ITMI991967A1 - IMPROVED ROLLER TERMINALS FOR INTRAVENOUS ADMINISTRATION GROUP AND METHOD TO MAKE THE SAME - Google Patents

Description

Description of the industrial invention entitled:

"Improved roller clamps for intravenous administration group and method of achieving the same"

DESCRIPTION

Related applications

This application is a partial continuation of my previous application serial number 09 / 196.920, filed on November 19, 1998 which, in turn, is a partial continuation of my previous application serial number 08 / 646.214, filed on May 7, 1996.

Field of the invention

The present invention relates to roller clamps for intravenous (I.V.) administration and more particularly to an improved roller clamp for IV groups. having the unique combination of advantages including the benefits of decreasing the effort required to adjust the pinch degree on the tube and improve the grip on the tube following preferred housing size ratios as set forth below as well as a reduced manufacturing cost.

Prior art

In the period between 1940 and 1950 approximately, intravenous administration groups evolved from reusable to disposable.

Previously, a technique had been developed for producing and storing medical-grade fluids for human infusion, for example, water, as well as dilute solutions of biological liquid, dextrose, and other fluid nutrients as well as certain medications. These fluids were stored in sealed glass containers and administered using sterile surgical rubber tubing. The tubing and other administration components were re-sterilized and reused. The control of the rate of fluid administration was adjusted by varying the degree of pinching on the rubber tube. Several staple clamps have been developed for this application.

With increasing use, the advent of polyvinyl chloride (PVC) pipes for medical use and the need to reduce or eliminate serious patient / hospital problems due to cross-contamination, disposable administration units have been introduced. This solved the problem of cross contamination, but introduced a new one; that of variable flow rates over time, that is, variations from the initial import of the desired flow rate over time. The clamped plastic tube had the problem of gradual sliding or plastic sliding when clamped and this caused a variation in the flow rate over time, usually this variation was considerable (in the order of 40% during the first 10 minutes and increasing) and very often there was a decrease in range.

The first clamping clamp (which did not act in parallel) to solve the problem of the flow rate that varied over time was described in about 1967, and a series of improved parallel action clamps were introduced in the following years, along with several other significant improvements. The main improvement of this newly developed clamp was, before 1967, ease of adjustment and, after 1967, usually, a combination of ease of use and / or adjustable ranges that would undergo a slight modification over time.

Another category of improvements was that of a clamp that offered a better grip on the pipe because if the clamp was accidentally released, the resulting increase in flow or in extreme case, the unhooking could be dangerous to health or even fatal. .

Cost of production was normally a secondary factor as is the case with high volume consumer products. Typical cost reduction factors available and used were: (1) making small parts to preserve material, (2) using lower cost material, and (3) making parts that are easy to assemble to keep labor costs low.

Injection molded plastic is a popular approach to making disposable clamps. Typically, plastic materials such as acrylonitrile butadiene styrene resin (ABS) or polypropylene (PS) can be used with a rubber additive, the ABS material being denser than polypropylene or other plastics, which have been used. According to 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 keep down or reduce costs in the healthcare sector, the enormous volume of use of brewing units and the ever-increasing cost of plastic resin combine to greatly increase interest in finding a clamp that meets the requirements. aforementioned need for: (1) ease of use, (2) reduce flow rates that vary over time and (3) a firmer grip on the pipe, as well as a clamp that allows production at an even lower cost than that obtained from the obvious steps of making smaller parts, increasing the number of production cavities and / or using a lower cost resin.

Roll clamps for infusion groups for intravenous administration, sometimes also called I.V. and typically thrown away together with I.V. groups, after a single use, are well known and designed primarily to regulate the flow of liquid passing through a bendable and deformable soft plastic tube, normally polyvinyl chloride with a low degree of extractable substances. The pinch degree of the tube is normally used to decrease and therefore adjust the flow rate to a desired value, normally measured in drops per minute when using a drip chamber, the latter representing the prescribed rate at which the affected fluid is to be administered. intravenously. These pinch clamps are also used as an on / off device, i.e. to both allow flow and stop flow. It goes without saying that the clamp clamp should, once set, precisely control the flow rate over time and also be able to completely shut off the flow when desired.

Typical prior art clamps are those of prior Adelberg patents, as follows: U.S. Pat. No. 4,047,694 of 1977; 4,013,263 of 1977; 3,685,787 of 1972; 5,014,962 of 1991; 4,725,037 of 1988 and Re 31,584 of 1984 whose descriptions are referred to and whose descriptions are incorporated herein at the reference level.

Generally, there have been two basic types of roller gripper clamps of the I.V. group, one being the "inclined ramp" clamp and the other being called the "parallel acting" clamp or one whose wheel travels in a relationship generally parallel to what is generally referred to as the clamping surface. In this case, in principle, the clamp comprises a housing in which a wheel (roller) typically supported by the housing with the plastic tube received by the housing is received and positioned between a base or clamping surface in the housing and roller.

Regardless of the type of clamp, in one extreme position of the roller there is "full flow", that is, a flow not regulated at the full flow capacity of the I.V. is a non-flow position in which there is no flow through the pipeline. This is typically a closed position. In some clamps there is another closed position, more properly a locking position in which the movement of the roller is positively prevented, as will be described, and there is no flow through the tube. Between the full flow position and the no flow position, there is typically a roller displacement zone in which the flow can be controlled, that is, the so-called "flow control" zone. The length of the flow control zone may be shorter, in an axial direction, than the maximum distance over which the roller travels, and particularly if there is a locking position.

In the case of an inclined ramp clamp, the flow control is obtained by an "inclined ramp" principle in which the roller is forced, by the operator's thumb, to go up a ramp, causing a decrease in the opening between the roller. and the opposite surface of the housing on which the tube rests, thereby creating the desired degree of pinching and thereby controlling the flow rate. As the roller or wheel advances, the opening between the roller and the surface of the housing on which rests the tube decreases and, in the extreme position, creates a total closure (clamped tube). For an import of typical clamp capacity, the tube opening is totally closed in the wide central area of the tube cross section (where the radius of curvature of the tube is wide), while a pair of ports is formed on both sides, where the bend radius of the clamped tube is smaller and therefore offers the greatest resistance to clamping. plastic impact or gradual flow in the plastic tube explains why the newly formed ports continue to break down and cause a decrease in flow rate after the roller is brought in and remains in its new position.

In a parallel action (double action) clamp, the effects of smooth sliding or creep are reduced or, ideally, eliminated by having a section of the housing anywhere in the flow control region of the housing guiding the roller so that an opening in the tube is formed which causes in any particular cross-section of the tube, at least one and usually both, the ports which tend to form on one or both of the outer edges, in order to be clamped so as to completely close. The range varies by varying the cross section of the light that is formed elsewhere. Fine control of speed in any tube cross section is achieved on that tube section by varying the ratio of the pinched part so that it closes completely, of the pinched tube so that the other part remains open, since there is a vent part in base or housing or wheel where no or less staple is applied. The action, or movement, of the roller must not be precisely or even almost parallel to the opposite stapling surface of the housing. The criterion for a parallel action clamp is to have an opening between the roller and the housing which causes the local part of the tube to be clamped so as to be totally closed and to have the remainder of the tube positioned in front of a section of the housing surface or in some designs a portion of the outer roller surface, which is in contact with or close to the tube forming a vent portion which allows and / or encourages the formation of an open port in the tube.

In the parallel action clamp type, the roller in a typical gripper station in order to totally close a part of the tube and usually a vent in the housing is used to determine a certain desired degree of clamping or partial closure of the tube. When the term "parallel" is used, it is not intended to describe a geometric parallelism or a device in which the displacement of the roller is in a precisely parallel manner over its entire range of displacement; and such "parallel" action is only necessary in the order of flow control of the roll displacement. Indeed, a parallel action clamp can, and usually does, include a small relative angle between the roll displacement and the surface. opposite that the tube rests on and is clamped, for example, as a result of the "draft" used in the design of the injection mold, as will be discussed. However, this relatively small angle is, in itself, insufficient nor is it intended to make a primary control or variation in flow velocity since the modification of the opening between the roller and the surface on which the tube is clamped is insufficient to directly vary the surface of the flow cross section, as opposed to a sloped ramp clamp. also the case that in the area of the housing before the flow control and after the closure or the non-flow position, as opposed to the locking position, the action of the clamp may also not be parallel in its structure.

Since these are areas other than those in which the flow control is carried out, the need for even an approximate parallel action, as described here, is not relevant or necessary.

Although the design of a parallel acting roller clamp in which only one cheek of the tube is clamped to be fully closed may be an improvement in clamps designed for good performance with respect to time varying flow rates (flow which varies over time). ), totally clamping a light that would otherwise form and tend to have a gradual sliding or a plastic sliding, more advanced projects clamp so as to totally close both cheeks of the soft clamped plastic tube.

The feature that distinguishes a parallel action (dual action) roller clamp of a roller clamp from a sloped ramp clamp is how flow control is performed. In most roller clamps acting in parallel, flow control is achieved by clamping to fully close one cheek and normally both tubing cheeks over the full flow control range and varying the ratio from clamped to so as to completely close to non-pinched or partially pinched, open part of the tube according to the position of the roller in the flow control area. It is evident that for a given pipe cross section, pinching to fully close one or both cheeks, but not the adjacent pipe section, is only necessary in that range of roll displacement which is effectively the range of flow control. In the case of an inclined ramp clamp, flow control is achieved by varying the opening between the roller and the opposite clamping surface. It is therefore evident that even if a true parallelism cannot exist in a clamp "acting in parallel", the non-parallelism value is insufficient to vary the opening of any value that substantially effects a change in the tube opening or in the correspondence of the range. This is especially true if one or both cheeks are pinched so that they are fully closed in the range of movement of the roller in the flow control zone.

