US3005431A - Hydraulic press - Google Patents

Description

H. MLLER HYDRAULIC PRESS Oct. 24,

5 Sheets-Sheet 1 Filed Nov, 7, 1956 oct' 24, 1961 H. MOLLER 3,005,431

HYDRAULIC PRESS Filed NOV. 7, 1956 5 Sheets-Sheet 3 1&3.

Ul NIU l IM IUI u :1 ZZer 3g? @9 m United States @hice Patented Oct. 24., 1961 Claims priority, application Switzerland Nov. 10, 1955 1 Claim. (Cl. 113-44) This invention relates to hydraulic presses for the forming of sheet metal blanks, comprising a press table carrying a forming tool `and a press head adapted to be raised and lowered and to be locked in lowered position, and a hydraulic forming attachment carried by the press head and located centrally above the forming tool. The hydraulic forming attachment comprises a cylinder with a working piston slidable therein and which opens.

downwardly into a liquid receptacle. The bottom of the liquid receptacle is closed by an elastic wall, and the piston is adapted to place the liquid in the receptacle under pressure and thereby press, by means of the elastic wall, a sheet metal blank inserted between the receptacle and the forming tool to the shape of the forming tool. The press of this invention is characterized by the fact that the hydraulic forming attachment is located in the press head and the working piston extends upwardly into a pressure chamber formedrin the press head, in which chamber fluid under pressure may be introduced when the press head is locked in its lowered position, to exert downward force upon the piston.

In the following description, the invention will be more specifically described with reference to the attached drawings, in which:

FIGURE 1 is a perspective, sectional View of one embodiment of the invention;

FIGURE 2 is a View of the locking mechanism by which the press head is releasably secured in its lowered position, said view being partially in horizontal section and partly in plan; and

FIGURE 3 is a fragmentary view of the bottom portion of the press, partly in side elevation and partly'in Vertical section.

The press of this invention generally comprises a press table 1, a press head 2 with a hydraulic forming attachment, a balance cylinder unit 3, a pressure cylinder unit 4, columns 5 with locking means 6, andan up-pressure device 7.

The press table 1 has a number of vertical holes 10 y therethrough in which .pressure pins llvare axially slidable, and it carries an annular tool holder of ring 12 which encompasses a forming tool 13. The press head 2 is vertically slidably guided on the columns 5 and is arranged to be retained in its lowermost position by the locking means 6. In the bottom of the press head there is a downwardly opening well or liquid receptacle 14, closed at its bottom by a wall 15 of rubber or similar elastic material. The wall 15 is part of Va rubber cup having a rim 16 which is sealingly secured in an annular groove 17 in the inside of the well or liquid receptacle 14 to fasten the wall 15 in place. The upper portion of the well or receptacle comprises a cylinder 18 which opens at its top into a cylindrical pressure chamber 19 having a larger diameter than'that of the cylinder 18. Axially slidable in the cylinder 18 is a working piston 20 which extends upwardly into the pressure chamber 19 and has at its upper end a head 21 fitting in the pressure chamber. v

To obtain a iiuid-tight seal between the piston and the upper cylinder portion 18 of the well or liquid receptacle 14 there is an annular groove 22 in the inside of the cylinder, in whichV is seated a U-shaped elastic gasket 23 engaging the piston, the'inner portion of the U facing downwards and communicating through one or more channels 24 with the liquid receptacle 14. The working piston is forced downwards by hydraulic uid vunder pressure, which is introduced into the upper end of the pressure chamber 19 via a pipe line 25 from a suitable source, and which acts uponthe upper surface of the piston head 21 to thereby impose pressure upon the liquid in the well or receptacle 14 and thus in turn,

cause the elastic wall 15 to force a sheet metal blankv 26, positioned under the wall, down into the forming tool 13.

'Ihe upward movement of the piston 20 is obtained by a pressure fluid, preferably compressed air, which is introduced from a source thereof via a line 27 into the lower part of the pressurechamber to act upon the underside of the piston head 21.

