Abstract:
A hand-held pipettor comprising a piston received in one end of a cylinder, a pipettor tip removably secured to an opposite end of said cylinder, means for reciprocating said piston through a selected stroke to aspirate fluid into and to expel the thus aspirated fluid from said pipettor tip, mutually spaced stop members operatively associated with said manually driven means for defining the range of said stroke and motor driven means for varying the spacing between said stop members to thereby vary the volume of fluid being aspirated into and expelled from said pipettor tip.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority of provisional patent application Ser. Nos. 60/329,704 and 60/329,706, each filed on Oct. 16, 2001. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to transfer and dispensing devices for liquid reagents and samples, and more particularly to hand-held pipettors. 
     BACKGROUND OF THE INVENTION 
     Pipetting systems are widely utilized in laboratories and hospitals for withdrawing and dispensing relatively small, predetermined quantities of liquids from one location to another, such as between test tubes, microplates and other liquid receptacles. Portable, or hand-held, pipettors are one type of pipetting system. Hand-held pipettors generally include a housing, a cylinder including two cylinder ends, with one end positioned within the housing and the other end extending from the housing to form a pipettor tip holder, a piston that moves within the cylinder to withdraw liquid from a supply receptacle and dispense the liquid to a receiving receptacle, and a plunger that drives the piston. While not a permanent part of the pipettor, a disposable pipettor tip is commonly attached to the end of the tip holder to retain the liquid to be transferred. This tip can be removed from the tip holder, disposed of, and replaced with a new tip. These hand-held pipettors may be configured to transfer liquids by automated or manual actuation of the pipettor. Automatically operated hand-held pipettors generally include a motor for actuating the plunger to move the piston within the pipettor cylinder for liquid transfer. Manually operated hand-held pipettors require the pipettor user to apply force to the plunger head, usually with a thumb or a finger, to actuate the piston. 
     Hand-held pipettors may be designed as fixed volume pipettors, where only one predetermined liquid volume is withdrawn and dispensed, or as adjustable pipettors, where the user may set a desired volume to be dispensed within a given volume range. Stop features located within a pipettor determine the distance that a piston will travel, also known as the stroke. The stroke corresponds to the volume of liquid to be withdrawn and dispensed. Hand-held pipettors commonly include two stops to establish the limits of the stroke. For purposes of the foregoing description, these two stops will be referred to as a front stop and a rear stop. In this description, the front stop is the stop closest to the tip holder and the rear stop is the stop closest to the plunger head, or in a manual pipettor, the end of the plunger that is manually actuated by a pipettor user. The stops in a fixed volume pipettor are fixed, and the piston travels the same stroke during each complete actuation of the plunger. In an adjustable volume pipettor, at least one of the stops is movable to adjust the stroke length of the piston, and thus the volume to be withdrawn and dispensed. 
     In manual pipettor applications where the volume of liquid to be transferred may vary frequently within a single application, the pipettor user must frequently change the volume settings on the pipettor, which can cause fatigue and potentially inaccurate volume settings on the pipettor. 
     SUMMARY OF THE INVENTION 
     In one embodiment of the invention, a hand-held pipettor comprises a housing including a front stop and a rear stop, a cylinder, a piston that moves within the cylinder to draw and expel liquid, and a plunger that moves the piston, the rear stop being movable by a motor to adjust the volume of liquid to be aspirated and dispensed by the pipettor. 
     In another embodiment of the invention, the pipettor includes a voice recognition system that coacts with a central processing unit to translate verbal commands for volume settings into electronic signals that control the motor moving the rear stop. 
     In another embodiment, a hand-held pipettor for dispensing specific liquid volumes comprises a cylinder having one end defining a tip holder that accepts a disposable pipettor tip, a piston that moves within the cylinder to withdraw and dispense liquid, and a manually actuated plunger that moves the piston to at least one point of resistance, the housing containing a tactile blow-out mechanism that facilitates manual expelling of a remnant liquid in the pipettor tip following the dispensing of specified liquid volumes. The blow-out mechanism requires the pipettor user to apply a force to the plunger through a first point of resistance to a second point of resistance to expel remnant liquid from the pipettor tip. 
