Surgery – Means for introducing or removing material from body for... – Treating material introduced into or removed from body...
Reexamination Certificate
2001-08-24
2004-11-16
Casler, Brian L. (Department: 3763)
Surgery
Means for introducing or removing material from body for...
Treating material introduced into or removed from body...
C604S218000, C604S152000, C604S155000, C128SDIG001, C128SDIG001, C215S364000, C215S355000, C215SDIG003
Reexamination Certificate
active
06817990
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to improvements in infusion pumps such as those used for controlled delivery of medication to a patient. Additionally, this invention relates to an improved fluid reservoir and piston for use in combination with such infusion pumps.
BACKGROUND OF THE INVENTION
Infusion pump devices and systems are relatively well-known in the medical arts, for use in delivering or dispensing a prescribed medication such as insulin to a patient. In one form, such devices comprise a relatively compact pump housing adapted to receive a syringe or reservoir carrying a prescribed medication for administration to the patient through infusion tubing and an associated catheter or infusion set.
The infusion pump includes a small drive motor connected via a lead screw assembly for motor-driven advancement of a reservoir piston to administer the medication to the user. Programmable controls can operate the drive motor continuously or at periodic intervals to obtain a closely controlled and accurate delivery of the medication over an extended period of time. Such infusion pumps are used to administer insulin and other medications, with exemplary pump constructions being shown and described in U.S. Pat. Nos. 4,562,751; 4,678,408; 4,685,903; 5,080,653 and 5,097,122, which are incorporated by reference herein.
Infusion pumps of the general type described above have provided significant advantages and benefits with respect to accurate delivery of medication or other fluids over an extended period of time. The infusion pump can be designed to be extremely compact as well as water resistant, and may thus be adapted to be carried by the user, for example, by means of a belt clip or the like. As a result, important medication can be delivered to the user with precision and in an automated manner, without significant restriction on the user's mobility or life-style, including in some cases the ability to participate in water sports.
These pumps often incorporate a drive system which uses a lead screw coupled to motors. The motors can be of the DC, stepper or solenoid varieties. These drive systems provide an axial displacement of the syringe or reservoir piston thereby dispensing the medication to the user. Powered drive systems are advantageous since they can be electronically controlled to deliver a predetermined amount of medication by means well known in the art.
In the operation of these pump systems, the reservoir piston will be fully advanced when virtually all of the fluid in the reservoir has been dispensed. Correspondingly, the axial displacement of the motor lead screw is also typically fully displaced. In order to insert a new reservoir which is full of fluid, it is necessary to restore the lead screw to its original position. Thus the lead screw will have to be rewound or reset.
DC motors and stepper motors are advantageous over solenoid motors in that the former are typically easier to operate at speeds that allow rewinding the drive system electronically. Solenoid based drive systems, on the other hand, often must be reset manually, which in turn makes water resistant construction of the pump housing more difficult.
Lead screw drive systems commonly use several gears which are external to the motor.
FIG. 1
shows such a lead screw arrangement which is known in the art. A motor
101
drives a lead screw
102
which has threads which are engaged with a drive nut
103
. Thus the rotational force of the lead screw
102
is transferred to the drive nut
103
which causes it to move in an axial direction d. Because the drive nut
103
is fixably attached to a reservoir piston
104
by a latch arm
110
, it likewise will be forced in an axial direction d_, parallel to direction d, thus dispensing the fluid from a reservoir
105
into an infusion set
106
. The lead screw
102
is mounted on a bearing
111
which provides lateral support. The lead screw
102
extends through the bearing and comes in contact with the occlusion detector
108
. One known detector uses an “on/off” pressure limit switch.
Should an occlusion arise in the infusion set
106
tubing, a back pressure will build up in the reservoir
105
as the piston
104
attempts to advance. The force of the piston
104
pushing against the increased back pressure will result in an axial force of the lead screw
102
driving against the detector
108
. If the detector
108
is a pressure limit switch, then an axial force that exceeds the set point of the pressure limit switch
108
will cause the switch to close thus providing an electrical signal through electrical leads
109
and to the system's electronics. This, in turn, can provide a system alarm. The entire assembly can be contained in a water resistant housing
107
.
FIG. 2
shows a different drive system and lead screw arrangement which also is known in the art. In this arrangement, a motor
201
(or a motor with an attached gear box) has a drive shaft
201
a
which drives a set of gears
202
. The torque is then transferred from the gears
202
to a lead screw
203
. The threads of the lead screw
203
are engaged with threads [not shown] in a plunger slide
204
. Thus the torque of the lead screw
203
is transferred to the slide
204
which causes it to move in an axial direction d_, parallel to the drive shaft
201
a
of the motor
201
. The slide
204
is in contact with a reservoir piston
205
which likewise will be forced to travel in the axial direction d_ thus dispensing fluid from a reservoir
206
into an infusion set
207
. The lead screw
203
is mounted on a bearing
209
which provides lateral support. The lead screw
203
can extend through the bearing to come in contact with an occlusion detector
210
. As before, if the detector
210
is a pressure limit switch, then an axial force that exceeds the set point of the pressure limit switch
210
will cause the switch to close thus providing an electrical signal through electrical leads
211
and to the system's electronics. This, in turn, can provide a system alarm. The assembly can be contained in a water resistant housing
208
.
As previously noted, these lead screw drive systems use gears which are external to the motor. The gears are in combination with a lead screw with external threads which are used to drive the reservoir's piston. This external arrangement occupies a substantial volume which can increase the overall size of the pump. Moreover, as the number of drive components, such as gears and lead screw, increases, the torque required to overcome inherent mechanical inefficiencies can also increase. As a result, a motor having sufficient torque also often has a consequent demand for increased electrical power.
Yet another known drive is depicted in
FIGS. 3
a
and
3
b
. A reservoir
301
fits into the unit's housing
302
. Also shown are the piston member
303
which is comprised of an elongated member with a substantially circular piston head
304
for displacing the fluid in the reservoir
301
when driven by the rotating drive screw
305
on the shaft (not visible) of the drive motor
306
.
As is more clearly shown in
FIG. 3
b
, the reservoir
301
, piston head
304
and piston member
303
comprise an integrated unit which is placed into the housing
302
(
FIG. 3
a
). The circular piston head
304
displaces fluid in the reservoir upon axial motion of the piston member
303
. The rearward portion of the piston member
303
is shaped like a longitudinal segment of a cylinder as shown in
FIG. 3
b
and is internally threaded so that it may be inserted into a position of engagement with the drive screw
305
. The drive screw
305
is a threaded screw gear of a diameter to mesh with the internal threads of the piston member
303
. Thus the motor
306
rotates the drive screw
305
which engages the threads of the piston member
303
to displace the piston head
304
in an axial direction d.
While the in-line drive system of
FIG. 3
a
achieves a more compact physical pump size, there are problems associated with the des
Enegren Bradley J.
Geismar Eric P.
Gulati Poonam
Hudak Philip J.
Kovelman Paul H.
Casler Brian L.
Medtronic MiniMed, Inc.
Medtronic MiniMed, Inc.
Rodriguez Cris L.
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