US2475321A

US2475321A - Molded core

Info

Publication number: US2475321A
Application number: US491765A
Authority: US
Inventors: Clarence A Horn
Original assignee: HENRY L CROWLEY
Current assignee: HENRY L CROWLEY
Priority date: 1943-06-22
Filing date: 1943-06-22
Publication date: 1949-07-05
Anticipated expiration: 1966-07-05

Description

July 5, 1949. c. A. HORN 2,475,321

MOLDED CORE Filed June '22, 1943 IINV ENTOR. Clarence A H0571! 79 A .v fi 6J Aftys.

Patented July '5, 1949 MOLDED CORE Clarence A. Horn, West Orange, N. 3., asslgnorto Henry L. Crowley, South Orange, N. J.

Application June 22, 1943, Serial No. 491,765

3 Claims. 1

This invention relates to improved machinery and methods by means of which improvements in molded metal products may be secured.

The subject matter of this invention is concerned with metal bodies molded from metal powders and particularly with iron cores molded from powdered iron and constructed for use as a core for current carrying coils of electrical apparatus of various types. For example in some forms of radio circuits it is a practice at the present time to provide the tuning coils thereof with iron cores which may be longitudinally adjusted with respect to the coils to vary the inductance thereof. In order to facilitate such adjustments these cores are provided with a threaded rod or screw at one end which is secured in place by being molded therein during the formation of the core. The threaded rod extends beyond the end of the core a suitable distance and in use passes through a plate or other support in threaded engagement so that upon rotation the core is caused to move longitudinally.

Cores of this type are molded from extremely fine iron powders under very high pressures in a ram type of press having a fixed die forming a pocket into the opposite ends of which the rams move to compactthe powder under such high pressure as to cause the particles to become permanently bonded together. The durability of such core is commonly increased by sintering the molded product after compression.

vOne of the movable rams is provided with a central bore in which the threaded rod for the core is mounted with the end projecting so as to be inserted into the powder during molding. The rams, of course, have a sliding fit in the fixed die, but there is suflicient clearance so that under the extremely high pressures encountered some of the powdered metal will flow around the periphery of the ram a short distance into the space between it and the adjacent wall of the fixed die. Likewise some of the powder will flow under pressure into the space around the threaded rod between it and the surrounding wall forming the recess in the ram in which the screw is mounted. As the result of this escape of powdered metal there are formed fins which are termed in the art flashes at the ends of the core around the outer peripheral edges and around the projecting screw. The outer peripheral fins are easily removed, but it is a more difficult and less satisfactory operation, as well as an expensive one, to remove the flash around the screw which, of course, is molded into the threads of the screw.

If the material of the flash around the screw is not completely removed it will ultimately work loose when the core is in use, producing a fine iron powder or dust which gets through the electrical equipment and becomes a nuisance even if it does not, as it often may, disturb the electrical characteristics of the equipment. For example, in the case of ultra high frequency radio circuits a small amount of iron powder loose in the coils may cause electrical disturbances of undesirable magnitude.

The subject matter of this invention is concerned with a method of molding metal cores and projecting screws so as to overcome the diihculty particularly encountered with the flash which forms about the screw.

This invention resides substantially in the combination, construction, arrangement, relative location of parts, steps, series of steps, and the product, all as hereinafter described in full detail.

In the accompanying drawing,

Figure 1 is a vertical, central, cross-sectional view through a metal powder molding press showing the manner of molding the screw in a molded body and the flash forms;

Figure 2 is a similar view of such a press modifled in accordance with this invention;

Figure 3 is a vertical, central, cross-sectional view of one end of a core manufactured in accordance with this invention; and

Figure 4 is a top plan view thereof. In the usual metal outer molding process a press capable of producing very high pressures.

per square inch, say of the order of 100,000 pounds per square inch is provided. It includes a fixed die l0 which is a-body of steel having a passage therethrough of the configuration of the body to be molded. The core illustrated is of circular cross-section, and hence the passage through the fixed die lllis circular in cross-section. The lower end of the passage is closed by a bottom ram ll. With the ram H in lowermost position closing the bottom end of the opening, a predetermined quantity of metal powder is poured into the chamber thus formed. The top ram I2 is provided with a recess IS in which the screw It to be molded into the core is inserted. As the rams are moved towards each other the metal powder is compressed into a coherent body It: in which the screw it is embedded. Due to the enormous pressures employed some of the powder will flow into the space between the ram l2 and the die in to form a flash or fln, as indicated at [6. In a like manner a flash I! will form around the screw. Of course, a flash will form 7 3 at the bottom of the core [5 around the bottom ram, although this has not been illustrated in the drawings. The rams arewithdrawn, freeing the molded body. The flash i9 is easily broken oil, but the flash it is harder to eliminate. The description of the above old practice will be helpinvention.

This subject matter is illustrated in Figures 2, 3 and 4. The fixed die l and bottom ram ii are the same as the arrangement of Figure 1. The top ram i2 is however provided with a projecting collar I8 surrounding the recess l3 and of a length beyond the end of the ram at least equal to the normal length of the flash H which forms. When the body i5 is formed by compression the flash it will form as well as one at the bottom end and the flash i'i will also form around the screw M. However, as illustrated in Figure 3, the recess M in the end of the core or body i5 is of such longitudinal length that the flash B? which forms will be within the end of the core, and hence out of the region of that portion of the screw I 4 which must cooperate with a threaded support. Thus it is not necessary to o to the expense or bother of removing the flash i7 and it is so positioned and projected that it will not normally be broken loose during the use of the device. Of course, the flash formed around the outer periphery at the ends of the core is easily removed, and therefore no' provision is made in accordance with this invention for special handling thereof as in the case of the flash ET.

From the above description it will be apparent to those skilled in the art that the subject matter of this invention is capable of some variation, and I do not, therefore, desire to be strictly limited to the disclosure as given for illustrative purposes, but rather by the scope of the claims granted me.

What is claimed is:

1. A molded body composed of densely compacted particles of metal having a screw embedded therein and projecting beyond one face 4m in understanding the subject matter of this 4 thereof, said body having a recess surrounding said screw of an axial len th at least equal to the material of the body which flashes around the screw.

2. A magnetizable core comprising a formsustaining body of iron particles with a metal insert embedded therein and projecting beyond one face thereof, said body having a recess opening at said iaceand' lying concentric with said metal insert whereby the material which flashes around the insert will lie in the recess.

' 3. A method of molding a body of powdered metal with an insert embedded therein and projecting from one face, which comprises compacting the metal powder into a shape to form a recess in the resultant body surrounding the insert and simultaneously forming a flash at the periphery of said face and in the recess in said face surrounding the insert, and fixing said insert extending through said recess and beyond said face, said recess having an axial length at least equal to the height of the flash surrounding the insert.

CLARENCE A. HORN.

REFERENCES (Ci'lilED The following references are of record in the file of this patent:

UNITED STATES PATENTS Great Britain Oct. 7, 1935-