An adjustable utility light having a body section, two independently movable hooks, a pivoting lamp section having fluorescent tubes and/or light emitting diodes, a component retention tray, at least one keyhole mounting slot, and a movable reflector, wherein the pivoting lamp section and the movable reflector pivot about the same pivot axis.

1. Technical Field of the Invention
The present invention relates generally to utility lights, and more specifically to an adjustable task, 'trouble', drop or work light with multiple suspension or mounting options, wherein a lamp section pivots open up to slightly greater than 90 degrees (or up to 180 degrees in an alternate embodiment) exposing the lamp section from one or both sides when in use, thereby providing the ability to aim the light in a selected direction or at a selected area. A pivoting reflector may selectively be utilized to augment and direct light where desired.
2. Description of Related Art
Task or utility lights are typically utilized to extend light into a non-illuminated or poorly illuminated location, often remote from a power source, such as, under an automobile during service, in attic areas, and in exterior locations for use at night. Such lights typically undergo severe handling and are often utilized in close quarters. Often, the direction of illumination of the utility light is limited to the positioning of the utility light itself, which can be quite awkward and inefficient in a tightly confined workspace. Those who have used utility lights will quickly recognize that because of the frequently changing location of the utility light, finding a location for hanging and correctly orienting the light is often difficult. Further, those skilled in the art will readily appreciate that different levels of illumination are required for different work locations.
While previous lights existed with incandescent sources, more commonly fluorescent lighting is used. However, both incandescent light sources and fluorescent light sources comprise glass bulbs or tubes that are subject to breakage and which thus must be protected, typically by a rigid metal screen shell (that casts shadows) or where unimpeded radiation is required, by a clear plastic lens that adds complexity and weight to the lighting device, and also reduces light by about 10%.
One previous device provides dual bulbs to increase light and has hooks at both ends for hanging the task light. However, once installed (hanging by its hooks or lying on a flat surface), the lamp lacks a facility for further adjustment. Further, hooks that protrude can be bent, broken or can snag on other objects during use and/or transport.
Another prior task light has a hook at the top and allows for pivoting forward of the bulb section by up to 90 degrees for positioning of the lamp towards the work site. While this provides some flexibility, it does not adequately provide the ability to illuminate different areas unless the device is removed from its support. Further, because the pivoting movement is part of the bulb removal operation, the bulb is exposed when pivoted, thereby rendering the bulb susceptible to damage and the user to potential injury from broken glass and/or burns.
Yet another prior utility flashlight provides a hook at the top thereof, but, while portable, requires a heavy battery base for operation. This device pivots approximately 90 degrees from its base and cannot be operated when removed from its base. This device further provides a snap-on reflector that facilitates directing of light; however, this reflector is a separate component that can become misplaced and thus unavailable. Once disposed on the lamp, the reflector must be completely removed when not needed.
Therefore, it is readily apparent that there is a need for an adjustable utility light and methods of use thereof, wherein the adjustable utility light comprises a pivotal lamp portion that can provide full 90 degree plus (or up to 180 degrees in an alternate embodiment) maneuverability for aiming of light beams once the utility light is in place, along with a reflector that can be selectively positioned to provide full or partial reflection, or can be pivoted away when not in use. The utility light should be capable of securing to a variety of fixed locations. Further, the device should be robust and capable of being manufactured utilizing different light sources.

Adjustable utility light and methods of use thereof


A method of producing a sintered multi-layer ceramic body used for ceramic parts of various electronic devices such as multi-layer substrates for LSI packaging and highly functional structural materials and by applying a pressure and/or constraining force to an outermost surface of the laminate. The method is featured by the shape of the surfaces to which a pressure and/or constraining force are not applied, ranges of the pressure and/or the constraining force, and the like.

