US3205749A - Hydraulic cutting and punching press - Google Patents

Description

Sept. 14, 1965 Filed March 21, 1963 BULB] H.D.SCHENK HYDRAULIC CUTTING AND PUNCHING PRESS 7 Sheets-Sheet 2 KMXM Sept. 14, 1965 H. D. SCHENK HYDRAULIC CUTTING AND PUNCHING PRESS 7 Sheets-Sheet 3 Filed March 21, 1963 1M \MLML Sept. 14, 1965 H. D. SCHENK 3,205,749

HYDRAULIC CUTTING AND PUNCHING PRESS Filed March 21, 1963 7 Sheets-Sheet 4 Sept. 14, 1965 H. D. SCHENK 3,205,749

HYDRAULIC CUTTING AND PUNCHING PRESS Filed March 21, 1963 7 Sheets-Sheet 5 MMML P 14, 1955 H. D. SCHENK 3,205,749

HYDRAULIC CUTTING AND PUNCHING PRESS Filed March 21, 1963 '7 Sheets-Sheet 6 5 I W cr. w.

Sept. 14, 1965 H. D. SCHENK HYDRAULIC CUTTING AND PUNCHING PRESS Filed March 21, 1963 Fly. 17 5 7 Sheets-Sheet 7 United States Patent 3,205,749 HYDRAULIC CUTTING AND PUNCHWG PRESS Horst Dieter Schenk, 12 am Gatherhof,

. Dusseldorf, Germany Filed Mar. 21, 1963, Ser. No. 266,918 20 Claims. (Cl. 83--639) The invention relates to hydraulic presses for metalworking and more particularly to hydraulic presses as used for cutting and punching metal sheets and blanks and for a combination of drawing and cutting operations.

As is well known to those skilled in the art, a hard shock of stress-relieving occurs at each cutting stroke when the metal sheet is breaking, due to the compressibility of the power-transmitting fluid of the driving means in the hydraulic press.

Consequently, such presses and their tools are liable to damage so that heavy repair work is required after a short time of continuous cutting operations.

The principal object of the invention is to provide a hydraulic press in which metal cutting or punching work can be performed at the same time preventing any harmful shock of stress-relieving that otherwise may damage the hydraulic press and its tools.

Another important object of the invention is to provide a hydraulic press in which metal cutting or punching work can be performed at the same time preventing the explosive sounds which usually occur while the metal sheet to be cut is breaking and tearing apart, so that cutting work can be performed almost noiselessly.

A further object of the invention is to provide a hydraulic press in which metal cutting or punching work can beperformed in a way that the scrap adheres loosely to the workpiece after completion of the cutting operation. This serves to ease the charging conditions when it is intended to obtain the workpiece and the scrap from the press simultaneously.

Still further specific objects, features and advantages of the invention will become apparent as the description is read in the light of the accompanying drawings illustrating a preferred embodiment of the invention, in which:

FIG. 1 is a front view of a hydraulic press equipped with cutting and punching means;

FlG. 2 is a side view of the press shown in FIG. 1;

FIG. 3 is a vertical sectional view of the press, taken on the line II of FIG. 1;

FIG. 4 is a vertical sectional view of the press, taken on the line Illl of FIG. 1;

FIG. 5 is a diagrammatic view illustrating the press with its hydraulic circuits for controlling the operations of the machine, according to the invention;

FIG. 6 is an enlarged view of the left-hand screw in detail with its holder, as shown in FIG. 1, FIG. 2 and FIG. 3;

FIG. 7 is a horizontal sectional view of the left-hand screw with its holder, taken on the line III-III of FIG. 6;

FIG. 8 is a vertical sectional view of the left-hand screw with its holder, taken on the line lV-IV of the FIG. 6;

FIG. 9 is an enlarged view of one of the counteraction cylinders, as shown in FIG. 1, FIG. 2 and FIG. 4;

FIG. 10 is a horizontal sectional view of one of the counteraction cylinders, taken on the line VV of FIG. 9;

FIG. 11 is a plan view of one of the counteraction cylinders, shown in FIG. 9;

FIG. 12 is a diagram of the spring rate of the ram driving cylinder, shown in FIG. 5 g

3,295,749 Patented Sept. 14-, 1965 FIG. 13 is a diagram of the spring rate of the counteraction cylinders, shown in FIG. 5 and FIG. 10;

FIG. 14 is a simplified stress-strain diagram of the metal sheet to be cut. It is drawn on the cutting line of the metal sheet and symbolizes the increase and the decrease of the cutting resistance as a function of the proper cutting way within the metal sheet.

FIG. 15 is an enlarged sectional view of the throttle, shown in FIG. 5. The sectional view is taken on line VIVI of FIG. 16;

FIG. 16 is a side view of the throttle, shown in FIG. 15.

H6. 17 is an enlarged sectional view of one of the solenoid valves belonging to the counteraction system, shown in FIG. 5.

