Reverse break stamp hook assembly

Details Reverse break stamp hook assembly Reverse break stamp hook assembly

2002-07-24

2003-12-09

Lin, Kuang Y. (Department: 1725)

Metal founding

Process

Shaping liquid metal against a forming surface

C164S264000, C425S806000

Reexamination Certificate

active

06659160

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a reverse break stamp hook assembly for use in breaking a biscuit from a casting and a method of breaking a biscuit from a casting using a reverse break stamp hook assembly.
2. Description of Related Art
The die casting process is used to produce accurately dimensioned, sharply defined, smooth and/or textured-surface metal parts. In the die casting process, molten metal such as, for example, aluminum and alloys of aluminum, is forced under high pressure into a cavity between two die halves. The injected molten metal quickly solidifies in the die cavity, then the two die halves are drawn apart and the casting is ejected.
The ejected casting typically includes extraneous material (e.g., flash, which is a thin web or fin of metal on a casting that occurs at die partings, vents and around moveable cores) that must be removed from the casting in order to obtain an acceptable part. In addition, castings formed using a cold chamber die casting machine will have a gate or biscuit, which is the excess of ladled metal remaining in the shot sleeve, that must be removed. The extraneous material and biscuit are typically removed in a stamping operation using a pair of trim dies and a die casting biscuit breaking apparatus. The trim dies include cutting/trimming surfaces as well as punches or other desired tooling.
FIGS. 1A and 1B
show a schematic front view of a conventional die casting biscuit breaking apparatus
10
. The apparatus
10
consists of an upper trim die holder
18
, an upper trim die
20
, a lower trim die holder
28
, and a lower trim die
30
. A part
40
(or several parts) is placed between the dies
20
,
30
, typically on the lower trim die
30
. The part
40
will typically include extraneous material (e.g., flash) that needs to be trimmed, surfaces to be punched, as well as a gate or biscuit
50
that needs to be removed. As shown in
FIG. 1
B, the upper trim die holder
18
is moved downwardly to press the upper trim die
20
against the part
40
on the lower trim die
30
and thereby trim away the extraneous material from the part
40
. Conventionally, the upper trim die holder
18
also includes a stamp cutter
60
that presses downwardly against the biscuit
50
or gate to break the biscuit from the part
40
.
One of the problems with a conventional die casting biscuit breaking apparatus
10
is that the biscuits
50
tend to break off a distance from the part
40
, leaving a portion of biscuit material, sometimes referred to as a “high gate”
70
, remaining on the part
40
. These high gates
70
must be removed by hand, typically using angle grinders. This results in additional processing time and effort. On occasion, a high gate
70
will not be noticed upon inspection or will be improperly removed by hand. An overlooked high gate
70
can cause damage to tooling in downstream processes, resulting in machine down time and additional losses in production time due to the need to hand sort parts to find the missed high gates
70
.
SUMMARY OF THE INVENTION
The present invention provides a reverse break stamp hook assembly for use in breaking a biscuit from a casting, and a method of breaking a biscuit from a casting using the reverse break stamp hook assembly. Surprisingly, the reverse break stamp hook assembly and method according to the invention facilitate the removal of biscuits without creating a high gate. Moreover, the reverse break stamp hook assembly may be used with conventional stamping machines without modifying the operating sequence of the machine.
In accordance with the present invention, a reverse break stamp hook assembly is mounted in place of a stamp cutter on conventional stamping equipment. The reverse break stamp hook assembly includes a hook and a mounting bracket. The hook, which includes a downwardly extending leg and a counterweight arm, hangs from a pivot attached to the mounting bracket. A distal end of the hook leg has an angled front portion and a catch portion.
In further accordance with the present invention, as the upper trim die of the stamping equipment moves toward the lower trim die during the downstroke, the angled front portion of the hook contacts and slides over an edge of a biscuit, causing the hook to pivot away from the biscuit until the catch portion passes below the biscuit. The counterweight arm, which is on the opposite side of the pivot, causes the hook to pivot back toward the biscuit, positioning the catch portion under the biscuit. During the upstroke, the catch portion engages the bottom side of the biscuit and pulls the biscuit upwardly away from the part, causing the biscuit to break from the part as the upper trim die is raised. The biscuit breaks cleanly, and does not leave a high gate requiring further hand grinding. Accordingly, a rough cleaned and trimmed part results from use of the trim dies incorporating the reverse break stamp hook assembly of the present invention.


REFERENCES:
patent: 3672437 (1972-06-01), Bennett
patent: 3772946 (1973-11-01), Sarra
patent: 4607680 (1986-08-01), Mills et al.
patent: 4799534 (1989-01-01), Ueno et al.
patent: 5664471 (1997-09-01), Dundas
patent: 5839497 (1998-11-01), Fujino et al.

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