Source: http://www.docstoc.com/docs/50164077/Compact-Pump-Drive-System---Patent-6248093
Timestamp: 2014-09-21 19:22:24
Document Index: 318472495

Matched Legal Cases: ['art, 40', 'art, 40', 'art, 40', 'art, 8', 'art, 40', 'art, 40']

Compact Pump Drive System - Patent 6248093
United States Patent: 6248093
6,248,093
An improved pump is provided for controlled delivery of fluids wherein the
pump includes a reservoir and a movable piston. A plunger slide is in
removable contact with the movable piston. A motor, is operably coupled to
a drive member, such as a drive screw. The motor is disposed in-line with
the drive member and the plunger slide. The drive member is operably
connected to the plunger slide and is disposed to be substantially
enclosed by the plunger slide when the plunger slide is in at least one
position. The drive member is adapted to advance the plunger slide in
response to operation of the motor.
Moberg; Sheldon (Granada Hills, CA)
09/429,352
604/131  ; 128/DIG.12; 604/151
A61J 1/00&amp;nbsp(20060101); A61M 5/162&amp;nbsp(20060101); A61M 5/145&amp;nbsp(20060101); A61M 39/12&amp;nbsp(20060101); A61M 39/00&amp;nbsp(20060101); A61M 5/14&amp;nbsp(20060101); A61M 005/00&amp;nbsp()
604/131,151,154,155 128/DIG.1,DIG.12,DIG.13
D347894
Zalesky et al.
5554134
5722545
0544653
PCT Application PCT/US99/25413, Search Report mailed Mar. 7, 2000..
60/106,237, filed Oct. 29, 1998 and which is incorporated herein by
1.  A portable medical device for dispensing liquid from a liquid reservoir having a piston which defines an axis of travel, the medical device comprising:
at least one plunger slider coupled to the gearbox and adapted to translate from a retracted position to an extended position to displace the piston along the piston axis of travel in response to rotation of the drive motor drive shaft wherein
the at least one plunger slider substantially radially surrounds at least a portion of a length of the gearbox when the at least one plunger slider is in the retracted position;  and
2.  The medical device according to claim 1,
wherein the medical device includes a first drive gear positioned to be rotatably actuated by the drive motor drive shaft, said first drive gear having internal threads;  and
wherein the at least one plunger slider includes a second drive gear having external threads positioned to be engaged by the first drive gear internal threads and linearly actuated by rotation of the first drive gear internal threads;  and
3.  The medical device according to claim 1,
wherein the medical device includes a first drive gear positioned to be rotatably actuated by the drive motor drive shaft, said first drive gear having external threads;  and
wherein the at least one plunger slider includes a second drive gear having internal threads positioned to be engaged by the first drive gear external threads and linearly actuated by rotation of the first drive gear external threads;  and
4.  The medical device of claim 3 wherein the second drive gear defines a cavity and the second drive gear internal threads encircle the second drive gear cavity.
5.  The medical device of claim 1, wherein the releasable coupler includes a first threaded member carried by the at least one plunger slider and a second threaded member is carried by the reservoir piston and adapted to engage the first threaded
6.  The medical device of claim 5, wherein the first threaded member comprises a screw extending from the at least one plunger slider and having external threads, and the second threaded member comprises a cavity defined by the reservoir piston
and having internal threads positioned to be engaged by the screw external threads.
7.  The medical device of claim 6 wherein the external threads of the screw are made of a material having a first hardness and the internal threads of the piston cavity are made of a material having a second hardness.
8.  The medical device of claim 6 wherein the external threads of the screw have a first lead and wherein the internal threads of the piston cavity have a second lead.
9.  The medical device of claim 4 further comprising a housing enclosing the drive motor, the first and second drive gears, the releasable coupler and the reservoir and wherein the housing further includes a vent port containing a hydrophobic
10.  The medical device of claim 3 wherein the second drive gear comprises a telescoping lead screw formed from at least two segments.