Essentially, the press as illustrated in the drawings, consists of a frame 10, a driving cylinder 12 with its piston 14 a press ram 18 guided in V-Ways 16, an ejector 22 guided in V-ways 20 and a piston 24 of said ejector. The piston 24- is supported by a cross beam 26, which is fastened to the frame 10 by means of tie-bolts 28 and nuts 3%. The lower die 32 is mounted on a bolster plate 34 in the frame ltl. A stripper plate 36, guided by the lower die 32, is supported by pins 38 on the ejector 22. The upper die 45) is fastened to the press ram 18. The screw holders 4-2, which are shown in greater detail in the FIGS. 6, 7 and 8, are fixed to the right-hand side to the left-hand side of the press ram 18 by means of screws 44 and keys 46. The screw holders 42 are provided with bronze nuts 48, into which the screws 50 are engaged by threads. For adjustment purposes the screws 56 are provided with splined bushings 52, which are fastened to the upper end of said screws. The screws 50 are adjustable in the direction of the ram motion by means a handwheel 54. Two worm gears 5'6, which are coupled to their driving shafts by a connecting shaft 58, serve for transmission of motion from the handwheel 54 to the screws 50. The splined shafts 60, which are fixed to the driven shafts of the worm gears 56, serve as further motion-transmitting members. The adjustable screws 50 co-operate with counteraction cylinders 62, which are supported on pistons 64 by means of com pression springs 66. The compression springs 66- contain a number of disc springs guided on rods 68, which are screwed in the bottoms of the counteraction cylinders 62, as shown in detail in FIGS. 9, 10 and 11. The counteraction cylinders 62 are provided with bronze bushings 7'0 and are guided by pistons 64. Packings 72 of chevron type provided for these pistons seal the counteraction cylinders 62. The position of the pistons 64 relative to the frame 19 is determined by threaded pins '74 as shown in Fl'G. 9. To one of the counteraction cylinders 62 a cam plate 76 is fixed, which actuates a limit switch 78. Limit switch 73 is adjustably fastened to a gib 89. A cam plate 82 fixed to the press ram 18 can actuate limit switches 86, S8 and 90, which are adjustably fastened to a gib 34. A further cam plate 92 fixed to the ejector 22 can actuate limit switches 96 and 98, which are adjustably fastened to a gib 94, in a similar manner as limit switches 86, 88 and 90.

A fluid pump 1%, driven by an electric motor 102, serves to drive the press ram 18 and the ejector 22. The inlet of pump tee is connected to the tank 1% containing the hydraulic fluid 1638 by a conduit 104. Tank 1106 is arranged in the upper part of the frame 10 and is provided with an air filter 116. From the outlet of the pump 1% a conduit 112 extends to a solenoid-operated valve block 114. The valve block 114 comprises the required valves for controlling the operating cycle of the hydraulic press. The valve block 114 is connected to the cylinder chamber lid at the head end of the piston 14 by a conduit I18. By means of a conduit the valve block 114 cylinder chamber 132 at the head end of the piston 24,

and by a conduit 134 it is connected to the cylinder chamber 136 at the rod end of the piston 24. A relief valve 138 protects the pump 100 against overload. The pump 100 and the valve block 114 are arranged on the top of the frame 10, which is accessible for maintenance routine by the ladder 140.

It should be stressed that the fluid circuit of both counteraction cylinders 62 related to the cutting equipment is only connected to the tank 106 and is independent of the fluid circuit which supplies the press ram 18 and the ejector 22. The cylinder chambers 142 at the head end of the pistons 64 of the counteraction cylinders 62are separately connected to the solenoid-operated valves 144 by a conduit 146. Each solenoid valve 144 is connected to the tank 106 by a conduit 148. Further on, the conduits 150 extend to an elastic coil-like conduit 152 and to the counteraction cylinders 62 from the Said throttle 154 is connected .to the tank 106 by a conduit 156 which terminates just below the fluid level in the tank 106. The elastic coils 152 of the conduits 150 are fixed at one end to the frame by the holders 158 and at the other end to the counteraction cylinders 62 by the holders 160.

The pump motor 102 and the solenoids of the valves 144 and of the valve block 114 are energized by electric power. The electric power is supplied to the switchboard 164 from a feeder line 162. The switchboard 162 comprises the electrical equipment required for operating the hydraulic press. Suitable electric lines 166 run from the switchboard 164 to the pump motor 102, to the solenoid-operated valves 114 and 144, to the limit switches 78, '86, 88, 80,96, 98, and to the control panel 168. The control panel 168 contains the push buttons 170 for controlling the press, the pressure gauges 172 for indication of the tonnage, and the valves 174 for adjusting the tonnage of the hydraulic press.

Now, an operating cycle of the hydraulic press is described preferably in connection with FIG. 5.

At the beginning of the cycle the press is on standstill. The press ram 18 stands at'is highestposition and the limit switch 86 is actuated by the cam plate 82. The ejector 22 stands at its lowest position and the limit switch 98 is actuated by the cam plate 92. The hydraulic fluid, preferably oil, which is supplied by the pump 100, flows through the conduit 112, passes the valve block 114 and then flows through the conduit 124 back to the tank 106. The valve block 114 shuts oif the conduit 120, which leads to the cylinder 12, as well as the conduits 130 and 134, which lead to the ejector piston 24, but connects the conduit 128 for controlling the prefill valve 126 to the conduit 120 and the chamber 122. of the cylinder 12; and the conduit 118 from the cylinder 12 is connected to the conduit 124, which leads to the tank 106. The fluid passage inside the valve block 114, connecting conduit 118 to conduit 124, is of very small sectional area at standstill of the press. The holdup pressure inside the cylinder chamber 122 at the rod end of the piston 14 is established by the weights of the press ram 18 and the members fixed on it; the pressure has opened the prefill valve 126 by the conduits 120 and 128. The counteraction cylinders 62, which are supported on the pistons" 64 are held in their highest position by the compression springs 66. The cylinder chambers 142 at the head end of the pistons 64 are connected to the tank 106 by the conduits 146,. the open solenoid valves 144- and the conduits 148, 150 and 156.

The cutting operation begins after the workpiece 176,

throttle 154. i

part, is put on the lower die 32.

