EP0399118A1 - Pumping mechanism - Google Patents

Pumping mechanism Download PDF

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Publication number
EP0399118A1
EP0399118A1 EP89307675A EP89307675A EP0399118A1 EP 0399118 A1 EP0399118 A1 EP 0399118A1 EP 89307675 A EP89307675 A EP 89307675A EP 89307675 A EP89307675 A EP 89307675A EP 0399118 A1 EP0399118 A1 EP 0399118A1
Authority
EP
European Patent Office
Prior art keywords
fingers
tube
cam lobes
pumping mechanism
round shaft
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP89307675A
Other languages
German (de)
French (fr)
Inventor
Charles R. Botts
David E. Kaplan
David Burkett
Laurence Warden
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Imed Corp
Original Assignee
Imed Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to US35565989A priority Critical
Application filed by Imed Corp filed Critical Imed Corp
Publication of EP0399118A1 publication Critical patent/EP0399118A1/en
Priority to US355659 priority
Application status is Withdrawn legal-status Critical

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Classifications

    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04BPOSITIVE DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B43/00Machines, pumps, or pumping installations having flexible working members
    • F04B43/08Machines, pumps, or pumping installations having flexible working members having tubular flexible members
    • F04B43/082Machines, pumps, or pumping installations having flexible working members having tubular flexible members the tubular flexible member being pressed against a wall by a number of elements, each having an alternating movement in a direction perpendicular to the axes of the tubular member and each having its own driving mechanism

Abstract

A snap-together peristaltic pumping mechanism (18) comprises a pump housing and a support (70) for creating a holding cavity for a peristaltic drive mechanism. Specifically, the peristaltic drive mechanism comprises a plurality of fingers (60) which sequentially urge against a resilient tube (16) to create a moving zone of occlusion therealong. The plurality of fingers (60) are reciprocally moved by a plurality of rotating cam lobes (41) which are assembled onto and coaxially held along a stationary round shaft. The cam lobes (41) are interconnected to controllably cause their respective fingers (60) to engage with and disengage from the resilient tube (16).

