Patent Description:
Programmable infusion pumps are used to carry out controlled delivery of liquid food for enteral feeding and medications for various purposes such as pain management. In a common arrangement, an infusion pump receives a disposable administration set comprising flexible tubing having a resiliently deformable tubing segment designed to be engaged by a pumping mechanism of the infusion pump. For example, the pumping mechanism may include a plurality of fingers sequentially driven against the tubing segment to locally deform the tubing segment in a peristaltic manner to force liquid through the tubing toward the patient. During pumping, a platen member of the infusion pump is held at a fixed position on a side of the tubing segment opposite from the pumping mechanism to provide a platen surface along the tubing segment for keeping the tubing segment in place against the pressure of the pumping mechanism. In prior art infusion pumps, the platen member of the pump is a one-piece member rotatably mounted on a body of the pump, whereby the platen member may be pivoted about a hinge axis between an open position and a closed position. In the open position, the platen member is pivoted away from the pump body to allow an administration set to be loaded in the infusion pump with the tubing segment adjacent the pumping mechanism. In the closed position, the platen member is pivoted toward the pump body and latched or locked with respect to the pump body such that the platen surface is held at an operating position adjacent to the tubing segment and opposite from the pumping mechanism. An example of the arrangement described above is disclosed in <CIT>.

It is recognized that infusion pumps are subject to damage which may affect pumping performance and patient safety. Infusion pumps, especially so-called "ambulatory" infusion pumps designed to be carried by a patient for daily use, may be dropped from time to time, whereby the platen member may be deformed. Depending upon the extent of deformation, undetectable free flow and/or uncontrolled or inaccurate fluid flow may occur, creating a safety risk that the patient may receive too much or too little infusion liquid relative to the prescribed amount. Prior art infusion pumps have no way of detecting and assessing platen damage, or making a decision as to whether the damage renders the infusion pump unsafe to use.

Patent application publication <CIT> relates to an administration set for an infusion pump, including a free-flow prevention device having a movable plunger that includes a cam surface defining an uneven profile along a direction of movement of the plunger, wherein the shape of the cam surface profile indicates the administration set is authorized for use with the infusion pump and may further indicate the specific type of administration set. This document discloses the combination of features of the preamble of claim <NUM>.

The present invention provides an infusion pump as set out in appended claim <NUM>. The present disclosure provides a damage-resistant and damage-tolerant platen assembly for an infusion pump. The platen assembly includes a first platen member rotatably coupled to a body of the infusion pump to pivot relative to the pump body about a first hinge axis and a second platen member rotatably coupled to the first platen member to pivot relative to the first platen member about a second hinge axis. The platen assembly is pivotable about the first hinge axis to an open position in which the second platen member and the first platen member are positioned away from a pumping mechanism in the pump body, and to a closed position in which the second platen member and the first platen member are positioned opposite and in proximity to the pumping mechanism for operation of the pump.

The first platen member may include a bend or a curve between the first hinge axis and the second hinge axis such that a load path through the first platen member from the second hinge axis to the first hinge axis is non-linear, thereby creating a moment about the first hinge axis to resist damage to the platen assembly if the pump is dropped.

The platen assembly has a damage-tolerant design including a plurality of alignment counter-features arranged to mate with corresponding alignment features on the pump, wherein the platen assembly may still close after the pump is dropped or damaged only if resulting deformation of the platen assembly is within an allowable tolerance for safe pumping.

The first platen member may include a first platen surface and the second platen member may include a second platen surface, wherein the first platen surface and the second platen surface engage tubing of an administration set received by the infusion pump when the platen assembly is in the closed position. In the closed position of the platen assembly, the first and second platen surfaces may follow a single surface profile, for example an arcuate surface profile in the case of a curvilinear peristaltic pump.

The first platen member may include a mounting portion configured for rotatably mounting the first platen member on the pump body for rotation about the first hinge axis and a branch extending from the mounting portion. The mounting portion may be thicker than the branch in a direction of the first hinge axis, and the branch may be located between and spaced from opposite axial ends of the mounting portion, so that tubing of the administration set can enter the pump through a gap or opening immediately in front of the first platen member or through a gap or opening immediately to the rear of the first platen member.

