US3661008A

US3661008A - Presses

Info

Publication number: US3661008A
Application number: US20377A
Authority: US
Inventors: Barry Anthony Richardson
Original assignee: Wickman Machine Tool Sales Ltd
Current assignee: Wickman Machine Tool Sales Ltd
Priority date: 1970-03-17
Filing date: 1970-03-17
Publication date: 1972-05-09
Anticipated expiration: 1989-05-09

Abstract

A toggle press, in particular a coining press, in which a press slide is reciprocated towards and away from a thrust member by a first toggle linkage connected between the press slide and a stationary point and which is operated by a second toggle linkage connected between the first toggle linkage and a stationary point and which in turn is operated by a crank or eccentric driven at constant speed, the said two toggle linkages being of opposed angularity, and the length of the link of the said second toggle linkage which is connected to the said stationary point being shorter than the other link of the said second toggle linkage so that the press slide spends a greater part of its operating cycle near the top of its stroke removed from the thrust member than it does near the bottom of its stroke close to the thrust member. Additionally, the crank or eccentric deflects the second toggle linkage to one side of its center line for the major part of the operating cycle, and also deflects the second toggle linkage to a lesser extent to the other side of its center line during the remaining minor part of the operating cycle. Preferably, the lengths of the links of the second toggle linkage are substantially in the ratio 1:2 and the stroke of the press slide or ram is relatively short so that it remains close to the thrust member throughout its operations cycle.

Description

United States Patent Richardson PRESSES [72] inventor: Barry Anthony Richardson, Coventry, En-

gland Wickman Machine Tool Sales Limited, Coventry, England 221 Filed: Mar. 17, 1970 211 Appl. No.: 20,377

[73] Assignee:

[52] U.S. Cl ..72/451 [51] Int. Cl. ..B2lj 9/18 [58] Field of Search ..72/45 1; 83/604, 630

[56] References Cited UNITED STATES PATENTS 1,433,953 10/1922 Kennedy ..72/451 2,l20,356 6/1938 Glasner ..72/45I X Primary E.\'aminer-Milton S. Mehr A1mrne \--Scrivener, Parker, Scrivener and Clarke [57] ABSTRACT A toggle press, in particular a coining press, in which a press slide is re c'iprocated towards and away from a thrust member by a first toggle linkage connected between the press slide and a stationary point and which is operated by a second toggle linkag connected between the first toggle linkage and a stationary point and which in turn is operated by a crank or ec- ;centric driven at constant speed, the said two toggle linkages being of opposed angularity, and the length of the link of the said second toggle linkage which is connected to the said stationary point being shorter than the other link of the said second toggle linkage so that the press slide spends a greater part of its operating cycle near the top of its stroke removed from the thrust member than it does near the bottom of its stroke close to the thrust member. Additionally, the crank or eccentric deflects the second toggle linkage to one side of its center line for the major part of the operating cycle, and also deflects the second toggle linkage to a lesser extent to the other side of its center line during the remaining minor part of the operating cycle. Preferably, the lengths of the links of the second toggle linkage are substantially in the ratio 1:2 and the stroke of the press slide or ram is relatively short so that it remains close to the thrust member throughout its operations cycle.

11 Claims, 2 Drawing Figures PATENTEDMAY 91972 3.661008 SHEET 1 [IF 2 PATENTEDHAY 9mm sum 2 [1F 2 USN PRESSES This invention relates to presses, especially coining presses, and has as an object to provide a press in which a tool-carrying slide or ram operates to perform a reciprocating motion towards and away from a thrust member, characterized in that it spends a greater part of its operating cycle near the top of its stroke removed from the thrust member than near the bottom of its stroke close to the thrust member. Such a motion is particularly advantageous in high speed presses, such as in modern coining presses, in which a feed mechanism has to operate during each cycle of the press to feed work between the ram and thrust member, as it allows the feed mechanism a maximum time in which to operate and thereby removes any need to operate the press at a reduced speed to accommodate the feed mechanism.

Where a press slide is driven directly by a crankshaft or eccentric, its velocity varies approximately in a simple harmonic manner, being low near the top and bottom of the stroke and at a maximum in the middle of the stroke, so that the slide has a certain degree of dwell at the top as required, but also has a similar dwell at the bottom which is undesirable. A normal toggle press in which a slide is reciprocated by a toggle linkage connected between the slide and a stationary point, is even worse than a crankshaft press in that there is a considerable degree of dwell at the bottom of the stroke with the velocity rising to a maximum at the top. In these known toggle presses, the toggle linkage is normally driven directly through a connecting rod by a crank, but it has also been proposed to drive the toggle linkage through a second or auxiliary toggle linkage which is connected between the midpoint of the first toggle linkage and a stationary point, and which is itself driven through a connecting rod by a crank. It has, further, been proposed that the angularity of the two toggle linkages should be opposed (i.e., when one toggle linkage is straight the other is substantially in its position of maximum deflection and vice versa, each toggle linkage operating substantially on one side only of its center line) in order to arrange that the slide exerts a substantially constant force throughout its stroke. In none of these arrangements, however, has the object of the present invention been achieved. In fact, presses have always been preferred in which the ram or slide dwells at the bottom of its stroke as it then applies a maximum force to the work.

