US2797455A

US2797455A - Die casting machine

Info

Publication number: US2797455A
Application number: US504593A
Authority: US
Inventors: Richard K Schrecongost
Original assignee: Koehring Co
Current assignee: Koehring Co
Priority date: 1955-04-28
Filing date: 1955-04-28
Publication date: 1957-07-02
Anticipated expiration: 1974-07-02

Description

y 1957 R. K. SCHRECONGOST 2,797,455

DIE CASTING MACHINE INVHVTOR. r RICHARD K. SCHRECONGOST BY V ATTORNEYS July 2, 1957 R. K. SCHRECONGOST 2,797,455

DIE CASTING MACHINE 3 Sheets-Sheet 2 Filed April 28. 1955 Fig.5

72 K76 ss INVENTOR. RICHARD K. SCHRECONGOST BY (bf ATTORNEYS y 957 R. K. SCH'RECONGOST 2,797,455

DIE CASTING MACHINE Filed April 28, 1955 3 Sheets-Sheet 3 IN V EN TOR.

RICHARD K. scHREcoNsosT ATTORNEYS UnitcdStates PatentO DIE CASTING MACHINE Richard K. Schrecongost, Galion, Ohio, assignor, by

mesne assignments, to Koehring Company, Milwaukee, Wis., a corporation of Wisconsin The invention relates in general to press type machines and more particularly to machines developing a force between two movable parts by means of wedges wherein meansare provided to stress the wedges almost entirely in shear alone rather than in a combination of shear and bending.

Die casting machines are a form of a press type machine wherein there is a movable platen movable relative to a frame carrying a fixed platen, and wherein the movable and fixed platens are adapted to be forced together very tightly so that injection of molten metal into dies carried between the platens will not spurt outwardly. Die casting'machines generally have some form of tie rods or strain rods to hold the fixed platen relative to a stationary frame head on the machine. The movable platen may then be moved toward the fixed platen by some force means which may include wedges. The force means exert a maximum force to squeeze together the two platens and this pre-stresses the tie rods to a given tensile stress which limits the tonnage capacity of the press or die casting machine. limit of tonnage on the machine because, if the injection of molten metal were to exceed the amount of pre-stressing, then the tie rods would stretch even further causing the dies to open and hot molten metal would spurt outwardly which would be not only detrimental to accurate die castings but also extremely dangerous to workers and observers.

When wedges are forced between some part of the frame and the movable platen to hold it in place, these wedges are generally loaded in both shear and bending, the bending moment occurring because thereis a tendency to cock or twist the wedge as well as a tendency to shear off the wedge along the line of contact of the Wedge with the frame and with the platen. This bending or cocking tendency, even though slight, need only give one or two thousandths of an inch under the injection pressure to permit spurting of molten metal out of the dies. Since the wedges must slide in order to be usable, it would be extremely diflicult to make such Wedges with sufficiently small sliding clearances to permit the sliding yet to withstand the bending moment necessary to prevent separation of the dies and consequent spurting of hot metal. i

Consequently, an object of this invention is to provide an improved die casting machine which eliminates separation of dies during injection pressure.

Another object of the invention is to provide a press or die casting machine with wedges so constructed and arranged to substantially eliminate any bending moment on the wedges.

Another object of the invention is to provide a rugged press wherein wedges are used to hold a movable platen in place and with the wedges moved by a toggle mechanism.

Another object of the invention is to provide in a' press a combined toggle and wedge mechanism to apply force This pre-stressing is the to a movable platen from a hydraulic power means with the linkage such that a long stroke is obtained with the toggle collapsed; and then as the toggle straightens, a much greater mechanical advantage is achieved on the movable platen.

Another object of the invention is to provide in a press a combined toggle and wedge linkage mechanism wherein a pivotal connection between the toggle andthe wedge provides a knuckle joint which takes the entire force of the toggle to eliminate stress on the pivot pin holding the knuckle joint together, and with this knuckle joint also taking the stress of the retractile force to pull the wedges out of engagement with the frame of the press, again without stress on the pivot pins.

Another object of the invention is to provide a press frame with longitudinal grooves in which external teeth on a sliding part may complementarily fit so that, as the sliding part moves past the end of the grooves, solid surface wedges may extend between the zigzag lines established by the grooves and teeth to provide a shear line on the wedges which is greater than the width of the Wedges and which easily may be made approximately twice the length of the width of the wedges. This zigzag line establishes the wedge substantially entirely in shear rather than in both bending and shear.