The nature and mode of operation of the present invention will now be more fully described in the following detailed description of the invention taken with the accompanying drawing figures, in which:.

<FIG> and <FIG> show an infusion pump <NUM> formed in accordance with a disclosed embodiment. In <FIG>, infusion pump <NUM> is shown alone, whereas in <FIG>, infusion pump <NUM> is shown with a disposable administration set <NUM> loaded in the pump, wherein administration set <NUM> is designed to be removably received by infusion pump <NUM>. Administration set <NUM> includes flexible tubing acted upon by pump <NUM> to convey a flow of infusion liquid from a source reservoir (not shown) to a patient (not shown).

Infusion pump <NUM> comprises a pump body <NUM> including a pumping mechanism <NUM>. Pump <NUM> also comprises a platen assembly <NUM> which includes a first platen member <NUM> rotatably coupled to pump body <NUM> to pivot relative to pump body <NUM> about a first hinge axis HA1, and a second platen member <NUM> rotatably coupled to first platen member <NUM> to pivot relative to first platen member <NUM> about a second hinge axis HA2. First hinge axis HA1 and second hinge axis HA2 may be parallel to one another. As shown in <FIG>, platen assembly <NUM> is pivotable about first hinge axis HA1 to an open position in which second platen member <NUM> and first platen member <NUM> are positioned away from pumping mechanism <NUM>. When platen assembly <NUM> is in the open position depicted in <FIG>, pumping mechanism <NUM> is exposed, thereby allowing a disposable administration set <NUM> to be loaded into infusion pump <NUM> such that a tubing segment 12A of the administration set is adjacent to pumping mechanism <NUM>. As may be understood from <FIG>, platen assembly <NUM> is pivotable about first hinge axis HA1 to a closed position in which second platen member <NUM> and the first platen member <NUM> are positioned opposite and in proximity to pumping mechanism <NUM>.

Pumping mechanism <NUM> may be a peristaltic pumping mechanism having a plurality of extendable and retractable pumping fingers <NUM> that are driven in sequential peristaltic fashion to engage and temporarily deform tubing segment 12A such that liquid is pumped through the tubing of administration set <NUM> in the direction of the patient. In the illustrated embodiment, pumping mechanism <NUM> has a curvilinear configuration, and pumping fingers <NUM> are moved generally radially by rotation of a motor-driven eccentric cam <NUM>. Pumping mechanism <NUM> may take other forms, such as a linear peristaltic pumping mechanism having axially spaced fingers moved by respective cams mounted on a rotary shaft, or a rotary pumping mechanism having a motor-driven rotor about which tubing segment 12A is partially wound for engagement by pumping elements on the rotor.

Platen assembly <NUM> is now further described with reference to <FIG> and <FIG> in addition to <FIG> and <FIG>.

First platen member <NUM> may include a bend or a curve <NUM> between first hinge axis HA1 and second hinge axis HA2, whereby a direct linear load path between second hinge axis HA2 and first hinge axis HA1 is avoided. Such a configuration of first platen member <NUM> is advantageous because impact force imparted to second platen member <NUM> if pump <NUM> is dropped will result in a moment about first hinge axis HA1 to help resist damage to platen members <NUM>, <NUM>. First platen member <NUM> may include a first platen surface <NUM>, which may be located between bend or curve <NUM> and second hinge axis HA2, wherein first platen surface <NUM> engages tubing segment 12A of administration set <NUM> when platen assembly <NUM> is in the closed position. First platen member <NUM> may include a mounting portion <NUM> configured for rotatably mounting first platen member <NUM> on pump body <NUM> for rotation about first hinge axis HA1 and a branch <NUM> extending from mounting portion <NUM>. Mounting portion <NUM> may be thicker than branch <NUM> in a direction of first hinge axis HA1, and branch <NUM> may be located between and spaced from opposite axial ends of mounting portion <NUM>, thereby providing both a front opening 34F in front of branch <NUM> and a rear opening 34R behind branch <NUM> for tubing of administration set <NUM> to enter pump <NUM>. As a result, the user may load the tubing such that the tubing extends either through front opening 34F as shown in <FIG> or through rear opening 34R as shown in <FIG> because both of these arrangements are intended and correct. Branch <NUM> may be centrally located between the opposite axial ends of mounting portion <NUM> to define two equal openings 34F and 34R. First platen member <NUM> may have a distal end <NUM> configured for rotatable coupling of second platen member <NUM> thereto.