1. Field of the Invention
The present invention relates to a sintered multi-layer ceramic body and a method for making the same and in particular, to a sintered multi-layer ceramic body which can assure high dimensional accuracy and high reliability and a method for making the same.
2. Description of Prior Art
Multi-layer technology for ceramics has become essential especially in the fields of electronic industries. For example, mention may be made of techniques such as miniaturization or enhancement of performance of electronic ceramic devices such as multi-layered ceramic capacitors and piezoelectric devices and application to ceramic multi-layer substrates which are essential for high-density packaging of semiconductor devices. These are generally produced by a green sheet method and are known as sintered multi-layer ceramic bodies.
However, ceramics generally undergo a large dimensional change (shrinkage) when sintered, which is apt to be affected by variation of starting materials or processes. Therefore, keeping the dimensional accuracy when sintered at a high level is very difficult. Furthermore, the high dimensional accuracy is also required for a sintered multi-layer ceramic body and especially when the sintered body is used as a multi-layer substrate, a high positional accuracy (surface dimensional accuracy) of wiring formed on the surface of substrate is required since semiconductor chips must be mounted thereon and connection with the chips must be formed. Furthermore, these ceramic substrates are subsequently subjected to operations such as plating, attaching of pins and formation of a thin film layer, and mechanical reliability in these operations is also an important requirement.
Furthermore, when thin film multi-layer wirings must be formed on these ceramic substrates in later steps, it is also an important requirement that the ceramic substrate can be set on a device for the production of thin film circuits with high accuracy. In such case, since the substrate is set based on the periphery of the substrate, it is necessary that the external size (maximum size) and peripheral shape of the sintered body are high in accuracy.
In general, a multi-layer ceramic laminate is fired without application of load (pressureless firing). This has merits of simplicity and low costs, but it cannot avoid uneven shrinkage upon firing and it is very difficult to stabilize surface dimensional accuracy to a large extent. Especially when the laminate has complicated conductor layers therein, it is difficult to assure the dimensional accuracy and besides, occurrences of warpage, peeling and blister are severe problems.
For these problems, Japanese Patent Kokai Nos. 57-32657, 62-5848 and 63-31754 have proposed methods of applying a small load of 0.5-20 g/cm.sup.2 to the laminate in firing thereof. According to these methods, warpage, peeling and blister of the laminate can be diminished without hindering the firing shrinkage of the laminate, but uneven firing shrinkage cannot be simultaneously diminished. Therefore, these methods cannot assure the high dimensional accuracy.
Japanese Patent Kokai Nos. 60-137884 and 1-225546 disclose methods of sintering the ceramic laminate under application of a load of 25-200 kg/cm.sup.2 for inhibition of shrinkage at the sintering. However, according to these methods, a frame must be used in firing in order to sinter the laminate without causing substantially any change in surface dimension. If the laminate is sintered with its side faces being free without using the frame, in fact, the sintered body is collapsed owing to the very large load and the accuracy of the surface and external dimensions of the sintered body cannot be ensured (its shape cannot be retained). On the other hand, when firing is carried out using the frame, the sintered body is reacted with the frame material and adheres to the frame, resulting in the side faces of irregular shapes or the frame material bonds firmly to the sintered body which necessitates grinding to remove the frame material or there occur severe problems in costs and operability because the frame must be thrown away after use.
On the other hand, Japanese Patent Kokai No. 62-260777 discloses a method of sintering the laminate under application of a medium pressure between those employed in the above two methods, to thereby avoid shrinkage in XY plane, upward warpage and distortion. This method can inhibit sintering shrinkage in the XY plane of substrate, but makes no mention of the shape of its side faces and means for controlling the shape.
In the above-mentioned conventional methods, the reduction of dimensional accuracy in the surface layer caused by uneven firing shrinkage cannot be avoided when no pressure or a relatively low pressure is applied. A further problem is that ideally the side faces must be in the same flat state as before firing, but actually the uneven shrinkage occurs due to inner wiring or the like, resulting in irregular side faces.
When a large load is applied, the laminate is considerably collapsed during firing, or the laminate reacts with and bonds to the frame used for prevention of the collapse and in either case it is difficult to control the external dimensional accuracy of the sintered body.

Method for producing multilayer ceramic body with convex side faces


Examples for determining printing device functionality based on consumption and payment are described herein. In some examples, signals indicative of an amount of utilized print consumable by a printing device and signals indicative of payment for the amount of utilized print consumable are received at a computing device. Signals to cause the printing device to alter a functionality based on the signals indicative of an amount of utilized print consumable and the signals indicative of payment for the amount of utilized print consumable are transmitted by the computing device.

Printing devices may consume a print consumable, which may include a print substance (e.g., ink, toner, etc.), supplies, kits and/or components. A service provider may provide the print consumable to an end-user for use by a printing device. Service providers may offer, among other things, printing devices and print consumables to customers.
Throughout the drawings, identical reference numbers designate similar, but not necessarily identical, elements. The figures are not necessarily to scale, and the size of some parts may be exaggerated to more clearly illustrate the example shown. Moreover the drawings provide examples and/or implementations consistent with the description; however, the description is not limited to the examples and/or implementations provided in the drawings.

Printing device functionality based on consumption and payment

Hewlett-Packard Development Company, L.P.


A transition metal carbide is formed from a precursor mixture comprising at least one of the group consisting of: a transition metal, a transition metal carbide and a transition metal oxide. The precursor mixture may contain the desired transition metal carbide (e.g., WC), but if the desired transition metal carbide is present in the precursor mixture, there is necessarily a significant amount of another compound such as a transition metal oxide, undesired carbide (e.g., W2C) or transition metal. The method involves forming an admixture by mixing the precursor mixture with a sufficient amount of carbon to carburize the precursor mixture to the transition metal carbide and reacting the admixture in an inert or reducing atmosphere at a temperature for a time sufficient to convert the admixture to the transition metal carbide, wherein the admixture is reacted in the presence of a means to enhance transfer of heat into the admixture, an inert or reducing gas flowing through at least a portion of the admixture or combination thereof.

