Patent Application
20230027445
The field of the invention relates to a printing apparatus comprising a heat transfer system for transferring heat away from or to a print medium, and in particular for cooling a print medium.
Printing may be performed by means of several alternative printing methods. A printing apparatus typically comprises a plurality of rollers configured to drive a print medium through the printing apparatus. Each of the plurality of rollers rotates at a predetermined speed, such that a movement speed of the print medium is continuous. The print medium is typically conditioned to control the printing results. To that end the printing apparatus may comprise a heat transfer system, typically comprising a heat transfer roller.
When using a heat transfer roller, a print medium moving through the printing apparatus is heated or cooled by guiding it over the roller through which a heat transfer fluid is circulated. Typically, a printing apparatus comprises a plurality of rollers to guide the print medium through the printing apparatus. Such rollers typically include a drive roller, a tension roller, and one or more further guiding rollers. The drive roller may correspond with a heat transfer roller and/or any other roller may be a heat transfer roller. The required torque for driving a heat transfer roller may be high in order to be able to provide the required amount of heat transfer. This may cause the roller to grip, resulting in disturbances in the movement speed of the print medium which may result in imperfections when printing on the print medium. To avoid such disturbances additional electro-motors may be provided to drive the heat transfer roller. However, an extra electro-motor adds complexity to the drive system regulation system.
The object of embodiments of the invention is to provide a printing apparatus, preferably a digital printing apparatus, comprising a heat transfer system, and in particular a heat transfer system allowing driving the print medium in a more efficient way compared to prior art solutions.
According to a first aspect of the invention there is provided a printing apparatus comprising a heat transfer system for transferring heat away from or to a print medium moving in a movement direction through the printing apparatus. The heat transfer system comprises a heat transfer member and a fluid circulation means. The heat transfer member has a rotatable support surface configured for supporting the print medium. The heat transfer member is provided with at least one channel. The support surface is rotatable around an axis in order to move the print medium in the movement direction. The fluid circulation means is configured for supplying a fluid through the at least one channel. The at least one channel is configured such that, in operation, when fluid is supplied through said at least one channel, torque is generated in a fluido-mechanical manner around said axis. This will cause or at least contribute to a rotational movement of the support surface of the heat transfer member.
By at least partially driving the heat transfer member in a fluido-mechanical manner using the at least one channel, an additional fluido-mechanical force is applied to the rotatable support surface. More in particular, the kinetic energy of the fluid is used to rotate the support surface around the axis or to contribute to the torque needed to rotate the support surface around the axis. In that manner the heat transfer member may exchange heat between the fluid and the print medium whilst at the same time contributing to the force needed to ensure a continuous rotation of the support surface. This enables the use of smaller electrical motors in comparison to prior art solutions. In some cases it may even allow rotating the support surface without the need for an additional drive means.
Preferably, the at least one channel comprises at least one driving channel, preferably a plurality of driving channels, arranged non-parallel to the axis. In this way, a portion of the kinetic energy of the fluid is converted into a torque adding to the rotational motion of the support surface while the heat exchanging performance of heat transfer member is substantially maintained. Note that the at least one driving channel may also comprise a straight channel portion. Such straight channel portion may be driving channel portion (e.g. a straight channel portion arranged at an angle with respect to the axis) or a non-driving channel portion (e.g. a straight channel portion arranged parallel to the axis). More generally, the at least one driving channel may comprise a combination of driving channel portions and non-driving channel portions.
Preferably, the at least one channel comprises at least one substantially helically shaped driving channel. A helix has a helix angle which is the angle between the helix and a line parallel to the axis of rotation. Preferably, a helix angle of the at least one substantially helically shaped driving channel (i.e. the angle between the driving channel and the axis) is smaller than 40°, more preferably smaller than 30°, even more preferably smaller than 20°, and for example smaller than 10°. The helix angle is preferably larger than 2°. For typical dimensions (e.g. diameter between 30 mm and 1000 mm, and length between 300 and 2000 mm), this helix angle will correspond with a pitch which is larger than the length of the at least one channel, more preferably larger than two times the length of the channel.
Preferably, the at least one substantially helically shaped channel portion comprises a plurality of helix portions, wherein each helix portion has a respective helix angle, wherein the helix angle for each helix portion is different. In an exemplary embodiment the helix angle may increase in a continuous and/or discontinuous manner looking in the flow direction of the fluid. The inventiveness hereof is based on the insight that the fluid transported through the at least one helically shaped driving channel will also start to rotate in conjunction with the rotational motion of the support surface. This reduces the conversion efficiency of the kinetic energy of the fluid to rotational motion. By varying the helix angle looking in the flow direction, the conversion efficiency of kinetic energy to rotational motion may be substantially maintained. This further improves the overall rotational performance of the support surface. For example, if the incoming fluid flow is under an angle then the design of the at least one channel could start with a decreasing helix angle to make use of the incoming direction of the flow, continuing with an increasing helix angle once the direction of the fluid starts to change.
