DISPENSING APPARATUSThis invention relates to dispensing apparatus especially, but not exclusively, for use in association with transfer printing apparatus employing thermoplastic printing inks.
In the ceramic industry articles of ceramic ware are commonly decorated by producing an image of a pattern to be applied to the ware on an engraved printing plate. Printing ink is spread over the surface of the plate, wiped off the raised portions by a doctor blade so as to remain only in the recessed portions defining the pattern and then transferred by a flexible transfer member from the plate to the surface of the ware to be decorated.
The printing inks employed in such processes are thermoplastic in nature and the temperature of the printing plate, the transfer member and the ware are controlled in order that the ink adheres to the transfer member and releases from the plate at the first stage of the operation and adheres to the ware and releases from the transfer member at the second stage. Accurate temperature control of the thermoplastic printing ink is accordingly crucial to effective operation of such systems.
It is also necessary periodically to replenish the ink supplied to the plate in order to ensure sufficient ink remains to fill the engraved portions of the plate and maintain the integrity of colour and consistency of the pattern transferred to the ware. Hitherto this has required supplies of printing ink to be maintained in heated cabinets remote from the printing machine itself and to be transferred manually to the machine and applied to the printing plate when replenishment is necessary. This is a time consuming and cumbersome task and it is an object of the present invention to obviate or mitigate this disadvantage.
According to one aspect of the invention there is provided dispensing apparatus for thermoplastic printing ink comprising a container for ink, means enabling the container to be mounted on a transfer printing machine adjacent to a printing plate to be inked, means for controlling ink temperature and means for delivering measured quantities of ink from the container to the printing plate.
The invention also provides a transfer printing machine incorporating a printing plate, a dispenser mounted adjacent the printing plate and incorporating a container for printing ink, means for controlling ink temperature and means for delivering measured quantities of ink from the container to the printing plate.
Preferably said means for delivering measured quantities of ink includes a delivery pipe extending between the container and the printing plate.
Preferably also said means for controlling ink temperature includes heater means associated with said delivery pipe.
Said means for controlling ink temperature preferably also includes electrically-operated heating means in surface contact with said container. The heater means associated with said delivery pipe preferably comprises electrically-operated cable means extending along and in contact with said pipe.
Preferably said means for delivering measured quantities of ink comprises a dispensing unit including a chamber communicating with the interior of said container and with a dispensing outlet connected to said delivery pipe, piston means movable through said chamber to dispense the contents thereof through said outlet, and control means operable to actuate said piston means when a further supply of ink is required at the printing plate. Said piston means is preferably operated by compressed air.
An embodiment of the invention will now be described, by way of example only, with reference to the accompanying diagrammatic drawings, in which:Fig. 1 is a vertical cross-section through one form of dispensing unit according to the invention mounted on a transfer printing machine; andFig. 2 is a plan view of the unit shown in Fig. 1.
Referring to the drawings, the dispensing unit is detachably mounted on a transfer printing machine incorporating an engraved printing plate 4 from which an image is picked up by a printing member (not shown) and transferred to an article of ware to be decorated. The dispensing unit is mounted on the printing machine by means of upright support members 5 adapted at their lower ends for attachment to a convenient location on the printing machine. A generally horizontal base member or platform 6 is mounted on the support members 5 by means of collars 7 and may be clamped at different vertical positions on the support members by adjustable clamping means (not shown).
An electrically-operated heating unit 8 is supported by feet 9 on the base plate 6 and surrounds the lower portion of a hopper 10. The heater and hopper are vertically adjustably mounted on the support members 5 by adjustable clamp means 11. The upper portion of the hopper 10 projects above the heater casing 8 and incorporates a chute 12 by means of which a supply of printing ink may be introduced into the hopper. The heating unit incorporates a control panel 13 by means of which the hopper 10 may be maintained at a predetermined temperature and the printing ink contained therein at a desired consistency.