Another object of the invention is'to provide a press mechanism wherein a clamping force means acts only along a single longitudinal axis, yet the force of this force means translates a wedge and a wedge support first longitudinally for rapid movement at low values of force, and then near the final closing movements of the press the wedge is moved transversely to move the Wedge support longitudinally at a slower rate of speed and a much greater mechanical advantage.

Other objects and a fuller understanding of this invention may be had by referring to the following description and claims, taken in conjunction with the accompanying drawings, in which:

Figure 1 is a perspective view of the entire die casting machine;

Fig. 2 is a longitudinal sectional view of the wedge and toggle mechanism;

Figure 3 is an isometric view of the toggle and wedge mechanism;

Figure 4 is an isometric view of the wedge and toggle mechanism in the collapsed position; and

Figure 5 is a section on the line 44 of Figure 2.

The Figure 1 shows generally the entire die casting machine 11 which includes a clamp unit 12 and an injection unit 13. The clamp unit 12 includes a frame 15 having a frame head 16 and a fixed platen or die head 17. A plurality of tie rods or strain rods 18, in this case four in number, interconnect the frame head and fixed platen to resist separation of these two units. Ways 19 are provided on either side of the frame 15 to support the weight of a movable platen or die head 20. Holes 21 in the movable platen 20 circumscribe the tie rods 18 so that the movable platen 20 may longitudinally move along the tie rods relative to the fixed platen 17. The above described die casting machine is typical of the general form of die casting machines or presses in general, and it is thus illustrative of one form of machine which may use the improved toggle and wedge mechanism of the present invention. A wedge support 24 is longitudinally slidable within the confines of the tie rods 18, and this wedge support 24 has extending ears 25 which are slidably supported on ways 26 on the frame 15. The frame head 16 has an opening 27 which is defined by upper and

lower surfaces

28 and 29, respectively, and by side surfaces 30. The ways 26 extend within the side surfaces 30 so that the wedge support 24 maylpass within the opening 27. The upper surface ZS-has a tion.

plurality of longitudinal grooves 33 shown as two in number, and the lower surface 29 has similar longitudinal grooves 34. The wedge support 24 has external surfaces or teeth 35 which are complementary to the grooves or internal surfaces 33, and similarly, external teeth 36 are complementary to the grooves 34 in the lower surface 29. The

teeth

35 and 36 make a sliding fit with the

grooves

33 and 34, and they may or may not actually touch, as desired. In this die casting machine. 11 the weight of the wedge support 24 is carried by the ears 25 and ways 26 so that actual sliding contactbetween the teeth and the grooves is not required. The wedge support 24 may be connected to the movable platen 20 by a die adjusting screw 39 for die height adjustment to adjust the position of the movable platen 20 relative to the fixed platen 17 for a given position of the wedge support 24.

Hydraulic power means 40 provides a clamping pressure of the movable platen relative to the fixed platen. This hydraulic means 40 includes a cylinder 41 containing a piston 42 which moves a piston rod or connecting rod 43 longitudinally along the axis of the machine. A toggle mechanism 45 and wedge means 46 provide linkage be tween the piston rod 43 and the wedge support 24. The toggle mechanism 45 includes two pairs of toggle links, the first pair consisting of

toggle links

47 and 48 and the second pair consisting of the

toggle links

49 and 50. The inner ends of all toggle links are connected by a pivot pin 5110 a bearing block 52 on the connecting rod 43. The inner ends of these toggle links 47-50 have arcuate bearing surfaces 53 so that the pairs of toggle links bear against each other when the toggle is straightened as shown in Figure 3. Stops 54 are provided on the inner ends of the toggle links 47--50.

The outer ends of the toggle links 4750 are connected to the wedge means 46. This wedge means includes first and

second wedges

56 and 57. The

wedges

56 and 57 are held by tongue and groove means 58 to positively connect the wedges to the wedge support 24 but to permit sliding movement of the wedges in a vertical or transverse direc- A knuckle joint 60 isprovided between the outer ends of the toggle links 4750 and the wedge means 46. This knuckle joint includes

pivot pins

61 and 62 and includes an external arcuate surface 63 on the outer end of the toggle links which is approximately two hundred seventy degrees of arc. Each of the

wedges

56 and 57 has an internal arcuate surface 64 for complementary engagement with the external surfaces 63, with these internal surfaces being approximately two hundred degrees of arc. Of this two hundred degrees, approximately fortyfive degrees of are is provided in a pull-back surface portion 65 of the internal surface 64 with this forty-five degree are lying inboard of a point 66 at which a reference plane normal to the axis is tangent to the external surface 63. The

wedges

56 and 57 have wear plates 69 fastened thereon.

