Syringe pump abstract
It is an object of the present invention to provide a multiple-syringe-pump
driving apparatus having superior liquid discharging and drawing-up
precision. A syringe-pump driving apparatus of the present invention
is used for controlling discharge from and drawing-up into a plurality
of syringe pumps interconnected in parallel. The syringe-pump driving
apparatus 10 comprises: a syringe holder 18 for supporting syringes
14a to 14h of the plurality of syringe pumps 12a to 12h so as to
be arranged in parallel; a plunger holder 20 for supporting plungers
16a to 16h contained in the syringes 14a-14h so as to be arranged
in parallel; three or more drive screws 24-1 to 24-3 for moving
the plunger holder 20 and the syringe holder 18 relative to each
other in a straight line in a syringe axial direction 30; and one
or a plurality of motors 26 serving as a source of motive power
for the drive screws 24-1 to 24-3. The three or more drive screws
24-1 to 24-3 are connected to the syringe holder 18 or the plunger
holder 20 at three or more driving points to transmit motive power
to the syringe holder 18 or the plunger holder 20 via the three
or more driving points.
Syringe pump claims
1. A syringe-pump driving apparatus for controlling discharge from
and drawing-up into a plurality of syringe pumps interconnected
in parallel, comprising: a syringe holder for supporting syringes
of the plurality of syringe pumps so as to be arranged in parallel;
a plunger holder for supporting plungers contained in the syringes
so as to be arranged in parallel; three or more drive screws for
moving the plunger holder and the syringe holder relative to each
other in a straight line in a syringe axial direction; and one or
a plurality of motors serving as a source of motive power for the
drive screws; wherein the three or more drive screws are connected
to the syringe holder or the plunger holder at three or more driving
points to transmit motive power to the syringe holder or the plunger
holder via the three or more driving points.
2. A syringe-pump driving apparatus according to claim 1 wherein
the positions of the three or more driving points of the drive screws
for the syringe holder or the plunger holder are disposed such that
the loads acting at the three or more driving points from the syringes
and/or the plungers are made substantially equal.
3. A syringe-pump driving apparatus according to claim 1 wherein
the number of the drive screws is three.
4. A syringe-pump driving apparatus according to claim 1 further
comprising a fixed support base for fixing one of the syringe holder
and the plunger holder, the other holder being moveable.
Syringe pump description
RELATED APPLICATIONS
[0001] This application claims priority to the Japanese Patent
Application 2004-258215 dated on Sep. 6 2004 and is hereby incorporated
with reference for all purposes.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to an improved driving mechanism
for a syringe-pump driving apparatus for controlling the discharge
and drawing-up of a plurality of syringe pumps.
[0004] 2. Description of the Related Art
[0005] Syringe pumps are widely used in a variety of tests and
measurements for controlling the amount of liquid discharged and
drawn-up with high precision. The amount of liquid discharged and
drawn-up is determined by the amount of movement of a plunger, and
drive screws are generally used as the driving mechanism therefor.
[0006] Driving apparatuses that discharge and draw up liquid in
multiple flow paths, by connecting a plurality of syringe pumps
in parallel and driving them simultaneously, are also used. One
example of such an apparatus is described in U.S. Pat. No. 5988236.
The syringe-pump driving apparatus described in U.S. Pat. No. 5988236
adopts a structure in which a holder that fixes a plurality of syringes
is driven by means of a single drive screw, and the holder is kept
in balance by means of a plurality of guide rails while moving.
However, since the apparatus described in U.S. Pat. No. 5988236
has only a single driving point, when the resistance of each syringe
is changed due to deterioration, thus degrading the dynamic balance
of the holder, it is difficult to move the holder while keeping
it straight. As a result, there is a drawback in that the precision
of the syringes when discharging and drawing-up liquid is reduced.
SUMMARY OF THE INVENTION
[0007] The present invention has been conceived in light of the
problems described above, and it is an object thereof to provide
a multiple-syringe-pump driving apparatus having superior liquid
discharging and drawing-up precision.
[0008] A syringe-pump driving apparatus of the present invention
is used for controlling discharge from and drawing-up into a plurality
of syringe pumps interconnected in parallel. The syringe-pump driving
apparatus according to the present invention comprises: a syringe
holder for supporting syringes of the plurality of syringe pumps
so as to be arranged in parallel; a plunger holder for supporting
plungers contained in the syringes so as to be arranged in parallel;
three or more drive screws for moving the plunger holder and the
syringe holder relative to each other in a straight line in a syringe
axial direction; and one or a plurality of motors serving as a source
of motive power for the drive screws. The three or more drive screws
are connected to the syringe holder or the plunger holder at three
or more driving points to transmit motive power to the syringe holder
or the plunger holder via the three or more driving points.
