Patent Description:
Various fluid management systems rely on the control of fluid flow rates. Commonly such systems employ variable rate pumps to regulate flow. Such systems tend to be expensive. For example, a system that regulates, or meters, flow for three fluids might require three separate pumps. If the pumps are peristaltic pumps then three separate pumping tube portions would be required for a disposable fluid circuit as well as the three separate actuators and their associated weight and cost. From CN <NUM><NUM> A a variable flow restrictor is known, comprising: a tube support having a hollow and holding a flexible tube; a free rod element trapped in the hollow, the free rod element having a pinching end and a driven end; and a linear actuator having a rod which can move in a linear direction and has at is end an end effecter which is configured to push the driven end of the free rod element progressively such that the free rod element moves linearly and the pinching end of the free rod element progressively pinches the tube against a first wall of said hollow, wherein the hollow has second and third walls and the free rod element is a longitudinal member and the linear actuator is configured to push the driven end of the free rod element such that said driven end rides along the third wall while a middle of rod element slides along the second wall. From <CIT> and <CIT> further variable flow restrictors are known. From <CIT> a flow mixing system having variable flow restrictors is known.

The object of the present invention is to provide an improved variable flow restrictor. This is achieved by a variable flow restrictor according to claim <NUM>. Further embodiments are subject of the dependent claims. A variable pinch valve provides precise flow control by progressively pinching a tube. The pinching element creates a gradually-increasing mechanical advantage that increases the force pinching the tube as the tube approaches full occlusion. A system having inventive variable flow restrictors can serve as a basis for a flow regulation system in which the variable pinch valves each controls the flow of a separate fluid. The fluids may be combined to form a mixture. Each fluid may be driven by a hydraulic source fluid which feeds a flexible-walled isolation element so the hydraulic source fluid does not mix with the separate fluids. The ratio of volumes of the separate fluids may be determined by the variable pinch valves and a relative flow therethrough.

Embodiments will hereinafter be described in detail below with reference to the accompanying drawings, wherein like reference numerals represent like elements. The accompanying drawings have not necessarily been drawn to scale. Where applicable, some features may not be illustrated to assist in the description of underlying features.

Referring to <FIG>, a tube support 100A has a hollow <NUM> that confines a free lever element <NUM>. A tube <NUM> is held by a tube support <NUM>. Free lever element <NUM> progressively pinches the tube <NUM> by pushing a pinching end <NUM> of the free lever element <NUM> into the tube <NUM> as an opposite driven end <NUM> of the free lever element <NUM> is pushed, by an end effecter <NUM> of a linear actuator <NUM>, along a wall <NUM> causing the pinching end <NUM> to slide along a wall <NUM>. More specifically, the linear actuator <NUM> has a rod <NUM> which can move in a linear direction (horizontal direction in <FIG>), and the rod <NUM> has at its end the end effecter <NUM>, which is positioned to press on free lever element <NUM>. In other words, the linear actuator <NUM> pushes the free lever element <NUM> so that it pivots and such that its pinching end <NUM> is driven into the side of the tube <NUM> thereby pinching it progressively closed. This motion creates a gradually-increasing mechanical advantage that increases the force pinching the tube <NUM> as the tube <NUM> approaches full occlusion. The displacement of the linear actuator <NUM> thereby determines the amount by which the tube <NUM> is pinched and thereby determines the cross-sectional area of the inside of the tube <NUM>. This gradually changes the magnitude of a flow restriction represented by the tube <NUM>.

Note that the engagement of the free lever with the walls <NUM> and <NUM> may be identified as joints, namely, sliding joints. Their engagement may also be identified as revolute joints. Thus an equivalent kinematic mechanism may be provided where the free lever is a link, through revolute joints, two sliding joints at the end of the free lever.

In <FIG>, the free lever element <NUM> is shown pinching the tube <NUM> to a small degree. In <FIG>, the free lever element <NUM> is shown pinching the tube <NUM> to a larger degree. In <FIG>, the free lever element <NUM> is shown pinching the tube <NUM> to a maximal degree, effectively fully occluding the tube <NUM> to prevent any flow therethrough.