The frame head 16 has an inner surface 70 on which is mounted

wedge shoes

71 and 72. These wedge shoes may also be considered as wear plates and may be adjustable by the holding screws 73. The wedge shoes 71 and 72 also have surfaces defining extensions of the

grooves

33 and 34. Thus the wedge support 24, because of the

external teeth

35 and 36, defines first sigzag lines or

contact lines

75 and 76; and similarly, the

grooves

33 and 34 in the wedge shoes, 71 and 72 establish second zigzag lines or contact lines 77 and 78. When the toggle mechanism 45 is expanded or straightened as shown in Figure 3, the

wedges

56 and 57 extend transversely suf ficiently far to be in engagement with both the zigzag lines 75 and .77 and with the

zigzag lines

76, and 78. A prong 79 is an extension of the connecting rod 43 and extends through a hole 80 in the wedge support 24 for stabilizing the movement of the entire linkage mechanism.

An ejector mechanism 83 maybe provided inside the die adjusting screw 39 to eject the die cast parts which, of

course, are die cast in dies 82 which may be mounted on the fixed and movable platens 17 and 20. The fixed platen 17 is provided with an aperture 84 through which an injection piston 85 from the injection unit 13 may extend. This injection unit 13 may be of any suitable form such as having the pump unit 86 supplying hydraulic pressure to the cylinder 87 for the motive force for the injection piston 85.

Operation The Figure 4 shows the toggle mechanism 45 collapsed with the hydraulic piston 42 retracted, and the Figures 1, 2, and 3 show the toggle mechanism 45 straightened whereat the dies 82 are closed. Figures 1 and 2 also show in phantom view the position of the toggle and wedge mechanisms in the open or retracted position. In this retracted position the movable platen 20 and wedge support 24 have been retracted to separate the dies 82 for removal of the finished. die casting as assisted by the ejector mechanism 83. A long stroke is provided for easy access to the finished die cast part. As the piston rod 43 moves forwardly, that is, toward the fixed platen 17 from the open position shown in Figure 4 to the closed position shown in Figure 2, there is first a translation of the toggle mechanism 45, the wedges or wedge blocks 56 and 57, and the wedge support 24. These parts move at the same rate of speed as the piston 42 for a majority of the stroke of the piston. During this initial portion of the stroke the toggle is collapsed with the toggle links at an angle of generally ninety degrees to each other and with the stops 54 in engagement which establishes the inner limit position of the

wedges

56 and 57. In this position the outer ends of the

wedges

56 and 57 just clear the upper and

lower surfaces

28 and 29. Also during this movement the

external teeth

35 and 36 slide within the

grooves

33 and 34.

Near the end of the stroke of the piston 42 the wedge support 24 is almost in its closed position, and in such condition the wedge support 24 is past the end of the

grooves

33 and 34. As soon as the

wedges

56 and 57 extend beyond the wedge shoes 71 and 72, the wedges begin to slide outwardly in the tongue and groove means 58. This effects a straightening of the toggle mechanism 45, and the final movement of the piston rod 43 is to establish the toggle mechanism 45 in a substantially straight line with the wedge blocks 56 and 57 wedged between the wedge shoes and the wedge support 24 and with the wedges in wedging engagement with the zigzag surfaces -78. Preferably, the prong 79 has a slide clearance with the hole so that, if there is any misalignment or wear on the wedge shoes 71 and 72, or on the wedges 56 and 5'7, the piston rod43 and prong 79 can shift tlaterally a slight amount to even the stress as applied from the wedge support 24 to the upper and lower halves of the frame head 16. The die adjusting screw or other adjustrnent means, such as spacers, are adjusted so that with the dies 82 in place and the toggle link straightened, the

wedges

56 and 57 are wedged tightly enough to pre-stress the tie rods 18 a predetermined amount. This predetermined amount is the rated tonnage of the press so that as molten metal is forced into the dies by the injection piston this injection pressure will not cause parting of the dies. The

