Abbott Laboratories Corporation

Vernon R Natwick

Michael W Lawless

Joseph E Doll

Chung-You C Wu

A cam assembly and method for providing a substantially constant load to a motor that drives the cam assembly. A torque compensated cam assembly (142,300) includes a plurality of tracks (140,150,152/310,312,314) that are profiled with a surface that varies radially as the cam rotates, thereby actuating cam followers, each of which rolls along a different track. A tangential force developed by the cam followers as they move over rapid radial changes in the surfaces of the tracks produces a total net torque that at times tends to aid the rotation of the cam and at times tends to impede its rotation. In the application of the torque compensated cam assembly disclosed, the cam is used in a volumetric pump (30) that accurately delivers a desired volume of fluid at a desire rate. To assist in maintaining the accuracy of these parameters, the torque compensated cam assembly presents a substantially constant load to a motor (146,304) that drives the cam. In one embodiment, the cam assembly includes a torque compensation track (170/316) disposed at one end of the cam, and in another embodiment, the torque compensation track is disposed circumferentially around the cam. A torque compensation roller (172,320) is biased against the torque compensation track by a flexure (174), providing a force that develops the required compensating torque. The profile of the torque compensation track is defined so as to produce a torque that is substantially equal in magnitude, but opposite in the direction, that it tends to rotate the cam assembly, compared to the net torque developed by the cam followers.

Method of making torque compensated cam assembly

A cam assembly and method for providing a substantially constant load to a motor that drives the cam assembly. A torque compensated cam assembly (142,300) includes a plurality of tracks (140,150,152/310,312,314) that are profiled with a surface that varies radially as the cam rotates, thereby actuating cam followers, each of which rolls along a different track. A tangential force developed by the cam followers as they move over rapid radial changes in the surfaces of the tracks produces a total net torque that at times tends to aid the rotation of the cam and at times tends to impede its rotation. The cam is used in a volumetric pump (30) that accurately delivers a desired volume of fluid at a desire rate. To assist in maintaining the accuracy of these parameters, the torque compensated cam assembly presents a substantially constant load to a motor (146,304) that drives the cam. In one embodiment, the cam assembly includes a torque compensation track (170/316) disposed at one end of the cam, and in another embodiment, the torque compensation track is disposed circumferentially around the cam. A torque compensation roller (172,320) is biased against the torque compensation track by a flexure (174), providing a force that develops the required compensating torque. The profile of the torque compensation track is defined so as to produce a torque that is substantially equal in magnitude, but opposite in the direction, that it tends to rotate the cam assembly, compared to the net torque developed by the cam followers.

Torque compensated cam assembly and method

A volumetric pump and method for displacing a predetermined quantity of fluid at a predefined cracking pressure, independent of supply and output pressures. The volumetric pump (30) includes an inlet cracking valve (46), an outlet cracking valve (52), and a plunger (48)for displacing fluid from a pumping portion (34b) of flexible tubing (34) that extends through the volumetric pump. The pumping portion of the flexible tube fills with liquid when the inlet cracking valve is fully opened and is urged to expand by jaws (236) on pivotally-mounted arms (234). The arms are forced to pivot, as tubing reshaper rollers (160), disposed on the plunger, roll along the inner surface (232) of each arm. During a pumpback-pressurization segment of the pumping cycle, the inlet cracking valve applies a cracking force to the flexible tubing, while the plunger compresses the pumping portion of the flexible tubing sufficiently to develop a cracking pressure that displaces excess fluid back through the inlet cracking valve toward a container (32). After the excess fluid has been forced from the pumping portion of the flexible tubing, a pumping segment of the cycle begins, wherein the inlet cracking valve closes fully and the outlet cracking valve applies a cracking force to compress the flexible tubing. Fluid is then forced by the plunger from the pumping portion of the flexible tubing into a distal portion (34c). The volumetric pump compensates for variations in elasticity of the flexible tubing that would otherwise cause variations in the cracking pressure, using balance blocks (42 and 58).

Volumetric pump tube reshaper and method

A volumetric pump and method for displacing a predetermined quantity of fluid at a predefined cracking pressure, independent of supply and output pressures. The volumetric pump (30) includes an inlet cracking valve (46), an outlet cracking valve (52), and a plunger (48) for displacing fluid a pumping from a pumping portion (34b) of flexible tubing (34) that extends through the volumetric pump. The pumping portion of the flexible tube fills with liquid when the inlet cracking valve is fully opened and is urged to expand by jaws (236) on pivotally-mounted arms (234). The arms are forced to pivot, as tubing reshaper rollers (160), disposed on the plunger, roll along the inner surface (232) of each arm. During a pumpback-pressurization segment of the pumping cycle, the inlet cracking valve applies a cracking force to the flexible tubing, while the plunger compresses the pumping portion of the flexible tubing sufficiently to develop a cracking pressure that displaces excess fluid back through the inlet cracking valve toward a container (32). After the excess fluid has been forced from the pumping portion of the flexible tubing, a pumping segment of the cycle begins, wherein the inlet cracking valve closes fully and the outlet cracking valve applies a cracking force to compress the flexible tubing. Fluid is then forced by the plunger from the pumping portion of the flexible tubing into a distal portion (34c). The volumetric pump compensates for variations in elasticity of the flexible tubing that would otherwise cause variations in the cracking pressure, using balance blocks (42 and 58). A volumetric pump (400) for use with a cassette (300) comprises a second embodiment of the volumetric pump, in which inlet and outlet cracking valves are defined in respect to the forces applied by actuators against a flexible membrane (340) in the cassette, while a plunger (326) displaces fluid from a pumping chamber (360) in the cassette. Volumetric pump (400) applies appropriate forces to an inlet valve actuator (318) and an outlet valve actuator (332) to achieve cracking and closure forces, just as in the first embodiment.

