Plastic and nonmetallic article shaping or treating: processes – With step of making mold or mold shaping – per se
Reexamination Certificate
2000-05-17
2002-07-30
Kuhns, Allan R. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
With step of making mold or mold shaping, per se
C164S006000, C264S221000, C264S317000
Reexamination Certificate
active
06426027
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method of creating a fluid meter housing. More specifically, the present invention provides a method of manufacturing the housing for a fluid meter in which a molten material is injected into a cavity formed between a core and a mold. The core and mold are configured so that the cavity is shaped as desired for the fluid meter housing. After allowing the molten material to harden, the housing and enclosed core are removed from the mold. The core is then heated to its melting point and drained from within the fluid meter housing.
BACKGROUND OF THE INVENTION
Fluid meters have traditionally been constructed from various metals such as bronze and copper. As new materials and methods of using them have developed, the economic feasibility of substituting such materials for metals in the construction of fluid meters has improved. Thermoplastics represent one such class of material that can not only result in savings in the cost of materials but can also be more suitable for use with certain fluids.
Traditionally, plastic parts have been molded using conventional plastic injection molding techniques. Such techniques generally involve creating a mold having an internal cavity into which the plastic is injected in a molten state. Upon cooling the mold, the resulting plastic part may be removed by extraction or by opening the mold. Such techniques have been streamlined for mass production of plastic parts ranging from computer connectors to automobile components.
Unfortunately, traditional plastic injection molding techniques are difficult to apply when the part being manufactured has complex internal configurations. Fluid meters generally have complex internal passage ways complicating the use of conventional plastic injection molding techniques to manufacture housings or casings for fluid meters. While it is possible to manufacture such housings using conventional molding techniques, this proves to be time consuming and labor intensive.
For example,
FIG. 1
depicts a cross-section of an exemplary mold
20
used with conventional plastic injection molding techniques. Mold
20
includes a cavity defined in part by internal walls
22
which correspond in shape to the external surface of a desired fluid meter housing. Multiple interconnected inserts
24
, shown in
FIG. 2
, are placed within the cavity and correspond in shape to the internal surface of the fluid meter housing
26
. Interconnected inserts
24
are typically constructed from a metal, such as stainless steel, having a relatively high melting point. Using the specifications of the fluid meter housing
26
sought to be formed, interconnected inserts
24
are carefully machined so that when assembled the external surface of the interconnected inserts
24
conforms to the internal surface of the fluid meter housing
26
. Together, inserts
24
and internal walls
22
configure the shape of the cavity to correspond to the shape of housing
26
.
Upon placing interconnecting inserts
24
into the cavity, mold
20
is closed under a press capable of applying forces of up to
150
tons to maintain closure of the mold
20
. While closed, a molten thermoplastic material is injected at high pressures through port
28
. A sufficient amount of material must be injected to fill the cavity that exists between walls
22
of mold
20
and the external surface of interconnected inserts
24
. As the molten thermoplastic material begins to cool, it also begins to solidify and assume the shape of the fluid meter housing
26
. Simultaneously, the thermoplastic material also begins to shrink. As a result, mold
20
must be quickly reopened so that fluid meter housing
26
, now containing interconnecting inserts
24
, can be removed. Interconnecting inserts
24
are then removed from the interior of housing
26
. If the removal of interconnecting inserts
24
is not performed quickly after the thermoplastic material begins to cool, the interconnecting inserts
24
will be trapped inside the fluid meter housing
26
.
The conventional technique above described is disfavored for several reasons. First, the temperature required for injecting the molten thermoplastic material complicates the handling of interconnecting inserts
24
. Gloves or special equipment must be used to maneuver the inserts
24
. Second, interconnecting inserts
24
are expensive to manufacture and a set is required for each mold being used in the manufacturing process. Third, if the interconnecting inserts
24
are not rapidly removed as the thermoplastic material cools, fluid meter housing
26
must be destroyed in order to remove the interconnecting inserts
24
, and the entire process must be repeated.
SUMMARY OF THE INVENTION
The present invention provides a method of manufacturing a housing or casing for a fluid meter. In one example, the method of the present invention provides for injecting a molten material into a cavity or space formed between a core and a mold. The core and mold are configured such that the cavity between the surfaces of the core and mold forms the shape of the desired fluid meter housing. Upon allowing the molten material to cool or become rigid, the housing and the enclosed core are removed from the mold. The core is then heated to its melting point, or otherwise liquified, and drained or removed from inside the fluid meter housing. The present invention overcomes disadvantages of the prior art by providing a process whereby a fluid meter housing having relatively complex internal characteristics may be manufactured without the necessity of using expensive inserts or having to rapidly disassemble such inserts at high temperatures.
While variations of the present invention may be envisioned using the teachings disclosed herein, in one example of the present invention a first mold is provided having an internal surface that corresponds to the desired internal shape for a fluid meter housing. A metal in a molten state is injected into this first mold. The molten metal is then cooled until the metal solidifies to form a metal core in the shape of the internal surface of the fluid meter housing. After cooling, the resulting metal core is removed from the first mold.
A second mold is a provided having an internal surface that corresponds to the external shape desired for the fluid meter housing. This second mold and the core are configured so that upon placing the core into the second mold, a cavity is created that corresponds to the shape of the desired fluid meter housing. Upon placing the metal core into the second mold so as to create this cavity, a molten thermoplastic material is injected into the cavity so as to fill the cavity and form the fluid meter housing between the metal core and the second mold. The second mold and thermoplastic material are then cooled to cause the thermoplastic material to solidify into the shape of the fluid meter housing. The resulting fluid meter housing is then removed from the second mold. At this point in the process, the fluid meter housing may still contain the metal core. The metal core is heated until the metal reaches a molten state and can then be removed from the fluid meter housing. Alternatively, the metal core may be removed while the fluid meter housing is still within the second mold. This alternative requires that the materials used to construct the molds and housing have appropriate relative melting point temperatures.
The first and second mold can be configured with a variety of features desired for the fluid meter housing. By way of example only, the first and second molds may be configured for defining a fluid inlet and a fluid outlet for the housing. The first and second molds may also be configured for providing a plurality of tabs and a locking boss on the surface of the housing such that a register or other device may be attached. The first and second molds may also be configured such that the fluid meter housing is provided with resealable threaded connectors at the fluid inlet and the fluid outlet for connecting the housing to conduit or t
Scarborough, III John R.
Walden Brent M.
Dority & Manning P.A.
Kuhns Allan R.
Neptune Technology Group Inc.
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