US2475394A - Link mechanism for pressure casting machines - Google Patents

Description

July 5, 1949. N, LESTER 2,475,394

LINK MECHANISM FOR PRESSURE CASTING MACHINES Filed Feb. 15, 1946 2 Sheets-Sheet l INVENTOR. NATHAN LESTER la Z ya@ E' ATTORNEYS l VJuly 5, 1949.

, N. LESTER LINK MECHANISM FOR PRESSURE CASTING MACHINES Filed Feb. 13, 1946 2 Sheets-Sheet 2 INVENTOR.

NATHAN LESTER ATTORNEYS Patented July 5, 1949 LINK MECHLNISM FOR PRESSURE CASTING MACHINES Nathan Lester, Shaker Heights, Ohio, assignor to Lester Engineering Company, Cleveland, Ohio, a corporation of Ohio Application February 13, 1946, Serial No. 647,259

(Cl. i4- 110) 4 Claims.

The present invention relates to improvements in a link mechanism for imparting the final high pressure closing movement to the die plates of a pressure casting machine. In such machines the die plates carry the mold members or die blocks in which the mold cavity is formed when such die plates are in closed position and into which cavity the material to be cast is forced under very high pressure. The die plates must therefore be held in a closed position under a relatively great force which is sufficient to withstand the casting pressure tending to open them. Heretofore, toggle link mechanisms having wedge means associated therewith have been utilized to acquire this high pressure final closing movement. However, in these prior devices the wedge means have been usually engaged only in line contact with one another except at the last instant of the nal closing movement, at which time they finally engage in surface contact with one another. Thus, even small forces applied through these Wedge means prior to the last instant of the final closing movement impart extremely high unit stresses in the engaging portions of the wedge means with the result that the wedge means will be deformed or will score or seize with one another or otherwise be rendered inefficient.

It is one of the principal objects of this invention to provide in such a toggle link mechanism wedge means which, when engaged, continuously engage one another in surface contact during the entire final closing movement, thereby materially reducing the unit stresses on the wedge means and thus minimizing the damage to the wedge means and also permitting application of much greater forces during the nal closing movement.

Another object of this invention is to provide means wherein the area of surface contact between the wedge means increases as the closing force on the die plates increases.

Another object of this invention is to provide simple means for accomplishing the aforesaid continuous surface contact without requiring the use of complex universally mounted wedge means.

Additional objects and advantages of the invention will become apparent as the following description proceeds.

To the accomplishment of the foregoing and related ends, said invention then comprises the features hereinafter fully described and particularly pointed out in the claims, the following description and the annexed drawings setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principle of the invention may be employed.

1n the drawings:

Fig. 1 is a front elevation view partly in vertical section of that portion of a pressure casting machine containing the die plate actuating mechanism, such mechanism having been operated to fully close the die plates;

ig. 2 is similar to Fig. 1 except that the die plate actuating mechanism has been operated to fully open the die plates;

Fig. 3 is a vertical cross section of the actuating mechanism taken along line 3 3 of Fig. 1;

Fig. 4 is a plan view of the actuating mechanism as viewed from the top of Fig. 1;

Figs, 5 and 6 are enlarged views partially schematic of the link mechanism just prior to commencement of the final closing movement of the die plates, and at the last instant of the final closing movement, respectively; and

Fig. 'l is a schematic enlarged view of the link mechanism clearly showing the relationship between the wedge means of the link mechanism for accomplishing the objects of this invention.

Referring now to the drawings, the machine as a whole includes a frame l which reciprocably carries a die plate 2 and which die plate, as is well known to those skilled in the art, carries a die block engageable and disengageable with a die block and die plate, not shown, nxedly mounted on the frame l. Reciprocating movement of the die plate 2 is effected by means of a hydraulic piston and cylinder assembly 3 having the piston rod portion 6 connected thereto. The piston and cylinder assembly 3 is provided with passages i and 5 and by means of suitable valves, not shown, fluid under pressure can be directed at will to either end of the cylinder to move the piston therein in opposite directions. The connection of piston rod 6 to the die plate 2 is effected through a toggle link mechanism which linkage is arranged in cooperation with the frame i to effect movement of the piston rod and die plate rapidly in unison during the opening and closing movements, but with very great relative movement during the final closing and initial opening move- 3 ments to attain the great mechanical advantage necessary in order to eifect nal closing of the die plates with very high pressure.

