A cutter head with at least one insert clamp. Each insert clamp includes a wedge member fastened to the cutter head. The cutter head includes an insert slot, a clamping slot, and a threaded aperture. The wedge member, in one embodiment, is wedge shaped and includes a thru-opening. A fastener engages the threaded aperture in the cutter head and passes through the thru-opening in the clamping member. A cutter insert fits into the insert slot in the cutter head, and the wedge member secures the cutting insert against a surface of the cutter head.

1. Field of Invention
This invention pertains to a cutting tool for use in a rotary power tool. More particularly, the invention relates to a rotary cutter head for releasably holding cutting blades formed with cutting edges which extend radially outwardly from and generally axially along the outer periphery of the cutter head. Cutter heads of this general type are typically used in power machines such as routers, edgebanders, or tenoners and are typically used to chamfer, round, or otherwise shape an edge portion of a workpiece of either ferrous or non-ferrous material.
2. Description of the Related Art
Rotary cutting tools consist of a disc-like body having disposable cutting inserts protruding radially from the disc periphery. The cutting inserts are held firmly to the disc body when in use, but must be readily removable for replacement when the cutting edge of the insert is blunted or broken.
There have been many proposals in relation to the manner in which the cutting inserts are held in the body. Such proposals include cutting inserts held in place in the cutting body by some form of separate retaining means. Typical forms of construction falling in this first category are described and illustrated in U.S. Pat. No. 1,700,333, issued to Pond; U.S. Pat. No. 3,887,975, issued to Sorice, et al.; U.S. Pat. No. 4,363,576, issued to Zweekly, and U.S. Pat. No. 5,647,699, issued to Martin, et al.
The Pond and Sorice, et al., patents set forth arrangements utilizing camming members which bear against appropriately shaped portions of the cutting inserts to achieve clamping. The Zweekly patent shows a camming arrangement which bears against a clamping blade which in turn bears against the insert. This blade is welded into the body to ensure integrity of position. The Martin, et al., patent discloses a cutter head forming an integral clamp that secures the insert.


A magnetic core of superparamagnetic core shell nanoparticles having a particle size of less than 200 nm; wherein the core is an iron cobalt ternary alloy and the shell is a silicon oxide is provided. The magnetic core is a monolithic structure of superparamagnetic core grains of an iron cobalt ternary alloy directly bonded by the silicon dioxide shells. A method to prepare the magnetic core which allows maintenance of the superparamagnetic state of the nanoparticles is also provided. The magnetic core has little core loss due to hysteresis or eddy current flow.

Field of the Invention
The present invention relates to a magnetic core having performance and stability properties which make the core particularly suitable for utility in power generation parts such as stators, rotors, armatures and actuators or any device whose function is dependent upon an efficient magnetic core, i.e., a magnetic core having minimal magnetic hysteresis and no or little eddy current formation.
Discussion of the Background
Magnetic materials generally fall into two classes which are designated as magnetically hard substances which may be permanently magnetized or soft magnetic materials which may be reversed in magnetism at low applied fields. It is important in soft magnetic materials that energy loss, normally referenced as "core loss" is kept to a minimum whereas in hard magnetic materials it is preferred to resist changes in magnetization. High core losses are therefore characteristic of permanent magnetic materials and are undesirable in soft magnetic materials.
Soft magnetic core components are frequently used in electrical/magnetic conversion devices such as motors, generators and transformers and alternators, particularly those found in automobile engines. The most important characteristics of soft magnetic core components are their maximum induction, magnetic permeability, and core loss characteristics. When a magnetic material is exposed to a rapidly varying magnetic field, a resultant energy loss in the core material occurs. These core losses are commonly divided into two principle contributing phenomena: hysteresis and eddy current losses. Hysteresis loss results from the expenditure of energy to overcome the retained magnetic forces within the core component. Eddy current losses are brought about by the production of induced currents in the core component due to the changing flux caused by alternating current (AC) conditions.
The use of powdered magnetic materials allows the manufacture of magnetic parts having a wide variety of shapes and sizes. Conventionally, however, these materials made from consolidated powdered magnetic materials have been limited to being used in applications involving direct currents. Direct current applications, unlike alternating current applications, do not require that the magnetic particles be insulated from one another in order to reduce eddy currents.
Conventionally, magnetic device parts are constructed from powders by compaction of the powders to a defined shape and then sintering the compact at temperatures of 600° C. or higher. Sintering the part following compaction, is necessary to achieve satisfactory mechanical properties in the part by providing particle to particle bonding and hence strength. However, sintering may cause volume changes and results in a manufacturing process with poor dimensional control.
In other conventional processes designed to prepare parts having minimum eddy current losses, the magnetic particles are coated with thermoplastic materials before pressing. The plastic is provided to act as a barrier between the particles to reduce induced eddy current losses. However, in addition to the relatively high cost of such coatings, the plastic has poor mechanical strength and as a result, parts made using plastic-coated particles have relatively low mechanical strength. Additionally, many of these plastic-coated powders require a high level of binder when pressed. This results in decreased density of the pressed core part and, consequently, a decrease in magnetic permeability and lower induction. Additionally, and significantly, such plastic coatings typically degrade at temperatures of 150-200° C. Accordingly, magnetic parts made in such manner are generally limited to utility in low stress applications for which dimensional control is not critical.
Thus, there remains a need for magnetic powders to produce soft magnetic parts, having increased green strength, high temperature tolerance, and good mechanical properties, which parts have minimal or essentially no core loss.
Conventionally, ferromagnetic powders have been employed for the production of soft magnetic core devices. Such powders are generally in a size range measured in microns and are obtained by a mechanical milling diminution of a bulk material. Superparamagnetic nanoparticle materials having particle size of less than 100 nm have found utility for magnetic record imaging, as probes for medical imaging and have been applied for targeted delivery of therapeutic agents. However, the utilization of superparamagnetic powders for production of core magnetic parts has until now, been limited.
For example, Toyoda et al. (U.S. 2011/0104476) describe a soft magnetic material of iron or an iron alloy particle having a grain size of from 5 to 400 μm which is provided with an oxide insulative coating including silicon oxide. The coated particles are mixed with an organic substance which is a non-thermoplastic resin and at least one of a thermoplastic resin and a higher fatty acid. The content of the organic substance in the mixed material is from 0.001 to 0.2% by mass. The mixed material is compression molded and then subjected to a heat treatment at a temperature between the glass transition temperature and the thermal decomposition temperature of the non-thermoplastic resin. The molded and heat treated structure is indicated to be useful for electric and electronic components such as a motor core or a transformer core.
Anand et al. (U.S. Pat. No. 6,808,807) describes encapsulated ferromagnetic powders obtained by coating a ferromagnetic core with a polyorganosiloxane or polyorganosilane and thermally treating the coated core to convert the polymer to a residue containing silicon and oxygen. The core alloy may be any of iron alloyed with silicon, aluminum, nickel, cobalt, boron, phosphorous, zirconium, neodymium and carbon. Ferromagnetic core particles having an average diameter of less than 2 mm are suitable for this composition. A plurality of the particles may be compacted to a desired shape. Hot isostatic pressing as a method of compaction is described.
Lashmore et al. (U.S. Pat. No. 6,251,514) describes a ferromagnetic powder containing particles of about 40 to 600 microns. Examples of the ferromagnetic material include carbon steel, tungsten steel, Vicalloy (Fe/Co/V alloy) and iron powder. The particles are coated with a combination of an iron oxide and another iron oxate salt such as iron chromate. Compaction followed by annealing provides soft magnetic parts.
Gay et al. (U.S. Pat. No. 6,193,903) describes ceramic coated ferromagnetic powders. The powders are iron or an iron alloy and the encapsulating layer on the particle may be one of a group of ceramics such as a metal oxide, metal nitride, metal silicate and a metal phosphate. The particle size is from 5 to 1000 microns. Silica is listed as one of a large group of ceramic materials suitable as the coating. The powders may be compacted to form a magnetic article. Inclusion of a polymer or lubricant is described in the compaction and the unit is then annealed.
Liu (U.S. 2010/0054981) describes a system of magnetic nanoparticles which is a composite of a hard magnetic material and a soft magnetic material. For example, a "bimagnetic" FePt/Fe3O4 nanoparticle is described. Liu describes "warm compaction of the material to produce a bulk nanocomposite magnet.
Ueta et al. (U.S. 2003/0077448) describes a ferromagnetic raw metal powder (primarily iron) having a coating of various oxide materials including silicon. Claim 1 provides a ferromagnetic powder which is surface coated with a silicone resin and a pigment. The coated particle has a diameter on the order of 100 microns. Warm pressing of the powder to produce a core is described as well as annealing of a core at elevated temperature.
Tokuoka et al. (U.S. Pat. No. 7,678,174) describe an iron based powder particle having an iron or iron alloy core and an oxide type insulating coating, including silicon oxide. An ester wax is also added to the particle surface. The coated powder particles are on the order of 200 microns in size as described in Example 1. The lubricated powder is pressure molded to form a molded body and the molded body heat treated.
Soileau et al. (U.S. Pat. No. 4,601,765) describes a core obtained by compaction of iron powder which has been coated with an alkali metal silicate and then a silicone resin polymer. The iron particles to which the coating is applied have a mean particle size of 0.002 to 0.006 inches. The core is prepared by compaction of the powder at greater than 25 tons per square inch and then annealing the pressed component.
Tajima et al. (IEEE Transactions on Magnetics, Vol. 41, No. 10, October, 2005) describes a method to produce a powder magnetic core described as warm compaction using die wall lubrication (WC-DWL). According to the method an iron powder coated with a phosphate insulator was compacted under a pressure of 1176 MPa at a temperature of 423° K to produce a core type structure.
Moorhead et al. (U.S. Pat. No. 6,051,324) describes particles of an alloy of iron/cobalt/vanadium having a particle size of less than 44 microns (325 mesh) which are coated with a glass, a ceramic or a ceramic glass, including silicon dioxide. Densification of the material by sintering under pressure is described as well as hot compression to form disks. The formation of strong bonds between the glass ceramic including SiO2 and the metal alloys under warm compression is disclosed.
Nitta et al. (U.S. Pat. No. 5,338,508) describes an Iron-Cobalt-Vanadium-type powder having an average particle diameter of 20 microns or less which is suitable for injection molding. The particles are obtained by atomization of the melted alloy. Nitta describes that a film of SiO2 on the particle surface prohibits formation of a desired spherical form. The particles are injection molded employing organic binders.
Mamiya et al. (JP 06-342715) describes compression molding of a iron-cobalt-vanadium alloy powder by coating the powder with a silicone resin. The compressed green body is subsequently heat treated and during this treatment the resin is converted to SiO2. The alloy powder was prepared by an atomization method and has a mean particle size of 50 μm.
Tsurumaki et al. (JP 03-291335) (Abstract) describes forming a green compact of an atomization method prepared powder of an iron-cobalt-vanadium alloy. The green body is calcined and dewaxed, then recompacted and sintered.
Yamada et al. (JP 03-153838) (Abstract) describes surface treatment of an iron/cobalt/vanadium powder with a compound containing silicon and an alkoxy group (such as vinyl triethoxysilane). No description of particle size or method to produce the alloy particle is provided. The powder is molded or extruded with addition of a thermoplastic resin and the formed green body is degreased and sintered.
Park et al. (J. Phys.: Condens. Matter 20 (2008) 204105) describes the synthesis of nanoparticles of a temperature sensitive ferrite, the ferrite being an alloy of iron/calcium/nickel/zinc. The particles are coated with a silica shell by treatment with TEOS at alkaline pH. Use of the coated particles for a magnetic fluid is described.
Bumb et al. (Nanotechnology, 19, 2008, 335601) describes synthesis of superparamagnetic iron oxide nanoparticles of 10-40 nm encapsulated in a silica coating layer of approximately 2 nm. Utility in power transformers is referenced, but no description of preparation of core structures is provided.
None of the above references disclose or suggest a monolithic magnetic core constructed by heated compression of a nanoparticular iron cobalt ternary alloy encapsulated in a silicon dioxide coating shell, wherein the particles are directly compacted without addition of lubricant or other material to facilitate particle adherence.

