Abstract:
A pipetting system having a plurality of tip fittings whose spacing can be simultaneously, quickly, and accurately adjusted so that the spacing between each adjacent tip fitting is substantially identical. The tip fittings are attached one to another by a linkage such as a pantographic linkage. The spacing is limited by an adjustable, slidable stop. Uniformly increasing and decreasing the spacing is accomplished by pulling and pushing a rod attached to one tip fitting.

Description:
RELATED APPLICATIONS 
     This application claims priority under 35 U.S.C.§119 (e) to commonly-owned, co-pending U.S. provisional patent application Ser. No. 60/112,316 entitled “Uniformly Expandable Multi-channel Pipettor,” filed Dec. 14, 1998 by Torti et al., which is incorporated herein by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     This invention relates generally to liquid transfer devices used in laboratories and, more particularly, to a multi-channel pipetting device which enables the user to uniformly, rapidly and accurately adjust the spacings between pipette tips. 
     BACKGROUND OF THE INVENTION 
     Pipetting systems are used in laboratories for the transfer of relatively small quantities of liquids. The liquid is normally drawn into the tips by suction and is subsequently released into the wells of microtiter plates or other receptacles. Frequently the transfer involves patient samples which are moved from one set of spaced receptacles to another set of receptacles having a different spacing. A multi-channel pipettor capable of being simply manipulated to vary the spacing between the pipette tips is often used for this purpose. Typically, the pipettor has a tip removing assembly that, with a minimum of force, removes tips safely and efficiently regardless of the positions of the tips and their fittings on the pipettor. One shortcoming of some prior art pipettors is that the pipette tips can only be adjusted between two uniform standard spacings of the receptacles. The standard settings must be preselected prior to manufacture. An example of such a prior art structure is found in U.S. Pat. No. 5,061,449. 
     A second type of multi-channel pipettor, such as that shown in U.S. Pat. No. 5,057,281, allows the spacings between the tip fittings to be varied by the user. However, the spacings between each fitting must be individually set. Thus, considerable manipulation is required to move the tip fittings from one set of spacings to another and it is difficult to accurately set the tip fittings to the desired spacings. 
     Therefore, it is desirable to have a multi-channel pipettor in which the tip fittings may be quickly and accurately set at a variety of uniform spacings. Moreover, it is desirable to easily vary the spacings while maintaining uniform spacing between tip fittings. 
     SUMMARY 
     The foregoing drawbacks of existing pipetting systems are overcome by the pipetting system of the present invention which uniformly and accurately spaces the tip fittings within a range of spacings, while still providing for easy tip removal. Moreover, the tip fittings may be rapidly moved from one set of uniform spacings to another. In addition, a desired spacing may be readily adjustably set. 
     One embodiment of the invention is a multi-channel pipetting system including a housing for the pipetting system, a slotted track connected to the housing, a plurality of pipette tip fittings slidably in a line mounted on the track, and an actuator for varying the size of the spacings between adjacent tip fittings. Each of the tip fittings is coupled together by a linkage to maintain a substantially identical spacing between each adjacent pair of tip fittings, regardless of a size of the spacing between adjacent tip fittings. 
     Another embodiment of the invention is a multi-channel pipetting system that includes a plurality of ducts, a housing for the pipetting system, a slotted track in the housing, and a plurality of pipette tip fittings, with one tip fitting being connected to each duct. All but one tip fitting is slidably mounted on the track. A pantographic linkage is connected to each of the tip fittings. An actuating rod is attached to one end of the tip fittings for varying spacing between adjacent tip fittings. 
     Another embodiment of the invention is a multi-channel pipetting system that includes a plurality of ducts, a housing for the pipetting system, a slotted track in the housing, and a plurality of pipette tip fittings. One tip fitting is connected to each duct. All but one tip fitting is slidably mounted on the track. The system also includes means interconnecting the tip fittings to form an array and enabling all but one tip fitting on the plate to move relative to the other tip fittings thereon. The spacing between adjacent tip fittings is substantially identical regardless of the size of the spacing. An actuating rod is attached to one of the tip fittings for varying the spacing between adjacent tip fittings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The objects, advantages and features of this invention will be more clearly appreciated from the following detailed description when taken in conjunction with the accompanying drawings in which: 
     FIG. 1 is a side elevational view of the multi-channel pipettor of this invention; 
     FIG. 2 is a cross-sectional side view of the multi-channel pipettor of FIG. 1 showing the pipettor tips and tip fittings in a closely spaced position; 
     FIG. 3 is a partial cross-sectional view of the pipettor of FIG. 2 showing the tip fittings and tips in the position of FIG. 2; 
     FIG. 4 is a partial cross-sectional view of the pipettor of FIG. 2 showing the tip fittings and tips in an intermediate spaced position; 
     FIG. 5 is a partial cross-sectional view of the pipettor of FIG. 2 showing the tip fittings and tips with the maximum spacing; 
     FIG. 6 is a cross-sectional view of the pipettor taken along the section line  6 — 6  in FIG. 1; 
     FIG. 7 is a cross-sectional view of the pipettor taken along the section line  7 — 7  in FIG. 1; and 
     FIG. 8 is a bottom plan view of the pipettor of FIG. 1 in which the tip fittings are not shown. 
