US2491279A - Safety overload pitman for power presses - Google Patents

Description

D 13, 1949 D. A. ROGERS l-:TAL 2,491,279

SAFETY OVVERLOD PITMAN FOR PWER PRESSES Filed June 25, 1947 5 She'ets-Sheet 1 WENTORS DAYTON/I. Rocas/es Hei AT-rO/vrf.

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De@ 13, 1949 D. A. ROGERS Erm. 2,491,279

SAFETY OVERLOAD PITMAN FOR POWER PRESSES Filed June 25, 1947 5 sheets-sheet 2 Hes /M/ENTOES DAYTaA/A. ROGERS oHN 7T GONDEK Dec. 13, 1949 D. A. ROGERS ,EAL '2,491,279'

SFETY OVERLOAD PITMAN FOR POWER PRESSES vvENmes DA YToN/l. Ro GERS y JOHN 7'. GONDEK Avg/VE Yr Dec. 13, 1949 D. A. RQGERS ET AL l 2,491,279

SAFETY OVERLOAD PITMAN FOR POWER PRESSES l Filed June 25, 1947 5 Sheets-sheet 4 F/e. v

/NvE/vTa/es 02h/70N A. Eos/SES JH/v 72 GOA/DEA Dec. 13,1949 D. A. Rosa-Rs E rAL y 2,491,279

SAFETY OVERLOAD PITMAN FIOR POWER PRESSES Filed June 25, 1947 s sheets-sheet 5 ResERV/R 4- JOHN 60A/DEM Arrone/V536' Patented Dec. 13, `1949 SAFETY OVERLOAD PITMAN'FOR POWER PRESSES- Dayton A. Rogers and John T.Y Gondek, Minneapolis, Minn., assignors to Dayton Rogers Manufacturing Co., Minneapolis, Minn., a corporation of Minnesota Application June 25, 1947, serial N o. 756,966

8 Claims.

This invention relates to new and useful improvements in power presses and more particularly to a novel pitman for such presses having means embodied therein for automatically permitting the overall length of the pitman to shorten in the event the press is momentarily subjected to an overload, thereby to prevent damage to the press, die members or work. y

In the operation of power presses, particularly of the larger sizes wherein the work often requires a working pressure of from thirty or more tons. serious damage may sometimes result to the press, die members or the work in the event the press is momentarily subjected to an overload. If the overload is of such a nature that the press ram cannot force the die members into their proper co-acting relation, then in a conventional press, it is obvious that something must give Way, because the inertia of the usual y wheel of the press in conjunction with the power supplied thereto to operate the press may be suicient to carry the crank through its working cycle, even though the working movement of the pitman may be momentarily interrupted as a result of an overload.

Obviously, when such a contingency arises, one

or more of three things may happen: the press crank shaft may be sprung or broken; the side frame members of the press may crack; or the die members and work may be crushed between the ram and bed plate. Such damage to the press and other parts may be expensive, because in addition to the cost made necessary by the required repairs, many man hours may be lost during the period the press is inoperative for such repairs. It is therefore highly desirable that means be provided whereby each time the press becomes momentarily subjected to an overload, the pitman may readily shorten, when a predetermined maximum safe pressure is reached, thereby positively preventing damage to the press or die members.

The present invention therefore, pertains more particularly to a safety mechanism which may readily be embodied in the pitman of a power press, and which is so constructed that it may quickly be adjusted to any desired safe working pressure or tonnage commensurate with the maximum press capacity, and to protect any given set of tools or dies from damage in the event the press is subjected to an overload, which may occur from various causes well known to the trade, the overall length of the pitman automatically relatively shortening when the load on the pitman exceeds a predetermined safe maximum pressure, thereby automatically relieving the press, dies and tools of dangerous excessive pressure and assuring that no damage can come to the press or its tools or die members as a result of an overload momentarily being imposed on the press.

. A further object of the invention is to provide a safety pitman for power presses comprising a' cylinder having means for mounting it on the usual Vcrank of a power press, and a piston being' non-rotatably supported in said cylinder and adapted for limited axial movement therein wherebythe overall length of the pitman may shorten when the press is subjected to an overload, the inner end cf the piston cooperating with the adjacent wall of the cylinder to provide a high pressure fluid chamberV having a suitable over- V load valve in communication therewith throughV which a portion of the pressure uid in said chamber may escape when a predetermined overload pressurevis imposed on the pitman.