Description

  • This invention relates generally to pumping mechanisms. More specifically, the present invention relates to linear peristaltic pumping mechanisms, and, in particular, to a linear peristaltic pump which can be assembled by snapping together its various components. This invention is particularly, but not exclusively, suited for assembling a linear peristaltic mechanism used for the infusion of medical solutions to a patient.
  • Peristaltic pumps have been used in the medical industry for many years to infuse intravenous (I.V.) fluids into patients. The general principles of the operation for peristaltic pumps are common to both rotary and linear peristaltic pumps. In each case, the objective is to create a moving zone of occlusion along a resilient tube for the purpose of pumping fluid through the tube. The many diverse ways in which this objective is accomplished is manifested in the wide variety of types of peristaltic pumps. Typically, peristaltic pumps include a pumping mechanism which is an assembly of many different components made from many different materials. As expected, the complexity of the interaction of these components increases with the sophistication of the pumps. Accordingly, this causes a corresponding increase in the difficulty of assembling the pump. In part, this difficulty is caused by the need for precise interaction of the pump's components. Additionally, the difficulty stems from the need to assemble a large number of parts. The main problem, however, at least insofar as manufacture and assembly is concerned, turns on how best to attach or connect the pump's individual components with acceptable precision.
  • Various techniques have been employed throughout the medical device industry for the assembly of peristaltic pumps. As is well known by those skilled in the pertinent art, such techniques include welding, bonding, gluing, and bolting to name but a few. In such cases, the particular technique used will depend to some extent on the required tolerances, materials used and ridigity consideration at the connections.
  • Recently, a snap-together linear peristaltic pump has been disclosed in U.S. Patent No. 4,755,109. In the above U.S. patent, there is a recognition that the beneficial attributes of reliability, durability and accuracy can still be accomplished by using a snap-together method of assembly for the operative components of the pump.
  • With respect to the operation of linear peristaltic pumps, to generate a moving zone of occlusion along the tube, the tube is placed between a platen and a series of occlusion members, such as fingers. The series of finger are sequentially pressed against the resilient tube to provide a wavelike occlusion action for smoothly urging fluid through the tube. A problem with linear peristaltic pumps exists when the occlusion members pressing on the tube cause a short term deformation of the tube, and periodically allow pressure to be built up within the tube. This results in a pulsatile flow of fluid through the tube, rather than linear flow as desired.
  • Some of the problems associated with a pulsatile flow of fluid can be alleviated by increasing the number of fingers making sequential contact with the tube. It has been found that the flow of fluid through a linear peristaltic pump becomes increasingly linear in nature when the number of fingers exceeds eight. For practical purposes, it has been found that the number of fingers should range between eleven and fourteen to obtain the optimal linear effect.
  • Even with an optimal number of fingers, however, there is still some unwanted pulsatile flow which may occur. The first through the last of a series of fingers sequentially occlude the tube in wavelike fashion to cause fluid to flow through the tube. To establish a continuous wave cycle for continuous flow of fluid, it is necessary that the first of a series of fingers begins a new cycle of occlusion at the same time the last finger in the series terminates the previous cycle of occlusion. Unfortunately, this may cause the first finger and last finger to occlude the tube at the same time. At that point in time, fluid is trapped between the two points of occlusion which creates a tapped mass of fluid, or bolus, within the tube. Also, at that time, other fingers are in the process of urging against the tube to create their respective points of sequential occlusion. Accordingly, the pressing engagement of these other sequentially urging fingers against the tube causes the pressure of the fluid trapped between the two points of occlusion of increase disproportionately with respect to the down-stream fluid pressure. When the last finger is then lifted off the tube as a new cycle of wavelike occlusion is started along the tube, the pressurized fluid within the bolus is suddenly released, and the surge of fluid thus results in a nonlinear or pulsatile flow of fluid to the patient. The present invention therefore recognizes the further need for a mechanism to reduce such surging of fluid to a patient.
  • The present invention further recognizes that while unwanted increases in pressure can result from two simultaneous points of occlusion on the tube, other external problems can cause the resilient tube to become pressurized. Therefore, it would be further beneficial to monitor the pressure inside the tube to detect any excessive pressure therein.