[0009] In the syringe-pump driving apparatus of the present invention,
it is preferable that the positions of the three or more driving
points of the drive screws for the syringe holder or the plunger
holder are disposed such that the loads acting at the three or more
driving points from the syringes and/or the plungers are made substantially
equal.
[0010] In the syringe-pump driving apparatus of the present invention,
it is preferable that the number of the drive screws is three.
[0011] In the syringe-pump driving apparatus of the present invention,
it is preferable that the apparatus further comprises a fixed support
base for fixing one of the syringe holder and the plunger holder,
the other holder being moveable.
[0012] Since a syringe-pump driving apparatus of the present invention
has a structure in which a plunger holder or a syringe holder is
moved via three or more driving points, the amount of liquid discharged
and drawn-up can be controlled with high precision.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is an outlined structural view of a syringe-pump
driving apparatus according to an embodiment of the present invention.
[0014] FIG. 2 is a diagram of the syringe-pump driving apparatus
according to the embodiment of the present invention, as viewed
from a syringe axial direction.
[0015] FIG. 3 is an outlined structural view of a dissolution test
apparatus provided with the syringe-pump driving apparatus of this
embodiment.
[0016] FIG. 4A and FIG. 4B depict the operation of the dissolution
test apparatus shown in FIG. 3.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0017] A preferred embodiment of the present invention will be
described below with reference to the drawings.
[0018] FIG. 1 is an outlined structural view of a syringe-pump
driving apparatus according to an embodiment of the present invention.
A syringe-pump driving apparatus 10 shown in FIG. 1 includes a syringe
holder 18 for supporting syringes 14a to 14h of a plurality of syringe
pumps 12a to 12h so as to be arranged in parallel; and a plunger
holder 20 for supporting plungers 16a to 16h corresponding to the
syringes 14a to 14h, so as to be arranged in parallel. In this embodiment,
eight syringe pumps are illustrated, but the number of syringe pumps
is not particularly limited to this number.
[0019] The syringe holder 18 and the plunger holder 20 are arranged
so as to move in a straight line relative to each other in the axial
direction 30 of the syringe pumps 12a to 12h. In this embodiment,
the syringe holder 18 is defined as a fixed holder and the plunger
holder is defined as a moving holder. More precisely, the syringe
holder 18 is fixed to a fixed support base 22 and the plunger holder
20 is configured to be movable with respect to the syringe holder
18.
[0020] One end of each of three drive screws 24-1 to 24-3 is supported
at the syringe holder 18 and the other end thereof is supported
at the fixed support base 22 so as to be rotatable about the axes
thereof. The type of drive screws is not particularly limited; for
example, ball screws may be preferably used. The plunger holder
20 contacts the drive screws 24-1 to 24-3 at three driving points.
The rotary force of the three drive screws 24-1 to 24-3 is converted
to a linear driving force for the plunger holder 20 at these driving
points. More precisely, three screw followers 25-1 to 25-3 are fixed
to the plunger holder 20 and the screw followers 25-1 to 25-3 are
engaged with the respective drive screws 24-1 to 24-3 (see FIG.
2). Then, by rotating the drive screws 24-1 to 24-3 the rotary
force thereof is converted to linear motion by means of the screw
followers 25-1 to 25-3 which is transmitted to the plunger holder
20. In addition, the drive screws 24-1 to 24-3 are connected via
belts 28a and 28b to a motor 26 serving as a source of motive power.
[0021] FIG. 2 is a cross-section, taken along I-I in FIG. 1 viewed
from the syringe axial direction of the syringe-pump driving apparatus
of the present embodiment shown in FIG. 1. As shown in FIG. 2 the
positions of the three driving points (the screw followers 25-1
to 25-3) of the three drive screws 24-1 to 24-3 on the plunger holder
20 are preferably disposed such that the loads acting at the three
driving points are substantially the same. In the example shown
in FIG. 2 two driving points are arranged so as to sandwich the
plungers 16a to 16h, which are arranged in parallel in a row, from
positions close to both longitudinal sides and the other driving
point is positioned close to the center of the row of syringes but
shifted transversely. Thus, the three driving points are disposed
so as to form an isosceles triangle in which the straight line joining
the first two driving points defines a base and the remaining point
defines the apex thereof. Moreover, the syringes are disposed on
a straight line that passes through a point dividing a perpendicular
drawn from the apex to the base in a ratio of 2-to-1 and that is
at right angles to the perpendicular.
