The Experts below are selected from a list of 6 Experts worldwide ranked by ideXlab platform

Douglas J Reinemann - One of the best experts on this subject based on the ideXlab platform.

  • the history of Vacuum regulation technology
    2005
    Co-Authors: Douglas J Reinemann
    Abstract:

    An inordinate amount of time, money and anguish has been invested in changing the ways that Vacuum is controlled in milking machines. These extraordinary efforts have not resulted in a commensurate improvement in milking performance. There are two fundamental methods of influencing the Vacuum in the milking machine: 1) a device to regulate ‘system’ Vacuum, usually located near the receiver and 2) design and configuration of system components to reduce the Vacuum difference between the regulated system Vacuum and the Vacuum at the teat end. The ‘system’ regulation devices are the primary emphasis in this paper but the influence of components and design will also be covered to put these two contributions to milking Vacuum stability in perspective. System regulation devices control the Vacuum at a point downstream (in the direction of airflow) of the receiver. This control strategy tragically, CANNOT have any influence on the major causes of Vacuum drop between the milkline and the milking unit and Vacuum stability at the teat end, namely (in approximate order of significance): • Vacuum drop in the long milk tube and the associated Vacuum fluctuations caused by slugs of milk in the tube and intermittent air admission to the milking unit. • Vacuum drop and Vacuum fluctuations produced in the short milk tube due to milk slugs. • Vacuum fluctuations at the teat end caused by the opening and closing of the liner • Slugging in the milkline The Vacuum measurement of most interest to the cow and her teats is the average Vacuum in the claw during milking. The only legitimate function of most Vacuum Regulators is to provide a relatively stable reference Vacuum in the receiver. If the milkline is designed correctly this same Vacuum will also be supplied to the entire length of the milkline. The milkline Vacuum together with knowledge of the relationship between milk flow rate and the milkline-claw Vacuum difference will allow the competent evaluator to adjust the regulator Vacuum to achieve the desired average claw Vacuum for the majority of the time that milking units are attached to cows. As we will see, the history of Vacuum regulation has shown an improvement receiver Vacuum stability but the history of Vacuum stability at the “business end” of the cow, her teat ends, has not progressed in this same orderly manner. The Beginning of Recorded Machine Milking Time This brief history of Vacuum regulation is taken from the well researched and entertaining works by Hall (1959 and 1977) and Dodd and Hall (1992). Milking machines were first introduced in the late 1800’s. It is presumed that the Vacuum was set by trial and error to arrive at a Vacuum level that worked reasonably well.

A. V. Sumin - One of the best experts on this subject based on the ideXlab platform.

  • “Artificial heart” pneumatic drive with improved energy characteristics
    Biomedical Engineering, 1990
    Co-Authors: V. V. Vorob'ev, A. V. Sumin
    Abstract:

    Pneumatic drives are being employed extensively at present for devices that completely replace the pumping function of a heart. They utilize the physical properties of compressed air as an energy medium. The traditional pneumatic scheme of such a drive has two independent units that separately control the lefthand and right-hand artificial ventricles of the heart, and each of these units contains a pneumatic station and its own pneumatic drive. The pneumatic station includes a compressor, a Vacuum-pump and a receiver. The pneumatic drive contains pressure and Vacuum Regulators, and also a pneumatic distributor that makes connections, in accord with signals from a control system, to the pneumatic chamber of an artificial ventricle or to an excess-pressure channel, or to a Vacuum channel. One way to improve a pneumatic drive would be the functional and structural combination of one or another of the subassemblies and units. Thus, for example, a compressor is used as a source of excess pressure and of Vacuum. Another variant would be a combination of a pneumatic distributor and a compressor. In this case the drive for a device that replaces the pumping function of the heart is realized in the form of a piston-type compressor where the cavity under the piston is connected with the pneumatic chamber of the pumping arrangement. Such construction makes it possible to do without a pneumatic distributor, the Regulators, and receivers. However, the large inertia of the piston's mass substantially reduces the operating speed of a drive or causes substantial expenditures of energy to control it. Upon comparing the known control methods for an artificial heart it is possible to distinguish two basic trends. In the first, blood is moved by connecting the energy source periodically to the left-hand and right-hand ventricles of the heart in phase with the systole, and in this case the capacity of the output drive should be equal to the sum of the instantaneous capacities for both ventricles. In the second method the energy stored in accumulators (receivers) is moved periodically to the left-hand and right-hand ventricles. In this case the output capacity of the pressure source should be equal to the sum of the average capacities of the left-hand and right-hand pumping arrangements in the systolic phase. Thus, from the standpoint of energy expenditure the second method of controlling the operation of an artificial heart is more favorable. A typical feature of a pneumatic drive for pneumatic-drive apparatus that replaces the pumping function of a heart, that is implemented by a piston-type compressor, and that realizes the first control method is that at the end of a systolic phase the volume of the piston chamber and the volume of the pneumatic chamber of an artificial ventricle constitute an accumulator in which some energy of the compressed gas is stored. This energy can perform useful work. In an ideal, piston-type compressor for which the force of friction is negligible and the thermodynamic processes are isothermal, the increase in the piston chamber AV because of the energy of the compressed gas can be found from the following expression:

V. V. Vorob'ev - One of the best experts on this subject based on the ideXlab platform.

  • “Artificial heart” pneumatic drive with improved energy characteristics
    Biomedical Engineering, 1990
    Co-Authors: V. V. Vorob'ev, A. V. Sumin
    Abstract:

    Pneumatic drives are being employed extensively at present for devices that completely replace the pumping function of a heart. They utilize the physical properties of compressed air as an energy medium. The traditional pneumatic scheme of such a drive has two independent units that separately control the lefthand and right-hand artificial ventricles of the heart, and each of these units contains a pneumatic station and its own pneumatic drive. The pneumatic station includes a compressor, a Vacuum-pump and a receiver. The pneumatic drive contains pressure and Vacuum Regulators, and also a pneumatic distributor that makes connections, in accord with signals from a control system, to the pneumatic chamber of an artificial ventricle or to an excess-pressure channel, or to a Vacuum channel. One way to improve a pneumatic drive would be the functional and structural combination of one or another of the subassemblies and units. Thus, for example, a compressor is used as a source of excess pressure and of Vacuum. Another variant would be a combination of a pneumatic distributor and a compressor. In this case the drive for a device that replaces the pumping function of the heart is realized in the form of a piston-type compressor where the cavity under the piston is connected with the pneumatic chamber of the pumping arrangement. Such construction makes it possible to do without a pneumatic distributor, the Regulators, and receivers. However, the large inertia of the piston's mass substantially reduces the operating speed of a drive or causes substantial expenditures of energy to control it. Upon comparing the known control methods for an artificial heart it is possible to distinguish two basic trends. In the first, blood is moved by connecting the energy source periodically to the left-hand and right-hand ventricles of the heart in phase with the systole, and in this case the capacity of the output drive should be equal to the sum of the instantaneous capacities for both ventricles. In the second method the energy stored in accumulators (receivers) is moved periodically to the left-hand and right-hand ventricles. In this case the output capacity of the pressure source should be equal to the sum of the average capacities of the left-hand and right-hand pumping arrangements in the systolic phase. Thus, from the standpoint of energy expenditure the second method of controlling the operation of an artificial heart is more favorable. A typical feature of a pneumatic drive for pneumatic-drive apparatus that replaces the pumping function of a heart, that is implemented by a piston-type compressor, and that realizes the first control method is that at the end of a systolic phase the volume of the piston chamber and the volume of the pneumatic chamber of an artificial ventricle constitute an accumulator in which some energy of the compressed gas is stored. This energy can perform useful work. In an ideal, piston-type compressor for which the force of friction is negligible and the thermodynamic processes are isothermal, the increase in the piston chamber AV because of the energy of the compressed gas can be found from the following expression: