Rotary expansible chamber devices – Grooved abutting cylinder-rotating member end surfaces
Reexamination Certificate
1999-04-06
2001-01-09
Vrablik, John J. (Department: 3748)
Rotary expansible chamber devices
Grooved abutting cylinder-rotating member end surfaces
C418S144000, C418S191000, C418S206400, C418S206600
Reexamination Certificate
active
06171089
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to precision metering pumps, and more particularly to external gear metering pumps for pumping viscous materials.
BACKGROUND OF THE INVENTION
Small precision metering pumps, designed for metering, for example, viscous materials such as hot melt adhesive or molten nylon or other polymers, in certain applications include a housing enclosing a pair of circular gears with external, intermeshing teeth. The gears are disposed within a pump cavity between a pair of housing plates, with the side surfaces of the gears in direct, sealed engagement with the plates to prevent internal fluid leakage between the high and low pressure zones in the pump cavity. Fixed thrust or wear plates are sometimes provided between the gear plates and the housing plates to reduce or eliminate wear and provide the necessary fluid seal. Various vents and grooves have been provided in the plates to balance the plates against the gears.
Inlet and outlet passages in the housing direct the viscous material into and out of discharge grooves formed in the surface of one or both plates, adjacent the intermeshing teeth, so that the gears meter the viscous fluid upon rotation. One of the gears (the drive gear) rotates on a drive shaft permanently mounted within the housing and extending outwardly therefrom. The drive shaft is typically journaled on a bushing mounted within the housing for smooth rotation of the gears over a range of operating torques and pressures. Appropriate O-seals supported by the housing seal around the drive shaft to prevent fluid from leaking out of the pump, and contaminants from entering the pump. The drive shaft is remotely connected to the drive shaft of a motor (prime mover), typically by a female-to-female connector.
The other, secondary gear of the set can be mounted for example, on a fixed stud or arbor supported between the housing plates. For more viscous materials, the secondary gear may also be driven by a second drive shaft permanently mounted within the housing, journaled on a second bushing, and remotely connected to a second prime mover. The stud for the secondary gear is supported generally parallel to the drive shaft for the drive gear. Alternatively, or in addition, a second set of circular gears can be provided, with external teeth, mounted adjacent the first set of gears in the same manner as described above. Such a second set of gears also facilitates pumping highly viscous material through the pump.
U.S. Pat. Nos. 2,818,023; 3,499,390; 4,277,230 and 5,496,163, for example, illustrate metering pumps such as described above.
While the precision metering pumps described above have been found appropriate for many applications, it is believed that the pumps are still too large for some applications, and that the industry has been demanding still further reductions in size. The use of a pump drive shaft and associated bushings, while heretofore believed necessary, serve to increase the over-all size of the pump. In some applications, a substantial number of pumps are mounted together on large spinning or processing machines, and the size of each pump can be an impediment to reducing the over-all size (and cost) of the machines.
As such, it is believed that there is a demand in the industry for an improved precision metering pump which has a reduced size, and which still operates effectively over a broad range of operating conditions. It is also believed there is a continual demand in the industry for metering pumps of a compact size which are easy to manufacture and assemble, and which are reliable over a long operating lifetime.
SUMMARY OF THE PRESENT INVENTION
The present invention provides a new and unique metering pump for viscous liquids which operates effectively over a broad range of operating pressures and torques. The pump does not require a permanent drive shaft and associated bushings, which significantly reduces the overall size of the pump. The pump is also manufactured from few parts, which makes the pump easy to assemble and maintain, and provides a long operating lifetime.
According to the present invention, the metering pump includes a pair of externally-toothed gears rotatably supported between a pair of housing plates. A gear plate with appropriate openings for the gears is interposed between the housing plates, and surrounds the gears. The gears are supported such that certain teeth of the gears intermesh in a gear chamber. The housing plates each include a central opening. A first of the gears, the drive gear, also includes a central opening, aligned with the central openings in the housing plates. The central opening in the drive gear can have splines or teeth, to directly receive the drive shaft of a motor or other prime mover inserted through the central opening in one of the housing plates, and allow rotation of the drive gear by the prime mover.
An annular face-type seal bounds the central opening in the drive gear, on each side surface of the gear. The face-type seal has a U-shape in cross section, and opens radially outward, with one wall of the seal in sealing engagement with the drive gear side surface, and the other wall of the seal in sealing engagement with the associated housing plate surface. The face seal can be located in an annular channel or groove formed in the housing plate, surrounding the central opening in the plate, and a corresponding shallow annular channel can be formed on the gear surface. The face seal prevents fluid leaking from the high pressure zone of the gear cavity into the central opening of the drive gear, that is, into the drive shaft receiving cavity of the pump.
The drive gear engages the inside surface of the opening in the gear plate surrounding the gear during rotation, which the gear uses as a bearing surface. The diameter of the drive gear spreads the load over a substantial portion of the gear to reduce wear on the gear. Pressure balancing grooves on the opposing faces of the housing plates, and pockets in the gear plate formed in the area of the intermeshing teeth, also reduce the loading on the drive gear during rotation. The drive shaft of the prime mover can be inserted into, or removed from, the central opening of the drive gear without disassembly of the housing.
The metering pump of the present invention has a reduced, compact size as the drive shaft of the prime mover is connected directly to the drive gear of the pump. There is no internal drive shaft or bushings necessary for the pump, which reduces the overall size of the pump without affecting the functionality of the pump. The metering pump effectively pumps fluid across a range of operating pressures and torques, and has a long operating lifetime. Because of the reduced number of components in the pump, the pump is easy to manufacture and maintain.
Further features of the present invention will become apparent to those skilled in the art upon reviewing the following specification and attached drawings.
REFERENCES:
patent: 2818023 (1957-12-01), Lundstrom
patent: 3120190 (1964-02-01), Schmitter et al.
patent: 3179331 (1965-04-01), Paschke et al.
patent: 3251309 (1966-05-01), Schmiel et al.
patent: 3499390 (1970-03-01), Prijatel
patent: 3802813 (1974-04-01), Butler
patent: 4277230 (1981-07-01), M{umlaut over (u)}ller
patent: 5096396 (1992-03-01), Welch
patent: 5496163 (1996-03-01), Griese et al.
patent: 5522714 (1996-06-01), Orimo et al.
patent: 5586875 (1996-12-01), Ondrejko et al.
patent: 1956528 (1971-05-01), None
patent: 1320674 (1963-01-01), None
Hunter Christopher H.
Parker-Hannifin Corporation
Vrablik John J.
LandOfFree
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