     In a further embodiment, a hand-held pipettor for pipetting applications comprises a cylinder having and end configured and arranged to accept a disposable pipettor tip, a piston that moves within the cylinder to withdraw and dispense liquid, a plunger that moves the piston, and a manually actuatable tip ejector assembly configured and arranged to dislodge the pipettor tip for disposal following a pipetting application. 
     These and other features and advantages of the present invention will now be described in greater detail with reference to the accompanying drawings, wherein: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a vertical sectional view taken through a manual hand-held pipettor in accordance with the present invention; 
         FIG. 2  is a horizontal sectional view on an enlarged scale taken along line  2 — 2  of  FIG. 1 ; 
         FIG. 3  is an enlarged view of a portion of  FIG. 1 ; and 
         FIG. 4  is a schematic diagram of the voice recognition system. 
     
    
    
     DETAILED DESCRIPTION 
     A pipettor in accordance with the present invention is generally indicated at  10  in FIG.  1 . The pipettor includes a housing  12  with an axially projecting cylinder  14 . Cylinder  14  has a tapered distal end defining a pipettor tip holder  16 . A pipettor tip  18  is removably secured by friction to the tip holder  16 . The opposite end of the cylinder has an enlarged head  20  with an internal ledge  22  on which is seated an O-ring  24  supporting an apertured seal  26 . A sleeve  28  has an apertured lower end  30  received in the cylinder head  20 . The sleeve  28  has an intermediate interior shoulder  32  and an internally threaded open upper end  34 . A front stop collar  36  is biased upwardly against the internal shoulder  32  by a spring  38 . 
     A piston  40  in the cylinder head  20  projects downwardly through the seal  26 . The piston is biased upwardly against the lower end of a plunger  42  by a main spring  44 . Plunger  42  extends upwardly through the apertured lower end  30  of sleeve  28 , and through the front stop collar  36  and a tubular externally threaded screw  46 , with its upper end projecting from the top of the housing  12  and into an axially depressable cap  48 . 
     An enlarged intermediate section  58  of the plunger  42  defines upper and lower shoulders  52  and  54 . Shoulder  52  is biased against the lower end of the screw  46  by the force of the main spring  44  acting on the piston  40 . The lower screw end thus serves as a rear stop. 
     As can best be seen by additional reference to  FIG. 2 , the upper end of the screw  46  is provided with external ribs  56  slidably received in internal grooves  57  in a rotatable drive collar  60 . An external gear  62  on the drive collar  60  meshes with a drive pinion  64  on the output shaft of a motor  66 . 
     Actuation of motor  66  will cause the drive collar  60  to rotate, and the mechanical interengagement of the ribs  56  and grooves  57  will result in a corresponding rotation being imparted to the screw  46 . The threaded engagement of the screw  46  with the upper end  34  of the fixed sleeve  28  will result in the screw being shifted axially to a desired setting of its lower end, which provides a rear stop for the plunger  42  and the piston  40  biased agains its lower end by the main spring  44 . 
     The setting of the rear stop will limit the extent to which the piston  40  can be retracted from the tubular portion of the cylinder  14 , which in turn will control the volume of liquid that can be drawn into the pipettor tip  18  during aspiration. 
     Aspirated liquid is dispensed from the pipettor tip by manually depressing the cap  48  to advance the plunger  42  and the piston  40  against the biasing force of the main spring  44 . The plunger will continue to advance until the lower shoulder  54  of its enlarged intermediate section  58  engages the front stop  36 , creating a first point of resistance which indicates that most of the aspirated liquid has been dispensed. By manually applying additional force to the plunger  42  in order to overcome the resistance of spring  38 , the piston will be advance further to insure that any residual liquid will be “blown out” of the pipettor tip  18 . 
