U.S. patent number 3,655,906 [Application Number 05/081,759] was granted by the patent office on 1972-04-11 for lamp ballast and method of producing same.
This patent grant is currently assigned to General Electric Company. Invention is credited to Robert E. Robb.
United States Patent |
3,655,906 |
Robb |
April 11, 1972 |
LAMP BALLAST AND METHOD OF PRODUCING SAME
Abstract
A lamp ballast wherein a magnetic core and coil assembly is
encased within a housing and is spaced from the housing with a
suitable filler material filling the space between the magnetic
core and coil assembly and the housing. The magnetic core and coil
assembly is suspended within the housing having an open top, being
spaced from the sides and bottom thereof by suspension means. The
housing or casing is then partially filled with the suitable filler
material in liquid form, to a level wherein at least a portion of
the magnetic core and coil assembly is immersed in the filler
material. After the filler material has hardened to an extent that
it will support the core and coil assembly, portions of the
suspension means are removed such that when the housing is
completely filled with the filler material the core and coil
assembly will be completely surrounded by the filler material and
the suspension means will not extend from the core and coil
assembly to the casing. Thus, the suspension means does not provide
a surface joining the casing and the core and coil assembly along
which moisture entering the casing may reach the core and coil
assembly.
Inventors: |
Robb; Robert E. (Danville,
IL) |
Assignee: |
General Electric Company
(N/A)
|
Family
ID: |
22166209 |
Appl.
No.: |
05/081,759 |
Filed: |
October 19, 1970 |
Current U.S.
Class: |
174/521;
174/DIG.2; 264/278 |
Current CPC
Class: |
H01F
41/005 (20130101); H01F 27/022 (20130101); Y10S
174/02 (20130101) |
Current International
Class: |
H01F
27/02 (20060101); H01F 41/00 (20060101); H05k
005/06 () |
Field of
Search: |
;174/DIG.2,52PE
;336/96,68 ;264/274,275,277,278 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Myers; Lewis H.
Assistant Examiner: Tone; D.A.
Claims
What I claim as new and desire to secure by Letters Patent of the
United States is:
1. A method of producing a lamp ballast having at least one
magnetic core and coil assembly which is encased in a housing, said
method comprising the steps of: suspending by a temporary
suspension means said at least one magnetic core and coil assembly
in said housing in a spaced relationship such that said at least
one magnetic core and coil assembly does not contact said housing,
partially filling said housing with a liquid filler material to a
level such that upon hardening said magnetic core and coil is
maintained in the spaced relationship; removing the suspending
effect of said temporary suspension means, completely filling said
housing with said filler material to completely encase said core
and coil assembly in said housing.
2. A method of producing a lamp ballast having at least one
magnetic core and coil assembly which is encased in a housing, said
method comprising the steps of: attaching temporary suspension
means to said at least one magnetic core and coil assembly,
suspending by engaging said temporary suspension means with said
housing said at least one magnetic core and coil assembly in said
housing in a spaced relationship such that said at least one
magnetic core and coil assembly does not contact said housing,
partially filling said housing with a liquid filler material to a
level such that upon hardening said magnetic core and coil assembly
is maintained in the spaced relationship, removing at least that
portion of said temporary suspension means which engages said
housing, completely filling said housing with said filler material
to completely encase said core and coil assembly in said
housing.
3. A method of producing a lamp ballast having at least one
magnetic core and coil assembly which is encased in a housing, said
method comprising the steps of: engaging said at least one magnetic
core and coil assembly in the bight of at least one U-shaped
support member which has a bight portion joining two leg portions
and a hook portion formed at the free ends of said leg portions,
suspending by engaging said hook portions of said at least one
U-shaped support member with said housing, said at least one
magnetic core and coil assembly in said housing in a spaced
relationship such that said at least one magnetic core and coil
assembly does not contact said housing, partially filling said
housing with a liquid filler material to a level such that upon
hardening said magnetic core and coil assembly is maintained in the
spaced relationship, severing and removing at least said hook
portions of said at least one U-shaped support member, completely
filling said housing with said filler material to completely encase
said core and coil assembly in said housing.
4. A lamp ballast having at least one magnetic core and coil
assembly, a housing, and a hardenable filler material encasing said
at least one magnetic core and coil assembly; formed by: suspending
said at least one magnetic core and coil assembly in said housing
in spaced relationship thereto by engaging said at least one
magnetic core and coil assembly and said housing with temporary
suspension means; partially filling said housing with said filler
material to a level sufficient to support said at least one
magnetic core and coil assembly in spaced relationship within said
housing; removing said temporary suspension means from engagement
with said housing; and substantially completely filling said
housing with said hardenable filler material.
