US2107846A

US2107846A - Metal extrusion press and method of operation

Info

Publication number: US2107846A
Application number: US702872A
Authority: US
Inventors: Ralph W Atkinson
Original assignee: General Cable Corp
Current assignee: General Cable Corp
Priority date: 1933-12-18
Filing date: 1933-12-18
Publication date: 1938-02-08
Anticipated expiration: 1955-02-08

Description

Feb. 8, 1938. R. w. ATKINSON .1

METAL EXTRUSION PRESS AND METHOD OF OPERATION Filed Dec. 18, 1933 2 Sheets-Sheet l 1 r HI lllll- I m I MU W INVENTOR Ra/ofi W/W/hJO/ Y ATTORNEYS Feb. 8, 1938. R. w. ATKINSON METAL EXTRU SION PRESS AND METHOD OF OPERATION Filed Dec. 1a, 1953 .2 ShQetS Sheet 2 YNVENTOR amx at .E n m A M KQ m M Patented Feb. 8, 1938 UNITED STATES,

PATENT OFFICE EXTRUSION PRESS AND METHOD OF OPERATION Application December 18, 1933, Serial No. 702,872

11 Claims.

This invention relates to metal extrusion presses and the method of operating such presses. More particularly the invention is concerned with presses for extruding metal sheaths on electrical cables. Ordinarily, cable sheaths are made of lead or an alloy of lead. It is an object of this invention to provide improved apparatus for extruding metal, and also to provide an improved method of operating such apparatus in which the metal to be extruded is not exposed to air or other gases. Other objects and advantages of the invention will appear hereinafter.

The invention will be best understood from the following description when read in the light of the accompanying drawings illustrating a certain specific embodiment of the invention.

In the drawings:

Fig. l is an elevation of a press for extruding cable sheaths and of the container for supplying a molten metal to the press;

' Fig. 2 is a top plan view to enlarged scale of the stuffing box which connects the upper end of the press cylinder and the press ram;

Fig. 3 is a vertical section through the stuffing box substantially on the line 3--3 of Fig. 2;.

Fig. 4 is a vertical section through the stuffing box substantially on the line 4-4 of Fig. 2; and

Fig. 5 is a section through one of the openings in the stufiing box Wall substantially on the line 30 5-5 of Fig. l, but to the same scale as Figs. 2

In sheathing electrical cables with metal there are two types of vertical presses in general use. In one of these the press cylinder is stationary and the press rarn moves, while in the other the press ram is stationary and the press cylinder moves. The present invention may be used with both types of presses, but merely for convenience it is illustrated herein with reference to a press in m which the cylinder is stationary.

The actual extrusion of metal is not continuous in either type of press for the reason that it is necessary to separate the ram and the cylinder and recharge the cylinder with metal when a majority of the original charge of metal has been extruded from the cylinder. In recharging, the cylinder is filled with molten metal, and then it is necessary to wait until the metal cools sufficiently to solidify before the extrusion operation can be continued.

Heretofore it has been the common practice in charging a press cylinder to separate the cylinder and the ram, and then to fill the cylinder with molten metal from a nearby melting pot by 55 opening a valve at the bottom of the pot and permitting metal to flow down an inclined trough, the lower end of which has been moved over the open end of the press cylinder. When the cylinder has been filled with molten metal the valve at the bottom of the pot is closed, and 5 an effort is made to remove the dross on the top surface of the metal in the cylinder either by flotation or by skimming. The ram is moved downwardly to seal the charge and then it is necessary to suspend operations until the molten 10 metal in the press cylinder has solidified. After solidification of the charge the extrusion operation may be continued.

