Rotary kinetic fluid motors or pumps – With sound or vibratory wave absorbing or preventing means...
Reexamination Certificate
2000-04-24
2001-07-03
Kwon, John (Department: 3745)
Rotary kinetic fluid motors or pumps
With sound or vibratory wave absorbing or preventing means...
C181S202000
Reexamination Certificate
active
06254337
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention concerns a low-noise air blower unit that produces a stream of warmed air to inflate a thermal blanket.
2. Description of the Related Art
Augustine, et al. first described the use of temperature-controlled forced air to regulate
10
the body temperature of patients, especially during and after surgery. U.S. Pat. No. 4,572,188, for example, used convective warming to prevent or treat hypothermia. In the '188 patent, temperature-controlled air is supplied by a blower unit that is connected to an airflow cover by a hose. In later-issued patents owned by the assignee of this application, the term “inflatable thermal blanket”, synonymous with “airflow cover”, is introduced. See, for example, U.S. Pat. No. 5,324,320, for “Thermal Blanket”.
Inflatable thermal blankets assume a variety of shapes and sizes for specialized use. and include various inflatable structures that wrap around or drape over a patient. See, for example, U.S. Pat. Nos. 5,300,102 and 5,336,250. The mechanism for delivering heated air to a patient has also been expanded, beyond inflatable blankets, to include self-supporting tubes and plenums. See, for example, U.S. Pat. Nos. 5,300,101 and 5,350,417.
For ease of description, the various mechanisms for delivering a flow of temperature-controlled air to bathe a patient are referred to herein as “thermal blankets.” Patient-warming systems that use thermal blankets such as these may be collectively referred to as “convective warming systems.” The basic convective warming system includes an air blower unit, a thermal blanket, and a flexible delivery hose connecting the two. These convective warming systems provide acknowledged clinical benefits. However, in certain situations, patients and medical personnel alike would benefit from having an air blower unit that operates as quietly as possible. Some patients, for example, may be sensitive to noise due to their particular medical conditions. Also, the operating room must be kept quiet to avoid distracting the operating team, and to aid the doctors and nurses in hearing vital sign monitors. Furthermore, quiet surroundings are desirable in post-operative recovery rooms, to help patients gently emerge from anesthesia-induced sleep. Moreover, a reduced-noise air blower unit provides a competitive advantage in selling and marketing such units, whether for use in operating rooms, intensive care units, or a patient's hospital room.
FIGS. 1 and 2
illustrate the components of a typical air blower unit
100
(also “blower unit”) in greater detail. The blower unit
100
includes a blower
102
powered by an electric motor
104
. In many cases, the blower
102
comprises a squirrel cage blower. This type of blower typically has a short cylinder with a plurality of fan blades that are positioned around the circumference of the cylinder and oriented longitudinally. The blower
102
withdraws ambient air into an inlet
106
and creates an airstream that continues through an outlet
108
. The outlet
108
is coupled to a tube
116
that connects to a thermal blanket
118
via a coupling ring
120
. Filter media
10
may be provided proximate the inlet
106
to cleanse the ambient air. The stream of air created by the blower
102
is heated by a heater
112
. which may comprise a resistive heating coil, receiving power from an electric power supply
114
.
In operation, the blower unit
100
rests on the supporting surface
122
, supported by feet or rollers
124
. In this position, the blower
102
revolves about an axis of rotation
126
. The blower
102
generates an airstream by drawing in air through the intake
106
in a direction
128
that is substantially parallel to the axis of rotation
126
. The airstream flows through the intake
106
and is redirected by the blower
102
in a direction
130
that is substantially perpendicular to the axis of rotation
126
. The airstream flows in the direction
130
out of the blower
102
, through the heater
112
and out of the outlet
108
into the tube
116
. In the prior art blower unit
100
. the heater
112
is downstream of the blower
102
. between the blower
102
and the outlet
108
. The motor
104
is entirely out of the airstream, being neither upstream nor downstream of the blower
102
.
Viewed differently, the vertical orientation of the axis of rotation
126
with respect to the air flow means that noise
132
will be emitted vertically upwardly, and noise
134
will be emitted parallel to the floor
122
.
As mentioned above, known blower units would further benefit their users by operating with reduced noise. As an example, a significant amount of noise occurs as the airstream created by the blower
102
exits the unit
100
through the outlet
108
. This airstream typically carries a measurable amount of noise generated by the motor
104
and the rotating blades of the blower
102
. Since the airstream flows in the direction
130
, so does the accompanying noise
132
. And, if the unit
100
rests upon the floor
122
, the noise
132
will be projected upward
130
in the direction
130
, toward the patient. Moreover, a significant portion of the noise
132
may be carried via the tube
116
directly into the blanket
118
, as shown by the noise
136
.
Another significant source of noise is found at the inlet
106
of the blower
102
. In particular, some noise from the blower
102
and motor
104
projects outward through the inlet
106
, opposite to the direction
128
. Depending upon the placement of the blower unit
100
. this noise
134
may be projected directly at medical staff and patient.
One approach to reducing the noise of a convective warming system is found in U.S. patent application Ser. No. 08/383.880, filed Feb. 6, 1995, for “A Source of Inflating Medium With Active Noise Cancellation for an Inflatable Thermal Core Apparatus”, which is assigned commonly with this application and incorporated herein by reference. Here noise reduction is achieved by positioning active cancellation elements in the blower hose. This approach, however. does not quiet the blower unit itself.
In view of these considerations, then, there is a manifest need for a blower unit that is compact and operates with reduced noise, while providing a regulated, thermally controlled airstream.
SUMMARY OF THE INVENTION
Broadly, the present invention concerns a low-noise air blower unit that produces a stream of warmed air for inflating a thermal blanket, while reducing noise caused by its own operation. The blower unit includes a housing with an inlet at a first end and an outlet at a second end. A support positions the housing above a support surface such that the inlet points toward the support surface, and the outlet does not point upward. The housing may be rested on a floor, for example, or hung above the floor, from a stand used to administer intravenous fluids.
A rotatable blower, such as a squirrel cage fan in the housing, creates an airstream by flowing ambient air into the housing through the inlet and out of the housing through the outlet. The outlet is coupled to a delivery conduit having an elbow that absorbs noise from the blower, and reflects other noise downward. The delivery conduit may be connected to a convective thermal blanket, for example.
The blower rotates under power supplied by a motor, mechanically linked to the blower. The motor, residing in the housing, is placed in the airstream upstream of the blower. A heater, interposed between the blower and the motor, heats the airstream as it passes the heater.
The present invention provides its users with a number of distinct advantages. For example, the motor's presence in the airstream helps warm the air, thereby reducing the heater's workload. Also, unlike prior arrangements, the heater heats the air prior to passing through the blower, thereby efficiently mixing the heated air and avoiding any “channeling.”
The invention provides another advantage by directing its outgoing airstream horizontally with respect to the support
Augustine Medical, Inc.
Gray Cary Ware & Freidenrich
Kwon John
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