Wedges

56 and 57 are solid, that is, have a solid surface front and rear so that there is a continuous surface engaging the zigzag or contact lines 75-78. In the priorart form of. presses without any internal grooves and complementarily external teeth a wedge inserted between the wedge support and the frame head would have a shear iline which was a straight line. In the present case the shear line on thewedge blocks is a zigzag line, and this zigzag line assures that there is no bending or cocking of the

wedges

56 and 57 because substantially entirely the stress on the Wedges is a shear stress. The wedges can much more readily absorb this shear stress than they could a combined shear stress and bending moment; andhence, by the present design there has been eliminated the tendencyfor the dies to part under the injection pressure. r a

The knuckle joint 60 relieves stress on the pivot pins 61 and 62. This is because at the final closing portion ofthe stroke, when the stress is the greatest between the toggle links 4750 and the

wedges

56 and 57, the external and internal

arcuate surfaces

63 and 64 are in engagement for approximately one hundred fifty degrees of arc, with this being a large surface etxending the majority of the width of the

wedges

56 and 57, and therefore this large arcuate surface absorbs the compressive stress to relieve the stress on the pivot pins 61 and 62. Also, at this time the arcuate bearing surfaces 53 on the inner ends of the toggle links transfer the compressive stress directly to each other to relieve the stress on the pivot pin 51. This makes the entire toggle mechanism and wedge means 45 and 46 very rugged with an absolute minimum of tolerance or working clearances.

The knuckle joint 60 also has another function in that the pull-back surface portion 65 which is closer to the axis than the center of the pivot pins 61 and 62 will coact with the external arcuate surfaces 63 so that as the piston 42 is retracted the toggle mechanism 45 will collapse and the external surfaces 63 will bear against the pull-back surface portion 65 to retract the

Wedges

56 and 57. T1118 thus assures that the pivot pins 61 and 62 are at least partially relieved of the stress of initially withdrawing the wedges from their former wedging engagement of the clamped position.

Although this invention has been described in its preferred form with a certain degree of particularity, it is understood that the present disclosure of the preferred form has been made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and the scope of the invention as hereinafter claimed.

What is claimed is:

1. In a machine having first and second members one of which is movable and having force means to establish a force between said members, the provision of a toggle mechanism operable from a motive power source and coacting between said first and second members, dual pivoted link members connected at one end to said power source, complementary teeth on said first and second members for a sliding fit in a direction substantially parallel to the movement of said one of said members, a pair of solid surface sliding wedges slidably connected to said second member and adapted to wedgingly move against said first member in a direction substantially perpendicular to the direction of movement of said one of said members, pivot means interconnecting the other end of said link members and said wedges with said wedges extending between and into engagement with the opposed surface of the protruding complementary teeth on each of said first and second members for a zigzag shear line on each wedge for resisting the force of said force means in shear rather than in bending.

2. In a machine having first and second members the second of which is movable and having force means to establish a force between said members, the provision of a toggle mechanism operable from a piston rod and coacting'between said first and second members, dual pivoted link members interconnected at one end to said piston rod, complementary teeth on said first and second members for a slidingfit in a direction substantially parallel to the movement of said second member, a pair of solid wedges positively and slidably connected to said'second member and adapted to wedgingly move against said firstmember in a direction substantially perpendicular to the direction of movement of said second member, knuckle joints interconnecting the other end of said link members and said Wedges with said wedges extending between and into engagement with the opposed surface of the protruding complementary teeth on each of said first and second members for a zigzag shear line on each-wedge for resisting the force of said force means in shear rather than in bending.

3. In a machine having a member movable relative to a frame to exert a force therebetween, the provision of force means mounted on said frame to move said member, a plurality of grooves in said frame, complementary teeth in said member for movement in said grooves, said member and said frame being spaced apart in a first position of said member, Wedge surface means on one of said frame, and member adjacent said grooves and teeth, wedge means on said machine movable into engagement with said wedge surface means with said member in said first position, and a toggle connected between said force means and said wedge means to move said wedge means, whereby said force means may move said wedge means and member and said toggle in a collapsed position until said teeth are positioned beyond the end of said grooves with said member generally in said first position, whereupon further movement of said force means effects a straightening of said toggle to move said Wedge means into wedging engagement with said Wedge surface means to be in engagement with a zigzag end of said grooves and a zigzag end of said teeth to load said wedge means substantially only in shear along a zigzag shear line.

4. In a machine having a base with a frame head and a generally fixed platen interconnected by strain rods, the provision of a movable platen longitudinally movable on said base, at least two generally opposite internal surfaces in said frame head defining an opening therein and each lying in other than a single plane and being longitudinally disposed relative to said base, external surfaces on said movable platen for complementary sliding engagement with said surfaces in said frame head to permit said longitudinal movement of said movable platen, power means having a longitudinally movable connecting rod, first and second toggle links each having first and second ends, pivot means connecting the first ends of said toggle links to said connecting rod, first and second wedge blocks, second pivot means interconnecting said toggle links and said first and second wedge blocks, means establishing sliding connection of said wedge blocks on the outboard face of said movable platen for transverse sliding movement of said wedge blocks, said external surfaces establishing first zigzag contact line means adjacent said wedge blocks, wedge shoes on the inboard surface of said frame head for complementary engagement with said wedge blocks, said wedge shoes being contiguous with the ends of said internal surfaces to establish second zigzag contact line means, said wedge blocks having an outer limit position established when said toggle links are straightened, whereby said connecting rod may longitudinally move said toggle links when in a collapsed por sition, Wedge blocks and movable platen with said external surfaces sliding relative to said internal surfaces, and whereby as said wedge blocks extend past the end of said internal surfaces said toggle links expand and straighten to move said wedge blocks to said outer limit position to force said wedge blocks between said wedge shoes and said movable platen to be in engagement with both said first and second contact line means to establish a zigzag shear line on said wedge blocks greater than the Width of said wedge blocks.

5. In a machine havinga base with a frame head and a generally fixed platen interconnected by strain rods,v

the provision of a movable platen longitudinally movable on said base, a surface defining an opening in said frame head,'at least two grooves in each of two generally opposite surfaces of said opening in said frame head with said grooves being longitudinally disposed relative to said base, external teeth on two sides of said movable platen for complementary sliding engagement with said grooves to permit said longitudinal movement of said movable platen, power means having a longitudinally movable connecting rod, first and second toggle links each having first and second ends, pivot means connecting the, first ends of said toggle links tosaid connecting rod, first and second wedge blocks, second pivot means interconnecting said toggle links and said first and second wedge blocks, means connecting said wedge blocks and the outboard face of said movable platen for transverse sliding movement of said wedge blocks, said teeth establishing first zigzag lines adjacent said wedge blocks, wedge shoes on the inboard surface of said frame head for complementary engagement with said wedge blocks, said wedge shoes being contiguous with the ends of three sides of said grooves to establish second zigzag lines, said wedge blocks having outer and inner translational limit positions, said outer limit position established when said toggle links are straightened and said wedge blocks are in contact with said wedge shoes, stops near said first ends of said toggle links to limit the collapsed position of said toggle links to a position of about ninety degrees therebetween, said inner limit position of said wedge blocks being established when said toggle links are collapsed and said stops thereon are in engagement, whereby said connecting rod may longitudinally move said toggle links when in a collapsed position, wedge blocks and movable platen with said teeth sliding in said grooves, and whereby as said wedge blocks extend past the end of said grooves said toggle links expand and straighten to move said wedge blocks to said outer limit position to force said wedge blocks into engagement with said wedge shoes and continue longitudinal movement of said movable platen in the same direction at a much greater mechanical advantage, the distance between said outer and inner limit positions of one of said wedge blocks being greater than the depth of said grooves so that said wedge blocks are disposed in engagement with both of said first and second zigzag lines to establish a zigzag shear line on said wedge blocks equal in length to the width of said wedge blocks plus the quantity of twice the depth of said grooves times the number of grooves.

