GB1598183A

GB1598183A - Rotary embossing machine having intermeshing adjustable dies

Info

Publication number: GB1598183A
Application number: GB32940/77A
Authority: GB
Original assignee: Chambon Ltd
Current assignee: Chambon Ltd
Priority date: 1977-08-05
Filing date: 1977-08-05
Publication date: 1981-09-16
Also published as: BE869525A; LU80075A1; FR2399326B1; IT1104930B; IE781490L; DK346678A; DE2833618A1; NL7808133A; FR2399326A1; IT7883444A0; IE47142B1; NL179193C

Description

(54) ROTARY EMBOSSING MACHINE HAVING INTERMESHING ADJUSTABLE DIES (71) We, CHAMBON LIMITED, a British Company of Riverside Works, Standish Road, Hammersmith, London, W.6, England, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to a rotary embossing machine having intermeshing adjustable dies.

Embossing, that is to say the production of a raised design on paper or board, is used in many industrial applications, for example in the production of blanks for forming cigarette packs or cartons. Embossing can be carried out by either a flat embossing machine, or by a rotary embossing machine.

Flat embossing machines usually have a pair of complementary dies. One of these dies, say that die having the design in female form, is fixed to a stationary bed and the other die (bearing the design in the male form) is movable towards, and away from, the stationary die so as to emboss a sheet of paper or card trapped between the two dies.

In order to form a good emboss, it is important that the two dies are accurately formed. Generally speaking, the female die is formed first, either by a hand cut or by generation from a master. The male die is then formed from the female die by a casting process with the interposition of a thin sheet of material. When the thin sheet of material is removed, the male and female dies mate together with a slight clearance round the cooperating parts of the design. This intermeshing of the dies results in a very good emboss, as a good outline and a good compression factor are then possible. The quality of the emboss is enhanced by the fact that the embossing is carried out over the entire area of the design at the same time. The disadvantage of the flat embossing process is that it is not suitable for use with modern high-speed rotary printing machines, it being necessary for the sheet of card or paper being embossed be stationary during the embossing process.

Rotary embossing machines have two cylinders, one of which carries a plurality of female dies and the other of which carries male dies. The cylinders are so arranged that upon rotation in opposite directions a sheet of paper or card fed therebetween is embossed by the co-operating pairs of dies.

Consequently, this type of machine can be placed in-line with a high-speed rotary printing machine.

Unfortunately, such a machine often suffers from other disadvantages, namely a poor quality emboss and the possibility of misalignment between the embossed design and the design which has already been printed.

The former fault arises from the fact that it has hitherto been impossible to form economically substantially complementary male and female dies for a rotary embossing machine, and the latter fault from the fact that shrinking or distortion of the card or paper after printing, or from the photographic process on which the accuracy of the printed design depends, can cause misalignment.

Rotary embossing machines are also known in which the embossing cylinders are each formed in one-piece, male and female dies forms being raised from or cut into the cylinder surfaces. Here again, misalignment problems occur.

According to the present invention, there is provided a rotary embossing machine having a pair of co-operating cylinders, a first of the cylinders being provided with a first die carrying a design in female form, and the second cylinder being provided with a second die carrying said design in male form, the second die being positioned to co-operate with the first die to form an emboss on a sheet of material passing between the cylinders, wherein each of the dies is adjustably mounted on the cylindrical surface of its cylinder, and wherein the second die is substantially complementary to the first die but is such that a clearance of substantially constant thickness is left between the two design forms as the cylinders roll over one another with said sheet pressed therebetween.

Preferably, the first cylinder is provided with a plurality of identical first dies and the second cylinder is provided with a plurality of identical second dies, each second die being positioned to co-operate with a corresponding first die to form an emboss on a sheet of material passing between the cylinders. Advantageously, each die is removably attached to its cylinder by means of bolts.

Preferably, each die is located on its cylinder by means of a respective set of locating pins, and is adjustable relative thereto by the interposition of metallic strips.

This adjustability of the dies overcomes the misalignment problems referred to above.

Each cylinder may be rotatably mounted in a framework by means of axial end bearings. In order to accommodate sheets of different sizes and thickness, it is preferable for each of said bearings to be mounted in a respective bearing block which is adjustably mounted on the framework.

