Many surgical devices rely on positive displacement pumps to deliver or remove irrigating fluid during an operation. These devices are well known in the art and take many forms.
Typically, these "peristaltic" pumps employ a fixed position pump head, a rotating mandrel with one or more rollers spaced around its periphery, and a cavity or shoe which compresses the tubing sufficiently to allow a pumping action of the fluid. Peristaltic pumps have been used as surgical aspirators to provide suction of irrigating fluid and tissue from surgical sites; and to deliver irrigation fluid to provide lubrication for evacuated material, cooling for surgical probes, and to provide a safety barrier between the probe and surrounding tissue.
The known devices used for such purposes have recognized limitations and deficiencies. For example, volumetric fluid delivery is often inconsistent from operation to operation when using pumps having a fixed gap between the aforementioned mandrel and shoe. The fixed gap yields variations in tubing occlusion and thus variations in pump efficiency and rate of fluid delivery. As indicated hereinabove, this can be particularly significant when pumping small volumes of fluid in medical applications.
The known pumps are also sensitive to manufacturing tolerances of the tubing (outer diameter, inner diameter, wall thickness and/or durometer), as well as to variations in machined part or assembly tolerances. These factors all have the potential for producing undesirable variations in pump performance making it difficult to maintain the calibration of these devices.
Problems also arise in working with the tubing used in the known pumps. In particular, it is often awkward and confusing to insert the tubing into the pump head of known devices. In many pump arrangements no mechanical advantage exists when closing the pump shoe to compress the tubing making for a difficult operation that could result in a crimped tube condition or require the use of two hands to pull and stretch the pump tubing before latching the shoe closed.
The potential also exists for inserting the tube in such a way as to cause fluid flow in the wrong direction, and furthermore, tubing has the propensity to "walk" which in many known pumps has the potential for causing a tubing jam, or even a separation or rip in the fluid line.
Further yet, the fixed occlusion rate of known peristaltic pumps requires that the wall thickness of the compressible tube inserted into the pump be precise and consistent. Manufacturing tolerances for the tubes and pump components (like the aforementioned shoe), are not well tolerated without having an effect on pump performance.
Tube life is also affected by pump performance and can be adversely affected by devices which do not compensate for manufacturing tolerances in the tubing, pump shoe and other components which cooperate to produce the desired pumping action.
Many attempts have been made to address the aforementioned limitations and deficiencies of peristaltic pumps that utilize a fixed position pump head.
Peristaltic pumps have been devised that utilize an adjustable shoe as part of self adjusting pump head; rather then a fixed position pump head; actuating means have been developed that are coupled to an adjustable shoe for positioning/forward biasing the shoe to compress a tube; and means for compensating for the manufacturing tolerances of a tube introduced a peristaltic pump have been developed, including means for applying a continuous reaction force on the shoe.
Peristaltic pumps have also been devised that utilize snap-on manifold cartridges having a fixed length U-shaped tube attached, where the cartridge can only be installed one way onto the pump. Such cartridges have also been developed to enable the operator to install the cartridge using a single hand, with the cartridge being a tie bar structure having an attached U-shaped tube.
In fact, the art is extremely crowded with many attempts being made to address the aforementioned limitations and deficiencies of peristaltic pumps that utilize a fixed position pump head and those that feature the use of variable position pump heads as well.
The following issued U.S. Patents are set forth as examples of teachings which illustrate the present state of the art.
U.S. Pat. No. 3,829,249 to Pursley describes a portable siphonic pump for transferring gasoline that includes a motor driven wheel with rollers that squeeze a tube The rollers are retractable along wheel spokes against springs; however there is no showing of a compressive reactive force being used against a shoe.
U.S. Pat. No. 4,728,265 to Cannon describes a peristaltic pump that utilizes a cam action compensator as means to normally urge a peristaltic mechanism toward a platen (compression shoe). The compensator yields as necessary to limit the force the peristaltic mechanism can exert against a tube.