6. In a die casting machine having a base with a frame head and a generally fixed platen interconnected by strain rods, the provision of a movable die head longitudinally movable on said base, opposite internal surfaces in said frame head, at least two grooves in each of said opposite internal surfaces with said grooves being longitudinally disposed relative to said base, external teeth on opposite sides of said movable die head for complementary engagement with said grooves to permit said longitudinal movement of said movable die head, hydraulic cylinder and piston means having a longitudinally movable connecting rod, first and second toggle links each having first and second ends, a pivotal connection between the first ends of said toggle links and said connecting rod, first and second wedge blocks slidably connected to said movable die head and pivotally connected to said toggle link second ends, said teeth establishing a first zigzag line adjacent said wedge blocks, Wedge shoes on the inboard surface of said frame head for complementary engagement with said wedge blocks, said wedge shoes being contiguous with the ends of three sides of said grooves to establish a second zigzag line, said wedge blocks having outer and inner translational limit positions, said outer limit position established when said toggle links are straightened and said wedge blocks are in contact with said Wedge shoes, stops near said first ends of said toggle links to limit the collapsed position of said toggle links such that the ends of said wedge blocks are closer togethcr than said opposite internal surfaces, said inner limit position of said Wedge shoes being established when said toggle links are collapsed and said stops thereon are in engagement, whereby said connecting rod may longitudinally move said toggle links when in a collapsed position, wedge blocks and movable die head with said teeth sliding in said grooves, and whereby as said wedge blocks extend past the end of said grooves said toggle links straighten to move said wedge blocks to said outer limit position to force said wedge blocks into engagement with said wedge shoes and continue longitudinal movement of said movable die head in the same direction at a much greater mechanical advantage,- the distance between said outer and inner limit positions of-one of said wedge blocks being greater than the depth of said grooves so that said wedge blocks are disposed in engage ment with both of said first and second zigzag lines to establish a shear line on said wedge blocks equal to the width of said wedge blocks plus the quantity of twice the groove depth times the number of grooves.

7. In a die casting machine having a base with a frame head and a generally fixed platen interconnected by strain rods, the provision of a movable die head longitudinally movable on said base, a surface defining an opening in said frame head, at least two grooves in each of the upper and lower surfaces of said opening in said 1 frame head with said grooves being longitudinally disposed relative to said base, external teeth on the upper and lower sides of said movable die head for complementary engagement with said grooves to permit said longitudinal movement of said movable die head, hydraulic cylinder and piston means having a longitudinally movable connecting rod, first and second toggle links each having first and second ends, a pivot pin connecting the first ends of said toggle links to said connecting rod, a knuckle joint on the second ends of each of said toggle links, first and second wedge blocks, tongue and groove means interconnecting said Wedge blocks and the outboard face of said movable die head for vertical sliding movement of said wedge blocks, said teeth establishing a first zigzag line adjacent said wedge blocks, a socket on each of said wedge blocks to receive said knuckle joint,

" said knuckle joint having an external arcuate surface of at least two hundred seventy degrees, said socket having an internal arcuate surface of at least two hundred degrees, at least forty-five degrees of said two hundred degree are lying on the axis side of a point to which a plane normal to said axis is tangent to said are, wedge shoes on the inboard surface of said frame head for com plementary engagement with said wedge blocks, said wedge shoes being contiguous with the ends of three sides of said grooves to establish a second zigzag line, said wedge blocks having outer and inner translational limit positions, said outer limit position established when said toggle links are straightened and said wedge blocks are in contact with said wedge shoes, stops near said first ends of said toggle links to limit the collapsed position of said toggle links to a position of about ninety degrees therebetween, said inner limit position of said wedge blocks being established when said toggle links are collapsed and said stops thereon are in engagement, whereby said connecting rod may longitudinally move said toggle links, wedge blocks and movable die head with said teeth sliding in said grooves, and whereby as said wedge blocks extend past the end of said grooves said toggle links expand and straighten to move said wedge blocks to said outer limit position to force said wedge blocks into engagement with said wedge shoes and continue longitudinal movement of said movable die head in the same direction at a much greater mechanical advantage, with the force on said Wedge blocks from said toggle links being borne by at least one hundred fifty degrees of arc of said two hundred degree internal arcuate surface, the distance between said outer and inner limit positions of one of said wedge blocks being greater than the depth of said grooves so that said wedge blocks are disposed in engagement with both of said first and secondzigzag lines to establish a shear line on said wedge blocks equal in length to the width of said wedge blocks plus twice the depth of said grooves, and whereby said movable die 'head may be retracted by reverse reciprocable movement of said connecting rod such that such toggle links collapse and said fortyfive degree arcuate surface on the said Wedge blocks bears the force of the retractile movement of said wedge blocks to said inner limit position.

