Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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The present invention generally relate4 to moisture
sensing devices and more particularly a sensing device for
use in refrigeration systems for detecting the presence of
moisture or moisture related contaminants in the refrigera-
tion system to enable corrective action to be taken prior to
the occurence of damage to the system.
One of the major problems occurring in refrigeration
systems is damage caused by moisture or water in the refrig-
eration system. Frequently, water, and water-related con-
taminants such as acids in the refrigerant liquid, gas, or
oil will cause damage to various components of the refrigera-
tion system and has been the cause of many major repairs.
This problem has been recognized and some efforts have been
made to detect contaminants in the refrigeration system. U,S.
f
Patent No. 3,288,960 issued November 29, 1966 to E. J. Miller
discloses electrical contacts in the flow path of a fluid to
provide a warning or rendèr the system lnoperative when the
quality or characteristics of the fluid in the flow path has
changed. Other patents disclose electrical circuits in which
absorbent members are associated with electrodes to control
an electrical circuit in response to moisture absorbed by the
absorbent, U.S. Patent No. 3,671,912 issued ~une 20, 1972
to L. S. LaSota discloses an exemplary arrangement of this
type. However, such prior devices perform after contact with
undissolved contaminants such as moisture to dissolve a soluble
material, acid to attach the twisted wires or water in insul-
ating oil and do not solve the problem of detecting small
~ quantities or concentrations of moisture and contaminants that
- may become absorbed in a refrigerant system which is necessary
29 in order to sense a condition before it causes damage.
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The present invention relates to a sensing devlce for
detecting the presence of low concentrations of moisture and
moisture related contaminants in refrigerant systems comprising
an anode and cathode disposed in spaced relation in the flow
path of the refrigerant system and adapted to be connected into
an electrical circuit, absorbent means disposed between the
anode and cathode and in the flow path with the absorbent means
including material capable of change of electrical conductivity
in response to moisture absorption including dissolved and
undissolved moisture and moisture related contaminants in the
refrigerant system whereby changes of conductivity will enable
electrical flow in the circuit for enabling detectlon o the
presence of moisture or moisture related contaminants in the
refrigerant system, the anode and cathode being in the form of
spaced plates spaced from each other by desiccant material,
means maintaining contact pressure between the plates and
desiccant material thereby maintaining electrical contact with
changes in electrical conductivity of the desiccant material
being proportional to absorption of moisture or moisture related
contaminants from the refrigerant system.
Figure 1 is a schematic illustration of a refrigeration
system with the sensing device of the present invention
incorporated therein.
Figure 2 is an elevational view of the sensing device
installed in a flow line of the refrigeration system.
Figure 3 is a longitudinal, sectional view, on an
enlarged scale, taken substantially upon a plane passing along
section line 3-3 of Pig. 2 illustrating the specific structural
details of the probe, anode, cathode, absorbent material,
retainer and related structure.
Figure 4 is a transverse, sectional view taken sub-
stantially upon a plane passin~ along section line 4~4 of Fig.
3 illustrating further structural details of the absorbent
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material and retainer therefor.
Flgure 5 is a sectional view similar to Fig. 2
illustrating another embodiment of the sen~ing device.
Figure 6 is a sectional view illustrating the specific
details of the embodiment of the device illustrated in Fi~. S.
Figure 1 illustrates schematically a standard
refrigeration system including a compressor 10, water-cooled
condenser 12, liquid refrigerant, dryer
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14, expansion tevlce 16 and evaporator assombly 18 whlch 1~ shown as the type
for chllllng or cooling water or other llquid heat exchang~ medlum. The pro-
portlonal sensing devlce of the present invention i8 generally te~lgnated by
the numeral 20 and i8 illuatrated in the llquld r~friger~nt llne between the
receiver-dryer and expansion dqvlce. However, a~ set forth in more tetall
hereinafter, the senslng devlce may have many locatlon~ d~pending upon the
particular refrigeration system lnvolved. A~ lllustra~ed, the ~ensing tevice
may be lncorporated into the refrigera~t flow path 22 by insertio~ into the
branch 24 of a stantart T coupl~ng 26.
