U.S. patent number 3,827,675 [Application Number 05/241,742] was granted by the patent office on 1974-08-06 for oscillating bellows.
Invention is credited to Mark Schuman.
United States Patent |
3,827,675 |
Schuman |
August 6, 1974 |
OSCILLATING BELLOWS
Abstract
One or more bellows are driven in an oscillatory manner in
response to a mass of compressible fluid that is cyclically heated
and cooled. The fluid is heated in a thermal lag heating chamber in
fluid flow relationship with the bellows which cools the fluid.
Cooling of the bellows, and therefore the fluid within the bellows,
is augmented by fans blowing cool air over the folds of the
bellows. An optical chamber for analyzing gas being pumped by the
bellows is provided.
Inventors: |
Schuman; Mark (Washington,
DC) |
Family
ID: |
22911992 |
Appl.
No.: |
05/241,742 |
Filed: |
April 6, 1972 |
Current U.S.
Class: |
356/311; 60/520;
356/51; 60/517; 250/343; 417/207 |
Current CPC
Class: |
G01N
21/3518 (20130101) |
Current International
Class: |
G01N
21/31 (20060101); G01N 21/35 (20060101); G01j
003/30 () |
Field of
Search: |
;356/51,85,96,97
;60/24,25,517,520 ;417/339,340,342,328,379,209,207 ;250/343 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: McGraw; Vincent P.
Attorney, Agent or Firm: Lowe, King and Price
Claims
I claim:
1. An oscillating device comprising a chamber containing
compressible fluid, an independent heat source for heating a
portion of the chamber, a bellows, means for connecting the chamber
and the bellows in a fluid flow relationship, and means, including
the heating of fluid flowing into the chamber and the cooling of
fluid flowing into the bellows, for sustaining oscillation of the
bellows, wherein the variable exposure of thermal lag passageways
formed by the bellows folds is the primary means for reducing the
pressure of the fluid in the chamber as the bellows volume is
decreasing.
2. The device of claim 1 wherein the means for cooling includes fan
means for producing an external flow of cool fluid proximate to the
bellows.
3. The device of claim 1 wherein the heated portion is shaped to
form fluid passageway means.
4. The device of claim 3 wherein the heated passageway means
includes at least one elongated passageway having an average length
substantially greater than its average width.
5. The device of claim 3 wherein the heated passageway means
includes at least one elongated passageway having an average
breadth substantially greater than its average width.
6. The device of claim 3 wherein the heated passageway means
includes at least one passageway having an average length and an
average breadth which are each substantially greater than its
average width.
7. The device of claim 3 wherein the heated passageway means
includes at least one elongated passageway having a width which is
substantially constant throughout its length.
8. The device of claim 1 further including regenerator means
located between the heated portion and the bellows.
9. The device of claim 1 further including means for controlling
the oscillation.
10. The device of claim 9 wherein the means for controlling
includes means for varying the rate at which heat is supplied to
the heated portion.
11. The device of claim 9 wherein the means for controlling
includes means including a fan for varying the average temperature
of the bellows.
12. The device of claim 9 wherein the means for controlling
includes means for monitoring pressure variations resulting from
oscillation of the bellows.
13. The device of claim 1 further including a second chamber
connected in fluid flow relationship with the fluid containing
chamber, whereby heated fluid flows into and out of the second
chamber.
14. The device of claim 13 wherein the second chamber is an optical
chamber containing one or more optical windows for transmitting
spectral radiance variations derived at least in part from the
heated fluid.
15. The device of claim 1 further including a second bellows
connected in a fluid flow relationship with the chamber, whereby
synchronous oscillation of the first and second bellows is
obtained.
16. The device of claim 1 further including a starter pump for
initiating the oscillation.
17. The device of claim 1 wherein the bellows is within a second
chamber containing cool fluid, whereby the means for sustaining
further includes the exposure of the cool fluid to the bellows
folds when the bellows is expanded, wherein the bellows folds are
heated on one side by fluid flowing from the heated portion and are
cooled on the other side by cool fluid in the second chamber.
18. The device of claim 17 wherein a portion of the second chamber
is shaped to form an optical chamber including means for enabling
variations in spectral radiance, resulting at least in part from
fluid flowing in and out of the optical chamber, to be
monitored.
19. The device of claim 1 wherein the heated portion is within the
bellows.
20. The device of claim 19 further including an oscillator
comprising another chamber containing the compressible fluid, a
heat source for heating a portion of the another chamber, another
bellows, means for connecting the another chamber and the another
bellows in a fluid flow relationship, and means, including the
heating of fluid flowing into the another chamber and the cooling
of fluid flowing into the another bellows, for sustaining
oscillation of the another bellows, wherein the variable exposure
of thermal lag passageways formed by the another bellows folds is
the primary means for reducing the pressure of the fluid in the
another chamber as the another bellows volume is decreasing, and
means for connecting the device and oscillator in a fluid flow
relationship for synchronized operation thereof.
21. The device of claim 1 further including a second chamber
connected in fluid flow relationship with said device, whereby
pressure variations are supplied to the second chamber.
22. The device of claim 21 wherein the second chamber is an optical
chamber designed for monitoring variations of spectral radiance
produced by the pressure variations.
23. The device of claim 1 further including valve means responsive
to pressure variations in the bellows for pumping fluid.
24. The device of claim 1 wherein the chamber is shaped to form an
optical chamber suitable for monitoring variations in spectral
radiance resulting at least in part from pressure variations of
fluid within the optical chamber.
25. The device of claim 1 further including an optical chamber
located between the heated portion and the bellows, said optical
chamber being suitable for monitoring variations in spectral
radiance resulting at least in part from the oscillatory gas flow
therein.
26. The device of claim 24 wherein the means for connecting
includes optical stop means for attenuating radiation traversing
the connecting means.
27. The device of claim 25 wherein the means for connecting
includes optical stop means for attenuating radiation traversing
the connecting means.
