US2382077A - Power press brake and die set - Google Patents

Description

F. H. LESLIE 2,382,077

POWER PRESS BRAKE AND DIE SET Filed Aug. 3, 1942 s She ets-Sheet 2 Z a. 7 am 1 K m a a j WW1 6 4 m m n w; a w fi m w 5 W I! m q @U flunk. m M w w m m f/ w m m g o m m fi "J 7 Z .4 0i MM. 3 "M /3M6 m K y P V j J u 7 \\\\M// w www \24 4 il V W? L Aug. 14, 1945.

I-T-I-T-I qs- F. H. LESLIE 2,382,077

POWER PRESS BRAKE AND DIE SET I Filed Aug. 3, 1942 3 Sheets-Sheet ,3

[61E J4 g 156 Patented Aug. 14, 1945 UNITED STATES PATEN T- OFF ICE POWER PRESS BRAKEAND D'I-E sn'r- I Freeland H. Leslie, ChicagoJll.

Application August 3, 1942, Serial No. 453,306

19 Claims. c1.1s4 fss)' This invention relates to power press brakes and die sets, sometimes called sub-presses. It embodies self -ba1ancing concepts disclosed in applicants United States Letters Patent No. 2.260,- 183 and in applicants copending application Serial No. 394,971 which is a continuation in part'oi said patent. i

The general object'ol this invention is. to provide a sub-press which will make it possible to perform punching operations on press brakes no matter how old, wornoutandsprung' thepress brake may been long as it will move its ram up and down.

Applicant attains this object by holding the punch holder and the die shoe in alignment by means independent of a given relationship'between the ram 61 a press and its bdand by then moving the punch holder towardthe die shoe by means of the ram, there being no rigid connection between the ram and the punch holder. Contrasting th s with present practice, generally speaking, the punch holder which holds the which is held in a verticalpath by means of slides and ways, it has been common practice to maintain alignment between the punch holder and die shoe by means of leader pins and bushings. Thus, in a rectangular leader pin-die set, there may b projecting upwardly from the die shoe a pair of leader pins'at each-end thereof which register with bushings in thepunch'holder. When this die set is positioned in apress, the die shoe is rigidly fastened to the bed and the punch holder is rigidly fastened 'to the ram with the result that the leader pins acting on the bushings tend to align the ram with the bed of the press and to assist the ways and slides guiding the ram.

In the present "invention. applicant departs from the practice'oi ta'steningthe punehholder to the ram but relies solely upon the die set for holding the punches and dies in alignment and and diesin alignment without assistance from t T; j j

More specifically, the object of this invention is to provide a superior the set tor' use impress brakes and,'as will be seen, the'advantages mentioned above resulting from the employment of a nonrigid connection'between the ramand the die set are particularly important inpress brake applications." 1

' A press brake is a tool formaking' bends in metal sheets; Essentially it 'consists'of two upright" end members held inspac'ed relationship by a. bottom member and atop memberwith a; ram having a length approximately equal to the width of the pressbrake and a'depth of two or three inches, said ramdependir'rg'irorn-theupper part ofthe frameand capable of vertical movement in response to the application of power. Disposed below theram is-a bed of similar widthand similar depth. For'bending'operations, a die-as for example a V-shaped"die will be mounted on thebed and a V-shaped punch for seating itself in the die will bemounted on the bottom of the ram. By-placing apiece of work-on the die and causing the ram to descend, the two ends -o1'='the piec of the work will bend upwardly to place the'requisite bend in the piece of work. "These press brakes may have a, width as high asBOieet and the'tolerances= of the'guiding'means for the ram are so great that it -.is not good practice to attempt punching operations with a press: brake. Indeed the successful' iunctioning oi 'press brakes uin bending operations depends to no small extent upon the fact thatthe dies are able -to:a1ign themselvesand upon the-=fact that it is possible to employ punches which have'aligning portions for engagement with complementary portions in presses thedeader pin die setwhenused-ima press brake has its die shoe rigidly fastened to the press brake bed and its punch holder rigidly fastened to the ram.- depress brake, however, must surmount an additional problem. In the case of the straight sidepunch-press, the area of the bed of the press and the bottom of the ram determine approximatelythe maximum area of the punch holder anddieshoeotthe die set.

In the press brake, on the other hand, the bottom of the ram may be only an inch or two deep and the same is true of the bed. The die set that it is desired to mount there'between,

may be as wide as the press brake and one or consist of heavy pieces of metal, approximately coextensive with the width of the press brake between the two vertical frame members and having a depth, or a portion extending in front of the ram and behindthe ram, of perhaps as much as a foot. In the case of the upper bolster plate, which is mounted centrally of'the ram, there are angle supports extending upwardly to engage the front and the back of the ram. The lower bolster plate is the same as the upper bolster plate but is turned upside down. In the case of a foot press brake, the two bolster plates may weigh several tons.

