US3126769A - Hecht - Google Patents

Description

Marh 31, 1964 H. HEcHT 3,126,769

MECHANICAL PRESS Filed May l5, 1961 3 Sheets-Sheet 1 lIilvIl /Nv 15A/Tap HELMl/ HECHT 3M.: 1,2/1 My @WMA March 31, 1964 H. HEcHT MECHANICAL PRESS 3 Sheets-Sheet 2 Filed May l5 1961 Fig. 3

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3 Sheets-Sheet 3 United States Patent 3,126,769 MECHANlCAL PRESS Helmut Hecht, Goppingen, Germany, assigner to MAY- Pressenbau Ltd., Schwabisch Gmuntl, Germany Filed May 15, 1961, Ser. No. 110,200 3 Claims. (Cl. 78-39) The present invention relates to a mechanical press having a table, which is preferably stationary, and a reciprocating ram operated by a crank or eccentric.

In quite a number of operations, for example in the cold deforming of metal it is unfavorable if the ram reciprocated by the crank or eccentric acts on the work piece treated as it were with a blow. On the contrary it is particularly advantageous in many cases, when the pressure applied by the ram after its impact on the Work piece increases comparatively slowly to a maximum so that the material of the work piece has sufficient time for being deformed. In order to achieve this it has hitherto been of advantage to use for certain operations hydraulic presses, which make a less hard impact on the work piece and the pressure of which is controllable. On the other hand it has not been possible hitherto to develop mechanical presses in a manner favorable for these operations.

The present invention has the principal object of providing mechanical presses, for example crankor eccentric-presses, the pressure of Whose rams applied to the work pieces upon impact is smaller than the end pressure.

With this and other objects in view which will become apparent later from this specification and the accompanying drawings I provide a mechanical press comprising in combination: a table, a drive, a ram operatively connected to said drive and in operation reciprocated by said drive relative to said table, a presser member mounted in said ram opposite said table movably relative to said ram in the axial direction of the latter, abutments arranged on said ram limiting the movement of said presser member relative to said ram to a pre-determined length in either direction, hydraulic pressure fluid in operation contained in a hydraulic pressure chamber enclosed between the said ram and the said presser member resisting the receding of said pressure member into said ram under the reaction of the pressing force applied by said presser member to a work piece resting against said table, and restoring the said presser member to its starting position upon said pressing force ceasing to act.

rl`his arrangement acts as a damping device, by which the pressure upon impact of the ram on the work piece is reduced to a minimum and gradually increases to a predetermined value, so that the pressure applied to the Work piece is not a hard blow but comparatively soft. Consequently the material to be deformed is not set in motion suddenly, but in a desirable manner gradually, whereby a more favorable and faultless ilow of the material is achieved.

The arrangement may be made in such a manner that the reaction of the pressure Huid during the receding of the presser member under the pressing force is progressively increased by a control means, preferably up to the magnitude of the pressing force itself. This may for example be attained in that the pressure iluid displaced is forced through a throttle member, for example one or more restricted passages.

A particularly simple and reliable construction is achieved, when the control means has a passage the area of which gradually diminishes as the presser member recedes, namely if desired so far that this passage is completely or almost completely closed in the retracted end position of the said presser member. In this case the final maximum pressure of the ram is attained at the end of the receding movement of the presser member.

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The control of the through-flow passage may for example be effected by a control element having the form of a projection matching the shape of the through-how passage and attached to the end face of the presser member averted from the table. The shape of this projection depends accordingly on the shape of the through-flow passage. For example one component defining the through-low passage may be conical, and then the said projection has likewise conveniently a conical shape. By suitably shaping the through-How passage and the control element the pressure rise upon the receding of the presser member may in any case be influenced in a predetermined manner.

As a pressure fluid preferably a liquid is used, which acts directly on the presser member and flows through the control means, which liquid is subject to a gaseous pressure medium, so that similar to a liquid accumulator a movement of the liquid is possible either under the iniluence, or against the action, of the compressed gas, respectively.

Conveniently moreover a through-flow adjustment member operable from outside is provided on the ram by the aid of which the effective through-flow area is adjustable.

