in a slip region, and the power-outputting clutch decreases torque capacity during an initial phase of the transfer of torque while its torque capacity is greater than necessary to maintain its adhered state. In the final state of the transfer of torque, the power-receiving clutch transmits the entire drive torque.

The invention relates to a method for shifting two clutches of a transmission according to the preamble of claim 1. Such methods are used primarily for controlling clutches in automatic or automated transmissions in motor vehicles.
DE 101543722 discloses a method according to the preamble of claim 1 in which, with a chronological overlap, a power-receiving clutch which is assigned to the new gear speed is closed and a power-outputting clutch which is assigned to the old gear speed is opened, the clutches being embodied as slip-controlled wet clutches. The closing of the power-receiving clutch takes place approximately up to a working pressure which corresponds to the clutch capacity of the power-outputting clutch, the closing of the power-receiving clutch being preceded by filling with a filling pressure which is terminated with an end of filling. The method provides that, in a manually triggered power shift (traction upshift and overrun downshift), the filling of the power-receiving clutch with an increased filling pressure which corresponds to the order of magnitude of the clutch capacity of the power-outputting clutch unit is carried out in such a way that the end of filling is determined and that when the end of filling is detected the power-outputting clutch is opened with a chronological overlap and the clutch capacity of the power-receiving clutch is adapted.
A disadvantage of this method is that the power-outputting clutch cannot be opened until the end of filling has been detected, which leads to a high control complexity and control difficulties and to an unnecessarily long shifting period.
U.S. Pat. No. 4,527,678 discloses a shifting method according to the preamble of claim 1 for a double clutch transmission. The double clutch transmission has two transmission input shafts which can each be connected to the drive, an internal combustion engine, by means of a clutch, and which can be connected to a transmission output shaft by means of various gear speeds. The function of a mechanical freewheeling mechanism is provided by means of a suitable method of slip-based transfer of torque with subsequent engine speed adaptation phase in that the power-outputting clutch is moved into the slip region at the start of the transfer of torque, which can be detected from an increased engine speed or drive rotational speed.
In U.S. Pat. No. 6,385,520 a method is described for controlling the transfer of torque in automatic transmissions as a function of the rotational speed or transmission ratio, said method constituting a development of U.S. Pat. No. 4,527,678. Here, it is important, in particular at the end of the transfer of torque, i.e. when the power-receiving clutch has reached the level of the current engine torque, to set the torque of the power-outputting clutch to zero. If this is not suitable, the torque, which is available at the output, is reduced owing to a stressed state. If the transmission is installed in a motor vehicle, when there is slight stress the output torque or the acceleration of the vehicle will drop below the level of the connecting gear speed, which is evaluated by the driver as detrimental to comfort, whereas severe stressing of the transmission can cause the drive wheels to lock, which is not acceptable for reasons of safety.
DE19522834 discloses a method for overlapping shifting in automatic transmissions in which the overlapping time of the clutches is dependent on the load which is applied to the transmission. Furthermore, an optimum harmonic differential rotational speed is restored. The overlapping time of the clutches is adapted here to the requirements of the thermal capacity of the clutches involved and the actuating speeds of the electrohydraulic actuating system, and optimized. However, said method also exhibits two significant weak points of the previously proposed torque transfer methods. These are the necessary increase in rotational speed by permitting the slipping of the power-outputting clutch and the limitations when selecting the period of time for the transfer of torque.
Since drivers expect high levels of comfort especially from automatic transmissions and accordingly react in a sensitive way to an increase in the rotational speed of the engine, the magnitude of the slip which is set at the power-outputting clutch due to the method, as well as its rising gradient and falling gradient, must be kept very small and held at low dynamic values.
A further shifting method for a double clutch transmission having a plurality of gear speeds which are shifted by means of synchronizing gears is known from DE 196 31 983. Here, the torque zero crossover of the power-outputting clutch is detected by disengaging a modified synchronizing sleeve which is under tensile stress. Here, the sensitivity of the synchronizing gear which is configured with an undercut is not sufficient to bring about jolt-free decoupling of the power-outputting clutch, for example when there are relatively small torques such as usually occur in town traffic. Since a form-fit connection is broken with slight application of torque, the remaining residual torque of the outputting clutch is suddenly decreased and it will thus generate a jolt which the driver can feel or produce audible acoustic interactions.
Basically the previously published methods for transferring torque have attempted to ensure that the sum of the individual torques which are transmitted by the clutches corresponds, as a total, to the current engine torque. This is necessary since both clutches are to be held in the overrun state and this is also used as a basis for the rotational speed controller or transmission ratio controller. As a result, the processing of the shifting operation is wide in scope and requires a lot of time. The power-outputting clutch must firstly be moved into the overrun state, which takes some time, approximately 150 to 300 ms, which the driver feels is a disadvantage since the transmission does not shift spontaneously. This applies in particular to automatic transmissions and double clutch transmissions which drive with strategies in which a gear speed is already preselected. The processing of the shifting operation could start directly here but its start is delayed by the setting of the slip in advance.
Furthermore, it is disadvantageous that the sum of the individual torques which are transmitted by the clutches corresponds, as a total, to the current engine torque since when there are small faults in the torque which is set the engine speed which is transmitted through these torques reacts immediately by either rising below the current engine torque when the total torque is reduced, or dropping above the level of the engine torque when the total torque increases. Therefore, during the phase of the transfer of torque, the profile of the engine speed will very easily be subject to severe fluctuations since both clutches are operated in the slipping state and therefore react directly to very small changes.
