Rotary expansible chamber devices – With mechanical sealing – Axially movable end wall or end wall portion
Reexamination Certificate
2001-10-19
2004-10-26
Denion, Thomas (Department: 3748)
Rotary expansible chamber devices
With mechanical sealing
Axially movable end wall or end wall portion
C418S144000, C418S257000, C418S070000
Reexamination Certificate
active
06808374
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to gear pumps, and more particularly to a sanitary design gear pump in which two gear shaft bearing blocks constitute hand removable structural end bodies of the pump.
BACKGROUND OF THE INVENTION
Among the many types of known rotary positive displacement pumps, gear pumps constitute an old and well developed patent and commercial art. Gear pumps are most frequently found in the patent art and commercial practice as liquid transfer devices and as pressure pumps for hydraulic systems. They are well characterized as to their relative pumping virtues as well as their limitations in application and use. Gear pumps are also employed and well understood as metering pumps and more recently as dosing, dispensing or liquid filling pumps. For example, Oden Corporation of Buffalo, N.Y., USA manufactures a liquid filling machine product known as SERVO/FILL
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which now uses the gear pump of the present invention coupled to a servo controlled motor to define a liquid dose or fill volume based upon the amount of rotation of the gear pump, the flow rate being determined by the rate of rotation of the pump.
Among the applications for rotary positive displacement pumps are the so-called sanitary markets. These include pharmaceutical, biomedical, food, personal care and cosmetics and the like. These sectors are largely served by only a few types of rotary sanitary pumps.
One type is termed a sanitary externally timed rotary lobe pump. This type of rotor pump has an external gearbox which times or positions pump rotors such that they rotate in correct relationship with one another within a pump housing. The rotors are non-contacting but in close tolerance to each other. A variation on this rotor pump type is known as a circumferential piston pump. In either case, these pumps are very expensive by virtue of their complexity and extensive and robust construction requirements. An example of this type of pump is the Universal Series as manufactured by Waukesha Cherry-Burrell of Delavan, Wis., USA.
Another type of rotary positive displacement sanitary pump is termed a Sine pump (U.S. Pat. No. 4,575,324) as manufactured by Sine Pump of Arvada, Colo., USA. The sanitary Sine pump uses a sine wave shaped rotor running through a sliding gate such that a positive pumping action is created. This pump type is very expensive because of the complex shape of the rotor, the close tolerances, robust construction and the expensive materials utilized in its construction.
Still another type of sanitary rotary positive displacement pump is the progressing cavity type as manufactured, for example, by Moyno Industrial Products of Springfield, Ohio, USA. The progressing cavity pump uses a complex helix-like rotor running in close contact and tolerance to a progressing cavity shaped stator. These sanitary pumps are, like the other common types, very expensive by virtue of their complex structures, expensive materials of construction and robust design requirements.
Regardless of the sanitary rotary positive displacement pump type, certain common characteristics can be noted. Among these are an ability to rapidly tear down or open the fluid flow pathway of the pump for easy and thorough inspection and cleaning, often without the need for tools; the extensive use of stainless steels to assure non-contaminating and non-corroding liquid pumpage contact surfaces; the use of simple sanitary seal structures; the minimization or elimination of areas within the interior of the pump which could cause contamination of the pumpage; low RPM operation for gentle liquid handling; ability to operate at elevated temperatures; an ability to pump liquids ranging from very low viscosity to very high viscosity; and conformance to generally recognized sanitary standards, particularly the Standards For Centrifugal and Positive Rotary Pumps For Milk and Milk Products, 0-09, as promulgated in the US by the 3-A Sanitary Standards Symbol Administrative Council. This standard, which appears as Appendix A to this application, applies not only to dairy uses but also is the de facto standard for most sanitary pump uses.
Notably absent from rotary positive displacement sanitary pump types are gear pumps. This is true in terms of commercial art, and relatively few examples are found in the prior patent art. This may be generally the case because available industrial service (non-sanitary) gear pumps are not designs which are acceptable or easily adaptable for sanitary service. This is also the case even though many such otherwise suitable industrial gear pumps are available with the major fluid flow components such as the pump body, shafts and gears fabricated from materials appropriate to sanitary use, such as stainless steel.
Even though sanitary versions of gear pumps are not generally known in commercial practice, it is nevertheless true that industrial service gear pumps are often used in sanitary applications even though such pumps do not meet generally accepted sanitary standards or regulatory statutes and requirements. This is the case because the gear pump design unto itself is broadly competent in pumping many sanitary liquids, but is much less expensive than true sanitary rotary positive displacement designs available in the marketplace. For one comparative example, a 316 stainless steel industrial gear pump costs less than 33% of the price of the most widely used externally timed sanitary rotary circumferential piston pump of equivalent pumping capability.
It is also widely understood that industrial service (non-sanitary) gear pumps are often used in sanitary applications requiring critical metering or dosing capabilities, these being applications for which precision gear pumps can be more suited than other types of sanitary positive displacement pumps. It is also generally understood that where low or very low flow rates are required, sanitary positive displacement designs are generally commercially unavailable.
It is also to be noted that among knowledgeable and experienced designers of sanitary devices, equipment and pumps there has long been held the general opinion that the external gear type pump is unsuitable for sanitary service and applications because the bearings which support each gear shaft are usually internal to the pump and in contact with the liquid being pumped. This leads to concerns regarding bearing materials suitable to sanitary liquids, and further to the ease of access and cleanability and inspectability of the bearings, which almost always have a depth much greater than diameter or shaft bore.
Because of the limitations presented by sanitary service rotary positive displacement pumps of known type, which are principally economic, and because of the technical and economic need for a gear pump which satisfies and meets the requirements for sanitary service, it is the primary objective of this disclosure to present and describe a unique and novel gear pump of sanitary design. In this regard it is important to note that there are a wide array of uses of gear pumps in general industrial and non-sanitary applications of every type and nature. In many such applications, a gear pump such as that herein disclosed capable of rapid tear down without tools, easy cleaning and inspection, and constructed of corrosion resistant materials, can provide important advantages for rapid changeover of pumpage, elimination of contamination and substantially improved pump productivity. The detailed and numerous particular objects of this invention are set forth further on in this specification.
Numerous rotary positive displacement sanitary pump designs have been set forth in the prior patent and commercial art. The most prominent characteristics of several are herein reviewed by way of technical background.
Dale and Reed (U.S. Pat. No. 2,635,552) teach an externally timed rotary positive displacement rotor pump particularly designed for sanitary service, the pump being provided with studs and wing nuts for rapid removal of the pump housing without tools, and with dowel pins for precis
Amyotte Frank L.
Jezuit, Jr. Richard J.
Maki Bruce A.
Messing David C.
Phallen Iver J.
Denion Thomas
Niagara Pump Corporation
Thompson John C.
Trieu Theresa
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