GB2299962A - Press for working material - Google Patents

Abstract

A material working press which comprises a rotary input drive (11), first and second die carriers which are relatively movable between a release position and a forming position effective against a blank of material inserted between the die carriers, and a linkage (14) which couples together the input drive (11) and one of said die carriers (12) to effect linear reciprocation of said one die carrier, upon rotation of said input drive (11), and in which said linkage (14) comprises: ```a two-part hinged link (15, 16) having a first part (15) which is eccentrically connected at its free end (16) to said input drive (11), and a second part (17) pivotally connected at its free end (18) to said one die carrier (12); ```a two-armed rocker (20) pivotally mounted to carry out rocking movement about a fixed axis (21); ```a first link arm (24) pivotally connected at one end to one arm (22) of said rocker (20), and pivotally connected at its other end via a crank arm (25) to the input drive (11); and ```a second link arm (26) pivotally connected at one end to a second arm (23) of said rocker (20), and pivotally connected at its other end to a hinge connection (19) between the first and second parts of said two-part hinged link (15, 17).

Description

PRESS FOR WORKING MATERIAL This invention relates to a press for working material and is particularly, though not exclusively, concerned with a coining press for minting coins from blank material placed between a pair of co-operating die carriers.

Thus, a coining press usually comprises a pair of cooperating die carriers, which are moveable relatively towards and away from each other to carry out a die-forming action on a metal blank. Usually, each die carrier is moveable under the action of its own drive linkage, though what is essential is that relative movement takes place between an operative forming position and a release position, and therefore it is possible that one die carrier may be fixed and the other may be moveable.

In a coin-forming operation, it is desirable to provide a drive linkage for at least one of the die carriers which has a sufficient "dwell" period, after completion of a forming stroke, so that the forming operation can be completed, before the release stroke takes place. It is important also that the components of the linkage, and any rotary drive input e.g. a crank drive should be arranged to be dynamically balanced, as far as possible, so as to avoid, or minimise the generation of out of balance forces.

The invention seeks to provide a press for working material having an improved drive linkage to one of the die carriers.

A material working press according to one aspect of the invention is defined in claim 1.

A material working press according to a second aspect of the invention is defined in claim 2.

By such an arrangement according to the invention, as defined above, linear reciprocation of said one die carrier is effected, under the action of the two part hinged link, and in which the motion of the two part hinged link is controlled partly by the eccentric connection at the free end of said first part to the rotary input drive, and also by lateral movement applied to the hinged connection between the first and second parts via the crank drive motion transmitted to said rocker via said first link arm and then from the second link arm to the hinged connection.

By careful design over the relative proportions and arrangements of the components of the linkage, any desired speed of reciprocation of said one die carrier can be obtained, and including any required variation in linear speed during each of the forming stroke and the release stroke, and also any desired "dwell" periods during each cycle of operation.

Conveniently, the input drive to operate the linkage comprises a drive shaft, and having any suitable cranks coupled with the shaft to convert rotary motion of the shaft into generally linear reciprocating motion of the components of the linkage coupled therewith, namely said first part of the two part hinged link, and said first link arm of said rocker.

Usually, it will be desirable for said one die carrier to be guided so that it carries out linear reciprocation, and preferably the second die carrier, to co-operate therewith has a separate drive linkage which is operated, in conjunction with rotation of the input drive, so that the die carriers move towards and away from each other during forming and release strokes respectively.

Two preferred embodiments of material working press according to the invention will now be described in detail, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a schematic illustration of the essential component parts of a first embodiment of press according to the invention, and in which drawings a to d show the positions taken up by the components during successive stages of a cycle of operation; and Figure 2 is a side view showing in more detail one practical form of the schematic illustration of Figure 1; Figure 3 is a schematic illustration, similar to Figure 1, of a second embodiment of press according to the invention; Figure 4 is a side view showing a practical form of the schematic illustration of Figure 3; and, Figure 5 is a diagram of distance / time for the crank and linkage drive mechanism of Figure 4.

Referring now to Figures 1 and 2 of the drawings, a material working press according to the invention is designated generally by reference 10, and for the sake of example only, it can be assumed that the press is a coining press having a pair of co-operating die carriers which are moveable relatively towards and away from each other to carry out a die-forming action on a blank, which will be a metal blank in the case of a coin forming operation. Usually, each die carrier will be arranged to be moveable under the action of its own power linkage, although what is important is that relative movement takes place between an operative forming position and a release position, and therefore one die carrier could be fixed, and the other one could be arranged to be moveable.

In the embodiment illustrated in the drawings, only one moveable die carrier is illustrated.

