US2357508A - Hydraulic press - Google Patents

Description

Sept. 5, 1944.- w. ERNST HYDRAULIC PRESS Filed 001;. l, 1942 R T M W ATTO R N EY Patented Sept. 5, 1944 HYDRAULIC PRESS Wal Ernst, Mount Gilead, Ohio, assignor to The Hydraulic Development Corporation, Inc., Wil-- mington, Del., a corporation of Delaware Application October 1, 1942, Serial No. 460,454

- 1 Claim.

This invention relates to hydraulic presses and, in particular, to hydraulic presses adapted to allow of the press platen being moved in either direction by a predetermined fine and precise distance.

Hydraulic press systemshave been developed in which the delivery of the pump, feeding the press cylinder, may be varied by small predetermined values to cause the press ram to perform a' desired fine stroke. However, these presses are not safe when used for various specific purposes as, for instance, for'die spotting". operations, according to which two cooperating dies are made to fit each other by scraping, grinding, filing and bluing the parts. Such operations are performed by spacing the upper die from the lower die so .as to allow the die maker to enter between these dies while they are on the press and to enable him to effect the necessary corrections.

Then the upper die is again lowered and spotted relative to the other die and, if necessary, further corrections are effected as mentioned above.

If, with the hydraulic press systems mentioned above, it should happen that the pressure line, leading from the pump to the press cylinder, breaks while the die maker operates between the dies on the press, it will be obvious that the press ram and thereby also the'upper die connected thereto will drop instantaneously and not only ruin the dies but also severely injure the die maker.

To avoid such accidents in connection with similar work, presses have been built in which the hydraulic drive of the press -ram has been replaced by huge screws and an electric motor turning these screws for lifting and lowering the ram. While these screws are a safeguard against accidental dropping of the upper die, these presses have other disadvantages, consisting in that their efficiency is rather low in view of the fact that these screws arepower screws operated under load and are called upon to move heavy weights. The movement of these screws on the heavy load results in a rapid wear of the screws, thereby making desired precise and minute movements sible.

It is, therefore, an object of this invention to provide a press which will hav the advantages of the screw driven press mentioned above, without having the disadvantages thereof.

It is another object of this invention to provide a press in which the press platen is hydraulically lifted and lowered while means is, provided for preventing a material accidental of the press platen'imposdrop of the press ram if, fOr some reason, the

hydraulic lifting force should'suddenly fail to hold the ram in lifted position.

Another object of this invention consists in the provision of a hydraulic press in which the press platen is reciprocated by pressure fluid from a fluid source, the delivery of which may be controlled in a fine and precise manner by means adapted, in case fluid connection should accidentally be interrupted between the fluid.

source and the press cylinder, automatically to prevent the press platen from dropping beyond a predetermined point of the possible stroke thereof.

It is still another object to provide a press in which the press platen is hydraulically reciprocable by pressure fluid from a pressure fluid source, while screw means'is provided adapted not only to control the flow of fluid from said fluid source to the press cylinder in a fine and accurate manner, but also to prevent the press platen from moving by more than a slight and predetermined distance away from its respective position if, for some reason, the hydraulic lifting force for the press platen should fail. These and other objects and advantages of the invention will appear more clearly from the following specification in connection with the accompanying drawing, in which:

Figure 1 diagrammatically illustrates an embodiment of the present invention, while Figure 2 shows a detail of Figure 1.

General arrangement The press according to the present invention is so, constructed that normally the press platen is reciprocated by pressure fluid from a pressure fluid source.

The delivery of the pressure fluid source to the press cylinder is adapted to be controlled in a fine and accurate manner by screw means, which latter engages the press platen so as to be able, at any time in any position of the press platen, to positively prevent the latter from moving away from its respective position by more than a slight and predetermined distance'if, for some reason, the lifting force, created by the pressure fluid source, should fail to hold the press platen in its respective'position.

Structural arrangement 2 interconnected in any conventional manner shaft 45 has keyed thereto a beveled gear by means of strain rods, not shown in the drawing.

The press head 2 carries a press cylinder 3 in which is reciprocably mounted a press ram 4. The press ram 4 has connected thereto a 5 press platen 5 slidable on guiding means 6. Connected with the lower end of the cylinder 3 is a conduit 1 comprising a check valve 8 and communicating with a conduit 3 leading to the upper portion of a surge valve it], which latter is 10 mounted on the cylinder 3 and has its upper portion extending into a fluid reservoir or tank II. The tank ii is mounted on the head 2 and connected therewith in any convenient manner.

The surge valve l0 does not form a part of the present invention and may b of any conventional design, for instance, of the type disclosed in U. S. Patent No. 2,193,248 to Walter Ernst.

The purpose of the surge valve 10 consists in prefilling the upper portion of the cylinder 3 when the ram 4 moves downwardly by gravity, and also to allow fluid to escape from the upper portion of the press cylinder 3 into the tank duit M with the lower portion of the press cylinder 3. The variable delivery pump I3 is provided with centering springs, not shown, which continuously tend to move the flow control member of the pump into and hold the same in its neutral or no delivery position. The pump I3 may be of any standard design, the type disclosed in the U. 2,280,190 to Ernst.

The movement of the flow control member is for instance, of S. Patent No.

controlled by a control rod i5 which, in its turn, is pivotally connected by means of a linkage system IS with a bellcrank lever i'l, which latter is pivotally connected by means of a pivot l8 with an arm IS on the press head 2. 'The lever arm 20 of the bellcrank lever l1 engages a collar 2i on a screw or spindle 22 which is reciprocable in and guided by sleeves 23 and 24 mounted in the press head 2. The spindle 22 threadedly engages a protruding portion 25 of the platen 5 and is provided at the lower end with a longitudinal 5o groove 26 slidably engaged by a key 21 carried by the beveled gear 23. The lower end of the spindle 22 is also slidable in and guided by the sleeve 29 carried by the spacing member 30, interposed between the press head and press bed.