[0022] The above is an outline of the structure of the present
embodiment; next, the operation thereof will be described with reference
to FIG. 1 again.
[0023] The rotary force of the motor 26 is transmitted to the drive
screw 24-1 and via the belts 28a and 28b to the drive screws 24-2
and 24-3. Thus, the rotations of the drive screws 24-1 to 24-3 are
interconnected with one other.
[0024] As described above, driving points for the drive screws
24-1 to 24-3 are defined at three appropriate points on the plunger
holder 20 and the rotary forces of the drive screws 24-1 to 24-3
are converted to driving forces in the syringe axial direction 30
of the plunger holder 20 at these driving points. That is, the amount
of motion of the moving holder 20 is controlled by controlling the
amount of rotation of the drive screws 24-1 to 24-3.
[0025] Also, the amount of rotation and the rotation direction
of the motor 26 are controlled by a control apparatus, which is
not shown, and the amount of motion and the moving direction of
the plunger holder 20 are controlled thereby.
[0026] As described in U.S. Pat. No. 5988236 in a system combining
one drive screw and a plurality of guide rails, it is necessary
to align the driving point of the drive screw with the center of
the load; however, if the load balance is lost because of individual
syringe differences occurring due to deterioration of the syringes
or the like, smooth motion becomes impossible.
[0027] Conversely, since the syringe-pump driving apparatus of
the present embodiment has a structure in which it actively moves
at three appropriate points on the holder by means of the three
drive screws, even if the sliding resistance of the plurality of
syringes attached to the holder changes due to deterioration or
the like, causing the dynamic balance of the holder to shift, it
is possible to achieve precise motion while keeping the holder straight.
As a result, the amount of fluid discharged from and drawn up into
each syringe is precisely ensured.
[0028] With the embodiment described above, the syringe holder
is defined as fixed and the plunger holder is defined as moving;
conversely, however, the plunger holder may of course be defined
as fixed and the syringe holder defined as moving.
[0029] In the embodiment described above, driving of the three
drive screws is performed with a single motor; however, a structure
in which a plurality of motors are synchronized to perform driving
of the drive screws is also permissible.
[0030] In the embodiment described above, the number of the drive
screws is three. But the number of drive screws may be above three.
[0031] Next, an example in which the syringe-pump driving apparatus
of the embodiment described above is used as a liquid discharge
mechanism in a dissolution test apparatus will be described. A dissolution
test apparatus is used to measure the amount of elution and so on
when a tablet-type drug is immersed in a predetermined test solution.
[0032] FIG. 3 is an outlined structural view of the dissolution
test apparatus, partially taken in cross section. A dissolution
test apparatus 100 in FIG. 3 includes a plurality of vessels 130a
to 130c in which a test solution and a sample are placed; a plurality
of mixing paddles 132a to 132c for agitating the liquids in the
corresponding vessels 130a to 130c; a plurality of nozzles 134a
to 134c for injecting liquids into the vessels 130a to 130c and
for drawing up liquids therefrom; a syringe-pump driving apparatus
110; and tubes 136a to 136c for connecting syringes in the syringe-pump
driving apparatus 110 with the corresponding nozzles 134a to 134c.
The number of vessels, mixing paddles, nozzles, and tubes shown
in the figure is three, but it is not particularly limited to this
number.
[0033] The mixing paddles 132a to 132c are set in an agitator head
138 and the agitator head 138 is configured to be movable upward
and downward.
[0034] The nozzles 134a to 134c are set in a nozzle head 140 and
the nozzle head 140 is also configured to be movable upward and
downward. In addition, the agitator head 138 and the nozzle head
140 are configured as independent motion mechanisms.
[0035] The mixing paddles 132a to 132c and the nozzles 134a to
134c of the dissolution test apparatus 100 stand-by in a raised,
preparatory state, as shown in FIG. 3. Then, as shown in FIG. 4A,
in order to agitate the contents of the vessels 130a to 130c with
the mixing paddles 132a to 132c, first, only the agitator head 138
is moved downward to position the mixing paddles 132a to 132c at
predetermined locations inside the vessels 130a to 130c.
[0036] After a predetermined time has elapsed, in order to draw
up the liquid from inside the vessels 130a to 130c, the nozzle head
140 is also moved downward to position the nozzles 134a to 134c
at predetermined locations inside the vessels 130a to 130c. Then,
the liquids inside the vessels 130a to 130c are drawn up into the
corresponding syringes by the syringe-pump driving apparatus 110.
[0037] Thus, the syringe-pump driving apparatus of this embodiment
is suitable for use in an apparatus in which it is necessary to
precisely discharge and draw up liquid, such as the dissolution
test apparatus described above. |