In order to vary the damping of the presser member attainable by the invention within wide limits it is convenient to provide, parallel to the main through-flow passage controlled by the presser member, at least one by-pass or secondary passage the area of which is adjustable by means of a throttle valve operable preferably from outside. By suitable choice of the cross section area of this by-pass it may for example be attained that the damping is a minimum when said by-pass is completely open since in this case practically the throughflow of the liquid through the main through-flow passage is no longer decisive, since the liquid can flow olf through the by-pass without difficulty, and the damping is in this case practically determined exclusively by the pressure of the compressed gas acting on the pressure fluid. By suitable adjustment of the throttle valve the characteristic of damping may be varied within wide limits in a manner desirable for the working operations.

Advantageously several by-passes may be arranged on a pitch circle at an equal angular spacing from one another in order thus to prevent an unequal pressure distribution with respect to the presser member.

lf desired, on the presser member moreover a central member may be arranged, which penetrates through the main through-flow passage, so that the latter assumes an annular shape. By this arrangement it is made possible to provide centrally in the ram or presser member, respectively, some auxiliary members such as for example an ejector for ejecting the work piece.

These and other features of my said invention will be clearly understood from the following description of an embodiment and a modification thereof given by Way of example with reference to the accompanying drawings, in which:

FIG. l is a front elevation of a first embodiment of a press according to the present invention;

FIG. 2 is a side elevation to FIG. l;

FIG. 3 is a part-section on the line 3-3 of FIG. 2 on a larger scale;

FIG. 4 is a part-section corresponding to FIG. 3 of a modified embodiment of the present invention.

In the FlGS. 1-3 a press fr-arne is denoted 10' as a whole, which has two side portions i111 and 12, and a table 13.

The drive of the press is effected by a drive motor (not shown) through a drive shaft 15 carrying a gear pinion *16 in mesh with a spur gear 17 mounted on a lay shaft 18 journalled in the lower portion of frame 16.

The drive shaft .115 is extended through and beyond the lower portion of the frame, and carries at its left hand side end in FIG. l a further gear pinion 2&1 in mesh with a further spur gear Z1 which is likewise keyed to the lay shaft 18. On the outside of the drive gear 17 and 21, respectively, a crank pin Z7 and 28, respectively, is arranged, on which a connecting rod 34Bl and 3K1, respectively, is articulated.

The two connecting rods 30 and 31 are arranged at both sides of the table on the side portions L1 and 12 in such a. manner as to form a crank press having two uprightis and a symmetrical drive on both sides. Above the table in a guide 3S a ram denoted 36 as a whole is slidably mounted, which has a projection 37 on each side (see FIGS. 3 and 4) on which an adjustment mechanism is arranged for the `adjustment of the connecting rods 30 and 311. As will be seen in FIGS. 3 and 4, at each of the upper ends of the connecting rods 30 and 31 an adjustment member 40 is itted which is screwed into a sleeve 41. This sleeve is mounted rotatable in the projections but is restrained longitudinally, and its rotation is effected by means of externally rotatable Worms 42 in mesh with Worm wheels arranged on the sleeves 41.

The details of the rst embodiment of the ram according to the invention will now be explained in more detail with reference to FIG. 3.

The ram body 50 of the ram 36 is formed partly hollow internally and -has an inner hub-like attachment boss 51 in which a pressure member 52 is arranged. The later has a tlange 53- Which is arranged in a corresponding cylindrical recess S4 on the underside of the ram body S and can move therein in the axial direction a predetermined path, the upper abutment of this movement being formed by the end face 55 of said cylindrical recess 54, and the 4lower abutment by the head S6 of at least one screw 57 iixed in the ram body. As Will be seen in FIG. 3, the presser member S2 may accordingly move a predetermined path a in the axial direction.

The presser member 52 has an inner cylindrical recess 6i) serving for the attachment of tools. This recess is closed on top by a closure piece 61.