Preferably, the at least one driving channel is arranged at a constant radial distance measured from the axis. In that manner, the additional fluido-mechanical force is applied in a uniform way.
Preferably, the at least one driving channel comprises a plurality of driving channels distributed uniformly around the axis. In this way, the force generated by the fluid is uniformly applied to the heat transfer member. This improves the overall rotational performance of the support surface.
Preferably, the plurality of driving channels comprises at least three, preferably at least four driving channels. More preferably, the plurality of driving channels comprises at least ten, preferably at least twenty, more preferably at least twenty-five driving channels. By increasing the number of driving channels, the uniformity of the thermal exchange may be improved. Further, the number of driving channels in combination with the layout and the shape of the driving channels may influence the applied torque.
Preferably, the at least one channel comprises at least one supply channel and at least one return channel extending between a first end of the heat transfer member and a second end of the heat transfer member. The at least one supply channel and/or the at least one return channel may comprise one or more driving channels. Preferably, the at least one supply channel is arranged at a first radial distance of said axis, and the at least one return channel is arranged at a second radial distance of said axis, wherein said first and second radial distance are different. In that manner, the resulting torque will be determined by the sum of the torque generated by the flow in the supply channel and the torque generated by the flow in the return channel. Typically, the channel arranged at the larger radial distance will generate more torque than the channel arranged at the smaller radial distance. In an embodiment where, for example, the at least one supply channel generates a torque in a first direction contributing to the rotational movement of the support surface and the at least one return channel generates a rotational torque in an opposite direction, the resulting torque is such that it contributes to the rotational movement of the support surface of the heat transfer member when the first radial distance is larger than the second radial distance. Such an embodiment may be more easily produced.
When a plurality of driving channels is provided, preferably a handedness of the plurality of driving channels is such that, in operation, the direction of the generated torque is the same for each of the plurality of driving channels. In the context of the application, handedness is defined as a rotational direction of the driving channel, e.g. a helically shaped driving channel, when moving from the first end to the second end of the heat transfer member or vice versa. In that manner all driving channels can add torque in the same rotational direction, which further increases the generated moment.
Preferably, the heat transfer member comprises a roller. Optionally, the roller may have an at least partially hollow core, wherein the at least one channel is arranged around the hollow core. In that manner the heat transfer member can weigh less. More in particular, a central portion of the roller may comprise a hollow cylindrical passage. Optionally, radially oriented interconnecting ribs or plates may be arranged in the hollow core for giving extra strength to the heat transfer member. More preferably, the at least one driving channel is arranged at a radial distance which is larger than 60% of the radius, preferably larger than 75%. By increasing the radius, the torque generated by the fluid on the at least one driving channel, and thus on the support surface is increased. In this way, the continuous rotation of the support surface may be further improved. Further, when multiple supply and/or return driving channels are present, the multiple driving channels may be at different radial distances from the axis. Preferably, at least one of the multiple driving channels is arranged at a radial distance which is larger than 60% of the radius, more preferably larger than 75%.
Preferably, the roller has a diameter which is larger than 30 mm, preferably larger than 100 mm, and e.g. larger than 500 mm.
In an exemplary embodiment, the roller comprises an inner and outer cylinder coaxially arranged at a radial distance of each other such that an intermediate chamber is formed, wherein a surface of the inner and/or outer cylinder is provided with at least one fin extending in said intermediate chamber, such that the at least one channel is formed. Preferably, the at least one fin extends over the full radial distance between the inner and outer cylinder. Optionally, the at least one fin extends substantially helically around the axis. In this way, at least one substantially helically driving channel is formed in a robust and simple manner.
In an exemplary embodiment, the heat transfer member comprises a coupling flange and a roller coupled to the coupling flange, wherein the at least one channel comprises at least one channel portion in said coupling flange and at least one associated channel portion through said roller. By having a coupling flange comprising at least one channel portion of said at least one channel, this channel portion may drive the heat transfer member. More generally, the at least one channel portion in the coupling flange and/or the at least one channel portion in the roller may be configured to generate torque. For example, a cooling roller with coaxial tubes or straight channel portions may be combined with a coupling flange configured to generate torque. Preferably, the at least one channel portion in the coupling flange comprises a plurality of channel portions, and the coupling flange has a central inlet dividing in the plurality of channel portions. Optionally, each channel portion extends spiral-like from the central inlet to a respective branch outlet thereof. In this way a swirl is formed in the central inlet. This will further improve the efficiency at which kinetic energy from the fluid is converted to rotational motion of the support surface. Optionally a first and second coupling flange may be provided at a first and second end of the roller, to further increase the generated torque.
