Patent Application
20180328352
Biological systems including tubes or channels such as the intestines or ureters perform a fluid pumping action called peristaltic pumping, in which waves of smooth muscle contraction move along the length of the biological tube. In the remainder of this disclosure, naturally-occurring peristaltic pumps in biological systems are referred to as “biological peristaltic pumps”.
Artificial peristaltic pumps which mimic the action of biological peristaltic pumps have been developed since 1855. In the remainder of this disclosure, the term “peristaltic pump” without the preceding adjective “biological” should be understood as referring to an artificial peristaltic pump.
A peristaltic pump, often called a roller pump, is a fluid pump in which an enclosed flow channel is compressed by roller or rollers, or by a series of compression blocks or fingers, to propel a fluid along the channel from a channel entrance to a channel exit, in rough analogy with the peristaltic pumping action of biological peristaltic pumps. Advantageously, the fluid being pumped contacts only the interior surfaces of flow channel, and complex components such as valves or pistons, which would be subject to leakage or sliding wear, are avoided.
The first peristaltic pump, patented in the US in 1855, employed an elastic tube. Improvements were made but the peristaltic pump was not widely used before 1932. Currently, peristaltic pumps are ubiquitous, with uses including hemodialysis, cardiopulmonary bypass, pharmaceutical manufacturing, drug infusion, chemical handling, slurry pumping, and general laboratory use. There are hundreds of manufacturers of peristaltic pumps in the USA.
All early versions of peristaltic pumps used soft, round tubes or hoses, and the use of soft, round tubes or hoses continues to the present.
Flow channels for peristaltic pumps having a non-round cross sectional shape, which herein will be called the Davis-Butterfield shape, or DB shape, after the inventors, potentially have performance advantages over a round tube or hose, including low spallation, low mechanical stress, long channel life, and high pressure capability. There is, however, a potential drawback of this shape, regarding lateral expansion of the flow channel under vertical compression, which has not previously been acknowledged or discussed. There is, therefore, a need for designs that directly address this issue, facilitating adoption of such channels in peristaltic pumps.
Most existing peristaltic pumps are roller pumps, and most roller pumps can be called “circumferential roller pumps” as the peristaltic pump tubing is disposed around a curved path on a rigid backing member and is driven by rollers which compress the tubing against the circumference of the curved path. There are, however, several peristaltic pump designs which can be called “face roller pumps”. In these, the peristaltic pump tubing is disposed on a planar face of a rigid backing member and is compressed against that planar face by rollers rolling in a circular path around an axis perpendicular to the planar face.
Wearable insulin pumps are a growing market, mainly for use by Type I diabetes patients, also known as juvenile diabetes patients. When combined with a blood glucose sensor in an electronic feedback loop, the result can be called an “artificial pancreas.” A typical wearable insulin pump comprises a small disposable syringe containing insulin, the syringe being driven by a stepper motor controlled by electronics, the whole package being small enough to wear on a belt clip. A typical wearable insulin pump is the Medtronic Minimed Model 670G. An insulin pump is one type of infusion pump.
Every three days the patient or caregiver using a wearable insulin pump must discard the old syringe to minimize bacterial contamination, and must refill a new syringe with insulin. Installing a new syringe is a thirteen-step process, using four separate disposables. It requires good two-handed manual dexterity, with several chances for septic contamination. For the many Type I diabetes patients who are children, this process can be a daunting task for them and their parents.
Thus, there exists a need for a compact wearable insulin pump having a simpler insulin refill process with reduced chances for septic contamination.
The present invention includes a flow channel plate suitable for use with a peristaltic pump. The flow channel plate comprises: a planar substrate; a flow channel in the planar substrate; and mechanical strain relief means in the planar substrate, allowing lateral expansion of the flow channel during vertical compression of the flow channel. In one aspect, the path of the flow channel in the flow channel plate is nonlinear. In another aspect, the flow channel is characterized by a Davis-Butterfield cross sectional shape. In yet another aspect, a disposable kit for an infusion pump comprises the flow channel plate of claim 1 and one or more additional elements; wherein the flow channel plate and the one or more additional elements are integrated to form a single assembly.
The present invention further includes a roller pump head comprising: a flow channel plate; a roller cage; tapered rollers held in position by the roller cage; and a drive rotor comprising one of a tapered rotor and a rotor having a radially limited zone of contact on the sloping portions of the tapered rollers; wherein lower surfaces of the tapered rollers apply force to the flow channel plate and upper surfaces of the tapered rollers receive force from the drive rotor.
Embodiments described herein include a peristaltic flow channel and mechanical strain relief features disposed in a planar fashion suitable for incorporation into a compact face-roller peristaltic pump. Embodiments further include a face-roller peristaltic pump incorporating a peristaltic flow channel disposed in a planar fashion.
