Powder compacting apparatus

Details Powder compacting apparatus Powder compacting apparatus

1998-08-27

2002-06-11

Nguyen, Nam (Department: 1722)

Plastic article or earthenware shaping or treating: apparatus

Means for molding powdered metal

C264S109000, C425S352000, C425S415000

Reexamination Certificate

active

06402493

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for compacting a metal powder into a gear blank such as a helical gear blank.
2. Description of the Related Art
It has been customary to manufacture gears for use in automobiles as sintered gears.
FIG. 1
of the accompanying drawings shows one known powder compacting apparatus
51
for producing a compacted helical gear blank for use in automobiles.
As shown in
FIG. 1
, the powder compacting apparatus
51
comprises a horizontal lower plate
53
fixedly mounted on a foundation base
52
, a horizontal floating plate
55
vertically slidably mounted on an intermediate portion of a vertical guide post
54
mounted on the foundation base
52
and floatingly supported by a floating mechanism (not shown), and an upper plate
56
vertically slidably engaging an upper end of the vertical guide post
54
. A vertical lower punch
57
is mounted on the foundation base
52
and the lower plate
53
. A floating die
58
is rotatably mounted on the floating plate
55
. A vertical upper punch
59
is mounted on a horizontal punch holder plate
56
a
which is integrally mounted on the upper plate
56
.
The lower punch
57
has external helical teeth p on its outer circumference, and the floating die
58
has internal helical teeth s on its inner circumference. The internal helical teeth s are held in mesh with the external helical teeth p.
The upper punch
59
comprises a vertical inner punch member
59
b
fixed to the punch holder plate
56
a
and a vertical outer punch member
59
a
disposed around the inner punch member
59
b
for rotation about its own axis. The outer punch member
59
a
has external helical teeth q on its outer circumference which can be held in mesh with the internal helical teeth s of the floating die
58
.
The powder compacting apparatus
51
operates as follows: Initially, the upper punch
59
is in an elevated position. After a powdery material is filled in a die cavity space defined by the inner circumferential surface of the floating die
58
and the upper surface of the lower punch
57
, the upper punch
59
is lowered to bring the external helical teeth q of the outer punch member
59
a
into mesh with the internal helical teeth s of the floating die
55
. Upon continued downward movement of the upper punch
59
, the upper punch
59
and the lower punch
57
compact the powdery material into a compacted helical gear blank W. As the upper punch
59
descends, the outer punch member
59
a
and the floating die
58
rotate about their axes to keep their helical teeth q, s out of interference with each other.
However, the powder compacting apparatus
51
suffers a disadvantage as described below. As shown in
FIG. 2
of the accompanying drawings, the compacted helical gear blank W has different densities in the vertical direction. Specifically, the compacted helical gear blank W has a lower portion whose density is smaller than the density of an upper portion thereof.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a powder compacting apparatus for producing a compacted helical gear blank which is free from density differences in the direction in which a powdery material is compacted into the compacted helical gear blank.
According to the present invention, there is provided a powder compacting apparatus comprising an upper punch having external helical teeth, a lower punch having external helical teeth, and a floating die is supported around the lower punch and having internal helical teeth meshing with the external helical teeth of the lower punch. The floating die and at least one of the upper and lower punches are rotatable about their own axes, the floating die and the lower punch jointly defining a die cavity space for being filled with a powdery material therein. The upper and lower punches are movable relatively toward each other to compact the powdery material in the die cavity space into a helical gear blank during a powder compacting process while the external helical teeth of the upper punch are meshing with the internal helical teeth of the floating die. The powder compacting apparatus has a floating die lowering mechanism for forcibly lowering the floating die a predetermined stroke with respect to the lower punch in a latter period of the powder compacting process.
If the floating die were not forcibly lowered, the helical gear blank being compacted would be caught by the internal helical teeth of the floating die. Therefore, upward reactive forces applied from the lower punch would not be sufficient, making the density of a lower portion of the helical gear blank smaller than the density of an upper portion of the helical gear blank. The floating die is forcibly lowered in order to increase the reactive forces from the lower punch.
When the floating die is forcibly lowered, even if the helical gear blank is caught by the internal helical teeth of the floating die, the helical gear blank is released from the internal helical teeth and has its lower surface reliably held against the upper surface of the lower punch. The lower punch can then apply sufficient upward reactive forces imposed on the helical gear blank which is being compacted between the upper punch and the lower punch.
The floating die lowering mechanism may comprise a presser rod for starting to lower the floating die when the upper punch is lowered a predetermined stroke.
The lower punch may be mounted on a lower plate, and the upper punch may be mounted on an upper plate, the upper plate being vertically movable toward the lower plate. A floating plate may be floatingly disposed between the upper plate and the lower plate, the floating die being mounted on the floating plate. The presser rod may be mounted on the upper plate and extend downwardly toward the floating plate.
The above and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which a preferred embodiment of the present invention is shown by way of illustrative example.


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patent: 5043123 (1991-08-01), Gormanns et al.
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