The invention is directed to the production of carbides of the transition metals Ti, Zr, Hf, V, Nb, Ta, Cr, Mo and W and solution carbides of said transition metals.
There are generally two forms of tungsten carbide; monotungsten carbide (WC) and ditungsten carbide (W2C). It is well-known that WC is useful in the manufacture of commercially worthwhile items such as cutting tools, dies and drilling tools, whereas W2C generally is not. In fact, W2C degrades the properties such as strength of WC objects even when present only in small quantities.
In producing said WC items, it is common for a tungsten carbide powder to be combined with a metal such as cobalt and subsequently densified into a WC/Co cemented carbide by heating. The heating may take place at a pressure ranging from vacuum to pressures greater than atmospheric pressure.
In a cemented carbide part, the tungsten carbide, grain size and grain size distribution and grain chemistry greatly influence the final part properties. As already stated above, W2C should be avoided when making cemented tungsten carbide parts. Generally, smaller grain size in a cemented part results in improved strength. In addition smaller grain sizes often result in higher hardness at a given cobalt addition. Non-uniformity of grain size in a cemented tungsten carbide part adversely affects the strength of and the surface condition of the part after grinding. The non-uniformity of grain size in the cemented WC part is primarily due to exaggerated grain growth during the densification of the part. The grain growth can be controlled by addition of grain growth inhibitors such as VC, Cr3C2 or TaC or starting with a WC powder having as narrow (i.e., uniform) as possible particle size distribution.
WC powder which has an average particle size less than 0.2 to 0.3 micrometer can cause exaggerated grain growth due to the increased reactivity associated with the fine particle size. It has also been reported that standard grain growth inhibitors, as described above, are not effective when sintering a cemented WC part using said fine WC powder. The critical parameter to sinter said fine WC powders was reported to be the WC powder grain size distribution (Suzuki et al, J. Jap. Soc. Powder and Powder Met., Vol. 19, p. 106-112, 1972). Thus, it is desirable to be able to increase the particle size or control the particle size distribution of very fine WC powder (less than 0.2 to 0.3 micrometer) to reduce the possibility of grain growth during the densification of a cemented WC part.
Typically, monotungsten carbide is formed by the carburization of tungsten metal. The basic process steps commonly are:
(a) calcining of ammonium paratungstate or tungstic acid to one of the stable forms of tungsten oxide, such as WO3, WO2.83, WO2.65 and WO2,
(b) reducing the tungsten oxide to tungsten metal powder,
(c) mixing the tungsten metal powder with a powdered form of carbon,
(d) carburizing the tungsten and carbon mixture at a temperature in excess of 1100xc2x0 C. in a reducing (hydrogen containing) atmosphere.
The resultant WC particle size is controlled by the size of the W metal powder formed in the above step (b). Tungsten metal particle size, as described by U.S. Pat. No. 3,850,614, is controlled mainly by:
(1) depth of powder bed during reduction,
(2) flow rate of hydrogen,
(3) dew point of the hydrogen gas and
(4) reduction temperature.
Smaller particle size tungsten powder is produced by increasing gas flow, decreasing bed depth, reducing the dew point of the hydrogen gas and decreasing reduction temperature. By reducing the bed depth and reducing the temperature, the amount of tungsten powder that can be carburized to WC in a given period of time is decreased. The mechanism of growth has been attributed to a volatile WOH species directly associated with the water concentration in the gaseous environment (U.S. Pat. No. 3,850,614). Processes requiring the carburization of tungsten metal to form monotungsten carbide are typically limited to producing WC powder having a particle size of about 0.8 micron or larger because of the difficulty in producing W metal much smaller than this size due to, for example, the pyrophoric nature of such a fine tungsten metal powder. Because of the high hardness of WC, it is also difficult to grind WC to this small particle size. Even if WC were easily ground to the fine particle size, the grinding process inherently produces a wide particle size distribution compared to a controlled synthesis process.
Other methods of producing monotungsten carbide include the following methods. Steiger (U.S. Pat. No. 3,848,062) describes reacting a volatile tungsten species such as WCl5, WCl4, WCl2, WO2Cl2, WOCl4, WOF4 and W(CO)6 with a vaporous carbon source such as a volatile hydrocarbon or halogenated hydrocarbon. The vaporous carbon source is present in a quantity at least equal to WC stoichiometry during the above vapor phase reaction. The product from this reaction, a mixture of WC, W2C and carbon, is then calcined at a temperature of about 1000xc2x0 C. for about 1 to 2 hours resulting in monotungsten carbide substantially free of ditungsten carbide.
Miyake (U.S. Pat. No. 4,008,090) describes a process having a first step of reacting a tungsten oxide with a carbon powder at a temperature greater than 1000xc2x0 C., thereby removing the oxygen and a second step of reacting the product of the first step at a temperature higher than the first step in hydrogen to produce monotungsten carbide. Miyake specifies that the temperature must be greater than 1000xc2x0 C. in the first step to remove the oxygen. The removal of oxygen is necessary to avoid the reaction of hydrogen with oxygen forming water vapor which consequently reacts with carbon forming a volatile carbon-oxygen species, thus effecting the carbon content of the second step product (i.e., desired monotungsten carbide).
Kimmel (U.S. Pat. No. 4,664,899) describes a method to form monotungsten carbide comprising mixing tungsten oxide or ammonium paratungstate with carbon powder to form a resulting mixture, reducing said mixture in a non-reducing atmosphere for a sufficient time at a suitable temperature to produce resulting reduced mixture comprising tungsten, ditungsten carbide and monotungsten carbide, said reducing being carried out in the presence of sufficient carbon to produce a carbon content of less than 6.13 percent by weight in said resulting reduced mixture, determining the carbon content of said resulting reduced mixture, adding sufficient carbon to said resulting reduced mixture to increase the carbon content to at least the stoichiometric amount needed to form monotungsten carbide and carburizing said adjusted reduced mixture to form monotungsten carbide. Kimmel further describes that the product of the reducing of the tungsten oxide is a mixture of W, W2C, WC and free carbon and that all of the oxide is reduced.
All of the above described processes to produce monotungsten carbide require the reduction of a tungsten oxide or tungsten compound (e.g., WCl4) to either tungsten or a mixture of tungsten metal, carbides of tungsten and free carbon. The tungsten or mixture is substantially free of oxygen (i.e., tungsten oxide) before carburizing to form monotungsten carbide. The oxygen is essentially completely removed to avoid the volatile loss of carbon by oxidation or hydrolysis during the carburization of tungsten metal or said mixture. The removal of carbon during the carburization causes non-uniform carbon contents of the resultant carbide product (i.e., W2C in the product). Non-uniform carbon contents are particularly a problem in industrial processes because of the larger volume of carbide that must be processed.
