US3869927A

US3869927A - Geared drag link-slider-crank press

Info

Publication number: US3869927A
Application number: US394914A
Authority: US
Inventors: John G Lose; John F Roth
Original assignee: Gulf & Western Ind Prod Co
Current assignee: Gulf & Western Ind Prod Co; EW Bliss Co Inc
Priority date: 1973-09-06
Filing date: 1973-09-06
Publication date: 1975-03-11
Anticipated expiration: 1992-03-11

Abstract

A geared drag link-slider-crank press mechanism is disclosed which includes a slide movable along a path between first and second positions defining a slide stroke. The slide is driven through a geared drag link and slider-crank mechanism including a geared slide crank having a link connected between the crank and slide so that rotation of the slide crank imparts reciprocating movement to the slide. Rotation of the geared slide crank is achieved by a drag link mechanism including a second crank rotated at constant speed and a third crank driven by the second crank at a variable speed. The third crank includes a gear in driving engagement with the geared slide crank, whereby rotation of the second crank at constant speed imparts variable speed rotation to the geared slide crank. Desired slide velocity and motion characteristics are achieved by providing for the driving and driven gears of the mechanism to have a ratio of rotation other than 1:1.

Description

States Pate 11 1 Lose et al.

1 51 Mar. 11, 1975 [75] Inventors: John G. Lose, Lansdowne; John F.

Roth, Booth Wyn, both of Pa.

[73] Assignee: Gulf & Western Industrial Products Company, Salem, Ohio 22 Filed: Sept. 6, 1973 21 Appl. No.: 394,914

Primary Examiner-Wesley S. Ratliff, Jr.

57 ABSTRACT A geared drag 1ink-slider-crank press mechanism is disclosed which includes a slide movable along'a path between first and second positions defining a slide stroke. The slide is driven through a geared drag link and slider-crank mechanism including a geared slide crank having a link connected between the crank and slide so that rotation of the slide crank imparts reciprocating movement to the slide. Rotation of the geared slide crank is achieved by a drag link mechanism including a second crank rotated at constant speed and a third crank driven by the second crank at a variable speed. The third crank includes a gear in driving engagement with the geared slide crank, whereby rotation of the second crank at constant speed imparts variable speed rotation to the geared slide crank. Desired slide velocity and motion characteristics are achieved by providing for the driving and driven gears of the mechanism to have a ratio of rotation other than 1:1.

14 Claims, 13 Drawing Figures GEARED DRAG LINK-SLIDER-CRANK PRESS The present invention relates to the art of presses and, more particularly, to a drive mechanism for imparting desired velocity and'motion characteristics to the slide of a mechanical metal working press.

It is well known in the art of metal working presses, such as drawing presses, to drive the slide member of the press by means of a crank which is drivingly interconnected with the slide by means. of a link member having opposite ends pivotally interconnected one with the crank and the other with the slide member. Rotation of the crank imparts reciprocating movement to the slide member between a top dead-center position and a bottom dead-center position defining the press stroke. Succeeding portions of the stroke approaching and leaving the bottom dead-center position define the working stroke of the slide during which a metal forming member or die attached to the slide performs work on a blank or workpiece supported therebeneath on the press.

Slider-crank presses of the foregoing character are frequently provided with two speed clutches which allow for the production rate of the press to be increased by enabling high speed operation of the slide during the return and advance portions of the stroke thereof and low speed operation of the slide during the work stroke. Such clutch arrangements, however, are extremely costly and difficult to maintain and service. Moreover, controls are required for shifting a clutch between the high and low speeds thereof on each crank cycle, and high energy dissipation reduces clutch life to a minimum.

Slider-crank presses of the foregoing character further require special linkage mechanisms in order to achieve slow down of the slide during the working stroke. Such linkage mechanisms frequently have undesirable conditions of balance. In this respect, each moving link contributes a sinusoidal influence to the motion of the slide. During the work stroke of the slide, the sine waves are controlled to yield the desired slow down, but during the advance and return portions of the slide stroke the sine waves frequently reinforce one another causing high slide accelerations that occur quite suddenly. If such high acceleration occurs at or near the top dead-center position of the slide, forces are imposed on the clutch and brake components of the drive mechanism which reduce the life of these components. Further, the linkage arrangements required to slow down the slide often have links on which bending forces are imposed when the press slide is at the bottom dead-center position. Such links in bending reduce the rigidity of the press structure.

Conventional slider-crank presses of theforegoing character are frequently larger than the size required by the part being transferred into and out of the press. More particularly, longer total strokes are required in order to obtain additional handling time for transferring workpieces into and out of the press while the slide is moving through the return and advance portions of the stroke. It will be appreciated that the increase in press size to achieve the longer stroke increases the expense of the machine.

ln accordance with the present invention, a press slide drive mechanism is provided by which the desir able aspects of slider-crank presses heretofore known are retained without the undesirable characteristics heretofore necessary to achieve these desired operating characteristics. In this respect, the drive mechanism of the present invention provides for high speed slide movement during the return and advance portions of the stroke and a slow down of the slide during the advance portion of the work stroke, thus to increase production rate. Moreover, the mechanism of the present invention provides a slow down on the return portion of the work stroke which provides for increased die life. The variable speed operation is advantageously achieved without the necessity of a two speed clutch and associated control components. Quite importantly, the mechanism of the present invention further provides a dwell in the movement of the slide member in that portion of a slide stroke at or near the top dead center position of the slide, and this dwell not only provides for increasing drive clutch and brake life by reducing the work which these components have to do, but also provides increased time for introducing and removing workpieces from the press between succeed ing strokes thereof. Accordingly, the press size is reduced and a savings in the expense of the press is achieved.