8. A die casting machine comprising a horizontal base, .a generally fixed platen upstanding at one end of said base, a generally upstanding frame near the other end of said base, four longitudinal strain rods interconnecting said fixed platen and said upstanding frame, a movable platen having four corners each circumscri'bing one of said strain rods for translational movement on said strain rods, a movable die head, an adjusting screw interconnecting said movable platen and said movable die head, a surface defining an opening in said upstanding frame, first and second guideways on opposite sides of said framelpresenting a generally horizontal guide surface, guide blocks on said movable die head cooperating with said guideways for horizontal longitudinal movements of said movable die head relative to said base, at least two grooves in each of the upper and lower surfaces of said opening in said upstanding frame with said grooves being longitudinally disposed relative to said base, external teeth on the upper and lower sides of said movable die head for complementary engagement with said grooves to permit said horizontal longitudinal movements of said movable die head, :a hydraulic cylinder longitudinally disposed outboard of said upstanding frame, a piston in said cylinder, a piston rod longitudinally disposed on said frame and extending from said piston toward said movable d-ie head, first and second toggle links each having first and second ends, a pivot pin connecting the first ends of said toggle links to said piston rod, a knuckle joint male part on the second ends of each of said toggle links, first and second wedge blocks, tongue and groove means interconnecting said wedge blocks and the outboard face of said movable die head for vertical sliding movement of said wedge blocks, said teeth establishing a first zigzag line adjacent said wedge blocks, a female socket on each of said wedge blocks to receive said knuckle joint, said knuckle joint male part having an external arcuate surface of at least two hundred seventy degrees, said socket having an internal arcuate surface of at least two hundred degrees, at least forty-five degrees of said two hundred degree are lying on the axis side of a point to which a plane normalto said axis is tangent to said arc, Wedge shoes on the inboard surface of said upstanding frame for, complementary engagement with said wedge blocks, said wedge shoes being contiguous with the ends of three sides of said grooves to establish a second zigzag line, said wedge blocks having outer and inner translational limit positions, said outer limit position established when said toggle links are straightened and said wedge blocks are in contact with said wedge shoes, stops near said first ends of said toggle links to limit the collapsed position of said toggle links to a position of about ninety degrees therebetween, said inner limit position of said wedge blocks being established when said toggle link is collapsed and said stops thereon are in engagement, whereby said piston rod may translationally move said toggle links, wedge blocks and movable die head with said teeth sliding in said grooves, and whereby as said wedge blocks extend past the end of said grooves said toggle links expand and straighten to move said wedge'blocks to said outer limit position to force said wedge blocks into engagement with said wedge shoes and continue translational movement of said movable die head in the same direction at a much greater mechanical advantage, with the force on said wedge blocks from said toggle links being borne by at least one hundred fifty degrees of arc of said two hundred degree internal arcuate surface, the distance between said outer and inner limit positions of one of said wedge blocks being greater than the depth of said grooves so that said wedge blocks are disposed in engagement with both of said first and second zigzag lines to establish a shear line on said wedge blocks equal to the width of said wedge blocks plus the quantity of twice the groove depth times the number of grooves, andwhereby said movable die head may be retracted by reverse reciprocable movement of said piston rod such that such toggle links collapse and said forty-five degree arcuate surfaces on the said wedge blocks effect the retractile movement of said wedge blocks to said inner limit position.

9. In a machine having a base with a fixed head and a movable head longitudinally movable on said base, the provision of a plurality of internal surfaces on said fixed head, at least two longitudinal grooves in each of said internal surfaces, external teeth on outer sides of said movable head for complementary engagement with said grooves to permit said longitudinal movement of said movable head, a plurality of 'wedge blocks mounted for lateral movement relative to said movable head, toggle linkage, knuckle joints interconnecting said toggle linkage and each of said wedge blocks at a socket, power means to longitudinally move said toggle linkage relative to said base and between said internal surfaces, said teeth establishing a first zigzag line adjacent said wedge blocks, each said socket having an internal arcuate surface with at least thirty degrees thereof lying on the axis sideof a point to which :a plane normal to said axis is tangent to said arc, the inboard surface of said fixed head being contiguous with the ends of three sides of said grooves to establish a second zigzag line, said wedge blocks having an inner translational limi-t position established when said toggle linkage is collapsed, whereby said power means may longitudinally move said toggle linkage, wedge blocks and movable head with said teeth sliding in said grooves, and whereby as said wedge blocks extend past the end of said grooves said toggle linkage expands and straightens to move said wedge blocks toward an outer limit position to force said wedge blocks into engagement with said fixed head inboard surface and continue longitudinal movement of said movable head in the same direction at a much greater mechanical advantage, with the force on said wedge blocks from said toggle linkage being borne by said sockets, the distance between said outer and inner limit positions of one of said wedge blocks being greater than the depth of said grooves so that said wedge blocks are disposed inengagement with both of said first and second zigzag lines to establish a shear line on said Wedge blocks equal in length to the width of said wedge blocks plus twice the depth of said grooves, and whereby said movable head may be retracted by reverse reciprocable movement of said power means such that such toggle linkage collapses and said thirty degree arcuate surface on the said wedge blocks bears the force of the retractile movement of said wedge blocks to said inner limit position.

