US2946303A

US2946303A - Hydraulically operated presses

Info

Publication number: US2946303A
Application number: US694042A
Authority: US
Inventors: Schmid Mathias
Original assignee: G Siempelkamp GmbH and Co KG
Current assignee: G Siempelkamp GmbH and Co KG
Priority date: 1957-02-01
Filing date: 1957-11-01
Publication date: 1960-07-26
Anticipated expiration: 1977-07-26
Also published as: DE1145018B

Description

July 26, 1960 Filed NOV. 1, 1957 M. SCHMID 2,946,303

HYDRAULICALLY OPERATED PRESSES 4 Sheets-Sheet 1 WAfH/AS SCH/VA July 26, 1960 M. SCHMID 2,946,303

HYDRAULICALLY OPERATED PRESSES Filed Nov. 1, 1957 4 Sheets-Sheet 2 FREQ/PE /N FREQ CYLINDER a a b c c MOVEMENT 0F mass cyan/05R MATH/A5 SCH/V/D July 26, 1960 M. SCHMID HYDRAULICALLY OPERATED PRESSES 4 Sheets-Sheet 3 Filed Nov. 1, 1957 Inveman MATH/A5 SCH/7Z2 v 1960 M. SCHMID 2,946,303

R HYDRAUL-JICALLY OPERATED PRESSES Filed Nov. 1. 1957 4 Sheets-Sheet 4 Inventor? MATH/A5 5 (l/MID Fania HYDRAULICALLYUPERATED PRESSES Mathias Schmid, Krefeld, Germany, assignor to G. Siempelkamp and Company, Krefeld, Germany Filed Nov. 1, 1957, Ser. No. 694,042

Claims priority, application Germany Feb. 1, 1957 18 Claims. (Cl. 113- 45) Hydraulically operated presses, particularly extrusion presses or drop-forge presses are, in most cases up to now, driven directly by air-cushioned high-pressure water accumulators. With such known arrangements, it is difiicult to accomplish the forming and relieving operation of a press within short time intervals as is often necessary or at least desirable in order to attain the proper speed for the forming process which speed depends, on the type of material to be formed or on other reasons. Particularly, the forming of hot titanium sheets becomes difiicult if done in presses employing a rubber pad or cushion as a counter die and in which the time for forming and relieving is of relatively long duration inasmuch as the rubber pad is unable to withstand the application of high temperatures over a relatively long period of time as it will heat up to a point where the rubber is damaged or destroyed.

This problem for forming hot workpieces becomes particularly acute when titanium is used in place of conventional aluminum rnctalstwhich may be formed in a cold condition, as, for instance, in the manufacture of the skin of aircrafts or rockets which travel at supersonic speeds. The production of forged titanium parts in a conventional manner with a stationary die and a rubber pad or other resilient material as a counter die, leads to difiiculties inasmuch as titanium, contrary to aluminum alloys, must be formed at extremely high temperatures. Since a counter die made of rubber rapidly loses its strength when heated, titanium cannot be forged successfully with conventional presses employing a rubber pad as a counter die.

in order to overcome these difficulties, it was suggested to employ drop hammers for forging titanium workpieces, particularly sheets, so as to shorten the time of contact between the forming tool and the hot wor. piece and thereby avoid undue heating of the rubber. However, the efiiciency of such drop hammers is very poor due to the fact that the hammer, in forming titanium sheets, must consist of a rubber block.

it is, therefore, an object of the present invention to accelerate the forming and relieving operation of hydraulically operated presses without the necessity of unduly increasing the high-pressure accumulator or of intolerably increasing the pressure level therein.

Therefore, the present invention relates to hydraulically operated presses, particularly extrusion presses or drop-forge presses employing rubber pads which are operated, for instance, by means of an air cushioned highpressure accumulator. The invention resides therein that a high-pressure transformer is arranged between the high-pressure accumulator and the press by which the actual forming process is accomplished after the press has been initially closed. This pressure transformer is operatively adjustable in various ways so that its: operation is advantageously suitable for the forming process. It-is advantageous to also arrange a low-pressure trans.-v former between the high-pressure accumulator and the press for efiecting the initial closing operation thereof.

2,946,303 Patented July 26, 1960 In order to assure-continuous operation of the hydraulic press without special attention, the functional control thereof, according to the present invention is such, that after the press has initially closed and the actual forming process is about to commence, the highpressure transformer is automatically brought into operation by making use, for instance, of the pressure rise which occurs in the press cylinder as the workpiece is brought into contact with the rubber pad or counter die at the end of the initial press closing operation. For this purpose, appropriate control valves may be combined with the pressure transmitters, as required.