Second platen member <NUM> may be arranged and sized to extend over pumping fingers <NUM> of pumping mechanism <NUM> when platen assembly <NUM> is in the closed position such that a second platen surface <NUM> provided on second platen member <NUM> engages tubing segment 12A. Second platen member <NUM> may be configured to have a clevis-shaped end <NUM> for receiving distal end <NUM> of first platen member <NUM>.

Platen assembly <NUM> includes a plurality of alignment counter-features <NUM>, <NUM> for respectively mating with a plurality of alignment features <NUM>, <NUM> provided on pump body <NUM>, whereby movement of platen assembly <NUM> to the closed position will be prevented if platen assembly <NUM> is deformed beyond a predetermined tolerance limit, as may occur for instance if pump <NUM> is accidentally dropped. In the illustrated embodiment shown, alignment counter-features <NUM>, <NUM> are provided on second platen member <NUM>. First alignment counter-feature <NUM> may be located adjacent to a proximal end of second platen surface <NUM>, and second alignment counter-feature <NUM> may be located adjacent to an opposite distal end of second platen surface <NUM>. Mating of first alignment feature <NUM> with first alignment counter-feature <NUM>, and mating of second alignment feature <NUM> with second alignment counter-feature <NUM>, occurs when platen assembly <NUM> is pivoted about first hinge axis HA1 to its closed position. By providing multiple alignment features <NUM>, <NUM> on pump body <NUM> and corresponding counter-features <NUM>, <NUM> on second platen member <NUM>, and by locating an alignment feature and corresponding alignment counter-feature adj acent to each opposite end of second platen surface <NUM>, safety-critical positioning of second platen surface <NUM> with respect to tubing segment 12A is confirmed upon closure of platen assembly <NUM>. The alignment features <NUM>, <NUM> may be embodied as pins and the alignment counter-features <NUM>, <NUM> may be embodied as slots in accordance with the drawing figures. Alternatively, the alignment features <NUM>, <NUM> may be embodied as slots and the alignment counter-features <NUM>, <NUM> may be embodied as pins, or the alignment features <NUM>, <NUM> may include at least one pin and at least one slot and the counter-features <NUM>, <NUM> may include at least one slot and at least one pin.

The manner by which first platen member <NUM> may be rotatably coupled to pump body <NUM> may vary. In one example example, first platen member <NUM> may be rotatably coupled to pump body <NUM> by a pivot pin <NUM> mounted on pump body <NUM> and arranged to extend through a cylindrical bushing <NUM> provided in mounting portion <NUM> of first platen member <NUM>. Likewise, the manner by which second platen member <NUM> may be rotatably coupled to first platen member <NUM> is subject to variation. By way of example, a pivot pin <NUM> provided at clevis-shaped end <NUM> of second platen member <NUM> and arranged to extend through a hole <NUM> in mating distal end <NUM> of first platen member <NUM>. Of course, other arrangements for rotatably coupling first platen member <NUM> to pump body <NUM>, and second platen member <NUM> to first platen member <NUM>, may be used.

As mentioned above, pumping mechanism <NUM> may have a curvilinear configuration, wherein pumping fingers <NUM> are moved generally radially. In this case, first platen surface <NUM> associated with first platen member <NUM> and second platen surface <NUM> associated with second platen member <NUM> may be arcuate platen surfaces configured to follow a single arcuate profile when platen assembly <NUM> is in the closed position, as may be seen in <FIG>. In the closed position, second platen surface <NUM> may oppose all the pumping fingers <NUM>, and first platen surface <NUM> may oppose an upstream pressure sensor as described below. It is also possible to reconfigure platen assembly <NUM> such that some of the pumping fingers <NUM> are opposed by first platen surface <NUM>.

