Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~ 3 6 t~5 T-1375-6
SHOCK HAZARD PROTECTION SYSTEM
. This invention relates generally to electrlcal hazard
preventlon, and more speclflcally to a shock hazard prevention
sy~tem for di~connecting an electrical load from an electrical
soul-ce when a shock hazard condltlon exi~ts withln the load.
Devices for protectlng human life and property agalnst
electrical shock and damage re~ultlng from a shock hazard
condltion within an electrlcal load are known. For example,
the model No. 6199 ground fault circult interruptor (GFCI~
mar~eted by the assignee of the present invention is capable of
senslng and responding to the lnadvertent grounding of the
neutral conductor of an A-C electrical distrlbution system. It
is noted, however, that in certain application~ the utilization
of ~uch a GFCI is not practical.
In partlcular, the GFCI is a relatlvely expensive and
complex device which requires the utilization of several
transformers. In addition, the GFCI i5 often hardwired ln a wall
outlet or receptacle and is neither portable nor readily
disconnected. Thus, unless each outlet in which an electrical
device such as, for example, an appliance is to be utilized 19
protected by a GFCI, the user of the appllance ïs sub~ect to
possible injury if a shock hazard condition ~hould exist in
con~unction with a non-protected outlet.
In addition, ln certain environment~ the utllization
of a conventional GFCI would not afford any ~hock hazard
protection to the user of an appliance. More specifically, a
~213665
conventional GFCI devlce of the type known to appllcants wlll not
be effectlve or work ~f the user of an electrical appliance drops
the appllance in a plastic insulated bathtub.
Another potential drawback, exl~t3 regarding the use of
a GFCI for certaln types of portable electrical appliances such
as, for example, a hair dryer. Although the owner of a halr
dryer may have hls or her residence outlets adequately protected
by GFCI devices, lt is possible that other places, such as
hotels, the residence of relatives, friends, etc., where lt ls
deslred to use the hair dryer may not be protected by such
devices.
Accordingly, it is clear that what is needed is a shock
hazard protector which i9 as~ociated with the appllance to be
protected itself rather than with the elec~rical outlet ln which
the appliance is plugged and energized. It is belleved that
prior to the present invention, this need has gone unfulfilled.
A need exists for a shocX hazard protector which
possesses attributes including having a minimum number of
components, reliability, cost and portability.
It ls accordlngly a general object of thls invention to
overcome the aforementioned limitations and drawbacks associated
with the known devices and to fulfill the needs mentioned by
provldin5 a hazard protection system having all of the
desirable attributes noted above.
12~366S
It ls a particular object of the present lnvention to
provide a shock hazard protector capable of disconnect~ng an
electrical source from an electrlcal load in re~ponse to the
detection of a shock hazard condltion wlthin the electrical load.
Another object of the present invention i9 to provide a
shock hazard protector capable of detecting and responding to a -
water-related shock hazard condition within an electrical
appliance.
A ~urther object of the present invention is to provide
a shock hazard protectlon system, as above, incorporating
immer~ion detection circuitry.
A still further object of this invention is to provide a
shock hazard protection system, as above, whereln a feature is
provided for detecting a po~sible break or discontinuity ln a
sensing or guard wire.
Yet another object of this invention is to provide a
system, as above, wherein a solenoid-type electromechanical
mechanism acts as a circuit breaking or interrupting means.
A further object is to provide such a sy~tem wherein a
relay and associated clrcuitry and mechanical means enable the
desired re~ult.
Yet a further ob~ect of this invention is to provide a
detection system whlch detects or senses the presence of a
conductive medium, and which causes an event in response thereto.
. - 3 -
~Z13i~5
Another ob~ect of this invention ls to provlde a
detectlon system whlch detects or sense~ the absence of the
presence of ~ conductive medium, and whlch causes an event ln
response thereto.
Other ob~ects will be apparent from the following
deta~led de~cription and practice of the ~nvention.
The foregoing and other ob~ects and advantage~ which
will be apparent in the follow~ng detailed descriptlon of the
preferred embodlment, or in the practlce of the lnvention, are
achleved by the invention disclosed hereln, which generally may
be characterlzed as a hazard protector. The hazard protector
includes detecting means associated with a load for detectlng a
hazard conditlon within the load, an lnterrupting means
associated with a source to which the load i5 operatively
connected, and conducting means connected between the detecting
mean3 and the interruptlng means. In response to the detection
of a hazard condition within the load by the detecting means, the
interruptlng means operatively disconnects the source from the
load.
