IES930137A2 - A cutting die - Google Patents

Abstract

A cutting die for producing self-adhesive stamps spacedapart on a peel-off backing film, the die comprising a die body having a number of spaced-apart stamp cutters upstanding on the body, each stamp cutter having a serrated outer cutting edge simulating the outline of a postage stamp with perforated edges, the serrations formed by a number of spaced-apart straight portions interconnected by arcuate portions with a gradual transition between each straight and arcuate portion and the cutting edge has a number of serrated sides interconnected by rounded corner projections.

Description

A Cutting Die stamp.s., .-in-particular for use in producing self-adhesive press-on postage stamps.

According to the invention there is provided a cutting die 5 for producing self-adhesive stamps spaced-apart on a peeloff backing film, the die comprising a die body having a number of spaced-apart stamp cutters upstanding on the body, each stamp cutter having a serrated outer cutting edge simulating the outline of a postage stamp with perforated edges, the serrations formed by a number of spaced-apart straight portions interconnected by arcuate portions with a gradual transition between each straight and arcuate portion and the cutting edge has a number of serrated sides interconnected by rounded corner projections.

In one embodiment of the invention there is provided a cutting die for producing self-adhesive stamps spacedapart on a peel-off backing film, the die comprising a cylindrical roller having a pair of spaced-apart upstanding bearers and mounted therebetween one or more stamp cutters upstanding on the roller between the bearers, each stamp cutter having a serrated outer cutting edge simulating the outline of a postage stamp with perforated edges, the serrations formed by a number of spaced-apart straight portions interconnected by arcuate portions with a gradual transition therebetween and the cutting edge has a number of serrated sides interconnected by rounded corner projections. - 2 IE 930137 Preferably each cutter has an upstanding wall with substantially parallel sides terminating in a pointed tip.

In another aspect the invention provides a roll or sheet of stamps whenever produced by the cutter comprising a number of spaced-apart peel-off self-adhesive stamps on a backing film.

In a further aspect the invention provides a stamp whenever produced by the rotary cutting die as previously described .

In a still further aspect the invention provides a method for producing a cutting die as previously described, said method comprising the steps of:15 (a) preliminary machining to form a blank die body; (b) preparing numerical control data for defining the multiple milling and engraving operations to be carried out by machine tools in forming each stamp cutter with reference to an operations axis, each stamp cutter having a serrated cutting edge with a preset desirable profile; (c) defining on the surface of the blank body one or more reference operations axes about which each individual stamp cutter is to be formed; (d) recording the co-ordinates of each operations axis; (e) carrying out an operation by a machine tool with respect to an operations axis in accordance with the numerical control data; IE 930137 - 3 (f) moving the machine tool to another operations axis if more than one operations axis is defined and repeating the operation; (g) repeating the one operation for all operations axes; and (h) carrying out the next operation by a machine tool with respect to all the operations axes until the required operations by the machine tools are performed.

Conveniently a rotary cutting die may be produced by a method comprising the steps of:(a) preliminary machining to form a cylindrical blank of required length and outside diameter with centre bores at each end; (b) machining support shafts and bearing surfaces at each end of the blank; (c) preparing numerical control data for defining the multiple milling and engraving operations to be carried out by machine tools in forming each stamp cutter with reference to an operations axis, each stamp cutter having a serrated cutting edge with a preset desirable profile; (d) defining on the surface of the blank one or more reference operations axes about which each individual stamp cutter is to be formed; (e) recording the co-ordinates of each operations axis; IE 930137 - 4 (f) carrying out an operation by a machine tool with respect to an operations axis in accordance with the numerical control data; (g) moving the machine tool to another operations axis if more than one operations axis is defined and repeating the operation; (h) repeating the one operation for all operations axes; and (i) carrying out the next operation by a machine tool with respect to all the operations axes until the required operations by the machine tools are performed.

Ideally the serrated cutting edges are formed having a pitch between centres of adjacent serrations of 2.154 mm.

