Patent Grant
11752758
This national stage application claims priority to International Application No. PCT/EP2020/079209 filed on Oct. 16, 2020, which claims priority to United Kingdom Application No. 1915458.2 filed on Oct. 24, 2019, which are incorporated by reference in their entireties.
The present invention relates to a lightweight interchangeable sleeve and a method of manufacture thereof. In particular, the invention provides a sleeve having a generally continuous cylindrical exterior surface which is inherently or extrinsically magnetic, either in multiple specific discrete areas thereof or more pervasively, such that a typically flexible ferromagnetic plate having a mounting surface and an oppositely disposed functional surface, and being of appropriate shape and dimensions, may be firmly and substantially only magnetically secured around at least some portion of the exterior cylindrical surface of the sleeve with its mounting surface disposed most proximate, and preferably in contacting relationship with, the sleeve exterior surface. Typically the axial and circumferential positioning of the plate on and around the sleeve will be of critical importance, as the functional surface of the plate will, in use, typically come into contact with a substrate material on which some function is to be performed (e.g. printing, coating, lacquering, varnishing, and the like), so it is generally essential that the plate is precisely positioned on the exterior surface of the sleeve so that the plate is automatically precisely aligned and in registration with the substrate.
More specifically, the present invention relates to a the provision of a magnetic sleeve which is comparably very lightweight as compared to current cylindrical magnetic mounting components, and which is furthermore adapted to be very easily and quickly interchangeable, in that any sleeve according to the present invention can be easily and quickly installed (and removed from) within much larger machinery, for replacement or maintenance, by a single person, safely and without significant extraneous support or assistance, and in a manner which nevertheless ensures accurate and precise axial and radial mounting of both the sleeve and the plate magnetically affixed thereto.
Within the printing and other industries, the physical principle of magnetism is commonly employed as useful means of releasably securing ferromagnetic components to magnetized surfaces, particularly when such ferromagnetic components are likely to require frequent replacement, or there is a requirement for speedy interchange of such components, and where the magnetic force of attraction exerted on the component by the magnetized surface on which it is most commonly directly mounted will generally be sufficient to ensure a robust and reliable connection between the two.
There are many examples of modern industrial and commercial machinery within which components are magnetically secured to one another. For example, modern commercial and industrial print presses and other web- and sheet-fed machines commonly utilise magnetic cylinders and/or platens as a means of securing correspondingly dimensioned steel printing, coating or varnishing plates, or cutting dies, to the cylinder or platen. Heretofore, the magnetic cylinder has always been a very substantial, weighty component consisting essentially of a solid steel or aluminium cylinder with journaled ends to allow the cylinder to be mounted within the press. In order that the exterior surface of the cylinder be rendered magnetic to a sufficient degree (i.e. provided with sufficient radially projecting magnetic field strength over substantially its entire cylindrical exterior surface), a series of circumferentially evenly spaced, uniformly dimensioned slots may be milled therein, each slot extending essentially longitudinally over the cylindrical outer surface of the sleeve, from one end thereof to the other. The slots may be essentially straight and thus parallel with the longitudinal axis of the sleeve or they may extend arcuately in spiral fashion over the cylindrical exterior surface, but in any event, a plurality of individual metal magnets and intervening ferromagnetic keepers or pole pieces are alternately inserted into the slots in parallel fashion adjacent one another all along each and every slot, and adhered both to the side faces of the slot and to each other, for example with a high strength epoxy resin. Once all the slots are filled in this manner, the cylinder is then subjected to grinding and finishing in order that the exterior surface is perfectly cylindrical and generally smooth.
In order that the exterior cylindrical surface of the cylinder can magnetically attract a steel or other ferromagnetic material printing plate with sufficient force, the individual magnets inserted into each and every slot must themselves be inherently magnetic to a sufficient degree, and their magnetic fields must be both concentrated and directed such that their magnetic fields essentially project normally upwardly away from the exterior cylindrical surface. The most common arrangement therefore is that each and every magnet, in the form of a thin (<5 mm) rectangular shim, is inserted into the slot laterally followed by an intervening ferromagnetic keeper or pole piece of similar size, such that in any single slot, there may be as many as 30-100 or more individual magnets and respective pole pieces. The North (N) and South (S) poles of each magnet will typically coincide with their largest rectangular faces (orientated such that the plane of those faces lies orthogonally to the longitudinal axis of the cylinder), and their alignment and arrangement within the slots is such that the most adjacent poles of any two magnets on either side of an intervening pole piece are of the same polarity. Such arrangement ensures that each and every intervening pole piece is one of North (N) or South (S) polarity, and the magnetic field from the magnets on either side is thus both concentrated in and directed through the pole pieces towards the cylindrical surface.
The types of magnets most commonly employed in prior art magnetic cylinders are ferrite ceramic magnets, for example being either fundamentally Strontium- or Barium-based, because such ferrite compositions have good resistance to corrosion and demagnetisation, and can be readily ground, finished and (in some cases) polished, much like the solid metal or alloy cylinder in which they are disposed.
Although magnetic cylinders of the type described above are in widespread use in printing and other heavy engineering machinery, their primary and pervasive disadvantage is their weight. As the skilled reader will appreciate, solid magnetic cylinder components are very heavy (often >>30 kg) and therefore very unwieldy—in most cases, magnetic cylinders cannot be manipulated and handled by one, or even two persons. In some cases, if the cylinder itself is damaged, fails or requires servicing, then its removal from within the machine in which it operates is a non-trivial and substantial procedure. A yet further disadvantage is that solid magnetic cylinders of the type described are largely prohibitively costly, and very labour-intensive and thus time-consuming to manufacture, and their use is therefore limited to only such applications where there the speed and simplicity as regards detaching, removing and replacing a printing plate or die are of paramount importance and outweigh the underlying cost of the magnetic cylinder which provides such facilities.
In order to mitigate the above disadvantages, tubular constructions have been proposed wherein a steel, aluminium or other metal or alloy tubular base component is provided, being essentially annular in cross-section, and through which thus extends a cylindrical hollow bore. Slots to receive the magnets and respective pole pieces must of course still be provided in the exterior cylindrical surface as described above, but naturally a tubular component will always weigh significantly less than a corresponding solid component. However, despite this overall weight reduction, the ease with which such tubular components can be reliably, securely and (most importantly) accurately mounted in print and other machinery is more complicated than for a fixed-in-place solid component.
