U.S. patent number 3,894,213 [Application Number 05/390,753] was granted by the patent office on 1975-07-08 for fluid circulating heating pad.
This patent grant is currently assigned to Everest & Jennings, Inc.. Invention is credited to Bhaskar Kumar Agarwala.
United States Patent |
3,894,213 |
Agarwala |
July 8, 1975 |
Fluid circulating heating pad
Abstract
A fluid heating and temperature control unit is provided for a
system utilizing a circulating fluid type heating pad or thermal
blanket. The unit comprises a bulkhead with a fluid reservoir
mounted below and a cover mounted above including means for
directing the flow of ventilating air. The bulkhead carries a
heater extending into the reservoir, a fluid circulator and a
thermostatic temperature control device including a sensor having
channels, one of which carries inflowing fluid and the other of
which carries outgoing fluid so that the control of temperature is
responsive to both inflowing and outflowing fluids, substantially
to the average temperature thereof. In this manner a more
satisfactory control of temperature of the heating pad is achieved
than if the control were made responsive either to the temperature
of the hotter fluid flowing into the pad or the cooler fluid
returning therefrom.
Inventors: |
Agarwala; Bhaskar Kumar (West
Los Angeles, CA) |
Assignee: |
Everest & Jennings, Inc.
(Los Angeles, CA)
|
Family
ID: |
23543786 |
Appl.
No.: |
05/390,753 |
Filed: |
August 23, 1973 |
Current U.S.
Class: |
392/471; 126/204;
219/212; 392/451; 607/104; 165/46; 219/528; 392/485 |
Current CPC
Class: |
F24H
1/202 (20130101); H05B 3/342 (20130101); A47C
21/048 (20130101); G05D 23/275 (20130101); H05B
2203/022 (20130101) |
Current International
Class: |
A47C
21/04 (20060101); A47C 21/00 (20060101); F24H
1/20 (20060101); H05B 3/34 (20060101); G05D
23/275 (20060101); F24H 001/20 () |
Field of
Search: |
;219/212,296-298,306,315-316,528 ;126/204 ;165/46,74-75,108 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Albritton; C. L.
Attorney, Agent or Firm: Knobbe, Martens, Olson, Hubbard
& Bear
Claims
What is claimed is:
1. In a controlled-temperature circulating fluid system:
a fluid reservoir having inlet and outlet ports;
fluid heating means connected to said inlet and outlet ports, said
fluid heating means comprising a fluid heater with a heating
element in said reservoir;
inlet and outlet channels each connected to one of said ports, each
of said channels having a passageway into the reservoir;
a temperature control device responsive to temperatures in both of
said channels for energizing or deenergizing said heating means as
the temperature affecting said temperature control device falls
below or rises above predetermined temperature levels; and
fluid circulating means interposed into one of said passageways
having an output port connected to the channel connected to the
reservoir outlet port.
2. In a controlled-temperature circulating fluid system:
fluid heating means having inlet and outlet ports;
inlet and outlet channels each connected to one of said ports;
a temperature control device responsive to temperatures in both of
said channels for energizing or deenergizing said heating means as
the temperature affecting said temperature control device falls
below or rises above predetermined temperature levels;
a fluid reservoir; and
a bulkhead supporting:
said fluid heater;
said channels; and
said temperature control device in combination with said fluid
reservoir mounted under said bulkhead.
3. In a controlled-temperature circulating fluid system:
fluid heating means having inlet and outlet ports;
inlet and outlet channels each connected to one of said ports;
a temperature control device responsive to temperatures in both of
said channels for energizing or deenergizing said heating means as
the temperature affecting said temperature control device falls
below or rises above predetermined temperature levels; and
a temperature limiting device independent of said temperature
control device.
4. Apparatus as described in claim 2 including a temperature
limiting device responsive to temperature of fluid in the
reservoir.
5. Apparatus as described in claim 4 wherein the temperature
limiting device includes a probe extending through the bulkhead
into the fluid reservoir.
6. Apparatus as described in claim 4 wherein the temperature
limiting device is adapted to operate at a higher temperature than
said first mentioned temperature control device.
Description
BACKGROUND OF THE INVENTION
Thermal blankets and heating pads, particularly for use for
patients in hospitals, have been proposed in which a warmed or
heated fluid circulating through ducts of a pad or blanket is
utilized instead of an electric blanket or heating pad having
resistance wires imbedded in the blanket or pad. Such circulating
fluid heating or warming devices avoid the hazard of electrical
circuits in close proximity to a patient or a sleeping person with
the attendant hazards of fires in the event of short circuits or
electrical shock in the event of defective insulation or the
accidental connection of the supply circuit to a high voltage
source.
