US2781015A - Draw press - Google Patents

Description

Feb. 12, 1957 Filed June 11, 1952 R. F. DEHN EFAL DRAW PRESS 4 Sheets-Sheet 1 INVENTORS Roy F D-EHN lmM- WAR 4 Sheets-Sheet 2 DRAW PRESS R. F. DEHN El'AL Feb. 12, 1957 Filed June 11, 1952 INVENTORS Roy 1-? DEHN BY WIl/(Ah Win Q, Arron-w Feb. 12, 1957 R. F. DEHN ETAL 2,781,015

DRAW PRESS Filed June 11, 1952 4 Sheets-Sheet a INVENTORS Roy E DEHN BY Wll/IAM. WARD Feb.

Filed June 11, 1952 R. F. DEHN ET AL DRAW PRESS so 90 no no ran 15a I40 I50 so no Ian I50 200 2|o2l5 Q0 A DEHN BY Will/AM E. WARD UnitedStates Patent (3 DRAW PRESS Roy F. Dehn, Wickliife, and William E. Ward, Shaker Heights, Ohio, assignors to The Cleveiand (Irene & Engineering Company, Wickliife, Ohio, a corporation of Ohio Application June 11, 1952, Serial No. 292,828

6 Claims. (Ci. 11338) The present invention relates to crank operated presses and the like, particularly adapted for deep drawing operations.

The principal object of the present invention is the provision of a new and improved crank operated draw press or the like, having a crank driven at a substantially constant rate and a ram reciprocated thereby through mechanism operative to produce a substantially constant, relatively slow rate of movement of the ram throughout the drawing portion of its stroke, and a relatively rapid return movement following the drawing stroke.

A more specific object of the invention is the provision of a new and improved crank operated draw press having a ram connected with the crank pin or eccentric thereof through twopivotally connected levers constituting a toggle linkage, one of which levers is pivotally connected with the crank pin and the other pivotally connected with the ram, and means operated in synchronism with movement of the crank to shift the pivotal connection between the two levers to one side of a line through the axis of the crank shaft and the center of the pivotal connection between the ram and the lever connected therewith, the movement of the pivotal connection being synchronized with the crank during the draw ing stroke movement thereof to cause the resultant movement of the ram to be at a substantially constant rate and less than the maximum speed of the crank pin so that the draw stroke of the ram occurs during movement of the crank substantially in excess of 180, the pivotal joint being returned to the aforementioned line at substantially the end of the drawing portion ofthe revolution of the crank pin whereby the maximum pressure exerted by the crank on the ram is through a straight line linkage. V

Another object of the invention is the provision of a new and improved press of the character referred to in which the pivotal joint of the two levers forming a toggle linkage interconnecting the crank pin and ram is moved in an elliptical path during each revolution of the crank, the elliptical path extending across the line through the axis of the crank shaft and the center'of the pivot between the ram and the lever connected thereto, the pivotal connection having its greatest excursion from the aforementioned line during the. return stroke movement of the crank pin whereby the crank pin and levers return the ram to its uppermost position during movement of the crank shaft through an'angle appreciably less than 180.

The invention resides in certain constructions and combinations and arrangementsiof parts and further objects and advantages will be apparent to those skilled in the art to which it relates from the following description of the preferred embodiment described with reference fit to.the accompanying drawings forming a part of this 2,781,015 Patented Feb. 12, 19 517 ice Fig. 3 is a schematic representation of the relative movements between certain parts of the press mechanism throughout a cycle of operation;

Fig. 4 is a graph representing the speeds of the die slides or rams of a conventional crank operated draw press and the press shown in Figs. 1 and 2; and

Fig. 5 is a graph illustrating the relative pressure-inches stroke of a conventional crank operated press and the press shown in Figs. 1 and 2.