To this end, one of the push buttons 170 has to be pressed so that the solenoid-operated valve block 114 connects the conduits 112 to 118 and 120 to 124. Now the press ram 18 and the piston 14 fall downwards under the action of their own weights with a high speed. Thereby the fluid is discharged from the reducing cylinder chamber 122 at the rod end of the piston 14 and flows to the tank 106 passing the conduit 120, the valve block 114 and the conduit 124. Inside the increasing cylinder chamber 116 at the head end of the piston 14 the fluid is sucked off the tank 106 through the conduit 129 and the prefill valve 126. At the same time pump supplies fluid, which flows through the conduit 112, the valve block 114 and the conduit 118 into the cylinder chamber 116.

Upon downward movement of the press ram 18 the cam plate 82, which is fixed to the press ram 18, actuates the limit switch 88. One of the solenoids of the valve block 114 is engaged by the limit switch 88, and by this action, the valve block 114 is actuated so that the sectional area is reduced, which connects conduit 120 with 124 in said valve block. By that means, the press ram 18 slow down its speedy downward motion so that a smooth contacting between the adjusted screws 50 and the counteraction cylinders 62 is provided.

Upon further motion of the press ram 18 the counteraction cylinders 62 with the compression springs 66 are moved downwards by the screws 50 upon the action of the weights of the press ram 18 and the piston 14 etc. Fluid can discharge to the tank 106, substantially pressureless from the lessening cylinder chambers 142 of the counteraction cylinders 62 through the conduits 146, the open solenoid valves 144 and the conduits 148.

When the upper die 40 contacts the workpiece 176, which is to be cut along the line 178 to remove the edge material 180, the cam plate 76 of the counteraction cylinder 62 actuates the. limit switch 78. As a result, the solenoid valves 144 are actuated and block the fluid discharge to the tank 106 from the counteraction cylinders 62 through the conduits 146 and 148.

When the upper die 40 has contacted the workpiece 176 the press ram 18 has stopped its downward movement. For providing a continuous downward movement of the upper die 40 the prefill valve 126 must shut and block the sucking flow through the conduit 129 from the tank 106. The pump 100 supplies fluid to the cylinder chamber 116 at the head end of the piston 14 whereby the pressureless fluid in this cylinder chamber 116 becomes pressurized in a manner that, the ram force increases to an amount which compels the metal sheet of the workpiece 176 to yield along the line 178.

Upon continuation of the ram movement the upper die 40 begins to penetrate the metal sheet whilst the Counteraction cylinders 62 are pressed downwards by the screws 50, which are fastened to the pressram 18 by the holders 42 and the nuts 48. By this action the fluid inside the cylinder chambers 142 of the counteraction cylinders 62 is discharged into the tank 106 by passing the conduits 150, the throttle 154 and the conduit 156. 1

The throttle 154 tends to impede the flow and causes a resistance, which depends on the velocity of the fluid flow. As a result of it a counteracting force generates inside the cylinder chambers 142 of the counteraction cylinders 62 while the upper die 40 penetrates the metal sheet of the workpiece 176. This counteracting force in addition to the cutting resistance opposes the ram force and tends to retard the movement of the press ram 18 respective to decelerate the cutting velocity. The amount. of this counteracting force increases with the velocity of flow through the throttle 154. The velocity of flow through the throttle 154 increases to an extent that a certain state of equilibrium occurs between the ram force on the one side and the cutting resistance plus the counteracting force on the other side.

5. The resulting cutting velocity, or in other words, the instantaneous penetration velocity of the upper die 40 when the metal sheet of the workpiece 176 continues yielding is mainly determined by the sectional area of the throttle 154 and by the pressure dependent velocity of fluid flow through the throttle 154, provided that the output of the pump 100 is large enough to maintain the maximum of the cutting velocity, which is self-adjusting by said factors. If the output of the pump 100 is larger than required by the said factors of the self-adjusting maximum of the cutting velocity, then the excessive output is discharged by the pressure adjusting valve 174 which is placed in the control panel 168. I

To obtain an economic cutting velocity it is necessary to provide a ram force which is about 2% larger than would be required to overcome the ultimate cutting resistance. The excessive ram force serves to press the fluid volume from the counteraction cylinders 62 to the tank 106 through the conduits 150, the throttle 154 and the conduit 156.

As soon as the press ram 18 attains a certain downward position so that the upper die 40 overcomes the ultimate strength of the metal sheet of the workpiece 176 by penetration, the edge material 180 tears off at the line 178.

At this time the cutting resistance decreases to zero; but as a result of an almost simultaneous equalization of the pressure between the cylinder chambers 116 and 142, a state of equilibrium between ram force, decreasing cutting resistance and counteracting force is maintained in a way that the press ram 18 continues to move with substantially the same load and velocity as before, overcoming the ultimate strength of the metal sheet of the workpiece 176. This equalization of pressure during decreasing of the cutting resistance is due to the partial expansion of the pressurized fluid volume inside cylinder chamber 116 which compresses the fluid volume inside cylinder chambers 142 by means of piston 14, press ram 18, holders 42, nuts 48, screws 50 and cylinders 62 to an amount until the aforesaid state of equilibrium occurs.

Upon completion of the stroke the press ram 18 changes its direction of motion after the cutting operation When the counteraction cylinders 62 are in a downward position so that they are supported directly on the pistons 64. In this position the adjusted limit switch 90, which is arranged below the limit switch 88 on the gib 84, is actuated by the cam plate 82. As a result of the actuation of the limit switch 90 the valve block 114 is engaged to a control position that shuts the conduits 120, 130 and 134 and brings the press ram 18 to a short standstill. At the aforesaid control position of the solenoid-operated valve block 114 the pump 100 runs on idling and supplies its fluid through the conduit 112, the valve block 114 and the conduit 124 back into the tank 106, whilst the pressurized fluid inside the cylinder chamber 116 at the head end of the piston 14 is pressure-relieved in a smooth manner by a small passage between conduits 118 and 124 inside the valve block 114. After pressure drop inside the cylinder chamber 116 and therewith inside the cylinder chamber 142 too, a time relay, which belongs to the electrical equipment in the switchboard 164, and actuated previously by the limit switch 90, engages the solenoid-operated valve block 114 so that it connects the conduit 112 to 120 and 128 and conduit 118 to 124; the conduits 130 and 134 are blocked.