In an industrial process it would be desirable to provide a method to produce a transition metal carbide which is relatively insensitive to the oxygen concentration of the precursor mixture used to make said carbide. In addition, it would be desirable to have a process in which said carbide particle size can be significantly controlled by the process and not solely dependent on the particle size of the precursor mixture (i.e., start with small particle size and grow to a desired size). In particular, it would be desirable to provide said method for producing monotungsten carbide.
The object of this invention is a method to produce a transition metal carbide from a precursor mixture in which the precursor mixture is comprised of a product of at least a partial reduction or partial carburization of a transition metal compound, the method being comprised of:
a) forming an admixture by mixing the precursor mixture with a sufficient amount of carbon to carburize the precursor mixture to the transition metal carbide and
b) reacting the admixture in an inert or reducing atmosphere at a temperature for a time sufficient to convert the admixture to the transition metal carbide
wherein the admixture is reacted in the presence of
(i) a means to enhance transfer of heat into the admixture,
(ii) an inert or reducing gas flowing through at least a portion of the admixture, or
(iii) combination thereof.
The method of this invention, in particular, allows monotungsten carbide to be uniformly formed even when the precursor mixture has a significant amount of tungsten oxide present. It is believed that the present invention overcomes the chemical non-uniformity of product caused by hydrolysis or oxidation of carbon which occurs during carburization of the precursor mixture by reducing the inhomogeneity of the reactions taking place in the admixture during said carburization.
For monotungsten carbide, it has now been discovered that the particle size of the monotungsten formed is inversely proportional to the gas flow rate through the hereinabove described admixture. The gas flow rate effect is unexpected and surprising since U.S. Pat. No. 3,850,614 describes tungsten particle size and, hence, monotungsten carbide particle size being directly proportional to gas flow passing over, not through, a precursor mixture to form a tungsten powder. In addition, the particle size of said monotungsten carbide can also be controlled by temperature.
Transition Metal Carbide Product
The method of this invention is directed at forming transition metal carbides, solid solution transition metal carbides or a combination thereof. The transition metal carbides that are formed can be any carbide containing a transition metal selected from the group consisting of: Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W and a solution carbide of said transition metals. The transition metal carbide is preferably monotungsten carbide (WC), monotitanium carbide (TiC), monotantalum carbide (TaC), monovanadium carbide (VC), monohafnium carbide (HfC), monozirconium carbide (ZrC), mononiobium carbide (NbC), dimolybdenum carbide (Mo2C) or trichromium dicarbide (Cr3C2). Preferably the method according to this invention produces monotungsten carbide or monotungsten carbide in combination with at least one of the above transition metal carbides or solid solution metal carbides. Most preferably the invention forms a monotungsten carbide.
When producing monotungsten carbide by the method of this invention, the monotungsten carbide formed, as determined by X-ray diffraction, preferably has no detectable tungsten metal, no detectable tungsten oxide and less than about 5 percent by weight ditungsten carbide, more preferably less than about 1 percent by weight ditungsten carbide and most preferably no detectable ditungsten carbide. The quantitative analysis is performed by X-ray diffraction described hereinafter.
The free carbon concentration in the produced monotungsten carbide is desirably less than about 0.5 weight percent. Preferably the free carbon in the produced WC is less than about 0.2, more preferably less than about 0.1 and most preferably less than about 0.05 weight percent. The free carbon is determined by an acid digestion process described hereinafter.
First Step (a)
The first step of the method according to this invention is mixing the precursor mixture with a sufficient amount of carbon to form an admixture having sufficient carbon to carburize the precursor mixture to the transition metal carbide.
Carbon
The carbon can be crystalline, amorphous, organic material or combination thereof. Suitable crystalline or amorphous carbon includes graphite or carbon black such as acetylene carbon black which is commercially available under the trade name xe2x80x9cSHAWANIGAN.xe2x80x9d Suitable examples of organic material include organic polymers such as phenol-formaldehyde resins, epoxies, cross-linked polystyrenes and cellulosic polymers, carbohydrates such as sugars and starches and hydrocarbons.
Precursor Mixture
The precursor mixture is comprised of the product of at least a partial reduction or carburization of a transition metal compound such as a transition metal oxide described herein. The precursor mixture is comprised of at least one transition metal compound selected from the group consisting of: a transition metal, a transition metal carbide and a transition metal oxide. In addition, free carbon may be present in the precursor mixture. The transition metal can be a transition metal selected from the group consisting of: Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W and solid solutions thereof. The transition metal carbide can be one or more carbide of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo or W, or a carbide compound containing at least two of said transition metals. The transition metal oxide can be one or more oxide containing Ti, Zr, Hf, V, Nb, Ta, Cr, Mo or W, or an oxide compound containing at least two of said transition metals. The carbon which may be in the precursor mixture is either a residual reactant or is formed during the formation of the precursor mixture. The free carbon can be crystalline or amorphous. The free carbon can originate from such carbon sources such as carbon black, graphite or organic material, each described hereinabove.
The product of at least a partial reduction or carburization of a transition metal compound may result in a precursor mixture having the desired transition metal carbide (e.g., WC). However, if the desired transition metal carbide is present in the precursor mixture, there must be, according to this invention, a significant amount of another transition metal compound such as a transition metal oxide, undesired transition metal carbide (e.g., W2C), transition metal or combination thereof. Herein, greater than about 5 percent by weight of the precursor mixture is a significant amount of another transition metal compound.
When the transition metal carbide to be produced is monotungsten carbide, the precursor mixture may be comprised of:
(1) tungsten;
(2) tungsten, ditungsten carbide and monotungsten carbide or
(3) tungsten, ditungsten carbide, monotungsten carbide, carbon and at least one form of tungsten oxide.