Volumetric pump with pump plunger support and method

A method for determining if fluid is being displaced by a volumetric pump. The volumetric pump (30) includes an inlet cracking valve (46) and an outlet cracking valve (52) disposed on opposite sides of a plunger (48) used to displace fluid by compressing flexible tubing (34). During a pumping segment of a pumping cycle for the volumetric pump, the outlet cracking valve is closed with a cracking force that compresses the flexible tubing until the pressure of the fluid displaced by the plunger exceeds a cracking pressure, at which time the outlet cracking valve opens to enable fluid flow from the volumetric pump. A cracking flexure (182) provides the cracking force. As the outlet cracking valve opens in response to the fluid pressure exceeding the cracking pressure, a flow detector (54) mounted to the cracking flexure responds to the stress generated in the cracking flexure thereby, producing a signal indicative of fluid flow from the volumetric pump. Since a compressible gaseous fluid in the pumping portion of the flexible tubing does not develop the cracking pressure, the flow detector also provides an indication when a source of liquid (31) for the volumetric pump has run dry. The method comprises the steps of processing the signal to determine if it exceeds a predefined threshold that varies as a function of the rate at which the pump is set to deliver fluid.

Method for monitoring fluid flow from a volumetric pump

A volumetric pump and method for displacing a predetermined quantity of fluid at a predefined cracking pressure, independent of supply and output pressures. The volumetric pump (30) includes an inlet cracking valve (46), an outlet cracking valve (52), and a plunger (48) for displacing fluid from a pumping portion (34b) of flexible tubing (34) that extends through the volumetric pump. The pumping portion of the flexible tube fills with liquid when the inlet cracking valve is fully opened and is urged to expand by jaws (236) on pivotally-mounted arms (234). The arms are forced to pivot, as tubing reshaper rollers (160), disposed on the plunger, roll along the inner surface (232) of each arm. During a pumpback-pressurization segment of the pumping cycle, the inlet cracking valve applies a cracking force to the flexible tubing, while the plunger compresses the pumping portion of the flexible tubing sufficiently to develop a cracking pressure that displaces excess fluid back through the inlet cracking valve toward a container (32). After the excess fluid been forced from the pumping portion of the flexible tubing, a pumping segment of the cycle begins, wherein the inlet cracking valve closes fully and the outlet cracking valve applies a cracking force to compress the flexible tubing. Fluid is then forced by the plunger from the pumping portion of the flexible tubing into a distal portion (34c). The volumetric pump compensates for variations in elasticity of the flexible tubing that would otherwise cause variations in the cracking pressure, using balance blocks (42 and 58). A volumetric pump (400) for use with a cassette (300) comprises a second embodiment of the volumetric pump, in which inlet and outlet cracking valves are defined in respect to the forces applied by actuators against a flexible membrane (340) in the cassette, while a plunger (326) displaces fluid from a pumping chamber (360) in the cassette. Volumetric pump (400) applies appropriate forces to an inlet valve actuator (318) and an outlet valve actuator (332) to achieve cracking and closure forces, just as in the first embodiment.

Volumetric pump with spring-biased cracking valves

A method and apparatus for detecting proximal and distal occlusions of flexible tubing in a positive displacement pump. A volumetric pump (30) includes a motor (146) that rotatably drives a cam assembly (142). The rotating cam assembly actuates a plunger (48), causing it to compress a pumping portion (34b) of a flexible tubing (34), compression of the tubing displaces fluid trapped within the pumping portion, causing it to flow past an outlet cracking valve (52). A proximal pressure sensor (44) and a distal pressure sensor (56) each produce signals indicative of the pressure within the proximal portion and distal portion of the flexible tubing, which are used to determine whether a proximal or distal occlusion of the flexible tubing has occurred. Both pressure sensors comprise strain gauges connected to flexures that apply a spring-biased force against the proximal and distal portions of the flexible tubing. These sensors thereby respond to the cross-sectional size (diameter) of the tubing, as affected by fluid pressure therein. Proximal and distal pressures are thus monitored without violating the integrity of the flexible tubing passing through the volumetric pump.

