US3871202A

US3871202A - Forging press

Info

Publication number: US3871202A
Application number: US463039A
Authority: US
Inventors: Harry Claesson
Original assignee: ASEA AB
Current assignee: ABB Norden Holding AB
Priority date: 1973-05-03
Filing date: 1974-04-22
Publication date: 1975-03-18
Anticipated expiration: 1992-03-18
Also published as: FR2227915A1; JPS5014564A; DE2419220A1; GB1458424A; SE379656B

Abstract

A forging press includes a forging chamber into which a forging cylinder can be pressed. The forging cylinder is integral with a main piston arranged in a working cylinder to which pressure fluid can be supplied. The forging piston is slidable within an annular member which is fixed in an axially slidable sleeve, and which can be moved by pressure fluid supplied to either end thereof. Within the main piston is a pressure-equalizing chamber, into which fits a stationary back-pressure piston. Passages are provided connecting the pressure equalizing chamber with the forging chamber. The cross-section of the back-pressure piston is less than that of the forging piston. In the bottom part of the forging chamber there is arranged a groove which connects with a discharge passage. When pressure fluid is applied to the sleeve, it moves downwardly and the annular member engages the bottom of the forging chamber and closes the outlet groove so as to prevent the escape of fluid therefrom. Pressure in the main cylinder then pushes down the forging piston. As the cross-section area of the back-pressure piston is smaller than that of the forging piston, the increase in volume of the pressure-equalizing chamber will not be as great as the decrease in volume of the forging chamber. This in turn leads to an increase in pressure in both chambers. The relation between the cross-section areas of the back-pressure piston and the forging piston is chosen so that a suitable pressure increase is obtained in the chambers.

Description

United States Patent 1191 Claesson Mar. 18, 19 75 FORGING PRESS [75] Inventor: Harry Claesson, Vasteras, Sweden [73] Assignee: Allmanna Svenska Elektriska Aktiebolaget, Vasteras, Sweden [22] Filed: Apr. 22, 1974 [21] Appl. No.2 463,039

[30] Foreign Application Priority Data May 3, 1973 Sweden 7306177 [52] US. Cl. 72/60, 72/453 [51] Int. Cl B2lj 9/02 [58] Field of Search 72/60, 453; 352, 358, 57,

[56] References Cited UNITED STATES PATENTS 3,383,891 5/1968 Geitz 72/57 3,415,088 12/1968 Alexander 72/60 3,686,910 8/1972 Fuchs 72/60 3,707,864 l/l973 Pigott 72/60 FOREIGN PATENTS OR APPLICATIONS 1,195,826 6/1970 lJnitedKingdorn 72/377 Primary Examiner-C. W. Lanham Assistant ExaminerGene P. Crosby [57] ABSTRACT A forging press includes a forging chamber into which a forging cylinder can be pressed. The forging cylinder is integral with a'main piston arranged in a working cylinder to which pressure fluid can be supplied. The forging piston is slidable within an annular member which is fixed in an axially slidable sleeve, and which can be moved by pressure fluid supplied to either end thereof. Within the main piston is a pressureequalizing chamber, into which fits a stationary backpressure piston. Passages are provided connecting the pressure equalizing chamber with the forging chamber. The cross-section of the back-pressure piston is less than that of the forging piston. in the bottom part of the forging chamber there is arranged a groove which connects with a discharge passage. When pressure fluid is applied to the sleeve, it moves downwardly and the annular member engages the bottom of the forging chamber and closes the outlet groove so as to prevent the escape of fluid therefrom. Pressure in the main cylinder then pushes down the forging piston. As the cross-section area of the back-pressure piston is smaller than that of the forging piston, the increase in volume of the pressure-equalizing chamber will not be as great as the decrease in volume of the forging chamber. This in turn leads to an increase in pressure in both chambers. The relation between the cross-section areas of the back-pressure piston and the forging piston is chosen so that a suitable pressure increase is obtained in the chambers.

9 Claims, 6 Drawing Figures p p p F ORGING PRESS BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to a forging press operated by pressure fluid.