,'A further object is to provide a safety overload pitman for power presses comprising a cylinder having a piston mounted therein with its inner end normally spaced from the adjacent end of the cylinder to provide a pressure chamber having av power presses comprising relatively movable parts in the form of a cylinder and piston, the inner end of said piston being normally spaced from the adjacent end of the cylinder and cooperatingtherewith to provide a high pressure fluid cham- Iber adapted to contain a pressure uid for normally holding the piston in a relatively fixed position within the cylinder, an overload valve being in communication with said chamber for releasing a portion of the fluid therefrom when the pressure in the chamber reaches a predetermined gure, and a pump being mounted on the piston and operable by rotation of the crank shaft to constantly pump fluid into the chamber and thereby maintain a predetermined safe working pressure. therein.

A further object is to provide a safety pitman which readily lends itself for use on conventional presses, and by the use of which a constant ram pressure is assured at the point of operation regardless of stock thickness Variation on suon operations as Iorming, pressing, riveting, briquetting or assembling various parts.

Other objects of the invention reside in the unique construction of the pitman which, it will be noted by rererence to the application drawings, is extremely simple and inexpensive, and substantially all of the working parte of the safety mechanism are mounted directly upon and carried by the pitman; in the arrangement of the high pressure pump provided for constantly pumping fluid into the high pressure chamber thereby to maintain a constant predetermined safe working pressure therein which may readily be varied to suit each particular job; in the provision of the overload valve which functions only in the event of a predetermined overload being imposed on the piston whereby it permits a portion of the fluid in the pressure chamber to return to the fluid supply reservoir; in the unique construction of the overload mechanism which comprises a unitary structure in the form of a rectangular body comprising suit-V able uid passages, a reservoir, a pump for continually pumping fluid into the high pressure chamber in the cylinder, an overload valve, and other associated parts necessary to provide a unitary structure which may be assembled independently of the pitman and subsequently mounted thereon whereby said body becomes in effect an integral part of the pitman, the unique construction of said body being such that it may b e quickly detached from the pitman to facilitate making repairs or inspections of the parts thereof without disrupting the mounting of the pitman;l in the provision of a safety pitman which may be easily and quickly installed on any conventional punch press, whereby definite hydraulically controlled power on the press ram is assured at lall times; and which p itman requires little or no servicing when in use.

Other objects of the invention Will appear from the following description and the accompanying drawings and will be pointed out in the annexed claims.

In the accompanying drawings there has been disclosed a structure designed to carry out the various objects of the invention, but it is to be understood that the invention is not confined t the exact features shown, as various changes may b e. made within the scope of the claims which follow.

In the drawings:

Figure l is a view showing a portion of one side of a conventional power press with the invention embodied therein;

Figure 2 is an enlarged front view of the pitman and also showing a portion of the crank shaft of the press;

Figure 3 is a vertical sectional View substantially on the line 3-3 of Figure 2, showing the pressure chamber between the pitman cylinder and piston;

Figure 4 is an enlarged detail sectional view on the line 4 4 of Figure 2, showing the overload valve and associated parts;

Figure 5 is an enlarged detail sectional View on the line 5-5 of Figure 2, showing the pump for constantly pumping fluid into the pressure chamber during the operation of the press, and also showing the check valves in the uid passage between the pump and the pressure chamber in the pitman;

Figure 6 is an enlarged detail view substantially on the line -G of Figure 3;

Figure '7 is a top view of Figure 6;

Figure 8 is a sectional plan View substantially on the line .ee-3 of Figures 4 and 6;

Figure 9 is a similar View substantially on the line Q of Figure 6;

Figure 10 is a perspective view of the improved safety overload pitman removed from the press;

Figure 1l is a detail sectional view on the line H-Il of Figure 4; and

Figure 12 is a schematic drawing showing the interconnections between the various elements of the fluid circulating means.

In the selected embodiment of the invention herein disclosedY there is illustrated in Figure 1, for purposes of disclosure, a portion of a conventional power press comprising the usual frame 2 having a crank shalt 3 mounted in suitable bearings provided i-n the upper portion thereof. The crank shaft has a crank si to which the upper end of a pitinan, generally designated by the numeral e, is pivotally connected.

The frame 2 of the press is shown provided with a suitable bed plate il to which the usual bolster plate i is secured, as is well known. A lower die member 8 may be secured to the bolster plate in the usual manner. The frame of the press, including the bed plate and the usual die cushions, form no part of the present invention, and it is therefore believed unnecessary to further illustrate the press frame in the application drawings.

An important feature of Athe present invention resides in the means embodied in the pitman 5 whereby should the press accidentally be subjected to an overload, the pitman will automatically shorten in overall length, whereby the crank shaft may go through its usual cycle of operation without causing any damage to the press frame or the usual die members or tools or" the press.

