BACKGROUND OF THE INVENTION

Field of the Invention

[001] The subject invention is directed to peristaltic pumps.

Description of the Prior Art

[002] 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.

[003] 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.

[004] 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.

SUMMARY OF THE INVENTION

[005] 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.

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

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

DESCRIPTION OF THE DRAWINGS

[008] Figure 1 shows a peristaltic pump formed in accordance with the subject invention.

[009] Figure 2 shows the peristaltic pump of Figure 1 with the shroud removed.

[010] Figure 3 shows the assembly of Figure 2 with the motor removed.

[Oil] Figure 4 shows the assembly of Figure 3 with the drive plate removed and with the optional cage being utilized.

[012] Figure 5 shows the assembly of Figure 3 with the drive plate removed and with no optional cage being utilized.

[013] Figure 6 shows a channel, with membrane, useable with the subject invention.

[014] Figure 7 shows the channel of Figure 6 without the membrane. [015] Figure 8 shows the channel and membrane of Figure 6 formed in a base plate, adjacent to a motor support, in accordance with the subject invention.

[016] Figure 9 is a top plan view of the channel and membrane of Figure 6.

[017] Figures 10-13 show the channel and membrane of Figure 6 with transitions.

[018] Figures 14 and 15 are partial cross-sectional views of a peristaltic pump in accordance with the subject invention.

[019] Figure 16 is a cross-sectional view of a channel and membrane arrangement useable with the subject invention.

[020] Figure 17 is a perspective cross-sectional view of a base plate with the channel and membrane arrangement of Figure 16.

[021] Figures 18-20 show schematically the functioning of a peristaltic pump formed in accordance with the subject invention.

DETAILED DESCRIPTION

[022] With reference to the Figures, a peristaltic pump is shown and designated with reference number 10. The peristaltic pump 10 generally includes a rotatable drive plate 12, a closed-loop channel 14, a flexible membrane 16, and at least one roller 18. The flexible membrane 16 fluidically connects a fluid inlet 20, located at a first location along the channel 14, with a fluid outlet 22, located at a second location along the channel 14 spaced from the first location, to define a closed fluid path 24 between the fluid inlet 20 and the fluid outlet 22. The at least one roller 18 is captively disposed between the channel 14 and the drive plate 12 such that rotation of the drive plate 12 causes the at least one roller 18 to traverse the channel 14, the at least one roller 18 causing downward deflection of the flexible membrane 16 in passing therealong to constrict the closed fluid path 24 in displacing fluid within the closed fluid path 24 from the fluid inlet 20 to the fluid outlet 22. [023] The drive plate 12 is annular with a central opening 13 in which is received drive shaft 26. As shown in Figure 14, the peristaltic pump 10 may include a motor 28 coupled to the drive shaft 26 to cause rotation of the drive plate 12 about an axis of rotation R. The motor 28 may be mounted atop a motor support 30, located adjacent to the drive plate 12, on base plate 32. In this manner, the motor 28 may be cantilevered to extend to the drive shaft 26. The drive shaft 26 may be coupled to the drive plate 12 in any known manner to transmit rotational force thereto, including having one or keys received in corresponding apertures in the drive plate 12 or vice versa or combinations thereof. With use of a keys/apertures arrangement, the motor 28 is easily assembled to, or removed from, the drive plate 12 with the drive shaft 26 being inserted or withdrawn from the central opening 13 of the drive plate 12.

[024] The motor support 30 may include a cradle 34 for receiving the motor 28. In addition, a shroud 36 may be provided for enshrouding the motor 28 atop the motor support 30. The shroud 36 may be provided with a plurality of retention apertures 38 formed to snap engage retention detents 40 located on the motor support 30. To provide additional securement, at least one barrier 42 may be provided on the base plate 32, including on an opposite side of the drive plate 12 from the motor support 30, having retention detent(s) 40 which may be snap engaged by retention aperture(s) 38 of the shroud 36.

[025] The drive plate 12, with the motor 28 removed, as shown in Figure 3, is exposed. The drive plate 12, as shown in Figures 14-15, has a first face 44 which faces the channel 14. Preferably, the channel 14 is a closed loop generally lying in a single plane P with the first face 44 being generally parallel thereto. At least one recess 45 is formed in the first face 44 in which the at least one roller 18 is seated. One recess 45 is provided for each roller 18. As shown in Figures 14-15, with the at least one roller 18 disposed in the channel 14, interengagement of the at least one roller 18 and the drive plate 12 causes the at least one roller 18 to traverse the channel 14 with rotation of the drive plate 12. With the roller 18 being seated in the recess 45, interference is created between the drive plate 12 and the roller 18 with rotation of the drive plate 12 resulting in movement of the roller 18.