in operating presses as described above, impurities are accumulated by or formed in the molten metal, and also on the exposed surface of the hot metal slug remaining in the cylinder, and on the thin layers of hot metal on the surfaces of the cylinder and ram. Exposure of the molten metal to the air as it issues from the melting pot 2G and flows through the trough to the press cylinder is accompanied by oxidation of the metal. This oxidation results in the formation of dross which is carried into the press cylinder. The upper surface of the slug left in the cylinder at the completion of an extrusion operation also begins to oxidize as soon as the ram leaves it on its up-travel. Likewise the thin film of metal on the inner surface of the cylinder and the end of the ram oxidizes and finds its way into the charge. This oxidized film tends to prevent perfect welding of the new charge, and while a portion of the oxide may float to the top and be skimmed off, a part of it will remain in the charge. This oxide may reduce the strength of the bond in the cable sheath. Furthermore, some metal may cling to the trough at the com pletion of a charging operation. Such metal will oxidize in the air and build up into large particle sizes which will be carried, possibly with other dirt, into the cylinder with the molten metal during the next charging operation.

In charging a press in the manner just described the metal which runs into the cylinder strikes the relatively cold wall of the cylinder and freezes in an irregular lump. The surface of this lump films over instantly and is continuously spattered with more hot metal, forming a larger lump containing oxide and gas bubbles which eventually must appear in the cable sheath. These entrapped air or gas pockets are compressed to very small size during the extrusion operation, and expand again after passing out of the die. If the pocket is near the surface of the sheath it will explode outwardly and perhaps may be discovered and repaired, but it is just as likely that the pocket will occur adjacent the inner surface of the sheath and burst inwardly, to the detriment of the cable insulation, as well as the sheath. These pockets weaken the sheath mechanically, even if they do not burst.

According to the present invention a commercially practicable method and apparatus is provided for extruding cable sheaths, in which oxidation of the slug remaining in the cylinder prior to a charging operation is prevented, and in which molten metal passes from the melting pot or other container to the press cylinder without exposure to the air or any other gas at any point during its movement. Fwthermore, the inner surfaces of the cylinder and lower end of the ram, both of which come in contact with the metal, are not exposed to the air or other are therefore free from oxides.

R ferring first to 1, extending upwardly cm the base 23 are the vertical columns 2i, four number, which support near their upper ends press canopy comprising the hydraulic r .c. Vertically movable within the cylr .3 is the hydraulic piston 24. Secured on lower e -d of the hydraulic piston as by cans of the SClLWS 25', is the downwardly exte g press ram 26. The press ram passes downwarly through the stuiifing box 2?, to be described more fully hereinafter, into the upper end of the press cylinder 33.

The press cylinder 23 is secured on top of the die block 25, having a horizontal die opening 33 rough which the cable passes during the sheathng operation. The die blocir rests on the base lovement or" the press ram into and out of the ress cylinder for the purpose of extruding metal herefrom is accomplished by means of the hydraulic cylinder and piston in the usual manner.

Surrounding the press ram 26 and secured to the upper end of the press cylinder 33, as by means of the screws 32 is the stumng box 2?. Connected in an opening through the wall of the stuffing box is a pipe 33 through which the press cylinder is charged with molten metal. The pipe conveniently is connected, as by means of pipe flanges and the pipe 34, with the outlet pipe 35 of a container 38 for molten metal, for example the melting pot. Conveniently an expansion joint, (not shown) may be included in this pipe connection. Flow of molten metal from the container 33 through the

pipes

35, 34 and 33 to the press cylinder 23 conveniently may be controlled by means of a valve, (not shown) located within the container 36 and operated by the valve stem 3'! extending upwardly through the top of the container 36. The

pipes

33, 34 and 35 may be covered with heat insulating material if desired.

The construction of the stuffing box 21 is shown more clearly in Figs. 2 to 5 inclusive. Conveniently the stuifing box is formed in two

pieces

38 and 39 which are connected together in posi tion about the press ram by means of the screws 43 passing through openings in the outwardly extending flanges H. A gas-tight connection between the two parts of the stufling box is obtained by means of the gaskets 42, for example asbestos, compressed between the flanged edges 4i.

Between the upper end of the press cylinder 28 and the lower edge of the stufling box 2! is a. packing ring 43, which is compressed as the screws 32 are turned down to secure the stufling box in position on the upper end of the cylinder. The

box is shown in Fig. 3.

packing 43, for example asbestos, insures gastight connection between the press cylinder and the stufhng box.

