1. Field of the Invention
The present invention relates to a dry washing device to wash an object by dispersing a cleanser to collide with the object, an object holder used in the dry washing device, and an anti-cleanser dispersing element set in the object holder.
2. Description of the Related Art
To manufacture print circuit boards, in soldering process with a flow soldering tank, a masking jig is often used for masking an area of a board other than that to be soldered. Such a masking jig is a plate with openings called dip palette or flow palette. It is necessary to periodically wash the surfaces of the jig to remove fluxes accumulated thereon in a repeated use, which decrease masking accuracy.
To remove fluxes or adhesives from an object such as jig, the top and bottom surfaces of the object is washed with an injected solvent in a tank, rinsed with water to remove the solvent, and dried with warm air. However, washing the object with a solvent by a washing machine not only uses a large amount of solvent but also consumes a large amount of energy for the disposal of liquid waste containing the fluxes and the drying process. This increases manufacturing costs and brings a large load on the environment.
To deal with the problem, a dry washing machine is available which blasts off a solid, light-weight, dispersive cleanser in a washing tank at a high speed, allows the cleanser to continuously contact or collide with an object, and separates attached matters on the object without using a solvent. This dry washing machine can effectively clean the object with a small amount of solvent by circulating the cleanser in the washing tank to repeatedly collide with the object. Especially, by use of a cleanser of a thin flexible plate-like shape, it can exert cleaning performance with a less amount of cleanser as much as that of ultrasonic cleaning.
For example, Japanese Patent No. 4531841 discloses a washing device having a downsized washing tank which can efficiently wash an object with uneven surfaces with a dispersed cleanser by placing the object outside the washing tank and sliding it relative to the opening of the tank. This device can prevent the cleanser from leaking to outside the tank and properly return it to the tank area so that it can maintain the number of cleanser particles to collide with the object and exert good, stable cleaning performance.
Specifically, referring to FIG. 15, this device comprises a semi-cylindrical washing tank 6 with an opening 6a and an object holder 3. The holder 3 holding a flow palette 4 is set on the opening 6a of the tank. It also includes a pool portion 19 on the side of the opening in which the cleanser is accumulated. While the holder 3 is holding the object 4, the pool portion is moved in horizontal direction in the drawing. A cleanser 5 is a thin resin plate but is represented by circles in the drawing for better understanding.
An acceleration nozzle 11 is provided on the center of the bottom of the washing tank 6 to inject air streams to disperse the cleanser 5 and remove the fluxes from the object 4. The cleanser is absorbed into a suction duct 18 connected with a not-shown suction unit, returned to the washing tank 6 and used again. Further, the cleanser 5 which has lost motion energy and has been accumulated in the pool portion 19 is returned to the washing tank by a scraper 26 provided on the bottom surface of the object holder 3.
The object holder 3 is a plate longer than the object 4 and includes at the center a concave portion 23 in a form in conformity with the shape of the object 4. The concave portion 23 is made from an elastic material such as polyurethane rubber or foamed resin and the object 4 is pressed into the concave portion 23 and held by friction. The object holder is configured to tightly hold the object with no gap to prevent the cleanser from clogging and not to leak the air streams. This aims to prevent the cleanser accelerated by compressed air from scattering from the openings of the flow palette and maintain the cleaning performance of the washing tank.
Referring to FIG. 16, a description is made on how to set the object 4 in the opening of the washing tank. The object 4 is pressed into the concave portion 23 of the holder 3 and the holder is reversed and set in the pool portion 19 of a tank unit 2. The holder 3 is slid by a not-shown moving mechanism to move the surface of the object for washing. FIG. 16 shows a linear guide 20 and a side guide 21 of the pool portion 19.
However, the object holder of the above machine faces problems as follows:
1. Since the concave portion of the holder is formed in accordance with the shape of a specific object, it cannot hold objects of different shapes and is lack of general versatility. Different holders need to be prepared for different objects.
2. It is troublesome to reverse the object to face the washing tank after setting it in the holder. Also, it will be difficult to reverse a large object, which requires labor.
3. Holding the object by friction is not stable, and the object may be suctioned by negative pressure in the tank and come off from the holder.
For the above reasons, a frame type object holder including a cover for closing only the opening of a washing tank and pins to partially hold an object is mostly in practical use. An object is placed from above in the frame of this holder fixed in a washing machine and supported by the pins on the bottom surface of the frame. The size of the frame is designed to match with the outer shape of an object. To hold a different object of a different outer shape, one side of the frame is slid for size adjustment. For a flow palette as a cleaning object, an operator first sets a printed circuit board or a plate of the same size as that of the printed circuit board on the surface of the flow palette opposite to the one to wash, to cover the openings of the flow palette. Then, the operator places the flow palette and the plate in the frame, and fixes them with the pins. The openings of the flow palette are closed with the plate and the side faces thereof are tightly attached to the inner surfaces of the object holder with no gap from which the cleanser can be scattered. Thus, the plate functions as an anti-cleanser dispersing element.
However, this kind of holder faces the following problems:    1. It cannot deal with objects of different lateral and longitudinal sizes.    2. It cannot deal with objects of shapes other than rectangular.    3. It is troublesome to change the plate for washing different kinds of objects.