MXPA01004452A - Pipette with improved pipette tip and mounting shaft combination - Google Patents

Abstract

An air displacement pipette (10) having axially spaced annular sealing and frusto-conical lateral support zones (36, 38) and regions (46, 48) on the pipette's mounting shaft (32) and tip (40), respectively, in combination with means (52) for insuring uniform depth of mounting shaft penetration into the pipette tip to maintain uniform tip interference with the mounting shaft as successive tips are mounted on and ejected from the mounting shaft whereby the pipette tip is easily and firmly mountable on and ejectable from the pipette tip mounting shaft by the application of reduced user generated axial forces.

Description

PIPETTE WITH IMPROVED COMBINATION OF PIPETTE TIP AND MOUNTING AXLE Related Application This application is an application that is partially a continuation of U.S. patent application serial number 09 / 188,032, filed on November 6, 1998, assigned to the same assignee of the present patent application.

FIELD OF THE INVENTION The present invention relates to improvements in pipettes and, more particularly, to air displacement pipettes, including a unique pipette tip tailored to the distal end of the pipette tip mounting shaft. , so that the user of the pipette can easily insert the tip of the pipette into the mounting shaft in a fluid-tight position in which the tip is secured against an unwanted oscillatory movement or displacement from the y-axis, after use, the user of the pipette ejects it easily from the shaft.

BACKGROUND OF THE INVENTION During the development of the single pipette tip disclosed in United States Patent Application Serial No. 09 / 188,030, filed on November 6, 1998 and entitled "Easy Ejection Pipette Tip," and the development of this novel combination of pipette tip and tip mounting shaft described in U.S. Patent Application Serial No. 09 / 188,031 and entitled "Pipette with Improved Pipette Tip and Mounting Shaft", both applications being have been reproduced as if they were inserted to the letter, the special combination of the pipette tip and the mounting axis was discovered, which provides easier tip mounting, better lateral stability of the tip and easier ejection of the tip. tip that the pipette tips available in the market and the tip / shaft combinations. Below is a brief description of the novel pipette tip combination and the uncovered assembly shaft combination.

SUMMARY OF THE INVENTION The present invention incorporates into a pipette that displaces the air the concept of remote and proximal trunk end portions-similar cones on a pipette mounting shaft and a pipette tip, respectively. The parts of the distal and proximal ends have gradually varying surfaces that are substantially parallel inwards and downwards, which incorporate axially and laterally spaced apart regions and support regions on the mounting axis and the tip, respectively. In addition, the present invention incorporates cooperative means on the shaft and tip to ensure uniform depth of penetration of the mounting shaft into the pipette tip to maintain uniform interaction of the tip with the mounting shaft while the tips are mounted successive and are ejected from the assembly axis.

In particular, the present invention comprises a combination of mounting shaft for pipette tip and pipette tip in an air displacement pipette. The mounting axis comprises an elongate body in axial form including a portion of the trunk-end remote end having an external axially varying surface with annular regions on the external surface axially spaced defining an annular sealing zone and an area of lateral support of gradual axial variation. The pipette tip is an elongated tube comprising an open part of the trunk end -nearly contoured, a distant conical open end and annular inner surface regions axially spaced on the internally-tapered internal axially varying surface of the part of the proximal end that defines an annular sealing region and a gradual lateral annular support region. The axial gradual variation of the mounting axis and the pipette tip are to a degree or degree and a half or more from the longitudinal center line of the shaft and preferably between one and one and a half to five or six degrees. The diameter The outer sealing zone on the mounting axis is slightly larger than the internal diameter of the annular sealing region on the pipette tip and the lateral wall of the tip in the area of the annular sealing region is sufficiently thin for that the annular sealing region expands slightly to form an interaction fit and a tight seal between the mounting shaft and the pipette tip when the sealing zone penetrates the sealing region. The axial separation of the sealing and support areas is practically equal to the axial separation of the sealing and support regions. As well, the external diameters of the mounting axis in the axially varying lateral support region are slightly smaller or substantially the same as the corresponding internal diameters of the proximal end portion of the tip in at least some circumferential portions of the lateral region of axial gradual variation, so that the sealing zone penetrates the sealing region. This allows minimal contact between the support zone and the region, without creating a secondary hermetic seal that would result in the undesirable increase in the axial forces required to mount and eject the pipette on and from the shaft. With said structural configuration, when the sealing zone penetrates the sealing region, the support region receives the support zone and provides the lateral support in this aspect that avoids the transverse oscillatory movement of the pipette tip on the mounting axis. that could otherwise occur during the explosion of the pipette tip and the undesirable unclogging of the tip from the shaft.