The invention will be more clearly understood from the following description of an embodiment thereof given by way of example only, with reference to the accompanying drawings in which :Fig. 1 is a perspective view of a postage stamp rotary cutting die according to the invention; Fig. 2 is an enlarged diagrammatic plan view of portion of a shaped stamp cutter formed on the die; Fig. 3 is a sectional view taken along the line III-III of Fig. 2; Fig. 4 is a view similar to Fig. 2 showing the stamp cutter at an intermediate stage of its formation; IE 930137 - 5 Fig. 5 is a sectional view along the line V-V of Fig. 4; Figs. 6(a) to 6(e) are diagrammatic plan views showing steps in engraving a pointed blade on the stamp cutter; Figs. 7(a) to 7(e) are elevational views along the line VII-VII of Fig. 6 corresponding to the views of Figs. 6(a) to 6(e); Fig. 8 is a diagrammatic illustration of movement of a 10 machine tool to form a row of the stamp cutter blades on the die; Fig. 9 is a diagrammatic plan view of portion of a cutting edge of the stamp cutter; Fig. 10 is a diagrammatic plan view of a corner portion 15 of a cutting edge of the stamp cutter; Figs. 11 and 12 are elevational views of stamps formed using the die; Fig. 13 is an elevational view of portion of a roll of stamps formed using the die; and Fig. 14 is a diagrammatic illustration of a flat cutting die according to another embodiment of the invention.

Referring to the drawings and initially to Figs. 1 to 13 thereof, there is illustrated a rotary cutting die according to the invention indicated generally by the reference numeral 1. The rotary cutting die 1 has a generally cylindrical body 2 with cylindrical bearing shafts 4 projecting outwardly at each end. Centre bores IE 930137 - 6 6 are provided at an outer end of each bearing shaft 4. The body 2 has a pair of spaced-apart bearers 8 adjacent each end for bearing against a complementary anvil roller in a stamp cutting apparatus in use. A central portion 9 of the body 2 between the bearers 8 has a number of stamp cutters 10 formed around the die 1.

Each stamp cutter 10 has an upstanding wall 11 projecting radially outwardly of an outer surface 12 of the die 1. An upper end of the wall 11 is sharply pointed to form a cutting blade 13 having a sharp tip 14. It will be noted that the bearers 8 stand proud of the tips 14 of the cutters 10 by a distance equal to the thickness of the backing film which is to be used for stamps formed by the die 1 in use. The stamp cutters 10 are arranged in a number of rows extending continuously around the die 1.

To produce the die 1 preliminary machining is carried out on a cylindrical blank to form a cylindrical blank of the required length and outside diameter with the centre bores 6 at each end. Then the support shafts 4, bearers 8, and central portion 9 are roughly machined on the blank. The support shafts 4 and bearers 8 are flame hardened. Next the blank is mounted in a cylindrical grinder and the bearing shafts 4, bearers 8 and the central portion 9 of the body 2 which is to carry the stamp cutters 10 are ground between centres to ensure concentricity.

After grinding, the blank is mounted on a numerically controlled milling machine. For each die 1 numerical control data is prepared for operation of the milling machine. The data defines the multiple milling and engraving operations to be carried out by machine tools in forming each stamp cutter 10 with reference to an operations axis 30 (see Fig. 8). As shown a series of reference operations axes 30 are defined about which each IE 930137 - 7 stamp cutter 10 is formed. A datum centre line 40 is defined which in this case is co-incident with the central operations axis 30 of each row of stamp cutters 10. The control data is defined to operate the milling machine to move the cutting tool of the milling machine from the datum centre line 40 to the operations axis 30 at one end of a row of stamp cutters 10, to carry out the required milling or engraving operation with reference to that operations axis 30 and then move the tool to the next adjacent operations axis 30. Movement of the tool between operations axes 30 along a row of stamp cutters 10 is illustrated by arrows in Fig. 8. At the end of each row of stamp cutters 10 an imaginary stamp cutter 42 is defined (shown in broken outline in Fig. 8) such that when the tool moves from the last stamp cutter 10 in a row of stamp cutters 10 to the operations axis 30 of the imaginary cutter 42 the tool is moved back to the centre line 40. The die blank is then rotated on the milling machine to a position for forming the next adjacent row of stamp cutters 10. The machine tool thus forms each stamp cutter 10 along a row in turn and steps around each row of stamp cutters 10 in turn. Preferably, after each full cycle of machining operations the machine tool is moved around the die 1 carrying out the next set of machining operations in reverse order with reference to the operations axes 30.

