Plastic and nonmetallic article shaping or treating: processes – Recycling of reclaimed or purified process material – Of excess solid particulate
Reexamination Certificate
2000-02-04
2001-11-06
Vargot, Mathieu D. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Recycling of reclaimed or purified process material
Of excess solid particulate
C264S040400, C264S109000, C425S140000, C425S148000, C425S352000, C425S447000, C425S260000, C425S405100
Reexamination Certificate
active
06312629
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to apparatus and methods for pressing powders, and more particularly to the making of ammunition and explosive charges.
2. Description of the Related Art
A variety of articles are prepared by pressing, or consolidating, powders either directly to form pellets, or into casings. In particular, the pressing of powders made from energetic materials to make explosive pellets or to fill projectile casings is associated with a number of problems.
A typical procedure for pressing energetic materials involves a large number of manual steps, many associated with safety issues of the pressing of energetic materials. The process requires manual weighing of powder, manual filling of a die or case, consolidating the powder, and manually performing off-line control testing.
When automatic filling is performed based on volume of powder, it is common for an improper amount of powder to be added to the die, resulting in a defective product that must be discarded after identification in a post-manufacturing inspection. With an energetic material, disposal of the defective product is a significant issue. Generally, determination of the quality of a produced item can only be determined by inspection after it is produced. In addition, record keeping for such a process is generally performed manually. This is tedious and involves substantial amounts of time after manufacture for correlating the manufactured items with the records.
In addition, improper filling of the die cavity of the press due to delivery of an improper amount of powder may additionally pose a safety issue. For example, too much of an energetic powder could conceivably increase the risk of explosion during the pressing step.
Moreover, the large number of manual steps associated with the process makes the process slow. In particular, it is necessary at several points in the process for the operators to leave the vicinity of the press to a safe room for fear of an explosion during a pressing step. This is tedious and adds considerably to the production time.
Examples of the contemporary art dealing with delivering controlled amounts of material are seen in the following U.S. Pat. No 4,843,579, to Andrews et al., entitled Weighing And Filling Method And Apparatus, describes a method and apparatus for dispensing measured amounts of powdered materials. The apparatus has a vibratory feeder, and deposits powdered material using a feeder trough into a container where it is electronically weighed.
U.S. Pat. No. 4,771,836, to Naito et al., entitled Control For A Weighing System, describes a system for combinational weighing.
U.S. Pat. No. 5,005,657, entitled Powder Dispensing and Measuring Device, describes an apparatus with a vibrating barrel for transferring powder, and a scale for weighing the discharged powder.
U.S. Pat. No. 5,114,630, entitled Continuous Manufacture And Casting, describes a system for manufacturing fluid products, particularly highly filled materials.
U.S. Pat. No. 5,387,095, entitled An Apparatus For Injection Molding High-Viscosity Materials, describes an apparatus for injection molding highly viscous materials. The apparatus is not designed for the handling of powders, however.
None of the above patents deals specifically with the issues of delivering weighed powder to a press.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an improved method and apparatus for pressing (consolidating) powders.
It is also an object of the invention to provide an apparatus and method allowing better quality control of pressed powder articles.
It is a further object of the invention to provide an apparatus and method for avoiding waste of the powder material.
A yet further object of the invention is to provide an apparatus and method allowing data logging of the production parameters for the product.
A still further object of the invention is to provide an improved apparatus and method for pressing energetic powders.
A still yet further object is to provide an apparatus and method which allow more rapid production of pressed products.
Another object of the invention is to provide an apparatus and method which allows safer pressing of energetic materials.
To achieve the above and other objects, the present invention provides an apparatus having a powder compaction press, a gravimetric feeder for feeding powder to the press, a programmable logic controller (PLC) connected to the press and the gravimetric feeder, for receiving information from and sending information to the press and feeder. The gravimetric feeder includes a powder feeder, a dump bucket and an electronic scale. The gravimetric feeder has means for weighing the dump bucket, and for directing the contents of the dump bucket to the press when a desired amount of powder is in the dump bucket. Moreover, the gravimetric feeder has means for directing the contents of the dump bucket away from the press for recovery or recycling when a non-desired weight of powder is in the bucket. The means for directing the contents of the dump bucket may be an electronically controlled diverter or a moveable chute.
The apparatus of the present invention is controlled by the PLC. In addition, the control of the present invention includes solenoid valves which operate press cylinders, located in a hazard area. The PLC is also connected to a feeder controller operating the powder feeder in the hazard area, and to a scale controller receiving data from the projectile scale in the hazard area. The PLC is also connected to a dump controller and pneumatic controls, which in turn control door operation, a chute activator, and a dump bucket. The PLC also receives pneumatic signals from the press. Scale controls and press electronic sensors are also connected to the PLC. The PLC is further connected through a switch (SW) to a personal computer (PC) for automatic, time-stamped data logging.
The present invention also encompasses a method of preparing pressed articles. The method of the present invention includes the steps of: feeding powder to a bucket; weighing the bucket using an electronic scale; determining if the weight of powder in the bucket is a desired weight; and if the weight of powder is a desired weight, then dumping the powder to a first location, and if the weight of powder in the bucket is an undesirable weight, dumping the powder to a second location; conveying the powder from the first location to a press and pressing the powder; obtaining pressing parameter data, conveying the pressed powder article from the press, and storing the pressing parameter data. The pressing parameters may include hydraulic pressure, temperature and ram height.
The powder dumped to the second location may be returned to a hopper to be fed again to the bucket. The dumping of powder to a first location may entail dumping the powder to a shoe which will be moved to the die cavity of the press, or to a chute which may be directed to a casing to be filled. The pressing may be performed with an opposed-ram press, and the movement of the shoe over the die cavity may be used to convey a previously pressed article from the press. Additional steps may include post-pressing inspection of the article and automatic diversion of an unacceptable article, as well as labeling, packaging and warehousing of the article.
The method of the present invention may be carried out using the apparatus of the present invention, under control of the PLC.
REFERENCES:
patent: 2338491 (1944-01-01), Cutler
patent: 2664557 (1953-12-01), Sargrove
patent: 3266096 (1966-08-01), Thomas et al.
patent: 4142847 (1979-03-01), Ripani
patent: 4771836 (1988-09-01), Naito et al.
patent: 4843579 (1989-06-01), Andrews et al.
patent: 5005657 (1991-04-01), Ellion et al.
patent: 5074774 (1991-12-01), Nose et al.
patent: 5114630 (1992-05-01), Newman et al.
patent: 5213724 (1993-05-01), Saatkamp
patent: 5387095 (1995-02-01), Mahony et al.
Gusack James A.
Kneisl Philip
Lowell Mark D.
Homer Mark
The United States of America as represented by the Secretary of
Vargot Mathieu D.
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