WO2005002855A1

WO2005002855A1 - Apparatus for positioning dies on the bed of a press

Info

Publication number: WO2005002855A1
Application number: PCT/GB2004/002881
Authority: WO
Inventors: Christopher Stephen Cook; Laurence David Cook; James John Cook
Original assignee: SIL-DIE SYSTEMS Ltd
Current assignee: SIL-DIE SYSTEMS Ltd
Priority date: 2003-07-02
Filing date: 2004-07-02
Publication date: 2005-01-13
Anticipated expiration: 2006-01-02
Also published as: GB2403451A; GB0315416D0

Abstract

An apparatus for mounting dies on a bed (10) of a press is described which comprises a support plate (14) removably mountable in a predetermined position on the bed (10) of the press, a plurality of holes (16) formed in the support plate (14), and securing means (28) receivable within the holes (16) in the support plate (14) for securing the dies (22) to a front face (18) of the support plate (14) and for maintaining the dies (22) in position on the support plate (14) when the support plate (14) is removed from the bed (10) of the press. In the invention, the holes (16) in the support plate (14) have at least one undercut, and each of the securing means comprises a clip (28) having a leg (38) received in one of the holes (16) in the support plate (14), the leg 938) having at least one flange (40) which engages behind the undercut to prevent the leg (38 from being pulled out of the hole (16).

Description

Apparatus for Positioning Dies on the Bed of a Press

Field of the invention The present invention relates to apparatus for positioning dies on the bed of a press used, for example, in hot foil blocking and embossing.

Background of the invention

There are several applications where a sheet is pressed against a die in order to make an impression on the sheet. In hot foil blocking, for example, a foil is pressed by means of a heated die to apply a coating made of, or resembling, a metal foil to selected regions of a carrier sheet. In embossing, a carrier sheet is compressed between complementary male and female dies to achieve the desired raising of selected regions of the sheet from its plane. Most presses used in such applications comprise two horizontal beds, also referred to as chases, on which dies are mounted. Where the beds are horizontal, the upper one is commonly pneumatically operated and carries the dies. In operation, the beds are separated by raising the upper bed and/or lowering the lower bed, a carrier sheet is introduced between the two beds, the beds are brought together to make the desired impression on the carrier sheet and finally the carrier sheet on which an impression has been made is removed and replaced by the next carrier sheet.

Such presses are required to operate at high speed and in order to reduce the time taken to complete a given run, it is usual to make numerous impressions on different areas of a carrier sheet all at the same time. For example, if an area of gold lettering is to be applied to a small cardboard package, then the blanks for several such packages may be formed on a single large carrier sheet of cardboard which is cut into individual blanks after the printing and foil blocking operations have been completed.

In such an application, it is not viable to produce a single die to make the multiple impressions. The primary reason for this is that the spacing between impressions may need to be adjusted to compensate for thermal expansion of the dies as well as for stretching or shrinking in the sheets on which impressions are made. Aside from these factors, it would be necessary for the entire die to be replaced if any part of it were to be damaged. For these reasons,, several separate dies are produced and they are all individually mounted on the bed(s) of the press. To this end, it is known to form at least one of the beds of the press as a thick plate of steel having a regular matrix of anchoring holes. Expanding pegs, referred to in the art as dogs, which grip within these holes, are used to anchor the individual dies to the bed. In other presses, the beds do not have a matrix of holes and the dies are screwed directly into the beds. The dies are themselves made of a metal plate (typically copper, steel, brass, magnesium or zinc) onto which the desired pattern has been formed by a photographic etching process that is well known in itself and need not be described within the context of the present invention.

Conventionally, all the individual dies are positioned on the beds using dogs and a test is run to ensure that their position is in register with the existing markings on the cardboard carrier sheets. Adjustments are made to the individual dies and the test procedure is repeated until all the dies are in their correct position. This setting up procedure of the dies may take several hours. At the end of a run, the dies are removed to allow the same press to be used for another job and should a fresh run later be required, the setting up procedure of the dies must be repeated and during this time no other use may be made of the press.

To avoid wasting time in repeating the procedure of setting up the dies for each run and to reduce the down time of the press, it has previously been proposed, for example in GB 2372963 and GB 2346589, to place a thin support plate between the dies and the bed and to secure the dies to the support plate so that they can be removed from the bed and replaced while remaining in their correct relative position.

To avoid modification to the beds of the press, it is necessary for the combined thickness of the dies and the support plate to be equal to the thickness of a conventional die, this being typically about 6 mm. This places a limitation on the thickness of the support plate, which is normally around 2 mm. With so little metal to grip, it has proved difficult to secure the dies to the support plate. To avoid this problem, GB 2372963 proposes attaching to the support plate threaded inserts that protrude from the rear of the support plate (the front being the face to which the dies are secured) into holes formed in the bed. However, the threaded inserts need to be pre-fitted to the support plate before the latter is placed on the bed, because the holes into which they fit have to be countersunk and the heads of the inserts have to be ground flat.