To explain further, in the case of a solid cylinder with accurately machined and located journals at either end, the position and orientation of the solid cylinder is automatically ensured when the journals are disposed in appropriate oppositely disposed fixed bearings within the machine in which the cylinder is to operate. With a tubular component however, the mounting procedure is more complicated because firstly, the tubular component must firstly be slid over an arbor or mandrel of some kind, and secondly, and thereafter as a separate step, the tubular component must then be mechanically secured to that arbor or mandrel in a manner which ensures not only a robust connection of the tubular component to the arbor or mandrel, but which also ensures that the exterior surface of the cylinder is in precisely parallel alignment with the axis of the arbor or mandrel on which it is mounted to avoid rotation eccentricities. As can be seen in prior art documents WO2014/039534 and WO2015/010013 (both in the name of Bunting Magnetics Company, and which cover their PlateMaster™ magnetic sleeve), mechanically intricate connection components are commonly required to achieve a reliable, robust and accurate mounting of a tubular magnetic component. Furthermore, in the PlateMaster™ system, in order to achieve precise axial and circumferential positioning of the sleeve relative to a spindle on and over which the mandrel is mounted, one end of this particular sleeve is provided with largely integrated a solid hub component having adjustment screws therein, further complicating the design. One final important disadvantage of the PlateMaster™ system is that although the sleeve alone may be relatively significantly lighter than a corresponding solid cylinder component, the annular thickness of the sleeve is not only still quite substantial, e.g. at least 30 mm thick at one end and >40 mm thick at the alternate (the reasons for which will become apparent from the further description below), but once the adjustment hub is inserted into one end, which is a solid component, the overall weight of the assembly can still be significant.
In certain types of flexographic and gravure printing machinery, and in machinery developed specifically for what is known as “metal decoration”, being essentially the printing, coating, lacquering and varnishing of beverage and food cans (see for example machinery available from Stolle Machinery Company, LLC., in particular the Concord™ Metal Decorator and Rutherford™ Decorator and Basecoater), the adoption and use of magnetic cylinders and/or magnetic tubular components is becoming more common.
It has also been proposed to replace other non-magnetic solid cylindrical components such as printing and impression cylinders, Anilox rolls, metering rolls, and the like, with corresponding tubular components, albeit still primarily comprised of structurally robust metals such as steel and Aluminium. For instance, the replacement of printing and Anilox cylinders with low cost, lightweight print and Anilox sleeves, still primarily constituted of metal, has been proposed, such sleeves being releasably mounted within more conventional print (i.e. not metal decoration) machinery around what are known as bridge mandrels. Bridge mandrels are essentially cylindrical adapters which on one hand are essentially permanently and axially and circumferentially precisely mounted on a rotating arbor within the machine, and which on the other hand provide an exterior and precisely orientated cylindrical surface to and around which the print or Anilox sleeve can be releasably attached. To release (and to install) the sleeve, the bridge mandrel is connected to a supply of compressed air which is typically delivered through the mandrel to its exterior surface to cause a compressible inner layer of the removable Anilox sleeve to expand, thus releasing the connection therebetween and enabling the sleeve to be axially slid over and eventually completely off (during removal) the bridge mandrel. In terms of relevant prior art, U.S. Pat. No. 5,904,095 discloses the fundamental aspects of bridge mandrels in general, and the Applicant's own application WO2017/089221 describes an Anilox sleeve essentially consisting of a steel or aluminium tube for use in machinery with a bridge mandrel. Of course, similar arrangements may be utilised for components other than Aniloxes, for example print and impression rolls.
Up until the present time, all sleeve constructions, and certainly those described above and intended for use in print and other engineering machinery, consist primarily and fundamentally of metal, most commonly Aluminium or steel, due to the fact that such rotating components must, in order to properly and effectively perform their intended operative function, exert some non-negligible (and often considerable) force on some other component.
In the particular case of magnetic sleeves, and importantly in the context of the present invention, significant amounts of material are required to be machined out from the initially annular sleeve, for example by milling or drilling, to create the plurality of magnet-receiving slots which will most commonly be provided in, and indeed all around the cylindrical exterior surface of the sleeve, and therefore the annular thickness of the initially annular sleeve becomes very important, as will be explained further below.
To provide some specifics on how existing magnetic sleeves are currently machined out, a conventional magnetic sleeve adapted for use on existing metal decorating machinery may have an axial length of apprx. 200 mm and have internal and external diameters of apprx. 190 mm and 230 mm (and thus an annular thickness of 20 mm) respectively. Naturally, the annular thickness of the initial tubular billet must be greater (in prior art constructions, at least 2 times) than the depth of the magnet-receiving slots which are to be machined into and around its exterior cylindrical surface—usually, the depth of the slots will be of the order of 10-19 mm, this dimension of course depending on the depth of the magnets and accompanying keepers which the slot is to receive. Furthermore, as it is very important that the ferromagnetic plate which is to be magnetically secured around the exterior surface of the sleeve is firmly held in place, especially in the region of its lateral edges, the axial length of the slots (and ultimately the arrangement of magnets and keepers within them) generally extend almost completely from one axial end of the sleeve to the other, and may be, for example, 185-195 mm long, or even possibly more, thus leaving only very small, axially thin lands of sleeve material between the end of each machined slot and the end of the sleeve itself, e.g. maybe only 2.5-5.5 mm, or even less. Finally, in terms of the number of slots to be machined in the exterior cylindrical surface and their resulting width, this is again significant, because in order that the resulting exterior cylindrical surface of the sleeve is provided with sufficient magnetic field strength to firmly secure the ferromagnetic plate thereto, current thinking is that at least 40%, and possibly as much as 60-80% of the sleeve exterior cylindrical surface must be magnetic, i.e. be constituted of magnet- and keeper-containing slots, as opposed to the relatively non-magnetic lands of sleeve material defined between any pair of circumferentially adjacent slots. Therefore, depending on the overall outer diameter of the sleeve, as many as 12-24 separate slots, most commonly aligned with the central axis of the sleeve and having a width (measured circumferentially) of apprx. 15-35 mm may be machined into and over the sleeve exterior cylindrical surface.
