WO1996015908A1

WO1996015908A1 - Cleaning and sealing station for a printing head

Info

Publication number: WO1996015908A1
Application number: PCT/NL1995/000397
Authority: WO
Inventors: Paulus Maria Schut; Hermanus Marinus Ignatius Koot
Original assignee: Techniku B.V.; Francotyp-Postalia Gmbh
Priority date: 1994-11-21
Filing date: 1995-11-21
Publication date: 1996-05-30
Also published as: EP0799135A1; DE69508432T2; ATE177686T1; DE69508432D1; NL9401941A; EP0799135B1

Abstract

A cleaning and sealing station (CSS) (1) for a printing head (400) comprises a cap unit (100) provided with sealing chambers (110), and means (112) for establishing a sealing contact between the sealing chamber (110) and the printing head (400). For cleaning a main surface (403) of each printing head (400), the CSS (1) comprises a wiping member (302) slidably mounted relative to the cap unit (100), in such a manner that during a displacement, the wiping member (302) moves along the front of the sealing chamber (110). Further, guide means (3, 4, 5) are provided for displacing the CSS (1) in a direction (P2) perpendicular to the top face (104) of the cap unit (100), the sealing chambers (110) comprise aeration valves (120), and means are provided to ensure that the aeration valves (120) are opened before the sealing chambers (110) move away from the printing heads (400).

Description

Title: Cleaning and sealing station for a printing head

The invention relates to a cleaning and sealing station for a printing head of a printing apparatus.

A printing head of the ink jet type has a main surface into which ink channels open. In many cases, a printing apparatus has several printing heads juxtaposed. Via those ink channels, ink can be fed to a recording medium such as paper. This may involve a contamination of that main surface. Also, when the printing head is not in use, the ink in the ink channels may dry up, which may cause the ink channels to clog up. To prevent this, it is known in the art to provide a printing apparatus with a cleaning and sealing station, hereinafter also referred to as CSS. The purpose of a CSS is multiple: the CSS should provide that the main surface of each printing head is wiped clean, for which purpose the CSS comprises a wiping member; the CSS should provide for the sealing of (the ink channels of) each printing head when they are not used, for which purpose the CSS comprises a sealing chamber for each printing head, which sealing chamber can be pressed against the main surface of the relevant printing head;

The CSS should provide for the suctioning of excess ink in the printing head, for which purpose the sealing chamber can communicate with a suction pump. ith a CSS as described in EP-0.574.268, the wiping member is formed by a rotating wiping blade positioned next to a cap comprising the sealing chambers. For performing a wiping operation, the printing heads are displaced along the rotating wiping blade. This construction has a number of drawbacks. In the first place, such a construction having a rotating wiping blade takes up quite some space. In addition, the wiping blade is effective only during a small portion of its rotary movement, viz. only when the wiping blade contacts the printing head. With the construction known from the above- mentioned publication, the longitudinal direction of the printing head should be parallel to the axis of rotation of the wiping blade, so that the wiping direction of the wiping blade is oriented according to the smallest dimension of the printing head, and the rotary movement of the wiping blade should be synchronized with the translatory movement of the printing heads in such a manner that in each case, the wiping blade precisely touches the passing printing head. To ensure that the wiping blade touches the entire surface of the printing head, the wiping blade should be rather high and flexible. Further, the rotating wiping blade will in each case strike the printing head, as it were, which may cause wear. With a CSS as described in EP-0.398.347, the wiping member is formed by a stationary wiping blade mounted on a support for the sealing chambers. In this case, a wiping operation is carried out by having the printing heads perform a translatory movement along the stationary wiping blade. The two known constructions have as a drawback, inter alia, that the printing heads should be laterally displaced from a printing position to a rest position, which in fact implies that the lateral dimension of the application apparatus should be greater than required for the actual printing operation. Further, such constructions can only be employed with application apparatuses provided with translation means for the printing heads.

The object of the invention is to provide a compact CSS which can also be used with application apparatuses whose printing heads do not carry out a translatory movement. To that end, the CSS according to the invention has a wiping blade which is slidably mounted on a frame portion in such a manner that during a displacement, the wiping blade moves along the front of the sealing chambers.