One major object of this invention is to impose the entire burden of resisting forward and backward rocking of the punch holder and die shoe upon the punch'holder and the die shoe or upon the die set. Certain important advantages or results follow from the attainment of this object and these. will be discussed after this object'has been clarified. A press brake will be used as an illustration. If a die set consisting of a punch holder and die shoe with leader pins and bushings were simply positioned between the shallow ram and' the shallow" bed of a Dress brake there would be some difficulty n establishing the-conventional rigid connections between the ram and the punch holder on the one hand and the die shoe and the bed on the other. Additionally if the die set were loaded forwardly or rearwardly off center, conflicting forces would [be set up in theram which would tend to put uneven strain on the slides and ways uidin the ram. For this reason, there is placed between the bottom ofthe die shoe and t e be a heavy bolster plate which extends ap oxirnately as far forwardly and as far rearwa dl the bed as does-the die shoe. A similar bolster plate inverted is positioned between the op of the punch holder and the bottom of the ram. These {bolsters have inwardly directed arms to en age 'the front and the back walls of th ram and bed to prevent forward and backward ock'- ing between the punch holder and ram and be.- tween the die" shoe and the bed when the die set islo'aded forwardly or rearwardl off center. The surfaces of the bolster plates which en a e the punch holder and the die shoe are, of course, horizontal and these bolster plates are very heavy. They are intended to take up certain distortional forces and consequently the weight or strength of the punch holder and die shoe is not so important a factor. In the case of applicant's present invention, however, the punch holder and the die shoe or whatever part of the die set which is actually 'holdingthese two members must be capable of withstanding'all of these distort n forces because there is no rigid connection between the ram and the die set.

By providing-"punch holders and die shoes, or more broadly by'pro'viding a die'set having the strength to take up all forward and backward rocking of thepunch holder and die shoe with respect to each other due to off-center loading of the 'die set, applicant attains two important advantages which are particularly striking in the case of the pres brake. In the first place applicant eliminates the need for the bolster plates. By eliminating the bolster plates, applicant h s removed a die set erection problem of considerable proportions. In order to convert a press brake which was being used for bending operations to a device useful for punching and blanking, it has always been necessary to mount these bolster plates on the ram and the bed, and in the case of a 20 foot press brake these bolster plates weigh several tons. In order to mount the bolster plates, special hoists and other equipment, is necessary. Applicant's construction, employing a. sub-press similar to that shown in applicants Patent No. 2,260,183 and in the copending application Serial No. 394,971, renders the bolster plates unnecessary. The second advantage arises from the fact that applicant may use whatever weight'punch. holder and die shoe is necessary to handle the particular number of punches actuallyto be used in a given opera tion whereas at the present time the weightof the punch holder and the weight'of the die shoe is controlled primarily by the bulk and the size of the press brake. Thus under present practice, one may see a 20 foot press brake raising and lowering enormous bolster plates andthe punch holder of an enormous vdieset when upon inspection itis found there ,may be a dozen or so small blanking dies distributed over the 20 foot length of the sub-press which blanking dies require only a few tons of pressure to drive throu h, for example an aluminum ,airplanewingsection. The actual punching capacity could be handled by an ordinary punch presshavine a'bed six inches by six inches. -By applicants construction, on the other hand, a comparatively light punch holden-and die shoe can be used as component parts ofthe die set or sub-press and the press brake will function with very little load on it.

Another object of this invention is to make a die setwherein punches and diesmaybe readily changed while the die set'is in the press brake. Mention has been made before of the greatweight of conventional die sets and bolster plates and of the fact that the bolster plates completely cover the top of the punch holder and the bottom of the die shoe and make it impossible, under conventional punch mounting, to remove a punch or a die without taking the die set out of the press brake. By vapplicants invention, .wherein the ram is in non-rigid engagement with -the upper part of the die set,v no tortional force are transmitted to the ram since it performs no aligning function whatever for the punches and dies. The same is -trueof the relationship between the die shoe and the bed with the result that applicant eliminates both the upper and lower'bolster plates. This requires considerable explaining; Treating of the die shoe, a die is mounted on a die shoe by mean of dowels, which are here unimportant, and headed screws with the heads on the outer side of the die shoe. These heads fit into counter bores" so that the bottom of the die shoe will befiat so as to permit it to rest upon the flat top of a bolster. When a die becomes dull, the surface of the die is ground to make it sharp and'if the screw heads were adjacent the surface of the die, it would be necessary to lower the counter bore. For this reason general practice has the screw heads onthe side thereon;

Figure 2 isaview taken onstheline 22 of Figure 1 and showingthe sub-presswith the punches immediately above the dies;

. gure 3 is a view,'partly cut away similar-to Figure 2 showing applicants sub-press-inthe-open position; 7 r

Figure4 is a view taken-on the line 44 of rFigure 2; i

,c Figure 5 is an enlargement of the for ward part of -the upper leaf of applicant's sub-press and the lower portion'of the ram for the purpose of illustrating the nature of the contact between the bottom of the ram and the top of said leaf;

