US 2587746 A
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Description (OCR text may contain errors)
March 4, 1952 O, H MAY 2,587,746
'IOGGLE PRESS LINKAGE Filed Feb. 28, 1949 s Sheets-Sheet 1 March 4, 1952 o. H, MAY 2,587,746
TOGGLE PRESS LINKAGE Filed Feb. 28, 1949 3 Sheets-Sheet 2 'F|G.6. 9, n
c b w f K a March 4, 1952 o. H. MAY 2,587,745
TOGGLE PRESS LINKAGE Filed Feb. 28, 1949 3 Sheets-Sheet 3 of hot or cold metal into elongate shapes.
Patented Mar. 4, 1952 TOGGLE PRESS L KAGE Otto Hermann May, Schwabisch Gmund, Germany Application February 28, 1949, Serial No. 78,763 In Switzerland August 24, 1948 4 Claims.
This invention relates to toggle presses, and with regard to certain more specific features, to improved linkages therefor.
It is customary to move the toggle system of toggle presses either by a crank drive or by links acting upon the knee joint of the system such that the ram has a velocity-displacement curve which droops considerably at its ends, approximately (though not exactly) according to a sine function. With a constant driving force this produces a force-displacement curve having the inverse characteristic, namely a considerable droop in its middle portions. While this is advantageous for certain classes of work, it is disadvantageous for other classes, such as extrusion These should extrude from their dies at a fairly constant rate under a fairly constant force. 'While hydraulic presses will produce the proper functions, they are more expensive to build than the toggle type.
Another disadvantage inherent in the prior driving mechanism used for toggle presses is the comparatively small stroke of the knee joint. Experience has shown that in the toggle systems of today this stroke is limited, because the angular displacement of the toggle system (angles between the toggle arms and the lines connecting the terminal points of the system) must notbe too large.
driven members decreases so much that toggle systems are no longer useful.
It is the object of this invention to eliminate the aforementioned disadvantages and limitations of toggle systems without affecting their inherent advantages in any way. Thus it is the primary object of this invention to provide improved driving means acting upon the knee joint of the toggle system, consisting more particularly of pin-connected links whose pin-joint is forced to travel along a predetermined path.
As will be shown, it is possible, by fixing the travel of the aforementioned pin-joint, to provide for any desired velocity-displacement relaplacement has in itself been greatly increased If a certain limit is exceeded, the mechanical advantage between driving and Cross-hatching by the invention as compared with known toggle presses.
The invention accordingly comprises the elements and combinations of elements, features of construction, and arrangements of parts which will be exemplified in the structures hereinafter described, and the scope of the application of which will be indicated in the following claims.
In the accompanying drawings, in which several of various possible embodiments of the invention are illustrated,
Fig. 1 is a kinematic diagram illustrating one form of the invention;
Figs. 2-4 are kinematic diagrams illustrating a second form of the invention in three different positions of operation (upper dead point, Fig. 2 intermediate position, Fig. 3; and lower dead point, Fig. 4)
Fig. 5 is a kinematic diagram of another form of the invention;
Fig. 6 is a kinematic diagram illustrating a symmetrical arrangement of two of the linkages shown in Figs. 2-4 operated from a common pinconnected driving block;
Fig. 7 is a'kinematic diagram showing a modified means for actuating the driving block, being illustrated in connection with the form of the invention shown in Figs. 2-4; and,
Fig. 8 is a kinematic diagram showing a form of the invention employing a toggle linkage which acts in tension.
In order to avoid circumlocution, parts that play the same role in certain forms of the invention shown in Figs. 1'7 are given the same letter throughout the various modifications. indicates connections to the usual frame of the machine.
In Figs. 1-7, the connecting rod of the toggle system is uniformly denoted by a, the crank arm by b. The fulcrum pin of the system with the frame y is called c, the knee joint the moving pin-joint with the ram 2 is denoted d and the guide for the ram ise. The transmission system consists of two links, an operating link 9 and a driving link q.
in Fig. 1, links 9 and q are pinned at h. This pin is forced to follow a curved path by means of a guide 11 in the frame. Link q is pin-connected to a nut m in the form of a crosshead or slider block which is driven by a threaded spindle n along guide 0. Substantially constant rotary motion of the threaded spindle n is reversibly controlled to reciprocate the slider block or nut m. The shape of'the curved guide p (Fig. 1)
determines the path of the pin-joint h. In Fig.
3 1 it is curved but non-circular. The arrangement is such that the direction of pull of link 9 remains nearly tangent to the entire circular path of the knee joint f over the useful part of the motion of the toggle system. The most desirable velocity-displacement relationship of the ram 2 is controlled by the curvature of the guide p. Thus it is possible, if this be desired, very quickly to accelerate and decelerate the ram at the beginning and end of its stroke, and to maintain therebetween a substantially constant velocity for practically the entire length of the stroke. If the velocity-displacement relationship of the ram is then plotted, the result will be substantially a straight line parallel to the path of d for practically the entire stroke.