Serving to illustrate exemplary embodiments of the
inventlon are the drawlngs, of which:
Fig. 1 i~ a perspectlve-type v~ew of a hair dryer and
its assoclated cord set incorporatlng the system accordlng to the
present invention;
~2~36~
Flg. 2 i~ a block dlagram of the shock hazard
protector, in accordance with the present lnvention;
Fig. 3 is a ~chematic diagram of one embodlment of the
shock hazard protector, in accordance with the present invention;
Fig. 4 is a schemat~c diagram of a second embodlment of
the shock hazard protector, in accordance with the present
invention;
Fig. 5 ls an enlarged partial sectlonal elevatlonal
view taken through a cord set plug of a relay embodiment of the
10 present invention;
Fig. 6 is a partial fragmentary sectional plan view
taken along the llne 6-6 of Fig. 5;
Fig. 7 is a schemat~c circ~it dlagram of the embodiment
of the present invention as~ociated with Figs. 5 and 6;
Fig. 8 is an elevational vlew of the cord set plug
illu~trated in Fig. 1 and taken along line 8-8 of that ~ame Fig. 1
depicting the assembled plug with its cover removed;
Fig. 9 is a partial sectional elevatlonal vlew taken
along line 9-9 of Fig. 8;
Fig. 10 i~ a ~ectlonal view taken along llne 10-10 of
Fig. 8;
Fig. 11 is a fragmentary sectional view taken along
line 11-11 of Fig. 8; and
Fig. 12 is an exploded-type perspect$ve view of
components of the present inventlon illustrated in Fig. 8.
lZ13~65
Referrlng now in more detail to the drawlng~, F~g. 1
presented ln its form to lllustrate a halr dryer 12 and it~
associated cord set 14 a~ wholly containing and constitutlng or
comprlsing the shock hazard protection system 10 of the present
invention. It is applicants' intention and de~ire to emphasize -
here the fact that this in~ention contemplates an electrical
appliance, such as of the personal health care type (hair dryer~,
etc.) which possesses all of the features and advantage~ of the
invention. It is also an intention of appl~cants to provide the
10 system of the present invention in the form of an OEM product
available for sale to manufacturers of such appliances.
A plug assembly 16 i9 illustrated in Flg. 1 as
lncluding polarlzed blades 18 extending from housing 20. Whereas
15 commerclally avallable hair dryers, as an example of a personal
health care appliance, normally include a c~rd set havlng two
conductors or wire~, a third wire 22 ls lllustrated in the case
of cord set 14 electrically communicatlng with a bare copper wire
24 whose path (in the example given in Fig. 1) includes proximity
to and looped clrcuit near a dryer hou~ing opening through whlch
an on-off switch a~sembly 26 extends, and thence upward to
another loop proxlmate a dryer housing air inlet opening through
which fan 28 driven by motor 30 pulls air to be heated by heatlng
ccil 32 before exiting the dryer housing air outlet opening ln
1213~iS
which grill 34 i~ positioned. After leavlng the ~econd loop
described as being ad~acent the alr inlet openlng, wire 22
extends to a thlrd loop ad~acent grill 34.
Slnce heater coil 32 carries and operates on current ln
the "hot" or phase llne, and with the provi~lon of conductor or
wire 24 wired a~ part of the neutral side of the line, the
presence of a conductlve medlum such a~, bu~ not llmlted to,
moisture or water between them wlll create a conductlve path
,contemplated by the invention as enabling lnterruption of current
to the load 12. Thls embodiment is distinguishable from another
embodiment of the present invention wherein a pair of conductor~,
as opposed to a single guard or sensing conductor 24, are located
at or near moisture/water hou~ing penetration points.
Configurations of one or more sen~ing or guard conductor~ other
than those illu~trated herein are contemplated as coming wlthln
the scope of this invention.