A typical arrangement to ensure that one and both cheeks of the tube are clamped to be fully closed is to provide an opening between the bottom of the roller and the opposite surface of the housing against which the tube is clamped, which is generally no more than twice the wall thickness of the non-crimped tube and, in many cases, less than twice the wall thickness of the tube. In general, an opening of less than twice the wall thickness works satisfactorily to ensure that one or both cheeks are fully stapled. Again, it is understood that this defined opening is only needed in the flow control zone. In fact, the opening is greater at the inlet end of the housing and may be somewhat smaller near the outlet end of the housing, particularly if there is a separate locking block.

In the "parallel acting" clamp, the opening between the roller and the clamping surface of the opposite housing may or may not vary with the position of the roller, but this variation of the opening with the position of the roller does not substantially control the size of the light formed. Control, in this case, is achieved by varying the ratio of the clamped closed wall portion of the soft tube to the unclamped portion along the control portion of the housing.

In the design of the inclined ramp clamp, as the roll advances, the center section of the clamped tube can bend and be totally closed, but the opening between the roll and the opposite housing surface: (1) is wide enough to allow the lights to form, and normally, on one or both cheeks of the tube, and (2) vary to create the desired size (s) of light and corresponding range.

In a lesser known version of parallel action clamp, the vent is located in the surface of the roller. A general feature of these types of clamps is that the cross-sectional open area of the tube varies as the roller advances along its path, the size of the open area being related to the configuration of the vent on the clamping surface. As is known, the vent can take on a wide range of configurations and can be closed towards one side of the housing or under the pipe or in any other position which is usually of variable width and / or variable depth or both. Its function is to vary the open flow zone of the tube in response to the movement of the roller. In effect, the variation of the formed light acts to vary the flow rate and the various devices which act in parallel have this common feature. For purposes of the present invention, by "parallel action" is meant a pincer clamp having a roller and a housing and means for varying the span of the tube formed to vary the flow rate and in which there is some form of vent in the surface of the roller. or in the housing or clamping surface and in which the roller travels in a parallel relationship to the clamping surface, the parallel path being as already explained.

In almost all models and types of collet clamps that use a roller and in a housing, the axis of the roller is supported controlling a guide surface when the position of the roller wheel is altered and also when it is in place creating the desired staple degree.

There are special requirements in the pinch grips to which the present invention refers, and some important ones are as follows: (1) the upper surfaces of the housing should be designed to resist compression due to contact with the roller axis . (2) the upper surface of the housing should be designed to resist bending as well as outward rotation when subjected to an upward force such as that caused by the axis of a pinch wheel. (3) the side walls of the housing should be designed to withstand the tension. (4) the lower surface of the housing should be designed to resist bending as well as to act in compression, provide a venting action of varying width as well as an ideal position for bespoke raised elements. The raised elements, if used, have variable heights, variable widths and distances. (5) the housing should be made of plastic that can be injection molded, should have a cross-sectional surface designed to facilitate the flow of the injected molded plastic to fill the entire cavity of the steel mold, and provide the necessary rigidity for mold ejection, subsequent assembly, and normal use.

When parallel action clamps were introduced to the market in commercial volumes around 1975, the housings measured approximately 2 inches in length. Competitive sloped ramp terminal housings measured approximately 1.4 inches in length. Parallel Acting Clamps have earned a significant share of the market due to their better performance than sloped ramp clamps and, around 1978, they totaled nearly all sales of one (Abbott Labs) of the two (Baxter Travenol is the other). ) larger companies in the United States that produced products that required clamps to be used in I.V. groups. Around 1983, Baxter began using a longer, patented clamp. After that, others, such as Cutter (who actually started at an earlier date), McGaw, Ivac and Boria, introduced clamps with two-inch housing and a trend in clamp length was established.

With wider use of longer clamps, manufacturing costs increased substantially for a large portion of the market, even though many of the longer clamps did not offer the improved performance of the patented clamp acting in parallel. Some of these companies have simply followed the trend of a longer housing length. In the case of Abbott's parallel action clamps, there was a functional reason for the length, as well as providing a flow that did not vary over time, a firmer grip on the tube, the longer roll path allowed for finer degree adjustment of stapling and therefore of the range.

Therefore, in an effort to conform to the trend of longer length the market has introduced heavier grips, apparently showing little interest in, or giving a lower priority to, the resulting increased production costs of these relatively heavier grips. These cost increases represent a substantial sum given the number of clamps used on an annual basis.

Recently, the cost of producing a roller collet clamp, and many other plastic items, has increased dramatically from a plastic resin cost percentage to a fraction of 50% of the manufacturing cost compared to today when the cost of resin plastic forms a dominant or significant part of the cost of production. At present, the molding cost fraction is relatively small, and the raw material cost fraction is relatively high and increasing. Therefore, if the usable, printable part can be redesigned to provide at least as good a function but using significantly less plastic resin, large savings in manufacturing costs can be realized.

Most forms of clamps have a housing whose wall thickness cross section is remarkably uniform throughout its length. Such a design parameter is simple to specify when designing the clamp by focusing attention on the important configurations of the internal surface: clamping surface of the housing, guide of the wheel axis, width of the wheel groove, etc. and then completing the project by simply specifying a uniform wall thickness across the length.

The new shape of the clamp of the present invention not only offers the desired gripping point (if parallel action, the side walls of the tube clamped so as to be totally closed, etc.) but also adds strength (modulus of flexibility, etc.) and mold design (injected plastic that completely fills the passages) and has a structure to achieve a substantial reduction in the material required for each clamp.

Currently, typical roller clamps have dimensions in the following order:

(1) width of the largest diameter of the roller of 1.3 to 1.8 the outside diameter of the nominal pipe, e

(2) thickness of the housing part in the order of two to generally three times greater than the wall thickness of the non-deformed soft plastic tube, and

(3) uniform wall thickness over the entire cross section and said cross section being the same over the entire operating length of the housing where the flow regulation occurs (flow control area).

An obvious approach to reducing the weight of parts is to reduce the length of the housing. However, this is not desirable as a part of the length of the housing, usually in its wide end, is necessary to facilitate the introduction of the wheel in order to make the combination feasible. The remainder is primarily to provide a reasonable range of travel for the roller to gradually pinch the tube to any position along the vent or control section of the housing.

It is not practical to decrease the total or main width or height of the cross section of the clamp housing because if you do this, it will be difficult to surround and clamp a certain diameter of soft plastic tube. .

The current gripper clamp housings have a uniform wall thickness of the order of 0.3 to 0.5 times the external diameter of the pipe that the clamp must clamp.

There is a practical minimum housing length. For the most commonly used size pipes having an outside diameter on the order of 31⁄4 to 4 1⁄2mm, the minimum housing length is on the order of 23mm to 55mm, or approximately 7 to 25 times the outer diameter of the tube.

The wall thickness of the clamp housing is typically 1.2 to 1.7 mm or approximately 0.2 to 0.5 times the outer diameter of the pipe. Most importantly, the clamp housing is normally uniform in the thickness of the cross section of the wall. This is apparently achieved (that of the uniform housing wall thickness) because:

1. It is simple to specify.

2. It is a traditional design parameter for injection molded parts. The uniform wall thickness facilitates the filling of the steel mold with the injected plastic.

3. Most clamp designs pay little attention to variations in the expected mechanical deviation of the plastic housing when subjected to the stresses associated with pipe clamping.

The mechanical deflection (stress) depends on many parameters and for a given plastic resin material, say ABS (acrylonitrile butadiene styrene), which is the preferred material according to the present invention, depends in part, on the level of stress and the type of stress (tension, bending, compression, torsion, etc.). A good design will minimize the deviations when under load, or it will, through the design, allow a deviation, but that deviation must be within the elastic limit, or, if the elastic limit is exceeded, it will make sure to reduce to a minimum the amount of deviation or degree of excess, beyond the elastic limit.

When a clamp housing is used, that is, assembled with a wheel and a clamped tube and the other components of the I.V. group, the expected deviations of the clamp take place, and the quantity depends, in part, on the type (tension, bending, etc. .) of the stress that is applied.

The side walls of the clamp housing are mainly in tension while the top edge or top wall is mainly bending or bending, with a secondary component of local compression, due to the pressure applied by the axis of the roller wheel where it enters contact with this upper surface. In the case of an injection molded pinch clamp having one or more housing wall sections in tension, according to the present invention, this requires a smaller cross section than the top or bottom walls which are not primarily in tension. Distortion, or mechanical deviation of the housing, when used to clamp the tube, will be due to:

1. Mainly bending or bending on at least two ways of the upper edge or wall of the housing.

2. Secondly due to the tension of the side wall of the housing.

3. An even smaller measure, due to the local compressive force exerted directly by the wheel shaft on the upper edge of the housing where the contact is made.

4. The pressure applied by the greater circumference of the wheel against the underside of the housing surface, through the double wall thickness of the clamped soft plastic tube.

Now, if you look at previous patents related to clamps, most patents make no written reference that the side walls are thinner than the top and bottom walls of the housing and that the top wall is thicker in section than to the lower wall. Further, the drawings of some of the roller clamp patents tend to describe a variety of configurations, but offer no teaching as to why the wall thickness dimensions are as illustrated. For example, US Patents 1,411,731; 1,959,074; 2,595,511; 3,135,259; Nos. 3,189,038 and 3,289,999 appear to illustrate structures of uniform wall thickness. US patents 3,099,429; 3,125,394; 3,215,395; Nos. 3,297,558 and 4,430,201 include drawings that could be interpreted as illustrating a thin-walled structure. Of these, U.S. Patent 3,099,429 issued to Broman. deserves a special comment. Broman illustrates a clamp with thinner side and top walls and the clamping surface or bottom wall appears to be thicker than the side walls. In Broman, the guide surface is the same thickness as the thin side wall and is much thinner than the clamping surface. Broman doesn't mention any weight savings, strength considerations (flex, tension, etc.). No mention is made of why the wall thickness was as illustrated and it would appear that the cross-sectional thickness at various points was merely an arbitrary illustration.

