EP0351574B1 - Removable pipette tip shaped as a container adapted to the shape of a receiving piece, especially a tapered pipette end - Google Patents

Abstract

A fittable pipette tip consists of a vessel which is designed to fit a particularly conical fitting head of a pipette and which may be conical and has a fitting top opening and a bottom opening for receiving and discharging a pipette. A sealing portion with which the pipette tip is adapted to contact the fitting head is spaced from the top end of the pipette tip and is formed with a smooth inside seating surface and has a smaller wall thickness than other portions of the pipette tip so that the sealing portion of the pipette tip is yieldable for adaptation to the fitting head. The pipette tip is reduced in wall thickness at least in the sealing portion by a provision of recesses in the outside and inside surfaces of the wall of the pipette tip.

Description

The invention relates to an attachable pipette tip according to the preambles of claims 1 and 8.

Furthermore, the invention relates to a form of such a pipette tip in the form of an at least partially conical vessel, in which the sealing region is designed with a smooth seat at a distance from the plug-on opening at the upper end of the pipette tip.

A cylindrical design in the area of the plug-on head piece is also reserved.

The reference to the smooth seat does not rule out roughening of the surface. In this respect, there can also be slight profiles which improve the seal on the working cone. Basically, a smooth seat is preferred.

In addition, it is noted that the plug-on head piece of a pipette can represent a cone per se, which has a passage and is inserted into the conical wall part of the pipette tip. This includes the fact that such a plug-on cone can also be arranged projecting outwards on a tip part of the pipette, i. H. that it projects in a ring shape so that the sealing seat of the attachable pipette tip is only reached in its area.

From the point of view of a sealing seat, it is included that the outwardly projecting push-on headpiece has a spherical surface in its ring-shaped seating area. This also creates a sealing seat, in particular on an elastic and resilient seat surface, of the pipette tip, the elasticity causing the pipette tip to fit tightly against the ring-shaped seat region of the plug-on head piece.

Pipette tips with a conical seat are known for example from DE-C-10 90 449. The push-on cone is conical over its entire length. A flexibility of the push-on tip itself is included, but only a small tolerance compensation between the cone of the tip and the push-on cone of the pipette is possible. Therefore, leaks have been repeatedly observed in the practical use of this arrangement.

From DE-C-12 91 142 a pipetting device is known, on which the attachable pipette tip has an upper projecting edge in order to stabilize it. The wall thickness runs from top to bottom. In the upper area, which still includes the sealing area, the shape has been strengthened by axial wall bars. A stiffening should be brought about in the area of the seat. This measure also did not provide a reliable seal.

The same results from DD-B-50 016, according to which the plug-on vessel can be placed with a conical plug-on head piece of the pipette with a conical seat. The upper opening is stiffened by a rim.

This aspect of stiffening in the area of use of the plug-on pipette tip is evident from US Pat. No. 3,732,734. There, the push-on area is just reinforced by an outer wall part that protrudes outwards in steps. If annular ribs are then arranged on the inside, these do not represent a weakening of the wall thickness to make the wall more flexible, but only form circular ring-like sealing strips, the base of which is also arranged on a practically non-deformable wall part of the pipette tip. This wall part is also conical in the area of these ribs in the basic shape like the plug-on head piece of the pipette.

Such ribs do not form a secure fit or a quasi smooth seating area. This known version has, for example, only a peripheral edge web at the upper edge goes through with the same wall thickness over the major part of the pipette tip length. At most, the wall thickness is reduced in the area of the lower discharge opening.

A pipette tip according to US-A-4,349,109 is made up of several sections, the uppermost of which, as a truncated cone, has an inner surface with a conical shape, for example of 3 °, and forms a wedge seat on a pipette. This section with the seat, which forms the sealing area, has the greatest wall thickness of the pipette tip and is therefore particularly unyielding. The seat surface passes through an inclined step surface into the lower wall section of the pipette tip, which is offset with respect to the upper section with the seat surface in order to also make it possible for pipettes of smaller volume to find a seat. However, the upper edge of the lower section is particularly firm and unyielding due to the outwardly projecting wall of the upper section. In this respect, there is no adaptability and, because of the wall offset with respect to a center line, there is also no overlap of wall contours.