The sen~lng device 20 ehow~ in Fig~. 2-4 lnclutes a screw-threaded
body 28 that i8 externally thrested a~t i~ tetachably engaged with the inter-
nally threatet branch 24 of the coupling 26. The boty 28 lnclutes a polygonal
wrench receiving area 30 to facllltate installation of the devlce. A cathode
wire 32 is connected to the boty 28 by a seandart screw-type connection 34 80
that the wire 32 19 electrically connectet to the boty 28 which i8 of conductive
material. The cathode ~ire 32 may be connected to any portlon of a totally
grountet refrigeration system wlth the connection to body 28 only being neces-
sary when the probe assembly 20 18 screwed into nonconducting material.
Dlsposet longitudinally through the body 28 which is provided with a
- 20 cylintrlcal internsl bore is an insulati~ng ~leeve 26 of porcelaln, plastic or
other sultable insulating materlal with the ends of the sleeve 36 extending
both lnwardly of the body 28 and outwardly thereof. Extending longltudinally
through the in~ulating sleeve 36 is a contuctor rod or electrode 38 which
extend~ beyond each e~d of the insulating sleeve 36. The outer end of the
electrode 1~ CDnnectet to an electric~l conductor 40 by a stantard screw-type
c connection 42 thus electricslly connecting the conductor 40 to the electrode
38 with the inner end of the electrode tending beyond the inner end of the
insulating sleeve 36. Thus, the conductors 32 and 40 are insulated from each
other and the conductive boty 28 is insulated from the conductive rod or
` 30 electrode 38.
- The rod 38 i8 provided with a threaded end 39 which recelves an
adapter 44 having internal threaded bores 46 formed therein. The outer bore 46
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threadedly rece~ves an externally thre6ded rod 48 whlch ensbleo ~arlstlon ln the
length Qf the probe or tepth o~ the probe by threading the rod 48 lnto and out
of the threatet bore 46. A lock nut 50 is psovidet on the threadet rot 48 to
lock it i~ sd~ustet posltion.
The threaded rod 48 lncludes a perlpheral boss or ~houlder 52 thereon
snd an axlally extending rod 54 pro~ecti~g therefro~ ln oppo~ite relation to
the threaded rod 48. The free end of the rod 54 i3 externally threaded at 56
for receiving a pressure ad~usting and retaining nut 58. Positionet between
the shoulder 52 and the nut 58 is a cathode disc 60 snd 8n anote disc 62 wlth
the anode dl3c 62 restlng against the nut 58 and placed dlrectly on the threaded
rod 54. The cathode tisc 6Q la spaced froM the shoulder 52 ~y an in~ulating
disc 64 a~d insulated and spaced from the threadod rot 54 by a~ ln3ulating
sleeve 66 whlch may be integral wlth or ~eparate from the di~c 64 And constructed
of plast$c or other insulating ~aterial.
Interposed bet~een the cathode disc 60 and the anode di~c 62 is a
layer of desiccant materlal 68 which i8 ~oisture absorbent and may be in particu-
late form ~uch a~ granules or crystals of silica gel, or flilic~ gel ln pellet
or powder form or any other hygroscopic materlal that changes it~ electrical
characterlstics with the absorption of moisture. The desiccant material 68
is reta~ned ln place between the discs 60 and 62 by a fabric ring or gro~met
70 which ha~ a cross-~ectional area generally equal to the ~pace between the
disc~ 60 ~nd 62 and forms an an~ular poroua clo~ure for the ~pace bet~een the
discs 60 and 62 thereby retaining the desiccant material within the annular
space definet by the tiscs 60 and 62 ant by the external ~urface of the rod 54
and the in~ernal surface of the an~ular fabric ring 70. The an~ular fabric
ring 70 i8 of a porous fabric matersl which enables moi~ture or moi~ture con-
ta~lnants to be absorbed by the desiccant materlal 68. The ~abric ring 70
also serYes as a ~trainer to prevent the desiccant material from becoming plug-
ged by conta~inant~.
