Creasing devices

Abstract

A creasing device is provided that includes a counter-rotating male drum and female drum. The male drum carries a conventional creasing ring with a central rib flanked by shoulders. The female drum comprises a central channel aligned with the creasing rib on the male drum; and a pair of projecting lateral ribs on each side of the central channel that are aligned with the shoulders on the male drum. The lateral ribs press a sheet of the card or paper stock against the shoulders of the creasing ring to better define the edges of the crease and to reduce the tendency of a printed coating on the stock to crack during subsequent folding. The pair of lateral ribs may be provided by a pair of inserts. Alternatively, both ribs and the central channel may be provided by a single insert.

Claims

1. A creasing device comprising: a female drum that comprises: an outer surface; a central channel that extends around the circumference of the drum; and a pair of lateral ribs that extend around the circumference of the drum adjacent to and on each side of the central channel, the lateral ribs projecting radially outwards relative to a region of the outer surface adjacent to the lateral ribs; and a male drum that comprises: a resilient creasing ring, wherein a profile of the creasing ring comprises a single central rib; and a pair of resilient shoulders flanking the single central rib; wherein the male and female drums are arranged with their axes parallel, wherein the single central rib of the creasing ring extends into the central channel of the female drum to crease a sheet of stock therebetween; and wherein the lateral ribs of the female drum engage with the resilient shoulders of the male drum to compress the sheet of stock therebetween, wherein the resilient shoulders of the male drum are integral with the resilient creasing ring.

2. A creasing device according to claim 1, wherein the radially outer part of each lateral rib has a rounded profile.

3. A creasing device according to claim 1, wherein the central channel has side walls formed by the respective lateral ribs.

4. A creasing device according to claim 1, wherein the central channel has a base with a flat profile.

5. A creasing device according to claim 4, wherein the region of the outer surface of the female drum has a first radius, and wherein the base of the central channel has a second radius that is smaller than the first radius.

6. A creasing device according to claim 5, wherein a further region of the outer surface that is not immediately adjacent to the lateral ribs is cylindrical, having a third radius that is larger than the first radius.

7. A creasing device according to claim 1, wherein the pair of lateral ribs and the central channel are formed by a single insert that is located in a single circumferential groove in the female drum.

8. A creasing device according to claim 7, wherein the insert also comprises the adjacent region of the outer surface of the female drum.

9. A creasing device according to claim 7, wherein the insert further comprises at least one axial projection for anchoring the insert in a recess in a side wall of the circumferential groove.

10. A creasing device according to claim 7, wherein the insert is made from nylon.

11. A creasing device according to claim 1, wherein the pair of lateral ribs are formed by a pair of inserts that are respectively located in a pair of circumferential grooves in the female drum.

12. A creasing device according to claim 11, wherein the inserts are made from rubber.

13. A creasing device according to claim 12, wherein the single central rib of the creasing ring of the male drum engages with the base of the central channel of the female drum to compress the sheet of stock therebetween.

14. A method of creasing stock in a creasing device according to claim 1, comprising: counter-rotating the male and female drums; feeding the stock between the drums; creasing the stock between the single central rib of the creasing ring of the male drum and the central channel of the female drum; and compressing the stock between the lateral ribs of the female drum and the resilient shoulders of the male drum.

15. A method of creasing stock according to claim 14, further comprising compressing the stock between the single central rib of the creasing ring of the male drum and the base of the central channel of the female drum.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The accompanying drawings incorporated in and forming a part of the specification illustrate several aspects of the present invention and, together with the description, serve to explain the principles of the invention. In the drawings:

(2) FIG. 1 is a partial cross section showing the profiles of male and female drums of a creasing device known in the prior art;

(3) FIG. 2 shows the manner in which creased stock is folded and illustrates the location of cracking in the prior art;

(4) FIG. 3 is a partial cross section showing the profiles of a female drum according to a first embodiment of the invention;

(5) FIG. 4 is a partial cross section showing the profiles of male and female drums of a creasing device according to the first embodiment of the invention;

(6) FIG. 5 shows the folding of stock that has been creased in accordance with the invention;

(7) FIG. 6 is a partial cross section similar to FIG. 3, which labels the dimensions of the female drum;

(8) FIG. 7 is a partial cross section showing the profiles of a female drum according to a second embodiment of the invention; and

(9) FIG. 8 is a partial cross section showing the profiles of male and female drums of a creasing device according to the second embodiment of the invention.

