Pumps – Three or more cylinders arranged in parallel – radial – or... – Radial cylinders
Patent
1996-07-15
1998-07-14
Thorpe, Timothy
Pumps
Three or more cylinders arranged in parallel, radial, or...
Radial cylinders
417293, 13762525, F04B 104
Patent
active
057794529
DESCRIPTION:
BRIEF SUMMARY
This invention relates to pumps and in particular to positive displacement pumps.
Typically these pumps may be used in industry, in mines and on shipboard for raising and transferring water, oil, liquid products, effluent and so on. Such pumps will vary in capacity from 20 litres/minute to 1,000 litres/minute and will be capable of creating a suction of 7 metres of water and a delivery pressure of up to 8 bar. Sometimes they will need to be self-priming and able to handle a mixture (or alternation) of liquid and gas, as well as small solid particles suspended in liquids.
Hitherto such pumps have mainly been based on the progressive cavity screw principle (manufactured for example by Mono), the meshing gear or lobe principle (Jabsco et al), the sliding-shoe principle (Megator Limited) or the classic triple-ram principle. These are known as positive-displacement pumps to distinguish them from centrifugal pumps, which do not meet the performance criteria outlined above.
The performances of such pumps usually depend upon fine clearances between the working components and the manufacturers therefore have to make a painful choice between low performance and high cost of manufacture. If the material being pumped is abrasive or contains gritty particles, wear of the components will cause these clearances to increase rapidly and degrade the performance.
This drawback is not shared by the sliding-shoe pump, in which one moving part is slightly flexible and envelopes the other moving part in such a way that they are squeezed together by the pressure developed in pumping. Thus a tight seal is maintained even after considerable wear has taken place. This type of pump is therefore exceptionally positive and can develop an unusually high suction. The sliding-shoe pump is also inherently self-priming because the body, in which the pumping elements are submerged, always remains full of liquid even though the pump may temporarily be pumping only air.
This combination of virtues is offset by the following disadvantages of the sliding-shoe pump:--it is expensive, comprising intricate castings and sophisticated mouldings (the shoes), all of which parts have to be in a range of sizes; it contains hidden passages and recesses and is therefore unattractive to the food industry on sanitary grounds; it cannot be run in reverse; it cannot readily be constructed in stainless steel or plastics; it is noisy and vibrates; it is bulky and heavy; and there is a loss of volumetric efficiency due to the virtual line contact between the shoes and the rapidly rotating discs.
GB-822155 (Megator) discloses a pump comprising a plurality of pairs of pistons, each slidably mounted within its own associated cylinder, the cylinder having inlet ports and outlet ports for the entry and egress of fluid. The pistons are connected to eccentric parts driven by a shaft which move the pistons back and forth inside the cylinder and bring the ports into and out of registration with the inlets and outlets. GB-843420 (Holdener) discloses a pump having four radially directed pistons rigidly arranged on a ring and each running in a cylinder. The ring is mounted on an eccentric driven by a shaft. The cylinders are guided so as to be transversely displaceable by the eccentric movement so that ports in the pump housing into are brought registration with inlet and outlet ports for the cylinder. These pumps have a great many moving parts, however, and are bulky for the volume of fluid they can pump per revolution.
It is one object of a first aspect of the present invention to provide an alternative pump which for example has some of the same advantages as the sliding-shoe pump, but which overcomes some or all of the drawbacks listed above. This is achieved in one embodiment by means of a novel construction, in which a central impeller is sandwiched between fixed walls and is driven through a circular path of small radius, but is prevented from rotating by a ring-shaped shuttle or slider which surrounds and guides it. The shape of the impeller and slider are such that
REFERENCES:
patent: 1630953 (1927-05-01), Levine
patent: 3104618 (1963-09-01), Holdener
patent: 3211107 (1965-10-01), Bush
patent: 4605360 (1986-08-01), Swartwood
patent: 4907950 (1990-03-01), Pierrat
patent: 5004404 (1991-04-01), Pierrat
"Baseplates and Drives", Mono Merlin Options & Variations, Brochure, Mono Ltd., 1 page, (Pub. prior to Oct. 30, 1993).
"Jabsco Industrial Pump Range", Brochure, Jabsco Ltd., pp. 2-3, (Pub. prior to Oct. 30, 1993).
"Operating Instructions and Parts List ", Megator Types L+H Pumps, Megator Pumps & Compressors Ltd., Sunderland, England, pp. 1-19, (Aug. 1978).
Thorpe Timothy
Tyler Cheryl J.
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