The quantity of oxygen in the precursor for forming monotungsten carbide (WC) may be as great as about 5 percent by weight Preferably, the oxygen is less than about 3, more preferably less than about 2 and most preferably less than about 1 percent by weight as determined by combustion analysis described hereinafter. Practically, the oxygen concentration is never 0 percent by weight because the formation of an oxide of tungsten is thermodynamically favored over the carbide at room temperature in air. The oxygen level may be as low as practically feasible but this is not necessary for the method of this invention. For example, in performing the method of this invention, the precursor oxygen can be greater than about 0.5 percent by weight. The oxygen is taken to be in the form of an oxide of tungsten and conveniently assumed to be WO3 for calculation of stoichiometry described hereinbelow.
Generally, the precursor mixture is formed by at least partial reduction of a transition metal oxide powder by either carburization or reduction by hydrogen. Methods that are suitable to form the precursor mixture described hereinabove include methods that are described by U.S. Pat. Nos.: 4,008,090; 4,644,899; 3,850,614 and 3,848,060, each being incorporated herein by reference. Preferably the precursor mixture is prepared by the rapid carbothermal reduction methods described below and by U.S. Pat. No. 5,380,688, incorporated herein by reference.
The precursor mixture is preferably prepared by mixing a solid particulate carbon source (e.g., carbon black), as described hereinabove, with a transition metal oxide. The quantity of carbon added to the oxide is an amount sufficient to carburize a majority of the oxide forming a transition metal carbide. Preferably the quantity of carbon is added in a quantity less than or equal to stoichiometry of the desired transition metal carbide. For example, in producing a precursor mixture to make WC, the amount of carbon present should be a stoichiometric or less than stoichiometric amount. The stoichiometric amount corresponds to 4 moles of carbon per mole of WO3 (i.e., WO3+4C=WC+3CO).
The transition metal oxide can be a single transition metal oxide (single oxide) or an oxide containing more than one transition metal, referred to herein as a transition metal oxide alloy. The oxides are oxides of the transition metals described previously. Preferably the transition metal oxide is a single oxide or combination of single oxides. When a combination of single oxides are used in the rapid carbothermal reduction method, a solid solution carbide may be formed as described by U.S. Pat. No. 5,380,688. Preferably the transition metal oxides have a purity greater than about 99 percent and a uniform particle size wherein all of the particles and agglomerates pass through a 325 mesh screen (i.e., the largest oxide particle or agglomerate is less than about 45 microns in diameter). Suitable examples include single oxides such as tungsten trioxide (WO3) available under the trade name xe2x80x9cTO-3xe2x80x9d from GTE Products corp., titanium dioxide (TiO2) available under the trade name xe2x80x9cTITANOXxe2x80x9d from Veliscol Chemical Corp., and ditantalum pentoxide (Ta2O5) available from Aldrich Chemical Company.
The transition metal oxide and carbon can be mixed in any apparatus suitable to mix powders. Examples of mixing apparatus include, but are not limited to, a sigma mixer, muller mixer, V-blender and cone blender. If further particle size reduction of the transition metal oxide or carbon is desired, said oxide or carbon can be milled before mixing or mixed and milled simultaneously in any apparatus capable of milling (reducing powder particle size) such as a ball mill, jet mill, vibratory mill or an agitated mill such as an attritor. If milling is performed requiring milling media, for example in a ball mill, the milling media is preferably cemented tungsten carbide-cobalt milling media. The carbon and transition metal oxide(s), transition metal oxide alloy(s) or combination thereof, after being mixed, will be referred to hereinafter as the oxide-carbon reactive mixture.
The oxide-carbon reactive mixture is advantageously reacted by rapid carbothermal reduction in a drop or an entrainment method. The drop method involves heating a graphite crucible in the hot zone of an induction furnace to the desired reaction temperature. The crucible is heated in a non-oxidizing atmosphere such as flowing argon. The crucible is maintained at the reaction temperature for a time sufficient (about 30 minutes) to equilibrate the crucible and furnace at that temperature. Aliquots of the reactive mixture are dropped in said graphite crucible in the induction furnace producing heating rates in the range of 100 to 10,000 K per second. The extent of the reaction is monitored by measuring the reactant by-product CO level in the crucible as function of time. When the CO level decreases back to a CO level equivalent to about the CO concentration before beginning the reaction, the reaction is stopped by cooling the crucible as rapidly as possible back to room temperature to minimize particle agglomeration and grain growth of the reacted oxide-carbon reactive mixture.
The entrainment method involves the use of a vertical graphite tube reaction furnace of the type described by U.S. Pat. No. 5,110,565, incorporated herein by reference. The oxide-carbon reactive mixture is placed into a feed hopper, which allows flowing non-oxidizing gas, such as argon, to entrain the powdered mixture and deliver it to the furnace reaction chamber as a dust cloud. The powder or particulate mixture is heated in the reaction chamber at rates of between about 10,000 to 100,000,000 K per second, while the average residence time of powder in the furnace is on the order of seconds. As for exiting the hot zone of the reaction chamber, the flowing gas carries the powder into a water cooled stainless steel jacket which rapidly cools reacted powder below 283 K. The preferred method to make the precursor mixture of this invention from the oxide-carbon reactive mixture is by the entrainment method, because the entrainment method is capable of more uniform reaction conditions and, thus, greater capability in forming uniform small particle size precursor mixture powder.
The oxide-carbon reactive mixture is reacted (i.e., carburizing of the oxide) by heating from room temperature up to the reaction temperature at a rate preferably at least 100 to 10,000 K per second and optimally on the order of 10,000 to 100,000,000 K per second. The reaction temperature must be high enough such that the reaction is thermodynamically favorable. One way of expressing this is to say that the Gibbs free energy change for the reaction must be negative. In other words, the free energy of formation of reaction products must be less than the free energy of formation of components of the reactant mixture. It must also be less than the melting point of any intended reaction product(s). For tungsten carbide, a reaction temperature of at least 1673 K is considered beneficial, while temperatures of 1823 K to 2673 K are preferred. Approximate temperatures at which free energy of formation of reaction products is less than free energy of formation of components of the reactant mixture needed to form the reaction products are as follows: tungsten carbide (WC) 950 K; titanium carbide (TiC) 1555 K; tantalum carbide (TaC) 1381 K; vanadium carbide (VC) 932 K; hafnium carbide (HfC) 1934 K; niobium carbide (NbC) 1228 K; zirconium carbide (ZrC) 1930 K; dimolybdenum carbide (Mo2C) 742 K and trichromium dicarbide (Cr3C2) 1383 K.
