Valves and valve actuation – Tube compressors – Roller tube contacting element
Reexamination Certificate
2000-07-25
2002-01-29
Fox, John (Department: 3753)
Valves and valve actuation
Tube compressors
Roller tube contacting element
Reexamination Certificate
active
06341757
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a flow regulator. More particularly, this invention relates to a flow regulator of the type which compresses a tube to vary a flow rate of a fluid passing through the tube. Even more particularly, this invention relates to a flow regulator of the roller type. The invention is useful in medical applications, to control the flow rate of intravenous fluids, parenteral fluids, blood, plasma, etc.
BACKGROUND OF THE INVENTION
Intravenous tubes have been widely used for supplying nutrients and medication to patients. Most existing manually adjustable clamps for regulating the flow rate through an intravenous tube have a high degree of inaccuracy, particularly after the clamped tubing has been in use for a period of time in excess of one hour. In addition, existing manually actuated clamps cannot be used where the fluid being delivered through the tubing is viscous, for example, blood. If a substantial degree of accuracy in flow rate maintenance is required, it has been necessary to utilize an expensive pump system. Even pumps systems are limited in their accuracy.
A particularly common kind of flow regulator in medical applications is the so-called Adelberg clamp which uses the combination of an inclined plane or V-grooved surface and a roller that is moved along the inclined plane or grooved surface to variably compress the tube to allow more or less liquid to flow through the tube. Although widely used, the Adelberg clamp is less than ideally accurate and reliable, so as to require continual monitoring and adjustment to maintain a desired flow rate. The position of the roller is easily shifted in the V-grooved and ramped versions since the clamp design has not taken into consideration the direct effect of stress and strain as a critical contributing factor in maintaining an accurate and consistent flow rate through the roller clamp.
OBJECTS OF THE INVENTION
An object of the present invention is to provide an improved manually adjustable flow regulator of the above-described roller type.
Another object of the present invention is to provide a manually adjustable flow regulator which has enhanced accuracy and reliability.
An additional object of the present invention is to provide such a flow regulator which is inexpensive and easy to manufacture.
A further object of the present invention is to provide a manually adjustable flow regulator which is utilizable where a medical fluid is to be delivered through a flexible tube.
These and other objects of the present invention will be apparent from the descriptions and illustrations herein. It is believed that each of the above-described objects is achievable in one or more embodiments of the invention described herein.
BRIEF DESCRIPTION
A flow regulator comprises, in accordance with the present invention, a pair of side walls extending generally parallel to one another, a bottom wall connecting the side walls to one another and defining an elongate channel for receiving a compressible tube, a roller rotatably and shiftably mounted to the side walls for rolling along the tube in the channel and compressing the tube against the bottom wall. The bottom wall is provided with a formation which varies from a first end of the channel towards an opposite, second end thereof, whereby a compressive force applied to the tube via the roller is different at different longitudinal positions of the roller along the channel. A reinforcement bracket is disposed about the side walls at one end of the channel. The bracket is in contact with outer surfaces of the parallel side walls only in regions of the side walls spaced from the bottom wall. In a different embodiment, the bracket is replaced with a bridge of relatively flexible construction spanning the two side walls, disposed at the flow regulator shut off end. Advantageously, the side walls and a bottom wall, including all parts of the clamp with the exclusion of the bracket or bridge, are made from a material more rigid than the material from which the bracket or bridge is made.
As suggested above, prior V-grooved or ramped roller clamps suffer from setpoint drift attributable to shifting of the roller position. The prior clamp structures are not believed to have taken into adequate consideration the direct effect of stress or strain as a critical contributing factor in degrading an accurate flow rate performance of the roller clamp. The relationship of a stiffness of the bridge to the flow regulator chamber or channel walls, as well as the contributory factor of differences in intrinsic elasticity of the materials used for component manufacture are critical in maintenance of accurate device performance. The present invention describes an effective method of taking cognizance of stress and strain in the device, and controlling these factors for optimum performance.
U.S. Pat. No. 5,718,409 to the same inventor implicitly dealt with stress and strain in a roller clamp by introducing a reinforcing bracket to an existing design. In further tests of similar devices it has become evident that modifying the flexibility or stiffness relationships between the chamber walls and the bridge or bracket component further improved the accuracy and consistency of the device, by limiting the flexing of the side walls and simultaneously reducing a strain state of the bridge or bracket.
U.S. Pat. No. 5,718,409, the disclosure of which is incorporated herein, shows a bracket contacting the outer surface of the sidewalls of the roller clamp body at a shut-off or maximally restricted flow end of the device. In the prior art, the roller tended to roll towards the shut off end during operation of the clamp. The movement is presumed to have arisen as an effect of operating stresses in the interrelated parts of the roller clamp assembly. As the roller pinches the tube, pressure is generated on the plastic walls of the device. This pressure causes an end of the clamp to flair open to various degrees, depending on a position of the roller. In order to control the effect of stress on the device, structure defining the roller clamp chamber requires a more rigid material construction. The elastic relationship of the roller clamp chamber structure—comprising parallel side walls and bottom wall—to the bracket or bridge structure is an important design parameter, as the two parts structure interact to accommodate the varying stresses resulting from different roller setting in the operating device.
The bracket previously described in U.S. Pat. No. 5,718,409 serves to maintain flow constancy by controlling a change in a gap distance between the parallel side walls of the roller clamp, engaging the walls predominantly at the shut off end. Simultaneously, the bracket provides the side walls with a controlled springy effect which means that, as the roller starts to roll towards the shut off end, the controlled springy flexibility of the walls will respond to the roller's tendency to roll down; at times when the amount of fluids delivered lessen, it would cause a decrease in the degree of stress and strain between the bracket and the chamber, and the pressure between the roller and the tube where the roller might otherwise change its position, with bracket feature on the clamp the roller will be held constant by the springy effect of the parallel side walls. After this discovery was initially made by the inventor by numerous in-house tests and several official laboratory tests, improvements were made in the design which make this device easier and less expensive to manufacture, while maintaining the original objectives of maintaining superior and constant flow regulating. These improvements result in a device having a predetermined and controlled elastic performance relationship during stress effects which involve the entire assembly.
The bracket or bridge is preferably disposed at the end of the flow regulator where the tube is subjected to the greatest compressive forces and the controlled flow rate is the lowest. The bracket prevents an undue flexing of the side walls away from each
Fox John
Miskin Howard C.
Tsui-Yip Gloria
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