However, for use in hospitals such apparatus must operate reliably
without excessive need for attention in order to conserve nurses'
time and must not introduce other hazards.
It is accordingly an object of the invention to provide a
circulating fluid system which is simple in operation, light and
compact, readily transported from one location to another, which
maintains a desired temperature without attention, without regard
to movement of the patient or the patient's position in relation to
the warming pad or blanket and which is free from hazards in the
event of stoppage of flow of fluid through the apparatus as a
result of a leak in the pad or blockage in one of the
passageways.
Other and further objects, features and advantages of the invention
will become apparent as the description proceeds.
SUMMARY OF THE INVENTION
In carrying out the invention in accordance with a preferred form
thereof a compact unitary construction is employed for fluid
heating and temperature control apparatus for connection to a
heating pad of the circulating fluid type. The fluid heating and
control unit comprises a bulkhead with the elements of the unit
mounted thereon, a fluid reservoir mounted below the bulkhead and a
cover or hood mounted above the bulkhead. A fluid heater is mounted
on the bulkhead with an electric heating element extending downward
through the bulkhead into the fluid reservoir.
A temperature sensor is also mounted on the bulkhead containing two
channels one of which is connected to an output port and the other
to an inlet port for connection to inlet and outlet tubing from the
heating pad. There is a pump or fluid circulator having an output
port connected to one of the channels of the sensor and an inlet
port connected to tubing dipping into the reservoir. An adjustable
thermostat is provided which is in temperature-conducting
relationship to the sensor so that it is responsive to both the
inflowing and outflowing fluid temperatures of the heating pad. In
addition there is an overload or temperature-limiting thermostat
having a probe extending into the reservoir. These thermostats have
contacts connected in series with the electric heating element and
an electric power supply so that the sensor thermostat regulates
the temperature produced by the heating element and the
temperature-limit thermostat turns off the electric power supply in
the event that temperature in the reservoir becomes excessive as a
result of stoppage of fluid flow resulting from loss of fluid from
the pad or plugging up of one of the lines. The circulating pump
also carries a fan so arranged as to create a movement of air from
the temperature sensor to the heater so that the sensor remains
unaffected by direct radiation, conduction or convection of heat
from the heater.
A better understanding of the invention will be afforded by the
following detailed description considered in conjunction with the
accompanying drawings.
DRAWINGS
In the drawings:
FIG. 1 is a perspective view of the assembly of a temperature
heating and temperature control unit connected by tubing to a
heating device of the circulating fluid type such as a fluid
blanket for use in cold climates or in hospitals or a heating pad
or the like;
FIG. 2 is a plan view of the fluid heating and temperature control
unit with the cover removed to expose elements of the unit mounted
upon a bulkhead;
FIG. 3 is a view of an elevation of the apparatus of FIG. 2 with
the cover and fluid reservoir represented as cut by a vertical
plane 33 through the center of the apparatus of FIG. 2;
FIG. 4 is an enlarged fragmentary view of a portion of the
apparatus of FIGS. 2 and 3 as seen from the bottom and represented
as cut by a broken plane 4--4 indicated in FIG. 3;
FIG. 5 is a fluid circuit diagram illustrating the fluid flow of
the apparatus; and
FIG. 6 is an electrical circuit diagram of the apparatus.
Like characters are utilized throughout the drawing to designate
like parts .
DETAILED DESCRIPTION
As shown in FIG. 1, a fluid circulating, heating and temperature
control unit 11 is provided for connection to a thermal blanket or
heating pad 12 having fluid circulating ducts therein connected to
the unit 11 through an inlet tube 13 and an outlet tube 14. The
unit 11 comprises a flanged bulkhead 15, shown in FIGS. 2 and 3,
upon which most of the parts are mounted, a reservoir 16 for a
suitable fluid such as water and a cover or hood 17 to form a
unitary integral closed structure. The reservoir 16 is secured to
the lower surface of the bulkhead 15 and the cover 17 is secured to
the flange 18 of the bulkhead 15. The cover 17 is provided also
with a handle 19 for carrying the unit, rendering it readily
portable.
The bulkhead 15 has suitable openings for mounting a fluid heater
21, a drive motor and pump assembly 22, a filler spout 23 and a
fluid temperature sensor block 24. As shown, the motor pump
assembly 22 comprises an electric motor 25 directly coupled to a
fluid circulator 26 in the form of a centrifugal pump. The common
motor-pump shaft 27 also carries an air circulator or fan 28. It
will be understood that suitable shaft packing is provided to
prevent water from the pump 26 or the reservoir 16 from entering
the motor 25.