When injection molded housings used for roller clamps are used, the sidewalls are generally in tension. While their upper and lower walls are exposed to a bending or compressive load as these tensioned walls support heavier weights, the wall thickness required for a good design is generally thinner for the side walls. Interestingly, none of the cited patents make any mention of thinner sidewalls. These patents include: Dabney et al., United States 3,802,463 of 1974; Becker, United States 4.340.201 of 1982; Becker, United States 4,475,709 of 1984; Karpisek, United States 4,869,721 in 1989; Forberg, United States 4,895,340 in 1990; Nakada, United States 5,190,079 of 1993 and Germany DT 28,55,572 of 1979.

A German company called Clinico produces a roller clamp for use in Germany similar to those found on! US market and with a weight-to-length ratio of 0.594 grams per cm. That clamp has about 10% less wall thickness than US clamps, yet weighs nearly 22% less on average. This weight difference is partly due to the type of pipe support incorporated in the clamp housing. The tube support is at the end of the clamp on the open or inlet end of the clamp. In the Clinical clamp, the tube support is much smaller than that of the US clamps and, furthermore, it is believed that the Clinical clamp is molded in a resin having a density lower than ABS.

Many commercially available clamp housings have an order length of 5.2 to 5.7 cm, are molded in ABS or polystyrene and have a weight-length ratio of 0.65 to 0.72 grams / cm. In return, a clamp according to the present invention can have a length of 5.6 cm and a weight-to-length ratio of 0.393 g / cm, measured in the same way, see description below.

It is therefore an object of the present invention to provide a pincer clamp that is easier to adjust, provides a firm grip on the pipe, whose performance is as good as currently commercially available clamps, one that includes a top wall that is thicker in cross section relative to the lower wall, the side walls which are thinner than the upper walls and preferably thinner than the lower wall, as well as one which is economical to manufacture.

Brief summary of the invention

The objects of the present invention are achieved by providing improved roller clamps for I.V. and in particular to an improved roller clamp for L.V. having unique advantages of substantially reduced manufacturing costs and the benefit of good performance by decreasing the effort required to adjust the pinch degree and improve the grip on the tube when the preferred housing size ratios and preferred relative sizes are as shown below .

Therefore, the preferred and practical approach of the present invention is to selectively specify the parts of the terminal housing section. An improvement according to the present invention is also to vary the section according to its position along the axis of the length of the housing. For example, the cross section in the area of the housing part designed to allow the insertion of the wheel has reduced strength requirements. In this area, the axis of the wheel does not forcibly rest on the surface of the opposite housing through a clamping action on the tube.

Also, there is usually little or, very often, no pinching action on the tube in this area. On the other hand, in the generally longer operating section of the housing, the so-called flow control area, the structure must anticipate greater efforts resulting from the interaction of the wheel, the housing and the clamped tube.

Therefore, taking into account all the factors discussed regarding similar stresses and deflections, a new and unique clamp housing design and an improved and new roller clamp for use with LV, assemblies. according to this invention it relates to the flow control part, a housing having:

to. an upper edge or upper wall of thick cross-section for housing.

b. a generally thin sidewall housing, as described.

c. a thick bottom wall (but not as thick as the top wall or top edge) of the housing.

Important is the relationship of the ratio of the cross-sectional thickness of the upper wall to the cross-sectional thickness of the side wall which, according to this invention, is in the order of 1, 3 to 4.0.

It should be noted that a thick cross-sectional top wall or edge as per (a) is used to minimize the degree of at least two types of bend or flex, as said deviation can be large and a thick cross-section will minimize it. . A second justification for point (a) above is to minimize the degree of local deviation or indentation of the housing surface right where the wheel axis will apply a relatively large local force.

(b) above is used to reduce the weight of the clamp housing material and to take advantage of the fact that there is relatively smaller deflection when under tension, and also the fact that thin walls of plastic are able to handle forces of relatively large voltage.

(c) above is used to stiffen (but no more than necessary) the lower wall to cope with bending and bending. Parameter (a) above is designed for the housing to be subjected to a relatively large force that causes bending and flexing, which force is applied by the wheel axis. Parameter (c) is designed to respond to a similar opposite force, even causing bending and bending, by this force it is more distributed as it is transmitted and applied by the clamped section of the soft plastic tube, and also because this surface is wider.

The greatest degree of flexion will take place when the wheel is positioned centrally between, and in this way at approximately equal distance from, the end supports of the housing. Therefore, the axially centered portion of the upper wall portion should accordingly be thicker than at one of the ends. However, this is not practical for injection molded parts as the "draft angle" of the part will not be present to allow for the removal of the newly molded part which, when traditionally injection molded, will shrink to grip firmly. to the core of the mold. A practical trade-off, however, is a design where the wall thickness of the housing has decreased near the small end of the housing, but is not decreased as much at the open end of the housing.

A gradual sliding or a plastic sliding can take place in the wheel or in the housing of the pincer clamp (normally it occurs for a greater extent in the clamped soft plastic pipe). To exist, the applied load must cause the part to exceed its elastic limit. If there is gradual creep or plastic creep, the direction of the part can change over time, without any external modification to the load and this will contribute to a time-varying flow rate of the fluid through the clamped tube. To avoid this unwanted phenomenon, the load should be limited, or the cross sections of the wall should be large enough (and consequently strong) to prevent exceeding the elastic limit or minimizing stress. On the other hand, the deviations must be anticipated as the deformation usually accompanies the stress. It is generally advisable to operate within the elastic limit.

Since the part described in this invention is made of plastic and preferably molded, for suitable injection molding, a "fill" or tunnel cross section is needed in the part to ensure that the molten plastic resin, normally at a temperature in the part. order from 350 ° F to 500 ° F, flow promptly so as to quickly and completely fill the cavity. If the tunnel or fill cross section is too small, the molten plastic will cool too quickly and freeze before there is a full fill. At lower temperatures, the viscosity of the injected plastic resin, which depends very much on the temperature, will be so high that only partial filling can be obtained. A tunnel that is too wide or a filling cross section will eliminate the problem of partial filling but will result in a part that uses an excessive (and expensive) amount of plastic resin and also unnecessarily increases the time (and therefore the cost of production) required to cool the injected plastic to a temperature that allows the formed part to be ejected from the mold cavity and is still able to hold its newly formed part (without winding etc.) A type of long stay in the mold increases the mold costs, usually in a linear fashion. That is, if the cycle time for producing the molded part by the molding machine is doubled, the molding cost is approximately doubled.

With respect to the molding operation and mold design, it is important for the present invention to suitably select and combine the size and location of the fill cross section or fill tunnel having the cross section suitably designed for providing both the strength needed when the part is subsequently gripped to perform its performance by being sufficiently stiff or strong in the manner of bending, flexing or pulling as well as providing a fully formed part. Thus, the preferred mold shape for suitable molding has an internal cavity and external core surfaces sized and positioned and useful for the independent requirements of having:

1) An adequately positioned and sized filling tunnel, or a filling cross section that is adequate but not large enough to unnecessarily increase the weight of the part and / or slow down the production cycle.

2) A cross section of tension or tension positioned and sized appropriately to provide the desired strength, stiffness or deflection desired, just but not too large.

3) Walls having an adequately thin cross section that meets other requirements of tensile strength or integrity of the part, or using the minimum amount of plastic in order to keep the total weight low and also facilitate a short cooling time for a time of faster production. The faster production time makes possible larger production volumes for a given molding and machine time interval, typically a doubling of the cross section increases the cooling time of the molded part and consequently the cost of molding by approximately 4 times.

As explained above, the upper wall of the housing is made thicker in order to have the necessary strength to obtain the necessary crack rigidity and to prevent excessive penetration (indentation) due to the local force of the wheel axis.

At the level of explanation, if the top wall or top rail were of a thickness less than the minimum value, the penetration of the wheel axle could be so large as to cause permanent deformation which would result in flow rates varying over time through the clamped tube. , due to the gradual sliding or plastic sliding that forms on the top rail / top wall of the housing. This gradual creep and plastic creep occur when the plastic used to mold the housing exceeds its elastic limit. Excessive penetration will also make it difficult for the operator to adjust the wheel position. This is because a deep penetrating axle will require relatively large force to advance the wheel to a new position. A plastic material with a high Rockwell hardness value will offer the best resistance to local penetration by the wheel axle, but the cost of the plastic material and printability will be negative compared to the contribution of a large hardness value.

According to the present invention, the top wall or rail of the housing, when used under load or in use, must withstand three types of deformation. The main task is to resist bending over the entire length of the housing while applying the desired clamping force on the roller axis, in addition, as mentioned, the top wall must resist excessive indentation of the roller axis in the surface room of the upper wall, i.e. the upper part of the groove in the trunnion. A third consideration is the resistance to external rotation of the upper wall which causes the wheel to “come out”, as will be discussed In each of these cases, it is important that the upper wall does not exceed the suitable elastic limit.

However, a thick-walled section generally requires a longer cooling time, a necessary step in injection molding.

This longer cooling time makes manufacturing costs higher due to the longer cycle time for the mold. All of the above is correct and true when the cooling is one-dimensional, such as the case of a part having a small thickness compared to its other dimensions.

However, where another dimension, perpendicular to the thickness dimension, is equivalent to the thickness, cooling is actually two-dimensional and consequently takes much less time. Therefore, to avoid excessive cooling times, the top of the thick wall should have a thickness comparable to its width. This gives a dual function of providing faster two-dimensional cooling, as well as providing a generous flow passage for the injected molten plastic by facilitating full filling of the adjacent thin sidewall portion of the housing.