More particularly, the foregoing operating characteristics and advantages derived therefrom are achieved in accordance with the present invention by an improved gear drive and linkage mechanism for mechanical presses which combines a crank driven drag link mechanism and a slider-crank mechanism through a geared transmission ratio. The output of the drag link mechanism imparts variable speed rotation to the slide crank and, in accordance with the present invention, the geared transmission ratio connecting the output of the drag link mechanism to the input of the slider crank mechanism is other than 1:1. The input to the drag link mechanism is through a constant speed crank, and this constant speed rotation is transformed to the variable speed output for driving the slide crank. The transmission ratios employed in accordance with the present invention provide results heretofore unattainable, including those mentioned hereinabove, and provide for press operation as a unicycle or multicycle press wherein one, two or more repeating specialized cycles of slide motion can be obtained during a given slide stroke or during succeeding slide strokes.

Geared transmission ratios in accordance with the present invention relate to the output rotation from the drag link mechanism relative to the input rotation to the slider-crank mechanism. For example, if the transmission ratio is 2:1, the drag link mechanism makes two complete revolutions for each revolution of the slidercrank mechanism. The transmission ratios employed in accordance with the present invention provide for many specialized motions to be imparted to the press slide to provide for increased production rate, longer die life, and increased time for handling workpieces.

The geared transmission ratio in accordance with one aspect of the present invention is any integer number greater than 1 to l and, for example 2:1 or 3:1. Such a transmission ratio will provide a unicycle press. If the transmission ratio is 3:1, for example, such a unicycle press will, during operation thereof, produce three speed variations on one cycle of slider-crank motion.

In accordance with another aspect of the invention, the geared transmission ratio is any non-integer rational number to l. A transmission ratio of this form provides for the press to operate as a multicycle press in which different motion characteristics of the slide are realized upon each advance of the slide during a stroke thereof. This transmission ratio form may be changed to the form of any integer number to a different integer number such as, for example, 3:2. The number on the right corresponds to the number of different motion characteristics of the slide during'a complete cycle of operation, and the number on the left corresponds to the number of speed variations imposed on the slide during the same period of operation thereof. In otherwords, the slide would move through two strokes each having a corresponding motion characteristic, and during the two strokes three cycles of speed variation would be imposed on the slide.

The transmission ratios which provide for unicycle press operation enable a metal drawing press to be provided which is capable of matching the position, velocity, and force characteristics dictated by the deep drawing of specialized parts at high speed and in situations where only one stroke of the ram or slide per part is required. These transmission ratios provide for many specialized motions to be imparted to the slide which enable increased production, longer die life, and increased workpiece handling time. More particularly, such a unicycle press provides a slow down of the slide on the down stroke immediately prior to entry into the working zone of the press, and such slow down allows for increased production rate. Such a unicycle. press also achieves a slow down of the slide on the up stroke through the same region of the working zone, and the latter slow down increases die life by reducing impact as the die is withdrawn from the workpiece. Still further, such a unicycle press provides a dwell period at the top of the slide stroke by extending the amount of time required for reversing the direction of the slide, and this dwell provides for extended handling time for insertion and removal of the workpiece being formed. Further advantages of the dwell at the top of the stroke are that braking effort required to stop the press mechanism during single stroke operation thereof is reduced, and the total stroke of the press is reduced in size, thus to decrease the cost of the press.

The transmission ratios which provide for multicycle press operation enable a press to be provided which is capable of performing several specialized operations on a single part, such as where several modes of forming the same part are required. One such multicycle press equipped with a multi-die set can perform the specialized forming operations on a part in that the varying slide speed on each stroke of the slide enables such operation. With such a press, the part would be transferred from one die to another within the one press between strokes of the slide. The transmission ratios by which multicycle press operation is achieved also provides the foregoing advantages of slow down during the work stroke and dwell time when the slide is at the top of its stroke.

The geared drag link-slider-crank mechanism of the present invention is of relatively simple structure and provides press strength or stiffness in the direction of the slide motion at the bottom dead-center position thereof which is essentially identical to that of conventional slider-crank mechanisms, whereby the advantages of such strength are retained. Advantageously,

the mechanism of the present invention provides for the specialized motion and velocity characteristics de scribed hereinabove to be achieved and at the same time for prolonged bearing life and minimized shaking forces to be achieved. In this respect, the specialized motion linkages heretofore employed with slider-crank mechanisms frequently have oscillating rather than rotating bearings that carry the full load generated by the press. In the present mechanism, the full load is carried by the slider-crank segment and the drag link segment is located on a shaftrotating at a higher speed than the slider-crank. Therefore, there will be a reduction in torque carried by the drag link segment in proportion to the particular gear ratio employed, and good bearing life can accordingly be expected. A reduction in shaking forces is achieved by using as many rotating drive members as possible, rather than oscillating drive members, to produce the specialized motion.

Accordingly, it is an outstanding object ofthe present invention to provide an improved press drive mechanism by which specialized motions can be imparted to a press slide to provide for increased production, longer die life, and increased handling time.

Another object is the provision of a press drive mechanism by which a slow down of the slide during entry into the working zone is achieved together with a slow down of the slide during return movement thereof through the same zone of the work stroke.

Still another object is the provision of drive mechanism of the above character by which a dwell period at the top of the slide stroke is achieved to increase workpiece handling time, reduce the size of the total stroke of the slide, and reduce the braking effort required to stop the press mechanism.

Still another object is the provision of a press drive mechanism which enables specialized motion characteristics to be imparted to the slide while maintaining desirable strength and stiffness of the press mechanism Yet a further object is the provision of a press drive mechanism which provides for specialized motion characteristics to be imparted to the slidewhile prolonging bearing life and minimizing shaking forces imparted to components of the present mechanism during operation thereof.

A.further object is the provision of a press drive mechanism including a geared slider-crank mechanism driven by a geared drag link mechanism through a geared transmission ratio of other than 1:].

Still another object is the provision of a press drive mechanism of the foregoing character wherein the geared transmission ratio provides for unicycle press operation.

Yet a further object is the provision of a press drive mechanism of the foregoing character wherein the geared transmission ratio provides for multicycle press operation.

Still another object is the provision of a press drive mechanism wherein constant speed rotation of an input crank member is transformed into variable speed rotation of a driving gear to impart variable speed rotation to a geared slide crank of the press and wherein the ratio of rotation between the driving gear and slide crank gears is other than 111.

