Note: Descriptions are shown in the official language in which they were submitted.
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NOISE-REDUCED VACUUM APPLIANCE
BACKGROUND
The present invention relates generally to vacuum appliances.
s Vacuum appliances are well known. For example, vacuum appliances that are
capable of picking up both wet and dry material, commonly referred to as
wet/dry
vacuums or wet/dry vacs, are often used in workshops and other environments
where
both wet and dry debris can accumulate. Wet/dry vacuums conventionally consist
of a
collection canister or drum, usually mounted on a dolly having wheels or
casters, and a
~o powerhead within which a motor and impeller assembly is mounted. The motor
and
impeller assembly creates a suction within the drum, such that debris and/or
liquid are
drawn into the drum through an air inlet to which a flexible hose can be
attached. A filter
within the drum prevents incoming debris from escaping from the drum while
allowing
filtered air to escape.
~s A typical wet/dry vacuum motor and blower assembly includes a motor having
a
closed-face, multiple-blade blower wheel or impeller disposed on a drive shaft
thereof.
The motor and blower assembly is typically disposed in a collection canister
lid assembly,
with the rotating blower wheel disposed within a blower chamber, sometimes
referred to
as a collector chamber. The collector chamber is accessed via an air intake,
such that a
Zo suction created by rotation of the impeller within the collector chamber
causes air to be
drawn into the air intake.
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A conventional wet/dry vacuum has two air flow systems. A first air flow
system
is established for cooling the motor. The second air flow system is the blower
wheel or
impeller airflow, which affects the suction performance of the vacuum (and the
blowing
performance, for those vacs which are adaptable or convertible between and
vacuum and
s a blower).
A common problem with vacuum cleaners, and especially wet/dry vacuums, is the
excessive and irritating noise generated by the vacuum cleaner. The vacuum
motor itself
generates noise, and in vacuum cleaners having blowing ports, the high-
velocity air
exiting the blowing port further creates an especially annoying high-pitched
"whine."
~o While providing a muffler device on the blowing port and/or adding noise
muffling
materials inside the appliance is effective at reducing some noise, other
components of
the appliance continue to contribute to noise production.
The present application addresses shortcomings associated with the prior art.
SUMMARY
~ s In accordance with certain teachings of the present disclosure, a vacuum
appliance
such as a wet dry vacuum includes a motor having a rotatable shaft. An air
flow
generating member, such as a blower wheel and/or cooling fan, is connected to
the shaft.
The air flow generated by the rotating member generates noise having a
frequency and
corresponding wavelength. In motors having a commutator, such as a universal
motor,
Zo the rotating commutator further generates air flow and corresponding noise.
An air flow
path receives air generated by the rotating member. The air flow path has
first and second
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channels, the lengths of which define a predetermined difference therebetween
to cancel
the noise. In certain embodiments, the difference is corresponds to one-half
wavelength.
BRIEF DESCRIPTION OF THE DRAWINGS
Other objects and advantages of the invention will become apparent upon
reading
s the following detailed description and upon reference to the drawings in
which:
Figure 1 is a block diagram conceptually illustrating portions of a vacuum
appliance in accordance with certain teachings of the present disclosure.
Figures 2A-2D are graphs illustrating passive noise cancellation
effectiveness.
While the invention is susceptible to various modifications and alternative
forms,
~o specific embodiments thereof have been shown by way of example in the
drawings and
are herein described in detail. It should be understood, however, that the
description
herein of specific embodiments is not intended to limit the invention to the
particular
forms disclosed, but on the contrary, the intention is to cover all
modifications,
equivalents, and alternatives falling within the spirit and scope of the
invention as defined
~s by the appended claims.
DETAILED DESCRIPTION
Illustrative embodiments of the invention are described below. In the interest
of
clarity, not all features of an actual implementation are described in this
specification. It
will of course be appreciated that in the development of any such actual
embodiment,
zo numerous implementation-specific decisions must be made to achieve the
developers'
specific goals, such as compliance with system-related and business-related
constraints,
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which will vary from one implementation to another. Moreover, it will be
appreciated
that such a development effort might be complex and time-consuming, but would
nevertheless be a routine undertaking for those of ordinary skill in the art
having the
beneft of this disclosure.
s Figure 1 is a block diagram conceptually illustrating portions of a vacuum
appliance 100 in accordance with certain teachings of the present disclosure.
The
vacuum 100 includes a collection canister or drum 110 and a powerhead 112
within
which a motor and impeller assembly is mounted. The powerhead I 12 creates a
suction
within the drum 110, such that debris and/or liquid are drawn into the drum
110 through
to an air inlet 114 to which a flexible hose can be attached. A filter 120
within the drum
prevents incoming debris from escaping from the drum I 10 while allowing
filtered air to
escape through an air exhaust port (not shown).
The powerhead 112 includes a motor 130 having a blower wheel or impeller 132
disposed on a drive shaft thereof, with the rotating blower wheel disposed
within a
is blower chamber 134, sometimes referred to as a collector chamber. The motor
130
includes a cooling fan 136. A universal motor is used in exemplary vacuum
systems.
The appliance 100 has two air flow systems. One is established for cooling the
motor 130
with the cooling fan 136, and the other is the blower wheel 132 or impeller
airflow which
generates the suction inside the drum 110.
zo As noted in the background section herein, it is desirable to continue to
reduce
noise generated by vacuum appliances such as wet/dry vacuums. Sources of noise
generated by the powerhead include the blower wheel 132, the motor's
commutator/brush
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interface, and the cooling fan 136. By manipulating passageways for the motor
cooling
air and the motor exhaust air such that the length of the passageway
corresponds to
wavelengths of noise frequencies to be eliminated, the overall noise level of
the appliance
is reduced without the addition of noise-reducing hardware. The passageways
are created
s so that the wavelengths are 180 degrees out of phase for the particular
frequency to be
eliminated.
In one exemplary implementation, dual air channels were provided in a wet/dry
vacuum for each of three noise sources, with corresponding frequency
(cycles/second)
and wavelength (inches):
~o Blower wheel: 2,333,3 cycles/sec; 5.80 inches
Cooling Fan: 3,666,7 cycles/sec; 3.69 inches
Commutator: 7,333.3 cycles/sec; 1.85 inches.
The channels of the dual air channels corresponding to each of these noise
sources
is one-half wavelength different in length, so one channel "cancels" the noise
of the other
i s channel.
Figures 2A-2D are graphs illustrating motor frequency, frequency with
commutator cancellation, frequency with cooling fan cancellation and frequency
with
both commutator and cooling fan cancellation, respectively. As shown in the
graphs,
substantial noise reduction is achieved with both commutator and cooling fan
Zo cancellation.
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In tests where the difference between the two flow length paths for the
various air
channels was varied, the noise level was minimal when the difference between
flow
length channels was one-half wavelength. In contrast, the noise level was
maximum
when the difference between the flow length channels was one-quarter
wavelength,
s because at this difference, the noise is additive and not canceling.
The particular embodiments disclosed above are illustrative only, as the
invention
may be modified and practiced in different but equivalent manners apparent to
those
skilled in the art having the benefit of the teachings herein. Furthermore, no
limitations
are intended to the details of construction or design herein shown, other than
as described
io in the claims below. It is therefore evident that the particular
embodiments disclosed
above may be altered or modified and all such variations are considered within
the scope
and spirit of the invention. Accordingly, the protection sought herein is as
set forth in the
claims below.
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