Infusion pump <NUM> may comprise an upstream pressure sensor <NUM> and a downstream pressure sensor <NUM> arranged to detect fluid pressure within tubing segment 12A of administration set <NUM> at locations upstream and downstream from pumping mechanism <NUM>, respectively. Upstream pressure sensor <NUM> may be arranged to detect fluid pressure at a location opposite from first platen surface <NUM>, and downstream pressure sensor <NUM> may be arranged to detect fluid pressure at a location opposite from second platen surface <NUM>. This arrangement has the advantage that upstream pressure sensor <NUM> may be used to detect a pressure drift if first platen member <NUM> is deformed beyond an allowable tolerance, and downstream pressure sensor <NUM> may be used to independently detect a pressure drift if second platen member <NUM> is deformed beyond an allowable tolerance. By way of example, pressure sensors <NUM>, <NUM> may each include a plunger having one end arranged to engage an outer surface of tubing segment 12A and an opposite end arranged to engage a strain beam transducer, wherein expansion and contraction of the tubing segment due to fluid pressure changes is transmitted to the strain beam transducer to generate a corresponding voltage signal representing fluid pressure at the location where the plunger contacts the tubing segment.

To secure platen assembly <NUM> in its closed position for pumping operation after administration set <NUM> is loaded in the pump, platen assembly <NUM> may include a latch member <NUM> for engaging a latching feature <NUM> on pump body <NUM>. Latch member <NUM> may be rotatably coupled to second platen member <NUM> by a pivot pin <NUM>. Pivot pin <NUM> may be arranged to extend through a slightly elongated passage <NUM> proceeding transversely through second platen member <NUM>, and a spring <NUM> may be arranged to bias pivot pin <NUM> toward an upper end of passage <NUM>. Latch member <NUM> may be provided with a latching counter-feature <NUM> arranged and configured such that when platen assembly <NUM> is in the closed position and latch member <NUM> is pivoted in a clockwise direction as viewed in <FIG> and <FIG>, latching counter-feature <NUM> will engage with latching feature <NUM> in a cam-like manner to progressively pull the end of second platen member <NUM> downward relative to latch member <NUM> against the bias of spring <NUM> until latching feature <NUM> is received at an inner end region of latching counter-feature <NUM>, at which point second platen member <NUM> is forced in an upward direction relative to latch member <NUM> by spring <NUM> to securely hold latching feature <NUM> in engagement with latching counter-feature <NUM> in spring-biased fashion, thereby locking platen assembly <NUM> in its proper static position opposite pumping mechanism <NUM>. Latch member <NUM> may include a magnet <NUM> detectable by a latch sensor <NUM> (see <FIG>) housed in or on pump body <NUM> to generate a latching signal indicative of whether or not platen assembly <NUM> is properly latched. For example, latch sensor <NUM> may be a Hall effect sensor.

When platen assembly <NUM> is properly closed and latched, second platen surface <NUM> of second platen member <NUM> may interact with pumping fingers <NUM> to create a peristaltic pumping of fluid through tubing segment 12A. Second platen member <NUM> including second platen surface <NUM> is located and locked in a specific static position to ensure controlled and accurate delivery of fluid. As mentioned above, second platen surface <NUM> may be curved around pumping fingers <NUM>, and tubing segment 12A may be located between second platen surface <NUM> and pumping fingers <NUM>. Alignment features <NUM>, <NUM> and alignment counter-features <NUM>, <NUM> may be configured and arranged to mate even if platen assembly <NUM> is damaged or deformed, so long as the damage or deformation of platen assembly <NUM> is within an allowable tolerance for which controlled and accurate delivery of fluid is maintained. If platen assembly <NUM> is damaged or deformed beyond the allowable tolerance, then alignment features <NUM>, <NUM> will not properly mate with alignment counter-features <NUM>, <NUM>, and pump <NUM> may be disabled to prevent a user from using the pump in an unsafe condition.