Summary of the invention

With a view to mitigating the foregoing disadvantages, there present invention provides an apparatus for mounting dies on a bed of a press, comprising

• a support plate removably mountable in a predetermined position on the bed of the press,

• a plurality of holes formed in the support plate, and • securing means receivable within the holes in the support plate for securing the dies to a front face of the support plate and for maintaining the dies in position on the support plate when the support plate is removed from the bed of the press, characterised in that • the holes in the support plate have at least one undercut, and • each of the securing means comprises a clip having a leg received in one of the holes in the support plate, the leg having at least one flange which engages behind the undercut to prevent the leg from being pulled out of the hole. The front of the support plate refers herein to the surface on which the dies rest and the rear to the surface in contact with the bed of the press.

The undercut in the support plate forms a rearward facing surface. This enables the clip to have a leg which engages this surface to retain the clip on the support plate yet that is no longer than the thickness of the support plate. Thus the leg need not protrude from the support plate, and this allows the plate to rest on a bed that is not formed with holes to align with the holes in the support plate. Consequently, the same support plate with dies mounted on it can be used with any type of bed.

Preferred features of the invention

Preferably each die securing clip comprises

• a block to rest on the front face of the support plate adjacent the associated die, and

• clamping means on the block for contacting a side edge of the associated die to prevent movement of the die relative to the support plate. The clamping means may conveniently comprise a screw received in a threaded bore in the block.

In an embodiment of the invention, the screw protrudes laterally from the block in the opposite direction to the flange of the leg, thereby exerting a force to ensure that the leg cannot be removed from the hole in the support plate. It is however preferred to provide two flanges engaging two diametrically opposed undercuts so that the retention of the leg in the hole in the support plate does not depend on the clamping forced applied laterally to the associated die.

It is preferred for the screw not to make direct contact with the edge of the die to avoid its indentation. This may be achieved if the clamping means further includes a spring steel plate slidably mounted between the block and the support plate and incorporating an inclined strip located between the end of the screw and the side edge of the die. A preferred alternative to this construction is for the clamping means to comprise a clamping jaw mounted on the block for sliding movement parallel to the surface of the support plate and urged by the screw into contact with the edge of the associated die.

A further advantage of not having any legs protruding from the rear surface of the support plate is that it allows the use of cylindrical support plates for mounting in presses having a rotating cylindrical bed.

A further benefit achieved by the invention results from the fact that dies can be pre-positioned on the support plate without mounting the support plate on the bed of a press. This means that while the press is being used for one job, dies can be set up correctly on a separate support plate for the next job, thereby avoiding any down time for the press between jobs. Brief description of the drawings

The invention will now be described further, by way of example, with reference to the accompanying drawings, in which : Figure 1 is a partial section through a first apparatus embodying the invention, Figure 2 is a similar partial section of a further embodiment of the invention, Figure 3 shows a modification of the embodiment of

Figure 2 in which a spring steel plate is introduced between the block of the die securing clip and the support plate, Figure 4 is a perspective view of the spring steel plate of Figure 3, Figure 5 is a perspective view of a, further embodiment of the invention using an alternative design of die securing clip, Figure 6 shows in plan an alternative shape for the holes in the support plate, and Figures 7 and 8 are sections along the lines VII-VII and VIII-VIII in Figure 6, respectively.

Detailed description of the preferred embodiments Figure 1 shows a bed or chase 10 of a hot foil blocking press. Dies 22 are fitted to the upper surface of the bed as viewed but it should be noted that the bed is shown upside down as compared to its orientation when the press is in use .

The bed 10 has holes 12 that are conventionally used to receive dogs for locating the dies 22 in their desired position. However, for reasons mentioned previously, mounting dies on the bed in this manner would prolong the setting up time at the commencement of each run. Instead, of securing the dies directly to the bed of the press, a support plate 14 is placed between the bed 10 and the dies 22. This support plate 14 is used to support the dies 22 in their correct relative position before they are mounted on the press and allows the dies to be retained in their correct relative positions while they are in storage between runs.

