Measuring and testing – Sampler – sample handling – etc. – Capture device
Reexamination Certificate
1997-09-09
2001-01-09
Raevis, Robert (Department: 2856)
Measuring and testing
Sampler, sample handling, etc.
Capture device
Reexamination Certificate
active
06170343
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates generally to an electronically monitored mechanical pipette. More specifically, the invention relates to an electronically monitored volume delivery adjustment mechanism for a pipette. Even more specifically the invention relates to a microswitch for signalling the electronic system of an electronically monitored mechanical pipette when volume setting adjustment is taking place.
2. Prior Art
Mechanically operated micropipettes are well known in the art as exemplified by U.S. Pat. No. 4,909,991 to Oshikubo. In such prior art devices, the volume of liquid to be dispensed by the pipette is generally indicated to the operator by means of a mechanical display. The display commonly consists of a set of rotary drums driven by a gear mechanism attached to the actuating shaft of the pipette, such that rotation of the actuating shaft causes the drums to rotate to display a new setting. However, due to unavoidable mechanical wear and tear on pipettes, the amount of fluid actually being delivered by a pipette may not actually correspond to the volume being indicated by the mechanical displayed. Further, accuracy may degrade over time as the actuating elements, such as the shaft, gears, and rotary drum, wear out.
Electrically driven pipettes are also well known in the art as exemplified by U.S. Pat. No. 4,905,526 to Magnussen, Jr. et al. This type of instrument commonly includes an electronic display for displaying the volume of fluid to be dispensed by the pipette, and an actuator generally comprised of an electric drive mechanism, such as a stepper motor. The stepper motor generally drives a rotor, which is attached by a threaded screw to an actuator shaft, the threaded screw changes the rotational motion of the motor into linear motion of the actuator shaft. The shaft thereafter drives a piston to displace fluid for pipetting. Although electrically operated pipettes have some advantages over mechanically operated pipettes, they nevertheless suffer from several drawbacks. First, the enlarged size of an electrically operated pipette, due to the need to accommodate the electric driving mechanism, and the added electronic hardware, make the device very difficult to handle for the operator. Further, the electronic motor can be very power demanding and thus necessitate connection of the pipette to a power source, or the use of large batteries which can be rapidly drained of power.
Electrically monitored mechanical pipettes are also known in the art as exemplified by U.S. Pat. No. 4,567,780 to Oppenlander et al. This type of instrument generally includes a plunger having an adjustable stroke length which is generally adjusted by rotating the plunger itself. The electrical monitoring system monitors plunger rotation and electronically displays the volume delivery setting corresponding to the plunger position. The device continuously monitors the plunger position and volume delivery setting of the pipette. Although this device overcomes several of the disadvantages of mechanical and electrical pipettes, it nevertheless fails to completely resolve the problem of high power demands during operation.
OBJECTS AND SUMMARY OF THE INVENTION
The principal object of the present invention is to provide an electrically monitored mechanical pipette with a continuous volume delivery setting display and low power consumption.
Another object of the present invention is to provide an electrically monitored mechanical pipette which activates the electrical volume monitoring system thereof only when the volume delivery setting is being changed.
Another object of the present invention is to provide an electrically monitored mechanical pipette which includes a microswitch as a part of the volume delivery adjustment mechanism which reduces power consumption of the pipette by providing a signal to power up the electrical volume monitoring system only when the volume delivery setting is being changed.
Briefly, and in general terms, the present invention provides for electronically monitoring a mechanical pipette which enables low power operation of the electronics thereof during use of the device to pipette fluid, and engages high powered electronics only when necessary to provide monitoring of the pipette while the operator is resetting the desired fluid volume delivery setting and for recomputation of the new setting.
In the presently preferred embodiment shown by way of example and not necessarily by way of limitation, an electrically monitored mechanical pipette made in accordance with the principals of the present invention includes a volume delivery adjustment mechanism which includes a plunger, an advancer, a driver, and a threaded bushing. The volume delivery adjusted mechanism is monitored by an electrical volume monitoring system which preferably includes a transducer assembly having two Hall-effect sensors, and an electronics assembly which includes a microprocessor and a display. During volume delivery adjustment, the sensors send a set of transducer signals to the electronics assembly computes and displays the new fluid volume delivery setting.
A microswitch assembly is provided for detecting relative rotational motion between the volume delivery adjustment mechanism and the pipette and to signal the electronics assembly that the fluid volume delivery setting is being changed. Upon receipt of a signal, in the form of an interrupt signal from the microswitch, the electronics assembly powers up the transducer assembly which then tracks the motion of the volume delivery adjustment mechanism. The transducer sensor signals are received by the electronics assembly which computes and displays the new fluid volume delivery setting Once the volume delivery adjustment mechanism is no longer being rotated, the electronics assembly shuts down the power to the transducer assembly to minimize power use of the pipette.
In one preferred embodiment of the microswitch assembly a bobber mechanism is positioned such that the volume delivery adjustment mechanism causes a switch, such as a metal contact pad, in the mechanism to move up and down as the volume delivery adjustment mechanism rotates. This up and down motion of the switch causes it to intermittently contact and release a stationary switch pad mounted on the electronics assembly. In this manner, a signal such as an interrupt signal is sent by the bobber mechanism to the electronics assembly each time the bobber switch pad contacts the stationary electronics switch pad. The interrupt signal causes the electronics assembly to power up the transducer assembly for monitoring the motion of the volume delivery adjustment mechanism.
Another preferred embodiment of the microswitch assembly includes a bobber which is in physical contact with a spring loaded switch which is activated each time the bobber moves up and down.
These and other objects and advantages of the present invention will become apparent from the following more detailed description, when taken in conjunction with the accompanying drawings in which like elements are identified with like numerals throughout.
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patent: 4442722 (1984-04-01), Meyer
patent: 4567780 (1986-02-01), Oppenlander et al.
patent: 4671123 (1987-06-01), Magnussen, Jr. et al.
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patent: 4779467 (1988-10-01), Rainin et al.
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patent: 4905526 (1990-03-01), Magnussen, Jr. et al.
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patent: 5021217 (1991-06-01), Oshikubo
patent: 5187990 (1993-02-01), Magnussen, Jr. et al.
Appal Eugene R.
Conley Paul G.
Alice Ronald W.
Raevis Robert
Tyco Group S.a.r.l.
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