The press ram18 moves upwards until it actuates the limit switch 86 by the cam plate 82. The prefill valve 126 is opened during the upward movement of the press ram 18 and remains open.

At the beginning of the upward movement of the press ram 18 the solenoid-operated valves 144 are opened whereby the conduits 146 are connected to 148. During upward movement of the counteraction cylinders 62, which is caused by their compression springs 66, fluid flows from the tank 106 into the cylinder chambers 142 through the conduits 148 and 146.

As a result of the actuation of the limit switch 86 by the press ram 18 the solenoid-operated valve block 114 is moved to a control position that blocks the conduits 118 and and accordingly the press ram 18 comes to a standstill at its highest position. The conduit 128 of the prefill valve 126 remains connected to the conduit 120.

At the aforesaid control position, the valve block 114 temporarily connects the conduits 112 to 130 and 124 to 134, whereby the ejector 22 will be moved upwards to the limit switch 96; by its upward movement it ejects the workpiece 176 out of the lower die 32 by means of the pins 38 and the stripper plate 36. On actuating the limit switch 96 by the cam plate 92 the valve block 114 is moved to a control position that temporarily connects the conduits 112 to 134 and 124 to 130, whereby the ejector 22 is moved downwards to the limit switch 98, and there it comes to a standstill. Upon actuation of the limit switch 98 the valve block 114 is moved to a control position that blocks the conduits 120, 130 and 134, whilst the conduit 112 is connected to the conduit 124 so that the pump 100 can circulate its fluid on idling. Furthermore upon standstill of the press the conduits 120 to 128 and the conduits 118 to 124 are connected by a passage of very small cross section the valve block 114. The working cycle is terminated.

As a result of the dispositions and objects aforesaid it is evident that the exact lay-out of the throttle 154, respectively the dimension of the sectional area of this flow passage and the length of it together with the dimensions of the conduits 146 and and of the cylinder chambers 142 are of great importance.

On the one hand the sectional area and the length of the throttle 154 should preferably be chosen in a dimension that the cutting procedure can be effected sufiiciently long in order to cut off the waste material from the workpiece without the explosive sounds which usually occur while the material is breaking and tearing apart.

On the other hand the sectional area and the length of the throttle 154 must be chosen in a dimension that the driving fluid inside the cylinder chamber 116 of the cylinder 12 is prevented from any substantial hydraulic decompressions, which otherwise may shock and damage the press while the material is breaking and tearing apart.

To obtain the aforesaid eflects in a good and adequate manner it is necessary to lay out such a throttle with a length of about 0.1 inch up to 1 inch whilst the sectional area of the throttle should be the V4500 up to 4 part of the pressing area of the counteraction cylinders.

The dimensions of the throttle are not only dependent on the amount of effect desired and on the dimensions of the pressing area of the counteraction cylinders, but they are also dependent on the viscosity of the fluid used. It is possible to replace such a short throttle with a small sectional area as aforementioned, by a longer throttle with a more extended sectional area than aforesaid, but the throttle has to be chosen of such a dimension that the amount of its resistance against passing the fluid is sufficient to obtain the aforesaid effects.

Also of great importance is the shape of the cylinder chambers 142 of the counteraction cylinders 62 and also the extent of compression stress which is loaded on the enclosed fluid.

In order to reduce the compressibility of the enclosed fluid to a minimum and in order to control the yielding rate of the sheet material to be cut so that the usual sound effect occurring at material breaking point will be avoided, it is of importance to burden the enclosed fluid inside of the cylinder chambers 142 of the counteraction cylinders 62 and inside of the conduits 146 and 150 with a pressure which should not exceed 10,000 pounds per square inch, whilst the aforementioned chambers 142, 146 and 150 should be as small as possible in their volumes.

According to the aforesaid the cylinder chambers 142 have to be shaped. in a manner that the diameters D of 7 the cylinder chambers 142 are large, whilst the height H of these cylinder chambers is small.

Furthermore, because of their large sectional area, which is required by the amount of fluid flow for the filling of the cylinders 62, the conduits 146 from the pistons 64 to the solenoid valves144 should be as short as possible. In comparison with conduits 146 the conduits 150, which extend from the counteraction cylinders 62 to the throttle 154, are long as necessarily determined by the press construction but, therefore, they can be made of small sectional area.

Approximately shockless cutting by a hydraulic press equipped in aforesaid manner is already attainable when the diameters D D of the cylinder chambers 116 and 142 are made at a ratio of 1/ 0.4 up to 1/ 0.63 and simultaneously when the height H /H of the aforesaid cylinder chambers are made at a ratio of 1/ 0.2 up to l/ 0.5. But with said dimensions the explosive-like sound effect at material breaking point cannot be avoided.

Perfectly shockless cutting by a hydraulic press equipped in aforesaid manner, in a way that the exposive-like sound at material breaking point is avoided, can be attained when the diameters D1/D2 of the cylinder chambers 116 and 142 are made at a ratio of 1/0.6 up to 1/0.7 and when simultaneously the height H of the cylinder chambers 142 and the thickness S of the sheet material are made in a proportion of H /S=l/0.5 up to 1/1 at the moment of cutting.