The opening 46 in the top of the stuffing box preferably has a sliding fit with the press ram 225. This opening 46 is enlarged near the outer surface of the stuihng box to receive a packing ring ll, for example asbestos, which may be compressed by means of the pacln'ng gland 48 and the screws 49 securing the packing gland to the stufilng box 21'. For convenience in assembling, the packing gland may be made in two pieces, as shown in Fig. 2, and when it is forced downwardly by means of the screws 49 the packing ring ll will be pressed against the surface of the rain '18, forming a seal to prevent passage of air or other gas into the press cylinder between the press ram and the stuffing box.

As may be seen in Figs. 3 and 4, the lower edge of that portion of the stuiilng box having a sliding fit with the press ram preferably is in the form of a scraping edge 56. As the ram is withdrawn from the cylinder at the conclusion of an extruding operation this edge will scrape from the stu face of the ram any metal which may have escaped past the end of the ram during the extruding operation.

The metal so removed from the ram will collect within the stufling box 21, and preferablymeans are provided for melting this metal so that it may return to the press cylinder while the cylinder is being charged with molten metal. This heating means conveniently may take the form of an electrical heating unit 53 located within the stuffing box, and preferably separated from the lower inner wall of the stuffing box by space or by thermal insulation so as to minimize the heat lost by the unit 53 by conduction. Ordinarily the amount of metal escaping past the end of the ram during an extruding operation is small, and it will not be necessary to melt the metal accumulated within the stuifing box each time that the press cylinder is charged with molten metal.

The connection of the pipe 33 to the stuifing It will be apparent that molten metal entering the stufiing box through the pipe 33 will continue down the inclined chute 56 formed in the inner surface of the stuffing'box and be discharged into the press cylinder 28. During the charging operation the press ram 26 is Withdrawn from the press cylinder as shown in broken lines in Fig. 3.

Throughout the charging and extruding operations the press cylinder and the stuffing box desirably are evacuated. Connecting with the interior of the stuffing box through an opening in the wall thereof is a pipe 58 connected, for example through a valve H, to a vacuum pump, indicated diagrammatically at 12. Desirably, a very high vacuum is maintained so that the interior of the press cylinder and the stuffing box are substantially free from air and other gases which might cause dross to form, or which might be included in the molten metal in the form of gas pockets.

Conveniently means are provided for observing the level of the molten metal as it nears the top of the press cylinder during a charging operation. As shown in the illustrative embodiment such means may take the form of oppositely disposed windows BI and 62.

The cross section through one of the windows shown in Fig. 5 illustrates the construction more fully. The window opening in the wall of the llll III

. stufiing box is provided with a removable rim 64 held in place by means of screws 65 and the wing nuts 66. Mounted in the rim 64 is a thick pane 01' glass 61, conveniently held therein along with the gasket $8 by means of the ring 69 secured to the rim M with screws ill. As the ring 64 is tightened in place by screwing down the wing nuts 8% the gasket 68 provides a gas-tight seal between the stuffing box 2'? and the glass 61.

The operation of the extruding apparatus will now be described. Upon the completion of an extruding operation the press ram 26 is withdrawn upwardly from the press cylinder 28 until the lower end of the ram is completely clear of the cylinder as shown in broken lines in Fig. 3. As the ram is withdrawn from the cylinder any metal which may have escaped past the end of the ram during the preceding extruding operation, is scraped from the wall of the ram by the scraping edge 56, and collects inside of the stuifing box 2?, without injury to the packing ring 4i". 7

The valve controlling the flow of molten metal from the container 35 through the

pipes

35, 3d and 33 is then opened to permit molten metal to flow from the container 36 into the press cylinder. If the amount of metal scraped from the wall of the ram and collected within the stufiing box is sufiiciently great the electrical heating units 53 may be operated to melt this metal so that it will flow down the inclined inner wall of the stufiing box into the press cylinder.