For the sealing of the printing heads, the sealing chambers are placed against the printing heads, with a sealing element such as a rubber ring located between each printing head and the associated sealing chamber. This prevents the printing heads from drying up. When at a later stage the sealing chambers should be removed from the printing heads to enable the printing heads to be used for a printing operation, a partial vacuum is created in the sealing chamber because of the sealing action of the sealing element. On the one hand, this uncontrolled pressure drop may cause damage to components in the printing heads, such as piezo-elements. On the other hand, it requires considerable force to overcome that partial vacuum, in particular if, for suctioning ink from the printing heads, the sealing chambers are connected via suction conduits to a suction pump. If this partial vacuum were removed by reversing the direction of the pump motor, this entails the risk that ink flows back from the suction conduits to the sealing chambers. To prevent these problems, the sealing chambers of the

CSS according to the present invention comprise aeration valves, and means are provided to ensure that these aeration valves are opened before the sealing chambers move away from the printing heads.

These and other aspects, characteristics and advantages of the present invention will be explained by the following description of a preferred embodiment of a CSS according to the invention, with reference the accompanying drawings, wherein:

Figs. 1A and IB are perspective views of a cleaning and sealing station according to the invention, from two different viewing positions;

Fig. 2 is a top plan view of the cleaning and sealing station of Fig. 1;

Fig. 3 is a section of a portion of the cleaning and sealing station according to the line A-A in Fig. 2; Fig. 4 is a perspective view of a cap unit of the cleaning and sealing station of Fig. IB, viewed from the same viewing direction as Fig. IB;

Fig. 5 is a perspective view of the cap unit, viewed from below; Fig. 6 is a top plan view of a pump unit;

Fig. 7 is a cross section of the pump unit according to the line A-A in Fig. 6; Fig. 8 is a cross section of the pump unit according to the line B-B in Fig. 6;

Fig. 9 is a cross section of a holder with a wiping member; Fig. 10 is a longitudinal section of a portion of a holder with a wiping member;

Fig. 11 diagrammatically illustrates the positional relation between a printing head system and the CSS; Figs. 12A-C illustrate the operation of the CSS; and Fig. 13 illustrates a detail of the coupling of the cap frame and CSS frame.

Figs. 1A and IB show a perspective view of a cleaning and sealing station 1, which will hereinafter also be referred to as CSS. The CSS l comprises a CSS frame 2, intended to be mounted in an application apparatus such as a printer. Mounted on the CSS frame 2 is a cap unit 100 and a pump unit 200.

The cap unit 100 comprises sealing chambers 110, intended to be brought into sealing contact with printing heads of the application apparatus. In the example shown, the cap unit 100 comprises three of such sealing chambers 110, for use with an application apparatus having three printing heads; however, it will be understood that the number of sealing chambers 110 of three may differ.

The cap unit 100 further comprises a wiping device 300. The wiping device 300 comprises an elongated holder 301 wherein an elongated wiping member 302 is mounted, manufactured from an elastic material such as rubber. The holder 301 is displaceable relative to the cap unit 100 in a direction perpendicular to its longitudinal direction, with the holder 301 moving over the sealing chambers 110 with an interspace. Preferably, the direction of movement of the holder 301 substantially corresponds to the longitudinal direction of the printing heads, and hence to the longitudinal direction of the sealing chambers 110. In the example shown, the sealing chambers 110 are accommodated to a printing apparatus having slightly inclined printing heads, for which purpose the sealing chambers 110 are also slightly inclined. The displacement of the holder 301 can be effected in different manners. In the example shown, the cap unit 100 comprises a cap frame 101 to which two guide bars 303, 304 are attached on two sides of the cap unit 100. Provided at a first end of the holder 301 is a first guide block 305 having a first through opening through which the first guide bar 303 reaches. This first guide block 305 can slide across the first guide bar 303, which can be fixed in the cap frame 101. The contour of the first through opening is accommodated to the contour of the first guide bar 303; both contours may be circular. Provided at a second end of the holder 301 is a second guide block 306 having a second circular through opening through which the second guide bar 304 reaches. The second guide bar 304 has an external screw thread, and the second opening of the second guide block 306 has a mating internal screw thread. The second guide bar 304 is rotatably mounted in the cap frame 101, and can be driven for rotation by an electromotor 307 with the interposition of a transmission system 308. Energization of the electromotor 307 brings about a rotation of the second guide bar 304, which, accordingly, acts as a screw spindle, whereby the holder 301 is displaced on account of the mating screw threads.

