Plotting instrument for ink-jet printing
By setting up a clustering room buffer that can expand the diaphragm in the recycling circuit of the inkjet printing system, the problem of ink pressure fluctuations caused by sliding acceleration and deceleration are solved, and the printed quality and the stability of the nozzle are improved.
Patent Information
- Application Number
- CN202380047501.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2023-05-23
- Filing Date
- 2023-06-15
- Publication Date
- 2025-01-28
AI Technical Summary
In a multi-channel inkjet printing system, pressure fluctuations caused by the carriage during acceleration and deceleration can affect the ink pressure in the print head, resulting in nozzle failure and print quality degradation.
By setting the concentration room as a buffer in the re -cycle circuit, the volume of the aggregation room is used to increase the volume of the aggregation room, and the pressure is reduced in the pressure, thereby stabilizing the pressure of the ink material.
Effectively compensated the pressure fluctuations in the re -cycle circuit, and maintained the pressure of the ink material in the print head within the scope of the schedule, which improved the stability and print quality of the nozzle.
Smart Images
Figure CN119384360A_ABST
Abstract
Description
[0001] The present invention relates to a plotter for inkjet printing. More specifically, the present invention relates to a plotter for multi-channel inkjet printing, in which ink droplets having a volume of several picoliters are deposited in a controlled manner on a substrate (e.g., a ceramic substrate, a textile substrate, a plastic film, etc.) by means of one or more print heads equipped with a plurality of dispensing nozzles.
[0002] In a multi-channel inkjet plotter, the print head is mounted on a carriage that slides in two opposite directions along a guide that travels along the entire width of the substrate to be printed, while the substrate is advanced perpendicularly to the sliding direction of the carriage. During ink deposition, the carriage travels along the guide at a substantially constant deposition speed. When the carriage has to reverse the sliding direction along the guide, the carriage undergoes a deceleration (necessary to stop the carriage from the deposition speed) and a subsequent acceleration (necessary to return the carriage to the deposition speed).
[0003] The ink supplied to the printheads is drawn from tanks, each containing a specific color of ink. Typically, one or more printheads are configured to dispense a specific color of ink and are then placed in fluid connection with one or more corresponding tanks.
[0004] The printhead is of the ink recirculation type, i.e. the ink supply circuit to the printhead comprises a recirculation circuit comprising a delivery branch through which ink is drawn from the tank and supplied to the printhead, and a return branch through which the portion of ink not dispensed by the nozzles during printing is returned to the tank. One or more pumps circulate the ink in the recirculation circuit and / or regulate the flow rates and pressures involved in the various circuit components.
[0005] For correct operation of the printhead, the ink inside the printhead must be kept at a constant operating pressure, a few millibars below the external pressure. This operating pressure is predetermined and is associated with the dimensions, hydraulic and fluid dynamic characteristics and operating requirements of the specific printing device. In the plotter outlined above, it is necessary to keep the weight of the carriage as low as possible, which can slide at speeds of up to 2 m / s and can withstand accelerations and decelerations of 1 g when the carriage has to reverse direction.
[0006] The applicant has noted that, in order to limit the weight of the carriage, it is avoided to arrange the ink tank integrally with the carriage, for example by arranging the ink tank integrally with the plotter frame. In this case, the recirculation loop may comprise flexible tubes connecting the tank fluidically to the print heads. The tubes may be arranged with a first section extending from the tank to the carriage guide, a second section extending along the full length of the carriage and arranged parallel to the guide, and a third section connected to the print heads. The second sections may be provided with a first end fixed to the frame and with a second end integral with the carriage. When the carriage travels along the track, the second end of the second section follows the movement of the carriage, thereby ensuring fluid connection with the tank. In inkjet plotters for large-scale printing, such a recirculation loop may reach a length far exceeding 10 meters.
[0007] However, the Applicant has demonstrated that the strong accelerations and decelerations to which the carriage is subjected are transmitted to the ink circulating in the recirculation circuit, causing temporary pressure increases and decreases in the recirculation circuit and therefore in the print head.
[0008] In fact, according to the Applicant's experience, the pressure variation (understood as an increase or decrease in pressure within the recirculation circuit) is proportional to the density of the ink, the acceleration of the carriage and the length of the recirculation circuit pipe measured in the same direction as the acceleration. Since the aforementioned second section of the pipe extending parallel to the carriage guide and along the entire length of the carriage guide (and therefore parallel to the direction of acceleration and deceleration of the carriage) can exceed 10 meters in length, the increase or decrease in pressure within the recirculation circuit is not negligible.
[0009] The applicant has also noted that even when the printhead is driven to dispense a large amount of ink, a temporary pressure drop may occur inside the printhead (eg because a portion of the substrate is printed with a large amount of the same colour).
[0010] However, deviations of the pressure in the print head from a predetermined value can cause the nozzles to malfunction in dispensing ink. In fact, when the pressure drops too low compared to the operating pressure, the nozzles cannot dispense enough ink, and when the pressure rises above the operating pressure, the nozzles tend to dispense an excessive amount of ink during printing. In both cases, the resulting print may not be of sufficient quality.
[0011] The applicant realized that by placing an accumulation chamber on the recirculation loop (which is capable of increasing its volume when the pressure inside it increases and reducing its volume when the pressure inside it decreases), temporary pressure increases in the recirculation loop can be compensated by increasing the volume of the accumulation chamber, and temporary pressure decreases in the recirculation loop can be compensated by reducing the volume of the accumulation chamber.
[0012] The applicant has therefore discovered that by having at least one buffer on the recirculation circuit, between the tank and the print head, the at least one buffer comprising an ink accumulation chamber, which is fluidly connected to the recirculation circuit and separated from the ink accumulation chamber by an expandable diaphragm, the volume of the ink accumulation chamber increases and decreases respectively in response to an increase and decrease in pressure in the recirculation circuit caused by deformation of the expandable diaphragm.
[0013] The applicant has also found that by arranging the buffer on the carriage and therefore in close proximity to the print heads, the buffer is able to compensate for temporary increases and decreases in pressure in the recirculation circuit near the print heads, making the pressure within these print heads essentially insensitive to temporary increases and decreases in pressure in the recirculation circuit.
[0014] The invention therefore relates in its first aspect to a plotter for inkjet printing.
[0015] Preferably, a frame is provided which comprises a sliding guide.
[0016] Preferably, a carriage is provided which is slidably constrained to the sliding guide.
[0017] Preferably, such a carriage is movable along a sliding guide in a first printing direction and in a second printing direction opposite to the first printing direction.
[0018] Preferably, the first printing direction and the second printing direction are contained in the sliding plane.
[0019] Preferably, the sliding plane is parallel to the sliding guide.
[0020] Preferably, the carriage supports at least one group of print heads.
[0021] Preferably, each printhead in the group of at least one printhead comprises a plurality of ink dispensing nozzles.
[0022] Preferably, there is at least one tank configured to contain ink.
