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Dec. 31, 1946.
Original Filed Sept. 12, 1940
mumr/o
2,413,363
H.-J. MCCARTHY
THERMAL RELAY FOR FLUORESCENT LAMPS
'
I Patented Dec. 31, 1943
2,413,363 - A
UNITED STATES ‘PATENT OFFICE
2,413,363
I
THERMAL RELAY FOR FLUORESCENT
,
LAMPS
-
'
Henry J. McCarthy, Danvers, Mass., assignor to
Sylvania Electric Products, Inc., Salem,
Mass.,
a corporation of Massachusetts
Continuation of application Serial No. 356,566,
September 12, 1940. This application January
, 1943, Serial No. 471,200
v
2 Claims- (Cl. 200—122)
V
i.
This invention refers to electric gaseous dis
charge lamps and in particular to'thermal relays
for operating ?uorescent lamps. This applica
tion is a continuation of my coepending applica
tion Serial No. 356,566, filed September 12, 1940.
An object of this invention is to provide ‘a start
ing switch for electric gaseous discharge lamps
which will permit the cathodes of the lamp to be
plil‘eheated
before the discharge is started between
t em.
Another object is to provide a starting switch
9
ported between and connected to the lead-in
wires ‘l and t, is also mounted on the mounting
plate 2 but on the side opposite the condenser E.
The leadn-in wires ‘l and ii of the resistance rod
3 are joined to the lead-in wires 3 of the con
denser at'the eyelets d. The joining ofv these
two sets of lead-in wires at the eyelets 6 may be
done by spot-welding, soldering or somesimilar
means. The lead-in wires 3 of the condenser l
10 are projected through the eyelets 4% in the‘rnount
ing plate 2 and extend down through the eyelets
9 in the circular base plate illv and into the base
will elapse for the
of
pins 5 where they may be soldered. Although
the cathode than is absolutely necessary.
.eyelets 4 and 9 are used in the mounting plate 2
A further object is to provide a. switch which 15
“and the base plate l0, respectively, any other
will function under all possible conditions of
material may be used that will permit a joining
starting and restarting,
and ?xing of the lead-in wires at these points.
Another object is to provide a switch which
which will be so timed in its action that no greater
interval of time
‘
preheating
will be so mounted as to be capable of withstand
Eyelets, or some similar means are necessary due
to the fact that the base plate and mounting
ing accidental, careless or rough usage without
are made of Bakelite or ‘some similar in
having the precisely adjusted parts thrown out 20 plate
sulating material.
v“
of alignment.
p The supporting arm ll of nickel or some simi
A feature of this starting apparatus is that it
lar material extends inwardly from the lead-in
‘eliminates the unnecessary time lag present in
many switches during the starting and restart 25 wire 71, and attached to the inward end thereof
is the bimetallic strip it? which is bent around
lng period.
the resistance rod 6. Attached to the inner side
Another feature of this switch is that it is so
of the free end of the bimetallic strip l? is the
mounted that even if it were dropped or other
low resistance contact 25. The resistance rod
wise mishandled, the precisely adjusted parts
would not be disturbed.
'
Other objects, advantages and features will be
apparent from the following speci?cations taken
may have thereon an insulating coating ill of,
30 for example, alumina and shellac.
'
I have found that an insulating coating of
alumina and shellac is best suited for the par
in conjunction with the accompanying drawing
ticular purpose for which it is herein employed.
in which:
2 apply two coats of a dewaxed shellac and then
Figure 1 isa ‘front perspective of the thermal
two coats of an alumina-shellac mixture. Each
relay assembly.
coat isbake'd before another coat is applied. Al
Figure 2 is a side elevation detail of the thermal
though I have‘ used two coats of shellac and two
relay.
coats of alumina and shellac the number of coats
Figure 3 is, a front perspective viewed .from I
be varied inasmuch as uniformity of the
below of the thermal relay assembly with the 40 may
coating is the object to be attained. I have just
container partly cut away to show the insulating
applied two coats of shellac before applying any
alumina because with the shellac foundation a
Figure 4 is a schematic wiring diagram of the
higher breakdown voltage is obtained. This coat
thermal relay.
l
I
ing also prevents the bimetallic strip irom cut—
Similar reference characters refer to similar
ting through the resistance rod.
parts in the several views of the drawing and in
The supporting arm I4 of nickel or some slml- ‘
the speci?cations which follow.
'
lar material extends inwardly from the lead-in
The switch in my invention comprises a con
wire 8 and attached thereto and projecting up
denser. a resistance rod supported between and
wardly
and parallel to the bimetallic
connected to the two lead-in wires, a bimetallic 60 strip 12 therefrom
is the strip IE to which is attached the
strip bent around the resistance rod, and a high means.
_
.
'
andetwo‘lowresistance polnts..
’
U-shaped arm l6 of nickel or some similar ma-'
terial. Attached to one end of this .U-shaped
The condenser I is mounted on the mounting
arm is the high resistance contact H, which may
plate 2, having its. lead-in wires 3- extending
beof carbon-and ‘which is normally closed with
thrpughthe eyelets 4. The resistance rod 8, sup 55 the
bimetallic strip l2. Attached to the other
'
_
_
2,418,868
4
I
.
the plate 2 and base Ill resides in the lead wires
end of the ueshaped arm-is the low resistance
contact l8, which may be of silver and which is
3. Resting of plate 2 on base I 0 provides a con
normally open in respect to the bimetallic strip
' tact between the plates, but not a connection.
l2.