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

FIG. 1 is a schematic illustration of a geared drag link-slider-crank mechanism of the present invention;

FIG. 2 is a graph illustrating the relationship between crank speed and crankshaft rotation for the drag link and slide crank segments of the mechanism illustrated in FIG. 1, I

FIG. 3 is a graph comparing the relationship between slide displacement and slide crank rotation of slidercrank mechanisms provided heretofore and the mechanism illustrated in FIG. 1 and having a gear ratio of 3:1;

FIG. 4 is a graph illustrating the relationship between slide displacement and crank rotation for a specific press drive mechanism made in accordance wtih the present invention;

FIG. 5 is a schematic illustration of desired relationships between components of the mechanism illustrated in FIG. 1;

FIG. 6 is a graph illustrating the relationship between slide displacement and crank angle for the mechanism illustrated in FIG. 1 and in which the gear ratio is 3:2;

FIG. 7 is a plan view, in section, of a preferred arrangement of components providing a geared drag linkslider-crank mechanism made in accordance with the present invention;

FIG. 8 is an elevational view of the mechanism illustrated in FIG. 7, the view being along line 8-8 in FIG.

FIG. 9 is an elevational view of the mechanism illustrated in FIG. 7, the view being along line 9-9 in FIG.

FIG. 10 is a schematic illustration of another embodiment of a geared drag link-slider-crank mechanism of the present invention, particularly suited for a hot forging press;

FIG. 11 is a graph illustrating the relationship between slide displacement and crank rotation for the mechanism illustrated in FIG. 10;

FIG. 12 is a schematic layout of a geared drag linkslider-crank mechanism for a hot forging press; and,

FIG. 13 is a sectional elevation view of a portion of the mechanism illustrated in FIG. 10, the section being with respect to line 13l3 in FIG. 12.

Referring now in greater detail to the drawings wherein the showings are for the purpose of illustrating preferred embodiments of the present invention only and not for the purpose of limiting the same, a geared drag link-slider-crank mechanism is schematically illustrated in FIG. I. The mechanism is comprised of a slide member 10 which is supported by the press frame in a well known manner for reciprocating movement in opposite directions along a linear slide path and through a stroke in which the slide member has a top deadcenter and a bottom dead-center position. Reciprocating movement is imparted to slide 10 by a slider-crank mechanism 12 comprised ofa crank arm 14 having one end pivotally interconnected with the press frame for rotation about an axis 16. The slider-crank mechanism further includes a link 18 having one end pivotally interconnected with crank arm 14 at axis 20 and having its other end pivotally interconnected with slide 10 at axis 22. Accordingly, it will be appreciated that rotation of crank arm 14 imparts reciprocating movement to slide 10 along the slide path.

Slider-crank mechanism 12 further includes a gear 24 suitably mounted and supported by the press frame for rotation about axis 16. Crank arm 14 is suitably interconnected with gear 24 for rotation therewith, whereby the gear and crank arm together define the slide crank. Gear 24 and crank arm 14 can be interconnected in any suitable manner, and many mechanical arrangements will be obvious to those skilled in the art.

For example, gear 24 and crank arm 14 could be fixer. to a common drive shaft. It will be appreciated too that the corresponding end of link 18 could be pivotally connected to gear 24, whereby the gear would define the slide crank.

The geared drag link-slider-crank mechanism further includes a drag link portion 26 comprised of an input crank including crank arm 28 supported by the press frame for rotation about an axis 30. The drag link portion further includes an output crank including crank arm 32 and gear 42 supported for rotation relative to the press frame about an axis 34. The outer ends .of crank

arms

28 and 32 are interconnected by a link member 36 having one end pivotally interconnected with crank arm 28 at axis 38 and having its outer end pivotally interconnected with crank arm 32 at axis 40. Crank arm 32 is of course interconnected with gear 42 for rotation therewith. Any suitable arrangement for interconnecting gear 42 and crank arm 32 for this purpose may be employed. The teeth of

gears

24 and 42 are disposed in meshing engagement for the purpose set forth hereinafter, and the gears have a transmission ratio other than 1:1.

Axes

30 and 34 are fixed with respect to the press frame and accordingly with respect to one another, whereby the distance therebetween remains constant and the portion of the frame therebetween defines a rigid link element in the drag link assembly.

Crank arm 28 is adapted to be rotated by any suitable drive arrangement, not illustrated, and in the schematic illustration of FIG. 1 crank arm 28 is rotated counterclockwise. Crank arm 28 is driven at a constant speed of rotation, and the mechanical relationship between crank arm 28, link 36 and crank arm 32 causes crank arm 32 and thus gear 42 to be rotated counterclockwise at a variable speed of rotation. In order to achieve freedom of continuous rotation of both

cranks

28 and 32, the following conditions with respect to the dimensional length relationships between the crank arms and links must be satisfied. The length dimensions are with respect to the distance between the pivot axes at opposite ends of the crank arms and links. With respect to the length relationships, the distance between pivot axes 30 and 34 must be shorter than the lengths of each of the

crank arms

28 and 32 and link 36. Further, the lengths of link 36 and crank arm 32 together must be greater than the combined length of crank arm 28 and the distance between

axes

30 and 34. Still further, the difference between the length of crank arm 32 and the distance between

axes

30 and 34 must be greater than the difference between the lengths of crank arm 28 and link 36. Many crank arm, link and spaced axes dimensions will, of course, meet these requirements.

As mentioned hereinabove, gears 42 and 24 have a transmission ratio other than 1:1. The discussion hereinafter will be in conjunction with a mechanism in which the gear ratio is 3:1, in other words gear 42 will make three complete revolutions for each revolution of gear 24. This gear ratioprovides for unicycle press operation. It will be appreciated that other gear ratios of any integer number greater than 1:1 will provide for such press operation.

