EP0754556A2

EP0754556A2 - Liquid container

Info

Publication number: EP0754556A2
Application number: EP96111558A
Authority: EP
Inventors: John Adrian Bostock
Original assignee: Willett International Ltd
Current assignee: Willett International Ltd
Priority date: 1995-07-20
Filing date: 1996-07-18
Publication date: 1997-01-22
Also published as: GB9514899D0; EP0754556A3

Abstract

The present invention relates to a reservoir container containing a first fluid, for example an ink, under pressure and adapted to feed that fluid to the ink flow system of an ink jet printer via a valved outlet to the container, characterised in that:

a. the container comprises a first compartment defined by a collapsible envelope located within a second compartment defined by an external pressure retaining envelope;
b. the collapsible envelope contains a said first fluid, notably an ink, to be dispensed through the said valved outlet of the reservoir container and suitable for use in the ink flow system of an ink jet printer;
b. the external pressure retaining envelope contains a pressurising fluid medium under pressure and acting upon the collapsible envelope to urge the collapsible envelope into its collapsed configuration so as to eject the first fluid through the said valved outlet.

The invention also provides an ink jet printer, characterised in that at least part of the ink or other fluid required for the operation of the printer is provided by a first fluid under pressure in a reservoir container of the invention.

The invention further provides a reservoir container of the invention mounted upon a support member, the support member having pressure regulation means for regulating the pressure at which the said first fluid is discharged to the ink flow system.

Description

The present invention relates to a container and its use, notably to a pressurised container for an ink and its use in an ink jet printer.

BACKGROUND TO THE INVENTION:

Ink jet printers apply ink or other printing medium to a substrate by ejecting discrete individual droplets to a desired location on the substrate. In one form of printer, the droplets are ejected individually from one or more nozzle orifices arranged in an array so as to deposit individual droplets from the nozzles onto the substrate, and variations of this form of printer are known as a drop on demand or impulse jet printers. In another form of ink jet printer, a jet of ink is ejected from the nozzle and this is then broken up into the individual droplets which are electrically charged and guided to the desired location on the substrate by an electrical deflection field, and this form of printer is known as a continuous jet printer. The present invention can be applied to either form of ink jet printer.
In both types of ink jet printer, ink is fed under pressure to a nozzle orifice. Typically, this pressure is generated by a pump circulating the ink through an ink flow system or by pressurising the reservoir from which the ink is supplied to the ink flow system. However, this requires the provision of pressurising or circulating pumps and means for controlling the pressure generated so that a consistent flow of ink through the nozzle orifice is achieved. This adds cost and complexity to an ink jet printer. It has also been proposed to apply air under pressure to the head space above the ink in a sealed reservoir. However, such pressurization of the ink or make up solvent reservoir can cause aeration of the ink or solvent which is undesirable.
In order to reduce the cost and complexity of the printer, it has been proposed to hold the ink in a flexible bladder which is surrounded by a distended rubber or similar sleeve. The sleeve seeks to collapse the bladder and hence applies pressure to the ink. However, the form of the bladder and sleeve have to be designed carefully to ensure that the sleeve collapses the bladder uniformly and does not cause necking of the bladder, trapping at least part of the ink within the bladder and preventing its discharge. Problems are also encountered in maintaining a substantially uniform discharge pressure as the bladder collapses.
We have now devised a form of ink reservoir which can be pressurised so as to provide a pressurised source of ink for an ink jet printer and which reduces the above problems. The invention also provides a self contained pressurised reservoir for the ink which enables replenishment of the ink in an ink jet printer to be achieved merely by replacing an empty container with a fresh container. Since the container retains its contents and pressure when removed from the printer, the invention can also find use where a print run is interrupted to replace one colour ink with another. The invention can also be applied to reservoirs for other fluids which are to be fed to the ink jet printer, for example flushing fluids or make up solvents. The term fluid is therefore used herein to denote any fluid which is to be fed to the ink flow system of an ink jet printer.

