GB2532279A

GB2532279A - Printing apparatus

Info

Publication number: GB2532279A
Application number: GB1420333.5A
Authority: GB
Inventors: Paris Raymond; Moss Adrian
Original assignee: PostJet Systems Ltd
Current assignee: PostJet Systems Ltd
Priority date: 2014-11-17
Filing date: 2014-11-17
Publication date: 2016-05-18
Anticipated expiration: 2034-11-17
Also published as: GB2532279B; GB201420333D0

Abstract

A printing apparatus (10, Fig.1) has a nozzle surface 21 defining an ink ejection plane 26 and a wiper (25, Fig.2) displaceable over the nozzle surface 21 to remove debris from the nozzle surface 21. A wiper displacement mechanism is located behind the plane of the nozzle surface 26. The wiper (25, Fig.2) may comprise a wiping part 27 and a locating part 28. The wiping part 27 may include a wiping material such as PTFE. The displacement mechanism may be a flexible endless drive belt 30. The ink jet printing apparatus is particularly suited for postal printing applications. There is also provided a method for detecting deteriorating print quality and initiating a cleaning or wiping cycle.

Description

PRINTING APPARATUS

Field of the Invention

This invention relates to printing apparatus and in particular, though not necessarily solely, to postal printing apparatus.

Background to the Invention

Printers are known for printing onto postal items at postal sorting and/or distribution centres. The type of information printed may include bar codes, address or re-address information, cancellation marking, and branding and promotional data.

The present applicant has been developing, manufacturing and selling print engines for use in postal applications for a number of years, the print engines incorporating a drop-on-demand (DOD) print head. These print engines are incorporated into a variety of postal printing systems.

Postal printing presents particular challenges. Not only must printing be effected at high speed throughputs (4.0 to 4.5 metres/second), but the printing environment is extremely dusty. The inkjet heads used in these printers are extremely sensitive to dust which can not only distort the printed code but also become entrapped in ink and cause blockage of the inkjet nozzles Considerable effort has been applied to reducing the effects of dust in postal printers. The use of some form of vacuum extraction is an obvious solution but, as a supplier of print engines that are used in a variety of end-user systems, it is not possible to apply an extraction system that is suitable for a sufficient number of individual systems.

It is an object of the present invention to provide printing apparatus, or systems or methods having application in printing which will go at least some way in minimising the above-mentioned problems; or which will at least provide a novel and useful choice.

Summary of the Invention

Accordingly, in one aspect, the invention provides a ink jet printing apparatus having a nozzle surface defining an ink injection plane such that, in use, ink is ejected ahead of said ejection plane; a wiper displaceable over said nozzle surface; and a wiper displacement facility operable to displace said wiper with respect to said nozzle surface said print head being characterised in that said wiper displacement facility is located substantially behind said ink ejection plane.

Preferably said wiper comprises a wiping part and a locating part, said locating part extending rearward of said ink ejection plane.

Preferably said wiping part and said locating part are integrally formed from stainless steel.

Preferably said nozzle surface has a wiping axis, and said wiping part has a leading edge arranged at an angle with respect to said wiping axis.

Preferably said wiping part includes a wiping material. Said wiping material may be PTFE.

Preferably said displacement facility includes a flexible, endless, drive belt.

Preferably said apparatus further includes a positional detecting facility.

Preferably said positional detecting facility is provided, in part, by the locating part of said wiper.

In a second aspect the invention provides a postal printer including the inkjet printing apparatus set forth above.

Preferably said postal printer has an incoming mail side and a mail exit side, wherein said wiper has a park position closer to said incoming mail side.

In a third aspect the invention provides a method of controlling a postal printer, said method including analysing a print effected using said printer and, in the event said print is of a quality less than a pre-determined quality, initiating a print head cleaning cycle.

Preferably said method is applied to a postal printer having an inkjet print head.

Preferably said print head cleaning cycle is effected using apparatus as set forth above.

Preferably said method includes bleeding ink through the print head prior to initiation of said cleaning cycle.

Many variations in the way the invention may be performed will present themselves to those skilled in the art, upon reading the following description. The description should not be regarded as limiting, but rather as an illustration only, of one manner of performing the invention. Where appropriate any element or component should be taken as including any or all equivalents thereof whether or not specifically mentioned.

Brief Description of the Drawings

One working embodiment of apparatus incorporating the invention will now be described with reference to the accompanying drawings in which: Figure 1: shows a schematic view of a postal printer ncluding the invention; Figure 2: shows an enlarged view of a print head and wiper included in printing apparatus according to the invention; Figure 3: shows a view similar to Figure 2 but with the face plate removed to reveal further detail; and Figure 4: shows a schematic view of a positional control facility included in the apparatus shown in Figures 1 & 2.

Description of Working Embodiment

Referring firstly to Figure 1, a postal printing system 10 is shown having a conveyor 11 on which items 12 of mail are conveyed to and from a printing station 13 having an incoming mail side 14 and an outgoing mail side 15. In the printing station 13 print is applied to the mail items 12, the print being in the form of barcodes, addressing or re-addressing information, cancellation marking and/or various forms of branding and/or promotion marking. The precise form of, or reason for, marking is not essential to an understanding of this invention or of the scope thereof The system 10 preferably further includes a monitoring system, indicated generally at 16, that monitors the marking applied in the printing station 13 and initiates corrective action in the event that the quality of the marking falls below an acceptable threshold. This will be described in greater detail below.

Referring now to Figure 2, at the heart of the printing station 13 is a print engine comprising an inkjet print head 20 positioned within face plate 21, the print head having a row of ink ejection nozzles 22 defined in a planar nozzle surface 23; and a control facility 24, the control facility being an electronic facility to control and drive the operation of the print head 20. A characteristic feature of the print engine shown in Figure 2 is the inclusion of a wiper 25 which is displaceable, preferably also under the control of control facility 23, over the nozzle surface 23 to clear debris from the surface 23 and, in particular, from the ejection nozzles 22.