When the linear actuator is withdrawn to pull away from the opposite driven end <NUM>, the position of the free lever element <NUM> may be pushed back to a more relaxed position by the resilience of the tube <NUM> or the pressure of fluid within it. Alternatively, in a further embodiment 100B shown in <FIG>, a spring <NUM> may be provided to return the free lever element <NUM> to a non-occluding or lower-occluding position. That is, the linear actuator <NUM> pushes the end effecter <NUM> into the opposite driven end <NUM>, a side of the free lever element <NUM> is pushed against and compresses the spring <NUM>. The spring may be partially recessed in the wall <NUM> as illustrated. A secondary function of the spring <NUM> is to prevent backlash. Note other types of springs may be provided such as leaf springs and this applies to any of the embodiments described or claimed. Note also that the spring <NUM> may be a tension spring with the function of preventing backlash in the linear actuator <NUM>.

In <FIG>, the free lever element <NUM> is shown pinching the tube <NUM> to a small degree. In <FIG>, the free lever element <NUM> is shown pinching the tube <NUM> to a larger degree. In <FIG>, the free lever element <NUM> is shown pinching the tube <NUM> to a maximal degree, effectively fully occluding the tube <NUM> to prevent any flow therethrough. When the linear actuator withdraws by moving in progression shown by the sequence of <FIG>, to 1D, the spring <NUM> pushes the free lever element opposite driven end <NUM> back along with the end effecter <NUM> following it backwards and withdrawing the pinching end of the free lever element away from the tube <NUM> thereby allowing the tube to relax. As a result the internal area of the tube <NUM> expands allowing progressively more flow.

Referring to <FIG>, another tube support 100C has a dual-action pinching mechanism. The pinching end <NUM> of a distal element <NUM> carries a roller <NUM>. The distal element <NUM> is a link (and will also be referred to as link <NUM>) connected to an intermediate link <NUM> by a revolute joint <NUM>. The intermediate link <NUM> is connected to the effecter <NUM> of a linear actuator <NUM> by a revolute joint <NUM>. Rollers <NUM> and <NUM> allow the revolute joints <NUM> and <NUM> to roll along the walls <NUM> and <NUM> of hollow <NUM>, respectively. The tube <NUM> is held by tube support <NUM>. The dual action motion of the link <NUM> generates a progressively-increasing mechanical advantage that increases the force pinching the tube <NUM> as the tube <NUM> approaches full occlusion. The linear actuator <NUM> extend withdraws the effecter <NUM> pulling the intermediate link <NUM> downwardly and forcing the roller <NUM> and the revolute joint <NUM> along the wall <NUM> thereby driving the roller <NUM> into the tube <NUM>. The tube <NUM> is shown fully occluded in <FIG> and partially occluded in <FIG>.

The linear actuator <NUM> may restore the links <NUM> and <NUM> to their non-occluding position due to the connection by the revolute joint <NUM> at the end of the effecter <NUM>. That is, as the linear actuator <NUM> extends the effecter <NUM>, the revolute joint <NUM> is pushed away from the linear actuator <NUM> causing the roller <NUM> to roll along the wall <NUM> and thereby causing the roller <NUM> to roll along wall <NUM> taking the revolute joint <NUM> with it. In other embodiments 100D, a spring <NUM> may be provided to reduce the force required to return the links <NUM> and <NUM>. Such an embodiment is shown in <FIG>. The spring <NUM> pushes the joint <NUM> away from the wall <NUM> to assist in causing the roller <NUM> to retract from the tube <NUM>. Note that spring <NUM> may be a tension or compression spring. The function of the spring is to prevent backlash in the linear actuator <NUM>.

Referring to <FIG>, a system employs multiple variable flow restrictors <NUM> to <NUM> to regulate, independently, flows of first fluid <NUM>, second fluid <NUM> and water from second bag <NUM>. A first fluid <NUM> is held in a bag in a confining container <NUM> with a second bag containing water <NUM> such that when water is pumped into the second bag <NUM>, the first fluid <NUM> is forced out through a line <NUM> regulated by a variable flow restrictor <NUM>. A second fluid <NUM> is held in a bag in a confining container <NUM> with a second bag containing water <NUM> such that when water is pumped into the second bag <NUM>, the second fluid <NUM> is forced out through a line <NUM> regulated by a variable flow restrictor <NUM>. The pressure of fluid in both bags <NUM> and <NUM> is maintained by a pump <NUM>. A flow splitter <NUM> conveys fluid to the bags <NUM> and <NUM> and a line <NUM>. Water flow is regulated through line <NUM> by a variable flow restrictor <NUM>. The water from line <NUM> and the fluid in lines <NUM> and <NUM> may be mixed in a mixing unit <NUM> to produce a mixture at <NUM>. The variable flow restrictors may be as described according to any of foregoing embodiments including 100A through 100D.