In
Descriptive language in this disclosure and in associated claims refers to flow channels in the orientations shown in
In
The word “round” used herein to describe flow channel shapes connotes flow channels having a lumen which, when viewed from inside the lumen, has a shape which is concave everywhere, such as a circle, oval, or ellipse. Flow channel shapes having points, cusps, tips, or regions which are convex when seen from within the lumen are non-round.
Thus, whether the flow channel is a round tube, or has a Davis-Butterfield shape, or has some other shape, the flow channel undergoes lateral expansion when it is vertically compressed.
Prior to the present invention, it has been known that the Davis-Butterfield channel shape may be fabricated by extruding a shaped profile, or by bonding together two separate sheets such that the edge of the bonded areas forms the tips of the shaped profile. The possibility of bonding together two separate sheets such that the shaped profile of the channel is set within a larger planar area has not previously been disclosed, and nor has the issue of fabricating channels which are not straight-line in form but instead follow a curving path which is generally planar. The present invention is inspired in part by a realization that the use of a peristaltic pump flow channel following a curving path, and situated in planar fashion within a larger planar area, would have utility advantages which are worth pursuing for wearable insulin pumps and other uses. But the lateral expansion of the flow channel under vertical compression is a problem which must be addressed to use such channels successfully.
That problem of constrained lateral expansion can be addressed by introducing strain relief means situated outside the edges of the channel.
Strain relief means 66 are shown in
The flow channel plate 60 can be formed by laminating together two separate sheets of material or by other means. For example, it can be formed by fine-featured three dimensional printing means known as micro-stereolithography, using a single printing material or various materials. Other possible means of fabricating flow channel plate 60 include, but are not limited to, stereolithography, three-dimensional printing, injection molding followed by lamination, vacuum forming followed by lamination, lamination around a mandrel, and investment casting.
The material comprising flow channel plate 60 may be one or more of poly-ether ether ketone (PEEK), polycarbonate, cyclic olefin copolymer (COC), polyvinyl chloride (PVC) with plasticizers, polyvinyl chloride without plasticizers, polymethyl methacrylate (PMMA or Plexiglass®), polyethylene, high density polyethylene, ultra high density polyethylene, polyethylene terephthalate (PET or PETE), polypropylene, Formlabs printing resin, other printing resin, silicon, glass, silicone rubber, polyimide, stainless steel, brass, and bronze. The use of other materials is also possible.
Rollers 74 are tapered to provide non-grinding rotation on shim plate 77 over flow channel plate 60, or on flow channel plate 60 if shim plate 77 is not present. If cylindrical rollers instead of tapered rollers were to be used, it is known that a grinding action on the pump components would occur. Large cylindrical rollers are sometimes used in grinding mills.
In operation, tapered drive rotor 73 has frictional contact with tapered rollers 74, tapered rotor 73 turning more than twice as fast as cage 75 which holds tapered rollers 74. For the approximately 37 degree taper angles of the rollers shown in
Drive shaft 72 may be driven directly by a drive motor, such as a stepper motor or a DC motor, or indirectly, by a gear connected to a drive motor, by a drive belt connected to a drive motor, or by other means. Electronics and/or computer controllers may be connected to a drive motor to control the position and rotational speed of drive shaft 72. Sensors may be attached to drive shaft 72 and/or to cage 75 to monitor the angular position of drive shaft 72 and/or rollers 74. Various other electronics, sensor, and computers may be used in connection with the use of the pump head.
A retention collar, not shown, may be firmly attached to drive shaft 72 above base plate 71 and extending loosely beneath cage 75, so that it does not contact the cage nor the other pump structures when the pump head is fully assembled, but when the pump head is disassembled, the cage, rollers, rotor, and drive shaft can be lifted upward as a single assembly. Further, drive shaft 72 may include (not shown) means, such as a groove or collar, of snapping downward into a rotatable retention structure such as a spring-loaded retention structure beneath base plate 71 during pump head assembly, and of coming quickly out of the retention structure during pump head disassembly, thus enabling different flow channel plates to be swapped in and out of the pump head quickly and easily. A thrust bearing, not shown, may be connected to the retention structure.
The cross section view in
Cage 75 may be a unitary body into which the rollers can be snapped into place, or may be an assembly which can be assembled around the rotors.
