Metal deforming – By use of closed-die and coacting work-forcer – Cup or shell drawing
Reexamination Certificate
1999-06-03
2001-05-01
Larson, Lowell A. (Department: 3725)
Metal deforming
By use of closed-die and coacting work-forcer
Cup or shell drawing
Reexamination Certificate
active
06223579
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the invention
The invention is directed in general to core plugs, and more particularly, to a core die apparatus for the formation of core plugs and an associated method of manufacturing a core plug.
2. Background of the invention
Core plugs, which include, among others, cup plugs, core hole plugs, freeze plugs and welsh plugs, have been known in the art. These are typically used to seal openings in, for example, automobile engines, transmissions, throttle body parts, water pumps, cylinder heads, and other housings. Generally, the core plug is slightly larger than the opening to be sealed, but also slightly softer. As such, when the plug is forced into the opening, a tight press-fit can be achieved which insures a proper mating of the surfaces of the plug to the opening, and, in turn, a leak-proof seal.
With many applications, such as with automobile engines, adhesive is utilized with the outer surface of the core plugs, further promoting the mating of the core plug to the opening, to, in turn, render better seal and reduce the risk of failure. Current manufacturing techniques apply a wet adhesive to either the opening or the smooth outer surface of the core plug. Subsequently, the core plug is forced into the opening. While such a method may achieve a solid bond between the core plug and the opening, the process is inefficient. First, a station must apply a wet adhesive to either the core plug or the opening. Next, a separate station forces the plug into the opening. As such, in the case of automobile engine assembly, the assembly line must stop at two stations. Inasmuch as factory output decreases every time the assembly line stops, two separate stations substantially affecting output, and, eliminating one station would be a significant improvement.
One improvement is disclosed in U.S. Pat. No. 4,750,457 issued to Bonutti. This reference discloses machining core plugs, to include grooves about their smooth outer circumferential surface. These grooves are then pre-filled with a dry-to-the-touch adhesive. This type of adhesive is activated, generally, by the absence of air. In the case of automobile engine assembly, these pre-filled core plugs are, at a single station, forced into the engine opening. Once forced into the opening, the adhesive becomes activated, and dries to form a solid leak-proof seal. While this method appears to reduce the engine assembly time by eliminating a station, there are other drawbacks associated with this process.
Specifically, the cost of machining grooves into the outer circumference of the core plug can be cost prohibitive. Indeed, machining of the core plug is labor intensive and time consuming. Additionally, to make a large volume of plugs, a multitude of expensive milling equipment is necessary. Accordingly, any savings realized by the elimination of a station is more than offset by the increased costs associated with the machined core plug. Notwithstanding the availability of this method, the auto manufacturers have continued to utilize the wet adhesive (two station) method, inasmuch as it appears to be less costly than the machined core plug.
SUMMARY OF THE INVENTION
The invention comprises a method for manufacturing a core plug from core blank. The core blank includes an outer rim, top surface and a bottom surface. The method comprises the step of positioning the core blank into a stamping apparatus. Next, a recess region is stamped into the outer rim of the bottom surface of the core blank. The bottom surface of the core blank is then positioned into a blank accepting region of a core die formation apparatus. The core blank is propelled through an opening extending through the core die formation apparatus. A portion of the outer rim is thereby deformed upward and inward to render a core plug. The recessed region stamped into the core plug is unaffected by the deformation step.
In a preferred embodiment, the method further comprises the step of removing the core plug from the core die formation apparatus. Further, in another preferred embodiment, the method may comprise the step of applying an adhesive to at least a portion of the recessed region.
In a preferred embodiment of the invention, the recessed region stamped into the core blank comprises a uniform groove concentric with an outer perimeter of the core blank. Additionally, the recessed region may comprise stippling or a zigzag pattern.
The invention may further comprise a core plug formed by the above-identified methods wherein the core plug includes a base region, an outer rim and a recessed region. The outer rim extends upward from the base region, around the outer perimeter of the base region and includes an exterior surface. The recessed region extends about the exterior surface of the outer rim. In a preferred embodiment, the core plug includes an adhesive operably applied to a portion of the recessed region.
The invention further comprises a, core die formation apparatus for the formation of a core plug from a core blank, wherein the core blank includes a recessed region. The core die formation apparatus comprises a second die member. The second member includes a top surface, a blank accepting region and a substantially perpendicular opening extending through the second die member. The opening includes an introduction region proximate the blank accepting region, a transition region and an end region. The size of the opening at the introduction region is smaller than the size of the core blank and greater than the size of the opening at the end region. The transition region comprises a continuous convex surface providing a smooth, gradual transition from the introduction region to the end region. This surface, in turn, facilitates smooth formation of the core blank into the core plug, and the recess regions of the core plug are unaffected by the core die formation apparatus.
Additionally, the core die formation apparatus includes propelling means which propel the core blank from the top surface of the second die member through the end region of the opening, to render the core plug.
In a preferred embodiment, the transition region comprises a uniform acute angle relative to an axis perpendicular to the top surface of the second die member. The junction between the introduction region and the transition region is rounded, as is the junction between the transition region and the end region.
In another preferred embodiment, the opening is substantially circular in cross-section. Additionally, the second die member may include a bottom surface wherein the opening extends from the top surface to the bottom surface of the second die member.
In a preferred embodiment, the propelling means may comprise a punch member matingly configured to force the core blank through the opening of the second die member.
In a preferred embodiment, the core die formation apparatus further includes means for removing the formed core plug from the core die after formation of the core plug. In such a preferred embodiment, the removing means may comprise a biased prying member operably positioned proximate the propelling means. The biased prying member is slidably engagable with the propelling means, and, in turn, the core plug.
In a preferred embodiment, the second die member may comprise a carbide material having a TI-8 coating. Additionally, in another preferred embodiment, the second die member may comprise a high carbon tool steel.
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Larson Lowell A.
Mercury Products Corporation
Shaftal and Associates, Ltd.
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