This patent is subject to a terminal disclaimer.

Iron cobalt ternary alloy and silica magnetic core

Toyota Motor Engineering & Manufacturing North America, Inc.


Method of dispensing moist, sticky or statically charged bulk material into a fluid pervious container having an opening for receiving said bulk material, which comprises conveying a bulk material, as a suspension or dispersion in a fluid, from a reservoir, and introducing said suspension or dispersion into the fluid-pervious container through said opening in the container to pass the fluid component of the suspension or dispersion through and out of the fluid-pervious container while the retaining the bulk material within the container, and recirculating the fluid to the reservoir.

The invention relates to a method of loading moist, sticky or statically charged bulk material, in particular catalyst material, into fluid pervious containers.
The published specifications DE 197 01 045 A1 and EP 0 640 385 A1 (=U.S. Pat. No. 5,536,699) disclose catalyst packaging which is provided with closable bags into which catalyst material can be introduced as bulk material and which are reusable to at least some extent when the catalyst is replaced. The filling of the catalyst bags or the replacement of the catalyst in the bags, in particular the filling of the catalyst bags, is in practice time-consuming and associated with further problems, since the catalyst material is frequently moist, sticky or statically charged and therefore does not flow readily.
It is an object of the invention to provide a method which makes it possible for packaging or containers of the type mentioned to be readily and quickly filled with moist, sticky or statically charged bulk material.
This object is achieved by a method of loading moist, sticky or statically charged bulk material, in particular catalyst material, into fluid-pervious containers which have a multiplicity of fine openings, wherein the bulk material is conveyed from a reservoir as a suspension or dispersion in a fluid, preferably a liquid, particularly preferably in water, and is introduced into the container through an opening in the container and in that the fluid exits through a multiplicity of openings in the container while the bulk material is retained in the container; and the fluid is recirculated to the reservoir.
The containers are preferably configured as a series of individual compartments in strip form, and are preferably formed of a woven metal mesh.
The method is suitable for introducing solid, granular or gel-form, catalytically, biologically or adsorptively active materials of various particle sizes, as finely divided particles suspended or dispersed in a fluid, into structured fluid-pervious containers which can serve dual functions. The first of said dual functions is to provide a very high contact area between two or more phases, for mass transfer between them. The structured fluid-pervious containers comprise closed fluid-pervious compartments comprised of a woven mesh or fabric, or of a membrane which is permeable to at least one fluid present in the process in which the loaded containers are to be used. The solid material which, as a second function, is active in the process in which it is used is present in the compartments and remains in the compartments after the compartments are closed, subsequent to being filled with the solid material. It is possible to vary the volume and number of the compartments in the containers, as well as the degree of fill of the container compartments in accordance with the requirements of the process in which they are used and the characteristics of the active solid material.
It can be a substantial advantage in various physicochemical processes for chemical, biological or other materials conversion processes to be superimposed on physical mass transfer processes, e.g. rectification or absorption, and vice versa. It is necessary to provide, on the one hand, a contact area sufficient for mass transfer between the fluid phases and, on the other hand, a very large active surface to achieve the dual functionality, with both functions, viz. mass transfer and materials conversion, having to be able to be varied to a wide degree in accordance with process requirements.
In such a context, catalytically active mass transfer packing is used for particular applications, e.g. heterogeneously catalyzed chemical reactions in the liquid phase, and is described, inter alia, in the patent specifications DE 197 01 045 A1, EP 0 631 813 A1, WO 98/58721 and WO 97/24174.
A significant disadvantage of the known apparatuses for simultaneously carrying out mass transfer and materials conversion is the comparatively great effort required to introduce the catalytically or biologically or absorptively active materials into the containers to be used, which sometimes have a complicated geometry. In particular, filling of the containers with such materials can be difficult or problematical from the point of view of occupational hygiene when the materials are not-free-flowing, or are sticky or dust-forming or gas-releasing or statically charged solids or granular materials or gel-form solids. In the hitherto customary procedure for filling the container compartments in structured packing having dual functionality, a basic prerequisite is for the material to be introduced to flow more or less well. In the filling procedure, the material which is catalytically active, biologically active or otherwise active is first conveyed manually or mechanically via a funnel or a similar device through a filling orifice of the chambers into the latter and is then distributed as uniformly as possible in the chamber by means of, for example, a shaking motion.
In the above-described prior art method, particularly in the case of granulated materials which have very poor flow, there are numerous difficulties, e.g. non-uniform distribution of the material in the chambers, voids or differing degrees of fill of the individual chambers, etc.
It is therefore an object of the present invention to provide a significantly simplified and practical method which offers significant advantages in respect of the abovementioned difficulties in filling the chambers. In addition, the time and effort required for filling the dual function elements should be significantly reduced. This object is achieved by the method of the invention.
In particular, the method of the invention for introducing solid, granular, catalytically, biologically or adsorptively active materials into structured multipurpose packing with dual function elements involves introducing the active material in the form of finely divided solid particles as a suspension or dispersion in a fluid into openings in the compartments of the container. The solid material is retained within the compartments, because the openings of the mesh forming the compartment walls are too small for the solid to pass through, but at the same time the mesh walls are permeable to the fluid, which therefore passes through the compartment walls and flows out. When the walls are formed of a membrane, the membrane allows the fluid, but not the solid material, to pass through. After the compartments are filled with the desired or predetermined amount of solid material, the openings through the materials were introduced are closed.
The present invention is therefore a method of loading moist, sticky or statically charged bulk material into a fluid pervious container having an opening for receiving said bulk material, which comprises conveying a bulk material, as a suspension or dispersion in a fluid, from a reservoir, and introducing said suspension or dispersion into the fluid-pervious container through said opening in the container to pass the fluid component of the suspension or dispersion through and out of the fluid-pervious container while retaining the bulk material within the container, and recirculating the fluid to the reservoir
In one embodiment of the method, a flowable solid/liquid suspension or dispersion is produced in a fluidization vessel in a first step. The fluidization vessel is preferably a vessel or reactor which is provided with a stirrer as mixing element. Alternatively, the suspension or dispersion can also be produced merely by introduction of the fluid used for mixing or a second fluid into the fluidization vessel.
In this way, even granular materials which do not flow or flow only with difficulty, (e.g. ion-exchange resins which are moist with water or are impregnated with organic solvents) can be brought into a form which can be conveyed continuously. Furthermore, it is possible, for example, to avoid the formation of dusts during filling by the production of a suspension in a liquid, or to overcome difficulties in handling statically charged granular materials (e.g. oxidic catalysts which suffer from dust formation caused by abrasion when conveyed dry or ion-exchange resins which suffer from static charging in the water-free state).
Preference is given to a method in which an additive is added to the fluid containing the bulk material before introduction into the containers.
The additive is particularly preferably mixed in by a static or dynamic mixing unit.
As bulk material to which the method is applied, preference is given to a heterogeneous catalyst, in particular an ion-exchange resin, an oxidic catalyst or hydrogenation catalyst or an adsorbent or absorbent solid, in particular activated carbon or a support material with a biofilm.
As fluid, preference is given to an inorganic or organic solvent, particularly preferably methanol, ethanol, heptane or water.
In a particularly preferred embodiment of the method, the bulk material is an acidic or basic ion-exchange resin and the fluid used is water.
Preference is also given to an embodiment of the method which is characterized in that an additive which is a cocatalyst is added to the suspension or dispersion of fluid and bulk material.
Suitable fluids are, in particular, media which do not irreversibly change the physical, chemical, biological or other properties of the solid to be packaged or the total system which are desired for the intended use. Thus, preference is given to liquids or gases which are chemically inert towards the catalytically, biologically or absorptively active materials, or inactive in the intended use or in the production of the active materials, or are at least part of the working medium or of the use environment without exercising an undesirable influence in the operating state of the filled containers in intended use (e.g.: ion-exchange resins as active granular material and organic solvents such as methanol, ethanol or heptane as fluids). However, it is also possible to use fluids which can be removed completely from the system directly after filling of the containers or at the latest when operation of the process in which the loaded containers are used is started to such a degree that the desired operating state is not adversely affected, e.g. ion-exchange resins and water as fluid. A significant advantage of the novel method of introduction can thus rise from, for example, various intermediate steps in the production or conditioning of the active solid, for example separation from liquid or drying, becoming unnecessary or being able to be carried out more simply and more effectively in the packaged state in an industrial plant.
After the granular material has been brought into a continuously conveyable form in the fluidization vessel, the suspension or dispersion is transported, for example via a hose or pipe, to the containers to be filled. At the end of the hose or pipe there is, in particular, a nozzle which is flattened or has a shape corresponding to the requirements of the geometries of the container compartments to be filled, and allows clean introduction of the suspension or dispersion into the container compartments. The energy required for transport can be provided either by pumping or by application of a pressure gradient. A turbulence of the flow in the pipe or hose ensures that the solid remains finely suspended or dispersed in the fluid.
Furthermore, it is possible to integrate an additional mixing section into the filling apparatus so as to allow additives to be added to the active material. Such additives can, for example, be suitable for influencing the properties of the solid in a desired way. A very considerable advantage here is that the addition of the additive into a mixing section through which turbulent flow occurs enables very good distribution to be achieved. An example which may be mentioned is the coating of catalyst particles with a cocatalyst, in which case reliable, very uniform application is of great importance.