Another aspect of the present invention is the relative ease with which the currently existing molds can be modified to obtain the benefits of the invention. One feature includes a relatively simple change of the injection mold cavity by bringing the two half cavities closer together to produce thinner side walls (which must resist tensile forces during use).

Another feature includes (1) displacement of the mold core relative to the cavity to (a) increase the thickness of the guide portion of the housing wheel shaft (to provide the necessary bending strength as well as resistance to penetration by the wheel axis), (b) locate the injection mold port so as to ensure good distribution of the molten plastic, (c) significantly reduce the wall thickness of the clamping surface of the housing (due to the its inherently wider cross-sectional wall surface), (d) introducing and retaining two dimensional heat transfers (cooling) where the wheel shaft guide in the housing has the thickest wall section (so as to keep low the production molding cycle time).

In the case of the housing, over a flow control range, the cross section of the housing according to the present invention is such that:

1. the side wall thickness is of the order from 1.2 to 2.2 times the wall thickness of the soft plastic tube (nominal) and not deformed (and not from 2.2 up to 3 times).

2. The upper wall thickness (wheel axis guide) is 2 to 3.3 times the tube wall Made of non-deformed soft plastic (this is in the typical range or thicker).

3. the lower wall thickness is preferably lower than that of the upper wall (unlike the fact that it is generally the same).

4. The thickness of the side wall is approximately 0.3 to 0.6 that of the thickness of the upper wall (as opposed to being generally the same). As noted above, the ratio of the cross-sectional thickness of the upper wall to the sectional thickness of the side wall is in the order of 1.3 to 4.0.

Further details are provided below. In this way, the objectives noted above are achieved.

The present invention has many other advantages and other objectives, which will become more clearly evident from the evaluation of the different forms in which this can be realized. Certain versions of said forms are shown in the accompanying drawings and forming part of the present description. These forms will now be described in detail in order to illustrate the general principles of the invention; but it is understood that said detailed description is not to be considered in a limiting sense.

Brief description of the drawings

Figure 1 is a perspective view of a typical prior art clamp;

Figure 2 is a sectional view of the current form of pinch clamps as used in the prior art;

Figure 3 is a sectional view of a clamp housing according to the present invention;

Figure 4 is a schematic view of the prior art mold; Figure 4A is a view similar to that of Figure 4 illustrating a mold according to the present invention; And

Figure 5 is a schematic view comparing a modification form (left side) of the new part to illustrate the effect of the same (the right side illustrates a traditional section for comparison);

Figure 6 is an enlarged schematic view of a preferred shape of the transition zone according to the present invention (right side) compared to another shape of transition area (left side) according to the present invention.

Detailed description of the present invention

Referring to Figures 1 and 2, a prior art parallel acting clamp 10 is illustrated for the purpose of explanation, although it is understood that the present invention may also be applied to an inclined ramp clamp. The clamp 10 comprises a housing 12, a roller in the form of a roller 14 having a wheel axis 16 received in grooves formed in the upper part of the housing. In this form of explanation, the housing comprises a bottom surface or bottom wall 17, the latter having a groove 18, a V-groove being shown for illustrative purposes, the space between the bottom of the roller and the receiving surface 17 a tube 20 through which fluid flows in a controlled manner based on the position of the roller.

Most roller clamps have a plain wheel whose width at its largest diameter is similar to half the circumference of the tube to be clamped, and the axles protruding from each side of the wheel. The housing channel usually has a bottom surface (the top surface of the bottom wall) having a width large enough to accommodate both the pinch tube and the pinch wheel width. The side walls of the housing are usually adjacent to the bottom channel or bottom wall and form the bottom side walls which act to guide the tube to be pinched to position between the wheel and the pinch surfaces of the housing. Away from the housing channel or bottom wall of the housing and in front of the wheel axles, the side walls of the housing include a pivot pin section for receiving and guiding the axles.

The upper surface of the inner trunnion wall typically slides roughly parallel (more for a parallel action clamp, less for a sloped ramp clamp) to the lower housing clamp wall (lower channel or lower wall ), and is interrupted to form a slot through which the upper part of the wheel protrudes. The result is that two generally distinct parts of the side walls and the housing are normally found; the larger lower portion, as well as a smaller upper portion containing the trunnions and lateral end walls of the trunnion. The trunnions have a lateral end wall of the trunnion opposite the outer end of the wheel axle and a distance (height) to accommodate just the diameter of the wheel axle. A lower and upper portion of the pivot pin portion, each normally has an amplitude (width) compared to the projection length of the wheel axle.

The inner upper surface of the pivot pin often slides more or less axially to the clamping surface of the housing or lower wall and, when the tube is clamped, supports the local compressive load applied by the axis of the protruding roller. To distribute this localized axle load, the wheel axle is shaped like a cylinder, having a uniform diameter throughout its protrusion length. This concentrated support load would tend to become even more concentrated if the projecting axis was not of uniform diameter.

Accordingly, the upper surface of the inner trunnion side is required to have a generally acute 90 ° angle where it joins the inner face of the end wall of the vertical trunnion side, which right angle generates a stress concentration during tube clamping. Another stress concentration zone is located where the lower portion of the inner side end wall of the trunnion joins the inner portion of the lower end wall. Due to the need to maintain a uniform diameter of the protruding wheel axle, a radius or curve or concave fitting cannot be positioned where the inner top surface of the trunnion joins the vertical portion of the lateral end wall of the pin. of articulation.

The tube material is normally plasticized polyvinyl chloride of the type used to date in I.V. groups, although other medical grade plastic tubes may also be used. Typically, said tubes have an internal diameter from about 2.3 mm to 3.0 mm and an external diameter from about 3.5 mm to 4.5 mm and a Shore D hardness that exceeds about 68 and is usually below 80. A tube of the type described can also be used with the clamp of the present invention. The groove 18 is a groove with variable cross-section along its length to vary the area of the pipe in section through which the fluid can flow.

For this parallel action clamp illustration, the thumbwheel functions to fully pinch the side walls of the tube for the reasons discussed and the variable cross section groove serves to vary the open portion of the tube to adjust the fluid flow rate. In the illustrated form, the flow control zone extends approximately from zone 22 to zone 23, the lower surface comprising an element 25 raised perpendicular to the extreme end of the clamp which acts as a lock to ensure complete closure, even if the the closure zone is immediately upstream of the element 25. Indeed, there is no flow with the roller positioned in the zone on the end of the groove and before the swelling. In this form, the path of the wheel along its path is generally close, but not necessarily precisely, to a parallel relationship on the flow control zone by providing shaft grooves on the outer periphery, as illustrated, which they are broadly in a relationship almost, or exactly, parallel to the surface 17 in the flow control zone. The path of the wheel on element 25 is non-parallel, but there is no flow control in this area, as discussed. Typically, the opening between the bottom of the wheel and the surface 17 is generally less than and not greater than twice the nominal wall thickness of the tube 20 used with the clamp. Since hoses of very different sizes can be used, the opening between the surface 17 and the bottom of the wheel in the flow control zone can vary from one type of clamp that uses a hose of one size to another to maintain the pinch. total on each side of the pipeline. There are also clamp structures, not shown, in which only one side of the pipeline is clamped to be totally closed since, in such a design, the flow port is closed to one side. Also shown, on the broad end of the housing, away from the perpendicular element 25 is the tube support structure 26.

Referring to Figure 2, it can be seen that the housing is substantially uniform in section from about 0.3 to 0.6 times the outer diameter of the tube, typically between 1.2 mm and 1.7 mm, the length of the housing being between 20 mm and about 55 mm. The uniform cross section can be seen from the cross section of the lower wall 17a which forms the surface 17 and the wall 18a in the part of the lower groove 18. The lower side walls 27, 28 of the housing are essentially the same cross-sectional thickness as the wall. lower 17a and the groove wall 18a. There is a transition zone 29 between the lower walls 27 and 28 which include a portion having a cross section of the walls 27 and 28 and trunnion wall portions 31 and 32 which form the lateral end walls of the trunnion grooves. articulation in which the axis 16 of the wheel moves. The transition zone 29 serves to better distribute the stress between the trunnion wall and the walls 27 and 28 under the trunnion walls. This transition zone comprises and forms the lower shoulders 31a and 32a of the grooves on which the axis 16 of the wheel moves. Above the shoulders 31a and 32a are the upper edges or the upper walls 36 and 37 of the housing, the latter forming the upper part of the trunnion groove. As can be seen in the prior art clamps, these upper edges or upper walls have a cross-sectional thickness practically equal to that of the side walls 27 and 28. Thus, the upper wall 36 and 37, the lower side walls 27 and 28, the walls 31 and 32 of the pivot pin and the lower wall 17a, as well as the groove 18a, in principle, all have the same cross-sectional dimension.

As can be seen in Figure 2, the pivot end side walls 31 and 32, which are effectively part of the side walls, but smaller in vertical length than the total side wall, are baseline parallel to the walls 27 and 28 lower side. It should be noted, however, that the lateral end walls of the pivot pin are generally parallel and spaced outwardly from the lower lateral walls 27 and 29 so as to accommodate the axis of the roller, the axis being inside the walls lateral ends 31 and 32.

