Adjustably Controllable Accuracy-Enhancing Pump Arrangement and Method

This invention relates to the pumping of various fluids by digitally incrementally actuated motor-driven peristaltic pumps, such as pulse-actuated rotary stepping motor-driven rotary peristaltic pumps, and more particularly to an improved digitally incrementally actuated peristaltic rotary pump arrangement and method which enables simple and easy enhancement of accuracy of the output quantity of fluid pumped by the pump, and which improved pump arrangement and method is particularly useful for the pharmaceutical use area where a high degree of accuracy is frequently required in pumping various fluids for various purposes.

Conventionally, rotary peristaltic pumps have heretofore utilized stepping motors to incrementally actuate a peristaltic pump rotor to thereby pump a selected fluid through a peristaltic pumping conduit which is typically formed by a tube set having flexible inlet and outlet tubes connected by a peristaltic pumping tube section of desired ID to effect a desired flow rate. Some of such pumps have employed computer controls for controlling the number of pulses fed to the pump-driving stepping motor. However, there are many variables affecting the accuracy of a specific tube set and application. The pump may calculate the theoretical required number of rotary steps for a known tube diameter, pump speed, inlet and outlet pressure and other variables if known. However, as a practical matter for a pump such as this with a wide variety of applications, it is not possible to know all of the variables.

Further, the accuracy of a rotary peristaltic pump is dependent on a large number of variables, including inside diameter accuracy, wall thickness accuracy, length of the pump tube or stretch over the rollers, elasticity of the rubber, speed of the rotor, line suction pressure at the inlet and the flow restriction and outlet back pressure.

In addition, there will be some tolerance in the tube dimensions or physical characteristics which will affect accuracy.

All of the above variables, and probably other factors also, make it impossible to precisely accurately compute the fluid output of a rotary peristaltic pump in terms of the total movement of pump rotor relative to the pumping conduit or tube set. It is an object and feature of the invention to enable achievement of high accuracy with ease, by entering the actual first cycle delivered volume into the controls of the pump and to have this data used in computing the needed accuracy adjustment in total rotation movement of the pump rotor and its rollers, so that subsequent pumping cycles, under the same operating conditions and for the same volume, will be adjusted by the same accuracy adjustment factor and will thus have a highly accurate adjustment-corrected adjusted total rotor movement for the given volume.

For many pharmacy operations, the tube set employed, as well as other operating conditions such as inlet pressure drop and outlet back pressure, will remain constant for succeeding fill cycles, with the only change being the desired delivered volume. It is accordingly a further object and feature of the invention immediately indicated above that after an accuracy adjustment factor is determined for the first volume setting, such accuracy adjustment factor may thereafter be selectively automatically carried over and applied for additional fill cycles, including those fill cycles for which the volume is changed.

It is accordingly an object and feature of this invention to provide an accuracy-enhancing method and apparatus which enables accuracy adjustment by simply employing the measured actual volume pumped and the desired pumped volume to effect a new actual volume pumped which will be adjusted for the difference between the desired and previously measured output volume.

It is a further object and feature of the invention to provide a method an apparatus which enables enhancement of accuracy of pumped volumes by digitally actuated peristaltic pumps, in which an adjustment factor is formulated and may be repeatedly applied to pumping cycles for any selected quantity or quantities, and which adjustment factor is a function of a desired volume input quantity value relative to a measured actual volume pumped as a result of input of such desired quantity value.

Still a further object and feature of the invention is to provide a pump and method in which accuracy of pumping may be readily and simply enhanced by formulating and applying a correction factor based on a desired volume input for a given pumping conduit tube set relative to the measured actual volume pumped with such desired volume input, and in which such adjustment factor may be repeatedly reapplied, without need for reformulation, to subsequent pumping cycles for pumping the same quantity as originally desired or for pumping various different quantities desired to be pumped for the same fluid and fluid-pumping conduit arrangement.

Still other objects and attendant advantages will become apparent from a reading of the following detailed description of an illustrative and preferred embodiment and mode of practice of the invention, taken in conjunction with the accompanying drawing, wherein:

FIG. 1 is an electromechanical schematic block diagram illustrating an embodiment and mode of practice of the invention.

To provide the user with a simple and easy recalibration adjustment, this invention utilizes a means of inputting the actual delivered volume from a measured initial test volume delivered by the pump. The computer control will then calculate the ratio of the desired volume relative to the actual delivered volume and use this ratio to modify the number of pulsed rotary steps of the stepping motor to provide the desired correct volume. The computer may then collectively retain the adjustment or correction ratio in memory, if desired, so that this correction can be made for subsequent input desired volumes when the same tube set and inlet/outlet conditions exist.

Referring now to FIG. 1 of the drawing, a suitable clock generator 11, which may be formed by a fixed-rate or adjustable-rate oscillator (although a stable fixed frequency oscillator such as a quartz controlled oscillator is preferred) feeds a higher frequency (e.g., 4 Mhz) signal than will be utilized for pump operation, through an adjustable divider 13 which provides a suitable lower frequency signal which is within a frequency range acceptable by a stepping motor M.