Referring to Fig. 2, a block dlagram of a shock hazard
protector according to the present lnventlon ls illustrated. ~s
shown therein, it comprises a source operatively connected to a
load by first and second conductors 110 and 120, respectively, a
detector 200 as~ociated with the load, a control circult 300
connected to the detector by a ~ensing or third conductor 130,
and an interruptor circuit 400 as~ociated with the source and
connected to the control circuit 300. In the case of an
electrical A-C source, conductors 110 and 120 are tied to a phase
and the neutral terminal, respectively, of the A-C source.
~Z~3~
In the normal mode of operation, that is, in the
absence of a hazard condition withln the load, the control
circuit 300, which changes from a flrst state to a second state
in re~ponse to the detection of a hazard condltlon wlthln the
load, remains ln the first state. Upon the detection by detector
200 of a predefined fault or hazard condition withln the load,
the control circuit 300 changes from the first to the second
state, whlch causes the interruptor circuit 400 to o~eratlvely
disconnect the source from the load.
It is noted that the present lnventlon co~templates
certain applications where the system sensitlvity;need not be
accurately controlled, and the control circult 300 can be
ellminated. In this situation the interruptor circuit 400 is
connected to the detector 200 by the third conductor 130, and
responds directly to the detection by detector 200 of a hazard
condition within the load.
In either situation, the sensing or third conductor 130
communlcates the presense of the hazard conditlon wlthin the load
to the control circuit 300 or the interruptor clrcuit 400.
Referring now to Flg. 3, a schematic dlagram of one
embodiment of the invention particularly sultea for use ln
con~unction with water-related shock hazard condltions wlthln an
electrical appliance operatively connected to an A-C source (not
shown) by electrical conductors 110, 120, respectively, ls
illu~trated. As shown therein, detector 200 comprise~ a palr of
~Z136~i~
hazard or lmmerslon detection conductors 210 and 220, which are
positloned in a non-contacting relationship and contalned withln
the electrical load. A pair of immersion detectlon conductor~
210 and 220 are preferably located in proximity to each port of
the appliance to be protected where water can enter.
~ or ease of description, lt will be assumed that the
appliance to be protected only contalns one port or opening
through which water may enter. For this ~ltuatlon, one end of
,one of the palr of immersion detection conductors 210 is
operatively connected to the phase terminal of an A-C ~ource (not
shown) via electrlcal ~conductor 110, and one end of the second of
the pair of immersion detection conductors 220 is connected to
the load end of the third electrlcal conductor 130. The other
ends of lmmerslon detection conductors 210, 220 are unconnected
and are maintained in a spaced-apart relatlonship, typically for
example, not more than one inch.
Shock hazard or lmmersion detection conductors 210, 220
may comprise, for example, a pair of bare electrlcal conductors
or a pair of conducting plated llnes on a printed circult board
or other physical configurations that will enable a conductive
path between the unconnected ends thereof.
Control clrcuit 300 comprises a solid state switching
control circult and includes a first re~istor Rl connected
in-line between the gate of a silicon controlled rectifier SCR
and the sour~e end of the third electrical conductor 130.
lZ13665
Resistor Rl limits the current applled to the gate of the SCR.
In addltion, control circuit 300 include~ a parallel network
comprising reslstor R2, capacitor C and dlode D connected between
the gate and cathode of the SCR. These components provide ~
measure of noi~e immunity and protection agalnst damage across
the gate to cathode ~unction of the SCR.
Interruptor circult 400 compri~es an electromechanioal
lnterrupting clrcuit and includes an energizing coll L and a
flrst and second contact or switch Sl, S2 connected ln-line with
the flrst and second electrical conduc}ors 110, 120,
respectively. Switches Sl and S2 are responsive to th'e flow of
current through energizing coil L and are closed when such
current i5 not flowing. In response to the flow of such current
they switch from the normall~ closed positlon to the shock hazard
condltion open position. One end of energizing coil L is
connected to the first electrical conductor 110 and the other end
thereof is connected to the anode of the SCR. The cathode of
the SCR is operatively connected to the second electrical
conductor 120.