Since, according to the invention, the rotational speed controller can detect the start of the transfer of torque only from a slight dip in the rotational speed—which also brings about a dip in the output torque—it is, on the one hand, complicated to make this transition stable during the matching process, and on the other hand it is easily possible for the driver to notice this dip in the torque and thus in the acceleration of the vehicle. Furthermore, this controller must react, or be matched, to different frictional relationships of the clutch and a different reaction behavior of the hydraulic system, a large number of different parameters such as temperature or power (high or low torque, gear speed, traction or overrun operating state) having to be taken into account. The matching which has to be carried out is therefore very time consuming and very large resources are required for this in the transmission controller. This problem is aggravated if the rotational speed differences which are to be set are very small. The control of the rotational speed must therefore be of a very high quality and be very rapid, which can be achieved only at great cost in the entire scope of the transmission.
Furthermore, the rotational speed controllers react to the different natural frequencies of the drive train, for which reason when matching the controllers for the rotational speed, slip or transmission ratio it is necessary to ensure that the corresponding frequencies are correspondingly damped. This in turn however restricts the control dynamics, for which reason a transfer of torque cannot be made as short as desired. The rotational speed controllers which are used for control have, by way of the principle, sensitivity to natural frequencies in the drive train. If, for example, due to a process in the drive train, there are already vibrations present, these are either not damped by rotational speed controllers or, in an unfavorable case, even amplified. For this reason, optimum matching can be carried out only with difficulty and it leads to less dynamic matching processes which in turn prolong the shifting time.
The same applies to suitable transitions when transferring the torque. In order to increase the comfort for the driver it is clear that jumps and bends in the shifting process are to be avoided since they lead to jolts and jerks. It is disadvantageous here to limit the dynamics of the underlying control process since suitable predefined torque profiles can only be followed inadequately and if the controllers cannot follow or if it is attempted to compensate for these faults by a corresponding increase in the amplification factors, the system tends to oscillate.
In contrast, when there are relatively long transfers of torque, the probability of the rotational speed controller hitting a corresponding frequency of the drive train, and then becoming unstable, that is to say oscillating, increases. This is due to the longer time period of the process which occurs, as a result of which the number of faults which occur rises, with the result that the probability of the occurrence of an instability also increases.
The fundamental control dynamics of the rotational speed controller limits the speed of the torque transition from the power-outputting clutch to the power-receiving clutch since the conditioning of the rotational speed signals and rotational speed gradients takes place only after a delay and also includes dead time components which cannot be appropriately resolved for all the known control concepts. A very rapid transfer of torque is thus not possible. This leads to a lengthening of the shifting time, which is undesired by the driver.
Furthermore, when matching the rotational speed controllers it is necessary to take into account the viscosity of the transmission oil which decreases with the temperature since this changes the dynamics of the controlled system. Different natural frequencies of the drive train are also present in different gear speeds, for example low natural frequencies around 2 Hz are present at low gear speeds, and relatively high natural frequencies around 8 to 10 Hz are present at high gear speeds. This makes it necessary to match the temperature, gear speed and type of shifting process with a correspondingly high degree of expenditure on sensor systems, control methods and control capacity.
An end of the torque transfer process can generally only be recognized from a dip in the rotational speed. This has the disadvantage of a further change in the acceleration, for example a jolt, which is possibly felt to be unpleasant by the driver. Furthermore, the precise time of the end of the transfer of torque can be detected only with difficulty since, during the matching process, it is necessary to find a suitable compromise between the detection of the termination and the occurrence of slight oscillations in the drive train which have nothing to do with the conclusion of the transfer of torque. The precise chronological sequence of the shifting process is, under certain circumstances, prolonged by this.
Since the methods are generally reliant on the detection of the end through the drop in the rotational speed, the torque profile is also defined by the rotational speed profile which is provided. Since this influences the gear transition into the subsequent rotational speed adaptation phase, in which the engine speed is adapted to the new transmission ratio, neither the rest of the profile of the rotational speed nor the subsequent torque profile can be freely selected.
The object of the invention is therefore to improve a method for shifting two clutches in such a way that the known disadvantages from the prior art are at least partially overcome, and in particular that the shifting comfort is increased and the shifting period and control complexity are reduced.
This object is achieved by means of the features of claim 1.
At least the first phase of the transfer of torque can be carried out by simple control of the two clutches by virtue of the fact that, during the transfer of torque, the power-receiving clutch increases torque capacity in the slip region and the power-outputting clutch decreases torque capacity, the power-outputting clutch having, in the initial phase of the transfer of torque, a higher torque capacity than is necessary to maintain its adhered state. As a result, complex control of the clutch capacities and complex sensing of rotational speed fluctuations etc., such as are known from the prior art processes, are unnecessary. The power-outputting clutch remains connected fixed in terms of rotation to the drive shaft of the engine, although the torque capacity of said clutch is reduced, while the power-receiving clutch increases its torque capacity under slip.
Since the power-outputting clutch is intentionally held in an above-capacity state over a wide range of the transfer of torque, only the slipping, power-receiving clutch determines the torque transition and thus the profile of the torque which is available at the output, and thus the acceleration of the vehicle. It is advantageous here that the engine speed cannot continue or drop and that the profile of the output torque or the acceleration profile of the vehicle is determined exclusively by the torque receiving clutch. Interference between the control circuits of the two clutches, which would affect the stability of the engine speed or the profile of the vehicle acceleration, does not occur here.
Preparation time is also not required for a shifting process and undesired rises in rotational speed do not occur during the preparation of the transfer of torque.