Referring to the drawings, the crank operated draw press shown comprises a conventional frame 10 having a die bed 11 and spaced upright guides 12 in which-a die slide or ram 13, which may be of any suitable construction, slides vertically. The ram is adapted to carry asuitable punching die which cooperates with a die attached to the bed to form a relatively deep draw in a metal blank. The dies are not shown as they are well known to the trade, nor is the usual blankholding means comprising die cushions, pressure pads, etc. The particular press shown has a drawing stroke of approximately fifteen and one half inches and the dies will draw metal during approximately seven and one half inches of the stroke, it being understood that a separation between the dies of at least the depth of the draw is required to permit removal of the drawn Work.

A crank shaft 16 is suitably journaled in the upper part of the frame and is driven by a pair of bull gears '17, 18 attached to the ends thereof. The bull gears are driven by pinions 19, only one of which appears in the drawings, which are supported on a drive shaft 20 at the rear of the press. The shaft 20 is preferably driven by an electric motor 21 through a conventional one revolution clutch mechanism 22 which may be of any well known construction and includes a suitable control device such as a push button, pedal or lever, not shown, which is actuated by the press operator to cause the clutch to drive the shaft 20 and rotate the bull gears 17, 18 through one revolution in a counterclockwise direction as viewed in Figs. 2, 3.. The details of the driving mechanism for the shaft 16 are not shown since such drives are well known in the'art. The crank shaft 16 has a crank pin or eccentric 24, and in the particular press shown, the eccentric has a throw of five inches; that is to say, the center of the eccentric is otfset from the axis of the crank shaft five inches. 7

The eccentric 24 is connected with the ram 13 through a bell crank lever or eccentric strap 25 journaled thereon and a link or lever 26 pivotally connected at one end to the arm 27 of the bell crank lever 25 and at the other end to the ram 13, the arm 27 and link 26.forming a toggle-like linkage. The arm 27 of the bell crank lever comprises two spaced flanges 28, 28 between which the upper end of the link 26 is received. This end of the link has a tubular bearing therein for receiving a wrist pin 31 supported in openings through the'flanges 28, 28'. The lower end of the link 26 is pivotally connected to the ram 13 by a knuckle joint 32. This linkage between the eccentric 24 and ram is similar to a toggle and by oscillating the bell crank lever '25 about the eccentric, the center of the joint comprising the wrist pin 31, which maybe termed the knee of the linkage, can be shifted from one side to theother of a line a, which extend's" through the axis of the crank shaft and the center of'the joint 32, to thereby raise the ram 13 or produce-relative line of the press and, as vi'e wed'in Figs. 2, 3, the left hand side thereof is referred to as'the forward or front side and the right hand side is referred toasthe rear side. i V v l 7 'By shifting the joint comprising the pinfil forwardly of the line a and returning it to the line during the down- 7 ward sweep of the eccentric 24, the resultant rate of movement of the ram downwardly can be constant and substantially below the speed at which it would move joint comprising the pin 31 to the 'rearrof the 'line -a during the .up-sweep of'the eccentric, the.1'esu1tant-,.upward movement of the ram 13 is substantially inexcess of the speed at which it would moveif connected to'the eccehtric'by a solidpitman, and the return stroke of the ram l3r can be .eflected by considerably less than 180 rotation of the eccentric. V

According to theinvention the bellicranklever 1s tric -so' that the joint Iformed hythe pin :31 moves in if connected to the eccentric by .a solid;pitman,..as in,

- conventional crank .pressconstructions. By shifting the oscillated ih itimed relation to the rotation ofthe eccenan elliptical path dy as seen in 3, which intersects V the .verticalcenter line a, and its excursion to the forward side of the lineis appreciably .lessthan 11131168.!- tvar dly ofj'theline. The center :of therj oint formed hy Ethe. pinf31coincides with lline a at the timetheeccentric 1Z4reaches the end o'f its downsweep at whichtime its lcenteris'likewise coincident with the line a so that the ings in the ends thereof and the bearing in.one end .is

pivoted to the bracket 37 by a wrist pin 38 which Vextends therethrough and is supported-in openings through two spaced parallel. lugs 39 of the bracket, and-the other end of theilihkfifi hasits'hean'ng pivoted to the arm of thclhell crank lever 25 by a wrist pin 42 extending therethrough and supported-inopenings .in two spaced. j lugs 45, 44 which 'comprisethefarm 37 of the bellcrank levers-25; .Theicenter of the pivot pin- 42liesona lihe extending at .about 135 from a line through the centers'of .theeccentr'ic '24 and the joint comprising the ,pm 31; arid whenfthe shaft .16 rotates .the., ec'centric,' ihe link causes the .center of the pivot pin-42, to

' travel in an, are extending at apbfoximately from thefhoiizonteilline through theaxis vof theehaft'lfi.

