TECHNICAL FIELD

[0001] The present disclosure relates to printmaking. More specifically, this disclosure relates to an improved packing and frontings locking mechanism for printing presses.

SUMMARY

[0002] In certain precision roller presses, including roller intaglio presses, a substrate upon which an image is to be printed is carried through the press on one or more webs of fibrous material, also known as a board. As part of the printing process, the one or more webs and the substrate to be printed upon, are drawn over an impression cylinder comprising one or more (often three) sets of gripper mechanisms configured to retain and tension sections of material, including packings and frontings which cover the impression cylinder. Depending on parameters of the printing application, different packings and frontings can be mounted upon the impression cylinder. When new packings and frontings are installed, they are retained and drawn tight to an appropriate tension by the sets of gripper mechanisms on the impression cylinder.

[0003] For certain industrial-scale roller presses (for example, some models of Komori intaglio presses), the operation of the press causes the gripper mechanisms of the impression cylinder to frequently work loose, with the effect that frontings and packings are no longer drawn tight. From a practical standpoint, the inability of the impression cylinder gripper mechanism to keep frontings and packings tensioned can in frequent downtime on print runs, wherein operators need to stop the press to re-tension the gripper mechanisms to ensure that the packings and frontings on impression cylinder are properly tensioned. Maintaining proper tension of packings and frontings helps to ensure precise registration of printed features, and to minimize the risk of ink being accidentally transferred from the plate cylinder to the packing or frontings.

[0004] For certain applications, including, without limitation, precision printing of security documents, such as currency notes, passports and the like, the use of increasingly thicker packing and frontings has been observed to exacerbate the problems associated with gripper mechanisms working loose during routine operation. [0005] Accordingly, resisting loosening of impression cylinder gripper mechanisms remains a source of technical challenges and opportunities for improvement in the art. The present disclosure illustrates embodiments of an improved tightening mechanism for the impression cylinder of an intaglio press.

[0006] In a first embodiment, a tensioning bracket member includes a body portion, wherein the body portion includes a through hole configured to receive a tensioning bolt, and an internal channel disposed substantially perpendicular an axis of the tensioning bolt, a spring disposed within the internal channel, and a ratchet pin disposed in part within the internal channel and configured to engage the spring at a first end, and a crown gear affixed to the tensioning bolt at a second end.

[0007] In a second embodiment, a tensioning bracket includes a tensioning bolt having a crown gear proximate to a head of the tensioning bolt. The tensioning bracket further includes a body portion, the body portion including a through hole configured to receive the tensioning bolt, and an internal channel disposed substantially perpendicular to an axis of the tensioning bolt. Additionally, the tensioning bracket includes a spring disposed within the internal channel, a ratchet pin disposed in part within the internal channel and configured to engage the spring at a first end, and a crown gear affixed to the tensioning bolt at a second end of the ratchet pin, and a worm gear retained within the body portion and connected to an end of the tensioning bolt distal from the head of the tensioning bolt.

[0008] Other technical features may be readily apparent to one skilled in the art from the following figures, descriptions, and claims.

[0009] Before undertaking the DETAILED DESCRIPTION below, it may be advantageous to set forth definitions of certain words and phrases used throughout this patent document. The term “couple” and its derivatives refer to any direct or indirect communication between two or more elements, whether or not those elements are in physical contact with one another. The terms “include” and “comprise,” as well as derivatives thereof, mean inclusion without limitation. The term “or” is inclusive, meaning and/or. The phrase “associated with,” as well as derivatives thereof, means to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, have a relationship to or with, or the like. The phrase “at least one of,” when used with a list of items, means that different combinations of one or more of the listed items may be used, and only one item in the list may be needed. For example, “at least one of: A, B, and C” includes any of the following combinations: A, B, C, A and B, A and C, B and C, and A and B and C.