This low resistance contact acts as an aux-~ '
iliary starting means for if the ?laments of the
lamp have not been suf?ciently heated to start
the discharge across the lamp, by the time the
The lead wires 3 cushion am! shock received by
the base I!) and are rigid enough to act as sup
ports and yet resilient enough'to provide cush
ioning action for the plate 2 and the various
bimetallic strip breaks away from the high re
members mounted thereon.
'
I
The entire switch unit may be inserted in a
rod 6 will continue to heat the bimetallic strip l2 10 metal container l9 and may be insulated there
and cause the strip l2 ‘to bend back causing the ' from, by‘ a thin tube of insulating paper 22
around the-inner wallof the container l9 and a '
low resistance contact 25 attached thereto, to
wafer 21 of insulating material in the top of the
touch the low resistance contact l8 thus short
container. This container may have several
circuiting the resistance‘ rod and starting the pre-_
tangs 20, on the open end which may extend over
heating of the lamp ?laments.
the base plate l0 after the switch has been in
The resistance rod should have a high resist- _
serted in the container. The base plate I0 has
ance, say 40,000 ohms. For this resistance I have
, sistance contact H, the current in the resistance
' used, for example, a resistance rod, 0.45 inch .
several notches 2|, therein, over which the tangs
long and 0.65 inch in diameter. For my_high
20 are bent. If these tangs 2!] ever became loose
and permitted the base plate to move, the switch
‘would not be affected, for the movement of the
resistance contact I have used carbon, having a
contact resistance of about 15 to 30 ohms. For
my low resistance contacts I have used silver,_
having a resistance of a fractional part of an
ohm. Although I have used these particular ma
terials, my invention does not necessitate the use
of these exact same materials. It' is su?icient
switch would be absorbed by the ?exible wires
3 of the condenser, thereby protecting the more
sensitive and vital parts of the switch and pre
venting them from being thrown out of align-L
ment.
ance contact points and a high resistance rod be
used. A condenser of .006 microfarad across the
contacts has proven to be advantageous for the
base pins may be ?at or grooved depending on
the type of contacts used. If a wire contact is
used, I have found that pins with grooved sides
provide a ?rmer contact surface.
. the base plate I0,-,but is so cut as to be elevated
from the base plate at the points-where the con
denser lead-in wires 3 extend down into the base
If this were not done it would be quite
What I claim is:
dif?cult to centrally locate the mounting plate
2 on the base plate In and still have the wires 3 _
extending down into the base pins in their proper
positions. The base pins may be of the type suit
'40
able for use in a socket of the type described in
Patent #2,261,170, in my name, and datedNo
vember 4, 1941.
The manner in which this switch is mounted
allows for considerable accidental misuse. . Due
to the fact that several of the parts which are,
vital tothe operation of the switch are very ?nely
proportioned and the slightest change therein
would cause ine?ective or ine?icient operation,
this switch is mounted in a manner asto have 1
‘those parts which are not ?nely proportioned
and sensitive, absorb the shocks of accidental
misuse.
The lead-in wires 3 of the condenser I are quite
?exible. Due to this ?exibility of these wires,
and the fact that the mounting plate 2 is not
?ush mounted 'on the base plate l0, any move
ment or disturbance of the base plate will not
disturb the switch elements because the switch
_
any desired shape. The contour, as shown in
Figure 1, has been selected because it facilitates
and makes easier the welding operations on the.
thermal relay. The contour of the sides of the
elimination of radio interference.
The mounting plate 2 is not mounted ?ush on
‘ pins 5.
,
The contour of ‘the mounting plate may take
that a high resistance contact point, low resist
'
1. A thermal relay unit for electric discharge
lamps comprising a horizontal rigid base plate of
insulating ‘material, arigid thermal switch sup
porting plate of insulating material perpendicu
lar to said base plate, a U-shaped conductor
member of relatively stiff wire disposed in sub
stantially parallel spaced relation to said plate
and having a high resistance portion in the por- _
tion between its side sections, rigid anchoring
means for securing the free ends of said conduc
tor member to said thermal switch supporting
plate; a bimetallic member in close proximity to
said resistance portion, a supporting arm ?xed
to one of the side sections of said conductor act
ing to support said bimetallic member, a contact
member adjacent the free end of said bimetallic
member, a supporting arm ?xed to the other side
section of the conductor member acting‘ to sup
port said contact member, a pair of contact pins
?xed in said base plate and semi-?exible lead
wires connected to the points of attachment of
the conductor member with said vertical plate
acting ?exibly to support said vertical plate and
mount as a unit will merely bend forward or 60 the thermal switch thereon from said base plate.
backward, the shock being entirely absorbed by i
2. A thermal relay unit for electric discharge
the ?exible lead-in wires of the condenser.
The mounting plate 2 may rest on the base
lamps having the elements de?ned in claim 1
and in which the said vertical supporting plate
plate “1 although it is preferably held in spaced
relation therewith. The only connection between
is I-beam shaped in outline.
HENRY J. McCARTI-IY.
'
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