2. The Prior Art During forging operations in presses where a great reduction of the forged billet isrequired or where the material in the billet is very brittle, it is impossible to employ conventional methods without encountering difficulties, for example the formation of cracks at the edges of the billet. One way of avoiding this is to forge the billet in a high-pressure chamber where the free surfaces of the billet are subjected to a hydrostatic pressure of a few kilobars. One known way of forging in this manner is to have the forging chamber in the form of a cylinder into which thebillet to be forged is inserted. The cylinder is then filled with oil and the forging piston acting as a punch is inserted into the opening of the cylinder. As the forging piston is inserted into the cylinder, the pressure in the cylinder increases radpidly, and, in order that the pressure should not be too high; it is necessary to drain off oil from the chamber. This draining is performed through a reduction valve which is adjusted so that the desired pressure is obtained in the forging chamber. Forging is performed by the fact that the punch or the forging piston hits the billet and compresses it, while at the same time the billet receives a support pressure from the oil on the surfaces which are not supported by the punch and the bottom of the cylinder, respectively. The forging itself can of course be satisfactorily carried out in this way, but a serious drawback of this procedure is that reduction valves used in this system are rapidly worn out and must be replaced at frequent intervals. Another drawback is that a loss of power naturally occurs in the reduction valve.

SUMMARY OF THE INVENTION The present invention relates to a forging press which is not subject to these drawbacks. The forging press is provided with a pressure chamber into which a back pressure piston with a smaller piston area than the forging piston can be inserted in a sealing'manner. A connection is provided between the pressure-equalizing chamber and the forging chamber. The pressureequalizing chamber with its back pressure piston is arranged so that its volume is increased when the forging piston is inserted into the forging chamber, thus decreasing the volume of the forging chamber. Because the piston area of the back pressure piston is smaller than the piston area of the forging piston, an increase in pressure in the forging chamber is obtained in this operation. This increase in pressure can be calculated in advance by choosing a suitable ratio between the respective piston areas in relation to the volumes of the rest of the chambers. A forging press in accordance with the embodiment described consequently does not have to be provided with a reduction valve at the outlet from the forging chamber. When the forging piston reaches the billet and seals against it, an additional force is also obtained in the forging pressure which corresponds to the oil pressure on a surface corresponding to the contact surface between the billet and the punch.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is best understood with reference to the accompanying drawings wherein:

FIG. 1 shows the forging press in cross-section.

FIGS. 2-6 show the positions of the various pistons in cross-section at various stages of the work cycle of the forging press.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, l designates a frame which is suitably wound with steel strips. In the frame a forging tool 2 is arranged. The forging tool 2 has a forging chamber 3 into which a forging piston 4 is sealingly insertable for the forging of a billet 5 positioned in the forging chamber 3. Furthermore, the forging tool 2 is provided with an annular maincylinder 6 in which a main piston 7 moves. In the main piston 7 there is arranged a pressure-equalizing chamber 8. A back-pressure piston 9, which is connected to the frame 1 and is thus stationary during a working cycle of the tool, is sealingly insertable into the pressure-equalizing chamber 8. The

channels

10 and 11 connect the forging chamber 3 with the pressure-equalizing chamber 8 and are arranged in the main piston 7.

The walls of the forging chamber 3 are formed by a tubular member 12. This tubular member 12 is movable along its central axis. It is connected to an outer, axially movable jacket 13. At the top this jacket 13 fits slidingly into an annular slot 14 in the main piston 7. At the bottom it fits slidingly into a corresponding annular slot 15 provided in the bottom piece 16 of the forging tool 2. The ends of the jacket 13 thus act as pistons in the respective

annular slots

14 and 15.

For operation of the jacket 13 pressure oil can be transferred by means of a pump 17 either through a conduit 18 to the slot 15 or through a conduit 19 to the slot14. The oil is pumped from the container 20 and the switching between the different conduits l8 and 19 is performed by means of the valve 21.

Supply of oil to the pressure-equalizing chamber 8 is also performed from the container 20 by way of the pump 22, the valve 23 and the conduit 24, which opens out in the channel 25 which, in turn, opens out into the pressure-equalizing chamber 8. In the conduit 24 a check valve 26 is arranged, which prevents the oil from flowing from the back pressure chamber 8 back into the container 20. When switching the valve 23, the conduit 24 is disengaged from the pump 22 which is now connected directly to the return pipe 27.