From DE-C-25 26 296 a plug-on pipette tip of the type specified above is already known, which has a wall thickness weakening in the sealing area, so that an adaptation to the conical plug-on head piece can take place. This presupposes that the pipette tip consists of a material, in particular plastic, which is particularly elastic, at least flexible, but preferably has certain recovery properties that are caused when it expands. In addition to a rubber material, for example Plastic, as it is on the market under the trade name polypropylene.

From the cited literature it also follows that the resilient adaptability in terms of improving the fit should compensate for inaccuracies in both the pipette tip and the plug-on head piece, so that greater manufacturing tolerances are permitted, but at the same time an improved seal is achieved. The forces during actuation, i.e. when sliding on and also when removing the pipette tip.

The wall thickness weakening already known in this sense has proven itself. This weakening of the wall thickness is arranged on the outside. It either runs around the circumference or is formed in places by groove-like depressions. In the case of the wall thickness weakening arranged on the outside, it is taken into account that this is made stronger at the upper edge of the sealing area than at the lower end of the pipette tip. It is taken into account that there is an annular step on the outside at the upper edge of the sealing area and that the wall thickness of the pipette tip in the sealing area decreases towards the top.

Such an embodiment in the arrangement on the outside is also preferably included because it is relatively easy to implement using appropriate injection molds. In practice, however, it has been shown that this measure can only be used to a limited extent from the point of view of demoldability by avoiding undercuts. Especially with slim pipette tips with low conicity, it is very difficult to find an adequate one To achieve wall thickness weakening in the sealing area and to carry out this wall thickness weakening evenly over the entire area of a defined sealing zone. Typically, the wall thickness changes over the sealing area. For this reason, the sealing area of such pipette tips is also poorly visible, which can lead to uncertainties for the user.

The present invention is therefore based on the object of creating a pipette tip in which the weakening of the wall thickness can be chosen as desired, the sealing area is clearly visible and can be produced without harmful undercuts impairing the demoldability. This applies in particular to slim pipette tips with low conicity up to at least approximately cylindrical designs.

This object is achieved by claims 1 and 8. The weakening of the wall thickness is therefore provided by recesses in the pipette tip wall, at least in the sealing area, outside and inside. This has the particular advantage that the wall thickness in the seat area or sealing area becomes more uniform, to the extent that an identical wall thickness is created over the entire sealing area.

In the preferred embodiment, the object is achieved in that an outer wall thickness weakening coming from below and an inner wall thickness weakening coming from above overlap in a defined sealing area.

Starting from the wall of a pipette tip, the expression of a weakening of the wall thickness progressing to overlap arises in such a way that it starts directly from the wall and ultimately ends in one step in the weakening. The step lies in the internal weakening of the wall thickness with respect to the insertion opening below and the outer wall thickness weakening above.

This results in the surprising advantage that, in the case of larger wall thicknesses, a reduction in wall thickness that is arbitrarily reduced in the overlap area, clearly limited at the top and bottom, clearly visible and effective can also be achieved with pipette tips of low conicity.

While the disadvantage of the prior art is that there is a different wall thickness in the sealing area, which e.g. decreases from bottom to top, the simultaneous arrangement of an inner wall thickness weakening results in addition to the above the further advantage that special wall thickness profiles can be selected.

Due to the weakening of the wall thickness coming from below on the outside and coming from above on the inside, there are ring steps at the end of the wall thickness weakening, and a further advantage is the use of the inner ring step as a stop for the plug-on headpiece of the pipette, whereby a defined, reproducible fit is achieved.

With a wall thickness weakening outside upwards to the push-on opening to an upwardly widening ring step for the transition into the normal wall thickness, there are limits, which are determined by the greatest wall thickness weakening, and secondly there is the disadvantage that there is a different wall thickness in the sealing area, which tapers from bottom to top. Due to the simultaneous arrangement of an inner wall thickness weakening, not only can the wall thickness in the seating area or sealing area be evened out, to the extent that an identical wall thickness is created over the entire sealing area, but special wall thickness profiles can also be selected.