[0023] Preferably, at least one tank is arranged in a fixed position relative to the frame.
[0024] Preferably, an ink recirculation loop is provided.
[0025] Preferably, the ink recirculation loop comprises a delivery branch configured to cause ink to flow from the at least one tank to the at least one group of print heads.
[0026] Preferably, the ink recirculation loop comprises a return branch configured to allow ink to flow from the at least one group of print heads to the at least one tank.
[0027] Preferably, the ink recirculation circuit comprises a plurality of tubes.
[0028] Preferably, the tubes of the plurality of tubes extend at least partially parallel to the sliding plane.
[0029] Preferably, at least one buffer is provided integrally with the carriage.
[0030] Preferably, at least one buffer is connected at least one between the delivery branch and the return branch of the ink recirculation loop.
[0031] Preferably, at least one buffer is connected between at least one tank and at least one group of print heads.
[0032] Preferably, at least one buffer comprises an ink accumulation chamber and a compensation chamber fluidly separated from the accumulation chamber.
[0033] Preferably, the compensation chamber is fluidly separated from the accumulation chamber by a expandable diaphragm.
[0034] Preferably, the ink accumulation chamber is in fluid communication with an ink recirculation circuit.
[0035] Preferably, the compensation chamber is in fluid communication with the external environment or with a compressed air source or a vacuum pump.
[0036] In the remainder of this specification and in the appended claims, a "sliding plane" may be identified as a plane tangential to the lower end of the sliding guide. This plane is perpendicular to the nozzle firing direction and, under operating conditions of the plotter, parallel to the substrate to be printed. In a preferred embodiment of the invention, this plane corresponds to a horizontal plane with reference to the positioning of the plotter under normal operating conditions.
[0037] In the remainder of this specification and in the appended claims, "nozzle firing direction" refers to a direction contained in a plane substantially perpendicular to the first and second printing directions. This direction is also substantially perpendicular to the first and second printing directions.
[0038] In the remainder of this specification and the appended claims, when referring to a tube, pipe or conduit, the term "flexible" is used to denote the ability of such a tube, pipe or conduit to follow different paths without becoming permanently deformed and damaged. In contrast, when referring to a tube, pipe or conduit, the term "rigid" is used to refer to a tube, pipe or conduit that follows only one path and is not configured to follow different paths without becoming permanently deformed or damaged.
[0039] The present invention may have at least one of the preferred features described below. Such features may therefore be present in the plotter for inkjet printing of the present invention individually or in combination, unless explicitly stated otherwise.
[0040] Preferably, the group of at least one print head comprises at least one print head.
[0041] Preferably, the collecting chamber of at least one buffer has an elongated shape.
[0042] Preferably, the focusing chamber has a prevailing development axis parallel to the sliding plane and perpendicular to the first printing direction.
[0043] In this way, the effects of the acceleration and deceleration of the carriage on the ink contained in the gathering chamber in terms of the increase and decrease in the ink pressure are minimized due to the fact that the dominant development axis of the gathering chamber is parallel to the slide plane and perpendicular to the first printing direction. This orientation of the dominant development axis of the gathering chamber is substantially perpendicular to the direction of acceleration and deceleration to which the carriage is subjected during operation of the plotter.
[0044] Preferably, the focusing chamber has a width dimension in a direction parallel to the sliding plane and parallel to the first printing direction.
[0045] Preferably, the focusing chamber has a length dimension in a direction parallel to the sliding plane and perpendicular to the first printing direction.
[0046] Preferably, the ratio between the width dimension and the length dimension of the focusing chamber is comprised between 0.1 and 0.6, more preferably between 0.2 and 0.4, even more preferably between 0.25 and 0.35.
[0047] Preferably, the compensation chamber of at least one buffer has an elongated shape.
[0048] Preferably, the compensation chamber has a dominant development axis parallel to the sliding plane and perpendicular to the first printing direction.
[0049] Preferably, the compensation chamber has a width dimension in a direction parallel to the sliding plane and parallel to the first printing direction.
[0050] Preferably, the compensation chamber has a length dimension in a direction parallel to the sliding plane and perpendicular to the first printing direction.
[0051] Preferably, the ratio of the width dimension to the length dimension of the compensation chamber is comprised between 0.1 and 0.6, more preferably between 0.2 and 0.4, even more preferably between 0.25 and 0.35.
[0052] Preferably, the collection chamber comprises a first opening and a second opening.
[0053] Preferably, the first opening of the collecting chamber is connected to at least one tank via a tube of the plurality of tubes.
[0054] Preferably, the second opening of the collecting chamber is connected to the group of print heads via a distributor.
[0055] Preferably, at least one buffer is placed at a fixed and predetermined distance from the group of at least one print head in a direction perpendicular to the sliding plane.
[0056] This fixed distance between the buffer and the group of printheads clearly determines the pressure to which the ink in the collection chamber must reach, given the operating pressure of the printheads.
[0057] Preferably, the expandable membrane is an elastically deformable membrane or a movable membrane configured to change the internal volume of the accumulation chamber.
[0058] Preferably, an increase in the volume of the focusing chamber corresponds to a decrease in the volume of the compensation chamber.
[0059] Preferably, a reduction in the volume of the focusing chamber corresponds to an increase in the volume of the compensation chamber.
[0060] Preferably, a change in the volume of the focusing chamber (measured in absolute value) corresponds to an equal change in the volume of the compensation chamber (measured in absolute value).
[0061] Preferably, the expandable diaphragm comprises an elastic membrane.
[0062] Preferably, the elastic membrane is configured to expand in an expansion direction towards the compensation chamber in order to increase the internal volume of the accumulation chamber and to reduce the internal volume of the compensation chamber of the buffer.
[0063] Preferably, the elastic membrane is configured to expand in an expansion direction towards the gathering chamber to increase the internal volume of the compensation chamber and to reduce the internal volume of the gathering chamber of the buffer.
[0064] Preferably, the compensation chamber comprises an opening.
[0065] Preferably, the opening in the compensation chamber places the compensation chamber in fluid communication with the external environment.
[0066] In an alternative embodiment, the opening in the compensation chamber places the compensation chamber in fluid communication with the source of compressed air or with a vacuum pump.
[0067] Providing a compressed air source or a vacuum pump fluidly connected to the compensation chamber makes it possible to introduce pressurized air into the compensation chamber or remove air from the compensation chamber and actively control the expansion of the inflatable diaphragm.
[0068] Providing a source of compressed air fluidly connected to the compensation chamber also allows cleaning of print head nozzle blockages or residues. For example, when at least one buffer is connected to the delivery branch of the recirculation loop, the cleaning operation is performed by introducing compressed air at a pressure much higher than atmospheric pressure, so as to cause a sudden increase in the volume of the compensation chamber. This results in a sudden increase in the pressure of the ink in the accumulation chamber, which is delivered to the print head at high pressure.
[0069] Preferably, the at least one buffer comprises a first buffer connected to the return branch of the recirculation loop.