28. The device of claim 1 wherein the chamber is shaped to form an
optical chamber suitable for monitoring variations in spectral
radiance resulting at least in part from temperature variations of
fluid within the optical chamber.
29. The device of claim 1 wherein the chamber is shaped to form an
optical chamber suitable for monitoring variations in spectral
radiance resulting at least in part from pressure and temperature
variations of fluid within the optical chamber.
30. A spectrometric analyzer for enabling the presence of a
constituent of a compressible fluid to be determined comprising a
substantially fixed volume optical chamber, means for repeatedly
forcing a hot mass of said fluid into the optical chamber and for
withdrawing a hot mass of said fluid therefrom so that in response
to the hot fluids being repeatedly forced into and withdrawn from
the chamber there is derived a repeated variation in spectral
radiance in the chamber, and means for detecting said
variation.
31. The device of claim 30 wherein the means for repeatedly forcing
includes a thermally driven oscillatory device.
32. The device of claim 30 wherein the means for repeatedly forcing
includes a thermally driven oscillating bellows.
33. A spectrometric fluid analyzer for enabling the presence of a
constituent of a fluid to be determined comprising an optical
chamber, means for repeatedly forcing a cool mass of the fluid into
the optical chamber, means for heating at least a portion of the
cool fluid within the optical chamber, means for withdrawing a mass
of the fluid from the optical chamber, whereby there is derived a
variation in spectral radiance in the chamber in response to the
fluid masses being forced into and withdrawn from the chamber and
the cool fluid being heated within the chamber, and means for
detecting said variation.
34. The device of claim 33 wherein the means for repeatedly forcing
cool fluid includes a thermally driven oscillatory device.
35. The device of claim 33 wherein the means for repeatedly forcing
cool fluid includes a thermally driven oscillating bellows.
36. The device of claim 33 wherein the chamber has a substantially
fixed volume.
37. An oscillating device comprising a chamber maintained in a
substantially closed condition during at least a portion of the
oscillatory cycle, a compressible fluid in the chamber, a bellows
forming a portion of the chamber and arranged so that expansion of
the bellows tends to decrease the volume of the chamber, means for
sustaining oscillation of the bellows, said sustaining means
including means for heating the bellows to a temperature greater
than chamber wall portions adjoining the bellows whereby: fluid is
expelled from within folds of the bellows into the chamber while
the bellows is contracting, and the expelled fluid is cooled by the
adjoining chamber wall while the bellows is contracted and
continues to be cooled as the bellows begins to expand, and fluid
flows from the chamber into the folds of the bellows while the
bellows is expanding, and the fluid in proximity with the bellows
is heated by the bellows folds while the bellows is expanded and
continues to be heated as the bellows begins to contract.
38. An oscillating apparatus comprising a chamber device having
walls, a bellows device having walls in fluid flow relationship
with the chamber device, means for sustaining oscillation of the
bellows device, a compressible fluid within the chamber, said means
for sustaining including means for heating walls of one of said
devices and for cooling walls of the other device, whereby fluid
flows from within folds of the bellows device to the chamber device
while the bellows and folds are moving to a contracted state and
fluid flows from the chamber device into the folds of the bellows
device while the bellows folds are moving to an expanded state, the
bellows folds and chamber device being thermal lag devices
responsive to the means for heating and cooling and providing
sufficient energy to maintain the bellows in oscillation so that
the fluid flowing from the one device to the other device is cooled
by the other device while the bellows folds are in one of said
states and as the bellows folds begin to move toward the other
state, and the fluid flowing from the other device to the one
device is heated by the one device while the bellows folds are in
the other state and as the bellows folds begin to move toward said
one state.
39. A spectrometric fluid analyzer for monitoring the concentration
of a constituent of a compressible fluid comprising an optical
chamber, fluid recirculation means for alternately and
substantially periodically replacing a substantial amount of cool
fluid in the chamber with hot fluid and a substantial amount of the
hot fluid in the chamber with cool fluid, whereby there are derived
a substantially periodic spectral radiant emission by the fluid in
the chamber and a substantially periodic spectral absorption of
radiant energy in the chamber by the fluid in the chamber in
response to its changing temperature and concentration, said
periodic emission and said periodic absorption being substantially
out of phase with each other and adding vectorially to produce a
resultant, substantially periodic, spectral radiant intensity
variation in the chamber, and means for monitoring said
variation.
40. The analyzer of claim 39 wherein the optical chamber has a
substantially constant volume.
41. The analyzer of claim 39 further including a radiant source
emitting radiant energy into the chamber for augmenting the
intensity of radiant energy in the chamber, whereby energy from the
source is substantially periodically absorbed in response to the
alternate and substantially periodic replacement of the cool and
hot fluids.
42. The analyzer of claim 39 wherein the means for replacing
includes a cooling chamber and a heating chamber each connected in
fluid flow relationship with the optical chamber.
43. The analyzer of claim 39 wherein the means for replacing hot
fluid with cool fluid includes a cooling chamber connected in fluid
flow relationship with the optical chamber.
44. The analyzer of claim 43 further including fan means for
cooling the cooling chamber.
45. The analyzer of claim 39 wherein the optical chamber is an
internally reflective, substantially random path, optical
chamber.
46. An electro-optical type fluid analyzer for analyzing a
compressible fluid comprising an optical chamber having a highly
reflective internal surface, means for alternately and
substantially cyclically circulating cool and hot samples of the
fluid through the chamber such that a substantial amount of the hot
fluid in the chamber is swept from the chamber by cold fluid which
replaces it and a substantial amount of the cold fluid in the
chamber is swept from the chamber by hot fluid which replaces it,
whereby there is derived a substantially cyclical variation in
spectral radiance in the chamber in response to the alternate
circulation, and means for detecting said variation.
47. The analyzer of claim 46 wherein the volume of the optical
chamber is substantially constant.
48. The analyzer of claim 46 wherein the means for circulating
includes a heating chamber connected in fluid flow relationship
with the optical chamber.