From this point of view, a preferred feature in an embodiment in which the wall thickness weakening increases from the outside upwards towards the push-on opening towards an upwardly widening step surface for the transition into the normal wall thickness is that the wall thickness weakening inside in the sealing region in the opposite sense from top to bottom increases at the bottom and has a retracted ring step at the lower end. It is expediently included that the inner conical ring step drawn in downwards has a slight slope of the order of 30 °. In this respect, there is a smooth transition in the interior, whereby it can be assumed that a projecting push-on head piece has only a certain depth or axial length and in this respect a seat improvement is achieved by a slight slope of the transition if, due to the elasticity of the material of the pipette tip an effective contraction takes place.

It is particularly preferred, however, that the opposite wall thickness weakening, which increases in the opposite direction, forms an essentially parallel wall section of the pipette tip in the sealing region between the outside and inside.

This ensures that both with a conical shape of the push-on head piece and with a spherical shape, the uniform fit is improved, in particular with a spherical shape, the edging is favorably influenced, the push-on and release forces being relatively low. In this version, too, the inner ring step is preferably used as a stop for the conical plug-on head piece of the pipette tip, whereby the additional advantage of a defined, reproducible seat can be used.

From the above point of view, it is included in an advantageous embodiment that due to the opposing weakening of the wall thickness inside and outside, there remains a wall section which runs obliquely to the wall center line of the conical pipette tip and which has at least a lower conicity than the wall center line.

If the wall thickness in the sealing area remains the same, there are possibilities to adapt conicity to special working conditions or, in this context, to include special conditions for fitting and loosening the tip when deviating from the conicity.

It is particularly preferred, however, that due to the opposing weakening of the wall thickness inside and outside there remains a wall section which runs obliquely to the wall center line of the conical pipette tip and which is essentially cylindrical around the central axis of the pipette tip. This design creates an advantageous fit if the plug-on head piece of a pipette has an outwardly projecting step that is spherical. This spherical design has the same diameter at the top and bottom, so that the overlapping of a cylindrical seating area of a pipette tip with expansion and elasticity enables a particularly tight and firm fit, which also creates the requirement of a seat as a kind of joint between the pipette and the pipette tip .

Without loosening the seat or reducing the seal, it is possible on the one hand to change the axial alignment between the pipette tip and the pipette, if desired, within certain limits, or on the other hand, as already mentioned above described in connection with the inner ring step to achieve a defined, reproducible fit. In this connection, the strength of the seat can advantageously be improved further by creating a wall section that runs obliquely to the wall center line of the conical pipette tip and that forms a cone around the central axis of the pipette tip, which forms from the top to the bottom extended and designed in the opposite direction to the cone of the continuous pipette tip wall.

Although there is a slight undercut, this is not harmful, but on the contrary, when the mold is opened, causes the pipette tip to remain fixed on the inner mandrel until it is stripped off by an ejector. The desired reproducible spray cycles are achieved in this way. Another advantage of this design is the fact that the material is elastic, which results in a certain snap or push-button effect which, in conjunction with the inner ring step that can be used as a stop, leads to a particularly secure and defined fit of the pipette tip.

The embodiment according to the invention with a wall thickness weakening inside and outside therefore has advantages and, in the preferred embodiment, also enables a particularly simple design of the manufacturing mold while avoiding slides or similar mechanisms that would be necessary for realizing undercuts. The overlap of the outer and inner wall thickness weakening according to the invention arises after the corresponding design of the molding tools in a simple manner when joining the inner and outer shape in each injection cycle.

Fig. 1

eine Seitenteilansicht einer Pipettenspitze einer erfindungsgemäßen Ausführungsform im Schnitt;

Fig. 2

eine Teildarstellung eines oberen Abschnittes einer Pipettenspitze im Schnitt zur Erläuterung einer zylindrischen Ausgestaltung;

Fig. 3

eine Seitenteilansicht zur Erläuterung einer Wand einer Pipettenspitze im oberen Bereich in der Nähe der Einstecköffnung, wobei der Dichtbereich mit einem sich nach oben öffnenden Konus ausgeführt ist.

The invention is explained below with reference to exemplary embodiments which are shown in the drawing. The drawing shows:

Fig. 1

a partial side view of a pipette tip of an embodiment according to the invention in section;

Fig. 2

a partial view of an upper portion of a pipette tip in section to explain a cylindrical configuration;

Fig. 3

a partial side view for explaining a wall of a pipette tip in the upper region near the insertion opening, the sealing region being designed with a cone opening upwards.