[0070] Preferably, the first opening of the accumulation chamber of the first buffer corresponds to the ink outlet of the accumulation chamber.
[0071] Preferably, the second opening of the accumulation chamber of the first buffer corresponds to an ink inlet into the accumulation chamber.
[0072] Preferably, the at least one buffer comprises a second buffer connected to a delivery branch of the ink recirculation loop.
[0073] Preferably, the second buffer is identical to the first buffer.
[0074] Preferably, the first opening of the accumulation chamber of the second buffer corresponds to an ink inlet into the accumulation chamber.
[0075] Preferably, the second opening of the gathering chamber of the second buffer corresponds to the ink outlet of the gathering chamber.
[0076] Preferably, at least one group of print heads comprises a plurality of print heads.
[0077] Preferably, the ratio between the volume of the collecting chambers of all buffers and the average flow rate of ink flowing in the recirculation loop is comprised between 10% and 100%, more preferably between 20% and 80%, even more preferably between 30% and 50%, for example equal to about 36%.
[0078] Preferably, the average ink flow in the recirculation loop is calculated according to the formula Q = Vn × Nn × Nh × f, where Vn = the volume of ink emitted by each nozzle in a single activation, Nn = the number of nozzles per print head, Nh = the total number of print heads, and f = the frequency of nozzle firing.
[0079] Preferably, the distributor comprises a main return conduit connected to the first buffer.
[0080] Preferably, the dispenser comprises a main delivery conduit connected to the secondary buffer.
[0081] Preferably, the main return duct and the main delivery duct extend parallel to the sliding plane and perpendicular to the first printing direction.
[0082] Preferably, the main return pipe is connected to the first buffer via a first connecting pipe.
[0083] Preferably, the main return conduit is connected to the first buffer via an ink inlet in the accumulation chamber of the first buffer.
[0084] Preferably, the main delivery conduit is connected to the second buffer via a second connecting conduit.
[0085] Preferably, the main delivery conduit is connected to the second buffer via an ink outlet of the accumulation chamber of the second buffer.
[0086] Preferably, the distributor comprises a plurality of secondary return conduits, each of the secondary return conduits being connected to the main return conduit.
[0087] Preferably, the distributor comprises a plurality of secondary delivery conduits, each of the secondary delivery conduits being connected to the primary delivery conduit.
[0088] Preferably, the secondary return duct and the secondary delivery duct extend perpendicular to the sliding plane and are also connected to the plurality of print heads.
[0089] Preferably, the secondary return conduit has a fixed, predetermined length dimension in a direction normal to the sliding plane.
[0090] Preferably, the secondary delivery conduit has a fixed, predetermined length dimension in a direction orthogonal to the sliding plane.
[0091] Preferably, the secondary return conduit and the secondary delivery conduit are of equal length dimensions.
[0092] Preferably, the primary return conduit, the primary delivery conduit, the secondary return conduit and the secondary delivery conduit are rigid conduits.
[0093] Preferably, the primary return conduit, the primary delivery conduit, the secondary return conduit and the secondary delivery conduit are substantially straight.
[0094] Preferably, the primary return conduit and the secondary return conduit are part of a return branch of an ink recirculation loop.
[0095] Preferably, the primary delivery conduit and the secondary delivery conduit are part of a delivery branch of an ink recirculation loop.
[0096] Preferably, each printhead of the plurality of printheads is connected to a secondary return conduit and a secondary delivery conduit.
[0097] Preferably, each secondary return conduit is connected to an ink outlet of a printhead of the plurality of printheads.
[0098] Preferably, each secondary delivery conduit is connected to an ink inlet of a printhead of the plurality of printheads.
[0099] Preferably, the distributor comprises at least one bypass conduit connected between the main return conduit and the corresponding end of the main delivery conduit.
[0100] The provision of a bypass conduit connected in this way establishes an additional flow of ink that circulates continuously in the main return conduit and the main delivery conduit. This additional flow prevents the ink from accumulating and stagnating at the ends of the main return conduit and the main delivery conduit.
[0101] Preferably, there are a plurality of print head groups, each print head group comprising a corresponding plurality of print heads, a corresponding first buffer, a second buffer and a corresponding dispenser.
[0102] Preferably, a first pump is provided, which is configured to adjust the pressure at at least one between the first buffer and the second buffer.
[0103] Preferably, the first pump is connected to a first buffer.
[0104] Preferably, the first pump is configured to regulate (preferably indirectly) the pressure of ink flowing into the accumulation chamber of the first buffer.
[0105] Preferably, the first pump is configured to actively control the expansion of the inflatable diaphragm.
[0106] Preferably, the first pump is configured to operate in response to changes in pressure at an inlet to the plurality of print heads.
[0107] Preferably, the first pump is fluidly connected to the compensation chamber of the first damper to regulate the air pressure in the compensation chamber.
[0108] Preferably, the first pump is configured to apply an underpressure in the compensation chamber of the first damper.
[0109] Preferably, the first pump is configured to increase the low pressure applied in the compensation chamber of the first buffer in response to a decrease in inlet pressure acting on the plurality of print heads.
[0110] Preferably, the first pump is a vacuum pump.
[0111] A second pump at constant pressure is provided, which second pump is preferably connected in parallel with the return branch of the recirculation loop.
[0112] Preferably, the second pump is configured to set a predetermined, preferably constant, pressure value at the ink outlet of the first buffer.
[0113] Preferably, the third pump is set to deliver a constant ink flow rate, the first pump being connected to the delivery branch of the recirculation loop.
[0114] Preferably, a first pressure sensor is mounted along the delivery branch of the ink recirculation loop to measure the pressure at the inlet of the plurality of print heads.
[0115] Preferably, the first pressure sensor is connected between the second buffer and the main delivery conduit.
[0116] Preferably, the first pressure sensor is connected at a central region of the second main conduit, the central region being comprised between both ends of the main delivery conduit.
[0117] Preferably, the first pressure sensor is connected to the second connecting pipe.
[0118] Preferably, the output of the first pressure sensor is used to control the first pump.
[0119] In some embodiments, there are a plurality of first pressure sensors, each first pressure sensor being connected proximate an ink inlet of each printhead in the plurality of printheads.
[0120] Providing a first pump that actively regulates ink pressure in the first buffer allows it to react quickly to pressure fluctuations at the inlet to the printhead, thereby restoring a predetermined pressure differential for the printhead associated with optimal nozzle operation.
[0121] Preferably, the at least one sensor comprises a second pressure sensor mounted along the return branch of the ink recirculation loop.
[0122] Preferably, the second pressure sensor is connected between the first buffer and the main return pipe.
[0123] Preferably, the second pressure sensor is connected at a central region of the main return pipe, the central region being included between both ends of the main return pipe.
[0124] Preferably, the second pressure sensor is connected to the first connecting pipe.
[0125] Alternatively, the second pressure sensor is connected to the first buffer or in the vicinity of the first buffer for measuring the pressure acting in the first buffer.