One form of rotary embossing machine constructed in accordance with the invention will now be described by way of example, with reference to the accompanying drawings in which: Figure 1 is a perspective view of the rotary embossing machine; Figure 2 is a plan view of a female die; Figure 3 is a cross-section taken on the line III-III of Figure 2; Figure 4 is a plan view of a male die complementary to the female die of Figure 2; Figure 5 is a cross-section taken on the line V-V of Figure 4; Figure 6 is an axial cross-section of the two cylinders of the machine showing the cooperation of two complementary dies; Figure 7 is a transverse cross-section of the two cylinders showing the co-operation of two complementary dies; and Figure 8 is a schematic cross-section showing the formation of a die by a machine engraving process.

Referring to the drawings, Figure 1 shows a rotary embossing machine having a first embossing cylinder 1 which is rotatably mounted in a machine frame 2. A second embossing cylinder 3 is also rotatably mounted in the machine frame 2, this mounting being accomplished by means of end plates 4 (only one of which can be seen in Figure 1) which permit the cylinder 3 to be adjusted with respect to the cylinder 1.

A plurality of identical male dies 5 are adjustably mounted on the cylindrical surface of the cylinder I by means of accurately positioned locating pins 6, the dies being equispaced. Similarly, a plurality of identical equispaced female dies 7 are adjustably mounted on the cylindrical surface of the cylinder 3 by means of accurately positioned, complementary locating pins 8. Throughout this specification the term "male die" should be taken to mean a die having a design to be embossed in male form. Similarly, the term "female die" should be taken to mean a die having a design to be embossed in female form. Each of the dies 5 and 7 is axially adjustable over a distance a (see Figures 1 and 6) and is circumferentially adjustable over a distance b (see Figures 1 and 7). In the former case the adjustment is carried out by the insertion of strips of metal (similar to feeler gauges) between the die concerned and the corresponding locating pins. It should be noted that each of the dies 5 and 7 is fixed to its cylindrical 1 or 3 by means of four bolts (not shown) and that these bolts are slackened off during the adjustment of the dies.

As can be seen in Figures 2 to 5, stepped holes 9 are provided in the dies 5 and 7 for receiving the bolt heads.

The design on each male die 5 is complementary to that on each female die 7 but is so formed that, when a sheet of card 10 of thickness t passes between the cylinders 1 and 3, a clearance of less than t exists between the co-operating parts of the male and female design forms. Consequently, the card 10 is embossed with the design as it passes between the two cylinders 1 and 3.

The clearance is arranged to be substantially constant over the entire design. The design of the dies 5 and 7 shown in Figures 2 to 5 is different from that of the dies shown in Figure 1, and shows part of a Registered Trade Mark.

It will be apparent that the machine described above overcomes the disadvantages of the known embossing machines.

Thus, the combination of the adjustability of the dies 5 and 7 with the fact that their designs are capable of intermeshing, ensures that good quality embossing occurs and that the embosses can be accurately positioned at the required location on pre-printed card.

Another advantage of this machine is its versatility. Thus, for certain types of carton, for example cigarette cartons, many changes of design occur over a period of time. By suitably arranging the locating pins, it is possible to change both a design and the relative position of the embossing, within predetermined limits, without having to change any part of the machine except the dies.

Moreover, by a slight modification to the machine illustrated, further versatility can be achieved. This additional versatility is necessary to accommodate certain types of carton, for example cigarette cartons, which differ dimensionally by relatively small amounts.

With known types of machine, a change of diameter of the embossing cylinders is necessary to deal with each such different carton.

With the machine described above, however, it is possible to use the same cylinders for a predetermined range of carton dimensions.

This is accomplished by a suitable choice of base cylinder diameter, and by varying the thickness of the embossing dies. In this case, the cylinders would be mounted in the frame with their axial end bearings positioned in adjustable bearing blocks which would permit the distance between the cylinder axes to be varied and set by means of packing pieces.

These packing pieces would vary in thickness according to the required separation of the axes. Obviously in this case it would be necessary to change the intermeshing gears associated with the two cylinders.