: 30 Electrical contact ia mate with the cathode disc 60 by 8 co~ductlve
coil compression sprlng 72 whlch has the end convolution thereof closely en-
circling the in~ulating di~c 64 and in eng~gement with the surfsce of the cathode
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di~c 60 ln opposet relatlon to the fabrlc ring 70 and the ab30rbent materl~l or
deslccant m~terlal 68 ~o that the coll ~prlng wlll be pooltloned ~ith the con-
volutlons thereof ~psced fro~ the rod or eloctrode 38 throughout the length
thereof. The oth~r ent of the ~prlng 18 engaged with the ond of tho bodg 28
dlopo~ct ineerlorly of the branch 24 of the coupllng 26. Thu~, the spring 72
~erves as a cathode or electrlcal connoctor between the body 28 ant the cathode
tl~c 60 and i9 lnsulated fro~ and spaced from the electrote 38. The spr~ng
6erves to maintain a constant compreasive force or pressure a8ainst the dlsc 60
thereby oaintainlog flrm electrlcal contact between the di3c 60 and body 2B in
order to be certaln to tran~it even fl~ll conductivity changes of the silica
gel. The nut 58 1B pro~ided for clamping engagement of the 811ica gel between
the discs 60 and 62 and after ad~ustment has been mate, the threaded ent 56 of
the rod 54 ~ay be rivetet over thus locking the nut 58 1Q posltlon.
~ Flgs. 5 and 6 of the drawings illustrate a ~odlfied form of the
- lnvention in whl~h a~ alternate structure 18 employed. The adapter 44 illus-
trated in Figs. 2 ~nd 3 is rem~ved and a senslng ~le~ent 120 18 attached
dlroctly to the externall~ threadet ent portlon 39 of the electrode 38. Thls
arran8ement provite~ for a reductlon ln lQngth of the aosembly 80 that the
sensing element 18 orlented adJacent the portlon of the plpe coupllng 26 havlng
the branch 24 therein. The structure of the probe externally of the coupling
26 18 the sdme as that ln Plgs. 2-4 and the same reference nu~eral~ are employed
; to de~i8nate these st N ctural feaeures.
:~ The senfilng ele~ent in ~lgs. 5 ~ud 6 includes a bod~ 122 having an
internally threaded bore 124 which is threated onto the threated end 39 of the
electrode 38. The body 122 18 provided with a shoulder 126 and an extenting
rod 128 havlng an e~ternally threaded end portion 130. A cathode dlsc 132 i8
s ~ountcd on the rod 128 in ln~ulated relatlon fro~ the rod 128 by an i~sulating
sleeve 134 and lnsulated fro~ the flsnge or shoulder 126 by en inaulating disc
136. An ~node di~c 138 1B ~ounted on the rod 128 in opposet spaced relatlon
to the cathote tisc 132. Conflnet bet~een the dlscs 132 snd 138 1~ desiccant
~aterlal 140 and a retalning rlng 142 of porous fabrlc ~aterial. The struc-
ture of the di~cs 132 and 138 and the deslccant ~nterlal and retaini~g ring
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thercfor are ~ubstantially the ~ame as the corrosponding Atructure lllustrated
in Figs. 2-5.
For applylng pressuro to th~ tlsc 138, a ~ut 144 i~ threaded onto the
threaded end 130 of the anote rot 128. A locknut 146 18 appll~t to the threaded
e~d 130 externally of the nut 144 wleh the locknut and correspontlng e~d of the
; threadet end 130 belng ground off to substantlally a sh llow conlcal conflgura-
tlon as lllustrated ln Flg. 6 after the lock~ut 146 ha8 been ti~htened.
Originally, the locknut would be substantially the same polygo~al shape and
configuratlon as the nut 144 and after the nut 144 ha6 been tightened, the
locknut 146 i8 tightened after which the locknut and the threaded end 130 are
ground to the shape and cou~lguratlon illustrated ~n Fig. 6.