The holder 301 for the wiping member 302 has two extreme positions relative to the cap frame 101. A first extreme position is the rest position shown in Fig. 1A; a second extreme position is located opposite that first extreme position and is referred to as cleaning position. At these extreme positions, the holder 301 is located adjacent sidewalls 102, 103 of the cap frame 101. For a proper control of the CSS 1, it is desired that a signal be available which is representative of the position of the container 301. For this purpose, one could use two approach detectors such as microswitches, disposed adjacent the above-mentioned sidewalls 102, 103 of the cap frame 101, which approach detectors are operated by the holder 301. A problem thereof is that two of such approach detectors 102, 103, disposed adjacent the sidewalls of the cap frame 101, would occupy too much space. In a preferred embodiment of the CSS 1 according to the invention, only one position detector 310 is present, positioned under the sealing chambers 110, as is shown in the bottom view of Fig. 5. This position detector 310, a microswitch in the example shown, is operated by the holder 301 with the interposition of a hysteresis member 311. This hysteresis member 311 has a substantially U-shaped form, having a longitudinal bar 312 which forms the bottom of that U and two guide blocks 313, 314 which are disposed at the ends thereof. Provided in each of those guide blocks 313, 314 is a through hole through which the above-mentioned first guide bar 303 extends. The longitudinal bar 312 comprises a projection 315 operating the microswitch 310. The first guide block 305 of the holder 301 is located between the two guide blocks 313, 314 of the hysteresis member 311.

The operation hereof is as follows. If the holder 301 is located at an intermediate position, somewhere between the two end positions mentioned, there is no contact between the first guide block 305 of the holder 301 and the hysteresis member 311. At such an intermediate position, the motor 307 is in principle in operation, and the holder 301 is displaced towards one of the end positions. Shortly before the holder 301 reaches that end position, the first guide block 305 of the holder 301 contacts the hysteresis member 311 and the holder 301 carries that hysteresis member 311 along, causing the hysteresis member 311 to operate the microswitch 310.

In the example shown in Fig. 5, the holder 301 is in its first extreme position, the rest position, to the left in the drawing. By the first guide block 305 of the holder 301, the hysteresis member 311 is displaced leftwards relative to the first guide bar 303, and the left guide block 313 of the hysteresis member 311 abuts against.the left sidewall 102 of the cap frame 101. In this position of the hysteresis member 311, the microswitch 310 is pressed by the projection 315 of the hysteresis member 311. When the motor 307 is energized for displacing the holder 301 towards the cleaning position, i.e. rightwards in Fig. 5, then the first guide block 305 of the holder 301 is released from the left guide block 313 of the hysteresis member 311; accordingly, the hysteresis member 311 does not change position, and the microswitch 310 remains pressed. When the holder 301 reaches its cleaning position, the first guide block 305 of the holder 301 contacts the right-hand guide block 314 of the hysteresis member 311, to displace the hysteresis member 311 rightwards across the first guide bar 303 until the right guide block 314 of the hysteresis member 311 abuts against the right sidewall 103 of the cap frame 101; in this position of the hysteresis member 311, the projection 315 of the hysteresis member 311 has released the microswitch 310. The released condition of the microswitch 310 is therefore indicative of the cleaning position being reached.

Similarly, the microswitch 310 will not be pressed by the projection 315 of the hysteresis member 311 until the holder 301 has reached its rest position. Hence, the pressed condition of the microswitch 310 is indicative of the rest position being reached.

Presently, reference is made to Fig. 3. Each sealing chamber 110 has an inlet mouth ill in the top face 104 of the cap frame 101, and comprises an elastic sealing member 112, for instance made of rubber, extending around that inlet mouth ill and, in the version shown, having the form of a collar. This sealing member 112 serves to provide a hermetic seal between a printing head and the sealing chamber 110 when the sealing chamber 110 is pressed against that printing head. In each sealing chamber 110 a moisture-retaining element 113 is arranged, such as for instance a sponge, serving to provide and maintain a substantially constant relative humidity in the sealing chamber 110. Thus it is ensured that when the printing head is not used and the sealing chamber 110 is pressed against the printing head, the ink in the printing head cannot dry up.

Provided on the rear side of the sealing chamber no is a hose pillar 114. Connected to this hose pillar 114 is a flexible hose for connection with a suction pump 210, which, however, is not shown in Fig. 3 for the sake of simplicity. For each sealing chamber 110 a separate suction pump 210 is present which forms part of the pump unit 200 shown in Figs. 1A and IB, and all suction pumps 210 are driven by a shared motor 202, as will now be described in more detail with reference to Figs. 6-8.

