US2667788A - Long-stroke press drive means - Google Patents

Description

Feb. 2, 1954 MAY ETAi 2,667,788

LONG-STROKE PRESS vDRIVE MEANS Filed Dec. 14, 1950 2 Sheets-Sheet l Feb. 2, 1954 0. MAY ETAL.

LONG-STROKE PRESS DRIVE MEANS 2 Sheets-Sheet 2 Filed Dec. 14, 1950 g WQ w -W Patented Feb. 2, 1954 LONG-STROKE PRESS DRIVE MEANS Otto May, Schwabisch Gmund, and Helmut Hecht, Goppingen, Germany Application December 14, 1950, Serial N 0. 200,734

Claims priority, application Germany December 16, 1949 3 Claims.

This invention relates to toggle presses, and with regard to certain features, to improved linkages therefor.

It is customary to move the toggle system of a toggle press either by a crank drive or by links acting upon the knee joint of the system. In these arrangements it has been diincult to achieve an appreciable stroke of the knee joint, as is desirable in certain classes of work, without unduly enlarging the proportions of the press. This limited motion of the knee joint, and thus of the ram, has in general restricted the use of toggle presses to coining, crushing, and similar operations, i. e., Work where only a small stroke and a high fina1 pressure are required. The methods suggested so far to increase the stroke have led to rather unwieldy constructions of excessive cost.

It is the object of this invention to eliminate the aforementioned disadvantages and limitations of former structures without affecting their inherent advantages in any way. Thus it is the primary object of this invention to provide improved means acting upon the knee joint of the toggle system consisting more particularly of pinccnnected links forced to travel along a predetermined path. As will be shown, it is possible by properly arranging the linkage and the path of the driving force to have the knee joint swing around the fixed fulcrum of the toggle system through an angle exceeding 90 degrees. With such an arrangement the stroke of the knee joint, and thus of the ram, is materially enlarged without appreciably enlarging the proportions of the press. The driving force is arranged in such a way that the force exerted is for the greater part of the travel substantially tangential to the link actuating the knee joint.

Although a number of ways have been devised to force the pin-connected links along a predetermined path, only a preferred embodiment of the invention will be described in the following, in which the knee joint is connected to the driving force by means of two pin-connected links, and in which the pin-point is adapted to swing around a fixed point at or approximately at the fulcrum of the system. This is achieved by another link being pivotally connected to said pin-point and said fixed point. The arrangement is materially simplified when the fixed point coincides with the fulcrum pin of the toggle system. In this type of construction the two links connected to the fulcrum pin and the connecting link between these two form a rigid triangle, and it is thus possible to construct this component of the linkage no longer by means of three separate links, but to replace them by an equivalent triangular member combining them without in any essential Way changing the operation of the system.

Though it will be understood that there are a number of ways adapted to force the pin-connected links along a predetermined path, the invention will in the following be described only by way of the aforementioned simplified constructions.

In the accompanying drawings, in which three embodiments of this simplified construction are illustrated:

Fig. 1 is a kinematic diagram illustrating one form of the invention with the linkage in its initial position;

Fig. 2 is the same arrangement with the linkage in its final position;

- Fig. 3 is a kinematic diagram illustrating a second form of the invention with the linkage in its initial position;

Fig. 4 is the same arrangement as before with the linkage in its final position;

Fig. 5 is a kinematic diagram illustrating a third form of the invention with the linkage in its initial position;

Fig. 6 is the same arrangement as before with the linkage in its final position.

In order to avoid circumlocution, parts that play the role in the three different forms of the invention shown in Figs. 1 to 6 are given the same letter throughout. Cross-hatching indicates connections to the usual frame of the machine.

In Figs. 1 and 2 the connecting rod of the toggle system is denoted by a, the crank arm by b. The fulcrum pin of the system with the frame is called 0, the knee-joint f, the moving pin-joint with the ram 2 is denoted d, the guide for the ram is e. The transmission system consists of two links, an operating link g and a driving link q. Link q is pin-connected to a nut m which is driven by a threaded spindle it along a guide 0. By the provision of a guiding link 2' rotating about a fixed pin-joint k, the joint h is forced to move along a strictly circular path, the radius of the circle being determined by the length of the guiding link 2.