[0126] In an embodiment, the second pressure sensor is connected to the compensation chamber of the first damper for measuring the pressure in the compensation chamber acting on the first damper.
[0127] Preferably, the output of the second pressure sensor is used to control the second constant pressure pump.
[0128] Preferably, the second pump is configured to adjust the operating point of the first pump based on the output of the second pressure sensor.
[0129] Preferably, the second pump is configured to return the first pump to its optimal operating point after a deviation.
[0130] Preferably, the plurality of tubes extend at least partially parallel to the first printing direction and the second printing direction.
[0131] Preferably, the tubes of the plurality of tubes are at least partially flexible.
[0132] Preferably, the sliding guide has a straight extension.
[0133] Further characteristics and advantages of the invention will become more apparent from the following detailed description of preferred embodiments of the invention provided by way of indicative and non-limiting examples with reference to the accompanying drawings, in which:
[0134] - Figure 1 is a schematic front perspective view of a plotter according to the present invention;
[0135] - Figure 2 is a schematic rear perspective view of a plotter according to the present invention;
[0136] - Figure 3 yes Figure 1 A schematic elevation view of components of a plotter;
[0137] - Figure 4 yes Figure 1 A schematic side view of components of a plotter;
[0138] - Figure 5 yes Figure 1 A schematic perspective view of components of a plotter;
[0139] - Figure 6 yes Figure 5 An exploded schematic diagram of the components of the plotter shown in ;
[0140] - Figure 7 is based on Figure 5 A cross-sectional view of plane AA shown in FIG. 1 ; and
[0141] - Figure 8 yes Figure 1 A schematic perspective view of components of a plotter; and
[0142] - Fig. 9 is a schematic diagram of a plotter according to another embodiment of the present invention.
[0143] exist Figure 1 and Figure 2 In the drawing, a plotter is indicated by reference numeral 1.
[0144] The plotter 1 comprises a frame 10 which is connected by cross members 14 ( Figure 1 The structure is formed by connecting columns 12 (only some of which are shown) and other structural components known in the prior art.
[0145] The frame 10 comprises two lateral first 13 and second 14 load-bearing structures which are configured to rest on the ground at respective bases 15 , 16 provided with feet 17 .
[0146] The supporting structures 13 , 14 are connected to one another by a bridging structure 18 , which is arranged at a distance from a plane containing the bases 15 , 16 of the supporting structures 13 , 14 .
[0147] The empty space included between the carrying structures 13, 14 and below the bridge structure 18 of the frame 10 defines a printing area 20 adapted to receive a substantially planar substrate (not shown) to be printed. In the operating condition of the plotter 1, the substrate to be printed is introduced into the printing area 20 by means of a conveyor belt, rollers or other suitable handling means mounted on a suitable support frame.
[0148] The frame 10 includes a slide rail 22, which defines a first straight printing direction S1 and a second straight printing direction S2. Figure 1 The second straight printing direction is opposite to the first printing direction S1 and extends from left to right in Figure 2 Extends from right to left.
[0149] The first printing direction S1 and the second printing direction S2 are contained in a sliding plane P which is tangential to the lower end of the sliding guide 22 and corresponds in the case shown to a horizontal plane. In the operating condition of the plotter 1, the sliding plane P is also parallel to the substrate to be printed.
[0150] The slide rail 22 extends between a first end 21 at the first bearing structure 13 and a second end 23 at the second bearing structure 14 , through the bridge area 18 and over the printing area 20 . The slide guide 22 comprises one or more rails 25 .
[0151] The plotter 1 comprises a carriage 24 which is slidably constrained to a sliding guide 22. The carriage 24 is moved along the sliding guide 22 by one or more electric motors (not shown), for example.
[0152] During printing, when the carriage 24 slides along the slide guide 22 , the substrate to be printed advances in the printing area 16 parallel to the sliding plane P and orthogonal to the first printing direction S1 and the second printing direction S2 .
[0153] As in Figure 3 and Figure 4 As can be better seen in FIG. 1 , the carriage 24 is configured as a receiving structure including a base 28, an upper wall 30 and four side walls 32, two of which have been removed for clarity. Figure 3 and Figure 4 Removed.
[0154] The carriage 24 houses a plurality of print heads 34 .
[0155] The print head 34 is of the ink recirculation type and is designed to distribute ink onto a substrate to be printed when the plotter 1 is in operation. The print head 34 comprises an internal chamber into which the ink flows, and a plurality of ink firing nozzles at one of the lower faces 36 of the print head. For simplicity, the print head 34 is shown in FIG. Figure 4 Ink firing nozzles at the lower face 36 of the print head 34 are shown at 37, these ink firing nozzles are not directly visible.
[0156] The pressure inside each print head 34 must be set to a predetermined pressure difference relative to the external environment for optimal operation of the nozzles 37. Preferably, the pressure difference is 2 mbar lower than the external environment.
[0157] In the embodiment illustrated in the drawings, the print heads 34 are divided into groups 40 of ten print heads 34. Each group 40 of print heads 34 includes eight print heads 34, which are divided into two parallel rows of four print heads 34, such as from Figure 3 and Figure 4 Can be deduced.
[0158] The lower face 36 of the print head 34 is exposed from below through an opening made in the base 28 of the carriage 24 so as to expose the outlets of the nozzles 37 externally.
[0159] The plotter 1 is configured in particular to perform an inkjet printing process. Each of the nozzles 37 of the print head 34 comprises a selective activation mechanism which may be based on thermal technology or piezoelectric technology (comprising a resistor in the first case and a channel of piezoelectric material adjacent to the nozzle outlet in the second case), and an associated circuit configured to activate the resistor or the piezoelectric channel.
[0160] The plotter 1 also includes one or more tanks 200, Figure 1 As schematically shown in FIG. 8 , ink is stored in the tank to be supplied to the print head 34 during printing.
[0161] The storage tank 200 is in a fixed position relative to the frame 10 of the plotter 1. For example, the storage tank 200 may be arranged in a Figure 1 The right side of the frame 10 is within the space defined by the uprights 12 and the cross member 14 of the supporting structure 17 .
[0162] The plotter 1 includes an ink recirculation circuit (generally referred to as C in the figure) configured to supply ink to the print head 34 .
[0163] The recirculation loop C includes a plurality of tubes 39 configured to circulate ink from the tank 200 to the print head 34 and from the print head 34 to the tank 200 .
[0164] The recirculation circuit C comprises a delivery branch Cm, through which ink is supplied from the tank 200 to the printheads 34, and a return branch Cr, through which ink is returned from the printheads 34 to the tank 200. The continuous recirculation of ink not used for printing counteracts ink stagnation and prevents it from drying up in the printheads 34, thus clogging their nozzles 37.
[0165] The plurality of tubes 39 are included in Figure 2 Visible in and Figure 4 Schematically shown in FIG. 3 are first flexible main tubes 38 , which form part of the delivery branch Cm.