The line. described which extendsnthrough 42 is,

if: =eifect, arm 35' and it will he vseen thatiitleittends into the quadrant ihounde'd bythe vertical -.center,line a and it'hehoriiont-al line .thr'ough the axisandinto which I the eccentricmoveswhen it;crosses,the'vertical-center line inxthe initial movement thereof to effect a d ra wstroke. By anchoring the arm 35 0f the bell crank lever 25,as described, the'hell cranklever 25 is.oscillated about'the eccentricidastthe latter is rotatedtto effect the shifting 1 "off the jointaat the pm and actuate ,the .ram asujescribed. j

' uis mentiohed previously the ,press shown by .way' of examplefhas a'ram stroke-.01"; fifteen and onerhalf inches; and j't o oota inithe most desirable operating characteristics of V the ,pressithei effective; lengthof thc earm 21 me i sd m- Cente Of secse n'r wane-ax f: th P 31 i "se le 'm a h s; h u ts h ,q lete ez i m asured 'fr'ornlthe, .cent er of pinfil tolthe center pf w[the .32 Tris; twenty-.three incheg" the ilength of the i l 'i t xmsest ts r m h heat 10f he ecceni i241 ofpin 38 .is located from the vertical center gline quarter inches below thehorizontal lineithroi gh' the axis pin locations and lengths ofrthe arms, lever and link "should remain in proportion to the stroke approximately as indicated.

It is to be understood that only those parts of the press have been shown and described which are essential to the understanding of the mechanism for operating the ram, and that additional well known structures, such as an adjusting mechanism-between the ram and the link 26, have not been shownas they are well-known in the trade. 1

. The operation of theram canjbe readily uhders'tood by referring to Fig. 3 which shows various elements of the press schematically and in theirrespective positions at different angular positions of the crankshaft. When the press is idle, thecrankshaft 16 is in a position in which the center of the eccentric 24 is at 24a and'since link 36'limits or guides the portion of the arm 35 in which the wrist pin142 is supported in the arcuate ,path b the, pin .42 is at 42*1andthe ebell-cr anklever 25 is thus positioned'about the eccentric so that the joint comprising .wrist ,pin .31 .is at 31 which is (considerably to the rear of .the vertical .center line, and the end of link 26 comprising the joint 32 between the link and ram '13 is at 32 the upperendofIits travel or stroke.

As counterclockwise rotation .of thecrank shaft .is initiated, .the eccentric is movedinithe circular .path 0 up- Wardand across center line a, moving the. joint :com-,

prising wrist pin .42 upwardly :along arc .b which ,tilts the bell crank .lever25 clockwiseabout the eccentric and moves the joint comprising pin 31 along the e1- liptical path d toward ,the center linea therehytending to .straightenlthe angle-.between arml7 .of the bell crank lever 25 and thezlever 26 whichvlowers the i-ramihrough a .greater distance than .the verticalv movement of the j ;eccentric.

7 As the eccentric .sweeps through the .first guadrant at the left of vertical .line 1i, the crank --leve r' :25 con 7' tinuesclockwiseabout,theteccentric andwhen the cenportionoflitss'troke. As the eccentric ,moves "to point 24. 'thejoint. atpin .42fis .movedtoA-Z and the.bel1- f3 ,1at thejleftorfront ofl the linemandathereby break the straight anglebetween the arm 2 :7,and lever 26 which actionitends to. raise lthe ramj j The eccentric at this point, 7 however, is .sweepingdownwardlyat a rategin aexcess of the rate at which the breaking of the ar-113 21 lve'rlfiitend tmraise theiram s13 solthat the resultant rate of descent of the ram is thealgebraic umgof'these e twofactors and-the joint $2,;is,at132, is nj'the 'drawmortion to'fdtssttoke. When athelcentcr :of ithe eccentric reaches 25 it :is traveling .at ritsl greatest rate a ter of the eccentric-reaches the pointv24b .the respective joints comprising pins 42 .and 31 are at ,42 andSlP,

and theangle' between arm ;27 and-lever 26 israpidly approaching l..

