JPS6217179Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a powder compacting device mainly used in the field of powder metallurgy.

As shown in Fig. 2, the general configuration of a powder compacting device is such that a die 1 having a mold hole of a desired shape and a lower punch 2 that is always fitted into the die cavity form a die cavity. The scraped and filled raw material powder is compressed and shaped between an upper punch 3 and a lower punch 2.

However, when the upper end surface of the powder compact to be molded has irregularities as shown in FIG. 1, the above-mentioned conventional molding apparatus has the following problems.

That is, in order to form a recess on the upper end surface of the powder compact, a protrusion corresponding to the recess is provided on the lower end surface of the upper punch, so that when the upper punch is lowered, the tip of the protrusion touches the powder inside the die. As shown on the right side of FIG. 2, the hole of the die and the outer periphery of the upper punch are not yet fully fitted. Therefore, especially when the protrusion is close to the edge of the die, a portion of the powder within the die overflows through the gap as shown in the figure, resulting in defects in size, weight, and density of the green compact. This is one of the problems.

In addition, when discharging the green compact from the die after molding,
When the die is pulled down while the green compact is held down by the upper punch, the green compact slightly expands in the diametrical direction due to spring back, and as a result, the uneven parts of the green compact are pressed against the uneven parts of the upper punch and come into contact. Frictional resistance on the surface increases. Therefore, when the upper punch rises, the green compact also rises together with the green compact remaining attached to it, which may cause a double-strike accident in the next molding cycle. This is another problem.

To solve the first problem, there is a so-called underfill method in which the die is slightly raised just before pressurization, but this requires a press with a built-in underfill mechanism and is not suitable for this method. There are also shaped compacts.

This invention is achieved by sliding a skirt 5 around the outer periphery of the upper punch 3 and supporting it so that it can slide vertically within a predetermined range, as shown in the embodiments of FIGS. 4 and 5. Therefore, the two problems mentioned above can be solved at the same time.

Comparing the devices shown in both figures, in the former case, the pneumatic device 71 is used to move the skirt 5 up and down, so the skirt 5 can be stopped at any position. The length of the skirt 5 is set so that its lower end at the bottom dead center is below the tip of the protrusion provided on the upper punch 3.
In the figure, 6 is a holder, which also serves as an air cylinder here.

On the other hand, in the latter case, the skirt 5 is always pushed downward by the spring 72, so
As long as there is no external force acting against the spring, it will always be at bottom dead center. Also, unlike the former case, there is an expansion (spring back) of the green compact on the inner periphery of the lower part.
A relief portion 51 is provided. and,
The length of the skirt 5 is set so that its lower end is below the tip of the protrusion provided on the upper punch 3 at the bottom dead center, and the upper step of the relief section 51 is below the end surface of the upper punch. has been done.

Next, the operation of the apparatus shown in FIG. 4 will be explained with reference to FIG. First, when the upper punch is lowered from the powder filling state A, the lower end surface of the skirt 5 first comes into close contact with the upper surface of the die 1, as shown in B, to prevent the powder from overflowing.
Thereafter, the protrusion of the upper punch comes into contact with the powder and begins compression, and the die 1 also descends slightly to perform a double-pushing action, completing the molding in the state shown in (c). During this time, the skirt 5 maintains contact with the die 1 by controlling the air pressure.

Therefore, when the die 1 is lowered to the same level as the upper surface of the lower punch 2 while keeping the upper punch 3 and skirt 5 in the position C, the green compact 4 expands in the diametrical direction due to spring back as it is released from the die. However, as shown in Figure D, the outer diameter of the bulging portion 41 is larger than the inner diameter of the skirt 5. At the same time, the contact pressure between the inner surface of the groove of the powder compact and the inner surface of the projection of the upper punch increases, and the two adhere to each other due to frictional resistance. Therefore, if the skirt 5 is lowered and the upper punch 3 is raised while suppressing the bulge 41 with the tip of the skirt 5, the powder compact remains on the lower punch 2. After that, one cycle of molding is completed by eliminating this by an appropriate means.

Next, FIG. 7 explains the operation of a device (see FIG. 5) that uses a spring to operate the skirt 5, and the spring is not shown.

Comparing the operation of this device with that in Fig. 6, we find that
Steps 1 to 3 are exactly the same, and only steps 2 to 5 are different due to the difference in the skirt operation method. That is, when the die 1 is pulled down from the powder compacting state C, unlike the case shown in the previous figure, the skirt 5 also descends together, causing interference with the powder compact that is about to expand. The reason why the relief part 51 is provided on the inner periphery of the skirt 5 is to avoid this interference, and it is sufficient to provide the relief part 51 with the minimum necessary dimensions in both the diameter direction and the height direction. When the upper punch 3 is raised from the state of 2, the powder compact E rises while adhering to the upper punch until its bulging part 41 hits the relief stepped part provided in the skirt, and then it separates from the upper punch. Lower punch back up. The rest is to eliminate this by appropriate means and complete one cycle of molding, as in the case of the previous figure.

In addition, although the above-mentioned embodiment was explained in the case of the lower punch fixed/die movable type, this invention is not limited to this, but can also be applied to a relative case of the lower punch movable/die fixed type. .

As detailed above, this invention was able to simultaneously solve the two problems mentioned above in conventional powder compacting equipment, and although there are few changes in the mechanism, the resulting effects are significant. be.

[Brief explanation of the drawing]

Fig. 1 is a drawing showing the shape of a compacted powder body in an embodiment of this invention, Figs. 2 and 3 are drawings explaining problems of conventional powder compacting equipment, and Figs. 2 is a drawing showing the mechanism and operation of the device. 1...Die, 2...Lower punch, 3...Upper punch, 4...Powder compact, 5...Skirt, 6...Holder.

Claims (1)

[Scope of utility model registration request] In a device that compresses and molds raw material powder filled in a cavity formed by a die 1 and a lower punch 2 fitted therein between an upper punch 3 and a lower punch 2, the outer periphery of the upper punch 3 A powder molding apparatus characterized in that a skirt 5 is slidably fitted to the upper punch 3 and the skirt 5 is supported so as to be vertically slidable along the outer periphery of the upper punch 3.