It will be observed that the guide for the slider 11:. (Figs. 1-7) and for the slide 29 (Fig. 8) is substantially parallel to the straightened position of the toggle. It will also be observed that the curvilinear path of the joint n (Figs. 1-7) or joint 2| (Fig. 8) is convex toward the fulcrum (Figs. 1-7) or 35 (Fig. 8). The curvilinear guide means also lies primarily on the side of l from the guide is substantially normal to the,
guide and a tangent at the other end which lies toward the guide is substantially parallel to it. Thus the slide such as m applies maximum force to the toggle linkage when the latter is in its position of least mechanical advantage (Fig.
2). On the other hand, it applies decreasing force to the toggle linkage as the latter approaches its position of maximum mechanical advantage. Thus is force compensation provided for between the toggle linkage and the drag link so that a substantially constant force is obtained on the ram.
If it be satisfactory that the velocity remain practically constant for the greater part of the stroke (as distinguished from practically all of it), the guide 11 can be made circular. But in this event, the guiding system for point it can be simplified as illustrated in Figs. 2-4. Here the joint h is forced to move along a strictly circular path by provision of a guiding link i, rotating about a fixed pin-joint k. The radius of the circle is determined by the length of the guiding link i and the center k lies within the sector swept by crank arm b. If in the system wherein the guiding link i forces joint 71. along a circular path, the velocity-displacement curve of the ram is plotted, it is found that this curve is practically a straight line parallel to the path of point d, showing drooping characteristics of the velocities occurring only near the ends of the stroke.
- Through this manner of changing the velocitydisplacement characteristic of a toggle linkage over a wide range, it is possible to adapt toggle presses to work, which to date has been completely outside of their scope. In other words, advantageously it becomes possible with such a press to keep both pressure and velocity of the ram constant over a large portion of the stroke without changing the driving force.
One of the stated advantages of the invention will be seen from Figs. 2-4. This is that even for a large initial angular displacement of b, the
mately tangential. tion of parts is shown. As the block m travels up, link i is raised (Fig. 3) and the pull of link 9 on the knee joint 1 remains fairly tangential as a and b straighten. This tangential relationship is deviated from only in the relationship of the parts shown in Fig. 4 (wherein the toggle links a, b are almost in line) If desired, the link 9 (as shown in Fig. 5), instead of being coupled to the link i at joint h, may be coupled thereto at a joint w which is displaced inward from h, which somewhat simplifies the mechanical design of joint h without deviating far from the advantages stated. Various positions of w on i may be selected.
In Fig. 6 is shown a symmetrical compound arrangement of the structure illustrated in Figs. 2-4. In this Fig. 6, symmetrical parts corresponding to the parts of Figs. 2-4 are similarly lettered, except that those on the right are primed. In this case the frame is lettered 12/. Both links q and q are attached to a common block m operated upon by a common threaded reversing spindle n. The joints d and d may be carried on separate rams (as shown) or the same ram.
In Fig. '7 is shown an arrangement like that illustrated in Figs. 2-4, except that the driving mechanism does not consist of the threaded spindle n and block m for forming a guided crosshead. In this case a piston-operated crosshead :c is employed, which moves along the straight-line guide 0. The crosshead is reciprocated by means of a piston rod r connected to a reciprocating piston s moving in cylinder 1.. This motion is transmitted to the system through the driving link q.
As described, the link i is pivoted to the frame at k. The pressure-displacement relationships above mentioned can be changed by adjusting the position of this pivot point It.
In Fig. 8 is shown an arrangement wherein the connecting rod of the toggle is actuated in tension and the table of the press is close to the pivot of the crank, so that the frame of the machine has compressive stresses only applied in a limited portion of it.
Referring to Fig. 8, numeral l indicates the frame parts. The toggle crank is indicated at 3, pinned at 1 to a connecting rod 5. The connecting rod 5 is pinned at 9 to the ram or slide ll, operating in a guide l3 of the frame I. Pinned to the frame at [5 is a triangular-shaped link I! (rigid within itself). The link I! carries pin joints l9 and 2|. A link 23 connects joint IS with joint I. A link 25 connects joint 2| with a joint 21 on the threaded driving block or crosshead 29.
The reversing spindle 3! is threaded through the driving block 29 for reciprocating it. If the driving block be moved upward, the link I! is moved anticlockwise to draw down the pin joint l9 and consequently to draw down the pin joint 1. This draws down the connecting rod 5 in tension, so that the slide ll moves downward. It carries the tool that operates on a piece carried in the frame and supported upon a platen such as shown, for example, at 33. During the downward travel of the slide l I, the crank 3 and connecting rod 5 approach a coincident arrangement. The advantageous relationship between the drag link 23 and crank 3 is more or less maintained throughout the action, namely, the pull of 23 remains more or less tangential to the path of the joint I. Also, the pull of rod 25 is substantially tangential to thepath of its driving end at 2| throughout most of the stroke, deviation occur.-
I ring as toggle members 3 and 5 approach alignment. This form of the invention has the advantage that the connecting rod is in tension, and the parts of the press frame above the platen 33 are not stressed. The required stress is in the rod 5 as tension. The only primary stresses that occur in the press frame are compressive stresses between the platen 33 and the center of rotation 35 of the crank 3. This simplifies the design of the press frame, allowing it to be made with much less bulk above the platen 33.
