Patent Application
20080175734
The present invention relates generally to peristaltic pumps and, more particularly, to a tube retaining system for retaining a fluid carrying tube in a peristaltic pump.
Rotary peristaltic pumps are typically used for moving liquids through flexible tubing. A typical peristaltic pump has a rotor assembly with pinch rollers that apply pressure to the flexible tubing at spaced locations to provide a squeezing action on the tubing against an occlusion bed. The occlusion of the tubing creates increased pressure ahead of the squeezed area and reduced pressure behind that area, thereby forcing a liquid through the tubing as the rotor assembly moves the pinch rollers along the tubing.
The spacing between the occlusion bed and the pinch rollers of the rotor assembly is critical for proper pump operation. The spacing between the occlusion bed and the pinch rollers is unforgiving from a tolerance standpoint since it is used both to provide a compressive force between the rotor assembly and occlusion bed and to locate the occlusion bed with respect to the rotor assembly. Tubing that is too loose in the pump may lead to flapping while tubing that is too tight may lead to excessive wear on the tubing. Improper installation of the tube may lead to poor pump performance and shortened tube life.
A typical peristaltic pump 10 is shown in
Other pumps may use retaining systems with retainers having v-shaped notches to hold the tubing, instead of using tube stops, such as the pump disclosed in U.S. Patent Application Publication 2005/0196307 A1, which is incorporated herein by reference in its entirety. These pumps are an improvement over those that require tubing with tube stops as the v-shaped notched clips serve to hold the tubing in place, eliminating the need and added expense of the tube stops. The v-shaped notches work well for a multitude of different tubing sizes and materials. Improvements may be made, however, to the notched retainers that would assist in avoiding any undesired results for large diameter tubing or low durometer tubing materials.
Accordingly, there is a need for a tube retaining system that provides the ability to retain automatically a wide range of tubing diameters and durometers, and provides consistent tube tensioning independent of the type of tube used.
The present invention overcomes the foregoing and other shortcomings and drawbacks of tube retainer systems heretofore known. While the invention will be described in connection with certain embodiments, it will be understood that the invention is not limited to these embodiments. On the contrary, the invention includes all alternatives, modifications and equivalents as may be included within the spirit and scope of the present invention.
The invention addresses these and other problems associated with known peristaltic pumps by providing a tube retaining system that eliminates the need for “stop” tubing by providing a retaining assembly having a base and a retainer. In one embodiment, the base has a generally planar tube engaging surface. The retainer has a wall with notch that is formed by an arcuate first portion and an arcuate second portion that converge at a juncture. The first and second arcuate portions of the notch are oriented toward the base and the retainer is slidably translatable from a first open position to a second closed position with the base so that the tube is retained between the retainer and the base.
According to one aspect of the invention, the lengths of the arcuate portions forming the notch in the wall may differ in length where the length of the arcuate first portion is greater than the length of the arcuate second portion. The first and second arcuate portions forming the notch in the wall of the retainer may be convex and the juncture of the two arcuate portions of the notch in the wall of the retainer may be arcuate.
According to another aspect of the invention, the retainer of the retaining assembly may be spring biased toward the closed position. When flexible tubing is positioned between the base and the retainer, the flexible tubing contacts the generally planar surface of the base and the top surface of the wall of the retainer and is held in place by the force exerted by the spring bias on the retainer.
Other advantages of the invention may include automatically retaining tubing in a peristaltic pumping application; being able to retain a wide range of tubing diameters using the same retention system; elimination of specialty tubing required for retention purposed; and lower tubing costs due to the elimination of the tubing stops.
These and other objects and advantages of the present invention will be made apparent from the accompanying drawings and the description thereof.
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with a general description of the invention given above, and the detailed description given below, serve to explain the principles of the invention.
Referring now to the figures, wherein like numbers denote like parts throughout the several views,
The exemplary pump 16 has a cover 20 attached to a body 22. A rotor assembly with a shaft 24, two plates 26, and several rollers 28 are also attached to the body 22. The plates 26 are fixed to the shaft 24, generally perpendicular to the axis of the shaft 24. The rollers 28 are secured, by means of respective axles, between the two plates 26. The rollers 28, being nearly identical in diameter, are situated at essentially the same radial distance from and equally spaced angularly about the rotor shaft axis. In turn, the shaft 24 is connected to a motor (not shown) that applies a rotational force to the shaft. Thus, when power is applied to the motor; the shaft rotates, causing the rollers 28 to describe an orbital path.
An occlusion bed 30 has a larger radius than the orbital path of the rollers 28, and is positioned so that the axis of the occlusion bed surface is coincident with the axis of the rotor assembly. Flexible hollow tubing (not shown) is positioned between the occlusion bed 30 and the rollers 28. When the rotor is turned, pressure applied by each roller 28 to the tubing (not shown) provides a squeezing action between the roller 28 and the occlusion bed 30, creating increased pressure ahead of the squeezed area and reduced pressure behind that area, thereby forcing a liquid through the tubing.
Each of the two tube retainer systems 18 primarily comprises a base 32 protruding from the body 22 of the pump 16 and a retainer 34 as shown in more detail in
Referring now to
The first arcuate portion 52 forming the notch 48 in the wall 36 has a length 64 which may be greater than the length 66 of the second arcuate portion 56 forming the notch 48 in the wall 36. Similarly, the length of the first arcuate portion 54 forming the notch 50 in the wall 38 may be greater than the length of the second arcuate portion 58 forming the notch 50 in the wall 38. In the present embodiment the two walls 36, 38 are separated by a distance 68. The separation may provide additional retention help by means of adding an offset to the tubing path. The distance 68 may be varied to adjust the amount of offset.
The nonlinear shape of the notches 48, 50 may provide a number of advantageous characteristics for embodiments required to handle a multitude of tubing sizes. The nonlinear shape may accommodate a larger variation in tubing diameters while requiring less retainer travel than a retainer with a v-shape notch. As a result, the clamping force provided by the retainer's spring or springs varies less as the tubing sizes change. The variation in the clamping forces is proportional to the change in tubing sizes as the spring force providing the clamping is a function of the amount of spring deflection, i.e. the larger the tubing, the more deflection. When tubing is subjected to the clamping forces provided by the retainers, it is deformed in such a way that may result in a restriction of flow in the tubing. The nonlinear shape provides a means for tuning the point of tangency of the retainer's arc and the outer diameter of the tube, minimizing the restriction. The compressed tube's configuration may be altered by changing the retainer's arc size and spring character. The nonlinear shape may also be an advantage when working with tubing of different material hardness. These points would apply as well to embodiments with retainers that would not have to accommodate different tubing sizes.
Referring now to
While the present invention has been illustrated by a description of various embodiments and while these embodiments have been described in considerable detail, it is not the intention of the applicant to restrict or in any way limit the scope of the appended claims to such detail. For example, while embodiments for peristaltic pumps are illustrated and described herein, the tube retainer system of the present invention may be utilized in other systems or applications that require holding flexible tubing in place without slippage and distortion. In addition, other advantages and modifications will be readily apparent to those skilled in the art. The invention in its broader aspects is therefore not limited to the specific details, representative apparatus and method, and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of Applicants' general inventive concept.
