Peristaltic Pump

The subject invention is directed to peristaltic pumps.

Peristaltic pumps are well known in the art. These are particularly useful in applications where contact with a pumped liquid is of concern. Peristaltic pumps apply moving pressure along the outside of a conduit, never contacting the liquid being conveyed. Peristalsis is achieved with volumes of liquid being sequentially conveyed. As a result, a pumping action is generated with suction being generated at the inlet, drawing in the liquid to be pumped.

Typical peristaltic pumps have a rotating rotor or disc with a plurality of circumferentially spaced-apart rollers. A liquid conduit is arranged to extend about the circumference of the rotating rotor or disc. With rotation of the rotor or disc, the rollers move along the conduit in pressing engagement with a “wiping” action, thereby positively displacing liquid trapped ahead of each of the rollers. The rollers convey liquid from an inlet of the pump to the outlet of the pump. The rollers come out of engagement with the conduit at the outlet and rotate from the outlet to the inlet to start a new pumping cycle.

Peristaltic pumps are used extensively in medical applications, e.g., where sterility of pumped liquids must be maintained. In addition, peristaltic pumps are useable with small volumes and are mechanically simplistic. Even with all these advantages, size constraints and ease-of-manufacturing may limit its usefulness.

A peristaltic pump is provided herein including: a rotatable drive plate; a closed-loop channel; a fluid inlet located at a first location along the channel; a fluid outlet located at a second location along the channel, spaced from the first location, wherein a first portion of the channel extends between the fluid inlet and the fluid outlet, and a second portion of the channel, separate from the first portion of the channel, extends between the fluid outlet and the fluid inlet; a flexible membrane extending between, and fluidically connecting, the fluid inlet and the fluid outlet, the flexible membrane defining a closed fluid path between the fluid inlet and the fluid outlet along the first portion of the channel; and, a first roller captively disposed between the channel and the drive plate such that rotation of the drive plate causes the first roller to traverse the channel, the first roller causing downward deflection of the flexible membrane in passing therealong to constrict the closed fluid path in displacing fluid within the closed fluid path from the fluid inlet to the fluid outlet. Advantageously, the subject invention provides a planar peristaltic pump having a drive plate overlaying the fluid path allowing for top-down assembly with parts assembled along a single vertical axis.

References to liquid and fluid are interchangeable herein, with the subject invention being intended to work in connection with an incompressible fluid or liquid.

These and other features of the subject invention will be better understood through a study of the following description and accompanying drawings.

With reference to the Figures, a peristaltic pump is shown and designated with reference number. The peristaltic pumpgenerally includes a rotatable drive plate, a closed-loop channel, a flexible membrane, and at least one roller. The flexible membranefluidically connects a fluid inlet, located at a first location along the channel, with a fluid outlet, located at a second location along the channelspaced from the first location, to define a closed fluid pathbetween the fluid inletand the fluid outlet. The at least one rolleris captively disposed between the channeland the drive platesuch that rotation of the drive platecauses the at least one rollerto traverse the channel, the at least one rollercausing downward deflection of the flexible membranein passing therealong to constrict the closed fluid pathin displacing fluid within the closed fluid pathfrom the fluid inletto the fluid outlet.

The drive plateis annular with a central openingin which is received drive shaft. As shown in, the peristaltic pumpmay include a motorcoupled to the drive shaftto cause rotation of the drive plateabout an axis of rotation R. The motormay be mounted atop a motor support, located adjacent to the drive plate, on base plate. In this manner, the motormay be cantilevered to extend to the drive shaft. The drive shaftmay be coupled to the drive platein any known manner to transmit rotational force thereto, including having one or keys received in corresponding apertures in the drive plateor vice versa or combinations thereof. With use of a keys/apertures arrangement, the motoris easily assembled to, or removed from, the drive platewith the drive shaftbeing inserted or withdrawn from the central openingof the drive plate.