49. The analyzer of claim 46 further including a radiant source for
augmenting the intensity of radiance within the optical chamber to
thereby augment the irradiation of the sample in the optical
chamber.
50. The analyzer of claim 46 wherein the means for circulating
includes a cooling chamber connected in fluid flow relationship
with the optical chamber.
51. The analyzer of claim 46 wherein the means for detecting
includes synchronous detection means.
52. The analyzer of claim 48 further including a radiant source
emitting radiant energy into the optical chamber to increase the
cyclical variation in spectral radiance.
53. The analyzer of claim 48 wherein fluid circulated through the
optical chamber is alternately recirculated between the optical
chamber and the heating chamber and between the optical chamber and
a cooling chamber external to the optical chamber.
54. The analyzer of claim 46 wherein the optical chamber is a
substantially random path optical chamber.
55. An electro-optical type analyzer of a compressible fluid
comprising an optical chamber, a cooling chamber external to the
optical chamber, means for connecting the cooling chamber and the
optical chamber in a fluid flow relationship, means for alternately
recirculating fluid between the optical chamber and the cooling
chamber, whereby recirculating fluid flowing into the cooling
chamber is cooled in the cooling chamber, means including alternate
cooling of fluid circulating through the optical chamber for
substantially cyclically modulating the temperature and
concentration of the fluid circulating through the optical chamber,
wherein the cooling of the fluid in the cooling chamber is the
primary cooling means for the alternate cooling of fluid
circulating through the optical chamber; whereby there is derived a
substantially cyclical variation in apectral radiance in the
optical chamber in response to the modulation of the fluid, and
means for monitoring said variation.
56. The analyzer of claim 55 wherein the optical chamber is a
substantially random path optical chamber.
57. The analyzer of claim 55 wherein the means for modulating the
temperature and concentration of the fluid circulating through the
optical chamber further includes means for alternately circulating
hot fluid through the optical chamber.
58. The analyzer of claim 55 wherein the means for modulating the
temperature of the fluid circulating through the optical chamber
includes means for heating fluid.
59. The analyzer of claim 55 wherein the means for modulating
includes a heating chamber external to the optical chamber, and
means for connecting the heating chamber and the optical chamber in
a fluid flow relationship.
60. The analyzer of claim 59 wherein the volume of the optical
chamber is substantially constant during the cycle.
61. The analyzer of claim 55 wherein the internal surface area of
the optical chamber is substantially constant.
62. The analyzer of claim 59 wherein the means for modulating
further includes means for alternately recirculating fluid between
the optical chamber and the heating chamber, whereby recirculating
fluid flowing into the heating chamber is heated therein.
63. The analyzer of claim 62 wherein the heating and cooling of
fluid in the heating and cooling chambers, respectively, constitute
the primary heating and cooling means for the modulation of the
fluid.
64. The analyzer of claim 55 further including a radiant source
emitting electromagnetic energy into the optical chamber, said
electromagnetic energy being absorbed by the fluid to augment the
variation in apectral radiance.
65. The analyzer of claim 55 further including means for connecting
the cooling chamber in fluid flow relation with the optical chamber
throughout at least most of the cycle.
66. The analyzer of claim 55 further including means for connecting
the cooling chamber in fluid flow relation with the optical chamber
throughout substantially all of the cycle.
67. The analyzer of claim 55 wherein the alternate recirculation of
hot and cool fluid through the optical chamber is the primary means
for modulating the temperature and concentration of the fluid
circulating through the optical chamber.
68. The analyzer of claim 55 including fan means for cooling the
cooling chamber.
69. The analyzer of claim 59 wherein the cooling and heating
chambers each communicate with the optical chamber throughout most
of the cycle.
70. The analyzer of claim 62 wherein the cooling and heating
chambers each communicate with the optical chamber throughout
substantially all of the cycle.
71. The analyzer of claim 55 wherein the variation in spectral
radiance is substantially periodic, and wherein the means for
detecting said variation includes synchronous detection and
filtering.
72. An electro-optical instrument for monitoring the concentration
of a constituent of a compressible fluid comprising a substantially
fixed volume optical chamber, a cooling chamber external to the
optical chamber, means for connecting the cooling chamber and the
optical chamber in a fluid flow relationship, means for alternately
recirculating fluid between the optical chamber and the cooling
chamber, whereby recirculating fluid circulating through the
optical chamber and alternately into the cooling chamber is cooled
in the cooling chamber, means including the alternate cooling of
fluid circulating through the optical chamber for substantially
cyclically modulating the temperature and concentration of the
fluid circulating through the optical chamber; whereby there is
derived a variation in spectral radiance in the optical chamber in
response to the modulation of the fluid, and means for monitoring
said variation.
73. The instrument of claim 72 wherein the means for modulating
includes a heating chamber external to the optical chamber, and
means for alternately recirculating fluid between the optical
chamber and the heating chamber.
74. The instrument of claim 72 wherein the means for modulating
includes a heating chamber and means for alternately circulating
hot and cool fluid from the heating and cooling chambers into the
optical chamber.
75. The instrument of claim 74 further including a radiant source
emitting electromagnetic energy into the optical chamber.
76. The instrument of claim 73 wherein the heating chamber is in
fluid flow communication with the optical chamber during at least
most of the cycle.
77. The instrument of claim 74 further including means for
connecting the heating and cooling chambers in fluid flow
communication with the optical chamber during at least most of the
cycle.
78. The instrument of claim 74 further including means for
connecting the heating and cooling chambers in fluid flow
communication with the optical chamber during substantially all of
the cycle.
79. The instrument of claim 72 wherein the means for monitoring
includes means for synchronously detecting the variation.
80. The instrument of claim 72 wherein the optical chamber is a
substantially random path optical chamber.
81. The analyzer of claim 62 wherein the heating of fluid in the
heating chamber constitutes the primary heating means for the
modulation of the fluid.
82. The analyzer of claim 55 wherein the volume of the optical
chamber is substantially constant.