The main piston is operated by pumping oil from the container 20 by way of the pump 28, the valve 29, the conduit 30 and the channel 31 to the main cylinder 6. Emptying of the main cylinder 6 is performed by reversing the valve 29, the conduit 30 thus being connected to the open return pipe 33 and the pump 28 to the return pipe 32.

Outside the forging chamber there is a drain groove 34 which is in open connection with the oil container 20 by way'of a channel 35 and a conduit 36.

Finally, between the tubular member 12 and the main piston 7 there is a spacing member 37.

The forging press operates in the following manner. FIG. 1 shows the forging tool 2 in the starting position for pressing. This means that the tubular slot 15 is under pressure because the pump 17 is pumping oil to the slot 15. On the other hand, the annular slot 14 communicates freely with the oil container. The main piston 7 is'supported by the spacing members 37 on the tubular member 12, which in turn is connected to the jacket 13 which, in the starting position, is in its upper position because of the oil pressure in the slot 15.

Further, the oil pressure is zero in the pressureequalizing chamber 8 and the main cylinder 6 because these are in free connection with the oil container 20.

With the forging tool in this position the billet is placed into the forging chamber.

FIG. 2 shows the next stage in the working cycle. Here the annular slot 15 has been brought into free connection with the oil container by the switching of the valve 21, and at the same time the slot 14 has been pressurized. This has caused the jacket 13 with its tubular member 12 to change its position and it is now located in its lower end position. In this way the forging chamber is sealed off from the draining groove 34 and a pressure-tight space is formed by the bottom piece 16, the member 12 and the forging piston 4, disregarding the connection of the space with the pressureequalizing chamber 8 by way of

channels

10 and 11.

With the tool in this position, the valve 23 is switched so that the pump 22, instead of pumping oil back to the container through the return pipe 38, now pumps oil through the conduit 24 to the pressure-equalizing chamber 8 and the forging chamber 3.

After the forging chamber 3 has been filled with oil, the next phase in the working cycle begins, as shown in FIG. 3. Here the valve 29 has now also been switched so that the pump 28 forces oil through the conduit 30 to the main cylinder 6. This causes the main piston 7 to be driven downward, the forging piston 4 being pressed into the forging chamber 3, the volume of which decreases. At the same time the volume of the pressure-equalizing chamber 8 increases, and oil flows from the forging chamber 3 over to the pressureequalizing chamber 8 through the

channels

10 and 11. However, the piston area of the back-pressure piston 9 is smaller than the piston area of the forging piston 4, which means then the increase in volume of the chamber 8 will not be as great as the decrease in volume of the forging chamber 3. This, in turn, will of course lead to an increase in pressure in both

chambers

8 and 3. The relation between the areas of the different pistons is adjusted so that a suitable pressure increase, for example up to 4 kilobars, is obtained in the forging chamher. The pressure increase can also be adjusted if one does not start filling oil into the forging chamber 3 until the forging piston 4 has been pushed somewhat into the forging chamber 3. This results in the transfer of a smaller volume of oil from the forging chamber to the pressure-equalizing chamber, which, in turn, of course leads to a somewhat smaller increase in pressure at the same ratio between the piston areas in the different cases.

FIG. 4 shows the forging proper. It should be pointed out that, when the forging piston 4 hits the surface of the billet 5, an'additional pressure is obtained in the forging pressure, which corresponds to the oil pressure on a surface corresponding to the contact surface between the billet 5 and the forging piston 4. In FIG. 5 the forging process is completed and'the valve 29 has been switched so that the main cylinder 6 has been brought into free connection with the container 20. Under high pressure in the forging chamber 3 and the pressureequalizing chamber'8, the oil then tends to increase the volume, resulting in an upward pressure on the main piston 7. To be able to lift the main piston 7 to its upper position, however, further oil must also be pumped into the slot 14. This results in a complete decompression of the oil in the forging chamber 3 which can now be opened. 7

In FIG. 6, finally, the pump 17 has been connected to the slot 15, the jacket 13 with the tubular member 12 being raised to its upper position. The main piston 7 again is supported by the spacing members 37 on the member 12. As the tubular member 12 is lifted from the bottom piece 16, the oil in the forging chamber 3 is able to run out through the draining groove 34 and the channel 35 down into the container 20. With the forging tool 2 in this position, the billet 5 which has now been forged can be removed from the tool.

