Surgery – Means for introducing or removing material from body for... – Treating material introduced into or removed from body...
Reexamination Certificate
2001-01-02
2001-10-09
Kennedy, Sharon (Department: 3763)
Surgery
Means for introducing or removing material from body for...
Treating material introduced into or removed from body...
C604S151000
Reexamination Certificate
active
06299600
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a liquid transferring pump system to be used for transferring a liquid such as liquid medicine or blood, wherein a flexible tube, in which the liquid flows, is squeezed with a movable squeezing member such as a roller and the movable squeezing member is moved by means of a motor so as to constant-flow-transfer the liquid in the tube.
BACKGROUND ART
A roller pump is conventionally known as one of drivers of constant-flowtransferring of a liquid in a flexible tube.
In this roller pump, free rollers stands at uniform intervals on a periphery portion of a disc to be rotated by a motor, which free rollers are supported by respective pivots. Outside surfaces of the free rollers protrude over the disc, and a supporting member is arranged oppositely to the free rollers. The flexible tube is put between the free rollers and the supporting member, and the disc is rotated so that the liquid in the flexible tube can be constant-flow-transferred according to the rotation speed of the disc.
In the field of medicine for example, the above roller pump is used for the artificial dialyzer for circulating the blood, especially when a relatively large quantity of liquid is constant-flow-transferred. When a relatively small quantity of liquid is constant-flow-transferred as in case of dosing liquid medicine by means of an intravenous injection, a drip tube provided between an injection needle and a liquid medicine bag is generally used.
In this way, the reason for using the roller pump for constant-flow-transferring a relatively large quantity of liquid is to carry out the feedback control necessary for securely carrying out the constant-flow-transferring, not because of the limitation of function of a motor.
More specifically, flow fluctuation could generally occur during the constant-flow-transferring of the liquid. When flow fluctuation degree is the same, the larger the flow rate is, the smaller the flow fluctuation rate is. That is, the degree of losing the transferring constantivity is larger when a relatively small quantity of liquid is transferred.
Accordingly, when the motor is continuously rotated with low speed in order to constant-flow-transfer a relatively small quantity of liquid, the motor rotation must be monitored in a shorter period in executing the feedback control, which requires a device to accurately detect the motor rotation number.
However, an encoder, which is used to detect the motor rotation, has structurally a limitation of upper frequency of pulse to be output according to the motor rotation number. Therefore, when the motor rotation speed is too low, the motor rotation number can not be detected with a required high resolution corresponding to the transferring rate when the relatively small quantity of liquid is constant-flow-transferred.
Based on such a background, in the field of medicine, a drip tube has been conventionally used for the small constant-rate dosing of liquid medicine. And, in case that it is difficult to use the drip tube since the dosing amount is too much to use a liquid medicine bag, the roller pump is operated by intermittently driving the motor.
However, though the above operation of the roller pump could keep the above small transferring in a long span of time, the liquid transferring completely stops in a short span of time since the motor intermittently stops. Some liquids or substances to be transferred, however, could not allow such an intermittent transferring. Or, the above intermittent operation could make an operator misunderstand that failure arose, which requires a means to show the intermittent operation.
DISCLOSURE OF THE INVENTION
In view of the foregoing, an object of the present invention is provide a liquid transferring pump system such as a roller pump for constant-flow-transferring a liquid in a flexible tube from the upstream side to the downstream side by squeezing the tube by a movable squeezing member to be moved along the tube, wherein the transferring constantivity can be kept high even if the transferring rate (per unit time) of the liquid is relatively small.
And, in order to achieve the above object, the liquid transferring pump system of the present invention as set forth in claim
1
, wherein a motor for moving a movable squeezing member, which squeezes a flexible tube so as to transfer a liquid therein from an upstream side toward an downstream side thereof, is driven according to a drive pulse signal having a frequency determined correspondingly to a target flow rate of the liquid in the tube, and the frequency of the drive pulse signal is increased and decreased according to the frequency determined correspondingly to the target flow rate on a basis of the frequency of the drive pulse signal and a frequency of a rotation pulse signal which is output by an encoder correspondingly to rotation number of the motor so that a flow rate of the liquid in the tube agrees with the target flow rate, and wherein comprising a frequency multiplying means to receive the rotation pulse signal to be output by the encoder and then to output a multiplied pulse signal to be obtained by multiplying the frequency of the rotation pulse signal by n and a drive frequency adjusting means to increase and decrease the frequency of the drive pulse signal according to the frequency determined correspondingly to the target flow rate so that a frequency of the multiplied pulse signal converges in the frequency determined correspondingly to the target flow rate are provided, is characterized in that the drive frequency adjusting means has a desirable drive pulse calculating means to calculate pulse number, per unit time, of an ideal drive pulse signal for converging the frequency of the multiplied pulse signal in the frequency determined correspondingly to the target flow rate at every determined time period when the frequency of the multiplied pulse signal is calculated based on sampling number of the multiplied pulse signal, an integer judging means to judge whether or not the pulse number, per the unit time, of the ideal drive pulse signal is integer, an approximate pulse calculating means to calculate a first approximate pulse number and a second approximate pulse number, which are two integers smaller and larger, respectively, than the pulse number, per the unit time, of the ideal drive pulse signal, when the integer judging means has judged that the pulse number, per the unit time, of the ideal drive pulse signal is not integer, and a period calculating means to calculate the first period time and the second period time wherein a total of a first value of multiplying the first approximate pulse number by the first period time and a second value of multiplying the second approximate pulse number by the second period time is equal to a value of multiplying the pulse number, per the unit time, of the ideal drive pulse signal by the unit time and also another total of the first period time and the second period time is equal to the unit time, wherein, when the integer judging means has judged that the pulse number, per the unit time, ofthe ideal drive pulse signal is not integer, increase and decrease of the frequency of the drive pulse signal according to the frequency determined correspondingly to the target flow rate is carried out by means of successively executing a pulse signal output of the first approximate pulse number over the first period time and a pulse signal output of the second approximate pulse number over the second period time.
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patent: 5695464 (1997-12-01), Viallet
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Ikeda Atsushi
Masaoka Katsunori
Saitoh Teruhisa
Baker & Daniels
JMS Co. Ltd.
Kennedy Sharon
LandOfFree
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