US3855839A

US3855839A - Drive linkage for double action press

Info

Publication number: US3855839A
Application number: US00444338A
Authority: US
Inventors: J Lose; J Roth
Original assignee: Gulf and Western Manufacturing Co
Current assignee: EW Bliss Co Inc
Priority date: 1974-02-21
Filing date: 1974-02-21
Publication date: 1974-12-24
Anticipated expiration: 1991-12-24
Also published as: AU7681474A; DE2507098A1; IT1026196B; JPS50115369A; GB1440420A; JPS5433386B2; DE2507098B2; AU473163B2; DE2507098C3; FR2261818B1; CA1010714A; FR2261818A1

Abstract

Drive mechanisms are disclosed for underdriven and top driven, double action, sheet metal drawing presses. The drive mechanisms include a rotating crank, a connecting link, a constraining link, a slide link between the connecting link and press plunger, and a slide link between the constraining link and work holder crosshead. The crosshead is drivingly interconnected with the work holder slide through a separate linkage arrangement. Rotation of the crank reciprocates the plunger slide to impart motion characteristics thereto during the total plunger stroke which includes high approach and return velocities with respect to the work stroke of the plunger and a slow down of the plunger during the work stroke. Further, the blank holder slide is driven in response to rotation of the crank to have an extended dwell in the blank holding position with a minimum rise of the blank holder slide during dwell.

Description

Lose et a1.

States atent [1 [4 1 Dec. 24, 1974 [75] Inventors: John G. Lose, Lansdowne, Pa.; John F. Roth, Salem, Ohio [73] Assignee: Gulf & Western Manufacturing Company, New York, N.Y.

221 Filed: Feb. 21, 1974 211 Appl. No.: 444,338

Primary Examiner-Lowell A. Larson [57] ABSTRACT Drive mechanisms are disclosed for undcrdrivcn and top driven, double action, sheet metal drawing presses. The drive mechanisms include a rotating crank, a connecting link, a constraining link, a slide link between the connecting link and press plunger, and a slide link between the constraining link and work holder crosshead. The crosshead is drivingly interconnected with the work holder slide through a separate linkage arrangement. Rotation of the crank reciprocates the plunger slide to impart motion characteristics thereto during the total plunger stroke which includes high approach and return velocities with respect to the work stroke of the plunger and a slow down of the plunger during the work stroke. Further, the blank holder slide is driven in response to rotation of the crank to have an extended dwell in the blank holding position with a minimum rise of the blank holder slide during dwell.

36 Claims, 19 Drawing Figures PATENTE B BEC24IEI74 SHEET 0111f 11 PATENTED DEC24 I974 SHEET DEUF 11 mmrmnmz 5 3.855.839

SHEET DSUF 11 PATENTED UEC24I974 SHEET 08 0F 1 PATENTEDUEEZMQM SHEET U7UF 11 DRIVE LINKAGE FOR DOUBLE ACTION PRESS The present invention relates to the art of presses and, more particularly, to drive mechanisms for underdriven and top driven, double action metal working presses.

Double action presses of the character to which the present invention relates include a reciprocable blank holder and a relatively reciprocable plunger. During a stroke of operation of the press, a workpiece such as a sheet metal blank is clamped between the reciprocable blank holder and a fixed blank holder component mounted on the press bolster plate. Following clamping of the workpiece, the plunger moves relative to the blank holder and through a work stroke during which the blank is shaped. The plunger then returns toward its top dead center position and the blank holder moves away from the fixed blank holder component, whereby the shaped blank can be withdrawn from the press.

In double action presses of the foregoing character, it is desirable to slow down the plunger during the work stroke thereof to achieve the best possible forming results with respect to drawing of the metal blank. At the same time, it is desirable to operate the press at a high production rate as measured, for example, by strokes per minute of the press. A slow velocity of the plunger during the work stroke requires a slow down of the plunger slide and, at the same time, a dwell of the blank holder slide for a sufficient duration to allow the plunger slow down. Moreover, blank holder dwell must be without a rise of the blank holder slide beyond acceptable limits. All mechanical type blank holder linkages rise slightly during the dwell portion of the stroke, and if the rise is excessive die setting becomes difficult, blank holding pressure may be relaxed during the forming operation, and tolerances become difficult to hold. Mechanically driven double action presses heretofore provided have not satisfactorily, practically or economically achieved the characteristics of operation by which increased production rate is realized.

Generally, double action press drives heretofore provided have had separate linkages driving the blank holding and plunger slides from corresponding crankshafts or a common multi-throw crankshaft in such a way that the linkages driven by the cranks swept out identical arcs. Thus, there is a limited crank angle sweep during the work stroke and during which the blank holder slide can dwell with a minimum of rise while the work is being performed by the plunger. Likewise, control of the velocity of the plunger slide during the work stroke thereof is limited by such crank and linkage drives whereby, for a given maximum velocity of the plunger through the work stroke, production rate is undesirably low.

In accordance with the present invention, a double action press drive arrangement is provided which enables the production capability to be considerably in creased over that of conventional slider-crank type, double action press drives. More particularly, in the drive mechanism according to the present invention, both the plunger slide and blank holder slide are driven by a common single throw crank through a linkage arrangement which provides for a quick advance of the plunger from top dead center toward the work stroke, a slow down during the work stroke, and a quick return to the top dead center position. This motion characteristic of the plunger slide through its total stroke enables a considerable increase in the production rate of a press as measured, for example, in strokes per minute of the plunger. In this respect, for a given maximum velocity of the plunger through the work stroke, the high speed advance and return more than compensate for the time lost by the slow down through the work stroke, whereby operation of the press at an increased strokes per minute output is achieved.

The limits with respect to the dwell of blank holder slides in conventional slider-crank driven double action presses undesirably limit the duration of the work stroke as measured by degrees of rotation of the plunger drive crank, limit the production rate of the press, and imposes restrictions on the mechanical advantage achieved through the crank and linkage arrangements. The drive mechanism in accordance with the present invention advantageously overcomes these limitations by increasing the angle swept by the drive crank during dwell of the blank holder slide, whereby an extended plunger work stroke is achieved without excessive rise and fall of the blank holder slide during its holding operation. The extended dwell of the blank holder slide enables an increase in production rate and- /or a longer work stroke in proportion to the total stroke of the plunger and/or an increase in the mechanical advantage of the component parts of the drive mechanism. Moreover, the drive mechanism is compact and requires fewer parts and less maintenance than would be required to achieve the same result with other drive mechanism modified to provide extended blank holder dwell and plunger slow down through the use of, for example, two speed clutches, DC drives or electromechanical arrangements. In accordance with the present invention, the linkage drive employed to achieve plunger slow down is utilized in a unique manner to achieve extended dwell of the blank holder slide, whereby the mechanism employs a minimum number of links and, accordingly, is more compact and is less expensive to manufacture and maintain than other mechanisms designed to achieve the same end.

As an example of the benefits derived from the drive arrangement of the present invention, a conventional slider-crank driven, double action underdriven sheet metal drawing press rated at 1,250 tons and having a total plunger stroke of 42 inches and a 16 inch effective draw stroke and operating with a maximum velocity of the plunger through the work stroke of feet per minute can be run at a production rate of up to 8 strokes per minute without exceeding the maximum plunger velocity. Such conventional presses provided with two speed clutches can be run at 1 1 strokes per minute. The drive mechanism of the present invention employed with an underdriven press of the same tonage and stroke size can be run at a production rate of 15 strokes per minute without exceeding a plunger velocity of 90 feet per minute through the draw stroke. Based on the l 1 strokes per minute of a conventional press, the drive mechanism of the present invention provides an increase in production capability of about 36 percent. Moreover, the drive mechanism of the present invention provides for a double action press to be operated with a 20 to 30 percent reduction in input torque required to drive the crankshaft, whereby smaller drive components such as gears, shafting and clutches are required.

Accordingly, an outstanding object of the present invention is the provision of an improved crank and linkage mechanism for driving a double action metal working press.

Another object is the provision of a drive mechanism for a double action press which enables an increase in the production capability of the press with respect to mechanically driven double acting presses heretofore provided.

Yet another object is the provision of an improved drive mechanism for a double action press by which a greater work stroke in proportion to the total stroke is achieved relative to existing mechanically driven double action presses.

A further object is the provision of an improved drive arrangement for a double action press by which the mechanical advantage of the drive components is increased and the input torque requirement is decreased.

Still another object of the present invention is the provision of a drive mechanism for a double action metal working press which provides for a slow down of the plunger through the work stroke and an extended dwell of the blank holding slide in its blank holding position, thus to enable operation of the press at a higher production rate and/or with a greater work stroke in proportion to the total stroke and/or with increased mechanical advantages.

Still a further object is the provision of a drive arrangement of the foregoing character in which the press plunger and work holder slides are driven through a unique system of links and a common single throw input crank.

Yet another object is the provision of a double action press drive mechanism of the foregoing character which is comprised of a minimum number of component parts, is more compact, and is less expensive to manufacture and maintain than mechanical drive arrangements heretofore provided for double action presses.

The foregoing objects, and others, will in part be obvious and in part pointed out more fully hereinafter in conjunction with the written description of preferred embodiments of the invention illustrated in the accompanying drawings in which:

FIG. 1 is a perspective view of an underdriven double action press;

FIG. 2 is a side elevation view of the press shown in FIG. 1;

FIG. 3 is a front elevation view of the press as seen along line 33 in FIG. 2;

FIG. 4 is a side elevation view of the press drive mechanism, the view being along line 4--4 in FIG. 3;

FIG. 5 is a side elevation view, partially in section, of the press drive mechanism, the view being along line 5-5 in FIG. 3;

FIG. 6 is a front elevation view of the press drive mechanism taken along line 6-6 in FIG. 4 and showing the bottom and one side portion of the drive mechamsm;

FIG. 7 is a detail view, in section, of a portion of the drive mechanism as seen along line 7-7 in FIG. 4;

FIG. 8 is a detail view, in section, of a portion of the drive mechanism as seen along line 8-8 in FIG. 4;

FIG. 9 is a detail view, in section, of a portion of the drive mechanism as seen along line 99 in FIG. 4;

FIGS. 10 and 10A are schematic illustrations of the crank and link components of the drive mechanism illustrated in FIG. 4 and showing the plunger slide in the top and bottom dead center portions, respectively;

FIG. 11 is a phase diagram illustrating the positions of the plunger and blank holder slides with respect to the position of the input crank;

FIG. 12 is a displacement diagram illustrating corresponding positions of the plunger and work holder slides during one complete revolution of the input crank;

FIG. 13 is a graph showing the relative velocities of the plunger slide of a conventional slider-crank drive and the drive mechanism of the present invention through the work stroke of the plunger;

FIGS. 14 and 14A are schematic illustrations of the linkage and crank components of a drive mechanism in accordance with the present invention for a top driven double action press;

FIG. 15 is a phase diagram showing the plunger and blank holder slide positions relative to the input crank position for the drive arrangement illustrated in FIGS. 14 and 14A;

FIG. 16 is a displacement diagram illustrating the positions of the plunger and blank holder slides during one complete rotation of the input crank of the drive mechanism illustrated in FIGS. 14 and 14A; and,

FIG. 17 is a graph comparing the velocity of the plunger slide of a conventional slider-crank drive mechanism with the velocity of the plunger slide of the drive mechanism illustrated in FIGS. 14 and 14A, the comparisons being through the work strokes of the plunger slides.

Referring now in greater detail to the drawings wherein the showings are for the purpose of illustrating preferred embodiments of the invention only and not for the purpose of limiting the invention, an underdriven double action sheet metal drawing press is illustrated in FIGS. 1-3 and includes a frame having an upper portion 10 and a lower portion 12. Upper portion 10 of the frame includes side portions 14 provided with guideways 16 for a vertically reciprocable blank holder slide 18, and guideways 20 for a vertically reciprocable plunger slide 22. Lower portion 12 ofthe frame supports a bolster plate 24 beneath the blank holder and plunger slides and toward and away from which the slides move during reciprocating movement thereof.

As is well known, cooperable blank holding components and mating drawing die components are mounted on the lower ends of the plunger and blank holder slides and on the bolster plate to achieve the desired forming of a sheet metal blank in response to movement of the blank holder and plunger slides through a cycle of operation thereof. Moreover, as is well known, during a cycle of operation of the press the sheet metal blank to be formed is positioned on the blank holding component mounted on the bolster plate, the blank holder slide descends for the holding component mounted thereon to engage and hold the blank relative to the drawing die component on the bolster plate, and the plunger descends for the die component on the lower end thereof to displace the metal of the blank relative to the die component on the bolster plate and to the desired drawn configuration of the blank. The plunger slide then ascends followed by the blank holder slide, whereby the formed blank is accessible for removal from the press.

The drive mechanism by which the plunger and blank holder slides are reciprocated relative to the press frame includes a portion housed within lower portion 12 of the frame and a portion housed inside side portions 14 of the frame and drivingly interconnected with the plunger and blank holder slides. The drive mechanism is suitably driven, such as by an electric motor 26 mounted on bottom portion 12 of the frame and a flywheel 28 which is driven by motor 26 through endless belts 30. Rotation of flywheel 28 imparts rotation to a drive pinion for the press drive mechanism as set forth more fully hereinafter.

The drive mechanism by which reciprocating movement is imparted to the plunger and blank holding slides of the press is illustrated generally in FIGS. 2 and 3 and in detail in FIGS. 49 of the drawing. The drive mechanism disclosed includes components in bottom portion 12 and both side portions 14 of the press frame, which are identical with respect to a vertical reference plane through the press and centrally between and parallel to side portions 14. To facilitate the description, the components to one side of the reference plane will be described and it will be appreciated that the components described are duplicated on the other side of the reference plane.

' Referring now to FlGS. 2-9 of the drawing, the drive mechanism includes an input crank 32 supported by the frame and in the lower portion 12 thereof for rotation about a fixed axis 0. Rotation of the crank about axis 0 is achieved through a gear 34 keyed or otherwise attached to the crankshaft, and a drive pinion 36 integral with or otherwise secured to a pinion shaft 38 supported by the frame for rotation relative thereto. A gear 40 is keyed or otherwise mounted on shaft 38 and is driven by a pinion 41 which in turn is driven by flywheel 28 through motor 26, as shown in FIG. 3. Other arrangements for imparting rotation to the crankshaft can of course be employed.

Crank 32 is provided adjacent one side of the press frame with a pair of crank arms 42 interconnected by a crank pin 44 having an axis A offset with respect to axis 0 of the crankshaft. The drive mechanism further includes a connecting link 46 pivotally interconnected with crank pin 44 for pivotal movement relative thereto about axis A. A constraining link 48 is pivotally mounted on the'press frame by means of a pin 50 for pivotal movement relative to fixed axis C. Axis C is spaced above fixed axis 0 and is parallel to and in vertical alignment with axis 0. Connecting link 46 and constraining link 48 are pivotally interconnected for relative pivotal movement therebetween about axis '8 spaced from axis A. Further, a pair of slide links 52 have their opposite ends pivotally interconnected, one with connecting link 46 for pivotal movement relative thereto about axis D, and the other with a plunger slide crosshead 54 for pivotal movement relative thereto about axis E. Axis B is between axes A and D and is offset from a line through the latter axes in the direction toward fixed axis C, whereby a line through axes A and B intersects a line through axes A and D at an angle Y.

Plunger slide crosshead 54 is supported for guided vertical reciprocating movement relative to the press frame, by means not illustrated, and the crosshead is interconnected with plunger slide 22 by links 58 having their opposite ends interconnected with crosshead 54 and slide 22 by corresponding pins having axes M and N, respectively. Though links 58 are employed in the embodiment illustrated, it will be appreciated that cross-head 54 and slide 22 could be otherwise interconnected and that links 58 could be eliminated and slide links 52 pivotally interconnected directly to the plunger slide. Plunger slide 22 is guided for vertical reciprocating movement relative to the press frame by guide elements 20, and it will be appreciated, therefore, that the plunger crosshead and plunger slide reciprocate together and the same distance along a linear path defined by the corresponding guides.

A second slide link 62 has its opposite ends pivotally interconnected one with constraining link 48 at axis F and the other with a blank holder crosshead slide 64 at axis G. Axis F is between axes B and C and isspaced above a line therebetween, whereby a line between axes C and F intersects a line through axes B and C at an angle X. Blank holder crosshead slide 64 is supported for guided vertical reciprocable movement relativeto the frame, by means not shown, and is interconnected with blank holder slide 18 by a linkage

arrangement including links

66, 68 and 70. More particularly, a pair of identical links 66 have corresponding ends thereof pivotally interconnected with blank holder crosshead slide 64 at axis H which is spaced from and horizontally parallel with axis G. The other ends of links 66 are pivotally interconnected with link 68 at axis J intermediate the opposite ends of link 68. One of the opposite ends of link 68 is supported by the press frame for pivotal movement about a fixed axis Q, and the other end of link 68 is pivotally interconnected with one end of link 70 at axis K. The other end of link 70 is pivotally interconnected with blank holder slide 18 at axis L. Blank holder slide 18 is supported by the press frame for guided vertical reciprocation by guides 16.

The linkage arrangement between blank holder crosshead slide 64 and blank holder slide 22 is operable in a well known manner, and in response to reciprocation of the crosshead slide, to reciprocate the blank holder slide and provide a dwell in the stroke thereof while it is performing its blank holding function. As described more fully hereinafter, however, the drive mechanism in accordance with the present invention advantageously increases the duration of such dwell in conjunction with providing motion characteristics for the plunger slide which enables an increase in the strokes per minute operation of the press.

The structural interrelationship of the crank and links described hereinabove by which the benefits of the present invention are derived will be better understood with reference to FIGS. 10-13. FIGS. 10 and 10A are schematic showings of the drive mechanism described above and, accordingly, the various link components, slide members and pivot axes are identified by the same numbers and letters employed in connection with the discussion of FlGS. 1-9. In FIGS. 10 and 10A line P represents the common axis of the linear slide paths for blank holder crosshead slide 64 and blank holder slide 18 and for plunger crosshead slide 54 and plunger slide 22. Line T is a vertical reference line through axis L of blank holder slide 18 and fixed axis 0 of link 68, which axes are accordingly vertically aligned and spaced the same lateral distance from path P. Line V is a reference line through fixed axis 0 and with respect to which lines T and P are perpendicular. All of the pivot axes between the crank, links and slides described above are horizontal and parallel to one another.

As will be seen from FIGS. 10 and 10A, rotation of arm 42 counterclockwise about fixed axis imparts reciprocating movement to plunger crosshead slide 54 and thus plunger slide 22 through slide link 52. During movement of the crank arm through one complete revolution, axis D between connecting link 46 and slide link 52 traces an imaginary illipsoidal path, known as a couplar curve, as indicated by broken line 72. Path 72 is inclined with respect to and intersects slide path P, and the inclination of path 72 is indicative of the motion characteristics imparted to the plunger slide during each cycle of rotation of crank arm 42. In this respect, the degree of incline with respect to path P is indicative of slide velocity during a complete stroke thereof beginning and ending at the top dead center position (FIG. and including a work stroke portion which begins just ahead of the bottom dead center position (FIG. 10A). Accordingly, as will be seen from FIGS. 10 and 10A, slide 22 approaches the work stroke at a relatively high velocity, slows down as it moves into the work stroke and through bottom dead center, and has a high return velocity following the work stroke. The actual plunger slide velocity for a press made in accordance with the present invention is set forth more fully hereinafter.

In accordance with the present invention, the slow down of the plunger slide during the work stroke provides for achieving an extended dwell of the blank holder slide during its blank holding operation. More particularly, the extended blank holder dwell is achieved by driving blank holder crosshead slide 64 through crank arm 42, connecting link 46, constraining link 48 and slide link 62. In this respect, rotation of crank arm 42 through one complete revolution causes oscillation of constraining link 48 about axis C to reciprocate blank holder crosshead slide 64. During rotation of crank arm 42, axis B between connecting link 46 and constraining link 48 follows an arcuate path defined by the distance between axis 8 and fixed axis C. As a result of the crank, connecting link and constraining link relationship which provides for plunger slow down in the work stroke, constraining link 48 oscillates at a variable speed. During the portion of the cycle of oscillation of link 48 corresponding to the slow down movement of plunger slide 22 through the work stroke, the speed of oscillation decreases. This decrease in speed is transmitted to crosshead slide 64 through slide link 62, whereby the velocity of crosshead 64 is decreased during that portion of the cycle of movement thereof corresponding to dwell of the blank holder slide 18 during the blank holding operation. Accordingly, the period of dwell is extended considerably and without excessive rise or fall of blank holder 18 during the holding operation.

A specific example of the present invention will be given with respect to an underdriven double action sheet metal drawing press having a 1,250 ton capacity, a plunger slide stroke of 42 inches and a 16 inch effective draw stroke, and a blank holder stroke of 38 inches. The dimensions of the component parts making up the drive mechanism are identified below and the dimensions given are with respect to the letters employed in the schematic illustration of FIG. 10. Accordingly, link lengths are with respect to distances between axes thereof.

Crank member 42 Distance O-A 24.543 inches Link member 46 Distance A-B 53.995 inches Link member 46 Distance A-D 73.630 inches Link member 46 Angle Y ll.6 Link member 48 Distance B-C 53.995 inches Link member 48 Distance C-F 47.500 inches Link member 48 Angle X 2 Link member 52 Distance D-E 152.987 inches Link member 62 Distance F-G 65.500 inches Slide member 64 Distance G-H 31.000 inches Link member 66 Distance H-J 17.890 inches Link member 68 Distance J-Q 13.000 inches Link member 68 Distzmce Q-K 26.000 inches Link member 70 Distance KL 100.00 inches Reference distance O-C 73.630 inches Reference distance 0-? 48.767 inches Reference distance O-T 97.276 inches Reference distance V-Q 142.500 inches The double action sheet metal drawing press having a drive mechanism in which the components are dimensioned as listed above has a continuous operating stroke rate of 15 strokes per minute and an intermittent stroke rate of 12 strokes per minute. The press is driven by a 300 horsepower motor operating at 1,800 rpm. Further, the blank holder slide has a 142 dwell with respect to input crank rotation and a maximum rise during dwell of 0.010 inch when operated at 15 strokes per minute without exceeding a velocity through the draw stroke of the plunger of feet per minute.

As will be seen from the phase diagram of FIG. 11 for the example described above, the plunger reaches its top dead center position when the crank arm has rotated 57 counterclockwise from a vertical 0 reference point. Further, it will be seen that the blank holder slide reaches its top dead center position when the crank has rotated counterclockwise 41 from the reference point. When the crank rotation reaches the blank holder slide is in the blank holding position and begins its dwell in this position. At 176 of crank rotation the plunger enters the working stroke and at 285 the plunger reaches its bottom dead center position. At 297 the blank holder dwell ends and the plunger and blank holder slides move upwardly toward the top dead center positions thereof.

The relative displacements of the blank holding slide and plunger slide during one complete revolution of the crank arm from the vertical 0 reference point therefor is depicted in the graph of FIG. 12. It will be seen from the graph that the vertical displacement of the plunger slide per angle of crank rotation during the work stroke is considerably less than that preceding the beginning of the work stroke and following movement of the plunger slide through the bottom dead center position thereof. This, of course, is indicative of the desired slow down of the plunger slide velocity during the work stroke.

The graph of FIG. 13 is an actual plot of the relative slide velocities of the sheet metal drawing press of the foregoing example and a conventional slider-crank driven double action press of the same tonage, both presses being operated at a rate of 15 strokes per minute. The graph compares the velocities of the two presses through the 16 inch work stroke thereof, and it will be seen that the press drive according to the present invention provides a considerable decrease in velocity from the entrance of the plunger into the work stroke to the bottom dead center position thereof.

The press drive mechanism of the present invention is equally well applicable to a top driven double action metal working press. In this respect, FIGS. 14 and 14A illustrate the crank and linkage components of an overdrive arrangement and by which plunger slide slow down and extended blank holding slide dwell is achieved. The link and slide components for the top drive mechanism are the same by name and function as the components depicted in the schematic illustration of FIG. 10. Accordingly, like numerals and letters with primes added appear in FIGS. 14 and 14A to designate elements of the top drive arrangement corresponding to those of the underdrive arrangement. While the components of the two drive mechanisms are functionally similar, there are distinctions with respect to the orientation of certain of the pivot axes between the components. In this respect, as shown in FIGS. 14 and 14A, fixed axis C is horizontally offset from fixed axis in the direction toward path P, whereby a line through fixed axes O and C inclines with respect to vertical at an angle Z. Further, it will be noted that reference line V through fixed axis 0' is perpendicular to the line through fixed axes O' and C and thus is inclined downwardly from horizontal by an angle corresponding to angle Z. Still further, it will be seen that axis D' between connecting link 46' and slide link 52' is disposed between axes A and B at the opposite ends of the connecting link and intersects a line extending longitudinally of the connecting link through axes A and B. Further, slide link 52' is directly connected to plunger slide 22' at axis E, andaxes G and H of blank holder slide 64' are both laterally spaced and vertically offset. Slide path line P and reference line T through axes Q' and L are vertical.

The drive illustrated in F IGS.[14 and 14A operates to impart reciprocating movement to plunger slide 22' with a slow down through the work stroke of the plunger slide as is indicated by the couplar path 72 tracedby axis D in response to rotation of crank arm 42' clockwise one complete revolution. Moreover, the interconnection between constraining link 48' and blank holder crosshead slide 64' by link 62' provides for the blank holder slide 18' to have an extended dwell during the blank holding operation thereof without excessive rise or fall.

As a specific example of the application of the present invention to a top driven double action press, the following dimensions are applicable to the components of the arrangement illustrated in FIG. 14 for a press having a rating of 350 tons, a 26 inch slide stroke and a inch effective draw stroke, and a blank holder slide stroke of 21 inches.

Link member 66' Link member 68' Distance H'-J 14.850 inches Distance J'-Q' 7.900 inches Link member 68 Distance O'K' 13.250 inches Link member 70' Distance K'L' 29.00 inches Reference angle 2 22.587

Continued Reference distance Reference distance Reference distance Reference distance The foregoing top drive press has a continuous stroke rate of 22 strokes per minute and a velocity of about 76 feet per minute entering the work stroke. The blank holder slide has a 144 dwell with respect to crank rota tion with minimum rise and drop of the blank holder slide during dwell. A press of comparable size having a conventional slider-crank drive mechanism and a 10 inch work stroke operated at a rate of 12 strokes per minute has a plunger velocity entering the work stroke of 88 feet per minute. It will be appreciated, therefore, that the conventional press running at only 55 percent of the stroke rate of a top driven press according to the present invention, has a plunger velocity entering the work stroke which is 16 percent higher than that provided by the drive mechanism of the present invention.

The phase diagram in FIG. 15 shows the relative positions of the blank holder slide and plunger slide of the top driven double action press dimensioned as set forth above during one complete revolution of the input crank in the clockwise direction as viewed in FIG. 14. The 0 reference point for the crank is the point of intersection of axis A with the line between fixed axes O'C' and which in the specific example disclosed herein is an angle of 22.587 counterclockwise from vertical. It will be seen from the phase diagram that the blank holder reaches its top dead center position at 320 of crank rotation and that the plunger slide reaches its top dead center position at 328 of crank rotation. At 52 of crank rotation the blank holder slide begins its work holding function and dwell, and at 54 of crank rotation the plunger slide enters the work stroke. The plunger slide reaches the bottom dead center position thereof at 180 of crank rotation and then begins to rise, and at 196 of crank rotation dwell of the blank holder slide ends and the latter moves toward its top dead center position.

The relative displacements of the plunger and blank holder slides for one complete revolution of the crank from the 0 reference point therefor is depicted in the graph of FIG. 16. It will be seen from the graph, that the vertical displacement of the plunger slide per degree of rotation of the crank decreases as the plunger slide moves into the work stroke in comparison with the displacement thereof prior to entering the work stroke and after moving through the bottom dead center position thereof.

The velocity comparison made hereinabove between the top drive mechanism of FIG. 14 and a conventional slider-crank drive is illustrated in the graph of FIG. 17. In the graph, the solid line curve represents the velocity of the plunger slide of the top drive mechanism dimensioned as set forth hereinabove and operated at a rate of 22 strokes per minute, and the broken line curve represents the velocity of the plunger slide of a conventional slider-crank drive mechanism operated at a rate of 12 strokes per minute. From the graph, it will be seen that the plunger slide driven in accordance with the present invention enters the 10 inch work stroke at a velocity of 76 feet per minute and after a movement into the work stroke of 2 inches the velocity has decreased to about 60 feet per minute. The plunger slide of the conventional press, on the other hand, enters the 10 inch work stroke at a velocity of 88 feet per minute and does not reach a velocity of 60 feet per minute until it has passed into the work stroke a distance of about 7 inches. As mentioned hereinabove, the ability to slow down the plunger slide during the work stroke enables a slow down in displacement of the blank holder crosshead slide whereby extended dwell of the blank holder slide is achieved.

While considerable emphasis has been placed herein on specific linkage arrangements and specific link lengths for underdriven and top driven double action presses, it will be appreciated that the linkage arrangements and dimensions will vary from one press to another depending on the press size and the kinematic and dynamic operational characteristics sought. Many modifications of the linkage arrangements illustrated and described herein can be made to achieve the same end results without departing from the principles of the present invention. Accordingly, it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the present invention and not as a limitation.

What is claimed is:

1. In a double action metal working press comprising a frame, work holding slide means supported by said frame for reciprocating movement along a linear path to hold and release a workpiece relative to said frame, plunger slide means supported by said frame for reciprocating movement along said path and through a work stroke relative to a workpiece held by said work holding slide means, said work holding slide means including driven and work holding slides and linkage means interconnecting said slides for reciprocation of said driven slide to impart intermittent reciprocating movement to said work holding slide, and drive means for reciprocating said plunger slide means and said driven slide, the improvement comprising: said drive means including crank means supported by said frame for rotation about a first axis, connecting link means pivotally interconnected with said crank means at a second axis spaced from said first axis, first slide link means having opposite ends pivotally interconnected one with said connecting link means at a third axis spaced from said second axis and the other with said plunger slide means, constraining link means pivotally interconnected with said frame at a fourth axis spaced from said first axis and pivotally interconnected with said connecting link means at a fifth axis spaced from said second axis, and second slide link means having opposite ends pivotally interconnected one with said constraining link means at a sixth axis spaced from said fourth andfifth axes and the other with said driven slide.

2. The improvement according to claim 1 wherein, a line through said first and fourth axes extends vertically with respect to said frame.

3. The improvement according to claim 1, wherein said fifth axis is between said second and third axes.

4. The improvement according to claim 3, wherein said fifth axis is offset from a line through said second and third axes.

5. The improvement according to claim 4, wherein the offset of said fifth axis from said line is in the direction toward said fourth axis.

6. The improvement according to claim 3, wherein said fifth axis is closer to said third axis than to said second axis.

7. The improvement according to claim 1, wherein said sixth axis is between said fourth and fifth axes.

8. The improvement according to claim 7, wherein said sixth axis is offset from a line through said fourth and fifth axes.

9. The improvement according to claim 7, wherein said sixth axis is closer to said fourth axis than is said fifth axis.

10. The improvement according to claim 8, wherein said offset provides for said sixth axis to be spaced above said line through said fourth and fifth axes.

11. The improvement according to claim 1, wherein said fourth axis is horizontally and vertically offset with respect to said first axis.

12. The improvement according to claim 11, wherein said horizontal offset of said fourth axis is in the direction from said first axis toward said linear path of movement of said work holding slide means and plunger slide means.

13. The improvement according to claim 11, wherein said third axis is between said second and fifth axes.

14. The improvement according to claim 13, wherein said third axis is closer to said fifth axis than to said second axis.

15. The improvement according to claim 14, wherein said third axis intersects a line through said second and fifth axes.

16. The improvement according to claim 15, wherein said third axis is closer to said fifth axis than to said second axis.

17. The improvement according to claim 11, wherein said sixth axis is between said fourth and fifth axes.

18. The improvement according to claim 17, wherein said sixth axis is offset from a line through said fourth and fifth axes.

19. The improvement according to claim 17, wherein said sixth axis is closer to said fifth axis than to said fourth axis.

20. The improvement according to claim 18, wherein said offset of said sixth axis from said line through said fourth and fifth axes is in the direction providing for said sixth axis to be spaced further from said first axis than in said fifth axis.

21. An underdriven double action sheet metal drawing press comprising, a frame, plunger means supported by said frame for reciprocating movement through a stroke, a work holding slide supported by said frame for reciprocating movement through a stroke to hold and release a workpiece relative to said frame, a work holding crosshead slide supported by said frame for reciprocating movement, said plunger slide means, work holding slide and crosshead slide being relatively reciprocable along linear paths having a common axis, linkage means interconnecting said crosshead slide and working slide for reciprocation of said crosshead slide through a stroke thereof to impart intermittent reciprocating movement to said working holding slide during the stroke thereof, and a drive mechanism for imparting reciprocating movement to said crosshead slide and plunger slide means, said drive mechanism including an input crank rotatable about an axis and having an end spaced from said axis, a connecting link having opposite ends, one of said opposite ends being pivotally interconnected with said end of said crank, a first slide link having opposite ends pivotally interconnected one with said plunger slide means and the other with the other of said opposite ends of said connecting link, a constraining link having a first end supported by said frame for pivotal movement about a fixed axis spaced above said crank axis and having a second end pivotally interconnected with said connecting link at a point intermediate said opposite ends of said connecting link, whereby during one revolution of said crank said constraining link oscillates about said fixed axis at a varying velocity and constrains said plunger slide means to reciprocate at a varying velocity during the stroke thereof, and a second slide link having opposite ends pivotally interconnected one with said crosshead slide and the other with said constraining link at a point spaced from said first and second ends thereof, whereby the variable velocity of oscillation of said constraining link imparts variable velocity reciprocating movement to said crosshead slide during the stroke thereof.

22. The press according to claim 21, wherein said fixed axis is vertically aligned with said crank axis.

23. The press according to claim 22, wherein a line through the pivotal connections at said one and said other ends of said connecting link is disposed at an angle with respect to a line through said pivotal connection at said one end of said connecting link and the pivotal connection between said connecting link and said second end of said constraining link.

24. The press according to claim 23, wherein said pivotal connection between said connecting link and second end of said constraining link is closer to said other end of said connecting link than to said one of said connecting link.

25. The press according to claim 24, wherein a line through said fixed axis and the pivotal connection at said second end of said constraining link is disposed at an angle with respect to a line through said fixed axis and the pivotal connection between said second slide link and said constraining link.

26. The press according to claim 22, wherein a line through said fixed axis and the pivotal connection at said second end of said constraining link is disposed at an angle with respect to a line through said fixed axis and the pivotal connection between said second slide link and said constraining link.

27. The press according to claim 26, wherein the pivotal connection between said second end of said constraining link and said connecting link is closer to said other end of said connecting link than to said one end thereof and is further from said fixed axis of said constraining link than is said pivotal connection between said constraining link and second slide link.

28. A top driven double action sheet metal drawing press conmprising, a frame, plunger slide means supported by said frame for reciprocating movement through a stroke, a work holding slide supported by said frame for reciprocating movement through a stroke to hold and release a workpiece relative to said frame, a work holding crosshead slide supported by said frame for reciprocating movement, said plunger slide means, work holding slide and crosshead slide being relatively reciprocable along linear paths having a common axis, linkage means interconnecting said crosshead slide and work holding slide for reciprocation of said crosshead slide through a stroke thereof to impart intermittent reciprocating movement to said work holding slide during the stroke thereof, and a drive mechanism for imparting reciprocating movement of said crosshead slide and plunger slide means, said drive mechanism including an input crank rotatable about a crank axis and having an end spaced from said crank axis, a connecting link having opposite ends, one of said opposite ends being pivotally interconnected with said end of said crank, a first slide link having opposite ends pivotally interconnected one with said plunger slide means and the other with said connecting link at a point intermediate said opposite ends of said connecting link, a constraining link having a first end supported by said frame for pivotal movement about a fixed axis spaced above said crank axis and having a second end pivotally inter-connected with said connecting link at said other of said opposite ends of said connecting link, whereby during one revolution of said crank said constraining link oscillates about said fixed axis at a varying velocity and constrains said plunger slide means to reciprocate at a varying velocity during the stroke thereof, and a second slide link having opposite ends pivotally interconnected one with said crosshead slide and the other with said constraining link at a point spaced from said first and second ends thereof, whereby the variable velocity of oscillation of said constraining link imparts variable velocity reciprocating movement to said crosshead slide during the stroke thereof.

29. The press according to claim 28, wherein said fixed axis is horizontally offset with respect to a vertical line through said crank axis and in the direction of said common axis of said slide paths.

30. The press according to claim 29, herein said point of interconnection between said first slide link and said connecting link intersects aline through the points of pivotal connection at the opposite ends of said con necting link.

31. The press according to claim 30, herein said point of interconnection between said first slide link nd connecting link is closer to said other end'of the connecting link than to said one end thereof.

32. The press according to claim 31, wherein a line between said fixed axis and the pivotal connection at said second end of said constraining link is disposed at an angle with respect to a line through said fixed axis and the pivotal connection between said constraining link and said second slide link.

33. The press according to claim 32, wherein said pivotal connection between said constraining link and second slide link is closer to said fixed axis than is the pivotal connection at said second end of said constraining link.

34. The press according to claim 29 wherein a line between said fixed axis and the pivotal connection at said second end of said constraining link is disposed at an angle with respect to a line through said fixed axis and the pivotal connection between said constraining link and said second slide link.

35. The press according to claim 34, wherein said pivotal connection between said constraining link and second slide link is closer to said fixed axis than is the pivotal connection at said second end of said constraining link.

36. The press according to claim 35, wherein said point of interconnection between said first slide link and connecting link is closer to said other end of the connecting link than to said one end thereof.

Claims

1. In a double action metal working press comprising a frame, work holding slide means supported by said frame for reciprocating movement along a linear path to hold and release a workpiece relative to said frame, plunger slide means supported by said frame for reciprocating movement along said path and through a work stroke relative to a workpiece held by said work holding slide means, said work holding slide means including driven and work holding slides and linkage means interconnecting said slides for reciprocation of said driven slide to impart intermittent reciprocating movement to said work holding slide, and drive means for reciprocating said plunger slide means and said driven slide, the improvement comprising: said drive means including crank means supported by said frame for rotation about a first axis, connecting link means pivotally interconnected with said crank means at a second axis spaced from said first axis, first slide link means having opposite ends pivotally interconnected one with said connecting link means at a third axis spaced from said second axis and the other with said plunger slide means, constraining link means pivotally interconnected with said frame at a fourth axis spaced from said first axis and pivotally interconnected with said connecting link means at a fifth axis spaced from said second axis, and second slide link means having opposite ends pivotally interconnected one with said constraining link means at a sixth axis spaced from said fourth and fifth axes and the other with said driven slide.

30. The press according to claim 29, herein said point of interconnection between said first slide link and said connecting link intersects a line through the points of pivotal connection at the opposite ends of said connecting link.

31. The press according to claim 30, herein said point of interconnection between said first slide link nd connecting link is closer to said other end of the connecting link than to said one end thereof.