The heater 21 comprises a mounting plate 31 carrying an immersion
type electrical resistance heater 32 projecting downward into the
reservoir 16 and terminals 33 and 34 above the bulkhead 15 for
making electrical connections.
As illustrated in FIG. 2, the cover 17 is formed with a recessed
portion 35 to provide access to the filler spout 23 without
removing the cover 17. The filler spout 23 is formed with a reduced
diameter threaded nipple portion 36 with suitable means such as a
knurled nut 37 and gasket 38 for non-leakably securing it in the
bulkhead 15. A threaded filler cap 39 is also provided.
The sensor 24 is in the form of a block in which two channels 48
and 49 are formed, each substantially in the form of an elbow as
illustrated in FIGS. 2 and 3. One channel 48 forms a connection
between the pump outlet port 41 through tubing 42 to a reservoir
outlet port 43. The other channel 49 in the sensor block 24
provides a connection between a reservoir inlet port 44 and a
passageway through tubing 45 into the reservoir 16. The pump 26,
tubing 42, and the channel in the sensor block 24 connected thereto
form a portion of a passageway from the fluid in the reservoir 16
at the pump inlet port 46 to the reservoir outlet port 43 (FIG.
4).
Thus, a fluid circuit is provided from the pump inlet 46 through
the pump 26, the pump outlet port 41, the tubing passageway 42, one
channel 48 in the sensor block 24, the reservoir outlet port 43,
heating pad inlet tubing 13, the pad 12, pad outlet tubing 14, the
reservoir inlet port 44, and the second channel 49 in the sensor
block 24 with a return passageway into the interior of the
reservoir 16 through the tubing 45.
In order to obtain better and more satisfactory control of the
actual temperature affecting the user of the pad 12, the control is
made responsive to the temperatures of both the inflow into the pad
12 and the outflow therefrom instead of merely to one or the other
of these temperatures or the temperature of the fluid within the
reservoir 16. This is accomplished by providing a thermostat 47
subjected to the temperature of the sensor block 24.
The thermostat 47 is mounted upon the sensor block 24 with the
block 24 in heat conducting relationship to the thermostat 47 so
that the thermostat responds to both the inflowing and outflowing
temperature of the pad 12 of the fluid flowing through the channels
48 and 49 in the sensor block 24, acting substantially in
accordance with the average temperature. The thermostat 47 is
mounted in thermal relationship to the sensor block 24 by means of
a bracket 51 which is integral with or clamped directly against the
block 24. The block 24 and the bracket 51 are composed of suitable
high heat conductivity material such as brass or copper. Moreover,
the block 24 is large enough so that it has large mass compared to
the thermostat 47, and its thermal or heat storing capacity is
large in relation to the thermostat 47. Consequently, fluctuations
in ambient temperature have relatively little effect on the
temperature control unless fluid temperature is varied.
The thermostat 47 is shown being of the bi-metallic type, having a
bi-metal strip 52 carrying an electrical contact 53 cooperating
with a flexible blade contact 54. The bi-metal strip 52 and the
blade contact 54 are connected to electrical circuit conductors 55
and 56, respectively.
In order that the controlled temperature may be adjusted, the
thermostat blade contact 54 is made flexible and adjustable in
position. Means are provided for adjusting the position which may
take the form, for example, of a threaded pin 57 having a tip 58
bearing against the contact blade 54. Means are provided for
biasing the blade 54 in a position toward the pin 57, which may
take a form for example of a button of insulating material 59
carried by a metal strip 61. It will be understood that the
electrical contact members 52 and 54 are electrically separated
from each other and from the supporting bracket 51 by a suitable
means such as blocks 50 composed of a material which is
electrically insulating but which conducts heat.
Inlet louvers 62 and outlet louvers 63 are provided in the cover 17
in order that the fan blades 28 may produce air flow in the
direction of the arrows 64 around the fan 28 from the thermostat 47
and the sensor block 24 toward the heater 21 in order that the
sensor 24 will not be affected directly by the heat produced by the
heater 21. The recessed portion 35 of the cover 17 serves not only
for providing access for the filler spout 23 but also as a baffle
to direct the flow of air along the arrows 64, so that the air is
caused to enter through the louvers 62 and leave through the
louvers 63 and to travel in a desired direction with respect to the
sensor 24 and the heater 21.
A temperature limit thermostat 65 is provided for safety in the
event that the blockage of any of the passageways or leakage of
fluid from the pad 12 or elsewhere in the system should interrupt
the flow of heated fluid through the channels 48 and 49 of the
sensor 24 so as to interfere with the operation of the thermostat
47 in cutting off the heater 21.