Method of loading moist, sticky bulk material into a fluid pervious container


A machine for producing cushioning product is provided which allows a user to select a length of product to be produced from a plurality of selectable lengths. The machine comprises a frame, a plastic sheet supply assembly mounted on the frame, a forming assembly mounted on the frame downstream of the plastic sheet supply assembly which forms the plastic sheet into a tube with the lateral edges of the plastic sheet overlapping, a pulling assembly mounted on the frame downstream of the forming assembly which pulls the plastic sheet from the plastic sheet supply assembly to and over the forming assembly, a first heat sealing assembly mounted on the frame downstream of the forming assembly which is selectively activatable to longitudinally heat seal the overlapping lateral edges of the tube together a selected length from a continuous plurality of selectable lengths, and a second heat sealing assembly mounted on the frame downstream of the first heat sealing assembly which transversely heat seals the tube at each end of the longitudinal seal formed by the first heat sealing assembly to thereby form an air pillow.

In the process of shipping an item from one location to another, a protective packaging material is typically placed in the shipping carton or box, to fill any voids and/or to cushion the item during the shipping process. Some conventional protective packaging materials are plastic, for example expanded polystyrene, foam peanuts and starch peanuts. While these conventional materials seem to perform adequately as cushioning products, they are not without disadvantages.
The most serious drawback of these types of cushioning products is the mess that is tended to be made when unpacking a carton or box shipped with such loosefill as the cushioning material. The peanuts tend to be strewn about the unpacking area, requiring time intensive cleanup. Further aggravating matters, in the case of plastic peanuts, is the tendency of the plastic peanuts to cling to the item shipped in the box, to people, to clothing, to carpet and to other structures in the unpacking area, due to static electricity.
One proposed solution for overcoming the deficiencies of loosefill as described above is the Flo-Pak Pouch.TM. marketed by Free Flow Packaging International, Inc. of Redwood City, Calif. The Flo-Pak Pouch.TM. utilizes a cylindrical plastic sleeve which is filled with polystyrene loosefill and the ends of which are gathered and tied off to form a cylindrical shaped or "sausage" shaped bag of loosefill. While the Flo-Pak Pouch.TM. does prevent the mess described above caused by loosefill, it is not without its own drawbacks. For example, the Flo-Pak Pouch.TM. is somewhat difficult to utilize when packing articles to be shipped, as the cylindrical shaped bags do not bend easily to conform about an article within a box. Furthermore, the Free Flow Packaging machine which makes the Flo-Pak Pouch.TM. does not include any capability for producing a string of bags of loosefill interconnected end-to-end, i.e. the Free Flow Packaging machine has the capability for producing only individual filled bags.
It would be desirable to better harness such loosefill material for cushioning purposes to exploit the cushioning properties of such loosefill but at the same time to eliminate the drawback of the mess associated therewith, while at the same time solving the problems presented by the Flo-Pak Pouch.TM..
To this end, the invention disclosed in application Ser. No. 09/065,221 filed Apr.23, 1998, assigned to the assignee of the present invention and hereby incorporated by reference herein as if fully set forth in its entirety, provides a number of cushioning products utilizing loosefill yet which avoid the prior problem of mess associated therewith, and which also provide for convenient loading of the product to be shipped into a carton therewith. One such cushioning product comprises a bag filled with loosefill packing material. The bag has a length, a width and a thickness, with the length and the width being substantially greater than the thickness. The loosefill packing material may be plastic peanuts, for example expanded polystyrene peanuts, or starch peanuts. A filled bag of loosefill according to this invention is preferably generally rectangular when viewed in side elevation and in end elevation, to promote wrapping an item to be shipped. The bag, which preferably is made of plastic, or even transparent plastic, preferably allows air to escape from it. To that end, the bag preferably includes a number of small holes therein. By allowing air to escape a "balloon" effect of the bags is avoided and the cushioning effect derives only from the cushioning qualities of the loosefill, rather than the compressability of the air within the bag and/or the elasticity of the bag. The cushioning product of that invention may also comprise a plurality of bags filled with loosefill packing material, with the bags being connected end-to-end in a string. In that case, a web of preformed and interconnected bags is provided, and loosefill packing material is inserted into the bags which are then sealed.
The invention of application Ser. No. 09/065,221 thus provides the cushioning qualities of loosefill, for example plastic or starch peanuts, yet without the attendant difficulties associated therewith. In addition, the preferred geometry of the bags of loosefill provide for easy insertion into a shipping box or carton as well as wrapping around the item to be shipped.
One limitation of the invention of application Ser. No. 09/065,221, however, is that the length of the cushioning product is not readily varied since the length of the cushioning product is dependent upon the length of the preformed interconnected bags which are purchased in web form and loaded onto the machine in a roll. It would be desirable to be able to vary the length of cushioning product produced without having to remove the existing roll of bags of one length and replacing that roll of bags with another roll of bags of the desired length.
Another feature of the invention of application Ser. No. 09/065,221 is the provision of loosefill for filling the bags to provide cushioning capability. In some applications it might be desirable to do away with the loosefill if an acceptable cushioning product can still be produced.
One attempt at eliminating the web of preformed and interconnected bags in forming a product containing bag has been made by Dibipack of Italy. The Dibipack machine uses a sheet of plastic film which is unrolled off of a roll, is formed into a cylindrical container, is filled with product and is then sealed. That machine comprises a frame, a plastic sheet supply assembly mounted on the frame, a forming assembly mounted on the frame downstream of the plastic sheet supply assembly which forms the plastic sheet into a tube with the lateral edges of the plastic sheet overlapping, a pulling assembly mounted on the frame downstream of the forming assembly which pulls the plastic sheet from the plastic sheet supply assembly to and over the forming assembly, a first heat sealing assembly mounted on the frame downstream of the forming assembly which heat seals the overlapping lateral edges of the tube together, and a second heat sealing assembly mounted on the frame downstream of the first heat sealing assembly which transversely heat seals the tube at each end of the longitudinal heat seal formed by the first heat sealing assembly. This machine is limited, however, in that the first heat sealing assembly is comprised of a fixed length heat sealing bar which is movable into and out of contact with the overlapping lateral edges of the tube to longitudinally heat seal the overlapping lateral edges. Thus, a user is limited to the length of bag capable of being produced on this machine to multiples of the length of this longitudinal heat sealing bar. Stated differently, this machine provides no capability of forming a desired length of bag other than in a length equal to the length of the longitudinal heat sealing bar or multiples thereof.