As mentioned hereinabove, crank arm 28 is rotated at a constant angular speed, whereby gear 42 is rotated through the drag link mechanism at a variable angular speed. This relationship is illustrated in FIG. 2. It will be noted from FIG. 2 that the angular output speed of 7 gear 42 ranges from considerably faster to considerably slower than that of crank arm 28 for'each complete revolution of the latter crank arm. Accordingly, the drag link mechanism provides for the constant input speed through crank arm 28 to be transformed into an output speed through crank arm 32 and gear 42 that varies between above and below the constant input speed.

The output speed of crank arm 32 and accordingly gear 42 is transmitted to slide crank gear 24. Since

gears

42 and 24 have a transmission ratio of 3:1, crank arm 14 and gear 24 of the slider-crank mechanism will make one revolution while crank-

arm

28 and 32 and gear 42 make three revolutions. This defines one cycle of operation and during the cycle slide 10 is moved through one stroke. The variable output speed of gear 42 rotates gear 24 and thus crank arm 14 at a variable angular speed, 'and the three phases of speed variation of gear 42 during three revolutions thereof imposes three phases of angular speed variation on gear 24 for each revolution thereof, as illustrated in FIG. 2 of the drawing. Thus, crank arm 14 and gear 24 are rotated at variable speed during each revolution thereof, whereby three varying characteristics of movement are transmitted through link 18 to slide 10 during each complete stroke of the slide.

The variations in slide movement will be best understood by referring to the graphin FIG. 3. In this respect, the solid line graph in FIG. 3 illustrates the relationship between slide displacement and slide crank rotation for one complete revolutionof a slider-crank mechanism in which the slide crank is rotated at a constant speed. As shown, the slide is displaced, during one revolution of slide crank rotation, from the top deadcenter position of the slide through the bottom deadcenter position thereof and thence back to the top dead-center position along a generally uniform sinusoidal path.

The broken line graph in FIG. 3 represents the ex-- pected slide displacement pattern for rotation of the slide crank, during one complete revolution thereof, with the geared drag link arrangement illustrated in FIG. 1 and the gear ratio of the present embodiment, namely 3:1. As shown in FIG. 3, during rotation of the slide crank through approximately the first 30 to 40 the slide dwells in the region of its top dead-center position, whereas the slide represented by the solid line graph has at the same time begun its descent. During the following 50 to 60 of rotation of the slide crank the slide decends much more rapidly than the slide represented by the solid line. At approximately the 90 point of rotation of the slide crank the slide enters the work stroke, and from this point to the bottom deadcenter position at 180 of rotation of the slide crank the slide descent is slowed down substantially uniformly. From the 180 position to the 360 position of the slide crank the slide displacement reverses, whereby upward displacement is slow and substantially uniform from the 180 point to about the 270 point, rises sharply from the 270 point to about the 330 point and thereafter dwells in the region of the top dead-center position which is reached at the 360 point. Thus, it will be seen that the geared drag link-slider-crank mechanism described hereinabove provides a distinct difference in slide movement during rotation of the slide crank through one complete revolution in comparison with prior arrangements.

FIG. 4 is a graph of an actual plot of the position of the slide of a press having a geared drag link-slidercrank mechanism of the character schematically illustrated in FIG. 1 and in which the components of the mechanism have the following dimensions:

Crank arm 28 16.5 inches Link 36 20.0 inches Crank arm 32 9.5 inches Axis 30 to Axis 34 3.25 inches Crank arm 14 8.0 inches Link I8 inches Gear ratio 24 to 42 3:1

The graph of FIG. 4 is a plot from the readout of a computerizedanalysis of the kinematic motion of the geared drag link-slider-crank mechanism illustrated in FIG. 1 and having the foregoing dimensions. The input crank arm corresponding to arm 28 was rotated at 84 rpm, and the slide operated at 28 strokes per minute. The press has a total stroke ofl6 inches and a work stroke of approximately 4 inches. It will be seen from FIG. 4 that the slide displacement in actual practice corresponds substantially to the expected displacement pattern illustrated inFIG. 3.

It will be noted from FIG. 1 that the axes of rotation of crank

arms

28, 32 and 14 lie in a straight line which intersects the pivot axis 22 between slide 10 and link 18. It is not necessary that the pivot axes 30, 34 and 16 lie'ina straight line. It is important with respect to the example illustrated and described herein, however, that crank arm 14 be phased 10 past bottom dead-center when crank arm 32 is parallel to the slide path. This relationship is illustrated in FIG. 5.

In the embodiment described hereinabove the geared transmission ratio has the form of any integer number greater than 1:1. As mentioned, this provides for unicycle press operation. In FIG. 6, there is graphically illustrated the relationship between slide displacement and crank position for a geared drag link-slider-crank mechanism of the character illustrated in FIG. 1 and in which the transmission ratio is of the form of any noninteger rational number to l, or any integer number to different integer number. More particularly, the graph in FIG. 6 represents slide displacement versus crank position for a gear transmission ratio of 3:2. Such a gear ratio provides for multicycle press operation in which, as described hereinabove, different motion advances are imposed on the slide together with different speed variations during the same period of operation. For example, with a 3:2 gear ratio the slide undergoes two complete strokes in each of which a different motion is imparted to the slide and during which strokes three cycles of speed variations are imposed on the slide. The graphical illustration in FIG. 6 is based on a computerized analysis of kinematic motion of a press in which the geared drag link-slider-crank mechanism components have the dimensions identified hereinabove in connection with the discussion of FIG. 4. In the present instance, of course, the gear ratio is 3:2 rather than 3:1.

As shown in the graph of FIG. 6, crank arm 28 and thus gear 42 rotate exactly three times for every two complete revolutions of gear 24 and crank arm 14. As in the preceeding embodiment, the press had a total stroke of 16 inches and a work stroke of approximately 4 inches. In the present embodiment crank arm 28 was rotated at 30 rpm, and the slide was actuated at 20 strokes per' minute.