Description
BACKGROUND OF THE INVENTION
The present invention relates to an electric discharge lamp
ballast, and particularly to a fluorescent lamp ballast having
improved moisture resistance.
One factor that reduces the life of fluorescent lamp ballasts,
particularly in applications where the ballast is exposed to a wide
range of conditions, such as humid and corrosive atmospheres and
relatively high and low temperature environments as may be
encountered in various extremes of weather, is the entrance of
moisture through the case to the core and coil assembly. The
entrance of moisture into the core and coil assembly and
particularly into the coil may cause an electrical failure of the
coil. Any member, regardless of whether it is formed of a metallic
or insulating material, which extends between the core and coil
assembly and the housing may potentially provide a path for the
entrance of moisture into the core and coil assembly. Moisture may
enter the core and coil assembly in the presence of two conditions,
the presence of a path for the entrance of moisture into the casing
in a region where a member extending from the core and coil
assembly contacts the housing, and the presence of a path for
moisture flow along the member extending between the case and the
core and coil assembly. The later path may for instance be provided
along the surface of a member extending between the case and the
core and coil assembly when there is not complete and continuous
adhesion between the member and the filler material. In the absence
of complete adhesion, a continuous void may be provided along the
surface of the member between the housing and the core and coil
assembly, through which moisture may pass from the housing to the
core and coil assembly. The entrance of moisture into the coil may
cause a degradation of the insulating material of the coil and an
eventual failure of the coil and therefore of the magnetic core and
coil assembly.
OBJECTS OF THE INVENTION
It is therefore a primary object of this invention to provide a
novel and improved lamp ballast having increased resistance to the
entrance of moisture to the core and coil assembly of the lamp
ballast, and a method of producing such a lamp ballast.
It is another object of the present invention to provide a novel
and improved lamp ballast and method of producing the same which
minimizes the possibility of the entry of moisture into the core
and coil assembly, particularly when the lamp ballast is exposed to
a wide range of conditions, such as relatively high humidity and
relatively high and low temperature variations as may be
encountered in various extremes of the weather in outdoor
applications.
It is a further object of this invention to provide a novel and
improved lamp ballast and method of producing the same which
incorporates a minimum number of inexpensive parts which are
readily assembled with minimal effort and skill.
SUMMARY OF THE INVENTION
The foregoing objects are accomplished in accordance with this
invention when in a preferred embodiment a magnetic core and coil
assembly is placed within a housing and supported therein out of
contact with the housing by temporary suspension means. The
magnetic core and coil assembly, and other electrical components
making up the lamp ballast, are positioned within the housing with
the leads for making external connections to the coils and other
electrical components extending from the housing through one or
more apertures in the housing which are provided with insulating
and sealing grommets. The temporary suspension means suspends the
magnetic core and coil assembly within the housing in a spaced
relationship with respect to both the side walls and the base of
the housing. The housing is then partially filled with suitable
filler material in liquid form to a level wherein upon
solidification the filler material will support the magnetic core
and coil assembly within the housing. At least those portions of
the temporary suspension means which engage or extend without the
housing are then removed. thereafter the housing is completely
filled with the filler material so as to completely surround the
magnetic core and coil assembly. The assembly of the lamp ballast
is thereafter completed by applying a cover to the housing.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a top plan view of a preferred embodiment of the novel
and improved lamp ballast of this invention in a first step of
construction.
FIG. 2 shows an elevation view of the novel and improved lamp
ballast in a longitudinal section taken along the line 2--2 in FIG.
1, but at a second step of construction.
FIG. 3 is an elevation view of the lamp ballast in transverse
section taken along the line 3--3 in FIG. 1.
FIG. 4 is an elevation view of the lamp ballast in transverse
section taken along the line 4--4 in FIG. 2.
FIG. 5 is an elevation view of the completed lamp ballast.
FIG. 6 is an elevation view of the lamp ballast in transverse
section taken along the line 6--6 in FIG. 5.