Referring now in particular to Figs. 1 and 4 to 7 the formation of each stamp cutter 10 will be described. Firstly, a radial reference hole 45 (Fig. 1) is drilled in each blank to allow re-setting of the die 1 on a milling machine at a future date for subsequent repair and refurbishment of the die 1. Next a milling tool is directed to mill out excess material from a surface of the central portion 9 of the body 2 to define a land 50 roughly in the shape of the stamp cutter 10. As will be IE 930137 - 8 seen from Fig. 5 the land 50 will have substantially vertical side faces 51 and a flat top surface 52. Then an engraving tool is mounted on the milling machine and the milling machine is directed to move the tool along the land 50 in the sequence shown in Figs. 6(a) to 6(e) to form the pointed blade 13. It will be noted that the engraving tool shapes the blade 13 in a number of passes. The tool first removes the corners 53 of the land 50 forming sloped shoulders 54 as shown in Figs. 6(b) and 6(c). This is done for all the lands 50. Then in a second pass which preferably is carried out in reverse order with reference to the operations axes 30, the blade 13 with the sharp tip 14 is formed as shown in Figs. 6(d) and 6(e). In some cases more than two passes of the engraving tool may be required to form the blade 13.

When all the stamp cutters 10 have been formed, the die 1 is chrome plated to provide hardness typically in the order of 70 Rockwell. The finished die 1 is then mounted in a test jig and operated, passing stamp material between the die 1 and a rotary anvil on the jig to ensure correct operation of the die.

Fig. 9 shows portion of a cutting edge or tip 14 of the stamp cutter 10, serrations being formed by a number of spaced-apart straight portions 60 interconnected by arcuate portions 61. A gradual curved transition is made between such straight portions 60 and its adjacent arcuate portions 61. It will be noted that the pitch X of each serration is 2.154 mm. This has been found to give serrations which look similar to the perforations on conventional stamps. Advantageously with this modular type of serration stamp cutters of any desired size can be readily easily produced.

IE 930137 - 9 Fig. 10 shows a corner detail wherein arcuate portions 51 from adjacent side edges are interconnected by a corner projection 62. It will be noted that the corner projection 62 has two substantially perpendicular straight portions 63 interconnected by a curved bend 64. A gradual curved transition is made between the corner portion 62 and each adjacent arcuate portion 61.

Figs. 11 and 12 show two postage stamps 70, 71 of different sizes formed by the die. Fig. 13 shows a row of the stamps 71 mounted spaced-apart on a peel-off backing film 72, each stamp 71 having adhesive on it's rear face such that it can be peeled off the backing film 71 and pressed onto an envelope or the like. Conveniently a roll of stamps can be provided.

Referring now to Fig. 14, there is illustrated a flat cutting die according to the invention indicated generally by the reference numeral 80. The die 80 has a generally rectangular metal body 81 with a number of spaced-apart bolt holes 82 for mounting the die 80 on a stamping machine (not shown). A number of spaced-apart stamp cutters 83 are upstanding on an upper surface 84 of the body 81. Each stamp cutter 83 is shown diagrammatically in Fig. 14 and is generally similar to the stamp cutters shown on the die of Figs. 1 to 13. The stamp cutters 83 are formed in similar fashion to the stamp cutters on the die of Figs. 1 to 13. Each stamp cutter has a serrated outer cutting edge formed by a number of spaced-apart straight portions interconnected by arcuate portions, the cutting edge having a number of serrated sides interconnected by rounded corner projections. Each cutter has an upstanding wall with substantially parallel sides terminating in a pointed tip.

IE 930137 - 10 The invention is not limited to the embodiment hereinbefore described which may be varied in both construction and detail.

Claims (5)

1. A cutting die for producing self-adhesive stamps spaced-apart on a peel-off backing film, the die comprising a die body having a number of spaced-apart 5 stamp cutters upstanding on the body, each stamp cutter having a serrated outer cutting edge simulating the outline of a postage stamp with perforated edges, the serrations formed by a number of spaced-apart straight portions interconnected by arcuate portions with a 10 gradual transition between each straight and arcuate portion and the cutting edge has a number of serrated sides interconnected by rounded corner projections.

2. A cutting die as claimed in claim 1 wherein each cutter has an upstanding wall with substantially parallel 15 sides terminating in a pointed tip.

3. A cutting die substantially as hereinbefore described with reference to the accompanying drawings.

4. A roll or sheet of stamps whenever produced by the cutting die as claimed in any preceding claim 20 comprising a number of spaced-apart peel-off selfadhesive stamps on a backing film.

5. A stamp whenever produced by the cutting die as claimed in any of claims 1 to 3.