[0010] Definitions for other certain words and phrases are provided throughout this patent document. Those of ordinary skill in the art should understand that in many if not most instances, such definitions apply to prior as well as future uses of such defined words and phrases.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] For a more complete understanding of the present disclosure and its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings, in which like reference numerals represent like parts:

[0012] FIGURE 1 illustrates an example of a tensioning bracket of an impression cylinder, suitable for use with bracket members according to certain embodiments of this disclosure;

[0013] FIGURES 2A-2B illustrate examples of tensioning bracket members according to various embodiments of this disclosure;

[0014] FIGURE 3 illustrates aspects of the operation of a tensioning bracket member according to some embodiments of this disclosure; and

[0015] FIGURE 4 illustrates an example of a crown gear according to certain embodiments of this disclosure.

DETAILED DESCRIPTION

[0016] By way of background, in certain roller presses, an impression cylinder contacts a plate cylinder to apply pressure to, inter alia, a moving substrate pinched between the impression and plate cylinders. In an intaglio press, the pressure upon the moving substrate is sufficient to force the substrate into ink-filled recesses of the substrate, producing the signature hard-to reproduce intaglio print effect. To ensure that the pressure between the impression cylinder and plate cylinder both remains consistent between impressions and is uniformly applied across the plate cylinder / impression cylinder interface, a removable layer of one or more sheets of material (i.e., packings and frontings) under tension is mounted on the exterior of the impression cylinder. To retain and tension the packing and fronting material, an impression cylinder has one or more (often three) sets of grippers, which allow for fine adjustment of the tensioning force applied to the materials on the exterior of the impression cylinder. The packings and frontings wrap, at least partially, around a tensioning rod with a gear at one end, wherein the gear at the end of the tensioning rod engages with a worm gear within a tensioning bracket mechanism. Rotation of worm gear causes rotation of the tensioning rod, which controls the extent to which the packings and frontings wrap around the tensioning rod, and by implication, the tension in frontings and packings. In this way, the combination of the tensioning rod and worm gear of the tensioning bracket mechanism operate similarly to the tuning machines of a guitar or other fretted string instrument.

[0017] FIGURE 1 illustrates aspects of a bracket 100 through which the tensioning force upon a gripper can be generated and tuned.

[0018] FIGURE 1 illustrates, in exploded view, components of a tensioning bracket 100 for a gripper mechanism. According to certain embodiments, the bracket shown in FIGURE 1 is mounted on a base (i.e., a flat end) of an impression cylinder, and is configured to engage a gear (not shown) connected to a retaining structure within the impression cylinder. In this non-limiting example, the tension in the material drawn over the impression cylinder is a function of the angle of rotation of the gear, and the angle of rotation of the gear is modulated through rotation of a worm gear 8, which engages with the gear connected to the retaining structure.

[0019] As shown in the explanatory example of FIGURE 1, worm gear 108 is retained in, and can rotate within a pair of circular recesses in first bracket half 106 and second bracket half 105. A tensioning bolt 101 passes between tines of retaining member 107 and a hollow portion of the circular recess in second bracket half 105. Further, in some embodiments, a bushing, bearing or other friction-relieving member 104 is disposed between worm gear 108 and first bracket half 106. In certain embodiments, the bushing is made of brass or a low friction polymer, such as TEFLON.® Turning tensioning bolt 101 causes worm gear 108 to rotate, and in turn, changes the angle of rotation of the gear of the retaining structure, which engages with the ramped exterior threads of worm gear 108, thereby changing the tension in a packing/fronting mounted on the exterior of the impression cylinder. In this example, retaining member 107 comprises a wishbone-shaped leaf spring which provides an upwards axial force upon the tensioning bolt to, in theory, hold the tensioning bolt in place once tightened. However, experience has shown that retaining member 107 is often inadequate to resist loosening forces generated through routine operation of certain presses, which cause the tensioning bolt to rotate, releasing the tension in the packing/fronting layer. This inability to hold the tensioning bolt at a position associated with an appropriate tension of the packing/fronting layer can present a significant operational problem, resulting in downtime to check and re-tension the tensioning bolts actuating worm gears of gripper mechanisms.

