Dispensing – Plural sources – compartment – containers and/or spaced jacket – With discharge assistant for each source
Reexamination Certificate
2003-09-25
2004-10-26
Bomberg, Kenneth (Department: 3754)
Dispensing
Plural sources, compartment, containers and/or spaced jacket
With discharge assistant for each source
C417S269000, C417S470000, C417S510000, C417S512000, C091S499000
Reexamination Certificate
active
06808086
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a paste ejection apparatus for ejecting slurry-like paste in which a viscous substance and a filler component are mixed, such as conductive paste.
As a method of joining electronic parts such as a semi-conductive chip to a print board or a lead frame, a resin adhesive is used much. As a kind of resin adhesive, conductive paste has been known, in which a conductive component such as metal powder is added in the resin thereby to apply conductivity to the joint. Since the conductive paste has a function of the adhesive, and also can cause the joint to conduct electrically, it is much used in order to secure a semi-conductive element onto the board and cause the semi-conductive element to conduct to an electrode of the board.
This conductive paste is obtained by mixing a main component as a resin adhesive such as epoxy resin, curing agent for curing the epoxy resin, or cure accelerator, with metal powder having conductivity. As the metal powder, silver powder is much used. The conductive paste is supplied in the shape of slurry in which silver powder having each kind of shape in order to improve the conductivity, for example, a grain-shaped silver powder or flake-shaped silver powder, is mixed with the resin adhesive.
For an applying apparatus of applying this conductive paste, an ejection apparatus for ejecting the conductive paste is provided. A plunger type ejection apparatus has been known, which sucks the conductive paste into a cylinder room and ejects it by a reciprocating movement of a plunger. Since the ejection by the reciprocating of the plunger is performed only intermittently, in case that it is necessary to perform paste applying of high efficiency by performing the ejection incessantly, a multi-plunger type paste apparatus having plural plungers is generally used, for example disclosed in JP-U-02-078773 (Japanese Utility Model Application Publication Number: Hei02-078773).
For such the multi-plunger type paste ejection apparatus, it is necessary to eject the paste ejected from the respective plungers in order from one fixed ejection port. Therefore, its ejection apparatus has aport switching function. Regarding this port switching, generally, an opening surface of a cylinder block for which a plunger hole is provided is brought into slide-contact with a fixed block for which an ejection port is provided, and the opening portion of each plunger is communicated with the ejection port in order. In this type, the slide-contacting surface between the opening surface of the cylinder block and the fixed block function as a seal portion for preventing the paste from leaking between the two members. Therefore, such paste leakage preventing measures are adopted that surface-finishing of high accuracy for this slide-contact surface in parts working in order to prevent occurrence of clearance, and use of a mechanism which applies the predetermined surface pressure at the operation time.
However, since the conductive paste is the slurry including a large amount of filler components such as silver powder and solid particles, in the conventional paste ejection apparatus, depending on constituent parts, the solid particles interposed between the slide clearance of the seal portion are easy to be attached onto the sliding surface, so that closeness of the sliding surface is hindered and it is not prevented that the paste leaks from the seal portion to the outside.
In addition, in such the paste ejection apparatus, the slurry-like liquid that is high in viscous and includes the metal powder is ejected. Therefore, since leakage of the liquid inside the ejection mechanism causes a bad operation and parts wear, the plunger sliding portion and the port switching portion require high sealing ability. However, generally to secure the high sealing ability increases sliding resistance of the plunger. Therefore, a load onto the drive mechanism which reciprocates the plunger increases, so that a large-sized drive mechanism is required. As described above, it was difficult to realize a compact paste ejection apparatus which secures the high sealing ability.
SUMMARY OF THE INVENTION
Therefore, an object of the invention is to provide a paste ejection apparatus which can prevent the paste from excessively leaking from the seal portion.
Furthermore, another object of the invention is to provide a small-sized and compact paste ejection apparatus which can secure the high sealing ability.
In accordance with the invention, there is provided a paste ejection apparatus for ejecting slurry-like paste in which a viscous substance and a filler component are mixed, comprising: a cylinder block being rotatable about a rotational axis by a rotation drive means, and contacting slidably with a seal surface of a seal member through a slide surface orthogonal to the rotational axis; plural cylinder holes provided in the direction of the rotational axis of the cylinder block and including opening portions formed at equal intervals on the same circumference of a circle having the rotational axis of the slide surface as a center; a plunger inserted into each cylinder hole; a plunger drive means reciprocating this plunger in synchronization with the rotation of said cylinder block; first and second communicating ports provided on the seal surface and communicating with the opening portions of the cylinder holes in the predetermined rotary position of the cylinder block; first and second external ports communicating respectively with the first and second communicating ports through the seal member; a housing portion located on the peripheral side of the seal surface, closed and surrounded by the seal member and the cylinder block to be a circular ring-shaped space; and a ring-shaped external seal member attached into the housing portion, including a first seal material having self-lubrication and a second seal material being rich in elasticity.
Furthermore, in the paste ejection apparatus according to the invention, the housing portion is formed by opposing an outer surface of the seal member to an inner surface extending axially from the cylinder block.
Furthermore, in the paste ejection apparatus according to the invention, the second seal material of the external seal member is fitted onto the outer surface of the seal member, and the first seal member of the external seal member slidably contacts with the inner surface of the cylinder block.
In another aspect of the invention, the housing portion is formed by opposing an inner surface extending axially from the seal member to an outer surface of cylinder block.
Furthermore, in the paste ejection apparatus according to the invention of the above aspect, the first seal member of the external seal member slidably contacts with the outer surface of the cylinder block, and the second seal material of the external seal member is fitted onto the inner surface of the seal member.
Preferably, the first seal member has a recess portion, and the second seal member is held by the recess portion of the first seal member.
In another aspect of the invention, the paste ejection apparatus comprises cylinder block being rotatable about a rotational axis by a rotation drive means, and contacting slidably with a seal surface of a seal member through a slide surface orthogonal to the rotational axis; plural cylinder holes provided in the direction of the rotational axis of the cylinder block and including opening portions formed at equal intervals on the same circumference of a circle having the rotational axis of the slide surface as a center; a plunger inserted into each cylinder hole; a plunger drive means reciprocating this plunger in synchronization with the rotation of said cylinder block; first and second communicating ports provided on the seal surface and communicating with the opening portions of the cylinder holes in the predetermined rotary position of the cylinder block; first and second external ports communicating respectively with the first and second communicating ports through the seal member; a housing p
Ozono Mitsuru
Sasaguri Shinji
Bomberg Kenneth
Pearne & Gordon LLP
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