The cla~ping of the tesiccant 68 or 140 between the two discs wlth
subst~tlal pressure is slgnificant inasmuch as the pressure crushes the desic-
cant ~aterial to sub~tantially a powder for~. The fabrlc retain~ng ring also
functions to hold the deslcc3nt in place during the initiel application of
pressure and, of course, retains the loose powter resulting from assembly. In
actu~l prac~ice, most of the powder will stay in positlon without the retainer
, ring although the retainer rin8 of porous fabric dces signiflcantly reduce the
plugging of the te~icCAnt ~aterial tue to the absorption of co~taminant material
from the refrigerant. The ~pring 72 serves to assure tra~6mittal of current
i from disc 60 or 132 to the boty or screw-threaded plug 28 and to compensate
for any probe depth atJustment. Continuous sub~tantial pressure is erted on
the desiccant by the cLamp nut and locknut asse~bly and for practical applica-
tion of the cha~ge in conductivity, an ~plifylng circuit is e~ployed for
controlling the refrigeration system.
While the tevice has been illustrated in association wlth a T coupling,
it is pointed out that lt may be associated with any type of plpe coupling or
inserted into flo~ lines or flow paths of various conflgurations. For example,
the assembly could be incorporated into a Y-strainer and can be a~ociated with
the flow path by using absorbent materials by which moisture or moisture
related contamlnants could be transmlttet to the dssiccant material by capillary
action or tbe like. Other materials could be employed to retain the desiccant
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mAte~lal in po~ltion as long as they are flexlble, porou~ ant nonconductlve.
The sensing dev~ce, when ln~talled, will requlre only standard plpe fittings,
bushings, reduclng ~leeves, nipples, coupllngs and the like. Also, while the
~ensing device has been illustrated ln an elementary refrigeratlon circuit in
Fi8. 1 illustrating only one probe point, ln more sophl~tlcated refrigerant
circuits, such as pre~ently u~ed hot gas reheat, hot gas tefrost, reverse cycle,llquid ln~ection motor compressor cooling ~ystems and the like, the probe may
be located at various locations, amplifier clrcuiting or the like may be
employed ant the se~slng device or devices as~ociated with the refrigerating
0 8y8t~m in such a manner to properly protect the sy~te~- The senoing device is
operative in assoclatlon with refrlgerant liquids, cold liquid~, cold gas and
other phases of refr1~eration ~y8tem8.
One example of a typical installatlo~ 18 the incorporation of a con-
ventional relay clrcuit to shut down the entire system wlth probe locations
belng ~elected for each individual installation depending upon the installation
requirements of each system.
It ls of ~lg~if~cance in this i~vention thst the sensing tevice not
only wlll sense the presence of undls~olved moi~ture but also detect abnormal
dissolved contamlnants thus detecting potential trouble before it ~tarts and
! 20 providing an audio-visual or mechanical corrective reaction. While fluorinated
hydrocarbon refri8erant~ are ma~ufactured under certain ~tandards of moisture
csntent, the ability to absorb and hold moisture vsries with the temperature.
It ia possible that moisture content above the evaporator saturation may occur
in the refrigerant from normal operatlon, g~sket, evaporator and condenser tube
leaks, etc., with such moisture totally absorbed in the liquid refrigerant by
high temperature and released in the evaporator and carried through the com-
pression cycle ~nt then re-absorbed i~ the compression and condensing cycle,
- whlch contition generates acids and water related contaminants. In order to
s detect small quantities of moisture snd contaminants which are ab~orbed in the
- 30 refrlgorant system thereby avoidlng posslble damage before it occurs, an absorbent
has been used that i8 able to pick up moisture ln extremely low concentrations
and which changes its electrical chsracteristlcs as a result of the moisture
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absorptlon. In addition, flrm contact 18 malntalned between the anote, cathode
and absorbent mater~al ln order to tranYmlt small conductivlty changes. Thl~
i8 accomplished in the pre~ent lnventlon by employlng dlsc~, initlal adJustment
by the lock nut ant fine ~d~ustment o~ the probe depth wlth the entlre unlt
belng self-contained ant completing an electrlcal clrcuit through the coll
6pring. Basic ampllfier and relay arrangements ~ay be e~ployed tepenting upon
the in~tallation requirements and the devlce may be used to operate proportlonal
motor~, modulating control program proportioning swltches or any other deslred
control apparatus. By calibratlng a standard ohm~eter ln a humidity ~cale,
direct humldity readings can be achleved by inserting into tucts or the llke in
order to maintain control of the humltity conditlons thereln.
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