83. An electro-optical type fluid analyzer for analyzing a
compressible fluid comprising a substantially constant volume
optical chamber, means for repeatedly: (1) during a first time
interval, forcing a cool mass of the fluid into the chamber while
withdrawing a mass of the fluid from the chamber, and (2)
thereafter, during a second time interval, forcing a heated mass of
the fluid into the chamber and withdrawing a mass of the fluid from
the chamber, whereby there is derived a substantially cyclical
variation in spectral radiance in the chamber in response to the
repeated forcing of the fluid into and withdrawal of fluid from the
chamber, said variation being characteristic of the fluid, and
means for monitoring said variation.
84. The analyzer of claim 83 further including a radiant source
emitting radiant energy into the chamber to be absorbed by the
fluid, whereby said radiance variation is augmented.
85. The analyzer of claim 83 wherein the means for forcing heated
fluid includes transfer of heat from a radiant source to the
fluid.
86. The analyzer of claim 85 wherein the radiant source emits
radiant energy into the chamber to be absorbed by the fluid.
87. The analyzer of claim 83 wherein the chamber has a
substantially constant geometry.
88. The analyzer of claim 83 wherein the monitoring means includes
means for synchronously detecting said variation.
89. The analyzer of claim 83 wherein the chamber is a reflective,
random path chamber.
90. The device of claim 83 wherein the means for repeatedly forcing
and withdrawing includes a thermally driven oscillatory device.
91. The device of claim 83 wherein the means for repeatedly forcing
and withdrawing includes a thermally driven oscillating bellows.
Description
FIELD OF INVENTION
The present invention relates generally to thermally operated
oscillatory devices and, more particularly, to a thermally driven
oscillating bellows.
BACKGROUND OF THE INVENTION
Presently available oscillating bellows are usually activated by a
motor through a mechanical drive mechanism. The drive mechanism
results in wear and vibration, as well as electrical and audible
noises, all of which are generally undesirable and increase as a
function of the bellows oscillation frequency. Further, the
mechanical drive requires a number of moving parts, so that it is
relatively complex and subject to failure. In addition, due to the
fixed stroke of the drive mechanism, the bellows compression ratio
is generally fixed which, in certain instances, is not
desirable.
Oscillating bellows have found considerable use in pumping
different types of compressible fluids. For example, they are
widely employed for pumping fluids that cannot be contaminated by
the pumping mechanism, since the fluid is in contact only with the
bellows, valves and tubing and is not subject to possible contact
with foreign matter such as lubricants and wear particles that are
in other types of pumps.
BRIEF DESCRIPTION OF THE INVENTION
In accordance with the present invention, one or more bellows are
driven in an oscillatory manner in response to a mass of
compressible fluid that is cyclically heated and cooled. The fluid
is preferably heated in a thermal lag heating chamber in fluid flow
relationship with the bellows. The fluid is cooled while in the
bellows, which function as variable volume, thermal lag cooling
chambers. As described in my patent 3,489,335 and in my copending
patent application entitled "Oscillating Piston Apparatus", Ser.
No. 227,514, filed Feb. 18, 1972, a thermal lag chamber has one or
more passageways having sufficient width and thermal time constant
for relatively continuous heating or cooling of fluid forced into
the passageways. Gas at one temperature enters the thermal lag
chamber, resides therein, and escapes from the chamber at a
significantly later time from its entry and at a different
temperature. If the thermal lag chamber includes a heater, the
escaping gas has a higher temperature than the inlet gas. If the
thermal lag chamber includes a cooling means, such as cooling fins
or cool folds of a bellows, the escaping gas has a lower
temperature than the inlet gas.
In the present invention, compressible fluid is compressed into the
thermal lag heating chamber by the oscillating bellows as the
bellows is contracting. While the fluid is resident in the thermal
lag heating chamber, it is heated by the thermal lag chamber
passageways. Spring effects of the bellows folds and of the trapped
compressed fluid combine with the increasing gas pressure due to
gas heating to overcome the inertia of the contracting bellows and
reverse its direction. The fluid reaches a maximum temperature and
pressure after the oscillatory bellows has begun to expand due to
continuous heating of the fluid in the chamber, and the fluid
expands out of the thermal lag heating chamber into the bellows to
assist expansion of the bellows. Expanding fluid moving into the
expanding bellows is subsequently cooled by the opening bellows
folds, which act as thermal lag cooling surfaces. To augment the
cooling effect of the opened bellows folds, cool air may be blown
across the folds. The fluid being cooled in the bellows assists in
contraction of the bellows since the fluid reaches a minimum
temperature and pressure after the oscillating bellows has begun to
contract. The instantaneous compression ratio may be defined as the
ratio of the maximum system volume to the instantaneous system
volume. It has been found that the phase lags of the temperature
and pressure variations with respect to the instantaneous
compression ratio result in a higher average pressure while system
volume is increasing than while system volume is decreasing, so
that the thermal lag heating and cooling is more than sufficient to
overcome spring and viscous losses, thereby enabling the device to
perform useful work.
One particularly advantageous application of the invention is a
pump for sampling a gaseous mixture and periodically compressing
the mixture in a reflective optical chamber which includes means
for detecting the periodic spectral radiant emission or absorption
by the mixture, whereby the concentration of various constituents
of the mixture can be monitored. Heat from the thermal lag heater
vaporizes liquids in the mixture, to avoid condensation in the
optical chamber, to improve sensitivity and accuracy of the
monitoring device. For gases that emit infrared radiation,
sensitivity is, in general, also increased as a result of the
increase in periodic spectral infrared emission resulting from the
heat absorbed by the gas.
While the device is particularly useful as a pump in combination
with a spectrometric analyzer of a gas, it can be employed in many
applications where it is desired to drive or pump a compressible or
non-compressible fluid in a periodic manner, or for applications
where a bellows may be employed as a mechanical vibrator, shaker,
or as a means for driving another bellows. Except for valves which
may be used for pumping or sampling, the device includes as its
only moving parts, the oscillating bellows, and generally this
facilitates a significant reduction in problems of the prior art,
relating to wear, vibration, complexity and noise. A further
feature of the invention is that the frequency and amplitude of
bellows oscillation can be controlled in a facile manner merely by
controlling a heater for the thermal lag heating chamber and/or the
amount of cooling for the bellows. In some applications, such as
infrared emission or radiant absorption gas analysis, the heat
and/or radiance given off by the heating chamber are also useful.
