Dispensing – With discharge assistant – Container with follower
Patent
1996-08-02
1999-04-27
Derakshani, Philippe
Dispensing
With discharge assistant
Container with follower
7386401, B67D 542
Patent
active
058970347
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to dispensing devices such as pipettes.
BACKGROUND OF THE INVENTION
In laboratories, pipettes are often used in conjunction with pipette fillers. Pipette fillers are commonplace titration aids which comprise a mechanism that is fitted over the end of the pipette and is operated manually to control the dispensing of the titrating fluid.
The pipette filler also protects the health and safety of the operator by removing the necessity for the operator to place their mouth over the non-dispensing end of the pipette is order to suck up the fluid; operators can pass on infections and harmful chemicals may be accidentally sucked into the mouth.
However, these known pipette fillers are relatively expensive. Moreover, they are prone to malfunction caused by leakage through their simple valve mechanisms. When fitted to the pipette, the known pipette fillers make the dispensing equipment top heavy, preventing the equipment being left to stand safely in smaller sized graduated cylinders. Also, the vacuum release principal on which the known pipette fillers work is an indirect control method, which results in poorer control of the dispensing process than is achievable by positive displacement methods.
U.S. Pat. No. 3,848,777 discloses a pipette for receiving and dispensing liquid wherein a plunger in a cylinder is connected to a plunger rod guided in the cylinder and the free end of the rod is U-shaped with a free end having a projection thereon to be engageable in any one of a series of grooves provided at spaced intervals along the outside of the cylinder so as to provide a detent system for dispensing of liquid, the U-shaped portion of the plunger rod having two corrugations to be engaged by the thumb of the user.
U.S. Pat. No. 4,493,704 discloses a portable syringe with a U-shaped thin flexible plunger stem which can be bent over to lie upon the outside of a body of the syringe, the plunger stem having closely spaced teeth thereon engaged by a screw driven by a motor to cause dispensing of liquid.
SUMMARY OF THE INVENTION
According to one aspect of the present invention, there is provided a dispensing device comprising a tube having a dispensing nozzle at one end and the other end being open, a piston head slidable in the tube, and a piston rod extending from the piston head and projecting from the open end of the tube, wherein the surface of the piston rod has a high coefficient of friction such that a force applied to the side of the piston rod adjacent the open end of the tube, by application by a digit of a user to the side of the piston rod adjacent the open end of the tube and at an inclined angle to the axis of the tube, can have a frictional component sufficient to move the piston rod and piston head along the tube.
This aspect of the invention therefore provides a simple construction of a simple to operate, positive displacement dispensing device in which the piston rod is directly responsive to the operator's digit.
According to another aspect of the invention, there is provided a dispensing device comprising a tube having a dispensing nozzle at one end and the other end being open, a piston head slidable in the tube, and a piston rod extending from the piston head and projecting from the open end of the tube so that the piston rod and piston can be manually moved along the tube, the piston rod being flexible so that as the piston head is urged by the piston rod towards the dispensing nozzle the piston rod is supported at least part-way along its length by the tube and that portion of the piston rod outside the tube curls up due to "plastics memory".
This aspect of the invention thus provides a simple construction of a positive displacement dispensing device in which the piston rod can hang down or be curled up, and which piston rod can be bent while operating the piston.
According to another aspect of the invention, there is provided a method of dispensing fluid from a dispensing device comprising a tube having a dispensing nozzle at one end and the oth
REFERENCES:
patent: 3735900 (1973-05-01), Gores
patent: 3828987 (1974-08-01), Drummond et al.
patent: 3848777 (1974-11-01), Sarstedt et al.
patent: 4276878 (1981-07-01), Storz
patent: 4487081 (1984-12-01), De Vaughn et al.
patent: 4493704 (1985-01-01), Beard et al.
patent: 4662545 (1987-05-01), Kenney
patent: 5052588 (1991-10-01), Schlosser
patent: 5261882 (1993-11-01), Sealfon
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