[0020] FIGURE 2A illustrates an example of a second bracket half 200, which when substituted for second bracket half 105 in FIGURE 1, can dramatically reduce the tendency of the worm gear setting the tension in the packings and frontings to rotate during operation, and by implication, the tensioning bolt to move away from an initially set position, thereby releasing the tension of the packings/frontings mounted on an impression cylinder. As such, in certain embodiments according to this disclosure, the need to check and re-tighten tensioning bolts whose tension is set and maintained in part by a worm gear retained in second bracket half 200, during routine operation of a press can be largely eliminated.

[0021] Referring to the explanatory example of FIGURE 2A, a second bracket half 200 according to certain embodiments of this disclosure is illustrated. In this example, four views of bracket half 200 are provided. According to certain embodiments, the second bracket half of FIGURE 2A is reverse-compatible with other components (for example, the first bracket half, tensioning bolt, retaining bolts and worm gear) of other tensioning brackets (for example, the tensioning bracket shown in FIGURE 1), and second bracket half 200 can be substituted for an original second bracket half.

[0022] According to certain embodiments, second bracket half 200 comprises a body portion 201 made of metal (for example, aluminum or mild steel) comprising a raised portion with a pair of through-holes 203a and 203b drilled to accommodate the shanks of bolts holding the second bracket half to a first bracket half (for example, first bracket half 6 in FIGURE 1). Additionally, second bracket half 200 comprises a flat portion having a third through-hole 205 configured to retain a bushing through which a tensioning bolt (for example, tensioning bolt 101 in FIGURE 1), and in some embodiments, lower flange of a worm gear passes. According to certain embodiments, the tensioning bolt is one whose head has an exterior surface upon which a crown gear can be mounted.

[0023] Referring to the non-limiting example of FIGURE 2A, in certain embodiments, second bracket half 200 comprises an internal channel 207 disposed substantially perpendicular to the axis of the tensioning bolt in a first plane 215 and directed slightly away from the axis of the tensioning bolt in a second plane, such that the extended centerline 213 of the internal channel does not pass through central axis 215 of the tensioning bolt. Rather, in certain embodiments, when viewed from above (i.e., along the central axis of the tensioning bolt) the extended centerline of the internal channel passes through the tensioning bolt along a chord which does not include the center of the tensioning bolt. According to some embodiments, a spring 209 and ratchet pin 211 are disposed in internal channel 207 such that the spring 209 pushes ratchet pin 211 against a crown gear mounted on the head of the tensioning bolt. The engagement of ratchet pin 211 against the crown gear affixed to the head of the tensioning bolt provides a consistent retaining force on the tensioning bolt, arresting the tendency of the tensioning bolt to work loose during routine operation of a press.

[0024] FIGURE 2B, illustrates a further example of a second bracket half 250 according to various embodiments of this disclosure. For convenience of cross reference, elements common to both FIGURES 2A and 2B are numbered similarly.

[0025] Referring to the non-limiting example of FIGURE 2B, in some embodiments, instead of a bushing, a needle bearing 251 is seated in the through-hole through which the tensioning bolt passes. Testing has shown that carrying the tensioning bolt on a roller bearing provides smooth actuation of the tensioning bolt and can further reduce the incidence of stiction or other force imbalances in the tensioning mechanism, which, over time, can lead to variations in the tension of packings, and in turn jams and stoppages.

[0026] Second bracket halves according to certain embodiments, can, as shown in FIGURE 2B, be manufactured as a unitary member (for example, machined from a single steel billet), or in two or more pieces held together under the tension of the retaining bolts holding the second bracket half to the impression cylinder. For example, second bracket half 250 comprises a first portion 253 and a second portion 255, which are held together by the bolts in through-holes 203 a & 203b. In some embodiments, where layered multi -piece construction is used for the second bracket half, one or more dowel pins (for example, dowel pins 257a & 257b) are disposed between the layered pieces of the second bracket half to ensure the correct alignment of the pieces and to resist loosening forces.

[0027] FIGURE 3 illustrates aspects of how, in certain embodiments, a spring- loaded ratchet pin in 301 the second bracket half engages with crown gear 305 to resist unwanted movement of the tensioning bolt to which the crown gear is affixed.