11.  A medical device for dispensing liquid from a liquid reservoir having a piston which defines an axis of travel, the medical device comprising:
wherein the second drive gear substantially radially surrounds at least a portion of a length of the gearbox when the second drive gear is in the retracted position;  and
12.  A method of dispensing liquid from a portable liquid reservoir having a piston which defines an axis of travel, the method comprising:
translating the at least one plunger slider from a retracted position to an extended position in response to rotation of the gears in the gearbox to move the reservoir piston along the piston axis of travel using the at least one plunger slider
to dispense the liquid from the reservoir;  and
wherein the at least one plunger slider substantially radially surrounds at least a portion of a length of the gearbox when the plunger slider is in the retracted position;  and
13.  The method of claim 12, further comprising coupling a second reservoir piston of a second reservoir to the at least one plunger slider following releasing the first reservoir piston.
14.  The method of claim 12, wherein the coupling includes driving a first threaded member carried by the at least one plunger slider into engagement with a second threaded member carried by the reservoir piston.
15.  The method of claim 14 wherein the first threaded member comprises a screw extending from the at least one plunger slider and having external threads, and the second threaded member comprises a cavity defined by the piston and having
internal threads positioned to be engaged by the screw external threads.
16.  The method of claim 15 wherein the external threads of the screw are made of a material having a first hardness and the internal threads of the piston cavity are made of a material having a second hardness.
17.  The method of claim 15 wherein the external threads of the screw have a first lead and wherein the internal threads of the piston cavity have a second lead.
18.  The method of claim 14 wherein the releasing includes rotating the reservoir piston to unscrew the first threaded member from the second threaded member.
19.  The method of claim 12 further comprising venting a housing enclosing the drive motor and linear actuator through a vent port containing a hydrophobic material.
20.  A portable medical device for dispensing liquid from a liquid reservoir having a piston which defines an axis of travel, the medical device comprising:
wherein the second drive member substantially radially surrounds at least a portion of a length of the driving means when the second drive member is in the retracted position;  and
21.  The medical device of claim 20 further comprising a housing enclosing the first and second drive members, the driving means and the linear actuating means, wherein the housing includes means for venting the housing to the atmosphere without
permitting liquids to pass through said venting means.
22.  A medical device according to claim 1, wherein the at least one plunger slider substantially radially surrounds at least a portion of a length of the drive motor when the at least one plunger slider is in the retracted position.
23.  A medical device according to claim 22, wherein the drive motor includes an encoder.
24.  A medical device according to claim 1, wherein the liquid reservoir is rotatably removable from the plunger slider and another liquid reservoir may be used to replace the liquid reservoir, and the at least one plunger slider is permanently
coupled to the gearbox.
25.  A portable medical device for dispensing liquid from a liquid reservoir having a piston which defines an axis of travel, the medical device comprising:
a drive shaft mechanically coupled to rotate in response to actuation of the solenoid, and coaxially aligned with the piston axis of travel;  and
at least one plunger slider coupled to the drive shaft to translate from a retracted position to an extended position to displace the piston along the piston axis of travel and dispense liquid form the reservoir in response to rotation of the
drive shaft, wherein the at least one plunger slider substantially radially surrounds at least a portion of a length of the solenoid when the at least one plunger slider is in the retracted position.
26.  A medical device according to claim 25, wherein the at least one plunger slider is releasably coupled to the piston.  Description
This invention relates generally to improvements in infusion pumps such as those used for controlled delivery of medication to a patient.  More specifically, this invention relates to an improved infusion pump having a modified and
space-efficient drive system.
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.
periodic intervals to obtain a closely controlled and accurate delivery of the medication over an extended period of time.  Such infusion pumps are utilized to administer insulin and other medications, with exemplary pump constructions being shown and
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
In the operation of these pump systems, the reservoir piston will be fully advanced when vitually 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.
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, it likewise will be forced in an axial
direction d&#39;, parallel to direction d, thus dispensing the fluid from the reservoir 105 into the infusion set 106.  The entire assembly can be contained in a water resistant housing 107.
FIG. 2 shows a different 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 201a 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&#39;,
parallel to the drive shaft 201a 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&#39; thus dispensing fluid from the reservoir 206 into the infusion set 207.  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 is used to drive the reservoir&#39;s piston.  This external arrangement
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. 3b 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.
Moreover the design of FIG. 3a is not water resistant.  Because the reservoir, piston head and threaded piston member are removable, the drive screw 305 and motor 306 are exposed to the atmosphere.  Any water which might come in contact with the
drive screw 305 and motor 306 will result in corrosion and probable motor failure.
