Printing – Stenciling – Processes
Reexamination Certificate
2000-03-21
2001-07-10
Yan, Ren (Department: 2854)
Printing
Stenciling
Processes
C101S115000
Reexamination Certificate
active
06257137
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to improvements in operating multi color screen printing machines of the type where the substrate to be printed travels sequentially from one printing or curing station to the next.
BACKGROUND TO THE INVENTION
Screen printed garments are usually printed on rotary or oval multi print head machines in which the garments mounted on pallets are moved about the periphery of the machine where there are a series of print heads, curing stations and a load and an unload station. Patents relating to these machines include U.S. Pat. Nos. 4,407,195, 4,934,263, 5,154,119. Machines vary in size up to 20 stations which means there are up to 18 printing or curing heads plus the load and unload station. The operator sets up each print station with the appropriate screen, color and print settings before the garments are loaded. Usually the garments are printed in all the colors required and cured in one revolution of the machine.
Because of the complexity of the machine operation computer based control has become common. U.S. Pat. Nos. 5,483,881 and 5,678,482 are typical examples of the control systems employed.
In some cases the printed colors need to be cured before the next color is applied. Machines may not have sufficient print stations to accommodate all the curing and printing steps required. This problem has been overcome by carrying out the printing operation in more than one revolution of the machine. The machine is loaded with garments and in the first revolution all the garments are printed at certain heads only the time between the printing heads allowing the ink to cure. On the next revolution printing occurs at another set of heads and as many as 8 or 9 revolutions may be required to print the garments.
U.S. Pat. No. 5,595,113 is one attempt to provide a central programmed controller to assist the operator in carrying out this multi revolution printing sequence. The controller is programmed to select a printing station in a particular revolution, to index a garment to the selected print station, to determine whether the item is present at the print station and when the printing operation is complete. The controller stores the print head settings for each revolution in different buffers in the memory. In order to program the controller it is necessary to sequentially enter the revolution number, whether a head is active or inactive, whether it is a flash or print head and whether the print has one or two passes. Each pallet holding a garment is tracked by the controller and each station counts from the beginning of each revolution until the count equals the number of garments. This can be a cumbersome program. If an error is made in setting out the entire sequence the program must be deleted and re-entered. The controller senses the end of the operation by checking if there are any active heads in the next cycle and if not, the present revolution is the last. This is indicated to the operator by an alarm when the final revolution is half over so that the operator can commence unloading. A problem with this type of operation is that all the garments must be loaded before the printing sequence can begin and all the garments must be unloaded before the next sequence can begin. This makes the multi revolution printing process much more time consuming and costly.
It is an object of this invention to simplify the control program for multi revolution printing and to reduce the time taken for entering and a program and operating the machine, to improve productivity.
BRIEF DESCRIPTION OF THE INVENTION
To this end the present invention provides a method of controlling a multi-printhead screen printing machine where a plurality of pallets, adapted to carry a garment, sequentially move from a load station past each print head, which may be a print station, flash station or inactive, to an unload station, which includes the steps of
a) loading at least one pallet with a garment
b) identifying the first garment loaded at the load station as garment number 1
c) setting at least one print head into active mode
d) providing functional settings to said active printhead
e) moving said pallets until garment number 1 arrives at the first active printhead
f) setting a counter on said first active print head to a value of y where y is the number of garments to be loaded on the machine
g) carrying out the functions set at said first active printhead
h) moving said pallet with said garment number 1 to the next printhead and changing the counter on said first active head to y−1
i) continuing the sequence e) to h) for each active print head as the pallets move from one print head to another until the counter value at each active print head is zero
j) changing to the next cycle when the pallet number 1 leaves the load station and repeating steps c) to i) for each cycle until all cycles are completed
k) and unloading the printed garments from the pallets.
Preferably step j) commences before step l) is completed so that garment number 1 commences the next cycle while the other garments finish the cycle. The advantage of this method is that unlike the prior art it avoids tracking all of the pallets and is thus more economical in its use of computing power.
It is usual with multi lap printing that all garments have to be unloaded before a new process sequence of laps [cycles] can commence. This means that with the last lap, the unloaded pallets have to pass another lap before they are reloaded with new garments.
Throughout this specification the term “print head” refers to the location on the machine at which screen printing usually occurs but which may be substituted with a flash cure or other ink curing device.
In another aspect the present invention provides a method of controlling a multi-printhead screen printing machine where a plurality of pallets, adapted to carry a garment, sequentially move in a plurality of index steps from a load station past each print head, which may function as a print or cure station, to an unload station, wherein the process of completely printing all the garments requires the garments to pass the unload station without being removed and to pass the print heads in at least one further lap, with a different set of print heads being active in each lap,
in which the process steps include
a) maintaining in a first register the total number of index steps required for each process to be completed wherein the total=(y+1)n−1 where y is the number of laps and n is the number of pallets
b) maintaining in a second register a record of the location of the first garment to leave the load station as the pallets are indexed past the printheads in a plurality of laps
c) maintaining in a third register a record of which pallets have garments
d) maintaining at each print head a counter for the garments to be printed and reducing this number by 1 with each index of a lap
e) each printhead being functional when the value in the printhead counter is greater than 0
f) the garments being loaded onto the pallets during the first lap of the process such that at the end of the first lap the first loaded garment has been treated at each active print head while the last loaded garment has not yet moved to an active printhead
g) optionally, when the first loaded garment has completed y.n−2 indexes signal means at the unload station indicates that the garment may be removed
h) after y.n indexes, the second register is reset to commence tracking the first garment of a new process sequence, and the third register is reset sequentially as new garments are loaded so that during the first lap of the new process sequence the last lap of the preceding process sequence is completed.
This has the advantage that operator idle time between process sequences is eliminated. Where the number of laps is 3 this results in a 25% increase in output over a given time period. It has been found that the most common number of laps is 3 however the number could be as great as the number of print heads on the machine eg 8 for an eight color mach
Connolly Bove & Lodge & Hutz LLP
Reefdale Proprietary Limited
Yan Ren
LandOfFree
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