By arranging bellows in pairs, forces can be cancelled and
vibration of the device substantially eliminated.
It is, accordingly, an object of the present invention to provide a
new and improved drive system for an oscillating bellows.
Another object of the invention is to provide a new and improved
thermally driven pump.
Another object of the invention is to provide a new and improved
device for oscillating a bellows, wherein the need for a drive
source having moving parts is obviated.
A further object of the invention is to provide a new and improved
oscillating bellows having a drive mechanism that is simple, quiet,
has very low wear and vibration, and does not produce electrical or
audible noises.
A further object of the invention is to provide a new and improved
drive mechanism for an oscillating bellows, wherein the frequency,
amplitude and/or means position of the bellows can be
controlled.
Yet another object of the invention is to provide a new and
improved thermally driven oscillating pump particularly adapted for
periodically driving hot or cool gaseous mixtures into a periodic
emission or absorption spectrometric gas analyzing device.
Yet another object of the invention is to provide a new and
improved simply constructed, sensitive, spectrometric gas analyzing
device wherein a gas sample being analyzed is heated, cooled and
pumped by the same device, to provide periodic or modulated
spectral radiant emission and/or absorption by the gas, without
causing condensation of the gas in an optical chamber.
The above and still further objects, features and advantages of the
present invention will become apparent upon consideration of the
following detailed description of several specific embodiments
thereof, especially when taken in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a schematic diagram of one embodiment of the present
invention wherein a thermal lag heater is located between a pair of
thermally driven bellows and is in direct communication with an
optical chamber;
FIG. 2 is a modification of the system of FIG. 1, wherein the
optical chamber is in direct communication with the outside of a
pair of bellows;
FIG. 3 is a modification of the system of FIG. 1, wherein a thermal
lag heater is positioned within each of a pair of oscillating
bellows, and an optical chamber is responsive to gases within one
of the bellows; and
FIG. 4 is a modification of the system of FIG. 1, wherein gases
from thermally driven bellows and three alternative thermal lag
heating chambers are all in fluid flow relationship with an optical
chamber.
DETAILED DESCRIPTION OF THE DRAWING
Reference is now made to FIG. 1 of the drawings wherein there is
illustrated a thermal lag heating chamber 1 providing heat for
sustaining oscillation of thermally driven oscillating bellows 10.
Bellows 10 has a relatively high Q (greater than one) so that the
energy which the bellows is capable of storing during each cycle is
greater than the energy which it will dissipate during each cycle.
Bellows 10 also preferably has good heat transfer properties and is
capable of handling hot gases; one preferred material for bellows
10 is a metal, such as steel. Thermal lag heating chamber 1
comprises a housing 5, which normally would be thermally insulated
externally, and separated heating fins 3 forming thermal lag
passageways 4 along the separations. An electrically activated,
resistance heater plug 2 supplies heat to the heating fins 3,
independently of the instantaneous position of the bellows and is
preferably continuously energized. Conduit 6 provides a fluid flow
passageway between port 7 in thermal lag housing 5 and port 8 in
fixedly mounted plate 9 that carries oscillating metal bellows
10.
Except for ports leading to optical chamber 30 and optional bellows
20, chambers 1 and 10 form a substantially closed chamber
containing compressible fluid. The compressible fluid may be
completely gaseous or it may be a mixture of gas and vaporizable
liquid, illustrated in a rest condition on the bottom of bellows 10
by reference numeral 11.
While bellows 10 is contracting it forces cool fluid at low
pressure through conduit 6 into thermal lag heating chamber 1,
wherein the fluid is continuously heated and expands at higher
pressure back into the bellows while the bellows is expanding.
Bellows folds 13 provide thermal lag cooling passageways which open
and cool the fluid drawn from chamber 1 into the exposed surface
area of the bellows folds and lower the internal temperature and
pressure of this fluid during subsequent contraction of bellows 10.
The variable exposure of the thermal lag passageways formed by the
bellows folds is the primary means to reduce the pressure of the
fluid in the chamber as the bellows volume is decreasing. Thus
bellows 10 acts as a variable volume cooling chamber, as well as a
chamber providing a variable exposure of a cool surface. Thereby,
thermal lag heating and cooling provide sufficient energy during
the cycle to sustain oscillation of bellows 10 and overcome losses
due, inter alia, to spring losses of bellows folds 13, frictional
losses, and any work done by the device.
An optional thermal regenerator 14, which may not be necessary, may
be provided in conduit 6 between ports 7 and 8. Regenerator 14
stores and releases thermal energy during the oscillating cycle of
bellows 10. The stored and released energy may be useful under
certain conditions to increase the amplitude of pressure variations
during the cycle. Regenerator 14, which may be a mesh of thin wire
segments establishing a positive temperature gradient in a
direction from bellows 10 to thermal lag heater 1, is not necessary
but may be included to modify performance. To a certain extent the
bellows folds function as regenerators.
Starter 15, which may comprise a piston and cylinder, provides a
pneumatic starting impulse to the device via conduit 16 which leads
to conduit 6. Starter 15 could be manually or solenoid operated.
Other means, such as mechanical or magnetic means, for providing an
impulse to plate 12 of bellows 10 can also be used to start the
oscillation cycle.
Optional bellows 20 is similar to bellows 10 but is connected via a
conduit in fluid flow relationship to the opposite side of housing
5. Bellows 20 oscillates in synchronism with bellows 10 in response
to the heated fluid escaping from chamber 1 so that both bellows
are simultaneously moving away from and toward housing 5. Bellows
20 can be used to cancel vibrational effects of bellows 10 and to
do additional work. Any practical number of synchronized bellows
can be thus connected to thermal lag heating chamber 1 or,
alternatively, to a common conduit leading to chamber 1. Thus, the
remote end plates of all the bellows tend to move away from chamber
1 in phase, then stop and accelerate toward chamber 1 in phase.
