US20090257904A1

US20090257904A1 - Device and method for pressing a metal powder compact

Info

Publication number: US20090257904A1
Application number: US12/082,425
Authority: US
Inventors: Roger Lawcock; Mark Haiko; Frank Ma
Original assignee: Stackpole Ltd
Current assignee: Stackpole Ltd
Priority date: 2008-04-11
Filing date: 2008-04-11
Publication date: 2009-10-15
Also published as: WO2009124380A1

Abstract

A method of pressing a powder metal compact comprising partially filling a die cavity with powder metal, engaging a second die with the first die, extending radially inwardly punches for forming a transverse feature in the compact, filling the die cavity with powder metal, compressing the powder metal with a punch, relieving pressure on the compact, withdrawing the radially inwardly punches so as to allow axial movement of the compact, withdrawing the second die, and ejecting the compact from the die while simultaneously filling the die cavity.

Description

FIELD OF THE INVENTION

The invention relates to a device and method for pressing a powder metal compact having a transverse feature by use of radially extending punches, which punches are radially removable upon release of punch compacting pressure.

BACKGROUND OF THE INVENTION

The prior art shows a device for pressing metal powder compacts to be sintered which comprises a split die having a cylindrical cross section, each die cooperatively engaged in a horizontal plane, the horizontal plane being perpendicular to the direction of their longitudinal axis. This device further comprises punches that are movable toward each other in a direction that is perpendicular to the horizontal plane, each of which is associated with the split die and is adapted for pressing one of the metal powder compacts. The axes of movement of the punches is vertical. The powdered metal material is fed to the upper die when the punch associated therewith is lifted from the die. Suitable means are provided for moving the punches one towards and away from the other in order to compress the powdered material to press the compact and to eject the compact.
The device of the kind described does not, however, permit pressing of compacts with transverse features which otherwise could not be removed from the compacts from the dies solely by axial displacement of the punches and the dies. For instance, with a device of this kind it is not possible to press compacts having a recessed transverse feature.
Representative of the art is U.S. Pat. No. 3,752,622 which discloses a device for moulding compacts with undercut compacts to be sintered by compaction of powdered material. A two compact die forms the chamber in which the compact is moulded. A pair of opposed punches pass through the die to compact the powdered material. The two compacts of the die are held firmly in contact with one another during the stroke of the punches by an annular collar with inclined surface engaging oppositely inclined surfaces on the die. After the material has been compacted, the two compacts of the die are separated in such a direction as not to interfere with the undercut portions of the compacts. After the die has opened, one of the punches retracts while the other continues its stroke to move the compact from between the two compacts of the die.
What is needed is a device and method for pressing a powder metal compact having a transverse feature by use of radially extending punches, which punches are radially removable upon release of punch compacting pressure. The present invention meets this need.

SUMMARY OF THE INVENTION

The primary aspect of the invention is to provide a device and method for pressing a powder metal compact having a transverse feature by use of radially extending punches, which punches are radially removable upon release of punch compacting pressure.
Other aspects of the invention will be pointed out or made obvious by the following description of the invention and the accompanying drawings.
The invention comprises a method of pressing a powder metal compact comprising partially filling a die cavity with powder metal, engaging a second die with the first die, extending radially inwardly punches for forming a transverse feature in the compact, filling the die cavity with powder metal, compressing the powder metal with a punch, relieving pressure on the compact, withdrawing the radially inwardly punches so as to allow axial movement of the compact, withdrawing the second die, and ejecting the compact from the die while simultaneously filling the die cavity.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and form a compact of the specification, illustrate preferred embodiments of the present invention, and together with a description, serve to explain the principles of the invention.

FIG. 1 is a perspective cross-sectional view of the compacting apparatus.

FIG. 2 is a perspective cross-sectional view of the compacting apparatus.

FIG. 3 is a perspective cross-sectional view of the compacting apparatus.

FIG. 4 is a perspective cross-sectional view of the compacting apparatus.

FIG. 5 is a perspective cross-sectional view of the compacting apparatus.