On the attachment boss :1 a cylindrical extension piece 62 is attached, which is sealed against the presser member 52 by the aid of gland rings 63. Between the upper end face of the closure piece 61 and the underside 65 of the extension piece 62 a cylindrical cavity 66 is ormed, the axial height of which exceeds the path a.

The closure piece 61 carries in the middle a frustoconical control pin 68, which co-operates wih a conical portion 69 of a through-How passage 649/70, which includes moreover a cylindrical portion '70. On the extension piece 6-2 a cover '7K4 is arranged in such a manner that between the underside of the cover 74 and the face 75 of the extension piece 62 a cavity 76 is formed, which is in communication through connecting line 77 with a pressure vessel 78 to which a source of compressed gas (not shown in the drawing) is connected by means of a connector 79.

In the cover 74 moreover a control member l82` is provided in the form of an axially adjustable screw, which at its lower end has a conical control head '83 co-operating with the cylindrical portion 70 of the through-110W passage 69, 70.

The manner ci functioning of the device described is as follows:

In a state of rest the presser member is in the position shown in FIG. 3 and accordingly contacts lthe abutment screw 57. Then the cavity 66 is entirely and the cavity 76 is partly filled with liquid, namely the latter up to a liqfuid level denoted 84. The compressed air contained in the pressure vessel 78 acts on this level so that under Vthis action the liquid serving as the transmission medium constantly tends to move the presser member 52 into its lower position illustrated in FIG. 3.

When in the pressing operation a pressure is applied on the lower en d'face ci the pressure member in the upward direction the presser member is moved upward relative to the ram body 5i) at a certain pressure exceeding the pressure of the compressed air, and thereby the liquid contained in the space `66 is forced through the passage 69, 7i), which during the upward movement of the presser member is progressively reduced by the cooperation of the control pin v68 with the passage 69', 70, so that the pressure required for forcing the liquid through said passage progressively increases. In the uppermost position oi the presser member, i.e. when the same has moved axially upward the amount a, the passage is completely or nearly .completely closed, and in this position the presser member 52 is carried along immediately by the body Sti, i.e. at this moment the action of the slidably proper member is completely abolished.

In FIG. 4 a second embodiment of the device according to the invention is illustrated.

Likewise in a ram body here a presser member 86 is so arranged, that the latter may move a predetermined length a relative to the ram body. The presser member 86 is closed by a closure member 87 on which a central member 8S is attached which penetrates through this closure member. This central member has a conical control collar 89 which cor-operates with a corresponding conical portion 90 of an annular extension 91 of the ram body.

The ram body is closed on top by a cover 92 through which penetrates the said central member 88 and which is sealed against this central member by means of a gland 93.

`On the lower end of the central member S8 a lock mit 1101 is screwed whereby the contical control collar 89 is iirmly pressed against the closure member 87. On the upper end of the central member `88 a lock nut 102 is screwed. This nut 1012 can rest on a cover plate i103 inserted in the cover 92.

In the aforesaid cover 92 an adjustment screw '94 is provided, which at its lower end (FIG. 4) is provided with a valve cone 95 cooperating with a valve seat 96 by a by-pass duct 97, which connects the chamber 98 with the `chamber 99. Glands 104 on the closure member 87 seal the same ofi against the chamber 98.

The by-pass duct 97 maybe varied in its effective crosssection area at will by adjusting the adjustment screw 94, in order to influence the damping characteristics of the damping device in the manner desired.

While I have described herein and illustrated in the accompanying drawing what may be considered a typical and particularly useful embodiment of my said invention I Wish it to be understood that I do not limit myself to the particular details and dimensions described and illustrated; for obvious modifications will occur to a person skilled in the art.

What -I claim as my invention and desire to secure by Letters Patent is:

1. A mechanical press comprising a press ram having a recess, means for reciprocating said press ram in an axial direction, a piston located in said recess axially movable relative to said press ram from an: inoperative to an operating position leaving exposed a partial volume of said recess, a lfirst stop means limiting the movement of said piston in said recess when in inoperative position, a second stop means limiting the movement of said piston in lsaid recess ywhen in operating position, said ram having a cavity containing a liquid under pressure, ya passage connecting said partial volume and said cavity in said inoperative position of said piston, said passage inclnding a part extending in said axial direction, the width of said part gradually diminishing in the direction of movement of said piston from said inoperative position to said operating position, throttling means rigidly ixed to said piston and in said inoperative position of said piston extending with lateral clearance into said part of said passage, said clearance being gradually reduced upon movement of said piston from` said inoperative position to said operating position to increase the action of said throttling means.