, Figure'6 is a diagrammatic illustration showing the position of theflexing leaf with respect to limiting stops when the die set is loadedoficenter forwardly at the moment when the'punches enter. the work;

Figure"? is a diagrammaticillustration simiof applicant's punch plateillustratinguniform positioning of holes for mounting pun'ch'holders Applicqntfs die set used rz-recz'procdtcb le ram,

' Referring to Fi gure l of thedrawings, the numeral lfl generally identifies a press brake. The pressbrake isof a conventional type and consists of two upright end supporting walls l2 and I4 'held in upright relationship by a lower con necting member 5 and upper connecting member"l8.= The throat of the press brakemay be seen" in Figure 2 and bears the numeral 20. Returning to Figure 1, ordinarily in press brakes, if the workpiece is narrower thanthe distance between thetwo end walls [2 and I4, thework may be advanced straight through the pressthat is withdrawn from the back. The depth'of the throat, that is the distance from the'vertical plane containing the ram, shortly to be'described, back to the rear of a gap in the end walls' varies and- 44 to .a punch holder; "The flexible leaves 38 are. all-in alignment with eachother and it will .be'understood thati thisemployment of a plurality. otuppenleaves and a like plurality of complementary lowerleaves connected by a plurality oiflexible leavesis anadaptation of applicants invention in United'StatesLetter Pat.-

ent, No. 2,260,133, ,t' -a situation where; a very broad punch plateiis to beused. The parts. actually: making up the die set can 'be better seen in Figure 2 where it will be noted that the flex ible leaf 3,8. is rigidly iastened atgits outer end .t the upperchannel; member...4 through the medium ;of. .an elongated. pressure block 48 while .itiis rigidly attached ;to; the lower channel member' 34 through. the rnedium of; a block 50. .The lower .limitin'g-memberfiz and the upper limiting'me'mber ifl clearlyshown in Figure 2 are auxiliary featureswhich wilL be discussed later.

. .The .means 'for assembling .I applicants subpresswith the pressbrake squite simple, Rigidlyfafstened to the bottom of. the die shoe 32 along itsrnedianline is a 117 shapedmember 56 having a depending tongue 58 adapted to fitbetweentwo heavy plates 60 and 62,; pontinuing to refer" to Figure], 2, which in...this. particular press brake together make up tnebedn. It is of course understood ,.'that; the bed of .a press brake may consist r; single plate having agroove therein to receive the tongue..5 8." The ends. of set screws .(see l in: Figure 2);. the bed: 22" are screwed against the tongue; 58 130 ;clamp the T shaped member 55 rigidly to, the bed 22. 5 1t is important at. thispoint tobear in mind-that the bed of the press brake, while. it.- may be removable oradjustable-uprand.downuis in operationa fixed eleend. walls, one of which--brackets"carries the nuaccordin'gto the capacity of the press. Generally speaking in press brakea the depth is not very r t" a "Mounted in the forward lower portion of the press brake Ill is a bed 22 which may be removable or fixed and of various shapes. Generally speaking the bed is coextensive or slightly exceeds the distance between thewall members 12 and I4 01' the press brake and generally speaking has ade'pth, that is from the point 24 to thep'oint 26, of-one to three inches. Disposed above the bed and in general vertical alignment therewith is a ram 28 which may be reciprocated vertically by means 32 and 34, which means may assume a v variety of types and need not'here be discussed.

Suflice it to say, for applicant's purpose, the

, press brake must have a bed and a ram reciprobers, 34 and 36 which in turn are .connected through a plurality of flexibleleaves suchas v 38 and similar upright channel members 40,- .42

ment, that is to say it-3'bealS a-rigidr relationship to "the two end zwalls l2 and J4 and -theconnectingmembers l6 and I8 oi thezpress brake.-

The rear. otthe sube'press 30 is suspended from a.-pair of brackets; attached to I the .inside of the meral 64 and anotheris suggested in dotted outline and carries the numeral W's-Extending across the rear of' the press brake'and connecting the two brackets '64 and-66'to each other is a'heavy channel member '68. This heavy channelmember 68, referring now to :Figure 4; connected to the blocks'suchias 50, whiche'xterid-briboth sides of the lower channel memberi34 by-"b01ts 10 and 1-2pa'ssed' through spacermen'ibers If-and 16. 'Ihes'e'conne'ctions areall tight;