  • Moreover, when a linear peristaltic pump is turned off, it is important that there be at least one point of occlusion which remains on the resilient tube. This one point of occlusion is necessary to ensure that there is no flow of fluid to or from the patient when the pump is not in operation. It has been found there is a point of occlusion along the tube which results in the least amount of unwanted pressure build up within the resilient tube.
  • It is an object of this invention to provide an improved pumping mechanism.
  • According to one aspect of this invention there is provide a pumping mechanism for pumping fluid through a resilient tube to a patient by rotating interconnected cam lobes to establish sequential urging of a plurality of fingers against the tube, said pumping mechanism comprising:
    a support;
    a round shaft fixedly mounted on said support for receiving said interconnected cam lobes so that said inter­connected cam lobes can be coaxially aligned with said fixed round shaft for rotation about said fixed round shaft; and
    means for selectively reciprocating said fingers against said tube by rotation of said interconnected cam lobes about said fixed round shaft.
  • According to another aspect of this invention there is provided a pumping mechanism for pumping fluid through a resilient tube, said pumping mechanism comprising:
    a support;
    a plurality of fingers;
    a round shaft fixedly mounted on said support;
    a plurality of interconnected cam lobes coaxially aligned for rotation on said fixed round shaft, each of said cam lobes being operatively engaged with one of said fingers;
    a finger guide for restraining said respective fingers to reciprocal linear movement along substantially parallel paths;
    means for biasing said fingers against said tube; and
    a motor for rotating said cam lobes to sequentially reciprocate said fingers against said tube to create a moving zone of occlusion along said tube.
  • According to another aspect of this invention there is provided a method for assembling a peristaltic pump which moves fluid through a tube comprising the steps of:
    • (A) connecting a plurality of cam lobes together about a fixed round shaft;
    • (B) engaging a plurality of fingers having follower rings onto said cam lobes;
    • (C) positioning said fingers onto a finger guide having slots therein for allowing reciprocal movement of said fingers;
    • (D) connecting bearing blocks having pivots to each end of said fixed round shaft carrying said cam lobes;
    • (E) pivotally connecting said bearing blocks to a support having a casing for receiving said plurality of fingers positioned on said finger guide;
    • (F) connecting biasing elements to said bearing blocks and said support for urging said plurality of fingers against said tube; and
    • (G) coupling a motor to one end of said plurality of said connected cam lobes for causing rotation of said plurality of cam lobes to reciprocate said fingers and sequentially occlude said tube in wavelike fashion to move fluid through said tube.
  • A preferred embodiment of the snap-together linear peristaltic pump includes a housing and a support which couple together to create a cavity for holding a peristaltic drive mechanism. The peristaltic drive mechanism may comprise a plurality of fingers which sequentially urge against a resilient tube in wavelike fashion to create a moving zone of occlusion along the tube to pump I.V. fluid from an I.V. source to a patient. Specifically, the plurality of fingers may be reciprocally moved by cam lobes which are coaxially aligned on a round shaft. The cam lobes may have key segments so that when they are assembled together along the round shaft, the cam lobes are arranged in a helical manner for operative engagement with the plurality of fingers. In its operation, the interconnected cam lobes may be rotated by an external motor about the round shaft which is fixedly held at both ends. A special key segment may be provided on two preselected cam lobes which may be shaped to reduce pulsatile flow to ensure the preselected cam lobes are properly coupled together at the proper position on the round shaft.
  • A pressure transducer may be operatively connected to the resilient tube for detecting unusually high pressures inside the tube. Additionally, the motor may be connected to a programmable controller for varying the speed of infusion of I.V. fluid to a patient. Further, an encoder wheel may be carried on the round shaft with the cam lobes to detect the position of the fingers by an associated light sensing mechanism. The encoded wheel and its associated light sensing mechanism may be provided to ensure that a specified finger occludes the tube at a predetermined point when the pump is stopped in order to prevent any undesired flow of fluid to or from a patient.