[026] The channel 14 is formed below the drive plate 12 such that the drive plate 12 overlies the channel 14. The channel 14 is preferably circular in shape. The first face 44 of the drive plate 12 preferably has a sufficient diameter to overlap diametrically-opposed portions of the channel 14. This best ensures good contact between the at least one roller 18 and the drive plate 12 throughout traversal of the full length of the channel 14. With the channel 14 being circular, the at least one recess 45 may rotate about the axis of rotation R at a fixed radius aligned with the channel 14.

[027] In addition, the drive plate 12 is positioned to apply downward pressure on the at least one roller 18. Downward pressure is utilized to cause the at least one roller 18 to compress the flexible membrane 16 as the at least one roller 18 moves therealong. The compression of the flexible membrane 16 causes constriction of the closed fluid path 24 which 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 roller 18 with the flexible membrane 16 with the constriction moving along the flexible membrane 16 with movement of the at least one roller 18.

[028] The channel 14 may be formed in the base plate 32. As shown in Figure 7, the fluid inlet 20 and the fluid outlet 22 may extend through the base plate 32, being defined by the base plate 32 and/or being tubes extending through the base plate 32. The channel 14 includes two portions: a first portion 14A, extending from the fluid inlet 20 to the fluid outlet 22; and, a second portion 14B, extending from the fluid outlet 22 to the fluid inlet 20. The second portion 14B is separate from the first portion 14A. The first and second portions 14A, 14B may collectively cover the full length of the channel 14.

[029] The channel 14 includes sidewalls 46 shaped to support the at least one roller 18 in rolling or sliding motion therealong. For example, as shown in Figures 14-15, with the at least one roller 18 being ball shaped, the sidewalls 46 may be arcuate to match the radius of the at least one roller 18. The at least one roller 18 may be formed with other shapes, e.g., barrel shaped, conical shaped, or block shaped. The sidewalls 46 may be formed to match the profile of the at least one roller 18 accordingly to allow for rolling or sliding motion therealong.

[030] The flexible membrane 16 fluidically connects the fluid inlet 20 with the fluid outlet 22 to define the closed fluid path 24 between the fluid inlet 20 and the fluid outlet 22. The fluid inlet 20 and the fluid outlet 22 define openings in communication with the closed fluid path 24, covered by the flexible membrane 16, as shown in Figure 6. Liquid introduced through the fluid inlet 20 may be conveyed to the fluid outlet 22 through the closed fluid path 24 continuously covered by the flexible membrane 16 to be out of contact with the at least one roller 18. [031] The flexible membrane 16 may 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 membrane 16 be provided with sufficient resiliency and memory to be compressed, to constrict the closed fluid path 24, and to regain generally its original profile, to re-open the closed fluid path 24 after compression. An elastomeric material may be selected based on durometer to achieve the desired functioning. It has been found that a membrane with durometer of 70 Shore A may be used with the subject invention. Pump size, flow rate, and pressure requirements may also affect durometer selection.

[032] The flexible membrane 16 is secured to portions along the first portion 14A of the channel 14. The flexible membrane 16 may extend between the sidewalls 46 to define a bottom of the first potion 14A of the channel 14. With the channel 14 being formed in the base plate 32, the flexible membrane 16 may be secured to the base plate 32 along the first portion 14A of the channel 14. The flexible membrane 16 may define the closed fluid path 24 with adjacent portions of the base plate 32. The base plate 32 may be provided as a single plate or may be formed of multiple, joined layers. As shown in Figure 16, with multiple layers, top layer 32 A may be provided to lay atop, and be joined to, lower layer 32B. A lower channel 48 may be undercut in the top layer 32A, following the profile of the channel 14. The lower layer 32B may have a raised ridge 50 formed to extend into the lower channel 48, with trough 52 being formed along the ridge 52. The trough 52 may define the closed fluid path 24 with the flexible membrane 16. The flexible membrane 16 may be domed above the trough 52 to define the closed fluid path 24.