[0166] The first main tube 38 extends above a sliding plane P between the corresponding first end 41 a and second end 41 .
[0167] The first end 41a of the first main pipe 38 is connected to the first delivery connector 44a of the ink tank 200 (at Figure 1 ) is part of the delivery branch Cm of the recycling loop C.
[0168] The delivery branch Cm also includes a second delivery connector 44 ( Figure 3 ), the second delivery connector is connected to the second end 41 of the first main pipe 38 and is configured to send ink to the print head 34.
[0169] The first end 41a of the first main tube 38 is in a fixed position relative to the frame 10 of the plotter 1, for example, Figure 1 The bearing structure 14 on the middle right side is close to the second end 23 of the sliding guide 22 .
[0170] The second end 41 of the first main pipe 38 is made integrally with the carriage 24 so that the second end is pulled by the carriage 24 during its sliding movement along the sliding guide 22 in the first printing direction S1 and the second printing direction S2 .
[0171] In order to be able to follow the movement of the carriage 24 , the first main pipe 38 forms a loop 52 between the first section 48 of the first main pipe 38 and the second section 50 of the first main pipe 38 .
[0172] The first section 48 and the second section 50 extend substantially parallel to each other and to the first sliding direction S1 and the second sliding direction S2. The second section 50 of the first main pipe 38 substantially overlaps the first section 48. The first section 48 is supported by a first housing 53, which is fixed to the sliding guide 22 ( Figure 4 ), above the track 25, the carriage 34 is hooked onto the track.
[0173] When the carriage 24 is located at the first end 21 of the slide guide 22, as in Figure 1 In the case shown, the first section 48 assumes a maximum extension and the second section 50 assumes a minimum extension.
[0174] When the carriage 24 is at the second end 23 of the sliding guide 22 , the first section 48 assumes the minimum extension and the second section 50 assumes the maximum extension. In this case, the ring 52 is located in the central region of the sliding guide 22 at the bridge structure 18 of the frame 10 .
[0175] The plurality of tubes 39 include a second flexible main tube 54, Figure 1 Visible in and Figure 4 Depicted in FIG. 1 , the second flexible main pipe forms part of the return branch Cr.
[0176] The second main tube 54 extends between respective third and fourth ends 56, 57 above the sliding plane P. The second main tube 54 extends parallel to the first main tube 38 of the delivery branch Cm along a direction transverse to the first sliding direction S1.
[0177] The first return connector 44 b , which connects the third end 56 of the second main pipe 54 to the ink tank 200 , is part of the return branch Cr of the recirculation loop C.
[0178] The return branch Cr also includes a second return connector 61 connected to the fourth end 58 of the second main pipe 54 and configured to receive ink from the print head 34 .
[0179] The third end 56 of the second main tube 54 is in a fixed position relative to the frame 10 of the plotter 1, for example, near the first end 41a of the first main tube 38, at Figure 2 The support structure 14 is located on the left side of the middle portion and is close to the second end 23 of the sliding guide 22 .
[0180] The fourth end 58 of the second main pipe 54 is made integrally with the carriage 24 so as to be dragged by the carriage 24 in its sliding movement along the sliding guide 22 in the first printing direction S1 and the second printing direction S2 .
[0181] Similar to what is described above with respect to the first main pipe 38 , the second main pipe 54 forms a loop 60 between a third section 57 of the second main pipe 54 and a fourth section 59 of the second main pipe 54 .
[0182] The third section 57 and the fourth section 59 extend substantially parallel to each other and to the first sliding direction S1 and the second sliding direction S2. The fourth section 59 substantially overlaps the third section 57 of the second main pipe 54. The third section 57 is supported by the second housing 55, which is fixed to the sliding guide 22 ( Figure 4 ), above the rail 25 on which the carriage 34 is hooked.
[0183] When the carriage 24 is at the first end 21 of the slide guide 22, as in Figure 1 In the case shown in , the third section 57 assumes the maximum extension and the fourth section 59 assumes the minimum extension.
[0184] When the carriage 24 is at the second end 23 of the sliding guide 22 , the third section 57 assumes the minimum extension and the fourth section 59 assumes the maximum extension. In this case, the ring 60 is located in the central region of the sliding guide 22 at the bridge structure 18 of the frame 10 .
[0185] There are one or more pumps (not shown) configured to move the ink along the recirculation circuit C. For example, there may be a first flow control pump connected along the delivery branch Cm of the recirculation circuit C and configured to deliver a constant flow of ink, and a pressure control pump located parallel to the return branch Cr and configured to operate at a constant pressure.
[0186] The plotter 1 comprises a plurality of buffers 62 in fluid communication with the recirculation circuit C, Figure 4-Figure 6 One of the buffers is shown in FIG.
[0187] Each buffer 62 comprises a container body 64 including a first shell 66 and a second shell 68 made of a rigid material, which are joined together at corresponding coupling flanges 70 , 72 by means of fastening members 73 (eg screws, bolts, etc.).
[0188] The first housing 66 and the second housing 68 define a first recess 74 and a second recess 76, respectively, facing each other in the assembled state of the buffer 62. The first recess 74 and the second recess 76 are bounded by corresponding edges 78, 80 having substantially corresponding peripheral extensions ( Figure 7 ).
[0189] The buffer 62 comprises a membrane 82 made of, for example, an elastomeric material.
[0190] In the assembled state of the buffer 62, the membrane 82 is inserted between the first shell 66 and the second shell 68. The peripheral edge 84 of the membrane 82 is fastened at the coupling flanges 70, 72 using the same fastening means used to hold the first shell 66 and the second shell 68 together.
[0191] In the assembled state, the membrane 82 is held between the edges 78, 80 of the first recess 74 and the second recess 76. In this way, the membrane 82 closes the first recess 74 and the second recess 76 and physically separates them from each other.
[0192] Each buffer 62 includes an accumulation chamber 88. The accumulation chamber 88 is defined between the first recess 74 of the first housing 66 and the membrane 82. The accumulation chamber 88 includes a first opening 90 and a second opening 92 formed at the first housing 66.
[0193] Each buffer 62 includes a compensation chamber 94. The compensation chamber 94 is defined between the second recess 74 of the second housing 68 and the membrane 82. The compensation chamber 94 includes a third opening 96 formed at the second housing 68.
[0194] The accumulation chamber 88 is distinct from and fluidically separated from the compensation chamber 94 .
[0195] A first connector 102 and a second connector 104 are also provided at the first opening 90 and the second opening 92, and the first opening and the second opening are configured to place the accumulation chamber 88 of the buffer 62 in fluid connection with the ink recirculation circuit C. A plug 107 is provided at the third opening 96, and when the plotter is in use, the plug is removed to connect the compensation chamber 94 to the external environment or the compressed air source 150 (in Figure 5 ) or vacuum pump 151 (shown schematically in Figure 5 The two components are connected (shown schematically in FIG. 1 and indicated by dotted lines).