To thus prevent an overload irom causing damage to the press frame or other equipment, the pitman 5 is shown comprising two members; one, in the form of a cylinder Sl, shown having its upper end secured to a suitable split bearing Il by bolts Il. The bearing il is adapted to receive the usual crank l of 'the crank shaft 3, as Will be understood by reference `to Figure 3.

The lower member lil of the pitman comprises the usual ball l2 adapted to be seated in a concave bearing I-S of the usual ram l of the press and retained therein by a ball nut I4, received in threaded engagement with the ram, as will be understood by reference to Figure l. The ram l5 is vertically slidable in the usual guides provided in the side frame members of the press, as indicated at i6 in Figure l, and may be of conventional construction and therefore yneed not be further described.

The upper end of the lower part l0 of the pitman is in the form or" a piston il which is slidable in the cylinder 5 and its lower end i3 arranged to engage an annular abutment i9 to thereby limit the movement of the piston Il' in a downward direction. The piston is shown provided with a tubular extension 2| which is guidingly supported in an opening 22 provided in a retaining cap 23 secured to the lower end of the cylinder. The retaining cap 273 serves as the abutment le for limiting downward movement of the piston within the cylinder. The tubular extension 2l of the piston is shown internally.

threaded, as indicated at 24 iny Figure 3, to receive a threaded shank 25 to the lower end of which the ball I2 is secured, and whereby the effective or working length of the pitman may be varied by relative rotation between the shank 25 and piston l1, as will readily be understood by reference to Figure 3.

A split lock ring 26 is shown fitted onto the lower reduced end portion 21 of the piston extension 2| for locking shank 25 in adjusted position relative to the piston |1. It is to be understood also that the reduced end portion 21 of the sleeve portion 2| is split in an axial direction to permit said portion to be contracted into rm contact with the threaded periphery of the shank 25, thereby to prevent it from relatively rotating therein, when the press is in operation.

To prevent the piston |1 from relatively rotating in the cylinder 9, a suitable screw 28 is shown received in a threaded aperture provided in the wall of the cylinder. The inner end of the screw 28 projects into an axial groove 29 in the periphery of the piston, as shown in Figure 3, whereby said terminal will prevent the piston from relatively rotating within the cylinder. The overall length of the piston |1 is such that when the lower end of the piston is seated against the abutment I9 of the retaining cap 23, a pressure chamber 3| is provided between the upper end of the piston and the adjacent walls of the cylinder 9, as clearly shown in Figure 3.

An important feature of the present invention resides in the novel construction of the pitman 5, shown in Figure l0, whereby should the press accidentally become overloaded from any cause whatsoever, during the working cycle of the press, the length A of the pitman will automatically shorten and thus relieve the press frame and the die members of excessive damaging strains. To thus relieve the press of an overload, a suitable inelastic fluid is retained under a predetermined pressure in the chamber 3| of the pitman.

Fluid is supplied to the chamber 3| from a reservoir 33, shown provided within an upright member or body, generally designated by the numeral 34. This body, which preferably is constructed of metal, may be 4suitably secured to the front face of the bearing bracket of the pitman by suitable bolts 35, indicated in Figures 4 and 6. The construction of the member 34 is important, in that it contains al1 of the working parts and substantially all of the uid conducting passages and ports required to automatically direct the pressure fluid to and from the pressure chamber 3|, each time the pitman is actuated to prevent an overload from momentarily being imposed upon the press frame or working parts thereof.

To prevent overloading the press, a novel overload valve, generally designated by the numeral 36, is shown mounted in the reservoir 33 and comprises a tubular housing 31 having its lower end portion received in a counterbore 38 provided in the bottom wall of the reservoir 33, as best illustrated in Figure 4. The lower portion of the housing 31 has an annular collar 39 suitably secured thereto shown seated on the bottom wall of the reservoir. The upper end of the housing 31 is preferably internally threaded as shown at 4| to adjustably receive a threaded plug 42. The plug 42 has a reduced cylindrical portion 43 extending upwardly through an aperture 44 in the top wall or cover plate 45 of the reservoir, and through a suitable clamping ring or collar 41 of the plug 42 is squared or flattened to receive a suitable wrench to facilitate rotating the plug 42, when it is desired to relatively adjust the overload valve, as will subsequently be described. The clamping ring 46 is so constructed and secured to the top wall 45 of the reservoir that it may readily be manipulated to iixedly secure the plug against rotary and axial movement by manipulation of a clamping screw 43, shown in Figure 4.

Movably mounted Within the tubular housing 31, directly beneath the plug 42, is an abutment member 49 shown supported against upward movement by an anti-friction element or ball 5| interposed between the adjacent ends of the plug 42 and abutment member 49, as best illustrated in Figure 4.

