Article comprising an incremental positioner

Details Article comprising an incremental positioner Article comprising an incremental positioner

1999-09-14

2001-01-23

Nappi, Robert E. (Department: 2837)

Electricity: motive power systems

With particular motor-driven load device

Power- or motion-transmitting mechanism

C073S864340

Reexamination Certificate

active

06177770

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to motion controllers or positioning stages. More particularly, the present invention relates to a positioner capable of fast, incremental motion.
BACKGROUND OF THE INVENTION
In research and development laboratories, among other types of facilities, there are applications that require moving an element (e.g., test strips, a microtitre plate, etc.) a precise distance to a desired location to perform a function at that location. Typically, such movement must be accomplished in a repetitive manner at a precise time interval. Such a task can be performed by an incremental positioner/motion controller.
Sophisticated or “intelligent” motion controllers are often used for such service. Motion controller
100
, depicted in
FIG. 1
, is typical of such intelligent controllers.
Intelligent motion controller
100
includes a control unit
102
and a motorized stage
110
. Control unit
102
includes control means
104
, depicted figuratively as a collection of switches and rheostats that control a variety of parameters related to stage movement. Control means
104
may control, for example, the direction of stage motion (e.g., forward or reverse), stage speed, coarse or fine stage movement, and the acceleration and deceleration of every movement. Hence the designation “intelligent.”
A first cable
106
provides electrical connection between control unit
102
and motorized stage
110
, and a second cable
108
attaches to a power supply. Motorized stage
110
, which is depicted as a linear stage, includes a motor
112
that is operatively connected to a stage
114
.
While such intelligent motion controllers are usually capable of positioning a stage to a high degree of resolution (i.e., about 1 micron accuracy for linear positioners and about 0.004° for rotary positioners), and are quite flexible within the parameters of their operation, they do suffer from several significant shortcomings. In particular, such motion controllers are relatively slow and they are rather expensive. Regarding cost, a motion controller having the capabilities of intelligent motion controller
100
may sell for over $2000 (at least about $800 for the control unit and about $1,200.00 for the motorized stage). Moreover, in view of the complexity of such devices, reliability may be an issue as well.
There may be some applications in which the flexibility offered by such an intelligent controller justifies its cost. There will, however, be many other applications in which process parameters remain fixed (e.g., the positional increment is fixed) so that it may be difficult to cost-justify such an intelligent motion controller. Also, high-speed positioning may be required, which may be beyond the capabilities of the aforedescribed intelligent controllers. Or, a smaller and less expensive system may be desired.
As such, the art would benefit from a fast, inexpensive and reliable incremental positioner.
SUMMARY OF THE INVENTION
In accordance with some embodiments of the present invention, an incremental positioner that avoids the shortcomings of the prior art is disclosed.
The present incremental positioner comprises an intermittent motion-imparting means that engages a rack ((i.e., a bar having a multiplicity of spaced teeth). The rack is characterized by a pitch, which is a characteristic incremental distance between the leading edge of successive teeth in the rack.
In the illustrated embodiments, the intermittent motion-imparting means comprises a drive means, such as a motor and drive shaft, and a motion converter. The motion converter transmits and converts the continuous rotary (or other) motion of the drive means to an intermittent motion (typically linear) of the rack.
To generate such intermittent motion, the motion converter is physically configured such that, even though the motion converter is in constant motion (while in operation), it urges the rack to motion on a periodic basis. In particular, given a cycle of the motion converter (i.e., the time for one rotation of the motion converter), the rack “dwells” (i.e., does not move) during a first portion of the cycle, and advances during a second portion of the cycle. Each time the rack advances, it does so by the aforementioned characteristic incremental distance.
The intermittent motion imparted to the rack can be used employed in a variety of applications. For example, in one embodiment of the present invention, the incremental positioner is used in conjunction with a dispensing operation, wherein the positioner advances a receiver, such as a microtitre plate. In this application, the rack is operatively engaged to a stage that receives the microtitre plate. Each advance of the rack incrementally advances the plate (e.g., row-by-row), such that successive rows of “wells” in the plate are positioned to receive liquid from a dispenser.
Unlike the prior art, wherein the drive means is disadvantageously successively energized and de-energized to cause incremental positioning, the drive means (e.g, motor, etc.) of the present invention is always on (during operation). Thus, no sophisticated controller is required to control motor operation and timing. Both the “dwell” and “advance” function is provided by the motion converter, which is typically a trivially inexpensive part. Notwithstanding its low cost, the motion converter provides much of the functionality of the control units of the intelligent motion controllers of the prior art.
The present incremental positioner is capable of very high speeds, which is primarily a function of the speed of the drive means. Comprising relatively few and simple mechanical parts, the present incremental positioner is expected to be very reliable. And, it is far less expensive to produce than the intelligent motion controllers of the prior art.
These and other features of the present invention, including a specific implementation of the motion converter, are described later in this Specification in the Detailed Description with reference to the attached Figures.


REFERENCES:
patent: 3667306 (1972-06-01), Bush
patent: 3871690 (1975-03-01), Wright et al.
patent: 4016774 (1977-04-01), Baker et al.
patent: 4276974 (1981-07-01), Ladin
patent: 4555957 (1985-12-01), Frankel et al.
patent: 4579117 (1986-04-01), Spolyar

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