The pipette tip 1 has an upper attachment opening 2, which can be widened by an edge bevel. The upper section is bordered by a relatively thick wall 3. This is reinforced on the outside by ribs 4, so that stability is present here. On this wall, a web 3 'running around can still be arranged on the upper edge outside.

This wall thickness continues up to area 5 and is uniform. This area ends at 6. Below the transverse line 6, the wall thickness decreases. A longitudinal section, which contains the sealing region 10, adjoins the transverse line 6. This sealing area extends to the transverse line 7. Below this, the pipette tip with essentially the same wall thickness, which is present above the transverse line 6, continues downwards to a lower receiving and dispensing opening 8. In addition, it is noted that also included becomes that the wall thickness can typically taper towards the lower discharge opening from the wall thickness below the sealing region 10.

The center surface of the wall of the conical body of the pipette tip 1 is designated with 9 on the whole and by the dash-dotted wall center line. It runs in the middle of the wall above cross line 6 and below cross line 7.

In the sealing area 10 between the transverse lines 6 and 7 - the sealing area not having to extend exactly to these transverse lines, but rather being less in the axial length of the pipette tip - the wall thickness is reduced.

On the outside there is a recess running around as a wall thickness weakening 11, which has an inner axial lateral surface 12 which extends at an angle to the wall center line 9. It is at least less conical. At its lower end at 13, approximately in the region of the transverse line 7, it starts from the outside of the normal wall thickness and approaches the normal wall thickness again at the top through an annular step 14 which widens conically outwards. Such a weakening of the wall thickness alone would result in a different wall thickness over the sealing region 10. In the described embodiment, a corresponding wall thickness weakening 15 is now arranged on the inside. It starts approximately from the point of use of stage 14 and deepens downward approximately to the height of end 13, at which the external weakening of the wall thickness begins. Because the inner wall thickness weakening 15 now increases downwards, it then passes through a conical ring ring 16 which contracts inwards into the wall 17 of the pipette tip which is of normal thickness. The lower conical ring step 16 drawn in has, for example, a slope of 30 °.

It can be seen that the outer wall thickness weakening 11 comes from below and the inner wall thickness weakening 15 comes from above with regard to the pipette tip, the top being determined by the plug-on opening 2. This direction results from the increasing thickness of the wall thickness weaknesses in their course, and it can also be seen that the two wall thickness weaknesses 11 and 15 overlap.

The wall section 18 between the wall thickness weakenings 11 on the outside and 15 on the inside has the same thickness over the length of the sealing region 10 if the surfaces forming the wall are parallel.

2 shows an example of a cylindrical design of the pipette tip in the upper region. At the plug-on opening 2, the pipette tip has a wall 3 with normal, considerable wall thickness. From the plug-on opening 2, a cylindrical, inner wall thickness weakening 19 goes down to an annular step 20. This wall thickness weakening 19 comes from above.

In contrast, on the outside, a wall thickness weakening 21 comes from below and ends in an upper, downward ring step 22. In the area between the opposing ring steps 20 and 22, the sealing area 10 is arranged, in which the two wall thickness weakenings overlap and thus create a considerable wall thickness weakening becomes. This weakening of the wall thickness can be achieved by appropriate dimensioning of the inner diameter 23 and the outer diameter 24, i.e. in the end can be made arbitrarily thin by designing the wall thickness weakenings.

3 shows an embodiment in which a outer wall thickness weakening 25 coming from the outside ends in an upper conical ring step 26, while an inner wall thickness weakening 27 coming from above ends in a lower conical ring step 28. In the sealing area 10 there is therefore a wall section 29 with a smaller wall thickness than above and below the sealing area, but the seat surface in the sealing area is conical, essentially with a cone tightening of 1:15. This example is given in order to explain the possibility within the scope of the invention of setting an upwardly widening cone angle in the sealing area, the wall thickness being essentially constant even in the sealing area. The wall section 29 has less conicity than the total wall of the pipette tip or the wall center line.