Cushioning product and machine and method for producing same


Pickering emulsions, which are finely disperse systems of the water-in-oil or oil-in-water type, comprising

The present invention relates to emulsifier-free finely disperse systems of the oil-in-water and water-in-oil type, preferably as cosmetic or dermatological preparations, in particular as cosmetic or dermatological light-protection preparations.
Emulsions are generally taken to mean heterogeneous systems which consist of two liquids which are immiscible or have only limited miscibility with one another, which are usually referred to as phases. In an emulsion, one of the two liquids is dispersed in the form of very fine droplets in the other liquid.
If the two liquids are water and oil and if oil droplets are finely dispersed in water, then this is an oil-in-water emulsion (O/W emulsion, e.g. milk). The basic character of an O/W emulsion is defined by the water. In a water-in-oil emulsion (W/O emulsion, e.g. butter), the principle is reversed, the basic character here being determined by the oil.
In order to achieve permanent dispersion of one liquid in another, emulsions in the traditional sense require the addition of an interface-active substance (emulsifier). Emulsifiers have an amphiphilic molecular structure, consisting of a polar (hydrophilic) and a nonpolar (lipophilic) molecular moiety, which are spatially separate from one another. In simple emulsions, finely disperse droplets of one phase, surrounded by an emulsifier shell, (water droplets in W/O emulsions or lipid vesicles in O/W emulsions) are present in the second phase. Emulsifiers lower the interfacial tension between the phases by positioning themselves at the interface between two liquids. At the phase boundary, they form oil/water interfacial films, which prevent irreversible coalescence of the droplets. Emulsions are frequently stabilized using emulsifier mixtures.
Traditional emulsifiers can, depending on their hydrophilic molecular moiety, be divided into ionic (anionic, cationic and amphoteric) and nonionic:
The most well-known example of an anionic emulsifier is soap, which is usually the term used for the water-soluble sodium or potassium salts of saturated or unsaturated higher fatty acids.
Important examples of cationic emulsifiers are quaternary ammonium compounds.
The hydrophilic molecular moiety of nonionic emulsifiers frequently consists of glycerol, polyglycerol, sorbitans, carbohydrates and polyoxyethylene glycols, and, in most cases, is linked to the lipophilic molecular moiety via ester and ether bonds. The lipophilic molecular moiety usually consists of fatty alcohols, fatty acids or isofatty acids.
By varying the structure and the size of the polar and nonpolar molecular moiety, the lipophilicity and hydrophilicity of emulsifiers can be varied within wide limits.
A decisive factor for the stability of an emulsion is the correct choice of emulsifiers. The characteristics of all substances present in the system are to be taken into consideration here. In the case of, for example, skincare emulsions, polar oil components and, for example, UV filters lead to instability. As well as the emulsifiers, therefore, other stabilizers are also used which, for example, increase the viscosity of the emulsion and/or act as protective colloid.
Emulsions are an important type of product in the field of cosmetic and/or dermatological preparations.
Cosmetic preparations are essentially used for skin care. The main aim of skin care in the cosmetics sense is to strengthen or rebuild the skin""s natural function as a barrier against environmental influences (e.g. dirt, chemicals, microorganisms) and against the loss of endogenous substances (e.g. water, natural fats, electrolytes). If this function becomes impaired, increased resorption of toxic or allergenic substances or attack by microorganisms may result, leading to toxic or allergic skin reactions.
Another aim of skin care is to compensate for the loss by the skin of lipids and water caused by daily washing. This is particularly important if the natural regeneration ability is inadequate. Furthermore, skincare products should protect against environmental influences, in particular against sun and wind, and delay skin ageing.
Medicinal topical compositions usually comprise one or more medicaments in an effective concentration. For the sake of simplicity, in order to distinguish clearly between cosmetic and medicinal use and corresponding products, reference is made to the legal provisions in the Federal Republic of Germany (e.g. Cosmetics Directive, Foods and Drugs Act).
The use of customary emulsifiers in cosmetic or dermatological preparations is in itself acceptable. Nevertheless, emulsifiers, like ultimately any chemical substance, may in certain circumstances cause allergic reactions or reactions based on oversensitivity of the user.
For example, it is known that certain light dermatoses are triggered by certain emulsifiers, but also by various fats and simultaneous exposure to sunlight. Such light dermatoses are also called xe2x80x9cMallorca acnexe2x80x9d. There has thus been no lack of attempts to reduce the amount of customary emulsifiers to a minimum, in the ideal case even to zero.
A reduction in the required amount of emulsifier can, for example, be achieved by taking advantage of the fact that very finely divided solid particles have an additional stabilizing action. The solid substance accumulates at the oil/water phase boundary in the form of a layer, as a result of which coalescence of the disperse phases is prevented. It is not the chemical properties of the solid particles which are of fundamental importance here, but the surface properties.
Around 1910, Pickering prepared paraffin/water emulsions which were stabilized merely by the addition of various solids, such as basic copper sulphate, basic iron sulphate or other metal sulphates. This type of emulsion is thus also referred to as a Pickering emulsion.
The original forms of Pickering emulsions initially surfaced, as it were, as undesired secondary effects in a variety of industrial processes, such as, for example, in secondary oil recovery, the extraction of bitumen from tar sand and other separation processes involving two immiscible liquids and fine, dispersed solid particles. These are generally W/O emulsions which are stabilized by mineral solids. Accordingly, investigation of corresponding systems, such as, for example, the oil/water/soot or oil/water/slate dust systems was initially the focus of research activity.
Basic experiments have shown that one characteristic of a Pickering emulsion is that the solid particles are arranged at the interface between the two liquid phases, where they form, as it were, a mechanical barrier against the combining of the liquid droplets.
It is a relatively new technical development to use Pickering emulsions as a base for cosmetic or dermatological preparations.
One way of achieving solids stabilization in the sense of a pickering emulsion in a cosmetic or dermatological preparation is, according to May-Alert (Pharmazie in unserer Zeit [Pharmacy in our time], Vol. 15, 1986, No. 1, 1-7) for example, to use emulsifier mixtures which comprise both anionic and cationic surfactants. Since mixing anionic and cationic surfactants always results in the precipitation of insoluble, electroneutral compounds, deliberate precipitation of these neutral surfactants in the oil/water interface makes it possible to achieve additional solids stabilization.
European Laid-open Specification 0 686 391, moreover, describes emulsions of the water-in-oil type which are free from surface-active substances and are stabilized only by solids. Stabilization is achieved here using spherical polyalkylsilsesquioxane particles which have a diameter of from 100 nm up to 20 xcexcm. These emulsions can be referred to as Pickering emulsions according to that mentioned above.
Pickering emulsions are stabilized by the use of suitable solids or pigments. However, Pickering emulsions of the prior art in general have the disadvantage that they only act unsatisfactorily against UV light, in particular against UV-A light, since pigments which are particularly suitable for the stabilization of this type of emulsion in general have an inadequate light-protection action.
The harmful action of the ultraviolet part of the solar radiation on the skin is generally known. Depending on its particular wavelength, the rays have various actions on the organ skin: the so-called UV-C radiation having a wavelength which is less than 290 nm is absorbed by the ozone layer in the earth""s atmosphere and therefore has no physiological importance. However, rays in the range between 290 nm and 320 nm, the so-called UV-B range, cause erythema, simple sunburn or even burns which are more or less severe. The narrow range around 308 nm is indicated as a maximum of the erythema activity of sunlight.
For a long time, it has been falsely assumed that the long-wave UV-A radiation having a wavelength between 320 nm and 400 nm only has a negligible biological action and that, accordingly, the UV-B rays are responsible for most light damage to the human skin. Since then, however, it has been confirmed by numerous studies that UV-A radiation is far more hazardous than UV-B radiation with respect to the triggering of photodynamic, especially phototoxic, reactions and chronic changes in the skin. The harmful effect of the UV-B radiation can also be further increased by UV-A radiation.
Preventive protection against UV radiation, for example by application of sunscreen filter substances in the form of a cosmetic or dermatological formulation to the skin, is therefore of fundamental importance. In particular, this also applies to formulations whose main purpose is not protection from sunlight, but which in general are applied to body parts which are customarily exposed to daylight, such as, for example, face- and bodycare preparations.
The object was therefore to remedy the disadvantages of the prior art. In particular, the intention was to provide cosmetic and dermatological bases for cosmetic and dermatological preparations which are characterized by good skin tolerability and high UV protection performance, in particular high UV-A protection performance.
In addition, an object of the present invention was to provide products with the widest possible variety of applications. For example, the intention was to provide bases for preparation forms such as cleansing emulsions, facecare and bodycare preparations, but also distinctly medicinal-pharmaceutical presentation forms, for example preparations against acne and other skin conditions.
It was surprising and in no way predictable by the person skilled in the art that Pickering emulsions, which are finely disperse systems of the water-in-oil or oil-in-water type, comprising
(1) an oil phase,
(2) a water phase,
(3) at least one type of microfine particles which
a) have an average particle size of less than 200 nm, which
b) display both hydrophilic and lipophilic properties, i.e. which have amphiphilic character, and are dispersible both in water and in oil and which
c) have optionally been coated on the surface,
(4) at least one type of non-amphiphilic metal oxide pigments and
(5) at most 0.5% by weight of one or more emulsifiers,
overcome the disadvantages of the prior art.
According to the invention, it is particularly advantageous if the preparations comprise significantly less than 0.5% by weight of one or more emulsifiers or are even entirely free from emulsifiers.
The preparations according to the invention are extremely satisfactory preparations in every respect which are particularly suitable to serve as a base for preparation forms having a variety of applications. Moreover, the preparations according to the invention are distinguished by an excellent skin tolerability.
It was furthermore surprising that preparations according to the invention have a higher efficacy against UV radiation, in particular a higher UV-A protection performance, than customary sunscreen formulations based on Pickering emulsions.
While preparations of the prior art having a pigment content of as little as 1% by weight produce a dull feel following their application to the skin, which increases further with higher pigment concentrations, the preparations according to the invention, surprisingly, do not leave a dry or dull impression on the skin, but on the contrary exhibit excellent cosmetic properties.
Although the prior art recognizes, in addition to Pickering emulsions, emulsifier-free, finely disperse cosmetic or dermatological preparations, which are generally referred to as hydrodispersions and which are dispersions of a liquid, semisolid or solid inner (discontinuous) lipid phase in an outer aqueous (continuous) phase, the prior art was unable to point the way to the present invention.
In the case of hydrodispersions of a liquid lipid phase in an external aqueous phase, the stability can be guaranteed, for example, by building up a gel structure in the aqueous phase, in which the lipid droplets are stably suspended.
