GB2057291A

GB2057291A - Safety pipette filler

Info

Publication number: GB2057291A
Application number: GB7930277A
Authority: GB
Original assignee: Hackett W J
Current assignee: Hackett W J
Priority date: 1979-08-31
Filing date: 1979-08-31
Publication date: 1981-04-01

Abstract

A pipette filler (1) for avoiding ingestion of liquid (18) to be measured by the pipette (2) and for avoiding inhalation of fumes from such a liquid (18) comprises a piston-cylinder assembly (5 and 8) defining a variable volume chamber (10) having a vent (13). The head end (6) of the cylinder (5) carries a connector (15) for attachment to the upper end of the pipette (2). A rubber tube (14) is suitably connected to the vent (13) for controlling the opening of the vent (13). To fill the pipette (2), the vent (13) is closed, e.g. by squeezing the tube (14), and the piston (8) is withdrawn from the cylinder (5). To empty the pipette (2), the vent (13) is opened, e.g. by releasing the tube (14). <IMAGE>

Description

SPECIFICATION Safety pipette filler Technical field of the invention The invention relates to a deviceforfilling pipettes with liquids which are dangerous or unpalåtatable when taken into the mouth or which have dangerous or unpleasant fumes.

Background art When a pipette is used to extract a measured volume of liquid from a container, it is normal to dip the bottom end of the pipette into the liquid and to suck the top end of the pipette with the mouth.

Liquid is sucked into a bulbous portion of the pipette and into the top end of the pipette until the level of the liquid is above a volume marker in the top end of the pipette. The top end of the pipette is then removed from the mouth and a finger is placed over the open top end of the pipette to prevent the liquid running from the pipette. The volume marker is then held at eye level and the finger blocking the top end of the pipette is raised slightly so as to allow liquid to run from the pipette until the liquid level is aligned with the volume marker. The measured contents of the pipette may then be transferred to a point of discharge where they are required.

In order to ensure a high degree of accuracy in the volume measured by a pipette, the bore at the top end of the pipette is normally very much smaller than the bore of the bulbous portion. This ensures that any minor deviation of the liquid level from the volume marker, in the top end of the pipette, results only in a very minor variation in the volume measured. However, as an unfortunate consequence of this form of construction, it takes much less suction to cause the liquid level to rise through a given distance in the upper end of the pipette than in the bulbous portion and, after sucking hard in order to fill the bulbous portion, continued sucking causes the liquid to rise rapidly through the top end of the pipette into the mouth.

This can be a very unpleasant experience where the liquid is unpalatable and, even worse, can cause damage where the liquid is poisonous or corrosive.

Moreover, for liquids which give off dangerous fumes, such as concentrated acids or highly volatile liquids, it is not merely necessary to avoid ingestion of the liquid, it is also necessary to avoid inhalation of the fumes.

Disclosure of the invention It is therefore an object of the invention to provide a device for filling pipettes without the risk of ingestion of the liquid being measured by the pipette and without the inhalation of fumes given off by this liquid.

According to the invention, there is provided a safety pipette filler comprising a cylinder having a head end and an open end; a piston reciprocable in the cylinder and having one end cooperating with the head end of the cylinder to define a variablevolume chamber and another end projecting from the open end of the cylinder; a connector at the head end of the cylinder adapted for attachment to the top end of a pipette so that liquid can be drawn into the bottom end of the pipette; and a controllable vent, preferably provided in the head end of the cylinder, for communicatively connecting the variablevolume chamber to the atmosphere so that, when the vent is opened, atmospheric air can flow freely into the cylinder so as to allow liquid drawn into the pipette to flow from the bottom end of the pipette under gravity.

In use of this device, liquid can be drawn into the pipette until the liquid level in the top end of the pipette rises above a volume marker. The volume marker may then be raised to eye level and the vent in the head end of the cylinder may be opened slightly so as to allow liquid to run from the pipette until the liquid level is perfectly aligned with the volume marker.

To facilitate this control of the vent, a flexible tube may be connected to the vent so that control of the vent may be effected by squeezing and releasing this tube, remote from the vent.

In a preferred embodiment of the invention, the connector comprises a rigid tubular portion extending from the head end of the cylinder and a sleeve of flexible material fitted over and extending beyond the rigid tubular portion of fitting over the top end of the pipette. This provides a very simple and inexpensive way of connecting the device to the pipette.