The construction of pumps to be water resistant give rise to operational problems.  As the user travels from various elevations, such as might occur when traveling in an air plane, or as the user engages in other activities which expose the pump
to changing atmospheric pressures, differential pressures can arise between the interior of the air tight/water-resistant pump housing and the atmosphere.  Should the pressure in the housing exceed external atmospheric pressure, the resulting forces
Thus it is desirable to have an improved, compact, water resistant drive system which permits safe user activity among various atmospheric pressures.  Moreover it is desirable that such a system employ inexpensive medication reservoirs.
An improved pump is provided with a reservoir for accommodation of a liquid and a movable piston for varying the size of the reservoir and adapted to discharge the liquid from the reservoir through the outlet.  In a certain aspect of the present
inventions, a plunger slide is releasably coupled with the movable piston and has at least two positions.  A driving device, such as a motor, is operably coupled to a drive member, such as a drive screw.  The motor is disposed in-line with the drive
screw and the plunger slide.  The drive screw is operably connected to the plunger slide and is disposed to be substantially enclosed by the plunger slide when it is in at least one position.  The drive screw is adapted to advance the plunger slide in
In one alternative, a housing for the reservoir, the movable piston, the plunger slide, the drive screw and the motor is provided along with a sealing device, such as an O-ring, that separates the portion of the housing which encloses the movable
piston from the portion of the housing which encloses the drive screw and the motor.
In another preferred embodiment, a coupler is attached to the plunger slide.  The coupler is removably attached to the movable piston to prevent separation of the movable piston from the plunger slide when the air pressure in the housing exceeds
the pressure external to the water resistant housing.
In still another embodiment, the housing includes a vent port between the exterior and interior of the housing.  The vent port contains a hydrophobic material or a relief valve, either of which will permit air to pass through the vent, but will
prevent water from passing.
In another alternative, the driving device is a motor which is attached to the housing with a compliance mount.  In another embodiment, the plunger slide comprises a telescoping lead screw formed from at least two segments.
In yet another embodiment , the pump includes a key which is coupled with the plunger slide and which is operable to permit movement of the plunger slide in the direction of the at least two positions but prevent movement of the plunger slide in
that require compact and accurate drive mechanisms.
In addition, other embodiments use a telescoping drive member (or lead screw) to minimize the packaging dimensions of the drive mechanism and the overall configuration of the medication pump.  Still further, a ventilation feature using
hydrophobic materials or a relief valve can be employed to equalized any pressure differentials which might otherwise exist between the atmosphere and the interior of the pump housing.  As a back up to this ventilation feature, a threaded attachment
permits a secure coupling between the reservoir piston and the in-line drive.
FIG. 4 shows a side plan, cut-away view of an infusion pump drive mechanism according to a preferred embodiment of the inventions, in which a housing 401, containing a lower section 402 for a power supply 420 and electronic control circuitry 422,
and a removable vial or reservoir 406.  The reservoir 406 includes a plunger or piston 407 with O-rings or integral raised ridges for forming a water and air tight seal.  The reservoir 406 is secured into the housing 401 with a connector 431 which also
serves as the interface between the reservoir 406 and the infusion set tubing (not shown).  In a preferred embodiment, the reservoir piston 407 is coupled to the plunger slide 405 by a releasable coupler.  In the illustrated embodiment, the coupler
includes a female portion 424 which receives a male portion 426 carried by the plunger slide 405.  The female portion 424 is positioned at the end face 428 of the piston 407 and includes a threaded cavity which engages the threads of a male screw
extending from the end 430 of the plunger slide 405.
