GB2033275A

GB2033275A - Hydraulic Forging Press

Info

Publication number: GB2033275A
Application number: GB7930790A
Authority: GB
Original assignee: Kawasaki Hydromechanics Corp; KAWASAKI YUKOH KK
Current assignee: Kawasaki Hydromechanics Corp; KAWASAKI YUKOH KK
Priority date: 1978-09-05
Filing date: 1979-09-05
Publication date: 1980-05-21
Also published as: FR2435304A1; FR2435304B1; JPS561973B2; DE2935656A1; GB2033275B; DE2935656C2; JPS5536044A

Abstract

A hydraulic forging press is provided which includes a pump ram (2), a press ram (3) and punch ram (7). A cavity (8) filled with hydraulic fluid provides a hydraulic communication between the pump ram and the press and punch rams so that movement of the pump ram causes simultaneous movement, utilising the common hydraulic fluid supply, of the press ram and the punch ram, the pressure provided by the pump ram being initially used to cause the press ram to close dies (4, 5), whereafter the available pressure acts on the punch ram to drive it into the material (6) being forged to compress it into all parts of the cavity formed by the closed dies. <IMAGE>

Description

SPECIFICATION Hydraulic Forging Press This invention relates to a hydraulic forging press.

In a closed forging press, a metallic material is forged by being enclosed completely by two dies, the press producing a rough forging as a preliminary process step. To cause the metal closely to follow the shape of the dies, one or more punch rams are pushed through the dies that have been closed completely or are being closed and, as a result, the metallic material is pressed hard against the inner walls of the dies.

It is an object of the present invention to provide a forging press which combines the operation of the press ram and the punch ram and to increase the yield rate as compared with known presses.

According to the present invention, there is provided a hydraulic forging press comprising a pump ram in hydraulic communication with a press ram and with a punch ram and there being means for mechanically imparting reciprocal movement to said pump ram, movement of said pump ram causing said pump ram to act simultaneously on said press ram and said punch ram by means of said hydraulic communication.

For a better understanding of the invention-and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 is a diagrammatic, longitudinal sectional view of one form of hydraulic forging press, Figures 2 to 4 are longitudinal, sectional views iilustrating sequential steps in the operation of the press shown in Figure 1, Figure 5 is a diagrammatic, longitudinal sectional view of a second form of hydraulic forging press, and Figure 6 is a diagrammatic, longitudinal sectional view of a third form of hydraulic forging press.

Referring firstly to Figures 1 to 4, the hydraulic forging press includes a cylinder 1 in which is slidably reciprocally mounted a pump ram 2, a press ram 3 and a punch ram 7. A cavity 8 is provided between the pump ram 2 and the rams 3 and 7, this cavity normally being completely filled with hydraulic fluid such as oil. Accordingly, reciprocal movement of the pump ram 2 can be transmitted through the hydraulic fluid in the cavity 8 to work the rams 3 and 7. In the embodiment shown in Figure 1, the pump ram 2 and the press ram 3 are of the same external diameter although they can have a different diameter from one another.

Two complementary dies, viz. an upper die 4 and a lower die 5 define between them a cavity of any desired shape to be produced by the press on a slug of forging material 6. The upper die 4 is attached to the press ram 3 and moves with it.

The punch ram 7 has a punch end 7a and is arranged to slide reciprocably through the upper die 4 along the axis of the cylinder 1. The punch 7 is constrained in its reciprocal movement by the press ram 3 and the upper die 4. Means is provided for mechanically imparting reciprocal movement to the pump ram 2, this means being in the form of a crank 10 rotating around the axle 11, a connecting rod being connected between the crank 10 and the pump ram 2 in order to provide the reciprocal movement of the pump ram 2.

From the above description, it will be appreciated that the cavity 8 provides a hydraulic communication of the pump ram 2 with the press ram 3 and the punch ram 7 and the same hydraulic fluid is utilised to cause the pump ram 2 to act simultaneously on the press ram 3 and punch ram 7.

A hydraulic circuit is provided to ensure that the cavity 8 is always full of hydraulic fluid and to maintain the pressure of the hydraulic fluid during working of the press.

As can be seen in Figure 1, the hydraulic circuit includes a reservoir 9 from which a line leads to a check valve 1 3 which is controlled by a changeover valve 14, these latter components serving to circulate the hydraulic fluid between the cavity 8 and the reservoir 9 and to maintain the oil pressure in the cavity 8 during working of the press.