German Laid-open Specification 44 25 268 describes stable finely disperse, emulsifier-free cosmetic or dermatological preparations of the oil-in-water type, which in addition to an oil and a water phase contain one or more thickeners from the group consisting of the acrylic acid polymers, polysaccharides and their alkyl ethers, where a lowering of interfacial tension may not be measurable for these thickeners.
Based on similar hydrodispersions, German Laid-open specification 43 03 983 discloses cosmetic or dermatological sunscreen formulations which are essentially free of emusifiers, inorganic micropigments which serve as UV filter substances being incorporated into the lipid phase of the hydrodispersion.
O/W Pickering emulsions within the meaning of the present invention, however, are obtainable by first dispersing amphiphilic particles according to the invention suitable for the preparation of O/W Pickering emulsions in the water phase and then combining the water phase with the fatty phase. W/O Pickering emulsions according to the invention, however, are obtainable by dispersing amphiphilic particles according to the invention suitable for the preparation of W/O Pickering emulsions in the fatty phase.
The non-amphiphilic metal oxide pigments selected from the group consisting of the oxides of titanium (TiO2), zinc (ZnO), iron (e.g. Fe2O3), zirconium (ZrO2), silicon (SiO2), manganese (e.g. MnO), aluminium (Al2O3), cerium (e.g. Ce2O3), mixed oxides of the corresponding metals and mixtures of such oxides are advantageous within the meaning of the present invention. Non-amphiphilic pigments based on TiO2 are particularly preferred.
The non-amphiphilic pigments are advantageously present according to the invention in hydrophobic form, i.e. in that they have a water-repellant treatment on the surface. This surface treatment can consist in providing the pigments with a thin hydrophobic layer according to processes known per se. Advantageous hydrophobic TiO2 pigments are obtainable, for example, from Degussa under the trade name T 805 (CAS-No. 100209-12-9, ex 13463-67-7).
A further advantageous hydrophobic coating consists of aluminium hydroxide or hydrated aluminium oxide (also: alumina, CAS No.: 1333-84-2), to which stearic acid is then applied. It is moreover also preferred to apply other hydrophobic coatings to metal oxide particles pretreated with alumina, such as, for example, polyorganosiloxanes. Advantageous non-amphiphilic titanium dioxide pigments coated with alumina and stearic acid are obtainable, for example, from Kemira under the trade name UV Titan M160.
According to the invention, advantageous dispersions are furthermore those of ultrafine titanium dioxide in oils or oily titanium dioxide suspensions, e.g. titanium dioxide in caprylic/capric triglyceride, a mixture of triglycerides mainly of caprylic acid [CH3(CH2)6COOH] and of capric acid [CH3(CH2)8COOH]. The oily titanium dioxide suspensions obtainable from Solaveil under the trade name Tioveil TG, for example, are preferred.
Within the meaning of the present invention, the non-amphiphilic metal oxide pigments are furthermore preferably selected from the group consisting of the hydrophilic or hydrophilically coated pigments. The surface treatment can consist in providing the pigments with a thin hydrophilic layer by processes known per se.
Aqueous dispersions of hydrophilic titanium oxide pigments, for example, which can also contain other constituents, e.g. preserving constituents, such as, for example, propylene glycol, are furthermore advantageous. The aqueous titanium dioxide suspensions obtainable from Solaveil under the trade name Tioveil AQ, for example, are preferred.
The total amount of non-amphiphilic metal oxide pigments, in particular hydrophobic micropigments in the finished cosmetic or dermatological preparations is advantageously chosen to be less than 20% by weight, preferably between 0.5 and 10.0% by weight, based on the total weight of the preparations.
It is also advantageous, although not obligatory, for the Pickering emulsions according to the invention to comprise auxiliaries which can additionally increase the stability of these preparations, for example substances (one or more) which are chosen from the group of waxes and/or oil thickeners, of hydrocolloids and of electrolytes.
It is also advantageous for the Pickering emulsions according to the invention to comprise auxiliaries which can contribute to reducing or preventing a dull or dry feel on the skin following their application, where it is possible that the main purpose of these substances is a different one. Preferably, these substances are, for example, chosen from the group of unsymmetrically substituted s-triazine derivatives, cyclodextrins, film formers and polymeric moisturizers, it being possible for these substances to be present either individually or in a mixture.
The cosmetic properties of the Pickering emulsions according to the invention can additionally, for example, be further improved by also using oils in the oil phase which have a viscosity of less than 30 mPa.s, in particular of less than 20 mPa.s (determined using a rheometer from Contraves (Rheomat 108E) at a shear gradient of 500/s and a temperature of 25xc2x0 C.).
Microfine amphiphilic particles:
The amphiphilic character of the microfine particles according to the invention is evident, for example, from the fact that they are dispersible both in water and in oil.
It is advantageous to choose the average particle diameter of the amphiphilic particles to be between 1 nm and 200 nm, particularly advantageously between 5 nm and 100 nm.
It is also advantageous to choose the concentration of all amphiphilic particles according to the invention to be greater than 0.1% by weight, particularly advantageously between 0.1% by weight and 30% by weight, based on the total weight of the preparations.
For the purposes of the present invention, advantageous particles are all amphiphilic particles which are suitable for stabilizing Pickering W/O emulsions or Pickering O/W emulsions. It is essentially insignificant for the present invention in which of the potentially naturally occurring modifications the particles are present.
To stabilize the Pickering emulsions, preference is given to using untreated, virtually pure pigment particles, for example those which can be used as dyes in the food industry. Examples of advantageous pigments are the zinc oxide pigments available from Merck which are available under the trade names Zinkoxid neutral from Haarmann and Reimer or NanoX from Harcros Chemical Group.
For the purposes of the present invention, Pickering emulsions are likewise advantageously stabilized by inorganic pigments which have been surface-treated (xe2x80x9ccoatedxe2x80x9d) to repel water, where at the same time the intention is to form or retain the amphiphilic character. This surface-treatment can, for example, consist in providing the pigments partially with a thin hydrophobic layer or else almost completely with an amphiphilic layer by processes known per se.
One such process, which is described below using titanium dioxide as an example, consists in, for example, producing the hydrophobic surface layer according to the following reaction
n TiO2+m (RO)3Sixe2x80x94Rxe2x80x2xe2x86x92n TiO2 (surf.).
n and m are arbitrary stoichiometric parameters, and R and Rxe2x80x2 are the desired organic radicals. Particularly advantageous are TiO2 pigments, for example those coated with aluminium stearate, available under the trade name MT 100 T from TAYCA.
A further advantageous coating of the inorganic pigments consists of dimethylpolysiloxane (also: dimethicone), a mixture of completely methylated, linear siloxane polymers which are terminally blocked with trimethylsiloxy units. For the purposes of the present invention, particularly advantageous pigments are zinc oxide pigments which are coated in this way.
Also advantageous is a coating of the amphiphilic pigments with a mixture of dimethylpolysiloxane, in particular dimethylpolysiloxane having an average chain length of from 200 to 350 dimethylsiloxane units, and silica gel, which is also referred to as simethicone. It is particularly advantageous if the amphiphilic pigments have been additionally coated with aluminium hydroxide or hydrated aluminium oxide (also: alumina, CAS No.: 1333-84-2). Particularly advantageous are titanium dioxides which have been coated with simethicone and alumina, it being possible for the coating to also comprise water. One example thereof is the titanium dioxide available under the trade name Eusolex T2000 from Merck.
For the purposes of the present invention it is also advantageous to use a mixture of different pigment types either within a crystal, for example as mixed iron oxide, or by combination of two or more pigment types within a preparation.
The Pickering emulsions are also preferably stabilized by boron nitride particles, for example by the boron nitrides listed below:
It is advantageous to choose the average particle diameter of the boron nitride particles used to be less than 20 xcexcm, particularly advantageously less than 15 xcexcm. For the purposes of the present invention, Pickering emulsions are likewise advantageously stabilized by boron nitride particles which have been surface-treated (xe2x80x9ccoatedxe2x80x9d) to repel water, where at the same time the intention is to form or retain the amphiphilic character.
An advantageous coating of the boron nitride particles consists of dimethylpolysiloxane (dimethicone). The boron nitride particles treated with dimethicone and available from Carborundum under the trade name Trxc3xa8s BN(copyright) UHP 1106 are advantageous, for example.
Also advantageous is a coating of the boron nitride particles with polymethylhydrogensiloxane, a linear polysiloxane which is also referred to as methicone. Advantageous boron nitride particles treated with methicone are, for example, those available from Carborundum under the trade name Trxc3xa8s BN(copyright) UHP 1107.
It is also advantageous to stabilize the Pickering emulsions according to the invention using microfine polymer particles.
For the purposes of the present invention, examples of advantageous microfine polymer particles are polycarbonates, polyethers, polyethylenes, polypropylenes, polyvinyl chloride, polystyrene, polyamides, polyacrylates and the like.
Advantageous according to the invention are, for example, microfine polyamide particles which are available under the trade name SP-500 from TORAY. Also advantageous are polyamide 6 (also: nylon 6) and polyamide 12 (also: nylon 12) particles. Polyamide 6 is the polyamide formed from xcex5-aminocaproic acid (6-aminohexanoic acid) or xcex5-caprolactam [poly(xcex5-caprolactam)], and polyamide 12 is a poly(xcex5-laurolactam) from xcex5-laurolactam. For the purposes of the present invention, Orgasol(copyright) 1002 (polyamide 6) and Orgasol(copyright) 2002 (polyamide 12) from ELF ATOCHEM, for example, are advantageous.
Other advantageous polymer particles are microfine polymethacrylates. Such particles are available, for example, under the trade name POLYTRAP(copyright) from DOW CHEMICAL.
It is particularly advantageous, but not obligatory, if the microfine polymer particles used have been surface-coated. This surface-treatment can consist in providing the pigments with a thin hydrophilic layer by processes known per se. Advantageous coatings consist, for example, of TiO2, ZrO2 or also other polymers, such as, for example, polymethyl methacrylate.
Particularly advantageous microfine polymer particles for the purposes of the present invention are also obtainable by the process, described in U.S. Pat. No. 4,898,913, for the hydrophilic coating of hydrophobic polymer particles.
It is advantageous to choose the average particle diameter of the microfine polymer particles used to be less than 100 xcexcm, particularly advantageously less than 50 xcexcm. In this connection, it is essentially insignificant in which form (platelets, rods, spherules, etc.) the polymer particles used are present.
In addition, it is advantageous to stabilize the Pickering emulsions according to the invention using modified polysaccharides.
For the purposes of the present invention, modified polysaccharides are, for example, obtainable by reaction of starch with mono-, bi- or polyfunctional reagents or oxidizing agents in reactions which proceed in a largely polymer-analogous manner.
Such reactions are based essentially on modifications of the hydroxyl groups of the polyglucans by etherification, esterification or selective oxidation. This produces, for example, so-called starch ethers and starch esters of the general structural formula
in which R can, for example, be a hydrogen and/or an alkyl and/or an aralkyl radical (in the case of starch ethers) or a hydrogen and/or an organic and/or inorganic acid radical (in the case of starch esters). Starch ethers and starch esters are advantageous, modified polysaccharides for the purposes of the present invention.