In an exemplary embodiment, the heat transfer member comprises a turbine device comprising an impeller structure on a drive shaft, and a roller coupled to the drive shaft of the turbine device. The at least one channel comprises at least one channel portion around said impeller structure and at least one channel portion through said roller, wherein the impeller structure is arranged such that, in operation, when fluid is supplied through said at least one channel portion around said impeller structure, torque is generated for rotating the drive shaft. Optionally the at least one channel portion through the roller may correspond with at least one driving channel portion configured to further add torque. Preferably, the turbine device may be an axial or a radial turbine device. By converting kinetic energy of the fluid to rotational motion using the impeller structure, the continuous rotational motion of the heat transfer member is further improved. Optionally a first and second turbine device may be provided at a first and second end of the roller, to further increase the generated torque.
Preferably, the heat transfer member is made at least in an outer part thereof of any one of the following materials aluminium, aluminium alloy, magnesium alloy, steel, copper, steel alloy, copper alloy, titanium, a titanium alloy, a composite, a fibre based composite, graphite based materials, plastic, or a combination thereof. For example, the heat transfer member may be made using any machining tools including milling tools. It may also comprise an extruded member. Also, the heat transfer member may be a 3D printed member, e.g. a plastic and/or metal based member, or a member comprising titanium (e.g. 3D printed) combined with a copper meltable jacket.
Optionally, the heat transfer member is provided with a coating at the support surface, preferably a coating made of any one of the following materials: a polytetrafluoroethylene (PTFE) based material such as a nickel-PTFE based material, a perfluoralkoxy alkane (PFA), fluorinated-ethylene-polypropylene (FEP), a ceramic material, a diamond-like-carbon (DLC) material, a metal. The coating may have a thickness e.g. between 0.5 micron and 300 micron. A coating will increase the wear resistance and may further enhance the smoothness of the surface. Alternatively, the heat transfer member may have a polished surface. In that manner the surface can have a low surface energy and can have similar advantageous properties as achieved with a coating.
It is noted that the heat transfer member may be made in different materials. For example, the heat transfer member may comprise a cylindrical outer part made in any one of the materials mentioned above and a cylindrical inner part made in plastic or rubber e.g. for easy mounting and corrosion prevention. Further, when it is desirable to tune or diminish the thermal exchange between the at least one return and supply channel, many water resistant, more or less thermal conductive materials can be used, including rubber or plastic.
In an exemplary embodiment, the at least one channel comprises a plurality of substantially straight driving channels which are non-parallel to the axis and which extend at a substantially constant radial distance of the axis. Such channels also allow to generate torque and have the advantage that they may be arranged in a roller in a simpler manner as compared to helically shaped channels.
Preferably, the at least one channel is configured to generate a torque of at least 0.05 Nm, preferably at least 0.1 Nm, most preferably at least 0.4 Nm. Typically, the at least one channel is configured to generate a torque smaller than 20 Nm, preferably smaller than 15 Nm.
Preferably, the fluid circulation means is configured to supply a fluid through said at least one channel at a rate of at least 0.5 kg/min, preferably at least 1 kg/min. It is noted that the rates may also be much higher than 1 kg/min, depending on the dimensions of the heat transfer member. For example, the rate may be higher than 50 kg/min or even higher than 100 kg/min.
In an exemplary embodiment the printing apparatus further comprises a motor for driving the heat transfer member to rotate the support surface, wherein the motor and the at least one channel are configured to rotate the support surface at a speed of at least 0.08 m/s, preferably at least 0.125 m/s.
Preferably, the printing apparatus further comprises a roller system with a plurality of rollers for guiding the print medium in the movement direction, wherein the heat transfer member corresponds with a roller of said plurality of rollers. In other words, a roller may have both the function of guiding the print medium as well as of controlling the temperature of the print medium, wherein the flow of fluid through the roller will contribute to the rotation of the roller.