It will also be seen that the junction between the lateral end walls 31 and 32 and the underside of the upper walls 36 and 37 which form the upper trunnion wall are in an acute angle base line, i.e., at right angles, as is the case with the junction between the side end walls 31 and 32 and the lower pivot walls 31a and 32a respectively. These acute angles, illustrated as right angles within the side end walls and grooves of the upper and lower trunnion pin form stress concentration zones and generally cannot be curved or arched to reduce the stresses that tend to occur, in these joints since the wheel axis has a cylindrical shape and should travel in a true linear fashion axially along the clamp body. The use of a variable cross-section or tapered wheel axle is not practical as the need for maximum contact that cannot readily be achieved with a tapered wheel axle which generally follows the contour of any level or radius on the corners between the upper trunnion guide, the lateral trunnion end walls and the lower trunnion guide and the lateral trunnion end walls immediately above the lower trunnion guide. However, in the case of transition zones 29, located outside the lateral end walls and the lower end walls, a transition zone can be provided, as illustrated, to reduce the stress concentration, since it does not interfere with the tightening operation and tends to relieve stresses in what would normally be a relatively high stress concentration zone.

A wall subjected to tension or bending and having a sudden angle or change of direction will have a stress concentration zone on the corner making that part exposed to a greater stress than the adjacent part and thus, closer to structural failure. Where it is not practical to use a concave radius, bend or fillet, thicker walls have been used in the joints or splices of the walls to provide an area of greater strength. This, however, must be minimized as it also tends to increase the weight of the clamp body.

Referring to Figure 3, a preferred form of roller clamp of the present invention is illustrated, again in the form of a parallel action clamp having the parts, housing, V-groove, roller tubing, etc., already described . For purposes of the description, however, only the housing 50 will be discussed. The clamp housing cross section can be divided into three zones, each to meet individual and special requirements according to the present invention so as to reduce weight while maintaining performance, particularly in terms of ease of adjustment and greater grip on the pipeline, largely due to the fact that the dimensional ratios shown above and the ranges and various ratios described above are used.

The upper zone comprising the zone comprising the upper edges or upper walls 51 and 52, the portion above the trunnion shoulders 53 and 54 and above the underside of the trunnion upper walls 51a and 52a and above the walls 61 and 62. The top walls 51 and 52 include side portions 51b and 52b which extend slightly below the underside of the upper pivot walls 51a and 52a and which also form part of the top wall and the top zone. The upper zone should be able to withstand a notch, a bending load (arcing) as well as resist an outward rotational movement following the clamping of the tube and imposed by a wheel axis whose position varies over the length of the housing. Therefore, the top wall has a cross section that is at least 20% thicker than the side walls. The articulation pin of the wheel rests against the underlying part 51a and 52a of the upper edges or upper walls during the tightening operation. The undersides should be able to withstand the penetration of the wheel axle or pivot pin as a consequence of the tightening and imposing action of the wheel axle which has a relatively small radius of curvature. This localized penetration typically is in the form of local indentation by the wheel axle. A less obvious requirement is that during molding, a flow passage is provided for injecting the molten plastic to flow through a large portion of, or, ideally, the entire axial length of the part without being exposed to a large area. of contact, which area of contact causes cooling and, if too large, a consequent premature solidification. A lateral flow is also required to form the side walls 57 and 58. In addition, to facilitate flow, the cross sections of the upper edges 51 and 52 have an almost circular cross section, as illustrated. The second zone is the lateral zone, which broadly includes the lower side walls 57 and 58 and the wall part comprising the shoulders 53 and 54 forming the horizontally arranged lower walls of the trunnion grooves and the walls of the groove or cross sections 61 and 62 of guide wall of the axis of the upper roller extending under the lower side walls 51b and 52b of the upper wall 51 and 52. The transition zone is that part of the lateral zone between the lower side walls 57 and 58 and the lateral end walls 61 and 62 of the pivot pin, correspond to the curved transition zones 29, as described and explained above. The transition zone according to the present invention is positioned on the outside of the housing, as illustrated, becomes progressively thicker as soon as the inside of the outer face of the lateral end walls 61 and 62 reaches a maximum in the intersection of the side walls. lateral ends and in the adjacent lower lateral walls 57, 58, and progressively decreases to the cross section of the lower lateral walls 57 and 58.

As can be seen in the dotted lines on the right side of Figure 3, for illustrative purposes, it being understood that the same is true for the left side, the section 61a of the side wall 61 under the lower pivot pin 53 is substantially the same thickness. in cross section of that of the side wall 61. The section 57a of the lower side wall 56 joins and is integral with the section 61a, the section 57a being substantially of the same thickness and cross section as the side wall 57. According to the present invention, the outer concave fitting or spoke 29 extends the length of the trunnion groove and represents only a relatively small amount of weight since the outer radius of the concave fitting preferably does not exceed twice the wall thickness 57. This is in contrast to a portion of the prior art roller clamps in which there is no al with a radius, but the transition zone is square.

This lateral zone must have sufficient strength to adequately withstand the tensile forces to which it is exposed during use, resulting from the clamping action generated inside the clamp housing. The lateral zone must have a lower section, but nevertheless, sufficient flow so that the injected molded plastic can flow the vertical distance to adequately fill the lateral zone part of the housing without premature cooling and thus solidifying before fill this area. Depending on the position of the "ports" that first admit the molten plastic into the cavity, the side must also have a flow cross section to fill an adjacent area not served by this port.

It should be noted that the surface area of the side end walls 61 and 62 of the pivot pin is lower than the surface area of the bottom bottom side walls 57 and 58. The cross-sectional thickness of the lateral end walls of the pivot pin could be made less than the cross-section of the lower side walls and thereby reduce the overall weight of the clamp. Conversely, the lower side walls could be thinner in cross section than the side end walls of the trunnion.

According to the present invention, the cross-sectional thickness of the lateral end walls of the trunnion is approximately equal to that of the lower side walls and is preferably between 0.8 and 1.2 times the cross-sectional thickness of the lower side walls, provided the other dimensional ratios discussed here are also used. In a preferred form of the invention, the cross section of the side end walls 61 and 62 of the trunnion is essentially that of the lower side walls 57 and 58, again provided the other dimensional ratios discussed here are used. Except for the additions of materials that reduce the two stresses (transition 29), the wall thickness of the walls (61, 62) of the vertical lateral ends of the trunnion and that of the lower walls (57, 58), should have, for minimum weight, equal thickness, as each bears the same tensile load. The thickness of the cross section of the upper wall is preferably between 1, 3 and 4.0 times the thickness of the cross section of the side walls.

The lower zone which in principle includes the lower wall 60 and the part of the wall formed by the groove 65 should be able to withstand the bending loads similar to the upper zone. The bottom wall has a cross-sectional thickness that is greater than the side walls. It is also the case that the end of the bottom wall beyond the closed position and the locking position is slightly tapered. This taper is well beyond the flow control region and is in the baseline between the roll path limit and the extreme end of the clamp body.

The bending load of the lower zone is similar to that of the upper zone, however, as the bending load applied to the lower zone is applied through the larger diameter of the roller which, in turn, presses through a double layer of plastic tubing, the need to withstand the penetration load is greatly reduced. Also, since the cross-sectional zone of the lower zone has a larger cross-sectional width (left to right) than the combined cross-sectional widths of the upper left and right zones, the cross-sectional thickness of the lower zone can be smaller to obtain the zone of cross-sectional area required to withstand the required bending load.

Thus, in an ideal form, the top wall is at least 30% thicker than the side walls, the trunnion end side walls and the lower end walls are substantially of equal cross-sectional thickness, and the bottom wall is thicker in cross section than the lower side walls and upper side end walls, but thinner in cross section than the upper wall cross section.

Still other loads and requirements should also be met. However, these are normally met (with a reasonable safety margin) if the above-mentioned requirements are adequately met.

As already pointed out, the housing regions of the upper zone, according to the present invention, are larger in cross-sectional dimension than the regions of both the lateral regions and the regions of the lower zone. The lateral zone regions are thinner in cross-sectional dimension than the upper zone regions and the lower zone regions. The regions of the lower zone are thicker in cross section than the regions of the lateral zone but of lower cross-sectional thickness than the regions of the upper zone. In a preferred form, the end walls 61 and 62 of the pivot grooves, which form part of the lateral zone, have a cross section approximately equal to that of the lateral walls 57 and 58, it being understood that the walls 57 and 58 do not they must be of the same cross section but should have a smaller cross section than the bottom wall 60.

These requirements can be met with housing dimensions expressed in various relations in the approximate order as shown below:

(1) side wall thickness from 1.1 to 2.3 times the wall thickness of the non-deformed soft plastic pipe (nominal);

(2) upper wall thickness of 2.5 to 4.5 times the wall thickness of non-deformed soft plastic tube;

(3) bottom wall thickness from 0.4 to 1.0 times the top wall thickness;

(4) side wall thickness from 0.3 to 0.8 that of the top wall thickness;

(5) a clamp housing weight-to-length ratio of 0.48 g per centimeter or less, preferably in the order of 0.48 to 0.2 and optimally in the order of 0.3 to 0.4 the weight (grams) -length (centimeters) ratio of the clamp housing, and a resistor capable of clamping completely closing a PVC pipe with an internal diameter of 2.28 to 3.18 mm and an external diameter of 3, 0 to 6 mm having a Shore D hardness of the order of 65 to 90 and an uncompressed wall thickness of the order of 0.5 to 1.0 mm.

In terms of normalized parameters, where the weight-to-length ratio is also divided by the specific gravity of the plastic, the above values for ABS are modified as follows:

weight-to-length ratio for ABS:

general range: 0.48 to 0.2 g / cm

preferred range: 0.3 to 0.4 g / cm

weight-to-length ratio for all plastics:

general range: 0.39 to 0.17 g / cm

preferred range: 0.25 to 0.33 g / cm.

(6) a lower and upper side wall thickness of less than two thirds of the wall thickness in the guide section of the upper roller in that region of the housing forming the flow control region, as described above.