  • It is an advantage of the present invention that it provides a linear peristaltic pump whose components can generally be assembled in a snap-together manner. Additionally, an advantage of the present invention is that it provides a linear peristaltic pump which reduces the surging of liquid caused when there are two simultaneous points of occlusion on a resilient tube. Still further, an advantage of the present invention is that it provides a pressure transducer to detect pressure inside the resilient tube. Another advantage of the present invention is that it provides a linear peristaltic pump which occludes the tube at a predetermined point when the pump is turned off for stopping the flow of fluid to or from a patient. Yet another advantage of the present invention is that it provides a linear peristaltic pump which is cost effective, reliable, and accurate. Finally, an advantage of the present invention is that it provides a linear peristaltic pump which is durable and easily serviced and maintained.
  • Reference is now made to the accompanying drawings in which:-
    • Figure 1 shows the linear peristaltic pump in its intended environment for infusing solutions from a fluid source through a tube to a patient;
    • Figure 2 is an exploded perspective view of the linear peristaltic pump showing the components of the present invention;
    • Figure 3 is a perspective view of a finger guide for aligning the plurality of fingers; and
    • Figure 4 is a perspective view of a finger used to urge against the tube to create a moving zone of occlusion along the tube.
  • Referring initially to Figure 1, a linear peristaltic pump generally designated 10 is shown in its intended environment. the pump 10 is mounted on I.V. pole 12 in a manner well known in the art. An I.V. fluid source 14 is suspended from the I.V. pole 12, and an I.V. tube 16 is connected in fluid communication with fluid source 14 for operative connection with pump 10 in a manner as generally illustrated in Figure 1. Downstream from its point of operative connection with pump 10, I.V. tube 16 is coupled with patient 20 for the infusion of medical solutions to the patient 20.
  • Figure 2 is a perspective exploded view of the pumping mechanism, generally designated 18, which is shown here in isolation from pump 10 for purposes of clarity. It should be understood that the order in which components of pumping mechanism 18 are assembled may vary. In the preferred embodiment, however, a motor 22 is initially assembled with its corresponding harness 26. The motor 22 is preferably a variable speed motor, such as a stepper motor. Harness 26 comprises a plurality of wires which are electrically engaged to a connector 28. Connector 28 is subsequently electrically coupled to a programmable controller (not shown) which controls the rate of motor 22. Motor 22 is equipped with a cylindrical-­shaped motor shaft 24.
  • Motor shaft 24 is engageable with a motor coupling 30 which is used to rotate the internal moving parts of the pumping mechanism 18. Motor coupling 30 comprises a plurality of teeth 31 which can be secured to a drive shaft coupling 32. Motor coupling 30 is preferably made of an elastic material, such as silicone. The drive shaft coupling 32 has a tube 33 extending therefrom for engagement with corresponding rotating members of pumping mechanism 18 as will be further discussed below. Attached to the circumference of tube 33 is a washer 34 which forms a slot 36 between the washer 34 and the drive shaft coupling 32. Slot 36 is used to hold the moving parts of pumping mechanism 18 in place, as will be further discussed below.
  • Still referring to Figure 2, there is provided a round shaft 40 engageable with a plurality of cam lobes generally designated 41. Each cam lobe 41 has a cam lobe surface and an interior receiving hole 43 for receiving round shaft 40. In the preferred embodiment, cam lobes 41 are integrally formed together in pairs, as dual cam lobes 42 for enabling easier assembly of the pump 10. Dual cam lobes 42 are snappingly engageable with each other having key segments such that upon complete engagement along the round shaft 40, the interconnected dual cam lobes 42 are helically oriented along a common longitudinal axis, coaxial with the axis of the longitudinal axis of the round shaft 40.
  • Depending on the number of fingers utilized, a set of corresponding number of dual cam lobes 42 can be connected together on a round shaft 40. In the preferred embodiment illustrated herein, there are twelve fingers 60, and thus twelve corresponding cam lobes 41. There are four dual cam lobes 42 (i.e., eight cam lobe surfaces) associated with the first finger 60a through the eighth finger 60b. Cam lobe 44 is integrally formed with a spacer 45, and is associated with the ninth finger 60c. Cam lobe 46 is integrally formed with a spacer 47, and is associated with tenth finger 60d. Cam lobe 48 is a special dual cam lobe associated with the penultimate and ultimate (eleventh and twelfth) fingers 60e, 60f, respectively. To provide proper interconnection between special dual cam lobe 48 and cam lobe 46, a special key segment 52 is provided to ensure that during assembly, while the dual cam lobes 42 are allowed to interconnect with each other as well as with cam lobe 44, dual cam lobes 42 are not allowed to interconnect with special dual cam lobe 48. Specifically, key 52 permits only special dual cam lobe 48 to be connected to cam lobe 46.
  • When assembling the dual cam lobes 42 and cam lobe 44 onto round shaft 40, an encoder wheel 50 is held between the spacer 45 and spacer 47. Encoder wheel 50 has a short hole 54 and a long hole 56. The purpose of encoder wheel 50 is to indicate the rotational position of the shaft to a programmable controller as more fully discussed below.