The advantages which are attained with the arrangement according to the present invention, above all, reside therein that it is possible with presses of this type to perform the actual forming of the workpiece in an extremely short time, even with the largest size presses. It is, for instance, possible to close the press, up to a point where the die touches the rubber pad, in a few seconds and to perform the actual forming process in one or two seconds and to completely retract the forming tool in a few additional seconds.

A further essential advantage of the present arrangement resides therein that, contrary to hydraulic presses which are directly driven by high-pressure accumulators, considerable energy is saved, as will be explained in more detail later on.

Finally, in an arrangement according to the present invention, the working pressure in the press may be increased markedly whereby the power actuating parts may be made smaller and, as a result thereof, the space required becomes less than for arrangements wherein the press is actuated directly from an accumulator.

As an added feature of the present'invention, the lowpressure transformer includes a small high-pressure piston combined with a lowpressure piston of the size corresponding to the weight of the parts that must be moved .in initially closing the press. It is especially advantageous, as mentioned above, to control the pressure in the high-pressure transformer during the forming process in such a way that it coincides with the pressure characteristic actually required for the forming operation. A further saving on energy is thereby possible, inasmuch as the pressure rise thus coincides with that actually desired in the press during the forming operation whereby the expended energy is limited to the absolute required amount.

The high-pressure transformer itself consists, in itssimplest form, of driving and driven pistons whereby, through transmission of forces from the driving piston which is supplied by the high-pressure accumulator to the driven piston, the pressure transformation and control thereof is accomplished. Preferably the movement of the driving pistons is perpendicular to that of thedriven pistons and the pistons are directly interconnected with each other by connecting rods so that, in the simplest manner, the rise in pressure at the driven pistons coincides with the pressure characteristic desired in the press.

In order to require only a single high-pressure transformer in the present arrangement, regardless of the height or depth of the die, the pressure rise in the highpressure transformer is; limited by a' pressure-limit valve. This pressure-limit valve may beconnected to the driving pistons, respectively, to their cylinders. Furthermore, it is preferable that the high-pressure transformer is constructed in such a way that it operates at the same time as acontrol of the press pressure during the unloading of thepress as, for instance, in such a way that the two driving pistons of the high-pressure transformer are arranged coaxially intwo. cylinders and that these two pistons are connected with each other by a rigid piston rod while the connecting rods of the driven pistons, which are attached thereto, move in a direction substantially perpendicular to the movement of the driving pistons.

With such an. arrangement, a variable force ratio between driving pistons and driven pistons is attained in a mostjsimple mannerand at the sametime a'variablepressure transformer that works as follows:

. The driven pistons, at the beginning of their movement, produce only a small hydraulic pressure while at the dead center position of the connecting rods they theoretically produce an infinitely large hydraulic pressure whereby thedelivery of these driven'pistons in relation to the travel of the driving pistons is in the inverse ratio to the pressure they produce. It can easily be seen that the hydraulic pressure in such a pressure transformer increases along a similar characteristic as isdesirable in drop-forges and particularly extrusion presses with rubber pads. A further advantage in the operation of the present hydraulic press resides thereinthat it is possible to have 4 porates a conventional solid die 2 and a rubber cushion 3 that acts as a counter die. The pressing or forming operation of the workpiece S is accomplished with a conventional press piston or ram 4 and the general structure of the press itself, being also of conventional design, does not need to be described in detail.

For the hydraulic operation of the press, a conventional accumulator 5 with a working liquid, such as water, is provided. The water in the accumulator 5 is kept under pressure in a conventional manner by compressed air. The Water is supplied to this accumulator 5 by a pump through the pump discharge line 21. This line 21 includes a check valve 22, an automatic shut-01f valve 23,

leads to an operating control valve assembly -29 including thepress piston or ram as well as the driven piston of,

the high-pressure transformer operate with oil, whereas, the driving pistons of the pressure transformer and the high-pressure accumulator can be operated with water.

Accordingly, an object of the present invention is to provide a hydraulically operated press in which the time two control valves 2% and 2%. From the valve assembly 29, a line 30 leads to the cylinder space 32 of a low pressure transformer 31 which includes a differential piston 33 comprising a smaller high pressure piston 33a and a larger low pressure piston 33b.

for the forming and relieving process can be reduced to any desired value regardless of the size of the press.

It is another object of the present invention to provide a hydraulically operated press in which the high-pressure accumulator is of relatively small size and the working pressure therein of relatively small magnitude.

