Measuring and testing – Sampler – sample handling – etc. – Capture device
Reexamination Certificate
1999-11-01
2002-12-31
Noland, Thomas P. (Department: 2856)
Measuring and testing
Sampler, sample handling, etc.
Capture device
C073S861000, C073S863020, C073S864110, C222S063000
Reexamination Certificate
active
06499365
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to an electronic metering device.
Electronic metering devices are applied in the laboratory for metering fluids. They are known in various embodiments. Metering devices functioning according to the air cushion principle have an integrated piston-cylinder unit, by way of which an air column is displaceable in order to suction sample fluid into a metering syringe and to expel this from the syringe. With this the piston-cylinder unit does not come into contact with the fluid. Only the metering syringe which as a rule consists of plastic is contaminated and may be exchanged after use.
With direct displacement metering devices on the other hand a syringe is directly filled with sample fluid. The piston and the cylinder of the syringe are thus contaminated by the fluid so that the syringe before the exchange of the fluid mostly must be replaced by a new syringe or be cleaned. Also this syringe consists as a rule of plastic.
Pistonless metering devices may comprise a metering tip with a balloon-like end section which is expanded for suctioning fluid, and for expulsion is compressed. Such metering tips are also already conceived as an exchange part.
Micro-metering devices may have a micro-membrane pump and/or a free jet meterer, wherein at least one of these components is designed with micro-system technology, in particularly with silicon, glass and plastic injection molding technology and/or plastic imprinting technology. The metering is achieved by deformation of a wall of a container which is filled with fluid. The electrical drive for the deformation of the wall may be piezoelectric, thermoelectric, electromagnetic, electrostatic, electromechanical, magnetorestrictive, etc.
Air cushion, direct displacement, pistonless and micro-metering devices may have an unchangeable or changeable metering volume. A changing of the metering volume is achieved by adjustment of the displacement of the displacement means, i.e. of the displacement path of the piston or of the degree of deformation of the balloon-like end section or of the chamber wall.
Dispensers are metering devices which may repetitively dispense an accommodated fluid in small part quantities.
Furthermore there are multi-channel metering devices which have several “channels” by way of which it is simultaneously metered.
All metering devices may in particular be designed as a hand apparatus and/or stationary apparatus.
All previously mentioned metering devices may be electronic metering devices in the meaning of this application. With this they comprise a drive means with an electrical drive for driving a displacement means with which it may be the case of the piston-cylinder unit or the balloon-like end section of a metering tip, or a chamber with a deformable wall. The electrical drive in particular may be an electrical drive motor, electric linear drive or an electrical drive mentioned in the context of the micro-metering devices. Furthermore an electronic control means for the drive and an electrical voltage source for the supply of the control means and the drive is present. Electronic metering devices have in particular the advantage of the high reproducibility of meterings. In particular by way of preset constant metering speed (&mgr;l/s) more exact results may be achieved than with manually driven metering devices. Furthermore they have the advantage of a broad area of application since they may fulfill simple pipetting functions as well as dispensing functions. The electrical voltage source may comprise a battery, an accumulator and/or mains electricity part.
With conventional electronic metering devices the electrical voltage source is dimensioned such that in the normal condition it makes available a sufficient power for the drive with all operating loads of the drive means. With a battery or an accumulator this requires a suitable number of cells. However with an advanced discharging and thus reducing feed voltage increasingly operating malfunctions occur. With a reducing feed voltage specifically the torque of the drive reduces so that the drive means no longer drives the displacement means with all occurring loads in the desired manner. In particular with the design of the drive as a stepper motor steps may be lost and by way of this metering errors arise. Therefore for a reliable operation over a desired time a complicated battery or accumulator supply with corresponding costs, volume and weight are required. The same applies to the embodiment of the electrical voltage source as a mains electricity part.
BRIEF SUMMMARY OF THE INVENTION
Proceeding from this it is the object of the invention to provide an electronic metering device with which the cost for the electrical voltage source, in particular its costs, space requirement and weight is reduced and the drive in spite of this at all operational loads is supplied with the required voltage.
This object is achieved by an electronic metering device with the features of claim 1. Advantageous formations of the electronic metering device are specified in the dependent claims.
The electronic metering device according to the invention has
a drive means comprising an electric drive,
at least one displacement means drivable by the drive means, for metering the fluid and
an electronic control and/or regulating means for the drive with a transducer which converts a feed voltage delivered by an electrical voltage source into a supply voltage for the drive, this supply voltage being matched in size to the respective load of drive means.
According to the invention thus the control and/or regulating means makes available to the drive via a transducer a supply voltage which is matched to the respective load of the drive means. Thus for example at the beginning of the drive procedure it may increase the supply voltage in order to overcome start resistances of the displacement means. Thereafter it may reduce the supply voltage to a nominal value which is sufficient for the further drive of the displacement means set in motion. In the case that the metering device can be equipped with various displacement means which represent varying loads for the drive means, for example syringes of differing size, the supply may be matched to the respective displacement means. The control and/or displacement means controls the operation of the metering device, for example according to control commands which may be inputted via a keyboard so that it recognizes the respective operating condition of the metering device. According to predetermined criteria the control and/or regulating means may find a suitable supply voltage for each operating condition and make this available via the transducer. Furthermore information on the respective present displacement means, e.g. a coding of a syringe may be automatically read by the metering device or inputted separately. Furthermore the control and/or regulating means may evaluate the respective load which may be unforeseeably changed by external influences and on account of the evaluation result regulate the supply voltage. Thus the matching of the supply voltage to the respective load may be achieved.
The invention is not limited to the application of step-up transducers. Included is also the case in which the supply voltage required by the electrical drive lies below the feed voltage of the voltage supply. Thus for example Lithium Ion (Li-Ion) accumulators are available which deliver a relatively high voltage (approx. 3V per cell), so that by way of series connection of only a few cells a relatively high feed voltage may be made available. In the state of the art, in particular with the application of stepper motors, with a low load of the drive means the high feed voltage is partly converted into waste heat. This is undesirable for various reasons. Within the scope of the invention then in such cases a stepping-up convertion of the feed voltage to the supply voltage at the level required with the respective load may be effected. Also the invention includes the case in which the supply voltage from the tran
Eppendorf AG
Noland Thomas P.
Sidley Austin Brown & Wood LLP
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