The combined thickness of the plate 14 and the die 22 in Figure 1 is about 6 mm, this being the thickness of a conventional die that is intended to be mounted directly on the bed 10. Typically, the support plate has a thickness of around 2 mm and the die a thickness of 4 mm. The support plate 14 has a front face 18 on which the dies 22 are placed and a rear face 20 that contacts the surface of the bed 10. The support plate 14 is formed with a series of holes 16 that receive clips 28 which secure the dies 22 to the support plate 14. It is also formed with larger holes 42 for receiving conventional bolt and lock clips (not shown) to retain the support plate 14 on the bed 10. The holes 16 in the support plate 14 may align with the holes 12 in the bed of the press as shown in Figure 1 and this would permit the clips 28 to protrude from the rear surface of the support plate 14. However, as will be clear from all the illustrated embodiments, the invention allows the retaining clips not to protrude from the support plate 14, thereby enabling the same support plate to be used on beds with misaligned holes or beds without any holes.

The dies 22 has raised regions 26 that are used in forming the desired impression on the carrier sheet. The edge regions 24 of the dies 22 are tapered at a slight angle to help in clamping them down onto the surface 18 of the support sheet 14. The clamping of the dies is effected by means of the clips 28. Each clip 28 comprises a small block 30 that is less thick than the dies 22 so as not to leave any impression on the carrier sheet during the pressing operation. The block 30 is formed with a threaded bore 32 that is generally parallel to the surface 18. A grub screw 34 engaged in the threaded bore protrudes from the block 30 into contact with the edge 24 of the die and a locking screw 36 is used to prevent unintentional loosening of the grub screw 34. The bore 32 is preferably inclined relative to the surface 18, at an angle of less than 5°_/ to allow easier access to the head of the screw 34 when using an implement such as a screwdriver or an Allen key.

When two or more such clips 28 are placed around a die 22, it is firmly held in place and prevented from moving from side to side. Furthermore, the inclination of the edge 24 and the screw 34 creates a component of force that urges the die 22 tightly against the surface 18 of the support plate 14.

Each clip 28 is held in place on the support plate 14 by means of a leg 38 depending from the block 30 which passes into one of the holes 16 in the support plate 14. The holes 16 are formed with an undercut, those in Figure 1 being countersunk from the rear of the support plate. The leg 38 is formed with projecting flange 40, in the form of a tapered toe, which engages behind the undercut to prevent the leg 38 from being pulled out of the hole 16. Because the screw 34 and the flange 40 extend in opposite directions, the single action of tightening the screw 34 acts to clamp both the clip 28 and the die 22 to the support plate 14.

The embodiment of Figure 2 is similar in principle to that of Figure 2 but the sides of the holes 16' are stepped by counter-boring from the rear instead of being countersunk. The leg 38' can this time be L-shaped with the flange 40' engaging the shoulder in the side of the hole 16' and the leg can be sufficiently short to fit within the thickness of the support plate 42' .

The screw 34 in each of the above described embodiments is harder than the material of the dies 22 and there is a tendency for it to indent the die 22 when it is tightened. The presence on an indentation makes it difficult to make a small adjustment to the position of the die because the screw 34 will tend always to centre itself in the existing indentation. To avoid this problem, it is possible, as shown in Figure 3, to sandwich a spring steel plate 48 between the block 28 and the support plate 14. As shown in Figure 4, the spring steel plate 48 has an elongate slot 52 to receive the protruding leg 38 of the block and an inclined strip 50 at one end to rest between the screw 34 and the die 22. The strip 50 prevents the screw 34 from indenting the die but its flexibility allows the die 22 to be held down firmly.

Though illustrated as a modification of the embodiment of Figure 2, the spring steel plate 48 can of course be used in the embodiment of Figure 1.

The embodiment of Figure 5 comprises a block 30" shaped as a dovetail that slidably supports a clamping jaw 60 which is urged by the screw 34 against the side 24 of the die 22. The advantage of this construction is that the same blocks 30" can be used to support a variety of different jaws 60 which present different thicknesses of metal between the end of the screw 34 and the side 24 of the die 22. This enables the range of permissible distances from the die to the hole 16" to be increased, which in turn allows the holes 16" in the plate 14" to be positioned further apart in order to avoid the support sheet 14" being weakened excessive by the holes 16".

In the embodiments of Figures 1 to 3, a single flange 40 on the leg 38 projects in the opposite direction to the screw 34 so that as the screw 34 is tightened the leg 38 is more securely retained in the hole 16. In such a construction, if the die should be accidentally dislodged then the clip 28 will also tend to fall out of its hole at the same time.

In order to avoid this, it is possible in any of the embodiments of the invention to form the holes in the support plate 14 in the manner shown in Figures 6 to 8. The hole 70 in these figures has two flattened sides 72 when viewed from its front surface and has a circular outline when viewed from its rear surface, as represented by dotted lines 74 in Figure 6. Beneath the flattened sides 72 are two undercuts as shown in the sections of Figures 7 and 8. The leg in this case has an end which is conically flared and has two flattened sides. By correctly aligning the leg, its end can be inserted into the hole 70 and when the leg is then rotated through 90°, its flared end engages behind both undercuts and prevents the clip from being removed.