2. A mechanical press comprising a press ram having a recess, means for reciprocating said press ram in an axial direction, a piston located in said recess axially movable relative to said press ram from an inoperative to an operating position leaving exposed a partial volume of said recess, a lirst stop means limiting the movement of lsaid piston in said recess When in inoperative position, a second stop means limiting the movement of said piston in said recess when in operating position, said ram having a cavity containing a liquid under pressure, a passage connecting said partial volume and said cavity in said inoperative position of said piston, said passage including a part extending in said axial direction, the Width of said part gradually diminishing in the direction of movement of said piston from said inoperative position to said operating position, throttling means rigidly fixed to said piston and in said inoperative position of said piston extending with lateral clearance into said part of said passage, said clearance being gradually reduced upon movement of said piston from said inoperative position to said operating position to increase the action of said throttling me-ans, said partial volume, said passage and said cavity containing a liquid forming a level of liquid in said cavity, and supply means for pneumatic pressure connected to said cavity to resiliently 'charge said level of liquid by said pneumatic pressure.

3. A mechanical press comprising a press ram having a recess, means for reciprocating said press ram in an axial direction, a partition in said fram dividing said recess into a first and a second pressure chamber, a cylindrical tool support in said lirst chamber axially movable relative to said press ram from an inoperative to an operating position, sealing means upon said tool support cooperating with the wall of said first pressure chamber to seal the latter when said tool support is moved relative to said ram, -a rst stop means limiting the movement of said tool support in said ram when in inoperative position, a second stop means limiting the movement of said tool support in said ram when in operating position, a passage connecting said two chambers in said inoperative position, said passage including a part extending in said axial direction, the Width of said part gradually diminishing in the direction of movement of said piston from said inoperative position to said operating position, throttling means rigidly xed to said piston and in said inoperative position `of said piston extending with lateral clearance into said part of said passage, said clearance being `gradually reduced rupon movement of said piston from said inoperative position to said operating position to increase the action of said throttling means, said chambers and said passage containing a liquid forming a level of liquid in said second pressure chamber, and pneumatic pressure supply means connected to said second pressure chamber to resiliently charge said level of liquid by said pneumatic pressure.

References Cited in the lile of this patent UNITED STATES PATENTS 933,010 Wilzin Aug. y31, 1909 1,780,531 Messier Nov. 4, 1930 2,007,290 Treer lJ'uly 9, 1935 2,164,640 Cannon July 9, 1939 2,333,529 Ernst Nov. 2, 1943 '2,482,280 Lerma Sept. 20, 1949 2,924,446 Williamson Feb. 9, 1960

Claims (1)

1. A MECHANICAL PRESS COMPRISING A PRESS RAM HAVING A RECESS, MEANS FOR RECIPROCATING SAID PRESS RAM IN AN AXIAL DIRECTION, A PISTON LOCATED IN SAID RECESS AXIALLY MOVABLE RELATIVE TO SAID PRESS RAM FROM AN INOPERATIVE TO AN OPERATING POSITION LEAVING EXPOSED A PARTIAL VOLUME OF SAID RECESS, A FIRST STOP MEANS LIMITING THE MOVEMENT OF SAID PISTON IN SAID RECESS WHEN IN INOPERATIVE POSITION, A SECOND STOP MEANS LIMITING THE MOVEMENT OF SAID PISTON IN SAID RECESS WHEN IN OPERATING POSITION, SAID RAM HAVING A CAVITY CONTAINING A LIQUID UNDER PRESSURE, A PASSAGE CONNECTING SAID PARTIAL VOLUME AND SAID CAVITY IN SAID INOPERATIVE POSITION OF SAID PISTON, SAID PASSAGE IN-

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