The upper wall 3 below the push-on opening 2 is made thicker than the wall in the sealing area and the pipette tip according to FIG. 3 also has a wall 17 of normal thickness below the sealing area.

Claims (9)

1. A fittable pipette tip shaped as a vessel, in particular a tapered vessel, which has at least a portion thereof adapted to the shape of a receiving piece, in particular a cone of a pipette, said pipette having a top fitting opening (2) and a bottom opening (8) for receiving and dispensing a liquid, wherein the sealing area (10) where the pipette (10) is engaging the receiving piece comprises a smooth inside seat surface in the wall of the pipette tip at a location spaced from the top end of the pipette tip and is yieldable and adaptable by a wall thickness reduction (11) relative to the pipette tip wall (3), the wall thickness reduction of the pipette tip wall being provided by a recess at least in the outer sealing area, which recess increases in depth in an upward direction toward said top opening (2) to a location where the reduced wall thickness merges into the normal wall thickness at an external shoulder (14), characterized in that said wall thickness reduction (15,27) of the pipette tip wall is provided at least in the inner sealing area by a recess (15, 19,27) which increases in depth in a downward direction to a location where the reduced wall thickness merges into the normal wall thickness at an internal shoulder (16,20,28).
2. A pipette tip according to claim 1, characterized in that an external wall thickness reduction (11,21,25) from below and an internal wall thickness reduction (15,19, 27) from above extend both in a defined area (6,7) including said sealing area (10).
3. A pipette tip according to claim 1 or claim 2, characterized in that said internal shoulder is a downwardly flaring, conical annular shoulder of a small taper of an order of 30°.
4. A pipette tip according to any of claims 1 to 3, characterized in that said wall thickness reductions (11, 21,25; 15,19,27) increasing in depth in mutually opposite directions define between them, on the outside and inside, in the sealing area (10) a wall portion (18,29) of the pipette tip (1) which has substantially parallel surfaces.
5. A pipette tip according to any of claims 1 to 4, characterized in that said opposite wall thickness reduction means (27,25) at the inside and outside provide for a wall portion (29) to extend obliquely with respect to the wall center line of the conical pipette tip (1), which wall portion (29) is at least of a smaller taper than the wall center line.
6. A pipette tip according to any of claims 1 to 4, characterized in that said opposite wall thickness reductions (11,15) at the inside and outside provide for a wall portion to extend obliquely with respect to the wall center line (9) of the conical pipette tip (1), which wall portion is substantially cylindrical about the central axis of the pipette tip.
7. A pipette tip according to any of claims 1 to 4, characterized in that the opposite wall thickness reductions (11,15) at the inside and outside provide for a wall portion to extend obliquely with respect to the wall center line (9) of the conical pipette tip (1), which wall portion forms a cone about the central axis of the pipette tip, which cone is upwardly flaring and is of a taper opposite to that of the cone of the continuous pipette tip wall (3, 17).
8. A fittable pipette tip shaped as a vessel, in particular a tapered vessel, which has at least a portion thereof adapted to the shape of a receiving piece, in particular a cone of a pipette, said pipette having a top fitting opening (2) and a bottom opening (8) for receiving and dispensing a liquid wherein the sealing area (10) where the pipette (10) is engaging the receiving piece comprises a smooth inside seat surface in the wall of the pipette tip at a location spaced from the top end of the pipette tip and is yieldable and adaptable by a wall thickness reduction (11) relative to the pipette tip wall (3), the wall thickness reduction of the pipette tip wall being provided by a recess at least in the outer sealing area, which recess extends in an upward direction toward said top opening (2) to a location where the reduced wall thickness merges into the normal wall thickness at an external shoulder (14), characterized in that said wall thickness reduction (15,27) of the pipette tip wall is provided at least in the inner sealing area by a recess (15,19,27) which extends oppositely in a downward direction to a location where the reduced wall thickness merges into the normal wall thickness at an internal shoulder (16,20,28), and in that the inner and outer wall thickness reduction (19,21) are of cylindrical shape.
9. A pipette tip in accordance with claim 8, characterized in that the inside cylindrical wall thickness reduction (19) and the outside cylindrical wall thickness reduction (21) are provided on a cylindrical wall portion of a pipette tip in an overlapping relationship in the sealing area (10).

Images