The shifting process can be started as soon as the power-receiving clutch is capable of receiving torque. Since the driver will then immediately sense a change in the acceleration of the vehicle, the shifting operations which are carried out with this method are felt to be spontaneous and quickly responsive. Furthermore, the method is insensitive to fluctuations in torque and/or imprecisions of the torque specifications of the engine since they are not used directly to control the transfer of torque, rather the transfer of torque is determined only by the rise in the torque component of the power-receiving clutch. Fluctuations in the clutch properties and, under certain circumstances, in the lubricant as a result of temperature, aging and wear are also thus compensated without difficulty.
The transition of the power-outputting clutch into the slip region can take place at any time during the transfer of torque as long as the transmission or the output shaft is not blocked. That is to say it is irrelevant how much of the drive torque is taken up by the power-receiving clutch, whether 10%, 50% or even 90%; the transition depends alone on the further demands the control system makes of the slip control of the two clutches.
In the first region of the transfer of torque, where the power-outputting clutch is still slipping, for this purpose this clutch is specifically operated with excess capacity. This means that the power-outputting clutch is kept in a securely closed state. For the first phase of the transfer of torque, this thus results in a sum of the transmittable torques of the clutches which is greater than the current torque which is fed into the system by the engine or drive. The sum of the torques which can be transmitted by the clutches is not reduced to, or slightly below, the level of the engine torque, thus causing the power-outputting clutch to slip, until in the last phase of the transition into the slip region of the power-outputting clutch.
The method can preferably be used for traction upshift and overrun downshift processes, but also as desired, i.e. independently of whether the drive is driving or braking and whether the rotational speed of the power-receiving clutch is higher or lower than that of the power-outputting clutch.
In this consideration it is insignificant whether the clutches are running with identical or different drive rotational speeds. Identical drive rotational speeds occur, for example, in a double clutch transmission which has a drive shaft and two concentric input shafts and two clutches which are arranged thereon. Different input rotational speeds occur, for example, when there are two clutches and/or braking belts of different wheel sets of an automatic transmission. In the latter case, when the torques are calculated, there is still the effect of the different drive rotational speeds to be taken into account, but said effect gives rise, if standardized to a uniform rotational speed, to the same profile of the rotational speed capacities as described in the previous paragraph.
The power-outputting clutch advantageously moves into the slip region if the slipping, power-receiving clutch transmits a considerable part of the drive torque. The slipping of the power-outputting clutch is preferably restricted to a very late time in the sequence of the transfer of torque, at which time the power-outputting clutch is already only transmitting a very small amount of torque, i.e. more than 50% of the drive torque. Errors which occur in the torque control can thus only have a very small effect since the power-receiving clutch has already taken over the main part of the torque. The probability of rotational speed harmonics and faults in the acceleration of the vehicle occurring is thus restricted to a very great degree. This increases the comfort and permits a simpler, and thus more reliable, embodiment of the control technology and of the control elements such as the transmission controller, electric and hydraulic actuator elements etc.
Imprecisions in the calculation of the engine torque also have no significant effect on the method. In the previously known methods, an incorrect engine torque easily gives rise to faulty actuations of the rotational speed controller, as a result of which rotational speed harmonics are possible due to spontaneous veering away of the clutch with correspondingly high rotational speed gradients at full engine torque at a given moment, but such harmonies are felt to be disruptive by a driver. These rotational speed harmonics cannot occur since the power-outputting clutch is in the adhering friction region, and the rotational speed of the input shaft of the power-outputting clutch thus continues to correspond to the engine speed for the majority of the time of the transfer of torque.
In a further embodiment of the invention, the period of the transfer of torque can be set as desired. Since the method is essentially controlled, it is not necessary to take account of complex control circuits but rather the control proceeds correspondingly slowly or quickly without the transfer of torque being in itself uncontrollable. As a result, allowance can be made for the shifting behavior or the comfort requirements of the driver and/or different operating states. If the driver intentionally wishes to drive in a sporty fashion or comfortable fashion, a correspondingly shorter or longer period is selected. When the torque capacity is low and/or at low drive rotational speeds, this time period can also be shorter, while, when the drive power levels are large and/or the drive rotational speeds are high the time period can be increased in order to ensure satisfactory control. This also applies to shifting processes at low or high gear speeds of the transmission, and the time period can also be adapted to different values here in accordance with the requirements.
Furthermore, the times at which the reduction in the torque capacity of the power-outputting clutch and the increase in the torque capacity of the power-receiving clutch start can be set as desired, it being possible for the times to be simultaneous or offset. Offset means that either the power-outputting clutch firstly reduces the torque capacity, but not below the adhesion limit, and the power-receiving clutch then increases the torque capacity. Or conversely, the power-receiving clutch first starts to increase the torque capacity and only then does the power-outputting clutch begin to reduce it. As a result, the shifting speed and/or shifting comfort can be increased, for example if two clutches of a different type are used, or if an open or closed clutch requires a run up time.
This measure also prevents problems occurring if, when initiating shifting processes in transmissions, it is necessary, for example, to adapt the pressure level of the supplying hydraulic system in order to be able to carry out the shifting process. The actuator elements can change their specific properties in the course of operation, but this does not have any influence on the shifting process for the time being. The functions which are used for control can even compensate deviations of the manipulated variables in the course of the shifting process, and even the displacements of the working points, which has to take place before the shifting process according to the prior art.
This applies in a similar way also to double clutch transmissions with dry friction plates or partial traction force supporting transmission concepts. Here, according to the prior art, actuator elements must often also be used for example by means of quick-acting lockup clutches at corresponding working points. Since these actuating processes cannot be carried out without jolting, the incipient slip control phase of the power-outputting clutch is disrupted. All this does not occur in the method according to the invention since these actuating processes are part of the transfer of torque itself. The entire shifting process can thus be carried out more quickly and reliably.