-- 10 --
lZ~3~S
~ he exlstence of a water-related ~hock hazard condltlon
within the electrical appliance is detected when both unconnected
ends of the pair of lmmersion detection conductors 210, 220 are
immersed in the water. More specifically, the immersion of both
unconnected ends of the palr of immersion detection conductors
210, 220 causes the electr~cal A-C source to be operatively
connected to the gate of the SCR via the path provided by the
first electrical conductor 110, the first lmmersion detection
~onductor 210, the electrically conductlng path provlded by the
water in which the unconnected ends of the first and second
lmmersion detection conductors 210, 220 are immersed, the second
immersion detection conductor 220, the third e~ectrical conductor
130, and resistor Rl. In response thereto, the SCR switches from
the normally non-conducting ~tate to the shock hazard condition
conducting state, thereby providing a path for current to flow
through the energizlng coll L causing switches Sl and S2 to
switch from the normally closed position to the shock hazard
condition open position and thus operatively disconnecting the
A-C source from the electrical appliance.
To in~ure that the shock hazard protector ls operable
prior to utilization of the appliance lt protects, a test clrcuit
~not shown) comprislng, for example, a resistor in series wlth
a normally open switch connected between the pair of immersion
detection conductors 210, 220 may be utilized. Closlng the
normally open swltch causes the xesistor to be connected acros~
lZ136~S
the lmmerslon detectlon conductors and, if the shock haz~rd
protect~r ~s operating, as descrlbed above, causes the A-C source
~o be operatively dlsconnected from the appliance. Preferably,
the test circuit is contained within the electrical appliance.
In con~unction with said test clrcult, diode D could be replaced
with a light-emitting-diode ~LED). If the LED is llluminated
with the te~t switch ln the closed position it indicates that the
shock hazard protector is not operating properly.
Preferablyl electrical conductors 110, 120 and 130
comprise a three wire conductor having an A-C source compatible
plug at the source end, the control circuit 300 and interruptor
circuit 400 are contalned in the plug, and the detector 200 i~
contained wlthin the appliance.
Thu~ in the case where the electrical appliance 15, is,
for example, a hair dryer, the detector 200 would be located
lnternally within the dryer and, as noted a~ove, ln proximlty to
each port thereof where water can enter the dryer. It should be
emphasizèd here that while water is given as the electrlcally
conductive medium, this invention contemplates a response to any
electrically conducting medium, such that the appliance is
electrically disconnected from the A-C source in response to the
presence of such a conductive medium.
Exemplary values for the circuit illustrated ln Figure
3 are as follow~: Rl-2000 ohms, R2-1000 ohms, C-0.1
microfarads, D-lN4004, SCR-2N5064.
Referring now to Figure 4, a schematic diagram of a
second embodiment of the present invention particularly suited
121366S
for u~e in conjunction with water-related shock hszard condltions
withln an electrical appliance 1~ lllustrated. This embodlment
provldes an add~tlonal feature not present in the first
embodlment lllustrated ln Figure 3. In partlcular, the
embodlment illustrated in Figure 3, provides shock hazard
protection if any of e~ectrical conductor~ 110, 120, individually
or in combination, are broken, but does not provlde shock hazard
protection if electrical conductor 130 is broken. The embodlment
illustrated in Flgure 4 provides an additional mea~ure of ~hock
hazard protection by rendering the electrical appliance
inoperative if any of electrical conductors 110, i20 and 130,
individually or in combination, are broken.
Thls addltional measure of protection i8 provided by
the additlon of a first diode Dl connected in series between the
~econd immersion detection conductor 220 and the thlrd electrical
conductor 130, the replacement of the capacitor connected between
the gate and cathode of the SCR wlth an approprlate charglng
capacitor, the addition of a flrst charging circuit comprislng
resist~r RN and diode DN connected between the first and third
electrical conductors 110, 130, the addition of a zener diode in
series with the diode connected between the gate and cathode of
the SCR, the addltion of a second charging circuit comprlsing
resistor Rp and diode Dp connected between the flrst electrlcal
conductor 110 and the gate of the SCR, and the ellminatlon of
resistor R2 connected between the gate and cathode of the SCR.
- 13 -
i2~ 6S
The operatlon of the clrcuit illu~trated in Figure 4 i9
as follows. Assuming that the senslng or third conductor 130, is
ln tact, the appllance is not lmmersed in water and that it ls
energized, during the negative half cycle of the A-C signal on
electrical conductor llO a negative charging path via diode DN,
reslstor RN, third conductor 13D, resistor Rl provides charge to-
capacitor C, thereby charging it negatively. During the positlve
half cycle diode DN blocks, however a po~itive charging path via
resistor Rp and diode Dp provides charge to capacitor C, thereby
charging it positively. Since the time constant of res1stsr RN
and capacitor C, is roughly 33 tlmes greater than;the time
constant of resistor Rp and capacitor C, the capacitor C charges
much faster in the negative sense, so that under steady state
conditions a negatlve voltage exists on the gate of the SCR
thereby keeping it in a non-conducting state. In order to limit
that negative voltage to a value that would not damage the ga~e
to cathode junction of the SCR a three volt zener diode is added
in serie~ with diode D2, also in parallel with capacitor C.