SUMMARY OF THE INVENTION:

Accordingly, the present invention provides a reservoir container containing a first fluid, for example an ink, under pressure and adapted to feed that fluid to the ink flow system of an ink jet printer via a valved outlet to the container, characterised in that:

The invention also provides an ink jet printer, characterised in that at least part of the ink or other fluid required for the operation of the printer is provided by a first fluid under pressure in a reservoir container of the invention.
The invention further provides a reservoir container of the invention mounted upon a support member, the support member having:

a. mounting means which engage the reservoir container and retain and locate the reservoir container upon the support member;
b. actuating means engaging with and actuating the outlet valve of the reservoir container so as to cause discharge of the said first fluid under pressure from the said first compartment of the container; and
c. pressure regulation means in flow connection with the outlet valve of the reservoir container and adapted to be in flow connection with the ink flow system of an ink jet printer, the regulation means regulating the pressure at which the said first fluid is discharged to the ink flow system.

Preferably, the reservoir container of the invention is provided as a generally cylindrical outer vessel, typically a metal or similar can, having a valved outlet crimped or otherwise secured in a wall, typically one transverse end wall, of the vessel. The collapsible envelope within the outer vessel is preferably a bladder type container which can be collapsed radially and/or axially to eject the ink or other fluid from the bladder. However, other forms of collapsible envelope can be used. For example, at least part of the wall defining the collapsible envelope can be of a bellows construction so that the collapsible envelope collapses axially as the concertina folds of the bellows side walls are collapsed. Alternatively, the collapsible envelope can be provided by a diaphragm wall which is distended as ink or other fluid is initially fed into the first compartment defined by this diaphragm wall so as to form a tensioned bladder containing the said fluid.
Such collapsible envelopes operate by reducing the volume of the first compartment to eject the fluid from the compartment. A further alternative of the collapsible envelope is provided by a piston member journalled for axial sliding movement within a generally cylindrical bore, the piston defining a wall separating the first and pressurised compartments of the reservoir container. The piston reduces the internal volume of the first compartment as it moves within the cylinder.
It will be appreciated that in some of the above forms of the collapsible envelope for the said first fluid, the envelope applies pressure to the first fluid due to the stretching of one or more of the walls defining the collapsible envelope. However, it is preferred that this pressure be minimal and that the pressure acting on the fluid in the first compartment be derived predominantly from the fluid under pressure in the second compartment of the reservoir container. It is therefore preferred that the collapsible envelope be provided by a bladder made from a natural or synthetic rubber or other flexible fluid impervious material, the bladder having a relaxed volume which corresponds substantially to the volume of fluid which it is desired that the reservoir should hold when initially charged with the first fluid.
For convenience, the invention will be described hereinafter in terms of the use of such a bladder, which can be of spherical, cylindrical or any other suitable shape according to the shape of the external pressure retaining envelope within which it is mounted.
The bladder has an outlet which is in fluid flow connection to the valved outlet of the reservoir container. Typically, the bladder will have an open ended neck extending therefrom and the open end of this neck is secured to the valved outlet, for example by being crimped to the valve assembly or to the reservoir container end wall assembly carrying the outlet valve.
The bladder is mounted within an outer pressure retaining envelope. As stated above, this is preferably a conventional cylindrical can of the type used in the production of pressurised dispensers commonly known as aerosol dispensers. The bladder can be mounted by any suitable means within the can so that it is in flow communication with the valved outlet to the can but is isolated from the external pressurised envelope around the collapsible envelope. It is preferred that the bladder be mounted so that it is positioned radially symmetrically within the can so that the bladder will collapse substantially uniformly as its contents are discharged. It is particularly preferred to secure the open end of the neck of the bladder to or around the valve mechanism located in a transverse end wall of the container. For example, the open end of the neck of the bladder can be crimped between components of the valve assembly or between the valve assembly and the end wall of the can though which the valve assembly is mounted.
The valved outlet to the container can be of any suitable type. However, it is preferred to mount the valve mechanism in or upon a transverse end wall of the container and that the valve mechanism is a spring loaded mechanism which is depressed axially with respect to the container so as to actuate the mechanism. Such valve mechanisms are commercially available for use as the valved outlets for pressurised dispensing devices, for example those used to control the release of fluids from cans containing liquefied gaseous propellants.
Thus, in a preferred embodiment, the reservoir container comprises an inner collapsible first compartment defined by a bladder wall, optionally also by part of the internal walls of the container; and a second compartment defined by the bladder wall and the walls of the container and separated from said first compartment by said bladder wall; and a valved outlet to the said first compartment, said valved outlet being mounted in a transverse end wall of the container. Such two compartment containers are available commercially for other purposes and can be used as such in the present invention.