As the skilled person will understand, the material from which the sleeve is manufactured must possess significant inherent rigidity, structural strength and machinability such that a sleeve can not only be machined out in the manner described without significantly elastic or plastic deformation, cracking, tearing, or other permanent structural weakening, but also the sleeve must possesses sufficient residual structural strength and rigidity once the machining is completed such that the machined-out sleeve is still capable of withstanding the considerable forces to which it will be subjected in operation. It is for these fundamental reasons that the thickness of the initially annular sleeve must still be significant because, naturally, the structural integrity and dimensional stability of the initially solid annular sleeve component will inevitably be weakened as each and every slot is progressively machined out in the manner described. As the skilled reader will appreciate, the structural and dimensional stability of such components is ultimately often an essential factor in their ultimate performance, it is essential that the machined-out sleeve construction be similarly robust.
A further consideration in the manufacture of magnetic sleeves is that magnets and keepers, in repeating alternate fashion, are inserted into and generally adhered within the machined-out slots provided in the exterior surface of the sleeve. As also mentioned, the outer diameter of the sleeve is generally a critical dimension in the specification and operation of any sleeve, because it is the outer diameter which determines (after a ferromagnetic plate of known thickness is secured on and around the exterior cylindrical surface of the sleeve) the distance of the operative or functional surface of the plate from the axis of rotation of the sleeve, and in turn the relative weight or pressure which that functional surface may exert on the substrate being printed, coated or otherwise acted upon. Therefore, in order that the outer diameter of the sleeve can be accurately defined, it is generally mandatory that the exterior cylindrical surface of the sleeve be ground, finished and/or polished down to a precise outer diameter dimension, after the magnets and their intervening keepers have been adhered in place within the slots. Therefore, typically a sleeve will be initially provided with an outer diameter slightly larger than that ultimately required so that the exterior cylindrical outer surface can be appropriately and accurately surface ground down (and often also polished) to the required ultimate outer diameter. Currently, the keepers employed in conventional sleeves are usually of steel, and the magnets are usually of a ferrite material which can also be relatively easily ground (and polished) by the same equipment, thus rendering the grinding (and polishing) relatively straightforward. This would not be the case if the sleeve were constructed of a material or composition whose structural and physical properties were significantly different from those of the magnets and their keepers, or if the nature of the material of which the sleeve was primarily constructed did not lend itself to grinding or polishing (for example synthetic fibrous, or fibre-reinforced, materials and compositions).
Although a steel sleeve can adequately fulfil most requirements (provided initially annular sleeves are sufficiently thick), their fundamental disadvantage is still their weight, as steel is relatively dense. For example, a sleeve having the abovementioned dimensions will have a total material volume of apprx. 2.6×10−3 m3. If manufactured in steel, this sleeve would have an approximate weight of over 20 kg, whereas if made in Aluminium the weight would drastically reduce to a much more manageable 7 kg (excluding any machining, the effect of which is considered to be negligible here because the machined slots are completely filled with magnets and keepers having considerable weight themselves). Although it would of course be possible for a single individual to lift of a steel sleeve of 20 kg, manually manipulating and manoeuvering components of this weight at any significant height above ground level, as is often required, can still be problematical, especially for a single person.
In terms of other candidate materials, as the skilled person will appreciate, there are already in existence a wide array of engineering plastics and plastics composite materials of even lower densities than Aluminium and therefore could offer yet further weight reductions if sleeves were manufactured entirely or substantially in such materials. However, almost universally, the most suitable engineering plastics (at least without the benefit of fibre reinforcement of any kind) lack the required physical, structural and mechanical properties, typified most conventionally by the Young's modulus (often termed the modulus of elasticity or ultimate tensile strength), and also the bulk modulus (the measurement of how resistant a material is to compression). For example, the Young's modulus and bulk modulus of Steel are in the region of 200 GPa (N/m2) and 160 GPa respectively, whereas for a common engineering plastic known as Nylon® 66 (having a density of 1140 kg/m3), these values are 3.5 GPa and 2.9 GPa respectively, notably greater than one order of magnitude less. Thus, although while a sleeve made from an engineering plastics material may offer a significant reduction in weight as compared to a sleeve made of Steel (e.g. a sleeve having the specific dimensions abovementioned and made from Nylon® 66 could weigh as little as 3 kg), unfortunately the physical, structural and mechanical properties of such plastics cannot, on their own at least, be adequately or successfully machined, or indeed withstand the rigours of operative use.
Indeed, although the Young's modulus and bulk modulus of Aluminium are of the order of 20 times greater than those of Nylon 66 above (at 70 GPa and 76 GPa respectively), machining pure Aluminium sleeves, particularly those with relatively thin annular walls as is the case for sleeves of the present invention, is still particularly difficult to conduct, not least because Aluminium is particularly ductile and its tendency to deform during machining is still very much greater than that of steel.
It is therefore a primary object of the present invention to provide an interchangeable sleeve construction within which magnet-receiving slots, channels, recesses or other voids can be machined or otherwise provided and subsequently filled with magnetized components or compositions, and which is of significantly reduced weight as compared to sleeves of the prior art.
It is a yet further object of the present invention to provide such a sleeve which can withstand the rigours of both machining (if required) and conventional operative use, despite the existence of the plurality of magnet or magnetic composition-filled voids that inevitably and necessarily reduce the overall structural integrity of the sleeve.
It is therefore a further object of the invention to provide a new type of sleeve construction which incorporates an initial annular sleeve component made either of an engineering plastics material or a lightweight metal such as Aluminium, and having a comparatively much reduced annular thickness as compared to prior art sleeve, but which can nevertheless still be both successfully and reliably machined without being structurally compromised, and which in use, can successfully and reliably withstand the loads to which the sleeve construction will be commonly subjected during use.
It is a further object of the invention to provide a sleeve construction, which is of significantly reduced cost as compared to the corresponding components primarily constituted only of metal or an alloy thereof, both in terms of the materials used in the manufacture of the said component, and also in terms of the costs of labour and time involved in manufacturing such a sleeve construction.
