Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Graphite – coal – or elemental carbon
Reexamination Certificate
2000-01-27
2001-09-18
McAvoy, Ellen M. (Department: 1764)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Graphite, coal, or elemental carbon
C508S116000, C508S130000, C508S131000, C508S142000, C508S148000, C508S155000, C508S167000, C106S038220, C164S072000
Reexamination Certificate
active
06291407
ABSTRACT:
BACKGROUND OF THE INVENTION
Die casting methods are old in the art. The methods permit continuous manufacturing of die cast products with a high degree of quality, such that the methods are commonly used.
In conventional metallic die casting, molten metal is introduced into a shot sleeve or shot chamber. Generally, the molten metal is superheated before it enters the shot sleeve, and thus is introduced to the shot sleeve at a temperature between about 1100° F. and 1600° F., for aluminum, for example. A plunger then slides into the shot sleeve and forces the molten metal into a die cavity. Increased pressure is required to be exerted by the plunger at the end of the fill cycle to compress and force the molten metal in the casting dies. The overall strength of the piece being die cast is dependent, in part, upon the amount of pressure applied by the plunger and upon the initial temperature of the molten metal and its quality. Frequently, tight tolerances are necessary between the plunger and the shot sleeve to minimize any metal blow by around the plunger tip.
Tight tolerances also have the effect of creating additional friction between the plunger and the shot sleeve walls. Further, mechanical and thermal stresses may add additional friction between the plunger and the shot sleeve wall. It is conventional, in cold chamber die casting, that the inside walls of the shot sleeve are lubricated with a lubricant to counteract the frictional forces. It is a goal of the applied lubrication to minimize the wear of the plunger and shot sleeve walls, to prevent blow by and to permit the die casting process to operate continuously.
Conventional lubricants include both solid and liquid materials of various compositions. The liquids may be aqueous based or oil based and may contain various organic and inorganic lubricants. Solid lubricants may include both organic and inorganic materials. The organic materials include a variety of oils, greases and waxes of both natural and synthetic origin. The inorganic materials may include a variety of high pressure lubricants. For example, the inorganic materials may include talc, various nitrides, such as boron nitride, sulfur compounds, such as molybdenum disulfide, silica compounds and may also include graphite and carbon. The inorganic lubricants in particular are inexpensive and highly effective lubricants, as noted by U.S. Pat. No. 5,014,765. However, these materials are typically commercially available in a finely divided particulate form. This finely divided particulate form presents difficulties in handling and dispensing, requiring special methods of application, and may create airborne dust.
Prior U.S. Pat. No. 5,154,839 attempted to solve the problems created with the use of inorganic solid lubricants. The patent discloses the use of an inorganic granulated lubricant which has been coated with an organic polymer or metal soap. While coating the inorganic lubricant with a polymer or metal soap may reduce the dusting problems experienced with the use of prior solid lubricants, the lubricant disclosed by the patent produces a lubricant which may not maintain the integrity of the particles sufficiently and may not be as desirable for use with metering and dispensing apparatus without caking or blocking.
Organic lubricants, including those containing some inorganic material, have an additional problem. In use, these materials frequently generate an open flame and smoke. Organic materials, such as oils and waxes in conventional lubricants, are volatile and flash under the temperature conditions to which these materials are exposed. Frequently a plume of flame and smoke flashes back through the shot hole when the molten metal comes in contact with the applied lubricant.
Applicant is aware of the following U.S. patents, the disclosures of which are incorporated by reference herein.
3,645,319
5,076,339
3,779,305
5,154,839
5,014,765
5,400,921
SUMMARY OF THE INVENTION
It is desirable to have a solid lubricant material which doesn't cake and which retains its integrity during shipping and handling. Further, it is desirable that this material have a size distribution and other properties to permit its use in conventional dispensing apparatus without caking and blocking. The composition should preferably be formed of an inorganic and an organic material that can maintain its lubrication properties despite an exposure to high pressures and high temperatures. Furthermore, it is desirable to have a solid powder lubricant which has the aforementioned positive qualities, but yet remains in an agglomerated form capable of being automatically fed to a shot sleeve, with conventional metering equipment, and which will also effectively lubricate the shot sleeve when so introduced.
In accordance with the present invention there is provided a non-caking solid lubricant composition for use in lubricating the inner surfaces of a shot sleeve and plunger for use in the die casting of molten metals using cold chamber die casting machines. The non-caking solid lubricant of the present invention is in the form of durable individual agglomerates. Each agglomerate is preferably formed of finely divided inorganic lubricant material agglomerated around or to a solid organic core with a binder material in such a manner that the lubricant retains its form and integrity during shipping, handling and dispensing. Further, the lubricant effectively lubricates a shot sleeve when introduced therein. It is believed that under the pressure and temperature conditions of the shot sleeve, the agglomerated particles break up and the inorganic lubricant is effectively distributed in the shot sleeve to lubricate the moving parts and surfaces. The high temperature of the shot sleeve may flash the organic content of the agglomerated particles freeing the finely divided inorganic particles from the agglomerate and permitting their distribution in the shot sleeve. These fine particles may be of the materials described herein. The carbon residue from the flashed organic material may also add to the lubricating ability of the material in the shot sleeve.
The organic materials of the present invention may include materials which have an additional, unexpected, advantage in that they produce a lubricant having a suppressed rate of combustion or flash. This low or slow flash results in little or no flash back of smoke and flame from the shot hole when the lubricant is introduced to the shot sleeve and exposed to the high temperature conditions of the shot sleeve and the introduction of molten metal. It is believed that carbonization and flash of the organic portion occurs substantially within the confines of the shot sleeve after the pour hole or shot hole has been closed by movement of the plunger. The carbon produced is effective to lubricate the shot sleeve and plunger, and there is less pollution and waste.
It is an object of this invention to provide a material and method for effectively lubricating the shot sleeve and plunger of a cold chamber die casting machine.
It is an object of this invention to provide a solid material for effectively lubricating the shot sleeve and plunger of a cold chamber die casting machine.
It is an object of this invention to provide a solid material for effectively lubricating the shot sleeve and plunger of a cold chamber die casting machine, the material having a substantial content of inorganic lubricant.
It is an object of this invention to provide a material for effectively lubricating the shot sleeve and plunger of a cold chamber die casting machine, the material being in the form of agglomerated particles of lubricant compounds.
It is an object of this invention to provide a material for effectively lubricating the shot sleeve and plunger of a cold chamber die casting machine, the material being in the form of agglomerated particles of inorganic lubricants and organic lubricants.
It is an object of this invention to provide a material for effectively lubricating the shot sleeve and plunger of a cold chamber die casting machine, the material effectively re
Howell & Haferkamp LC
LaFrance Manufacturing Co.
McAvoy Ellen M.
LandOfFree
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