Printing – Stenciling – Traveling-inker machines
Reexamination Certificate
2001-10-26
2004-03-02
Evanisko, Leslie J. (Department: 2854)
Printing
Stenciling
Traveling-inker machines
C101S114000, C222S080000
Reexamination Certificate
active
06698346
ABSTRACT:
This application is based on Japanese Patent Application No. 2000-332831 filed on Oct. 31, 2000, the contents of which are incorporated hereinto by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general to a screen-printing agent replenishing device, and more particularly to a device arranged to replenish a screen printer with a printing agent.
2. Discussion of Related Art
A screen printer is used, for example, to apply a printing agent such as a solder paste (solder cream) to a circuit substrate such as a printed-wiring board, by a screen printing technique. JP-A-11-227156 discloses an example of this type of screen printer, wherein a solder paste is printed onto the circuit substrate through a mesh of a printing screen or stencil while a mass of the solder paste is moved on the screen by a squeegee. When it becomes necessary to replenish the solder paste, a solder-paste replenishing device is operated to replenish the screen with a mass of the solder paste. Some type of screen printer uses a solder dispenser of closed or sealed type for accommodating a solder paste, and an extruder for extruding a mass of the solder paste from the solder dispenser to be printed on the circuit substrate. In this type of screen printer, the solder dispenser is replenished with the solder paste.
For example, the solder-paste replenishing device includes a solder-paste container for accommodating a solder paste, an extruding device for extruding the solder paste from the solder-paste container, and a moving device for moving the solder-paste container and the extruding device relative to the printing screen. When the solder paste is replenished, the solder-paste container is moved by the moving device to a position above the printing screen, and the solder paste is extruded by the extruding device from the solder-paste container, so that the extruded solder paste is fed through a delivery nozzle onto the screen or into the solder dispenser. When the extrusion of the solder paste from the extruder is terminated, a mass of the solder paste may bridge a space between the discharge open end of the delivery nozzle and the screen or the solder dispenser, or may droop down from the discharge end of the deliver nozzle.
In view of the above drawbacks, the solder-paste replenishing device used in the screen printer disclosed in the above-identified publication is provided with a solder-paste cut-off device operable to cut off the solder paste upon termination of the extrusion of the solder paste from the delivery nozzle. The cut-off device is arranged to cut-off the solder paste with a cutting gut. The cutting gut is held by a body of the cut-off device, and includes a cut-off portion extending in a diametric direction of the delivery nozzle. The solder-paste cut-off device and the solder-paste container are mounted on a vertically movable member, so that the solder-paste cut-off device can be vertically moved with the vertically movable member toward and away from the printing screen. The vertically movable member is moved by the above-indicated moving device, so that the solder-paste cut-off device can be moved in a plane parallel to the screen. The solder-paste cut-off device is mounted on the vertically movable member such that the cut-off device is movable by a drive device, relative to the solder-paste container in two mutually perpendicular directions that are parallel to the axis of the delivery nozzle and the direction of extension of the cut-off portion of the cutting gut, respectively. With movements of the solder-paste cut-off device by the drive device relative to the solder-paste container, the cut-off portion of the cutting gut can be positioned such that the cut-off portion extends at right angles with respect to a mass of the solder paste as delivered from the delivery nozzle, and such that the cut-off portion is located slightly below the discharge open end of the delivery nozzle.
However, there are various problems encountered when the solder paste is cut off. For instance, the problems includes a need of moving the solder-paste cut-off device relative to the delivery nozzle of the solder-paste container, for cutting off the solder paste, with a result of increased complexity of the solder-paste replenishing device. Another problem is difficulty of the cutting gut to cut off the solder paste due to the operating position of the gut which is only slightly spaced from the discharge open end of the delivery nozzle. This difficulty results in possible contamination of the open end face of the delivery nozzle and the adjacent components with the solder paste. Namely, a piece of the solder paste adhering to the cutting gut may be transferred onto the open end face of the delivery nozzle. Where the screen printer uses a solder paste which is relatively hard to be cut off, the components near the discharge open end of the delivery nozzle are likely to be contaminated with a piece of the solder paste not completely cut-off.
A further problem is a need of adjustment of a distance between the cut-off portion of the cutting gut and the discharge open end of the delivery nozzle, with a result of an increased time required for the adjustment and inspection of the distance. In addition, replenishment of the solder dispenser with the solder paste and replacement of the broken cutting gut with a new one may require removal of at least one of the solder-paste container and the solder-paste cut-off device from the vertically movable member. In this instance, the above-indicated distance must be re-adjusted, and this re-adjustment is time-consuming and cumbersome.
It is also noted that the solder-paste container is mounted with its delivery nozzle extending downwards, so that the solder paste droop downwards from the discharge end of the delivery nozzle due to its own weight when the container waits for the replenishment of the solder paste. The solder paste drooping from the delivery nozzle may drop down off the delivery nozzle, resulting in wasting of the solder paste.
While the problems where a solder paste is used as a printing agent for a screen printer have been described, similar problems are encountered where a screen printer is provided with a printing-agent replenishing device for replenishing a container with other printing agents: such as a soldering aid in the form of a paste which does not include a solder and is applied to a circuit substrate, in order to facilitate a soldering operation on the circuit substrate; and an adhesive agent used for bonding electric components (typically, electronic components) to a circuit substrate. Further, similar problems are encountered where a screen printer is provided with a printing-agent replenishing device for replenishing a dispenser or other printing-agent replenishment object with a printing agent to be applied to an object other than circuit substrates such as a printed-wiring board.
SUMMARY OF THE INVENTION
The present invention was made in view of the background art discussed above. It is therefore an object of the present invention to provide a printing-agent replenishing device which includes a replenisher having a container for accommodating a printing agent and a delivery nozzle at one end of the container and operable to deliver the printing agent from the delivery nozzle for replenishing a printing-agent replenishment object in a screen printer, and which does not suffer from at least one of the above-described problems, that is, structural complexity, contamination with the printing agent upon cutting-off of the printing agent, requirement for cumbersome adjustment of the relative position of the printing-agent container and the printing-agent cut-off device, and drooping of the printing agent. The above object may be achieved according to any one of the following modes of the present invention, each of which is numbered like the appended claims and depends from the other mode or modes, where appropriate, to indicate and clarify possible combinations of elements or technical features. It
Adachi Jun
Mizuno Manabu
Shimizu Toshinori
Evanisko Leslie J.
Fuji Machine Mfg. Co. Ltd.
Oliff & Berridg,e PLC
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