By means of the FIGS. 12, 13 and 14 these relations are to be explained in more particular:

FIG. 12 shows the energy, which is accumulated inthe cylinder chamber 116 of the driving cylinder 2 by com pression of the enclosed fluid, as a triangular area of the spring diagram with the angle at and the cathetus F and After the cutting resistance C has dropped suddenly, after overcoming ultimate strength of the sheet material by the cutting tools, the press ram 18 and the piston 14 are abruptly accelerated by the energy shown in FIG. 12, whilst the frame and the hydraulic system are abruptly unloaded with a heavy shock, unless an increasing counteracting force F replaces the cutting resistance C which has suddenly decreased to zero.

When the cutting resistance C drops to zero the counteracting force P will be established in the counteraction cylinders 62 to the required amount by means of a partial expansion of the highly-pressurized fluid volume inside the cylinder chamber 116 of the driving cylinder 12. The partial expansion in the cylinder 12, which in the end will be compensated by an increase responsive to the output of the pump 100, is transmitted to the cylinder chambers 142 of the counteraction cylinders 62 by means of piston 14, press ram 18, holders 42, nuts 48 and screws 50.

As a result of the equalization of pressure between cylinder chamber 116 of the driving cylinder 12 and cylinder chambers 142 of the counteraction cylinders 62 a state of equilibrium between the ram force F on the one side and the decreasing cutting resistance C and increasing counteracting force F on the other side is maintained at each moment of cutting movement. Thereby the .cutting velocity changes in a range which is determined by the quantity of fluid that discharge from the counteraction cylinders 62 by passing the throttle 154.

It is, obvious that the volume of fluid flow through the throttle 154, and with it the cutting velocity, increase to a maximum when the cutting resistance C decreases to zero and the whole ram force F is then acting on the counteraction cylinders 62. If the ram force F exceeds an amount of 2% of a force which would be required to overcome the ultimate cutting resistance the fluid flow through the throttle 154, and the ratio of maximum cutting velocity to a minimum cutting velocity is substantially 7 to 1. For example, the maximum cutting. velocity may be 0.35 inch per second whilst the minimum velocity is 0.05 inch per second;

The increaseof the counteracting force F is shown in FIG. 13, which represents the triangular spring diagram of the counteraction cylinders 62 with the angle 8 and the cathetus F and h It requires asmall height k to obtain an abrupt'increase of spring rate or to obtain a large angle 5 or, what means the same, to obtain a fast increase in the counteracting force F To control the yielding velocity of the metallic sheet material in the manner demanded so that the explosivelike sound is avoided when the sheet material is breaking and tearing apart, the angle {3 of the'spring diagram FIG. 13 of the counteraction cylinders 62 has to be approximately equal or preferably larger than the angle "y of the strain-stress diagram of the sheet material, shown in FIG. 14.

In FIG. 14 the angle 7 indicates the rate of decrease of the cutting resistance C, while the sheet material is tearing apart and the letter 5 indicates the yielding elongation of the sheet material with'the thickness S.

To obtain the aforesaid effects it is also of importance to provide a permanent self-venting of the counteraction system. Therefore the counteraction cylinders 62 and the pistons 64 are arranged in a preferred manner, that the pistons 64 are fastened to the frame 10whilst the cylinders 62 are movable. This permits, for venting the cylinder chambers 142, the conduits with their holders to befixed to an upper point of these chambers. Additionally the conduits 150-are laid in a continuous rise from the cylinder chambers 142 to the throttle 154. The conduit 156 from the throttle 154 to the tank 106 is also laid in a continuous rise and terminates within the fluid volume of the tank 106.

The throttle 154 has to be without any air pocket insigle it. This kind of throttle is shown in FIGS. 15 and 1 i To avoid anyair pockets and to achieve a very tight shutoff of the conduits 146 the solenoid valves 144 are preferably of seat valve type. This kind of valve is shown in FIG. 17.

- As is obvious from the preceding description of this invention, the height H of the cylinder chambers 142 can be adjusted in a manner that at end of the cutting procedure the cylinder bottoms are supported directly against the pistons 64, whilst the cutting edges of the upper die 40 and of the lower die 32 are on an approximately equal horizontal plane.

This kind of stroke limitation by a fixed stop is of advantage if the scrap is to adhere loosely to the workpiece 176 in order to obtain both the parts 176 and 180 from the press simultaneously.

As is obvious from the preceding description of this invention in connection with FIG. 5, there exists a further possibility by which the principal object of the invention can be obtained, so that any harmful shock of stress-relieving is prevented, which otherwise may damage. the hydraulic press and its tools. The principal object of the invention can be obtained by application of the ejector'22 as a counteraction cylinder. To obtain this, it is necessary to support the workpiece 176 by the stripper plate 36, the pins 38 and the ejector 22 and to connect the cylinder chamber 132 of the ejector 22 to the tank 106 by a conduit, like said conduit 150, with a throttle in this conduit, likev said throttle 154, and to provide the conduit containing the throttle and connecting the cylinder chamber 132 to the tank 106 with arelief cannot move downwards under the action of its dead weight.

At the beginning of the cutting operation the ejector 22 stands at its highest position, whereby the limit switch 96 is actuated by the cam plate 92, and the workpiece 176 placed on the lower die 32 is additionally supported by the stripper plate 36 and the pins 38 on the ejector 22.

When the upper die 40 contacts the workpiece 176 and penetrates into it on the line 178 to cut ofi the scrap 180 the ejector 22 with the stripper plate 36 and the pins 38 will be pressed downwards and it then acts as counteraction cylinder in said manner.