A further advantageous embodiment provides that the reduction of the torque capacity of the power-outputting clutch does not take place continuously during the transfer of torque. In particular, in the case of the power-outputting clutch, reductions can be carried out more quickly towards the end of the transfer of torque than at the start of the transfer of torque. This can be utilized so that, at the start of the transfer of torque, the power-outputting clutch is slowly adjusted to the point from which the torque capacity starts to drop slowly and then the torque capacity drops very severely to a value which is just above the current adhesion friction limit of the power-outputting clutch. As a result, the power-outputting clutch can be adjusted using simple control methods.
At the end of the transfer of torque by means of the power-outputting clutch, a slip controller which brings about automatic termination of the transfer of torque is advantageously produced. Alternatively, at the end of the transfer of torque by means of the power-receiving clutch it is possible to produce a slip controller which brings about an automatic termination of the transfer of torque. For a very short period, both clutches are then offset in the slip state, as a result of which the torque which has been transmitted by the clutches is unambiguously determined by virtue of the fact that the transmitted torques of the two slipping clutches are determined by means of the slip controller and the drive torque is thus adapted from the total torque of the clutches. In this region, the rotational speeds of the engine and transmission are advantageously kept approximately constant so that it is not necessary to take into account any power components from the acceleration or deceleration of rotational masses which are subject to inertia. A slight change in rotational speed can be accepted here since it is only of short duration and/or leads to the new input rotational speed.
The end of the transfer of torque is preferably determined by monitoring a clutch pressure which is set or a clutch position which is set. This data can be determined very easily and robustly so that sensors require little effort to configure and the acquired signals can be further processed using simple control methods.
The drive rotational speed is advantageously adapted to the rotational speed of the power-receiving clutch after the transition of the power-outputting clutch into the slip region. During each shifting process, the rotational speed of the drive shaft must also be adjusted from the rotational speed of the power-outputting clutch to the rotational speed of the power-receiving clutch, it being possible for this to be either an increase in rotational speed or a reduction in rotational speed, in the traction mode or in the overrun mode. The adaptation of the rotational speed is normally not carried out until the torque has been completely transferred to the power-receiving clutch. Owing to the late time of the slipping of the power-outputting clutch it is possible with this method for the drive rotational speed still to be changed directly to the rotational speed of the power-receiving clutch during the transfer of torque. As soon as the power-outputting clutch slips, the torque capacity of the power-receiving clutch is increased to the extent that the torque capacity of the power-outputting clutch and that of the power-receiving clutch are higher than the current drive torque. The shifting period is thus advantageously reduced overall, in particular owing to the shortened rotational speed adaptation phase.
As is customary, the drive rotational speed can be adapted to the rotational speed of the power-receiving clutch after the power-outputting clutch has been completely opened. The torque capacity of the power-receiving clutch is then set in such a way that the adaptation of the rotational speed takes place continuously.
The period of adaptation of the drive rotational speed can advantageously be set as desired. When the drive rotational speed is adapted, an oscillating or braking effect occurs at the output shaft, depending on the rotational speed ratio and whether the traction mode or overrun mode is present. However, this effect should be avoided if possible or at least kept as small as possible since the driver senses this as undesired jolting, i.e. a brief acceleration or braking. Since the duration of the adaptation becomes variable, the shifting behavior and the comfort requirements of the driver and/or different operating states can be allowed for. If the driver intentionally wishes to drive in a sporty or comfortable fashion, a correspondingly shorter or longer time period is selected. When the torque capacity is low and/or at low drive rotational speeds, this time period can also be shorter, while at high drive power levels and/or high drive rotational speeds the time period can be increased in order to ensure as far as possible jolt-free adaptation of the rotational speed. This also applies to shifting operations at low or high gear speeds of the transmission, and here too the time period can be adapted to different values in accordance with the requirements.
The drive torque is preferably briefly increased and/or reduced during the shifting process. As a result, the effect of the rise or fall in torque can be compensated owing to the adaptation of the torque with subsequent rise or fall in the torque, which is due to the adaptation of the rotational speed and leads to the jolting described above, by intentionally briefly increasing and/or reducing the drive power. As a result, the output torque profile at the output shaft becomes less unsteady, and at best continuous, during the entire shifting process. The additional drive torque or braking torque can be generated here by the engine itself and/or made available by assemblies which are also present and are connected to the drive shaft, such as for example electric motors, hydraulic pumps, starter-generators etc.
A gear speed which is connected to the power-outputting clutch is advantageously disengaged directly after the end of the transfer of torque so that, in the case of a fault during the transfer of torque, an undesired stressed state is avoided.
The inventive method may be used in a double clutch transmission with two transmission input shafts and one output shaft, each input shaft being assigned a clutch in the case of an automatic transmission and in the case of all other known transmissions in which a torque is to be transferred from one clutch to another clutch, as has already been partially described in DE 10153722.
The term "clutches" means all mechanical elements which can bring about a releasable frictional and/or non-positively locking connection between shafts are meant. These may be dry frictional clutches, wet frictional clutches such as multidisk clutches and/or brake belts of an automatic transmission. With this method, it is also particularly advantageous that two clutches of a different design can be controlled, for example a brake belt and a wet multidisk clutch of an automatic transmission. The build up of the torque capacity, i.e. the activation of the clutch, can be carried out here by means of hydraulic, mechanical, electrical or pneumatic actuator elements, or by means of other suitable actuator elements. Due to the design, it is also self-evident that each clutch can either be a power-outputting clutch or a power-receiving clutch, depending on which gear speed is being transmitted at a particular time and the gear speed into which shifting is to be performed.