The motor supportmay include a cradlefor receiving the motor. In addition, a shroudmay be provided for enshrouding the motoratop the motor support. The shroudmay be provided with a plurality of retention aperturesformed to snap engage retention detentslocated on the motor support. To provide additional securement, at least one barriermay be provided on the base plate, including on an opposite side of the drive platefrom the motor support, having retention detent(s)which may be snap engaged by retention aperture(s)of the shroud.

The drive plate, with the motorremoved, as shown in, is exposed. The drive plate, as shown in, has a first facewhich faces the channel. Preferably, the channelis a closed loop generally lying in a single plane P with the first facebeing generally parallel thereto. At least one recessis formed in the first facein which the at least one rolleris seated. One recessis provided for each roller. As shown in, with the at least one rollerdisposed in the channel, interengagement of the at least one rollerand the drive platecauses the at least one rollerto traverse the channelwith rotation of the drive plate. With the rollerbeing seated in the recess, interference is created between the drive plateand the rollerwith rotation of the drive plateresulting in movement of the roller.

The channelis formed below the drive platesuch that the drive plateoverlies the channel. The channelis preferably circular in shape. The first faceof the drive platepreferably has a sufficient diameter to overlap diametrically-opposed portions of the channel. This best ensures good contact between the at least one rollerand the drive platethroughout traversal of the full length of the channel. With the channelbeing circular, the at least one recessmay rotate about the axis of rotation R at a fixed radius aligned with the channel.

In addition, the drive plateis positioned to apply downward pressure on the at least one roller. Downward pressure is utilized to cause the at least one rollerto compress the flexible membraneas the at least one rollermoves therealong. The compression of the flexible membranecauses constriction of the closed fluid pathwhich is utilized to trap liquid in causing it to be positively displaced. The constriction is defined below the point of contact of the at least one rollerwith the flexible membranewith the constriction moving along the flexible membranewith movement of the at least one roller.

The channelmay be formed in the base plate. As shown in, the fluid inletand the fluid outletmay extend through the base plate, being defined by the base plateand/or being tubes extending through the base plate. The channelincludes two portions: a first portionA, extending from the fluid inletto the fluid outlet; and, a second portionB, extending from the fluid outletto the fluid inlet. The second portionB is separate from the first portionA. The first and second portionsA,B may collectively cover the full length of the channel.

The channelincludes sidewallsshaped to support the at least one rollerin rolling or sliding motion therealong. For example, as shown in, with the at least one rollerbeing ball shaped, the sidewallsmay be arcuate to match the radius of the at least one roller. The at least one rollermay be formed with other shapes, e.g., barrel shaped, conical shaped, or block shaped. The sidewallsmay be formed to match the profile of the at least one rolleraccordingly to allow for rolling or sliding motion therealong.

The flexible membranefluidically connects the fluid inletwith the fluid outletto define the closed fluid pathbetween the fluid inletand the fluid outlet. The fluid inletand the fluid outletdefine openings in communication with the closed fluid path, covered by the flexible membrane, as shown in. Liquid introduced through the fluid inletmay be conveyed to the fluid outletthrough the closed fluid pathcontinuously covered by the flexible membraneto be out of contact with the at least one roller.

The flexible membranemay be formed of elastomeric or polymeric material, such as silicone (e.g., room-temperature-vulcanizing (RTV) silicone) or polyurethane. It is preferred that the flexible membranebe provided with sufficient resiliency and memory to be compressed, to constrict the closed fluid path, and to regain generally its original profile, to re-open the closed fluid pathafter compression. An elastomeric material may be selected based on durometer to achieve the desired functioning. It has been found that a membrane with durometer ofShore A may be used with the subject invention. Pump size, flow rate, and pressure requirements may also affect durometer selection.

The flexible membraneis secured to portions along the first portionA of the channel. The flexible membranemay extend between the sidewallsto define a bottom of the first potionA of the channel. With the channelbeing formed in the base plate, the flexible membranemay be secured to the base platealong the first portionA of the channel. The flexible membranemay define the closed fluid pathwith adjacent portions of the base plate. The base platemay be provided as a single plate or may be formed of multiple, joined layers. As shown in, with multiple layers, top layerA may be provided to lay atop, and be joined to, lower layerB. A lower channelmay be undercut in the top layerA, following the profile of the channel. The lower layerB may have a raised ridgeformed to extend into the lower channel, with troughbeing formed along the ridge. The troughmay define the closed fluid pathwith the flexible membrane. The flexible membranemay be domed above the troughto define the closed fluid path.

