Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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The present invention relates to an improved door frame, for example, for a
gaming or video lottery terminal, and to a method of making same.
BACKGROUND OF THE INVENTION
Conventionally door frames for gaming and video lottery terminals are
5 manufactured according to a variety of processes requiring a considerable amount of technical
skill. These methods currently require taking various sheet metal components and turning
them into a single piece sheet metal door through the use of fusion welding. The frames
conventionally have highly reflective surfaces and, for security reasons, must be strong and
durable. Thus, they tend to be heavy.
Cu~lenlly, the most durable finish being applied to door frames for gaming and
video lottery terminals is that of chrome plating. Such a finish itself imposes special
requirements on the fabrication process. Chrome by its very nature tends to highlight surface
imperfections of a product.
The current method of construction of door frames for gaming and video
lottery terminals consists of the following steps:
(1) Shear/punch/break-form various gauges of sheet metal components in
preparation for welding.
(2) Using a weld fixture to precisely hold the component parts in correct
relation to each other, they are then welded. The weld fixture must
be designed in such a way as to compensate for weld shrink:~e and the
heat distortion inherent in the welding process. Welding is
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accomplished using either gas tungsten arc welding or gas metal arc
welding processes.
(3) After the door frame is welded, the welds are dressed. The dressing
operation can be broken into three distinct steps: grinding, buffing and
polishing.
(4) Chrome is then applied to exterior surfaces of the door frame.
Conventionally, such a complicated procedure for manufacturing door frames
for gaming and video lottery lel.llinals, and indeed any other currency-operated commercial
machines such as vending machines, has been because of the extremely close tolerances
10 required for such door frames, to accommodate the aesthetic requirements as well as the
security requirements inherent therein.
OBJECTS OF THE PRESENT INVENTION
It is an object of the present invention to provide a door frame for such
machines, and a method of making same, which will elimin~te many of the technical skills
15 and requirements required in conventional methods of making such door frames, to minimi7e
the potential for product rejects and provide a better, final quality door frame.
It is a further object of the present invention to provide a more consistent,
lighter product at a lower per-part cost.
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SlJDaMARY OF THE INVENTION
In accordance with the present invention there is provided a method of making
a metal door frame for a currency-opeMted commercial machine. The method comprises the
steps of: passing predetermined relative amounts of metals to form a predetermined
5 thixotropic-metal alloy into a temperature controlled barrel of a screw extruder; heating the
metals under high shear-rate mixing to a semi-solid state to form a thixotropic mixture of
said metals; injecting the thixotropic mixture of metals at high speed into a mold of the
desired shape of the metal door fMme; cooling the mixture in the mold and ejecting the
cooled mixture from the mold in the form of a solidified, net-shape door fMme.
The invention also relates to a door frame for a gaming or video lottery
terminal, or a door for a vending machine, made according to this method.
It will be understood that the door fMme made according to the present method
requires no welded parts. In addition, it requires no grinding and polishing steps. As will
be described in more detail subsequently, the thixotropic alloys which can be used for making
lS such door fMmes are relatively lightweight. Furthermore, the thixotropic molding process
applied to such door fMmes permits the door fMmes to be made according to close tolerances
with more reliability.
While the invention will be described in conjunction with an example
embodiment, it will be understood that it is not intended to limit the invention to such
20 embodiment. On the contMry, it is intended to cover all alternatives, modifications and
equivalents as may be included within the spirit and scope of the invention as defined by the
appended claims.
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DETAILED DESCRIPTION OF THE INVENTION
The use of thixotropic materials in a molding process is a relatively new
process, aspects of which are described and illustrated in U.S. Patents Nos. 4,694,881 and
4,694,882 of Busk issued September 22, 1987. In applying thixotropic molding processes
5 to the manufacturing of doors for gaming and video lottery tellllinals and the like, the
technologies of die-casting and plastic-injection molding using magnesium based alloys is
used to produce a "net shape" casting in one step in a single machine. The term "net shape"
is used to indicate that parts produced according to this process do not require additional
machining to dimensionally meet machine drawing requirements.
The process in question consists of introducing alloy feed stock (for example
alllmimlm and magnesium in relative amounts to produce a thixotropic mixture and a final
alloy product having the desired characteristics) at room temperature to the heated barrel and
screw of a modified injection molding machine. The temperature of the alloy feed stock
material is then raised to the semi-solid region under high shear rate mixing. This results
15 in a thixotropic (viscose) material that flows like a plastic. The semi-solid mixture is then
injected at a very high speed, m~ ing its ideal flow throughout the injection phase, into
a pre-heated metal mold under vacuum to produce a net shape part. While aluminum-
magnesium alloys are considered being the ideal thixotropic material for the process and
products of the present invention, it is envisaged that other metal alloy compositions will also
20 be suitable.
The mold in question is fabricated once the dimensions of a particular door
frame have been fin~li7ecl That may be a single piece part or modular piece parts which
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would allow for various configurations of doors to be built-up from a minim~l number of
molds. The mold is fabricated from heat treated tool steel. The surface finish desired for
the f1ni~hecl net shape product is applied to the interior of the mold. For example a high
polish surface finish would be applied to the interior of the mold for the equivalent
reflectivity accomplished by chrome plating according to conventional processes. The
desired surface finish would be consistently reproduced by the mold on every part produced
in the mold.
With the mold completed, it is then used in the door frame production process.
Cycle times can vary depending on the mass of the part being molded. Typical cycle times
are less than sixty seconds.
The part or parts produced from the mold would be subjected to whatever
minor fini~hing work was required depending on the end finish being applied to the part.
The final door frame is then ready to be shipped to a customer.
The thixotropic molding process applied to such door frames allows the
following unique advantages:
(1) More complex door frame designs are possible, including thick and
thin areas in the same part, without distortion. As well, intricate core
shapes such as threads and exceptionally small holes can be provided.
(2) Superior dimensional tolerances can be accomplished. These may be
up to five times better than die-casting processes, due to the low
shrink~ge of magnesium.
(3) The thixotropic molding process results in a product having very low
porosity which is capable of holding pressure and vacuum without
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additional impregnation. The door frame parts produced can also be
heat treated.
(4) Generally the surface as produced by the molds requires very minim~l
or no finishing at all. The surface can, if required, be further chrome
S plated, powder coated or wet painted.
(5) Door frame parts produced according to the process of the present
invention are from 30% to 50% lighter than conventional die-cast
~hlminllm door frame parts and typically 20 times stiffer than
engineered resins.
(6) Currently parts as thin as .040 inches to as thick as .750 inches have
been molded according to the method of the present invention, with
excellent results.
(7) Excess or rejected parts can be recycled for use again in the molding
process.
(8) Rec~llse of the density of the net shape part, parts can also be fusion
welded.
Thus, it is apparent that there have been provided in accordance with the
invention a currency-operated commercial machine door frame, such as a gaming and video
lottery terminal door frame and method of making same, that fully satisfy the objects, aims
20 and advantages set forth above. While the invention has been described in conjunction with
a specific embodiment thereof, it is evident that many alternatives, modifications and
variations will be apparent to those skilled in the art in light of the foregoing description.
Accordingly, it is intended to embrace all such alternatives, modifications and variations as
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fall within the spirit and broad scope of the invention.