Thecenter .of the joint 32 is then .at 32 and'theiamis approaching thelow'enhalf or draw lever is: swung to move the joint -,c'on 1prising ;pin 31 ;to

in the vertical componentand: at zthe tsame time 1 thezjo'int comprisinglpinl is approachingiitsvmaximum 'excursion 4' of the crank. shaft. It is to he understood that these 4 mi gn wo anlyxample d ermeyhe n immers s hayin fis smaml strok ;al oug .th

-,.ofthe eccentric." i U g rth'elcen terof tlIe'eccentric reapproachesg line' a,

bellerank3-lever25 istm'oved counterclockwise thereabout to swingithi'ezjoirit'icoinprising 'pin' 31 back toward ine V p g V V 7 V a; thecebylradding Io ithedowhwardtmovement of he gguide link 32measureg1 trornithe .center ofg pin A w 7 35 to the center of pin 3124s sixteen inches; The axis I to the frontzof line-a and increasing the break ifrom the .straight r angle-between ,arm..27 :and1 lever' 26 'so' that {the rate at .which it tends 'to'lrais'e the -ram is incifeased 'toi closely :corre spohd itotthe increase jryth'e downwardfrate' the resultant straight line linkage. g V I v As the crank shaft continues its rotation and moves the eccentric in its upward sweep, the link 36 forms a pivot about which lever 25 rotates whereby the joint comprising pin 31 is swung .wide and rapidly to the rear of the line a and imparts a quick withdrawing movement to the ram 13. This withdrawing action of the levers 25 and 26 combining with that of the eccentric quickly returns the ram to its uppermost position, at which point the crank shaft is stopped.

In connection with thetransmission of force from the eccentric to the ram, the excursion of the pivot joint at pin 31 forwardly of the vertical center line a during the draw stroke is limited so that'the lever 26 is not shifted over about 11 from vertical whereby the lateral thrust on the ram guides is low and will not be sufficient to cause appreciable wear or inaccuracy in the operation of the dies. It will be noted that the maximum pressure is applied at or near the in-line position of the arm 27 and link 26.

It is apparent that the downward or drawing stroke of the ram is effected by an appreciably greater angular movement of the crankshaft 16 than that required to return the ram to its uppermost position. In the press shown, the drawing or working stroke occurs during about 220 movement of the crankshaft as against 180 movement of the crankshaft of a conventional crank operated press. Thus, the R. P. M. of the crankshaft of the improved press can be substantially increased over that of a conventional crank operated press without increasing the maximum drawing speed of the ram.

The relativerates of travel-of the ram of the improved press and that of a conventional crank operated press having the same length of stroke is illustrated in the graph shown in Fig. 4. In this graph line 50 represents the lineal movement of the ram 13 relative to the angular movement of the crankshaft16 which is represented by the parallel longitudinally extending lines which are spaced from one another to represent ten degrees of crankshaft rotation. The zero. degree or starting position of the crankshaft is represented by the first line at the left end of the graph. It will be seen that during the first one hundred degrees of rotation of the crankshaft the ram is lowered through approximately the first half of the. draw stroke, which merely brings the dies together. The last half of the stroke in which the work is drawn by the dies, the rate of travel of the ram or the movement thereof per degree of rotation of thecrankshaft'is substantially constant, until just before the end of the stroke. The last half of the stroke that is, the working or drawing portion of the stroke is effected by about one hundred and twenty degrees of rotation of the crankshaft. The return stroke of the ram occurs in about one hundred and forty degrees of movement of the crankshaft. Broken line 51 of the graph illustrates the movement of the ram of the conventional crank press and it will be seen that the movement of the ram per degree of rotation of the crankshaft during the greater part of the drawing portion of the stroke is considerably in excess of that of the improved press. As a result, the R. P. M. of the crankshaft of the conventional press must be considerably less so that the maximum permissible draw speed is not excessive. In fact, the R. P. M. of the improved press can be 82% higher than that of conventional crank presses having like ram strokes.