Preferably, the printing apparatus further comprises a printing means, wherein the plurality of rollers comprises a first roller upstream of the printing means and a second roller downstream of the printing means, wherein the heat transfer member corresponds with the first roller and/or with the second roller. Optionally, the first roller is a drive roller. Optionally, the second roller is a tension roller. For example, the first roller may be used for conditioning the print medium prior to printing, and/or the second roller may be used for cooling the print medium after printing. When the first roller is a drive roller, the flow of fluid through the channel will add torque to the torque generated by a drive means for driving the roller. The printing means may be a digital printing means, e.g. an inkjet printing means or a xerography printing means, e.g. a dry toner printing means.
Preferably, the printing apparatus further comprises a fusing or drying station configured for fixing or drying an image printed by the printing means, said fusing or drying station being arranged downstream of the printing means and upstream of the second roller. The second roller may then be used for cooling the print medium after the fusing or drying step. The fusing station may be an intermediate fusing station for pinning an image printed by the printing means. In the latter case, optionally further printing means may be provided downstream of the intermediate fusing station.
In an exemplary embodiment, the printing apparatus may comprise control means for controlling the fluid flow generated by the fluid circulation means. The control means may comprise for example any one or more of the following: a control valve, a guide vane, a bypass valve. Also, the control means may be configured to control the fluid circulation means and/or the motor, based on e.g. any one of the following: a temperature of the fluid, a speed of the print medium, a motor state, etc.
The accompanying drawings are used to illustrate presently preferred non-limiting exemplary embodiments of devices of the present invention. The above and other advantages of the features and objects of the invention will become more apparent and the invention will be better understood from the following detailed description when read in conjunction with the accompanying drawings, in which:
The heat transfer member 100 has a rotatable support surface 101 configured for supporting the print medium M. The heat transfer member 100 is provided with at least one channel 110, and the fluid circulation means 300 is configured to transport fluid through the at least one channel 110. The rotatable support surface 101 of the heat transfer member 100 extends in a lateral direction W of the heat transfer member 100. The lateral direction W may be oriented substantially perpendicular to the movement direction L1, L2 of the print medium. The support surface 101 is rotatably around an axis A. The axis A is substantially parallel to the lateral direction W. The rotation of the support surface 101 may be driven using drive means (not illustrated), such as a motor, configured to rotate the support surface 101 at a predetermined speed. In the illustrated embodiment the heat transfer member 100 comprises a roller, and the roller may be rotatably mounted around the axis A and driven by the drive means. The roller has a diameter d. Preferably, the diameter d may be larger than 30 mm, preferably larger than 100 mm, and e.g. larger than 500 mm. In the illustrated embodiment, the roller is a cylindrical roller. In other embodiments the roller may be a polygonal roller, such as a square or triangular roller, a conical roller, double conical roller, a crowning roller or a combination thereof.
The fluid circulation means 300 is configured for supplying a fluid through the at least one channel 110. The fluid may be a heat transfer fluid configured for storing thermal energy. The temperature of the fluid may be controlled to have a predetermined temperature. In an exemplary embodiment the fluid may be a liquid such as water. Alternatively, other heat transfer fluids may be used such as oil or a refrigerant. Preferably, the heat transfer fluid is water based. Preferably, the heat transfer fluid comprises a mixture of different fluids, for example water may be mixed with alcohol or antifreeze. Moreover, in the context of the application a fluid may be considered as including substances in liquid or gaseous phase, or a combination thereof. The fluid may also be a phase change material which, in an exemplary case, may change from the liquid phase to the gaseous phase between 20° C.-30° C.
The at least one channel 110 is configured such that in operation, when a fluid is pushed through the at least one channel, torque is generated which adds to the torque generated by the drive means for at least partially driving the heat transfer member 100 in a fluidomechanical manner. It is noted that the torque generated by the fluid circulating in the at least one channel 110 may be sufficient to rotate the heat transfer member 100 around the axis A. However, in other embodiments the generated torque may be insufficient to cause a rotation on its own, but it will add to the torque generated by the drive means, and the sum of these torques will then be sufficient to cause the rotation of the heat transfer member 100. In this way, the print medium may be moved in the movement direction L1, L2.
Preferably the at least one channel 110 comprises at least one driving channel. In the illustrated embodiment, the entire at least one channel will contribute to the driving, but it is also possible to use at least one channel which contributes only in one or more portion thereof to the driving. The at least one driving channel 110 is arranged non-parallel to the axis A. In the example of
The at least one substantially helically shaped driving channel 110 is arranged at a constant radial distance r from the axis A. The radial distance r is preferably larger than 60% of a radius of the roller, more preferably larger than 75%. By increasing the radial distance the generated moment of force around the axis A is larger.