The diameters D /D of the cylinder chambers 116 and 132 can be made at a proportion of 1/0.6 up to 1/ 0.8 and the heights H /H of the aforementioned cylinder chambers can be made at a proportion up to 1/ 0.5

By way of an example an embodiment of the hydraulic press for cutting and punching of metallic sheet material in an almost noiseless Way will be demonstrated.

Example To this the FIGS. 5, 12, 13 and 14 are to be referred.

Ram force F 500,000 kg. Cutting resistance C 490,000 kg.

Maximum pressure in the pressed cylin- 5 is assumed with 22% of the thickness S. Drawing sheet material of commercial quality has a yielding elongation up to 30% Power transmitting medium Hydraulic oil. Compressibility factor K of hydraulic oil 60/ 10 Compression I1 of cylinder chamber 116 of cylinder 12 at a pressure of p=250 Conversion of measurements:

1 kg.=2.2 lbs. 1 kg./cm. 14.22 lbs. per sq. inch.

Comparison between angle ,8 and angle '7 shows that B 'y.

To cut or to punch in an almost noiseless way, so that the explosive-like sounds are avoided when sheet material is tearing apart, it is necessary to control the yielding velocity of the sheet material. This can be obtained when the angle 5, which represents the increase of the counteracting force, is made approximately equal to or rather larger than the angle 7, which represents the decrease of the cutting resistance. It is demonstrated by the afore- 10 going calculation that the angle ,8 is obtainable larger than angle 7.

I have illustrated and described a present preferred embodiment of my invention, but it will be understood that the same is not limited thereto but may be otherwise embodied or practiced within the scope of the appended claims.

I claim:

11. Hydraulic press having frame means with a table opposed to at least one press cylinder fixed to said frame means, a ram driven hydraulically by a piston guided by and sealed within said press cylinder, tool means for cutting and punching work containing at least two member-s, one of which atrlxed to said ram, the other of which affixed to said table, hydraulic means containing first control means and power means supplying said press cylinder with pressure fluid, a combination of thrust transmitting means being connected to said ram and of shock eliminating means being connected to said frame means, said shock eliminating means acting together with said thrust transmitting means at least during proper cutting operating to prevent any harmful shock of stress relieving substantially in said press cylinder and in said hydraulic means while the workpiece to be cut is breaking and tearing apart, said shock eliminating means provided by at least one counteraction cylinder and its associated piston and a volume of liquid enclosed within said counteraction cylinder and second control means in fluid connection with said volume of liquid, said second control means containing at least one throttle means controlling the flow of liquid emerging from said counteraction cylinder during cutting operation and at least one shut-oft" valve means having inlet means to permit quick restoring of said volume of liquid within said counteraction cylinder of said shock eliminating means after said cutting operation when said ram is being retracted, said volume of liquid within said counteraction cylinder being dimensioned during said proper cutting operation such that the ratio of the height of the liquid volume within said press cylinder to the height of the liquid volume within said counteraction cylinder multiplied with the ratio of the pressing area displaceable within said counteraction cylinder to the pressing area displaceable within said press cylinder is greater than 1.6 and said ratio of the height of the liquid. volume within said press cylinder .to the height of the liquid volume within said counteraction cylinder is greater than 1/0.5 and said throttle means being dimensioned so that a resistance to the liquid flow through a throttle having a length of 0.1 inch up to 1 inch and a cross-sectional area, the ratio of which to the pressing area of said counteraction cylinder is smaller than /2,500-

2. Hydraulic press according to claim 1, wherein said throttle means is positioned at the top of said volume of liquid within said counteraction cylinder for venting said liquid volume.

3. Hydraulic press according to claim 1, wherein said shut-off valve means is positioned very close to said volume of liquid within said counteraction cylinder for minimizing the volumes of liquid in conduit means between said shut-otf valve means and said counteraction cylinder.

4. Hydraulic press according to claim 1, wherein feeding conduit means is controlled by said shut-off valve means and rises to liquid supply tank at a level above said counteraction cylinder from said volume of liquid in said counteraction cylinder for venting said feeding conduit means, and said feeding conduit means terminates at the bottom of said liquid supply tank for preventing air suction to said counteraction cylinder.

5. Hydraulic press according to claim 1, wherein adjusting means for varying the height of said liquid volume within said counteraction cylinder such that said height is somewhat lesser than the thickness of the metal to be cut, whereby waste pieces loosely adhering to said metal workpiece at completion of operating cycle.

6. Hydraulic press having frame means with a table opposed to at least one press cylinder fixed to said frame means, aram driven hydraulically by a piston guided by and sealed within said press cylinder, tool means for cutting and punching work containing at least two members, one of which aflixed to said ram, theother of which aflixed to said table, hydraulic means containing first control means and power means supplying said press cylinder with pressure fluid, a combination of thrust transmitting means being connected to said. ram and of shock eliminating means being connected to said frame means, said shock eliminating means acting together with said thrust transmitting means at least during proper cutting operation to prevent any harmful shock of stress relieving substantially insaid press cylindcr and in said hydraulic means, while the workpiece to be cut is breaking and tearing apart, said shock eliminating means provided by at least two counteraction cylinders and associated pistons, each containing a volume of liquid enclosed within said counteraction cylinders and second control means in fluid connection with said volumes of liquid, said second control means containing at least one throttle means controlling the flow of liquid emerging from said counteraction cylinders during cutting operation and at least one shut-off valve means having .inlet means to permit quick restoring of said volumes of liquid within said counteraction cylinders of said shock eliminating means after said cutting operation when said rain is being retracted, said volumes of liquid within said counteraction cylinders being dimensioned during proper cutting operation such that the ratio of the height of the liquid volume within said press cylinder to the height of the liquid volumes within said counteraction cylinders multiplied with the ratio of the total of the pressing areas displaceable within said counteraction cylinders to the pressing area displaceable within said press cylinder is greater than 1.6 and said ratio of the height of the liquid volume within said press, cylinder. to the height of .the liquid volumes within saidcounteraction cylinders is greater than 1/0.5 and said throttle A 7. Hydraulic press according to claim 6, wherein said throttle means is positioned at the top of said volumes of liquid within said counteraction cylinders for venting said liquid Volumes. I