Return cylinders 1 5 house respective pistons 17 depending from the press ram 3. Oil or other hydraulic fluid pressure is transmitted from a pump 16 driven by a motor 19 to the pistons 17 in the cylinders 1 5 to act on the press ram 3 to raise and return it after a working operation.

Return movement of the press ram 3 also returns the punch ram 7 and this is assisted by flow of hydraulic fluid from the cylinders 1 5 through bores 18 in the pistons 17, these bores 18 extending through the press ram 3 into a cavity surrounding the punch ram 7 beneath its head so that hydraulic fluid under pressure in these bores 18 can push the head of the punch ram 7 against the upper flange of the push ram 3. A pressure accumulator 20 and a relief valve is disposed in the output line from the pump 1 6 to the cylinders 15.

A relief valve 21 controls the maximum hydraulic fluid pressure in the cavity 8.

An adjustable stop means 22, which can have a construction as that described in United States patent No.4,148,209 (British patent application No. 7535/78-Serial No. ), is provided to limit the stroke S, of the press ram 3 from the die opened position to the die closed position, the distance S, being equal to the distance between the upper die 4 and the lower die 5.

Operation of the press will now be described with reference to Figures 1 to 4. Figure 1 shows the press in a condition before an operating step and Figure 2 shows the press in a state where the cavity 23 between the dies 4 and 5 is closed completely when the upper die 4 is pushed down the stroke distance S, onto the die 5 tightly by the press ram 3 as a result of the rotation of the crank 10 clockwise from the position shown in Figure 1.

In so doing, the material 6 undergoes a first plastic deformation.

Figure 3 shows the stage where the crank 10 has further rotated to achieve its bottom dead centre position. Since the press ram 3 is already at its lowermost position, only the punch ram 7 can be moved and so the pump ram 7 is accelerated into the core of the material 6.

To achieve a punch ram stroke of 8g2 a pump ram stroke S2 is required as follows: A2 S2= S 2 A, where A, is the cross-sectional area of the pump ram 2 A2 is the cross-sectional area of the punch ram 7.

Accordingly, the descending velocity of the punch ram 7 is much faster than that of the press ram 3 and the relationship of the velocity V, of the press ram 3 at the time of closing the dies 4 and 5 and the velocity V2 of the punch ram 7 is as follows: A, v2=-v1 A2 The velocity V2 is faster than that of a conventional closed forging press and this serves effectively to prevent the punch tip 7a from losing its strength and reducing its service life by the heat transmitted from the hot material 6. Also, because of the speed of the punch 7, the tip 7a pushes the material 6 into every part of the cavity 23 so that it is completely filled with the material 6 due to the force of the punch.

Ideally, the work done completely to fill the cavity 23 with the material 6 should be completed at the same time as the crank 10 reaches bottom dead centre. However, in practice, it is important to adjust the performance parameters so that this work is finished a little while before the crank 10 reaches bottom dead centre to ensure that the material 6 properly fills the cavity 23. Even so, it will be appreciated that the stopping position of the punch ram 7 at the end of its driving stroke varies to a considerable extent depending on the error in weighing the material 6 before introduction to the press. The descending movement of the pump ram 2 from its lowermost, stopped position to the bottom dead centre of the crank 10 is converted to the work that compresses the hydraulic fluid in the cavity 8.

Comparing the total volume of the hydraulic fluid in the cavity 8, the compressed volume of the working oil is very little different and so little pressure is lost by compression of the hydraulic fluid. For example, supposing that the pressure rises to a maximum of 485 kg/cm2, the hydraulic fluid in the cavity 8 is compressed by an amount which is equivalent to a stroke of 11 mm of the pump ram. If the descending movement of the punch ram 7 is stopped at a position 5 mm before the bottom dead centre position of the crank 10, the additional pressure rise thereafter is estimated approximately as follows: 5 15"d 485 kg/cm2x-( )2=73 kg/cm2 11 26"d In such a case, when the normal operating pressure is set at 400 kg/cm2, the hydraulic fluid pressure rises to about 473 kg/cm2.The pressure rise of this grade does not harm the forging press but, in the case where the size of a material to be forged is too large or where the hydraulic fluid pressure rises more than the predetermined limit value by other abnormal conditions, the relief valve 21 acts to protect the forging press and releases the excess pressure.