1 Referring now to Figure 2 therefor we may view the lower leaf "'or lowe'r' portion of! applicants sub-press whenmounte'd in the press brake asa part of a rigidbed extending from the bracket 64 to the bed 22. "Whatever-movement; 'is' to be permittedfbtween' the upper and lower parts of applicants'sub-pre'ss williwi th respect [to the press brake as w e e gccur commencing with i ji'b t e f xibl e was b were. i i i i Referrin g'to Figure 2,1attenti n is directed to a, w... fi nd lo k. .8 wh ch. a ma be see i Figure 1,1 is disp osedat the end o'fgthe die shoe. The. top',,s r aqapf. th 9 9. lies in" a l n parallel tQtheIp lane' of the top of the die shoe 32 whishrla s th e e vel, sflls e ure 2 inlea chdie' to; which it isdes'ired to permit the punchjto. penetrate, .It will be. understood from reading" United I States. Letters Patent .No. 2,269,183 lthat, punches mounted in. ,applicantfs. s u pr'ess' aremoving, along'an are. .IheQwal-lshf thedie and the wins of the punch are approgd:

te y n ent to heazoat. thes rt a e oaths die, that is the point e he-punchleutersthe die, and it follows that thep nch mustn t be, permitted to penetra e. the d me s. in b cause it ill Wear its walls inst thetdiewal v.'.I'.he. lower en block 8 nct ns ha im lar b o k .see i ure n. c n u c ion ithtth up er.

nd blocks 85 and 88 to prexc tt ep nches-from penetrating the dies to annndesirablapoint. i e 1. the sub-press is s o n iiillyl osed, that iswith the, end blocks ali and, wrestingon th end l s, "a d. .8 resp cti e y eth t th Punches have atta ned their maximum'tdepthin, the dies. ,In Fi ure 2 t e bottom of the punches are shown just above the tops oif'the dies :so that there is a space between the; end block l fland 86. This position never egists, as a mat er of Practice. a It isshown for. the purpose of illustrating the plane containing the topsuriaces of the dies which is atrightangleatothe siilwfllls o thepunches. This plane alsooontainsthe flexf ible leaf 38. W henth punches aredrawn above or depressed below that plane, they are moying along an archaving aslts center. some po nt i e flexible l q In Figure 3 the uppermost position of; the, upper leaf 40 of applicantssubepressis shown... Mount l ed centrally of the length of t he top ofthepunoh holder 46 is a strip, which .thierefQre IiesdIrect -LQ 1y below the ram 28. The lower edge of the rain is cut out to receive a barhavingan inyertd' L cross section 90. The bar Bills held bya'scond' bar 92, having a grooyerM therein, by-bolts such as 95. Referring vforthe. moment to Figure 1, bolts as and mo, Deri'orrnin'g theQfiln ctiohs of bolt 95 also hold a bracket lilfto the. forwa d lower. edge of therarfn 2,8, "Similarly bolts [.04 and 106 hold a bracket. Iiifl to the lower feclge'o'f the ram 28 near its other and. .Rle'ferifing both to Figure 1 and Figural, two double brackets H and H2 arem'ountedon theftollte'r top sur face of the punch holder 46 [and piv'otally sup; ported in each are lift'rods. ll l and l lion the upp r end o jwhieh' are isteem mbers mend I211, the position of' whichon'theflift'rodS H4 and 116 may be adjust'edbyth threaded con.- nection th re n. and the position'flxed by'lock nuts I22 and 1124,,ReIerrineftofiureB.th t p member H8 is s ibnedfat'falheight such that the punch holder 45 will heflitted by the rising ram for perhaps half a'n inch duringfthe last part of the upstroke. The stroke of'thej ram may be Several inches; but allfof this stroke not used in applicants' sub-presses. The" bar-"80 m y be alled a striking banana its strikin ed ay be oiled. Ordina ily thegp nches'jareraised above the dies by .a distance jujs tisu'flicie'nt to permit the ready insertion' or {Withdrawal of the work. k f It' will be noted that thf constr ction shown does not include a strilmtr'. irisistve11j1 y stood in the art; when the punches; 'passthrongh the w rk. p e wi h? d e antigthen more ba k upward th w 'c rrytli work p ece upwardly unless some means is'prov'ided for stripe ping the work piece'froln the pu ches. It was. not thought wise'to include, a stripper. int e present embodiment a The structure thus far'described has certain advantages when employed in a reeiprocatingram press. Inizth e' first pla e, rel e ring to Fi ure, 2.. the die shoe lqt e-v e a P at 45-1 sufficient strengthfironi frontl to backdn conjunction with en e b f memb ur aei i esi killer's re dit et n cause by the form used tor-P nch n 9. q nt y when ho de ii endt he die shoe can be of Whatever size is necessary to accommodate the total length and width of thecutting surfaces of .thepunches to be employed; the thickness-and hardness ofthe work piece: also being taken into consideration. Ifthewqrk piece is light and the punches are few,-the'weightlof the die shoe 32 and punch holder 46 as Well es the other members or the sub-press; may bercore res'pondingly lighten'edi This willfacilitatehandlirig; L 1 I ut a -An appreciation of the value of appllcants'sub press may perhaps be more quickly conveyed by using the term self-balancing." The forces that damage punch presses and dies areiorces which cause the punches tomove' horizontally out of alignment with the dies. -Where the-punchfholding means and'th'e die shoe are rigidly fas'tenedto the ram 0! a'press' brake or-a' press-:andto the bed; the. distorting'forcas are transmittedlto the ram and tothe bed. This is true ot leadergpln die sets in which the punohx-holdingnieanslis rigidly fastened to the ram and' the dieholding means is rigidly fastened to the bedof'tlief pres's brake' or '=punoh press. In applicant's 'seIfebaI- arming die set all of these forces are exhausted within athe sub-press its'eltand :arenot trans mitted in any way to the press brakeor the punch press. The're 'are no horizontal forces afiecting the 1 amor the bad. Oonsequently a. perfect; bal-iance-is obtained with vertical tomes only, regard. less of'where the punches are located ona-the punch plate. No horizontal strains can'be trans! mitted to the ranrorhed. J- ...f-i.".t w Moreover, I for purposes; of illustration, the dotted lines I26, 128, 13! and. I32. indicate the shape, as viewed from the sideiniigure 2 ,,of the heavy bolsterplates that:areaordinarily-hung from the bottom of a ram and placed. abo'v'ethe top 'of' a vbedlfo'r asqistingdn-holding the punch holder rigidly on the ram and-the die; shoe rigidly onthe bed. Applicanthascompletely. dispensed with these bolster "plates beoauseno attempt 'is made to relate the up and down :movqment .oi the "ram to the .alignment problem.-of thesubepress. Referringto Iig'ure'ii, 'it'willhe noted that the bottom of the striking bar 90 engages the strip 48. It is immaterial whether thexat-riir-- ins bar engages the 'strip between the polnts I34 and lilor' between. thepoints Inland-I88. The net-result of this is' thatlit does not make any difference whether themleansnior {guiding the ram' 28' in its'vertieal'movements is worn to much that the ram 28 may alsomove sidewise betweenthe points ill and m or "whether its guiding means isso accurate that the ram 28 m ves vertically withing; tolerance bfor'i tenthousandth of an inch in its sidewisei motioni" So far' as moi/ ing the upper-leaf 40 "earrying th punch holder 'or-applicants s b preseus coneerne'd," the; alignment between the-pun hes rid the dies will bejust'as good when the sut ress is in {m m use press brakeili which the ram has'a' forward and backward play Mane-sixteenth of. an inch as "when applicantsfs ub-p'ess "is mountedjon a new pressibraige nevi p toler an e offoneeten-thousandth 'o'ra'n, inch i such 8;