A suitable spring 52 has one end seated against the lower end of the member 49 and its opposite end against a collar 53 provided on a needle valve 54 having its lower end normally closing an aperture or duct 55 adapted to establish communication between the interior of the housing 31 and a horizontal bore or fluid passage 56 provided jointly in the lower intermediate portion of the body 34 and bearing bracket as best illustrated in Figure 4. The needle valve 54 may be integrally formed with the collar 53, and has an upwardly extending stem 51 passing through the spring 52 and having its upper end guidingly supported in a socket 58 provided in the abutment member 49. The cylindrical wall of the housing 31 is provided with opposed openings 59 which preferably extend upwardly from the annular collar or flange 39 to the intermediate portion of the housing, as illustrated in Figure 4.

The horizontal fluid passage 56 is in communication with the pressure chamber 3| in the pitman through an upright passage 6| provided in the upper wall 32 of the pitman cylinder and in the lower portion of the bearing bracket as best shown in Figure 3.

Provided within the lower portion of the body 34 is an upright bore 62, the upper end of which is in communication with the reservoir 33 through a suitable filter screen 63. The axis of the bore 62 preferably intersects the axis of the horizontal fluid passage 56, as will be understood by reference to Figures 4 and 8.

A valve device, which will hereinafter be referred to as a bleeder valve 60, comprises a body 64 shown suitably mounted in the member or body 34, as best shown in Figures 4 and 8. A spring actuated valve 65 is provided in the inner end of the body 64 of the bleeder valve60,andnor mally loses an opening 66 leading from an upright passage 61 in the valve body 64 to the horizontal fluid passage 56, through an apertured plug 68 shown received in threaded engagement with the inner end of the body 64 of the bleeder valve 66. The ball valve 65 of the bleeder valve 66 is normally retained in closed position and is adapted to be unseated by a stem 1| provided on the inner end of a threaded stem 12 having a knurled head 13 to facilitate rotating said stem.

The valve 56 serves as a combination bleeder and filler valve to facilitate initially iilling the system with fluid, and to drain the fluid from the system, when necessary. Normally, the inner reduced stem 1| is out of engagement with the ball valve 65, as shown in Figures 4 and 8. When the system is initially lled with fluid, the threaded element 12 is manipulated to unseat the ball valve 65 from its seat, whereby fluid de- 46 secured to the cover 45. The uppermost end 75 livered into the reservoir through the filler openaulo 1527.9

i'ngfor'JCuplk-shown 'finfY Figure flu-maw readily iiow into all l ef?4 the' duetsand-'luidlpassages lprovided ing the composite? pitman, whieh includes the cylinder' il,y piston'l A1;ibearingfbracketll and upright bodyi34.

l`Another*importantA feature of the invention resides iin the provision of fmeans-forfmainta'ining the-fluid in the 'chamber 3l c-fata constant predetermined pressure -duri1'ig'-rtlfiel opera-tion -lof the press. To accomplish this, a suitable pump,igen era'Ily' 'designated sby the Y Ynumeral =1 5 *is shown mounted in a boref lily-provided' infthe 'b'o`dyi34, as bestfillustratedfin Figures-"5 and 9. "Thel'pump isfslf-'contain'ed and'compri's'esa tubular member '16 having' 'a reduced portion 1'! -iat 'its 'lower ende which yis exteriorlyI threaded' to' receive a' retaining member 78 which detachablysecures, what may -be' termed a" 'cy'lin'der l79;- to the'lower erfdofthe member 'lgfas 'illustrated-'in 'Figure 5.

8 I into'l the' lower end ofwhi'ch'- thegupperportion of thecylnder'f'lil -is tt'ed tdprovideenannular seat for'on'e end of a suitablespring'82. The upperfend offspring'SZ 'is seated againsttan outwardly 1directedv flange'83' 'l'orovided-atv the'upper end"Y ofi a cup-shaped ime'n'i'ber v 811 which provides as'uppo'rt for" the vupper venlarged head1'85 Poffa piston 86 thai/'ing 'itslower endf'r'eceived 'in `the cylinder' 19.