8. Hydraulic press according to claim 6, wherein said shut-off valve means is positioned very close to said volumes of liquid within said counteraction cylinders for minimizing the volumes of liquid in conduit means between said shut-off valve means and said counteraction.

cylinders.

9. Hydraulic press according to claim 6, wherein feeding conduit means is controlled by said shut-off valve means and rises to liquid supply tank at a level above said counteraction cylinders from said volumes of liquid in said counteraction cylinders for venting said feeding conduit means, and said feeding conduit means ter-.

minates at the bottom of said liquid supply tank for preventing air suction ,to said counteraction cylinders.

10. Hydraulic press according to claim 6, wherein adjusting means for varying the height of said liquid volumes within said counteraction cylinders such that said. height is somewhat lesser, than the thickness, of the metal to be cut, whereby waste pieces loosely'adheres to said metalworkpiece at completion of operating cycle.

11. Hydraulic press having frame means" with a table opposed to at least one press cylinder fixed to said frame means, a ram driven hydraulically by a piston guided by and sealed within said press cylinder, tool means for cutting and punching work containing at least two members, one of which affixed to said ram, the other of which afiixed to said table, hydraulic means containing first control means and power means supplying said press cylinder with pressure fluid, a combination of thrust transmitting means being connected to said ram and of shock eliminating means being connected to said frame means, said shock eliminatingmeans acting together with said thrust, transmitting means at least during proper cutting operation to prevent explosive sounds occurring usually while the workpiece to be cut is breaking and tearing apart, so that cutting work can be performed in a substantially noiseless manner, said shock eliminating means provided by at least one counteraction cylinder and its associated piston and a volume of-liquid enclosed within said counteraction cylinder and second control means in' fluid connection with 'said volume of liquid, said second control means containing at least one throttle means controlling the flow of liquid emerging from said counteraction cylinder during said cutting operation and at least one shut-off valve means having inlet means to permit quick restoring of said volume of liquid within said counter-actioncylinder of said shock eliminating means after said cutting operation when said ram is being retracted, said volume of liquid within said counteraction cylinder. being dimensioned during said proper cutting operation such that the ratio of the height of the liquid volume within said counteraction cylinder to the thickness of the workpiece to be cut is smaller than l/ 0.5 as well as the ratio of the pressing area displaceable within said press cylinder to the pressing area displaceable Within said counteraction cylinder is smaller than 1/O.72 and said throttle means being dimensioned so that a resistance to the liquid. flow emerging from said counteraction cylinder during said cutting operation being caused in correspondence with a resistance to a liquid flow through a throttle having a length of 0.1 upv 1 smaller than /2,500-

12. Hydraulic press according to claim 11, wherein said throttle means is positioned at the top of said volume of liquid within said counteraction cylinder for venting said liquid volume.

13. Hydraulic press according to claim 11, wherein said shut-oft? valve means is positioned very close to said volume of liquid within said counteraction cylinder for minimizing the volume of liquid in conduit means between said shut-off valve means and said counteraction cylinder.

14. Hydraulic press according to claim 11, wherein feeding conduit means is controlled by said shut-off valve means and rises to liquid supply tank at a level above said counteraction cylinderfrom said volume of liquid in said counteraction cylinder fortventing said feeding conduit means, and said feeding conduit terminates at the bottom of said liquid supply tank for preventing air suction to said counteraction cylinder.

- 15., Hydraulic press according to claim 11, wherein adjusting means for varying said height of said liquid volume within said counteraction cylinder such that said height is somewhat lesser than the thickness of the metal to be cut, whereby waste pieces loosely adheres to said metal workpiece at completion of operating cycle.

16. Hydraulic press having frame means with a table opposed to at least one press cylinder fixed to said frame means, a ram driven hydraulically by a piston guided by and sealed within said press cylinder, tool means for cutting and punching work containing at least two members, one of which affixedto said ram, the other of which affixed to said table, hydraulic means containing first control means and power means supplying said press cylinder with pressure fluid, a combination of 13 thrust transmitting means being connected to said ram and of shock eliminating means being connected to said frame means, said shock eliminating means acting together with said thrust transmitting means at least during proper cutting operation to prevent explosive sounds occurring usually while the workpiece to be cut is breaking and tearing apart, so that cutting work can be performed in a substantially noiseless manner, said shock eliminating means provided by at least two counteraction cylinders and associated pistons, each containing a volume of liquid enclosed within said counteraction cylinders and second control means in fluid connection with said volumes of liquid, said second control means containing at least one throttle means controlling the flow of liquid emerging from said counteraction cylinders during cutting operation and at least one shut-off valve means having inlet means to permit quick restoring of said volumes of liquid within said counteraction cylinders of said shock eliminating means after cutting operation when said ram is being retracted, said volumes of liquid Within said counteraction cylinders being dimensioned during said proper cutting operation such that the ratio of the height of the liquid volumes within said counteraction cylinders to the thickness of the workpiece to be cut is smaller than 1/0.5 as well as the ratio of the pressing area displaceable within said press cylinder to the pressing areas displaceable within :said counteraction cylinders is smaller than 1/0.72 and said throttle means being dimensioned so that a resistance to the liquid flow emerging from said counteraction cylinders during said cutting operation being caused in correspondence with a resistance to a liquid flow through a throttle having a length of 0.1 up to 1 inch and a cross-sectional area, the ratio of which to the pressing areas of said counteraction cylinders is smaller than 17. Hydraulic press according to claim 16, wherein said throttle means is positioned at the top of said volumes of liquid within said counteraction cylinders for venting said liquid volumes.