(7) a lower and upper side wall thickness less than the lower wall thickness;

(8) an upper and lower sidewall thickness of less than one quarter of the width of the major diameter of the roller;

(9) an upper and lower side wall thickness of less than two and a half times the wall thickness of the (pinched) tube when the tube is in a non-deformed state;

(10) a ratio of thickness, of the lower and upper side wall to the upper wall thickness of less than 0.7 over the length of the clamp housing where flow through the pipe is controlled;

(11) a top wall dimensioned so that its thickness relative to the width dimension, in cross section, is on the order of 0.5 to 1.0;

(12) a bottom wall of 1.2 to 2.5 times the uncompressed pipe wall thickness, e

(13) a wheel width of 0.175 to 0.270 inches.

The clamp housing may also have an upper wall roller guide section whose cross section has a width-to-height ratio of less than 2.0.

From the above, it is evident that the present invention encompasses a clamp housing whose lower lateral and / or upper wall thickness is reduced in the non-control region (inlet section and beyond total closure) when said thickness (thicknesses) of wall is compared with the thickness of a corresponding part in the region where the tube can be pinched to achieve flow control or flow closure.

From the foregoing description it is evident that the lateral zone regions represent a substantial part of the clamp structure and therefore the reduction in the cross-sectional dimension of the lateral wall regions, for example, the walls 57 and 58 and the walls 61 and 62 of the pin of articulation act to reduce the weight of the clamp. The cross-sectional dimension of each of 57, 58, 61 and 62 need not necessarily be the same, but each should be less than the cross-sectional dimension of the lower wall 60. In a preferred form, each of 57, 58 and 61 and 62 has the same sectional dimension as described. According to the present invention, the walls of the V-groove 65 may have a smaller cross-sectional dimension than that of the lower wall 60 and smaller than the regions of the upper zone, and in a preferred form they are smaller than the section of the lower wall and by about the same cross-sectional dimension as walls 57 and 58.

Another aspect of the present invention is the ability to improve an existing mold and realize the present invention for a mold that produces housings for an olilo-type collet clamp which can now be modified to exhibit many of the desirable features of the present invention. . The approach described is applicable to either an inclined roller clamp or a parallel acting clamp.

The cross sections of the clamp housing typical of the prior art are illustrated in Figure 2. Figure 3 illustrates a preferred embodiment in the ranges described for this invention. It should be noted that by comparing the structure of Figure 2 with that of Figure 3, in the structure of the present invention, the upper guide surface of the roller (51, 52) is widened in the cross section, the lower clamping surface 60 remains essentially unchanged or slightly thinner and the thickness of the lower side walls (57, 58) and the upper part of the upper side ends walls (61, 62) is significantly decreased and the upper wall has the largest cross section as already described. Figure 5 is an illustration that facilitates comparison.

The lower clamping surface (walls adjacent to the V-groove groove) can and should be made thinner than the upper one (upper wall). This is due to the fact that its width is greater than that of the guide surface of the upper wheel axle. Both the upper and lower surfaces are subjected to approximately the same bending forces. Flexural strength is, when other dimensions remain similar, nominally proportional to the cross-sectional area. Therefore, a thinner section is preferred for the lower clamping surface for a balanced structural design.

The guiding surface of the upper roller has, due to the opening to allow the movement of the roller, a smaller width than the lower surface and, to ensure adequate resistance to bending, resistance to external rotation and also resistance to Notched by the delta wheel axis, this thickness of the upper guide of the wheel and the cross section should be greater.

The cross-sectional thickness of the side wall is greatly decreased by using a thin wall. This is due to the fact that the primary load of the side wall when the clamp is used is traction. For ABS, polystyrene, and other commonly used thermoplastics such as SAN, rigid acetals and rigid nylons, the tensile strength is relatively large and their elongation modulus is relatively small. Therefore, substantial weight savings can be achieved by designing properly for the application.

In production, almost all roller clamp designs of infusion sets are suitable for injection molding. Their internal and external surfaces are tapered (have a draft) to facilitate easy ejection from the mold, they can normally be made with simple two-plate molds, etc. In the case of a parallel acting clamp, this draft provides a small angle on what is sometimes called the clamping surface; however, this small angle (for example, in the order of half a degree) plays no role in controlling the flow as already discussed. The intended function; ease of use, ease of adjustment, good grip on the tube, etc. are all determined by the design of the mold core. It is the core that forms the internal configuration and dimensions of the housing. Core size, shape, dimensional tolerances, etc. determine the clamping performance of the molded part. Therefore, it seems likely that, for almost all roller clamps, the function of the designed part is centered on the core and, the cavity shape, dimensions, etc. are normally derived by simply specifying a uniform wall thickness for the part which is typically in the order of 0.045 to 0.060 inches.

Otherwise, according to the present invention, the key elements constituting the improvement are mainly concentrated on the design of the cavity and very little, if at all, on the design of the core. To convert an existing mold, the mating surfaces of the half cavities are lightly scraped, as has been and will be discussed further, and then joined. The cavity is also slightly offset from the core. The core is essentially left unchanged, but the door (s) is / are repositioned to allow for feeding of the plastic injected into the guide surface of the wheel, now made thicker. A typical housing cavity in a mold is constructed in the manner of a shell valve and often the halves 70 and 75 are approximately or exactly symmetrical, see Figure 4. As is known, a mold core is also used which is placed in the cavity 76 in a stamping operation. To modify a design of a prior art mold used to produce one of the prior art clamps, two relatively simple steps are required to produce a modified mold for the production of improved clamps according to the present invention.

1. The mating halves of the cavity should be smoothed to a relatively small extent to produce a new housing wall thickness, on the order of 40% to 80% of the original wall thickness. In Figure 4A this is illustrated by roughing the surfaces 70A and 70B and 75A and 75B. If the wall thickness of the part already had a typically modest taper (slightly thinner on the small end of the housing and typically slightly larger on the larger end of the housing, then that taper should remain. A typical draft should have the wall thickness varying by a few thousandths of an inch for each inch of length. A draft is used to facilitate the removal of the part from the mold). This slight taper can usually be maintained by stripping (trimming) an identical depth of material along the contact surface of the half cavity. 2. With the half cavities separated from each other, as can be seen in Figure 4A, a small amount of material can be removed from that part of the mold surface that forms the outside of the molded housing wheel guide. In Figure 4A these surfaces are identified as 70C and 75C. Since this is done only on this special area, certain important dimensions of the molded part, such as the critical shape formed by the mold core, are not altered. The effect of the above is to shift the halves of the half cavities closest to each other by an amount equal to 25% to 60% of the side wall thickness of the original printed part. The vertical displacement of the core is typically in the order of 20% to 70% of the original top wall thickness.

These two steps are relatively simple to perform and can be performed quickly and at low cost. By following this approach, there is no great need to modify the usually more expensive core part of the mold. The already cheaper part of the cavity of the mold only needs to be subjected to a relatively minor procedure. All of this can be countered by the much higher cost of building a new multi-cavity mold.

As previously mentioned, one of the potential problems with prior art roller clamps is that they "run out". Referring to Figure 6, a partial view of a clamp housing 100 for a parallel acting clamp comprising a section 100a on the left side and a section 100b on the right side in comparison level is shown. As described, the housing comprises upper walls or rails 102a and 102b, side walls 104a and 104b, the latter comprising lower wall sections 104c and 104d positioned below the side wall portions 104e and 104f, the latter forming pivot pins which receive the wheel axle, not shown. Positioned between the side walls 104a and 104b and under the upper walls 102a and 102b is the lower wall 105, with a V-shaped groove 107 therein, as described above. Also partially illustrated is a form of tube support 109, similar in function and position to 26, but in a basic line composed of curved fingers 109a and 109b, open at their ends for the passage of the tube.

With a tube assembled in the housing, it rests on the lower wall, while the roller axis is received in the pivot pins 104 and 104f. The roller is pushed down by the axis which rests against the upper walls 110a and 110b of the pivot pin. It can thus be seen that the force acting on the lower wall 105 is not aligned with the upper force on the upper walls 110a and 110b of the trunnion with the result that a rotational moment is created indicated by the arrows 115a and 115b. This rotational moment tends to pull the axle out of the trunnion if the top wall or top rail is unable to withstand this force. A rigid top rail will resist overflow, but this resistance will depend on the cross-sectional thickness of the top rail and the modulus of the material used for the housing. The use of side walls that are thinner than the top walls also tends to promote ease of adjustment of the wheel while the wheel grips the tube firmly due to the relative stiffness of the top wall.

It can be shown with a simplified model that the rotational deviation is proportional to the third power of the upper wall thickness. Consequently, large benefits can be expected by modestly increasing the thickness of the top wall or rail. Also, since the flow rate through the pinch tube orifice is proportional to the second or third power of the hydraulic beam, a change in the pinch opening as a result of the deflection can be increased to the fifth power as reflected in the new flow rate.

As can be seen in Figure 6, the left lateral structure 100a comprises a transition zone 125 between the lower part 104c of the lateral wall 104a and the lower wall 125a of the pivot pin. According to the present invention, the side wall is reasonably uniform in cross-sectional thickness except for the transition zone 125. As illustrated, the transition zone 125 has a width, as measured from any point on the inner surface 128 to the nearest point on the outer surface 129 that is not greater than substantially 150% of the side wall cross section except in the transition zone. .

It should be noted that the angle 130 formed on the inner surface between the inner face of the lower side wall 104c and the lower wall 125a represents a stress concentration point. While such a stress concentration point can be tolerated if the transition zone is sized as discussed, the stress concentration point can be eliminated as illustrated in the left side wall 100b where the transition zone 130 is essentially the same thickness. in cross section of the adjacent sections and the side wall, i.e., the cross section of the transition zone, measured as described is less than 150% of the cross section of the adjacent side wall and is preferably of the same size as the side wall.