[0196] By virtue of its elasticity, the membrane 82 is able to deform along an expansion direction E perpendicular to the sliding plane S, thereby expanding towards the compensation chamber 94 or towards the collection chamber 88. During its expansion, the membrane 82 remains constrained to the container body 64 at the peripheral border 84.
[0197] The membrane 82 expands in an expansion direction E towards the compensation chamber 94 or towards the accumulation chamber 88 , respectively, in response to the ink pressure in the accumulation chamber 88 being below or above the predetermined operating pressure and under the effect of the constant pressure in the compensation chamber 94 .
[0198] The buffer 62 also includes a gasket 98 for sealing the accumulation chamber 88 and the compensation chamber 94 .
[0199] The collecting chamber 88 and the compensating chamber 94 are elongated in a direction perpendicular to the first sliding direction S1 .
[0200] The focusing chamber 88 and the compensation chamber 94 have the same length dimension L2 and width dimension L1, both of which are Figure 6 In the example shown, the ratio between the width dimension L1 and the length dimension L2 of the focusing chamber 88 and the compensation chamber 94 is comprised between 0.15 and 0.55, preferably between 0.25 and 0.45, more preferably between 0.25 and 0.40, for example 0.3.
[0201] like Figure 3 , Figure 4 and Figure 8 As can be seen in FIG. 1 , the plotter 1 comprises a first buffer 62a connected to the return branch Cr of the ink recirculation circuit C and a second buffer 62b connected to the delivery branch Cm of the ink recirculation circuit C. The first buffer 62a and the second buffer 62b are identical to each other.
[0202] In the preferred embodiment, ten pairs 63 of buffers 62 are provided, each pair of buffers comprising a first buffer 62a and a second buffer 62b. Each pair 63 of buffers 62 is fluidly connected to a group 40 of print heads 34 via a corresponding distributor 46.
[0203] Figure 8 A pair 63 of buffers 62 connected to the distributor 46 is schematically illustrated.
[0204] Each buffer 62 is connected to a corresponding distributor 46 via a support element 100 .
[0205] The distributor 46 includes a delivery portion 45 including a straight main delivery conduit 106 and a plurality of secondary delivery conduits 108 ( Figure 8 Only one is shown).
[0206] The main delivery conduit 106 extends parallel to the sliding plane P and orthogonal to the first sliding direction S1 and the second sliding direction S2. Figure 8 As shown, the secondary delivery conduit 108 extends perpendicular to the primary delivery conduit 106 in a vertical direction.
[0207] The main delivery conduit 106 is connected to the second buffer 62b via a second connecting pipe 110 connected to the second connector 104 located at the second opening 92 of the second buffer 62b.
[0208] The distributor 46 includes a return portion 112 including a straight main return pipe 114 and a plurality of secondary return pipes 116 ( Figure 8 Only one is shown).
[0209] The main return duct 114 extends horizontally in the drawing parallel to the sliding plane P and orthogonally to the first flow direction S1 and the second flow direction S2 (see also FIG. Figure 3 and Figure 4 ).like Figure 8 As shown, the secondary return conduit 108 extends in a vertical direction orthogonal to the primary return conduit 114 .
[0210] The main return pipe 114 is connected to the first buffer 62 a via a first connecting pipe 118 , which is connected to the second connector 104 at the second opening 92 of the first buffer 62 a .
[0211] The distributor 46 connects the first buffer 62 a and the second buffer 62 b to the group 40 of print heads 34 .
[0212] Specifically, each of the secondary delivery conduits 108 is connected to an ink inlet 120 of a printhead 34 of the group 40 of printheads 34 .
[0213] Each of the secondary return conduits 116 is connected to an ink outlet 122 of a printhead 34 of the group 40 of printheads 34 .
[0214] The secondary delivery conduit 108 and the return conduit 116 may be connected to the print head 34 directly or with the aid of an additional connector 124, such as at Figure 3 Those additional connectors illustrated in , are connected to the print head 34 and are separated from the secondary delivery conduit 108 and the return conduit 116 for simplicity of illustration.
[0215] The preferred embodiment includes a bypass conduit 126 connecting an end 128 of the main delivery conduit 106 with an end 130 of the main return conduit 114 .
[0216] like Figure 4 As shown, the first buffer 62a and the second buffer 62b are placed at a fixed predetermined distance D (measured in a direction perpendicular to the sliding plane P) from the ink inlet 120 and the ink outlet of the print head 34.
[0217] The pressure inside the printhead 34 is provided by the sum of the pressure inside the collection chamber 88 of the buffer 62 and the equivalent pressure of a column of ink having a height equal to the distance D separating the buffer 62 from the printhead 34 in the vertical direction.
[0218] This predetermined operating pressure is therefore set so that the pressure inside the print head 34 is exactly equal to a predetermined pressure difference relative to the external environment (eg, which is equal to 998 mbar).
[0219] This operating pressure setting is implemented by setting the pump acting on the recirculation circuit C.
[0220] For example, there is a first pressure sensor 132 connected to the first delivery branch 106 and configured to measure the pressure in the main delivery conduit 106. The first pressure sensor 132 is configured to at least indirectly measure the pressure inside the focusing chamber 88 of the second buffer 62b and thus measure the inlet pressure to the plurality of print heads.
[0221] Alternatively or in combination, the second pressure sensor 134 is connected to the main return pipe 114 and is configured to measure the pressure in the main return pipe 114. The second pressure sensor 134 is configured to at least indirectly measure the pressure inside the accumulation chamber 88 of the first buffer 62a.
[0222] The first buffer 62a and the second buffer 62b have similar or identical behavior during steady-state operation of the plotter 1 and during a sudden drop or rise in pressure of the recirculation loop C. Therefore, what follows regarding one buffer 62 applies to all buffers on the plotter 1 .
[0223] During steady-state operation of the plotter 1, ink is drawn from the ink tank 200 and sent to the second buffer 62b via the delivery branch Cm of the recirculation circuit C. A small portion of the ink is dispensed through the print head 34 and the remainder of the ink is sent to the first buffer 62a and then to the tank via the return branch Cr of the recirculation circuit C.
[0224] A second constant pressure pump (placed parallel to the return loop Cr) maintains the pressure in the recirculation loop C at a pressure such that the pressure in the accumulation chamber 88 is equal to a predetermined operating pressure corresponding to a predetermined pressure difference in the print head 34 relative to the external environment.
[0225] When the carriage 24 undergoes an acceleration (or deceleration) which causes an immediate pressure drop in the recirculation circuit C, or when the printhead dispenses a significant amount of ink, the significant amount of ink causes a pressure drop in the printhead 34 which is immediately propagated into the accumulation chamber 88. This pressure drop in the accumulation chamber 88 is immediately compensated by the expansion of the membrane 84 which expands in the accumulation chamber 88 under the effect of the constant pressure (e.g., atmospheric pressure) in the compensation chamber 94, thereby raising the ink pressure in the accumulation chamber 88. This increase in pressure in the accumulation chamber 88 returns the pressure in the accumulation chamber 88 to the predetermined operating pressure.