$he next condition to look at is a broken third
conductor 130. Under this condition a negative charging path no
longer exists for the negative voltage to be impressed on
capacitor C, and, therefore during positive half cycles capicjtor
C wlll dlscharge po~itively and eventually the voltage on the
~ate of the SCR will get high enough to trip the SCR, causlng it
to switch to the conducting state thereby operatively dis-
- 14 -
12136~5
connectlng the A-C ~ource from the appliance, puttlng you in a
safe conditon. Exemplary values for the circuit illustratea ln
Figure 4 are as follow~: Dl, D2, DN, Dp-lN 4004,
RN-30,000 ohm~, Rp-l,000,000 ohms, Rl-2000 ohms, C-l
microfarad,SCR-2N50~4, Z-3 volt zener diode.-
Preferably, the component3 comprislng the flrstcharglng circui~ RN, DN and diode Dl are contained within the
electrical appllance and are water proof, the components
compri~ing the second charging circu~t Rp, Dp and the zener diode
D are contained in the plug.
It is noted that with minor modifications the above
described invention has many other appllcations. For example, in
the situatlon where the electrical appliance comprlses a power
tool, such as, a drlll, hav1ng an electrically conducting houslng
the teachings of the present invention may be utilized by
ellminating immer~lon detection conductor 220 and connecting the
third electrical conductor 130 to the électrically conducting
housing. The immersion ln water of the unconnected end of shock
hazard detection conductor 210 provides an electrically
conductive path between the shock hazard detectlon conductor and
the electrically conducting hou~ing of the drill causing, a~
described above, the drill to be operatively disconneFted from
the ~-C source.
- 15 -
12136~S
Referrlng now to an embodiment of the pre~ent inventlon
whlch utilizes the ~pproach of a relay mechanism to accompllsh
the circuit interruptlng goal of the lnvention, Flg. S
lllustrates a shock hazard protector embodlment of a plug
assembly S10 ~ormed wlth a hou~ing wlth a base and cover body
S halves 512 and 514, respectively, ~oined at a housing reference -
line 516. A ~traln rellef 518 comprises part of cord 520 and, ln
cooperative combination with the shape and contour of annulAr
surfaces 522, 524, 526 and 528, serves as à mean~ for protecting
the lntegrity of electrical connections dur~ng use.
Blades 530 extend outwardly from surfacé 532 of hou~ing
hal~ 512 and serve the functlon of matingly and electrically
engaging electrical contacts wlthln a receptacle (not shown) or
electr~cal outlet in the home, for example. A fixed contact 534
is associated and integral wlth each of the blades 530, contacts
534 being fixed or stationary as opposed to movable when
assembled.
A pair of movable contacts 536 are provlded and are
integral with leaf springs 538 which, in turn, are anchored by
means of eyelets 540 extending through openings ln an end portlon
of the leaf ~pring~ 538 spaced from the movable contacts 536.
~hese eyelets further extend through openings through a printed
circuit board 542 supported by ledges 544 and 546 ad~acent
upstandlng wall~ 54~ and 550, as shown in Fig. 5.
12~36~ii5
A tab 552 assoclated with each leaf sprlng 538 further
anchors the leaf springs to the prlnted circuit board in ~paced
relatlon~hip with re~pect to the aforesaid eyelets, thereby
serving an addltlonal function of preventing undesirable rotatlon
of the leaf springs S38, assuring alignment and rel$ably repeated
engagement between the fixed and movable contacts 534 and 536,
respectively. Leaf springs 538 are conflgured to normally bias
the movable contacts 536 away from the fixed contacts 534 when ln
an unstressed condition, thereby normally interrupting an
electrical path between these contacts. The ends of leaf springs
538 are formed with upstandlng flanges 554 to which conductors
556 are connected.