In addition, the preferred embodiment of the present invention includes the controlled hermetic interaction adjustment, the coinciding lateral annular support region and region, as well as the cooperative means on the pipette and the pipette tip to limit the axial path of the tip on the mounting axis. This ensures the uniform depth of the penetration of the mounting shaft into the pipette tip by maintaining uniform the desired interaction of the tip with the mounting shaft while mounting the successive tips and expelling from the mounting shaft.

In addition, for pipette tip and shaft combinations where the interaction fit between the sealing region and region is approximately .075 mm to approximately .2 mm and the wall thickness of the pipette tip in the region of When sealing is between .2 and .5 mm, it has been found that even the minimum desired tip assembly and ejection forces associated with the present invention can be achieved as well as further improving the stability of the shaft tip when there is a small adjustment of interaction between the region and support zone. The minimum interaction is provided when the lateral region of support of the tip has an internal diameter slightly smaller than the external diameter of the lateral support zone of the shaft, that is, less than .075 mm. In addition, when the axis and tip are concentric and practically circular in the area and region of support, a secondary seal can be created between the zone and region of support without creating an undesirable increase in the axial forces required to mount and eject the tip on and from the axis.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a side view of a standard manual pipette having a pipette tip mounted on a mounting spindle adjacent to the lower end of the pipette tip ejector mechanism.

Fig. 2 is a side cross-sectional view of one embodiment of the combination of pipette tip and mounting shaft according to the present invention showing the hermetic seal between the sealing region and the sealing zone, the coincidence relation of the region and the lateral support zone and a preferred embodiment of the cooperative means including a protrusion on the tip of the pipette to limit the penetration of the mounting shaft into the tip.

Figure 3 is a side view of fragmentary fragmented section of the sealing region within the circle 3 for the pipette tip in Figure 2.

Figure 4 is an enlarged fragmentary side view of an upper part of the combination pipette tip and mounting shaft similar to that of Figure 2, showing a first alternative embodiment of the cooperative means, including a projection on the axis of mounting to limit the penetration of the mounting shaft into the tip.

Figure 5 is similar to Figure 2 and shows a modality in which the axial location of the zone and the sealing region is reversed in relation to the axial location of the support region and region shown in Figure 2.

Figure 6 is similar to Figure 4 and shows an embodiment wherein the axial location of the sealing region and region is reversed relative to the axial location of the support region and region shown in Figure 4.

Fig. 7 is similar to Fig. 2 and is a side cross-sectional view of one embodiment of the combination of pipette tip and mounting spindle according to the present invention, showing the hermetic seal formed by the interaction adjustment between the sealing region and the sealing zone, a minimum interaction adjustment between the region and lateral support zone and a preferred embodiment of the cooperative means, including a protrusion on the pipette tip to limit the penetration of the mounting shaft into the tip.

Figure 8 is an enlarged fragmentary side view of an upper part of the pipette tip and mounting shaft combination similar to that of Figure 7, showing a first alternative embodiment of the cooperative means, including a projection on the axis of mounting to limit the penetration of the mounting shaft into the tip.

Figure 9 is similar to Figure 7 and shows a mode in which the axial location of the sealing region and region is reversed relative to the axial location of the support region and region in Figure 7.

Figure 10 is similar to Figure 8 and shows an embodiment wherein the axial location of the zone and the sealing region is reversed relative to the axial location of the support region and region shown in Figure 8.

DETAILED DESCRIPTION OF THE INVENTION Figure 1 shows a standard manual pipette similar to the PIPETMAN pipette sold exclusively in the United States by Rainin Instrument Co. Inc., assignee of the present invention. The manual pipette is designated in Figure 1 by the number 10 and includes a pipette tip ejector mechanism 12 described in US Pat. No. 3,991,617, issued on November 16, 1976, which is considered to be reproduced as if it were inserted. to the letter.

The pipette 10 comprises a push button 14 connected by a rod to a piston (not shown) located in the body or housing 18 of the pipette. The pressure button 14 can be depressed by a user exerting a downward force on the push button to cause a downward movement on the pipette of the pipette. When the pressure button 14 is released, a quantity of sample liquid is sucked into a disposable pipette tip 20 releasably secured to a lower end of the pipette tip mounting shaft 22 of the pipette. The sample can then be transferred to another container by once again exerting a downward force on the pressure knob 14. After said use, it is common practice to eject the pipette tip 20 from the mounting shaft 22 and replace it with a new tip. pipette to repeat the operation of the pipette 10 to aspirate and supply a new sample fluid.