It should be added that the degree of the increase in volume in the forging chamber 3 and the pressureequalizing chamber 8 together can be easily adjusted to the compressibility of the pressure fluid, when the forging is being carried out, by choosing a suitable starting position for the forging piston 4.

Furthermore, the mechanical guiding of the forging piston 4 has a very appropriate design, which contributes to causing the upper and lower forging tools to meet each other with good precision. The guiding of the forging piston 4 is performed against the tubular member 12, which in turn is guided by the jacket 13.

I claim:

1. Forging press comprising a forging chamber (3), a forging piston (4) sealingly insertable into the forging chamber (3) for forging billets (5) arranged in the forging chamber (3), a main cylinder (6) and a main piston (7) arranged in the main cylinder (6) for imparting movement to said forging piston (4), means for filling said forging chamber (3) with oil which is compressed when the forging piston (4) forces its way into the forging chamber (3), a pressure-equalizing chamber (8), means connecting the forging chamber (3) with the pressure-equalizing chamber (8), a bacl -pressure piston (9) with a smaller piston area than the forging piston (4) sealingly insertable into the pressure-equalizing chamber (8) and the main piston (7) being operatively connected to the forging piston (4) to effect a change in the volume of the forging chamber (3) and the pressure-equalizing chamber (8), respectively, the volume of the pressure-equalizing chamber (8) thereby increasing when that of the forging chamber (3) decreases.

2. Forging press according to claim 1, in which the back-pressure piston (9) is stationary and the pressureequalizing chamber (8) is arranged in the main piston (7).

3. Forging press according to claim 1, in which the peripheral wall of the forging chamber (3) consists of an annular member (12), in one end of which the forging piston (4) is sealingly slidable.

4. forging means according to claim 3, in which the annular member (12) is displaceable axially.

5. Forging press according to claim 3, having an outer, axially movable jacket (13) surrounding and secured to the annular member (12), and means to move the jacket (13) axially.

6. Forging press according to claim 5 having outlet means (35) from the forging chamber and means conconnecting means between the forging chamber (3) and the pressure-equalizing chamber (8) consists of means (10,11) in the main piston (7).

9. Forging press according to claim 1, wherein a conduit (24). connecting the forging chamber (3) and-the pressure-equalizing chamber (8) connected thereto are connected to an oil container (20).

Claims

1. Forging press comprising a forging chamber (3), a forging piston (4) sealingly insertable into the forging chamber (3) for forging billets (5) arranged in the forging chamber (3), a main cylinder (6) and a main piston (7) arranged in the main cylinder (6) for imparting movement to said forging piston (4), means for filling said forging chamber (3) with oil which is compressed when the forging piston (4) forces its way into the forging chamber (3), a pressure-equalizing chamber (8), means connecting the forging chamber (3) with the pressure-equalizing chamber (8), a back-pressure piston (9) with a smaller piston area than the forging piston (4) sealingly insertable into the pressureequalizing chamber (8) and the main piston (7) being operatively connected to the forging piston (4) to effect a change in the volume of the forging chamber (3) and the pressure-equalizing chamber (8), respectively, the volume of the pressure-equalizing chamber (8) thereby increasing when that of the forging chamber (3) decreases.

2. Forging press according to claim 1, in which the back-pressure piston (9) is stationary and the pressure-equalizing chamber (8) is arranged in the main piston (7).

6. Forging press according to claim 5 having outlet means (35) from the forging chamber and means connected with the annular member (12) to close said oil means.

7. Forging press according to claim 6, in which the outlet means comprises a drain groove (34) communicating with the forging chamber (3) for draining off oil present in the forging chamber into an oil container when the forging chamber (3) is opened after a completed work cycle.

8. Forging press according to claim 1, in which the connecting means between the forging chamber (3) and the pressure-equalizing chamber (8) consists of means (10,11) in the main piston (7).

9. Forging press according to claim 1, wherein a conduit (24) connecting the forging chamber (3) and the pressure-equalizing chamber (8) connected thereto are connected to an oil container (20).