Microcentrifuge tube
This is a continuation of co-pending application Ser. No. 07/398,152 filed on Aug. 24, 1989, now abandoned. 
    
    
     FIELD OF THE INVENTION 
     The present invention is in the field of laboratory equipment. 
     BACKGROUND OF THE INVENTION 
     The present invention is an improved microcentrifuge tube. Microcentrifuge tubes are small conical tubes. The top opening of the tube generally has a lid which is connected to the top of the tube by means of a plastic strip or hinge. These tubes are widely used by molecular biologists and biochemists. Despite their wide use, there are problems associated with these tubes. The tubes are difficult to distinguish from each other especially when they are in a centrifuge. The lids of the tubes very often do not remain securely fastened. Also contaminates such as RNases and proteases can be introduced into the tube by the investigators when the investigator removes the lid with his fingers or thumb. These contaminants can totally break down RNA or proteins thus ruining an experiment. 
     SUMMARY OF THE INVENTION 
     The present invention is an improved test tube. The test tube is comprised of a tube having a sealed bottom end, an open top end and a lid which seals the top opening of the tube. The present invention is comprised of several improvements to the above-described test tube. A first improvement is an improved lid in which the top of the lid has a recessed well into which an identifying disk can be placed for easy identification of the tube especially when the tube is in a centrifuge. 
     A second improvement is a means for securing the lid so it does not pop open when it is inserted in the opening of the tube. The lid has a central plug which extends downwardly from the bottom of the lid into the opening of the tube, the improvement is an expanded circumference of the lower portion of the plug and a protrusion which protrudes inwardly about the circumference of the inner wall of the tube such that the expanded circumference of the lower plug fits beneath the inwardly projecting rim when the lid is inserted into the the tube thus securely fixing the lid into the top of the test tube. 
     A third improvement is a vertical flange which is attached to the bottom side of the rim of the top of the lid such that the flange extends downwardly over the edge of a portion of the outer wall of the tube preventing contact of the investigator&#39;s fingers and thumbs with the edge of the tube and with the outer surface of the central plug extending from the bottom surface of the lid. Thus the risk of contamination of the reagents within the tube by RNases and proteases from the investigator&#39;s fingers or thumbs is prevented when the investigator opens or closes the tube. The flange should be long enough to extend below the outer edge of the opening of the tube. Preferably, the length of the flange should be as long as or longer than the length of the central plug which extends downwardly from the bottom of the lid. The flange should be wide enough so an investigator&#39;s thumb will only come into contact with the flange and not the edge of the opening of the tube or with the outer surface of the central plug when the investigator removes the lid from the tube. The flange should preferably be at least approximately three sixteenths (3/16) of an inch (4.7 mm) wide. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is illustrated in the accompanying figures wherein like reference numbers represent like elements and in which: 
     FIG. 1 is a longitudinal cross-section of a microcentrifuge tube showing the improvements of the present invention. 
     FIG. 2 is a perspective view of the microcentrifuge tube with the lid opened showing the bottom of the improved lid of the present invention. 
     FIG. 3 is a top view in perspective of the improved lid of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 is a longitudinal cross-section and FIG. 2 is a perspective view of a plastic microcentrifuge tube 10 showing the improvements of the present invention. Microcentrifuge tube 10 has a narrowed, pointed sealed bottom 12 and an opened upper section 14 which has a lid 16 inserted into the opening of upper section 14. Lid 16 is hingably connected to the upper section 14 of tube 10 by means of a plastic strip 18. The top of lid 16 contains a recessed well 20 into which an identification disk 22 can be inserted as is shown in FIG. 3. The identification can be of several different types. The disk can be color coded, numbered or lettered to name just a few possibilities. 
     The bottom of lid 16 has a central circular plug 24 which extends downwardly and inserts into the opening of tube 10. The lower portion of plug 24 expands out to an expanded circumference 25 beyond the circumference of the upper portion of the plug. The upper inner surface of the tube has an inward protrusion 26 which circles the upper inner surface such that when plug 24 is inserted into the opening of tube 20 expanded circumference 25 fits beneath inward protrusion 26 thus securing lid 16 in the opening of tube 20. 
     The top of lid 16 has a rim 28 which extends over the edges of the top of tube 10. Rim 28 has a lip 30 which extends out beyond the rest of rim 28. Extending vertically, downwardly from lip 30 is a flange 32. The presence of flange 32 helps to prevent contamination of tube 10 from the investigator&#39;s fingers and thumbs because it prevents contact between the investigator&#39;s fingers and thumbs with the edge of the opening of tube 10 and with the outer surface of central plug 24 when the investigator opens or closes the tube. Flange 32 should be long enough to extend below the outer edge of the opening of the tube. Preferably, the length of flange 32 should be as long as or longer than the length of central plug 24. Flange 32 should also be wide enough so an investigator&#39;s thumb will only come into contact with the flange and not with the outer edge of the opening of the tube and not with the outer surface of central plug 24 when the investigator removes the lid from the tube. The flange should preferably be at least approximately three sixteenths (3/16) of an inch (4.7 mm) wide. 
     While this invention has been described with respect to certain embodiments, it is not so limited, and it should be understood that variations and modifications thereof may be made which are obvious to those skilled in the art without departing from the spirit or scope of the invention.