A rotary input drive is provided to operate the press, and takes the form of a drive shaft which is shown schematically by reference 11 in Figure 1, and takes the form of a crank shaft H shown in Figure 2. As shown in Figures 1 and 2, a first die carrier is operated by a slide 12 mounted for linear reciprocation within a guide 13 so as to move the die carrier between a release position and a die-forming position in co-operation with the other die carrier and against a metal blank inserted between the die carriers. A linkage which is designated generally by reference 14 couples together the input drive shaft 11 and the moveable die carrier so as to effect linear reciprocation of the die carrier upon rotation of the drive shaft 11.

The linkage 14 comprises a two part hinged link (15, 16) having a first part 15 which is eccentrically connected at its free end 16 to the drive shaft 11, and a second part 17 is pivotally connected at its free end 18 to the slide 12. There is also a hinged connection 19 between first part 15 and second part 17, and the movement of the hinged connection 19, during a cycle of operations is shown in Figures 1a to 1d.

A two armed rocker 20 is pivotally mounted on the press frame to carry out rocking movement about a fixed axis 21, and comprises first and second rocker arms 22 and 23 respectively which are joined together in a rigid assembly, to move jointly about the pivot axis 21. It should be understood that Figure 1 is a schematic representation only of the rocker 20, and that what is important is that there is pivoted connection to rocker 20 via further parts of the linkage, and which pivot connections are off set from the pivot axis 21.

A first link arm 24 is pivotally connected at one end to rocker arm 22, and at its other end it is pivoted via a crank arm 25 to the input drive shaft 11. A second link arm 26 is pivotally connected at one end to rocker arm 23, and at its other end to the hinge connection 19 of the two part hinged link (15, 17).

Figures 1a to 1d show positions taken up by the components of the linkage during successive stages of a cycle of operation. It should be noted that the radial off set of the eccentric connection 16 relative to the axis of shaft 11 is relatively small, so that only a small circular orbit of link end 16 takes place about the axis of shaft 11, whereas the orbit of the pivot connection of link arm 24 to the end of crank arm 25 has a larger radius about the axis of shaft 11.

The relative angular separation of eccentric connection 16 and the connection of link arm 24 to the end of crank arm 25, relative to the axis of the shaft 11, can be seen in Figures la to ld, and this angular separation is carefully chosen to give the required linear motion imparted to the slide 12 during each cycle of revolution of input shaft 11.

Figure 1 is a schematic illustration of the geometry of the component parts of the linkage, and a practical example of the invention is shown in more detail in Figure 2, to which reference will now be made.

The mechanism shown in Figure 2 is primarily intended to operate the slide of a coining or minting press, and comprises crank shaft H having three crank pins, namely a main crank pin having a "throw" t, and two secondary crank pins located one on each side of the main crank pin, and each having a "throw" t,.

The secondary crank pins are concentric with each other, and are displaced at an angle from the main crank pin.

A coupling A on the main crank pin is coupled to a link B which, in turn, is coupled to slide C. The two secondary couplings F on the secondary crank pin are coupled to respective bell crank levers E which are pivoted on brackets G which are attached to the press frame. The linkage is then completed by links D which are coupled to the bell crank levers E at one end and to an external pin forming a hinged connection between coupling A and link B.

The linkage is shown in Figure 2 in the working position, and the short length of a retraction stroke is shown by reference S in Figure 2. During a cycle of operation, the slide C retracts through stroke S, then remains stationary for 1300 of crank rotation, and then completes a return stroke back to the working position.

Going back now to Figure 1, and which shows successive stages in the working cycle, Figure 1a shows the linkage with the slide in the working position; Figure 1b shows the slide retracting under the control of the main crank pin and the displacement of the coupling link joint caused by the secondary coupling bell crank levers and the link D; Figure 1c shows the linkage when the crank has rotated 1800 from the position shown in la, and with the main coupling and the link B in line; and Figure 1d shows the linkage at the start of the working stroke.

Between the positions shown in 1b and 1c, the slide remains stationary for 1300 of crank rotation, to provide any required "dwell" period.

Referring now to Figures 3 and 4 of the drawings, this shows a second embodiment of material working press according to the invention, and which comprises a frame, a multieccentric crank shaft mounted for turning relative to the frame about a crank axis, a working tool carrier constrained by the frame to move in a rectilinear path and a multi-linkage drive mechanism for transmitting motion to the working tool carrier.

This mechanism has primarily been devised for use in machinery where a substantial "dwell" in the movement of the working tool carrier is required in some part of the process, such as component feeding where changing the input speed to the mechanism is not reasonably practicable. Generally, it is the primary intention that the working tool of the mechanism in this second embodiment remains stationary, whilst a new component or work piece is fed, or indexed, into the tooling area.

This second embodiment will now be described with reference to Figures 3 and 4, in which Figure 3 is a schematic illustration (generally similar to Figure 1), and Figure 4 is a practical form of a design corresponding with the schematic illustration of Figure 3.