The first compartment of the reservoir container of the invention is charged with a predetermined volume of the ink or other first fluid which is to be fed to the ink flow system of the printer. The predetermined volume may be that required to fill the bladder to its relaxed but fully deployed configuration or may only partially fill the bladder. Typically, the ink will fill the bladder to at least 50% of its relaxed but fully deployed configuration. The ink can be of any type used in an ink jet printer. Thus, it can be a solution of a dyestuff in an aqueous or solvent based carrier medium or can be a dispersion of a pigment in a liquid carrier medium. Typically, the ink will be one which forms a visible image on the substrate to which it is to be applied. However, the ink may contain ingredients which are not normally visible to the human eye but which fluoresce under UV, IR or other radiation. It is also within the scope of the present invention for the ink to contain ingredients which are detected by other means, for example electromagnetically. Furthermore, the invention can also be applied to a reservoir container for the supply of make up solvent or carrier to the ink flow system to make up losses of such solvent or carrier from the system due to evaporation. The term ink is therefore used herein to denote any fluid composition which is to be fed to the flow system of the ink jet printer and includes inks comprising a material which can be detected visually or by a machine reader using optical, florescent, electromagnetic or other means in a liquid carrier medium and the liquid carrier medium for such a composition or flushing compositions which are to be fed to the ink flow system to cleanse the system.
For convenience, the invention will be described hereinafter in terms of an ink containing a visible dyestuff or pigment dissolved or dispersed in an aqueous or solvent carrier medium. Such inks can be of conventional composition as used in an ink jet printer.
The reservoir container of the invention has a fluid under pressure within the second compartment surrounding the collapsible first compartment. This fluid can be a liquefied propellant gas, for example a CFC, propane or butane, which vaporises within the second compartment to apply pressure substantially uniformly upon the exposed wall of the bladder. However, such a liquefied propellant applies a substantially constant pressure which is determined by the composition of the gas and cannot readily be varied. It is therefore preferred that the fluid under pressure be a compressed gas, notably compressed air.
The bladder may be filled with different volumes of ink, for example 500cls for one reservoir, but only 250 cls for another. The bladder may therefore be in a fully or partially deployed configuration initially. The volume of gas under pressure fed to the second compartment of the reservoir container of the invention can therefore be adjusted to compensate for such variations in the initial configuration of the bladder and the pressure at which the gas is held within the second compartment can readily be adjusted to suit the pressure regulator and the ink pressure required in the ink flow system of the printer, which cannot readily be done when a liquefied propellant is used.
For convenience, the invention will be described hereinafter in terms of the use of a pressurised gas in the second compartment.
The pressurised gas can be fed to the second compartment of the reservoir container by any suitable means. For example, there can be an aperture in either end wall of the can and the gas is fed under pressure through that aperture into the space between the bladder wall and the internal face of the can wall. The filling can be done in a pressurised environment so that the aperture can be sealed, for example by applying a molten metal or other sealant to the aperture, before the can is removed from the pressurised environment. Alternatively, the aperture can have a one way valve which automatically closes when the pressurised gas feed is removed. In a further alternative, the outlet valve assembly for the container can be spring loaded so that it will move axially away from the end wall of the can or the housing of the valve assembly to create a passage between the external environment and the space between the bladder and the can wall through which pressurised gas can flow into that space. Release of the external gas pressure will allow the valve assembly to reseat in its housing to close the passage and thus trap the pressurised gas within the second compartment.
The second compartment can be pressurised during manufacture of the container. However, this will result in a container which requires a consistent charge of the first fluid when the container is replenished. It is therefore preferred to supply the container with the second chamber initially at ambient pressure and to pressurise it to the desired extent to suit the charge of first fluid to the first compartment. If desired, pressurising fluid may be fed to the second chamber during discharge of the first fluid from the first container, for example through the valved inlet to the second compartment to which gas or fluid under pressure is fed from an external source, so as to maintain a substantially uniform pressure within the second compartment at all times. However, we have found that the variation of pressure within the second compartment as the first fluid is discharged from the first compartment does not materially affect the performance of the ink jet printer and is acceptable, so that there is no need to top up the pressure within the second compartment.
The valve outlet to the first compartment can be of the conventional design as used in an aerosol can. As stated above the valve outlet is in fluid flow communication with the first compartment, the bladder, so that it regulates the discharge of ink from the bladder. Thus, the valve assembly preferably has the outlet neck of the bladder secured to or around it as described above. The outlet from the first compartment need not be valved where some alternative form of valve mechanism is provided elsewhere in the flow path of ink from the bladder to the ink system of the printer, for example at the pressure regulator described below. However, for convenience, the invention will be described hereinafter in terms of the use of a conventional valved outlet to the can which communicates directly with the first compartment of the reservoir container. Such a valve mechanism typically comprises an outlet tube which is depressed against a spring bias to actuate the valve.
Such methods for charging the bladder and the second compartment of the can are similar to those used in the filling and pressurisation of two compartment aerosol cans, except that the pressurising fluid in the container of the invention can be fed at any desired pressure having regard to the initial charge of first fluid in the collapsible envelope. In a conventional two compartment aerosol can, the pressurising fluid is fed to the second compartment during manufacture of the can and the volume and pressure of the pressurising fluid cannot thereafter be varied. In the preferred forms of the container of the invention, the pressurising fluid can be fed to or released from the second compartment so as to adjust the pressure applied to the first fluid.
