Pumps – Motor driven – Fluid motor
Patent
1980-06-13
1983-07-05
Smith, Leonard E.
Pumps
Motor driven
Fluid motor
91275, 91436, 418 88, F04B 1700
Patent
active
043915710
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION OF INVENTION
This invention is concerned with improvements relating to liquid pumping apparatus.
In, for example, the pumping of liquids such as sewage slurry into a filter press, conventionally there is used apparatus comprising a pumping device, comprising a pumping piston reciprocably mounted in a cylinder to cause slurry to be drawn through an inlet port into a chamber, conveniently afforded by the cylinder, and pumped from the chamber through an outlet port into the filter press. The apparatus also comprises an operating device comprising a drive piston reciprocably mounted in a cylinder and which is connected to the pumping piston by a connecting member, the admission of fluid under pressure to one of two inlet ports of the drive cylinder causing the drive piston, and hence the pumping piston, to move. As the drive piston reaches its uppermost position, it is necessary to operate a valve to reverse the application of fluid pressure to the drive cylinder, and when the drive piston reaches its lowermost position, it is necessary to operate the valve again to reverse the application of fluid under pressure to the drive cylinder.
At present, operation of the valve is effected by a linkage connected to the piston rod, or a cross-head thereof, movement of the linkage to an from its extreme positions effecting switching of the valve in a mechanical operation. Such a method is not only cumbersome, but is also dangerous, in that it is difficult or impractical to fully enclose the moving parts of the apparatus, for example by a safety screen.
According to the invention there is provided apparatus suitable for use in the pumping of a slurry and comprising a pumping device which comprises a cylinder and a piston mounted therein, and which is operative to cause liquid to be drawn through an inlet port and expelled through an outlet port, an operating device comprising a cylinder and piston mounted therein, valve mechanism which is operative to control the admission of fluid under pressure to the cylinder of the operating device, and a connecting member extending between the piston of the pumping device and the piston of the operating device, the apparatus comprising control mechanism which comprises two sensor members respectively responsive to the connector member of a part fixedly secured thereto reaching its two extreme positions of movement, to cause switching of the valve mechanism.
The moving parts of apparatus of the kind set out in the last preceding paragraph may readily be enclosed behind a safety screen, conveniently in the form of a perspex screen, reducing the possibility of injury to personnel supervising operation of the apparatus.
The sensor members may be provided by switches (e.g. micro switches) which are positively actuated by the connector member, or such part fixedly secured thereto. Whereas such switches may form part of a fluid pressure circuit of the control mechanism, to reduce response time, it would, in such circumstances, be necessary to position the control mechanism close to the valve mechanism. Thus, advantageously such switches form part of an electrical circuit of the control mechanism.
Preferably, however, the sensor members are provided by proximity switches responsive to the presence of the connector member, or such part fixedly secured thereto, at the extreme positions of movement, without any mechanical inter-action therebetween. Most conveniently the proximity switches are reed switches which are switched at the extreme positions of movement of the connector member by the proximity of a permanent magnet fixedly secured to the connector member, or a cross-head thereof. However, other forms of proximity switches, such as switches responsive to change in electrical capacitance, may be utilised.
It will of course be appreciated that the sensor members may be so positioned as to be activated immediately prior to the connector member reaching its extreme positions, especially where the control mechanism and/or the valve mechanism operates under a brief time delay. Ad
REFERENCES:
patent: 2424300 (1947-07-01), Becker
patent: 2462571 (1949-02-01), Thompson et al.
patent: 2582564 (1952-01-01), Schneck et al.
patent: 2646025 (1953-07-01), Deardorff
patent: 2836122 (1958-05-01), Johnson
patent: 2955460 (1960-10-01), Stevens et al.
patent: 3071926 (1963-01-01), Olson et al.
patent: 4119113 (1978-10-01), Meginniss
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