P a P e wie a t 'liie structure .'desqr bed and dram; shows; a e "for "per orm ng "pu 'sihi ef opera i htes jb akes matt r. ho wpr'xi put we.

mphases h e e ert so mov i s mm ewe- 48 as .a lever to. put'a slightkink .1121. in the leaf 3B. .In other-words, while the leaf 38. hassuffie cient structural strengthto act as; a column when misaligningforceis applied .along an arrow such as .114, when the misaligning force is applied along such as indicated by the force 1.16

the leaf will yield .In;.yielding; itimay draw the upper leaf assembly. includin the. channel member." and punch holderdhslightlyi to the right, which would getthepunches and dies out of alignment. l. v..

In order to. defeat: this ...effect, and -.bea-ring in mind; not only that .theleaf 7'88 .isllying ape proximately the .same plane :asthe topofthe dies and that .the punchesv are permitted to enter the dieslby only a short. distance such as onereighth of an. inch, applicant has positioned a stopv block I18 beneath the free end of the leaf 38 to. actas, a stop preventing the freenend of the.-.leaf,-.38 from being depressed --.below the; level-necessary to. permit thepunches .to enter the diesapproximately one-eighth of aniinch... Beneath theflexibleleaf 38 .is. alower limitin member .52, the. function .of..whicmwfllshortly be described. but. which. occupi a portioniof the, space between the flexibleleaf. and the block I18, a spacewhichucouldbe. occupied by. theblock 1.18 if the lower; limiting-.membenfl were. not. employed.. 1 Under normal operating conditions where the sup-mess is loaded on. center or substantially. on center,v the1.10w er limiting member 52, attached to the .flexibleileaf. .Will only. touchtheblock. [18 when the. punches have penetrated the dies. to, their. maximumextent, When, however, thereiissubstantialforward oil: c nterloadi e and theeffect or, the. force I58 operatingacross-the ram force. as a;fulcrum is to depress the block 8 abnorm ly q-th ti would twistsand damage: the. flexible leaf 38, this action is permitted nly unti the-leaf and lower limiting member Slengages thebloclpllii, at which time. the block, 8 be om s the i111: crumland the ram firce I64.;..QY 0m $.the force 1.68 andforcesthe punch througnthe work piece into the die,. No substantial, damage. is caused totheflexibleleaffl. ,wn n, on the other-handrreferring: now-t Figure '1, the off-centerwloadingpis .rearwardly, that is. behind theram, the Dunchentering the work. sets/up. a. force I88; which t nds .to u iliz the ram force I64 as a fulcrum and movethe lnieriendv including. :the block .48 upwardly. The effect-of thisaction; if the .leaf138-.-had.no..support; to the left of. the .dottedqline 1B2.',would.be toso seriouslyt strainthezflexibletleaf 38 at :the pointl astolbreakit quicklyi i 1...