A shouldered Aplug ``8|"is mounted :in thet upper end of .thebore'l*iny the lmember"lil-'land hasfa reduced cylindrical "portion "88 which projects through a guide openi'ngf'SSfin the upper 'end of the memberil, asfshowninFig'ure'B. 'A' coupling pin 8|' isA shown vhaving'one end'enga'gedwith the head 85 of the piston 'and' 'itsv'oppo'site end is seated "in the'bottom of 'a bore 921p`rovided in the plugf'. The'fdepth' of the boie'92`fis'isuch-'that the 'lower'endiof the plug '81- is spaced slightly from'the upper end Iof the c'upsha'ped'4 member 84, whereby the A"action 'of -the spring *'82 will constantly exert an upwardthrustflon'the'coupling pin 9|,'thereby retaining the ycylindrical endfportionSS ofZ the plug l8l 'inlitsi n'orn'iall elevated position, t'shown ini Figure l5. 1A 'shoulder &l3"atthe upper `end of thef'fbore-'S'I'rl'imitsthe upward` movement' of' the-plug' las will'- beVA understood. I

The tubular member or-cas'ingli'of the/'pump is secured in -iixed position "within 'fthe 'bore "FG byisuitable screw threads '94. Y`Suitable packings Sii are'provided wherevernecessarytc preventI leakage of the fluid around andffbe'tween 'connected parts of-the..apparatus.

'Thexlower reduced-end portion 'of ther ey'linder 'i Q isreceived in fa 'stepped bore "56 fwhich 'is in communication with ythe 4interior'of theA lower' end of they cylinder'S and with 'one `en'dfof a'fduct-'Siy sl'iowni in" full lines inf Figure 'an'd' indicated 'in dotted lines in 'Figure 9. The "o'ppositeen'd'fof the duct IV$3 'I I is in' communication 'witha 'multiple stepped boref98 in which two checkfvalvesi9'9fa'nd l are "mounted The'- check valve f'99is'-s'up ported in a suitable cage 'or-fplu'glilZ -whichis secured in' the lrelatively"'largerel portion' l'3 of`the'bore-98fby suitable"threadsV |04. A- suitable packing' |135 is shown'interposedbetweenthe plug |82 anda shoulder m6 top'revent possible leakage of the'fluid from thebo're`98 around the valve cagefor body |02. y

*A uid duct |07 in lt'he'lower-portion of the valve body |02 is normally cl'osed at-its'upper end by the clieckvalve 99, andf-thelower enfdof said fduct 'isfin oommunicatn with' crossf'ducts -|08,provided in thefplu'g |82. 'The'plgf-isaniularly L'groov'ed, 'fas shown wat '109 to .establish communication Ebetween fthe? ends of A'the cross ducts T183, vas will' be understood. The annular groove'l |19 isin communieationwith one endv 'of adu'ct" I,y the opposite 'end ofwhich connects 'withtheupright bore, Aas best indicatedin Figures 5 and 9. The checkvalvef's normally retainedupon itsr seat4 by a-su'itable compression spring H2, lthe -upper en'd y'of "which'is r'seated againstlf'a nutf||3 having "a 'u'id passageHll therein.

The check tvvalve 0 YisE AInormally positionedto close'the "intakeE |`|5 fprovided" in the Ylo'vve1^`?er'id of`a valve cage'Hfnountedfinthe bore 98 and havirga' reduc'edl-prtion received inthreasde'd engagement i with the''b"ottom''vwall portion' ofl` the bore 98, asfsliownatll'l'iniligure. Aspr'ing ISf'eonsta-ntlyurges the check `valve finto closing engagementi-withthe"duct H5. Thefupper end-'ofthespr'ing is shown engaged'wifth-''a suitable nut I lhaving an openingv |2| there'infor establishing leommunication between the valve chamber 4and asuetion passage |22, the upper end of which isSlIoWn-incommunica-tion -witha horizontal passage |23 connecting Itlhefduct' |22 with'the horizontal bore lleadingto the pressure chamber@ To eliminate any possible danger 4of the pressure in the chamberll dropping-#below'a 'predetermined figure lduring thel normal -operation of the press. which may occurasa result'of `leakage,'-'mea-ns` is -provided for 'intermittently actuating the pump piston'S-each'cycle of the press, and is shown -comprisingf'an' arnfv 24' mounted for rocking movement upona suitablepivot |25. The arm |213 AhasfanantiLfrictionv roller or wheel |26 mounted thereon adapted tofbefl engagedibyf-a cam |21' carried by the'L crank YshatS, asclearly illustrated in -Fgure -v3. The f cam |21 engages |:lf'le"'wheelE |26 once ea'chfrevolution of'ftlieeiank shaft, --andthereby os-eil-l-ates the'a'rmfabout its pivot 25,411@indicatedbythe-fu11 4and. dotted. lines-lin Figure 5.