[0226] When the cause of the pressure drop in the recirculation loop C ceases, the temporary pressure drop in the recirculation loop C ceases and the membrane 84 expands in the compensation chamber 94 (against the constant pressure existing in the compensation chamber 94), thereby returning the accumulation chamber 88 to its initial volume and pressure conditions.
[0227] When the carriage 24 undergoes an acceleration (or deceleration) that results in an immediate pressure increase in the recirculation loop C, this pressure increase is immediately propagated into the accumulation chamber 88. This pressure increase in the accumulation chamber 88 is immediately compensated by the expansion of the membrane 84, which expands in the compensation chamber 94 (opposite to the constant pressure in the compensation chamber 94), thereby reducing the ink pressure in the accumulation chamber 88. This pressure reduction in the accumulation chamber 88 returns the pressure in the accumulation chamber 88 to the predetermined operating pressure.
[0228] When the cause of the pressure increase in the recirculation circuit C ceases, the temporary pressure increase in the recirculation circuit C ceases and the membrane 84 expands in the accumulation chamber 88 under the action of the constant pressure in the compensation chamber 94, thereby returning the accumulation chamber 88 to its initial volume and pressure conditions.
[0229] Because the ink leaving the second buffer 62b arrives at the fluid inlet 124 of the print head 34 via the distributor 46, and because the distributor 46 includes a primary rigid delivery conduit 106 and a secondary rigid delivery conduit 108, and the first buffer 62b is positioned at a fixed and predetermined distance D from the opening of the print head 34, the ink arrives at the print head 34 without any pressure change relative to the outlet from the first buffer 62b.
[0230] For example, the plotter 1 may include eighty print heads 34, which are divided into ten groups of eight print heads 34. Each group of print heads 34 is configured to distribute one color of ink and is connected to the first buffer 62a and the second buffer 62b. The total number of buffers 62 is 20.
[0231] For example, each print head 34 may include 1536 nozzles 37. Each nozzle 37 is configured to fire ink droplets having a volume of approximately 10 picoliters at a firing frequency of 20 kHz.
[0232] In this embodiment, the average ink flow rate Q flowing into the recirculation loop C in each print head group is about 147 ml / min, where the average ink flow rate Q is calculated according to the following formula (1):
[0233] Q=Vn×Nn×Nh×f (1)
[0234] in:
[0235] Vn = volume of ink emitted by each nozzle in a single activation
[0236] Nn = number of nozzles on each print head
[0237] Nh = number of print heads
[0238] f = nozzle firing frequency.
[0239] In this embodiment, the volume of the collection chamber 88 of each buffer 62 acting on the group of print heads is approximately 27 ml.
[0240] Fig. 9 The diagram schematically illustrates an ink recirculation circuit C of a plotter 1 according to a particularly preferred embodiment.
[0241] To keep it simple, Fig. 9 The figure shows a single pair 63 of buffers 62 fluidly connected to a single group 40 of print heads 34 via a distributor 46, the following also applies mutatis mutandis when the plotter 1 comprises multiple groups 40 of print heads 34 served by multiple pairs 63 of buffers 62.
[0242] The construction of the first and second buffers 62a, 62b, their positioning along the recirculation loop C and their operation (except for the active control mode of the first buffer 62a, as described below) are completely similar to those described with respect to the previous figures.
[0243] The plotter 1 comprises a first pump 300 connected to the compensation chamber 94 of the first buffer 62a, positioned along the return branch Cr of the recirculation loop C. The first pump 300 is, for example, Figure 5 Vacuum pump 151 is shown.
[0244] A second constant pressure pump 302 (simply the second pump 302 ) and a third constant flow pump 304 (simply the third pump 304 ) are also provided in the loop to move the ink along the recirculation loop C.
[0245] The second pump 302 is arranged in parallel with the return branch Cr of the recirculation loop C (the bypass pipe 303 is schematically shown by a dotted line), and when the plotter 1 operates, the second pump 302 sets a predetermined and constant pressure value backward along the return branch Cr and at the ink outlet 305 at the gathering chamber 88 of the first buffer 62a.
[0246] The third pump 304 is located on the delivery branch Cm of the recirculation loop C and is configured to draw ink from the tank 200 and deliver the ink to the inlet of the accumulation chamber 88 of the second buffer 62b at a constant flow rate.
[0247] The first pump 300 operates under suction by applying an underpressure in the compensation chamber 94 of the second buffer 62a and at least partially counteracting the negative pressure set in the accumulation chamber 88 by the second pump 302. The combined action of the first pump 300 and the second pump 302 maintains the diaphragm 84 of the first buffer 62a in a specific equilibrium position.
[0248] The operation of the first pump 300 is controlled according to the pressure read by the first pressure sensor 306 at the inlet of the group 40 of print heads. Fig. 9 As in the case shown, it is positioned upstream of the distributor 46 (in this case, it corresponds to Figure 8 Alternatively, a plurality of first sensors 306 may be provided, each of which is positioned at one of the tubes belonging to the distributor 46 or adjacent to the ink inlet 120 of a single print head 34 ( Figure 4 ).
[0249] The provision of the first pump 300 allows the pressure in the accumulation chamber 88 of the first buffer 62a to be quickly adjusted by actively intervening in the position of the membrane 84 when the pressure in the circuit deviates from the optimum operating pressure.
[0250] For example, when the first pressure sensor 306 reads a decrease in the pressure at the inlet of the group 40 of print heads relative to the operating pressure, the first pump 300 is controlled to increase the low pressure applied in the compensation chamber 94 of the first buffer 62b (in other words, to reduce the negative set point pressure to be achieved). In this way, the membrane 84 contracts towards the compensation chamber 94, thereby increasing the volume and reducing the hydraulic resistance of the accumulation chamber 88. This causes a higher fluid draw of the first buffer 62a and a consequent increase in the pressure at the group 40 of print heads.
[0251] Similarly, when the first pressure sensor 306 reads an increase in the pressure at the inlet of the group 40 of printheads relative to the operating pressure, the first pump 300 is controlled to reduce the low pressure applied in the compensation chamber 94 of the first buffer 62b (in other words, to increase the negative set point pressure to be achieved). In this way, the membrane 84 expands towards the accumulation chamber 88, thereby reducing the volume and increasing the hydraulic resistance of the accumulation chamber 88. This causes the first buffer 62a to draw less fluid and a consequent drop in the pressure at the group 40 of printheads.
[0252] The operation of the second pump 302 is controlled according to the pressure read at the first buffer 62a by the second pressure sensor 308. For example, the second pressure sensor 308 reads the air pressure in the compensation chamber 94 of the first buffer 62a, but in a variation not shown, it can be positioned and set to measure the ink pressure in the accumulation chamber 88 or the inlet / outlet pressure from the first buffer 62a.