According to the present invention we propose a toggle press in which a press slide or ram is reciprocated towards and away from a thrust member by a first toggle linkage connected between the press slide and a stationary point and which is operated by a second toggle linkage connected between the first toggle linkage and a fixed point and which in turn is operated by a crank or eccentric driven at a constant speed, the two toggle linkages being of opposed angularity and the length of the link of the second toggle linkage which is connected to the stationary point being shorter than the other link of the second toggle linkage so that the press slide spends a greater part of its operating cycle near the top of its stroke removed from the thrust member than it does near the bottom of its stroke close to the thrust member. The first toggle linkage has an adverse velocity characteristic as in a normal toggle press, but the fact that the second toggle linkage is opposed in angularity to the first causes it to act so as to compensate for this adverse velocity characteristic, and by a suitable arrangement of the angularities and lengths of the links to over-compensate, so as to give the required motion, the press slide moving rapidly away from the thrust member during the initial part of its upstroke, but then dwelling, or moving a minimum amount over a large angle of crank movement at the upper end of its stroke.

According to a further feature of the invention, where the press is a coining press in which the press slide carries an upper die and the thrust member carries a lower die and blanks are coined between the dies in a collar plate, the stroke of the press slide is made relatively short so that the upper die remains relatively close to the lower die and forms a stop to prevent coined blanks from being uncontrollably ejected from the collar plate by the lower die. Clearly, in such a press the feed mechanism can only operate when the upper die is fairly near the top of its stroke and thus it is even more important that the slide and upper die move quickly over the bottom of their stroke to clear the feed mechanism and then dwell for a substantial proportion of the cycle near the top of the stroke while the feed mechanism operates to remove a coined blank and introduce a new blank between the dies.

The invention will now be described by way of example with reference to the accompanying drawings, in which:

FIG. 1 shows a side elevational view of a coining press according to the invention; and

FIG. 2 shows a graph to illustrate the manner in which the upper die of the coining press of FIG. 1 moves.

The coining press comprises an upper tool-carrying slide 1 and a lower thrust member 2 which both carry a replaceable die 3 and are positioned so that the dies are vertically aligned facing one another. Both the slide 1 and the member 2 are guided to move vertically in channel-shaped guide means 4 fixed to the frame 5 of the press. The upper slide 1 is connected through a toggle linkage 6 at its upper end to a support assembly 7 connected to the guide means 4, and is reciprocated vertically in the guide means by drive means comprising a second toggle linkage 8 connected to the first toggle linkage 6. The lower thrust member 2 normally assumes a lowermost rest position engaging against a lower support member 9 which is connected to the guide means 4. In this position the thrust member 2 is adapted to support a blank on the face of the lower die 3 carried by the thrust member so that the blank is coined between the dies when the upper slide 1 descends to the bottom of its stroke.

A new blank is introduced and the coined blank is removed from between the dies in a single action by feed means 10 of the rotary index plate type in which an index plate 11 with a series of outwardly opening notches around its periphery to receive the blanks, rotates to align each notch in turn with the dies. New blanks are loaded into the notches at a loading station by a pusher member which slides radially of the index plate to push a blank into each notch as it comes into position at the loading station. The new blanks are stored in a stacker tube 12 which is fed blanks at its upper end from a hopper l3 and which is adapted so that the pusher member pushes the lowermost blank from it each time it operates. The newly loaded blanks are then indexed towards the dies, and in the process they slide across the surface of a base plate 14 until each notch and blank is aligned with the dies 3 when the blank is free to pass through an aperture in the base plate to lie on the face of the lower die ready to be coined. Once the blank is coined it is raised to the level of the index plate 11 by the lower thrust member 2 (as shown in FIG. 1) so that as the index plate rotates again to bring a new blank into position, the coined blank is carried away in the same notch which delivered it. The coined blanks are finally ejected through a duct in the base plate at an unloading station and the unloaded notches are indexed towards the loading station to be reloaded.