The balance cylinder unit 3 serves to balance and raise the press head 2 with the hydraulic forming attachment described above, and it comprises a stationary,V

closed balance cylinder 28 mounted on the columns 5 and having movably mounted therein a balance and raising piston 29, from which the press head 2 is suspended by means of a plunger rod 30. The balancing and raising of the press head with the forming attachment thereon is provided for by introducing pressure iluid, Ypreferably compressed air, vfrom a source thereof via a line 31 intothe balance cylinder to act upon the underside of the` piston 29, the upper part of the balance cylinder communicating with ythe open air through a line 31.

The lowering orf the press head with Vthe forming attachment is effected by means of the pressure cylinder unit `4 comprising a comparatively small pressure cylinder 32 fitted on the top of the balance cylinder 28 and having a pressure piston 33 movable therein. The piston33` is connected to the balancing and raising piston. 29 by avr plunger rod 34 extending coaxially through the balance cylinder. A pressure uid is introduced via a line 35 into the upper end of the cylinder 32 and acts on Vthe upper side of the piston 33 thereby overcoming the pres sure the balance cylinder 28, whereby the press head 2 with the forming attachment is pressed down. vWhen `the press head has reached its lower position it is` locked in place by the |locking means 6, whereby the reaction pressure `from the Well or receptacle 14' is absorbed by the columns 5 via the locking means.

The locking means 6 are operated by a double acting cylinder piston assembly 36, and consist of pairs of jaws 37 and 38 arranged to be moved to and from a locked position in which they embrace each one of the columns 5 immediately below an adjustable nut 39 by means of Y which the position of the press head is adjustable. Each' adjustable nut 39 may be secured in any desired position of axial adjustment by means of a locking nut 40. The jaws 37 land 38 `are each pivoted on a pin 41 and 42 and provided with toothed segments 43 and 44 'respectively, coaxial with the pivot pins, by which the movements of each of lthe pairs of the jaws are controlled. One of the jaws 37 has a lever 45, the outer end of which is connected to a turn-stile 48 by means of a link-arm 47 adjustable in length by means of a nut 46 and connected to the lever 45 andl to the turn-stile 48 by means of pivot pins 49. The turn-stile 48 is rotatably carried on the plunger rod 30 and receives its rotational movement from lthe cylinder piston assembly 36.V

When the press head is raised Iabove its lowermost s position, the jaws 37 and 38 are swung apart, about their pivot pins 41 and 42, to clear the adjusting nut@ 39 and lock nut y40. When the press head -2 has reached its lowermost position, a pressure fluid is introducedv through a line 50I into one end of the cylinder piston means of the lever 45 and the toothed segments 43 and 44, into positions gripping the columns 5. Opening of the locking means 6 is don-e by admitting the pressure iluid into the other end of the cylinder piston assembly via a line 51.

The up-pressure device 7 comprises a cylinder 52, a piston 54 slidable in the cylinder, and a pressure disc 55 Supported on the piston S4 andv 0n which the bottom ends of the raising pins 11 rest. In the bottom of the cylinder 52 there is a check valve 56 and a pressure regul'ating valve 57. InV addition, the piston 54 has a plunger rod 58 connected to the piston 67 of a locking device 59'.

The up-pressure device 7 acting th-rough* the raising pins 11, exerts the necessary blank holding pressure upon a blank holding ring 81, described hereinatter, and can also serve to raise the forming tool 13 out of its position in the tool holder 12.

The necessary pressure on the raising pins is obtained in the following manner. From a source of oil under pressure, such as an accumulator, oil is permitted to enter the cylinder 52 via a line 60, a channel 61 and past a check valve 56. The prevailing pressure of the oil will thus be exerted on the bottom surface of the piston 54 and the resultant lifting of the raising pins is utilized as above stated when moderate blank holding pressures are required and to raise the forming tool L13 out of the tool holder 12 when needed. When a higher blank holding pressure is required, this is provided by admitting compressed air through another line 63 connected to the pressure regulating valve 57.