FIG. 7 is a perspective view of a preferred form of the temporary
core and coil assembly suspension means.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to FIGS. 1 and 2 the novel and improved lamp ballast
10 and method of producing the same will be described. The lamp
ballast 10 is contained within a suitable housing which is shown as
a metallic casing 12. The casing 12 is formed with a base 14,
upstanding sidewalls 16 and 18 and end walls 20 and 22. As shown in
the preferred embodiment of this invention, the electrical
components of the lamp ballast include a core and coil assembly 24
and a capacitor 26. However, in ballasts for different types of
electric discharge lamps and for different numbers of electric
discharge lamps other components such as additional capacitors and
additional core and coil assemblies may be included within the
housing.
The electromagnetic core and coil assembly includes a shell-type
core 28, preferably formed of a plurality of layers of laminations
30. The layer of laminations are made up of punchings which form a
pair of outer legs 32 and 34 and a central leg 36 shown by the dash
line in FIG. 1. Window openings 38 and 40 are formed between the
central leg 36 and the outer legs 32 and 34 of the core 28. A pair
of winding or coil assemblies 42 and 44 are mounted on the central
leg 36 and occupy most of the space in the windows 38 and 40. When
the shell-type core formed of laminations 30 is assembled with the
coil assemblies 42 and 44, the complete assembly is held together
by a pair of end clamps 46.
Electrical connections between the coil assemblies 42 and 44 and
the capacitor 26 are made through a pair of terminal boards 48 and
50 supported from the end clamps 46. Terminals 52 are secured to
insulating boards 54 in some manner, such as by staking, and the
insulating boards 54 are secured to the end clamps 46 such as by
tabs 56 provided on the end clamps. While not shown in the figures,
the leads extending from the coil assemblies 42 and 44 are soldered
or otherwise electrically connected to the appropriate terminals
52. Appropriate electrical interconnections between the capacitor
terminals 58 and the coil assemblies 42 and 44 are made by
insulated leads 60 extending between the capacitor terminals 58 and
appropriate terminals 52.
External electrical connections to the core and coil assembly and
the capacitor 26 are made by way of insulated leads 62 which extend
through apertures in the end walls 20 and 22 of the housing.
Grommets 66 are provided in these apertures to further insulate the
insulated leads 62 from the end walls 20 and 22, and to assure that
the apertures are substantially closed so as to prevent the outflow
of the liquid filling material.
In order to insure that the insulated leads 60 and 62
interconnecting the coil assemblies and the capacitor and extending
external of the lamp ballast do not contact the walls or the top of
the housing, a pair of resilient loops such as rubber bands 67 are
placed over the insulated conductors and the core and coil assembly
24 and the capacitor 26 to hold the insulating leads close
thereto.
In constructing or assembling a ballast in accordance with the
method of this invention, a temporary suspension means comprising a
pair of U-shaped support members 68 are placed around the end
clamps 46 with the bight portion 70 extending beneath the clamp as
viewed in FIG. 2 and the leg portions 72 extending along the side
portion of the clamp as viewed in FIG. 2. The free ends of the leg
portions 72 are provided with outwardly extending hooks 74 which
engage the upper edges of the side walls 16 and 18 of the housing
as the core and coil assembly 24 is lowered into the housing 12.
The preferred support member as shown in FIG. 7 is formed of a
cylindrical, fairly rigid, steel wire which is formed in a general
U-shaped with a bight portion 70, leg portions 72, and outwardly
extending hooks 74 formed at the free ends of the legs 72.
Referring to FIGS. 1 and 3, it will be observed that the core and
coil assembly 24 as suspended within the housing 12 by the support
members 68 is spaced from the side walls 16 and 18, from the end
walls 20 and 22 and from the base 14. Thus, no portion of the core
and coil assembly is in contact with the housing 12.
As the core and coil assembly is placed within the housing 12 and
suspended therein by the support members 68, the capacitor 26 is
also placed within the casing. An insulating film 76 is wrapped
around the capacitor 26 to further insulate the capacitor should
moisture in any way enter the housing 12. In the preferred form of
this invention, the capacitor 26 would be supported by its leads
and the resilient loop or rubberband 26 and would not contact any
portion of the housing 12. After the core and coil assembly 24 and
the capacitor 26 are placed in the housing 12, the insulating leads
62 are threaded through the grommets 66 to extend through the end
walls 20 and 22 of the housing.