Another cost comparison should be the manufacturing cost of the recently modified part when compared to the cost of the original part. Weight savings of 30%, for example, will typically translate into overall manufacturing cost savings of the order of 20%. The reason is due to the fact that the cost of the raw material is a large fraction of the total production cost. Significant additional savings in production cost will also be achieved because the new project will speed up the production cycle. This is due to the fact that, for the part, due to certain parts of the wall which are generally thinner, and also because the part made thicker is subjected to a two-dimensional cooling and not to a one-dimensional cooling, a time of bottom cooling.

The following data represent a comparison of the clamp of the present invention with respect to the clamps available on the market, identified by source.

These data demonstrate the considerable difference in the weight-length ratio of the different clamps and the fact that the clamp having the lowest weight-to-length ratio, unlike that of the present invention, has about twice the weight-length ratio of the clamp of the present invention. The clamp of the present invention also has a significantly lower weight-to-length ratio than the clinical clamp (0.594 g / cm and apparently made of a less dense material).

All the advantages of the new project will be maintained as long as the door {-door) is (/ are) properly positioned (s). A logical position should be that the plastic is symmetrically injected into the cavity on one end of the guide surface of the housing wheel axis (end port). For this position, the flow passage of the injected plastic has an almost ideal shape, that of an approximately circular and not too small cross section. This flow tunnel can then be "fed" to the thinner side walls and remaining portions of the housing cavity as may be necessary. An alternate location for the door (s) would have the plastic entering at one end of the lower clamping surface of the housing (can also be considered an end door). Here too, the flow section is large and has excellent access to the thin side walls. To ensure that a part has symmetrical properties, normally two doors on opposite sides of the cavity are used or a wider door positioned in the center. Said central position, as a rule, being in the center of the lower clamping surface.

Essentially, the lower cost improvement requires a relatively modest modification in the cavity by roughing the contact surface of the two halves and slightly widening the wheel axle surface. Also, a slight displacement of the core relative to the cavity in the order of 20% to 70% of the original top wall thickness in one direction so as to make the top wall thicker and the bottom wall thinner. The potential economic benefits of the mold modification approach, as opposed to building new molds, to reflect an improved design, are relatively large. This is due to the fact that companies that can derive immediate benefits already have molds for a substantial production and have substantial market shares. The modification of their molds can be done with very modest costs and with very modest downtime required for conversion.

It should be understood that the present invention is not limited to the detailed descriptions set forth herein which detail preferred embodiments of the present invention. The modifications thereto will be apparent to those skilled in the art on the basis of the detailed description above, but said modifications based on this description cannot be considered as not falling within the spirit and scope of the present invention as reported in the attached claims.

Claims (41)