Meshing with the beveled gear 28 is a beveled gear 3| which is keyed to a shaft 32. The shaft 32, which is rotatably mounted in the bearing 33 carried by the spacing member 30, has keyed thereto a spur gear 34 meshing with the spur gear 60 35, which latter is keyed to the driving shaft 33 of an electric motor3'i. Also keyed to the shaft '38 is a hand wheel 33 adapted to be operated for manually rotating the spindle 22 through the shaft 36 and the gears 35, 34 and 3|. The motor 6 31 is a reversible electric motor controlled by the switch 33.

Also meshing with the beveled gear 3| is a beveled gear 43 keyed to a shaft 4| rotatable in the bearing 42 and having furthermore'keyed thereto a beveled gear 43. The gear 43 meshes with a beveled gear' 44 keyed to one end of a shaft "which is iournalled in bearings 43 and 41 in the press bed I. The other end of the meshing with a beveled gear 49 which is connected to the spindle ill by a key and groove arrangement in the same manner as the beveled gear 23 and the spindle 22. The spindle 50 also threadedly engages a protruding portion 51 on the press platen 5. The spindle 50 is not adapted to actuate the bellcrank lever i1 and has been provided merely in order that the press platen 5 may be threadedly engaged on both sides thereof.

' Operation It may be assumed that all parts 01' the press occupy the position shown in the drawing and that it is now desired to effect a working cycle or the press platen. To this end, the operator starts the motor, not shown, for driving the pump l3 and then, either manually by actuation of the hand wheel 38 or electrically by the motor 31, rotates the spindles 22 and 50 in such a manner that, since at this time the platen 5 is stationary, they will move upwardly. Upward movement of the spindle 22 causes the bellcrank lever ii to move in clockwise direction,'thereby causing the pump I3, through-the linkage system i6 and the control rod ii, to move into forward stroke position.

As soon as the flow control member of the pump l3 has reached a predetermined position, pressure fluid from the pump l3 flows through conduit l2 into the upper portion of the cylinder 3, while fluid is withdrawn from the lower portion of the cylinder 3 to the other side'of the pump i3, which now constitutes the suction side. The press platen 5, therefore, moves downwardly the lower portion of the cylinder 3. The suction created by this movement in the upper portion of the cylinder 3 causes the surge valve I! to open so that fluid from the tank ii passes through the passageways 5i and 52 of the surge :alve l0 into the upper portion of the cylinder along during, its downward movement so that the centering springs in the pump i3 gradually return the flow control member of the pump to its neutral or no delivery position.

From the above, it will be clear that a predetermined longitudinal adiustment of the spindles 22 and 50, without further rotation of the spindles, will result in a predetermined stroke of the platen i and it is evident that, since the screws 22 and I may be adjusted in a line and precise manner, itispossible to cause the platen 5,! to eflect a corresponding fine and precise stroke.

1!, however, it is desired to maintain the delivery of the pump l3, it is merely necessary to continue the rotation of the spindles 22 and 53 at such'a speed that the collar 2|, in spite of the 76 downwardmovement of the platen 5, will mainu 15 lever II will move. in anticlockwise direction and by gravity as fast as fluid is withdrawn fromrod shift the pump 13 into retraction stroke position. Pressure fluid from the pump l3 will then be conveyed through the conduit H to the lower portion of the cylinder 3 while fluid will be withdrawn from the upper portion of-the cylinder 3 through the conduit l2. Pressure fluid will also be conveyed from the lower part of the cylinder 3 through the conduit I to the surge valve ID, to thereby open the latter and allow a part of the fluid in the upper. portion of the cylinder 3 to escape through the surge valve .into the tank II. The ram 4 and thereby also the platen 5 will then move upwardly.

It the rotation of the spindles 22 and 50 were stopped immediately after the pump l3 had begun to deliver pressure fluid to the lower portion of the cylinder 3, the ram 4 would soon come to a stop, for the reason mentioned above in connection with the description of the downward movement of the ram 4, whereas, if the rotation of the spindles 22 and 50 were continued, also the upward movement of the ram 4 and platen 5 would continue.

It will be appreciated that, while the spindles 22 and 50 move longitudinally, the lower endsslide in the beveled gears 28 and 49 respectively,

although, however, always remaining in driving connection with these beveled gears.

It may now be assumed that, while the press platen 5 occupies the position shown in'Figure 1 and, the operator is working between the platen I and the press bed I, a break occurs in the conduit l4. This will immediately release the pressure prevailing in the lower portion of the press cyl- It is, of course, understood that the collars 2| and 53 and the spindles 22 and are so dimensioned as to be able to fully support the load of the ram and press platen and the die connected thereto during the slight accidental drop of the press platen. I

It will be understood that I desire to comprehend within my invention such modifications as hydraulic motor means, a plurality of rods which threadedly engage with opposite sides of the platen, means for rotating the rods in the same direction comprising a source of power, a drive shaft, and a gear attached to the drive shaft, a pair of pinion gears in mesh with said firstnamed gear, each of said pinion gears being in driving relation with a difierent one of said threaded rods, means for controlling said regulating means connected for actuation by one of said threaded rods, said one threaded rod having a sliding connection with its pinion gear and all other rods having sliding connections with their drive means, and stop means on all of said rods coacting with the press frame whereby the stop means on each threaded rod may engage said press frame to prevent said ram from dropping more than a predetermined distance irrespective of the position of the ram in the event of failure of fluid pressure from said source.

WALTER ERNST.

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