The Cannon patent describes the use of a hinged cam action compensator which provides a yielding or complaint movement between the platen and drive mechanism; however the platen appears to be fixed in all embodiments. It should also be noted that the cam action compensator used by Cannon, and other types of cam action compensators and controls mechanisms, used in the past to provide a yielding or complaint movement between a shoe and drive mechanism against which a tube is compressed, are undesirable from both mechanical complexity and packaging requirements points of view when compared with the invention to be described hereinafter.
U.S. Pat. No. 4,482,347 to Borsanyi describes a low volume peristaltic pump (an application where the present invention finds significant utility), having a resilient surface set into the face of a platen.
U.S. Pat. No. 4,519,754 to Minick describes a peristaltic pump having variable occlusion rates. The pump includes a reaction member further including a "reaction surface adapted to at least partially encircle the circular path traversed" by a set of compression rollers. The reaction member has cam control means associated therewith which enables adjustment of the reaction member so as to select a variable occlusion rate of the tube.
The Minick patent requires a reaction surface to cover about 270 degrees of path travelled by rollers and requires cam control means which, as indicated hereinabove, is undesirable in many applications form mechanical and packaging points of view.
U.S. Pat. No. 3,876,340 to Thomas describes a peristaltic pump having a pivotal reaction means. Each of a plurality of tubes has a support against which it is pressed by the rollers. The support is resiliently yieldable in order to avoid placing excess flattening pressures on the tube.
In a preferred case each support is a spring loaded block which may be of a resilient material. Alternatively, a belt which is spring urged towards the tubes being compressed is also described.
FIG. 3 of the Thomas patent illustrates a peristaltic pump including a floating shoe, single spring and slider crank arrangement (slide pins 42, spring 44 & shoe 36). Each block (shoe) 36 presents a surface 38 which engages the tube and which is yieldable away from the rollers. An adjustment plug 44 is used to adjust the tension on spring 42 and hence the depicted device is not self-adjusting.
U.S. Pat. No. 3,990,444 to Vial describes, with reference to FIG. 3, a blood transfusion apparatus that uses a pair of springs in a slidable member to compress a tube. The pair of springs allows the slidable member to float. A hook device 21 is used to keep the device closed.
U.S. Pat. No. 5,049,047 to Polaschegg et al., describes an infusion pump with means for measuring the internal diameter of a pump supply tube where the means for measuring can be a counterpressure device.
U.S. Pat. No. 4,725,205 to Cannon et al., describes a linear peristaltic pump for pumping medical solutions which uses a complaint means for urging the peristaltic mechanism towards the platen; but which yields to limit force against the tube. The peristaltic means is urged toward the base using cam action compensation means. It should be noted that the Cannon et al. reference describes in great detail one of the significant problems existing in prior art peristaltic pump arrangements, namely that once a particular tube is selected, specific predetermined dimensional limitations are introduced into the combination.
Cannon et al. recognized that the tube itself cannot be expected to provide the necessary resilience to obviate the problem and that rather then absorbing the excess forces with tube resiliency, the effort is more properly focused on ways to limit the force exerted on the tube.
Cannon et al. indicates that one way in which excess forces in a peristaltic can be alleviated is to allow the platen to yield and uses U.S. Pat. No. 4,373,525, to Koboyashi to illustrate a peristaltic pump which makes use of a spring loaded platen (The Koboyashi patent is directed to methods and apparatus for detecting occlusions in tubing).
U.S. Pat. No. 4,705,464 to Arimond describes a medicine pump that includes a pump head having spring loaded plungers for accommodating variances in tubing thickness; but each plunger supports a roller bearing. There is no teaching of spring biasing the compression shoe.
U.S. Pat. No. 4,210,138 to Jess et al., describes fluid metering apparatus that includes a pressure plate slidably mounted to a housing; however the plate is not spring biased.
U.S. Pat. No. 4,648,812 to Kobayashi et al., describes methods and apparatus for preventing pulsations in a peristaltic pump by using a platen mounted on a single support spring.