As the level of metal in the press cylinder approaches the top of the cylinder it may be observed through the windows 6! and B2, and when the metal reaches the desired level the valve may be closed to stop further flow. The charge may then be sealed, and when it has solidified the metal may be extruded by downward movement of the press ram.

Throughout the charging and extruding operations the space within the stufiing box 2'I and within the press cylinder desirably is evacuated through the pipe connection 58. No air or other gases are present, or come in contact with the metal from the time the molten metal leaves the container 36 until the solidified metal is extruded from the opening 30 in the die block 29. Consequently there can be no oxidation or other dross formation in the metal, and the formation of gas pockets or bubbles in the press cylinder is prevented.

Instead of maintaining a high vacuum in the space within the stufiing box and the press cylinder during the charging operation it maybe desirable in some cases to introduce into this space steam or some liquid which is inert chemically with respect to the metal being extruded, and which is a vapor at the temperature of the press cylinder and at atmospheric pressure, but which may be liquefied at the melting point of the extruded metal. other inert material may be supplied to the press cylinder through the pipe 58, connected, for ex ample through a valve 13, with a source of the inert material indicated diagrammatically at I4.

Steam not only is inert chemically with respect to lead, but steam is a vapor at the temperature of the cylinder and atmospheric pressure, and yet is liquefied by a reasonable pressure at any temperature that is reached by the cable sheath. If a bubble of permanent gas or very low boiling liquid be compressed within the mass of the lead during the extruding operation the bubble may expand substantially to its original volume after Conveniently, the steam or extrusion, with the harmful consequences set forth hereinabove. In the case of steam, however, the compression within the cylinder will produce a liquid, with a vast reduction in volume, and expansion to gaseous form is prevented by a relative moderate pressure even at the temperature of the lead as it is being extruded. The comparatively small volume of the space in which the liquid will be found will result in the lead surrounding it having sufiicient strength to maintain the liquid in its original volume without ex pansion to vapor form, even at the extruding temperature.

Applicant has provided improved apparatus whereby metal sheaths may be extruded about electrical cables, and in which oxidation of the metal during the extruding operation is prevented. Furthermore, introduction of impurities and formation of gas pockets in the metal dining the press charging operation is prevented.

It will be understood that the present invention may be variously modified and embodied within the scope of the subjoined claims.

I claim:

1. In apparatus for extruding metal sheaths on electrical cables the combination of a cylinder, a die block having an opening for the passage of a cable therethrou'gh connected to one end of said cylinder, 9. ram extending into the other end of said cylinder, means for causing relative movement between the cylinder and the ram, sealing means connecting the cylinder and the ram preventing the entrance of air into the cylinder around the ram while permitting relative movement therebetween, and means for removing substantially all air and other gases from the space between the cylinder and the ram under the said sealing means.

\ 2. In apparatus for extruding metal sheaths on electrical cables the combination of a cylinder, a die block having an opening for the passage of a cable therethrough connected to one end of said cylinder, a ram extending into the other end of said cylinder, means for causing relative movement between the cylinder and the ram, sealing means connecting the cylinder and the ram preventing the entrance of air into the cylinder around the ram while permitting relative movement therebetween, and an acute angled scraping edge closely encircling the ram below the sealing means for removing any metal which may have been forced out between the cylinder wall and the head of the ram during an extruding operation from the surface of the ram and for directing the metal away from the ram as the latter is I withdrawn from the cylinder.

3. In apparatus for extruding metal sheaths on electrical cables the combination of a cylinder, 2. die block having an opening for the passage of a cable therethrough connected to one end of said cylinder, 9. ram extending into the other end of said cylinder, means for causing relative movement between the cylinder and the ram, sealing means connecting the cylinder and the ram preventing the entrance of air into the cylinder around the ram while permitting relative movement therebetween, a scraping edge closely encircling the ram below the sealing means, for

removing any metal which may have been forced.

out between the cylinder wall and the head of the ram during an extruding operation from the surface of the ram as the latter is withdrawn from the cylinder, and means for melting any such metal and causing it to return to the cylinder during a charging operation.