The top layerA and the lower layerB may be separately manufactured. For assembly, the flexible membranemay be disposed along the ridgewith the top layerA being mounted onto the lower layerB. With the ridgebeing received in the lower channel, edge portionsof the flexible membraneare captured between the top layerA and the lower layerB to fix the flexible membranerelative to the channel. Retention ridgesmay be provided on the top layerA formed to press into the edge portionsof the flexible membranein enhancing retention thereof. The top layerA and the lowerB may be formed of polymeric material (e.g., thermoplastic) and joined using any known technique, such as adhesion, fusion, and so forth.

With the base platebeing a single plate, the troughmay be formed as a depression extending below the sidewallsof the first portionA of the channel. The flexible membranemay be secured to the sidewalls(at lower edges thereof) using any technique, such as adhesion, fusion, and so forth.

As shown in, it is preferred that reliefsbe defined about the flexible membraneto define voids between the flexible membraneand the base plateinto which the flexible membranemay flow into under compression. The reliefsmay be defined by shaping the profile of the flexible membrane, e.g., by having inwardly curved portionsA along the sidewalls, and/or by avoiding full face-to-face contact between the edge portionsand the top layerA to define voidsB.

The second portionB of the channelis formed outside of the closed fluid path. The channelmay have a solid baseextending between the sidewalls. The solid basemay be formed to match the shape of the corresponding at least one roller, extending continuously the profile of the sidewalls. The solid basemay be formed in the base plate. The second portionB acts as a return to allow the at least one rollerto return to the fluid inletfrom the fluid outletto continuously repeat the pumping action.

An elevational difference may exist between the first and second portionsA,B of the channel, particularly due to the thickness of the flexible membrane. It is preferred that transitionsbe provided at the intersections of the first and second portionsA,B to act as ramps in allowing for gradual transition between the first and second portionsA,B. For example, as shown in, with the second portionB being lower than the first portionA, the transitionsare ramp-shaped to gradually join the first and second portionsA,B, with the transitionshaving the same profile of the channel.

The drive platemay be assembled when ready to use to not apply pressure to the at least one rollerduring storage. Prolonged compression in one or more distinct spots on the flexible membranemay inadvertently cause permanent distortion. If the spring mountand the springare utilized, these may be assembled when ready to use, as well.

In addition, to compensate for any elevational differences between the first and second portionsA,B, and/or to best generate consistent downward pressure on the at least one roller, the drive platemay be provided with a spring mountabout the central opening, securable to the drive shaft, as shown in. The drive platemay be also formed with a spring channelformed about the central opening. A spring(e.g., a coil spring) is disposed in the spring channelto pressingly engage the spring mount. It is preferred that the springbe disposed in the spring channelin compression to prestress the drive platedownwardly towards the at least one roller. This arrangement allows for the drive plateto pressingly engage the at least one rollerwith changes in elevation between the first and second portionsA,B of the channel, and ensures consistent application of pressure to the at least one rollerto best ensure proper compression of the flexible membrane. Downward extension of the base plate, resulting from biasing force of the spring, is limited with contact with the at least one roller.

To provide additional stability, optionally, an annular cagemay be provided disposed between the drive plateand the channelabout the central opening. The cageincludes a lower facefacing the channeland an upper facefacing away from the channel. At least one seatis formed in the lower facefor receiving the at least one roller. An openingmay be formed in the upper facein alignment with the at least one seatto allow a portion of the at least one rollerto protrude from the upper facewith the at least one rollerseated in the at least one seat. The portion of the at least one rollerprotruding from the openingmay be received in the recess. The at least one rolleralso protrudes from the lower faceto be received in the channel. A seat, and corresponding opening, are provided for each rollerand recess.