U.S. Pat. No. 1,998,337 to Spiess, describes a folding machine which includes a roller, a cam mounted on a shaft compressed against the roller.
U.S. Pat. No. 3,737,251 to Berman et al., describes, with reference to FIG. 2, a peristaltic pump having a pair of pump shoes 16, leaf springs 17 and adjusting screws 18 used to compensate for variations in a pump rotor, support bracket, rollers, tubing diameters (inside and outside), concentricity, fluid viscosity and temperature. Berman et al., requires a manual screw to perform the desired compensation function.
U.S. Pat. No. 2,434,802 to Jacobs describes a pump block, for a peristaltic pump, mounted on a pair of springs, with the springs being designed to yield if non-compressible matter traverses the tube. The pump block can be manually adjusted to sit in a predetermined position.
U.S. Pat. No. 3,353,491 to Bastien describes a back-up member 32 for a pumping device, which is in relatively free slidable engagement with a support 12 and is connected thereto only be tension means, such as stretch spring 46a, to allow play in the back-up member when an occlusion passes in the tube.
U.S. Pat. No. 4,218,197 to Meyer et al., describes a peristaltic pump and valve flow controller. FIG. 1 depicts a type of tie bar 56, referred to as a frame member, with U-shaped tubing attached thereto. A compression spring 68 is used to compress rollers 66 and the tubing; but the spring is located between tie bar and roller assembly.
U.S. Pat. No. 4,544,336 to Faeser et al., describes a peristaltic pump having a support part 2 acted upon by springs 26 to produce a desired nipping force on a pipe placed between the support and rollers mounted on a wheel.
U.S. Pat. No. 4,585,399 to Baier describes a hose pump, for drawing fluids from a body cavity, with different inlet and outlet connectors to prevent improper installation.
U.S. Pat. No. 4,599,055 to Dykstra describes a fluid flow chamber cassette carrying a U-shaped flexible tube on one side that is loaded into a peristaltic pump. In particular, FIG. 1 of the Dykstra patent depicts a peristaltic pump including a snap on cassette 28 and U-shaped tube 30, having a fixed length. It is possible to install Dykstra's cassette using one hand.
U.S. Pat. No. 4,708,604 to Kindera describes a pressure plate, for a peristaltic pump utilizing flexible tubing, having an arcuate surface and a pivot mount. The arcuate surface is retained in operative association with the flexible tubing by a spring bias.
U.S. Pat. No. 4,861,242 to Finsterwald describes a self loading peristaltic pump.
U.S. Pat. No. 5,082,429 to Soderquist et al., describes a peristaltic pump that uses a camming mechanism for opening and closing the pump.
U.S. Pat. No. 4,824,339 to Bainbridge et al., describes a cartridge for use with the self loading peristaltic pump described in the 4,861,242 patent to Finsterwald.
U.S. Pat. No. 5,024,586 to Meiri describes a peristaltic pump that corrects for tube walking (also referred to as "tube creep") using spring biased rollers to apply a constant force to the tube. The spring biased rollers apply a force that is substantially independent of minor tube wall thickness variations.
U.S. Pat. No. 5,110,270 to Morrick describes a peristaltic pump that uses a spring and slider combination; but on the pump rotor, using spring biased clamps to hold a tube in place.
U.S. Pat. No. 5,173,038 to Hopfensperger et al., describes a rotatable compression member for a peristaltic pump including a leaf spring.
U.S. Pat. Nos. 3,137,241 and 3,227,091 to Isreeli and Isreeli et al., respectively, describe a spring biased platen for a pumping device.
U.S. Pat. No. 3,167,397 to Skeggs et al., describes a spring biased (or possibly supported) platen for an analysis system including a pump.
U.S. Pat. No. 4,473,342 to lies describes, with reference to FIG. 7, a peristaltic pump that includes a plurality of pivotably mounted track members provided with an associated leaf spring (36) which is fixed at one end to the underside of track carrier for biasing a track member toward the rollers 3 and can act to compensate for variations in tube wall thickness. The lies patent requires pivotably mounted track members.
