GB2249171A - Liquid sampling - Google Patents

Abstract

A device for taking liquid samples has a casing (11) with at least one inner cylindrical passage (12) and a plunger (13). At the bottom of the casing (11) is a tip or head-pieces (23) arranged coaxially with the passage (12). The tip (23) houses a compression spring (25) with one end secured to the bottom end of the casing (11). The other end has a straight portion (27) extending coaxially in the lower part of the tip (23) and projecting outside the lip. The spring (25) effects stirring of liquid samples taken via the tip (23). <IMAGE>

Description

DbVIUt FO AKING LIwUI Ai4i DVICss SGH TAXIiiG LIvUID o 'LES This invention relates to equipment for chemical and physical laboratories, and more particularly to devices for taking liquid samples.

She invention can find application in biochemical, biological and chemical research, as well as for carrying out analyses in applied biology, chemistry and medicine.

There is known a device for taking liquid samples (cf., US, P, 4,526,046) in the form of a syringe comprising a casing fashioned as a cylindrical tube having an additional passage extending from the upper end of the tube and confining the interior of the tube to accommodate a measured quantity of liquid. The lower end of the tube has a hole communicating with the interior of the tube. A piston slides at the top part of the tube between its uppermost and lowermost positions. The syringe also includes a replaceable headpiece communicating with the hole at the lower end of the tube. The interior of the tube accommodates a ferromagnetic bar element to stir measured quantities of liquid by executing vertical movements in response to the application of an alternating magnetic field.

In order to take a liquid sample, the piston is moved to the lowermost position. The lower hole of the replaceable headpiece is immersed in the liquid, and the piston is raised to the uppermost position.

Under the action of a pressure difference in the interior of the tube under the piston and outside a measured volume of the liquid is conveyed to the tube interior. In order to stir the thus taken sample of the liquid, an external alternating magnetic field is applied to the device at a location of the ferromagnetic bar. The ferromagnetic bar is thereby caused to vertically reciprocate inside the tube and stir the measure volume of the liquid. After stirring the liquid is forced out of the syringe by moving the piston the lowermost position.

However, stirring is accompanied by the formation of liquid drops between the inner walls of the tube and ferromagnetic bar due to the forces of surface tension to result in less accurate measuring of the quantities of liquid. In addition, stirring the measured quantities of liquid necessitates the provision of an alternating magnetic field which overcomplicates the device structurally.

The present invention aims at providing a device for taking liquid samples in which means for stirring measured quantities of liquids would be so constructed as to simplify the device in general and ensure a higher accuracy of measuring.

The invention broadly resides in a device for taking liquid samples comprising a tip portion defining a cavity and having a hole at the end thereof, means for drawing liquid into the cavity through the hole, and means comprising a spring disposed in the cavity for agitating liquid therein, one end of the spring being fixed relative to the tip portion and the other end of the spring having an element projecting through said hole.

More specifically the aims of the invention are attained by a device for taking liquid samples comprising a casing with at least one inner cylindrical passage, plungers provided in each inner cylindrical passage to be capable of moving axially of these passages, means for measuring the quantity of the liquid secured at the casing, replaceable headpieces sealingly secured at the bottom of the casing to be coaxial with each ~~~~~~~~~~~~ inner cylindrical passage communicating with these passages and having a hole at their lower end, and at least one means for stirring the measures quantities of the liquid, according to the invention, the means for stirring the measured quantities of liquid has the form of a compression spring mounted inside each replaceable headpiece, one end of this spring being secured to the bottom of the casing, whereas the other end of the spring has a straight portion extending coaxially in the lower part of the replaceable headpiece and projecting outside the headpiece through the hole of the replaceable headpiece.

In order to ensure that the device could operate with chemically corrosive liquids, the compression spring of the stirring means should be fabricated from a chemically resistant material.

Ihe present invention simplifies the means for stirring the liquid while ensuring a higher accuracy of metering the liquid, stirring of the measured quantities of liquid being executed by simple reciprocations of the stirring means vertically.

The invention will now be described in greater detail with reference to a specific embodiment thereof taken in conjunction with the accompanying drawings, in which: Fig. 1 shows a longitudinal sectional view of the lower part of a syringe for taking liquid samples according to the invention; and Fig. 2 is a partial longitudinal section of a pipette for taking liquid samples according to the invention.

Referring to Pig. 1, a device for taking samples of a liquid in the form of a syringe comprises a casing 1 having a passage 2 accommodating a plunger 3 capable of movement along axis 4 of the passage 2.

The bottom part of the casing 1 accommodates a replaceable headpiece 5 arranged coaxially with the inner cylindrical passage 2 and communicating with this passage 2. A hole 6 is provided at the lower end of the replaceable headpiece 5. The replaceable headpiece 5 in turn aconmDdates a means for mixing samples of the liquid in the form of a compression spring 7 one end of which is secured on a projection 8 provided at the bottom part of the casing 1, the other end of the spring 7 having a straight portion 9 extending coaxially with the headpiece 5 at the bottom part of the replaceable headpiece 5 and projecting outside through the hole 6 of the headpiece 5 away from the headpiece 5.The casing 1 is fabricated from a transparent material with the outer surface thereof having a scale 10 to monitor the quantity of sample taken.