Such oper-ation of the arm" |25 intermittently tuates'the -pumpfplunger 88, which intlirn acti-iateslthe pump lpiston' 86 whereby va small quantityfof iluid -is pumped Yinto fthe, pressure ehemberi 3 I 'of 'the reservoir, each cycle' of the erank;-whieh'fiwfillA eompen'sate for'la-ny leakag'eiof the 'fluidib'etween any -of "the operating `parts-of the uid 'circulatorysystein i Shouldthe v'operating parts of the ap'paratusbe` s-uiciently leakproofto preventany material drop-in pressure in the Vchamber'fi ,I itl maybe foundl unnecessary to-operatethe pmnp-each cycle-fof the -crank. This may-read-ilyebe accomplished lby removal ef thecamZ'l fremth'e crankshaft. lInv-actual operation, however, it has been found moref'practicalto operate-the #pump Vwith the cam- |21," 'because -the'nthe operator `'isI assuredl ofi-a' working pressure-being-maintained inthe chamberL'S hat all times 'during normaltoperationof the press. TheI arm I 24-preferably has -a'reduced portion |28 which maybe'conveniently/grasped by the operatr-'When it is deemed advisable to -manuallyact'uatey thepump, as vwhen initially filling the fcirculatory system ofthe-apparatus 4'with Vfluidjjand which may be required periodically; s'houldl the press be operated with the cam |21, as above stated.

Toaiord aclearer--understanding of the opera.- tion olL the novel-hydraulic overlead Ypitman `hereinfdisc'lose'd, there-is-illustrated in Figure'lla schematic represen-tation :of the various voperating elements -of the-'fuid lcir'eulatoryf system'rof *the pitman shown interconnected by the various uid circulating passages and ducts hereinbefore described.

Before starting the press for a given job the fluid circulatory system of the pitman is lled with a suitable inelastic fluid which may be introduced into the reservoir 33 through a suitable ller tting 14, best illustrated in Figure 10. During the filling of the system the bleeder valve 6I) is manipulated to unseat the ball valve 65 so that the iiuid may freely flow from the bore 62 into the horizontal passage 56 of the chamber 3|. The bore 62, in effect, constitutes the bottom of the reservoir 33. At the same time the various fluid ducts in the member 34, which lead to the check valves and pump, are filled with fluid, or, at least partially lled. During the filling operation, the operator may manually operate the pump 15 by manipulation of the hand lever |28 which will cause all of the fluid control elements and the fluid circulating passages and ducts therebetween to become completely lled with fluid.

A suitable uid level sight guage |29 is provided on the exterior of the reservoir 33', as best shown in Figure 10, to facilitate lling the reservoir to the proper level. The reservoir 33 is iilled to substantially the level shown in Figures 4 and 12, to allow ample space in the reservoir to accommodate the sudden rush of fluid thereinto in the event the pitman is accidentally subjected to an overload, as hereinbefore described, and whereby the level of the uid in the reservoir will not rise above the ller tting 14. After the apparatus has been completely lled with iluid, the press may be started whereupon it will operate as a conventional press, under all normal operating conditions. Each time the crank goes through a cycle of operation, the pump is operated as a result of the cam |21 engaging the wheel |26. Such operation of the pump 15 will cause a small portion of the fluid in the reservoir to be pumped into the pressure chamber 3| which, if up to full pressure will cause the overload valve 36 to momentarily open to release any excessive pressure which may develop in the chamber 3| and the connections leading thereto. The fluid released through the overload valve is returned to the reservoir through the openings 59 provided in the tubular housing of the overload valve, as clearly illustrated in Figure 4. In Figure 12` connection 59 represents the openings 59 provided in the housing of the overload valve, as will be understood.

During the suction stroke of the pump piston 86, fluid is drawn from the reservoir 33 through the conduit check valve 99, passage S31-96, into the pump cylinder. When the pump piston 86 is next forced downwardly, as a result of the cam |21 engaging the roller |23 of the arm |24, a portion of the iiuid is forced out of the conduit 96-91 through the check valve |0| and through the passages |22 and |23 and into the horizontal passage 56, thence through the passage 5| connecting the horizontal passage 56 with the chamber 3 I.

When the pressure in the chamber 3| and the connections leading thereto from the pump and the overload valve becomes excessive, the overload valve will automatically open to release a portion of the fluid. The bore 8| in the pump housing 1B in which the spring 82 is mounted is shown having a fluid duct |3| connecting it with the reservoir 33, thereby to prevent the formation of any uid pressure in the bore 8|.