Also, separate thermally driven bellows devices, each with their
own thermal lag heating chamber and bellows, may be synchronized by
suitably connecting the thermal lag heating chambers together by
conduits.
Any two of the following three bellows oscillation parameters,
frequency, amplitude, and means position, can be controlled by
monitoring the temperature and/or pressure variation within the
bellows or at a load driven by the bellows and adjusting the rate
of fluid heating and cooling. Cooling of bellows 10 and 20 in a
controlled manner is performed with fans 28 that are positioned to
circulate cool air at controlled flow rates into the folds of the
bellows. Temperature and pressure probes 25 and 26 are respectively
located outside of bellows 10 and 20 to sense temperature and
pressure variations of a fluid pressurized by the oscillating
bellows. In the alternative, probes 25 and 26 can be positioned
within the substantially sealed confines of the device and sense
temperature and pressure variations of the fluid resident therein.
Signals derived from probe 25 or 26 are fed to control network 27
which, if desired, can be used to control the temperature of heater
2 and the speed of fans 28. Cooling fans 28 augment the cooling
normally resulting from the periodic flexing of the folds of
oscillating bellows 10 and 20 and are useful for controlling the
oscillation. As an example of control, by simultaneously increasing
the heating and cooling effects of heater plug 2 and fans 28 the
amplitude of bellows oscillation can be increased without major
change in average fluid temperature or frequency. By varying the
relative amount of heating and cooling, frequency can be varied
without major change in amplitude.
The thermally driven bellows of FIG. 1 can be used to modulate the
pressure of a substantially infinite gas volume in an enclosure
surrounding the bellows, as well as to drive other types of loads.
For example, end plate 12 of bellows 10 could abut against and
oscillate one end plate of another bellows (not shown) of a bellows
pump, which, in turn, samples a gaseous mixture and modulates the
pressure of the mixture in a radiant emission or absorption optical
chamber for analysis of the sample. Although the working fluid of
such a device is isolated from the gas analyzer, heat transmitted
through the abutting end plates of the two bellows is transferred
to the analyzed mixture each cycle. By heating the mixture each
cycle rather than heating the mixture before it enters the pump and
optical chamber, peak gas temperature is reduced for a given gas
analysis sensitivity. Thereby, the probabilities of thermal
decomposition and chemical reaction of the sample are reduced. The
material and design of the bellows plates can be chosen to provide
the proper amount of heat to the sample being analyzed.
Another load that can be driven is a gas analyzer including fixed
volume, reflective optical chamber 30 that is connected in fluid
flow relation to heating chamber 1 by tube 33. Operation of the
bellows device produces a periodic concentration variation of hot
gas within chamber 30, thereby producing periodic spectral radiant
emission and absorption by the gas sample, i.e., the pressure of
gas in chamber 30 is modulated. If the gas in chamber 30 is a known
gas, gas in chamber 30 can be used as a known periodic source of
spectral emission and/or absorption, according to principles and
techniques known to those skilled in the field of infrared and
ultra-violet gas analysis. By adding valves 90, 91, 92, as
illustrated in FIG. 4, an unknown sample can be drawn into chamber
30 and analyzed by virtue of the periodic spectral emission and/or
absorption by the unknown sample induced by the periodic modulation
of its pressure, concentration, and temperature.
The periodic emission and/or absorption of the gas in chamber 30 is
monitored by providing the chamber with one or more windows 31
transparent to the wavelengths of interest. Radiation propagated
through each of windows 31 is directed to a separate spectrometric
radiance analyzer 56 that enables correlations to be made between
spectral energy at various wavelengths to qualitatively and
quantitatively identify gases in the mixture.
If periodic radiant absorption of a gas is monitored, a radiant
source 58 that emits either a substantially non-varying or
modulated radiant beam into optical chamber 30 is generally
required to augment the intensity of radiant energy in chamber 30,
and thus the sensitivity of the analyzer. In this instance,
analyzer 56 responds to the energy passed through the periodically
modulated gas and includes suitable processing devices for
performing amplification, filtering and synchronous detection. The
processing devices feed suitable output devices, e.g., recorders
and/or displays; the processing devices are provided in radiance
analyzer 56. For qualitative and quantitative analyses of the gas
mixture, it is usually necessary to monitor and control the
periodic variation in temperature and/or pressure of the gas being
analyzed. To this end, temperature and/or pressure probes may be
located in optical chamber 30. Signals from the probes would be
coupled to analyzer 56, to facilitate signal processing and thence
to control device 27 so that heating and cooling of the gas can be
controlled. If emission is monitored, there is no need for source
58, as the varying concentration of hot gas in chamber 30 causes a
variation in spectral radiant emission in chamber 30 characteristic
of the gaseous constituent.
Oscillatory gas flow in chamber 30 may result in thermal cycling of
the internal wall surface of chamber 30 and any coating of material
on this surface. Thermal cycling of the surface results in periodic
radiant emission, primarily in the infrared, by the surface
material. Although the component of the wall emission signal which
is 90.degree. out of phase with the gas emission or absorption
signals may be useful for calibration and for reducing output
drift, as described in my U.S. Pat. No. 3,516,745, it is possible
to reduce drift to some extent merely by reducing the thermal
transfer between the gas and the wall surface, and thereby reduce
the amplitude of thermal cycling and the amplitude of the resulting
wall surface emission signal.
For this purpose, tube 33 is provided with an optional extension 34
having ports 35 near the center of optical chamber 30. Gas flow
parallel to the internal surfaces of chamber 30 is thereby reduced,
as is the thermal transfer rate, and the gas flow into and out of
chamber 30 via ports 35 is primarily radial. This reduces the
periodic wall emission signal due to thermal cycling of the surface
material. The decrease in thermal transfer also decreases the load
on the oscillating bellows device, so that the amplitude of
pressure variation in chamber 30, and therefore sensitivity of the
gas analyzer, are increased.