An advantage of the pump head 70 design, as opposed to previous face-roller pump designs in the prior art, is that little or no force is exerted on the axle pins or axles by the tapered rollers. Instead, all of the vertical bearing force coming from drive shaft 72 is exerted by the tapered rotor 73 on the rollers 74, and by the rollers 74 on the underlying structures 77, 60, and 71. Thus, a much greater force can be safely applied by a thrust bearing to the drive shaft, enabling much better high pressure operation than was possible with prior art designs, where the allowable force magnitude on roller axles limits high pressure performance. Collar 76 and rotor lip 78 act to contain the tendency of the rollers to slide radially outward during pump operation.
In pump head 70, fluid flow in straight sections 69 of the peristaltic flow channel 601 passes between base plate 71 and collar 76. Advantageously, one or both of base plate 71 and collar 76 can feature shallow recessed areas such as shallow recessed areas 79 to avoid vertical pinching of the fluid flow channel in straight sections 69 between the base plate 71 and the collar 76. In
The pump head 70 is shown in
An advantage of using more than three rollers is that the volume of fluid trapped in the flow channel between adjacent rollers is reduced. When three rollers spaced 120 angular degrees apart are used, the minimum fluid aliquot which can be expelled from the pump is the volume trapped in a 120-degree segment of the flow channel flow channel. When five rollers are used, a 72-degree segment of the flow channel volume comprises the minimum aliquot. Thus using a flow channel with a small cross sectional area, and using as many rollers as feasible, enables the pump head 70 to more easily compete with the minimum aliquot available from syringe pumps presently used in wearable insulin pumps.
The pump head embodiments shown in
The pump head embodiments shown in
In other embodiments, a different rotor may have contact with rollers 74 along a radially limited zone of contact instead of the radially larger zone of contact present if a tapered drive rotor is used.
In operation of pump head 90, tension force on drive shaft 92 is transferred to rotor 93, and thence to O-ring 904, which bears vertically downward on the tapered rollers 74 along a radially-limited zone of contact 906. The zone of contact intersects each roller at a small contact patch, not shown, similar to the contact patch of a rolling automobile tire on pavement. As is the case with pump head 70, the rotor 93 turns roughly 2.3 revolutions for every revolution of the cage 75 for the value of angular taper shown.
In operation of pump head 100, tension force on drive shaft 102 is transferred to rotor 103, and thence to O-ring 1004, which bears vertically downward on the tapered rollers 74 along a radially-limited zone of contact 1006. As is the case with pump head 70, the rotor 103 turns roughly 2.3 revolutions for every revolution of the cage 75 for the value of angular taper shown.
In other embodiments, not shown, with non-tapered rotors, the radially-limited zone of contact can be broadened, relative to zones 906 or 1006, by using an elastomeric band encircling the rotor, the band surface being angled to follow the tapered surfaces of the rollers 74 and providing a flat contact area to rotors 74. For purposes of discussion and in the claims below, a rotor having an elastomeric band encircling the rotor is considered to include the elastomeric band.
For good pump performance it is important to have a non-skid interface between rotor 73 and rollers 74, or between O-ring 904, 1004 and rollers 74, or between an elastomeric band, not shown, and rollers 74. A non-skid interface between rollers 74 and plate 60, or between rollers 74 and shim plate 77, is desirable but less important, especially for three-day disposable applications. Non-skid interfaces may be achieved by various means which will occur to those skilled in pump design.
The rotor 93, 103 may comprise a stiff material having a high elastic modulus in order provide adequate downward force on the rollers 74 through O-ring 904, 1004. O-ring 904, 1004 may be made of a soft elastomer for low pressure applications. For high pressure applications, O-ring 904, 1004 may comprise a hard, stiff material with a tough nonskid outer coating. For example, the O-ring may comprise a core having the form of a stainless steel coil spring and a coating layer of polyimide.
Tapered rotor 73 shown in
The rotor 93 as shown in
The rotor 103 as shown inf
For good performance, force exerted on tapered rollers 74 by a rotor such as rotor 93 or 103, the rotor having a radially limited contact area on the sloping portions of tapered rollers 74 through O-ring 904 or 1004, should transmit force though the rollers to bear near the radial center of flow of the flow channel 601 in flow channel plate 60, to avoid having too little compression force at the radially inward edge of the flow channel 601 or too little compression force near the radially outward edge of the flow channel.
The rotors 73, 93, and 103 have performance advantages over prior-art rotor structures using flat disks or soft washers used to drive rolling elements in peristaltic pump heads.
A rotor comprising a flat disk is unsuitable for use with tapered rollers because a flat disk would have bearing force only at small regions on the radially outward top surfaces of the rollers, and not on the sloping portions of the rollers, thereby providing too little compressive force on the radially inward extents of the tapered roller walls. In addition, a flat disk bearing on the top outward surfaces of tapered rollers, rather than on the sloping portions of the tapered rollers, has no self-centering action.