The ejector mechanism of the pipette tip 12 is used to eject the tip 20 from the mounting shaft 22. In this regard, the mechanism 12 comprises a push button 24 connected with a rod located in a passage (not shown) provided in the upper part of the manually held housing 18 of the pipette 10. The passage and the rod are arranged in order to be able to impart to the rod a translation movement parallel to a pipette axis opposite a spring (not shown) which normally impels the rod to an ascending position. A removable ejector member or arm 26 that includes a tubular upper portion and extends from the lower end of the rod and from the rod, follows the general outer contour of the housing 18 of the pipette to terminate in a sleeve 28. the jacket 28 surrounds a lower conical end 30 of the pipette tip mounting shaft 22 that densely receives the upper end of the disposable pipette tip 20. To eject the pipette tip 20 from the lower end of the mounting shaft 22, the user holds the housing 18 of the pipette and, using his thumb, presses downwardly on the pressure button 24. The downward force on the pressure button is transferred through the rod to the ejector arm of the tip 26 and therefore towards the jacket 28, which presses downwards on the upper end of the pipette tip. When the downward force transferred by the sleeve 28 exceeds the friction between the pipette tip 20 and the mounting shaft 22, the pipette tip is pushed from the mounting shaft. Upon release of the pressure button 24, the spring returns the ejector mechanism of the tip 12 to its normal position with the sleeve slightly spaced from the upper end of a replacement pipette tip that is inserted into the mounting shaft 22, leaving pipette 10 ready for its next aspiration and suction operation.

A preferred embodiment of the structure of the pipette tip and mounting shaft combination of the present invention is shown in Figure 2. As described therein, the mounting axis 32 comprises an elongated body in axial form that includes a part of the truncated-conical distal end 34 having an external surface of gradual axial variation inwardly from the main or upper part of the shaft. The external axially varying surface of the distal end portion 34 comprises axially spaced annular external surface regions defining an annular sealing region 36 adjacent an upper end of the distal end 34 and an annular lateral support zone of variation Gradual downward and inward axial 38 on the far end portion 34 near the lower end of the mounting shaft 32.

The pipette tip is represented by the number 40 and is an elongated plastic tube comprising the open trunk-conical proximal end portion 42, the open conical distal end portion 44 and the annular and axially spaced inner surface regions on the internal surface of gradual downward and inward axial variation 43 of the proximal end portion 42 defining an annular sealing region 46 and an axially tapering lateral support region 48 to coincide with the sealing and support zones 36 and 38 respectively , on the mounting axis 32. As illustrated, the truncated-conical inner surface of the proximal end portion 42 of the tip 40 is similar and slightly larger than the external truncal-conical surface of the distal end portion 34 of the axis 32. Also, in an axial vertical plane, the external surface of the truncated-cone end portion distant from the axis 32 is substantially parallel to the surface trunk internal - conical of the near end portion 42 of the tip 40. As used in this context, "practically parallel" means that the external axially varying surface of the far end portion 34 is in a range of one and a degree and a half of the axial gradual variation of the inner surface 43 of the proximal end portion 42 of the tip 40.

Fig. 3 illustrates in detail a preferred embodiment of the sealing region 46 and comprises the part of the pipette tip 40 of Fig. 2 within the circle 3. As shown, the sealing region 46 is formed by a rim in substantially inwardly extending "V" shape 49, which extends radially inwardly from the side wall 50 of the pipette tip 40. The innermost surface of the flange 49 forms a narrow band or annular sealing line for coupling the sealing zone 36 to the mounting shaft of the pipette tip 32 to form the hermetic seal previously described between the tip and the mounting shaft.

As described in FIG. 2, the outer diameter of the annular sealing area 36 is slightly larger than the internal diameter of the annular sealing region 46 on the pipette tip 40, while the lateral wall 50 of the tip on the The area of the annular sealing region 46 is thin enough so that the annular sealing region expands slightly to form an interaction fit and seal between the mounting shaft 32 and the pipette tip 40 when the sealing zone 36 penetrates sealing region 46. In practice, it was found that the desired interaction adjustment is formed when the difference between the outer diameter of the sealing ring region and the internal diameter of the annular sealing region is at least. 075 mm (mm.). Furthermore, it was found that in practice the thickness of the wall of the pipette tip in the area of the sealing region 46 preferably has between 20 and 50 mm.