' The improved press not only is capable of operating at a much higher speed than conventional crank operated presses of comparable strokes, but it is capable of delivering considerably greater tonnage to the ram from equal power input. Referring to Fig. 5, the graph therein illustrates tonnages by the vertical appearing lines and the depth of the drawing die is indicated by the horizontal appearing lines spaced apart to represent half inches of depth of the die, the bottom of the die being represented by the bottom line. The broken curved line 54 represents the pressure curve on the ram of a conventional crank operated press and the curved line 55 represents the pressure curve on the ram of the improved press having the same power and ram stroke as the conventional press. It will be seen that the improved press delivers consideraly greater tonnage to the ram in the upper part of the drawing stroke and that the tonnage delivered to the ram of the conventional press does not approach that of the improved press until the last inch or so of the stroke.

It is apparent that the objects enumerated as well as others have been attained and that a new and improved press of the. character referred to has been provided which materially increases the speed of operation of metal drawing operations over conventional crank operated presses without exceeding safe drawing speeds, and that the efliciency of the press with respect to the tonnages deliverable to the punch ram is substantially increased over that of conventional crank operated presses. While but one form of the invention has been shown and described, it is our intention to cover'hereby all other forms, modifications and adaptations, thereof falling within the claims appended hereto.

Having thus described our invention, we claim:

1. In a draw press, a frame, an eccentric journaled in said frame, means to rotate said eccentric in one direction about a fixed axis, a ram, means to move said ram in a drawing stroke comprising two levers connected together by a pivot joint, one of said levers being journaled on said eccentric and the other lever pivotally connected with said ram, and means operatedin synchronism with the rotation of said eccentric to move said joint to one side of a line through said axis and the center of the pivot connection between said ramv and said lever. connected thereto during the ram drawing stroke movement of said ram and to return said joint substantially to said line as said eccentric'reaches the extremity of its drawing stroke movement whereby the centers of said joint and said eccentric lie substantially on said line, and 0perable to move said joint to the opposite side of said line during the ram return movement of said eccentric, the excursion of said joint on' said opposite side of said line being substantially in excess of its excursion to the first mentioned side of said line.

2. In a draw press, a frame, a ram slidable in said frame in a drawing stroke, an eccentric journaled in said frame, means to rotate said eccentric in one direction about a fixed axis, a drive between said eccentric and ram comprising two levers connected to one another by a pivot joint, oneof said levers being pivotally connected with said eccentric and the other of said levers pivotally connected with said ram, an arm rigidly connected with the first mentioned lever and projecting into a quadrant defined by a line in a plane containing said levers extending through said axis and the center of thepivotal connection of said ram and said lever connected therewith and a second line through said axis and normal to the first mentioned line and said axis and which quadrant is initially entered by said eccentric passing through the first mentioned line in moving said ram in its drawing stroke, and a pivoted lever for guiding a point on said arm in an arcuate path extending at approximately 45 with respect to said second line and having its pivot point to one side of said second line and in the quadrant adjoining the first mentioned quadrant and on the other side of the second line whereby said one lever is oscillated by rotation of said eccentric about said axis to swing said joint in an elliptical path intersecting the first mentioned line.

3. In a draw press, a frame, a ram slidable in'said frame in a drawing stroke, an eccentric journaled in said frame, means to rotate said eccentric in one direction about a fixed axis, a drive between said eccentric and ram comprising two levers connected to one another by a pivot joint, one of said levers being pivotally connected with said eccentric and the other of said levers pivotally conjframe at a point in a-p laner parallel to said second line' between said axis andram and in a quadrant adjoining {the first mentionedquadrant, said link projecting 'into' said quadrant and being pivotally connected to said arm.