It is a further object of the invention to provide a method of manufacturing industrial, commercial and engineering magnetic sleeve constructions comprising or consisting essentially of an annular sleeve made from an engineering plastic or plastic composite material, or a relatively (to steel) lightweight metal or alloy thereof, not being generally magnetic and having an attachment surface which is rendered magnetic in an essentially separate machining step after the annular sleeve is initially formed, said attachment surface thus facilitating the substantially purely magnetic attachment of some other functional component.
According to the present invention there is provided a sleeve assembly according to the claims thereof.
For the avoidance of doubt, the phrase “substantial proportion” as appearing in the claims should be understood to mean at least 50%, and preferably at least 60%, more preferably at least 70-75%, yet further preferably at least 75-85%, and even further preferably at least 90%-95%. For example, for a cylindrical tube having initial outer and inner diameters of 227 mm and 210 mm respectively, and thus an annular thickness of 8.5 mm, slots may be 6 mm deep and 20 mm wide, leaving only 2 mm of sleeve material remaining between the base of the slot and the interior cylindrical surface of the tube, and leaving only (approximately) 193 mm of the total circumferential dimension of 713 mm the of the exterior surface not recessed.
Preferably, the relative moduli of elasticities of the end rings and the material of which the tube is constituted should be at least a factor of 2 greater, and further preferably at least a factor of 3-5 greater, and most preferably at least one order of magnitude (i.e. a factor of 10) greater.
Preferably, the end rings are constituted substantially entirely of a metal, most preferably steel, or any similarly structurally capable metal or alloy thereof.
In the most preferred embodiment, the tube is constituted entirely of Aluminium, but in embodiments where the tube is constituted of an engineering plastics material, this is preferably a synthetic polymer, which is most preferably non-fibrous and/or not reinforced with fibres or otherwise. In most preferred arrangements, the synthetic polymer is one of, or some combination of: an acetal-based homopolymer or copolymer (such as Delrin®, available from the DuPont® company), a polyamide (such as Nylon 6 or Nylon 6, 6), and a polyester.
To provide some specifics on the mechanical strength of such plastics materials, most “Delrin®”, Nylon 6 or 6,6 polymers have a modulus of elasticity of the order of 3 GPa at 23 deg. C. (room temperature), whereas the corresponding measure for mild steel is of the order of 200-210 GPa, and for Aluminium is 70 GPa.
Preferably the liner is of multi-laminar construction, and comprises a first, radially innermost fabric base wrap layer, a second compressible layer disposed radially to the outside of the first layer and being of a closed- or open-celled foam material, and a third bulking or build-up layer, disposed radially to the outside of the second layer, and being again fibrous in nature, and preferably being thoroughly impregnated with a resinous composition which, once cured, provides the liner with rigidity. Further preferably the third layer is constituted substantially of resin-impregnated coir mat. Most preferably, the liner further includes at least one intervening barrier layer disposed between the second and third layers, said intervening layer most preferably being constituted most simply of common masking tape wrapped around the exterior cylindrical surface of the second compressible layer to prevent any pre-cured resin present in the third layer from migrating into the compressible layer during construction.
Most preferably the exterior cylindrical surface of the liner is securely and firmly bonded to the interior cylindrical surface of the tube by means of a high strength epoxy-based adhesive which, once cured, provides an effective and rigid bridge between the adjacently disposed cylindrical surfaces of liner and tube respectively, over substantially the entirety of those surfaces.
Most preferably, once screwed in position, possibly after having been surface ground or otherwise machined, the axially outermost annular end surfaces of the end rings lie substantially flush with the annular end surfaces of the tube.
In some embodiments of the invention, preferably at least one (and most preferably both) of the annular shoulders are provided internally of the tube at a sufficient axial depth from the respective annular end surfaces thereof such that said at least one, and preferably both, of said annular shoulders is disposed radially beneath at least one (and preferably all) of the recesses provided in and generally axially along the exterior cylindrical surface of the tube. In this configuration, the annular shoulder(s) provided internally of the tube essentially undercut the recesses provided around the exterior surface of the said tube to some extent. In this configuration, it is thus of course essential that the depth of any (or all) of the recesses which are so undercut must be less than the annular thickness of the rebated end regions of the tube, and in most preferred embodiments, the depth of the recesses will be between 1-10 mm less than the annular thickness of the annular end surfaces of the tube, which will be preferably between 5-20 mm.
It is also to be noted that in this configuration, the ends of the recesses will necessarily axially overlie the screwed-in-place end rings to some extent, and the end rings, being significantly more structurally strong and rigid than the material of which the tube is constituted, thus importantly contribute to the structural strength, at least in a circumferential sense, of the partially machined out end regions of the tube.
The issue of recess depth as compared to the general annular thickness of the tube in which the recesses are provided is an important one because, as the skilled person will appreciate, the machining out of a significant number of deep recesses in an already relatively thin-walled tube is obviously a mechanically unsound practice, not least because the removal of significant amounts of the material from the tube in this manner can seriously compromise the structural rigidity and stability of the remaining article, which may be rendered somewhat flimsy as a result. Furthermore, as previously described, the flimsier a structure becomes, the more difficult it becomes to perform further machining on, in and around that structure. Again, in extreme cases, the structure may become so flimsy that it is ultimately cracked, ripped, torn apart or otherwise irreparably damaged as soon as the machining tool commences any work on the flimsy tube structure having already been weakened by earlier machining.
The present invention overcomes such problems by internally reinforcing the tube by firstly providing screwed-in-place metallic (most preferably steel) end rings which are significantly mechanically and stronger and elastically much more resilient than the tube into which they are screwed. Secondly, although the interior liner construction is inherently radially compressible, such compressibility is provided by an intermediate compressible layer provided as part of the multi-layer construction of the liner, and such compression is achieved predominantly against the outermost bulk-up or build-up layer of the liner throughout which a cured, and thus rigid, resin is impregnated. Thus in its own right, the liner is self-supporting and, externally at least, a relatively rigid structure, even before it is adheringly affixed within the tube as described above. What is less obvious is that by selecting a suitable epoxy- or similar type adhesive to bond the liner to and within the tube, and ensuring that an adhesive layer substantially completely fills the tiny annular interstice which may exist between the exterior cylindrical surface of the liner and the interior cylindrical surface of the tube, and then allowing that adhesive to cure into a rigid layer which binds the liner to the tube, the resulting sleeve assembly is immediately strengthened, both circumferentially and axially, and over the axial length of the tube within which the liner is bonded. Mechanically, this is because the rigid interior liner structure essentially becomes part of tube, and the response thereof to machine tools working on the exterior cylindrical surface thereof, at least in those regions beneath which the liner is disposed, is much more like a tube having a much greater annular thickness.