The toggle linkage comprises links l' and 8 pivotally connected to one another and to the piston rod 6 and die plate 2, respectively. As shown, one end of each link 'I is pivotally connected to the die plate 2 about a pivot pin 9 which passes through the link 1 and through the spaced ear portions I on the die plate. Each of the ear portions I0 has a hardened metal insert il secured4 thereto in engagement with 'a hardened metal insert I-'2 secured to each 'link 1. The faces of inserts II and I2 which are in engagement with one another are cylindriform with each pivot pin 9 as an axis. As will become-more apparent as the description proceeds, a shearing,

stress on the pins 9 will be relieved or limited by the bearing or compressionstress taken. up bythe engagement of these inserts with one an'- other. Each link 'I has a laterally projecting leg iS thereon, the end of which is engageable with a corresponding leg on the other link l to limit the pivotal movement of., the links 'l toward one another. Each link 'I is' also provided with two shelf vportions =`I`3, slidably engageable With'correspending-shelf portions I-'YI in the frame -I. A wear strip-I is secured to each shelf I3 to take up the wear between the -shelf lportions of the links r'l and the frame I.

A plurality o'f links f8' are vpvotally connected about pivot pins I1 and I8 to the links-l and to ahead I8, respectively, which head is secured to the .piston lrod. .Hardened metal `inserts 2t 'between the links fl-Jandia operate lto relieve or limit "the shearing stress-onpins I1 as described above in relation to pin eandinserts lfI and I2.

VSecured"to frame I andi to the vouter ends of linksil are 'hard'ened-metal'wedge inserts Z'I and 22, respectively. For thel present, let `it suffice to say that asthe llinks l'I'.are swung outwardly about pins '9, the insertsi. and 22` will engage one another to effect relative lmovement between the framel and the die plate f2.

As :for the .'generalzoperaition .of the .toggle linkage, letLusassumethatz'die plate 2 is fully opened asshownin Fig; .2. 1n this-positionlinks .'I are collapsed inwardly Ywith .legs .'IH'fthereof vin' engagement and 'with the shelf portions I3 of 'the links in .engagement with the Ishelf portions I4 inthe 'frame -I.; Now, if1it '.bedesired to move the die plate-2 toward the :right 'toa closed position into engagement 'with .the l'other die plate, not shown, :pistonrod 6=iscaused to be'rnoved toward the right. In :so doing, the :piston .rod 6 and die plate :2 willmove in Iunisonsby reason lof the fact that links 7 are constrained ,bythe shelf portions SI 4 'from being :swung .outwardly `by the .force appliedto the links-,28. However, as soonzas the die plate-'2 lightly :engages the other die plate and the shelf portions I3 andM vdisengage from one vanother :and v.the inserts 2| and 2 2. lare iin the position `shown 'in Fig. .5, .further movement of the piston rod i5. toward-:the right will, throughV thelinks 8, cause the :links 'I to :be swung outplate-2. .The fnalizclosjed.' `position ofpthedie plate. is .attained fwhenthe, links Tf'and-fbearerelationn 4 to one another, as shown in Figs. 1 and 6. In Fig. 6, the distance through which die plate 2 has been moved relative to the frame I during the final closing movement is indicated by the dimension line 30.

To clearly set forth the principal feature of this invention, reference will now be made primarily to Fig. 7 and also to Figs. 5 and 6 which schematically show the relation of the surfaces of the inserts 2l and 22 to one another and to the axis of pin 9. Inasmuch as the movement between frame I` and die plate 2 is relative, the following description, in order to simplify and clarify the same, will proceed on the assumption that frame I is movable and that die plate 2 is fixed. When the inserts 2l and 22 are in the position` shown in Fig. 5 and as shown in full lines in Fig. 7, the axes 23 of the cylindrical faces Z4 and 25 of the inserts are coincident but eccentric 'of' the axis 26 'of pin Si. The relative movement between frame I and the die plate is indicated in lamount land direction by the dimension 2? and the straight line 28. Thus, at the attainment of the final closing movement, axis 23 will have moved to positionA. New, in order that surface 25 will engage surface 2li in surface cer;- taot as the linkl rotates about axis 25,'it is necessary that axis 23 of surface 25 always be coincident with axis23of surface 24. From a theoretic standpoint, thiszcan be accompiishedoniy by moing vaxis 23 of surface 25' in a straight line 28 as does the axis 23 `of surface 2t. However, from a practical standpoint',fsuchcan be satisfactorily accomplished by selectingthe axis 2B along a line which is the perpendicular bisector rof y'the lim 28. In such `case,axis '2'3 of surface 25 will move in a circular 'path .29 -of radius equal to the e2- centric'ityvof the axis S23 with respect to the 2t, as the link l is 'rotated about axis 25. For