The index plate and pusher member of the feed means 10, the lower thrust member 2 and the upper slide 1 are all driven in a synchronized manner from a mainshaft 15 so that a new blank is coined during each revolution of the mainshaft. The main shaft 15 carries a flywheel l6 and is driven at a constant speed through a belt drive by a motor 17. The upper slide is operated through the two

toggle linkages

6 and 8 and a connecting rod 18 which is connected between the second toggle linkage 8 and a crank 19 on the main shaft 15. The lower thrust member 2 is operated through a bell-crank lever 20, one arm of which engages the thrust member through a push rod 21 which is connected to the thrust member 2 and which is spring urged downwards, and the other arm of which carries a cam follower 22 which engages a cam 23 on the main shaft. The feed means 10 is provided with an index mechanism 24 which is driven through a gear-train 25 from the main shaft.

As already described above, the upper slide 1 is operated through the two

toggle linkages

6 and 8. The first toggle linkage 6 comprises two links 6 of equal length which are aligned vertically when in their straightened or center position. The second toggle linkage 8 comprises two links of unequal length, their lengths being substantially in the ratio of 1:2. The longer link 8' is pivotally connected to the center pivotal joint between the links of the first toggle linkage 6, and the shorter link 8" is pivotally connected to a stationary point on the press frame 5 so that when the second toggle linkage 8 is in its straightened state its links extend substantially horizontally to one side of the first toggle linkage 6. Further, the two

toggle linkages

6 and 8 are arranged so that they are of opposed angularity, i.e., when one toggle linkage is straight the other is in, or at least near, its position of maximum deflection and vice versa, each toggle linkage operating substantially on one side only of its center line. As shown in FIG. 1, the second toggle linkage 8 is substantially in its straightened position and the first toggle linkage 6 is in its position of maximum deflection, the upper slide 1 then being substantially at the top of its stroke. To move the slide downwards through its stroke the second toggle linkage has to be deflected downwards to straighten the first toggle linkage. This is achieved by the connecting rod 18 which extends substantially vertically upwards from the crank 19 on the main shaft and which is connected to the intermediate joint of the second toggle linkage 8 at its upper end. As shown in FIG. 1, the crank 19 is in its top dead-center position so that rotation of the main shaft 15 causes the connecting rod 18 to shift downwards so as to deflect the second toggle linkage downwards as required. Clearly, when the crank is in its bottom dead'center position, the first toggle linkage 6 is straightened and the upper slide is at the bottom of its stroke. As the crank 19 continues to rotate back to its top dead-center position the upper slide returns to the top of its stroke. Thus, one rotation of the main shaft causes the upper slide to perform a complete cycle of movement towards and away from the lower thrust member 2.

The manner in which the upper slide moves throughout its stroke is illustrated in the graph of FIG. 2, in which the position of the upper slide is shown on a linear scale against angular movement of the crank 19 over 180 from its top deadcenter position to its bottom dead-center position. From this it can be seen that the slide moves only slowly while the crank moves through the first 60 and then picks up speed so as to move faster towards the bottom of its stroke over the next 90",

finally slowing over the last 30 before reversing its direction of movement at the bottom of the stroke. During the upward return stroke the slide moves in a similar manner but in reverse, it beginning by moving quickly and slowing towards the top of the stroke as it completes the cycle. Thus, the upper slide tends to dwell at the top of its stroke for about a third of the time it takes to make a complete cycle, and it is during this time that the index plate 11 operates to remove the coined blank and introduce a new blank ready for coining. This motion results directly from the fact that the two toggle:

linkages

6 and 8 are of opposed angularity, and that the one link 8" of the second toggle linkage is shorter than the other link 8. If the links of the second toggle linkage 8 were of the same length, the upper die would tend to move at a substantially constant speed throughout its stroke and the index plate 11 would not then have time to operate properly without reducing the speed of the press, i.e., without increasing the period of the cycle of the press slide.

A further feature of the

toggle linkages

6 and 8 which helps to give the upper slide an increased dwell period at the top of its stroke, is the fact that the second toggle linkage 8 is not exactly in its dead-center position when the slide 1 is at the top of its stroke, but instead is deflected slightly upwards towards the other side of the center line from that side on which this toggle linkage 8 normally operates. Because of this fact, the upper slide moves slightly upwards as the crank I9 first moves from its top dead-center position and straightens the second toggle linkage. Once the toggle linkage 8 is straightened,

further rotation of the crank causes the upper slide to descend to the bottom of its stroke. Still further rotation of the crank causes the slide to rise again finally descending slightly at the top of its travel as the second toggle linkage passes overcenter. Thus the over-center arrangement of the toggle linkage 8 causes the upper slide to perform a superfluous stroke at the top of its main stroke. This superfluous stroke increases the dwell period at the top of the main stoke, but it should be noted that the extra dwell time which can be introduced in this way is limited by the fact that the superfluous stroke must not be so great as to interfere with the index plate 11, which is rotating at the time of this superfluous stroke to feed a new blank between the dies.