[0028] Referring to the non-limiting example of FIGURE 3 a top view of the head of the tensioning bolt 300 (shown as a hexagon within crown gear 305), a spring-loaded ratchet pin 301, and heads of a pair of bolts 303a and 303b, attaching a second bracket half to a first bracket half, are shown in the figure. In this explanatory example, the rotation of bolt 300 controls the rotation of a worm gear (for example, worm gear 108 in FIGURE 1), which engages with a gear on a retaining mechanism. In this way, the tension of the packings and frontings on the impression cylinder are function of the rotational position of bolt 300. If bolt 300 rotates, the tension of the packings and frontings on the cylinder changes according to the direction of the movement of bolt 300.

[0029] According to various embodiments, spring-loaded ratchet pin 301 engages with the teeth of crown gear 305 of the tensioning bolt 300 head at a slight offset, on what is shown as the lower left hand side of the head of crown gear 305. In certain embodiments, an end of ratchet pin 301 may be connected to, or in contact with a compressed spring (for example, spring 209 in FIGURE 2A) disposed in an internal channel of a tensioning bracket. In this way, the spring provides a force maintaining contact between ratchet pin and crown gear 305. In embodiments where the tensioning bolt is right threaded, ratchet pin 301 can provide a torsional force to resist counter-clockwise movement (i.e., loosening) of tensioning bolt 300 due to vibrational or other forces arising during operation of a printing press. At the same time, by virtue of the relatively steep angle of engagement between ratchet pin 301 and crown gear 305, certain embodiments according to the present disclosure permit movement of the tensioning bolt in both directions, when a comparatively larger torque is applied to the bolt by a tool adapted to fit the tensioning bolt. While in the non-limiting example of FIGURE 3, the teeth of crown gear 305 are biased to engage ratchet pin 301 at different angles of engagement depending on the direction in which tensioning bolt 300 is turned, embodiments according to this disclosure are not so limited, and include embodiments in which the gear faces of crown gear 305 engage with ratchet pin 301 at similar angles in both the clockwise and counterclockwise directions.

[0030] FIGURE 4 illustrates multiple views of an example of a crown gear 400 according to some embodiments of this disclosure.

[0031] Referring to the non-limiting example of FIGURE 4, crown gears according to certain embodiments of this disclosure are made of metal (for example, tool steel or case-hardened steel), and comprise an inner surface 401 shaped and dimensioned to slide over and engage with a tool engagement surface of the tensioning bolt. According to certain embodiments, the tolerances between inner surface 401 and the head of a tensioning bolt are such that crown gear 400 is press-fit onto the head of the tensioning bolt. In this illustrative example, the inner portion has a substantially hexagonal profile permitting the crown gear to be press-fit onto the head of the tensioning bolt. In some embodiments, the inner portion of the crown gear can be configured to engage with other bolt heads, such as socket-head machine screws. According to some embodiments, crown gear 400 further comprises an exterior profile 403 comprising a set of teeth configured to engage with the spring-loaded ratchet pin in the second bracket half. As noted with reference to the illustrative example of FIGURE 3, according to certain embodiments, exterior profile 403 of crown gear 400 may comprise a gear tooth profile which is biased to offer greater resistance to rotation in one direction (for example, a loosening direction) than the other direction of rotation.

[0032] Examples of tensioning bracket members according to various embodiments of this application include tensioning bracket members comprising a body portion, the body portion comprising a through hole configured to receive a tensioning bolt, and an internal channel disposed substantially perpendicular an axis of the tensioning bolt, a spring disposed within the internal channel, and a ratchet pin disposed in part within the internal channel and configured to engage the spring at a first end, and a crown gear affixed to the tensioning bolt at a second end.

[0033] Examples of tensioning bracket members according to various embodiments of this application include tensioning bracket members comprising a bushing disposed in the through hole.

[0034] Examples of tensioning bracket members according to various embodiments of this application include tensioning bracket members comprising a needle bearing disposed in the through hole.