Also, according to Figure 2, the axial separation of the sealing region and region is practically equal to the axial separation of the support region and region. Also, the external diameters of the axle 32 within the axially tapering lateral support zone 38 are slightly smaller than, or substantially equal to, *** the corresponding internal diameters of the near end portion within at least some parts circumferential of the lateral support region of axial gradual variation. This allows minimal contact between the support region and region without creating a secondary seal that would result in an undesirable increase in the axial forces required to mount and eject the pipette tip on and off the shaft. With said structural configuration, while the sealing zone 36 penetrates the sealing region 46, the support region 48 receives the support zone 38 and provides lateral support for it, which avoids the transverse oscillatory movement of the pipette tip 40. on the mounting axis 32, which could otherwise occur during the "explosion" of the pipette tip and the inherent undesirable unclogging of the tip from the shaft. In this aspect, it is preferred that the axial separation of the matching lateral support zone 38 and the region 48 from the sealing region and region (36, 46) be substantially equal to the internal diameter of the pipette tip 40 in the of the support region that is coupled with the support area. Said length ratio provides excellent lateral stability for the pipette tip 40 on the mounting shaft 32.

In addition, as illustrated in Figure 2, the present invention includes cooperative means 52 over the pipette of the present invention, and pipette tip 40 to limit the axial path of the tip on the mounting shaft 32. This ensures the depth uniform penetration of the mounting shaft into the pipette tip to maintain uniform interaction of the tip with the mounting shaft while mounting and ejecting successive tips on and from the mounting shaft. In the embodiment illustrated in Figure 2, said cooperative means 52 comprises an annular projection 53 facing upwards and directed inwardly on the inner surface of the pipette tip 40 immediately adjacent to the lateral support region 48. The projection 53 it is designed in such a way that the upper surface thereof is coupled to a downward facing surface such as at the bottom 54 of the distal end 34 of the mounting shaft 32 in an outer circumferential part thereof.

An alternative embodiment of the cooperative means 52 is shown in Figure 4, comprising an annular projection 53 facing outwards and directed downwards on the mounting axis of the pipette tip 32 in which, at the time of inserting the shaft in the next open 42 of the tip engages the upper annular edge 56 of the tip to prevent subsequent penetration of the shaft into the tip.

While, in accordance with the aforementioned, particularly preferred embodiments of the pipette tip of the present invention have been described in detail, changes and modifications can be made without departing from the spirit of the present invention. For example, Figures 5 and 6 show alternative embodiments of the combinations illustrated in Figures 2 and 4 respectively, wherein the axial location of the sealing zone 36 and the region 38 are reversed relative to the axial location of the area 46. and support region 48, respectively.

To further illustrate it, Figures 7, 8, 9 and 10 are similar to Figures 2, 4, 5 and 6 respectively, and show alternative embodiments of the present invention where there is a minimum adjustment of interaction between the lateral support region 48. and the support zone 38 to further improve the lateral stability of the tip 40 on the shaft 32 without introducing an undesirable increase in the axial forces required to mount and eject the tip from the shaft. In this regard, and as illustrated in each of the figures from 7 to 10, it was found that for those pipette tip and shaft combinations where the interaction adjustment between seal zone 36 and region 46 is of about .075 mm to about .2 mm and the thickness of the wall of the pipette tip in the sealing region 46 and in the lateral support region 48 is between .2 and .5 mm. , the lateral stability of the tip 40 on the shaft 32 can be further improved while retaining the desired minimum of tip and ejection assembly forces associated with the present invention when there is minimal adjustment interaction between the region and bearing zone. The minimal interaction is provided by the lateral support region 48 of the tip 40 which has an internal diameter slightly smaller than the external diameter of the lateral support zone 38 of the shaft 32, that is, less than .075 mm. Further, when the shaft 32 and the tip 40 are concentric and practically circular in the region 38 and support region 48, a secondary seal can be created between the support region and region without obtaining an undesirable increase in the required axial forces. to mount the tip on the shaft and eject it from it.

Accordingly, the present invention is limited in scope only by the terms contained in the following claims.