With the electrical components of the lamp ballast thus assembled
and supported within the housing 12, the housing is partially
filled with a suitable filler 78, such as an asphalt compound that
is both electrical insulating and heat conducting. Due to the
spacing of the core and coil assembly 24 and the capacitor 26 from
the side walls, end walls and base of the housing 12, to the extent
that the housing 12 is filled with the filler material 78, as shown
in FIG. 2 and 4, the filler material 78 insulates all portions of
the electrical components from the housing 12. The filler, which is
placed in the housing 12 in a liquid state, is permitted to
solidify to the extent that it will support the core and coil
assembly 24 and the capacitor 26 and prevent them from sinking and
engaging the base 14 of the housing 12. After the filler 78 has so
solidified, the free ends of the leg portions 72 of the support
members 68 are severed and removed to the greatest extent possible
as is shown in FIG. 6.
Thereafter, the remainder of the housing 12 is filled with the same
filler material 78, to completely fill the housing and thereby
completely cover the electrical components including in the
specific embodiment shown the core and coil assembly 24 and the
capacitor 26 as is shown in FIG. 6. The assembly of the lamp
ballast is completed by securing a cover 80 to the top of the
housing 12 as shown in FIG. 5.
Summarizing, FIGS. 3, 4, and 6 show three steps in the assembly of
a lamp ballast in accordance with the method of this invention.
FIG. 3 showing the support member 68 supporting the core and coil
unit assembly 24 in a space relationship with respect to the casing
before any filler material 78 is added. FIG. 4 shows the addition
of filler material 78 to a first level, wherein the filler material
is permitted to solidify to the extent necessary to support the
core and coil assembly 24 such that the temporary suspension means
may be removed. FIG. 6 shows the same cross-section of a completely
assembled lamp ballast wherein the legs 72 of the support member 68
have been severed, the housing 12 has been completely filled with
filler material 78, and a cover 80 has been secured to the housing
12 to completely encase the lamp ballast 10.
While in accordance with the preferred embodiment of this
invention, the support members 68 are shown to have a particular
U-shaped configuration, were it desirable to support the core and
coil assembly at some other position, or in some other manner, the
support member or members might take an entirely different
configuration. In producing a lamp ballast in accordance with the
method of this invention, what is required is that it be possible
to suspend the core and coil assembly 12 in the housing 12 out of
contact with the side walls, the end walls, and the base of the
housing 12 while a suitable filler material 78 is added to a level
wherein upon solidification it will support the core and coil
assembly. Thereafter, that portion of the temporary suspension
means which engaged the housing or extended therefrom thru the open
top to support the core and coil assembly 24 is removed. When the
housing 12 is completely filled with the filler material 78, the
core and coil assembly is completely encased by the filler material
78. In a completely assembled lamp ballast no portion of the
temporary suspension means extends through the filler material 78
from the core and coil assembly 24 to the housing 12.
While the novel and improved lamp ballast and method of producing
the same in accordance with this invention, eliminated any contact
between the core and coil assembly and the housing, and eliminates
any suspension members extending therebetween, it can not of course
eliminate the insulated leads extending from the core and coil
assembly through the housing for external connections. However, the
elimination of any contact between the core and coil assembly, or a
member supporting it and the housing is of course desirable for the
reasons previously set forth.
In order to minimize the possibility of moisture entering the core
and coil unit by way of creepage along the insulated leads, the
filler material and the insulation on the leads are chosen to
provide maximum adhesion therebetween. Thus, while a lamp ballast
constructed in accordance with the method of this invention does
not eliminate the connecting leads extending from the core and coil
assembly through the casing, it does eliminate all direct contacts
and other members extending therebetween and thereby significantly
improves the resistance of the lamp ballast to the entrance of
moisture into the core and coil assembly.
In an alternate arrangement in accordance with this invention, some
sort of temporary suspension means would be secured to an upper
portion of the core and coil assembly as viewed in FIG. 2. After
the filler material 78 is added to a level such as is shown in FIG.
2, and the filler material has solidified to support the core and
coil assembly, the suspension means may be removed. For instance, a
clamping device with sufficient clamping force to support the core
and coil assembly might engage the outer edges of the outer legs 32
to support the core and coil assembly in the desired predetermined
position in the housing 12. After sufficient filler material 78 has
been added to the casing such that upon solidification it will
support the core and coil assembly 24, and the filler material 78
has solidified, the supporting clamping device would be removed and
the housing 12 completely filled with the filler material.
While in accordance with the patent statutes the preferred
embodiment of this invention has been shown and described, it will
be obvious to those skilled in the art that various changes and
modifications may be made without departing from this invention in
its broader aspects and, therefore, it is intended that the
appended claims cover all such changes and modifications a fall
within the true spirit and scope of this invention.
* * * * *