[0035] Examples of tensioning bracket members according to various embodiments of this application include tensioning bracket members wherein the body portion comprises two sections of material aligned by two or more dowel pins.

[0036] Examples of tensioning bracket members according to various embodiments of this application include tensioning bracket members wherein the internal channel is disposed substantially perpendicular to an axis of the tensioning bolt in a first plane and directed slightly away from an axis of the tensioning bolt in a second plane.

[0037] Examples of tensioning bracket members according to various embodiments of this application include tensioning bracket members wherein an extended centerline of the internal channel passes through a chord of the tensioning bolt, wherein the chord of the tensioning bolt does not include a centerline of the tensioning bolt.

[0038] Examples of tensioning brackets according to some embodiments of this disclosure include tensioning brackets comprising a tensioning bolt comprising a crown gear proximate to a head of the tensioning bolt, a body portion, the body portion comprising a through hole configured to receive the tensioning bolt, and an internal channel disposed substantially perpendicular to an axis of the tensioning bolt, a spring disposed within the internal channel, a ratchet pin disposed in part within the internal channel and configured to engage the spring at a first end, and a crown gear affixed to the tensioning bolt at a second end of the ratchet pin, and a worm gear retained within the body portion and connected to an end of the tensioning bolt distal from the head of the tensioning bolt.

[0039] Examples of tensioning brackets according to some embodiments of this disclosure include tensioning brackets comprising a bushing disposed in the through hole.

[0040] Examples of tensioning brackets according to some embodiments of this disclosure include tensioning brackets comprising a needle bearing disposed in the through hole.

[0041] Examples of tensioning brackets according to some embodiments of this disclosure include tensioning brackets wherein the body portion comprises two sections of material aligned by two or more dowel pins.

[0042] Examples of tensioning brackets according to some embodiments of this disclosure include tensioning brackets wherein the internal channel is disposed substantially perpendicular to an axis of the tensioning bolt in a first plane and directed slightly away from an axis of the tensioning bolt in a second plane.

[0043] Examples of tensioning brackets according to some embodiments of this disclosure include tensioning brackets wherein an extended centerline of the internal channel passes through a chord of the tensioning bolt, wherein the chord of the tensioning bolt does not include a centerline of the tensioning bolt.

[0044] Examples of tensioning brackets according to some embodiments of this disclosure include tensioning brackets wherein the crown gear comprises an exterior profile biased to provide more resistance to rotation in a first direction than a second direction.

[0045] Examples of methods according to certain embodiments of this disclosure include methods comprising attaching a first end of a fronting to a retaining mechanism within an impression cylinder, wherein the retaining mechanism comprises a tensioning rod holding the first end of the fronting and a first gear disposed along an axis of rotation of the tensioning rod, a tensioning bracket comprising, a tensioning bolt comprising a crown gear proximate to a head of the tensioning bolt, a body portion, the body portion comprising, a through hole configured to receive the tensioning bolt, and an internal channel disposed substantially perpendicular to an axis of the tensioning bolt, a spring disposed within the internal channel, a ratchet pin disposed in part within the internal channel and configured to engage the spring at a first end, and a crown gear affixed to the tensioning bolt at a second end of the ratchet pin, and a worm gear retained within the body portion and connected to an end of the tensioning bolt distal from the head of the tensioning bolt, wherein the worm gear is configured to engage with the first gear; and rotating the tensioning bolt to set a tension in the fronting.

[0046] Examples of methods according to certain embodiments of this disclosure include methods wherein the tension in the fronting is maintained during operation of the impression cylinder through engagement of the ratchet pin against a face of a gear of the crown gear.

[0047] Although the present disclosure has been described with various embodiments, various changes and modifications may be suggested to one skilled in the art. It is intended that the present disclosure encompass such changes and modifications as falling within the scope of the claims.

[0048] The present disclosure should not be read as implying that any particular element, step, or function is an essential element, step, or function that must be included in the scope of the claims. Moreover, the claims are not intended to invoke 35 U.S.C. § 112(f) unless the exact words “means for” are followed by a participle.