The residence time of the oxide-carbon reactive mixture at the reaction temperature depends in part upon the heating rate and reaction temperature, but must be high enough to reduce at least a major portion of the metallic oxide from the reactant mixture. The residence time is preferably in the range of about 0.1 second to 1/2 hour, depending upon the heating method, heating rate, reaction temperature and the ultimate particle size desired. In the drop method, typical preferred residence times are from about 5 minutes to 2 hours for a reaction temperature of 1773 K with a heating rate of about 100 to 10,000 K per second. In the entrainment method, a residence time of from about 0.2 to 10 seconds for a reaction temperature of 1823 K or above with a heating rate of about 10,000 to 100,000,000 K per second is preferred. At the higher heating rate, residence times substantially greater than 10 seconds may undesirably produce sintered aggregates rather than particulate product. Whatever combination of reaction temperature, residence time and heating rate is selected, however, it should be adequate to convert the reactive particulate mixture of carbon and metal oxide into a product composed mainly of metal carbide. In other words, the product, for example, for making WC would be the precursor mixture previously described.
Forming the Admixture
The admixture is formed by mixing the previously described carbon and precursor mixture together. Preferably the carbon is a solid carbon such as carbon black. The carbon and precursor are mixed or milled together by the same techniques and methods previously described for mixing the oxide and carbon to form the oxide-carbon reactive mixture. Preferably the carbon and precursor mixture are mixed in a ball mill having cemented tungsten carbide cobalt media.
The quantity of carbon which is added to the precursor mixture is typically determined empirically with respect to the transition metal carbide desired. For example, when producing WC from an admixture of the precursor mixture and carbon in a 5 percent hydrogen-95 percent argon gas mixture, Applicants have found that an amount of carbon comprising the sum of about 0.67 stoichiometric with respect to the oxygen (i.e., WO3+(0.67 )4C=WC+3CO) in the precursor mixture, and stoichiometric with respect to W2C and free metal (W) in the precursor mixture typically converts the precursor mixture to a monotungsten carbide having low free carbon and low total oxygen. Typically, the amount of carbon to be added to the tungsten carbide precursor made by the entrainment method usually amounts to about 1 to about 5 weight percent based on the precursor mixture weight, more typically the amount is in the range of about 2 to about3 weight percent. The amount of carbon which is necessary to convert the admixture to a desired transition metal carbide may change depending on, for example, the reactor, atmosphere and precursor mixture. For any conditions according to this invention, the quantity of carbon may be determined by routine experimentation by those skilled in the art.
Second Step (b)
The second step of the method according to this invention is reacting the admixture in an inert or reducing atmosphere at a temperature for a time sufficient to convert the admixture to the transition metal carbide wherein the admixture is reacted in the presence of (i) a means to enhance transfer of heat into the admixture, (ii) an inert or reducing gas flowing through at least a portion of the admixture or (iii) combination there of.
The admixture is reacted at a temperature e and time sufficient to convert substantially all of the precursor mixture to the desired transition metal carbide. For example, when forming monotungsten carbide (WC) the admixture can be heated to a temperature of between about 900xc2x0 C. to 1800xc2x0 C. for any time sufficient to convert the admixture to the WC described hereinbefore. Preferably the temperature of the admixture reaction is between about 1000 to 1600xc2x0 C.. The temperature of the reaction has been shown to be directly proportional to the WC product particle size. The time of the reaction is desirably as short a period of time as possible to convert the admixture to WC. Preferably the reaction time is at least about 5, more preferably at least about 15, and most preferably at least about 30 minutes to preferably at most about 10, more preferably at most about 5 and most preferably at most about 2 hours.
The atmosphere can be any reducing or inert atmosphere. Gases which are suitable to create the atmosphere include hydrogen, a hydrogen-argon mixture or argon. Preferably the gas is a 2-6 percent hydrogen in argon gas mixture because these mixtures provide a reducing environment while the amount of hydrogen in the mixture is below the explosive limit. It is also preferred that initially the atmosphere be inert, for example argon, until substantially all of the oxygen present in the admixture is removed (i.e., little or no CO is being generated by the re action) and then subsequently the gaseous atmosphere is changed to a reducing atmosphere such as 5 percent hydrogen in argon. The use of an inert gas followed by a reducing gas may a void or reduce the formation of water vapor which can subsequently react with carbon forming CO (i.e., H2+O=H2O and subsequently H2O+C=CO+H2).
During the reacting of the admixture, the atmosphere is preferably created by a flowing gas. The gas is desirably flowing to allow th e removal of unwanted gaseous species such as water vapor. Excess water vapor may react with carbon to form CO gas, thus changing the carbon concentration of the transition metal carbide formed. The quantity of flowing gas per weight of admixture can be any flow sufficient to react the admixture to form the desired transition metal carbide. Preferably the gas flow is about 5 to about 500 standard liters/min-Kg and more preferably from about 25 to about 250 standard liters/min-Kg.
The admixture can be reacted in a batch or continuous apparatus. Suitable apparatus to react the admixture include, for example, a tube furnace, pusher furnace, belt furnace, rotary furnace, elevator furnace, fluid bed reactor and rotary crucible furnace. It is desirable for the apparatus to be constructed of materials which do not contaminate the admixture during the reaction. Preferably the furnace or reactor is constructed of carbon materials in at least the hot sections of the furnace or reactor. The carbon material should have a purity as described for a carbon object in the following paragraph.
When reacting the admixture, the admixture is reacted in the presence of a means to enhance transfer of heat into the admixture, an inert or reducing gas flowing at least partially through the admixture or combination thereof. The means to enhance transfer of heat into the admixture is any object which conducts heat at a significantly higher rate than the bulk admixture, such as a dense carbon or ceramic object. The object is significantly larger than the admixture particle size wherein the object is separable from the admixture by simple mechanical means such as picking it up by hand. A dense carbon object or objects include graphite or carbon/carbon composite object(s). Preferably the object or objects are carbon objects. The carbon object(s) should be of a purity which does not significantly contaminate the admixture. Commercial graphite commonly has significant silicon contamination. Therefore, a graphite or carbon object which is used to perform the method of this invention preferably has a silicon and total metal contamination of less than about 25 parts per million (ppm) and more preferably less than about 10 ppm.