Another object of the present invention resides in the relativelysmall size of the force transmitting parts as well as the high etficiency of the working cycle.

-A further object of the present invention resides therein that the rate of pressure rise of the operating fluid in the press cylinder increases during the forming process and that the pressure reaches a maximum as the forming process is completed. 7

Still another object of the present invention resides there nthat the forming and relieving process may be accomplished extremely fast by the inventive action of thehigh-pressure transformer, becausea reversal of the fluid flow to the driving piston of the transformer is not required during the two above-mentioned processes. I These and further objects and advantages of the present inventionwill become more obvious from the following description of a hydraulically operated press when taken ml connectionv with the accompanying drawing which shows, for the purpose of illustration only, several embodiments in accordance with the present invention, and wherein: r Figure l is a schematic arrangement of the hydraulically operated press in accordance with the present invention. 7

Figure 2 is a diagram showing the pressure course in the high pressure transformer and press cylinder during one complete press cycle;

- Figure 3 is a schematic arrangement of the hydraulically operated press according to the present invention showing the essential elements for automatic operation thereof;

. Figure 4 is a cross-sectional view through the lowpres sure transformer of a modified construction;

, Figure 5, is a cross-sectional view through the highpressure transformer; and

Figure 6 is a cross-sectional view through a modified various views to designate like parts,the extrusion or drop-forge press which, as illustrated in Figure 1, incor- A second line 34 branches off the high pressure line 21 leading to operating

control valve assemblies

35 and 36, each of which includes two

valves

35a, 35b and 36a, 36b, respectively. Lines 37 and 38 lead from the

valve assemblies

35 and 36 to cylinder spaces 39 and 4th of a high pressure transformer 41. Within the cylinder'spaces 39 and 4t), driving actuator pistons 39a and 4011 are slidably arranged and are rigidly connected with each other.

Lines

42 and 43 branch oif from

lines

37 and 33 and 7 lead to a check valve assembly 44 consisting of two check valves 44a and 44b. The check valve assembly 44 in '7 turn is connected to a cylinder space 45a in the pressure limit valve 46 through line 45. The pressure limit valve 46 comprises a cylinder space 49 and a difierential piston valve 47 slidably arranged in the cylinder spaces 45a and 49 and is spring loaded by a spring 43. The control valves 2%, 35b and 36a are connected through line 51 to the water reservoir 27.

The cylinder space 52 above the dilierential piston 33b which contains a working fluid, preferably oil, is in communication with the press cylinder 40 through line 53 in which a check valve 54 is arranged. A line 56 branches ofi the line 53 behind the check valve 54 and leads to a spring loaded pressure limit valve 57 and from there continues to the cylinder space 49 of the pressure limit valve 46. A line 55 leads from the cylinder space 49 to the oil reservoir 64, while a line 55 leads from the discharge side of the pressure limit valve 57 to the reservoir 64.

A second line 58 is connected to line 53 behind the check valve 54 and leads to an operating control valve 59 and from there connects to the intake of a check valve 60. The discharge side of the valve 60 is connected to line 53 ahead of the check valve 54 through line 61 while the intake side thereof is connected to the oil reservoir 64 through line 65.

The high pressure transformer 41 further comprises two driven pistons 66 and 67, the center line of which is preferably disposed perpendicularly to the center line of the driving pistons 39a and 40a and which are slidably arranged in cylinders 66a and 67a. The driven pistons 66 and 67 are operatively connected to the driving piston assembly 39a, 40a, by connecting rods 68a and 68b at joint a. From the cylinder spaces '66:: and 67a of the high pressure transmitter 41, lines 69 lead to line 56.

Operation I Assuming the press piston 4, die 2 and the workpiece 8 are in the position as shown in Figure l, the press is initially closed, i.e., the press piston is moved up until the workpiece 8 touches the rubber cushion 3. This initial movement of press piston or ram 4 is, accomplished by opening valves 23, 2:4 and 29a, whereby water under pressure of about 300 kg./cn 1. from the high pressure accumulator is admitted to the cylinder space 31 through

lines

21, 28 and 30. The differential piston 33 is thereby raised whereby the oil in the cylinder space 52 is forced by the piston 33b into the press cylinder 4a whereby the press piston or ram 4 is also raised in turn thereby exerting a slight pressure on the workpiece as it comes into contact with the rubber cushion 3. Due to the fact that the diameter of the piston 33b of the differential piston 33 is considerably larger than the piston 33a, thev specific pressure exerted on the ram 4 is con-. siderably smallerthan that in the high pressure accumulator 5; that. is, the pressure in the cylinder 4a is reduced in the ratios of the areas of pistons 33b to 33a. Actually, the piston in the press cylinder 4a must only be of a magnitude suificient to raise the moving weights of the press 1 during initial closing of the press.