4. In apparatus for extruding metal sheaths on electrical cables the combination of a cylinder, a die block having an opening for the passage of a cable therethrough connected toone end of said cylinder, 2. ram extending into the other end of said cylinder, means for causing relative movement between the cylinder and the ram, means for charging the cylinder with molten metal, and means for removing substantially all air and other gases from the cylinder during a charging operation.

5. In apparatus for extruding metal sheaths on electrical cables the combination of a cylinder, 9. die block having an opening for the passage of a cable therethrough connected to one end of said cylinder, a ram extending into the other end of said cylinder, means for causing relative movement between the cylinder and the ram, means for charging the cylinder with molten metal, and means for supplying steam to the cylinder during a charging operation.

6. The method of operating apparatus for extruding metal sheaths on electrical cables, comprising a cylinder, die block and ram, which method comprises charging the cylinder with molten metal free from impurities, permitting the molten metal to cool and solidify, preventing access of air to the molten metal during the charging and cooling operations, removing from the cylinder during the charging operation any gas which may have been entrained in the molten metal, and effecting relative movement between the cylinder and the ram to extrude the solidified metal through the die block.

7. The method of operating apparatus for extruding metal sheaths on electrical cables comprising a cylinder, die block and ram, which method comprises charging the cylinder with molten metal free from impurities, permitting the molten metal to cool and solidify, preventing access of air to the molten metal during the charging operation by maintaining a blanket of steam over the metal in the cylinder, and eilecting relative movement between the cylinder and the rain to extrude the solidified metal through the die block.

8. In an apparatus for charging an extrusion press cylinder having a cooperating ram nor mally retirable from the cylinder to permit charging of the same through the ram entrance aperture thereof, a receptacle normally empty of fused material supported upon the cylinder and having an aperture in the bottom thereof provided with a beveled edge for providing an entrance into the cylinder and aligned with the ram entrance aperture of the cylinder, said receptacle constituting a seal between the cylinder and the rain to exclude the atmosphere from the cylinder, and means for charging the cylinder with fused material through the wall of the receptacle.

9. In apparatus for extruding metal sheaths on electrical cables the combination of a cylinder, a die block having an opening for the passage of a cable therethrough connected to one end of said cylinder, a ram extending into the other end of said cylinder, means for causing relative movement between the cylinder and the ram, an annular casing surrounding the ram and connected fluid tight to the end of the cylinder, a packing secured in the wall of the annular casing encircling the ram and preventing entrance of air into the cylinder around the ram while permitting relative movement therebetween, and means connected to said annular casing for removing substantially all air and other gases from the space between the cylinder and the ram and under the annular casing.

10. In apparatus for extruding metal sheaths on electrical cables the combination of a cylinder. a die block having an opening for the passage of a cable therethrough connected to one end of said cylinder, a ram extending into the other end of said cylinder, means for causing relative movement between the cylinder and the ram, sealing means connecting the cylinder and the ram preventing the entrance of air into the cylinder around the ram while permitting relative move- I ment therebetween, and an acute angled scraper between said sealing means and the head of the ram for removing any metal which may have been forced out between the cylinder wall and the head of the ram during an extruding operation from the surface of the ram and for directing the metal away from the ram as the latter is withdrawn from the cylinder.

11. In apparatus for extruding metal sheaths on electrical cables the combination of a cylinder, a die block having an opening for the passage 0! a cable therethrough connected to one end of said cylinder, a ram extending into the other end of said cylinder, means for causing relative movement between the cylinder and the ram, sealing means connecting the cylinder and the ram preventing the entrance of air into the cylinder around the ram while permitting relative movement therebetween, means beween said sealing means and the head of the ram for removing any metal which may have been forced out between the cylinder wall and the head of the ram during an extruding operation from the surface of the ram as the latter is withdrawn from the cylinder, and an electrical heating element for melting any such metal and causing it to return to the cylinder during a charging operation.

RALPH W. ATKINSON.