.' small amounts of vrelative movement, the clrcuiar path .2Q-Will at allv times bet veen the `limits o line 28 be so nearly straight that for all practical purposes, axesy 23 ofthe .surfaces 2li and 2:5 will be coincidentrduring movement. of the insert 22 .from'the-solidiline .position 'to the Ldotted line position. Naturally, as the ratio of the eccentricity to .the .amount of. relative vmovement approaches infinity, the path. of the axs which describes facircul'ar `path `will approach a straight line path. v

Tn "an actual machine, :thexrelative movement during the `final :closingmovement is fon Vthe order of 'only .several `thousandths lof aniin'ch iand there fore the error due vtothe theoretical noni-'c ncidence iof 'the .axes 23Y can 'be ,disregarded and it canbefconsidered, as :apractical matter, that surface 25 will 'engagesurface 24 .in'surface 'Contact throughout `its "movement v.from the solid line position to ther 'dotted line position of Fig. 7. Thus, ;it "will .be seen that as l.tim-'closing force increases', .the 'area::df'surfaees 2id 'and 25 in contact. likewise .increases .andbecause there is vsurface contact, as` distinguished from line contact, much greater forces vcan Vbe transmitted to the die plate 2 Without vcausing .damage vor excess Wear tothe inserts 121i and 22;

Other imodes of applying 'the principle of the invention may lbeuemployed', change .being made as regards 'the 'detailsdescribed,V provided the features stated in :anyfof 'the following claims or the equivalent of such .be 'employed and 'while described with particular reference to its 'use in a Apressure ycastingmachine, .it will. be understood that mylimprnyedlinkmeenanism imay 'be used y'in' fconjunction, any: mainline for f'device" wherein it is desired to impart high pressure relative movement between two relatively movable members.

I therefore particularly point out and distinctly claim as my invention:

1. In a linkage mechanism for pressure casting machines and the like, the combination with two relatively movable members of a link pivotally connected to one of said members for swinging movement into abutting engagement with the other of said members, said link and other member being formed with abutting cylindrical surfaces bearing fixed relation to said link and other member respectively, the axes of such surfaces being disposed eccentrially of the pivot axis of said link and coinciding during swinging movement of said link as aforesaid.

2. In a linkage mechanism for pressure casting machines and the like, the combination with two relatively movable members of a link pivotally connected to one of said members for swinging movement into abutting engagement with the other of said members, said link and other member being formed with abutting cylindrical surfaces bearing iixed relation to said link and other member respectively, the axes of such surfaces being disposed eccentrically of the pivot axis of said link and coinciding during swinging movement of said link as aforesaid, the pivot axis of said link lying on a line perpendicularly bisecting the line of relative movement of said members effected by swinging of said link as measured by the line of movement of the axes of the abutting surfaces of said link and other member relative to the pivot axis of said link. l

3. In a linkage mechanism for pressure casting machines and the like, the combination with two relatively movable members of a link pivotally connected to one of said members for swinging movement to a wedged position between said members, said link and the other of said members being formed with abutting cylindrical surfaces bearing xed relation to said link and other member respectively, the axes of such surfaces being eccentric of the pivot axis of said link and coinciding when said link is in a position with its cylindrical surface adjacent that of said other member and during movement of said link to a wedged position between said members.

4. In a linkage mechanism for pressure casting machines and the like, the combination with two relatively movable members of a link pivotally connected to one of said members for swinging movement to a wedged position between said members, said link and the other of said members being formed with abutting cylindrical surfaces bearing xed relation to said link and other member respectively, the axes of such surfaces being eccentric of the pivot axis of said link and coinciding when said link is in a position with its cylindrical surface adjacent that of said other member and during movement of said link to a wedged position between said members, the pivot axis of said link lying on a line perpendicularly bisecting the line of relative movement of said members effected by swinging of said link from a position with its cylindrical surface adjacent that of said other member to a position wherein said link is wedged between said members.

NATHAN LESTER.

REFERENCES CITED The following referenlces are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 494,502 Whitacre Mar. 28, 1893 638,990 Replogle Dec. 12, 1899 972,689 Gillespie Oct. 11, 1910 2,186,030 Lester Jan. 9, 1940

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