Typically, the desired volume of ink is charged to the bladder at or about ambient pressure and temperature and the pressurised gas is fed to the second compartment at a pressure of from 5 to 15 bar, typically about 7.5 to 10 bar until the internal pressure in the bladder equates to the applied pressure. If desired, the initial pressure in the second compartment can then be reduced to a lower level, for example to a level of about 5 bar. This is closer to that required in the operation of some forms of ink jet printer and yet provides sufficient pressure within the bladder to ensure that substantially all of the ink in the bladder is discharged at a pressure sufficiently high to inject the ink into the ink flow system of the printer. By pressurising the second compartment after the ink has been charged to the first compartment any partial filling of the first compartment is automatically compensated for.
The charged reservoir container of the invention provides a simple and effective means for storing, transporting and handling ink with minimal risk of contamination or loss of the ink. Furthermore, the exterior of the container can be colour coded or otherwise marked to identify the type and volume of ink within the bladder.
The reservoir container of the invention is connected to the ink flow system of an ink jet printer to provide a source of ink under pressure to the printer. However, the pressure under which the ink is held in the bladder may exceed the pressure desired within the ink flow system of the printer. It is therefore usually required to incorporate a pressure regulator in the flow path between the bladder and the ink flow system so as to reduce the pressure of the ink to between 0.5 and 5 bar. This can be achieved using any conventional fluid pressure regulator, preferably with a filter, typically mesh or ceramic frit filter with a mesh or pore size of less than 30 micrometres, to remove undesirable contaminants from the ink.
As indicated above, it is preferred to combine the filter and pressure regulator with a support for the reservoir container of the invention to provide a unitary ink pressure system for the printer. Typically, the support member comprises a cup or the like into which the outlet end of the container is a sliding fit. The container will usually have one or more annular crimped joints connecting the valve assembly to the transverse end wall of the container and connecting the end wall of the container to the body of the container, as with a conventional aerosol can. Such annular crimped joints will provide an annular recess or bead which can be used to locate and retain the container in the support member. Preferably, the support member will have a co-operating continuous or interrupted circumferential rib, which is a snap fit into the annular recess of the crimper joint. If desired, the container can be retained in the support member by mutually engaging components which secured the container in position. Thus, the container can carry a screw thread upon its end which engages a corresponding screw thread in the support member; or the container can be secured by a bayonet type fastening. It may be preferred to provide the screw threaded member carried by the container as a sleeve which is retained upon the container by the crimped joint securing the valve mechanism to the end wall of the container, and to provide the sleeve with a hexagon, knurled or other shaped outer surface whereby the sleeve can be engaged with and screwed tight upon a male screwed spigot extending from the support member. It may also be preferred to provide the engaging portions of the means for securing the container to the support member with uniquely configured inter-engaging portions so that only a container presenting the correct portions can be secured to the support member.
The support member will also comprise means which actuate the valved outlet to the first compartment of the container when the container is mounted fully home in the support member. As stated above, the valve outlet mechanism usually comprises an outlet tube which is depressed to open the valve. The support member typically will have a member which engages this outlet tube and depresses it as the container is mounted upon the support member. Preferably, such an actuating member comprises a tube which registers axially with the outlet tube of the valve mechanism and carries a radial flange or other projection which bears against the outlet tube to move it axially. Preferably, such a tube has a closed end which seats into the bore of the outlet tube, the closed end having a plurality of apertures in it which allow ink to flow from the outlet tube into the actuating tube. The actuating tube is in flow communication via the pressure regulator to the ink flow system of the printer.
Preferably, the pressure regulator is mounted upon the support member to form with the container of the invention a unitary assembly which can be substituted for the ink reservoir and pressurising pumps in an ink jet printer. Such an assembly can be incorporated into a printer during construction thereof or as a retro-fit assembly in an existing printer. The assembly can be incorporated into the ink flow system of the printer at any suitable point in the ink flow path. However, it will usually be preferred that the assembly replace the existing ink reservoir in a conventional design of printer.
In use, a container of the invention is inserted into the support member, for example a cup shaped recess in the support member, and is mounted fully home so that the outlet valve to the can is actuated and pressurised ink is fed through the pressure regulator to the ink flow system of the printer. If desired, the container and the support member can have uniquely inter-engaging components, for example axial splines and corresponding axial recesses into which the splines engage, so that a support cup will only accept given containers. This will reduce the risk that an incorrect container, for example one containing a solvent as opposed to an ink, is inserted into that support cup. The invention thus provides a simple and effective means for providing ink under pressure in known amounts to an ink jet printer without the need for pumps or other ink pressurising means in the printer. By providing the ink in sealed containers which are opened to the ink system of the printer only when mounted fully home in the support member, problems of spillage and contamination are reduced. The reservoir containers of the invention can be designed so that they can be re-used, thus further reducing the overall cost of operation of the printer.