The output frequency of divider 13 may be suitably controllably varied by a speed control 13a which may function to vary the speed of motor M by varying the divisor y inputted to divider 13. The desired suitably lower frequency signal output from divider 13 is fed to a count accumulator register 55 and to a pulse generator 15 which forms pulses at the same frequency and having characteristics suitable for driving a rotary stepping motor M which in turn rotates a rotor 21 as by a common shaft connection 31 from the stepping motor M to rotor 21 of a peristaltic pump 20, relative to a fixed stator 23 having a constant radius peristaltic pumping surface 23c whose center of radius is the same as rotor 21.

Rotor 21 preferably has rollers 22 at its ends for progressive rolling peristaltic squeezing pumping contact with a pumping conduit 41 which may be removably mounted along the pumping zone between the face 23c of stator 23 and the rotor 21.

The peristaltic pump 20 has laterally open-slotted connector/anchor elements 25, 27 at its input and output ends for removably connecting a flexible pumping conduit thereto and for effectively anchoring the conduit 41 in position to withstand the longitudinal pulling motion exerted thereon by the rotation of the rotor 21 thereagainst during peristaltic pumping action. Concomitantly, the flexible pumping conduit 41 has spaced pairs of flanges 41a and 41b formed thereon for laterally slidably removable anchoring engagement with respective slotted connector/anchor elements 25, 27.

The output of count accumulator register 55 is continuously inputted to a comparator 57 whose other input is from a desired end count register 61. When the count accumulator register 55 has accumulated a count equal to that in the desired end count register 61, the comparator forms an output signal which actuates and opens previously closed motor start/stop control switch 59 through which the motor-actuating pulse output from pulse generator 15 is fed to motor M. This opening of switch 59 blocks the feeding of pulses to the motor M, thus effectively stopping the motor M and drive shaft 31 and thereby cutting off further driven rotation of rotor 21 and concomitant pumping of fluid by the pump 20.

The desired end count register 61 is set to a desired value by inputting a desired volume and/or by subsequently inputting an actual measured volume V.sub.M resulting from operation of the pump 20 based on the initial setting of a desired volume V.sub.D. As is subsequently described, the measured volume V.sub.M may be utilized in conjunction with the desired volume V.sub.D to adjust the desired end count register 61 to reflect any noted difference in actual flow rate through the given conduit 41 or 151 relative to the expected estimated or calculated flow rate.

Desired volume V.sub.D may be suitably inputted in digital form at desired volume input 71 as by a touch pad or keyboard which accommodates volume quantity inputs, e.g., liter, ml, etc, and this input 71 is fed to a multiplier 73 which converts the value V.sub.D to a suitable corresponding count (N.sub.D)(n) by multiplication by a constant n which correlates with the pulse quantity/volume estimated or calculated to be pumped by the stepping motor-driven pump 20 for a pumping conduit of the base size which causes direct feeding of count accumulator register 55, as distinguished from the indirect feeding thereof through multiply/divide adjuster 53.

The resulant product output (V.sub.D)(n) is fed to a desired volume estimated count register 75 which has been suitably reset to zero prior to entry of the desired volume count (N.sub.D)(n).

Initially, the output (V.sub.D)(n) of register 75 is passed through OR gate 77 to the desired end count register 61, the output of which register 61 in turn is inputted as one comparison input to comparator 57, against which comparison input the comparator compares as its other comparison input the running count accumulation output from count accumulator register 55. Thus, when the set quantity in register 61 is equalled by the accumulated count in register 55 the comparator 57 will actuate the motor start/stop switch 59 to off or open condition, where it will remain until it is again manually or otherwise suitably automatically or otherwise reactuated to on or closed condition.

While the calculated or estimated value n of pulses/unit volume as employed may provide an acceptable degree of accuracy in some instances, there may nevertheless be situations where greater accuracy is required in the actual volume of fluid delivered. To this end, according to the invention, provision is made for adjustment of the desired volume estimated count value (V.sub.D)(n) by a factor which effectively substantially compensates for the difference between the desired pumped volume and the actual measured pumped volume V.sub.M resulting from use of the calculated or estimated pulses/quantity pumped. According to a preferred mode of practice of the invention, after conclusion of operation of the pump 20 with a given tube set fluid conduit 41 or 151 and fluid being pumped, the volume V.sub.M of fluid pumped from the conduit 41 is measured, either visually or otherwise as desired. It has been found that, for most normal conditions and requirements, personal visual measurement is adequate to provide an acceptable basis for adjustment of the pumped volume V.sub.M to a value well within acceptable tolerance limits relative to the desired volume V.sub.D.