  • The plurality of fingers 60 are operatively coupled to the appropriate cam lobe 41. Referring to Figure 3, the interconnection between fingers 60 and a finger guide 62 can be readily appreciated. Finger guide 62 has a plurality of ribs 64 formed thereon to create a plurality of slots 66. Finger guide 62 also has a notch 71 formed thereon which provides clearance for the encoder wheel 50 and a pressure sensing mechanism as will be subsequently discussed. As can be appreciated, when fingers 60 are assembled onto finger guide 62, the fingers 60 are restrained within slots 66 for reciprocal linear movement along substantially parallel paths with respect to each other. Still referring to Figure 2 and Figure 3, shoes 68a and 68b are formed onto finger guide 62 for attachment to sleeves 69a and 69b which are formed within support 70.
  • It can be seen with reference to Figure 4 that a finger 60 comprises an aperture 58 for operative engagement with its corresponding cam lobe 41. Additionally, an opening 124 is provided in each finger 60 for receiving the finger guide 62. Further, finger 60 includes an upper guide 126 and a lower guide 128 for sliding engagement with ribs 64 and slots 66 of finger guide 62. Finger 60 also has an edge 130 formed on the outer surface of the finger 60 to enable sliding engagement with the walls of cavity 94 of support 70. Additionally, for ensuring there is proper engagement between each finger 60 and tube 16, a blade 132 is formed onto finger 60 such that tube 16 is occluded upon complete engagement of finger 60 with the tube, which is typically held in place against a platen (not shown).
  • Referring further to Figure 2, there is a support 70 having a flexible membrane bottom (not shown). A bottle side bearing block 72 fixedly holds one end of round shaft 40, and on the patient side of support 70, a patient side bearing block 74 fixedly holds the other end of round shaft 40 so that the shaft does not rotate about its longitudinal axis. As can be appreciated, inter-connected cam lobes 41 are rotatably engaged to a bearing 76a and a bearing 76b which are contained within bearing blocks 72 and 74, respectively. Bottle side bearing block 72 and patient side bearing block 74 each have a pivot slot 82a and 82b, respectively, formed thereon for pivotally connecting the bearing blocks 72 and 74 at pivot tower 80a and pivot tower 80b.
  • A spring interconnection between bearing blocks 72, 74 and support 70, is provided by bias elements such as springs 84a and 84b attached to bearing block hooks 86a and 86b at one end of each spring; and to support hooks 88a and 88b at the other end of each spring. In operation, the engaged springs 84a and 84b provide a mechanism for biasing the plurality of fingers against the flexible membrane bottom of support 70, and thus against the tube. Top housing 90 is threadably connected to bearing blocks 72 and 74 by a plurality of screws 92. With top housing 90 connected to bearing blocks 72 and 74, a closed cavity is formed inside top housing 90 and support 70. When top housing 90 and support 70 form closed cavity 94, the plurality of cam lobes 41, round shaft 40, finger guide 62 and the plurality of fingers 60 are held therein to comprise the pumping mechanism 18.
  • Motor 22 is connected to a mounting block 96 having a double adhesive backed resilient foam pad (not shown) to reduce noise transmission. Mounting block 96 also has a plurality of holes 98 formed therein for attachment to housing plate 100. Motor 22, motor coupling 30 and drive shaft coupling 32 are connected to the plurality of interconnected cam lobes 41 when mounting block 96 is attached to plate 100. Top housing 90 has a housing plug 112 formed therein for snapping engagement with an optical switch 102. Optical switch 102 comprises a light emitter 104 and a light sensor 106. As can be understood by the skilled artisan, when encoder wheel 50 rotates about the longitudinal axis of fixed round shaft 40 at a specific speed, short hole 54 and long hole 56 cause light sensor 106 to receive light from light emitter 104 in a predetermined cyclic manner. Rotation of encoder wheel 50 by optical switch 102 causes an electrical signal to be sent through cable 108 to a connection 112 which sends a message to a progammable controller (not shown). When electrical signals are received by the programmable controller, the rotational position of round shaft 40 and its corresponding cam lobes 41 can be determined.
  • In order to monitor the internal pressure of tube 16, a pressure transducer 114 is connected to tube 16. The electrical signal of pressure transducer 114 is sent through a harness 116 to a connection 118 and sent to a programmable controller (not shown). As in the optical switch 102, pressure transducer 114 supplies the necessary electrical signal to the programmable controller (not shown) which provides information to the operator.