Prior art has discussed the idea of using a soft washer to drive tapered rollers but has not described an embodiment which does so. A rotor comprising a soft washer is unsuitable for use with tapered rollers in embodiments like those of the present invention because a soft washer can't provide enough downward bearing force for high-pressure operation of peristaltic pumps, and because the radial position of bearing force provided by a soft washer, onto tapered rollers and thence onto a flow channel such as flow channel 601, is difficult to predict or control. If a flat, soft washer were larger in radial extent than the radial extent of tapered rollers 74 it would not provide a self-centering action.
In one embodiment of the present invention, a disposable flow channel plate, such as plate 60, can be combined with other components, such as a septum-puncturing receiver for an insulin cartridge and a flexible tube connected to a hypodermic needle, and integrated to form a kit comprising a single assembly. Using such a kit could reduce a patient's insulin filling process from the thirteen steps typically required for a syringe pump to four steps, would use only one disposable instead of four disposables, and require less dexterity, with less chance of septic contamination. The four steps required when using a kit of the present invention comprise inserting the kit into place in an opened pump head, closing the pump head by snapping an assembly of rotor, roller, cage, and axle into place in an underlying retention structure, attaching an insulin vial, and running the pump until all air bubbles exit the attached tubing of the kit.
A planar flow channel plate such as flow channel plate 60 can be combined in a manifold with other fluidic elements such as flow channels and valves.
Multiple parallel flow paths driven by one pump head may be included in a planar flow channel plate similar to plate 60.
Multiple planar peristaltic flow channels driven by multiple pump heads can be formed in a single planar manifold which may incorporate other fluid elements. Additional fluidic, electronic, or optical elements may be incorporated in such a planar manifold and may extend outward above or below the plane of the manifold.
A flow channel plate such as flow channel plate 60 of the preset invention need not be made from a single material. Composite or laminated combinations of more than one material may be used to form the flow channel plate without departing from the scope and spirit of the invention. As one example, the interior walls of a flow channel in plate 60 may comprise hard material while the exterior walls of the flow channel may comprise softer material, providing the advantage of low spalling of interior walls while providing the advantage of low closing force for the channel in low pressure applications. As another example, the strain relief means 66 may comprise soft elastomeric regions while the remainder of plate 60 may comprise a harder material.
The use of the Davis-Butterfield cross sectional channel shape is advantageous in the present invention, but is not a necessity of the invention. A channel having a round cross sectional shape or other cross sectional shape may be used, with the consequence that the stain relief means 66 must possibly accommodate a larger lateral expansion of the flow channel.
Embodiments described herein provide various benefits. In particular, embodiments provide for planar flow channel plate designs that include strain relief features that accommodate lateral expansion of the flow channel during vertical compression of the flow channel during operation with peristaltic pumps. This benefit is likely to be of great value when channels of the DB shape, providing advantages of low spallation, long service life, and high pressure pumping capability, are involved, but will be useful for other channel shapes too.
The formation of the flow channel plate in a generally planar shape can allow inexpensive manufacturing for use in medical disposable devices.
A planar flow channel plate can also be advantageous in allowing for rapid interchange of flow channels in a pump head for uses such as medical disposable use.
A three-roller pump head with tapered rollers has been designed to use the planar flow channels in a manner that provides low stress on the roller axle pins or axles for long service life of the pump head, either when used with disposable channels or when used with long-service-life flow channels. The load on the pump rollers can be adjusted using a spring-loaded thrust bearing attached to the pump's drive shaft to provide partial or full flow channel occlusion during use and to adjust the overpressure value at which desired leakage through the flow channel can occur.
The benefits discussed are likely to be of great value in medical applications, such as insulin pumps, and also in many other applications in manufacturing and in laboratories in general.
Although the description has been described with respect to particular embodiments thereof, these particular embodiments are merely illustrative, and not restrictive.
It will also be appreciated that one or more of the elements depicted in the drawings/figures can also be implemented in a more separated or integrated manner, or even removed or rendered as inoperable in certain cases, as is useful in accordance with a particular application.
Thus, while particular embodiments have been described herein, latitudes of modification, various changes, and substitutions are intended in the foregoing disclosures, and it will be appreciated that in some instances some features of particular embodiments will be employed without a corresponding use of other features without departing from the scope and spirit as set forth. Therefore, many modifications may be made to adapt a particular situation or material to the essential scope and spirit.
This application claims priority from U.S. Provisional Patent Application Ser. No. 62/505,900, entitled “Improved peristaltic pump technologies”, filed on May 13, 2017 which is hereby incorporated by reference as if set forth in full in this application for all purposes.
| Number | Date | Country | |
|---|---|---|---|
| 62505900 | May 2017 | US |