Particularly advantageous starch ethers are, for example, those which are obtainable by etherification of starch with tetramethylolacetylenediurea and which are referred to as non-mucilaginous starch (nonswelling starch).
Also particularly advantageous are starch esters and salts thereof, for example the sodium and/or aluminium salts of half-esters of starch which have low degrees of substitution, in particular sodium starch n-octenyl succinate of the structural formula (II) in which R is characterized by the following structure
and which is available, for example, under the trade name Amiogum(copyright) 23 from CERESTAR, and aluminium starch octenyl succinates, in particular those available under the trade names Dry Flo(copyright) Elite LL and Dry Flo(copyright) PC from CERESTAR.
It is advantageous to choose the average particle diameter of the modified polysaccharide used to be less than 20 xcexcm, particularly advantageously less than 15 xcexcm.
The list of given modified polysaccharides which are able to stabilize Pickering emulsions according to the invention is of course not intended to be limiting. For the purposes of the present invention, modified polysaccharides are obtainable in a large number of ways known per se, both of a chemical and a physical nature.
The abovementioned amphiphilic particles are outstandingly suitable both for the stabilization of W/O Pickering emulsions and for the stabilization of O/W Pickering emulsions. Microfine particles according to the invention are mentioned below which advantageously particularly stabilize one of the two emulsion types W/O or O/W.
W/O Pickering emulsions:
The water phase proportion in the W/O Pickering emulsions according to the invention is preferably chosen from the range of from 0.5 to 75% by weight, based on the total weight of the formulations.
Also particularly advantageous for stabilizing W/O Pickering emulsions are magnesium silicates (also: talc), for example those available under the trade name Talkum Micron from Grolmann.
O/W Pickering emulsions
The fatty phase proportion of the O/W Pickering emulsions according to the invention is preferably chosen from the range of 0.5 to 75% by weight, based on the total weight of the formulations.
Particularly advantageous for the stabilization of O/W Pickering emulsions within the meaning of the present invention are also untreated, almost pure pigment particles, for example titanium dioxide pigments, in particular those which are obtainable from Kronos Titan under the trade name KRONOS(copyright) 1171 (TiO2).
O/W Pickering emulsions within the meaning of the present invention are furthermore particularly advantageously stabilized by amphiphilic metal oxide particles which are coated with aluminium hydroxide and/or silicon dioxide. Advantageous embodiments are, for example, titanium dioxide particles which are obtainable from Merck under the name EUSOLEX(copyright) TA.
It is also advantageous, but not obligatory, to combine the amphiphilic particles according to the invention with other particles which may or may not also be able to contribute to the stabilization of the Pickering emulsions.
Such particles are, for example, titanium dioxide pigments which have been coated with octylsilanol, and/or silicon dioxide particles which have been surface-treated to repel water. Suitable silicon dioxide particles are, for example, spherical polyalkylsilsesquioxane particles, as mentioned in European Laid-open Specification 0 686 391. Such polyalkylsilsesquioxane particles are available, for example, under the trade names Aerosil R972 and Aerosil 200V from Degussa. Suitable titanium dioxide particles are available under the trade name T805, also from Degussa.
The Pickering emulsions according to the invention can be used as bases for cosmetic or dermatological formulations. These can have the customary composition and be used, for example, for the treatment and care of the skin, as lipcare products, as make-up products or make-up remover products in decorative cosmetics or as light protection preparations. For use, the cosmetic and dermatological preparations according to the invention are applied to the skin in sufficient amounts in the manner customary for cosmetics.
Accordingly, for the purposes of the present invention, cosmetic or topical dermatological compositions may, depending on their structure, be used, for example, as skin-protection creams, cleansing milks, sunscreen lotions, nourishing creams, day creams or night creams, etc. In some instances, it is possible and advantageous to use the compositions according to the invention as bases for pharmaceutical formulations.
The cosmetic and dermatological preparations according to the invention can comprise cosmetic auxiliaries, as are customarily used in such preparations, e.g. preservatives, bactericides, perfumes, antifoams, dyes, pigments which have a colouring effect, thickeners, emollients, moisturizers and/or humectants, fats, oils, waxes and other customary constituents of a cosmetic or dermatological formulation, such as alcohols, polyols, polymers, foam stabilizers, electrolytes, organic solvents or silicone derivatives.
Pickering emulsions according to the invention may also contain thickeners to improve the tactile properties of the emulsion.
In particular, the Pickering emulsions according to the invention may also comprise antioxidants. According to the invention, favourable antioxidants which can be used are any antioxidants suitable or conventional for cosmetic and/or dermatological applications.
The antioxidants are advantageously chosen from the group consisting of amino acids (e.g. glycine, histidine, tyrosine, tryptophan) and derivatives thereof, imidazoles, (e.g. urocanic acid) and derivatives thereof, peptides, such as D,L-carnosine, D-carnosine, L-carnosine and derivatives thereof (e.g. anserine), carotenoids, carotenes (e.g. xcex1-carotene, xcex2-carotene, lycopene) and derivatives thereof, chlorogenic acid and derivatives thereof, lipoic acid and derivatives thereof (e.g. dihydrolipoic acid), aurothioglucose, propylthiouracil and other thiols (e.g. thioredoxin, glutathione, cysteine, cystine, cystamine and the glycosyl, N-acetyl, methyl, ethyl, propyl, amyl, butyl and lauryl, palmitoyl, oleyl, xcex3-linoleyl, cholesteryl and glyceryl esters thereof) and the salts thereof, dilauryl thiodipropionate, distearyl thiodipropionate, thiodipropionic acid and derivatives thereof (esters, ethers, peptides, lipids, nucleotides, nucleosides and salts) and sulphoximine compounds (e.g. buthionine sulphoximines, homocysteine sulphoximine, buthionine sulphones, penta-, hexa-, hepta-thionine sulphoximine) in very low tolerated doses (e.g. pmol to xcexcmol/kg), and also (metal) chelating agents (e.g. xcex1-hydroxy fatty acids, palmitic acid, phytic acid, lactoferrin), xcex1-hydroxy acids (e.g. citric acid, lactic acid, malic acid), humic acid, bile acid, bile extracts, bilirubin, biliverdin, EDTA, EGTA and derivatives thereof, unsaturated fatty acids and derivatives thereof (e.g. xcex3-linolenic acid, linoleic acid, oleic acid), folic acid and derivatives thereof, ubiquinone and ubiquinol and derivatives thereof, vitamin C and derivatives (e.g. ascorbyl palmitate, Mg ascorbyl phosphate, ascorbyl acetate), tocopherols and derivatives (e.g. vitamin E acetate), vitamin A and derivatives (vitamin A palmitate) and coniferyl benzoate of benzoin resin, rutinic acid and derivatives thereof, xcex1-glycosylrutin, ferulic acid, furfurylideneglucitol, carnosine, butylated hydroxytoluene, butylated hydroxyanisole, nordihydroguaiac acid, nordihydroguaiaretic acid, trihydroxybutyrophenone, uric acid and derivatives thereof, mannose and derivatives thereof, zinc and derivatives thereof (e.g. ZnO, ZnSO4), selenium and its derivatives (e.g. selenomethionine), stilbenes and their derivatives (e.g. stilbene oxide, trans-stilbene oxide), and the derivatives (salts, esters, ethers, sugars, nucleotides, nucleosides, peptides and lipids) of said active substances which are suitable according to the invention.
The amount of the abovementioned antioxidants (one or more compounds) in the preparations according to the invention is preferably from 0.001 to 30% by weight, particularly preferably from 0.05-20% by weight, in particular 1-10% by weight, based on the total weight of the preparation.
If vitamin E and/or derivatives thereof are used as the antioxidant or antioxidants, their respective concentrations are advantageously chosen from the range of 0.001-10% by weight, based on the total weight of the formulation.
If vitamin A or vitamin A derivatives or carotenes or derivatives thereof are used as the antioxidant or antioxidants, their respective concentrations are advantageously chosen from the range of 0.001-10% by weight, based on the total weight of the formulation.
Cosmetic and dermatological preparations which are in the form of a sunscreen are also favourable. These preferably comprise at least one UV-A filter substance and/or at least one UV-B filter substance.
For the purposes of the present invention, it is, however, also advantageous to provide such cosmetic and dermatological preparations whose main purpose is not protection against sunlight, but which nevertheless additionally comprise substances which protect against UV. For example, UV-A and UV-B filter substances are commonly incorporated into day creams.
The preparations according to the invention can advantageously comprise other substances which absorb UV radiation in the UV-B range, the total amount of filter substances being, for example, from 0.1% by weight to 30% by weight, preferably from 0.5 to 10% by weight, in particular from 1.0 to 6.0% by weight, based on the total weight of the preparations, in order to provide cosmetic preparations which protect the hair and/or the skin from the whole of ultraviolet radiation.
If the emulsions according to the invention contain UV-B filter substances, these can be oil-soluble or water-soluble. Advantageous oil-soluble UV-B filters according to the invention are, for example:
3-benzylidenecamphor derivatives, preferably 3-(4-methylbenzylidene)camphor, 3-benzylidenecamphor;
4-aminobenzoic acid derivatives, preferably 2-ethylhexyl 4-dimethylaminobenzoate, amyl 4-dimethylaminobenzoate;
esters of cinnamic acid, preferably 2-ethylhexyl 4-methoxycinnamate, isopentyl 4-methoxycinnamate;
esters of salicylic acid, preferably 2-ethylhexyl salicylate, 4-isopropylbenzyl salicylate, homomenthyl salicylate,
derivatives of benzophenone, preferably 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-4xe2x80x2-methylbenzophenone, 2,2xe2x80x2-dihydroxy-4-methoxybenzophenone;
esters of benzalmalonic acid, preferably di(2-ethylhexyl) 4-methoxybenzalmalonate,
triazine derivatives which are symmetrical with respect to the C3 axis of the triazine parent structure, preferably tris(2-ethylhexyl) 4,4xe2x80x2,4xe2x80x3-(1,3,5-triazine-2,4,6-triyltriimino)trisbenzoate,
benzotriazole derivatives, preferably 2,2xe2x80x2-methylenebis(6-(2H-benzotriazol-2-yl)-4-(1,1,3,3,-tetramethylbutyl)phenol)
and UV filters bonded to polymers.
Examples of advantageous water-soluble UV-B filters are:
salts of 2-phenylbenzimidazol-5-sulphonic acid, such as its sodium, potassium or triethanolammonium salts, and the sulphonic acid itself;
sulphonic acid derivatives of benzophenones, preferably 2-hydroxy-4-methoxybenzophenone-5-sulphonic acid and salts thereof;
sulphonic acid derivates of 3-benzylidenecamphor, such as, for example, 4-(2-oxo-3-bomylidenemethyl)benzenesulphonic acid, 2-methyl-5-(2-oxo-3-bornylidene-methyl)sulphonic acid and salts thereof.
The list of UV-B filters mentioned which can be used in the Pickering emulsions according to the invention should, of course, be non-limiting.
It can also be advantageous to use other UV-A filters which hitherto have customarily been contained in cosmetic preparations in Pickering emulsions according to the invention. These substances are preferably derivatives of dibenzoylmethane, in particular 1-(4xe2x80x2-tert-butylphenyl)-3-(4xe2x80x2-methoxyphenyl)propane-1,3-dione and 1-phenyl-3-(4xe2x80x2-isopropylphenyl)propane-1,3-dione.
Other advantageous UV-A filter substances are phenylene-1,4-bis(2-benzimidazyl)-3,3xe2x80x2-5,5xe2x80x2-tetrasulphonic acid:
and its salts, particularly the corresponding sodium, potassium or triethanolammonium salts, in particular the bis-sodium salt of phenylene-1,4-bis(2-benzimidazyl)-3,3xe2x80x2-5,5xe2x80x2-tetrasulphonic acid:
and 1,4-di(2-oxo-10-sulfo-3-bornylidenemethyl)benzene and salts thereof (particularly the corresponding 10-sulfato compounds, in particular the corresponding sodium, potassium or triethanolammonium salt), which is also referred to as benzene-1,4-di(2-oxo-3-bornylidenemethyl-10-sulphonic acid) and is characterized by the following structure:
Preparations which contain other UV-A filters are also a subject of the invention. The amounts used for the UV-B combination can be employed.
The examples below serve to illustrate the present invention without limiting it. The numerical values in the examples are percentages by weight, based on the total weight of the respective preparations.