While preferred embodiments of the present inventions are directed to disposable, pre-filled reservoirs, alternative embodiments may use refillable cartridges, syringes or the like.  The cartridge can be pre-filled with insulin (or other drug or
Referring again to FIG. 4, as the drive shaft 432 of the motor 403 rotates, the drive screw 404 drives the plunger slide 405 directly to obtain the axial displacement against the reservoir piston 407 to deliver the predetermined amount of
medication or liquid.  When using a DC or stepper motor, the motor can be rapidly rewound when the reservoir is emptied or as programmed by the user.  A sealing device, such as an O-ring seal 409 is in contact with the plunger slide 405 thus allowing it
to move axially while maintaining a water resistant barrier between the cavity holding the reservoir 406 and the motor 403.  This prevents fluids and other contaminants from entering the drive system.
piston 407.  Accordingly, the plunger slide 405 is sized to fit within the housing of the reservoir 406, such that when the reservoir piston 407 and the plunger slide 405 are in the fully extended position as shown, the reservoir piston 407 has forced
most, if not all, of the liquid out of the reservoir 406.  As explained in greater detail below, once the reservoir piston 407 has reached the end of its travel path indicating that the reservoir has been depleted, the reservoir 406 may be removed by
twisting such that the threaded reservoir piston 407 (not shown in FIG. 7b) disengages from the male portion 426 of the coupler.
In a preferred embodiment, the motor drive shaft 432, gear box 501, drive screw 404, and plunger slide 405 are all coaxially centered within the axis of travel 440 (FIG. 4) of the reservoir piston 407.  In certain of the alternative embodiments,
FIG. 9 illustrates a split lead-screw (or plunger slide) design in accordance with an embodiment of the present inventions.  The use of a split lead-screw or telescoping lead screw allows the use of an even smaller housing for the drive
mechanism.  A telescoping lead-screw formed from multiple segments allows the pump to minimize the dimensions of the drive mechanism, in either in-line or gear driven drive mechanisms.
In preferred embodiments, an interior shaft 901 is rotated by a gear 906 which is coupled to a drive motor (not shown).  This in turn extends a middle drive segment 902 by engaging with the threads of an internal segment 904.  The middle segment
902 carries an outer segment 903 forward with it in direction d as it is extended to deliver fluid.  When the middle segment 902 is fully extended, the internal segment 904 engages with a stop 905 on the middle segment 902 and locks it down from pressure
with the threads between the middle and internal segments.  The locked middle segment 902 then rotates relative to the outer segment 903 and the threads between the middle segment 902 and the outer segment 903 engage to extend the outer segment 903 in
direction d to its full length.
To address this problem, a preferred embodiment of the inventions includes a venting port which resists the intrusion of moisture.  Referring to FIG. 7b, venting is accomplished through the housing 401 into the reservoir cavity 601 via a vent
port 605.  The vent port can be enclosed by a relief valve (not shown) or covered with hydrophobic material.  Hydrophobic material permits air to pass through the material while resisting the passage of water or other liquids from doing so, thus
permitting water resistant venting.  The preferred embodiment uses a hydrophobic material such as Gore-Tex.RTM., PTFE, HDPE, UHMW polymers from sources such as W.I.  Gore &amp; Associates, Flagstaff, Az., Porex Technologies, Fairbum, Ga., or DeWAL
Industries, Saunderstown, R.I..  It is appreciated that other hydrophobic materials may be used as well.
1001 (FIG. 10a) or a cylinder 1002 (FIG. 10b) and pressing it into a cavity in the pre-molded plastic housing.  Alternatively, a label 1003 (FIG. 10c) of this material could be made with either a transfer adhesive or heat bond material 1004 so that the
As described in greater detail in copending application Ser.  No. 09/428,818 filed contemporaneously herewith (Attorney docket No. 0059-0307), which application is incorporated by reference in its entirety, the connector and infusion set refers to the
tubing and apparatus which connects the outlet of the reservoir to the user of a medication infusion pump.
up which will retard ventilation.  In yet another alternative embodiment however, vent ports with hydrophobic material could be placed in both the pump housing and in the connector portion of the infusion set.
the external face of the reservoir piston 407.  The threaded cavity 424 engages the threads of the male portion 426 which in turn is attached to the end 430 of the plunger slide 405.