From the foregoing, it will thus be noted that for each cycle of the crank shaft, the pump 15 may be actuated to pump a small portion of iiuid into the chamber 3| from the reservoir, which will assure the operator that a predetermined working pressure is constantly maintained in the chamber 3|. Should the press suddenly become subjected to an overload, the excessive pressure momentarily developed within the pressure chamber 3| in the pitman will cause the overload valve 36 to function and automatically release the uid from the pressure chamber 3|, whereby the pitman may momentarily shorten to prevent damage to the frame or crank shaft of the press, or to the die members, during such overload. As soon as the obstruction has been cleared, normal working pressure is.

quickly restored in the chamber 3| by the pump 15, whereupon the press may again be operated in a normal manner, as will be understood.

The predetermined overload pressure at which the overload valve will release the fluid from the pressure chamber, may be varied in accordance with the nature of the work to be done, by adjustment of the upper member or plug 42 in the tubular member 31. It will also be noted that the pitman embodying the invention herein disclosed, is extremely simple and inexpensive. The overload valve, pump and check valves, are all supported within the member 34, as best shown in Figures 4 and 5, thereby greatly simplifying the construction of the fluid control mechanism. The pump operating member |24 is also carried by the member 34, as shown.

By so constructing and assembling the parts, there is less danger of the parts becoming inoperative from contact with other articles, and

it permits the entire mechanism to be .removed from the pitman as a unit for inspection and repairs whenever necessary. It also results in a very compact and well balanced pitman, as will be noted by reference to Figure 10.

It will be apparent to those skilled in the art that we have accomplished at least the principal objects of our invention, and it will also be apparent to those skilled in the art that the embodiments herein described may be variously changed and modified without departing from the spirit of the invention, and that the invention is capable of uses and has advantages not herein specifically described; hence it will be appreciated that the herein disclosed embodiments are illustrative only, and that our invention is not limited thereto.

We claim as our invention:

l. A safety overload pitman for a power press comprising complemental members mounted for relative axial movement and cooperating to pro-` vide a chamber therebetween, an inelastic pressure fluid in said chamber for normally retaining the pitman members in extended operative positions, pump means for maintaining a predetermined iluid pressure in said chamber, and an overload relief valve in communication with the chamber adapted to release a portion of the fluid from said chamber in the event of an excessive pressure therein, said pump being automatically operable to pump additional iiuid into said chamber and circulatory passages to compensate for leakage `or loss of fluid from any cause,-

and thereby maintain the fluid withinv said chamber at a predetermined working pressure.

2. A safety overload pitman for a power press comprising a cylinder having a piston operable therein, the inner end of the piston cooperating with the adjacent end wall. of the cylinder.l to form a`h`igh'pres`sure 'iiuid chamber, .an inelasticJ pressure"x fluid' in said` chamber for normally. ni'aintainingthe'pitman and "piston in extended operating positions under agiveny safe operating. pressure, an overloadvalvein connectionwith' said" chamber adapted to be openedbylexcessive pressure' in said chamber` and automatically. release'a portion of the pressure from the charnber" and permit the. pitinan' to shorten when. subjected to a' predetermined`1 overloadj. and' afor` automatically introducing. additional iiid` into' the chamber to replace uid. lost'b'y.- leakage orbyan' overload,` while the press is in" operation;

3'. In aV pitr'n'an fora power-pressa` cylinder,-V havingbearing' meansat one end fon connecting.,Y trie cylinder to` the usual crank shaft offthe press; a' pistonmoun'ted for limited'axial move-v nen't'insaidcylnderand having. means on its projecting end for"securing`a' ram. thereto,.said` pistonV normally beingsp'acedfrom the adjacent end' of the"cylind'er"to provide' a .pressure iiuid'. chamber, means carried 'by'the pitinan. andjprovidi'ng aV fluid" reservoir, an overload Valve inl communication with the`r'eservoir, a uid pump, fl'ui'd" circulatingpassages-"between the reservoi.) cliamberfand" theo'v'erload valve and A pump,- and -Iea'ns for'actuatingthe pump to pump fluidinto the' chamber -in the'cylii'd'erto maintain a con'- stant pressure therein". during". normal operation I"`l` th" press.