Emulsifier-free finely disperse systems of the oil-in-water and water-in-oil type

Abstract: (1) an oil phase which contains a wax and/or an oil thickener,

Abstract: (2) a water phase,

Abstract: (5) at most 0.5% by weight of one or more emulsifiers.


A device for loading and unloading a tool into/from the tool magazine of a machine-tool or the like comprises a door, which separates the area of the tool magazine from an external protected area, and a tool-bearing slide, which can be displaced between a backed-off position outside the door and an advanced position inside the door and close to the tool magazine. The slide is connected to the door by a mechanical transmission in such a way that a movement of advance of the slide causes a simultaneous movement of opening of the door, and a movement of backing off of the slide causes a simultaneous movement of closing of the door.

The present invention relates to any type of machine-tool, machining station or centre or the like equipped with a tool magazine, in which a machining head is able to be brought up to a tool magazine for carrying out an automatic tool change in the course of a machining cycle. In machines of the type referred to above, the tool magazine, which is, for instance, built in the form of a rotary wheel carrying along its periphery a plurality of tool-bearing seats, is periodically supplied with new tools as replacements for tools that have previously been used, for example, on account of failure or wear, or also following upon the need to change the type of machining operation to be carried out. According to traditional techniques, the operation of replacing one or more tools in the corresponding positions in the tool magazine is performed manually. However, this operation is frequently somewhat inconvenient, on account of the limited spaces available around the magazine and also entails safety problems for the operator. There is, moreover, the problem of installing a new tool in a correct angular position in the magazine, this constituting a further difficulty in carrying out the tool-change operation.
The purpose of the present invention is to overcome the aforesaid drawbacks by enabling loading of a new tool into the tool magazine or unloading of a tool from the magazine with extremely simple, easy and fast operations and with total safety of the operator.
With a view to achieving the above purpose, the subject of the invention is a device for loading and unloading tools into/from the tool magazine of a machine-tool or the like, characterized in that it comprises:
a protection wall, which separates the tool magazine from an external protected area;
a door provided on said protection wall for access to the tool magazine;
a tool-bearing slide, having a tool-bearing support designed to receive a tool to be loaded into the magazine or to be unloaded from the magazine, said slide being slidably mounted on a supporting structure outside the protection wall between an advanced position, in which the tool-bearing support is in a position corresponding to the magazine for loading or unloading of a tool, and a backed-off position, in which the tool-bearing support is in the protected area outside the protection wall for loading or unloading of a tool,
in which said door is connected by a mechanical transmission to said slide in such a way that a movement of the slide from its backed-off position to its advanced position, and vice versa, produces a simultaneous movement of the access door from its closed position to its open position, and vice versa.
Thanks to the device according to the invention, the operator always remains at a distance from the area of the tool magazine, thus guaranteeing his complete safety. At the same time, the operation of loading and unloading a tool into/from the tool magazine is extremely easy and rapid. In the case where it is necessary to load a new tool into the magazine, the operator simply has to position the new tool on the tool-bearing support of the slide of the device. The tool is able to control (manually, in the case of the preferred embodiment, which will be described in what follows) an advance of the slide from its backed-off position to its advanced position. Following upon this movement of advance, the access door to the tool magazine opens automatically, and the tool-bearing support reaches a position corresponding to the position of the tool magazine, in which the new tool is to be loaded. The actual operation of loading and unloading can be carried out in any known way. For instance, according to a technique in itself known, each position of the tool magazine can be equipped with an elastic device for picking up the tool, so that, when the slide reaches its advanced position, the tool carried by it engages, in snap fashion, the pick-up device in the desired position of the magazine, after which a backing-off of the slide causes disengagement of the tool from the tool-bearing support of the slide itself, which in turn can be equipped with a device for uncoupleable connection of any type. When the slide backs off, the door closes again, thus guaranteeing separation of the areas of the tool magazine from the external protected area. Likewise, should it be necessary to carry out unloading of a tool from the magazine, the slide is brought into its advanced position, with the tool-bearing support of the slide initially empty, until snap-like engagement of the tool to be unloaded from the magazine into the gripping device carried by the slide is obtained. Following upon an activation of a pick-up device carried by the slide, the next backing-off of the slide causes disengagement of the tool from the magazine and its conveyance outside the magazine-access door, which simultaneously re-closes upon the backing-off movement of the slide.
According to a preferred embodiment, the aforesaid door has two panels, which can slide away from and up to one another in a direction transverse to the direction of movement of the slide. Once again in the case of this embodiment, the two panels are connected in an articulated way to two arms, set outside the protection wall, which have their opposite ends articulated to said supporting structure so as to be mobile between a first closed position and a second open position corresponding to the closed and open conditions of the door, said slide having engagement members co-operating with guide means arranged on the aforesaid two arms in such a way that a displacement of the slide between the backed-off position and the advanced position causes a corresponding displacement of the panels of the door between the closed condition and the open condition. Once again in the case of the preferred embodiment, the aforesaid guide means consist of a slit made in each of the two arms, within which a pin carried by the slide is engaged in a slidable way. Preferably, the slide includes a cross member carrying, at its ends, the aforesaid pins engaged in the guide slits of the two articulated arms.
According to a further characteristic, the tool-bearing support is provided with sensor means for detecting the presence of the tool, and there are further provided sensors designed to detect the operative position of the slide. The signals of said sensor means are sent to an electronic control unit which guarantees proper operation of the device, in synchronization with the operating cycle of the machine-tool, the operative position of the tool magazine being taken into account.

