US1850499A - Pipette - Google Patents

Description

C. B. FRANCIS PIPETT-E Filed July 13 Inventor March 22, 1932.

[fatness Patented Mar. 22, 1932 PATENT OFFICE CHARLES B. FRANCIS, OF PITTSBURGH, PENNSYLVANIA IPIPETTE Application filed July 13, 1926. Serial No. 122,170.

This invention relates to pipettes used in making gas analysis and the like, and more particularly to that class of pipettes known as the bubbling type of pipettes, and has for its object the provision of a pipette of this type having an automatic control valve.

Heretofore, there have only been three types of pipettes in general use. One of these types required shaking to secure the desired contact between the reagent and gas; another contained a plurality of glass tubes adapted to retain films of the reagent, and the gases were adapted to flow through the tubes and make contact with the films of reagent. This type of pipette secured a very limited contact. The third type of pipette was of the bubbling type, and caused the gas to bubble through the reagent. This last type secured the desired contact of the gas with the reagent, but required a hand operated, three-way cook or valve to control the flow of gas in and out of the chamber.

Aside from the manipulation of this valve, the valve required constant attention, as it was liable to develop a leak and, with some reagents, it was prone to stick or freeze in its socket.

The present form of pipette is free of all the objections of the pipettes of the prior art, since it remains stationary during operation,

secures the proper amount of contact due to the fact that the gas bubbles through the reagent, and is provided with an automatic control valve which will not stick.

In the drawing The figure is a vertical section through the center of a pipette constructed in accordance with this invention.

Referring more particularly to the drawing, the numerals 2 and 3 designate the pipette vessels which are connected at their lower ends by a conduit or tube 4. The upper end of the vessel 2 is necked and provided with an openin 5 thrpugh which the reagent may be poured. A removable closure or stopper 6 having a vent pipe or tube 6 is provided for closing the opening 5. The vessel 3 has its upper end closed with the exception .of a small opening 7 A small valve chamber 8 is connected or joined to the upper end of the vessel 3 and communicates with said vessel through the opening 7. A gas tube 9 extends vertically through the upper end of the vessel 3 and down into said vessel to a point short of the lower end thereof.

A connecting tube 10 is connected with the upper endof the valve chamber 8 and with an opening in said gas tube, so as to form a communicating channel between said valve casing and said gas tube. A hollow glass float valve 12 is mounted in the chamber 8, and is adapted to'be seated in the opening 7 to prevent the flow of gas from said gas tube passing through the valve chamber into the vessel 3. The valve 12 is preferably provided with a guide stem 13 to guide it into seating position.

A baflie lip 1O extends from the side of the valve chamber 8 over at least aportion of the opening in the upper end of the valve chamber and is adapted to baflle the gases passing through the opening and also to prevent the valve 12 from entering and closing the opening when the gases are being withdrawn from the vessel 3.

The lower end of the gas tube preferably terminates in a hollow spherical distributing member 15, which has its walls perforated, as at 16, so as to cause the gas to be discharged into the reagent in a plurality of separate streams.

In operation, a liquid reagent will first be poured into the pipette through the opening 5 in the vessel 2 until the vessels 2 and 3 are over half full at atmospheric pressure. The pressure in the gas tube 9 will then be lowered below atmospheric pressure until sufficient of the liquid reagent is drawn from the vessel 2 into the vessel 3, valve chamber 8, and tubes 9 and 10, to a point in the tube 9 above the tube 10. As the reagent enters the valve chamber 8, the float valve 12 will rise or float to the upper part of the valve chamber. The gas to be treated or analyzed is then admitted to the tube 9 at a pressure greater than the reduced pressure in the pipette, and forces the reagent down out of the tubes 9 and 10, and valve chamber 8, and causes it to rise in the vessel 2. As the reagent leaves the valve chamber 8, the valve 12 i sealed by the reagent.

will be automatically seated and cause the gas to flow through the tube 9 into the vessel 3. The valve 12 willremain seated due to the differential pressure set up, the pressure of the gas on the top of the valve being greater than the pressure in the vessel 3, by the height of the reagent in the vessel 2 above that at the end of the gas tube 9. As the gas is dis: charged from the lower end of the tube 9, it will bubble up through the reagent in the vessel 3 until the reagent in thevessel 3is lowered to the level of the lower end of the tube 9, which is the limit of capacity of the apparatus. v

After the limit of capacity of the apparatus has been reached, or when the gas supply is exhaustechthe pressurein the tube 9 is again lowered to below atmospheric pressure,- to reverse the maximum and minimum 1 points of the difl'erential pressure, so that the pressure at the bottom of. the valve 12 is greater than the'pressure at the top of. the valve or in the valve chamber. This is due to'thefact that'the lower end of the tube 9 is This reversal of the differential pressures unseats the valve 12, thus permitting all the gas in the vessel 3 to flow out through the valve chamber 8 and tube 10. As the gas flows out the liquidreagent will rise through the apparatus and sweep all thegas before it.

It will be understood that the expression a pair'of vessels as used in the claims is intended to include either a pair of vessels placed side by side as shown in the drawing, or a pair of vessels arranged in any other manner such as one within the other, and also that theex-pression connecting passage as used in some of the claims is intended to include any communicating opening or passage'between the vessels, such as a port or ports when one vessel is within the other as suggested above} vhile I have shown and described one specific embodiment of my invention, it will be understood that I do not wish to be limited thereto, since various modifications may be made without departing from the scope oi my invention as defined in the appended claim.

I 'claim In a pipette comprising a pair of vessels having a connecting passage at their lower ends, a spherical valve chamber formed integral with the upper end of one of said vessels and having an opening in its lower end communicating with said vessel and a second opening in its upper end diametrically opposite said first named opening, an inverted pear-shaped float valve in said valve chamber adapted to control the flow through said opening in the lower end of said valve chamber, a'platinum wire guide stem projecting from the lower end of saidvalveand into said vessel with which said valve chamber communicates to guide said valve into seating position, a gas tube projecting through the center of and. fused with the top wall of the vessel with which said valve chamber communicates, said tube extending into said vessel, a conduit connecting the opening in the upper end of said valve chamber and said gas tube at a point above said valve chamber and said vessel in which said tube extends, said conduit being fused to the wall of said valvechamberand to said gas tube, and a bafiie member in said valve chamber and projecting over at least a part of the opening in the up er end of said valve a chamber and adapte to bafile the gases flowing out from said second named vessel through said conduit, andto prevent said valve from entering the opening in the upper end of saidvalve chamber. 7 V In testimony whereof, I have hereunto signed my name.

I 7 CHARLES B. FRANCIS.

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