Referring now to <FIG>, a further pinching mechanism configuration is shown. A pair of legs <NUM> and <NUM> are joined at a hinge with a roller <NUM> such that when one leg <NUM> is pushed toward the other, the roller <NUM> is pushed into the tube squeezing it closed. It will be observed that the force of the roller <NUM> rises with displacement of the leg <NUM> toward a maximum value in the position shown in <FIG>. A linear actuator <NUM> having an end effecter <NUM> pushes the leg <NUM> toward the leg <NUM>. Roller <NUM> rolls along the tube <NUM> thereby squeezing the tube <NUM> closed as shown in <FIG>. A two-part tube support with pressure relief blocks <NUM> and <NUM> and spring <NUM> may be used to limit the amount of force that is applied to the tube <NUM>. Rollers <NUM> and <NUM> roll along the recess <NUM>. A leaf spring <NUM> prevents any backlash of the linear actuator <NUM> and the end effecter <NUM> by continuously applying a restoring force to the leg <NUM>. The recess <NUM> is defined within a frame <NUM>.

Referring now to <FIG>, a lever element 427A is driven by an end effecter <NUM> moved by a linear actuator <NUM>. The lever element 427B is similarly driven by the end effector at its end. By moving the end effecter to the left, the lever element 427B releases pressure on a tube 314B while lever element 417B increase pressure on the tube 314A. In this way, the tubes are oppositely squeezed for a given motion of the end effecter. Note each tube is forced against a respective stop <NUM>. Each lever element rides an internal surface <NUM> of a respective block element <NUM>. In <FIG>, the tube 314B is shown being released by the lever element 427B and in <FIG> the same tube 314B is shown being squeezed. In <FIG>, the tube 314B is shown squeezed by the lever element 427B and in <FIG> the same tube 314B is shown being released. In this way the tubes can be ratiometrically pinched by the lever elements which are driven by a single linear actuator.

Referring now to <FIG>, a flow restrictor <NUM> has constraints, except for the linear actuator, that are all provided by links with revolute joints. Referring specifically to <FIG> in which a tube <NUM> is only slightly pinched by a pinching effecter <NUM>. The pinching effecter <NUM> is guided or constrained by a link <NUM> connected to a chassis portion <NUM> by a revolute joint <NUM>. Chassis portion <NUM> may be fixedly connected to all the chassis portions <NUM>, <NUM>, and <NUM> to fixedly support all revolute joints <NUM>, <NUM>, and <NUM> as well as tube <NUM>. That is, all the chassis portions may be parts of the same component such that none of them moves with respect to the others when the flow restrictor <NUM> is actuated to pinch the tube <NUM>. The linear actuator <NUM> is supported on a revolute joint <NUM>. The effecter <NUM> pushes on a pair of concentric revolute joints centered at <NUM> to drive links <NUM> and <NUM> to make the angle between them more or less obtuse depending on the direction of movement of the linear actuator <NUM>. Note that pinching effecter <NUM> may revolve around revolute joint <NUM> or not. That is, the pinching effecter <NUM> may be fixedly attached to link <NUM> or <NUM> or it can revolve around the revolute joint <NUM> instead. Comparing <FIG> with <FIG> illustrates the operation of the mechanism shown and makes clear that only revolute joints, apart from the linear actuator, are required to push the pinching effecter <NUM> into the tube in the manner whereby the mechanical advantage increases as the tube is increasingly pinched.

An aspect common to embodiments disclosed herein includes the non-linearity of the relationship between pinching force delivered to the tube and the displacement of the linear actuator. In the case of the embodiments described, the pinching force the valve is capable of delivering for a given size motor increases as the linear actuator is displaced. This provides a benefit in that it takes more force to close a tube close to full occlusion than it takes to close it initially. Thus, it is possible to provide an automatic valve in which the power capability of the motor can be smaller than for a valve actuator that does not have this feature.

Another aspect common to embodiments disclosed herein is that the non-linear relationship between displacement of the motor and deformation of the walls of the tube by the part of the valve in contact with the tube which actually deforms it to reduce the flow. This is beneficial because for a given pressure, the relationship between the rate of flow and the deformation of the tube is also non-linear. That is, the flow rate drops less and less for each increment of displacement of the walls of the tube as the tube is pinched such that at the beginning of a closure, very little reduction in flow occurs and at the end of the closure a larger reduction in flow occurs. By coupling the non-linearity in relationship of displacement of the motor to the deformation of the walls with the non-linear relationship between deformation of the tube to incremental rate of change in flow, the relationship between the motor displacement and the change in flow rate becomes more linear.