The speed of the upward movement of the diflerential piston 33 which also determines the speed, of the upward movement of the ram 4 during the initial closing operation of the press may be adjusted to any desired value by adjusting the flow area through the check valve assembly 54, as, for instance, by limiting the lift of the check valve or by other means.

When initial closing of the press is completed, valves 35a and 36b are opened and pressure fluid from the accumulator 5 is applied to the cylinder space 3 9 of the high pressure transformer 41. As a result, the piston assembly 39a, 46a is moved to the left. At the, same time, working fluid, that is, water remaining in the cylinder space 40, is discharged through the open valve 36b and 1ine51-to the water reservoir 27.

As a result of the movement to the left of the driving piston assembly 39a, 4% from a position a to a position b, the driven pistons 66 and 67 are moved outwardly by means of the connecting rods 68a and 6%, thereby displacing the oil in the cylinder spaces 66a and 67a through

lines

69, 56 into the pressed cylinder 4a. As a result thereof, the ram 4 together with the die 2 are moved upwardly whereby the actual forming operation of the workpiece 8 is performed.

Asthe driving piston assembly 39a, 40a continues its movement from the position b to the position 0, the driven pistons 66 and 67 reverse the direction of their outward movement and are now moved inwardly to their inner dead center. This inward movement of pistons 66 and 67 effects drawing of working fluid from the press cylinder 4a through lines 56 and '69 into the cylinder spaces 66:; and 67a and as a consequence of this withdrawal of oil from the press cylinder 4a, the pressure therein is relieved and the press piston 4 begins to move downwardly and effects opening of the die 2 to a point where it formerly began the actual forming operation.

In order to further open the press to remove the finished workpiece 8 therefrom, valve 29a is closed, and

valves

29b and 59 are opened. The operation of valve 29b, on the one hand, permits the water in the cylinder space 32 to escape through line 51 into the water reservoir 27 and opening of the valve 53, on the other hand, establishes communication between the

cylinder spaces

4a and 52 through line 58, control valve 59, check valve 60 and line 61. As a result, the differential piston 33 in thelow pressure transformer 31 moves downwardly by its own weight or by spring means drawing oil out of the press cylinder 4a whereby the press piston 4 together with thedie 2 are also allowed to move downwardly to thereby open the press to its initial starting position.

The speed of the downward movement of the differential piston 33, which also determines the speed of the downward movement of the ram 4 during the opening operation of'the press may be adjusted to any desired degree by corresponding dimensioning of the flow passages through the valves 59 and 60 as, for instance, by limiting the effective lift of these valves or other means.

A 2. thered from the description of the operat tion, it is. apparent that the, movement of the press ram 4 and die 2 during the actual forming operation of the workpiece, 8 is produced by the movement of the driving piston assembly 39a, 40a from a position a to the center position b. and the corresponding outward movement of the driven pistons 66 and. 67. The movement of the driving piston assembly 39a, 40a from the center position b to the position 0 produces the relieving movement of the press piston 4. The fluid pressure characteristic in the press cylinder during this movement from a to c is represented in the diagram of Figure 2. The positionsv a, b, e indicated thereon represent the corresponding positions of the press ram 4 during the forming and the relieving operation. The distance a'.a represents the initial closing movement of the press piston, whilev the distance c-.c' representsopening of the press to its initial starting position. The pressure in the press cylinder 4a during the initial closing of the press rises very slightly, as shown in the diagram, While during the forming operation the pressure rises rather rapidly attaining theoretical infinity at position b. It is also apparent from the diagram of Figure 2 that with this mode of power transmission from driving to driven pistons a variable pressure transmission is created wherewith the driven pistons 66 and 67 produce only a small pressure at the beginning of their outward movement while they produce a theoretical infinite hydraulic pressure as they reach their outermost position corresponding to the position b and the working fluid delivered by these; driven pistons is in the inverse ratio to the distance travelled by the driving piston assembly 359a, 40a. Accordingly, it is apparent that the hydraulic pressure produced by the pressure transformer 41 increases during the forming operation in amanner which is desired in the operation of a drop-forge press.