Figs. 6-8 illustrate a preferred embodiment of a pump unit 200 having four suction pumps 210, each suction pump 210 being designed as a hose pump. Fig. 7 clearly shows that for each hose pump 210, a pump frame 201 of the pump unit 200 comprises a pump wall 211 having a contour of a cylinder segment. In the pump frame 201, a support 220 is rotatably disposed, concentrically with this cylinder segment, which support 220 supports two travelling rollers 221, 222 which are pressed outwards radially in the direction of the pump wall 211 by a spring 223. Disposed between this support 220 and this pump wall 211 is a portion of a flexible hose 212, which is for instance manufactured from rubber. An inlet end 214 and an outlet end 215 of that hose 212 project outside the pump frame 201. The inlet end 214 is connected to the suction hose pillar 114 of a sealing chamber 110, as mentioned hereinabove, and the outlet end 215 is connected to an inlet hose pillar 231 of a collecting chamber 230. Fig. 6 shows that the collecting chamber 230 has four inlet hose pillars 231 and an outlet hose pillar 232.

Where a travelling roller 221 touches the hose 212, the hose 212 is pressed shut by that travelling roller 221 against the pump wall 211. Upon clockwise rotation of the support 220, as viewed in Fig. 7, the pressed-shut portion of the hose 212 is displaced, creating a partial vacuum at the inlet end 214. Thus, during operation of the CSS 1, when the sealing chamber 110 is fitted against a printing head, ink is suctioned from the printing head, which ink is received in the collecting chamber 230 and can be discharged via the outlet hose pillar 232.

Fig. 8 shows that the pump unit 200 is of symmetrical construction with a centrally disposed pump motor 202, two supports 220, 220' being disposed on both sides of the pump motor 202 with their axes of rotation perpendicular to the axis of rotation of the pump motor 202. The pump motor 202 drives the two supports 220, 220* via a transmission system 203. Fig. 8 clearly demonstrates that in the embodiment shown, each travelling roller 221, 222 of each support 220, 220' in each case cooperates with two of the hoses 212 mentioned. Further, Fig. 8 clearly demonstrates that the travelling rollers 221, 222 of one support are shifted 90° relative to the travelling rollers 221', 222' of the other support 220*, as a result of which the load of the pump motor 202 is more uniform, so that the pump motor 202 has to develop less peak capacity.

The pump unit 200 discussed provides four individual suction pumps 210, which, it is true, are driven jointly, but which operate independently of one another. This has the significant advantage that the pump action of each individual suction pump 210 is not affected by the pump action of the other pumps. Further, if the sealing chambers 110 were suctioned by one shared pump, then, in the event of one chamber becoming clogged, the suctioning would to an increased extent be effected by the other chambers, and there would be a considerable risk that this stoppage is not drained off.

Three of the four suction hoses 212 mentioned are intended to be connected to the suction hose pillar 114 of a sealing chamber. The fourth suction hose 212 is intended to be connected to a suction hose pillar 324 for cleaning the wiping member 302, as will now be further explained with reference to Figs. 3 and 9-10. As is clearly shown in Fig. 3, the holder 301 has the shape of a trough having a substantially U- shaped cross section. More in particular, that troughed holder 301 comprises a trough bottom 331 and two raised trough walls 332, 333. Preferably, the free top ends 334, 335 of those trough walls 332, 333 are bent inwards.

The wiping member 302 provided in the holder 301 has a substantially inverted T-shaped cross section. More in particular, the wiping member 302 comprises a base 341 placed on the trough bottom 331, and a wiping blade 342 at a central portion of the base 341, disposed substantially perpendicularly to the base 341. Provided at the edges of the base 341 are upwardly extending base walls 343, 344, parallel to the wiping blade 342. Preferably, the wiping member 302 is manufactured in one piece.

By the above-mentioned form two receiving troughs 345, 346 are defined on both sides of the wiping blade 342, for receiving ink which is wiped from the printing heads by the wiping blade 342 and which flows downwards along the wiping blade 342. For discharging the ink received, the wiping member 302 is at a central location thereof provided with a discharge opening 350, as is illustrated in more detail in Figs. 9 and 10. Fig. 9 is a cross section over the center of that discharge opening 350, to.an enlarged scale, whereas Fig. 10 is a longitudinal section of a portion of the length of the wiping member 302. In these Figures it is clearly shown that for defining the above-mentioned discharge opening 350, the base 341 of the wiping member 302 directly below the wiping blade 342 is removed over a given length L. The width B of this removed base portion 351 is substantially equal to the width of the bottom side of the wiping blade 342 and can, as shown, be slightly larger, as a result of which on both sides of the wiping blade 342 two narrow slots 352, 353 are present between that wiping blade 342 and the base 341 to ensure that the connection between the wiping blade 342 and the remaining base 341 is broken. On both sides of the removed base portion 351, at the bottom side of the base 341, two recessed portions 354, 355 are provided, for instance through removal of the base 341 over a part of the thickness thereof, so that on both sides of the wiping blade 342 the base 341 defines two closing lips 347, 348 having a thickness less than the thickness of the base 341.