(10) While the invention will be described in connection with certain preferred embodiments, there is no intent to limit it to those embodiments. On the contrary, the intent is to cover all alternatives, modifications and equivalents as included within the spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE INVENTION

(11) FIG. 3 shows a female drum 20 of a creasing device according to a first embodiment of the invention. FIG. 4 shows the creasing device comprising the female drum of FIG. 3 in use with a male drum 2 and creasing ring 4 that are the same as shown in FIG. 1. The female drum 20 comprises a cylindrical outer surface 22, in which are formed a pair of grooves 24 extending around the circumference of the drum 20. In each of the grooves 24 is mounted a rib 26 that projects from the mouth of the groove 24 beyond the radius of the cylindrical outer surface 22. The lateral ribs 26 define between them a circumferential central channel 30.

(12) In use, the central channel 30 is aligned with the creasing rib 6 on the creasing ring 4 of the male drum 2. The spacing of the lateral ribs 26 of the female drum is such that they are respectively aligned with the shoulders 8 of the creasing ring 4 of the male drum 2. When the male and female drums 2,20 are counter-rotated and a sheet of the stock 14 is fed between them, the sheet therefore is pushed into the central channel 30 by the creasing rib 6 to form the centre of the crease. The lateral ribs 26 compress the stock 14 against the shoulders 8 of the creasing ring 4 to define the edges of the crease. Preferably the depth of the central channel 30 is such that the rim of the creasing rib 6 also compresses the stock 14 against the base 32 of the channel 30 at the centre of the crease. The compression points are indicated by arrows 31 in FIG. 4.

(13) As illustrated, the profile of each of the lateral ribs 26 is square at the base 28 to rest in the base of the groove 24 and rounded at the rim 29 to be suitable for applying pressure to the sheet of stock 14 without damaging it. The lateral ribs 26 may be made of a material such as rubber that can deform resiliently when pressure is applied to them. The regions 34 of the outer surface 22 that are immediately adjacent to the lateral ribs 26 are formed with a reduced radius. This creates a circumferential recess 34 alongside each rib 26 that gives it more space to deform laterally if required (i.e. by bending or spreading in a direction parallel to the axis of the drum 20). It is not essential that these recesses 34 be rectangular in cross-section: either the wall or the base of the recess (or both) could be inclined relative to the axis.

(14) The side walls of the central channel 30 are formed by the lateral ribs 26 themselves. The base 32 of the channel 30 is formed by a cylindrical surface of the female drum 20. Preferably, as shown, the base 32 of the channel has a smaller radius than the outer surface 22 of the drum so that the channel 30 is recessed relative to the outer surface 22. However, if the height of the lateral ribs 26 is great enough, the base 32 may be aligned with the outer surface 22 and still define a channel 30 of sufficient depth for creasing.

(15) FIG. 5 corresponds to the prior art in FIG. 2 and illustrates the different form of fold created in stock 14 that has been creased in accordance with the present invention. The compression of the stock 14 between the creasing rib 6 and the base of the central channel 30 results in a broader, flatter crease in the central area 36. The edges 38 of the crease are more sharply defined than in the prior art as a result of the compression of the stock 14 between the lateral ribs 26 on the female side and the shoulders 8 of the creasing ring 4 on the male side. It has also been found that compressing the printed stock 14 in this area during the creasing process reduces or eliminates the tendency of the printed coating to crack during folding.

(16) A single female drum 20 may provide more than one such creasing arrangement comprising a central channel 30 with its associated pair of lateral ribs 26. For example, a set of a channel 30 with a pair of ribs 26 may be provided near each of the two axial ends of the female drum 20 (not illustrated). The respective channels 30 and/or pairs of ribs 26 may differ in their dimensions or materials in order to accommodate different types of stock or different widths of crease in a single creasing device. Further alternatives may be provided on further drums 20. FIG. 6 illustrates the profile of the female drum 20 of FIG. 3 with various dimensions labelled a to g. Some of these dimensions may be varied between the different sets of channels 30 and ribs 26. Table 1 below lists possible values for these dimensions for four sets of channels and ribs, provided on two female drums, which between them can accommodate a good range of thicknesses of card stock 14. The maximum outer diameter of the drum 20 in each case is 44.0 mm.

(17) TABLE-US-00001 TABLE 1 (mm) a b c d e f g Set A 0.5 0.65 1.08 0.5 1.425 0.625 2.8 Set B 0.5 0.96 1.08 0.5 1.55 0.75 2.8 Set C 0.5 1.16 1.08 0.5 1.6 0.75 2.8 Set D 0.5 1.26 1.08 0.5 1.7 0.75 2.8

(18) FIG. 7 shows a female drum 40 according to a second embodiment of the invention. FIG. 8 shows a creasing device comprising the female drum 40 of FIG. 7 in use with a male drum 2 and creasing ring 4 that are the same as shown in FIGS. 1 and 4. In this embodiment, the creasing parts of the female drum 40 are provided by a single insert 42 that is located in a single circumferential groove 44. The insert 42 has a generally U-shaped cross section to define a central channel 46 with a square profile at its base 48. The side walls of the channel 46 are formed by two projecting lateral ribs 50. In this example, the projecting rims 52 of the lateral ribs 50 have a much smaller radius than in the first embodiment. This would allow them to be formed much closer together (i.e. with a narrower central channel 46) than illustrated, in order to create a narrower crease suitable for a thinner stock such as paper. In this example, the U-shaped insert 42 further comprises shoulders 54, which define the portion of the outer surface of the drum 40 immediately adjacent to the lateral ribs 50. In alternative embodiments of the invention, the tips of the lateral ribs may formed with such a small radius that they would not naturally be described as rounded. They may form nibs or blades, provided that they are not sharp and rigid enough to cut the paper or damage its surface.