A plunger or core 558 is disposed vertically within a
bobbin coil 560, as lllustrated in Fig. 5. A reset button 564
contacts the uppermost portions of plunger 558, while a butterfly
cross bar 562 extends laterally across the plug housing and in
contact with upper surfaces of leaf springs S38. The upward
biasing forces of leaf springs 538 maintain the cross bar 562,
plunger 558 and reset button 564 ln the positlons shown in Fig.
5, while a metal strap 566 extends about portions of coil 560 as
shown. The cross sectional shape of reset button 564 ls
polygonal, such as sguare, to prevent rotatlon thereof, while the
cross sectional shape of core or plunger 558 $s round to provide
maximum electromagnetic efficiency ln lts lnteraction with bobbln
coil 560. Fig. 6 lllustrates ln a cross sectional view what
- 17 -
, ~ .
12~3~
~pplicants refer to as the "butterflyl' wlth arm~ 5~8 belng
~played outwardly from a center rlvet member 570 aligned wlth
plunger 558.
In operation, power for the printed clrcuit board
electronic components is supplied by a copper path on the board
vla pins 572 extending downwardly from the bobbln coil 560.
Prior to a shock hazard predetermined condition, the system of
Flg. 5 ls "set" by means of depressing ~et or reset button 564
inwardly, which results ln movement of the plunger and the cro~
bar against the opposing biaslng force~ of leaf sprlngs 538.
This depression of the set or re3et button w~ll result in
movement of the leaf springs until the movable contacts engage
the flxed contact~, thereby completlng an electrlcal clrcuit.
The completion of the electrical clrcuit ~ust described
re~ults in current flow to the bobbin coil whlch, ln turn,
electromagnetically "keeps" and hold~ the plunger ln its
d~pressed position until an lnterruption of such current flow.
The interengagement of the movable and fixed contacts further
serves to enable the supply of power to the load or appliance
with which the lnventlve assembly of Fig. 5 is assoclated, agaln,
until an interruptlon in current flow to the bobbin coll.
In the event of the presence of a shock hazard
condition, as a result of the operation of clrcultry of Fig. 7
described in detail below, current to the bobbin coll ls
interrupted, wlth the result that the upward biasing force~ of
- 18 -
~Zi36~5
leaf springs 538 rapldly cau~e a separation of the movable
contacts away from the fixed contact~, thereby in turn causing an
interruption of power from the source through the blades t~ the
load or appllance.
Referring now to Fig. 7 of the drawings, the aforesald
circuitry assoclated with the devlce of Flg. 5 ls illustrated
wlth like components ln Figs. S and 7 carrying like reference
characters. Wlth the relay of Flg. 5 being fed wlth half wave
~ect$fled alternating current, or pulsating direct current, there
is some current flow durlng the negative half cycle or the half
cycle other than that when line current 1~ flowing. A free
wheellng diode FWD contlnues current flow.
The main contacts Mc are normally open. When lt ls
desired to turn on the appliance after plugging lt lnto a
receptacle power source, pushlng a momentary double pull Dp wlth
respect to the normally open swltch (set or reset button 564).
This applles half wave rectified direct current to the bobbln
coil. Thls results in applying a voltage from the phase line
through the double pole ~ingle throw switch DPST, through a diode
Dl, thence through the bobb~n coil, w~th the other end of the
coll going through another contact of the double pole switch to
neutral. Thus, by pushing the swltch or re3et button, the coll
is energized, and the maln contact Mc is closed.
1 9
.. ,, . i
lZ136~5
Once the main contact M~ 1~ closed, a parallel path ~or
the current i9 provided through another diode D2,~such that there
ls current flow from phase through diode D2 through the coll wlth
its free wheeling diode ln parallel wlth lt, thence through the
collector of a transistor Ql~ the emitter of the translstor Ql
being connected to neutral. The transistor is kept on by a
resistor going from phase to the base. Rl 1~ the resistor
between phase and the base.
Once the coil energizes itself as de~crlbed, the
transistor 1~ turned on and then the momentary contact in the
DPST is released and the coil is self-holdlng. Should the load
or appllance be dropped lnto water, creating a shock hazard
condition, the current ln a sense line is rectified by diode D3
and a reslstor R2 puts a negative voltage onto the base of the
transistor. A capacitor Cl is provided between the transistor
base and the emitter which will essentially store whatever
voltage was ~resent to smooth it out. By setting the value of R2
relatively small with respect to the value of Rl, the time
constant of the negative current is shorter than that of the
positive curren~ and ln this way there is a negative charge
turning off the transistor with the result that the movable
contacts separate from the fixed contacts (Fig. 5).