[033] The top layer 32A and the lower layer 32B may be separately manufactured. For assembly, the flexible membrane 16 may be disposed along the ridge 50 with the top layer 32A being mounted onto the lower layer 32B. With the ridge 50 being received in the lower channel 48, edge portions 54 of the flexible membrane 16 are captured between the top layer 32A and the lower layer 32B to fix the flexible membrane 16 relative to the channel 14. Retention ridges 56 may be provided on the top layer 32A formed to press into the edge portions 54 of the flexible membrane 16 in enhancing retention thereof. The top layer 32A and the lower 32B may be formed of polymeric material (e.g., thermoplastic) and joined using any known technique, such as adhesion, fusion, and so forth. [034] With the base plate 32 being a single plate, the trough 52 may be formed as a depression extending below the sidewalls 46 of the first portion 14A of the channel 14. The flexible membrane 16 may be secured to the sidewalls 46 (at lower edges thereof) using any technique, such as adhesion, fusion, and so forth.

[035] As shown in Figure 16, it is preferred that reliefs 58 be defined about the flexible membrane 16 to define voids between the flexible membrane 16 and the base plate 32 into which the flexible membrane 16 may flow into under compression. The reliefs 58 may be defined by shaping the profile of the flexible membrane 16, e.g., by having inwardly curved portions 58A along the sidewalls 46, and/or by avoiding full face-to-face contact between the edge portions 54 and the top layer 32A to define voids 58B.

[036] The second portion 14B of the channel 14 is formed outside of the closed fluid path 24. The channel 14 may have a solid base 60 extending between the sidewalls 46. The solid base 60 may be formed to match the shape of the corresponding at least one roller 18, extending continuously the profile of the sidewalls 46. The solid base 60 may be formed in the base plate 32. The second portion 14B acts as a return to allow the at least one roller 18 to return to the fluid inlet 20 from the fluid outlet 22 to continuously repeat the pumping action.

[037] An elevational difference may exist between the first and second portions 14A, 14B of the channel 14, particularly due to the thickness of the flexible membrane 16. It is preferred that transitions 62 be provided at the intersections of the first and second portions 14 A, 14B to act as ramps in allowing for gradual transition between the first and second portions 14A, 14B. For example, as shown in Figures 11-13, with the second portion 14B being lower than the first portion 14 A, the transitions 62 are ramp-shaped to gradually join the first and second portions 14A, 14B, with the transitions 62 having the same profile of the channel 14.

[038] The drive plate 12 may be assembled when ready to use to not apply pressure to the at least one roller 18 during storage. Prolonged compression in one or more distinct spots on the flexible membrane 16 may inadvertently cause permanent distortion. If the spring mount 64 and the spring 68 are utilized, these may be assembled when ready to use, as well.

[039] In addition, to compensate for any elevational differences between the first and second portions 14A, 14B, and/or to best generate consistent downward pressure on the at least one roller 18, the drive plate 12 may be provided with a spring mount 64 about the central opening 13, securable to the drive shaft 26, as shown in Figures 14-15. The drive plate 12 may be also formed with a spring channel 66 formed about the central opening 13. A spring 68 (e.g., a coil spring) is disposed in the spring channel 66 to pressingly engage the spring mount 64. It is preferred that the spring 68 be disposed in the spring channel 66 in compression to prestress the drive plate 12 downwardly towards the at least one roller 18. This arrangement allows for the drive plate 12 to pressingly engage the at least one roller 18 with changes in elevation between the first and second portions 14A, 14B of the channel 14, and ensures consistent application of pressure to the at least one roller 18 to best ensure proper compression of the flexible membrane 16. Downward extension of the base plate 12, resulting from biasing force of the spring 68, is limited with contact with the at least one roller 18.

[040] To provide additional stability, optionally, an annular cage 70 may be provided disposed between the drive plate 12 and the channel 14 about the central opening 13. The cage 70 includes a lower face 72 facing the channel 14 and an upper face 74 facing away from the channel 14. At least one seat 76 is formed in the lower face 72 for receiving the at least one roller 18. An opening 78 may be formed in the upper face 74 in alignment with the at least one seat 76 to allow a portion of the at least one roller 18 to protrude from the upper face 74 with the at least one roller 18 seated in the at least one seat 76. The portion of the at least one roller 18 protruding from the opening 78 may be received in the recess 45. The at least one roller 18 also protrudes from the lower face 72 to be received in the channel 14. A seat 76, and corresponding opening 78, are provided for each roller 18 and recess 45.