In Figure 3, this shows four successive stages 1, 2, 3 and 4, in a cycle of operation, and in which: illustration 1 shows the working tool carrier in its working position; illustration 2 shows the working tool carrier at the start of the dwell period; illustration 3 shows the working tool carrier at middwell position; illustration 4 shows the working tool carrier at the end of the dwell period, and about to start to return to the working position.

Referring now to Figure 4, the illustrated mechanism is intended to move the working tool carrier of a press, such as a coin-forming press. The mechanism comprises a crank shaft Hl with at least two crank pins or eccentrics. The main crank pin has a throw "t" and the second crank pin has a throw "t,". The second crank is off-set from the first crank pin by an angle xO measured in an anti-clockwise direction i.e. in advance of the first pin. The crank shaft Hl is supported in journals which form part of the frame.

A coupling Al on the main crank pin is connected to a main link Bl by a pin J', and the link Bl is in turn connected to the working tool carrier Cl by pin Kl.

A secondary coupling Fl on the second crank pin is connected to a bell crank lever E' by pin Ml. The bell crank E pivots independently on a shaft Nl which is supported on a bracket Gl which forms part of the frame.

The remaining link D1 is connected to the bell crank lever E1 by pin L' and to pin J', which connects coupling Al to main link Bl.

The mechanism of Figure 4 is shown in a position in which the working tool carrier is in its outermost or working position. When the crank shaft Hl is rotated, in an anticlockwise direction as indicated by the arrow in Figure 4, the working tool carrier retracts the length of the working stroke and remains stationary for the next 1300 of crank rotation, and thereafter the working tool carrier returns to its outermost or working position.

The movement and action of the linkage drive mechanism of the embodiment of Figure 4 will now be described. When the working tool carrier is at the working position, the toggle formed by the main coupling and the main link does not close (this eliminates the possibility and danger of the mechanism locking, under load, with the pivot centres in line). The reaction on pin J' is taken by the link D', and the bell crank lever El, which are again not quite in line to prevent a potential locking-up.

The movement of the working tool carrier as it returns to the dwell position is effected by a combination of the position of the main crank pin, the position of link Dl and the rotation of the bell crank lever E' in a clockwise direction about pin Nl, which is controlled by the secondary crank pin and the secondary coupling Fl, thereby displacing the pin J'. In this instance, the effect of displacing pin J' increases the angular displacement of the coupling Al and the link Bl.

During the dwell period of the mechanism, the second crank pin and the secondary lever Fl rotate the bell crank lever E1 in an anti-clockwise direction. The link Dl, which is connected both to the bell crank E' and link Bl through pin Jl, then modifies the angular displacement of link Bl to compensate for the movement of coupling A', thus allowing the working tool carrier to remain stationary.

After completing the "dwell", the combination of the movement of the main crank pin and the coupling A', and the bell crank lever E' rotating once again in a clockwise direction towards its central position, serve to move the working tool carrier back to its working position through link D'.

Figure 5 is a diagram of distance / time of the crank and linkage drive mechanism of Figure 4.

Claims (1)

1. A material working press which comprises a rotary input drive, first and second die carriers which are relatively movable between a release position and a forming position effective against a blank of material inserted between the die carriers, and a linkage which couples together the input drive and one of said die carriers to effect linear reciprocation of said one die carrier, upon rotation of said input drive, and in which said linkage comprises: a two-part hinged link having a first part which is eccentrically connected at its free end to said input drive, and a second part pivotally connected at its free end to said one die carrier; a two-armed rocker pivotally mounted to carry out rocking movement about a fixed axis; a first link arm pivotally connected at one end to one arm of said rocker, and pivotally connected at its other end via a crank arm to the input drive; and a second link arm pivotally connected at one end to a second arm of said rocker, and pivotally connected at its other end to a hinge connection between the first and second parts of said two-part hinged link.

2. A press according to Claim 1, in which said input drive to operate the linkage comprises a drive shaft, and cranks coupled with said shaft to convert rotary motion of the shaft into generally linear reciprocating motion of the components of the linkage coupled therewith, namely said first part of the two part hinged link, and said first link arm of said rocker.

3. A press according to Claim 1 or 2, in which said one dye carrier is guided so as to carry out linear reciprocation, and the second dye carrier, to co-operate therewith, has a separate drive linkage which is operated, in conjunction with rotation of the input drive, so that the dye carriers move towards and away from each other during forming and release strokes respectively.

5. A material working press which comprises a frame, a single crank with at least two eccentrics mounted for turning relative to the frame about a crank axis, a working tool carrier guided by the frame for reciprocation along a rectilinear path, and a linkage for transmitting motion from the crank to the working tool carrier, wherein the linkage comprises a first toggle mechanism to transfer load to the tool carrier in the working position, and a second toggle mechanism to control the required working stroke, and the required "dwell".