The holder 301 is provided with a hole 336 in the bottom thereof, which hole 336 is aligned with the above-mentioned discharge opening 350 of the wiping member 302. This hole 336 may have a round contour.

As appears in particular from Fig. 3, in the top face 104 of the cap frame 101 there is provided a suction opening 322 at a position which is aligned with the discharge opening 350 of the wiping member 302 when the holder 301 is in the second extreme position, which is the cleaning position, to the left in Fig. 3. This discharge opening 322 comprises an annular sealing member 323, preferably made of rubber, which abuts against the holder 301 when it is in the cleaning position, for providing a liquid-tight seal between the holder 301 and that suction opening 322. Provided at the bottom side of the cap frame 101 is a fourth hose pillar 324, communicating with that suction opening 322 in a liquid-tight manner. To this fourth hose pillar 324, the fourth suction hose 212 is connected, which is not shown in the Figures for the sake of simplicity.

When the holder 301 is in the cleaning position, the ink received in the receiving troughs 345, 346 can be suctioned through energization of the pump motor 202. Then, via the fourth suction hose 212, a partial vacuum is created in the space below the wiping blade 342, defined by the removed base portions 351, 354, 355, as a result of which the closing lips 347, 348 are drawn downwards, into the recessed base portions 354, 355, for enlarging the slots 352, 353 next to the wiping blade 342. The closing lips 347, 348 are easier to bend downwards according as the thickness of the closing lips 347, 348 is less. Through the enlarged slots 352, 353, the ink flows from the receiving troughs 345, 346 to the suction opening 322 in order to be suctioned out.

Presently, the operation of the CSS 1 according to the present invention will be further described, with reference to Figs. 11 and 12A-C. Fig. 11 diagra matically shows a portion of an application apparatus, such as a printer, with the CSS 1 and a system of printing heads 400. The system of printing heads 400 is pivotable about a pivot 401 which is perpendicular to the plane of the drawing. In an operating position shown in dotted lines, the system of printing heads 400 is ready for printing on a recording medium 402 such as a band of paper, also indicated in dotted lines in Fig. ll, and the direction of movement of the band of paper is perpendicular to the plane of the drawing. When the system of printing heads 400 is not used any longer, the system is pivoted from the operating position into a parking position indicated in full lines in Fig. 11, which pivotal movement is indicated by the arrow PI in Fig. ll. in that parking position, the main surfaces 403 of the printing heads 400 are located opposite and parallel to the top face 104 of the cap frame 101 of the CSS 1.

Relative to a machine frame of the application apparatus (not shown) , the CSS 1 is linearly displaceable in a direction perpendicular to the top face 104 of the cap frame 101, as is indicated by the arrow P2, permitting the sealing chambers 110 to be brought into a position where they seal the respective printing heads 400. Fig. IB shows that for that purpose, the CSS frame 2 comprises guide supports 3 having guide openings 4 for engagement with guide rods, not shown, of the above- mentioned machine frame of the application apparatus. Further, the CSS frame 2 comprises an engagement eye 5, with which an operating hook controlled by a control member of the application apparatus can engage, as will be understood by a person skilled in the art. Alternatively, the CSS frame 2 may for instance be displaced by means of a screw spindle for which purpose at least some of the guide openings may then have an internal screw thread, while, if necessary, a separate operating motor may be present for rotation of that spindle. Fig. 12A shows the CSS 1 in a first operating position, which can be referred to as the press-on position, wherein the sealing chambers 110 are pressed against the respective printing heads 400. For simplicity's sake, in Figs. 12A-C only the contours of the printing heads 400 are shown, and details of the printing heads 400 are left out. As mentioned before, in this press-on position, each combination of a sealing chamber 110 with associated printing head 400 is hermetically sealed from the outside world by the sealing member 112 located therebetween. Optionally, ink is suctioned from the printing heads 400, as a result of which a partial vacuum already prevails in each sealing chamber no. In accordance with the invention, each sealing chamber 110 comprises an aeration valve 120 for aerating the sealing chambers 110 when the CSS 1 is being uncoupled from the printing heads 400, in such a manner that the aeration valves 120 are opened before the sealing chambers 110 are displaced, as will be further explained.

Fig. 12B shows the CSS 1 in a second operating position, which can be referred to as the wiping position. In this position, the distance S3 between the top face 104 of the CSS 1 and the front face of the printing heads 400 is such that the wiping motor 307 can be operated for displacing the holder 301 with the wiping member 302, with the wiping blade 342 wiping clean the main surfaces 403 of the printing heads 400. During this wiping operation, the holder 301 moves from its first extreme position (rest position) to its second extreme position (cleaning position) .