A yet further structural enhancement, particularly as regards the rigours of machining and general use, is the axial compression to which that portion of the tube between the end rings is subjected as a result of the end rings being screwed firmly (but not excessively so), for example by using a torque wrench or similar, within the rebates defined at either end of the sleeve assembly and up against the annular shoulders rebated out from the end regions of the tube as aforementioned. This compressive force yet further enhances the resistance of the tube, particularly to axial forces it will inevitably experience when the machine tool moves axially along the exterior cylindrical surface of the tube, as it will inevitably repeatedly do as the (usually, preferably) elongate recesses are machined out of that surface. Thus, in conjunction with the interior liner, the end rings and their structurally enhancing and rigidifying effects effectively render what would otherwise be an inherently flimsy and unmachinable tubular article into a machinable one.
Furthermore, the end rings also provide significant circumferential (and axial, though over a relatively short axial distance) structural support and resilience specifically for the end regions of the tube, where such support and resistance is arguably most required. This is because the nature of sleeve assemblies according to the present invention is that recesses must be machined out over substantially the entire axial length of the tube, so the machining tool will inevitably approach the annular end surfaces of the tube, where the axial resistance of the tube is inevitably significantly reduced as compared to that offered by the material of the tube when the machine tool is working much closer to the axial mid-point of the tube. Thus, by providing a sleeve assembly having the construction described, it is possible to reliably machine both very close to the annular end surfaces of the tube, and in some cases (if it is desired to provided partially or completely open-ended recesses) completely through said annular end surfaces without significantly compromising the overall structural integrity of the overall sleeve assembly construction.
In the most preferred arrangement, wherein the annular shoulders provided within the tube undercut the recesses disposed radially above, the machine tool necessarily axially traverses into the end regions of the tube within which the end rings are provided, and therefore the end rings provide additional radial support to allow the machining to continue without the end region being damaged.
A yet further advantage of the sleeve construction described arises when the sleeve assembly is in operative use, and is being subjected to significant radial compression forces all along its axial length. Specifically, in use, both the liner and end rings provide the additional structural internal support for the liner to enable it resist such forces without significantly deforming, whether elastically or plastically, and without sustaining any other type of more significant damage. The resulting sleeve construction is therefore highly dimensionally stable, which is very important for sleeve constructions adapted to receive printing or coating plates which, in use, contact a substrate, both in precise registration and with a precise, predetermined contact pressure, in order to achieve optimum printing or coating performance.
In view of the above, the relative axial locations of the ends of the recesses as compared to the axial depths at which the annular shoulders are provided internally of the tube should be considered as an important aspect of the present invention. Indeed, in a most preferred embodiment, at least one, some or all of the ends of the recesses are undercut to some extent, and the terminal ends of at least one, some or all of said recesses are provided at an axial depth from the annular end surfaces of the tube which is less, by a non-negligible amount (e.g. at least 1 mm, preferably 2-15 mm) than that at which the annular shoulders are provided.
Most preferably, the recesses provided in the exterior cylindrical surface of the tube are axially aligned with the longitudinal axis of the sleeve assembly as a whole, and further preferably, each recess contains an alternating arrangement of magnet-keeper pairs which substantially fill each recess and are adhered or otherwise firmly and immovably secured within said recesses, the uppermost surfaces of all said magnet-keeper pairs lying substantially flush with the plastics material lands defined between each adjacent pair of recesses and thus disposed circumferentially to one or other side thereof. In an alternative embodiment, the said recesses may be provided in spiral arrangement over the exterior cylindrical surface of the tube.
In preferred arrangements, the axial depth dimension of one or both end rings is of the order of 8-25 mm, most preferably of the order of 10-15 mm, with between 50-90% of this dimension being threaded. Preferably, the pitch of the threads is between a Unified Coarse Thread (UNC) measurement of #12-24 and #1-64 (i.e. between 1.058 mm-0.397 mm). Where the tube is constituted of an engineering plastics material, the thread pitch is selected to be at the larger end these two extremes on account of the difficulty in successfully machining very finely pitched (e.g. <1 mm pitch) threads in plastics materials. Furthermore, the provision of threads of relatively large pitch in both the exterior cylindrical surfaces of the metal end rings and the corresponding inner cylindrical surfaces of the rebates provided in the tube allows not only for easy and immediate thread location and interengagement, but also for the end rings to be screwed into the said rebates with sufficient force (without rupturing, stripping or otherwise damaging the threads in the plastics material) such that the mid-section of the tube between respective end rings can be sufficiently axially compressed to enhance the overall structural rigidity of the sleeve assembly as a whole.
Most preferably, prior to screwing engagement of the end rings within the tube, an epoxy or similarly capable curable adhesive is applied to one or both of the threaded portions of end ring and the rebates.
Preferably, the adhesive is initially fluent but sufficiently viscous, for example having a viscosity similar to that of engine grease, so that it can be smeared into, over and around substantially the entire threaded region(s) of one or both respective parts of the sleeve assembly, and be retained therein and thereby without flowing or dripping under gravity. Thus after the adhesive is applied, the end rings can then be screwed into each end of the tube, and the mechanical advantage achieved as a result of circumferential motion of the end ring as compared to the thread pitch allows the end rings to be not only very firmly screwed into the tube, but also in a manner which allows for the application of at least some axially compressive force to be applied between the said end rings when the second of them is screwed into position. As the end rings are screwed in, of course, the adhesive will be forced into and around substantially all the threads, such that significant portions thereof will be well coated with the adhesive. Once the end rings have been screwed into place with the desired, preferably predetermined, torque, the adhesive is then allowed to cure effectively securely bonding the end rings in place within the tube.