In the illustrated embodiment, first platen member <NUM> is configured and arranged to absorb and/or divert impact energy if pump <NUM> is dropped, thereby protecting the structural integrity of second platen member <NUM>. Impact energy may be transmitted from second platen member <NUM> to first platen member <NUM> through the coupling at second hinge axis HA2, however some of the impact energy will be diverted to cause rotational displacement between first platen member <NUM> and second platen member <NUM> about second hinge axis HA2, and rotational displacement between first platen member <NUM> and pump body <NUM> about first hinge axis HA1. Impact energy not diverted to cause rotational displacement may be absorbed by first platen member <NUM> through deformation. As may be understood, rotational displacement and/or deformation of first platen member <NUM> resulting from compression force at impact can only result in a shortening of the distance between pivot pins <NUM> and <NUM> (to make this distance longer it is necessary to apply a high tension stress, which is not possible from dropping pump <NUM>). Any change in the position of second platen member <NUM> from dropping pump <NUM> will always have a downward component toward pumping mechanism <NUM> rather than an upward component away from pumping mechanism <NUM>. Because upward displacement of second platen member <NUM> and second platen surface <NUM> away from pumping mechanism <NUM> may cause a dangerous free-flow condition, the disclosed platen assembly <NUM> reduces safety risk associated with dropping pump <NUM>.

Reference is now made to <FIG>. In another aspect of the present disclosure, signals generated by upstream pressure sensor <NUM>, downstream pressure sensor <NUM>, and latch sensor <NUM> may be provided to a pump controller <NUM> which controls a drive motor <NUM> of pumping mechanism <NUM>. The respective signals may be evaluated by control logic programmed into memory associated with pump controller <NUM> to disable the motor <NUM> of pumping mechanism <NUM> and thereby prevent pump operation if the upstream pressure signal from upstream pressure sensor <NUM> is not within predetermined limits as expected, if the downstream pressure signal from downstream pressure sensor <NUM> is not within predetermined limits as expected, or if the latching signal from latch sensor <NUM> indicates that platen assembly <NUM> is not properly latched. Thus, if platen assembly <NUM> is still able to be physically latched after pump <NUM> has been dropped, but there is some deformation in the platen assembly that disturbs the location of first platen surface <NUM> and/or second platen surface <NUM> relative to pumping mechanism <NUM> and causes pressure drift, this condition can be sensed prior to pumping and corrective action can be taken.

Claim 1:
An infusion pump (<NUM>) comprising:
a pump body (<NUM>) including a pumping mechanism (<NUM>);
a platen assembly (<NUM>) including a first platen member (<NUM>) rotatably coupled to the pump body to pivot relative to the pump body about a first hinge axis (HA1) and a second platen member (<NUM>) rotatably coupled to the first platen member to pivot relative to the first platen member about a second hinge axis (HA2);
wherein the platen assembly is pivotable about the first hinge axis to an open position in which the second platen member and the first platen member are positioned away from the pumping mechanism allowing a disposable administration set (<NUM>) to be loaded into the infusion pump such that, in use, a tubing segment (12A) of the administration set is adjacent to the pumping mechanism;
characterized in that the platen assembly is pivotable about the first hinge axis to a closed position in which the second platen member and the first platen member are positioned opposite and in proximity to the pumping mechanism such that, in use, the first and second platen members engage said tubing segment (12A);
the pump body includes a first alignment feature (<NUM>) and a second alignment feature (<NUM>), the platen assembly includes a first alignment counter-feature (<NUM>) and a second alignment counter-feature (<NUM>), and the first alignment feature and second alignment feature respectively mate with the first alignment counter-feature and the second alignment counter-feature when the platen assembly is in the closed position; and
the first alignment counter-feature and the second alignment counter-feature are included on the second platen member, and movement of the platen assembly to the closed position will be prevented if the platen assembly is deformed beyond a predetermined tolerance limit.