Valves and valve actuation – Tube compressors – Roller tube contacting element
Reexamination Certificate
1999-05-26
2002-07-23
Morris, Lesley D. (Department: 3754)
Valves and valve actuation
Tube compressors
Roller tube contacting element
Reexamination Certificate
active
06422529
ABSTRACT:
FIELD OF INVENTION
The present invention relates to roller clamps for intravenous administration (I.V.) sets and more particularly to an improved roller clamp for I.V. sets having the unique combination of advantages including the benefits of diminishing the effort required to adjust the degree of pinch on the tube and improving the grip on the tube by following the preferred housing dimensional relations as hereinafter set forth as well as reduced manufacturing cost.
BACKGROUND OF THE INVENTION
Sometime during the period of approximately 1940-50, Intravenous Administration sets evolved from being reusable to being disposable. Earlier, a technique was developed to produce and store medical grade fluids for human infusion, for example, water, as well as dilute solutions of saline, dextrose, and other fluid nutrients as well as certain medicines. These fluids were stored in sealed glass containers and were administered using sterile surgical rubber tubing. The tubing and other administration components were usually re-sterilized and reused. Control of the rate of fluid administration was adjusted by varying the degree of pinch on the rubber tubing. Various pinch clamps were developed for this application.
With increasing usage, the advent of medical grade polyvinyl chloride (PVC) tubing and the need to reduce or eliminate a serious patient/hospital problem of cross-contamination, disposable administration sets were introduced. This solved the cross-contamination problem, but introduced a new one; that of time varying flow rates, i.e., variations from the initial setting of the desired flow rate over time. The pinched plastic tube exhibited the problem of creep or cold flow when pinched and this caused the flow rate to vary with time, usually this variation was large (on the order of 40 percent during the first ten minutes and increasing) and most often was a decrease in flow rate.
The first pinch clamp (which was not parallel acting) to address the time varying flow rate problem was described in about 1967, and a series of improved parallel acting clamps were introduced in the following years, as well as a number of significant refinements. The primary thrust of such newly developed clamps were, prior to 1967, ease of adjustment, and, subsequent to 1967 usually a combination of ease of use and/or adjustable flow rates which also would change little over time.
Another category of improvement was that of a clamp offering a better grip on the tube because if the clamp were accidentally released, the resultant increase in flow, or in the extreme, run away, could be life threatening or deadly.
Manufacturing cost was usually an underlying factor as is the case with most high volume usage products. Typical cost reduction factors available and employed were: (1) make parts small to conserve material, (2) use lower cost materials, and (3) make parts easy to assemble to keep labor costs-down.
Injection molded plastic is the popular approach to producing a disposable clamp. Typically, plastic materials such as Acrylonitrile Butadiene Styrene (ABS) resin or Polypropylene (PS) may be used with a rubber additive, the ABS material generally being more dense than Polypropylene or other plastics which have been used. In accordance with this invention, the preferred material is ABS or PS or PS with the possible addition of Butadiene containing polymer or other rubber like material.
The combination of economic pressures to hold down or reduce costs of health care, the enormous volume of use of infusion sets and the ever increasing cost of plastic resin combine to greatly increase interest in finding a clamp which satisfied the above mentioned need of: (1) ease of use, (2) reduce time varying flow rates and, (3) firmer grip on the tubing, as well as one which permits production at a cost still lower than that obtained by the obvious steps of making the part smaller, increasing the number of production cavities and/or using a lower cost resin.
Roller clamps for intravenous administration infusion sets, sometimes referred to as I.V. sets and typically disposed of, along with the I.V. set, after one use, are well known and are designed primarily to regulate the flow of liquid passing through a soft plastic pliable and deformable tube, usually polyvinyl chloride with a low degree of extractables. The degree of pinch of the tube is normally used to decrease and thereby regulate the flow rate to a desired value, normally measured in drops per minute when utilizing a drip chamber, the latter representing the prescribed rate at which fluid of interest is desired to be intravenously administered. These pinch clamps are also used as an on/off device, that is, either to permit flow or to stop flow. It goes without saying that the pinch clamp should, once set, accurately control the flow rate over time and also be capable of fully shutting off flow when that is desired.
Typical of the prior art clamps are those of the prior Adelberg patents, as follows: U.S. Pat. No. 4,047,694 of 1977; U.S. Pat. No. 4,013,263 of 1977; U.S. Pat. No. 3,685,787 of 1972; U.S. Pat. No. 5,014,962 of 1991; U.S. Pat. No. 4,725,037 of 1988 and U.S. Pat. No. Re 31,584 of 1984 whose disclosures are referred to and incorporated herein by reference.
In general, there have been two basic types of IV set roller pinch clamps, one being the “inclined ramp” clamp and the other being what is hereby referred to as a “parallel acting” clamp or one whose wheel travels in a generally parallel relation to what is generally referred to as a clamping surface. In each case, the clamp basically includes a housing in which is received a wheel (roller) typically supported by the housing with the plastic tube received in the housing and located between a base or clamping surface in the housing and the roller.
Regardless of the type of clamp, in one extreme position of the roller, there is “full flow”, i.e., unregulated flow at the full flow capacity of the I.V. set. In another position of the roller, typically spaced from the full flow position, there is a no flow position in which there is no flow through the tubing. This typically is a shut off position. In some clamps, there is another shut off position, more properly a lock position in which movement of the roller is affirmatively prevented, as will be described, and there is no flow through the tubing. Between the full flow position and the no flow position, there typically exists a region of travel of the roller over which flow may be controlled, i.e., the region of “flow control” so called. The length of the flow control region may be less, in an axial direction, than the maximum distance over which the roller travels, especially if there is a lock position.
In the case of an inclined ramp clamp, flow control is achieved by an “inclined ramp” principle in which the roller is forced, by the operator's thumb, to climb a ramp, causing a decrease in the clearance between the roller and the opposed housing surface upon which the tubing rests, thereby creating the desired degree of pinch and thus controlling the flow rate. As the roller or wheel advances, the clearance between the roller and the surface of the housing upon which the tube rests diminishes and, in the extreme position, creates full (pinched tube) shut off. For typical flow rate settings of the clamp, the tube lumen is fully collapsed in the large center region of the tube's cross-section (where the tube radius of curvature is large), while a pair of lumens form at either side, where the radius of curvature of the pinched tube is smallest and thereby offers the greater resistance to pinch, The phenomenon of cold flow or creep in the plastic tube explains why the newly formed lumens continue to collapse and cause the flow rate to decrease, after the roller is brought to and remains in its new position.
In a parallel acting (dual action) clamp, the effects of creep or cold flow are reduced or, ideally, eliminated by having everywhere in the flow control region of the housing, a section of the housing which guides the wheel such that
Keasel Eric
Morris Lesley D.
Sheppard Mullin Richter & Hampton LLP
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