Inasmuch as an. infinite pressure can be produced with the high pressure transformer 41, its absolute magnitude is limited by apredetermined setting of the pressure limiting valve 57. Dueto the tact that the forming stroke of the press must be variable to accommodate various shapes of workpieces, it could happen, with shallow dies for instance, that the maximum pressure is obtained at a position of the driving: piston assembly 39a, 49a between a and b. In order to be sure that the driving piston assembly 39a, 40a in every case moves from a to 0 under the pressure. available from the accumulator or pump, the spring 48- in, the pressure limit valve 46 is so adjusted that the differential piston valve 47 is moved upwardly if the pressurein line 45 and cylinder space 45a reaches a magnitude equalto the pressure. of the accumulator minus 10 percent. If the pressure in the cylinder space 45a and line 45 reaches such a magnitude, the differential piston valve 47; moves upwardly whereby communication between the press cylinder 4a and. the oil reservoir 64 is established through lines. 5 6 and 55. Under such condi tions, the pressure in. the press cylinder 4a, produced by the high pressure transformer 41 remains constant over the remaining part of the forming stroke of the press. The, 10 percent pressure diiierential is needed to overcome the flow resistance from the high pressure accumulator 5 to the driving pistons 39a and 40a of the high pressure transformer 41. The pressure limit valve 46 provides an assurance that the driving piston assembly 39a, 40a does not become stuck at a point between a, and b due to excessive resistance to movement produced, in the cylinders 66a and 67a of the driven pistons 66 and 67.

It should be noted that with such any arrangement the direction of the driving fluid to the driving pistons. 39 a and '40:; during the forming and relieving stroke of the press does. not have to be reversed as is the case in, con; ventional hydraulic presses in which a reversal of the driving fluid occurs subsequent torthe completionof the forming operation. i

Inasmuch as there is no reversal of direction ofa driving fluid from the accumulator 5 necessary during the 7 forming and relieving operation, the present arrangement presents a way for closing and relieving presses in the shortest possible time. q J

To start a newpres-s cycle'the operation as outlined above remains the same except that after the initial closing of the press,

valves

36a and 35b are opened which produces a movement of the driving piston assembly 39a, 40a from a position c back to the original position a.

It is understood that the various

operating control valves

23, 29a, 29b, 35a, 35b, 36a, 36b and 59 ,could be operated either manually, hydraulically, pneumatically, electrically, mechanically or by any other means and further that liquids other than water and oil could be used as working fluids. I

The arrangement shown in Figure 3 difiers from that shown in Figure 1 only to the extent that the various steps in the operation of the hydraulic press, according to the present invention, are performed automatically. To accomplish automatic operation, the pump 20, the suction side of which is connected to the water reservoir 27 through line 26, discharges into line 101 which is in com munication with the high pressure accumulator and an operating control valve 102. A line 103 connects valve 102 with an automatic reverse valve 104. This automatic reverse valve consists of -a piston 105 slidably arranged in the cylinder 106 and urged to one side of the cylinder 106 by a spring 107. A piston valve 108, comprising two

collars

109 and 110, is slidably arranged in a cylinder 111 which is separate from the cylinder 106. The piston 105 is connected with the piston valve 108 by a connecting rod 112. V

-A line 113 leads from cylinder 1111 to the cylinder space 114 of the low-pressure transformer 115. The construction and functioning of the low-pressure transformer 115 is similar to that described in connection with Figure 1 except that a spring 116 is provided which tends to force the differential piston assembly 11 7 downwardly at all times. A line 120 branches off line 113 and is con-. nected to the cylinder 106 of the automatic reverse valve 104 and a second line 118 connects line 113 with an operating control valve 119. A return line 121 connects valve 119 with the water reservoir 27.

A second line 126 leads from cylinder 111 of the automatic reverse valve 104 to a four-way valve 127, and

lines

128 and 129 connect the four-way valve 127 with the

cylinder spaces

139 and 140, respectively, of the high pressure transformer 141. The four-way valve 127 is also connected with line 121 through line 130. Line 126 and consequently cylinder 111 are further in communication with cylinder 132 of a pressure limit valve 133, wherein a piston 134 is slidably arranged in the cylinder 132 and is urged to one side thereof by a spring 136. A valve piston 135 is slidably arranged in a cylinder 137 which is separate from cylinder 132. The piston valve '135 divides the cylinder 137 into two cylinder spaces 122 and 123. A piston rod 138 connects piston 134 with piston valve 135.

The cylinder space 152 of the low-pressuretransformer is in communication with the press cylinder 4a through line 53 including a check valve 54 similar to the arrangement shown in Figure 1. A by-pass line 124 around the check valve 54 includes an operating control valve v14 2. The

control valves

102, 119 and 142 are operatively connected together by a connecting rod 143 so that they may be operated simultaneously.