In further preferred embodiments, one or both of the annular end surfaces of the liner and adjacent annular shoulders, and the corresponding annular end surfaces of the end rings which will, once fitted, be disposed substantially adjacent the liner annular end surfaces have applied thereto an initially fluent viscous gasket composition which once cured, creates a seal in the axially small annular gap which may (in some embodiments) exist between the end ring annular end surface and the corresponding annular end surface of the liner. This cured-in-place gasket compound also has the additional desired effect of sealing the annular end surfaces of the liner, thus preventing fluid ingress thereinto when the sleeve assembly is in use. In some embodiments, the adhesive may be applied to these surfaces and perform the function of a viscous but ultimately curable gasket composition.
Effectively robustly securing the end ring within the tube in the manner described is important because at least one of the end rings will commonly, and preferably, be provided with at least one, and preferably two registration notches which will receive or engage with one or two correspondingly shaped pins provided on the mandrel onto and over which the sleeve assembly is to be fitted, thus ensuring that the sleeve assembly is circumferentially extremely accurately located relative to the mandrel. In preferred embodiments, where two registration notches are provided, one notch is larger than the other, and the correspondingly shaped pins provided on the mandrel are likewise comparatively sized. In a yet further preferred embodiment, the exposed annular end surface of one end ring is provided with a radially extending mark, indentation, or other easily visible indicator whereby an operator can immediately identify one end of the tube from the other, and whereby said operator can readily angularly correctly orientate said tube relative to a similar or corresponding indicator provided on the mandrel on and over which said tube is to be mounted by rotating the tube into a position whereby the respective indicators provided on mandrel and tube are in general alignment.
Further preferably, the exterior cylindrical surface of the tube is provided which at least a pair, in some cases two pairs of plate positioning formations, one preferably being circular and the other preferably being oval-shaped, each of said pair of formations being preferably provided within one of the lands of plastics material between a pair of adjacent recesses, and both of said formations being precise axially aligned with the longitudinal axis of the sleeve assembly as a whole, as well as being extremely accurately circumferentially located with respect to the registration formation provided in the end ring. As the skilled person will appreciate, the provision of these registration features, and the accuracy of their positioning, are important because they automatically ensure that a printing or coating plate, having apertures corresponding in shape and relative separation to the plate-positioning formations provided on the exterior cylindrical surface of the sleeve, can be accurately and manually positioned on the exterior cylindrical surface of the sleeve assembly, for example initially along one lateral edge thereof before being subsequently wrapped around the sleeve assembly exterior surface and being progressively increasingly magnetically secured thereto as it is so wrapped. Most preferably, the exterior cylindrical surface of the tube is provided with a scribe line which extends circumferentially substantially completely around the exterior cylindrical surface of the tube, said scribe line coinciding with the centroid of the cross-sectional shape of one or other, or (where two scribe lines are provided) both of the plate-locating formations (or both pairs thereof) provided on the exterior cylindrical surface of the tube.
As regards the construction of the liner, preferably, the base wrap radially innermost layer is formed from a fibrous material impregnated with a curable composition such as an epoxy- or other resin-based adhesive. Most preferably, the base layer is a resin-impregnated fibreglass layer which is cured to form a generally rigid structure which is nevertheless elastically expansible under radially applied compressive force. The compressible layer of the liner is preferably one of: a foam, a sponge, cellular construction. Further preferably, the compressible layer is made from one of: a naturally occurring and a chemically synthesised material. Preferably, the compressible layer consists essentially of one or more of the following common polymeric foams: Ethylene-vinyl acetate (EVA) or polyethylene-vinyl acetate (PEVA) foam, Low-density polyethylene (LDPE) foam, Nitrile rubber (NBR) foam (being any copolymers of acrylonitrile (ACN) and butadiene), Polychloroprene foam or Neoprene, Polyimide foam, Polypropylene (PP) foam, including expanded polypropylene (EPP) and polypropylene paper (PPP), Polystyrene (PS) foam, including expanded polystyrene (EPS), extruded polystyrene foam (XPS) and polystyrene paper (PSP), Styrofoam, including extruded polystyrene foam (XPS) and expanded polystyrene (EPS), Polyurethane (PU) foam, LRPu low-resilience polyurethane, Polyethylene foam, Polyvinyl chloride (PVC) foam. As previously mentioned, the radially outermost bulking layer may also be formed from a resin- or other adhesive-impregnated fibrous material such as coir mat soked with an epoxy resin which is cured therein.
In further aspects of the present invention, there are provided methods of manufacturing a sleeve assembly as described above, and a sleeve assembly resulting from the performance of that method.
In particular, in as second aspect of the present invention there is provided a method of manufacturing a sleeve assembly, the method comprising the following fundamental steps:
Starting with cylindrical tube having outer and inner diameter (OD, ID) dimensions respectively greater than and less than the ultimately required OD/ID dimensions of the finished sleeve assembly,
The method may include the further steps of
In a preferred embodiment, the method includes the further step of machining out a second pair of recesses in the exterior cylindrical surface of sleeve construction, said second pair of recesses also adapted to receive plate-locating formations and being firstly disposed in perfect axial alignment with the central axis of the sleeve construction and in precisely diametrically opposed relationship to the first pair of similar recesses. Most preferably, the machining out of said recesses is conducted to a depth which is less than, and preferably of the order of only 10-50% of the annular thickness of the tube so that the liner provided within the interior of the sleeve construction is not impacted or affected by said machining in any way. Most preferably, the size of the said recesses, and the machining of one or both of said pairs thereof is performed completely within a first, and optionally (if two pairs of recesses are provided) a second diametrically opposed land of tube material disposed between a respective adjacent pair of magnet-receiving recesses having been previously machined out from the exterior cylindrical surfaces of the tube. Provided that the plate-location formation receiving recesses are of a circumferentially smaller dimension than the particular land of tube material in which they are machined, and the angular position of the machining is approximately at the circumferential mid-point of that particular land of material, then of course neither of the most proximate side walls the respectively adjacent magnet-receiving recesses disposed circumferentially on either side of that particular land will be impinged upon, and thus neither the magnets or magnet assemblies disposed therein will be compromised.
