Hold-down system for compacting press

Details Hold-down system for compacting press Hold-down system for compacting press

1999-08-03

2001-03-13

Pyon, Harold (Department: 1722)

Powder metallurgy processes

Powder metallurgy processes with heating or sintering

Consolidation of powder prior to sintering

C425S078000, C425S260000, C425S448000

Reexamination Certificate

active

06200525

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a compacting press that includes a system for holding a feed shoe down against a platen, and more particularly, to such a press for making powder metal compacts.
2. Description of the Prior Art
It is known to produce metal parts by compacting metal powder and heating the compacted metal powder to sinter the metal particles to produce a finished metal product. In one type of commercially available compacting press, metal powder is typically delivered to a feed shoe, or shuttle assembly. The feed shoe is movable on the press table between a retracted position and an extended position. In the extended position, metal powder in the feed shoe drops into a die cavity. The feed shoe is then retracted and then upper and lower punches compact the metal powder in the die cavity to form a green compact. A core rod is also extended to form any inner diameter of the powder metal part. The compact is then ejected from the die cavity. When the compact is ejected, the press table lowers and then is raised back to the original level after the compact is removed. More raw metal powder is delivered to the feed shoe, and the feed shoe is extended over the die to feed another quantity of metal powder to the die. The cycle continues as additional green compacts are made.
In such presses, it is necessary to hold the feed shoe against the top surface of the press table or platen to ensure that the metal powder is properly distributed to the die. If the feed shoe were to raise up, an inadequate quantity of metal powder may be fed to the die, and the green metal compact produced could fall below quality criteria.
Two different types of prior art compacting presses are illustrated in
FIGS. 9-11
. In the type of press
200
illustrated in
FIG. 9
, the feed shoe
202
is smaller than the feed shoe
302
in the type of press
300
illustrated in
FIGS. 10-11
. In the
FIG. 9
type of press, the feed shoe
202
is typically about 4 inches wide, while the feed shoe
302
of the
FIGS. 10-11
type of press may more typically be about 11 inches wide.
In the
FIG. 9
type of press, the feed shoe
202
is moved toward and away from a die in the platen
204
and an overlying punch
206
during each cycle of operation. The feed shoe
202
is moved by a pivoting drive mechanism shown in FIG.
9
. As the element shown at
208
is pivoted, the feed shoe
202
is pushed or pulled across the platen
204
. The feed shoe
202
is held against the platen by a single air cylinder
210
acting against a bridge
212
between two lever arms
214
. The air cylinder
210
is behind the feed shoe
202
, and behind the feed tube
216
leading to the feed shoe
202
. The air cylinder
210
is set at an angle of about 45° from vertical. The
FIG. 9
type of press has somewhat limited utility, given the relatively small size of the feed shoe.
In the prior compacting press
300
illustrated in
FIGS. 10-11
, the feed shoe
302
is moved across the platen
304
by a linear drive. A system of rails and bearings has been used to hold the feed shoe
302
down against the surface of the press table or platen
304
. The rails
306
are fixed to the platen
304
. Springs
308
push roller bearings
310
up to bear against the rails
306
, and the springs
308
push the feed shoe
302
down against the press platen
304
, while allowing the feed shoe
302
to be extended and retracted. The rails
306
are long enough so that the feed shoe
302
is pushed against the press platen
304
throughout the range of horizontal motion of the feed shoe
302
.
The use of the rails
306
, springs
308
and bearings
310
has been problematic. The friction of the bearings
310
against the rails
306
may cause these elements to wear out relatively quickly. Uneven wear can cause part of the feed shoe
302
to raise away from the surface of the press table
304
, resulting in uneven powder distribution and poor part quality. Replacement of worn elements has been time consuming, requiring removal of bolts holding the rails
306
to the press table
304
.
SUMMARY OF THE INVENTION
The present invention is directed to providing a press with a hold-down assembly that holds the feed shoe against the press platen in an efficient manner using less expensive components, and that is versatile, allowing use of relatively large feed shoes.
In one aspect, the present invention provides a press for compacting raw material into a compact during a cycle of operation. The press comprises a vertically movable platen having a surface with a bore. A die is below the platen surface and aligned with the bore in the platen surface. A feed shoe is on the platen and is movable with vertical movement of the platen. The feed shoe is also movable horizontally across the platen surface from a press position spaced from the bore to a feed position overlying the bore to deliver raw material to the die. The press includes a movable punch to compact raw material in the die, a horizontally movable frame, a lever arm, and a force-transmitting device. The lever arm is connected to the frame and the feed shoe. The force-transmitting device is connected to act against the frame and the lever arm. The press includes a linear drive mechanism and a supplemental support connected, sized and positioned to relieve stress on the linear drive mechanism from operation of the force-transmitting device. The linear drive mechanism is connected to move the frame horizontally over at least part of the platen toward and away from the bore in the platen surface. The feed shoe, lever arm, force-transmitting device and at least part of the supplemental support move horizontally with the frame during each cycle of operation. The force-transmitting device urges the feed shoe against the platen during at least part of the horizontal movement of the feed shoe, force-transmitting device, lever arm and frame. The frame, linear drive mechanism and supplemental support are vertically fixed during each cycle of operation of the press. The feed shoe and platen move vertically during each cycle of operation of the press.
In another aspect, the present invention provides a press for compacting raw material into a compact during a cycle of operation. The press comprises a vertically movable platen having a surface with a bore. A die is below the platen surface and aligned with the bore in the platen surface. A feed shoe is on the platen and is movable with vertical movement of the platen. The feed shoe is also movable horizontally across the platen surface from a press position spaced from the bore to a feed position overlying the bore to deliver raw material to the die. The feed shoe has a front and a back. The press includes a movable punch to compact raw material in the die, a horizontally movable frame, a lever arm, and a force-transmitting device. The lever arm is connected to the frame and to the feed shoe. The force-transmitting device is connected to act against the frame and lever arm. A linear drive mechanism is connected to move the frame horizontally over at least part of the platen toward and away from the bore in the platen surface during each cycle of operation. The feed shoe, lever arm and force-transmitting device move horizontally with the frame during each cycle of operation. The force-transmitting device urges the feed shoe against the platen during at least part of the horizontal movement of the frame, feed shoe, lever arm and force-transmitting device. The frame and the linear drive mechanism are vertically fixed during each cycle of operation of the press, and the feed shoe and platen move vertically during each cycle of operation. At least part of the force-transmitting device lies between a vertical plane at the back of the feed shoe and a vertical plane at the front of the feed shoe during at least part of each cycle of operation.
In another aspect, the present invention provides a press for compacting raw material into a compact during a cycle of operation. The press comprises a vertically movable platen hav

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