-A line 143 in communication with the cylinder spaces 166a and 167a of the high-pressure transformer 141 is connected to line 53 between the check valve 54 and press-cylinder space 4a. A line 144, which includes a check valve 145 connects line 143 with the oilresenvoir 64. a 1

Cylinder space 123 is in direct communication with the oil reservoir 64 while line 1143 is also" connected to cylinder137 of the pressure limit :valve 133.

Automatic operation The automatic operation of the present hydraulically operated press is explained on hand of the schematic flow diagram of Figure 3, as follows:

The pump 20 draws water from the reservoir 27 and matic reverse valve 104 through line 103 and from there into cylinder space 114 of the low-pressure transformer 115 through line 113, moving the piston 133a upwardly. The piston =133b which is rigidly connected to the piston 133a through a piston rod 116 compresses the oil in the cylinder 152 to a pressure equal to the accumulator pressure reduced in the ratio of the piston area 1331) to 133a. As a result, the oil in the cylinder space 152 is pushed through line 53 and the check valve 54 into the press cylinder 4a of the press 1 and moves the'press plunger or ram 4 upwardly. The die 2, Figure 1, with the working piece 8 resting thereon, is :also moved upwardly until the workpiece 8 contacts the rubber pad or counter die 3. When this occurs,the pressure in the

cylinder chambers

4a, 152 and 114 begins to rise.

If the pressure in the cylinder space1 14 and 106, which acts on the piston of the automatic reverse valve 104, rises sufficiently to overcome the force of the spring 107, the control plungers 109 and are moved to the right and the water from the high-pressure accumulator now flows through line 126 to the four-way valve 127 and to the high pressure transformer tl. v

In the position as shown in Figure 3, the four-way valve 127 allows the flow of water into the cylinder space 139 and forces the plunger 139a to the left whereby the water remaining in the cylinder chamber 140-is forced through line 129, the four-way valve 127, line to the water reservoir27.

As the plungers 139a and a begin to move towards the left, the driven pistons 166 and 167, which are operatively connected with the driving

pistons

139a and 140a through connecting rods 168a and 16811, are moved outwardly. The oil in the cylinder spaces 166a and l167t1 is delivered through

lines

163, 143, 53 into the press cylinder 4a of the press 1. The check valve 54 prevents the oil from cylinders 166a and 167a from flowing back into the cylinder chamber 152 of low-pressure transformer 115. As the press piston 4 of the press 1 moves toward its maximum outer position, the pressure in

lines

143 and 126 increases rapidly as indicated in the pressure diagram, Figure 2. When the water pressure in the cylinder chamber 132, which acts on the piston 134, rises sufficiently toovercome the spring pressure 136, the control plunger 135, in moving upwardly establishes communication between the high-pressure line 143 and the oil reservoir 64 through cylinder chamber 123 and line 145.

-As the driving plunger assembly 139a, =1-40a of the high pressure transformer has reached the center position b (Figure l), the driven pistons 166 and 167 reverse their outward motion and commence to move toward their inner dead center whereby they will draw ofi oil from the press cylinder 4a of the press 1 through lines 53 and e 143. As a result, the press piston 4 moves downwardly and the pressure on the workpiece is thereby released.

' In order to further retract the press piston 4 to its initial starting position, the

valves

102, 119, 142, which are operatively connected with each other by connecting rod 143, are turned 90 either manually or mechanically by a moving part of the high-pressure transformer by which action the operating control valve 102 is closed and the valves 1 19 and 142 are opened. Communication between the automatic reverse valve104 and the high-pressure accumulator 5 is thereby disrupted. On the other hand, the press cylinder 4a is connected with the cylinder chamber 152 of the low pressure transformer 115 by by-passing the check valve 54" through lines 124 and control valve 142. Due to the rotation of the control valve 119 into anopen position, the water in the cylinder space 114- can now-escape to thewater'reservoir 27 by way of

lines

113, 118 and 121 by the action of the spring 116. As the piston 153a moves downwardly; the piston 13% also moves downwardly and draws oil from the press cylinder 40 through

line

53, 124, valve 142 into the cylinder space 152 whereby the press piston or ram 4 is returned to its starting position.

As the pressure in the cylinder space 114 drops, the pressure in the cylinder space 106 of the automatic reverse valve 104 is also lowered and the spring 107 moves the piston assembly 105-, 109, 110' to the left and the line 103 from the control valve 102 is again connected to the cylinder chamber 114 of the low-pressure transformer. By this last action, the Working cycle is completed.