Fig. 12C shows the CSS 1 in a third operating position, which can be referred to as rest position. In this position, the distance S4 between the CSS 1 and the printing heads 400 is thus large that the pinting heads 400 can pivot towards the printing position (the position indicated in dotted lines in Fig. 11) . The holder 301 has reached its cleaning position, and the ink removed from the printing heads 400 by the wiping blade 342 can be suctioned through energization of the pump motor 202. The suctioning operation of this ink removed by the wiping blade 342 is completed within a relatively short period, for instance approximately 3 seconds. After this ink has been suctioned, the holder 301 is returned into its rest position (to the right in Fig. 3) , and the CSS 1 remains in its rest position.

It is observed that for suctioning the ink removed from the printing heads 400 by the wiping blade 342, it is not necessary that the CSS l has reached its rest position; this suctioning operation can already take place when the holder 301 has reached its cleaning position while the CSS l is still in the wiping position.

It is further observed that in practice it is necessary to blow printing heads through, with ink being blown from the channels of the printing heads, which ink is to be received by the sealing chambers, as is known per se. The means for effecting the blow-through operation are also known per se, so that a detailed description thereof can be omitted. However, to avoid contamination of the application apparatus, it is desired that during the blow-through operation, the distance between the printing heads and the sealing chambers is small. The device according to the present invention has as an advantage that in the wiping position, this distance S3 is relatively small (approximately 4 mm) , so that in this wiping position, the blow-through operation can be carried out as well.

Presently, the operation of the aeration valves 120 will be described in more detail, with reference to Fig. 3 and

Fig. 12A. As is shown in Fig. 12A, as well as in Fig. IB, the cap frame 101 is not rigidly fixed relative to the CSS frame 2, but there is a freedom of movement in the direction of the arrow P2 in Fig. 11. Arranged between the cap frame 101 and the CSS frame 2 are spring means 140, pushing the cap frame 101 away from the CSS frame 2. In the embodiment shown, these spring means 140 are constructed as spiral-shaped helical springs, which are positioned around supporting posts 141, which are fixed relative to the CSS frame 2 and which, in the pres-on position illustrated in Fig. 12A, also act as a stop for the cap frame 101. The freedom of movement of the cap frame 101 in the direction away from the CSS frame 2 is limited by hook-shaped coupling members 142 which are mounted on the CSS frame 2 and whose hook-shaped ends 143 cooperate with counter-coupling members 144 mounted on the cap frame 101. Those counter- coupling members 144 may also have a hook shape, as is shown in the diagrammatic, detailed view of Fig. 13; those counter- coupling members 144 may also be defined by an opening in the cap frame 101. Further, it is possible that the coupling members 142 and the counter-coupling members 144 have changed positions. Within the framework of the present invention, it is of essential importance that the press-on position, wherein the cap fame 101 is pressed against the stop of the CSS frame, a first play Si is present between the coupling members 142 of the CSS frame 2 and the counter-coupling members 144 of the cap frame 101. A value that proved to be suitable for this play is approximately 0.8 mm.

The aeration valve 120 comprises an aeration channel 121 in the cap frame 101, a first end of which debouches at the top face 104 of the cap frame 101, next to the sealing chamber 110 but within the portion surrounded by the sealing member 112, and a second end of which communicates with the free atmosphere. At that second end, a seat 122 is formed for a sealing plug 123, which may have an at least partly spherical shape, and which is mounted on an operating rod 124. Preferably, the operating rod 124 and the spherical sealing plug 123 are manufactured in one piece. A support 125 is attached to the cap frame 101 in any suitable manner, for instance through clamping or screwing. A first end of a compression spring 126 presses against this support 125, the other end of which presses against the spherical sealing plug 123 to press it against the above-mentioned seat 122, as a result of which the valve 120 is closed.

The operating rod 124 is substantially directed according to the direction of displacement of the CSS 1 as indicated in Fig. 11 by the arrow P2. At the end of the operating rod 124 remote from the spherical sealing plug 123, an operating grip 127 is mounted, for instance through clamping, in the exanple shown, the operating grip 127 has the shape of a cylinder having a diameter larger than the diameter of the operating rod 124, and comprises resilient wings 128. The operating rod 124 reaches through an opening 129 in a portion 130 of the CSS frame 2, which opening 129 is sufficiently large to let through the operating grip 127 during assembly of the cap frame 101 on the CSS frame 2, in which case the resilient wings 128 are depressed radially. After the passage of the operating grip 127, the resilient wings 128 have sprung outwards again to catch behind the portion 130 of the CSS frame 2. To ensure a proper sealing of the valve 120, a second play S2 is present between (the wings 128 of) the operating grip 127 and the portion 130 of the CSS frame 2, preferably in the press-on position, wherein the cap frame 101 is pressed against the stop 141 of the CSS frame 2. within the framework of the present invention, it is of essential importance that this second play S2 is less than the first splay Si between the coupling members 142, 144 of the CSS frame 2 and the cap frame 101. A value that proved to be suitable for this second play is approximately 0.3 mm.