10. In a machine having a base with a fixed head and a movable head longitudinally movable on said base, the provision of opposite internal surfaces on said fixed head, at least two longitudinal grooves in each of said opposite internal surfaces, external teeth on opposite sides of said movable head for complementary engagement with said grooves to permit said longitudinal movement of said movable head, first and second wedge blocks mounted for lateral movement relative to said movable head, toggle linkage, knuckle joints interconnecting said toggle linkage and each of said wedge blocks at a socket, power means to longitudinally move said toggle linkage relative to said base and between said opposite internal surfaces, said teeth establishing a first zigzag line adjacent said wedge blocks, each said socket having an internal arcuate surface with at least forty-five degrees thereof lying on the axis side of a point to which a plane normal to said axis is tangent to said arc, the inboard surface of said fixed head being contiguous with the ends of three sides of said grooves to establish a second zigzag line, said wedge blocks having an inner translational limit position established when said toggle linkage is collapsed, whereby said power means may longitudinally move said toggle linkage, wedge blocks and movable 1 1 head with said teeth sliding in said grooves, and whereby as said wedge blocks extend past the end of said grooves said toggle linkage expands and straightens to move said.

wedge blocks toward an outer limit position to force said wedge blocks into engagement with said fixed head inboard surface and continue longitudinal movement of said movable head in the same direction at a much greater mechanical advantage, With the force on said wedge blocks from said toggle linkage being borne by said sockets, the distance between said outer and inner limit positions of one of said wedge blocks being greater than the depth of said grooves so that said wedge blocks are disposed in engagement with both of said first and second zigzag lines to establish a shearrline on said wedge blocks equal in length to the width of said wedge blocks plus twice the depth of said grooves, and whereby said movable head maybe retracted by reverse reciprocable movement of said power means such that such toggle linkage collapses and said forty-five degree arcuate surface on the said wedge blocks bears the force of the retractile movement of said wedge blocks to said inner limit position.

ll. in a machine having a base with a fixed head, the provision of a movable head longitudinally movable on said base, opposite internal surfaces on said fixed head, at least two longitudinal grooves in each of saidopposite internal surfaces, external teeth on opposite sides of said movable head for complementary engagement with said grooves to permit said longitudinal movement of said movable head, first and, second wedge blocks mounted for lateral movement on the outboard face of said movable head, toggle linkage, knuckle joints interconnecting said toggle linkage and each of said wedge blocks at a socket, power means to longitudinally move said toggle linkage relative to said base and between said opposite internal surfaces, said teeth establishing a first zigzag line adjacent said wedge blocks, each said knuckle joint having an external arcuate surface of at least two hundred seventy degrees, each said socket having an internal arcuate surface of at least two hundred degrees, at least forty-five degrees of said two hundred degree are lying on the axis side of a point to which a plane normal to said axis is tangent to said are, wedge shoes on the inboard surface of said fixed head for complementary engagement with said wedge blocks, said wedge shoes being contiguous with the ends of three sides of said grooves to establish a second zigzag line, said wedge blocks having an inner translational limit position, stops near the centerof said toggle linkage to limit the collapsed position thereof, said innerlimit position of said wedge blocks being established'when said toggle linkage is collapsed and said stops thereon are in engagement, whereby said power means may longitudinally move said toggle linkage, wedge blocks and movable head with said teeth sliding in said grooves, and whereby as said wedge blocks extend past the end of said grooves said toggle linkage expands and straightens to move said wedge blocks toward an outer limit position to force said wedge blocks into engagement with said wedge shoes and continue longitudinal movement of said movable head in the same direction at a much greater mechanical advantage, with the force on said wedge blocks from said toggle linkage being borne by at least one hundred fifty degrees of are of said two hundred degree internal arcuate sur face, the distance between said outer and inner limit positions of one of said wedge blocks being greater than the depth of said grooves so that said wedge blocks are disposed in engagement with both of said first and second zigzag lines to establish a shear line on said wedge blocks equal in length to the width of said wedge blocks plus twice the depth of said grooves, and whereby said movable head may be retracted by reverse reciprocable movement of said power means such that such toggle linkage collapses and said forty-five degree arcuate surface on the said wedge blocks bears the force of the retractile movement of said wedge blocks to said inner limit position.

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