It will be seen from the graph of FIG. 6 that the slide moves through two complete strokes between the top and bottom dead-center positions thereof for each three revolutions of crank arm 28. The top dead-center position of the slide during the first stroke is reached at approximately 60 rotation of crank arm 28, the bottom dead-center position is reached at about 360, and the first stroke is completed by the slide reaching the top dead-center position at about 660 of rotation of crank arm 28. It will be appreciated that the slope of the line of the graph is indicative of slide velocity, and it will be seen that during the first stroke the slide descends at a substantially uniform and slow rate toward the bottom dead-center position and then rises quickly to the top dead-center position, and that there is a dwell as the slide approaches the top dead-center position. In contrast, it will be seen that during the second stroke the slide descends quite rapidly from the top dead-center to the bottom dead-center position, passes through the bottom dead-center position at a relatively low velocity, and then rises rapidly back toward the top dead-center position. Thus, two different motion characteristics are obtained for each three revolutions of crank arm 28, and three cycles of velocity variation are imposed on the slide during the same period. These dif ferent velocity characteristics provide for the press to be capable ofperforming several specialized operations on a single workpiece.

FIGS. 7-9 illustrate a typical two-point press having I a geared drag link-slider-crank mechanism of the character described hereinabove and in which the gear transmission ratio between the drag link portion and the slider-crank portion is 3:1. With reference to FIGS. 7-9, a press structure is illustrated which includes a press frame 50 including an upper frame portion 52 housing the geared drag link-slider-crank mechanism and a lower frame portion 54 which includes means, not illustrated, to support a slide member 56 for vertical reciprocating movement towards and away from a work supporting surface 57 of the press. It will be appreciated, of course, that the press frame is structured for supporting the press relative to an underlying surface such as a floor.

In the press illustrated, reciprocating movement is imparted to slide 56 by a pair of links 58 having lower ends pivotally interconnected with slide 56 by corresponding pivot pins 60.'The upper ends oflinks 58 are pivotally interconnected with corresponding gears 62 which are of the same size and each of which is supported by the press frame for rotation about a corresponding axis 64. The pivotal interconnection between each link 58 and the corresponding gear 62 is eccentric with respect to the gear axis 64. In this respect, each gear 62 is provided with a fixed eccentric element 66 about which the upper end ofthe corresponding link 58 isjournaled for rotation. Each eccentric element 66 has a corresponding axis 68 which rotates about the corresponding gear axis 64 in response to gear rotation. It will be appreciated, therefore, that rotation of each gear 62 about its axis 64 imparts rotation to the corresponding eccentric element 66 about axis 64, whereby links 58 are displaced upwardly and downwardly relative to gear axes 64 to impart vertical reciprocating movement to slide 56.

Rotation is imparted to gear 62 through a drive pinion 70 and an idler gear 72. Pinion 70 meshes with one of the gears 62 and idler 72 meshes with the other of the gears 62. Drive pinion and idler gear 72 are in meshing engagement, whereby rotation of drive pinion 70 imparts rotation to the gear 62 with which it meshes and imparts rotation to idler gear 72 for the latter to impart rotation to the gear 62 with which it meshes. Drive pinion 70 and idler gear 72 are of the same size, whereby gears 62 are driven at the same rotational speed.

It will be appreciated that gears 62, links 58 and the eccentric interconnection between the links and gears 62 provide a slider-crank mechanism corresponding to gear 24, crank arm 14 and link 18 of the mechanism schematically illustrated in FIG. 1. The drag link portion of the mechanism and the interconnection thereof with the slider-crank portion will best be understood with reference to FIGS. 7 and 8 of the drawing.

The drag link portion of the mechanism includes the drive pinion 70 which corresponds to gear 42 in the schematic illustration of FIG. 1. Accordingly, in the embodiment herein described, gears 62 and drive pinion 70 have a ratio of 3:1. Drive pinion 70 is supported by the press frame for rotation about an axis 74. More particularly, the press frame supports an apertured mounting member 76 through which the shaft 78 of pinion gear 70 extends. The end of shaft 78 opposite gear 70 is fixedly secured in the aperture of a crank member 80 which corresponds with crank arm 32 in FIG. 1. Crank member 80 is thus rotatable about axis 74 to drive pinion gear 70.

The end of mounting member 76 spaced from gear 70 is provided with an annular seat 82 which receives and rotatably supports an externally toothed gear 84. Mounting member 76 is fixed relative to the press frame, whereby gear 84 rotates relative to the mounting member. The annular seat which rotatably supports gear 84 is eccentric with respect to axis 74 of drive pinion 70, whereby gear 84 rotates about a fixed axis 86. Rotation is imparted to gear 84 through a drive gear 88 suitably supported relative to the press frame and connected to drive means which rotates gear 88 and thus gear 84 at a constant speed of rotation. A link member 90 has one end thereof pivotally interconnected with gear 84 by means of a pivot pin 92, and its other end pivotally interconnected with the outer end of crank member 80 by means of a pin 94. The axes of

pins

92 and 94 correspond respectively to pivot

axes

38 and 40 of the schematic illustration of FIG. I.

It will be seen that constant speed rotation of input gear 88 imparts rotation to gear 84 about axis 86 at a constant speed. The radial distance along gear 84 from axis 86 to pivot pin 92 defines a crank arm corresponding to crank arm 28 in the schematic illustration of FIG. 1. Rotation of gear 84 at a constant speed operates through link 90 and crank arm 80 to rotate pinion shaft 78 about axis 74. The crank arm and link relationship thus provides for pinion shaft 78 and thus gear 70 to be rotated at a variable speed as described hereinabove, whereby variable speed rotation is imparted to gears 62 of the slider-crank portion of the mechanism.