This thread engagement reduces or prevents the effect of atmospheric pressure differentials acting on the water resistant, air-tight housing 401 (not shown in FIG. 1) from causing inadvertent fluid delivery.  The threads of the male portion 426
act to inhibit or prevent separation of the reservoir piston 407 from the plunger slide 405 which, in turn, is secured to the drive screw 404 (not shown in FIG. 1) by engagement of the external threads of the drive screw 404 with the internal threads of
the plunger slide 405.  As a result, the coupler resists movement of the reservoir piston 407 caused by atmospheric pressure differentials.
position (FIGS. 4 and 6).  A new reservoir 406, however, may not be full of fluid.  Thus the reservoir piston 407 may not be located in the furthest possible position from the reservoir outlet.  Should the reservoir piston 407 be in such an intermediate
position, then it may not be possible to engage the threads of the male portion 426 of the coupler (which is in a fully retracted position) with those in the female portion 424 of the coupler in the reservoir piston 407 upon initial placement of the
contact with the reservoir piston 407 and the threads of the coupler male portion 426 of the coupler engage the threads in the female portion 424 in the reservoir piston 407.  When the threads engage in this fashion in the illustrated embodiment, they do
so not by twisting.  Rather, they rachet over one another.
The purpose of this intentional cross threading is to reduce the force necessary to engage the threads as the plunger slide 405 seats into the reservoir piston 407.  In addition, the 2 start, 40 TPI threads of the coupler female portion 424 are
preferably made from a rubber material to provide a degree of compliance to the threads.  On the other hand, the 5 start, 40 TPI threads of the male coupler portion 426 are preferably made of a relatively hard plastic.  Other threading arrangements and
profiles could be employed resulting in a similar effect.
While the advantage of utilizing a common thread pitch would be to provide a maximum ability to resist axial separation of the reservoir piston 407 from the plunger slide 405, there are disadvantages.  In engaging the threads, the peak force is
high and could result in excessive delivery of fluids as the plunger slide 405 moves forward to seat in the cavity of the reservoir piston 407.  As described in greater detail in copending application Ser.  No. 09/428411 filed contemporaneously herewith
(Attorney Docket No. 0059-0308), which application is incorporated by reference in its entirety, the pump may have an occlusion detection system which uses axial force as an indicator of pressure within the reservoir.  If so, then a false alarm may be
generated during these high force conditions.
Therefore, the insertion force profile is preferably more flat than that shown in FIG. 13a.  To accomplish this, the cross threading design of the preferred embodiment causes the relatively soft rubber teeth of the female portion 424 at the end
of the reservoir piston 407 to rachet or swipe around the relatively hard plastic teeth of the coupler resulting in a significantly lower insertion force for the same degree of thread interference.  (See FIG. 13b) This is due to the fact that not all of
the thread teeth ride over one another simultaneously.  Moreover, the cross-sectional shape of the threads are ramped.  This makes it easier for the threads to ride over one another as the plunger slide is being inserted into the reservoir piston.
However, the flat opposite edge of the thread profile makes it much more difficult for the plunger slide to be separated from the reservoir piston.
Referring to FIGS. 11 and 12, the 5 start, 40 TPI (0.125&quot; lead) thread profile of the coupler male portion 426 was chosen in consideration of the thread lead on the preferred embodiment of the connector 431.  The connector 431 is secured into the
pump housing with threads 433 (FIG. 7b) having a 2 start, 8 TPI (0.250&quot; lead) profile.  Therefore the 0.250&quot; lead on the connector is twice that of the reservoir piston 407 which is 0.125&quot;.  This was chosen to prevent inadvertent fluid delivery during
removal of the reservoir from the pump housing, or alternatively, to prevent separation of the reservoir piston 407 from the reservoir 406 during removal from the pump housing.  When the connector 431 is disengaged from the pump, the connector 431 as
well as the reservoir 406 will both travel with the 0.250&quot; lead.  Since the threaded coupler lead is 0.125&quot;, the plunger slide 405 will disengage somewhere between the 0.125&quot; lead of the threaded coupler and the 0.250&quot; lead of the infusion set 1103.
Therefore, the rate that the reservoir piston 407 is removed from the pump is the same down to half that of the reservoir 406/connector 431.  Thus any medication which may be present in the reservoir 406 will not be delivered to the user.  Additionally,
the length of the reservoir piston 407 is sufficient such that it will always remain attached to the reservoir 406 during removal from the pump.  Although the preferred embodiment describes the plunger slide 405 having a coupler male portion 426 with an
external thread lead that is different from the connector 431, this is not necessary.  The thread leads could be the same or of an increment other than what has been described.