FIG. 6 is a perspective cross-sectional view of the compacting apparatus.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 is a perspective cross-sectional view of the compacting apparatus. The apparatus generally comprises a lower die 10 and punches 11, 12, 13, 14 which are axially moveable within die 10. Powdered metal material is filled into the die cavity 16 by a moveable feeder shoe 15. When not in use, feeder shoe 15 is withdrawn and rests adjacent to the die 10, for example, upon a staging surface 17. Feeder shoe 15 is moveable between the position shown in FIG. 1 and the staging surface 17. Feeder shoe is connected to a powder material hopper known in the art (not shown) or other suitable means of conveying the metal powder material to the die.
FIG. 2 is a perspective cross-sectional view of the compacting apparatus. Cavity 16 is first filled with powder. Upper die 20 is then moved into position over die 10. Upper die 20 can be moved vertically into position by use of either hydraulic or mechanical means.
Upper die 20 comprises radially moveable punches 21. “Radial” is determined with respect to the direction of movement of punches 11-14. Punches 11, 12, 13, 14 may each be moved vertically to compress the powder to form a compact. Punches 12, 13 and 14 each provide the means by which various elevation surfaces are formed into the compressed “green” compact.
Radially moveable punches 21 are then moved radially inward until they contact the outer surface of punch 12. Punches 21 may be moved by a variety of means, but the preferred method is hydraulically. The remainder of the cavity is then filled with powder to a level substantially equal with the top surface 19 of die 20. Feeder shoe 15 is then withdrawn, and in doing so the upper surface of the powder material is trimmed of excess powder. This results in the proper amount of powder in the die cavity, ready for compaction.
FIG. 3 is a perspective cross-sectional view of the compacting apparatus. Punch 22 and punch 23 compress the powder in cavity 16 by moving axially toward die 10, punches 21, and punches 11, 12, 13, 14. Compression of punch 22 toward punches 11, 12, 13, 14, 21 fully compacts the compact. Punch 23 cooperates with punch 14 to fully form a bore through compact 100.
During final compaction punch 11 moves vertically toward punches 22 and 21. This is to avoid damaging portions 21 by imposing an otherwise unsupported bending moment. Hence, punch 11 compresses one end of the compact in part against portions 21, and punch 22 compacts the opposite end of the compact in part against punch 21.
Feeder shoe 15 is shown withdrawn to surface 17.
FIG. 4 is a perspective cross-sectional view of the compacting apparatus. Once compaction is completed, punch 22 and 23 and die 20 are vertically withdrawn, thereby relieving pressure on radial punches 21. Punches 21 are withdrawn radially. Vertical movement between punch 11 and die 10 assists in removing compact 100 from die cavity 16 and thereby moving the “green” compact above the upper surface of die 10. This results in fully undercut portions or transverse features in the compact which extend completely through the compact 100. In the preferred embodiment the apparatus comprises a plurality of extending radially punches 21. However, the method may use a single punch 21 for forming a desired single undercut or transverse feature with equal success.
FIG. 5 is a perspective cross-sectional view of the compacting apparatus. Die 20 and punches 22, 23 are shown withdrawn, thereby freeing compact 100 from die 10. At this stage compact 100 is borne upon punch 11.
Punches 21 are moveably connected to upper die 20. Punch 22 holds compact 100 stationary while punches 21 are withdrawn.
FIG. 6 is a perspective cross-sectional view of the compacting apparatus. The cycle is then repeated when the feeder shoe 15 is moved across die 10, thereby ejecting compact 100 laterally from die 10 and the apparatus. Feeder shoe 15 then pours powder material into cavity 16 and the described sequence is repeated.
The “green” compressed compact is then processed using known sintering methods which are not described herein but are well known in the art.
Although a form of the invention has been described herein, it will be obvious to those skilled in the art that variations may be made in the sequence, construction and relation of parts without departing from the spirit and scope of the invention described herein.

Claims

1. A method of pressing a powder metal compact comprising:

partially filling a die cavity with powder metal;

engaging a second die with the first die;

extending radially inwardly punches for forming a transverse feature in the compact;

filling the die cavity with powder metal;

compressing the powder metal with a punch;

relieving pressure on the compact;

withdrawing the radially inwardly punches so as to allow axial movement of the compact;

withdrawing the second die; and

ejecting the compact from the die while simultaneously filling the die cavity.

2. The method as in claim 1 further comprising:

ejecting the compact by extending a shoe for filling the die cavity.

3. The method as in claim 1 further comprising:

extending a plurality of punches for forming different surfaces in the compact.

4. The method as in claim 1 further comprising:

trimming a powder surface by withdrawing a shoe for filling the die cavity.