Rotary kinetic fluid motors or pumps – Working fluid passage or distributing means associated with... – Casing having tangential inlet or outlet
Reexamination Certificate
1998-12-18
2001-04-03
Look, Edward K. (Department: 3745)
Rotary kinetic fluid motors or pumps
Working fluid passage or distributing means associated with...
Casing having tangential inlet or outlet
C415S206000, C416S183000
Reexamination Certificate
active
06210109
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to blowers using an impeller to draw in and centrifugally accelerate a fluid for controlled discharge thereof.
2. Background Art
Portable power blowers are widely used by homeowners and professionals, particularly in the landscape and maintenance industries. The most popular version of the power blower is a hand-holdable, gas powered unit which uses a forwardly projecting discharge conduit that can be conveniently oriented to control air discharge by an operator in use. An impeller, with a laterally extending rotational axis, draws air inwardly as it rotates. In one construction, the impeller has an unbladed core volume with radially projecting blades having upstream ends at the core volume and downstream ends located radially outwardly therefrom. Operation of the impeller causes air to be drawn into the core volume, picked up by the blades, centrifugally accelerated in a volute, and diverted at a point of separation from the downstream ends of the blades at high volume to the discharge conduit.
The assignee herein offers a line of such blowers which are lightweight and capable of producing a high volume air discharge. One significant problem with these gas powered blowers is that they generate a significant amount of noise during operation. Designers are constantly seeking ways to attenuate the noise generated at different locations throughout the unit to make it more environmentally compatible.
The assignee herein has done a substantial amount of research regarding noise generation in this type of blower. One noise source is where laterally/axially directed incoming air encounters the impeller and abruptly stops and changes direction to a radial flow. The radial flow is in turn abruptly halted and redirected to a curved flow path around the impeller axis in the volute as the radial flow encounters the surface bounding the volute. This abrupt halting and redirection of air flow produces unwanted noise.
Another problematic noise source is at a branching location where the accelerated flow in the volute divides to be either a) directed through the discharge conduit or b) redirected into the volute for recirculation. Directly between these divided flow paths, the accelerated air is abruptly halted, which may generate significant noise as the impeller blades travel past this location and shear the air. Also, the air re-entering the volute passes through a restriction, where the volute has its smallest volume. The noise generation thereat can be reduced by enlarging the volume of the volute at the re-entry point. However, by doing this, the efficiency of the unit may be compromised. Thus, designers in the past have generally opted to produce a more efficient unit while contending with a significant amount of operating noise.
Aside from the noise generated by the air flow and air shearing by the impeller blade in operation, the gas powered drives for these impellers generate noise that must be independently contended with. Conventional two cycle engines generate a significant amount of noise in operation. Communities are now legislating to restrict noise levels to below those which many existing two cycle engines used on power blowers operate at. Whereas, in the past, noise reduction in this field was desired, this noise reduction is now becoming a necessity. The search for solutions to the noise problem has, or is soon likely to, become a priority for most manufacturers of this type of equipment.
One manner of reducing noise generation is to use a motor to drive the impeller which operates off of an AC or DC power source. The use of AC power may be impractical where a source of AC power is unavailable or not readily accessible.
With respect to DC power sources, current technology is such that DC power sources, portable enough to be moved in a practical manner with the equipment that is powered, have a relatively limited life before recharging is required. Equipment efficiency is paramount in systems operating using a DC power supply.
SUMMARY OF THE INVENTION
The invention is directed to a portable fluid blower having a housing defining an intake region for incoming fluid, an output region, and a fluid path for controllably communicating fluid entering the intake region to the output region at which fluid is discharged from the housing. An impeller on the housing is rotatable around a first axis and draws fluid into the fluid path through the intake region and accelerates fluid drawn into the fluid path so that the fluid drawn into the fluid path through the intake region is accelerated in the fluid path and discharged in an accelerated state at the output region. A drive rotates the impeller around the first axis. The fluid path has a first curved fluid path portion that extends at least partially around the first axis, and a second transition path portion through which fluid communicates from the input region towards the first curved fluid path portion. At least part of the second transition path portion is defined by a guide surface, that extends continuously around a central axis that is substantially coincident with the first axis, and has a diameter that increases progressively from the intake region axially relative to the central axis towards the first curved fluid path portion so that fluid moving from the intake region towards the first curved fluid path portion is guided progressively radially outwardly relative to the central axis through the part of the second transition path portion.
In one form, the impeller has an axial extent along the first axis and the guide surface extends over substantially the entire axial extent of the impeller.
The impeller may have a plurality of blades each having a length extending axially relative to the first axis.
In one form, one of the blades has a length that is less than the length of another of the blades.
The blades may be reversely curved along the lengths of the blades.
In one form, the plurality of blades includes a plurality of blades having a first length and a plurality of blades having a second length that is different than the first length, with there being a blade having the first length between two blades having the second length and a blade having the second length between two blades having the first length.
The blades having the first and second lengths may alternate around the entire circumference of the impeller.
In one form, each of the blades projects radially from the guide surface relative to the first axis and the amount of radial projection for each blade varies over the length of each blade.
In one form, each blade has an upstream edge and a downstream edge and the upstream edge of one of blades is substantially straight and orthogonal to the central axis.
The upstream edge of a second blade may be substantially straight and orthogonal to the central axis, with the upstream edges of the one and second blades being substantially parallel to each other and diametrically oppositely located relative to the central axis.
The downstream edge of one of the blades may be substantially straight and parallel to the central axis.
In one form, the impeller has a diameter and an edge at a location where the diameter of the impeller is the largest and the downstream edge of the blade is substantially flush with the edge at the location where the diameter of the impeller is the largest.
A cup-shaped element may be provided at the upstream end of the impeller and has a surface that blends into the guide surface.
In one form, the impeller rotates in a drive direction and the blades have a leading surface which is inclined in the drive direction.
The drive may be one of a gas powered drive, a drive operated by an alternating current power source, and a drive operated by a direct current power source.
The housing may have a surface with a funnel-shaped portion adjacent to the intake region.
In one form, the blades each have an edge that faces radially outwardly relative to the central axis and the housing has a wall with a surface that conforms to the
Comerford Michael G.
Griffin Randall J.
Will Lawrence
Echo Incorporated
Look Edward K.
McDowell Liam
Wood Phillips VanSanten Clark & Mortimer
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