The dies 5 and 7 are made by a machine engraving process from masters. This can be done in either of the two following ways:- A. (i) The design is formed as a female impression in a plastics member, the design being four times the size of the design to be embossed.

(ii) A soft metal female master is machined from the plastics member, the female master bearing the design at twice the required embossing size.

(iii) A male master is moulded in epoxy from the female master, the male master also having the design at twice the required embossing size.

(iv) A working female master is moulded in epoxy from the male master, the design still being double size.

(v) A working male master is moulded in epoxy from the female master, the design being double size.

(vi) The dies are produced from the working masters by a machine engraving process utilising a pantograph to reduce the design to actual size. The cutter for the female die 7 is a standard pointed cutter, whereas the cutter for the male die 5 has a cutter radius r=t.f where f is the compression factor of the card 10. This results in the formation of the required clearance between the two dies 5 and 7. Figure 8 schematically shows how this machine engraving process works for the male die 5. Here, the follower of the pantograph is indicated by the reference numeral 11 and the cutter by the reference numeral 12. The profile of the male working master is denoted by the reference nun ral 13 and the profile of the generated male die by the reference numeral 14. After the design has been generated, the cutter 12 is lowered by a distance t-r and a second cut is made around the periphery of the raised contour of the male design form.

The profile after this second cut is denoted by the reference numeral 15. The female die 7 is formed in the same way but a pointed cutter is used in place of the cutter 12.

B. (i) The design is formed as a female impression in a plastics member, the design being four times the size of the design to be embossed.

(ii) A steel female master is machined from the plastics member, the female master design size being twice that of the design size being twice that of the design to be embossed.

(iii) An intermediate male member is moulded in epoxy from the female master, the design being double size.

(iv) A steel male master is machined from the intermediate male member, the design still being double size.

(v) The dies are produced from the master by a machine engraving process utilising a pantograph. This process is identical to that described in A (vi) above.

As an alternative to making allowance for the required clearance at step B (v), this could be done at step B (iv) during the machine engraving of the male master. In either case, method B allows for the production of trial dies which can be tested in a rotary embossing machine. Slight alterations can then be made (if and where necessary) to the masters prior to their being hardened.

Both methods A and B have the advantage that masters can be produced relatively cheaply for say 150 instead of 1,000 for the prior art masters.

Obviously both methods A and B could start with a plastics male member instead of a plastics female member, in which case references to "male" should be taken to be taken to be "female" and vice versa. Moreover, the two methods can be varied somewhat. Thus, in method A an epoxy male master may be moulded from the original plastics member instead of machining a soft metal master. Moreover, some of the steps of either method could be dispensed with, for example the working masters of method A are not absolutely necessary and the dies could be produced directly from the ordinary masters.

The method of making the dies is also described, and claimed, in the application of our co-pending British Patent Application No. 7923125. (Serial No. 1598184).

WHAT WE CLAIM IS: 1. A rotary embossing machine having a pair of co-operating cylinders, a first of the cylinders being provided with a first die carrying a design in female form, and the second cylinder being provided with a second die carrying said design in male form, the second die being positioned to co-operate with the first die to form an emboss on a sheet of material passing between the cylin

