Cleaning and liquid contact with solids – Apparatus – With means to movably mount or movably support the work or...
Patent
1993-07-09
1995-03-28
Lieberman, Paul
Cleaning and liquid contact with solids
Apparatus
With means to movably mount or movably support the work or...
134169R, 134170, B08B 302
Patent
active
054008123
DESCRIPTION:
BRIEF SUMMARY
This invention relates to cleaning apparatus and cleaning methods and particularly, although not exclusively, to apparatus for and methods of cleaning printing screens, for example, cylindrical nickel printing screens.
In textile printing, paper-thin cylindrical nickel printing screens, for example, having a length of 3.5 m and a diameter of 202 mm, may be utilized. Such screens are very fragile and are easily damaged.
After printing, a printing screen needs washing to remove residual ink and fabric, transferred from the textile being printed upon, which has built up on the screen.
A number of means have been used to clean printing screens. For example, a screen to be washed may be sprayed with water from a hose pipe. However, such random spraying may cause unequal, random forces on the fragile screen and may cause total collapse of the screen where the spray impinges. An alternative known cleaning apparatus, shown in end elevation in FIG. 1, comprises two contrarotating abrasive brushes 1 which are arranged to dislodge fabric from the screen 2 by abrasion. The brushes, however, have limited effect in the cleaning of the paper-thin screen. Removal of fabric from screens has also been accomplished by chemical means. For example, a strong chemical may be applied to a screen to degrade fabric attached thereto. However, the use of chemical means is potentially hazardous to personnel applying the chemical and, furthermore, the cost of chemicals is not insignificant.
In general terms, it is also noted that the aforementioned means of cleaning screens tends to result in a screen being handled manually to a relatively large degree. Since the screen is of relatively large length and is made of paper-thin nickel, such handling results in damage to the screen. For example, the screen may fairly readily fold or become dented.
It is an object of the invention to improve upon the aforementioned problems.
According to a first aspect of the present invention, there is provided apparatus for cleaning a screen, the apparatus comprising first fluid directing means arranged to direct a cleaning fluid towards a first position on a first side of a screen and second fluid directing means arranged to direct a cleaning fluid towards a second position on a second side of the screen, wherein said first and second positions are substantially superimposed.
Said first position may comprise a first area and said second position may comprise a second area. Said first and second areas are preferably substantially equal. Said first and second areas may suitably not be directly superimposed but overlap each other to some extent. This may be important when a perforated screen is being cleaned, since if the areas are directly superimposed, the fluid directing means may cancel each other out.
Preferably, said first and second fluid directing means are arranged such that the force of fluid impinging the screen at said first position due to said first fluid directing means is substantially balanced by the force of fluid impinging the screen at said second position due to said second fluid directing means. To achieve this, said first and said second fluid directing means are suitably fed with fluid from the same fluid source.
Suitably, said first and/or said second fluid directing means are arranged to receive and direct a fluid having a pressure of up to 1500 psi (1.times.10.sup.7 N/m.sup.2).
Said first fluid directing means and/or said second fluid directing means may be arranged to direct fluid towards a plurality of positions on first and second sides of the screen respectively. Fluid directed to each of said plurality of positions on the first side is preferably superimposed by fluid directed to said plurality of positions on the second side.
Preferably, the first fluid directing means is arranged to direct a substantially endless band of cleaning fluid at a screen to be cleaned. Preferably the second fluid directing means is arranged to direct a substantially endless band of cleaning fluid at a screen to be cleaned. Preferably, said endless
REFERENCES:
patent: 3679483 (1972-07-01), Zweig
patent: 4808237 (1989-02-01), McCormick et al.
Douyon Lorna M.
Jenkins Richard E.
Lieberman Paul
Technijet Limited
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