From the above it will be seen that the invention may be summarized as follows: The ram of the press is directly actuated by the toggle linkage. The driving block is connected with the knee joint through what may be referred to as concatenated drag links, a joint of which is constrained to move in a curved path (preferably circular).
The press constructed according to the invention above-described is especially suited to be employed for conditions that ordinarily require a hydraulic press, such as presses for plastics, extrusion (hot or cold), etc. It should be understood, however, that the invention has other applications such as to crushers and the like, and the term press is intended to comprehend any apparatus wherein pressure is required to be exerted substantially constantly over a wide range.
For the purpose of the appended claims, the following terminology is used herein: The main toggle system is composed of a press frame, a ram slide, a crank pivoted to the frame, and a connecting rod connecting the crank with the ram slide, the crank and the connecting rod being adapted to be swung from a substantial angular relationship to a small angular relationship near the dead point. These parts in Figs. 1-7 are, respectively, frame y, ram a, crank 12 and connecting rod a, with corresponding primed letters in Fig. 6. In Fig. 8 these parts are the frame I, ram l l, crank 3 and connecting rod 5.
This toggle system is coordinated with What may be called a drag link system composed of the frame, the crank, the drag link, and guiding curve means for one end of the drag link. In Fig. 1 the drag link system is constituted by the frame 11, crank b, drag link g and the curved guide p. In Figs. 2-7 this drag link system is the frame y, crank b, drag link g, and crank i, primed letters in Fig. 6 corresponding to corresponding parts. In Fig. 8 the drag link system is constituted by the frame I, crank 3, drag link 23 and crank IT.
The above-mentioned drag link system is operated by a slider mechanism which is constituted by the frame of the machine, a driving slider, a connecting rod between the driving slider and one of the cranks of said drag link system or the curved glide. In Fig. l the slider mechanism is the frame 11, crosshead m and connecting rod q and. guide p. In Figs. 2-7 the slider mechanism is the frame 3 the crosshead m, connecting rod q and crank i, primed letters in Fig. 6 corresponding to corresponding parts. In Fig. 8 the slider mechanism is constituted by the frame I, crosshead 29, connecting rod 25 and crank [1.
In the above the frame has been mentioned as part of each mechanism system specified because in each case it is kinematically necessary to ensure constrained operation of each divided system. Wherever other links are considered as parts of more than one system, it is because they are so used to ensure kinematic constraint.
In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.
As many changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.
1. In a press, a frame, a combination of a toggle system and an articulated compensating drag link system adapted to produce a mechanical advantage throughout the driving movement of the press which is substantially more uniform than that of which the toggle system alone is capable; said toggle system comprising a crank arm pivot-\ ed at a fulcrum and pivoted at a knee joint to a ram-controlling first connecting rod; said drag link system comprising a drag link connected at one end to the toggle system, means establishing a curvilinear trajectory for the other end of the drag link, a driving slide in a guide which extends in a direction substantially parallel with the straightened position of the toggle system and primarily on the side of the toggle system opposite its break side, said trajectory lying primarily between the straightened position of the toggle system and said guide means and being convex toward the fulcrum and having a tangent at one portion which is substantially angled to the guide means and having a second tangent which lies at a smaller angle to the guide means, and a second connecting rod pivoted at one end to the slide and at its other end having an operative connection with the drag link.
2. Apparatus made according to claim 1, wherein the pair consisting of the crank arm and said drag link on the one hand and the pair consisting of said drag link and the second connecting rod on the other hand each remain at a relatively constant angle until the toggle system nearly reaches its straightened position.
3. Apparatus made according to claim 1, wherein the means establishing the trajectory is a guide in the frame, and a follower member in the guide which is connected to the drag link.
4. Apparatus made according to claim 1, wherein the means establishing the trajectory is a link pivoted to the frame at a point "near the fulcrum.
OTTO HERMANN MAY.
REFERENCES CITED The following references are of record in the file of this patent:
UNITED STATES PATENTS Number Name Date 643,832 Swan Feb. 20, 1900 1,091,659 Hewlett Mar. 12, 1912 1,387,729 McGarry Aug. 16, 1921 1,675,494 Jennings, et al July 3, 1928 1,680,729 Davis Aug. 14, 1928 1,820,051 Davis Aug. 25, 1931 1,945,496 Sloan Jan. 30, 1934 2,269,308 Gates Jan. 6, 1942 2,318,814 Strong May 11, 1943 -FOREIGN PATENTS Number Country Date 246,892 Germany Aug. 29, 1909