Various objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings.

Control method for shifting a powershift transmission


The invention relates to a multilayer plastic pipe (1), preferably for use in heating systems. The multilayer pipe comprises an inner core (2) and a barrier layer (6) surrounding the core and preventing oxygen diffusion through the multilayered pipe. The core (2) is made of a material having viscoelastic properties, preferably cross-linked polyethylene, and the barrier layer (6) is surrounded by an outer layer (8) of a material having adhesive properties. The invention also relates to the use of a multilayer pipe for providing pipe couplings.

The present invention relates to a multilayer plastic pipe, preferably intended for water piping in central heating systems. The multilayer pipe comprises an inner core and an outer barrier layer which is surrounding the inner core and is made of a material which prevents oxygen diffusion through the multilayered pipe. The invention also relates to the use of a multilayer plastic pipe.
Plastic pipes have previously been used, for example, for water distribution. Such pipes are preferably made of polyolefins, such as cross-linked polyethylene (PEX), polypropene or polybutylene. Plastic pipes which are to be used for water distribution in heating systems, such as for example, those for floor heating or for radiator systems, must be provided with an oxygen barrier layer so as to prevent oxygen diffusion into the water and thus causing corrosion on the metal components which are part of the heating systems.
In order to prevent oxygen diffusion through the pipe, it is a commonly used method to coat the outer surface of the pipe with a barrier layer of a material which prevents diffusion, such as for example, ethylene vinyl alcohol (EVOH). An intermediate layer of an adhesive material, an adhesive layer, may be provided between the inner core and the barrier layer, said intermediate layer being effective to create or to increase the adhesion between the inner core, such as a PEX-pipe, and the outer barrier layer.
An advantageous technique for connecting plastic pipes with different types of couplings and fittings in water distribution systems is previously known, i.a. from SE-C2-500665 and SE-C2-501555. The described technique is used for pipe couplings for plastic pipes having viscoelastic properties, or memory properties, i.e. plastic pipes having a tendency to automatically shrink back to their original shape after, for instance, an expansion. A pipe material having this property is, for example, cross-linked polyolefin, especially cross-linked polyethylene (PEX). The mechanical properties of the material allows a deformation of the pipe at temperatures as low as at least xe2x88x9220xc2x0 C. In order to mount the plastic pipe on the pipe coupling, the end of the plastic pipe is expanded and a nipple is inserted into the expanded end of the pipe and is kept in the pipe until the pipe end shrinks back over the nipple. This known technique is advantageous as it is quick and easy to preform and provides a safe and water-tight coupling.
In accordance with the technique described above, the pipes are substantailly expanded in a radial direction. This has proven to function very satisfactorily when PEX-pipes are being used. However, this advantageous coupling technique is disadvantageous when it is used on pipes having an oxygen barrier layer as described above. In the process of an substatial, radial expansion of the pipe, cracks may appear in the outer barrier layer, said cracks occurring especially at low temperatures, such as temperatures below about 15xc2x0 C. The cracks which occur in the barrier layer have shown a tendency to propagate into the pipe wall during the expansion process of the pipe, thus causing pipe fractures leading to leaking pipe couplings.
Attempts have been made to solve the above problem by modifying know barrier materials. The object has been to try to find modified barrier materials which may withstand an expansion without cracking. So far, a modified barrier material which provides an acceptable solution to the expansion cracking problem has not been found.
The object of the present invention is thus to provide a solution to the above problem, in that the advantageous coupling technique may be used on the plastic pipes which are specially made for use in heating systems.
This object has been achieved according to the invention by means of a multilayer plastic pipe having the characterizing features as defined in the claims.
The inventive solution provides the advantage that the advantageous coupling technique, which is quick, efficient and inexpensive, may be applied to a hole range of different pipes. This means that plumbers working with installations at the site do not require different couplings for different types of pipes, but may instead use just one type of couplings.
According to the invention the problem has been solved by coating the plastic multilayer pipe with an additional layer of an adhesive material, an adhesive layer. The adhesive layer may consist of the same or similar material as the intermediate adhesive layer which is applied between the inner core and the barrier layer so as to increase the adhesion between the layers. The inventive multilayer pipe which is coated with an outer adhesive layer can be radially expanded without crack formation occurring in the barrier layer or in other parts of the pipe wall.
In a plastic pipe having an outer layer, such as a barrier layer, stress concentrations naturally occur especially in the outer layer, when the pipe is expanded. Therefore, stress cracks appear mainly in the outer layer and these cracks may propagate, as described above, into the pipe wall during the expansion of the pipe and cause pipe fractures. According to the invention the outer barrier layer is coated with an additional layer which in itself is sufficiently pliable to absorb stress concentrations and which also adheres to the brittle barrier layer such that this layer is xe2x80x9csupportedxe2x80x9d. This prevents or reduces the tendency to form cracks in the pipe wall.
The mechanical properties of crystalline materials, and also of semi-crystalline materials such as for example EVOH, depend among other things upon the crystalline structure of the material. The crystalline structure is dependent upon the rate of crystallisation, i.e. the cooling rate. On extrusion of a plastic pipe with a barrier layer, the outer layer is exposed directly to ambient air outside the extruder die. An extruded pipe with no additional outer layer is subjected to rapid cooling and crystallisation. On extrusion of a pipe having an outer adhesive layer according to the invention, the cooling of the barrier layer is slower and the thus obtained crystalline structure of said barrier layer has improved mechanical properties.
