Coating apparatus – Control means responsive to a randomly occurring sensed...
Reexamination Certificate
2001-12-10
2004-05-18
Crispino, Richard (Department: 1734)
Coating apparatus
Control means responsive to a randomly occurring sensed...
C118S315000, C118S323000, C118S683000, C222S413000, C222S061000, C222S146200, C222S373000, C222S399000, C239S130000, C239S139000, C239S337000, C239S373000, C239S135000
Reexamination Certificate
active
06736900
ABSTRACT:
This application is based on Japanese Patent Application No. 2000-379103 filed on Dec. 13, 2000 and No. 2001-001983 filed on Jan. 9, 2001, the contents of which are incorporated hereinto by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a highly-viscous-fluid applying apparatus for applying a highly viscous fluid to an object, and more particularly to a technique for controlling an amount of the fluid to be applied to the object.
2. Discussion of Related Art
JP-B2-2863475 discloses an example of a highly-viscous-fluid applying or applying apparatus in the form of an adhesive applying apparatus arranged to apply a highly viscous fluid in the form of an adhesive agent to a circuit substrate in the form of a printed-wiring board. In this adhesive applying apparatus, the adhesive agent is accommodated in a syringe, and is extruded from the syringe with a compressed air introduced into the syringe, so that a suitable amount of the adhesive agent is applied to predetermined fluid-applying spots on the printed-wiring board. The amount of delivery of the adhesive agent from the syringe can be changed by adjusting the time of introduction of the compressed air into the syringe or the pressure of the compressed air. In view of this fact, the fluid applying apparatus disclosed in the above-identified publication is arranged to operate an image-taking device to taken an image of a mass of adhesive agent applied to the printed-wiring board, obtain an amount of the applied adhesive agent, on the basis of image data representative of the image, compare the obtained amount with a reference value, and adjust the time of introduction or pressure of the compressed air. If the obtained amount of the applied adhesive agent is smaller than the reference value by more than a predetermined amount, the time of introduction or pressure of the compressed air is increased. If the amount of the applied adhesive agent is larger than the reference value by more than a predetermined amount, the time of introduction or pressure of the compressed air is reduced. Thus, the amount of the adhesive agent to be delivered from the syringe to the printed-wiring board is suitably controlled.
Since the air is compressible, however, it is difficult to accurately control the amount of delivery of the adhesive agent by adjusting the time of introduction or pressure of the compressed air. Namely, the amount of delivery of the adhesive agent from the syringe does not change accurately in proportion with an amount of change of the time of introduction or pressure of the compressed air, due to compression of the compressed air. The difficulty to control the amount of delivery of the adhesive agent from the syringe increases with a decrease in the amount of the adhesive agent left in the syringe and a consequent increase in the amount of the compressed air in the syringe.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a highly-viscous-fluid applying apparatus, which permits an accurate control of the amount of delivery of the adhesive agent. This 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 is to be understood that the present invention is not limited to the technical features or any combinations thereof which will be described for illustrative purpose only. It is to be further understood that a plurality of elements or features included in any one of the following modes of the invention are not necessarily provided all together, and that the invention may be embodied without some of the elements or features described with respect to the same mode.
(1) A highly-viscous-fluid applying apparatus comprising:
a fluid supply device operable to supply a highly viscous fluid;
a delivery nozzle from which the highly viscous fluid is delivered;
a pump disposed between the fluid supply device and the delivery nozzle, and operable to feed the highly viscous fluid received from the fluid supply device, to the delivery nozzle;
and a pump control device operable to control the pump, for controlling an amount of delivery of the highly viscous fluid to be delivered from the delivery nozzle.
The highly viscous fluid to be delivered from the present delivery nozzle of the highly-viscous-fluid applying apparatus may be an adhesive agent, or a solder paste or cream. The pump may be a screw pump or a gear pump.
The highly viscous fluid supplied from the fluid supply device is fed by the pump to the delivery nozzle, from which the fluid is delivered onto an object. The amount of the highly viscous fluid to be fed from the pump to the delivery nozzle is substantially proportional to the operating amount of the pump, without an influence of the compressibility of compressed air conventionally used to feed the fluid. Accordingly, the amount of the fluid to be delivered from the delivery nozzle can be accurately controlled by controlling the pump with the pump control device.
(2) A highly-viscous-fluid applying apparatus according to the above mode (1), wherein the pump is a screw pump including a pump housing having a screw chamber having a circular shape in transverse cross section, the screw pump further including a screw which is substantially fluid-tightly disposed within the pump housing such that the screw and the pump housing are rotatable relative to each other, the pump control device including a pump drive device operable to rotate the pump housing and the screw relative to each other.
With the relative rotation of the pump housing and the screw, the highly viscous fluid is fed from the screw chamber and delivered through the delivery nozzle. Since the fluid has a relatively high degree of viscosity, the relative rotation of the pump housing and the screw will cause the fluid to be fed along a helical thread of the screw. The screw is substantially fluid-tightly disposed within the screw chamber, so that the fluid is substantially prevented from flowing in the reverse direction through a gap between the screw and the inner circumferential surface of the pump housing which defines the screw chamber. Accordingly, the amount of the fluid to be fed in the forward direction from the screw chamber toward the delivery nozzle is substantially proportional to the angle of relative rotation of the pump housing and the screw. By controlling the angle of the relative rotation, therefore, the amount of delivery of the fluid from the delivery nozzle can be controlled with high accuracy. Further, the diameter of the screw pump may be easily made relatively small, so that the screw pump can be disposed relatively near the delivery nozzle.
(3) A highly-viscous-fluid applying apparatus according to the above mode (2), wherein the pump housing is stationary, while the screw is rotated within the pump housing, by the pump drive device.
(4) A highly-viscous-fluid applying apparatus according to the above mode (2), wherein the screw is stationary, while the pump housing is rotated about the screw, by the pump drive device.
(5) A highly-viscous-fluid applying apparatus according to any one of the above modes (2)-(4), wherein the delivery nozzle extends from one end of the screw pump, coaxially with the screw pump.
In the above mode (5), the highly viscous fluid is fed by the screw pump in its axial direction to the delivery nozzle, and is delivered from the delivery nozzle in the same axial direction. Since the direction of feeding of the fluid is not changed, the fluid does not suffer from a flow resistance due to the change of the feeding direction, permitting an easy, smooth movement of the fluid from the screw pump to the delivery nozzle, so that the amount of delivery of the fluid from the delivery nozzle onto the object can be controlled with high accuracy.
(6) A highly-viscous-fluid applying apparatus according to any one of th
Isogai Takeyoshi
Katsumi Hiroshi
Yamasaki Toshihiko
Crispino Richard
Fuji Machine Mfg. Co. Ltd.
Lazor Michelle Acevedo
Oliff & Berridg,e PLC
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