18. Hydraulic press according to claim 16, wherein said shut-oil? valve means is positioned very close to said volumes of liquid within said counteraction cylinders for minimizing the volumes of liquid in conduit means between said shut-off valve means and said counteraction cylinders.

19. Hydraulic press according to claim 16, wherein feeding conduit means is controlled by said shut-off valve means and rises to liquid supply tank at a level above said counteraction cylinders from said volumes of liquid in said counteraction cylinders for venting said feeding conduit means, and said feeding conduit means terminates at the bottom of said liquid supply tank for preventing air suction to said counteraction cylinders.

20. Hydraulic press according to claim 16, wherein adjusting means for varying the height of said liquid volumes within said counteraction cylinders such that said height is somewhat lesser than the thickness of the metal to be cut, whereby waste pieces loosely adheres to said metal workpiece at completion of operating cycle.

References Cited by the Examiner UNITED STATES PATENTS 897,048 8/08 Astfalck 1l3--45 2,200,998 5/40 Schmuck 113-45 2,612,951 10/52 Palmleaf 83-639 ANDREW R. J UHASZ, Primary Examiner.

Claims (1)

1. HYDRAULIC PRESS HAVING FRAME MEANS WITH A TABLE OPPOSED TO AT LEAST ONE PRESS CYLINDER FIXED TO SAID FRAME MEANS, A RAM DRIVEN HYDRAULICALLY BY A PISTON GUIDED BY AND SEALED WITHIN SAID PRESS CYLINDER, TOOL MEANS FOR CUTTING AND PUNCHING WORK CONTAINING AT LEAST TWO MEMBERS, ONE OF WHICH AFFIXED TO SAID RAM, THE OTHER OF WHICH AFFIXED TO SAID TABLE, HYDRAULCI MEANS CONTAINING FIRST CONTROL MEANS AND POWER MEANS SUPPLYING SAID PRESS CYLINDER WITH PRESSURE FLUID, A COMBINATION OF THRUST TRANSMITTING MEANS BEING CONNECTED TO SAID RAM AND OF SHOCK ELIMINATING MEANS BEING CONNECTED TO SAID RAM FRAME MEANS, SAID SHOCK ELIMINATING MEANS ACTING TOGETHER WITH SAID THRUST TRANSMITTING MEANS AT LEAST DURING PROPER CUTTING OPERATING TO PREVENT ANY HARMFUL SHOCK OF STRESS RELIEVING SUBSTANTIALLY IN SAID PRESS CYLINDER AND IN SAID HYDRAULIC MEANS WHILE THE WORKPIECE TO BE CUT IS BREAKING AND TEARING APART, SAID SHOCK ELIMINATING MEANS PROVIDED BY AT LEAST ONE COUNTERACTION CYLINDER AND ITS ASSOCIATED PISTON AND A VOLUME OF LIQUID ENCLOSED WITHIN SAID COUNTERACTION CYINDER AND SECOND CONTROL MEANS IN FLUID CONNECTION WITH SAID VOLUME OF LIQUID, SAID SECOND CONTROL MEANS CONTAINING AT LEAST ONE THROTTLE MEANS CONTROLLING THE FLOW OF LIQUID EMERGING FROM SAID COUNTERACTION CYLINDER DURING CUTTING OPERATION AND AT LEAST ONE SHUT-OFF VALVE MEANS HAVING INLET MEANS TO PERMIT QUICK RESTORING OF SAID VOLUME OF LIQUID WITHIN SAID COUNTERACTION CYLINDER OF SAID SHOCK ELIMINATING MEANS AFTER SAID CUTTING OPERATION WHEN SAID RAM IS BEING RETRACTED, SAID VOLUME OF LIQUID WITHIN SAID COUNTERACTION CYLINDER BEING DIMENSIONED DURING SAID PROPER CUTTING OPERATION SUCH THAT THE RATIO OF THE HEIGHT OF THE LIQUID VOLUME WITHIN SAID PRESS CYLINDER TO THE HEIGHT OF THE LIQUID VOLUME WITHIN SAID COUNTERACTION CYLINDER MULTIPLIED WITH THE RATIO OF THE PRESSING AREA DISPLACEABLE WITHIN SAID COUNTERACTION CYLINDER TO THE PRESSING AREA DISPLACEABLE WITHIN SAID PRESS CYLINDER IS GREATER THAN 1.6 AND SAID RATIO OF THE HEIGHT OF THE LIQUID VOLUME WITHIN SAID PRESS CYLINDER TO THE HEIGHT OF THE LIQUID VOLUME WITHIN SAID COUNTERACTION CYLINDER IS GREATER THAN 1/0.5 AND SAID THROTTLE MEANS BEING DIMENSIONED SO THAT A RESISTANCE TO THE LIQUID FLOW THROUGH A THROTTLE HAVING A LENGTH OF 0.1 INCH UP TO 1 INCH AND A CROSS-SECTIONAL AREA, THE RATIO OF WHICH TO THE PRESSING AREA OF SAID COUNTERACTION CYLINDER IS SMALLER THAN 1/2.500.

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