[0253] In this way, the second pump 302 is able to indirectly and dynamically adjust the operating point of the first pump 300. When the second pressure sensor 308 detects a change in pressure at the first buffer 62a, which is an indication that the first pump 300 has actively changed the position of the membrane 84 due to the imbalance, the second pump 302 changes the predetermined pressure value set at the ink outlet 305 of the first buffer 62a to return the membrane 84 to its equilibrium position, in which the first pump 300 operates at its optimal operating point.
[0254] Obviously, a person skilled in the art may make numerous modifications and variations to the invention described above in order to meet specific and contingent needs, while remaining within the scope of protection defined by the appended claims.
Claims
1. A plotter for inkjet printing (1), comprising: A frame (10) comprising a sliding guide (22); a carriage (24) slidably constrained to the sliding guide (22) and movable along the sliding guide (22) in a first printing direction (S1) and in a second printing direction (S2) opposite to the first printing direction (S1), wherein the first printing direction (S1) and the second printing direction (S2) are contained in a sliding plane (P) parallel to the sliding guide (22), and wherein the carriage (24) supports a group (40) of at least one print head (34), wherein each print head (34) of the group (40) of at least one print head (34) comprises a plurality of ink dispensing nozzles (37); at least one tank (200) configured to contain ink, arranged in a fixed position relative to the frame (10); an ink recirculation circuit (C), the ink recirculation circuit comprising a delivery branch (Cm) configured to allow the ink to flow from the at least one tank (200) to the group (40) of at least one printhead (34), and a return branch (Cr), the delivery branch being configured to allow the ink to flow from the group (40) of at least one printhead (34) to the at least one tank (200), the recirculation circuit (C) comprising a plurality of tubes (39) extending at least partially parallel to the sliding plane (P), Characterized in that the plotter comprises at least one buffer (62) integral with the carriage (24), placed between the at least one tank (200) and the group (40) of at least one printhead (34) and connected to at least one of the delivery branch (Cm) and the return branch (Cr) of the ink recirculation circuit (C), Wherein, the at least one buffer (62) includes an ink accumulation chamber (88) and a compensation chamber (94), wherein the compensation chamber is fluidically separated from the ink accumulation chamber (88) by an expandable diaphragm, the ink accumulation chamber (88) is in fluid communication with the ink recycling circuit (C), and the compensation chamber (94) is in fluid communication with the external environment or with a compressed air source (150) or with a vacuum pump (151).
2. The plotter (1) according to claim 1, wherein: The set (40) of at least one print head (34) includes at least one print head (34).
3. The plotter (1) according to claim 1 or 2, wherein: The collecting chamber (88) of the at least one buffer (62) has an elongated shape with a dominant development axis parallel to the sliding plane (P) and perpendicular to the first printing direction (S1).
4. A plotter (1) according to any one of the preceding claims, wherein: The collecting chamber (88) has a width dimension (L1) in a direction parallel to the sliding plane (P) and parallel to the first printing direction (S1) and a length dimension (L2) in a direction parallel to the sliding plane (P) and perpendicular to the first printing direction (S1); the ratio between the width dimension (L1) and the length dimension (L2) is preferably between 0.1 and 0.6, more preferably between 0.2 and 0.4, and even more preferably between 0.25 and 0.
35.
5. A plotter (1) according to any one of the preceding claims, wherein: The collection chamber (88) includes a first opening (90) and a second opening (92); the first opening (90) is connected to the at least one tank (200) through a tube of the plurality of tubes (39), and the second opening (92) is connected to the group (40) of print heads (34) through a distributor (46).
6. A plotter (1) according to any one of the preceding claims, wherein: The at least one buffer (62) is placed at a fixed and predetermined distance (D) from the group (40) of at least one print head (34) along a direction perpendicular to the sliding plane (P).
7. A plotter (1) according to any one of the preceding claims, wherein: The at least one buffer (62) comprises a first buffer (62a) connected to the return branch (Cr) of the ink recirculation circuit (C), and The plotter (1) includes a first pump (300) connected to the first buffer (62a), the first pump being configured to adjust the pressure of ink flowing into the collecting chamber (88) of the first buffer (62a) in response to a pressure change at an inlet of the group (40) of at least one print head (34).
8. The plotter (1) according to claim 7, wherein: The first pump (300) is connected to the compensation chamber (94) of the first buffer (62a) to adjust the air pressure in the compensation chamber (94).
9. The plotter (1) according to claim 7 or 8, wherein: The first pump (300) is configured to apply a low pressure in the compensation chamber (94) of the first buffer (62a).
10. The plotter (1) according to any one of claims 7 to 9, wherein: The first pump (300) is configured to increase the low pressure applied in the compensation chamber (94) of the first buffer (62a) in response to a decrease in pressure at the inlet of the group (40) of the at least one print head (34), and to decrease the low pressure in response to an increase in pressure at the inlet of the group (40) of the at least one print head (34).
11. A plotter (1) according to any one of claims 7 to 10, comprising a first pressure sensor (306) mounted along the delivery branch (Cm) of the ink recirculation circuit (C) to measure the pressure acting at the inlet of the group (40) of at least one print head (34), the output of the first pressure sensor (306) being used to control the first pump (300).
12. The plotter (1) according to any one of claims 7 to 11, comprising a second constant pressure pump (302) connected in parallel to the return branch (Cr) of the recirculation loop (C), the second pump (302) being configured to set a predetermined, preferably constant pressure value at the ink outlet of the first buffer (62a).
13. The plotter (1) according to any one of claims 7 to 12, comprises a second pressure sensor (308), which is installed along the return branch (Cr) of the ink recirculation loop (C) and connected to the first buffer (62a) or near the first buffer (62a) to measure the pressure acting in the first buffer (62a), and the output of the second pressure sensor (308) is used to control the second constant pressure pump (302).
14. A plotter (1) according to any one of the preceding claims, wherein: The at least one buffer (62) comprises a second buffer (62b) connected to the delivery branch (Cm) of the ink recirculation circuit (C).
15. A plotter (1) according to claim 14 when directly or indirectly dependent on claim 7, wherein: The group (40) of at least one print head (34) includes a plurality of print heads (34), and the distributor includes: a main return pipe (114) and a main delivery pipe (106), a plurality of secondary return pipes (116) and a plurality of secondary delivery pipes (108), the main return pipe is connected to the first buffer (62a), the main delivery pipe is connected to the second buffer (62b), the main return pipe (114) and the main delivery pipe (106) are extended parallel to the sliding plane (P) and perpendicular to the first printing direction (S1); each of the plurality of secondary return pipes is connected to the main return pipe (114); each of the plurality of secondary delivery pipes is connected to the main delivery pipe (106); wherein the secondary return pipe (116) and the secondary delivery pipe (108) are extended perpendicular to the sliding plane (P) and are further connected to the plurality of print heads (34).
16. The plotter (1) according to claim 15, wherein: The distributor (46) includes at least one bypass conduit (126) connected between respective terminal ends (128, 130) of the main return conduit (114) and the main delivery conduit (106).
Citation Information
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