.To overcome this 'difficulty applicantuses the upper limiting member-54 and. the lower limiting member v52 which'have curving surfaces .184; I

and I88. Asthe force 180 is applied,..the flCXi-r ble' leaf 38 follows -the curvei l. 8l', -the 'actual flexing point moving to theleftsfromthe point I82. The distance between? the curved edges [84 and I86 less thethickness'of .the flexible .leaf 38- is' slightly greater than :ther-opening J88 .beneath the lower limitingl 'membernfl and the block I18, referring to Figure 2 when the: press is in normal condition. The result is that the. lower limiting member.Slzengagesfone side. of the flexible leaf Y 38 while ::the upper limiting member 54 engages the opposite side ofthe leaf 88 after the distortiona1.;force:|.88, see :Figurel'l', has been permitted to function for. atshorttin e;

it will be ur'iderstood that itcisnecessaryrto permit a slightly greater upward movement pf the leaf 38 than. downward movement because the leaf must be raised .by. thepress brake to permit the insertion and removal of work. This is illustrated in Figure 8 where the leaf is. raised to its-maximum position. .It is noted that under suchcircumstances the curved Surface I88 of the lower limiting member 52 does not engage the leaf 38 atall. The curvatures of limitin mem bers 52 and 54., that limit thedegree of flexing of leaf 38, aresuch that it is not p s ible for lea 3.8 to be bent so severely .at any pointthat its metal is strained. beyond'the practical working strain for springs. l

'Method of making applicants sub-press One of the features of applicants invention resides in the method of joining the various parts oi -the press to each-othen 'which in turn makes it possible to use ordinary hotrolled plateS angIe irons and channel irons to make applicants invention in conjunction with a planer. Referring to Figure 2, the die shoe 32 may be made from a hot rolled plate by means of a planer. It is, of course absolutely essential that the, top of the lower block 58 be in a plane absolutely paral lel tothetop of the die shoe .32. After theblock 58 and channel member 34 havebeen ,welded. to' setter a shown y. wel s 1, Fi ure' t w l ed assembly isplaned on surface Hill and on the top. oj block. 5 0 in .one settingtherebyl insuring that-these surfaces are parallel. Channel irons 34 and lu may be assembledwith the die sh'oe 3'2, and'punch holder .88 respectively by means of s rew and owe esa E 'Th P 1.- face ,of the lower b lo ck 58, continuing to refer to Figure 4, will be parallelto the fplarie of the top of the die shoe and may be used as aba'se for bt nin a su p rt t the re f fpuhqh pr whi h, will. result in the sub-press occupying a nolmalh rizontal position.

l .Y Ihe foregoing is a disclosure I of the general idea of several featuresv of applicants invention. It will be-understood that fundamentally the'lack of anon-rigid connection'betw'een theram and 7 the topof the punch plate eliminates th messity. of maintaining exact alignment of the rain during its reciprocating vertical movement. By separating the punch plate frorn'the ratinfmbieover, the employmentof bolster plates has been eliminated with the resultthatjtop of applicant's punch plate is expos d and 'protrudingiscrew' headsmay be ,used, for'hold'ing punch plates to t r n hholder wi h.;t fo unat e li t h anelate mayjbt. e'i cved rm "applic nts "s5 while the s'ubgpress remains mounted ingl pr s; brake. Certain improvements in stops"forprotecting-'the"'flexible' leaf have been discloseqfa efnas a l; bf-press which ma 'be In'atiefrdm hot rolled plates and channel or 'angle stook'withgreat accuracy 'with' the type'of tools that almost every" machine sho'p' possesses. a e

A gr "at advantage" of the sub-press disclosed here" for'the first time by applicant-lies :in the fact. referring Figure" 2,that the dieishoe 32 and the lower channel member 34 areidenticaL in weight 'arid 'stre'ngth with the punch holder .48 and=upper channel member 48. This construction'differs fromv that. disclosed in applicant's is: sued Patent No. 2,2,60,183and in applicants co pen'ding' application Serial No. -;394,97 ,1 .1 hittii thosestructures the lower arm. or leaf of appli; cantfs sub-pressgwas much heavier ,and consequently. p po ionately .ore flei hl than 1 the u per member. n.. e ese iqlifi iuetionthey are equally inflexible with the result that, re-

ferring to Figure :6, where the off-center loading forwardly of the ram force I64 is very great so as to slightly bow the upper channel member 40, a like reverse bowing will occur in the lower channel member '34 with the result that the-bot-v tom of a punch depending from the punch holder 46 will be moved outwardly of its original position to exactly the same extentas will the top of its associated die member mounted-n the die shoe 32. This result would not obtain where the upper channel member 40 is substantially'lighter than the lower channel member 34. Under such circumstances, the upper channel member 40 would bow much more than the lower channel member 34. The curved lines I98 and I98 in Figure'6 exaggerate the degree of curvature of the channel members 40 and 34 that may occur. In Figure 7 the curved lines 200 and 202 similarly exaggerate the inward bowing that may result where the load represented by the force I80 is disposed behind "the ram represented b the force l64.-