Other features, aspects and embodiments of the method of manufacture described above will become apparent from the further specific description of the invention provided below.
In a further aspect of the invention, there is provided a sleeve assembly manufactured according to the method(s) prescribed above.
Thus the invention provides an entirely novel sleeve construction which is not only of significantly reduced weight as compared to the conventional solid cylindrical and tubular steel magnetic sleeves currently in use, but is also of entirely sufficient and more than adequate structural strength and dimensional stability to withstand the rigours of both machining and operative use, despite having been significantly weakened as a result of the extensive machining out of magnet-receiving slots. One of the primary innovative factors of the sleeve construction of the present invention is the manner in which the various component parts of the sleeve construction are assembled together, and the important relative differences in their physical and mechanical properties, all of which act in concert to lend what could potentially be a relatively flimsy structure with the required mechanical, structural strength and dimensional stability to enable such a lightweight sleeve construction to perform as required.
A specific embodiment of the invention is now described by way of example and with reference to the accompanying drawings wherein.
Referring firstly to
Specifically, sleeve assembly 2 consists essentially of a plastics material outer cylindrical tube 4 having and extending between annular end surfaces, one of which is referenced at 4A, and within which is bonded, for example by means of an epoxy- or other high-strength resinous adhesive, a cylindrical tubular compressible liner 6 which also has, and extends axially between, a pair of annular end surfaces, one of which is referenced at 6A. Ideally, the plastics material chosen for the tube is one which is both structurally and dimensionally stable and thus rigid, resilient, but not brittle, and one which can be machined with relative ease and without cracking, tearing or without experiencing extensive plastic deformation. Suitable plastics materials include, without limitation, Delrin®, Nylon 6, Nylon 6, 6 or other Polyoxymethylene (POM), acetal, polyacetal, and polyformaldehyde, polyamide, or polyester.
The geometric planes in which the annular end surfaces 4A, 6A lie are most preferably exactly orthogonal to the central longitudinal axis of the sleeve assembly as a whole, referenced “CL” in this and other Figures. Importantly, and as can be seen in the Figure, the liner 6 is axially shorter than the tube 4 within which it is bonded so that, when the liner 6 is initially slid completely within the tube 4 prior to bonding and disposed substantially axially centrally and thus symmetrically therein, the annular end surfaces 6A of the liner are set back from those of the tube so that a pair of identical annular rebates (one of which is referenced at 8) is automatically created at either end of the sleeve assembly internally of the tube 4. Said rebates 8 are defined, on one hand, by those portions of the interior cylindrical surface 4B of the tube 4 which remain exposed and extend beyond the annular end surfaces 6A of the liner 6, and on the other hand by said liner annular end surfaces 6A.
In accordance with the invention (and as can be seen more clearly in
In some embodiments of the invention, and depending on whether there exist remnants of cured adhesive at the interface between the annular end surfaces of the liner and the immediately adjacent cylindrical surface of the tube, it may be necessary or preferable to additionally machine, for example by grinding, the annular end surfaces of the liner, both to remove such adhesive remnants, and also to ensure that the annular end surfaces of the liner lie in a plane which is exactly orthogonal the central (datum) axis of the sleeve assembly as a whole. It is to be mentioned here that it is of course equally if not more important that the geometric plane in which the annular shoulders machined into the interior of the tube as mentioned above and described more fully below lie is also exactly orthogonal to the central (datum) axis of the sleeve assembly as a whole because any offset of the/those places from orthogonality would immediately compromise the axial compression which the end rings apply on the tube between them, with the result that the tube could be subjected instead to undesirable torsional and shear forces.
In further accordance with the invention, screw threads 4C are machined into the said interior cylindrical surfaces 4B, said threads being provided over at least some of the axial length of those interior cylindrical surfaces as illustrated, preferably between 25%-75% of the axial length thereof. Preferably, the pitch of the threads machined into this surface is at least 0.5 mm, more preferably at least 1 mm, and most preferably in the range 1-2.5 mm, this being on account of the fact that machining threads of very fine pitch (e.g. less than 0.5 mm, and commonly less than 1 mm) in plastics materials is exceedingly difficult if not impossible, at least with standard thread-machining equipment. Obviously the particular requirement for larger thread pitch does not apply for tube constituted of metal or alloys thereof, as such can generally be machined with much greater precision.
Once the threads 4C have been machined in the partially complete sleeve assembly of
At this point, it is useful to provide exemplary dimensions for a conventional metal decorating sleeve assembly—the sleeve assembly illustrated in the Figures and in particular
Referring now to
One further dimensional feature of the end rings deserves mention. It can be seen in the Figure (and also in more detail in
Turning now to the exterior cylindrical surface of the sleeve assembly illustrated in
However, the illustrated, axially aligned, terminated configuration of the recesses is preferred because straight-sided recesses can readily accept a pre-assembled similarly straight and appropriately dimensioned magnet assembly as illustrated in
For these reasons, not only do the recesses terminate axially very close (e.g. of the order of only a very few mm) to the annular end surfaces of the tube, but their depth is also comparatively a significant proportion of the overall annular thickness of said tube, for example being anything from 50-90% of that thickness. Thus without the structural reinforcement being provided by the already secured-in-place interior liner and encapsulating end rings, it would be generally impossible to machine out all the recesses to the required lengths, widths, and radial depths without structurally damaging or indeed destroying the tube.
As can be seen in the figure therefore, the machining out of the recesses in spaced apart relationship leaves lands 4E of the tube 4 between each recess. Of course, the substantially circumferentially even spacing of the recesses is the most preferred arrangement to avoid any unwanted rotational inertial imbalance, and therefore it is most desirable that the width of each of the lands 4E is substantially identical over the entire exterior cylindrical surface. It is also desirable that the axial separation distances between the terminal ends of each and every recess and the respective most proximate annular end surface of the tube are also identical so that the sleeve assembly as a whole is essentially perfectly inertially symmetric. This condition of rotational or inertial balance is an important consideration, because in use, inertial forces arising from the high speed (many 10s if not hundreds of revolutions per second) can be significant, and for lightweight plastics sleeves become of significantly greater concern, at least as compared to the more conventional but significantly heavier metal sleeve assemblies.