Turning now to Figures 3 & 4, the nozzle surface 22 defines an ejection plane 26 such that ink is ejected from the nozzles 22 ahead of the ejection plane 26 and the operating mechanism for the wiper 25 is positioned substantially entirely behind the ejection plane 26.

The wiper 25 comprises a wiping part 27 that overlies the nozzle surface 23, and a locating part 28 that links the wiping part 27 to a displacement facility whereby the wiping part may be displaced longitudinally of the nozzle surface 23 to remove debris therefrom. The wiping part is provided with a contact surface 29, such as PTFE, to bear against the nozzle surface 23 without causing damage thereto. It will further be seen from Figure 2 that the leading edge 26a of the wiping part is angled with respect to the longitudinal axis of the print head 20 (which in turn defines a wiping axis). As a result, debris encountered as the wiper moves over the nozzle surface 23 is displaced transversely and off the surface.

The wiping part 27 and locating part 28 are conveniently formed integrally from spring stainless steel. This enables the wiping part to conform to the nozzle surface 23.

In the form shown the locating part 28 is crimped or otherwise fixed to an endless belt 30. The belt 30 passes around locating pulleys 31 and 32 positioned adjacent to opposite ends of the print head 20 and around idler pulleys 33 and 34, the idler pulleys 33 and 34 maintaining the belt around drive pulley 35 mounted on the output shaft of drive motor 36.

The apparatus is preferably further provided with a position detecting facility to control movement and parking of the wiper. This position detecting facility preferably includes two optical sensors 40 & 41, sensor 40 being cut by locating part 28 of the wiper to provide a datum position for the wiper, and sensor 41 interacting with encoder wheel 42 provided on the motor shaft to provide a count feedback for the wiper position. Both sensors are preferably linked to control facility 24 to control the movement of the wiper 25.

In normal use it is preferred that the park or home position of the wiper is at that end of the print head closest to the incoming mail side 14 of the printer. When a cleaning cycle is required, the motor 36 is operated to displace the wiper 25 to the opposite end of the print head and then immediately return the wiper to the home position.

The combination of position detecting facility and control facility allows for fault diagnosis and correction of position in software. When the printer is initialised, the wiper 25 should be at the home position, but this cannot be guaranteed. Hence a start-up routine may be provided to drive the motor 36 at slow speed in its expected direction, for an encoded distance, sufficient to interrupt the sensor 40. The control facility then causes the motor to reverse the wiper a defined number of steps to the home position defined and maintained by the control facility. If the wiper should be on the wrong side of sensor 40 during the routine described above, the locating part 28 will meet a dead stop to stall the motor 36 before the locating part can hit the pulley teeth. A further routine is then initiated to return the wiper to the correct position A cleaning cycle, wherein the wiper is driven along the nozzle surface 23 to remove debris from the nozzles 22, may be initiated in any suitable manner, including manually. It is preferred, however, that the print quality be monitored downstream of the printing station 13 by an optical character recognition device 16 that feeds back signals to the control facility 24. In the control facility the signals fed back from device 16 can be compared with the print command signals and, when the signals from device 16 indicate a deterioration of print quality exceeding a threshold, a cleaning cycle is initiated.

It will thus be appreciated that the invention provides a print engine particularly suitable for postal printers that incorporates a print head cleaning facility which, because of its positioning behind the ejection plane, does not interfere with the mail passing through the printer and allows the print engine to be incorporated in a wide variety of printing applications.

Claims

Claims Ink jet printing apparatus having a nozzle surface defining an ink injection plane such that, in use, ink is ejected ahead of said ejection plane; a wiper displaceable over said nozzle surface; and a wiper displacement facility operable to displace said wiper with respect to said nozzle surface said print head being characterised in that said wiper displacement facility is located substantially behind said ink ejection plane.

Ink jet printing apparatus as claimed in claim I wherein said wiper comprises a wiping part and a locating part, said locating part extending rearward of said ink ejection plane.

Ink jet printing apparatus as claimed in claim 2 wherein said wiping part and said locating part are integrally formed from stainless steel.

Ink jet printing apparatus as claimed in claim 2 or claim 3 wherein said nozzle surface has a wiping axis, and said wiping part has a leading edge arranged at an angle with respect to said wiping axis.

5. Ink jet printing apparatus as claimed in any one of claims 2 to 4 wherein said wiping part includes a wiping material.

Ink jet printing apparatus as claimed in claim 5 wherein said wiping material comprises PTFE.

Ink jet printing apparatus as claimed in any one of claims 1 to 6 wherein said displacement facility includes a flexible, endless, drive belt.

Ink jet printing apparatus as claimed in any one of claims 1 to 7 wherein said apparatus further includes a positional detecting facility.

Ink jet printing apparatus as claimed in claim 8 wherein said positional detecting facility is provided, in part, by the locating part of said wiper.

10. A postal printer including the inkjet printing apparatus claimed in any one of claims 1 to 9.

11. A postal printer as claimed in claim 10 having an incoming mail side and a mail exit side, wherein said wiper has a park position closer to said incoming mail side.

12. A method of controlling a postal printer, said method including analysing a print effected using said printer and, in the event said print is of a quality less than a pre-determined quality, initiating a print head cleaning cycle.

13. A method as claimed in claim 12 when applied to a postal printer having an inkjet print head.

14. A method as claimed in claim 13 when applied to a postal printer having ink jet printing apparatus as claimed in any one of claims 1 to 9.

15. A method as claimed in claim 14 including bleeding ink through the print head prior to initiation of said cleaning cycle.