With reference to Fig. 2, a device for taking liquid samples has the form of a pipette, and includes a casing 11 with an inner cylindrical passage 12 ac ccooodating a plunger 13 capable of movement along axis 14 of this passage 12. A push button 16 is provided outside the casing 11 at a top end 15 of the plunger 13. The casing accommodates a rotatable nut 17 for presetting the volume of liquid with a cylindrical scale 18 to accurately meter the volume of liquid and an indicator line Iu, and a means for visually metering the liquid volumes in the form of a rough volume scale 20 graduated at a round plate 21 having an indicator line 22.

Elements of the kinematic linkage and the operating principle of the plunger 3, nut 17 for presetting the volume of liquid to be metered, and means for visually monitoring the volumes of liquid metered are widely known in the art (cf., e.g., SU, A, 1,154, 779).

Provided at the lower tapered part of the casing 1 is a sealed replaceable tip or headpiece 23 having a hole at its bottom end. The headpiece 23 accommodates a means for mixing liquid samples in the form of a compression spring 25. One end of the compression spring 25 is secured at a projection 26 of the casing 11. The other end of the compression spring 25 has a straight portion 27 extending coaxially in the bottom part of the replaceable headpiece 23 and projecting outside the headpiece 23 through the hole 24.

When the device for taking liquid samples has the form of a multichannel pipette, the casing includes several internal passages, each accommodating a plunger. The lower part of the casing has srojections equal in number to the number of the inner cylindrical channels with each such channel having replaceable tips sealingly secured thereon. Each replaceable tip of headpiece aconmodates a liquid mixing means constructed substantially as described with reference to Fig.2.

To ensure safe operation with chemically corrosive liquids the compression spring 25 is made of a stainless steel.

The proposed device for taking liquid samples in the form of a syringe operates in the following manner.

The repleceable headpiece 5 is fitted onto the lower tapered part of the casing 1 (Pig, 1) to take a sample. The plunger 3 is moved to its bottom position. The headpiece 5 is immersed in the liquid and the plunger 3 is moved upwards to a distance read at the scale IO.

Under the action of a pressure difference in the space under the plunger 3 and outside the replaceable headpiece 5 is filled with a volume of liquid corresponding to the stroke of the plunger 3.

Then other liquids are sucked in by moving the plunger 3 upwards to a distance corresponding to the desired quantity of the liquid sample.

after thid the liquids filling the syringe are mixed. The end of the straight portion 9 of the compression spring 7 projecting outside from the hole 6 of the replaceable headpiece is caused to bear on the bottom of the chemical glassware (not shown).

While holding the device in the vertical position, the operator executes multiple vertical reciprocations of the device.

The spring 7 is caused to be compressed and extended, the distance between the coils of the spring 7 changes, and the samples of the liquid sucked into the replaceable headpiece 5 are vigorously stirred.

During operation of the pipette associated with successively sucking several accurately measured quantities of the liquid into the replaceable headpiece 25 (Fig. 2), the volume of each such sample of the liquid is preset by rotating the nut I7 until the required figure on the scale 20 registers with the indicator line 22. While holding the casing 11 of the pipette vertically, the button 16 is pressed until it bears on the top part of the casing 11, whereby the plunger 13 moves to the lowermost position. Then the replaceable headpiece 23 is immersed in the liquid to be sampled, and the button 16 is released. The plunger then moves upwards, and a measured quantity of liquid is delivered to the replaceable headpiece 23.

The stroke of the plunger 13 determined by the volume of the liquid being sampled is monitored by the reading of the fine scale 48 and coarse scale 20.

Then the operator holds the casing of the pipette in the vertical position to stir the measured quantities of the liquids in the replaceable headpieces 25 secured at the bottom part of the casing as has been described.

The invention simplifies the device for taking liquid samples structurally and makes the device more convenient in operation. In multichannel pipettes it is possible to carry out approximate immunological analysis directly in the replaceable tips of the pipette.

Claims (4)

CLAIMS:

1. A device for taking liquid samples comprising a tip portion defining a cavity and having a hole at the end thereof, means for drawing liquid into the cavity through the hole, and means comprising a spring disposed in the cavity for agitating liquid therein, one end of the spring being fixed relative to the tip portion and the other end of the spring having an element projecting through said hole.

2. A device for taking liquid samples comprising a casing with at least one inner cylindrical passage, plungers provided in each such inner cylindrical passage to be capable of moving axially of these passages, a means for measuring the quantity of liquid secured on the casing, replaceable headpieces sealingly secured at the bottom part of the casing to be co-axial with each inner cylindrical passage, communicating with these passages, and having a hole at their lower end, at least one means for stirring the measured quantities of the liquid in the form of a compression spring mounted inside each replaceable headpiece with one end of the spring being secured to the bottom of the casing and the other end of the spring having a straight portion extending coaxially in the lower part of the replaceable headpiece and projecting outside through the hole of the headpiece.

3. A device as claimed in claim 1 or 2, in which the compression spring of the means for stirring the measured quantities of liquid is made of a chemically resistant material.

4. A device for taking liquid samples substantially as described in the description with reference to the accompanying drawings.