In preparation of the next Working cycle, the four-way valve 127 is rotated by- 90 whereby the connections to the

cylinder chambers

139 and 140 of the high-pressure transformer 141 are interchanged so that the

piston assembly

139a, 140a moves from the left to right if pressure fluid from the accumulator 5 is received. In order to initiate the next working cycle, the control valves 102, 11 9; 142 are turned into the original position, as shown in Figure 3, through rod 143 whereby the new working cycle commences.

The structure shown in Figure 4 represents a lowpressure transformer modified from that shown in Figure 3 in that a spring 216 is arranged within the cylinder space 252 for forcing the piston assembly downwardly when the pressure in the cylinder-space 214 is reduced.

Figure 5 is an enlarged view of the high-pressure transformer indicating the connectinglines thereto by numerals as they appear in Figures 1 and 3.

Figure 6' is a modified construction of the automatic reverse valve 104 shown in Figure 3.

Instead of the piston 105 in Figure 3 being rigidly con nected with the piston "alves 199 and 110 by a connecting rod 112 the piston 205 according to the embodiment of Figure 6 is resiliently connected to the

piston valve assembly

209, 210 in the following manner:

The piston 205 is in resilient engagement with a snapring 270 by Way of a connecting rod 271 having a shoulder 272 at its end and being guided in a bore 273 thereof. Springs 274 and 275 on each side of the shoulder 272 retain the shoulder 272 in an approximately central position. of bore 273. Two V-shaped grooves 276 and, 277 are provided on the circumference, of the snap ring. 270 and the snap ring is held in position by a spring loaded ball 27S engaging one of the grooves.

When the piston 205 is first actuated by the increase in presure in line 120, Figure 3, to the right, Figure 6, the

piston valve assembly

209, 210 does not begin to move immediately to the right but first the spring 275 is compressed to a point where it exerts sufficient pressure on the snap ring to disengage the spring loaded ball 278 after which the snap ring 270 together with the

piston valves

209 and 210 snap to the right and the ball 278 engages with the groove 276.

By this action communication between

lines

103 and 113 is disrupted and communication between

lines

103 and 126 is established.

As the pressure in cylinder chamber 206 decreases, the spring 207 moves the piston 205 to the left and the auxiliary spring 274 is compressed to a point sufiicient to disengage the ball 278 from groove 276 whereafter the snap ring 270 together with the

piston valves

209 and 210 are moved to their original position as shown in Figure 6.

From the schematic illustration of Figure l and Figure 3, the pertinent advantage of the present invention can be readily recognized which resides therein that the forming stroke and release stroke are performed with a highpressure transformer at the fastest possible movement 10 from a to 001 etc a without the necessity of reversing anyvalves. With such an arrangementit is possible to perform the forming and releasing of a big press. in'one to two seconds.

While I have shown several embodiments of my invention, it is understood that the same is not limited thereto but is susceptible of many changes and modifications within the scope of person skilled in the art, and I intend to cover all such changes and modifications as encompassed by the appended claims.

I claim:

- I. A hydraulically operated press particularly for forming materials at elevated temperatures comprising a relatively stationary part and relatively movable part, hydraulic means including pressure supply means operatively connected with said press for initially closing said press during a first stage of operation and including piston means displaceable from an initial position for supplying high-pressure to the press and thereafter toward said initial position for releasing the application of said highpressure to the press, a movable actuator means connected to the piston means and movable continuously in one direction for displacing said piston means both from and toward said initial position for thereupon further actuating said relatively movable part relatively rapidly in the closing direction to form said material and for thereafter moving said relatively movable part in the opposite direction during a second stage of operation.

2. A hydraulically operated press particularly for forming materials at elevated'temperatures comprising a relatively stationary part and a relatively movable part, hydraulic means including first piston means and pressure supply means operatively connected with said press for initially closing said press during a first stage of operation, high-pressure transformer means operatively connected with said pressure supplymeans and said press including second piston means displaceable froman initial position for supplying high-pressure to the press and thereafter toward said initial position for releasing the application of said high-pressure to the press, a movable actuator means connected to the second piston means and movable continuously in one direction for displacing said second piston means both. from and toward said initial position for further actuation of said relatively movable part at a relatively rapid rate in the closing direction to form said material and for thereafter moving said relatively movable part in the opposite direction during a second stage of operation.