In the press-on position shown in Fig. 12A, the CSS frame 2 is pressed completely upwards, and the cap frame 101 is pressed upwards against the printing heads 400 by the stop 141, with the sealing members 112 tightly abutting against the front face 403 of the printing heads 400. By the compression spring 126, the spherical sealing plug 123 of each aeration valve 120 is pressed against the associated seat 122, so that each aeration valve 120 is closed. Consequently, each sealing chamber 110 is hermetically sealed from the outside world. As mentioned hereinabove, after the ink has been suctioned from the printing heads 400, a partial vacuum may prevail in each sealing chamber 110. When the CSS frame 2 is moved downwards (through engagement with the engagement eye 5) , the cap frame 10l initially stays in position, while the cap frame 101 remains pressed against the front face 403 of the printing heads 400 by the springs 140. During this initial stage of the downwards displacement of the CSS frame 2, the aearation valve 120 remains closed. When the CSS frame 2 has been moved downwards through a distance corresponding to the above-mentioned second play S2, the operating grip 127 of each aeration valve 120 will, upon further downwars displacement, be carried along by the frame portion 130, causing the spherical sealing head 123 to come off the seat 122. Because this second play S2 is smaller than the first play SI, the cap frame 101 stays in position also during this second stage of the downwards displacement of the CSS frame 2, and the cap frame 101 still remains pressed against the front face 403 of the printing heads 400 by the springs 140. As the aeration valves 120 are now opened, the sealing chambers 110 are in open communication with the free atmosphere, so that a partial vacuum, if any, in the sealing chambers 110 is removed and an increase of the distance between the sealing chambers 110 and the printing heads 400 does not cause a pressure drop.

When the CSS frame 2 is then moved downwards through a distance corresponding to the first play SI, the cap frame 101 will, upon further downwards displacement of the CSS frame 2, be taken along by the interlocking coupling members 142, 144. Thus it is ensured that the downwards movement of the cap frame 101 with the sealing chambers 110 is not hindered by the partial vacuum in the sealing chambers 110, and that damage to the printing heads by decrease of pressure is prevented.

in a particular embodiment of the CSS according to the present invention, a cover screen for the sealing chambers is provided, to protect the sealing chambers against possible contamination by dust particles when the CSS is in the operating position illustrated in Fig. 12C, i.e. when the application apparatus is in operation for printing. Such a cover screen can advantageously be rolled up on a reel which is disposed next to the first sidewall 102 of the cap frame 101, with an axis of rotation of that reel directed parallel to the longitudinal direction of the holder 301, and the free end of that cover screen being attached to that holder 301, as a result of which that cover screen is automatically provided over the sealing chambers 110 when the holder 301 moves from its rest position towards its cleaning position.

It will be appreciated by anyone skilled in the art that it is possible to change or modify the embodiment shown of the device according to the invention, without departing from the inventive concept or the scope of protection. For instance, it is possible that the number of sealing chambers differs from three, and that, accordingly, the number of suction pumps will be adapted thereto.

Further, it is possible that the projection 315 of the hysteresis member 311 is replaced by a recess for operating a position detector.

Claims

1. A cleaning and sealing station (CSS) (1) for a printing head (400) of a printing apparatus, comprising: a cap unit (100) provided with at least one sealing chamber (110) ; means (112) for establishing a sealing contact between a sealing chamber (110) and a printing head (400) ; and a wiping device (300) for cleaning a main surface (403) of each printing head (400) ; characterized in that: the wiping device (300) comprises a holder (301) slidably mounted relative to the cap unit (100) , having mounted therein a wiping member (302) , in such a manner that during a displacement, the wiping member (302) moves along the front of the sealing chamber (110) .

2. A cleaning and sealing station according to claim l, wherein the holder (301) is displaceable transversely to its longitudinal direction.

3. A cleaning and sealing station according to claim 2, wherein two guide bars (303, 304) are mounted on both sides of a cap frame (101) of the cap unit (100) ; and wherein the holder (301) is at its ends provided with guide blocks (305, 306) having through openings, adapted for displacement along said guide bars (303, 304).