According to this aspect of the invention, the measured volume V.sub.M, resulting from operation of the pump when a desired volume V.sub.D has been inputted, is inputted as through manual actuation of measured volume input unit 81, which may be a keyboard, touchpad or other suitable digital input device, the measured value V.sub.M being inputted being in the same selected unit of measure for quantity as employed for inputting the desired input V.sub.D. This value is multiplied in multiplier 83 by the factor n to provide a measured volume count (V.sub.M)(n) which is inputted to cleared measured volume count register 85, the output (V.sub.M)(n) of which is inputted as the divisor to divider 87. Also inputted to divider 87 as the dividend therefore is the count value (V.sub.D)(n) from the volume estimated count register 75. The quotient V.sub.D /V.sub.M output from divider 87 reflects in usable nearest digital count value forms the ratio of the desired volume V.sub.D relative to the actual measured volume V.sub.M produced by employing the estimated or calculated multiple n to provide the pulse quantity (V.sub.D)(n) for operation of the pump 20 in an effort to pump the desired volume V.sub.D.

Output V.sub.D /V.sub.M from divider 85 is fed through selectively opened normally closed gate 88 into cleared register 89, after which gate 88 is closed until a new value V.sub.D /V.sub.M is desired to be inputted to register 89, at which latter time register 89 may be cleared by its reset input, and gate control 88a may be actuated to open gate 88 and permit passage of the new value of V.sub.D /V.sub.M into V.sub.D /V.sub.M register 89.

The output V.sub.D /V.sub.M of register 89 is continuously available and inputted as one multiplier input into multiplier 91, the other input to multiplier 91 being the desired volume estimated count (V.sub.D)(n) from register 75. The product (V.sub.D.sup.2)(n)/(V.sub.M) is a count value (which may be suitably rounded off to the nearest whole digital value) which reflects the original estimated count V.sub.D (n) adjusted by the ratio or percentage adjustment factor V.sub.D /V.sub.M to thereby make a correction for the measured variation in pumped quantity resulting from use of this count value (V.sub.D)(n) as the pulse generating input for pump 20.

Register 61 is suitably reset/cleared, and the OR gate 77 is thereupon actuated by a suitable gate control 79 to switch the input to the cleared desired end count register 61 so that the output (V.sub.D.sup.2)(n)/(V.sub.M) from multiplier 91 is inputted through OR gate 77 to the desired end count register 61. Thereupon, the pump 20 is restarted by start actuation of start/stop switch 59, and when the count accumulator register 55 registers the same number of counts as the count value (V.sub.D.sup.2)(n)/V.sub.M outputted from the desired end count register 61, the comparator 57 effects an output signal which actuates the on/off switch to its normal off condition, thereby blocking passage of further pulses from pulse generator 15 to motor M and thus effectively stopping the pulse driven actuation of motor M and pump 20 driven thereby. The pumped quantity of the given fluid through the given conduit 41 will thus be an amount which is adjusted for the measured difference between the desired volume V.sub.D and the measured volume V.sub.M, the adjustment representing a ratio of increase or decrease reflected by the product of the desired volume V.sub.D multiplied by the adjustment factor ratio of the desired volume V.sub.D relative to the measured volume V.sub.M.

The V.sub.D /V.sub.M register 89 may retain its registered value until such register 89 is reset and gate 88 is subsequently opened to enable registry of a new value V.sub.D /V.sub.M therein, as may result from pumping action with different conditions, such as using a different pumping conduit 41 , and/or pumping a different fluid. Thus, by retaining the value V.sub.D /V.sub.M in memory register 89, additional further desired volume quantities V.sub.D, which may be the same as previously inputted at desired volume input 71 may again be outputted by pump 20 by merely start reactuating start/stop switch 59, as the desired end count register 261 will retain the adjusted desired end count for the previous desired volume input V.sub.D until reset. Alternatively, the previously determined ratio value V.sub.D /V.sub.M may be retained in register 89 and reused as a further input to multiplier 91, for a desired new input value of V.sub.D inputted through input 71 and multiplier 73 to cleared desired volume estimated count register 75, and by operating OR gate 77 to pass the resulting new output (V.sub.D.sup.2)(n)/(V.sub.M) to desired end count register 61, the same previously resulting correction or adjustment factor V.sub.D /V.sub.M applicable for operation of the pump 20 to pump an identically proportionately adjusted more accurate quantity of fluid will be reflected in the pump operation, without necessity for again measuring the quantity pumped and inputting such through input 81, with essentially the same degree of corrected accuracy, assuming the same conditions are maintained for the pump, including same pump speed, same conduit, and same fluid, etc., the only operating difference being the desired volume quantity V.sub.D. When any condition other than desired volume to be pumped is changed, it is desirable that the V.sub.D /V.sub.M register be cleared, and the previously described test pumping, measuring and, if necessary, adjusting of fluid quantity pumped, by forming and registry in register 89 of a new adjustment factor V.sub.D /V.sub.M by appropriately opening and then closing of gate 88 as by gate control 88a.

While the foregoing system and method has been illustrated and described generally in hardware form and terms, it will be appreciated that such may be, and in a given instance may preferably be, effected in large measure by suitable corresponding software and/or firmware programming and operation of a computer or computers by such programming in conjunction with such hardware of the system as may be deemed desirable.

While the invention has been illustrated and described with respect to illustrative embodiments and modes of practice, it will be apparent to those skilled in the art that various modifications and improvements may be made without departing from the scope and spirit of the invention. Accordingly the invention is not to be limited by the illustrative embodiments and modes of practice, but only by the scope of the appended Claims.