Rotary kinetic fluid motors or pumps – With cutter or comminutor for debris in working fluid
Reexamination Certificate
1999-05-06
2001-05-01
Look, Edward K. (Department: 3745)
Rotary kinetic fluid motors or pumps
With cutter or comminutor for debris in working fluid
C415S169100, C415S206000
Reexamination Certificate
active
06224331
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to centrifugal pumps, and in particular, pumps of this type that have a chopping or cutting capability.
A variety of centrifugal pumps are known currently which are capable of pumping liquids and slurries containing solid matter such as small pieces of garbage or other disposed items. These pumps have the capability of chopping or cutting solid matter in the liquid mixture permitting the output from the pump to be disposed of more readily.
U.S. Pat. No. 3,155,046 issued Nov. 3, 1964 to James E. Vaughan describes a centrifugal pump for pumping a mixture of liquid and stringy solid material that includes a housing with a peripheral wall having a discharge aperture therein, a closed end, and an open end. The pump has an impeller secured on a shaft and the impeller has radially disposed impeller blades. Edges of these vanes adjacent to the pump inlet co-operate with sharpened edges of pump inlet apertures to cut solid material entering the pump.
One pump known in the prior art is the ABS “Piranha” Grinder pump. This pump incorporates sharpened spiral cutting grooves on the inside of an intake plate of the pump. Front edges on the impeller vanes of the pump rotate against the grooves to produce a cutting action. The edges of the vanes are flat in profile. This pump design is susceptible to binding problems from material being wedged between the impeller edges and the intake plate.
Another known pump is the Vaughan chopper pump disclosed in U.S. Pat. No. 5,256,032 issued Oct. 26, 1993. Features to chop and expel material from behind the impeller of the pump are incorporated into the design. The pump incorporates elongated curved vanes of the impeller operating in close cutting relationship with axially protruding ribs on a back plate of the casing. The vanes of the pump produce a cutting action as they pass over the ribs on the back plate.
Yet another known centrifugal pump is the screw centrifugal pump which utilizes spiral grooves in the rear face of the impeller of the pump and on the back plate of the casing of the pump. The rotating groove in the rear of the impeller operates against the stationary grooves in the casing backplate providing the function of discharging solids from the space between the backplate and impeller of the pump.
A known Allis-Chalmers type “SSOR” pump designed especially for pumping paper stock in a paper mill employs an impeller that rotates in a pump casing having a frontal inlet and a side outlet. This known impeller has a partial back shroud and two vanes project forwardly from this back shroud. These vanes, which are twisted along their length, sweep backwardly from around a leading edge. This pump does not have any capability of chopping or cutting solids that enter the pump.
An object of the present invention is to provide a novel and durable centrifugal pump effective for pumping a mixture including solids suspended in a liquid.
A further object of the invention is to provide an efficient and reliable centrifugal pump having an improved impeller with radially extending vanes.
Preferably the present pump is provided with a radial partial back shroud with sharpened leading shroud edges that cooperate with grooves formed on a back plate of the pump casing. The sharpened shroud edges and the grooves interact to cut solids that have entered the pump through the intake port.
SUMMARY OF THE INVENTION
According to one aspect of the invention, a centrifugal chopper pump comprises a pump casing having a frontal intake port and a pump outlet in a side thereof and a rotatable drive shaft extending into the casing from a rear side of the casing. The drive shaft rotates about an axis of rotation in a preselected direction of rotation. An impeller is mounted on the drive shaft for rotation therewith. This impeller has a set of radially extending vanes and a generally radial back shroud joined to an elongate side edge of each vane. The vanes each have a sharpened leading edge that extends generally radially in relation to the axis of rotation. Each vane projects forwardly from the back shroud and sweeps backwardly from the leading edge relative to the direction of rotation to a trailing edge. Narrow elongate cross-sections of each vane taken in a series of consecutive axial planes as defined by the axis of rotation are rotated relative to one another from an initial cross-section near the leading edge that extends generally radially to a trailing cross-section adjacent the trailing edge which extends at a substantial angle to the initial cross-section. At least one cutter member is rigidly mounted on the pump casing and is located in the intake port. This cutting member has an inner edge that extends generally radially in relation to the axis of rotation. During operation of the pump, the leading edges of the vanes rotate closely past the at least one cutter member to cut incoming solid material caught between the leading edges of the vanes and the cutter member.
Preferably the impeller includes a central hub through which the drive shaft extends and both an inner side edge of each vane and the back shroud are rigidly connected to this hub.
According to another aspect of the invention, an impeller is provided for a centrifugal chopper pump having a frontal intake port formed in a casing of the pump and a drive shaft rotated about an axis of rotation. This impeller comprises a central hub connectible to the drive shaft for rotation in a predetermined direction and two or more similar vanes extending radially outwardly from the hub and connected thereto. Each vane has an elongate sharpened leading edge that extends generally radially in relation to the axis of rotation and each vane sweeps backwardly from this leading edge relative to the direction of rotation to a trailing edge. Each vane defines narrow, elongate vane cross-sections taken along various consecutive axial planes as defined by the axis of rotation. These consecutive cross-sections are rotated relative to each other from an initial elongate vane cross-section near the leading edge of the vane that extends generally radially to an elongate trailing cross-section adjacent the trailing edge. The latter cross-section extends at a substantial angle to the initial vane cross-section.
In the preferred embodiment, the pump casing includes an intake plate that forms the intake port and at least a portion of the inner sidewall of this intake plate has spiral grooves which interact with sharpened edges of the vanes to provide further cutting of solids entering the pump.
According to a further aspect of the invention, a centrifugal pump suitable for pumping a liquid mixture containing solids includes a rotatable drive shaft defining an axis of rotation, an impeller mounted on this drive shaft and a pump casing for forming a pump bowl that surrounds the impeller. The impeller has radially extending vanes and a back shroud located at rear edges of these vanes. The shroud has cutouts located between adjacent vanes and forming leading shroud edges adapted for cutting the solids. The casing also forms an intake port adjacent to a front side of the impeller and a pump outlet. A back plate of the casing is located adjacent the back shroud and has cutting edges that extend at a substantial angle to the leading shroud edges that are adapted for cutting. These leading shroud edges and the cutting edges on the back plate closely interact to cut solids that have entered into the pump bowl.
Preferably the cutting edges on the back plate are formed by at least one spiral shaped groove formed on an inner surface of the back plate.
In a preferred embodiment of the pump, a disintegrator is mounted on the end of the drive shaft to provide initial cutting of solids as they enter the pump through the intake port.
Further features and advantages will become apparent from the following detailed description of a preferred embodiment, taken into conjunction with the accompanying drawings.
REFERENCES:
patent: 368416 (1887-08-01), Mosher
patent: 746007 (1903-12-01), Brünck
Cohen Carlos
Hayward John
Baker & Daniels
Hayward Gordon Limited
Look Edward K.
McAleenan James M
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