Figure 4 shows the stage where the crank 10 has further rotates beyond bottom dead centre and the pump ram 2 is on its ascending stroke.

The effective area of the bores 18 and the cavity between the punch ram 7 and press ram 3 are such that the punch ram 7 first starts to be pushed up and returned within the press ram 3 by the oil pressure in the return cylinder 15, the end 7a of the punch being pulled out of the material 6 whilst the dies 4 and 5 are still kept tightly in contact with one another. Thereafter, the press ram 3 is caused to ascend by the action of the pistons 1 7. It is to be understood that the ascending velocity of the punch ram 7 is much faster than that of the pump ram 2.

In the embodiment shown in Figure 5, a plurality of punch rams 24 are provided soars to be operable in horizontal directions on the material 6. The punch rams 24 are mounted in cylinders 25 which are connected to the cavity 8 by conduits 26 and so, as with Figure 1 , there is a common hydraulic connection between the pump ram 2 on the one hand and the press ram 3 and the punch rams 24 on the other hand.

In the same way as Figure 5 shows that the punch rams 24 can be placed so as to act in different directions from the working direction of the press ram 3, the embodiment of Figure 1 can be modified so that punch rams 7 are provided to operate from both the upper and lower sides of the material 6.

The embodiment shown in Figure 6 shows that the pump portion and the press portion can be separated from one another. Two blocks of press ram 3a and 3b and one block of punch ram 7 interposed therebetween are connected to the pump ram 2 by means of the conduits 27,28, 29 and 30 and are again disposed so as to utilise a common hydraulic fluid pressure provided by the pump ram 2. In other respects, this embodiment has a similar construction to the previously described embodiments.

It will be appreciated that with the present types of forging press, it is possible to produce a forged material which produces no flash at the joining surface between the dies 4 and 5. This contributes to reduce the power expended for the actuation of the press as well as to enhance the yield rate of the material as compared with conventional methods, which normally produce some flash.

It will be further appreciated that the process described can be equally well used for both cold forging and hot forging. In addition, the press is capable of adjusting the punch ram punching-in distance automatically by utilising the compressibility of the hydraulic fluid.

Claims

1. A hydraulic forging press comprising a pump ram in hydraulic communication with a press ram and with a punch ram and there being means for mechanically imparting reciprocal movement to said pump ram, movement of said pump ram causing said pump ram to act simultaneously on said press ram and said punch ram by means of said hydraulic communication.

2. A press as claimed in claim 1, wherein said means for mechanically imparting movement to said pump ram includes a crankshaft connected by a connecting rod to the pump ram so that the pump ram is raised and lowered thereby during a forging operation.

3. A press as claimed in claim 1 or 2, wherein a cavity which receives hydraulic fluid is provided between said pump ram and said press and punch rams.

4. A press as claimed in claim 1,2 or 3, wherein two complementary dies are provided, one of these dies being fixed in position and the other of these dies being attached to said press ram for movement therewith.

5. A press as claimed in any one of the preceding claims, wherein said punch ram is slidably mounted within said press ram and is arranged so that a tip thereof can punch into material being forged after said press ram has completed its working stroke.

6. A press as claimed in any one of the preceding claims and including a hydraulic circuit for supplying and maintaining hydraulic fluid in said hydraulic communication, this circuit including a reservoir, a check valve, a change-over valve and a pressure relief valve, the check valve serving to maintain pressure in said hydraulic communication during a working stroke of said pump ram and to supply hydraulic fluid to a return cylinder to return the press ram and the pump ram to their original positions after completion of their working strokes.

7. A press as claimed in claim 4 or claim 5 or 6 as appendant to claim 4 and being arranged such that a working stroke of said press ram initially causes a working stroke of both said press and punch rams until said press ram reaches the limit of its stroke whereupon the dies are closed, the punch ram thereafter continuing its stroke at a greater speed than the stroke of said press ram to punch the material being forged to cause the material completely to fill the cavity formed by the two closed dies.

8. A press as claimed in any one of the preceding claims except claim 5, wherein said punch ram is arranged to act at right angles to the stroke of said press ram.

9. A hydraulic forging press, substantially as hereinbefore described with reference to any one of the embodiments illustrated in the accompanying drawings.