     In another aspect of the invention, the pipettor includes a tip ejector assembly generally indicated at  68  for removing a pipettor tip  18  from the pipettor tip holder  16 . As can best be seen by a combined reference to  FIGS. 1 and 3 , the tip ejector assembly  68  includes a tip ejector actuator  70 , a tip ejector shaft  72 , a tip ejector sleeve  73  movable with the tip ejector shaft, and a lock collar  74 . The lock collar allows one way movement of the tip ejector shaft  72  and sleeve  73  in the direction of arrow A in  FIG. 3 , but does not allow movement of these components in the opposite direction, the direction of arrow B, when the lock collar is oriented in its locking position, as illustrated. Therefore, when a disposable tip  18  is wedged upwardly onto the tip holder  16 , the tip ejector sleeve  73  is pushed upwardly in the direction of arrow A. At the same time, the tip ejector shaft  72  will also move up a distance equal to the distance traveled by the tip ejector sleeve due to the fixed connection therebetween. The lock collar  74  will allow movement of the tip ejector shaft  72  in the direction of arrow A without resisting movement. However, the tip ejector shaft  72  will be prevented from moving in direction B toward the disposable tip  18  by the locking action of the lock collar  74 . 
     A spring  76  is positioned to bias the lock collar into an angled, or locking position. The spring  76  keeps the tip ejector shaft  72  locked by the lock collar  74 , and thus prevents the tip ejector shaft and the ejector sleeve  73  from moving in the direction of arrow B to dislodge and eject the pipettor tip  18 . 
     Depressing the tip ejector actuator  70  in the direction of arrow C will cause its tapered lower end  78  to coact with a mating inclined surface of a ramp wedge  80 , causing the ramp wedge to shift in the direction of the lock collar, and creating a force lifting the lock collar from its angled locked position to a raised unlocked position. Once the lock collar is unlocked, the tip ejector shaft is released to move through the lock collar in the direction of arrow B under the force of spring  82 . The tip ejector sleeve  73  will be correspondingly moved, causing the pipettor tip  18  to be dislodged and ejected from the end of the pipettor tip holder  16 . 
     In another embodiment of the invention, a damper mechanism includes a piston  84  formed at the upper end of the tip ejector shaft  72 . The piston is encircled by an O-ring seal and enclosed in a chamber  86  vented to atmosphere by a one way check valve  88 . Movement of the tip ejector shaft in direction A causes air to be expelled from the chamber  86  via the check valve, whereas movement in direction B is retarded by the rate at which air can be readmitted to the chamber via a smaller bleed hole  90 . The retarded rate of travel in direction B beneficially retards the velocity at which the pipettor tip is ejected. 
     In another embodiment of the invention, as can be seen by reference to  FIGS. 2 and 4 , the adjustment drive collar  60  is surrounded by an encoder wheel  92  that rotates with the adjustment drive collar and that comprises part of an encoder assembly  94 . The pipettor includes a voice recognition system VRS that translates verbal commands  96  for volume settings and outputs the result  98  to a central processing unit CPU. The CPU generates an electronic signal  99  that controls the motor  66 , and may optionally receive input  100  from the encoder assembly  94  indicative of the position of the adjustable stop. The pipettor&#39;s adjustment mechanism is thus moved automatically to the position corresponding to the voice input setting. 
     In light of the foregoing, it will be understood by those skilled in the art that although the present invention has been described with reference to a pipettor having a manually actuated piston, certain aspects of the invention including the motor driven stop adjustment mechanism, the voice recognition system, and the tip ejection mechanism, are also applicable to pipettors having motor driven pistons. 
     Modifications and improvements within the scope of the present invention will become apparent to those skilled in the art. The above description is intended to be purely illustrative, and does not define the limits of the present invention.