Typical dimensions for the recesses (such as may be provided around the exterior surface of the particular sleeve assembly having the specific dimensions abovementioned) may be (for all recesses): axial length 172 mm, width 20 mm, depth 6 mm, and a total number of slots, 26, in 2 sets of 13 on respective diametrically opposite halves of the sleeve assembly, such being separated by the pair of plate locating formations (see further description below).
A final feature of the partially completed sleeve assembly of
Referring now to
Of course, it is equally possible, although less efficient, to manually fill the recesses with an alternating sequence of individual magnets and keepers, as is currently conventionally done, particularly for spirally arranged recesses. The important considerations for both methods of construction are merely that the magnets and keepers are substantially of the same depth, that depth is broadly identical to the depth of the recess, and that the recess is substantially completely filled over its entire axial length with magnets and their respective keepers. Regardless of the manner in which the recesses 12 are filled with magnets and keepers, once all the recesses are so filled, the entire exterior cylindrical surface of the sleeve assembly is then subjected to precision surface grinding whereby the overall outer diameter (OD) of the sleeve assembly is slightly reduced (e.g. by 0.5-1.5 mm) down to required ultimate OD, a critical dimension for operative performance. Notably, this grinding step also removes any cured adhesive residue extant on the surface, and furthermore results in the arcuate smoothing of the exterior-facing surfaces of the magnets and their respective keepers so that not only do the edges of the magnets and keepers lie precisely flush with the adjacent plastics material lands and thus the interface regions therebetween are perfectly smooth and thus essentially continuous, but the entire exterior surface of the sleeve assembly is rendered perfectly cylindrical about the central axis.
It should be mentioned here that there is a further possible alternate arrangement for the recesses, namely that instead of being machined out or otherwise created in a generally linear, axial direction relative to the sleeve assembly as a whole, the recesses could of course be disposed circumferentially and axially adjacent each other along substantially the entire exterior cylindrical surface of the sleeve. Thus, in this alternative embodiment, the recesses would extend generally circularly around the sleeve exterior surface as opposed to the illustrated embodiment wherein the recesses extend generally axially linearly from one end of the sleeve to the other. Of course, a sleeve assembly with recesses arranged in this alternative way would still result in the exterior surface thereof being substantially magnetic once the recesses were occupied by suitable magnet-keeper assemblies, and thus capable of adequately securing a printing plate or other work component thereto. Also, aspects of the present invention which require that the end rings provide structural support in the region of, and possibly also directly underneath the recesses would still, at least to some extent, still apply in the alternate arrangement, because the two circular recesses most remote from one another and disposed at one or other end of the sleeve assembly would still of course be required to be provided very close to the ends of the sleeve assembly for exactly the same reasons as the linear recesses of the primary embodiment extend similarly very close to the ends of the sleeve assembly. Those two, but only those two recesses would still therefore require the structural support provided by the substantially more rigid end rings disposed immediately below them in the sleeve assembly.
Referring now to
In order that the plate 40 can be applied to and precisely mounted on and around the exterior cylindrical surface of the sleeve assembly, a pair of appropriately sized, shaped and dimensioned holes are punched though the plate, said holes being in precise alignment with the most proximate lateral edge of the plate, and spaced apart by exactly the same distance as that axial distance between the correspondingly shaped plate locating formations 14, 16. Thus, when the plate is to be mounted on the sleeve assembly, the plate is manoeuvred so that the punched holes therein are directly above the plate locating formations, and then the relevant edge of the plate is place in position so that the plate locating formations pass through the punched holes. Thereafter, the remaining length of the plate is wrapped around the exterior cylindrical surface of the sleeve assembly. The plate, being generally thinner than the distance by which plate locating formations 14, 16 stand proud of the exterior cylindrical surface of the sleeve assembly will therefore, as illustrated, lie beneath said plate locating formations, which thus also stand proud of the exterior surface of said plate. As a final means of ensuring that the plate 40 is precisely correctly positioned on the sleeve assembly, a scribe line 42 is created circumferentially completely around the exterior cylindrical surface of the sleeve assembly so that a scribe line registration formation 44 formed or otherwise provided on plate 40 can be aligned with the scribe line, and thus the plate can be axially and circumferentially precisely positioned on the sleeve.
One further final feature of the end rings, shown in
It is worth mentioning here that the end ring which is provided with the one or more registration notches 4F is generally always regarded as provided the “datum”, i.e. it is that end ring from which all other relevant dimensions of the sleeve are determined, particularly axially.
Referring to
From
Finally, as can again be seen from
It should also be mentioned here that although much of the foregoing description of the present invention has been couched in terms of the resistance that structurally much stronger, e.g. steel, end rings provides for the sleeve assembly as a whole, in terms of its being able to withstand the rigours of machining and machine tools working directly on and in the plastics material, it is of course possible that the tube 4 may be cast, formed, extruded, or otherwise created with the recesses already in place, i.e. created as a result of the casting or other forming process. In this case, there would of course be no requirement for the recesses to be separately machined. Despite this, however, there will generally always be the requirement that exterior cylindrical surface of the sleeve assembly be machined, for example by surface grinding, which itself can entail significant circumferential and radial forces which will inevitably be of most concern at the end regions of the sleeve assembly where, were it not for the existence of the structurally much stronger end rings and the robust manner in which they are secured within the sleeve assembly, the plastics material would be bound to fail.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1915458 | Oct 2019 | GB | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2020/079209 | 10/16/2020 | WO |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2021/078648 | 4/29/2021 | WO | A |
| Number | Name | Date | Kind |
|---|---|---|---|
| 4920630 | Leanna | May 1990 | A |
| Number | Date | Country |
|---|---|---|
| 1261165 | Jan 1972 | GB |
| 2544785 | May 2017 | GB |
| 200911537 | Mar 2009 | TW |
| Entry |
|---|
| International Searching Authority, European Patent Office, International Search Report and Written Opinion, PCT/EP2020/079209, dated Feb. 25, 2021. |
| International Preliminary Examining Authority, European Patent Office, International Preliminary Report on Patentability, PCT/EP2020/079209, dated Oct. 5, 2021. |
| Number | Date | Country | |
|---|---|---|---|
| 20220410559 A1 | Dec 2022 | US |