The pressure generating means consists of a pressure intensifying plunger 65 working in a cylinder 64. The outer end of the plunger, which is exposed to the compressed air entering through line 63, has a larger diameter than the inner end, which is exposed to the oil pressure in the cylinder 52 through -a bore 66 made in the wall of cylinder 52 and providing a seat 66', against which the inner end of the plunger is arranged to seat. Iff plunger 65 is seated, oil can return through line 60 from beneath piston 54 only if a suiiicient downward force is exerted upon pis/non 54 to unseat plunger 65, that is, the pressure which piston 54 imposes upon the oil in the cylinder 52 must be great enough to enable the oil to'overcome the force of the air pressure acting on the large diameter end of plunger 65, to permit the oil to ilow into line 60 through bore 66, since otherwisethe check valve 56 prevents reverse A:How of such oil back through the channel 61.

The locking device 59 of the up-pressure device 7 is needed when the latter has to be locked at its lower limit of travel during a certain period of the upward movement of the press head 2. At its lower end, the plunger rod 58 is provided with a piston 67, sealingly but slidably :fitted in a cylinder 68. The lower end of the cylinder 68 is closed by means of a cover 69 and is lled with oil, the cylinder being connected to a second pressure regulating valve 72 through bores 70 and 71 in the wall of the cylinder. Similarly toi the regulating valve 57, the pressure regulating means in valve 72 consists of a pressure intensifying plunger 73 slidable in a cylinder 74. The outer end of the plunger 73 is enlarged to provide an increased pressure area, which is adapted to be acted upon by compressed air admitted into the cylinder 74 through lines 75 and 76 while the inner end of the plunger has Aa smaller area, which is arranged to engage a seat 77 in the bore 70 and thereby close the latter.

The locking device A59 of the up-pressure device 7 operates in the following manner. When the up-pressure device 7 is in its uppermost position, the oil quantity lling the cylinder 68 is under the piston 67. Upon the descent of the up-pressure device, the piston 67 is moved down by the plunger rod 8, whereby the oil under the piston 67- is forced'via the bore 70, the valve seat 77 and the bore 71 to the cylinder space above the piston 67. During this time, the line 75 serves as an exhaust and air under pressure is fed into the line 76 to thus actuate the plunger 73 to its outer position in which it leaves the valve seat 77 open.

When the up-pressure device 7 -has reached its lower limit of travel, the line 76r serves as an exhaust and compressed airis fed into line 75. This causes the plunger 73 to be moved into sealing, engagement with the valve seat 77, in which position it prevents the oil in the cylinder space above the piston 67l from passing'through the bore 70, whereby the up-pressure device .7 is locked in its lowerrnost position.

It will be seen that when one of the lines 75 and 76 has compressed air fed thereinto, the other is used as an exhaust, and the position of plunger 73 vn'll be determined by whichever of those two lines has compressed air fed into it. Control of lines 75 and 76 is provided by means of a valve 78 connected with said lines and with another line 79 which is connectable with a source of compressed air. The valve 78 can obviously be actuatedV by a solenoid or other automatic means, and in any event it provides for locking of the up-pressure device at times when the press head 2' is moving upwardly from its lower limit of travel, such locking being eifected' by seating of the plunger 77` to prevent iiowv of oil from one side of piston 67 to the other. If the up-pressure device were not locked down while the press head was rising, the blank holding ring 81 would be forced upwardly by the pressure pins 11, pressing the newly formed part against the elastic wall d5 and tending to deform the part. However, when the press head nears the upper limit of its rising movement, the valve 78 provides for reversal of the connections to lines 75 and 76 by which the plunger 73 is unseated, permitting oil to flow through the bore 70 and passage 71, and thus permitting movement of piston 67 In my United States Patent No. 2,761,405, is shown and described a hydraulic forming attachment for presses wherein a conventional die having a cavity is used. As will appear from the drawing, the present embodiment of the hydraulic press comprises a specific arrangement of the forming tool I3 for deep drawing of sheet metal blanks. 'Ihe tool arrangement comprises a rigid stationary tool part or punch 80,. which is attached to the press table so as to project upwardly in thecenter of the annular bore in the toolY holder or ring 12, to be encircled by a movable tool part or blank. holding ring 81, the: latter being guided for up and down movement by slidably fitting in the `annular tool holder. Normally,.the movable tool part or blank holding ring is supportedby the pins 11 in a position at which its top sur-face is ilush with the top of the tool holder, but during theforming operation the movable tool part or block holdingring is pressed down into the tool holder against the yielding resistance oiered by the up-pressure device 7.