In this case, in order to be able to clamp both longitudinal and transverse edges of the die, it is necessary to provide two different forms of clip 28 with the flat sides of the flared ends of the legs oriented parallel to and perpendicular to the screw 34, respectively.

It is an advantage of all the embodiments of the invention that the clips 28 and the dies 22 can be positioned as necessary before or after the support plate 14 has been mounted on the bed of the press. After the dies have been placed in their desired positions, clips 28 are pushed into nearby holes 16 in the support plate 14 and the screws 34 are tightened to clamp the dies in position. The size of the clips 28 and the separation of the holes 16 are chosen so that there are always holes sufficiently near the edge of any die to be within the adjustment range of the screw 34. As the sides of dies are normally square (parallel to the sides of the bed) , it helps in this respect if the holes 16 are arranged in the support plate so that their centres lie on a line inclined to the sides of the bed. Though described by reference to a press having flat beds, it will be clear to the person skilled in the art that the invention can equally be applied to presses that have counter-rotating cylindrical beds. In this case, the support plate 14 may be constructed of separate arcuate shoes that are secured to the surface of the drum-like bed or of a single hollow sleeve that is slipped over the cylindrical bed from one end and tightened to grip it firmly. The only difference in the dies and the clips will be that the previously flat surfaces will need to be cylindrically curved to match the curvature of the bed but in an axial section such embodiments would look no different from the embodiments of Figures 1 to 3.

It will be appreciated that various modification may be made to the embodiments described without departing from the scope of the invention as set out in the appended claims. For example, the clamping means need not simply be a screw but may comprise a cam plate mounted on the block to engage the side of the die. If a screw is used as a clamping means in need not lie generally parallel to the surface of the support plate but at right angles to it. In this case, the screw may bear down on a foot that projects laterally from the edge of the die.

Claims

1. Apparatus for mounting dies on a bed (10) of a press, comprising • a support plate (14) removably mountable in a predetermined position on the bed (10) of the press,

• a plurality of holes (16) formed in the support plate (14), and

• securing means (28) receivable within the holes (16) in the support plate (14) for securing the dies (22) to a front face "(18) of the support plate (14) and for maintaining the dies (22) in position on the support plate (14) when the support plate (14) is removed from the bed (10) of the press, characterised in that • the holes (16) in the support plate (14) have at least one undercut, and • each of the securing means comprises a clip (28) having a leg (38) received in one of the holes (16) in the support plate (14), the leg 938) having at least one flange (40) which engages behind the undercut to prevent the leg (38 from being pulled out of the hole (16) .

2. Apparatus as claimed in claim 1, wherein each die securing clip comprises

• a block (30) to rest on the front face (18) of the support plate (18) adjacent the associated die (22), and

• clamping means (34) on the block (34) for contacting a side edge (24) of the associated die (22) to prevent movement of the die (22) relative to the support plate (14) .

3. Apparatus as claimed in claim 2, wherein the clamping means comprises a screw (34) received in a threaded bore (32) in the block (30) .

4. Apparatus as claimed in claim 3, wherein a locking screw (36) is mounted in the threaded bore (32) to be tightened on to the end of the grub screw (34) .

5. Apparatus as claimed in claim 3 or 4, wherein the threaded bore in the block of the die securing clip is inclined at an angle of between 0° and 5° to the face of the block in contact with the support plate.

6. Apparatus as claimed in claim 3, 4 or 5, wherein - the screw (34) is a grub screw of which only one end ^{~ '}. protrudes from the block.

7. Apparatus as claimed in claim 6, wherein the leg (38) has a single flange (40) engaging a single undercut and the screw (34) protrudes laterally from the block (30) in the opposite direction to the flange (40) of the leg (38).

8. Apparatus as claimed in any one of claims 1 to 6, wherein the leg is formed with two diametrically opposed flanges which engage with diametrically opposed undercuts in a hole (70) in the support plate when the leg is rotated after insertion into the hole.

9. Apparatus as claimed in any of claims 3 to 8, wherein the clamping means further includes a spring steel plate (48) slidably mounted between the block and the support plate and incorporating an inclined strip (50) located between the end of the screw and the side edge of the die (22) .

10. Apparatus as claimed in any of claims 3 to 8, wherein the clamping means comprises a clamping jaw (60) mounted on the block for sliding movement parallel to the surface of the support plate and urged by the screw (34) into contact with the edge (24) of the associated die (22).

11. Apparatus as claimed in any preceding claim, for mounting in a press having a rotating cylindrical bed wherein the support plate is curved to wrap around the bed of the press.