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. for example cigarette cartons, which differ dimensionally by relatively small amounts. With known types of machine, a change of diameter of the embossing cylinders is necessary to deal with each such different carton. With the machine described above, however, it is possible to use the same cylinders for a predetermined range of carton dimensions. This is accomplished by a suitable choice of base cylinder diameter, and by varying the thickness of the embossing dies. In this case, the cylinders would be mounted in the frame with their axial end bearings positioned in adjustable bearing blocks which would permit the distance between the cylinder axes to be varied and set by means of packing pieces. These packing pieces would vary in thickness according to the required separation of the axes. Obviously in this case it would be necessary to change the intermeshing gears associated with the two cylinders. The dies 5 and 7 are made by a machine engraving process from masters. This can be done in either of the two following ways:- A. (i) The design is formed as a female impression in a plastics member, the design being four times the size of the design to be embossed. (ii) A soft metal female master is machined from the plastics member, the female master bearing the design at twice the required embossing size. (iii) A male master is moulded in epoxy from the female master, the male master also having the design at twice the required embossing size. (iv) A working female master is moulded in epoxy from the male master, the design still being double size. (v) A working male master is moulded in epoxy from the female master, the design being double size. (vi) The dies are produced from the working masters by a machine engraving process utilising a pantograph to reduce the design to actual size. The cutter for the female die 7 is a standard pointed cutter, whereas the cutter for the male die 5 has a cutter radius r=t.f where f is the compression factor of the card 10. This results in the formation of the required clearance between the two dies 5 and 7. Figure 8 schematically shows how this machine engraving process works for the male die 5. Here, the follower of the pantograph is indicated by the reference numeral 11 and the cutter by the reference numeral 12. The profile of the male working master is denoted by the reference nun ral 13 and the profile of the generated male die by the reference numeral 14. After the design has been generated, the cutter 12 is lowered by a distance t-r and a second cut is made around the periphery of the raised contour of the male design form. The profile after this second cut is denoted by the reference numeral 15. The female die 7 is formed in the same way but a pointed cutter is used in place of the cutter 12. B. (i) The design is formed as a female impression in a plastics member, the design being four times the size of the design to be embossed. (ii) A steel female master is machined from the plastics member, the female master design size being twice that of the design size being twice that of the design to be embossed. (iii) An intermediate male member is moulded in epoxy from the female master, the design being double size. (iv) A steel male master is machined from the intermediate male member, the design still being double size. (v) The dies are produced from the master by a machine engraving process utilising a pantograph. This process is identical to that described in A (vi) above. As an alternative to making allowance for the required clearance at step B (v), this could be done at step B (iv) during the machine engraving of the male master. In either case, method B allows for the production of trial dies which can be tested in a rotary embossing machine. Slight alterations can then be made (if and where necessary) to the masters prior to their being hardened. Both methods A and B have the advantage that masters can be produced relatively cheaply for say 150 instead of 1,000 for the prior art masters. Obviously both methods A and B could start with a plastics male member instead of a plastics female member, in which case references to "male" should be taken to be taken to be "female" and vice versa. Moreover, the two methods can be varied somewhat. Thus, in method A an epoxy male master may be moulded from the original plastics member instead of machining a soft metal master. Moreover, some of the steps of either method could be dispensed with, for example the working masters of method A are not absolutely necessary and the dies could be produced directly from the ordinary masters. The method of making the dies is also described, and claimed, in the application of our co-pending British Patent Application No. 7923125. (Serial No. 1598184). WHAT WE CLAIM IS:

1. A rotary embossing machine having a pair of co-operating cylinders, a first of the cylinders being provided with a first die carrying a design in female form, and the second cylinder being provided with a second die carrying said design in male form, the second die being positioned to co-operate with the first die to form an emboss on a sheet of material passing between the cylin

ders, wherein each of the dies is adjustably mounted on the cylindrical surface of its cylinder, and wherein the second die is substantially complementary to the first die but is such that a clearance of substantially constant thickness is left between the two design forms as the cylinders roll over one another with said sheet pressed therebetween.

2. A rotary embossing machine as claimed in claim 1, wherein the first cylinder is provided with a plurality of identical first dies, and the second cylinder is provided with a plurality of identical second dies, each second die being positioned to co-operate with a corresponding first die to form an emboss on a sheet of material passing between the cylinders.

3. A rotary embossing machine as claimed in claim 1 or claim 2, wherein each die is removably attached to its cylinder by means of bolts.

4. A rotary embossing machine as claimed in any one of claims I to 3, wherein each die is located on its cylinder by means of a respective set of locating pins, and is adjustable relative thereto by the interposition of metallic strips.

5. A rotary embossing machine as claimed in any one of claims 1 to 3, wherein each cylinder is rotatably mounted in a framework by means of axial end bearings.

6. A rotary embossing machine as claimed in claim 5, wherein each of said bearings is mounted in a respective bearing block which is adjustably mounted on the framework.

7. A rotary embossing machine substantially as hereinbefore described with reference to, and as illustrated by, Figs. 1 to 7 of the accompanying drawings.