- 20
lZ136~S
The reader is cautioned not to con~true the examples
presented in thls speclficatlon, such a~ in de~crlbing halr
dryers or other appllance~, as limlting the inventlon to these
example~. Any electrical appllance or apparatus wlth whlch a
shock hazard may be as~ociated is contemplated as being favorably
affected by the advantages and features of the pre~ent lnven~lon.-
Referrlng now to another embodlment of the pre~entinvention illustrated in Figs. 8-12, wherein a novel electro-
jmechanical and electromagnetlc combination servles a circuit
interrupting or breaklng function, as well as other functions. In
Fig. 8 a plug assembly 600 of the type designated reference
character 16 in Fig. 1 is shown wlth cover hou~ing half 602
removed to lllustrate base houslng half 604 wlth lts assembled
subassemblles in place. A pair of movable contact arms 606 and
lS 608 are each anchored at thelr respectlve angled depending legs
610 and 612 wlthln slot~ or rece~ses 614 and 616 of base houslng
half 604. Near ends 618 and 620 of movable arms 606 and 608,
respectively, remote from thelr ends 610 and 612, ~llver contacts
622 and 624 are rivoted to its arm.
Flexible conductors 626 are welded at 628 to depending
legs 610 and 612 at one of thelr ends, and at thelr other end~
630 the flexible conductors are welded to plug insertlon blades
632. Blade~ 632 are conflgured with mountlng shoulders 634 so as
to be held relatlvely integral with base 604 when assembled.
- 21 -
~;~136ti5
Movable contact arms 606 and 608 are normally blased ln
the direction ~hown in phantom lines within FlgO 11 such t~at
they bla~ the silver contacts 622 and 624 away from flxed sllver
contacts 636 and 638 which are riveted to fixed contact term1nals
640 and 642, respectively. The flxed contact terminals 640 and
642 themselves are phy~ically and electrically connected to a
printed circuit board 644 which carrles one of the eleckrical
circuit embodiments described above and contemplated by the
,lnvention.
A latch member 646 formed with a tang 648 ls a~soclated
with each movable contact arm and each i~ mounted and pivoted at
its upper end on pivot points 650 formed on legs 652 of a
set/reset button 654. At their lower ends 656, latches 646 are
formed w$th downward bend or leg, as viewed in Fig. 11, these
latter legs giving the latches structural stablllty for added
rellability. The full lin~s of Fig. 11 illustrate latches 646 in
their latched or set position, with tangs 648 holding the ends of
mGvable contact arm5 606 and 608 such that movable silver
contact~ 622 and 624 are in physical and electrlcal engagement
with fixed silver contacts 636 and 638, thereby enabllng current
flow through blades 632 ~rom a source such as an electrlcal
receptacle to a load, such a~ hair dryer 12.
12~3~65
Reset button 654 ls normally biased ln a direction away
from blades 632 by mean~ of helical compre~ion springs 658 shown
in Figs. 9 and 12, for example. Springs 658 are held captive
between and exert force~ against opposlng surfaces 660 and 662 of
the underside of the reset button 654 and a metallic frame 664
(see Flg. 9). Set/reset button 654 ls vi~lble to the user
through a window -668 formed within cover housing half 602 and
preferably carries indicia of the type illustrated ln Flg. 8 to
draw attention to lts functlon.