  • A feature has been provided for pumping mechanism 18 to ensure that the position of the plurality of cam lobes 41 is maintained along the longitudinal axis of round shaft 40. This feature includes a groove 122 formed within bearing block 74 for the engagement of an index key 120. It can be appreciated that upon engagement of index key 120 with groove 122, the index key 120 is placed inside slot 36 of drive shaft coupling 32. Washer 34 and drive shaft coupling 32 rotate about both sides of the index key 120 to ensure that the interconnected cam lobs 41 are fixedly held about the longitudinal axis of the round shaft 40.
  • The operation of the round shaft linear peristaltic pump 10 should be understood after further disclosure below.
  • In the operation of the linear peristaltic pump 10, round shaft 40 is fixedly held between bearing blocks 72 and 74. The interconnected cam lobes 41 are coaxially aligned with respect to round shaft 40 for rotational engagement about round shaft 40. As can be appreciated, upon rotation of the interconnected cam lobes 41, fingers 60 reciprocally move within the closed cavity 94 so that the fingers 60 are urged against the tube 16 sequentially in wavelike fashion, to create a moving zone of occlusion along tube 16.
  • During the operation of peristaltic pump 10, during rotation of the interconnected cam lobes 41 which move the plurality of fingers 60 through each cycle, there is a point in time where two fingers are simultaneously at the occlusion position on tube 16. Typically, these are the first finger 60a and last finger 60f. Simultaneous occlusion at these two points creates a trapped pocket full of I.V. fluid 14 within tube 16. The pressure in the pocket increases further still as a result of other fingers 60 also in the process of being urged against tube 16. Ordinarily, if no pressure reduction mechanism is provided to alleviate the pressure, when the finger 60f is subsequently lifted off tube 16, the release of the pressure built up inside tube 16 will cause a surge of fluid to flow to patient 20. The pumping mechanism 18 reduces the pressure build up in the pocket by increasing the rate of lift off of the last and next to last fingers of the series, i.e. fingers 60f and 60e. It has been found, that if the next to last, or eleventh, finger 60e is lifted off tube 16 at a rate faster than the downward reciprocal movement of subsequent occluding fingers 60, then less pressure is allowed to be built up inside the pocket. Further, when the last, or twelfth, finger 60f is lifted off tube 16 at a rate faster than the other fingers 60, a build up of overall pressure inside the pocket is prevented. The rate of lift off of the eleventh and twelfth fingers 60e and 60f from tube 16 can be increased by selectively forming the shape of cam lobe surfaces 41 of corresponding special dual cam lobe 48.
  • To further aid in linearizing the flow of fluid to patient 20, the duration of occlusion caused by the last, or twelfth, finger 60f may be reduced further by shortening the dwell time of twelfth finger 60f. The corresponding cam lobe surface of special dual cam lobe 48 is selectively formed so that there is a shortened dwell time and thus shortened occlusion time of the twelfth finger 60f is achieved.
  • Further in operation, linear peristaltic pump 10 includes a mechanism for selectively determining the location of the interconnected cam lobes 41 about the round shaft 40. Specifically, the sensing mechanism includes the optical switch 102 having light emitter 104 and light sensor 106. Optical switch 102 is inserted into top housing 90 at the housing plug 112. When the optical switch 102 is engaged, clearance inside pump 10 is provided by the notch 71 on finger guide 62. In operation, interconnected encoder wheel 50 rotates about the longitudinal axis of round shaft 40. When light emitter 104 is electrically activated,light sensor 106 intermittently detects the light from emitter 104 which passes through either short hole 52 or long hole 54. An electrical signal representative of the position of the encoder wheel with respect to said holes 52, 54 is sent from light sensor 106 through cable 108 to connection 110 and subsequently to a programmable controller (not shown). As can be appreciated, by knowing the location and size of holes 52 and 54 formed in encoder wheel 50, the location of each interconnected cam lobe 41 and its associated finger 60 can be readily determined.
  • The speed of rotation of motor shaft 24 of motor 22 can further be regulated by a programmable controller (not shown). When the operator desires to increase or decrease the rate of rotation of the interconnected cam lobes 41, the programmable controller (not shown) may be programmed to vary the rate of stepper motor 22. In addition, pressure transducer 114 detects the internal pressure of tube 16 and accordingly sends pressure information through harness 116 to connection 118 which is electrically connected to a programmable controller (not shown). By knowing the pressure of tube 16, the programmable controller (not shown) can safely operate the pump 10 and ensure that the pressure within tube 16 does not become excessive.
  • While the particular linear peristaltic pump as herein shown and disclosed in detail is fully capable of obtaining the objects and providing the advantages hereinbefore stated, it is to be understood that it is merely illustrative of the presently preferred embodiments of the invention and that no limitations are intended to the details of construction or design herein shown other than as defined in the appended claims.