'4. V In a draw press, a frame, a ram vertically slidable in said frame, a first le ver pivotally connected at one 'end to said ram jfcrreciprocating 'the latter, the pivotal connection between said lever'an'd sai'd ram'moving along a vertical line, "an 'eccentricrotatalily supported in said frame with its axis of rotation-normal to and intersecting said line, aneccentri'c strap. rotatably supported by'said eccentric and including aniarm pivotally connectedto the other end of said lever'and "forming a "toggle "linkage therewith, lever means connected to said strap for positioning said am along said line whenthe center ofsaid eccentric is at'its lowest point in its'path o'f rotationand for causing the pivotal connection to gswingto one side of said line for more than 180" but less than 270 'of rotation of the eccentric from its lower position and then' "to swing .to the other side ofsaid line until the center of said eccentric again reaches its lowestpoint with'the' movement ,Gf the pivotal connection between said arm and said'lever 'defining a substantially elliptical path 'gen erally transverse jtogan'd intersecting said line with the excursionoffthefcoiinection to the first-mentioned side of the :line being substantially greater than its excursion "to the second-mentioned side of said line. 7 I "5. :Ina drawrpress, a frame, aram vertically slidable in said frame, a first lever ,pivotally connected atone end to said rarn for vertically reciprocating theleitter, the pivotal connection between said lever and. said ram rmovin said frame withits axis of rotation normal'to and intersecting said line, an eccentric strap rotatably sup- 7 ported by said eccentric and including afirst armpivota'bly :butl ess than .270? tofiotationof the centerof the eccentric from its lowest position and then to swing :to the other" side ot fsaid :line until the center of said eccentric again reaches'its lowestipoint with the movement of'the :pivotal connect-ion between said arm and saidlever defining a substantially elliptical path ge'nerally transverse to and intersecting said line and with the excursion of said pivotal-connection-to the-'first-menti'oned 'side of the line being substantially greater than its' excursionto'theisecondmentioned sider of'said line, I

6. In a draw press, a frame,;ia iall lf -Ve'lfic ally 'slida'ble in said frame, a first lever pivotally connected at one 7 end to said ram for reciprocating' the latter, the pivotal connection between said lever and said ra'rn moving along a vertical line', an eccentric rotatably supported in said frame with'its :axis of rotation normal to and intersecting said Hire, an eccentric strap rotatably supported by said eccentric and includinga first arm pivotably connected to the other end of said lever, forming a toggle linkage therewithand 'a second 'arm-defini'ng an obtuse angle with 5 saidsfirst arm and extending into the quadrant in which thex'cen'ter :of said 'eccentric begins its downward movement upon rota'tion thereof, a pivoted 'lever pivotally connected to said second arm for constraining a point thereon toxmove-al'ong-an arc in said quadrant and for positioning sa'id first arm along said'line When-the center of said eccentric is-at its lowest point in its path of rota- 'tion and to cause the pivotal connection to swing to one side of said linefoi' more than 180*but less than 270 of rotation of the'eccentric from its 'l'ower'position and athen toswing 'toitheother sideof said line nntilthe center of said eccentric again reaches its lowest point with "the movement {of *the pivotal connection between said arm and said lever defining a substantially-elliptical path genrera lly transverse to and intersecting-Said line with fill!) excursionof the connection to "the first-mentioned side a ing along a vertical line, an eccentric rotatablysupportedi connected to the other end of said lever forming a toggle r 7 linkage therewith and a second arm defining an obtuse angle with said first arm and extendingint'o the quadrant 7 in whichfthe center ofsaid eccentric begins itsdown'wai'd movement uponrotatiori thereof, lever means connected to said second arm 'for'positioning said first arm along saidiine when the center of said eccentric is at its lowest 7 7 point in its path of rotation andfior constraining the pivotal connection between said first farm and f-saiddever to swing to one side o ffsa'id line forjrnore than jl" of the line being substantially greater than its excursion V to the secondmentioned'sideof said =line, -'and means pivotany supporting the last sai'd lever in the quadrant entered by the center of the eccentric upon leaving the jfir'st sa'id quadrant. I

'References Citedm the meet this patent" 2,688,296 7' "panly u g n Septe7, 1954

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