The objects can be of any geometry such as a plate, tube, rod or an array of plates, tubes or rods. The object is preferably placed in the admixture such that at least a portion of the object is not within the admixture. For example, the admixture is placed in a circular, square or rectangular graphite boat having a graphite rod or plate in the center of the boat wherein the rod or plate is in contact with the bottom of the boat (e.g., the longitudinal axis of the rod extends from the bottom of the boat to the top of the boat). The top of the boat being the open end. It is also preferred that the object or objects extend beyond the top of the admixture in the boat. The object can be contacted with the boat such that the object is an integral part of the boat. For example, the object can be screwed, cemented, or slotted into the bottom of the boat. An example of a suitable cement is a phenol-formaldehyde resin which decomposes to a carbonaceous material upon heating to a high enough temperature in a non-oxidizing atmosphere. In addition, the boat can be machined such that the object is a contiguous part of the boat. The admixture in the boat can be covered or uncovered and subsequently reacted, as described herein, in a batch furnace or continuous furnace such as a pusher furnace. Preferably the furnace is a continuous furnace and more preferably a pusher furnace.
Another example of forming a transition metal carbide with said object or objects is the reaction of the admixture, as described herein, in a rotary furnace. In this example, rods are contacted with the inner diameter of the rotary furnace wherein the longitudinal axis of the rods extend radially in towards the center of the rotary furnace. Desirably the rotary furnace has a rotary section (tube) which is graphite or carbon/carbon composite and said rods are periodically screwed into the inner diameter and along the longitudinal axis of said tube. The rods may also beneficially mix and deagglomerate the admixture in the rotary furnace. When the admixture is reacted in the presence of a means to enhance transfer of heat into the admixture (e.g., carbon objects), a more chemically uniform transition metal carbide, particularly WC, is formed compared to when no said means to enhance heat transfer into the admixture is present. More chemically uniform leads to less undesirable transition metal carbide (e.g., W2C), less oxygen, less carbon or combination thereof present in the transition metal carbide product.
When the admixture is reacted in the presence of an inert or reducing gas at least partially flowing through the admixture, similar apparatus described above can be used. For example, the circular, rectangular or square graphite boat can have an outlet at the bottom of the boat in which gas can pass through but the admixture cannot. Suitable outlets can involve at least one hole through the bottom of the boat in which the hole(s) have a porous membrane capable of passing the inert or reducing gas but not the admixture. Suitable membranes include graphite felt, carbon fiber mesh or a porous graphite. An example would be a boat having a first bottom having one hole in the center of said bottom traversing from the outside of the boat to the inside of the boat. The first bottom is an integral part of the boat. Said boat has a second bottom fully covering and positioned on top of the first bottom within the boat wherein a space exists between the first and second bottom. The second bottom has multiple holes through it which are parallel to the hole in the first bottom. The second bottom also has graphite felt placed thereon.
When reacting the admixture, as described herein, in the above described boat, the admixture is put in the boat on the graphite felt and placed, for example, in a batch furnace which has means to introduce or exhaust gas through the hole in the first bottom of the boat. Means to exhaust or introduce gas is, for example, a graphite tube traversing the furnace bottom which then engages (e.g., by screw threads) the boat bottom on the inner diameter of the hole in the bottom of the boat. The boat just described can, of course, have an object previously described to enhance transfer of heat into the admixture.
Another example of reacting the admixture, as described herein, in the presence of an inert or reducing gas flowing through at least a portion of the admixture, can be to insert a graphite tube described above through the furnace top wherein the end of the tube is position some depth into admixture contained in a boat having a solid bottom. The gas is then flowed into the admixture, the gas passing through some portion of the admixture and subsequently exhausting out of the furnace elsewhere. The end of the tube placed in the admixture may be configured by any number of configurations to best disperse the gas into the admixture. For example, the end of the tube in the admixture can have a plugged end wherein the gas exits the tube through passageways traversing from the outer diameter to the inner diameter at the end of the tube. In this example, the tube may also function as the thermal enhancement means. Inert or reducing gas flow through at least a portion of the admixture unexpectedly results in a transition metal carbide (particularly WC) particle size which is inversely proportional to the flow rate of the gas. In addition, an increase in flow rate results in less or no W2C formation at otherwise identical reaction conditions.
The transition metal carbide powder(s) and, in particular, WC formed according to the method of this invention are useful as items such as abrasives and as a constituent in forming cemented carbide wear resistant parts such as cutting tools and blast nozzles of all types and dies.
Test Methods
The following are typical methods for analyzing a transition metal carbide described herein.
Carbon
The carbon concentration in a transition metal carbide of this invention is determined using a xe2x80x9cLECOxe2x80x9d IR-212 carbon analyzer(trademark). A xe2x80x9cLECOxe2x80x9d supplied tungsten carbide standard having 6.16 percent by weight carbon is used to calibrate the analyzer. The analyzer is calibrated using at least 4 standard analyses as described by the manufacturer (LECO). Each sample and standard is analyzed with a scoop of LECOCEL II(trademark) and iron chips. The scoop is provided by the manufacturer (LECO). At least four carbide samples are analyzed.
Oxygen
The oxygen concentration in a transition metal carbide of this invention is determined using a xe2x80x9cLECOxe2x80x9d TC-136 oxygen determinator(trademark). A 0.0246 percent by weight oxygen standard is used. The oxygen determinator is calibrated using at least 4 standard analyses as described by the manufacturer of the determinator. A carbide sample is analyzed by placing about 0.2 gram of sample in a manufacturer supplied tin capsule and nickel basket. At least four carbide samples are analyzed.
Surface Area
Surface area of the transition metal carbide is determined by nitrogen gas adsorption as described by the BET method (Brunauer, Emmett and Teller). The analysis is performed on a Quantachrome Autosorb 1 analyzer.
Free Carbon
The free carbon in a transition metal carbide of this invention is determined by acid digesting an amount of transition metal carbide (e.g., WC) in hydrofluoric and nitric acid, filtering the carbon residue onto a silver filter and determining the carbon on the silver filter by the method described above for determining carbon concentration.
Phase Determination
The phases and quantity of differing transition metal carbide phases is determined by X-ray diffraction. The quantity of phases is determined by a method involving the ratio of peak heights or integrated peak areas between peaks caused by differing phases. For example, the quantity of W2C is calculated from the ratio between 2 times the peak height of the W2C peak at a xe2x80x9cdxe2x80x9d spacing of 2.276 Angstroms divided by the heights of the WC peaks at a xe2x80x9cdxe2x80x9d spacing of 2.518 and 1.884 Angstroms.