The geared drag link-slider-crank mechanism of the present invention also provides slide motion characteristics which are desirable in connection with the hot forging of metal blanks. In this respect, in the work stroke of a conventional crank press the tool impacts the workpiece at a high velocity, slows down gradually until the tool reaches the bottom dead-center position of the stroke and then speeds up gradually as it moves from bottom dead-center and out of the work stroke. In certain hot forging processes, such as the forging of projectiles for ammunition for example, neither high velocity impact nor a gradual velocity decrease and increase through the work stroke is necessary. The geared drag link-slider-crank mechanism of the present invention provides an improved forging tool motion by reversing the aforementioned characteristics of a conventional crank press. Accordingly, tool impact is reduced by lowering the contact velocity, and contact time between the tool and workpiece is reduced by increasing the tool velocity through the work stroke.

The slide motion characteristics achieved in connection with a hot forging press will be more clearly understood with reference to a specific example of a geared drag link-slider-crank mechanism for a hot forging press. FIG. 10 of the drawing schematically illustrates such a mechanism for a 1,700 ton forging press having a total slide stroke of-48 inches and a working stroke of 6.75 inches. The mechanism illustrated in FIG. 10 is comprised of the same basic components as the mechanism schematically illustrated in FIG. 1, and the operative interrelationship between the components in the two Figures is the same. Accordingly, like numerals with primes added thereto are employedin FIG. 10 for the components illustrated therein which correspond to the components in FIG. 1.

Referring to FIG. 10, the drag link-slider-crank mechanism illustrated is comprised of a slide member 10 which is supported by the press frame for reciprocating movement in opposite directions along a linear slide path and through a stroke in which the slide member has a top dead-center and a bottom dead-center position. The slider-crank mechanism 12' is comprised of a crank arm 14 having one end pivotally interconnected with the press frame for rotation about an axis 16. The slider-crank mechanism further includes a link 18' having one end pivotally interconnected with crank arm 14 at axis 20' and having its other end pivotally interconnected with slide 10' at axis 22'. Gear 24 is suitably mounted and supported by the press frame for rotation about axis 16', and crank arm 14 is interconnected with gear 24' for rotation therewith.

'Drag link portion 26 of the mechanism includes an input crank 28 supported by the press frame for rotation about axis 30, and an output crank 32 and gear 42 supported for rotation relative to the press frame about axis 34'. The outer ends of crank

arms

28 and 32 are interconnected by a link 36-having one end pivotally interconnected with crank arm 28 at axis 38' and having its other end pivotally interconnected with crank arm 32 at axis 40. Crank arm 32 is interconnected with gear 42' for rotation therewith, and the teeth of

gears

24 and 42 are disposed in meshing engagement. In connection with the forging press drive of the present embodiment, gears 24' and 42 have a ratio of 3:1. Further, as illustrated in FIG. 10, crank arm 14 preferably is phased past bottom dead-center when crank arm 32 is parallel to the slide path. The phase angle may, however, be varied for the purpose of varying the slide velocity through the work stroke. In this respect, the phaseangle preferably is maintained within to either side of bottom dead-center. Phasing ahead of bottom dead-center decreases the slide velocity, while phasing past bottom dead-center increases slide velocity.

FIG. 11 is a graph of an actual plot of the position of the slide of a forging press having a geared drag linkslider-crank mechanism of the character schematically illustrated in FIG. 10 and in which the components of the. mechanism have the following dimensions:

Crank arm 28' 33.00 inches .Link 36 22.284 inches Crank arm 32 28.598 inches Axis 30 to axis 34' l0.506 inches Crank arm 14' 24.000 inches Link 18' 84.000 inches Gear ratio 24' to 42' 3:]

The graph of FIG. 11 represents a plot from the readout of a computerized analysis of the kinematic motion of the geared drag link-slider-crank mechanism illustrated in FIG. 10 and having the foregoing dimensions. It will be seen from FIG. 11 that for each three revolutions of input crank arm 28' one revolution is imparted to slide crank arm 14', whereby slide 10' is displaced through a complete stroke between the top dead-center and bottom dead-center positions thereof. The slide path motion is depicted by the solid line in the graph. Superimposed thereon is a broken line representation ofthe slide motion through the bottom dead-center position for a conventional crank press. The inclination of the curves between the top dead-center and bottom dead-center positions of the slide are indicative of slide velocity.

It will be seen from a comparison of the curves in FIG. 11 that the geared drag link-slider-crank mechanism of FIG. 10 provides for the slide to dwell for a period of time in which the slide is near the top deadcenter position. As the slide approaches the beginning of the work stroke at 6.75 inches from bottom deadcenter, it will be seen that the slide velocity is less than that for the conventional crank press, whereby tool impact'with the workpiece is reduced. It will be further seen that during movement of the slide through the work stroke, the velocity thereof is greater than that of the conventional crank press, whereby tool contact time with the workpiece is reduced. These characteristics advantageously lead to increased tool and press component life and to decrease in the time required to produce a part from a workpiece.

FIG. 12 is a schematic layout of a preferred geared drag link-slider-crank mechanism particularly suited for ahot forging press, and FIG. 13 is a detail view of the drag link assembly. The mechanism structure, as will become more apparent from the following description, advantageously eliminates the eccentric loaded cantilever pins heretofore employed in drag link mechanisms in the press industry. The present structure advantageouslyprovides for pin and bearing stresses in the drag link mechanism to be no higher than the stresses elsewhere in the total drive arrangement. Further, the arrangement provides for balanced loading of the components during press operation and a reduction in load torque on the mechanism as a result of the drag link arrangement.

Referring now to FIGS. 12 and 13, a geared drag link-slider-crank mechanism is illustrated as being mounted relative to and supported by press frame components and 102. Advantageously, as will become apparent, the components of the mechanism are arranged symmetrically with respect to a reference plane through line P-P and perpendicular to the plane of FIG. 12. The arrangement includes a crank shaft 104 supported for rotation relative to frame

components

100 and 102 about an axis 106 which corresponds to axis 16' in FIG. 10. The crankshaft has offset journals 108 for connection with links corresponding to link 18 in FIG. 10. The outer ends of the crankshaft extend through corresponding openings in

frame members

100 and 102 and are provided with like gears 110 which are suitably keyed or otherwise fixed on the crankshaft ends. Gears 110 correspond to gear 24 in FIG. 10.

Frame components

100 and 102 support axially aligned quill components 112 which are suitably fixed to the frame components against rotation relative thereto. Quills 112 are provided with aligned openings which receive and rotatably support corresponding ends of a pinion shaft 114. The opposite ends of shaft 114 carry like pinion gears 116, and the teeth of gears 116 are in meshing engagement with the corresponding crankshaft gear 110. Gears 116 correspond to gear 42 in FIG. 10. Pinion shaft 114 has an axis 118 which is offset from the axis of quills 112, which latter axis is indicated by the numeral 120 in FIGS. 12 and 13. Axis 118 of the pinion shaft and axis 120 of the quills correspond, respectively, to

axes

34' and 30 in FIG. 10.

The inner ends of quills 112 rotatably support corresponding identical gears 122'for rotation about axis 120, and gears 122 are provided with aligned openings for receiving and rotatably supporting pin ends 124 projecting from the corresponding side of a connecting link 126 disposed between gears 122. Pin ends 124 have an axis 128 which corresponds to axis 38' in FIG. 10. Pinion shaft 114 is provided centrally thereof with an arm 130 which is keyed or otherwise rigidly at tached thereto. for rotation therewith. Arm 130 projects radially from shaft 114 and has its outer end pivotally interconnected with link 126 such as by a pin 132 extending through arm 130 and corresponding openings in a pair of rigid arms 134 of link 126. Pin 132 has an axis 136. Link 126 corresponds to link 36 in FIG. 10, and pin

axes

128 and 136 correspond, respectively. to axes 38' and 40' in FIG. 10.

It will be seen from the foregoing description that rotation of gears 122 about axis 120 at a constant speed causes link 126 to displace arm 130 about axis 118, whereby pinions 116 rotate about axis 118 at a variable speed of rotation to impart a variable speed of rotation to crankshaft gears 110. The crankshaft gears and pinion gears 116 have a gear ratio of 3:1, whereby gears 110 make one complete revolution for every three revolutions of the drag link mechanism.

Preferably, gears 122 are driven by corresponding like gears 138 mounted on a drive shaft 140 having opposite ends rotatably supported by

frame components

100 and 102. Further, the portion of drive shaft 140 between each of the gears 138 and the corresponding frame component is provided with a gear 142 which is concentric with and fixed to shaft 140 for rotation therewith. The input drive arrangement, in the embodiment disclosed, is completed by a pair of drive pinions 144 mounted on or integral with a drive shaft 146 having opposite ends rotatably supported by

frame components

100 and 102. One of the outer ends of input shaft 146 is provided with a flywheel and clutch arrangement 148 by which shaft 146 is'adapted to be driven by a motor, not illustrated, in a well known manner. The other end of input shaft 146 is provided with a suitable brake mechanism 150 by which the shaft is adapted to be braked during use in a well known manner.

Drive arrangements for gears 122 other than that specifically described above could be employed. The drive arrangement illustrated is preferred, however, in that it provides continuity in the balanced arrangement of components between the crankshaft and the drive input through driveshaft 140 and gears 138 thereon. In this respect, it will be seen from the schematic illustration in FIG. 12 that the loads imposed on the various components ofthe drive arrangement are balanced and divided equally along transmission paths through the components. It is to be noted in particular that the loads on pin 132 of the drag link mechanism are balanced by arms 134 of link 126, whereby cantilever pin loading is advantageously avoided. Further, loading of pin 132 in this manner provides for the load thereon to be distributed equally through link 126 to pin ends 124 and gears 122, thereby balancing the load imposed on the remaining portion of the gear train drive. Still further, any unbalanced load on gears which might result during a pressing operation is not transmitted through the drag link mechanism in that such a load is imposed on pin 132 through arm on pinion shaft 114, whereby the load is thereafter balanced with respect to the drag link mechanism.

While the description herein makes reference in particular to gear transmission ratios of 2:1 and 3:1 for unicycle press operation and 3:2 for multicycle press operation, it will be appreciated that other transmission ra- I tios which are other than 1:1 can readily be employed. Basically, the geared drag link'slider-crank mechanism of the present invention provides for the slider-crank and drag link portions of the mechanism to be rotated at a ratio of rotation of XsY, wherein X denotes the cycles of speed variations imposed on the slide and Y denotes the number of different motion characteristics imposed on the slide during the same period. By varying the gear ratio as described hereinabove, unicycle or multicycle press operation can be achieved to provide desired motion characteristics on each stroke of the slide. Moreover, it will be appreciated that various dimensions ofthe components of the mechanism may be employed without departing from the spirit ofthe present invention. Still further, it will be appreciated that many structural arrangements for achieving the desired press drives can be employed, and that many such arrangements will be apparent to those skilled in the art upon reading the foregoing description. Accordingly, as many possible embodiments of the present invention may be made and as many possible changes may be made in the embodiments herein illustrated and described, 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.

We claim:

1. A press comprising, frame means, a slide member supported in said frame means for reciprocating movement along a path between top dead-center and bottom dead-center positions, a toothed slide crank gear having an axis of rotation, a link member having opposite ends pivotally interconnected one with said slide member and the other with said slide crank gear at a pivot axis parallel to and spaced from said gear axis, whereby rotation of said slide crank gear about said gear axis imparts reciprocating movement to said slide member,

second toothed gear means drivingly engaging said slide crank gear, said slide crank gear and second gear means having a ratio of rotation other than 1:1, and means for rotating said second gear means at a varying rotational speed, whereby said slide crank gear is rotated at a varying rotational speed.

2. The press according to claim 1, wherein said second gear means has an axis of rotation and said means for rotating said second gear means includes input crank means, means for driving said input crank means at a constant rotational speed, and second link means having opposite ends connected one to said input crank means and the other to said second gear means at a point spaced from said axis of rotation of said second gear means.

3. The press according to claim 2, wherein said ratio of rotation between said slide crank gear and second gear means is 3:1.

4. The press according to claim 3, wherein said input crank means includes input gear means having an axis of rotation, said one end of said second link means being pivotally connected tosaid input gear means at an axis parallel to and spaced from said axis of rotation thereof.

5. A press comprising, frame means, a slide member supported in said frame means for reciprocating movement along a path between top dead-center and bottom dead-center position, slide crank means having an axis of rotation, link means having opposite ends pivotally interconnected one with said slide member and the other with said slide crank means for rotation of said slide crank means about said axis to impart reciprocating movement to said slide member, said slide crank means including slide crank gear means for rotating said slide crank means about said axis, second gear means drivingly engaging said slide crank gear means, said slide crank gear means and second gear means having a ratio of rotation of 3:1, means for rotating said second gear means at a varying rotational speed, whereby said slide crank gear means is rotated at a varying rotational speed, said second gear means having an axis of rotation, said means for rotating said second gear means including input crank means, means for driving said input crank means at a constant rotational speed, and second link means having opposite ends connected one to said input crank means and the other to said second gear means at a point spaced from said axis of rotation of said second gear means, said input crank means including input gear means having an axis of rotation, said one end of said second link means being pivotally connected to said input gear means at an axis parallel to and spaced from said axis of rotation thereof, said axes of rotation of said slide crank means, second gear means and input gear means being perpendicular to a reference plane through said press, and said slide crank gear means, second gear means and input gear means each including two identical gears disposed symmetrically on opposite sides of said reference plane.

6. The press accordingto claim 5, wherein said one end of said second link means is disposed between said two input gears and said other end of said second link means is disposed between said second gear means, and said second link means is bisected by said reference plane.

7. The press according to claim 6, wherein said means for driving said input crank means at a constant rotational speed includes a pair of like gears each in driving engagement with one of said input'gears, said like gears being disposed symmetrically with respect to said reference plane.

8. The press according to claim 7, wherein said frame means supports a pair of axially aligned and spaced apart quill components having outer surfaces concentric with respect to a quill axis through said components and apertures axially aligned with one another and offset with respect to said quill axis, each said input gears being supported on one of said quill components for rotation about said quill axis, said second gear means including shaft means rotatably supported by said quill components and extending through said aligned apertures therein, an arm fixed to and extending radially of said shaft means and having an outer end, said arm being bisected by said reference plane and said outer end of said arm being pivotally interconnected with said other end of said second link means.

9. The press according to claim 8, wherein said slide crank means includes a slide crank arm and said arm fixed to said shaft means defines a second crank arm, said slide crank arm being phased about 5 from a line through the axes of rotation of said slide crank means and second gear means when said slide member is adjacent said bottom dead-center position and said second crank arm is between the latter said axes of rotation and coincides with said line therethrough.

10. A press comprising a frame, a slide member supported in said frame for reciprocating movement along a path between first and second positions, drive means for said slide member comprising a first toothed gear rotatable about a first axis, a first link member having opposite ends pivotally interconnected one with said slide member and the other with said first gear at a point raidally spaced from said first axis, whereby rotation of said first gear imparts reciprocating movement to said slide member, a second toothed gear drivingly engaging said first gear, means supporting said second gear for rotation about a second axis parallel to and spaced from said first axis, crank means rotatable about a third axis parallel to and spaced from said first and second axes, second link means having opposite ends pivotally interconnected one with said crank means at a point radially spaced from said third axis and the other to said second gear at a point radially spaced from said second axis, said first and second gears having a ratio of rotation other than 1:1, and means to rotate said crank means at substantially constant rotational speed, whereby said first gear is rotated at a varying rotational speed through said second link means and said second gear.

11. The press as defined in claim 10, wherein said means supporting said second gear for rotation about said second axis includes means to support said crank means for rotation about said third axis.

12. The press as defined in claim 10, wherein said ratio of rotation of said second gear to said first gear is X:Y and Y is l and X is an integer number other than 1.

13. The press as defined in claim 10, wherein said ratio of rotation of said second gear to said first gear is X:Y and X is an integer number and Y'is an integer number other than X.

14. The press as defined in claim 10, wherein said ratio of rotation of said second gear to said first gear is X:Y and X is a non-integer rational number and Y is l.

Claims

1. A press comprising, frame means, a slide member supported in said frame means for reciprocating movement along a path between top dead-center and bottom dead-center positions, a toothed slide crank gear having an axis of rotation, a link member having opposite ends pivotally interconnected one with said slide member and the other with said slide crank gear at a pivot axis parallel to and spaced from said gear axis, whereby rotation of said slide crank gear about said gear axis imparts reciprocating movement to said slide member, second toothed gear means drivingly engaging said slide crank gear, said slide crank gear and second gear means having a ratio of rotation other than 1:1, and means for rotating said second gear means at a varying rotational speed, whereby said slide crank gear is rotated at a varying rotational speed.

4. The press according to claim 3, wherein said input crank means includes input gear means having an axis of rotation, said one end of said second link means being pivotally connected to said input gear means at an axis parallel to and spaced from said axis of rotation thereof.

6. The press according to claim 5, wherein said one end of said second link means is disposed between said two input gears and said other end of said second link means is disposed between said second gear means, and said second link means is bisected by said reference plane.

7. The press according to claim 6, wherein said means for driving said input crank means at a constant rotational speed includes a pair of like gears each in driving engagement with one of said input gears, said like gears being disposed symmetrically with respect to said reference plane.

9. The press according to claim 8, wherein said slide crank means includes a slide crank arm and said arm fixed to said shaft means defines a second crank arm, said slide crank arm being phased about 5* from a line through the axes of rotation of said slide crank means and second gear means when said slide member is adjacent said bottom dead-center position and said second crank arm is between the latter said axes of rotation and coincides with said line therethrough.

12. The press as defined in claim 10, wherein said ratio of rotation of said second gear to said first gear is X:Y and Y is 1 and X is an integer number other than 1.

13. The press as defined in claim 10, wherein said ratio of rotation of said second gear to said first gear is X:Y and X is an integer number and Y is an integer number other than X.