DESCRIPTION OF THE DRAWINGS:

The invention will now be illustrated by reference to a preferred form thereof as shown in diagrammatic axial cross-section of a container of the invention in the accompanying drawing.

DESCRIPTION OF THE PREFERRED EMBODIMENT:

The container of the invention comprises a metal or similar generally cylindrical can 1 having its open end closed by a transverse wall 2 secured thereto by a crimp around its periphery which forms the radially projecting annular rim 3. Substantially centrally on wall 2 is mounted a valve mechanism shown diagrammatically as 4. The valve mechanism passes through an aperture in wall 2 and is secured in position by a crimp connection between the rim of the aperture and a radial flange carried by the valve mechanism. This crimp forms the radially projecting annular rim 5.
Valve mechanism 4 has an axially projecting outlet tube 6 through which the contents of a bladder 7 mounted within can 1 are discharged upon depression of the outlet tube 6 axially with respect to the valve mechanism 4. There is a space 8 within can 1 between the inner face of the can wall and the outer face of the bladder 7.
Such a can construction is commercially available and may be used in its commercially available form in the present invention.
The bladder is charged with an ink composition through valve outlet tube 6 in the conventional manner for filling such a can. The space 8 is charged with sufficient compressed air to apply the desired pressure to the bladder 7. The compressed air can be fed through an aperture 10 in either the end wall 2 as shown or through an aperture in the domed other end wall of the can. The aperture can incorporate a one way valve, for example a simple internal flap valve, or the whole container can be held in a pressurised environment during pressurisation of the space 8 so that the aperture 10 can be sealed, for example by a blob of molten metal or solder once the space 8 has been pressurised. However, where the can is to be re-used, it will usually be desired to provide space 8 with a valved inlet so that the volume and pressure of the gas in space 8 can be varied to accommodate different fluids and/or amounts of fluids in the bladder 7.
The pressure in space 8 applies a pressure to the contents of bladder 7 and causes the bladder to collapse as the contents of the bladder are discharged through outlet tube 6.
The can is mounted in a support cup 20 which serves to support the can and to locate the outlet tube 6 upon a discharge tube 21. Tube 21 is dimensioned or has radial projections so that tube 6 is engaged by tube 21 and axially depressed as can 1 is pushed fully home into cup 20. This actuates the valve mechanism and allows ink to discharge from bladder 7. If desired, the free end of tube 21 can have radially directed orifices to aid flow of ink from tube 6 into tube 21. Cup 20 is provided with one or more radial projections which engage either or both of rims 3 or 5 in a snap fit to locate and retain can 1 within the cup 20. These projections can be provided by a split ring 22 or any other suitable means. If desired, these projections and rim 5 can be formed with uniquely inter-engaging parts so that one the correct container can be mounted in cup 20, thus reducing the risk that the incorrect container can be used, for example to prevent a solvent top up can from being mounted in a support cup connected to an ink line of the printer.
The tube 21 connects with a pressure regulator shown diagrammatically as 30 which reduces the pressure in the ink from say 10 bar in the bladder to the pressure required in the ink flow system of the printer, typically about 0.5 to 5 bar. Ink passing through the pressure regulator is preferably filtered using fine mesh filter, not shown. The ink at reduced pressure issues from regulator outlet 31 and enters the ink flow system of the printer (not shown) at any suitable point.
The can 1 can readily be detached from cup 20 when the can is empty or it is desired to exchange one colour of ink for another. As the can is withdrawn from cup 20, valve outlet tube 6 is allowed to move axially and thus close off the flow of ink through the valve mechanism 4. The container can then be handled and stored without loss of its contents until required again.