4'. Iri'a' pi'tma'riiona' powerpress, a cylil'iderliaviriiq"be^arl`ng means at"`orie"endl` for .connecting y the cylinder to the usualicr'ank sliaft'oflthe 1;

press; a pistonl m'oismted`r fr limited" axial move` mentf-iisa'id'cyl'inrler and"havii'g`means on its` projecting en'd for"securing'aA ram' thereto, said i pistor'rnorm'ally b'eing'spaced 'from tlie adjacent@ end oi" the' cylinder^to provideia pressure'iid" chamber; a" body carried bythepitnanand liav'# ing a` iluid reservoir; a passage" connecting, said reservoir with thechamberr" the' cylinder,' anV overload vali/'e `in`cozririunicationwith the reservoii" a id pump, a fluid." circulating. passage between the pump' and reservoir'iiaving cheek"l Valves'therein for controlling the loW of` Huid flf'OYYI" 'the' pump" to tlie" reservoir, and' meansvv 'r automatically alcl'l'latllg"` the pimilj t0" pump" fluid` into the chamber' in" the' cylinder to com"- pensa-teifor leakage-'ariditomiaiiitain a'x constant iidpressure' in said chamber" during normal' operation of the pressi 5f- I'i a; power press includin'g a crank" shaft" and a bed plate, a pitman'comprisingacyliider' having a piston mountedff'orlimited` axialmovemeriti trie'rein, oneV end` of sa'id pitma-n having means forconn'eotl'z'i'g-A it' to'v the crank sliaft and' th'aoppositeendfof the pitnia'n Having' means for coni'iectir'ig` it-tov a ram, the innerl end ofA the piston normally being'spaced from'the ad-` jacent'- eid? of the cylinder to' provide a fluidv chamber,A a' body carried by' the' pitnari andv hav'ingl' aI reservoir therein, a" iid circulating passage? coni-iectirig"thez reservoir with the chamberi insaid cylinder, ai lpump 'interposed' in said passage andi comprisii'figi anVv operating! element, an'df. means on 1 the i cranki shaft adaptedVV to'- engagesaid'elementduring Seach? cycle of f tlie'- crank shaft, l, whereby.4 theA pump is constantlyactuated" tofpumpadditional lfluid into'said 'chamber when the: press is* inl normal operation, and` means for releasing". fluid from --sa'idl chamber Whenitriepressure therein reaches a predeterminedfmaximunrfgure..

I the-cylinder and having means on'its:projectiii1gr en'dfor securing aram thereto, theinner end. oflsaid piston bei-ng.1 spaced from,v the adjacent` end vof "tlie'cylinder to provide a -iiiiidllchamberta body" carriedby, the pitrnan and4v having, a.

i, reservoirltherein, a .Huid passage` connecting .the`

reservoir'Witlitheeliamber in saidcylide'r, checkl v'a'lvesin"said:'passage,. and a pump. -ori pumping; fluidfrom the reservoir into saidf. chamber, afv Huid return' passage. between thechamber andv reservoir, and! an overload.v valve in Said returnpassage" which must be actuated l to. permit`- the 'iid' discharging from the chamber to..return:.

' to. the reservoir.

7T In" a" power press including.. alcrank.. shaft. anla .b'edfplat a pitinan comprising va cylinder: h'aviignieans fr'eormecting it to the.. crank.-y slaft; a' piston mounted lfor axial movementin the cylinder andhaving means onnitsprojectina` end for securing a ram thereto,.th`elinner.. end of" saidA piston" being' spaced from. th'e-V adjacent` end"ofthe' cylinderito providea iiuidichamber,. an elrigatedbody. carriedby. the pit'rnanand..A havi'ngga reservoir therein.. a viiuidpassagey conriectii'g'thereservoir with the chamber infsaid cylinder, checlvalves' in said .passagaa pump.

for" pumpiri'giuid* from the reservoir intdsaid.; chamber; ar fluid return passage between. the: cliamberandreservoir, an overloadfvalve .insaidi` return passage'which'must be actuated. to. per- .mit the" ui'ddischargig, from. the cylinder' toV return to' the reservoir, andsaid. overload valve. being a'd'justable:v whereby the maximum. safe.- Diessure" at which the iiuid `lis released from theu pressure"chamber;`when the pitman is subjected. to' an"overlo`adj may"b"e varied" to suitl difieren-t.A conditions.

8. A" safety" overload pitman for., a powen press. comprising axially movable members nent-cally extendeditoproivide apre'ssure ch mbe-r.. there between; an inelastic pressure fluid shamber fornormally'retainin'g saidpitinan membersH in"extended'iop'erativ'positions, Aa pump. in com-- mun'icatiorr with" a'f source o'f duid I and! withr said chamber, arrdfnie'ans 'forautomatically actuatii'ig.Y thepizr'np `tof introduce additional '.-u'id into said L chainber'- Wfil 'tl'iepres's 'is 'in operation, ,to compensate*-foriilakageor the release. of iuid from'. tllcrmber' as"- a result of' an overload.,

DAYTON A; ROGERS. JOHNT. GONDEK.

REFERENES CTE) '.l'ie: following? references. are of. record 1in*v thei ille of' this patent:

UNITED STATES" PATENTS

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