One of the" major advantages of applicants sub-press over the conventional leader pin die set as' used inpress brakes arises from its aligning means which does not incorporate leader pins or bushings. The capacity of a leader pin and bushing to hold a'punchholder and die shoe in alignment in the case of off-center loading of the punches is additionally conditioned uponthe ac-' curacy of the alignment of the ram to which the punch holder in the conventional leader pin die set is afiixe'd. When the slides and ways'which guide the ram in its vertical course permit a great deal of play, the aligning load is transmitted to the leader'pins. When these leader pins are not constantly oiled and even when oiled, when the ram is greatly out of alignment, the leader pin will jam in the bushings, will force the bushings out of the punch holder and in somecases will destroy the punch holder. leader pins is primarily'res'ponsible through the little use currently of leader pin die sets in press brakes. It will be understood that applicant is at present employing conventional means for removing slugs from the dies. In Figure 2 dotted lines through the'die shoe from the two forward dies indicate a vertical and a sloped discharge slot. ways for removing such slugs.

,Having thus described my invention what I desire to claim as new and useful is: V

1. A machine of the character described comprising a frame, a bed for supporting a die shoe, means supported on the frame for holding a punch holder. above the die shoe and movable along an arc toward the die shoe, areciprocatable ramnormally spaced above said unch holder and engageable therewith for causing said punch holder to approach and ,withdraw from said die shoe, and means responsive to the movement of the ram toward its normal position for moving the punch holderv away from the die shoe for facilitating the insertion of a work piece.

2. A machine of the character described comprising a frame, a bed, a sub-press disposed on said bed, a ram spaced from said sub-press when the ram is in normal position, means forreciprocatingsaid ram so as to cause it to strike and close the sub-press, and an elongated bar disposed between the ram and the sub-press for transmitting the ram force to the sub-press whereby the upper surface of the sub-press is exposed.- y

In conventional practice there are other,

of the reciprocatable ram; and a narrow bar hav- This action of the 1 ing a lengthapproximating one dimension of the tool carrying member and disposed between the ram and the tool carrying member for transmittin ram force to the tool carrying member, whereby the upper surface of the sub-press is exposed. a I

4. A machine of the class described comprising a frame, a bed, a punching zone above said bed, a tool holding member having a free end adapted for holding tools positioned in said punching zone, and its other end mounted on said frame outside the punching zone, means for per-:

mitting'the free end of said tool holding member to rotate through a limited arc toward the bed about a substantially fixed axis, a reciprocatable ramnormally spacedly positioned above thefree end of said tool holding member, and'a com-' paratively narrow striking bar substantially parallel to said axis positioned between the ram and thetool holding member. I

-5. A machine of the class described comprising a frame, a bed, a punching zone above said bed,"

a tool holding member having a free end adapted for holding tools positioned in said pu'nchingzone; and its other end mounted on said frame'outside the punching zone, means for permitting the free end of said tool holding member to rotate through a limited arc toward the bed about a substantially fixed axis, a reciprocatable ram normally spacedly positioned above the free end of said tool holding member, and a comparatively narrow striking bar suspended from said ram parallel to said axis for engaging the top of: the

tool holding member whereby the resulting com paratively small surface engagement between the striking bar and the tool holding member will confine distortional forces moving in directions not parallel to the ram motion to the tool holding member. I v

6. A machine of the class described comprising a frame, a bed, a punching zone above said bed, a tool holding member having a free end adapted for holding tools positioned in said punching zone, and its other end mounted on said frame outside the punching zone, means for permitting the free end of said tool holding member to rotate through a limited arc toward the bed about a substantially fixed axis, a reciprocatable ram normally spacedly positioned above the free end ,of said tool holding member, a comparatively narrow striking bar substantially parallel to said axis positioned between'the ram and the tool holding member, and means connecting the-tool holding member to the ram for raising the tool holding member as the ram approaches its normal po-, sition.

7. A punch press comprising a frame, a bed, aram, a punch holder disposed beneaththe ram and having portions projecting beyond opposite sides of the ram,the tops of said portions being exposed, and means accessible from the exposed top of said portions for removably holdingpunchmg tools to the punch holder, whereby the. punching tools maybe removed from the punch holder without removing' 'the' punch-holder frombeneath theram.'- a "-8. A punch'pressi-comprisingia frame, abed, a ram, a 'punchholdrdisposed beneath the ram and having portions projectingbeyondopposite'si'des of the ram, the tops of said portions being exposed," holes through aid exposed portions of the punch'holder and means disposed in said holes for holding unching toolsto'thepuncn holder, said means being removable from above whereby a punch may be accurately positioned in the punch holder by accurately positioning it in a punch plate.