4. A cleaning and sealing station according to claim 3, wherein a guide bar (304) is designed as a screw spindle.

5. A cleaning and sealing station according to any one of the preceding claims, wherein the holder (301) has a substantially U-shaped cross section, the wiping member (302) having a substantially inverted T-shaped cross section with a base (341) , a wiping blade (342) substantially perpendicular thereto, and upwardly extending walls (343, 344) at the edges of the base (341), so that two receiving troughs (345, 346) for ink are defined between the wiping blade (342) and said walls (343, 344).

6. A cleaning and sealing station according to claim 5, wherein the wiping member (302) is at a central location thereof provided with a discharge opening (350) corresponding with a hole (336) in the bottom of the holder (301) .

7. A cleaning and sealing station according to claim 6, wherein said discharge opening (350) is defined by a removed base portion (351) under the wiping blade (342) , and two recessed base portions (354, 355) on both sides of said removed base portion (351) for defining two closing lips (347, 348) next to the wiping blade (342) , whilst between the wiping blade (342) and the closing lips (347, 348) respective slots (352, 353) are located.

8. A cleaning and sealing station according to claim 6 or 7, wherein the cap unit (100) is provided with a suction opening (322) connected to a suction pump (210) , the position of said suction opening (322) being chosen so that said hole (336) in the bottom of the holder (301) communicates with said suction opening (322) when the holder (301) is located at a cleaning position.

9. A cleaning and sealing station according to any one of the preceding claims, comprising one position detector (310) and a hysteresis member (311) for detecting a position of the holder (301) .

10. A cleaning and sealing station according to claim 9, wherein the hysteresis member (311) comprises: a longitudinal bar (312) and two guide blocks (313, 314) at the ends thereof, said guide blocks (313, 314) engaging the first guide bar (303) adjacent the ends thereof, the first guide block (305) of the holder (301) being located beween said guide blocks (313, 314), and the hysteresis member (311) further comprising a portion (315) which operates the position detector (310) .

11. A cleaning and sealing station according to any one of the preceding claims, wherein each sealing chamber (110) is connected to a separate suction pump (210) , said suction opening (322) being connected to a separate suction pump (210) , and all suction pumps (210) being driven by a shared motor (202) .

12. A cleaning and sealing station according to claim 11, wherein the suction pumps (210) are designed as hose pumps, at least two supports (220, 220') being rotatably disposed in a pump frame (201), each support (220; 220*) supporting two travelling rollers (221, 222; 221', 222') which press a flexible hose (212) shut against a pump wall (211) , and the travelling rollers (221, 222) of one support (220) being shifted 90° relative to the travelling rollers (221', 222') of the other support (220').

13. A cleaning and sealing station, preferably according to any one of claims 1-12, wherein guide means (3, 4, 5) are provided for displacing the CSS (1) in a direction (P2) perpendicular to the top face (104) of the cap unit (100) , the sealing chambers (110) comprising aeration valves (120) , and means being provided to ensure that the aeration valves (120) are opened before the sealing chambers (110) move away from the printing heads (400) .

14. A cleaning and sealing station according to claim 13, wherein the cap unit (100) comprises a cap frame (101) which is slidable relative to the CSS frame (2) in the direction of displacement (P2) of the CSS (1) and which is biased by spring means (140) in the direction of displacement (P2) of the CSS (1) ; wherein each aeration valve (120) comprises a sealing plug (123) for sealing an aeration channel (121) , said sealing plug (123) being mounted on an operating rod (124) which further comprises an operating grip (127) capable of cooperating with a portion (130) of the CSS frame (2) , whilst between said operating grip (127) and said portion (130) of the CSS frame (2) a second play (S2) is present when said cap frame (101) is pressed, against the action of said spring means (140) , against a stop (141) of the CSS frame (2) ; wherein the the CSS frame (2) comprises coupling members (142,

143) capable of engaging coupling members (144) of the cap frame (101), whilst between said coupling members (142, 143;

144) a first play (SI) is present when said cap frame (101) is pressed, against the action of said spring means (140) , against a stop (141) of the CSS frame (2) ; and wherein the first play (SI) is greater than the second play (S2) .

15. A cleaning and sealing station according to any one of the preceding claims, comprising a cover screen for the sealing chambers, said cover screen being rolled up on a reel, the free end of the cover screen being attached to the holder (301) .

16. An application apparatus such as a printer, comprising a system of printing heads (400) which are pivotable about a pivot (401) between an operating position intended for printing and a parking position in which the main surfaces (403) of the printing heads (400) are substantially horizontally directed, and further comprising a CSS (1) according to any one of the preceding claims.