If desired, optical chamber 30 can be made nearly spherical to
further reduce tangential gas flow so that the flow becomes
substantially radial, thermal transfer is reduced further and made
more uniform, and wall emission and thermal losses greatly
reduced.
A near spherical shape, or other shape having a high volume to
surface area ratio, is also desirable for a random path optical
chamber since surface losses by radiant absorption are reduced and
sensitivity of the gas analyzer thereby increased. A perfectly
spherical shape may not be desirable, however, in the case of a
random path optical chamber, since rays travelling in a plane
passing through the center of the sphere will be in a stable mode
of reflection and will seldom exit through an optical window 31 for
measurement.
The devices illustrated in FIGS. 2-4 generally include heating and
cooling control and gas monitoring devices, as well as a starter,
similar to those of FIG. 1, although these devices are not
hereafter discussed unless they differ materially from the
corresponding devices of FIG. 1.
In FIG. 2, there is disclosed a thermally driven bellows device
that is generally similar to the device of FIG. 1. In FIG. 2,
however, bellows 10 and 20 are enclosed in separate chambers 52
having sealed housings 53. Housings 53 are positioned on opposite
sides of a centrally located load that is to be periodically
pressurized; such a load is an optical chamber 30. The walls of
housings 53 closest to chamber 30 include ports connected to
conduits 55 that are connected to opposite walls of chamber 30,
whereby there are provided oppositely directed fluid flow paths
from housings 53 to chamber 30. Bellows 10 and 20 are positioned in
housings 53 so that the free oscillating ends thereof are facing
the chamber ports leading to conduits 55 and the other ends thereof
are fixed to the walls of housings 53 opposite from the walls
carrying the ports leading to conduits 55. The volumes enclosed by
the interiors of bellows 10 and 20 are connected in fluid flow
relationship to opposite ends of thermal lag heater 1 by conduits
6. Because gas in chamber 30 is sealed off from the thermal lag
heater 1, this gas never reaches a very high temperature, so that
the heater can be operated at a higher temperature and greater
efficiency, relative to the device of FIG. 1, without thermally
decomposing gas in chamber 30. The natural cooling of the walls of
chambers 30 and 52 augmented by cooling fans 28 further reduce the
maximum temperature of gas in chamber 30 to avoid decomposition of
unstable gases and to help sustain bellows oscillation.
In FIG. 2, there is a thermal lag effect on the outside, as well as
inside, of bellows 10 and 20. Thus, when bellows 10 and 20
simultaneously expand, gas in chambers 52 is forced toward and
within the opening folds of bellows 10 and 20, which are warmer
than the gas and act as variably exposed, variable volume, thermal
lag heating surfaces. Maximum temperature and pressure of the gas
in chambers 52 are not reached until after the bellows have begun
to contract, thereby assisting mechanical and pneumatic spring
forces in contracting the bellows. Heated gas leaving the
contracting bellows folds is cooled by the walls of chambers 52 and
30 by virtue of natural external cooling of these walls augmented
by fans 28, tending to reduce the gas pressure by thermal lag
cooling to assist subsequent expansion of the bellows. The flexing
folds 13 of bellows 10 and 20 serve as variable volume, variably
exposed surface area, heating chambers on their outside surfaces
while the inside surfaces thereof simultaneously function as
variable volume cooling chambers. Thus, the bellows 10 and 20 of
FIG. 2 are driven from both ends rather than single-endedly as in
FIG. 1. Although the double ended effect is theoretically present
in FIG. 1, the large size of the outer enclosure generally makes
the outside driving force insignificant.
In FIG. 2 an alternate or additional starter 60 is pneumatically
connected to chamber 52, as well as starter 15 that is connected to
conduit 6.
The embodiment of FIG. 3 is quite similar to those of FIGS. 1 and 2
but illustrates a compact design wherein the thermal lag heater is
located within the bellows. Bellows 20 is pneumatically connected
to bellows 10 by means of tube 70 for synchronized bellows
oscillation. Tube 70 conducts fluid between port 71 in fixed plate
9 of bellows 10 near heating fins 3 through port 72 in fixed plate
9' in a corresponding location of bellows 20. If bellows 10
contains some liquid, as indicated by the dotted line 11, tube 70
may extend to a point slightly above liquid layer 11 in bellows 20,
as shown. Alternatively, bellows 10 and 20 may be operated in a
closed chamber 52 or in an essentially infinite enclosure.
Another embodiment is shown in FIG. 4 wherein heating elements 80
heat the walls of optical chamber 30 which is connected by conduits
81 and 82 to bellows 10 and 20. Thereby, optical chamber 30 serves
as thermal lag heating chamber for oscillating bellows 10 and 20.
Optical stop 83, an opaque plate, in a widened portion of conduit
81 optically shields chamber 30 from the periodic radiance emitted
and reflected by bellows 10 as a result of its changing geometry,
temperature, pressure, and gas flow. An alternate optical stop is
illustrated as a turn or bend in conduit 82. Both optical stops
attenuate the periodic radiance within the conduits by direct
radiation absorption and by inducing multiple reflections.
Cool gas flowing into chamber 30 from bellows 10 and 20 is
continuously heated while in the chamber by the chamber walls, and
the resulting temperature increase of the gas in chamber 30 tends
to increase the intensity of spectral emission monitored by
detector 56 during this portion of the cycle. Detector 56 may also
monitor radiant emission by the walls of chamber 30 as modulated by
spectrally absorbing gas flowing into and out of chamber 30.