A delivery unit 15 extends centrally through the hopper 10 and comprises a chamber 16 located towards the lower end of the hopper 10. A tubular member 17 defining a cylinder extends upwardly from the top of the chamber 16 and a piston 18 is slidably mounted in the cylinder 17 to define a ram member. The upper end of the piston 18 is connected to an air cylinder 19 mounted on a generally horizontal bracket 5A detachably connected to the upper ends of the support members 5 by a threaded fastener 5B. The lower end of the chamber 16 is connected through an outlet passage 20 and releasable coupling members 21 to a delivery pipe 22 through which the contents of the chamber 16 can be dispensed into a reservoir (not shown) forming part of the printing plate 4. A pair of diametrically opposed apertures 25 are provided at the lower end of the cylinder 17 to enable ink contained in the hopper 10 to flow into the chamber 16.
The delivery pipe 22 is heated by means of an electric heater cable 23 wound around the outer surface of the pipe. The heating unit 8 and heater cable thus maintain the desired degree of fluidity of the printing ink throughout the system between the hopper 10 and the outlet end of the delivery pipe 22 through which the ink is deposited on the printing plate.
In operation of the device, printing ink of the appropriate colour and composition is previously mixed and inserted into the hopper 10 by way of the chute 12.
The ink flows through the openings 25 into the chamber 16 and the unit is primed by successive operations of the piston 18 until the outlet 20 and pipe 22 are filled with ink which is retained therein by virtue of the viscosity of the ink composition. The heating unit 8 and the heater cable 23 maintain the ink at the required temperature and consistency both in the hopper 10 and delivery pipe 22. The temperature is controlled such that the ink is not sufficiently fluid to flow through the pipe 22 of its own accord, but flows when subjected to pressure from the piston 18. The apparatus remains in this condition until delivery of ink to the printing plate 4 is required.
When a further supply of printing ink is required at the printing plate, the operator actuates control means to energise the air cylinder 19. The piston 18 is thus moved downwards as viewed in Fig. 1 of the drawings and ejects a measured quantity of ink corresponding to the volume of the chamber 16 through the outlet end of the pipe 22 into the reservoir incorporated in the printing plate 4. When the piston reaches the bottom of chamber 16 the cylinder 19 is reversed to withdraw the piston upwardly clear of the apertures 25. Additional printing ink then flows from the hopper 10 through the apertures 25 into the chamber 16 to restore the apparatus to its original condition ready for subsequent operation.
Ink delivered to the printing plate is spread over the plate by a squeegee and cleaned off by a doctor blade in known manner during each subsequent printing operation and printing continues until the operator assesses that further ink is required, whereupon the dispensing unit is actuated once again to effect a further delivery. The hopper 10 may be of any convenient size but may advantageously have a capacity of, for example, 200 ml, sufficient for several hours normal operation.
The unit may be readily dismantled for cleaning purposes to enable it to be used to dispense ink of a different colour. The delivery pipe 22 may be detached by disconnecting one or other of the couplings 21 and the heater cable 23. The pipe may be cleaned if required but will generally be stored uncleaned for subsequent re-use to dispense the same colour of ink.
The fastener 5B may then be released to enable the bracket 5A to be detached from the support members 5.
The lower end of the hopper 10 and delivery unit 15 may then be released by unscrewing a clamping nut 10A, thereby enabling the hopper and delivery unit to be lifted upwardly and removed for cleaning purposes.
After re-assembly and fitting of a new outlet pipe 22, the unit is ready for re-use with ink of a different colour.
By virtue of the arrangement described, the ink supply is contained at the printing machine itself and the operator can arrange for re-inking without leaving the machine. There is also a substantial saving in time and convenience compared with arrangements employed hitherto. The apparatus is of generally simple construction and as such is not liable to malfunctioning. Moreover in the event a problem were to arise the unit may be readily removed from the machine and replaced by a similar unit while repairs are attended to.
Various modifications may be made without departing from the invention. For example, the container or chamber in which the printing ink is contained may take a number of forms, alternative heating means may be employed and the delivery unit may be of different construction provided only it is arranged to dispense measured quantities of printing ink to the printing plate when required. If desired the outlet pipe may be movably mounted to enable ink to be deposited at different locations on the printing plate.
The unit may also be adjustable to enable the quantity of ink delivered at each operation of the unit to be varied if desired. The apparatus may also be hydraulically rather than pneumatically operated and could be used to deliver ink or other thermoplastic material to other forms of printing apparatus or to apparatus other than printing apparatus if desired.
Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/o shown in the drawings whether or not particular emphasis has been placed thereon.