Detecting occlusion of proximal or distal lines of an IV pump

A 'cracking valve' for use in a volumetric pump. A volumetric pump (30) includes a plunger (48) for compressing a pumping portion (34b) of a flexible tubing that extends through the pump. An inlet cracking valve (46) and an outlet cracking valve (52) are disposed so that they compress the flexible tubing to control fluid flow therethrough. The inlet cracking valve operates in three modes, including a fully open mode, a closed mode that stops fluid flow through the flexible tubing, and a cracking mode. The outlet cracking valve only operates in the closed mode and the cracking mode. As the plunger compresses the flexible tubing, fluid pressure within the pumping portion of the flexible tubing initially builds until it exceeds a predefined cracking pressure, forcing open the inlet cracking valve, which is in its cracking mode, so that excess fluid is forced back to a container (32). After the pumping portion of the flexible tubing is compressed to a predefined volume, fluid at the cracking pressure is forced through the outlet cracking valve, which is then in its cracking mode. To compensate for changes in the elasticity or stiffness of the flexible tubing, balance blocks (42, 58) cooperate with the inlet cracking valve and the outlet cracking valve, respectively. The balance force developed by the balance block as a function of the stiffness of the flexible tubing is added to the force of a cracking flexure to produce the desired predefined cracking force at the inlet cracking valve and the outlet cracking valve. A 'T-shaped' formation comprising a transverse ridge (166) and a longitudinal ridge (168) comprises valve faces (106a, 106b) at both cracking valves. The transverse ridge controls fluid flow, whereas the longitudinal ridge has a surface area over which the fluid pressure within the pumping portion of the flexible tubing acts to overcome the cracking force.

Spring-biased valve for use in a positive displacement volumetic pump

A volumetric pump and method for displacing a predetermined quantity of fluid at a predefined cracking pressure, independent of supply and output pressures. The volumetric pump (30) includes an inlet cracking valve (46), an outlet cracking valve (52), and a plunger (48) for displacing fluid from a pumping portion (34b) of flexible tubing (34) that extends through the volumetric pump. The pumping portion of the flexible tube fills with liquid when the inlet cracking valve is fully opened and is urged to expand by jaws (236) on pivotally-mounted arms (23). The arms are forced to pivot, as tubing reshaper rollers (160), disposed on the plunger, roll along the inner surface (232) of each arm. During a pumpback-pressurization segment of the pumping cycle, the inlet cracking valve applies a cracking force to the flexible tubing, while the plunger compresses the pumping portion of the flexible tubing sufficiently to develop a cracking pressure that displaces excess fluid back through the inlet cracking valve toward a container (32). After the excess fluid has been forced from the pumping portion of the flexible tubing, a pumping segment of the cycle begins, wherein the inlet cracking valve closes fully and the outlet cracking valve applies a cracking force to compress the flexible tubing. Fluid is then forced by the plunger from the pumping portion of the flexible tubing into a distal portion (34c). The volumetric pump compensates for variations in elasticity of the flexible tubing that would otherwise cause variations in the cracking pressure, using balance blocks (42 and 58). A volumetric pump (400) for use with a cassette (300) comprises a second embodiment of the volumetric pump, in which inlet and outlet cracking valves are defined in respect to the forces applied by actuators against a flexible membrane (340) in the cassette, while a plunger (326) displaces fluid from a pumping chamber (360) in the cassette. Volumetric pump (400) applies appropriate forces to an inlet valve actuator (318) and an outlet valve actuator (332) to achieve cracking and closure forces, just as in the first embodiment.

A flow detector for use in a volumetric pump to determine if fluid is being displaced by the pump. The volumetric pump (30) includes an inlet cracking valve (46) and an outlet cracking valve (52) disposed on opposite sides of a plunger (48) used to displace fluid by compressing flexible tubing (34). During a pumping segment of a pumping cycle for the volumetric pump, the outlet cracking valve is closed with a cracking force that compresses the flexible tubing until the pressure of the fluid displaced by the plunger exceeds a cracking pressure, at which time the outlet cracking valve opens to enable fluid flow from the volumetric pump. A cracking flexure (182) provides the cracking force. As the outlet cracking valve opens in response to the fluid passage exceeding the cracking pressure, a flow detector (54) comprising in one preferred embodiment a strain gauge (198) mounted to the cracking flexure responds to the stress generated in the cracking flexure thereby, producing a signal indicative of fluid flow from the volumetric pump. Other types of sensors, including an optical sensor (300), and a linear variable displacement transformer (LVDT) (318) are alternatively used for sensing movement of an outlet valve arm (180) as fluid flows from volumetric pump (30). Since a compressible gaseous fluid in the pumping portion of the flexible tubing does not develop the cracking pressure, the flow detector also provides an indication when a source of liquid (31) for the volumetric pump has run dry.

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Los Altos, CA, United States of America

Vernon R Natwick