Claims (11)

1. An air displacement pipette (10) comprising: a mounting shaft for pipette tip (32) and a pipette tip (40) including zones (36, 38) and lateral support regions (46, 48), respectively, separated in axial form and of annular of coincidence and troncal -conical of gradual variation inwards and descenders; and means (52) to ensure uniform depth of penetration of the mounting shaft into the pipette tip to preserve a uniform interaction of the tip with the mounting shaft while mounting and ejecting successive tips on and from the mounting shaft.
2. In an air displacement pipette (10), the combination comprising: a pipette tip mounting shaft (32) comprising an axially elongated body including a truncated-cone end portion (34) having a external trunk-conical surface having annular surface regions and axially spaced defining an annular sealing zone (36) and an annular support side region of axial and inward gradual variation (38); a pipette tip (40) comprising an elongated tube having a portion of the trunk proximal end - open cone (42), a portion of the open conical distal end (44) and annular internal surface regions and axially spaced apart a truncal-conical inner surface of the proximal end portion defining an annular sealing region (46) and an annular lateral region of axial and inward gradual variation (48) to match the sealing region and region respectively; and cooperative means (52) on the pipette shaft (32) and pipette tip (40) to limit the axial path of the tip on the mounting shaft to ensure uniform penetration depth of the mounting shaft at the tip of pipette to preserve the uniform interaction of the tip with the mounting axis while assembling the successive tips on the assembly axis and expelling from it.
3. The combination according to claim 2, wherein the cooperative means (52) comprises an upward facing protrusion (53) on an inner surface of the pipette tip for coupling a lower surface (54) of the distal end (34). ) of the pipette tip mounting shaft (32).
4. The combination according to claim 2, wherein the cooperative means (52) comprises a downward annular projection extending outwardly (53) on the pipette tip mounting shaft (32) to engage at one end face up (56) of the pipette tip (40).
5. The combination according to claim 2, wherein the annular sealing region (36) on the mounting shaft (32) has an external diameter slightly larger than the internal diameter of the annular sealing region (46) on the tip of the seal. pipette (40) and the pipette tip in an area that includes the annular sealing region that includes a sidewall thin enough for the annular sealing region to expand slightly to form an interaction fit and an airtight seal between the shaft of assembly (32) and the pipette tip (40) when the sealing zone (36) penetrates the sealing region (46).
6. 6. The combination according to claim 5, wherein the side wall has a thickness between .2 and .5 mm.
7. 7. The combination according to claim 5, wherein the sealing region (46) has an internal diameter of at least .075 mm smaller than the outer diameter of the sealing zone (36).
8. 8. The combination according to claim 2, wherein the axial separation of the sealing and support areas (36, 38) is practically equal to the axial separation of the sealing and support regions (46, 48) so that while the sealing zone penetrates the sealing region, the support region receives the support zone and provides lateral support in that aspect, which avoids the transverse oscillation of the pipette tip on the mounting axis that could otherwise occur during the explosion of the pipette tip and the inherent undesirable unclogging of the tip from the shaft.
9. . The combination according to claim 2, wherein the axial separation of the lateral zone (38) and support region (48) from the sealing zone (36) and region (46) is practically equal to the internal diameter of the tip pipette (40) in the support region.
10. 10. The combination according to claim 2, wherein the inner surface of the proximal end portion (42) of the tip (40) is substantially parallel to the outer surface of the distal end portion (34) of the mounting shaft (32)
11. 11. The combination according to claim 8, wherein the annular sealing region (36) on the mounting shaft (32) has an external diameter slightly larger than the internal diameter of the annular sealing region (46) on the tip of the seal. pipette (40) and the pipette tip in an area including the annular sealing region comprises a side wall thin enough for the annular sealing region to expand a little to form an interaction fit and an airtight seal between the shaft of assembly and the pipette tip when the sealing zone penetrates the sealing region, and wherein the annular bearing area on the mounting shaft has an external diameter slightly larger than the internal diameter of the annular region of support on the tip of the cap. pipette, and the pipette tip in an area including the annular support region comprises a side wall thin enough for the annular support region to expand a little to form a small adjustment of interaction between the mounting axis and the pipette tip when the support region penetrates the support region [sic]. The combination according to claim 11 wherein the side wall of the pipette tip of the sealing region (46) and of the support region (48) has a thickness of between .2 and .5 mm. The combination according to claim 12, wherein the sealing region (46) has an internal diameter of about .075 mm to about .2 mm less than the outer diameter of the sealing zone (36) and wherein the region support (48) has an internal diameter smaller than the outer diameter of the support zone (38) of .075 mm or less.