The barrier layer of a pipe with no additional outer layer is directly exposed to air when it leaves the extruder die at a temperature of above 200xc2x0 C. An oxidative degradation of the barrier layer takes place at this stage which deteriorates the mechanical properties of-the material. In a pipe coated with an additional layer outside the barrier layer according to the invention, the outer layer protects the barrier layer against said degradation during the cooling period and therefor the mechanical properties of the barrier layer is improved.

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A suspension system for supporting fore- and aft extending frame members of a vehicle chassis on a hollow axle, the system on one side of the vehicle being duplicated on the opposite side. Included in the suspension on each side are: (1) a frame bracket for pivotally supporting the fore or leading end of an asymmetric leaf spring; (2) a spring end support mounted on the frame side member for supporting the aft or trailing end of the leaf spring, and (3) a suitable assembly for attaching the leaf spring at a location intermediate its opposite ends to the axle so that the spring is divided into two cantilever limbs extending in opposite directions from the center line of the axle. The spring is formed so that one of the cantilever limbs has a stiffness substantially greater than the stiffness of the other limb. In all forms, at least one leaf of the asymmetric spring extends the full length of the spring. In one particular form the spring has a shorter leaf with an end portion extending over the axle with an air spring mounted either directly over the axle or on one side of the axle. Instead of having two leafs, the asymmetric spring may be formed as a tapered convolute single-leaf spring.

This invention relates generally to innovations and improvements in axle suspensions for trucks and particularly to suspensions for the front steering axles of trucks wherein the axles are hollow and fabricated by welding. However, the invention also has application to rear axles and also to solid cast or forged solid axles. In all applications of the invention roll stability of the vehicles is materially enhanced.
The suspensions of the present invention incorporate asymmetric leaf springs extending in a fore-and-aft direction with one end pivotally attached to a mounting bracket on a generally fore-and-aft extending side frame member of a chassis with the opposite end suitably secured to the frame member. As used herein, the term "asymmetric" is not meant to denote different lengths of the cantilever limbs of the leaf spring, but rather their differing respective spring rates. At a location intermediate its opposite ends the leaf spring is suitably mounted on the adjacent end of an axle. If desired, the resilient support provided by the leaf spring may be augmented by the incorporation in the suspension of an air spring thereby providing the vehicle with "air ride" features.
The asymmetric leaf springs used in suspensions according to the invention are of two types. One type combines at least one leaf that extends the full length of the spring from end to end and at least one additional shorter leaf which extends from the end which is pivotally attached to a spring mounting bracket to the axle. Examples of such a leaf spring are disclosed in U.S. Ser. No. 09/522,585, filed Mar. 10, 2000, the disclosure of which is hereby incorporated herein by reference. The other type of spring incorporates a tapered convoluted single-leaf leaf spring which extends for the full length of the spring and is formed with a relatively thick cantilever limb extending in one direction from the axle to the pivotally attached end and a second relatively thin cantilever limb extending in the opposite direction from the axle to its opposite end. The thicker cantilever limb has a relatively high spring rate and is substantially stiffer than the relatively thin cantilever limb which has a relatively low spring rate and is substantially less stiff. An example of such a leaf spring is disclosed in U.S. Pat. No. 5,938,221, Aug. 17, 1999, issued to Wilson, the disclosure of which is hereby incorporated herein by reference. Alternatively, features of both types could be used, as disclosed in the aforementioned U.S. Ser. No. 09/522,585.
It will be understood that the construction of the suspension on one side of the vehicle supporting one side frame member on one end of an axle is duplicated on the opposite side of the vehicle.
In its preferred embodiments the axle suspensions of the present invention are characterized by being relatively light weight, low cost with high roll stability. Accordingly, the object of the invention, generally stated, is to provide axle suspensions which exhibit high roll stability and which are relatively light weight and commercially producible at relatively low cost from readily available components.
A more specific object of the invention is the provision of light weight, low cost axle suspensions by combining the high torsion stiffness of a hollow axle body with the torsion action provided by a leaf spring mounted on the axle with one cantilever limb having a stiffness substantially greater than the stiffness of the other cantilever limb, preferably in a ratio of at least 4 to 1.
Certain other objects of the invention will be apparent to those skilled in the art in view of the following detailed description taken in connection with the accompanying drawings wherein:
Referring to FIGS. 1 and 2 a suspension is indicated generally at 5 therein comprising a pair of fore-and-aft extending chassis side frame members indicated generally at 6-6 mounted on opposite ends of an axle indicated generally at 7. The axle 7 may for example, be a hollow fabricated front steering axle of a truck. The chassis is supported on the axle 7 in part by composite fore-and-aft extending leaf springs indicated generally at 8-8 and a pair of air springs indicated generally at 10-10. The fabricated axle 7 is hollow in cross section and of known type being fabricated by welding instead of being cast or forged with a solid cross section. Being hollow the fabricated axle 7 is characterized by having high torsional resistance considering its relatively low weight. It will be understood that other forms of axles may be used such as the hollow axle housings used in connection with rear drive axles.
Each fore-and-aft extending spring 8 is formed by a relatively thin full length single-leaf leaf spring 11 which may have a stiffness of about zero to four hundred pounds per inch combined with a relatively thick shorter leaf spring 12 which may have a stiffness of about one thousand or more pounds per inch, but always maintaining at least a four-to-one stiffness ratio between the front cantilever limb and rear cantilever limb. The leaf 12 is formed with an eye 13 at one end and an offset raised platform 14 at the opposite end on which one of the air springs 10 is mounted. If desired, the platform 14 may be formed as part of the top pad of 19 the axle clamping structure. The full length leaf spring 11 is formed with an eye 15 on one end which wraps around the eye 13 on the shorter leaf 12. At its opposite end the full length spring 11 is formed with an eye 16 which is pivotally connected to one end of a shackle 17 in known conventional manner. The interfitting eyes 13 and 15 constitute a so-called "military wrap" which is pivotally connected to the lower end of a bracket indicated generally at 18 the upper end of which is mounted on the side of a frame member 6. As is well known in the art, a military wrap connection provides redundancy in the event that one of the interfitting spring eyes breaks or fails for some reason.