3. A hydraulically operated press particularly for forming materials at elevated temperatures comprising a relatively stationary part and a relatively movable part, bydraulic means. including pressure supply means, lowpressure transformer means including first piston means operatively connected with said supply means and said press for initially closing said press during the first stage of operation, and high-pressure transformer means operatively connected with said pressure supply means and said press including second piston means displaoeable from an initial position for supplying high-pressure to the press and thereafter toward said initial position for releasing the application of said high pressure to the press, a movable actuator means connected to the second piston means and movable continuously in one direction for displacing said second piston means both from and toward said initial position for further actuation of said relatively movable part at a relatively rapid rate in the closing direction to form said material and for thereafter moving said relatively movable part in the opposite direction during a second stage of operation.

4. The combination according to claim 2, further comprising control means for automatically bringing said high-pressure transformer into operation after completion of said first stage of operation, said control means being responsive to the rise in pressure in said press at the end of said initial closing operation.

5. The combination according to claim 3, further comprising control means for automatically bringing said high-pressure transformer into operation after completion of said first stage of operation, said control means being responsive to the prevailing pressure in said lowpressure transformer at the end of said initial closing operation.

6. The combination according to claim 3, wherein control valves are included in said pressure transmitter.

7. The combination according toclaim 3, wherein said low-pressure transformer includes a high-pressure piston having a relatively small diameter and a low-pressure piston of a relatively large size, the ratio of said diameters being such that the pressure produced by said lowpressure piston is capable of moving said relatively movable part during said initial closing of said press. a

8. The combination according to claim 2, wherein said high-pressure transformer includes at least one driving actuator piston and at least one driven piston, pressure transformation being accomplished by transmission of power from said driving piston to said driven piston.

9. The combination according to claim 8, wherein said driving actuator piston is directly connected with said driven piston by means of a connecting rod, the movement of one of said pistons being at an angle to the movement of the other of said pistons.

;Ihe combination according to claim 2, wherein the pressure produced in said high-pressure transformer for said further actuation of said relatively movable part increases progressively during said actuating movement.

11. The combination according to claim 2, wherein the pressure produced in said high-pressure transformer isof variable magnitude. 7

12. The combination according to claim 2, wherein the pressure in said high-pressure transformer is selec tively limited in magnitude by a pressure-limit valve.

13. The combination according to claim 8, wherein said driven piston is movably guided in a cylinder including a pressure-limit valve.

14. The combination according to claim 2, wherein said high-pressure transformer includes two driving pistons slidably arranged in coaxial cylinders and connected with each other by a rigid piston rod, two driven pistons the movement of which is in a perpendicular direction of that for said driving pistons, connecting rods pivotally connecting said driving and said driven pistons with each other, said connecting rods being disposed sub: stantially perpendicular to the direction of movement of said driving pistons.

15. The combination according to claim 3, wherein the working fluid from .said pressure supply means to said transmitters is. water while the working fluid between said transmitters and said press is oil.

16. The combination according to claim 2, wherein the connection of said second piston means to said actuator means comprises a linkage providing an increased mechanical advantage in transmitting the forces from said actuator means to said piston means during movement of said actuator means near the position thereof corresponding to the position of the press being fully closed.

17. A hydraulically operated press particularly an extrusion press or drop-forge press for forming materials comprising a relatively stationary part and a relatively moveable part, hydraulic means including pressure supply means, a high-pressure transformer means operatively connected with said pressure supply means and said press including at least one driving piston and at least one driven piston, said driving piston being directly connected with sm'd driven piston by means of a connecting rod, the movement of one of said pistons being at an angle to the movement of the other of said pistons, pressure transmission being accomplished by transmission of power from said driving piston to said driven piston for actuation of said relatively moveable part at a relatively rapid rate in the closing direction to form said material and for thereafter moving said relatively moveable part in the opposite direction.

18. A hydraulically operated press particularly an extrusion press or drop-forge press for forming materials comprising a relatively stationary part and a relatively moveable part, hydraulic means including pressure supply means, low-pressure transformer means operatively con-' -mission 'being accomplished by transmission of power from said driving piston to said driven piston for further actuation of said relatively moveable part at a relatively rapid rate in the closing direction to form said material and for thereafter moving said relatively moveable part in the opposite direction during a second stage of operation.

References Cited in the file of this patent UNITED STATES PATENTS 1,888,990 Kurath Nov. 29, 1932 2,200,998 Schnuck May 14, 1940 2,239,339 Oeckl Apr. 22, 1941 2,403,912 Doll July 16, 1946 2,573,993 Sedgwick Nov. 6, 1951 2,737,138 Derbyshire Mar. 6, 1956