CLAIMS 1. Plastic roller type pinch clamp assembly for use in an I.V. comprising: a plastic injection molded housing comprising upper and lower side walls, an upper wall, a lower wall between said side walls and comprising a lower surface, an upper roller guide section and roller guides provided therein, said upper roller guide section including an upper roller guide surface and a lower roller guide surface, guide side end walls of the roller forming said upper side walls and extending under said lower wall towards said lower side walls, a roller wheel having a roller axis mounted for movement generally along the axis of said housing, said roller axis being received in said roller guides, said roller having such a dimension as to leave a clamping space of the tube between the lower surface of said housing and the opposite section of said roller, a deformable plastic tube received in said housing and comprising a part positioned in the space and between said lower surface and said roller, said lower wall having a greater cross-sectional thickness than said side walls, said side walls having a lower cross-sectional thickness than that of the upper wall, e said upper wall having a greater cross-sectional thickness than the lower wall. 2. Plastic roller-type clamp assembly as set forth in claim 1, wherein said upper and lower side walls have a lower cross-sectional thickness than the upper wall, and said upper lateral walls having a cross-sectional thickness which is between 0.8 and 1.2 times that of said lower lateral walls. 3. Plastic roller-type clamp assembly as set forth in claim 2, where each of said upper and lower side walls has a lower cross-sectional thickness than that of the lower wall. 4. Plastic roller-type clamp assembly as set forth in claim 2, where each of said lower and upper side walls has substantially the same cross-sectional thickness. 5. Plastic roller clamp assembly as set forth in claim 1, where each of said upper side walls forms the lateral end walls of said upper guide section of the roller, said lateral end walls being joined with said lower lateral walls, said upper side walls and said lower side walls having a cross-sectional thickness which is less than the cross-sectional thickness of said upper wall, a transition zone on the outside of said housing at the intersection of each of said lower side wall and each of said upper side wall and extending at least to the axial length of said upper section of the roller guide, said transition zone comprising a surface internal and external surface, e said transition zone being a curved surface whose cross-sectional thickness as measured from the inner surface to the closest point of the outer surface is not greater than 150% of the side wall thickness except in said transition zone. 6. Plastic roller gripper clamp assembly as set forth in claim 1, where each of said upper lateral walls forms the lateral end walls of said upper guide section of the roller, said lateral end walls being joined to said lower lateral walls, a transition zone on the outside of said housing at the intersection between each of said lower side wall and each of said upper side wall, said transition zone being a curved surface whose thickness in cross section progressively increases from said upper side wall to a maximum and progressively decreases from said maximum to the cross section of said lower side, the cross section of said upper side wall, except in the transition zone being between 0.8 and 1.2 times the cross section of the lower side wall excluded in said transition zone, and said upper wall being between 1, 3 and 4, 0 times the cross-sectional thickness of the lower side wall. 7. Plastic roller-type clamp assembly as set forth in claim 6, where said clamp is a parallel action clamp and further comprises means for varying the gap formed during use and therefore for varying the flow rate. 8. Plastic roller gripper clamp assembly as set forth in claim 1, where each of said upper side walls forms the lateral end walls of said upper guide section of the roller, said end side walls being joined to said lower side walls, a transition zone on the outside of said housing at the intersection between each of said lower side walls and each of said upper side walls, said transition zone being a curved surface whose thickness in cross section progressively increases from said upper side wall to a maximum and progressively decreases from said maximum to the cross section of said lower side, said lower wall having a cross-sectional thickness at least substantially equal to the cross-sectional thickness of said upper side wall, and said upper wall cross-sectional thickness exceeding the cross-sectional thickness of one of said upper side wall and said lower side wall by a ratio of 1.3 to 4.0. 9. Plastic roller-type clamp assembly as set forth in claim 1 wherein said clamp is a parallel action clamp and further comprises means for varying the gap formed during use and therefore for varying the flow rate. 10. Plastic roller clamp assembly as set forth in claim 1, wherein said housing, if made of ABS, has a weight-to-length ratio between 0.2 and 0.48 g / cm or a normalized weight ratio -length between 0.17 and 0.39 and a resistance capable of clamping completely closing a polyvinyl chloride tube having an internal diameter between 2.18 mm and 3.18 mm and an external diameter between 3.0 and 6, 0 mm and having a Shore D hardness in the order of 65 to 90. 11. Plastic roller-type clamp assembly as set forth in claim 3, where said clamp is a parallel action clamp and further comprises means for varying the gap formed during use and therefore for varying the flow rate. 12. Plastic roller-type clamp assembly as set forth in claim 3, where said side walls are between 1.1 and 2.3 times the thickness of the walls of said plastic pipe. 13. Plastic roller-type clamp assembly as set forth in claim 6 where said side walls are between 1.1 and 2.3 times the thickness of the walls of said plastic pipe. 14. Plastic roller-type clamp assembly as set forth in claim 1 wherein said clamp is a parallel action clamp and further comprises means for varying the gap formed during use and therefore for varying the flow rate. 15. Plastic roller clamp assembly as set forth in claim 1, wherein said clamp clamp comprises a flow control region, and the cross section of the upper and lower side walls in said flow control region is less than two thirds of the thickness of the upper wall. 16. Plastic roller-type clamp assembly as set forth in claim 1, where the thickness of each of said side walls is less than the thickness of said lower wall. 17. Plastic roller clamp assembly as set forth in claim 16, where said housing comprises a guide section of the upper axis of the roller and where said side wall thickness is less than two thirds of the thickness of one of said sections upper guide of the axis of the wheel and of said lower wall. 18. Plastic roller-type clamp assembly as set forth in claim 10, where said clamp is a parallel action clamp and further comprises means for varying the gap formed during use and therefore for varying the flow rate. 19. Plastic roller clamp clamp assembly for use in an I.V. as set forth in claim 1 wherein said clamp assembly has a roller path range over which flow through said tube can be adjusted, said roller roller traveling in parallel relationship with said lower surface for the range of the path of the roller in which flow through said tube can be adjusted, and said roller-type clamp assembly further comprises means for varying the gap formed during use and therefore for varying the flow rate. 20. Plastic roller clamp clamp assembly for using an I.V. as reported in claim 19 where said opening is of a dimension less than double the thickness of the undeformed wall of said tube. 21. Plastic roller clamp clamp assembly as set forth in claim 1, said clamp having a non-flow control region between an inlet section of the housing and a closed position, and the thickness of the upper, lateral and lower wall having a reduced thickness in the non-flow control region with respect to the corresponding part where the tube is pinched to obtain flow control or flow closure. 22. Plastic roller clamp clamp assembly as set forth in claim 1, where the guide section of the upper wall wheel has a cross section whose width-to-height ratio is less than 2.0. 23. Plastic roller clamp clamp assembly for use in an I.V. comprising: a plastic injection molded housing comprising spaced sidewalls, a top wall, a bottom wall including a bottom surface, pivot pins in each side wall under said top wall, a roller wheel having a substantially cylindrical roller axis mounted for movement generally along the axis of said housing, said roller axis being received in said pivot pins, said roller having such a dimension as to leave a clamping space of the tube between the lower surface of said housing and the opposite section, in front, of said roller, a deformable plastic tube received in said housing and comprising a portion positioned in the space and between said lower surface and said roller, said side walls comprising a lower and upper side wall with a transition zone between them, the cross-sectional thickness of said side walls being thinner than the upper wall and said lower wall, the cross-sectional thickness of said upper wall being greater than said lower wall, and said housing if made of ABS, having a weight-to-length ratio of the order from 0.2 to 0.48 g / cm or a normalized weight-length ratio between 0.17 and 0.39. 24. Plastic roller-type clamp assembly as set forth in claim 23 where said clamp is a parallel action clamp and further comprises means for varying the gap formed during use and therefore for varying the flow rate. 25. Plastic roller clamp group for use in a group I.V. comprising: a plastic injection molded housing comprising spaced side walls, an upper wall, a lower wall including a lower surface, and pivots spaced above said lower wall for receiving the axles of a roller wheel, a roller wheel having an axis wheel mounted for movement generally along the axis of said housing, said wheel axis being received in and traveling in said pivot pins, said roller having such a dimension as to leave a clamping space of the tube between the lower surface of said housing and the opposite section, in front, of said roller, deformable plastic tube received in said housing and comprising a portion positioned in the space and between said lower surface and said roller, said pivot pins comprising a side end wall forming the upper side walls of said housing, said side wall comprising lower side walls under said upper side walls, a transition zone between said upper and lower side walls, the ratio of the cross-sectional thickness of the side wall to the cross-sectional thickness of said upper and lower side walls except in said transition zone being in the order from 1, 3 to 4.0, and said upper side walls having a cross-sectional thickness between 0.8 and 1.2 times that of the lower side walls. 26. Plastic roller-type clamp assembly as set forth in claim 25, where said clamp is a parallel action clamp and further comprises means for varying the gap formed during use and therefore for varying the flow rate. 27. Plastic Roller Clamp Clamp Assembly for use in an I.V. comprising: a plastic injection molded housing comprising spaced apart side walls, an upper wall, a lower wall comprising a lower surface, an upper roller guide section and roller guides provided therein, said upper roller guide section including an upper roller guide section, a roller wheel having a roller axis mounted for movement generally along the axis of said housing, said roller axis being received in said roller guides, said roller having a size such as to leave a tube clamping space between the lower surface of said housing and the opposite-facing section of said roller, a deformable plastic tube received in said housing and comprising a part positioned in the space and between said lower surface and said roller, said side walls comprising a lower and upper side wall and a transition zone between the upper and lower side walls and positioned outside the housing, the ratio of the cross-sectional thickness of the upper wall to the cross-sectional thickness of the side walls being in the order of 1, 3 to 4.0, each of said upper and lower side walls being substantially of the same thickness in cross section except in the transition zone, and said upper and lower side walls having a lower cross-sectional thickness than that of the upper and lower walls. 28. Plastic roller-type clamp assembly, as reported in claim 27 where said clamp is a parallel action clamp and further comprises means for varying the gap formed during use and therefore for varying the flow rate. 29. Plastic Roller Clamp Clamp Assembly for use in an I.V. comprising: a plastic injection molded housing comprising spaced side walls, an upper wall, a lower wall comprising a lower surface, an upper roller guide section and roller guides provided therein, said upper roller guide section including an upper roller guide section, a roller wheel having a roller axis mounted for movement generally along the axis of said housing, said roller axis being received in said roller guides, said roller having a size such as to leave a clamping space of the tube between the lower surface of said housing and the opposite section, in front, of said roller, a deformable plastic tube received in said housing and comprising a portion positioned in the space and between said lower surface and said roller, said side walls comprising upper and lower side walls and a transition zone between the upper and lower side walls and said transition zone being positioned outside the housing, the ratio of the cross-sectional thickness of the upper wall to the cross-sectional thickness of the side wall being in the order of 1.3 to 4.0, the cross-sectional thickness of the upper side wall, except in said transition zone, being between 0.8 and 1, 2 the cross-sectional thickness of said lower lateral wall, except in the transition zone, said upper wall having a greater cross-sectional thickness than each of said upper and lower side walls, except in the transition zone, and greater than that of the lower wall, and said housing having a weight-length ratio normalized in the order of between 0.2 and 0.48 g / cm. 30. Plastic roller clamp group as reported in claim 29 where said clamp is a parallel action clamp and also comprises means for varying the gap formed during use and therefore for varying the range. 31. Plastic Roller Clamp Clamp Assembly for use in an I.V. comprising: a plastic injection molded housing comprising spaced apart side walls, an upper wall, a lower wall comprising a lower surface, an upper roller guide section and roller guides provided therein, said upper roller guide section including an upper roller guide section, said roller guides including lateral end walls of said upper roller guide section, said side walls comprising lower side walls extending from said lower wall towards said upper roller guide section, a roller wheel having a wheel axis mounted for movement generally along the axis of said housing, said wheel axis being received in said wheel guides, said roller having such a dimension as to leave a clamping space of the tube between the lower surface of said housing and the opposite section, in front, of said roller, a deformable plastic tube received in said housing and comprising a portion positioned in the space and between said lower surface and said roller, the ratio of the cross-sectional thickness of the upper wall to the cross-sectional thickness of the upper and lower side walls each being in the order of 1, 3 to 4.0, said upper and lower side walls being each between 0.8 and 2.5 times the thickness of the walls of said pipe when in the uncompressed condition, the cross-sectional thickness of the upper and lower side walls being less than the cross-sectional thickness of each of said upper and said lower walls, the cross-sectional thickness of said upper wall being greater than the cross-sectional thickness of said lower wall and said lower and upper side walls, and said housing, if made of ABS, having a weight-length ratio between 0.2 and 0.48 g / cm or a normalized length-weight ratio between 0.17 and 0.39. 32. Roller collet clamp assembly as described in claim 31 wherein said housing comprises a small end and a large open end with a central portion between the two, and said upper wall being of a thickness in at least one of said small end and of said open end which is less than the thickness of the upper wall in said central part of said housing. 33. Plastic roller-type clamp assembly as set forth in claim 31 where said clamp is a parallel action clamp and further comprises means for varying the gap formed during use and therefore for varying the flow rate. 34. Plastic roller clamp clamp assembly for use in an I.V. as described in claim 23 wherein said housing has a length-to-weight ratio normalized in the order of 0.3 to 0.4 g / cm2. 35. Plastic roller clamp clamp assembly for use in an I.V. as described in claim 29, wherein said housing, if made of ABS, has a weight-to-length ratio in the order of from 0.3 to 0.4 g / cm or a normalized weight-to-length ratio of between about 0.25 and 0.33 g / cm. 36. Plastic roller clamp clamp assembly for use in a 1.V assembly. as described in claim 31, wherein said housing, if made of ABS, has a weight-to-length ratio in the order of from 0.3 to 0.4 g / cm or a normalized weight-to-length ratio of between about 0.25 and 0.33 g / cm. 37. Plastic roller clamp assembly as described in claim 1, where the ratio of the thickness of the upper wall to the thickness of the uncompressed wall of said tube is in the order of 2.5 to 4.5, the ratio of the side wall thickness to the uncompressed wall thickness of said pipe is in the order of 2.1 to 2.3, and where the ratio of the lower wall thickness to the uncompressed wall thickness of said pipe is of the order from 1.2 to 2.5. 38. Plastic roller clamp clamp assembly for use in a 1.V assembly. comprising: a housing having a bottom wall a pair of mutually spaced side walls extending upwardly from said bottom wall to generally form a generally U-shaped cross section, each of said side wall comprising an upper side wall portion and a lower sidewall part, said lower sidewall parts defining an internal cavity for receiving a hollow tube within them, said upper sidewall being generally parallel to and spaced laterally outwardly relative to said lower sidewall parts to partially define an elongated groove extending along the length of each of said upper sidewall parts, a pair of upper rails extending inwardly from said upper sidewall parts to form the upper wall, said rails forming the upper surface of called grooves, a roller facing said lower wall, said roller having an outwardly extending axis which is received in said grooves for directing the movement of said roller axially along said flow control region of the housing to control the flow of the fluid through said tube, said axis resting against lateral rails when compressing said tube, said upper rails having a predetermined thickness sufficient to resist significant deflection of said rails away from said lower wall when said lower wall compresses said tube, said sidewall portions having a narrower thickness so that the thickness of each upper rail is approximately 1.3 to 4.0 times greater than the thickness of each side wall portion, so that said housing is formed to minimize the amount of plastic in the housing while maintaining the effectiveness of the clamp to resist in a manner appropriate to the applied forces and to provide suitable control of fluid flow through said tube, e each of said lower and upper walls being substantially in uniform cross-section along their entire length. 39. A method for modifying a mold used during the production of plastic roller clamp housings where said mold has been used to produce roller clamp housings having an upper wall section, said method comprising the step of moving the core into a direction with respect to the cavity so as to make the upper wall of the molded housing thicker, said displacement being in the order of 20% to 70% of the original thickness of the upper wall. 40. Method for modifying a mold used in the production of plastic roller clamp housings where said mold has been used to produce plastic clamp housings having an upper wall section, said method comprising the step of modifying the cavity of said mold to bring the internal side walls thereof closer to each other in this way by changing the molded part to have thinner side walls than those produced with the mold prior to said mold modification, and the magnitude of said displacement being in the order from 20% to 70% of the original wall thickness of said housing. 41. Method for low cost modification of a mold consisting of two half cavities and a core to produce housings for a plastic roller clamp, said housings comprising an upper wall section, spaced side walls with a lower wall between them , said method including the steps of: move the core in one direction relative to the cavity so as to make the upper wall of the housing thicker, e bringing the internal side walls of said cavity of said mold closer to each other in this way by changing the molded part so as to have thinner side walls than those produced before such modification in this way said means results in a considerable weight reduction in the housing while producing a housing structure having upper walls which are thicker than the side walls thereof.