[041] The cage 70 is independently rotatable from the drive plate 12. More particularly, the drive plate 12, as discussed above, is coupled to the drive shaft 26 to rotate therewith. The cage 70 is not fixed to the drive plate 12, the channel 14, the at least one roller 18, or the drive shaft 26. This allows the cage 70 to rotate with the at least one roller 18 being driven. Moreover, the cage 70 may adjust with the at least one roller 18 in response to any elevational changes between the first and second portions 14A, 14B of the channel 14. The drive plate 12 causes the at least one roller 18 to move along the channel 14 without any effect from the cage 70. The at least one roller 18 is captive between the drive plate 12 and the channel 14, independent of the cage 70. [042] As will be appreciated by those skilled in the art, any quantity of the rollers 18 may be utilized. As shown in the Figures, the subject invention may utilize three of the rollers 18. It is preferred that with a plurality of rollers 18, the rollers 18 be evenly spaced about the channel 14, e.g., having recesses 45 be evenly spaced about the first face 44 of the drive plate 12. Even spacing provides more even pumping and more evenly distributed support for the drive plate 12 (thereby avoiding eccentric loading).

[043] Figures 18-20 show operation of the peristaltic pump 10 utilizing three rollers 18, designated as A, B, C. With the position shown in Figure 18, and taking into consideration clockwise rotation, roller A is entering the first portion 14A of the channel 14 to cross the inlet 20 in beginning a pumping cycle. As roller A enters the first portion 14A, a pumping cycle is initiated with roller A causing compression of the flexible membrane 16 to constrict the closed fluid path 24, as shown in dashed lines in Figure 16, and trap a volume of liquid between roller A and roller C. The rollers A, B, C each cause constriction of the closed fluid path 24 while moving along the flexible membrane 16 to convey liquid from the fluid inlet 20 to the fluid outlet 22. Roller C is mid-way along the first portion 14A conveying liquid trapped between rollers C and B towards the fluid outlet 22. Movement of the roller C from the fluid inlet 20, with constriction of the closed fluid path 24, causes suction to be generated at the fluid inlet 20 in drawing liquid into the closed fluid path 24 from the fluid inlet 20. 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 22, having caused liquid, which had been trapped between the rollers B and A, to discharge through the fluid outlet 22. Roller B is entering the second portion 14B of the channel 14 to return to the fluid inlet 20. In this position, roller B is blocking discharge of the liquid trapped between the rollers C and B.

[044] Figure 19 shows clockwise rotation of the rollers A, B, C from the position shown in Figure 18. Here, the roller A is now fully within the first portion 14A, continuously causing constriction of the closed fluid path 24, in conveying liquid trapped between the rollers B and A towards the fluid outlet 22. Roller A is also creating suction at the fluid inlet 20 to cause liquid to be drawn into the closed fluid path 24. Roller C continues to traverse the first portion 14A towards the outlet 22, also continuously causing constriction of the closed fluid path 24. In the position shown in Figure 19, with the passage of the roller B across the fluid outlet 22, the closed fluid path 24 between the roller C and the fluid outlet 22 is unobstructed thus allowing liquid to be discharged through the fluid outlet 22 under force of movement of the roller C. Discharge through the fluid outlet 22 is permitted with the passing of a leading roller into the second portion 14B. From the position shown in Figure 19, roller C will continue to urge liquid through the fluid outlet 22 as it further approaches the fluid outlet 22. Roller B is mid-way along the second portion 14B, returning to the fluid inlet 20.

[045] Figure 20 shows further clockwise rotation of the rollers A, B, C from the position shown in Figure 18. Here, roller A has assumed the position of roller C in Figure 18, roller B has assumed the position of roller A in Figure 18, and roller C had assumed the position of roller B in Figure 18. 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 22. 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 portion 14B in returning to the fluid inlet 20, while causing an obstruction of the fluid outlet 22 for the liquid trapped between the rollers A and C.

[046] As will be appreciated by those skilled in the art, various liquids may be conveyed by the peristaltic pump 10 including liquid drug, solutions, or bodily liquids. The peristaltic pump 10 is well-suited for small and micro volume applications.

[047] Variations of the peristaltic pump 10 are possible, where, for example, the flexible membrane 16 is provided in tube form. This allows for the flexible membrane 16 to be disposed along the channel 14 to define the closed fluid path 24.