Fluent material handling – with receiver or receiver coacting mea – Processes – With material treatment
Reexamination Certificate
2001-04-09
2002-01-08
Douglas, Steven O. (Department: 3751)
Fluent material handling, with receiver or receiver coacting mea
Processes
With material treatment
C141S073000, C425S218000, C425S253000, C425S447000, C264S308000
Reexamination Certificate
active
06336480
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to methods and systems for measuring, dispensing and spreading of powders. In particular, the invention relates to a method for measuring and dispensing a powder for use in a three dimensional printing or solid freeform fabrication system.
BACKGROUND OF THE INVENTION
The construction of articles of manufacture using solid free-form fabrication (SFF) methods has been disclosed in U.S. Pat. No. 5,490,962, and in U.S. Pat. No. 5,387,380 on three-dimensional printing (3DP). These SFF and 3DP methods have the ability to construct a wide range of objects using construction materials in powdered form. A limitation in building practical devices useful for implementing SFF and 3DP methods is a powder handling system that can be used to dispense selected amounts of a variety of powders under computer or manual control, with a minimum of human intervention and with a minimum of cross-contamination between powders. The present invention is a system designed to dispense powders while satisfying these needs.
There are many arts which require the measurement of quantities of a powder and the dispensing of such powder. At times a measured powder sample is needed for blending with another powder sample. Technological arts such as pharmaceutical manufacturing, powder coating, confection manufacturing, powder metallurgy, cosmetics, spices, and flavorings are some examples of areas of technology which have a need for such powder handling methods. There is an especially important need for efficient powder dispensing and distribution in the use of SFF methods. SFF and 3DP use one or more powders dispensed from a reservoir into a container typically called a build bed to fabricate articles of manufacture. In these methods of fabrication a portion of at least one powder is transferred from the reservoir to the build bed to form a layer of powder. Various techniques are used to form a solid from a portion of the layer of powder. In the case of 3DP a binder is printed onto a layer of powder in a build bed to convert a portion of the layer from a powder into a solid. Successive portions of the same or a different powder are then dispensed and spread over an existing layer in the build bed and subjected to additional printing on selected portions of each successive layer of powder.
It has been disclosed in U.S. Pat. No. 5,204,055 that in a 3DP process a powder being applied in a layer on a build bed can be distributed from a dispensing head passing over a build bed. In U.S. Pat. No. 5,387,380 is disclosed the use of a sieve drum for dispensing powder over a build bed. Both of these disclosed systems and methods of operation suffer from problems. The thickness of a layer of powder deposited on a build bed is known in the art to be an important parameter in how well 3DP or SFF works in manufacturing an article. The thickness of a layer depends on both any method used for compacting the powder, and the amount of powder dispensed onto the build bed. The dispensing head and sieve drum disclosed in these two patents require a complicated multicomponent apparatus adapted for motion over a build bed for their operation. If only one dispensing head or sieve drum is used in a given 3DP or SFF apparatus, then the dispensing head or sieve drum used would require cleaning during a changeover to a second powder if multiple powders were used in the 3DP or SFF fabrication of an article. The complexity of the dispensing head and sieve drum and the risk of cross-contamination of powders in a multipowder 3DP or SFF fabrication method are serious disadvantages in the disclosed powder dispensing systems.
A method and an apparatus for use in 3DP were disclosed in U.S. Pat. No. 5,647,931. A method for dispensing powders, that can be used in 3DP processes, was disclosed in that patent. That method is described as having a selected powder metered from a reservoir by use of a rotating notched drum feeding device. The powder so metered is allowed to fall by gravity into a movable container. This movable container is adapted for motion above a build bed, and for distributing the powder onto the build bed. This apparatus and method both have the disadvantage of increased complexity. The apparatus disclosed uses a movable container fitted with a means for vibrating the container to distribute powder over a build bed. The movable container would need to be cleaned from time to time to ensure that powder is not retained in its interior. The movable container has a large surface area contacting the powder, and which would require cleaning. The present invention provides an apparatus and a method for measuring and distribution of powders for SFF use, that are simpler and that require less complex equipment than that disclosed in the U.S. Pat. No. 5,647,931.
SUMMARY OF THE INVENTION
A method for dispensing a powder is disclosed here which uses a rotating cylindrical dispenser to meter measured portions of a powder from a dispensing hopper. A powder dispensed from said hopper is dropped by force of gravity to a platen, said platen being movable horizontally from a first position under said hopper to a second position along a build bed container for containing powder to be consolidated into fabricated articles of manufacture. Any of the SFF methods of fabrication could be used with the invention such as but not limited to 3DP, selective laser sintering, or stereolithography. The method of the present invention discloses distribution of the powder from the platen across the build bed to distribute the powder as a layer over the upper surface of the build bed.
The rotating cylindrical dispenser may comprise a rotating cylinder having an elongate recess, and adapted for rotation from a position allowing powder flow from the hopper into the recess, to a position allowing powder flow from the recess onto the platen. This rotating cylinder is referred to as a rotating spoon. The rotating cylindrical dispenser may also comprise a rotating screw adapted to convey powder from the interior of the hopper to the exterior of the hopper, from where the powder can fall to a platen.
The system repeats the process a selected number of times necessary to deposit a selected number of layers of powder on the build bed. The number of layers is selected by the operator of the system depending on the size of the articles to be fabricated, the nature of the powder or powders used in the build bed, and the amount of detail to be incorporated into the fabricated articles.
By use of an elongate platen in the method of the present invention, multiple powders can be used in fabricating articles using SFF and 3DP. According to the teachings of the invention an elongate platen is mounted under a plurality of hoppers for containing powder. The length of the elongate platen is determined by the length of the hoppers and the distance between the hoppers, a suitable platen extending under each powder hopper being used in the method.
It is an object of the present invention to provide a method for dispensing a powder for use in SFF and especially 3DP which can be automated.
It is an object of the present invention to provide a method for dispensing multiple powders for use in SFF and especially 3DP which can be automated.
It is an object of the present invention to provide a method for dispensing multiple powders for use in SFF and especially 3DP which minimizes the number of mechanical parts necessary in an apparatus used for SFF and 3DP.
It is an object of the present invention to provide a method for dispensing multiple powders for use in SFF and especially 3DP which allows for refilling a powder dispenser while a SFF and 3DP apparatus is in operation.
It is a further object of the present invention to provide a method for dispensing multiple powders for use in SFF and especially 3DP which minimizes cross-contamination between the powders used.
A method for dispensing multiple powders is disclosed herein which can be automated and which also provides for the minimization of potential cross-contamination between the powd
Fedor Jeffrey A.
Gaylo Christopher M.
Imiolek Ireneusz J.
Douglas Steven O.
Therics, Inc.
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