Adjacent its distal end on which the platform 14 is formed the relatively thick leaf 12 and the full length leaf 11 are mounted on the axle 7 by known axle clamping structure as shown in FIGS. 1-3. Preferably each air spring 10 is mounted in known manner on a platform 14 with the upper end being attached to a bracket 20 mounted on a side frame member 6. Alternatively, the air spring 10 can be mounted directly over the axle 7 in the manner shown in FIG. 3. However, mounting the air spring 10 on the platform 14 to the side of the axle 7 opposite the bracket 18 is preferred since it provides an increased mechanical advantage for the air spring to support the vertical load.
In the arrangement shown in FIGS. 1 and 2 the air spring 10 and the cantilever limb indicated generally at 21 in FIG. 2 will together provide most of the vertical load support for the chassis while the cantilever limb indicated generally at 22 in FIG. 2 and formed in the full length leaf 11 may provide less than 10% of the support for the vertical load. The main function of the relatively thin full length leaf 11 is to react to side loads on the suspension and provide redundancy. This two-piece composite spring has the same high rate differentiation as stated in Wilson U.S. Pat. No. 5,938,221 dated Aug. 17, 1999 the disclosure of which is incorporated by reference herein.
The suspension arrangement shown in FIGS. 1 and 2 with the air spring 10 mounted on the platform 14 and offset from the center line of the front steering axle 7 provide beneficial results in the steering kinematics when axle 7 is a front steering axle. Thus, it is generally known in the art that springs arc about an imaginary point in space which is called the "Ross" point which in turn determines the sq-called "Ross Line". The Ross point is indicated at R in FIG. 4 and the Ross Line is indicated at RL. It is known that the Ross Line should be as flat and long as possible and the Ross Line geometry should match the drag link geometry of the vehicle.
As shown in FIG. 4, as the composite spring 8 is loaded the fact that the air spring 10 is cantilevered behind the axle center causes the limb 11 to rotate towards more caster. This produces a long and flat Ross Line (RL). When the air spring 10 is mounted over the axle 7 as shown in FIG. 3 the Ross Line is relatively short and steep and the Ross Point is located inwardly (i.e. to the right) of the eye of the spring 8.
The suspension configuration shown in FIGS. 1 and 2 with the air springs 10 mounted on the platforms 14 in cantilever behind the center line of the axle 7 allows the fore-and-aft extending spring 8 to be designed to fit existing vehicle packages. Thus, the front eyes 13, 15 of the springs may be fitted to an existing hanger. The front cantilever limb 22, the rear cantilever limb 21 and the load on the air spring 10 may be optimized to the point where the Ross Line characteristics may be tuned to match the existing steering linkage installation of the vehicle.
While the composite springs 8 offer the several advantages referred to above they may be replaced by tapered convolute single-leaf leaf springs indicated generally at 25 in FIGS. 6 and 7. The construction and functioning of the spring 25 are shown and described in detail in U.S. Pat. No. 5,938,221 dated Aug. 17, 1999 the disclosure of which is incorporated by reference herein. The spring 25 is formed with an eye 26 at one end which may be attached to the mounting bracket 18 (FIGS. 2-3). The front cantilever limb of the spring 25 is indicated generally at 27 and extends from the eye 26 to an aperture 28 located within the mid portion of the spring. As shown, the cantilever limb 27 extends in a generally continuous direction from the eye 26 to the point 28 so that no corrugations are formed within the limb. The cantilever limb which extends from the point 28 to the end of the spring indicated at 30 is indicated at 31. The cantilever limb 31 extends in a generally continuous direction from the point 28 to its end 30 with no corrugations formed therein.
The cantilever limb 27 includes an axle area indicated generally at 32. This seat area includes the bottom most point 28 of the tapered convolute leaf spring 25 when the leaf spring is connected to a vehicle chassis frame.
A reverse arch portion in the cantilever limb 31 is indicated generally at 33. It will be noted that the thickness of the spring 25 is greatest in the cantilever limb 27 and tapers to a thinner thickness in the cantilever limb 31. Except for the end 30 the spring 25 has a uniform width as shown in FIG. 7.

Truck suspensions incorporating asymmetric leaf springs


A vacuum cleaning tool for a vacuum cleaning device has a housing having a vacuum connector connected to the vacuum cleaning device. The housing has an underside and an elongate intake opening arranged in the underside. A brush roll is arranged in the housing parallel to the elongate intake opening. A drive is arranged in the housing and drivingly coupled to the brush roll. An exchangeable vacuum shoe is detachably connected to the housing and has two wall portions extending at least approximately parallel to the brush roll. The brush roll is arranged between the two wall portions.

1. Field of the Invention
The invention relates to a vacuum cleaning tool for a vacuum cleaning device, in particular, for cleaning floors. The vacuum cleaning tool comprises a housing having a vacuum connector for the vacuum cleaning device and an elongate intake opening provided at the underside of the housing wherein a brush roll is provided which extends parallel to the intake opening and is coupled with a drive.