The 2 start thread profile of the coupler female portion 424 on the reservoir piston 407 of the preferred embodiment provides another advantage.  Some versions of these reservoirs may be designed to be filled by the user.  In such an instance, a
handle (not shown) will need to be screwed into the threaded portion of the reservoir piston 407 in order for the user to retract the reservoir piston 407 and fill the reservoir.  The number of rotations necessary to fully insert the handle depends upon
the distance the handle thread profile travels to fully engage the reservoir piston 407 as well as the thread lead.
For example, a single start, 40 TPI (0.025&quot; lead) thread requires 4 complete rotations to travel a 0.10&quot; thread engagement.  However, a 2 start, 40 TPI (0.050&quot; lead) thread only requires 2 complete rotations to travel the 0.10&quot; thread engagement. Therefore, an additional advantage of a 2 start thread as compared to a single start thread (given the same pitch) is that half as many rotations are needed in order to fully seat the handle.
In alternative embodiments which are not shown, the end of the plunger slide 405 may include a detente or ridge to engage with a corresponding formation in the reservoir piston 407 to resist unintended separation of the plunger slide 405 from the
reservoir piston 407.  In other embodiments, the plunger slide 405 is inserted and removed by overcoming a friction fit.  Preferably, the friction fit is secure enough to resist movement of the reservoir piston 407 relative to the plunger slide 405 due
to changes in air pressure, but low enough to permit easy removal of the reservoir 406 and its reservoir piston 407 from the plunger slide 405 once the fluid has been expended.  In other embodiments, the detente or ridge may be spring loaded or activated
to grasp the reservoir piston 407 once the drive mechanism has been moved forward (or extended), but is retracted by a switch or cam when the drive mechanism is in the rearmost (or retracted) position.  The spring action could be similar to those used on
collets.  In other embodiments of the inventions, the threaded coupler may be engaged with the threaded cavity of the reservoir piston by twisting or rotating the reservoir as it is being manually placed into the housing.
As set forth above, the reservoir piston 407 is made of rubber.  In the illustrated embodiment, an insert 1201 (FIG. 12) which is made of hard plastic may provided in the upper portion of the reservoir piston 407.  The insert 1201 provides
stiffness to the rubber reservoir piston 407.  This reduces undesirable compliance which is associated with the reservoir.  Without the insert 1201, the flexibility in the reservoir piston 407 due to its rubber composition could cause it to deform under
varying reservoir fluid back pressures.  This deformation could in turn vary the internal volume of the reservoir 406.  Such variances may adversely affect the controlled delivery of the fluid from the reservoir 406 via the infusion set to the user.
It can be appreciated that the design of FIGS. 4-12 results in an arrangement where; the plunger slide 405 is reliably but releasably coupled to the drive screw 404.  When it is time to replace the reservoir 406, it can be detached from the male
end of the coupler without affecting the plunger/drive screw engagement.  Moreover in the preferred embodiment, the plunger slide 405 is shaped as a hollow cylinder with internal threads.  Thus it completely encircles and engages drive screw 404.  When
the plunger slide 405 is in a relatively retracted position, it encloses any gears which couple the motor 403 with the drive screw 404 thus achieving an extremely compact design.  Alternative embodiments include an arrangement where the plunger slide 405
encloses the motor 403 itself.  A vent port covered with hydrophobic material as well as a threaded coupler provide redundant means for permitting exposure of the pump to changing atmospheric pressures without the unintended delivery of medication.
modifications as would fall within the true scope and spirit of the present inventions.  The presently disclosed embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the inventions being indicated
Compact pump drive system, Moberg, Sheldon Moberg, Application number 09 429-352, Surgery, DRIVE SYSTEM, United States of America, the fluid, infusion pump, Patent and Trademark Office, IP Services, Patent Search, Document Number, PCT Applications, Patent Office
1. Field of the InventionThis invention relates generally to improvements in infusion pumps such as those used for controlled delivery of medication to a patient. More specifically, this invention relates to an improved infusion pump having a modified andspace-efficient drive system.2. Description of the Related ArtInfusion 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 housingadapted 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 atperiodic intervals to obtain a closely controlled and accurate delivery of the medication over an extended period of time. Such infusion pumps are utilized to administer insulin and other medications, with exemplary pump constructions being shown anddescribed 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 beextremely 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 p
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