Device for loading and unloading tools into/from the tool magazine of a machine-tool or the like


A compensation system for calibrating an amplifier having a compensation input including a sigma delta converter, a counter, a memory, adjust logic, a DAC, a pair of compensation capacitors, and a pair of current to voltage (I/V) converters. The converter converts an offset voltage to a bit stream. The counter stores a sum value indicative of the output offset. The memory stores a digital bias value. The adjust logic determines an adjust value based on the sum value and adjusts the stored digital bias value based on the adjust value. The DAC converts the digital bias value to a differential bias current. The compensation capacitors apply a compensation voltage to a compensation input of the amplifier. The I/V converters charge the compensation capacitors using the differential bias current. The adjust logic may use upper and lower thresholds and adjust the digital bias value by one LSB for each compensation cycle.

The present invention relates to amplifier calibration, and more particularly to DC compensation for amplifiers including transparent calibration during operation of a circuit using the amplifiers.
Many electronic functions employ preamplifiers to amplify signals for various purposes. The present disclosure, for example, describes an analog to digital converter (ADC) that employs a stack of preamplifiers to amplify reference and/or interpolated voltages for purposes of comparison and digital conversion. It is noted that the present invention is not limited to ADC applications but may be applied to any application in which preamplifiers are employed and in which it is desired to maintain a requisite accuracy level. The terms xe2x80x9camplifierxe2x80x9d and xe2x80x9cpreamplifierxe2x80x9d are used interchangeable herein depending on manner of use in a circuit. The desired level of linearity, accuracy and resolution of the particular ADC described herein is relatively high and requires 14-bit resolution of the output digital values. The level of accuracy necessary for the preamplifiers depends upon their intended use within the ADC. The ADC described herein employs several preamplifier arrays in stages at the front end during initial conversion in which the results are used throughout the conversion process. For example, between the first and second stages, a selected portion of a sequential series of reference voltages from a main reference ladder are applied as first inputs to an array of preamplifiers, where the second inputs of each preamplifier is the sampled analog signal. In this manner, it is desired that the first and second preamplifier arrays maintain better than 14-bit accuracy.
Each preamplifier inherently generates a DC offset voltage that is amplified and added to the output voltage of the amplifier thereby introducing a significant amount of error. A DC compensation input is provided for each preamplifier whose inputs have a capacitor that can be charged with a bias voltage. For differential configurations, a pair of compensation inputs are provided to compensate a differential input. Several problems exist for designers attempting to achieve relatively high levels of accuracy and performance by providing the appropriate amount of DC compensation for each preamplifier. The output offset is difficult to measure while the preamplifiers are operating in accordance with the normal circuit function. It is also difficult to accurately measure output offsets given the limitations of the underlying substrate. The measurement problem is aggravated by the presence of noise and interference that may skew measurements and lead to erroneous results.
The ADC is intended to be incorporated into a monolithic unit on one substrate of an integrated circuit (IC) or chip. The overall passive component match for most silicon processes is 0.1% in accuracy. This translates into overall accuracy of approximately 10 bits. Only a slight improvement is possible by careful optimization and use of dummy components in the layout of the passives. Sometimes, statistical matching using arrays of passives can yield up to an order of magnitude improvement in the overall accuracy.
Correction and calibration techniques are known to improve the resolution, such as laser trimming or fuse blowing. Such post-processing techniques, however, must be performed on a part-by-part basis thereby unduly complicating and increasing cost of the manufacturing process. Also, such post-processing techniques operate under fixed conditions and do not correct for inaccuracies or changes due to temperature, aging and/or operating conditions. Integrated calibration techniques are also known and usually operate to measure error at the backend and apply a correction factor. Such calibration techniques are limited by quantization and usually limit correction to one-half bit of resolution of the converter itself. Also, the calibration techniques are incorporated in silicon and thus subject to the same limitations of the target circuitry.
It is desired to provide calibration for amplifiers (including those used as preamplifiers) that is not limited by the underlying substrate, that does not interfere with or overly complicate the manufacturing process, that operates transparently in the background and that corrects for any potential inaccuracies that may arise during normal operation.
A compensation system according to an embodiment of the present invention transparently calibrates at least one amplifier of an array of amplifiers during operation of a circuit employing the amplifier array. Each amplifier has a compensation input for receiving a compensation bias intended to minimize its output offset. The compensation system includes first and second redundant amplifiers coupled on either side of the amplifier array, an interpolative resistive ladder, a measurement circuit, a switching circuit, a compensation circuit, and a control circuit. The redundant amplifiers each have inputs coupled to inputs of a corresponding amplifier on a corresponding side of the amplifier array. The interpolative resistive ladder is coupled between the outputs of the redundant amplifiers and across the outputs of the amplifier array. The measurement circuit measures an output offset of a coupled amplifier. The switching circuit disconnects inputs and outputs of an amplifier of the amplifier array from the circuit and connects the inputs of the disconnected amplifier to a common mode voltage and connects the outputs of the disconnected amplifier to the measurement circuit to place the disconnected amplifier under calibration. The compensation circuit applies a compensation bias to the compensation input of an amplifier under calibration and adjusts the compensation bias in an attempt to reduce a measured output offset of the amplifier under calibration. The control circuit controls the calibration process.
The measurement circuit may include a sigma delta converter, a counter and adjust logic. The sigma delta converter converts an output offset into a bit stream indicative of the output offset. The counter receives the bit stream from the sigma delta converter and stores a sum value indicative of the output offset. The adjust logic determines an adjust value based on the sum value.
The compensation circuit may include a memory that stores a digital bias value and a converter that converts the stored digital bias value to a bias voltage and that applies the bias voltage to the compensation input of the amplifier under calibration. The adjust logic is configured to adjust the stored digital bias value for an amplifier under calibration. The adjust logic may include digital compare logic that compares the sum value with upper and lower thresholds, where the adjust logic adjusts the stored digital bias value only if a threshold is reached. The adjust logic may further be configured to adjust the digital bias value only by one least significant bit (LSB) at a time for each compensation cycle. This technique avoids large swings at the correction node if an erroneous decision is made by the calibration loop.
The converter may include a pair of compensation capacitors, a digital to analog converter (DAC) and a current to voltage converter. The compensation capacitors collectively apply a differential compensation voltage to a differential input of the amplifier under calibration. The DAC converts the digital bias value into a differential bias current. The current to voltage converter converts the differential bias current into a differential pair of voltages and charges the pair of compensation capacitors with the differential pair of voltages. Charging switches may be provided and controlled by the control logic to selectively recharge the pair of compensation capacitors using the differential bias current.
The memory may store a plurality of digital bias values, each for a corresponding one of the amplifiers of the amplifier array. The control circuit may conduct calibration for each amplifier of the amplifier array one at a time. For each amplifier, the control circuit controls the switching array to place an amplifier under calibration, controls the measurement circuit to measure an output offset of each amplifier under calibration and controls the compensation circuit to apply compensation to each amplifier under calibration. The control logic selectively addresses the appropriate digital bias value from the memory.
A method of transparently calibrating at least one amplifier of an array of amplifiers during operation of a circuit employing the amplifier array according to an embodiment of the present invention includes providing a pair of redundant amplifiers on either side of the amplifier array, providing an interpolative resistive ladder across the outputs of the amplifier array and outputs of the redundant amplifiers, removing inputs and outputs of an amplifier of the amplifier array from the circuit, shorting the inputs of the removed amplifier to a common mode voltage, measuring an output offset of the removed amplifier, adjusting a corresponding compensation bias applied at the compensation input of the removed amplifier in an attempt to reduce the measured output offset, and re-connecting the inputs and outputs of the amplifier to the circuit. The method may include sequentially calibrating each of the amplifiers of the amplifier array by repeating the removing, shorting, measuring, adjusting, and re-connecting for each amplifier.
The method may include storing a digital bias value, converting the digital bias value to the compensation bias, measuring an output offset of the removed amplifier using a sigma delta converter and applying an output bitstream of the sigma delta converter to a counter, and adjusting the digital bias value based on a value in the counter. The method may include storing a plurality of digital bias values, each corresponding to one amplifier of the amplifier array, and selecting a digital bias value corresponding to the removed amplifier being calibrated.
The method may further include comparing the value in the counter with predetermined upper and lower thresholds and adjusting the digital bias value only if either threshold is reached. The adjusting of the digital bias value may include incrementing or decrementing the digital bias value by one LSB at a time.
The method may further include providing a bias capacitor at the compensation input of each amplifier, and converting the digital bias value to a bias voltage for storage on a bias capacitor of a removed amplifier. A pair of bias capacitors may be provided at a corresponding differential pair of compensation inputs of each amplifier. If so, the method may include converting the digital bias value to a differential bias current and charging the pair of bias capacitors using the differential bias current.
A compensation system for calibrating an amplifier having a compensation input according to an embodiment of the present invention includes a sigma delta converter, a counter, a memory, adjust logic, a DAC, a pair of compensation capacitors, and a pair of current to voltage converters. The sigma delta converter converts an offset voltage to a bit stream indicative of the offset voltage. The counter creates a sum value indicative of the output offset. The memory stores a digital bias value. The adjust logic determines an adjust value based on the sum value and is configured to adjust the stored digital bias value based on the adjust value. The DAC converts the digital bias value to a differential bias current. The current to voltage converters turn the differential bias current into a differential output voltage which charges the compensation capacitors. The adjust logic may include digital compare logic that compares the sum value with upper and lower thresholds and that adjusts the stored digital bias value only if a threshold is reached or exceeded. The adjust logic may further be configured to adjust the digital bias value only by one LSB for each compensation cycle.

System and method of DC calibration of amplifiers