    
    
     DETAILED DESCRIPTION 
     With reference now to the drawings, and more particularly to FIGS. 1-3, the pipettor  10  of the present invention will now be described. The pipettor  10  of this invention has a boot-shaped housing  1  as shown in FIG. 1 that includes a handle section  2  and a lower section  3 , having a bottom section  8 , from which a plurality of tip fittings  7  project downwardly. In the embodiment shown, eight tip fittings are included, but it should be appreciated that the number may vary, depending upon a user&#39;s needs. 
     The housing  1  of the pipetting system typically is formed of a pair of mating half shells  1   a  (not illustrated) and  1   b . The shells  1   a  and  1   b  include sidewalls  19  and  20  (not illustrated) and front and back walls  21  and  22  that together define the handle section  2  and the lower section  3 . The front, back and bottom of the lower section  3  are enclosed by the walls  21 ,  22  and  23 , while the top of the bottom section forward of the handle is enclosed by wall  24 . 
     As shown in FIG. 8, all but one (fitting  7   a ) of the tip fittings  7  slide along an elongated aperture  25  provided in the bottom wall  23 . The aperture  25  extends substantially the full length thereof symmetrical with respect to the parting line  26  that joins the two shells. FIGS. 6 and 7 show a tip fitting mounting plate  80 , which is secured immediately above the bottom wall  23  of the housing by slots  81  formed in each half shell  1   a  and  1   b . The tip fitting mounting plate  80  includes an elongated slotted track  82 . The elongated slotted track  82  is narrower and somewhat shorter than the aperture  25  in the bottom wall  23 . 
     As shown in FIG. 7, each of the tip fittings disposed in the elongated slotted track  82  includes a stem  94 . The width of stem  94  at its upper end is larger than the width of the elongated slotted track  82 . Consequently, the edges of the stem  94  bear against the lower surface of the mounting plate  80 . Above the stem  94  each tip fitting has a waist  96  which rides along the elongated slotted track  82 . Each tip fitting has a shoulder  95  above the waist  96 . The shoulder  95  has a width greater than the elongated slotted track  82 , which forms a track along which all the tip fittings  7  are slidably disposed, and which guides tip fittings  7 . Tip fitting  7   a  is fixed with respect to the track and does not move. Therefore, with the exception of tip fitting  7   a , the tip fittings may be moved toward and away from the front wall  21 . 
     Referring now to FIG. 2, pipette tips  6  are attachable to the tip fittings  7 . Those of ordinary skill in the art will recognize that many types of pipette tips are available which may be used interchangeably provided that they are compatible with the size of the tip fittings  7 . The upper end of each tip fitting carries a nipple  98  which in turn is connected to a duct  115 , only an exemplary one of which is shown. A passage extends through each tip fitting from the lower end of the stem  94  to the upper end of nipple  98 , which passage is in fluid communication with each duct  115 . The pipetting system  10  includes a means for drawing liquid in metered volumes into the tips  6  and for expelling the liquid from the tips. This feature is not part of the present invention, and is well known to one of ordinary skill. This feature is described in U.S. Pat. No. 5,061,449, assigned to the assignee of the present application and specifically incorporated herein by reference. 
     The tip fittings  7  are connected together by a linkage that maintains a substantially identical, uniform spacing between each of the tip fittings, regardless of the position of the tip fittings. In a preferred embodiment shown in FIGS. 2-5, a pantographic linkage  89  is used. As shown in FIG. 3, the pantographic linkage of the preferred embodiment includes intersecting first links  83  and second links  84 . A first, lower end of each first link  83  is pivotably mounted to an associated tip fitting  7 . An upper, second end of each second link  84  is pivotably mounted to an upper second end of an immediately adjacent first link  83 . A second, lower end of each second link is pivotably mounted to an immediately adjacent tip fitting  7 . Associated first links  83  and second links  84  are pivotably coupled at their respective centers. 