The at least one substantially helically shaped driving channel 110 comprises a helix angle H measured between the at least one substantially helically shaped driving channel and a line parallel to the axis A. The helix angle H is preferably at least 2°. By increasing the helix angle H, a conversion efficiency of kinetic energy to rotational motion is improved. Tests have shown that the energy conversion and optimal heat exchanging performance may be achieved at a helix angle H which is relatively small, e.g. between 3° and 10°. The length L of the heat transfer member 100 may be e.g. between 50 mm and 2000 mm. As illustrated in
The at least one substantially helically shaped driving channel 110 further comprises a handedness. In the context of the application, handedness is defined as a screwing motion of the helically shaped driving channel moving from the first end to the second end or vice versa.
Preferably, the heat transfer member 100 is made of any one of the following materials: aluminium, aluminium alloy, magnesium alloy, steel, copper, steel alloy, copper alloy, titanium, a titanium alloy, a composite, a fibre based composite (such as a carbon fibre based composite), graphite based materials, plastic, or a combination thereof. Optionally, the heat transfer member has a polished surface. Optionally, the heat transfer member 100 may be provided with a coating at the support surface 101, preferably a coating made of any one of the following materials: a polytetrafluoroethylene, PTFE, based material such as a nickel-PTFE based material, a perfluoralkoxy alkane (PFA), fluorinated-ethylene-polypropylene (FEP), a ceramic material, a diamond-like-carbon, DLC, material, a metal. Such a coating provides a low surface roughness and hence a low friction coefficient to the heat transfer member 100, whilst also having good heat conductive properties. Further the coating may have a good wear resistance. The coating may have a thickness e.g. between 0.5 micron and 300 micron. Different elements of the heat transfer member may also be made from different materials. For example, an outer part of the heat transfer member may be made of a material with good heat conduction properties whilst and inner part of the heat transfer member 100 may be made from a material which is a bad heat conductor, e.g. a plastic material. Also, for example, a surface delimiting a driving channel 110 may be coated with a first coating material, while the outer surface of the heat transfer member 100 may be coated with a second different coating material or may be a polished surface. In an embodiment the support surface of the heat transfer member may comprise grooves configured for evacuating air present between the print medium and the support surface.
In the illustrated embodiment of
At least one channel extends through the coupling flange 600 and the roller 700. The at least one channel comprises at least one supply channel and at least one return channel. In the exemplary embodiment four supply channels and four return channels are illustrated. Each of the at least one supply and return channels comprises a channel portion 120a, 120b, 120c, 120d, 130a, 130b, 130c, 130d extending in the roller 700 and a respective channel portion 610a, 610b, 610c, 610d, 620a, 620b, 620c, 620d extending through the coupling flange 600. The channel portions 610a, 610b, 610c, 610d extend outwardly and spiral like-form the central inlet 601 to a respective supply channel portion 120a, 120b, 120c, 120d. In this way each of the channel portions 610a, 610b, 610c, 610d forms a driving channel portion. The channel portions 620a, 620b, 620c, 620d corresponding to the return channels extend inwardly and spiral-like from the respective return channel portions 130a, 130b, 130c, 130d to the central outlet 602. In this way each of the channel portions 620a, 620b, 620c, 620d forms a driving channel portion. In the illustrated embodiment the supply and return channel portions 120a, 120b, 120c, 120d, 130a, 130b, 130c, 130d extending in the roller 700 are straight channel portions which are parallel to the axis A and which extend at a substantially constant radial distance of the axis A. However, in other embodiments the supply and return channel portions may be driving channel portions, e.g. substantially helical driving channels.
The fusing station 910 is configured for fixing an image printed by the printing means 900 and may be arranged upstream of the second roller 820. When the second roller 820 corresponds with a heat transfer member, the second roller 820 may, for example, cool the medium M after fusing of the image printed by the printing means 900. The fusing station 910 may be configured to use any of the thermal exchange principles: drying by radiation, convection, conduction. The fusing station 910 may be a contact fuser or a non-contact fuser. For example, the fusing station 910 may comprise any one of the following: an ultraviolet (UV) dryer, a hot air dryer, an infrared (IR) or near-infrared (NIR) dryer, a microwave dryer, a contact dryer, an RF dryer, or any combination thereof. Also, the fusing station 910 may be an intermediate fusing station for pinning an image printed by the printing means 900. In the latter case, optionally further printing means (not shown) may be provided downstream of the intermediate fusing station 910.
Whilst the principles of the invention have been set out above in connection with specific embodiments, it is to be understood that this description is merely made by way of example and not as a limitation of the scope of protection which is determined by the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2024338 | Nov 2019 | NL | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2020/083524 | 11/26/2020 | WO |