The temperature limit thermostat 65, shown in FIG. 6, comprises a
bi-metal contact member 66 and a blade contact member 67 which are
so mounted, in electrically insulating relation but thermal
conducting relationship to a probe 70 extending into the reservoir
16, as to separate the contact members 66 and 67 whenever the
temperature of the fluid in the reservoir 16, exceeds a
predetermined value. This value is selected to be somewhat higher
than the maximum temperature setting of the adjustable thermostat
47. It will be apparent that the probe 70 will become overheated so
as to open the contacts of the temperature limit thermostat 65
whenever the fluid such as water or, in the event of leakage from
the reservoir 16, air in the reservoir 16 reaches an excessive
temperature.
As shown in FIGS. 2 and 6, the thermostats 65 and 47 are connected
in series with the heater coil 32 to input lines 68 and 69 from
electrical input terminals 71 adapted to be connected to a source
of electrical current such as the central station lighting system.
Thus an electrical circuit is formed from the line 68 through a
conductor 72, the heater coil 32, a conductor 73, the contact
members 67 and 66 of the temperature limit thermostat 65, a
conductor 74, the conductor 55, thermostat 47, the conductor 56,
conductors 79 and 81 and switch contacts 75 of a switch 76, back to
the input line 69. A parallel electrical circuit for the pump and
fan driving motor 25 is provided from the input terminals 71
through the conductor 68, a conductor 78, the motor 25, conductors
77 and 81, and the switch contact 75 back to the current supply
line 69.
Preferably, check valves 83 and 84 are provided in the fittings
forming the inlet and outlet ports 43 and 44 of the reservoir 16.
Likewise connectors 85 and 86 are preferably provided at the ends
of the hose lines 13 and 14 to the pad 12 which contain check
valves 88 and 89, respectively. In this manner the heating and
temperature control unit 11 may be disconnected from the pad 12
without loss of fluid from either of them. As illustrated in FIG.
4, each of the connectors 85 and 86 is provided with a threaded
sleeve cooperating with the mating thread on the fitting of the
reservoir 16 so that fluid tight connections may be made.
In order that the check valves will be open when the connectors
have been threaded onto the fittings in the position shown for the
fitting 84 in FIG. 4, one set of check valves for example the check
valves 88 and 89 of the hose connectors are provided with depressor
pins 92 and 93. The pins 92 and 93 are of the length that when the
connection is made both check valves such as the ball check valve
94 in the reservoir inlet fitting 44 and the cone check valve 95 in
the connector 86 are moved away from their seats, against the force
of biasing springs 96 and 97. However, when the parts are
disconnected, as shown for the outlet fitting 43 and the connector
85, the springs press the ball check valve 83 and the cone check
valve 88, respectively, against their seats so as to close the
openings and prevent leakage of fluid. This permits the apparatus
to be carried about without loss of fluid or spillage.
As illustrated in FIG. 1, the heating pad 12 comprises two sheets
of flexible, fluid-impervious material such as rubber or synthetic
sheet with edges 98 heat sealed and a plurality of straight and
right-angle lines heat sealed to form parallel ducts extending from
the inlet hose 13 to the outlet hose 14. A right angled heat sealed
line 101 separates inlet ducts from outlet ducts. A heat sealed
line 102 divided the inlet area into two inlet ducts. The inlet
ducts are left open at the ends of the heat sealed lines 101 and
102 at 103 and 104 to permit the circulating fluid to divide and
travel in parallel ducts 105, 106, 107, 108, 109, 110-123, formed
by straight heat sealed lines 124, 125, 126 for example, and right
angle lines 127, 128 and 129, for example.
In this manner a plurality of parallel passageways or ducts are
provided. Near the inlet ends of the ducts the flow in the ducts
near the edge of the pad is in longer paths but near the outlet end
the flow is in shorter paths. In this manner the lengths of the
various parallel paths of flow are substantially equalized.
Consequently, substantial equalization of the amount of flow in the
various ducts takes place and the heating effect of the fluid is
well distributed. It is unnecessary to provide a single long
circuitous path for the fluid in order to obtain equalization of
the fluid throughout the pad. The use of the parallel ducts
provides considerably less resistance to flow of fluid and enables
adequate rates of flow to take place although a very small pump
motor 25 is required.
A specific embodiment of the invention has been illustrated and
described by way of illustration, but it will be understood that
the invention is not limited to the specific arrangements disclosed
and comprehends modifications falling within the scope of the
invention.
* * * * *