Fig. 1 shows the system in its initial and Fig. 2 in its final position. The stroke w determined from the two relative positions is achieved by the rotation of crank arm I) through an angle a. exceeding 90 degress as indicated in Fig. 2 and is considerably larger than in conventional toggle presses where this angle is below 90 degrees.

When in a system, wherein the guiding link 2' forces joint it 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 the joint 11, showing drooping characteristics of the velocities only near the ends of the stroke.

Figs. 3 and-4 illustrate a modification of the systern shown in Figs. 1 and 2. In this case the fixed pin-joint k coincides with the fulcrum 0, both joints being now denoted by the letter 0. As in this simplified system the three links 1),, g and 2' form a closed triangle, their relative position is definitely fixed with the result that the system is in no way changed in its operation when these three links are replaced by a triangular member having pin-joints on every corner and with sides corresponding to the links 17, g and The Figs. 3 and 4 show this triangular member arranged in such a manner that the movable driving block m and the knee-joint f are on opposite sides of the fulcrum c.

Fig. Bshows the system in its initial and Fig. 4 in its final position. The stroke 20 determined from the two relative positions is achieved by the rotation of link I) through angle a. exceeding 90 degrees as indicated in- Fig. 4 and is considerably larger than in conventional toggle presses where this angle is below 90 degrees. 7

Referring now to Figs. 5 and 6, the system shown is modified incertain parts as compared to that illustrated in Figs. 3 and 4 in that the movable driving block a: and the knee-joint f are arranged on the same side of the fulcrum c. In addition the system is no longer driven by a nut moving along a threaded spindle, but operated by the block :1: moving along the straight-line guide 0. The block is reciprocated by means of a piston rod r connected to a reciprocating piston s moving in cylinder t.

Preferably hydraulic means are provided for moving pistons, said means being not shown in the drawings.

The motion of block- ;n istransmitted to the system through the driving link q.

Fig. 5 shows the system in its initial and Fig. 6 in its final position. The stroke 10' determined from the two relative positions-is achieved by the rotation of link b through angle a. exceeding 90 degrees as indicated in Fig. 6 and is considerably larger than in conventional toggle presses where this angle is below 90 degrees.

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 construction (as, for example, different driving system) 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.

We claim:

1. A toggle press comprising a frame, a toggle linkage consisting of a crank having a fulcrum pivot on the frame and having a knee-joint, a ram movable in a frame guide toward and away from the fulcrum pivot, a connecting rod between the ram and the knee-joint on the crank, a driving block moving in a guide the center line of which is approximately parallel to the direction of ram movement, a pivot, means constraining movement of the pivot substantially in a circle having its center approximately at said fulcrum, a rigid connection between the pivot and said knee-joint, and a draw link connecting said pivot and the driving block, said draw link in any position assuming approximately equal angles relative to the substantially parallel center lines of movement of the block and the ram, the center line of the driving block being sufiiciently close to the center line of the ram that said crank during a complete driving movement of the block will be movable from a final position in which it is closely in line with the connecting rod to a retracted positlOlIl'WhlCh is not less than 90 from said final position, said block throughout a working stroke of the ram being movable in a direction adapted to decrease said equal angles.

2; A toggle press made according to claim 1, wherein said block and said ram move in opposite directions throughout working and retractive strokes of the latter.

3. A toggle press made according to claim 1, wherein said block and said ram move in the same direction throughout working and retractive strokes of the latter.

OTTO MAY. I-IELMUT HEC'HT.

References Cited in the file of this patent FOREIGN PATENTS Number Country Date 246,892 Germany Aug. 29, 1909 708,935 France July 30, 1931 720,875 Germany Apr. 16, 1942

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