It will be observed that the shaping of the blank is accomplished by rolling or pressing; down the blank over the rigid punch. and that the` ring 81 serves to yieldingly support, by means of the pins 111, the blank 26 in its lgradual downpressing movement over the punch.

Having described only one preferred embodiment of the invention, I do not wish toy be .limited to the specific details set forth, but wish to reserve to myself any variations or modifications that may appear to those skilled in the art and fall Within the scope of the following claim.

I claim:

In a press for forming sheet metal: a xed press bed; a press head mounted above the press bed between a lowered press-closed and raised press-open position; an annular tool holder on the press bed; a male forming tool supported on and projecting up from the press bed inside said annular tool holder, withL the top thereof no higher than the top of the holder; a movable tool part vertically slidably tted in said annular tool holder for movement between la raisedposition at whichtthe top thereof is ilush with the top of the, annular tool holder to. support a blank l to be formed, to a depressed position inside the annular tool holder, said movable tool part being apertured to accommodate the station-ary male forming tool; fluid pressure means below the press bed to yieldingly support the movable tool part and resist depression thereof into the annular tool holder, said uid pressure means including a plurality of pins vertically slidable through the press bed and bearing against the underside of the movable tool part; means on the press head defining a shallow downwardly opening cylindrical well coaxial with the annular tool holder and of a diameter no greater than that of the tool holder; an elastic membrane fixed to the head and extending across the mouth of the well to close the same; means in the head defining a vertical working cylinder above and spaced rom the inner end of the well, land a coaxial bore substantially smaller in diameter than said Working cylinder connecting the Well and the working cylinder; a piston slidable up and down in the working cylinder; a plunger xed to ythe underside of the piston and slidably titted into the bore; the elastic membrane, the walls of the well and the lower end of the plunger providing a liquid-tight chamber; a liquid lilling said chamber; means on the press to move the press head from its raised press-open position affording Iaccess to the tool holder and permitting the placement of a blank thereon, to its lowered press-closed position in which the elastic membrane clamps the blank against the movable tool part and coacts therewith to hold the blank during the forming thereof over the stationary m-ale tool part; means on the press to lock the press head in its lowered press-closed position;

means on the press for introducing uid under pressure into the working cylinder above the piston therein, to force it and the plunger downwardly and thereby cause downward distension of the membrane with great force into said annular tool holder, so as to form the blank over the male tool part, while the movable tool part coacts with the membrane to hold the unformed part of the blank; and means on the press to introduce iluid under pressure into the working cylinder below the piston therein, while venting uid from the cylinder above the piston, to force the plunger upwardly and thereby release pressure in said chamber and return the membrane to its undistended condition.

References Cited in the file of this patent UNITED STATES PATENTS 442,246 Chapman Dec. 9, 1890 464,737 Stapley Dec. 8, 1891 2,162,164 Febrey June 13, 1939 2,394,636 Rode Feb. 12, 1946 2,409,254 Conzelman Oct. 15, 1946 2,584,339 George Feb. 5, 1952 2,605,731 Schulze Aug. 5, 1952 2,696,183 Chyba Dec. 7, 1954 2,749,867 Engel June 12, 1956 2,754,786 Schulze July 17, 1956 2,761,405 Moller Sept. 4, 1956 2,766,711 Dever Oct. 16, 1956

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