The cageis independently rotatable from the drive plate. More particularly, the drive plate, as discussed above, is coupled to the drive shaftto rotate therewith. The cageis not fixed to the drive plate, the channel, the at least one roller, or the drive shaft. This allows the cageto rotate with the at least one rollerbeing driven. Moreover, the cagemay adjust with the at least one rollerin response to any elevational changes between the first and second portionsA,B of the channel. The drive platecauses the at least one rollerto move along the channelwithout any effect from the cage. The at least one rolleris captive between the drive plateand the channel, independent of the cage.

As will be appreciated by those skilled in the art, any quantity of the rollersmay be utilized. As shown in the Figures, the subject invention may utilize three of the rollers. It is preferred that with a plurality of rollers, the rollersbe evenly spaced about the channel, e.g., having recessesbe evenly spaced about the first faceof the drive plate. Even spacing provides more even pumping and more evenly distributed support for the drive plate(thereby avoiding eccentric loading).

show operation of the peristaltic pumputilizing three rollers, designated as A, B, C. With the position shown in, and taking into consideration clockwise rotation, roller A is entering the first portionA of the channelto cross the inletin beginning a pumping cycle. As roller A enters the first portionA, a pumping cycle is initiated with roller A causing compression of the flexible membraneto constrict the closed fluid path, as shown in dashed lines in, and trap a volume of liquid between roller A and roller C. The rollers A, B, C each cause constriction of the closed fluid pathwhile moving along the flexible membraneto convey liquid from the fluid inletto the fluid outlet. Roller C is mid-way along the first portionA conveying liquid trapped between rollers C and B towards the fluid outlet. Movement of the roller C from the fluid inlet, with constriction of the closed fluid path, causes suction to be generated at the fluid inletin drawing liquid into the closed fluid pathfrom the fluid inlet. The liquid being drawn in by movement of roller C will be trapped between the rollers A and C with further clockwise rotation. Roller B is shown traversing the fluid outlet, having caused liquid, which had been trapped between the rollers B and A, to discharge through the fluid outlet. Roller B is entering the second portionB of the channelto return to the fluid inlet. In this position, roller B is blocking discharge of the liquid trapped between the rollers C and B.

shows clockwise rotation of the rollers A, B, C from the position shown in. Here, the roller A is now fully within the first portionA, continuously causing constriction of the closed fluid path, in conveying liquid trapped between the rollers B and A towards the fluid outlet. Roller A is also creating suction at the fluid inletto cause liquid to be drawn into the closed fluid path. Roller C continues to traverse the first portionA towards the outlet, also continuously causing constriction of the closed fluid path. In the position shown in, with the passage of the roller B across the fluid outlet, the closed fluid pathbetween the roller C and the fluid outletis unobstructed thus allowing liquid to be discharged through the fluid outletunder force of movement of the roller C. Discharge through the fluid outletis permitted with the passing of a leading roller into the second portionB. From the position shown in, roller C will continue to urge liquid through the fluid outletas it further approaches the fluid outlet. Roller B is mid-way along the second portionB, returning to the fluid inlet.

shows further clockwise rotation of the rollers A, B, C from the position shown in. Here, roller A has assumed the position of roller C in, roller B has assumed the position of roller A in, and roller C had assumed the position of roller B in. Roller B is beginning a new pumping cycle with constriction of the closed fluid path in trapping liquid between the rollers B and A. Roller A continues to convey liquid trapped between rollers A and C toward fluid outlet. Roller C is completing its pumping cycle having caused the full amount of trapped liquid to be discharged through the fluid outlet. Roller C is entering the second portionB in returning to the fluid inlet, while causing an obstruction of the fluid outletfor the liquid trapped between the rollers A and C.

As will be appreciated by those skilled in the art, various liquids may be conveyed by the peristaltic pumpincluding liquid drug, solutions, or bodily liquids. The peristaltic pumpis well-suited for small and micro volume applications.

Variations of the peristaltic pumpare possible, where, for example, the flexible membraneis provided in tube form. This allows for the flexible membraneto be disposed along the channelto define the closed fluid path.