     An actuating rod  11  carrying a knob  12  on its distal end projects rearwardly away from the lower section  3  and is secured at its proximal end  15  within the housing  1  to the rear-most tip fitting  7   b . By manually pushing and pulling the knob  12  and rod  11 , the tip fittings are quickly and accurately moved to the desired spacings between uniformly spaced minimum and maximum positions. FIG. 3 shows the tip fittings with the minimum spacing. FIG. 4 shows an intermediate spacing, while FIG. 5 shows the linkage  89  fully extended so that the tip fittings  7  are at their maximum spacing. 
     As shown in FIG. 1, side wall  19  has an elongated opening  71 . Referring now to FIGS. 1 and 6, upper and lower rails  72  and  73  are disposed parallel to and on either side of opening  71 . The rails  72  and  73  extend along the direction of travel of the tip fittings. The rails include respective opposed surfaces  72   a  and  73   a  that form an acute angle with respect to plate  80  and that are angled with respect to one another such that the surfaces  72   a  and  73   a  of respective rails  72  and  73  are closer together facing side wall  19  than facing inwardly away from side wall  19  and toward side wall  20 . The surfaces  72   a  and  73   a  of respective rails  72  and  73  are friction surfaces and contain serrations or ridges or are otherwise roughened as shown in FIGS. 6 and 7. A finger actuated stop  75  such as a button having a finger engageable surface  78  is also slidably engaged with the rails. The stop  75  has serrated, ridged or roughened friction surfaces  76  and  77  disposed parallel to respective surfaces  72   a  and  73   a  of respective rails  72  and  73 , and which are urged into positive engagement with the rails  72  and  73  by biasing spring  79 , as shown in FIG.  6 . Spring  79  bears against rails  72  and  73  and pushes stop  75  outwardly. Applying finger pressure to the stop  75  toward wall  19  compresses the spring and releases the surfaces  76  and  77  from engagement with surfaces  72   a  and  73   a  of respective rails  72  and  73 . The stop is then movable along rails  72  and  73  and within opening As shown in FIG. 1, a second finger actuated stop  110  may be included within the rails to limit the contraction of the pantographic linkage. 
     Preferably, a spacing indicator  74  is slidably engaged with the rails  72  and  73  and is connected to the rear-most tip fitting  7   b . However, indicator  74  could be affixed to another tip fitting  7 , if desired. Indicator  74  moves with tip fitting  7   b  and provides an indication of the spacing between adjacent tip fittings. Indicator  74  extends through opening  71  to be externally visible. A visual scale  105 , as shown in FIG. 1, is provided along opening  71  and is calibrated to provide the spacing between each tip fitting for a particular location of indicator  74  with respect to scale  105 . When the spacing indicator  74  engages a shoulder  75   a  or surface on the stop  75 , or on stop  110  the spacing between the tip fittings is that shown on scale  105  with which indicator  74  is aligned. The spacing between the tip fittings may alternatively or additionally be positively established by notches provided in the rod  11  corresponding with a ball detent as disclosed in U.S. Pat. No. 5,061,449. 
     It will be appreciated that the tip fittings  7  are designed to slide in the tip fitting mounting plate  80  in response to movement of linkage  89 . When linkage  89  is extended, the spacing between tip fittings  7  increases. Conversely, when linkage  89  is contracted, the spacing between tip fittings  7  decreases. Pulling the actuating rod  11  away from the housing  1  increases the spacing between tip fittings  7 . Conversely, pushing the actuating rod  11  toward the housing  1  decreases the spacing between tip fittings  7 . 
     In operation, the finger actuated stop  75  may be adjustably set with reference to the scale  105  to provide a uniform spacing between tip fittings. Stop  75  is pushed inwardly with a finger and slidably moved within the opening  71  until stop  75  is aligned with a desired reading on scale  105 . Stop  75  is then released and surfaces  76  and  77  engage respective surfaces  72   a  and  73   a  to hold stop  75  in place. The user then grasps knob  12  and moves rod  11  until indicator  74  abuts shoulder  75   a  on stop  75 , or on stop  110 . At that point, tip fittings  7  are uniformly spaced apart as indicated by the reading on the scale  105  aligned with indicator  74 . The pipettor is now ready for use. 
     Modifications and improvements will occur within the scope of this invention to those skilled in the art, and the above description is intended to be exemplary only. The scope of this invention is defined only by the following claims and their equivalents.