Conveniently, the piston-assembly of the device may be provided by a conventional syringe, such as a hypodermic syringe. In this case, the channel leading from the head end of the cylinderfor communicative connection to the hypodermic nee dle would normally have to be enlarged to provide a rigid tubular portion which did not unduly restrict the flow of air into and out of the syringe. The volume markings normally provided on the cylinder of a hypodermic syringe could also be omitted because these are not accurately enough calibrated for chemical analysis and, in any case, accurate volume control is only available if the measured volume of entrained liquid is allowed to drain freely from the pipette.

An embodiment of the invention is hereinafter described, by way of example, with reference to the accompanying drawings.

Brief description of the drawing The drawing is a schematic sectional elevation of a pipette fitted with a safety filler, in accordance with the invention, showing how the safety filler would be used to measure a volume of liquid.

Best mode of carrying out the invention As shown in the drawing, a safety filler 1 is connected to a glass pipette 2 having top and bottom ends 3 and 4 on opposite sides of a bulbous portion 17 having a much larger cross-sectional area than the top end 3. The bottom end 4 dips into a liquid 18 contained in a vessel 19.

The safety filler comprises a cylinder 5 having a closed, head end 6 and an open end 7 and a piston 8.

The piston 8 has an external cross-section which is substantially identical to the internal cross-section of the cylinder 5 and has an inner end 9, which cooperates with the head end 6 of the cylinder 5 to define a variable-volume chamber 10, and an outer end 11 extending through the open end 7 of the cylinder 5 for reciprocating the piston 8 inside the cylinder 5.

To form an airtight seal between the cylinder 5 and the piston 8, a gasket 20 is mounted in a peripheral groove around the inner end 9 of the piston 8.

Moreover, although the head end 6 of the cylinder 5 is provided with a vent 13, a rubber tube 14 is connected to this vent 13 so that by controlling the deformation of the tube 14, the chamber 10 enclosed by the cylinder 5 and the piston 8 can be isolated from and connected to the ambient atmosphere.

The top end 3 of the pipette 2 is inserted into a rubber sieeve 16 which is fitted over a tubular portion 15 extending from the head end 6 of the cylinder 5. Thus, in order to use the pipette 2 to measure a precise volume of liquid 18, the tube 14 is pressed by finger pressure against the cylinder 5 so as to seal the chamber 10. The piston 8 is then raised and liquid 18 flows into the pipette 2 until the level of the liquid 18 rises above the volume marker 21. The safety filler 1 and the pipette 2 are then raised until the volume marker 21 is at eye level and pressure on the tube 14 is released slightly so as to allow atmospheric air to seep slowly into the space 10.

This is allowed to continue until the level of the liquid 18 is precisely aligned with the volume marker 21. The tube 14 is then squeezed more tightly and the bottom end 4 of the pipette 2 is then placed above a receptacle for the measured volume of liquid 18.Thisliquidissimplytransferredfromthe pipette by releasing the tube 14.

Claims

1. A safety filler (1), for a pipette (2) having top and bottom ends (3 and 4), characterized by: a cylinder (5) having a head end (6) and an open end (7); a piston (8) reciprocable in the cylinder (5) and having one end (9) cooperating with the head end (6) of the cylinder (5) to define a variable-volume chamber (10) and another end (11) projecting from the open end of the cylinder (5); a connector (12) at the head end (6) of the cylinder (5) for attachment to the top end (3) of the pipette (2); and a controllable vent (13) for communicatively connecting the variable-volume chamber (10) to the atmosphere.

2. A safety filler, according to Claim 1, characterized in that the controllable vent (13) is provided in the head end (6) of the cylinder (5).

3. A safety filler (1), according to Claim 1 or Claim 2, characterized in that a flexible tube (14) is connected to the vent (11).

4. A safety filler (1), according to any preceding claims, characterized in that the connector (12) comprises a rigid tubular portion (15) extending from the head end (6) of the cylinder (5) and a sleeve (16) of flexible material fitted over and extending beyond the tubular portion (15).

5. A safety pipette filler, substantially as hereinbefore described with reference to and as illustrated in the accompanying drawing.