U.S. Pat. No. 4,673,334 to Allington et al. describes a cassette for a peristaltic pump having spring means for engaging the drive means of the pump with a bias force to permit self adjustment. The cassette acts as a compression shoe.
U.S. Design Pat. No. 264,134 to Xanthopoulos depicts a disposable cassette for a peristaltic pump.
U.S. Pat. No. 4,025,241 to Clemens describes a peristaltic pump having pump tubing compressed against a spring loaded (pair of springs) movable base member improved by the addition of at least one actuating member capable of movement to or away from an actuating position with respect to the base member.
U.S. Pat. No. 3,778,195 to Bamberg describes a pump for parenteral injections and the like including pivotally mounted spring loaded plate like members positioned for engagement with a cam lobe.
U.S. Pat. No. 5,125,891 to Hossain et al., U.S. Pat. No. 4,798,580 to DeMeo et al., and U.S. Pat. No. 4,537,561 to Xanthopoulos, teach disposable peristaltic pump cassette systems.
U.S. Pat. No. 4,604,038 to Belew describes a remotely operable peristaltic pump requiring the use of two compression shoes.
U.S. Pat. No. 4,500,266 to Cummins describes a peristaltic pump that uses a series of gear driven compensating shoes that linearly move in and out of contact with a tube.
U.S. Pat. No. 3,918,854 to Catarious describes the use of a spring biased shoe to compensate for a variety of problems in a peristaltic pump; however only a manual compensation mechanism is described.
U.S. Pat. No. 4,813,855 to Leveen et al., describes the use of an adjustable shoe in a peristaltic pump, that is positioned using a cam shaft.
U.S. Pat. No. 4,189,286 to Murry et al., describes a peristaltic pump that uses a compressive reactive force for tube sizing. A cam mounting is required and a pivot shaft is called for. Additionally, the shoe used in Murry et al. rotates.
U.S. Pat. No. 4,256,442 to Lamadrid et al., describes use of a mechanically advantaged pressure plate for a peristaltic pump; however, the pressure plate, which is pivot mounted, is retained in one of two positions and does not "float".
U.S. Pat. No. 4,288,205 to Henk describes a variable volume peristaltic pump that uses a manual adjustment screw to adjust the effective length of a flexible band located between the tube and pump rollers.
U.S. Pat. No. 4,886,431 to Soderquist et al. describes a peristaltic pump that cooperates with independently adjustable cartridges.
U.S. Pat. No. 4,925,376 to Kahler describes a peristaltic pump with a tube holding mechanism that requires the use of a cam shaft to effect shoe movement and the use of a locking surface to prevent tube walking.
None of the aforementioned patents, or indeed any known peristaltic pump, satisfactorily address the problem of assuring a consistent pumping action, which affects fluid delivery rate (particularly for those applications involving the pumping of small volumes of fluid); while at the same time addressing (1) the mechanical complexity, cost and space limitations imposed by cam action compensation means used in conjunction with variable position pump shoes; (2) the safety issues associated with insuring that a tube introduced into a pump is properly installed, that the tube does not walk or be subject to forces that increase the risk of tube spilling, etc.; (3) the concern that the manual operation required to introduce a tube is a user friendly, preferably one handed, operation; and (4) the need to automatically compensate for manufacturing tolerances in tube wall and shoe construction without requiring manual intervention, such as by having to turn manual adjustment screws or the like to perform the compensation function.
In view of the above, it would be desirable to provide methods and apparatus which, when integrated into a peristaltic pump, simultaneously solve all of the aforementioned problems, and which provide the capability to solve individual problems such as simplifying the mechanical aspects of the aforementioned automatic compensation function, relaxing the packaging constraints for such means, offering a control mechanism that is simple and easy to use from a manual operations point of view, etc.