Metal founding – Process – Shaping a forming surface
Reexamination Certificate
2001-08-28
2003-10-21
Elve, M. Alexandra (Department: 1725)
Metal founding
Process
Shaping a forming surface
C164S045000, C164S007100, C164S160100, C264S221000, C264S227000
Reexamination Certificate
active
06634410
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to an improved mold apparatus and method. In particular, the invention relates to an apparatus and method for creating designs on the interior of molds. Even more particularly, the invention relates to an apparatus and method for creating investment cast molds with complex designs on the interior and/or on the interior and exterior of the molds.
BACKGROUND OF THE INVENTION
A tension arises when a business attempts to create objects with unique designs. The tension results from a conflict between various competing interests a business has. On one hand, businesses are interested in obtaining objects with unique designs that meet or exceed the customer's requirements. On the other hand, the business must keep time and cost to a minimum in order to remain profitable. If time and money are no object, almost any object may be created with any unique designs imagined. Since time and money are always a concern, however, there is a practical limitation to the creation of objects with unique designs that results in the practical impossibility of creating some objects and some designs in a commercially reasonable, i.e. profitable, manner.
By way of example and not limitation, it is known throughout the munitions industry that certain types of notch patterns or grooves cut into the inside, and outside, walls of a projectile or warhead case dramatically improves their fragmentation characteristics, thereby increasing overall effectiveness. Typically, such notches are cut utilizing traditional machining methods such as broaching, shaping, milling and sawing.
A major drawback to these traditional machining methods is their inherent low production rate and high cost. The cost of the cutting tools, machinery, and labor required to implement these traditional machining methods can easily create a situation in which it is cost prohibitive or unprofitable to produce such items on a mass production basis. As a result, even though a number of warheads/projectiles in existence or currently in production do employ notches, they are very simple or less than optimal notch patterns. That is, currently straight-line configurations i.e. straight up-and-down notches or circumferential rings, are the only practical configurations for machined/broached projectile cases. Furthermore, while designs on the outside of the casing are easier, the preferred casing has designs on the inside or on the inside and outside in combination, which is, again , extraordinarily difficult to accomplish.
The prior art machined or broached warhead/projectile cases perform only adequately, because the fragments have a tendency to slab (not separate) due to the straight-line broaching
otching configuration limitation. As a result, fragmentation and, consequently, lethality is only modestly controlled and predictable when cases are created with the limited machine options known in the prior art.
Attempts have been made to create complex shapes without machining. Galliger, U.S. Pat. No. 6,019,927 discloses the use of a flexible and resilient positive pattern to make solid parts with complex geometry. However, the flexible and resilient pattern is simply used to create a hard shell into which metal is poured. That is, the Galliger device can only be used to create a solid thing and can not be used to create a casing with an interior with a complex geometry.
A further serious drawback of the prior art warhead/projectile case creation processes is that typically warhead/projectile cases are machined or forged from solid bar stock. Consequently, as much as seventy-five percent of the high-quality steel used to manufacture a warhead/projectile case goes into the scrap bin. This results in a huge waste of energy, time and material.
Still another serious drawback of the prior art techniques is that any hole, regardless of depth, that is machined in the solid bar stock, must have a zero draft angle (straight walls). A draft angle (taper), from the bottom of the hole to the beginning of the hole, creates a variation in wall thickness which is not acceptable in the munitions industry, for example. While complex, three dimensional, nonlinear designs can be created on the inside of cases with no draft angle, a myriad of specialized tooling and hardware is required which, for all practical purposes, makes the end product prohibitively expensive.
The investment casting process, also known as the “lost-wax ”casting process, provides a viable solution to many of the problems associated with traditional machining methods. Despite an industry bias against cast casings, by its very nature, the investment casting process lends itself well to the creation of protruding or indented features, such as the aforementioned notches. Another advantage is the significant reduction in material waste as well as a reduction in the time required to perform any necessary finish machining operations, since parts may be cast to near-net shape.
The first step in the traditional investment casting process is to produce a wax replica of the part to be cast. This item is commonly referred to as a wax pattern or wax mold. Typically, wax patterns are produced by injecting melted wax into an aluminum mold assembly with internal cavities and/or cores conforming to the desired was pattern shape. Upon cooling and solidifying, the wax pattern must be removed from the aluminum assembly.
For the purposes of the present invention, this is where problems with the prior art arise. A hollow wax pattern with a round cross section, such as a wax pattern for producing the aforementioned warhead/projectile casing with an internal notch configuration, can not be produced by an aluminum mold of conventional design. That is because, in order to produce the hollow, notched interior surface, the mold design would have to incorporate an aluminum core, and, in addition this core would have to have protrusions in order to create indentations (notches) in the wax pattern. This creates an interference condition in which the removal of the wax pattern from the aluminum core is impossible without destroying the wax pattern.
Thus, there is a need in the art for an inexpensive apparatus and method for creating designs on the inside and outside of cases and other objects.
SUMMARY OF TIE INVENTION
Accordingly, an apparatus for creating designs on the interior of molds includes a resilient form with an exterior and an interior, with a design formed on the exterior. A rigid support member is removably attached to the interior of the resilient form. A mold pattern, conformed to removably receive the rigid support member and the resilient form in combination, completes the basic assembly.
In one aspect of the invention, a passageway in the rigid support member is provided for introducing a gas between the rigid support member and the resilient form. In a further aspect of the invention, the design is a three dimensional design. In another aspect of the invention, a vacuum application device is provided for applying a vacuum to the resilient form. In a further aspect of the invention, the vacuum application device has a draft angle. In another aspect of the invention, the vacuum application device includes a plurality of extensions conformed to create a draft angle. In yet another aspect of the invention, the exterior of the resilient form has no draft angle and the interior has a draft angle. In another aspect of the invention, a lubricant is provided between the resilient form and the rigid support member.
In another embodiment of the invention, an apparatus for creating designs on the interior and exterior of a mold includes a first resilient form with an exterior and an interior, with a design on the interior. A rigid base is conformed to removably receive the exterior of the first resilient form. A second resilient form with an exterior and an interior, with a design on the exterior, is provided. A rigid support is removably attached to the interior of the second resilient form. The rigid base and the interior of the first resilient form is conformed to
Wilson John H.
Wilson John T.
Wilson Robert E.
Elve M. Alexandra
McHenry Kevin
Shaffer Jr. J. Nevin
LandOfFree
Mold apparatus and method does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Mold apparatus and method, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Mold apparatus and method will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3130830