(19) In this embodiment the base 48 of the central channel 46 and the two lateral ribs 50 are all formed from the same material so a compromise must be found between the relative rigidity that is desirable for the channel base 48 and the relative flexibility that is desirable for the lateral ribs 50. Nylon is one suitable material that can meet both these requirements, is hard-wearing and reasonably gentle on the stock 14 to be creased. The form of the lateral ribs 50 could be altered to increase their flexibility if desired. Because the lateral ribs 50 of this embodiment are not intended to deform laterally, the adjacent recesses 34 shown in FIG. 3 are not provided here; the adjacent region of the outer surface provided by the shoulders 54 has the same radius as the further region 56 of the outer surface of the drum 40. However, the use of such recesses in combination with a single insert is not excluded from the scope of the invention.

(20) Various different methods of anchoring the creasing ring 4 in the groove 3 of the male drum 2 have been disclosed in the prior art. If the creasing ring 4 is made from a sufficiently elastic material, it can be formed as a continuous ring that is stretched over the drum 2 and allowed to relax into the groove 3, where it is held in place by its own tension. Alternatively, the creasing ring 4 may be split at one circumferential location to for two abutting ends. This permits the ring 4 to be removed completely from the drum 2 and replaced without dismounting the drum 2 from the axle (not shown) of the creasing device but then the ring 4 can no longer be held in the groove 3 under its own tension. Arrangements have been disclosed in the prior art for anchoring the two abutting ends of the ring 4 at the location of the split, or for anchoring axial projections from the ring 4 within recesses in the side walls of the groove 4. As a final alternative, it may be possible to make the split ring from a material that is sufficiently flexible that the split can be prised open to allow the ring to pass around the drum but sufficiently stiff that the split will then snap closed and the ring 4 will remain in position in the groove 3.

(21) Any of these alternatives may also be employed for mounting the inserts 26,42 in the grooves 24,44 of the female drum 20,40. The method of using a continuous ring may be most appropriate for the pair of discrete lateral ribs 26 formed from rubber as shown in FIG. 3, while a stiff split ring may be most appropriate for the single insert 42 formed of nylon that is shown in FIG. 7. FIG. 8 shows how the single insert 42 in the form of a split ring may be anchored in the groove 44 by providing the insert 42 with axial projections 58 that engage in recesses 60 formed in the side walls of the groove 44 to prevent the insert 42 being withdrawn radially from the groove 44. In this case, the body of the female drum is formed in two parts that meet at the groove 44, namely a collar 62 that is mounted by a screw thread (not shown) on a hub 64. When it is desired to replace the insert 42, the collar 62 can be unscrewed to displace it a short distance axially relative to the hub 64, thereby widening the groove 44 enough for the insert 42 to be removed.

(22) It is also possible to form the insert of the female drum from steel or another suitable metal or other rigid material. The creasing ring 4 on the male side of the sheet 14 may be sufficiently flexible to prevent damage to the stock from the rigid lateral ribs. In this case, even if split, the insert would have no flexibility to allow it to be fitted over the axle from one side. It must either be in the form of a continuous ring that is fitted by sliding from the end of the axle while the axle is demounted, or the insert could be provided in two semi-circular parts that fit together around the axle and are then clamped between the other drum parts.

(23) The resilient shoulders 8 of the male drum 2 are conveniently formed as part of the profile of the resilient creasing ring 4, as shown in the illustrated embodiments. However, the shoulders could alternatively be provided as separate components, formed either as resilient inserts in shallow channels on the male drum that flank the central rib 6, or as resilient strips mounted on the surface of the male drum. The shoulders 8 are illustrated as flat (i.e. with their outer surface parallel to the axis) but that is not essential. In some applications it might be advantageous to provide them with a pre-formed groove to receive the lateral ribs 26,50 of the female drum 20,40; or to provide a groove in the male drum 2 behind the shoulders 8 to allow them to deform into the groove under pressure from the lateral ribs 26,50.

(24) It will be understood that the embodiments of the invention described here are illustrative only and not limiting. In particular, features shown here in separate embodiments may be used together in various combinations.

(25) All references, including publications, patent applications, and patents cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.

(26) The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) is to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.

(27) Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.