One or more of alternative thermal lag heating chambers 84 or 87
can be provided around optical chamber 30, i.e., instead of heating
the optical chamber in which case primary means for periodically
heating gas circulating through optical chamber 30 comprises
heating chamber means external to the optical chamber. Chamber 84,
heated by heating element 85, continuously heats cool gas flowing
from chamber 30 into heated passageways 4 of chamber 84. Heated gas
flowing into bellows 10 and 20 from optical chamber 30 is cooled by
the bellows folds, which thereby function as primary cooling means
for the periodic cooling of gas circulating through the optical
chamber. Thus the use of heating chamber 84 in conjunction with
bellows 10 and/or 20 results in an alternate and periodic
replacement of hot gas with cool gas and cool gas with hot gas in
chamber 30. Thus, there is an alternate recirculation of fluid
between the optical chamber 30 and the cooling chamber formed by
bellows 10 and/or 20. Correspondingly, there is a periodic
recirculation of fluid between optical chamber 30 and the external
heating chamber means formed by at least one of chambers 84 or 87.
It is therefore evident that if the alternative thermal lag chamber
means is employed, the alternate heating and cooling of fluid
external to optical chamber 30 is the primary means for modulating
the temperature and concentration of the fluid circulating through
the optical chamber. Heating chamber 87 is quite similar to heating
chamber 84 but has a neck 88 which shields optical chamber 30 from
the radiant energy absorption by, and emission from, heated
passageways 4. However, heating chambers 87 and 84, the heating
elements 80, and the walls of chamber 30 heated by the heating
elements 80, all serve to various degrees as sources of radiant
emission, primarily in the infrared region of the spectrum. The
varying concentration of gas in chamber 30 causes a periodic
absorption of radiant emission from such sources as well as from
optional radiant source 58 which, for example, may emit radiance in
the ultra-violet and near infrared. This periodic absorption adds
vectorially to the periodic gas emission, which depends primarily
on the gas concentration and temperature (or the gas pressure and
temperature) in chamber 30, to produce a resultant periodic
spectral radiant intensity variation in chamber 30.
Valves 90, 91 and 92 provide flow of a gaseous sample through
chamber 30. Valve 90 is an intake check valve polarized to pass gas
only into chamber 30. Valve 91 is a check valve which is polarized
similarly to valve 90 but is spring biased to allow a small,
adjustable mass flow from chamber 30 to valve 92 at relatively low
pressure differential. Pressure differential above a selected value
automatically closes valve 91, which thus acts as a flow limiter
valve. Valve 92 is a check valve polarized to pass gas only from
valve 91 to the outside or exhaust region.
Alternatively a known gas may be sealed into chamber 30 and bellows
10 and 20, if the device is to be used as a periodic, known
spectral source for gas analysis or other purposes.
Although the thermal lag heating chambers and bellows communicating
with them in FIGS. 1 through 3 are illustrated as sealed with
respect to the outside environment, they may communicate with the
outside via a slow leakage port, filter, or valves. Thus the
differential pressure between inside and outside may be established
or controlled. This may be useful to vary or control performance.
Such valves may also be useful for utilizing the internal pressure
variations for sampling or pumping gases or other fluids.
While the source of heat is illustrated herein as electrical, any
source of heat may be utilized. Correspondingly, the air cooling
shown herein is only an illustrative example of cooling.
In the above embodiments, the width of the heated passageways 4 is
generally chosen to be small enough for reasonable penetration by
heat from the passageway walls of gas flowing into the passageways,
but large enough to reduce fluid drag and to provide a reasonable
thermal phase lag necessary for sustaining bellows oscillation at
the operating frequency. Thus, the optimum passageway width for
power or efficiency depends on the frequency of operation. The
breadth and length of the passageways characteristically are each
substantially greater than the passageway width in order to provide
a compact and efficient heat transfer chamber providing adequate
volume for admitting gas and adequate surface area for heating gas
while keeping the average passageway length, and therefore fluid
drag, to a minimum. The resulting heating chamber design is
relatively compact and the passageway walls provide good paths for
heat flow from the heat source to the passageway surfaces.
The thermal time constant of the thermal lag heating chamber, which
is affected by the width, breadth, length, and smoothness of the
passageways, is generally selected according to the desired
frequency of bellows oscillation to provide a compromise between
the degree of heating of gas flowing into and out of the
passageways and the phase lag, or continuity, of heating of the
flowing gas while within the passageways each cycle, both of which
factors are important for providing adequate power and efficiency.
An excessively large passageway width increases the phase lag but
decreases the degree or amount of heating of a gas portion, while
an excessively small passageway width increases the degree of
heating while undesirably decreasing the thermal phase lag.
Generally the width of a thermal lag passageway is substantially
uniform throughout its length in order to produce a substantially
uniform thermal time constant for heating or cooling gas in the
passageway.
The bellows folds act as thermal lag cooling surfaces or
passageways having a varying exposure to the hot gas, and a varying
passageway width, volume, and, to a lesser extent, length. The
bellows folds also have an average breadth and length, both of
which are each substantially greater than the average width of the
passageways which they form. Also, the portions of the bellows
folds nearer to a particular chamber are more shielded from the
external heating or cooling source than are the remote or most
distant portions and thus act, to some extent as a regenerator for
that particular chamber.
The heated walls of chamber 30 in FIG. 4 form a relatively wide
heated passageway with very good thermal lag and very poor
penetration into the gas in chamber 30 by the heat from the walls,
and are thus an exception to the above principles. However, because
chamber 30 simultaneously serves as a heating chamber and an
optical chamber, or load, for the device, and because of the
simplicity and different electrooptical characteristics of the
device of FIG. 4, it may have practical uses.
It should be understood that the concept of increasing radial flow
and decreasing tangential flow of gas in a chamber which is nearly
spherical or otherwise has a high volume to surface area ratio, as
described in connection with chamber 30 of FIG. 1, is applicable to
all of the embodiments illustrated herein. This technique decreases
thermal loss, wall surface radiant emission, and output drift, and
increases gas analysis sensitivity.
While there have been described several specific embodiments of the
invention, it will be clear that variations in the details of the
embodiments specifically illustrated and described may be made
without departing from the true spirit and scope of the invention
as defined in the appended claims.
* * * * *