10. A sub-press comprising a pair of spaced tool holding members afllxed to each other along one side, a flexible member disposed between said tool holding members near the point of said amxation, whereby the free side of said spaced members may be moved toward each other to define a punching zone, and means for limiting the flexing in said flexible member so as to hold the bendin of the leaf at any one point below its elastic limit.

11. A sub-press comprising a pair of tool holding members disposed in spaced relationship, said spaced relationship being maintained by a flexible leaf member having one side attached to one tool holding member and the other side attached to the other tool holding member, and limiting means for positively limiting the amount of bending of the leaf to a predetermined safe point,

12. A sub-press comprising a pair of spaced tool holding members, said spaced relationship being maintained by a flexible leaf member having one side attached to one tool holding member and the other side attached to the other tool holding member, limiting means engageable with the opposite surfaces of the leaf for limiting the degree of bend per linear unit to a point below its elastic limit, and stop means for positively stopping bending of said leaf after a selected degree of bending has been attained.

13. A sub-press comprising a pair of spaced tool holding members, said spaced relationship being maintained by a flexible leaf member having one side attached to one tool holding member and the other side attached to the other tool holding member, and stop means for positively stopping bending of said leaf after a selected degree of bending has been attained.

14. A sub-press comprising a base tool holding member generally horizontally disposed, a block on the upper side thereof, a flexible leaf having one end mounted on said block and disposed in a substantially horizontal position, a second tool holding member having one end aflixed to the free end of said flexible leaf so that the free end of the second tool holding member will be disposed adjacently to the free end of the first tool holding member, a limiting member mounted on top of the flxed end of the leaf and having a curved surface extending from contact with the leaf. upwardly androutwardly in, thedirection of Q the free end of the deaf, wherebythe free end of the leaf I if: :nioved upwardly contact the .urvedsurface and: eliminate excessive bending at any one point in'the flexiblezleaf, and :a'. sec 0nd limiting member'imounted beneath-"the free end of the learan'dhavii'ig a curved surface-extending from contactrwiththe leaf downwardly and inward-lydn therdirectionof the fixed-end'of "the leaf substantially underneath :the' nrststop,

whereby flexing of the leaf 'willabe held "within tiie curvedsurfaceomhe stops. -1

15. A sub-press comprising a punch holder and a die shoe maintained in facin spaced relationship, said spaced relationship being maintained by a plurality of substantially rigid arms extending from one side of the punch holder to predetermined points, a like number ofarms extending from the same side of the die shoe adjacent to said predetermined points, and a like number of aligned flexible leaves joining the end of each punch holder arm to the complemental die shoe arm whereby movement of the punch holder toward the die shoe will establish in the flexible leaves a plurality of fulcrums lying substantially in a single axis.

16. For use in a conventional power press brake, a sub-press comprising a die holding means having a width approximating the breadth dimension for the work of the pressbrake in which the sub-press is to be used and a depth dimension substantially exceeding the depth dimension of the bed of the press brake so that said subpress die holding means when positioned on the press brake bed will project forwardly and rearwardly thereof, a plurality of arms extending from one side of said sub-press die holding means to predetermined aligned points, punch holding means above the die holding means and of similar dimensions, a plurality of arms extending from one side of the punch holding means so that their ends are adjacent to said predetermined aligned points, whereby one arm attached to the punch holding means and the adjacent arm attached to the die holding means may be considered as a pair of complemental arms, and means joining the free ends of each pair of complemental arms for holding the same in said assembled relationship and for permitting movement of the punch holding means toward the die holding means, said plurality of means being in substantial align-v ment so that the punch holding means and die holding means may be moved toward and away from each other along an arc.

17. A sub-press comprising means for holding punches, means for holding dies, a plurality of substantially rigid arms extending from one side of the punch holding means to predetermined points lying in transverse alignment, a like plurality of arms extending from the die holding means to points adjacent to such predetermined points whereby one arm attached to the punch holding means-and the adjacent arm attached to the die holding means may be considered as a pair of complemental arms, and a like number of joining means connecting the free ends of each pair of complemental arms at said predetermined points and for permitting movement of the punch holding means toward and away from the die holding means in an are about said joining means.

18. A sub-press comprising a punch holder and a die shoe maintained in facing spaced relationship, said spaced relationship being maintained by a plurality of substantially rigid arms extending from one side of the punch holder to predetermined vpoints, a like number of arms extending' from the same side of the die shoe adjacent to said predetermined points, a like number of aligned flexible'leaves joining the end of each punch holder arm to the complemental dieshoe arm whereby movement of the punch'holder to- Ward. the die shoe will establish in the flexible leaves a plurality of flexing points lying substantially in-a single axis, and means for positively limiting the degree of bending of each of said aligned flexible leaves.

19. A sub-press comprising a pair of tool holdingt members disposed in facing relationship and

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