When the movable contact arms 606 and 608 are ln the
posltions shown ln Fig. 11 in phantom outline, resting against a
wall 666 formed ln base housing half 604, ~uch that the
electrical circuit is in an interrupted ~tate wlth the movable
and flxed contact~ spaced in opposition with respect to one
another, the user of the present lnvention is able to close the
clrcuit, assuming no hazard conditlon is present, by depressing
with his or her flnger the set/reset button 654. This depression
of the button 654 causes latches 646 to move ln the same
dlrection as the movable button 654 and in sliding engagement
with the ends of the movable contact arms 606 and 608 until and
such that tangs 648 ride over these arm ends. Release of the
formerly depressed button 654 results in its only partlally
returning under the influence of springs 658 towards its original
position, with a result~ng pulling of the movable contacts 622
lZ13~5
and 624 lnto engagement wlth thelr respective opposlng contact~
636 and 638 by latch tangs 648 again~t the undersides of the
movable arm ends, there~y settlng the system and closing the
clrcu~t. Latches 646 and thelr tang~ 648 hold the movable
contacts in the last posltion ~ust descrlbed until a hazard
conditlon is sensed or detected. In such an event, a plunger 67
shown ln Flgs. 8 and 9 as belng normally biased away from its
assoclated windlng or coll 672 by means of a helical compresslon
spring 674 is caused to rapidly approach the core of coll 672 as
a result of its belng energized. Plunger 670 is formed with a
neck 676 adjacent its end remote from coil 672, with which a
clevis 678 of what will here by referred to as a banger 680
matingly engages. Banger 680 i8 further formed wlth pairs of
trip and reset dogs 682 and 684 movable paths that coinclde wlth
latch 646. Upon energization of coll 672, trip dogs 682 rapldly
come into contact with and "bang" against the surfaces of latches -
646 facing wall 666, forclbly disengaging the latches 646 and
their tangs 648 from the movable contact arms, with the result
that these arms return to thelr rest positions agalnst wall 666,
and interrupt current flow through the movable and fixed
contact~. Once the current is ~nterrupted, the compresslon
forces within sprlng 674 cause the plunger 670 and lts
lnterconnected banger 680 to return to the poslt1on illu~trated
ln Fig. 9, with the reset dogs 684 comlng into contact wlth and
blasing the latches 646 against the ends of the movable contact
arms 606 and 608.
- 24 -
lZ136~S
Frame 664 compri~e~ part of the magnetic clrcult
assoclated with an operating wlnding or coil 672, and for that
purpo~e enclo~e~ a portlon of the coll. A straln rellef 686
formed in the lnsulation of a cord set 688 ls shown ln Figs. 8
and 9 held between oppo~ing annular walls 690 and 692,
respectlvely, of housing halve~ 602 and 604 which, ln turn, are
releasably ~ecured together by means of fasteners 694. Cord set
688 corresponds to the cord set 14 illustrated in Flg. 1.
Fig. 8 illustrates the printed circuit board 644 ln
broken-line outline ln the position it occupie~ atop the banger
a~embly and the fixed contacts. Fig. 8 further illustrates the
three wires, phase/neutral 696 and the guard or sens~ng wire 698
whlch extend through and a~ part of cord set 688, through the
strain relief 686, and into the conflnes of plug assembly 600.
Sensing wire 698 corresponds to the third wire 22 of Fig. 1 which
electrically communicates with a sensing wire in the load, such
as sensing wire 24 of Fig. 1, and wire 698 is coupled to the PC
board 644 while the phase and neutral lines are electrically
secured to the fixed contact terminals 640 and 642. Terminals
640 and 642 are 90ft soldered to the PC board 644 by means of
mountlng tabs 700.
- 25 -
'''
lZ~3~6S
The pre~ent lnventlon thus provlde~ the user with a
~hock hazard protection 6ystem which: has a reponse time that
conforms to Underwriters Laboratories requlrements; i~ trlp free;
possesses a double pole lnterrupting mechanism wlth an alr gap
swltch; operates wlth reverse polarity; requlres only a 2 pole
receptacle; operate~ ln an ungrounded environment, such as a
plastlc tub; ls of a reasonable slze and cost; provldes the user
with a vlsible trip indication; meets Underwriters Laboratorles
,overload, short circuit, and endurance requirements; po~sesses -
electrical noise lmmunity so as to minimize false tripping;
provides protection in the event the cord is broken, wlth proper
polarlty assumed; provides adequate stra~n relief; ls usable with
a combinatlon swltch/receptacle; and provldes protectlon whether
the load or appliance switches are on or off, or are at medium or
hlgh settings.
The embodiments of the present invention herein
described and d1sclosed are presented merely as examples of the
lnvention. Other embodlment~, forms and structures coming wlthin
the scope of this lnvention wtll readily suggest themselves to
those ~kllled in the art, and shall be deemed to come withln the
scope of the appended claims.
