Method and apparatus for depositing precisely metered quantities of liquid on a surface

Abstract

Abstract A METHOD AND APPARATUS ARE DISCLOSED FOR DEPOSITING PRECISELY METERED QUANTITIES OF A LIQUID ON A PLATE OR LIKE SURFACE. A TUBULAR NEEDLE IS POSITIONED VERTICALLY IN A NON-DEPOSITION POSITION ABOVE THE SURFACE ON WHICH DEPOSITION IS TO BE EFFECTED, AND A POOL OF THE LIQUID IS MAINTAINED A DISTANCE ABOVE THE PLATE, THE SURFACE LEVEL OF TE POOL BEING SPACED AT OR SLIGHTLY BELOW THE LEVEL OF THE LOWER TIP END OF THE NEEDLE WITH THE LIQUID IN THE POOL BEING COMMUNICATED TO THE NEEDLE THROUGH A SUITABLE CONDUIT. DUE TO THE RELATIVE LOCATION OR POINTS OF ELEVATION OF THE LOWER TIP END OF THE NEEDLE IN SUCH NON-DEPOSITION POSITION AND THE POOL SURFACE, NO HEAD PRESSURE IS EXERTED IN THE LIQUID AT THE NEEDLE LOWER TIP END WHICH WOULD TEND TO CAUSE OUTFLOW OF LIQUID FROM THE NEEDLE. FURTHER, BACKFLOW OF LIQUID FROM THE NEEDLE AND CONDUIT TO THE POOL IS RESISTED BY CAPILLARY ACTION IN THE LIQUID DUE TO THE SIZE OF THE NEEDLE AND CONDUIT IN RELATION TO THE VISCOSITY OF THE LIQUID SO THAT THE NEEDLE AND CONDUIT ARE FILLED WITH LIQUID AT ALL TIMES. THE TUBULAR NEEDLE IS THEN STROKED DOWNWARDLY FROM ITS NON-DEPOSITION POSITION TOWARD THE PLATE AT A CERTAIN SPEED CREATING A HEAD PRESSURE IN THELIQUID AT THE NEEDLE LOWER TIP END BY REASON OF THE INCREASING DIFFERENTIAL BETWEEN THE POOL LEVEL AND THAT OF THE NEEDLE LOWER TIP END, AND CAUSING, DUE TO HEAD PRESSURE AND KINETIC ACTION, CREATION OF A BALL OF LIQUID OF CERTAIN SIZE AT THE LOWER TIP END DURING DOWNWARD MOVEMENT OF THE NEEDLE WITH THE BALL BEING RETAINED AT THE LOWER TIP END DUE TO CAPILLARY ACTION. THE DOWNWARD DISPLACEMENT OF THE NEEDLE IS TERMINATED IN A SECON OR DEPOSIT POSITION THEREOF WHEN THE BALL OF LIQUID CONTACTS THE PLATE ON WHICH DEPOSITIONS IS TO TAKE PLACE, AND THE ADHESIVE ATTRACTION OF THE PLATE DRAWS THE BALL OF LIQUID FROM THE NEEDLE TIP WHEREUPON THE NEEDLE IS RETRACTED UPWARDLY TO ITS FIRST POSITION LEAVING DEPOSITED ON THE PLATE A PRECISELY METERED QUANTITY OF LIQUID. APPARATUS FOR DEPOSITING THE LIQUID ON THE PLATE IN A PLURALITY OF SEPARATE DEPOSITS IN A SUITABLE MATRIX ARRANGEMENT ALSO IS DISCLOSED.

Inventors

• 👤 C Pickett
• 👤 J Molnar

Bibliographic Details