Claims

A reservoir container containing a first fluid under pressure and adapted to feed that fluid to the ink flow system of an ink jet printer via a valved outlet to the container, characterised in that:
a. the container comprises a first compartment defined by a collapsible envelope located within a second compartment defined by an external pressure retaining envelope;

b. the collapsible envelope contains a said first fluid to be dispensed through the said valved outlet of the reservoir container and suitable for use in the ink flow system of an ink jet printer;

b. the external pressure retaining envelope contains a pressurising fluid medium under pressure and acting upon the collapsible envelope to urge the envelope into its collapsed configuration so as to eject the first fluid through the said valved outlet.
An ink jet printer, characterised in that at least part of the ink or other fluid required for the operatidn of the printer is provided by a first fluid under pressure in a reservoir container as claimed in claim 1.
A reservoir container as claimed in claim 1, mounted upon a support member, characterised in that the support member comprises:
a. mounting means which engage the reservoir container and retain and locate the reservoir container upon the support member;

b. actuating means engaging with and actuating the outlet valve of the reservoir container so as to cause discharge of the said first fluid under pressure from the said first compartment of the container; and

c. pressure regulation means in flow connection with the outlet valve of the reservoir container and adapted to be in flow connection with the ink flow system of an ink jet printer, the regulation means regulating the pressure at which the said first fluid is discharged to the ink flow system.
A reservoir container or ink jet printer as claimed in any one of claims 1 to 3, characterised in that said first fluid is selected from an ink composition, a solvent or carrier medium for an ink or a flushing fluid.
A reservoir container of ink jet printer as claimed in any one of the preceding claims, characterised in that the collapsible envelope is provided by a bladder or membrane.
A reservoir or ink jet printer as claimed in any one of the preceding claims, characterised in that the said second compartment in provided with an inlet whereby pressurising fluid can be fed to or removed from said second compartment so as to accommodate different amounts of said first fluid in said first compartment.
A reservoir or ink jet printer as claimed in any one of the preceding claims, characterised in that the carries one component of a pair of inter-engaging components whereby the container is secured in a support member for mounting on an ink jet printer ink flow system.
A reservoir or ink jet printer as claimed in any one of the preceding claims, characterised in that the reservoir container comprises an inner collapsible first compartment defined by a bladder wall, optionally also by part of the internal walls of the container; and a second compartment defined by the bladder wall and the walls of the container and separated from said first compartment by said bladder wall; and a valved outlet to the said first compartment, said valved outlet being mounted in a transverse end wall of the container.
A reservoir or ink jet printer as claimed in any one of the preceding claims, characterised in that:
a. the reservoir container comprises a generally cylindrical rigid outer vessel having a valved outlet crimped or otherwise secured in a transverse end wall thereof; and

b. the collapsible envelope within the outer vessel is a bladder type container which can be collapsed radially and/or axially to eject the ink or other first fluid from the first compartment defined by said bladder and which has a relaxed capacity to contain the desired amount of the ink or other first fluid.
A reservoir or ink jet printer as claimed in any one of the preceding claims, characterised in that the pressure within said second compartment is from 5 to 15 bar.