2. Description of the Related Art
Vacuum cleaning tools are used primarily for cleaning floors. They are provided with rotating brush rolls for removing dirt from the floor. The brush rolls are arranged in the area of the intake opening. The bristle arrangement of such brush rolls is employed, depending on the type of floor, i.e., smooth floors or carpeting, with an action of different strength, wherein the bristles for a soft floor penetrate deeper than for a hard, smooth floor. As a function of the number of bristles as well as their elasticity as well as the rotational speed of the corresponding roll, a polishing effect can also be achieved which, however, is very limited as a result of the minimum weight of such universal vacuum cleaning tools. For this reason, special polishing devices have been proposed which are required in addition to a vacuum cleaning tool and have an electrical drive with considerable weight acting on a disc with a polishing bristle arrangement rotating about a vertical axis.
It is an object of the present invention to provide a vacuum cleaning tool of the aforementioned kind which can be universally used for different types of flooring and which can be manipulated easily.
In accordance with the present invention, this is achieved in that a vacuum shoe is exchangeably connected to the housing and comprises at least two wall portions extending substantially parallel to the brush roll between which the brush roll is received.
By providing a vacuum shoe that is exchangeable, the operator can adapt in a simple way the vacuum cleaning tool to the respective requirements of the floor to be treated so that the respective type of flooring can be cleaned and cared for in the proper way. Accordingly, for the different types of requirements only a single device is needed which can be easily manipulated.
According to a further embodiment of the invention, the vacuum shoe is provided at the ends of the wall portions with sidewalls which provide the spacing of the wall portions relative to one another. The vacuum shoe forms thus a frame which is exchangeable in its entirety. Preferably, the sidewalls and wall portions of the vacuum shoe form a monolithic body and are comprised, in particular, of a plastic material. In order to facilitate the exchange of the vacuum shoe, a clamping connection, clip connection or snap connection is provided for attachment of the vacuum shoe to the housing. In this context, it is expedient for the vacuum shoe to have openings to be engaged by projections on the housing. These openings are expediently arranged in the sidewalls of the vacuum shoe, and the projections are in the form of pins projecting laterally from the housing. In order for the pins to be able to provide a double function, i.e., on the one hand, attachment of the vacuum shoe, and, on the other hand, providing a bearing action for the brush roll, the pins are arranged coaxially to the rotational axis of the brush roll. It may be expedient to provide the openings in the form of bores in elastically deformable sidewalls of the vacuum shoe so that the introduction of the pins in the bores as well as the detachment therefrom can be realized by temporary deformation of the sidewalls. As an alternative, the openings for receiving the pins can be of a substantially circular shape and can have connected thereto a radial slot extending away from the opening wherein the end of the slot adjacent or connected to the opening has a width that is smaller than the diameter of the pin.
In order for the vacuum cleaning tool not to scrape on the floor to be treated and to facilitate movement of the vacuum cleaning tool across the floor, rollers are provided at the underside of the vacuum shoe with which the vacuum cleaning tool is supported on the floor. For the treatment of carpets and soft floors, the vacuum shoe is expediently of a flat configuration so that the bristles of the brush roll project through the air intake opening.
For treating hard floors, a polishing roll is provided in a vacuum shoe of a different design. It extends parallel to the intake opening and substantially fills out the intake opening. The polishing roll with its mantle surface projects past the plane of the underside of the vacuum shoe. The drive of the polishing roll is realized preferably such that the bristles of the rotating brush roll of the vacuum cleaning tool engage the surface of the polishing roll and thus cause rotation of the polishing roll. As an alternative to this, the polishing roll can have an intermediate gear for driving the polishing roll which preferably cooperates with a gear wheel provided at an end face of the polishing roll. For enabling a simple removal of the polishing roll, for example, for the purpose of cleaning the polishing roll, the polishing roll is received in bearings that can be locked or secured within the sidewalls of the vacuum shoe.
As a drive for the brush roll and the polishing roll an air turbine is preferably provided which is arranged in a turbine chamber. It is also possible to provide an electric motor as a drive for the rolls instead of the air turbine. The shaft of the air turbine, or of the electric motor, is expediently provided with a toothed disc, and the shaft is coupled by means of a toothed belt with the brush roll.
The polishing roll is comprised preferably of a core with axle pins at the end faces and with a cover arranged on the core and formed preferably of a textile material. In this connection, it is possible to design the cover such that it forms a uniform covering over the entire axial length and is connected to the core only in the vicinity of the axial ends of the core. The textile cover is loose (unattached) relative to the roll-shaped core across the axial length of the core between the connecting locations of the cover and the core so that as a result of the circumferential speed and the resulting centrifugal forces the cover is forced into the uneven portions and cracks of the hard flooring.
The cover can also be comprised of several portions sequentially arranged in the axial direction wherein the textile covering in the respective portions has different heights and/or different degrees of hardness. For example, the portions with a higher (taller), soft covering can have a length of approximately 3 mm and the portions with a lower (shorter), hard covering can have a length of approximately 10 mm. Since the polishing roll as a result of its weight or the weight of the vacuum cleaning tool rests with the portions of the harder textile covering on the hard flooring, the fluffy textile covering of the soft portions is forced outwardly upon rotation of the polishing roll by the resulting centrifugal forces so that this covering reaches the uneven portions of the hard floor and thus produces a cleaning effect thereat. The cover of the polishing roll can be attached on the core by adhesives or by welding.
According to a further embodiment of the invention, the polishing roll is supported in a floating fashion in the sidewalls of the vacuum shoe by means of elastic components. This provides an automatic adaptation of the drive of the polishing roll.

Vacuum cleaning tool with exchangeable vacuum shoes