The blanks are supported on the lower die 3 within an annular collar plate as they are coined, and as a result of the coining operation the blanks expand radially to tightly engage the bore of the collar plate. Thus, when the lower die 3 is raised to return the coined blank to its notch in the index plate 11, substantial force has to be applied to the blank to eject it from the collar plate. Because of this there is a tendency for the ejected blank to be shot upwards in an uncontrolled manner which could cause it to interfere with the correct operation of the index plate. In order to prevent this from happening the stroke of the press is made relatively short so that the upper die remains relatively close to the lower die even at the top of its stroke, and thereby forms a stop to prevent coined blanks from being uncontrollably ejected from the collar plate. Typically, the stroke of the press may be of the order of 0.4 inches. Clearly, because of this short stroke it is essential to have the upper slide 1 and its die 3 move as shown in FIG. 2, as the upper die will have to move through a substantial proportion of its stroke before the index plate is free to operate, and it must do this quickly.

In order to change the dies in the press, a clamping nut 26 which secures each die 3 has to be axially unscrewed. However, because of the short stroke of the upper die, the dies cannot be moved apart sufficiently far, in the normal way, to allow this to be done. Thus, means are provided to allow the dies to be moved apart especially for this purpose comprising a wedge 27 clamped between a lower portion 29 and an upper portion 28 of the support assembly 7, so that the transverse position of the wedge determines the axial position of the lower portion 29, and thus the axial position of the first toggle linkage 6 and upper slide and die. The upper portion 28 is connected to the guide means 4, and the lower portion 29 is guided to move within the guide means 4. Two tie bars 30 pass through axial bores in the two

portions

28 and 29 and are connected to the lower portion 29, and a coil spring 31 surrounds each tie bar 30 and acts between the upper end of the tie bar 30 and the upper portion 28 to urge the two portions together to clamp the wedge 27 between them. The transverse position of the wedge is controlled by a screw 32 through a hand wheel 33. A similar wedge may also be provided for the lower die.

It will be appreciated that although we have described the invention above with reference to a coining press, it could equally well be applied to any press in which it is desirable that a ram or slide is moved in the above described manner. Further, it will be appreciated that the 1:2 ratio of the lengths of the links of the second toggle linkage given above is given only by way of example and that provided that the link 8' is longer than the link 8" the object of the present invention is satisfied.

What we claim is:

1. A toggle press comprising a thrust member and an opposing slide member; drive means which reciprocates the press slide towards and away from the thrust member comprising a first toggle linkage connected between the press slide and a stationary point, a second toggle linkage connected between the first toggle linkage and a stationary point, a crank mechanism connected to the second toggle linkage and means to drive the crank mechanism at a constant speed, the said two toggle linkages being of opposed angularity, and the length of the link of the said second toggle linkage which is connected to the said stationary point being shorter than the other link of the said second toggle linkage so that the press slide spends a greater part of its operating cycle near the top of its stroke removed from the thrust member than it does near the bottom of its stroke close to the thrust member; and feed means which operates during each operating cycle to feed work between the press slide and thrust member when the press slide is removed from the thrust member.

2. A press as claimed in claim 1 in which the ratio of the length of the said link of the second toggle linkage which is connected to the stationary point, to the length of the other link of the second toggle linkage is less than 2:3.

3. A press as claimed in claim 2 in which the ratio of the lengths of the links of the second toggle linkage is substantially 1:2.

4. A press as claimed in claim 1 in which the crank or eccentric deflects the second toggle linkage to one side of its center line for the major part of the operating cycle, but also deflects the second toggle linkage to a lesser extent to the other side of its center line during the remaining minor part of the operating cycle.

5. A press as claimed in claim 3, in which the links of the first toggle linkage are of substantially the same length.

6 A press as claimed in claim 5, in which the links of the first toggle linkage are of substantially the same length as the shorter link of the second toggle linkage.

7. A press as claimed in claim 6 in which the longer link of the second toggle linkage is connected to the intermediate pivot of the first toggle linkage.

8. A press as claimed in claim 1 for stamping blanks in which the feed mechanism is of the rotary index plate type in which blanks are received in notches around the periphery of an index plate and in which the index plate is rotated to align the notches one at a time between an opposing pair of dies carried on the press slide and thrust member.

9. A press as claimed in claim 8 in which the blanks are stamped while disposed in a collar plate and in which the stamped blanks are ejected from the collar plate by the thrust member.

10. A press as claimed in claim 9 in which the stroke of the press slide is relatively short so that it remains close to the thrust member and thereby acts as a stop to prevent stamped blanks from being ejected in an uncontrolled manner from the collar plate.

11. A press as claimed in claim 10 in which the lowermost position of the press slide is controlled by a wedge clamped between a fixed member and a member to which the stationary end of the first toggle linkage is connected.

Claims

6. A press as claimed in claim 5, in which the links of the first toggle linkage are of substantially the same length as the shorter link of the second toggle linkage.