Method to produce a transition metal carbide from a partially reduced transition metal compound


An anti-lock brake control system for an automotive vehicle, comprises a wheel-brake cylinder adapted to provide a braking action, a hydraulic pressure actuating unit adapted to be fluidly connected to the wheel-brake cylinder to feed and exhaust brake fluid to and from the wheel-brake cylinder, and having at least one reservoir tank provided for temporarily storing brake fluid exhausted from the wheel-brake cylinder via a return line and a return pump driven by an electric motor and provided for exhausting the brake fluid within the reservoir tank toward a main brake-fluid line, sensors provided for detecting wheel speeds, a controller for executing a skid control of the hydraulic pressure actuating unit in response to signals from the sensors, a diagnostic system for making a diagnosis on a trouble of said electric motor, and a monitoring device for monitoring an amount of brake fluid stored in said reservoir tank when said diagnostic system determines that said electric motor is in trouble. The controller terminates the skid control of the hydraulic pressure actuating unit when the amount of brake fluid reaches the full capacity.

1. Field of the Invention
The present invention relates to an anti-lock brake system which prevents wheel lockup during braking and thus avoids skidding, and specifically to an automotive anti-lock brake control system which is capable of making a self-diagnosis on the trouble of an electric motor adapted to rotate a return pump employed in the system.
2. Description of the Prior Art
In recent years, there have been proposed and developed various anti-lock brake systems which are designed to prevent skidding and thus provide maximum effective braking. On more later-model cars with an anti-lock brake system, a self-diagnostic system is often incorporated in the anti-lock brake system, to make a self-diagnosis on motor wire troubles such as a loose motor wire connector of an electric motor of a return pump, often called "ABS pump," fluidly disposed in a hydraulic actuator of the anti-lock brake system. As is generally known, the typical anti-lock brake system uses a reservoir tank as well as a return pump. The return pump is adapted to reduce the hydraulic pressure in a wheel-brake cylinder for a certain road wheel selected for the purpose of skid control. The reservoir tank is fluidly disposed in a brake line connected to both the inlet port of the return pump and the wheel-brake cylinder for temporarily accumulating the brake fluid exhausted from the cylinder as a result of reduction in the pressure in the cylinder. The return pump included in the ABS is usually driven by way of an electric motor. In the event that the motor wire connector of the motor-driven return pump is disconnected or the motor wire itself is burnt out during operation of the ABS, the anti-skid control terminates in an abrupt manner (for a brief moment such as 0.1 sec or less). Thus, it is necessary to make a self-diagnosis upon the abnormality of the motor associated with the return pump. On conventional anti-lock brake systems with a self-diagnostic system which makes a self-diagnosis on the abnormality of the motor of a return pump, the anti-lock brake system is generally designed to terminate the system operation and to permit normal application of the brakes, immediately when the self-diagnostic system decides the presence of abnormality of the electric motor of the ABS pump during operation of the ABS. As can be appreciated, if normal application of the brakes restarts as soon as the system decides the motor of the ABS pump is in trouble during the skid control, a satisfactory anti-lock brake control action cannot be provided and thus a satisfactory convergence of a skid of the skidding less-traction wheel cannot be accomplished due to a rapid transition from skid control to normal braking.

Anti-lock brake control system for automotive vehicles