Note that in any of the embodiments where linkages transfer force of the linear motor to a final element that pinches a tube, the linkages, collectively, will be understood to be a force transfer mechanism, a kinematic chain, a transmission, or other similar identifier of its function. Any sliding constraint may be identified as a joint, namely a sliding joint.

According to embodiments, the disclosed subject matter includes a variable flow restrictor with a tube support having a hollow with a flexible tube therein. A free lever element is trapped in the hollow. An actuator is configured to push the free lever element progressively such that it progressively pinches the tube against a first wall of said hollow.

In variations thereof, the foregoing embodiments includes ones in which the free lever element is a longitudinal member. In variations thereof, the foregoing embodiments includes ones in which the actuator is configured to push the free lever element such that an end thereof rides along second wall of said hollow. In variations thereof, the foregoing embodiments includes ones in which the free lever element is a longitudinal member and the actuator is configured to push one end thereof such that another end thereof rides along a second wall of said hollow. In variations thereof, the foregoing embodiments includes ones in which the hollow has second and third walls and the free lever element is a longitudinal member and the actuator is configured to push one end thereof such that said one end rides along the third wall while another end thereof rides along the second wall.

In variations thereof, the foregoing embodiments includes ones in which the actuator has first and second links connected by a revolute joint, a distal one of which is connected by a further revolute joint to the lever element. In variations thereof, the foregoing embodiments includes ones in which wheels are attached at each of the revolute joints. In variations thereof, the foregoing embodiments includes ones in which the first, second, and third walls are straight. In variations thereof, the foregoing embodiments includes ones in which the first link is connected to a linear actuator.

In variations thereof, the foregoing embodiments includes ones in which the free lever element is forced by a return spring.

In variations of the foregoing embodiments, the free lever element is a longitudinal member. In variations of the foregoing embodiments, the actuator is configured to push the free lever element such that an end thereof rides along second wall of said hollow. In variations of the foregoing embodiments, the free lever element is a longitudinal member and the actuator is configured to push one end thereof such that another end thereof rides along a second wall of said hollow. In variations of the foregoing embodiments, the hollow has second and third walls and the free lever element is a longitudinal member and the actuator is configured to push one end thereof such that said one end rides along the third wall while another end thereof rides along the second wall. In variations of the foregoing embodiments, the actuator has first and second links connected by a revolute joint, a distal one of which is connected by a further revolute joint to the lever element. In variations of the foregoing embodiments, wheels are attached at each of the revolute joints. In variations of the foregoing embodiments, the first, second, and third walls are straight. In variations of the foregoing embodiments, the first link is connected to a linear actuator. In variations of the foregoing embodiments, the free lever element is forced by a return spring.

Claim 1:
A variable flow restrictor (100A, 100B, 100C, 100D), comprising:
a tube support (<NUM>) having a hollow (<NUM>, <NUM>) and configured to hold a flexible tube (<NUM>);
a free lever element (<NUM>, <NUM>) trapped in the hollow (<NUM>, <NUM>), the free lever element (<NUM>, <NUM>) having a pinching end (<NUM>, <NUM>) and a driven end (<NUM>); and
a linear actuator (<NUM>, <NUM>) having a rod (<NUM>, <NUM>) which can move in a linear direction and has at its end an end effecter (<NUM>) which is configured to push the driven end (<NUM>) of the free lever element (<NUM>) progressively such that the free lever element (<NUM>, <NUM>) pivots and the pinching end (<NUM>, <NUM>) of the free lever element (<NUM>, <NUM>) is configured to progressively pinch the flexible tube (<NUM>) against a first wall of said hollow to thereby, in use, progressively close the flexible tube (<NUM>),
wherein the hollow (<NUM>, <NUM>) has second (<NUM>, <NUM>) and third (<NUM>, <NUM>) walls and the free lever element (<NUM>, <NUM>) is a longitudinal member and the linear actuator (<NUM>, <NUM>) is configured to push the driven end (<NUM>) of the free lever element (<NUM>, <NUM>) such that said driven end (<NUM>) rides along the third wall (<NUM>, <NUM>) while the pinching end (<NUM>, <NUM>) slides along the second wall (<NUM>, <NUM>).