Printing – Stenciling – Traveling-inker machines
Reexamination Certificate
2001-12-06
2003-09-02
Evanisko, Leslie J. (Department: 2854)
Printing
Stenciling
Traveling-inker machines
C101S114000
Reexamination Certificate
active
06612231
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general to a squeegee for use in a screen printing, and also to a squeegee device equipped with the squeegee.
2. Discussion of Related Art
In an operation with a screen printing machine, a print material is provided to be put on a surface of a mask screen which has print holes or apertures and which is placed on an object such as a board for providing a printed circuit board. A plate-like squeegee is slidably moved on the surface of the mask screen while the squeegee is held by a squeegee holding device in a forward tilted or inclined posture, i.e., in such a manner that the squeegee is inclined such that a distal free end portion of the squeegee is positioned on a rear side of a proximal end portion of the squeegee as viewed in a printing direction in which the squeegee is moved relative to the mask screen. With the sliding movement of the squeegee on the surface of the mask screen, the surface of the mask screen is wiped by the squeegee, namely, the print material arranged substantially in a line on the mask screen is carried or raked by the squeegee, so as to be forced or squeezed into the print apertures of the mask screen. The squeegee is commonly made of a rubber material having a high degree of elastic deformability which permits the squeegee to be held in close contact with the mask screen during the sliding movement, without separation of the squeegee from the mask screen even if a force acts on the squeegee in a direction away from the mask screen, so that the print material is reliably raked by the squeegee. That is, the rubber-made squeegee is held in close contact with the mask screen owing to the elastic deformation in its entirety, particularly, in its free distal end portion. Even in presence of the force acting on the squeegee in the direction away from the mask screen, the distal end portion of the squeegee is not separated from the mask screen, since the acting force causes simply a reduction in amount of the elastic deformation of the squeegee. However, the distal end portion of such a rubber-made squeegee having a high degree of elastic deformability tends to enter or bite into the apertures of the mask screen, so that the print material once received in the apertures is likely to be forced out of the apertures. Thus, the use of the rubber-made squeegee is likely to cause a problem that a sufficient amount of the print material is not printed on a print surface of the object, or a problem that the print material printed on the print surface of the object is not formed into a pattern corresponding to arrangement of the apertures.
The rubber-made squeegee may be replaced with a squeegee made of a metallic material which is more rigid or harder than a rubber material, for avoiding entrance or biting of a local part of the distal end portion of the squeegee into the apertures of the mask screen, so as to prevent the print material received in the apertures from being forced out of the apertures. Thus, owing to the use of the metallic squeegee, a desired amount of the print material is printed on the print surface of the object, and the print material printed on the print surface is accordingly formed into a desired pattern. However, the metallic squeegee is likely to be displaced in a direction away from the mask screen by a reaction force of the mask screen, so as to be easily separated from the mask screen. Due to the separation of the squeegee from the mask screen, the surface of the mask screen is not sufficiently wiped by the squeegee, so that some of the print material is left behind the squeegee, without being raked by the squeegee. While the above-described rubber-made squeegee can be elastically deformed particularly in its local portion, i.e., the distal end portion in which the squeegee is held in contact with mask screen, the metallic squeegee can not be locally deformed although the metallic squeegee has some degree of flexibility so as to be brought into contact with the mask screen with being somewhat bent in its entirety. Therefore, if a force acts on the metallic squeegee in a direction away from the mask screen, the metallic squeegee is undesirably separated from the mask screen, unlike the rubber-made squeegee which maintains its close contact with the mask screen owing to the sufficient amount of the elastic deformation of its distal end portion.
For solving the drawback indicated above, it is considered possible, for example, to adapt the squeegee to be slidably moved on the surface of the mask screen while the squeegee is held by the squeegee holding device in a rearward tilted or inclined posture, i.e., in such a manner that the distal end portion of the squeegee is positioned on a forward side of the proximal end portion of the squeegee as viewed in the printing direction in which the squeegee is moved relative to the mask screen. In this arrangement in which the distal end portion of the squeegee is constantly forced onto the mask screen during the sliding movement of the squeegee relative to the mask screen, the squeegee can be held in close contact with the mask screen even where the squeegee is made of a metallic material or other hard material. That is, in this arrangement, the metallic squeegee is not separated from the mask screen even when a reaction force is applied to the metallic squeegee from the mask screen, so that the metallic squeegee exhibits a satisfactory performance of raking the print material from the surface of the mask screen. Further, even in this arrangement in which the distal end portion of the squeegee is constantly forced onto the mask screen, the metallic squeegee which has a higher degree of hardness than the rubber-made squeegee does not allow considerable deformation of a local part of its distal end portion, and accordingly does not enter or bite into the apertures of the mask screen, whereby the print material once received in the apertures is prevented from being forced out of the apertures, leading to stable distribution of a sufficient amount of the print material into each of the apertures, and the consequently stable printing of the print material on the print surface of the object.
It is possible to adapt the squeegee to be elastically deformed in its entirety to be convexed toward the mask screen so as to be held in close contact at a larger area of its distal end portion with the mask screen, by increasing the degree of elastic deformability of the squeegee, for example, with an increase in the width of the squeegee, i.e., with an increase in the dimension of the squeegee in the printing direction. However, if the width of the squeegee is increased, the print material is likely to be mounted on the squeegee during the sliding movement of the squeegee on the surface of the mask screen. The print material mounted on the squeegee is eventually solidified without being received into the print apertures of the mask screen, thereby possibly producing a defectively printed product. That is, if the solidified print material is dropped from the squeegee onto unsolidified print material remaining on the mask screen, the solidified print material is mixed with the unsolidified print material, and the mixture is then forced into the apertures of the mask screen. The apertures are inevitably clogged with the mixture including the solidified print material, so that the print material is not allowed to be passed through the apertures so as to be printed on the object. This problem is encountered also in an arrangement in which the print material is accommodated in a space between a pair of squeegees such that the accommodated print material is moved together with the pair of squeegees while being raked by one of the squeegees which takes a rearward inclined posture.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a squeegee or squeegee device which is capable of efficiently raking a print material from a surface of a mask screen with minimized risk of biting of a distal end portion of the sque
Adachi Jun
Mizuno Manabu
Shimizu Toshinori
Tsuda Mamoru
Evanisko Leslie J.
Fuji Machine Mfg. Co. Ltd.
Oliff & Berridg,e PLC
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