Claims (16)

1. A pumping mechanism for pumping fluid through a resilient tube to a patient by rotating interconnected cam lobes to establish sequential urging of a plurality of fingers against the tube, said pumping mechanism comprising:
a support;
a round shaft fixedly mounted on said support for receiving said interconnected cam lobes so that said inter­connected cam lobes can be coaxially aligned with said fixed round shaft for rotation about said fixed round shaft; and
means for selectively reciprocating said fingers against said tube by rotation of said interconnected cam lobes about said fixed round shaft.
2. A pumping mechanism according to Claim 1 further comprising a finger guide for restraining said fingers to reciprocally move along a path substantially parallel with respect to other said fingers.
3. A pumping mechanism according to Claim 2 further comprising a motor coupled to said interconnected cam lobes for rotating said cam lobes about said fixed round shaft.
4. A pumping mechanism according to any preceding claim comprising means for biasing said fingers against said tube.
5. A pumping mechanism for pumping fluid through a resilient tube, said pumping mechanism comprising:
a support;
a plurality of fingers;
a round shaft fixedly mounted on said support;
a plurality of interconnected cam lobes coaxially aligned for rotation on said fixed round shaft, each of said cam lobes being operatively engaged with one of said fingers;
a finger guide for restraining said respective fingers to reciprocal linear movement along substantially parallel paths;
means for biasing said fingers against said tube; and
a motor for rotating said cam lobes to sequentially reciprocate said fingers against said tube to create a moving zone of occlusion along said tube.
6. A pumping mechanism according to Claim 4 or 5 wherein said means for biasing said fingers against said tube comprises;
two bearing blocks;
said round shaft being fixedly mounted at its end to each of said bearing blocks;
a pivot formed on each of said bearing blocks;
two pivot towers formed on said support for engagement with said pivot on said bearing blocks; and
bias elements connected between said bearing blocks and said support for urging said fixed round shaft and said support together to urge said fingers against said tube.
7. A pumping mechanism according to any of Claims 3 to 6 wherein said motor is a stepper motor.
8. A pumping mechanism according to any of Claims 2 to 7 wherein said finger guide has a plurality of ribs formed thereon for aligning said fingers along substantially parallel paths upon reciprocal linear movement.
9. A pumping mechanism according to any of Claims 1 to 8 further comprising an index key for holding said interconnected cam lobe with respect to said fixed round shaft about a common longitudinal axis.
10. A pumping mechanism according to any preceding claim further comprising a sensing mechanism for controllably determining the location of said interconnected cam lobes about said fixed round shaft.
11. A pumping mechanism according to Claim 10 wherein said sensing mechanism comprises:
a light emitter;
a light sensor; and
an encoder wheel interposed between said light emitter and light sensor and held between two of said interconnected rotatable cam lines, said encoder wheel having holes therein for allowing light to pass from said emitter to said sensor to indicate the location of said encoder wheel about said fixed round shaft.
12. A pumping mechanism according to Claim 10 or 11 further comprising a pressure transducer for detecting the pressure of the fluid within said tube.
13. A pumping mechanism according to any preceding claim wherein said cam lobes include a last cam lobe and next to last cam lobe, and wherein said interconnected cam lobes have a predetermined alignment for positioning said last and next to last cam lobes.
14. A pumping mechanism according to Claim 13 wherein said fingers include a last finger and a next to last finger and said last and next to last cam lobes are formed to lift said last and next to last fingers from said tube at a rate faster than the rate at which said other said fingers are lifted from said tube.
15. A pumping mechanism according to Claim 14 wherein said last cam lobe is formed to cause said last finger to urge against said tube for a duration shorter than said other fingers.
16. A method for assembling a peristaltic pump which moves fluid through an IV tube comprising the steps of:
(A) connecting a plurality of cam lobes together about a fixed round shaft;
(B) engaging a plurality of fingers having follower rings onto said cam lobes;
(C) positioning said fingers onto a finger guide having slots therein for allowing reciprocal movement of said fingers;
(D) connecting bearing blocks having pivots to each end of said fixed round shaft carrying said cam lobes;
(E) pivotally connecting said bearing blocks to a support having a casing for receiving said plurality of fingers positioned on said finger guide;
(F) connecting biasing elements to said bearing blocks and said support for urging said plurality of fingers against said tube; and
(G) coupling a motor to one end of said plurality of said connected cam lobes for causing rotation of said plurality of cam lobes to reciprocate said fingers and sequentially occlude said tube in wavelike fashion to move fluid through said tube.
EP89307675A 1989-05-23 1989-07-27 Pumping mechanism Withdrawn EP0399118A1 (en)

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Application Number Priority Date Filing Date Title
US35565989A true 1989-05-23 1989-05-23
US355659 2003-01-31

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EP0399118A1 true EP0399118A1 (en) 1990-11-28

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EP89307675A Withdrawn EP0399118A1 (en) 1989-05-23 1989-07-27 Pumping mechanism

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Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5217355A (en) * 1991-08-05 1993-06-08 Imed Corporation Two-cycle peristaltic pump with occlusion detector

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4755109A (en) * 1987-04-03 1988-07-05 Fisher Scientific Company Inc. Snap-together peristaltic mechanism
EP0283614A1 (en) * 1987-02-24 1988-09-28 Imed Corporation Apparatus for pumping fluids through a tube

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0283614A1 (en) * 1987-02-24 1988-09-28 Imed Corporation Apparatus for pumping fluids through a tube
US4755109A (en) * 1987-04-03 1988-07-05 Fisher Scientific Company Inc. Snap-together peristaltic mechanism

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